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ASTKONOMY.

CHAMBERS.

THE SUN, PLANETS, AND COMETS.

a 2

Bonbon
HENRY FROWDE

OXFORD UNIVERSITY PRESS WAREHOUSE
AMEN CORNER, E.G.

f-a

As
c

A HANDBOOK

DESCRIPTIVE AND PRACTICAL
ASTRONOMY.

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

OF THE INNER TEMPLE, BAHBI8TEB-AT-LAW I

Author of "A Practical and Conversational English, French, and German Dictionary;

"The Tourist's Pocket-Book; " "A Digest of the Law relating to Public

Health;" "A Digest of the Law relating to Public Libraries

and Museums;" "A Handbook for Public Meetings;"

and other Works,

' The heavens declare the glory of God ; and the firmament sheweth his handywork."

Psalm xix. i.

THE SUN, PLANETS, AND COMETS.
FOURTH EDITION.

FIG. 2.

August 26. September 9.

THE JIJRD SATELLITE OF JUPITER IN 1855. (StCcM.)

AT THE CLARENDON PRESS.

1889.
[All right* referred.]

PREFACE TO THE FOURTH EDITION.

PT^HE remarks which appear in the Preface to the Third Edition
(see post] apply almost word for word, so far as they go, to
the Fourth Edition. Yet it is necessary for me to write an in-
dependent Preface in order to call attention to the altered
circumstances under which this work is now presented to the
reader. If the development of Astronomy between 1867 and
1877 was great, its development between 1877 and 1889 has
been still greater. And besides this, there were important omis-
sions in the ground-plan of the book which I have long been
very desirous of making good, whenever time or opportunity
became available.

The last edition having reached to nearly 1000 pages it
became quite clear that the now necessary additions would have
swelled the work to a bulk and consequent price which probably
the Public would not have regarded with favour. Accordingly
when its division into two volumes became a necessity, I deter-
mined to make the two into three, and to complete the under-
taking as originally conceived twenty-nine years ago.

The work will therefore henceforth be published in three
divisions as follows : —

I. The Sun, Planets, and Comets.
II. Instruments and Practical Astronomy.
III. The Starry Heavens.

It is intended that each volume shall be paged, indexed, and
sold separately.

viii PEEFACE TO THE FOUETH EDITION.

This arrangement, whilst it will be financially more acceptable
to the Public, will probably permit in after-years of new editions
being brought out at lesser intervals of time than has hitherto
been possible.

Subject to the above explanations, it may be further stated
that the whole work has been revised everywhere, and enlarged
and rearranged wherever alterations seemed necessary or ex-
pedient.

A very large number of additional engravings have been
prepared, and the list now includes a certain number selected
from the various publications of the late Admiral W. H. Smyth.
My grateful thanks are due to the surviving representatives of
the lamented Admiral for their great kindness and liberality in
regard to these engravings and other literary materials which
they have placed at my disposal. Nor must I omit, in referring
to engravings, to mention the kind help which I have received
from the Secretaries of the Royal Astronomical Society, the
Editor of the Observatory, and M. Gauthier Villars of Paris.

The Second Volume will it is hoped be published in the
Autumn of 1889, and the Third Volume in 1890.

I have been glad to avail myself of the kind assistance of
several astronomical friends in passing this volume through the
press. To Mr. A. C. Eanyard, Mr. F. C. Penrose, and Mr. W. F.
Denning especial thanks are due for particular chapters which
are duly noted as they occur ; whilst the whole volume has been
read for press by the Rev. /. B. Fletcher, M.A., of Trinity College,
Dublin, and Vicar of All Souls, East-Bourne, and by Mr. W. T. Lynn,
who has also made himself responsible for all calculations depend-
ing on the new value of the Sun's parallax. It may be added that
this has been taken at 8'8o", as probably a very close approxi-
mation to the truth.

It is now twenty-seven years since the first edition of this
work was offered to the public, and from that time (December
1861) to the present it has been, seemingly, a popular and

PEEFACE TO THE FOUETH EDITION. ix

appreciated book both in England and America, maintaining
a steady sale from year to year. I am duly grateful for this,
the more so as twenty-seven years ago I was a very young
Author, with no reason to anticipate such a measure of success,
and nothing to back me up in obtaining it.

During this interval of more than a quarter of a century
many things have happened in the World of Science, of which
Astronomy is only one field. Many new and wholly unlooked-
for discoveries have been made : new methods and processes
have been introduced. Photography and Spectroscopy in their
Astronomical applications may be said to be wholly the creatures
of the period above named. New instruments have been in-
vented, and the manufacture of old ones has been enormously
developed. In 1860 the 1 2-inch refractor of the Greenwich
Observatory was brought into use and was regarded as a grand
advance. Now 12-inches counts for almost nothing in the race
between different nations and different makers to obtain tele-
scopes of large size for the exploration of the Heavens.

Looking back on these years, the question forces itself upon
our notice : ' Where are we now, in the effort to discover First
Causes ? ' And the answer is : ' Very much where we were a
quarter of a century ago.' The Theory of Evolution may be true
or it may be false, but, be it one or the other, I agree very much
with Professor Mivart, (who believes it,) when he says : " There is
no necessary antagonism between the Christian Revelation and
Evolution." Evolution is " an attempt to guess at a process ;
it does not touch the Author of that process, and never will."

a. jr. c.

NOKTHFIELD GBANGE,

EAST-BOURNE, SUSSEX :
June, 1889.

PREFACE TO THE THIRD EDITION.

(EXTRACT.)

ADVANTAGE has been taken of the call for a new edition
-£^- of this work to subject the whole, from the first page to
the last, to a searching revision. This has proved to be a task
of unusual difficulty and labour, in consequence of the astonishing
developement which has taken place in the science of Astronomy
during the last ten years. And moreover the demands on my
time made by professional work have of late been such as to
render it very difficult for me to give to Astronomical Studies
that close attention which is indispensable if the author of an
Astronomical Book would keep his pages up to date and so
do justice alike to himself and his readers. It is not open to
doubt that this is a matter which sits very lightly upon the con-
sciences of some writers of Text-books. There is scarcely a
single page which has not been, to a greater or less extent,
dressed up, or in some way amended, with the object of making
its statements more accurate in substance or intelligible in
diction.

I have to acknowledge a great amount of very useful advice
and assistance from observers in all parts of the world, most
of them total strangers to me, many of them being persons I
had never heard of until the receipt of their letters. Indeed,
the letters that I have received, especially from the United States
of America, have been a very gratifying encouragement to me to
persevere in improving this work in every possible way.

0. jr. c.

December, 1876.

(EXTRACT.}

ASTRONOMY is not cultivated in this country, either as a
-*--*- study or as a recreation, to the extent that it is on the
Continent of Europe and in America. And there is a lack of
works in the English language which are at one and the same
time attractive to the general reader, serviceable to the student,
and handy, for purposes of reference, to the professional Astrono-
mer ; in fact, of works which are popular without being vapid,
and scientific without being unduly technical.

The foregoing observations will serve to indicate why this
book has been written. Its aim, curtly expressed, is, general
usefulness.

Preferring facts to fancies, I have endeavoured to avoid all
those mischievous speculations on matters belonging to the
domain of Recondite Wisdom, which have within the last few
years borne such pernicious yet natural fruits.

In regard to the matter of bringing up to date, it is believed
that the present volume will compare favourably with any of
its contemporaries.

0. jr. c.

March, 1867.

PREFACE TO THE FIRST EDITION.

(EXTRACT)

ENGLISH literature, abundant though it may be in other
respects, is undoubtedly very deficient in works on Astro-
nomy. Our choice is limited either to purely elementary books,
few in number, on the one hand ; or to advanced treatises, of
which there is a similar paucity, on the other. The present
work is designed to occupy a middle position between these two
classes: to be attractive to the general reader, useful to the
amateur, and ' handy ' also, as an occasional book of reference,
to the professional astronomer.

In pursuance of the plan laid down from the first, theoretical
matter is, as a rule, excluded ; but in many cases it has been
thought desirable not to abide with perfect strictness by this
limitation.

Finally, it is hoped that this book may be the means of in-
ducing some, at least, to interest themselves in the study of that
noble Science, which in so conclusive a manner shows forth the
wonderful Wisdom, Power, and Beneficence of the Great Creator
and Omnipotent Ruler of the Universe.

0. jr. c.

EAST-BOUKNE, SUSSEX :
August, 1 86 1.

CONTENTS.

BOOK I.

THE SUN AND PLANETS.

CHAPTEK I.

THE SUN. ©

Astronomical importance of the Sun. — Solar parallax. — The means of determining
it. — By observations of Mars. — By Transits of Venus. — Numerical data. —
Light and Heat of the Sun. — Gravity at the Sun's surface. — Spots. — Descrip-
tion of their appearance. — How distributed. — Their duration. — Period of the
Sun's Rotation. — Effect of the varying position of the Earth with respect
to the Sun. — Their size. — Instances of large Spots visible to the naked eye. —
The Great Spot of October 1865. — Their periodicity. — Discovered by Schwabe.
— Table of his results. — Table of Wolfs results. — Curious connexion between
the periodicity of Sun-spots and that of other physical phenomena. — The
Diurnal variation of the Magnetic Needle.— Singular occurrence in September
1859. — Wolfs researches. — Spots and Terrestrial Temperatures and Weather.
— Ballot's inquiry into Terrestrial Temperatures. —The Physical Nature of
Spots. — The Wilson-Herschel Theory. — Luminosity of the Sun. Historical
Notices. — Scheiner. — Faculae. — Luculi. — Nasmyth's observations on the cha-
racter of the Sun's surface. — Huggins's conclusions. — Present state of our
knowledge of the Sun's constitution. — Tacchini's conclusions. Pages 1-53

CHAPTER II.

THE PLANETS.

Epitome of the motions of the Planets.— Characteristics common to them all.—
Kepler's Laws.— Elements of a Planet's orbit. — Curious relation between the
distances and the periods of the Planets.— The Ellipse.— Popular illustration
of the extent of the Solar system.— Bode's law. — Miscellaneous characteristics
of the Planets.— Curious coincidences. — Conjunctions of the Planets. —
Conjunctions recorded in History. — Different systems. — The Ptolemaic
system.— The Egyptian system. — The Copernican system.— The Tychonic
system. ... ... ... ... ... 54~74

xiv Content*.

CHAPTEK III.
VULCAN (•> .

Le Verrier's investigation of the orbit of Mercury. — Narrative of the Discovery of
Vulcan. — Le Verrier's interview with M. Lescarbault. — Approximate elements
of Vulcan. — Concluding note by Le Verrier. — Observations by Lummis at
Manchester. — Instances of Bodies seen traversing the Sun. — Hind's opinion. —
Alleged Intra-Mercurial planets discovered in America by Watson and Swift
on July J 9, 1878 75-85

CHAPTEK IV.
MERCURY. $

Period, &c. — Phases. — Physical Observations by Schroter. Sir W. Herschel,
Denning, Schiaparelli and Guiot. — Determination of its Mass. —When best
seen. — Acquaintance of the Ancients with Mercury. — Copernicus and Mer-
cury.— Le Verrier's investigations as to the motions of Mercury. — Tables of
Mercury 86-92

CHAPTEE V.

VENUS. ?

Period, &c. — Phases resemble those of Mercury. — Most favourably placed for
observation once in 8 years. — Observations by Lihou. — By Lacerda. — Daylight
obervations. — Its brilliancy. — Its Spots and Axial Rotation. — Suspected moun-
tains and atmosphere. — Its "ashy light." — Phase irregularities. — Suspected
Satellite. — Alleged Observations of it. — The Mass of Venus. — Ancient observa-
tions.— Galileo's anagram announcing his discovery of its Phases. — Venus
useful for nautical observations. — Tables of Venus. ... ... 93-106

CHAPTER VI.

THE EARTH. ©

Period, &c. — Figure of the Earth. — The Ecliptic.— The Equinoxes. — The Sol-
stices.— Diminution of the obliquity of the ecliptic. — The eccentricity of the
Earth's orbit. — Motion of the Line of Apsides. — Familiar proofs and illustra-
tions of the sphericity of the Earth. — Foucault's Pendulum Experiment. —
Madler's tables of the duration of day and night on the Earth. — Opinions of
ancient philosophers. — English mediaeval synonyms. — The Zodiac. — Mass of
the Earth. ... ... ... ... ... ... ... ... 107-17

CHAPTER VII.

THE MOON. ([

Period, &c. — Its Phases. — Its motions and their complexity. — Libration. — Evec-
tion. — Variation. — Parallactic Inequality. — Annual Equation. — Secular ac-
celeration.— Diversified character of the Moon's surface.— Lunar mountains. —
Seas. — Craters. — Volcanic character of the Moon. — Bergeron's experiment. —
The lunar mountain, Aristarchus. — Teneriffe. — Lunar atmosphere. — Re-
searches of SchrOter, &c. — Hansen's curious speculation. — The Earth-shine. —
The Harvest Moon. — Astronomy to an observer on the Moon. — Luminosity
and calorific rays. — Historical notices as to the progress of Lunar Charto-
graphy. — Lunar Tables. — Meteorological Influences. ... ... 118-41

Contents. xv

CHAPTER VIII.
THE ZODIACAL LIGHT.

General description of it. — When and where visible. — Sir J. Herschel's theory.
— Historical notices. — Modern observations of it. — Backhouse's Con-
clusions. ... ., ... ... ... ... ... ... ... 142 7

CHAPTER IX.

MARS. <j

Period. &c. — Phases.— Apparent motions. — Its brilliancy. — Telescopic appear-
ance.— Its ruddy hue. — Schiaparelli's "Canals." — General statement of the
physical details of Mars. — Map of Mars on Mercator's projection. — Polar
snow. — Axial rotation. — The seasons of Mars. — Its atmosphere. — The Satel-
lites of Mars. — Ancient observation of Mars. — Tables of Mars. . . . 148-63

CHAPTER X.
THE MINOR PLANETS.

Sometimes called Ultra-Zodiacal Planets. — Summary of facts. — Notes on Ceres. —
Pallas. — Juno. — Vesta. — Olbers's theory.— History of the search made for them.
— Independent discoveries. — Progressive diminution in their size. 164-70

CHAPTER XL

JUPITER. I

Period, &c. — Jupiter subject to a slight phase. — Its Belts. — Their physical nature.
— First observed by Zucchi. — Dark Spots. — Luminous Spots. — The great Red
Spot. — The great White Spot. — Hough's observations. — Alleged Connection
between Spots on Jupiter and Spots on the Sun. — Axial rotation of Jupiter. —
Centrifugal force at its Equator. — Luminosity of Jupiter. — Its Apparent
Motions. — Astrological influences. — Attended by 4 Satellites. — Are they visible
to the Naked Eye? — Table of them. — Eclipses of the Satellites. — Occupations.
— Transits. — Peculiar aspects of the Satellites when in transit. — Singular
circumstance connected with the interior ones. — Instances of 'all being
invisible. — Variations in their brilliancy. — Observations of Eclipses for
determining the longitude. — Practical difficulties. — Romer's discovery of the
progressive transmission of light. — Mass of Jupiter. — The "Great Inequality."
— Tables of Jupiter J73-99

CHAPTER XII.
SATURN, h

xvi Contents.

sented by them under different circumstances. — Rotation of the Ring. —
Secchi's inquiries into this. — The Ring not concentric with the Ball. —
Measurements by W. Struve. — Other measurements. — Miscellaneous par-
ticulars.— Theory of the Ring being fluid. — Now thought to consist of an
aggregation of Satellites. — The "Beaded" appearance of the Ring. — O.
Struve's surmise about its contraction. — Irregularities in the appearances of
the ansae. — Rings not bounded by plane surfaces. — Mountains suspected on
them. — An atmosphere suspected. — Physical observations between 1872 and
1876 by Trouvelot. — Observations by MM. Henry. — By Keeler. — Brightness
of Rings and Ball. — Bessel's investigations into the Mass of the Rings. —
Saturn attended by 8 Satellites. — Table of them. — Physical data relating to
each. — Elements by Jacob. — Coincidences in the Rotation-periods of certain
of them. — Transits of Titan. — Celestial phenomena on Saturn. — Lockyer's
summary of the appearances presented by the Rings. — Peculiarity relative
to the illumination of lapetus. — Mass of Saturn. — Ancient observations. —
Saturn ian Astronomy. ... ... ... ... 200-41

CHAPTEE XIII.

URANUS, y

Circumstances connected with its discovery by Sir W. Herschel. — Names pro-
posed for it. — Early observations. — Period, &c. — Physical appearance. — Belts
visible in large telescopes. — Position of its axis. — Attended by 4 Satellites. —
Table of them. — Miscellaneous information concerning them. — Mass of
Uranus. — Tables of Uranus. ... ... ... ... ... ... 242-51

CHAPTER XIV.

NEPTUNE. H*

Circumstances which led to its discoveiy. — Summary of the investigations of
Adams and Le Verrier. — Telescopic labours of Challis and Galle. — The
perturbations of Uranus by Neptune. — Statement of these perturbations by
Adams. — Period, &c. — Attended by i Satellite. — Elements of its orbit. —
Mass of Neptune. — Observations by Lalande in 1795. ... ... 252-60

BOOK II.

ECLIPSES AND ASSOCIATED PHENOMENA.

CHAPTER I.

GENERAL OUTLINES.

Definitions. — Position of the Moon's orbit in relation to the Earth's orbit. — Con-
sequences resulting from their being inclined to each other. — Retrograde
motion of the nodes of the Moon's orbit. — Coincidence of 223 synodical periods
with 19 synodical revolutions of the node. — Known as the " Saros."— State-
ment of Diogenes Laertius.— Illustration of the use of the Saros. — Number of
Eclipses which can occur. — Solar Eclipses more frequent than Lunar ones. —
Duration of Annular and Total Eclipses of the Sun 261-9

Contents. xvii

CHAPTEE II.

ECLIPSES OF THE SUN.

Grandeur of a Total Eclipse of the Sun. — How regarded in ancient times. —
Effects of the progress of Science. — Indian Customs. — Effect on Birds at
Berlin in 1887. — Solar Eclipses may be Partial, Annular, or Total.— Chief
phenomena seen in connexion with Total Eclipses. — Change in the colour of
the sky. — The obscurity which prevails. — Effect noticed by Piola. — Physical
explanation. — Baily's Beads. — Extract from Baily's original memoir. — Prob-
ably due to irradiation. — Supposed to have been first noticed by Halley in
1715. — His description. — The Corona. — Hypothesis advanced to explain its
origin. — Probably caused by an atmosphere around the Sun. — Remarks by
Grant. — First alluded to by Philostratus. — Then by Plutarch. — Corona visible
during Annular Eclipses. — The Red Flames. — Remarks by Dawes. — Physical
cause unknown. — First mentioned by Stannyan. — Note by Flamsteed. —
Observations of Vassenius. — Aspect presented by the Moon. — Remarks by
Arago. ... ... ... 270-85

CHAPTER III.

THE TOTAL ECLIPSE OF THE SUN OF JULY 28, 1851.
Observations by Airy. — By Hind. — By Lassell 286-90

CHAPTER IV.

THE ANNULAR ECLIPSE OF THE SUN OF MARCH 14-15, 1858.
Summary of observations in England 291-4

CHAPTER V.

THE TOTAL ECLIPSE OF THE SUN OF JULY 18, I860.

Extracts from the observations of Sir G. B. Airy. — Observations of the Red Flames
by Bruhns. — Meteorological observations by Lowe. ... ... 295-302

CHAPTER VI.

RECENT TOTAL ECLIPSES OF the SUN.

Eclipse of August 18, 1868.— Observations by Col. Tennant and M. Janssen at
Guntoor.— Summary of results.— Observations of Governor J. P. Hennessy and
Capt. Reed, R.N.— Eclipse of August 7, 1869.— Observations in America by
Prof. Morton and others.— Summary of results.— Eclipse of December 22, 1870.
—English expedition in H. M. S. Urgent to Spain.— Observations in Spain
and Sicily.— Eclipse of December n, 1871.— Observed in India.— Eclipse of
April 16, 1 874.— Summary by Mr. W. H. Wesley of the recent observations as
to the Physical Constitution of the Corona 303-20

CHAPTER VII.

HISTORICAL NOTICES.

Eclipses recorded in Ancient History.— Eclipse of 584 B.C.— Eclipse of 556 B.C.—
Eclipse of 479 B.C.— Eclipse of 430 B.C.— Eclipse of 309 B.C.— Allusions in old
English Chronicles to Eclipses of the Sun , 33I~5

xviii Contents.

CHAPTER VIII.

ECLIPSES OF THE MOON.

Lunar Eclipses of less interest than Solar ones. — Summary of facts connected with
them. — Peculiar circumstances noticed during the Eclipse of March 19, 1848. —
Observations of Forster. — Wargentin's remarks on the Eclipse of May 18,
1761. — Kepler's explanation of these peculiarities being due to Meteorological
causes. — Admiral Smyth's account of the successive stages of the Eclipse of
Oct. 13, 1837.— The Eclipse of Jan. 28, 1888.— The Eclipse of Sept. 2, 1830, as
witnessed in Africa by R. and J. Lander. — Chaldaean observations of Eclipses.
— Other ancient Eclipses. — Anecdote of Columbus. 326-33

CHAPTER IX.

A CATALOGUE OF ECLIPSES 334-6

CHAPTER X.

TRANSITS OF THE INFERIOR PLANETS.

Cause of the phenomena. — Lord Grimthorpe's statement of the case. — Long
intervals between each recurrence. — Useful for the determination of the Sun's
parallax. — List of transits of Mercury. — Of Venus. — Transit of Mercury of
Nov. 7, 1631. — Predicted by Kepler. — Observed byGassendi. — His remarks. —
Transit of Nov. 3, 1651. — Observed by Shakerley. — Transit of May 3, 1661. —
Transit of Nov. 7, 1677. — Others observed since that date. — Transit of Nov. 9,
1 848. — Observations of Dawes. — Of Forster. — Transit of Nov. 1 1 , 1 86 1 . — Observa-
tions of Baxendell. — Transit of Nov. 5, 1868. — Transit of May 6, 1878. — Transit
of Nov. 7, 1 88 1. — Summary by Jenkins of the main features of a Transit. —
Observations by Prince. — By Langley. — Transit of Venus of Nov. 24, 1639. —
Observed by Horrox and Crabtree. — Transit of June 5, 1761. — Transit of June
3, 1769. — Where observed. — Singular phenomenon seen on both occasions. —
Explanatory hypothesis. — Other phenomena. — Transit of Dec. 8, 1874. —
Transit of Dec. 6, 1882. 337~54

CHAPTER XL

OCCULTATIONS.

How caused. — Table annually given in the "Nautical Almanac." — Occultation
by a young Moon. — Effect of the Horizontal Parallax. — Projection of Stars
on the Moon's disc. — Occultation of Jupiter, January 2, 1857. — Occultation
of Saturn, May 8, 1859. — Occultation of Saturn, April 9, 1883. — Historical
notices. ... ... ... ... ... ... ... ... ... 355~6o

BOOK III.

PHYSICAL AND MISCELLANEOUS ASTKONOMICAL
PHENOMENA.

CHAPTER I.

THE TIDES.

Introduction.— Physical cause of the Tides. — Attractive force exercised by the
Moon.— By the Sun.— Spring Tides. —Neap Tides. — Summary of the principal
facts.— Priming and Lagging.— Diurnal Inequality. 361-5

Contents. xix

CHAPTEE II.

LOCAL TIDAL PHENOMENA.

Local disturbing influences. — Table of Tidal ranges. — Influence of the Wind. —
Experiment of Smeaton. — The Tides in the Severn at Chepstow. — Tidal phe-
nomena in the Pacific Ocean. — Remarks by Beechey. — Velocity of the great
Terrestrial Tidal wave. — Its course round the earth, sketched by Johnston. —
Effects of Tides at Bristol. — Instinct of animals. — Tides extinguished in
rivers. — Instances of abnormal Tidal Phenomena. — The "Mascaret" on the
Seine. — Historical notices. ... ... 366-73

CHAPTEK III.

PHYSICAL PHENOMENA.

Secular Variation in the Obliquity of the Ecliptic. — Precession. — Its value. — Its
physical cause. — Correction for Precession. — History of its discovery. —
Nutation. — Herschel's definition of it. — Connexion between Precession and
Nutation. 374~79

CHAPTEK IV.

ABERRATION AND PARALLAX.

Aberration. — The constant of Aberration. — Familiar illustration. — History of the
circumstances which led to its discovery by Bradley. — Parallax. — Ex-
planation of its nature. — Parallax of the heavenly bodies. — Parallax of the
Moon. — Importance of a correct determination of the Parallax of an Object. —
Leonard Digges on the distance of the Planets from the Earth. . . . 380-86

CHAPTEE V.

REFRACTION AND TWILIGHT.

Refraction. — Its nature. — Importance of a correct knowledge of its amount. —
Table of the correction for Refraction. — Effect of Refraction on the position
of objects in the horizon. — History of its discovery. — Twilight. — How caused.
— Its duration. ... 3^7-94

BOOK IV.

COMETS.

CHAPTEE I.

GENERAL REMARKS.

Comets always objects of popular interest, and sometimes of alarm. — Usual
phenomena attending the development of a Comet. — Telescopic Comets. —
Comets diminish in brilliancy at each return.— Period of revolution. —
Density. — Mass.— Lexell's Comet. — General influence of Planets on Comets.
—Special influence of Jupiter.— Comets move in i of 3 kinds of orbits.—
Element of a Comet's orbit.— For a parabolic orbit, 5 in number.— Direction
of motion. — Eccentricity of an elliptic orbit.— The various possible sections
of a cone.— Early speculations as to the paths in which Comets move. —

b a

xx Content*.

Comets visible in the daytime. — Breaking up of a Comet into parts. —
Instance of Biela's Comet. — Liais's observations of Comet iii. 1860. — Comets
probably self-luminous. — Existence of phases doubtful. — Comets with Plane-
tary discs. Phenomena connected with the tails of Comets. — Usually in the
direction of the radius vector. — Secondary Tails. — Vibration sometimes
noticed in tails. — Olbers's hypothesis. — Transits of Comets across the Sun's
disc. — Variation in the appearance of Comets exemplified in the case of that
of 1769. — Transits of Comets across the Sun. ... ... ... 395-414

CHAPTEK II.
PERIODIC COMETS.

Periodic Comets conveniently divided into three classes. — Comets in Class I. —
Encke's Comet. — The resisting medium. — Table of periods of revolution. —
Tempel's Second Comet. — Winnecke's Comet. — Brorsen's Comet. — Tempel's
First Comet. — Swift's Comet. — Barnard's Comet. — D' Arrest's Comet. —
Finlay's Comet. — Wolfs Comet. — Faye's Comet. — Denning's Comet. —
Mechain's Comet of 1790.— Now known as Tuttle's Comet. — Biela's Comet.
— Di Vico's Comet of 1844. — List of Comets presumed to be of short periods
but only once observed. — Comets in Class II. — Westphal's Comet. — Pons's
Comet of 1812. — Di Vico's Comet of 1846. — Olbers's Comet of 1815. — Brorsen's
Comet of 1847. — Halley's Comet. — Of special interest. — Re"sumt$ of Halley's
labours. — Its return in 1759. — Its return in 1835. — Its history prior to 1531
tra ;ed by Hind. — Comets in Class III not requiring detailed notice. 415-45

CHAPTER III.
REMARKABLE COMETS.

The Great Comet of 1811.— The Great Comet of 1843.— The Great Comet of 1858.
—The Comet of 1860 (iii.).— The Great Comet of 1861. — The Comet of
1862 (iii.).— The Comet of 1864 (ii.)— The Comet of 1874 (iii.).— The Comet
of 1882 (iii.) 446-81

CHAPTER IV.

CERTAIN STATISTICAL INFORMATION RELATING TO COMETS.

Dimensions of the Nuclei of Comets. — Of the Comae. — Comets contract and expand
on approaching to, and receding from, the Sun. — Exemplified by Encke's in
1838. — Lengths of the Tails of Comets. — Dimensions of Cometary orbits. —
Periods of Comets. — Number of Comets recorded. — Duration of visibility of
Comets. — Unknown Comet found recorded on a photograph of the Eclipse of
the Sun of May 17, 1882. 482-86

CHAPTER V.

HISTORICAL NOTICES.

Opinions of the Ancients on the nature of Comets. — Superstitious notions
associated with them. — Extracts from ancient Chronicles. — Pope Calixtus III.
and the Comet of 1456. — Extracts from the writings of English authors of the
i6th and i7th centuries. — Napoleon and the Comet of 1769. — Supposed
allusions in the Bible to Comets.— Conclusion ... 487-90

Contents.

xxi

CHAPTER VI.

SECTION 1. — Preliminary. ... ... 49 1-4

SECTION 2. — On the proportioning of the Areas in the different Segments of the

Projection 494-5

SECTION 3. — The Latitudes and the Inclination of the Plane of the Orbit. 496-7
SECTION 4. — To find a Parabola having its Focus at S and which shall coincide with

two Points of the Orbit ... ... 498

SECTIONS. — The Measurement of the Areas in a Parabola 498-9

SECTION 6. — The Relations between the Time-intervals and the Longitude

Lines ... ... ... ... ... ... ... ... ... 499-501

SECTION 7- — Checks available, derived from certain properties of Parabolic

Orbits. ... ... ... ... 501

SECTIONS. — Examples of the Graphical Process 5°J~9

SECTIONS. — To form an ephemeris of a Comet ... ... ... ... 509-10

CHAPTER VII.

A CATALOGUE OF ALL THE COMETS WHOSE ORBITS HAVE

HITHERTO BEEN COMPUTED 5 11-47

A Summary of the preceding Catalogue ... 548^9

CHAPTER VIII.

A CATALOGUE OF COMETS RECORDED, BUT NOT WITH SUFFICIENT
PRECISION TO ENABLE THEIR ORBITS TO BE CATALOGUED. 550-88

BOOK V.

METEORIC ASTRONOMY.

CHAPTER I.

AEROLITES.

Classification of the subject.— Aerolites.— Summary of the researches of Berzelius.
Rammelsberg, and others. — Celebrated Aerolites. — Summary of facts.—
Catalogue of Meteoric Stones.— Arago's Table of Apparitions.— The Aerolite
of 1492.— Of 1627.— Of 1795.— The Meteoric Shower of 1803.— The Aerolite of
1876 (Rowton).— The Aerolite of 1881 (Middlesborough).— The Aerolite of
1887 (Soko Banja). 589-98

CHAPTER II.
FIREBALLS.

General Description of them.— Fireball of Nov. 12, 1 86 1.— Monthly Table of appar-
itions.—Dates of greatest frequency.— Results of calculations with reference
to these bodies. 6o1 '

xxii Contents.

CHAPTER III.

SHOOTING STARS.

Have only recently attracted attention. — Are visible with greater or less frequency
every clear night. Summaries of the monthly and horary rates of apparition
from observations by Coulvier-Gravier and Denning. — Number of known
meteor showers. — Their distribution amongst the constellations. — Monthly
number of meteors catalogued. — Early notices of great meteor showers. — The
showers of 1799, 1831, 1832, 1833, 1866, and following years. — The shower
of Aug. 10. — Of Nov. 27, 1872, and Nov. 27, 1885. — Nomenclature of meteor
systems. — Views of Olbers. — Monthly summary of great meteoric dis-
plays. 608-25

CHAPTER IV.

THE THEORY OF METEORS.

Meteors are planetary bodies. — Their periodicity. — Meteoric orbits. — Researches of
Newton and Adams. — Orbit of the meteors of November 13. — Identity of the
orbits of cornet^ and meteors. — The meteor showers of Nov. 13 and 27. — Recent
progress of Meteoric Astronomy. — Table of the chief radiant points. 626-38

CHAPTER V.

RADIANT POINTS.
Explanation of Reference Letters in the List of Radiant Points. . . . 639-43

CHAPTER VI.

TELESCOPIC METEORS.

Our knowledge of them limited. — Observations. — Probable heights in the
atmosphere. — Showers of telescopic meteors. — Summary of Prof. Safarik's
observations and deductions. — Fireball observed in a telescope on Oct. 19,
1863 644-50

BOOK VI.

TABLES OF THE PLANETS.

The Major Planets ... ... .. ... 651-3

The Minor Planets 654-71

INDEX 672

LIST OF ILLUSTRATIONS.

Fig. Page

1. Encke's Comet, 1848 : on Sept. 22 . . Plate I, Frontispiece.

2. The Illrd Satellite of Jupiter in 1855 .... Title-page.

3. General Telescopic appearance of the Sun .... 8

4. Spot on the Sun, September 29, 1826. (Capocci.) , Plate II. n

5. Spot on the Sun, May 23, 1861. (Birt.) . „ n

6. Spot on the Sun, May 27, 1861. (Anon.) . . „ n

7. Paths of Sun Spots at different times of the year . . .16

8. Great Sun Spot visible on June 30, 1883. (Ricco.) . . . 18

9. The same Sun Spot on July 2, 1883. (Ricco.) . . . .18

10. Great Sun Spot visible on July 25, 1883. (Ricco.) . . .19

11. The same Sun Spot on July 27, 1883. (Ricco.) . . . .19

12. The Great Sun Spot of October 1865, Oct. n, ii A.M. (Brodie.) Plate III. 21

13. The Great Sun Spot of October 1865, Oct. ii, 12-30 P.M. (Brodie.) „ 21

1 4. The Great Sun Spot of October 1 865 , Oct. 1 2 , 9- 30 A. M. (Brodie. ) , , 21

15. The Great Sun Spot of October 1865, Oct. 12, 10-30 A.M. (Brodie.) „ 21

16. The Great Sun Spot of October 1865, Oct.- 1 2, 12-30 P.M. (Brodie.} „ 21

17. The Great Sun Spot of October 1865, Oct. 12, 2-30 P.M. (Brodie.) „ 21

18. The Great Sun Spot of October 1865. Pectinated edge

visible on Oct. 12. (Brodie.) . . . . .23

19. Diagram illustrating the connection between Aurorse,

Terrestrial Magnetism, and Spots on the Sun . Plate IV. 30

20. Change of form in Spots owing to the Sun's rotation . . -39

21. Spot on the Sun, May 5, 1854, showing cyclonic action. (Secchi.) . 40

22. Large Spot on the Sun in 1866 showing successive

changes of form ....... 41

23. Spot seen on the edge of the Sun in 1884 exhibiting

itself as a depression ..... -4*

24. Faculse on the Sun, December 3, 1865. (Tacchini.) . . -45

25. Spot on the Sun, July 29, 1860, showing the "Willow-

leaf" Structure. (Nasmyth.) . . . • -47

26. Spot on the Sun, January 20, 1865. (Secchi.) . . .48

27. " Rice-like " particles seen on the Sun. (Stone.) ' . -49

28. Ideal View of the "Granular" Structure of the Sun.

(Huggins.) .....-•• 51

29. Solar granules, 1866, showing cyclonic arrangement. (Hug<jin*. ja

30. Solar granules, 1866, ordinary arrangement. (HttpffM.] • ••'

xxiv List of Illustrations.

Fig. Page

31. Phases of an Inferior Planet . . . . . -55

32. Apparent movements of Mercury, 1708-1715 .... 56

33. Diagram illustrating Kepler's Second Law .... 58

34. The Ellipse ........ 61

35. Relative apparent size of the Sun, as viewed from the

different Planets named ...... 62

36. Comparative Sizes of the Planets . . . . .63

37. Comparative Sizes of the Sun and Planets . . Plate V. 65

38. Conjunction of Venus and Jupiter, July 2 1, 1859 ... 69

39. Conjunction of Venus and Saturn, December 19, 1845 . . 70

40. The Ptolemaic System . . . . . . .71

41. The Egyptian System . . . . . . .72

42. The Copernican System . . . . . .72

43. The Tychonic System . . . . . . . 73

44. House at Woolsthorpe where Newton was born ... 74

45. Flight of Cranes seen crossing the Sun .... 80

46. Mercury, Sept. 17, 1885. (Guiot.} ..... 89

47. Mercury, Sept. 22, 1885. (Guiot.) ..... 89

48. Venus near its Greatest Elongation. (Schroter,} 93

49. Venus near its Inferior Conjunction. (Schroter.) . . . 94

50. Venus, Nov. 10, 1885. (Lihou.} ..... 95

51. Venus, Dec. 23, 1885. (Lihou.} ..... 95

52. Venus, Sept. 8, 1884. (Lacerda.) . . . .96

53. Venus, Sept. 9, 1884, (Lacerda.} ..... 96

54. Venus, Oct. 8, 1884. (Lacerda.} ..... 97

55. Venus, Oct. n, 1884. (Lacerda.} ..... 97

56. Foucault's Pendulum experiment for demonstrating

the Earth's Rotation .... Plate VI. 113

57. View of a portion of the Moon's Surface. (Nasmyth.} . , . 1 23

58. Imitation of the structure of the Moon's Surface,

(Bergeron's experiment.) . . . . . .125

59. The Lunar Mountain Aristarchus, illuminated . . .126

60. The Lunar Mountain Aristarchus, waxing . . . .127

61. The Lunar Mountain Aristarchus, waning . . . .127

62. The Peak of Teneriffe . . . . . . .128

63. The Lunar Mountain Archimedes . . . Plate VII. 129

64. The Lunar Mountain Pico . . . . ,, 129

65. The Lunar Mountain Copernicus. (Nasmyth.') . „ 129

66. The Lunar Mountain Archimedes. (Weinek.) . Plate VIII. 131

67. The Lunar Mountain Gassendi. (Weinek.} . . „ 131

68. The Lunar Gulf Sinus Iridum. (Weinek.) . . „ 131

69. The Lunar Mountains Kepler and Encke. (Weinek.}. „ 131

70. The Lunar Mountain Frascatorius. (Weinek.} . ,, 131

71. The Lunar Mountain Plato. (Weinek.} . . ,, 131

72. The Lunar Mountain Eudoxus. (Trourelot.} .... 133

73. The Gulf of Iris seen when the Moon is 10 days old . . . 133

74. Mars, 1858. (Secchi.) ..... Plate IX. faces 148

75. Mars, 1858. (Seccfii.) . . . . . „ ,,148

List of Illustrations.

Fig.

76. Mars, 1856. (Brodie.) .....

77. Mars, on Mercator's projection. (N. E. Green.}

78. The Polar Snows of Mars ....

79. The Polar Snows of Mars ....

80. The apparent Orbits of the Satellites of Mars.

81. Jupiter, 1857. (Dawes.) ....

82. Jupiter, 1858. (Lassell.) ....

83. Jupiter, 1860. (Jacob.} ....

84. Jupiter, 1860. (Baxendell) ....

85. Jupiter, 1856. (De La Rue.} ....

86. Jupiter, 1871. (LasseU.) ....

87. Jupiter, 1857, October 6. (Sir W. K. Murray.)

88. The Great Ked Spot on Jupiter, 1887. (Denning.)

89. Jupiter and its Satellites ....

90. Jupiter and its Satellites, seen with the Naked Eye,

1863. (Mason.) .....

91. Jupiter and its Satellites, seen with a Telescope, 1863.

(Mason.) ......

92. The IVth Satellite of Jupiter, 1873. (Roberts.)

93. The IIIrd Satellite of Jupiter, 1860. (Dams.)

94. The IVth Satellite of Jupiter, 1849. (Dawes.)

95. Jupiter with the IInd Satellite in Transit, 1828

96. Jupiter's Ist Satellite in Transit, with a double shadow.

(Trouvelot.) ......

97. Plan of the Jovian System ....

98. Saturn, 1856. (De La Rue.) . . . .

99. Saturn, 1883. (Holden.) ....

100. Saturn, 1665. (Ball.) .....

101. Saturn, 1675. (Hevelius.) ....

102. Saturn, 1676. (Cassini.) ....

103. Saturn, 1853. (Dawes.) ....

104. Saturn, 1848. (W. C. Bond.) ....

105. Saturn, 1856. (Jacob.) ....

106. Saturn, 1 86 1. (De La Rue.)

107. Saturn, 1861. (Jacob.) . .

108. Saturn, 1861. (Jacob.) .....

109. Saturn, 1861. (Anon.) ....

no. Saturn, 1861. (Wray.) .....

in. Saturn, 1862. (Wray.) ....

112. General View of the Phases of Saturn's Rings

113. Phases of Saturn's Rings at the dates specified

114. Saturn, 1883. (Ranyard.) ....

115. Saturn, 1884. (Henry.)

116. Saturn, 1887. (Terby.)

117. Diagram illustrating the phenomenon of Saturn's

Ring " Beaded ".....

11 8. Diagram illustrating the phenomenon of Saturn's

Ring " Beaded ".....

Plate X.

Plate XI.

Plate XII.

Plate XIII.

Plate XIV.

Plate XV.

Plate XVI.

XXV

Page
151
153
157
157
161
172
172
172
172

174
176
177
179
183

184

184
189
189
189
190

191
193

201
204
208
208
208
210
2IO
210
313
313
213

"5
2»5
218
219
224
224
324

226

22$

XXVI

List of Illustrations.

Fig.
I19.
1 2O.
121.

122.

123-
I24.

125.
126.

127.
128.
I29.
130.

13I-
132.

'33-
134-
'35-
I3«.
137-
138.

139-

I40.

141.
142.

143-
144.

145-

146.
I47.

148.
149.
150.
I5I.
I52.
153.
154.
155-
156.
'57-
158.
159-
1 60.

161.

General View of Saturn and its Satellites

Plan of the Saturnian System .

Diagram to facilitate the identification of the

Satellites of Saturn, 1888 .
Uranus, 1884. (Henry.)
Plan of the Uranian System .
Apparent Orbits of the Satellites of Uranus .
Diagram illustrating the Perturbation of Uranus by
Neptune ....

Geometrical diagram of the Perturbation of Uranus
by Neptune ......

Plan of the Orbit of Neptune's Satellite
Orbit of the Satellite of Neptune
Theory of a Total Eclipse of the Sun
Theory of an Annular Eclipse of the Sun
Theory of an Eclipse of the Moon
" Baily's Beads "...

the Red Flames.

the Red Flames,

the Red Flames.

the Annulus

Plate XVII.

Page
232

235

240
246
249

250

256

Eclipse of the Sun, 1851
Eclipse of the Sun, 1851
Eclipse of the Sun, 1851
Eclipse of the Sun, 1851
Eclipse of the Sun, 1851
Eclipse of the Sun, 1851
Eclipse of the Sun, 1858
Eclipse of the Sun, 1860
Eclipse of the Sun, 1 860
Eclipse of the Sun, 1860

257
259

259

262
262
263
277

(Airy.') Plate XVIII. faces 286
(Carrington.) ,, 286

(Dawes.). „ 286

(Hind.} . ,, 286

(Sfeptenam.) ,, 286

(<?. Williams.') ,, 286

,, 291

the Corona. (Feilitzsdi.') . Plate XIX. faces 297

the Red Flames. (Bmhns.)
the Red Flames. (Bruhns. )
Eclipse of the Sun, 1860 the Corona. (Tempel.)
Diagram representing the Rays of the Corona, 1868.
(Hennessey.") ......

Eclipse of the Sun, 1851, 1860, 1869: Diagrams of
the Corona ......

Eclipse of the Sun, 1870: Diagram of the Corona
Eclipse of the Sun, 1871 : Diagram of the Corona

Plate XX.

Eclipse of the Sun, 1874.
Eclipse of the Sun, 1875 :
Eclipse of the Sun, 1878 :
Eclipse of the Sun, 1882 ;
Eclipse of the Sun, 1883 :
Eclipse of the Sun, 1885
Eclipse of the Sun, 1886
Eclipse of the Sun, 1887
Eclipse of the Sun, 1887 :
• Conditions of Eclipses of the Moon
Eclipse of the Moon, Oct. 13, 1837. (Smyth.).
Mercury during its transit, Nov. 5, 1 868
Venus during its transit in 1769
Venus during its transit in 1769

(Bright.) .

Diagram of the Corona
Diagram of the Corona
Diagram of the Corona
Diagram of the Corona
Diagram of the Corona
Diagram of the Corona
Diagram of the Corona
the Corona. (Khandrikoff.) ,

297
297
299

305

312

313

3^5
316

317

319
320
320

Plate XXI. faces 320
327
330
343
348
349

L/ist of Illustrations.

XXV11

Fig.

Page

162.

Venus just before the commencement of its transit in

1882. (Prince.) .....

35°

I63.

Venus during its transit in 1874. First formation of

ligament. (Stone.) .....

Plate XXII. 351

164.

Venus during its transit in 1874. Apparent contact

not perfect. (Stone.) ....

» 35'

I65.

Venus during its transit in 1874. Apparent contact.

(Stone.) ......

351

1 66.

Venus during its transit in 1874. The ligament

broad. (Stone.) .....

!! 35'

167.

Venus during its transit in 1874. The ligament

broader. (Stone.) .....

351

168.

Venus during its transit in 1874. The ligament

broadest. (Stone.) .....

» 35'

169.

Venus during its transit in 1882

353

170.

Venus during its transit in 1882

353

171.

Venus during its transit in 1882

353

172.

Occultation of Jupiter, January 2, 1857. (Lassett.) .

. . 358

173.

Occultation of Saturn, April 9, 1883. (Loomis.)

359

174.

The " Mascaret " or '' Bore " on the river Seine

37*

'75-

Diagram illustrating the phenomenon of Aberration

. 381

176.

Diagram illustrating the phenomenon of Parallax

• 384

177.

Diagram illustrating the phenomenon of Eefraction .

388

178.

Telescopic Comet without a Nucleus .

396

179.

Telescopic Comet with a Nucleus .

396

1 80.

Comparative sizes of the Earth, the Moon's orbit, and

certain Comets .....

Plate XXIII. 398

181.

Diagram illustrating the influence of Jupiter on

Comets ......

. - 402

182.

The various Sections of a Cone

. 406

183.

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

4°7

184.

Biela's Comet in 1846. (0. Struve.)

. 408

185.

Diagram illustrating the changes in the directions of

the tails of Comets ....

1 86.

Encke's Comet in 1828. (W. Strure.) .

. 418

187.

Encke's Comet in 1871. (Carpenter.)

423

188.

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

436

189.

Halley's Comet, 1683, showing luminous Sector.

(Hevelius.) ....••

. 438

190.

Plan of the orbit of Halley's Comet compared with the

orbits of certain Planets

• 438

191.

Halley's Comet, 1835 •

44<>

192.

Halley's Comet, 1066 : (from the Bayeux Tapestry) .

Plate XXIV. 442

193-

Halley's Comet, 684 : (from the Nuremburg Chron-

icle) ....•••

443

194.

The Great Comet of 1 8 1 1

447

J95-

Donati's Comet, 1858. (Pape.) .

Plate XXV. 449

196.

Donati's Comet, 1858. -(Pape.) .

Plate XXVI. 45'

XXV111

A <'."••/ of Illustrations.

Fig.

197.

198.

I99.

200.

2OI.

202.

203.

304.

205.

2O6.

207.

208.

209.

210.

211.

212.

2I3.

214.

2I5.

2l6.

217.

218.

219.

220.

221.
222.
223.
224.
225.
226.
227.
228.
229.
230.

331.
232.

233-
234-
235-
236.

237-

the Coma,
the Coma.

Donati's Comet, 1858. (Smyth.} ,

Donati's Comet of 1858 passing Arcturus

Donati's Comet, 1858 : the Coma. (Pope.)

Donati's Comet, 1858

Donati's Comet, 1858 : the Coma.

Comet III. 1860.

(Pope.)
(Anon.}
(Pope.)
(Pope.)

(CappeUetti and Rosa.}
(Cappettetti and Rosa.}
(CappeUetti and Rosa.}

Plate XXVII.

Plate XXVIII.

Comet III. 1860. (CappeUetti and Rosa.} . . „

The Great Comet of 1861 : the Coma. (Welb.} . Plate XXIX.

The Great Comet of 1861 : the Coma. (Brodie.} , „

The Great Comet of 1861 : naked-eye view. (Brodie.} „

The Great Comet of 1861 : naked-eye view. (Chambers.} „

The Great Comet of 1861. (0. Williams.} . . Plate XXX.

Coggia's Comet of 1874 : skeleton outline. (Brodie.} .
Comet III. 1862. (Chattis.} .... Plate XXXL

Comet III. 1862. (Cliattis.) .... „

(CholUs.} .... „

(Oiallis.} .... „

(Chattis.} .... ,,

(Chattis.} .... „

Coggia's Comet of 1874 : the Coma. (Brodie.}. . Plate XXXII.

The Great Comet of 1882 : the Nucleus. (Prince.)

(Hopkins.) .....

(Flammarion.)

(WiUis.} . . .PlateXXXIII.

the compound Nucleus
the compound Nucleus
Eclipse of the Sun of May 17, 1882, showing an unknown Comet
Graphical determination of a cometary orbit : Relation of the
Equator to the Ecliptic ......

Graphical determination of a cometary orbit : Scheme for adjusting
the Subtended Areas ......

Graphical determination of a cometary orbit : Diagram for finding

Points of Projection when Node and Inclination are given
Graphical determination of a cometary orbit : Diagram for finding

the Perihelion from given points on the Orbit

Graphical determination of a cometary orbit : Diagram for com-
prising Arcs ........

Graphical determination of a cometary orbit : Orbit of Comet III.,

1881 . . . Folding Plate, XXXIV. Faces

Graphical determination of a cometary orbit : Orbit of Comet II.,

1881 .... Folding Plate, XXXV. Faces

Meteorite of Sako-Banja, Oct 13, 1877. .

Comet III. 1862.
Comet III. 1862.
Comet III. 1862.
Comet III. 1862.

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

IV-r

453
454
455
455
455
455
455
459
459
459
459
459
459
463
463
463
463
465
468
469
469
469
469
469
469
47i
475
476

477
479
481
481
486

493
495
496
498

502
506

List of Illustrations. xxix

Fig. Page

238. Fireball of Aug. 18, 1783. (Saxby and Robinson.) . Plate XXXVI. 600

239. Fireball of Aug. 1 8, 1783. (Saxby and Robinson.) . ,, . 600

240. Fireball of June 7, 1878. (Denning.) ...,,. 600

241. Fireball of Oct. 19, 1863. (Schmidt.) ...,,. 600

242. Meteor of Nov. 12,1861. (Webb.) ..... 602

243. Curious form of trail left by Fireball of October 19, 1877 . . 605

244. Trail left by Fireball of November 13, 1888 .... 606

245. Distribution of Meteor Streams in Right Ascension . . . 6ia

246. Relative number of Meteors catalogued during the several months

of the year ........ 615

247. The Meteor Radiant Point in Leo : tracks of Meteors seen at

Greenwich, Nov. 13, 1866 ...... 619

248. Intersection of the plane of the Orbit of the Earth by the Shooting

Stars of August 10 . . . . . . . 622

249. Orbit of the Leonids of November 13 relatively to the Orbits of

certain Planets ....... 632

250. Positions of Biela's Comet at the time of the Meteor Showers of

1798, 1838, and 1872 ...... 633

251. Radiant Point of Geminids (Dec. 12) on Nov. 28- Dec. 9, 1864 . 636

252. Radiant Point of Orionids (Oct. 18-21) on Oct. 20, 1865 . . 637

253. Flight of Telescope Meteors. (Brooks.) .... 646

ADDENDA ET COKKIGENDA.

Page

3, note e. Add : — A further description of the principle of the method
will be found in Challis's Lectures on Practical Astronomy,
p. 301.

1 6, Fig. 7. The dotted lines on these 4 discs have been somewhat

exaggerated. The curves should neither be quite so sharp, nor
the inclination of the straight lines quite so great, as the'engraver
has made them.

17, line 1 8. A good description of the details of the structure of a sun-

spot is given by Janssen (Comptes Eendus, vol. cii. p. 80. 1886).

56, line 3, for " Eastern " read " Western."

„ line 5, for " Western " read " Eastern."

„ line 6, for " motion " read " the apparent motion of revolution
round the Sun."

68, line 15, for "appendix" read "Book VI."

78, line 15. For 0-132' read 0-132.

126. In connection with Sir W. Herschel's supposition that he had seen
a volcano in action, on the Moon, attention may be called to some
remarks by Prof. Holden in The Observatory, vol. xi. p. 334,
Sept. 1888.

165, line 8. The minor planet Thule (279) is now the most distant one
known.

„ line 1 6, for "Massalia" read " Massilia."

1 86, line 8. Add: — Lord Stratford De Eedcliffe relates that on his
voyage to America in September 1820 one night " at anchor on
board ship I had occasion to observe the wonderful clearness of
the atmosphere. From the Spartan's deck I saw with my
naked eye the satellites of Jupiter." (Life of Stratford Canning,
vol. i. p. 299, Lond. 1889.)

1 89, note f. Add : — Some useful information relating to the physical

features of Jupiter's satellites will be found in E. Engelmann's

Uber die Helligkeitsverhdltnisse der Jupiterstralanten. Leipzig,

1871.

200, line 5 of Chapter Contents, for " the brothers Ball " read "Cassini."

Addenda et Corrigenda. xxxi

Page

233. For an account of some curiously mysterious circumstances con-
nected with the discovery of the satellite Titan see a letter by
Lynn in The Observatory, vol. xi. p. 338, Sept. 1888, and other
letters in the numbers of that Magazine for March and April
1889.

250. Newcomb's mass of Uranus is

259. Newcomb's mass of Neptune is

320. The Total Eclipse of the Sun of Jan. i, 1889 was successfully
observed in America. Professor Pickering noticed the corona to
be longer and more irregular in its shape than usual, and that
it exhibited great detail in its filaments.

367. With regard to Wicklow Head, there is another reason why the
rise and fall of the tide there is so small. That Head is only
about 22 miles N. of Courtown, where the tide waves entering
the Irish Sea by the South and by the North of Ireland nearly
cancel each other. At Courtown the range of the tide is only
1 8 inches, and that place is at the head of a bay, though a wide
and shallow one.

375, line 16, dele "periodical."

376, lines 8 and 10, for " ecliptic" read " zodiac."

377, line 10 from bottom, read Aristillus.

„ line 3 from bottom, for " effect of" read " solar."
385, line 14, after "these" insert "latter."

THE GKEEK ALPHABET.

*#* The small letters of this alphabet are so frequently
employed in Astronomy that a tabular view of them, together
with their pronunciation, will be useful to many unacquainted
with the Greek language.

a Alpha.
ft Beta.
y Gamma.
8 Delta.
€ Epsllon.
^ Zeta.
?/ Eta.
0 Theta.
t Iota.
K Kappa.
A Lambda,
u Mu.

v Nu.

*Xi.

o O-mlcron.

TT Pi.

p Rho.

a- Sigma.

T Tau.

v Upsilon.

0 Phi.

XChi.

^ Psi.

o) O-mega.

BOOK I.

THE STJIST AND PLANETS.

CHAPTEK I.

THE SUN. O

" 0 ye Sun and Moon, bless ye the LOKD : praise Him, and magnify
Him for ever." — Benedicite.

Astronomical importance of the Sun. — Solar parallax. — The means of determining
it. — Sy observations of Mars. — By Transits of Venus. — Numerical data. — Light
andHeatofthe Sun. — Gravity at the Sun's surface. — Spots. — Description of their
appearance. — How distributed. — Their duration. — Period of the Sun's Rota-
tion.— Effect of the varying position of the Earth with respect to the Sun. —
Their size. — Instances of large Spots visible to the naked eye. — The Great Spot
of October 1865. — Their periodicity. — Discovered by Schwabe. — Table of hit
results. — Table of Wolfs results. — Curious connexion between the periodicity of
sun-spots and that of other physical phenomena. — The Diurnal variation of the
Magnetic Needle. — Singular occurrence in September 1 859. — Wolf's researches.—
Spots and Terrestrial Temperatures and Weather. — Ballot's inquiry into Ter-
restrial Temperatures. — The Physical Nature of Spots. — The Wihon-Herschel
Theory. — Luminosity of the Sun. — Historical Notices. — Scheiner. — Facula. —
Luculi. — Nasmyth's observations on the character of the Sun's Surface. —
Hugffins's conclusions. — Present state of our knowledge of the Sun's constitu-
tion.— Tacchini's conclusions.

TF there is one celestial object more than another which may
be regarded as occupying the foremost place in the mind of
the astronomer, it is the Sun: for, speaking generally, there
is scarcely any branch of astronomical inquiry with which,
directly or indirectly, the Sun is not in some way associated.
It will be only appropriate therefore to deal with this important

2 The Sun and Planets. [BOOK I.

body at the very commencement of a treatise on Descriptive
Astronomy*.

By common consent, the mean distance of the centre of the
Earth from the centre of the Sun is taken as the chief unit of
astronomical measurement.

The most approved method of determining the value of this
was at one time believed to be by the aid of observations of
transits of the planet Venus across the Sunb (as was first pointed
out by Halley). The problem is, for various reasons, an
intricate one in practice, but when solved places us in possession
of the amount of the Sun's equatorial horizontal parallax ; in other
words, gives us the angular measure of the Earth's equatorial
semi-diameter as seen from the Sun's centre, the Earth being at
its mean distance from the Sun. With this element given, it
is not difficult to determine, by trigonometry, the Sun's distance,
expressed in radii of the Earth ; reducible thereafter to miles.

Encke, of Berlin, executed an able discussion of the observations
of the transits of Venus in 1761 and 1769, and deduced 8-571" as
the amount of the angle in question0. From this it was found
that the mean distance of the Earth from the Sun is 24065-1
times the equatorial radius of the former (3963 miles), equal
to 95,370,000 miles ; but these results, excellent as they were
once thought to be, have long ceased to command the acceptance
of astronomers, the fact being that modern experience has dis-
credited Halley's method.

At a meeting of the Royal Astronomical Society, on May 8,
1857, Sir G. B. Airy proposed to adopt a suggestion of Flam-
steed's d for determining the absolute dimensions of the solar
system, founded upon observations of the displacement of Mars
in Right Ascension, when it is far E. of the meridian and far
W. of the meridian, as seen from a single observatory; such

• Every one who wishes thoroughly b See Book II. post.

to "get up" the Sun should read Young's c Der Venusdurchgang von 1769,

Sun. Secchi's magnificent work Le Soleil, p. 108. Gotha, 1824. Followed by later

of which a second and much enlarged and better results in the Berlin Abhand-

edition was published in 1875, must not lungen for 1835, P- 295-

be forgotten. d Baily, Life of Flams'eed, p. 32.

CHAP. I.] The Sun. 3

observations to commence a fortnight before and to terminate
a fortnight after the Opposition of the planet. In consequence
of the great eccentricity of the orbit of Mars, this method is only
applicable to those Oppositions during which the planet is nearly
at its least possible distance from the Earth. Airy pointed out
the several advantages of this method, viz. : — that Mars may
then be compared with stars throughout the night ; that it
has 2 observable limbs, both admitting of good observation ; that
it remains long in proximity to the Earth ; and that the nearer
it is, the more extended are the hours of observation ; in all of
which matters Mars offers advantages over Venus for observations
of displacement in Right Ascension. Airy also entered into
some considerations relative to certain of the forthcoming
Oppositions, and named those of 1860, 1862, and 1877, as favour-
able for determining the parallax in the manner he suggested6.

Le Verrier announced in 1861 f that he could only reconcile
discrepancies in the theories of Venus, the Earth, and Mars, by
assuming the value of the solar parallax to be much greater than
Encke's value of 8^57 i". He fixed 8-95" as its probable value,
though, as Stone pointed out, this conclusion taken by itself
rests on a not very solid foundation «.

The importance of a re-determination was thus rendered more
and more obvious, and Ellery, of Williamstown, Victoria, suc-
ceeded in obtaining a fine series of meridian observations of
Mars, at its Opposition in the autumn of 1862, whilst a corre-
sponding series was made at the Royal Observatory, Greenwich.
These. were reduced by Stone, and the mean result h was a value
of 8-932" for the solar parallax, with a probable error of only
003 2". This result was singularly in accord with Le Verrier's
theoretical deduction. Winnecke's comparison of the Pulkova
and Cape observations of Mars yielded 8- 964".

8 Month. Not., vol. xvii., pp. 208-21. vol. iv., p. 101. Paris, 1861.

May, 1857. Some practical hints on the e Month. Not.,\ol. xivii., p. 241. April

conduct of observations are given by A. 1867.

Hall in Ast. Nach., vol. Ixviii., No. 1623, h Month. Not., vol. xxiii., p. 185, April

Jan. 16, 1867. 1863.

' Annales de V Observatoire Imperial,

B 2

4 The Sun dti</ Planet*. [BooK I.

The Opposition of 1877 was observed under favourable circum-
stances by Gill at the Island of Ascension, and his observations
yielded as their final result a parallax of 8-78", with a probable
error of 0-012". This implies a mean distance of the Earth from
the Sun of 93,080,000 miles1.

Thus, though there may be some uncertainty in the amount of
the correction, there is no doubt that the Sun is nearer than was
formerly considered to be the case.

The distance amended to accord with a parallax of 8-8" is
about 92,890,000 miles, with an error not likely much to exceed
150.000 milesk.

Hansen contributed something towards the elucidation of the
matter. As far back as 1854 that distinguished mathematician
expressed his belief that the received value of the solar parallax
was too small, and in 1 863 he communicated to Sir G. B. Airy
a new evaluation, derived from his Lunar theory by the agency
of the co-efficient of the parallactic inequality. The result was
8-9 1 59", a quantity fairly in accord with the other values set
forth above1.

Such is a brief statement of the circumstances which caused
such special interest to attach to the transits of Venus which
were to happen on December 8, 1874, and December 6, 1882:
for it was supposed, that, all things considered, transits of
Venus were most to be relied on for the purpose of ascertaining
the amount of the Sun's parallax. The particular circumstances
of the transits in question will come under notice hereafter.
Meanwhile it may be stated that Stone has deduced 8-823"
as the general result of all the British observations of the

1 Mem., R. A. S. xlvi., p. I, 1881 : put as the measurement of a ball one

Month. Not., vol. xli., p. 323. April 1881. foot in diameter seen from a station nearly

k C. A. Young in Sid. Mess., vol. vi., 4-4 miles distant from the ball. Unless

p. n, Jan. 1887. the observer can "determine the diameter

1 Month. Not., vol .xxiv., p. 8. Nov. of the ball so that he shall not be un-

1863. The amount of the correction certain in his measure to the amount of

to Encke's determination is about equal 0-03 of an inch, his work will not add

to the apparent breadth of a human hair anything useful to present knowledge."

seen from a distance of 125", or that of (Sid. Mesg., vol. vii., p. 101, March
a sovereign at a distance of 8 miles. The
whole amount of the parallax has been

CHAP. I ] Th,e Sun. 5

1882 transit. The Brazilian result by Wolf and Andre is
8-808".

It is almost needless to add that the acceptance of a new
value for the solar parallax necessitates the recomputation of all
numerical quantities involving the Sun's distance as a unit.

The real mean distance of the Earth from the Sun being
ascertained, it is not difficult to determine by trigonometry the
true diameter of the latter body, its apparent diameter being
known from observation m ; and, as the most reliable results
show that the Sun at mean distance subtends an angle of
32' 3-6", it follows that (assuming, as above, a parallax of 8-8") its
actual diameter is 866,200 miles. It is generally accepted that
there is no visible compression. The surface of this enormous
globe therefore exceeds that of the Earth 1 1 ,900 times, whilst
the volume is i ,306,000 times greater ; since the surfaces of two
spheres are to each other as the squares of their diameters, and
the volumes as the cubes.

The linear value of i" of arc at the mean distance of the Sun
is about 450 miles.

The Sun's mass, and consequently its attractive power, is
332,260 times that of the Earth, and (approximately) is 749 times
the masses of all the planets put together.

By comparing the volumes of the Sun and the Earth and
bringing in the value of their masses, we obtain the relative
specific gravity or density of the two.

The Sun's volume is to that of the Earth in the ratio of
1,306,000 to i ; the Sun's mass is to the Earth's in the lesser
ratio of 332,260 to i. Therefore the density of the Sun is to
the density of the Earth as 332,260 to 1,331,570, or approxi-
mately as i to 4. Then taking Baily's value of the density of
the Earth (5-67 times that of water), the density of the Sun is
i -42 times that of water.

Some interesting points may conveniently be noted here re-

m Lindenau in 1809 and Secchi in 1872 to periodical change, but thoee ideas met
propounded some strange ideas about the with no favour. (Auwers in Month. Not.,
visible diameter of the Sun being subject vol. xxxiv., p. 22, Nov. 1873.)

6 The Sun and Planets. [BOOK I.

specting the consequences which result from the stupendous
magnitude and mass of the Sun. At the surface of the Earth
a body set free in space falls i6aft in the first second of time,
with a velocity increasing during each succeeding second. A
body similarly set free at the surface of the Sun would start with
a velocity 27-4 times as great as that of a body falling at the
surface of the Earth. This is equivalent to saying that a pound
weight of anything on the Earth would, if removed to the Sun,
weigh more than 27lb. Liais has pointed out a singular conse-
quence of this fact: — "An artillery projectile would have on the
Sun but very little movement. It would describe a path of
great curvature, and would touch the surface of the Sun a few
yards from the cannon's mouth." The centrifugal force due to the
rotation of any body diminishes gravity at its surface. At the
Earth's equator the total diminution is ^1^ pait ; whilst at the
Sun's equator the centrifugal force is only about i^J^ Part °f
the force of gravity. It would be necessary that the Sun should
turn on its axis 133 times quicker than it does, for the force of
gravity to be neutralised. In the case of the Eaith, however,
a speed of rotation 17 times as great as it is would suffice to
produce the same result. The insignificance of centrifugal force
at the Sun's equator, compared with the amount of the force of
gravity, suffices to explain the absence of appreciable polar com-
pression in the case of the Sun's disc.

A consideration of the comparative lightness of the matter
composing the Sun led Sir J. Herschel to think it "highly
probable that an intense heat prevails in its interior, by which
its elasticity is reinforced, and rendered capable of resisting [the]
almost inconceivable pressure [due to its intrinsic gravitation]
without collapsing into smaller dimensions n." That the internal
pressure exerted by the gases imprisoned within the luminous sur-
face or photosphere of the Sun, must be absolutely stupendous, we
have evidence of in the fact of the almost inconceivable velocity
(100 to 200 miles per second) of the uprushes of incandescent gas
and metallic vapours, which are almost constantly taking place

n Outlines of Ast., p. 297.

CHAP. I.] The Sun. 7

at various parts of its surface. It would seem all but certain that
the Sun is nearly wholly gaseous, and that its photosphere con-
sists of incandescent clouds, in which the aqueous vapour of our
terrestrial clouds is replaced by the vapours of metals. These
considerations, however, introduce a difficulty of a precisely
opposite character to that which Sir J. Herschel essayed to
combat ; inasmuch as, in the light of our present knowledge,
it seems hard to conceive how a mere shell of metallic vapour
should be able to confine gases at the incomprehensible pressure
at which those which rush out in the form of the now well-
known "Red Flames" (see_po#f) must be confined.

The Sun is to be regarded as a fixed body so far as we are con-
cerned ; when therefore we say that the Sun " rises," or the Sun
" sets," or the Sun moves through the signs of the zodiac once
a year, we are stating only a conventional truth ; it is we that
move and not the Sun, the apparent motion of the latter
being an optical illusion.

The Sun is a sphere, and is surrounded by an extensive and
rare atmosphere ; it is self-luminous, emitting light and heat
which are transmitted certainly beyond the planet Neptune, and
therefore more than 2700 millions of miles. Of the Sun's heat,
it has been calculated that only assiTnjTTTTTnr Pftr^ reaches us0,
so that what the whole amount of it must be it passes human
comprehension to conceive : like many other things in science.
Our annual share would be sufficient to melt a layer of ice all
over the Earth iooft in thickness, or to heat an ocean of fresh
water 6oft deep from 32° F. to 212° F., according to Herschel
and Pouilletp. Another calculation determines the direct light
of the Sun to be equal to that of 5563 wax candles of moderate
size, supposed to be placed at a distance of one foot from the

0 Ganot, Physics, p. 391, 7th Eng. ed. face, had their clothes burnt by coming

1875. This was calculated on the old under the focus of the convex lenses

value of the solar parallax. placed in the bell to let in the light.

P To show the great power of the And houses have been set on fire by the

calorific rays of the Sun, it may be men- Sun's rays. Langley puts the thickness

tioned that in constructing the Plymouth of the layer of ice which could be melted

Breakwater, the men, working in diving at i6oft. (New Ast., p. 95.)
bells, at a distance of 30" below the sur-

The Sun and Planets.

[BOOK I.

Fig. 3-

observer. The light of the Moon being probably equal to that
of only one candle at a distance of i2ft, it follows, according to
Wollaston, that the light of the Sun is 801,072 times that of the
Moon. Zb'llner's ratio is 6 1 8,000 to i , and Bouguer's 300,000 to i .
But all these results rest on a very weak foundation.

If we represent the luminous surface of the Sun when the
Earth is at its mean distance, by 1000, the numbers 967 and

1035 will represent
the same surface as
it appears to us when
the Earth is in Aphe-
lion (July) and Peri-
helion (January) re-
spectively.

When telescopically
examined, there may
frequently be seen
in the equatorial re-
gions of the Sun dark
spots'1 or macula*, each
usually surrounded by
a fringe of a lighter
shade, called a penum-
bra*, the two not passing into each other by gradations of tint,
but abruptly. In the few cases in which a gradual shading has

GENEKAL TELESCOPIC APPEARANCE OF THE SUN.

* It will appear from what is stated
further on that the familiar term "spot"
is merely a conventional one used to con-
vey a general idea of what is seen on
viewing the Sun. In no precise sense
are "spots on the Sun " truly " spots."

r Lat. macula, a blemish. Dawes up-
held a further classification : he applied
to the ordinary black central portions
the term umbra (shadow), on the highly
probable ground that the blackness is
mainly relative. Patches of deeper black-
ness are occasionally noticed in the
umbrae ; Dawes limited to these the
designation nucleus, sometimes indiscri-
minately applied to all the blackish area.

This classification is adopted in the text.
Mr. Langley of the Alleghany Observa-
tory, however, viewing spots with the
13-inch Equatorial of that institution,
and a polarising eye-piece (which admits
of the employment of the whole aperture),
sees that the umbral structure is quite
complex, and made up of sunken banks
of " filaments " (see post). He further
perceives that the nucleus which Dawes
spoke of as "intensely black," is not
black at all, nor even dark (save rela-
tively), but is brilliant with a violet-
purple light. (Month. Not., vol. xxxiv.
p. 259. March 1874.)

• Pene, almost ; and umbra, a shadow.

CHAP. I.] The Sun. 9

been noticed, Sir J. Herschel believed that the circumstance
may be ascribed to an optical illusion, arising from imperfect
definition on the retina of the observer's eye. It is not how-
ever always the case that each spot has a penumbra to itself,
several spots being occasionally included in one penumbra.
And it may further be remarked that cases of an umbra with-
out a penumbra, and the contrary, are on record. Umbrae
without penumbrae are exceptional, and may be considered as
closely related to physical changes just commencing or termina-
ting. A marked contrast subsists in all cases between the
luminosity of the penumbra and that of the general surface
of the Sun contiguous. Towards their exterior edges penumbrae
aie (by contrast) usually darker than nearer the centre. They
are frequently very irregular in their outlines (though often
they conform somewhat closely to the general contour of the
umbrae which they circumscribe), but the umbrae, especially
in the larger spots, are frequently of regular form (compara-
tively speaking, of course) ; and the nuclei of the umbrae still
more noticeably exhibit a compactness of outline.

Spots are for the most part confined to a zone extending 35°,
or so,, on each side of the solar equator, and are neither per-
manent in their form nor stationary * in their position, frequently
appearing and disappearing with great suddenness.

The multitude of facts concerning them, accumulated from the
journals of many observers extending over long periods of years,
is so great as to bewilder one, and to marshal these in a suitable
manner is a task of extreme difficulty : and howsoever per-
formed it is certain that much will have been left out that
might with advantage have been inserted.

The general limits in latitude of the spots may be stated, as
above, at 35°, but instances of spots seen beyond these limits are
on record. In 1871, B. Stewart saw one 43° distant from the
solar equator; in 1858, Carrington one 44° 53'; in 1826, Capocci
one 46° ; in 1846, C. H. F. Peters one 50° 55' ; and La Hire, in the

* This is not said merely in view of the Sun's rotation ; spots sometimes possess
an absolute motion of their own.

10 The Sun and Planets. [BOOK I.

last century, is said to have seen one in latitude 70°. They are
often confined to two belts on either side of the Sun's equator,
being frequently absent from the equatorial regions except at
particular epochs : from 8° to 20° is their most frequent range,
or to be more precise still, their favourite latitude is 17° or
18°. They are often more numerous and of a greater general
size in the Northern hemisphere; the zone between 11° and
15° north is particularly noted for large and enduring spots.
A gregarious tendency is very obvious, and where the groups
are very straggling, the longer line joining extreme ends will
pretty generally be found to be more or less parallel to the
equator, and not only so, but extending across nearly the whole
of the visible disc.

Sir John Herschel remarked : — " These circumstances ....
point evidently to physical peculiarities in certain parts of the
Sun's body more favourable than in others to the production of
the spots, on the one hand ; and on the other, to a general
influence of its rotation on its axis, as a determining cause in
their distribution and arrangement, and would appear indicative
of a system of movements in the fluids which constitute its
luminous surface ; bearing no remote analogy to our trade-
winds — from whatever cause arising u." In reference to the
distribution in latitude of the spots, the observations of Carring-
ton have placed us in possession of some important facts. That
observer found that as the epoch of minimum approached, the
spots manifested a very distinct tendency to advance towards
the equatorial regions, deserting to a great extent their previous
haunts above the parallels of 20° or so. After the minimum
epoch had passed, a sudden and marked change set in, the
equatorial regions becoming almost deserted by the spots, which
on their reappearance showed themselves chiefly in parallels
higher than 20°. Wolf finds that the observations of Bohm
reveal the fact that the same peculiarity was noticed by that
observer in the years 1 833-6 v. Sir John Herschel remarked
that if this should prove to be a general rule, " it cannot but

• Outlines ofAst., p. 251. v Month. Not., vol. xix., p. 325, July 1859.

Figs. 4-6.

Plate II.

1826: September 29. (Capocci.}

1861: May 21. (Birt.)

1861 : May 27. (Anon.}

SPOTS ON THE SUN.

CHAP. I.] The Sun. 13

stand in immediate and most important connexion with the
periodicity itself, as well as with the physical process in which
the spots originate."

Confirming Carrington's results in a great measure, Sporer,
who has devoted many years to assiduous observation of the Sun,
finds that between the time of one minimum and another the
region of greatest frequency gradually drifts downward from the
zone of 30 — 25° of latitude to the immediate neighbourhood of
the equator ; and that at the time of maximum its seat lies in
about 17° or 18°. As the next minimum approaches, spots more
than 15° from the equator become more rare than spots of 35°
and upwards were at the time of maximum. But directly the
minimum is past, spots begin to appear again in those higher
latitudes where but very few have been seen for several years.
This sudden transfer of the seat of energy from a zone where it
has been manifested year after year to another and distant zone
where pothing has been going on for a long time previously, is a
remarkable fact, the import of which cannot at present be
explained w.

The duration of individual spots is a matter associated with
extremes both ways. Some remain visible for several months,
others scarcely for as many minutes ; but a few days or weeks
will commonly be found the usual extent of permanency. Some
are formed and vanish during the period of a single semi-rotation
(rather more than I2|d), others remain during several successive
rotations ; for it will be readily understood that the Sun, being
endued with an axial rotation, and the spots being fixed (or
nearly so) on the Sun's surface, it will not be possible for any
one spot to remain in sight continuously for longer than half the
duration of the Sun's rotation.

With respect to the distribution of spots in longitude there is
little to be said, for it does not certainly appear that they have
a preference for any one longitude more than another. Never-
theless Kirkwood believes that this statement so far needs

w Ast. Nach., vol. cvii., No. 2565. Dec. 31, 1883. See also V Astronomic, vol. i.,
p. 70, April 1882.

14 The Sun and Planets. [BOOK I.

modification that there is one particular longitude in which
planetary influences (see post) are specially effective. Sporer also
seems to think that there are special localities of disturbance.

When observed for any length of time, a spot will first be
noticed on the Eastern limb, disappearing in little less than a
fortnight on the Western limb ; after an interval of nearly
another fortnight, the spot, if still in existence, will reappear on
the Eastern side, and in like manner traverse the disc as before.
This phenomenon necessarily can only be accounted for on the
supposition that the Sun rotates on its axis ; and observations
specially conducted with that object in view will give the
period of this rotation, which Laugier fixed at 2jd 8h iom ;
Carrington at 25d 9h 7m ; and Sporer at 25d 5h 31 m — results fairly
in accord with Bianchini's determination of 25d 7h 48°*, deduced
in 1718, when the difficulties attending the observations due to
the ever- varying forms and actual proper motions of the spots
are taken into consideration.

The entire period required by a spot to make a whole visual
rotation (27d 7h) is greater than that of the Sun's actual
rotation, owing to the Earth's progressive movement in its
orbit.

On February 19, 1800, Sir W. Herschel was watching a group,
but after looking away for a single moment, he could not
find it again1. The same observer followed a spot, in 1779,
for 6 months ; and, in 1840 and 1841, Schwabe observed one and
the same group to return 1 8 times, though not in 1 8 consecu-
tive rotations of the Suny.

In July, August, and September 1859, a large group was
followed through several apparitions, and another very notice-
able instance of the kind occurred in the autumn of 1865.
Similar cases are by no means very rare. It has been sur-
mised, and Sir J. Herschel thought " with considerable apparent
probability," that some spots at least are generated again and
again, at distant intervals of time, over the same identical

1 Phil Trans., vol. xci., p. 293. 1801.

* Ast. Nach., vol. xviii. No. 418, March 18, 1841.

CHAP. I.] The Sun, 15

points of the Sun's body. There appears to be some evidence
to bear out this hypothesis2. Webb says: — "Fritsch stated
that he saw one stand nearly still for 3 days ; and Lowe
that he even witnessed retrogradation — but these assertions
involve a suspicion of mistake. Schrb'ter and others have
ascribed to them a more moderate locomotion. This was
micrometically established in a lateral direction by Challis in
1857 ; and Carrington has subsequently made known his very
interesting discovery, that there appear to be currents in the
photosphere, drifting the equatorial spots forward in comparison
with those nearer to the poles, with deviations in latitude of
smaller amount : the neutral line as to both these drifts lying in
about 15° of latitude. With these shifting landmarks, it is not
surprising that the Sun's period of rotation is still doubtful.
. . . Hewlett and several others have found that spots near the
limb require a different focus from those in the centre ; arising,
no doubt, as Dawes says, from the effect on the retina of very
different degrees of brightness*." According to Maunder a
relative displacement amongst the members of the same group
amounting to 7000 miles a day is not unusual.

With respect to proper motion, Carrington found that most
spots have an independent proper motion of their own (hence
uncertainties in conclusions respecting the duration of the Sun's
rotation), and not only so, but that the proper motion of spots
varies systematically with the latitudes of the spots.

The varying position of the Earth with reference to the Sun,
combined with the inclination of the axis of the latter to the
plane of the ecliptic (amounting to 82° 45' according to Car-
rington ; to 83° 3' according to Sporerb), gives rise to the fact
that at no two periods of the year do the spots appear to traverse
the Sun's disc exactly in the same way. About June 5 and
December 6 the Earth is in the line of nodes of the spots — or, in

* Sir John seems afterwards to have b The longitude of the ascending node
changed his opinion. In a Memoir in the for 1850 was 73° 40' ; BO that the North
Quart. Jour. Sc., vol. i. p. 225, April 1864, pole of the Sun's axis points nearly to it
he says exactly the reverse. Draconis, and the South one to o Trian-

* Celest. Objects, p. 33. (3rd ed.) guli Australia.

The Sun and Planets.

[BOOK I.

other words, its longitude, as seen from the Sun, corresponds
nearly with the points of intersection of the solar equator and
the ecliptic — and the paths of the spots are then inclined straight
lines. In March the South pole is turned towards us, and the
tracks are concave towards the South ; in September the condi-
tions are precisely reversed in every respect, the North pole is

Fig. 7.

PATHS OF SUN SPOTS AT DIFFERENT TIMES OF THE YEAR.

turned towards us and the tracks are concave towards the North ;
at other intermediate periods (not being very near to June 5 or
December 6) the paths are both inclined and curved at the same
time.

Individual spots also possess many peculiarities of their own.
Dawes observed one on January 17, 1852, which, by the 23rd
of that month, had rotated in its own plane through 90°. Birt

CHAP. I.] The Sun. 17

believed that the same thing happened with a spot which he scru-
tinised in February and March 1 859°. Schwabe saw occasionally
spots of a reddish-brown colour, under circumstances of contrast
precluding the possibility of deception ; on one occasion 3 tele-
scopes and several bystanders certified to this. In 1826, Capocci
perceived a violet haze issuing from each side of the bright central
streak of a great double umbra ; and during the eclipse of March
15, 1858, Secchi saw a rose-coloured promontory in a spot visible
to the naked eye. On April 24, 1886, Hopkins saw a spot with
4 umbrae, 2 of which were black and 2 reddish-brown. The colour
was very marked and was visible in different eyepieces, and a
bystander confirmed the observation. The colour disappeared
in 20 minutes after the observation was commenced d. Schwabe
described the penumbrse as made up of a multitude of black dots,
usually radiating in straight lines from the umbra ; Secchi with
greater optical power, defined these radiations to be alternate
streaks of the bright light of the photosphere and dark veins
converging to the umbra6.

Some Sun-spots are of such prodigious size, as to be visible
to the naked eye. A few recent instances are here given. A
spot measured by Pastorff on May 24, 1828, was computed to have
an area about 4 times the entire surface of the Earth. In
June 1843, Schwabe observed one 2' 47", or 75,000 miles in dia-
meter. It was seen for an entire week without the aid of a
telescope. On March 15, 1858, the day of the celebrated eclipse,
a spot having a breadth from W. to E. of 4', or 108,000 miles,
attracted considerable attention. On September 30, in the same
year, one having a breadth from W. to E. of 5' 21", or 144,450
miles, was observed f. On January 26, 1859, and during August
1859, large spots were seen; one visible in the latter month
measured nearly 58,000 miles, according to Newall, who saw it
distinctly as a notch on the edge of the Sun's disc, the like of

c Month. Not., vol. xix., p. 182, March authority of Webb, Celest. Objects, p. 25.
1859. He gives no reference, so I am unable to

d Month. Not., vol. xlvi., p. 393, May verify them.
1886. ' Ast. Nach., vol. 1., No. 1 182, Feb. 25,

e The preceding facts are given on the 1 859.

Tlie Sun and Planets.

[BOOK I.

which he had only seen once before — namely, on March 25, 1850*.
During April and May 1870, and April 1882, several large spots,

Fig. 8.

GREAT SUN-SPOT VISIBLE ON JUNE 30, 1883. {HicCO.}

easy to be seen by the naked eye, were visible. The last-named
had on April 19 a length of 2' 15" and a breadth of i' 15".

Fig. 9.

THE SAME SUN-SPOT OX JULY 2, 1883.

g Letter in the Times, Aug. 27, 1859.
" An indentation on a globe will dis-
appear in profile unless its breadth and
depth are considerable : hence such ob-
servations would be rare, but they are
recorded by La Hire, 1 703 ; Cassini,

1719; W. Herschel, 1800; Dollond and
others, 1846 ; Lowe, 1849 '•> Newall, 1850,
1859 ; Observers at Kew and Dessau,
1868."— Webb, Celest. Objects, p. 28
(n.). Of late years Indentations have
been often recorded in photographs.

CHAP. I.]

Violent magnetic storms accompanied its appearance. These
storms continued from April 14 to April 2Oh.

Fig. 10.

GREAT SUN-SPOT VISIBLE ON JULY 25, 1883. (JBlCCO.)

Figs. 8— ii represent 2 large and important spots observed
during the summer of 1883 by M. Ricco at Palermo. Their

Fig. ii.

THE SAME SUN-SPOT ON JULY 27, 1883. (B'-CCO.)

" Hewlett, Month. Not., vol. xlii. p. 356, May 1882.
C 2

20 The Sun and Planets. [BOOK I.

size relatively to the Earth will be realised generally by com-
paring them with the shaded ball in the corner of each sketch
marked " La Terre."

One of the most interesting large spots ever subjected to careful
scrutiny was that which was conspicuously visible in October
1865. Many elaborate observations of it were made by astro-
nomers, and a series of drawings by the Rev. F. Hewlett are well
known. 1 here present copies of drawings by Brodie, exhibited
at the Royal Astronomical Society1, which will be useful for com-
parison with Hewlett's. Brodie furnished me with the following
revised transcript of his notes : —

"OCTOBEB ii, 1865. — The definition was fine enough to allow this spot to be
examined with a power of 470 on an equatorial telescope of 8^ in. aperture and
ii-J- ft. long. The shape of the spot was tolerably rectangular, the umbra being
about 18,000 miles long and 9700 miles wide, or in measures of arc 41 -3" long
and 22-3" wide. The penumbra 86'9" long and 73*5" wide. There was an exceed-
ingly long promontory of luminous matter projecting over the umbra from one end
of the spot, and running tolerably parallel to the side. Near the end of this promon-
tory was an elongated portion of detached luminous matter of similar shape to that of
the promontory itself, about 4000 miles long [see Plate III. Fig. 12]. This portion
had elongated itself in a remarkable manner in the previous 15 minutes, for when first
observed it was not more than 3000 miles long. The long promontory seemed
drifting towards the penumbra, while the detached portion was moving rather away
from it, indicating a cyclonic action of the forces in operation.

" About i^ hours later I found that the detached portion of luminous matter had
formed a junction with the long promontory [see Plate III. Fig. 13]. That side of
the umbra opposite to this promontory was covered with a sort of ' mackerel sky '
formation of misty luminous matter, which extended more or less marked over the
whole portion of the umbra. The Hack nucleus of the umbra first noticed by
Mr. W. R. Dawes, as generally to be seen in spots, was absent in this umbra. This
misty cloud-like appearance of the umbra can only be seen with large telescopes ; it
seems to be formed by the nodules of luminous matter that break off from the
pectinations which fringe the whole of the edge of the umbra ; these soon after
become more and more diffused, until they become a sort of cloudy stratum floating
over the umbra. These nodules invariably drift from the edge of the penumbra
towards the centre of the umbra, which would seem to indicate a downward rush of
gases from the surface of the sun. On October 1 2th there were five of these nodules,
that had broken off from the ends of the small promontories or pectinations at the
edge of the penumbra and had begun to drift on to the umbra, while one had not
quite broken away, but was preparing to do so [see Fig. 18]. There was now also
another change on the umbra at the end of the long promontory ; the misty cloud-like
masses of luminous matter began to form into bridge-like formations [see Plate III]

1 Month. Not., vol. xxvi., ]>. 21, Nov. 1865.

Flys. 12-17.

Plate III.

October n ; n a.m.

October n ; 12.30 p.m.

October 1 2 ; 9.30 a.m.

October 12 ; 10.30 a.m.

October 12 ; 12.30 p.m.

October 12; 2.30 p.m.

THE GREAT SUN-SPOT OP OCTOBER 1865.

(Drawn by Brodie.}

CHAP. I.]

The Sun.

Fig. 13] ; but these formations were not nearly so bright and defined as the long
portion of the promontory : there was also another shorter promontory formed on the
opposite side to that of the long one, or it might be termed an extreme lengthening
of one of the pectinations. The rapidity of change in all parts of the umbra was re-
markable, the cloudy strata seeming to condense and diffuse very similar to our earth
clouds on a summer's day.

" OCTOBER is. — The shape of the umbra was very greatly altered, and its size was
much increased. [See Plate III. Fig. 14]. Its length was nearly 29,000 miles, with
a width in the greatest part of 10,400 miles, or 6^2" of arc long, and 23-6" wide,
the penumbra being 50,000 miles long and 34,000 broad. The long promontory
of yesterday had quite disappeared, and there was another formed at the opposite end
of the spot of a serpentine form ; this was observed at 9.30 A.M. Within an hour
another change took place, and at 10.30 this long serpentine promontory had broken

Fig. i 8.

THE GREAT SDK-SPOT OP OCTOBER 1865. PECTINATED EDGE VISIBLE ON

OCTOBER 12. (Brodie.)

into two portions, the shorter end floating on the penumbra. [See Fig. 15]. At
12.30 P.M. the one end of that portion that had broken off had bodily floated towards
the penumbra, and formed a junction, as seen in Fig. 16. At 2.30 P.M. the spot was
again observed, and the portion originally broken off from the serpentine promontory
of the morning had formed a complete bridge across the umbra, [see Fig. 17], while
the part from which it was broken had bent round, forming nearly a semicircle. The
outline of the spot did not seem to change perceptibly. The figure of the spot was
thrown by the telescope on to a board and sketched from its own image.

" OCTOBER 13. — The shape of the spot slightly altered only, but the bridge across
had quite disappeared, while the semicircular promontory had formed a junction with
the penumbra."

Schwabe said that good eyes would detect without optical aid
any spots more than 50" in diameter, but this is very doubtful.

24 The Sun and Planets. [BOOK I.

Probably the minimum limit must be fixed in general at i' or
even more.

"The origin of a spot, when it can be observed, is usually
traceable to some of those minute pores or dots which stipple the
Sun's surface, and which begin to increase, to assume an umbral
blackness, and acquire a visible and, at first, very irregular and
changeable shape. It is not till it has attained some measur-
able size that a penumbra begins to be formed — a circumstance
strongly favouring the origination of the spot in a disturbance
from below, upward ; vice versa, as the spots decay they become
bridged across, the umbrae divide, diminish in size, and close up,
leaving the penumbne, which, by degrees, also contract and
disappear. The evanescence of a spot is usually more gradual
than its formation. According to Professor Peters and Mr.
Carrington, neighbouring groups of spots show a tendency to
recede from one another k." And not only so, but neighbouring
spots in the same group show the same tendency, particularly in
longitude. The relative drift of members of the same group
is far more noticeable than the relative drift of different
groups.

The most casual observer can hardly fail to be struck with
the rapidity of the changes which take place in solar spots.
Dr. Wollaston says: — "Once I saw, with a 1 2-inch reflector, a
spot burst to pieces while I was looking at it. I could not
expect such an event, and therefore cannot be certain of the
exact particulars ; but the appearance, as it struck me at the
time, was lite that of a piece of ice when dashed on a frozen
pond, which breaks in pieces, and slides on the surface in various
directions. I was then a very young astronomer, but I think I
may be sure of the fact." Their immense number is likewise
very noticeable. On April 26, 1 846, Schmidt at Bonn counted
upwards of 200 sing'le spots and points in one of the large groups
then visible, and 180 in another cluster, in August 1845. On
August 23, 1 86 1, 1 counted 70 distinct spots with a telescope of
only 3 inches aperture charged with a power of 2 1 . Schwabe

k Sir J.Hersehel, in Quart. Journ.Sc., vol. i. p. 225. April 1864.

CHAP. I.] The Sun. 25

found that the Western members of a group disappear first, and
that at the Eastern end fresh ones are apt to form, where also
the junior members are most numerous ; that the small points
are usually arranged in pairs (much after the appearance of the
" Dumb-Bell" Nebula); and that, when near the edge of the Sun,
the penumbrse are much brighter on the side next the limb.
Sir J. Herschel often noted the penumbrse to be least defined
on the preceding side ; and Capocci found the principal spot of
a group usually the leader. The same observer believed the
umbrae to be better defined in their increase than in their
decrease. The leader is usually the most black, symmetrical,
and enduring of the group, according to Chacornac.

Maunder disagreeing with Schwabe (as above) says that the
leader of a group of spots, i.e. the most Westerly one, is the
darkest and most enduring. He notes that the groups first begin
to waste in the central members : then the Eastern members
perish ; and last of all the Western members.

Attention has now to be directed to one of the most curious
and interesting discoveries of modern astronomy — the periodicity
of the solar spots. Schwabe, of Dessau, the hero of this l, shall
be introduced to the reader in the words of the late Mr. M. J.
Johnson, when, as President of the Royal Astronomical Society,
he spoke on the award to him of the Society's Gold Medal in
1857:-

" What the Council wish most emphatically to express is their admiration of the
indomitable zeal and untiring energy which he has displayed in bringing that
research to a successful issue. Twelve years, as I have said, he spent to satisfy
himself ; six more years to satisfy, and still thirteen more to convince, mankind. For
thirty years never has the Sun exhibited his disc above the horizon of Dessau without
being confronted by Schwabe's imperturbable telescope, and that appears to have
happened, on an average, about 300 days a year. So, supposing that he observed
but once a day, he has made 9000 observations, in the course of which he discovered
4700 groups. This is, I believe, an instance of devoted persistence (if the word were
not equivocal, I should say pertinacity) unsurpassed in the annals of astronomy.
The energy of one man has revealed a phenomenon that had eluded even the sus-
picion of astronomers for 200 years ™."

1 Wolf has pointed out that Chris- to a periodicity. (R. Wolf, GeschicMe
tian Horrebow first suggested the idea dcr Astronomie, p. 654.)
that the spots on the Sun were subject ™ Month. Not.,\ol.xvn.p. 129. Feb. 1875.

The Sun and Planets.

TABLE OF SCHWABE'S RESULTS n.

Year.

Days of
Observation.

Days of no
Spots.

New Groups.

Mean diurnal
Variation in
Decimation of
the Magnetic
Needle.

1826

277

118

9'-75

1827

273

161

"•33

1828

282

225

11-38

1829

244

199

14.74

1830

217

190

12-13

1831

*39

149

12*22

1832

270

1833

247

139

1834

273

120

5»

1835

244

173

9-57

I836

200

272

J2-34

1837

168

333

12-27

1838

202

282

12-74

1839

205

162

11-03

1840

263

152

9.91

1841

283

IO2

7-82

1842

3°7

7-08

1843

312

149

7-i5

1844

321

6-61

1845

332

114

8-13

1846

314

'57

8-81

1847

276

257

9-55

1848

278

33°

11-15

1849

285

238

10-64

1850

308

1 86

1044

1851

308

J5i

8.32

1852

337

125

8-09

1853

299

7-09

1854

334

6-81

1855

313

146

6-41

1856

321

193

5-98

1857

324

6-95

1858

335

188

7.41

1859

343

205

xo-37

i860

332

211

10-05

1861

322

204

9.17

1862

3»7

1 60

8-59

1863

33°

124

8-84

1864

325

130

8-02

1865

307

8-14

1866

349

7-65

1867

312

195

7.09

1868

301

101

8-15

Schwabe's observations, as published, end with 1868. The
thread is not however absolutely broken, for Wolf had previously

n Month. Not., vol. xvi., p. 63. Jan. 1856. Continued to 1868.

CHAP. I.]

The Sun.

started a series of his own. A table of his results, as prepared
by himself for this work, at my request, is subjoined : —

Year.

Days of
Observation.

*•

Days of no
Spots.

Relative
Number.

Mean diurnal variation in Mag-
netic Declination at Prague.

Observed.

Calculated.

1849

313

95-9

10-27

IO-2I

1850

325

66-5

9-97

8-88

1851

64-5

8-32

8-79

1852

322

54-2

8-09

8-33

1853

332

39-°

7-09

7-64

1854

348

2O-6

6-Si

6-82

1855

352

223

6-7

6-41

6-19

1856

356

256

4-3

.r98

6-08

1857

363

70 22-8

6-95

6-92

1858

335

2 54-8

7.41

8.36

1859

334

o 93-8

10-37

1O-II

1860

363

o 95-7

10-05

10-20

1861

364

2 77-2

9-17

9-36

1862

359

4 59- r

8-59

8-55

1863

361

44-0

8-84

7-87

1864

352

46-9

8-02

8-00

1865

361

3°-5

7-80

7.26

1866

363

16-3

6-63

6-62

1867

360

219

7-3

6-47

622

1868

351

37-3

7-27

7-57

1869

34i

73-9

9-44

9.22

1870

354

J39-1

11.47

12-15

1871

363

III- 2

1 1-60

10-89

1872

365

101-7

10-70

10.47

1873

363

66-3

9-°5

8-87

1874

363

44.6

7.98

7.90

1875

365

132

17.1

6-73

666

1876

366

189

"•3

6.47

6-40

1877

365

142

123

5-95

6.44

1878

365

28l

3-4

5-65

6-04

1879

36.5

217

6-0

5-99

6-16

1880

366

32-3

6-85

7-34

1881

365

54-2

7.90

8-33

1882

365

59'6

7.92

8-57

1883

365

63-7

8-34

8-76

1884

366

63-4

8.27

8-74

1885

365

52-2

7-83

8-24

1886

365

25-4

7-40

7-°3

1887

3°9 ?

86?

13-5?

6-72

6-48?

The gist of this discovery may be given in a few words:— the
spots are subject to a periodical variation in prevalence, extend-
ing over about ny; during this time their numbers follow
a cycle which has a maximum and a minimum. At epochs of

28 The Sun and Planets. [BOOK 1.

minima, on many days absolutely no spots are to be seen, as was
the case in 1 856. It has been hinted that at epochs of maxima,
spots are more permanent in character, that is, can be more often
watched through several rotations than is the case at epochs of
minima : but the idea needs confirmation.

A remarkable discovery has grown out of Schwabe's ; namely,
that the diurnal variation in the declination of the magnetic
needle is characterised by an n-year period, and (this is the
singular circumstance) that the epoch of maximum variation
corresponds with the epoch of the maximum prevalence of sun-
spots, and vice versa, minimum with minimum. Lamont of
Munich announced decisively, about 1850, the fact of the period,
and General Sabine, in March 1851 °, the fact of the coincidence ;
Gautier and Wolf making the same deduction independently of
Sabine and of each other.

Perhaps it might be well just to explain here very briefly
what the diurnal variation of the magnetic needle is. The needle
is subject daily to a minute change of direction of an oscillatory
character. The change is in the nature of an effort on the part
of the needle to turn towards the Sun. When the Sun is on the
meridian the needle has its mean position ; this happens twice
in every 24 hours, corresponding to the upper and lower meridian
passages of the Sun. Again, when the Sun is mid- way between
these positions — also of course twice in every 24 hours — the
needle has a mean position because its N. and S. ends make
respectively equal efforts (so to speak) to direct themselves
towards the Sun. Four times in the day then the needle has
its mean position, or, in other words, is directed towards the
magnetic meridian. But when the Sun is not in any one of the
4 positions mentioned, that end of the needle which is nearest
the Sun is slightly turned away from its mean position and
towards the Sun. These diurnal vibrations are not uniform in
amount from day to day during a succession of days and months
and years: they vary in extent by gradual steps through
a period of years, now recognised as being about i iy. And

0 Phil. Trans., vol. cxlii. p. 103. '852.

Fig. 19.

Plate IV.

CHAP. I.] The Sun. 31

this fact underlies the coincidence mentioned in the previous
paragraph.

Two other curious discoveries have been made in close con-
nection with the foregoing, and it is now accepted that aurorae
and magnetic earth currents (currents of electricity which
frequently travel below the surface of our globe, and interfere
with telegraphic operations) likewise have an i i-year period, and
that their maxima and minima are contemporaneous with those
of the two phenomena dealt with above ; " so that," in the words
of Balfour Stewart, " a bond of union exists between these four
phenomena. The question next arises, What is the nature of
this bond 1 Now, with respect to that which connects Sun-spots
with magnetic disturbances, we can as yet form no conjecture ;
but we may, perhaps, venture an opinion regarding the nature
of that which connects together magnetic disturbances, aurorse,
and earth-currents p." The reality of the coincidences just
adverted to will be best understood by an examination of the
accompanying engraving of curves, which I copy from Loomis,
who has investigated with great care the historical evidence
available for drawing trustworthy conclusions in respect of these
matters. Loomis points out that the discrepancies in the coinci-
dences of critical periods in the three phenomena of Sun-spots,
magnetic declination, and aurorse are both few and insignificant.
His memoir will well repay attentive perusal q.

Much more might be said on these matters, but a fuller
elucidation of them would lead us into non-astronomical fields.

I may here advert to a remarkable phenomenon seen on Sep-
tember i, 1859, by two English observers whilst engaged in
scrutinising the Sun. A very fine group of spots was visible at
the time, and suddenly, at nh i8m a.m., two patches of in-
tensely bright white light were seen to break out in front of the
spots. They were at first thought to be due to a fracture of the
screen attached to the object-glass of the telescope, but such was

P Proceedings of the Royal Inst., vol. p. 245. April 1873; vol. 50. (2nd s.) p.
iv. p. 58. 1863. 153. Sept. 1870.

i Silliman's Journal, vol. v. (3rd s.)

32 The Sun and Planets. [BOOK I.

not the case. The patches of light were evidently connected
with the Sun itself; they remained visible for about 5m, during
which time they traversed a space of about 33,700 miles. The
brilliancy of the light was dazzling in the extreme ; but the most
noteworthy circumstance was the marked disturbance which (as
was afterwards found) took place in the magnetic instruments
at the Kew Observatory simultaneously with the appearance in
question, followed in about i6h by a great magnetic storm r,
during which telegraphic communication was impeded, some
telegraph offices were set on fire, and aurorse appeared. A storm
on the sun not altogether unlike this, it would seem, was
observed on September 7, 1871, in America by Professor C. A.
Young. A prominence (or uprush of gas) which he was
examining with a spectroscope suddenly burst into fragments
with great violence. He calculated that the velocity of ascent
was as great as 166 miles per second. A portion of the frag-
ments of matter reached 200,000 miles from the Sun's surface 8.
An aurora occurred in the evening*.

A more recent and extremely striking instance of the cor-
relation of these physical forces occurred on April 16, 1882. A
magnificent aurora, violent electrical disturbances, and numerous
and large Sun-spots presented themselves simultaneously. The
aurora was seen only in America, but the electrical disturbances
and of course the Sun-spots were recorded in Europe also. No
one can read Mr. H. C. Lewis's paper cited below without being
convinced of the intimate association subsisting between these
phenomena. Hardly less certain is their magnetic character. Mr.
Lewis thus concludes his paper on the aurora in question: —
" The theory is not improbable that Sun-spots are the result of
solar electrical or magnetic storms, and that auroras are the
result of a disturbed electrical condition of the earth, caused by

r Carrington and Hodgson, Month. Not., * For an account of 2 explosions on

vol. xx. pp. 13-16. Nov. 1859. Se® *ne Sun seen, the one by Rapin at Lau-

also an account of a similar phenome- sanne, on Sept. 14, 1883, and the other

non noted by Brodie, in vol. xxv. p. 21. by C. W. Irish, at Iowa (U. S.), on

November, 1864. April 10, 1884, see IS Astronomic, vol.

• Nattire,\6l. iv. p. 488. Oct. 19,1871. iii. p. s8r. October 1884.

CHAP. I.]

The Sun.

induction from the Sun. The common cause for both phenomena
is probably cosmigal u."

Wolf has tabulated all the observations of spots which he
could collect. These date from 1611, but do not assume good
regularity till 1749. Annexed is a copy of Wolf 's table w. He
divides his materials into 2 groups, corresponding to the periods
1610-1738, and 1745-1870, and his deductions as to the average
duration of the sun-spot period are as follows : —

SEBIES I.

Years.

From Mimima, 11.20 + 2.11.
.. Maxima, 11-20+2-06.

SERIES II.

Years.
From Minima, 11-11 + 1.54.

., Maxima, 10-94 + 2-52.

Minima.

Maxima.

1
Minima.

Maxima.

1610-8

1615-5

1745-0

I750-3

8-2

10-5

IO-2

11*2

1619-8

1626-0

1755-2

1761-5

15-0

13-5

"•3

8-2

1634-8

I639-5

1766-5

1769-7

II-O

9-5

9-0

8-7

1645-0

1649-0

1775-5

1778.4

IO-O

II-O

9-2

9-7

1655-0

1 660-0

1784.7

1788-1

II-O

15-0

13-6 16-1

1666-0

1675-0

I798-3

1804-2

13-5

IO-O

12-3

12-2

I<579-5

1685-0

1810-6

1816-4

IO-O

8-0

12-7

13-5

1689.5

1693-0

1823-3

1829-9

12-5

10-6

7-3

1698-0

1705-5

1833-9

1837-2

14-0

12-7

9-6

10-9

1712-0

1718-2

1843-5

1848-1

"•1

9-3

12-5

I2-O

I723-5

I727-5

1856-0

1 860- 1

10-5

II-2

10-5

17340

I738-7

1867-2

1870-6

u Proceedings Amer. Philos. Soc., vol.
xx. p. 290, 1882. For further information
on the connection between solar outbursts
and magnetic storms see the Stonyharst
College Observations for 1882, &c.
(Observatory, vol. vi. p. 307, Oct. 1883.)

w Mem. E. A. S., vol. xliii. p. 202,
1877. Wolf's results, as recorded in

his paper, will well repay careful study.
His system of "relative numbers" to
represent the monthly and annual energy
displayed by the Sun is extremely in-
teresting, and the preparation of his
table to record this energy from July
1749 to June 1876 must have involved
incredible labour and research.

34 The Sun and Planets. [BOOK I.

The general result may be stated to be, that the period equals
1 1 «ii i years (u years 6 weeks,) but may vary as much as
2 years either way from this average.

Wolf has also considered himself warranted in asserting this
law : — " Greater activity in the Sun goes with shorter periods,
and less with longer periods ''; and further, that there are grounds
for the opinion that solar spots and variable stars are due to
similar agencies.

Generally speaking, there appears a tendency with maxima
to anticipate the middle time between the consecutive minima,
the interval ii'iiy being divided into two unequal sub-intervals
of 4|y and 6Jy, or, as it may be otherwise put, the maximum
appears to fall about the 5th year of the period comprised be-
tween 2 minima x. Observations of various kinds discussed by
De La Rue, Stewart, and Lowy confirm this inequality of interval,
but make the sub-intervals 37y and 7'4y. or i to 2. As respects
the law of increase and decrease in given spot-periods their con-
clusion differs in an important respect from that of Wolf. He
appears to consider that when the spot frequency has descended
rapidly or slowly from a maximum value to the next minimum,
it ascends with corresponding (relative) rapidity or slowness to
the next maximum. De La Rue and his associates prefer to put
it that when the spot frequency has passed rapidly or slowly
from a minimum to the next maximum, it descends with corre-
sponding (relative) rapidity or slowness to the next minimum y.

Besides the irny-period Wolf finds another period 5 times as
long, and a third period 3 times the length of the second : in
other words, that the activity of the Sun goes through a further
series of changes every 55^y and i66y. He fancies that in
adjacent or nearly adjacent ny-periods of unequal length, a
greater activity during the shorter tends to compensate, in the
total number of spots produced, for a less energy in the longer.
The earlier observations are necessarily very imperfect z.

Schwabe's original period was ioy: but the ii-ny-period is

* Herschel, Outlines of Ast., p. 253. z Mem. Soc. Phil, de Berne, 1852.

y Month. Not., vol. xxxii. p. 177. Feb. The Table for 1749-1860 is given in

1872. Month. .AW., vol. xxi. p. 77. Jan. 1861.

CHAP. I.] The Sun. 35

now considered preferable ; even Schwabe himself assented to
it a, and the investigations of Hansteen and others have shown
that it is also the average period of the variation in the magnetic
declination.

The examination by Fritsch of a large number of auroral
observations enabled him to extend to auroral displays also the
56y-period, as preferable to the 65y-period proposed by Olmsted
without any reference to the spots.

Another supposed coincidence has now to be adverted to. By
carefully examining Schwabe's observations, Wolf thinks that
he has detected the existence of minor periods of spot-prevalence,
depending in some way upon the Earth, Venus, Jupiter, and
Saturn b. " Thus he finds a perceptibly greater degree of apparent
activity to prevail annually on the average of months of Sep-
tember to January than in the other months of the year ; and
again, by projecting all the results in a continuous curve, he
finds in it a series of small undulations succeeding each other at
an average interval of 7^65 months, or O'637y. Now the periodic
time of Venus (225*) reduced to the fraction of the year is 0-616,
a coincidence certainly near enough to warrant some considerable
suspicion of a physical connection c." It is proper to state that
Wolf does not appear to have made any use of Schwabe's obser-
vations taken subsequent to 1 848 d.

B. Stewart concurred in the opinion that Planetary influences
on the Sun can be traced, and he thinks that Jupiter and
Mercury, as well as Venus, are concerned. The general result as
to Venus is that spots have a tendency to break out at that
portion of the Sun which is nearest to Venus. "As the Sun
rotates carrying the newly-born spot farther away from this
planet, the spot grows larger, attaining its maximum at the
point farthest from Venus, and decreasing again on its approach-
ing this planet."

Doubts must be deemed to attach to the influence assigned to

a Ast. Nach., No. 1521, vol. Ixix. Ap. c Sir J. Herschel, Quart. Journ. Sc.,

3, 1865. vol. i. p. 238. April 1864.

b Month. Not., vol. xix. p. 86. Jan. d Miltheilungen, No. 10.

1859.

D 2

3(5 The S'ni <in<l Planet*. [BOOK I.

Jupiter and Saturn. As Jupiter's period (i r8y) is nearly identical
with the Sun-spot period, it has even been suggested that the
prevalence of Sun-spots depends mainly on influence exerted by
Jupiter in different parts of its orbit, in perihelion or aphelion,
as the case may be, but the notion seems open to question for
several reasons.

Schwabe was disposed to find a connection between Sun-spots
and meteoric showers. There is something of a coincidence
between three Sun-spot periods and one shower period, but it is
no doubt accidental e.

