The story of the comets, simply told for general readers

THE

STORY OF THE COMETS

SIMPLY TOLD FOR GENERAL READERS.

BY

GEORGE F. CHAMBERS, F.R.A.S.

OF THE INNER TEMPLE, BARRISTER- AT-LAW.

AUTHOR OF

"A HANDBOOK OF ASTRONOMY," "A CONVERSATIONAL ENGLISH-FRENCH-GERMAN
DICTIONARY,'' "THE TOURIST'S POCKET-BOOK,'' AND OTHER WORKS.

DISCOVERY FIELD OF BROOKS S COMET OF 1895 (iii.).

" If there be aught throughout the pearly deep
Of Heav'n's unfathomable ocean wide,
That doth affect man's soul
With wonder and delight
Beyond the rest of vast Creation's wealth,
"Tis Thou, Mysterious Star."

(Anon., March, 1843.)

OXFORD
AT THE CLARENDON PRESS

1909

HENRY FROWDE, M.A.

PUBLISHER TO THE UNIVERSITY OF OXFORD

LONDON, EDINBURGH, NEW YORK

TORONTO AND MELBOURNE

PREFACE.

THIS volume scarcely needs a preface, for the title-
page tells its aim, and implies the motives which
have inspired it. It may, however, be confessed that
the great public interest which seems to have sprung
up in connection with the expected return this year
or next of " Halley's Comet " had something to do
with the non-publication of the book last year and
its non-postponement till next year.

I have modelled it on the Comet chapters of my
well-known Handbook of Astronomy, but every line of
those chapters has been rewritten, altered, corrected,
or expanded, and new chapters added, to embody the
different conditions of our knowledge in 1909 con-
trasted with the circumstances of nearly a quarter of
a century ago.

I have to thank various friends for advice and
assistance in making the book more useful than it
would have been without such advice and assistance ;
in particular, Mr. A. C. D. Crommelin, B.A., F.R.A.S.,
of the Royal Observatory, Greenwich, and Mr. W. E.
Rolston, F.KA.S., of the Solar Physics Observatory,
South Kensington ; and Mr. D. Smart, F.RA.S. ;
whilst as regards the illustrations I owe thanks to
the Council of the Royal Astronomical Society ; to

iv Preface.

the Proprietors ofPtmch ; and to various private friends,
English and American, amongst whom I must mention
Professor H. H. Turner of Oxford, Mr. ^Percy Morris,
F.R.A.S., of Sutton, Surrey, and Professor E. E.
Barnard and Mr. Morehouse in America. I am also
under great obligations to Mr. R. C. Slater, M.A., of
St. Peter's College, Cambridge : and the Rev. R. D.
Pierpoint of St. John's College, Cambridge, for reading
the Proof-sheets, and making various suggestions.

0. JF. C.

LETHEN GRANGE,
SYDENHAM :
July, 1909.

CONTENTS.

CHAPTEK I.

GENERAL REMARKS.

Popular appreciation of Comets and Eclipses and shooting stars. — Comets
always objects of popular interest and sometimes of alarm. — Quotation
from a writer of the 17th century. — Physical appearance of an ordinary
Comet. — Comets without Tails more numerous than Comets with Tails.
— General description of a Comet. — The Nucleus. — The Coma. — The
Tail. — Small Comets usually circular in form or nearly so. — Path of
a Comet. — Great diversity in the size and brilliancy of Comets. — Comets
usually diminish in brilliancy at each return. — Halley's Comet, a case
in point. — But this opinion has been questioned. — Holetschek's In-
quiries.— Actual Dimensions of Comets. — The Colour of Comets.

Pages 1-9

CHAPTEE II.

PHYSICAL DESCRIPTION OF COMETS.

Comets probably self-luminous. — Existence of phases doubtful. — Erratic
changes of brilliancy. — Comets with planetary discs. — Transformations
undergone by Comets. — Transits across the Sun never recorded. — Flimsy
nature of cometary matter. — Breaking up of a Comet into fragments. —
The instance of Biela's Comet. — Observations by Liais of the Comet of
1860 (iii.). — Other instances of Comets breaking up. — Berberich's in-
vestigations respecting Comets which may have broken up. — Comets
which follow one another in nearly identical orbits.- — Do Comets perish
by the exhaustion of their materials? — Summary of opinions as to what
those materials probably are. ... ... ... ... ... 10-21

CHAPTEK III.
THE TAILS OF COMETS.

Tails usually a prolongation of the Radius Vector. — Occasionally the tail
faces the Sun. — Then called a " beard ". — Comets with several tails. —
The Comet of 1825.— The Comet of 1744 with 6 tails.— Curvature of

vi Contents.

Tails.— Repulsive Action of the Sun on Tails of Comets.— Changes of
Direction of Tails.— Tails probably hollow cones or hollow cylinders.—
Vibration of Tails.— Jets of Light in the heads of Comets.— Formation of
Envelopes. — Fans of Light.— Abnormal Changes in the Tails of certain
recent Comets.— Swift's Comet of 1892 (i.).— Brooks's Comet of 1893 (iv.).
— Observations by Barnard.— Morehouse's Comet of 1908 (in.).— Specu-
lations as to the formation of Tails. — Bredichin's classification of Tails.—
(1) Long straight Rays.— (2) Curved plume-like Trains.— (3) Short,
stubby, and sharply-curved brushes of light. — What is the material of
which Tails are made?— Speculation on the subject not very profitable.—
Electricity and Light-pressure probably co-operating influence. — Sum-
mary by Maunder. ... ... ... ... ••• 22-37

CHAPTEE IV.

THE MOVEMENTS OF COMETS.

Periodical Comets. — Non-periodical Comets. — The density of Comets. — The
Masses of Comets. — Lexell's Comet. — The risk of collision of Comets with
the Earth. — No real danger. — The Influence of Planets on Comets very
real. — Special Influence of Jupiter. — List of Comets affected by Jupiter.
— Comets that are said to be associated with Planets. — The Inquiries
made when a new Comet is discovered. — Old Astronomers puzzled by
the movements of Comets. — Sir I. Newton's investigations. 38-45

CHAPTEE V.

THE DISCOVERY AND IDENTIFICATION OF COMETS.

How Comets are discovered. — The great French Comet-hunter, Messier. —
Much Comet-hunting now carried on in America. — Suitable occupation
for amateur astronomers. — Designation of Comets. — Appropriation of
observers' names to Comets. — Comets only identified by the elements of
their orbits. — Physical appearance of Comets no certain proof of identity.
— Identity of elements not always conclusive. — Possibility of more than
one Comet following the same path. — Photography as an aid to the dis-
covery of Comets. — Ancient Chinese records of great value. — Medals for
successful Comet-hunters. — Telegraph codes for transmission of cometary
announcements. 46-57

Contents. vii

CHAPTEK VI.

PERIODIC COMETS OF SHORT PERIODS.

Periodic Comets conveniently divided into 3 classes. — Short-period Comets
in two groups. — Comets in Group I. — Encke's Comet. — The supposed
Resisting Medium in space. — Its supposed effect on Encke's Comet. —
Brief summary of its History. — The Resisting Medium theory not gene-
rally accepted. — Remarkable Observations in 1871. Tempel's Second
Periodical Comet (1873, ii.). — Winnecke's Comet. — Brorsen's Comet. —
Tempel's First Periodical Comet (1867, ii.). — Tempel(3)-Swift's Comet.
— Finlay's Comet. — D'Arrest's Comet. — Wolf's Comet. — Holmes's Comet.
—Brooks's Second Periodical Comet (1889, v.).— Faye's Comet.— Tuttle's
Comet. — Short-period Comets in Group II. — Barnard's First Periodical
Comet (1884, ii.). — Brooks's First Periodical Comet (1886, iv.).— Bar-
nard's Second Periodical Comet (1891, iv.). — Spitaler's Comet (1890, vii.).
— Perrine's Comet (1896, vii.). — Kopffs Comet. — Giacobini's Second
Periodical Comet (1900, iii.).— Swift's Second Periodical Comet (1889, vi.).
— Borelly's Comet (1905, ii.).— Swift's First Periodical Comet (1885, ii.).
Denning's Second Periodical Comet (1894, i.).— Metcalfs Comet (1906,
vi.). — Denning's First Periodical Comet (1881, v.). — Giacobini's First
Periodical Comet (1896, v.). ... 58-85

CHAPTEK VII.

LOST COMETS.

LexelFs Comet. — Its mysterious disappearance. — Efforts made to identify
other Comets with it. — Biela's Comet. — Its division into 2 portions. — Its
disappearance. — Di Vico's Comet. — Other supposed Short-period Comets
which have never been seen a second time. — Grischau's Comet. — Helfen-
zrieda's Comet. — Pigott's Comet. — Blainpain's Comet. — Peters's Comet.
— Coggia's Comet. ... ... ... ... ... 86-95

CHAPTEE VIII.
PERIODIC COMETS OF LONG PERIODS.

Periodic Comets of between 70 and 80 years. — Westphal's (1852, iv.). —
Pons's (1812).— Di Vico's (1845, iv.).— Olbers's (1815).— Brorsen's (1847,
v.). — Halley's. — Particulars of each of these Comets. — Return of Pons's
Comet in 1883. — Observations of it by Trepied and others. — Many comets
no doubt revolving in elliptic orbits, but with periods of hundreds or
thousands of years. — Selected List of some of these. — The Comets of 1264
and 1556.— The Comets of 1532 and 1661. 96-101

viii Contents.

CHAPTER IX.

HALLEY'S COMET.

Halley's Comet by far the most interesting of the Periodic Comets. — Sir I.
Newton and the Comet of 1680. — This Comet the first to which the
theory of Gravitation was applied. — The Comet of 1682. — Description of
it by various observers. — Luminous Sector seen by Hevelius. — Halley's
application to it, and the Comets of 1531 and 1607, of Newton's mathe-
matical researches. — He finds the elements of the three very similar,
and suspects the three comets are really one. — With a probable period
of 75 years. — Suspects the disturbing influence of planets on Comets. —
Of Jupiter's influence especially. — Halley's final conclusion that the
Comet would reappear in 1758. — Preparations by Clairaut and Lalande
to receive it. — The Comet found by an amateur named Palitzsch near
Dresden. — Some account of this man. — The Comet generally observed in
Europe. — Trick played by Delisle on Messier. — Return of the Comet in
1835. — Great preparations by Mathematicians to receive it. — These
specially took into account planetary perturbations. — Predicted date of
perihelion passage. — The Comet discovered by telescopes as expected. —
Some particulars of the observations. — The past history of Halley's
Comet traced back through many centuries. — Researches of Hind. —
Confirmed in the main by Crommelin and Cowell. — Some quotations
from old Chroniclers. — Observations by the Chinese of great value. —
Halley's Comet in 1066. — Figured in the Bayeux Tapestry. — The Comet's
various returns ascertained with certainty backwards to B.C. 250.

102-25.

CHAPTER X.

REMARKABLE COMETS.

Suggested list of those which deserve the name. — The Great Comet of 1811.
—The Great Comet of 1843.— The Great Comet of 1858.— Evidence to
enable these three Comets to be compared. — The Great Comet of 1861. —
The Comet of 1862 (iii.).— The Comet of 1874 (iii.).— The Comet of
1880 (i.).— The Great Comet of 1882 (iii.).— Peculiarities of its orbit.—
The Comet of 1887 (i.).— Sawerthal's Comet of 1888 (i.).— The Comet of
1901 (i.) 126-59

CHAPTER XI.

THE ORBITS OF COMETS.

All Cometary Orbits sections of a Cone. — The different kinds of Sections. —
The Circle.— The Ellipse.— The Hyperbola.— The Parabola.— The last-
named the most easy to calculate. — An ellipse very troublesome to
calculate. — The elements of a Comet's Orbit. — For a Parabolic Orbit 5 in
number. — Statement of various details connected with Orbits. — Direction
of motion. — Eccentricity of an Elliptic Orbit. — The various elements
represented by certain symbols. — Number of comets whose orbits have
been calculated. — The significance of the different orbits pursued by
comets. 160-73

Contents. ix

CHAPTER XII.

COMETS IN THE SPECTROSCOPE.

The application of the Spectroscope to Comets. — Photography as applied to
the Spectra of Comets. — Historical Survey of the progress made. — Four
varieties of carbon Spectra. — Three Comets which have yielded special
results. — Conclusions of Hasselberg.— The great Comets of 1881 and
1882. — Schaberle's Comet. — Wells's Comet. — Instruments of a special
kind needed for the Spectra of Comets — Frost's Dictum. — Borelly's
Comet of 1890 (i.).— Brooks's Comet of 1890 (ii.).— Swift's Comet of
1892 (i.) : Holmes's Comet of 1892 (iii.).— Rordame's Comet of 1893 (ii.).—
Perrine-Griggs's Comet of 1902 (ii.).— Brooks's Comet of 1904 (i.).—
Daniel's Comet of 1907 (iv.).— Morehouse's Comet of 1908 (iii.).— One of
the most remarkable on record. — Summary of the present state of our
knowledge. — Importance of Photography in the study of Comets. —
Newall's Theory as to cometary radiation. ... ... ... 174-91

CHAPTEE XIII.
THE RELATION OF COMETS TO METEORS.

Association of Comets and Meteors.— Facts connected with Meteors necessary
to be borne in mind. — Summary statement of these. — Meteor Showers
of 1799 and 1832. — Shower of 1866. — Evident periodicity. — Researches
of Quetelet and H. A. Newton. — Investigations by J. C. Adams. —
Schiaparelli and the August Meteors. — Orbits of certain Meteor Swarms
identical with the Orbits of certain Comets. — Four such cases of identity
recognised. — The August, or Perseid, Meteors. —The Nov. 12, or Leonid,
Meteors. — The April, or Lyrid, Meteors. — The Nov. 27, or Andromedes,
Meteors. — The disappearance of Biela's Comet. — The certainty of the
connection of the Andromedes Meteors with that Comet. — Recent in-
vestigations as to that Comet. Review of the whole subject. 192-201

CHAPTEE XIV.

COMETS IN HISTORY AND POETRY.

Comets, objects of terror and alarm in all ages. — Opinions of the ancient
Greeks. — Of Anaxagoras. — Of Democritus. — Of Apollonius and Zeno. —
Sir G. C. Lewis's Summary of Greek opinion. — Ptolemy silent as to
Comets. — Twelve varieties mentioned by Pliny. — Opinions of Seneca. —
Of Paracelsus. — Napoleon and Comets. — The Romans not given to
Astronomy. — Quotations from Virgil. — From Suetonius. — From Juvenal.
— From Pliny. — From Plutarch. — Opinions of the old Chroniclers. —
Quotation from William of Malmesbury.— Pope Calixtus III. and the
Comet of 1456. — Admiral Smyth on this matter. — Leonard Digges. —
John Gadbury. — Shakespeare's frequent mention of Comets. — Quotation
from Julius Caesar. — From Henry VI.— From Hamlet. — From Henry IV.
— From The Taming of the Shrew. — Quotations from Milton. — Milton
apparently a plagiarist from Tasso. — Quotation from Thomson. — From

Contents.

Pope. — From Lord Byron.— From Young.— Some modern Poetry. — An
American Incident.— Comets and Hot Weather. — The Earl of Malmes-
bury. — Arago rebukes wild speculations. — French writers. — Fontenelle. —
Lambert. — Supposed allusions in the Bible to Comets. — Maunder1 s
opinion 202-20

CHAPTEK XV.

COMETAKY STATISTICS.

Statistics not generally appreciated. — Difficulty of being precise in dealing
with Cometaiy Statistics. — Nuclei. — Comae. — Tails. — Orbits. — Number of
Comets recorded and calculated. — Duration of visibility. — Periodical
Comets and their returns. — Direction of Motion of Periodical Comets. —
Perihelia. — Ascending Nodes. — Inclinations of Orbits. — Perihelion Dis-
tances.— Direction of Motion. ... ... ... 221-31

APPENDIXES :

I. A Catalogue of Recent Comets, 1888-1908. 232

II. A Supplementary Catalogue of Comets recorded, but not with

sufficient precision to enable their Orbits to be calculated 242

III. The Literature of Comets 245

IV. Ephemeris of Halley's Comet, January- July, 1910 246

GENERAL INDEX : 250

LIST OF ILLUSTRATIONS.

FIG. PAGE

1-3. Halley's Comet, 1835-1836 at various dates . Plate I. Frontispiece.

4. Discovery Field of Brooks's Comet (1895, iii.) . . Title-page.

5. Telescopic Comet without a Nucleus .... 3

6. Telescopic Comet with a Nucleus ..... 3

7. Comparative sizes of the Earth, the Moon's orbit, and certain

Comets, named .... Plate II. 7

8. Comet I. 1847 visible at Noon, on March 30. (Hind.) . . 8

9. Biela's Comet, Feb. 19, 1846. (0. Strure.) ... 15

10. Diagram illustrating the changes in the directions of the Tails

of Comets ....... 25

11. Comet III. I860. June 26. (Cappelletti and Rosa.) Plate III. faces 26

12. Comet HI. 1860. June 28. (Cappelletti and Rosa.) ,, 26

13. Comet III. 1860. June 30. (Cappelletti and Rosa.) ,, 26

14. Comet III. 1860. July 1. (Cappelletti and Rosa.) ,, 26

15. Comet III. 1860. July 6. (Capptlletti and Rosa.) ,, 26

16. Comet III. 1860. July 8. (Cappelletti and Rosa.) ,. 26

17. Ideal Diagram of " Envelopes " ..... 28

18. Diagram : Recognition of a Comet . . Plate IV. faces 30

19. Brooks's Comet (1893, iv.). Oct. 21 .. „ 30

20. Morehouse's Comet (1908, iii.) on Oct. 15. (Morris.) Plate V. follows 32

21. Morehouse's Comet (1908, iii.) on Oct. 30. (Morris.) Plate VI. „ 32

22. Morehouse's Comet (1908, iii.) on Sept. 30 . Plate VII. „ 32

23. Morehouse's Comet (1908, iii.) on Oct. 1. . „ ,, 32

24. Morehouse's Comet (1908, iii.) on Oct. 15. . Plate VIII. „ 32

25. Morehouse's Comet (1908, iii.) on Nov. 15. . „ ., 32

26. Bredichin's Three Types of Comet Tails .... 34

27. Diagram illustrating the influence of Jupiter on Comets . 40

28. Discovery Field of Brooks's Comet (1890, ii.) ... 47

29. Diagram of an ellipse, parabola, and hyperbola ... 53

30. Encke's Comet, Nov. 30, 1828. (W. Struve.) ... 62

31. Encke's Comet, Sept. 22, 1848 . . . Plate IX. faces 64

32. Encke's Comet, Nov. 9, 1871. (J. Carpenter.) ... 65

33. Henry's Comet, Sept. 3, 1873. (Tempel.) . . Plate X. faces 70

34. Respighi's Comet, Jan. 5, 1864. (Tempel.) . ,, 70

35. Thatcher's Comet, May 5, 1861. (Tempel.) . „ 70

36. Brorsen's Comet, 1873. (Tempel.). . . ,,70

37. Faye's Comet, 1873. (Tempel.) ... .,70

38. Holmes's Comet, 1892, and the Andromedae Nebula. Plate XI. faces 74

Xll

FIG.

39.
39 a.
40.
41.
42.
43.
44.
45.
46.
47.
48.
49.
50.
51.
52.
53.
54.
55.
56.
57.
58.
59.

60.
61.
62.

63.
64.
65.
66.
67.
68.
69.
70.
71-

81.

82.

83.
84.
85.
86.
87.
88.

List of Illustrations.

Pons's Comet, Jan. 19, 1884. (Trepied.) ... 98

Portrait of Edmund Halley . . Plate XI a. faces 102

Medal of the Comet of 1680 ..... 103

Halley's Comet, 1683 : Luminous Sector. (Hevelius.) . . 105

The Orbit of Halley's Comet and Planetary Orbits . . 108

Halley's Comet, Oct. 11, 1835. (Smyth.) .
Halley's Comet, 1066. (Bayeux Tapestry.)
Halley's Comet, 684. (Nuremberg Chronicle.)
The Great Comet of 1744. (De Cheseaux.)
The Great Comet of 1811 .
The Great Comet of 1 843 .
Donati's Comet, Oct. 5, 1858. (Pope.)
Donati's Comet, Oct. 9, 1858. (Pape.)
Donati's Comet, 1858 : the Coma, Sept. 22.

115
Plate XII. 119

121
Plate XIII. faces 128

130
Plate XIV. faces 132

Donati's Comet, 1858 :
Donati's Comet, 1858:
Donati's Comet, 1858
Donati's Comet, 1858 :

Plate XV.
Plate XVI.
(Pape.) Plate XVII.
(Pope.) „

the Coma, Sept. 29.
the Coma. (Anon.) . ,,

the Coma, Oct. 6. (Pape.) ,,

the Coma, Oct. 12. (Pape.) „

Donati's Comet, Sept. 30, 1858. (Smyth.)
Donati's Comet, 1858, passing Arcturus on Oct. 5
The Great Comet of 1861. June 30. (G. Williams.) Plate XVIII.

The Great Comet of 1861 :

(Well.) .
The Great Comet of 1861 :

(Brodie.)
The Great Comet of 1861

July 2. (Brodie.)
The Great Comet of 1861

July 2. (Chambers. )
Comet III. 1862. Aug.
Comet III. 1862.
Comet III. 1862.
Comet III. 1862.
Comet III. 1862.
Comet III. 1862.

the Coma, July 8.
the Coma, July 2.
: naked-eye view.
; naked -eye view.

Plate XIX.

133
135
136
136
136
136
136
137
138
140

143
143
143

(Cliallis.)
(Challis.)
(Challis.)
(Challis.)
(Challis.)
(ChaUis.)

Plate XIX a.

Plate XX.

143
146
146
146
146
146
146
148
149

Plate XXI. faces 150

Aug. 18.
Aug. 18.
Aug. 19.
Aug. 22.
Aug. 29.

Coggia's Comet, 1874, skeleton outline. (Brodie.)
Coggia's Comet, 1874. July 13. (Brodie.)
80. Coggia's Comet, 1874, 10 views of the Coma.

April 20 to July 8. (Tempel.)
Diagram showing path and developement of

Coggia's Comet, 1874. April 20 to June 25. Plate XXII. follows 150
Diagram showing path and developement of

Coggia's Comet, 1874. June 25 to July 14. Plate XXIII. follows 150
the Nucleus. (Prince.) . . 152

(Hopkins.) .... 154
(Flammarion.) . . . .154

Oct. 19. (Willis.) . Plate XXIV. 155

The Great Comet of 1882 : the compound Nucleus, Oct. 13. (Holden.) 157
The Great Comet of 1882 : the compound Nucleus, Oct. 17. (Holden.) 157

The Great Comet of 1882
The Great Comet of 1882.
The Great Comet of 1882.
The Great Comet of 1882.

List of Illustrations. xiii

FIG. PAGE

89. The Greab Comet of 1901 (ii.). (Lunt.) . . . .158

90. Brooks's Comet of 1902 (i.) (Brooks.} .... 159

91. The various Sections of a Cone ..... 160

92. Portrait of Sir Isaac Newton . . . Plate XXV. faces 160

93. Diagram of a Parabolic and an Elliptic Orbit . . . 161

94. The Construction of an Ellipse ..... 167

95. Discovery Field of Brooks's Comet of 1890 (ii.) (Brooks.) . 169

96. The Brooks-Borelly Comet of 1900 (ii.) (Brooks.) . . 169

97. Five Parabolas at $, 1, 2, 3, and 4 Radii of the Earth's Orbit. (Gibbs.) 170

98. Spectra of Olefiant Gas and Winnecke's Comet, 1868 . . 176

99. Morehouse's Comet of 1908 (iii.) on Dec. 11 Plate XXVI. faces 188
100-1. Photograph and Spectrograph of Morehouse's

Comet of 1908 (iii.) .... .,188

102. Orbit of the Leonids of Nov. 13 ..... 193

103. The Meteor Radiant Point in Leo, Nov. 13, 1866 . . 195

104. Position of Biela's Comet, 1798, 1838, 1872 . . .198

105. Discovery of a Comet at Greenwich Observatory. Plate XXVII. faces 208

106. Eclipse of the Sun of May 17, 1882, showing an Unknown

Comet. (Ranyard.) ...... 227

ADDENDA ET CORRIGENDA.

26, line 27. Add: — "It was suggested by Bessel that some of
the changes which he noticed to have been undergone by
Halley's Comet in 1835-6 were the result of a rotation on
its axis in a period of about 5 days, and a similar
suggestion was made with respect to Morehouse's Comet
of 1908 (iii). Both comets also suffered the loss, in
a certain sense, of their tails for a time. "

82. It is not quite certain to whom the pictures forming
Plates VII. and VIII. should be ascribed, as some of the
American photographs reached me without authors' names.

163, line 2. Add: — "Another term used in connection with the
elliptic orbits of comets is ' the Epoch of Osculation ',
which is the time for which the perturbed orbit has been
calculated. To get the time of perihelion passage from it
take the Mean Anomaly, M (or 360°— M, if M is near 360°) ;
reduce it to seconds and then divide it by the mean daily
motion in seconds (p.) ; the quotient is th£ interval in days
between the Epoch and the time of perihelion. Where M
is an angle of a few degrees it means that perihelion
precedes the Epoch, but where M is near 360° it means
that perihelion follows the Epoch."

213, line 2. Add: — "But Pope in speaking of a 'Eed Comet'
when he describes Minerva's rapid descent from Heaven
has tampered with the original Greek, for Homer says not
a word about any comet, but evidently alludes to a falling
star, or meteor of some kind." (Pope, Iliad, book iv, line
101 ; iv, 75, in the Greek.)

THE

STORY OF THE COMETS.

CHAPTER I.
GENERAL REMARKS.

Popular appreciation of Comets and Eclipses and shooting stars. — Comets
always objects of popular interest and sometimes of alarm. — Quotation
from a writer of the 11 th century. — Physical appearance of an ordinary
Comet. — Comets without Tails more numerous than Comets with Tails. —
General description of a Comet. — The Nucleus. — The Coma. — The Tail. —
Small Comets usually circular in form or nearly so. — Path of a
Comet. — Great diversity in the size and brilliancy of Comets. — Comets
usually diminish in brilliancy at each return. — Halley's Comet, a case in
point. — But this opinion has been questioned. — Holetschek's Inquiries. —
Actual Dimensions of Comets. — The Colour of Comets.

QUITE irrespective of the remarkable growth of a taste for
Astronomy which has marked the last quarter of a century,
alike in Great Britain, Greater Britain, and North America,
to say nothing of the Continent of Europe, there can be no
doubt that comets have, and always have had, a great fasci-
nation for that student of science newly named " the man in
the street". And next in order of interest certainly come
Eclipses, Solar and Lunar, and Fire-balls and " Shooting Stars";
but these do not concern us now. It is not difficult to see why
all these phenomena should be attractive to the popular mind :
they are all sights which can be seen, and in a measure be
studied, without professional teaching, and without much (or
any) instrumental assistance.

a From the Greek KOJHJTTJJ, the ing behind her, is often a not inapt
"long-haired one ". A woman's head, representation of a comet with a head
with long dishevelled tresses stream- and tail.

CHAMBERS B

•2 The Story of the Comets. CHAP.

In bygone times, before the invention of telescopes, it was
only of course the larger comets which were or could be
recorded ; and as these frequently appeared with great sud-
denness in the nocturnal sky, usually in the first instance not
far from the Sun, either after sunset or before sunrise, and
often had attached to them tails of great size which were
sometimes very bright, comets were well calculated in the
earlier ages of the world to attract the attention of all and to
excite the fear of many. It is the general testimony of
History during many hundreds of years, one might even say
during fully 2000 years, that comets were always considered
to be peculiarly " ominous of the wrath of Heaven and as
harbingers of wars and famines, of the dethronement of
Monarchs and the dissolution of Empires ". It is quite within
the limits of truth to say that ideas such as these have not
yet died out. One quotation of 17th-century origin will
sufficiently summarize the opinions of many writers and
thinkers. A poet of the epoch just named wrote thus : —

"A Blazing Star,

Threatens the World with Pamin, Plague and War ;
To Princes, death ; to Kingdoms many crosses ;
To all Estates, ineuitable Losses ;

To Herd-men, Rot ; To Ploughmen, haplesse Seasons ;
To Saylors, storms ; to Cities, ciuil Treasons." b

Some further quotations of an analogous character are
reserved for a subsequent chapter which deals with comets in
history and poetry.0

However little attention might have been paid by the
Ancients to the ordinary displays of natural phenomena,
certain it is that Comets and Total Eclipses of the Sun were
not easily forgotten or lightly ignored ; hence it is that the
aspects of many remarkable comets seen in olden times have
been handed down to us, often in language of circumstantial
minuteness, and still more often in language of grotesque
extravagance. The Chinese hold the palm under this head
of literary style.

t b Du Baitas, His Diuine Weekes mid Workes, trans. J. Sylvester, 1621, p. 33.
c See Chap. XIV (posf).

I.

General Remarks.

The physical difference between different comets is a matter
very little appreciated or understood by people in general.
With such, every thought is concentrated on the comet's tail,
if it has one ; or if it has not a tail, then the verdict is " 110
comet ". Yet the facts of the case are that the comets with
tails are, and always have been, considerably outnumbered by
the comets without tails. An explanation of the popular
view is to be found in the fact that the tailed comets are very
frequently visible to the naked eye, whilst the tailless comets
may be said to be never so visible.

An ordinary comet when first discovered by means of a
telescope either consists of, or sooner or later developes, three
parts. In the latter case the developement takes place some-
Fig. 5. Fig. 6.

TELESCOPIC COMET
WITHOUT A NUCLEUS.

TELESCOPIC COMET
WITH A NUCLEUS.

what in the following manner : the telescope reveals a faintly
luminous speck ; its size increases gradually, and after some
little time a nucleus appears. This word indicates that
a portion of the comet is more condensed in its light than the
rest. Both the size and the brilliancy of the object progres-
sively increase; the cloud-like mass around the nucleus
(called the coma d), becomes less symmetrical, and this loss of
symmetry, when it occurs, betokens the early developement
of a tail. Nucleus and coma taken together are generally
spoken of as the head of the comet. When a tail has become
manifest it will be found to be brighter near the head than at
the tip, and often brighter on one side than on the other.

d Latin for "hair".
B2

4 The Story of the Comets. CHAP.

" Tip " as applied to the tail of a comet is generally little
more than a figure of speech, because it is, as a rule, impossible
to say what is the tip, that is, to say where the tail comes to
an end. Occasionally the tail increases to a length, it may be,
of 10 or 20 degrees of arc or more. In the case of comets of
great size and brilliancy this tail sometimes spreads across
a large portion of the heavens ; sometimes there are more tails
than one. An ordinary tail presents the appearance of
a stream of milky-white light which is always fainter and
usually broader the further from the head that one examines
it. Occasionally the broadening of the tail towards its ex-
tremity becomes a very marked feature.

The nucleus of a small comet is generally circular, as indeed
is the whole comet, but a nucleus is sometimes oval, and, in
very rare cases, may present a radiated appearance. The
nucleus, if visible to the naked eye (the comet itself being
a small one), generally looks like, and may easily be mistaken
for a star or a planet, the coma not being visible until a tele-
scope is brought to bear on the comet. But in a telescope
such a comet will show as a point of light surrounded by
a fog of light. Sometimes, of course, the foggy appearance
may reveal itself even to the naked eye if the comet as
a whole is sufficiently luminous. Arago remarked that the
nucleus is generally eccentrically placed in the head, lying
towards the margin nearest the Sun. I do not, however,
think that this can be considered an established law applic-
able to the majority of the small comets; and under any
circumstances it would seem to betoken the forthcoming
appearance of something of the nature of a tail. Sometimes
a comet will have 2 or more nuclei or bright centres of light,
but one is the normal number.

The newly found comet approaches the Sun in a curvilinear
path which frequently differs but little from a straight line.
It generally crosses that part of the heavens in which the
Sun is situated so near the Sun as to be lost in its rays, but
it emerges again on the other side frequently with increased
brilliancy and increased length of tail. The phenomena of
disappearance are then not unlike those which marked the

I. General Remarks. 5

original appearance, but in the reverse order. To this it may
be added that a comet discovered in the Northern Hemisphere
usually passes into the Southern Hemisphere after it has
made its nearest approach to the Sun, and disappears in that
hemisphere. Conversely, a comet discovered in the Southern
Hemisphere generally comes North, and disappears in the
Northern Hemisphere, but exceptions to this rule are not
uncommon.

In size and brilliancy comets exhibit great diversity. It
sometimes, but not very often, happens that one appears which
is so bright as to be visible when the Sun has not yet sunk
below the horizon ; but the majority are invisible to the naked
eye, and need either a little, or a great deal of, optical assist-
ance. All these latter are " telescopic comets ". The appear-
ance of the same comet at different periods of its visibility
varies so much that we can never certainly identify a given
comet with any other by any mere physical peculiarity of
size, shape, or brightness. Identification only becomes possible
when its " elements " have been calculated and compared with
those of some other comet previously observed. It is now
known that " the same comet may, at successive returns to
our system, sometimes appear tailed, and sometimes without
a tail, according to its position with respect to the Earth and
the Sun ; and there is reason to believe that comets in general,
for some unknown cause, decrease in splendour in each
successive revolution ".e Halley's Comet, which we are all
expecting in 1910 or sooner, has been thought to have
diminished in brilliancy during the many centuries that have
elapsed since it was first recognized, judging by a comparison
of the descriptions given of it; but doubts have been cast
on this supposition by Holetschek, who concludes that for
a thousand years from 837 A.D. to 1835 its magnitude has
remained fairly constant, between the 3rd and 4th star
magnitudes; whilst between 1456 and 1835 there was no
great variation in the length of its tail.

Holetschek has carried out some investigations as to the
magnitude and brilliancy of comets and their tails from the

e Smyth, Cycle, vol. i, p. 235.

(> The Story of the Comets. CHAP. I.

earliest times till 1760 which deserve mention here. His
object was to arrange in order of magnitude those comets
whose orbits have been computed, in much the same way that
stars are classified in orders of brightness. In addition, he
has attempted to derive the true length of the tail from the
records of apparent length, and to examine to what extent
the developement of tails depends upon the magnitude of
comets and their perihelion distances. Holetschek endeavoured,
and with some success, to apply mathematical formulae to
the question of the comparative brilliancy of different comets.
His chief conclusions are that some 70 comets lend themselves
to a fairly satisfactory determination of magnitude when
reduced to the common standard of the Earth's distance from
the Sun taken as Unity ; and that to about 50 a numerical
value can be assigned to the length of their tails. The
magnitudes (taken in star magnitudes) range from — 1 (the
great Comet of 1744) to 9|f; but the greater number fall
between the magnitudes 4 and 6. So far as regards the tails
it would not be safe to draw any more precise conclusion
than, that the tail is greater the greater the magnitude, and
the closer the approach to the Sun. When the magnitude of
a comet (reckoned in star magnitudes) is about the 6th or less,
then, as a rule, no tail is developed that can be seen with the
naked eye ; except under specially advantageous circumstances^
as when the comet comes near the Earth. When the magnitude
is as great as the 4th, almost all comets when near perihelion
have tails visible without optical aid. But when the perihelion
distance is large the tail developement is very slight.8

Plate II represents the comparative diameters of the heads
of the well-known comets which are named, as they were
measured on particular occasions, compared with the size of
the Moon's orbit round the Earth. The woodcut is drawn
to scale, but it must not be inferred that the dimensions
indicated are in any sense permanent, or very trustworthy.

f The ambiguous figure — 1 as ap- e. r/. Sirius and a few others,

plied to indicate the magnitude of a g Ast. Nacli., vol. cxl, no. 3859,

star means, speaking roughly, a June 15, 1896 : summarized in Nature,

doubly-bright 1st magnitude star, vol. liii, p. 93. Nov. 28, 1895.

Fig. 7.

Plate II.

8 The Story of the Comets. CHAP.

The dimensions may be taken as typical of those of many
other comets.

Few things are more remarkable to witness, and more
paradoxical to explain, than the changes of bulk which the
head of a comet generally undergoes in approaching to, or
receding from, the Sun. One might expect, reasoning from
terrestrial analogy, that as a comet approaches the Sun the
increased heat to which it is submitted would expand its head,
whereas the effect observed is the contrary ; it grows smaller
as it grows hotter. And when receding from the Sun the
observed changes are of a converse character; the comet's
head seems to expand as it gets farther away and grows

cooler. No satisfactory ex-
planation of this anomaly has
been given unless it is per-
missible to accept Sir J.
Herschel's idea that the change
of bulk is due to some part of
the cometary matter remote
from the nucleus being eva-
porated, as it were, under the
influence of the Sun's heat,

THE COMET OF 1847 (i.), VISIBLE Just as & morning mist is
AT NOON ON MARCH 30. evaporated and disappears as

(Hind.} *v a • • -LI- i

the oun rises in the heavens
and its radiant heat becomes more potent.

History informs us that some comets have shone with such
splendour as to have been distinctly seen in the day-time.
The comets of B.C. 43, A.D. 575(3), 1106, 1402 (i.), 1402 (ii.),
1472, 1532, 1577, 1618 (ii.), 1744, 1843 (i.), 1847 (i.), 1853 (Hi),
1861 (ii.), 1882 (i.), are the principal ones which have been thus
observed. Perhaps we might assume that about 4 or 5 comets
are so visible in every century. The Comet of 1853 (iii.) was
seen on June 10 at Olmiitz only 12° distant from the Sun,
and again, after perihelion, on Sept. 2, 3, and 4 at noon.

What is the colour of a comet? Have comets ever any
colour? From my own observations, extending over many
years (and I suppose I have telescopically examined more

I.

General Remarks.

comets than most people), I should not have hesitated to
answer these questions in the negative, and have said that all
comets exhibit a more or less silvery-grey hue. On the other
hand, however, there is a certain amount of evidence available
which conflicts with this statement. Passing over what
I cannot but consider the sensational assertions of many
ancient and mediaeval writers of comets appearing of the
colour of blood, or fiery red, and so on, we do find in the
writings of modern astronomers sufficient evidence to show
that such tinges as " yellowish ", or " yellow ", or " ruddy ",
are not unprecedented both as regards nuclei and tails. The
Comet of 1769, the great Comet of 1811, the great Comet of
1843, Donati's Comet of 1858, Coggia's Comet of 1874, and
Fabry's Comet of 1886 (i.),h are cases in point. To this it
must be added that in a few rare cases mention is made of
" bluish-green " as a tinge which has been noticed. After all
said and done, however, I find that in looking into the
published accounts of many comets by many observers in
different parts of the world, there is a decided preponderance
of testimony in favour of " white " or " silvery-grey ", or
something of that sort, as being the ordinary hue of most
comets.

h "Ruddy brown" is the expression used in this case. Month. Not. R.A.S.,
vol. xlvi, p. 436. June 1886.

CHAPTEK II.
PHYSICAL DESCRIPTION OF COMETS.

Comets probably self-luminous. — Existence of phases doubtful. — Erratic changes
of brilliancy. — Comets with planetary discs. — Transformations undergone
by Comets. — Transits across the Sun never recorded. — Flimsy nature of
cometary matter. — Breaking up of a Comet into fragments. — The instance
of Stela's Comet. — Observations by Liais of the Comet o/1860(iii.). — Other
instances of Comets breaking up. — BerbericVs investigations respecting
Comets which may hare broken up. — Comets which follmr one another in
nearly identical orbits. — I)o Comets perish by the exhaustion of their
materials ? — Summary of opinions as to what those materials probably are.

IT was long a question whether comets are self-luminous,
shining with some intrinsic light of their own, or whether, as
in the case of the planets, they shine with light reflected
from the Sun. Whilst it cannot be doubted that they do
exhibit independent light of their own, yet it is now generally
believed that to a certain extent some of the light which they
yield is received by them from the Sun. It cannot, however,
be said that astronomers are agreed upon the point ; and
further evidence from advocates on both sides of the con-
troversj' is much to be desired. The spectroscope negatives
the idea that comet light is sunlight, whilst the polariscope
seems to indicate the presence of reflected light. Like the in-
struments named, observers of high repute have taken opposite
sides. Sir W. Herschel, from his observations of the Comets of
1807 and 1811 (i.), was in favour of the idea that comets were
self-luminous,11 but the observations of Airy and others on
Donati's Comet in 1858 point to exactly the opposite conclu-
sion as regards the tail of that comet.b If we know little
about the heads of comets we know still less about their tails,
for they are such strange ethereal structures. If the existence
of phases in the case of a comet could be certainly known

• Phil. Trans., vol. cii,p. 115. 1812. b Green. 06s., 1868, p. 90.

II. Physical Description of Comets. 11

this would furnish an unquestionable proof that the comet
exhibiting such phases shone by reflected sunlight. It has
been asserted from time to time that such phases have been
seen, but the evidence is very far from satisfactory. Delambre
mentions that the Records of the Paris Observatory afford
undoubted evidence of the existence of phases in the Comet
of 1682; but neither Halley nor any other astronomer
who observed that comet has left any intimation of phase
phenomena having been noticed by them. James Cassini
mentions the existence of phases in the celebrated Comet of
1744;c on the other hand, Heinsius and De Che'seaux, who
paid particular attention to that comet, positively deny having
seen anything of the kind. More recently Cacciatore of
Palermo expressed a decided conviction that he had seen
a crescent in the Comet of 1819. There were 4 comets in
that year and apparently the second is the one referred to.
Arago sums up by saying that Cacciatore's observations only
prove that the nuclei of comets are sometimes very " irregular",
by which word I suppose he means that they conform to no
regular laws.d Sir W. Herschel states that he could see no
signs of any phases in the Comet of 1807 although he fully
ascertained that a portion of its disc was not illuminated by
the Sun at the time of his observation. Pons's Comet of 1812
was found at its return in 1883-4 to be brighter than the
theory of its orbit led one to expect; indeed, it under-
went during its visible career various ups and downs of
brilliancy instead of varying gradually as its distance from
the Earth varied. Niesten suggested that this fact was
a proof of the comet being endued with some inherent light
of its own. This surmise may be applied to Holmes's Comet
of 1892, and Morehouse's Comet of 1908, both of which
underwent remarkable fluctuations of brilliancy, in accordance
apparently with no definite law. As to both these comets
more will be said hereafter.

A critical reader might suggest that the foregoing paragraph
conveys an uncertain sound, and the complaint would be
well-founded. I should therefore like to take leave of the

c Mem. AccuLcles Sciences, 1744, p. 303. d Pop. Ast., vol. i, p. 627, Eng. Ed.

12 The Story of the Comets. CHAP.

subject by quoting from a well-known American writer of
great experience his view of the case, to which I think the
same criticism applies. Says the late Professor Young: —
" There has been much discussion whether these bodies shine
by light reflected or intrinsic. The fact that they become less
brilliant as they recede from the Sun, and finally disappear
while they are in full sight simply on account of faintness
and not by becoming too small to be seen, shows that their
light is in some way derived from the Sun. The further fact
that the light shows traces of polarization also indicates the
presence of reflected sunlight. But while the light of a Comet
is thus in some way attributable to the Sun's action the
spectroscope shows that it does not consist, to any considerable
extent, of mere reflected sunlight, like that of the Moon on
Planets." e The writer adds : — '; If a comet shone with its own
independent light, like a star or a nebula, then, so long as it
continued to show a disc of sensible diameter, the intrinsic
brightness of this disc would remain unchanged; it would
only grow smaller as it receded from the earth, not fainter"
This last remark does not seem sound.

It occasionally happens that a telescopic comet, especially
when first discovered, exhibits a round and well-defined disc.
History indeed records this as the attribute of several naked-
eye comets discovered either before the invention of the
telescope or when the telescopes in use were of a very juvenile
character. Seneca, speaking of the second comet of 146 B.C.,
which appeared after the death of Demetrius, King of Syria,
says that it was but little inferior to the Sun, being a circle
of red fire sparkling with a light so bright as to surmount the
obscurity of night. It is to be presumed that he meant that
it was but little inferior to the Sun in size. The Comet of
1652, seen by Hevelius, was almost as large as the Moon
although not nearly so bright. The Comets of 1665 and 1682
are said to have been as well-defined in their outlines as the
Planet Jupiter. It is doubtful whether these statements can
be received as literally true : at any rate I am not acquainted

* C. A. Young, General Astronomy, Ed. of 1898. p. 442.

II.

Physical Description of Comets.

13

with any modern observations of large comets in respect of
which such precise language is used.

The transformations which comets undergo are so varied
and numerous that it is not easy to reduce them to writing in
any very orderly fashion. The following is an excellent
instance of these transformations. On August 8, 1769, Messier,
while exploring the Heavens with a 2-foot telescope, perceived
a round nebulous body which turned out to be a comet. On
August 13 a tail about 6° long was visible to the naked eye ;
on Aug. 28 it measured 15° ; on September 2 it measured 36° ;
on the 6th 49° ; and on the 1 Oth 60°. The comet then plunged
into the Sun's rays and ceased to be visible. On October 8 the
perihelion passage took place; on Oct. 24 the comet again
became visible but with a tail only 2° long ; on November 1 the
tail measured 6°, on the 8th it was only 2^° long, on the 30th
only 1^°. After that the comet ceased to be visible. Changes
of this character may not unfrequently be noticed.

Transits of comets across the Sun no doubt occasionally
happen, but there is no clearly authenticated instance known.
The German sun-spot observer Pastorff noticed on June 26, 1819
a round dark nebulous spot on the Sun. It had a bright
point in its centre. Subsequently when the orbit of the
Comet of 1819 (ii.) came to be investigated, Olbers pointed
out that the comet must have been projected on the Sun's disc
between 5h and 9h a.m. Bremen M. T. Pastorff asserted that
his " round nebulous spot " was the comet. Olbers, and with
him Schumacher, disputed the claim, and the matter seems
not free from doubt/ The Comet of 1826 (v.) was calculated
to cross the Sun on Nov. 18 of that year, but owing to bad
weather in Europe only 2 observers, Gambart and Flaugergues,
saw the Sun on that day, and neither of them obtained any
trace of the comet in transit. The Comet of 1823 is said also
to have crossed the Sun but without having been seen.

f For some further particulars as
to this controversy see Webb's Celest.
Obj., 4th Ed., p. 40, where there is also
a facsimile of PastorfFs original
sketch. See also an important paper

by Hind in Month. Not., vol. xxxv,
p. 309. May 1876. Hind seems to
have thought that there was either
error or fraud in PastorfFs narrative.

14 The Story of the Comets. CHAP.

The unsubstantial and flimsy nature of comets is shown by
the numerous recorded instances of comets passing in front
of stars without dimming their light, much less obliterating
them. Sir J. Herschel once watched Biela's Comet pass in
front of a cluster of stars without any obliterating effect
being noticed; and observations of this kind have so often
been recorded since that it is not worth while to cite instances
in detail. There are, however, some observations to the
contrary on record. A partial stoppage of light seems
suggested by what Sir W. Herschel stated respecting the
Comet of ] 807. He says that stars seen through the tail lost
some of their lustre, and that one near the head was only
faintly visible by glimpses.8 Again, on Sept. 13, 1890, an
11th mag. star is said to have completely disappeared during
the passage in front of it of Denning's Comet. It un-
fortunately happens that we possess no clearly expressed
record of the nucleus of a comet having been seen to occult
a star, and therefore the extent of the solidity which is to be
regarded as an attribute of cometary nuclei is at present
indeterminate. According to Max Wolf the Comet of 1903
(iii.) seemed to absorb some of the light of stars which it
passed over. These citations suggest that the comets in question
were more dense than the general run of comets.

A question of great interest which is often raised is, " Do
comets ever break up and disperse and disappear?" The
question must certainly be answered in the affirmative, but
the cases on record are not numerous,11 and except in a few
instances the evidence is not very definite. Seneca mentions
on the authority of Ephorus, a Greek author, that the Comet
of 371 B. c. separated into two parts which pursued different
paths.1 Seneca seems to distrust the statement which he
repeats, but Kepler accepted it after what he himself had

g Phil. Trans., vol. xcviii, p. 153. such catastrophes need not be rare.
1808. i Qwest. Nat, lib. vii, cap. 16. But

h Callandreau has formed the con- he says, however, of the writer he

elusion that the limit of distance at quotes : — " Ephorus vero non est

which the breaking up of comets by religiosissimae fidei ; siepe decipitur,

the action of the Sun and Jupiter is saepe decipit," which strikes a blow

possible is not considerable, and that at the value of his testimony.

II. Physical Description of Comets. 15

seen in observing the great Comet of 1618. In the case of
this comet Cysatus noticed an evident tendency in it to break
up. When first seen it was a nebulous object, but some
weeks afterwards it appeared to consist of a group of several
small nebulosities. But the best authenticated instance of
this character is that of Biela's Comet in 1845-6. When first
detected, on November 28, it presented the appearance of
a faint nebulosity, almost circular, with a slight condensation
towards the centre : on December 19 it appeared somewhat
elongated, and by the end of the month the comet had actually
separated into two distinct nebulosities, which travelled

Fig. 9.

BIELA'S COMET, FEB. 19, 1846. (0. Struve.)

together for more than 3 months : the maximum distance
between the parts (about 160,000 miles) was attained on
March 3, 1816, after which it began to diminish until the
comet was lost sight of in April. At its return in 1852 the
separation was still maintained, but the interval had increased
to 1,270,000 miles. As I shall have a good deal to say about
Biela's Comet in a later chapter no more need be said about
it here.

Biela's Comet does not stand alone among modern comets
as regards its duplicity. A comet seen in February and
March, 1860, only by E. Liais, a French observer in Brazil,
consisted when discovered of a principal nebulosity accom-

16 The Story of the Comets. CHAP.

panied at a short distance by a second and fainter nebulosity,
which disappeared before the principal nebulosity was lost to
view. It is to be regretted that this object remained visible
for so short a time as a fortnight, and that our knowledge of
it depends on the authority of only one observer.11 The
Comet of 1881 (ii.), according to the testimony of 2 observers,
threw off a fragment which became virtually an independent
comet, and lasted as such for some days, when all trace of it
was lost 1 ; but a still more interesting case is that of Brooks's
Comet of 1 889 (v.) described in some detail in a later chapter.01
Another very striking instance is afforded by Swift's Comet
of 1899 (i.) which was carefully studied by Bredichin. It
was discovered on March 13, 1899, by L. Swift, and passed its
perihelion about a month later. Before this it had a stellar
nucleus of the 10th mag., a coma 7' in diameter, and a small
tail. After perihelion it became visible to the naked eye and
brightened up to the 3rd mag. with a tail several degrees long.
On May 7 the nucleus was observed at the Lick Observatory
to be double, and the 2 portions gradually separated until on
May 21 they were 29' apart. The fainter portion was followed
till June, until it was too faint to be seen. The comet
eventually assumed what is known as the " scymitar " form,
and showed indications of twisting which suggested the idea
of rotation or oscillation about the line drawn from the Sun
to the comet. The tail was of type I of the Bredichin types,
with the exception of a faint stream which was of type III.D
There was no difficulty in tracing on photographs the outward
and vibratory motion of the material of the tail, and Bredichin
says that the extremity of the tail, as seen on May 19, was
formed of matter which had left the head 4 days earlier. He
does not hesitate to say that the partition of the tail was
caused by the disturbing influence of the Sun, and that both
nuclei were moving in hyperbolic paths, the smaller nucleus

k Ast. Nach., vol. lii, no. 1248. m See p. 78 (post}.

April 14, 1860. n These types will be described in

1 Bone, Month. Not., vol. xlii, p. 105, a subsequent chapter. See p. 34

Jan., 1882 ; Gould, Nature, vol. xxiv, -(jposf).
p. 342, Aug. 11, 1881.

II. Physical Description of Comets. 17

pursuing a hyperbola of greater eccentricity than that affected
by the larger nucleus. In the memoir from which the fore-
going facts are gathered, Bredichin argues that parabolic
orbits may be converted into elliptical ones not only by
planetary perturbations, but by the action of the sun causing
disruption of nuclei, some portions of which will be driven
into elliptical orbits whilst others fall into hyperbolic orbits.0

Supposing a comet to become split up into 2 or more
portions, it is conceivable that each might travel round the
Sun in an orbit of its own, with an independent period of
revolution, and become in all senses an independent body.
Undoubtedly there would be a family resemblance between
the orbits as regards size, shape, and position relatively to the
Sun, and the term i; a family of comets " has come into use in
this connection.1* This certainly has often led astronomers
engaged in computing orbits to draw (or jump at) conclusions
of identity. It cannot be said that any case yet put forward
of a broken-up comet has yielded satisfactory evidence of the
identity of any parts of such a comet ; but a German astronomer,
Berberich, some 15 years ago, offered some suggestions on this
subject which I give for what they are worth. Speculation
on the subject has been rife since 1770, when Lexell's Comet
was discovered, and found, as was supposed, to have a period of
only 5^ years. It was therefore expected that, allowing for
planetary perturbations, it would be seen again in 1779, but it
was not seen, and never has been seen since, though not a few
comets which have been visible during the last 140 years
have been suggested to be identical with Lexell's.

The German astronomer just named is responsible for the
assertion that the great Comet of September 1882 (iii.), was
divided into 4 parts, each of which became a comet revolving
round the Sun ; the respective periods being 670, 770, 880,
and 960 years. He went on to suggest that the Comets of
1668, 1689, 1835 (sic), 1880 (i.), and 1887 (i.) had a similar

0 Bulletin de IJAcad. des Sciences de in connection with groups of comets

St. Petersburg, 5th series, vol. xiv, associated with planets, to be treated

p. 183. May 1901. of in Chap. IV (p. 41, post).

p But this expression is also used

18

The Story of the Comets.

CHAP.

common origin in some giant comet, centuries previously.
The comet discovered by Coggia and Winnecke, in November
1873, as it has an orbit resembling Biela's, may have sprung
from a common stock, whilst its orbit is very similar to that
of 1818 (i.). Similar relationships may be traced between
Barnard's Comet of 1884 (ii.), Wolf's Comet of 1884 (iii.),
Wolf's Comet of 1875,i and Coggia's Comet of 1874 (iii.);
also between the comets of 1807, 1880 (v.), 1881 (iii.), 1888 (i.),
1889 (iv.), and 1892 (i.). The periods of the first 5 range
from 1700 years to 5130 years. The period of the last
named is 20,200 years, its greater length being due to the
influence of Saturn. I give all these details on the authority
of Berberich, but do not hold myself responsible for them.

A less ambitious and more justifiable scheme of grouping
than any of those just mentioned is that which puts together
the comets (all of them " great " ones) of 1668, 1843 (i.), 1 880 (i.),
1882 (iii.), and 1887 (i.). The members of this group all have
orbits remarkable for their small perihelion distances, and
also have elements almost identical, yet they cannot possibly
be different appearances of one and the same comet. Their
elements are : —

1668

1843 (i.)

1880(i.)

1882 (iii.)

1887 (i.)

0

0

0

0

0

7T =

277

278

278

276

274

a =

357

1

356

346

337

i =

35

35

36

37

43

q =

0-004

0.005

0-005

0-008

0-005

Motion =

Retrograde

Retrograde

Retrograde

Retrograde

Retrograde

€ =

1.0

0-9998

0.9994

0-9964

1.0

What these figures mean is this : that we have been visited
by 5 comets pursuing nearly the same orbits, and following
one another round the Sun at varying intervals as if they

q Sic in orig. in Sinus, vol. xxi
(N.S.), p. 153. July 1893. This
" 1875 " is misprinted as " 1885 " in
Journ. B.A.A., vol. iii, p. 460, July

1893, but both dates are wrong ; Wolf
had no comet in either year, and
I have been unable to unravel the
mystery of the mistake.

II. Physical Description of Comets. 19

had at some time formed one body, or had come from the same
source of origin. It is conceivable that the 1843 Comet
might be identical with the 1668 Comet, but the 1880 and
1882 Comets can by no possibility be either identical with one
another or identical with either of the 2 earlier ones, for all
the computers who investigated the orbit of the 1882 comet
assigned to it periods varying from 600 to 900 years.1

These comets are not only kindred in regard to their orbits
but physically very much alike as regards size and brilliancy.
Moreover they came to the Sun from the direction of the star
Sirius (aCanis Majoris), that is, from the direction/rom which
the Sun is moving with respect to the stars, and escaped
notice in the Northern Hemisphere until near perihelion;
and passed nearly half-way round the Sun in a few hours at
very short absolute distances from the Sun.

On the point of jumping at conclusions as to the identification
of comets, Young has remarked that caution must be observed,
for : — " Even if the result of this investigation appears to
show that the comets are probably identical, we are not yet
absolutely safe in the conclusion, for we have what are known
as 'cometary groups'. These are groups of comets which
pursue nearly the same orbits, following along one after the
other at a greater or smaller interval, as if .they had once
been united, or had come from some common source. The
existence of such groups was first pointed out by Hoek of
Utrecht in 1865. The most remarkable group of this sort is
the one composed of the great comets of 1668, 1843, 1880, and
1882; and there is some reason to suspect that the little
comet visible on the picture of the Corona of the Egyptian
Eclipse [of 1882]8 also belongs to it. The bodies of this
group have orbits very peculiar in their extremely small peri-
helion distance (they actually go within ^ a million miles of
the Sun's surface), and yet, although their elements are almost
identical they cannot possibly all be different appearances of

r For more on this subject, see der Cometen, 1843, &c. [no. 1. of "Ab-

Journal, B.A.A., vol. xi, p. 248, April handlungen . . . zu den Astrono-

1901, quoting from a memoir by mischen Nachrichten ". Kiel. 1901.]
Kreutz, Untersuchungen ilber das System s See p. 227 (posf).

20 The Story of the Comets. CHAP.

one and the same comet. So far as regards the Comets of
1668 and 1843, considered alone, there is nothing absolutely
forbidding the idea of their identity : Perturbations might
account for the differences between their 2 orbits. But the
comets of 1880 and 1882 cannot possibly be one and the same ;
they were both observed for a considerable time and accurately,
and the observations of both are absolutely inconsistent with
a period of 2 years, or anything like it. In fact for the
Comet of 1882 all of the different computers found periods
ranging between 600 and 900 years." *

Hoek has suggested a considerable number of other comet
groups besides those already named.u

The immense mass of material ejected from the heads of
comets and added to the tails has suggested that comets in
time must perish from the exhaustion of their material. The
idea seems startling, but it cannot be said to be primd facie un-
sound, and there certainly are facts to support it. Miss Clerke's
reflections on this subject are to the point : — " Kepler's remark
that comets are consumed by their own emissions, has un-
doubtedly a measure of truth in it. The substance ejected
into the tail must, in overwhelmingly large proportion, be for
ever lost to the central mass from which it issues. True, it is
of a , nature inconceivably tenuous; but unrepaired waste,
however small in amount, cannot be persisted in with im-
punity. The incitement to such self spoliation proceeds from
the Sun ; it accordingly progresses more rapidly the more
numerous are the returns to the Solar vicinity. Comets of
short period may thus be expected to ivear out quickly." x

In the light of all that has been said on the subject in these
pages and elsewhere, can any summary statement be made in
answer to the question, "' What are comets made of ? "

I give, under great reserve, the answer : that probably the
heads are a mixture of solid and gaseous matter, and that

1 C. A. Young, General Astronomy, vol. xviii, p. 129. March 1868.

p. 434. x A. M. Clerke, Hist. ofAst,, 4th ed.,

u See his papers in Month. Not. p. 91. Kepler's account will be found

R.A.S., vol. xxv, p. 243, June 1865 ; in De Cometis., Op. vol. vii, p. 110.
J6., vol. xxvi, p. 1, Nov. 1865 ; Ib.,

II. Physical Description of Comets. 21

the tails are gaseous, the gaseous matter in the tails being the
result of the volatilisation of the solid matter of the heads or
of some of it. The connection between Comets and Meteors
(to be unfolded in a later chapter) seems to imply the presence
in comets of solid matter; and the spectroscope shows that
gases also are a constituent of many, or of all, comets. To
say what is the size of the solid particles is impossible : paving
stones, brick-bats, and grains of sand have in turn been
suggested by people fond of speculation.

CHAPTER III.
THE TAILS OF COMETS.

Tails usually a prolongation of the Radius Vector. — Occasionally the tail faces
the Sun. — Then called a " beard". — Comets with several tails. — The Comet
of 1825. — The Comet of 1744 with 6 tails.— Curvature of Tails. — Repulsive
Action of the Sun on Tails of Comets. — Changes of Direction of Tails. —
Tails probably hollow cones or hollow cylinders. — Vibration of Tails. —
Jets of Light in the heads of Comets. — Formation of Envelopes. — Fans of
Light. — Abnormal Changes in the Tails of certain recent Comets. — Swift\i
Comet of 1892 (i.). — Brooks's Comet of 1893 (iv.). — Observations by
Barnard. — Morehouse's Comet of 1908 (iii.). — Speculations as to the
formation of Tails. — Bredichins classification of Tails. — (1) Long straight
Rays. — (2) Curved plume-like Trains. — (3) Short, stubby, and sharply
curved brushes of light. — What is the material of which Tails are made? —
Speculation on the subject not very profitable. — Electricity and Light-
pressure probably co-operating influences. — Summary by Maunder.

SOME of the more usual and prominent features connected
with the tails of comets from the standpoint of recorded facts
will now be dealt with, leaving more or less on one side the
vast mass of theory and speculation which surrounds the
subject.

It was observed by Peter Apian that the trains of 5 comets
seen by him between the years 1531 and 1539 were turned
from the Sun, forming more or less a prolongation of the
radius vector, which is the name given to an imaginary line
joining the centre of the Sun and the centre of the head of a
comet.* This may be regarded as a general rule, although
exceptions do occur. Thus the tail of the Comet of 1577
deviated 21° from the line of the radius vector. Valz stated
that the tails of the Comets of 1863 (iv. and v.) deviated from
the planes of the orbits, and that only 2 other comets are
known the tails of which did the same. In some few
instances, where a comet has had more than one tail, the second

a Comptes Eendus, vol. Iviii, p. 853. 1864.

CHAP. III. The Tails of Comets. 23

tail has extended more or less toivards the Sun. Such a tail
has been sometimes spoken of as a <: beard ". Amongst the
recent comets which have had such an appendage may be
mentioned those of 1823, 1848 (ii.), 1851 (iv.), 1877 (ii.), and
1880 (vii.).

Although the credit of noticing that the tails of comets are
usually turned away from the Sun is ascribed to P. Apian,
the researches of E. Biot shows that this fact was noted by
the Chinese long before the time of Apian, to wit, in the year
837 A.D., when a brilliant comet was visible.b

Although comets usually have but one tail, 2 are not
uncommon, whilst even that number is often increased by the
presence of slender streamers, which are virtually independent
tails. The great Comet of 1825 seen by Dunlop in Australia
had 5 tails, and that of 1744 had as many as 6. This last
statement depending as it did, for a long time, on the uncon-
firmed testimony of a Swiss astronomer named De Che'seaux,
used not to be believed, but there is now no doubt as to its
authenticity.0 The 3rd Comet of 1903 (Borelly's) was photo-
graphed at Greenwich showing 9 tails, all told, but they
required some looking for.d It seems certain now that photo-
graphy often reveals tails of which telescopes and naked eyes
take no account.

When a comet has 2 tails it may happen that both are of
about the same size and length ; or that the second tail is not
so much to be regarded as a second independent tail as a little
offshoot of one main tail. In this case the secondary tail is
usually less bright and much shorter than the main tail. For
instance, Pons's long-period Comet of 1812 at its reappear-
ance in 1886 had on December 29 a principal tail 8° long and
a secondary one very faint and only 3° long ; but the secon-
dary tail is not always the shorter of the 2. Swift noted the
secondary tail of the Comet of 1881 (ii.) to have been 55° long
— the longest secondary tail on record.8

b Comptes Rendus, vol. xvi, p. 751. 84. December 1903.
1843. e Work of the Warner Observatory,

c See Chap. X. (p. 127, post}. vol. i, p. 22.
d Month. Not. R.A.S., vol. Ixiv, p.

24 The Story of the Comets. CHAP.

Curvature of the tail is a very common feature, especially
ID the case of large naked-eye comets. Sometimes the appear-
ance is that of a tail originally straight, which has become
bent into the form of a cavalry sabre ; at others the bending
is accompanied by a lateral swelling out at the extremity, after
the fashion of a Turkish scymitar. The Comets of 1844 (iii.)
and Donati's Comet of 1858 are good examples of comets with
curved tails, whilst the great Comet of 1882 was a notable
example of a scymitar tail at one period of its visibility — but
of that comet more hereafter, for other reasons.

After a tailed comet has passed round the Sun at the epoch
of perihelion and starts on its way back into Space the tail
usually more or less precedes the head instead of following it.
This fact opens up a difficulty which can be stated more easily
than it can be solved. Whilst the doctrine of Gravitation
assuredly applies to comets which come within the reach of
the Sun and are thus drawn towards the Sun, yet even before
as well as after they have reached their least distance from
the Sun they mysteriously become subject to a repulsive
solar action of some sort which it is difficult to define or
explain, which has been truly said to have " no known
counterpart in any other observed fact of nature", and
weakens the theory of Gravitation.

The Comet of 1769 had a double curved tail thus -*•> accord-
ing to La Nux, who observed it at the Isle of Bourbon. The
great Comet of 1882 exhibited a striking and uncommon
form of tail, some account of which will be given in a later
chapter/

Fig. 10 illustrates the changes in the direction of the tail of
a comet as it comes up to the Sun, passes its perihelion, or
point of nearest approach to the Sun, and then goes away
from the Sun. It is intended to show that a tail which, when
the comet is still far oft' from the Sun, is straight becomes
curved as the comet's motion becomes more rapid. That as
the curvature of the orbit gets sharper so will the tail exhibit
itself as curved will be seen from inspection of the diagram to

f See Chap. X. (pcsf).

III.

The Tails of Comets.

25

be a natural result of things, independently of the question
what is the form of the tail, whether cylindrical, or flat, or
solid, or hollow.

As regards the actual formation of comet tails, probably in
all cases they are hollow, but whether hollow cones or hollow
cylinders depends on circumstances. In either case this
theory accords, as it naturally should do, with the observed
fact that single tails usually are divided in the middle by
a dark band, the brilliancy of the margins exceeding that of
the more central portions ; but it must be confessed that this
theory breaks down where the outer edges of a tail are fainter

Fig. 10.

DIAGRAM ILLUSTRATING CHANGES IN THE DIRECTIONS OF THE TAILS OF COMETS.

than the centre, which seems to have a luminous spine of light
running down it.g Where the tail increases in width towards
its extremity it is permissible to suppose that its general form
is that of a hollow cone ; where the width is fairly uniform
from end to end the tail may be regarded as a hollow
cylinder.

The trains of some great comets are said to have been seen
to vibrate in a manner somewhat similar to the Aurora
Borealis. The tails of the Comets of 1618 (ii.) and 1769 may
be cited as instances ; the observer in the latter case was

s The great Comet of 1874 (Coggia's) had at one time such a spine of light
running down it.

26 The Story of the Comets. CHAP.

Pingre, whose great knowledge of comets adds weight to his
testimony. The vibrations commenced at the head and
appeared to traverse the whole length of the comet in a few
seconds. It was long supposed that the cause was connected
with the physical nature of the comet itself; but Oilers
pointed out that such appearances could only be fairly attri-
buted to the effects of the Earth's atmosphere, and for this
reason : — " the various portions of the tail of a large comet
must often be situated at widely different distances from the
Earth ; so that it will frequently happen that the light would
require several minutes longer to reach us from the extremity
of the tail than from the end near the nucleus. Hence, if the
coruscations were caused by some electrical emanation from
the head of the comet, even if it occupied but one second in
passing over the whole surface, several minutes must neces-
sarily elapse before we could see it reach the tail. This is
contrary to observations,11 the pulsations being almost in-
stantaneous." Instances of this phenomenon are not very
common ; Coggia's Comet of 1874 is the most important
modern example. An English observer at Hereford named
With, well known for his astronomical mirrors, noticed an
" oscillatory motion of the fan-shaped jet upon the nucleus as
a centre, which occurred at intervals of from 3 to 8 seconds.
The fan seemed to ' tilt over ' from the preceding to the
following side, and then appeared sharply defined and fibrous
in structure ; then it became nebulous, and all appearance of
structure vanished." * A flickering of the tail of this comet
was observed by Newall.

The mention of the word "jet " in the preceding quotation
suggests the necessity of something more being said, based on
this word. Without being able exactly to dogmatise on the
subject, it seems certain that not a few of the larger comets
which have been subjected to telescopic scrutiny during the
last half-century have exhibited changes which can only be
compared to the appearance of a jet of water rising from the
nozzle of a fountain and rising higher and higher, until at last

h Mem. Acad. des Sciences, 1775. p. ' Ast. Keg., vol. xiv, p. 13. Jan.

302. 1876.

Figs. 11-16.

Plate III.

June 26.

June 30.

June 28.

July 1.

p. 26.

July 6. July

THE COMET: (186O, iii.);
(Drawn by Cappelletti and Rosa.)

III. The Talk of Comets. 27

gravity overcomes the pressure upwards of the water and the
water begins to curl over, umbrella fashion, and to fall to
the ground.

Several modern comets exhibited what may be termed jet
features. The accompanying illustrations [Plate III, Figs.
11-16] bring out this idea without the necessity of any
verbal description.

Closely akin to the jets of light just alluded to are the
" envelopes " of which observers of large comets nearly always
make mention. The best idea of what these envelopes are,
and of the way in which they are given off, is to be had by
comparing the nucleus of a comet to the core of an onion, and
the successive envelopes of the comet to the successive skins
of the onion as they come off, one by one. The existence and
developement of these envelopes will usually become known
and proceed somewhat in the following manner. If the
comet, already possessing a bright nucleus, is approaching the
Sun (and the Earth) and day by day becomes brighter, there
will sooner or later be noticed something in the form of an
arc or a semi-circle of light half encompassing the nucleus on
the side away from the Sun. This arc of light (the outline
of which will be not truly semi-circular but parabolic) will
gradually stretch out and become the commencement of a tail,
or if a tail already exists will become lost in it. Other arcs
of light will one by one manifest themselves and spread as
the first one did, so that eventually there may be half a dozen
or more of these envelopes, concentric with the first, and
remaining with a certain amount of permanency grouped
around the nucleus. It will sometimes be seen that the
innermost arc is linked with the nucleus by one or more
bridges, as they may be called (often fan-shaped), the inner-
most end of the bridge joining on to and forming part of the
nucleus, whilst the outermost extremity is lost in the nearest
arc which forms a temporary boundary to it. It must
be pointed out that the arcs and fans spoken of are not
truly such, but only appear to be such by the unavoidable
effect of perspective. The true form of an arc under such
circumstances is what is called a " paraboloid of revolution "

28 The Story of the Comets. CHAP.

surrounding the nucleus on all sides except that turned from
the Sun. Accordingly, nothing within the easy reach of an
ordinary reader will bring the actual condition of things more
clearly home to him than the simile of the onion, supple-
mented, as it may be, by a personal inspection of a simple jet
of water rising straight up from the nozzle of a fountain, and
presenting, when looked at from a near position, the outline
of a curvilinear bell tent.

The formation of envelopes in the head of a comet, when
such show themselves, will be easily understood by an attentive
consideration of Fig. 17, the idea of which is due to Newcomb
and Holden.k

The diagram is intended to represent four successive stages

Fig. 17.

IDEAL DIAGRAM OF THE FORMATION AND DEVELOPEMENT OF "ENVELOPES"
IN THE HEAD OF A COMET.

m the developement of the envelopes. The Sun is supposed
to be above the diagram, and the tail below. When the
appearance is as a, the cometary matter, whatever it may be,
has just begun to start rising upon the nucleus. In b it has
risen higher, and spread on each side wider. In c it has
spread still further, and may be regarded as distinctly moving
away from the nucleus but encompassing it on 2 sides though
at a distance. Finally in d the movement and developement
has proceeded so far, that the uppermost portions of the
cometary matter has become so attenuated as often to have
almost disappeared, the larger portion of the envelope having,

k Astronomy for Schools and Colleges, 4th Ed., p. 391.

III. The Tails of Comets. 29

in a sense, lost its individuality and become merged in the
tail. Before the stage c is reached, it will often happen that
a second envelope will have begun to rise as at a, so that two
or even three envelopes, more or less concentric, may be
visible at the same time, one inside another.

If, with the foregoing description clearly in his mind of the
envelopes usually seen in the heads of large comets, the reader
will turn to Chapter IX (post), and will examine the illus-
trations there given of the heads of the Comets of 1858 (vi.),
1861 (ii.), 1862 (iii.), and 1874 (iii.) in particular, he will have
no difficulty in realising the features which generally present
themselves in the heads of large comets ; and which from time
to time are described by different observers, under the varying
terms of "jet", "fan", "luminous sector", " envelope ", and
so on. Bessel considered that the changes which he observed
in the head of Halley's Comet in 1835 justified him in
assuming that a systematic oscillation of the head and nucleus
took place in the plane of the comet's orbit, almost amounting
to a movement of rotation.1

Three comets of recent date are noteworthy as having
undergone tail transformations quite without precedent,
though the credit of our knowledge respecting them is in
part due to the assistance of photography, which has furnished
records of changes more full and more accurate than eye
observation could have done.

The first of these comets is Swift's Comet of 1892 (i.). On
April 4, the tail was 20° long, bifid, straight, and slender.
Between the 2 branches scarcely any cometary matter was
visible. The next morning a new tail had appeared in the
interspace, and each of the 3 main tails was found to be made
up of several, side by side. At least a dozen distinct streaks
of cometary matter could be counted. After the lapse of
another day one of the original 3 tails had vanished and the
other 2 had become blended. Then one of these brightened
up and the other faded away. The bright one had a sharp

1 His observations and opinions will be found in the Connaissances des
Temps, 1840, "Additions," p. 79.

30 The Story of the Comets. CHAP.

bend in it, as if it had encountered and been turned aside by
some obstacle. Near the point of deflection there were 2 dark
spots in the brightest part of the tail. Finally the surviving
tail split up into 6 strips. All these changes, and some others,
took place in the space of 5 days.

Brooks's Comet of 1893 (iv.), discovered on Oct. 17, started
with a main tail which was straight whilst there was also
a secondary tail. A photograph taken on Oct. 21 revealed
extraordinary changes which Barnard thus describes : —

" It presented the comet's tail as no comet's tail was ever seen before.
The graceful symmetry was destroyed ; the tail was shattered. It was bent,
distorted, and deflected, while the larger part of it was broken up into knots
and masses of nebulosity, the whole appearance giving the idea of a torch
flickering and streaming irregularly in the wind. The short northern tail
was swept entirely away, and the comet itself was much brighter. The very
appearance at once suggested an explanation, which is probably the true one.
If the comet's tail, in its flight through space, had suddenly encountered
a resisting medium which had passed through the tail near the middle,
we should have precisely the appearance presented by the comet. It is
not necessary that the medium should be a solid body ; if it possessed
only the feeblest of ethereal lightness it would deflect, distort, and shatter
the tail. What makes this explanation all the more probable is that the
disturbance was produced from the side of the tail that was advancing
through space.'' m

Another recent comet which displayed extraordinary
changes in its tail was Morehouse's Comet of 1908 (iii.),
watched with great success by a numerous body of photo-
graphic-astronomers. Amongst other things some outbursts
in the nature of explosions seem to have occurred in the
tail. This comet is also noticeable from the fact that it
travelled from Pole to Pole during the period of its visibility ;
and having been circumpolar during many weeks in the
autumn of 1908, continuous observation for many consecu-
tive hours was possible, which much facilitated the photo-
graphing of it.

This comet was unique from the first. The art by which
it was discovered (photography) so faithfully followed its
every movement, from such variety of longitudes, that a more

m Popular Astronomy, vol. i, p. 146. Dec. 1893.

Figs. 18-19

Plale IV.

DIAGRAM.

TO ILLUSTRATE THE RECOGNITION OF A COMET AS
DISTINGUISHED FROM A NEBULA.

BROOKS'S COMET (1893, iv.). October 21,

p. 30.

III. The Tails of Comets. 31

perfectly continuous life history of a comet has never been
obtained. Moreover those who studied it were bounteously
rewarded by the number of unexpected transformations which
they saw.

The first of these transformations occurred from September
30 to October 2. On September 29 the tail showed no signs
of the coming catastrophe, being perfectly normal. During
the next 24 hours it presented unprecedented activities. Its
appearance changed continuously throughout the night of
September 30, these changes ending on October 1 in a com-
plete disruption. The photographs on the former date showed
a bright contracted coma joined to the tail by a narrow
tapering neck. Near the head the tail was strong, violently
twisted, and cyclonic in form. At about 1° from the head it
spread into a broad fan-shaped mass which was very irregular
on the s%> side, and extended for 8° as a bright curved
projection on the nf. October 1 will be memorable as the
date on which the comet lost its tail ; and it disappeared to
all but the photographic eye. The great masses which had
formed the tail on the previous night were now seen some
2° out from the coma and attached to it by slender streamers.
The nucleus was the same as on the former plate. It was the
tail that was gone. Photographs of October 2 show 3 distinct
tails ; one broad and fan-shaped, and two smaller ones. They
were all faint and changing slowly.

The second great disturbance began on October 15. This
was wholly different from the one just described. The plate
of October 14 showed a tail at least 7° long with distinct
lines running through it longitudinally. It was bright, with
marked irregularities near the head. The 12 hours that
followed recorded extraordinary changes. The comet had
broken in two. The photographs taken in the United States
show two great condensations in the tail about -|° from the
head. A bright, short, spike-like projection, with one end
between the two masses and the broad end attached to the
coma, formed the new tail. The old tail was very faint,
irregular in outline, and curved on its sp side. Photographs
taken at the observatory of Geneva by Pidoux at 7h 35m

32 The Story of the Comets. CHAP.

T.M.E.C. and at Juvisy by Quenisset at 8h 55m T. M. E. C.
show great bends (the latter one the stronger) in the tail at
about the place where the condensations appear. It therefore
seems that these masses were not thrown out by the comet's
head, but caused by a localisation of the particles in the tail
due to some encountered force. On the plate of October 16
these masses can still be seen about 1|° from the head and
connected with the newly-formed tail by slender threads of
light.

About the middle of November a third distinctive feature
developed. The comet was now characterised by long slender
rays extending at measurable angles to the tail, and by
undulations in the body of the tail itself. This appearance is
most striking in the photograph of November 15 where
slender streamers shoot out from the main body of the tail
with tremendous velocity. The two on the s p side have very
interesting structures. They are made up of still finer rays
which cross each other alternately, and at the end make a bend
in the direction of the comet's motion and then return to their
original direction. At about 5° from the head the tail makes
an abrupt turn toward the N. as if it had encountered
a resisting medium. It is strongly convoluted on the nf side
and full of detail through its whole length. On the following
night, November 16, the entire aspect had changed. The coma
was much stronger both visually and photographically. The
tail showed marked signs of pulsations. On November 18
the comet was a beautiful object. The slender straight rays
were predominant. The tail was broken into waves and a
conspicuous dark streak extended along its N. side for some
distance from the head.

On November 19, the head was seen to give off straight jets
at small angles. The tail for a short way back was composed
of individual strands which intertwined like the strands of
a rope, whilst near the end they separated into broad ribbon-
like bands.

It repeatedly lost its tail and formed new ones. Instead of
submissively settling down to one of the three established
types of comet tails, it took on a variety of types in one

Fig. 20.

Plate V.

MOREHOUSE'S COMET (19O8, Mi.). October 15.
(Photographed by P. Morris.}

p. 320.

Ftg. 21.

Plate VI.

MOREHOUSE'S COMET (19O8, iii.). October 3O.

(Photographer! by P. Morris.")

f 32 1>.

Figs. 22-23.

Plate VII.

. xxx ^

X V

September 30, 17h 16m G.M.T.

October 1, 19h 43m G.M.T.

MOREHOUSE'S COMET (19O8, iii.).

(Photographed at the Yerkes Observatory.}

P. 32 c.

Figs. 24-25.

Plate VIII.

October 15, Hh 31m G.M.T.

November 15, 12h 6m G.M.T.

MOREHOUSE'S COMET (19O8, Mi.).

(Photographed at the Yerkes Observatory.)

III. The Tails of Comets. 33

day. Condensations, waves, straight rays, twisted funnels,
and numerous unrecognised forms made up its wonderfully
active tail.

Not only was it exceptional in its actions, but also in
its constituent material. Its spectrum was quite different
from previous comets. In place of the familiar hydrogen gas
was found the poisonous cyanogen element. Other ingredients
not recognised seem to have been present. Altogether it gave
to astronomers a wealth of data which it will require years
to digest and interpret properly.11

The literature of comets' tails may be likened to the literature
of Free Trade and Tariff Eeform in the world of Politics : it
is superabundant and more than superabundant. In the
pages which have gone before I have somewhat exhaustively
described these tails from the standpoint of the mere star-
gazer, armed, or not, as the case may be, with a telescope.
It remains now to consider, and I shall do so very briefly,
some of the more definite conclusions which have been
arrived at as to the theory of tails; by which is meant
the dynamical circumstances under which they are usually
evolved. Speculation ° as to this has proceeded of late years
on a gigantic scale, and vast quantities of ink and paper
have been (as I think fruitlessly) expended on the subject,
the details of which would not have much interest for the
general reader.

It is to a Russian astronomer, Bredichin,p that we owe
what seems the most thoughtful and best classification of
comets' tails ; and his conclusions are the more valuable that
they do not run into extravagances of speculation. Briefly
stated, he divides the tails of comets into 3 classes or
types :—

n The foregoing account of More- p This gentleman's name is fre-

house's comet is mainly founded on quently spelt Bredikhine, I suppose

information kindly supplied to me in consequence of the difficulty of

in MS. by Morehouse himself for the transliterating Kussian spelling into

purposes of this volume. Eoman spelling, but the spelling in the

0 A sort of index to some of this text was his own way of rendering his

will be found in Month. Not. R.A.S., name when writing in Roman charac-

vol. Ixiv, p. 347. Feb. 1904. ters, and in the French language.
CHAMBERS D

The Story of the Comets.

CHAP.

(1.) Long straight rays.

(2.) Curved plume-like trains.

(3.) Short, stubby, and sharply curved brushes of light.

Tails which belong to Bredichin's first type are formed of
matter upon which the Sun's repulsive action is supposed to

Fig. 26.

BREDICHIN S THREE TYPES OF COMET TAILS.

be 12 or more times greater than the attractive action due to
Gravitation ; so that the particles quit the head of the comet
with a relative velocity which is gradually increased as they
recede, until it becomes enormous. The straight rays noticed

III. The Tails of Comets. 35

in many of the engravings of the tail of Donati's Comet of
1858 are streamers of this type, composed, according to
Bredichin, of hydrogen.

Tails of the second type are by far the most common, and
in them the repulsive force is much less than in the first type,
and is least of all at the inner edge of the tails of this type.
It may be supposed that such tails are composed of some
hydro- carbon gas.

Tails of the third type, examples of which are not numerous,
owe their short stubby form to the twin facts that the repul-
sive force to which they are due is only a fraction of Gravita-
tion ; and that they are composed of something much heavier
than is the case with the other kinds of tails, namely, the
vapour of iron, with possibly an admixture of the vapours
of other substances, especially sodium.

Thus far we have been considering the tails of comets
looked at as regards their whole length, and the consequent
outlines which they exhibit, but something must be said as
to where the material of the tail comes from, and how it is
evolved. Here again, whilst we can see many interesting
transformations going on there is still the difficulty to be
faced of what is the material and whence come the boundless
supplies which mark the career of all the large and brilliant
comets which we sometimes see and can always read about.

Of course the obvious and necessary answer is that this
material is ejected from the nucleus, a fact which will be fully
realized by the most cursory inspection, say for instance, of
Plate III (ante), but no clue is afforded us as to what the
material is, and speculation, it is admitted, is futile.

Speculation has been indulged in by many astronomers as
to what becomes of the matter ejected from the heads of
comets which after forming for a while part of the tail goes
off into Space. Is it simply dispersed in Space, or what
happens ?

The generally accepted idea is that the fragments of a comet
thus sent adrift are first of all dispersed hither and thither
through Space, where if a planet falls in with them it annexes
them, and they become, shall we say, " shooting stars " to that

D2

36 The Story of the Comets. CHAP.

planet, be it the Earth or some other planet ; and help in
an infinitesimal degree to feed that planet with new material
from an external source of supply.

It must be confessed that progress in the collection of facts
up to this point has done little or nothing to settle the
questions, " Why should any comet have a tail 1 " and " What
is the nature of the Solar or other influence which causes
tails ? " Many have been the sober, and still more the
ridiculous, suggestions which have been put forth on this
subject, but it may safely be said, following Olbers, Bessel, and
Sir J. Herschel, that electricity, operating in some unknown
and indefinite way, is the primary agent in setting on foot all
cometary tails, but as to why and how, there is no agreement
amongst astronomers.

As an alternative to, or rather, a co-operating force with,
electricity much support has been accorded to the idea that
" Light-Pressure " is now and again (or always) to some
extent concerned in the repulsive action of the Sun on the tails
of comets. The subject of Light-Pressure is one which belongs
rather to the domain of Physics than of Astronomy. I will
therefore only say that it is supposed that all sources of light
exercise a certain amount of repulsion, or push, on all material
substances which face the source of light, whatever may be
the material, or whatever the source of the light.

Maunder has summarised the questions both of the heads
and of the tails of comets in a way which seems to represent
all that we really know. He says : —

" Though the bulk of comets is huge, they contain extraordinarily little
substance. Their heads must contain some solid matter, but it is probably
in the form of a loose aggregation of stones enveloped in vaporous material.
There is some reason to suppose that comets are apt to shed some of these
stones as they travel along their paths, for the orbits of the meteors that
cause some of our greatest ' star showers ' are coincident with the paths of
comets that have been observed. But it is not only by shedding its loose
stones that a comet diminishes its bulk ; it loses also through its tail. As
the comet gets close to the Sun its head becomes heated, and throws off con-
centric envelopes, much of which consists of matter in an extremely fine
state of division. Now it has been shown that the radiations of the Sun
have the power of repelling matter, whilst the Sun itself attracts by its
gravitational force. But there is a difference in the action of the 2 forces.
The light-pressure varies with the surface of the particle upon which it is

III. The Tails of Comets. 37

exercised : the gravitational attraction varies with the mass or volume. If
we consider the behaviour of very small particles, it follows that the attrac-
tion due to gravitation (depending on the volume of the particle) will
diminish more rapidly than the repulsion due to light-pressure (depending
on the surface of the particle) as we decrease continually the size of the
particle, since its volume diminishes more rapidly than its surface. A limit
therefore will be reached below which the repulsion will become greater than
the attraction. Thus for particles less than the TC&VT part of an inch in
diameter the repulsion of the Sun is greater than its attraction. Particles in
the outer envelope of the comot below this size will be driven away in a con-
tinuous stream, and will form that thin, luminous fog which we see as the
comet's tail."q

The latest idea in tails is due to Barnard, who has suggested
that there is evidence to show that the same causes (on the
Sun ?) which give rise to (?) auroral displays have some influ-
ence over the changes in the tails of Comets. He speaks of
there being " some kind of disturbing medium in Space which
can shatter and distort a tail when encountered by it." r

q E. W. Maunder, The Astronomy of r Astrophysical Journal, vol. xxix.
the Bible, p. 105. p. 70, Jan. 1909.

CHAPTER IV.
THE MOVEMENTS OF COMETS.

Periodical Comets. — Non-periodical Comets. — The density of Comets. — The
Masses of Comets. — Lexell's Comet. — The risk of collision of Comets with
the Earth. — No real danger. — The Influence of Planets on Comets very
real. — Special Influence of Jupiter. — List of Comets affected by Jupiter. —
Comets that are said to be associated with Planets. — The Inquiries made
when a new Comet is discovered. — Old Astronomers puzzled by the move-
ments of Comets. — Sir I. Newton s investigations.

So far as their movements are concerned comets may be
divided into two classes : (1) those which may be regarded
as permanent members of the solar system ; and (2) those
which have once, and once only so far as is known, visited
the solar system. The comets belonging to Class 1 must be
further subdivided into two great sub-classes : (a) those which
have been ascertained by calculation and observation to be
regular visitors to the neighbourhood of the Earth, and there-
fore of course permanently attached to the Sun ; and (6) comets
which are believed, so far as calculation goes, to belong to the
solar system, but which as yet have only been once seen by us
on the Earth. Later on we shall find it expedient to classify
in more detail both types of comet, but these broad general
divisions will suffice for the present.

The comets which have just been alluded to as permanent
members of the solar system are called " Periodical Comets ",
but their periods vary between the extremes of 3 or 4 years
and thousands of years. Comets with periods between 3 years
and about 80 years are numerous, and may be regarded as
familiar and well-recognised friends, but those whose periods
run into hundreds or thousands* of years are those which
astronomers have found reason to believe are periodic but

a Scheller found the period of the years ! ! ! Ast. Nach., vol. clvii, No. 3763.
Comet of 1845 (ii.) to be 115,000 Jan. 18, 1902.

CHAP. IV. The Movements of Comets. 39

as to which they can do no more than prophesy that they will
return to our parts of Space some day. These different
circumstances bring it about that comets vary greatly in the
distances to which they recede from the Sun. Whilst the
orbit of the Comet known as Encke's is contained within
the orbit of Jupiter, the orbit of Halley's Comet stretches
out beyond that of Neptune, whilst many other comets recede
to far greater distances than this. A comet can only come
back to the Sun after having appeared and then disappeared,
provided it moves in an elliptic orbit. The chance visitors
spoken of in a previous paragraph pursue curved paths known
as " parabolas " or " hyperbolas " ; but the further considera-
tion of these details is reserved for a later chapter.

The density and also the mass of comets is exceedingly
small, and their tails consist of matter of such extreme tenuity
that even small stars are visible through them, a fact first
recorded by Seneca. That the matter of comets, whatever it
may be, is exceedingly rare is sufficiently proved by the fact
that instances are on record of comets having passed very
near to some of the planets without disturbing in any appre-
ciable degree the motions of the said planets. For instance,
the Comet of 1770 (Lexell's) in its approach towards the Sun
enveloped the satellites of Jupiter, and remained near them
for 4 months without affecting them as far as we know.
From this fact it can be shown that the mass of this comet
could not have been so much as -^QQ-Q that of the Earth. This
comet came very near to the Earth on July 1, 1770: its
distance at 5h on that day being about 1| millions of miles.
Had its matter been equal in quantity to that of the Earth
its attractive force would have caused the Earth to move in
an orbit so much larger than it does at present that the length
of the year would have been increased by 2h 47 m, yet no
sensible change took place.

The idea of any danger happening to our planet, or to any
other planet, from the advent of any of these wandering
strangers, may be dismissed once and for all, especially as we
now know that the Earth passed bodily through the tail of
the great Comet of 1861, on June 30 of that year.

40

The Story of the Comets.

CHAP.

As regards the influence of comets on planets, instead of
comets exercising any influence on the motions of planets
there is most conclusive evidence that the converse is the
case — that planets disturb the movements of comets. This
fact is strikingly exemplified in the history of the Comet
of 1770 just mentioned. After its discovery it was found

270

DIAGRAM ILLUSTRATING THE INFLUENCE OF JUPITER ON COMETS.

to be moving in an elliptical orbit requiring for a com-
plete revolution only 5| years; yet though this comet was
a large and bright one it had never been observed before, and
it is doubtful whether it has ever been seen since, the reason
being that the Planet Jupiter completely changed the char-
acter of its path, probably by enlarging it.

IV. The Movements of Comets. 41

Although suggestions have been thrown out that several
short-period comets discovered during recent years might
possibly be returns of Lexell's Comet, yet the evidence is
inadequate and unsatisfactory. Arago has a remark on this
subject which deserves quotation. He says : — " Du Sejour
has proved that a comet whose mass is equal to that of the
Earth which would pass at a distance of 37,500 miles only,
would extend the length of the year to 367 d 16h 5m and could
alter the obliquity of the ecliptic to the extent of 2°. Not-
withstanding its enormous mass and the smallness of its

o

distance, such a body would then produce upon our globe only
one kind of revolution — that of the Calendar V

The influence of the larger planets on comets is now so
thoroughly recognised that it has become customary to speak
of such planets having " families " of comets belonging to
them.

The influence of Jupiter on certain periodical comets which
constitute its " family " may be inferred from Fig. 2^, without
the necessity of any detailed statement. Many other comets
besides those included in the engraving may be regarded as
subject to Jupiter's influence.0 The following are the names
of some of these arranged in the order of their aphelion
distances, but the list is by no means complete, because it
is limited to comets which have been observed more than once,
whilst there are a number of comets which are believed to be
Jupiter comets, but which have only at present been seen once.
A full list of these will be found elsewhere.*1

b Arago, Pop. Ast., vol. i, p. 642, Astronomy and Astro-Physics, vol. xii,

Eng. Ed. p. 800. Nov. 1893.

c A large scale Plan of all the d Seep. 80 (post}. Perhaps not all of

Jupiter comets up to date appears in those there given are Jovian comets.

The Story of the Comets.

CHAP.

Name.

Mean Distance from
the Sun in Radii of
Earth's orbit.

Encke's

4-09

Tempel's Second (1873, ii.)
Tempel's First (1867, ii.)

4-76
4-89

JUPITER

4-9 to 5-5

Tempel-Swift (1869, iii., 1880, v.)
Winnecke's ...

5.17
5-58

Wolf's

5.60

Brorsen's

5-61

D' Arrest's

5.77

Faye's ...

5-97

Finlay's (1886, vii.)

6.06

Biela's

6.16

It has been pointed out by W. W. Payne that there is
a manifest tendency with the Jupiter comets for their peri-
helions to gather towards one particular region lying in the
general direction of the vernal equinox. Jupiter's absolute
motion in the region of the opposite, or autumnal equinox,
must approximately equal his mean motion plus that of the
" Sun's Way " (so-called). " Jupiter therefore would overtake
or meet more comets in that part of its orbit than in others,
and so the possibility of disturbing influence in that region
would be greater than elsewhere." e

It may be remarked that great as is the attractive power of
Jupiter in drawing comets into its own sphere of influence it
does not follow that a comet moving in a parabolic orbit can
be captured at one effort of disturbance. Thus, Brooks's
Comet of 1889 (v.), now moving in an orbit of 7 years, had up
to 1886 an orbit requiring 27 years for its journey round
the Sun.

The idea that certain comets are associated with particular
planets, or perhaps as a better way of putting it, that certain
planets have certain comets in groups attached to them, is
a somewhat modern one, started by Laplace, who put forth the

e Astronomy and Astro-Physics, vol. xii, p. 800. Nov. 1893.

IV. The Movements of Comets. 43

surmise that such comets had been " captured " by the parti-
cular planets, and this theory has now met with general
acceptance. Flammarion, making use of the labours of some
who went before him, including especially an American named
Kirkwood, who was great at coincidences, has worked out the
idea in a way which* has yielded some results too curious and
interesting to be passed over. In addition to the Jupiter
group to which reference has been made above, he finds that
every major planet beyond Jupiter seems to have a group of
comets revolving in elliptic orbits attached to it ; and, more-
over, as there is a group of comets without a known planetary
leader, he makes bold to speculate that this fact is a proof
that a trans-Neptunian planet exists and will one day be
found. Since Flammarion published this scheme of his about
a quarter of a century ago, the last-named notion has been
vigorously taken up and pushed by Professor G. Forbes, but
he assigns to his planet a period of 1076 years f, — more
than three times the period assigned by Flammarion to his
hypothetical planet.

The following are Flammarion's groups, the figures ap-
pended representing in radii of the Earth's orbit the mean
distances of the respective planets and the aphelion distances
of the respective comets : —

2nd Group (Saturn's Family).

SATURN 9-0 to 10-1

Tuttle's Comet 10-5

3rd Group (Uranus's Family).

URANUS 18-8 to 20-1

Comet of 1866 (i.) ; and November Meteors ... ... 19-7

Comet of 1867 (i.) 19-3

4th Group (Neptune's Family).

NEPTUNE 29-8 to 30-3

Comet of 1852 (iv.) (Westphal) 29 to 32

Comet of 1812 (Pons) 33

Comet of 1846 (iv.) (Di Vico) 34

Comet of 1815 (Gibers) 34

Comet of 1847 (v.) (Brorsen) 35

Halley's Comet 35

f Month. Not, B.A.S., vol. Ixix, p. 160. Dec. 1908.

44 The Story of the Comets. CHAP.

5th Group (?).

Trans-Neptunian planet 47 to 48?

Comet of 1862 (iii.) ; and August Meteors ... 49

Comet of 1532 and 1661 48

Flammarion finally submits the speculation that the undis-
covered planet must, if it be related to the comets of the
5th group, revolve at somewhere about twice the distance of
Neptune, say, in a period of 300 years.g

Forbes's speculations do not in any way fit in with Flam-
marion's. Forbes gives his planet a mean distance of
100 radii of the Earth's orbit — more than double the distance
assigned by Flammarion. And his group of comets is not
constituted as Flammarion's is. They are 8 in number, viz. :
1556, 1840 (iv.), 1855 (i.), 1855 (ii.), 1861 (i.), 1843 (i.), 1880 (i.),
and 1882 (ii.), but Forbes treats the last 3 as fragments
resurrected of the Comet of 1556, which seems to have dis-
appeared : at any rate it did not return in 1848 as expected.11

To complete the information respecting families of comets,
it may be stated that the reason why the smaller planets near
the Sun, Mercury, Venus, the Earth, and Mars have no comets
under their control would seem to be that their masses (i.e.
their powers of attraction) are so much less than the masses
of the much larger distant planets ; and, moreover, because
comets coming up to the Sun are moving through our
neighbourhood at speeds much greater than they are endued
with when passing in the vicinity of the more distant planets,
and can therefore more easily run away out of reach of
enemies (e. g. planets).

When a comet is discovered the first questions asked about
it by the ordinary searcher after knowledge is, " When and
where can we see it ? " " How long will it last ? " and " Has it
got a tail 1 " — whilst the professional astronomer wants to
know, " What are its elements ? " The answers to be given
to the first two questions always depend upon the answer
which has been given to the last question. To the majority

g U Astronomie, vol. iii, p. 89. March French original.

1884. I have corrected several im- h Month. Not. R.A.S., vol. Ixix, p.

portant mistakes or misprints in the 159. Dec. 1908.

IV. The Movements of Comets. 45

of amateurs these elements are almost unintelligible ; and even
to advanced students they often convey only a vague idea of
the true form and position of the orbit. But all questions as
to orbits will be dealt with in a separate chapter.1

To the early astronomers the motions of comets caused great
embarrassment. Tycho Brahe thought that they moved in
circular orbits ; Kepler suggested that comets moved in right
lines. Though he was wrong as to this he was more correct
in concluding that they were further off than the Moon. He
formed this opinion by noting that the Comet of 1577 seemed
to occupy the same position amongst the stars whether viewed
from Uraniburg or from Prague, 400 miles distant. Hevelius
seems to have been the first to remark that cometary orbits
were much curved near perihelion, the concavity being towards
the Sun. He also threw out an idea as to the parabola being
the ordinary form of a comet's path, though it does not seem
to have occurred to him to assume that the Sun was likely to
be the focus of such a path. Borelli suggested the ellipse or
the parabola as likely curves to be pursued by a comet.
Sir William Lower was probably the first to hint that comets
sometimes moved in very eccentric ellipses; this he did in
a letter to his " especiall good friende Mr. Thomas Harry ot ",
dated Feb. 6, 1610. Dorfel, a native of Upper Saxony, was
the first practical man, for he came to the conclusion that the
Comet of 1680 moved in a parabolic orbit. Sir I. Newton
also gave his attention to the subject. Confirming Dorfel,
Sir Isaac showed further that the motion of that comet was in
accordance with the general theory of Gravitation.

1 See Chap. XI (post].

CHAPTER V.

THE DISCOVERY AND IDENTIFICATION
OF COMETS.a

Hoic Comets are discovered. — The great French Comet -hunter, Messier. — Much
Comet-hunting now carried on in America. — Suitable occupation for
amateur astronomers. — Designation of Comets. — Appropriation of observers
names to Comets. — Comets only identified by the elements of their orbits. —
Physical appearance of Comets no certain proof of identity. — Identity of
elements not always conclusive. — Possibility of more than one Comet follow-
ing'the same path. — Photography as an aid to the discovery of Comets. —
Ancient Chinese records of great value. — Medals for successful Comet-
hunters. — Telegraph codes for transmission of cometary announcements.

" How does a new comet become known ? '' " Who looks
out for comets 1 " " Who organises observations of comets ? "
These are questions which are often asked, and which are
seldom answered in set terms in the text-books ; and there-
fore it may be worth while to devote a short chapter to the
subject.

In early times and down to the invention of the telescope
and for quite a century and a half after that event, the
discovery of comets may be said to have been left to chance :
in other words they discovered themselves; that is to say,
manifested themselves to anybody who happened to be
looking at the heavens by night. It was not until 2 French
astronomers towards the close of the 18th century took up the
matter that any definite effort seems to have been made
systematically to watch for or to search for comets. Messier,
whose first comet dates from 1760, and Pons, whose first
comet dates from 1802, are the 2 Frenchmen here referred to,

a Some useful hints on the search well-known and useful American
for and observation of comets by Magazine, Popular Astronomy, vol. x,
Denning will be found in the p. 69. Feb. 1902.

V. The Discovery and Identification of Comets. 47

Fig. 28.

but Messier had a rival in Mechain who, between 1781 and
1799, discovered 8 comets.

Delambre has preserved the following anecdote of Messier
as related by La Harpe : — " Some years ago he lost his
wife : looking after her hindered him from seeing a comet
for which he was on the watch, and of which Montaigne of
Limoges had pilfered him. He was in despair. After a while
some one spoke to him of the loss he had sustained ; he
replied, still thinking of his comet : ' Alas, I have found 12
comets and Montaigne has robbed me of my 13th !' Thereupon
tears filled his eyes : then remembering that it was for his wife
that he ought to weep, he set
to work to do so, saying, ' Ah !
Poor woman,' but it was really
for the comet that he was
weeping." b

After the beginning of the
19th century comet-hunting
went out of fashion until
about 1880, from which time
onwards till the present year
several American observers
have worked most industri-
ously and successfully in this
field. Accordingly in the
catalogues of comets dis-
covered during the last 30

years the names of Brooks, Barnard, Perrine and Swift
recur with monotonous frequency, and these 4 astronomers
have distanced all their rivals in the world ; even the
Germans, who have done a great deal in connection with
comet-hunting, have been distanced. Between 1877 and 1908
inclusive, no fewer than 20 first discoveries stand to the
credit of Brooks, 19 to Barnard, 13 to Perrine, and 11 to
Swift. These figures compare very favourably with the
13 comets discovered by Messier between 1760 and 1798 and
the 27 discovered by Pons between 1803 and 1827. The

b Histoire de I'Astronomie au dix-huitieme slide, Paris, 1827, p. 770.

W

DISCOVERY FIELD OF BROOKS S
COMET (1890, ii.) ON MARCH 19,

1890.

48 The Story of the Comets. CHAP.

most successful European comet-hunter seems to have been
Giacobini of Nice, who has 12 comets to his credit.

Comet-hunting is a pursuit which may well be taken up
by amateurs with plenty of spare time on their hands because,
if the truth must be told, it involves an immense waste of
time, with results which only present themselves at long
intervals. Hence the difficulty of public observatories with
defined programmes taking to the work. Except for this,
comet-hunting may be said to be an easy matter, given
a telescope of moderate, that is, handy size (say from 4 to 6
inches of aperture) ; a clear horizon in the neighbourhood of
the Sun either in the W. after sunset, or in the E. before
sunrise ; and plenty of patient, plodding perseverance on the
part of the observer. An eye-piece of low power and with
a large field should always be used; whilst sometimes an
enthusiastic seeker after comets will provide himself with
an achromatic telescope specially designed for the work and
known as a "comet-seeker", but this may be regarded in
general as unnecessary. A comet-seeker is nothing more
than a cheap equatorial provided with an inferior object-glass
and coarsely divided circles, and contrived optically to com-
mand the largest possible field in proportion to its inches of
aperture.0 A good catalogue of nebulae is an essential adjunct,
because most comets may at a first view be easily mistaken
for nebulae, and it is only by their being possessed of movement
that they can be distinguished. [See Fig. 18, Plate IV.]

Concerning the designation of comets it is expedient to say
something, because there is no fixed rule, and the practice is
very arbitrary and inconsistent. At its first discovery the
discoverer's name is usually attached to a comet. .Thus, the
comet which was discovered by Morehouse on Sept. 3, 1908,
was known during the whole period of its visibility as
" Morehouse's Comet ".d On the other hand Biela's Comet

c The comet-seeker of the Washing- fashion, which seems inclined tocome

ton Observatory, aperture 44 inches into use in England, of designating

and focal length only 2ft. 10 in., is comets according to the French idiom,

engraved in the Washington Observa- whereby Morehouse's Comet would

tions, 1845, Plate II. be called "Comet Morehouse ",follow-

d Let me here protest against the ing the silly fashion adopted by some

V. The Discovery and Identification of Comets. 49

takes its name from, not its first discoverer who was Montaigne
in 1772, nor its second discoverer Pons in 1805, but from
its third discoverer Biela in 1826. Then again, the cornet
universally called " Encke's " takes its name from a man who
possibly never saw it at all6 until after the time when his
name had become permanently attached to it. But he dedicated
so vast an amount of time and labour to an examination of
its orbit that astronomers with one consent coupled his name
to it. Nowadays it is usual to identify comets first of all
temporarily by an italic letter of the alphabet joined to the
year of discovery, and then afterwards by an ordinal number
which indicates the order of the date of its perihelion passage
amongst the comets of a particular year. Thus, Morehouse's
Comet was first of all " Comet c of 1908 ", but it is permanently
enrolled as the 4th Comet of 1908, usually printed as " Comet
iv. 1S08 ", or " the Comet of 1908 (iv.) ".

A word of caution is perhaps desirable in connection with
the system now in vogue of numbering the comets of a year.
It was a long time before the system became settled, and
previous to that being the case things were in great confusion ;
and the old confusion is even now operative to lead astray
persons hunting up old comets in the indexes to Scientific
Publications prior to 1872. It seemed very obvious to number
the comets of a year in succession according to the dates of
their discovery from January to December, but this pre-
supposed that they passed perihelion in the same chronological
order in which they were discovered. This, however, would
be by no means always the case, so that, for instance, the
3rd comet in the order of discovery might prove to be the 2nd
in the order of perihelion passage ; and it might during the

of the London Hotels ; so that if you
are writing to a friend at the large
Hotel in Russell Square you are ex-
pected to call it " Hotel Russell ", in
which case the postal address should
be " Square Russell ", which shows
the absurdity of the whole thing.

e Encke's Comet was first dis-
covered in 1786 by Me'chain at Paris ;

it was rediscovered in 1795 by Miss
Caroline Herschel ; it was again re-
discovered in 1805 by Thulis at
Marseilles, and for the third time
rediscovered in 1818 by Pons at
Marseilles, so that Encke's connection
with it came quite late in the day,
yet nobody ever challenged, so far as
I know, the attachment of his name.

50 The Story of the Comets. CHAP.

year get into the periodicals as Comet No. 3 of a year, but
would have to have its number altered subsequently during
the year and have become No. 2 when the index was compiled.
As comet discoveries multiplied the confusion became intoler-
able ; hence the system now in vogue of letters of the alphabet
as provisional designations, not to be replaced by numbers
until a sufficient time has elapsed to make it certain that no
disturbance of the order of perihelion passage could reasonably
be anticipated. The credit of settling the present system on
its existing basis is due to Dr. C. A. F. Peters, the editor of
the German Periodical, Astronomische Nachrichten, expanding
in 1872 a system suggested by the German Astronomical
Society (The " Astronomische Gesellschaft ") in 1867, but
which missed its mark because it took no account of the
order of discoveries being very often different from the order
of perihelion passage/ It remains to be seen whether photo-
graphy will give cause to the creation of fresh confusion
arising from the fact that a photograph plate will " take "
a comet and the plate may remain (as has happened) un-
examined, and the existence thereon of a comet unknown, for
weeks, or it may be for months, after the photographer has
performed his share of the work.

An attempt was made some years ago to introduce the use
of a couplet of names in the case of a comet proved to be
periodic by reason of its making a second visit to us. Thus,
the comet found in 1812 by Pons, was rediscovered in Sept.
1883 by Brooks. When the identity of the Comet of Sept. 1883
(which is now enrolled as 1884, i.) with that of 1812 became
certain, it was called by American writers the " Pons-Brooks
Comet ", but the practice has happily not spread, and is not
commendable. The awkwardness of it is shown in the follow-
ing cryptogram : The " Tempel (3)-Swift " Comet, which
means the third of the periodical comets discovered by Tempel,
which was afterwards rediscovered by Swift and taken to be
a new comet.

It has already been stated that the identification of a new

f For the details of the controversy 1871, 1872. Nov. 1871 — Jan. 1872.
see Ast. Nach., vol. Ixxviii, Nos. 1869,

V. The Discovery and Identification of Comets. 51

comet can only be determined with any certainty when the
" elements " of its orbit have been ascertained, and that the
question of elements is of sufficient importance to need
a separate chapter. But without forestalling what will be
said there something more may conveniently be said here in
dealing with the discovery of comets.

When a comet has been found it must be confessed that
astronomers are always in a little nutter pending the inquiry
whether the new comet is really a new one, or one that has
been seen before, showing itself again to our ken for the
second or third time. When the 3 observations necessary for
•determining its orbit have been made the computers set to
work at once to see what is the size and shape and position
of its orbit. These facts being ascertained resort is had to
a catalogue of previous comets, which is searched in order
to see whether the elements of the new comet's orbit bear
any resemblance to those of any old comet. If any striking
resemblance should be noticed between the longitude of the
perihelion, the longitude of the ascending node, the inclination
and the perihelion distance of the new comet and of any old
€omet, there is a primd facie probability that the new comet
is really the old one come again. Accordingly, further
observations, prolonged through several weeks, are anxiously
.awaited in order to see whether they yield results which tally
with the first provisional orbit. If they do, so much the
better. If there is evidence to show that the new body is
moving in an elliptic orbit, that is to say in an orbit which
enables the comet to go round and round the Sun, then it
becomes possible to assign a period for the comet's revolution
round the Sun. This done, the question of identity with
some comet already seen becomes very interesting. To quote
a medical phrase, " an acute crisis " has been reached ; but it
is not safe at this stage to jump at conclusions as to identi-
fication because both the old and the new comets may have
been subjected to disturbances of their orbits (called technically
"perturbations") which may have considerably, or even
completely, changed the shape and character of either or
both orbits.

E2

52 The Story of the Comets. CHAP.

Very little stress can ever be laid on the personal appear-
ance of 2 comets because, whilst many of them resemble one
another very closely, the same comet at different epochs has
often been known to present very different appearances.
Reliance must not in all cases be placed on an apparent
similarity of elements even where similarity to a striking
degree seems to exist.8

When a new comet has been found it is a matter of the
greatest importance to determine very accurately its position
in the heavens from day to day; and this is sometimes not
very easy, especially when the comet is viewed in twilight.
But whatever may be its place, that is determined by measuring,
by means of a micrometer, its angular distance from particular
stars, whose exact position in Right Ascension and Declination
is either accurately known, or can be ascertained at leisure.
The stars used for this purpose are spoken of as " comparison
stars ". Ordinarily an equatorial has to be made use of, and
its circles should of course be in very accurate adjustment.
If, however, by good fortune the cornet can be caught on the
meridian and seen through a meridian instrument the resulting
places will usually be more accurate than if an equatorial is
employed. Only 3 perfect observations are necessary for
determining the general nature of a comet's orbit ; but at best
the first result will only be provisional, especially if the
intervals between the observations are short, such as 2 or 3
days. Such observations will only yield an orbit in the form
of a provisional parabola. If by any chance the comet is
moving in an elliptic orbit, the intervals must amount to 2 or
3 weeks at the least for the character of the ellipse to be
ascertained with any reasonable accuracy. The plane of
the orbit and the comet's perihelion distance, ascertained
provisionally, will not generally be varied much by the
utilisation of subsequent observations ; but it is another
matter to determine accurately the eccentricity of the orbit,
the dimensions of the major axis, and the corresponding
period. The more the observations are prolonged the more
the figures for these three elements will vary from those first

« See p. 18 (ante).

V. The Discovery and Identification of Comets. 53

obtained ; and of course the longer the interval of time on which
they are based the more trustworthy the figures will become.
The reason why the exact character of a comet's orbit is
often very uncertain is that we on the Earth only see a comet
when it is more or less near the Sun, near, that is, the focus
of the orbit : and the shape of an orbit, whether really
elliptic, parabolic or hyperbolic, differs very little at, and
immediately on either side of, the perihelion point or point of

Fig. 29.

DIAGRAM SHOWING THAT WHEN A COMET IS NEAR PERIHELION AN ELLIPSE,
PARABOLA AND HYPERBOLA DIFFER VERY LITTLE IN PLAN.

nearest approach to the Sun, as may be inferred by an
inspection of Fig. S9.

Recently photography has come to play some part in the
work of comet-hunting,'1 and it may here be mentioned that
the Comet of 1892 (v.), discovered by Barnard on Oct. 1:2,
was the first discovery which was due to a comet having
recorded itself on a photographic plate arranged for stellar
survey. He exposed a plate for a certain time, directed to the
neighbourhood of a Aquilae. On developing the plate a trail,

h Special photographic lenses may essential asnowing to their faintness,

be had which permit of a large field comets need a long exposure before

of view being embraced ; but a good they will reveal themselves,
driving clock for the telescope is

54- The Story of the Comets. CHAP.

conjectured to have been impressed by a comet, was observable,
and a few days later was easily picked up with a telescope.
Though the comet had no particular interest in itself, its orbit
soon attracted notice because it was seen to resemble very
closely the orbit of Wolf's Comet, and Schulhof pointed out
the extreme probability of the 2 bodies being two portions of
one original — a case of Biela over again. It may be added
that a good photograph generally discloses much more detail
in a comet than can be recognised by the eye with a telescope.
Barnard's Comet of 1892 (v.) does not stand alone as an
instance of astronomers having been assisted in their labours
by the photographic art. After their discovery in the usual
way it was found that several recent comets had impressed
themselves on photographic plates long before their discovery
visually. Thus Brooks's Comet of 1904 (i.) was photographed
in May 1903, giving an interval thus covered by observation
of 753 days. Again, KopfFs Comet of 1905 (iv.) was found
on a plate exposed on Jan. 10, 1904, 783 days before its visual
discovery, so that its period of visibility thus regarded might
be said to have been more than 3^ years. Such records are
of great value in tracing the movements of a comet because,
thanks to the perfection which has been attained in celestial
photography, photographic plates can be read and brought
into line with the stellar co-ordinates of Right Ascension and
Declination as effectively as if the services of a meridian
instrument had been available for fixing the place of the
comet at a given time on a given day.

So many of our observations of ancient comets (and those
observations by far the most valuable) depend on Chinese
records and descriptions of them that it may interest the
reader to see how an ancient Chinese astronomer sought to
convey his information to posterity. The following is Ma-
tuan-liu's account of Halley's Comet in 837 : —

" In the 2nd year of the Epoch Kae Ching, the 2nd Moon, day Ping Woo,
there was comet in S. D. Wei. It was about 7 cubits in length. It pointed
towards Nan Tow. On the day Woo Shin it was to the south-west of S. D.
Wei. It was bright, and moved rapidly. On the day Kwei Chow its place
was in S. D. Heu. On the day Sin Yew its length was about 10 cubits. It
went to the west, gradually pointing to the South. On the day Jin Seuh

V. The Discovery and Identification of Comets. 55

its place was in Woo Neu: its length was about 20 cubits, and was 3 cubits
in breadth. On the day Kwei Hae the tail was still broad. In the 3rd Moon,
day Kea Tsze, its place was in Nan Tow. On the day Yih Chow its length
was 50 cubits, the end [of the tail] being divided into two branches, the one
pointing to S. D. Te, the other covering S. D. Fang. On the day Ping Yin
its length was 6 cubits, and was no longer branched. It pointed to the
North. Its place was in the 7th degree of S. D. Kang. On the day Ting
Maou it went to the North-west, pointing to the East. On the day Ke Sze
its length was about 80 cubits : its place was then in S. D. Chang. On the
day Kwei Wei it was but 3 cubits in length : its place was to the right of
Heen Yuen. After this it was no longer visible."

In the foregoing extract " S. D." stands for " Sidereal
Division ". The Chinese divided the whole ecliptic into
28 Sidereal Divisions, equivalent, in a sense, to our 12 Signs of
the Zodiac. For the fullest possible information on these
matters the reader is referred to the work mentioned in the
footnote.1

Twice it has happened that the search for comets has been
stimulated by the promise of a distribution of loaves and
fishes, if the metaphor may be permitted in a solemn scientific
book. In the year 1835 the King of Denmark of the period,
Frederick VI., instituted a gold medal to be given to the
discoverers of telescopic comets, and several such medals were
awarded.k Amongst the recipients the only English name
we find is that of J. R. Hind. The grant of this medal was
continued after the King's death in 1839 by his successor
Christian VIII., but it was discontinued after the death of the
last-named king in 1848. The Vienna Academy of Sciences
formerly gave a gold medal to the discoverer of every new
comet. This was discontinued about 1880. Mr. H. H. Warner,
an American, then offered 200 dollars for every unexpected
comet found in the United States or Canada. This was given
up after a time, and then, after an interval, the idea was
revived again by a wealthy American, Mr. J. A. Donohoe, in
the year 1890, and a bronze medal is now regularly presented

1 Observations of Comets from B.C. 611, 4to. London, 1871.
to A.D. 1640, extracted from the Chinese k Ast. Nach., vol. xvii, No. 400, May

Annals. Translated, with introductory 14,1840; Month. Not. E.A.S., vol. vi,

remarks. By John Williams, F.S.A. p. 86, June 1844

56 The Story of the Comets. CHAP.

to the discoverer of any unexpected comet on the report of
a Committee of the Astronomical Society of the Pacific.

In 1900 a German gentleman named A. F. Lindemann,
living at Sidmouth, placed at the -disposal of the German
Astronomische Gesellschaft a fund to encourage the com-
putation of cometary orbits. The sum of £5 (in marks) is
paid for each definitive orbit whether of a modern or an
ancient comet. This example deserves to be followed !