Sir W. Herschel, considering that the prevalence of numerous
spots on the Sun's disc was an indication that probably violent
chemical action (with the extrication of an unusual amount
of light and heat) was going on, was led to think that years of
abundant spots would also be noted for high temperatures and
good harvests, and years of few spots for low temperatures and
bad harvests f. Wolf finds decisive evidence " that years rich in
solar spots are in general drier and more fruitful than those of
an opposite character, while the latter are wetter and stormier
than the former &." This idea is supported by meteorological facts
collected by an examination of the chronicles of Zurich from
1000 to 1800 A.D. Gautier, from a discussion of 62 sets of
observations, extending over i iy, and taken at various places in
Europe and America, arrived at exactly the opposite conclusion h.
A note of Arago's is highly appropriate here ; " In these matters
we must be careful not to generalise until we have amassed a
large number of observations."

The general question of the influence of the Sun on the meteoro-
logy of the Earth is a large and complex one, and it has re-
ceived very little attention. I propose now to state what is at
present known on this subject, though this will scarcely serve
any more definite purpose than that of awakening a desire for
further knowledge.

Some relationship certainly seems to subsist between solar

6 Month. Not., vol. xxvii. p. 286. June g Mitlheilungen,'&o. 10.

1867. b Sibl. Univ. de Oentve, vol. li. p. 56.

' PAH. Trans., vol. xci. p. 316. 1801. 1844.

CHAP. I.] , The Sun. 37

spots and terrestrial cloudiness and rainfall. Baxendell considered
that diversities of solar activity are to be regarded as causing
changes in the magnetic condition of the Earth, and so producing
changes in the directions and velocities of the great currents of
the atmosphere and in the distribution of barometric pressure,
temperature, and rainfall. "The future progress of meteorology
must depend to a much greater extent than has been generally
supposed, upon the knowledge we may obtain of the nature and
extent of the changes which are constantly taking place on the
surface of the Sun'."

M. Poey. from an elaborate catalogue of tropical storms, going
back as far as i75°> finds evidence of 12 storm cycles indicated
by 12 epochs of frequent and severe storms: 10 of these epochs
of maximum atmospheric disturbance correspond to maxima of
Sun-spots. With respect to epochs of minima the coincidences
are less noticeable; for in ir storm minima only 5 coincidences
with Sun-spot minima are to be traced. M. Poey notes that
years marked by storm maxima generally follow by one or two
years the years of Sun-spot maxima k.

A Canadian observer, Mr. A. Elvins, affirms that years in which
maxima and minima of Sun-spots occur, are distinguished by
general cloudiness, intermediate years being apparently much
more free from clouds. He further states that records of the
height of the water in Lake Ontario extending over 18 years
indicate that a relation subsists between the changes in the Sun's
surface and the height of the said water. This latter element is
to be viewed of course as indicative of the amount of precipita-
tion that has taken place. Mr. Elvins's general conclusions are
that years of maxima and minima of Sun-spots are years of small
rainfall and low temperature. He considers, however, that the
year immediately preceding a maximum or minimum is usually
a specially wet year. If future observations should confirm these
ideas, it will (among other things) follow that the rainfall curve

' See the statistics on which this is p. 249. Feb. 1873.

based in Proc. Lit. and Phil. Soc. of k Comptes Rendut, vol. Ixxvii. p. 1226.

Manchester, vol. xi. p. in. They are 1873.
summarised in Month. Not., vol. xxxiii.

38 The Sun and Planets. [BOOK I.

is more abrupt than the Sun-spot curve. As regards there being
a cycle for storms, Elvins confirms Poey l.

Some investigations by an American meteorologist named
Brocklesby, of observations extending over 60 years, have led
him to consider that in 3 cases out of 5, years of maximum spot
energy are years of excess of rainfall ; years of minimum spot
energy to the number of 5 being, on the other hand, years notice-
able in every case for deficiency of rainfall. He thinks that his
inquiries justify the general deduction that "the rainfall tends to
rise above the mean when the Sun-spot area is in excess, and to
fall below when there is a deficiency of solar activity"1."

Professor C. P. Smyth is amongst those who have paid much
attention to the subject of Sun-spot cycles and terrestrial tem-
peratures. He considers that a great wave of heat passes over
the Earth "every n years and a fraction, and nearly coincidently
with the beginning of the increase of each Sun-spot cycle of the same
1 1 -year duration. The last observed occurrences of such heat-wave
(which is very short-lived, and of a totally different shape from
the" Sun-spot curve), were in 1834*8, 1846-4, 1857-8, 1 868-8, whence,
allowing for the greater uncertainty in the earlier observation, we
may expect," he said, writing in 1872, " the next occurrence of the
phenomenon in or about 1 880-0." Somewhat less pronounced
than the foregoing is the extreme cold close on either side of the great
heat-wave. Professor Smyth further said in 1872: "We may
perhaps be justified in concluding that the minimum temperature
of the present cold wave was reached in 1871-1, and that the
next similar cold wave will occur in 1878-8." Finally, between
the dates of these 2 cold- waves there are 3 "moderate" and nearly
equi-distant heat-waves, with their 2 intervening and " very
moderate " cold-waves n. Prince, however (a very experienced
meteorologist as well as astronomer), says that he does not
believe in any weather cycles whatever, though he admits that
"a very cold wave was present in 1879," and that "1880 was
above the average," and so in a measure confirms Smyth.

1 Ast. Register, vol. x. pp. 171, 221, p. 447. Dec. 1874.

and 265. 1872. » Nature, vol. v. p. 317. Feb. 22, 1872.

m Sillimuris Journal, 3rd Ser., vol. viii.

CHAP. I.]

The Sun.

Stone0, making use of observations at the Cape of Good Hope,
extending over 30 years, and Abbe p, of observations at Munich
extending over 60 years, have both traced a connection between
the Sun-spot period and terrestrial temperatures. Stone's con-
clusion, based upon a comparison of curves, is thus expressed by
himself: — " I cannot but believe that the same cause which leads
to an excess of mean annual temperature leads equally to a dissi-
pation of solar spots." Abbe's conclusion is that there is "a
decrease in the amount of heat received from the Sun during the
prevalence of the spots." Observations at Oxford (1864-70) show

Fig. 20.

CHANGE OF FORM IN SPOTS OWING TO THE S0N*S BOTATION.

that the mean azimuthal direction of the wind there varied year
by year through a range of 58° on the whole, between maximum
and minimum of Sun-spots, the tendency of the wind to a west-
ward direction increasing with the increase of the spots.

The only other observation which it appears necessary to cite
here is by Ballot of Utrecht. He thinks he has established (by
means of thermometric observations made at Haarlem, Zwanen-
bourg, and Dantzig, during a great number of years) the fact that

0 Proc. Eoy. Soc., vol. xix. p. 391. 1871.

i* Silliman's Journal, and Ser., vol. 50. p. 345. Nov. 1870.

The Sun and Planets.

[BOOK I.

at each period of 27- 7d (that of the Sun's visual axial rotation)
there is in these localities a small elevation of temperature, and
a depression at the intermediate epochs.

Respecting the physical nature of the spots much uncertainty
exists. Up to a comparatively recent period the generally re-
ceived opinion, however, was that first enunciated by Professor
Wilson of Glasgow in 1779, as modified by Sir W. Herschel —
namely, that the Sun is surrounded by two atmospheres, of which
the outer one is luminous (thence usually termed, after Schroter,
the photosphere], and the inner one, nearest to the Sun's surface,

Fig. 21.

SPOT ON THE SUN MAY 5, 1854, SHOWING CYCLONIC ACTION.

non-luminous, and that the spots are rents or apertures in
these atmospheres through which we see the solid body of the
Sun, otherwise known to us as the "nucleus" of the spots. This
idea is supported by the fact that, when near either limb, the
spots are narrower (fore-shortened) than when seen directly in
the centre of the disc. The lower stratum is assumed to receive
some illumination from the photosphere, and thus to appear
penumbral; to occupy, in the matter of luminosity, a medium
position between the photosphere reflecting much light, and the
solid matter reflecting little, or, perhaps, none at all. The tern-

CHAP. I.]

The Sun.

porary removal-of both the strata, but more of the upper than of
the lower, he conceived to be effected by powerful- upward
atmospheric currents, the origin of which is unknown. All,
however, that now appears certain is that the nucleus of a spot
is lower than the penumbra, and that both are beneath the level

Fig. 22.

July 3-

June 30.

June 29.

July 8.

July 7. July 6.

July 5.

July 4.

LARGE SPOT ON THE SUN VISIBLE IN l886, AND SHOWING SUCCESSIVE
CHANGES OF FORM OWING TO THE SUN'S ROTATION.

of the Solar photosphere. Detached masses of luminous matter
are seen actually to cross a spot without producing any alteration
in it. It would seem also that the gases in the space occupied
by a spot are at an appreciably lower temperature than those in

The Sun and Planets.

[BOOK I.

the brighter parts of the Sun, — and this for the present represents
practically the sum of our actual knowledge. That movements
of a cyclonic character sometimes occur on the Sun, is sufficiently
shown by a well-known drawing made by Secchi on May 5, 1854,
of a spot in which a spiral motion is perfectly obvious. Above
these atmospheres it is strongly believed that a thin and gaseous
envelope exists, more nearly akin to what we understand by the
word '; atmosphere " as applied to the envelope which surrounds
the Earth ; and this supposition finds confirmation in the fact

Fig- 23.

A SPOT SEEN ON THE EDGE OF THE SUN EXHIBITING ITSELF AS A
DEPRESSION IN THE SUN'S SURFACE.

that the margin of the Sun's disc is in general less luminous
than the centre — a very obvious result on this hypothesis.

Fig. 22 is a rough sketch of a large spot on the Sun seen in
June and July, 1886, with the naked eye by various observers15.

Fig. 23 is a representation obtained by photography at Dehra-
Dun in India, in 1884, of a spot which, having arrived at the
limb of the Sun, exhibited itself as a depression in the Sun's
surface.

As regards the luminosity of the Sun's disc at the edge and at

P L'Astronomie, vol. v. p. 387, Oct. 1886.

CHAP. I.] ^ . The Sun. 43

the centre, Laplace gives the ratio at 30 to 48 ; Arago at 40 to
41. The latter figures very greatly underrate the inequality.
Secchi, taking the centre at i, said that the margin is only £rd
or jth as bright. He said that at times he found himself im-
peded in his investigations by a ruddiness in the light near the
limb. Vogel, the most recent, and, it may be added, the most
methodical investigator of this subject, obtained by a photo-
graphic expedient the following results ; taking the Sun's radius
at 12 and the brightness at the centre at 100, the brightness was
found to lessen thus :—

Centre = 100.

4 = 96-

8 = 77.

i<J = 51.

Edge = 13.

Zollner's investigations indicate that an average black umbra
of a Sun-spot is 4000 times as bright as an equal area of surface
on a full Moon. This conclusion is supported by the spectro-
scope, for even a very black umbra yields a spectrum exhibiting
all the details of full sunlight q.

Representing the general brightness of the Sun's disc by 1000,
according to Sir W. Herschel that of the penumbrse is 469 and of
the nuclei only 7. But it may well be doubted whether all
these evaluations are not too fictitiously precise, however
generally correct.

The chemical rays given out by different parts of the surface
of the Sun also appear to be of unequal power, but whether, like
the rays of light, they vary regularly from centre to edge, seems a
moot point.

As regards the rays of heat, these likewise are radiated more
from the centre than from the edges. The Polar regions, too, are
colder than the Equatorial, and Secchi has shown that the heat
radiated from the spots is less than that from the disc generally.
Sir J. Herschel believed one hemisphere to be hotter than the
other. That the luminous envelope of the Sun is an incandescent
gas, Arago's Polariscope experiment is held to prove r. Sir John

i Schellen, Spectrum Analysis, Eng. ed. p. 293.
r See his Pop. Ast., vol. i. p. 419.

44 The Sun and Planets. [BOOK I.

Herschel showed that Arago's experiments were by no means
conclusive, but spectroscopic observations have brought this
matter more within reach of demonstration.

Schwabe's observations seem to indicate that at epochs of
minimum spot-display the Sun's surface is more uniformly
bright than at other times ; that is to say, that there is less
absorption or enfeeblement of the Solar light towards the
margin of the Sun's disc than is usually the case.

Spots on the Sun seem to have been discovered by J.
Fabricius8 and Galileo, independently, early in 1611, and by
Harriot, also independently, in December of the same year. It
will readily be understood that the observation of them was one
of the first discoveries resulting from the invention of the
telescope, though as spots large enough to be visible to the
naked eye are now and then visible, they were occasionally seen
before that event. Adelmus, a Benedictine monk, makes
mention of a black spot on the Sun on March 17, 807*. It is
also stated that a similar spot was seen by a Spanish Moor
named Averroes, in the year 1 161 u. An instance of a solar spot
is recorded by Hakluyt. He says, that in December 1590, the
good ship "Richard of Arundell" was on a voyage to the coast
of Guinea, and that her log states that " on the 7 at the going
downe of the sunne, we saw a great blacke spot in the sunne,
and the 8 day, both at rising and setting, we saw the like,
which spot to our seeming was about the bignesse of a shilling,
being in 5 degrees of latitude, and still there came a great
billow out of the southerboardx." The spot was also observed
on the 1 6th.

The natural purity of the Sun seems to have been an article of
faith with the ancients, on no account to be called in question ;
so that we find that when Schemer (who was a Jesuit at
Ingolstadt) reported to his Superior what he had seen, the idea

8 An interesting account of Fabricius's n Commentary on the Almagest, quoted

first observations of a spot on the Sun by Copernicus, De Stvol. Orb. Cel.,

will be found in Guillemin's Sun, p. 127, lib. x.

Eng. Ed. * The Principal Navigations, Voiages,

* Bede ; Polydorus Vergilius, Anglicce Traffiques, and Discoveries of the English

Hi*tori(K. Nation, rf-c.,vol. ii. p. 131. London, 1599.

CHAP. I.]

The Sun.

was treated as a delusion. " I have read," replied the Superior,
"Aristotle's writings from end to end many times, and I can
assure you that I have nowhere found anything in them similar
to what you mention. Go, my son, tranquillise yourself; be
assured that what you take for spots in the Sun are the fault of
the glasses or of your own eyes." Scheiner in the end, though
permitted to publish his opinions7, was obliged to do so anony-
mously, so great were the difficulties with which he had to
contend as a member of the Church of Rome desiring to cultivate

science.

Fig. 24.

FACUL.S: ON THE SUN, DEC. 3, 1865. (Tacckini.)

In addition to spots, streaks of light may frequently be re-
marked upon the surface of the Sun towards the equatorial
margin of the disc. These are termed f acute*, and are generally
found near spots (just outside the penumbrae) or where spots
have previously existed or are soon about to appear; when
near the limb of the Sun they are more or less parallel to it.
They are of irregular form, and may be likened somewhat to
certain kinds of coral, and are more luminous than the solar

y In 3 letters addressed to Welser,
chief magistrate at Augsburg. Printed
copies of these letters were sent to
Galileo and others. Schreiner's well-
known Rosa Ursina, &c. was of later
date (1630). Alluding to this enormous
book, Delambre says : " There are few

books so diffuse and so void of facts. It
contains 784 pages ; there is not matter
in it for 50 pages." — Hist. Ast. Mod.,
vol. i. p. 690. Either printing must have
been cheap or authors rich in those
days.

1 Latin facula, a torch.

46 The Sun and Planets. [BOOK I.

surface surrounding them. Secchi considered them to be not
brighter than the centre of the Sun. They are elevations or ridges
in the photosphere, as is proved by Dawes having seen one pro-
ject above the limb in turning the (apparent) corner into the in-
visible hemisphere3, and they have been seen on photographs
projecting like a tooth from the limb. Sir W. Herschel saw a
facula on December 27, 1 799, 2' 46" or 74,000 miles longb. Faculse
are first alluded to by Galileo in his third letter to Welserc.

Prominences give gaseous, i. e. bright line spectra ; faculse con-
tinuous spectra. Faculse are seen in high latitudes much more
frequently than spots are.

Short, the optician, seems to have noticed during the eclipse
of July 14, 1748 (o. s.), that the surface of the Sun was
covered with irregular specks of light, presenting a mottled
appearance not unlike that of the skin of an orange, but rela-
tively much less coarse. The term lucr.HA has been applied to
the constituent specks. This may perhaps only be an allusion,
and the first recorded, to the " granulations " recognised in
modern times.

Schwabe found that faculge and luculi are usually absent at
epochs of spot minima e.

Of late years the Sun has received an unusual amount of
attention from astronomers, and many interesting facts have
been brought to light concerning its physical appearance f . In
1 860 Nasmyth with his great reflector (alluded to hereafter) ascer-
tained, it would seem for the first time, that the Sun's surface
is covered with a tolerably compact agglomeration of entities,
which he likened to willow leaves ; that is to say, they presented
to his eye an appearance similar to that which a rather thin but
flattened layer of willow leaves might be expected to exhibit.

As an acrimonious controversy arose in regard to this alleged
discovery, it may be fair to lay before the reader Nasmyth's own
statement on the subject.

* Month. JVo£.,vol.xx. p. 56. 000.1859. ''Month. Not., vol. xxvii. p. 286.

b Phil. Trans., vol. xci. p. 284. 1801. June 1867.

c Istoria e Dimottrazioni intorno alle f See especially a paper by the Rev.

Mncchie Solan, p. 131. Rome, 1613. S. J. Perry in Aat. Reg., vol. xxii. p. 257.

d Latin lucus, a shining. Nov. 1884.

CHAP. I.] „ The Sun. 47

" In order to obtain a satisfactory view of these remarkable objects, it is not only
requisite to employ a telescope of very considerable power and perfection of denning
capability, but also to make the observation at a time when the atmosphere is nearly
quite tranquil, and free from those vibrations which so frequently interpose most

SPOT ON THE SUN, JULY 29, l86d, SHOWING THE " WILLOW-LEAF "

STRUCTURE. (Nasmyth.)

provoking interruptions to the efforts of the observer ; without such conditions as I
allude to, it is hopeless to catch even a glimpse of these remarkable and delicate
details of the solar surface.

**********

"The filaments in question are seen, and appear well defined, at the edges of the
luminous surface, where it overhangs ' the penumbra,' as also in the details of the
penumbra itself, and most especially are they seen clearly defined in the details of
' the bridges/ as I term those bright streaks which are so frequently seen stretching
across from side to side over the dark part of the spot. So far as I have as yet had
an opportunity of estimating their actual magnitude, their average length appears to
be about 1000 miles, the width about 100.

' ' There appears no definite or symmetrical arrangement in the manner in which
they are scattered over the surface of the Sun ; they appear to be across each other
in all possible variety of directions. The thickness of the layer does not appear to be
very deep, as I can see down through the interstices which are left here and there

The Sun and Planets.

[BOOK I.

between them, and through which the dark or penumbral stratum is rendered visible.
It is the occurrence of the infinite number of these interstices, and the consequent
visibility of a corresponding portion of the dark or penumbral stratum, that gives to
the general solar surface that peculiar and well-known mottled appearance which has
for a long time been familiar to the observers of the Sun.

" When a solar spot is mending up, as was the case with the one represented,
these luminous filaments or willow-leaf-shaped objects (as I term them) are seen to

Fig. 26.

SPOT ON THE SUN, JANUARY 2O, 1865.

pass from the edges and extend across the spots, thus forming ' the bridges,' or
bright streaks across the spots ; if these are carefully observed under favourable
conditions, the actual form of these remarkable details, of which ' the bridges ' are
composed, will be revealed to sight.

" Subsequent observations and considerations of the subject have not caused me
to desire to modify or alter the description in the letter above referred to e ; but only
to confirm me in its general correctness. I have no desire to embark in any
controversy on the subject, as I prefer to leave to the Sun itself, when carefully
observed by adequate means and on favourable occasions, the complete confirmation
of what I claim to be the first to discover, delineate, and accurately describe in
reference to the structure of his entire luminous surface, as well as the precise form

g Month Not., vol. xxiv. p. 66. Jan. 1864.

CHAP. I.] The Sun. 49

of the structural details, which, from their general similitude in respect to form, I at
once compared with willow leaves h."

Nasmyth's views were much canvassed. Several eminent
observers of unquestioned good faith, and possessed of first-class
instruments and great experience, declared the alleged conforma-
tion of the solar surface a myth, whilst others, equally entitled
to be heard with respect, avouched their belief -in the reality of
the discovery. I believe it to be an impartial summing up of the
whole case pro and con to say that there is a very general agree-
ment that innumerable detached (?) masses of unknown nature
are scattered over the Sun's surface, and that whether " willow
leaves," "rice grains," "granulations," or "shingle beach" be
employed to designate them, is rather a matter of taste than
evidence of substantial variance. Further, that in the main they
do partake of an elliptic outline, and that the average ratio of
the axes, whether it be 10 to i, as Nasmyth first had it, or 4, 3,
or 2 to i, as other observers have since stated it, is, after all, the
main point concerning which issue is joined, and even here
apparent discrepancies may be ascribable to actual physical
change in the bodies themselves.

Writing from Greenwich under date of February 25, 1864,
Stone made the following remarks : —

" At the first good opportunity I turned the telescope on the Sun. I may state
that my impression was, and it appears to have

been the impression of several of the assistants here, Fig. 27.

that the willow leaves stood out dark against the
luminous photosphere. On looking at the Sun I
was at once struck with the apparent resolvability
of its mottled appearance. The whole disc, as far
as I examined, appeared to be covered over with
relatively bright rice-like particles, and the mottled
appearance seemed to be produced by the inter-
lacing of these particles. I could not observe any
particular arrangement of the particles, but they
appeared to be more numerous in some parts than
in others. 1 have used the words rice-like particles „ RICE.LIKE » PARTICLES SEEN
merely to convey a rough impression of their form ; QN THE SUN (Stone.)

I consider them like the figure.

h The preceding paragraphs are taken himself, with a brief supplementary note
from a letter reproduced by Nasmyth appended.

50 The S'u, «i«l Mntctx. [BOOK I.

•' 1 have seen these rice-like particles on two occasions since, but not so well as on
the first day, when the definition was exceedingly good. Yesterday (Feb. 24) I saw
them for a few minutes, but with great difficulty. I use the full aperture, 12 J
inches, and a low power. On the first day I saw them [end of January 1864] I
called Mr. Dunkin's attention to them. He appears to have seen them, and
considers the figure above to represent them fairly. He says, however, that he
should not have noticed them if his attention had not been called to them '."

A valuable synopsis of the question was presented to the Eoyal
Astronomical Society in 1866 by Hugginsk. The following is
a brief summary of its contents : —

1. Grannie is the best word to describe the luminous particles
on the Sun's surface, as no positive form is thereby implied.

2. The granules are seen all over the Sun, including (occasion-
ally) the surfaces of umbrae and penumbne. More rarely they
can be detected in faculse.

3. With low powers " rice grains " is a very suitable expres-
sion for these granules, but the regularity implied in this
designation disappears to a great extent under high magnifiers.
There is, however, undoubtedly, a general tendency to an oval
contour.

4. The average size of the more compact granules is i", of
those more elongated \\", a few might be 3", many less than i".
They appear to be not flat discs, but bodies of considerable
thickness.

5. The granules are sometimes packed together rather closely
in groups of irregular and straggling outline ; at other times they
are sparsely scattered. The well-known "mottling" arises
wholly from the latter species of combination.

6. The Sun's surface is by no means uniformly level The
whole photosphere appears corrugated into irregular ridges and
vales, and the granules are possibly masses of rather dense cloud-
like matter floating about in the photosphere, considered as
composed of more aeriform matter. If the granules really are
incandescent clouds, their general oval form may be due to the
influence of currents.

1 Proceedings of Manchester Lit. and k Month. Not., vol. xxvi. p. 260. May

Philos. Soc., vol. iii. p. 250, 1864. 1866.

CHAP. L]

The Sun.

The accompanying figure [28] shows some of the most charac-
teristic modes of grouping of the bright granules noticed by
Huggins on different occasions and on various parts of the
Sun's surface, brought together, however, in one woodcut for
convenience of comparison.

Fig. 28.

IDEAL VIEW OF THE "GRANULAR" STRUCTURE OF THE SUN. (HttffffinS.)

Huggins has called attention to the fact that Janssen's photo-
graphs of 1877 disclose, amongst other important features, a
frequent tendency of the granules to arrange themselves in a
spiral form, accompanied by more or less loss of distinctness of
outline of the individual granules. The same observer has put
on record the fact that a similar appearance was noticed by
himself as long ago as 1866 : —

K" 2

The Sun and Planets.

[BOOK I.

" Saw distinctly the granules. A spiral band of closely associated granules,
ending in one of larger size [fig. 26]. In one area near the centre of the Sun's disks
the granules appeared more elongated than usual [fig. 30], rather sparsely scattered,
and the larger diameters very nearly in the same direction. In neighbouring area,
the granules smaller and less elongated. Amongst these no general direction was
observed '."

Fig. 29.

Fig. SO-

GKAKDLES 1 866, SHOWING CYCLONIC
ARRANGEMENT.

SOLAR GRANULES 1866, SHOWING

ORDINARY ARRANGEMENT.

(Hugging.)

The present state of our knowledge respecting the physical
constitution of the Sun, stated as shortly as possible, is, that
the central solid or gaseous body of the Sun is surrounded by a
series of concentric envelopes, the order of which reckoning out-
wards is as follows : —

(1) The photosphere, the visible source of the solar light which
reaches the Earth, defined by Young as a " shell of luminous
clouds formed by the cooling and condensation of the conden-
sible vapours at the surface where exposed to the cold of outer
space."

(2) The chromosphere, a thin casing of self-luminous gaseous
matter, chiefly hydrogen gas in an incandescent state, and the
seat of the solar prominences (formerly known as the " red flames "
and seen only during total eclipses of the Sun until Lockyer and
Janssen independently in 1868 conceived the idea that they
might be rendered visible irrespective of the Sun being eclipsed).

1 Month. Not., vol. xxxviii. p. 102. Jan. 1878.

CHAP. I.] The Sun. 53

(3) The corona, a vast shell of unknown vapours in a highly
attenuated state, many thousands of miles thick, and oberved to
extend to at least £° from what is ordinarily taken to be the
visible edge of the Sun.

Tacchini arrived at the following general ideas from obser-
vations made by him on 281 days during 1880.

As to the distribution of solar phenomena over the Sun's
surface : The spots remain near the equator and present two
maxima between the parallels 10° and 20° on either side. At the
equator they are rare, or wholly absent. Faculse always occur
at the equator ; they show maxima between + 20° and + 30°, and
come nearer the poles than the spots. Protuberances are rare
near the equator ; they present two principal maxima between
+ 50° and + 60°, and two secondary ones in the latitudes of the
faculae maxima. They reach further from the equator than the
facutee, but the polar caps remain free of them. Of the two
hemispheres the northern showed, during 1880, the greater
activity.

To the cloudy stratum giving rise to the penumbrae Petit assigns
a depth exceeding 4000 miles. On the other hand, Phillips con-
sidered 300 miles a probable amount. Neither estimate is primd
facie entitled to much consideration.

_ Sir W. Herschel supposed that one of the hemispheres of the Sun
is by its physical constitution less adapted to emit light and heat
than the other, but the grounds of this conclusion are not known.

The study of the Sun has during the last few years taken a
remarkable start, owing to the fact that by the aid of the spec-
troscope we have been enabled to obtain much new information
about its physical constitution. This subject being, however, a
physical rather than an astronomical one, and involving a great
amount of chemical and optical detail, it cannot conveniently be
discussed at length in a purely astronomical treatise, though some-
thing will be said concerning it later on in the portion of this
work dedicated to spectroscopic matters.

54 The Sun and Planet*. [BOOK I.

CHAPTER II.

THE PLANETS.

Epitome of the motions of the Planets. — Characteristics common to them all.- —
Kepler s laws. — Elements of a Planet's orbit. — Curious relation between the
distances and the periods of the Planets. — The Ellipse. — Popular illustration
of the extent of the Solar system. — TfwJe's law. — Miscellaneous characteristic*
of the Planets.— Curious coincidences. — Conjunctions of the Planets. — Conjunc-
tions recorded in History. — Different systems. — The Ptolemaic system. —
The Egyptian system. — The Copernican system. — The Tychonic system.

A ROUND the Sun, as a centre, certain bodies called Planets8
•*"•" revolve at greater or less distances11. They may be
divided into two groups, (i) the "inferior" planets, or those
whose orbits are within that of the Earth, namely Vulcan (?).
Mercury, and Venus; and (2) the "superior" planets, or those
whose orbits are beyond that of the Earth, namely Mars, the
Minor Planets, Jupiter, Saturn. Uranus, and Neptune.

If viewed from the Sun all the planets would appear to the
spectator to revolve round that luminary in the order of the
zodiacal signs ; such, however, cannot be the case when the
observation is made from one of their number itself in motion,
and therefore to us on the Earth the planets appear to travel in
a capricious manner; and, further, the inferior and superior
planets differ the one class from the other in their visible
movements.

The Inferior planets are never seen in those parts of the
heavens which are in Opposition to the Sun ; in other words.

" ir\avriTT)s, a wanderer. reckoned in all cases from the centre of

" The distances of the planets are the Snn. and not from its surface.

CHAP. II ] The Planets. 55

they are never on the meridian at midnight, being always
within a short angular distance of the Sun, to the E. or W. of it
as the case may be. Twice in every revolution an inferior
planet is in Con junction with the Sun [Fig. 31]; in Inferior
Conjunction when it conies between the Earth and the Sun, and
in Superior Conjunction when the Sun intervenes between the
Earth and the planet. When it attains its greatest distance (as
we see it) from the Sun, E. or W., it is said to be at its Greatest
Elongation, E. or W., as the case may be. In the former case the
planet is an "evening star," in the latter a "morning star."

Inferior 6 .
PHASES OF AN " INFERIOR" PLANET.

Although a planet always truly moves in the order of the
signs, yet there are periods when it appears stationary ; sometimes
even periods when its motion appears retrograde or reversed.
These peculiarities are owing to the fact that the Earth has
simultaneously a motion of its own in its orbit ; and it will
readily be understood that they are only apparent and not real.
They also obtain with the superior planets. It sometimes
(though very rarely) happens that an inferior planet, when
in Inferior Conj unction, passes directly between the Earth and
the Sun, and is consequently projected on the disc of the latter,
which it crosses from E. to W. : this phenomenon is termed a
transit*. Transits will be considered more particularly in Book

Trattflre, to gr> across.

The Sun and Planets.

[BOOK I.

A superior planet can have any angular distance from the
Sun not greater than 180°. After starting from Conjunction
with the Sun it successively reaches its Eastern Quadrature (at
an angular distance of 90°) ; and its Opposition at 180°. Pro-
ceeding onwards it comes to its Western Quadrature, 270° from

APPARENT MOVEMENTS OP MERCURY BETWEEN IfoS AND 1715.

the Sun reckoned in the direction of its motion, but only 90°
reckoned in the other direction. Another stage of 90° brings it
again into Conjunction. A planet cannot have a greater angular
distance from the Sun than 180°, because when that is attained
it begins to approach the Sun again on the other side, for an
obvious geometrical reason.

An exhaustive account of the motions of the planets does not
fall within my scope, but the books named in the note may

CHAP. II.] The Planets. 57

be consulted*1. How complicated these motions are will be
readily understood by an inspection of Fig. 32, which represents
the apparent movements of Mercury amongst the stars between
the years 1708 and 1715.

There are certain characteristics common to all the planets,
which are thus enunciated by Hind : —

1. They move in the same invariable direction round the Sun;
their course, as viewed from the north side of the ecliptic, being con-
trary to the motion of the hands of a watch.

2. They describe oval or elliptical paths rQund the Sun, not however
differing greatly from circles.

3. Their orbits are more or less inclined to the ecliptic, and inter-
sect it in two points, which are the " nodes;" one half of the orbit lying
north, and the other half south of the Earth's path.

4. They are opaque bodies like the Earth; and shine by reflecting
the light which they receive from the Sun.

5. They revolve upon their axes in the same way as the Earth.
This we know by telescopic observation to be the case with many
planets, and, by analogy, the rule may be extended to all. Hence they
will have the alternation of day and night, like the inhabitants of
the Earth ; but their days are of different lengths to our own.

6. Agreeably to the principles of gravitation, their velocity is
greatest at those parts of their orbit which lie nearest the Sun, and
least at the opposite parts which are most distant from it ; in other
words, they move quickest in perihelion*, and slowest in aphelion*.

From a long series of observations of the planet Mars, Kepler
found that certain definite laws might be deduced relative to the
motions of the planets, which may be thus stated : —

T. The planets move in ellipses, having the Sun in one of the foci.

2. The radius vector of each planet describes equal areas in equal
times.

d Sir J. Herschel's Outlines of Ast., greater eccentricity of cometary orbits :

p. 301 et seq. ; Hind's Introd. to Ast., thus the velocity of Donati's comet at

p. 63 et seq. (very good). perihelion is 127,000 miles per hour,

e *€pl round, and T/AJOS the Sun. but at aphelion only 480 miles per

' dwo from, and ^\tos. The fact here hour.— (Hind, Letter in the Times, Oct.

referred to is more strikingly manifest 25, 1858.)
in the case of a comet, owing to the

58 The Sun and Planets. [BOOK i.

3. The squares of ike periodic titties of the planets are proportional
to the cubes of their wean distances from the Sun.

These laws hold good for all the planets and all their satellites.
I have already referred in general terms to the Ist law ; it may,
however, be desirable to say that the orbit of a planet with re-
ference to its form, magnitude, and position, is determined by
the 5 following data or elements : —

1. The longitude of perihelion, or the longitude of the planet,
when it reaches this point, — denoted by the symbol 77.

2. The longitude of the ascending node of the planet's orbit, as
seen from the Sun. — S3 .

33-

DIAGRAM ILLUSTRATING KEPLKR'.S SECOND L.V\V.

3. The inclination of the orbit, or the angle made by the plane of
the orbit with the ecliptic. — i.

4. The eccentricity. — e. This is sometimes expressed by the
angle <£, of which e is the natural sine.

5. The semi-axis-major, or mean distance. — a.

And in order to compute the place of a planet at any given
moment, we further need to know : —

6. Its periodic time (obtainable from (5) by Keplei's 3rd law) ;
and : —

7. Its mean longitude, or place in its orbit, at a given epoch.
Kepler's 2nd law will readily be understood from the annexed

diagram. Let P P2 P4 be the elliptic path of a planet, and let it
move from P to P1, from Pz to P3, and from P4 to P'"' in equal

CHAP. II.]

Tin'

intervals of time ; then the 3 shaded areas, which are assumed to
correspond with the movement of the radius vector, will all be
equal in area

The 3rd law involves a curious coincidence, which may be thus
expressed : — If the squares of the periodic times of the planets be
divided ly the cubes of their mean distances from the Sim, the
quotients thus oltained are the same for all the planets. The follow-
ing table exemplifies this: it should be remarked, however, that
the want of exact uniformity in the fourth column 8 is owing to
inexactness in the observations on which the calculations are
based, as also to the perturbations which the planets mutually
exercise on each other's orbits : —

Planot.

i>"
a»

Vulcan '

O-I41

10*7

I 32716

Mercury
Venus

. ... 0-38710
0-723^3

87.969
224-701

J3.M-21
133413

Earth

I -OOOOO

^65-2^6

i 33408

Mars . .

1-52369

686-970

133410

Ceres . . .

2-77602

1670-8^^

132210

Jupiter .

v 20277

4332 58=1

133294

Saturn
Uranus

9-53858
19-18239

10759 220
30686-821

133375
133422

Neptune . ....

30-03627

60126-722

i334'3

This law also holds good for the satellites11, as will be seen
from the following tables calculated for the purpose of exempli-
fying it.

THE SATELLITES OF MARS.

Name.

«=>

De:mos

2-50

0-319

736II

Phoboa 6-00

1-262

73733

' The decimal pointing is neglected in
all cases in the 4th column, that the eye-
appreciation of the coincidences may not
be interfered with.

h This is not rigorotisly true when the
mass of the primary has an appreciable
ratio to that of the Sun.

The Sun and Planets.

THE SATELLITES OF SATURN.

[BOOK I.

Name.

Mimas

3-36

0-94

23295

Enceladus

. 4-31

i-37

23443

Tethys

5-34

1-89

23458

Dione

6-84.

2. *!A

2^460

Rhea

Q.CC

A.S.2

21457

Titan

22-14.

I VQ^

23442

Hyperion

26-86

21-30

23412

lapetus

64-54

79-33

23409

THE SATELLITES OF JUPITER.

No.

P2
0»

6-05

1.77

14147

II.

9-62

3-55

14156

III.

15-35

7-I5

14135

IV.

26-99

16-69

14168

THE SATELLITES OF URANUS.

No.

p '

p2
a»

6-94

2-51

18848

II.

9-72

4-14

18664

III.

15-89

8-70

18909

IV.

21-27

13.46

18827

Kepler's laws are the foundation of all planetary astronomy,
and it was from them that Newton deduced his theory of
gravitation. Arago says : " These interesting laws, tested for
every planet, have been found so perfectly exact, that we do not
hesitate to infer the distances of the planets from the Sun from
the duration of their sidereal revolutions ; and it is obvious that
this method of estimating distances possesses considerable ad-

CHAP. II.]

The Planets.

Fig. 34-

vantages in point of exactness ; for it is always easy to determine
precisely the return of each planet to a point in the heavens,
while it is very difficult to determine exactly its distance from
the Sun."

Sir J. Herschel discussed the theoretical considerations con-
nected with these laws with great perspicuity; and the reader
will do well to consult his remarks1.

A few definitions as to the properties of an ellipse will here be
appropriate.

In Fig. 34, S and S' are the foci of the ellipse ; A C is the
major axis ; B D the minor or conjugate axis ; O the centre : or,
astronomically — O A is the
semi-axis-major or mean dis-
tance, O B the semi- axis -
minor ; the ratio of O S to
O A is the eccentricity ; the
least distance, S A, is the
perihelion distance ; the great-
est distance, S C, the aphe-
lion distance. SBO is the
angle <£ referred to on p. 58.
Where an eccentricity is
stated in the form of a vulgar

fraction, O S is the numerator and O A the denominator. A
decimal expression is to the like effect.

It will not be difficult to follow in the mind the additional
characteristics of a planetary orbit. The orbit in the figure is
laid down on a plane surface ; incline it slightly as compared to
some fixed plane ring and the element of the inclination (as
regards its amount) will present itself. (The astronomical fixed
plane in this case is that of the ecliptic.) Imagine a planet
following the inclined ellipse ; at some point it must rise above
the level of the fixed plane : the point at which it begins to do
so, measured angularly from some settled starting-point, gives
the longitude of the ascending node. Then the planet's position in
1 Outlines of Ast., pp. 322-7.

THE ELLIPSE.

Tlif Snn an<i

[BOOK I.

the ellipse when it comes closest to the principal focus, gives us,
when projected on the plane ring, the place of nearest approach to

the focus, in other words, the longitude of the perihelion. Follow-
ing these steps, it is not a matter of much difficulty to form a

CHAP. II.]

general conception of a planetary orbit in space, for though the
method is rather crude, it is so far strictly accurate.

The following scheme will assist the reader to obtain a fail-
notion of the magnitude of the planetary system. Choose a

64 The Sun and Planets. [BOOK I.

level field or open common ; on it place a globe 2 feet in
diameter, for the Sun ; Vulcan (?) will then be represented
by a small pin's head, at a distance of about 27 feet from the
centre of the ideal Sun ; Mercury by a mustard seed, at a
distance of 82 feet; Venus by a pea, at a distance of 142 feet;
the Earth also by a pea, at a distance of 215 feet; Mars by
a small pepper-corn, at a distance of 327 feet ; the minor planets
by grains of sand, at distances varying from 500 to 600 feet:
if space will permit, we may place a moderate-sized orange
nearly £ mile distant from the central point to represent Jupiter ;
a small orange £ of a mile for Saturn ; a full sized cherry | mile
distant for Uranus; and lastly a plum i£ miles off for
Neptune, the most distant planet yet known.

Extending this scheme, we should find that the aphelion
distance of Encke's Comet would be at 880 feet ; the aphelion
distance of Donati's Comet of 1858 at 6 miles; and the nearest
fixed star at 7500 miles.

According to this scale the daily motion of Vulcan (?) in its
orbit would be 4f feet ; of Mercury 3 feet ; of Venus 2 feet ;
of the Earth i| feet; of Mars i\ feet; of Jupiter 10^ inches;
of Saturn 7^ inches ; of Uranus 5 inches ; and of Neptune
4 inches. These figures illustrate also the fact that the orbital
velocity of a planet decreases as its distance from the Sun
increases.

Connected with the distances of the planets, Bode of Berlin in
1772 published the following singular 'law' of the numerical
relations existing between them, which, although not discovered
by him but by Titius of Wittemberg in 1766, usually bears his
name.

Take the numbers —

o 3 6 12 24 48 96 192 384;

each of which (the second excepted) is double the preceding;
adding to each of these numbers 4 we obtain

4 7 10 16 28 52 100 196 388;
which numbers approximately represent the distances of the

MARS. EAKTH

VENUS. MERCURY.

COMPARATIVE SIZES OF THE SUN AND PRINCIPAL PLANETS.

%* The diie on the left of the Sun's centre repretentt URANUS ;
and that on the right, XEPTUNE.

CHAP. II.]

The Planets.

planets from the Sun expressed in radii of the Earth's orbit, as
exhibited in the following table : —

Planets.

True Distance
from (^\

Distance by
Bode' a Law.

Mercury ...

3-87

4-OO

Venus . .

7'23

7-OO

Earth .. ..

IO-OO

Mars

15*23

16-00

Ceres . .

27-66

28-00

Jupiter ...

52-03

52-00

Saturn

05.30

IOO-OO

Uranus

Kii-Sa

106-00

Neptune

300-37

388-00

Bode having examined these relations, and noticing the void
between 16 and 52 (Ceres and the other minor planets not being
then known), ventured to predict the discovery of new planets ;
and it may reasonably be believed that this conjecture guided or
suggested the investigations of subsequent observers ; though some
have disputed this k. In the above table the greatest deviation
between the assumed and the true distance is in the case of
Neptune. We may sum up Bode's law as follows : — That the
interval between the orbits of any two planets is about twice as great
as the inferior interval, and only half the superior one 1.

Separating the major planets into two groups, if we take Mer-
cury, Venus, the Earth, and Mars as belonging to the interior ;
and Jupiter, Saturn, Uranus, and Neptune to the exterior group,
we shall find that they differ in the following respects : —

k As far back as 450 B.C. Democritus
of Abdera thought it probable that even-
tually new planets would, perhaps, be
discovered. (Seneca, Qucest. Nat.,\il>. vii.
cap. 3 and 13.) Kepler was of opinion
that some planets existed between the
orbits of Mars and Jupiter, but too small
to be visible to the naked eye. The same
philosopher conjectured that there was
another planet between Mercury and
Venus.

1 Many attempts have been made by
ingenious dabblers in Astronomy to dis-
cover other arithmetical coincidences
formed after the spirit of Bode's law.
The following is the only one I have met
with which deserves reproduction. Take
the series o, i, 2, 4, 8, 16, 32, and 64:
add 4 to each, and the resulting figures
represent with some approach to accuracy
the relative distances of the satellites of
Saturn from their primary.

68 The Sun and Planets. [BOOK I.

1. The interior planets, with the exception of the Earth and
Mars, are not, as far as we know, attended by satellites, while
the exterior planets all have satellites. We cannot but consider
this as one of the many instances to be met with in the universe
of the beneficence of the Creator — in other words, that the
satellites of these remote planets are designed to compensate for
the small amount of light which their primaries receive from the
Sun, owing to their great distance from that luminary.

2. The average density of the first group considerably exceeds
that of the second, the approximate ratio being 5:1.

3. The mean duration of the axial rotations, or mean length of
the day, of the interior planets is much longer than that of the
exterior m ; the average in the former case apparently being about
24h, but in the latter only ioh.

In the Appendix will be found a full tabular summary of
information concerning the Sun, Moon, and Planets brought
up to the latest possible date.

The following coincidences may or may not deserve to be
mentioned : —

1. Multiply the Earth's diameter (7912 miles) by 108, and we
get 854,496 = + the Sun's diameter in miles.

2. Multiply the Sun's diameter (852,584 miles) by 108, and
we get 92,079,072 = + the mean distance of the Earth from the
Sun.

3. Multiply the Moon's diameter (2160 miles) by 108, and
we get 233,280 = + the mean distance of the Moon from the
Earth.

A phenomenon of considerable interest, especially on account
of its rarity, is the conjunction, or proximity, of two or more
planets within a limited area of the heavens. A noticeable
instance is depicted in Fig. 38. It occurred on the morning of
July 21, 1859, when Venus and Jupiter came very close to each

m This can only be presented as a except the Earth and Mars. It may be

general conclusion the truth of which presumed, however, that size has more to

seems probable ; for it cannot be said do with this than distance from the Sun.

with any great confidence what are the (See a paper by Denning in the 06-

rotation periods of any of the planets gervatory, vol. vii. p. 40, Feb. 1884.)

CHAP. II.] The Planets. 69

other; at 3h 44™ A.M. the distance between the two planets
was only 1 3", and they accordingly appeared to the naked eye as
one object.

On Aug. 9, 1886, Venus, Saturn, and b Geminorum appeared
in the same field of the telescope.

During February, 1881, Venus, Jupiter, and Saturn were
all in the constellation Pisces, and within a few degrees of one
another.

In Sept. 1878, Mercury and Venus were together in the same

Fig. 38-

VENDS AND JUPITER, July 21, 1859.

field of the telescope for some hours. Venus looked like clean
silver ; Mercury more like lead or zinc, according to Nasmyth.

On Jan. 29, 1857, Jupiter, the Moon, and Venus were in a
straight line with one another, though not within telescopic
range.

On Dec. 19, 1845, Venus and Saturn appeared in the same
field of the telescope. [See Fig. 39.]

On Oct. 3, 1801, Venus, Jupiter, and the Moon were in close
proximity in Leo, and Saturn was not far off.

On Dec. 23, 1 769, Venus, Jupiter, and Mars were very close
to each other.

The Sun and Planets.

[BOOK I.

On March 17, 1725, Venus, Jupiter, Mars, and Mercury
appeared together in the same field of the telescope.

On Nov. n, 1544, Venus, Jupiter, Mercury, and Saturn were
enclosed in a space of 10°.

On Nov. n, 1524, Venus, Jupiter, Mars, and Saturn were very
close to each other, and Mercury was only 16° distant.

In the years 1507, 1511, 1552, 1564, 1568, 1620, 1624, 1664,
1669, 1709, and 1765, the three most brilliant planets — Venus,
Mars, and Jupiter — were very near each other.

Fig- 39-

VENDS AND SATURN, Dec. 19, 1845.

On Sept. 15, 1 1 86, Mercury, Venus, Mai's, Jupiter, and Saturn
were in conjunction between the Wheat-ear of Virgo and Libra.

The earliest record we possess of an occurrence of this kind
is of Chinese origin. It is stated that a conjunction of Mars,
Jupiter, Saturn, and Mercury, in the constellation S/ti, was
assumed as an epoch by the Emperor Chuen-hio, and it has been
found by MM. Desvignoles and Kirch that such a conjunction
actually did take place on Feb. 18, 24463.0., between 10° and 18°
of Pisces n. Another calculator, De Mailla, fixes upon Feb. 9,

n Bailly, Astron. Ancienne, p. 345. p. 166, and Kirch's in vol. v. p. 193 of
Desvignoles's original memoir appears the game series.
in Mem. de TAcad. de Berlin, vol. iii.

CHAP. II.]

The Planets.

2441 B.C., as the date of the conjunction in question ; and he
states that the four planets named above, and the Moon besides,
were comprised within an arc of 12°, extending from 15° to 27°
of Pisces. It deserves mention that both the foregoing dates
precede the usually received date of the Noachian deluge. It
may therefore only be that the planetary conjunction in question
was ascertained at some subsequent time.
De Mailla gives the following positions0: —

E.A.

12
21

47
ii

Fig. 40.

Mercury ... ... ... ... 344 56

Jupiter ... ... 347 2

The Moon ... 353 1 8

Saturn 354 39

Mars ... 356 45

A few general remarks on the different theories of the solar
system which have at various times been current will appro-
priately conclude this chapter.

The Ptolemaic system claims the first place in consequence of
its wide acceptance and the
fame of the astronomer
whose name it bears. It
would, however, be more
correct to say that Ptolemy
reduced it into shape rather
than that he actually origin-
ated it. The Earth was
regarded as the centre, and
around this the Moon ( D ),
Mercury ( $' ), Venus ( ? ),
The Sun (0), Mars (<?),
Jupiter ( 2/ ).and Saturn( fj ),
all called planets, were as-
sumed to revolve in the
order in which I have here given them.

More accurate ideas were, however, current even before

0 Hist. Gen. de la Chine, vol. i. p. 155.

THE PTOLEMAIC SYSTEM.

The Sun and Planets.

[BOOK I.

Fig. 41.

THE EGYPTIAN SYSTEM.

Ptolemy's time, but they found few supporters. Aristarchus
of Samos, who lived about 280 B.C., supposed, according to

Archimedes and Plutarch,
that the Earth revolved
round the Sun, for which
'heresy' he was accused
of impiety. Cleanthes of
Assos, who flourished but
20 years later, was, accord-
ing to Plutarch, the first
who sought to explain the
great phenomena of the
universe by supposing a
motion of translation on the
part of the Earth around
the Sun, together with one
of rotation on its own axis.

The historian relates that this idea was so novel and so con-
trary to the received no-
tions that it was proposed
to arraign Cleanthes also
for impiety.

The Egyptian system dif-
fered from the Ptolemaic
only in regarding Mercury
and Venus as satellites of
the Sun and not primary
planets.

A long period elapsed
before any new theories
of importance were started,
but in the i6th century

THE COPKRN1CAN SYSTEM. „ „,, . .

oi the Christian era Coper-

nicug came forward and propounded his theory, which ulti-
mately superseded all others, and is the one now (in substance)
adopted. It places the Sun in the centre of the system as the

Fig. 42.

CHAP. II]

The Planets.

point around which all the primary planets revolve It must not
be supposed, however, that the Polish astronomer attained to our
existing amount of knowledge on the subject. Far from it: his
ideas were defective in more than one important particular. In
order to account for the apparent irregularities in the motions
of the planets, as seen from the Earth, he upheld theories which
subsequent advances in the science showed to be unnecessary
and to rest on no substantial basis. Amongst other things he
retained the theory of Epicycles. The ancients considered that
the planetary motions must be effected uniformly and in circles,
because uniform motion appeared the most perfect kind of motion,
and a circle the most perfect and most noble kind of curve.
There is at any rate a reverential spirit in this idea which, not-
withstanding our enlightenment, we need not despise. Copernicus
announced his system in a treatise entitled De Revolutionibus Orbium
ccelegtium, the actual publication of which, in 1543, he only just
lived to see, for he died the same year ; for him this was perhaps
fortunate rather than otherwise, because the work was condemned
by the Papal ' Congregation of the Index.' Had it been possible
for the reverend gentlemen who formed that body to have got
the author within their clutches,
it is more than likely that he
would have suffered as well as
his book ; as did Galileo after
him.

Tycho Brahe was the last great
astronomer who ventured on any
original speculations in this field.
Influenced either by bond fide
scruples resulting from an erro-
neous interpretation of certain
passages in Holy Scripture, or
it may be. simply by a desire to
perpetuate his name, he chose to

regard the Earth as immoveable, and occupying the centre of the
system : the Moon as revolving immediately round the Earth :

THE TYCHONIC SYSTEM.

The Sun and Planets.

[BOOK I.

and, exterior to the Moon, the Sun doing the same thing — the
various planets revolving round the latter as solar satellites.

Kepler and Newton finally set matters right by perfecting
the Copernican system, and so negativing all the others ; yet
down to quite recent times there have survived on the part of
utterly ignorant people remnants of disbelief (real or professed)
in the Copernican system, but even the most cursory examination
of these remnants would be most unprofitable.

Fig- 44-

THE HOUSE AT WOOLSTHORPE, LINCOLNSHIRE, IN WHICH NEWTON WAS BORN,
SHOWING THE SUNDIALS HE MADE WHEN A BOY.

%* One of these dialt teas taken out of the wall about 1844,
and pretented to the Royal Society.

CHAP. III.] Vulcan. 75

CHAPTEE III.

VULCAN (?).

Le Terrier's investigation of the orbit of Mercury. — Narrative of the Discovery of
Vulcan. — Le Terrier's interview with M. Lescaroault. — Approximate elements of
Vulcan. — Concluding note by Le Verrier. — Observation* by Lummis at Man-
chester.— Instances of Sadies seen traversing the Sun. — Hind' s opinion. — Alleged
Intra-Mercurial planets discovered in America by Watson and Swift on July
29, 1878.

"OEFOE.E entering upon the story of the supposed discovery of
-*-^ a new planet to which this name has been given, a brief
prefatory statement seems necessary.

M. Le Verrier, having conducted an investigation into the
theory of the orbit of Mercury, was led to the conclusion that a
certain error in the assumed motion of the perihelion could only
be accounted for by supposing the mass of Venus to be at least
TV greater than was commonly imagined, or else that there
existed some unknown planet or planets, situated between
Mercury and the Sun, capable of producing a disturbing action.
In laying his views before the scientific world in the autumn
of 1859% Le Verrier suggested the latter theory as a probable
solution of the difficulty b.

On these views being made public, a certain M. Lescarbault,
a physician at Orgeres, in the Department of Eure-et-Loire.
France, came forward and stated that on March 26 in that year
(1859), ne nad observed the passage of an object across the Sun's

* Compt. Rend., vol. xlix. p. 379. in detail by Newcomb in Astron. Papers
1859. for use of Amer. Naut. Almanack, vol. i.

b Objections to this theory are stated p. 474. Washington, 1882.

76 The Sun and Planets, [BOOK I.

disc which he thought might be a new planet, but which he
did not like to announce as such until he had obtained a con-
firmatory observation ; he related in writing the details of his
observation, and Le Verrier determined to seek a personal
interview with him.

The following account of the meeting will be read with
interest.

" On calling at the residence of the modest and unobtrusive medical practitioner,
he refused to say who he was, but in the most abrupt manner, and in the most
authoritative tone, began, ' It is then you, Sir, who pretend to have observed the
intra- Mercurial planet, and who have committed the grave offence of keeping your
observation secret for nine months. I warn you that I have come here with the
intention of doing justice to your pretensions, and of demonstrat'ng either that you
have been dishonest or deceived. Tell me then, unequivocally, what you have seen.'
The doctor then explained what he had witnessed, and entered into all the particulars
regarding his discovery. On speaking of the rough method adopted to ascertain the
period of the first contact, the astronomer inquired what chronometer he had been
guided by, and was naturally enough somewhat surprised when the physician pulled
out a huge old watch with only minute hands. It had been his faithful companion in
his professional journeys, he said ; but that would hardly be considered a satisfactory
qualification for performing so delicate an experiment. The consequence was, that
Le Verrier, evidently now beginning to conclude that the whole affair was an im-
position or a delusion, exclaimed, with some warmth, ' What, with that old watch,
showing only minutes, dare you talk of estimating seconds ? My suspicions are
already too well founded.' To this Lescarbault replied, that he had a pendulum by
which he counted seconds. This was produced, and found to consist of an ivory ball
attached to a silken thread, which, being hung on a nail in the wall, is made to
oscillate, and is shown by the watch to beat very nearly seconds. Le Verrier is now
puzzled to know how the number of seconds is ascertained, as there is nothing to
mark them ; but Lescarbault states that with him there is no difficulty whatever in
this, as he is accustomed ' to feel pulses and count their pulsations,' and can with ease
carry out the same principle with the pendulum. The telescope is next inspected,
and pronounced satisfactory. The astronomer then asks for the original memoran-
dum, which, after some searching, is found ' covered with grease and laudanum.1
There is a mistake of four minutes on it when compared with the doctor's letter,
detecting which, the savant declares that the observation has been falsified. An
error in the watch regulated by sidereal time accounts for this. Le Verrier now
wishes to know how the doctor managed to regulate his watch by sidereal time,
and is shown the small telescope by which it is accomplished. Other questions are
asked, to be satisfactorily answered. The doctor's rough drafts of attempts to ascer-
ta'n the distance of the planet from the Sun ' from the period of four hours
which it required to describe an entire diameter ' of that luminary are produced,
chalked on a board. Lescarbault's method, he being short of paper, was to make his
calculations on a plank, and make way for fresh ones by planing them off. Not
being a mathematician, it may be remarked he had not succeeded in ascertaining the
distance of the planet from the Sun.

CHAP. III.] Vnloa-n. 11

" The end of it all was. that Le Verrier became perfectly satisfied that an intra-
Mercurial planet had been really discovered. He congratulated the medical practi-
tioner upon his discovery, and left with the intention of making the facts thus
obtained the subject of fresh calculations c."

In March or April, 1860, it was anticipated that the planet
would again pass across the Sun, which was carefully scrutinised
by different observers on several successive days, but no trace of
it was obtained then, and in a certain sense Lescarbault's obser-
vation continues unconfirmed. However, this proves nothing,
and many are prepared to regard the existence of this planet as
a fact, to be fully demonstrated on some future occasion.

The following approximate elements were calculated by Le
Verrier from Lescarbault's rough observations: -

Longitude of ascending node ... . . ... ... = 12° 59'

Inclination of orbit ... ... ... — I2°io'

Semi-axis major ( © = o) ... ... ... ... = o- 1 43

Daily heliocentric motion ... ... ... ... = i8°i6'

Period ... ... ... ... ... n)d ijb

Mean distance ... ... ... ... ... = 13,082,000 miles.

Apparent diameter of © from Vulcan ... ... ... = 3° 36'

Do. do. do. (®=j) — 6-79

Greatest possible elongation ... ... ... =8°

The application of Kepler's third law yields, as has already
been shown, a result sufficiently consistent with the results in
the cases of the other planets to demand attention ; but, as will
now be seen, some additional evidence can be adduced as to the
reality of the discovery, much as it has been called in question.

On March 20, 1862, Mr. Lummis, of Manchester, was examining
the Sun's disc, between the hours of 8 and 9 A.M., when he was
struck by the appearance of a spot possessed of a rapid proper
motion. He called a friend's attention to it, and both remarked
its sharp circular form. Official duties most unfortunately
interrupted him, after following it for 20™ ; but he had not the
slightest doubt about the matter. The apparent diameter was
estimated to be about 7", and in the 20™ it moved over about
12' of arc. The telescope employed was 2| inches in aperture.

c Epitomised from the North British in Cosmos, vol. xvi. pp. 22-8, 1860; see
Rfvieio, vol. xxxiii. pp. 1-20, August, also Cosmos, same vol. pp. 50-6.
1860. A full account will also be found

78 Tfte Sun and Planets. [BOOK I.

and was charged with a power of 80. Mr. Lumniis communicated
with Mr. Hind on the subject of what he had seen ; and the
latter, by the aid of the diagram sent, determined that 1 2' was
too great an estimate of the arc traversed by the spot in the
time, and that 6' would be a nearer value d.

Two French calculators deduced elements from Lummis's
observations : the orbits which they obtained, though neces-
sarily very imperfect, are fairly in accord both with each other,
and with Le Verrier's earlier orbit.

The first result is adopted from Valz's elements, the second
from Radau's.

I. II.

Longitude of ascending node ... ... = 2° 52'

Inclination of orbit ... ... ... ... = io°2i'

Semi-axis major ( ® = I -o) ... ... ... — 0-133' ... 0-144

Daily heliocentric motion ... ... ... = 20° 32' ... i8°5'

Period = I7di3h ... I9d22h

Mean distance in miles ... ... ... = 12,076,000 ... 13,174,000

From the heliocentric position of the nodes, it appears that
transits can only occur between March 25 and April 10 at the
descending, and between September 27 and October 14 at the
ascending node.

Instances are not wanting of observations of spots of a
planetary character passing across the Sun which may turn out
to have been transits of Vulcan e. The following are a selection
of these instances.

On October 10, 1802, Fritsch, at Magdeburg, saw a round spot
pass over the Sun. In 3™ it had moved 2', and after a cloudy
interval of 4h had disappeared.

On October 9, 1819, Stark, at Augsburg, saw a well-defined
and truly circular spot, about the size of Mercury, which he
could not find again in the evening.

d Month. Not., vol. xxii. p. 232. April America and by Sporer in Europe. (Ast.

1862. Lummis's observations were very Nach.,vol.xciv. No. 2253, April 16, 1879.)

severely criticised by Prof. C. H.F.Peters, Certainly Peters's argument is strong,
who claimed to have identified Lummis's e Month. Not., vol. xx. p. 100. Jan.

"planet" beyond question with a par- 1860; also pp. 192-4. March, 1860;

ticular Sun-spot recorded by himself in Webb, Celest. Objects, p. 40.

CHAP. III.] Vulcan. 79

On October 2, 1839, Decuppis, at Rome, saw a perfectly
round and defined spot moving at such a rate that it would
cross the Sun in about 6 hours f .

On October n, 1847, Schmidt saw a small black point rapidly
pass across the Sun.

On March 12, 1849, Lowe and Sidebotham watched for half
an hour a small round black spot traversing the Sun.

On October 14, 1849, Schmidt saw a black body, about 15"
in size, pass very rapidly from East to West before the Sun.
"It was neither a bird nor an insect."

In the works whence these instances are cited, others are
given ; but, though suspiciously suggestive of planets, the dates
do not come within the necessary limits for them to have been
apparitions of Vulcan, so it is not worth while to transcribe
them ; but nevertheless they are interesting, and worthy of
attention s.

Fig. 45 will be useful, if for no other purpose, as a warning to
observers not to jump too hastily at conclusions as to what they
see with their telescopes. On November 30, 1880, M. Ricco at
Palermo, whilst making his customary daily observations of Sun-
spots with a telescope of 3^ inches aperture, saw a swarm of
black bodies slowly traverse the Sun's disc. He thought at first
that he had the singular good fortune to be gazing on a shower
of meteors, but sustained attention revealed the fact that the
objects seen were evidently birds with wings. Subsequent con-
sultation with certain zoologists rendered it tolerably clear that
what M. Ricco saw was a swarm of cranes. Some calculations,
the details of which need not be gone into here, imply that they
were flying at an elevation of 5! miles h.

It is right here to state that M. Liais asserts that being in
Brazil he was watching the Sun during the period in which
Lescarbault professes to have seen the black spot, and that he is

f Complex Rendus, vol. ix. p. 809. E. Ledger's Lecture on Intra-Mereurial

1839. Planets, Svo. Cambridge, 1879.

B For an exhaustive summary of all h I? Astronomic, vol. vi. p. 66. Feb.

the recorded observationa of black ob- 1887.
jects seen on the Sun, see the Rev.

The Sun and Planet*.

[BOOK I.

positively certain that nothing of the kind was visible, though
the telescope he employed was considerably more powerful than
that of the French physician. He adds that parallax will not
explain the discrepancy'. There is, however, in Liais's paper

Fig. 45-

FLIGHT OF CRANES SEEN CROSSING THE SUN AT PALERMO. NOV. 30, l88o.

a malicious bitterness of tone, presumably intended to annoy
Le Verrier, which greatly impairs the value of the writer's
testimony.

Though it is the fashion to repudiate the reality of Vulcan's
existence, yet it is scarcely prudent to dogmatise on the subject
as some have done, considering that an astronomer of Hind's
experience leans to the affirmative side. He says :—

" It is a suspicious circumstance that the elements as regards the place of the node,
or point of intersection of the orbit with the ecliptic, and it? inclination thereto, as

1 A*f. Nach., vol. liv. No. 1281. Nov. I, 1860.

CHAP. III.] Vulcan. 81

worked out by M. Va'.z of Marseilles, from the data I deduced from a diagram
forwarded to me by Mr. Lummis, are strikingly similar to those founded by M. Le
Verrier upon the observations, such as they were, of Dr. Lescarbault. It is true if
the place of the node and inclination were precisely as given by this astronomer, the
object which was seen upon the Sun's disc on the 26th of March could not have been
projected upon it as early as the 2Oth of March. But, considering the exceedingly
rough nature of the observations upon which he had to rely, perhaps no stress need
be placed upon the circumstance. Now the period of revolution assigned by M. Le
Verrier from the observations of 1859 was 19-70 days. Taking this as an approxi-
mate value of the true period, I find, if we suppose 57 revolutions to have been
performed between the observations of Dr. Lescarbault and Mr. Lummis, there would
result a period of 19-81 days. On comparing this value with the previous observa-
tions in March and in October, when the same object might have transited the Sun
at the opposite node, it is found to lead to October 9, 1819, as one of the dates when
the hypothetical planet should have been in conjunction with the Sun. And on this
very day Canon Stark has recorded the following notable observation, — ' At this
time there appeared a black, well-defined nuclear spot, quite circular in form, and as
large as Mercury. This spot was no more to be seen at 4.37 P.M., and I found no
trace of it later on the 9th, nor on the I2th, when the Sun came out again.' The
exact time of this observation is not mentioned, but appears likely to have been about
noon, one of Stark's usual hours for examining the solar disc. Hence I deduce a
corrected period of 19-812 days."

In the communication from which this is taken k Hind throws
out suggestions for a scrutiny of the Sun at certain dates. It
must be admitted that the scrutiny took place and that no
planet was found, and here the matter rests.

Notwithstanding, however, the strong negative evidence then
existing against the existence of Lescarbault's planet Vulcan,
Le Verrier, in December 1874, re-iterated his announcement
that the orbit of Mercury is perturbed to an extent rendering it
necessary to augment the movement of the perihelion. He put
the amount at 31" in a century. "The consequence" (he said)
" is very clear. There is, without doubt, in the neighbourhood
of Mercury, and between that planet and the Sun, matter
hitherto unknown. Does it consist of one, or several small
planets? or of asteroids, or even of cosmic dust 1 Theory cannot
decide this point 1."

Le Verrier died in 1877, and the question had in great measure
gone to sleep, when some observations made on the occasion of
the eclipse of the Sun of July 29, 1878, brought the whole

k Letter in the Times, Oct. 19, 1872.

1 Compt. Send., vol. Ixxix. p. 1424. 1874.

82 The Sun and Planets. [BOOK I.

matter again before the scientific world, though not precisely in
the same shape.

The total eclipse in question was visible over a large part of
the western regions of North America. Two of the many
American observers, Professor J. C. Watson and Mr. L. Swift,
applied themselves to the task of searching for Intra-Mercurial
planets, and with what result we shall now see.

Professor Watson's observations, as described by himself, shall
first be set out in full : —

" As soon as the total phase began, I commenced a systematic sweep for objects
visible near the Sun. From my previous experience in work of this character I had
determined not to undertake to sweep over too much space. Accordingly, I confined
my search to a region of about 15° in Eight Ascension, and i£° in breadth. I had
previously committed to memory the relative places of stars near the Sun down to
the seventh magnitude, and the chart of the region was placed conveniently in front
of me for ready reference whenever required. Before the totality began, I examined
the regions distant from 8° to 15° on the E. side, and also on the W. side of the Sun,
without finding any stars. As soon as the total phase had begun I placed the Sun
in the middle of the field and began a sweep by moving the telescope slowly and
uniformly towards the E. Then I retraced the path thus examined, moved the tele-
scope one field further S., and again swept out and back over a distance of about 8°.
In the first of these sweeps I saw 5 Cancri and other known stars. Then I placed the
Sun again in the field and swept in the same manner towards the W. Between the
Sun and 0 Cancri, and a little to the S., I saw a ruddy star whose magnitude I
estimated to be 4^. It was fully a magnitude brighter than 6 Cancri, which I saw at
the same time, and it did not exhibit any elongation, such as might be expected if it
were a comet in that position. The magnifying power was 45 and the definition
excellent. My plan did not provide for any comparison differentially with a neigh-
bouring star by micrometric measurement, and hence I only noticed the relation of
the star to the Sun and 6 Cancri. Its position I proceeded at once to record on my
circles in the manner I have described ; and I recorded also the chronometer time of
observation. This star was denoted by a. Previously to the commencement of the
total phase I had recorded a place of the Sun in the same manner, which I designated
by Sp Having made the record I assured myself that the pointing of the telescope
had not been disturbed in the least, and I continued the search, sweeping out to
about 8° W. from the Sun. Then I went back to the Sun, moved the telescope nearly
one field S., and swept out again towards the W. In this sweep I came across a
bright star, also ruddy in appearance, which arrested my attention, and for fear that
the Sun might reappear before I could make an examination of its surroundings,
I determined to make a record of its place upon my circles. This I next proceeded
to do, and just as I had completed the record the Sun reappeared. This object was
designated by b...

" On September 15 I examined, with the same telescope and magnifying power
used in the eclipse observations, the stars in this part of Cancer, with the moon
in the western sky and the bright twilight in the E., so as to obtain as nearly as

CHAP. III.] Vulcan. 83

possible the conditions of sky-illumination which existed at the time of the eclipse.
Having a very distinct recollection in respect to the brilliancy of the stars which I
saw, and by observing when the approaching daylight had reduced the light of certain
stars which were E. of the Sun at the time of the total eclipse, so as to be just
visible in the telescope as they were then, I have been enabled to form a still more
definite opinion of the relative brilliancy of 0 Cancri, the two new objects which I
observed, and f Cancri. The fainter of the two planets, that near 0 Cancri, was cer-
tainly brighter than f Cancri, and much more than a magnitude brighter than its
neighbouring star. I am inclined to think that (a) should be classed as a good 4th
magnitude, and that ( J) should be classed as a 3rd magnitude, at the time of the ob-
servations on July 29. It is, of course, impossible to determine from these observa-
tions the planetary character of the stars observed. They did not exhibit such
appearances as might be expected if they were comets near the sun ; and since theory
demonstrates the existence of such planets, I feel warranted in expressing the belief
that the foregoing observations give places of two Intra-Mercurial planets. It is
true that they were not so bright as might be expected if they were of size sufficient
alone to account fur the outstanding perturbations of Mercury, but it should be re-
membered that this expectation is based upon the assumption that the reflecting
power of the surfaces of these planets is the same, or nearly the same, as that of Mer-
cury. Now we know from actual observations that the intrinsic brilliancy of Mercury
is scarcely ^th that of Venus when reduced to the same distance, and hence we
cannot safely assume that the Intra-Mercurial planets must have the same relative
brilliancy that they would have if their surfaces could reflect the light to the
same extent as that of Mercury. I feel assured that by suitable devices these
planets may be observed in full daylight near their elongations. Whether they are
identical or not with moving spots which have been seen on the Sun's surface at dif-
ferent times it does not yet seem possible to determine m."

Swift's account of his work runs as follows : —

" I reluctantly broke away from the wondrous scene [the Corona], and Immedi-
ately essayed the well-nigh hopeless task which I had chosen — the finding of an
Intra-Mercurial planet. To my dismay I soon found that I had forgotten to untie
the string holding the pole in place, and this prevented all search E. of the Sun, as if
I attempted a move in that direction the lower end would plunge into the ground
and against the little tufts of buffalo-grass. It is, perhaps, to this circumstance alone
that I owe the discovery of Vulcan some 5 minutes after its detection by Professor
Watson, totality having terminated at his station before its commencement at
mine.

" Almost the first sweep made to the westward of the Sun I ran across 2 stars
presenting a very singular appearance, each having a red round disc and being free
from twinkling. I at once resolved to observe these with great care. Time was
precious and yet 6 questions demanded an immediate answer, viz :

1 . What were their distances from the Sun ?

2. What from each other ?

3. What direction from the Sun ?

4. What from each other ?

m Washington Observations, 1876, App. Ill, " Reports on Total Solar Eclipses,"
pp. 119-23.

G 2

84 The Sun and Planets. [BOOK I.

5. What the magnitude of each ?

6. What stars were they ?

" My telescope, though equatorially mounted, had no circles, and consequently
no measurements were possible, but I endeavoured to be as accurate as existing
circumstances would allow. My estimated answers were as follows : —

1 . About 3° from Sun's centre to midway between the stars.

2. About 8'.

3. South of West.

4. They were both on a line with the Sun's centre.

5. Equal, and of the 5th magnitude.

6. Probably, one was Theta Cancri ; the other an Intra-Mercurial planet.
"After completing these observations I resumed the quest, sweeping again southerly

and W., but my fettered telescope behaved badly, and no regularity in the sweeps
could be maintained, and I was surprised to find, in a few seconds, 2 stars in the field
answering, in every particular, to the above description, and, sighting along the top
of the tube on the outside, as in the first instance, I found they were the same objects.
Again, I went through with the above comparisons, though I devoted only about
one-fourth of the time given on the first occasion. Finding no necessity for modi-
fying any of the above estimates, I, for the third time, renewed my sweeps, this time
nearly along the ecliptic, though I feared to go too far to the W. lest I might not be
able to get the glass back again to make a third and final observation of them, and
also of the closing scenes of totality. I could place no dependence on the sweeps,
and after a few seconds more (though it seemed longer) had them again in the field,
This proved to be the last time. I again asked myself the already twice repeated
questions, but found no appreciable change had taken place between the first and
third observations — an interval of probably i^ minutes. Again I searched, but saw
nothing, and, recollecting that I had no more time to spare, I endeavoured to refind
the stars for a last observation, but unfortunately a small cloud (the only one within
50°) passed over them, and I was unsuccessful. I saw no stars but these i, Hot even
Delta, so near the Eastern limb of the Sun. As soon as totality was ended, I
recorded in my note-book aa follows : ' Saw 2 stars about 3° S.W. of Sun,
apparently of 5th magnitude some 12' apart, pointing towards Sun. Red.' On my
homeward journey the thought occurred to me that the distance between the stars
was, according to memory, a little greater than half that between Mizar and Alcor,
whatever that might be. Consulting ' Webb's Celestial Objects,' I found they were
but 1 1 £' apart, which would make the distance of the two stars not to exceed 8', instead
of 12', as hastily written at the time. While scanning them, I asked the mental
question, ' What star looks at night to the naked eye as bright as do these through
the telescope now ? ' Instantly, I answered ' The Pole-star.' That one was Theta
Cancri is in the highest degree probable, and the other a planet is beyond all ques-
tion, for on the morning of the roth instant I observed Theta robbed of the com-
panion I saw during the eclipsed Sun n."

These discoveries were hotly canvassed and their authenticity
directly called in question, but not, I think, on fair or adequate
grounds. It will be worth while, however, to examine the details

" Washington Observations, 1876, App. Ill, "Reports on Total Solar Eclipses,"
p. 229.

CHAP. III.] Vulcan. 85

of the controversy. Watson's idea of what he saw may be thus
expressed. He first noticed a star which he thought was 8 Cancri,
then 6 Cancri, and near to 0 an unknown body which he de-
signated a ; then a second strange object (designated b] which
he saw near to the place in which he expected to find
£ Cancri, the discovery of which, because he presumed it to
be £ Cancri, led him to search no further in that part of his
field of view.

The theory of the hostile critic, Professor C. H. F. Peters °, is,
that a was 9 Cancri and b was £ Cancri, and that some error in
Watson's circles led to both his observations being vitiated in
the same direction and to the same extent. This insinuation
was however warmly repudiated by Watson p. Peters dealt with
Swift's record in a still more simple fashion : charged him with
describing objects which he did not see at all, and implied that
he concocted his alleged discovery after the publication of a
telegram from Watson ! Swift's reply to all this was as digni-
fied as it was emphatic q.

Swift's observations seem, in part at least, irreconcileable with
Watson's, and if we assume the reality of Swift's 2 planets then
Watson's a is a 3rd object and perhaps his b a 4th, so that in
point of fact the 2 observers in question would seem to have
discovered between them 4 Intra-Mercurial planets, which is in
the highest degree improbable. Here the matter rests r, except
that the observers of the Total Solar Eclipse of May 6, 1883,
say that they saw no object which could have been a planet,
although specially searching for the purpose of finding a planet,
if possible.

0 Ast. Nach., vol. xciv. No. 2253, evidence which appears in the Sidereal
Apr. 16, 1879. Messenger (U.S.), vol. vi. p. 196 (May,

P Ast. Nach., vol. xcv. No. 2263, 1887), seems to make the reality of some

June 17, 1879. discovery perfectly clear ; on the contrary

1 Ast. Nach., vol. xcv. No. 2277, side, reference maybe made to remarks
Sept. 17, 1879. by Prof. Young in Sid. Mess., vol. vi.

r A summary review by Colbert of the p. 21, Jan. 1887.

86 The Sun and Planets. [BOOK I.

CHAPTER IV.

MERCURY. £

Period, tfc. — Phases. — Physical Observations by Schroter, Sir W. Herschel, Denning,
ScJiiaparelli and Guiot. — Determination of its Mass. — When best seen. — Ac-
quaintance of the Ancients with Mercury. — Copernicus and Mercury. — Le
Verrier's investigations as to the motions of Mercury. — Tables of Mercury.

1%/TERCURY is, of the old planets a, the one nearest to the
-L*-'- Sun, round which it revolves in 87d 23h I5m 43-9 i8, at a
mean distance of 35,958,000 miles. The eccentricity of the orbit
of Mercury amounting to 0-205, the distance may either extend
to 43,347,000 miles, or fall as low as 28.569,000 miles. The
apparent diameter of Mercury varies between 4-5" in superior
conjunction, and 12-9" in inferior conjunction: at its greatest
elongation it amounts to about 7". The real diameter may be
about 3008 miles or lessb. The compression, or the difference
between the polar and equatorial diameters, has usually been
considered to be too small to be measureable, but Dawes, in
1 848, gave it at /y

Mercury exhibits phases resembling those of the Moon. At
its greatest Elongation (say W.) half its disc is illuminated, but
as it approaches Superior Conjunction the breadth of the illu-
minated part increases, and its form becomes gibbons ; and
ultimately, when in Superior Conjunction, circular: at and near
this point the planet is lost in the Sun's rays, and is invisible.

a In case it should be thought that as it has been thought for several reasons

these accounts of the planets are de- undesirable to encumber the Text of

ficient in statistical data, it may here be Book I. with too many figures.
remarked that they are intended to be b An American observer, D. P. Todd,

read in connexion with the tabulated in 1880, put it at 2971 miles.
statistics in the Appendix of this volume.

CHAP. IV.] Mercury. 87

On emerging therefrom the gibbous form is still apparent, but the
gibbosity is on the opposite side, and diminishes day by day till
the planet arrives at its greatest Elongation E., when it again
appears like a half-moon. Becoming more and more crescented,
it approaches the Inferior Conjunction; and having passed this,
the crescent (now on the opposite side) gradually augments
until the planet again reaches its greatest W. Elongation.

Owing to its proximity to the Sun, observations on the
physical appearance of Mercury are obtained with difficulty, and
are therefore open to much uncertainty. The greatest possible
elongation of the planet not exceeding 27° 45' (and it being in
general less), it can never be seen free from strong sunlight0,
under which conditions it may occasionally be detected with the
naked eye during i|h or so after sunset in the spring (E.
Elongation) and before sunrise in the autumn (W. Elongation),
shining with a pale rosy hue. With the aid of a good telescope
equatorially mounted, Mercury can frequently be found in the
daytime.

Mercury has not received much attention from astronomers in
the present day, and the observations of Schrb'ter, at Lilienthal,
and those of Sir W. Herschel, are the main sources of information.
The former observer and his assistant Harding obtained what
they believed to be decisive evidence of the existence of high
mountains on the planet's surface : one in particular, situated in
the Southern hemisphere, was supposed to manifest its presence
from time to time, in consequence of the Southern horn, near
Inferior Conjunction, having a truncated appearance, which it
was inferred might be due to a mountain arresting the light of
the Sun, and preventing it from reaching as far as the cusp
theoretically extended3. The extent of this truncature would
serve to determine the height of the mountain occasioning it,

c When Mercury's Elongation is the greatest possible Elongation is a W. one

greatest possible, the planet's position is which happens at the beginning of April,

(in England) S. of the Sun, and there- The least (17° 50') an Elongation (also

fore the chances of seeing it are not so W.) which happens at the end of Sep-

good as when an Elongation coincides tember.

with a more Northerly position, albeit the d This has also been seen by Noble

Elongation is less considerable. The (Ast. Reyit-ter, vol. ii. p. 106. May 1864).

88 The Sun and Planets. [BOOK I.

which has been set down at 10-7 miles, an elevation far ex-
ceeding, absolutely, anything we have on the Earth, and in a still
more marked degree relatively, when the respective diameters
of the 2 planets are taken into consideration. Schroter, pursuing
this inquiry, announced that the planet rotated on its axis in
24h 5m 48". Sir W. Herschel was unable to confirm these re-
sults either in whole or even in part6, and the alleged period
of rotation we are justified in considering to be wholly a
myth, so far at least as observation is concerned. Schiaparelli
considers Schroter's rotation-period to be " very far from the
truth."

Denning and Schiaparelli think that Mercury is more easy to
observe than Venus, and that its physical aspect resembles that
of Mars more than any other planet. Schiaparelli 's most suc-
cessful observations have been obtained with the planet near
Superior Conjunction, when the defect of the diameter was
compensated for by the fact that nearly the whole disc was to be
seen. In such position it is then more strongly illuminated
than at epochs of quadrature.

Denning's observations above alluded to were made on
November 6, 7, 9, 10, 1882, with a lo-inch reflector, power 212.
He says: —

" Some dark, irregular spots were distinctly seen upon the planet ; also a small
brilliant spot, and a large white area between the E. N. E. limb and terminator.
The south horn was also much blunted, especially on the two first dates of observation.
My results have led me to infer that the markings upon Mercury are far more
decided and easily discernible than those of Venus ; and that the aspect of the
former planet presents a close analogy to the physical appearance of Mars. The
rotation-period given by Schroter seemed too short to conform with the relative
places of the markings as I delineated them on the several dates referred to f."

Denning elsewhere g states that the large white area in ques-
tion had in its centre a very brilliant small spot, " with luminous
veins or radiations extending over the whole area."

• But it must not be forgotten in this r Month. Not., vol. xliii. p. 301.

connection that Sir William was never March 1883.

amicably disposed towards Schroter. g Observatory, vol. vii. p. 40. Feb.

(See Holden's Life and Works of Sir 1884.
W. Herschel, p. 91.)

CHAP. IV.]

Mercury.

Figs. 46-47 represent the planet Mercury as seen before sun-
rise in the autumn of 1885.

The observer remarked the truncated form of both of the
horns on the former occasion, and of the Southern horn on the
latter occasion. He makes no mention of any shading or spots.

Fig. 46. Fig. 47.

SEPT. 17, 1885, AT £h 25™ A.M. (Gwiot.)

SEPT. 22, 1885, AT 5h 30™ A.M. (Guiot.)

The phases of Mercury are noticeable, as it has sometimes
been found that the breadth of the illuminated portion is less
than according to calculation it should be. This does not rest
on the testimony of Schrb'ter alone, but is supported by Beer
and Miidler, from an observation made on September 29, 1832.

Mercury is not known to be possessed of an atmosphere ; and
if one exists, it must be very insignificant. Sir W. Herschel,
contradicting Schroter and Harding, pronounced against its
existence, and Zollner from photometric experiments on reflec-
tion from the surface of Mercury generally, thinks that there
cannot be any atmosphere sufficient to reflect the light of the
Sun. [But see Book II., Chap. X., " Transits," post.~\

Mercury is, as far as we know, attended by no satellite, and
the determination of its mass is a difficult and uncertain
problem. However, the small comet of Encke has furnished the

90 The Sun and Planets. [BOOK I.

means of learning something, and from considerations based on
the disturbances effected in the motion of this comet by the
action of Mercury, it has been calculated by Encke that the
mass of the latter is J^TTTTI ^na^ of the Sun. Le Verrier gives
STnrsinRF ; Littrow sTnrHiir ; and Madler 1 w^m ; but Newcomb
has fixed on a fraction widely different from all these, namely,

The ancients were not only acquainted with the existence of
this planet h, but were able to ascertain with considerable accu-
racy its period, and the nature of its motions in the heavens.
" The most ancient observation of this planet that has descended
to us is dated in the year of Nabonassar 494, or 60 years after
the death of Alexander the Great, on the morning of the i9th
of the Egyptian month Tkoth, answering to November 15 in the
year 265 before the Christian era. The planet was observed to
be distant from the right line joining the stars called /3 and 5
in Scorpio, one diameter of the Moon ; and from the star /3 two
diameters towards the North, and following it in Right Ascen-
sion. Claudius Ptolemy reports this and many similar observa-
tions extending to the year 134 of our era, in his great work
known as the Almagest*"

We have also observations of the planet Mercury by the
Chinese astronomers, as far back as the year 118 A.D. These
observations consist, for the most part, of approximations
(appulses) of the planet to stars. Le Verrier tested many of
these Chinese observations by the best modern tables of the
movements of Mercury, and found, in the greater number of
cases, a very satisfactory agreement. Thus, on June 9, 118 A.D.
the Chinese observed the planet to be near the cluster of stars
usually termed Praesepe, in the constellation Cancer; calcula-
tion from modern theory shows that on the evening of the day
mentioned Mercury was less than 1° distant from that group of
stars.

"Although the extreme accuracy of observations at the present

h Pliny, Hist. Xat., lib. ii. cap. 7 ; Cicero, De Jfaltird Deoriini. lib. ii. cap. 20.
• Hind, Sol. Sy*t., p. 23.

CHAP. IV.] Mercury. 91

day renders it unnecessary to use these ancient positions of the
planets in the determination of their orbits, they are still useful
as a check upon our theory and calculations, and possess, more-
over, a very high degree of interest on account of their remote
antiquity k."

La Place said : — " A long series of observations were doubtless
necessary to recognise the identity of the two bodies, which were
seen alternately in the morning and evening to recede from and
approach the Sun : but as the one never presented itself until the
other had disappeared, it was finally concluded that it was the
same planet which oscillated on each side of the Sun." Arago
considered that "This remark qf La Place's explains why the
Greeks gave to this planet the two names of Apollo, the god of
the day, and Mercury, the god of the thieves, who profit by the
evening to commit their misdeeds."

The Greeks gave Mercury the additional appellation of 6 2n'A-
PO>V, "the Sparkling One." When astrology was in vogue, it
was always looked upon as a most malignant planet, and was
stigmatised as a sidns dolosum. From its extreme mobility
chemists adopted it as the symbol for quicksilver.

It is rather difficult, in a general way, to see Mercury, and
Copernicus, who died at the age of 70, complained in his last
moments that, much as he had tried, he had never succeeded in
detecting it ; a failure due, as Gassendi supposes, to the vapours
prevailing near the horizon on the banks of the Vistula where
the illustrious philosopher lived. An old English writer, of the
name of Goad, in 1686, humorously termed this planet "a
squirting lacquey of the Sun, who seldom shows his head in
these parts, as if he were in debt."

When speaking on a previous page (see p. 75 ante) of the planet
Vulcan, mention was made of Le Verrier's conclusion that the
motion of Mercury's perihelion was influenced by some unknown
cause of disturbance. Not to discuss this matter at length here
it may be stated that Newcomb has given it as his opinion that
the discordance between the observed and theoretical motions

k Hind, Sol. *%«/.. p. 23.

92 The Sun and Planets. [BOOK I.

of the perihelion of Mercury first pointed out by Le Verrier
really exists, and is indeed larger than he supposed *.

In computing the places of Mercury, the Tables of Baron De
Lindenau, published in 1813, were long employed, but they are
now superseded by the more accurate Tables of Le Verrier m.

1 Astron. Papers for use of Amer. m Annales deTObs.de Paris, Memoires,

Naut. Almanack, vol. i. p. 472 ; 1882. vol. v. p. I ; 1859.

CHAP. V.]

Venus.

CHAPTEB V.

VENUS. ?

Period, fyc. — Phases resemble those of Mercury. — Most favourably placed for obser-
vation once in 8 years. — Observations by Lihou. — By Lacerda. — Daylight
observations. — Its brilliancy. — Its Spots and Axial Rotation. — Suspected moun-
tains and atmosphere. — Its " ashy light." — Phase irregularities. — Suspected
Satellite.- — Alleged Observations of it. — The Muss of Venus. — Ancient observa-
tions.— Galileo's anagram announcing his discovert/ of its Phases. — Venus useful
for nautical observations. — Tables of Venus.

"JVTEXT in order of distance from the Sun, after Mercury, is
Venus ; which revolves round the Sun in 224d i6h 49™ 8s,
at a mean distance of 67,190,000 miles. The eccentricity of the
orbit of Venus amounting
to only 0-007, the ex-
tremes of distance are
only 67,652,000 miles and
66,728.000 miles. This ec-
centricity is very small.
No other planet, major or
minor, has an eccentricity
so small. The apparent
diameter of Venus varies
between 9-5" in Superior
and 65-2" in Inferior Con-
junction. At its greatest

VENUS NEAK ITS GREATEST ELONGATION.

(Schroter.} •

Fig. 48.

Elongation its apparent
diameter is about 25'' '. A
numerous series of careful observations enabled Main to deter-
mine that the planet's diameter (reduced to mean distance) is

a Figs. 49-50 are copied, with an unimportant variation, from PI. xlii of Schroter's
Selenotopographische Fragmente.

The Sun

[BOOK I.

I7'55"y subject to a correction of —0-5" for the effects of
irradiation. Stone, from an elaborate discussion of a large
series of Greenwich observations, obtained 16-944", with a
probable error of +0-08". Tennant in 1874 (during the Transit)
obtained, as the mean of 68 measures, 16-9036" (reduced) with a
probable error of 0-0016" onlyb. The real diameter corre-
sponding to this latter evaluation is about 7500 miles, or, roundly,
Venus is a planet almost as large as the Earth. The com-
pression must be small, but Tennant thinks he found traces
thereof. Great difficulty must ever remain in clearly detecting
it, because the planet's diameter in Superior Conjunction is
so small.

Venus exhibits phases precisely identical in character with
those of Mercury.

Though under the most favourable circumstances Venus is
never farther removed from the Sun than 47° 15', and is there-
fore always more or less under the influence of twilight, yet it

is difficult to scrutinise this
planet for a reason addi-
tional to that which obtains
with Mercury, namely, its
own extreme brilliancy.
This is such as to render
the planet not unfrequently
visible in full daylight and
capable of casting a sen-
sible shadow at night. This
happened in January 1870,
and indeed occurs every
8 years, when the planet
is at or near its greatest
North latitude and about
5 weeks from Inferior Conjunction. Its apparent diameter is
then about 40", and the breadth of the illuminated part nearly
10", so that rather less than -J of the entire disc is illuminated :

fc Mo»tk. Xof.. vol. XXTV. p. 347. May 1875.

Fig. 49-

VENUS NEAR ITS I.NFtKIuR CONJUNCTION.

CHAP. V ]

1V////X.

but this fraction transmits more light than do phases of greater
extent, because the latter occur at greater distances from
the Earth. A lesser maximum of brilliancy, due to the same
circumstances less favourably carried out, occurs on either side
of the Sun at intervals of about 29 months. The planet's
angular distance from the Sun on these occasions is rather less
than 40° (in the superior part of its orbit) ; its phase therefore
corresponds with the phases of the Moon when nd and i7d old.
Figs. 50-1 are selected from some drawings by Lihou taken
in the winter of 1885-6 with a refractor of 4^ inches aperture.

Fig- 51-

Nov. 10, 1885.

Dec. 23, 1885.

He makes c the following remarks on what he saw : —

Nov. 10, 1885. — " With a telescope of about 4 inches aperture armed with a
magnifying power of 100 I was able to distinguish a grey spot in the northern
hemisphere. Spots on Venus being very difficult to see with small instruments, this
observation merits attention."

Dec. 8, 1885. — "Sky very pure. The light of Venus is so bright as to fatigue
the eye, but by making use of a coloured glass I am able to see the limbs sharply
defined."

Dec. 16, 1885. — "Sky very pure. The image of Venus is extremely sharp.
and the limbs well denned ; the northern cusp is sharply pointed, whilst the southern
i- slightly truncated."

Dec. 23, 1885. — " The northern cusp of Venus is sharply pointed, and the southern
cusp slightly truncated."

' L' Aflronmfilf. vol. v. p. 148, April 1886.

The Sun and Planet*.

[BOOK I.

Figs. 52-5 are intended to represent some drawings of Venus
made in 1884 by M. Lacerda of Lisbon. Respecting these he
writes as follows : —

"Sept. 8, 1884. — The crescent of Venus appears sensibly more narrow towards the
North Pole than towards the South Pole. With a magnifying power of 250 I
cannot distinguish the Southern spots, which, however, were very visible with a
magnifying power of 160. I notice that the Northern hemisphere is brighter than
the rest of the planet. A very obscure and elongated spot is visible near the North
Pole."

Fig- 52-

Fig. 53-

Sept. 8, 1884.

Sept. 9, 1884.

VENUS.

" Sept. 9, 1884. — There is a very bright thread of light concentric with the
Eastern limb of the planet ; perhaps some high clouds lying along a maritime shore
of Venus. Two large spots are also visible on the crescent ; the one, oblong, stretched
parallel to the bright spot ; the other, almost round, and much smaller, to the
North of the first. The Southern horn is always longer than the Northern one. The
elongated spot which hollows out the planet near the North Pole continues to be
very visible.

M. Lacerda says that on the following morning, Sept. 10, he
was unable to distinguish any spots.
His next observation is dated —

"Oct. 8, 1884. — The 2 dark spots have sensibly shifted their positions towards the
North. They disclose also a slight movement towards the West. The terminator
which seemed shrunk up towards the North Pole is to-day almost perfect ; but the
Southern horn continues to appear longer and more pointed than the Northern one.
The lustre of the planet seems uniform. The dark spot which cut into the crescent
near the North Pole is not visible."

CHAP. V.]

Venus.

" Oct. 13, 1884. — There is a great depression near the Southern horn. 2 spots are
visible on the planet ; one to the South ; the other, smaller, and to the North ; and
a third was suspected under the equator, near the illuminated limb and concentric
with it. The Northern horn is truncated."

M. Lacerda concludes his observations by remarking that the
most favourable time for observing Venus is between J an hour
before sunrise and i hour after sunrise. He adds that he was
never able to see any spots when the planet was in the west, at
or near the time of sunset0.

Fig. 54-

Fig- 55-

Oct. 8, 1884.

Oct. IT, 1884.

Observations of Venus in the daytime were made at a very
early period ; the following are the dates of a few instances :
398 A.D., 984, 1008, 1014, 1077, 1280, 1363, 1715, 1750. "Bouvard
has related to me," says Arago, " that General Buonaparte, upon
repairing to the Luxembourg, when the Directory was about to
give him a fete, was very much surprised at seeing the multi-
tude which was collected in the Rue de Tournon pay more
attention to the region of the heavens situate above the palace
than to his person or to the brilliant staff which accompanied
him. He inquired the cause, and learned that these curious
persons were observing with astonishment, although it was

c ISAstronomie, vol. iii. p. 462, Dec. 1884.
H

98 The Sun and Planets. [BOOK I.

noon, a star, which they supposed to be that of the Conqueror
of Italy; an allusion to which the illustrious general did not
seem indifferent when he himself with his piercing eyes re-
marked the radiant body. The star in question was no other
than Venus d."

The dazzling brilliancy of this planet is such6 that the
daytime is to be preferred for observing it, but under the best
of circumstances it is far too tremulous for physical observations
to be conveniently made. J. D. Cassini attacked it in 1667, and
some ill-defined dusky spots seen on various occasions during
April, May, and June, enabled him to assign 23** I5m for its axial
rotation. Bianchini, at Rome, in 1726 and 1727, favoured by an
Italian sky, observed spots with greater facility: thence he
inferred a rotation performed in 24 (Jays 8 hours. Cassini's son
came forward in defence of his father's observations, and assailed
Bianchini's conclusions by alleging that the latter, only seeing
Venus for a short time every evening by reason of the Barbarini
Palace interrupting his view, and finding the spots night after
night nearly in the same position, concluded that the planet had
rotated through a very small arc during the previous 24 hours,
whereas it had really made one complete rotation and part of
a second. After the lapse of 24 days it would exhibit exactly
the same portion of its surface, but in the 24-days' interval would
really have made 25 revolutions instead of one, as Bianchini had
supposed. Bianchini's observations thus interpreted imply a
period of 23h 2 £m.

Sir W. Herschel, desirous of arriving at some certain know-
ledge on the subject, devoted much care to the matter ; but,
failing to see any permanent markings on Venus, he was unable
to assign a precise period beyond believing generally that
Bianchini's statement was largely in excess of the true amount.
Schroter claimed to have seen certain spots which enabled him to
deduce a period of 23b 2im 7'988, and Di Vico and his colleagues

d Pop. Ast., vol. i. p. 701, Eng. ed. times -as bright as the brightest part of

6 Lord Grimthorpe states that Venus the full moon. (Ast., 3rd ed.,p. 149.)
has been experimentally found to be 10

CHAP. V.] Venus 99

at Rome, in 1840-2, rediscovering as they thought Bianchini's
markings, assigned a period of 23h 2im 23'93S.

In spite of the seemingly circumstantial character of these
evaluations it cannot be said that astronomers generally are
satisfied to accept them, or to think that anything at all con-
clusive is at present known as to the real duration of Venus's
axial rotation.

Sir W. Herschel saw a few transient spots, but his opinion
was that they were in the atmosphere, and did not belong to
the solid body of the planet. Di Vico, however, professed to
have found the spots just as they had been delineated by
Bianchini, with one exception. Of the several observers who
worked with Di Vico the most successful were those who had
most difficulty in catching very minute companions to large
stars, the reason of which is obvious. A very sensitive eye,
which would detect the spots readily, would be easily over-
powered by the light of a brilliant star, so as to miss a very
minute one in its neighbourhood.

On Nov. 10, 1885, Lihou saw a gray spot in the Northern
hemisphere of Venus as depicted in Fig. 50, ante.

Mountains probably exist on Venus, though the testimony on
which the statement must rest is not so conclusive as could be
desired. In August 1700 La Hire, observing the planet in the
daytime near its Inferior Conjunction, perceived in the lower
region of the crescent inequalities which could only be produced
by mountains higher than those in the Moon. Schroter asserted f
the existence of several high mountains, in which he was con-
firmed by Beer and Madler, but his details as to precise elevation
measured by toises must be accepted with great reserve, amongst
other reasons because it is doubtful whether his micrometers
were of sufficient delicacy. Sir W. Herschel disbelieved him on
some points, and attacked him in the Philosophical Transactions
for I793g: his reply was published in the volume for the year
but one after h ; it was calm and dignified, and vindicated the

' Phil. Trans., vol. Ixxxii. p. 337. 1792. h Phil. Trans., vol. Ixxxv. p. 117.

g Phil. Trans., vol. Ixxxiii.p. 202. 1793. i?95-

H 2

100 The Sun and Planets. [BOOK I.

mountains, if not the measurements. Di Vico, at Rome, in April
and May 1841, appears to have noticed a surface-configuration
akin to that of the Moon ; and Lassell, when at Malta in January
1862, observed the same sort of thing. Browning, on March 14,
1868, saw mottlings on the surface of Venus which reminded him
of the look of the Moon as seen in a small telescope through a
mist. A bluntness of the southern horn, referred to by Schroter,
was also seen by the Roman astronomers, and often by Breen
subsequently with the Northumberland telescope at Cambridge.

That Venus has an atmosphere is almost certain ; that it is of
considerable density is likewise an opinion apparently well
founded. During the transits of 1761, 1769, and 1874, the planet
was observed by several persons to be surrounded by a faint
ring of light, such as an atmosphere would account for.
Schroter, too, discovered what appeared to him to be a faint
crepuscular light extending beyond the cusps of the planet into
the dark hemisphere. From micrometrical measures of the
space over which this light was diffused he considered the
horizontal refraction at the surface of the planet to amount to
30' 34", or much the same as that of the Earth's atmosphere.
Sir W. Herschel confirmed the discovery as a whole h, and more
recently Madler, in 1849, was able to do the same with the mere
modification of making the amount somewhat greater, or equal
to 43-7'. With this the Transit results of 1874 fairly agree ; e.g.,
Prof. C. S. Lyman, 44-5'. '

It is quite worth while to dwell upon the observations on
which these conclusions rest, for the subject deserves much more
telescopic investigation than has hitherto been given to it, and
it is one within the reach of many amateurs.

The observations must be made when the planet is very near
Inferior Conjunction. Under such circumstances the limb of the
planet which is farthest from the Sun is often to be seen
illuminated, exhibiting a curved line of light ; this is a con-

11 Phil. Trans., vol. Ixxxiii. p. 214. 54-4' and 53-5' respectively, an error

1793. having crept in owing to an erroneous

1 Neison suggests that Madler's and formula having been used. (Month. Not.,

Lyman's results must be increased to vol. xxxvi. p. 347, June 1876.)

CHAP. V.] Venus. 101

tinuation of the narrow crescent of the planet itself, and the
result is, that the planet seems to be surrounded by a complete
circle of light. " If only half the globe of the planet were
illuminated by the Sun, this appearance could never present
itself, as it is impossible for an observer to see more than half
of a large sphere at one view. There is no known way in which
the Sun can illuminate so much more than the half of Venus as
to permit a complete circle of light to be seen, except by the
refraction of an atmosphere k."

The existence of snow at the poles of Venus has been suspected
by Webb and Phillips, but the idea awaits confirmation, though
there is no prima facie reason why it should not be well founded ;
indeed rather the reverse.

A phenomenon analogous to the lumiere cendree, or ' ashy light,'
of the Moon is well attested in observations of Venus when near
Inferior Conjunction, having been first seen by Riccioli on
Jan. 9, 1643. Many observers have noticed the entire contour
of the planet to be of a dull grey hue beyond the Sun-illumined
crescent. Webb used the expression "the phosphorescence of the dark
side " ; this certainly is an objectionable phrase, for phosphor-
escence notably conveys the idea that some inherent light is spoken
of, whereas there can be little doubt that refraction and reflec-
tion jointly are in some way or other the cause of what is seen
in the case of Venus, though it may be difficult at present to
specify the precise nature of it ]. Derham noticed this appear-
ance, and refers to it in his bookm ; and Schroter, Sir W.
Herschel, Di Vico, and Guthrien are amongst those that have
seen it. Green, Winnecke, Noble, and others have repeatedly
seen the unilluminated limb of Venus distinctly darker than the
back-ground on which it was projected. The most recent
observations in detail of this phenomenon are those made by
Zenger, at Prague, in Jan. 1883. He speaks in strong terms of

k Newcomb, Popular Astronomy, p. m Physics and Astro-theology, vol. ii.

293- book v. ch. I.

1 The supposition of the existence of Month. Not., vol. xiv. p. 169. March

some such phenomenon as our Aurora 1854.
Borealis rests on no foundation.

102 The Sun and Planets. [BOOK I.

the beauty of the spectacle when seen under favourable circum-
stances as regards the planet's position and the condition of the
Earth's atmosphere. He noticed, and considered the most im-
portant point of all, a brownish red ring all round the planet's
disc, " more pronounced on the illuminated side than on the dark
part of the limb, but of a peculiar coppery hue, the close resem-
blance of which to the coppery hue the Moon's disc assumes
when totally eclipsed was very striking." He goes on to
express the opinion that the two appearances owe their origin to
precisely similar causes °.

The peculiarity about Mercury's phases already pointed out
(the measured breadth being different from the calculated)
obtains also with Venus. At the Greatest Elongations, the line
terminating the illumination ought to be straight, as with a
Half-Moon, but several observers have found an uncertainty
varying between 3d and 8d in the first (or last) appearance of
the dichotomisalion (according as to whether it was the E. or the
W. Elongation that was in question). Thus, at the Western
Elongation of August 1793, Schroter found the terminator
slightly concave, and it did not become straight till 8d after the
epoch of Greatest Elongation.

Previous to the present century testimony was not wanting
that Venus had a satellite, but nothing has been ascertained
about it in recent times, and Webb, with great propriety, called
the matter "an astronomical enigma." On Jan. 25, 1672, J. D.
Cassini saw, between 6h 52™ and 7h 2m A.M., a small star re-
sembling a crescent, like Venus, distant from the Southern horn
on the Western side by a space equal to the diameter of Venus.
On Aug. 28, 1686, at 4h 15™ A.M., the same experienced observer
saw a crescent-shaped light East of the planet at a distance of
snhs of fa diameter. Daylight rendered it invisible after ^ an
hour. On Oct. 23, 1740 (o.s.), Short, the celebrated optician,
with 2 telescopes and 4 different powers, saw a small star
perfectly defined but less luminous than the planet, from which

0 Zenger's paper should be consulted Month. Not., vol. xliii. p. 331. April
by all who wish to study this subject. 1883.

CHAP. V.] Venus. 103

it was distant 10' 2". On 4 different occasions between May 3
and u, 1761, Montaigne, at Limoges, saw what he believed to
be a satellite of Venus. It presented the same phase as the
planet, but it was not so bright. Its position varied, but its
diameter appeared equal to "h that of the planet. The follow-
ing extract is from the Dictionnaire de Physique, a French work
published in 1789. "The year 1761 will be celebrated in
astronomy in consequence of the discovery that was made on
May 3 of a satellite circulating round Venus. We owe it to
M. Montaigne, member of the Society of Limoges, who observed
the satellite again on the 4th and 7th of the same month.
M. Baudouin read before the Academy of Sciences of Paris a
very interesting memoir, in which he gave a determination of
the revolution and distance of the said satellite. From the
calculations of this expert astronomer we learn that the new
star has a diameter about % that of Venus, that it is distant
from Venus almost as far as the Moon is from the Earth, that
its period is 9d 7h, and that its ascending node is in the 22nd
degiee of Virgo." Wonderfully circumstantial! In March 1764
several European observers, at places widely apart, saw a
supposed satellite. Rb'dkier, at Copenhagen, on March 3 and 4,
saw it : Horrebow, with some friends, also at Copenhagen, saw
it on the ioth and nth of the same month, and they stated that
they took various precautions to make sure there was no
optical illusion. Montbaron, at Auxerre, on March 15, 28, and
29, saw the satellite in sensibly different positions p.

This is the plaintiff's case, if I may be pardoned for using
such an expression : on the other side it can only be said that
no trace of a satellite has ever been found by any subsequent
observer with larger telescopes. And with the care bestowed
on Venus by Sir W. Herschel and Schroter during so many
years, it is difficult to understand that, if a satellite existed, they
should not have seen it at some time or other q.

p Scheuten says he saw a satellite ac- letter by Lynn in The Observatory, vol.

company Venus across the Sun during x. p. 73, March 1887.
the transit of 1761. See Ast. Jahrbuck, 1 The question of the existence of a

1778. Keference may also be made to a satellite of Venus is very fully discussed,

104 The Sun and Planets. [BOOK I.

Lambert combined all the observations in a very tolerable
orbit r, but, as Hind points out 8, notwithstanding its agreement
with the observations, there is one fatal objection to it — if it
were correct, the mass of Venus would be 10 times greater than
what other methods show it to be, namely 4^^2x1 *na^ °f the
Sun. Encke gives TTrrV5jF> Littrow TtnrV7T> Miidler TTTTVT^,
Le Verrier ^r^mF» and Newcomb T^^^S- There are several
methods of ascertaining this quantity, the most obvious of which
is based on the disturbing influence exerted by Venus on the
Earth's annual motion.

Venus has ever been regarded as an interesting and popular
planet, and it is somewhat remarkable that it is the only one
whose praises are sung by the great Greek bard, who thus
apostrophises it: —

" "Eairepo j, Ss Ka\\urros tv ovpavy i<JT<nti dar^p*."

This refers to it as the Evening Star, but elsewhere in the
Iliad n we meet with it in its other function of the 'EaxrQopos, to
which the Latin Lucifer corresponds. Some have thought, and
perhaps not without reason, that it is the object referred to in
Isaiah xiv. 12.

The earliest recorded observations of Venus date from 686 B.C.,
and appear on an earthenware tablet now in the British
Museum x.

" Claudius Ptolemy has preserved for us in his Almagest many
observations of Venus by himself and other astronomers before
him, at Alexandria in Egypt. The most ancient of these obser-
vations is dated in the 476th year of Nabonassar's era and 13th of

and from a new standpoint, in a paper seen; and in one instance possibly it
by M. Bertrand in IS Astronomic, vol. i. was Uranus which was seen and mistaken
p. 201 , August 1882 ; but it does not seem for a satellite of Venus.
worth while to go more fully into the sub- r Bode's Jahrbach, 1777.
ject here. And see also M. Stroobant's 8 Sol. Syst., p. 27.
very interesting Etude sur le satellite * Homer, Hind, lib. xxii. v. 318.
tnigmatique de Venus published at u Lib. xxiii. v. 226. Pythagoras (or,
Brussels in 1887. His researches show that according to others, Parmenides) deter-
in almost all cases stars which can be iden- mined the identity of the two " stars."
tified were mistaken for a satellite ; in a T Month. Not., vol. xx. p. 319. June
few instances where the identity is 1860.
doubtful possibly a minor planet was

CHAP. V.] Venus. 105

the reign of Ptolemy Philadelphia, on the night of the 17*'' of the
Egyptian month Messori, when Timocharis saw the planet eclipse
a star at the extremity of the wing of Virgo. This date answers
to 271 B.C., Oct. 12 A.M.y" As this was not a telescopic observa-
tion, it and all others recorded before telescopes came into use,
are open to this uncertainty, that the two objects may merely
have been in juxta-positon so as to have appeared as one without
actual super-position taking place. The recorded occultation of
Mercury by Venus on May 17, 1737, was no doubt an occultation
in the strict sense of the word.

The interesting discovery of the phases of Venus is due to
Galileo z, who announced the fact to his friend Kepler in the
following logogriphe or anagram a : —

" Haec immature, a me, jam frustra, leguntur. — oy."
"These things not ripe [for disclosure] are read, as yet in vain, by me."

Or, as another interpretation has it —

" These things not ripe ; at present [read] in vain [by others] are read by me."

The "me" in the former case being the ordinary reader ; in
the latter, Galileo.