An interesting example of the way in which science has
been promoted in America by the introduction into scientific
fields of American commercial methods has been neatly
sketched by Professor H. H. Turner, of Oxford. The Board
of Visitors of the Observatory at Albany, doubting the value
of some desk work (that is, non-telescopic work) which their
Director was carrying on, " inquired tentatively whether it
would not rather add to the reputation of the Observatory if
some discovery, such as that of a comet, could be made ; and
were promptly informed that nothing was easier if they
would sanction the devotion of a certain sum of money to the
purpose, as salary for a person of average intelligence while
making the necessary search. The challenge was accepted on
the spot; the money subscribed; the searcher set to work,
and within the allotted time a fine comet was found. Pro-
fessor Boss undoubtedly took a certain risk in undertaking to
catch a comet, just as a man would who undertook to catch
a fish within a definite time. But he was anxious to vindicate
his views of the relative importance of different kinds of work,
and deserved the success he ventured to count upon ".*

American astronomers have shown their national acuteness
and labour-saving cleverness even in their way of transacting
comet business. Some years ago they instituted a Comet
Telegraph Code for transmitting, with a certain amount of
detail, but in very concise visible form, information as to the
discovery of new comets.™ A specimen of a message in this

1 Lecture on HaUey's Comet to the 179, May, June, 1896 ; Astronomical

British Association, 1908, p. 10. Journal, Boston, U.S., vol. vii, p. 189.

m Publications of the Astronomical March 23, 1888.
Society of the Pacific, vol. viii, pp. 109,

V. The Discovery and Identification of Comets. 57

code (known as the Science Observer Code) may be given as
follows : —

"Butler
Barnard
Nashville
Rol

October
Kan-upale

Bun-alist

Dar-ation

Duz-ogoon

Baf-ofant

Baf-olute

Beetle."

Boz-odate

Which means : — " A faint comet was discovered by Barnard at Nashville on
October 14. Its position October 15, at 9h 30m 15s is R.A. 2h 27m 13-5'.
N.P.D. 27° 13' 23". Its daily motion in R.A. is (-72s), and in N.P.D.

(-8')."

The advantage of a code is obvious, and the rules for
working this one seem sufficiently clear to obviate serious
mistakes in telegraphing. The head quarters of the move-
ment is at the Harvard College Observatory, Cambridge,
Massachuse tts.

The code in use in Europe is on a different basis, and suits
the difference in the European telegraph charges as compared
with the American charges, and on the whole is more simple
and more comprehensive. The head quarters of the European
Use is the German Observatory at Kiel. The following is
a sample message : —

"Comete Pechule 16 D<§cembre 06500 Copenhague 28215 07929 36129
35745 14518 brillante, circulaire, condensation. Pechule."

Which means : — " Une comete a ete de"couverte par Pechule :
Dec. 16 6h 50-0 T.M. Copenhague

A.R. - 282° 15
N.P.D. = 79 29
Mouv. diurne en A.R. : + 1° 29' :
en N.P.D. : -2° 15'
Comete brillante, circulaire avec condensation. PECHULE."

CHAPTER Vl.a
PERIODIC COMETS OF SHORT PERIODS.

Periodic Comets conveniently divided into 3 classes. — Short-period Comets in
two groups. — -Comets in Group I. — Encke's Comet. — The supposed Resisting
Medium in space. — Its supposed effect on Encke's Comet. — Brief summary
of its History. — The Resisting Medium theory not generally accepted. — Re-
markable Observations in 1871. — Tempers Second Periodical Comet
(1873, ii.). — Winnecke's Comet. — Brorsen's Comet. — Tempel's First
Periodical Comet (1867, ii.). — Tempel (S)-Swift's Comet. — Finlay's
Comet. — If Arrest's Comet. — Wolfs Comet.— Holmes' s Comet. — Brooks 's
Second Periodical Comet (1839, v.). —Faye's Comet. — Tuttle's Comet.— Short-
period Comets in Group II. —Barnard's First Periodical Comet (1884, ii.). —
Brooks s First Periodical Comet (1886, iv.% — Barnard's Second Periodical
Comet (1831,iv.).—Spitaler's Comet (1890. vii.).— Perrine's Comet (1896,
vii.). — Kopjes Comet. — Giacobini's Second Periodical Comet (1900, iii.). —
Swift's Second Periodical Comet (1889, vi.). — Borelly's Comet (1905, ii.). —
Swift's First Periodical Comet (1885, ii.). — Denning's Second Periodical
Comet (1894, \.}.—Metcalfs Comet (1906, vi.).— Denning' 's First Periodical
Comet (1881, v.}.— Giacobini's First Periodical Comet (1896, v.).

THE comets which will be dealt with in this volume under
the general designation " Periodic " may be conveniently
divided into 3 main classes: —

(I.) Comets of Short Periods.

(II.) Comets revolving in about 75 years, more or less.
(III.) Comets of Long Periods.

The comets belonging, or supposed to belong, to Class I
must be put into 3 groups : —

(i.) Recognised members of the Solar System returning
regularly at stated intervals.

a If it should be suggested that an therefore to visibility to us on the

undue amount of space has been Earth : and that consequently they

allotted in this work to the Short- are available for furnishing many

period Comets I would answer that chances of study to the readers for

scarcely a year ever passes that some whom this work is mainly intended,

of them do not return to the Sun and namely, amateurs.

CHAP. VI. Periodic Comets of Short Periods.

59

(ii.) Recent discoveries believed to be periodic but

whose orbits are not very certainly known,
(iii.) Discoveries of such old date that as the comets have
not reappeared they must be given up as " lost ".

FIRST GROUP. RECOGNISED REGULAR COMETS.

No.

Name of Comet.

Period :
Years.

Last
Observed
Return.

Next
Return.

1

Encke's

3.29

1908

1911

2
3

4

Tempel's Second (1873, ii.)
Tempel-Swiffs (1869, iii. : 1880, v.)
Winnecke's

5-15
5-53
5-54

1904
1908
1898

1909
1914
1909

5

Brorsen's

5-58

1879

1912

6

7

Tempel's First (1867, ii.)
Finlay's..

5-98
6-54

1879
1906

1910
1913

8

D'Arrest's

6.64

1897

1910

9

Wolf's

6.76

1898

1912

10

Holmes's

6-85

1906

1913

11
12

Brooks's Second (1889, v.)
Faye's ... .

7.07
7-44

1903
1894

1910
1911

13

Tuttle's (1858, i.i

13-66

1899

1913

All the foregoing comets, except perhaps Brorsen's, may be
regarded as assured members of the Solar System, and certain
to be seen again, sooner or later.

(1.) ENCKE'S COMET.

Comet No. 1 in the foregoing list is by far the most
interesting of all, and therefore its history deserves to be
given in some detail.

On Jan. 17, 1786, Me"chain at Paris discovered a small
telescopic comet near (3 Aquarii. On the following day he
announced his discovery to Messier who, owing to bad weather,
did not see it till the day after, on which night it was also
observed by J. D. Cassini Jun. and by Me'chain himself. It
was tolerably large and well defined, and had a bright nucleus
but no tail, and was not seen again.

60 The Story of the Comets. CHAP.

On Nov. 7, 1795, Miss Caroline Herschel discovered a small
comet, about 5' in diameter, without a nucleus, but showing
a slight central condensation of light. Olbers observed it 011
Nov. 21, but it was too faint to allow of the field being
illuminated, and he was obliged to compare it with stars in
the same parallel by noting the times of transit across the
field of view. It was round, badly defined, and about 3' in
diameter. The orbit greatly perplexed the calculators, and
Prosperin declared that no parabola would satisfy the
observations.

On Oct. 19, 1805, Thulis at Marseilles discovered a small
comet faintly visible to the naked eye. Huth stated that on
the 20th it was very bright in the centre, though without
a nucleus, and was 4' or 5' in diameter. On Nov. 1 a tail
3° long was visible. Several parabolic orbits were calculated,
and an elliptic one by Encke to which a period of 12-12 yrs.
was assigned.

On Nov. 26, 1818, Pons at Marseilles discovered a small
and ill-defined telescopic comet. As it remained visible for
nearly 7 weeks a fairly complete series of observations was
obtained. Encke, finding that under no circumstances what-
ever would a parabolic orbit represent them, determined to
investigate the elements rigorously according to the method
of Gauss then but little practised. So doing, he found that
the orbit was certainly an ellipse, with a period of no more
than about 3^ years. On looking over a catalogue of the
comets whose orbits had been calculated up to that time he
was struck by the similarity which the elements obtained by
him bore to those of the Comets of 1786 (i.), 1795 and 1805,
and he was strongly impressed with the idea that all these 4
comets were really one and the same comet, especially as
reckoning backwards from 1818 intervals of 3^ years, or
multiples of that period, would nearly or quite coincide with
the perihelion passages of the comets of 1805, 1795 and
1786 (i.). The question could only be settled positively and
conclusively by calculating backwards the effects of planetary
perturbation and the necessary calculations Encke was able to
accomplish by an extraordinary effort in 6 weeks, The result

VI. Periodic Comets of Short Periods. 61

was that he was able to assure himself of the identity of the
Comet of 1818 with the 3 comets just mentioned, and that
between 1786 and 1818 it had passed through perihelion
7 times without being noticed. But Encke was not content
to let the matter rest there so he proceeded to calculate the
date of the comet's next return, and found himself justified in
announcing that the comet would arrive at perihelion on
May 24, 1822, affeer having been retarded about 9 days by
Jupiter.

" So completely were these calculations fulfilled, that
astronomers universally attached the name of ' Encke ' to the
Comet of 1819, not only as an acknowledgement of his
diligence and success in the performance of some of the most
intricate and laborious computations that occur in practical
astronomy, but also to mark the epoch of the first detection
of a comet of short period — one of no ordinary importance in
this department of science."

It unfortunately happened that in 1822 the position of the
comet in the heavens was such as to render it only visible in
the Southern hemisphere. It was therefore systematically
watched by only one observer, Riimker, who discovered it on
June 2 at the private observatory of Sir T. M. Brisbane at
Paramatta. N.S.W., and he was only able to follow it for
3 weeks. Riimker's observations were however so far valuable
that, besides showing that the comet actually did come back,
they furnished Encke with the means of predicting with
greater certainty its next return which he found would occur
on Sept. 16, 1825. On this occasion it was first seen on
July 13 by Valz, but was discovered independently by other
astronomers. Cacciatore of Palermo described it as being
round, with a faint nebulosity, and about 1° 30' in diameter.

The next return to perihelion took place on Jan. 9, 1829.
Struve at Dorpat found it on Oct. 13, 1828. Harding at
Gottingen and Gambart at Marseilles both saw it for the first
time on the same day, Oct. 27, the former having been on the
look out for it since August 19. On Nov. 30 it was visible to
the naked eye as a star of the 6th magnitude, and the week
afterwards it had become as bright as a star of the 5th

62 77/6- Story of the Comets. CHAP.

magnitude. The outline of the coma was slightly oval with
the minor axis (on one occasion at least) pointing towards

the Sun.

The comet returned in 1832 but was only seen by one
European observer, Harding at Gottingen, owing to its path
lying chiefly in the Southern hemisphere.

Passing over the return of 1835, when the comet was seen
both in Europe and at the Cape, we come to that of 1838.
As the comet's apparent path would allow of observations
beino- made in Europe under very favourable conditions it
was looked for with much interest. Boguslawski discovered
it on Aug. 14, but it was not generally seen till the middle of

October. In the first week
Fig. 30. in November it was visible to

the naked eye in Draco. With
a telescope a rather bright
nucleus was seen, and the
general form of the coma was
that of a broad parabola. It
was this return which brought
into prominence a peculiarity
of the comet's motion which
raised a question which still

1 ft^ft

continues open for discussion.

Encke found that, notwith-
standing every allowance being made for planetary influences,
the comet always attained its perihelion distance about
2^ hours sooner than his calculations led him to expect. In
order to account for this gradual diminution of the period
of revolution, which in 1789 was nearly 1213d, but in 1838
was scarcely 1211 ^d, Encke conjectured the existence of a thin
ethereal medium, sufficiently dense to produce an effect on
a body of such extreme tenuity as the comet in question,
but incapable of exercising any sensible influence on the
movements of the planets. Hind thus soliloquised on the
subject : — " This contraction of the orbit must be continually
progressing, if we suppose the existence of such a medium ;
and we are naturally led to inquire, What will be the final con-

VI.

Periodic Comets of Short Periods.

63

sequence of this resistance ? Though the catastrophe may be
averted for many ages by the powerful attraction of the larger
planets, especially Jupiter, will not the comet be at last pre-
cipitated on the Sun ? The question is full of interest, though
altogether open to conjecture." b

The following table, published by Encke,0 will more clearly
illustrate the changes in the comet's periodic time : —

Year of PP.

Period, Days. ' Year of PP.

1786

(1789) 1212-79

(1792) 1212.67

1795 1212-55

(1799) 1212.44

(1802) 1212-33

1805 1212-22

(1809) 1212.10

(1812) 1212-00

(1815) 1211-89

1819 1211-78

1822 . . 1211-66

Period, Days.

1825 1211-55

1829 1211-44

1832 1211-32

1835 1211-22

1838 1211.11

1842 1210-98

1845 1210-88

1848 1210-77

1852 1210-65

1855 1210.55

1858 , ,. 1210-44

So far as it goes this table seems conclusive in its facts, but
observations made at a return 10 years later than the last in
the above table, namely in 1868, showed a sudden diminution
in the retardation by nearly one-lialf the previously-noticed
amount. And both the reality and also the permanence of
this alteration were made clear in 1885. Some physical
alteration in the comet has been suggested as the necessary
explanation, but there is no visual evidence to lend colour to
this idea.

The soundness of the explanation which assumes the
existence of a Resisting Medium has been long and warmly
canvassed, and it does not command the assent of astronomers
generally. One strong point against it is that, with the
exception perhaps of Winnecke's Comet (1858, ii.), none of
the other short-period comets (all of them of small size and
presumably slight mass) yield any indications of being subject
to a like influence. d On the other hand Von Asten, who

b The Comets, p. 66. d See a notice of a paper by A. Hall

c Month. Not, vol. xix, p. 70. Dec. in Month. Not., vol. xxxiii, p. 239.

1858.

Feb. 1873.

64 The Story of the Comets. CHAP.

worked at the problem very assiduously, thought there ought
to be no hesitation in accepting the idea, subject to the limita-
tion that the medium does not extend farther from the Sun
than the orbit of Mercury.

The 1838 return is also noticeable for an important discovery
in physical Astronomy which it indirectly was the cause
of evolving. In August 1835 the comet passed very near the
planet Mercury — so near in fact that Encke shewed that if
Laplace's value of Mercury's mass was correct the planet's
attractive power would diminish the comet's Geocentric R. A.
on Nov. 2. 1838, by 58', and increase its Declination by 17'.
As the observations indicated no such disturbance of the
comet's orbit it was obvious that the received mass of the
planet was much too great, and as a matter of fact a much
lower value has since been adopted.6

Passing over the returns of 1842 and 1845 as offering no
points of particular interest we find that in 1848, on Sept. 24,
the diameter of the comet's head was 8' and that it was just
visible to the naked eye on Oct. 6, and for some weeks sub-
sequently. The adjacent illustration [Fig. 31, Plate IX.] will
convey a good idea of the telescopic appearance of the comet
during the month of September 1848. Early in November it
had a tail about 1° long turned as usual from the Sun, and
another and smaller one pointing towards the Sun. On Nov. 22
the comet was within 3,600,000 miles of Mercury.

Since 1848 Encke's Comet has been observed so many times
that it would be monotonous and unprofitable to detail all the
several appearances. I shall therefore only make a selection
of apparitions which yielded some observations of interest and
importance, more or less.

In 1871 the comet was well seen and numerous observations
made. Some physical peculiarities were noted which deserve
mention. In October, soon after its first discovery, the comet
was a nearly round and faint nebulosity without apparent con-
densation anywhere. By the beginning of November it had

e In Hind's Comets, p. 65 et seq. the with the clearness of language for
general principles upon which these which that distinguished astronomer
inquiries are conducted are laid down was noted.

Fig. 31.

Plate IX.

ENCKE'S COMET.
AS SEEN AT THE HARTWELL OBSERVATORY, SEPTEMBER 22, 1848.

P. 64.

VI.

Periodic Comets of Short Periods.

65

acquired a remarkable fan-like form, but the precise character
of the exterior outline differed a good deal according to the
power of the telescope employed.
Mr. Carpenter said f : —

"I was able to make out a considerable extension of the illumination
beyond the bright fan-shaped condensation, but on one side (the spreading

ENCKE'S COMET: NOT. 9, 1871. (J. Carpenter.)

side) only. On the opposite side this diffused illumination appeared to be
cut off nearly in a straight line immediately behind (following) the apex of
the fan."

f Month. Not., vol. xxxii, p. 26. Nov. 1871.

CHAMBERS

66 The Story of the Comets. CHAP.

The Rev. H. C. Key, speaking in the first instance of what
he saw on December 3. said g : —

"The train following the comet was quite broad in my telescope, and could
not be termed a 'ray '. You will observe two rays on the preceding side ;
these I have drawn as you see, but I am not perfectly certain that the effect
was not in my own eye and not a reality. I took every precaution to find
out ; and at the time (as well as now) felt pretty well convinced that it was
no illusion. Four or five times I left the telescope, and upon returning
there were the rays in exactly the same spot and direction. I feel pretty
confident of their reality (they were extremely faint), but, as I say, am not
quite certain, as I sometimes see dark lines in the field when first going to
the telescope. The comet never seemed to me to lose its elliptical form from
the first night I saw it, Oct. 20. I detected a nucleus for the first time on
Nov. 7. The train I mentioned before was much fainter than the main
body of the comet, and I was able to trace it to a distance of about 32' from
the nucleus. I saw nothing like the drawing of the comet made at
Greenwich."

The return of 1871 was also important because it was found
not to have been accelerated in accordance with the Resisting
Medium theory as previous returns had been, since the first
discovery of the comet in 1786. Von Asten's conjecture as
to this is that in 1869 the comet might have come into
collision with some minor planet which violently deranged
and modified its orbit in some degree.h

Passing over the returns of 1875 and 1878 we come to that
of 1881, in which year the comet passed through perihelion on
Nov. 18. Common, using a 3 -ft. reflector, noted the comet to
be about 2' in diameter, very faint even in an instrument of
that size, and with slight indications of an increased bright-
ness in the centre. Tacchini found the spectrum exhibiting
bright bands in the yellow, green, and blue respectively,
coinciding with the 3 principal bands seen in the spectra of
the hydro-carbons. As in the case of some other comets, the
bands were shaded off to the blue. A faint continuous
spectrum was also detected.1 The spectrum was considered to
have undergone no change since the previous examination in
1878.

Since 1881 Encke's Comet has returned and been observed

* Month. Not., vol. xxxii, p. 217. vol. v ; Observatory, vol. i, p. 21, April
March 1872. 1877.

u Bulletin de VAcad.de St. Petersbourg, ' Gomptes Eendus, vol. xciii, p. 947.

VI. Periodic Comets of Short Periods. 67

in 1884, 1888, 1891, 1895, 1898, 1901, 1905, and 1908. It
does not seem necessary to refer to these returns in detail
unless it be to say that in 1895 (that is, at the end of 1894)
and in 1898 the comet was very faint and observed with diffi-
culty, whilst in 1904 it was found traced on a photographic
plate as early as Sept. 11, though not generally seen till
October and later months, when it was observed under very
favourable circumstances at many Northern observatories. In
1908 it was not visually seen at all, but left a record of itself
on a photographic plate. The only other remark which is
worth making is, that comparing these recent returns as a
whole it does not appear that the average brilliancy of the
comet under average circumstances has varied much or at all
during the 122 years that have elapsed since its first discovery.
Berberich has written an interesting paper on the brightness
of this comet at its many successive apparitions.k Perhaps
it may be well to add that in 1888, 1898, and 1908 it was
observed only or chiefly in the Southern hemisphere.

The period of Encke's comet is 3-315 years, so that it
returns to the Sun 30 times in a century. The shortness of
its period suggested to Miss Clerke that it might naturally be
expected to u'ear out quickly, but there is not a tittle of
evidence to justify this rash forecast.

(2.) TEMPEL'S SECOND PERIODICAL COMET (1873, ii.).

On July 3, 1873, Tempel at Milan discovered a faint comet
fully 2' in diameter, somewhat elongated in shape, with an
eccentric condensation of light, and a granular appearance.
When its orbit came to be calculated it soon became evident
that the comet moved in an elliptic orbit with a period of
rather more than 5 years. Hind pointed out that soon after
passing its ascending node and when near aphelion the comet
passes close to the orbit of Jupiter, to which fact is due its
periodicity ; and it is now to be regarded as, after Encke's,
the comet which leads the group known as " Jupiter Comets ". 1

k Ast. Nach., vol. cxix, No. 2836. Apr. 24, 1888.
1 See p. 42 (ante].

F 2

68 The Story of the Comets. CHAP.

Tempel's Comet returned again to perihelion in August 1878.
It was seen at Oxford with difficulty in the 12-inch refractor
of the University Observatory and resembled a faint round
nebula 1' in diameter with a very slight central condensation.
It was missed at its returns in 1883 and again in 1889,
but it was seen in 1894 and 1899. In 1899 it was described as
a fairly easy object in a 6-inch telescope ; but it is thought to
have become fainter at each return. A short diffused tail was
noticed on a photographic plate. It was seen again during
the winter of 1904-5.

(3.) THE TEMPEL(3)-SwiFT COMET.

On Oct. 10, 1880, Swift, at Rochester. New Jersey, U. S.,
found a small comet with a very diffused and ill-defined disc
several minutes in diameter. It was soon ascertained that
the orbit was elliptic with a period of about 6 years, and that
the comet was identical with the Comet of 1869 (iii.) discovered
by Tempel on Nov. 27, 1869. Hence astronomers designate
this object by the very inconvenient title prefixed to this
paragraph. The comet was very unfavourably circumstanced
for observation at the return of 1874, and escaped detection,
not only then but 12 years later, namely, in 1886. But at its
next return in 1891 it was detected by Barnard on Sept. 27.
Of no particular interest in itself, it may at least be said that
its orbit is interesting in so far that when the comet returns
to perihelion its position is such that it is alternately favour-
ably and unfavourably placed for observation. Consequently
its history thus far is as follows : — Seen in 1869 it was missed
in 1875; seen in 1880 it was missed in 1886; seen in 1891 it
was missed in 1897, when it passed through perihelion in June
but was always at a great distance from the Earth. The above
rule did not hold good in 1902 when the comet was due in
January, and was not seen in that year; but it was seen
again in 1908.

VI. Periodic Comets of Short Periods. 69

«

(4.) WINNECKE'S COMET.

A comet was discovered by Pons on June 12, 1819. Encke
assigned to it a period of 5f years, which, as the table shows,
was a very close approximation to the truth. It was not,
however, seen from that time till March 8, 1858, when it was
detected by Winnecke at Bonn, and by him regarded as a new
comet ; but he soon ascertained the identity of the 2 objects.
It must have returned in 1863 but was not then favourably
placed for observation. The next return to perihelion occurred
in June 1869. It was discovered by Winnecke himself on
April 9 of that year, and is described by him as being faint,
but as much as 6' or 8' in diameter. Some calculations by
Oppolzer led him to think that this comet was observed pre-
viously to the occasion which has usually been regarded as its
first discovery (namely, its detection by Pons in 1819) and
that it is identical with the comet discovered by Pons in
February 1808, which was only visible for 3 days and whose
orbit was never calculated.

Visible again in 1875, but missed in the autumn of 1880,
its next return was in 1886, when it was seen only in the
Southern hemisphere after perihelion. It passed its perihelion
12 days earlier than it was predicted to do, and Oppolzer
considered that its movements could not be completely
explained by the theory of gravitation alone, but that the
existence of some resisting medium was indicated : thereby
confirming, according to the knowledge of 20 years ago, the
theory then current as to the movements of Encke's Comet,
spoken of on a previous page, but which theory has otherwise
remained unconfirmed. This comet was observed in 1 892 and
1898, but missed in 1904, in which year its perihelion passage
was fixed for Jan. 21. Let us hope it may be seen 1909-10.

(5.) BRORSEN'S COMET.™

This comet was detected by Brorsen at Kiel on Feb. 26,
1846. The observations showed an elliptic orbit, and the

m A very interesting history of this G. A. Hill, appears in Astronomy and
«omet by Kreutz, with additions by Astro-Physics, vol. xi. p. 7. Jan. 1892.

70 The Story of the Comets. CHAP.

epoch of the next perihelion passage was fixed for Sept. 26,
1851, but the comet's position then was not favourable owing
to its proximity to the Sun, and it escaped observation.
Bruhns re-discovered it on March 18, 1857. I remember to
have seen it on March 23. It possessed the usual nebulous
appearance of telescopic comets generally, and appeared to
have a diameter of about 2'. though its position in the morning
twilight probably marred its brilliancy. This comet again
returned to perihelion in Oct. 1862 (not seen), in April 1868,
in Oct. 1873, and in March 1879. The spectroscopic observa-
tions on the last-named occasion by Konkoly in Hungary and
C. A. Young in America tended to show that the spectra of
this comet and of Encke's Comet were identical with one
another, and with a hydro-carbon spectrum. This comet
escaped notice at its return in Sept. 1884, and -\vas missed
again in 1890, although favourably placed and sought for by
powerful instruments. It was due to return to perihelion
again in Aug. 1895 but was missed, and was again missed in
1900-1 and in 1906, so that it is not very clear whether we
are entitled to recognize it as a permanent member of the
Solar system. [See Fig. 36, Plate X.]

The period of Brorsen's Comet has been gradually diminishing
owing to the effect of planetary perturbation.11 Thus : —

In 1846 ; period = 2034 days.
In 1857 ; „ = 2022 .,
In 1868 : „ = 2002 „
In 1873 ; ., = 1999 „
In 1879; „ =1994 „

and this diminution appears to have been going on ever since
1879.

The period being now 5-5 years, more or less, it results
that the comet is alternately visible in spring and autumn,
and the former apparitions are specially favourable for
observations, because at this season, in consequence of the
great inclination of the orbit, the comet reaches a high

» According to Axel Moller this is no question of a Resisting Medium.

Figs. 33-37.

Plate X.

Respighi (1863, v.).

VARIOUS TYPES OF COMETS.

(Drawn by W. Tempel.}

VI. Periodic Comets of Short Periods. 71

northern decimation. Another point which has been noted
is that several weeks after perihelion the comet rapidly
diminishes in brightness whilst its diameter increases con-
siderably, even to 8' or 10' of arc.

According to D'Arrest the present orbit was due to the
action of Jupiter in 1842, and according to W. E. Plummer
serious disturbances from the same cause will happen in 1937,
if the comet should last as long.0

(6.) TEMPEL'S FIRST PERIODICAL COMET (1867, ii.).

On April 3, 1867, Tempel at Milan discovered a small comet.
It had a nucleus eccentrically placed in an oval coma, and
Talmage, on May 3, thought that the nucleus appeared to
have a division across its centre. The comet remained visible
for about 4 months, which enabled its orbit to be ascertained
to be without doubt an ellipse of short period, which Searle
fixed at 2064 days and Bruhns at 2074 days. It returned
to perihelion in 1873 and was found by Stephan at Marseilles
on April 3. It was due to return to perihelion in May 1879,
in Sept. 1885, in March 1892, in Oct. 1898, and in April
1905, and not having been seen in any of those years, perhaps
it ought to be regarded as lost. Gautier found that the period
of the comet, which was at first supposed to be about 6 years,
had by 1885 been increased by no less than 5 months owing
to the influence of Jupiter on its orbit.

(7.) FINLAY'S COMET.

On Sept. 26, 1886, Finlay, at the Royal Observatory, Cape
of Good Hope, discovered a small tailless comet, 1'in diameter.
It was at first thought that it might possibly be identical
with the lost Comet of Di Vico, but subsequent investigation
disproved this idea ; this comet is, however, now to be regarded
as a recognised member of our system. It was re-discovered
on May 17, 1893, shining like a star of the 11th mag. and
still without a tail. It wras missed in the winter of 1899-1900

0 Naturervol. xxx, p. 301. July 24, 1884.

72 The Story of the Comets. CHAP.

owing to its being close to the Sun, coupled with its intrinsic
faintness. It again returned to perihelion in 1906, being
discovered by Kopff, and passing perihelion early in September.
Owing to its being missed in 1900 some uncertainty existed
as to its probable path in 1906, and its discovery in that year
was very fortunate, for in 1910 it will approach so close to
Jupiter as to be seriously affected by that planet. To this it
may be added, that it is thought that its proximity to Jupiter
in the year named will afford an opportunity for obtaining
a new value for the mass of that planet.

(8.) D'ARREST'S COMET.

On June 27, 1851, D' Arrest, at Leipzig, discovered a faint
telescopic comet in Pisces. Within a fortnight of its discovery
the observations of its path through the heavens were found
to be irreconcilable with a parabolic orbit ; and the ellipticity
of the orbit was soon placed beyond a doubt. Though the
comet was visible for more than 3 months, the calculations of
the orbit yielded very discordant results, and the successful
prediction of the comet's return in the winter of 1857-8 must
be regarded as something in the nature of a successful guess.
Sir T. Maclear, at the Royal Observatory, Cape of Good Hope,
was the only observer of the comet at this apparition.

Villarceau communicated to the Academy of Sciences at
Paris on July 22, 1861, a memoir on the orbit of this comet
which may be usefully placed on record here (in an epitomised
form) as it will give some insight into the nature of the
mathematical investigations which the calculators of cometary
orbits are called upon to conduct.

The perturbations experienced by this comet are owing chiefly to the action
of Jupiter, to which it is so near, that during the month of April of the
present year [1861] its distance was only 0-36, or little more than one-third
of the Earth's distance from the Sun. Before and after this epoch, Jupiter
and the comet have continued, and will continue, so little distant from one
another, as to produce the great perturbations to which the comet is at
present subject.

From a table of the elements of the perturbations produced by Jupiter,
Saturn, and Mars, in the interval between the appearance of the comet in

VI. Periodic Comets of Short Periods. 73

1857-8 and its return to its perihelion in 1864, M. Villarceau obtained the
following results : —

(1) The longitude of the perihelion will have diminished 4° 35' to Aug.
1863, and will remain sensibly stationary for about a year from that epoch.
(2) The longitude of the node will have continually diminished to the
amount of 2° 8'. (3) The inclination will have increased 1° 49' to the
middle of 1862, and will diminish 6' during a year, continuing stationary
during the year following. (4) The eccentricity, after having increased to
the middle of 1860, will diminish rather quickly, and will remain stationary
from 1863-5 to 1864-6. " But of all these perturbations," says M. Villarceau,
" the most considerable are those of the mean motion and the mean anomaly.
After having increased from 5" to July 1860 the mean motion diminishes
9" in one year, and nearly 12" in the year following, remaining stationary
in the last year, and with a value 15", 5" less than at its origin. The per-
turbations of the mean anomaly, after having gradually increased till 1860,
will increase rapidly till 1861, when they will amount to 10° 28' ; and setting
out from this, they will increase 9', and in 1863 and 1864 they will have
resumed the same value which they had in 1861."

The effect of the first of these perturbations will be to increase the time of
the comet's revolution by about 69 days ; and of the second, to hasten by
49 days the return of the comet to its perihelion in 1864. It will pass its
perihelion on Feb. 26, whereas without the influence of these perturbations
it would have passed it on April 15.

As was anticipated, the comet escaped notice at its return to
perihelion in 1864, being unfavourably placed. But in 1870
it was found and followed for 4 months. In dealing with
the observations of this return Winnecke pointed out that
D' Arrest's Comet was undoubtedly the faintest of the known
periodic comets, but probably that remark is no longer true.
The comet was seen also in 1877, missed in 1884, and seen
again in 1890, but its great southern declination limited the
observations. Its light was reported to be feeble, and observa-
tions difficult even with large telescopes. Inasmuch as at its
return in 1897 Perrine, at the Lick Observatory, saw the comet
in a 3^-inch Finder it seems almost certain that Winnecke's
remark just quoted 110 longer holds good. In 1903 the comet
was very unfavourably placed and was not seen.

(9.) WOLF'S COMET.

The history of the first discovery of this comet presents
some novel points of interest. In the ordinary course of
narrative we should say that Wolf, at Heidelberg on Sept. 17,

74 The Story of the Comets. CHAP.

1884. discovered a small telescopic comet which was described
by Tuprnan, a week later, as about 2' in diameter and
possessing a stellar nucleus 3" in diameter ; but it appears
that Copeland, at Dunecht, found it by means of the spectro-
scope, independently, on Sept. 22. 1884.p At its next return
this comet was probably first seen at Vienna by Spitaler on
May 1, 1891, and certainly by Barnard at the Lick Observa-
tory on May 3. Under the influence of Jupiter the orbit of
this comet suffered a complete transformation in 1875, and we
may now regard it as permanently attached to our system, for
at its return in 1898 the error of the ephemeris of its move-
ments computed beforehand was only I" in R.A. and 4" in
Declination. It was not seen in 1905, being unfavourably
placed.

(10.) HOLMES'S COMET.

On Nov. 6, 1892, E. Holmes, at Islington, discovered a bright
comet in Andromeda, which was also discovered independently
on Nov. 9 by Davidson in Queensland. The comet was
described by Holmes as 5' in diameter, and bright enough to
be seen by the naked eye. The greatest theoretical brilliancy
should have occurred in September, when the comet should
have been rather brighter than on Nov. 6, and was well
situated for observation in the Northern hemisphere. It is
therefore remarkable that it should not have been detected
sooner, but the explanation is no doubt to be found in the fact
that the comet underwent great fluctuations of brilliancy
during the time it was visible in the winter of 1892-3.

The most complete and interesting account of Holmes's
Comet which we have is due to E. E. Barnard, whose observa-
tions and remarks q will now be given in a compressed form : —

" From several points of view it was one of the most remarkable comets
ever observed.

At the time of discovery it was distinctly visible to the naked eye as
a slightly ill-defined star of the 6th magnitude. The remarkable fact that

p Sid. Mess., vol. x, p. 288. June of a spectroscope.

1891. This would seem to be the q Astrophysical Journal, vol. iii, p.

only comet ever discovered by means 41. January 1896.

VI. Periodic Comets of Short Periods. 75

the comet had attained naked-eye visibility when discovered, coupled with
the further fact that this region must .have been repeatedly swept over by
comet-seekers to within a few days of the discovery, shows that the comet
must have rather suddenly attained its conspicuous visibility. When found
this object was already some five months past perihelion, and had been
theoretically for several months in a far better condition for discovery.
From the care and skill shown by the large number of astronomers now
engaged in comet-seeking, there can be no doubt whatever but that this
comet did not exist during that time with anything like one-tenth of the
brightness it had at discovery.

From this, and its subsequent remarkable behaviour, several astronomers
argued that the object was not a comet in the true sense of the word, and
that it must be the product of some celestial accident. This idea was further
strengthened when its orbit was computed, and was found to lie within the
asteroid zone. This orbit differed altogether from that of the ordinary comet
by being almost circular. According to the orbit the comet ought to have
been easily visible at every previous opposition and should have been
discovered long ago.

It seemed highly probable at least that it should be seen at its next
opposition when it would be very favourably placed for observing. Though
carefully searched for, no trace of the comet could be seen with the 12-inch
and the 36-inch of the Lick Observatory.

From the fact that the orbit lay out among the asteroids Corrigan and
Kirkwood suggested that possibly two asteroids had collided and produced
the phenomenon of a comet. However much faith may be placed in this
hypothesis, I think, from the peculiar phenomena witnessed during the
visibility of the comet, that it does not now exist in the cometary form, and
furthermore, I do not think that it will ever be seen again, though it should
return to perihelion in 1899. All the circumstances connected with it
rather tend to show that it was of only a temporary nature.

The announcement of the discovery of this comet was received at the
Lick Observatory on November 8, 1892, and it was observed that night with
the 12-inch refractor. Its appearance was absolutely different from that of
any comet I had ever seen. It was a perfectly circular and clean cut disk
of dense light, almost planetary in outline. There was a faint, hazy nucleus
with a slight condensation some 5" south following the nucleus. With the
naked eye the comet was just as bright, exactly, as the brightest part of the
Great Nebula of Andromeda, near which it was visible.

At 8h Om a careful estimate of its diameter made it 260". At 9h 40m careful
micrometer measures made the north and south diameter 286".

On November 9, at 6h 5m the comet was brighter to the naked eye than
the brightest part of the Andromeda nebula. At 6h 20m the measured
diameter was 337" north and south, with the 12-inch telescope ; there was
a faint diffused glow 12' in diameter surrounding the comet symmetrically
and a short, faint diffusion south following. The nucleus preceded the
centre about f while at the centre there was a slight condensation. With
the naked eye at 8h Om the comet looked like a small star and almost equal in
brightness to v Andromeda, and could not be distinguished from a star.
At 8h 30m it was looked at with the 4-inch comet-seeker — the diffused haze
could be seen surrounding it with faint traces of a tail."

76 The Story of the Comets. CHAP.

After November 9 the comet gradually became fainter, and
on November 16 Barnard found "nothing different in its appear-
ance from the ordinary comet, except its size." It continued
to grow fainter, and on January 4, 1893, "there was only
the most excessively faint trace of the comet — a feeble glow
extremely difficult to see." Barnard then goes on to say : —

"Bad weather interfered with observations until January 16, when it
cleared at dark. It seemed scarcely possible that the comet could be seen
again, but from the importance of any positions of it, I thought it worth
trying once more. The 12-inch was set for it, and upon looking in the
telescope I was surprised to see a small, bright, hazy star. Thinking some
mistake had been made, the telescope was again set only to find the same
object. It seemed impossible that this star-like object could be the excessively
faint and diffused nebulosity previously seen. Observations for motion,
however, soon showed that it was in reality the comet. ... In the finder,
however, it appeared perfectly stellar and could not possibly be distinguished
from an 8th magnitude star. At 9h 50m the mean of two measures gave
-32". 4 for the diameter. At this time there had begun to appear in the con-
densation a small nucleus which had not been visible at first. It seemed
to brighten rapidly while being watched, and soon became very distinct.
At 10h 20m there was no question but that the nucleus was brightening ; it
seemed to form and become clear and distinct right before one's eyes.

At 10h 30° the 36-inch was turned upon the comet. It appeared very
beautiful and remarkable in the great telescope. With this instrument its
diameter was measured = 44". In the great telescope it looked exactly as it
did on November 8 when first seen with the 12-inch. It was pretty well
terminated and had a pretty bright nucleus. A few minutes later another
set of measures was made of its diameter = 47".

The nebulosity was bluish, but the nucleus was hazy and yellowish and
central. At 10h 55m there was a feeble glow about the comet, something like
1' in diameter. Further measures were made with the great telescope : at
llh 13m diameter = 47". 3. On this night there was no question whatever
but that the nucleus actually formed in a few hours' time, while the comet
was under observation ; at the same time the body of the comet appeared to
be expanding gradually."

During the next following nights the comet was watched
gradually growing in size, and on —

" January 20, with the 36-inch at 6h 45™ the measured diameter was 136".
The nucleus was of the 10th magnitude and quite conspicuous, while the
comet was much brighter in the middle. Taken altogether the object looked
like a spherical mass of vapour, rounding up beautifully, with the nucleus
shining in the middle.

January 22. With the 36-inch the comet was very diffused and was
estimated to be 3' or 3'. 5 in diameter. At 7h 30m the nucleus was very
indistinct and about 12th magnitude. There was a hazy glow close about
the nucleus that seemed to partially hide it.

VI. Periodic Comets of Short Periods. 77

January 24. On the moonlit sky, the comet, in the 12-inch, appeared to be
about 1' in diameter — its greater portion being lost in the brightness of the
sky. There was no nucleus. With the finder the comet appeared rather
bright and cometary — like a large and conspicuous nebula. After this,
absence from the Observatory prevented the comet from being followed
further."

Photographs of the comet were made : the most interesting
and important of these was the one made on November 10.
but Barnard remarks : —

"That the central, well-defined body of the comet has been lost in the
half-tone, the outline shown being that of the diffused haze surrounding
the comet proper. The nebulous appendage, however, is fairly well
shown. . . .

There is one other thing that this photograph shows (and which seems
to have been generally overlooked) that must sometime be of the highest
importance in the solution of the mystery surrounding this extraordinary
object. To the south-east of the comet, distant about one degree or so,
is shown a large irregular mass of nebulosity covering an area of one square-
degree or more, and noticeably connected with the comet by a short hazy
tail. Evidences of this diffused nebulosity had been seen when examining
the region about the comet with a low power on the 12-inch. This very
extraordinary appendage deserves the earnest attention of those who are
at all interested in this comet."

On Jan. 18, 1893, Palisa found the comet to shine as a star of
the 8th mag. surrounded by a nebulosity no more than 20" in
diameter. The striking variations which this comet under-
went would seem to explain the fact that it had remained
undetected at previous apparitions, for it is now a recognised
short-period comet fully entitled to a place on the regular list.
It returned in 1899, passing through perihelion on April 13, and
discovered by Perrine at the Lick Observatory on June 10,
shining as a star of the 6th mag. It returned again in 1906,
passing perihelion about the middle of March, but it was very
faint, and seen only in some of the largest telescopes in the
world. It has been thought that Holmes's Comet not improb-
ably belongs to a family of which the lost Di Vico is a member.
Its sudden outburst of brilliancy at the time of its first
discovery in Nov. 1892 would seem to have been an incident
in the comet's history without precedent, so far as we know,
and one which has never been repeated. Holmes's Comet has
the least eccentric orbit of any of the comets moving in elliptic

\

78 The Story of the Comets. CHAP.

orbits, the eccentricity being 0-41 ; Tempel's First Periodical
Comet comes next with an eccentricity of 0-46.

Fig. 38, Plate XI. is a representation of Holmes's Comet
in the same field as the Great Nebula in Andromedse (31 M.),
enlarged from a photograph taken by E. E. Barnard on
Nov. 10, 1892.

(11.) BROOKS'S SECOND PERIODICAL COMET (1889, v.).

The comet discovered by Brooks on July 6, 1889, is interest-
ing both in itself and as regards its orbit. When first seen it
was rather faint and had a short wide tail, and did not undergo
any great change of appearance during the remainder of the
month, but on Aug. 1 it was found to have thrown off frag-
ments 4 in number. Two of these were very faint and soon
disappeared, but the other 2 brighter ones were miniatures of
the main body, each having a nucleus and a tail. For a while
they moved away from their primary. In 3 weeks the nearer
companion ceased to recede; it then expanded, and finally
disappeared. The farther companion continued to recede
until it had become (a month from discovery) brighter than
the parent comet. In another month it began to approach its
parent; its head swelling and becoming faint, the tail dis-
appearing. Altogether, the history of these transformations
is very curious.' The small inclination and direct motion
noticed when its orbit was determined suggested that the
comet was a periodical one, and this fact was soon established.
The orbit at aphelion approaches very closely to that of
Jupiter, and Chandler found that in 1886 the comet's distance
from the planet did not exceed -£Gib of the Earth's mean
distance from the Sun, from which fact it has been assumed
that the comet's orbit acquired its present ellipticity then and
on that account : and that Jupiter or Jupiter's Satellites had
had some share in fracturing the comet as above described.

This comet returned in 1896, and was found by Javelle at
Nice on June 20, as a single comet, no companions or frag-

r Ast. Nach., vol. cxxii, No. 2919, Aug. 29, 1889 ; Ibid., No. 2922, Sept. 6,
1889.

VI. Periodic Comets of Short Periods. 79

ments being visible. But it is possible that this failure may
have been clue to the faintness of the nucleus at that appari-
tion. The observations did not favour the probability of the
comet being identical with Lexell's, as was first thought. In
1903 this comet was again in perihelion and was discovered
by Aitken at Lick on Aug. 20. The greatest diameter was
about 3', and the brilliancy that of a 14th mag. star. The
steady diminution in the brightness of this comet is so marked
that it is hazardous to predict its future. At its last return
in 1903 it was so much more faint than at its previous appari-
tions that it was only visible in some of our largest telescopes.
It is due to return in 1910 and again in 1917. Shall we see
it 1 Perhaps we shall : perhaps we shall not. But if we do
see it on either of these 2 occasions it will still be leading
a threatened life, for in 1921 it will again approach very close
to Jupiter, and very likely that may end its career ; or if not,
it will certainly lead to a serious transformation of its orbit.

(12.) FAYE'S COMET.

After Encke's Comet, Faye's may be regarded as the best-
known and most regular of the short-period comets. It was
discovered by Faye at the Paris Observatory on Nov. 22, 1843,
in the constellation Orion. It exhibited a bright nucleus with
a short tail, but was never sufficiently brilliant to be seen by
the naked eye. That the comet's path was an ellipse, and the
comet itself therefore a periodical one, seems to have been soon
suspected by several astronomers, but to Le Verrier is due the
credit of having exhaustively investigated its orbit. He
showed that the comet came into our system at least as far
back as the year 1747, when it suffered much perturbation
from Jupiter ; and that its next perihelion passage would
occur on April 3, 1851. It was rediscovered by Challis on
Nov. 28, 1850. O. Struve described it under the date of
Jan. 24, 1851, as having a diameter of 24". During the whole
of this apparition it scarcely exhibited any signs of nucleus or
tail. Faye's Comet returned in due course, and was seen in
1858, 1866, 1873, 1880, 1888, and 1895, but it was missed in

80

The Stoi'y of the Comets.

CHAP.

1903, though it would have been interesting to have ascer-
tained whether the influence of Jupiter had accelerated its
return by 4 months, as Stromgren calculated would have been
the case. The orbit of Faye's Comet is the least eccentric
of all the short-period orbits. A sketch of Faye's Comet by
Tempel will be found on Plate X.

(13.) TUTTLE'S COMET.

This comet was first seen by Mechaiii on Jan 9, 1790. It
was only followed for a fortnight. On Jan. 1 1 Messier could
see only a confused nebulosity without any indications of
a nucleus. It was not reobserved until its return in 1858, on
Jan. 4 of which year it was discovered by H. P. Tuttle at
Harvard College Observatory, Cambridge, U.S., passing its
perihelion on Feb. 23. It was found to be a periodical comet
with a period of about 13^ years. It returned again to peri-
helion and was seen in Nov. 1871, August 1885, and May 1899.
Its orbit has been thoroughly investigated by Rahts.

SECOND GROUP. COMETS PROBABLY PERIODIC.

No.

Name of Comet.

Period :
Years.

Last
Observed
Return.

Next Ex-
pected
Return.

1

Barnard's First (1884, ii.)

5.5

1884

1911

2

Brooks's First (1886, iv.)

6-3

1886

1909

3
4

Barnard's Second (1891, iv.)
Spitaler's (1890, vii.)

6.3
6-3

1891
1890

1911
1910

5

Perrine's (1896, vii.') . ... ...

6-4

1896

1910

6

Kopff's(1906. iv.)

6-6

1906

1913

7

Giacobini's Second (1900, iii.)

6.7

1900

1914

8
9

Swift's Second (1889, vi.)
Borelly's (1905, ii.)

7.0
7.0

1889
1905

1910
1912

10

Swift's First (1885, ii.)

7-2

1885

1913

11
12

Denning's Second (1894, i.)
Metcalf's (1906, vi.)

7-4
7.6

1894
1906

1909
1914

13
14

Denning's First (1881, v.)
Giacobini's First (1896, v.)

8.8
7-9?

1881
1896

1915

9

VI. Periodic Comets of Short Periods. 81

The comets in this group are all recent discoveries, but as
none of them have been seen more than once their claims to
be regarded as permanently attached members of the solar
system must be regarded as in suspense for the present.

(1.) BARNARD'S FIRST PERIODICAL COMET (1884, ii.).

On July 16, 1884, E. E. Barnard, at Nashville, Tennessee,
U.S., using a. 6-inch refractor, discovered a nebulous object
which he thought had a suspicious appearance. Some days
however elapsed ere its cometary character was ascertained
beyond a doubt, by reason of it being found to be moving.
Perrotin described it as exhibiting on Aug. 15, an ill-defined
nebulosity about 1^' in diameter. The ellipticity of the orbit
was soon ascertained. If Berberich's period of 5-49 years is
correct the comet must have approached very near to Mars in
April 1868, and have had its orbit interfered with by that
planet.

This comet should have returned in 1889, but was missed
in that year, and again also in June 1895. It was also missed
in Oct. 1900, though about the time it was expected 25 photo-
graphs were taken over a range of sky covering the comet's
expected position. Nor was it seen in 1906. Whether this
comet should be transferred to the list of " lost " comets
remains for future consideration.

(2.) BROOKS'S FIRST PERIODICAL COMET (1886, iv.).

This comet was discovered by Brooks on May 22, 1886.
It passed its perihelion on June 6. A period of 6-3 years
was assigned to it. It was not seen when expected in 1892,
1899, and 1903, and therefore its continued existence must be
regarded as an unknown quantity. We must see what the
years 1909 and 1910 bring forth.

(3.) BARNARD'S SECOND PERIODICAL COMET (1891, iv.).

The circumstances under which this comet was discovered
by means of a photograph on Oct. 12, 1892, have already
been mentioned. Suffice it to say here that a period of

82 The Story of the Comets. CHAP.

6-3 years was assigned to it. It was expected to return in
April 1898, but was not seen, the position in the heavens
being unfavourable; nor was it seen in 1905, when again
expected to have been in perihelion.

(4.) SPITALER'S COMET (1890, vii.).

Whilst searching for Zona's Comet, which had been dis-
covered at Palermo on Nov. 15, 1890, Spitaler of Vienna
detected a faint nebulous object near the reported place of
Zona's Comet.8 This turned out to be a new comet, and
though the observations were somewhat limited the ellipticity
of its orbit was quite free from doubt, and a period of about
6^ years or less was assigned to it. It was thought that the
comet had only recently entered the Solar System, because in
1887 at its descending node it approached so closely to Jupiter
that its orbit must have been seriously affected. The comet
was calculated to be due to appear again in March 1897, but
it escaped detection, and as the same thing happened in 1903
it must be regarded, at any rate for the present, as lost.

(5.) PERRINE'S COMET (1896, vii.).

On Dec. 8, 1896, Perrine at the Lick Observatory discovered
a small comet which was found to be moving in an elliptic
orbit with a period of 6-44 years. It should have returned
in 1903 and have passed through perihelion in April, and
perhaps did so, but it escaped notice. This was, however, not
to be wondered at, because not only was it near the Sun, but
its estimated brightness was only y^tu of what it was when
the comet was seen for the last time in 1897.

(6.) KOPFF'S COMET (1906, iv.).

On Aug. 26, 1906, Kopff at Heidelberg discovered a small
comet which was found to be revolving in an elliptic orbit
with a period of about 6| years.

'Barnard pointed out the "re- 1° of each other, as a thing which had

mark able coincidence" of 2 comets never happened before, and was never

totally unconnected with each other likely to happen again. (Sidereal

being visible at the same time within Messenger, vol. x, p. 18. Jan. 1891.)

VI. Periodic Comets of Short Periods. 83

(7.) GIACOBINI'S SECOND PERIODICAL COMET (1900, iii.).

On Dec. 20, 1900, Giacobini at Nice discovered a small
comet which was found to be moving in an elliptic orbit with
a period of about 6f years. The elements bear a considerable
resemblance to those of the comets of Wolf and Barnard
(1892, v.). The comet had passed its perihelion when dis-
covered, and its increasing f aintness, and unfavourable position
in the sky, rendered observation of it very difficult towards
the end of the 8 weeks during which it was in view. It was
not seen at its expected return in 1907, so we shall have no
chance of knowing anything more about it until 1914.

(8.) SWIFT'S SECOND PERIODICAL COMET (1889, vi.).

This comet, discovered by L. Swift on Nov. 16. 1889,
presented the ordinary appearance of a telescopic comet
without pronounced nucleus or tail. The ellipticity of its
orbit soon became evident, and a period of about 7 years was
assigned to it. It ought to have returned in 1898 but escaped
notice ; and we can only say now that as the character of its
orbit is so very uncertain no forecast of its future career is
possible.

(9.) BORELLY'S COMET (1905, ii.).

On Dec. 28, 1904, Borelly at Marseilles discovered a small
comet which remained visible for 5 months. Its orbit was
found to be elliptic, with a period of about 7 years. It has
been suggested that this cornet was identical with the Comet
of 1783 (i.), for which a period of 5-9 years was assigned by
C. H. F. Peters. Its expected return in 1911, or 1912, will
be awaited with interest.

(10.) SWIFT'S FIRST PERIODICAL COMET (1885, ii.).

On Aug. 20, 1885, L. Swift detected a faint comet in Pisces
which during its whole period of visibility of about 2 months
was never very conspicuous. Observation soon showed that
the comet was a periodical one, and a strong suspicion was

G2

84 The Story of the Comets. CHAP.

put forth that it was a reappearance of the long-lost comet of
Lexell of 1770. Unfortunately the period and the position
of the orbit are such that no return favourable for observation
can be expected before 1931 ; and it is doubtful whether the
observations of 1895 were sufficiently complete to enable the
character of the orbit to be determined with precision.
The period assigned by Schulhof is 7-19 years.

(11.) DENNING'S SECOND PEKIODICAL COMET (1894, i.).

On March 26, 1894, Denning discovered in Leo Minor a
faint comet which was becoming fainter because the perihelion
passage had occurred as far back as Feb. 9, and the comet
was receding both from the Sun and the Earth. That its
orbit was elliptic, with a period of about 7-| years, was soon
ascertained, but owing to the lack of an adequate number
of observations definitive elements could not be assured.
Schulhof called attention to the fact that the point of nearest
approach between the orbits of the comet and Jupiter coincided
very nearly with the point at which Brorsen's Comet and
Jupiter were nearest one another. This fact was further
emphasised by Hind, who showed that the two comets were
actually very near one another 13 years previously, namely
in April 1881.

This comet awaits further consideration before it can be
regarded as a recognised short-period comet. Although
expected to return in 1901 it was not seen in that year. Nor
in 1909 thus far.

(12.) METCALF'S COMET (1906, vi.).

On Nov. 14, 1906, J. Metcalf at Taunton, Mass., U.S., dis-
covered a very faint comet shining as a 12th mag. star. It
proved to be revolving in an elliptic orbit with a period of
rather more than 7^ years; and to be one of the Jupiter
family of comets. Though the elements resemble those of
the comets of Faye, Wolf, 1892 (v.), 1896 (v.), and 1900 (in.),
identity with any of these is not possible.

VI. Periodic Comets of Short Periods. 85

(13.) DENNING'S FIRST PERIODICAL COMET (1881, v.).

On Oct. 4, 1881, Denning at Bristol discovered a bright
telescopic comet in the constellation Leo. It was circular in
form, about 1' in diameter with a slight central condensation.
It soon became known that its orbit was elliptical, and its
period about 8f years. It was expected to return in 1890
but was not found; the explanation perhaps being that the
expected date of its perihelion passage indicated a path
unfavourable for observation. As it could not be found in
1899 nor in 1907, in both of which years it was due to return
to perihelion, and as its orbit could not be determined very
accurately in 1881 for the lack of sufficient observations, this
comet must for the present at least be set down as "lost".

The elements bear some resemblance to those of the Comet
of 1819, discovered by Blainpain. Winnecke suggested that
the comet seen by Goldschmidt at Paris in May 1855, and
then regarded as perhaps Di Vice's, and Hind's Comet of
1846 (ix.), may both have been apparitions of Denning's
Comet ; but it can only be said of this suggestion that it is at
best a plausible one.

(14.) GIACOBINI'S FIRST PERIODICAL COMET (1896, v.).

Giacobini at Nice on Sept. 4, 1896, whilst searching for
a faint comet discovered by Sperra on Aug. 31, detected
a faint comet in Ophiuchus. It soon became evident that it
was one of short period, but the early observations yielded
very discordant results. In fact the first period obtained
was only 17 months. The comet was not seen in 1903, when
it was expected on the supposition that its period was
6-6 years, according to Ebell's calculation, but the Lick
observations imply a period of 9 years.

CHAPTER VII.
LOST COMETS.

Le.rell's Comet. — Its mysterious disappearance. — Efforts made to identify it with
other Comets. — Biela"s Comet. — Its division into 2 portion*. — Its disappear-
ance.— Di Vim's Comet. — Other supposed Short-period Comets which have
never been seen a second time. — Grischaus Comet. — Helfenzriedd '* Comet. —
Pigotfs Comet. — Blainpains Comet. — Peters's Comet. — Coggia's Comet.

THUS far we have been considering comets which are
either known for a certainty to be revolving in elliptic orbits,
and which have themselves verified the fact by returning
one or more times to our view, or comets, the ellipticity
of whose orbits seems open to no doubt, but which have not
yet fulfilled the predictions which have been made in respect
of them. It now becomes necessary to speak of some comets,
to 3 of which in particular an extraordinary amount of
unsolved mystery attaches.

LBXELL'S COMET.

This comet has already been mentioned,1 but something
more needs to be said in regard to its claims to be considered
a short-period comet.

Astronomers in the present day have to lament the " loss "
of several comets which, at first, were regarded as assured
members of the Solar System, because of the comparative
smallness of their orbits, and the apparent certainty that
their periods of revolution were under 10 years, but this
loss is not unprecedented, and the comet which we have now
to consider is not only the oldest, but in some senses the most
notable instance which can be adduced of a " lost " comet.

On June 14, 1770, Messier at Paris discovered a fairly

11 See pp. 17, 39, 79, 84 (ante).

CHAP. VII. Lost Comets. 87

bright comet with a stellar nucleus. On July 1 it had greatly
increased in apparent size, and though no tail was visible
the nebulosity surrounding the nucleus had swollen to a
diameter 2-|-0 or more than five times the diameter of the
Moon— dimensions still remaining wholly unprecedented. The
comet remained visible altogether for nearly 4 months,
and disappeared from view owing to the increase of its dis-
tance from the Earth, it having become when last seen very
small and faint. Various attempts were made by different
astronomers, but unsuccessfully, to reconcile the observations
with a parabolic orbit. Some years later Lexell, a member of
the Academy of Sciences at St. Petersburg, investigated anew
the orbit, which he found for a certainty to be elliptic ; and
that the comet's period was about 5^ years. Supposing this
had been correct the comet should have returned to perihelion
in 1776, but it was not seen, though Messier and others were
constantly on the watch for new comets generally.

Lexell's researches disclosed to him the fact that in May,
1767, the comet had passed very close to Jupiter, and had
remained for a considerable time exposed to the influence of
this planet. Lexell thought that this fact had exercised such
a material effect on what had been the previous orbit of the
comet as to transform that orbit into the short-period ellipse
which he found represented the comet's movements in the
year 1770. With the materials before him, Lexell put forth
the suggestion that the comet ought to be seen again in the
Summer of 1781, after again passing under the powerful
influence of Jupiter in the Summer of 1779. Diligent, but
unsuccessful, search was made for it at the time of its expected
reappearance ; and the conclusion drawn by Lexell was that
as Jupiter in 1767 had driven the comet into its small elliptic
orbit, so in 1779 the same planet had driven the comet out of
its small elliptic orbit into a new one which could not be,
and never has been, traced. It was because of the prolonged
and comprehensive labours of Lexell on this comet that
astronomers have always agreed to attach his name to it.

Nothing more was done in the matter until 1806 when
Burckhardt, an eminent French Mathematician, traversed

88 The Story of the Comets. CHAP.

anew the ground gone over by Lexell, and was able to con-
firm substantially Lexell's conclusions. This remark, how-
ever, more especially applies to what Lexell suggested as to
the influence ol! Jupiter, but Burckhardt varied Lexell's
conclusions by suggesting that after the comet escaped from
the clutches of Jupiter in 1779, its orbit was enlarged to an
ellipse with a period of more than 16 years, and with
a perihelion distance so great that the comet would for ever
be at so great a distance from the Earth that we could never
hope to see it again.

After the lapse of nearly half a century the orbit of Lexell's
Comet was again investigated, and this time by Le Verrier,
in a paper presented to the Academy of Sciences at Paris, in
May, 1848. Le Verrier's calculations in some respects support,
and in others differ from those of his predecessors, but the
questions involved would occupy more space than it is con-
venient to allot to them in these pages. Hind's summary of
them is as follows : — " The final conclusion from Le Verrier's
investigations is that the Comet of 1770 may be considered
lost until it is accidentally rediscovered in the ordinary course
of searching for these bodies, when his formulae will enable
the astronomer to recognise in the new comet that interest-
ing wanderer."