This, when transposed, becomes —

"Cynthiae figuras aemulatur Mater Amorum."
" The Mother of the Loves [Venus] imitates the phases of Cynthia [the Moon]."

The letters ' o y ' are, it will be observed, redundant, so far that
they cannot be made use of in the transposition.

To the mariner, owing to its rapid motion, Venus is a useful
auxiliary for taking lunar distances when continuous bad weather
may have prevented observations of the Sun.

In computing the places of Venus the tables of Baron De Lin-
denau, published in 1810, were long in use. but they have now

y Hind, Sol. Syst., p. 32. more distinctly, they would be found to

1 It was one of the objections urged do so. Prof. De Morgan believes the

to Copernicus against his theory of the anecdote to be apocryphal. (Month. Not.,

solar system that if it were true then the vol. vii. p. 290. June 1847.) But "se

inferior planets ought to exhibit phases. non e vero, e ben trovato."

He is said to have answered that if ever * Opere di Galileo, vol. ii. p. 42. Ed.

men obtained the power of seeing them Padova, 1 744.

106 The Sun and Planets. [BOOK I.

been superseded by those of Le Verrier, for amongst other causes
of error there existed a long inequality (first suspected by Sir G.
B. Airy about 1828, and fully expounded in 1831 b) affecting the
heliocentric places of the Earth and the planet to a very sensible
amount. This inequality goes through all its changes in about
239y, and when at a maximum displaces Venus by 3" and the
Earth by 2", as viewed from the Sun.

b Phil. Trans., vol. cxviii. p. 23, 1828 ; vol. cxxii. p. 67, 1832.

CHAP. VI.] The Earth. 107

CHAPTEK VI.

THE EARTH. ©

" 0 let the Earth bless the Lord : yea, let it praise Him, and magnify Him
for ever." — Benedicite.

Period, Sfc. — Figure of the Earth. — The Ecliptic. — The Equinoxes.— The Solstices. —
Diminution of the obliquity of the ecliptic. — The eccentricity of the Earth's
orbit. — Motion of the Line of Apsides. — Familiar proofs and illustrations of
the sphericity of the Earth. — Foucaulfs Pendulum Experiment. — Madler's tables
of the duration of day and night on the Earth. — Opinions of ancient philosophers.
— English mediceval synonyms. — The Zodiac. — Mass of the Earth.

^f^HE Earth is a planet which may perhaps be said to be in
all essential respects similar to Venus and Mars, its nearest
neighbours ; but as we are on it, it is needless to point out the
impossibility of treating of it in the same way as we treat of the
other planets. It revolves round the Sun in <$6$d 6h 9m 9'6S, at
a mean distance of 92,890,000 miles. The eccentricity of its
orbit amounting to 0-01679, this distance may either extend to
94,450,000 miles or diminish to 91,330,000 miles ; and these
differences involve variations in the light and heat reaching the

I Earth which will be represented by the figures 966 and 1033,
the mean amount being 1000.
The Earth is not a sphere, but an oblate spheroid ; that is to
say, it is somewhat flattened at the poles and protuberant at the

108

The Sun and Planets.

equator; as is the case with probably all of the planets,
following table gives the latest authentic measurements.

[BOOK I.
The

Airy ».

Besselb.

Polar Diameter

Miles.
78QQ-I7O

Miles.
•78QQ.II4

Equatorial Diameter

7925-648

7925-604

Absolute Difference

26-478

26-490

Excess of the Equatorial, ex-
pressed as a fraction of its
entire length

2 ..(8*330

2»»' 192

The close coincidence between these results affords a good
guarantee of the accuracy of both, and is noticeable as an illus-
tration of the precision arrived at in the working out of such
problems, the difference between the two values of the equatorial
diameter being only 77 yards. If we represent the Earth by a
sphere i yard in diameter, that diameter will make the polar
diameter |- inch too long.

Further, it has been suspected by General Schubert and
Colonel A. R. Clarke that the equatorial section of the Earth is
not circular, but elliptical. Colonel Clarke's conclusion is that
the equatorial diameter, which pierces the Earth through the
meridians 13° 58' and 193° 58' E. of Greenwich, is i mile longer
than the equatorial diameter at right angles to itc.

A consideration of the method in which such investigations
are conducted does not fall within the scope of the present
sketch, but in Airy's Popular Astronomy the subject of the Figure
of the Earth is handled with much clearness d.

The great circle of the heavens apparently described by the
Sun every year (owing to our revolution round that body) is
called the Ecliptic6, and its plane is usually employed by astro-
nomers as a fixed plane of reference. The plane of the Earth's
equator, extended towards the stars, marks out the equator of
the heavens, the plane of which is inclined to the ecliptic at an

• Encycl Meirop., art. Fig. of Earth,
vol. v. p. 220.

b Ant. Nach.. vol. xiv. Nos. 333-5 ; vol.
xix. No. 438.

c Mem. R.A.S., vol. xxix. p. 39. 1861.

d See p. 242 et seq.

e " The line of eclipses."

CHAP. VI.] The Earth. 109

angle which, on Jan. i, 1880, amounted to 23° 27' i7'55"; this
angle is known as the Obliquity of the Ecliptic. It is this inclination
which gives rise to the vicissitudes of the seasons during our
annual journey round the Sun. The two points where the
celestial equator intersects the ecliptic are called the Equinoxes { ;
the points midway between these being the Solstices*. It is from
the vernal (or spring) equinox that Right Ascensions are
measured along the equator, and Longitudes along the ecliptic.
The obliquity of the ecliptic is now slowly decreasing at the rate
of about 46" in JOG years. "It will not always however, be on
the decrease ; for before it can have altered 1 1° the cause which
produces this diminution must act in a contrary direction, and
thus tend to increase the obliquity. Consequently the change
of obliquity is a phenomenon in which we are concerned only as
astronomers, since it can never become sufficiently great to pro-
duce any sensible alteration of climate on the Earth's surface.
A consideration of this remarkable astronomical fact cannot but
remind us of the promise made to man after the Deluge, that
' while the earth remaineth, seedtime and harvest, and cold and
heat, and summer and winter, and day and night shall not cease.'
The perturbation of obliquity, consisting merely of an oscillatory
motion of the plane of the ecliptic, which will not permit of its
[the inclination] ever becoming very great or very small, is an
astronomical discovery in perfect unison with the declaration
made to Noah, and explains how effectually the Creator had
ordained the means for carrying out His promise, though the way
it was to be accomplished remained a hidden secret until the
great discoveries of modern science placed it within human
comprehension V

It is stated by Pliny that the discovery of the obliquity of the
ecliptic is due to Anaximander, a disciple of Thales, who was

f From cequus equal, and nox a night; still ; because the Sun when it hag reached

because when the Sun is at these points, these neutral points has attained its

day and night are theoretically equal greatest declination N. or S. as the case

throughout the world. In 1890 this oc- may be. In 1890 this occurs on June

curs on March 20 at 4h, and Sept. 22 at 21 at oh, and Dec. 21 at 9h, G.M.T.
I4h, G.M.T. » Hind, Sol. Syst., p. 33.

* From .90? the Sun, and store to stand

110 Tlie Sun and Planets. [BOOK I.

bom in 610 B.C. Other authorities ascribe it to Pythagoras or
the Egyptians, while Laplace believed that observations for the
determination of this angle were made by Tcheou-Kong in
China not less than noo years before the Christian era1. The
accord between the various determinations ancient and modern
is very remarkable, and indicates the great care bestowed by the
astronomers of antiquity on their investigations.

The eccentricity of the Earth's orbit amounts (to be more
precise than above) to o-oi679i7, and it is subject to a very
small diminution, not exceeding 0*000041 in the course of 100
years. Supposing the change to go on continuously, the Earth's
orbit must eventually become circular ; but we learn from the
Theory of Attraction that this progressive diminution is only to
proceed for a certain time. Le Verrier has shown that this
diminution cannot continue beyond 24,000 years, when the
eccentricity will be at its minimum of '0033 : it will then begin
to increase again ; so that unless some external cause of pertur-
bation arise, these variations may continue throughout all ages,
within certain not very wide limits. They are due to the
attractive influence of the Planets. The above value of the
eccentricity is for i Sco'o A.D.

The line of apsides is subject to an annual direct change of
1 1 '7 7", independent of the effects of precession (to be described
hereafter) ; so that, allowing for the latter cause of disturbance,
the annual movement of the apsides may be taken at rather more
than i'. One important consequence of this motion of the major
axis of the Earth's orbit is the variation in the lengths of the
seasons at different periods of time. In the year 3958 B.C., or,
singularly enough, near the epoch of the Creation of Adam, the
longitude of the Sun's perigee coincided with the autumnal
equinox ; so that the summer and autumn quarters were of equal
length, but shorter than the winter and spring quarters, which
were also equal. In the year 1267 A.D. the perigee coincided
with the winter solstice ; the spring quarter was therefore equal
to the summer one, and the autumn quarter to the winter one,

1 Conn, des Temps. 1811, p. 429.

CHAP. VI.] T/ie Earth. Ill

the former being the longest. In the year 6493 A-D- *ne perigee
will have completed half a revolution, and will then coincide
with the vernal equinox ; summer will then be equal to autumn,
and winter to spring; the former seasons, however, being the
longest. In the year 11719 A.D. the perigee will have completed
three-fourths of a revolution, and will then coincide with the
summer solstice ; autumn will then be equal to winter, but longer
than spring and summer, which will also be equal. And finally
in the year 16945 A.D. the cycle will be completed by the coinci-
dence of the solar perigee with the autumnal equinox. This
motion of the apsides of the Earth's orbit, in connection with
the inclination of its axis to the plane of it, must quite obviously
have been the cause of very remarkable vicissitudes of climate
in pre- Adamite times k.

One result of this position of things we may readily grasp at
this moment. As a matter of fact, in consequence of our seasons
being now of unequal length, the spring and summer quarters
jointly extend to i86d, whilst the autumn and winter quarters
comprise only i78d. The Sun is therefore a longer time in the
Northern hemisphere than in the Southern hemisphere : hence
the Northern is the warmer of the two hemispheres. Probably
it may be taken as one result of this fact, that the North
Polar regions of the Earth are easier of access than the
South Polar regions. In the Northern hemisphere navigators
have reached to 81° of latitude, whereas 71° is the highest
attained in the Southern hemisphere.

It is not a very easy matter in treating of the Earth to deter-
mine where astronomy ends and geography begins ; but a brief
allusion to the means available for deciding the form of the Earth
seems all that it is now necessary to add here. We learn that
the Earth is a sphere (or something of the sort) by the appear-
ance presented by a ship in receding from the spectator : first
the hull disappears, then the lower parts of the rigging, and
finally the top-masts. The shadow cast on the Moon during a

k See Papers by Croll, Phil. Mag,, 4th xxxvi. pp. 141 and 362, Aug. and Nov.
Ser., vol. xxxv. p. 363, May 1868; vol. 1868; Geikie's Great Ice Age, &c.

112 The Sun and Planets. [BOOK I.

lunar eclipse, and the varying appearances of the constellations
as we proceed northwards or southwards, are amongst the other
more obvious indications of the Earth's globular form.

Fig. 56, Plate VI, represents an experimental proof of the
Earth's rotation on its axis. This particular form of proof excited
no small interest in scientific (and unscientific) circles when it
was first promulgated by the French savant Foucault in the year
I85I1. If a pendulum, or its equivalent, a heavy weight sus-
pended by a long wire, could be erected at either pole of the
Earth, and be set swinging in any direction and a note of the
direction taken, it is evident that if the plane of oscillation
were observed to be perpetually shifting with regard to the
terrestrial point noted at the beginning of the experiment, it
would be a proof that either the terrestrial station was shifting
with respect to the pendulum or the pendulum was shifting with
respect to the station. The latter idea being contrary to reason
tne former alternative must be adopted. It is evident that both
poles of the Earth being inaccessible to us, the experiment
cannot be carried out in the theoretically simple fashion sug-
gested above ; but in a modified form it can be tried and will
yield an intelligible result at a station on the Earth's surface
between the Pole and the Equator, provided it be not very near
the Equator. The rationale of the experiment is simply this,
that the weight being made to oscillate in a straight line (and
starting it by burning the thread which holds it should secure
this) it will swing backwards and forwards in an invariable
plane. If the building in which the experiment is tried were at
rest, the plane of oscillation would be constantly parallel to a
line joining any 2 points in the building if the pJane of oscilla-
tion had been parallel to that line when the start was made.
But if the building moves in consequence of an axial rotation
of the Earth, the angle between the plane of oscillation and the
line parallel thereto at the start will be continually varying and
in the course of some hours will vary through an angular space
of many degrees. Could the experiment be tried at the Pole the

1 See Proc. Soy. Inxt., vol. i. p. 70: Arago, Pop. Ast., Eng. ed., vol. ii. p. 27.

Fig. 56.

Plate VI.

FOUCAULT'S PENDULUM EXPERIMENT TO SHOW

THE EARTH'S AXIAL ROTATION.

CHAP. VL] The Earth. 115

angular variation would be the whole 360° of a circle, in the time
24 hours, being the duration of the sidereal day.

At the Equator there will be no visible effect, for the point of
suspension will be carried round the Earth's axis equally with
the ground beneath the weight ; on the other hand, because the
point of suspension at the Pole was at the Pole it would have
no motion at all and the plane of vibration would be telling its
own tale every instant. For a station intermediate between the
Pole and the Equator the effect will be, so to speak, of an
intermediate character ; the ground will shift to a certain extent,
but not through the angle of 360° in 24 hours. The extent of
the shifting will vary with the latitude, so that it will not
always be easy to obtain a covered building free from currents
of air, and with an available point of suspension sufficiently
elevated above the ground to insure the vibration going on long
enough to enable the experiment to be readily visible to an
audience.

This experiment was first tried by Foucault at the Pantheon in
Paris, and subsequently in London at The Russell, London, Poly-
technic, and Royal Institutions and King's College, and at York,
Bristol. Dublin, Aberdeen, New York, Ceylon, and other places.
The angular deviation for i hour was found to be at Paris n-i°;
at Bristol uf°; at Dublin nearly 12°; and at Aberdeen about
i2|°, whilst at New York (Lat. 40°) it was only 9!° and in
Ceylon (Lat. 7°) only 1-8°.

Binet calculated that the time required for one revolution of
the pendulum in the latitude of Paris would be 32h 8m. At
Dublin a complete revolution was watched and observed to
occupy 28h 26m.

In the engraving the figures i, 2, 3, 4, 5, 6, are supposed to
indicate the hours of the duration of the experiment after the
pendulum has been set in motion by the severance by the candle-
flame of the cord which held the weight at rest.

The following table of the greatest possible length of the day
in different latitudes I cite from Madler1": —

m Populare Astronomie, Berlin 1861, p. 30.
I 2

116

The Sun and Planets.

[BOOK I.

Hours.

O O 12 65 48 22

16 44 13 66 21 23

30 48 14 66 32 24

41 24 15 67 23 I month.

49 2 16 6q .51 2

54 31 • J7 73 40 3

58 27 18 78 ii 4

61 19

63 23

64 50

The 8646 hours which make up a year, are, according to
Madler, thus distributed : —

Hours.

o /

65 48

66 21

66 32

67 23

69 51

73 40

78 ii

19 84 5

90 o

At the Equator.

4348 hours Day,

852 „ Twilight,
3449 „ Night.

At the Poles.

4389 hours Day,
2370 „ Twilight,
1887 „ Night.

Among the ancients, Aristarchus of Samos, and Philolaiis,
maintained that not only did our globe rotate on its own axis,
but that it revolved round the Sun in 12 months0. Nicetas of
Syracuse is also mentioned as a supporter of this doctrine0.
The Egyptians taught the revolution of Mercury around the
Sunp ; and Apollonius Pergseus assigned a similar motion to
Mars, Jupiter, and Saturn — but I am digressing.

Hesiod states that the Earth is situated exactly half-way
between Heaven and Tartarus : —

" From the high heaven a brazen anvil cast,
Nine days and nights in rapid whirls would last,
And reach the Earth the tenth ; whence strongly hurl'd,
The same the passage to th' infernal world."

Theogonia, ver. 721.

Our ancestors 300 or 400 years ago termed the ecliptic the
"thwart circle"; the meridian, the "noonsteede circle"; the
equinoxial, "the girdle of the sky"; the Zodiac, "the Bestiary,"

n Archimedes, In Arenario ; Plutarch,
De Placit. Philos., lib. ii. cap. 24 ; Diog.
Laert. In Philolao.

0 Cicero, Acad. Quast., lib. ii. cap. 39.
p Macrobius, Comment, in Somn. Scip.,
lib. i. cap. 19, and others.

CHAP. VI.] The Earth. 117

and "our Lady's waye." The origin of the division of the
zodiac into constellations is lost in obscurity. Though often
attributed to the Greeks, it now seems certain that the custom
is of much earlier date ; and is possibly due to the Egyptians
or even to the ancient Hindus or the Chinese, in whose behalf,
however, a claim to prior knowledge is always put in, whenever
we Europeans fancy that we have made a discovery.

The following are recent values of the mass of the Earth com-
pared with that of the Sun: — Encke ssgVsT* Littrow -3-5^0^775
Madler -s-g-s-f-g-g, and Le Verrier -g^Vstf- Le Verrier, however,
once seemed to consider that these values were all too small, but
that in our state of uncertainty as to the Sun's parallax it was
not possible to assign with confidence a definitive value q.
Newcomb taking the Earth and the Moon together gives for
their combined mass the fraction ^yVc^ or f°r the Earth alone

See Month. Not., vol. xxxii. pp. 302 and 323. 1872.

118 The Sun and Planets. [Boon I.

CHAPTER VII.

THE MOON. <[

Period, if c.— Its Phases. — Its motions andtkeir complexity. — Libration. — Ececlion. —
Variation — Parallactic Inequality. — Annual Equation. — Secular acceleration.
— Diversified character of the Moon's surface. — Lunar mountains. — Seas. —
Craters. — Volcanic character of the Moon. — Bergeron's experiment. — The lunar
mountain, Aristarchus. — Teneriffe. — Lunar atmosphere. — Researches ofSchroter,
&c. — Hansens curious speculation. — The Earth-shine. — The Harvest Moon. —
Astronomy to an observer on the Moon. — Luminosity and calorific rays. —
Historical notices as to the progress of Lunar Chartography. — Lunar Tables. —
Meteorological Influences.

rriHE Moon, as the Earth's satellite, is to us the most important
of the " secondary planets," and will therefore receive a
somewhat detailed notice.

The Moon revolves round the Earth in 27d /h 43™ n-46ns, at
a mean distance of 237,300 miles. The eccentricity of its orbit
amounting to 0-0662, the Moon may recede from the Earth to a
distance of 253,000 miles, or approach it to within 221,600 miles.
Its apparent diameter8 varies between 29' 21" and 33' 31". The
diameter at mean distance is 31' 5". It will fix this in the
memory to note that the apparent diameter is the same as the
Sun's, and equals £°. The real diameter, according to Madler, is
2159-6 miles; according to Wichmann 2162 miles. Recent re-
searches shew that these values are too great ; and that a
correction of about 2" (Airy) or 2-15" (De La Rue) must be
applied to the measured visual diameter of the Moon, to allow

• These figures must be regarded as of the Moon will be found to vary con-

geometrically rather than practically siderably. And the diameter at mean

true, for under varying circumstances of distance is not the arithmetical mean of

altitude above the horizon the diameter the extremes of apparent diameter.

CHAP. VII.] The Moon. 119

for the exaggeration of its dimensions by irradiation. This
reduction amounts to about 2 miles. The most delicate measure-
ments indicate no compression.

The Moon has phases like the inferior planets ; and of the
various influences ascribed to it, that which results in the tides of
the ocean is the most important, and will hereafter be treated at
some length.

The motions of the Moon are of a very complex character :
they have largely occupied the attention of astronomers during
all ages, and it is only within a recent period that they can be
said to have been mastered.

Speaking roughly, we may say that the same hemisphere of the
Moon is always turned towards us ; but although this is, in the
main, correct, yet there are certain small variations at the edge
which it is necessary to notice. .The Moon's axis, although
nearly, is not exactly perpendicular to the plane of its orbit,
deviating therefrom by an angle of i° 32' 9" (Wichmann) ;
owing to this fact, and to the inclination of the plane of the
lunar orbit to that of the ecliptic, the poles of the Moon lean
alternately to and from the Earth. When the North pole leans
towards the Earth we see somewhat more of the region sur-
rounding it, and somewhat less when it leans the contrary way ;
this is known as librarian in latitude10. The extent of the dis-
placement in this direction is 6° 47'. In order that the same
hemisphere should be continually turned towards us, it would
be necessary not only that the time of the Moon's rotation on its
axis should be precisely equal to the time of the revolution in its
orbit, but that the angular velocity in its orbit should, in every
part of its course, exactly equal its angular velocity on its axis.
This, however, is not the case, for the angular velocity in its
orbit is subject to a slight variation, and in consequence of this
a little more of its Eastern or Western edge is seen- at one
time than another : this phenomenon is known as the libration
in longitude, and was discovered by Hevelius, who described it in
1647°. The extent of the displacement in longitude is 7° 53'.

'' Librans, balancing. c In his Selenoffraphia.

120 The Sun and Planets. [BOOK I.

The maximum total libration (as viewed from the Earth's centre)
amounts to 10° 24'. On account of the diurnal rotation of the
Earth, we view the Moon under somewhat different circum-
stances at its rising and at its setting, according to the latitude
of the Earth in which we are placed. By thus viewing it in
different positions, we see it under different aspects ; this gives
rise to another phenomenon, the diurnal libration, but the
maximum value of this is only i° i' 24".

This periodical variation in the visible portion of the Moon's
disc seems to have been first remarked by Galileo — a discovery
very creditable to him when we consider the materials with
which he worked. According to Arago, the various librations
enable us to see altogether -Tyff of the Moon's surface, the portion
always invisible amounting only to TVtr of the same.

The following account of the chief perturbations in the motion
of the Moon is, in the main, abridged from that invaluable
repertory of astronomical facts, Hind's Solar System.

1. The Erection depends on the angular distance of the Moon
from the Sun, and on the mean anomaly of the former. It
diminishes the equation of the centre in the syzygies and in-
creases it in the quadratures, increasing or diminishing the
Moon's mean longitude by i° 20' 29-9". Period, about
3id J9h 3Om. Discovered by Ptolemy, but previously suspected
by Hipparchus.

2. The Variation depends solely on the angular distance of the
Moon from the Sun. Its effect is greatest at the octants, and
disappears in the syzygies and quadratures, the longitude of the
Moon being altered thereby 35' 41-6" when at a maximum.
Period, half a synodical revolution, or about I4d i8h. Its
discovery is usually ascribed to Tycho Brahe, but Sedillot and
others claim it for Abul Wefa, who lived in the 9th centur}7. It
was the first lunar inequality explained by Sir I. Newton on the
Theory of Gravitation.

3. The Parallactic Inequality arises from the sensible difference
in the disturbing influence exerted by the Sun on the Moon,
according as the latter is in that part of its orbit nearest to,

CHAP. VII.] The Moon. 121

or most removed from, the Sun. At its maximum it alters the
Moon's longitude by about 2'. Period, one synodical revolution,
or 29d i2h 44ra.

4. The Annual Equation is that inequality in the Moon's
motion, which results from the variation in the -velocity of the
Earth, caused by the eccentricity of its orbit. At its maximum
the Moon's longitude is altered by n' IJ>97". Period, one
anomalistic solar year, or 365* 6h 13™ 49'3S.

5. The Secular Acceleration of the Moon's mean motion had been
supposed to be caused wholly by the diminution in the eccen-
tricity of the Earth's orbit which has been going on for many
centuries, as has already been pointed out; but in 1853 it was
shewn by Professor Adams that the amount of this acceleration
is just double that which such diminution per se would account
for. At present the mean motion of the Moon is being increased
at the rate of about 12" every 100 years. This inequality was
detected by Halley in 1693 from a comparison of the periodic
time of the Moon, deduced from Chaldsean observations of
eclipses, made at Babylon in the years 720 and 719 B.C., and
Arabian observations made in the 8th and 9th centuries A.D.
Laplace first reasoned out and explained the theory of the
inequality, and up to the date of Adams's researches his calcu-
lations were supposed to be complete. It was, however, shewn
by our great geometer that Laplace had neglected certain
quantities in his calculations, and so estimated the accelerating
effect of the increase of the minor axis of the Earth's orbit at
double its true amount. It has been suggested by Delaunay and
others that half of this seeming acceleration has its origin in the
real increase in length of our terrestrial day, which has actually
lengthened and continues to lengthen by a small fraction of a
second annually ; and this slower rotation of the Earth (for that
is what it amounts to) is conceived to have its origin in the
friction of the tides, which act as a break on the Earth rotating
beneath them.

Hansen elucidated, a few years ago, two other inequalities in
the Moon's motion, due, the one directly and the other indirectly

122 The Sun and Planets. [BOOK I.

to the influence of Venus d; and it was hoped that when these
were taken into account it would have been found possible to
say that the position of the Moon deduced from theory is almost
precisely the same as that obtained by direct observation, and
therefore that our knowledge of the Moon's motion is almost
perfect ; but further research by Sir G. B. Airy has cast a doubt
on the matter.

Some matters connected with the Moon's orbit which are of
importance in relation to eclipses will be referred to when we
come to deal with eclipses (Book II., post) ; but it is desirable
to note here the fact that the line of nodes of the lunar orbit
revolves round the ecliptic in a retrograde direction in
i8y 2i8d aih 22m 46". "This retrogression of the nodes is
caused by the action of the Sun which modifies the central
gravity of the Moon towards the Earth. It is not, however, an
equable motion throughout the whole of the Moon's revolution ;
the node, generally speaking, is stationary when she is in
quadrature, or in the ecliptic ; in all other parts of the orbit it
has a retrograde motion, which is greater the nearer the Moon is
to the syzygies, or the greater the distance from the ecliptic. The
preponderating effect at the end of each synodic period is,
however, retrocessive, and gives rise to the revolution of the line
of nodes in between 18 and 19 years6."

This motion must not be confused with the motion of the line
of apsides of the lunar orbit. " The line of apsides or major
axis of the lunar orbit has, from a similar cause, a direct motion
on the ecliptic, and accomplishes a whole revolution in
8y 310* i3h 48™ 53s, so that in 4y I55d the perigee arrives where
the apogee was before. This motion of the line of apsides, like
the movement of the nodes, is not regular and equable through-
out the whole of a lunar month ; for when the Moon is in
syzygies the line of apsides advances in the order of signs, but is

d The statement in the text is not with the Earth. The second of these

quite correct, so far that in the case of Hansen inequalities runs its course in

one of these inequalities (the 239-year 273 years. See on the whole subject a

one) what Hansen did was to trace the paper by Airy in Month. Not., vol.

operation on the Moon of that influence xxxiv. p. i. Nov. 1873.

of Venus which Airy connected only e Hind, Sol. Syst., p. 42.

CHAP. VII ]

The Moon.

123

retrograde in quadratures. But the preponderating effect in
several revolutions tends to advance the apsides, and hence
arises their revolution in between 8 and 9 years."

Fig- 57-

VIEW OF A PORTION OF THE MOON'S SURFACE ON THE

S.E. OF TYCHO. (Nasmyth.}

When viewed by the naked eye the Moon presents a mottled
appearance ; this arises from our satellite being unequally
reflective, a fact which the telescope teaches us to be due to

124 The Sun and Planets. [BOOK I.

numerous mountains and valleys on its surface, as was dis-
covered by Galileo. The proof of the existence of these is found
in the shadows cast by the high peaks on the surrounding
plains, when the Sun shines obliquely ; these shadows disappear,
however, at the full phase, as the Sun then shines perpendicularly
on the Moon's surface. Between the times of New and Full
Moon the boundary line of the illuminated portion (often called
the "Terminator") has a rough jagged appearance: this is
caused by the Sun's light falling first on the summits of the
peaks, the surrounding valleys and declivities being still in
shade ; thus a disconnected form is given to the whole edge, and
so arises the jagged aspect above referred to.

Most of the lunar mountains have received names, chiefly those
of men eminent in science, both ancient and modern. Biccioli
proposed this nomenclature as preferable to that of Hevelius, who
adopted terrestrial geographical names. Beer and Madler, to
whom we owe so much of our knowledge of the Moon, measured
the heights of 1095 lunar elevations, several of which exceed
2O,oooft. But the absence of water on the Moon makes the
choice of a datum line difficult.

Grey plains, or seas, analogous probably to our "steppes" and
prairies, form another noticeable feature in the topography of
the Moon. They were called " seas " from their supposed nature,
but though the opinion is overthrown the appellation is retained,
and specific names have been applied to several of them.

The crater mountains are by far the most curious objects shewn
by the telescope. These are apparently of volcanic origin, and
usually consist of a basin with a conical elevation rising from
the centre. Their outline is generally circular or nearly so, but
oblique view will often give those in the neighbourhood of the
limb an apparently elliptical contour. Their immediate formation
is probably due to the escape of gases from the interior of the
Moon when that body was in a semi-fluid state, as it is conceived
once to have been. The effect of the passage of air through a
semi-fluid substance may be seen in the case of lime slaked by
builders for fine plastering, when the air-bubbles, having forced

CHAP. VII.]

The Moon.

125

their way upwards to the surface and burst, leave apertures
rising in cones forming a good imitation of many lunar craters.

Some further experimental proof is to be had of the soundness
of this view. Bergeron, having noticed the manner in which
gases or vapours, when they pass through a pasty mass, leave
a series of funnel-shaped holes behind them, and struck with
the analogy which these holes present to the craters of the
Moon, tried to reproduce the phenomenon on a larger scale, and
for that purpose caused a current of hot air to pass through

Fig. 58.

!^^''^^^^^ .:'. '&

. js ' -:A

K '\:-

IMITATION OF THE STRUCTURE OF THE MOON S SURFACE.

(Bergeron's experiment?)

a mass of molten metal. For the convenience of the experiment
the metal chosen was an alloy fusible at a comparatively low
temperature, Wood's alloy, which melts at about 158° F., being
the first employed. A current of hot air was forced through
the alloy, which was melted in a hot- water bath. Then, as the
metal was allowed to cool slowly, the supply of air being kept
up, a bubbling was created, which drove away the particles
which were beginning to solidify from over a considerable area
and a large ring was formed. The air still being blown through,

126

The Sun and Planets.

[BOOK I.

the edges of the ring rose little by little, and a perfect model
of a crater was produced ; and as the process of cooling went
on a cone was formed, and the crater at the same time grew
deeper, its inner slopes shewing a much greater inclination than
the outer. When the process of forcing the air through the alloy
was interrupted, a second inner ring was formed, reminding the
experimenter of the appearance presented by Copernicus, Archi-
medes, and other lunar craters. M. Bergeron considers that his
experiments throw much light on the past history of the Moon.
Instead of air, various vapours may have given rise to the craters
and ring-mountains. These vapours rose freely from the Moon
when it was in a fluid state, but the exterior of the planet being
cooled more rapidly than the interior, the latter, still fluid,
continued to give off vapours when the surface had already become
a pasty mass. These vapours passed through this envelope and

found a vent at certain

Fi£- 59- points only, doubtless

where the tendency to
solidification was least f .

Cassini, Sir W. Herschel,
Kater, Smyth, and other
observers have fancied a
mountain named Aristar-
chus to be a volcano in
action. It is now generally
understood that the faint
illumination discerned on
the summit is merely due
to the " Earthshine " ; but,
in the words of Sir J.
Herschel, " decisive marks
of volcanic stratification,

arising from successive deposits of ejected matter, and evident
indications of lava currents streaming outwards in all di-
rections, may be clearly traced with powerful telescopes. In

' Comptes Sendvs, vol. xcv. p. 324, 1882.

THE LUNAR MOUNTAIN, AKI8TARCHU8,
ILLUMINATED.

CHAP. VII.]

The Moon.

127

Lord Rosse's magnificent reflector the flat bottom of the crater
called Albategnius is seen to be strewed with blocks, not
visible in inferior telescopes, while the exterior ridge of another
(Aristillus) is all hatched over with deep gullies radiating
towards its centre8." The accompanying engraving represents
Aristarchus as seen by Smyth on Dec. 22, 1835, with its peak
illuminated. Figs. 60 and 61 shew under opposite phases

Fig. 60.

Fig. 61.

THE LUNAR MOUNTAIN, ARISTARCHUS.

of illumination the streaky radiations surrounding Aristarchus
which may or may not betoken streams of lava which have
flowed away in various directions after being erupted from the
crater. The external height of Aristarchus has been calculated
to be 2500 ft, and its internal depth 7000 ft. Of Copernicus it
may be remarked that it is near the Terminator and is seen
under the most favourable conditions of illumination a day or two
after the ist Quarter.

Outlines of Ast., p. 283.

128

The Sun and Planets.

[BOOK I.

The Volcanic origin of the lunar craters cannot be more plainly
demonstrated than by comparing an engraving such as Fig. 62,
which represents a knoicn volcano — Teneriffe — with any good
engraving of a lunar crater, e.g. Copernicus, Fig. 65. The simi-
larity is too striking to admit of there being any doubts as to the
identity of the physical causes which have originated each
surface.

Fig. 62.

I**

THE PEAK OF TENERIFFE. (C. P. Smyth.}

A systematic topographical description of the Moon would be
entirely beyond the compass of this work, and there is the less
occasion for it as that by the Rev. T. W. Webbh is a very ex-
haustive one. The works of Hind i and Arago k also contain
briefer accounts.

The question as to whether or not the Moon has an atmosphere l

h Celest. Objects for common Tele-
scopes.

1 Sol. Syst., p. 48 et seq.

k Pop. Ast., vol. ii. p. 258 et seq.,
Eng. ed.

1 See an important memoir by Bessel

in Ast. Nach., vol. xi. p. 411. July
1 6, 1834. -^n<i tne reader will do well
to consult a paper by Prof. Challis in
Month. Not., vol. xxiii. p. 231. June
1863. And Neison has written on this
subject. (The Moon, p. 19.)

Figs. 63-65.

Plate VII.

ARCHIMEDES. (Schroter.')

Pico. (Schroter.}

COPERNICUS. (Nasmyth.'}

LUNAR MOUNTAINS.
K

Figs. 66-71.

Plate VIII.

ARCHIMEDES. April 3, 1884.
8h 45ra to 9h 45™ p.m.

GASSENDI. April 6, 1884.
9h ora to ioh 45ra p.m.

SINUS IRIDUM. July 3, 1884.
9h 45m to iih 15™ p.m.

KEPLER AND ENCKE. Aug. 8, 1884.
gh 2ora to ioh 15™ p.m.

FRASCATORIUS. Aug. 10, 1884.
i4h ora to ih 41".

PLATO. Nov. 10, 1884.

I 8" Ira._1gh -m_

LUNAR MOUNTAINS.

(Dr L. WeinfJc.
K 2

CHAP. VII.]

The Moon.

133

Fig. 72.

must be answered in the negative, though some affirmative testi-
mony is forthcoming. Schroter considered there is one, but
he estimated the height at only 5376", and Laplace thought
it to be more attenuated
than the best attainable
vacuum of an air-pump.
Schroter arrived at his
conclusion by following
up a remark of Au-
zout's m, that if the Moon
had an atmosphere the
phenomenon of twilight
would in consequence
present itself. He was at
length able, he thought,
to determine that when THE LUNAR MOUNTAIN EUDOXUS, SHOWING WALL

ACROSS THE CBATEK. (TrOUVelot.}

the Moon exhibited a

very slender crescent, a faint crepuscular light, extending from

each of the cusps along the circumference of the unenlightened

Tig. 73-

portion of the disc to a distance
of i' 20", could be perceived ;
its greatest breadth being 2".
He thence inferred the height
of the atmosphere to be only
o'94", corresponding to the
5376" given above n. The
Moon would describe this arc
in less than 2 seconds of time,
and this circumstance was
adduced by Schroter as an
explanation of the difficulty
attending its direct detection THE GULF OF IRIS SEEN WHEN THE MOON

, IS IO DAYS OLD.

during eclipses and occulta-

tions. Sir J. Herschel considered that we are entitled to conclude

m Mem. Acad. des Sciences, vol. vii. p.
1 06.

11 Phil. Trans., vol. Ixxxii. p. 354.
1792.

134 The Sun and Planet*. [BOOK I.

the non-existence of any atmosphere at the Moon's surface dense
enough to cause a refraction of \" , i.e. having TTnro- the density
of the Earth's atmosphere °. Both Beer and Madler thought that
the Moon has an atmosphere, but that it is of insignificant extent,
owing to the smallness of our satellite's mass ; and they also
say, " It is possible that this weak envelope may sometimes,
through local causes, dim or condense itself," — an idea which, if
proved, would help to clear up some of the conflicting details of oc-
cultation phenomena. The suddenness with which occultations of
stars by the Moon take place is, however, commonly regarded as
one of the best proofs that a lunar atmosphere does not exist.
And the spectroscope supplies negative evidence of like import.

" Professor Hansen has recently started a curious theory, from
which he concludes that the hemisphere of the Moon which is
turned away from the Earth may possess an atmosphere. Having
discovered certain irregularities in the Moon's motion, which he
was unable to reconcile with theory, he was led to suspect that
they might arise from the centre of gravity of the Moon not
coinciding with her centre of figure. Pursuing this idea, he found
upon actual investigation that the irregularities would be almost
wholly accounted for by supposing the centre of gravity to be
situated at a distance of 33 \ miles p beyond the centre of figure.
Assuming this hypothesis to be well founded, Professor Hansen
remarks that the hemisphere of the Moon which is turned to-
wards the Earth is in the condition of a high mountain, and that
consequently we need not be surprised that [little or] no trace of
an atmosphere exists ; but that on the opposite hemisphere, the
surface of which is situated beneath the mean level, we have no
reason to suppose that there may not exist an atmosphere, and
consequently both animal and vegetable life q." Professor New-
comb however has disputed these conclusions of Hansen, which
it is obvious must be very difficult of either proof or disproof.

For a few day s, both before and after New Moon, an attentive

0 Outlines of Ast., p. 284. This frac- erroneously so, though how the mistake

tion is probably erroneous. Neison makes has crept in is not clear,

it *$-$. i Note by translator, Arago's Pop.

P " 1740 " in the English original, but Att., vol. ii. p. 276, Eng. ed.

CHAP. VII.] The Moon. 135

observer may often detect the outline of the unilluminated portion
without much difficulty. This lustre is the light reflected on the
Moon by the Earth — " Earth-shine " in fact ; the French call it
la lumiere cendree, following the Latin lumen incinerosum, or the
" ashy light." In England it is popularly known as " the Old
Moon in the New Moon's arms." This light is stronger during
the waning of the Moon than at any other time ; as was noticed
by Galileo, whose opinion was confirmed by Hevelius and other
more modern astronomers. Hevelius remarked, moreover, that
in the waning Moon the illumination is less intense than when
the phases are increasing — a fact which would seem to indicate,
as Arago has pointed out r, that the Western part of the lunar
disc is on the whole better adapted for reflecting the solar rays
than the Eastern part ; assuming this to be true, an obvious
explanation is furnished for the fact that the Earth-shine is more
luminous before the New Moon than after it. Janssen, in 1881,
succeeded in photographing the " Earth-shine " on the Moon when
the latter was 3 days old. In the photographs the " continents "
were plainly distinguishable from the " seas s."

The Harvest Moon is the name given to that full Moon which
falls nearest to the autumnal equinox ; as our satellite then rises
almost at the same time on several successive evenings, and at a
point of the horizon almost precisely opposite to the Sun (so that
the duration of its visibility is about the maximum possible), it
is of much assistance to the farmer at that important period of
the year. In the words of Ferguson, " The farmers gratefully
ascribe the early rising of the full Moon at that time of the year
to the goodness of God, not doubting that He had ordered it so
on purpose to give them an immediate supply of moonlight after
sunset, for their greater conveniency in reaping the fruits of the
Earth*." Although this near coincidence in several successive
risings of the Moon takes place in every lunation when our
satellite is in the signs Pisces and Aries, yet the phenomenon is

r Arago, Pop. Ast., vol. ii. p. 300, Eng. ed.
8 Nature, vol. xxiii. p. 518. March 31, 1881.
* Astronomy, p. 136. Ed. of 1757.

136 The Sun and Planets. [BOOK I.

only prominently noticeable when it is "full" in these signs, which
only occurs at or near the autumnal equinox, and when the Sun
is in Virgo or Libra. The rationale of the harvest Moon is this : —
Suppose the Moon to be full on the day of the autumnal equinox,
the Sun is then entering Libra, and the Moon, Aries ; the
former setting exactly in the West, the latter rising exactly
in the East: the Southern half of the ecliptic is then entirely
above the horizon, and the Northern half entirely below, and the
ecliptic itself makes the least possible angle with the horizon.
The Moon in then advancing 13°, or one day's portion, in its
orbit (which is but slightly inclined to the ecliptic) will become
less depressed below the horizon, and will therefore have a less
hour-angle to traverse by the diurnal motion after sunset in order
that it may come into view the next night than at any other
timeu. That harvest Moon is (astronomically} most favourable
which happens about Sept. 23, with the Moon in the ascending
node of her orbit, which then coincides with the vernal equinox.
Under such circumstances the Moon may rise for 2 or 3 nights,
later, night by night, by no more than about iom.

As a rule however, the variation between the times of two
successive risings will seldom be less than about i7m; whilst
the greatest possible variation is about ih i6m ; this takes place
when the Moon is in Libra, and at the same time at or near its
descending node.

The Moon next after the Harvest Moon is (or used to be)
called the Hunter s Moon.

It is in winter (just when it is most wanted, indeed) that
there is most moonlight for dwellers in the Earth's Northern
hemisphere. That is to say, the Moon is at its full at the same
time that it is at its highest possible Northern altitude, and
therefore longest above the horizon ; in other words, the Earth's
Northern hemisphere experiences the maximum possible amount
of exposure to Moonlight. All this is the necessary result of the
fact that Full Moon happens when our satellite is 180° away

u In Lockyer's Elementary Lessons in diagram and description dealing with
Astronomy (p. 172) there is a good this matter.

CHAP. VII.] The Moon. 137

from the Sun, i. e. exactly opposite to it. At midwinter, the Sun
being at its maximum depression, obviously the Moon is at its
maximum elevation, with the result above stated. This recital
will be complete by adding that the nights of short Moon in winter
are also the nights before and after New Moon, when there is the
smallest possible amount of Moonlight to lose. In summer, of
course, in the Earth's Northern hemisphere the reverse of all this
is the condition of things : the Moon's elevation above the
horizon is the minimum possible, and the Earth's exposure to
the Moon's rays is consequently also the minimum possible.

As seen from the Sun, with the Earth in perihelion and the
Moon in apogee, the Moon never departs more than 10' 42" from
the Earth at its greatest Elongation. Since the axis of the Moon
is very nearly perpendicular to the plane of her orbit, our
satellite has of course scarcely any change of seasons. At its
equator the mean solar day has a constant length of 354h 22m,
or I4d i8h 22m of our mean solar time; in other words, it is
equal to half the period of the Moon's synodical revolution round
the Earth. As is the case on the Earth, the length of the longest
day on the one hand and of the shortest on the other increases
and diminishes according as the assumed place of observation
approaches the lunar poles : so that at the selenographic latitude
of 45° these times become I4d 2ib 19™ and I4d J5h 26™ ; and at
the latitude of 88°, i8d i7h 28m and iod i9h i6m respectively.

By an observer placed on the Moon some astronomical pheno-
mena would be witnessed under circumstances widely different
from those under which we see them. The apparent diameter
of the Earth would be about 2°, and its apparent superficial
extent 13 times greater than the apparent superficial extent of
the Moon as seen from the Earth. More than this: the Earth
is almost a fixed object in the lunar heavens, only altering its
place by the amount of the libration, or traversing backwards
and forwards a space having an extent of 15° 30' in longitude
and 13° 1 8' in latitude. The Earth exhibits to the Moon exactly
the same kind of phases which the latter does to us, but in a
reverse order. For when the Moon is Full, the Earth is invisible

138 The Sun and Planets. [BOOK I.

to the Moon ; and when the Moon is New, the Earth is Full to
the Moon. These remarks apply only to those parts of the lunar
surface which are turned towards our globe ; for a spectator
on the opposite side would never see the Earth at all, and
spectators located on the apparent borders of the lunar disc
would only now and then obtain a glimpse of it in their horizon,
for which they would be indebted to the librations in longitude
and latitude already noticed.

If the whole sky were covered with Full Moons they would
scarcely make daylight, for Bouger's experiments1 give the brilli-
ancy of the full Moon as only 7!nnnnr that of the Sun. Wollaston's
value is OTTTTT/ Zollner's ^rsVfr^ and G. P. Bond's TT0Vwz

The Moon's surface is supposed to be much heated, possibly,-
according to Sir J. Herschel, to a degree much exceeding that
of boiling water* ; yet we are not in a general way conscious of
there being any heat at all available for warming the Earth.
This need not however excite surprise, for it is probably very
small in amount, and what there is of it is doubtless quickly
absorbed in the upper strata of our atmosphere. Melloni, in 1 846,
thought that he detected a sensible elevation of temperature by
concentrating the rays of the Moon in a lens 3ft in diameter.
C. P. Smyth, in 1 856, also thought that he obtained evidence on
Teneriffeb of the Moon's rays possessing calorific power, but his
instrumental appliances were not very perfect. Professor Tyndall
has stated that his experiments in 1861 seem to show that the
Moon imparts to us, or at least to the Professor's thermometric
apparatus, " rays of cold" More recently, however, the Earl of Kosse,
M. Marie-Davy, and Prof. Langley have conducted experiments
which seem to give conclusively affirmative results, and on the
whole the balance of evidence leans to this view of the question0.

* Cited by La Place, Systeme du c See a summary of all the experi-

Monde, Bk. I., cap. 4. ments hitherto made given by Carpenter

y Phil. Trans., vol. cxix. p. 27. 1829. in Pop. Sc. Rev., vol. ix. p. i. January

1 Month. Not., vol. xxi. p. 200. May 1870. Lord Rosse's experiments will be

1 86 1. found described in Phil. Trans., vol.

» Outlines of Ast., p. 285. clxiii. p. 587. 1873. See also Month.

b An Astronomers Experiment, &c., Not., vol. xxxiv. p. 197. Feb. 1874.
p. 213.

CHAP. VII.] The Moon. 139

Prof. Langley's summary of his own observations and deduc-
tions is as follows : — " While we have found abundant evidence
of heat from the Moon, every method we have tried, or that has
been tried by others, for determining the character of this heat
appears to us inconclusive ; and, without questioning that the
Moon radiates heat earthward from its soil, we have not yet
found any experimental means of discriminating with such
certainty between this and reflected heat that it is not open to
misinterpretation*1."

The first astronomer who paid much attention to the delinea-
tion of the Moon's surface was Hevelius, who in his well-known
Selenographia, published in 1647, gave a detailed description of it,
. accompanied by one general and some 40 special charts ; which,
taking into consideration the inferior optical means at his dis-
posal, were very creditable to the industry of the illustrious
observer of Dantzig. Four years later Riccioli brought out a
map of the Moon, having proper names assigned to many of the
principal localities: and this nomenclature, improved and en-
larged, is still in general use. J. D. Cassini and T. Mayer of
Gottingen published charts in the years 1680 and 1749 respec-
tively, the latter of which was the only one used by observers
for many years subsequent to the opening of the present century.
In 1791 Schroter published a large work entitled Selenotopogra-
phische Fragmenie, in which are given diagrams of many of the
principal spots6. Schroter was an industrious observer, but his
descriptions are not always satisfactory.

In 1824, W. G. Lohrmann of Dresden published the first 4 of
a series of 25 excellent lunar charts, but was prevented by
failing sight from continuing the work. It was, however, taken
up by others and completed in 1 878 f. Beer and Madler's elaborate
Mappa Selenograpkica was published in 1837, and is undoubtedly
the best of the kind yet published ; but the most generally
useful and also most generally accessible map for the class of

d Mem. Nat. Acad. Sciences, vol. iii. Plate XVI, and Pico from Plate XXII.

p. 42. 1885. ' Month. Not., vol. xxxix. p. 267.

e The two engravings on Plate VII are Feb. 1879. Published by J. A. Earth,

copied from this work ; Archimedes from Leipzig ; price, with book, 50 marks.

140 The Sun and Planets. [BOOK I.

readers whom I address is the Rev. T. W. Webb's, reduced from
Beer and Madler's. Undoubtedly, however, the most minutely
accurate and elaborate lunar map yet made is the one of 7-67"
in diameter, by Schmidt of Athens, published at the expense
of the German Government in 1878. Maps by Russell and by
Blunt are in circulation, but they are not of much value as
regards details.

The British Association for the Advancement of Science,
through a sub-committee, began in 1866 the preparation of an
entirely new map of the Moon, but this was eventually aban-
doned by the Association. The late Mr. W. R. Birt, however,
continued it for a time.

A wax model of the whole lunar surface was executed many
years ago by a Hanoverian lady named Witte, and Nasmyth has
modelled in plaster of Paris several single craters8. Photo-
graphy, too, has been called in by De La Rue, Rutherford, and
others, with good results.

In computing the places of the Moon the Tables of Burckhardt,
published in 1812, were formerly used, but in 1862 the new and
more perfect Tables of Hansen were introduced at the Nautical
Almanac office ; and these have entirely superseded Burckhardt's.
Damoiseau, Plana, Carlini, Pontecoulant, Lubbock, and after-
wards Delaunay, in addition to Hansen, did much to improve
the theory of the Moon. Delaunay's labours earned for him a
foremost place in the rank of geometrical astronomers. More
recently still, Sir G. B. Airy has been treating the subject by
a new method. His memoir entitled the " Numerical Lunar
Theory" was published in 1887. He is understood to be still
investigating some points in it which need further elucidation11.

According to a recent determination by Stone the Moon's
mass is gx1^ that of the Earth.

To record a tithe of the influences ascribed to the Moon would
be a herculean task ; nevertheless (in addition to the tides) one

8 Fig. 65 is from a photograph of one h Month. Not., vol. xxxiv. p. 89. Jan.

of these. But they are of little value, 1874.
being very inexact.

CHAP. VII.] The Moon, 141

deserves notice. Evening clouds at about the period of Full
Moon will frequently disperse as our satellite rises, and by the
time it has reached the meridian a sky previously overcast will
have become almost or quite clear. I first observed this in 1857,
and subsequently found that Sir J. Herschel1 had made the same
remark. The idea has been disputed k, but I am firmly convinced
of its truth. Humboldt speaks of it as well known in South
America, and Arago indirectly confirms the theory when he
shows that more rain falls at about the time of New Moon
(cloudy period] than at the time of Full Moon (cloudless period
according to the theory). According to Forster, Saturday new
Moons result in 3 weeks of wet weather. He alleged that
observations extending over 80 years showed this coincidence1.
Bernadin asserts it as a fact that many thunderstorms occur
about the period of New or Full Moon. With these possible
exceptions it is safe to assert that " changes " of the Moon have
no discoverable influence on the weather m.

1 Outlines of Ast., p. 285. ! Month Not., vol. ix. p. 37. Dec. 1848.

k Ellis, Phil. May., 4th Ser., vol. m See Nasmyth and Carpenter, Moon,

xxxiv. p. 61. July 1867. p. 180.

142 The Sun and Planets. [BOOK I.

CHAPTEK VIII.

THE ZODIACAL LIGHT.

General description of it. — When and where visible. — Sir J. HerscheVs theory. —
Historical notices. — Modern observations of it. — Backhouse's Conclusion*.

ASTRONOMICAL writers are not agreed as to the proper head
-£JL- under which to describe and discuss the Zodiacal Light. I
deal with it here, because, whatever its origin, it is a matter of
terrestrial cognizance, and therefore a description of it may,
without any serious incongruity, be associated with what has to
be said about the Earth.

The Zodiacal Light is a peculiar nebulous light of a conical or
lenticular form a, which may very frequently be noticed in the
evening soon after sunset about February or March, and in the
morning before sunrise about September. It extends upwards
from the Western horizon in the spring and from the Eastern
horizon in the autumn, and generally, though by no means
always b, its axis is nearly in a line with the ecliptic, or, more
exactly, in the plane of the Sun's equator. The apparent an-
gular distance of its vertex from the Sun's plane varies, according
to circumstances, between 50° and 70° ; sometimes it is more ;
the breadth of its base, at right angles to the major axis,
varies between about 8° and 30°. During its evening apparition
it usually reaches to a point in the heavens situated not far from
the Pleiades in Taurus. It is always so extremely ill-defined at

• Lens, a lentil. b Month. Not., vol. xxx. p. 151. March 1870, ft infra.

CHAP. VIII.] The Zodiacal Light. 143

the edges that great difficulty is experienced in satisfactorily
determining its limits. In Northern latitudes the Zodiacal Light
is generally, though not always, inferior in brilliancy to the
Milky Way; but in the Tropics it is seen to far greater ad-
vantage. Humboldt said that it is almost constantly visible in
those regions, and that he himself had seen it sufficiently
luminous to cause a sensible glow on the opposite quarter of the
heavens c. In the winter of 1 842-43 it was remarkably well seen
in this country, the apex of the cone attaining a length of no less
than 105° from the Sun d. Lassell also mentions having seen the
light very conspicuous at Malta in January 1850®.

No satisfactory explanation has yet been given of this pheno-
menon ; it is, however, very generally considered to be a kind of
envelope surrounding the Sqn, and extending perhaps nearly or
quite as far as the Earth's orbit. Sir J. Herschel's opinion was
" that it maybe conjectured to be no other than the denser parts
of that medium which we have some reason to believe resists the
motion of comets ; loaded, perhaps, with the actual materials of
the tails of millions of those bodies, of which they have been
stripped in their successive perihelion passages [! !]. An atmosphere
of the Sun, in any proper sense of the word, it cannot be ; since
the existence of a gaseous envelope propagating pressure from
part to part — subject to mutual friction in its strata, and thereby
rotating in the same, or nearly the same, time with the central
body, and of such dimensions and ellipticity — is utterly incom-
patible with dynamical laws f." In connexion with this specula-
tion it may be mentioned that during the visibility of the great
comet of 1843 in March of that year, the Zodiacal Light was
unusually brilliant ; so much so, that by many persons it was
mistaken for the comet.

The Zodiacal Light is of a reddish hue, especially at its base,

c But on this point see Humboldt's xiv. p. 16, Nov. 1853. Observations by

later statement on p. 14$, post. Burr and Webb will be found at pp. 45,

d Detailed particulars will be found in 83, and 181 of the same volume; and see

the Greenwich Observations, 1842. a paper by T. Heelis in Mem. of the Lit.

e For observations by E. J. Lowe, see and Phil. Soc. of Manchester, 3rd Ser.,

Month. Not., vol. x. p. 124, March 1850; vol. ii. p. 437, 1865.

vol. xi. p. 132, March 1851; and vol. ' Outlines of Asf., p. 658.

144 The Sun and Planets. [BOOK I.

where also it is most bright, and where it effaces small stars.
Undulations and likewise a sort of flashing have been noticed
in it.

It has been suggested that the Zodiacal Light is identical with
what Pliny and Seneca call the "Trabes8," but more likely this
was the Aurora.

The Zodiacal Light was treated of by Kepler ; afterwards by
Descartes, about the year 1630 ; and then by Childrey, in i659h;
it was not, however, till J. D. Cassini, who saw it first on March
1 8, 1683, published some remarks on this phenomenon that much
attention was paid to it '.

In the year 1855, the Rev. G. Jones, Chaplain of the U. S.
Steam- Frigate Mississippi, published some remarks on this
phenomenon k, as brought under his notice during a cruise round
the world in the 2 preceding years. He stated: — "I was also
fortunate enough to be twice near the latitude of 23° 28' North,
when the Sun was at the opposite solstice, in which position the
observer has the ecliptic at midnight at right angles with his
horizon, and bearing East and West. Whether this latter circum-
stance affected the result or not, I cannot say ; but I there had
the extraordinary spectacle of the Zodiacal Light simultaneously
at both East and West horizons from 1 1 to i o'clock for several
nights in succession."

Mr. Jones concluded his very interesting letter as follows : —
" You will excuse my prolixity in stating these varieties of ob-
servations, for the conclusion from all the data in my possession
is a startling one. It seems to me that those data can be ex-
plained only by the supposition of a nebulous ring tcith the Earth
for its centre, and lying within the orbit of the Moon 1."

On the publication of the foregoing, Humboldt transmitted to

« Hist. Nat., lib. II. cap. 26. distrustful remarks on this comrnunica-

h Natural History of England, 1659. tion, to which the reader should refer,

Srit. Bacon., p. 183. 1661. and at p. 47 is some account of J. F. J.

1 Anc. Mem. de VAcad. des Sciences, Schmidt's work on the Zodiacal Light,

vol. viii. p. 121. ' See Jones's original memoir in vol.

k Gould's Astronomical Journal, No. iii. of the 4to. ed. of the U. S. Exploring

84, May 27, 1855. In the Month. Not., Expedition Narrative. (Washington,

vol. xvii. pp. 204-5, May 1857, are some 1856.)

CHAP. VIII.] The Zodiacal Light. 145

the Berlin Academy"1 some unpublished observations made by
him at sea in March 1803, to the effect that on one or two occa-
sions he also saw a 2nd light in the East contemporaneously with
the principal beam in the West ; he, however, then thought that
the 2nd light was merely due to reflection. He concludes by
saying that " the variations in the brightness of the phenomenon
cannot, according to my experience, be accounted for solely by
the constitution of our atmosphere. There remains much still to
be observed relative to the subject."

Jones seems in one sense to have been anticipated in his
" double end " view of the Zodiacal Light, as will appear from
the following extract, which is here cited for a twofold pur-
pose : — " The two extremities of the Zodiacal Light may be seen
on the same night about the time of the solstices, particularly the
Winter solstice, when the ecliptic makes, night and morning,
nearly equal angles with the horizon, and these are sufficiently
great to allow a considerable portion of the points of the light to
appear above the line of the twilight. It is thus that it was ob-
served by Cassini on Dec. 4, 1687, at 6h 3om P.M. and 4h 4OmA.M.
the following morning n."

Capt. C. Wilkes of the U.S. Exploring Expedition controverted
Jones's views on many material points, and regarded the Zodiacal
Light as the result of the illumination of that portion or section
of the Earth's atmosphere on which the rays of the Sun fall
perpendicularly in the Tropics °.

Jones's observations have been subjected to a very painstaking
and searching review by Searle, whose conclusions, embodying
as they do the observations of others besides Jones, may be thus
brought to a focus: — (i) The Secondary (or opposite) Light
(called by the Germans " Gegenschein ") is an undoubted fact and
its connection with the main Light highly probable ; (2) That
the Zodiacal Light lies further to the N., near the Autumnal

11 Monatsbericht der Kon. Preuss. ed., p. 106.

Akademie der Wissenschaften, July 26, ° Theory of the Zodiacal Light, p. 12.

^SS. P- 51?- Month. Not., vol. xvi. A Paper read at the Montreal Meeting of

p. 16. Nov. 1855. the American Association for the Ad-

n J. E. Jackson, What to Observe, 2nd vancement of Science, 1857.

146 The Sun and Planets. [BOOK I.

than it does near the Vernal Equinox, is also highly probable ; (3)
Atmospheric absorption largely affects the apparent positions of
the Zodiacal Light ; (4) The belt of sky occupied by the projec-
tions of the first 237 Minor Planets presents certain peculiarities
which correspond to those of the Zodiacal Light, and suggest
that it may be partly due to minute objects circulating in
planetary orbits p ; (5) The Light does not interfere with the
visibility even of small stars q ; (6) The final disappearance of
the Light occurs by its setting rather than by its fading q.

Heelis considers that his observations, made in 1862 on board
ship in the Tropics, point to the change of position in the Light
as depending on the time of year more than on the observer's
place of observation.

The most extensive recent observations on this subject which
are of value are those made in the years 1869-71 by Colonel
Tupman in the Mediterranean. He COD firms on many points
previous observers, but contradicts them on one very important
point. He asserts that the plane of the Light does not pass
through the Sun. He also remarks having noticed great want of
uniformity in the position of the axis of symmetry with respect
to the ecliptic. In August and September the axis. is frequently
inclined as much as 20° to the ecliptic, whilst in the winter it is
sensibly parallel to the ecliptic r.

On December 19 and 20, 1870, when in Sicily, whither he had
gone to observe the solar eclipse, Mr. A. C. Ranyard and some
friends (Secchi amongst them) examined the Zodiacal Light
through a Savart polariscope. His main conclusion is, that the
Zodiacal Light consists of matter which reflects the Sun's light.
He adds, that such matter either (i) exists in particles so small
that their diameters are comparable with the wave lengths of
light, or (2) is matter capable of giving specular reflection8.

Some observations by Birt are not unworthy of attention.
They were made chiefly in 1850, though a few of his notes refer

P Mem. Am(r. Acnd., vol. xi. p. 157, r Month. Not., vol. xxxii. p. 74. Jan.

1885. 1872.

•> Proc. Amer. Acafl., vol. xix. pp. 156, * Month. Not., vol. xxxi. p. 171.

163. March 1871.

CHAP. VIII.] The Zodiacal Light. 147

to April 1871. Birt drew attention to two special points: —
(i) The fact that the greater portion of the Light always lies to
the N. of the ecliptic ; and (2) That comparing the shape of the
cone of light month by month from February to April it becomes
progressively more and more blunt, so much so " as to lead to
the suspicion that we view the phenomenon differently as the
Earth advances in her orbit from the point at which we beheld
it in the winter months*."

Little or no progress has been made during recent years in
elucidating the theory of the Zodiacal Light : and this is the more
remarkable considering the development of all other branches of
Astronomy. Backhouse published in 1881 the results of 418
observations between 1867 and 1877, chiefly directed to a deter-
mination of the Light's Inclination to the ecliptic u. His deduc-
tions, though based on so large a series of data, are not very
conclusive. He finds the average deviation of the axis of the
Light from the plane of the ecliptic to be 2°, and the Longitude
of the Ascending Node, 35°.

A Dutch observer, Gronemann, after giving much attention to
the matter, has pronounced against the solar theory of the
Zodiacal Light ; he considers it to have a terrestrial origin. His
main contention is that the affirmed connection between the
evening and morning cones of light is not established, and that
the participation of the cones in the daily motion of the heavens
is likewise not proved to be a fact x.

Serpieri, the Director of the Meteorological Observatory at
Urbino, communicated to the Italian Spectroscopic Society
in 1876 a very elaborate memoir on the Zodiacal Light, summing
up all the results of previous observers7. He would see in
the phenomenon an electrical origin.

* Month. Not., vol. xxxi. pp. 177-82. * Archives Nterlandaises.

April 1871. y Memorie degli Spettr. Italiani,vol. v.

u Month. Not., vol. xli. p. 333. May, 1876.
1881.

L 2

148 The Sun and Planets. [BOOK I.

CHAPTEK IX.

MARS *. <j

Period, &c. — Phases. — Apparent motions. — Its brilliancy. — Telescopic appear-
ance.— Its ruddy hue. — Schiaparelli's " Canals." — General statement of the
physical details of Mars. — Map of Mars on Mercator's projection. — Polar
snow. — Axial rotation. — The seasons of Mars. — Its atmosphere. — The Satellites
of Mars. — Ancient observation of Mars. — Tables of Mars.

"1%/TARS is the first planet exterior to the Earth in the order
•^•'-l- of distance from the Sun, and, as we shall presently
see, bears a closer analogy to it than do any of the other
planets.

Mars revolves round the Sun in 686d 23** 30™ 41", at a mean
distance of 141,536,000 miles, which an orbital eccentricity of
0-093 may augment to 154,714,000 miles, or dimmish to
128,358,000 miles. The apparent diameter of Mars varies
between 4-i" in conjunction and 30-4" in opposition; and
owing to the great eccentricity of the orbit of Mars its
apparent diameter as seen from the Earth will vary much at
different oppositions. The diameter at mean distance of the
planet from the Earth being 7-28" (Le Verrier), the real
diameter is nearly 5000 miles. Very varying results have
been arrived at as to the compression of Mars. Sir W. Herschel
gave it at TV ; Schrb'ter contradicted this, and asserted that it
must be less than •£$ '•> Bessel merely decided that it was too

a Observers interested in Mars should exhaustive account of the planet which

consult a valuable memoir entitled Area- has ever appeared. A fine series of litho-

graphie presented to the Academic graphic views by N. E. Green will be

Royale de Belgique in June 1874 by found in Mem. R.A.S., vol. xliv. p. 123,

F. Terby of Louvain. It is the most 1879.

Figs. 74-5.

Plate IX.

1858 : June 3.

1858 : June 14.

MARS.
(Draum by Secchi.*)

CHAP. IX.] Mars. 149

small for measurement with his great heliometer at Konigsberg b ;
Arago from Paris observations extending over 36 years (from
1811 to 1847) deduced -£$• Hind considers that g^, and Main
that -^g is not very far from the truth. Kaiser's TyT confirms
Schroter.

Mars exhibits phases, but not to the same extent as the
inferior planets. In Opposition it is perfectly circular ; between
this and the quadratures it is gibbous ; and at the minimum
phase, which occurs at the quadratures, the planet resembles the
Moon 3d from the full. The character of these phases is a
sufficient proof that Mars shines by the reflected light of the
Sun. The phases of Mars were discovered by Galileo, who on
Dec. 30, 1610 wrote to Castelli, "I dare not affirm that I can
observe the phases of Mars ; however, if I mistake not, I think I
already perceive that he is not perfectly round."

After Conjunction, when Mars first emerges from the Sun's
rays, it rises some minutes before the Sun, and has a direct or
Easterly motion ; but since this motion is only half that of the
Earth in the same direction, Mars appears to recede from the
Sun in a Westerly direction, notwithstanding that its real motion
among the stars is towards the East. This continues for nearly
a year, and ceases when its angular distance from the Sun
amounts to about 137°; then for a few days it appears
stationary. After that, its motion becomes retrograde, or
Westerly among the stars, and continues so until the planet
is 1 80° distant from the Sun, or in Opposition, and consequently
on the meridian at midnight. At this period its retrograde
motion is swiftest ; it afterwards becomes slower, and ceases
altogether when the planet is again at a distance of about 137°
on the other side of the Sun. Its motion then again becomes
direct, and continues so, till once more the planet is lost in the
solar rays, when the phenomena are renewed, but with a
considerable difference in the extent and duration of the move-
ments. The retrogradation commences or finishes when the
planet is at a distance from the Sun which varies from 128° 44'

b See his memoir in Ast. Nach., vol. xxxv. p. 351. Dec. 17, 1852.

150 The Sun and Planets. [BOOK I.

to 146° 37', the arc described being from 10° 6" to 19° 35';
the duration of the retrograde motion in the former case is
6od i8h, and in the latter 8od i5h. The period in which all
these changes take place, or the interval between 2 Conjunctions
and 2 Oppositions, constitutes the synodical period, which
amounts to 78od. Mars and the Earth come nearly to the
same relative position every 32y ; but several centuries elapse
before precise coincidence occurs c.

Mars when in Opposition is a very conspicuous object in the
heavens, shining with a fiery red light, which from its striking
character has led to the planet being celebrated throughout the
historic period. It received from the Jews on this account an
epithet equivalent to " blazing," and the Greek one (Trupo'eis) bears
much the same meaning. Its name or epithet in many other
languages is substantially the same.

Its synodic period being 780 days, it comes to Opposition and
therefore attains its (general) maximum brilliancy, once in rather
more than 2y. When in perihelion and in perigee at the same
time, which occurs once in 7 synodical revolutions ( 1 4y 1 1 Jm),
Mars shines with a brilliancy rivalling that of Jupiter. In
August 1719, the planet being only 2^° from perihelion, its
brightness was such as to cause a panic d. The most favourable
Oppositions are those which occur on or about August 26 ; and the
least favourable those which occur about Feb. 22. Favourable
Oppositions will occur in 1892 and 1909.

With suitable optical assistance, Mars is found to be covered
with dusky patches, which have been supposed, and with good
reason, to be continents analogous to those of our own globe :
these are of a dull red blue ; other portions, of a greenish hue,
are believed to be tracts of water. The ruddy colour, which,
overpowering the green, gives the tone to the whole of the
planet, was believed by Sir J. Herschel to be due to " an ochrey
tinge in the general soil, like what the red sandstone districts on
the Earth may possibly offer to the inhabitants of Mars, only

c Smyth, Cycle of Celest. Objects, vol. •' l)e Zach, Con: Astronomique, vol.

i. pp. 151-2, — abridged and corrected. ii. p. 293. March 1819.

CHAP. IX.]

Mars.

151

more decided6." In a telescope Mars appears less red than to
the naked eye, and according to Aragof the higher the power
the less the intensity of the colour. Webb writes : — " The disc,
when well seen, is usually mapped out in a way which gives at
once the impression of land and water, the outlines, under
the most favourable circumstances, being extremely sharp : the

MAKS, APRIL 18, 1856. (Brodie.}e

bright part is orange, — according to Secchi, sometimes dotted
with red, brown, and greenish points ; sometimes found by
Schiaparelli filled with a complete network of their lines and
minute interspaces ; the darker regions, which vary greatly in
depth of tone, are in places brownish, but more generally of a dull
grey-green (or, according to Secchi, bluish tint), possessing the
aspect of a fluid absorbent of the solar rays. If so, the pro-
portion of land to water is considerably greater on Mars than
on the Earth ; so that the habitable area may possibly be

"• Outlines of Ast., p. 339. e Month. Not., xvi. p. 205. June

' Pop. Ast., vol. ii. p. 483. Eng. ed. 1856.

152 The Sun and Planets. [Boox I.

much more alike than the diameter of the planets. The water
however (if such it be) is everywhere in communication, and
long naiTow straits are more common than on the EarthV

In 1877, when Mars was in a part of its orbit favourable for
observation, Schiaparelli at Milan detected a number of minute
dusky bands, for the most part very narrow and straight,
traversing and cutting up the supposed continents in various
directions. These markings are commonly spoken of as
"Canals." They were seen again in 1879 and in 1882, in the
latter year considerably more numerous and exhibiting a much
more complex network. Though these markings have been
seen by other observers it cannot be said that their existence in
the sharply defined forms suggested by Schiaparelli is generally
recognisable.

The details of this planet are not readily seen with ah instru-
ment of small aperture, yet there are several features which are
well within the powers of a 4-inch refractor or 6-inch reflector.

The general tone of the disc is a reddish orange, and on it
there may be seen certain gray markings, the most important of
these being the "Kaiser Sea" in longitude 285°, sometimes
called the " V " mark, from its resemblance to that letter. It
commences above the equator on the Southern side, and extends
half way to the N. pole. The Kaiser Sea is connected with two
dark forms in the direction of the equator, that to the E. being
called " Herschel II." Strait, and that on the W. Flammarion Sea.
This large dark form cannot be mistaken, and if a telescope will
show anything on the planet it will show this.

It should be observed that the apparent form of the Kaiser
Sea differs greatly at different oppositions of Mars, in conse-
quence of the varying view we have of the poles. When the S.
pole is towards the Earth, Kaiser Sea is considerably fore-
shortened ; whereas when the N. pole is towards the Earth, it is
elongated.

Herschel II. Strait extends on the E. to the equator, where it
terminates in a well-known mark, the a of Beer and Madler, from

h Celest. Objects, 4th ed. p. 141.

CHAP. IX.] Mars. 155

which Martial longitudes are reckoned. This mark was dis-
covered by Dawes to be composed of two points, as shown in the
map, and it is appropriately named after that observer.

Between Dawes's forked bay and the next dark point, Burton
Bay, there is generally seen a space connecting the light portions
of the equatorial region with Phillips Island to the S. ; but
this was filled with shade during the opposition of 1877.

When Burton Bay has passed the meridian, a large dark mark,
called De La Rue Ocean, extends towards the S. pole, its Eastern
extremity being Christie Bay. On the S.E. of De La Rue Ocean
may be seen a well-defined round dark spot named Terby Sea in
the map. This mark is difficult to observe during those oppo-
sitions, when the N. pole is directed towards the Earth.

When Terby Sea has passed, a long dark streak, called Maraldi
Sea, comes into view, and continues till Flammarion Sea heralds
Kaiser Sea, with which we started, thus completing the circuit
of the planet.

The polar snow-spots are seen with great distinctness when
Mars is approaching Opposition ; from that time they decrease in
size, till it requires sharp and educated vision to detect their
presence.

There is a round orange spot in the Southern hemisphere in
longitude 300°, called Lockyer Land. This was seen during the
Opposition of 1873 to be white as though covered with snow. A
similar, though smaller spot exists in the Northern hemisphere at
210° of longitude, named Fontana Land. The details of the
Northern hemisphere are not only less important than those of
the Southern, but are the less known in consequence of the
greater distance of Mars when the N. pole is turned towards the
Earth.

One point of contrast there is between Mars and the Earth.
Whereas on the Earth the proportion of water to land is about
ii to 4, on Mars the proportions are probably about equal. It is
to be noted also that the water on Mars is for the most part dis-
posed in long narrow channels ; of wide expanses of water, such
as our Atlantic Ocean, there are few.

156 The Sun and Planets. [BOOK I.

In the vicinity of the poles brilliant white patches may be
noticed, which are now considered by astronomers to be masses of
snow — an idea which is materially strengthened by the fact that
they have been observed to diminish when brought under the
Sun's influence at the commencement of the Martial summer, and
to increase again on the approach of winter.

The observation of these white patches appears to date from the
middle of the 1 7th century, for they seem to be noticed in a figure
of the planet by Huygens ; Maraldi, in 1 704, first gave specific
representations of them. Sir W. Herschel1, who discovered the
circumstances attending their variation in size, found that they
were not always precisely opposite, both being sometimes visible
or invisible at the same time. Madler noted the S. polar spot to
undergo greater changes of magnitude than the Northern one,
an observation harmonising with the fact that from the eccen-
tricity of the planet's orbit it experiences a greater variety of
climate. The same observer found (and herein he was con-
firmed by Secchi) the N. patch concentric with the planet's
axis, but the S. one considerably eccentric, which agrees sub-
stantially with Sir W. Herschel's observation. It is not easy
to understand why they are not exactly opposite ; if both were
equally removed, and in opposite directions, from poles of
rotation, it would occur, as with the Earth, that the poles of
cold differed from those of rotation, but the subsisting facts are
inexplicable.

Figs. 78-79 represent the Polar snows of Mars as drawn by
Mr. N. E. Green, an observer who has paid much attention to
this planet J.

It will be seen that in Fig. 78 there is on the west side of the
Polar cap a detached point of light. Green regarded this as a
patch of snow which rested on elevated ground after the snow
had melted on the lower levels. This light was afterwards seen
on Sept. 8 and 10.

On Sept. 8, however, 2 patches were visible, and on Sept. 10

' Phil. Trans., vol. Ixxiv. p. 2 et seg. 1784.
•> Mem. R.A.S., vol. xliv p. 126.

CHAP. IX.]

Mars.

157

a faint line of points concentric with the zone of snow. The
observer thought that these alterations of form were in all

Fig. 78.

THE SOUTH POLE OF MARS, SHOWING SNOW. Sept. i, 1877. (Green.)

probability due to perspective ; the single point of Sept. I
appearing as two when less foreshortened, and that these when

Fig. 79.

THE SOUTH POLE OF MARS, SHOWING SNOW. Sept. 8, 1877. (Green.)

still further separated appeared still further increased in numbers
as they were seen nearer the central meridian of the disc. Green
further suggests that —

" This brilliant appearance of the spots when most to the West of the pole, and
their decrease in brilliance when passing the meridian, together with the most sig-
nificant fact that they were not seen at all on the Eastern side, can best be explained

158 The Sun and Planets. [BOOK I.

by supposing the slopes of the hills that retained the snow to have a South-westerly
aspect ; they would thus be sheltered from the Sun's rays during the greater part of
a revolution, but fully exposed to its light, and therefore better seen, just as they
were passing away towards the Western limb."

Spots on the body of Mars led at an early period to attempts
being made to ascertain the period of its axial rotation. J. D.
Cassini, in 1 666, found this to be effected in 24h 40™ ; Hooke k.
working contemporaneously, was unable to decide between 1 2h
and 24h. Madler1 fixed the time of revolution at 24h37m 23", —
a result which singularly accords with Cassini 's, and says much
for the accuracy and skill of the astronomer of Bologna.
Drawings by Hooke and by Huygens more than 200 years old
have been turned to account in modern times to throw light
upon the rotation of Mars. Using some of Huygens's sketches,
Kaiser was led to fix the period of Mars at 24h 37™ 22'628 ;
Proctor m, using some of Hooke's sketches, obtained as the
result 24h 37°* 22'7i8. The most recent observations, resting
on a prolonged basis, are those of Denning, who from 15 years'
observations ending in 1884 obtained a period of 24h 37™
22'34*. Sir W. Herschel's figures were 24h 39™ 2 1 '67" ; he
stated, though on wholly insufficient data, that the obliquity
of the ecliptic on Mars was 28° 42' — an angle so close to that
which obtains for the Earth, as, if confirmed, to warrant us
in asserting that the seasons of Mars are not materially different
from our own.

The Martial year consists of 668 Martial days and 16 hours,
the Martial day being longer than the terrestrial in the propor-
tion of 100 to 97. Owing to the eccentricity of the planet's orbit,
the summer half of the year in the Northern hemisphere con-
sists of 372 days, and the winter half of 296 days. As a matter
of course, the reverse state of things prevails in the Southern
hemisphere ; there the winter half-year consists of 372 days and
the summer of 296 days. Nevertheless, although the extremes
of temperature may, and probably do, differ widely in the two

k Phil. Trans., No. 14, p. 244. July 2, 1666.
1 Att. Nock., vol. xv. No. 349. April 7, 1838.
m Month. Not., vol. xxxiii., p. 558. 1873.

CHAP. IX.] Mars. 159

hemispheres, the mean temperatures of each may possibly differ
but little. The duration of the seasons in Martial days in the
Northern hemisphere is as follows: — Spring 191, summer 181,
autumn 149, winter 147. For the Southern hemisphere we
must reverse the seasons: this being done, it will appear that
spring and summer taken together are 76 days longer in the
Northern hemisphere than in the Southern.

The observations of Cassini led to the belief that Mars possessed
a very extensive atmosphere : this has not been confirmed, and
it is now only admitted that Mars has an atmosphere which is
moderately dense. Sir J. South, who paid much attention to
this subject, stated that he had seen one star in contact with the
planet and 2 occulted without change ; thus overthrowing an
opinion which resulted from an assertion of Cassini's that ty
Aquarii (a star of the 5th mag.) on one occasion, in Oct. 1672,
disappeared in a 3~feet telescope when 6' from the planet's
limb. But was the planet gibbous at the time ?

In former editions of this work it was stated that '•' Mars
possessed no satellite, though analogy does not forbid, but
rather, on the contrary, leads us to infer the existence of one ;
and its never having been seen, in this case at least, proves
nothing."

In the year 1877 an able American observer, Asaph Hall
disproved the first part of this statement, and confirmed the
closing inference. The Opposition of Mars in 1877 promised
by reason of the situation of the planet in the heavens to be
a very favourable one, and Hall conceived the idea that, having
the command of the fine refractor of the Washington Observatory
(aperture, 26 inches), he might perhaps be fortunate enough to
detect a satellite if Mare had one. Independently of the pro-
mising circumstances just mentioned, Hall had hopes that some
favourable result might come of his effort because, with the
exception of an attempt made by D' Arrest at Copenhagen in
1862 (or 1864), no systematic search for a Martial satellite had
been made since Sir \V. Herschel's failure as far back as 1 783.
Hall began his search early in August 1877. At first he found

160 The Sun and Planets. [BOOK I.

near the planet only some small stars ; but on the night of
August 1 1 he detected a faint object on the nf. side of the planet
which afterwards proved to be the outer satellite. Bad weather
hindered him until August 16, when a small object was again
seen which the observations of that night showed to be a satellite
in motion with the planet and near one of its Elongations. On
August 17, while waiting and watching for the satellite first
seen (the outer one), he discovered a second (the inner one).
Further observations on the following night placed beyond
doubt the character of the two objects and their discovery was
publicly announced. Nevertheless for several days Hall was
much puzzled by the apparent motions of the inner moon. It
seemed to appear on different sides of the planet the same night,
and he at first thought there must be 2 or 3 satellites within
the orbit of the outer one, since it seemed so unlikely that a
satellite should revolve round its primary in less time than the
primary rotated on its axis. In order to decide the point the
inner satellite was watched throughout the nights of August 20
and 21, by which means it was clearly ascertained that there
was but one inner satellite, and that revolving round its primary
in less than \TA of the time of the primary's own axial rotation —
a case unique in the solar system.

When the discovery of these satellites was made public
various observatories took up the matter, and between August
and the end of October 1877, that is to say, so long as Mars
remained favourably placed for observation, the satellites were
seen at several of the larger public observatories in Europe and
America, and likewise at the private observatories of Mr. A. A.
Common, Ealing, England, and Mr. W. Erck, Sherrington, near
Bray, Ireland. At the Opposition of 1879 these satellites were
both again observed in America, as also in 1881, but in the
latter year observations were few, Mars not being very favourably
placed for the purpose.

At the suggestion of Mr. Madan. of Eton, the outer satelli te was
named by the discoverer " Deimos " and the inner satellite
" Phobos " ; these being the mythological names of the horses

CHAP. IX.]

Mars.

161

which drew the chariot of Mars, although by Homer personified
and meaning the attendants of Mars.

" He spake and summoned Fear and Flight to yoke
His steeds, and put his glorious armour on n."

Considering the small size of these satellites it will not be
expected that much information can be given respecting them.

Phobos revolves round Mars in 7h 39™ at a distance of
about 6000 miles. Hall thinks the orbit may have a slight
eccentricity. The angular amount of the maximum distance
from the planet is about 12"; and the brightness at Opposition is
about that of a star of mag. 1 1£.

Deimos revolves round Mars in 3Oh i8ra at a distance of
about 15,000 miles. The orbit is almost circular. The angular
amount of the maximum distance from the planet is about
32", and the brightness at Oppo-
sition is about that of a star of
mag. 134.

The planes of the orbits of both
satellites are very nearly coin-
cident with the equator of Mars.
The hourly areocentric motion of
Phobos is 47°, and on account
of its rapid motion and its near-
ness to the planet this satellite
must present a very singular
appearance to an observer on Mars. It will rise in the W.
and set in the E.° and will meet and pass Deimos, whose
hourly areocentric motion is only ii'8°. The semi-diameter
of Mars being 2100 miles, the horizontal parallaxes of these
satellites are very large, amounting to 21° for Phobos. The
nearness of this satellite to the surface of the planet will pro-
duce apparent singularities in its motion, and cause it to
appear as a variable star. Some photometric observations by

Bryant's

THE APPARENT OKBITS OF THE
SATELLITES OF MARS.

n Homer, Iliad, lib. xv.
Translation.

0 The rationale of this is explained at
length in the Rev. E. Ledger's The Sun

and its Planets, p. 253 ; where will also
be found some other speculations as to
the phenomena connected with these
satellites.

162 The Sun and Planets. [BOOK I.

Pickering imply that Phobos has a diameter of 7 miles and
Deimos of 6 miles p.

It is interesting to note that there is extant a copy of a
letter by Kepler to his friend Wachenfels, written shortly after
the announcement of Galileo's discovery of the satellites of
Jupiter, in which Kepler expresses his eagerness for a telescope
wherewith to discover 2 satellites for Mars, that being the number
which " proportion seems to require q."

Dean Swift, too, in Gullivers Travels1 speaks of the astronomers
of Laputa having done more than the astronomers of Europe, for
" They have likewise discovered 2 lesser stars or satellites which
revolve about Mars." And Voltaire, in his romance oiMicromegas,
speaking of some of his characters says : " Us virent deux lunes
qui servent a cette planete [Mars] et qui ont e'chappe' aux regards
de nos astronomes." But of course these are nothing but happy
" shots ; " there could have been no tradition of 2 Martial
satellites as a historical fact.

The want of a known satellite long prevented anything more
than an approximation being arrived at of the mass of Mars.
But the disturbing influence of this planet being insignificant, an
extremely accurate determination of its mass is of no great con-
sequence to science. The most trustworthy value appears to be
A. Hall's, who by means of observations of the two satellites has
obtained the figures 77777^.

" The most ancient observation of Mars that has come to our
knowledge is one reported by Ptolemy in his Almagest (lib. x.
cap. 9). It is dated in the 52nd year after the death of Alexander
the Great, and 476th of Nebonassar's era, on the morning of the
21st of the month Athir, when the planet was above but very near
the star /3 in Scorpio. The date answers to B.C. 272, Jan. 17, at
1 8h on the meridian of Alexandria. An occultation8 of the planet

P The foregoing particulars are chiefly r Part III. ch. iii.

from A. Hall's Observations and Orbits * Inasmuch as the apparent diameter

of the Satellites of Mars, Washington, of Mars is (except under rare circum-

1878, a memoir issued by the U. S. stances) less than that of Jupiter, the

Naval Observatory. more correct expression would probably

i Brewster, Life of Kepler. be "a transit of Mars across Jupiter," Sect

CHAP. IX.] Mars. 163

Jupiter by Mars on Jan. 9, 1591, is recorded. Such a phenomenon
would be extremely interesting if viewed with the powerful tele-
scopes so common at the present day *."

In computing the places of Mars the tables of Baron De
Lindenau, published in 1811, were generally used until recently,
but they were superseded in 1861 by the more perfect tables of
Le Verrier u.

* Hind, Sol. Syst., p. 79.

u Annales de VObservataire de Paris, Mem., vol. vi., Paris, 1861.

M 2

The Sun and Planets. [BOOK I.

CHAPTER X.
THE MINOR PLANETS".

Sometimes called Ultra- Zodiacal Planets. — Summary of f axis. — Notes on Ceres. —
Pallas. — Juno. — Vesta. — Olbers's theory. — History of the search made for
them. — Independent discoveries. — Progressive diminution in their size.

BETWEEN the orbits of Mars and Jupiter there is a wide
interval, which, until the present century, was not known
to be occupied by any planet. The researches of late years, as
previously intimated in Chapter II., have led to the discovery
of a numerous group of small bodies revolving round the Sun,
which are known as the Minor Planets b, and which have received
names taken at the outset chiefly from the mythologies of ancient
Greece and Rome, but in recent years from all sorts of sources c,
many names being most fantastic and ridiculous.

These planets differ in some respects from the other members
of the system, especially in point of size, the largest being
probably not more than, even if so much as, 200 miles or 300
miles in diameter. Their orbits are also, as a general rule, much
more inclined to the ecliptic than the orbits of the major planets,
for which reason it was once proposed to term them the Ultra-

tt The use of symbols has been discon- disuse. Such a designation was not very

tinued, except for the four early ones, as appropriate; planetoids would have been

follows: Ceres £, Pallas \, Juno $, better. However, minor planets is pre-

Vesta (§ ; and even these are becoming ferable to either.

obsolete. Gould's suggestion to adopt by c The names Lumen, Bertha, and Zelia,

way of symbol the number in the order assigned by MM. Henry, are said to com-

of discovery enclosed in a circle thus : memorate members of the family of the

(jST), has been universally adopted. French astronomer Flammarion, a char-

*> The old name of asteroids, proposed acteristic specimen of the French way of

by Sir W. Herschel, has nearly fallen into doing things.

CHAP. X.] The Minor Planets. lf>5

Zodiacal Planets: and many orbits are eccentric to a degree for
which no parallel can be found amongst the major planets.

It is needless to give any detailed account of each, but a short
summary may not be out of place d.

The nearest to the Sun is Medusa @, which revolves round that
luminary in H39d, or 3-iy, at a mean distance of 198,134,000
miles. Next come Sita @, and Anahita. @.

The most distant is Thule @, whose period is 322od, or 8-8y,
and whose mean distance is 396,454,000 miles. Next come Hilda
@, Ismene @, and Andromache @. The last-named recedes farthest
from the Sun of any owing to the great eccentricity of its orbit.

The least eccentric orbit is that of Philomela @, in which e
amounts to only o-oi i.

The most eccentric orbit is that of JEthra @, in which e
amounts to 0-383.

The least inclined orbit is that of Massalia @, in which t
amounts to o°4i'.

The most inclined orbit is that of Pallas (T)5 in which i
amounts to 34° 44'.

The brightest, and, presumably, largest planet is by the con-
current testimony of Argelander, Stone, and Pickering, Testa (7)
The two former observers place Ceres Q second, and Pallas (£)
third.

The faintest cannot be specified.

The more recently discovered planets are all so small that it is
impossible to say which is the smallest.

It has been thought that many of the minor planets (especially
Vesta] are variable in their light. This may be nothing more
than the result of, and a proof of their axial rotation6. Prof.

d By far the most elaborate summary exhibit these changes are irregular cr

which has yet appeared will be found in polyhedral in form, and show sometimes"

an article by Niesten in the Annuaire de one and sometimes another face, or faces

I'Observatoire Soy. de Itruxelles, 1881, (as the cases may be), seems sublime

p. 226 ; and see Prof. D. Kirkwood's very fancy. But in the more modern form

exhaustive little treatise The Asttroids, that probably these planets rotate on

Philadelphia, 1888. their axes as do the major planets, his

Littrow's idea that the planets which theory may be admissible.

166 The Sun and Planets. [BOOK I.

M. W. Harrington, on the assumption that the surfaces of all
have the same reflecting power as Vesta, has estimated the volume
of Vesta as T5T of the first 230 planets ; and that Ceres and Vesta
together comprise about half the volume of the 230. Le Vender
calculated that the total mass of the whole number could not
exceed \ of the mass of the Earth. Even to approach this sum
total Niesten considers there would have to be several thousand
minor planets in all.

Several of the minor planets have been found only to be lost
again, and their positions cannot now be determined. Included
in this category are Scylla @, Sylvia @, Dike®, and Camilla @.
Others (e.g. Hilda @, Lydia @, Sirona ("*)) have been found
again after being lost.

Under favourable circumstances Ceres has been seen with the
naked eye, having then the brightness of a star of the 7th mag-
nitude ; more usually, however, it resembles an 8th magnitude
star. Its light is somewhat of a red tinge, and some observers
have remarked a haziness surrounding the planet, which has
been attributed to the density and extent of its atmosphere.
Sir W. Herschel once fancied that he had detected 2 satellites
accompanying Ceres ; but its mass can scarcely be sufficient for
it to retain satellites around it large enough to be visible to us.
Pallas, when nearest the Earth in Opposition, shines as a full 7th
magnitude star, with a decided yellowish light. Traces of an
atmosphere have also been observed. Juno usually shines as an
8th magnitude star, and is of a reddish hue. Vesta appears at
times as bright as a 6th magnitude star, and may then constantly
be seen without optical aid, as was the case in the autumn of
1858. The light of Vesta is usually considered to be a pure
white, but Hind considers it a pale yellow f. Hind found Victoria
to possess a bluish tinge.

The orbits most nearly alike are those of Fides and Maia, and
Lespiault has remarked that when at their least distance from
each other these planets are separated by a space which only

' Sol. Sy*t., p. 85.

CHAP. X.] The Minor Planets. 107

amounts to -£$ of the radius of the Earth's orbit, or about 4^
millions of miles.

Sir J. Herschel once remarked : — " A man placed on one of the
minor planets, would spring with ease 6oft, and sustain in his
descent no greater shock than he does on the Earth from leaping
a yard. On such planets giants might exist ; and those enormous
animals which, on Earth, require the buoyant powers of water
to counteract their weight, might there be denizens of the landg."
But to such speculations there is no end.

Respecting the past history, so to speak, of the minor planets,
little can be said. Olbers, in calculating the elements of the
orbit of Pallas, was forcibly struck with the close coincidence
he found to exist between the mean distance of that planet and
Ceres. He then suggested that they might be fragments of some
large planet which had, by some catastrophe, been shivered to
pieces. When this theory was started it appeared a not wholly
improbable one, but the discoveries of late years have upset ith.
Nevertheless, a very close connection does apparently exist
between these minute bodies, and on this subject D' Arrest
writes : — " One fact seems above all to confirm the idea of an
intimate relation between all the minor planets ; it is, that, if
their orbits are figured under the form of material rings, these
rings will be found so entangled, that it would be possible, by
means of one among them taken at hazard, to lift up all the rest."

The circumstances which led originally to a search for planetary
bodies in the space intervening between Mars and Jupiter, were
these. In the year 1800, 6 astronomers, of whom Baron De

* Outlines of Ast., p. 352. vinced that there had existed a planet

h It may be shown mathematically, between Mars and Jupiter, in our own

that if the disruption of a large planet system, of which the little asteroids, or

ever did occur, its fragments (no matter planetkins, lately discovered, are indubit-

how diverse their subsequent paths might ably fragments ; and ' Kemember,' said he,

be) must, if continuing to revolve round ' that though they have discovered only

the Sun, always pass through the point at 4 of these parts, there will be thou-

which the explosion occurred, at one part sands — perhaps 30,000 more yet dis-

of their orbits. Sir W. Herschel thus covered.' This planet he believed to

expressed himself on this subject to the have been lost by explosion." (Life and

poet Campbell according to a letter Letters of T. Campbell, vol. ii. p. 234.)
written by the latter : — " He was con-

168 The Sun and Planets. [BOOK I.

Zach was one, assembled at Lilienthal, and there resolved to
establish a society of 24. practical observers, to examine all the
telescopic stars in the zodiac, which was to be divided into 24
zones, each containing one hour of Right Ascension, for the
express purpose of searching for undiscovered planets1. They
elected Schroter their president, and the Baron was chosen their
secretary. Such organisation was ere long rewarded by the
discovery of 4 planets, but as no more seemed to be forthcoming,
the search was relinquished in 1 8 1 6.

It does not appear that any further labours in this field were
prosecuted for some years, or till about the year 1830, when M.
Hencke, an amateur of Driesen in Prussia, commenced the search
for small planets, with the aid of the since celebrated Berlin Star
Maps which contain all stars up to the 9th or ioth magnitudes
lying within 15° of the equator. It is evident that a non-stellar
body is much more likely to attract the notice of an observer
possessing and using maps of this kind than of one not so provided,
as a change of position virtually tells its own tale with com-
paratively little trouble to the astronomer. This series of maps,
one for each hour of R. A., was only completed in 1 859 ; therefore
when Hencke commenced he had only a few at his command,
and 15 years elapsed ere his zeal and perseverance produced any
result: but when once one planet was found, the discovery of
others quickly followed.

Several of these small planets were discovered independently
by two or more observers, each without a knowledge of what the
other had done. For example, Irene was found by Hind on May
19 1851, and by De Gasparis on May 23 ; Massilia by De Gasparis
on Sept. 19, 1852, and by Chacornac on Sept. 20 ; Amphritrite by
Marth on March i , 1 854, by Pogson on March 2, and Chacornac
on March 3 (3 separate discoveries) ; Virginia by Ferguson on
Oct. 4, 1857, and by Luther on Oct. 19; Eurynome by Watson
on Sept. 14, 1863, and by Tempel on Oct. 3 ; Hecate by Watson
on July n, 1868, and by Peters on July 14 ; Cassandra by Peters
on July 23, 1871, and by Watson on August 6 ; &c.

1 See p. 67, ante.

CHAP. X.] The Minor Planets. 169

Deducting duplicate discoveries, Palisa carries off the palm
for the largest number, for (up to the end of 1888) he had detected
68 minor planets. Then comes Peters with 47 ; Luther with 23 ;
Watson with 22; Borelly with 15; Goldschmidt with 14; Hind
with i o ; and so on.

The want of telescopes suitable and available for looking after
minor planets tends now to hinder new discoveries. All the
brighter ones have evidently been found ; and, speaking gener-
ally, each new one is fainter than its predecessors, and con-
sequently small telescopes are now incapable of doing the work.
The following table will show this better than any argument: —

Mean J*

Star Mag.

First Group : Planets ©to© ... ... 8-5

Second „ „ ©— © ... ... 9-6

Third „ „ ©-© ... ... 10-4

Fourth „ „ ©— © ... ... n-o

Fifth „ © © ... 10-9

Sixth ., „ ©— © ... •-. n-2

Seventh., „ ©— © ... ... 11-3

Eighth „ „ ©-© 11-6

Ninth „ „ ©-© ... ... n-6

Tenth „ „ ©-© 11-4

Eleventh „ @~© 11-5

The above numbers are not, it is true, in perfect sequence, and
it is not possible to complete the Table at present, but my
meaning will be sufficiently clear.

The figures in the column headed " Diameter " in the Table
(see Book VI, post) are the results of calculations by Stone k.
Photometric experiments made by Professor Stampfer of Vienna
yielded somewhat similar results 1. But both sets of figures are
probably more relatively than absolutely accurate. Argelander

k Month. Not., vol. xxvii. p. 302. June of certain of these planets will be found in

1867. Mem. of the American Acad., vol. V.,N.S.,

1 See Bruhns's De Planetis Minoribus, pp. 1 23-35 : an abstract appears in Month.

Berlin 1856, for details. Some physical Not., vol. xxi. pp. 55-7. Dec. 1860.
investigations by Newcombinto the orbits

170 The Sun and Planets. [BOOK I.

published some suggestions for determining the brightness of
these planets m. Pickering also has made a few endeavours in
this direction0. In Hornstein's opinion all the larger Minor
Planets have now been found, and those having a greater diameter
than 25 geographical miles are few in number. Omitting a few
of comparatively larger size, he puts the general diameter of the
bulk of them at from 5 to 15 miles °.

Below are given the names of the only minor planets for the
determination of whose places we as yet possess Tables. It is
not likely that this list will ever be much enlarged, for the in-
crease of late years in the number of these planets has severely
taxed the patience of astronomical computers.

By Becker : — Tables for Ampkitrile.

By Brunnow : — Tables for Iris, Flora, Victoria.

By Hansen : — Tables for Egeria.

By Lesser: — Tables for Metis, Lutetia, Pomona.

By Leveau : — Tables for Vesta.

By Moller : — Tables for Pandora.

By Schubert: — Tables for Parthenope, Eunomia, Melpomene,
Harmonia.

m Month. Not., vol. xvi. p. 206. June ° Sitzungsberichte der Math. Natur-

1856. Ast. Nach., vol. xlii. No. 996. wissenschaftlichen Classe der Kaiserlichen

Nov. 29, 1885. AJcademie, vol. Ixxxiv. pt. ii. p. 7. June 2,

n Annals of the Observatory of Har- 1881.
vard College, 1879.

Fiffg. 81-4.

Plate XL

1857 : November 27. (Dawea.')

1858: November 1 8. (Lassell.}

1860: March 12. (Jacob.]

1860: April 9. (Baxendell.}

JUPITER.

CHAP. XI.] Jupiter. 173

CHAPTER XI.

JUPITER a. l/

Period, fyc. — Jupiter subject to a slight phase. — Its Belts. — Their physical nature. —
First observed by Zucchi. — Dark Spots. — Luminous Spots. — The great Red
Spot. — The great White Spot. — Sough's observations. — Alleged Connection
between Spots on Jupiter and Spots on the Sun. — Axial rotation of Jupiter. —
Centrifugal force at its Equator. — Luminosity of Jupiter. — Its Apparent
Motions. — Astrological influences. — Attended by 4 Satellites. — Are they visible
to the Naked Eye 1 — Table of them. — Eclipses of the Satellites. — Occultations. —
Transits. — Peculiar aspects of the Satellites when in transit. — Singular cir-
cumstance connected with the interior ones. — Instances of all being invisible. —
Variations in their brilliancy. — Observations of Eclipses for determining the
longitude. — Practical difficulties.— Homer's discovery of the progressive trans-
mission of light. — Mass of Jupiter. — The "Great Inequality." — Tables of
Jupiter.

JUPITER, the largest planet of our system, revolves round the
Sun in 4332'6d or 11-86^, at a mean distance of 483,288,000
miles. The eccentricity of its orbit is 0-048, so the planet may
recede from the Sun to 506,563,000 miles, or approach it to within
460,01 3,000 miles. The planet's apparent diameter varies between
49-9" in opposition and 30-4" in conjunction, being 40-1 3" at its
mean distance, according to very elaborate measurements by
Main. The equatorial diameter is 88,400 miles or thereabouts.
The compression is greater than that of any other planet except
Saturn, and amounts, according to the trustworthy observations
of Main, to r^ FT- All the values of this quantity are closely in
accord: e.g. Lassell gave TT^T-

* Important modern delineations of ing) ; vol. xxxiv. p. 235. March 1874
Jupiter will be found as follows : — Month. (the Earl of Rosse) ; vol. xxxiv. p. 403.
Not., vol. xxxi. p. 34. Dec. 1870 (Brown- June 1874 (Knobel).

174

The Sun and Planets.

[BOOK I.

Jupiter is subject to a slight phase b: in quadratures it is
gibbous : for reasons referred to in treating of Mars, the illu-
minated portion always exceeds a semicircle, and in point of
fact, owing to the greatly increased distance of Jupiter, the
defalcation of light is very small, but perceptible nevertheless
in the form of a slight shading off of the limb farthest from the
Sun. Webb has noted that this is more easily seen in twilight
than in full darkness.

Fig. 85.

JUPITER, OCTOBER 25, 1856. (De La Sue.)

The principal telescopic feature of Jupiter — its belts— are well
known, at least by name, to every one. They are dusky streaks
of varying breadth and number, lying more or less parallel to
the planet's equator0. Various theories have been broached to
explain the belts, but it is generally supposed that the planet is
enveloped in dense masses of cloud, and that the belts are
merely longitudinal fissures in these clouds, laying bare the

b Sir J. Herschel says the contrary,
but that is certainly an oversight.

c A circumstance first remarked by
Grimaldi in 1648.

CHAP. XI.] Jupiter. 175

solid body beneathd. The belts, or, as we should on this theory
with more propriety call them, the atmospheric fissures, are
constantly changing their features : occasionally only 2 or 3
broad ones are seen ; at other times as many as 8, 10, or even a
dozen narrow ones appear. They are not permanent, but change
from time to time, and occasionally with extreme rapidity; even
in the course of a few minutes. On this point, writing in 1877,
Todd remarks : — " I was much impressed on some nights with
the sudden and extensive changes in the cloud belts, as though
some tremendous storm was in progress on the planet's surface,
changing the form and dimensions of the cloud belts in an hour
or two, or even less6." At other times the change they undergo
is but gradual, and they retain nearly the same forms for several
consecutive months. They are commonly absent immediately
under the equator, but North and South of this there is usually
one wide streak and several narrower ones. At each pole the
luminosity of the planet is feebler than elsewhere. The belts,
distinguished from the general hue of the planet (often rose-
coloured), are usually greyish ; but superior optical power brings
out traces of a brownish tinge, especially on the larger ones.
Occasionally (as, for instance, during the years 1869-72, accord-
ing to numerous observers) the belts are characterised by much
colour; "copper," "deep purple," "claret/5 "red," "orange,"
"Roman ochre," are some of the terms employed by Browning
and others. A sketch by Lassell is annexed. He described the
colours recorded in the margin as " unmistakable f." It is also
to be remarked that they fade away towards the margin of the
disc on either side — a circumstance which it may be presumed is
connected with the fact that the portions of the planet's atmo-
sphere near the limbs are necessarily viewed by us obliquely.
Sometimes, but rarely, oblique belts may be seen [Figs. 83-4] ;
and with large telescopes sundry irregularities show themselves,
which to smaller instruments are merged in fewer and simpler

d I have used the word "clouds" in e Month. Not., vol. xxxvii. p. 285,

the text, but their resemblance to the April, 1877.

clouds of our own atmosphere must, for ' Month. Not., vol. xxxii. p. 82. Jan.

many reasons, be only remote. 1872.

176 The Sun and Planets. [BOOK I.

outlines. Green has advanced various reasons for the opinion
that the bright surface on Jupiter is at a higher elevation than
the dark surface, thereby indeed supporting the theory already
mentioned g. The belts of Jupiter were first observed by Zucchi,
at Rome, on May 17, 1630, according to Ricciolih ; but a claim
has been put in on behalf of Torricelli1.

JUPITEE, DEC. 30, 1871. (Lassell.}

Spots are occasionally, but, with a special exception to be
noted presently, not very frequently, visible on Jupiter. Hooke
makes the first record of one in May i664k. He watched it
in motion for about 2h, and it seems to have been sheer idle-
ness that led him to neglect observations of it for determining
the planet's axial rotation — an honour reserved, as we shall
presently see, for J. D. Cassini. Between Dec. n, 1834 and
March 19, 1835, a remarkable spot was observed at Cambridge

* Observatory, vol. vi. p. 121. April ' Moll, Jour. Koyal Inst., vol. i. p.

1883. 494. May 1831.

11 Almag. NOK., vol. i. p. 486. k Phil. Trans., No. i.

CHAP. XI]

Jupiter.

Ill

by Airy : during a portion of this interval a second was seen.
In 1843 a very large black spot was observed by Dawes, and in
Nov. and Dec. 1858 two oblong dark spots were noted by Lassell
as interesting objects l. Luminous spots closely resembling
satellites in transitu were detected for the first time in 1849 by
Dawes m, and were seen in the following year by Lassell n. In
the autumn of 1 857 Dawes again noticed some, and forwarded

Fig. 87.

SATELLITE.

SPOTS ON JUPITER, OCTOBER 6, 1857. (Sir W. K. Murray.}
drawings of them to the Royal Astronomical Society, which will
repay examination. On Oct. 25 he counted no fewer than u,
all clustered together in the Southern hemisphere n. In Nov. of
the following year (1858) Lassell observed another cluster, in the
Southern hemisphere, but nearer the equator than those seen by
Dawes, and in a bright belt. [See PI. XL Figs. 81-4.] It was
much more difficult to catch these than the former ones.
Luminous spots were observed also in 1858, 1859, and 1860 by
Sir W. K. Murray0, and in 1870 by various observers.

1 Month. Not. vol. xix. p. 52. Dec.
1858. One of them (in the drawing at
least) is precisely like a garden slug !

m Month. Not., vol. x. p. 134. April
1850.

n Month. Not., vol. xviii. pp. 6 and 49.
Nov. and Dec. 1857.

0 Month. Not., vol. xix. p. 51. Dec.
18585 Ibid, vol. xx. p. 58. Dec. 1859;
Ibid., vol. xx. p. 331. June 1860.

178 The Sun and Planets. [BOOK I.

The most celebrated spot on Jupiter that has ever been recorded
is that which was known as " the great red spot," first con-
spicuously noticed in July 1878, and which occupied a position
immediately South of the dark belt on the Southern boundary
of the equator. Its large size and singular boldness of out-
line aroused the keenest interest amongst astronomers. From
measures made with the i8£-in. refractor at Chicago in the
years 1879-82, the mean dimensions and position of the spot
were as follows : — Length 11-73", Breadth 3-58", Latitude 7-25' S.
These figures correspond to a length of about 27,000 miles and
a breadth of 8000 miles. The intense red colour and permanency
of the spot called for especial remark. Very little change in
its shape or appearance occurred until the autumn of 1882, when
it sensibly began to fade ; and during the ensuing year it became
extremely faint, though still preserving its integrity of form.
By the spring of 1884 the spot was to be seen with difficulty, as
it became involved with the dusky belts, and lost much of its
definiteness of outline. This object offered an excellent means
for rediscussing the rotation-period of Jupiter. From some
observations in 1878, compared with his own up to the end of
1883, Denning found the period to be 9h 55m 36-2", from 4586
rotations ; but the motion was not uniform, for during the interval
of more than 5 years embraced by the observations the time
increased 5 seconds. At the Opposition of 1879 it was 9h 55™ 34",
but in 1883 had increased to 9h 55m 39". This extensive drift
in longitude proves the spot to have been atmospheric, and not
a fixed object on the actual surface of the planet. The rotation-
period it has exhibited may not therefore coincide with the true
period of Jupiter.

Fig. 88 represents the red spot on Jupiter as seen with a
lo-inch reflector in the summer of 1887.

During the last few years a brilliant white spot has been
visible on the equatorial border of the great Southern belt. A
curious fact in connection with this spot is, that it moves with a
velocity of some 260 miles per hour greater than the red spot.
Denning obtained 169 observations of this bright marking

CHAP. XI.]

Jupiter.

179

during the years 1880-83, an^ determined the period as 9h 50™ 8.7s
(5^ minutes less than that of the red spot), and this period
increased with the time. In 1 880-81 it was 9h 50™ 5-88, but
during 1883 augmented to 9h 50™ ii«48. The swifter motion of
this object enabled it to complete a revolution of Jupiter relatively

THE GREAT RED SPOT ON JUPITER, JOLT 16, 1887. (W. P. Denning.}

to the red spot in 45* i4h 37«5m. During the 1115 days which
elapsed from Nov. 19, 1880, to Dec. 9, 1883, it performed 25
rotations more than the red spot. Although the latter is now
somewhat faint, the bright spot gives promise of remaining
visible for many years.

During 1886 a large number of observations of Jupiter were
made at the Dearborn Observatory, Chicago, U.S., by Prof. G. W.
Hough, using the 1 8 £ -inch refractor of the observatory. Inasmuch
as these observations are not only of high intrinsic interest, but

N 2

180 The Sun and Planets. [BOOK I.

are in conflict to some extent with previous records, a somewhat
full abstract of them will be useful p : —

" The object of general interest is the great red spot. The outline, shape, and size
of this remarkable object has remained without material change from the year 1879,
when it was first observed here, until the present time. According to our observa-
tions, during the whole of this period it has shown a sharp and well-defined outline,
and at no time has it coalesced or been joined to any belt in its proximity, as has
been alleged by some observers.