These words were written in 1852, and persistent have
been the efforts of astronomers to find in each new short-
period comet the old Lexell, but the results thus far have
been inconclusive. It remains to be added that Briinnow has
confirmed in part Burckhardt's calculations.

When Lexell's Comet on July 1, 1770, was at its minimum
distance of about 1J millions of miles from the Earth,
the visible diameter of the comet was, as already stated,
2° 23' ; it follows therefore that the true diameter was 60,000
miles.

BIELA'S COMET.

On March 8, 1772, Montaigne at Limoges discovered a comet
which, from the want of suitable instruments, he was unable
properly to observe, or to observe at all after March 20.

VII. Lost Comets. 89

Messier, however, saw it 4 times between March 26 and
April 3.

On Nov. 10, 1805, Pons discovered a comet which was also
found by Bouvard on the 16th. It had a nucleus, and the
diameter of the coma on Nov. 23 was 6' or 7'. On Dec. 8 it
was at its nearest to the Earth, and Olbers saw it without
a telescope. Bessel and others calculated elliptic elements,
and its identity with Montaigne's Comet was suspected,
though no predictions as to when a return might be looked
for again seem to have been ventured on.

On Feb. 27, 1826, an Austrian officer named Biela, at
Josephstadt in Bohemia, discovered a faint comet which
Gambartb found on March 9. The observations extended
over a period of 8 weeks, and it was soon recognized that
not only was the comet's orbit an ellipse of moderate eccen-
tricity ; but that it was the same comet as those observed in
1772 and 1805.

In anticipation of its next return in 1832, investigations
into the orbit were undertaken by Santini, Damoiseau, and
Olbers. Santini found that the comet's period in 1826 was
2455 days, but that the attraction of the Earth, Jupiter, and
Saturn would hasten its return by rather more than 10 days,
and he accordingly fixed the next perihelion passage for Nov.
27, 1832. Damoiseau's investigations yielded much the same
result. In 1828 Olbers called attention to the fact that in
1832 the comet would pass within 20,000 miles of the Earth's
orbit, but that as the Earth would not reach that particular
point till one month after the comet had passed it, no danger
was to be apprehended. Astronomers were quite satisfied as
regards this matter, but their confidence was not shared by
" the man in the street " (to use the hackneyed modern phrase)
who was greatly alarmed lest a collision should take place,
and our globe suffer damage or destruction.

b Certain French writers following tion object to Biela's name the very
Arago persist in calling this comet least they might be expected, to do
"Gambart's", but outside France would be to call it "Montaigne's
Biela's name is universally attached Comet". The association of Gam-
to it. If" the French writers in ques- bart's name with it is indefensible.

90 The Story of the Comets. CHAP.

The comet returned to perihelion in Nov. 1832 within 12
hours of the time predicted by Santini. It was first seen at
Rome on Aug. 23, but owing to its excessive faintness was
not generally observed till two months later.

The next return was calculated to take place on July 13,
1839, but, in consequence of its close proximity to the Sun,
the comet was not seen on that occasion.

Santini continued his researches and fixed on Feb. 11,1 846,
for the next perihelion passage. This was anticipated by
astronomers with great eagerness, because it was foreseen
that the comet would be visible for a considerable period, and
so there would be the chance of obtaining a good body of
observations for correcting the theory of its motion. Di Vico
at Rome discovered it on Nov. 28, 1845, and Galle at Berlin
found it two days later; but it was not generally seen till
the 2nd or 3rd week in December. The striking incident of
the comet breaking up into two portions, alluded to in
a previous chapter,0 deserves further description.

The duplicity of Biela's Comet appears to have been first
seen on Jan. 13, 1846, at Washington, U.S. Three weeks pre-
viously to this, however, Hind remarked a kind of protuberance
towards the North of the nucleus which perhaps may be
regarded as the first sign that something unusual was going
to be developed. Two days after the American observation,
that is to say on Jan. 15, Challis at Cambridge noticed for
the first time the complete severance of the little comet from
the big one. His description of what he saw, and his com-
ments on the occurrence, are so very interesting as to deserve
transcription. He published his notes in a letter to the
President of the Royal Astronomical Society.

" On the evening of Jan. 15, when I first sat down to observe it, I said to
my assistant, ' I see two comets.' However, on altering the focus of the eye-
glass and letting in a little illumination, the smaller of the two comets
appeared to resolve itself into a minute atar, with some haze about it.
I observed the comet that evening but a short time, being in a hurry to
proceed to observations of the new planet. On first catching sight of it this
evening (Jan. 23) I again saw two comets. Clouds immediately afterwards
obscured the comet for half an hour. On resuming my observations I sus-

c See p. 15 (ante).

VII. Lost Comets. 91

pected at first sight that both comets had moved. This suspicion was after-
wards confirmed : the two comets have moved in equal degree, retaining
their relative positions. I compared both with Piazzi, Oh 120, and the motion
of each in 50m was about 1s in R.A. and 10" in N.P.D. What can be the
meaning of this ? Are they two independent comets ? or is it a binary
comet? or does my glass tell a false story? I incline to the opinion that
this is a binary or double comet, on account of my suspicion on Jan. 15.
But I never heard of such a thing. Kepler supposed that a certain comet
separated in two, and for this Pingre said of him, 'aliquando bonus dormitat
Homerus.' I am anxious to know whether other observers have seen the
same thing. In the meanwhile I thought, with the evidence I have, I had
better not delay giving you this information."

In a subsequent letter Professor Challis says : —

" There are certainly two comets. The north preceding is less bright and
of less apparent diameter than the other, and, as seen in the Northumberland
telescope, has a minute stellar nucleus. . . .

" The greater apparent distance between the comets on Jan. 24 is partly
accounted for by their approaching the Earth. I saw the comets on Jan. 25,
but took no observation. The relative positions were apparently unchanged.

" I think it can scarcely be doubted, from the above observations, that the
two comets are not only apparently but really near each other, and that they
are physically connected. When I first saw the smaller, on Jan. 15, it was
faint, and might easily have been overlooked. Noiv it is a very conspicuous
object, and a telescope of moderate power will readily exhibit the most
singular celestial phenomenon that has occurred for many years — a double
comet." d

The comets continued to be observed all through February
and March. On March 24 one only was visible, and on April
22 both had disappeared. To O. Struve on Feb. 21 there
appeared no material connection between the 2 bodies ; but
some days later Maury at Washington saw an arc of light
extending from the large comet to the small one, forming
a sort of bridge between the two. This was when the small
comet was at its brightest. When the large comet had
regained its superiority it threw out new rays, which gave
it the appearance of having 3 tails, each adjacent tail making
an angle of 120° with its neighbour, one of the tails being
the bridge to the small comet.

Maury's words were : —

" No. 2 appears to have thrown a light arch of cometary matter from its
head over to the other : and their tails stretching off below in the field, and
nearly in a parallel direction, gives these 2 objects the singular and beautiful

d Month. Not. B.A.S., vol. vii, p. 73. March 1846.

92 The Story of the Comets. CHAP.

appearance of an arched way in the heavens, through which the stars are
sometimes seen to pass.'' e

The total disappearance of Biela's Comet has now to be
narrated. It returned again to perihelion in Sept. 1852, and
was visible for 3 weeks in the condition of one principal
comet with a baby comet of the same shape travelling along-
side of it. The same reason which prevented it from being
seen in 1839 also caused it to pass undetected in May 1859,
so that its next anticipated return in Jan. 1866 was looked
forward to with much interest. Would it return? Would
the companion comet be there 1 If so, alongside the principal
comet ? or left behind at a greater or less distance ? That
the two would have to be treated as two distinct bodies was
sufficiently shown to be the judgment of astronomers by the
fact that in the sweeping ephemeris issued by Hind for
facilitating their rediscovery in 1859 two independent sets
of elements and positions were given.

But all in vain : neither the big nor the little comet were
seen, nor have they ever been seen since, except, perhaps, in
a totally transformed condition, as to which more anon. It
was calculated that in 1865-6 the comet would be very
favourably placed in the Heavens, and very elaborate search
was made for it, unsuccessfully, at numerous European
observatories/ Astronomers, with one exception, gave up
the matter in despair. The exception was Klinkerfues of
Gottingen. He kept his attention on the subject, and as the
result of his labours he sent on Nov. 30, 1872, to Pogson. at
Madras, a telegram worded as follows : — " JSiela touched Earth
on 27th: Search near Theta Centaur i" The search was
made and with the extraordinary result that a comet was
found. Observations of it were obtained on Dec. 2 and 3,

e Month. Not. R.A.S., vol. vii, p. 91. who said he saw something "cometic-

May 1846. looking" on Nov. 4, 1865, was an

f Some mysterious observations of observer of experience and un-

aileged comets formed a topic of con- doubted good faith. Buckingham,

versation at certain meetings of the whose observation was on Nov. 9,

Royal Astronomical Society in the 1865, had not the same repute as

spring of 1866, but there is no sum- Talmage. (Month. Xot. R.A.S., vol.

cient proof that they related to Biela's xxvi, pp. 241, 271.)
Comet. Talmage, one of the observers

VII. Lost Comets. 93

1872, but bad weather and the advance of twilight prevented
any further observations. Pogson described his comet as
circular ; 75" in diameter and having a bright nucleus with
a bright but distinct spreading tail 8' in length. This
description would not seem to fit in with the description
given of Biela's Comet at previous apparitions, but not much
stress should be laid upon that fact. However, on other
grounds it was the opinion of Bruhns that the comet seen by
Pogson could not possibly be Biela's, but an unknown comet,
which by a remarkable coincidence was in or near the place
where Biela's Comet ought to have been seen.

The question stood and still stands for consideration, '; Why
has Biela's Comet disappeared 1 " The answer to this question
seems now to belong not to the subject of cometary, but to
that of meteoric astronomy, and will be discussed in a separate
chapter.g

Di Vice's COMET.

This also is a comet which has a mysterious history, as to
which questions are constantly cropping up which cannot be
answered.

On Aug. 22, 1844, Di Vico at Rome discovered a telescopic
cornet which, towards the end of the following month, became
visible to the naked eye. With a telescope a bright stellar
nucleus and a short tail were seen. It soon became apparent
that the comet was travelling in an elliptic orbit, to which
Briinnow assigned a period of 1993 days. He calculated
that the comet's next return to perihelion would occur in the
spring of 1850, but that owing to the position of the comet
in its orbit relatively to the Sun for some months, it would
be impossible to see it at a sufficient distance clear of the
Sun's rays.

The next return to perihelion was fixed for Aug. 6, 1855,
and as theory suggested that the comet would be favourably
situated for observation, hopes were entertained that it would
be detected. They were, however, doomed to disappointment ;
and as a matter of fact, the comet has never for a certainty

* See p. 192 (post).

94 The Story of the Comets. CHAP.

been seen since. Bearing in mind its size and brilliancy
(unusual for a short-period comet), its non-appearance since
1844 is a remarkable fact, and one as to which no assured
explanation can be given. Some computations by Le Verrier
seemed to render probable that Di Vice's Comet was identical
with the comet of 1678, and several other identifications have
been suggested, but there is no certainty about any of them.
It is, however, worth mentioning that the elements of Finlay's
Comet (1886, vii.) closely resemble those assigned to Di Vice's
Comet by Briinnow ; but the resemblance appears to be for-
tuitous : that is to say that they are two distinct comets
moving in orbits similar in many respects but not in all.b

On Nov. 20, 1894, E. Swift in California discovered a small
comet, the elements of whose orbit closely resemble the
elements assigned to Di Vice's Comet; and Schulhof and
others are strongly impressed with the idea that the 2 objects
are identical. Future years may help to clear up the matter.
Should the question be decisively settled in the affirmative,
we must assume that the comet is subject to marked changes
of brilliancy. This comet was not seen either in the autumn
of 1900, nor in July, 1907, when it was expected; and it
must be regarded as " lost ", unless it should be found in
Dec. 1912. Its period has been put at 6-4 years.

This chapter may be suitably brought to a close by record-
ing, without entering into much detail, certain comets to
which short periods have been assigned, but as to which
our knowledge remains too imperfect for much to be said.1
These comets are the following: —

Grischau's (1743, i.) Peters's (1846, vi.)

Helfenzrieda's (1766, ii.) Tuttle's (1858, iii.)

Pigott's (1783, i.) Coggia's (1873, vii.)
Blainpain's (1819, iv.)

h Another instance of comets cer- Cooper s Cometic Orbits — two works

tainly different, but moving in orbits which everybody interested in this

which are similar, has been already branch of astronomy ought to possess,

mentioned. See p. 84 (ante). Those who read German will find

1 The reader will find a few brief Galle's Verzeichniss der Cometenbahnen,

particulars in Hind's Comets, or published in 1894, a useful book.

VII. Lost Comets. 95

Grischau's Comet of 1743 (i.), discovered on Feb. 10, 1743,
was very imperfectly observed for only a fortnight. Clausen
assigned to it an elliptic orbit with a period of 5-43 years,
and thought that the comet of 1819 (iv.) might be a return
of it.

Helfenzrieda's Comet of 1766 (ii.) was discovered at Dilleri-
gen on April 1, and remained visible for 6 weeks. It had a tail
3° or 4° long. Burckhardt calculated for it an elliptic orbit,
with a period of 5-0 years, but it has never been seen since.
This is the more remarkable having regard to its size, and
that the duration of its visibility was long enough one might
suppose for the orbit obtained to be open to no doubt.

Pigott's Comet of 1783 (i.), was discovered at York on
Nov. 19. Its orbit was undoubtedly elliptic, and Burckhardt
assigned to it a period of 5-6 years : other computers obtained
a longer period.

Blainpain's Comet of 1819 (iv.) was discovered at Marseilles
on Nov. 28, 1819, and was observed at Milan until Jan. 25,
1820, a length of time fully sufficient to have yielded an
accurate orbit. Encke investigated it and found it decidedly
elliptical with a period of 4-8 years ; but, strange to say, there
have been no modern tidings of the comet.

Peters's Cornet of 1846 (v.) was discovered at Naples on
June 26, and observed there till July 21. Peters and D' Arrest
agree in ascribing to it an elliptic orbit of short period.
Peters's result was 12-8 years with an uncertainty of about
1 year. It was badly placed for observation in 1859 and
1872 : nor was it seen in 1885 or 1898.

Tuttle's Comet of 1858 (iii.) was discovered at Cambridge,
U. S., on May 2. A parabola was supposed at first to satisfy
the observations, but subsequently elliptic elements were ob-
tained, and periods of 5-8 years and 7-5 years were assigned
by Schulhof ; but nothing further is known of the comet.

Coggia's Comet of 1873 (vii.) was the subject of an elaborate
investigation by Weiss, who thought it might be a return of
the comet of 1818 (i.), discovered by Pons on Feb. 23, 1818 ;
but he could not satisfy himself whether its period was 55-8,
18-6, or 6-2 years, though he gave the preference to 6-2 years.

CHAPTER VIII.

PERIODIC COMETS OF LONG PERIODS.

Periodic Comets of between 70 and 80 years. — WestphaVs (1852, iv ).—
Pans s (1812).— Di Vico's (1846, iv.).—Olbers'g (1815).— Brorseng (1847,
v.). — Halley's. — Particulars of each of these Comets. — Return of Ports' s
Comet in 1883 — Observations of it by Trepied and others. — Many comets
no doubt revolving in elliptic orbits, but with periods of hundreds or
thousands of years.— Selected List of some of these. — The Comets 0/1264
and 1556. - The Comets of 1532 and 1661 .

BESIDES the periodic comets mentioned in the last chapter
there are a large number of comets to which periods of far
greater length have been assigned, amounting in many cases
to thousands of years. It is obviously futile to talk about
these as recognised members of the solar system, but there is
a small group of 6 comets which may fairly be regarded as
members of our system, although it must be confessed that
at present only 3 out of the 6 have vindicated their claim
by having appeared a second time. These comets are the
following : —

No.

Name.

Period.

Probable next
Return.

Years.

1

Westphal's (1852, iv.)

67.77

1913

2

Pons's(1812)

70-68

1955

3

Di Vice's (1846, iv.)

73-25

1919

4

Olbers's (1815)

74-05

1960

5

Brorsen's (1847, v.)

74-97

1922

6

Halley's

76-78

1910

It has been suggested that 4 of the above may have
originally constituted a single comet; but independently of

VIII. Periodic Comets of Long Periods. 97

this idea Kirkwood gave reasons why some connection may
exist between Nos. 2 and 3 in the above table.

No. 1 was discovered by Westphal at Gottingen on June 27,
1852 ; and subsequently and independently by Peters at Con-
stantinople. It was described as " pretty bright ", and " above
I/ in extent" — language which does not err by being too
definite.

No. 2 was discovered by the indefatigable Pons on July 20,
1812, being the 16th comet found by him in 10 years. It had
an irregular nebulous form without tail or beard, and was
only visible with the aid of a telescope. Encke having
assigned to it a period of about 70f years the return of the
comet was anticipated about 1 883, and accordingly a sweeping
ephemeris for it was computed by Schulhof and Bossert.
By the aid of this, Brooks in America found it on Sept. 3. It
seems to have exhibited at this visit physical characteristics
differing altogether from anything recorded in 1812, unless
we assume that the observers of that date failed to do justice
to the comet's features. Chandler in America and Schiaparelli
in Italy saw it on several occasions in Sept. 1883, first as a
nebulosity, then as a star, and then as a nebulosity again;
whilst Miiller at Potsdam on Jan. 1, 1884, observed changes
backwards and forwards in magnitude and brightness to the
extent of -^ ths of a magnitude, in 1 f hours. Trepied observed
it daily from Jan. 13 to 18 without noticing anything very
remarkable ; but on Jan. 19 the aspect of the nucleus had so
changed that it was difficult to realise that the same object
was being scrutinised as had been viewed on previous days.
The head then exhibited 3 distinct zones as in Fig. 39.

" The interior and most brilliant zone was almost circular, and remarkable
owing to its milky aspect : it stood out sharply from the adjoining zone and
was of a leaden hue : outside this second zone came the ordinary nebulosity
of the tail, having on the south-west side a parabolic outline.

"The nucleus had undergone a considerable lengthening; it consisted of
2 distinct parts of very different brilliancy united by a very well marked
twisted link (etranglemeni) which occupied almost the centre of the inner
circular zone. The Southern part of the nucleus, which was by far the
brightest, was terminated by an elliptic arc very sharply denned and
tangential to the circumference of the zone ; the Northern part on the
contrary was suddenly cut off at the extremity of the diameter, whose
CHAMBERS H

98

The Story of the Comets.

CHAP.

direction coincided with that of the axis of the nucleus. This direction was
almost exactly identical with that of the axis of the tail. On January 20
the nucleus and the nebulosity which surrounded it had resumed their
accustomed aspect. I observed the comet up till the end of the 1st week in
February without being able to detect any changes like that which happened
on Jan. 19. It follows therefore that the transformations in question must
have run their course in a few hours ; and herein consists the remarkable
character of the whole phenomenon."

Fig. 39.

PONS'S COMET : JAN. 19, 1884. (Trepied.}

Trdpied's observations accord generally with those of
Perrotin, Thollon, and Rayet, which apply, however, to the
date of Jan. 13. It would appear from these various observa-
tions, taken together, that this comet underwent changes
which, whatever their nature, were in some sense periodic —
a circumstance additionally remarkable.

VIII. Periodic Comets of Long Periods. 99

No. 3. — Di Vice's Comet of 1846 (iv.) was discovered on
Feb. 28, and though his name is commonly attached to it, it
seems to have been found by Bond at Cambridge, U.S., two
days previously. It was under observation for more than
two months, and there does not appear to be any reason for
doubting that its period is much about what is stated in the
Table, or between 72 and 73 years.

No. 4. — Olbers's Comet of 1815 was discovered by him at
Bremen on March 6, and was last observed on Aug. 26. Bessel
made the periodic time in 1815 to be 74-04 years, whilst Nicolai
made it 74-79 years. Bessel calculated the perturbations
•onward to the next perihelion, and found that the comet's
return would be so expedited that the perihelion passage
would take place about February 9, 1887. This forecast was
not, however, borne out by the result, for the comet did not
pass its perihelion till Oct. 8. The comet was discovered by
Brooks in America on Aug. 24 and remained visible for 2
months.

No. 5. — Brorsen's long-period Comet was found on July 20,
1847, at Altona, and was observed for 8 weeks. Its orbit
was investigated by several astronomers, and there seems no
reason to doubt the accuracy of the period assigned by
D'Arrest, namely, nearly 75 years.

The 6th and last comet enumerated in the Table prefixed
to this chapter, namely, "Halley's", is one of such extreme
interest, and has such a long history, extending back as it does
for nearly or quite 2000 years, that it must have a chapter to
itself ; and this chapter will be completed by a brief enumera-
tion of some of the comets whose periods have, with some
reasonable probability, been estimated at hundreds or thousands
of years. But after all said and done, however near the truth
these figures may, or may not, be, it is obvious that they have
little practical interest for us except as showing the possi-
bilities of calculation as applied to comets. However, for
what they are worth here are some of them : —

H 2

100 The Story of the Comets. CHAP.

Comet's Date.

Period in Years.

The Comet of 1864 ii.)

2,800,000

The Comet of 18<>3 (i.)

1,840,000

The Comet of 1882 (i.)

400,000

The Comet of 1 845 ii.~)

115,000

The Comet of 1844 ii.x

102,050

The Comet of 1898 (x.)

87,000

The Comet of 1780 (i.)

75,314

The Comet of 1847 (iv.)

43,954

The Comet of 1877 (iii

28,000

The Comet of 1680

15,864

The Comet of 1874 (iii.1

13,918

The Comet of 1840 (IP

13,864

It would be a waste of space to extend this Table, but of
course there are many comets on record with periods less
than 10,000 years and more than 80 years.

Amongst the long-period comets enrolled as such by
astronomers the Comet of 1264 seems to deserve some special
mention, and for a threefold reason : its magnificent brilliancy;
the great amount of time which has been dedicated to the
study of its orbit during a century and a half, beginning with
Halley and ending with Hind ; and the extreme disappoint-
ment experienced both by astronomers and the public at its
non-appearance in 1858 or in the years immediately following,
for it was assumed that another very grand comet which
appeared in 3556 was identical with it.

Making every allowance for the extravagance of the
language often employed in bygone centuries to describe
comets, it seems extremely probable that both these comets
must have been comets of remarkable brilliancy. The observa-
tions of both have been handed down with unusual perspicuity
both by Chinese and European writers; and the numerous
and experienced computers who have worked at their orbits
had no difficulty in arriving at the conclusion that the comets
were identical, and that the period was something between
302 and 308 years. Reckoning backwards, Hind also found

VIII. Periodic Comets of Long Periods. 101

that, allowing for planetary perturbations, a great comet which
appeared in 975 followed a path which might be very closely
represented by a comet with the elements of the comet of
1556. Hind even went one step further, and concluded that
" a comet observed in China in the summer of 683, and one
seen in the circumpolar heavens A. D. 104, present some indica-
tions of identity with the grand comet of 1264 and 1556, but
the accounts we possess are too vague to admit of anything
more than conjecture ".a

It can well be imagined that this comet left its mark 011
history. In 1264 it was considered to have announced the
death of Pope Urban IV ; whilst, having regard to the par-
ticular time when it appeared in 1556, it was considered to
have brought about the abdication of the Emperor Charles V.
This, however, must be regarded as an exploded romance,
because the Emperor abdicated in 1555, but a thrilling story
was long in circulation based on materials gathered (I will not
say invented) by the great French cometographer Pingre.

There are some comets moving in elliptic orbits which can-
not conveniently be grouped, but which should be mentioned.
One of these is the Comet of 1661, which has been supposed
to be identical with the Comet of 1532. Halley and Mechain
both computed the orbit of the latter comet, as did Mechain
that of the Comet of 1661. The orbits obtained for the Comet
of 1532 differed materially, and Olbers, who made an inde-
pendent calculation, upheld Halley's results, and assigned to
the comet a period of 129 years. If this conclusion was well
founded the comet should have returned about 1789 or 1790,
but it is not known to have done so. However, to this nega-
tive evidence too much importance must not be attached.
It remains to be seen whether the comet reappears in or about
the year 1918. Sir J. Herschel picked out a number of other
comets as supplying coincidences of interval backwards, but
it does not appear that he carried out any rigorous investiga-
tions respecting them.

a The Comets, p. 123.

CHABTEK IX.
HALLEY'S COMET.

Halley's Comet by far the most interesting of the Periodic Comets. — Sir I. New-
ton and the Comet of 1680. — This Comet the first to which the theory of
Gravitation was applied. — The Comet of 1682. — Description of it by various
observers. — Luminous Sector seen by Hevelius. — Halley's application to it,
and the Comets of 1531 and 1607, of Newton's mathematical researches. —
He finds the elements of the three very similar, and suspects the three comets-
are really one. — With a probable period of 75 years. — Suspects the disturbing
influence of planets on Comets. — Of Jupiter's influence especially. —U alley* s
final conclusion that the Comet would reappear in 1758. — Preparations by
Clairaut and Lalande to receive it. — The Comet found by an amateur named
Palitzsch near Dresden. — Some account of this man. — The Comet generally
observed in Europe. — Trick played by Delisle on Messier. — Return of the
Comet in 1835. — Great preparations by Mathematicians to receive it. —
These specially took into account planetary perturbations. — Predicted date
of perihelion passage. — The Comet discovered by telescopes as expected.—
Some particulars of the observations. — The past history of Halley's Comet
traced back through many centuries. — Researches of Hind. — Confirmed in
the main by Crommelin and Cowell. — Some quotations from old Chroniclers.
— Observations by the Chinese of great value. — Halley's Comet in 1066. —
Figured in the Bayeux Tapestry. — The Comet's various returns ascertained
with certainty backwards to B. c. 250.

THE comet known as Halley's may be regarded as by far
the most interesting of all the comets recorded in history ;
and this, whether looked at from the standpoint of the
historian or of the astronomer ; and having regard to the
position which it has occupied during many centuries in
the public mind, and is likely also to occupy during the year
1910, it will be worth while to review its career in some
detail.

A few years after the advent of the celebrated Comet of
1680 Sir I. Newton published his epoch-making Principia,
in which he first promulgated the Theory of Gravitation, and
applied it to the orbit of that comet. He explained the

Fie. 39 a.

Plate XI «.

EDMUND HALLEY.

CHAP. IX.

Halley s Comet.

103

method of determining by geometrical construction the visible
portion of the path of the comet, and invited astronomers to
apply these principles to the comets on record, or some of
them. He considered that it was very probable that some
comets might move in elongated ellipses which near perihelion
would scarcely be distinguishable from parabolas ; and he
even thought that the recent Comet of 1680 a might be moving
in an ellipse the circuit of which would occupy about 575 years.

Fig. 40.

MEDAL STRUCK IN GERMANY TO ALLAY THE TERROR CAUSED
BY THE COMET OF 1680.

"The star threatens evil things: Only Trust!
God will make things turn to good."

Halley (to whose exertions the publication of the Principia
was in great measure due, for he bore the labour and expense
of its publication) also took this view. Although we now
know that the period of that comet is measured by thousands
of years Halley 's investigations were not without good fruit,
for they may be said to have drawn him into a systematic

a It should perhaps be mentioned,
if only in the humble form of a foot-
note, that this Comet of 1680 gave
rise to a special sensation some years
after its appearance. A clergyman
named Winston, best known to fame
as the editor of a standard edition of
the works of the Jewish historian
Josephus, published in 1696 A New
Theory of the Earth, in which he sought
to explain by the supposed agency of
a comet the geological records of the
Book of Genesis. At first he based his
theory upon nothing except his own
imagination, but when he found that

Halley had (erroneously) ascribed
to the Comet of 1680 a periodic
time of 575 years, Winston, working
backwards the materials of history
and fable within his reach, ascribed
the Noachian Deluge to one of the
regular visits of this comet, and
added that it would be by a future
visit of the same comet that the
prophecies of Holy Scripture as to
the destruction of the World would
be made good. I think this is suf-
ficient to indicate the value of the
Rev. William Whiston's labours in
the field of comets.

104 The Story of the Comets. CHAP.

study of cometary orbits which ended, as we shall soon see, in
a famous and remarkable prediction. He undertook to
investigate the movements of a large number of the comets
previously recorded, with the view of ascertaining whether
any, and if so which, of them had appeared to follow the
same path. Careful investigation soon showed that the orbits
of the Comets of 1531 and 1607 were similar to each other,
and similar in fact to that of the Comet of 1682 seen by
himself.

On Aug. 15, 1682, Flamsteed's assistant at the Royal
Observatory, Greenwich, discovered a comet. A few days
later the diameter of the head was about 2' of arc, and it had
a tail 5° long. On Aug. 21 the tail had become 10° long.
Flamsteed's observations seem not to have extended beyond
Sept. 9, when the head had become enfeebled and was scarcely
visible in the twilight. Halley himself, however, saw it
a day later. Picard at Paris found the comet on Aug. 26,
the head shining as a star of mag. 2. On Aug. 29 the tail
was curved, the concavity being on the E. side. On Sept. 11
the head was so confused that it was only with difficulty that
a luminous point could be perceived. Picard's last observation
was on Sept. 12. Hevelius at Dantzig says that the comet
was bright at the end of Aug. and could be seen all night
with a tail from 12° to 16° long. In large telescopes a nucleus
of an oval or gibbous form was constantly noticed. It was
also remarked that on many occasions the direction of the
tail was not exactly from the Sun, as P. Apian's observations
of earlier comets suggested.1* The most remarkable of the
matters mentioned by Hevelius was the existence of a luminous
ray, or sector, thrown out from the nucleus into the tail. He
has left behind a picture of this which is reproduced in the
opposite woodcut (Fig. 41).

This ray was first noted about Sept. 8, and even making
every allowance for the vagaries of the astronomical artists
of the 17th century it is impossible to doubt that some sort of
ray of light was thrown out from the head of the comet, and
we shall presently see that the same thing happened in 1835.

b See p. 22 (ante}.

IX. Halley s Comet. 105

The Comet of 1682 seems to have been very generally
observed by all the principal astronomers of the time, and
amongst those who have left behind them observations we
find the familiar names of Kirch of Leipzig, and Montanari of
Padua; and the less familiar names of Zimmermann of
Nuremberg and Baert of Toulon.

Halley, making use of Flamsteed's observations, calculated
parabolic elements of the comet in accordance with the rules
laid down by Newton ; and having also determined by the
same methods the orbits of the Comets of 1531 and 1607 he
was immediately struck by their similarity, and suspected
from^ '• the like situation of their planes and perihelions that
the comets which appeared in the years 1531, 1607, and 168.2

HALLEY' s COMET, JAN. 9, 1683 (N. s.), SHEWING LUMINOUS SECTOR.
(Drawn by Hevdius.^

were one and the same comet that had made three revolutions
in its elliptical orbit". This supposition implied that the
comet's period was somewhere about 7 5-| years. There were
nevertheless 2 circumstances which might be supposed to
offer some difficulty, inasmuch as it appeared that the intervals
between the successive returns were not precisely equal ; and
that the inclination of the orbit was not exactly the same in
each case. Halley, however, " with a degree of sagacity
which, considering the state of knowledge at the time, cannot
fail to excite unqualified admiration, observed that it was
natural to suppose that the same causes which disturbed the
planetary motions would likewise act on comets " ; in other
words, that the attraction of the planets might be expected to

c Annus climactericus, p. 1 39.

106 The Story of the Comets. CHAP.

exercise some disturbing influence on the motions of comets.
The discrepancies already pointed out in the orbits of the
3 comets just mentioned made Halley hesitate for some time
as to their identity, and in his memoir on comets published in
1705d he only, as it were, hinted his suspicions. Eventually,
however, he became much more confident. This appears to
have been the result of his investigations as to the probable
influence of the Planet Jupiter. He found that between 1607
and 1682 the comet had passed so near Jupiter that its velocity
in its orbit must have been considerably augmented, and its
period, consequently, shortened ; he was therefore induced to
predict its return about the end of 1758 or the beginning of
1759. Finally, when he had matured his labours, he thus
plaintively wrote on the subject : — " Wherefore if it should
return according to our prediction about the year 1758
impartial posterity will not refuse to acknowledge that this
was first discovered by an Englishman." On this Hind
judiciously remarked as follows : — " Nor has posterity at-
tempted to deprive him of the honours which were his due ;
his discovery forms an epoch, and an important one, in the
history of Astronomy. His calculations must have been
laborious in the extreme. He assures us himself they were
' prodigiously ' long and troublesome ; but the zeal which
induced such an amount of exertion was well rewarded by
the final result." e

Halley 's first formal announcement of his expectations
concerning his cornet appears to have been in the paper pre-
sented to the Royal Society, in which the following passage
(in Latin) occurs : — " Now many things lead me to believe
that the Comet of the year 1531, observed by Apian, is the
same as that which, in the year 1607, was described by
Kepler and Longomontanus, and which I saw and observed

d Phil. Trans., vol. xxiv, pp. 1882- afterwards it was not republished but

99, 1704-5. The memoir is entitled a new version was prepared, in D.

Astronomice Cometicw Synopsis. It was Gregory's Elements of Physical and Geo-

translated from Latin into English metrical Astronomy, 2 vols. London,

first of all in John Harris's Lexicon 1726.

Technicum, vol. ii, London, 1710, and e Hind, The Comets, p. 38.

IX. Halleys Comet. 107

myself, at its return in 1682. All the elements agree,
except that there is an inequality in the times of revolution ;
but this is not so great that it cannot be attributed to

o

physical causes. For example, the motion of Saturn is so
disturbed by the other planets, and especially by Jupiter,
that his periodic time is uncertain, to the extent of several
days. How much more liable to such perturbations is
a comet which recedes to a distance nearly 4 times greater
than Saturn, and a slight increase in whose velocity could
change its orbit from an ellipse to a parabola ? The identity
of these comets is confirmed by the fact that in the summer
of the year 1456 a comet was seen, which passed in a retro-
grade direction between the Earth and the Sun, in nearly the
same manner; and although it was not observed astronomically,
yet, from its period and path, I infer that it was the same
comet as that of the years 1531, 1607, and 1682. I may,
therefore, with confidence predict its return in the year 1758.
If this prediction be fulfilled, there is no reason to doubt that
the other comets will return."

Halley died in 1742 and was buried in the Churchyard of
St. Margaret's, Lee, not far from Greenwich, and it has lately
(1909) been announced that the Admiralty have decided to
repair his tomb at the public expense, no descendants of his
being known. The original top slab with an inscription was
illegally removed to the Greenwich Observatory in 1854.
Let us hope that it will be now restored, or a new one with
the original inscription put in place.

As years rolled on and 1758 began to draw near astronomers
naturally recalled Halley's prediction, and thought it worth
while to rely upon it in making preparations to receive the
comet. The French astronomer Clairaut was the man who
took the matter most seriously in hand, the important question
being to ascertain the extent of the perturbations of the
comet's orbit likely to be brought about by the influence of
Jupiter and Saturn. The history of the steps taken cannot
be better described than in the words of Hind: — "Having-
devised a method which appeared to possess all needful
accuracy, he commenced, in conjunction with the celebrated

108

The Story of the Comets.

CHAP.

Lalande and a lady, Madame Lepaute, the immense mass of
calculations requisite for the complete attainment of his
object. It was necessary to compute the distances of the
comet from the disturbing planets, Jupiter and Saturn, not
only from 1682, when it was last observed, but for the previous
revolution, or for a space of more than 150 years. This of
itself was a most laborious business ; but the succeeding part
of the work, where the disturbing force of each planet was
required for this long period, involved much greater and more
intricate calculations. Lalande minutely describes the plan
adopted : for 6 months they computed from morning to night,
with but little intermission, even, as he states, at meals ; and
he mentions, as one result of this assiduous attention to the

Fig. 42.

PLAN OF THE ORBIT OF HALLEY S COMET COMPARED WITH THE
ORBITS OF CERTAIN PLANETS.

work, that he contracted an illness which remained upon him
during the rest of his life. Madame Lepaute 's assistance is
said to have been so important, that without it they would
hardly have completed the investigation before the comet re-
appeared. However, by dint of these extraordinaiy exertions,
the calculations were brought to a close."

On Nov. 14, 1758, Clairaut announced in a paper addressed
to the Academy of Sciences at Paris, that by the influence of
Jupiter the comet would be retarded 518 days, and that to
this must be added 100 days due to Saturn, so that the total
retardation would be 618 days, or about 20 months. On this
basis he predicted April 13, 1759, as the date of the coming

IX. Halleys Comet. 109

perihelion passage. He did this, however, with a slight
reservation, because, having neglected some small quantities
in the calculations, he thought that the date named might be
wrong by a month either way. When Clairaut's conclusions
became generally known the astronomers of Europe were
soon on the qui vive, and several of them carried out a pro-
longed watch of the heavens, which in Messier's case extended
over the whole of the year 1758. It was not destined,
however, that a professional astronomer should be the first to
detect the comet on its anticipated return ; that honour was
reserved for an amateur student of Nature, said to have been
a farmer by occupation, named Palitzsch, living at Prohlis,
near Dresden, who saw it on the night of Christmas Day,
1758, with a telescope of 8 ft. focus. Some curious mis-
statements respecting this man have been widely circulated,
and perhaps even to this day may be considered as still in
circulation. Baron De Zach, who was personally acquainted
with the man, has left on record some interesting particulars
relating to him. Farmer though he was, he was a diligent
student of Astronomy ; was possessed of a strong sight ; and
was in the habit of scrutinising the heavens with the naked
eye, which fact may perhaps have given rise to the statement
that he found Halley's Comet with the naked eye at a time
when the professional astronomers were vainly searching for
it with their telescopes. The first man of note to find the
comet appears to have been Messier, who caught it in bad
weather on Jan. 21, and observed it regularly for 3 weeks.
It seems that Delisle, then Director of the Observatory of
Paris, would not allow Messier (who was his assistant) to
disclose the fact of his discovery, and he remained the only
professed astronomer who saw the comet before it became lost
in the Sun's rays at its perihelion passage. Let us hope that
Hind's remark on this incident will remain true : — " Such
a discreditable and selfish concealment of an interesting
discovery is not likely to sully again the annals of Astronomy."
This strange conduct of Delisle's carried its own punishment,
for when Messier's observations were afterwards published
some members of the French Academy treated them as

110 The Story of the Comets. CHAP.

forgeries ; but there appears to have been no sufficient ground
for this imputation, and it was eventually withdrawn. It
remains to be added that the comet passed its perihelion on
March 12, 1759 — just within the limits assigned by Clairaut.
After that, it was seen throughout Europe during April and
May, although to the best advantage only in the Southern
Hemisphere. On May 5, it had a tail 47° long.

Previous to the return of the comet in 1835, numerous
preparations were made to receive it.

The great progress which had been made since 1759 in
telescopes and methods of observation, especially under the
inspiration of the two Herschels, Sir William and Sir John ;
and also in mathematics applied to celestial motions by men
like Laplace, Lalande, La Grange, and other eminent foreigners,
rendered the study of the movements of this comet, both
visually when the time came to see it, and mathematically,
before that time, a problem of great interest. As long before
the expected return of the comet as 1817 the Academy of
Sciences at Turin offered a prize, open to astronomers of all
nations, for an Essay on the perturbations undergone by the
comet since 1759. Baron Damoiseau of Paris gained the
prize, and his Essay was published in 1820 in the Memoirs of
the Turin Academy, vol. xxiv. The following outline of the
researches of Damoiseau and others is epitomised from Hind's
statement of them.

After calculating the effects of the attraction of the larger
planets he fixed Nov. 4, 1835, at 8 p.m., Paris M.T., as the
moment of the comet's perihelion passage. After Damoiseau,
another Frenchman, Count de Ponte'coulant, took up the
matter, more or less on the same lines as Damoiseau, with
the result that his date for the perihelion was rather more
than a week later than Damoiseau's, or to be exact, he fixed
the perihelion for Nov. 12, at 17b, Paris M.T. The investi-
gations both of Damoiseau and Ponte'coulant were in a sense
defective because both of them had omitted to take account
of certain of the planets whose influence counted for some-
thing. Accordingly a German computer, Rosenberger of
Halle, started on a new and independent investigation.

IX. Halley's Comet. Ill

Damoiseau and Ponte'coulant had neither of them attached
sufficient importance to the actual ellipse described by the
comet in 1759. As 1759 was the starting-point from which
to determine the probabilities of 1835, it was important to
obtain the most accurate knowledge possible of the condition
of things in 1759. Rosenberger thought that he ought to go
much further back than either Damoiseau or Pontecoulant
had done, and that it would be impossible to make a trust-
worthy prediction for 1835 unless he began as far back as
1682, and computed the perturbations between 1682 and
1759, and so led up to 1835.

In performing his task Rosenberger took account not only
of the influence of the great planets Jupiter, Saturn, and
Uranus, but also of the smaller influence exerted by Venus,
the Earth, and Mars, with some allowance also for Encke's
supposed Resisting Medium as affecting his (Encke's) Comet.
Omitting in the first instance any allowance for a Resisting
Medium Rosenberger named Nov. 11, at Oh Paris M.T., for
the comet's perihelion passage. If an allowance supposed to
be appropriate were made for a Resisting Medium the
perihelion would fall about a week earlier or on Nov. 3 at 19h
Paris M.T. The actual effects on the comet's motion ascribed
to the smaller planets were as follows : — the Earth 15| days,
Venus about 5^ days, and Mercury and Mars together nearly
1 day. By these periods of time (namely, about 22 days)
added together, Rosenberger considered that the comet's
return would be hastened. " Professor Rosenberger's investi-
gation is remarkable for its extraordinary completeness, for
the pains taken to include every possible source of perturbation,
without regard to the numerical labour, and for the masterly
manner in which the whole of the vast work was conducted."

Rosenberger, however, had a competitor in his own country.
Lehmann thought there was room for another discussion of
the elements and disturbances of the orbit of Halley's Comet,
and though his labours were not in some respects as meritorious
as Rosenberger's they have a merit of their own, inasmuch
that Lehmann took the year 1607 as his starting-point. On
this basis he fixed Nov. 26 for the perihelion passage, which

112 The Story of the Comets. CHAP.

was a date a fortnight later than Pontdcoulant's and 3 \veeks
later than Damoiseau's/

As early as Dec. 1834, astronomers began to direct their
telescopes to that part of the heavens where it was supposed
that the comet would be first seen. Olbers had thrown out
suggestions that it might be possible to find the comet between
Dec. 1834 and April 1835, notwithstanding that the perihelion
passage would not take place till many months later. Olbers's
suggestion was largely acted upon, for it applied to the
constellations Auriga and Taurus which were very favourably
placed for observation in Northern and Central Europe, while
Sir John Herschel at the Cape employed his great reflector
also in sweeping for the anxiously expected body. But all
these early efforts were wasted.

It was not until the morning of Aug. 6 that the first
view of the comet was obtained, and the fortunate man was
Dumouchel, director of the Collegio Romano Observatory at
Rome, using a powerful telescope in a splendid climate. The
comet was close to the computed place which was near £ Tauri.
It was a faint, misty object, discernible with difficulty, and
moonlight and unfavourable weather during the next follow-
ing days delayed the comet's discovery elsewhere. However,
on Aug. .21 W. Struve found it with the great telescope at
Dorpat, and during the following week it was seen at all the
principal English and Continental observatories. The Dorpat
observations showed that Rosenberger's predicted place was
only 7' of arc wrong in R. A. and 17' in Declination. The
effect of this error was to retard the perihelion passage till
Nov. 16, or 5 days later than the epoch fixed upon by
Rosenberger. During the first 3 weeks of Sept. the comet's
brightness gradually increased, and on the 23rd it was seen
with the naked eye by Struve, and on the following day with
the naked eye by Kaiser at Leyden, though it was not

f The distracting effect of planetary at 74 years 5| months (the shortest

perturbations on the movements of on record), in 1222 and 1301 it was

comets is shown by the fact that 79 years 2 months (the longest on

whereas the interval between the record, the next longest having been

perihelion passages of Halley's Comet 1066 and 1145).
in 1835 and 1910 is to be set down

IX. Halleys Comet. 113

sufficiently bright to attract general notice till the end of the
month. A tail was first seen on Sept. 24, and during October
the comet was more or less conspicuous, but observers differed
very much in their estimates of the maximum length of the
tail. The average of the estimates would seem to have been
from 20° to 25°, though one observer did put it at 30°. The
comet was lost to view about the time of perihelion passage
disappearing below the S. W. horizon, and having, according
to most accounts, lost its tail before the comet itself was lost
to view. After the perihelion passage the comet was again
observed at some of the southern observatories of Europe and
at the Cape of Good Hope from Dec. 30 to the middle of
May 1836.

Smyth's observations deserve to be quoted. Under the dates
of Oct. 10 and 11 he wrote : -

"Oct. 10. The Comet in this evening's examination presented an
extraordinary phenomenon. The brush, fan, or gleam of light, before
mentioned, was clearly perceptible issuing from the nucleus, which was now
about 17" in diameter and shooting into the coma ; the glances at times
being very strong, and of a different aspect from the other parts of the
luminosity. On viewing this appearance it was impossible not to recall the
strange drawing of the ' luminous sector' which is given by Hevelius in his
Annus Climactericus as the representation of Halley's Comet in 1682 and
which had been considered as a distortion. [See Fig. 41, ante.']

" Oct. 11. . . . The tail was increasing in length and brightness, and,
what was most remarkable, in the opposite direction to it there proceeded
from the coma across the nucleus a luminous band or lucid sector more than
60" or 70" in length and about 25" broad, with 2 obtuse-angled rays, the
nucleus being its central point. The light of this singular object was more
brilliant than the other parts of the nebulosity, and considerably more so
than the tail ; it was therefore amazingly distinct. On applying as much
magnifying power as it would bear, the nucleus appeared to be rather gibbous
than perfectly round : but with the strange sector impinging it was a
question of difficulty."

The observations made at the Cape of Good Hope by
Maclear disclose a succession of phenomena somewhat calcu-
lated to chill the enthusiasm of any who may be expecting
great things of Halley's Comet in 1910. However, that is no
reason for suppressing the observations. Though the peri-
helion passage took place on Nov. 15, 1835, Maclear did not
begin to see the comet, or at any rate to record what he saw,

CHAMBERS

114 The Story of the Comets. CHAP.

till Jan. 24, 1836. He says that the alteration of form which
had taken place between the beginning of November and this
date, during which interval the comet had been lost in the
Sun's rays, was " remarkable ", and he goes on as follows : —

"Jan. 24. To the naked eye it was as bright as a star of the 2-3 or 3rd
magnitude : there was no tail. In the 14-feet reflector, it presented an
opaque, circular, planetary disc, tolerably well defined, encompassed by
a delicately bright coma or halo, which was likewise circular.

"Crossing the disc in a direction not deviating much from parallelism with
the equator, appeared an oblong, elliptical body, distinguished from the rest
of the disc by its superior whiteness, and a semblance of greater density.
The diameter of the disc measured 2' 11" ; of the coma, 8' 12".

" On the 25th, the circularity of the preceding limb of the cometary disc
was partially broken, its dimensions were increased, the elongated portion
was better marked, and its foHowing end was brighter than the preceding.

" On the 26th, the halo had diminished, and the dimensions of the disc,
or body, as it should now be called, were further increased. A spot like
a nucleus could be occasionally seen in the brighter end of the oblong
portion.

" On the 28th, the halo or coma had vanished. The nucleus was distinct,
like a faint small star in the following end of the oblong portion. The
dimensions of the body had greatly increased, while the intensity of its light
had proportionately diminished. The general outline of the cometary body
seemed approximating to a parabolic curve, the preceding end of which
might be represented by conceiving the tail, as seen before the perihelion
passage, abruptly separated from the head, leaving a serrated or ragged out-
line. The oblong portion with the nucleus resembled a small comet inclosed
in the body of a larger one.

"On the 30th, the body was rather more elongated. A line drawn trans-
versely through the nucleus measured 11' 42", being 5 times the diameter
on the 24th ; or 29 times the area of a circle of which 2' 11" is the diameter.
But the visible area of the whole body on the 30th could not be less than
35 times that of the 24th, excluding the halo. The nucleus was nearer to
the S. than to the N. side by 32".

"Throughout the succeeding three months the coma went on increasing,
until the outline finally became so faint as to be lost in the surrounding
darkness, leaving a blind, nebulous blotch with a bright centre enveloping
the nucleus of variable brightness, depending on moonlight or the state of
the atmosphere, and variable distance.'' *

The physical appearance of Halley's Comet at the 1835
apparition seems to have been in many respects very remark-
able, and, did the statements made not emanate from some of
the most distinguished astronomers of the time, it might be
permissible to distrust them. It is impossible, however, to

* Mem. R.A.S., vol. x, p. 92. 1837.

IX. Hattey's Comet. 115

distrust anything stated by such men of skill and high
character as Bessel, J. Herschel, W. Struve, and Maclear.
Struve compared the appearance of the nucleus about the
end of the first week of October to a fan-shaped flame
emanating from a bright point ; and subsequently to a red-
hot coal of oblong form. On Oct. 12 it appeared like the
stream of fire which issues from the mouth of a cannon at
a discharge and when the sparks are driven backwards by

Fig. 43.

HALLEY'S COMET, 1835, OCT. 11. (Smyth.')

a strong wind. At moments the flame was thought to be in
motion, or exhibiting scintillations similar to those of an
Aurora Borealis. A second small flame forming a great angle
with the principal one was also remarked. On Nov. 5 the
nebulosity independently of the flames (two of them being
visible) had a remarkable arched form somewhat resembling
a " powder horn ". These phenomena, under different and
varying names, were seen and commented upon by other
astronomers, British and foreign. The annexed sketch by

116

The Story of the Comets.

CHAP.

Admiral Smyth would seem to represent fairly well all the
remarks made by the various astronomers just cited.

I have given these details respecting Halley's Comet in
1835 at some length, thinking that they might be useful as
hints to observers as to what to look for in 1910.h

Before proceeding to deal with the preparations which have
been made against the return of Halley's Comet in 1910, it
will be interesting to consider what we know of the history
of this comet anterior to the apparitions already mentioned.
Halley, we have seen, satisfactorily traced back his comet to
1531, but since his time it has been traced very much farther
backwards, through a range indeed of some 14 centuries or
more, first by the labours of Hind/ and Laugier,k and quite
recently by those of Cowell and Crommelin 1 confirming Hind
for the most part, and enlarging his results. The years in
which identification may be regarded as more or less certain
are the following m : —

Year.

Interval in Years.

Year.

Interval in Years.

B. C. 11-8

77-8

989.7

76-5

A. D. 66-0

75-1

1066.2

79-0

141-2

77-2

1145-3

77-6

218-2

77-0

1222.9

79-3

295-2

78-6

1301-8

77-0

373-8

77-6

1378-8

77-5

451-5

79-3

1455.4

75-2

530-8

76-5

1531-6

76-1

607-3

77.5

1607-8

74-9

684-8

75.6

1G82-7

76.5

760-4

76-8

1759-2

76.7

837-2

75-0

1835-8

74-5?

912-2

77-4

1910.3 ?

b Drawings by Bessel will be found
in the Ast. Nach., vol. xiii, Nos. 300-2.
Feb. 10, 1836. Reference may also
be made to the Memoirs of the Astro-
nomical Society, vol. x (drawings by
C. P. Smyth); Sir J. Herschel's
Results of Astronomical Observations at
the Cape of Good Hope; and Struve's

Beobachtungen des Halkyschen Kometen.

1 The Comets, p. 50 et seq.

k Comptes Rendus, vol. xxiii, p. 183.
1846.

1 Month. Not. R.A.S., vol. Ixviii.
1908. (Five separate papers, at pp.
Ill, 173, 375,510, 665.)

m This table is from Hind, but

IX. Halleijs Comet. 117

Co well and Crommelin have found themselves justified in
adding to this table, backwards, the years B. c. 87 (May) and
240 (May); with no identification possible for the inter-
mediate return in June, 163 B.C., though comets are vaguely
mentioned in the years 166 and 165.

We owe the observations which have made these identifica-
tions possible mainly to Chinese records, supplemented, more or
less, by European monastic chroniclers of various sorts and
kinds, and by a few private authors. It would be tedious to
transcribe any of the originals of these, even in an abridged
form ; indeed, in point of fact their language is already generally
so curt as to be incapable of abridgement, so a concise digest is
all that will be offered to the reader and this will be often
given in the language of Hind n and chronologically backwards.

Halley surmised that the great Comet of 1456 was identical
with his, and Pingre' converted Halley's suspicion into a
certainty. This comet was described by the Chinese as having
had a tail 60° long, and a head which at one time was round,
and the size of a bull's eye, the tail being like a peacock's !

At the preceding return in 1378 the 'comet was observed
both in Europe and China ; but it does not appear to have
been as bright as in 1456.

In 1301 a great comet is mentioned by nearly all the
historians of the period. It was seen as far North as Iceland.
It exhibited a bright and extensive tail which stretched across
a considerable part of the heavens. Hind rejected the
European observations of 1301, finding them to be of no good
compared with the Chinese observations which proved con-
sistent— a reversal of 20th-century preferences !

The previous apparition was for some time a matter of
doubt. Hind treated as Halley's a comet which appeared in
July 1223, and was regarded as the precursor of the death of

altered where necessary to embrace vol. xxiii, p. 183. 1846.) Nor should

the researches of Cowell and Crom- the labours of Pingre and Burck-

melin. It should here be mentioned hardt be forgotten in this connection,

that some share of credit for these " Month. Not. B.A.S., vol. x, p. 61,

identifications is due to the French Jan. 1850 : The Comets, pp. 50-57.
astronomer Laugier. (Comptes Rendus,

118 The Story of the Comets. CHAP.

Philip Augustus, King of France. The records are vague
and inadequate ; and Cowell and Crommelin have given the
preference to a comet which was seen in August and September
1222 and which passed its perihelion probably in September.
The Waverley Abbey Annalist says that in the months named
a fine star of the 1st magnitude, with a large tail, appeared.
When first seen it was near the place where the Sun sets in
December. The Chinaman Ma-tuoan-lin says that on Sept. 25
it came from rj Bootis. The tail was 30 cubits long, and the
comet perished in two months. The question of the identi-
fication of one of these comets with Halley's is one of the few
instances in which Cowell and Crommelin have dissented from
Hind's identifications by deciding in favour of the Comet of
1222 in preference to Hind's 1223.

In April and May 1145 the European and Chinese chroniclers
record a comet with a tail 10° long, whose course among the
stars from the end of April to the beginning of July is stated
by Hind to have been perfectly in accord with the computed
path of Halley's Comet, supposing the perihelion passage to
have taken place about the 3rd week in April. The Chinese
accounts seem to speak of the July Comet as being different
from the April and May one, but whether this was so or not
cannot be determined with any certainty. Hind seemed to
regard the two to be one and the same.

In the April of the year 1066, the year in which the
Norman Conquest took place, a remarkable comet attracted
the attention of all Europe. In England it was viewed with
especial alarm and the success of the Norman invasion and
the death of Harold were attributed to the comet's baneful
influence. Zonares, the Greek historian, in his account of the
reign of the Emperor Constantirius Ducas (whose death
occurred in May 1067) describes a comet which was as large as
the full moon, and at first was without a tail, on the appearance
of which, it (which presumably means the head) diminished in
size. This transformation accords with the Chinese accounts,
which describe the comet's path among the stars in Chinese
fashion with great elaboration. The Chinese say that this
object was visible for 67 days, after which "the star, the

IX.

Halleys Comet.

119

120 The Story of the Comets. CHAI\

vapour, and the comet" all disappeared. It seems fairly
certain that this was Halley's Comet. At any rate it was
immortalised in the famous Bayeux Tapestry, as will be seen
from the annexed plate. [Plate XII.]

In 989 a comet was observed in China which is mentioned
also by several Anglo-Saxon writers. Burckhardt, the French
computer, investigated its orbit and found that the elements
bore a considerable resemblance to those of Halley's Comet.
The perihelion passage was found to have occurred about
Sept. 12.

Halley's Comet certainly appeared in 912, but there were
2 comets in this year and Cowell and Crommelin differ from
Hind in the identification, Hind selecting the earlier one and
Cowell and Crommelin the later one, which appeared in the
autumn.

Halley's Comet should have appeared in 837. There cer-
tainly was a comet in this year, but a comparison of the
European and Chinese accounts, taken literally, imply that
there were 2 comets in this year, one in perihelion in February
and the other in April. The latter would seem to have been
a most imposing object, but in Hind's opinion it could not
have been Halley's Comet. The Chinese records indeed imply
that there was a third or even a fourth comet in that year, in
the months of June and September, but we need not discuss
this question, which probably involves some misconceptions
and which does not concern us in discussing Halley's Comet.

A comet appeared in 760, which without any doubt what-
ever was Halley's. It is recorded in detail both by European
and Chinese annalists, and the orbit has been calculated and
identified by Laugier. By European writers we are told that
a comet like a great beam and very brilliant was observed
in the 20th year of an Emperor Constantine, first in the E.
and then in the W., for about 30 days. The Chinese gave it
a visibility of 2 months. Laugier calculated the perihelion to
have occurred on June 11.

In 684 the Chinese record a comet observed in the W. in
September and October. Hind pointed out that this state-
ment would accord with the course of Halley's Comet when

IX.

Halleys Comet.

121

the perihelion occurs about the middle of October, and, as the
epoch for the reappearance of the comet is about what it should
be, there is " a fair probability " in favour of the identity.

A comet observed by the Chinese in the constellations
Auriga, Ursa Major, and Scorpio in 608, was regarded by
Hind as probably Halley's, who said that the track assigned

Fig. 45.

HALLEY'S COMET, 684. (From the Nuremberg Chronicle.) "

would harmonise with a perihelion passage occurring about
Nov. 1. Cowell and Crommelin, however, identified the Comet
of 607 (i.) as Halley's.

The previous return should have occurred about 530. There
was a comet in that year, and none of the few circumstances
connected with it recorded by the European chroniclers are

0 This engraving and Plate XII
suggest that mediaeval artists were
given to " terminological inexacti-
tudes '' like many of their successors.
As regards Plate XII J. C. Bruce,
the editor of The Bayevx Tapestry
elucidated, says : — " This drawing is
remarkable as furnishing us with the
earliest representation we have of
these bodies." It requires a little
interpretation. The picture is sup-

posed to represent Harold in a state
of dire alarm on his throne, whilst
his people are huddled together
pointing with their fingers at the
fearful portent in the sky, the birds
even being upset at the sight. The
legend over the picture " Isti mirant
stella " records the popular feeling.
Underneath we are asked to take
notice of the ships of the invader.

122 The Story of the Comets. CHAP.

contradictory to the theory which implies that the comet was
Halley's. The Chinese records are silent as regards this year.

A comet appeared in 451, as to which there is little doubt
that it was Halley's, according to the investigations of Laugier.
It was seen in Europe about the time of the celebrated battle
of Chalons, when the Roman general Aetius defeated Attila,
the leader of the Huns, who had been ravaging central Europe.
In China the comet was observed from the middle of May till
the middle of July during which period it moved from the
Pleiades into Leo and Virgo, a track which agrees with the
path which Halley's Comet would have followed if its peri-
helion passage took place on July 3.

In 373 the Chinese annals record a comet in Ophiuchus
in October, which Hind thought would fit in with the probable
position of Halley's Comet if the perihelion passage took place
about the beginning of November. But another Chinese
authority records a comet much earlier in the year, namely
in March and April, which must have been visible all through
the summer if it were the same as the October comet.