"During the year 1885, the middle of the spot was very much paler in colour
than the margins, causing it to appear as an elliptical ring. The ring-form has
continued up to the present time. While the outline of the spot has remained
very constant, the colour has changed materially from year to year. During
the past three years [1884-6] it has at times been very faint, so as barely to be
visible.

"The persistence of this object for so many years leads me to infer that the
formerly-accepted theory, that the phenomena seen on the surface of the planet are
atmospheric, is no longer tenable. The statement so often made in text-books, that
in the course of a few days or months the whole aspect of the planet may be changed,
is obviously erroneous.

"The rotation-period of Jupiter from the red spot has not materially changed
during the past three years. The 'mean' period, 1884-5, was 9h 55m 40.4'.
Marth's ephemeris for the present year is based on a period of 9^ 55™ 40.6*. The
mean correction to this ephemeris is now [May 1887] only about minus 7 minute?,
indicating a slightly less value.

" The oval white spots on the Southern hemisphere of the planet, 9" S. of the
equator, have been systematically observed at every Opposition during the past
8 years. They are generally found in groups of three or more, but are rather
difficult to observe. The rotation-period deduced from them is nearly the same as
from the great red spot.

" These spots usually have a slow drift in longitude of about o-5° daily in the
direction of the planet's rotation, when referred to the great red spot ; corresponding
to a rotation-period of 20 seconds less than the latter."

It is not known what is the physical nature of either the dark or
the luminous spots, but observations by Brett indicate (he thinks)
that the large white patches on the equatorial zone of Jupiter
cast, shadows : thus showing that these patches project above the
general surface visible to us. The appearances presented point to
the conclusion that we do not see the actual body of the planet
itself either in the dark belts or in the bright ones q. The usual
form of both kinds of spots is more or less circular.

It has been already pointed out in Chap. I. (ante) that some

P Annual Report of Chicago Ast. Soc. 1 Month. Not., vol. xxxiv. p. 359.

1887, p. 10. May 1874. .

CHAP. XL] Jupiter. 181

relationship has been thought to exist between Sun-spots as
regards their period and the position of Jupiter in its orbit ; but
Ranyard extends this idea considerably. He points out an
apparent identity in point of time between the prevalence of
spots on the Sun and spots on Jupiter, and proceeds to infer that
spots on Jupiter are indicative of disturbance on Jupiter, and that
both classes of phenomena are dependent upon some extraneous
cosmical change, and are in no sense related as cause and effect,
the supposed cause being Jupiter's attraction, and the supposed
effect an atmospheric tide on the Sun. The observations of
Jupiter which are available for the confirmation of the truth of
this theory are, previous to 1850, too few and too casual to be
conclusive ; but such as they are they have been tabulated by
Ranyard, and unquestionably countenance his theory1*. Brown-
ing suggests that evidence exists to show that the red colour of
Jupiter's belts is a periodical phenomenon coinciding with the
epoch of Sun-spot maxima8. That in a general way the colour
of Jupiter varies from time to time he is firmly convinced.

Cassini, by closely watching the spot which he first saw in
July 1 665, noticed movement, and regarded this as a proof of the
planet's axial rotation, the period of which he found to be about
9h 56™. The independent observations of Airy and Madler in
J^35 giye 9h 55m 21 '3s, and 9h 55m ^'5S> and afford another
illustration of the care bestowed by Cassini on his astronomical
researches. The later observations of Cassini, those of Sir W.
Herschel, and those of Schroter indicate results not free from
anomalies ; Sir William's various determinations fluctuated to an
extent of nearly 5m, a discordance far beyond that which is
assignable to errors of observation ; and the unavoidable conclu-
sion is, that the spots employed by those 3 astronomers in their
investigations were affected (as they themselves believed) by a
proper motion of their own. Schmidt found the period to
be 9h 55m 28'78.

r Month. Not., vol. xxxi. p. 34, Dec. 5 Month. Not., vol. xxxi. p. 75, Jan.

1870; p. 201, May 1871; and p. 224, 1871.
June 1871.

182 Irie otm and Planets. [BOOK I.

The axial rotation of Jupiter being so much quicker than that
of the Earth, combined with its diameter being so much greater,
results in the rotating velocity of a particle at its equator being
greater than on any other planet — 466 miles per minute, against
the Earth's 17 miles per minute. It will at once be per-
ceived that the intensity of the centrifugal force must be very
great, and the polar compression likewise. Hind calls attention
to this rapid rotation as offering some compensation, by the heat
which it must evolve, for the diminished power of the Sun's rays
at the distance of Jupiter.

Under favourable circumstances Jupiter, like Mars, rivals
Venus in brilliancy, and even casts a shadow. G. P. Bond found
that for photographic purposes its surface reflects light better
than that of the Moon in the ratio of 14 to i *. Zollner has
calculated that Jupiter reflects 0*6 a of the light it receives, the
Moon reflecting but 0-17 of the incident light. Bond computed
that Jupiter actually emits more light than it receives (!) : but
whether we accept this problematical result, or the more trust-
worthy one obtained by Zollner, strong indications of inherent
luminosity in Jupiter seem to exist ; and this points to the
conclusion that this planet is itself a miniature Sun. The heat
derived from the Sun only would leave water on Jupiter's
surface above 500° below freezing point, so that any clouds must
arise from internal heat. Moreover, if we conceive the Earth
and Jupiter to have been simultaneously created, Jupiter would
retain its heat for ages after the Earth had cooled down.

Seen from the Earth the apparent motion of Jupiter is some-
times retrograde. The length of the arc of retrogradation varies
from 9° 51' to 9° 59', and the time of its performance from u6d
i8h to i22d I2h. The retrograde motion begins or ends, as the
case may be, when the planet is at a distance from the Sun,
which varies from 113° 35' to 116° 42'.u

e Month. Not., vol. xxi. p. 198. May planet is from the Sun, the less will be

1 86 1. the extent of its arc of retrogression, but

11 It may here be noted that, as a the greater will be the time occupied in

general rule, the farther a superior describing it.

CHAP. XL]

Jupiter.

183

In by-gone days Jupiter was not without its supposed astro-
logical influences. It was considered to be the cause of storms
and tempests, and to have power over the prosperity of the
vegetable kingdom. Pliny thought that lightning, amongst other
things, owed its origin to Jupiter. An old MS. Almanac for
1386 states, that " Jubit es hote and moyste, and doos weel til al
thynges, and noyes nothing."

Jupiter is attended by 4 satellites x, 3 of them seen for the first
time by Galileo, at Padua, on January 7, 1 6ioy, but not determined
to be satellites till the following day, whilst the whole four
were not seen all together till Jan. 13. They shine with the
brilliancy of stars of the 6th or 7th magnitude ; but, owing to
their proximity to their primary, are usually invisible to the

Fig. 89.

JUPITER AND ITS SATELLITES.

naked eye, though several instances to the contrary are on
record. Mr. C. Mason states that on April 15, 1863, finding
Jupiter conveniently placed for the purpose, he determined to
make a systematic attempt to solve the problem frequently
declared to be an impossibility. After a steady gaze of 8m or
iom he was able to assure himself that in close proximity to
Jupiter he could see a little star. Having resorted to various
precautions to prevent self-deception, he at length turned his

1 Named by Simon Marius, a frau-
dulent claimant of their discover}', lo,
Europa, Ganymede, Callisto. These
names have never been in use.

7 Siderius Nuncitis ; Opere di Gali-
leo, vol. ii. p. 15 et seq. Ed. Padua.
1 744. Au English Translation by E. S.
Carlos was published in London in 1880.

184

The Sun and Planets.

[BOOK I.

refractor of 4^ inches aperture on the planet and found in the
position corresponding to that indicated by the naked eye (allow-
ance being made for inversion) all the 4 satellites on the same
side of the planet. He states that until referring to the Nautical
Almanac a few minutes before using the telescope he had no idea

Fig. QO

JUP1TEB SEEN WITH THE NAKED EYE, APRIL 15, 1863. (Mason.)

as to their configuration, and is the more convinced that with
the naked eye he really did see the 4 as one2-. It is quite certain
that satellites II and III were seen on Jan. 15, 1860, by some
officers of H. M. S. "Ajax" in Kingstown Harbour, near Dublin a.
Mr. Levander and others at Devizes asserted that on April

Fig. 91.

JUPITER SEEN WITH A TELESCOPE, APRIL 15, 1863. (Mason.)

21, 1859, they saw 2 of these bodies. In 1852 an American
missionary of the name of Stoddard, at Oroomiah in Persia, re-
peatedly saw two satellites in the twilight, so long as Jupiter itself
was devoid of an overpowering glare. Wrangel, the celebrated
Russian traveller, stated that when in Siberia he once met an
hunter who said, pointing to Jupiter, " I have just seen that large

* Month. Not., vol. xxiii. p. 215. May
1863.

1860.

Month. Not., vol. xx. p. 212. March

CHAP. XI.]

Jupiter.

185

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186 The Sun and Planets. [BOOK I.

star swallow a small one, and vomit it shortly afterwards." The
Russian remarks that the sportsman here referred to an immer-
sion and subsequent emersion of the IIIrd satellite, on which
Arago, who makes the citation, says, " It is well known that the
acuteness of sight of those natives and of the Tartars has become
proverbial." Other similar observations, including one by him-
self, are given by Webbb. so that we may now regard the
question of possibility as decided in the affirmative.

The satellites of Jupiter are capable of being seen with so
little optical assistance that it is worth while to enter at some
length into a consideration of them.

They are distinguished by ordinal numbers preceding out-
wards. Thus the "Ist" satellite is the one nearest to the
primary ; the " IVth " the one most distant therefrom. To
determine which is which, the diagrams given in the Nautical
Almanac will usually be necessary, but the IIIrd, as the largest
and brightest, will generally be identified with least difficulty.
In small telescopes it is scarcely possible to say that there is
anything to distinguish the satellites from stars, beyond a
noticeably greater steadiness of light ; increased power will
reveal discs, but a very considerable augmentation is requisite
for detecting physical peculiarities. " The discovery of 4 bodies
revolving round a primary, exhibited a beautiful illustration
of the Moon's revolution round the Earth, and furnished a most
favourable argument in favour of the Copernican theory c. The
announcement of this fact pointed out also the long vista of
similar discoveries which have continued from time to time
down to the present day to enrich the solar system, and to shed
a lustre on the science of astronomy."

The eclipses, occultations, and transits of the Jovian satellites
offer an endless series of interesting, and indeed useful, pheno-
mena. The Ist, IInd, and IIIrd satellites, in consequence of the
smallness of the inclinations of their orbits, undergo once in

b Celest. Objects, p. 144. and Romish ecclesiastics, who assailed

c The argument, however, failed to Galileo's views respecting these satellites
command the acceptance of divers Popes with great bitterness for many years.

CHAP. XI.] Jupiter. 187

every revolution an eclipse in the shadow cast by the planet
into space. The IVth, however, frequently escapes this ordeal,
in consequence of the plane of its orbit being somewhat more
inclined than is the case with the others, and its distance from
the primary being so considerable.

When the satellites enter the shadow the immersion is said to
take place ; when they come out of it, the emersion — terms which
explain themselves. Closely associated with the eclipses are the
occultations — a word employed to express the concealment of the
satellites by the direct interposition of the planet itself, indepen-
dently of the shadow. When the planet has passed its conjunc-
tion with the Sun, the shadow is projected on the Western side,
and at this time both the immersions and emersions of the IIIrd
and IVth satellites may be observed, but not always those of the
IInd; and only the emersions of the Ist, in consequence of its
proximity to the planet causing it (after first undergoing an
occultation) to enter the shadow behind the planet. When
Jupiter is near its Opposition to the Sun, the immersions and
emersions take place very close to the planet's limbs. As the
planet again approaches Conjunction the shadow is projected on
the Eastern side, giving rise to phenomena partly comple-
mentary to those set forth above. In other words, whilst the
immersions and emersions of III and IV are always visible,
and those of II frequently visible, the immersions only of I can
be perceived because it emerges behind Jupiter ; when this one
does reappear it is on emersion from an occultation.

The occultations "generally require much more powerful
instruments for their satisfactory observation than the eclipses.
With a telescope of adequate power we may trace the gradual
disappearance of the satellite from the first contact with the limb
of the planet to its final obscuration behind the disc ; and, as
viewed with such an instrument, these phenomena are highly
interesting. The occultations of the IVth satellite are usually
visible both at disappearance and at reappearance ; those of the
IIIrd also are frequently so observable. But it happens much
more rarely that the complete phenomenon can be observed

188 The Sun and Planets. [BOOK I.

in regard to the IInd satellite, while the immersion and emer-
sion of the Ist can only be visible a day or two before or after
the Opposition of Jupiter, as at all other times either the im-
mersion or emersion must happen while the satellite is obscured
in the planet's shadow. Thus it most usually occurs that from
Conjunction to Opposition the reappearances only of the Ist and
IInd satellite can be observed, and the disappearances only from
Opposition to Conj unction d."

Far more interesting are the transits of the satellites and their
shadows across the planet — phenomena which, it is easy to under-
stand, are of frequent occurrence when the satellites are in those
parts of their respective orbits which lie nearest to the Earth.
The satellites appear on the disc of their primary as round lumi-
nous spots preceded or followed by their shadows, which show
themselves as round black or blackish6 spots. The shadow
precedes the satellite when Jupiter is passing from Conjunction
to Opposition, but follows it when the primary is between
Opposition and Conj unction. When actually in Conjunction the
shadow is in a right line with the satellite, and the two may be
superposed.

Some peculiarities in the appearance of the satellites during
transit are too well attested to be passed over. Ill in particular
is nearly always seen almost or quite as dark as its shadow, but
on rare occasions appears dusky and shaded. IV has been
often seen dark f, but, according to Dawes, II has never had the
slightest shading on the disc within his knowledge, and I only
a grey tinge, inferior by many shades to that usually possessed
by III. Contrast has evidently a good deal to do with the
bringing out of these shadings, but the circumstances attending

d Hind, Sol. Syst., p. 100. (Modified vol. viii. p. 37. Feb. 1870.)

in one place.) f Roberts (Month. Not., vol. xxxiii. p.

6 Blackish, because the visible margin 412. April 1873); Firmstone (Ibid., p.

is not that of the true shadow, but of a 460. May 1873) ; Burton (Ibid., p. 472.

penumbra which surrounds the shadow, Jnne 1873), &c. On Aug. 21, 1867,

though it is rare for this penumbra to Prince saw IV as a " round black spot,"

be observable as an actual ring sur- its colour being as nearly as possible that

rounding the shadow. (See an instance of its own shadow " (Month. Not., vol.

recorded by T. H. Buffham in Ast. Reg., xxvii p. 318).

CHAP. XL]

Jupiter.

189

Fig. 92.

the recorded variations in this intensity are less intelligible.

J. D. Cassini, Maraldi, Pound8, Messier h, Schrb'ter, and Sir W.

Herschel were amongst the earlier observers of

these peculiarities, and W. C. Bond, Lassell, and

Dawes amongst the more modern ones. Bond

saw III as a well-defined black spot on Jan. 28,

1848, and again on March n. He stated that,

on March 1 8, it entered upon the disc as a very

bright spot, more brilliant than the surrounding

surface ; that 2om later it had so decreased in

brightness as to be hardly perceptible, and that

in another few minutes a dark spot suddenly

appeared in its place, which was seen for 2|h. This spot was

sufficiently conspicuous to be measured with a micrometer, was

THE IVth SATELLITE

OF JDPITER,
MARCH 26, 1873.

(O-. W. Roberts.)

Fig- 93-

Fig. 94.

THE IIIrd SATELLITE OF
JDPITER, JAN. 31, i860.

THE IVth SATELLITE OF
JUPITER, FEB. 12, 1849.

Dawes.

perfectly black, nearly round, and on the satellite. The con-
verse of this — the satellite dark first and bright afterwards —
was witnessed by Prince and Brodie on Jan. 31, 1860*.

On June 26, 1828, II, having entered on the disc of Jupiter,
was seen 12™ or 13™ afterwards outside the limb, where it re-
mained visible for at least 4™ and then suddenly vanished.
Three observers of eminence (Sir T. Maclear, Adm. Smyth, and
Dr. Pearson) record this, so there can scarcely have been any

e Phil. Trans-, vol. xxx. p. 900.

h Phil. Trans., vol. lix. p. 459. 1769.

1 Month. Not., vol. xx. p. 212.
1860.

March

190 The Sun and Planets. [BOOK I.

individual optical illusion, much less deception. It has been
suggested that an eclipse of the satellite by another satellite
would meet the facts of the case, provided we could establish a
doubt as to whether these observers for a certainty saw the
satellite previously on the disc of the planet

Fig. 95.

JUWTBB WITH SATELLITE IN TRANSIT, JUNE 26, 1828. (Smyth.}

Lassell has found the shadow of IV very much larger than
the satellite itself, even to the amount of double the diameter,
and the same shadow larger than that of III, though the satel-
lite itself is smaller than III. The shadow of II has been seen,
it is said, to possess an irregular outline, but the observation is
not well attested.

On April 5, 1861, Mr. T. Barneby saw the shadow of III first
in the shape of a broad dark streak such as the cone of the
shadow would represent in a slanting direction, but it shortly
afterwards appeared as a circular spot perfectly dark and much
larger than the shadow (which was visible at the same time) of
I. I cite this passage chiefly because of the information about
the form of the projection of the shadow, which, though very
reasonable and obvious, is noticeable as the only instance I have
met with.

On April 17, 1861, the Rev. R. Main saw II occulted by I, and
the two appeared as one for some ym or 8m.

On Jan. 14, 1872, Mr. F. M. Newton saw I superposed on its
shadow, so that the satellite appeared to be surrounded by a
dark ring. This observation seems to be unique k. The nearest

k Letter in Eng. Mech., vol. xxiii. p. 562. Aug. n, 1876.

CHAP. XI.] Jupiter. 191

approach to it is an observation by Mr. G. D. Hirst, on May 13,
1876, of I in transit partly occulting its own shadow, so that
the shadow appeared as a narrow black crescent. The satellite
itself was not seen except when near the edge of the planet's
disc1.

Fig 96 represents a singular observation made by Trouvelot
at Cambridge, U.S., on April 24, 1887.

Fig. 96.

JUPITER'S IST SATELLITE IN TRANSIT, WITH A DOUBLE SHADOW,
APRIL 24, 1877. (Trouvelot,}

" The shadow of the first satellite which had entered on Jupiter
39 minutes previously had not yet quite gone a quarter of its
way across the disc. This shadow, black and of a sensibly
elliptical form, doubtless on account of the fact that it was seen
projected not far from the edge of a spherical surface, almost
touched at its most northern point the northern edge of the
pink equatorial zone. It was preceded on its western side by
a rather dark spot, which was of exactly the same shape and
size, and only separated from the shadow by a space equal at

1 Letter in Entj. Mech., vol. xiv. p. 535. Feb. 9, 1872.

192 The Sun and Planets. [BOOK I.

the most to one-third of the equatorial diameter of the shadow.
This remarkable spot was not exactly on the same horizontal
line as the shadow of satellite I, but lay about one third of
the vertical diameter of the shadow towards the South."

Trouvelot goes on to say that he watched the phenomenon for
altogether ih 20™, or until the primary shadow had accomplished
about f of its journey across the planet, when it ceased. He
assured himself that it was neither a planetary spot, properly so
called, nor a satellite that he had seen, and he regarded it as
simply a secondary shadow — a shadow of the main shadow seen
projected on a lower stratum of Jupiter's atmosphere (or even it
might be on the solid body of the planet), which would account
also for the secondary shadow being much less intense than the
primary or ordinary one m.

As to certain irregularities of figures presented by IV when
seen as a dark spot on the disc of Jupiter, reference may be made
to a paper by Burton11.

The phenomena exhibited by the satellites in transit have
been carefully studied by Spitta, and his conclusions in a
summary form will be useful for reference : — IV is fainter than the
others on approaching the limb of the planet ; bright for first i o
or 1 5 minutes of transit ; lost for about the same time ; reappears
as a dark spot, becoming jet black : II always bright during
transit; brilliancy least affected on approaching limb: III
sometimes becomes lost, reappearing as a dark spot ; at others,
remains white throughout : I after becoming lost, usually turns
one of the shades of grey to nearly black0.

Jupiter's satellites move in orbits nearly circular, and between
the motions of the first three a singular relation exists: — The
mean sidereal motion of I added to twice that of III, •/'* constantly
equal to three times that of II ; so that the sidereal longitude of I,
plus twice that of III, minus three times that of II, yields a re-
mainder always constant, and in fact equal to 180°. This relation

ra L'Astronomie,.vo\. vi. p. 414. Nov. 1887.
" Month. Not , vol xxxiii. p. 472. June 1873.
0 Month. Not., vol. xlviii. p. 34. Nov. 1887.

CHAP. XL]

Jupiter.

193

will be better understood by an inspection of the following
table : —

Sidereal motion
per second of time.

Satellite I. 8-478706 x i = 8-478706. (a)
„ II. 4-223947 x 3 = 12-671841. (/>)
„ III. 2-096567 x 2 = 4-193134. (c)

Fig. 97.

PLAN OF THE JOVIAN SYSTEM V.

P The satellite orbits in this and the
follow.ing chapters are all drawn to the
same scale. No diagram on a plane
on the same scale of the orbits of

the satellites of Mars is given in this
volume, because on the scale here em-
ployed, those orbits would be of micro-
scopic dimensions.

194 The Sun and Planets. [BOOK I,

Adding together a and c, we get 12-671840, which quantity is to
5 places of decimals the same as b. From this it follows that for
an enormous period of time the 3 interior satellites cannot
all be eclipsed at the same time; for in the simultaneous
eclipses of II and III, I will always be in conjunction with
Jupiter, and so onq. Making use of his own tables, Wargentin
has calculated that simultaneous eclipses of the 3 satellites
cannot take place before the lapse of 1,317,900 years1, and an
altefation of only 0-33" in the annual motion of II would
suffice to render the phenomenon for ever impossible.

D' Arrest pointed out the commensurability, within a few hours,
of 5187 revolutions of I, 2583 of II, 1281 of III, and 548 of
IV, in 25y 55d5 when the same geometric configuration will
recur.

The exact figures are given by him8 as follow :—

Revolutions. Days

Satellite I. 5187 = 9 [80-27.
„ II. 2583 = 9180-23.
„ III. 1281 = 9180-14.
„ IV. 548 = 9l8o>95-

Between satellites III and IV the following comparatively
coarse approximation subsists. Seven times the period of the .former
(5od ih 57m 53 '5 20s) exceeds by only 2im 19* 7s three times the
period of the latter (50* ih 36™ 33'8i38). Moreover the periods of
I, II, and III stand in the ratio of i, 2 and 4, as near as may be.
The following special elements are given by Hind*. " The
line of apsides of the IIIrd satellite revolves in about i37y, and
that of the IVth in about 5i6y. The lines of nodes of the 3
exterior satellites revolve in a retrogade direction, as is the case
with the nodes of the lunar orbit ; the period for the IInd is 3Oy,
for the IIIrd i40y, and for the IVth 52oy."

It occasionally, but very rarely, happens that all 4 satellites
are for a short time invisible, being either directly in front of, or

i Laplace demonstrated by the theory r Ada Soc. Upsal.,p. 41. 1743.

of Gravitation that if this relation be s Ast. Nach., vol. Iviii. No. 1377.

once approximately begun, it will always Aug. 25, 1862.

last. l Sol. Syst., p. 98.

CHAP. XI.] Jupiter. 195

behind, the planet. Such was the case, according to Molyneuxu,
on Nov. 2, 1681 (o. s.) The same thing was noticed by Sir W.
Herschel on May 23, 1802; by Wallis on April 15, 1826; by
Dawes and W. Griesbach on Sept. 27, 1843. Dawes published
in 1862 an account of his observations w. Jupiter's (apparent)
deprivation of its satellites lasted about 35™. A repetition of
this phenomenon occurred on Aug. 21, 1867, when the planet
was for ifh apparently without satellites projected on the sky.

The satellites appear to vary in brilliancy in a way wholly
inexplicable. I have already stated that III is commonly the
brightest • but Maraldi and Bond have seen the contrary. On
the whole, perhaps, we are justified in saying that the faintest is
IV ; but the lustre of this is irregular : in 1 7 1 1 Bianchini and
another, and on June 13, 1849, Lassell, saw it so feeble as to be
almost invisible, whilst Webb repeatedly saw it surpass III.
This observer wrote — " Spots . . . may easily cause this variable
light; but a stranger anomaly has been perceived, — the discs
themselves do not always appear of the same size or form.
W. Herschel noticed the former fact, and inferred the latter ; and
both have been since confirmed by others. Beer and Madler.
Lassell, Secchi and Buffham have sometimes seen the disc of
II larger than I; and Lassell, and Secchi and his assistant,
and Burton have distinctly seen that of III irregular and
elliptical; and according to the Roman observers the ellipse
does not always lie the same way: Mitchell also, with an i i-inch
achromatic, has observed this disc irregular and hazy. Buffham
has often found IV the smallest of all, and irregular-looking.
Phenomena so minute hardly find a suitable place in these pages,
but they seem too singular to be omitted ; and in some cases,
possibly small instruments [?] may indicate them ; at least,
with an inferior fluid achromatic reduced to 3 inches aperture I
have sometimes noticed differences in the size of the discs which
I thought were not irnaginaryx."

Sir W. Herschel, by attentive and prolonged observation, was

u Opticks, p. 271. w Month. Not., vol. xxii. p. 292. June 1862.

x Celest. Objects, 4th ed., p. 162.

O 2

19(> The Sun and Planets. [BOOK I.

led to infer that each of the satellites rotated on its axis in the
same time that it made a sidereal revolution round its primary
thus presenting an analogy to the case of our Moon. The imme-
diate reason which led to this conclusion was a belief that the
variation in their brilliancy always recurred in nearly the same
positions of the satellites with respect to Jupiter and the Sun,
which supposition had previously presented itself to the mind of
Cassiniy. But modern observations do not harmonise with these
statements ; that is to say, we are not entitled to affirm now
that peculiarities in the appearances of the satellites correspond
with definite orbital positions. On the contrary, the peculiar-
ities observed are not governed by any known law of time or
place.

Arago thus summed up Sir W. Herschel's photometric deduc-
tions. " The Ist satellite is at its maximum brightness when it
attains the point of its orbit which is almost midway between
the greatest Eastern Elongation and its Conjunction. The bright-
est side of the IInd satellite is also turned towards the Earth
when that body is between the greatest Eastern Elongation and
Conjunction. The brightness of the IIIrd satellite attains 2
maxima in the course of a revolution, namely at the 2 Elonga-
tions. The IVth shines with a bright light only a little before
and a little after Opposition2."

Various observers have assigned colours, or rather tinges of
colour, to the different satellites, but the results are not suffi-
ciently of accord to be worth citing.

Eclipses as viewed on Jupiter take place on a grand scale ; for
in consequence of the small inclinations of the orbits of the
satellites to the planet's equator and the small inclination of the
latter to the ecliptic, all the satellites, the IVth excepted, are
eclipsed some time in every revolution ; so that a spectator on
Jupiter might witness during the Jovian year 4500 eclipses of
the Moon (Moons) and about the same number of the Sun.

Soon after their discovery it suggested itself to the reflecting

y Mem. Acad. des Sciences, vol. i. p. 266.
* Pop. Ast., vol. ii. p. 549. Eng. ed.

CHAP. XL] Jupiter. 197

mind of Galileo that eclipses of the satellites of Jupiter might be
made useful for determining the longitude. Regarding eclipses
as instantaneous phenomena visible at the same moment in every
place which has the planet above its horizon, it is clear that a
comparison of observations recorded in 2 local times would afford
data for determining the difference of time (longitude) between
the places to which the times belong. Eclipses accurately pre-
dicted for one meridian when observed under another one would
afford a still more advanced means of ascertaining the difference of
longitude between them. These eclipses could be predicted if
sufficiently accurate tables of the satellites were in existence ;
but at sea, where the problem has chiefly to be solved, they
cannot be observed with the most refined accuracy, and on land
some difficulties present themselves ; so that the method to some
extent breaks down, and is only available where very rough
approximations will suffice.

It was to observations of one of the satellites of Jupiter, and
Homer's discussion of them in 1675, that we owe the discovery that
light is not propagated instantaneously through space*. It was
found that the calculated times of the eclipses did not correspond
with the observed times, and that the difference was a quantity
constantly affected by opposite signs of error according as Jupiter
was in perigee or apogee. In the former case the eclipse always
occurred before the calculated time ; in the latter, always after
it. The regularity with which these anomalies showed them-
selves led Homer to suspect that they had their origin in the
variations which occurred in the distance of Jupiter from the
Earth : that as this distance increased or diminished so a longer
or a shorter period was requisite for light to traverse the space
between the 2 planets. Assuming from the data in his posses-
sion that light travelled at the rate of 192,000 miles per second,
and required i6im to traverse the diameter of the Earth's orbit,
and applying this (as yet hypothetical) conclusion to the eclipses
in the form of a trial-correction, Homer promptly obtained proofs
of the accuracy of his reasoning ; but it was Bradley 's discovery
" Opere di Galileo, vol. ii. p. 33. Padua ed., 1 744.

198 The Sun and Planets. [BOOK I.

of aberration some half a century later which completely
demonstrated the soundness of Homer's views and caused their
general acceptance. The modern experiments of Fizeau have
given for the velocity of light a result but slightly differing in
amount from Romer's, namely, 194,000 miles per second b.

Like most new discoveries Romer's did not, when promulgated,
find favour in the scientific world, and many years elapsed ere it
was generally accepted.

The mass of Jupiter has never been a very doubtful quantity,
all the values of it being much more in accord with one another
than is usually the case. Laplace, from Pound's observations of
the IVth satellite, placed it at r^Vr 5 Bouvard, from the pertur-
bations of Saturn, at y^Y^ 5 Nicolai, from the perturbations of
Juno, at TtrsVrs-; Encke, from the perturbations of Vesta, at
Ttrsff 5 and from perturbations of the Comet bearing his name,
at xo-Vr ; Santini at T(r3o- ; Bessel at j^VsT ; Airy, from motions
of the satellites, at T^tWr ; Kriiger, from observations of Themis,
at TTT/TTT 5 Jacob, from the motions of the satellites, at j^V-ir 5
and Moller, from the motions of Faye's Comet, at xmrV-TF 5 Schur,
from heliometer measures of the satellites, at x7riV^¥- Any one
of the 4 last values may be taken to be substantially exact.

" The most ancient observation of Jupiter which we are ac-
quainted with is that reported by Ptolemy in Book X. chap. iii.
of the Almagest, and considered by him free from all doubt. It is
dated in the 83rd year after the death of Alexander the Great, on
the 1 8th of the Egyptian month Epiphi, in the morning, when the
planet eclipsed the star now known as 8 Cancri. This observation
was made on Sept. 3, B.C. 240, about i8h on the meridian of
Alexandria."

This is a convenient place to mention the " Great Inequality "
in the motion of Jupiter and Saturn, so far as the fact of its

b In consequence of the increase in before the parallax question came up

the received value of the Sun's parallax for general discussion pointed to the

a reduction in the velocity of light by same conclusion. The value for the

several thousands of miles per second velocity of light now generally accepted

must be assumed, and singularly enough is about 186,660 miles per second,
some experiments of Foucault's made

CHAP. XI.] Jupiter. 199

existence is concerned, for a particular account of it would be
altogether foreign to the purposes of this work c. The period of
each of these planets is subject to a continuous change owing to
the mutual influence exerted by each on the orbit of the other
and the time required for this change to go through its various
stages is the Period of the Great Inequality. It amounts to
918 years.

The Tables of Jupiter used till recently were those of A. Bou-
vard, published in 1821, but the new and far superior Tables of
Le Verrier have superseded themd. For the satellites, Damoi-
seau's Tables (published in 1836) are employed. As regards the
satellites there is room for much improvement in the Tables at
present employed. They fail to give results characterised by the
precision which modern science demands.

c See Sir J. Herschel's Outlines,^. 502. first time in England in the preparation
ll These tables were employed for the of the Nautical Almanac for 1878.

200 The Sun and Planets. [BOOK I.

CHAPTER XII.

SATURN ». Fj

Period, &c. — Figure and Colour of Saturn. — Belts and Spots. — Observations of
the Belts by Holden. — By Ranyard. — Bright spot recorded by Hall. — Probable
atmosphere. — Observations of Galileo, and the perplexity they caused. — Logo-
griph sent by him to Kepler. — Huygens's discovery of the Ring. — His logn-
ffriph. — The bisection of the Ring discovered by the brothers Ball. — Sir W.
HerscheVs Doubts. — Historical epitome of the progress of discovery. — The
" Dusky" Ring. — Facts relating to the Rings. — Appearances presented by them
under different circumstances. — Rotation of the Ring. — Secchis inquiries into
this. — The Ring not concentric with the Ball. — Measurements by W. Struve. —
Other measurements. — Miscellaneous particulars. — Theory of the Ring being
fluid. — Now thought to consist of an aggregation of Satellites. — The " Beaded "
appearance of the Ring. — O. Struve's surmise about its contraction. — Irregu-
larities in the appearances of the ans<B. — Rings not bounded by plane sur-
faces.— Mountains suspected on them. — An atmosphere suspected. — Physical
observations between 1872 and 1876 by Trouvelot. — Observations^ MM. Henry.—
By Keeler. — Brightness of Rings and Ball. — Bessets investigations into the
Mass of the Rings. — Saturn attended by 8 Satellites. — Table of them. —
Physical data relating to each. — Elements by Jacob. — Coincidences in the
Rotation-periods of certain of them. — Transits of Titan. — Celestial phenomena
on Saturn. — Lockyer^s summary of the appearances presented by the Rings. —
Peculiarity relative to the illumination of lapetus. — Mass of Saturn. — Ancient
observations. — Saturnian Astronomy.

TNFERIOR in size to Jupiter only, Saturn may fairly be pro-
nounced to be the most interesting member of the Solar
System. It revolves round the Sun in io759-2d or 29'45y at a

*• For drawings, &c. of Saturn, see (Dawes) ; Ibid.,xv. p. 79(Dawes); Ibid.,

Annals of Harvard Coll. Obs., vol. ii. vol. xvi. p. 120 (one fig. by Jacob); Ibid.,

(1 20 drawings by the Bonds); Ast. Nach., vol.xviii.p. 75 (abstract of Harvard Obs.) ;

vol. xxviii. No. 650, Nov. 1848 (J. F. J. and vol. xxii. p.. 89 (two figs, by Jacob) ;

Schmidt) ; Ibid., vol. xxxix. No. 929, Student, vol. ii. p. 240 (Browning).

Jan. 8, 1855 (Secchi) ; Mem. R.A.S., vol. Month. Not., vol. xliv. p. 407 (Pratt) ;

iv. p. 383 (Kater) ; Ibid., vol. xxi. p. 151 Ibid., vol. xlv. p. 401 (Green); Ast. Nach.,

(8 figs, by Lassell); Month. Not., vol. xi. vol. cxii. No. 2682 (Lamp) ; Month.

p. 23 (Dawes and Lassell) ; Ibid., vol. Not., vol. xlvii. p. 514 (Elger); L'Astro-

xiii. p. 1 6 (Dawes) ; Ibid., vol. xiv. p. 17 nomie, vol. vi. p. 208 (Stuyvaert).

Fig. 98.

Plate XII.

CHAP. XII.] Saturn. 203

mean distance of 886,065,000 miles, which an orbital eccentricity
of 0-056 may increase to 931,033,000 or diminish to 841,097,000
miles. Its apparent diameter varies between i5'i" in conjunc-
tion, and 20-7" in opposition, and its real (equatorial) diameter
may be taken at 75,036 miles. Its polar compression is larger
than that of any other planet, Jupiter not excepted: but it is
usually less noticeable than that of Jupiter because the ring
distracts the eye. Sir W. Herschel's value of the compression
is TirW; Bessel's T^T^ ; the Rev. R. Main's T.^b; and Hind's ^ .\^.

Saturn has no perceptible phases. The maximum defalcation of
light under extreme circumstances is so small that the maximum
breadth of the shaded area can hardly be ^ of a second of arc
— a quantity inappreciable.

The figure of Saturn is now quite understood to be that of an
oblate spheroid, but at one time considerable doubt existed about
the matter in consequence of Sir W. Herschel having advanced
the opinion, from observations made in April 1805, that the
planet was compressed at the equator as well as at the poles ;
or, as it is generally phrased, that it resembles a parallelogram
with the corners rounded off. so as to leave both the equatorial
and the polar regions flatter than they would be in a regular
spheroidal figure. This opinion, never received with much
favour (though not entirely unconfirmed by later observers), is
now almost universally repudiated, chiefly owing to the micro-
metrical measurements performed by Bessel in 1 833 and by Main
in 1848. Some optical illusion was probably at the foundation
of it, though it is right to say that the notion is believed in to
this day by some persons, and ascribed to an actual upheaval of
the planet's surface recurring from time to time and due to
quasi-volcanic causes. It must also be added, that (as in the
case of Jupiter) we only see the outline of Saturn's atmosphere and
not that of the solid (or fluid) body of the planet itself.

Belts exist on Saturn resembling those of Jupiter, but they

b See Month. Not., vol. xiii. p. 79, Jan. memoir by the same observer appears in
1853, for others, and same vol., p. 152, for Mem. M.A.S., vol. xviii.p. 27, 1850.
a note by the Rev. R. Main: an important

204

The Sun and Planets.

[BOOK I.

are very much fainter. They are probably of the same physical
character.

In November and December 1883 several observers noticed a
singular configuration of dark and bright belts on Saturn, the
character of which will be best understood by a careful perusal of
the following description by Professor E. S. Holden. Under date
Dec. 2 he writes : — " The S. pole is mottled, especially so near of the
shadows. The bright equatorial belt is bounded on the S. by a
narrow dark streak some 2" wide ; it is the darkest thing on the ball.

Fig. 99.

SATURN, Dec. 2, 1883. (Holden.}

S. of this is an equally narrow bright streak, then S. of this is the
nearly uniform S. hemisphere. N. of the equatorial bright belt
is a narrow dusky belt (i"*5 ?), then a narrow bright belt (i"\5 '?),
and then a dark band, which is the dusky ring itself (ring C).
The principal division is seen all around ; the division in ring A
is seen at both ends. The shadow of the ball on the ring is as
drawn. It is wider and of a different shape on the preceding side,
as drawn. I did not specially look for (nor see) the shadow of
the ball on the ring C " [this being a test of good images].

Fig. 114 (p. 224) gives a view of an isolated narrow belt,
stretching right across the ball, seen by Ranyard on Nov. 4.
1883, and subsequently.

CHAP. XII.] Saturn. 205

It was Lassell's opinion that, taking the planet as a whole, it
may be said that the South pole is generally darker than the
North pole and more blue in tinge. The dark belts on the planet
are often thought to exhibit a greenish hue. The planet's or-
dinary colour is yellowish white, the belts inclining to grayish
white. Browning finds that large apertures bring out the
existence of considerable diversities of colour on Saturn. Any
first-class telescope of 4 inches aperture will exhibit the marked
distinction between the yellow tint of Saturn's globe and the
silvery or bluish white hue of ring B.

The belts of Saturn differ from those of Jupiter in the respect
that they exhibit at times a sensible curvature, whilst those of
Jupiter are rectilinear. Hence we draw the conclusion that if
the belts of Saturn are parallel to the planet's equator (as
probably is the case), then the plane of this equator must make a
rather considerable angle with the ecliptic. A quintuple belt
furnished Sir W. Herschel with the means of determining the
period of the planet's axial rotation, which he fixed at
loh jgm O-448, from observations extending over 100 rotations
between Dec. 4, 1793 and Jan. 16, 1794°. He is said to have
subsequently made the period to be ioh 29™ i6-8s. Schroter's
results exceed this, but contradict one another considerably.
His highest result was as much as 1 2h.

Spots on Saturn are very rare. The instances on record
hardly number a dozen. On Dec. 7, 1876 A. Hall at Washington
observed a bright spot 2" or 3" in diameter, round, and well de-
fined, and brilliantly white. It lasted nearly a month, and was
seen by several observers'1. It yielded for the period of Saturn's
rotation ioh 14™ 23-8".

Sir W. Herschel considered that he had obtained decided
indications of the existence of an atmosphere on Saturn: the
satellites when undergoing occultation never disappeared instan-
taneously, but seemed to hang on the planet's limb, in one case
for as long as 2Om. Such a retardation would imply a horizontal

c Phil. Trans., vol. Ixxxiv. p. 62. 1 794.

11 Ast. Nach., vol. xc. No. 2146, Aug. 16, 1^77.

206 The Sun and Planets. [BOOK I.

refraction of 2", but no confirmation of this has been obtained by
any subsequent observer. The same observer found other proofs
of an atmosphere : an examination of the polar regions on various
occasions shewed that according as they were turned towards or
from the Sun a difference of hue was perceptible, which might
reasonably be supposed to be due to snow in those regions
melting under the Sun's rays, and accumulating in the absence
of those rays, as has been explained when speaking of Mars.

When Saturn was first telescopically examined by Galileo, he
noticed that it presented a very oval outline, which in his
opinion gave the notion of a large planet having on each side of
it one smaller one. He added, that with telescopes of superior
power, the planet did not appear triple, but exhibited an oblong
form, somewhat like the shape of an olive6.

Continuing his observations, the illustrious astronomer was not
long in noticing that the two (supposed) bodies gradually de-
creased in size, though still in the same position as regards their
primary f, until they finally disappeared altogether8. Galileo's
amazement at this was unbounded, and his third letter to Welser,
dated Dec. 4, 1613, in which he expresses his feelings on the
subject, is still extant. He remarks : —

" What is to be said concerning so strange a metamorphosis ?
Are the two lesser stars consumed after the manner of the solar
spots ? Have they vanished or suddenly fled ? Has Saturn, per-
haps, devoured his own children? Or were the appearances
indeed illusion or fraud, with which the glasses have so long
deceived me, as well as many others to whom I have shewn
them ? Now, perhaps, is the time come to revive the well-nigh
withered hopes of those who, guided by more profound contem-
plations, have discovered the fallacy of the new observations,
and demonstrated the utter impossibility of their existence. I
do not know what to say in a case so surprising, so unlocked for,
and so novel. The shortness of the time, the unexpected nature

0 Of ere di Galileo, vol. ii. p. 41. Padua 1612, when of course Saturn would in

ed., 1744. such a telescope as Galileo's appear to

f Ibid. be destitute of all appendages what-

* A nodal passage took place in Dec. ever.

CHAP. XII.] Saturn. 207

of the event, the weakness of my understanding, and the fear of
being mistaken, have greatly confounded meh." Galileo was so
disgusted that he entirely abandoned observations of Saturn.

The original discovery was announced to Kepler in the
following logogriph1: —

smaismrmilmepoetalevmibvnenvgttaviras ;

which, being transposed, becomes —

altissimvm planetam tergeminvm observavi ;
" I have observed the most distant planet to be tri-form.''

As time wore on, more correct ideas were obtained of the phe-
nomenon, which gradually came to be looked upon as due to the
existence of two ansse, or handles, to the planet, though the cause
of their disappearance from time to time was yet unexplained.
Astronomers are indebted to Mr. C. L. Prince for having called
attention to an important stage in the development of true ideas
as to the causes of the changes seemingly undergone by Saturn.
In 1876 he unearthed and had engraved some curious old
drawings made by Gassendi between 1633 and 1656, and pub-
lished in Gassendi's Works k. But it was not till after the lapse
of nearly 50 years from the time of Galileo's discovery that
the true cause of the appearance seen by him and others became
known. C. Huygens was the discoverer, and he intimated his
discovery in the following logogriph1 :-—

aaaaaaa ccccc d eeeee g h

iiiiiii 1111 mm nnnnnnnnn

oooo pp q rr s ttttt uuuuu ;

which letters, when placed in their proper order, give —

annulo cingitur, tenui, piano, nusquam cohaerente, ad eclipticam inclinato ;

" The planet is surrounded by a slender flat ring inclined to the ecliptic, but which
nowhere touches the body of the planet™."

h Opere di Galileo, vol. ii. p. 152. m T.Maurice (Indian Antiquities, vol.

Padua ed., 1744. vii. p. 605 ; see also vol. ii. p. 302) gives

' Opere di Galileo, vol. ii. p. 40. Padua an engraving of Sani, the Saturn of the

ed., 1744. Hindus, from an image in an ancient

k Vol. iii. Lyons, 1658. See Month. pagoda. A circle is formed around him

Not. E.A.S., vol. xxxvi. p. 108, Jan. 1876. by the intertwining of two serpents;

1 De Batumi Luna Olservatio Nova. whence the writer infers that, by some

Hagse, 1656. Followed in 1659 '3V ^e- means or other, the existence of Saturn's

tailed particulars in the Sy sterna Satur- ring may have been known in remote

nium. ages. The same thing is observable in

208

Tlic Sim and Planets.

[BOOK I.

It must not be supposed that this discovery was the result of
a chance inspiration. On the contrary, Huygens seems to have
spent several years in scrutinising Saturn before he finally
decided that the theory of a ring round the planet was the only
one which would reconcile the various observed facts.

With the view of commending his hypothesis to the attention
of astronomers, Huygens ventured to predict that in the month
of July or August 1671 the planet would again appear round;
and in this he was nearly correct, for Cassini, watching the
disappearance of the ring, found the planet presenting this aspect
in May 1671, or within 2 months of the time foretold by
Huygens.

Fig. 100.

Fig. 102.

(Ball, 1665.) (HeveUus, 1675.) (Cattini, 1676.)

THREE I7TH CENTURY SKETCHES OF SATURN AND ITS RING.

As advances have been made in the manufacture of telescopes,
so our knowledge of the Saturnian system has been increased.
In 1675, within a very few years of Huygens's discovery, Cassini
discovered that what Huygens saw as one ring was in reality
a combination of two, lying concentrically, one within the other".
Sir W. Herschel was for a long time very unwilling to allow
that this division was actually such in fact ; and he did not
become convinced until he had executed a very protracted series
of observations extending over several years. He coupled his
acceptance of the division with a strong assertion that it was the
only one that existed.

Assyrian sculptures ; but it must in can-
dour be added that this ring-surrounded
Deity possessed a signification (impossible
to be alluded to here) in the ancient
Phallic worship.

n For some particulars of a controversy
which raged in 1882 respecting the share
of credit for this discovery supposed to be

due to others besides Cassini see Observa-
tory, vol. v., 1882, passim. It arose out of
misconceptions as to the meaning of a
passage which appears in Phil. Trans.,
vol. i. p. 152. Cassini's sketch will be
found in Lowthorp's abridgement of Phil.
Tran*., vol. i. p. 288.

Figs. 103-5.

1853: Nov. 2. (Dawes.)

1848. (W. C. Bond.-)

1856: Jan. 8. (Jacob.)

SATURN.

CHAP. XII.] Saturn. 211

But we have now certain knowledge of the existence of more
than 2 rings, and the system must be described as a multiple one.

It is stated by Lalande ° that Short, the celebrated optician,
perceived several concentric streaks on the outer ring. It is not
known that Short left any record of his own relating to this.

Between June 19 and 26, 1780, Sir W. Herschelp perceived a
slight dark streak close to the interior edge of the western ansa.
It had disappeared on June 29, and no corresponding appearance
at all was seen on the other ansa.

In Dec. 1823 ^' Quetelet, at Paris, with a Cauchoix achro-
matic of 10 inches aperture, thought he saw a division in the
exterior ring q.

On Dec. 17, 1825, Capt. Kater, with a 6-inch Newtonian re-
flector, perceived in the exterior ring numerous black streaks
very close to each other1. On Jan. 16, 1826, with another
telescope, the same observer saw similar markings, but as on
Jan. 22, 1828, none whatever could be perceived, he concluded
that they had no permanent existence.

On April 25, 1837, Encke8, at Berlin, assured himself of the
existence of a division in the exterior ring ; on May 28 following
he was able to procure measurements which shewed that the old
ring was unequally divided, the wider portion lying outermost.

On May 29, 1838, Di Vico, at Rome, perceived not only this
division, but two similar divisions in the interior ring.

On Sept. 7, 1843, Lassell and Dawes * saw a decided division
in the exterior ring at both ends, but placed it near the outermost
edge, thereby failing to agree with Encke's measurements of 1837.

This subdivision of the exterior ring is now generally ac-
cepted u, and De La Rue's beautifully executed engraving (Fig. 98,
Plate XII) conveys a good idea of it.

0 Astronomic, vol. iii. Paragraph 3228. * Month. Not., vol. vi. p. 12.

2nd ed., Paris, 1771. u Jacob on the contrary expressed in

P Phil. Trans., vol. Ixxxii. p. 8. 1792. unequivocal terms his conviction that the

1 Mem. R. A. S., vol. iv. p. 388. 1831. black mark or so-called division in the
r Mem. E. A. S., vol. iv. p. 384. 1831. exterior ring was merely a depression.
8 Mathematische Abhandlungen der He was confident that it reflected the

Konigl. Akad. Wissenschaften Berlin, planet's shadow, shewing an apparent
1838, p. 5. projection, such as every shadow falling

P 2

212 The Sun and Planets. [BOOK I.

The discovery of another curious and interesting feature has
now to be dealt with. In 1838 Galle, in examining Saturn,
noticed a gradual shading off of the interior bright ring towards
the ball. He published a note of this observation, but little or
no attention seems to have been paid to it x. On Nov. u, 1850,
G. P. Bond perceived a luminous appearance between the ring
and the planet : subsequent observations by himself and his
father shewed that this luminous appearance was neither more
nor less than another ring. Neither of these observers could
satisfactorily determine whether this dusky ring (as it soon came
to be called) was actually in contact with the interior bright
ring, but they thought it was noty. Before the arrival of the
American mail conveying intelligence of this new ring, Dawes had
found it. On Nov. 29 he entered in his Journal the following
remark : " After a few seconds of uncommonly sharp vision, I
involuntarily exclaimed, ' Obvious.' There is a shading, like
twilight, at the inner portions of the inner ring2." This acute
observer was not long in ascertaining the annular character of
the " shading," and moreover he found (as did O. Struve also)
that the dusky ring was occasionally divided into 2 or more con-
centric rings. This fact is not indicated in De La Rue's en-
graving, but the transparent nature of the entire ring is well
shewn. On Dec. 3, Lassell, while on a visit to Dawes, saw " some-
thing like a crape veil covering a part of the sky within the inner
ring :" this observation was made in consequence of a hint given
by Dawes as to what he himself had seen a.

on a groove has. {Month. Not., vol. xvi. y Mem. Amer. Acad. of Arts and

p. 126, March 1856; vol. xvii. p. 174, Sciences, vol. v., (N.S.), p. in. 1855.

April 1857.) Hippisley and Watson dis- z Month. Not., vol. xi. p. 23. Dec. 1830.

believed in a division, and adhered to the • A passage in Phil. Trans., vol. xxxii.

opinion that the mark is merely a mark, p. 385, I723> by Hadley, almost leads one

and that its breadth varies. Month. Not., to infer that he had seen the dusky ring,

vol. xiv. p. 163, March 1854; vol. xvi. though without being able to make up his

p. 152, April 1856.) mind as to what it was. Hind, in Month.

x Math.AbhanrJl.Konigl. Akad. Wis- Not., vol. xv. p. 32, Nov. 1854, expresses

senschaften Berlin, 1838, p. 7. See also his belief that a record of Picard's will

Ast. Nach., vol. xxxii. No. 756. May 2, fairly bear the interpretation that on

1851; and Month. Not., vol. xi. p. 184. June 15, 1673, he saw the dusky ring, with

June 1851. the like comprehension as Galle.

Figs. 106-8.

Plate XIV.

1 86 1 : April 7. (De La Eue.)

1 86 1 : Nov. 13. (Jacob.}

1 86 1 : Dec. 4. (Jacob.)

SATURN.

Figs. 109-11.

Plate XV.

1 86 1 : November. (Anon.)

1861: Dec. 26. (Wray.~)

1862: Jan. 5. (Wray.)

SATURTST.

CHAP. XII.] Saturn. 217

The transparency of the dusky ring was not ascertained till
1852 ; Jacob, Dawes, and Lassell share this discovery between
them b.

Figs. 1 10-1 1 on Plate XV. relate to a very interesting observa-
tion made by Wray on Dec. 26, 1861. He saw — "A prolongation
of very faint light stretched on either side from the dark shade on
the ball, overlapping the fine line of light formed by the edge of
the ring, to the extent of about one-third its length, and so as to
give the impression that it was the dusky ring, very much thicker than
the bright rings, and seen edgewise projected on the sky c."

It has been thought that the dusky ring is wider and less faint
than formerly. On March 26, 1863, Carpenter found it to be
" nearly as bright as the illuminated ring," so much so that it
" might easily have been mistaken for a part of itd."

On Oct. 29, 1883, Davidson with a 6*4 inch refractor found an
undoubted difference in the brightness of the dusky ring at the
2 ansse, the preceding ansa being decidedly brighter than the
following one ; different eye-pieces yielded the same result, and
another observer concurred in the opinion e.

Having said this much on the history of these discoveries, some
facts connected with the rings must now be set out. Their true
form is no doubt circular, or nearly so ; but as we always see
them foreshortened, they appear more or less oval when the
Earth is above or below the plane of the rings, but when we are
nearly in the plane they appear as a single straight line, or
something like it. When we are exactly in the plane they dis-
appear altogether, except in very large telescopes. Figs. 112 and
113 will make this sufficiently clear. In the true position
of the rings during Saturn's revolution round the Sun there is
no change : they remain continually parallel to each other.

b Perhaps this sentence requires to be planet of deeper shade than usual,

qualified, for Galle, in his drawing, re- c Month. Not., vol. xxiii. p. 86. Jan.

presents the planet seen through the 1863.

ring; but it must be remarked that he d Month. Not., vol. xxiii. p. 195. April

did not know he was looking at a ring, 1863.

and only intended to draw what was (and e Observatory, vol. vii. p. 85. March

readily might be) taken for a belt on the 1 884.

218

The Sun and Planets.

[BOOK I.

The plane of the rings is inclined 28° 10' to the ecliptic, and
intersected it in 1860 in longitude 167° 43' 10" and 347° 43' 10"
(17!° of Virgo and Pisces) ; the former point being the place of
the ascending node, and the latter that of the descending node.
According to Bessel the longitude of the node of the ring
referred to the ecliptic increases at the rate of 46-46 z" per annum,

Fig. 112.

GENERAL VIEW OF THE PHASES OF SATUBN S KINGS.

Whether viewed from the Earth or from the Sun, the pheno-
mena seen in connexion with the rings of Saturn are much the
same, but the motion of the Earth in its orbit (the inclination of
which differs somewhat from that of Saturn) gives rise to certain
phases in the rings which would not be witnessed by an observer
placed on the Sun. " Thus it usually happens that there are 2,
if not 3 disappearances f, about the time of the planet's arrival at
the nodes. The plane of the ring may not pass through the
Earth and Sun at the same time, but the ring may be invisible

' There can really never be more than two disappearances. ^Procter, Saturn.
p. 90.)

CHAP. XII.]

Saturn.

219

under both conditions, because its edge only will be directed
towards us. It is also invisible when the Earth and Sun are on
opposite sides of its plane — a state of things that may continue
a few weeks : in this case we have the dark surface turned
towards our globe. In very powerful telescopes it has been found
that the disappearance of the ring is complete under the latter

Fig. 113-

1877

1885

1808

1891

PHASES OF SATUBN'S RINGS AT THE DATES SPECIFIED.

condition ; it has, however, been perceived as a faint broken line of
a dusky colour, not only when the Sun is in its plane, but like-
wise when its edge is directed to the Earth. Our remarks must
be considered as applying to observations with telescopes in
common use." The foregoing quotation is from Hind * ; a fuller
account is given by Sir John Herschel h.

Saturn's period being 29-45 8y, the half of this, or 14-729^ will
be the average time elapsing between 2 nodal passages. Such a

Introd. to Ast., p. 107.

Outlines of Ast., p. 343 et seq.

220 The Sun and Planets. [BOOK I.

passage took place in 1877. The Northern surface of the ring
had then been visible for J4'7y.

In June 1885 the planet was in 77.5° of longitude, one of the
two places at which the greatest opening of the rings occurs.
The breadth will diminish till 1891, when the motion of the
planet and of the Earth will again bring the ring edgewise to the
Earth and cause it to disappear, the Sun being South of the plane,
and the Earth crossing to the North.

In 1893 the Sun, passing through the plane of the ring, will
begin to illuminate its Northern surface, and the Earth being
also on that side, the ring will reappear. After a few months
the Earth will go to the South, and the Sun remaining on the
North, a second disappearance will take place. The ring will
remain invisible, in consequence of presenting its unilluminated
side to us, till the Earth once more passing through the plane of
the ring to the North, will bring the Northern side into view—
a state of things which will last till 1907.

It will be seen from De La Rue's drawing of 1856, and
from others taken at the epoch of maximum breadth, that
the ball is at such times entirely encompassed by the ring, and
that thus the outline of the whole system is a perfect ellipse :
this state of things always lasts for several months. The ring of
Saturn is most open when the planet is in either Gemini or
Sagittarius.

By a careful examination of the ring Sir W. Herschel ascer-
tained that it revolves round the ball in ioh 32™ 15"— a period
not greatly in excess of that of the planet's own axial rotation :
the direction is the same in both cases. There are, however, great
difficulties in the way of admitting this rotation '.

In 1 854-5-6, Secchi executed numerous measures of the rings,
but they exhibited considerable discordances. He afterwards
found that whilst those of 2 consecutive days did not harmonise,
those of 3 and 9 days did ; and the idea then occurred to him
that the results might be explained by supposing the ring to

! It is noteworthy that previously to in the text, Laplace calculated that the
Sir W. Herschel finding the result given rings ought to rotate in ioh 33™ 36".

CHAP. XII:] Saturn.

be elliptical, presenting sometimes its longer, sometimes its shorter
diameter. He failed to reconcile Herschel's period of rotation
with his own observations, but found that a period which corre-
sponds with that which a satellite placed on the margin of the ring
would have (namely, I4h 23™ i88) would satisfy themk.

O. Struve introduced a system for conveniently distinguishing
the rings from each other, in writing and speaking, which is now
generally adopted. He called the exterior bright ring A, the
interior bright ring B, and the dusky one C. When reference
is made to the system as a whole it is very usual to say ' ring,'
in the singular number, no one ring in particular being thereby
meant.

The ring is not concentric with the ball. Gallet of Avignon
announced this in ] 664, placing the ball nearer to the East ansa.

In 1827, Schwabe expressed his belief that the ring was
eccentric, but in the opposite direction to that assigned by Gallet.
Harding confirming Schwabe's opinion, W. Struve took the
matter in hand micrometrically, and found that at the mean
distance of Saturn from the Earth, whilst the diameter of the
Eastern vacuity was irzSS", that of the Western was only
u'073", shewing a difference of 0-215" in favour of the former.
This peculiarity has been shewn to be essential to the stability
of the system of the rings : without this feature and without
rotation they would fall upon the planet.

The following angular measurements, reduced to the mean
distance of the planet (and calculated on the solar parallax of
8-80"), are by the same observer : —

English
// Miles.

Outer diameter of exterior ring ... ... ... 40-095 = 172,240

Inner diameter ,, ... ... ... 35-289 = 151,590

Breadth „ ... ... ... 2-403 = 10,320

Outer diameter of interior ring ... ... ... 34-475 = 148,100

Inner diameter ,, ... ... ... 26-668 = 114,560

Breadth „ 3'9°3 = ^,765

Interval between the two ... ... ... 0-408 = 1,750

Distance of ring from ball ... 4-339 = 18,640

Equatorial diameter of ball ... ... ... 17-60 = 75,600

k Month. Not., vol. xvi. p. 52. Jan. 1856.

222

The Sun and Planets.

[BOOK I.

The measures of De La Rue1, Main™, and Jacob11 are appended
for comparison0 : —

De La Rue.

Main.

Jacob.

Outer diameter of exterior ring

39-83

30.75

sn-qq

Inner diameter , ,

35-33

35-82

Breadth ,, ...

2-2?

2-o8

Outer diameter of interior (middle) ring

33-45

34-85

Inner diameter ,, ,,

26-91

27.65

26-27

Breadth ,, ,,

3-27

4-29

Interval between the two

0-94

0-48

Distance of ring from ball

4-62

5-07

4-16

Equatorial diameter of planet

17-66

I7-RO

17-04

There are some particulars relating to the rings which cannot
well be classified. Sir J. Herschel estimated their thickness at not
more than 250 miles ; G. P. Bond cut this down to 40 miles.
Peircep thought that there were good grounds for supposing them
to be fluid rather than solid ; but the opinion which meets with
most favour now is that they are a dense aggregation of small
satellites, densest where brightest, widest apart where most faint.
In fact it may be shewn that if a system of rings of such propor-
tion was constructed of iron it must become semi-fluid under the
forces it would experience. Considered as a system, the rings
are sensibly more luminous than the planet (a fact which Hooke
pointed out as long ago as 1666), and B is brighter than A.
B itself is perceptibly less bright at its inner edge than elsewhere.
At the epoch of the Saturnian equinoxes the ansse do not both
disappear and reappear at the same time, and at these periods
they are sometimes of unequal magnitude.

On Oct. 9, 1714, 6 days before the actual passage of the Earth
through the plane of the ring, and whilst the ansse were de-
creasing, Maraldi noticed that the Eastern one appeared a little

1 Month. Not., vol. xvi. p. 43. Dec. 1855.

m Hid., p. 30.

" Ibid., p. 124 (March 1856).

0 An important series by Bessel will

be found in Ast. Nach., vol. xii. Nos.
274-5. Feb. 18, and March 7, 1835.

P Gould's Astronomical Journal, vol.
ii. p. 17. June 16, 1851.

DURING THE WINTER OF 1883-4. (Ranyard.)

Feb.-March, 1884. (Henry.)

Feb. 1887. (Terby.)

SATURTST.

CHAP. XII.] Saturn. 225

broader than the other for 3 or 4 nights, and yet it vanished
first q. He was induced to suspect that the anste had changed
places by rotation, and that at any rate the surface of the rings
was very irregular, the 2 rings lying moreover in different
planes.

Heinsius, Varela, Messier, and many others have noticed the
ansse to be of different lengths, and that one is frequently visible
without the other. When only one is visible, it is most fre-
quently that on the Western side — a fact for which it is difficult
to account.

Fig. 116 represents Saturn as drawn by Terby of Louvain with
an 8-inch Grubb Refractor. He remarks that the drawing
brings out especially the following features : — Encke's division ;
Henry's bright streak in ring A opposite Cassini's division ;
Struve's division between rings B and C especially on the East ;
the black patches in the dusky ring especially on its West side ;
the indentation of the shadow of the ball on the Cassini division
on the West ; the shadow cast by the ball on the dusky ring ;
and lastly the transparency of the dusky ring which permits the
ball to be seen through itr.

When at its nodes the ring frequently appears broken, shewing
merely luminous elongated beads seemingly detached from one
another. For a long time astronomers were in doubt as to the
cause of these appearances, and it was not till so recently as
1848 that the question was cleared up. In that year the ob-
servers at Harvard College, U. S., instituted a careful inquiry,
and their micrometrical observations shewed that these " beads "
were due to the concurrent effect of light reflected by the edges,
external and internal, of the rings. The Figures [117-18] are
copied from Bond's memoir, but ring C is omitted that matters
may be simplified. What follows I cite from Webb, who
devoted much time to the elucidation of Saturnian facts. " It
must be borne in mind that this design is an intentional exaggera-
tion for clearness' sake, representing the dark surface much

i Mem. Acad. des Sciences, 1715, p. 12.
r Observatory, vol. x. p. 163, April 1887.

226

The Sun and Planets.

[BOOK I.

more expanded than it ever really is, and the thickness of the
rings many (they say perhaps 10) times too great. To this
they add the qualification that the edges should be rounded ;

Fig. 117.

DIAGRAM ILLUSTRATING THE PHENOMENON OF SATURN'S RING " BEADED."

and I should be inclined to suggest another, that A may probably
be much thinner than B, so that its inner edge would add

Fig. 1 1 8.

DIAGRAM ILLUSTRATING THE PHENOMENON OF SATURN'S RING "BEADED."

little to the effect. Comparing, then, Fig. 117 with Fig. 118.
we should have, — i. A narrow dark band upon the planet.

CHAP. XII.] Saturn. 227

slightly curving upwards, and consisting of both the dark side,
of the ring and its shadow (the latter not inserted in Fig. 114).
2. The outer edge of A visible throughout, but with extreme diffi-
culty when alone, as between I and c, and f and ff, and towards
a and h. 3. Two brighter portions from c to d, and from e to /,
where the light of A is reinforced by that reflected by the inner
edge of B. 4. Two bright knots where the same light, strength-
ened by the concurrent reflection from the inner edge of A and
the outer of B (the latter, it may be presumed, many times out-
weighing the former), reaches us through the opening of [Cassini's]
division. This the Americans considered fully satisfactory, the
curvature of the black stripe having been noticed, and estimated
at O'25"; the extremities of the line, and the beads, falling be-
neath its direction, as from the diagram they ought to do, and
the accordance of measures fully bearing out the impression
of Nov. 3, that the ' interruptions in the light of the ring are so
plainly seen, that no one could for a moment hesitate as to their
explanation.' "

O. Stru ve many years ago propounded a theory B that the rings
were expanding inwards (so that ultimately they would come in
contact with the ball) ; and also that between the time of J. D.
Cassini and Sir W. Herschel the breadth of the inner ring had
increased in a more rapid ratio than that of the outer ring, while
the exterior diameter of A was unchanged. Struve drew this
conclusion from the early observations of Huygens and others :
but it is doubtful if these are to be relied upon ; and Main
considered that micrometric measures obtained by himself showed
the theory to be untenable. Kaiser also considered it to be
destitute of foundation1. On the other hand, both Hindu and
Secchix favour the idea of change.

The rings cast a shadow ; and from observing this shadow

8 Mem. de VAcad. des Sciences de St. Jan. 1856, for an abstract of Kaiser's

Pttersbourg, 6th ser., Math, et Phys., memoir.

vol. v. 1852. An abstract of it appears n Month. Not., vol. xv. p. 31. Nov.

in Month. Not., vol. xiii. p. 22. Nov. 1854.

1852. * Month. Not., vol. xvi. p. 50. Jan.

' See Month. Not., vol. xvi. p. 66, 1856.

Q 2

228 The Sun and Planets. [BOOK I.

some persons have been led to think that the surfaces of the rings
are con vex y, and that they do not lie in precisely the same plane.
Sir J. Herschel doubted the former being a legitimate conclusion
from observation, but admitted its theoretical probability2. Lassell
considered that C often changes colour, each end being alter-
nately bluish-gray and brownish a. This may indicate rotation.
Hippisley thought that there was evidence that the ring A lies
in a different plane from the others, and that B is thicker in the
middle than at either of the edges b. Sir W. Herschel surmised
that the ring is not flat, but that the inner edge was hemi-
spherical or hyperbolical0. The outer edge of B is commonly
the brightest portion of the system, but Schwabe and Webb
believed it to be variable. The inner edge of the same ring
is usually much the dullest, but occasionally it brightens up.
G. P. Bond in 1 856 regarded the dark shading visible at the inner
edge of B as a sharply-defined dark area, elliptical in form and
concentric with the rings, but of greater eccentricity. Prince
" is convinced " that C is becoming more and more illuminated d.
Lassell and De La Rue have suspected the existence of mountains
on the rings, in consequence of elevations appearing in the shadow
projected on the ball6. [Fig. 106, PL XIV.] Jacob saw the effect,
but doubted the assigned cause, preferring to think that it is an
illusion arising from inequalities in the depth or tone of the
shadow f. In 1848, when the unilluminated side was turned to-
wards us, Dawes saw traces of the shadow, of a coppery hue, and
he regarded this as an effect due to a rather dense atmosphere g :
but more than this, the atmosphere causing a refraction of the
solar light on each side of the ring would reduce the shadow of
the ring to a penumbra, and thus account for it being impercep-
tible when the Sun was in the plane of the ring. Sir W. Herschel

y De La Rue's drawing forcibly con- d Month. Not., vol. xx. p. 212. March

veys the impression of this as regards B. 1860.

* Outlines of Ast., p. 343. * Ibid., vol. xxi. pp. 177 and 236.

n Month. Not., vol. xiii. p. 147. March April and June 1861.

1853. ' Ibid., vol. xxi. p. 237. June 1861.

b Month. Not., vol. xiv. p. 163. March & Month. Not., vol. x. p. 46, De-

1854. cember 1849, and vol. xxii. p. 298, June
0 Phil. Trans., vol. xcvi. p. 463. 1806. 1862.

CHAP. XIL] Saturn. 229

had previously believed that an atmosphere surrounding the ring
alone would explain a distortion which he noticed in 1807, at
the South pole, in optical proximity to the ring ; the other pole
being at the same time clear of the ring and free from distortion11.
Between 1872 and 1876, using the 26-inch refractor of the
Washington observatory and 2 smaller instruments, Trouvelot
spent much time in carefulty studying the planet Saturn. His
observations were numerous, and the conclusions he drew,
important. The following are some of them in a condensed
form1: — The inner margin of A2, limiting the outer border of
the principal division, shewed on the ansse some singular dark
angular forms attributable to an irregular and jagged conform-
ation of the inner border of A2, either permanent or temporary;
the surface of A15 A2 and B frequently exhibited a mottled
or cloudy appearance on the ansse ; the thickness of the system
of rings increases from the inner margin of C to the outer margin
of B, a fact which is shown by the form of the planet's shadow
thrown upon the rings ; the cloud -forms seen near the outer
edge of B attain different heights and change their relative
position either by the rotation of the rings on an axis, or by
some local cause — a fact indicated by the rapid changes in the
indentation of the shadow of the planet ; the inner portion of C
disappears in the light of the planet at that part which is pro-
jected upon its disc ; contrary to the observations hitherto made,
C is not transparent throughout ; C grows more dense as it
recedes from the planet, so that at about the middle of its width
the limb of the planet entirely ceases to be visible through it;
the matter composing C is agglomerated here and there into
small masses which almost wholly prevent the light of the planet
from reaching the observer.

h Phil. Trans, vol. xcviii. p. 162. of the outer king, and calls C the ring

1808. which all other astronomers, following

' American Journal of Science and O. Struve, always indicate by the letter

Arts, 3rd Ser., vol. xii. p. 447. June B. I have altered Trouvelot's letters to

1876. Trouvelot has adopted a special accord with the recognised nomenclature,

nomenclatureofhisownwhichiscalculated indicating the sub-divisions of A by

to cause great confusion. He designates calling them A, and A2 respectively,
by A and B the outer and inner portions

230 The Sun and Planets. [BOOK I.

In February and March 18 84 the brothers Henry, using at the
Paris Observatory a refractor of 15 inches aperture, armed with
a power of 1000, remarked around the inner edge of A a narrow
bright ring bounded by a black line. This new ring, not (it
would seem) previously noted, was about 1*5" wide; in other
words, was about as wide as Cassini's well-known division.
But the fact which especially struck these observers was the
non-visibility of Encke's great division in A. That division,
so familiar to all who have observed and drawn Saturn during
the last 50 years, had in the judgment of MM. Henry completely
disappeared. They stated that nothwithstanding very favourable
atmospheric conditions it was impossible to detect on A any
markings but the narrow bright circle mentioned above k. The
disappearance of Encke's division seems to have been lately
remarked in America.

The following observations of Saturn by Keeler with the
great 36-inch telescope of the Lick observatory present some
very interesting and novel points : —

*' The object of greatest interest to me was the outer ring. It is usually drawn
with a division at about one-third of its width from the outer edge, sometimes fine
and sharp and sometimes broad and indefinite. Many drawings which I have
examined place this line or shade near the centre of the ring. In a series of drawings
which I made with the 1 2-inch equatorial of this observatory, from a careful study of
Saturn during the finest nights of the past summer [1887], the outer ring is repre-
sented with a faint broad shading in the centre, diminishing gradually toward the
edges, which are therefore relatively bright.

" The 36-inch equatorial shewed, at a little less than one-fifth of the width of the
ring from its outer edge, a fine but distinct dark line, a mere spider's thread, which
could be traced along the ring nearly to a point opposite the limb of the planet.
This line marked the beginning of a dark shade which extended inwards, diminishing
in intensity nearly to the great black division. At its inner edge the ring was of
nearly the same brightness as outside the fine division. No other markings were visible.

"It is easy to see how, with insufficient optical power, this system of shading
could present the appearance of an indistinct line at about one-third the width of the
ring from its outer edge. The broad band alone would make it appear near the
centre of the ring, and the effect of the line, itself invisible, would be to displace the
greatest apparent depth of shade in the direction of the outer edge. Two nights
after the observations just described I re-examined Saturn very carefully with the
12-inch equatorial, but could not perceive the narrow line, although I was then aware
of its existence, and the definition was excellent '."

k IS Astronomic, vol. iii. p. 230. June 1884.
1 Sid. Mess., vol. iii. p. 80. Feb. 1888.

CHAP. XII.] Saturn. 231

In general the brightness of the ball and of the rings is toler-
ably uniform, but there are exceptions to this rale. In April
1862 Lassell noted the rings to be very dull compared with the
ball, but this might have been due to the small elevation of the
Sun above the plane of the ring. Probably any peculiarities of
this nature which may be noticed from time to time are optical
effects, and do not depend on actual change. Trouvelot however
found the ball less luminous at its circumference than at its
centre, a fact which seems indicative of the existence of an
atmosphere.

Bessel entered upon some investigations to determine the mass
of the rings, by ascertaining their perturbing effect on the orbit
of the 6th satellite, Titan. He estimated it at y^ of the mass
of the planet™. The thickness of the rings being too minute
for measurement, no precise determination of their density is
attainable ; if, however, we assume it as approximately equal to
that of the planet, as is probably the case, it will follow that the
thickness is about 138 miles — a quantity which is very nearly
the mean of the 2 estimations of Sir J. Herschel and Bond.
Supposing this to be correct, at the mean distance of the planet
the rings would only subtend an angle of about 0-03"; it may
therefore be readily inferred that the ring will at stated times
become wholly invisible even in the most powerful telescopes.

Saturn is attended by 8 satellites, 7 of which move in orbits
whose planes coincide nearly with that of the planet's equator,
and therefore with the plane of the rings also : the orbit of the
remaining and most distant satellite is inclined about 12° 14'
(Lalande) to the aforesaid plane. One consequence of this coin-
cidence in the planes of the orbits of the first 7 satellites is that
they are always visible to the inhabitants of both hemispheres
when not under eclipse in their primary's shadow.

In dealing with the satellites of Saturn, I continue to follow
my usual plan of tabulating as much information as possible,
but when we have proceeded beyond Jupiter, data concerning

m Conn, des Temps, 1838, p. 29.

232 The Sun and Planets. [BOOK I.

satellites become both scarce and contradictory, and it is fre-
quently necessary to give alternative statements.

The figures in the column of "Diameter" are, with the ex-
ception of Titan's, extremely doubtful, and this impairs the value
of Proctor's calculations given at the foot of the Table opposite.

Mimas. Beer and Madler's reduction of Sir W. Herschel's ob-
servations in 1 789 gives for the epoch of Sept. J4d i3h 26m Slough
M.T., the Saturnicentric A. at 264° 16' $6", the longitude of the
peri-saturnium at 104-42°, and the eccentricity at 0-068.

Fig. 119.

GENERAL VIEW OF SATURN AND ITS SATELLITES.

Encetadits. Beer and Madler, also from Sir W. Herschel's ob-
servations, gave for the epoch of 1789, Sept. I4d nh 53™, the A.
at 67° 56' 26" : they considered the orbit to be circular in the plane
of the ring. Hind says that Enceladus was seen by Sir W.
Herschel on Aug. 19, 1787.

Tetkys. Lament, from his own observations in 1 836, found for
the epoch of April 23* 8h 27™ Greenwich M.T., the A to be 158° 31',
the longitude of the peri-saturniuin 357° 37', the & 184° 36',
the eccentricity 0-0051, and the inclination of the orbit to the

CHAP. XII.]

Saturn.

233

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234 The Sun and Planets. [BOOK I.

plane of the ring 1° 33'. Sir John Herschel, about the same time,
found the A to be 313° 43', the longitude of the peri-saturnium to
be 53° 40', the eccentricity 0-04217, and the orbit to be precisely
in the plane of the ring. The serious differences in these two
results are to be ascribed to errors in the observations arising
from the difficulty attending them, but such differences naturally
make us distrust the entire batch of figures.

Dione. Sir John Herschel in 1836 found the A to be 327° 40',
the longitude of the peri-saturnium 42° 30', the eccentricity 0*0206,
and the orbit to be precisely in the plane of the ring.

Rhea. Sir John Herschel in 1835-7 found the A to be 353° 44',
the longitude of the peri-saturnium 95°, and the eccentricity
0-02269. The inclination is very small.

Ti(ann, as the satellite most easily seen, has naturally received
most attention. Bessel's determination of its orbit is reputed to
be the most complete. For the epoch of 1 830-0 he gave the A at
137° 21', the longitude of the peri-saturnium at 256° 38", and the
eccentricity 0-029314. The line of apsides has a direct motion on
the ecliptic of 30' 28" annually, completing a revolution in 7 1 8
years, the nodes completing a revolution in 3600 years.

Hyperion has been so recently discovered that its orbit has not
been very fully investigated. From Washington observations
made in 1875 Hall found the A to be 120° 12', the longitude of the
peri-saturnium 173°, the eccentricity 0-118, and the inclination
of the orbit 6° 12'. Lassell's observations made at Malta in 1852
and 1853 agree with these conclusions in part, but Hall remarks
that neither Lassell's observations nor those at Washington " fix
the position of the satellite in its orbit with much certainty, since

n When Huygens discovered this sa- says : " 'Tis highly probable that there

tellite in 1655, he was imprudent enough may be more than 5 moons revolving

to predict that there were no others, round this remote planet [the number of

because Titan being the 6th secondary satellites which Saturn was then known

planet, and there being only 6 primary to possess] ; but their distance is so great

planets known, Nature's (supposed) laws as that they have hitherto escaped our

of symmetry were satisfied. The danger eyes, and perhaps may continue to do so

of prediction in matters of this kind is for ever ; for I do not think that our

well illustrated in the case of Mr. John telescopes will be much further im-

Harris, F.R.S. That learned gentleman proved !! "
published a book in 1729, in which he

Fig 1 20.

Plate XVII.

CHAP. XII.]

Saturn.

237

they were made when the plane of the orbit was nearly edgewise
to the observer." He adds : — " If we examine the elements we
shall see that Hyperion moves nearly in the plane of the orbit of
Titan, and considering the values of the eccentricities it will be
seen that these satellites can approach very near each other0."
Hyperion was seen by Bond on Sept. 16, 1847, and by Lassell on
Sept. 1 8, but it was not till the date given in the table that its
character was determined.

lapetus. Lalande for the epoch of 1790 gave the A. at 269° 37',
and the S3 at 150° 27', reckoned on the orbit.

The following elements are by Captain Jacob p: —

1857-
Jan. 0.
X

To Eclip.

€

Semi-axis
maj.
a

Daily

Sat' centric
Mot.
/*

Mimas

o /
2IO +

O 1

o /
1

0 1

o
^Sl-04.7

Enceladus

301 55

262.732

Tethys

281 42

109 7

167 37

28 10

0.01086

42-60

190-697

Dione

"5 3°

M5 4

167 37

28 10

0.003IO

54-85

I31-534

Rhea

288 43

185 o

167 19

28 8

O-OOO8O

76-I3

79-690

Titan

299 42

257 6

167 58

27 36

0-027937

I 76-90

22-577

Hyperion

lapetus . . .

78 9

349 20

143 i

18 37

0.028443

514-96

4-538

A. Hall considers that the orbits of the 5 inner satellites are
sensibly circular and that they move in the plane of the ring or
nearly so, but it will be readily understood that the small
apparent size of most of these satellites, and the consequently
limited number of telescopes and observers which can be brought
to bear on them, materially retards the attainment of any more
perfect acquaintance with their motions, though it is reasonable
to hope that the multiplication of large instruments and experi-
enced observers now taking place will ere long lead to a develop-
ment of our knowledge of the orbits of these satellites.

0 Ast. NacTi., vol. xcv. No. 2263. June
17, 1879.

p Month. Not., vol. xviii. p. i.

1857-

Nov.

238 The Sun and Planets. [BOOK I.

Sir J. Herschel pointed out the curious circumstance that the
period of Mimas is \ that of Tethys, and the period of Enceladus
\ that of Dione q. Monck puts these facts in the shape that the
ratio of these 4 periods are 2, 3, 4 and 6, adding that the period
of lapetus is very nearly 5 times that of Titan. D' Arrest further
called attention to the commensurability within yV1, or 2fh, of
274 revolutions of Mimas, 170 of Enceladus, and 85 of Dione*.

Kirkwood has discovered a still more complicated relationship,
which may be thus enunciated : To 5 times the daily angular
motion in its orbit of Mimas add the daily motion of Tethys,
and 4 times the daily motion of Dione, and the sum total will be
equal to 10 times the daily motion of Enceladus.

The disappearance of the ring, in 1862, was taken advantage
of by various observers for watching the rare phenomenon of a
transit of the shadow of Titan across the planet. The satellite
itself was not seen on any occasion, but Dawes and others ob-
tained several good views of the shadow8. Again in 1877 the
shadow of Titan was seen by Common, and others. The only
observation of this kind prior to 1862 appears to have been
made by Sir W. Herschel on Nov. 2, 1789. Dawes on May 25,
1 862, saw an eclipse of this satellite in the shadow of Saturn —
the only instance on record.

It must not be supposed that Titan is the only satellite of
which an eclipse, transit, or occultation is possible, for all the
satellites are occasionally subject to these effects. This is
especially true of the two innermost ones, but the small apparent
size of all except Titan hinders observation of them.

Celestial phenomena on Saturn must possess extreme grandeur
and magnificence, the rings forming a remarkable series of arches
stretched across the Saturnian heavens. The nearest satellite,
Mimas, traverses its orbit at the rate of 16' of arc in a minute of
time, so that, as viewed from Saturn, it moves in 2 minutes over
a space equal to the apparent diameter of the Moon. Considering

"> Month. Not., vol. vii.p. 24. Dec.i845- • Month. Not., vol. xxii. pp. 264, 297,

r A»t. Nach.,l\i\. No. 1364. June 14. &c. May and June 1862.
1862.

CHAP. XII.] Saturn. 239

the remoteness of Saturn from the Sun its satellites play a
somewhat important part in the Saturnian sky as reflectors of
sun-light. Nevertheless the space occupied by all of them, taken
together, is (as stated on a previous page) only about 6 times
that covered by the Moon.

Lockyer thus summarises the phases of Saturn's ring as seen by
an observer placed on the planet itself*: — "As the plane of the
ring lies in the plane of the planet's equator, an observer at the
equator will only see its thickness, and the ring therefore will put
on the appearance of a band of light passing through the East and
West points and the zenith. As the observer, however, increases
his latitude either North or South, the surface of the ring-system
will begin to be seen, and it will gradually widen, as in fact the
observer will be able to look down upon it ; but as it increases
in width it will also increase its distance from the zenith, until
in lat. 63° it is lost below the horizon, and between this latitude
and the poles it is altogether invisible. Now the plane of the
rings always remains parallel to itself, and twice in Saturn's
year — that is, in two opposite points of the planet's orbit — it
passes through the Sun. It follows, therefore, that during one-
half of the revolution of the planet one surface of the rings is lit
up, and during the remaining period the other surface. At night,
therefore, in one case, the ring-system will be seen as an illumin-
ated arch, with the shadow of the planet passing over it, like the
hour-hand over a dial ; and in the other, if it be not lit up by
the light reflected from the planet, its position will only be
indicated by the entire absence of stars.

" But if the rings eclipse the stars at night, they can also eclipse
the Sun by day. In latitude 40° we have morning and evening
eclipses for more than a year, gradually extending until the Sun
is eclipsed during the whole day — that is, when its apparent
path lies entirely in the region covered by the ring ; and these
total eclipses continue for nearly 7 years: eclipses of one
kind or another taking place for 8 years 292 days. This will
give us an idea how largely the apparent phenomena of the
4 Elementary Lessons in Astronomy, p. 117.

240

The Sun and Planets.

[BOOK I.

heavens, and the actual conditions as to climates and seasons,
are influenced by the presence of the ring."

The only physical fact which has been discovered in relation
to the satellites of Saturn concerns lapetus. Cassini lost that
satellite soon after its discovery, but a larger telescope enabled
him to find it again, and moreover to ascertain that it was
subject to considerable variations of brilliancy. Sir W. Herschel,
with a view of establishing this fact beyond doubt, paid much

Fig. 121.

THE APPARENT OBBITS OF THE SEVEN INNER SATELLITES OF SATUBN TO FACILITATE
THEIR IDENTIFICATION (l888).

*»* The date of Titan '* Eastern Elongation being known (= o), it will on subsequent days be
found in the positions corresponding to the daily intervals marked on the diagram.

attention to lapetus. He was able to confirm Cassini's opinion,
and decided that it actually did experience a considerable loss of
light when traversing the Eastern half of its orbit. He found
that 7° past Opposition was the place of minimum light. The
conclusions deducible from this are (as Cassini himself pointed
out), that the satellite rotates once on its axis in the same time
that it performs one revolution round its primary ; and that there
are portions of its surface which are almost entirely incapable of
reflecting the rays of the Sun.

The mass of Saturn has been given at 7^VT by Newton ; at
*sW by Laplace ; at ^^r? by Bouvard ; and at -5-5^-5 by Bessel.
Jacob thought from his own observations that the mass of the
whole Saturnian system did not differ much from ^TVs- The
most recent value is A. Hall's,

CHAP. XII.] Saturn. 241

" The most ancient observation of Saturn which has descended
to us was made by the Chaldaeans, probably at Babylon, in the
year 519 of Nabonassar's period, on the i4th of the month Tybi,
in the evening ; when the planet was observed to be 2 digits
below the star in the Southern wing of Virgo, known to us as
y Virginis. The date given by Ptolemy, who reports this observa-
tion in his Almagest [Kb. xi.], answers to B.C. 228, March iu."

An occultation of this planet by the Moon is recorded to have
been observed by one Thius, at Athens, on Feb. 2 1 , 503 A.D.

Cassini observed in 1692 the occultation of a star by Saturn's
satellite Titan. No other instance of this kind is on record.

From Saturn the Sun appears only about 3' in diameter, and
the greatest elongations of the planets are : Mercury, 2° 19';
Venus, 4° 21'; Earth, 6° i' ; Mars, 9° 11'; Jupiter, 33° 3' — so
that a Saturnian, assuming his visual powers to resemble ours,
can only see Jupiter, Uranus, and Neptune with the naked eye,
and Mars perhaps with some optical aid. Saturn, on account of
its slow dreary pace, was chosen by the alchemists as the symbol
for lead.

In computing the places of Saturn, the Tables of A. Bouvard,
published in 1821, were long used, but new Tables by Le Verrier
have superseded them. Tables of the satellites have still to be
formed, and are a great desideratum.

u Hind, Sol. Syst., p. 117.

242 The Sun and Planets. [BOOK I.

CHAPTEK XIII.

URANUS. $

Circumstances connected with its discovery by Sir W. Herschel. — Names proposed
for it. — Early observations. — Period, &c. — Physical appearance. — Belts visible
in large telescopes. — Position of its axis. — Attended by 4 Satellites. — Table of
them. — Miscellaneous information concerning them. — Mass of Uranus. — Tables
of Uranus.

ON March 13, 1781, whilst engaged in examining some small
stars in the vicinity of H Geminorum, Sir W. Herschel
noticed one which specially attracted his attention : and desirous
of knowing more about it, he applied to his telescope higher
magnifying powers, which (in contrast to their effect on fixed
stars) he found increased the apparent diameter of the object
under view considerably; this circumstance clearly proving its
non-stellar character. Careful observations of position shewing
it to be in motion at the rate of ?.\" per hour, Herschel con-
jectured it to be a comet, and made an announcement to that
effect to the Royal Society on April 26*. Four days after its
first discovery it was observed by Maskelyne, then Astronomer
Royal, who seems to have suspected at the time its planetary
character, and in the course of the following 2 or 3 months it
received the attention of all the leading observers of Europe. So
soon as sufficient observations were accumulated, attempts were
made by various calculators to assign parabolic elements for the
orbit of the new body ; though but little success attended their
efforts. It was found that although a parabola might be obtained
which would represent with tolerable accuracy a limited number

• Phil. Trans., vol. Ixxi. p. 492. 1781.

CHAP. XIII.] Uranus. 243

of observations, yet a larger range always revealed discrepancies
which defied all endeavours to reconcile them with positions
assigned on any parabolic hypothesis. The final determination
was only arrived at step by step, and to Lexell must be ascribed
the credit of first announcing, with any amount of authority,
that the stranger revolved round the Sun in a nearly circular
orbit, and that it was a planet and not a comet ; though priority
for this honour has been contested on behalf of Laplace.

The question of a name for the new planet was the next
subject of debate. Herschel himself, in compliment to his
sovereign and patron King George III, proposed that it should
be called the Georgium Siclus ; Lalande or, as some say, Laplace
suggested the personal name of Herschel ; but neither of these
gave satisfaction to the Continental astronomers, who all declared
for a mythological name of some kind. Prosperin considered
Neptune appropriate, on the ground that Saturn would then be
found between his two sons Jupiter and Neptune. Lichtenberg
advanced the claims of Astraa, the goddess of justice, who fled to
the confines of the system. Poinsinet thought that as Saturn
and Jupiter, the fathers of the gods, were commemorated astro-
nomically, it would be unpolite longer to exclude the mother,
Cylele. Ultimately, however, Bode's Uranus prevailed over all
others. A symbol was manufactured out of the initial of Her-
schel's surname, though in Germany, at the instigation of Kb'hler,
one not differing much from that of Mars was adopted.

It soon became a matter of inquiry whether the new planet
had ever been seen before, and here may be brought in a note
of Arago's : — " If Herschel had directed his telescope to the con-
stellation Gemini 1 1 days earlier (that is, on March 2 instead of
March 13), the proper motion of Uranus would have escaped his
observation, for on the 2nd the planet was in one of its stationary
points. It will be seen by this remark on what may depend the
greatest discoveries in astronomy b." A careful inspection of the

b On this remark of Arago's Holden motion. Does any one suppose that ' a

says: — "This is an entire misconception, new and singular star' like this would

since the new planet was detected by its have been once viewed and then for-

physical appearance and not by its gotten?" (Life of W. fferschel, p. 49.)

R 2

244 The Sun and Planets. [BOOK I.

labours of former astronomers shewed that Uranus had been ob-
served and recorded as a fixed star on 20 previous occasions :
namely, by Flamsteedc in 1690, on Dec. 13; in 1712, on March
22; in 1715, on Feb. 21, 22, 27, and April 18 (all o.s.) ; by
Bradley in 1748, on Oct. 21 ; in 1750, on Sept. 13, and in 1753,
on Dec. 3 ; by Mayer in 1756, on Sept. 25 ; and by Le Monnier
no less than 12 times — in 1750, on Oct. 14 and Dec. 3 ; in 1764,
on Jan. 15; in 1768, on Dec. 27 and 30 ; in 1769, on Jan. 15, 16,
20, 21, 22 and 23; and in 1771, on Dec. 18. Had Le Monnier
been a man of order and method it can scarcely be doubted that
he would have anticipated Sir W. Herschel. Arago recollected
to have been shewn by Bouvard one of Le Monnier's observations
of the planet written on a paper bag, which originally contained
hair-powder purchased at a perfumer's !

It will readily be understood that these early observations
have been of great service to computers, inasmuch as they have
been enabled to determine the elements of the planet's orbit with
greater accuracy than they could otherwise have done simply by
the aid of modern observations.

Uranus revolves round the Sun in 30,6867 days, or rather
more than 84 of our years, at a mean distance of 1,781,944,000
miles. The eccentricity of its orbit, which amounts to 0-04667
(rather less than that of Jupiter), may cause this to extend to
1,865,107,000 miles, or to fall to 1,698,781,000 miles. The
apparent diameter of Uranus varies but slightly, as seen from the
Earth ; and its mean value is about 3'4". ( Seeliger, 3^82" :
Millosevich, 3'96.") The real diameter is about 31,000 miles.
Sir W. Herschel saw the planet's outline strongly elliptical
in 1792 and 1794, after having noted it to be round in 1782.
Madler at-Dorpat in 1842 and 1843 measured the ellipticity to be
TO- or iV Arago however pointed out that a polar compression
may exist but not always be visible, because a spheroid, when
viewed in the direction of its axis, will necessarily present a truly

c Le Verrier, in his investigation of adopted another dated April 18,
the theory of Uranus, rejected Flam- (_Grant, Hit>t. Phys. Ant., p. 165.)
steed's observation of Feb. 22, 1715, and

CHAP. XIII.] Uranus. 245

circular outline, and this seems both the proper and a sufficient
way of reconciling discordances on the subject which have been
noted. Buff ham on Jan. 25, 1870, thought that the ellipticity
was " obvious d." Safarik after many observations between 1877
and 1883 considered the ellipticity to be "striking" and there-
fore in fact "considerable6." Prof. C. A. Young in 1883
measured the planet on several occasions and obtained an ellip-
ticity of TV- He considers that there can be no " reasonable doubt
that the planet's disc is considerably flattened, its equator lying
sensibly in the same plane with the satellite-orbits f." Schia-
parelli too in 1884 obtained as he thought clear proofs of an
ellipticity of TV But the measures of Seeliger at Munich and
Millosevich at Rome in 1883 negative the idea.

It has been calculated that the amount of light received by
Uranus from the Sun is equal to about the quantity which would
be afforded by 300 Full Moons. The inhabitants of Uranus can
see Saturn, and perhaps Jupiter, but none of the planets included
within the orbit of the latter.

The physical appearance of Uranus may be disposed of in a few
words. Its disc is commonly considered to be uniformly bright,
bluish in tinge and without spots or belts. Yet both Lassell and
Buffham have fancied they have seen traces of an equatorial belt
and of inequalities of brilliancy on the planet's surface. Writing
in 1883 Prof. C. A. Young says: — " Whenever the seeing was
good 2 belts were always faintly but unmistakeably visible on
each side of the equator much like the belts of Saturn. On one
or two occasions other belts were suspected near the poles g."
Schiaparelli too with an 8-inch refractor has detected faint spots
and differences of colour on the disc of Uranus. The period of
axial rotation is unknown, but analogy h leads us to suppose that
it does not differ materially from that of Jupiter or Saturn.
Buffham has ventured on a conjecture that some indications of

d Month. Not., vol. xxxiii. p. 164. f Observatory, vol. vi. p. 331. Nov.

Jan. 1872. 1883.

8 Ast. Nach., vol. cv. No. 2505. Ap. E Observatory, vol. vi. p. 331. Nov.

14, 1883. Observatory, vol. vi. p. 183. 1883.
June, 1883. h See p. 68, ante.

246 The Sun and Planets. [BOOK I.

spots seen by him imply a Kotation-period of I2h. Sir W.
Herschel once fancied he had seen traces of a ring or rings, but
the observation was not confirmed by himself, nor has it been by
others since. Uranus is just within the reach of the naked eye
when in Opposition, and may be found without a telescope if the
observer knows its precise place1.

The direction of the axis of Uranus was supposed by Sir W.
Herschel to be such that if prolonged it would at each end meet
the planet's orbit. In consequence of this " the Sun turns in a
spiral form round the whole planet, so that even the two poles
sometimes have that luminary in their zenith k." Buff ham very
roughly makes the inclination of the axis 10°.

Fig. 122.

URANUS, 1884. (Henry .)

MM. Henry of Paris, in giving the accompanying sketch of
Uranus as seen during 1884, say that they were able to detect
constantly the existence of 2 belts, straight and parallel to one
another, placed almost symmetrically on each side of the centre

1 It is a somewhat singular fact that discover the Georgium Sidus, and strip

the Burmese mention eight planets : the the illustrious Herschel of his recent

Sun, Moon, Mercury, Venus, Mars, Ju- honours."

piter, Saturn, and Rahii, which latter is k Sir W. Herschel, quoted in Smyth's

invisible. "An admirer of Oriental lite- Cycle, vol. i. p. 205.
rature," says Buchanan, " would here

CHAP. XIII.]

Uranus.

247

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248 The Sun and Planets. [BOOK I.

of kthe planet. Between these 2 belts there was discernible a
fairly bright zone, which seemingly corresponded to the equatorial
region of the planet. The 2 poles were darkish ; however, the
upper pole in the engraving always appeared brighter than the
lower. They also found as the result of a great number of
measures that the direction of the belts did not coincide with
the major axis of the apparent orbit of the satellites, but formed
with it an angle of 40°, so that the position- angles observed
were 56° for the belts and 16° for the major axis at the same
epoch. MM. Henry suggest that in supposing, as it seems
reasonable to do, that the belts of Uranus are parallel to its
equator, and remembering that the latitude of the Earth above
the plane of the orbit of the satellites when the observations
were made was about 9°, there follows the result that the angle
between the plane of the equator of Uranus and the plane of the
orbits of the satellites is about 41°.

Uranus is attended by at least 4 satellites, 2 of which were
discovered by Sir W. Herschel, and 2 by recent observers }.
Such is their extreme minuteness that only the very largest
telescopes will shew them, and for this reason our knowledge of
them is very limited. Their chief peculiarity is the inclination of
their orbits, which for direct motion amounts to + 98° ; in other
words, their Urani-centric motion is retrograde, the planes of the
orbits lying nearly perpendicular (180° — 98° = 82°) to the
planet's ecliptic. The satellites, as Sir W. Herschel remarked,
describe the Northern halves of their orbits, included between
the ascending and descending nodes, in virtue of movements
directed from E. to W.

Sir J. Herschel pointed out a test by which astronomers can
ascertain whether their instruments are sufficiently powerful and
their sight sufficiently delicate to undertake with any reason-
able hope of success a search for these satellites. Between the
stars /81 and ft2 Capricorni, about the middle of the interval in

1 Sir W. Herschel thought that he had that Herschel's conclusions must have

discovered 6 satellites, which with the 2 been based on some misapprehension :

discovered by Lassell and Struve would that is to say, that he mistook small stars

make a total of 8 ; but it is now accepted for satellites.

CHAP. XIII.] Uranus. 249

R. A. and slightly to the N., there is a double star whose com-
ponents are of mags. 16 and 17 [=13 and 13*6 of Argelander's
magnitudes], and 3" apart. No instrument incapable of shewing
these two stars is suitable for observing the satellites of Uranus.
In fact Sir John remarked that in comparison with the Uranian
satellites these two stars are "splendid objects™."

Under these circumstances I shall be pardoned if I omit the
details of the observations made by Sir William Herschel", his
son0, Lamontp, O. Struve, and Lassellq, more especially as the
substance of them has been reproduced by Hindr and Arago 8.
Suffice it then to remark that, according to Lassell, Ariel and
Umbriel are of nearly equal brightness, whilst Titania and
Oberon are both much brighter than the 2 innermost satellites.

Under date of Jan. n, 1853, Lassell said lie was fully persuaded
that either Uranus has no other satellites than these 4, or if it has,
they remain yet to be discovered • but the ™

assumption of 8 satellites was accepted
by Arago and other influential astron-
omers. Lassell, writing in 1864 from
Malta, on the occasion of his second
visit, reiterated his former statement.

It was found by Sir W. Herschel
that the satellites disappeared when
within a short distance (j' or there-
abouts) of the planet. This occurred

PLAN OF THE URANIAN SYSTEM.

whichever was the side of the planet

on which the satellites happened to be, thus negativing the
possibility of the phenomenon being due to an atmosphere on
Uranus ; and Sir William was led to assume that it was merely
an effect of contrast — the comparatively great lustre of the planet
overpowering the feeble glimmer of the satellites.

m Cited by Arago in Pop. Ast., vol. ii. P Mem. R.A S., vol. xi. p. 51. 1840.

p. 628, Eng. ed., and by Smyth, Celest. 1 Month. Not., vol. viii. p. 44, Jan.

Cycle, vol. ii. p. 475. 1848; vol. xii. p. 152, March 1852; vol.

a Pkil.T>-ans., vol. Ixxvii. p. 125, 1787; xiii. p. 148, March 1853. Mem. R.A.S.,

vol. Ixxviii. p. 364, 1788 ; vol. Ixxxviii. vol. xxxvi. p. 34, 1867.

p. 47, 1798; vol. cv. p. 293, 1815. r Sol. Syst., p. 121.

0 Mem. R.A.S., vol. viii. p. i. 1835. s Pop. Ast., vol. ii. p. 623.

250

TJie Sun and Planets.

[BOOK I.

Hind, from Lassell's observations at Malta in 1852, has deduced
the following elements : —

III. TlTANIA.

Radius of orbit at the mean distance of Ijl ... 33-88" = 288,000 miles.

Longitude of ascending node ... ... ... 165° 25'

Inclination of orbit ... ... ... ... 100° 34'

IV. OBERON.

Radius of orbit at the mean distance of 1$ ... 45-20" = 384,000 miles.
Longitude of ascending node ... ... ... 165° 28'

Inclination of orbit ... ... ... ... 100° 34'

From the distance of Titania the same computer obtained ^-5^-5
as the mass of Uranus, Oberon indicating ^r^ ; results fairly

THE APPARENT OBBITS OF THE SATELLITES OF URANUS.

*»* The small circle represents the planet : the arrows, the direction in which the tatellites move : each
black dot, a day's interval reckoned from O, the epoch of the preceding Northern elongation.

in accord with those of other observers, when the difficulties in
obtaining data are considered. Encke's value was -ST^V g-> Lament's
irr£tfT> Madler's ^Tlr^ ^- Hall's s-svsr> Adams's v^w Littrow's
¥Ttfinr> and Bouvard's T7|T^. Bouvard's value is now very
generally rejected as excessive.

In computing the places of Uranus the Tables of A. Bouvard,
published in 1821, were used up to quite a recent date. From
what appears in the following chapter it will be evident that they

CHAP. XIII.] Uranus. 251

were susceptible of material improvement, and they have now
given place to those completed in 1872 by an American astro-
nomer, Professor S. Newcomb, as to which it may be observed
that they do not countenance the idea that there exists a trans -
Neptunian planet. Newcomb has also framed Tables of the
Satellites of Uranus *.

i Washington Obs., 1873, Appendix I.

252 The Sun and Planets. [Boos. I.

CHAPTER XIV.

NEPTUNE a. T

Circumstances which led to its discovery. — Summary of the investigations of Adams
and Le Verrier. — Telescopic labours of Challis and Galle, — The perturbations
of Uranus by Neptune. — Statement of these perturbations by Adams. — Period,
&c. — Attended by I Satellite. — Elements of its orbit. — Mass of Neptune. —
Observations by Lalande in 1 795.

MORE than half a century ago an able French astronomer,
M. Alexis Bouvard, applied himself to the task of making
a refined investigation of the motion of Uranus, in order to
prepare Tables of the planet. He had at his disposal the various
observations by Flamsteed and others, made prior to the direct
optical discovery of Uranus, and those made by various astro-
nomers subsequent to that event in 1781. In working these up
he found himself able to assign an ellipse harmonising with the
first series, and also one harmonising with the second ; but by no
possibility could he obtain an orbit reconcileable with both. As
the less objectionable alternative, Bouvard decided to reject all the
early observations and to confine his attention solely to those
more recent b. In this way he produced, in 1821, Tables of the
planet, fairly representing its motion in the heavens. This
agreement, however, was not of long duration, and a few years

a Many French writers deal with the tended to rob a deserving Frenchman of

discovery of Neptune in a way that is not his share in the honours. Science ought

fair. Nothing is more common than to to be international, and to rise above

meet with a narrative of the incident such petty insinuations,
either without any mention, direct or in- b A memorable illustration of the folly

direct, of Mr. J. C. Adams, or with some and impolicy of rejecting any observation,

casual remark more or less implying that merely because it opposes — or seems to

the English version is a trumped-up story oppose— a pre-conceived theory,
due to national jealousy, and only in-

CHAP. XIV.J Neptune, 253

only elapsed before discordances appeared of too marked a
character to be possibly due to any legitimate error in the Tables :
constructed in the form in which they existed it was evident
that they were defective in principle. Eouvard himself, who
died in 1 840, seems to have fancied that an exterior planet was
alone the cause of the irregularities existing in the motion of
Uranus, and the Rev. T. Hussey was led to assert this in decided
terms in a letter to Airy in 1834. This conviction soon forced
itself on astronomers °, and amongst others on Valz, Madler, and
Bessel. Bessel, it would seem, entertained the intention of mathe-
matically inquiring into the matter, but was prevented by an
illness, which eventually proved fatal.

Mr. J. C. Adams, whilst a student at St. John's College, Cam-
bridge, resolved to attack the question, and, as he found sub-
sequently, entered a memorandum to this effect in his diary under
the date of July 3, 1841, but it was not till January 1843 that he
found himself with sufficient leisure to commence. He worked
in retirement at the hypothesis of an exterior planet for i f years,
and in Oct. 1845 forwarded to Airy some provisional elements
for one revolving round the Sun at such a distance and of such
a mass as he thought would account for the observed pertur-
bations of Uranus. This was virtually the solution of the
problem in a theoretical point of view, and it is much to bo
regretted that neither the result nor any of the circumstance.s
attending it were made public at the time.

In the summer of J 845, Le Verrier, of Paris, turned his atten-
tion to the anomalous movements of Uranus, and in the November
of that year published his first memoir to prove that they did
not depend solely on Jupiter and Saturn. In June 1846 the
French astronomer published his second memoir to prove that
an exterior planet was the cause of the residual disturbance. He

c As far back as October 25, 1800, La- This statement is reputed to depend on a

lande and Burckhardt came to the con- note to this effect found amongst Lalande's

elusion that there existed an unseen papers presented to the Academy of

planet beyond Uranus, and they occupied Sciences in 1852, but I am not acquainted

themselves in trying to discover its posi- with any other authority for it.
tion. (Year Book of Facts, 1852, p. 282.)

254 The Sun and Planets. [BOOK I.

assigned elements for it, as Adams had done 8 months previously.
A copy of the memoir reached Airy on June 23, and finding
how closely in accord Le Vender's hypothetical elements were
with those of Adams, which were still in his possession, he was
so impressed with the value of both, that on July 9 he wrote to
Professor Challis of Cambridge to suggest the immediate employ-
ment of the large "Northumberland" telescope in a search for
the planet. The proposal was agreed to, and on July u a
systematic search was commenced. Challis, not being in posses-
sion of the Berlin Star Map of the particular locality in which it
was supposed that the looked-for planet would be found, was
forced to make observations for the formation of a map for
himself ; this was done, but much valuable time was occupied.
When matters had reached this stage Sir J. Herschel seized an
opportunity which happened to present itself, and thus addressed
the British Association at Southampton on Sept. 10, 1846: —
The past year has given us the new planet Astrsea — " it has done
more — it has. given us the probable prospect of the discovery of
another. We see it as Columbus saw America from the shores
of Spain. Its movements have been felt, trembling along the
far-reaching line of our analysis, with a certainty hardly inferior
to that of ocular demonstration d." The Map was eventually got
ready, but it was not till Sept. 29 that Professor Challis found an
object whose appearance attracted his attention, and which was
subsequently proved to be the new planet so anxiously sought.
It was likewise ascertained afterwards that the planet had been
observed for a star on Aug. 4 and 12, and that the supposed star
of Aug. 12 was wanting in the zone of July 30. The non-
discovery of its planetary nature on Aug. 1 2 was due to the fact
of the comparisons not having been carried out quite soon
enough; a pardonable though regrettable circumstance. It
should be added that it was not until Oct. i that Challis heard
of Galle's success on Sept. 23. (See post.)

In August Le Yerrier published a third memoir, containing re-
vised elements, in which particular attention was paid to the

d Athenteum, Oct. 3, 1846, p. 1019.

CHAP. XIV.] Neptune. 255

probable position of the planet in the heavens. On Sept. 23 a
letter from him, containing a summary of the principal points of
this memoir, was received by Encke of Berlin, whose co-operation
in searching telescopically for the planet was requested. The
Berlin observers had the good fortune to have just become pos-
sessed of Bremiker's Berlin Star Map for Hour XXI. of R.A.,
which embraces that part of the heavens in which both Adams
and Le Verrier expected that the new planet would be found,
and resort to this Map was suggested by D'Arrest, then a young
student at the Berlin Observatory. On turning the telescope
towards the assumed place, Galle, Encke's assistant, called out
the visible stars one by one, and D'Arrest checked them by the
Map. After a while Galle saw what seemed to be a star of the
8th magnitude, which was not laid down on the Map. Further
observations on Sept. 24 placed it beyond a doubt that this
8th magnitude star was in reality the trans-Uranian planet ; a
discovery, the announcement of which, as may be well imagined,
created the liveliest sensation. The French astronomers, with
Arago at their head, disputed with unseemly violence the equal
claims of Adams to participate with Le Verrier in the honours ; but
Airy, then Astronomer Royal, laid before the Royal Astronomical
Society, on Nov. 13, such an overwhelming chain of evidence
in favour of our distinguished countryman's exertions as seems
to all impartial minds to have finally settled the question6.

The intellectual grandeur of this discovery will be best ap-
preciated, so far as a non-mathematical reader is concerned, by
placing in juxtaposition the observed longitude of the new planet
when telescopically discovered, and the computed longitudes of
Adams and Le Verrier.

e The foregoing is a very bare outline case will be found stated in Arago's Pop.
of the case, which is a most interesting Ast., vol. ii. p. 632 ; the English trans-
one. Grant (Hist. Phys. Ast., p. 165 et lator's notes to the passage are very
seq.) gives full particulars ; and reference appropriate. A very full statement of
may also be made to Month. Not., vol. the facts of the case from a quite recent
vii. p. 121, Nov. 1846; Mem. R.A.S., stand-point will be found in an obituary
vol. xvi. p. 385, 1847; Athen&um, Oct. notice of Prof. Challis, in Month. Not.,
3, 1846; Adm. Smyth's Speculum Hart- vol. xliii. p. 160. Feb. 1883. D' Arrest's
wellianum, p. 405 ; and Sir J. Herschel's share in the work will be found explained
Outlines of Ast., p. 533. The French in Copernicus, vol. ii. p. 63, 1882.

256

The Sun and Planets.

[BOOK I.

HELIOCENTRIC POSITIONS.

Observed by Galle 326° 52'

Computed by Adams ... 329° T9'

Computed by Le Verrier 3^6° o';

Adams A C — O = + 2° 27'

Le Verrier A C - O « - o° 52'.

From this it will be seen that Le Verrier' s computation proved
to be slightly the more accurate of the two, a fact which in no
respect militates against the equality of the merits of the two
great mathematicians.

After considerable discussion Neptune was the name agreed

upon for the new planet;
Galle's suggestion of Janus
being rejected as too signi-
ficant.

" Such," in the words of
Hind, "is a brief history
of this most brilliant dis-
covery, the grandest of
which astronomy can
boast, and one that is des-
tined to a perpetual record
in the annals of science —
an astonishing proof of the
power of the human intel-
lect."

The accompanying dia-
gram shews the paths of Uranus and Neptune from 1781 to 1840,
and will help to illustrate the direction of the perturbing action
of the latter planet on the former.

From 1781 to 1822 it will be evident, from the direction of the
arrows, that Neptune tended to draw Uranus in advance of its
place as computed independently of exterior perturbation.

In 1822 the two planets were in heliocentric conjunction, and
the only effect of Neptune's influence was to draw Uranus
farther from the Sun, without altering its longitude.

ILLUSTRATION OF THE PERTURBATION OP
URANUS BY NEPTUNE.

CHAP. XIV.] Neptune. 257

From 1822 to 1830 the effect of Neptune was to destroy the
excess of longitude accumulated from 1781, and after 1830 the
error in longitude changed its sign, and for some years subse-
quently Uranus was retarded by Neptune ; having by 1 846
fallen 128" behind its place as predicted from Bouvard's tables.

Prof. Adams has kindly furnished me f with the following ex-
planatory comment on the above diagram (Fig. 1 25) : —

" The arrows rightly represent the direction of the force with which Neptune acts
on Uranus taken singly, but the diagram does not represent the direction of the disturb-
ing force which Neptune exerts on Uranus relatively to the Sun, and this latter force
is what we must take into account in computing the planetary perturbations. To find
this disturbing force, we must take the force of Neptune on the Sun, reverse its
direction, and then compound this with the direct force of Neptune on Uranus.

"Thus if S denote the Sun, U Uranus, and N Neptune, the force of Neptune on

Uranus will be in the direction UN and will be proportional to ? and the force

of Neptune on the Sun will be in the direction SN and will be proportional to

Hence if we produce NS, if Fig. 1 26.

necessary, to V and take NV= ^ , the

reversed force of Neptune on the Sun will

be represented by NV, provided the direct

force of Neptune on Uranus be represented

by UN. Hence the disturbing force of

Neptune on Uranus relatively to the Sun

will be represented on the same scale in THE PERTUBBATTON OF URANUS BY

magnitude and direction by UV, the direc- NEPTUNE.

tion being indicated by the arrow in the ,,v

figure, and the magnitude of the disturbing force being proportional to _, •

" It is not possible to state the effect of Neptune's action on the motion of Uranus
in such simple terms as you have attempted to do, since it is necessary to take into
account the action of Neptune in order to find the correct elements of the orbit of
Uranus, and consequently the corrections of the assumed elements must be taken as
additional unknown quantities which must be determined simultaneously with the
perturbations depending on Neptune."

Neptune revolves round the Sun in 60,126 days, or 164-6 years,
at a mean distance of 2,791,750,000 miles, which an eccentricity
of 0-0087 will increase to 2,816,094,000 miles, or diminish to
2,767,406,000 miles. The apparent diameter of Neptune only
varies between 2-6" and 2-8". Its true diameter is about 37,200

f Private letter dated Cambridge, May 8, 1884.
S

258

The Sun and Planets.

[BOOK I.

miles — a diameter somewhat greater than that of Uranus. No
polar compression is perceptible.

Neptune is destitute of visible spots and belts, and at present
the period of its axial rotation is unknown. But it deserves to
be stated that on 14 nights in November and December 1883
Maxwell Hall in Jamaica observed periodical variations in the
light of Neptune which he thought might have been due to an
axial rotation occupying 7h 55m 1 2s. He arrived at this result
after finding that the planet's light seemed to change from a
maximum star mag. of 1\ to a minimum of 8^ in a period of
something under 4 hours g. Lassell, Challis, and Bond at various
times suspected the existence of a ring but nothing certain is
known on the subject. It would be very desirable to have a large
reflector like Lord Rosse's, or a large refractor like those at the
Lick and Vienna Observatories, devoted to a series of observations
of this planet and Uranus, for it is nearly certain that no other
existing instruments will add much to our present extremely
limited knowledge of the physical appearance of these planets.

Neptune is known to be attended by only one satellite, dis-
covered by Lassell in 1 846, but both that observer and the late
W. C. Bond subsequently imagined that they had obtained traces
of the existence of a second.

The following table furnishes all the information we at present
possess about Lassell's confirmed satellite : —

THE SATELLITE OF NEPTUNE.

Mean Distance.

Discoverer.

Sidereal Period.

Apparent
Star mag-
nitude.

Max.
Elong.

Radii of

T-1-

<l. b. in.

Lassell. 1846, Oct. 10

I2-OO

223,OOO

5 21 3

5-88

Changes appear to be in progress in the plane of the orbit of
this satellite the precise nature of which await further observa-
tion and explanation b.

* Month. Not., vol. xliv. p. 257. March 1884.
h Observatory, vol. xi. p. 446. Dec. 1888.

CHAP. XIV.]

Neptune.

259

Hind gives the following elements1 : —

Epoch 1852, Nov. o-o G. M. T.

o /

Mean anomaly .................. 243 32

Peri-neptunium .................. 177 30

8 ... 175 40

« ........................... 151 o

Eccentricity .................. 6 5=0-1059748

Period .....................

The elements are calculated for direct motion ; accordingly it
will be noticed that the actual Neptunicentric motion of the
satellite is retrograde — a circumstance which, except in the case of
the Uranian satellites, is without parallel in the solar system as
regards either planets or satellites; though there are many
retrograde comets.

Fig. 127.

PLAN OP THE ORBIT OF THE
SATELLITE OF NEPTUNE.

ORBIT OF THE SATELLITE OF
NEPTUNE.

The mass of Neptune has been variously estimated at a
by Safford ; at ^\^ by Bond ; at ^^ by A. Hall ; at
by Littrow; at r g^g^ by Peirce ; at TS^T^ by Holden ; at 1^7
Hind, from a combination of early measures ; at rrHir by Lassell
and Marth ; at TTTS^ by Hind from Lassell's Malta measures ;
a^ TTT7T by O. Struve ; and at TTlT-g- by Miidler.

The only known observations of Neptune made previously to
its discovery in 1846 are two by Lalande, dated May 8 and 10,
1795, and one by Lament of Oct. 25, 1845. Two by the same

1 Month. Not., vol. xv. p. 47. Dec.
1854. For some of Lassell's observations

see vol. xii. p. 155, March 1852, and vol.
xiii. p. 37, Dec. 1852.

S 2

260 Th,e Sun and Planets.

astronomer on Sept. 7 and n, 1846, were probably due to Le
Verrier's announcement made just before, and therefore are not
entitled to be regarded as casual ones.

Owing to its immense distance from the Sun, only Saturn and
Uranus can be seen from Neptune. Though deprived of a view
of the principal members of the solar system, the Neptunian
astronomers, if there be any, are well circumstanced for making
observations on stellar parallax ; seeing that they are in pos-
session of a base-line of 5,584,000,000 miles, or one more than
30 times the length of that to which we are restricted.

Our present knowledge of the movements of Neptune is de-
rived from the investigations of the late S. C. Walker, of Phila-
delphia, U.S., and from the Tables of M. Kowalski and Professor
S. Newcomb. Newcomb has also framed Tables of the satellite
of Neptune k.

The question of a possible planet beyond Neptune has received
some attention, but whether such a planet exists, and whether
we are ever likely to see it, are problems towards the solution of
which very little progress has yet been made *.

The question of the existence of a Trans-Neptunian planet has
been discussed from a novel stand-point by Flammarion. He
bases his conclusions that such a planet does exist on considera-
tions connected with the grouping of the comets whose periodicity
is open to no doubt. He seeks to show that all the 4 major planets
beyond Mars have seemingly a group of comets associated with
them in some way ; and that beyond Neptune there is a group of
comets to influence which no planet is yet known to exist. Hence
his conclusion that such a planet does exist but that we have not
yet seen it. This in brief is Flammarion 's argument, which is
worked out with considerable ingenuity and care, but with
materials borrowed, without acknowledgement, from others"1.

k Washington Obs., 1873, Appendix I. 8vo., Washington, U.S., 1880; Ast. Nach.,

1 See Prof. G. Forbes's Comets and vol. cxiii. No. 2698, Dec. 21, 1885.

Ultra-Neptunian Planets ; also a paper Todd's search extended over 4 months

by D. P. Todd of the American Nautical during the winter of 1877-8.

Almanac Office entitled "Preliminary m IS Astronomic, vol. iii. p. 81. March

account of a speculative and practical 1884. Forbes seems to have been the

search for a Trans-Neptunian planet," originator of this theory.

BOOK II

ECLIPSES*

CHAPTER I.

GENERAL OUTLINES.

Definitions. — Position of the Moons orbit in relation to the Earth's orbit. — Con-
sequences resulting from their being inclined to each other. — Retrograde motion
of the nodes of the Moon's orbit. — Coincidence of 223 synodical periods with
19 synodical revolutions of the node. — Known as the " Saros." — Statement of
Diogenes Laertius. — Illustration of the use of the Saros. — Number of Eclipses
•which can occur. — Solar Eclipses more frequent than Lunar ones. — Duration of
Annular and Total Eclipses of the Sun.

THE phenomena which are about to be described are those
which result from the interposition of some one celestial body
between a other bodies, the Earth in any case being one of the 3.
We know well that inasmuch as most of the heavenly bodies are con-
stantly in motion, the direction of lines drawn from one to another
must vary from time to time ; and it must occasionally happen that
3 will come into a right line. " When one of the extremes of
the series of 3 bodies which thus assume a common direction is
the Sun, the intermediate body deprives the other extreme body,

a The portions of this Book which re- edition by my friend Mr. A. C. Kanyard,
late to Eclipses of the Sun have been facile princeps in this department of
revised and much extended for this Astronomy.

262

Eclipses and Associated Phenomena. [BOOK II.

either wholly or partially, of the illumination which it habitually
receives. When one of the extremes is the Earth, the inter-
mediate body intercepts, wholly or partially, the other extreme
body from the view of observers situate at places on the Earth
which are in the common line of direction, and the intermediate
body is seen to pass over the other extreme body, as it enters upon
or leaves the common line of direction. The phenomena resulting
from such contingencies of position and direction are variously
denominated Eclipses, Transits, and Occultations, according to the
relative apparent magnitudes of the interposing and obscured
bodies, and according to the circumstances which attend them."
We will proceed to consider these several phenomena in detail
beginning with Eclipses.

Fig. 129.

THEORY OF A TOTAL ECLIPSE OF THE 8UN.

It must be premised that the Moon's orbit does not lie in
exactly the same plane as the Earth's, but is inclined thereto at
an angle which varies between 5° 20' 6" and 4° 57' 22", and for
which 5° 8' 45" may be taken as the mean value. The two points
where its path intersects the ecliptic are called the Nodes, and the
imaginary line joining these points is termed the Line of Nodes.

Fig. 130.

THEORY OF AN ANNULAR ECLIPSE OF THE SUN.

When the Moon is crossing the ecliptic from South to North, it
is passing its Ascending Node ( a ), the opposite point of its orbit
being its Descending Node ( <3 ). If the Moon should happen to
pass through either node at or near the time of conjunction, or
New Moon, it will necessarily come between the Earth and the

CHAP. I.]

General Outlines.

263

Sun, and the 3 bodies will be in the same straight line ; it will
therefore follow that to certain parts of the Earth the Sun's disc
will be obscured, wholly or partially as the case may be : this is
an Eclipse of the Sun. In the figures above, S represents the Sun,
E the Earth, and M the Moon. In a total solar eclipse the Moon's
shadow reaches to and beyond the Earth's surface, the Moon being
then at or near its minimum distance from the Earth ("perigee ").
In an annular eclipse the Moon's shadow falls short of the Earth,
the Moon being then at or near its maximum distance from the
Earth ("apogee").

The Earth and the Moon, being opaque bodies, must cast
shadows into space ; though of course, owing to the larger size
of the Earth, its shadow is much the larger of the two. If the
Moon should happen to pass through either node at or near
the time of Opposition, or Full Moon, it will be again, as before,
in the same straight line with the Earth and the Sun ; but the
Moon will be involved in the shadow of the Earth, and therefore
will be deprived of the Sun's light ; this causes an Eclipse of the
Moon.

Fig. 131.

THEORY OF AN ECLIPSE OF THE MOON.

In Fig. 131, S represents the Sun, E the Earth, and m n the
orbit of the Moon : that the Moon becomes involved in the Earth's
shadow in passing from m to n is obvious.

If the orbits of the Earth and the Moon were in the same plane,
an eclipse would happen at every conjunction and opposition, or
about 25 times a year ; but as such is not the case, eclipses are of
less frequent occurrence. According to trustworthy investiga-
tions, in order that an eclipse of the Sun may take place, the
greatest possible distance of the Sun or Moon from the true place

264 Eclipses and Associated Phenomena. [BOOK II.

of the nodes of the Moon's orbit is 18° 36', whilst the latitude of
the Moon must not exceed i° 34' 52". If, however, the distance
be less than 15° 19' 30", and the latitude less than 1° 23' 15", an
eclipse must take place, though between these limits the occurrence
of the eclipse at any station is doubtful, and depends upon the
horizontal parallaxes and apparent semi-diameters of the two
bodies at the moment of conjunction. In order that a lunar
eclipse may take place, the remark just made will equally
hold good, except that 12° 24', 9° 23', 63' 45" and 51' 57", must
be substituted for the quantities given above.

The nodes of the Moon's orbit are not stationary, but have a
daily retrograde motion of 3' 10-64" or an annual one of 1 9° 20' 1 9-7",
so that a complete revolution round the ecliptic is accomplished
in 18* 2i8d 2ih 22m 46s nearly. The Moon performs a revolu-
tion with respect to the node in 27d 5h 5m 36" (27-21222222^.
This is termed a " nodical revolution of the Moon b," and must not
be confounded with the " synodical revolution of the Moon." It
is shorter than the latter, because the retrograde motion of the
node upon the ecliptic brings the Moon into contact with it
before she comes again into Conjunction or Opposition as the
case may be.

A singular effect produced by the retrocession of the nodes on
the ecliptic must now be referred to. The Moon's synodical period,
or the time which she occupies in passing from one conjunction
or Opposition to another, is 29* I2h 44m 2-87" (29-53058872 J5d) ;
223 of these periods amount to 6585«32Jd (i8y iod 7h 43™); but
19 revolutions of the Sun with respect to the lunar node" (each
of 346-620 id) are completed in 6585-7 82d: the near coincidence
of these two periods produces this obvious result ; that eclipses

b Sometimes the Draconic Period. instead of remaining stationary. Since

c If the lunar nodes were immoveable the lunar nodes travel at only 3' 10" per

the Sun would return to the same poai- day, compared with the Sun's ecliptic

tions with respect to them every terres- motion of 59' 9", it follows that the nodes

trial tropical year ; but this luni-nodical require i8-6d to get over the angular

revolution of the Sun, if such an expres- distance which the Sun does in id. De-

sion maybe used, is less than the tropical ducting then i8-6d from 365«242d (the

year for the same reason that the nodical mean solar year), we get 346-(>42d, as

lunar month is less than the synodical above, for the period of the Sun's return

one, the node receding to meet the Sun to the same lunar nodes.

CHAP. I.] General Outlines. 265

recur in almost, though not quite, the same regular order after
the completion of 19 synodical revolutions of the Moon's node.
The difference between the two periods is 0-46 id, or ioh 49-6™ ;
during which time the Sun describes an arc of 28' 6" relative to
the lunar node.

These coincidences will be better brought out by the figures
being placed in column, thus : —

d. d.

242 Draconic Periods (27-21222 x 242) = 6585-35777.

223 Lunations (29-53058 x 223) = 6585-31934.

19 Returns of Sun ) .

™ ' AT j [-(346.6201 x 19) =6585-7819.
to Moon s Node j u

Some trifling discrepancies in the last column compared with
the results given above are due to different decimals having been
employed in the multiplication.

It was probably a knowledge of these facts which enabled the
ancient astronomers to predict the occurrence of great eclipses,
since it is quite certain that they did so in more than one instance
before the nature of eclipses was fully understood. This cycle
was known to the Chaldseans as the Saros d. Diogenes Laertius
records 373 solar and 832 lunar eclipses observed in Egypt; and
although his testimony is, generally, of no great value, yet it is very
singular that this is just the proportion of solar and lunar eclipses
visible above a given horizon within a certain period of time
(1200-1300 years) — a coincidence which cannot be accidental6.

From what I have just said it might be imagined that a
correct list of eclipses for 18-03 vears would be sufficient for all
purposes of calculation ; and that the occurrence of an eclipse
might be ascertained in advance at any distance of time by the
simple process of adding so many ecliptic periods as were found

d See Una. Cycl., art. Saros. It has and Colleges, New York, 1879, PP-
been stated that the Chaldaeans used a 180-4, an<i Newcomb's Popular As-
triple Saros of 54* 3id as more correct tronomy, Loud, ed., p. 29. The German
for purpose of prediction than a single translation of this latter work contains
one. For a good deal of interesting in- still further and better particulars,
formation respecting matters incidentally (Trans, by Engelmann, p. 26.)
connected with the Saros, see Newcomb e Hist, of Ast., L.U.K., p. 15.
and Holden's Astronomy for Schools

266 Eclipses and Associated Phenomena. [BOOK II.

requisite. This would be nearly correct if an eclipse appeared
under precisely the same circumstances as the one in the pre-
ceding or following period corresponding to it: but such is not
the case f. An eclipse of the Moon, which in the year 565 A.D.
was of 6 digits8, was in the year 583 of 7 digits, and in 601 of
nearly 8. In 908 the eclipse became total, and it remained so for
about 12 periods, or until the year 1088 : this eclipse continued to
diminish until the commencement of the i5th century, when it
totally disappeared in the year 1413. In a similar manner an
eclipse of the Sun, which appeared at the North Pole in June
1295, became more southerly at each period. On Aug. 27, 1367,
it made its first appearance in the north of Europe ; in 1439 it
was visible all over Europe; at its- 19th appearance, in 1601, it
was central in London ; on May 5, 1818, it was visible at London,
and was again nearly central at that place on May 15, 1836. At
its 39th appearance, August 10, 1980, the Moon's shadow will
have passed the equator, and, as the eclipse will take place near
midnight, it will be invisible in Europe, Africa, and Asia. At
every subsequent period the eclipse will go more and more towards
the south, until, finally, at its 78th appearance on Sept. 30, 2665,
it will go off at the South Pole of the Earth, and disappear
altogether. The time required for a lunar eclipse to go through
all its Saros changes (so to speak) is 865 years. A similar series
of solar eclipses will last much longer, or about 1 200 years.

In the 1 8-year eclipse period, there usually happen 70 eclipses,
of which 41. are solar and 29 are lunar. In any one year the

f Halley found that if this period were Moon's contour. The Companion to the

added to the middle of any eclipse, the Almanac for 1832 contains (p. 8) some

corresponding one might be predicted to useful memoranda about digits, and a

within ih 30™. According as 4 or 5 leap- description of the path of the central

years intervene, the period of the Saros line at different periods of the year,

will be 1 8* iod &c. or i8y nd &c. The older astronomers treated the digit

* A digit is the -fa part of the diameter as a measure of surface and indicated by

of the Sun or Moon ; and of course an its use that -fa of the visible area of the

eclipse of 6 digits will be understood to Sun, or Moon, was obscured, not -fa of its

be one in which £ the disc of the luminary diameter ; but in more recent times the

is hidden. In the case of a lunar eclipse, word was used as stated at the beginning

when the magnitude is said to exceed 12 of this note. It is now however quite

digits, it means that the Earth's shadow obsolete in both senses, and the magnitude

extends itself so many digits beyond the of every eclipse is expressed decimally.

CHAP. I.] General Outlines. 267

greatest number that can occur is 7, and the least 2 : in the
former case 5 of them may be solar, and 2 lunar ; in the latter
both must be solar. Under no circumstances can there be more
than 3 lunar eclipses in i year, and in some years there are
none at all. Though eclipses of the Sun are more numerous
than those of the Moon in the proportion of 41 to 29 (say of
3 to 2), yet at any given place more lunar eclipses are visible
than solar : because, whilst the former are visible over an entire
hemisphere, the area of the Earth over which the latter are
visible is in the case of total or annular eclipses a narrow strip,
which cannot exceed 180 and is seldom more than 140 miles or
so in breadth. In the case of partial eclipses of the Sun however
the range of visibility is, it is true, much wider; for at every
point of the Earth immersed in the penumbra more or less of the
eclipse will be seen.

In a solar eclipse the Moon's shadow traverses the Earth at the
rate of 1 830 miles an hour, or rather more than half a mile per
second. This corresponds to 30$ miles per minute; Lalande's
result is equivalent to 33-1 miles.

Du Sejour found that, counting from first to last, a solar eclipse
at the equator may last 4h 29™ 44s, and that at the latitude of
Paris the maximum period is 3h 26™ 22s, but that the interval
of time during which the Sun will be centrally eclipsed is very
small. The duration of the total obscuration is greatest when
the Moon is in perigee and the Sun in apogee ; for the apparent
diameter of the Moon being then the greatest possible, while that
of the Sun is the least possible, the excess of the former over the
latter, upon which the totality depends, is at a maximum. Now
the perigean diameter of the Moon =33' 31"; the apogean diameter
of the Sun=3i'3o".

A = 33'3i"-3i'3o" = a'i".

This then is theoretically the arc which has to be described by
the Moon during the greatest possible continuance of the total
phase, but in reality the ultimate result is complicated by the
Sun's apparent motion Eastward and the Earth's axial rotation
in the same direction. However, taking into consideration the

268 Eclipses and Associated Phenomena. [BOOK II.

rapid motion of the Moon, it will be readily understood that, under
the most favourable circumstances, the Sun cannot remain totally
eclipsed for more than a few minutes.

The duration of the obscuration in a total eclipse of the Sun
varies, catteris paribus, with the latitude of the place of observation,
and is greatest under the equator. Du Sejour h found that, under
the most favourable circumstances, the greatest possible duration
of the total phase at the equator was 7m 58s, and that at the
latitude of Paris it was 6m 10".

The duration of an annular eclipse is greatest when the Moon is
in apogee and the Sun in perigee, for then the apparent diameter
of the Sun is the greatest, whilst that of the Moon is the least
possible, and consequently the excess of the former over the latter
(upon which the annulus depends) is then at a maximum.

The perigean diameter of the Sun = 32' 35". The apogean
diameter of the Moon = 29' 22".

/. A = 32' 35" -29' 22"= 3' 13".

This then is theoretically the arc which has to be described by
the Moon during the greatest possible continuance of the annular
phase, but, as before, some qualification is requisite in dealing with
the facts which present themselves. Du Sejour found that under
the most favourable circumstances the greatest possible duration of
the annular phase at the equator1 was i2m 24% and that at the
latitude of Paris* it was 9m 56s.

It may be desirable briefly to point out the reasons why the
greatest possible duration of an annular eclipse exceeds that of a
total one. They are 2 in number : i 8t. Because the excess of the
perigean diameter of the Sun over the apogean diameter of the
Moon ( = 3' 13") is greater than the excess of the perigean diameter
of the Moon over the apogean diameter of the Sun ( = 2' i").
2nd. Because the motion of the Moon in apogee is much slower
than it is in perigee.

From the above remarks it will be readily understood that
though so many solar eclipses happen from time to time, yet

h Mem. Acad. des Sciences, 1777, p. 318.
' Ibid., p. 317. k Ibid., p. 316.

CHAP. I.] General Outlines. 269

the occurrence of an annular or total one at any particular
locality is a very rare phenomenon. Thus, according to Halley1,
no total eclipse had been observed at London between March 20,
1140, and April 22, 1715 (o. s.), though during that interval the
shadow of the Moon had frequently passed over other parts of
Great Britain111.

The calculation of eclipses is a matter of considerable com-
plexity. A paper by Woolhouse, in the supplement to the Nautical
Almanac for 1836, and the chapters in Loomis's well-known workn,
may be named as the best guides in our language0. Much
interesting historical matter concerning eclipses will be found in
the Rev. S. J. Johnson's Eclipses, Past and Present.

1 Phil. Trans., vol. xxix. p. 245. 1715. derived, ascertained that the eclipse of

ra It may here be noted that, according 1 140 was not centrally visible in London,

to recent investigations by Hind, the The line of totality crossed the Midland

Total solar eclipse of Feb. 3, 1916, will Counties, and did not approach London

not be visible as such in England, though nearer than Northamptonshire. (See

a statement to that effect may occasion- letters by Hind inAst. Reg., vol. vii. p. 87,

ally be met with. On June 30, 1954, April 1869, and vol. ix. p. 209, Sept. 1871;

occurs the next Total eclipse which will also a paper by the Rev. S. J. J ohnson in

be visible in Great Britain ; this will be Month. Not., vol. xxxii. p. 332. 1872.)
seen at the northernmost of the Shetland n Practical Astronomy, pp. 226-90.

Isles. The eclipse of Aug. n, 1999,18 ° It is recorded by Rittenhouse that in

the next that will be visible as a Total his early days he calculated eclipses on

one in England itself. The line of totality his plough-handle. For a brief sketch

will pass across Cornwall and Devonshire. of the career of this ' self-made ' man (a

Hind, in connection with the calcula- pioneer of astronomy in America) see

tions from which these particulars were Sid. Mess., vol. vii. p. 433, Dec. 1888.

270 Eclipses and Associated Phenomena. [BOOK II.

CHAPTER II.

ECLIPSES OF THE SUN.

Grandeur of a Total Eclipse of the Sun. — How regarded in ancient times. —
Effects of the progress of Science. — Indian Customs. — Effect on Birds at Berlin
in 1887. — Solar Eclipses may be Partial, Annular, or Total. — Chief phenomena
seen in connexion with Total Eclipses. — Change in the colour of the sky. — The
obscurity which prevails. — Effect noticed by Piola. — Physical explanation. —
Sally's Beads. — Extract from Sally's original memoir. — Probably due to irra-
diation.— Supposed to have been first noticed by Halley iniji 5 . — Sis description.
— The Corona. — Hypothesis advanced to explain its origin. — Probably caused
by an atmosphere around the Sun. — Remarks by Grant. — First alluded to by
Philostratus. — Then by Plutarch. — Corona visible during Annular Eclipses. —
The Red Flames. — Remarks by Dawes. — Physical cause unknown. — First
mentioned by Stannyan. — Note by Flamsteed. — Observations of Vasseniux. —
Aspect presented by the Moon. — Remarks"by Arago.

A TOTAL eclipse of the Sun is a most imposing spectacle,
especially when viewed from the summit of a lofty moun-
tain, and the moon's shadow is seen sweeping upward from the
horizon towards the observer with a velocity which has been de-
scribed as perfectly frightful. Professor Forbes, who observed
the total eclipse of 1 842 from the Observatory of Turin, was so
confounded by the frightful velocity with which the shadow
swept over the earth from the distant Alps towards him that he
felt as if the great building on which he was standing was com-
mencing to fall over in the direction of the coming darkness.
Words can but inadequately describe the grandeur and magni-
ficence of the scene. On all sides indications are afforded that
something unusual is taking place. At the moment of totality
the darkness is usually so intense that the brighter planets and

CHAP. II.] Eclipses of the Sun. 271

stars of the ist and 2nd magnitude are seen, birds go to
roost, flowers close, and the face of nature assumes an unearthly
cadaverous hue ; while not the least striking thing is the sudden
gust of wind which frequently sweeps over the country with
some violence at the commencement of totality ; sometimes
a considerable fall takes place in the temperature of the atmo-
sphere as the time of the greatest obscuration draws near.

" During the early history of mankind, a total eclipse of the
Sun was invariably regarded with a feeling of indescribable
terror, as an indication of the anger of the offended Deity, or the
presage of some impending calamity ; and various instances are
on record of the (supposed) extraordinary effects produced by so
unusual an event. In a more advanced state of society, when
Science had begun to diffuse her genial influence over the human
mind, these vain apprehensions gave place to juster and more
ennobling views of nature ; and eclipses generally came to
be looked upon as necessary consequences flowing from the
uniform operation of fixed laws, and differing from the ordinary
phenomena of nature only in their less frequent occurrence. To
astronomers they have in all ages proved valuable in the highest
degree, as tests of great delicacy for ascertaining the accuracy of
their calculations relative to the place of the Moon, and hence
deducing a further improvement of the intricate theory of her
movements. In modern times, when the physical constitution of
the celestial bodies has attracted the attention, of many eminent
astronomers, observations of eclipses have disclosed several in-
teresting facts, which have thrown considerable light on some
important points of inquiry respecting the Sun and Moon a."

Among the Hindus a singular custom exists b. When during

a Grant, Hist. Phys. Ast., p. 359. The general holiday, and the natives signified

truth of the last sentence of this extract the swallowing of the sun by a demon by

is now more striking than it was in the usual drumming, shrieking, and blow-

1852. ing of shells, with offerings of rice."

b In my first edition I wrote " is said Nor is this an isolated incident. The

to exist," but the following paragraph, cut following account was written of the

from a newspaper in 1868, and relating eclipse of the Sun of July 29, 1878, by a

to the great eclipse of Aug. 18, 1868, resident at Fort Sill, Indian Territory,

will shew that the present reading of the to Mr. Fox, Ex-Mayor of Philadelphia,

text is preferable : — " Tuesday was a U.S., who allowed its publication in the

272 Eclipses and Associated Phenomena. [BOOK II.

a solar eclipse the black disc of our satellite is seen advancing
over the Sun, the natives believe that the jaws of some monster
are gradually eating it up. They then commence beating gongs,
and rending the air with the most discordant screams of terror and
shouts of vengeance. .For a time their efforts are productive of
no good result — the eclipse still progresses. At length, however,
the terrific uproar has the desired effect on the voracious mon-
ster ; it appears to pause, and then, like a fish that has nearly
swallowed a bait and then rejects it, it gradually disgorges the
fiery mouthful. When the Sun is quite clear of the great
dragon's mouth, a shout of joy is raised, and the poor natives
disperse, extremely self-satisfied on account of their having
(as they suppose) so successfully relieved their deity from his
late perils. For us times have now happily altered. We do
not look on a total eclipse of the Sun as a dire calamity, but
merely as one of the ordinary effects resulting from the due
working of those laws by which the Supreme Being wills to
govern the universe.

The Eclipse of Aug. 19, 1887, deficient though it was in Astrono-
mical results, yielded some rather interesting observations with
respect to the effect of the eclipse on birds. In N. E. Germany,
foresters stated that the birds, which had already begun to sing
before the eclipse took place, became of a sudden quite silent, and

Philadelphia Inquirer: — "On Monday about his head in a series of extraordinary

last we were permitted to see the eclipse gesticulations, retreated to his own quar-

of the sun in a beautiful bright sky. ters. As it happened that very instant

Not a cloud was visible- We had made was the conclusion of totality. The

ample preparation, laying in a stock of Indians beheld the glorious orb of day

smoked glass several days in advance. once more peep forth, and it was unani-

It was the grandest sight I ever beheld, mously voted that the timely discharge

but it frightened the Indians badly. of that pistol was the only thing that

Some of them threw themselves upon their drove away the shadow and saved them

knees and invoked the Divine blessing ; from the public inconvenience that would

others flung themselves flat on the ground have certainly resulted from the entire

face downward ; others cried and yelled extinction of the sun."

in frantic excitement and terror. Finally See for recent instances of popular

one old fellow stepped from the door of excitement at eclipses, 2 engravings and

his lodge, pistol in hand, and fixing his n&rr&tiveBin IS Astronomic, vol. vi.p. 248,

eyes on the darkened sun mumbled a few July 1887, and relating to the eclipses of

unintelligible words, and raising his arm, Dec. 16, 1880, and March i, 1877, as

took direct aim at the luminary, fired off seen at Tashkend and Laos (Indo-China)

his pistol, and after throwing his arms respectively.

CHAP. II.] Eclipses of the Sun. 273

showed signs of disquiet when darkness set in. Herds of deer
ran about in alarm, as did the small four-footed game. In Berlin
a scientific man arranged for observations to be made by bird-
dealers of the conduct of their feathered stock. The results were
found to vary considerably. In some cases the birds shewed
sudden sleepiness, even though they had sung before the eclipse
took place. In other cases great uneasiness and fright were
observed. Parrots shewed far more susceptibility than canaries,
becoming totally silent during the eclipse, and only returning
very slowly to their usual state.

An eclipse of the Sun may be either partial, annular, or total :
it is partial when only a portion of the Moon's disc intervenes
between the Sun and the observer on the Earth ; annular, when
the Moon's apparent diameter is less than the Sun's, so that when
the former is projected on the latter it is not sufficiently large
completely to cover it, — an annulus, or ring of the Sun, being left
unobscured ; and total when the Moon's apparent diameter is
greater than that of the Sun, which is, therefore, wholly obscured.
In an annular eclipse, when the centre of the Sun and Moon
exactly coincide, it is said to be central and annular — the Sun ap-
pearing, for a very short time, as a brilliant ring of light around
the dark body of the Moon.

I shall now proceed to describe the principal phenomena which
are usually witnessed in connexion with solar eclipses.

Not the least remarkable is the almost invariable change of
colour which the sky undergoes. Halley, in his account of the
eclipse of 1715, says: "When the eclipse was about 10 digits
(that is, when about f of the solar diameter was immersed), the
face and colour of the sky began to change from a perfect serene
azure blue to a more dusky livid colour, intermixed with a tinge
of purple, and grew darker and darker till the total immersion
of the Sun c."

At the moment of totality the suddenly altered conditions of
illumination give rise to a further change of colour which is so

c Phil. Trans., vol. xxix. p. 247. 1715. Arago gives an elaborate explanation of this.
Pop. Ast., vol. ii. p. 358, Eng. ed.

274 Eclipses and Associated Phenomena. [BOOK II.

striking that few observers fail to notice it. The lower part of
the atmosphere within the Moon's shadow is illuminated by light
from the horizon which has passed through many miles of
atmosphere near to the earth's surface and has therefore lost
much from the violet end of the spectrum. The particles floating
in the lower atmosphere therefore disperse a ruddy light which
projected upon the deep blue of the upper atmosphere gives rise
to a combination of colour which may well be described as purple
or violet. Weeden, who observed the total eclipse of 1 860 near
Miranda in Spain, says that the heavens during totality seemed
like a dark purple canopy, hanging low down as it were, in the
shape of a watch-glass, and covering the earth, excepting
in a regular belt near the horizon, where the illuminated sky
beyond the range of the obscurity reflected an orange golden
light. De La Rue, observing the same eclipse, says that the
upper part of the sky was of a deep indigo colour, shading
through a sepia tint into red and orange as it approached the
horizon. Ranyard, observing the eclipse of 1870 in Sicily, de-
scribes the colour of the sky as a deep violet, which reminded
him of the colour of the spectrum near the line H.

It has also been found that whilst the sky changes colour
during the progress of an eclipse, similar effects are produced
upon terrestrial objects. This seems to have been noticed as far
back as 840 A.D.d Kepler mentions that during the solar eclipse
which happened in the autumn of 1590, the reapers in Styria
noticed that everything had a yellow tinge6. Similar effects
have also been described in modern times f. De La Rue, in
describing the eclipse of 1860, says that the peculiar light cast on
the spectators impressed him with a feeling of solemnity never
to be effaced.

The darkness which prevails during a total eclipse of the Sun
is not usually so considerable as might be expected. It is, how-
ever, subject to much variation. Ferrer, speaking of the eclipse

d Ad Vitellionem Paralipomena, p. f Mem. R.A.S., vol. xv. pp. 12, 14,

294. and 15, 1846; xxi. passim, 1853; An-

" Ibid., p. 303. nuaire, 1846, p. 291, &c.

CHAP. II.] Eclipses of the Sun. 275

of 1806, says that at the time of total obscuration <: without
doubt the light was greater than that of the full Moon «." In
general it has been found that the darkness is sufficiently great to
prevent persons from reading, though exceptions to this rule have
been known. The faint illumination which exists at the moment
of the totality is due to light reflected from those regions of the
atmosphere which are still exposed to the direct rays of the Sun.
The corona (which will presently be described) also, no doubt,
assists in the illumination, but the light received from the corona
is small compared with that derived from the clouds outside the
region of totality, for it has frequently been noticed that the
corona casts no shadow. The degree of obscuration will also
vary according as the observer is or is not deeply immersed in
the lunar shadow — a fact first pointed out by Halley h.

Observers inside houses, or so situated amongst buildings that
the light from the horizon cannot reach them, usually have difficulty
in distinguishing objects during totality. Mountains or clouds
upon the horizon and other local causes also seem to affect
the degree of darkness, so that during the same eclipse the ex-
perience of observers in different localities may differ considerably.
Thus during the total eclipse of 1851, Piazzi Smyth could read
small print, while Professor Adams had only just sufficient light
to read the face of a box chronometer ; and Sir G. B. Airy says :
" A candle had been lighted in a lantern about a quarter of an
hour before the totality. Mr. Hasselgren was unable to read the
minutes of the chronometer face, without having the lantern held
close to the chronometer. I had prepared for the occasion
a circle described upon a card : I desired much to make a
drawing of the prominences, at least of their positions on the
limb of the moon, by marking them on this circle, but it was
impossible for me to see it, and I was obliged to approach
very closely to the lantern, in order to make the smallest memo-
randum on the card."

Mr. Lassell, who observed the same eclipse at Trollhattan, said

6 Trans. Amer. Phil. Soc., vol. vi. p. 266. 1809.
h Phil. Trans., vol. xxix. p. 250. 1715.

T 2

27(3 Eclipses and Associated Phenomena [BOOK II.

that the amount of darkness may be appreciated from the fact
that on withdrawing his eye from the telescope he could neither
see the seconds-hand of his watch nor the paper sufficiently to
write the time down '.

As previously remarked, a solar eclipse of large magnitude and
still more a Total eclipse is always accompanied by a decided
decrease in the temperature of the air (in the shade). Mr. G. J.
Symons from observations in 1858, 1860, and 1870, concludes that
the air is coldest about £ hour after the time of the Conjunction
of the Sun and Moon.

In the case of the eclipse of 1 842, it was remarked by Piola at
Lodi, and by O. Struve at Lipesk, that although the obscurity was
such that stars of the 2nd and 3rd magnitudes ought to have been
visible, yet only those of the ist magnitude were actually seen k.
M. Belli explained this curious fact by reference to a physiological
principle. He remarked that during the short interval of total
obscuration the eye has not sufficient time to recover from the
dazzling effect of the Sun's rays, and consequently is unable to
take advantage of the obscurity which actually prevails J. The
suddenness with which the light succeeds the darkness after
a total eclipse of the Sun is well known. Halley suggested
2 explanations of the phenomenon. Ist. That previously to the
total obscuration the pupil of the eye might be very much
contracted by viewing the Sun, and consequently the organ
of vision would be less likely to suffer by the effulgence of the
light than at the instant of emersion, when the pupil has again ex-
panded. 2nd. That, as the Eastern margin of the Moon, at which
the Sun disappeared, had been exposed for a fortnight to the
direct action of the solar rays, the heat generated during this
period might cause vapours to ascend in the lunar atmosphere,
which, by their interposition between the Sun and the Earth,
would have the effect of tempering the effulgence of the solar
rays passing through them. On the other hand, the Western

1 Mem. E.A.S., vol. xxi. p. 47, 1853 ; Biblioth&que Universelle de Geneve, vol.
and see Mem. R.A.S., vol. xli. p. 185. xliv. p. 368.

k Giorn. delV lit. Lomb., vol. iv.p. 341 ; l Gioi*n. deW Int. Lomb., vol. iv. p. 341 .

CHAP. II.]

Eclipses of the Sun.

277

Fig. IS2-

margin of the Moon, at which the Sun re-appeared, had just
experienced a night of equal length, during which the vapours
suspended in the lunar atmosphere had been undergoing a course
of precipitation upon the Moon's surface under a process of
cooling. In this case, therefore, the solar rays would meet with
less obstruction in passing through the lunar atmosphere, and,
consequently, it was reasonable to suppose that they would
produce a more intense effect m. The second hypothesis requires
us to suppose the presence of a lunar atmosphere, the existence of
which modern observation tends to disprove. The first is doubt-
less the true explanation.

When the disc of the Moon advancing over that of the Sun has
reduced the latter to a thin crescent, it is usually noticed that
immediately before the beginning
and after the end of complete ob-
scuration, the crescent appears as
a band of brilliant points, separated
by dark spaces so as to give it the
appearance of a string of beads
which appear to move and merge
into one another. While the Moon's
limb is seen projected upon the
sun's disc it appears perfectly
smooth. No lunar mountains can
be detected projecting beyond the
general outline. The hypothesis usually advanced to account
for this smoothness of the Moon's limb is that the irradiation
from the bright background of the solar surface projects over
the lunar limb like a fringe, and forms a new even limb inside
the true rough lunar limb. As the solar crescent becomes thin,
the irradiation fringe vanishes wherever a lunar projection breaks
through the thin line of solar light.

These phenomena are generally known as Bailys Beads, having
received their name from the late Mr. Francis Baily, who was

BAILY S BEADS.

111 Phil. Trans., vol. xxix. p. 248. 1715.

278 Eclipses and Associated Phenomena. [BOOK II.

the first to describe them in detail n. His original memoir was
published in 1836, and from it I make the following quo-
tation : —

"When [previous to the totality] the cusps of the Sun were about 40° asunder, a
row of lucid points, like a string of bright beads, irregular in size and distance from
each other, suddenly formed round that part of the circumference of the Moon that
was about to enter, or which might be considered as having just entered, on the Sun's
disc. Its formation indeed was so rapid, that it presented the appearance of having
been caused by the ignition of a train of gunpowder. This I intended to note as the
correct time of the formation of the annulus, expecting every moment to see the
thread of light completed round the Moon, and attributing this serrated appearance
of the Moon's limb (as others had done before me) to the lunar mountains, although
the remaining portion of the Moon's circumference was comparatively smooth and
circular, as seen through the telescope. My surprise, however, was great on finding
that these luminous points, as well as the dark intervening spaces, increased in
magnitude, some of the contiguous ones appearing to run into each other like drops
of water ; for the rapidity of the change was so great, and the singularity of the
appearance so fascinating and attractive, that the mind was for the moment distracted
and lost in the contemplation of the scene, so as to be unable to attend to every
minute occurrence. Finally, as the Moon pursued her course, these dark intervening
spaces (which, at their origin, had the appearance of lunar mountains in high relief,
and which still continued attached to the Sun's border) were stretched out into long,
black, thick parallel lines, forming the limbs of the Sun and the Moon ; when, all at
once, they suddenly gave way, and left the circumferences of the Sun and Moon in
those points, as in the rest, comparatively smooth and circular, and the Moon
perceptibly advanced on the face of the Sun °."

Mr. Baily then goes on to describe the appearances which he
saw after the total obscuration ; they were, however, substantially
the same as those recorded above.

The most recent full account of " Baily's Beads " is due to
Mr. Lewis Swift, an American astronomer who observed the
eclipse of July 29, 1878, at Denver, Colorado. He says : —

"At the eclipse of 1869, I was so captivated with the number, magnitude, and
unexpected brilliancy of the protuberances, that I failed to give particular attention
to the beautiful phenomenon of Baily's Beads. On this occasion I observed it very
carefully, and found it one of the most striking and fascinating features of the
whole eclipse. Several seconds previous to the formation of the beads, I observed,
near each end of the solar crescent, a phenomenon which I have never seen described
in the books. Though reminding me of the ' Black Drop,' which I saw at the late
transit of Mercury, it was very different from it. At the risk of being considered
prolix, I will describe it, though to be appreciated it must be seen. Imagine a long

n They were noticed long before his time.
0 Mem. R.A.S., vol. x. p. 5. 1838.

CHAP. II.] Eclipses of the Sun. 279

and very narrow crescent cut in a door between two rooms, one brilliantly lighted,
the other dark, the observer being in the farther end of the latter (imagined to be a
very long one) looking at the crescent with his telescope. The appearance was as if
two concealed persons in the lighted room, one each side of the crescent, were busily
engaged in rapidly protruding and withdrawing a series of long slim black objects
like slate pencils. They were not broad at their bases as is the ' Black Drop,' and,
unlike the latter, were not, except in two instances, opposite each other. They were
seen only near each end of the crescent. This phenomenon was as unique as it was
unexpected, and lasted for but two or three seconds, and then entirely ceased at
each end simultaneously, but recommenced in one or two seconds, but farther from
the end of the lune, and the images were more blunt and less symmetrical, though
their motions were as before. This lasted but a short time, when all motion ceased,
as if preparing for a grand denouement, and from each end of the crescent, now
reduced to a narrow curved line of light, the beads (which are luminous, and thus
unlike the ' Black Drop ') began to form from each end simultaneously, and in less
than a half second were completed. They were nearly square, and increased in size
from each end of the crescent to the centre, which was the largest in exact mathe-
matical ratio. So symmetrical were they that if half of them had been superimposed
on the other half they would have agreed in number, curvature, shape, and distance.
They were visible but a short time — say two or three seconds — when, giving a few
pulsating tremors, they vanished altogether. When I take into consideration the
exact uniformity of their formation as to size, shape, etc., I cannot subscribe to the
dogma that they are only the sun's light shining through the interstices of the lunar
mountains. In this case part of the moon's contour, where they were formed, was
smooth, while the other was exceedingly rough, yet the beads were the same in both
localities. And those formed at the beginning are precisely similar to those at the
close of totality, and those of one eclipse just like those of all — total and annular —
that have occurred since they were first described by Baily. The assertion here
seems justifiable that the cause of Baily's Beads is still enshrouded in darkness P."

The earliest account of the phenomenon of the beads is con-
tained in Halley's memoir on the total eclipse of 1715. He says :
" About 2 minutes before the total immersion, the remaining part
of the Sun was reduced to a very fine horn, whose extremities
seemed to lose their acuteness, and fo become round like stars ; and,
for the space of about a quarter of a minute, a small piece of the
Southern horn of the eclipse seemed to be cut off from the rent by
a good interval, and appeared like an oblong star rounded at
both ends q." The first annular eclipse in which it appears that
any beads were seen was that of Feb. 18, 1736-7, observed by
Maclaurin r.

One of the most interesting appearances seen during a total

i> Washington Observations, 1876, Ap- 1 Phil. Trans., vol. xxix. p. 248. 1715.

pendix III. p. 227. r Phil. Trans., vol. xl. p. 177. i?37-

280 Eclipses and Associated Phenomena. [BOOK II.

eclipse of the Sun is the corona, or halo of light which surrounds
the Moon. It usually appears only a few seconds previous to the
total extinction of the Sun's light, and continues visible for
about the same interval of time after its reappearance. In
general, it may be compared to the nimbus commonly painted
around the heads of the Virgin Mary, the Apostles, &c. Different
explanations have been advanced to account for this phenomenon :
Kepler thought it due to the presence of an atmosphere round
the Moon s : La Hire suggested that it might be produced by the
reflection of the solar rays from the inequalities of the Moon's
surface, contiguous to the edge of her disc, combined with their
subsequent passage through the Earth's atmosphere*; the late
Professor Baden Powell once conducted a series of experiments
which tended strongly to support the idea that refraction was
the cause of it u : on the whole, however, it is now tolerably clear
that it is due to something in the nature of an atmosphere about the
Sun. Its figure, the nebulous structures which are seen in it
all gradually diminishing in density onwards, point to the sup-
position of its being due to matter encompassing the solar orb,
and gravitating everywhere towards its centre. Delisle con-
jectured that the luminous ring might be occasioned by the
diffraction of the solar rays which pass near the Moon's edge x,
but Sir David Brewster shewed that this theory, though ingenious,
is quite untenable y.

Judged by photographic results, the solar corona is very much
fainter than the Moon, for whilst its outer portion has been found
to fail utterly to make any impression on a plate after an exposure
of 5 seconds, the Moon has been photographed perfectly in O' i to
O'2 seconds. Moreover Federow in 1842 ; Swan and Chevallier
in 1851 ; and Lespiault, Burat, and Cuillier in 1860, all observed,
and specially recorded, that no shadow was cast by the corona.

The earliest historical allusion to the corona is made by Philo-
stratus. He mentions that the death of the Emperor Domitian

8 Ad Vitell. Paralipom., p. 302; Spit. u Mem. R.A.S., vol. xvi. p. 301. 1847.

Astron., p. 893. x Mem. Acad. des Sciences, 1715, p. 166

* Mem. Acad. des Sciences, 1 715, p. 161 el seq.

et seq. 1 Edin. Encyc., art. Astronomy.

CHAP. II.] Eclipses of the Sun. 281

had been ' announced ' previously by a total eclipse of the sun.
"In the heavens there appeared a prodigy of this nature. A
certain corona, resembling the Iris, surrounded the orb of the
Sun and obscured his light z ; " (i. e., it appeared coincidently
with the total obscuration of his light). Plutarch is still more
precise in his allusion. Speaking of a total eclipse of the Sun
which had recently happened, he endeavours to shew why the
darkness arising from such phenomena is not so profound as
that of night. He begins by assuming, as the basis of his
reasoning, that the Earth greatly exceeds the Moon in size, and
after citing some authorities, he goes on to say : — " Whence it
happens that the Earth, on account of its magnitude, entirely
conceals the Sun from our sight. . . . But even although the
Moon should at any time hide the whole of the Sun, still the eclipse
is deficient in duration, as well as amplitude, for a peculiar
effulgence is seen around the circumference, which does not
allow the obscurity to become very intense or complete." ('AAAa
u>erai TLS avyrj Tiepl rrjv trvv, OVK ewcra fiaOelav ylvta-Qai rr]v
KCU anparov*.) The luminous ring seems to have been
noticed by Clavius during the eclipse of April 9, 1567 : he
thought that it was merely the uncovered margin of the Sun's
disc ; but Kepler shewed that this was impossible.

There are one or two well-authenticated instances of the
corona being visible during partial eclipses of the Sun. In 1 842,
M. D'Hombre Firmas, at Alais, which was contiguous to, though
not actually in the path of the shadow, states that, " every one
remarked the circle of pale light which encompassed the Moon
when she almost covered the Sun b." Several observers of this
eclipse noticed that the ring at first appeared to be brightest on
the side of the solar disc which was first covered by the Moon,

*LifeofApolloniusofTyana,'by'P}iil- have given in the text. But I am not

ostratus, Bk. viii. cap. 23. The passage satisfied that he has done so on sufficient

will be found quoted in Ast. Nach., vol. grounds.

xxvii. No. 1838, March 31, 1871; and in • Plut., Opera Mor. et Phil. vol. ix. p.

Observatory, vol. ix. p. 129, March 1886, 682. Ed. Lipsiae, 1778.

where Lynn calls in question both the b Annuaire, 1846, p. 339.
statements and the deductions which I

282 Eclipses and Associated Phenomena. [BOOK II.

but that previously to the close of the total phase, it was
brightest at the part where the Sun was about to reappear0.

Not the least beautiful phenomena seen during a total solar
eclipse are the "Red Flames," which become visible around the
margin of the Moon's disc immediately after the commencement
of the total phase. Mr. Dawes so minutely described them,
as they appeared to him in July 1851, that I cannot do better
than quote his words. He says : —

" Throughout the whole of the quadrant from north to east there was no visible
protuberance, the corona being uniform and uninterrupted. Between the east and
south points, and at an angle of about 115° from the north point, appeared a large
red prominence of a very regular conical form. When first seen it might be about
i £' in altitude from the edge of the Moon, but its length diminished as the Moon
advanced.

" The position of this protuberance may be inaccurate to a few degrees, being
more hastily noticed than the others. It was of a deep rose colour, and rather paler
near the middle than at the edges.

"Proceeding southward, at about 145° from the north point, commenced a low
ridge of red prominences, resembling in outline, the tops of a very irregular range of
hills. The highest of these probably did not exceed 40". This ridge extended
through 50° or 55°, and reached, therefore, to about 197° from the north point, its
base being throughout formed by the sharply-defined edge of the Moon. The
irregularities at the top of the ridge seemed to be permanent, but they certainly
appeared to undulate from the west towards the east ; probably an atmospheric
phenomenon, as the wind was in the west.

" At about 220° commenced another low ridge of the same character, and extended
to about 250°, less elevated than the other, and also less irregular in outline, except
that at about 225° a very remarkable protuberance rose from it to an altitude of !•£•',
or more. The tint of the low ridge was a rather pale pink ; the colour of the more
elevated prominence was decidedly deeper, and its brightness much more vivid. In
form it resembled a dog's tusk, the convex side being northwards, and the concave to
the south. The apex was somewhat acute. This protuberance, and the low ridge
connected with it, were observed and estimated in height towards the end of the
totality.

"A small double-pointed prominence was noticed at about 255°, and another low
one with a broad base at about 263°. These were also of the rose-coloured tint, but
rather paler than the large one at 225°. 4

" Almost directly preceding, or at 270°, appeared a bluntly triangular pink body,
suspended, as it were, in the corona. This was separated from the Moon's edge when
first seen, and the separation increased as the Moon advanced. It had the appearance
of a large conical protuberance, whose base was hidden by some intervening soft and
ill-defined substance, like the upper part of a conical mountain, the lower portion of
which was obscured by clouds or thick mist. I think the apex of this object must
have been at least i' in altitude from the Moon's limb when first seen, and more than

c Mem. R.A.S., vol. xv. p. 1.6. 1846.

CHAP. II.] Eclipses of the Sun. 283

i £' towards the end of total obscuration. Its colour was pink, and I thought it paler
in the middle.

" To the north of this, at about 280° or 285°, appeared the most wonderful
phenomenon of the whole, A red protuberance, of vivid brightness and very deep
tint, arose to a height of, perhaps, i-jj-' when first seen, and increased in length to 2',
or more, as the Moon's progress revealed it more completely. In shape it somewhat
resembled a Turkish cimeter, the northern edge being convex, and the southern
concave. Towards the apex it bent suddenly to the south, or upwards, as seen in the
telescope. Its northern edge was well defined, and of a deeper colour than the rest,
especially towards its base. I should call it a rich carmine. The southern edge was
less distinctly defined, and decidedly paler. It gave me the impression of a somewhat
conical protuberance, partly hidden on its southern side by some intervening substance
of a soft or flocculent character. The apex of this protuberance was paler than the
base, and of a purplish tinge, and it certainly had a flickering motion. Its base was,
from first to last, sharply bounded by the edge of the Moon. To my great astonish-
ment, this marvellous object continued visible for about 5 seconds, as nearly as I could
judge, after the Sun began to reappear, which took place many degrees to the south of
the situation it occupied on the Moon's circumference. It then rapidly faded away,
but it did not vanish instantaneously. From its extraordinary size, curious form, deep
colour, and vivid brightness, this protuberance absorbed much of my attention ; and I
am, therefore, unable to state precisely what changes occurred in the other phenomena
towards the end of the total obscuration.

" The arc from about 283° to the north point was entirely free from prominences,
and also from any roseate tint."

Astronomers were long unable to determine the nature of
these rose-coloured emanations ; but it is now accepted that they
belong to the Sun and consist of gaseous matter (chiefly hydro-
gen) in an incandescent state rushing upwards with inconceiv-
able velocity.

One of these prominences, measured by De La Rue in 1860,
was 44,000 miles in vertical height above the Sun's surface.

Julius Firmicus, speaking of the eclipse of July 17, 334, makes
a remark which may apply to this phenomenon ; otherwise the
earliest recorded account of the Red Flames is by Captain
Stannyan, who observed them at Berne during the total eclipse
of 1 706. He writes to Flamsteed : —

"That the Sun was totally darkened there for 4^ minutes of time; that a fixed
star and a planet appeared very bright ; and that his getting out of his eclipse was
preceded by a blood-red streak of light from its left limb, which continued not longer
than 6 or 7 seconds of time ; then part of the Sun's disc appeared all of a sudden, as
bright as Venus was ever seen in the night ; nay, brighter ; and in that very instant
gave a light and shadow to things as strong as the Moon uses to dod."

d Phil. Tran*., vol. xxv. p. 2240. 1706.

284 Eclipses and Associated Phenomena. [BOOK II.
On this communication Flamsteed remarks ; —

" The Captain is the first man I ever heard of that took notice of a red streak
preceding the emersion of the Sun's body from a total eclipse. And I take notice
of it to you [the Royal Society], because it infers that the Moon has an atmosphere ;
and it3 short continuance, if only 6 or 7 seconds' time, tells us that its height was not
more than 5 or 6 hundredths part of her diameter6."

The Red Flames were seen by Halley, Louville f , and C. Hayes
in 1715, and afterwards by Vassenius, at Gottenberg, who

says : —

"But what seemed in the highest degree worthy, not merely of observation, but
also of the attention of the illustrious Royal Society, were some reddish spots which
appeared in the lunar atmosphere without the periphery of the Moon's disc, amounting
to 3 or 4 in number, one of which was larger than the other, and occupied a situation
about midway between the south and west. These spots seemed in each instance to
be composed of 3 smaller parts or cloudy patches of unequal length, having a certain
degree of obliquity to the periphery of the Moon. Having directed the attention of
my companion to the phenomenon, who had the eyes of a lynx, I drew a sketch of its
aspect ; but while he, not being accustomed to the use of the telescope, was unable
to find the Moon, I, again with great delight, perceived the same spot, or, if you
choose, rather the invariable cloud occupying its former situation in the atmosphere
near the Moon's periphery "."

A " Red-Flame " of a greenish-blue tinge has been noticed.
This Arago considered to be an effect of contrast.

The Red Flames have also been noticed in annular eclipses,
as in that of 1737, observed by Maclaurin, which appears to be
the earliest in which the phenomenon was seenh ; and in partial
eclipses, of which that of 1605, observed by Kepler, is probably
the first '.

The aspect presented by the Moon during eclipses of the Sun
is frequently very singular. Kepler stated that the Moon's surface
is occasionally distinguishable by a ruddy hue k. Baily, in his
account of the annular eclipse of 1 836, states, that " previous to
the formation of the ring, the face of the Moon was perfectly
black ; but on looking at it through the telescope, during the
annulus, the circumference was tinged with a reddish purjjle colour,
which extended over the whole disc, but increased in density of

" Phil. Trans., vol. xx. p. 2241. 1706. h Phil. Trans., vol. xl. p. 181. 1737.

f Mem. R.A.S., vol. xxi. p. 90. 1853. ' De Stelld Novd, p. 116.

8 Phil. Trans., vol. xxviii. p. 135. 1733. k Epit. Astron., p. 895.

CHAP. II.] Eclipses of the Sun. 285

colour, according to the proximity to the centre, so as to be in
that part nearly black1." Vassenius in 1733 and Ferrer in 1806
are the only observers who state that they have seen the irregu-
larities in the Moon's surface during a central eclipse, whether
total or annular m. Arago and others tried to do so in 1842, but
failed. The fact that the lunar inequalities sometimes are seen
and at other times are not seen is doubtless owing to meteoro-
logical causes.

In 1842 Arago saw the dark contour of the Moon projected
upon the bright sky 40™ after the commencement of the eclipse.
He ascribes the phenomenon to the projection of the Moon upon
the solar atmosphere, the brightness of which, by an effect of
contrast, rendered the outline of the Moon's dark limb discern-
ible n. The phenomenon appears to be a rare one : at least it is
recorded by only 3 recent observers °.

On several occasions attempts have been made to detect the
Moon's shadow in the course of its passage over the surface of
the Earth. Airy in 1851 succeeded in observing it, but he failed
in 1842, in which year, however, Plana and Forbes were more
fortunate. The difficulty arises from the immense velocity of the
shadow — about 30^ miles per minute. The earliest historical
record of the eclipse-shadow being seen occurs in Duillier's
account of the eclipse of May 12, 1706 p.

According to M. Laussedat, one of the horns of the solar
crescent in 1 860 appeared for a short time rounded and truncated.
The other horn was contracted nearly to a point, and a small
patch of light wholly detached was visible beyond the extremity
of this cusp.

1 Mem. R.A.S., vol. x. p. 17. 1838. Not., vols. xxvii. p. 185, March 1867, and

m Phil. Trans., vol. xxxviii. p. 135, xxxiii. pp. 468 and 577, June, &c. 1873;

J733; Trans. Amer. Phil. Soc., vol. vi. Ast. Reg., vol. xiii. p. 9, Jan. 1875.

p. 267, 1809. P Mem. Acad. des Sciences, 1706, p. 113

a Annuaire, 1846, p. 372. (Hist.); Phil. Trans., vol. xxv. p. 2243,

0 Noble, Pratt, and Neison, Month. 1706.

286 Eclipses and Associated Phenomena. [BOOK II.

CHAPTER III.

THE TOTAL ECLIPSE OF THE SUN
OF JULY 28, 1851.

Observations by Airy. — By Hind.— By Lassell.

NOT the least interesting of the total eclipses of the Sun that
have occurred within the last half-century was that of July
28, 1851. Though not visible in England, it was seen to great
advantage in Sweden, to which country many astronomers went
at the time for the purpose of observing the eclipse. The follow-
ing remarks are from the pen of Sir G. B. Airy, the then Astro-
nomer Koyal, who observed the eclipse at Gottenberg : —

" The approach of the totality was accompanied with that indescribably mysterious
and gloomy appearance of the whole surrounding prospect, which I have seen on a
former occasion. A patch of clear blue sky in the zenith became purple-black while
I was gazing on it. I took off the higher power with which I had scrutinized the
Sun, and put on the lowest power (magnifying about 34 times). With this I saw
the mountains on the Moon perfectly well. I watched carefully the approach of the
Moon's limb to that of the Sun, which my graduated dark glass enabled me to see in
great perfection : I saw both limbs perfectly well defined to the last, and saw the line
becoming narrower, and the curves becoming sharper, without any distortion or
prolongation of the limbs. I saw the Moon's serrated limb advance up to the Sun's,
and the light of the Sun glimmering through the hollows between the mountain
peaks, and saw these glimmering spots extinguished one after another in extremely
rapid succession, but without any of the appearances which Mr. Baily has described.
. . . . I have no means of ascertaining whether the darkness really was greater
in the eclipse of 1842. I am inclined to think, that in the wonderful, and, I may say,
appalling obscurity, I saw the grey granite hills, within sight of Hvalas, more dis-
tinctly than the darker country surrounding the Superga. But whether, because in
1851 the sky was much less clouded than in 1842 (so that the transition was from
a more luminous state of sky, to a darkness nearly equal in both cases), or from
whatever cause, the suddenness of the darkness in 1851 appeared to be much more
striking than in 1842. My friends, who were on the upper rock, to which the path

Figs. 133-8.

Plate XVIII.

(Airy.}

(Carrington.)

(Dawes.}

(Hind)

(R. Stephenson, M.P.)

(&. Williams.')

THE TOTAL ECLIPSE OP THE SUN OP JULY 28, 1851.

VIEW8 OF THE BED FLAMES.

CHAP. III.] Total Eclipse of the Sun, July 28, 1851. 287

was very good, had great difficulty in descending. A candle had been lighted in a
lantern, about a quarter of an hour before the totality ; Mr. Hasselgren was unable
to read the minutes of the chronometer's face without having the lantern held close
to the chronometer.

"The corona was far broader than that which I saw in 1842 ; roughly speaking,
its breadth was a little less than the Moon's diameter, but its outline was very
irregular. I did not remark any beams projecting from it which deserved notice as
much more conspicuous than the others; but the whole was beamy, radiated in
structure, and terminated (though very indefinitely) in a way which reminded me of
the ornament frequently placed round a mariner's compass. Its colour was white,
and resembling that of Venus. I saw no flickering or unsteadiness of light. It was
not separated from the Moon by any dark ring, nor had it any annular structure : it
looked like a radiating luminous cloud behind the Moon. . . . The form of the
prominences was most remarkable. One reminded me of a boomerang. Its colour,
for at least two-thirds of its width, from the convexity to the concavity, was full lake
red ; the remainder was nearly white. The most brilliant part of it was the swell
farthest from the Moon's limb ; this was distinctly seen by my friends and myself
with the naked eye. I did not measure its height; but judging generally by its
proportion to the Moon's diameter, it must have been 3'. This estimation, perhaps,
belongs to a later period of the eclipse. ... It was impossible to see the changes
that took place in the prominences, without feeling the conviction that they belonged
to the Sun, and not to the Moon.

" I again looked round, when I saw a scene of unexpected beauty. The southern
part of the sky, as I have said, was covered with uniform white cloud ; but in the
northern part were detached clouds, upon a ground of clear sky. This clear sky was
now strongly illuminated to the height of 30° or 35°, and through almost 90° of
azimuth, with rosy red light shining through the intervals between the clouds.
I went to the telescope, with the hope that I might be able to make the polariza-
tion-observation (which, as my apparatus was ready to my grasp, might have been
done in 3 or 4 seconds), when I saw the sierra, or rugged line of projections, had
arisen. This sierra was more brilliant than the other prominences, and its colour
was nearly scarlet. The other prominences had perhaps increased in height, but no
additional new ones had arisen. The appearance of this sierra, nearly in the place
where I expected the appearance of the Sun, warned me that I ought not now to
attempt any other physical observation. In a short time the white Sun burst forth,
and the corona, and every other prominence, vanished.

" I withdrew from the telescope, and looked round. The country seemed, though
rapidly, yet half unwillingly, to be recovering its usual cheerfulness. My eye, how-
ever, was caught by a duskiness in the south-east, and I immediately perceived that
it was the eclipse-shadow in the air, travelling away in the direction of the shadow's
path. For at least 6 seconds this shadow remained in sight, far more conspicuous to
the eye than I had anticipated a."

Mr. J. R. Hind watched the eclipse at Rsevelsberg, near Engel-
holm. He says: —

".The moment the Sun went out the corona appeared ; it was not very bright, but
this might arise from the interference of an extremely light cloud of the cirrus class

a Mem. E.A.S., vol. xxi. p. 5. 1853.

288 Eclipses and Associated Phenomena. [BOOK II.

which overspread the Sun at the time. The corona was of the colour of tarnished
silver, and its light seemed to fluctuate considerably, though without any appearance
of revolving. Bays of light, the aigrettes, diverged from the Moon's limb in every
direction, and appeared to be shining through the light of the corona. In the tele-
scope many rose-coloured flames were noticed ; one, far more remarkable than the
rest, on the western limb, could be distinguished without any telescopic aid ; it was
curved near its extremity, and continued in view 4 seconds after the Sun had dis-
appeared, i. e., after the extinction of ' Baily's beads,' which phenomena were very
conspicuous in this eclipse, particularly before the commencement of the totality.
In this case they were clearly to be attributed to the existence of many mountains
and valleys along the Moon's edge, the Sun's light shining through the valleys and
between the mountain ridges, so as to produce the appearance of luminous drops or
beads, which continued visible some seconds. The colour of the ' flames ' was a full
rose red at the borders, gradually fading off, towards the centres, to a very pale
pink. Along the southern limb of the Moon, for 40° or upwards, there was a
constant succession of very minute rose-coloured prominences, which appeared to
be in a state of undulation, though without undergoing any material change of
form. An extremely fine line, of a violet colour, separated these prominences from
the dark limb of the Moon. The surface of our satellite, during the total eclipse,
was purplish in the telescope ; to the naked eye it was by no means very dark, but
seemed to be faintly illuminated by a purplish grey light of uniform intensity, on
every part of the surface.

" The aspect of nature during the total eclipse was grand beyond description. A
diminution of light over the Earth was perceptible a quarter of an hour after the
beginning of the eclipse ; and about ten minutes before the extinction of the Sun, the
gloom increased very perceptibly. The distant hills looked dull and misty, and the
sea assumed a dusky appearance, like that it presents during rain ; the daylight that
remained had a yellowish tinge, and the azure blue of the sky deepened to a purplish
violet hue, particularly towards the north. But notwithstanding these gradual
changes, the observer could hardly be prepared for the wonderful spectacle that
presented itself, when he withdrew his eye from the telescope, after the totality had
come on, to gaze around him for a few seconds. The southern heavens were then of
a uniform purple-grey colour, the only indications of the Sun's position being the
luminous corona, the light of which contrasted strikingly with that of the surrounding
sky. In the zenith and north of it, the heavens were of a purplish-violet, and
appeared very near ; while in the north-west and north-east, broad bands of yellowish
crimson light, intensely bright, produced an effect which no person who witnessed it
can ever forget. The crimson appeared to run over large portions of the sky in these
directions, irrespective of the clouds. At higher altitudes the predominant colour
was purple. All nature seemed to be overshadowed by an unnatural gloom. The
distant hills were hardly visible, the sea turned lurid red, and persons standing near
the observer had a pale livid look, calculated to produce the most painful sensations.
The darkness, if it can be so termed, had no resemblance to that of night. At
various places within the shadow, the planets Venus, Mercury, and Mars, and the
brighter stars of the first magnitude, were plainly seen during the total eclipse.
Venus was distinctly seen at Copenhagen, though the eclipse was only partial in that
city ; and at Dantzic she continued in view 10 minutes after the Sun had reappeared.
Animals were frequently much affected. At Engelholm, a calf which commenced
lowing violently as the gloom deepened, and lay down before the totality had

CHAP. III.] Total Eclipse of the Sun, July 28, 1851. 289

commenced, went on feeding quietly enough very soon after the return of daylight.
Cocks crowed at Elsinborg, though the Sun was only hidden there 30 seconds, and
the birds sought their resting-places, as if night had come on V

Mr. W. Lassell, who stationed himself near the Trollhatten
Falls, thus describes the total obscuration : —

" I may attempt, but I cannot accomplish, an adequate description of the marvellous
appearances, and their effect upon the mind, which were crowded into this small
space of 3^ minutes, — an interval which seemed to fly as if it were composed of
seconds and not of minutes ! Perhaps a naked-eye observer would more fully grasp
the awful effect of the sudden extinguishment of light, — the most overpowering of
these appearances, — for, my eye being directed through the telescope, I must have
been less, though sufficiently, struck with the unprecedented sensation of such
instantaneous gloom. The amount of darkness may be appreciated from the fact
that, on withdrawing my eye from the telescope, I could neither see the second-hands
of my watch, nor the paper sufficiently to write the time down ; and was only able
to do so by going to the candle, which T had by me burning on the table. Probably
the suddenness of the gloom, not giving time for the expansion of the pupil of the
eye, increased the sensation of apparent darkness ; as I was obliged to repair close to
the candle for the requisite light. After registering the time, I looked out for a few
minutes with the naked eye over the landscape, north and south. The north was
clear, and the line of horizon could be distinctly seen. The Sun, covered by the
Moon, looking like a blue patch in the sky, had now the corona very symmetrically
formed around it ; but the Moon appeared to my unassisted eye to be not very round
or smooth at its edge, — more as if one had rudely cut out with a knife on a board a
circular disc of card, — the edges somewhat jagged and irregular in outline.

" The corona itself was perfectly concentric and radiating, some of the rays
appearing in some parts of the circumference a little longer than in others ; but the
inequality was not great. I am unable to say whether the corona when first found
was at all eccentric, for, as it is evident that any one observing with a telescope up to
the moment of obscuration must have time to take off the dark glass before the
corona can be seen, and as I had also to note the time, the centres of the Sun and
Moon must have been pretty closely approximating before I again applied the eye to
the telescope. It was indeed a great exercise of self-denial to spare the time from
the exciting phenomena, which was necessary for accurately recording the duration
of total darkness ; but being inclined to think such record would be disregarded by
many observers, I took my resolution to secure it."

The writer then proceeds to say that Venus was the only object
visible to the naked eye. The corona he describes as " brilliant,"
and he considers that it afforded, speaking roughly, as much
light as the Moon usually does when at its full.

" I had intended to direct my attention pointedly to the detection of the ' Red
Flames,' which I had heard described as but faint phenomena. My surprise and
astonishment may therefore be well imagined when the view presented itself

b Sol. Syst., p. 71.
U

290 Eclipses and Associated Phenomena. [BOOK II.

instantly to my eye as I am about to describe, or rather to attempt to give a
notion of.

" In the middle of the field was the body of the Moon, rendered visible enough by
the light of the corona around, attended by the apparent projections from behind the
Moon of which I have attempted to sketch the positions. The effect upon my own
mind of the awful grandeur of the spectacle I feel I cannot fully communicate. The
prominences were of the most brilliant lake colour, — a splendid pink, quite defined
and hard. They appeared to me to be not quiescent ; but the Moon passing over
them, and therefore exhibiting them in different phase, might convey an idea of
motion. They are evidently to my senses belonging to the Sun and not at all to the
Moon ; for, especially on the western side of the Sun, I observed that the Moon
passed over them, revealing successive portions of them as it advanced. In conformity
with this observation also, I observed only the summit of one, on the eastern side,
though my friends observing in adjoining rooms had seen at least two : the time
occupied by my noticing the time and observing with the naked eye not having
allowed me to repair again to the telescope until the Moon had covered one, and
three-fourths of the other. The point of the Sun's limit where the principal ' flame '
appeared was (I judged) a few degrees south of the place where the cluster of spots
was situated, and the flame which I observed on the eastern limb was almost exactly
where the eastern spot was situated. As, however, some prominences appeared
adjacent to parts of the Sun's limit not usually traversed by spots, the attempt to
trace a connexion fails. The first burst of light from the emergent Sun was exactly
in the place of the chief western flame, which it instantly extinguished. . . . . .

From the varying lengths of the red flames it is difficult to give an accurate estima-
tion of their magnitude ; but the extreme length of the largest, on the western
limb, may have been about 2\'. This estimation is rather rude, as I was so
absorbed in contemplating their general phenomena that I had not time for exact
measurement c."

c Mem. R.A.S., vol. xxi. p. 47. 1853.

CHAP. IV.] Annular Eclipse of the Sun, March 1858. 291

CHAPTER IV.

THE ANNULAR ECLIPSE OF THE SUN
OF MARCH 14-15, 1858.

Summary of observations in England.

OF the different eclipses which have from time to time been
visible in England, few have attracted such interest and at-
tention among all classes of society as that of March 14-15, 1858.
Though bad weather in most
cases interrupted or altogether
prevented observations, yet many
instructive features were noticed.
The line of central and annular
eclipse passed across England
from Lyme Regis, in Dorsetshire,
to the Wash, between Lincoln-
shire and Norfolk, traversing
portions of Somersetshire, Wilt-
shire, Berkshire, Oxfordshire,
and Northamptonshire. The
following summary of the obser-

ECLIPSE OP THE SUN, March 14-15,

1858 ; THE ANNULUS.

vations made, drawn up by Mr. Glaisher, will be read with
interest : —

" From returns received between Braemar and the Channel Islands, from 30 to 40
in number, it is shewn that the depression of temperature during the eclipse was
about 2-5° at stations north of the line, and nearly 3° at stations on and south of
the line of central eclipse ; that at places where the usual diurnal increase had taken
place in the morning the depression of temperature during the eclipse was greater :
and that at places where such increase had not taken place it was less than the

U 2

292 Eclipses and Associated Phenomena. [BOOK II.

above numbers. Also that at places where the sky was uniformly cloudy during
the day the decrease in the readings of a black bulb thermometer was less than 1 2°,
while at places where the sky was partially clear the depression was from 17° to
19°, and that, what temperature soever the black bulb thermometer indicated in
the morning, it fell during the eclipse to that of the temperature of the air at all
places.

" The humidity of the air was such that at places north of the line the wet bulb
thermometer read 2 '6° less ; and on and near the line the depression was 3' 2°, and
south of it was 3*7° below the adjacent dry bulb thermometer.

" At some places the humidity of the air increased at the time of the greatest
eclipse, but this was far from being universal.

" The sky was partially clear at some places on the east and south coasts, in the
Channel Islands and north of Scotland, and it was for the most part overcast else-
where. Near the southern extremity of the central line the sky was partially clear,
and at its northern extremity near Peterborough the clouds were broken ; at most
intermediate places the sky was wholly overcast. The complete ring was seen at
Charmouth, and neighbourhood near Lyme Regis, and at Peterborough, but, so far as
I can learn, at no other places. My own station was on the calculated line of central
eclipse, near Oundle, in Northamptonshire, and here I saw the Moon and Sun's
apparent upper limb coincident, or very nearly so, and therefore that I was situated
on or very near the northern limit of annularity, but distant from the centre line by
3 or 4 miles.

" It is very much to be regretted that the unfavourable weather precluded the
witnessing the very beautiful attendant phenomena upon large solar eclipses. The
time of year was unfavourable to all optical effects — whether of light and shade or
colour, independently of the particular character of the day, which was more fatal
still to their exhibition, for even where the Sun was visible their presence was only
feebly indicated at a few parts of the country.

" At Oundle the weather for some time previous to the commencement of the
eclipse was raw and ungenial for the time of year. The wind was gusty and the sky
overcast, chiefly with cirro-stratus, and dark scud hurrying past the Sun's place from
the north-west, the clouds occasionally giving way and allowing the Sun to be visible
by glimpses. Shortly after i o'clock the sky became uniformly overcast, and a small
steady rain set in for a considerable time.

" It was long before any sensible diminution of light took place. At 1 2h 39™ a
gloom was for the first time perceptible to the north, and the crescent of the Sun
shone out with a bright white light between breaks. At oh 43ra the gloom was
general, excepting around the Sun, which appeared the centre of a circle of light, and
illuminated with fine effect some bold irregular masses of cumulus in its vicinity. At
oh 45m the gloom increased, slight rain fell, and the wind rose, birds were heard
chirping and calling. At oh 53™ a severe storm might have been supposed impending,
and numerous birds were flying homewards. The deepening of the gloom was gradual
but very slow, and between ih and ih tm was at its greatest intensity ; but even at
this time the obscurity was not sufficient to require that any employment should be
suspended. Messrs. Adams and Symons, situated five feet from a shed in an
adjoining brickfield, spoke of the gloom as very intense for a period of 10 seconds,
and sufficient to render it difficult to take the readings of the thermometer. A body
of rooks rose from the ground at this moment and flew homewards ; a flock of
starlings rose together, and various small birds flew wildly about ; a hare was seen

CHAP. IV.] Annular Eclipse of the Sun, March 1858. 293

to run across a neighbouring field, as though it were daybreak ; straw rustled, and the
silence was peculiar and intense. The darkness and lull was that of an approaching
thunder-storm. Directly after the greatest intensity the gloom was sensibly and
instantaneously diminished, and the day was speedily restored to its ordinary
appearance.

"After oh 50™ the lark ceased to rise, and did not sing; at ih iom it rose again.
The collected information tends to shew that birds and animals, but particularly
the former, were affected in some degree in most places ; and that it is probable to
suppose the gloom was referred by them to the approach of evening, and this not so
much from the fact of the gloom as from the manner of its approach, without the
accompanying signs of atmospheric disturbance which usher in a storm, and to which
birds and animals are keenly sensitive.

" All over the country rooks seem to have returned to their rookeries during the
greatest obscuration ; starlings were seen in many places taking flight, whole flocks
of them together. At Oxford Dr. Collingwood remarked that a thrush commenced
its evening song. At Grantham pigeons returned to their cote. At Ventnor Dr.
Martin notes the fact that a fish confined in an aquarium, and ordinarily visible at
evening only, was in full activity about the time of the greatest gloom. In Greenwich
Park the birds were hushed and flew low from bush to bush, and at nearly all places
the song of many birds was suspended during the darkness. At Campden Hill it was
observed that the crocus closed about the same time, and at Teignmouth that its
colour changed to that of the pink hepatica.

" The darkness was not sufficient at any place to prevent moderate-sized print
being read at any convenient distance from the eye out of doors, but a difficulty was
sometimes experienced in reading the instruments. At Grantham the darkness is
described to have been about equal to the usual amount of light an hour before
sunrise ; near Oxford as about equal to that just after sunset on a cloudy day. The
general impression communicated was that of an approaching thunder-storm. The
sudden clearing up of the gloom after the greatest phase was likened by more than
one observer to the gradual, but somewhat rapid withdrawal of a curtain from the
window of a darkened room. The darkness is described to have been generally
attended by a sensation of chilliness and moisture in the air. At Oxford the clouds
surrounding the Sun were beautifully tinted with red, which merged into purple as
the obscuration increased. At Grantham as the eclipse progressed the light became
of a decided grey cast, similar to that of early morning, but at the time of the
greatest gloom it had a strong yellow tinge. At Teignmouth the diminution of light
was very great ; the sombre tints of the clouds became much deepened, and the
remaining light thrown over the landscape was lurid and unnatural. At Green-
wich the appearance of the landscape changed from a dull white to a leaden, and then
to a slate-coloured hue ; and as the darkness increased it had much the appearance
of a November fog closing in on all sides. At Wakefield the tints of the clouds
changed from the grey slate colour of clouds in a storm, and became of a purple hue.
At Oundle, my own station, the clouds were one uniform leaden grey or slate-colour,
and quite in accordance with the general character of the day, nor could I perceive
that the clouds appeared lower, or, in fact, that there was any very noticeable de-
parture from the gloom we constantly experience during dull winter weather.
Throughout the eclipse it occurred to me that the illuminating power of the Sun was
much more than might have been supposed commensurate with the unobscured
portion of the disc. When casual breaks permitted it to be visible the illuminated

294: Eclipses and Associated Phenomena- [BOOK II.

crescent up to the time of the greatest phase emitted beams of considerable brilliancy,
which marked out a luminous track in the gloom, and were clearly and well defined
in extent and figure. As the eclipse proceeded a decided change was to be observed
in the colour of the Sun itself, which became of a pure silvery brightness, like that
of Venus after inferior conjunction with the Sun. The absence of all colour in the
light was remarkable, and at the time when the annulus was nearly formed it
appeared like a line of silver wire. The departure from the usual amount of light we
are accustomed to receive on an ordinarily dull day during the greater part of the
eclipse was so inconsiderable, that we might infer approximately the real amount of
Sun our average daylight under a cloudy sky is equivalent to.

"As a photometric test during the eclipse, strips of photographic paper were
exposed for equal intervals of time every 5 minutes. The result was a scale of tints
which exhibited clearly the diminishing intensity of the light up to the period of
greatest obscuration, and the rapid increase beyond. The range of tints is low, owing
to the cloudy state of the sky, but this does not interfere with the proportionate
depths of tint ; the time of greatest darkness is distinctly shewn by the very feeble
discoloration of the paper. The instruments used at Oundle were made specially
for those observations, and were of a very delicate and accurate construction j the
meteorological observations were made by Messrs. Adams and Symons.

" In conclusion, I beg sincerely to thank those gentlemen whose returns have sup-
plied the data for this investigation, of which we may say, literally as well as
figuratively, that it exhibits only the faint outline of facts dimly visible through a
screen of clouds. I think, however, it is reasonable to infer that the great paucity of
effects and general phenomena witnessed even in places where the Sun was visible, is
due to the conditions of the atmosphere, attributable alike to climate, time of year,
and unfavourable weather, and should by no means lessen our confidence in previous
accounts of the grandeur and beauty of the attendant phenomenon upon solar eclipses.
Optical phenomena, we all know, are dependent upon the medium through which we
view them for the nature and power of the effects produced."

Defective as this record is, from a scientific point of view,
owing to the unfavourable weather having so generally inter-
fered with observations, yet it has some interest to Englishmen
by reason of the fact that phenomena of this character are so
rarely visible in England.

CHAP. V.] Total Eclipse of the Sun, July 18, 1860. 295

CHAPTER V.

THE TOTAL ECLIPSE OF THE SUN
OF JULY 18, 1860.

Extracts from the observations of Sir G. B. Airy. — Observations of the Red Flames
by Bruhns — Meteorological observations ly Lowe.

THE total eclipse of July 18, 1860, presented some noticeable
features : it owed its interest to the agreeable circumstances
connected with ita, and its importance to the very extensive
observations which were made by many astronomers in Europe,
Africa, and America.

Sir G. B. Airy stationed himself at the village of Pobes
in the North of Spain. From his memoir b I make the following
extracts : —

" On the progress of the eclipse I have nothing to remark, except that I thought
the singular darkening of the landscape, whose character is peculiar to an eclipse,
to be sadder than usual. The cause of this peculiar character I conceive to be the
diminution of light in the higher strata of the air. When the Sun is heavily clouded,
still the upper atmosphere is brilliantly illuminated, and the diffused light which
comes from it is agreeable to the eye. But when the Sun is partially eclipsed, the
illumination of the atmosphere for many miles round is also diminished, and the eye
is oppressed by the absence of the light which usually conies from it.

" I had a wax candle lighted in a lantern, as I have had at preceding total eclipses.
Correcting the appreciations of my eye by reference to this, I found that the dark-
ness of the approaching totality was much less striking than in the eclipses of 1842
and 1851. In my anxiety to lose nothing at the telescope I did not see the approach
of the dark shadow through the air ; but, from what I afterwards saw of its retreat,
I am sure it must have been very awful."

a It is to the Himalaya expedition to Spain that allusion is here made.
b Month. Not., vol. xxi. p. 9. Nov. 1860.

296 Eclipses and Associated Phenomena. [BOOK II.
After describing the Red Flames he says : —

" I may take this opportunity of stating, that the colour of these appearances was
not identical with that which I saw in 1842 and 1851. The quality of the colour
was precisely the same (full blush-red, or nearly lake), but it was diluted with white,
and more diluted at the roots of the prominences close to the Moon's limb than
in the most elevated points.

" About the middle of the totality I ceased for awhile my measures, in order to
view the prospect with the naked eye. The general light appeared to me much
greater than in the eclipses of 1842 and 1851 (one cloudy, the other hazy), perhaps
10 times as great; I believe I could have read a chronometer at the distance of
12 inches ; nevertheless, it was not easy to walk where the ground was in the least
uneven, and much attention to the footing was necessary. The outlines of the moun-
tains were clear, but all distances were totally lost ; they were in fact an undivided
mass of black to within a small distance of the spectator. Above these, to the height
perhaps of 6° or 8°, and especially remarkable on the north side, was a brilliant
yellow or orange sky, without any trace of the lovely blush which I saw in 1851.
Higher still, the sky was moderately dark, but not so dark as in former eclipses.
The corona gave a considerable body, but I did not remark either by eye-view or
by telescope-view anything annular in its structure ; it appeared to me to resemble,
with some irregularities (as I stated in 1851), the ornament round a compass card.
But the thing which struck me most was the great brilliancy of Jupiter and Procyon
so near the Sun. It was impossible that they could have been seen at all, except
under the circumstance of total absence of illumination on that part of the atmosphere
through which the light passed. I returned to my measures, but I was soon sur-
prised by the appearance of the scarlet sierra, announcing the approach of the Sun's
limb. It disappointed me, for I had reckoned on a much longer time. All our
party who were aware of the predicted duration fully believed that it must have been
very erroneous. How the time passed I cannot tell. The Sun at length appeared,
extinguishing the sierra, but the prominence and cloud remained visible, and my last
measures were taken after reappearance. The prominences, &c. were then rapidly
fading, and I quitted the telescope, not without the feeling that I had not done all
that I had intended or hoped to do."

The Red Flames were seen, and described by many of the ob-
servers ; the account given by M. Bruhns is the most complete c.
He says:—

"Just before the totality, there was visible, on the western border of the Moon,
only one protuberance and the corona ; but as the last rays of the Sun disappeared,
more protuberances started out on the eastern side, and the corona shone forth with
an intense white light, so lustrous in fact as to dim the protuberances. I remarked
that I saw them better when a clear red glass was held before my eye.

" During the totality I sketched 4 drawings, and also measured off the position-
angles of the different protuberances, counting round the circle from the north point
through the east, &c.

"The figure marked [Fig. 141. PI. XIX] was drawn during the first minute of
the totality. The first protuberance is the one already mentioned ; its position-angle

* Ast. Nach., vol. liv. No. 1292. Jan. 22, 1861.

Figs. 140-2.

Plate XIX.

(Feilitzsch.)

THE TOTAL ECLIPSE OP THE SUN OP JULY 18, I860.

TELESCOPIC VIEWS OF THE COBONA AKD BID FLAMES.

CHAP. V.] Total Eclipse of the Sun, July 18, 1860. 297

was 35°, the length of its base i|' or 2', and its height about the same. The summit
was somewhat curved, of an intense rose colour, but a little paler at the apex.

"The second protuberance, situated at 60°, was completely separated from the
Moon, there being between them an interval of %'. For part of its extent it was
parallel to the Moon's border, it then deviated from it, and ended in a point. Its
length was i^' or a', its height about |', and of a rose-colour.

"The third protuberance, having a position-angle of 75°, resembled a mountain,
and had a base of i£', and a height of fully 3'. Extending onwards for 50° from this
protuberance was a narrow fringe, first of a pale red, but a few seconds afterwards it
came over a splendid rose colour, and of a height of about £', which soon narrowed
as the Moon passed over it, until at length it was quite covered.

"A fourth protuberance existed at 155°; its base was not more than |', but the
height was as much as 1 1'. It had a hooked form with the curve trending northwards,
and likewise of a rose colour.

" During no part of the totality were there any protuberances visible in the
southern part of the Sun's disc.

"In the second minute the above-described protuberances became gradually
smaller; with the exception of the first, which retained its magnitude and figure
almost unchanged. The above-described unattached protuberance [No. a] was
reached by the Moon, and became gradually covered. By the end of the second
minute the fringe was entirely covered, and at this juncture, on turning to examine
the western border of the Moon, I perceived several protuberances, not previously
visible.

" The protuberance situated at 260°, which I will call No. 5, had, at the beginning
of the second [third?] minute, only a base of %', and about the same height, the
colour being rose.

" Between 270° and 300° extended a second streak about \' in height.

"A sixth protuberance was visible at 310°, having a base of 2', and a height of £'.

" Lastly, I found at 340° a seventh protuberance, having a base of i', and a height
of I', and of a rose colour, like all the preceding.

"On directing my attention to the first protuberance (the one at 35°), I fancied it
had grown considerably larger. The sharp edge, first seen, had disappeared, and for
a height of 3' or 4' flaming rays could be discerned, the colour (at the base a bright
rose) was, at the top, hardly perceptible, but seemed to fade off and become merged
in the corona.

" After I had observed these for about half a minute, without perceiving any
alteration, I quitted the telescope to observe the corona and the sky for a short time
with the naked eye. The black-looking Moon was surrounded by a crown of clear
light of unequal breadth. Below [S.] it was considerably greater than above [N.].
I estimated that in the former case it was f°, in the latter about |°, and the general
appearance of the thing gave me the idea that the Moon was eccentrically placed in
the corona.

" The general form of the corona appeared circular, but on the eastern side a long
ray shot out to a distance of about i° ; the breadth of its base was 3', but it tapered
down to about i£'. During the 10 seconds that my attention was directed to it,
neither the direction nor the length of the ray altered ; its light was considerably
feebler than that of the corona, which was of a glowing white, and seemed to
coruscate or twinkle.

298 Eclipses and Associated Phenomena. [BOOK II.

" With the naked eye I easily saw Venus and Jupiter, the former being much
brighter than the latter. Although I knew whereabouts Procyon, Castor, Pollux,
Mercury, and Saturn were, yet in the few seconds available for seeking for them I
failed to find them.

" My assistant, M. Auerbach, who observed the corona, and searched for the stars
during a longer period than I did, noticed in the south-western quadrant a curved ray
about 3^° in length, which I in my hurry probably overlooked. He also saw Pollux,
and another person saw Castor ; but, as far as I am aware, no more than the above 4
objects were seen by any person in Tarragona.

"Towards the end of the 3rd minute of the totality, I again looked through the
telescope, and made the drawing [Fig. 142, PI. XIX]. The western protuberances
had altered considerably since the 2nd minute ; the one at 35° had regained its original
form and size, the flaming rays, previously spoken of, having disappeared. The pro-
tuberance in 340° had become much larger, the length of its base being now about 2',
and the height i £'. The red streak extending from 270° to 300° had prolonged itself
so as to take in the protuberance at 310° [No. 6], and had altogether now a length of
50°, its height having also become augmented from \' to i', and its colour being au
intense rose. The protuberance at 260° [No. 5] was now separated by about \'
from the Moon, its breadth being nearly i', and its height |'. Finally, at 240° a new
and small protuberance had started into view, its base and height were both about j',
and rose-coloured.

"As the end of the totality advanced so the protuberances became less distinct,
the colour became brighter, and immediately after the 3rd minute of totality the pro-
tuberances at 240° and 260° disappeared ; the fringe extending itself to a length of
more than 90°, its height being i|', and embraced all the protuberances up to an
angle of 35°. On the first appearance of the solar rays all suddenly vanished, with
the exception of the first protuberance, which for some time afterwards remained
visible in the thin red glass."

Meteorology was not unrepresented in Spain, for Mr. E. J.
Lowe, at Fuente del Mar, near Santander, with 2 assistants,
during a period of 5 hours, made upwards of 4000 observations.
The following is an abstract of Mr. Lowe's results, in his own
words : —

"Commencing with underground temperature, a thermometer placed 6 inches below
the surface of the ground ranged between 67-9° and 70-7°, i.e. 2-8°; at this depth
the eclipse was not sensibly felt, whereas other thermometers, placed 4 inches,
2 inches, I inch, and \ an inch below the surface, all exhibited in a very marked
manner the effect of the eclipse. On the grass the temperature fell to 64° at 3h 5™ ;
at | inch below the surface, to 69° at 3h 15™ ; at I inch deep, to 69-5° at 3h 25™ ; at
2 inches, to 71° at 3h 55m ; at 4 inches, to 70-7° at 4h 30™ P.M.

"The temperature on the grass was 77-5° at noon, rising to 91-7° at ih 50™, and
then falling till 3h 5™, and again rising to 85° at 4* iom, giving a range of 27-7°. At
half an inch below the surface of the ground the temperature rose till ih 55™ P.M.,
when it was 78-5°, and then gradually fell to 69°, rising again to 74-7° at 4"' 30™ P.M.,
the range being 9-5°. At I inch below the surface the temperature rose till ih 55™ to
76-2°, fell till 3h 25m to 69-5°, and rose till 4h 55™ to 74-7°, the range being 6-7°. At

Fig. 143.

Plate XX.

THE TOTAL ECLIPSE OF THE SUN OP JULY 18, I860. (Tempel.)

CHAP. V.] Total Eclipse of the Sun, July 18, 1860. 301

2 inches below the surface the temperature rose till 2h 5™ to 74-4°, then fell till
3h 55ra to 7IlO°» and afterwards rose till 4h 55™ to 73-7°, the range being 3-4°; and at
4 inches below the surface the temperature rose till 2h 50™ to 73°, then fell till 4h 30™
to 7°'7°> au(i again rose till 6h P.M. to 73-2°, the range being 2-5°.

" The greatest cold on the ground occurred between 3h and 3h 5™ P.M. ; ditto, | an
inch below surface, 3h iom and 3h 15™ P.M. ; ditto, i inch, 3h 2om and 3h 25™ P.M. ;
ditto, 2 inches, 3h 5om and 3h 55™ P.M. ; ditto, 4 inches, 4h 25m and 4h 3ora P.M.

TABLE OF TEMPERATUKES.

Com-
mence-
ment of
Eclipse.

Middle
of
Eclipse.

End
of
Eclipse.

Range
during
Eclipse.

Of a blackened ball on grass

104-0

o
6.r5

94-o

o
38-5

Of a blackened ball in vacuo

131-0

66-0

104-0

65-0

In sunshine at 2 feet above ground

75-5

63-6

70-0

n-9

In sunshine 2 feet (wet bulb)

69- •>

59-3

65-5

10-2

Diff. between dry and wet bulb at 2 feet
In shade at 4 feet

6-0
70-0

4-4
64-7

4-5
71-0

1-6
6-3

In shade at 4 feet (wet bulb)
In shade at 3 feet ....

62-5
70-2

59-7
64-2

63-5
70-7

3-8
6-5

In shade at 2 feet

68-5

62-5

68-5

6-0

In shade at i foot ... .

70-7

64- 1;

70-2

*>7

"The barometer rose from ih 4Om till 2h iora 0-002 inch, then fell till 3h 5™ 0-0017
inch, and rose till end of eclipse, 0-009 incn-

"Intensity of photographic light, from salted papers conveyed, sensitised, in
Marion's dark box, exposed for 10 seconds (with a scale of from o to 5°), at the
commencement of the eclipse, 4^° becoming 4° at 2h 5m, 3° at 2h 15™, 2° at 2h 25™,
i° at 2h 40™, |° at 2h 5om, i° at 2h 55™ (clear about Sun), }° at 3", i° at 3h 5™,
2° at 3h 25™, 2^° at 3h 40™, 3° at 3h 50™, and 4° at 4h. During totality a paper exposed
for i minute gave £°.

" The wind was N.W. and N.N.W. till 4h 2om, then W.S.W., being S.W. at 4h 25™,
and South at 4h 45™. The wind was brisk at the commencement of the eclipse, quite
a calm during totality, and a gentle breeze afterwards. The distant prospect was
very clear, except during totality, when the mountains disappeared, and only near
objects were visible.

"The clouds, which were chiefly cumuli, diminished in amount till ih 50™, when
only -£$ of the sky was overcast, then increased till 2h 35™ with much cloud till
3h 55m> then again diminished to T% at the termination of the eclipse, the range
being \$ of the whole sky. Towards totality some of the cumuli became scud, which
lasted from 2h 5"" to 3h iom, giving the strongest impression that the change was due
to the eclipse.

"The morning was fine, and from 12'' 45 'r P.M. sunshine; at ih 25™ much open sky

302 Eclipses and Associated Phenomena. [BOOK II.

about the zenith; at 2h 15™ a blackness about W. horizon, and slightly so in N.
and S. ; at 2h 30™ the hills dark, and the blue sky in N. and E. very pale in colour;
at 2b 35m> hills dark, with a blue haze among the more distant mountains ; at
2h 40™, horizon due W. pink ; at 2h 45™, clear sky, in N. pink; at 2h 52™, splendid
pink in W. horizon, warm purple in summits of mountains in S., clear sky, in N.
deep lilac, and in E. very pale blue; at 2h 57ra, rapid change, the clear sky in N.
deep marine blue with a red line.

" Before totality commenced, the colours in the sky and in the hills were magnificent
beyond all description ; the clear sky in N. assumed a deep indigo colour, while in
the W. the horizon was pitch black (like night). In the E. the clear sky was very
pale blue, with orange and red, like sunrise, and the hills in S. were very red ; on the
shadow sweeping across, the deep blue in N. changed like magic to pale sunrise tints
of orange and red, while the sunrise appearance in E. had changed to indigo. The
colours increased in brilliancy near the horizon, overhead the sky was [of a] leaden
[hue]. Some white houses at a little distance were brought nearer, and assumed a
warm yellow tint ; the darkness was great ; thermometers could not be read. The
countenances of men were of a livid pink. The Spaniards lay down, and their
children screamed with fear ; fowls hastened to roost, ducks clustered together,
pigeons dashed against the sides of the houses, flowers closed (Hibiscus Africanus as
early as 2h 5m); at 2h 52m cocks began to crow (ceasing at 2h 57m, and recommencing
at 3h 5™). As darkness came on, many butterflies, which were seen about, flew as if.
drunk, and at last disappeared ; the air became very humid, so much so that the grass
felt to one of the observers as if recently rained upon. So many facts have been
noted and recorded that it is impossible to do more than give a brief statement of the
leading features."

The general result of the observations of the eclipse of 1860
was to shew conclusively that the Red Flames in solar eclipses
belong not to the Moon but to the Sun.

An interesting and valuable memoir on this eclipse was pre-
sented to the Royal Society by Mr. Warren De La Rued.

d Phil. Trans., vol. clii., 1862.

CHAP. VI.] Recent Total Eclipses of the Sun. 303

CHAPTER VI.

RECENT TOTAL ECLIPSES OF THE SUN.

Eclipse of August 18, 1868. — Observations by Col. Tennant and M. Janssen at
Gunloor. — Summary of results. — Observations of Governor J. P. Hennessy and
Capt. Reed, R.N. — Eclipse of Avgmt 7, 1869. — Observations in America by
Prof. Morton and others. — Summary of results. — Eclipse of December 22, 1870.
— English expedition in H. M.. S. Urgent to Spain. — Observations in Spain
and Sicily. — Eclipse of December II, 1871. — Observed in India. — Eclipse of
April 1 6, 1874. — Summary by Mr. W. H. Wesley of the recent observations as
to the Physical Constitution of the Corona.

eclipse of the Sun of July 18, 1860, described in the last
chapter, may be said to mark a turning-point in the history
of eclipse phenomena. It was the first in which photography
played a conspicuous part, and the experience acquired by the
numerous observers who went to Spain, paved the way for the
great photographic and other successes which marked subsequent
eclipse expeditions.

The reader who has studied what has been stated in the earlier
chapters of this Book, respecting the usual accompaniments of
eclipses of the Sun, will already have acquired a sufficiently com-
plete general insight into the subject, and therefore in the present
chapter his attention will be mainly invited to new points.

The eclipses which will be grouped together here are the fol-
lowinga: — Aug. 18, 1868; Aug. 7, 1869; Dec. 22, 1870; Dec.

* A very good general summary of the analyse. The information relating to

eclipse observations made in 1868, 1869, the 1870 eclipse is exclusively from

and 1870 (accompanied by numerous English sources drawn upon by the

illustrations) will be found in the Eng- translators. But the most exhaustive

lish edition of Schellen's Die Spectral- account by far is that furnished in Mem.

304 Eclipses and Associated Phenomena. [BOOK II.

u, 1871; April 16, 1874; April 5, 1875; July 29, 1878; May
17, 1882 ; May 6, 1883 ; Sept. 8, 1885 ; Aug. 29, 1886 ; Aug. 19,
1887.

To observe the eclipse of 1868, several expeditions were dis-
patched from Europe to the East Indies. The most important
of these was that which under the command of Major Tennant,
RE., went to Guntoor (Lat. 60° 17' 27" N., Long. 5h 2im 48s
E.) ; but important service was rendered to Science by a French
observer, M. Janssen, who, accompanied by his wife, stationed
himself at Guntoor. Another French party, under M. Stephan,
went to Siam, and a German party to Aden. This last-named
contingent included MM. Weiss, Oppolzer, and Thiele, all ex-
perienced astronomers.

Major Tennant' s arrangements were framed with the object of
( i ) investigating by the aid of a spectroscope the corona and red
names (the latter now very generally called the " Solar promin-
ences"), as regards the source of their light ; (2) examining the
light of the corona and prominences as regards the polarisation
thereof, and (3) obtaining photographs during the totality. By
a due subdivision of labour amongst the different members of
the expedition this programme was carried to a successful con-
clusion. Neglecting certain optical effects, common to every
total eclipse of the Sun, and sufficiently described already in
connection with previous eclipses, I proceed to note briefly, in
something like Major Tennant's own words, his deductions as
to the new results flowing from the labours of himself and his
colleagues b.

The corona is to be deemed an atmosphere of the Sun, not
self-luminous but shining by reflected light. This was proved
both by the spectroscope and the polariscope.

During the continuance of the totality, there was seen on the
North side of the Sun, an enormous horn of light, the apex of
which was calculated to be about 90,000 miles distant from the

K.A. S., vol. xli. 1876. This volume is to Mr. A. C. Ranyard's industry.

a magnificent compilation of Eclipse b Memoirs R.A. S., vol. xxxvii. p. i.

facts. For it science is mainly indebted 1869.

CHAP. VI.] Recent Total Eclipses of the Sun.

305

Fig. 144

Sun's limb. This object presented in a striking degree indica-
tions of a spiral structure, and was presumed to consist of
incandescent vapours of hydrogen, sodium, and magnesium.

Capt. Brannll observed that the corona was strongly polarised
everywhere in a plane passing through the Sun's centre.

The general phenomena of the total phase are thus described
by Mr. (now Sir J. P.) Hennessy c :—

"Ten minutes before the total eclipse there seemed to be a luminous crescent
reflected upon the dark body of the Moon. In another minute a long beam of light,
pale and quite straight, the rays diverging at a small angle, shot out from the

Westerly corner of the Sun's crescent.
At the same time Mr. Ellis noticed a
corresponding dark band, or shadow,
shooting down from the East corner of
the crescent. At this time the sea
assumed a darker aspect, and a well-
defined green band was seen distinctly
around the horizon. The temperature
had fallen, and the wind had slightly
freshened. The darkness then came on
with great rapidity. The sensation was
as if a thunderstorm was about to break,
and one was startled on looking up to
see not a single cloud overhead. The
birds, after flying very low, disappeared
altogether. The dragon-flies and butter-
flies disappeared, and the large drone-like
flies all collected on the ceiling of the
tent, and remained at rest. The crickets
and Cicadse in the jungle began to
sound, and some birds, not visible, also began to twitter in the jungle. The sea
grew darker, and immediately before the total obscuration the horizon could not
be seen. The line of round white clouds that lay near the horizon changed their
colour and aspect with great rapidity. As the obscuration took place, they all be-
came of a dark purple, heavy looking, and with sharply defined edges ; they then
presented the appearance of clouds close to the horizon after sunset. It seemed as if
the Sun had set at the four points of the horizon. The sky was of a dark leaden blue,
and the trees looked almost black. The faces of the observers looked dark, but not
pallid or unnatural. The moment of maximum darkness seemed to be immediately
before the total obscuration ; for a few seconds nothing could be seen except objects
quite close to the observers. Suddenly there burst forth a luminous ring around the
Moon. The ring was composed of a multitude of rays quite irregular in length and
in direction ; from the upper and lower parts they extended in bands to a distance

DIAGRAM REPRESENTING THE RAYS
OF THE CORONA.

Aug. 1 8, 1868. (Hennery.}

c Proc. Roy. Soc., vol. xvii. p. 84. 1868.

306 Eclipses and Associated Phenomena. [BOOK II.

more than twice the diameter of the Sun. Other bands appeared to fall towards one
side, but in this there was no regularity, for bands near them fell away apparently
towards the other side. When I called attention to this, Lieut. Ray said, ' Yes, I see
them ; they are like horses' tails ; ' and they certainly resembled masses of luminous
hair in complete disorder. I have said these bands appeared to fall to one side;
but I do not mean that they actually fell, or moved in any way, during the observa-
tion. If the atmosphere had not been perfectly clear, it is possible that the appear-
ance they presented would lead to the supposition that they moved ; but no optical
delusion of the kind was possible under the circumstances. During the second when
the Sun was disappearing, the edge of the luminous crescent became broken up into
numerous points of light. The moment these were gone, the rays I have just men-
tioned shot forth, and, at the same time, we noticed the sudden appearance of the
rose-coloured protuberances. The first of these was about £ of the Sun's diameter
in length, and about •£% of the Sun's diameter in breadth. It all appeared at the same
instant, as if a veil had suddenly melted away from before it. It seemed to be a
tower of rose-coloured clouds. The colour was most beautiful — more beautiful than
any rose-colour I ever saw ; indeed, I know of no natural object or colour to which
it can be with justice compared. Though one has to describe it as rose-coloured, yet
in truth it was very different from any colour or tint I ever saw before. This protu-
berance extended from the right of the upper limb, and was visible for 6 minutes.
In 5 seconds after this was visible, a much broader and shorter protuberance
appeared at the left side of the upper limb. This seemed to be composed of two
united together. In colour and aspect it exactly resembled the long one. This
second protuberance gradually sank down as the Sun continued to fall behind the
Moon, and in 3 minutes it had disappeared altogether. A few seconds after it
had sunk down there appeared at the lower corresponding limb (the right interior
corner) a similar protuberance which grew out as the eclipse proceeded. This also
seemed to be a double protuberance, and in size and shape very much resembled the
second one ; that is, its breadth very much exceeded its height. In colour, however,
this differed from either of the former ones. Its left edge was a bright blue, like a
brilliant sapphire with light thrown upon it. Next to that was the so-called rose-
colour, and, at the right corner, a sparkling ruby tint. This beautiful protuberance
advanced at the same rate that the Sun had moved all along, when suddenly it seemed
to spread towards the left until it ran around J of the circle, making a long ridge of
the rose-coloured masses. As this happened, the blue shade disappeared. In about
12 seconds the whole of this ridge vanished, and gave place to a rough edge of
brilliant white light, and in another second the Sun had burst forth again. In the
meantime the long rose-coloured protuberance on the upper right limb had remained
visible ; and though it seemed to be sinking into the Moon, it did not disappear
altogether until the lower ridge had been formed, and had been visible for 2
seconds. This long protuberance was quite visible to the naked eye, but its colour
could not be detected except through the telescope. To the naked eye it simply
appeared as a little tower of white light, standing on the dark edge of the Moon.
The lower protuberance appeared to the naked eye to be a notch of light in the dark
edge of the Moon — not a protuberance, but an indentation. In shape the long pro-
tuberance resembled a goat's horn. . . . Though the darkness was by no means so great
as I had expected, I was unable to mark the protuberances in my note-book without
the aid of a lantern, which the sailors lit when the eclipse became total. Those who
were looking out for stars counted 9 visible to the naked eye ; one planet, Venus,

CHAP. VI.] Recent Total Eclipses of the Sun. 307

was very brilliant. . . . On board the Rifleman the fowls and pigeons went to roost,
but the cattle showed no signs of uneasiness ; they were lying down at the time."