In 295 there was a comet observed in China, the identity of
which with Halley's Hind thought to be " nearly certain ".
It seems to have been visible in May after perihelion passage
at the commencement of April.

In the year 218 a large comet is recorded both by European
and Chinese chroniclers. Dion Cassius describes it as a very
fearful star with a tail extending from the W. towards the E.
The Chinese catalogue of Ma-tuan-lin gives it a path exactly
in agreement with the path which would be followed by
Halley's Comet when the perihelion falls about the first week
in April. The description given is that it was " pointed and
bright ".

In 141 the Chinese observed a comet in March and April,
" 6 or 7 cubits long " and of a bluish- white colour. The
elements of a comet following a path such as that described
in some detail by the Chinese annalist would not be widely
different from those of Halley's Comet ; and the comet is the
only one recorded about this epoch.

The preceding apparition should have taken place either

IX. Hallcys Comet. 123

in the summer of 65 or in the following winter of 65-66.
The Chinese record 2 comets : one in July 65 which remained
visible for 56 days, and the other in February 66 which
remained visible 50 days.

Hind suggested that most likely the last-named was
Halley's Comet, if the perihelion passage took place at the
end of January, and Cowell and Crommelin have definitely
confirmed this. Not improbably this comet was the sword-
shaped sign recorded as having hung over the city of
Jerusalem before the commencement of the war which
terminated in the destruction of the Holy City. Josephus
says that several prodigies announced the destruction of
Jerusalem : — " Amongst other warnings, a comet, of the kind
called Xiphias, because their tails appear to represent the
blade of a sword, was seen above the city for the space of
a whole yearp." Josephus rebuked his countrymen for
listening to false prophets while so notable a sign was in the
heavens.

Dion Cassius mentions a comet which seemed to be
suspended over the city of Rome before the death of Agrippa.
The date would be B.C. 11. The path of this comet was
recorded in great detail by the Chinese, and Hind thought
that the records afforded "the most satisfactory proof that
they belonged to the Comet of Hal ley ". The 3rd week in
October was suggested for the perihelion passage. The
comet was lost in the Sun's rays 56 days after its discovery.

Cowell and Crommelin have made systematic efforts to
trace Halley's Comet back further, and with some success,
and it is not beyond the bounds of possibility that further
identification will reward research because the Chinese records
go back for six centuries before the Christian era, and besides
them there exists a sprinkling of European observations,
although all these latter are very much lacking both in
precision of language and precision of dates.

The danger of jumping at conclusions in the case of
astronomy (as indeed in everything else) is painfully shown

9 Bella Jud<eorum, lib. vi, § 5.

124 The Story of the Comets. CHAP.

by an article in the Edinburgh Review of April 1835 (vol.
Ixvi, p. 91).

The writer, primed with the knowledge that the period of
Halley's Comet was then 75 years, and not knowing that it
was not always 75 years, looked through a catalogue of
previous comets and ticked off the following, separated by
intervals of 75 years or multiples thereof, as apparitions of
Halley's Comet, namely : 1456, 1380, 1305, 1230, 1005, 930,
550, 399, 323 A.D. and 130 B.C. We now know that every
one of these identifications except the first was wrong ! The
attraction exercised by the planets was ignored by the
writer !

The reader will remember that in anticipation of the
return of Halley's Comet, both in 1759 and in 1835, great
preparations were made by astronomers for the comet with
the view of its being discovered at as early a date as
possible, and of learning beforehand its probable path through
the heavens. I do not think it can be said that anything
like such extensive preparations have been made by mathe-
matical astronomers for the return of 1910; even the date
of its perihelion passage has not been predicted as confidently
as one might have expected, and certainly might have
wished. Seemingly, however, this will occur about the middle
of April, and on that assumption, if the comet is discovered as
early as December 1909, it will be an evening star up to the
beginning of March, about which time it will be lost in the
Sun's rays. Passing round the Sun it will reappear on
the other side and will become a morning star. It will then
be approaching the Earth, and will be nearest to us about
May 18. As it will then be in the morning twilight it seems
hopeless to expect that we shall see it as the magnificent
object which it is evident that our forefathers must have
seen at many of its previous apparitions, let alone the
unsolved problem whether it is a rule that cornets deteriorate
in brilliancy after every apparition.*1

q In Appendix IV. there will be July 1910, calculated partly by Crom-
found an Ephemeris of the comet melin and partly by D. Smart : to
for the months, November 1909 to which I have added a statement of

IX. Halleys Comet.

As early as Dec. 22, 1908, an American astronomer,
O. J. Lee, at the Yerkes Observatory, Chicago, commenced
a photographic search for Halley's Comet. Its then position,
according to Seagrave (confirmed by Co well and Crommelin's
independent Ephemeris), was R. A. 6h 3™ and Decl. 11° 26. As
no sign of the anxiously-expected object could be found Lee
concluded that it was too small for his telescope, and must
have been less bright than a 17th mag. star.

the comet's path among the constella- date 2| years different from the date

tions. Angstrom of Upsala in 1862, named by Pontecoulant, namely,

taking up Hind's identifications, April, 1910. (Nova Ada Societatis

startled astronomers by predicting Scientiarum Upsaliensis, vol. iv, N.S.,

that the comet would return at a 1863.)

CHAPTER X.

REMARKABLE COMETS.

Suggested list of those which deserve the name. — The Great Comet of 1811. —
The Great Comet of 1843. — The Great Comet O/1858. — Evidence to enable
these three Comets to be compared. — The Great Comet 0/1861. — The Comet
of 1862 (iii.).— The Comet of 1874 (iii.).— The Comet of 1880 (i.).— The
Great Comet of 1882 (iii.). — Peculiarities of its orbit. — The Comet of
1887 (\.}.—SawerthaVs Comet of 1888 (i.).— The Comet 0/1901 (i.).

THE comets which might be included in a list with the
adjective " remarkable " attached to it are very numerous ;
and I shall for the most part treat the word " remarkable "
as applying rather to naked-eye peculiarities and splendour
than to physical peculiarities revealed only by the use of the
telescope. I must therefore limit myself to a selection,
premising that Grant included the following as proper to
be classed as " remarkable " : —

1066
1106
1145
1265
1378
1402
1456

1531
1556
1577
1607
1618
1661
1680

]682
1689
1729
1744
1759
1769
1811

1823
1835
1843
1858
1861

Grant's list was, if I remember right, put forth in a lecture
which he gave at the Royal Institution in 1870, and the
additions which should be made to it to represent the period
1870-1909 are singularly few, the chief of them being
the Comet of 1874 (iii.), best known as Coggia's Comet; and
the Comets of 1881 (iii.), and 1882 (iii.); but the large comets
which appeared in the Southern hemisphere in 1880 (i.),
1887 (i.), and 1901 (i.) have some claim to notice. By the

CHAP. X. Remarkable Comets. 127

law of averages a good bright comet is now more than
overdue, and it remains to be seen whether Halley's, when
it attains its brightest developement in 1910, will come up
to the required standard.

The extravagant language used by the old writers, and
the bizarre character of the drawings which they have left
behind them, render it doubtful how far it is wise to attempt
to reproduce either their words or their pictures. I will
therefore start no farther back than the middle of the 18th
century in my endeavour to present the reader with authentic
information and authentic pictures of some comets of special
importance.

Although it is commonly considered that Donati's Comet
of 1858 (presently to be described) is the most beautiful
(though by no means the largest) on record, I cannot help
thinking that De Che'seaux's Comet of 1744, with its many and
very large tails, should receive the palm for striking beauty.
The recorded descriptions of these tails are, however, not very
detailed.

This comet was long under a cloud (metaphorically), because
nobody seemed inclined to believe that the only drawing and
description of it, with its 6 tails, known till recently to be
extant, could be true, depending as it was supposed to do on the
testimony of one man, and he of no particular astronomical
standing, whilst other astronomers of repute mentioned the
comet but made no allusion to its many tails. However,
all distrust of this man's honesty must now be regarded
as unreservedly withdrawn, ample confirmatory testimony
having been brought to light as recently as 1864.

The circumstances under which this came about are suffi-
ciently curious. Winnecke, in the year named, unearthed at
St. Petersburg some records in MS. by the French astronomer
Delisle, in which the fact of this comet having had several
tails was clearly stated. He also found in an anonymous
pamphlet printed at Berlin in 1744, and edited, it would
seem, by the well-known mathematician L. Euler, a very
detailed description of the comet and its multiple tail, fully
confirmatory of De Che'seaux's account, and written by a

128 The Story of the Comets. CHAP.

lady member of a well-known German astronomical family,
Fraulein Margaretha Kirch.a

De Chdseaux has left the following description (translated
from the French) of this comet : —

"It appears certain from all the observations up to March 1, that if this
comet had appeared under more favourable circumstances, e. g. in the middle
of a night instead of so near the setting Sun, and also clear of moonlight,
it would have been a more striking comet than had ever been known, alike
from the size of its head, and from the length of its tail, which up to this
time had been simply double ; but something much more surprising was
in store for us. The sky was quite overcast from the 1st to the 7th of March,
but on this last-named day the clouds became broken and gave us some
hope of seeing the comet's tail. I prepared myself for seeing over again
just about what I had seen during the closing days of February. At
4 o'clock on the morning of March 8, I went downstairs with a friend into
the garden with the East facing us. This friend walking in front of me
startled me by saying that instead of 2 tails there were 5. I hardly
believed him, but after having passed from behind several buildings which
had partly concealed the Eastern horizon from me, I did indeed see 5
tails in the form of whitish rays lying one above the other obliquely above
the horizon up to a height of 22°, and of about the same breadth in all.
These rays were each about 4° in width, but they became narrower towards
their lower extremities. Their edges were sufficiently distinct and rectilinear.
Each ray was made up of 3 bands ; the middle one was darker, and
double the width of the bands forming the edges. ' These last named
resembled precisely the brightest portions of the Milky Way between
Antinous and Sagittarius, and between Ophiuchus and Scorpio. The
interval between the chief rays was dark like the rest of the sky ; however,
at the bottom there was some luminosity resembling that at the extremity
of these rays, as if we were looking at the tips of other rays of shorter
length.11 Besides these 5 tails edged by white bands there was a sixth
in which one noticed no bands, perhaps because it was low down. This
sixth tail joined to the 10 brighter bands of the others presented the
appearance of there being 11 rays in allc."

De Cheseaux goes on to make some comments which seem
rather intended as a reply to certain persons who had
criticised unfavourably the idea that the object which they
had been looking at was really a comet. After referring

» All this story is fully set out by minor tails besides De Che'seaux's 5.
J. W. L. Dreyer in the Copernicus ° These details do not quite har-

Magazine, vol. iii, p. 104, 1884, ac- monise, it will be noticed, with the

companied by diagrams. engraving, but they appear to belong

b This surmise was founded on to the date of March 7-8, whilst the

fact, for the picture given by the engraving appears intended to apply

writer quoted above in Copernicus to 2 nights combined,
shows clearly that there were several

Fig. 46.

Plate XIII.

itte, ttMf* ^qu '&U&a,f>aru- its nmt&r 9«J 7 out- 'S/e^fiic 8 ate y Mars 2.1 '44
• I'fytuUii&s- cerate. ' \ . \ if' / / /

*" \\\ \ \ \\ ; /

* \ \ v \ ' i ' ' /

i e'a c&fes&U; \ ' \ v \ i / / / / /

I'^r/s,^,,*,. ~,~~ V * ' * • .t.ii

iw urt* fin* pwj rwjc. v cwts LCJJ ui&ttfluttfr f/as^ \ ^ ^

•A Utfrei rvy attir tsrusU pourne, p>a.} unktrtvufer ^ >v \ .)
'jMWif It4 cGnAttltfitifinA du-Dcnuynifi,,()it \ \ \

, /.A itvb fits, fjy*?r*rj.j*r*r3-*. /itJjt/afjSA s^atJfA

Figure <^ ta^uun ^e-la. Com
4 ta,tigne noire, represent*
OnAmtirqtUl)a.nj'celteiJiyw-e Us
eti/MUMjUts eColks a. l^gard

•maii on ria. p<u jugi devoir l&> didZi.
3«rf UtfreA rvy - "

., ,,

tU, eC Lei. main, ocudetiCcUe. dtc
eC iui*. pas-tit, de, to. Vcrye. It
L'hiuSt fief observations

Tat.V.

to. Cett- de, to. Comete. <jui eCoit
I'hortfon.

THE GREAT COMET OF 1744. March 7.
(Drawn by De Chvseanx.}

X. Remarkable Comets. 129

to the fact that 18 persons had seen the comet at Lausanne
and several at Berne, but that bad weather had pre-
vented any observations at Geneva or Paris, he says: —
" Astronomers must judge for themselves whether the pheno-
menon described was that of a celestial body ; and if it could
have been possible that any merely atmospheric phenomenon
could have maintained steadily during 24 hours its con-
dition unchanged, its size and colour the same, its position
with respect to the fixed stars the same, and have participated
with them in the diurnal movement." De Cheseaux reckons
his 24 hours from the night of March 7-8 to the following
night of March 8-9, after which he never saw the comet
again. He adds that "the sky was very serene without
the least cloud or haze, and that both Sun and Moon, (to
one or other of which only could the phenomenon be ascribed
if it was only atmospheric,) were both of them too far away
from the point of convergence of the tails." He then offers
some further remarks directed to show that if the rays were
tails of a comet, which had its head below the horizon,
everything would be explained satisfactorily.

The Comet of 1811 (i.) is one of the most celebrated of
modern times.* It was discovered by Flaugergues at Viviers
on March 26, 1811, and was last seen by Wisniewski at
Neu-Tscherkask in the south of Russia on Aug. 17, 1812,
a visibility of 17 months — a period then unprecedented.
It was a result of this long visibility that, owing to the
Earth's annual motion, the comet twice disappeared in the
Sun's rays, and twice reappeared after having been in
conjunction with the Sun. In the autumnal months of
1811 it shone very conspicuously with a bright nucleus and
tail, which became visible soon after sunset and continued
visible throughout the night for many weeks, owing to its
high northern declination. The extreme length of the tail
is dated for the 1st week in October, and was about 25°, with
a breadth of about 6°.

d This comet attracted the atten- omens were drawn from it. (See
tion of Napoleon in connection with p. 205, post.")
his invasion of Russia, and divers
CHAMBERS X

130 The Story of the Comets. CHAP.

Previously to this, in August, the tail, according to Bouvard,
was divided into two branches which were nearly at a right
angle to each other. Sir W. Herschel paid particular attention
to this comet, and his observations are of great value. He
states that it had a well-defined planetary disc by way of
nucleus, which was involved in the nebulosity forming the
head. From this measurement he calculated that the diameter

Fig. 47.

THE GREAT COMET OF 1811.

of the nucleus was 428 miles. When examined with high
powers the stellar character of the nucleus disappeared, and
the light was spread, though not uniformly. The nucleus had
a ruddy hue, but the surrounding nebulosity was of a bluish-
green tinge.0 The real length of the tail about the middle of
Oct. was upwards of 100,000,000 miles, and its breadth about

8 rhiL Trans., vol. cii, pp. 118, 119, 121. 1812.

X. Remarkable Comets. 131

15,000,000 miles. This comet is undoubtedly a periodical one.
Argelander, whose investigation of the orbit is the most
complete, assigned to it a period of 3065 years, subject to
an uncertainty of only 43 years/ The aphelion distance is
14 times that of Neptune, or, say, 40,000,000,000 miles.

The comet of 1811 obtained in Western Europe, and
especially in Great Britain, fame of a very un-astronomical
character. Its year of appearance was also the year of an
unusually celebrated port wine vintage in Portugal, and
"Comet Wine" figured for a long period of years, first of
all in the price-lists of wine merchants, and afterwards in
the cellar books of many private houses, and finally in the
advertisements of auction sales. The last such advertise-
ment which I remember to have seen appeared in the Times
somewhere in the "Eighties", so the wine and the label
thereof lasted long.

The Comet of 1843 (i.) was another very celebrated comet,
and I once came upon the following remarks made by one
who had seen Donati's Comet of 1858, as well as that of 1843,
and was able to compare the one with the other. General
J. A. Ewart wrote thus of the comet of 1843 : —

" It was during our passage from the Cape of Good Hope to the Equator,
and when not far from St. Helena, that we first came in sight of the great
comet of 1843. In the first instance a small portion of the tail only was
visible, at right angles to the horizon ; but night after night as we sailed
along, it gradually became larger and larger, till at last up came the head,
or nucleus, as I ought properly to call it. It was a grand and wonderful
sight, for the comet now extended the extraordinary distance of one-third
of the heavens, the nucleus being, perhaps, about the size of the planet
Venus." g

General Ewart thus speaks of Donati's Comet of 1858,
which will be described on a later page : —

'•'A very large comet made its appearance about this time, and continued
for several weeks to be a magnificent object at night ; it teas, however, nothing
to the one I had seen in the year 1843, when on the other side of the Equator."

Writing from the Cape of Good Hope on Nov. 12, 1843,

1 Berlin. Ast. Jahrbuch, 1825, p. 250.

* The Story of a Soldier's Life, vol. i, p. 75.

K O

132 The Story of the Comets. CHAP. X.

to his friend Admiral Smyth, Mr. (afterwards Sir Thomas)
Maclear said : —

"Of the casual observatory phenomena, the grand Comet of March takes
precedence ; and few of its kind have been so splendid and imposing.
I remember that of 1811 : it was not half so brilliant as the late one."

So far as I know this is the only account which has ever
appeared in print, written by one who had had the chance
of seeing both comets, and was capable of scientifically
appraising them. Sir John Herschel would have seen all
three of these bodies (1811, 1843, 1858), but he does not
appear to have left behind him any remarks on the earliest
one. This may not be extraordinary, seeing that he was
only an Undergraduate at Cambridge, and only aged 19 when
the comet appeared, and that he did not start his astro-
nomical career until 5 years afterwards. The Comet of 1843
was first seen in the Southern Hemisphere in the last week
of February, but nobody can be named as its first discoverer,
because it displayed itself suddenly, and was seen by a
multitude of persons. During the first fortnight in March
it shone with great brilliancy, and the journals of Australian
and New Zealand colonists make many allusions to it. It
was not visible in England until after March 15, when its
splendour had much diminished, but the suddenness with
which it made its appearance to observers in the Northern
Hemisphere, as it had done in the Southern, added not a
little to the interest which it excited. h The general length
of the tail during March, as seen in the Northern Hemisphere,
was about 40°, and its breadth about 1°.

The orbit of this comet is remarkable for its small peri-
helion distance, which according to the most trustworthy
calculation did not exceed about 500,000 miles; and the
immense velocity of the comet in its orbit when near peri-
helion occasioned some extraordinary peculiarities. Thus,
between February 27 and February 28 it described upon its
orbit an arc of no less than 292°. Assuming its true orbit
to be elliptical, as we are entitled to do, this would leave

h Be it remembered that in those graph cables to convey warning of
days there were no submarine tele- things that were going to happen.

Fig. 49.

DONATI'S COMET: OCTOBER 5, 1858.
(Drawn by Pape.}

134 The Story of the Comets. CHAP. X.

only 68° to be described during the time which would elapse
before its next return to perihelion. Various attempts have
been made, without any very definite measure of success,
to identify this comet with others which have gone before ;
but this is a matter which belongs to a previous chapter.1

The Comet of 1858 (vi.). On June 2 in that year G. B.
Donati, of Florence, descried a faint nebulosity slowly
advancing towards the North, and near the star A Leonis.
Owing to its immense distance from the Earth (something
like 240,000,000 miles) great difficulty was experienced in
laying down its orbit. By the middle of August, however
its future course, and the great increase in its brightness
which would take place in September and October, were
clearly foreseen. Up to August it had remained a faint
object, not discernible by the unaided eye. It was dis-
tinguished from ordinary telescopic comets only by the
extreme slowness of its motion (in singular contrast to its
subsequent career), and by the vivid light of its nucleus.
It has well been said that " the latter peculiarity was of itself
prophetic of a splendid destiny ". Traces of a tail were
noticed on August 20. and on August 29 the comet was faintly
perceptible to a keen unaided eye, but it was not until
Sept. 3 that I so saw it. For a few weeks the comet occupied
a Northern position in the Heavens, and it was therefore
seen both in the morning and in the evening. On Sept. 6
a slight curvature of the tail was noticed, which subsequently
became one of its most striking features. On Sept. 17 the
head equalled in brightness a star of the 2nd mag., the length
of the tail being 4°. The comet passed its perihelion on
Sept. 29, and was at its least distance from the Earth
on Oct. 10. Its rapid passage to the Southern Hemisphere
rendered it invisible in Europe after the end of October, but
it was followed at the Santiago-de-Chili and Cape of Good
Hope Observatories for some months afterwards, being last
seen by Sir T. Maclear at the latter place on March 4, 1859."
Its early discovery enabled Astronomers, while it was yet

1 See p. 19 (ante}. Reference should also be made to E. J. Cooper's Cometic
Orbits, pp. 159 69.

Fig. 50.

Plats XV J.

DONATI'S COMET: OCTOBER 9, 1858.
(Drawn by Pape.)

Figs. 51-55.

Plate XVII.

O
O

LU

I

H
li.
O

co

UJ

UJ

^

O
O

CO

CHAP. X. Remarkable Comets. 137

scarcely distinguishable in the telescope, to predict, some
months in advance, its approaching brilliancy, and thus the
comet was observed with all the advantage of previous pre-
paration and anticipation. "The perihelion passage occurred
at the most favourable moment for presenting the comet
to good advantage. When nearest the Earth the direction
of the tail was nearly perpendicular to the line of vision,

Fig. 56.

DONATI'S COMET, 1858, SEPT. 30. (Smyth.)

so that its proportions were seen without foreshortening.
Its situation in the latter part of its course afforded also
a fair sight of the curvature of the train, which seems to
have been exhibited with unusual distinctness, contributing
greatly to the impressive effect of a full-length view." This
comet, though surpassed by many others in size, has not
often been equalled in the intense brilliancy of its nucleus,

138 The Story of the Comets. CHAP.

and the unusual, and, so to speak, artistic conformation of
its tail, which features the absence of the Moon in the early
part of October enabled spectators to view to the very best
advantage. The passage of the comet in front of Arcturus
on Oct. 5 will ever remain treasured in the memory of those

DONATI'S COMET, 1858, PASSING ARCTURUS ON OCT. 5.

who saw it. There is no doubt that Donati's Comet revolves
in an elliptic orbit, the period of which has been variously
estimated at 1879. 2040, and 2138 years, and Kritzinger
thinks it may be identical with a great comet which is
recorded by Seneca as having appeared in B.C. 146, and dated
by the Chinese for the month of August in that year.

X.

Remarkable Comets.

139

The following is a table of the dimensions k of the comet's
nucleus and tail, at the undermentioned dates * : —

Date.

Diameter of Nucleus.

Length of Tail.

1858.
July 19

//

5
6
3

3

1-5

3-0
4-4
2-5

Miles.
= 5600
= 4660
= 1980

= 1280

= 400
800
= 1120
630

2
4
6
5
11
13
19
22
25
33
50
50
60
45

Miles.

= 14,000,000
= 16,000,000
= 19,000,000
*= 12,000,000
= 17,000,000
= 18,000,000
= 26,000,000
= 26,000,000
= 27,000,000
= 33,000,000
= 45,000,000
= 43,000,000
- 51,000,000
= 39,000,000

Aug. 30

Sept. 8

„ 12

„ 23

„ 25

„ 27

„ 28

„ 30 ... . ...

Oct. 2

„ 5

„ G

8

„ 10

„ 12

The head of Donati's Comet deserves some special description
because of the changes which it underwent and which have
already been mentioned m as features which often characterise
very large comets. Bond first noticed, on Sept. 20, envelopes,
2 in number, above the nucleus, the outer one at a distance of
16" above the nucleus, and the inner one about 3". The
outer one disappeared on Sept. 30 at the height of about 1'.
Meanwhile a third had appeared, the one originally second
having gradually expanded so as to take the place of the
first. Seven successive envelopes in all were seen to rise
from the comet, the last one starting on Oct. 20, when all
the others had been dissipated. It was calculated that the

k These measurements must be
read in the light of the caution given
in footnote a on p. 222 (post).

1 G. P. Bond, Math. Month. Mag.,
Boston, U.S., Nov. and Dec. 1858.
Bond subsequently published a mag-

nificent volume of notes and pic-
tures relating to this comet forming
vol. ii of the Annals of the Harvard
College Observatory, Cambridge, Mass.,
1862.
m See p. 30 (ante).

CHAP. X. Remarkable Comets. 141

envelopes moved upward at the general rate of something
like 30 miles an hour. The first one rose to a height of about
18,000 miles, when it wasted away ; but none of the others
reached so far, disappearing at elevations lower and lower,
the last being lost sight of at an elevation of about 6000
miles.

It has been calculated that at perihelion Donati's Comet
travels at a speed of 30 miles a second ; but that at aphelion
its speed is only 234 yards a second.

Few comets excited greater sensation by their sudden
appearance above the horizon than the great Comet of
1861 (No. ii. of that year). It was discovered by J. Tebbutt,
an amateur astronomer, at Windsor, N.S.W., on May 13,
previous to its perihelion passage, which took place on June 11.
Passing from the Southern Hemisphere into the Northern, it
became visible in this country on June 29, though it was not
generally seen until the following evening. It is so rare for
the inhabitants of the British Islands to have a big comet
all their own, as it were, that in this case the multitude
of observers and observations was so great that selection is
difficult.11

A good all-round description was that given by Sir John
Herschel, who observed the comet at his house, " Collingwood,"
Hawk hurst, Kent. He says : —

"The comet, which was first noticed here on Saturday night, June 29, by
a resident in the village of Hawkhurst (who informs me that his attention
was drawn to it by its being taken by some of his family for the Moon
rising), became conspicuously visible on the 30th, when I first observed it.
It then far exceeded in. brightness any comet I have before observed, those
of 1811 and the recent splendid one of 1858 not excepted. Its total light
certainly far surpassed that of any fixed star or planet, except perhaps Venus
at its maximum. The tail extended from its then position, about 8° or 10°
above the horizon, to within 10° or 12° of the Pole-star, and was therefore
about 30° in length. Its greatest breadth, which diminished rapidly in
receding from the head, might be about 5°. Viewed through a good
achromatic, by Peter Dollond, of 2|-inches aperture and 4-feet focal length,
it exhibited a very condensed central light, which might fairly be called
a nucleus ; but, in its then low situation, no other physical peculiarities
could be observed. On the 1st instant it was seen early in the evening,

n By far the most complete account the Month. Not. R.A.S., vol. xxii,
is that by the Rev. T. W. Webb in p. 305. 1862.

142 The Story of the Comets. CHAP. X.

but before I could bring a telescope to bear on it clouds intervened, and
continued till morning twilight. On the 2nd (Tuesday), being now much
better situated for observation, and the night being clear, its appearance
at midnight was truly magnificent. The tail, considerably diminished in
breadth, had shot out to an extravagant length, extending from the place
of the head above o of the Great Bear at least to ir and p Herculis ; that
is to say, about 72°, and perhaps somewhat further. It exhibited no
bifurcation or lateral oifsets, and no curvature like that of the Comet of
1858, but appeared rather as a narrow prolongation of the Northern side
of the broader portion near the comet than as a thinning off of the latter
along a central axis, thus imparting an unsymmetrical aspect to the whole
phenomenon.

" Viewed through a 7-feet Newtonian reflector of 6-inches aperture the
nucleus was uncommonly vivid, and was concentrated in a dense pellet
of not more than 4" or 5" in diameter (about 315 miles). It was round,
and so very little woolly that it might almost have been taken for a small
planet seen through a dense fog ; still so far from sharp definition as to
preclude any idea of its being a solid body. No sparkling or star-light
point could, however, be discerned in its centre with the power used (96),
nor any separation by a darker interval between the nucleus and the
cometic envelope. The gradation of light, though rapid, was continuous.
Neither on this occasion was there any unequivocal appearance of that sort
of fan or sector of light which has been noticed on so many former ones.

"The appearance of the 3rd was nearly similar, but on the 4th the fan,
though feebly, was yet certain ly perceived ; and on the 5th was veiy
distinctly visible. It consisted, however, not in any vividly radiating jet
of light from the nucleus of any well-defined form, but in a crescent-
shaped cap formed by a very delicately graduated condensation of the light
on the side towards the Sun, connected with the nucleus, and what may be
termed the coma (or spherical haze immediately surrounding it), by an
equally delicate gradation of light, very evidently superior in. intensity
to that on the opposite side. Having no micrometer attached, I could only
estimate the distance of the brightest portion of this crescent from the
nucleus at about 7' or 8', corresponding at the then distance of the comet
to about 35,000 miles. On the 4th (Thursday) the tail (preserving all the
characters already described on the 2'-d) passed through a Draconis and
T Herculis, nearly over rj and « Herculis, and was traceable, though with
difficulty, almost up to a Ophiuchi, giving a total length of 80°. The
northern edge of the tail, from a Draconis onwards, was perfectly straight, —
not in the least curved, — which, of course, must be understood with refer-
ence to a great circle of the heavens.

" Viewed, on the 5th, through a doubly refracting prism well achromatised,
no certain indication of polarisation in the light of the nucleus and head
of the comet could be perceived. The two images were distinctly separated,
and revolved round each other with the rotation of the prism without at
least any marked alternating difference of brightness. Calculating on
Mr. Hind's data, the angle between the Sun and Earth and the comet must
then have been 104°, giving an angle of incidence equal to 52°, and obliquity
38°, for a ray supposed to reach the eye after a single reflection from the
cometic matter. This is not an angle unfavourable to polarisation, but

Figs. 59-62.

Plate XIX.

July 8. (TTebft.)

July 2. (Brodie.)

(Cl.ambers.)

July 2. (Brodie.)

THE GREAT COMET OF 1861.

144 The Story of the Comets. CHAP.

the reverse. At 66° of elongation from the Sun (which was that of the
comet on the occasion in question), the blue light of the sky is very
considerably polarised. The constitution of the comet, therefore, is analogous
to that of a cloud ; the light reflected from which, as is well known, at that
(or any other) angle of elongation from the Sun, exhibits no signs of
polarity."

Williams's drawing of the Comet of 1861, reproduced in
Plate XVIII, gave a much more extensive and complex
character to the comet's tail than any of the other drawings
published.

A very interesting point was raised by Hind, and
developed, so to speak, by E. J. Lowe, the well-known
meteorologist. Hind stated that he thought it not only
possible, but even probable, that in the course of Sunday,
June 30, the Earth passed through the tail of the comet
at a distance of perhaps §rds of its length from the nucleus.
The head of the comet was in the Ecliptic at (> p.m. on
June 28, at a distance from the Earth's orbit of about
13,000,000 miles on the inside, its heliocentric longitude
(its longitude seen from the centre of the Sun) being 279°.
The Earth at that moment was rather more than 2° behind
that point, but would arrive there soon after 10 p.m. on
June 30. The tail of a comet is seldom an exact prolonga-
tion of the radius vector, or imaginary line joining the
nucleus with the Sun ; towards its extremity a tail is almost
invariably curved ; or, in other words, the matter composing
it lags behind what would be its position if it travelled with
the same speed as the nucleus. Now judging from the amount
of curvature on June 30, and the direction of the comet's
motion, Hind thought that the Earth very probably encoun-
tered the tail in the early part of that da}7 ; or, at any rate,
that it was certainly in a region which had been swept over
by cometary matter a short time previously. He added that
on the evening of June 30 there was a peculiar phosphor-
escence or illumination of the sky which he attributed at the
time to an auroral glare. It was remarked by other persons
as something unusual ; and it seems scarcely open to doubt
that the Earth's proximity to the comet had something to
do with it. Lowe confirmed Hind's statement of the sky

X, Remarkable Comets. 145

having a peculiar appearance on the evening of June 30.
He says that the sky had a yellow, auroral, glare-like look ;
and that the Sun, though shining, gave but a feeble light.
The comet was plainly visible during sunshine at 7.45 p.m.
In confirmation of the statement that there was something
unusual and indescribable happening, Lowe adds that in his
parish church the vicar had the pulpit candles lighted at
7 o'clock, which proves that some sensation of darkness was
felt even while the Sun was shining. Though unaware at
the time that the comet's tail was enveloping the Earth, he
was so struck by the singularity of what he saw that he
made the following entry in his day-book: — "A singular
yellow phosphorescent glare, very like diffused Aurora
Borealis, yet, being daylight, such Aurora could scarcely
be noticeable." The comet itself, he states, had a much
more hazy appearance than on any subsequent evening.

De La Rue attempted to photograph the comet, but it left
no impressions on 2 collodion plates, although neighbouring
stars did impress themselves on the plates.

No fewer than 11 envelopes were seen to spring from
the head of this comet between July 2, when portions of 3
were in sight, and July 19; a new one rising at regular
intervals every second day. And their evolution and dis-
persion took place with much greater rapidity than was the
case with Donati's Comet in 1858 ; each envelope taking but

2 or 3 days to go through its various changes instead of 2 or

3 weeks.

On the question of the polarisation of the light of the
comet, Secchi said : —

"The most interesting fact I observed was this : the polarisation of the
light of the comet's tail and of the rays near the nucleus was very strong,
and one could even distinguish it with the band polariscope ; but the nucleus
presented no trace of polarisation, not even with Arago's polariscope with
double coloured image. On the contrary, on the evenings of July 3, and
following days, the nucleus presented decided indications, in spite of its
extreme smallness, which, on the evening of July 7, was found to be
hardly 1*.

"I think this a fact of great importance, for it seems that the nucleus
on the former days shone by its own light, perhaps by reason of the incan-
descence to which it had been brought by its close proximity to the Sun.

Figs. 63-68.

Plate XIX".

Aug. 7.

Aug. 18.

Aug. 18. t

Aug. 19.

Aug. 22.

Aug. 29.

THE COMET OF 1862 (iii.).
(Drawn by ChcMis.}

CHAP. X. Remarkable Comets. 147

" During the following days the tail has been constantly diminishing, but
it is remarkable that it has always passed near to a Herculis, and that it
reached to the Milky Way up to July 6. It would seem that the two tails
were nearly independent, and that on July 5 the length and straightness
had gone off from the large one, and that this bent itself to the southern
side. Last night (July 7) the long train was hardly perceptible. The light
was polarised in the plane of the tail."

Observations on the polarisation of the light of the comet
were also made by Poey at Passy, near Paris. He found
that "the plane of polarisation seemed to pass sensibly per-
pendicular to the axis of the tail". Poey had in 1858
observed Donati's Comet for polarisation, and found that
its light was polarised in a plane passing through the Sun,
the comet, and the observer.

The Comet of 1862 (iii-), though not one of first-class
magnitude or brilliancy, was nevertheless a very interesting
object on account of the fact that a jet of light, frequently
altering in form, was observed for a long time to emanate
from its nucleus. Jets of light shooting forth under such
circumstances are not uncommon, as we have already seen,
but in the case of this particular comet there seemed an
unceasing supply thrown out from the nucleus without any
material deterioration of the luminosity of the source of
supply. It need hardly be added that the late Professor
Challis, to whom we owe the annexed drawings, was a skilful
and experienced observer. This comet had a tail which on
Aug. 27 was 20° long.

The Comet of 1874 (iii.), discovered by Coggia at Marseilles,
was one of considerable interest. The drawing from which
Plate XX. has been engraved (and of which Fig. 69 is
a skeleton outline) was made with an achromatic telescope
of 8| inches aperture and 11^ ft. focal length, on July 13,
the most favourable night of all for a careful scrutiny of
the comet, when its position in the heavens, its proximity
to the earth, and the absence of twilight, 3 favourable
circumstances, are jointly taken into consideration. The
southerly motion of the comet was so rapid that on July 14
the presence of twilight greatly interfered with the visibility
of the details shown in the drawing. The following descrip-
tion is from the pen of F. Brodie : —

L 2

148

The Story of the Comets. CHAP. X.

"The head of the comet presented the great peculiarity of having two
eccentric envelopes in addition to the ordinary bright envelope immediately
surrounding the nucleus. The first envelope was a bright and sharply
defined semi-circle surrounding the nucleus : the two eccentric envelopes
were nearly as bright, and also very sharply defined, also semi-circular,
having their centres placed (about) on the edge of the first envelope, and

Fig. 69.

a ' ''' N

COGOIA'S COMET OF 1874.
Skeleton outline on July 13. (Brodie.}

a. fir. a. Undefined outline of nebulous head.
b, c, b. Fairly defined outline of second envelope.
d, d. Sharply defined outline of first envelope, semi-circular, and very

bright.
e, e. Very sharply defined clear dark space between bifurcation of tail,

free from nebulosity.
f,f. Singular eccentric envelopes, sharply defined, fading away at and

into b b. The centres of those envelopes were at 3.

g, c. Between these two points several envelopes concentric with dd were
traceable.

intersecting each other. The second centrical envelope just embraced both
these eccentric envelopes, and was about half the width of the nebulous
head of the comet. Between this second envelope and the ill-defined
outline of the head (that is, between c and g} there were faintly marked
outlines of other concentric envelopes. The nucleus, which, according to
Hind, was 4000 miles in diameter, appeared to be somewhat flattened on

Fig. 70.

Plate XX.

COGGIA'S COMET, 1874: ON JULY 13.
(Drawn by Brodie.}

150 The Story of the Comets. CHAP.

the side opposite to the Sun. From this side also the head of the comet
divided itself into two distinct parts forming the commencement of the
tail : for some distance this bifurcation was remarkably sharply denned,
suggesting an intense repulsive force acting upon the nucleus of the comet ;
and the space enclosed between this bifurcation was strikingly free from
nebulous matter, until at some little distance away from the nucleus the
sharp definition faded into the general nebulosity of the tail."

The following remarks on this comet are by two French
observers, MM. Wolf and Rayet : —

" After having maintained for many days a great sameness of form, on
June 22 a series of changes in the shape of the head of the comet commenced.
On that day the comet, viewed with a Foucault telescope of 40 centimetres,
appeared to be enclosed in the interior of a very elongated parabola. Starting
from the nucleus, which was placed as it were at the focus of the curve,
the brightness decreased gradually towards the summit : but in the interior
of the parabola the diminution of the brightness was sudden, and the
boundary-line exhibited another parabola a little more open than the first,
and having at its own summit the brilliant nucleus itself. The outline
of the parabola which passed through the nucleus was prolonged so as
to form the lateral boundaries of the tail, the edges of which were well
defined and were much brighter than the interior parts. This tail had
then the appearance of a luminous envelope hollow in the inside. The
nucleus was always very sharp. On July 1 the general form of the comet
remained the same; it appeared always to possess a parabolic outline at
its exterior edge. The nucleus, however, jutted out into the interior of
the second parabola, and the opposite margins of the tail were not strictly
symmetrical. The West side, that is to say the side which had the greatest
K.A., was very sensibly brighter than the other. . . . From July 5, the want
of symmetry spoken of above became more and more marked, and near the
head the decrease of the brightness became less regular. On July 7, the
contrast between the two branches was striking, the Western branch of
the tail being about twice as bright as the Eastern. At the same time the
nucleus appeared to be becoming diffused, and it seemed to fade away in
the direction of the head of the comet, although still sharply defined on
the side nearest the tail ; one could not fail to remark its resemblance to
an open fan. . . . Our last observation of the comet was made on July 14
at 9.30 p.m. : important changes in the aspect of the head had manifested
themselves. The fan of light had disappeared on the West side, and was
replaced by a long spur of light which was traceable for a considerable
distance across the head ; on the West side the remnant of the fan
terminated abruptly, and the boundary-line there made but a small angle
with the main axis of the comet. On this same occasion two rays of light
were visible — two jets as they might be deemed — thrown forwards, the one
to the right and the other to the left ; these luminous rays seemed to have
their origin at the edge of the fan of which they formed a sort of prolongation.
The ray which pointed towards the East projected well forwards, and being
bent round towards the tail soon reached the preceding edge of the comet ;
it was faint and hardly surpassed the nebulosity in brilliancy. The raj-
projected towards the West was much more brilliant, and was similarlv

O «

f-t

.

o ^ «
o ^ S

o ?

o p

8 '
0 §

H
H

Fig. 82.

Plate XXIII.

COGGIA'S COMET OF 1874 (iv.).

PATH AND DEVELOPEMENT BETWEEN JUNE 25 AND JULY 14.

(Drawn by W. Tempel.')

p. 150?.

X. Remarkable Comets. 151

bent round towards the tail, which it assisted in providing with a bright
exterior edge."

The comet was nearest to the Earth on July 21, when
its distance was less than it had been on July 13 by
9,000,000 miles. During this week the comet's tail remained
visible, stretching towards the N. for some hours after the
nucleus had descended below the horizon. It would have
been an exceedingly striking object all this week if it could
have been seen as a whole, but it had got too close to the
Sun. The tail reached a length of 43° on July 19, but on
the evening when Brodie's sketch was made it was no more
than 20°. Coggia's Comet undoubtedly revolves in an elliptic
orbit, but there is great discordance in the values given of
the period. Seyboth's period is 5711 years; but Geelmuyden
put it as high as 10,445 years.

The Comet of 1880 (i.), generally called the " Great Southern
Comet of 1880", was noticed by several persons in Australia,
South America, and South Africa on Feb. 1, but its cometary
nature seems not to have been recognised till the following
night. Gould at Cordoba described the tail as 40° long and
from 1|° to 2|° broad, but at no time was the nucleus very
bright. The elements closely resemble those of the great
Comet of 1843, also celebrated, as we have seen, for the length
of its tail, but the identity of the 2 bodies has not yet been
satisfactorily established.0 This comet was unfavourably
placed for observation, and was only seen for 2 or 3 weeks.

The Comet of 1882 (iii.) was in some respects one of the
most remarkable seen by the present generation of astrono-
mers. It was conspicuously visible to the naked eye for some
weeks in September, and altogether remained in sight for the
long period of 9 months. The special peculiarities which seem
to differentiate this comet from all others which have been
exhaustively scrutinised, either before or since, were that the
head underwent changes in the nature of disruptions; that
the tail may have been tubular ; that the extremity of the
tail was not only bi-fid (or split), but that it was entirely

0 For detailed observations see 377, 623, March, April, 1880; ibid.,
Month. Not. R. A. S., vol. xl, pp. 295, vol. xli, p. 85, Dec. 1880.

152 The Story of the Comets. CHAP.

unsymmetrical, considered in relation to the greater part of
the tail ; and that on one occasion the comet seems to have
thrown off a mass of matter which became, and for several
days was observed as, a distinct comet. The changes which
took place in the nucleus and head were noted and described
by many observers. Prince wrote :—

" Oct. 13. I could notice, however, that there was a decided change in

the appearance of the nucleus. Instead of being of an oval shape, it had
become a long flickering column of light in the direction of the tail."

" Oct. 20. I noticed, however, at once, that a still further change had

occurred in the nucleus since the 13th, which amounted, in fact, to its
disruption into at least 3 portions."

Fig. 83.

THE CHEAT COMET OF 1882. FORMATION OF THE NUCLEUS. (C. L.

"Oct. 23. — The disruption of the nucleus which I had noticed on the
20th was now fully apparent. The nucleus proper had become quite linear,
having upon it the 4 distinct points of condensation which I have
endeavoured to represent in the subjoined sketch.

"It must be understood that the accompanying woodcut is to be considered
rather as a diagram of the head of the comet than as a view of what I actually
observed, and that the points in question are somewhat exaggerated in size,
as well as the linear character of the nucleus itself. I found it was very
difficult to represent, by means of a wood-block, such a nebulous object ;
but I think it will serve to illustrate the nature of the wonderful disruption,
and the relative distance of the several portions inter se : a was the most
difficult portion to discern ; b was by far the brightest of all ; c was con-
siderably less bright than b ; and d was nearly as faint an object as a, and
not quite so large. The linear nucleus, with these points ot condensation
upon it, was surrounded by a distinct oblong coma, which was rounded
off at the lower extremity, while the upper portion, following the direction
of the tail, terminated more decidedly in a point. Mr. G. J. Symons, F.R.S.,
was with me in the observatory, and his impression was that there were
five points of condensation, and he remarked that ' the nucleus was like

X. Remarkable Comets. 153

a string of beads '. At intervals I thought there icas another point of light
between b and c, but as I could not absolutely satisfy myself of its objective
existence, I have only represented the four portions, of the presence of
which I entertained no doubt whatever. Both Mr. Symons and myself
particularly noticed the frequent flickering of the light of the nucleus, which
was quite apparent both to the naked eye and in the telescope."

J. F. J. Schmidt published a sketch of the nucleus which is
not unlike Prince's ; and having seen Prince's he refers to it
as a good representation of what he had seen himself. He
noticed a vibratory motion in the fan.p

The suggestion that the comet's tail was tubular in form is
due to Tempel, who brought out the idea in some striking
sketches which he sent to the Royal Astronomical Society,
accompanied, for the sake of comparison, by a drawing of the
appearance of 2 hollow glass cylinders as seen in the focus of
an eyepiece."1

The peculiar shape of the extremity of the tail will be
sufficiently indicated by the accompanying woodcut of a
drawing by B. J. Hopkins.1 [Fig. 84.] His simile was that
the general form of the tail resembled the Greek letter y.

The peculiar shape of the tip of this comet's tail was
mentioned by most observers. This feature, though rare
as regards the comets of the last half century, may be con-
ceived to be the shape meant by old writers when they speak
(as they often do) of having seen a comet resembling in form
" a Turkish scymitar ".

The most noteworthy physical peculiarity of the Comet of
1882 was its throwing off a mass of matter which became
a satellite comet, as recorded by Schmidt at Athens, and by
Barnard and Brooks in America. Perhaps it is going too
far to speak quite as definitely as this, but the fact is clear
that Schmidt saw on Oct. 9, and on two or three later days,
a nebulous mass in the neighbourhood of the comet which
calculation indicated to be cometary matter moving round the
Sun in an orbit considerably resembling the orbit of the
comet. Brooks's observation made on Oct. 21 was that he
saw a nebulous mass on the opposite side of the comet to

P Ast. Nach., vol. cv, No. 2499. p. 322. April, 1883.
March 19, 1883. T Month. J\ot. E.A.S., vol. xlii, p. 90.

•> Month. Not. R.A.S., vol. xliii, Jan. 1883.

154

77/6- Story of the Comets. CHAP. X.

Fig. 84.

THE GREAT COMET OF 1882. NAKED-EYE VIEW ON NOV. 14. (B. J. HopklHS.}

Fig. 85.

THE GREAT COMET OF 1882, ON OCT. 9 AT 4h A.M.

Fig. 86.

Plate XXIV.

THE GREAT COMET OF 1882: OCT. 19.
(Drawn by Gen. G. H. Willis.}

156 The Story of the Comets. CHAP.

Schmidt's mass.8 With the evidence before us of what hap-
pened in 1846 in the case of Biela's Comet, it is impossible not
to draw the inference that the nebulous mass (or masses) was,
or had been, a part of the comet itself ; and this theory becomes
much strengthened when read in the light of the disruptive
changes which the nucleus underwent as already mentioned.

General Willis observed the comet at sea 70 miles E. of
Gibraltar on Oct. 19 at 5 a.m. with the air extremely clear
and calm. He says that in appearance the comet was so
" extremely delicate, light, and airy, that it would be almost
impossible to depict it on paper". The engraving [PlateXXIV.]
is a French reproduction of the original English lithograph.1

Holden contributed some information bearing on the
question of disruption. His sketches tell their own tale.
With reference to their dates, Oct. 13 and Oct. 17, it may be
remarked that two of the nuclei seen by Holden were seen
by Cruls at Rio de Janeiro at the intermediate date of Oct. 15.
Cruls found these nuclei to resemble stars of the 7th and
8th magnitudes respectively, the distance between them being
6f ". He was led to regard the peculiar appearance of the
tail as being really due to two tails, one superposed upon the
other, each connected with a nucleus of its own, independent
of the other.

Not only did this comet puzzle astronomers very much in
the matter of its physical appearance, but its orbit has also
been a source of great searchings of heart.u The elements
closely resemble those of the Comet of 1880 (i.), the " great
Southern Comet of 1880 " just described. This in turn was
considered to be a comet moving in an elliptic orbit with
a period of about 37 years, and to be in fact a return of the
celebrated Comet of 1843. It still remains a moot point what
interpretation is to be put upon these orbital resemblances, the
fact of which cannot be questioned. And there is the further
complication that since the advent of the Comet of 1882

8 Sidereal Messenger, vol. ii, p. 149. u This matter has already been

Aug. 1883. dealt with in some detail (see p. 17,

1 Month. Not. R.A.S., vol. xliv, p. 86. ante), but a recapitulation seemed

Jan. 1884. desirable.

X.

Remarkable Comets.

157

another one has presented itself, namely the Comet of 1887 (i.),
whose elements also bear a strong resemblance to those of the
3 comets just mentioned. The suggestion has been made that
these 4 comets, all of them large ones (and perhaps another
also), had a common origin, but that by some process of
disintegration the original mass yielded 4 or more fragments
which, pursuing paths only slightly different, have arrived at
perihelion at different epochs. It will be seen at once that
this is a very speculative question.x

The Comet of 1887 was seen only in the Southern hemi-

Fig. 87.

Oct. 13. (Holden.} Oct. 17. (Holden.)

THE COMPOUND NUC'LEUS OF THE GREAT COMET OF 1882.

sphere. It seems to have been first seen in South Africa by
a " farmer and fisherman " at Blauwberg near Cape Town on
Jan. 18. Finlay, who first saw it on Jan. 22, describes it as
" a pale, narrow ribbon of light, quite straight, and of nearly
uniform brightness throughout its length. There was no
head or condensation of any kind visible near the end, the
light simply fading away to nothing ". The tail was described
by Todd, at Adelaide, Australia, as a " narrow nebulous streak " ;
but the remarkable thing is that the tail was as much as 30°
or more long, according to several observers. To both Finlay
and Todd this comet recalled the great Southern Comet of

1 Month. Not., vol. xliii, p. 108, Feb.
1883; ibid.,- vol. xlviii, p. 199, Feb.
1888. For various drawings of the
Comet of 1882 see Ast. Nach., vol. civ,
No. 2489, Feb. 5, 1883 (Barnard) ; vol.

cvi, No. 2535, Aug. 31 , 1883 (Hartwig) ;
vol. cvii, No. 2550, Oct. 31, 1883
(Peters) ; Month. Not., vol. xliii, p. 288,
March, 1883 (Brett).

158

The Story of the Comets.

CHAP.

1880 as regards its appearance, and Finlay was so impressed
by the resemblance that he took steps to investigate its orbit,
and, strange to say, found that the resemblance even extended
to that detail. His conclusion was thus expressed : — " These
elements though of course, rough, prove conclusively that the
comet belongs to the family of ' Sun-grazers ' of which 1843 (i.),
1880 (i.), and 1882 (ii.) are members." *

Sawerthal's Comet of 1888 (i.) exhibited on March 27 a triple

Fig. 89.

THE GREAT COMET OF 1901 (ii.) ON MAY 12.

(Drawn by J. Lunt.)

nucleus not unlike that of the great Comet of 1882.z This
comet had a tail which on April 11 was 5° long. It revolves
in an elliptic orbit to which a period of 1615 years has been
assigned. The configuration of the head was very remarkable
and unusual.

The Comet of 1901 (i.), discovered at Paysandu in South
America 011 April 12, but scarcely reached from any obser-

y Month. Not. R. A. S., vol. xlvii,
p. 303. March 1887.

z Letter of M. Cruls in Ast. Nach.,
vol. cxix, No. 2842. May 26, 1888.

X. Remarkable Comets. 159

vatory in the Northern hemisphere except the Lick, in
California, has some claim to be called "remarkable". Its
main tail, which did not exceed 10° in length, was preceded
by a faint tail fully 30° long, which branched out from the
main tail, making with it an angle of about 40° or nearly
half a right angle. On April 24, although in twilight, the
nucleus was very bright and distinctly of a yellow tinge, as
seen by Innes at the Cape Observatory. On May 12, though
the comet had become intrinsically much fainter, it was still

Fig. 90.

BKOOKS'S COMET OF 1902 (i.) . (Drawn by W. R. Brooks.)

a magnificent object, and in between the 2 tails spoken of
above 2 other slender tails were visible. The spectrum
appeared to be continuous. The comet was visible for about
6 weeks, but bad weather both at the Cape and in Australia
and the comet's inconvenient position with respect to the Sun
interfered very much to prevent a good series of observations.
On May 2 the nucleus is said to have rivalled Sirius in lustre
and to have been distinctly elliptical in shape. Eddie, at
Naauwpoort in S. Africa, speaks of the matter composing the
long tail as being "striated" in appearance.4

a See Mon h. Xot. R. A. S., vol. Ixi, p. 508, June 1901 ; and ibid., vol. Ixii,
p. 194, Feb. 1902.

CHAPTEE XI.

THE ORBITS OF COMETS.

All Cometary Orbits sections of a Cone. — The different kinds of Sections. —
The Circle.— The Ellipse.— The Hyperbola.— The Parabola.— The last-
named the most easy to calculate. — An ellipse very troublesome to calculate.
— The elements of a Comet's Orbit. — For a Parabolic Orbit 5 in number. —
Statement of various details connected with Orbits. — Direction of motion. —
Eccentricity of an Elliptic Orbit. — The various elements represented by
certain symbols. — Number of comets whose Orbits have been calculated. —
The significance of the different Orbits pursued by comets.

IT has already been stated, but without much explanation,
that all comets move in orbits which are either elliptic,
parabolic, or hyperbolic — 3 of the 4 possible sections of a
Fig. 91. cone. Fig. 91 represents the

various sections of a right cone,
as it is called, and will con-
vey a better idea of Cometary
Orbits than a verbal descrip-
tion would do. When a right
cone is cut at right angles to
its axis the resulting section
A B, will be a Circle : no comet,
however, is known to revolve
in a circular, or even in any-
thing like a circular orbit,
though, on the other hand,
all the planetary orbits may
be said to be nearly circular.
When a cone is cut obliquely,
so that the inclination of the
cutting plane to the axis of the cone is greater than the constant
angle formed by the generating line of the cone and the axis, as
C D, the resulting section will be an Ellipse, the shape of which
will vary from almost a circle on the one hand to almost

THE VARIOUS SECTIONS OF A CONE.

Fig. 92.

Plate XXV.

SIR ISAAC NEWTON.

p. 1 60

XI. The Orbits of Comets. 161

a parabola on the other, according to the amount of the
obliquity. When a cone is cut in a direction so that the
inclination of the cutting plane to the axis of the cone is
less than the constant angle formed by the generating line
of the cone and the axis, as E F, the resulting section will
be a Hyperbola. When a cone is cut in a direction so that
the inclination of the cutting plane to the axis of the cone
is equal to the constant angle formed by the generating

Fig. 93.

DIAGRAM OF A PARABOLIC AND AN ELLIPTIC ORBIT.

line of the cone and the axis, as G H, the resulting section
will be a Parabola.

It will be evident from an inspection of the diagram that
no comet can be periodical which does not come to us fol-
lowing an elliptic path. In consequence, however, of the
comparative facility with which a parabola can be calculated,
astronomers are in the habit of seeking to apply that curve
to represent the orbit of any newly discovered body. Para-
bolic elements having been obtained, a search is then made
through a catalogue of comets whose orbits have already
been calculated, to see whether the new elements resemble

162 The Story of the Comets. CHAP.

those of any comet which has been previously observed :
if so (especially if the parabolic elements indicate a path
through the heavens which is evidently not the path being
followed by the comet), calculations for an elliptic orbit
are undertaken and a period (usually stated in years and
decimals of a year) is deduced. To compute an elliptic orbit
for a comet or planet will take even an experienced calculator
many hours of very hard work. An approximation may,
however, be obtained by a graphical process.*

It will be desirable to give the reader a little further
insight into the nature of cometary orbits without going
more deeply than can be helped into mathematical matters.b
The orbits of all comets, planets, and binary stars are in
form sections of cones, whose size, exact form, and position
in space are defined by numerical quantities technically
termed "elements", which for brevity's sake are usually
designated by symbols as follows : —

T = Moment of the body's Perihelion Passage or nearest
approach to the Sun,0 expressed in Greenwich, Berlin,
or Paris time according to the nationality of the
computer, Americans adopting Greenwich time.

A = Mean Longitude at an Epoch given. Instead of this
some computers give the " Mean Anomaly at Epoch ",
and often it is not explicitly stated which is intended.
But in neither case is it an independent element, since
it is deducible from the time of the Perihelion Passage
(T) and the Rate of Motion (/z). In fact, where this
element is given (namely, in elliptic orbits), the time

a Such as that framed by Mr. F. C. Harkness, in the Sidereal Messenger,

Penrose, which is presented in my vol. vi, p. 329. Dec. 1887. I have

Handbook of Astronomy, 4th ed., vol. i, epitomised some portions of that

p. 491 et seq. article in the next following state-

b Perhaps the best way of realising ment of the elements of an orbit,

clearly the nature of a comet's orbit. ° In the case of a binary star, of

and the difference between one orbit the nearest approach of the com-

and another, is by making cardboard panion star to the principal star ;

models. For instructions how to do in such case the point of nearest

this see an article by a distinguished approach is called the peri-aslron

American astronomer, Professor instead of the peri-helion.

XT. The Orbits of Comets. 163

of Perihelion Passage is generally not given, but left
to be inferred from the other.

TT = Longitude of the Perihelion, or the longitude of the
body when it reaches that point. In the case of
a comet (or planet), this is measured along the ecliptic
from the vernal equinox to the comet's ascending
node, and thence along the comet's (or planet's) orbit
to its Perihelion ; in the case of the Earth, it is
measured along the ecliptic from the vernal equinox
to the Perihelion. [Crommelin has drawn attention
to the fact that some founts of Greek type have the
small Pi in this shape (OT) instead of the common (TT).
This anomalous Pi too nearly resembles the Omega (o>)
employed in stating the elements of an orbit : hence
the risk of confusion.]

S3 = Longitude of the Ascending Node of the body's orbit
as seen from the Sun (or Primary) ; measured on the
ecliptic from the vernal equinox to the ascending node
of the orbit.

i = Inclination of the plane of the orbit to the plane of
the ecliptic.

e = Eccentricity of the orbit, sometimes given as a decimal,
and sometimes as an angle, <£. The decimal represents
the ratio of the linear distance of the centre of the
ellipse from the focus, to the semi-axis major, the latter
being taken as 1-0. When c6 is given, then e = the
natural sine of $. This is the angle formed by the
minor axis at its extremity on the border of the ellipse
with a line drawn from thence to the focus. The
greater this angle the more eccentric the ellipse.

q = Perihelion distance of the body ; expressed in terms of
the mean radius of the Earth's orbit as unity.

For a parabolic orbit e is always 1-0 (or Unity) ; and in
that case the elements are frequently given by stating T, co,
S3 , i, and log. q. Here TT has been replaced by : —

<o = TT — S, (1)

which is counted on the comet's orbit, backward, from the

M 2

164 The Story of the Comets. CHAP.

perihelion to the ascending node ; and the perihelion will lie
on the northern or southern side of the ecliptic according as
co is less or greater than 180°.

As TT and Q are counted from the vernal equinox, and i is
measured from the plane of the ecliptic, the quantities necessarily
refer to a particular equinox, and this is always specified.