Captain Reed, R.N., remarked as follows respecting the
corona : —

" The corona I should not describe as a ring, except in so far as concerned that
portion of it immediately surrounding the Moon's limb. From this edge it burst
forth in sharp, irregular-shaped masses, of exceedingly bright light, decreasing in
brightness as the distance from the Moon increased, and finally resolving into
numberless bright rays, the visible extremes of which were distant from two or three
diameters of the Moon. The general appearance of the corona, as seen through my
glass, struck me forcibly as resembling in form a Brunswick star ; the bright light
near the Moon resembling the prominent portions immediately surrounding the
centre, and the rays the more remote portions. I have heard the appearance
described as representing the glory one sees around the heads of saints in old
Italian pictures, and to my mind the general appearance could hardly be better
described."

The total eclipse of August 7, 1869, was observed by several
well-equipped parties in the United States. The American ob-
servations were carried out with great skill, and regardless of
labour or expense, and resulted in a very complete series of
excellent photographs d. One of these taken at Ottumwa repre-
sents the phenomenon of " Baily's Beads," and is, I believe, the
only photographic record of this phenomenon extant. Professor
Morton speaks of this as " simply the last glimpse of the Sun's
edge cut by the peaks of the Lunar Mountains into irregular
spots." The pictures taken during the partial phase all shew an
increase of light on the Sun's surface, in contiguity with the
Moon's limb, as was observed by De La Rue in 1860. Professor
Morton was at first inclined to attribute this to the existence of
a Lunar atmosphere ; but subsequent experiments have led him
to regard the cause as entirely chemical, and not corresponding
to any celestial phenomenon. An analogous appearance is
frequently to be seen in terrestrial photographs, and it is now
generally agreed that the effect is a mere photographic one.
Professor Pickering at Mount Pleasant noticed that while "the
sky was strongly polarised all round close up to the corona, that

4 Eeport on Observations of the Total p. 4, Nov. 1869; p. 173, May 1870;

EclipseofiheSun,Aug. 7, 1869. Edited Journal of the Franklin Institute, 3rd

by Commodore B. F. Sands. 4to. Wash- Ser., vol. Iviii. pp. 200, 249, and 354,

ington, 1869. Month. Not., vol. xxx. Sept.-Nov. 1869.

X 2

308 Eclipses and Associated Phenomena. [BOOK II.

object itself was not a source of polarised light." This obser-
vation is not in accord with the observations of other eclipses
(especially 1842, 1851, 1860. and 1868), for it has always been
found that the light of the corona was strongly polarised. Nor
indeed do Pickering's observations in 1869 tally with his own
conclusions arrived at in 1870 in Spain with superior instruments.
His observations in 1869 were made on an unmagnified image
of the corona, and his attention was chiefly directed to the polar-
ized condition of the atmosphere. Prof. Pickering is of opinion
that his more deliberate observations of the coronal polarization
made in 1870 are to be preferred, and that the small apparent
size of the corona and its dazzling brightness as seen with the
instrument used in 1869 prevented his noticing the polarization
colours in the coronal light.

Much more important in every sense than either of the fore-
going eclipses, wag the eclipse of December 22, 1870. Being
visible at some very accessible places in Spain, Sicily, and North
Africa, several expeditions were dispatched to observe it, and
eventually Her Britannic Majesty's Government placed at the
disposal of English astronomers, .^2000 and a ship, the Urgent,
for the conveyance of observers going to Spain and Africa ; and
the expenses of the party which travelled overland to Sicily
were defrayed out of this grant. Besides the observing parties
connected with the expeditions just named, a strong detachment
of American astronomers, nearly all of them Professors, came
to Europe. France was only represented by M. Janssen, for the
eclipse occurring towards the end of the Franco-German War,
the French had other things to think about. It deserves notice
that so great was M. Janssen's anxiety to observe the pheno-
menon, that he determined upon trying to escape from Paris in
a balloon, and succeeded, carrying with him his instruments.

Unfortunately the weather was very unsatisfactory, especially
in the North of Africa, where a cloudless sky had been confi-
dently anticipated, and accordingly the successful photographs
of Lord Lindsay's party at Cadiz and of the English party at
Syracuse, constitute the chief direct results of the efforts made.

CHAP. VI.] Recent Total Eclipses of the Sun. 309

The partial failure of the weather is the more to be regretted
because the preparations made to observe the eclipse were un-
usually elaborate and costly, and the services of a particularly
strong body of experienced observers had been secured. The
general results, though less than had been expected, were un-
doubtedly of great importance, and constituted a clear advance
in our knowledge of Solar physics.

Though attention was paid to other accompaniments of total
eclipses of the Sun, and useful confirmatory evidence as to other
matters was accumulated, yet the Sun's corona was in 1870 the
one main object of attack, and photography, polariscopes, spec-
troscopes, and ordinary telescopes were all brought to bear on
the elucidation of the question " What is the corona ? " and im-
portant information available for answering the question was
obtained.

The next eclipse that was widely observed was that of Decem-
ber 12, 1871, which was visible over a large and accessible tract
of country in Southern India, Ceylon, and Australia, though in
the last-named part of the world the weather failed. The
observations made were as before photographic, spectroscopic,
and polariscopic.

It was very generally noticed that the structure of the corona
was radiated, and several rifts were seen therein. A comparison
of photographs at different stations, indicates a fixity in these
rifts which renders it certain that they existed at an immense
distance from the observers ; in other words, that they were
neither terrestrial, nor lunar, but solar.

Fine photographs of the corona in which the definition is very
sharp were taken at Baikulby Mr. Davis, Lord Lindsay's photo-
graphic assistant, and six photographs on the same scale were
taken by Col. Tennant at Dodabetta; and although the dark
moon is represented by a circle only ^ of an inch in diameter
and the whole extent of the corona could be covered by a six-
pence, the definition is so good that on examination under suit-
able illumination some hundreds of details can be made out and
measured, and the two series of photographs are found completely

310 Eclipses and Associated Phenomena. [BOOK II.

to confirm one another as far as the smallest detail observable.
In addition to the corona photographs taken at Baikul and
Dodabetta in Central India, two photographs of the corona were
secured during this eclipse with an ordinary photographic camera
at a station near Tjebatjap in Java ; and though these are on a
very small scale and the definition does not compare with the
Indian photographs, the rifts and some of the larger structures
visible in the Indian photographs can be recognized upon them,
and as far as they go they show that the corona visible in India
was also visible in Java.

The line joining the two most marked rifts which are situated
near to the Sun's poles divides the corona into two halves which
are roughly symmetrical. The line of symmetry does not ac-
curately coincide with the Sun's axis, but is inclined to it
some 10° or 15°. On each side of these polar rifts are groups
of incurving structure which occupy an arc of some 40° on
the moon's circumference. The curved rays in these groups
are all bent inwards, and the straighter rays appear to be
inclined from the radial towards parallelism with the axes of
the groups.

Within the polar rifts are several narrow straight or but
slightly curved rays, none of which are quite radial to the Sun's
limb. It is worthy of remark that this inclination to the radial
cannot be a mere effect of perspective. For a line passing
through the Sun's centre could not be projected so as not to be
radial to the Sun's limb. There is abundant evidence that many
of the structures visible in other coronas, as well as that observed
during the eclipse of 1871, were inclined at considerable angles
to the normal to the surface of the photosphere. It is difficult
to conceive how explosions within a gaseous body like the sun
can give rise to oblique rays, but the evidence for the existence of
such rays is overpowering. Some of the oblique rays are straight,
or nearly straight, while others shew considerable curvature,
and others bend over in one direction in their lower parts, and
are again curved slightly in a contrary direction above. Such
double curvature, or contrary flexure, is also to be found in some

CHAP. VI.] Recent Total Eclipses of the Sun. 311

of the tree-like forms of structure which on a gigantic scale
remind the observer of a common type of prominence to be
seen in the chromosphere.

The existence of these curving forms is a matter of considerable
importance, as they appear to indicate the existence of an atmo-
sphere with currents carrying the matter of which the struc-
tures are composed, with different velocities at different altitudes.
The tree-like structures also seem to indicate the spreading out
within a resisting medium of matter rising from below. None
of these tree-like structures are to be found in the upper part of
the corona, though there are several forked and curving rays
whose form it seems difficult to account for by the action of ex-
plosive forces and gravity alone. As we proceed towards the
outer parts of the corona there are more straight rays, and fewer
contorted structures, indicating that the resisting atmosphere in
the upper part of the corona is less dense than in the lower.
The forms of the structures do not seem to afford evidence of a
repulsive force similar to that which drives the matter of a
comet's tail away from the Sun, but there are some of them
in which the bright coronal matter, after having been driven
upwards in an oblique direction, seems to fall again as if by
gravity towards the Sun. In most instances however the rays
which extend to the outer part of the corona grow gradually
fainter in their upper parts without exhibiting any change of
direction.

Mr. W. H. Wesley, the Assistant Secretary of the Royal As-
tronomical Society, who has given great attention to the numerous
drawings and photographs of the corona which have been ob-
tained, says e : —

" One of the most striking features in the corona of almost all the years under
examination is the existence of a more or less well-marked polar rift, roughly, but
perhaps never exactly, corresponding with the Sun's axis of rotation, to which it
appears sometimes inclined as much as 30°. In most cases this rift is shewn at both
poles, but sometimes at one only; in 1882 it does not appear at all. The northern
and southern rifts are seldom strictly opposite to one another, so that a line drawn
through them does not pass through the centre of the Sun. The polar rifts are

e Month. Not., vol. xlvii. p. 500. June 1887.

312 Eclipses and Associated Phenomena. [BOOK II.

generally filled with shorter, straighter, and more radial rays, with a background of
less density than in other parts of the corona.

" On either side of the polar rift there usually appears a somewhat conical mass,
composed of rays curving towards each other, forming groups of what Mr. Ranyard
has appropriately called ' synclinal structure,' which give the quadrilateral or
cruciform appearance frequently shewn in corona drawings. They mostly seem to be
situated over the zones of maximum sun-spot activity, and have frequently greater
extension than other parts of the corona."

ECLIPSE OP 1851, JOLY 28.

" Dr. Busch's daguerreotype is remarkable as the first instance of a successful
photograph of the corona. It shews the general form to a height nowhere much
exceeding | of a solar diameter. The corona is symmetrical and of hexagonal form,

Fig- 145-

OUTLINE OF THE CORONA.

with a well-marked rift not far from the north and south poles, the southern rift
being much the broader. On either side of these rifts are indications of synclinal
masses ; there are also similar masses in the equatorial regions fairly corresponding
on each side. The orientation of the plate is rather uncertain. Wolf gives 64-2 as
the relative number of sun-spots for July 1851."

ECLIPSE OF 1860, JULY 18.

" In the photographs taken at Desierto de las Palmas, of which I have only seen
positive copies, there is shewn a very broad rift towards the south pole, and a less
marked one on the north. The character of the synclinal groups is not clearly
marked. The corona is fairly symmetrical about a line not much inclined from the
Sun's axis. Wolfs relative number of sun-spots is 94-9."

ECLIPSE OF 1869, AUGUST 7.

" I have not seen the original negatives of the photographs taken at Shelbyville,
which are the only ones which shew any considerable extent of corona. The
northern and southern polar rifts are clearly marked and very broad. The bases of

CHAP. VI.] Recent Total Eclipses of the Sun.

313

the four synclinal groups can also be clearly made out, especially that in the north-
west quadrant. The general axis of symmetry is slightly inclined to the north-west
and south-east of the Sun's axis. Wolfs relative number of sun-spots is 77-6."

ECLIPSE OF 1870, DEC. 22.

" Mr. Brothers's negative, taken at Syracuse, shews a great extent of corona,
reaching in some parts quite 40' from the limb. The general outline is somewhat
circular, with a quadrilateral area

of greater brightness, brighter on Fig. 146.

the western side. The northern
polar rift is broad and ill-defined ;
to the east of the south pole is a
much narrower and more sharply
defined rift, easily traceable to the
limb. To the east and west of this
are other rifts, and there is struc-
ture evidently synclinal to the
north-west; otherwise the photo-
graph shews but little detail. The
general axis of symmetry appears
inclined to the north-west and
south-east of the Sun's axis as
much as 20°, but the orientation
is not very certain. The eclipse
occurred at a period of great solar
activity, Wolf's relative monthly

OUTLINE OF THE COBONA, 1870.

number being 135-4."

ECLIPSE OF 1871, DEC. 12.

"Lord Lindsay's and Col. Tennant's excellent series of negatives shew a corona
remarkably symmetrical, about a line inclined about 10° to the north-west and south-
east of the Sun's axis. The northern and southern polar rifts are well defined,
nearly opposite to one another, and very similar in character. The four synclinal
groups are well marked, appearing to indicate zones of synclinal structure extending
nearly from the pole to about 40° north and south latitude. These groups are
generally separated from the equatorial portions by narrow definite rifts. The
western margin of the south-east synclinal group shews a distinct tendency to double
curvature — a form which reappears in 1883 and 1885. The extension is greatest in
the equatorial regions, giving a somewhat hexagonal form to the corona. The great
polar rifts are filled with short straight rays.

"The greatest extent of the photographic corona does not exceed 27'} but the
minuteness of the detail near the limb, which with a strong transmitted light can be
seen through the densest part of film, has never been equalled in any subsequent
eclipse photograph. The remarkable feature of the lower structure is the prevalence
of rays completely curving over, and of branching rays, somewhat resembling a

314 Eclipses and Associated Phenomena. [BOOK II.

frequent form of solar prominence. Few of these reach a height of more than 5'
from the limb; above this height the rays are generally straight or more slightly
curved.

" It is impossible to be certain whether these lower details are really near the limb,
or whether they are rays on the nearer or further parts of the corona, seen fore-
shortened. In the latter case, they could hardly be the extreme ends of coronal rays,

Fig. 147.

OUTLINE OF THE CORONA, 1871.

as these invariably fade away so much towards their extremities that they would
certainly be lost on the dense background. On the whole, the difference of character
between the higher and the lower details lends great probability to the view that the
latter are really near the limb. Mr. Ranyard considers that the more contorted
character of these lower structures indicates the existence of a resisting atmosphere
in the lower part of the corona. It seems evident, at least, that many of the
curvatures of the coronal rays could not be caused by gravity alone. Still when we
consider what an intricate mass of crossing and interlacing rays must be produced by
perspective as we approach the limb, we must feel that the question cannot be
decided with certainty.

" The eclipse occurred at a time of somewhat less solar activity than that of the
previous year, Wolf's relative monthly number being 98 "O."

No photographs having been taken of the eclipse of 1874, no
annotations on the corona of that eclipse appear in Mr. Wesley's
paper. I have however thought it would be well to annex a
hand-drawing thereof.

CHAP. VI.] Recent Total Eclipses of the Sun. 315

Fig. 148.

THE TOTAL ECLIPSE OF THE SUN OF APRIL l6, 1874.

Naked-eye view of the outer Corona. (H. 2?. P. Bright.)

Mr. Wesley then proceeds to deal with the eclipses subsequent
to 1874:—

ECLIPSE OF 1875, APRIL 6.

" The small size of the photographs taken by Dr. Schuster renders it impossible to
make out more than the general character of the corona, and from the same cause the
orientation is not very accurately determined. The corona is somewhat symmetrical
about a line nearly coinciding with the Sun's axis, the northern and southern polar
rifts being very broad and well marked. Four synclinal groups are plainly seen,
their axes making angles of more than 45° with the Sun's axis. The polar rifts are
filled up, but not to a great height, the polar extension of the corona being only about

316 Eclipses and Associated Phenomena. [BOOK II.

Fig. 149.

half the equatorial, where the greatest height is nearly a solar diameter. The half of
the corona lying to the east of the axis is decidedly larger than that to the west, so
that the nearly straight lines which bound the corona north and south converge towards

the west. Dr. Schuster draws attention to the
remarkable similarity between this corona and
that of 1874, of which no photographs were
taken. He thinks this similarity extends to
the irregularity in the symmetry just men-
tioned ; but the want of accordance between
the drawings made in 1874 renders this un-
certain.

" Notwithstanding this general resemblance,
the solar activity, as indicated by the sun-
spots, was less than half as great as in the
previous year, Wolf's relative number for
April 1874 being 49*1, and for April 1875

OUTLINE OF THE CORONA, 1875. 2O'S."

ECLIPSE OF 1878, JULY 29.

"The photographs which I have examined are two negatives by Mr. Ranyard, made
at Denver, and a series of 9 positive copies on glass of the photographs taken by

Fig. 150.

OUTLINE OF THE CORONA,

Professor Harkness and Mr. Rogers at Creston and
La Junta. The exposures of Mr. Ranyard's plates
were so short that they show but a small extent of
corona. A drawing combining the detail o^ the
Creston and La Junta negatives, and shewing a
further extension of the equatorial rays, from a
smaller photograph by Mr. Peers, is given in the
Appendix to the Washington Observations for
1876. On comparing this drawing with the positives,
it does not seem very satisfactory. I can make out
as much or more detail on the positives as on the
drawing (except the equatorial extension), and no
doubt much more would be seen on the original
1^7^- negatives.

"The corona belongs to the same type as those of 1874 and 1875. The equatorial
extension greatly exceeds the polar, and both the northern and southern rifts are
widely opened, so that their eastern and western boundaries form nearly straight
lines tangential to the limb. The northern and southern synclinal groups are so
much depressed towards the equator that they appear to coalesce into one great mass,
occupying the whole equatorial region. The rifts are filled with fine rays, straight,
and nearly radial in the centre of the rift, and becoming more and more curved
towards its boundaries. In one rift there are as many as 20 separate rays, re-
markably uniform in length and distance apart, never branching or crossing. The
two rifts are almost identical in character, but are not opposite each other; the
northern rift having its general axis inclined about 15° towards the east from the
Sun's axis, and the southern being more symmetrical with it.

"The great equatorial extensions, of which the bases only are visible in the

CHAP. VI.] Recent Total Eclipses of the Sun,

317

positives, are very symmetrical in detail, but the western mass is the broader,
reaching further both to the north and south. These great masses are broadest near
the limb, and gradually become narrower, so that their northern and southern
boundaries would meet in a point about 2 diameters from the limb on the western
side, and rather less on the eastern. These equatorial extensions were, however,
observed by Newcomb, Langley, and others, to reach to a distance of at least 1 2
diameters. They must have been very faint, as in the American drawing, combined
from various negatives, they do not extend more than a diameter.

" It is a remarkable peculiarity, which I have observed in no other corona, that while
at the poles it is split up into a great number of fine rays, the equatorial extensions
are broad smooth masses, shewing scarcely any detail, even at their extreme edges.

" The eclipse occurred at a time of decidedly low solar activity, Wolf's relative
number being only 3*3."

ECLIPSE OF 1882, MAY 17.

" The negatives taken by Dr. Schuster shew a large extent of corona, reaching in
several places a height of a solar diameter, one straight ray in the south-west ex-
tending as far as ij diameter. The
corona presents none of the features
which characterised those of 1874, 1875,
and 1878. Although very irregular in
detail, it is approximately circular in
form, and is entirely without that great
difference between the polar and equa-
torial extensions which had been so
striking in the three last eclipses. At
the same time it shews none of that
symmetry about a line not very far
from the Sun's axis that had been more
or less apparent in most previously
photographed coronas, and especially in
that of 1871. This absence of an axis
of symmetry and of polar rifts is its
most striking feature. There are groups
of synclinal structure, but they are not
of a very definite character, and are

quite irregularly placed. The solar axis does not pass through the line of least
extension, as is almost always the case. The only approach to an axis of symmetry
seems to be about a line nearly at right angles with the Sun's axis. The orientation
was, however, very carefully made, and in Dr. Schuster's opinion is not more than
half a degree in error : it nearly agrees with that adopted by Professor Tacchini.

"The rays are rather more frequently straight than curved, and there is only one
instance of a ray completely curving over : this is in the south-east ; it reaches a
height of about 1 2' from the limb. Beneath it are two rays — the only ones shewing
any traces of a branching structure. There are distinct rifts on the western side,
reaching to the limb ; but they are more filled up with coronal matter than those of
1871. The rays are in all directions, from radial to tangential, and there are several
cases of rays crossing each other, but no clear case of a ray of double curvature.
The lower details of the corona are less distinct than in 1871 ; but this may be due

OUTLINE OF THE CORONA, 1882.

318 Eclipses and Associated Phenomena. [BOOK II.

to the great density of the film near the limb, which is common to all dry-plate
negatives. The definition of the outer portions is extremely fine. I cannot see any
evidence of the distinction between an outer and inner corona, which Dr. Schuster
thinks the photographs shew. Wolf's relative monthly number of sun-spots is 64-5 ;
a remarkable outburst had occurred during the preceding month, for which the
number was 95'8."

ECLIPSE OF 1883, MAY 6.

Fig. 152.

" Successful photographs were taken by M. Janssen, and also by Messrs. Lawrance
and Woods. The most prominent feature is an unusually well-marked rift, partly

filled with short straight rays,
near the north pole of the
Sun's axis, from which the
general axis of the rift is in-
clined at an angle of about
30° to the east. On each side
of this rift are most charac-
teristic groups of synclinal
structure, whose bases meet
at the limb : the easternmost
shews a double curvature on
both sides, but on the western
edge this appearance seems
caused by the superposition
of different rays. There seems
no regularity in the arrange-
ment of the rays in the rest
of the corona, nor any rift
in the south, corresponding
to that in the north. The
general outline of the corona
is somewhat circular, but the two synclinal groups extend farther than any other
part. In M. Janssen's long-exposed plate, one of these groups extends nearly as
far as two solar diameters, which is the greatest extension shewn by any corona
photograph. Indeed, M. Janssen says that it is much greater than it appeared to
the eye in his telescope.

" The solar activity was rapidly decreasing, Wolf's relative monthly number of
sun-spots being 32-1."

OUTLINE OF THE CORONA, 1883.

ECLIPSE OF 1885, SEPTEMBER 8.

" Several photographs were taken of this eclipse, but the weather was generally
unfavourable, and few shew much detail. The most marked feature is the southern
rift, which is broad and well marked, with clear indications of straight rays filling it.
The only distinctly synclinal group is to the south-east ; its axis makes an angle of
about 45° with the Sun's axis, and its extension is greater than any other part of the
corona. The western edge of this group presents a double curvature. The other
parts of the corona are very irregular, and there does not appear to be any distinct

CHAP. VI.] Recent Total Eclipses of the Sun. 319

rift on the north corresponding with the southern rift. There is a marked broad
depression in the corona, about 35° to the east of the north point of the axis. This
depression, and the southern rift, appear to divide the corona into two very unequal
parts, the western one being much the greater.

"The solar activity, as shewn by the sun-spots, was diminishing ; Wolf's relative
monthly number being 83-7 for the month of June, and 39-6 for September.

" The only generalisation with regard to the form of the corona which has seemed
well supported by the photographic evidence is
that of Mr. Ranyard, that there is a connection
between the general form of the corona and the
solar activity as shewn by the number of sun-spots.
The corona of a sun-spot maximum has generally
been somewhat symmetrical, with synclinal groups
making angles of 45° or less with its general axis.
The sun-spot minimum coronas shew polar rifts
much more widely open, synclinal zones making
larger angles with the axis, and being therefore
more depressed toward the equatorial regions, in
which there is usually greater extension. This

generalisation is well borne out by the maximum

, ., . . OUTLINE OF THE CORONA, 1885.

coronas of 1870 and 1871 and the minimum coronas

of 1867, 1874, 1875, 1878, and apparently 1887. On the other hand, the eclipses of
1883, 1885, and 1886, do not strikingly confirm the theory. The eclipse of 1883, at
a time of rapidly decreasing solar activity, shews all the characters of a sun-spot
maximum corona ; the same in a somewhat less degree may be said of 1885 and 1886,
at both of which times the solar activity was decreasing. Although the polar rifts
were wide in 1886, there was no very marked depression of the synclinal groups
towards the equator, nor any great equatorial extension, although the relative
number of sun-spots for August 1886 was only 19*0. Striking, therefore, as the
evidence in favour of the generalisation has been in many years, it still seems probable
that the form of the corona is modified by other causes at present unknown to us."

ECLIPSE OF 1886, AUGUST 29.

" Good photographs were taken at Grenada by Mr. Maunder, Dr. Schuster, and
Prof. W. H. Pickering. The northern and southern rifts are fairly symmetrical about
the Sun's axis, and are very wide. The synclinal groups bounding the rifts are well-
marked, but very unsymmetrical, being depressed towards the equator on the eastern
side, while the corresponding groups on the west are nearly radial. The south-west
synclinal group is narrow and conical, extending to a greater height than any other
part of the corona. On the eastern side the coronal extension is generally less than
on the western, and the mass of equatorial rays on the east is of much less breadth,
and is synclinal in character. The separation between the southern synclinal groups
and the equatorial rays is unusually well-marked. Both polar rifts are filled with
fine rays of the same character as the polar rays in 1878, but somewhat less regular.

" One of Pickering's negatives shews very remarkable rays on the western side,
extending to a height of 60' from the limb, and curving completely over. These are
by far the highest rays of this character that have ever been photographed. On this

320 Eclipses and Associated Phenomena. [BOOK II.

Fig. 154.

OUTLINE OF THE CORONA, 1 886.

account they are of great interest if they are genuine coronal features, but Prof.
Pickering can only detect them on one of his plates, and this was taken on a very
small scale. Wolfs relative monthly number of sun-spots was 19-0."

ECLIPSE OF 1887, AUGUST 19.

"The extremely unfavourable weather which prevailed over Europe greatly interfered
with the observations, and seems to have prevented successful photographs being
taken at any of the Russian Stations. A hand-drawing of the corona, made in Siberia

by Dr. Khandrikoff, is given on Plate XXI.
Successful photographs, of which positive copies
have been sent to England, were made by M.
Sugiyama in Japan. Judgingfrom these copies,
the corona somewhat resembles that of 1878,
but the peculiar characters of that year are
less strongly marked in 1887. The rifts are
more widely open than in 1886, and the
masses of rays bounding the rifts are more
depressed towards the equator. The northern
rift is filled with regular rays like the polar
rays of 1878, but in the southern rift are
broader, denser, and nearly radial masses,
OUTLINE OF THE CORONA, 1887. giving quite a different character to this part

of the corona. Synclinal groups, separated

from the general mass of equatorial rays, bound the southern rift, but cannot be
clearly made out in the north. Wolfs relative number of sun-spots for August
was 21-1, but the mean number for the year was less than that for 1886."

Fig. 156.

Plate XXI.

THE TOTAL ECLIPSE OP THE SUN OP AUQ. 19, 1887.

(Khandrikoff.*)

CHAP. VII ] Historical Notices. 321

CHAPTEE VII.

HISTORICAL NOTICES ».

Eclipses recorded in Ancient History. — Eclipse of 584 B.C. — Eclipse of 556 B.C. —
Eclipse 0/479 B.C. — Eclipse of 430 B.C. — Eclipse of 309 B.C.— A llusions in old
English Chronicles to Eclipses of the Sun.

THE earliest eclipse on record is one given in the Chinese
history named the Chou-king ; it has been supposed that a
solar eclipse happened on Oct. 13, 2128 B.c.b, and that that is
the one there alluded to. What happened in connection with it
was this, though I cannot vouch for the details. Ho and Hi the
Astronomers Royal of the period failed to give timely warning of
the eclipse, but got drunk instead. The eclipse happened there-
fore without the proper religious preparations having been made,
and the land was exposed to the anger of the gods. To appease
them the officials in question were forthwith executed. If this
is fact and not romance, the record is a very interesting one,
contemporaneous as it is with the Patriarchs of the Bible.

One of the most celebrated eclipses of the Sun recorded in his-
tory is that which occurred in the year 585 B.C. It is notable,
not only on account of its having been predicted by Thales, who
was the first ancient astronomer who gave the true explanation
of the phenomena of eclipses, but because it seems to fix the
precise date of an important event in ancient history. Herodotus

• See the Rev. S. J. Johnson's Eclipses of the Moon, Part I, "Observations on

past and future. The fullest general the Moon before 1750," pp. 27-54

account of all the early eclipses of im- (Washington, 1878).
portance is that which will be found in b Mem. E. A.S., vol. xi. p. 47. 1840.

S. Newcomb's Researches on the Motion

322 Eclipses and Associated Phenomena. [BOOK II.

describes a war that had been carried on for some years be-
tween the Lydians and the Medes ; and gives an account of
the following circumstances which led to its premature termina-
tion : —

" As the balance had not inclined in favour of either nation, another engagement
took place in the 6th year of the war, in the course of which, just as the battle was
growing warm, day was suddenly turned into night (ffvvrjveiKe uffrt TJJJ no-xn* ow(-
aTfdjffrjs rrjv ^i^fprjv f(airivr)s VVKTO. ytvtaOai). This event had been foretold to the
lonians by Thales of Miletus, who predicted for it the very year in which it actually
took place. When the Lydians and Medes observed the change they ceased fighting,
and were alike anxious to conclude peace." Peace was accordingly agreed upon and
cemented by a twofold marriage. "For without some strong bond, there is little
security to be found in men's covenants."

So adds the historian0. The exact date of this interesting
event was long disputed, and the solar eclipses of 610, 593, and
particularly 585 B.C., were each fixed upon as the one mentioned
by Herodotus ; and it is only within the last few years that the
point has been finally settled in favour of the last-mentioned
eclipse, and that chiefly through the researches of Sir G. B. Airy,
who gives, as the date of the eclipse in question, May 28, ,585
B.C. d This is reconcileable with the statements of Cicero and
Pliny.

Another important ancient eclipse is that mentioned by Xeno-
phon, in the Anabasis, as having led to the capture by the Persians
of the Median city Larissa. In the retreat of the Greeks on the
eastern side of the Tigris, not long after the seizure of their
commanders, they crossed the river Zapetes, and also a ravine,
and then came to the Tigris. At this place, according to Xeno-
phon, there stood —

" A large deserted city called Larissa, formerly inhabited by the Medes ; its wall
was 25 feet thick, and 100 feet high ; its circumference 2 parasangs ; it was built of
burnt brick on an understructure of stone 20 feet in height. When the Persians
obtained the empire from the Medes, the king of the Persians besieged the city, but
was unable by any means to take it till a cloud having covered the Sun and caused
it to disappear completely, the inhabitants withdrew in alarm, and thus the city
was captured e."

c Herod., lib. i. cap. 74.

d PAt7.2Vo««.,vol.cxliii. pp. 191-197. 1853. Month.Not.,vol.xrii\.p. 143. Mar. 1858.

6 Anal., lib. iii. cap. 4. § 7.

CHAP. VII.] Historical Notices. 323

The historian then goes on to say that the Greeks in continuing
their march, passed by another ruined city named Mespila. The
minute description given by Xenophon enabled Layard, Felix
Jones, and others, to identify Larissa with the modern Nimrud,
and Mespila with Mosul. It has been thought that the phenomenon
to which the Greek author refers as having led to the capture of the
above-mentioned city, was no other than a total eclipse of the
Sun, and Airy arrived at the conclusion that the eclipse referred to
is that which occurred on May 19, 557 B.c.f

In the same year as that in which, according to the common
account, the battle of Salamis was fought (480 B.C.), there oc-
curred a phenomenon which is thus adverted to : —

" At the first approach of spring the army quitted Sardis, and marched towards
Abydos ; at the moment of its departure the Sun suddenly quitted its place in the
heavens and disappeared (6 ij\io$ tKXnruv T^V kit rov ovpavov tSprjv d^av^s TJP), though
there were no clouds in sight, and the sky was quite clear ; day was thus turned into
night (avrl T)fj.(pr]s rt vii£ (ytvero) B"

This account, interpreted as a record of a total solar eclipse,
has given great trouble to chronologers, and it is still uncertain
to what eclipse reference is made. If Hind's theory that the
eclipse of Feb. 17, 478 B.C. is the one referred to, is sound, we
must consider that the battle of Salamis is an event less remote
by 2 years than has usually been supposed. Airy " thinks it ex-
tremely probable " that the narrative relates to the total eclipse
of the Moon, which happened 478 B.C., March 13* I5h G.M.T.h

A total eclipse of the Sun, supposed to have been that of
August 3, 431 B.C., nearly prevented the Athenian expedition
against the Lacedaemonians, but a happy thought occurring to
Pericles, commander of the forces belonging to the former nation,
the difficulty was got over.

"The whole fleet was in readiness, and Pericles on board his own galley, when
there happened an eclipse of the Sun. The sudden darkness was looked upon as an

f Month. Not., vol. xvii. p. 234. June Pelopidas, 31. Diod. Sic., lib. xv. cap.

1857. Newcomb doubts this being an 80. Grote, Hist, of Greece, vol. x. p. 424.

eclipse at all. And see a letter by Lynn h Phil. Trans., vol. cxliii. p. 197. 1853.

in Observatory, vol. vii. p. 380. Dec. See also Blakesley's Herod., in loco, and

1884. some criticisms by Lynn in Observatory,

^ Herod., lib. vii. cap. 37. Plutarch, vol. vii. p. 138, May 1884.

Y 2

324 EcMpses and Associated Phenomena. [BOOK II.

unfavourable omen, and threw the sailors into the greatest consternation. Pericles
observing that the pilot was much astonished and perplexed, took his cloak, and
having covered his eyes with it, asked him if he found anything terrible in that, or
considered it as a bad presage ? Upon his answering in the negative, he said, ' Where
is the difference, then, between this and the other, except that something bigger than
my cloak causes the eclipse ' ?' "

Thucydides says : —

" In the same summer, at the beginning of a new lunar month (at which time
alone the phenomenon seems possible), soon after noon the Sun suffered an eclipses ;
it assumed a crescent form, and certain of the stars appeared : after a while the Sun
resumed its ordinary aspect k."

An ancient eclipse, known as that of Agathocles, has also been
investigated by Sir G. B. Airy, and previously by Baily. It
took place on August 14, 310 B.C. This eclipse is, according to
ancient writers, associated with an interesting historical event.
Agathocles, having been closely blockaded in the harbour of
Syracuse by a Carthaginian fleet, took advantage of a temporary
relaxation in the blockade, occasioned by the absence of the
enemy in quest of a relieving fleet, and quitting the harbour of
Syracuse, he landed on the neighbouring coast of Africa, at a
point near the modern Cape Bon, and devastated the Cartha-
ginian territories. It is stated that the voyage to the African
coast occupied 6 days, and that an eclipse (which from the
description was manifestly total) occurred on the 2nd day. Dio-
dorus Siculus says that the stars were seen1, so that no doubt
can exist as to the totality of the eclipse. Baily, however, found
that there existed an irreconcileable difference between the cal-
culated path of the shadow and the historical statement, a space
of about 1 80 geographical miles appearing between the most
Southerly position that can be assigned to the fleet of Agathocles
and the Northerly limit of the phase. " To obviate this discord-
ance, it is only necessary to suppose an error of about 3' in the
computed distances of the Sun and Moon at conjunction, a very
inconsiderable correction for a date anterior to the epoch of the
Tables by more than 21 centuries01."

' Plutarch, Vita Peridls. lib. xxii. cap. 6.

k Thucyd., lib. ii. cap. 28. m Phil. Trans., vol. cxliii. pp. 187-191.

1 Diodor. Sic., lib. xx. cap. i. Justin.. 1853.

CHAP. VII.] Historical Notices. 325

In the work mentioned in the note below n there will be found
an extremely interesting epitome of all the discussions which
have taken place respecting the Eclipses of the Sun of 610, 603,
585, 557, and 310 B.C., together with charts of the tracks of the
shadow on each occasion. The writer, the late Mr. J. W.
Bosanquet, F.R.A.S., also brings out very clearly the way in
which these eclipses are available for settling points of chro-
nology.

In the writings of the early English chroniclers are to be found
numerous passages relating to total eclipses of the Sun. The
eclipse of August z, 1133, was considered a presage of misfortune
to Henry I. : it is thus referred to by William of Malmesbury : —

" The elements manifested their sorrow at this great man's last departure. For
the Sun on that day at the 6th hour shrouded his glorious face, as the poets say,
in hideous darkness, agitating the hearts of men by an eclipse ; and on the 6th day of
the week, early in the morning, there was so great an earthquake that the ground
appeared absolutely to sink down ; an horrid noise being first heard beneath the
surface °."

The same writer, speaking of the total eclipse of March 20,
1140, says: —

" During this year, in Lent, on the 13th of the calends of April, at the 9th hour of
the 4th day of the week, there was an eclipse, throughout England, as I have heard.
With us, indeed, and with all our neighbours, the obscuration of the Sun also was so
remarkable, that persons sitting at table, as it then happened almost everywhere, for
it was Lent, at first feared that Chaos was come again : afterwards learning the
cause, they went out and beheld the stars around the Sun. It was thought and said
by many, not untruly, that the king [Stephen] would not continue a year in the
government p."

n Messiah the Prince, or the Inspira- P Hist. Nov., lib. ii. See also Sax.

tionof the Prophecies of Daniel. 2nded., Chrnn., Thorpe's Trans., p. 233. 8vo.

8vo. Lond. 1869. London, 1861.

« Hist. Nov., lib. i.

326 Eclipses and Associated Phenomena. [BOOK II.

CHAPTER VIII.
ECLIPSES OF THE MOON.

Lunar Eclipses of less interest than Solar one*. — Summary of facts connected with
them. — Peculiar circumstances noticed duriny the Eclipse of March 19, 1848. —
Observations of Forster. — Wargentin's remarks on the Eclipse of May 18,
1761. — Kepler's explanation of these peculiarities beiny due to Meteorological
causes. — Admiral Smyth's account of the successive stages of the Eclipse of Oct.
13, 1837. — The Eclipse of Jan. 28, 1888.— The Eclipse of Sept. 2, 1830, a*
witnessed in Africa by S. and J. Lander. — Chaldeean observations of Eclipses. —
Other ancient Eclipses. — Anecdote of Columbus.

A N eclipse of the Moon, though inferior in importance in all
-£^- senses to one of the Sun, is nevertheless by no means
devoid of interest ; it is either partial or total a, according to the
extent to which our satellite is immersed in the Earth's shadow.
In a total eclipse the Moon may be deprived of the Sun's light
for ih 50™, and reckoning from the first to the last contact of the
penumbra, the phenomenon in its various stages may last 5h 30™,
but this is the outside limit. The obscuration is found to last
longer than calculation assigns to it. This is due to the fact
that no account is taken in the calculations of the denser strata
of the atmosphere through which the rays have to pass, which
cause an obstructive effect analogous to that of the solid matter
of the Earth. From numerous observations made during the
eclipse of Dec. 26, 1 833, Beer and Madler found that the apparent
breadth of the shadow was increased by -V on account of the
terrestrial atmosphere. " Owing to the ecliptic limits of the Sun

a But never annular, because the from the Earth, is always in excess of
diameter of the Earth's shadow, at the the diameter of the lunar disc,
greatest possible distance of the Moon

CHAP. VIII.] Eclipses of the Moon. 327

exceeding those of the Moon, there are more eclipses of the
former luminary than of the latter ; but on account of the com-
paratively small extent of the Earth's surface to which a solar
eclipse is visible, the eclipses of the Moon are more frequently
seen at any particular place than those of the Sun."

Fig. 157 is designed to illustrate roughly the different conditions
of eclipses of the Moon. A B is the ecliptic, C D the Moon's
path. The 3 black circles are imaginary sections of the Earth's
shadow, when in 3 successive positions in the ecliptic. If the

. 157-

CONDITIONS OF ECLIPSES OF THE MOON.

conjunction in longitude of the Earth and Moon occurs when
the Moon is at E, it escapes eclipse ; if the Moon is at F, it suffers
a partial obscuration, but if the Moon is at or very near its node,
indicated by G, it will be wholly involved in the Earth's shadow
and a total eclipse will be the result.

Whereas solar eclipses always begin on the Western side and
go off on the Eastern, lunar eclipses on the contrary commence
on the Eastern side and go off on the Western.

Even when most deeply immersed in the Earth's shadow, our
satellite does not, except on rare occasions, wholly disappear, but
may be generally detected with a telescope (and frequently with
the naked eye), exhibiting a dull red or coppery colour. This
was exemplified in a very remarkable manner in the case of the
eclipse of March 19, 1848, on which occasion the Moon was
seen so clearly that many persons doubted the reality of the
eclipse.

328 Eclipses and Associated Phenomena. [BOOK II.

Mr. Forster, who observed the eclipse at Bruges, writes as
follows : —

" I wish to call your attention to the fact which I have clearly ascertained, that
during the whole of the late eclipse of March 19, the shaded surface presented
a luminosity quite unusual, probably about three times the intensity of the mean
illumination of the eclipsed lunar disc. The light was of a deep red colour. During
the totality of the eclipse, the light and dark places on the face of the Moon could be
almost as well made out as on an ordinary dull moonlight night, and the deep red
colour where the sky was clearer was very remarkable from the contrasted whiteness
of the stars. My observations were made with different telescopes; but all presented
the same appearance, and the remarkable luminosity struck every one. The British
Consul at Ghent, who did not know there was an eclipse, wrote to me for an explana-
tion of the blood-red colour of the moon at 9 o'clock V

As a complement to this observation, I may quote one by
Wargentin of the total eclipse of May 18, 1761. He says that
i im after the commencement of the phase —

'* The Moon's body had disappeared so completely, that not the slightest trace of any
portion of the lunar disc could be discerned either with the naked eye or with the
telescope, although the sky was clear, and the stars in the vicinity of the Moon were
distinctly visible in the telescope c."

The red hue was long a phenomenon for which no explanation
could be found ; by some it was considered to be due to a light
naturally inherent to the Moon's surface, but Kepler was the first
to offer a more scientific explanation. He shewed that the phe-
nomenon was a direct result of the refraction of the Earth's
atmosphere, which had the effect of turning the course of the
solar rays passing through it, causing them to fall upon the Moon
even when the Earth was actually interposed between them and
the Sun. That the colour of the Moon's surface is red is due to
the fact that the blue rays of light are absorbed in passing
through the terrestrial atmosphere, in the same manner as the
Western sky is frequently seen to assume a ruddy hue when
illuminated in the evening by the solar rays. On account of the
variable meteorological condition of our atmosphere the quantity
of light actually transmitted is liable to considerable fluctuations,

b Month. Not. ,vol.vui.p.i$2. Mar.i848. stellis vicinis in tubo conspicuis." Other

c Phil. Trans., vol. li. p. 210. 1761. eclipses, where the same thing occurred,

The original runs thus: "Tota luna took place on June 15, 1620 (Kepler,

ita prorsus disparuerat, ut nullum ejus Epist. Ast., p. 825); April 25, 1642

vestigium, vel nudis, vel armatis oculis, (Hevelius, Selenog., p. 117); and June

sensibile restaret. coalo licet sereno, et TO, 1816 ^Beer and Madler).

CHAP. VIII.] Eclipses of the Moon. 329

and hence arises a corresponding variation in the appearances
presented by the Moon's surface during her immersion in the
Earth's shadow. If the portion of the atmosphere through which
the solar rays have to pass is everywhere tolerably free from
vapour, the red rays will be almost wholly absorbed, but not so
the blue, and the illumination will be too feeble to render the
Moon's surface visible : as in the instances cited in note c, p. 328.
If, on the other hand, the region of the atmosphere through which
the solar rays pass be everywhere highly saturated, the red rays
will be transmitted to the Moon in great abundance, and its
surface will consequently be highly illuminated d. Such was the
case in the eclipse of March 1 848 already referred to. If, more-
over, the region of the atmosphere through which the rays pass
be saturated only in some parts and not in others, it follows that
some portions of the Moon's disc will be invisible whilst others
will be more or less illuminated. Such an occurrence was seen
by Kepler6 on Aug. 16, 1598, and by Sir J. Herschel and Smyth
on Oct. 13, 1837.

Smyth has recorded what he saw at each stage of this eclipse
and it is worth while to give his account f , with the sketch which
accompanies it, for the two together will serve as a model for
observers desirous of knowing how to record the progress of an
eclipse of the Moon.

" 22h 55m os. A light grey penumbra appearing.

" 22h 55™ 40". The Moon suffused with a copper tint.

«22h57mi2s. The dark shadow impinged on the lunar limb, and gradually
marched over Grimaldus (a).

« 23!* im j^s. Touched the crater of Aristarchus, the shadow filling the valleys as
it advanced, then ascending the hills, and extinguishing their bright summits (i).

« jjh j^m 2£s_ Reached the fine regions of Copernicus, part of the cloud to the
South crossing Gassendus. The stars gradually increasing in brightness (c).

" 23h 32™ 38*. Across the lunar disc, and through the streaky range of Tycho.
Darkness increased so as to show the Milky Way (d]..

" 23h 44™ 47s. The umbra passed the rugged mountains of Theophilus, soon after
which sea-green tints were observable (e).

d Johnson does not consider that these doubt that the whole question needs more

explanations accord with the observed investigation and discussion,

meteorological facts. (Month. Not., vol. e Ad Vitell. Paralipom.

xlv. p. 44. Nov. 1884.) Monck takes ' Cycle ofCelest. Obj., vol. i. p. 144.
the same view, and it is- not open to

330 Eclipses and Associated Phenomena. [BOOK II.

" 23h 54m ios. The shadow became more transparent, and the whole orb visible,
so that the spots and other particulars of the selenography were revealed (/").

" oh 8m 8s. The sea-green tint spread all over the Moon. A star nearly in a line
with Aristarchus and Copernicus, close to the moon's limb, was occulted 25s
afterwards.

"oh 22™ 40'. The moon became lighter all over. Perhaps the retina of the eye
had been fatigued by the lunar brightness at first, and was now awakening to delicate
impressions.

" oh 58™ 40*. The shadows seemed to be of a dark neutral tint, diluted in its
intensity by refracted light ; a streak of sea-green towards Aristarchus. Turned the

ECLIPSE OF THE MOON, OCT. 13, 1837.

telescope upon the nebula 76 Messier, as a gauge, and saw it beautifully ; but it
gradually faded as the Moon emerged.

" ih 28™ 2is. While the experiments were being made on nebula, during the total
obscuration, the green tints were displaced by the copper ones, and a silvery light
appeared over Grimaldus (g).

" ih 40™ 29'. Aristarchus became uncovered, and its brightness rendered the
obscured part more opaque (A).

« ][h g2m I2s. Copernicus and Tycho uncovered. The smaller stars retiring and
all of them dimming (i).

" 2h 20™ 58'. Theophilus re-appeared almost in full splendour. The nebula 76
Messier only perceptible from a knowledge of its form and place (&).

CHAP. VIII.] Eclipses of the Moon. 331

" 2h 29™ 3os. The small obscured segment of a curious dark tint, lessening with
a smooth motion (Z).

" 2h 31™ 4s. The shadow entirely left the moon, and the eclipse terminated. The
smaller stars vanished, and none but the more brilliant visible. The moon as splendid
as ever."

The Rev. Canon Beechey writing of the eclipse of Oct. 4, 1884,
mentions that during totality the Moon presented " one equal
flat tint of cold grey, through which every feature of the lunar
surface was distinctly visible ; " and that the eclipse generally was
" remarkably similar to the one described by Smyth " as having
happened on Oct. 13, 1837.

The following account of the eclipse of Jan. 28, 1888, will be
found to present several points of interest g : —

"The phase of total eclipse began nominally at 10.30 G. M. T., but it was not
until fully 20 minutes after this that the last remains of the silvery shading along
the west limb of the Moon had entirely disappeared. Up till the time that it did
disappear the familiar coppery hue often seen in total eclipses of the Moon was not
at all uniformly spread over the Moon's disc ; indeed there was no more than a
coppery patch somewhat to the east of the centre of the disc for a long time, and I
doubted whether this usual concomitant of a lunar total eclipse was going to be at all
a conspicuous feature. However, as time wore on and the middle of the eclipse drew
near, the whole disc (at 11.20) became overspread with the coppery hue. I speak of
it under this name because it is the term usually employed, but in reality the tinge
was more pink than coppery in the usual sense of the word, and it was much paler
than usual; so much so indeed that in the middle of the totality (at 11.30) it was
easy enough not only to see the whole disc of the Moon but also to identify some of
the more conspicuous craters, such as Tycho, Copernicus, and Kepler, as well as
several of the larger ' seas.'

" By 11.37 a further change of aspect had manifested itself, and a silvery hue had
begun to appear on the east limb much sooner than one would have expected in the
ordinary course of things.

"During the next 10 minutes a further enfeeblement of the pink hue took place
more or less all round the margin of the disc, with the result that the Moon (looked
at with the naked eye) presented an appearance scarcely different from that which
she oftens presents during a common London fog.

" At 11.55, a small star which had been occulted by the Moon reappeared, and its
pure white light offered a curious contrast to the muddy pink of the Moon.

"Soon after this the atmosphere began to get hazy all round, and before the total
phase ended (at 12.10) the pink hue had become greatly enfeebled, though it did not
finally disappear for a considerable time — half an hour or more.

" The haze varied much from minute to minute, and every now and then, when a
little denser, its effect on the Moon was to make her look like a perfect snowy sphere,
and her globular form was brought out with intense reality, constituting a sight of
remarkable beauty."

* Letter in the Times, Jan. 31, 1888. (G.F.C.)

332 Eclipses and Associated Phenomena. [BOOK II.

The celebrated African explorers, the Landers, graphically de-
scribe what took place on the occasion of the eclipse of the Moon
of Sept. 2, 1 830. They say : —

" The earlier part of the evening had been mild, serene, and remarkably pleasant.
The Moon had arisen with uncommon lustre, and being at the full, her appearance
was extremely delightful. It was the conclusion of the holidays, and many of the
people were enjoying the delicious coolness of a serene night, and resting from
the laborious exertions of the day ; but when the Moon became gradually obscured,
fear overcame every one. As the eclipse increased they became more terrified. All
ran in great distress to inform their sovereign of the circumstance, for there was not
a single cloud to cause so deep a shadow, and they could not comprehend the nature
or meaning of an eclipse. . . .Groups of men were blowing on trumpets, which produced
a harsh and discordant sound; some were employed in beating old drums; others

again were blowing on bullocks' horns The diminished light, when the eclipse was

complete, was just sufficient for us to distinguish the various groups of people, and
contributed in no small degree to render the scene more imposing. If a European,
a stranger to Africa, had been placed on a sudden in the midst of the terror-struck
people, he would have imagined himself to be among a legion of demons, holding
a revel over a fallen spirit11."

It is to the Chaldaeans that we owe the earliest recorded obser-
vations of lunar eclipses, as mentioned by tolemy. The first of
these took place in the 27th year of the era of Nabonassar, the
first of the reign of Mardokempadius, on the 29th day of the
Egyptian month Thotk, answering to March 19, 720 B.C., according
to our mode of reckoning. It appears to have been total at
Babylon, the greatest phase occurring at about 9h 30™ P.M. The
second was a partial eclipse only; it happened at midnight on
the 1 8th of the month T/wt/t, or on March 8, 719 B.C. The third
took place in the same year, on the 15th of the month Phammuth,
or Sept. i, 719 B.C. The magnitude of the eclipse, according to
Ptolemy, was 6 digits on the southern limb, and it lasted 3 hours,
having commenced soon after the Moon rose at Babylon.

Three eclipses recorded by Ptolemy and which happened in
523, 502, and 491 B.C., assisted Sir I. Newton in ascertaining the
terminus a quo from which the "70 weeks " of years were to be
calculated which the prophet Daniel (ix 24) predicted were to
precede the death of Christ. And this terminus a quo is on good

h K. and J. Lander, Journal of an Expedition to explore the Niger, vol. i. p. 366,
New York, 1844.

CHAP. VIII.] Eclipses of the Moon. 333

grounds considered to have been the restoration of the Jews
under Artaxerxes in his 7th'year (457 B.C.)1.

An eclipse occurred in the 4th year of the 91"* Olympiad, the
19th of the Peloponnesian war, answering to Aug. 27, 412 B.C.,
which produced very disastrous consequences to the Athenian
army, owing to the obstinacy of their general Nicias J'. Modern
calculations shew that it was total at Syracuse.

The eclipse of the Moon which happened on March 13, 4 B;C.,
serves to determine the date of our SAVIOUR'S birth. This event
preceded, by a few weeks, the death of Herod, and, according to
Josephusk, that occurrence took place soon after a lunar eclipse
which has been identified as stated1. The Nativity took place
in the Autumn or Winter of 5 B.C.

An eclipse of the Moon, which happened on March i, 1504,
proved of much service to Columbus m. His fleet was in great
straits, owing to the want of supplies, which the inhabitants of
Jamaica refused to give. He accordingly threatened to deprive
them of the Moon's light, as a punishment. His threat was
treated at first with indifference, but when the eclipse actually
commenced, the natives, struck with terror, instantly commenced
to collect provisions for the Spanish fleet, and thenceforward
treated their visitors with profound respect.

1 H. G. Guinness, Approaching end of 1 See Wieseler, Chronological Synopsis

the Age, 5th ed., p. 516 : J. B. Lindsay, of the 4 Gospels, p. 51. I cannot see the

Chrono- Astrolabe, Lond., Bohn, pp. 75 et force of the Rev. S. J. Johnson's reasoning

seq. in favour of the eclipse of Jan. 9, o B.C.

J Plutarch, Vita Nicias. Thucyd., lib. (Eclipses, past and present, p. 21.)

vii. cap. 50. m W. Robertson, Hist, of America,

k Antiq., xvii. 4. loth ed., vol. i. book ii. p. 240.

334 Eclipses and Associated Phenomena. [BOOK II.

CHAPTER IX.

A CATALOGUE OF ECLIPSES «

rilHE eclipses visible in England have received much attention
-L from the Rev. S. J. Johnson, and papers of his cited below
will be interesting to many English readersb.

The following Catalogue contains all the eclipses which occur
during the remainder of the 19th century, excepting solar
eclipses hardly visible to any inhabited portion of the Earth, and
lunar eclipses in which less than TV of the Moon's diameter is
obscured. The time is approximately that of Greenwich, M.
standing for moming, and A. for afternoon. Under the head of
"Locality" the letter C points to the path followed by the
central line ; in cases where this passes very near the North or
South Pole, it is not traced, but those places only are named
where the eclipse will be visible (V). The letters N.E. or S.E.
following the name of a place, indicate the direction taken by the
shadow after passing the parts in question.

ft For Catalogues of Eclipses extending called to a very interesting memoir by S.

over long periods of time see Oppolzer's Newcomb, On the recurrence of Solar

Canon der Finsternisse in DenTcschriften Eclipses, with Tables of Eclipses from B.C.

der Kaiserlichen Akad. der Wissen- 7ootoA.D. 2300; in Astronomical Papers

schaften, vol. lii. Vienna 1887; and IS Art for the use of the American Ephemeris

de verifier lex dates, Paris 1818, vol. i. and Nautical Almanac, vol. i. Washing-

p. 269. ton, U.S., 1879.

In connection with the calculation of b Month. Not., vol. xxxiii. p. 402, Ap.

Solar eclipses attention may here be 1873: Ib. vol. xl. p. 436, May 1880.

CHAP. IX.]

A Catalogue of Eclipses.

335

Year.

Vlonth and
Day.

Hour.

Magni-
tude.

Locality.

1889

Jan. I

9 A.

C Behring's Straights ; Nootka ; Hud-

son's Bay.

—

(

Jan. 17

5iM.

0.68

United States.

—

June 28

9 M.

C S. Africa; Magagascar, S.E.

—

(

July 12

9 A.

0-46

Armenia.

—

Dec. 22

i A.

C Carthagena ; St. Helena ; Abyssinia.

1890

June 17

10 M.

C Cape Verde Islands; Smyrna; Pegu.

—

Dec. 12

3 M.

C Mauritius ; New Zealand ; Tahiti.

1891

(

May 23

7 A.

I-31

India.

—

June 6

4JA.

CN.W. America; N.Pole; Kussia.

—

(

Nov. 1 6

oJM.

1.44

Ireland.

1892

April 26

10 A.

C S. Pacific.

—

(

May ii

nJA.

094

France.

—

Oct. 20

7 A.

V N. America.

—

(

Nov. 4

4| A.

1-04

China.

1893

April 1 6

3 A.

C Easter Island; Guiana; N.E.Africa.

—

Oct. 9

9 A.

Sandwich Islands ; Peru.

1894

(

Mar. 21

2|A.

0.25

New Guinea.

—

April 6

4iM.

C Egypt ; China ; Pacific.

—

(

Sept. 15

4IM.

O-2I

Canada.

—

Sept. 29

5|M-

C Madagascar ; New South Wales ;

New Zealand.

1895

(

Mar. ii

4 M.

I.56

Barbados.

—

Mar. 26

10 M.

V Atlantic ; Europe ; N. Asia.

—

Aug. 20

of A.

V N. Asia.

—

(

Sept. 4

6 M.

i-54

Mississippi.

1896

(

Feb. 28

8 A.

0-83

E. Persia.

—

Aug. 9

4|M.

C Prussia ; E. Siberia ; Pacific.

—

(

Aug. 23

7 M.

0-66

New Mexico.

1897

Feb. i

8 A.

C New Caledonia ; Easter Is.; Guiana.

—

July 29

4 A.

C Gallipagos ; Barbados ; Guiana.

1898

(

Jan. 7

Midnt.

0-12

London.

—

Jan. 22

8 M.

C Fezzan ; Socotra ; N.China.

—

(

Julys

9|A.

O-92

Russia.

—

July 1 8

7 A.

V S. America.

—

Dec. 27

Midnt.

i-33

London.

1899

Jan. ii

ii A.

V E. Asia ; N. America.

—

June 8

7 M.

V N. Europe ; N. Asia.

336 Eclipses and Associated Phenomena. [BOOK II.

Year.

Month and
Day.

Hour.

Magni-
tude.

Locality.

1899

(

June 23

2|A.

I.50

New Guinea.

—

(

Dec. 17

i|M.

0-96

Cape Verde Islands.

1900

May 28

3 A.

C Mexico ; Azores ; Egypt.

—

Nov. 22

8 M.

C Benin ; Madagascar ; New South

Wales.

According to Hindc the following are the important total
eclipses of the Sun for the remainder of the present century,
which are likely to be available for increasing our knowledge of
solar physics: — Dec. 22, 1889, the totality of which lasts for
3™ 34s, and April 19, 1893, lasting 4m 44s.

c Month. Not., vol. xxxii. p. 178 (Feb. 1872).

CHAP. X.] Transits of the Inferior Planets. 337

CHAPTEK X.

TRANSITS OF THE INFERIOR PLANETS.

dell— Transit of Nov. 5, 1868 Transit of May 6, 1878.— Transit of Nov. 7,

1881. — Summary by Jenkins of the main features of a Transit. — Observations
by Prince. — By Langley. — Transit of Venus of Nov. 24, 1639. — Observed by
Horrox and Crabtree. — Transit of June 5, 1761. — Transit of June 3, 1769.—
Where observed. — Singular phenomenon seen on both, occasions. — Explanatory
hypothesis. — Other phenomena. — Transit of Dec. 8, 1874. — Transit of Dec. 6,
1882.

WHEN an inferior planet is in inferior conjunction, and
" has a [geocentric] latitude, or distance from the ecliptic,
less than the Sun's semi-diameter, it will be less distant from the
Sun's centre than such semi-diameter, and will therefore be
within the Sun's disc. In this case the planet being between
the Earth and the Sun, its dark hemisphere being turned towards
the Earth, it will appear projected upon the Sun's disc as an
intensely black round spot. The apparent motion of the planet
being retrograde, it will appear to move across the disc of the Sun
from E. to W. in a line sensibly parallel to the ecliptic." Such
a phenomenon is called a transit, and as it can only occur in the
case of inferior planets it is limited to Vulcan (if there be such a
planet), Mercury, and Venus. Observations of these planets — or
rather, in practice, of Venus only — are available for determining

338 Eclipses and Associated Phenomena. [BOOK II.

the parallax of the Sun, from which may be found the distance of
the Earth from that luminary a.

The rationale of the process is thus popularly set forth by Lord
Grimthorpe : — " If two men stand before a post with a wall behind
it, they will see different places on the wall eclipsed or hidden
by the post; and if the post is as far from the two eclipsed
places as it is from the men, the two eclipses will be exactly as
far apart as the two men are ; if the wall is twice as far from the
post, the two eclipses will be twice as far apart, and so on.

" Therefore two people on the Earth, as far apart as they can
conveniently get for them both to see the transit of Venus from
beginning to end, will see at the same time the two transit spots
twice and a half as far apart in real distance on the Sun as the
observers are distant from each other. Suppose they are 7200
miles apart (measuring through the Earth the shortest way) then
the two transit spots will be 1 8,000 miles apart on the Sun ; and
we have only one step more to take in order to find the diameter
of the Sun in miles ; and that is, to get an accurate map made of
the disc of the Sun with the exact positions of the two spots at
the same time ; for then we can measure their distance on the
map and see what proportion it bears to the diameter, and we
know that 1 8,000 miles bears that same proportion to the real
diameter of the Sun, and the business is done.

" The real difficulty is to get this Sun-map made accurate
enough to measure from, or to get the exact distance of the spots
at the same moment, remembering that the two observers are
nearly half way round the Earth from each other. For that
purpose the following contrivance is adopted. Instead of ob-
serving the transit at one moment only, each man observes the
whole path of Venus across the Sun ; or rather in reality he
observes the exact time it takes ; for they can observe the first
and last contact of the spot far more accurately than they can

• For a somewhat full account of the Sc., vol. xxii. p. 375, Nov. 1881 ; also an

principles which underlie the various Address by the same, Proceedings of the

methods and of the scientific value of the American Association for the Advance-

various results hitherto accomplished see ment of Science, vol. xxxi. Aug. 1882.
a paper by W. Harkness, Amer. Journ.

CHAP. X.] Transits of the Inferior Planets. 339

measure distances on the bright face of the Sun ; and it is not
necessary that they should see anything but the beginning and
the end of the transit. The places on the Earth are so chosen
that the paths may appear not only parallel, but at the widest
distance possible apart, forming two chords across the Sun,
parallel to the diameter which Venus would pass along if she
was exactly in the ecliptic and seen from the centre of the Earth.
The two paths may be on different sides of the Sun's centre if
Venus is exactly at a node, but they are more likely to be on
the same side, in which case their difference of length is greater,
and the observations more likely to give an accurate result.

" For the accuracy of the map depends on this : you have a
circle of known diameter to start with, because the time Venus
would take to cross the middle of the Sun is known from the
proportion which his diameter bears to the orbit of Venus, and
the time she takes to perform it. So if that time were known to
be 6 hours we might draw a circle of 6 inches diameter for the
Sun; and if one observer reported his transit to have lasted 5
hours we should find the place where a chord 5 inches long will
exactly fit ; and if the other transit lasted 5^ hours, we should
put in another chord 5^ inches long, parallel to and near the
former. (The real lengths could not be exactly these, but that
does not signify.) The distance between two chords of 5 and 5^
inches in a circle 6 inches wide can be calculated with the utmost
accuracy, and also the proportion of that distance to the diameter,
which is the proportion of the 18,000 miles to the real diameter
of the Sun, the thing we wanted.

" I have said nothing about the rotation of the Earth during
the time the transit lasts ; but of course due allowance has to be
made for that by methods known to astronomers b."

James Gregory (the inventor of the " Gregorian " Telescope)
seems to have been the first to point out this application of
planetary transit observations c.

b Astron. without Mathematics, 3rd account of the method see Airy's Lectures
ed., p. 185. on Astronomy, p. 145.

c Optica Promota, p. 130. For a lucid

340 Eclipses and Associated Phenomena. [BOOK II.

The transits of the inferior planets are phenomena of very rare
occurrence, especially those of Venus, which occur only at inter-
vals of 8, 105^, 8, iaif, 8, 105!, &c. years. Transits of Mercury
usually happen at intervals of 13, 7, 10, 3, 10, 3, &c. years.
This, however, is not altogether a correct expression of the
intervals ; for, owing to the considerable inclination of Mercury's
orbit, it requires a period of about 217 years to bring the transits
round in a completely regular cycle.

The following are the dates of the transits of Mercury and
Venus from the beginning of the I9th century onwards d : —

Mercury.

Venus.

d. h.

1802

November ...

8 20

1874

December . . .

8 16

1815

November ...

ii 14

1882

December . . .

6 4

1822

November . . .

4 14

2004

June ,

7 21

1832

May

5 o

2OI2

June

5 i3

1835

November ...

7 7

2117

December . . .

10 15

1845

May

8 8

2125

December . . .

8 3

1848

November ...

9 i

2247

June

II 0

1861

November . . .

II IQ

22*s;

June

8 16

1868

November ...

4 18

*)D
2360

December . . .

12 13

1878

May

6 6

2368

December . . .

IO 2

1881

November ...

7 2

2490?

June

12 3

1801

May

0 14

24Q8

June

o 20

y
1894

November . . .

y w
10 6

^y
2603

December . . .

15 12

The transits of Mercury, owing to the heliocentric position of
the nodes, always happen in May or November. When the
transit occurs in May, the planet is passing through the descend-
ing node, and when in November, through the ascending node.
Similar remarks apply to the transits of Venus, the only
difference being that the months are June and December.

d Lalande, Astron., vol. ii. pp. 457-61.
Lalande's original Table gives for Venus
the transits up to A.D. 2984 — some time
hence! For transits of Mercury 1891-
2108 see Astron. Papers for use of
American Nautical Almanack, Ed. by

S. Newcomb, vol. i. part vi. Washington,
1882. This memoir contains an ex-
tremely exhaustive discussion of all the
mathematical questions which arise in
connection with Transits of Mercury,
based on past records and on theory.

CHAP. X.] Transits of the Inferior Planets. 341

The shortest transit of Mercury yet observed was that of
Nov. 12, 1782. It lasted only ih i4m. The longest, that of May 6,
1878, lasted for 7h 47m. The average duration is about 4h.

The first observed transit of Mercury occurred on November 7,
1631, and was predicted by Kepler6, whose surmise was verified
by Gassendi at Paris. The latter remarks : —

" The crafty god had sought to deceive astronomers by passing over the Sun a little
earlier than was expected, and had drawn a veil of dark clouds over the Earth, in
order to make his escape more effectual. But Apollo, acquainted with his knavish
tricks from his infancy, would not allow him to pass altogether unnoticed. To be
brief, I have been more fortunate than those hunters after Mercury who have sought
the cunning god in the Sun ; I found him out, and saw him where no one else had
hitherto seen him V

The second observed transit of this planet happened on Nov. 3,
1651. It is chiefly interesting to us from the fact that it was
observed by a young Englishman, Jeremiah Shakerley; who,
having found by calculation that the phenomenon would not be
visible in England, went out to Surat in India for the purpose of
witnessing itg.

The third observed transit took place on May 3, 1661. It was
observed in part by Huygens, Street, and Mercator in London,
and by Hevelius at Dantzic. The last-named astronomer was
astonished to find that the angular diameter of the planet was
so small h : his determination of it agrees well with modern
results.

The fourth observed transit occurred on Nov. 7, 1677, an(^ ^8
noticeable from the fact that it was the first which was watched
throughout (by Halley) from ingress to egress.

The transits at which anything of particular interest was
noticed are the following : —

Transit of Nov. 3, 1697. Wurzelbau, at Erfurt, perceived a
strange greyish-white spot on the dark body of the planet.

Transit of Nov. n, 1736. Plantade remarked that the disc of
the planet appeared surrounded by a luminous ring.

Transit of May 7, 1799. Schroter and Harding observed the

0 Admonitio ad Astronomos, &c. & Wmg,AstronomiaBritannica,p.^2'

f Opera Omnia, vol. ii. p. 537. h Mercurius in Sole visus, p. 83.

342 Eclipses and Associated Phenomena. [BOOK II.

luminous halo seen by Plantade in 1736, and they likewise saw
two greyish spots on the planet when on the Sun. They ascribed
to them a motion corresponding to the rotation they subsequently
inferred from other observations. The halo or ring was of a
darkish tinge, approaching to violet.

Transit of Nov. 9, 1802. Fritsch and others saw a greyish
spot.

Transit of May 5, 1832. Moll, of Utrecht, saw a ring encircling
the planet when on the Sun, and also a spot on the planet's disc.
The ring had something of a violet tinge. Two spots were seen
by Harding, and Gruithuisen thought he saw one.

Concerning the transit of Nov. 8, 1 848, Dawes, who observed
it at Cranbrook in Kent, says : —

" Nothing remarkable was noticed till Mercury had advanced on the Sun's disc to
about three-quarters of its own diameter, when the cusps appeared much rounded off,
giving a pear-shaped appearance to the planet. The degree of this deformity, how-
ever, varied with the steadiness and definition of the Sun's edge, being least when
the definition was best. A few seconds before the complete entrance of the planet,
the Sun's edge became much more steady, and the cusps sharper, though still
occasionally a little broken towards their points by the undulations. At the instant
of their junction, the definition was pretty good, and they formed the finest con-
ceivable line, Mercury appearing at the same time perfectly round. . . . No difference
is recognised in the Nautical Almanac between the polar and equatorial diameters of
this planet; yet my observations, both with the 5 -foot achromatic and the Gregorian,
shew a perceptible difference, and nearly to the same amount. . . . The compression
would appear to be about ^ '."

Forster observed the transit at Bruges. He remarked the
extreme blackness of the planet compared with the spots : the
ratio of the intensities he estimated at 8:5. He also stated that
the planet had rather the appearance of a globe than of a disc,
and the difference of blackness between the planet and the
spots was less remarkable when he used a reflector with a red
shade k.

A transit happened on Nov. n, 1861. In England few
observations were made, owing to unfavourable weather. Mr.
Baxendell, of Manchester, remarked the excessive blackness of
the planet as compared with the nuclei of certain solar spots, and

1 Month. Not., vol. ix. p. 21. Dec. 1848.
k Month. Not., vol. ix. p. 4. Nov. 1848.

CHAP. X.] Transits of the, Inferior Planets.

that the planet's contour became pear-shaped immediately before
the egress1.

The transit of Mercury which happened on Nov. 5, 1868, was
visible in England. Important observations were made by
Huggins m. An aureola of light around the planet and a luminous
point of light on the body of the planet " nearly in the centre "
were seen, and thus previous observations were fully confirmed.
The breadth of the luminous annulus was about £ of the planet's
apparent diameter. There was no fading off at the margin, the

Fig. 159.

MEBCUEY DURING ITS TRANSIT, NOV. 5, 1 868.

brightness being everywhere about the same, and only slightly
in excess of that of the general surface of the Sun. Both the
aureola and the luminous spot were visible throughout the whole
transit.

Huggins's account of what he saw towards the end of the
phenomenon is as follows : —

"The following appearance was noticed almost immediately after the planet's disc
came up to the Sun's limb. The spot appeared distorted, spreading out to fill up
partly the bright cusps of the Sun's surface between the planet's disc and the Sun's

1 Month. Not., vol. xxii. p. 43, Dec.
1861.

m Month. Not., vol. xxix. p. 25. NOT.
1868.

344 Eclipses and Associated Phenomena. [BOOK II.

limb. This appearance increased as the planet went off the Sun, until when the disc
of the planet had passed by about one-third of its diameter, it presented the form
represented in the diagram, in which the margin of the disc from points at the end of
a diameter parallel to the Sun's limb, instead of continuing its proper curve, appeared
to go in straight lines up to the limb, thus entirely obliterating the cusps of light,
which would otherwise have been seen between the planet and the limb. In the
diagram the aureola and the bright spot are not repeated in the figure of the planet
on the Sun's limb."

The transit of May 6, 1878 was observed under such dis-
couraging circumstances of weather that a very brief allusion to
the results n will suffice. Several observers saw a minute bright
spot or patch on the planet, and several observers saw no such
spot or patch. Some saw what they described as a " ring " ;
some saw what they described as a " halo " — encompassing the
disc of the planet ; others detected no such phenomenon. Some
who noticed one or both of these things confess to a suspicion
that spot and ring were merely optical effects, or effects of
contrast.

The transit of Nov. 7, 1881 was well seen at several
stations in Asia and Australia0. Tebbutt at Windsor, New
South Wales, saw at intervals a faint whitish spot which at one
instant lengthened out into a streak across the disc. He con-
sidered the phenomenon an optical one not in any way connected
with the planet itself. He looked for but failed to see any halo
or ring. On the other hand Dr. Little at Shanghai states that
the planet was "always surrounded by a darkish halo, which
seemed well defined, extending to a distance about equal to the
planet's semi-diameter. With no power could any spots on the
planet be detected."

Jenkins, collecting and comparing all the results recorded up
to 1868, considered himself justified in advancing the following
propositions :—

ist. That in the May transits, when Mercury is near its aphelion,
the luminous spot is in advance of the planet, preceding the
centre ; in the November transits, when Mercury is near its
perihelion, the luminous spot follows the planet.

n Month. Not., vol. xxxviii. p. 397. ° Month. Not., vol. xlii. p. 101, &c.
May 1878. Jan. 1882.

CHAP. X.] Transits of the Inferior Planets. 345

2nd. The luminous spot has never been seen at the centre, but
always south of it, and therefore cannot be due to diffraction.

3rd. Sometimes in the same transit two spots have been seen
close together, where shortly before only one was observed.

4th. In the May transits the rings round the planet are dark
or nebulous and of a violet tinge ; in the November transits
they are bright.

5th. If we take the two transits which have received the most
careful observation, May 1832, observed by Moll, and November
1868, observed by Huggins, we find the contrast very great
and very typical : in the one case a diffused spot preceding the
centre, with dark ring surrounding the planet ; in the other a
sharply defined spot following the centre, with bright ring
surrounding the planet p.

The annulus round Mercury and the white spot on Mercury
during transits across the Sun may now be regarded as regular
concomitants of the phenomenon, but there is no agreement
amongst astronomers as to the cause of these appearances. The
white spot has been regarded by some as indicative of Volcanic
action, but this seems mere fancy. Prof. Powell, with more
show of reason, suggested that diffraction of light had something
to do with the matter, but it is an objection to this theory that
it presupposes the invariable centrality of the white spot ; now
the white spot, though often, is not always coincident in position
with the centre of the planet's disc, and therefore Huggins rejects
the hypothesis. It might conceivably have its origin in the
internal reflection of light in a Huygenian Eye-piece.

We now come to the transits of Venus q, which are more
important and more rare. In the year 1627 Kepler completed
the Eudolphine Tables, and being thus in a position to calculate
the motions of the planets with far more certainty than had ever
been attained before, he betook himself diligently to the work.

P Month. Not., vol. xxxviii. p. 337. Notes and Suggestions to Observers.

Ap. 1878. These should be consulted by persons

i Previous to the transit of 1878 Lord proposing to conduct observations of

Lindsay put forth in conjunction with future transits, but this will be a matter

Dr. U. Copeland an exhaustive paper of for many generations hence.

346 Eclipses and Associated Phenomena. [BOOK II.

The first result was, that he ascertained that during 1631 both
Mercury and Venus would traverse the Sun's disc, the former on
Nov. 7 and the latter on Dec. 6 ; which information he published
in a little tract in 1629'. Of the transit of Mercury I have
already spoken. With reference to that of Venus, Gassendi
made preparations for observing it ; and though Kepler's cal-
culations were to the effect that the ingress would not take
place till near sunset, the French astronomer, anticipating the
possibility of the calculated times being too late, (as had been
the case with Mercury a few weeks previously,) prepared to
commence his watch on Dec. 4, though bad weather prevented
him seeing the Sun till the 6th. He sought unsuccessfully for
the planet both on that and on the following day, and it is
now well known that the transit took place on the night of
Dec. 6 — 7.

The next transit of Venus (the first actually observed) took
place on Nov. 24, 1639 (o. s.) Kepler did not anticipate it, for
he said that none would take place between 1631 and 1761, and
so the honour both of predicting and of observing it rests with a
young English amateur, the Rev. Jeremiah Horrox, curate of
Hoole, a village in Lancashire, 20 miles N. of Liverpool. Horrox
had been engaged in computing the places of the planets by the
aid of Lansberg's Tables. Finding that these gave very
erroneous results he discarded them for Kepler's, from which he
found that on the above named Nov. 24, Venus, in passing its
inferior conjunction, would cross the heavens a little below the
Sun. As Lansberg's Tables indicated that the planet would
cross the upper part of the solar disc, he hoped that a mean of
the two results, so to speak, might be looked for, and that he
should see the planet actually on the Sun, towards the lower
extremity of its disc : further calculation assured him that his
anticipation would turn out to be correct. Owing to the short-
ness of the interval that would elapse previous to the actual
occurrence of the transit he was unable to give much publicity

r Admonitio ad Astronotnos rerumqtte anni 1631 Phcenomenig, Veneris puta et
celestium studiosos, de miris rarisque Mercuriiin Solemincitrsu. Lipsise, 1629.

CHAP. X.] Transits of the Inferior Planets. 347

to the result at which he had arrived ; indeed all that he seems
to have done was to inform his brother Jonas of Liverpool
and his friend William Crabtree, an enthusiastic amateur like
himself, who resided at Broughton, near Manchester, not many
miles distant from Hoole.

Horrox prepared to watch for the planet by transmitting the
image of "the Sun through a telescope on to a screen in a
darkened room. His final calculations gave 3h P.M. on Nov. 24
as the time of conjunction of the centres of the Sun and planet ;
but fearing to be too late, he commenced his scrutiny of the Sun
on Nov. 23. On the following day he began his observations at
Sunrise, and continued them till the hour of Church service.
(It was Sunday.) As soon as he was again at leisure — that is to
say at 3h 15™ P.M. — he resumed his labours, and, to quote his
own words, "At this time an opening in the clouds, which
rendered the Sun distinctly visible, seemed as if Divine Pro-
vidence encouraged my aspirations ; when, O most gratifying
spectacle ! the object of so many earnest wishes, I perceived a
new spot of unusual magnitude, and of a perfectly round form,
that had just wholly entered upon the left limb of the Sun, so
that the margin of the Sun and spot coincided with each other,
forming the angle of contact." Owing to the near approach of
Sunset, Horrox was unable to observe the planet longer than
half an hour ; but at any rate he had seen it, and had been able
to take some measurements 8.

Crabtree had also made arrangements for observing the phe-
nomenon. The Sun was, however, obscured during the whole of
the day, and he had given up in despair all hope of seeing the
transit, when, just before Sunset, the clouds broke up, and,
hastening to his observing chamber, he saw, to his infinite
delight, Venus depicted on the Sun's disc transmitted on to a
screen. He was, according to his own account, so entranced by
the spectacle that ere he recovered his self-possession the clouds
had again enshrouded the Sun, and he saw the planet no more.

5 Whatton, Memoir of Horrox, pp. 109 — 135. See also an article in the Obser-
vatory, vol. vi. p. 318, Nov. 1883.

Fig. 1 60.

348 Eclipses and Associated Phenomena. [BOOK II.

He subsequently found that a rough diagram, which he drew
from memory, agreed well with one drawn by Horrox.

No other transit occurred till June 5, 1761 : this was observed
in many parts of the world for the purpose of ascertaining, in
accordance with the special suggestion of Halley, the solar
parallax. But the results of the different observations were not
satisfactory.

Extensive preparations were made for observing the transit of
June 3, 1769, and King George III. despatched, at his own ex-
pense, a well-equipped expedition to Tahiti under the command

of the celebrated navigator
Cook, then a Lieut., R. N.
Many of the Continental
Powers followed the example
of England, and astronomers
were sent out to the most
advantageous points for ob-
servation. The chief of these
were St. Petersburg, Pekin,
Orenburg, lakutsk, Manilla,
Batavia, for the egress ; and
Cape Wardhus, Kola and
Kajeneburg in Lapland, Point Venus in Tahiti, and Fort Prince
of Wales and St. Joseph in California, for the entire phenomenon.
The observations were long looked upon as trustworthy, but
astronomers eventually came to the conclusion that an im-
portant correction in the final result must be accepted *. Accord-
ingly, the transits of Dec. 9, 1874 and Dec. 6, 1882 were
awaited with special eagerness.

Some phenomena were seen in connexion with the transits of
1761 and 1769 which require a passing mention. It was noticed
on both occasions, and by numerous observers, that the interior
contact of the planet with the Sun did not take place regularly
at the ingress, but that the planet appeared for a short time after

VENUS DURING ITS TRANSIT IN 1769.

See p. 2 ante.

CHAP. X.] Transits of the Inferior Planets.

349

Fig. 161.

it had entered upon the disc of the Sun to be attached to the
Sun's limb by a dark ligament. A similar phenomenon was
noticed at the egress. It was also found that even after the
planet had got wholly clear of the Sun's limb it did not acquire
circularity for several seconds11. Lalande suggested x that irradi-
ation was the cause of these phenomena, and this is doubtless the
true explanation.

It was remarked by several observers of the transits of 1761
and 1769, that, both at the ingress and egress, the portion of the
limb of the planet which was not then projected on the Sun was
rendered perceptible by reason of a faint
ring of light which surrounded it. More
than one observer noticed a ring round
Venus when it was entirely within the
disc of the Sun, similar, it would seem,
to that which has been seen to surround
Mercury when in the same situation.
Dunn stated that this annulus had a
breadth of 5" or 6", that it was some-
what dusky towards the limb of the
planet, and that its outer margin was
slightly tinged with blue. Hitchins described it as excessively
white and faint, and brightest towards the body of the planet.
Nairne spoke of it as brighter and whiter than the body of the
Sun. A comparison of the different accounts seems to shew that
the above-described rings are not identical, but no sufficient
explanation has been offered to account for either, though the
latter has been supposed to indicate the existence of an atmo-
sphere around the planet y.

One observer of the transit of 1769 is stated to have seen a
light on the disc possibly similar to that occasionally noticed on
Mercury during its transits z.

VENDS DURING ITS TRANSIT
IN 1769.

u See Phil. Trans., 1761, 1768, 1769,
1770: also HI em. A cad. dts Sciences for
the same years. •

* Mem. Acad. <1es Sciences, 1770, p.
409.

y For references for all these state-
ments, see Grant's Hist, of Phys. Ast.,

P- 431-

z Append. Ad. Ephem. Astron., 1766,

p. 62.

350 Eclipses and Associated Phenomena. [BOOK II.

Fig. 162.

A ring of light was seen by many observers round Venus
during the transit of Dec. 8, 1874, which the engraving above,
dated 1769, would seemingly represent equally well8.

Figs. 163 to 1 68 are 6 views of Venus at the transit of 1874,
drawn by E. J. Stone, who used the 7-inch refractor of the Cape
Observatory : their large scale renders them of great interest, but
it does not seem necessary to transcribe his notes on each, which
are however very brief b.

It will be remembered that transits of Venus are of importance
in two senses; firstly, as affording a means of ascertaining the
Earth's distance from the Sun ; and secondly, for what they dis-
close respecting the physical circumstances of the planet. In

this place we are dealing only
with the second subject, the
first having been handled in
Book I. Chapter I. (ante).

In anticipation of the transit
of 1882 very extensive prepar-
ations were made by all the
leading European Govern-
ments, and the American
Government c. And many
amateurs joined in the work.
In England a part only of the
transit was visible, and bad
weather generally prevailed
which interfered with such
part as otherwise might have
been seen. Shortly before the
planet entered on the Sun's
disc that portion of its limb which was outside the Sun appeared,
according to Prince, " to be illuminated by a brilliant silver line

VENUS JUST BEFORE THE COMMENCE-
MENT OP ITS TRANSIT, 1 88 2. (Prince.')

ft Month. Not., vol. xxxv. p. 133 (Jan.
l875); P- 310 (March 1875). For a full

c The American Government issued a
very important and exhaustive series of

account of the observations of 1874 see Instructions. (4to. Washington, U.S.

Mem. R.A.S., vol. xlvii. p. 31, 1883.
b Mem. R.A.S., vol. xlvii. p. 101. 1883.

1882.)

Figs. 163-168.

Plate XXII.

h. in. s.

At 19 7 12

FIRST FORMATION OF LIGAMENT.

h. ra. s.
At 19 8 5

APPARENT CONTACT.

h. in. g.

At 19 14 20

THE LIGAMENT BROADER.

h. m. 8.
At 19 7 29

APPARENT CONTACT NOT PERFECT.

h. m. s.
At 19 9 39

THE LIGAMENT BROAD.

h. m. g.
At 19 19 2O
THE LIGAMENT BROADEST.

VENUS DURING ITS TRANSIT IN 1874.

(Drawn by E. J. Stone.}

CHAP. X.] Transits of the Inferior Planets.

353

of light, which most distinctly marked the limb of that portion
of the planet, and which was doubtless produced by the refrac-
tion of sunlight passing through the planet's atmosphere. The
effect was very beautiful d."

This illuminated streak, but far less sharply defined than

Figs. 169 — 171.

At 14 55 3°
Loc. Sid. Time.

J4 55 56
Loc. Sid. Time.

14 56 ii
Loc. Sid. Time.

VENUS DURING ITS TRANSIT, 1882.

Prince saw it, was also observed in America by Prof. S. P.
Langley, who says : —

"It was therefore watched by me, with occasional interruptions, for about 7™.
Owing to the boiling of the limb, it was not easy to determine how much of this
light lay without, how much within, the planet's contour. When first seen, it
suggested for a moment the appearance of Baily's Beads, but the writer's very strong
final impression was that it at any rate extended to some degree within the planet,
and was brightest on the outside, with a slight gradation toward the planet's centre.
Its greatest width was estimated at one-fourth of the planet's radius. Every pre-
caution was taken against instrumental error. The spot was successively examined
in different parts of the field, the eye-piece was rotated, and the amount of light

lt Month. Not., vol. xliii. p. 64. Dec. 1882.

A a

354 Eclipses and Associated Phenomena. [BOOK II.

from the reflectors was varied. It was beyond any question a real, if a most
unexpected and unintelligible phenomenon, and it seems to me that it points to a
real local cause on the planet. It does not appear to be at all assimilable to the
concentric spots which some observers have believed they saw both on Venus and on
Mercury in transit, nor to the alleged phosphorescence on the dark side e."

This phenomenon, with variations of detail, was seen by
Brodief (by whom it was assumed to be a twilight effect
resulting from an atmosphere on Venus), by Horner8, and
probably by others.

Figs. 169-171 were drawn byM. Hatt atChubut, and represent
the phenomena seen at ingress. The observer seems to have
been much struck with the appearance presented by the fringe
of light which surrounded the planet just before the end of the
internal contact.

« Month. Not., vol. xliii. p. 72. Jan. 1883.
' Ibid., p. 76. B Ibid., p. 277.

CHAP. XI.] Occultations. 355

CHAPTER XI.

OCCULTATIONS.

How caused. — Table annually given in the "Nautical Almanac." — Occultation by a
young Moon. — Effect of the Horizontal Parallax. — Projection of Stars on the
Moons disc. — Occultation of Jupiter, January 2, 1857. — Occultation of Saturn,
May 8, 1859. — Occultation of Saturn, April 9, 1883. — Historical notices.

WHEN any celestial object is concealed by the interposition
of another, it is said to be " occulted," and the pheno-
menon is called an " occupation." Strictly speaking, an eclipse
of the Sun is an Occultation of that luminary by the Moon, but
usage has given to it the special name of " eclipse." The
most important phenomena of this kind are the occultations of
the planets and larger stars by the Moon, but the Occultation of
one planet by another, on account of the rarity of such an oc-
currence, is exceedingly interesting. Inasmuch as the Moon's
apparent diameter is about ^°, it follows that all stars and planets
situated in a zone extending j° on each side of her path will
necessarily be occulted during her monthly course through the
ecliptic, and parallax will have the effect of further increasing
considerably the breadth of the zone of stars subject to occulta-
tion. The great brilliancy of the Moon entirely overpowers the
smaller stars, but the disappearances of the more conspicuous
ones can be observed with a telescope, and a table of them is
inserted every year in the Nautical Almanac.

It must be remembered that the disappearance always takes
place at the limb of the Moon which is presented in the direction

A a 2

356 Eclipses and Associated Phenomena. [BOOK II.

of its motion. From the epoch of its New to that of its Full
phase the Moon moves with the dark edge foremost, and from
the epoch of its Full to that of its New phase with the illumi-
nated edge foremost: during the former interval, therefore, the
objects occulted disappear at the dark edge, and reappear at the
illuminated edge ; and during the latter period they disappear at
the illuminated, and reappear at the dark edge. If the occul-
tation be watched when the star disappears on the dark side
of the Moon, that is to say during the first half of a lunation, and
preferably when the Moon is not more than 2 or 3 days old, the dis-
appearance is extremely striking, inasmuch as the object occulted
is suddenly extinguished at a point of the sky where there seems
nothing to interfere with it. Wargentin relates that on May 18,
1761, he saw an occultation of a star by the Moon during a total
eclipse of the latter. He says that the star disappeared " more
quickly than the twinkling of an eye a." In consequence of the
effect of parallax, the Moon, as seen in the Northern hemisphere,
follows a path different from that which it appears to take as seen
in the Southern hemisphere ; it happens, therefore, that stars
which are occulted in certain latitudes are not occulted at all in
others, and of those which are occulted the duration of invisi-
bility, and the moment and place of disappearance and reappear-
ance, are different.

I must not omit a passing allusion to a circumstance occa-
sionally noticed by the observers of occultations ; namely, the
apparent projection of the star within the margin of the Moon's
disc.

Admiral Smyth gives an instance, under the date of October 15,
1829. He says: —

" I saw Aldebaran approach the bright limb of the Moon very steadily ; but, from
the haze, no alteration in the redness of its colour was perceptible. It kept the same
steady line to about £ of a minute inside the lunar disc, where it remained, as pre-
cisely as I could estimate, 2% seconds, when it suddenly vanished. In this there
could be no mistake, because I clearly saw the bright line of the Moon outside the
star, as did also Dr. Lee, who was with me b."

" Phil. Trans., vol. li. p. 210. 1761. the projection, though F. Baily and others
b Mem. R.A.S., vol. iv. p. 642. 1831. didnot see it.
Other observers, Maclear included, saw

CHAP. XI.] Occultations. 357

Sir T. Maclear saw the same thing happen to the same star on
October 23, 1831 :—

" Previous to the contact of the Moon, and star nothing particular occurred ; but
at that moment, and when I might expect the star to immerge, it advanced upon the
Moon's limb for about 3 seconds, and to rather more than the star's apparent diameter,
and then instantly disappeared c."

" This phenomenon seems to be owing to the greater propor-
tionate refrangibility of the white lunar light, than that of the
red light of the star, elevating her apparent disc at the time and
point of contact d."

In 1699 La Hire endeavoured to explain the apparition of stars
on the Moon's disc by supposing that the true disc is accompanied
by a parasitic light, or, as it was formerly termed, a circle of
dissipation, which enlarges the star's apparent diameter, and
through which it shews itself before passing behind the opaque
part of the lunar globe. Arago accepted this theory with the ex-
planation that the observer's eye-piece must be in imperfect
focus, and that so the false disc is caused. The fact that some
have and some have not seen the phenomenon he considered
confirmatory of this explanation e.

The present state of the question is that we do not possess any
certain explanation of the phenomenon.

A remarkable occurrence was noticed by Mr. Ralph Copeland,
on the occasion of the occultation of K Cancri on April 26,
1863:-

" About three-fourths of the light disappeared in the usual instantaneous manner ;
and after an interval of (as near as I can judge) rather more than half a second, the
remaining portion disappeared."

Dawes regarded this as a decisive indication that the star was
double, though he failed to verify this surmise f. On Oct. 30,

c Mem. E.A.S., vol. v. p. 373. 1833. by Stevelly discussing the Diffraction

d Smyth. hypothesis in Brit. Assoc. Hep., 1845 ;

. e Pop. Ast., vol. ii. p. 348, Eng. ed. Transactions of the Sections, p. 5. Also

For other remarks on this phenomenon, one by Plummer in Month. Not., vol.

see papers by Airy in Mem. E.A.S., vol. xxxiii. p. 345 (March 1873).

xxviii. p. 173, 1860, and Month. Not., f Month. Not., vol. xxiii. p. 221 (May

vol. xix. p. 208 (April 1859), and one 1863).

358 Eclipses and Associated Phenomena. [BOOK II.

1 863, I watched the emersion of x^1 Orionis, and it was unques-
tionably not instantaneous.

An occultation of the planet Jupiter took place on January 2,
1857. A dark shadowy streak which appeared projected on the
planet, from the edge of the Moon, was seen by several observers.

Fig. 172.

OCCDLTATION OF JUPITER BY THE MOON : January 2, 1857. (Lastell^
Mr. W. Simms, Sen. thus described it : —

"The only remarkable appearance noticed by me during the emersion was the
very positive line by which the Moon's limb was marked upon the planet ; dark as
the mark of a black-lead pencil close to the limb, and gradually softened off as the
distance increased8."

A representation of this appearance, from a drawing by Lassell,
is annexed [Fig. 172].

An occultation of the planet Saturn by the Moon took place
on May 8, 1859. Dawes thus described it : —

" At the disappearance, the dark edge of the Moon was sharply denned on the
rings and ball of the planet, without the slightest distortion of their figure. There
was no extension of light along the Moon's limb. Even the satellites disappeared
without the slightest warning, and precisely at the edge which was faintly visible.

" At the reappearance I could not perceive any dark shading contiguous to the
Moon's bright edge, such as was seen by myself and several other observers on
Jupiter on January 2, 1858 [Qy. 1857]. The dark belt south of the planet's equator
was clearly defined up to the very edge ; and there was no distortion of any kind,
either of the rings or ball.

"The very pale greenish hue of Saturn contrasted strikingly with the brilliant
yellowish light of the Moon h."

" Month. Not., vol. xvii. p. 81 (Jan. 1859). Other observations will be found
1857). a* P- 33^ of the same volume.

h Month. Not., vol. xix. p. 241 ^

CHAP. XI.J

Occultations.

359

Mr. W. Simms, Jun. did see a dark shading on the planet
contiguous to the Moon's bright edge ; but in 1857 he failed to
notice it.

The occultation of Saturn on April 9, 1883, was observed
by Mr. L. W. Loomis, who remarked on the impression being
vividly conveyed that the Moon was very much nearer to the
eye than Saturn. The successive disappearance of the rings was
an extremely interesting phenomenon.

Fig- 173.

OCCULTATION OF SATURN BY THE MOON : April 9, 1883. (L. W.

In an occultation of Saturn on Oct. 30, 1825, Messrs. R.
Cornfield and J. Wallis plainly saw both one ansa and the ball
flattened *.

The earliest record which we have of an occultation is that of
an occultation of Mars by the Moon, mentioned by Aristotle k.
Kepler found that it occurred on the night of April 4, 357 B,c. l

Instances are on record of one planet occulting another, but
these are of very rare occurrence. Kepler states that he watched
an occultation of Jupiter by Mai's on January 9, 1591. He also

1 Mem. R.A.S., vol. ii. p. 457. 1826. k De Coelo, lib. ii. cap 12.

1 Ad Vitell. Paralifom., p. 307.

360 Eclipses and Associated Phenomena.

mentions that Moestlin witnessed an occultation of Mars by
Venus on October 3, 1590. Mercury was occulted by Venus on
May 17, i737m. As these observations, with the exception of
the last, were made before the invention of the telescope, it is
possible that the one planet was not actually in front of the
other, but only that they were so close together as to have had
the appearance of being one object : as was the case with Venus
and Jupiter on July 21, 1859.

Sometimes stars are occulted by planets. J. D. Cassini men-
tions the occultation of a star in Aquarius by Mars on October i ,
1672".

m Phil. Trans., vol. xl. p. 394. 1738. Twining in Amer. Journ. of Science, and
11 See a paper on Occultationa by A. C. Ser., vol. xxvi. p. 15. July, 1858.

BOOK III.

PHYSICAL AND MISCELLANEOUS
ASTRONOMICAL PHENOMENA.

CHAPTEB I.

THE TIDES.

' O ye seas and floods, bless ye the LORD : praise Him, and magnify
Him for ever." — Benedicite.

Introduction. — Physical cause of the Tides. — Attractive force exercised by the
Moon. — By the Sun. — Spring Tides. — Neap Tides. — Summary of the principal
fact*. — Priming and Lagging. — Diurnal Inequality.

MANY inhabitants of a maritime country like Great Britain
have some acquaintance with the phenomena now to come
under consideration, but beyond a vague notion that the Moon
has something to do with the tides, very few people have an
intelligent idea of the way in which the tides are produced a.

These phenomena are very frequently attributed to the attrac-
tion of the Moon, whereby the waters of the ocean are drawn
towards that side of the Earth on which our satellite happens
to be situated ; in fact, that it is high water when the Moon is
on or near the meridian, of the place of observation.

This, though to a great extent true, by no means adequately

a See a paper by the late Sir J. Lub- by Sir G. B. Airy, in Encycl. Metrop..

bock, in the Companion to the Almanac vol. v. p. 241. There are maps of co-tidal

for 1 830, p. 49. And reference should lines around the British Isles, and over

also be made to an important and ex- the World generally, which will be found

haustive Memoir on "Tides and Waves " of interest.

362 Miscellaneous Astronomical Phenomena. [BOOK III.

represents the facts of the case, for high water is not only pro-
duced on the side of the Earth immediately under the Moon, but
also on the opposite side at the same time. The coincident tides
are therefore separated from each other by 180°, or by half the
circumference of the globe. Since the diurnal rotation of the
Earth causes every portion of its surface to pass successively
under the tidal waves in about 24h, it follows that there are
everywhere 2 tides daily, with an interval of about 1 2h between
each ; whereas, if the common supposition were correct, there
would be only one.

Such being the observed facts, and it being admitted that the
attraction of the Moon gives rise to the upper tide, some further
explanation must be sought to account for the lower one. The
solution is extremely simple as an elementary conception : it is
only necessary to bear in mind that not only does the Moon
attract the upper mass of water, but also the solid globe itself,
which is consequently compelled to recede from the waters
beneath, leaving them behind, and in a sense heaped together.

Besides the influence of the Moon in elevating the waters of
the ocean, that of the Sun is to some extent concerned, but it is
much more feeble than that of the former, on account of the
much greater distance of the solar globe. The mean distance of
the Sun from the Earth is 309-144 times that of the Moon; its
attractive power is consequently (309- 144)2, or 95,570 times less ;
but inasmuch as the mass of the Sun exceeds that of the Moon
in the ratio of 25,916,280 to i, which is much greater than
95,570 to i, it will naturally be said that surely the attraction
exercised by the Sun exceeds that of the Moon in the same
proportion that 25,916,280 exceeds 95,570 b. This, however, is
not the case, for a reason which will now be stated. It must be
borne in mind that the tides are due solely to the inequality of
the attraction in operation on different sides of the Earth, and
that the greater that inequality is the greater will be the
resulting tide, and vice versa. The mean distance of the Sun from

b To avoid complicating the obviously crude argument in the text certain thing?
are left out of consideration.

CHAP. I.] The Tides. 363

the Earth is 11,720 diameters of the latter, and consequently
the difference between its distance from the one side of the
Earth and from the other will be only TTTTTT of the whole dis-
tance, while in the case of the Moon, whose mean distance is
only 30 terrestrial diameters, the difference between the distances
from one side and from the other, reckoned from the Moon, will
be ^V of the whole distance. The inequality of the attraction
(upon which the height of the tidal wave depends) is therefore
much greater in the case of the Moon than of the Sun ; the ratio,
according to Newton, being 58 : 23, or about 1\ : i.

We thus see that there are 2 kinds of tides, lunar and solar.
When therefore the Sun, Moon, and Earth are in the same
straight line with each other, that is to say, when it is either
New or Full Moon, the attractions of the two former bodies act in
the same line, and we have the highest possible tidal elevations,
and what are known as "Spring tides ;" but when the Moon is
in quadrature, or 90° from the Sun, its attraction acts along a
line which is perpendicular to that along which the attraction
of the Sun acts, the two tidal elevations are 90° apart, and we
have the tides which are called " Neap"

It may be convenient to state here a few general facts relating
to the tides : —

1. On the day of New Moon, the Sun and Moon cross the
meridian at the same time, i. e. at noon, and at an interval after
their passage (varying according to the place of observation, but
unchangeable or nearly so for each place) high water occurs.
The water, having reached its maximum height, begins to fall,
and after a period of 6h 1 2m attains a maximum depression ; it
then rises for 6h 1 2m, and reaches a second maximum ; falls for
another interval of 6h 1 2m, and rises again during a 4th interval
of 6h I2m.° It has therefore 2 maxima and 2 minima in a period
of 24h 48m, which is called a Tidal Day.

2. On the day of Full Moon, the Moon crosses the meridian

c Practically this is somewhat incor- place at the mean moment between the
rectly expressed, for it is found that the two tides, the waters usually taking a
intermediate low water does not take shorter time to rise than they do to fall.

364 Miscellaneous Astronomical Phenomena. [BOOK III.

1 2h after the Sun, i. e. at midnight, and the tidal phenomena are
the same as in (i).

3. As time is reckoned by the apparent motion of the Sun, the
solar tide always happens at the same hour at the same place,
but the lunar tide, which is the greater, and thereby gives a
character to the whole, happens 48m 44s later every day ; it
therefore separates Eastwards from the solar tide, at that rate,
and gradually becomes later and later, till at the periods of the
I8t and 3rd quarters of the Moon it happens at the same time as
the low water of the solar tide : then the elevation of the high,
and the depression of the low water, will be the difference of the
solar and the lunar tides, and the tide will be neap.

4. The difference in height between the high and low water is
called the Range of the tide.

5. The spring tides are highest, especially those which happen
36h after the New, or Full Moon.

6. The neap tides are the lowest, especially those which
happen 36h after the Moon is in quadrature.

7. The interval of time from Noon to the time of high water
at any particular place is the same on the days both of New and
Full Moon. This interval is technically known as the "Establish-
ment of the port."

The reason why an interval of time elapses between the Moon's
meridian passage and the time of high water is, that the waters
of the ocean have to overcome a certain peculiar effect of friction,
which cannot immediately be accomplished ; it thus happens
that the lunar tidal wave is not found immediately under the
Moon, but follows it at some distance. Similar results ensue in
the case of the solar wave. The tidal wave is also affected in
another way, by the continued action of both these luminaries,
and at certain periods of the lunar month is either accelerated
or retarded in a way which will now be described : " In the Ist
and 3rd quarters of the Moon, the solar tide is Westward of the
lunar one ; and consequently the actual high water (which is the
result of the combination of the 2 waves) will be to the West-
ward of the place it would have been at if the Moon had acted

CHAP. I.] The Tides, 365

alone, and the time of high water will therefore be accelerated.
In the 2nd and 4th quarters, the general effect of the Sun is, for
a similar reason, to produce a retardation in the time of high
water. This effect, produced by the Sun and Moon combined,
is called the Priming and Lagging of the tides. The highest spring
tides occur when the Moon passes the meridian about i |h after
the Sun ; for then the maximum effect of the 2 bodies coincides."
The "priming" and "lagging" effect deranges the average
retardation, which from a mean value of 48m may be augmented
to 6om or be reduced to 36m.

The 2 tides following one another are also subject to a
variation, called the Diurnal Inequality, depending on the daily
change in declination of the Sun and Moon ; the laws which
govern it are, however, very imperfectly known.

Guillemin writes : — " The height of the tides again varies with
the declinations of the Moon and Sun ; it is by so much greater
as the two bodies are nearer the equator. Twice a year, towards
March 21 and Sept. 22, the Sun is actually in the equator. If,
at the same time, the Moon is near the same plane the tides
which occur then are the highest of all. These are the Equinoctial
Spring Tides, because the Earth is then at the vernal or autumnal
equinox. On the other hand, the smallest tides take place
towards the solstices, if the Moon attains its smallest or its
greatest meridional height at the same time as the Sun. Lastly,
the distances of the Moon and Sun from the Earth have also
their influence on the height of the tides Other things being
equal, the height of a tide is greater or less, according as the
attracting bodies are nearer to or farther from the Earth. Thus
the tides of the winter solstice are higher than those of the
summer oned."

ll The Heavens. Eng. ed., p. 461.

366 Miscellaneous Astronomical Phenomena. [BOOK III.

CHAPTER II.

LOCAL TIDAL PHENOMENA.

Local disturbing influences. — Table of Tidal ranges. — Influence of the Wind. —
Experiment of Smeaton. — The Tides in the Severn at Chepstow. — Tidal phe-
nomena in the Pacific Ocean.— Remarks by Beechey. — Velocity of the great
Terrestrial Tidal wave. — Its course round the Earth, sketched by Johnston. —
Effects of Tides at Bristol. — Instinct of animals. — Tides extinguished in rivers.
— Instances of abnormal Tidal Phenomena. — The " Mascaret" on the Seine. —
Historical notices.

WE have hitherto been considering the tidal wave, on the
supposition of the Earth being a perfect sphere covered
with water to a uniform depth ; but inasmuch as this is not the
case, it follows that the actual phenomena of the tides are
widely different and of a much more complicated character,
owing to the irregular outline of the land, the uneven surface
of the ocean bed, the action of winds, currents, friction, &c.
The effects of these disturbing influences are rendered especially
manifest in the difference of the range of the tide at different
places on the Earth's surface. If the surface of our globe were
entirely covered with water, the height of a solar tide would be
ift HsVnj and of a lunar tide 4ft oin ; but the differences
in the level of the water of the ocean brought about by tidal
influences are often far in excess of these figures. For instance,
in deep estuaries or creeks, open in the direction of the tidal

CHAP. II.] Local Tidal Phenomena. 367

wave, and gradually converging inward, the range is very much
greater than elsewhere, as at : —

Feet.

Bay of Fundy * ... ... ... ... ... ... ... 50

Gallegos River (Patagonia) ... ... ... ... ... 46

Mouth of the Avon ... ... ... ... ... ... 42

St. Malo ... ... ... ... ... ... 40

Bristol Channel (off Chepstow a) ... ... ... ... 38

Milford Haven ... ... ... ... ... ... ... 36

On the other hand, where promontories or headlands jut out into
the sea, the tidal range is frequently small ; thus : —

Feet.
Wicklow ... ... ... ... ... ... ... ... 4

Weymouth ... ... ... ... ... ... ... 7

The Needles ... ... ... ... ... ... ... 9

Cape Clear ... ... ... . . ... ... ... 1 1

In very large open waters, like the Atlantic or the Pacific Oceans,
and in confined seas, like the Baltic, the Mediterranean, &c., the
elevation of the tidal wave is inconsiderable ; thus : —

Feet. Inches.

Toulon ... ... ... ... ... ... ... i o

Antium ... ... ... ... ... i 2

Porto Rico (S. Juan) ... ... ... ... ... i 6

South Pacific i 8

St. Helena ... ... ... ... ... ... ... 3 o

The usual range of the tides at any particular place is also
affected by certain conditions of the atmosphere. At Brest, a
depression of iin in the barometric column causes a difference
of i6in in the elevation of the high-water mark ; at Liverpool,
corresponding to the depression of iin, the difference is about
ioin ; and at the London Docks about 7in : thus when the
barometer is low, an unusually high tide may be expected, and
vice versa. And the influence of the wind also is frequently very
considerable, so much so that during a violent hurricane, Jan. 8,
1839, there was no tide at all at Gainsborough on the river
Trent, a circumstance never before recorded. Smeaton found
experimentally in a canal 4 miles long, that the water-level at
one end was 4in higher than at the other, owing to the force
of the wind acting on the surface of the water.

» See Nature, vol. xix. p. 432. March 13, 1879.

368 Miscellaneous Astronomical Phenomena. [BOOK III.

Concerning the tides at Chepstow, Mr. A. Miller, the lessee of
the Fisheries there, wrote to me thus, under date of June 7,
1888:—

"The rise and fall of the spring tides at Chepstow, New
Passage on Severn, and Clevedon piers, is 45 to 46ft, taken
as the highest spring tide. There is scarcely 6in difference at
either of these points. I have had careful measurements taken
for several years. Four years ago [October 17, 1883], the tide
rose to 48ft or 49". This was caused by a gale of wind and a very
exceptional high flood from the hills, the result of unusually heavy
rain. The houses in the lower part of the town were flooded 2ft
deep, and the river overflowed its banks in the Bristol Channel.
The same thing occurred in 1854. These measurements were
taken from low-water mark to high- water mark, not from the bed
of the river or channel. The tidal wave or bore on the Severn
begins at the Lyde rock just below Beachley and immediately
above the mouth of the Wye. I have known it go up the Wye
for about 4 miles in the shape of an unbroken wave i8in high."

The tides in the Pacific Ocean present great anomalies. The
following remarks respecting them are by a missionary:—

" It is, to the missionaries, a well-known fact that the tides in Tahiti and the
Society Islands are uniform throughout the year, both as to the time of the ebb and
flow, and the height of the rise and fall, it being high water invariably at noon and
at midnight, and consequently the water is at its lowest point at 6 o'clock in the
morning and evening. The rise is seldom more than 1 8 inches or 2 feet above low-
water mark. It must be observed that mostly once, and frequently twice in the
year, a very heavy sea rolls over the reef, and bursts with great violence upon the
shore. But the most remarkable feature in the periodically high sea is, that it
invariably comes from the W. or S.W., which is the opposite direction to that
from which the Trade wind blows. The eastern sides of the island are, I believe,
never injured by these periodical inundations. I have been thus particular iu my
observations, for the purpose in the first place of calling the attention of scientific
men to this remarkable phenomenon, as 1 believe it is restricted to the Tahitian and
Society Island Groups in the South Pacific, and the Sandwich Islands in the North.
I cannot, however, speak positively respecting the tides at the islands eastward of
Tahiti ; but all the islands I have visited in the same parallel of longitude south-
wards, and in those to the westward in the same parallel of latitude, the same
regularity is not observed, but the tides vary with the Moon, both as to the time and
the height of the rise and fall, which is the case at Raratonga b."

b J. Williams, Narrative of Missionary Enterprises in the South Seas, p. 201.

CHAP. II.] Local Tidal Phenomena. 369

The late Admiral Beechey is, so far as I know, the only
person who ever attempted any solution of the question, and
he proposed as a simile, a basin to represent the harbour,
over the margin of which the sea breaks with considerable
violence, thereby throwing in a larger body of water than
the narrow channels can carry off in the same time, and con-
sequently the tide rises, and as the wind abates the water
subsides.

The writer above quoted objects to this explanation, and he
brings forward several arguments, and states several facts, of
which the following is an abstract : —

1. The undeviating regularity of the tide is so well under-
stood by the natives that they distinguish the hours of the day
by terms descriptive of the state of the tide, such as the
following: "Where is the tide1?" instead of, as we should say,
"What o'clock is it?"

2. There are many days during the year when it is perfectly
calm, and yet the tide rises and falls in the same way, and very
frequently there are higher tides in calms than during the pre-
valence of the Trade wind.

3. The tides are as regular on the West side of the island,
where the Trade wind does not reach, as on the East, from which
point it blows.

4. The Trade wind is most powerful from noon till 4 or 5
o'clock P.M., during which time the water ebbs so fast that it
reaches its lowest level by 6 o'clock P.M., instead of in the
morning, as Admiral Beechey states, at which time it is again
high water.

Admiral Beechey's explanation does not seem very satisfactory,
but we are not in possession of any other.

The velocity of the tidal wave is subject to much variation,
and we are not yet in a position to lay down the laws which
govern it. If the whole globe were uniformly covered, the
velocity would be rather more than 1000 miles per hour (7926 x
3-141 6-^- 24*8). It is probably, however, nowhere equal to this,
unless perhaps in the Antarctic Ocean.

370 Miscellaneous Astronomical Phenomena. [BOOK III.
The following table of velocities is given by Whewell c : —

Miles.

In latitude 60° S. 670

In the Atlantic ... ... ... ... ... ... 700

Azores to Cape Clear ... ... ... ... ... ... 500

Cape Clear to Duncansby Head ... ... ... ... 160

Buchan Ness to Sunderland ... ... ... 60

Scarborough to Cromer ... ... ... ... ... 35

North Foreland to London ... ... ... ... ... 30

London to Richmond ... ... ... ... ... ... 13

Concerning the general character of the great terrestrial tidal
wave, I cannot do better than quote the following description by
a well-known eminent geographer : —

" The Antarctic is the cradle of tides. It is here that the Sun and Moon have
presided over their birth, and it is here, also, that they are, so to speak, to attend on
the guidance of their own congenital tendencies. The luminaries continue to travel
round the Earth (apparently) from East to West. The tides no longer follow them.
The Atlantic, for example, opens to them a long, deep canal, running from North to
South, and after the great tidal elevation has entered the mouth of this Atlantic
canal, it moves continually Northward ; for the second 1 2 hours of its life it travels
north from the Cape of Good Hope and Cape Horn, and at the end of the first
24 hours of its existence, has brought high water to Cape Blanco on the West
of Africa, and Newfoundland on the American continent. Turning now round to
the Eastward, and at right angles to its original direction, this great tidal wave
brings high water, during the morning of the 2nd day, to the Western coasts of
Ireland and England. Passing round the Northern cape of Scotland, it reaches
Aberdeen at noon, bringing high water also to the opposite coasts of Norway and
Denmark. It has now been travelling precisely in the opposite direction to that
of its genesis, and in the opposite direction, also, to the relative motion of the Sun
and Moon. But its erratic course if not yet complete. It is now travelling from the
Northern mouth of the German Ocean Southwards. At midnight of the 2nd day it is
at the mouth of the Thames, and wafts the merchandise of the world to the quays of
the port of London. In the course of this rapid journey the reader will have noticed
how the lines [on the map] in some parts are crowded together closely on each other,
while in others they are wide asunder. This indicates that the tide- wave is travelling
with varying velocity. Across the Southern Ocean it seems to travel nearly 1000 miles
an hour, and through the Atlantic scarcely less ; but near some of the shores, as on
the coast of India, as on the East of Cape Horn, as round the shores of Great Britain,
it travels very slowly ; so that it takes more time to go from Aberdeen to London
than over the arc of 120° which reaches from 60° of Southern latitude to 60° North of
the Equator. These differences have still to be accounted for ; and the high velocities
are invariably found to exist where the water is deep, while the low velocities occur
in shallow water. We must therefore look to the conformation of the shores and
bottom of the sea as an important element in the phenomena of the tides d."

c Phil. Trans., vol. cxxiii. p. 212. 1833.
d Johnston, Phys. Atlas.

CHAP. II.] Local Tidal Phenomena. 371

Tidal effects on rivers are often very striking. Especially
is this the case with the Avon at Bristol : when the tide is at its
ebb, the river is little better than a shallow ditch, but when the
waters have risen to the maximum height, an insignificant stream
is converted into a broad and deep channel, navigable by the
largest Indiaman.

The instinct of animals in respect of the tides is often very
remarkable. A Scotch writer observes : " The accuracy with
which cattle calculate the times of ebb and flow, and follow the
diurnal variations, is such, that they are seldom mistaken, even
when they have many miles to walk to the beach. In the same
way they always secure their retreat from these insulated spots
in such a manner that they are never surprised and drowned."

In their passage up rivers, tides are gradually extinguished,
as will be seen from the following table relating to the Thames6:—

Height. Distance from Mouth.

London (Dock «) ... ... ... i8ft. loin. ... 60 m.

Putney JO 2 ... 67^

Kew 7 i ... 73

Richmond ... ... ... ... 3 10 ... 76

Teddington ... ... ... ... i 4^ ... 79

At certain places on the coast of Hampshire and Dorsetshire
the waters of the ocean ebb and flow twice in 1 2 hours instead
of only once, as is usual elsewhere. Southampton, Christchurch,
Poole, Weymouth, and the Firth of Forth, may be mentioned as
places where this singular phenomenon has been observed f .

Macculloch, the Scotch writer just quoted, says that in the
strait between the island of Isla and the islets of Chenzie and
Oersa the time of the ebb is lof hours, and that of the flood only
ij hour8.

Another abnormal tidal phenomenon, presenting some re-
markable features, occurs once a year in the rivers Severn,
Humber11, and Loire, and in some other rivers1 of the same

e Phil. Trans., vol. cxxiii. p. 204. 1833. ' The river Dordogne in France is oc-

f Phil. Trans., vol. cxxiii. p. 226. 1833. casionally the scene of a natural pheno-

g J. Macculloch, Description of the menon which would appear to present

Western Islands of Scotland., 1824, vol. some analogy to the "Bore "of the Severn.

ii. p. 225. And I believe that the Dee at Chester

h White, Eastern England, \o\.ii. ch.3. furnishes another instance.

B b 2

372 Miscellaneous Astronomical Phenomena. [BOOK III.

character as regards the formation of their banks. This is the
" hygre," or " bore," and is due to the fact that a wide estuary at
the mouth of the river suddenly contracts like a funnel. The
result is, that the estual spring tide rushes up with an over-
powering force, carrying all before it. This further peculiarity

Fig. 174.

THE "MASCABET" ON THE SEINE, FRANCE.

likewise subsists : namely, that there is no " slack-water," as is
ordinarily the case in other rivers, between the ebb and flow of
the tide. The approach of the bore on the Severn may be heard
at a considerable distance roaring, as it were, in its upward
progress. The head is about 3ft high, and it frequently does

CHAP. II.] Local Tidal Phenomena. 373

a good deal of mischief to property. The maximum effect is at
the 4th tide after the Full Moon.

Fig. 174, represents the tidal phenomenon known as the
" Mascaret " on certain French rivers, especially the Garonne
and the Seine, which corresponds with the "Bore" of the Severn.

An inspection of the engraving coupled with the remarks
made above will sufficiently indicate the general character of
the phenomenon11.

The evident connexion between the periods of the tides and
those of the phases of the Moon led to the tides being attributed
to the Moon's action long before their true theory was understood.
Aristotle x and Py theas of Marseilles m are both said to have
pointed out the connexion. Julius Csesar adverts to the con-
nexion existing between the Moon and spring tides n.

Pliny says : "^Estus maris accedere et reciprocare, maxime
mirum : pluribus quidem modis : verum causa in sole lundque °."
Kepler clearly indicated that the principle of gravitation is con-
cerned1*— an opinion from which Galileo strongly dissented q.
Wallis, in 1666, also published a tidal theory1'. Before Sir Isaac
Newton turned his attention to this subject, the explanations
given were at best but vague surmises. " To him was reserved
the glory of discovering the true theor}r of these most remarkable
phenomena, and of tracing, in all its details, the operation of the
cause which produces them."

h For further particulars in florid n De Bello Q-allico, lib. iv. cap. 29.

detail, see a paper by Flammarion in ° Pliny, Hist. Nat., lib. ii. cap. 99.

L' Astronomic, vol. v. p. 281, Aug. 1885. '' Epist. Ast., p. 555.

1 Tlfpl Koa/jLov, i Dialoffhi.

m Plutarch, DePlacitis,lib.m. cap. 17. r Phil. Trans., vol. i. p. 263. 1666.

374 Miscellaneous Astronomical Phenomena. [BOOK III.

CHAPTER III.

PHYSICAL PHENOMENA.

Secular Variation in the Obliquity of the Ecliptic. — Precession. — Its value. — Its
physical cause. — Correction for Precession. — History of its discovery. — Nutation.
— HerscheVs definition of it. — Connexion between Precession and Nutation.

Variation in the Obliquity of t/te Ecliptic. — Although
it is sufficiently near for most purposes to consider the
inclination of the plane of the ecliptic to that of the equator as
invariable, yet this is not strictly the case, inasmuch as it is
subject to a small but appreciable change of 46-45" (C. A. F.
Peters) per century. This phenomenon has long been known to
astronomers, on account of the increase it causes in the latitude
of all stars in some situations, accompanied by a corresponding
decrease in the opposite regions. Its effect at the present time
is to diminish the inclination of the planes of the equator and
the ecliptic to each other ; but this diminution will not go on*
beyond certain very moderate limits, after which it will again
increase, and thus oscillate backwards .and forwards through
an arc of 1° 21', the time occupied in one oscillation being
about 10,000 years. One effect of this variation of the plane
of the ecliptic — that which causes its nodes on a fixed plane to
change — is associated with the phenomena of the precession of
the equinoxes, and cannot be distinguished from it, except in
theory b.

Precession. — The precession of the equinoxes is a slow but

a Compare Genenis viii. 22. the epoch of January i, 1890, is 23° 27'

h The inclination of the ecliptic for i2"j<)".

CHAP. III.] Precession. 375

continual shifting of the equinoctial points from East to West c.
Celestial longitudes and right ascensions are reckoned from the
vernal equinox, and if this were a fixed point, the longitude of
a star would never vary, but would remain the same from age
to age as does its latitude (sensibly}. Such, however, is not the
case ; as it has been found that apparently all the stars have
changed their places since the first observations were made by
the astronomers of antiquity*1. Two explanations only can be
given to account for this phenomenon : we must either suppose
that the whole firmament has advanced, or that the equinoctial
points have receded. And as these points depend on the Earth's
motion, it is far more reasonable to suppose that the phenomenon
is owing to some perturbation of our globe rather than that the
starry heavens should have a real motion relative to these points.
The latter explanation is accordingly adopted, namely, that the
equinoxes have a periodical retrograde motion from Ea$t to West,
thereby causing the Sun to arrive at them sooner than it other-
wise would had these points remained stationary. The annual
amount of this motion is, however, exceedingly small, being only
equal to 50-2" e; and since the circle of the ecliptic is divided
into 360°, it follows that the time occupied by the equinoctial

c It may be well to mention that the shall see hereafter — have very consider-

equinoxes are the two points where the able proper motions,
ecliptic cuts the equator ; and are so e Bessel, by a careful discussion of the

called because when the Sun in its annual most reliable observations, fixed the value

course arrives at either of them, day and of general precession for the epoch of

night are equal throughout the world. 1750 at 50-21129", and the value of luni-

The point where the Sun crosses the solar precession at 5O'37572"- For the

equator, going north, is known as the epoch of 1800 he gave for the value of

vernal equinox ; and the opposite point, the latter 50-36354". The lunar preces-

through which the Sun passes going sion is about 2\ times the solar preces-

south, as the autumnal equinox. These sion, just as the lunar tide is 2\ times

intersecting points are also termed nodes, the solar tide, and for much the same

and an imaginary line joining the two, reason, namely, the difference of the at-

the line of nodes. The ascending node tractions. Dreyer's value for 1800 for

( 8 ) answers to the vernal equinox, and the general precession is 50-2365", and

the descending ( ?S ) to the autumnal. for the luni-solar precession 50-3752"

d By " change of place " is here meant (Copernicu*, vol. ii. p. 155. 1882). And

change of position of the Sphere as a see a paper by L. Struve, Mem. de I'Acad.

whole to certain fixed co-ordinates, not de St. Petersboury, ;th Ser.. vol. xxxv.

change of place of the stars inter se, so as p. 3, cited Observatory, vol. xi. p. 200.

to alter the figures of the Constellations ; April 1888.
although many individual stars — as we

376 Miscellaneous Astronomical Phenomena. [BOOK III.

points in making a complete revolution of the heavens is
25,817 years. It is owing to precession that the Pole-star varies
from age to age, and also that whilst the sidereal year, or actual
revolution of the Earth round the Sun, is $6$* 6h 9™ i r-o8, the
equinoctial, solar, or tropical year is only 365* 5h 48m 46-05"
(Airy). The successive returns of the Sun to the same equi-
noctial points must therefore precede its return to the same
point on the ecliptic by 2om 24«958 of time, which corresponds
to about 50-27" of arc. It is also on account of the precession
of the equinoxes that the signs of the ecliptic do not now corre-
spond with the constellations of the same name, but lie about 28°
Westward of them. Thus, that division of the ecliptic known as
the sign of Taurus lies in the constellation Aries, the sign of Aries
having passed into Pisces. It should be remarked, however,
that the signs and constellations coincided with one another
about 100 B.C. In recent times, the attempts that have been
made to establish the motion of the solar system through space
have rendered an accurate knowledge of precession indispensable ;
and the elaborate labours of C. A. F. Peters and O. Struve
have led to a slight modification in the value of the constants
of precession adopted by Besself. Their new value for the
general precession is, for 1800, 50-241 i" + 0-0002268" £.

" The cause of precession is to be found in the combined action
of the Sun and Moon^ upon the protuberant mass of matter
accumulated at the Earth's equator, the attraction of the planets
being scarcely sensible h. The attracting force of the Sun and
Moon upon this shell of matter is of a two-fold character ; one
parallel to the equator, and the other perpendicular to it. The
tendency of the latter force is to diminish the angle which the
plane of the equator makes with the ecliptic ; and were it not for
the rotatory motion of the Earth, the planes would soon coincide ;
but, by this motion, the planes remain nearly constant to each
other. The effect produced by the action of the force in question

1 Tabula, Regiomontance. precession, given at any time, includes

t Called hence, luni-solar precession. the variation caused by the planets, it is
h When the value of the constant of called the constant of gen era I precession.

CHAP. III.] Precession and Nutation- 377

is, however, that the plane of the equator is constantly, though
slowly, shifting its place in the manner we have endeavoured to
describe/'

In the reduction of astronomical observations the correction to
be applied for precession in right ascension is almost always
additive ; increasing in the regions round the poles of the
heavens, but becoming very small near the poles of the ecliptic.
It is in the space included between these poles in each hemisphere
that the correction becomes subtractive ; in the northern hemi-
sphere, this small space comprehends the constellations lying
near the XVIIIth hour of R.A., that being the R.A. of the North
ecliptic pole ; and in the southern hemisphere, the constellations
lying near the VIth hour, that being the R.A. of the South ecliptic
pole. The remarks I have just made apply only to those stars
whose declination North or South exceeds 67°. The annual preces-
sion in declination, however, depends on the star's right ascension
only, both as to amount and direction. At VI and XVIII hours
it is at ,zero ; at XII hours it reaches the Northern maximum of
20" ; and at XXIV it reaches a similar Southern maximum. From
XVIII to XXIV hours, and from XXIV to VI hours, the pre-
cession is N., consequently additive to stars of North declination,
but subtractive from those of South decimation : but from VI to
XVIII, the precession being S., it is additive to Southern, and
subtractive from Northern stars1.

The discovery of precession dates from about 1 25 B. c., when it
was detected by Hipparchus, by means of a comparison of his
own observations with those of Timocharis and Aristyllus, made
about 178 years previously: its existence was afterwards con-
firmed by Ptolemy k. It was Copernicus, however, who first gave
the true explanation of the phenomenon, and Newton who
discovered its physical cause.

Nutation 1. — It must be borne in mind that the effect of preces-
sion varies according to the time of year, on account of the
ever-varying distance of the Earth from the Sun. Twice a

' A useful table of precessions will be given in a later volume of this work.
k Almagest, lib. vii. l Nutatio, nodding.

378 Miscellaneous Astronomical Phenomena. [BOOK III.

year, (at the equinoxes,) the influence of the Sun is at zero ; and
twice a year also, (at the solstices,) it is at its maximum. On no
two successive days is it of exactly the same value, and con-
sequently the precession of the equinoctial points is uneven, and
the obliquity of the ecliptic is subject to a half-yearly variation ;
since the Sun's force which changes the obliquity is constantly
varying, while the rotation of the Earth is continuous. This then
gives rise to a small oscillating motion of the Earth's axis, termed
the solar nutation : of a far more considerable amount, however, is
the value of the nutation arising from the agency of the Moon ;
so much so that it was detected by Bradley before even its
existence had been inferred from theory m.

The nature of nutation cannot be better explained than in
nearly the words of Sir J. Herschel, who says : — " The nutation
of the Earth's axis is a small and slow gyratory movement, by
which, if subsisting alone, the pole would describe among the
stars, in a period of i8| years, a minute ellipse having its longer
axis equal to 18-5", and its shorter to 13-74" (the longer being
directed towards the pole of the ecliptic, and the shorter of course
at right angles to it) ; the semi-axis major is, therefore, equal to
9-25", which quantity is called the 'coefficient of nutation™.' The
consequence of this real motion of the pole is an apparent ad-
vance and recess of all the stars in the heavens to the pole in the
same period. Since, also, the place of the equinox on the ecliptic
is determined by the place of the pole in the heavens, the same
agency will cause a small alternating motion to and fro of the
equinoctial points, by which, in the same periods, both the longi-
tudes and the right ascensions of the stars will be alternately
increased and diminished.

" Precession and nutation, although for convenience here con-
sidered separately, in reality exist together ; they are, in fact, con-
stituent parts of the same general phenomenon : and since, while
in virtue of this nutation, the pole is describing its little ellipse

m Phil. Trans., vol. xlv. p. i. 1748. 9-2231", is the value finally adopted

n Other values are: Busch's 9'232o", by Peters. (Ntimcrus constans Xi'tci-

Lundahl's 9-2361", C. A. F. Peters's tionis, 4to. Petropoli, 1842: see p. 5 of

9-2164". A mean of these, namely W. Strnve1* Rapport on Peters's Memoir.)

CHAP. III.] Precession and Nutation. 379

of 18-5" in diameter, it is carried on by the greater and regularly
progressive motion of precession over so much of its circle round
the pole of the ecliptic as corresponds to i8| years — that is to
say, over an angle i8| times $0-1" round the centre (which, in a
small circle of 23° 28' in diameter, corresponds to 6' 20", as seen
from the centre of the sphere) ; the path which it will pursue in
virtue of the joint influence of the 2 motions will be neither an
ellipse nor an exact circle, but a slightly undulating ring.

" These movements of precession and nutation are common to
all the celestial bodies, both fixed and erratic ; and this circum-
stance makes it impossible to attribute them to any other cause
than the real motion of the Earth's axis, as we have described.
Did they only affect the stars, they might, with equal plausibility,
be considered as arising from a real rotation of the starry heavens
as a solid shell around our axis, passing through the poles of the
ecliptic in 25,868 years, and a real elliptic gyration of thai axis
in rather more than 1 8 years : but since they also affect the Sun,
Moon, and planets, which, having motions independent of the
general body of the stars, cannot without extravagance be sup-
posed to be attached to the celestial conclave, this idea falls to the
ground ; and there only remains, then, a real motion of the Earth
by which they can be accounted for0."

0 Treatise on Ast., p. 172. 1833. In the original version strikes me as being
his Outlines of Astronomy Sir John the better of the two, and therefore I
altered this statement of nutation, but retain it here.

380 Miscellaneous Astronomical Phenomena. [BOOK III.

CHAPTEE IV.

ABERRATION AND PARALLAX.

Aberration. — The constant of Aberration. — Familiar illustration. — History of the
circumstances which led to its discovery by Bradley. — Parallax. — Explanation
of its nature. — Parallax of the heavenly bodies. — Parallax of the Moon. — Im-
portance of a correct determination of the Parallax of an object. — Leonard
Digges on the distance of the Planets from the Earth.

/ABERRATION.— The aberration of light is another im-
-^-^- portant phenomenon which requires to be taken into
consideration in the reduction of astronomical observations.
Although light travels with the enormous velocity of 1 86,660 a
miles per second — a speed so great, that for all practical
terrestrial purposes we may consider it to be propagated
instantaneously; yet the astronomer, who has to deal with
distances of millions of miles, is obliged to be more precise.
A simple illustration will shew this : if we take the mean
distance of our globe from the Sun at 92,890,000 miles, and
consider that light travels at the rate of 186,150 miles
per second, we may ascertain by a simple arithmetical process
that the time occupied by a ray of light in reaching us from
the Sun is 8m 19", so that in point of fact, in looking at the Sun
at a given moment, we do not see it shining as it is, but as it was
gm j^s previously. If the Earth were at rest, this would be a

• A. Cornu (Proceedings of the Roy. Young and Forbes, 301,382 kilometres.

Inst., vol. vii. p. 472, May 1875) makes For a comprehensive review, historical

it 186,660 miles, but it is probably some- and practical, of the whole subject of the

what less. Other values obtained ex- velocity of light, see a Memoir by New-

perimentally are : Helmert, 299,990 kilo- comb in Astron. Paper* prepared for

metres; Michelson, 299,910 kilometres; American Naut. Aim., vol. ii. part III.

CHAP. IV.]

Aberration.

381

trivial matter; but as the Earth is in motion, it follows that
when the solar ray enters the eye of a person on its surface, he
will be some way removed from the point in space at which he
was situated when the ray left the Sun ; he will consequently
see that luminary behind the true place it actually occupies when
the ray enters his eye. In the course of 8m 19* the Earth will
have advanced in its orbit 20-49 a" ; this quantity is called the
Constant of Aberration b. Aberration may be defined to be a phe-
nomenon resulting from the combined effect of the motion of

Fig. 175-
,p

B -
ABERRATION.

light and of the motion of the Earth in its orbit0. Suppose
a ball let fall from a point P above the horizontal line AB, and
a tube, of which A is the lower extremity, placed to receive it ;
if the tube were fixed the ball would strike it on the lower side,
but if the tube were carried forwards in the direction AB, with
a velocity properly adjusted at every instant to that of the ball
while preserving its inclination to the horizon, so that when the
ball in its natural descent reached B the tube would have been
carried into the position BQ, it is evident that the ball through-
out its whole descent would be in the tube ; and a spectator

b Baily's value is 20-419" ; W. Struve's Struve's was long considered the best, but

is 20-445"; C. A. F. Peters's, 20-425", Nyren's is now accepted as such.
20-503", and 20-481"; Lindenau's, c See a paper by Challis in Phil. Mag.,

20-448"; Lundahl's, 20-550"; Maclear's, 4th ser., vol. ix. p. 430. June 1855.
20-53"; Main's, 20-335"; NyreVs, 20-492".

382 Miscellaneous Astronomical Phenomena. [BOOK III.

referring to the tube the motion of the ball, and carried along
with the former, unconscious of its motion, would fancy that the
ball had been moving in an inclined direction and had come
from Q. The following similes are frequently used to exemplify
aberration: a shower of rain descending perpendicularly will
appear to fall in its true direction to a person at rest, but if he
move rapidly through it, it will meet him in a slanting direction :
in other words, it will have an apparent as well as a real motion.
A cannon-ball fired from a shore- battery at a vessel passing up a
river will not pass through the ship in a line coincident with the
direction of the ball, but will emerge on the other side at a point
differing more or less from this line ; the amount of the variation,
however, will depend on the relative velocities of the ball and
ship at the time. If we suppose the cannon-ball to represent
light, and the movement of the ship the motion of the Earth in
its orbit, we have an excellent illustration of the phenomenon
of aberration d.

This unquestionably grand discovery resulted more immediately
from an attempt to detect stellar parallax. Although the facts
revealed by the invention of the telescope and the discovery of
gravitation had the effect of establishing beyond doubt the truth
of the Cppernican theory of the Universe, still it was much to be
desired that some more direct proof should be adduced. The
absence of any appreciable change in the positions of the fixed
stars when examined from opposite sides of the Earth's orbit, was
one of the earliest, and at the same time one of the most serious,
arguments brought against the system of Copernicus ; as it was
always considered that the detection of such a change would
furnish an irresistible proof that the Earth was not at rest, and
consequently was not the centre of the system. The first obser-
vation which ultimately led to the discovery of aberration was
made by Hooke, who selected the star y Draconis as suitable for
the detection of annual parallax e. After observing it carefully

d See Airy's Lectures on Astronomy, serve stars as near the zenith as possible,

p. 1 88. in order to avoid the effects arising from

8 Hooke considered it desirable to ob- any uncertainty as to the value of re-

CHAP. IV.] Parallax. 383

at different seasons of the year, he came to the conclusion that it
had a sensible parallax. It was soon found, however, that the
star was subject to a displacement in a direction contrary to
that which ought to have resulted had the star been affected
by parallax only ; and it was for the purpose of endeavouring to
ascertain the physical cause of this strange phenomenon that
Bradley was led to provide himself with an instrument, that he
might more conveniently study the subject of parallax and
anything that might arise connected therewith. His observations
completely confirmed those of Hooke, and " at length the happy
idea occurred to him, that the phenomenon might be completely
accounted for by the gradual propagation of light combined with
the motion of the Earth in its orbit."

Parallax " is the apparent change of place which bodies
undergo by being viewed from different points." This is the
general signification of the word ; but with the astronomer
it has a conventional meaning, and implies the difference be-
tween the apparent positions of any celestial object when viewed
from the surface of the Earth and from the centre of either the
Earth or the Sun, to one or other of which centres it is usual to
refer all astronomical observations. The position of a heavenly
body, as seen from the Earth's surface, is called its apparent place ;
and that in which it would be seen, were the observer stationed
at the Earth's centre, is known as the true place. It is plain,
therefore, that the altitudes of the heavenly bodies are depressed
by parallax, which is greatest at the horizon f, and decreases
as the altitude of the object increases, until it disappears al-
together at the zenith. In Figure 176, Z is the zenith, C P the
visible horizon, A B the rational horizon, O the position of an
observer, and R the centre of the Earth. From O the observer
will see the stars projected on the sky at P, P', and P", (apparent

fraction ; and -y Draconis happened to be ' This is the case because imaginary

the only bright star passing within a few lines, drawn from the object to the

minutes of the zenith of Gresham Col- observer, and to the centre of the

lege, where his instrument was erected. Earth respectively, will then have the

(Attempttoprovethe Motion of the Earth, greatest possible inclination to each

p. 7-) other.

384 Miscellaneous Astronomical Phenomena. [BOOK III.

placet) ; but, referred to the centre of the Earth, the points of
projection will be Q, Q', and Q" (geocentric places). The general
nature of parallax may be readily understood by supposing
2 persons placed each at the end of a straight line, to look at
a carriage standing in front of a house at the distance (say) of
50 yards from each station. It is evident that the carriage will
appear to each spectator projected upon different parts of the
house. The angle which this difference of position gives rise to,
that is to say the angle formed by the 2 lines of direction, is

PARALLAX.

the angle of parallax. Let us suppose the 2 observers (still
at the same distance from each other) to recede from the carriage ;
the angle of parallax will become more and more acute, until at
length it will become insensible. The example here adduced
may be applied to the heavenly bodies8.

Of all the heavenly bodies, the Moon is that of which the hori-
zontal parallax is the most considerable, because that luminary
is the nearest to the Earth. It is found in the following way : —

* A very good popular exposition of be found in Guillemin's Soleil, pp. 84-9,
the principles involved in the measure- 2nd French Edition,
ment of parallaxes by astronomers will

CHAP. IV.] Parallax. 385

Suppose that 2 astronomers take their stations on the same meri-
dian, one South of the equator, as at the Cape of Good Hope, and
the other North of the equator, as at Berlin, which 2 places lie
nearly on the same meridian : the observers would severally refer
the Moon to different points on the face of the sky — the Southern
observer carrying it farther to the North, and the Northern
observer farther to the South, than its true place as seen from
the centre of the Earth. The observations thus made at the
2 places furnish the materials for calculating, by means of trigo-
nometry, the value of the horizontal parallax of the Moon, from
which we can deduce both its distance and real magnitude. The
parallax thus obtained is called the diurnal, or geocentric, a term
used to distinguish such parallax from annual, or heliocentric,
parallax. And in general it may be stated that these terms
express the angular displacement of a celestial object according
as it is viewed from the Earth or the Sun respectively: in par-
ticular, however, it denotes half the angle formed by a imaginary
lines drawn from each extremity of the diameter of the
Earth's orbit to a fixed star. But this angle is generally too
small to be appreciable. It was this fact of the non-detection
of annual parallax which for a long period of time prior to
the invention of the telescope formed a great obstacle to the
progress of Copernican opinions relative to the system of the
universe.

The Sun, Moon, and planets, though separated from us by
millions of miles, are affected by parallax to a small but never-
theless appreciable amount. With but a few exceptions, however,
this is not the case with the fixed stars ; for in only a very
few instances has parallax been detected, and, so far as is yet
known, the star nearest to us is a Centauri, whose parallax is
equal to only 07 5", which is equivalent to many billions of
miles, as will appear hereafter b.

We may obtain some idea of the importance attaching to a

h As illustrating the delicacy of obser- inch in diameter would be seen at the

vations of this kind, the following remark distance of a mile. This is [that of] the

of Airy's is instructive: "An angle of star which shows the greatest parallax of

2" is that in which a circle T6U of an all." Lectures on Ast,, p. 196.

C C

386 Miscellaneous Astronomical Phenomena. [BOOK III.

correct determination of the parallax of an object by an inspection
of the following table : —

If the Sun's horizontal parallax were 1 i", the mean distance of the following planets
from the Sun in miles would be : —

The Earth. Mart. Jupiter. Saturn.

75,000,000 114,276,750 390,o34>500 7I5>5°4>5°°

If the Sun's parallax were 10", the above distance would become : —

82,000,000 124,942,580 426,478,720 782,28^,920

Errors arising from a mistake of only i" : —

7,000,000 10,665,830 36,444,220 66,780,420'

If the Sun's parallax be taken at 8-8o, the distances will be : —

92,890,000 141,536,000 483,288,000 886,065,000

It is only within comparatively the last few years that the
efforts of astronomers to detect stellar parallax have been
attended with any amount of success. The discovery of planetary
parallax is of course of older date. Pliny considered such in-
vestigations to be but little better than madness, and Riccioli
remarks, " Parallaxis et distantia stellarum fixarum, non potest
certa et evident! observatione humanitus comprehendi." Leonard
Digges, an old English writer, however, seems to have found
no difficulty in the matter ; he gives the following table of
distances, which, however, unfortunately for his reputation, has
turned out to be seriously incorrect. He adds, " Here dernon-
stracion might be made of the distaunce of these orbes, but that
passeth the capacity of the common sort." These are his
results k : —

Myles

" From the Earth to the Moone ... ... ... ... 15,750

From the Moone to Mercury ... ... ... ... 12,812

From Mercury to Venus ... ... ... 12,812

From Venus to the Sunne ... ... ... ... 23,437^

From the Sunne to Mars ... ... ... ... ... 15,725

From Mars to Jupiter ... ... ... ... ... 78,721

From Jupiter to Saturne ... ... ... ... ... 78,721

From Saturne to the Firmament ... ... ... ... 1 20,485."

Whence it follows, according to Digges, that the distance from
London to the stars is exactly 358,463^ miles !

1 Ferguson's Astronomy, p. 76, 2nd Edition, London, 1757.
k Prognostication Euerlastinge, 2nd ed. 1576, fol. 16.

CHAP. V.] Refraction and Twilight. 387

CHAPTER V.

REFRACTION AND TWILIGHT.

Refraction. — Its nature. — Importance of a correct knowledge of its amount. — Table
of the correction for Refraction. — Effect of Refraction on the position of objects
in the horizon. — Sistory of its discovery. — Twilight. — How caused. — Its
duration.

EFR ACTION.— Besides the change of place to which the
heavenly bodies are subjected by the effects of parallax,
atmospheric refraction gives rise to a considerable displacement ;
and it is this power which the air, in common with all trans-
parent media, possesses, which renders a knowledge of the
constitution of the atmosphere a matter of importance to the
astronomer. " In order to understand the nature of refraction
we must consider that an object always appears in the direction
in which the last ray of light comes to the eye. If the light
which comes from a star were bent into 50 directions before it
reached the eye, the star would nevertheless appear in a line
described by the ray nearest the eye. The operation of this
principle is seen when an oar, or any stick, is thrust into the
water. As the rays of light by which the oar is seen have their
direction changed as they pass out of water into air, the ap-
parent direction in which the body is seen is changed in the
same degree, giving it a bent appearance — the part below the
water having apparently a different direction from the part
above a."

0 Olmsted, Mechanism, of the Heavens, ueq.) there will be found a useful sum-
p. 94. Edinburgh edition. In Sir J. mary of information concerning refrac-
Herschel's Outlines of Ast. (pp. 27 et tion.

C C 2

388 Miscellaneous Astronomical Phenomena. [BOOK III.

The direction of this refraction is determined by a general
law in optics, that when a ray of light passes out of a rarer
into a denser medium — e.g. out of air into water, or out of
space into the Earth's atmosphere — it is bent towards a perpen-
dicular to the surface of the medium; but when it passes out
of a denser into a rarer medium, it is bent from the perpen-
dicular. Inasmuch then as we see any object in the direction
in which the rays emanating from it reach the eye, it follows
that the effect of refraction is to make the apparent altitude
of a heavenly body appear greater than the true altitude ; so

REFRACTION.

that for example any object situated actually in the horizon
will appear above it. Indeed, some objects that are actually
below the horizon, and which would be otherwise invisible
were it not for refraction, are thus brought into sight. It was
in consequence of this that on April 20, 1837, the Moon rose
eclipsed before the Sun had set ; and other like instances may
be conceived.

In Fig. 177, Z is the zenith, C D the visible horizon, A B a
parallel of latitude, A E B the boundary of the Earth's atmo-
sphere. Then the light of the star Q will, to the observer at O,
seem to come from the point P.

CHAP. V.] Refraction and Twilight. 389

A correct determination of the exact amount of atmospheric
refraction, or the angular displacement of a celestial object at
any altitude, is a very important, but a very difficult subject of
inquiry, owing to the fact that the density of any stratum of air
(on which its refractive power depends) is affected by the opera-
tion of meteorological phenomena with which we are at present
but very imperfectly acquainted. Thus, the amount of refraction
at any given altitude depends not only on the density but also
on the thermometric and hygrometric conditions of the air
through which the visual ray passes. And although we know
the general fact that the barometric pressure b and the tempera-
ture0 constantly diminish as we rise from the Earth's surface, yet
the law of this diminution is not fully ascertained. In conse-
quence of our ignorance on these points, some degree of un-
certainty is introduced into the determination of the amount of
refraction, which affects astronomical observations involving
extremely minute quantities. Nevertheless it must be re-
membered that inasmuch as the total amount of refraction
is never considerable, and in most cases very small, it can be
so nearly estimated as to offer no serious impediment to the
astronomer.

Tables are in use d, constructed partly from observation and
partly from theory, by means of which we can ascertain approxi-
mately the mean refraction at any given altitude ; additional
rules being given by which this average refraction may be
corrected according to the state of the air at the time of observa-
tion. At the zenith, or at an altitude of 90°, there is no refraction
whatever, objects being seen in the position which they would

b Since the barometer rises with an causes a decrease of density, it follows

increase in the weight and density of the that the rise of the thermometer dimin-

air, its rise is coincident with an augmen- ishes the effect of refraction, the baro-

tation, and its fall with a decrease, of meter remaining stationary. We may

refraction. It will be tolerably near the assume that the refraction at any

truth if we assume that the refraction at given altitude is increased or diminished

any given altitude is increased or dimin- by -f^ of its mean amount for each

ished by ^5-^ of its mean amount for degree by which the thermometer ex-

every ioth of an inch by which the baro- ceeds or falls short of the mean tem-

meter exceeds or falls short of 30 inches. perature of 55° Fahr.

c Also as an increase of temperature d See Vol. II, potf.

390 Miscellaneous Astronomical Phenomena. [BOOK III.

have were the Earth devoid of any atmosphere at all. In
descending from the zenith towards the horizon, the refraction
constantly increases, objects near the horizon being displaced in
a greater degree than those at high altitudes. Thus the re-
fraction, which at an altitude of 45° is only equal to 57", at the
horizon increases to nearly 35'. The rate of the increase
at high altitudes is nearly in proportion to the tangent of the
apparent angular distance of the object from the zenith ; but
in the vicinity of the horizon this rule ceases to hold good,
and the law becomes much more complicated in its expression.
Since the mean diameter both of the Sun and Moon is about
32', it follows that, when we see the lower edge of either
of these luminaries apparently just touching the horizon, in
reality its whole disc is completely below it, and would be alto-
gether hidden by the convexity of the Earth were it not for
refraction.

It is under these circumstances that one of the most curious
effects resulting from atmospheric refraction may often be
noticed, namely the somewhat oval outline presented by the
Sun and Moon when near the horizon. This arises from the
unequal refraction of the upper and lower limbs. The lower
limb being nearer the horizon, is more affected by refraction,
and consequently is raised in a greater degree than the upper
limb, " the effect being to bring the two limbs apparently closer
together by the difference of the two refractions. The form of
the disc is therefore affected as if it were pressed between two
forces, one acting above and the other below, tending to com-
press its vertical diameter, and to give it the form of an
ellipse, the lesser axis of which is vertical and the greater
horizontal."

The dim and hazy appearance of objects in the horizon is not
only occasioned by the rays of light having to traverse a greater
thickness of atmosphere (because their direction is oblique), but
also from their having to pass through the lower and denser
part. "It is estimated that the solar light is diminished 1300
times in passing through these lower strata, and we are thereby

CHAP. V.] Refraction and Twilight. 391

enabled to gaze upon the Sun, when setting, without being
dazzled by his beams." Or, as Bouguer put it, the Sun's
brilliancy at 40° above the horizon is 1000 times greater than
it is at i°.

" The dilated size (generally) of the Sun or Moon when seen
near the horizon beyond what they appear to have when high
up in the sky, has nothing to do with refraction. It is an
illusion of the judgment, arising from the terrestrial objects
interposed, or placed in close comparison with them e. In that
situation we view and judge of them as we do of terrestrial
objects — in detail, and with an acquired habit of attention to
parts. Aloft we have no associations to guide us, and their
insulation in the expanse of the sky leads us rather to under-
value than to over-rate their apparent magnitudes. Actual
measurement with a proper instrument corrects our error,
without however dispelling our illusion. By this we learn
that the Sun, when just on the horizon, subtends at our eyes
almost exactly the same, and the Moon a materially less angle
than when seen at a great altitude in the sky, owing to its
greater distance from us in the former situation as compared
with the latter f ." Guillemin remarks that if the Moon, when
in the horizon, be looked at through a tube, the illusion will
disappear.

Claudius Ptolemy was the first who remarked that a ray of
light proceeding from a star to the Earth undergoes a change
of direction in passing through the atmosphere8. He more-
over stated that the displacement is greatest at the horizon,
diminishes as the altitude increases, and finally vanishes altogether

e This explanation of Sir J. Herschel's Moon when low down towards the horizon
has been disputed, but its general correct- has much to do with the phenomenon,
ness is rendered highly probable by the but that it is mainly due to some physio-
fact that the apparent size of a balloon logical cause, connected with the direction
varies in precisely the same way, accord- of vision, which is worthy of further and
ing as it is high up in the air or near the special study.

horizon. See some remarks by Stroobant ' Sir J. Herschel, Outlines of Ast.,

quoted in Observatory, vol. viii. p. 130, p. 35.

April, 1885. This writer thinks that the * Almay., lib. vii. cap. 6.
loss of brilliancy suffered by the Sun and

392 Miscellaneous Astronomical Phenomena. [BOOK III.

at the zenith- an assertion which we have already seen to be
perfectly correct. In the 1 6th century Tycho Brahe also inves-
tigated the subject of refraction ; and his results, though by no
means so accurate as those of Ptolemy, are interesting from the
fact that they were the first which were reduced to the form of
a Table. Since this period many astronomers have devoted their
attention to the matter, and the Tables now in most general use
are those of Bessel.

Twilight. — This is another phenomenon depending on the
agency of the atmosphere with which the Earth is surrounded.
It is due partly to refraction and partly to reflection, but chiefly
to the latter cause. After sunset the Sun still continues to
illuminate the clouds and upper strata of the air, just as it may
be seen shining on the tops of hills long after it has disappeared
from the view of the inhabitants of adjacent plains. The air and
clouds thus illuminated reflect back part of the light to the
surface beneath them, and thus produce, after sunset and before
sunrise, in a degree more or less feeble according as the Sun is
more or less depressed, that which we call " twilight." Immedi-
ately after the Sun has disappeared below the horizon all the
clouds in the vicinity are so highly illuminated as to be able to
reflect an amount of light but little inferior to the direct light of
the Sun. As the Sun, however, sinks lower and lower, less and
less of the visible atmosphere receives its light, and consequently
less and less of it is reflected to the Earth's surface surrounding
the position where the observer is stationed, until at length,
though by slow degrees, all reflection is at an end, and night
ensues. The same thing occurs before sunrise ; the darkness of
night gradually giving place to the faint light of dawn, until
the Sun appears above the horizon and produces the full light
of day.

The duration of twilight is usually reckoned to last until the
Sun's depression below the horizon amounts to 1 8° : this,
however, varies: in the Tropics a depression of 16° or 17° is
sufficient to put an end to the phenomenon, but in England a
depression of 17° to 2ic is required. The duration of twilight

CHAP. V.] Refraction and Twilight. 393

differs in different latitudes ; it varies also in the same latitude
at different seasons of the year, and depends in some measure on
the meteorological condition of the atmosphere. Strictly speak-
ing, in the latitude of Greenwich there is no true night from
May 22 to July 21, but constant twilight from sunset to sunrise.
Twilight reaches its minimum 3 weeks before the vernal equinox
and 3 weeks after the autumnal equinox, when its duration is
ih 5om. At midwinter it is longer by about 17™, but the
augmentation is frequently not perceptible, owing to the greater
prevalence of clouds and haze at that season of the year, which
intercept the light and hinder it from reaching the Earth. The
duration is least at the equator (ih I2m), and increases as we
approach the Poles, for at the former there are 2 twilights every
24 hours, but at the latter only 2 in a year, each lasting about
50 days. At the North Pole the Sun is below the horizon for 6
months h ; but from January 29 to the vernal equinox, and from
the autumnal equinox to Nov. 1 2, the Sun is less than 1 8° below
the horizon : so that there is twilight during the whole of these
intervals, and thus the length of the actual night is reduced to
i\ months. The length of the day in these regions is about 6
months, during the whole of which time the Sun is constantly
above the horizon. The general rule is, that to the inhabitants of
an oblique sphere the twilight is longer in proportion as the place is
nearer the elevated pole1.

Under some circumstances a secondary twilight may be noticed,
" consequent on a re-reflection of the rays dispersed through the
atmosphere in the primary one. The phenomenon seen in the
clear atmosphere of the Nubian Desert, described by travellers
under the name of the ' After-glow,' would seem to arise from
this cause k."

The "Astronomical" Twilight is that Twilight which has
reference to the visibility and extinction of the smaller stars.

h This is not quite literally 6 months An abstract of it is given in the Intell.

o'wing to the operation of refraction. Obt., vol. vii. p. 135, March 1865.

' A valuable memoir on twilight, by k Sir J. Herschel, Outlines of Ait.,

J. F. J. Schmidt, will be found in Ast. p. 34.
Xach., vol. Ixiii. No. 1495, Oct. 14, 1864.

394 Miscellaneous Astronomical Phenomena.

The following is a table of its duration for different seasons and
latitudes : —

Latitude,

N. or 8.

Duration.

Winter Solstice.

Equinoxes.

Summer Solstice.

h. in.

I 19

I 12

I 19

I I9

I 12

I 20

I 19

I 13

I 21

I 20

I 15

I 24

I 23

I I?

I 28

I 26

I 20

i 33

i 3°

I 24

i 41

i 35

I 29

i 52

i 43

i 35

2 9

1 53

i 44

2 39

2 6

i 55

2 26

2 10

•*" ^

2 57

2 33

i ^-3 !!

4 3

3 8

; H *

BOOK IV,

COMETS.

CHAPTER I.

GENERAL REMARKS.

Comets always objects of popular interest, and sometimes of alarm. — Usual pheno-
mena attending the development of a Comet. — Telescopic Comets. — Comets
diminish in brilliancy at each return. — Period of revolution. — Density. — Mass.
— Lexell's Comet. — General influence of Planets on Comets. — Special influence
of Jupiter. — Comets move in I of 3 kinds of orbits. — Element of a Comet's
orbit. — For a parabolic orbit, 5 in number. — Direction of motion. — Eccen-
tricity of an elliptic orbit. — The various possible sections of a cone. — Early
speculations as to the paths in which Comets move. — Comets visible in the
daytime. — Breaking up of a Comet into parts, — Instance of Sielas Comet. —
Liais's observations of Comet Hi. 1860. — Comets probably self-luminous. —
Existence of phases doubtful. — Comets tvith Planetary discs. — Phenomena
connected with the tails of Comets. — Usually in the direction of the radius
vector. — Secondary Tails. — Vibration sometimes noticed in tails. — Olbers's
hypothesis. — Transits of Comets across the Sun's disc. — Variation in the appear-
ance of Comets exemplified in the case of that of 1769. — Transits of Comets
across the Sun.

THE heavenly bodies which will now come under our notice
are amongst the most interesting with which the astronomer
has to deal. Frequently appearing suddenly in the nocturnal sky,
and often having attached to them tails of immense size and
brilliancy, 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 unanimous testimony of history, during a period
of upwards of 2000 years, that comets were always considered to

396 Comets. [BOOK IV.

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." I shall hereafter examine this question
at greater length. Suffice it for me here to quote the words of
the Poet, who speaks of—

" A Blazing Star,

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

To Heard-men, Rot ; To Ploughmen, haplesse Seasons ;
To Saylors, Storms ; to Cities, ciuil Treasons «."

However little attention might have been paid by the ancients
to the more ordinary phenomena of nature (which, however,
were very well looked after), yet certain it is that comets and
total eclipses of the Sun were not easily forgotten or lightly
passed over ; hence the aspects of remarkable comets seen in

Fig. 178. Fig. 179.

TELESCOPIC COMET TELESCOPIC COMET

WITHOUT A NUCLEUS. WITH A NUCLEUS.

olden times have been handed down to us, often with circum-
stantial minuteness.

A comet usually consists of 3 parts, developed, it may be,
somewhat in the following manner : — A faintly luminous speck
is discovered by the aid of a good telescope ; the size increases
gradually ; and after some little time a nucleus appears — that is,
a part which is more condensed in its light than the rest, and is
sometimes circular, sometimes oval, and sometimes (but very

a Du Bartas, trans. .T. Sylvester, 1621, p. 33.

Plate XXIII.

COMPARATIVE SIZES OF THE EARTH, THE MOON'S ORBIT
AND CERTAIN COMETS, NAMED.

CHAP. I.] General Remarks. 399

rarely) presents a radiated appearance. Arago remarked that
this nucleus is generally eccentrically placed in the head, lying
towards the margin nearest the Sun. Eddie noticed that the
nucleus of Fabry's comet of 1886 was of a ruddy brown colour b.
Both the size and the brilliancy of the object progressively
increase ; the coma, or cloud-like mass around the nucleus,
becomes less regular ; and a tail begins to form, which becomes
fainter as it recedes from the body of the comet. This tail
increases in length so as sometimes to spread across a large
portion of the heavens ; sometimes there are more tails than one,
and occasionally the tail is much narrower in some parts than in
others. The comet approaches the Sun in a curvilinear path,
which frequently differs but little from a right line. It generally
crosses that part of the heavens in which the Sun is situated so
near the latter body 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 original appearance but
in the reverse order.

In magnitude and brightness comets exhibit great diversity :
at rare intervals one appears which is so bright as to be visible
in the daytime ; but the majority are quite invisible to the naked
eye and need more or less optical assistance. These latter are
usually called telescopic comets. The appearance of the same comet
at different periods of its return is so varying that we can never
certainly identify a given comet with any other by any mere
physical peculiarity of size or shape until its "elements" have
been calculated and compared. 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 c."

Fig. 1 80 represents the comparative diameters of the heads of 4
well-known comets as measured on particular occasions. The

b Month. Not., vol. xlvi. p. 456, June 1886. c Smyth, Cycle, vol. i. p. 235.

400 Cvmets. [BOOK IV.

woodcut is drawn to scale, but it must not be inferred that there
is any permanence in the sizes here indicated.

The periods of comets in their revolutions vary greatly, as also
do the distances to which they recede from the Sun. Whilst the
orbit of Encke's comet is contained within that of Jupiter, the
orbit of Halley's extends beyond that of Neptune. Some
comets indeed proceed to a much greater distance than this,
whilst others are supposed to move in curves which do not, like
the ellipse, return into themselves. In this case they never come
back to the Sun. These orbits are either parabolic or hyperbolic.

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 is exceedingly rare is
sufficiently proved by the fact that they have at times passed
very near to some of the planets without disturbing in any
appreciable degree the motions of the said planets. Thus the
comet of 1770 (Lexell's) in its advance towards the Sun, became
entangled amongst the satellites of Jupiter, and remained near
them for 4 months, without in the least affecting them so far as
we know. It can therefore be shown that this comet's mass
could not have been so much as -5-5^ that of the Earth. The
same comet also came very near to the Earth on July i — its
distance from it at 5h on that day being about 1,400,000 miles —
so that had its matter been equal in quantity to that of the Earth
it would, by its attraction, have caused our globe to move in an
orbit so much larger than it does at present that it would have
increased the length of the year by 2h 47™, yet no sensible
alteration took place. The comet of 837 remained for 4 days
within 3,700,000 miles of the Earth without any untoward con-
sequences. Very little argument, therefore, suffices to show the
absurdity of the idea of any danger happening to our planet from
the advent of any of these wandering strangers. Indeed, instead
of comets exercising any influence on the motions of planets,
there is the most conclusive evidence that the converse is the
case — that planets influence comets. This fact is strikingly

CHAP. I.] General Remarks. 401

exemplified in the history of the comet of 1770, just mentioned.
At its appearance it was found to have an elliptical orbit, requir-
ing for a complete revolution only 5! years; yet although this
comet was a large and bright one, it had never been observed
before, and has moreover never been seen since ; the reason being
that the influence of the planet Jupiter, in a short period, com-
pletely changed the character of its path. " 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 $6^ i6h 5™, and could alter the obliquity
of the ecliptic to the extent of a°. Notwithstanding its enormous
mass and the smallness of its distance, such a body would then
produce upon our globe only one kind of revolution, — that of the
calendar3."

Fig. 1 8 1 will illustrate, almost without the necessity of any
written description, the influence of Jupiter on the group of
periodical comets which have come within its reach. These
comets, arranged in the order of their aphelion distances, are as
follows : —

Radii of Earth's orbit.

Encke ... ... ... ... ... ... ... 4-1

Tempel's Second (1873, ii.) ... ... ... ... 4-7

Tempel's First (1867, ii.) 4-8

JUPITER 4.9 to 5-5

Tempel-Swift (1869, iii.) 5.1

Brorsen ... ... ... ... ... ... ... 5-6

Winnecke ... ... ... ... ... ... ... 5-6

D' Arrest ... ... ... ... ... ... ... 5-8

Faye 5.9

Biela ... ... ... ... ... ... ... 6-2

And it is probable that some other comets ought now to be added
to this list; e.g., Finlay's (1886, vii.), Wolfs (1884, iii.), and
Denning's (1881, v.).

A comet may move in either an elliptic, parabolic, or hyper-
bolic orbit ; but for reasons with which mathematical readers are
acquainted, no comet can be periodical which does not follow an
elliptic path. In consequence, however, of the comparative

d Arago, Pop. Axt,, vol. i. p. 642, Eng. ed.

D d

402

Comets.

[BOOK IV.

facility6 with which the parabola can be calculated, astronomers
are in the habit of applying that curve to represent first of all
the orbit of any newly-discovered body. Parabolic "elements"
having been obtained, a search is then made through a catalogue
of comets, to see whether the new elements bear any resemblance

Z1Q
DIAGRAM ILLUSTRATING THE INFLUENCE OP JUPITER ON COMETS.

to those of any object which has been previously observed ; if so,
calculations for an elliptic orbit are undertaken, and a period
deduced.

When a comet is discovered the first question asked about it
by the amateur astronomer is, " When and where can we see it,
and how long will it last ? " and by the professional astronomer,

* To compute elliptic elements for a
comet or a planet will take, even an
experienced calculator, several days of

very hard work. An approximation may
however be obtained by a graphical process
such as that described in Chap. VI (poxf).

CHAP. I.] General Remarks. 403

"What are its elements?" The answer to be given to the first
question always depends upon the answer given to the last
question. To the majority of amateurs these elements are almost
unintelligible, and even to adepts they often convey but a vague
idea of the true form and position of the orbit. The best way to
realize their exact import is by making a model f.

The orbits of all comets, planets, and binary stars are conic
sections whose size, form, and position in space are defined by
quantities called "elements," which, for brevity, are usually
designated by the following symbols : —

T = Moment of the body's Perihelion Passage or nearest ap-
proach to the Sun «.
A = Longitude at an Epoch given.

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.
Q = 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.

f — Eccentricity of the orbit, sometimes given in parts of
radius of the Earth's orbit, sometimes in seconds of arc,
and sometimes as an angle, $. Parts of radius are most
convenient, and seconds of arc may be reduced to that
unit by dividing them by 206,265". When $ is given,
then it is to be understood that e = sin. </>.

f For instructions how to do this see 8 In the case of a binary star, of the

an article by Professor Harkness in the nearest approach of the companion star

Sidereal Messenger, vol. vi. p. 329, Dec. to the principal star, in such case called,

1887. From the introduction to that not the perihelion, but the peri-astron

article the next few paragraphs are taken passage,
with verbal alterations.

D cl 2

404 Comets. [BOOK IV.

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 i-o (or unity), and in that
case the elements are frequently given by stating T, ta, Q, i, and
log. q. Here TT has been replaced by

0) = IT— 8, (l)

which is counted on the comet's orbit, backward, from the peri-
helion to the ascending node ; and the perihelion will lie on
the northern or southern side of the ecliptic according as o> is
less or greater than 1 80°.

As TT and. Q are counted from the vernal equinox, and t is
measured from the plane of the ecliptic, these quantities neces-
sarily refer to a particular equinox, and this is always specified.

It was long customary to measure longitudes in comets' orbits
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 foreign astronomers
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
o° and 1 80°. 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 quadrant 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
retrograde motion they are different, and in that case, if their
values according to the old system are designated by a subscript
o, the equations requisite for passing from the old to the Gaussian
system are : —

i = 180° — io to = 360° — <0o=— o)o

£2 = S30 IT = 280 — TTO.

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 77 and Q . In the old system of elements TT is

CHAP. I.] General Remarks. 405

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 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 following 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 perpen-
dicular, 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 t, the inclination of the
perpendicular shall be (i + 90°), and suppose an observer so situated
in the perpendicular that when i = o° 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 t 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. Which-
ever 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, he must set off o> in the
direction of the hands of a clock, from the perihelion of the
orbit.

The motion of a comet is said to be " direct " (or + ) when it
moves in the order of the signs of the zodiac ; and " retrograde "
(or — ) when it moves contrary to the signs of the zodiac.

In the case of an elliptic orbit given q and e we can ascertain

406

Comets.

[BOOK IV.

Fig. 182.

the length of the major axis (a), and consequently the periodic
time.

Given the mean daily motion (ju), we obtain the period in days
by dividing 1,296,000 (the number of seconds of arc in a circle)

by M-

Astronorners are accustomed to perform all these calculations
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.

Up to the present time the
orbits of more than 300 comets
have been calculated h : a Table
of these will be given hereafter.

Fig. 182 represents the various
possible sections of a right cone,
and will convey a better idea of
the orbits of comets than could
be given by description. When a
right cone is cut at right angles
to its axis, the resulting section
A B will be a circle ; no comet,
however, revolves in a circular
or even nearly circular orbit.

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 a
parabola on the other according to the amount of the obliquity.

THE VARIOUS SECTIONS OF A CONE.

h Gauss's Theoria Motus Corporum
Ccelestium, 4to. Hamburg, 1809, was
long reckoned the standard work on the
subject of orbits, but it has in some
degree been superseded by Oppolzer's
Lehrbuch zur Bahnbestimmuny der
Kometen und Planeten, 2nd ed., 2 vols.

8vo., Leipzic, 1882. A French translation
by a Belgian, M. E. Pasquier, was pub-
lished at Paris, 1886, under the title of
Traitt de la determination des orbites
des cotnetes et des planetes. See also a
paper by Airy, in Memoirs R.A.S., vol.
xi. p. 1 81. 1840.

CHAP. I.]

General Remarks.

407

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 line of the cone and the axis, as G H, the resulting
section will be a parabola.

To the early astronomers the motions of comets gave rise to
great embarrassment. Tycho Brahe thought that they moved in
circular orbits ; Kepler, on the other hand, suggested right lines.
Hevelius seems to have been the first to remark that cometary
orbits were much curved near the perihelion, the concavity being
towards the Sun. He also threw out an idea relative to the
parabola, as being the form of a comet's path, though it does not
seem to have occurred to him that the Sun was likely to be the
focus. Borelli suggested an ellipse or a parabola. Sir William
Lower was probably the first to hint that comets sometimes
moved in very eccentric ellipses ; this he did in his letter to his
" especiall goode friend, Mr. Thomas Harryot," dated Feb. 6, 1610.
Db'rfel, a native of Upper Saxony, was the first practical man ;
he showed that the comet of 1680 moved in a parabolic orbit.
Sir I. Newton also gave his attention
to the subject. Confirming Dorfel, Sir
Isaac further showed that the motion
of the comet was in accordance with
the general Theory of Gravitation.

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 (?),
1106, 1402 (i.), 1402(11.), 1472, 1532,
1577, 1618 (ii.), 1744, 1843 (i-)> l847 (i-)>
1853 (iii.), and 1882 (i.) are the prin-
cipal ones which have been thus observed.

There are some well-established instances of the separation of

Fig. 183.

THE 1st COMET OF 1847, VISIBLE
AT NOON ON MARCH 30.

(Hind.)

408

Comets.

[BOOK IV.

a comet into 2 or more distinct portions. Seneca mentions, on
the authority of Ephorus, a Greek author, that the comet of
371 B.C. separated into 2 parts which pursued different paths1.
Seneca seems to distrust the statement he repeats, but Kepler
accepted it after what he had himself seen in regard to the great
comet of 1618. In the case of this comet Cysatus noticed an
evident tendency to break up. When first seen this comet 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

Fig. 184.

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

condensation towards the centre: on Dec. 19 it appeared some-
what elongated, and by the end of the month the comet had
actually separated into two distinct nebulosities which travelled
together for more than 3 months : the maximum distance between
the parts (157,240 miles) was attained on March 3, 1846, 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 1,250,000 miles. As we shall
have to speak of Biela's comet again in a later chapter no more
need be said about it here.

1 QucBst. Nat., lib. vii. cap. 16. But he says however of the writer he quotes : —
" Ephorus vero non est religiosissimse fidei ; ssepe decipitur, saepe decipit."

CHAP. I.] General Remarks. 409

Biela's comet does not as regards its duplicity stand alone
amongst modern comets. A comet seen in February and March
1 860, only by M. Liais in Brazil, is said to have consisted of a
principal nebulosity accompanied at a short distance by a second
nebulosity. 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 but one observer, and he a French-
man^ The 2nd comet of 1881 according to the testimony of
2 observers threw off a fragment which became virtually an
independent comet, and lasted as such for some days until all
trace of it was lost 1.

The question whether or not comets are self-luminous seems
now satisfactorily settled; it cannot be doubted that they are
self-luminous, as indeed the spectroscope tells us. The high
magnifying power that may sometimes be brought to bear on
them tends to show that they shine by their own light. Sir W.
Herschel was of this opinion from his observations of the comets
of 1807 and 1811 (i.)m It is manifest, however, that if the
existence of phases could be certainly known, this would furnish
an irrefragable proof that the comet exhibiting such shone by
reflected light. It has been asserted from time to time that such
phases have been seen, but none of the statements ever made
seem to deserve attention. Delambre mentions that the registers
of the Royal Observatory at Paris exhibit undoubted evidence of
the existence of phases in the comet of 1682 : but neither Halley
nor any other astronomer who observed this comet has given the
slightest intimation that any phase-phenomena were visible.
James Cassini mentions the existence of phases in the comet of
1 744 n ; on the other hand, Heinsius and Che'saux, who paid
particular attention to this 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

k Ast. Nach., vol. Hi. No. 1248. April 342, Aug. n, 1881.

14, 1860. m Phil. Trans., vol. cii. p. 115. 1812.

1 Bone, Month. Not., vol. xlii. p. 105, n Mem, Acad. des Sciences, 1744, p.

Jan. 1882 : Gould, Nature, vol. xxiv. p. 303.

410 Comets. [BOOK IV.

comet of 1819. Arago sums up the matter by saying that the
observations of M. Cacciatore prove only that the nuclei of comets
are sometimes very irregular0. 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 observation p. The general opinion
is against the existence of phases, and thus we must consider
that comets shine by their own inherent light ; nevertheless the
observations of Airy and others on Donati's comet in 1858 point
to exactly the opposite conclusion, at least as regards the fail of
that comet*1, but then the tails of comets are strange ethereal
structures, and if we know little about the heads we know less
still about the tails. Pons's comet of 1812 was found at its
return in 1883 to be brighter than the theory of its orbit led one
to expect. Niersten suggested that this fact was a proof that
the comet in question was endued with some inherent light of its
own.

Some comets have been observed with round and well-defined
planetary discs. Seneca relates that one appeared after the death
of Demetrius, king of Syria, but little inferior to the Sun [in
size ?] ; being a circle of red fire, sparkling with a light so bright
as to surmount the obscurity of night. The comet of 1652, seen
by Hevelius, was almost as large as the Moon, though not nearly
so bright. The comets of 1665 and 1682 are described as having
been as well defined in their outlines as the planet Jupiter. It
will be remarked that all these instances were before the days
of good telescopes. I am not aware of any modern observations
to the same effect.

There are several curious phenomena connected with the tails
of comets which require notice. 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, the imaginary line joining the
Sun and the comet ; as a general rule, this has been found to be

0 Pop. Ast., vol. i. p. 627, Eng. ed. P Phil. Trans., vol. xcviii. p. 156. 1808.

i Green, Ob*,, 1858, p. 90.

CHAP. I]

General Remarks.

411

the case r, although exceptions do occur. Thus the tail of the
comet of 1577 deviated 21° from the line of the radius vector.
Valz has stated that the tails of comets iv. and v. of 1 863 deviated
from the planes of the orbits, and that only 2 other comets are
known the tails of which did the same s. In some few instances,
where a comet has had more than one tail, the 2nd has extended
more or less towards the Sun ; this was the case with the comets
of 1823, 1851 (iv.), 1877 (ii.), and 1880 (vii.). Although comets
usually have but one tail, yet 2 is by no means an uncommon
number ; and indeed the great comet of 1825 had 5 tails (Duiilop),

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

and that of 1744 as many as 6, or more*. The tails of many
comets are curved, so as to resemble in appearance a sabre ; such
was the case with the comets of 1844 (iii.), and 1858 (vi.), amongst
others. The comet of 1769 had a double curved tail, thus --»"
according to La Nux, who observed it at the Isle of Bourbon.
The great comet of 1882 exhibited a striking and uncommon

r The researches of M. E. Biot shew
that this fact was noticed by the Chinese
long before the time of Apian, to wit, in
837. Comptes Sendus, vol. xvi. p. 75 f-
1843.

s Comptes Rendus, vol. Iviii. p. 853.
1864.

* This statement long depended on the
unconfirmed authority of De Cheseaux, but
it is now certain that this comet did ex-
hibit a complete fan of separate tails. (See
a paper by Dreyer, with an engraving of
the tails, Copernicus, vol. iii. 1883.)

412 Comets. [BOOK IV.

form of tail, some account of which will be given in a later
chapter.

Occasionally a comet exhibits besides its principal tail a
secondary one usually less bright and shorter than the main tail.
For instance, Pons's long-period comet of 1812 at its apparition
in 1886 had on Dec. 29 a primary tail 8° long and a secondary
one very faint and only 3° long. But the secondary tail is not
always the shorter of the two. Swift noted a secondary tail in
the case of the comet ii. of 1881, which was some 55° long, the
longest secondary tail on record u.

The trains of some great comets 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 Pingre', whose great knowledge
of comets adds weight to his testimony. The vibrations com-
menced 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 nature of the comet itself, but
Olbers has pointed out that such appearances could only be fairly
attributed to the effects of our own atmosphere, 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 necessarily elapse before we could see it
reach the tail. This is contrary to observation x, the pulsations
being almost instantaneous." Instances of this phenomenon are
not very common. The most recent case is that of Coggia's
comet of 1874. An English observer at Hereford named With
noticed an "oscillatory motion of the fan-shaped jet upon
the nucleus as a centre which occurred at intervals of from

u Work of Warner Observatory, vol. * Mem. Acad. des Sciences, 1775, p.
i. p. 22. 302.

CHAP. I.] General Remarks. 413

3 to 8 sees. 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 y." A flickering of the tail of this comet was observed
also by Newallz.

Respecting the physical constitution of the tails of comets it
may be said that probably in many cases they are hollow cones.
This theory would accord with the observed fact that single
tails usually increase in width towards their extremities and are
divided in the middle by a dark band, the brilliancy of the
margins exceeding that of the more central portions. Similarly,
comets with tails of tolerably uniform width throughout may be
regarded as hollow cylinders a.

The following is an excellent instance of the ever-changing
appearance of comets; it relates to that of 1769. On Aug. 8,
Messier, whilst exploring with a 3-foot telescope, perceived a
round nebulous body, which turned out to be a comet. On the
1 5th the tail became visible to the naked eye, and appeared to be
about 6° in length ; on the 28th it measured 15°; on Sept. 2, 36°;
on the 6th, 49°; and on the loth, 60°. The comet having now
plunged into the Sun's rays, ceased to be visible. On Oct. 8, the
perihelion passage took place ; on the 24th of the same month it
reappeared, but with a tail only 2° long; on Nov. i the tail
measured 6° ; on the 8th it was only 2|° ; on the 3©th it was i£° :
the comet then disappeared.

Transits of comets across the Sun no doubt occasionally happen,
but only one such spectacle has ever been witnessed, and even
then the nature of the sight was not understood till afterwards.
The German Sun-spot observer, Pastorff, noticed on June 26,
1819, a round dark nebulous spot on the Sun ; it had a bright

y Ast. Reg., vol. xiv. p. 13. Jan. 1876. been broached respecting Comets. For

z Month. Not., vol. xxxvi. p. 279. some particulars as to these see a paper

March 1876. by Huggins, Proc. Roy. Inst., vol. x. p. 8,

* This work is a record of facts rather 1882 ; a paper by Bredichin, Remarques

than of theories, and is too bulky already. ginirales sur les queues des combtes;

Otherwise I might have given it a great also an article by Ranyard in Ast. Reg.,

expansion by embarking on a review of vol. xxi. p. 58, March 1883.

some of the chief theories which have

414 Comets. [Boox IV.

point in its centre. Subsequently when the orbit of couiet ii.,
1819 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 b. Comet v.
of 1826 was calculated to cross the Sun on Nov. 18, 1826, but
owing to the general prevalence of bad weather in Europe, only
2 observers were fortunate enough to be able to see the Sun
on that day, and neither of them could obtain a glimpse of the
comet.

Sir J. Herschel once watched Biela's comet pass in front of a
cluster of stars, but no obliterating effect was noticed, the
several stars being all clearly visible through the comet's ethereal
body.

b For some further particulars as to Month. Not., vol. xxxvi. p. 309, May 1876.

this controversy see Webb's Celest. Olij., Hind seems to have the idea of there

4th ed., p. 40, where there is also a fac- being either error or fraud involved in

simile of Pastorff s original sketch. See Pastorff 's narrative,
also an important paper by Hind in

CHAP. II.]

Periodic Comets.

415

CHAPTER II.

PEKIODIC COMETS*.

Periodic Comets conveniently divided into three classes. — Comets in Class I. — Encke's
Comet. — The resisting medium. — Table of periods of revolution. — TempeVs
second Comet. — WinnecJce's Comet. — Br or sen's Comet. — Tempel's First Comet. —
Swiff s Comet. — Barnard's Comet. — D' 'Arrest's Comet. — Finlay's Comet. — Wolfs
Comet. — Faye's Comet. — Denning 's Comet. — Mechain's Comet of 1790. — Now
known as Tuttle's Comet. — Stela's Comet. — Di Vim's Comet of 1844. — List of
Comets presumed to be of short periods but only once observed. — Comets in
Class II. — Westphal's Comet. — Pans' s Comet of 1812. — Di Vim's Comet of
1846. — Olbers's Comet of 1815. — Srorsen's Comet of 1847. — Halley's Comet. —
Of special interest. — Besume of Halley's labours. — Its return in 1759. — Its
return in 1835. — Its history prior to 1531 traced by Hind. — Comets in Class III
not requiring detailed notice.

THE comets which I propose to treat of in the present chapter
may be conveniently divided into 3 classes : —

1 . Comets of short periods.

2. Comets revolving in about 70 years.

3. Comets of long periods.

The following are the comets belonging to Class I, with which
we are best acquainted : —

Name.

Period.

Next Return.

i. Encke's

Years.
V2Q

1891 Oct.

2. Tempel's Second (1873, ii.)
3. Winnecke's

5-15

5.54

1894 Feb.
1891 Dec.

4. Brorsen's

«i-i8

1890 April

5. Tempel's First (1867, ii.)
6. Swift's (1880, v.)

5-98
6-00

1891 April
1892 Oct.

7. Barnard's (1884, ii.)
8. D' Arrest's

+ 6

6-64

1890
1890 Sept.

9. Finlay's

6-67

1893

10. Wolf s (1884, iii.)

6-76

1891 Aug.

ii. Faye's

7-4-4.

1895 Dec.

12. Denning's

8-86

1890 July

13. Tuttle's . .

M-66

1899 March

• If it should be suggested that I have
given too much space here to the

Periodic Comets, I would answer by
way of excuse that they are, historically

416 Comets. [BOOK IV.

ENCKE'S COMET.

No. i is by far the most interesting comet in the list, and I
shall therefore review its history somewhat in detail.

On Jan. 17, 1786, Mechain, at Paris, discovered a small tele-
scopic comet near the star /3 in the constellation Aquarius. On
the following day he announced his discovery to Messier, who,
owing to unfavourable weather, did not see it till the I9th, on
which night it was also observed by J. D. Cassini, Jun., and the
original discoverer. It was tolerably large and well-defined, and
had a bright nucleus, but no tail.

On Nov. 7, 1795, Miss Caroline Herschel, sister of Sir W.
Herschel, discovered a small comet, about 5' in diameter, without
a nucleus, but yet having a slight central condensation of light.
Olbers observed it on Nov. 21, when 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 calculator, and Pros-
perin declared that no parabola would satisfy the observations.

On Oct. 19, 1805, Thulis, at Marseilles, discovered a small
comet, which was faintly visible to the naked eye. Huth stated
that on the aoth it was very bright in the centre, though without
a nucleus, and 4' or 5' in diameter. On Nov. i the same
observer saw a tail 3° long. Several parabolic orbits were
calculated, and one elliptic one by Encke, to which a period of
1 2' 1 27 years was assigned.

On Nov. 26, 1818, the indefatigable Pons, of Marseilles, dis-
covered a telescopic comet in Pegasus, which was very small and
ill-defined. As it remained visible for nearly 7 weeks, or till
Jan. 12, 1819, a rather long series of observations was obtained ;
and Encke, finding that under no circumstances whatever would

and physically, very interesting objects ; Earth ; and that, consequently, they are

that scarcely a year ever passes that objects which furnish many instructive

some of them do not return to the Sun chances to the class of students for whom

and therefore to visibility as regards the this work is mainly intended.

CHAP. II.] Periodic Comets. 417

a parabolic orbit fairly represent them, determined rigorously to
investigate the elements according to the method of Gauss, then
but little practised. Having done this, he found that the true
form of the orbit was elliptical, and that it had a period of about
3 1 years. On looking over a catalogue of all the comets then
known, he was struck with the similarity which the elements
obtained by him bore to those of the comets of 1786 (i.), 1795, and
1 805, and he was strongly impressed with the idea that the comet
whose movements were then under investigation was identical
with those comets, more particularly as, on the assumption of
a 3^-year period, it might be expected to have been in perihelion
at about those epochs. This question could only be settled by
calculating backwards the effects of planetary perturbation,
which Encke by an extraordinary effort did in 6 weeks. He was
accordingly able to assure himself of the identity of the comet of
1818 with the 3 above-mentioned ones, and also that between
1786 and 1818 it had passed through perihelion 7 times without
being seen.

Encke then proceeded to calculate its next return, and he an-
nounced that the comet would arrive at perihelion on May 24,
1822, after being retarded about 9 days by the influence of the
planet Jupiter.

" So completely were these calculations fulfilled, that astrono-
mers universally attached the name of ' Encke ' to the comet of
1819, not only as an acknowledgment 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 at its return in 1822 the
position of the comet in the heavens was such as to render it
invisible in the Northern hemisphere. It was therefore systema-
tically watched by only one observer, M. Rumker, who discovered
it on June 2, at the private observatory of Sir T. M. Brisbane, at
Paramatta, New South Wales, and he was able to follow it for
only 3 weeks. Riimker's observations were, however, so far

E e

418 Comets. [BOOK IV.

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 by Valz, on July 13, but was
discovered independently by more than one other astronomer.
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

Fig. 1 86.

ENCKE'S COMET: NOV. 30, 1828. (W. Struce.)

time on the same day, Oct. 27, the former having been on the
look-out since Aug. 19, and it was very generally observed till
the end of December in the same year. On Nov. 30 it was
visible to the naked eye as a star of the 6th magnitude, and a
week afterwards it had become as bright as a star of the 5th
magnitude. The outline of the coma was slightly oval, with
the minor axis (on one occasion at least) pointing towards the
Sun.

The 4th of May, 1832, was calculated as the epoch of the next
perihelion passage. The comet was discovered by Mossotti, at
Buenos Ayres, on June i, and by Henderson, at the Cape of
Good Hope, on the following night. Harding, at Gottingen, who
saw it on Aug. 2 1 , was the only European observer who caught

CHAP. II.] Periodic Comets. 419

a glimpse of it, owing to its path lying chiefly in the Southern
heavens.

The next return to perihelion was fixed for Aug. 26, 1835.
The comet was seen both in Europe and at the Cape of Good
Hope.

Dec. 9, 1838, was the epoch of the next perihelion passage;
and as the comet's apparent path would be such as to allow
observations to be made in Europe under very favourable con-
ditions, it was looked for with much interest. Boguslawski dis-
covered it on Aug. 14 ; but Galle, at Berlin, did not see it till
Sept. 1 6 ; and it was not generally seen till the middle of October.
At about the end of the first week 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.

The account of this return would be incomplete were I not
to refer to a peculiarity connected with the comet's motion, which,
though it attracted Encke's attention as far back as 1818, may be
said not to have been brought into special prominence till the
return of 1838. He found that, notwithstanding every allowance
being made for planetary influences, the comet always attained
its perihelion distance about i\ hours sooner than his calculations
led him to expect. In order to account for this gradual diminu-
tion of the period of revolution, which in 1789 was nearly
I2i3d, but in 1838 was scarcely i2ii-rVd» 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. " 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 consequence of this resistance 1 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 precipitated on the Sun ? The question is full
of interest, though altogether open to conjecture."

E e 2

420

Comets.

[BOOK IV.

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

Year of PP. Period, Days.
1786

(I789) 121279

(1792) 1212-67

1795 1212-55

(1799) 1212-44

(1802) 1212-33

1805 I2T2-22

(1809) 1212-10

(l8l2) I2I2-OO

(1815) 1211 89

1819 I2II-78

1822 . . 1211-66

Year of PP. Period, Days.

1825 I2II-55

1829 1211-44

1832 1211-32

1835 1211-22

1838 I2II-II

1842 1210-98

1845 1210-88

1848 1210-77

1852 1210-65

1855 121055

1858 1210-44

The propriety of this explanation of a resisting medium has
been warmly canvassed at different times, and it cannot be said
yet to command universal assent. One strong point against it is,
that, with the exception perhaps of Winnecke's, none of the other
short-period comets (all of them of small size and, presumably,
unimportant mass) yield any indications that they experience a
like influence c. On the other hand, Von Asten, who worked at
the problem with great perseverance, thought there ought to be
no hesitation in accepting the idea, subject to the limitation that
the medium does not extend beyond 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 Aug. 1835 the comet passed very near the planet
Mercury — so near, in fact, that Encke showed that if Laplace's
value of Mercury's mass were 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 obser-
vations indicated no such disturbance of the comet's orbit, it was
obvious that the received mass of the planet was far too great,
and a much lower value has since been adopted d.

b Month. Not., vol. xix. p. 70. Dec. in Month. Not., vol. xxxiii. p. 239. Feb.
1858. 1873.

c See a notice of a paper by A. Hall d In Hind's Comets, p. 65 et seq., the

CHAP. II.] Periodic Comets. 421

Passing over the returns of 1843 and 1845, as offering no
features 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. Early in November it had a tail about i° long,
turned from the Sun, and another and smaller one directed
towards that luminary. On Nov. 22, at midnight, the comet was
distant but 3,600,000 miles from Mercury. The frontispiece to
this volume will convey a good idea of the appearance of the
comet at this apparition.

Passing over also the returns of 1852, 1855, and 1858, we
arrive at that of 1862, the 17th on record. The passage through
the perihelion took place on Feb. 6, but the comet was discovered
by Forster, at Berlin, as early as Sept. 28, 1861. It was then
very faint, and difficult of observation. The same character
applies to the return of 1865, which was observed only in the
Southern hemisphere. In 1868 the comet was unfavourably
placed and was seen by only a few observers.

In 1871, on the other hand, the comet was well seen and
numerous observations of it were made. For a day or two in
November, it was within the reach of telescopes of small dimen-
sions. Some physical peculiarities were noted at this apparition
which deserve mention. When first discovered in August, the
comet was a nearly round and faint nebulosity, without apparent
condensation in any part. By the beginning of November, it
had 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 e : —

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

general principles upon which these in- astronomer is noted in the treatment of

quiries are conducted are laid down with difficult matters.

that clearness of language for which that e 3fow/A.2Vro#.,vol.xxxii.p.26.Nov.i87i.

422

Comet*.

[BOOK IV.

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

" 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

Fig. 187.

ENCKE'S COMET: NOV. 9, 1871. (J. Carpenter.)

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. 2Oth. I detected a nucleus for the first time on

' Month. Not., vol. xxxii. p. 217. March 1872.

CHAP. II.] Periodic Comets. 423

Nov. 7th. 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 by reason of the fact
that it was found not to have been accelerated, in accordance
with the Resisting Medium theory, as all previous returns had
been. Von Asten's conjecture as to this is that in 1869 the
comet might have come into collision with some unknown minor
planet which violently deranged its orbit and modified the orbit
in some degree8.

Encke's comet returned to perihelion again in April 1875, but
no observations were made calling for notice.

In 1878 the comet was best seen in the Southern hemisphere.
Its diameter on August 10 was about 2', and it resembled
generally a star of the 8th magnitude, according to the account
given by Gould. In the Northern hemisphere it was observed
with extreme difficulty by Winnecke at Strasburg on Aug. 20
and by Tempel at Arcetri on Aug. 21. O. Struve, even with the
great 1 5-inch refractor at his command, did not catch sight of it
till Aug. 24.

In 1 88 1 the comet passed through perihelion on Nov. 18. It
was noted by Common, using a 3-ft. reflector, as about 2' in
diameter, very faint, and with slight indications of an increased
brightness in the centre. Tacchini found the spectrum to exhibie
bright bands in the yellow, green, and blue respectively, coin-
ciding with the 3 principal bands seen in the spectra of the
hydro-carbons. As in some other comets, the bands were shaded
off to the blue. A faint continuous spectrum was also detected11.
The spectrum was considered to have undergone no change since
the previous examination in 1878.

In 1884 the comet was observed by Tempel on Dec. 13, but it
was extremely faint. In 1888 it was seen only in the Southern
hemisphere, being first detected by Tebbutt at Windsor, N.S.W.,
on July 8, about 10 days after passiDg perihelion.

s Bulletin de PAcad. deSt.Petersbourff,vo\.v. Observatory, vol.i. p. 21. Aprili87Jr.
h Comptes Rendus, vol. xciii. p. 947.

424 Comets. [BOOK IV.

M. Berberich has written an interesting historial paper on the
brightness of Encke's comet at its many successive apparitions1.

TEMPEL'S SECOND PERIODICAL COMET.

No. 2. — On July 3, 1873, Tempel at Milan discovered a small
faint comet. It was described as being somewhat elongated, with
an eccentric condensation, and a granular appearance. The
diameter was at least 2'. It quickly became evident that the
comet moved in an elliptic orbit of short period. Hind pointed
out that soon after passing its ascending node and when near
aphelion the comet passes close to the orbit of Jupiter, in which
fact is to be found the cause of its periodicity.

This comet returned again to perihelion in August 1878. It
was seen at Oxford with difficulty in the 1 2-inch refractor of the
University Observatory, and resembled a faint round nebula i' in
diameter, with a very slight central condensation.

At the return of 1883 (PP. on Nov. 20) the comet was not seen
owing to its unfavourable position.

. WINNECKE'S COMET,

No. 3, was discovered by M. Pons, on June 12, 1819. Encke
assigned to it a period of 5| years, which, as the table will show,
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 two objects.
It must have returned in 1863, but was not on that occasion
favourably placed for observation. The next return to perihelion
occurred in June 1869. The comet was viewed by Winnecke
himself on April 9 of that year, and is described by him as
being faint, but not less than 6' or 8' in diameter. Winnecke's
comet was again visible in 1875 passing through perihelion on
March n.

Some calculations by Oppolzer led him to think that
this comet was observed previous to the occasion which has

1 Ast. Nach.,vol. cxix., No. 2836, Ap. 24, 1888.

CHAP. II.] Periodic Comets. 425

usually been considered its first discovery (namely its detection
by Pons in 1819), and that it is identical with the comet dis-
covered by Pons in Feb. 1808. (See the Catalogue of "Un-
calculated" Comets, post, p. 585.)

It was due again in the Autumn of 1880, but escaped notice.
In 1886 however it was seen in the Southern hemisphere after
perihelion passage. It passed its perihelion 1 2 days earlier than
it was predicted to do, and according to Oppolzer its movements
cannot be completely explained by the theory of gravitation alone,
but the existence of some resisting medium seems indicated.

BRORSEN'S COMET,

No. 4, was detected by M. Brorsen, at Kiel, on Feb. 26, 1846.
The observations showed an elliptic orbit, and the epoch of the
ensuing arrival at perihelion was fixed for Sept. 26, 1851, but
its position then was not very favourable, owing to its proximity
to the Sun, and it escaped observation. Bruhns again discovered
it on March 18, 1857. I saw it on March 23; it possessed the
usual nebulous appearance common to these objects, and had a
diameter of about 2', though it was unfavourably placed in the
morning twilight, which probably marred its brilliancy. This
comet again returned to perihelion in April 1868, Oct. 1873, and
March 1879. Spectroscopic observations on the last-named
occasion by Konkoly in Hungary and C. A. Young in America
tended to show that the spectra of this and of Encke's comet
were identical with one another, and with a hydro-carbon
spectrum J. Brorsen's comet escaped notice at its return in
Sept. 1884.

The period of Brorsen's comet has been gradually diminishing
owing to the effect of planetary perturbation. Thus :—
In 1 846 ; period = 2034 days.
» l857; » =2022 „

„ 1868; „ = 2002

» = J999 »
» l8795 „ = T994 „

Observatory, vol. iii. pp. 56, 105, June, August, 1879.

426 Comets. [BOOK IV.

It was missed, as stated above, at the returns of 1851 and 1862
owing to its unfavourable position. The present orbit was due
to the action of Jupiter in 1842, and, according to D' Arrest,
serious disturbances from the same cause will happen in 1937 k.

TEMPEL'S FIRST PERIODICAL COMET.

No. 5. — On April 3, 1867, Tempel at Milan discovered a small
telescopic comet. It had a nucleus which was eccentrically placed
in an oval coma, and Talmage, on May 3, thought that the
nucleus appeared to have a division across the centre. The
comet remained visible for about 4 months, which time sufficed
to make it evident that its orbit was an ellipse of short .period.
Searle's value of the period was 2064 days ; Bruhns's slightly
greater, 2074 days.

On July 3, 1873, Tempel discovered a comet which in his
telegram he described as " schwach " (faint). Several computers
obtained elliptic elements of its orbit, but, strangely enough,
some time elapsed before the comet's identity with comet ii. of
1867 was found out. It returned to perihelion in May 1879,
and is now recognised as a permanent addition to the List of
Short-period Comets. But it escaped detection at its return in
the Spring of 1885.

SWIFT'S COMET.

No. 6. — On Oct. 10, 1880, Prof. 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 by Chandler
that the orbit was elliptic with a period of 6 years, and the
comet identical with comet iii. 1869, discovered by Tempel on
Nov. 27 of that year. The comet had been very unfavourably
circumstanced for observation at the return of 1874, and had
escaped detection. It was also unfavourably placed at its return
in 1886. It is a peculiarity of this comet that it is well situated
for observation only at alternate returns to perihelion.

k Nature, vol. xxx. p. 301, July 24, 1884.

CHAP. II.] Periodic Comets. 427

BARNAED'S COMET.

No. 7. — On July 16, 1884, Mr. 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 it was found to be in motion and its cometary
character ascertained beyond a doubt. Perrotin described the
comet as exhibiting on Aug. 15 an ill-defined nebulosity about
iY in diameter, and having a granular structure towards its
centre. There is no doubt that the orbit is elliptical ; the period
is at present somewhat uncertain ; but it is probably about 6 years.
If Berberich's period of 5^49 years is correct, the comet must
have approached very near indeed to Mars between April 5
and 10, 1868, and have had its orbit perturbed by that planet.

D' ARREST'S COMET.

No. 8. — On June 27, 1851, D' Arrest, at Leipzig, discovered a
very faint telescopic comet in the constellation Pisces. Within a
fortnight of its discovery the observations appeared irreconcile-
able with a parabolic orbit, and it was soon placed beyond a
doubt that its true path was an ellipse. The comet was visible
for more than 3 months ; but notwithstanding this, the results
of the calculations of the orbit were very discordant, and the
predicted return of the comet in the winter of 1857-8 must be
regarded rather in the light of a successful guess than anything
else. Sir T. Maclear, at the Royal Observatory, Cape of Good
Hope, was the only observer of this apparition.

M. Villarceau communicated to the Academy of Sciences at
Paris, on July 22, 1861, an interesting memoir on the orbit of
this comet, which may be usefully placed on record (in an
epitomised form) as it will serve to 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
J upiter, to which it is so near, that during the month of April of the present year [ 1 86 1 ]
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

428 Comets. [BOOK IV.

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

(i) 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 inclina-
tion will have increased i° 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 *° 1864-6. " But of all these perturbations," says M. Villar-
ceau, " 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 1 2" in the year following, remaining stationary in the last year, and
with a value 15", 5" less than at its origin. The perturbations 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 altogether at its
return to perihelion in 1864. But in 1870, astronomers were
more fortunate, and were able to follow it for 4 months.
Winnecke has pointed out that D'Arrest's comet is undoubtedly
the faintest of all the known periodic comets 1. It came back
again to perihelion in 1877? but was not seen at its return in the
winter of 1883.

FINLAY'S COMET,

No. 9. — On Sept. 26, 1886, a small tailless comet 1'in diameter
was discovered at the Royal Observatory, Cape of Good Hope. It
was at first thought to be possibly identical with the lost comet
of Di Vico, but subsequent investigation negatived this theory :
it is however certainly a short-period comet, and its next return
will be looked forward to with interest.

1 Ast. Nuch., vol. Ixxv. No. 1824, Oct. 12, 1870.

CHAP. II.] Periodic Comets. 429

WOLF'S COMET.

No. 10. — On Sept. 17, 1884, Dr. Wolf of Heidelberg discovered
a small telescopic comet which Col. Tupman described a week
later as about 2' in diameter and possessing a stellar nucleus 3"
in diameter. It soon proved to be a short-period comet revolving
round the Sun in about 6^ years.

FAYE'S COMET,

No. u, was discovered by M. Faye, at the Paris Observatory, on
Nov. 22, 1843, it being then in the constellation Orion. It ex-
hibited a bright nucleus, with a short tail, but was never
sufficiently brilliant to be seen by the unaided eye. That the
comet's path was an ellipse seems to have been suspected in-
dependently by more than one observer. To Le Verrier, however,
is due the credit of having completely investigated its elements.
That astronomer showed that the comet came into our system at
least as far back as the year 1747, when it suffered much per-
turbation from Jupiter m ; and, further, that its next perihelion
passage would occur on April 3, 1851.

It was rediscovered by Challis, at Cambridge, on Nov. 28, 1850.
O. Struve described it, under the date of Jan. 24, 1851, as having
a diameter of 24". During the whole time it was observed it had
scarcely any nucleus or tail. This comet returned in due course
to perihelion on Sept. 12, 1858, having been detected 4 days
previously by Bruhns, at Berlin. It was also seen in 1866, 1873,
i88on, and 1888, and next after Halley's and Encke's comets may

m The intelligent reader may wonder no means friendly, with the colossal
why Jupiter is so constantly called to planet. It is, moreover, an incidental
account as the great bugbear of these indication of the potency of Jupiter's
short-period comets. The reasons are influence over comets, that so many short-
two in number: — (i) The immense mass period comets have periods amounting to
of Jupiter compared with that of any of between 5 and 6 years, being about the
the other planets ; and (2) the fact that time occupied by Jupiter in traversing
the. aphelia of all these comets lie very half its orbit. (See Fig. 181, on p. 402,
close to the orbit of Jupiter; so that ante.)

when at their greatest distance from the n For a fuller history of this comet

Sun, they are constantly liable to ren- see Month. Not., vol. xli. p. 246, Feb.

contres more or less intimate, though by 1881.

430 Comets. [BOOK IV.

be regarded as the best-known cometary member of the Solar
system.

DENNING'S COMET.

No. 12. — On Oct. 4, 1881, Mr. W. F. Denning at Bristol dis-
covered a bright telescopic comet in the constellation Leo. It was
circular in form, about i' in diameter, and showed a slight central
condensation. The ellipticity of its orbit soon became known to
those who undertook the computation of its elements, and there
is no doubt that it constitutes an interesting addition to our
list of short-period comets, and the first made by an Englishman.

The elements bear some resemblance to those of the comet of
1819 (iv.), discovered by Blainpain. Winnecke thinks that the
comet seen at Paris in 1855 by Goldschmidt, and then regarded
as perhaps Di Vice's, and Hind's comet of 1846 (ix.), may both
have been apparitions of Denning' s comet. The further con-
sideration of these suggestions must stand over till after the
next return of this object to perihelion, which will be awaited
with much interest by astronomers, the more so as it is known
that it must come much under the influence of several of the
major planets.

TUTTLE'S COMET,

No. 13, was detected by Mechain, on Jan. 9, 1790. It was only
followed for a fortnight. On Jan. n Messier could see but a
confused nebulosity, without any indications of a nucleus. It
was not re-observed vmtil its return at the commencement of
1858, on Jan. 4 of which year it was detected by H. P. Tuttle, at
Harvard College Observatory, Cambridge, U.S. It returned
again to perihelion in Nov. 1871 and Aug. 1885, and is now
accepted as a regular member of the group of short-period
comets. On the last occasion it was very faint, and was only
followed in the morning twilight for about a fortnight.

BIELA'S COMET.

Besides those enumerated in the Table, there is another very
remarkable periodic comet, even more interesting than Encke's.

CHAP. II.] Periodic Comets. 431

but for altogether a different reason : I shall therefore give its
history at some length.

On March 8, 1772, Montaigne, at Limoges, discovered a comet
in Eridanus, which, from want of suitable instruments, he was
unable properly to observe, or to see at all after the 2oth ;
Messier, however, saw it four times between March 26 and
April 3.

On Nov. 10, 1805, Pons discovered a comet, which was found
also by Bouvard on the i6th. 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 point to the Earth, and Olbers saw it without a telescope.
Bessel and others calculated elliptic elements, and its identity
with the comet of 1772 was suspected, though no predictions as
to its next return were ventured on.

On Feb. 27, 1826, M. Biela, at Josephstadt, Bohemia, discovered
a faint comet in Aries, which Gambart found on March 9. The
observations extended altogether over a period of 8 weeks, and it
was soon made evident that the orbit was an ellipse of moderate
eccentricity; and further, that the comet was the same as that
which had already been observed in 1772 and 1805.

In anticipation of its next return in 1832 investigations into
the orbit of the comet and the perturbations by which it would
be affected were undertaken by Santini, Damoiseau, and Olbers.
Santini found that its period in 1826 was 2455 days, but that the
attraction of the Earth, Jupiter, and Saturn would accelerate its
next return by rather more than 10 days, which he accordingly
fixed for Nov. 27, 1832. Damoiseau's investigations gave a
similar result. Early 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 unscientific many, who were greatly alarmed lest
a collision should take place, and our globe become a sufferer
thereby.

432 Comets. [BOOK IV.

Punctually at the time appointed the comet returned to peri-
helion, through which it passed within 1 2 hours of the time fixed
by Santini five years previously. It was first seen at Borne on
Aug. 23, but, owing to its excessive faintness, it was not
generally observed till two months later.

The next return was calculated to take place on July 23, 1839,
but in consequence of its close proximity to the Sun, the comet
was not detected.

Continuing his researches, Santini fixed on Feb. 1 1 , 1 846, as
the epoch of the next perihelion passage ; and as it would be
visible for a considerable period, much interest was excited
amongst astronomers, who anticipated that a remarkably good
opportunity would be afforded for correcting the theory of its
motion.

Di Vico, at Rome, with the powerful telescope at his command,
discovered it on Nov. 28, 1 845, and Galle, at Berlin, saw it two
days later ; but by the generality of observers it was not seen
till the second or third week in December. I have already
adverted to the very curious phenomenon which took place at
this apparition of Biela's comet. (See ante, p. 408.)

The comet returned again to perihelion in Sept. 1852, and was
visible for three weeks. The same reason which prevented it
from being seen in 1839 also caused it to pass undetected in
May 1 859 ; so that we were obliged to await its next return to
perihelion in Jan. 1866 for further information relative to its
physical condition. This return was looked forward to with
much interest ; as it was important to know what changes had
occurred during the preceding 13 years in the relative position
of the two portions so strangely rent asunder, as already narrated
— whether they still travelled through space in company or not.
That between 1846 and 1852 they had become, for all practical
purposes, two complete comets, seemed indisputable ; and in the
sweeping Ephemerides issued from the Nautical Almanac office,
by Mr. Hind, for facilitating their rediscovery in 1859, two
independent sets of elements and positions were given.

It was calculated that the comet would have been seen in

CHAP. II.] Periodic Comets. 433

1865-6 under very favourable circumstances, and search was
systematically made for it at numerous European Observatories,
but without success. Much disappointment was felt by astrono-
mers : and startling as such a suggestion may appear °, even the
continued existence of the comet seemed so open to uncertainty
that all hopes of seeing it again were given up. At least one
man, however, did not despair. M. Klinkerfues of Gb'ttingen
kept the subject before him, and as the result of his labours, he
sent, on Nov. 30, 1872, to Pogson at Madras, a telegram as
follows : "Biela touched Earth on zyth : search near 6 Centauri"
The search was made, and a comet found, and observations of it
were obtained on Dec. 2 and 3, 1872. Bad weather and the
advance of twilight prevented further success p. Here the matter
rests : it was however the opinion of Bruhns that the comet seen
by Pogson could not possibly have been Biela's, but was, by a
remarkable coincidence, some other.

The further consideration of the question " Why has Biela's
comet disappeared ? " seems now to belong to the subject not of
Cometic but of Meteoric Astronomy. Accordingly we shall have
more to say about it in Book V (post}.

Di Vice's COMET.

On Aug. 22, 1844, M. Di Vico, at Rome, discovered a tele-
scopic comet, which, towards the end of the following month,
became perceptible to the naked eye. With a telescope a bright
stellar nucleus and a short tail were seen. It some became evident
that the observations could not be reconciled with any parabolic
orbit, and elliptic elements were calculated by several computers.
The most complete investigation is due to Briinnow, who found
that the comet's periodic time was 1993 days. Carrying on his
researches to the next return to perihelion, which was calculated

0 I assume that we are required to spring of 1866. (See Month. Not., vol.

ignore certain alleged observations of xxvi. pp. 241 and 271.)

"something" which formed a topic of P Month. Not., vol. xxxiii. p. 116.

discussion at several meetings of the Dec. 1872.
Koyal Astronomical Society, in the

434 Comets. [BOOK IV.

to occur in the spring of 1850, he found that "when the comet
was near enough to the Earth to be otherwise discerned, it was
always lost in the Sun's rays, the geocentric positions of the Sun
and comet at perihelion being nearly the same, and continuing so
for some months, on account of the apparent direct movement of
both bodies."

Its next return to perihelion was fixed for Aug. 6, 1 855 ; and
as it would be favourably situated for observation, hopes were
entertained that it would again be detected. Such, however,
was not the case; nor was it seen in 1861, 1866, 1872, or 1877
and therefore we are no longer justified in including it in the list
of " known " short-period comets, but its size and brilliancy
(considerable for a short-period comet) render its non-appearance
since 1844 a remarkable fact. Certain computations by Le
Verrier render it probable that this comet is identical with that
of 1678.

On Sept. 26, 1886, Finlay discovered a small comet the
elements of whose orbit were found to resemble closely those
assigned to Di Vice's comet by Briinnow ; but the resemblance
appears to be fortuitous : that is to say, that they are 2 distinct
comets moving in orbits similar in many respects but not in all.

Another instance of this sort of thing seems to be exhibited
by the comets of 1843 (i.), 1880 (i.), and 1882 (ii.).

Short periods have also been assigned to the following comets ;
but too much uncertainty prevails with respect to them, to
justify their being included with the foregoing q: —

Clausen (1743, i.) Blainpain (1819, iv.)

Burckhardt (1766, ii.) Peters (1846, vi.

Lexell (1770, i.) Coggia (1873, vii.).
Pigott (1783)

The last-named of these comets (1873, vii.) was the subject of
an elaborate investigation by Weiss, who thought it a return of
the comet of 1818 (i.), but he could not satisfy himself whether

«i The reader will find a few brief par- body interested in this branch of as-

ticulars in the notes to the 1st catalogue tronomy ought to possess. Those who

(posf) ; but for further information he read German will find P. Carl's Reper-

must consult Hind's Comets, or Cooper's torium der Cometen-Astronomie, pub-

Cometic Orbits — two works which every- lished at Munich in 1864, a useful book.

CHAP. II.]

Periodic Comets.

435

its period was 55'8, 18-6, or 6*2 years, though he gives the pre-
ference to 6'2 years.

In Class II. we have the following comets : —

Name.

Period.

Probable next
Return.

i. Westphal (1852, iv.) ...

Years.

67.77

IQ2O

2. Pons (1812)

70-68

IQ54

3. Di Vico (1846, iv.)

72.35

IQIQ

4. Gibers (1815)

74-of;

1061

5. Brorsen (1847, v.)

74.07

IQ22

6. Halley

76-78

IQIO

It has been suggested (I know not by whom) that 4 of the
above may have originally constituted a single comet. Inde-
pendently of this, Kirkwood has given reasons why some
connection may exist between Nos. 2 and 3 in the above Table.

No. 2 was discovered by the indefatigable Pons on July 20,
1812, being the i6th comet found by him in 10 years. It had
an irregular nebulous form without tail or beard, and was only
visible through a telescope. Encke having assigned a period of
707 years, the return of the comet was anticipated about 1883,
and accordingly it was sighted on Sept. 3 by Brooks in America
by the aid of a sweeping ephemeris computed by Schulhof and
Bossert. It appears to have exhibited in 1883-4 physical
characteristics differing altogether from anything recorded in
1812. Chandler in America and Schiaparelli in Italy saw it on
several occasions in Sept. 1883, first as a nebulosity, then as a
star, then as a nebulosity again ; whilst Miiller at Potsdam on
Jan. i, 1884 observed changes up and down both in magnitude
and brightness to the extent of TV of a magnitude in if hour.

Trdpied 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. The head then exhibited
3 zones, as in Fig. 188.

F f 2

436

Comets.

[BOOK IV.

" 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 two distinct
parts of very different brilliancy united by a very well marked twisted link (itrangle-
menf) which occupied almost the centre of the inner circular zone. The Southern

Fig. 1 88.

PONS'S COMET: Jan. 19, 1884. (Trepied.)

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
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 ist week in February without being able
to detect any changes like that which happened on Jan. 19. It follows therefore

CHAP. II.] Periodic Comets. 437

that the transformations in question must have run their course in a few hours; and
herein consists the remarkable character of the whole phenomenon."

Trepied's observations accord generally with those of Perrotin,
Thollon and Rayet, which apply however to the date of Jan. 13.
It would appear therefore to follow that the changes in this
comet, whatever their nature, were in some sense periodic — a
circumstance additionally remarkable.

No. 4, Olbers's comet, came back to perihelion in 1 887. It was
discovered by Brooks in America on Aug. 24.

No. 6. The comet which has the most interesting pedigree is
undoubtedly that which bears the name of our illustrious
countryman Halley; and as its history will, moreover, serve to
exemplify various remarks made in previous pages on the nature
and appearance of comets, I cannot do better than give a
summary of the said history from the time of the comet's last
appearance, in 1835, back to the earliest ages.

A few years after the advent of the celebrated comet of 1680,
Sir I. Newton published his Principia, in which he applied to the
orbit of that comet the Theory of Gravitation first promulgated
in that work. He explained the method of determining, by
geometrical construction, the visible portion of the path of a
body of this kind, and invited astronomers to apply these prin-
ciples to the various recorded comets. He considered that it
was very probable that some comets might move in elongated
ellipses which near perihelion would be scarcely distinguishable
from parobolas, and even thought that the comet of 1680 might
be moving in one which it took about 575 years to complete.
The illustrious Halley (to whose solicitations and exertions the
publication of the Principia is in great measure due, for he bore
the whole labour and undertook the whole expense of its editing
and publication) also took this view. But although we now
know that the period of that comet is far longer and is in fact
measured by thousands of year, Halley 's investigations in a
subsequent instance led him to a conjecture which was fully
substantiated. He undertook the labour of examining the cir-
cumstances attending all the comets previously recorded with a

438

Comets.

[BOOK IV.

view to ascertain whether any, and, if so, which, of them,
appeared to follow the same path. Careful investigation soon
proved that the orbits of the comets of 1531 and 1607 were
similar, and that they were, in fact, the same as that followed
by the comet of 1682, seen by himself. He suspected therefore

Fig. 189.

HALLEY'S COMET, JAN. 9, 1683 (N.S.), SHEWING LUMINOUS SECTOB DRAWN BY HEVELius1".

(and rightly too, as the sequel showed) that the appearances at
these 3 epochs were produced by the 3 successive returns of one
and the same body, and that consequently its period was some-
where about 751 years. There were nevertheless a 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

Fig. 190.

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

that it was natural to suppose that the same causes which dis-
turbed the planetary motions would likewise act on comets ; "
in other words, that the attraction of the planets would exercise

r A a, > us climactericus, p. 139.

CHAP. II.] Periodic Comets. 439

some influence on comets and their motions. The truth of this
idea we have already seen exemplified in the case of the comet
of 1770. In fine, Halley found that in the interval between
1607 and 1682 the comet passed so near Jupiter that its velocity
must have been considerably increased, and its period con-
sequently shortened ; he was, therefore, induced to predict its
return about the end of 1 758 or the beginning of 1 759. 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." Although Halley did not sur-
vive to see his prediction fulfilled, yet, as the time drew near,
great interest was manifested in the result, more especially as
Clairaut had named April 13, 1759, as the day on which the
perihelion passage would take place. It was not destined,
however, that a professional astronomer should be the first8 to
detect the comet on its anticipated return ; that honour was
reserved for a farmer near Dresden, named Palitzsch, who was
also a student of Nature and who saw it on the night of
Christmas-day, 1758. But few observations were made before
the perihelion passage (on March 12), owing to the comet's
proximity to the Sun ; during the months of April and May,
however, it was seen throughout Europe, although to the best
advantage only in the Southern hemisphere. On May 5 it had a
tail 47° long.

Previously to the last return of this comet, in 1835, numerous
preparations were made to receive it. Early in that year Rosen-
berger, of Halle, published a memoir, in which he announced
that the perihelion passage would take place on Nov. n, though
Damoiseau and Ponte'coulant both fixed upon a somewhat earlier
period.

Let us now see how far these expectations were realised. The
comet was seen at Rome on Aug. 5 ; as it approached the Sun

s It was stated by Prof. R. Grant in a early date, but was ordered to hold his
lecture at the Royal Institution in 1870, tongue. I do not know what authority
that Messier detected this comet at an there is for this statement.

440 Comets. [BOOK IV.

it gradually increased both in magnitude and brightness, but did
not become visible to the naked eye till Sept. 20. On Oct. 1 9
the tail had attained a length of fully 30°. The comet was soon
afterwards lost in the rays of the Sun, and passed through its
perihelion on Nov. 15, or within 4 days of the time named by
Rosenberger. It reappeared early in Jan. 1836, and was ob-
served in the South of Europe and at the Cape till the middle of

Fig. 191.

HALLEY'S COMET, 1835, OCT. n. (Smyth.}

May, when it was finally lost to view, not to be seen again till
the year 1910*.

We have seen above that Halley traced his comet back to the
year 1531 ; we must now, therefore, briefly review its probable
history prior to that date, as made known by the labours of
modern astronomers. Halley surmised that the great comet of

1 Drawings by Bessel will be found in the Ast. Nach., vol. xiii. Nog. 300-2.
Feb. 20, 1836.

CHAP. II.]

Periodic Comets.

443

1456 was identical with the one observed by him in 1682, and
Pingre converted Halley's suspicion into a certainty. The pre-
ceding return took place, as Laugier has shown, in 1378, when
the comet was observed both in Europe and China ; but it does
not appear to have been so bright in that year as in 1456. In
Sept. 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

Fig- 193-

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

part of the heavens. This was most likely Halley's comet. The
previous apparition is not so well ascertained, but it most likely
occurred in July 1223, when it is recorded in an ancient
chronicle that a wonderful sign appeared in the heavens shortly
before the death of Philip Augustus of France, of which event
it was generally considered to be the precursor. It was only
seen for 8 days. Although but little information is possessed
about it, and that of a very vague character, yet it seems
probable that this was Halley's comet. In April 1145 a great
comet is mentioned by European historians, which is one of the
most certain of our series of returns. In April 1066 an im-
portant comet became visible which astonished Europe. It is

444 Comets. [BOOK IV.

minutely, though not very clearly, described in the Chinese
annals ; and the path there assigned to it is found to agree with
elements which bear a great resemblance to those of Halley's
comet. In England it was considered the forerunner of the
victory of William of Normandy, and was looked upon with
universal dread. It was equal to the Full Moon in size, and its
train, at first small, increased to a wonderful length. Almost
every historian and writer of the IIth century bears witness to
the splendour of the comet of 1066, and there can be but little
doubt that it was Halley's. Previous to this year the comet
appeared in 989, 912, 837, 760, 684, 608, 530, 451, 373, 295, 218,
141, 66 A.D., and n B.C., all of which apparitions have been
identified by Hindu.

Concerning the comets belonging to Class III. (comets of long
period), it is not necessary to notice them further here ; they will
be found in the Catalogue, passim.

Flammarion, making use of some previous labours in this field
by Kirkwood and others, has worked out the idea of particular
comets being associated with particular planets in a way which
has yielded some results too curious and interesting to be passed
over. In addition to the Ist or Jupiter group to which reference
has already been made*, he finds that every major planet beyond
Jupiter seems to have a group of comets attached to it; and
moreover, 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.

The following are Flammarion's groups, the figures appended
representing in Radii of the Earth's orbit the mean distances of
the respective planets and the aphelion distances of the re-
spective comets : —

2ND GBOUP.