It was long customary to measure longitudes in the orbits
of comets in the direction of the Earth's motion ; to limit i
to the first quadrant; and to specify the direction of the
comet's motion, whether " direct " or " retrograde" ; but many
astronomers, especially on the Continent, now follow Gauss in
regarding retrograde motion as a result of the inclination
passing into the second quadrant ; and in accordance with
that view they measure a comet's longitude always in the
direction of its own motion, and permit i to take any value
between 0° and 180°. The circumstance that i is measured
at the ascending node limits its range to the first and second
quadrants, for if it were to pass into the third or fourth
quadrants the ascending node would be converted into a
descending one. For a comet having direct motion the
numerical values of the elements are the same in Gauss's
system as in the old system, but for a comet having retro-
grade motion they are different, and in that case, if their
values according to the old system are indicated by a sub-
script o , the equations requisite for passing from the old to the
Gaussian system are : —

i = 180° - i

CO = 360 — CO = — CO

o o

7T = 2 8 — TT

There is frequently much confusion respecting the angles TT
and <o, and it is important to have a clear understanding of
the relations of co to TT and £3 . In the old system of elements
TT is measured from the vernal equinox, along the ecliptic in
the direction of the Earth's motion, to the ascending node
of the comet, and thence along the comet's orbit, still in the
direction of the Earth's motion, to the comet's perihelion. In
Gauss's system TT is measured from the vernal equinox, along
the ecliptic in the direction of the Earth's motion, to the

XI. The Orbits of Comets. 165

ascending node of the comet, and thence along the comet's
orbit, in the direction of the comet's motion, to the comet's
perihelion.

These definitions may perhaps be elucidated by the fol-
lowing statement. Imagine a perpendicular to the plane of
the ecliptic, erected from the Sun. Then to an observer
situated North of the ecliptic in that perpendicular, the
motion of the Earth will be contrary to the hands of a clock,
and longitudes in the Earth's orbit will increase in that
direction. Now consider a comet's orbit ; imagine a perpen-
dicular affixed to it in such a way that when the inclination
of the orbit to the plane of the ecliptic is i, the inclination
of the perpendicular shall be (i + 90°) ; and suppose an observer
so situated in the perpendicular that when i = Q° he shall
be North of the ecliptic. Then, according to the old system
of elements, for all possible values of i the observer will
remain North of the ecliptic, and the motion of the comet
will appear to him as contrary to the hands of a clock when
Direct, and with the hands of a clock when Retrograde;
but according to Gauss's system he will be North of the
ecliptic when i is less than 90°, South of it when i is greater
than 90°, and to him the apparent direction of the comet's
motion will always be contrary to the hands of a clock.

Whichever system is adopted, from this point of view TT
will always increase contrary to the clock, and to find the
intersection of the plane of the comet's orbit with the plane
of the ecliptic, or, in other words, the line of the nodes, the
observer must set off co in the direction of the hands of
a clock, from the perihelion of the orbit.

Cometary orbits cross the ecliptic at all sorts of angles
between 0° and 90°. A small inclination (say, under 15°) may
often be interpreted as a sign of periodicity ,d because all the
short-period cornets have small inclinations. By moving so
near the ecliptic their chances of being " captured " by planets
is great. On the other hand, a comet with a large inclination
(say 70° to 90°) runs small risk of being " captured ", because

d Because all the planets which have small inclinations ; except a few
are periodical bodies (so to speak) minor planets.

166 The Story of the Comets. CHAP.

its stay near the region of planets lying in wait, as it were,
for comets is limited in time. It runs down to the ecliptic :
is quickly across, and oft* again on the other side, and is soon
out of reach of a planet prowling along the ecliptic to see
what it can catch.

The motion of a comet is said to be " Direct " (represented
by -f- ) when it moves in the order of the signs of the Zodiac,
and ': Retrograde " (represented by — ) when it moves contrary
to the signs of the Zodiac.

In the case of an elliptic orbit, given g and e we can
ascertain the length of the major axis (a).

Given the daily motion (fj.) we can obtain the period in
days by dividing 1,296,000 (the number of seconds in a circle
of 360 degrees) by the value of /*.

Astronomers are in the habit of performing all these cal-
culations by logarithms because of the ease and convenience
of doing so.

Be it remembered that the " eccentricity " is not the linear
distance of the centre of the ellipse from either focus, but the
ratio of that quantity to the semi-axis major.

Fig. 94 represents the usual way of drawing an ellipse on
paper. A line joining AE would be the " axis " of the ellipse,
a line at right angles to this at A would be the " directrix "
of the ellipse. B and D are the foci; and taking B to be
the principal focus, B would be the place of the Sun, supposing
the ellipse to represent the path of a comet revolving in an
elliptical orbit. AC would be the "semi-axis major" or
" mean distance " ; and the eccentricity would be the ratio
of BC to AC, which in this particular diagram would be
about 7 to 10, or decimally 0-7. The diagram therefore
represents nearly the shape of the orbit of Winnecke's comet.

Up to the present time the orbits of nearly 400 different
comets have been calculated. This does not include orbits of
comets which have returned one or more times after their
first discovery and recognition as being periodical comets.6

e Gauss's Theoria Motus Corporum the subject of orbits, but it has in
Ccelestium, 4to, Hamburg, 1809, was some degree been superseded by
long reckoned the standard work on Oppolzer'sLehrbuchzurBahnbestimmung

XI.

The Orbits of Comets.

167

When a new comet has been discovered and its elements
have been ascertained, it is usual for some astronomer,
specially interested in the particular comet, to provide a
table of predicted places for the comet many days or
weeks in advance. Such a table is called an "ephemeris"
and will enable other astronomers to know where to look
for the new body, and, finding it, to obtain observations

Fig. 94.

THE CONSTRUCTION OF AN ELLIPSE.

which will be available for improving the accuracy of the
elements first circulated/

The significance of the various sections of a cone which
constitute the different forms of orbit affected by comets
is well and tersely stated by Howeg in the following
extract: — "Suppose that a small body is at a very great
distance from the Sun, and both bodies are motionless.
The body will begin to fall toward the Sun, its path being

der Kometen und Planeten, 2nd ed. ,
2 vols. 8vo, Leipzig, 1882. A French
translation by a Belgian, M. E.
Pasquier, was published at Paris,
1886, under the title of Traite de la de-
termination des orbites des cometes el des
planetes. See also a paper by Airy,
in Memoirs R.A.S., vol. xi, p. 181. 1840.

f Instructions how to compute an
ephemeris for a comet after the
elements have been ascertained will
be found in Popular Astronomy, vol. ix,
p. 311. June and July 1901.

g H. A. Howe, Elements of Descriptive
Astronomy, New York, 1897, p. 189.

168 The Story of the Comets. CHAP.

a straight line directed towards the Sun's centre. Another
small body, likewise at a distance practically infinite, has
a slight motion of its own, but is not moving directly toward
the Sun; urged on by the Sun's imperious attraction, its
velocity will continually increase; however, as it is not
going directly toward the Sun, it will not strike it, but
as it goes past, the pull of the Sun will cause its path
to be violently curved ; whirling around the Sun, it will
return toward the infinite depths of space from which it came,
its orbit becoming a parabola. A body which has originally
a very considerable velocity of its own will come down to
the sun in an hyperbolic orbit, and then retreat, never again
to visit us. A body moving in a parabola may have its
velocity checked, as it approaches the Sun, by the attraction
of some planet ; its orbit will thus be changed to an ellipse.
Were the movement of the body accelerated by the planet's
action, the orbit would become an hyperbola."

Scarcely less interesting than the question " What is a
comet?" are the cognate questions "Why do comets come
to us?" and "Where do they come from?" It is obvious
that these questions can only be answered in a hypothetical
and inadequate fashion, but still it is possible to say some-
thing. Two provisional answers suggest themselves: either
(1) comets are chance visitors wandering through space and
now and again casually caught up by the Sun, or by some of
the major planets acting like the old naval press-gang and
compelling them to attach themselves to the Sun and by
taking elliptic orbits to become permanent members of the
solar system ; or (2) they are aggregations of primaeval
matter not formed by the Creator into substantial planets,
but left lying about in space to be picked up and gathered
into entities as circumstances permit.

C. L. Poor has graphically summarised the situation. At
the risk of a little repetition. I will transcribe what he says : —
" They have been considered as true wanderers, travelling
through space, drifting hither and thither, just as the Sun,
with its attendant retinue of planets, is moving onward in
some unknown path. When the paths of the Sun and such

XI.

The Orbits of Comets.

169

Fig. 95.

W

DISCOVERY FIELD OF BROOKS's COMET OF 1890 (ii.) ON MARCH 19.

(Drawn by W. R. Brooks.)

Fig. 96.

July 23. July 26.

THE BHOOKS-BORELLY COMET OF 1900 (ii.).

(Drawn by W. R. Brooks.)

170

The Story of the Comets.

CHAP.

a free comet approach, the attraction of the Sun is to the
comet like the flame to the moth; the comet flutters for
a moment about the Sun, and passes on its way. But not
unscathed ; like the moth, the comet has been singed ; the
fierce light of the Sun has beaten upon it, and spread out its
particles and scattered them along its path.

" This idea that comets originate outside the solar system
rests upon the supposed character of their orbits. The great
majority of these strange bodies appear to travel in parabolas,
open curves leading from infinite space to and around the Sun

Fig. 97.

(IT. B. Gibbs, del.}

FIVE PARABOLAS
at J, 1, 2, 3, AND 4 HADII OF THE EARTH'S ORBIT.

and thence back into the region of the fixed stars. Sir Isaac
Newton first showed the possibility of comets moving in such
paths, and the prestige of his name and the ease and facility
with which parabolic orbits can be calculated led to the adop-
tion of this curve as representing the motions of these bodies.
Under the Law of Gravitation a body may travel about the
Sun in any one of the three conic sections, or curves, known
as the ellipse, the parabola, and the hyperbola. That is, if
there were in the universe but two bodies, the Sun and
a comet, then would the comet describe about the Sun one
of these three mathematical curves, the exact character and
size of the curve depending solely upon the speed of the

XI. The Orbits of Comets. 171

comet relative to the Sun at the beginning of time. But
the instant a third body is added to the system this is no
longer true. The parabola is a limiting curve, is what might
be called a curve of ' unstable ' motion. To describe a para-
bola about the Sun, a body must have at each point of its
path a certain definite velocity. If this parabolic velocity
be changed by the slightest amount, the path ceases at
once to be a parabola; if through any cause the velocity
be decreased the path becomes an ellipse ; if increased, an
hyperbola. Now if a comet start in a parabolic orbit, it
cannot continue for a single instant in that path, for it must
of necessity be attracted by Jupiter, by Saturn, or by some
or all of the planets, and such attraction will either increase
or decrease its speed. Thus a parabolic orbit is a physical
impossibility. h

" Yet to-day the greater number of newly discovered
comets are classed as parabolic, and their orbits are com-
puted and given as parabolas. This is because a very small
part of the actual orbit is seen, such a small part that it
is impossible to determine the exact character of the real
path. Near perihelion the difference between an elliptic
orbit of great eccentricity and a parabolic orbit is so slight
as to be inappreciable. * On the other hand, the labour of
keeping track of a body moving in a very eccentric elliptic
orbit is many, many times greater than that required to
keep track of a body moving in the corresponding parabola.
Parabolic orbits are thus computer's fictions, approximate
paths assumed for the purpose of lessening labour." k

An exemplification of some of the uses of logarithms in
connection with the orbits of elliptic comets may here be
given, because some computers in publishing the results of

h Though I quote this part of that are found are almost parabolic)

Poor's statement, his way of putting really shows that all comets belong

the matter is dissented from by to the Solar System, for if they came

Crommelin, in so far that the assured from without, quite a large number

existence of any hyperbolic comets is would have strongly hyperbolic

by no means very clearly assured. orbits, owing to the rapid motion

Crommelin's words in a letter to of the Solar System through Space.''

me are : ' ' The fact that hyperbolic * See Fig. 29 (ante, p. 53).

comets are almost unknown (those k The Solar System, p. 281.

172 The Story of the Comets. CHAP.

their calculations do not always give the perihelion distance
of a comet or its periodic time of revolution round the Sun ;
but limit themselves to announcing the angle of the eccen-
tricity (<£), the mean daily motion (jj.), and the logarithm
of the semi-axis major or mean distance (a) ; leaving the
student to find out for himself the perihelion distance (q)
and the period.

EXAMPLE.

Given, in the case of Holmes's Comet in 1906 —

The angle of eccentricity (</>) 24° 20' 26"

Log. semi-axis major (a) 0-557427

Mean daily motion (p.) 517"-44

To FIND THE PERIHELION DISTANCE (<?).

(i.) Look out in a Book of Tables the Natural Sine of
24° 20' 26".

(ii.) Subtract this from Unity (1-0).

(iii.) Find the logarithm of the result,

(iv.) Add this to the logarithm of a.

(v.) And this will give the logarithm of q.

EXAMPLE.

(i a.) Nat. Sine of 24° 20' 26" = 04121594.
(iia.) 1-0 -0-4121594 = 0-5878406.
(iii a.) Logarithm of 0-5878406 is 9-7692595.

(iva.) Add Log. a = 0-557427

Log. (1-e) = 9-769260

Log. (q) 0-326687
.'. q = 2-1217.

To FIND THE PERIODIC TIME IN YEARS.

(i.) Calculate number of seconds of arc in 360°.
(ii.) Find logarithm of that number of seconds.

XL The Orbits of Comets. 173

(iii.) Find logarithm of number of seconds travelled over
by comet in 1 day.

(iv.) Divide the number of seconds in 360° by number of
seconds travelled over by comet in 1 day by subtracting
the logarithm of the latter from the logarithm of the former.

(v.) Quotient will be comet's period in days.

EXAMPLE.
(ia.) 1296000".

(iia.) Logarithm of this number = 6-1126050.
(iii a.) Mean daily motion being 517" -44, logarithm of mean
daily motion = 2-7138600.

(iv a.) Subtract one of these logarithms from the other —

6-1126050

2-7138600

Log. Period in days = 3-3987450

.*. Period = 2504-7 days.
= 6-8 years.

CHAPTER
COMETS IN THE SPECTROSCOPE.

The application of the Spectroscope to Comets. — Photography as applied to the
Spectra of Comets. — Historical Survey of the progress made. — Four varieties
of carbon Spectra. — Three Comets which have yielded special results. — Con-
clusions of Hasselberg. — The great Comets of 1881 and 1882. — Schaberle'a
Comet. — Wells 's Comet. — Instruments of a special kind needed for the
Spectra of Comets. — Frost's Dictum. — Borelly's Comet of 1890 (i.). —
Brooks' s Comet O/1890 (ii.).— Swiff s Comet of 1892 (i.) : Holmes' s Comet
of 1892 (iii.). — Rordame's Comet of 1893 (ii.). — Perrine-Griggs's Comet of
1902 (ii.).— Brooks's Comet O/1904 (i.).— Daniel's Comet of 1907 (iv.).—
Morehouse's Comet of 1908 (iii.). — One of the most remarkable on record. —
Summary of the present state of our knowledge. — Importance of Photo-
graphy in the study of Comets. — Newall's Theory as to cometary radiation.

THE spectroscope has not been employed in the study of
comets on the same scale as it has been used for the purposes
of solar and stellar research, and consequently the harvest of
knowledge obtained by it has not been so great as one could
have wished. Until quite recently most cometary spectra
observations were made visually, thus excluding the violet
and ultra-violet radiations. Prior to 1902 all attempts to
photograph the spectra had been made with long-focus tele-
scopes and spectroscopes, primarily designed for stellar work,
a procedure now very generally recognised as inadequate
except in the case of an exceptionally bright comet.

A comet is a diffuse object, and is not, usually, very bright.
To obtain a spectrum of such an object it is essential that
the light be condensed as much as possible ; therefore long-
focus telescopes and spectroscopes which spread out the light
are unsuitable for cometary work. For this reason short-
focus prismatic cameras have recently been employed, and

a This Chapter is the joint work Rolston, two experts in spectroscopic
of Mr. E. W. Maunder and Mr. W. E. work.

CHAP. XII. Comets in the Spectroscope. 175

the first-fruits obtained give promise of a much richer
harvest to follow.

In the case of perhaps no class of heavenly bodies has the
spectroscope yielded information of so entirely an unexpected
nature as in that of comets. The first comet observed spectro-
scopically was the Comet of 1864 (i.) by Donati, who found
it to yield only 3 bright lines, showing the presence of a
glowing gas. Huggins and Secchi, in 1866, found Tempel's
Comet likewise gave 3 bright lines and a continuous spectrum
in addition. No dark lines were perceived in the latter, the
light being probably too faint. But in the continuous spectrum
yielded by Coggia's Comet of 1874 some dark lines were
seen, and therefore it is reasonable to conclude that the con-
tinuous spectrum when given by comets is due to reflected
sunlight.b

It was an important advance thus to learn that the light
of the comet came from two sources ; the one from the Sun,
by reflection ; the other from the comet itself. But the spectro-
scope speedily revealed a further and unsuspected fact : that
intrinsic cometary light was due to glowing hydro-carbon
vapour. For Huggins c and Secchi in examining the head of
Winnecke's Comet in 1868 saw 3 shaded bands, besides the
continuous spectrum, and on comparing them with the spectrum
of olefiant gas, found that they were exactly coincident with
the 3 principal bands of the so-called hydro-carbon spectrum,
agreeing with them not merely in position, but in general
appearance and in the manner in which they faded away.
Coggia's Comet yielded the same result. Since then various
comets have been subjected to spectroscopic scrutiny with
results which are, on the whole, in remarkable accordance.
Three comets, however, stand out from the rest, — Brorsen's
Comet as observed by Huggins in 1868; Comet iii. of 1877
as observed by Copeland at Dun Echt ; and Holmes's Comet
as observed by Keeler in 1892. Excluding these, all the
others have shown 3 bright bands coincident with one or
other of the carbon spectra.

b Month. Not. B. A. S., vol. xxxiv, c Fhil. Trans., vol. clviii, p. 555.

p. 491. 1874. 1868.

The Story of the Comets.

CHAP.

Although mention is made in the previous paragraph of
a spectrum there called the " Hydro-carbon " spectrum, its
real origin is still unsettled. There are four carbon spectra :

(1) a simple line spectrum undoubtedly due to carbon itself;

(2) a band spectrum given by the base of a candle flame and
often called the " Swan " spectrum after the name of its
discoverer; (3) a spectrum usually known as the carbonic
oxide spectrum, which also is banded ; and (4) a banded
spectrum due to cyanogen.

Much discussion has raged around the second, the so-called
hydro-carbon spectrum, and its real origin is still so un-
certain that Frost, in a recent discussion of Morehouse's

Fig. 98.

SPECTRA OF OLEFIANT GAS AND WINNECKE'S COMET, 1868.

A, Spectrum of Olefiant Gas ; B, Spectrum of Comet.

Comet, refuses to go further than to call it a " carbon "
spectrum. Smithells has apparently shown it to belong to
carbonic oxide, but the question is too involved for discussion
here.d

The question however arises, with which of the carbon
spectra do the cometary spectra coincide 1 With regard to the
brighter comets the testimony is clear ; the spectrum yielded
has been that given by the blue base of a candle-flame, or
by a Bunsen burner — the spectrum which Lockyer terms that
of hot carbon, but which Hasselberg and others consider as
characteristic of a hydro-carbon, probably of acetylene. The

d Phil. Mag , 6th series, vol. i, p.
476. April 1901. For further in-
formation the reader may consult

Baly's Spectroscopy, 1905 edition, p.
444.

XII. Comets in the Spectroscope. 177

wave-lengths of the edges of the three principal bands of
this spectrum are given by Kayser and Runge as 5635 for
the band in the yellow, 5165 for that in the green, and 4737
for that in the blue respectively. But the complete spectrum
contains 5 bands, one in the red at 6188 and one in the
violet at 4311. These have not often been detected in the
spectra of comets, but in the case of one or two of the brightest
(the first instance being that of Coggia's Comet in 1874 when
Secchi recognised their presence) they have been made out.
It appears, therefore, that it is only a question of brightness,
and that the whole series may be expected to be shown by
any comet of sufficient brilliancy.

In the case of some of the earlier and fainter comets the
bright bands were recorded by some observers as coincident
with that spectrum of carbon called by Lockyer that of cool
carbon, by others that of carbonic oxide, in distinction to the
hydro-carbon spectrum referred to above. The wave-lengths
of the bands in this spectrum are as follows : — yellow, 5609 ;
green, 5198; blue, 4834. It is not yet absolutely certain
whether these observations are to be accepted. It appears
probable in some cases, if not in all, that the faintness of the
spectrum prevented any accurate measurement of the cometary
bands, and that being compared with the carbonic oxide
spectrum writh only low dispersion, and a close approximation
being noted, it was assumed that the correspondence was
exact. Thus Christie observing the spectrum of Hartwig's
Comet on Oct. 7, 1880,6 measured the green band as at wave-
length 5201, or as being the band of the carbonic oxide
spectrum : four days later he measured the same band as at
5169, or as being the band of the hydro-carbon spectrum ;
and on Oct. 12 the observation was repeated. A comparison
of the individual measures renders it all but certain that
there was no change in the place of the cometary band, and
that the difference in the positions recorded was due entirely
to the difficulty of securing an accurate measurement of an
object so faint and diffused.

e Greenwich Spectroscopic 06s., 1880, p. 62.

CHAMBERS X

178 The Story of the Comets. CHAP.

Hasselberg reviewing the observations of the first 18 comets
subjected to prismatic analysis con eluded f :—

(1) That all observed cometary spectra belong to one type,
with the exception of the two doubtful cases of Comets
i. 1868, and iii. 1877, noted above.

(2) That this type is that of the hydro-carbons.

(3) That they deviate from the type in being incomplete ;
and, in general, in the relative brightness of the bands.

(4) That they are incomplete in so far as the red and violet
bands of the hydro-carbons are wanting, and also that the
maximum brightness of the bands is not at the less refrangible
edge, but somewhat towards the violet.

(5) That this circumstance explains why in the case of faint
comets the connection with hydro-carbon spectra has appeared
doubtful.

(6) That the displacement of the maxima of the bands of
most comets, with regard to those of hydro-carbons, is
approximately the same ; therefore it seems probable that
the differences of the physical conditions of the hydro-carbons
in the comets, from those which have hitherto been obtained
in observations of hydro-carbon spectra, are approximately
the same.

The observation of the red and violet bands in Coggia's
Comet and in several recent bright comets meets the allega-
tion of incompleteness made above in (4) ; whilst the shift of
the maximum brightness from the edge of the cometary band
towards the violet admits often of a very simple explanation.
To observe a faint comet the slit of the spectroscope must be
opened wide, and probably the light from the whole of the
head or from a considerable portion of it will be embraced
within the opening. This will not be of one homogeneous
brightness throughout, but will fade outwards from the centre ;
there will be more light near the centre of the slit opening
than close to either jaw, and consequently the cometary bands
will not only degrade towards the violet, but to a slight extent
towards the red as well, throwing the maximum brightness

1 Mem. Ac. Imp. de St. Petersbourg, series vii, vol. xxviii, No. 2 ; Copernicus,
Tol. i, p. 83.

XII. Comets in the Spectroscope. 179

towards the violet. Thus Konkoly found, when examining
Sawerthal's Comet (1888 i.), that the lines were not sharply
defined on either side. Consequently his measures of the
middle of the maximum light-intensity of the hydro-carbon
bands did not coincide with the laboratory wave-lengths. In
bright comets when a very narrow slit can be used, and when
therefore the entire breadth of the slit is filled with light of
practically the same intensity, this discrepancy between the
spectra of the comet and of the hydro-carbon disappears.
Maunder writes thus in regard to Tebbutt's Comet of 1881 : —

"With the spectra of the Comet and of the Bunsen-flame arranged one
above the other, and the flame adjusted until the bright sharp edge of the
green band was of the same intensity in each, the resemblance between the
two spectra was exceedingly striking, the three principal bands correspond-
ing exactly in position, in brightness, and in the manner and degree in
which they shaded off towards the violet."

If this be the correct explanation, there will be no reason to
suppose, as in paragraph (6), that the displacement arises from
any peculiarity in the physical condition of comets. The
displacement will be apparent only, and due to the difficulties
of observation.

Beside these shaded hydro-carbon bands, comets generally
give a continuous spectrum from the nucleus and the imme-
diate neighbourhood. This is largely due to reflected sun-
light, the Fraunhof er lines having been detected on favourable
occasions.

The years 1881 and 1882 were especially remarkable for
the fine comets which were then visible. Comet iii. of 1881,
discovered by Tebbutt, proved especially interesting as the
first which was itself successfully photographed, and the first
of which the spectrum was photographed, the former feat
being accomplished by Janssen, the latter by Huggins and by
H. Draper. As first seen in Northern latitudes, the spectrum
of Tebbutt's Comet was almost purely a continuous one ; it
was some few days before the cometary bands began to show
themselves. But as the nucleus faded they became more
apparent, and their precise coincidence with the bands from
a Bunsen-flame was rendered evident. The continuous

N 2

180 The Story of the Comets. CHAP.

spectrum on June 29 showed the Fraunhofer lines, F being
unmistakeably present. But the photographic plate had
anticipated the eye of the observer, Huggins's negative taken
on June 24 showing in the ultra-violet region both the hydro-
carbon bands and the solar absorption lines, and proving that
the spectrum in the visible portion and in that beyond the
grasp of the eye were essentially the same.

The spectrum of the tail of this comet was also examined,
and both Vogel and Young traced the carbon bands far down
its length, the former indeed to its very end. Probably the
spectrum of reflected sunlight was also present, though Young
could not trace it so far as he could the gaseous flutings.

Comet iv. of 1881 (Schaberle's) formed a striking contrast
to Tebbutt's, in that it gave almost a pure spectrum of bands.
The hydro-carbons were strongly in evidence; of reflected
sunlight there was scarcely a trace.

Both these comets afforded to Copeland and Lohse a further
proof of the origin of their banded spectra, for these observers
were able not merely to see simple shaded bands, but to break
them up into true flutings precisely as the hydro-carbon
spectrum can be resolved.

The Comets of 1882 were yet more important. All the
comets which had been previously examined had considerable
perihelion distances ; Comets i. and ii. of 1882 both approached
very near the Sun, the latter all but grazing its surface. The
former, known from its discoverer as Wells's Comet, at first
showed an almost purely continuous spectrum. The nucleus
was greatly condensed, and to direct eye observation and as
seen through the prism, it presented a very stellar appearance.
On May 27 Copeland suspected the presence of a bright line ;
the next night the line was seen to be coincident with the
D line, and as the result of what he saw on May 29 Copeland
wrote g : —

"The spectrum of the nucleus of Wells's Comet deserves the closest
attention, as it shows a sharp bright line coincident with D, as well as
strong traces of other bright lines, resembling in appearance those seen in
the spectra of 7 Cassiopeiae and allied stars."

* Copernicus, vol. ii, p. 229. 1882.

XII. Comets in the Spectroscope. 181

Copeland and Lohse followed the comet day by day till its
perihelion passage on June 10, and had the gratification of
seeing the bright sodium lines, D, develope in the most
striking manner. On June 6, the D lines were seen beauti-
fully double, and the continuous spectrum was so much the
less important, the light of the comet was so nearly mono-
chromatic, that with a wide slit Lohse was able to see "the
perfect image of the cornet, head and tail, ... in the light of
the D line, very bright and clear. . . . The sight was really
magnificent ; exactly like a prominence '.

Other bright lines were observed, especially in the red, and
there were faint traces of the ordinary carbon bands. But
the sodium light was predominant, and, next to that, the
general continuous spectrum.

The Great Comet of 1882 approached the Sun much nearer
than Wells's Comet had done ; and inferring that the develop-
ment of sodium light in the spectrum of that body had been
due to the heat it experienced as it approached the Sun,
Copeland and Lohse naturally expected to find the D lines
bright also in the spectrum of this new visitor. The inference
was justified. " The expected bright sodium lines exhibited
themselves to the eye of the observer with a brilliancy and
neatness quite comparable to the C line in prominences, so
well defined and clear did they stand out on the bright
daylight spectrum." But besides the D lines a number of
other bright lines were seen, notably the E lines and some
other prominent iron lines, together with 5 lines in the red
which had no counterparts in the dark lines of the solar
spectrum.

A beautiful illustration was afforded by this comet of the
effect of the motion of a body on the lines of its spectrum.
The comet was receding from the Earth at this time, and the
lines of its spectrum were therefore displaced a little towards
the red, the bright D and E lines being seen therefore just on
the redward side of their dark counterparts in the solar
spectrum. This observation was not only made by Copeland
and Lohse, at Dun Echt, but on the same day, Sept. 18, by
Thollon and Gouy at Nice ; and in both cases the displace-

182 The Story of the Comets. CHAP.

ment was estimated to be about | or -| the distance between
the D lines, a displacement which would correspond to a
motion of about 42 miles per second. The actual motion of
recession of the comet had been otherwise put at about 45
miles per second.11

As the comet receded from the Sun the various bright lines
faded away, the D lines lasting longer than the others, whilst
the carbon bands came into greater prominence. There is
every reason to believe that these changes are strictly typical ;
and that we may expect comets of short perihelion distance to
show, first, the hydro-carbon spectrum; then, when in the
neighbourhood of the Sun, the sodium lines ; and lastly, when
at closest approach, a number of other metallic lines, and
particularly those of iron. Lockyer carries this view of the
successive changes of cometary spectra much further, and has
drawn up a long list of the successive phases presented by the
spectrum of a comet as the body approaches or recedes from
the Sun.1

Since 1882 there has been no "great" comet, but improve-
ments in the methods of observation and an increased interest
in the physical conditions of these mysterious objects are
factors in the case which have more than counterbalanced
the lack of bright comets available for investigation. The
increased sensitiveness and reliability of the photographic
plates in use have also played an important part in the
investigations by bringing to light the ultra-violet radiations
in which cometary spectra are so rich and to which the eye is
blind.

It has already been remarked that the earlier photographic-
investigations of cometary spectra were made with instru-
ments designed for stellar researches only and unfitted for
cometary work. Thus Professor Frost records k that, on Oct. 30,
1908, an exposure of 158 minutes with the 40-inch Yerkes
refractor and the one-prism Bruce spectrograph failed to give

h Comptes Rendus, vol. xcv, p. 555, Jan. 10, 1889.

Sept. 25, 1882 ; and p. 712, Oct. 23, k Astrophysical Journal, vol. xxix,

1882. p. 56. January 1909.

1 Proc. Roy. Soc., vol. xlv, p. 190.

XII. Comets in the Spectroscope. 183

any trace of an impression due to the comet, whereas an
objective-prism spectrograph, in which the ratio of focal
length to aperture was only 6 to 1, gave a good spectrum in
30 minutes. Frost's dictum is that "the great refractor,
with its long focal length, is obviously unsuited for such an
object ".

It is obvious then, that if our knowledge of cometary
spectra is to be substantially increased by the appearance of
Halley's Comet, or by any other bright comet that may be
discovered, the number of these short-focus prismatic cameras
and specially designed spectroscopes must be multiplied. By
using them while the comets are faint, and then working
them in conjunction with the larger instruments — giving more
precise results — as the comets become brighter we may be able
to throw more light on any spectral changes which take place
as the comets approach their perihelia. It is probably behind
these spectral changes that the truth lies. That all cometary
spectra, at all times, are not exactly alike may now be
accepted as proven ; and it must be borne in mind that it is
from the variations between one comet and another, or in the
spectra of the same comet at various times, that we are likely
to learn most.

After this digression we will proceed to review the work
done during the interval since 1882, which has been an
interval marked by a large number of small comets.

Borelly's Comet of 1890 (i.) showed on Jan. 15, according
to Backhouse, the three characteristic bands with a faint
continuous spectrum, the latter being so faint four days later,
on January 19, that its presence was only suspected.

Fowler compared the spectrum of Comet 1890 (ii.) (Brooks's)
with the spectrum of the blue base of a spirit-lamp flame, and
found1 that the bands coincided, with the exception of the
bright fluting in the violet ; the continuous spectrum extended
from D to a little beyond the band at wave-length 474.

Examining the spectrum of Swift's Comet (1892. i.),
Konkoly found five lines which he gave m in the following

1 Nature, vol. xlii, p. 112. May 29, m Ast. Nach., vol. cxxix, No. 3087.

1890. April 25, 1892.

184 The Story of the Comets. CHAP.

order of intensity :— 5163-0, 5588'2, 5449-4, 4725'4, and 4687-8 ;
this was on April 1 and 2, 1892. But Campbell examining
the same object on April 5 saw n quite a different spectrum,
consisting of the characteristic bands 5630, 5170'3, and 4723,
with the relative intensities 1, 6, and 2. The wave-length of
the middle band appeared to vary, and Campbell suggested
that three bright lines formed at wave-lengths 5170, 5164,
and 5157, and disappeared in that order. If this were a real
change between April 1 and April 5, it is significant to note
that the perihelion occurred on April 6, but Campbell's
measures were not sufficiently delicate to detect any such
change about that time. Von Gothard photographed the
spectrum of this comet with the spectrum of a Bunsen flame
on the same plate, and found the two to be identical as far as
the fourth band (473-464)°. Beyond that, new unknown
lines and bands appeared and the band at 389-387 was
faintly represented. The new bands were similar in appear-
ance to the hydro-carbon bands, and this led Von Gothard to
the conclusion that the hydro-carbon in comets is different, or
exists under different conditions, from that appearing in the
Bunsen flame.

The next comet of importance to which reference must be
made was Holrnes's, discovered on November 6, 1892, and
described generally elsewhere.5 This was a remarkable body,
a diffuse, nebulous, tailless mass easily confounded with the
Andromeda nebula ; and its spectrum was just as peculiar.
Instead of the usual display of bands Keeler q saw simply a
fairly bright, continuous spectrum extending from D to about
half-way between F and G, the maximum brightness being
a little below h. Careful scrutiny failed to reveal any lines,
and the nucleus was seen as a brighter streak running through
the whole spectrum. Observations made by Campbell r on
November 8 and 9, 1892, showed a spectrum "of an extreme
type and probably unique ", a continuous spectrum, extending

n Astronomy and Astrophysics, vol. xi, q Astronomy and Astrophysics, vol. xi,

p. 698. Oct. 1892. p. 929. Dec. 1892.

0 Eder's Jahrbuch, 1893. r Ibid., vol. xii. p. 57. Jan. 1893.
p p. 74 (ante}.

XII. Comets in the Spectroscope. 185

from D to G, with a very slight condensation evidently due
to the familiar green band at wave-length 515, and a very
faint trace of the yellow band. Keeler examining the spectrum
again on January 29, 1893, after an anomalous brightening
of the comet on January 16, saw a very faint suspicion of the
green band of which he could never be certain.8

The spectrum of a strongly moonlit sky was exactly similar
to, but fainter than, that of the comet. It would appear
then that in this case they were dealing with an object almost
wholly illuminated by reflected light. It had been suggested
that this peculiar comet might have been formed by the
collision of two asteroids, but, as Keeler pointed out, the ob-
served spectrum negatives this hypothesis ; such a cataclysmic
birth would involve the production of a bright line, or banded,
spectrum.

The spectrum of Rordame's Comet (1893, ii.) was very fully
investigated, photographically, by Campbell,* who measured
28 bright lines, 14 of which were found to correspond with
lines and bands given by Kayser and Runge in the spectra of
carbon and cyanogen.

Visual observations by Keeler u showed that the spectrum
was a beautiful example of the hydro-carbon type, and he
called special attention to the sharpness of the bands at their
less refrangible edges, a phenomenon not usually seen in
cometary spectra.

The spectrum of the Comet 1902 (ii.) (Perrine-Grigg's)
was of special interest, because it was in photographing this
that Count De La Baume-Pluvinel first employed the short-
focus prismatic camera, now recognised as a sine qud non in
the photographic recording of the spectra of faint comets.

Experiments with larger instruments having proved fruit-
less, Baume-Pluvinel built up a camera v wherein the focal
length of the objective was but four times the aperture, and
to which he applied a prism of 20° refracting angle. Of

8 Astronomy and Astrophysics, vol. xii. u Ibid., vol. xii, p. 650. Aug

p. 272. March 1893. 1893.

''Ibid., vol. xii, p. 652. Aug. v Bull, de la Soc. Ast. de France, vol.

1893. xvii, p. 117. March 1903.

186 The Stomj of the Comets. CHAP.

course the negatives obtained with such an instrument are
practically useless for the fine determination of wave-lengths,
but they are capable of showing the qualitative variations
and coincidences of cometary radiations.

The spectrum obtained, with one hour's exposure, by
Chretien and Senoque, showed the three characteristic bands
564, 518, and 472, and the cyanogen band at 389. Almost
all the light of the comet was concentrated in the two bands
472 and 389, and Baume-Pluvinel remarks, parenthetically,
that objectives intended for comet photography should,
obviously, be especially corrected for this more refrangible
region of the spectrum. The heads of the bands at 564 and
518 were bright visually, but were much fainter, relatively,
on the photograph, although orthochromatic plates were used.
It is most essential that this difference of photographic and
visual intensities should be carefully considered when com-
paring the relative intensities of spectral lines.

The spectrum of Borelly's Comet of 1903 (iv.) was photo-
graphed by Deslandres x at Meudon, and found to be similar
to that of Rordame's Comet obtained by Campbell in 1893.

Perrine y also found the same five bands in the spectrum of
this comet as were recorded by Campbell in that of Rordame's
Comet, but noticed that the band at 420 was much weaker
relatively. Curtis also recorded the similarity with Rordame's,
and noted a strong continuous spectrum.

In 1904, Pickering employed an objective-prism camera to
photograph the spectrum of Brooks's Comet (1904, i.) which
he found to be nearly continuous, with two slight con-
densations.

The success of the prismatic camera as an engine of research
in the investigation of cometary spectra soon led to its more
general application, so that on the appearance of Daniel's
Comet of 1907 (iv.) several observers employed it to obtain
photographic records of the comet's radiations. A great
advantage of spectra thus obtained (in that they show mono-
chromatic images of all the sufficiently bright parts of the

* Compies Rendus, vol. cxxxvii, p. * Lick Observatory Bulletin. No. 47.

393. Aug. 17, 1903. 1903.

XII. Comets in the Spectroscope. 187

comet) was amply affirmed, for on spectra obtained by
Mr. and Mrs. Evershed,2 at Kodaikanal, India, and by
Deslandres,a at Meudon, it was found that the radiations of
the nucleus were not identical with those of the tail. Evershed
photographed the spectrum of Procyon alongside that of the
comet, and was thus able to determine the wave-lengths of
the cometary spectrum by direct comparison with the hydrogen
lines in that of the star.

The last comet to be considered here is the one discovered
by Morehouse on September 1, 1908.

No other comet has ever been so well, and so persistently,
observed, and certainly no other cometary spectrum ever
received so much detailed attention. Whilst the object itself
was remarkable for its vagaries, its lightning changes of
form, and its periodic outbursts, the spectrum observations
were, at first sight, almost as remarkable for their positive
disagreements. This may have been due, however, to some
extent, to the fact that so many observers were at work at
different times.

Count De La Baume Pluvinel and Baldetb photographed
the spectrum, with the prismatic camera, on October 4, 5, and 7.
The plates obtained showed seven monochromatic images of
the comet and indicated that the hydrocarbon radiations--
strong in the spectrum of Daniel's Comet, obtained with the
same instrument — were absent : the cyanogen spectrum, usually
represented by the band at 388 alone, was completely repre-
sented in the part of the spectrum photographed, and there
was no trace of continuous spectrum.

Evidence of change was afforded by the radiation at 376,
for whilst a tail accompanied the feeble image photographed
on October 5, there was no trace of it on the more intense,
nuclear image of October 7.

Deslandres and Bernard0 agreed on the absence of the
hydrocarbon radiations. But they found the two first heads

z Monthly Notices R.A.S , vol. Ixviii, b Comptes Rendus, vol. cxlvii, p. 666.

p. 16. November 1907. October 19, 1908.

a Comptes Rendus, vol. cxlv, p. 445. c Comptes Rendus, vol. cxlvii, p. 774.

Aug. 26, 1907. November 2, 1908.

188 77/6- Story of the Comet*. CHAP.

of band at 388 to be the only representatives of the cyanogen
spectrum, and recorded a very persistent continuous spectrum.
The three strongest bands of unknown origin were those at
456-1, 426-7, and 401-3 previously recorded by Evershed in
the spectrum of Daniel's Comet.

Another similarity of these two comets was found in the
fact that some of the bands were double.

The results obtained by Frost and Parkhurst,d at the Yerkes
Observatory, exhibited points of variance with both sets of
the French observations. Twenty-one spectrograms were
obtained between October 28 and December 2, 1908, and on
none was there a trace of continuous spectrum, thus showing
that at that epoch the amount of reflected sunlight was very
small as compared with the amount of intrinsic light emitted
by the incandescent carbon and other matter. [See Fig. 101,
Plate XXVI.]

Allowing for the uncertainty of wave-length measures
made on photographs of small dispersion, it appears that both
the hydrocarbon and cyanogen spectra are probably repre-
sented. Relative variations in the intensity of the tail images
indicate some difference between nuclear and tail matter
which is not explained by the behaviour of the matter con-
cerned when experimented upon in the laboratory.

An important feature of these spectra is that the separate
monochromatic images of the tail follow the bends seen on
the direct photograph, thus showing that particles having the
same chemical constitution were ejected at angles differing by
as much as 40°. Apparently we have, in this, a contradiction
of Bredichin's theory, according to which the comparatively
straight tails shown on these photographs should have been
seen only in hydrogen radiations and not in those of the
hydrocarbons and cyanogen.

Campbell and Albrecht6 made visual and photographic
observations, using, for the latter, a specially designed spectro-
graph in conjunction with the 36-inch Lick refractor. Their
results showed the presence of carbon and cyanogen, although
the second cyanogen band was, apparently, entirely absent.

d Astrophys. Journ., vol. xxix, p. 55. e Astrophys. Journ., vol. xxix, p. 84.

Jan. 1909. Jan. 1909.

Figs. 99, 100, 101.

Plate XXVI.

MOREHOUSE'S COMET $908, iii.). December 11.

PHOTOGRAPH AND SPECTROGRAPH OF MOREHOUSE'S
COMET (1908, iii.).

r. 1 88.

XII. Comets in the Spectroscope. 189

In a communication f to the Paris Academy of Sciences,
Deslandres, Bernard, and Bosler epitomised and discussed the
various observations of this comet, drawing therefrom some
valuable conclusions.

They pointed out that prior to 1907 the only cometary tail
spectrum observed was that of the great Comet of 1881, in
which the c: Swan ", or so-called " hydrocarbon " spectrum,
was recognised. But in the tails of Daniel's and Morehouse's
Comets, new radiations at 456, 426, and 401 were discovered.
Also, they disagree with Baume Pluvinel's partition of lines
into series.

The presence of a band at 3913-2, recognised as belonging
to the spectrum of nitrogen at low pressure, and produced by
cathode rays, suggests that the cometary matter may be
rendered incandescent by the passage of cathode rays emitted
by the Sun.

These observers consider that the new spectrum of doublets,
and its three principal radiations at 456, 426, and 401, probably
constitute the most constant character of cometary spectra,
for they appear as intense radiations in the Daniel and
Morehouse Comets in which the classical carbon bands showed
marked variations.

Thus we see that more recent researches have not tended to
simplify the question as to the nature of cometary spectra.
Besides the older conception of "hydrocarbons", cyanogen,
and reflected sunlight, we have many new lines, probably
indicating other substances, to be investigated. But that
carbon in one form or another plays an important part in the
constitution of comets, is certain ; and we now know that in
recent comets the cyanogen radiations, especially that at 388,
have taken up a large proportion of the comet's light. The
ultra-violet character of the light from Morehouse's Comet
was a very strong feature which becomes important when we
consider the problem of comet photography.

Morehouse, who discovered it by photography, described it
as having a conspicuous tail; Borelly, who found it inde-
pendently, and visually, could see scarcely any tail. An

f Comptes Rendus, vol. cxlvii, p. 805. March 29, 1909.

190 The Story of the Comets. CHAP.

observer with eyes sensitive to these more refrangible rays
would probably have seen this comet as a brilliant naked-eye
object.

The important part played by cyanogen in the spectra of
comets, considered in conjunction with solar and laboratory
observations of the cyanogen spectrum, led Newall to propound
the following interesting questions concerning the nature and
origin of cometary radiations.g " Is it not possible that the
hydrocarbons, nitrocarbons, etc., which seem to be evidenced
by the spectra of all comets, are always present in circumsolar
space, and rendered incandescent by some processes connected
either with the motion of the solid parts (including dust) of
the head of the comet through the vapours, or with the
emission of some influence from the comet head ? Are we to
say that all comets, wherever they may come from in the
universe, and whatever their main material may be, always
bring with them the cyanogen and hydrocarbons which give
them luminosity ? Or is it not more rational to say that the
spectra of all comets are approximately similar, because they
always find the same vapours spread in their path as they
approach the Sun, and can only elicit the spectra of these
vapours ? "

The author of this interesting theory has evidence of the
existence of cyanogen between the Sun and the Earth's
surface, and has worked out at some length the conditions
under which the luminosity could be generated. But for the
present, despite the delightfully simple way in which such
a theory would explain the similarity of cometary spectra in
general, we must be content to look upon the comet spectrum
as radiation, probably produced by electrical action of some
kind, from the particles of the comet itself. That the volatile
gases of the carbon compounds should be the first to be
excluded is not a matter of wonder, whilst the observation
that when the comets attain to lesser distances from the Sun,
and therefore become more strongly heated, both by the solar
radiation and by the increased number of collisions among
their own particles, sodium and iron are vaporised and

g Monthly Notices R.A.S., vol. Ixviii, p. 5. Nov. 1907.

XII. Comets in the Spectroscope. 191

rendered incandescent, is but another step in accordance with
the law of continuity.

Schiaparelli and others have taught us to associate closely

meteors with comets, and we now know of numerous instances

in which a comet and a meteor stream are actually travelling

on the same orbit. It might be expected that there would be

some resemblance between the spectra of the two classes of

bodies. But the rapid motion and evanescent character of

meteors makes their spectroscopic observation exceedingly

difficult. Browning, however, succeeded in observing no fewer

than 70 in August and November 1866, with an instrument

constructed by himself for the purpose.1' This consisted

simply of a direct-vision compound prism, and a plano-concave

cylindrical lens ; the latter being intended to diminish the

apparent angle through which the meteors fell. The heads

of the meteors gave spectra mostly continuous, though with

frequent differences in the relative preponderance of the

colours. In the tails, in every instance, orange-yellow light

oredominated, from which the presence of sodium may

Drobably be inferred. Konkoly looks upon this presence of

/he sodium line as possibly due rather to particles floating in

mr air and becoming incandescent with the meteor than to

,ny constituent of the meteor itself. But the same observer

a the spectrum of a magnificent fireball on Oct. 13, 1873,

bserved not merely the sodium lines, but also bands which

e was able to identify by direct comparison with the spectrum

f a hydrocarbon,1 thus affording an evidence from the

Dectroscopic side of the connection between comets and

eteors ; and remembering the brilliant sodium lines of the

•mets of 1882, it does not seem improbable that meteors

.ould show this metal also.

Other metallic lines have also been observed in meteors :
ose of Magnesium frequently, and the lines of lithium and
tassium sometimes.

Month. Not. R.A.S., vol. xxvii, p, 82. Dec. 1873. The word " light-
7. Jan. 1867. ning gas" is a misprint for "lighting

Month. Not. R.A.S., vol. xxxiv, gas ", that is to say, coal gas.

CHAPTER XIII.

Association of Comets and Meteors. -Facts connected with Meteors necessary
be borne in mind.-Summary statement of these.-Meteor Showers of 1
and 1832,-Shower of 18<tt.-Evident periodicity. -Researches ofQuete
and H. A. Newton.- Investigations by J. C. Adams.-Schmparelliand
Auaust Meteors.— Orbits of certain Meteor Swarms identical with the*
of certain C<ymets.-Four such cases of identity recognised. -The Augt
or Perseid, Meteors.-The Nov. 12, or Leonid, Meteors.-The April,
Lvrid Meteors.-The Nov. 27, or Andromedes, Meteors.— The disappe
ance of Bielas Comet.-The certainty of the connection of the Andron
Meteors with that Comet.-Recent investigations as to that Comet.-
of the whole subject.

NOT the least interesting of the modern developements
Cometary Astronomy is the discovery that in certain ca
a relation exists between comets and meteors. Time was,
so very long ago, when comets were considered (and righ
matters of pure Astronomy, whilst meteors of all kinds,
so-called "shooting stars" included, were looked upon
belonging to the domain of terrestrial Meteorology. How
association came to be known needs to be told in a
dealing with the matter from the astronomical side, bul
I desire to avoid going more deeply into the subject of met
than is absolutely necessary, I must ask the reader to tak
trust a few facts baldly stated, referring him to other w<

for details.

The facts contemplated in the foregoing remark are

following: (1) shooting stars may be seen on almost eM
night of the year in some part of the heavens ; (2) th<
more numerous at certain seasons of the year than at c
(3) whilst odd ones may often be noticed anywhere,

QII. The Relation of Comets to Meteors. 193

peak, there are about 100 or more particular centres in the
leavens which are specially centres from which they seem to
•adiate ; (4) the meteors coming from these centres are named

I ORBIT OF THE LEONIDS OK NOV. 13 AND OF THE COMET OF 1866 (i.) RELATIVELY TO
THE ORBITS OF CERTAIN PLANETS.

[by ugly fabricated names derived from the constellations in
which the centres are situated ; thus Leonids, Lyrids, Perscids,
Quadrantids, and so on; (5) the term « shooting star " is an

fold-fashioned one which has almost gone out of use, having

194 The Story of the Comets. CHAP.

been replaced in scientific circles by the term " luminous
meteor ", or simply " meteor ". This summary will suffice as
a preface to what is to follow.

In Nov. 1799, and 34 years afterwards, namely, in Nov.
]833, there happened magnificent displays of luminous
meteors, radiating from a point in the constellation Leo,
whence they have obtained the name of Leonids. Drawing
the conclusion, from a catalogue of such displays which had
been formed by a Belgian astronomer named Quetelet, that
these displays were periodic at stated intervals, an American
astronomer named Newton (following up some previous
investigations by two learned Americans, Olmsteda and
Twining, of New Haven, Connecticut) entered upon a thorough
investigation of the subject -with a view of ascertaining
whether any prediction as to future displays could safely be
put forth. He came to an affirmative conclusion by an-
nouncing that another great display would occur on Nov. 14,
1866 ; in other words, that these displays were undoubtedly
periodic, and that the period was about 33^ years. The
display duly happened as Newton had predicted, and was
a very beautiful one ; but we are not here concerned with any
descriptive details,1* except to say that a repetition of the
show on a much smaller scale occurred in 1867 ; and that the
swarm is so stretched out that it seems to take more than
3 years in passing a given point in its orbit whilst crossing
the Earth's orbit. Another great display was expected in
1899 or 1900 but did not occur, though in November 1898 and
November 1901 considerable displays did take place.

Taking advantage of the information which had been
gathered by previous workers in this field, Professor J. C.
Adams, of Cambridge (of Neptune fame), proceeded to calcu-
late elliptic elements for the orbit of the meteor swarm
treated as, in a sense, a concrete mass.0

a Olmsted seems indeed to have b See my Handbook of Astronomy,

broached as far back as 1834 the idea vol. i, p. 616, et seq.

that the shower of 1833 had some- c Month. Not R.A.S., vol. xxvii,

thing cometic about it. (Sillimari's p. 247. April 1867.
American Journal, vol. xxvi, p. 172.)

XIII. The Relation of Comets to Meteors. 195

Postponing for the moment Adams's conclusions we will
pass on to some researches carried out on kindred lines by
Schiaparelli of Milan. He took in hand the Perseid meteors
of August as he found them recorded on Aug. 9, 10, 11, 1866 ;
and treating them also as a concrete mass and assuming, as

Fig. 103.

THE METEOR RADIANT POINT IN LEO :
TRACKS OF METEORS SEEN AT GREENWICH, NOV. 13, 1866.

Adams had done, that their orbit was a section of a cone,
he arrived at certain figures on the supposition that the conic
section in question was a parabola. He had reached this
stage in his researches when he suddenly discovered that his
parabolic elements of the meteor group very closely resembled
the elliptic elements which had been obtained for the Comet

o 2

196

The Story of the Comets.

CHAP.

of 1862 (iii.). The resemblance will be best seen by putting
the two sets of figures side by side thus :—

Perihelion passage
Longitude of perihelion
Ascending node
Inclination of orbit ...
Perihelion distance ...

Period

Direction of motion .

August Meteors.

1862, July 13

343° 28'

138° 16'

64° 3'

0.9643

105 years ?

Retrograde

Comet of 1862 (iii.).

1862, Aug. 22. 9

344° 41'

137° 27'

66° 25'

0.9626

1234 years

Retrograde

Whilst it must be admitted that the estimate of the periods
is uncertain the general resemblance of the other elements of
the two orbits is too unmistakable to permit of any doubt
being thrown on the fact that meteors and comet were moving
in orbits identical in form. The return of this meteor-comet
is to be looked for in 1985.

Now we must go back to a consideration of Adams's results,
and they follow the precedent established by Schiaparelli ; for
the elements of the November meteors (treating their orbit as
an ellipse) were found reproduced almost precisely in the
elements of the Comet of 1866 (i.) as found by Oppolzer.
Adams presented them in the following form : —

Period

Mean distance ...

Eccentricity

Perihelion distance

Inclination

Longitude of node

Distance of perihelion from node
Direction of motion

33-25 years (assumed)
10-3402 ...

0.9047

0-9855

16° 46'

51° 28'

6° 5'

Retrograde

33-18
10-3248
0-9054
0.9765
17° 18'
51° 26'

9° 2'
Retrograde

A separate group of the Leonids is also suspected to exist,
preceding the principal one by about 12 years (or about ^rd of
a revolution) in its appearance. Notable meteor showers are
recorded to have taken place in 855-56, 1787, 1818-23, and
1852, agreeing exactly with the principal cluster in the day
and very closely also in the period of their returns.d The
original dismemberment of the comet (assuming that a comet
was in question) to which the ancient record of this widely

d Nature, vol. xi, p. 407, March 25, 1875 ; vol. xii, p. 85, June 3, 1875.

XIII. The Relation of Comets to Meteors. 197

scattered cluster points must have been of great antiquity,
since the interval of 12 years between the years 855-56 and
the next display in 868 differs very much from the distance
found to separate in modern times the well-marked minor
apparitions of the years 1787, 1820, and 1822 compared with
the modern appearances of the chief group in 1799 and 1833.
It may, therefore, be assumed that important consequences
may sooner or later be expected to be traced as the outcome
of investigations in this field of cosmical phenomena, for it
cannot be supposed that we have reached yet by a long way
the end of our tether in our knowledge of these subjects.
The next return of the Leonid meteor-comet is expected in
the summer of 1932.

It was subsequently found that the meteor shower belong-
ing to the date of April 20, and now known as the Lyrids,
matched, as regards their orbit, the Comet of 1861 (i.), whilst
the shower of Nov. 27, now known as the Andromedes,
similarly matched the orbit, as known up to that date, of the
missing Comet of Biela. There is not much to be said about
the Lyrids and their attached comet, but as regards the Biela
association a long tale can be unfolded.

When things had reached the stage of developement which
has just been, described, it naturally came into men's minds,
could the newly-acquired knowledge be brought to bear in any
way in elucidating the mystery of the disappearance of Biela's
Comet,6 which at that time was an unprecedented and wholly
inexplicable mystery 1 It was possible to give an affirmative
answer to the question. Though this comet had failed to
appear either in May 1859, or in Jan. 1866, hopes were enter-
tained that it might be picked up when next due, which would
be in Aug. and Sept. 1872, the perihelion passage having been
fixed for Oct. 6. These hopes were not realised, but the appear-
ance on Nov. 27, 1872/ of an abundant meteor shower corre-
sponding in the position of its radiant point, and in the date
of its appearance, with the position and date of a meteor

e See p. 88 (ante). revolutions of Biela's Comet assumed

' This date may be taken to repre- to have a period of 6-5 years,
sent as from 1859 two complete

198

The Story of the Comets.

CHAP.

stream following directly in the track which Biela's Comet
should have followed, and 12 weeks after the comet's calcu-
lated departure from the place, corroborated the inference,
already drawn from the previously known examples of
agreements, that a rich assemblage of meteors moving in the
rear of a cometary body follows the comet very closely in its

Fig. 104.

POSITION OF BIELA'S COMET AT THE TIME OF THE METEOR SHOWERS OF
1798, 1838, AND 1872.

orbit. The conclusion now seems recognised as inevitable
that Biela's Comet has ceased to exist as a concrete body.
What has just been stated appears, however, to be only a
portion of the truth, for showers of Andromedes seen in 1798,
1830, and 1838 would seem to have preceded Biela's Comet
along its track at different distances varying between ^th
and |rd of a circuit.

XIII. The Relation of Comets to Meteors. 199

Fig. 104 gives, according to H. A. Newton, the positions of
Biela's Comet in its orbit relatively to the Earth at the times
of the occurrence of the great meteor showers known to have
been manifested when the Earth was near this comet's orbit.
The line of the nodes, or the place of the Earth's nearest
approach to the comet's track, being at N, it appears that in
1798, when the Earth encountered at that point the great
meteor shower of Dec. 6 of that year, observed by Brandes,
Biela's Comet was at B, somewhat nearer to the Earth than in
1838 on the next occasion when a similar display was wit-
nessed. In the last-named year the comet was at A, about
300 millions of miles distant along its orbit from the Earth.
At the recurrence of the great meteor shower of Nov. 27,
1872, the comet must have been near C, or about 200 millions
of miles along its path from the node N. From this it would
seem that the meteoric particles must be thickly distributed
over a stretch of at least 500 millions of miles of the comet's
orbit, preceding the comet " to a distance of 300 millions of
miles, and following it to a distance of 200 millions of miles,
asin 1872*."

If Biela's Comet had maintained its existence it would
have reappeared in 1879, 1886, 1892, 1899, and 1906. It has
been suggested that in the years in which it would have been
due the Andromedes meteors were more pronounced than in
ordinary years, but I have not found sufficient evidence to
support this idea.

One case of a meteor shower pairing off with a comet in the
way above described might have been a mere coincidence ;
but four clear cases set astronomers thinking that there was
something important in the background. That something is
that all meteor showers are manifestations of broken-up
comets. This may be the case, but it is premature at pre-
sent to assert this dogmatically. Probably it may be safely
assumed that the more scattered a meteor shower is the longer

g H. A. Newton, Brit. Assoc. Report, A. S. Herschel, Month. Not. R. A. S.,

1875, p. 224. For further information vol. xxxii, p. 355, 1872; and by

respecting Biela's Comet in con- Denning, Month. Not. R. A. S., vol.

nection with meteors, see papers by Ixv, p. 851. June 1905.

200 The Story of the Comet*. CHAP.

it has been attached to the solar system ; and if it is really of
cometic origin, the longer is the time that has elapsed since the
catastrophe happened to the comet. As the Perseids are a
very scattered group, perhaps they have been long in our
system ; but the Leonids and the Andromedes may be much
more modern introductions if weight is to be attached to Le
Verrier's conclusion that it was a rencontre of Tempel's Comet
of 1866 (i.) with the planet Uranus, in the year 126 A.D.,
which brought that comet under the permanent influence and
control of the Sun.

From what has gone before it will be readily realised that
the two great meteor showers of November (12th and 27th as
they may be summarily styled) are very certain in their
cometary relations, but the same cannot be said in quite such
positive terms of the Lyrid shower of April, nor of the Perseid
shower of August. In the two first-named instances the
periodical returns of the meteors yielding special displays
have occurred at the predicted times, and the periods of revo-
lution of comets and meteors respectively are clearly identical.
But the same cannot be affirmed of the April and August
systems, because the periods are open to considerable un-
certainty owing to the orbits being of far greater eccentricity.

Kirkwood is responsible for the definite statement of another
comet-meteor alliance. He says : — '• The identity of the comets
of 1866 [i.] and 1366, first suggested by Professor H. A.
Newton, is now unquestioned. The existence then of a
meteoric swarm, moving in the same track, is not the only
evidence of the original comet's partial dissolution. The
Comet of 1866 was invisible to the naked eye ; that of 1366,
seen under nearly similar circumstances, was a conspicuous
object. The statement of the Chinese historian that ' it
appeared nearly as large as a tow measure', though some-
what indefinite, certainly justifies the conclusion that its
magnificence has greatly diminished during the last 500
years. The meteors moving in the same orbit are doubtless
the products of this gradual separation." h

How far we are justified in generalising on the whole sub-

h Comets and Meteors, p. 52.

XIII. The Relation of Comets to Meteors. 201

ject is an interesting question which must be handled with
discretion. There is no doubt that the trend of scientific
opinion is in the direction of suggesting that comets furnish
the numerous meteors which traverse space and frequently
manifest themselves to us on the Earth ; and to Schiaparelli
must be given the credit of first demonstrating the connec-
tion. Sir N. Lockyer goes beyond this, for in his view comets
are naught else but immense aggregations of meteors, and
naturally if they throw otf anything it is meteoric particles
which they throw off. It must, however, be confessed that
the subject has not made much progress of late, notwith-
standing the great number of comets which have appeared
during the last 20 years, coupled with the multiplication
of observers and observations of luminous meteors.1

Though to Schiaparelli the leading place of honour has
been given in the foregoing pages, the meritorious labours
must not be ignored of several other astronomers who cleared
the way and furnished many of the materials the utilisation
of which led to the actual discovery. Thus in 1861, several
years before Schiaparelli began his labours, Kirk wood broached
the theory that " meteors and meteoric rings are the debris of
ancient but now disintegrated comets, whose matter has be-
come distributed around their orbits ".k And writers even
earlier than Kirkwood had expressed ideas not materially
different ; but unfortunately they could not command the
data required to give practical support to their views, which
were in consequence disregarded as idle speculations.

J. Glaisher well summed up the matter in saying that
" The intimate connection now known to exist between comets
and meteors is perhaps the most striking and novel discovery
of a purely astronomical kind that has been made in our
time ", with the exception (I think I should like to add) of the
discovery of Neptune.

1 More than 30 years ago A. S. ibid., vol. xxxviii, p 369. May 1878.

Herschel put forth a long list of Denning informs me (and he is a high

75 suggested coincidences, but it does authority) that there is no sufficient

not appear that either he or anybody proof of the connections which

else followed them up. Month. Not. A. S. Herschel shadowed forth.

R. A. S., vol. xxxvi, p. 220, Feb. 1876 ; k Danville Quarterhj Rerieic, Dec. 1861.

CHAPTER XIV.
COMETS IN HISTORY AND POETRY.

Comets, objects of terror and alarm in all ages. — Opinions of the ancient
Greeks. — Of Anaxagoras. — Of Democritus. — Of Apollonius and Zeno. —
Sir G. C. Lewis's Summary of Greek Opinion. — Ptolemy silent as to Comets.
— Twelve varieties mentioned by Pliny. — Opinions of Seneca. — Of Para-
celsus.— Napoleon and Comets. — The Romans not given to Astronomy. —
Quotations from Virgil.— From Suetonius. — From Juvenal. — From Pliny.
— From Plutarch. — Opinions of the old Chroniclers. — Quotation from
William of Malmesbury. — Pope Calixtus III. and the Comet of 1456.
— Admiral Smyth on this matter. — Leonard Digges. — John Gadbury. —
Shakespeare's frequent mention of Comets. — Quotation from Julius Caesar.
— From Henry VI. — From Hamlet. — From Henry IV. — From The
Taming of the Shrew. — Quotations from Milton. — Milton apparently
a plagiarist from Tasso. — Quotation from Thomson. — From Pope. — From
Lord Byron. — From Young. — Some modern Poetry. — An American Inci-
dent.— Comets and Hot Weather. — The Earl of Malmesbury. — Arago
rebukes wild speculations. — French writers. — Fontenelle. — Lambert.— Sup-
posed allusions in the Bible to Comets. — Maunder's opinion.

ALREADY in my first chapter have I called attention to the
fact that comets have at all times been a source of great
interest to the world in general, but it will be worth while
to pursue the matter and rake up some of the historical
notices of comets from the early times down to the Middle
Ages and later ; with a glance now and again at what some of
the great poets have said on the subject.

Going back to the times of the earliest known students of
Astronomy — the Chaldaeans, it is to be noted that they seem to
have considered comets as analogous in their nature to
planets ; that is to say permanent bodies revolving round the
Sun in orbits, so much more extensive, however, that they
were only visible when they came near the Earth. This
opinion, which is the oldest hint we have of the existence of
periodical comets, was also held by philosophers of the
Pythagorean School.

CHAP. XIV. Comets in History and Poetry. 203

It is well known that many celebrated Greek philosophers
paid much attention to astronomical phenomena, and there-
fore to comets amongst other things. Anaxagoras explained
comets to be produced by the concourse of planets and by
their combined splendour. Democritus of Abdera, following
Anaxagoras, conceived that comets were the result of a con-
course of certain planetary stars. Apollonius and Zeno are
reputed to have upheld very similar ideas, but these two
are not quoted by Sir G. C. Lewis, the most modern chronicler
of ancient scientific ideas.a

Lewis's summary of Greek opinion is so conveniently con-
cise that I make no apology for transcribing what he said.
"Comets were the object of much speculation among the
early Greek astronomers; the opinions of Anaxagoras and
Democritus, of the Pythagoreans, and of Hippocrates of
Chios, and of his disciple ^Eschylus, respecting them, are
reported and analysed by Aristotle. Differing in other
respects they agreed in considering the comets to be planets.
Against this general position, Aristotle argues by saying that
the planets are always confined within the zodiacal band ;
whereas many comets have been seen without these limits,
and it has often happened that more than one comet has
been visible at the same time. He points out further, that
some of the fixed stars have been seen with a tail. For this
fact, he refers to the general report of the Egyptian observers :
he adds, however, that he had himself seen a star in the leg
of the constellation Sirius, with a faint tail. He states that
it could scarcely be seen if the vision was fixed directly upon
it, but it was more visible if the sight was turned slightly on
one side. Against the theory that comets were a congeries
of planets, he remarks that all those which had been seen in
his time disappeared without setting, while they were still
above the horizon : they faded away gradually, and left no
trace either of one planet or several. He adds that the great
comet in the Archonship of Asteius (373 B.C.) appeared in
the winter, in a clear sky : on the first day it was not visible,

a Historical Survey of the Astronomy of the Ancients, 8vo. London, 1862,
pp. 106, 140, 168.

204 The Story of the Comets. CHAP.

because it set before the Sun ; on the second day it was seen
imperfectly, for it set immediately after the Sun in the west ;
its brightness extended over a third part of the sky : it
reached as far as the belt of Orion, and there ceased.
Aristotle points out that a concourse of stars does not con-
stitute a comet. The Egyptian astronomers, he says, report
that conjunctions of planets, both with one another, and with
fixed stars, occur. He himself had observed Jupiter, in the
constellation Gemini, on two occasions, coming into con-
junction with a star, and occulting it, but without assuming
the appearance of a tail. Aristotle himself thinks that
comets are in the nature of meteors, and that their range
is in the region nearest the earth." b

The greatest Greek author of antiquity, HOMER, in the Iliad,
says : —

[The helmet of Achilles]

•f) 8', aarT)p us airib.anirev
"Iirirovpis Tpv<ba\eia, itepiaatiovro 8' tOeipai
Xpvfffai, a? "U<patffTos "id \6<f>ov u/jupl 6a/j.fias.

Thus rendered by Pope :—

[The helmet of Achilles shone]

" Like the red star, that from his flaming hair
Shakes down diseases, pestilence, and war."

(Iliad, Bk. xix, 11. 380-3.)

Pope has evidently borrowed from Milton, as below.

It is a somewhat remarkable fact that Ptolemy, so cele-
brated for his varied astronomical attainments, should no-
where have made any mention of comets, but seemingly that
was because he regarded them as objects terrestrial, not
celestial. On the other hand, Pliny appears to have paid
much attention to them, if we may judge by the fact that he
enumerates 12 varieties, each kind receiving its name from
some physical peculiarity of the objects belonging to it.

Hevelius gave sketches of 11 of Pliny's 12 forms, and their
titles as follows : —

Disci : disciformis = discs.

Pithei : doliiformis erectus = like an upright cask.

b G. C. Lewis, Astronomy of the Ancients, p. 168.

XTV. Comets in History and Poetry. 205

Hippei : equinus barbatus = like a horse's mane.

Lampadiae : (2) lampadiformis = torch-shaped.
Barbatus = bearded.

Cornutus bicuspidatus = double-pointed.

Acontiae : faculiformis lunatus = like a small torch.
Xiphise : ensiformis = sword-shaped.

Longites : hastiformis = spear-shaped.

Monstriferus = horror-producing.

It seems a pity that so much romance in the way of
classification should have been lost to astronomy and wasted
on meteorology !

Seneca considered that comets must be above (i.e. beyond)
the Moon, and he judged from their rising and setting that
they had something in common with the stars.

Paracelsus insisted that comets were celestial messengers
sent to foretell good or bad events, but he does not seem to
have suggested how to discriminate between the different
comets and the different events. It must be confessed that
this idea has not yet died out, but subsists as regards both
aspects. I believe I once saw it stated somewhere that
Napoleon looked upon the great Comet of 1811 as presaging
the success of his invasion of Russia, but in the event it
was the other way about. Napoleon had previously regarded
the great Comet of 1769 as his protecting genie, and as late as
1808 Messier published a book on it to uphold the idea.0

A story was told some 30 years ago in a well-known
French periodical that at Moscow an unfavourable omen was
drawn from the appearance of this comet. A conversation is
related as having taken place between the abbess of a certain
religious house and one of her nuns, to the following effect.
One evening on their way to Church, the nun suddenly
noticed the comet and uttered a cry of alarm, asking " what
that star was." The abbess replied, " It is not a star : it is
a comet." The nun rejoined, " But what is a comet ? I never
heard that word." The abbess then answered, " They are
signs in the heavens, which God sends before misfortunes."
The nun, who was the narrator of the story, thus comments
on the occurrence : " Every night the comet blazed in the

c La grande Comvte gui apparut a la naissance de Napoleon le Grand.

206 The Story of the Comets. CHAP.

heavens, and we all asked ourselves, what misfortune does it
bring? "d

Neither astronomy in general nor comets in particular
owe much to the ancient Romans, for they did not trouble
themselves much about astral phenomena, being more dis-
tinguished as warriors, lawyers, and bricklayers. Neverthe-
less they looked upon the Comet of B.C. 43 as a celestial
chariot carrying away the soul of Julius Caesar, who had
been assassinated shortly before it made its appearance.

It is reported of the Emperor Vespasian, on the authority
of Dion Cassius and Suetonius, that when nearing his end
he heard some of his courtiers discussing in a low tone of
voice the comet which was then visible. He seems to have
taken a philosophical and very unusual view of the matter,
for he is reported as having said : " This hairy star does not
concern me : it menaces rather the King of the Parthians, for
he is hairy, and I am bald."

VIRGIL compares a hero in his shining armour to
a comet : —

" Non secus ac liquida si quando nocte cometae
Sanguine! lugubre rubent." (Jlneid, lib. x, 11. 272-3.)

Thus rendered by Davidson : —

"The golden boss of his buckler darts copious fires; just as when in
a clear night the sanguine comets baleful glare."

In VIRGIL we find also another allusion to comets : —

"Non alias coelo ceciderunt plura sereno
Fulgura, nee diri toties arsere cometae."

(Georgica, Bk. I, 11. 487-8.)

Thus rendered by the Rev. Canon Newbolt : —

"At no other time did more thunderbolts fall in
A clear sky, nor so often did dread comets blaze."

SUETONIUS, in his life of the Emperor Nero, has the
following : —

"Stella crinita, qua? summis potestatibus exitium portendere vulgo
putatur." (Vita Neronis, c. 36.)

d Eeme des Deux Mondes, vol. cxvi, p. 200. July 1, 1873.

XIV. Comets in History and Poetry. 207

Thus rendered by A. Thomson : —

"A blazing star, which is vulgarly supposed to portend destruction to
Kings and Princes, appeared above the horizon several nights successively."
(Bohn's Suetonius, p. 366.)

JUVENAL, the Satirist, evidently gives utterance to the com-
monly received opinion as to comets : —

" Instantem regi Armenio Parthoque Cometem
Prima videt. (Satirce, vi, 11. 407-8.)

Thus rendered by L. Evans : —

"She is the first to see the Comet that
Menaces the Armenian and Parthian King."

(Bohn's Juvenal, p. 53.)

PLINY'S statement is comprehensive : —

" Cometas Graeci vocant nostri crinitas : horrentes crine sanguineo et
comarum modo in vertice hispidas." (Hist. Nat. Bk. II, c. 25.)

Thus rendered by P. Holland, Doctor in Physicke : —

"These blazing starres the Greekes call cometas, our Romanes crinitas,
dreadful to be scene, with bloudie haires, and all over rough and shagged in
the top like the bush of haire upon the head.'* (The Historie of the World, Fol.
London, 1601, p. 15.)

PLUTARCH'S account of comets might in modern language
be described as " prosy ". Here it is : —

" A Comet is one of those Stars which do not always appear, but after
they have run through their determined course, they then rise, and are
visible to us." [The writer then goes on to quote the opinions of a number
of Greeks as to Comets.] (Treatise on the Sentiments Nature Philosophers delighted
in, Lib. Ill, c. 2. Plutarch's Morals, vol. iii, p. 179, London, 1718.)

CLAUDIUS, who flourished early in the 5th century, remarked
that "a comet was never seen in the heavens without im-
plying disaster ".

In an ancient Norman Chronicle there occurs a curious
exposition of the Divine Bight of William I. to invade
England : — " How a star with 3 long tails appeared in the
sky ; how the learned declared that stars only appeared when
a kingdom wanted a king, and how the said star was called
a Comette." The well-known writer William of Malmesbury,
speaking in the year 1060, says : " Soon after [the death of
Henry, King of France, by poison] a comet denoting, as they
say, change in kingdoms — appeared, trailing its extended and

208 The Story of the Comets. CHAP.

fiery train along the sky. Wherefore a certain monk of our
monastery, by name Elmer, bowing down with terror at the
sight of the brilliant star, wisely exclaimed, ' Thou art come !
a matter of lamentation to many a mother art thou come;
I have seen thee long since; but I now behold thee much
more terrible, threatening to hurl destruction on this
country.' " e

The superstitious dread in which comets were held in the
Middle Ages is well exemplified in the case of what happened
with respect to the Comet of 1456 (Halley's). There was
a story long afloat that the Pope of the period, Calixtus III.
excommunicated the comet, and took various steps of the
necessary consequential character. This story has been proved
to be a myth so far as regards its special point, and the whole
incident must apparently be regarded as a remarkable
instance of the way in which mountains grow out of mole-
hills— to use a common simile. What happened appears to
have been this. The comet was visible. The astrologers
(I dare not call them astronomers) suggested that there would
follow " a grievous pestilence, death, or some great calamity ".
At that time the Turks were making great headway in
Central Europe. Inspired, no doubt, by these facts, Calixtus
" ordered supplications that if evils were impending for the
human race, the Almighty would turn them all upon the
Turks, the enemies of the Christian name. He likewise
ordered, to move God by continual entreaty, that notice
should be given by the Church bells to all the Faithful, at
midday, to aid by their prayers those engaged in battle with
the Turk ".

The foregoing sentence is translated from Platina's Lives of
the Popes* and it will be seen that there is no reference to
any bull, or exorcism, or excommunication, or imprecation
against the comet joined with the Turk. I suppose that what
follows is history, but I give it under the shelter of Admiral
Smyth's name. " By the way, while the cometa mon&triferus
was still in sight, Hunniades, the Pope's general, gained an

e De Gestis Regum Anglice, lib. ii, f Viice Pontificum, Venice, 1479.

cap. 225.

XIV. Comets in History and Poetry. 209

advantage over Mahomet, and compelled him to raise the
siege of Belgrade ; the remembrance of which Calixtus im-
mortalised, by ordering the festival of the Transfiguration
to be religiously observed throughout the Christian world.
Thus was established the custom, which still exists in [Roman]
Catholic countries, of ringing the bells at noon ; and perhaps
it was from this circumstance that the well-known cakes
made of sliced nuts and honey, sold at the church-doors in
Italy on Saints' days, are called comete." g

Leonard Digges, a writer of the Elizabethan epoch, says
that " Cometes signifie corruption of the ayre. They are
signes of earthquakes, of warres, of changying of Kyngdomes,
great dearthe of corne, yea a common death of man and
beast." h

John Gadbury, an astrological gentleman of the same epoch
says that " experience is an eminent evidence that a comet
like a sword portendeth war ; and an hairy comet or a comet
with a beard denoteth the death of Kings ". He also gives
a register of cometary announcements for upwards of 600
years, and adds in large Roman capitals : " as if God and Nature
intended by comets to ring the knells of princes esteeming
the bells in churches upon earth not sacred enough for such
illustrious and eminent performances."

Close upon the heels of the two writers I have quoted comes
the greatest of English writers, ancient or modern, Mr. William
Shakespeare, whose works contain several noteworthy and
very striking allusions to comets. Thus in Julius Ccesar :—

" When beggars die, there are no comets seen,
The Heavens themselves blaze forth the death of Princes."

(Act II, Sc. 2.)

In Henry VI. we find the oft-quoted passage :—

" Comets importing change of times and states
Brandish your crystal tresses to the sky,
And with them scourge the bad revolting stars
That have consented unto Henry's death."

(Parti, Act I,Sc. 1.)

* W. H. Smyth, Cycle, vol. i, p. 281. " to eat ".

It has been suggested that a more h Prognostication Euerlastinge, 2nd

rational derivation of the name of Ed., London, 1576, fol. 6.
these cakes is comedere, the Latin for
CHAMBERS p

210 The Story of the Comets. CHAP.

There is a mixture of ideas here, for comets are regarded as
prophetic of evil ; and stars, not specially defined, are treated
as co-operating in bringing about human misfortune.

There is another passage in Henry VI. which is even more
dogmatic : —

" Now shine it like a comet of revenge
A prophet to the fall of all our foes."

(Part I, Act III, Sc. 2.)

In Hamlet we find an evident allusion to comets though
the word is not used : —

"As Stars with trains of fire and dews of blood,
Disasters in the Sun." (Act I, Sc. 1.)

In Henry IV. we have a great truism respecting comets : —

"By being seldom seen, I could not stir,
But, like a comet, I was wonder'd at."

(Parti, Act III, Sc. 2.)

In the Taming of the Shrew we have a more general, but
still sufficiently clear, allusion to the results which follow the
appearance of a comet : —

" Some Comet or unusual prodigy." (Act III, Sc. 2.)

Shakespeare lived at an epoch when, as we have seen in
the quotations from Digges and Gadbury, Astronomy and
Astrology were confused in men's minds, and discredit cer-
tainly brought on the former by the latter; but such ideas
long remained current, and perhaps are by no means exploded
even now in the 20th century. Certainly they were not non-
existent in the 19th century. No wonder then that even in
still earlier centuries we find alarmist passages . in writers of
repute.

Thus (to quote a few more) SPENSER, describing a " goodly
Lady ", says :—

"And her faire yellow locks behind her flew,
Loosely disperst with puff of every blast :
All as a blazing starre doth farre outcast
His heavie beanies, and flaming lockes dispredd,
At sight whereof the people stand aghast ;
But the sage Wisard idles, as he has redd,
That it importunes death and dolefull dreryhedd.''

(Faerie Queene, Bk. Ill, Canto i, Stanza xvi.)

XIV. Comets in History and Poetry. 211

TASSO compares Argantes to a comet, and mentions divers
ill-effects proceeding from comets : —

"Qual con le chiome sanguinose horrende
Splender cometa suol per 1'aria adusta,
Che i regni muta, e i feri morbi adduce,
Ai purpurei tiianni infausta luce."

(Gerusalemme Liberata, Canto vn, Stanza lii.)

Rendered thus by Wiffen : —

"And last, his wonted sabre by his side
He girds, of purest steel, antique and rare,
As with its bloody locks let loose in air,
Horribly bright, the Comet shows whose shine
Plagues the parchf.d World, whose looks the Nations scare.
Before ivhose face States change, and Powers decline,
To purple Tyrants all, an inauspicious sign.''1

(Jerusalem Delivered, 5th ed., p. 160.)

DANTE'S reference to comets is on lines somewhat different
from most of those quoted in this chapter — not so awe-
inspiring : —

" Cosi Beatrice : e quelle anime liete
Si fero spere sopra fissi poli,
Fiammando forte a guisa di comete.'1'

(Paradiso, Canto xxiv, 1. 10.)

Thus rendered by Longfellow : —

"Thus Beatrice: and those souls beatified

Transformed themselves to spheres on steadfast poles,
Flaming intensely in the guise of Cornets."

(The Divine Comedy, Trans. — H. W. LONGFELLOW.)

MILTON'S two allusions to comets are well-known : —

" Satan stood

Unterrified, and like a Comet burn'd
That fires the length of Ophiuchus huge
In th' Artick sky, and from its horrid hair
Shakes pestilence and war." (Paradise Lost, Bk. II, 1. 706.)

Professor H. H. Turner thinks that Milton "almost cer-
tainly" was referring to a particular comet, namely, the
Comet of 1618, which Evelyn (in his Diary) held responsible
for the great " Thirty Years' War ". This comet did indeed
appear in Ophiuchus, but Milton was only 10 years old at the
time. Turner's argument is that, as the said comet was
a specially magnificent one with a tail 104° long, " the impres-

P 2

212 The Story of the Comets. CHAP.

sion made on the mind even of a boy of 10 may well have
lasted until he wrote the above lines as a man of 50. It has
been usual to regard the particular reference, if any, as being
to the Comets of 1664 and 1665 of which M. Auzout predicted
the movements, the former of which was believed to have led
to war with the Dutch, and the latter to the Plague of
London. But Milton never saw these comets, being already
blind : and unless the lines were added in revision, they were
probably written before 1664. Moreover, neither of these
comets, nor any intermediate comets (of which there were no
striking examples), was in Ophiuchus; and the explanation
offered of the use of this name because it was ' fine-sounding '
is scarcely satisfactory. It is true that Ophiuchus is not ' in
th' Arctic sky ', being by no means a northern constellation :
but these words probably refer rather to the attitude of the
poet himself, since Milton continually posed as a classical poet
writing from Italy ; and may in this case have desired to
make it clear that the comet had been seen from England 'V

Milton has another reference to a comet further on in the
same poem :—

" High in front adv<mc'd

The brandish'd sword of God before them blaz'd
Fierce as a Comet : which with Torrid heat,
And Vapours as the Libyan air adust,
Began to parch that Temperate clime."

(Paradise Lost, Bk. XII, 1. 632.)

This last passage from Milton seems evidently plagiarised
from Tasso, as quoted above, but for the comparison of the
sword of God to a comet Dunster refers to Du BARTAS'S
description of the flaming sword placed at the entrance of the
Garden of Eden after the expulsion of our first parents. Todd
thus rendered the passage : —

" For the Almighty set before the door
Of th' holy park a Seraphin that bore
A waving sword, whose body shined bright
Like flaming comet in the midst of night."

' " Lecture on Honey's Comet to the owes to a friend, seems to me a case

British Association, 1898," p. 6. The of drawing on one's imagination for

suggestion in the last sentence of one's facts !
this extract, which Turner says he

XIV. Comets in History and Poetry. 213

POPE, who dealt with many topics, did not forget
comets : —

"Could he, whose rules the rapid comet bind
Describe or fix one movement of his mind ?
Who saw its fires here rise and there descend
Explain his own beginning or his end."

(Essay on Man, Epistle II, 1. 35.)

The " he " in the foregoing challenge is Sir I. Newton.
In another of his works, desirous of satirising the notorious
Duke of Wharton, Pope sarcastically says : —

" Comets are regular, and Wharton plain.'5

(Moral Essays, Epist. i, 1. 209.)

If contemporary records are to be trusted, the Duke
resembled the average comet by being very irregular in
ways which defy description in these pages.

The next extract is from THOMSON :—

"Amid the radiant orbs

That more than deck, that animate the sky,
The life-infusing suns of other worlds ;
Lo ! from the dread immensity of space,
Eeturning, with accelerated course,
The rushing Comet to the Sun descends :
And, as he shrinks below the shading earth,
With auiful train projected o'er the heavens,
The guilty nations tremble.1' (Seasons, Summer.)

I have somewhere seen it stated that Lord BYRON wrote
of " The Comet of a Season ", but I have been unable to find
the reference. In his " Prayer to Nature " he evidently has
a comet in his mind when, addressing the Almighty, he says : —

"Thou who canst guide the wandering star
Through trackless realms of aether's space ;
Who calm'st the elemental war,
Whose hand from Pole to Pole I trace."

As might be expected, we find something about comets in
YOUNG :—

"Hast thou ne'er seen the Comefs flaming flight?
Th' illustrious stranger passing, terror sheds
On gazing Nations, from his fiery train
Of length enormous, takes his ample round

214 The Story of the Comets. CHAP.

Thro* depths of ether ; coasts unnumber'd Worlds,
Of more than solar glory; doubles wide
HeavVs mighty cape ; and then revisits earth,
From the long travel of a thousand years."

(Night Thoughts, No. iv.)

The quotation given on the title-page of this volume is the
first stanza of a poem published in the Illustrated London
Nev:s of March 25, 1843, concerning the great Comet of 1843.
Some other stanzas deserve reproduction : —

•'Thou comest whence no mortal seer can know —
Thou goest whither nothing human dreams —
Thy mission, tho' so bright,
Is speculation's gloom !
We can but gaze upon the starry dust
Thy lightening wheels upturn

"Along Heav'n's road, and call thee charioteer,
Or names which prove that man cannot baptize

Such giant births as thou

With aught descriptive term !
Comet, or fiery star, or feeding light

To myriad viewless suns.

"Roll on, thou child of wedded time and space,
Eccentric offspring of Eternal Pow'r, —

Be thy portent to us

Or good or ill, the same —
We'll pay thee symbol worship for thy cause,

And in submission bow.

" Com'st thou in anger, we will not repine —
Com'st thou in harmless beauty, we'll adore,

And through thee bless the ONE

Who by His simple Word
Can call creations like to thine from nought

And end them all again !

" Beautiful — lustrous as the heav'ns can be
On vernal nights with their commission'd stars,
How much more do they seem,
When unaccustom'd lights,
Like thine shoot forth from out the sapphire throne

Whereon the GREAT ONE sits!" " W."

Another poet took up the running in a subsequent number
of the same newspaper (April 22, 1843) : —

XIV. Comets in History and Poetry. 215

TO THE COMET.

"Thereby hangs a tail." — SHAKESPEARE.

"Lone wanderer of the trackless sk}' !
Companionless ! Say dost thou fly
Along thy solitary path,
A flaming messenger of wrath —
Warning with thy portentous train
Of earthquake, plague, and battle-plain ?
Some say that thou dost never fail
To bring some mischief in thy tail :
For ignorance doth ever see,
Wrapped in its vain credulity,
Coupled some dire mishap with thee." W. LATTEY.

That the terror inspired by comets had by no means died
out in the 19th century is well shown by the following
extract from an American newspaper published in the form
of a letter from Atlanta, Georgia, on the occasion of the
expected appulse of Biela's Comet in November 1872 : —
" The fear which took possession of many citizens has not
yet abated. The general expectation hereabouts was that
the comet would be heard from on Saturday night. As one
result, the confessionals of the two [Roman] Catholic churches
here were crowded yesterday evening. As the night advanced
there were many who insisted that they could detect a change
in the atmosphere. The air, they said, was stifling. It was
wonderful to see how many persons gathered from different
sections of the city around the newspaper offices with sub-
stantially the same statement. As a consequence, many
families of the better class kept watch all night, in order that
if the worst came they might be awake to meet it. The
orgies around the coloured churches would be laughable,
were it not for the seriousness with which the worshippers
take the matter. To-night (Saturday) they are all full, and
sermons suited to the terrible occasion are being delivered."

Let us hope that the late Earl of Malmesbury did not
exactly mean what he said when he wrote in his Diary
(Sept. 16, 1858) respecting Donati's Comet of 1858:— "The
largest comet I ever saw became visible with a very broad

216 The Story of the Comets. CHAP.

tail spread perpendicularly over the sky, the weather being
very hot. Every one now believes in war.'' k

Of the influences ascribed to comets in the popular mind
one which has survived quite to the present day is that
comets cause an abnormal developement of heat on the Earth.
When there has happened to be visible a comet of sufficient
importance or brilliancy to get into the newspapers, and the
season of the year has been the summer, or early autumn, and
the weather has been very sunny and hot, I have often been
asked in solemn tones (especially by ladies) whether the comet
was the cause of the heat ; the question being put in the form
called by a lawyer a "leading question", one to which an
affirmative answer is expected.

Lord Malmesbury, in the work just quoted, alludes casually
to this popular idea. Under the date of 1857, June 25, he
says : — " We are suffering under an extraordinary heat. People
are really getting alarmed, for if it is occasioned by the comet,
which is not yet visible, what must we expect when it reaches
our Globe ! " It does not appear what comet is here referred
to, but presumably it is that of 1556, whose return was
expected somewhere about 1858 or I860.1

The French astronomer Arago, more than 70 years ago,
complained that questions of the same type were raised in
France, and he wrote a somewhat satirical article dealing
with the subject,"1 in which he alluded to the scarcity of the
meanest knowledge of scientific facts amongst the middle
ranks of society. He condescended, however, to gather up
some statistical facts by way of showing the futility of the
suggestion. His labours were taken advantage of in England
in an article attributed to the late Professor De Morgan.11
Allusion is made therein to the supposition that the successful
vintage of 1811 was due, as already mentioned, to the great
Comet of 1811 ; and that the excessive heat of August and

k Memoirs of an Ex-Minister, vol. ii, lation in the form of a small book

p. 135. appeared in 1833.

1 See p. 100 (ante}. n Companion to the Almanac, 1833,

m Annuairedu Bureau des Longitudes, p. 1.
1832, see p. 238. An English trans-

XIV. Comets in History and Poetry. 217

September 1832 was occasioned by the approach of Biela's
Comet. De Morgan pertinently remarks that, " With a burning
Sun overhead we have heard those who might have known
better accusing the comet in the manner aforesaid."

Arago's article contains a statement of the mean tempera-
ture of every year from 1803 to 1831 inclusive; and side by
side is placed the number of comets visible in each year.
Inspection of the table conclusively shows that there is no
connection between the two things. Thus 1806 and 1811
were both hot years; the first, however, hotter than the
second, though the first had only one comet of no note, whilst
the second had two comets, one of which was of remarkable
brilliancy. Again, 1826 with its 5 comets was not nearly so
warm as 1831 with its one comet. That hot years have in
general more comets than cold ones is very true, and for the
simple reason that hot years generally giving clear skies are
more favourable for the discovery of comets than cold years,
which so often mean cloudy skies. Nor must it be forgotten
that the greater number of comets are not visible to the naked
eye. Thus all the years between 1803 and 1831 inclusive,
the temperature of which exceeded the average, mustered 29
comets between them ; and the remaining or cold years only
15. It is therefore more reasonable to say, not that the
comets brought the heat, but that the heat brought the
comets. I have not thought it worth while to attempt to
bring these figures up to date by comparing the temperatures
of the years 1832 to 1909 with the comets of those 78 years ;
but that would be a suitable occupation for anybody who is
fond of shooting the air. I cannot doubt what the result of
such a research would be.

French writers on scientific subjects are very fond of inter-
weaving with their facts a large mixture of fancies and
romance. Jules Verne and F. A. Pouchet are types of what
I mean. No wonder, therefore, that Astronomy is not exempt
from that sort of thing. Accordingly we find that Guillemin,
who with Flammarion may be taken to represent in French
literature the department of Astronomy, is not behind his
fellow-countrymen in sensational writing. In his book on

218 The Story of the Comets. CHAP.

comets he propounds a variety of questions, many of which
are altogether outside practical politics. I select one as
a sample of the rest. " Are comets habitable ? " I should
suppose that no Englishman who had read half-a-dozen
pages in any English book on comets would have paused
for a moment even to have discussed such a question,
and though it must be admitted that Guillemin answers his
question in the negative, he nevertheless wastes several pages
over it. citing De Fontenelle0 and Lambert p in particular.
The form of his question he evidently borrows from Lambert,
who seriously thought to advance reasons to permit us to
believe that comets, more numerous than the planets in the
Solar System, are habitable celestial bodies. I am sorry to
have to add that one erratic Englishman was found in 1772
to take up the same line of writing."1

During the visibility of Donati's Comet in 1858, 1 remember
that a correspondence took place in the newspapers as to
whether comets were mentioned, or in any sort of incidental
way referred to, in the Bible. The following passages were
adduced in support of an affirmative answer to this question : —

(1) In Leviticus xvii. 7, it is said, " They shall no more offer
their sacrifices unto Seirim " or " Shoirim ", which is rendered
in the Authorized Version "devils", and in other versions
" goats ". The Jewish writer, Maimonides, states that the
Sabian astrologers worshipped these " Seirim ", which seerns
to confirm the idea that they were celestial bodies of some sort.

(2) In Isaiah xiv. 12, we find, " How art thou fallen from
Heaven, O Lucifer, son of the morning ! How art thou cut
down to the ground which didst weaken the nations ! " In
this passage a certain Hillel is said to have fallen from Heaven,
but it is unknown what Hillel means. Some interpreters
derive the word from Hebrew verbs signifying to shine, to
glory, to boast, to agitate, to howl, &c. A writer minded to

0 Entretiens sur La PluraliU des comets and planets alike are in-

Mondes. (Eutres, vol. ii, Paris, 1766. habited. " Les cometes et les planetes

An English translation by J. Jacque sont egalement habitees." Systeme

was published in 1800. du Monde, 2nd ed., Paris, 1784, p. 45.

p Lambert explicitly asserts that q Andrew Oliver : Essay upon Comets.

XIV. Comets in History and Poetry. 219

obtain a far-fetched or expansive view of words suggested
that Hillel indicated a cornet, because comets answer to the
ideas of brightness, swift motion, and calamity.

(3) In the General Epistle of St. Jude, verse 13, certain
impious impostors are compared to " wandering stars to whom
is reserved the blackness of darkness for ever [for an aeon =
age]." The term "wandering stars" has been thought to
refer to comets.1

(4) In the Revelation of St. John the Divine, xii. 3 : — " There
appeared another wonder in Heaven ; and behold a great red
dragon . . . and his tail drew the third part of the stars of
Heaven ". Satan is here likened, it is supposed, to a comet,
because a comet resembles a dragon (or serpent) in form, and
its tail frequently may be said to compass, or to seem to grip
stars.

These ideas are given for what they are worth, and on this
point the reader must exercise his own judgement, especially
bearing in mind Maunder's words in his excellent and most
interesting book : — " We cannot expect to find in Scripture
definite and precise descriptions that we can recognize as
those of cornets. At the most we may find some expressions,
some descriptions, that to us may seem appropriate to the
forms and appearances of these objects, arid we may therefore
infer that the appearance of a comet may have suggested
these descriptions or expressions ".s

It may be added that Maunder leans to the suggestion made
by several writers that when Jerusalem was wasted by a
pestilence and David offered up a sacrifice of intercession at
the threshing-floor of Oman, the Jebusite, the king may have
seen in the scymitar-like tail of a comet (such as that of the
comet of 1882*), what was to be regarded as God's "minister,
a flaming fire ".u

To quote the actual words of the sacred writer will make
the point more clear : — " And David lifted up his eyes, and

T See Alford's New Test, for English Readers, in loco.
8 E. W. Maunder : The Astronomy of the Bible, p. 105.
1 See pp. 153-4 (ante). u Psalm civ. 4.

220 The Story of the Comets. CHAP. XIV.

saw the angel [messenger] of the Lord stand between the
Earth and the Heaven, having a drawn sword in his hand
stretched out over Jerusalem".1 It will not be forgotten
that Josephus used almost the same language many centuries
later under circumstances not altogether dissimilar/

The following extract from the quarto edition of Littre's
French Dictionary (sub. voc., Comete) will I think be new to
English Readers and may appropriately end this chapter :—

" Comet : a card game played with 2 packs of cards from
which the aces have been removed. One of the two packs
is printed in black ink, and the other in red. On one of the
cards the figure of a comet appears ; or, as a substitute, the
nine of diamonds in the black pack, and the nine of clubs in
the red pack are used." "It is true that she made more
progress in the game of comet and in backgammon than in
spelling, and she plays the comet card more easily than she
writes a letter."

The last sentence is given as a quotation from Voltaire
describing the educational developement of a certain Made-
moiselle Corneille.z

It may be added (though I have been unable to trace the
authorities) that it has been said that the origin of the phrase
the " Curse of Scotland ", applied to the Nine of Diamonds,
was that the " Game of Comet " was introduced into Scotland
by French members of the retinue of Mary, Queen of Scots,
and became so popular with the upper classes as to lead to
an immense developement of gambling, the game acquiring
its Scotch repute from the name of its Trump Card.

1 1 Chron. xxi. 16. ' See p. 123 (ante).

1 Lettres a M. le Comte D'Argental, Jan. 23, 1763.

CHAPTER XV.

COMETARY STATISTICS.

Statistics not generally appreciated. — Difficulty of being precise in dealing with
Cometary Statistics. — Nuclei. — Comce. — Tails. — Orbits. — Number of
Comets recorded and calculated. — Duration of visibility. — Periodical
Comets and their returns. — Direction of Motion of Periodical Comets. —
Perihelia. — Ascending Nodes. — Inclinations of Orbits. — Perihelion Dis-
tances.— Direction of Motion.

STATISTICS are usually supposed to be distasteful to the
general reader, and I shall not here submit any very elaborate
ones; and those which are presented may be passed over
altogether if the reader likes, for they are not essential
to a study of the subject of comets from a descriptive or
observational point of view. And, indeed, there is another
reason why they may be pardonably neglected : for if the
truth must be told, many of those which appear in this
chapter are in a certain sense untrustworthy. A moment's
reflection will make it plain why such should be the case.
Comets have, at the best, very ill-defined boundaries ; and as
a large telescope will reveal a greater spread of cometary
material than a small one, it follows, as a matter of
course, that dimensions measured in a small telescope may
differ very much indeed from those obtained by means of
a large telescope. Discrepancies are bound, therefore, to
occur in the measurements arrived at by different observers
using, even on the same day, telescopes of different optical
power.

The same remark applies to the differences which exist
between the sensitiveness of the eyes of different observers,
a fact which very often becomes very pronounced, when it is

222

The Story of the Comets.

CHAP.

a question of estimating the length of a comet's tail. One
observer may see, and perhaps even instrumentally measure,
a tail as being 5° long, when on the same night, in perhaps a
different and better atmosphere, and possessed of a more sensi-
tive eye, another observer will have no difficulty in tracing a
tail through 8° or even 10°. With these cautions and reserva-
tions the statistics of measurements which follow are offered
for what they are worth.

The following are the real diameters in English miles of
the nuclei of some of the comets which have been measured a
during the last 100 years or so.

Examples of a Large Nucleus.

Examples of a Small

Nucleus.

Miles.

Miles.

The Comet of 1845 (iii.; .

. . 8000

The Comet of 1798 (i.)

... 28

Donati's Comet, 1858

.. 5600

The Comet of 1806

. ... 30

The Comet of 1815...

.. 5300

The Comet of 1798 (ii.)

... 125

The Comet of 1825 (iv.) .

.. 5100

The Comet of 1811 (i.)

... 428

The dimensions of the cornea or heads of comets also vary
very greatly. Thus : —

Examples of a Large Coma.

Miles.

The Comet of 1811 (i.) 1,125,000
Halley's Comet, 1835... 357,000
Encke's Comet, 1828 ... 312,000

Examples of a Small Coma.

Miles.

The Comet of 1847 (v.) ... 18,000
The Comet of 1847 (i.) ... 25,500
The Comet of 1849 (ii.)... 51,000

The real dimensions of a comet vary very much at different
periods of the same apparition, for there is no doubt that
many of these bodies contract as they approach the Sun and

"• All the dimensions given in miles
in this chapter depend on the old
value (8-57") of the Sun's parallax.
They need to be augmented by about
aVh to harmonise them with what is
now regarded as the probable value
(8-8") of the Sun's parallax; but
for reasons which will be readily

inferred from what has been stated
at the commencement of this chapter,
it has been deemed unnecessary to
transform the figures, as it would be
affectation to present them with such
an appearance of exactitude, as
measures ending in figures, and not
cyphers would imply.

XV.

Cometary Statistics.

223

expand again as they recede from it ; a fact first noticed by
Kepler in the case of the Great Comet of 1618.

The following measurements of Encke's Comet in 1838,
when approaching the Sun, will illustrate this : —

Date.

Diameter.

Distance
from O.

1838.
Oct. 9 .

Miles.
181,000

1.42

25

120,500

1.19

Nov. 6

79,000

1-00

„ 13

74,000

0-88

„ 16

63,000

0-83

,, 20

55,500

0.76

23

38,500

0.71

24

30,000

0.69

Dec. 12

6,600

0-39

„ 14

5,400

0.36

16

4,250

0-35

„ 17

3,000

0.34

We have already considered the interesting questions, " Do
periodical comets diminish in brilliancy from time to time at
successive apparitions 1 " and, " Do they waste away ? "

It seems certain that both these questions must be answered
in the affirmative ; and I have already mentioned b Halley's
Comet as probably proving this point. Very likely there is
some significance in the fact that none of the now considerable
number of short-period comets exhibit more than what may
be called apologies for tails, and some of them not even the
semblance of a tail.

THE TAILS OF COMETS.

The tails of comets, more especially of those splendid ones
which now and again become visible to the naked eye, are
often of stupendous length, as the following Table will
show : —

b See p. 5 (ante).

224

The Story of the Comets.

CHAP

Name of Comet.

Length in Arc.

Length in Miles.

The Comet of 1744

o

24

19,000,000

The Comet of 1860 (iii.)
The Comet of 1861 (ii.)
The Comet of 1769

15
105
97

22,000,000
24,000,000
40,000,000

The Comet of 1858 (vi.)
The Great Comet of 1618
The Comet of 1680

50
104
60

42,000,000
50,000,000
100,000,000

The Comet of 1811 (i.)
The Comet of 1811 (ii.)
The Comet of 1843 (i.)

25
37
65

100,000,000
130,000,000
200,000,000

DIMENSIONS OF OKBITS.

We all know that in speaking of the dimensions of the
orbits of the planets we are brought face to face with stupen-
dous figures which the mind can with difficulty grasp ; but
such figures fade into insignificance when we come to consider
the distances to which some of the periodical comets recede
when at their greatest, or aphelion, distance from the Sun ;
though perihelion distances may in many cases be grasped
without difficulty. The following figures will illustrate these
2 points :—

1. Perihelion Distances.

Greatest known.
The Comet of 1729

Greatest known.

Miles.
383,800,000

Least known.
The Comet of 1843 (i.)

2. Aphelion Distances.

Miles.

The Comet of 1844 (ii.) 406,130,000,000 The Comet of Encke

Least known.

Miles.
538,000

Miles.
388,550,000

From the earliest period up to the present time the number
of comets of which we have any trustworthy record may be
put at something like 1200 ; but as it is only within the last
150 years that optical assistance has been made generally
available in systematic searching for them, and only within
the last 20 years that systematic search has been carried out
on a large scale, it can scarcely be doubted that the real

XV.

Cometary Statistics.

225

number of the comets which have visited our system during
what is called the " Historic Period " cannot be less than
several thousands, especially as our statistics until quite
recently have not embraced the Southern hemisphere. Comets
are often visible in the Southern hemisphere which escape the
notice altogether of the comet-hunters of Europe, of North
America, and of the Northern hemisphere generally.

TABLE OF NUMBER OF COMETS RECORDED.

Period.

Comets
Observed.

Orbits

Calculated.

Comets
Identified.

Before A.D.

81

4

1

Century 0—100

22

1

1

101—200

22

2

1

201-300

39

3

2

301—400

22

0

1

401-500

19

1

1

501—600

26

4

1

601—700

33

0

2

701—800

17

2

1

801-900

41

1

0

901—1000

30

2

3

1001—1100

38

4

2

1101—1200

31

0

1

1201-1300

30

3

3

1301—1400

34

7

3

1401—1500

45

12

1

1501—1600

40

13

4

1601—1700

35

20

5

1701—1800

73

64

8

1801-1900

335

313

86

1901— 1909 (Jan. 1) ...

39

36

8

1052

492 c

135

0 This number is greater by 3 than
the highest numbered orbit in the
catalogue because three additional

orbits are given which had to be
numbered bis, or rather a.

226 The Story of the Comets. CHAP.

VISIBILITY OF COMETS.

Comets remain visible for periods varying from a few days
to more than a year, but the most usual time is 2, 3, or 4
months. Much depends on the apparent position of the
comet with respect to the Earth and the Sun, and much on
its own intrinsic lustre. The statement just made of comets
being visible only for periods of a limited number of months
is not so generally true now as it was 20 years ago, for the
duration of their visibility is now affected very often by
2 circumstances of quite recent origin — the employment of
the very large American telescopes of 30 or 40 inches aper-
ture, and the use of photography. It is to the operation of
these 2 causes that the long periods of time disclosed in the
following table are due.

Name of Comet.

Duration of Visibility.

The Comet of 1905 (iv.)

3^ years

The Comet of 1889 (i.)

2 years

The Comet of 1890 (ii.)

22 months

The Comet of 1811 (i.)

17 months

The Comet of 1904 (i.)

12 months

Tie Comet of 1825 (iv.)...

12 months

The Comet of 1861 (ii.)

12 months

The Comet of 1907 (iv.)

10 months

The Comet of 1835 (iii.) (Halley's)
The Comet of 1847 (iv.)

9J months
9^ months

There are a few comets on record, even during the modern
telescopic period, which have only been seen on one or two
occasions, unfavourable weather, or unfavourable position in
the heavens, having prevented a more extended observation
of them. Fig. 106 is a case in point. It represents a comet
seen during the totality of the Eclipse of the Sun of May 17,
1882, which comet was never seen again, and whose history
and circumstances will probably remain for ever undisclosed.

And again, during the Eclipse of the Sun of April 16, 1893,
a comet was seen. But long before this, Seneca, quoting
Posidonius, records an eclipse comet. (Qucest. Nat., vii. 20.)

XV. Cometary Statistics. 227

It not unfrequently happens that a comet is only discovered
after its perihelion passage, when it will be receding from the
the Sun, and perhaps also from the Earth. As under such
circumstances its brightness will be day by day diminishing,
its visibility may only extend to a few days, or a few weeks.

From an examination of a complete catalogue of calculated

Fig. 106.

ECLIPSE OF THE SUN OB' MAY 17, 1882, SHOWING AN UNKNOWN COMET.

comets d we may obtain certain results which will here be
analysed.

It appears that 492 comet apparitions have been subjected
to mathematical investigation, viz. : —

Known periodical comets 30

Subsequent returns 108

Elliptic comets not yet verified, and parabolic comets 341

Hyberbolic comets 13

492

d See the Catalogue in the Ap- of Catalogue I. in my Handbook of
pendix (posf), read as a continuation Astronomy, 4th ed., vol. i, p. 511.

Q 2

228 The Story of the Comets. CHAP.

Of known periodical comets, we have the following, as the
number of the apparitions of each :—

30 of Encke's.

17 ofHalley's.

8 ofFaye's.

7 -t> ' of Winnecke's.

6 of Biela's.®

6 of D'Arrest's.

5 of Brorsen's.

5 ofTuttle's.

5 of Tempel's Ilnd.

4 of Tempel's Illrd-Swift's.

8 of Tempel's 1st.

3 of Brooks's Ilnd.

3 ofFinlay's.

3 of Holmes's.

8 ofWolfs.

3? ofDiVico's.

Also 2 of each of the following : —

961 : 1097 (i.) : 1231 : 1264 : 1362 (i.) : 1532 : 1596 : 1699 (i.) : 1790 (iii.)
1810 : 1812 : 1815 : 1818 (i.).

Elliptic orbits have been assigned in the Catalogue to
various comets, of which however no 2nd returns have as yet
taken place.

Elliptic orbits have been assigned by some computers to
certain other comets ; of which it must be said that the
probability is not sufficiently great at present to warrant
their being included in a list of undoubted elliptic comets.

The question, " How many comets are known to be moving
in elliptic orbits " is one rather difficult to answer. If in any
given case a period of less than 100 years can be assigned to
a comet it will generally be found that all the different com-
puters who have investigated its orbit will be agreed within
a few years. But it is very different where hundreds of
years are in question. An ellipse implying that length is so
elongated : in other words, is so nearly parabolic so far as
available observations go that one computer will pronounce

e For reasons very fully set forth to be included in a list of known
in Chapter I. (ante), it is doubtful periodical comets,
•whether this comet ought any longer

XV. Cometary Statistics. 229

for an ellipse when another equally competent and with
equally good materials (i. e. observations) to go upon, will
stand out for a parabola. I have often found it very difficult
in compiling catalogues and statistics of comets to hold the
balance between rival computers, and in no case do I wish
that any decision to include or exclude an elliptic orbit as
against a parabolic orbit or one ellipse as against another is
to be deemed above challenge.

The orbits of the following comets are hyperbolic : —

1729 : 1771 : 1774 : 1840 (i.) : 1843 (ii.) : 1853 (iii.) : 1866 (i.) : 1883 (i.) :
1890 (ii.) : 1896 (ii.) : 1897 (i.) : 1898 (vii.) : 1899 (i.) : 1900 (ii.).

Hyperbolic orbits have been assigned by some computers to
the following comets : but the probability is not sufficiently
great to warrant their being definitely given as such : —

1723 : 1773 : 1779 : 1818 (iii.) : 1826 (ii.) : 1830 (i.) : 1843 (i.) : 1844 (iii.) :
1845 (i.) : 1845 (ii.) : 1849 (iii.) : 1852 (ii.) : 1863 (vi.): 1886 (ii.).

The following are some of those comets which have been
supposed to be identical : —

1894 (iv.) with 1844 (i.), and 1678.

1895 (ii.) - 1770 (i.) (Lexell's).
1881 (v.) — 1855 (ii.).

1880 (i.) — 1843 (i.).

1880 (iii.) — 1569, 1506, 1444, or 1382.

1873 (vii.) — 1818 (i.).

1871 (ii.) — 1827 (i.).

1863 (v.) — 1490.

I860 (i.) — 1845 (ii.), 1785 (i.), and 1351.

1868 (vt) — 146 B.C.

1858 (iv.) — 1799 (ii.).

1857 (v.) — 1825 (i.), and 1790 (iii.).

1854 (iv.) — 1558.

1854 (ii.) — 1799 (ii.).

1853 (iv.) - 1582 (ii.).

1853 (i.) — 1664.

1852 (ii.) - 1819 (ii.).

1844 (i.) — 1678.

1843 (i.) — 1668 and many others.

1840 (iv.) — 1490.

1827 (iii.) — 1780 (i.).

1819 (iv.) — 1743 (i.).

1819 (iii.) — 1766 (ii.).

1661 — 1532.

230 The Story of the Comets. CHAP.

The Perihelion points are not distributed at all evenly in
longitude all round the Sun, for more than 60 per cent, are
concentrated within 45° of longitude on either side of what
has been called " the Sun's Way ", i. e. the line in space along
which the Sun with its attendant planets is supposed to be
travelling. I do not exactly know who was the first to point
out this concentration, but Denning has reminded me in
a private letter that " the circumstance is so marked that
there is certainly some significance in it ".

The Ascending Nodes are distributed all round the ecliptic,
with however a decided tendency to concentrate around two
points having respectively the longitudes of about 80° and
270°.

The Inclinations of the orbits of comets vary from 0° to
90° : in other words, comets may be found moving almost in
the ecliptic, or at any angle between that and a perpendicular
to the ecliptic. When a new comet is found to have a small
inclination (anything under 15°) it is not unlikely that the
orbit is an ellipse and the comet a periodical one.

The Perihelion Distances of comets vary greatly. 11 comets
have a perihelion distance less than 5 millions of miles : about
64 per cent, of all that have been calculated lie within the
Earth's orbit ; about 30 per cent, lie outside, but within twice
the Earth's distance from the Sun ; and 16 comets have been
observed with a perihelion distance exceeding that limit.
A single one, the Comet of 1729. had a perihelion distance
exceeding 4 radii of the Earth's orbit — as great a distance as
the remoter asteroids. Young well remarks : — ''• it must have
been an enormous comet to be visible at such a distance."

The figures which have yielded the foregoing results are
the following : —

Perihelia within the Earth's orbit 248

Perihelia outside the Earth's orbit within 2 Radii ... 117

Perihelia outside the Earth's orbit more than 2 Radii but less than 4 15

Perihelion beyond 4 Radii of the Earth's orbit 1

381

The Direction of Motion of a comet is a matter of some
interest. With 2 exceptions all the periodical comets of less

XV. Cometary Statistics. 231

periods than 80 years move in the order of the signs of the
Zodiac, or " direct " ( + ). The 2 exceptions are Halley's
Comet and the " Comet of the Leonid or November Meteors ".
The long-period comets and the parabolic and hyperbolic
comets show a slight preponderance for Retrograde Motion
( — ), or motion contrary to the order of the signs of the
Zodiac.

As an incidental matter of statistics, A. S. Herschel re-
marked on the rarity of the near approach of comets to the
Earth's orbit. He found that of 80 new comets observed
between 1872 and 1892, only 2 came at all near to the
orbit of the Earth, namely the Comets of 1881 (v.) and 1886
(vii.). These came within about 3,000,000, and 4,600,000 miles
respectively of the Earth's orbit, but these distances were not
sufficiently small for a Meteor shower to be visible as the
result of the appulse.f

' Month. Not. E.A.S, vol. Ivii, p. 280. Feb. 1897.

APPENDIX I.

A CATALOGUE OF RECENT COMETS.
1888-1908.

THE following Catalogue comprises all the comets which have
appeared, and whose orbits have been calculated, between 1888
and 1908 inclusive, and is a continuation in the same form of the
Catalogue No. I. which appears in my Handbook of Astronomy,
4th edition, vol. i ; and the progressive numbers are carried on
from that Catalogue, but with the last imperfect page repeated.
The arrangement of the columns is the same except that the old
Element, which used to be called the " Longitude of the Peri-
helion ", and was represented by the Greek letter IT, is replaced,
to meet modern usage, by the "Argument of Perihelion",
represented by the Greek letter to. This is recommended for
adoption by W. C. Winlock as having "a simpler geometrical
signification than the longitude of the Perihelion IT, and is now
much more commonly used by Computers ". For further remarks
on this matter reference may be made to Chapter XI (ante).

A very elaborate statistical catalogue of all the comets calcu-
lated up to 1895 will be found in the Publications of the Astronomical
Society of the Pacific, vol. viii, p. 141, June 1896. The compiler,
W. C. Winlock, after giving the catalogue proper, has put all his
comets into classes according to the different Elements, the
members of each class being arranged in order from zero to
the maximum figure, whatever it may be. degrees of arc, radii of
the Earth's orbit, or eccentricity, &c.

Another catalogue of some value compiled by J. G. Galle, appears
in Ast. Nacli., vol. cxii, Nos. 2665-6, June 5, 1885. It comprises
all comets from 1860 to date, and improved orbits of many older
comets, but its matter is embodied in Galle's book published in
1894 (see Appendix Til, post).

A Catalogue of Recent Comets. 233

In the appendix to the Index to vols. xxx to In of the Monthly
Notices E. A. S. there is a very useful table compiled by
A. C. D. Crommelin of Reference Letters, Year-numbers, Dates of
Discovery, Perihelion Passages, and Periods (if any) of comets
discovered between 1869 and 1894.

Several of the books on comets, mentioned under the head of
"The Literature of Comets" in Appendix III, contain catalogues
of comets, some of them very exhaustive, but unfortunately they
do not for the most part come down very near to the present
epoch.

234

Appendix I.

No.

No.

Year.

PP.

<a

S3

i

q

388

307

1888 iii.

d. h.
July 31 4

59 12

101 29

74 ii

09022

389

(170

— iv.

Aug. 19 22

2OI 13

209 35

ii 19

17381

390

308

V.

Sept. 1 3 o

291 o

137 34

56 24

1-5321

39i

3°9

1889 i.

Jan. 31 6

340 28

357 24

1 66 22

1-8151

392

310

— ii.

June 10 18

236 5

310 42

163 50

2-2553

393

3"

— iii.

June 20 1 8

60 8

270 58

31 12

1-1024

394

312

— iv.

July 19 7

345 5i

286 9

65 58

1-0397

395

313

V.

Sept. 30 8

343 35

17 59

6 4

1-9499

396

3'4

- vi.

Nov. 29 13

69 39

330 36

10 14

1-3537

397

315

1890 i.

Jan. 26 12

199 54

8 23

56 44

2-6972

398

316

— ii.

June i 13

68 56

320 20

120 33

1-9075

399

317

— iii.

July 8 13

85 39

14 18

63 20

0-7641

400

3i8

— iv.

Aug. 7 3

33i 21

85 22

154 19

2-0481

401

(J95)

V.

Sept. 17 12

172 58

146 16

15 42

1-3240

402

319

- vi.

Sept. 24 12

163 2

100 7

98 56

1-2602

403

320

— vii.

Oct. 26 3

13 5

45 8

12 51

1-8179

404

321

1891 i.

April 27 13

178 55

193 55

120 31

0-3970

405

(290)

— ii.

Sept. 3 10

172 48

2O6 22

25 14

1-5928

406

(105)

— iii.

Oct. 17 23

183 57

334 4i

12 54

03404

407

322

— iv.

Nov. 12 23

268 37

217 40

77 44

0-9763

408

(247)

V.

Nov. 14 23

1 06 43

296 31

5 23

i -0866

409

323

1892 i.

April 6 1 6

24 31

240 54

3842

10268

410

324

— ii.

May 10 o

128 40

253 17

89 44

I-975I

411

325

— iii.

June 13 5

14 12

33i 4i

20 47

2-1397

412

(Hi)

— iv.

June 30 21

172 6

104 4

14 31

0-8865

413

326

— v.

Dec. 1 1 3

170 19

206 42

31 10

1-4277

389. An apparition of Faye's Comet.

392. Very faint, say 12th mag., with a tail 15° long.

395. An elliptic orbit ; period assigned, 7-07 years.

396. An elliptic orbit ; period assigned, 8-53 years.

401. An apparition of D' Arrest's Comet.

402. An elliptic orbit.

403. An elliptic orbit ; period assigned 6-40 years.
405. An apparition of Wolfs Comet.

A Catalogue of Recent Comets.

235

f

/*

Calculator.

Date of
Discovery.

Discoverer.

Duration of
Visibility.

0-99990

+

Millosewich

1888, Aug. 7

Brooks

II weeks

0-54902

+

Mciller

— Aug. 9

Perrotin

4 months

I'D

+

Halm

- Oct. 30

Barnard

4 months or +

I'D

—

Berberich

- Sept. 2

Barnard

2 years or +

0-99952

—

Millosewich

1889, Mar. 31

Barnard

7 months

0-95666

+

Berberich

— June 23

Barnard

6 weeks

0-99650

+

Berberich

— July 19

Davidson

1 6 weeks

0-47077

+

Bauschinger

— July 6

Brooks

19 weeks

0-67584

+

Hind

— Nov. 1 6

Swift

2 months ?

ro

+

Kriiger

— Dec. 12

Borelly

3 weeks

1-00037

—

Bidschof

— Mar. 19

Brooks

22 i months

ro

+

Ebert

- July 1 8

Coggia

4 weeks

ro

—

Ristenpart

— Nov. 15

Zona

4 weeks

0-62712

+

Leveau

- Oct. 6

Barnard

6 weeks

0-99915

—

Bobrinskoy

- July 23

Denning

8 weeks

0-47274

+

Tennant

— Nov. 1 6

Spitaler

12 weeks

ro

—

Bellamy

1891, Mar. 29

Barnard

4 months

o-557i8

+

Thraen

May i

Spitaler

5 months

0-84647

+

Backlund

— Aug. i

Barnard

7 weeks

ro

+

Berberich

— Oct. 2

Barnard

9 weeks

0-65270

+

Bossert

- Sept. 27

Barnard

1 6 weeks

0-99861

+

Berberich

1892, Mar. 6

Swift

8 months

ro

+

Lorentzen

Mar. 1 8

D f nning

3 weeks

0-40988

+

Boss

• — Nov. 6

Holmes

12 weeks

0-72599

+

Von Haerdtl

- Mar. 1 8

Spitaler

6 months

0-57814

+

Porter

- Oct. 12

Barnard

2 weeks

406. Aii apparition of Encke's Comet.

407. An elliptic orbit ; Barnard's Second Periodical Comet.

408. An apparition of the Tempel-Swift Comet.

409. An elliptic orbit ; period assigned, 20,143 years.

411. An elliptic orbit ; period assigned, 6-90 years.

412. An apparition of Winnecke's Comet.

413. An elliptic orbit ; period assigned, 6-22 years.

236

Appendix I.

No.

No.

Year.

PP.

u

S3

i

<1

414

327

1892 vi.

cl. h.
Dec. 28 2

252 42

264 29

24 47

Q'9757

415

328

1893 i-

Jan. 6 12

85 13

185 38

143 5i

1-1951

416

329

— ii.

July 7 7

47 7

337 20

159 57

0-6745

417

(299)

— iii.

July 12 3

315 3i

S2 27

3 2

09891

418

330

— iv.

Sept. 19 8

347 43

174 56

129 48

08150

419

33i

1894 i.

Feb. 9 1 1

46 16

84 21

5 3i

1-1472

420

332

— ii.

April 13 10

324 12

206 23

86 59

0-9830

421

'254)

— iii.

April 23 6

185 5

121 IO

12 44

I-3S05

422

(53?)

- iv.

Oct. 1 2 4

296 35

48 48

2 57

1-3920

423

(105)

1895 i-

Feb. 4 18

184 39

334 44

12 54

0-3410

424

333

— ii.

Aug. 20 20

167 47

170 16

2 59

1-2978

425

334

— iii.

Oct. 21 20

298 46

83 5

76 14

0-84303

426

335

— iv.

Dec. 1 8 8

272 40

320 29

141 37

0-19193

427

336

1896 i.

Jan. 31 18

358 20

208 50

155 44

0-5873

428

(171)

— ii.

March 1 9 6

201 13

209 53

1 1 20

1-7404

429

337

— iii.

April 17 1 6

I 44

178 15

55 34

0-5663

43°

338

iv.

July 10 23

41 3

150 59

88 26

1-1428

43i

339

— v.

Oct. 28 2

139 29

192 5

ii 32

1-4816

432

(313)

vi.

Nov. 4 4

343 48

18 4

6 4

''959

433

340

— vii.

Nov. 24 14

163 53

246 34

13 40

I-II02

434

34i

1897 i.

Feb. 8 2

172 18

86 28

146 8

I-0628

435

095)

— ii.

June 2 19

J73 4

146 25

15 43

1-3269

436

342

— iii.

Dec. 8 15

65 53

32 3

69 35

13557

437

343

1898 i.

March 1 7 3

47 19

262 26

72 31

I 0952

438

(Hi)

— ii.

March 20 12

173 21

ioo 53

17 o

0-9241

417. An apparition of Finlays Comet.

419. An elliptic orbit ; period assigned, 7-419 years.

420. An elliptic orbit ; period assigned 1,143 years.

421. An apparition of Tempel's Second Comet.

422. An elliptic orbit ; period assigned, 5-85 years. Possibly a return of
Di Vim's Comet, and of the Comet of 1678.

423. An apparition of Encke's Comet.

424. An elliptic orbit ; period assigned, 7-06 years. Perhaps a return of
Lexell's Comet.

427. Discovered also by Lamp on February 15.

A Catalogue of Recent Comets.

237

•

/*

Calculator.

Date of
Discovery.

Discoverer.

Duration of
Visibility.

10

+

Oppenheim

1892, Aug. 28

Brooks

13 weeks

ro

—

Porter

— Nov. 19

Brooks

12 weeks

10

—

Cerulli

1893, July 8

Rordame

6 weeks

071950

+

Schulhof

— May 17

Finlay

15 weeks

ro

—

Kriiger

— Oct. 1 6

Brooks

7 weeks

069839

+

Gast

1894, Mar. 26 Denning

10 weeks

0-99112

+

Peck

- Apr. i

Gale

5 months

055108

+

Schulhof

— May 8

Finlay

5 weeks

057157

+

Scares

— Nov. 20 E. Swift

10 weeks

0-84600

+

Backhand

Oct. 31 Perrotin

4 months

064773

+

Berberich

— Aug. 20

Swift

8 weeks

ro

+

Wassilief

— Nov. 21

Brooks

3 weeks

ro

—

Lamp

— Nov. 17

Perrine

3 months

I 0

—

Buchholz

1896. Feb. 14

Perrine

5 weeks

0-54902

+

Strcimgren

— Sept. 26

Javelle

4 weeks

i 00047

+

Aitken

Apr. 15

Swift

5 weeks

I'O

+

Peck

— Aug. 31

Sperra

4 weeks

0-65748

+

Hussey

— Sept. 4

Giacobini

9 weeks

0-4694

+

Bauschinger

— June 20

Javelle

15 weeks

o 67929

+

Ristenpart

Dec. 8

Perrine

3 months ?

I 00093

—

Peck

— Nov. 2

Perrine

6 months

0-6261 1

+

Leveau

1897, June 28

Perrine

5 weeks

I'O

+

Wessell

— Oct. 1 6

Perrine

6 weeks

098038

+

Curtis

1898, Mar. 20

Perrine

8 months

071472

+

Von Haardtl

— Jan. 2

Perrine

428. An apparition of Faye's Comet.

429. A hyperbolic orbit.

430. Orbit nearly perpendicular to the ecliptic.

431. An elliptic orbit ; period assigned, 9-0 years.

432. An apparition of Brooks' s Second Comet.

433. An elliptic orbit ; period assigned, 6-44 years.

434. A hyperbolic orbit.

435. An apparition of D1 Arrest's Comet.

437. An elliptic orbit; period assigned, 417 years.

438. An apparition of Winnecke's Comet.

238

Appendix I.

No.

No.

Year.

PP.

<a

8

I

<1

439

(105)

1898 iii.

d. h.

May 24 12

183 59

334 46

12 54

0-3423

440

(290)

— iv.

July 4 13

'72 53

206 29

25 12

1-6030

441

344

V.

July 25 12

313 36

212 12

155 0

1-5013

442

345

— vi.

Aug. 1 6 7

204 54

259 8

70 I

°'6353

443

346

— vii.

Sept. 14 i

233 15

74 o

69 56

1-7016

444

347

— viii.

Sept. 20 3

4 37

95 51

22 30

2-2850

445

348

— ix.

Oct. 20 13

162 20

34 53

28 5I

0-4204

446

349

X.

Nov. 23 4

123 32

96 18

140 20

0-7560

447

35°

1899 i.

April 12 23

8 41

25 o

146 15

0-3265

448

(325)

— ii.

April 28 2

14 4

33i 44

2O 48

2-1282

449

(in)

— iii.

May 4 5

116 29

269 49

54 29

1-0191

45°

(254)

— iv.

July 28 12

185 36

120 57

12 38

1-389

451

35i

V.

Sept. 13 21

10 9

272 16

77 3

1-7830

452

352

1900 i.

April 28 4

23 8

40 7

146 37

1-3459

453

353

— ii.

Aug.. 3 4

12 25

328 o

62 31

I 02

454

354

— iii.

Nov. 28 4

171 29

196 32

29 S2

0-9342

455

355

1901 i.

April 24 6

203 2

109 38

131 5

0-2448

456

(105)

— ii.

Sept. 15 10

183 59

334 48

12 53

0-3430

457

356

1902 i.

April 24 6

203 i

109 37

131 5

02447

458

357

ii.

June 20 8

301 46

217 3i

16 43

0-5838

459

358

— iii.

Nov. 23 19

152 57

49 21

156 21

0-401 1

460

359

1903 i.

March 16 o

133 4i

2 17

30 55

0-4106

461

360

— ii.

March 23 12

5 43

117 29

43 54

2-7789

462

36i

— iii.

March 25 10

184 57

213 8

66 29

0-4994

463

362

- iv.

Aug. 27 15

127 21

293 32

84 59

03292

464

(313)

— v.

Dec. 6 10

343 38

18 4

6 4

I-9586

465

363

1904 i.

March 5 18

53 2

275 4i

125 6

2704

439. An apparition of Encke's Comet.

440. An apparition of Wolfs Comet.
443. A hyperbolic orbit.

445. Discovered independently by Chofardet on September 14.

446. An elliptic orbit ; period assigned, 87,000 years ! !

447. A hyperbolic orbit.

448. An apparition of Holmes's Comet.

449. An apparition of Tuttle's Comet.

A Catalogue of Recent Comets.

239

1

/*

Calculator.

Date of
Discovery.

Discoverer.

Duration of
Visibility.

0-84635

+

Iwanow

1898, June 7

Grigg

I week or more ?

0-55534

+

Thraen

- June 1 6

Hussey

9 months

ro

—

Hnatek

— June 1 8

Giacobini

9 weeks

i-o

+

Berberich

— June 14

Perrine

i week

1-00103

+

Merfield

- June 1 1

Coddington

15 months

i-o

+

Coddington

— Nov. 14

Chase

8 weeks

i-o

+

Berberich

Sept. 1 2

Perrine

2 weeks

0-99974

—

Scharbe

- Oct. 20

Brooks

4 weeks

1-00035

—

Merfield

1899, Mar. 3

Swift

5 months

0-82170

+

Rahts

Mar. 5

Wolf

17 weeks

0*54211

+

Schulhof

— May 6

Perrine

7 months

0-41133

+

Zwiers

— June 10

Perrine

3 months

i-o

+

Winther

— Sept. 29

Giacobini

9 weeks

I'O

—

Giacobini

1900, Jan. 31

Giacobini

8 months

1-00042

+

Poor

- July 23

Borelly

10 weeks

0-74168

+

Kreutz

— Dec. 20

Giacobini

8 weeks

I'O

—

Merfield

1901, Apr. 12

Many observers

0-84599

+

Thonberg

— Aug. 5

Wilson

4 weeks

0-99979

—

Merfield

1902, Apr. 14

Brooks

6 weeks

i-o

+

Grigg

— July 22

Grigg

12 days

I'O

—

Stromgren

Aug. 31

Perrine

7 months

i-o

+

Ebell

1903, Jan. 15

Giacobini

4 months

i-o

+

Ebell

1902, Dec. 2

Giacobini

7 months

i-o

+

Peck

1903, Apr. 1 6

Grigg

6 weeks

I'O

+

Fayet

— June 1 1

Borelly

19 weeks

0-46978

+

Neugebauer

• Aug. 20

Aitken

6 months

i-o

—

Yowell

1904, Apr. 1 6

Brooks

1 2 months or +

450. An apparition of Tempers Second Comet (1873, ii.).

453. Discovered also by Brooks the same evening as Borelly, but five hours
later : a hyperbolic orbit.

454. An elliptic orbit ; period assigned, 6-87 years.
456. An apparition of Encke's Comet.

461. Perihelion distance unusually large.

462. Elements not very certain.

464. An apparition of Brooks' s Second Comet (1889, v.).

465. Perihelion distance unusually large.

240

Appendix I.

No.

No.

Year.

PP.

CO

£3

i

1

466

364

1904 ii.

d. h.

Oct. 25 12

35 3i

217 35

0 1

99 10

i -8450

467

(254)

— iii.

Nov. 10 ii

185 44

120 59

12 38

13878

468

(i°5)

1905 i.

Jan. 1 1 8

184 36

334 27

12 36

0-3386

469

365

— ii.

Jan. 16 17

352 12

76 38

30 33

I-3946

470

366

— iii.

April 4 i

358 13

157 23

40 14

1-1151

47i

367

— iv.

Oct. 18 15

158 39

342 1 8

4 16

3-339

472

368

— V.

Oct. 25 18

132 42

222 56

140 34

1-0500

473

369

— vi.

Dec. 22 5

89 43

286 22

126 27

1-2955

474

370

1906 i.

Jan. 22 8

199 ii

92 5

43 39

0-2159

475

37i

— ii.

Feb. 20 17

274 46

71 47

84 36

o 7067

476

(325)

— iii.

March 14 4

M i.7

33i 45

20 48

2 I2l8

477

372

— iv.

May 2 14

19 3i

263 47

843

1-6985

478

(299)

V.

Sept. 8 8

3i5 48

52 22

3 3

0-9646

479

373

— vi.

Oct. 10 2

200 41

194 19

H 3i

16305

480

374

— vii.

Nov. 21 8

8 42

84 56

56 33

I-2I45

481

375

1907 i.

March 19 6

317 10

97 ii

141 39

I 1262

482

376

— ii.

March 27 13

328 47

189 2

109 39

0-9246

483

377

— iii.

May 27 4

34 3

161 5

15 44

I-26l

484

378

— iv.

Sept. 3 1 8

294 47

H3 2

9 9

0506

485

379

V.

Sept. 13 17

293 27

54 54

"9 23

0-9799

486

380

— vi.

Dec. 6 i

39 26

3i7 7

10 27

3-8415

487

(105)

1 908 i.

April 30 4

'83 35

334 3°

12 37

0-3376

488

(247)

— ii.

Sept. 30 21

334 1 8

290 1 8

5 26

I-I535

489

38i

— iii.

Dec. 25 21

171 39

103 ii

140 ii

09446

490

382

1909 i.

June 5 7

5 4

305 21

5' 54

0-8418

491

467. An apparition of Tempefs Second Comet (1873, ii.).

468. An apparition of Encke's Comet.

469. An elliptic orbit ; period assigned, 7-20 years.

470. An elliptic orbit ; period assigned, 279 years.

471. Perihelion distance the 3rd largest known. Found on a photographic
plate taken January 14, 1905, or more than a year before its discovery visually.

476. An apparition of Holmes's Comet.

477. An elliptic orbit ; period assigned, 6-640 years.

A Catalogue of Recent Comets.

241

f p-

Calculator.

Date of
Discovery.

Discoverer.

Duration of
Visibility.

i-o

Fayet

1904, Dec. 17

Giacobini

4| months

0-54219 +

Schulhof

• Nov. 30

Javelle

5 weeks

0-8472 +

Kaminsky

— Sept. 1 1

Kopff

3 months

062511 +

Wedermeyer

Dec. 28

Borelly

5 months

0-97388 +

Wedermeyer

1905, Mar. 26

Giacobini

2 weeks

i-o +

Weiss

1906, Mar. 3

Kopff

3£ years

i-o —

Wedermeyer

1905, Nov. 17

Schaer

2 months

I'O

Ebell

1906, Jan. 26

Brooks

3 months

i-o +

Schcinberg

1905, Dec. 6

Giacobini

14 weeks

i-o +

Stromgren

1906, Mar. 17

Ross

i month

0-41215 +

Zwiers

— Aug. 28

Wolf

6 weeks

0-5204 +

Ebell

— ' Aug. 21

Kopff

5 months

072415 +

Schulhof

— July 1 6

Kopff

5 months

0-578 +

Ebell

— Nov. 14

Metcalf

i month

i-o +

Dybeck

• Nov. ii

Thiele

2 months

I'O

Einarson, &c.

1907, Mar. 9

Giacobini

10 months

I'O

Weiss

• Apr. 9

Grigg

I-O +

Einarson, &c.

— June i

Giacobini

2 weeks

i-o +

Crawford

- June 9

Daniel

10 months

i-o

Ebell

— Oct. 13

Mellish

4 weeks

i-o +

Ebell

1908, Jan. 2

Wolf

3 weeks

0-8475 +

Kaminsky

- May 27

Woodgate

i week

0-63779 +

Maubant

— Sept. 29

Javelle

3 months

I'O

Kobold

— Sept. i

Morehouse

6 months or +

ro +

Kobold

1909, June 14

Borelly

478. An apparition of Finlay's Comet.

479. An elliptic orbit; period assigned, 7-588 years.

481. Elements resemble those of Comet 1890 (iv.), but identity impossible.

482. Elements resemble those of the Comet of 1742 (i.).
484. As bright as a 2nd mag. star, with a tail 17° long.

486. The 2nd largest perihelion distance on record. -Al these elements very
doubtful.

487. An apparition of Encke's Comet.

488. An apparition of the Tempel-Swift Comet.

489. Travels from pole to pole in the heavens.

490. Discovered by Daniel on June 15.

CHAMBERS i;

APPENDIX II.

A SUPPLEMENTARY CATALOGUE OF COMETS
RECORDED, BUT NOT WITH SUFFICIENT
PRECISION TO ENABLE THEIR ORBITS TO
BE CALCULATED.

THE following catalogue is supplementary to the catalogue
under the same title which appears in the 4th edition of my
Handbook of Astronomy. Every now and again one comes across
mention of comets (especially in the centuries which have gone)
which have escaped the notice of previous inquirers into cometary
history. The comets which follow are those which have come, or
which have been brought, under my notice during the last 20
years ; and it is quite possible that sooner or later some of them
may be identified with other comets, ancient or modern.

[1.] B.C. 1140.+ " Nebuchadnezzar invaded Elam in revenge for the con-
tinual plundering expeditions sent out from that country, and a remarkable
circumstance is mentioned with respect to this time. When the king was
on the expedition an enormous comet appeared, the tail of which stretched
like a great reptile from the N. to the S. of the heavens.'' — (G. Smith,
Hist, of Babylonia, S.P.C.K., p. 96.) [This seems to be the same comet as that
mentioned in the same connection by Sayce in his Babylonian Inscriptions.']

[2.1 B.c. 613. A comet was seen in the autumn in the constellation
Pih-tau. — (The Chum Tsin quoted in Lindsay's Chrono-Astrolabe.} Pih-tau is
Ursa Major.

[3.] A.D. 599-600. In the 811th year of the Seleucian Era (or Oct. 599 to
Oct. 600) there was seen "in the exact S.W. corner of the heavens a sign
which resembled a spear. Some people said of it that it was the besom of
destruction, and others said that it was the spear of War ''. — (Syriac Chronicle of
Joshua the Stylite, ed. W. Wright.)

[4.1 A. D. 635. A Japanese history records a "besom-star which went
round and was seen in the E." in January. This may have been a re-
appearance, after perihelion passage, of a comet mentioned by the Chinese
as last seen in Oct. 634, and which this Japanese history also records. The
Japanese date of this is ''Autumn, 8th month '', and the entry is : — "A long
star was seen in the S. The people of that time called it a besom-star.
Hahaki-boshi or Hoki-boshi is the present name for a comet.1' — (Month. Not.
M.A.S., vol. Ixvi. p. 72. Dec. 1905.)

A Supplementary Catalogue of Comets. 243

[5.] 639. On March 6 a long star appeared in the N.W. "Prest Bin
said it was a besom-star. When it appeared there was a famine.'' — (Japanese
History ; Month. Not. B.A.S., vol. Ixvi, p. 72. Dec. 1905.) [This seems not to
have been the comet recorded by the Chinese on April 30, 639.]

[6.] 678. " In the year of our Lord's incarnation 678, which is the
eighth of the reign of Ecgfrid, in the month of August, appeared a star,
called a comet, which continued for 3 months, rising in the morning, and
darting out, as it were, a pillar of radiant flame.'1 — (Church Historians of
England, ed. Kev. J. Stevenson, vol. I, part ii, Beda's Ecclesiastical History,
Lib. IV, ch. XII, § 288.)

[7.] 687. " In February a comet rose out of the W. and with great
brightness went to the E.'? — (Chronological History of the Air, Meteors, &c., 1749.)

[8.] 1059. A comet shone in Poland for some days. — (Chron. Magdeb. Func.}

[9.] 1077. "Upon Palm sondaye aboute noone appeared a Biasing starre
neare unto the sunne." a — [Pingre says that this was Venus near its Inferior
Conjunction.]

[10.] 1103 ? "On the first Quadragesima week, about even, the first day, an
uncommon star was seen in the W. for 25 days together, and shined at the
same hour." — (Chronological History of the Air, Meteors, &c., 1749.)

[11.] 1157. A comet was seen. — (Chronicon Nurembergense.}

[12.] 1171. "At Christmas were 2 stars of a fiery colour seen in the W. :
one star was great, the other small, they seemed joined at first, then
separated and a great way distant.'' — (Chronological History of the Air, Meteors,
&c., 1749.) [Pingre" dates this for 1167, "or some one of the following
years.'']

[13.] 1219. In England appeared a stupendous great comet. — (Chron.
Mugdeb.} [Pingre identifies this with the comet of 1221.]

[14.] 1438. A comet was seen. — (Chronicon Nurembcrgense.}

[15.] 1455. " This yeare in the month of June appeared a comet or starre
called Stella Cometa, betwixt the North and the East, extending his beams
towards the South." Probably this is the comet thus alluded to in Sir R.
Baker's Chronicle, published in 1684 : — " In July [1455] a Parliament is
holden in King Henrie's name : the forerunner whereof was a comet or
blazing Starre which appeared in the month of June, the beames whereof
extended themselves into the south." \_Query, Halley's Comet of 1456 mis-
dated ?]

[16.] 1544. "A Biasing Starre was scene at all times of the nighte, the
sixth, seaventh, eight, ninth and tenth of March."

[17.] 1612. "On 18 of November, a blazing star began to be seen in the
S.E. about 5 o'clock in the morning, the flame or stream whereof enclined

a This comet (presuming it to have in his possession of the probable
been such) and the comets below date of circa 1580 ; but as the title-
dated 1455 and 1554, were sent to me page was wanting he told me he
by Mr. S. Reed, of Baltimore, U.S., as could not supply either the exact
having been obtained by him from title, or the author's name, or the
an old Black-letter History of England exact date of publication.

R 2

244 Appendix II.

towards the W. This Comet in the opinion of Dr. Bembridge the great
mathematician of Oxford, was as far above the Moon as the Moon is above
the Earth ; what it portended is only known to God, but the sequel of it
was that infinite slaughters and devastations followed upon it both in
Germany and in other countries. It appeared for 10 months together." —
(Sir Richard Baker, Chronicle of the Kings of England, published in 1684.)

[18.] 1633. "A Comet like a launce hung over Barcelona." — (Chronological
History of the Air, Meteors, &c., 1749.)

[19.] 1664. Towards the end of the year a comet appeared; and after
that, two at once : the first was seen in the S.E. for about two months, the
other in the S.W., but their tails were opposite to one another. — (Hamel,
Travels in Corea.}

[20.] 1717. On Monday, June 10 (o. s.), Dr. Halley discovered a small
telescopic comet. Its position at 11 o'clock that evening was / 17° 12' and
4° 12' south latitude, near 2 stars. On June 11 and 15 the 2 stars were
recognised, but the comet was gone. — (Phil. Trans., vol. xxx, No. 354, p. 721.)

[21.] 1893. On April 16 a comet, with a tail more than 1° long, impressed
itself on certain photographs taken of the total eclipse of the Sun of that date,
but it was never seen afterwards. — (Schaeberle, in Astronomy and Astro-Physics,
vol. xiii, April, 1894.)

[22.] 1895. In Dec. Du Celli^e Muller of Nymegen in company with
a friend claimed to have seen a bright comet near Venus, with a tail
inclined to the horizon at an angle of 35°. This comet [?] was seen by
no one else ; and the reality of its existence was considered doubtful. —
(Ast. Nach., vol.cxxxix, No. 3332, Feb. 5, 1896 ; Month. Not. E.A. S., vol. Ivii,
p. 276, February 1897.)

[23.] 1896. On Sept. 20 a small bright comet was seen by L. Swift 1° E.
of the Sun. It was seen again the next day with a telescope, having moved
N. and become fainter. No position was given or suggested, and the
observation was never confirmed. Swift even fancied he had seen two
comets. — (Ast. Nach., vol. cxli, No. 3379, Sept. 26, 1896 ; 16., No. 3384, Oct. 28,
1896; Month. Not. E.A. S., vol. Ivii, p. 276, Feb. 1897.)

[24.] 1905. Three photographic plates taken at the Carnegie Observatory,
Mount Wilson, California, U.S., on July 22, were subsequently found to
disclose a comet in motion whose position was worked out to be as follows : —
1905, July 22, 16h 20m 15s G. M. T., B. A. 18h 23m 15' : Declination S., 20° 30'.
The R.A. and Decl. both increased during the 2| hours which elapsed
between the first and last photographs : as no other observations were
obtained the comet must be considered lost. — (E. E. Barnard, Ast. Nach.,
vol. clxxiv, No. 4153. Feb. 6, 1907.)

[25.] 1905. On Nov. 29 Slipher, at the Lowell Observatory, U.S., obtained
by a photographic plate evidence of the existence of two comets, one of which
showed a double tail. As the announcement was not made for some time
after the plate was taken, and as the motion of the comets was uncertain, no
further observations were possible. The part of the sky photographed was in
the constellation Aquarius.— (Month. Not. R.A.S., vol. Ixvi, p. 220, Feb. 1906.)
[Queer things are often reported from the other side of the Atlantic.]

APPENDIX III.

THE LITERATURE OF COMETS.

COMETAKY Astronomy, being only a branch of general Astronomy,
has naturally no great amount of special literature attaching to it ;
but readers of this volume who may desire to add to their
knowledge of comets may like to know what works to consult,
so I append the titles of the chief of those in circulation. They
are arranged in the order of date of publication.

LUBIENITZKI, S. DE, Theatrum Cumeticum. 2 vols., fol. Amsterdam, 1668.

[Contains accounts of 415 comets or supposed comets.]
PINGRE, A., Cometographie ; ou Traite historique et theorique des Cometes. 2 vols.

4to. Paris, 1783.
GAUSS, C. F., Theoria motus Corporum Ccelestium in sectionibus Coma's Solem

ambientium. 4to. Hamburg!, 1809. [A German translation by C. Haase

was published at Hanover in 1865 ; and a French translation by E. Dubois

was published at Paris at about the same date.]
ARAGO, D. J. F., The Comet. Scientific notices of Comets in general, and in particular

of the Comet 0/1832. Translated by C. Gold. 8vo. London, 1833.
OLBERS, W., Abhandlung uber die leichteste und bcquemste Mettwde, die Bahn eines

Cometen zu berechnen . . . von neuem herausgegeben von J. F. Encke. 8vo.

Weimar, 1847.
HIND, J. E., The Comets: a descriptive Treatise upon those bodies, with a condensed

account of the numerous modern discoveries respecting them ; and a Table of all

the calculated comets from the earliest ages to the present time. 8vo. London, 1852.
ARAGO, D. J. F., A Popular Treatise on Comets reprinted from ' Popular Astronomy ',

by Arago. Translated by W. H. Smyth and K. Grant. 8vo. London, 1861.
KIRKWOOD, D., Comets and Meteors : their phenomena in all ages : their mutual

relations and the theory of their origin. 12mo. Philadelphia, 1873.
COOPER, E. J., Cometic Orbits : with copious Notes. 8vo. Dublin, 1852.
CARL, P., Repertorium der Cometen -Astronomic. Miinchen, 1864. [A very com-
plete assemblage of comet orbits from B.C. 612 to 1864.]
OPPOLZER, T. VON, Lehrbuch zur Bahnbestimmung derKometen und Planeten. 2 vols.

4to. Leipzig, 1870-80.
GUILLEMIN, A., Tlie World of Comets. Translated from the French by J. Glaisher.

8vo. London, 1877.
GALLE, J. G., Verzeichniss der Elemente der bisher berechneten Cometenbahneti.

Leipzig, 1894. [Comets from B.C. 372 to 1893, with copious notes.]
BREDICHIN, T., Mechanische Untersuchungen uber Cometenformen. Ed. by E. Jager-

mann. St. Petersburg and Leipzig, 1903. [A complete exposition of

Bredichin's theories with an immense number of engravings and diagrams.]

APPENDIX IV.

EPHEMERIS OF HALLEY'S COMET.
SEPTEMBER 1909 — JULY 1910.

THE following ephemeris of Halley's Comet has been calculated
by Mr. A. D. C. Crommelin and Mr. D. Smart on the supposition
that the perihelion passage will take place about the middle of
April 1910.

Date.

Right A'scension.

Declination.

Distance from
Earth in radii of
Earth's orbit.

1909

h. m. s.

0

Sept. II

6 18 4

+ 17 16

„ 25

6 18 32

17 ii

Oct. 9

6 14 36

17 8

„ 22

6 4 52

17 2

Nov. 3

5 47 4

16 59

„ 14

5 20 32

16 48

.. 25

4 45 8

l6 22

Dec. 6

4 2 16

15 26

» 15

3 18 20

14 6

„ 25

2 37 40

12 30

1910

Jan. 3

2 3 56

10 58

„ 6

i 51 40

10 17

1-42

„ 10

i 39 44

9 43

1-46

„ 14

i 29 8

9 15

1-50

„ 1 8

i 19 44

8 50

i'54

„ 22

i ii 20

8 29

i'59

„ 26

i 3 56

8 n

1-63

» 30

o 57 32

7 57

1-67

Feb. 3

o 51 48

7 45

171

7

o 46 36

7 37

175

>, ii

o 41 56

7 3i

1-78

Ephemeris of Halleys Comet.

247

Date.

Bight Ascension.

Declination.

Distance from
Earth in radii of
Earth's orbit.

1910

h. in. s.

0 ,

Feb. 15

o 37 36

7 27

1-81

» t9

o 33 44

7 24

1-84

„ 23

o 30 8

7 22

i-85

„ 27

o 26 44

7 22

r86

Mar. 3

o 23 34

7 23

r87

» 7

0 20 14

7 24

1-87

„ ii

o 16 56

7 24

r86

» 15

o 13 40

7 25

1-83

» 19

o 10 24

7 27

178

„ 23

o 6 48

7 26

175

» 27

030

7 23

171

» 3i

23 58 52

7 17

1-64

Apr. 4

23 55 2

7 13

i-56

., 8

23 5i 8

7 6

i'47

„ 12

23 47 28

7 o

r36

„ 16

23 44 6

6 52

1-23

„ 20

23 4i 36

6 43

i '09

„ 24

23 41 20

6 48

o'95

„ 28

23 43 16

7 4

0-80

May 2

23 48 56

7 20

0-65

6

o i 44

8 18

0-49

» 7

o 6 32

8 28

o'45

8

o 12 16

8 43

0-41

,. 9

o 19 52

9 16

o'37

„ 10

o 29 8

9 48

o'33

» ii

o 40 56

10 25

0-30

„ 12

o 56 32

II 12

0-26

„ 13

i 16 56

12 II

0-23

„ 14

i 44 12

13 23

0-19

.» 15

2 28 44

14 25

o'i6

„ 16

3 10 56

16 2

0-15

» i?

4 13 56

15 50

o-i4

„ 18

5 23 52

IS 41

0-13

„ 19

6 30 16

13 38

O'i4

248

Appendix IV.

Date.

Bight Ascension.

Declination.

Distance from
Earth in radii of
Earth's orbit.

1910

h. m. s.

0 /

May 20

7 23 20

II II

O'i6

„ 21

8 2 40

8 55

o'lg

„ 22

8 31 56

7 5

0-22

„ 26

9 3i 28

2 53

0-36

» 30

9 56 16

i oN.

0-51

June 3

10 9 56

o 48.

0-66

7

10 19 48

o 43

0-81

» ii

10 27 28

i 15

0-97

» 15

10 31 56

i 42

ri2

» 19

'10 36 24

2 3

1-28

,, 23

10 40 16

2 24

i'40

„ 27

10 44 o

2 45

i '54

July i

10 47 28

3 6

170

5

10 50 36

3 24

r86

„ 9

10 53 40

3 4i

i '95

„ 13

10 56 40

4 i

2-07

„ 17

10 59 40

4 20

2*19

„ 21

II 2 36

4 38

2-31

•> 25

ii 5 28

4 S6S.

2'43

In September the comet will be in the constellation Gemini ; passing
through Taurus, it will reach the middle of Aries by New Year's Day, 1910.
On Nov. 29 it will be very close to Aldebaran (a Tauri, Mag. 1*0) about £° to
the S. of that star.

Then, starting with the month of January, 1910, on January 6 the comet
will be in Aries, about midway between o Piscium (4-4) and £' Arietis
(4-9), but 2° N. of the mid-interval between these two stars.

Both the B.A. and the Declination of the comet will then slowly
diminish until April 24, the comet remaining during the whole of that
interval in the constellation Pisces, and, unfortunately, passing near no
conspicuous stars.

On Jan. 12 the comet will have nearly the same E,A. as tt Piscium (5-6),
and be 2|° S. of that star.

On Jan. 29 the comet will have nearly the same B.A. as e Piscium (4'5),
and be i° N. of that star.

On Feb. 9 the comet will have nearly the same R.A. as 8 Piscium (4*6),
and be f ° N. of that star.

Ephemeris of Halleys Comet. 249

On March 12 the comet will have nearly the same R.A. as d Piscium (5'0),
and be only 2' S. of that star.

On March 21 the comet will have nearly the same K.A. as Algenib (7 Pegasi)
of mag. 3'0, and be 7|° S. of that star.

After about April 1 it will be matter of some uncertainty how long it will
be possible to see the comet as it approaches the Sun to make its perihelion
appulse. It will certainly cease to be visible much longer in the evening,
but will reappear in the morning early in May, still in the Northern
hemisphere, and still in Pisces, where it will be till about May 14. After
that its R.A. will rapidly increase, the Declination slowly diminishing till
about June 1, when the comet will pass into the Southern hemisphere and
remain there until it disappears altogether, which may be in June or July.

The comet will be nearest to the Earth (distance, 12 million miles) and
therefore at its maximum brilliancy about May 18, but the Moon, "new"
on May 8, will to some extent spoil the comet ; and May 21 will afford us
the best view, all things considered.

After quitting Pisces, about May 14, its path will be through Aries, Taurus,
Gemini, the head of Orion, Canis Minor, Hydra, Sextans, the feet of Leo, and
Virgo, where it will probably be last seen : but the long days and short
nights, and full Moon on May 22, with no true night at all during many
weeks, will seriously interfere with observations of the comet. During its
posi-perihelion career the comet will pass not far from a considerable number
of bright stars which may be a little help to those who, living in the
Southern hemisphere, at the Cape, or in Australia, or New Zealand, may
desire to follow the comet as long as possible. Aldebaran (a Tauri, mag. TO),
Betelgeuze (a Orionis, mag. 1-0), 7 Geminorum (2'0), and Procyon (o Canis
Minoris, mag. 0'5) are some of the stars to which the foregoing remark
applies.

In the Ast. Nock., vol. clxxxi, No. 4330, June 12, 1809, Matkiewitsch of
Pulkova gives an epliemeris differing only slightly throughout from the fore-
going.

INDEX.

%* This Index does not include names in the Appendices. Entries in small capital*
indicate Titles of Chapters.

Adams, J. C., 194, 196.

Airy, Sir G. B., 10, 167.

Aitken, R. G., 79.

Albrecht, 188.

Alford, Dean, 219.

Anaxagoras, 203.

Andromede Meteors, 197, 200.

Angstrom, A. J., 125.

Anomaly, Mean, 162.

Apian, P., 22, 104.

Apollonius, 203.

Arago, D. J. P., 41, 216.

Aristotle, 204.

Ascending Node, longitude of, 163,

230.

Asteius, the Archon, 203.
Astronomical Society of the Pacific,

56.

Astronomische Gesellschaft, 50.
Astronomische Nachrichten, 50.
Attila, leader of the Huns, 122.
Aurora Borealis, 25, 115, 145.
Auzout, 212.

Backhouse, T. W., 183.

Baert, 105.

Barnard, E. E., 47, 53, 68, 74, 76, 78,

82, 153.
Barnard's First Periodical Comet,

1884 (ii.), 81.

— Second Periodical Comet, 1891
(iv.), 81.

— Uncertain Periodical Comet, 1892
(v.), 83.

Bayeux Tapestry, Halley's Comet re-
corded on, 121.

Beard of a comet, 23.

Berberich, 17, 81.

Bernard, 187, 189.

Bessel, W., 29, 36, 99 ; observations
by, 115, 116.

Bible, suggested allusions to comets,
in, 218.

Biela, 89.

Biela's Comet, 15, 88, 156, 215;
meteors associated with it, 197.

CHAMBERS

Biot, E., 23.

Blainpain, 85.

Blainpain's Comet, 94, 95.

Boguslawski, 62.

Bond, G. P., 139.

— , W. C., 99.

Borelli, 45.

Borelly, A. 189.

Borelly's Comet of 1890 (i. ), 183.

— Comet of 1903 (iv.), 186.

— Periodical Comet of 1905 (ii.), 83.
Bosler, 189.

Bossert, 97.

Bouvard, A., 89, 130.

Breaking up of comets, 14, 15, 16, 17,

90.
Bredichin, T., 16, 33 ; his types of

comets' tails, 16, 33.
Brilliancy of periodical comets

diminishes, 5.
Brisbane, Sir T. M., 61.
Brodie, F., 143, 147.
Brooks, W. K., 47, 97, 99, 153, 159,

169.
Brooks's First Periodical Comet (1886,

iv.), 81.

— Second Periodical Comet (1889,
v.), 42, 78.

— Comet of 1893 (iv.), 30.

— Comet of 1894 (i.), 54.

— Comet of 1904 (i.), 186.
Brorsen's Long-Period Comet, 96,

99.

— Short-Period Comet, 69, 84, 175.
Browning, J., 191.

Bruhns, C., 71.
Briinnovv, F. F. E., 93.
Buckingham, J. H., 92.
Burckhardt, J. K., 87, 95, 117.
Burial-place of Halley, 107.
Byron, Lord, quoted, 213.

Cacciatore, N., 11, 61.
Calixtus III, Pope, 208.
Callandreau, O., 14.
Campbell, W. W., 184, 188.

Index.

251

Cappelletti and Rosa, drawings by,

27.
Capture of comets by planets, 42,

165.

Carbonic oxide spectrum, 176.
Carpenter, J., 65.
Cassini. James, 59.
— , J. D., 59.

CATALOGUE OF RECENT COMETS, 232.
CATALOGUE OF COMETS RECORDED BUT

NOT CALCULATED, 242.
Catalogues of comets, usefulness of,

161.

Chaldaean opinion on comets, 202.
Challis, J., 79, 90, 146.
Chambers, G. F.. 143.
Chandler, S. C., 78, 97.
Chinese accounts of comets, 23, 54,

100, 117, 200.
Chretien, 186.
Christie, Sir W. H., 177.
Chronicles, Old English, references

to comets in, 207.
Circle, no comet known to move in,

160.

Clairaut, A. C., 107, 108.
Claudius, 207.
Clausen, T., 95.

Clerke, Miss A. M., quoted, 20, 67.
Coggia's Comet of 1874, 9, 18, 25, 26,

30, 147, 175, 177.
— Short-Period Comet (1873, vii.),

94, 95.

Colour of comets, 8, 159.
Coma, meaning of the word, 3.
Comet, as portents, 2 ; appearance of,
when first discovered, 3 ; visible in
daylight, 8 ; light of, 10 ; break-
ing up of, 14 ; associated with
planets, 17 ; which are probably
periodic, 80 ; daily motion of, 166.
Comet of 371 B.C., 14.
1532, 101.
1577, 22, 45.
1618 (ii.), 25.
1652, 12.
1661,101.
1665, 12.
1668, 18.
1680, 45.
1682, 12.

1744, 11, 23, 127.
1769, 9, 25.
1807, 10. 14.
1811, 9/10, 129.
1812 (Pons's), 11, 23.
1819 (ii.), 13.
1823, 13.
1825, 23.
1826 (v.), 13. •

Comet of 1843, 9, 18, 131.
1858 (Donati's), 9, 10, 24, 30, 35,
131.

1860 (iii.), 27.

1861 (ii.), 39, 141.

1874 (Coggia's), 9, 18, 25, 26, 30.

1880 (i.), 18.

1881 (ii.), 16.

1881 (iii.), 189.

1882 (iii.), 17, 18, 24, 181.

1886 (i.), Fabry's, 9.

1887 (i.), 18.
1892 (i.), 29.
1892 (v.), 53.
1899 (i.), 16.
1903 (iii.), 14.

COMETARY STATISTICS, 221 ; see also

p. 166.

COMETS IN THE SPECTROSCOPE, 174.
COMETS IN HISTORY AND POETRY, 202.
Comet-seeker telescope, 48.
Comet wine, 131.
Common, A. A., 66.
Comparative sizes of comets, the

Earth, and the orbit of the Moon, 7.
Cone, various sections of, 162.
Conic sections, all comets move in,

52, 160, 167, 170.
Contraction and expansion of comets,

8.

Copeland, R., 74, 175, 180.
Corrigan, 75.
Cowell, P. H., 116.
Crommelin, A. C. D., 116, 171, 233.
Cruls, 156.

" Curse of Scotland ", 220.
Curvature of the tails of comets, 24.
Cvanogen in spectra of comets, 176,

"189.

Cypher codes, 56.
Cysatus, J. B., 15.

Daily motion of comets, 166.
Damoiseau, M. C. T. De, 89, 110.
Daniel's Comet of 1907 (iv.), 186,

189.

Dante's Paradiso quoted, 211.
D'Arrest, H. I., 71, 95, 99.
D'Arrest's Comet, 72.
Davidson, 74.

Davidson's Virgil quoted, 206.
Daylight, comets visible in, 8.
De Cheseaux, J. P. L., 11, 127.
De Fontenelle, 218.
De La Baume-Pluvinel, Count, 185,

187.

De La Rue, W., 145.
De Morgan, A., 216.
Delambre, J. B. J., 11.
Delisle, D. R., 109.

252

Index.

Democritus of Abdera, 203.

Denmark, medals given by King of,
55.

Denning, W. F., 46.

Denning's First Periodical Comet
(1881, v.), 85.

— Second Periodical Comet (1894,
i.), 84.

Density of comets, 39.

Deslandres, 186, 187, 189.

Developement of comets after dis-
covery, 3.

Digges, L., quoted, 209.

Dimensions of orbits, 224.

— of the heads of comets, 222.

— of the nuclei of comets, 139, 222.

— of the tails of comets, 139, 223.
Diminution of brilliancy of comets, 5.
Dion Cassius quoted, 122, 123, 216.
Direct motion, 231.

Direction of motion of comets, 164,
166, 231.

— of tails of comets, 24.
DISCOVERY AND IDENTIFICATION OF

COMETS, 46.

Di Vico, F., 90.

Di Vico's Comet, 93 ; supposed identi-
fications of, 71, 85.

— Long- Period Comet (1846, iv.), 96,
99.

Donati, G. B., 175.

Donati's Comet of 1858. 9, 10, 24, 30,

35, 131, 215.
Donohoe, J. A., his prizes for

cometary discoveries, 55.
DOrfel, 45.
Draper, H., 179.
Dreyer, J. W. L., 128.
Du Bartas quoted, 2, 212.
Du Sejour, A. P. D., 41.
Dumouchel, M., 112.
Dunlop, J., 23.
Dunster, 212.

Eccentricity of a comet's orbit, 52,

163.
Eclipse of the Sun, comets visible

during, 19, 226.
Ecliptic, plane of, 164.
Eddie, 159.

Edinburgh Review quoted, 124.
Elements of a comet's orbit, 5,

162.

— of meteor orbits, 196.
Ellipse, 160.

— , axis of. 166 ; directrix of, 166 ;

focus of, 166 ; construction of,

167.

Elliptic orbits, 228.
Emperor Charles V, 101.

Emperor Constantinus Ducas, 118.

— Napoleon, 129.
- Nero, 206.

— Vespasian, 206.
Encke, J. F., 49, 97.

Encke's Comet, 39, 49, 59, 69, 223.
Envelopes 27 ; formation of, 28.
Ephemeris of comets. 167.

— of Halley's Comet for 1910, 124.
Ephorus, 14.

Equinox, vernal, 164.

Euler, L., 127.

Evans, L., quoted, 207.

Evelyn, J., 211.

Evershed, J., 187, 188.

Ewart, Gen. J. A., 131.

Expansion and contraction of comets,

Fabry's Comet of 1886 (i.), 9.

Families of comets, 17.

Fans of light in heads of comets,

29.

Faye, H. A. E.,
Faye's Comet, 79, 84.
Finlay, W. H., 157.
Finlay's Comet, 71, 94.
Fire-balls. 1, 191.

Flammarion, C., 154. 217 ; his sug-
gested planetary influences, 43.
Flamsteed, J., 104.
Flaugergues, 13, 129.
1 Forbes, Prof. G., 43.
Fowler, A., 183.
Fraunhofer's lines, 179.
Frost, 176, 182, 188,

Gadbury, J., quoted, 209.

Galle, J. G., 90, 232.

Gambart, M., 13, 61, 89.

Game of comet, 220.

Gauss, C. F., his methods of calcu-
lating orbits, 60, 164, ]66.

Gautier, A., 71.

Geelmuyden, 151.

GENERAL REMARKS, 1.

Giacobini, 48.

Giacobini's First Periodical Comet

(1896, v.), 85.
- Second Periodical Comet (1900,

iii.), 83.
: Gibbs, W. B., 170.

Glaisher, J., 201.

Goldschmidt, H., Comet of 1855 (ii.),
85.

Gould, B. A., 151.

Gouy, 181.

Grant, E., his list of remarkable
comets, 126.

Index.

253

Gravitation, 24, 34, 45, 69, 102, 170.
Great comets, list of, 126.
Greek opinion on comets, 203.
Gregory, D., 106.
Grischau's Comet, 94, 95.
Guillemin, A., 217.

Hall, A., 63.

Halley, E., 101.

Halley's Comet. 5, 29, 39, 54, 96, 208,

223, 231.

HALLEY'S COMET, 102.
Harding, K. L., 61,62.
Harkness, W., 162.
Harris, J., 106.
Harryot, T., 45.

Harvard College Observatory, 57.
Hasselberg, 176, 178.
Heads of comets, 3, 6 ; changes in

dimensions of, 8 ; Sir J. Herschel's

theory of, 8.
Heinsius, G., 11.
Helfenzrieda's Comet, 94, 95.
Herschel, Sir J. F. W., 36, 101, 110 ;

observations by, 8, 14, 112, 115,

116, 132, 141.
Herschel, Sir W., 110; observations

by, 10, 14, 130.

Herschel, A. S., 199. 201, 231.
Herschel, Miss C., 49, 60.
Hevelius, J., 12, 45, 104, 204.
Hill, G. A., 69.
Hind, J. R., 13, 55, 62, 64, 67, 84,

88, 90, 94, 100, 106, 107, 116, 117,

144.

Hind's Comet of 1846 (ix.), 85.
Hippocrates of Chios, 203.
HISTORY AND POETRY, COMETS IN, 202.
Hoek, M., 20.

Holden, E. S., 28, 156, 157.
Holetschek, J., 5.
Holland, P., 207.
Holmes's Comet (1892, iii.), 11, 74,

80, 172, 175, 184.
Homer's Iliad quoted, 204.
Hopkins, B. J., 153, 154.
Howe, H. A., 167.
Huggins, Sir W., 175, 179.
Hunniades, Papal General, 208.
Huth, 60.

Hydro-carbon spectra, 175, 176.
Hyperbola, 161, 168.
Hyperbolic orbits, 229.

Identical, comets supposed to be, 229.
Identification of comets, 19, 50.
Illustrated London News, 1843, quoted,

214.
Inclination of a comet's orbit, 163,

165, 230.

Innes, R. T. A., 159.

Intrinsic light of comets, 10 ; Sir

W. Herschel's opinion as to, 10;

Sir G. B. Airy's observations, 10.

Jacque, J., 218.

Janssen, 179.

Javelle, 79.

Jerusalem, siege of, by Titus, comet

preceding, 123.
Jets of light, 26, 29.
Josephus, Jewish historian, quoted,

123, 220.

Julius Caesar, 206.
Jupiter referred to, 12.
Jupiter's influence on comets, 40, 63,

67, 71, 74, 78, 80, 84, 106.
Juvenal quoted, 207.

Kaiser, F., 112.
Kayser, 177, 185.
Keeler, J. E., 175, 184.
Kepler, J., 14, 20, 91, 223.
Key, Rev. H. C., 66.
Kiel Observatory, 57.
Kirch, G., 105.
— , Margaretha, 128.
Kirkwood, D., 75, 200, 201.
Klinkerfues, W., 92.
Konkoly, N. Von, 70, 183. 191.
Kopff, 72.

Kopff's Comet of 1905 (iv.), 54.
- Periodical Comet (1906, iv.), 82.
Kreutz, 19, 69.
Kritzinger, 138.

La Grange, J. L. de, 110.

La Harpe, 47.

La Nux, 24.

Lalande, J. J. Le F. De, 108. 110.

Lambert, J. H., 218.

Lapaute, Madame, 108.

Laplace, P. S. De, 110.

Laugier, P. A. E., 116, 117.

Le Verrier, U. J. J., 79, 88, 94, 200.

Lee, O. J., 125.

Lehmann, 111.

Leonid Meteors, 193, 194, 196, 200,
231.

Lewis, Sir G. C., Astronomy of the
Ancients, quoted, 203.

Lexell's Comet, 17, 39, 84, 86 ; sup-
posed identification of, 79.

Liais, E., 15.

Light-pressure, 36.

Lindemann, A. F., his prizes for
cometary calculations, 56.

LITERATURE OF COMETS, 245.

Lithium in Meteors, 191.

Littre's Dictionary quoted, 220.

254

Index.

Lockyer, Sir J. N., 176, 177, 182, 201.

Logarithms, usefulness of, 166, 171.

Lohse, J. G., 180.

Longfellow's Dante quoted, 211.

Longitude, Mean, 162.

LOST COMETS, 86.

Lowe, E. J., 144.

Lower, Sir W., 45.

Luminous sector, 20.

Lunt, J., 158.

Lyrid Meteors, 193. 197, 200.

Maclear, Sir T., 72, 113, 115, 132,

134.

Magnesium in meteors, 191.
Major axis of a comet's orbit, 52.
Malmesbury, Earl of, 215, 216.
Mass of comets, 39.
Ma-tuoan-lin, 118, 122.
Maunder, E. W., 36, 174, 219.
Maury, M. F., 91.

Mean distance of a comet's orbit, 166.
M<§chain, P. F. A., 47, 59, 80, 101.
Medal to commemorate the comet of

1680, 103.
Medals given for the discovery of

comets, 55.
Mercury, Laplace's value of its mass,

64.

Messier, 13, 46, 59, 80, 86, 109.
Messier and the Emperor Napoleon,

205.

Metcalf's Comet, 1906 (vi.), 84.
Meteors and comets, 44.
Milton, 204.
Milton's Paradise Lost quoted, 211,

212

Mallei-, A., 70.
Montaigne, 47, 49, 88.
Montanari, 105.
Morehouse, 48.
Morehouse's Comet of 1908 (iv.), 11,

30, 187 ; spectrum of, 187.
Moscow, the French at, 205.
Motion, direction of, 231.
— , mean rate of, 162, 166.
MOVEMENTS OF COMETS, 38.
Miiller, 97.

Napoleon, Emperor, and comets, 129,

205.

Nero, Emperor, 206.
Newall, H. F., 26, 190.
Newbolt, Canon, quoted, 206.
Newcomb, S., 28.
Newton, Sir I., 45, 102, 170, 213.
— , H. A., 194, 199, 200.
Nicolai, 90.
Niesten, 11.

Node, Ascending, longitude of, 163,
230.

Norman Conquest, 118.

Nucleus of a comet, 3, 4, 14, 97 ;
breaking up of, 152 ; general de-
scription of, 3.

Number of comets recorded, 224.

Olbers, W., 36, 60. 89, 101, 112.
Olbers's Comet, 96, 99.
Oliver, A., 218.
Olmsted, D., 194.
Oppolzer, T. Von, 166, 196.
Orbits, elements of, 52, 162, 230.
ORBITS OF COMETS, 160.

Palisa, J., 77.

Palitzsch, 109.

Pape, C. F., 133, 135.

Parabola, 161, 168, 170.

Paracelsus, 205.

Parkhurst, 188.

Pasquier, E., 167.

Pastorff, 13.

Paths of comets, 4.

Payne, W. W., 42.

Penrose, F. C., 162.

Perihelion, 230 ; longitude of, 163.

— distance, 52, 163, 230 ; small, 18,
230.

— passage, time of, 162.
PERIODIC COMETS OF LONG PERIOD, 96.
PERIODIC COMETS OF SHORT PERIOD, 58.
Periods of comets. 18, 100, 228.
Perrine, C. D., 47, 77.

Perrine's Comet (1896, vii.), 82.
Perrine-Grigg's Comet of 1902 (ii.),

185.

Perrotin, J., 81, 98.
Perseid meteors, 193, 200.
Perturbations of comets by planets,

20, 72, 107, 111.
Peters, C. A. F., 50.
— , C. H. F., 83.

Peters's Comet of 1846 (vi.), 94, 95.
Phases in comets, doubtful, 11.
Philip Augustus, King of France, 118.
Photography as applied to comets,

23, 30, 53, 182, 189.
PHYSICAL DESCRIPTION OF COMETS. 10.
Pi card, J., 104.
Pickering, 186.
Pidoux, 31.

Pigott's Comet, 94, 95.
Pingre, E.G., 91, 101, 117.
Plane of a comet's orbit, 52.
Planetary discs, comets with, 12.
Planets, influence of, on comets, 40.
Planets with comets associated, 17,

43.

Index.

255

Platina's Vitce Pontifcum quoted, 208.

Pliny quoted, 204, 207.

Plummer, W. E., 71.

Plutarch quoted, 207.

Poetical allusions to comets, 2, 202.

Poey, 147.

Pogson, N., 92.

Polarisation of a comet's light, 145.

Pens, the "comet-hunter", 47, 49,

89, 95 ; his comets, 60 ; his comet

of 1812.

Pont<§coulant, P. G. D. De, 110, 125.
Poor, C. L., 168.
Pope, A., quoted. 213.
Pope's Homer quoted, 204.
Pope Calixtus III, 208.
- Urban IV, 101.
Potassium in meteors, 191.
Pouchet, F. A., 217.
Prince, C. L., 152.
Prosperin, 60.
Ptolemy, 204.

Quadrantid meteors, 198.
Quenisset, 31.
Quetelet, L. A. J., 194.

Radius vector, 22.

Kayet, G., 98, 150.

RELATION OF COMETS TO METEORS, 192.

REMARKABLE COMETS, 126.

Resisting medium, 62.

Retrograde motion of comets, 164,

231.

Rolston, W. E., 174.
Rordame's Comet of 1893 (ii.), 185,

186.

Rosenberger, 0. A., 110.
Riimker, C. L., 61.
Range, 177, 185.

Santini, G., 89.

Saturn's influence on comets, 18.

Sawerthal's Comet (1888, i.), 158, 179.

Schiiberle's Comet (1881, rvO, spec-
trum of, 180.

Scheller, A., 38.

Schiaparelli, G. V., 97, 191, 195, 196,
201.

Schmidt, J. F. J., 153.

Schulhof, L., 54, 84. 94, 97.

Scymitar tails, 16, 24.

Seagrave, 125.

Seech i, A., 145, 175.

Self-luminous, comets probably are,
generally, 10.

Semi-axis major of a comet's orbit,
166.

Seneca, 14, 39, 205.

Senoque, 186.

Seyboth, 151.

Shakespeare, W., quoted, 209, 210.

Shooting stars, 1, 192, 193.

Short-period comets, 58.

Sirius (aCanis Majoris), 19.

Smithells, 176.

Smyth, Admiral W. H., 113, 208.

— , C. P., 116.

Sodium in comets, 191.

Spectroscope as applied to comets,
10, 33, 70, 174.

Spenser's Faerie Queene, quoted, 210.

Sperra, 85.

Spitaler, 74.

Spitaler's Comet (1890, vii.), 82.

Statistics of comets, 221.

St(§phan, E., 71.

Striations in comets, 159.

Struve, F. G. W., 61, 112 ; observa-
tions by, 115, 116.

-, O., 91*.

Suetonius quoted, 206.

Superstitions connected with comets,
2.

Swift, E., 94.

— , L., 23, 30, 47, 68.

Swift's Comet of 1892 (i.), 29.

— First Periodical Comet, 1885 (ii.),
83.

— Second Periodical Comet, 1889
(vi.), 83.

Symons, G. J., 152.

Tacchini, P., 66.

TAILS OF COMETS, 22.

Tails of comets, at first discovery,

3 ; length of, varies much, 4, 6,

13 ; probably hollow, 25.
Talmage, C. G., 92.
Tasso, Gerusalemme Liberata, quoted,

211, 212.
Tebbutt, J., 141.

Tebbutt's Comet, spectrum of, 179.
Telegraph codes for comets, 56.
Telescopic comets, 5.
Tempel, W., 153.
Ternpel's Comet of 1866 (i.), 175.

— First Periodical Comet, 71, 78.

— Second Periodical Comet, 67.
Tempel(3)-Swift's Comet, 68.
Thollon, M., 98, 181.

Thomson, A., his Suetonius quoted,

207.

Thomson, J., Seasons, quoted, 213.
Thulis, 49, 60.
Todd, Sir C., 157.
Todd's Du Sartas quoted, 212.
Transit of comets across the Sun, 13.
Tre"pied, 98.
Tupman, G. L., 74.

256

Index.

Turks and the Comet of 1456, 208.
Turner, Prof. H. H., 56 ; on Milton,

211.

Tuttle, H. P., 80.
Tuttle's Short-Period Comet (1858,

i.), 80.
— Short-Period Comet (1858, iii.),

94, 95.

Twining, A. C., 194.
Tycho Brahe, 45.

Valz, B., 22, 61.

Verne, J., 217.

Vespasian, Emperor of Rome, 206.

Vibrations in comets, 25, 153.

Vienna Academy of Sciences, medal

given by, 55.
Villarceau, Y., 72.
Virgil quoted, 206.
Visibility of comets, duration of, 226.
Vogel, 180.
Voltaire quoted, 220.
Von Asten, F. E., 63, 66.
Von Gothard, 184.

Warner, H. H., his prizes for comets,

55.
Weather, influence of comets on,

imaginary, 216.

Webb, T. W., 13, 141, 143.

Weiss, E., 95.

Wells's Comet (1882, ii.), spectrum

of, 180.

Westphal's Comet, 96, 97. '
Whiston, Rev. W., 103.
Wiffen's Tasso quoted, 211.
William of Malmesbury quoted, 207.
Williams, G., 140, 144.
— , J., 55.

Willis, Gen. G. H., 155, 156.
Winlock, W. C., 232.
Winnecke, F. A. T., 73, 85, 127.
Winnecke's Comet (1868, iii.), 63,

69, 166, 175.
Wisniewski, 129.
With, G. H., 26.
Wolf, 150.
-, M., 14.
Wolf's Comet, 54, 73, 83, 84.

Young, C. A., 70, 180 ; quoted, 12, 19.
Young, E., Night Thoughts, quoted, 213.

Zeno, 203.

Zimmermann, 105.

Zodiacal light, great Comet of 1843

mistaken for,
Zona's Comet, 82.

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