SATUBN 9-0 to 10-1

Tattle's Comet 10-5

u Month. Not., vol. x. p. 51. Jan. 1850. * See pp. 401, 402, ante.

CHAP. II.] Periodic Comets. 445

3RD GROUP.

URANUS 18-3 to 20-1

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

Comet of 1867 (i.) 19-3

4TH GROUP.

NEPTUNE 29-8 to 30-3

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

Comet of 1812 (Pons) 33

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

Cometof 1815 (Gibers) 34

Comet of 1847 (v.) (Brorsen) 35

Halley's Comet 35

5TH GROUP.

Trans-Neptunian planet ? ... ... ... ... 47 to 48 ?

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

Comet of 1532 and 1661... ... ... ... ... 48

Flammarion finally hints at 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 yearsy.

y L 'Astronomic, vol. iii. p. 89, March portant mistakes or misprints in the
1884. I have corrected several im- French original.

446 Comets. [BOOK IV.

CHAPTER III.

REMARKABLE COMETS.

The Great Comet of iSn.—The Great Cornel of 1843.— The Great Comet of 1858.
— The Comet of 1860 (iii.).— The Great Comet of iS6i.—The Comet of
1862 (iii.)-— The Comet of 1864 (ii.).— The Comet of 1874 ("*•)•— The Comet
of 1882 (iii.).

THE comets which might be included under the above head
are so numerous as to make it impossible that all should
receive full attention. I must therefore limit myself to some
few of the most interesting, premising that Grant includes the
following comets under the designation " remarkable " :—

1066 1531 1682 1823

1106 1556 1689 1835

"45 1577 I729 I843

1265 1607 1744 1858

1378 1618 1759 1861

1402 1661 1769

1456 1680 1811

The Comet of 1811 (i.) is one of the most celebrated of modern
times. It was discovered by Flaugergues, at Viviers, on March 26,
18 1 1, and was last seen by Wisniewski at Neu-Tscherkask, on
Aug. 17, 1812. In the autumnal months of 1811 it shone very
conspicuously, and its considerable Northern declination caused
it to remain visible throughout the night for many weeks. The
extreme length of the tail at the beginning of October was about
25°, and its breadth about 6°. Sir W. Herschel paid particular
attention to this comet, and the observations which he made are

CHAP. III.]

Remarkable Comets.

447

very valuable. He states that it had a well-defined nucleus, the
diameter of which he found by careful measurement to be 428
miles ; further, that the nucleus was of a ruddy hue, though the
surrounding nebulosity had a bluish-green tinge a. This comet

Fig. 194.

THE GREAT COMET OF l8ll.

undoubtedly is a periodical one. Argelander, whose investigation
of the orbit is the most complete that has been carried out, assigned
to it a period of 3065 years, subject to an uncertainty of only 43
years b. The aphelion distance is 14 times that of Neptune, or,
more exactly, 40,121,000,000 miles.

The Comet of 1 843 (i.) was one of the finest that has appeared
during the present century. It was first seen in the Southern
hemisphere towards the end of the month of February, and during

a Phil. Trans., vol. cii. pp. 118, 119, 121.
b Berlin. Ast. Jahrbuch, 1825, p. 250.

448 Comets. [BOOK IV.

the first fortnight in March it shone with great brilliancy. It was
not visible in England until after the 1 5th, when its splendour had
much diminished ; but the suddenness with which it made its
appearance added not a little to the interest which it excited.
The general length of the tail during March was about 40°, and
its breadth about i°. The orbit of this comet is remarkable for
its small perihelion distance, which did not exceed, according to
the most reliable calculations, 538,000 miles ; and the immense
velocity of the comet in its orbit, when near the perihelion,
occasioned some extraordinary peculiarities. Thus between
Feb. 27 and 28 it described upon its orbit an arc of 292°.
Supposing it to revolve in an ellipse, this would leave only 68°
to be described during the time which would elapse before its
next return to perihelion.

It has been thought by some that this comet was identical
with those of 1668 and 1689, but so little is known for certain
about this latter that we are not yet in a position to admit
or deny the identity of the 3 bodies. In the work to which
reference is made in the note the question is discussed with great
ability c.

The Comet of 1858 (vi.). On June 2 in that year, Dr. G. B.
Donati, at Florence, descried a faint nebulosity slowly advancing
towards the North, and near the star A. Leonis. Owing to its
immense distance from the Earth (240,000,000 miles), great diffi-
culty 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 this time (middle of August)
it had remained a faint object, not discernible by the unaided eye.
It was distinguished from ordinary telescopic comets only by the
extreme slowness of its motion (in singular contrast to its sub-
sequent career), and by the vivid light of its nucleus : " the latter
peculiarity was of itself prophetic of a splendid destiny." Traces
of a tail were noticed on Aug. 20, and on Aug. 29 the comet was

c E. J. Cooper, Cometic Orbits, pp. the supposed identity of this comet see
159-69. For something more concerning post, under the head of Comet iii., 1882.

Fig. 195.

Plate XXV.

DONATI'S COMET: October 5, 1858.

(Drawn by Pape.)

« fir

Fig, 196.

Plate XXVI.

DONATI'S COMET: October 9, 1858.

(Drawn by Pape.}
Gg 2

CHAP. III.]

Remarkable Comets.

453

faintly perceptible to the naked eye ; for a few weeks it occupied
a Northern position in the heavens, and it was therefore seen both
in the morning and evening. On Sept. 6 a slight curvature of
the tail was noticed, which subsequently became one of its most
interesting features. On Sept. 17 the head equalled in bright-
ness a star of the 2nd magnitude, the length of the tail being 4°.

Fig. 197.

DONATl's COMET, 1858, SEPT. 30. (Smyth.)

The comet passed through 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,
and was last seen by Sir T. Maclear at the latter place on March

4, i859-

"Its early discovery enabled astronomers, while it was yet
scarcely distinguishable in the telescope, to predict, some months

454 Comets. [BOOK IV.

in advance, the more prominent particulars of its approaching
apparition, which was thus observed with all the advantage of
previous preparation 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, so that its
proportions were seen without foreshortening. Its situation in

Fig. 198.

DONATI'S COMET, 1858, PASSING ARCTUEU8 ON Oct. 5.

the latter part of its course atforded 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 the nucleus, which
the absence of the Moon, in the early part of October, permitted
to be seen to the very best advantage. There is no doubt that
the comet of Donati revolves in an elliptic orbit with a period

Fiys. 199-203.

Plate XXVII.

•8

00
IO
00

CHAP. III.]

Remarkable Comets.

457

of about 2000 years (Stampfer, 2138^; Lowy, 2O4oy; Von
Asten, 1879?).

The following is a table of the dimensions of the comet's
nucleus and tail, at the undermentioned dates d : —

Date.

Diameter of Nucleus.

Length of Tail.

1858.
July 19

Miles.
5 — 5600

Miles.

Aug. 30

6 — 4660

= 14,000,000

Sept. 8

3 = 1980

= 16,000,000

„ 12

= 19,000,000

„ 23

1 — 1280

= I2,OOO,OOO

= 17,000,000

= l8,OOO,OOO

„ 28

= 26,000,000

„ 30

= 26,000,000

Oct. 2

= 27,000,000

i. 5 = 400

= 33,OOO,OOO

„ 6

3-0 = 800

5°

= 45,000,000

„ 8

4-4 = 1 1 20

5°

= 43,OOO,OOO

„ 10

2<5 ~ 630

= 5I,OOO,OOO

„ 12

= 39,000,000

The Comet of 1860 (iii.). In the latter end of June 1860,
a comet of considerable brilliancy suddenly made its appearance
in the Northern circumpolar regions. Bad weather prevented it
from being generally observed in England, but in the South of
Europe it was well seen ; copies of some drawings made at Rome
are annexed. [Plate XXVIII.]

Few comets created greater sensation than the Great Comet of
1861 (ii. of that year). It was discovered by Mr. J. Tebbutt, an
amateur observer in New South Wales, on May 13, previous to
its perihelion passage, which took place on June 1 1 . Passing
from the Southern hemisphere into the Northern, it became

d G. P. Bond, Math. Month. Mag.,
Boston, U.S., Nov. and Dec. 1858. Mr.
Bond subsequently published a magni-

ficent memoir on this comet in vol. ii. of
the Annals of the Harvard College Ob-
servatory. Cambridge, Mass., 1862.

458 Comets. [BOOK IV.

visible in this country on June 29, though it was not generally
seen till the next evening. So many accounts of it were pub-
lished that selection is difficult, but the following pages will
be found to contain an epitome of the most noticeable features e.
Sir J. Herschel observed it in 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 con-
spicuously visible on the 3Oth, 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 2f -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 Ist instant it was seen early in the evening, but before I could bring a telescope
to bear on it clouds intervened, and continued till morning twilight. On the 2ud
(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
offsets, 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
cornetic 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 certainly perceived ; and on the 5th was very 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,

e By far the most complete account is that by the Rev. T. W. Webb in the Month,
Not., vol. xxii. p. 305. 1862.

Figs. 204-209.

Plate XXVIII.

June 26.

June 30.

July 6.

June 28.

July i.

July 8.

COMET III: 1860.

{Drawn by Cappelletti^and Rosa.)

CHAP. III.] Remarkable Comets. 461

and what may be termed the coma (or spherical haze immediately surrounding it), by
an equally delicate graduation 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 2nd) passed
through a Draconis and T Herculis, nearly over rj and e 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 reference 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 polarisa-
tion, but 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."

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 two-thirds
of its length from the nucleus. The head of the comet was in the
ecliptic at 6 P.M. on June 28, at a distance from the Earth's orbit
of 13,600,000 miles on the inside, its longitude, as seen from the
Sun, being 279° i'. The earth at that moment was 2° 4' behind
that point, but would arrive there soon after 10 P. M. on Sunday,
June 30. The tail of a comet is seldom an exact prolongation of
the radius vector, or line joining the nucleus with the Sun ;
towards the extremity it is almost invariably curved ; or, in other
words, the matter composing it lags behind what would be its
situation if it travelled with the same velocity as the nucleus.
Judging from the amount of curvature on the 3Oth, and the direc-
tion of the comet's motion, Hind thought that the Earth very
probably encountered the tail in the early part of that day, or, at
any rate, that it was certainly in a region which had been swept
over by the cometary matter but a short time previously.

462 Comets. [BOOK IV.

In connexion with this subject, he added that on the evening of
June 30, while the comet was so conspicuous in the northern
heavens, there was a peculiar phosphorescence 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, con-
sidering how near we must have been on that evening to the tail
of the comet, it may perhaps be a point worthy of consideration
whether such an effect might not be attributable to this proximity.
If a similar illumination of the heavens had been remarked gener-
ally on the Earth's surface it would have been a very significant
fact.

Mr. Lowe, of Highfield House, confirmed Mr. Hind's state-
ment of the peculiar appearance of the heavens on June 30.
The sky, he says, had a yellow auroral glare-like look, and the
Sun, though shining, gave but feeble light. The comet was
plainly visible at a quarter to 8 o'clock (during sunshine), while
on subsequent evenings it was not seen till an hour later. In
confirmation of this, he adds that in the Parish Church the vicar
had the pulpit candles lighted at 7 o'clock, which proves that a
sensation of darkness was felt even while the Sun was shining.
Though he was not aware that the comet's tail was surrounding
our globe, yet he was so struck by the singularity of the appear-
ance, that he recorded in his day-book the following remark :—
" A singular yellow phosphorescent glare, very like diffused Aurora
Borealis, yet, being daylight, such Aurora would scarcely be
noticeable." The comet itself, he states, had a much more hazy
appearance than at any time after that evening.

De La Rue attempted to photograph the comet. After 3
minutes' exposure in the focus of his 1 3-inch reflector the comet
had left no impression upon a sensitised collodion plate, although
a neighbouring star, TT Ursse Majoris — close to which the comet
passed on the night of July 2 — left its impression twice over,
from a slight disturbance of the instrument. De La Rue also,
at that time, fastened a portrait camera upon the tube of his
telescope, and, with the clock motion in action, exposed a
collodion plate for 15 minutes to the open view of the comet with-

Figs. 210-213.

Plate XXIX.

JulyS. (Webb.)

July 2. (Brodie.)

July 2. (Brodie.}

July 2. {Chambers.}

THE GREAT COMET OF 1861.

Fig. 214.

Plate XXX.

CD
CO

EH
I

H
K

CHAP. III.] Remarkable Comets. 467

out any other effect than the general blackening of the surface by
the skylight, together with impressions of several fixed stars in
the neighbourhood.

Respecting 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 i".

" 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 incandescence to which
it had been brought by its close proximity to the Sun.

" 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 M. Poey, at Passy. This gentleman observed the
polarisation in Donati's comet at Havannah in 1 858, in which case
the light was polarised in a plane passing through the Sun, the
comet, and the observer ; but, in the case of the present comet,
" the plane of polarisation seemed to pass sensibly perpendicular
to the axis of the tail," which, he thought, might have been owing
to atmospheric refraction.

The comet of 1862 (iii.), though not one of first-class brilliancy,
was nevertheless a very interesting object, particularly on account
of the fact that a jet of light, frequently altering in form, was ob-
served for a long time to emanate from its nucleus. Annexed are
some views drawn by the late Prof. Challis of Cambridge. This
comet had a tail, which, on Aug. 27, was 20° long.

The comet of 1864 (ii.), visible in August, had a head unusually
large, scarcely less than £° in diameter. To the naked eye it
resembled on the 4th of that month a dull blurred star of the
3rd magnitude, but in the telescope it appeared as a circular mass
of nebulous matter with a central condensation very similar to the

H h 2

468

Comets.

[BOOK IV.

well-known planetary nebula in Virgo. There was a faint tail,
but it presented no special feature of interest.

The comet of 1874 (iii.), discovered by Coggia at Marseilles on
April 17, was one of considerable interest. The drawing from
which Plate XXXII has been engraved (and of which figure 215
is a skeleton outline), was made with an achromatic telescope
of 8^ inches aperture and n\ feet local length, on July 13, the

Fig. 215.

COGGIA'S COMET OP 1874.
Skeleton outline on July 13. (Srodie.)

a,y, a. Undefined outline of nebulous head.

6, c, b. Fairly denned outline of second envelope.

d, d. Sharply defined outline of first envelope, semicircular, and very bright.

e, e. Very sharply defined clear dark space between bifurcation of tail, free from nebu-

losity.

f, /. Singular eccentric envelopes, sharply defined, fading away at and into 6 b. The centres

of those envelopes were at d.

g, c. Between these two points several envelopes concentric with d d were traceable.

most favourable night during its appearance, when its position
in the heavens, its contiguity to the Earth, and the absence
of twilight are jointly taken into consideration. The Southward
motion of the comet was so rapid that on July 14 the presence

Figs. 216-221.

Plate XXXI.

Aug. 7.

Aug. 18.

Aug. 19.

Aug. 22.

Aug. 29.

COMET III, 1862.

(Drawn by Challis.)

Fig. 222.

Plate XXXII.

COGGIA'S COMET, 1874: on July 13.

(Th'fnvn by Srodie."}

CHAP. III.] Remarkable Comets. 473

of twilight greatly interfered with the details shown in the
drawing. The following description is from the pen of Mr.
F. Brodie : —

" 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 semicircle surrounding
the nucleus : the two eccentric envelopes were nearly as bright, and also very sharply
defined, also semicircular, having their centres placed (about) on the edge of the first
envelope, and 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 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 defined, 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 f on this comet are by two French ob-
servers, 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 bright-
ness 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 denned 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 I the
general form of the comet remained the same ; it appeared always to possess a para-
bolic 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 R.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

f Translated for this work from Guillemin's ComMes, p. 293.

474 Comet*. [BOOK IV.

sharply defined on the side nearest the tail ; one could not fail to remark its resem-
blance 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 ray projected towards the West was much more
brilliant, and was similarly bent round towards the tail, which it assisted in providing
with a bright exterior edge."

On July 13, the comet was 35,000,000 miles from the Earth,
and although it approached to within 26,000,000 miles on July 21 ,
it was then too nearly in Conjunction with the Sun to be seen.
The tail was calculated by Hind to have increased in actual
length from 4,000,000 miles on July 3 to 25,000,000 miles
on July 19, augmenting in angular length from 4° to upwards of
43°. On the evening on which Mr. Brodie's sketch was taken
the tail appeared to be rather arched towards the western horizon,
and could be traced by the naked eye for nearly 20°. This
comet certainly revolves in an elliptic orbit, but the period
is long. Geelmuyden's value is io,445y; Seyboth's, 57iiy. In
either case the semi-axis major must be some 300 or 400 times
the Earth's mean distance from the Sun.

The comet of 1882 (iii.) was in some respects one of the most
remarkable of modern times. 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 ; but these
facts, though noteworthy, would not have called for any special
remark had not other peculiarities been forthcoming to distin-
guish this comet from almost all others. Briefly stated, its
special features 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 bifid but totally
unsymmetrical ; and that on one occasion the comet seems to have

CHAP. III.] Remarkable Comets. 475

thrown off a mass of matter which became, and for several days
was observed as, a distinct comet.

Many observers noticed the changes which took place in the
nucleus and head. Prince said : —

" 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 I3th, which amounted, in fact, to its disruption into at least
3 portions."

"October 23. — The disruption of the nucleus which I had noticed on the 2oth 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.

Fig. 223.

THE GREAT COMET OF 1 882. FORMATION OP THE NUCLEUS. (C. L. Prince.)

" 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 considerably 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 of 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 observa-
tory, and his impression was that there were Jive points of condensation, and he
remarked that ' the nucleus was like a string of beads.' At intervals I thought
there was 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

476 Comets. [BOOK IV.

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 g."

J. F. J. Schmidt published a sketch of the nucleus, as seen by
himself, which is not unlike Prince's, and having seen the latter
he refers to it as a good representation of what he saw himself.
He noticed a vibratory motion in the fan h.

The tubular character of the comet's tail was suggested by
Tempel, who brought out the idea in some striking sketches sub-
mitted by him to the Royal Astronomical Society, accompanied,
for comparison's sake, by a drawing of the appearance of two
hollow glass cylinders as seen in the focus of an eye-piece '.

The peculiar conformation of the extremity of the tail of this
comet will be sufficiently indicated by the accompanying woodcutk.

Fig. 224.

THE GREAT COMET OF 1882. NAKED-EYE VIEW ON NOV. 14. (£. J. Hopkins.)

Most observers noticed this feature, which though rare as respects
the comets of the last half century may be conceived 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
scy miter."

Mr. Hopkins himself likened the general form of the tail to
the Greek letter y.

E Jlfon^.JVro/.,vol.xliii.p.85, Jan. 1883. « MoMh. Not., vol. xliii. p. 322, April

11 Ast. Nacli., vol. cv. No. 2499, March 1883.

19, 1883; Observatory, vol. vi. p. 157, k Month. Not., vol. xliii. p. 90, Jan.

May 1883. 1883.

CHAP. III.]

Remarkable Comets.

477

The last physical peculiarity of the great comet of 1882, to be
referred to, its throwing off a mass of matter which became a
satellite comet, was recorded by Schmidt at Athens and Barnard
and Brooks in America. Perhaps it is going beyond the legiti-

Fig. 225.

THE GREAT COMET OP 1 88 2, ON OCT. 9 AT 4h A.M. (frlammarion.)

mate limits of the available evidence to speak quite as plainly
as this, but the fact is clear that Schmidt saw on Oct. 9 and
on 2 or 3 later days a nebulous mass in the neighbourhood
of the comet, which calculation indicated was cometary matter
moving round the Sun in an orbit considerably resembling the

478 Comets. [BOOK IV.

orbit of the comet. Brooks's observation was made on Oct. 21 :
what he saw was a nebulous mass on the opposite side of the
comet to Schmidt's mass1. With the evidence before us of what
happened in 1 846 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 condition of the nucleus underwent, according
to the testimony of Prince and others, as above mentioned.

Even the orbit of the comet of 1882 has greatly puzzled astro-
nomers. It was found (see Catalogue I., post] that the elements
thereof closely resembled those of the comet of 1880 (i.), often
spoken of as the " great Southern comet of 1880." 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 which caused such a sensation in the March of
that year. It remains still a moot point what is the inter-
pretation to be put upon these orbital resemblances. The
question is a very speculative one, and it does not seem profitable
to discuss the matter more fully at present, except to record the
suggestion that the 4 great comets of 1 843, 1 880, 1 882, and 1887 (i.)
had at some past time a common origin, but by some process of
disintegration the original mass has yielded fragments, which
pursuing slightly different paths, arrive at perihelion at irregular
intervals m.

Gen. G. H. Willis observed the comet at sea 70 miles E.
of Gibraltar on Oct. 19 at 5 A.M., with the air extremely clear
and the wind 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 [Plate XXXIII]
is a French reproduction of the original English lithograph n.

1 Sidereal Messenger, vol. ii. p. 149, 2535, Aug. 31, 1883 (Hartwig) ; vol. cvii.

Aug. 1883. No. 2550, Oct. 31, 1883 (Peters); Month.

m Month. Not., vol. xliii. p. 108, Feb. Not., vol. xliii. p. 288, March 1883

1883. Month. Not., vol. xlviii. p. 199, (Brett).

Feb. 1888. For various drawings of the » Month. Not., vol. xliv. p. 86, Jan.

comet of 1882 see Ast. Nach., vol. civ. No. 1884.
2489,Feb. 5, 1883 (Barnard); vol.cvi.No.

Fig. 226.

Plate XXXIII.

THE GREAT COMET OP 1882: Oct. 19.

CHAP. Ill ]

Remarkable Comets.

481

With reference to Holden's sketches dated October 13 and
October 17, it may be remarked that 2 of the nuclei seen by
Holden were seen by Cruls at Rio de Janeiro, at the inter-
mediate date of October 15. Cruls found these nuclei to resemble

Fig. 227

Fig. 228.

Oct. 13. (Holden.} Oct. 17. (Holden.}

THE COMPOUND NUCLEUS OP THE GREAT COMET OP 1882.

stars of the 7th and 8th magnitudes respectively, the distance
between them being 6f". He was further led to regard the
peculiar appearance of the tail as being really due to 2 tails, one
superposed upon the other, each connected with a nucleus of its
own, independent of the other.

Sawerthal's comet of 1888 exhibited on March 27 a triple
nucleus not unlike that of the great comet of 1882 °.

0 Letter of M. Cruls in Ait. Nach., vol. cxix. No. 2842, May 26, 1888.

I 1

482

Cwriets.

[BOOK IV.

CHAPTER IV.

CERTAIN STATISTICAL INFORMATION RELATING
TO COMETS.

Dimensions of the Nuclei of Comets. — Of the Comce. — Comets contract and expand
on approaching to, and receding from, the Sun. — Exemplified by Encke's in
1838. — Lengths of the Tails of Comets. — Dimensions of Cometary orbits. —
Periods of Comets. — Number of Comets recorded. — Duration of visibility of
Comets. — Unknown Comet found recorded on a photograph of the Eclipse of the
Sun of May 17, 1882.

nnHE following are the real diameters a, in English miles, of
the nuclei of some of the comets which have been satis-
factorily measured1* within the last hundred years: —

Examples of a Large Nucleus.

Miles.

The Comet of 1845 (iii.) 8000

Donati's Comet, 1858 5600

The Comet of 1815 5300

The Comet of 1825 (iv.) 5100

Examples of a Small Nucleus.

The Comet of 1 798 (i.)

The Comet of 1806

The Comet of 1 798 (ii.)

The Comet of 181 1 (i.)

Miles.
28
3°

428

•l All the dimensions in miles in this
chapter depend on the old value of the
Sun's parallax. They need to be aug-
mented by about fa to accommodate them
to what is now regarded as the probable
amount of the Sun's parallax. This has not
however been done because all cometary
measures are so uncertain that to give
precise values in miles is affectation.

b This is in truth a very ambiguous
expression, for when one considers the
erratic motions of comets, the difficulty
of ascribing definite boundaries to them,
and the risk of error on the part of
observers owing to peculiarities of tele-
scope and weather, it will be readily
understood how easy it is to make serious
mistakes.

CHAP. IV.]

Cometary Statistics.

483

The dimensions of the coma, or heads, of comets also vary
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

It should be remarked that the real dimensions of comets are
found to vary greatly at different periods of the same apparition,
for there is no doubt that many of these bodies contract as they
approach the Sun, and expand again as they recede from it — a
fact first noticed by Kepler in the case of the great comet of 161 1.

The following measurements of Encke's comet in 1838, when
approaching the Sun, will illustrate this : —

Date.

Diameter.

Distance
from Q.

1838.
Oct. q

Miles.
281 ooo

1-42

2X. .

120,500

I-IQ

Nov. 6

7Q OOO

I-OO

74 OOO

0-88

„ 16 . ...

63,000

0-83

,, 2O

KK.KOO

O'76

, 23

^8-fiOO

o-yi

3O.OOO

0-60

Dec. 12

6 600

O-3Q

„ 14

i;,4Oo

0-36

„ 16

4.2SO

o-m

„ 17

3,000

<M4

Another point of considerable interest in regard to the dimen-
sions of comets is raised by the question, ' Do they waste away1? '
and it seems that the answer to this must be in the affirmative.
It has been supposed that Halley's comet as described by con-
temporary writers 1500 or more years ago was possessed of a
much larger and more brilliant tail than it has exhibited during
the last 2 centuries. And probably there is some significance
in the fact that none of the well-known short-period comets are

i i 2

484 Comets. [BOOK IV.

noted for tails or ever exhibit more than what may be called
apologies for tails.

The tails of comets, more especially of those visible to the
naked eye, are often of stupendous length, as the following table
will show : —

Greatest Length. Miles.

The Comet of 1 744 ... ... ... 24° = 19,000,000

The Comet of 1860 (Hi.) ... ... ... 15 = 22,000,000

The Comet of 1 86 1 (ii.) ... ... ... 105 = 24,000,000

The Comet of 1 769 ... ... ... 97 = 40,000,000

The Comet of 1858 (vi.) 50 = 42,000,000

The Great Comet of 1618 ... ... 104 = 50,000,000

The Comet of 1680 ... ... ... 60 = 100,000,000

The Comet of 1811 (i.) ... .. ... 25 = 100,000,000

The Comet of 1811 (ii.) .. ... 37 = 130,000,000

The Comet of 1843 (i.) ... ... ... 65 = 200,000,000

Cometary orbits are usually of immense extent. Thus : —
i. As to Perihelion Distance.

Greatett Known. Miles.

Leatt Known. Mile

The Comet of 1729 ... 383,800,000 The Comet of 1843 (i.) ... 538,000

2. As to Aphelion Distance.

Greatett Known. Miles.

The Comet of 1844 (ii.)4o6,i 30,000,000

Least Known. Miles.

The Comet of Encke ... 388,550,000

We have already seen that the period of the shortest comet
yet known is but little more than 3 years: this is in striking
contrast to the periods exhibited in the following table, which are
however so vast as to deserve little reliance : —

Years.

The Comet of 1882 (i.) 400,000

The Comet of 1844 (ii.) 102,050

The Comet of 1 780 (i.) 75,3 '4

The Comet of 1877 (Hi.) 28,000

The Comet of 1680 . ... 15,864

The Comet of 1847 (Hi.) • ••• J3,9l8

The Comet of 1840 (ii.) 13,864

A significant fact with respect to the periods of the known
periodical comets has already been mentioned0, namely that
there seems some disposition on the part of these comets to
become associated with particular planets. It is not improbable
that, as our knowledge becomes enlarged, some very interesting
facts may come to light, which are at present hidden.

c See pp. 401, and 444, ante..

CHAP. IV. Cometary Statistics. 485

TABLE OF NUMBER OF COMETS RECORDED.

Period.

Before A.D. 79

Century o — 100 22

101 — 200 22

201—300 39

3OI — 400 22

401 — 500 19

501 — 600 25

601 — 700 29

701 — 800 '7

801 — 900 .... 41

901 — 1000 30

1001 — noo 37

noi — 1200 28

1201—1300 29

1301—1400 34

1401—1500 43

1501 — 1600 39

1601 — 1700 32

1701—1800 72

1801—1888 (December) 270

Comets
Observed.

929

Orbits
Calculated.

3
o
i

4
o

2
1

4
o

249

392

Comets
Identified.

109

From the earliest period up to the present time, the number
of comets of which there is any trustworthy record is somewhat
over 900 ; but as it is only within the last 100 years that optical
assistance has been made generally available in a systematic
search for them, the real number of those that have appeared is
probably not less than several thousands, especially when we
consider that there have doubtless been many, visible only in
the Southern hemisphere.

Comets remain visible for periods varying from a few days to
more than a year, but the most usual time is a or 3 months.
Much depends on the apparent position of the comet with respect

486

Comets.

[BOOK IV.

to the Earth and the Sun, and much on its own intrinsic lustre.
Among the comets which remained longest in sight, are the
following : —

Months.

TheComet of 1811 (i.) ... ... 17

The Comet of 1825 (iv.) ... ... ... ... ... ... 12

The Comet of 1861 (ii.) ... 12

The Comet of 1835 (iii.), (Halley's) 9^

The Comet of 1847 (iv.) 9^

The Comet of 1858 (vi.) 9

The Comet of 1882 (iii.) 9

The Comet of 1884 (i.) 9

There are some few comets which have only been seen on one
or two occasions, unfavourable weather preventing more extended
observation of them. Fig. 229 is a case in point. It represents
a comet seen during the totality of the solar eclipse of 1882,
which was never seen again, and as to whose history and fate we
know nothing.

Fig. 229.

ECLIPSE OP THE SUN OP MAY If, 1882, SHOWING AN UNKNOWN COMET. (Eanyard.)

CHAP. V.] Historical Notices. 487

CHAPTER V.

HISTORICAL NOTICES.

Opinions of the Ancients on the nature of Cornels. — Superstitious notions associated
with them. — Extracts from ancient Chronicles. — Pope Cnlixtus III. and the
Comet of 1456. — Extracts from the writings of English, authors of the i6th and
ifth centuries. — Napoleon and the Comet of 1769. — Supposed allusions in the
Bible to Comets. — Conclusion.

GOING back to the early ages of the world, we find that the
Chaldseans considered comets to be permanent bodies
analogous to planets, but revolving round the Sun in orbits so
much more extensive, that they were therefore only visible
when near the Earth. This opinion, which, by the by, is the
earliest hint that we have of the existence of periodical comets,
was also held by philosophers of the Pythagorean school. Yet
Aristotle, who records this, insists that comets are merely
mundane exhalations, carried up into the atmosphere, and there
ignited.

Anaxagoras, Apollonius, Democritus, and Zeno considered that
these bodies were aggregations of many small planets.

It is a somewhat remarkable fact, that Ptolemy, so celebrated
for his varied astronomical attainments, should nowhere have
made any mention of comets ; his omission is, however, atoned
for by Pliny, who seems to have paid much attention to them.
He enumerates 12 kinds, each class receiving its name from
some physical peculiarity of the objects belonging to it.

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.

488 Comets. [BOOK IV.

Paracelsus gravely insisted that comets were celestial mes-
sengers, sent to foretell good or bad events — an idea which, even
in the present day, has by no means died out. The ancient
Romans did not trouble themselves much about astral phe-
nomena ; they nevertheless looked upon the comet of 43 B.C.
as a celestial chariot carrying away the soul of Julius Csesar,
who had been assassinated shortly before it made its appear-
ance.

In an ancient Norman Chronicle there occurs a curious ex-
position of the divine right 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."
Another old chronicler, speaking of 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 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 ; 1 have seen thee long since ; but I now behold thee
much more terrible, threatening to hurl destruction on this
country*.' "

The superstitious dread in which comets were held during the
Middle Ages is well exemplified in the case of the comet of 1456
(Halley's). We find that the then Pope, Calixtus III., ordered
the Church bells to be rung daily at noon, and extra Ave Marias
to be repeated by everybody. Whilst the comet was still visible
Hunniades, the Hungarian general, gained an advantage over
Mahomet II., and compelled him to raise the siege of Belgrade,
the remembrance of which the Pope preserved by ordering the
Festival of the Transfiguration, the anniversary of which was
kept a few days after the battle, to be observed throughout
Christendom with additional solemnities. " Thus was established
the custom, which still exists in Romish countries, of ringing the
* Will. Malmes., De gestis Regwn Anglice, lib. ii. cap. 225.

CHAP. V.] Historical Notices. 489

bells at noon ; and perhaps it is 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 cometeb."

Leonard Digges says that " comets signify corruptions of the
ay re. They are signs of Earthquakes, of warres, of chaungyng
of kingdomes, great dearth of corne, yea a common death of man
and beast"."

One John Gadbury says that " Experience is an eminent evi-
dence, 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 us 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 bells in Churches upon Earth not sacred enough for
such illustrious and eminent performances."

Shakespeare speaks of —

" Comets importing change of times and states
Brandish your crystal tresses in the sky,
And with them scourge the bad revolting stars
That have consented unto Henry's death d."

Milton says: —

" Satan stood

Unterrified, and like a comet burned,
That fires the length of Ophiuchus huge
In th' Arctic sky, and from its horrid hair
Shakes pestilence and war6."

The last comet employed in an astrological character was that
of 1769, which Napoleon I. looked upon as his protecting genie.
Indeed, as late as 1 808 Messier published a work on it, of which
the title is given below f.

During the visibility of Donati's comet in 1 858, the question
was mooted whether the Bible contained any reference to these

b Smyth, Cycle, vol. i. p. 231. A friend ed., London, 1576, fol. 6.

suggests a derivation which certainly & Henry VI., First Part, Act I. Scene I.

appears much more rational ; namely, ° Paradise Lost, Book II.

comedere, to eat. f La Grande Comete qui a paru d la

c Prognostication Euerlantinge, 2nd Naiseance de Napoleon le Grand.

490 Comets. [BOOK IV.

objects : the following passages were adduced in support of the
idea : —

1. In Leviticu* xvii. 7 it is said, "They shall no more offer
their sacrifices unto Seirim," or Shoirim, which is rendered in
the Authorised Version "devils," and in other versions "goats."
Maimonides states that the Sabian astrologers worshipped these
seirim, which seerns to confirm the idea that they were celestial
bodies.

2. In Isaiah xiv. i a 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 ! For thou hast said in
thy heart, I will ascend into heaven, I will exalt my throne
above the stars of God." 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 glory, boast, agitate, howl, &c. Hillel may therefore
signify a comet, for it answers 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 re-
served the blackness of darkness for an aeon [age]." In all
probability the passage may be taken to refer to comets g.

4. The last quotation which I make is from 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 to a comet, because a comet resembles a dragon (or
serpent) in form, and its tail frequently does compass or take
hold of the stars.

These ideas are given for what they are worth, and that is
probably not much.

8 See Alford's New Test, for English Readers. In loco.

CHAP. VI.] Determination of Orbits. 491

CHAPTER VI.

DETERMINATION OF THE ELEMENTS OF THE ORBIT
OF A COMET BY A GRAPHICAL PROCESS*.

SECTION I. Preliminary.

ri\HE first and most important step to be taken in applying
-•- the following graphical process for the investigation of the
orbit of a comet consists in working out the projection of the
orbit on the ecliptic, which involves finding such an inclination of
the plane of the orbit and such position of the node as shall be
at once consistent with the longitudes and latitudes reduced from
the observations available, and shall also satisfy Kepler's law of
equal (or proportional) areas being described round the Sun in
equal (or proportional) times ; and afterwards to compare the
developed orbit with one of the varieties of Conic Sections with
which it must necessarily be in accord. This in practice means
rinding the proper parabola, for leaving out of consideration a
few well-known elliptical comets of comparatively short period,
the curve, whether elliptical or hyperbolic, approximates almost
always so closely to the parabola that, until observations have
been multiplied and all corrections for parallax and aberration
have been applied, it is useless to attempt to discriminate between
them. Moreover, the graphical method is scarcely available to in-
dicate the course of a comet from only a few days' observations.
Let a scale, divided into 100 parts, be made, on card or stout

a This chapter has been specially of a paper contributed by him to the
written for this work by Mr. F. C. Royal Astronomical Society in 1881.
Penrose, F.R.A.S., and is an extension (Month. Not., vol. xlvi. p. 68. Dec. 1881.)

492 Comets. [Boox IV.

paper (as it may have to be bent round a curve), to represent the
Sun's mean distance ; and inasmuch as many tentative proportions
will have to be tried, the slide rule will be found a valuable
auxiliary ; but as the standard lines which represent the longitudes
of the different observations used should be laid down very
accurately, and are found once for all, it is better in the transfor-
mations of R. A.'s and Declinations into Longitudes and Latitudes
to use logarithms. The Nautical Almanack gives for every day at
noon the Sun's longitude and distance from the Earth. Inter-
polating these for the times of each observation we shall obtain
with sufficient accuracy (neglecting parallax) the relative places
of the observer and the Sun. Let the plane of the paper repre-
sent the ecliptic and lay down very carefully these terrestial
places, and through them draw straight lines in the directions
of the longitudes of the comet, already supposed to have been
worked out. These lines should be drawn in ink, that they may not
be erased in rubbing out the trial pencil-lines which will have
to be drawn between them. It will also be convenient to mark
down at this stage some subdivisions of the longitude lines
where the heights above the ecliptic are as the numbers 20, 30,
40, &c. ; these points being given by the co- tangents to the
latitude. These marks will of course be confined to those parts
of the longitude lines where the projection seems likely to pass.
Theoretically 3 observations suffice to determine the path of a
comet, but for the graphical investigation 4 are much better.

If the conversions from the equator to the ecliptic are performed
by calculation the following remarks may be found useful.

(i) In using the formula below and referring to Fig. 230 in
which P represents the North Pole and E the North Pole of the
ecliptic, and C being any place of the comet b, it should be
observed that when the comet's R. A. is between 12 hours and
24, the angle at P is acute ; and in the formula :

cos E C = cos P E cos P C + sin E P sin P C cos E P C
the latter value (cos E P C) will be positive, but for all other
hours of R. A. it will be negative.

b Supposed in the diagram to be in R. A. 2oh and N. P. D. 84°.

CHAP. VI.]

Determination of Orbits.

493

(2) When the comet's R. A. is between 6 hours and 18, the
supplement of the angle included between E P and E C must be
deducted from 270°; to give the proper longitude, but for the
other hours of R. A. the supplement of the said angle must be
added to 270°.

Fig. 230.

RELATION OF THE EQUATOB TO THE ECLIPTIC.

The general formula referred to gives the latitude only. The
longitude has to be derived from it and from the previous data
by the formula :

sin PEC_sinEPC
sin PC : : sin EC ;

and, as observed just above, the angle CES is to be added to
or subtracted from 270° according to circumstances.

Also, before proceeding to the graphic work it is desirable to
make a careful inspection of the longitude lines and the latitude
numbers just described, as from the relation of these numbers to
one another a sound hypothesis may usually be made of the
course of the comet as it passes the different longitude lines
by considering the connection between the heights above the
ecliptic and their distance from the Earth. Without this help
some doubt might at first arise in some cases as to which was
the direction of the comet ; that is, whether it was direct or

494 Comets. [BOOK IV.

retrograde. A few minutes devoted to this inspection may
save much time in the end. In addition to the above, any
information given in the recorded observations of variation in
brightness or development of the comet's tail should be taken
into account.

The first step now will be to take into consideration the lengths
on the projection of the arcs traversed between the observations.
These are not strictly proportional to the time-intervals either
on the orbit or on the projection, but unless the observations
record places very distant from one another the time-intervals
may be used at the first start, and a table of these should be
formed giving different numerical equivalents. For instance
suppose the time-intervals were 7, 8, 9.

Form a table such as the following, viz. :

7 =8:9,
8-75 : 10 : 11-25,
10.5 : 12 : 13.5;

which may be extended either by addition or interpolation as
may be required when the circumstances of the case indicate
which are likely to be the numbers most in request. The examples
will show how these are applied, and in Section 5 Rules are given
for correcting them for a second approximation.

The next step will be the adjustment of the areas and of the
latitudes. A few preliminary remarks on these heads will be
found useful.

SECTION 2. On the proportioning of the Areas in the different
Segments of the Projection.

Let the plane of the paper be that of the orbit, and let A BCD
be the places under examination. If there is no great amount
of deflection from the straight line as between A B and B C, the
subtended areas are to each other nearly as the triangles formed
by the chord with the radius vector ; and if C N be a straight
line drawn through K at right angles to SB, and if AN be
parallel to S B, the area subtended by A B is to that subtended

CHAP. VI.]

Determination of Orbits.

495

by B C very nearly as N K : K C ; but if the question lies between
such arcs as B C and C D, the difference in the areas inclosed
between the chords and the arcs cannot be neglected in the
comparison. In that case we may proceed thus : — Produce S C
to E, make EF = EB, and following the previously described
method cut off the arc C G, which approximately subtends the
same area as BC, and by similar construction the remaining
area subtended by G D can be measured.

Thus area B C S : area C D S : C H : C J.

Lines such as A N, F G, J D used in this construction may be
conveniently called area-measurers or pediometric lines.

Fig. 231.

SCHEME FOR ADJUSTING THE SUBTENDED AREAS.

In the figure given above (Fig. 231) the curve of the orbit has
been supposed, but the same holds good on the projection as
respects the areas, although the arcs are not in simple proportion.
A more exact rule for measuring the areas will be given in Sect. 5
(post], but the method just explained is sufficient for the purposes
of approximation, and is very rapidly performed graphically.

490

Comets.

[BOOK IV.

SECTION 3. The Latitudes and the Inclination of the Plane
of the Orbit.

In Fig. 232 let the plane of the paper represent the ecliptic,
and let E be the position of the observer. Let E L be the direc-
tion of the comet's longitude, S Q the node, and p P p' an arc of

Fig. 232.

DIAGRAM FOR FINDING POINTS OF PROJECTION WHEN NODE AND
INCLINATION ARE GIVEN.

the projection ; and the dotted line q Q q' an arc of the developed
orbit : that is, the plane of the orbit is supposed to revolve on its
node through the angle i until it coincides with the ecliptic, and
let / be the observed latitude.

The height of the point P above the ecliptic can be measured
either by P E tan I or P N tan i.

Let K be a point on E L, which for the sake of accuracy it is

CHAP. VI.] Determination of Orbits. 497

convenient to take at some distance from E. Through K draw
K D perpendicular to S Q , and make K D = K E tan I cot i. Join
E D, and at the point N where it cuts the node draw a straight
line perpendicular to the node. This line, if the angles and work
are correct, will pass through P, because from similar triangles
NP KD

_T_. _.„ „„ , 7 T,-^ ,

_P=, , . . N P = P E • - - — ; , or PE tan I — PN tan », as

P E K E tan *

above.

Thus with the node, latitude and inclination given, the point
P is found by the intersection of E D with S 8 . K may be any
point on E L, but it is convenient to take it at some definite
value of cot/; for instance (our scale being the Earth's mean
distance divided into 100 parts), K E tan / may be 100, 50, 25, &c.
according to circumstances, as will be seen in the examples,
post. When the projection has been found the developed orbit
is easily obtained by making N Q = N P sec i.

The above method, which can be constructed very rapidly, offers
a convenient plan for testing the accuracy of any given solution
of the elements of the orbit of a comet, but for the purpose of
the graphical working the process is as follows : — The direction of
the node and the inclination of the orbit having been previously
obtained, the method explained in this Section is used to bring
the whole work together and to average the individual obser-
vations. After this has been done, and the different points so
amended have been marked down, the work at this stage ought
to be tried by the rule of the areas, and if it stands this test
also, the small discrepancies which may still remain between
the developement and the proper conic section (presumably a
parabola) will be still further reduced by its comparison with
that curve, and it will be seen what are the slight modifications
which have to be made in the node or in the inclination, or
in both, in order to reduce the outstanding errors. Whatever
corrections are applied to these should be made by small instal-
ments, and to each separately, and the effect noted down.

498 Comets. [BOOK IV.

SECTION 4. To find a Parabola having its Focus at 8 and which
shall coincide with two Points of the Orbit.

In Fig. 233 let Q and P be the two points ; usually the
extremities of the developement. With the centre Q and at the
distance Q S, describe the arc S N F ; and with the centre P and
at the distance PS, describe the arc S MG. The straight line which

Fig- 333-

DIAGRAM FOB FINDING THE PEBIHELION FROM GIVEN POINTS ON THE ORBIT.

is tangent to the two circles at M and N will be the directrix of the
proper parabola, and from this all the other parts can be found.
The curve when drawn may be conveniently applied on tracing-
paper, keeping the focus on the place of the Sun and turning it
about until it best fits all the points of the developement.

SECTION 5. The Measurement of the Areas in a Parabola.
Fig. 233 may also be used to illustrate the exact rule for the
measurement of the areas in a parabola. Let A be the vertex,
A S = 0, and let P H and Q I be perpendiculars drawn from the
principal axis A X.

CHAP. VI.] Determination of Orbits. 499

If PSQ be the area of the space bounded between SP, SQ, and
the curve, then

= PSQ.

SECTION 6. TJie Relations between the Time-intervals and the
Longitude Lines.

At the first opening of the enquiry, except the help given by the
latitude numbers, as mentioned in Sect, i, there is usually little
to guide the student beyond the time-intervals and the longitude
lines. It is important therefore to consider their relation to one
another. Proportions founded on the time-intervals may gene-
rally be used as a useful first approximation unless the inclination
of the orbit is very steep or there is a great change of direction
in the path of the comet with respect to the node, between the
different observations. As this may not unfrequently be the
case, the remarks following should be taken into consideration.

In comparing the lengths of adjacent arcs in the orbit it can
easily be shown that they are to each other inversely as the
square root of the mean radius vector in each arc, and if the arcs
are of limited extent are practically as the inverse square roots
of the radii in the middle of each arc. This variation will of
course affect the projection also, with which we primarily have
to deal ; but the arc in the projection also depends upon the
general angle made with the node, which may frequently be
taken without sensible error to be the angle which the chord of
the arc makes with the node. Calling this angle, if measured on
the orbit, a, or if on the projection, ft, we should find that if s
be a small arc of the projection corresponding to S on the orbit,

* : S : : Vi — sin2a sin2 i : I ; or s : S : : i : Vi + tan2?' sin2j8 ; the
relation between a and j3 being tan /3 = tan a cos /.

It will be seen that when a or ft are small, and i not very
great, the projection will have almost the same length as the
original arc, and when these approach 90° the ratio of the
projection to the original will be as i to sec i. Also it will be
observed that when the inclination i is very steep it produces
great influence on these proportions.

K k 2

500 Comets. [BOOK IV.

It follows from the above considerations that although the
length of an arc traversed in a given time increases or diminishes
as the comet approaches or recedes from the Sun, yet when we
compare the adjacent arcs of the projection, this tendency may be

Fig. 234.

DIAGRAM FOB COMPARING ARCS.

greatly modified by the direction of its course with respect to
the node. In the first approximations it is not desirable to try
to calculate these effects minutely, although it will be useful to
take some account of them when possible. But it may often be
worth while to obtain a first approximation roughly, and from

CHAP. VI.] Determination of Orbits. 501

this to deduce the effect produced by the causes above referred to,
and then to rub out the first pencillings and proceed afresh with
an amended table of the intervals. The diagram here given (see
opposite, Fig. 234), which has been calculated from the formula

\/i + tan2 i sin2^

gives values of the length of a small arc of the projection com-
pared with the corresponding arc of the orbit.

If the orbit has been developed and the angular direction of
its course a ascertained, /3 is easily obtained from the relation
tan fi = tan a cos /. As an example of this diagram, if /3 = 30° and
i= 45°, it will be found by the scale that s : S = 9 : 10. Other
values can be found by interpolation.

SECTION 7. Checks available^ derived from certain properties of
Parabolic Orbits.

When the elements of a comet have been approximately ascer-
tained, a very useful check may be employed (confining our
attention to parabolic orbits) from a consideration of the fact
that the velocity of a comet in such an orbit at perihelion is to
that of a planet moving in a circular orbit c at the same distance
as >/2 to i.

The sine of the daily arc traversed by such a planet at Peri-
helion would be 1-7213 of our scale. In the comet at the same
distance it would be 2-43302, and for any other distance this
number must be divided by the square root of the distance.

It will often be useful to remember this principle at a pre-
liminary stage, when a consideration of it may help to point out
the distance at which the first approaches should be commenced.

SECTION 8. Examples of the Graphical Process.
The first example to be given is that of Schaberle's comet of
1881 (iv). Observations on 5 days will be considered. It is
proposed to find the elements of the orbit from the first 4 and
then to try them on the 5th for a test and final correction.

c The motion of the earth in its orbit. It will require very little calculation, as
although not quite circular, may without it has necessarily been laid down graphic-
serious error be used in this comparison. ally in the course of the work.

502 Comets. [BOOK IV.

The observations reduced to longitude and latitude yielded
the following apparent places : —

G. M. T. Longitude. Latitude.

o > ii a i n

Oxford

July 31-41

95 19 56

22 34 17

('•)

Aug. 4-42

99 2 24

25 8 9

(2-)

„ 10-44

108 5 14

29 49 o

(3-)

» J9-53

137 33 22

36 7 o

(40

Sept. 2-33

199 18 o

17 22 0

(5-)

Marseilles

The Sun's places at these times with respect to the observer
being —

Longitude. Distance,
o / it

(i.) 128 44 43 101-50

(2.) 132 35 i 101-42

(3.) 138 25 17 101-35

(4-) 147 5 43 101-16

(5.) 160 26 6 100-84

The plane of the paper represents the ecliptic, S being the
Sun's centre and S Y the line of the Equinoctial Node.

It is evident from the inspection of the latitude numbers (see
Sect, i) that during the first 4 observations the comet was
passing from left to right, that is with retrograde movement,
and approaching the Sun ; and when first observed must have
been a little beyond the point O where the first two longitude
lines intersect. In this example we seem obliged at first to
use the time-intervals as the only representatives of the lengths
of the arcs, for at present no theory can yet be formed
of modifications of their proportional length, as discussed in
Section 5.

The table of time-intervals will be formed of such terms as : —

4-01 6-02 9-09

8 12 18-10

10 15 22-60

1 1-3 17 25-70

12.6 19 28-6

16 24 36-2

If we lay the scale of hundredths of the Sun's mean distance
across the middle interval, and, allowing for moderate and con-
tinuous curvature, take in the adjacent spaces on each side, we

Fig. 235.

PLATE XXXIV. (faces p. 502).

CH.AP. VI] Determination of Orbits. 503

shall find that the two first terms of our table are out of the
question. Nor will 15 by any sort of arrangement combine with
10 on one side and 22-6 on the other: but with 17 combined with
11-3 and 25-7 the case is different, and we may note down its
points of coincidence, as at A, B, C, and D. It will be well
however at this stage to proceed further and try another value,
say 24, in the middle interval, and mark down also the places
given on the four longitude lines, namely, <z, b, c, A.

The reason for placing the scale at that particular obliquity to
L2 and L3 so as to fall upon the points a, b, c, d, rather than in an-
other way, nearer to or further from A, B, C and D, is the condition
that the curvature of the projection must be fairly continuous.
Nearer to A B C D it would have made abed too straight, or
even convex to the Sun, and further from A B C D it would have
been too abrupt. This consideration generally determines within
very moderate limits the direction that these trial lines ought to
take. The distance however will require a different discrimina-
tion, which we should now apply, namely, the area test. Join
SB, S C, and draw the pediometric lines as explained in Section 2,
namely, the offsets from M M' which fall near A, and from N N'
which fall near D, thus confirming very nearly the points
already chosen. When we apply a similar test to the other
trial-curve by joining S £, S c &c., we find that the pediometrics
m m' and n n' are quite discordant, especially n nf. Thus we
may feel satisfied that to obey this test the projection cannot be
far from a line passing through ABC and D. We now
proceed to consider the latitudes and to obtain the inclination
and the node. The heights above the ecliptic due to points on
the longitude lines having been marked, show that in this case
at the points A, B, C and D we have respectively 46-7, 45-7, 43-0
and 36-6. If these places were exact, the node could now be
so drawn through S (similar to the node in Sect. 3) that the
height of each of the above-named points, divided by the cor-
responding horizontal distance from the node, measured on the
projection, would give the same value of tan i. Here it is nearly
so, for we may so choose our base-lines passing through the Sun

504 Comets. [BOOK IV.

that the two outside points =~ and rr-^ g*ve 39C 3°'> whilst
^ give 39° 20'; the mean being 39° 25', and the

(jr r>

approximate node X X'.

This approximate node might be found tentatively, but a better
way is to join the two points under consideration, as A and D, and
draw from A and D offsets equal to, or proportional to, the
measure of their latitude number (or height above the ecliptic) ;
join the extremities of the offsets ; and produce as required to
meet the produced line A D. The point of intersection will lie
in the approximate node. That due to B and C will be found
by similar construction. We are now in a position to use this
approximate node and inclination to improve the figure by
introducing a modification of the lengths of the arcs of the
projection as explained in Section 6. If we draw perpendiculars
to the node to the middle parts of the arcs of the projection, and
develope them in the ratio of sec i : i , we can obtain approximate
places on the orbit and get a near value of the radius vector.
These distances appear to be in AB, B C, and C D respectively
about 75, 70 and 65, and on this account (as shown in Sect. 6)
the spaces traversed in equal times in the three arcs would be
to each other as F£T, ^T, ¥£T, but the angles which the chords
of the arcs on the projection make with the node seem to be
respectively 8° 10', 10° 45', and 18°.

Using the diagram of Section 6, and interpolating the values
above measured for /3 in combination with 2=40, we obtain for
the proportional lengths in the projection 0-99, 0-985, and 0-965.

The comparison of equal-time arcs therefore on these three
sequents will be as : —
99

The comparative arc intervals thus modified will have for their
proportions 3-9 ; 6-02 ; 9-2 ; very nearly as u ; 17 ; 26.

In this example the corrections above found are small because
the angle /3 of Section 6 is small, and i is not very large, but

CHAP. VI.] Determination of Orbits. 505

under certain circumstances they may become very significant.
It must be borne in mind that these modifications affect only
the lengths of the arcs, and in comparing the areas the true time-
intervals must be used.

In making the adjustments it seems unnecessary to alter D,
considering the favourable near coincidence of the pediometric
line with that point, but the other points should be shifted to
A', B' and C', giving them latitude values of 47-1, 46-3, and 43-8
respectively.

The value of i which now results from the corrected numbers and
the corresponding perpendiculars drawn to the node becomes
39° 45', which we take for the measure of i, and the node takes
the direction S S3 .

The next step is to use the method of Section 3, to establish
points on the various longitude lines in accurate accordance with
this node and inclination.

Choosing the latitude points 50, on each of the first four longi-
tude lines, draw from A' B' C' and D perpendiculars to S £3, 60-1
in length, which will make |$£ = tan i. Draw straight lines from
the extremities of these perpendiculars to their respective places
of observation, and where they cut the node, as T Ff, U G,' &c.,
erect perpendiculars to their proper longitude lines and produce
them upwards to form the developed figure by the method of
Section 3. These points will be Hj H2 H3 H4. By that of
Section 4 we can now obtain the parabola which will pass
through Hj and H4. Let this be drawn on tracing-paper and
applied as therein directed, and it will point out that, with the
vertex at P, it will produce a very good coincidence with the
four points of the developement, and will also satisfy very
closely the rule of the areas.

We have obtained this parabola from 4 observations only.
The fifth observation (that of September 2) may now be used to
test its accuracy.

We shall find that if this observation be worked out in a
manner similar to that of the others by obtaining the point Z
due to latitude mark 25, and finishing the construction, that the

506 Comets. [BOOK IV.

point of its developement H5 will fall at a distance of not more
than 0-5 from the arc of the parabola produced, and that if the
axis of the trial parabola 64 be reduced to 63-5 and the vertex
or perihelion be turned towards H5, a very small arc, about 2° 20',
there will be a very near coincidence indeed amongst all the
points. After these corrections have been made the perihelion
point measures along the curve 8-2 of the scale beyond the
point due to Aug. 19-53, a distance traversable in about 2-70
days.

This gives the date of the perihelion, August 22-23.

The longitude of this point is 328° 20'-

The longitude of the node is 97° 30'-

The elements of the orbit, stated in the usual way, are : —

T Aug. 22-23

W 328° 20'

q 0636

8 97° 3o'

• 39° 45'

H Retrograde.

Stechert's published elements of this comet are :—

T Aug. 22-29

» 334° 55'

? 0-633

8 97° 2'

39° 46'
/* Retrograde.

These last elements, if tried by the test of Section 3, do not
in some particulars satisfy the geometrical conditions so well as
those given above, found by the graphical process. In some of
them there is very little difference.

The second example is that of Tebbutt's Comet of 1881 (iii).
We will make use of 4 observations of apparent places reduced
to the ecliptic : —

G. M. T. Longitude. Latitude.

o / // o t

1. Cape of Hope May 31-21 69 38 6 —52 9

2. „ June 9-18 74 16 36 —38 31

3. Greenwich June 24-48 86 19 6 + 25 59
4- „ Joly i3'58 I02 37 33 +60 36

Fig. 236.

PLATE XXXV. (faces p. 506).

CHAP. VI.] Determination of Orbits. 507

The Sun's places at these times, with respect to the observer,
were : —

Longitude. Distance.

o /

1. 70 18-9 101-43

2. 78 54-0 IOI-5I

3. 93 29-6 101-66

4. in 42.5 101-64

As in the previous example the plane of the paper represents
the ecliptic, S being the Sun's centre, S Y in PI. XXXV, Diagram
A. is the line of the Equinoctial Node, and Lj L2 L3 L4 represent
the different longitude lines with some of the heights above the
ecliptic as derived from the latitude angles marked upon them.

The time-intervals in this case are : —
9-0 : 15-25 : 19-1.

It is clear however that at the time of the first and second
observations the comet was approaching the Sun, and afterwards
receding, and with a considerable change of angular direction.
We may therefore fairly assume, although it would be premature
to speak with exactness, that on the principles of Section 6 the
first and third values in the three columns of time-intervals will
be increased as compared with the middle column. Let us
assume the proportions of the arc-intervals to be —

9.8 15-25 19-7

ill-O 17-0 22-O

12-3 19-0 24-6

13-6 2I-O 27'2

Placing 1 7 across the middle space and bending the scale a little
so as to be slightly concave to the Sun, we find a fair agreement
with 22 towards L4, but the other interval is not well bridged, as
it extends only to G, considerably short of Lr The direction of
the curve is from near the 60 mark on ^ to the same figure on L4.

With 21 on the central space, 13-6 may be found to agree
fairly well with L15 but 27-2 is considerably too long for the
other space, and it overlaps it towards F, the direction being
from near 41 on L: to 31 on L4. It becomes therefore clear that
a better result is to be looked for between these two trials. With

508 Comets. [BOOK IV.

1 9 on the central space we can place both 1 2-3 on L: and 24-6 on
L4, the curve ranging from about 49 on L15 26 on L2, 14-2 on
L3 to 58 on L4 ; and we may now mark in the points A, B,C, D.

As in this example we have the opportunity of arriving very
closely at the direction of the node, it will be convenient to
obtain it at this stage. As the second observation was taken
below the ecliptic and the third above, it follows that the node
lies somewhere between these two. If, as in Diagram B. on Plate
XXXV, the chords of the three arcs A B, B C, CD be taken as
abscissae, and ordinates given to the points A, B, C, and D pro-
portional to the tangents of the latitude angles, we may construct
a curve which will determine very nearly indeed the point Q where
the latitude was zero, and we shall thus obtain the distance of the
node either from C or B. Set off this distance C 8 in the direction
C B, and join S Q ; this will be the node. It will be at once
apparent that neither of the two outside trial curves can satisfy
the condition that tan i = the latitude number divided by that of
the distance from the node, and it is unnecessary to apply the area
test to them. We may therefore confine our attention to the
points A, B, C, D.

On this curve the pediometrics M M' and N N' very nearly confirm
the points already chosen. A, however, has to be shifted to A'
at 47 -5, and D moved from 58 to 60. The combined heights of
these two, 107.5, divided by the distance between them (perpen-
dicular to the node), 51, representing tan/, gives for this angle
64° 36', whilst the angle derived from the two inner points B and
C is 65° 8' ; the mean 64° 42'.

At this point of the work it would usually be convenient to
rub out the first trial pencil lines referred to in Section i, and
proceed by the method of the latitudes (see Section 3), but as
that would destroy the previous work of this example, we proceed
to Diagram C. on Plate XXXV. On Lj at 80, L2 at 40, L3 at 30,
and on L4 at 80, ordinates are drawn, determined by the ratio
tan i = tan 64° 42'. Draw TF, UG, VI, and W K as in the last
example, and from the points F, G, I and K develope the orbit by
making F Hx = FA sec /, &c.

CHAP. VI.] Determination of Orbits. 509

By the method of Section 5. using Hj and H4, we determine the
perihelion distance and other elements of the parabola which
would pass through those two points. The distance so determined
is 72-7. It will be seen by Diagram C. how nearly it coincides
with H2 and H3. The vertex of the parabola (i. e. the perihelion) is
at P ; its longitude (TT) measuring 268° 55'. The time T may be
obtained thus : — By means of the pediometric line N N' cut off Q,
making the area subtended by H2 Q = that subtended by H! H2,
the time being 9 days. It is easy to measure the small arc R P
as 1-2 1 day. T therefore becomes June 9-18 + 9 — 1-21 = June
16-97. The elements of the orbit are now ascertained : —

T June 16-97

268° 55'
q 0-727 [= log. 9-86153]

S3 270° 48'

i 64° 42'

The elements calculated by Mr. Hind were : —

T June 16-457

» 265° 15' 44"

q 0-7346 [= log. 9-8657]

S 270° 57' 46"

i 63° 28' 46"

If we take the case of the comet dealt with in the last example
it will appear that the space due to the parabolic orbit between
the dates June 9 and June 24 should bear the proportion of about

1-671 : i- (viz. A/VW * ^2) to that traversed by the earth during
the same period — a proportion which it will be found by
measurement on the diagram has been very nearly obtained.

SECTION 9. To form an epTiemeru of a Comet.

If it be desired to form an ephemeris from the elements of a
comet's orbit the procedure graphically would be as follows : —

Taking the case of Example i, namely given the perihelion
distance 0-636, and the date of perihelion passage Aug. 22-23 ;
let it be desired to find the cornet's place in R. A. and Decl. for
Sept. 2-33.

510 Comets. [BOOK IV.

By dividing the normal value of daily motion at perihelion
(Sect. 7) by Vo-6$6 we obtain in this case in terms of our scale
3-051 8, and for the subtended area 97-049. This requires for 1 1 • i
days an area of 1077-24.

The formula given in Section 5, namely, A = — ' > would

suffice for finding the place on the orbit, but would require the
solution of a cubic equation, and as that might be tedious, it
would be more convenient to use the formula as a correction of a
value otherwise obtained. By the pediometric method we should
obtain 11-1x3-0518 = 33-875 for the ordinate. This however
would be somewhat too great, as the space inclosed between the
chord and the arc is too large to be neglected. But the excess
can be easily calculated.

From the equation to the parabola we readily obtain the
quantity 4-5107 as the abscissa due to 33-875, and from the

formula A = we obtain A = 1 105-25.

The area in excess, 28-01, is proportional to 0-29 of a day, so
that instead of the place due to Sept. 2-33 we have that of Sept.
2-52, which will probably answer the purpose aimed at nearly as
well : if not, an adjustment could be easily^made.

If the point H5 had been at a greater distance from the Peri-
helion, it would have been requisite to have approximated to it
by stages by the pediometric method, as shown in Section 2, the
place so obtained to be corrected by the formula used above.

The point H5 on the orbit having been obtained, draw through
it the straight line H R, perpendicular to the node, and find upon
it the point J where R J = R H5 cos i. Join E. J and this will

give the longitude of the required place. Also - - = tan /

£J6J

gives the latitude.

The R. A. and Decl. may now either be computed or solved
graphically.

CHAP. VII.] Catalogue.— No. I. 511

CHAPTER VII.

A CATALOGUE OF ALL THE COMETS WHOSE ORBITS HAVE
HITHERTO BEEN COMPUTED.

"1TTHEN a new comet has been discovered, the first thing to
be done is to obtain 3 observations of it, whereby the
elements of the orbit may be computed. The computer will
then examine a catalogue of comets to see if he can identify the
newly-found stranger with any that have been before observed*.
The value of a good catalogue is obvious ; and therefore I have
compiled as complete a one as possible.

In the preparation of the following list, care has been taken
that only the most reliable orbits that were to be obtained should
be inserted, the general rule being to prefer the one which was
derived from the longest arc, other things being satisfactory.
Among the authorities consulted may be mentioned Piwgre,
Hussey, Others, Cooper, Hind, Arago, Galle, and many others.

The Epoch of perihelion passage is expressed in Greenwich Mean
Time, N.S., since 1582.

The Longitudes of Perihelion and of the Ascending Node are
given for the respective epochs, but for any other epoch an
allowance must be made for the effect of precession. This
allowance is additive for subsequent dates and subtractive for
previous ones, as follows: i year = 50"; 100 years = i° 23 46";
1000 years = 13° 56' 50".

The periods assigned in the column of " Duration of Visibility "
are subject to much uncertainty, more especially in the case of the
ancient comets.

ft In the Annuaire de V Observatoire will be found a catalogue of comets
Royal de Sruxelles, 1883, at p. 70, there arranged in the order of the Inclinations.

512

Comets.

[BOOK TV.

No.

Year.

PP..

»r

370 B. C.

d. h.
Winter

0 0

150—210

O 0

270—330

o
above 30

very sm.

I36

April 29

230

22O

roi

July

300—33°

150 — I 80

o'8o

Oct. 8 19

280

10 +

0-58

o >

O /

o /

(4)

66 A. D.

Jan. 14 4

325 o

32 40

40 30

0-445

(4)

141

March 29 2

251 55

12 50

17 o

0720

178

Sept. beg.

290

190

0'5

(4)

218

April 6

240

Nov. 9 23

271 o

189 o

44 o

0-372

(4)

295

April i +

(4)

451

July 3 12

539

Oct. 20 14

3!3 30

58 or 238

0'34 l

565 ii.

July ii 18

158 45

60 30

0-775

568 ii.

Aug. 29 7

3i8 ?5

294 15

4 8

0-907

574

April 7 6

M3 39

128 17

46 3i

0-965

(4)

760

June 1 1

770

June 6 14

357 7

90 59

61 49

0-642

837 i-

Feb. 28 23

289 3

206 33

IO 12

0-580

961

Dec. 30 3

268 3

350 35

79 33

0-552

(4)

989 ii.

Sept. ii 23

264

0-568

1006

March 2 2

3°4

i? 30

0-583

(4)

1066

April i o

264 55

25 50

17 o

0-720

1092

Feb. 15 o

156 20

125 40

28 55

0-928

1097 i.

Sept. 21 21

332 30

207 30

73 30

0738

-5

1231

Jan. 30 7

134 48

*3 30

6 5

0-948

i. It is said to have separated into two parts.

3. It had a short but brilliant tail.

4. An apparition of Halley's comet (?), mentioned by Dion Cassius as having been
suspended over Home previous to the death of Agrippa.

5. An apparition of Halleys comet (?). It had a tail 8° long.

6. An apparition of Halley's comet.

9. Elements somewhat doubtful. It had a tail 30° long.

1 1. Undoubtedly an apparition of Halley's comet.

12. It had a tail 10 feet long ! !

13. A mean orbit. It had a tail 10° long.

14. Elements very reliable. On Sept. 8 it had a tail 40° long.

15. Elements very uncertain.

CHAP. VII.]

Catalogue. — No. I.

513

•

Calculator.

Date of
Discovery.

Discoverer.

Duration
of Visibility.

I'D

Pingre"

. .

Greek obs.

(?)

I'O

—

Peirce

Chinese obs.

5 weeks.

I'O

Peirce

68, July 23

Chinese obs.

j weeks.

I'O

Hind

n, Aug. 26

Chinese obs.

9 weeks.

I'O

Hind

66, Jan. 31

Chinese obs.

7 weeks.

I'o

Hind

141, Mar. 27

Chinese obs.

4 weeks.

I'O

Hind

218, April

.. ..

6 weeks.

I'O

Burckhardt

240, Nov. 10

Chinese obs.

6 weeks.

••

Hind

295

....

7 weeks.

I'O

Laugier

451, May 17

Chinese obs.

13 weeks.

I'O

Burckhardt

539, Nov. 17

Chinese oba.

9 weeks.

I'O

Burckhardt

565, Aug. 4

Chinese obs.

15 weeks.

I'O

Laugier

568, Sept. 3

Chinese obs.

10 weeks.

I'O

Hind

574, May 2

Chinese obs.

13 weeks (?).

I'O

Laugier

760, May 1 6

Chinese obg.

8 weeks.

I'O

Laugier

770, May 26

Chinese obs.

10 weeks.

Pingre1

837, Mar. 2*2

Chinese obs.

5 weeks.

I'O

Hind

962, Jan. 28

Chinese obs.

5 weeks.

I'O

Burckhardt

989, July 28

Chinese obs*

5 weeks.

I'O

—

Pingre"

1006, April

European obs.

3 or 6 weeks.

I'O

Hind

1 066, April i

Chinese obs.

6 weeks or + .

I'O

Hind

1092, Jan. 8

Chinese obs.

17 weeks.

I'O

Burckhardt

1097, Sept. 30

Chinese obs.

4 weeks.

I'O

Pingre-

1231, Feb. 6

Chinese obs.

4 weeks.

1 6. An apparition of Halley's comet.

17. It had a tail about 30° long.

18. Tolerably trustworthy. The maximum length of the tail was 80°, but it
dwindled down to 30° in a fortnight.

20. Probably an apparition of Halley's comet. Mentioned by several Saxon writers.

21. These elements appear to have escaped the notice of recent cometographers,
though given by Pingre ; but has it been confounded with the following ?

22. Possibly an apparition of Halley's comet. This is the famous object which
created such universal dread throughout Europe in 1066. In England it was looked
upon as a presage of the success of the Norman invasion.

23. Elements satisfactory.

24. A tail 50° long was seen in China, and much bifurcated.

I.I

514

Comets.

[BOOK IV.

No.

Tear.

pp.

1254

d. h.
July 15 23

O 1

272 30,

0 1

• '75 30

30 25

0-430

1299

March 31 7

3 20

107 8

68 57

0-318

(4)

1301 i.

Oct. 23 23

312

138

0-640

13371.

June 15 i

2 2O

93 i

40 28

0-828

1351

Nov. 25 23

Indeterminate.

It)

1362 i.

March 1 1 4

219

249

0-456

•»3

1366

Oct. 21 ii

48 4

217 25

27 37

0-979

(4)

1378

Nov. 8 1 8

299 31

47 17

'7 56

0-583

1385

Oct. 16 6

101 47

268 31

52 15

0774

'433

Nov. 7 1 8-

267 i

96 20

76 o

0-492

1449

Dec. 99

264 26

261 18

24 20

0-327

(4)

'456

June 8 5

298 57

43 56

'7 37

0-580

2.7

'457 iii-

Sept. 3 16

92 50

256 5

20 20

2-103

2.8

1462

Aug. 6 3

196

0-31

-9

1468 ii.

Oct. 7 6

356 3

61 15

44 19

0-853

1472

Feb. 28 5

48 3

207 32

i 55

0-539

1490 |

Dec. 24 ii
Dec. 35 21

58 40
"3

288 45
268

5i 37

0-738
0-755

1499

Sept. 6 1 8

326 30

0-954

1500

May 1 7

290

3io

''4

1506

Sept. 3 15

250 37

132 50

45 *

0-386

(4)

I53i

Aug. 24 21

3or 39

49 25

17 56

0-5670

Oct. 19 14

135 44

119 8

42 27

0-6125

J532 |

Oct. 19 22

in 7

So 27

32 36

0-5091

1533 {

June 14 21
June 16 19

217 40

IO4 12

299 T9
125 44

28 14
35 49

0-3269

0-2028

26. One of the grandest comets on record. Its tail is said to have been 100^ long.
Hoek has published several orbits all differing much from Pingr^'s.

27. Elements very doubtful.

28. Probably an apparition of HaHey's comet.

29. A fine comet. The elements assigned by Halley, Pingre1, and Hind differ
somewhat from those here given.

30. Very uncertain. No latitudes given.

31. Uncertain. The tail was 20 feet long, and the head was the size of a wine-glass/

32. Very uncertain.

• 33. An apparition of H alley's comet.
34. Tolerably certain. The tail was 10° long.

37. An apparition of Halley's comet. It had a splendid tail, 60° long. At one
time the head was round, and the size of a bull's eye, and the tail like that of a
peacock ! ! {Chinese Obs.)

38. Only approximate. It had a tail 15° long.

CHAP. VII.]

Catalogue. — No. I.

515

Calculator.

Date of
Discovery.

Discoverer.

Duration
of Visibility.

I'O

Pingrd

1264, July 14

Chinese & European

3 months.

I-O

Pingre"

1 299, Jan. 24

Chinese obs.

II weeks.

I-O

Laugier

1301, Sept. 16

Chinese & European

6 weeks.

I'O

Laugier

1337. May

Chinese & European

3 or 4 months.

Burckhardt

1351, Nov. 24

Chinese obs.

i week.

i-o

—

Burckhardt

1362, Mar. 5

Chinese obs.

5 weeks.

i-o

Hind

1366, Aug. 26

Chinese obs.

Several days.

Laugier

1378, Sept. 26

Chinese obs.

6 weeks.

I O

Hind

1385, Oct. 23

Chinese obs.

(?)

i-o

Celoria

1433. Oct. 12

Chinese obs.

3 months.

I-O

Celoria

1450, Jan. 19

Chinese obs.

7 weeks.

0-96

Celoria

1456, May 29

European & Chinese

i month.

Hind

1457, June

European obs.

3 months.

I'O

Hind

1462

Chinese obs.

i-o

Laugier

1468, Sept.

European obs.

2 or 3 months.

i-o

—

Laugier

1471, Dec.

Regiomontanus

3 months.

i-o
i-o

Hind -i
Peirce J

1491, Jan.

Chinese obs.

(?)

I'O

Hind

1499

Chinese obs.

(?)

i-o

Hind

1500, April

European & Chinese

3 weeks or + .

i-o

Laugier

1506, July 31

Chinese obs.

2 weeks.

i-o

—

Halley

i53i,Aug.i±

P. Apian

5 weeks.

i-o
i-o

Mdchain T
Halley J

1532, Sept. 22

P. Apian

1 6 weeks.

i-o

I'O

Olbers -i
Douwes J

I533> J«ne

P. Apian

i\ months.

40. Uncertain. It had a tail 30° long.

41. A celebrated comet. When at its least distance from the Earth (3,300,000
miles), on Jan. 21, it was quite visible in full daylight. It had a fine tail, which the
Chinese say was as long as a street I

42. Uncertain.

43. In the middle of August this Comet seems to have approached very near to
the Earth. — (Hind, MSS. communicated.)

44. Elements uncertain. It was as large as a ball ! and had a tail from 3° to

5° long-

46. An apparition of Ualley's comet. It had a tail 7° long.

47. It had a tail several degrees long. Olbers has computed an orbit which agrees
well with Halley's, but Me"chain's is considered the best.

48. According to Olbers, both these orbits will satisfy the observations, and it is as
yet impossible to decide between them. It had a tail 15° long.

516

Camels.

[BOOK IV.

No.

Tear.

PP.

(18)

1556

d. h.
April 22 o

0 /

274 14

175 25

30 12

0-5049

1558

Aug. 10 12

329 49

332 36

73 29

0-5773

1577

Oct. 26 22

129 42

25 20

75 9

0-1775

1580

Nov. 28 12

108 26

19 6

64 33

O'6O23

1582

May 6 1 6

245 23

231 7

61 27

0-2257

May 6 10

256 IS

229 18

60 47

0-1683

1585

Oct. 8 o

9 8

37 44

6 5

1-0948

1590

Feb. 8 o

217 57

165 37

29 29

0-5677

1593

July 18 13

176 19

164 15

87 58

0-0891

1596

July 25 5

270 54

330 20

5i 58

0-5671

(4)

1607

Oct. 27 o

300 46

48 14

17 6

0-584!

i6i8i.

Aug. 17 3

3l8 20

293 25

21 28

0-5I29

— iii.

Nov. 8 8

3 5

75 44

37 "

0-3895

1652

Nov. 12 15

28 18

88 10

79 28

0-8475

(35?)

1661

Jan. 26 21

115 16

81 54

33 o

OH427

1664

Dec. 4 12

130 33

81 15

21 18

1-0255

1665

April 24 5

?i 54

228 2

76 5

0-1064

i663

Feb. 24 18

4° 9

193 26

27 7

0-25II

Feb. 28 19

277 2

357 J7

35 58

0-0047

1672

March I 8

46 59

297 30

83 22

0-6974

1677

May 6 o

137 37

236 49

79 3

0-2805

1678

Aug. 1 8 7

322 47

163 20

2 52

I-I453

49. A rery fine comet, which was expected to return in 1860.

50. Hoek gives : PP. = Sept. 13 ; IT 2 1 5° ; Q 335° ; i 69° : q = 0-280.

51. It had a tail 22° long. This comet formed the subject of the observations of
Tycho Brahe for the detection of parallax.

52. Elements approximate. Observed also by Tycho Brahe.

53- Very uncertain. It had a faint tail 3° long, which resembled a piece of silk ! !

54. This orbit was computed some years ago, to see whether the comet of 1844 (ii)
was identical with this one.

55. It had a tail 7° long.

56. It had a tail 4^° long.

57. Discovered also by Tycho Brahe.

58. An apparition of Halley's comet. It had a tail 7° long.

59. Somewhat uncertain. Seen at Lintz, Aug. 27, and by Kepler, Sept. I.

CHAP. VII.]

Catalogue. — No. I.

517

Calculator.

Date of
Discovery.

Discoverer.

Duration
of Visibility.

Hind

1556, Feb. 28

P. Fabricius

10 weeks.

i-o

Gibers

1558, July 14

Landgrave of Hesse

6 weeks.

Woldstedt

1577, Nov. i

In Peru

12 weeks.

I'O

Schjellerup

1580, Oct. 2

Mcestlin

10 weeks.

i-o

Pingre'

1582, May 12

Tycho Brahe

3 weeks.

I'O

—

D'Arrest

I'O

C. A. Peters

1585, Oct. 19

Tycho Brahe &

4 weeks.

and Sawitsch

PtOthmann

I'D

Hind

1590, Mar. 5

Tycho Brahe

3 weeks.

i-o

La Caille

1593, July 20

De Rissen

6 weeks.

I'O

Hind

1596, July ii

Mrestlin

5 weeks.

0-96708

—

Lehmann

1607, Sept. ii

Kepler

9 weeks.

Pingre*

1618, Aug. 25

At Caschau

4 weeks.

i-o

Bessel

— Nov. 30

Many observers.

7 weeks.

i-o

Halley

1652, Dec. 20

Hevelius

3 weeks.

i-o

Me"chain

1661, Feb. 3

Heveliua

5 weeks.

i-o

Lindelof

1664, Nov. 17

In Spain

17 weeks.

I'O

Halley

1665, Mar. 27

At Aix

4 weeks.

I'D

Henderson i
Henderson i

1668, Mar. 5

Gottignies, etc.

3 weeks.

i-o

HaUey

1672, Mar. 2

Hevelius

7 weeks.

i-o

Halley

1677, April 27

Hevelius

12 days.

0-62697

Le Verrier

1678, Sept. ii

La Hire

4 weeks.

60. A splendid comet ; it had a tail, according to Longomontanus, 104° long, and
of a reddish hue. Said to have been visible in the daytime.

61. Elements only approximate.

62. By some supposed to be identical with the comet of 1532 ; it was not re-
observed, however, as was anticipated, about 1791.

63. It had a tail from 6° to 10° long.

64. It had a tail 25° long.

65. Seen chiefly in the southern hemisphere ; both orbits satisfy the observations,
and it is impossible to say which is the correct one.

66. It had a tail about i° long.

67. It had a tail about 6° long.

68. Elements only approximate.

518

Comets.

[BOOK IV.

No.

Year.

PP.

1680

d. h.
Dec. 17 23

262 49

o /

272 9

60 40

0-0062

(4)

1682

Sept. 14 19

301 55

51 H

i? 44

0-5829

1683

July 13 2

85 35

173 24

83 13

Q'5595

1684

June 8 10

238 52

268 15

65 48

0-9601

1686

Sept. 1 6 14

77 o

350 34

31 21

0-3250

1689

Nov. 29 4

269 41

90 35

59 4

0-0189

1695

Nov. 9 1 6

216

0-8435

1698

Oct. 18 16

270 51

267 44

II 46

0-69 1 2

1699 i.

Jan. 13 8

212 31

32i 45

69 2O

07440

1701

Oct. 17 9

'33 4«

298 41

4i 39

0-5926

1 702 ii.

March 13 14

13846

188 59

4 24

0-6468

1706

Jan. 30 4

72 29

13 ii

55 »4

0-4258

1707

Dec. ii 23

79 54

52 46

88 36

0-8597

1718

Jan. 14 21

121 39

I27 55

3i 8

1-0254

1/23

Sept. 27 15

42 53

14 14

50 o

0-9987

1729

June 13 6

320 31

3io 38

77 5

4^435

i73/i-

Jan. 30 8

325 55

226 22

18 20

O-2-228

— ii.

June 3 5

261 58

132 5

61 52

0-8349

1739

June 17 10

102 38

207 25

55 42

0-6735

I742i.

Feb. 8 4

2'7 35

185 38

66 59

0-7656

I743i-

Jan. 8 4

93 »9

86 54

i 53

0-86l5

— ii.

Sept. 20 21

247 o

6 2

45 37

0-5-229

1744

March i 8

197 12

45 45

47 8

O-222O

69. A splendid comet, whose tail ultimately attained a length of from 70° to 90°.
Halley conjectured that this was a return of the comet of 1106, 531 A.D., and 44 B.C.,
but this has since been shewn to be unlikely. The orbit here given supposes a period
of 88 1 4 years ; this, however, is subject to much uncertainty, inasmuch as the ob-
servations might possibly be satisfied by an 805 years' ellipse, or even by a hyper-
bolic orbit.

70. An apparition of ff alley's comet. It had a tail from 12° to 16° long.

71. It had a tail varying from 2° to 4°.

73. Its nucleus was as bright as a ist-magnitude star, and it had a tail 18° long.

74. Observed very roughly in the East Indies. It had a tail 60° long. Pingrd
makes the £3 = 323° 45'-

75. Observed still more imperfectly than the last in the southern hemisphere. It
had a tail 18° long.

76. Uncertain.

CHAP. VII ]

Catalogue. — No. /.

519

€

Calculator.

Date of
Discovery.

Discoverer.

Duration
of Visibility.

0-99998

Encke

1680, Nov. 14

G. Kirch

18 weeks.

0-96792

Eosenberger

1682, Aug. 15

Flamsteed

5 weeks.

IX)

Plummer

1683, July 23

Flamsteed

6 weeks.

l'O

Halley

1684, July I

Bianchini

2 weeks.

1X>

Halley

1686, Aug.

In India

I month.

I'O

Vogel

1689, Dec. 10

Bichaud

2 weeks.

BurckharJt

1695, Oct. 28

Jacob

3 weeks.

i-o

—

Halley

1698, Sept. 2

La Hire

4 weeks.

I'O

La Caille

1699, Feb. 17

Fontenay

2 weeks.

Burckhardt

1701, Oct. 28

Pallu

I week.

I'O

Burckhardt

1702, April 20

Bianchini

2 weeks.

I'O

La Caille

1706, Mar. 1 8

J. D. Cassini

4 weeks.

i-o

La Caille

1707, Nov. 25

Manfredi

8 weeks.

Argelander

1718, Jan. 18

C. Kirch

3 weeks.

Sporer

1723, Oct. 9

Uncertain

9 weeks.

1-00503

Burckhardt

1729, July 31

Sarabat

25 weeks.

Bradley

1737, Feb. 6

Tn Jamaica

4 weeks.

i-o

Hind

— Feb.

At Pekin

(?)

i-o

La Caille

1739, May 28

Zanotti

ii weeks.

i-o

La Caille

1742, Feb. 5

Cape of G. Hope

13 weeks.

0-72130

Clausen

1 743, Feb. 10

Grischau

2 weeks.

I'O

—

D'Arrest

— Aug. 1 8

Klinkenberg

4 weeks.

i-o

Betts

— Dec. 9

Klinkenberg

4 months (?)

78. Observed also by Thomas at Pekin.

79. Very roughly observed ; visible to the naked eye.
81. Discovered by J. D. Cassini, Nov. 29.

83. It was seen in Europe, with a faint tail i° long.

84. Scarcely perceptible to the naked eye. The orbit is a hyperbolic one, and
remarkable for its enormous perihelion distance, the greatest known.

86. Elements only approximate.

88. Visible to the naked eye, with a tail 6° or 8° long.

89. Very imperfectly observed. An elliptic orbit ; period assigned, 5-436 years.
' 90. Very uncertain. Visible to the naked eye.

91. The finest comet of the i8th century. On Feb. 15 it had a bifid tail, the
eastern portion being 7° long, and the western 24°. Visible in a telescope in the
daytime. Euler has calculated an elliptic orbit, to which he assigns a period of
122,683 years ! ! The statement of this comet having had six tails (at one time dis-
believed) has been confirmed by the testimony of De Lisle discovered by Winnecke.

520

Comets.

[BOOK IV.

No.

Year.

PP.

(17?)

1746

d. h.
Feb. 15 o

0 /

140 o

o /

33S o

o /

6 o

0'95

1747

March 3 7

277 2

147 18

79 6

2-1985

1748 i.

April 28 1 8

215 23

232 51

85 28

0-8404

— ii.

June 18 at

278 47

33 8

6? 3

0-6253

i/57

Oct. 21 7

122 58

214 it

12 SO

Q'3375

1758

June ii 3

267 38

230 5°

68 19

0-2153

(4)

1759 i-

March 12 13

3°3 10

53 5°

17 3<S

0-5845

— ii.

Nov. 27 2

53 24

139 39

78 59

0-7985

IOO

— iii.

Dec. 16 21

138 24

79 50

4 5i

0-9659

IOI

1762

May 28 8

104 2

348 33

85 38

i -0090

103

1763

Nov. i 20

8458

356 24

72 3i

0-4982

103

1764

Feb. 12 13

15 14

I2O 4

S^ 53

0-5552

I04

1 766 i.

Feb. 1 7 8

H3 15

244 10

40 50

0-5053

105

— ii.

April 26 23

251 13

74 H

8 i

0-3989

106

1769

Oct. 7 14

144 II

175 3

4° 45

0-1227

107

1770 i.

Aug. 13 12

356 16

131 59

i 34

0-6743

108

— ii.

Nov. 22 5

2O8 22

1 08 42

31 25

0-5282

109

1771

April 19 5

104 3

27 5i

Ii 15

0-9034

1772

Feb. 19 2

no 14

254 o

18 17

1-0136

III

1773

Sept. 5 14

75 I0

121 5

61 14

1-1268

112

1774

Aug. 15 19

3i7 27

1 80 44

83 20

1-4328

1779

Jan. 4 2

87 14

25 4

32 30

0-7131

114

1780 i.

Sept. 30 22

346 35

123 41

54 23

0-0963

92. Elements uncertain, but they strongly resemble those of the comet of 1231.
It passed very near the Earth,

93. Observed only during 1 746.

94. Discovered by J. D. Maraldi, April 30. Visible to the naked eye, with a tail
2° long.

95. Very uncertain.

96. Elements tolerably reliable. It had a small tail.

98. The first predicted apparition of Halley's comet. On May 5 its tail was 47°
long.

99. Visible to the naked eye, with a tail 5° long. Elements resemble those of the
comet of 1449.

100. This comet came near the Earth, and moved with great rapidity ; it had a
tail 4° long.

101. It bad a small tail.

102. An elliptic orbit ; period assigned, 7334 years. Lexell makes it 1137 years.

CHAP. VII.]

Catalogue. — No. I.

521

V-

Calculator.

Date of
Discovery.

Discoverer.

Duration
of Visibility.

I'O

Hind

1746, Feb. 2

Kindermans

4 weeks.

La Caille

— Aug. 13

Che"saux

15 weeks.

I'D

Le Monnier

1 748, April 26

At Pekin

9 weeks.

I'O

Bessel

— May 19

Klinkenberg

4 days.

I'O

Bradley

'757. Sept. IT

Gartner

5 weeks.

I'O

Pingre"

1758, May 26

La Nux

5 months.

0-96768

Rosenberger

— Dec. 25

Palitzch

5 months.

I'O

La Caille

1760, Jan. 25

Messier

8 weeks.

I'O

La Caille

— Jan. 7

At Lisbon

14 weeks.

I'O

Burckhardt

1762, May 17

Klinkenberg

6 weeks.

0-99868

Burckhardt

1763, Sept. 28

Messier

8 weeks.

I'O

Pingre*

1764, Jan. 3

Messier

6 weeks.

I'O

Pingre"

1 766, March 8

Messier

9 weeks.

0-8640

Burckhardt

— April I

Helfenzrieda

6 weeks.

0-99924

Bessel

1769, Aug. 8

Messier

1 6 weeks.

0-78683

Le Verrier

1770, June 14

Messier

15 weeks.

Pingre"

1771, Jan. 10

La Nux

8 days.

1-00936

Encke

— April i

Messier

15 weeks.

0-90314

Bessel

1772, Mar. 8

Montaigne

3 weeks.

I'O

Burckhardt

1773, Oct. 12

Messier

27 weeks.

1-02829

Burckhardt

17 74, Aug. ii

Montaigne

II weeks.

I'O

Zach

1779, Jan. 6

Bode

19 weeks.

0-99994

—

Cliiver

1780, Oct. 26

Messier

5 weeks.

103. Visible to the naked eye, with a tail i\° long.

105. Discovered by Messier, April 8. An elliptic orbit; period assigned, 5*025
years. Visible to the naked eye, with a tail 3° or 4° long.

106. Visible to the naked eye, with a tail from 60° to 80° long. Bessel assigns
2090 years as the most likely period of revolution. He has shewn that an error of
5" either may increase the period to 2673 years or diminish it to 1692 years.

107. The celebrated LexelTs comet. The diameter of the head, July I, was 2£°.
It had also a small tail, and approached within 1,400,000 miles of tbe Earth.

108. It had a faint tail, 5° long.

109. The orbit of this comet has been found hyperbolic. It had a tale about 2°
long. Recent calculations by Kreuz negative the hyperbola (A. N., 2469).

1 10. The first recorded apparition of JJiela's comet.

111. Just perceptible to the naked eye.

113. Discovered by Messier, Jan. 18.

114. An elliptic orbit ; period assigned, 75,314 years.

522

Comets.

[BOOK IV.

NO:

No.

Year.

PP.

•
2

i'5

1780 ii.

d. h.
Nov. 28 20

O /
246 52

o /

141 1

0 /

72 3

0-5152

116

1781 i.

July 7 4

239 II

83 o

81 43

07758

117

— ii.

Nov. 29 12

16 3

77 22

27 13

0-9610

118

100

1783 i.

Nov. 19 13

49 3i

55 12

47 43

1-4953

119

IOI

1784 i.

Jan. 21 4

80 44

56 49

5i 9

0-7078

120

102

— ii.

March 10 o

137

0-637

121

103

1785 i.

Jan. 27 7

109 51

264 12

70 14

i'i434

122

IO4

— ii.

April 8 8

297 29

64 33

87 31

o'4273

123

I°5

1786 L

Jan. 30 20

156 38

334 8

13 36

0-3348

I24

1 06

— ii.

July 7 21

»59 25

194 22

50 54

0-4101

I07

1787

May 10 19

7 44

106 51

48 15

0-3489

126

108

1788 i.

Nov. 10 7

99 8

156 56

12 27

1*0630

127

109

— ii.

Nov. 20 7

22 49

352 24

64 30

0-7573

128

1790 i.

Jan. 15 5

60 14

176 ii

3i 54

0-7581

129

III

— ii.

Jan. 28 7

ill 44

267 8

56 58

1-0632

130

112

— iii.

May 21 5

273 43

33 "

63 52

0-7979

131

1792 i.

Jan. 13 13

36 29

190 46

39 46

1-2930

132

114

— ii.

Dec. 27 6

'35 59

283 15

49 i

0-9662

133

1793 i-

Nov. 4 20

228 42

108 29

60 21

0-4034

*34

116

— ii.

Nov. 20 5

7i 54

2 0

51 31

I-495I

135

(105)

1/95

Dec. 21 10

156 4i

334 39

13 4*

0-3344

136

117

1796

April 2 19

192 44

17 2

64 54

1-5781

137

118

1/97

July 9 2

49 27

329 IS

50 40

0-5266

138

119

1798 i.

April 4 n

i°4 59

122 9

43 52

0-4847

139

I2O

— ii.

Dec. 31 13

34 27

249 30

42 26

°'7795

115. Discovered by Olbers on the same day.

116. Visible to the naked eye, Nov. 9, with a tail 3° long. It came very near the
Earth.

118. An elliptic orbit ; period assigned, 5*613 years.

119. Visible to the naked eye, with a tail 2° long.

1 20. Not only are the elements uncertain, but it is doubtful whether the comet
ever existed.

122. Visible to the naked eye, with a tail 8° long.

1 23. The first recorded apparition of Encke1* comet.
126. Visible to the naked eye, with a tail 2|° Ion?.

128. Imperfectly observed on four occasions. Elements only approximate.

CHAP. VII.]

Catalogue. — No. I.

523

- Calculator.

Date of
Discovery.

Discoverer.

Duration
of Visibility.

I'D

Gibers

1780, Oct. 1 8

Montaigne

3 days.

I'D

H-

Me"chain

1781, June 28

Me"chain

3 weeks.

I-O

Me"chain

Oct. 9

Me"chain

II weeks.

0-6784

H-

Burckhardt

1783, Nov. 19

Pigott

4 weeks.

I'O

Me"chain

— Dec. 15

La Nux

23 weeks.

Burckhardt

1784, April 10

D'Angos

5 days.

I O

Me"chain

1785, Jan. 7

Messier

5 weeks.

I'O

Me"chain

— Mar. II

Mechain

5 weeks.

o 84836

Encke

1786, Jan. 17

Me"chain

3 days.

i-o

Me"chain

— Aug. l

Miss Herschel

12 weeks.

Saron

1787, April 10

Mdchain

7 weeks.

i-o

Me"chain

1788, Nov. 25

Messier

5 weeks.

I'0

Mechain

— Dec. 21

Miss Herschel

4 weeks.

Saron

1 790, Jan. 7

Miss Herschel

2 weeks.

I'D

Mechain

— Jan. 9

Me"chain

3 weeks.

M(5chain

— April 1 8

Miss Herschel

10 weeks.

I'O

—

Mdchain

1791, Dec. 15

Miss Herschel

6 weeks.

I O

Prosperi n

1793, Jan. 8

Gregory

6 weeks.

I'D

Saron

— Sept. 27

Messier

15 weeks.

0-97342

D'Arrest

— Sept. 24

Perny

10 weeks.

0-84888

Encke

1 795, Nov. 7

Miss Herschel

3 wesks.

I'O

Gibers

1796, Mar. 31

Olbers

2 weeks.

i-o

Gibers

1/97, Aug. 14

Bouvard

3 weeks.

I'O

Burckhardt

1798, April 12

Messier

6 weeks.

i-o

—

Burckhardt

— Dec. 6

Bouvard

I week.

130. Visible to the naked eye, with a tail 4° long.

132. Discovered by Mechain and Piazzi, Jan. 10. There was a trace of a tail to
be seen.

134. Discovered by Miss Herschel, Oct. 7. An elliptic orbit ; period assigned, 422
years.

135. An apparition of Encltes comet. It was just visible to the naked eye.

136. Very faint.

137. Discovered by Miss Herschel and Lee on the same evening ; by Riidiger,
Aug. 15, and by Kecht, Aug. 16.

139. Discovered by Olbers, Dec. 1 8. Elements only approximate.

524

Comets.

[BOOK IV.

No.

Year.

PP.

140

121

1799 i.

d. h.

Sept. 7 5

0 I

3 39

99 3'

o /

5° 56

0-8399

141

(61)

— ii.

Dec. 25 21

190 20

326 49

77 I

0-6258

142

122

1801

Aug. 8 13

182 41

42 28

20 45

0-2564

»43

123

1802

Sept. 9 21

332 9

31° *5

57 o

1-0941

144

124

1804

Feb. 13 15

148 53

176 49

56 44

1-0772

(I05)

1805

Nov. 21 12

156 47

334 20

13 33

0-3404

146

(92)

1806 i.

Jan. i 23

109 32

251 15

13 38

0-9068

125

— ii.

Dec. 28 22

97 2

322 19

35 2

1-0815

148

126

1807

Sept. 1 8 17

27o 54

266 47

63 10

0-6461

149

127

1808 ii.

May 13 22

69 12

322 58

45 43

0-3898

ISO

128

— iii.

July 12 4

252 38

24 ii

39 l8

0-6079

'51

129

1810

Oct. 5 i

64 56

308 35

63 5

0-9685

152

13°

1811 i.

Sept. 12 6

75 o

140 24

73 2

i'0354

^53

131

— ii.

Nov. 10 23

47 27

93 i

3i i?

1-5821

154

I32

1812

Sept. 15 7

92 18

253 i

73 57

0-7777

155

133

1813 i.

March 4 12

69 56

60 48

21 13

0-6991

156

134

— ii.

May 19 10

197 43

42 40

8l 2

1-2-161

157

i3S

1815

April 25 23

149 2

83 28

44 29

1-2128

158

136

1816

March I 8

267 35

323 '4

43 5

0-0485

159

137

1818 i.

Feb. 3 5

76 18

256 i

34 ii

0-6959

160

138

— ii.

Feb. 25 23

182 45

70 26

89 43

1-1977

161

139

— iii.

Dec. 4 22

ioi 55

89 59

63 5

0-8550

162

(105)

1819 i.

Jan. 27 6 156 59

334 33

13 36

0-3352

140. Discovered by Olbers, Aug. 26. At first faint, but afterwards visible to the
naked eye, with a tail 10° long.

141. Probably a return of the comet of 1699. "Visible to the naked eye, with a
tail from i° to 3° long.

142. Discovered at Paris, July 12. Elements resemble those of the comet of 1462.

143. Discovered by Me'chairi, Aug. 28, and by Olbers, Sept. 2.

144. Discovered by Bouvard, March 10, and by Olbers, March 12.

145. An apparition of Encke's comet. Discovered by Pons, Huth, and Bouvard,
Oct. 20. Visible to the naked eye, with a tail 3° long.

146. An apparition of Biela's comet. Discovered by Bouvard, Nov. 16, and by
Huth, Nov. 2 2. Visible to the naked eye.

148. Discovered by Pons, Sept. 20. It wr.s visible to the naked eye, with a tail 5°
long. An elliptic orbit; period assigned, 1714 years, which may, however.be ex-
tended to 2157 years or reduced to 1403 years.

149. Discovered by Wisniewski, March 29.

150. Elements only approximate.

CHAP. VII.]

Catalogue. — No. I.

525

Calculator.

Date of
Discovery.

Discoverer.

Duration
of Visibility.

I'D

Burckhardt

1 779, Aug. 7

Me'chain

3 weeks.

I'O

—

Me"chain

— Dec. 26

Me"chain

lo days.

Doberck

1801, June 30

Reissig

3 weeks.

I'O

Gibers

1802, Aug. 26

Pona

6 weeks.

I'D

Bouvard

1804, Mar. 7

Pons

3 weeks.

0-84617

Encke

1805, Oct. 19

Thulis

3 weeks.

074578

Gambart

— Nov. 10

Pona

4 weeks.

I'O

—

Burckhardt

1806, Nov. 10

Pona

14 weeks.

0-99548

Bessel

1807, Sept. 9

Paris!

28 weeks.

I'O

Encke

1808, Mar. 25

Pons

I week.

I'O

Bessel

— June 24

Pona

lo days.

I'O

Thraeix

1810, Aug. 22

Pons

6 weeks.

0-99509

Argelander

1811, Mar. 26

Flaugergues

17 months.

0-98271

-t-

Nicolai

— Nov. 16

Pons

13 weeks.

°'95454

Encke

1812, July 20

Pona

10 weeks.

I'O

Nicollett

1813, Feb. 4

Pons

5 weeks.

I'O

—

Encke

— Mar. 28

Pona

6 weeks.

0-93121

Bessel

1815, Mar. 6

Gibers

25 weeks.

I'O

Burckhardt

1816, Jan. 22

Pons

II days.

i-o

Hind

1818, Feb. 23

Pona

4 days.

I'O

Encke

1817, Dec. 26

Pons

1 8 weeks.

I'O

Rosenberger

1818, Nov. 28

Pons

9 weeks.

0-84858

Encke

— Nov. 26

Pons

7 weeka.

152. A very celebrated comet, conspicuously visible in the evenings of the autumn
of 1811. It had a tail 25° long and 6° broad. The most reliable computations assign
a periodic term of 3065 years, subject to an uncertainty of not more than 43 years.
The orbit of this comet is liable to much planetary perturbation.

153. An elliptic orbit ; period assigned, 875 years. Visible to the naked eye.

154. An elliptic orbit; period assigned, 70-68 years. Visible to the naked eye,
with a tail 2° long.

156. Discovered also by Harding, April 3. Visible to the naked eye.

157. An elliptic orbit; period assigned, 70-049 years. Bessel anticipated that
planetary perturbation would bring it back to perihelion, 1887, Feb. 9. It had
a short tail.

158. Elements only approximate.

159. The observations were few and indifferent.

161. Discovered by Bessel, Deo. 22. It moved very rapidly. Rosenberger has
computed a hyperbolic orbit.

162. An apparition of Enche's comet, the periodicity of which was now discovered.

526

Comets.

[BOOK IV.

No.

Year.

PP.

•K

163

140

1819 ii.

d. h.
June 27 17

0 /

287 5

273 42

o /

80 44

0-3410

164

141

— iii.

July 18 21

274 4o

113 10

10 42

0-7736

165

142

— iv.

Nov. 20 5

67 18

77 13

9 *

0-8925

166

1821

March 21 12

239 29

48 40

73 3

0-0918

167

144

1822 i.

May 5 14

I92 43

177 26

53 37

0-5044

1 68

('05)

— ii.

May 23 23

157 "

334 25

13 20

0-3459

169

— iii.

July 15 20

"9 59

97 44

36 18

0-8473

170

146

— iv.

Oct. 23 18

271 4o

92 44

52 39

i 1450

171

1823

Dec. 9 10

274 34

303 3

76 ii

0-2265

172

148

1824 i.

July ii 12

260 16

234 19

54 34

0-5912

'7.<

149

— ii.

Sept. ig i

4 31

279 !5

54 36

1-0501

174

(112)

1825 i.

May 30 13

273 55

20 6

56 41

0-8891

175

150

— ii.

Aug. 18 17

10 14

192 56

89 41

0-8834

176

(-05)

— iii.

Sept. 1 6 6

157 H

334 27

13 21

0-3448

177

151

— iv.

Dec. 10 16

318 46

215 43

33 32

1-2408

178

(9*)

1826 i.

March 1 8 9

109 45

251 28

13 33

0-9025

179

152

— ii.

April 21 23

116 54

197 38

40 2

2-OJII

1 80

153

— iii.

April 29 o

35 48

40 29

5 i?

0-1881

181

154

— iv.

Oct. 8 22

57 48

44 6

25 57

0-8528

182

155

Nov. 1 8 9

315 31

235 7

89 22

0-0268

183

156

1827 i.

Feb. 4 22

33 3°

184 27

77 35

0-5065

184

'57

— ii.

June 7 20

«97 3i

318 10

43 38

0-8081

163. A very brilliant comet, with a tail 7° long.

164. An elliptic orbit ; period assigned, 5*618 years. Considered by Clausen as a
return of the comet of 1766 (ii).

165. Discovered by Pons, Dec. 4. An elliptic orbit ; period assigned, 4-810 years.
Clausen thought this comet might be identical with that of 1 743 (i).

166. Discovered by Nicollet on the same day, and by Blainpain, Jan. 25. Visible
to the naked eye, with a tail 2%° long.

167. Discovered by Pons, May 14, and by Biela, May 17.

1 68. The first predicted apparition of Encke's comet. Seen only in New South
Wales.

169. Its apparent motion was very rapid.

170. Discovered by Gambart, July 16. An elliptic orbit; period assigned, 5444
years. Visible to the naked eye, with a tail I %° long.

171. Discovered by Pons, Dec. 29; by Kohler, Dec. 30 ; and by Santini, Jan. 3.
This comet had, in addition to the usual tail turned from the Sun, another turned
towards it.

CHAP. VII.]

Catalogue. — No. I.

527

€

Calculator.

Date of
Discovery.

Discoverer.

Duration
of Visibility.

I'O

Bouvard

1819, July I

Tralles

1 6 weeks.

0-755I9

-f

Encke

— June 12

Pons

5 weeks.

0-68674

Encke

— Nov. 28

Blainpain

8 weeks.

I'O

Rosenberger

1821, Jan. 21

Pons

15 weeks.

I'O

Nicollet

1822, May 12

Gambart

7 weeks.

0-84446

Encke

— June 2

Riimker

3 weeks.

I'O

Hind

— May 31

Pons

2 weeks.

0-99630

Encke

— July 13

Pons

17 weeks.

I'O

Encke

1823, Dec. i

In Switzerland

13 weeks.

I'O

Riimker

1824, July 15

Riimker

4 weeks.

1-00173

Encke

— July 23

Scheithauer

22 weeks.

I'O

Clausen

1825, May 19

Gambart

8 weeks.

I'O

Clausen

— Aug. 9

Pons

3 weeks.

0-84488

Encke

— July 13

Valz

8 weeks.

Q'99536

Han sen

— July 15

Pons

12 months.

0-74657

Santini

1826, Feb. 27

Biela

8 weeks.

I'O

Clausen

1825, Nov. 6

Pons

22 weeks.

I'O

—

Clttver

1826, Mar. 29

Flaugergucs

9 days.

I'O

Argelander

— Aug. 7

Pons

15 weeks.

I'O

Cliiver

— Oct. 22

Pons

ii weeks.

I'O

Heiligenstein

— Dec. 26

Pons

5 weeks.

I'O

—

Heiligenstein

1827, June 20

Pons

4 weeks.

172. Seen only in the southern hemisphere.

173. Discovered by Pons, July 24, and afterwards by Gambart and Harding.

174. It had a tail i£° long. Elements resemble those of 1790 (iii).

175. Discovered by Harding, Aug. 23. Orbit remarkable for its great inclina-
tion.

176. An apparition of Encke's comet. Discovered by Plana, Aug. 10, and by Pons,
Aug. 14. _

177. Discovered by Biela, July 19. Very conspicuous early in October, with a
bifid tail 15° long. An elliptic orbit ; period assigned, 4386 years.

•178. An apparition of Biela' s comet, whose periodicity was now discovered. Found
by Gambart, March 9.

1 80. Elements uncertain.

181. The path of this comet crosses the ecliptic near the Earth's orbit.

182. Discovered by Clausen, Oct. 26, and by Gambart, Oct. 28. Visible to the
naked eye, with a tail |° long.

i8.j. Discovered also by Gambart. Elements resemble those of the comet of 1500.

528

Comets.

[BOOK IV.

No.

Year.

PP.

185

I58

1827 iii.

d. h.

Sept. 1 1 6

O /

250 57

0 /

*49 39

0 /

54 4

0-1378

186

(105)

1829

Jan. 9 17

157 17

334 29

13 20

C'3455

187

»59

1830 i.

April 9 7

212 II

2o6 21

21 l6

0*9214

1 88

1 60

— ii.

Dec. 27 15

3io 59

337 53

44 45

0-1258

189

(105)

1832 i.

May 3 23

157 21

334 32

13 22

0-3434

190

161

— ii.

Sept. 25 12

227 55

72 27

43 18

1-1839

191

(90

— iii.

Nov. 26 2

no o

248 15

13 13

0-8790

192

162

1833

Sept. 10 4

222 51

323 o

7 21

0-4584

'93

163

1834

April 2 15

276 33

226 48

5 56

0-5I50

194

164

1835 i-

March 27 13

207 42

58 19

9 7

2-0413

'95

(105)

— ii.

Aug. 26 8

157 23

334 34

13 21

o'3444

196

(4)

— iii.

Nov. 15 22

3«>4 31

55 9

17 45

0-5865

197

(105)

1838

Dec. 19 o

157 27

334 36

13 21

0*3440

198

165

1840 i.

Jan. 4 10

192 ii

"9 57

53 5

0-6184

199

1 66

— ii.

March 13 2

80 12

236 50

59 I2

1-2204

200

(16)

— iii.

April 2 12

3»4 20

186 4

79 5i

07420

201

167

— iv.

Nov. 13 15

22 31

248 56

57 57

1-4808

202

(i°5)

1842 i.

April 12 o

157 29

334 39

13 20

0-3450

203

1 68

— ii.

Dec. 15 22

327 17

207 49

73 34

0-5044

2O4

169

1843 i.

Feb. 27 9

278 39

I 12

35 41

0-0055

205

170

— ii.

May 6 i

281 29

157 14

52 44

1-6163

2O6

171

— iii.

Oct. 17 3

49 34

209 29

II 22

1-6925

185. At one time supposed to be a return of the comet of 1780 (i). An elliptic
orbit ; period assigned, 2611 years.

186. An apparition of Encke's comet, afterwards visible to the naked eye.

187. Discovered in the southern hemisphere. Visible to the naked eye, with a tail
8° long. >

1 88. Visible to the naked eye, with a tail 2^° long.

189. An apparition of Encke's comet. Discovered by Henderson, June 2. Only
one observation was made in Europe.

190. Discovered by Harding, July 29.

191. The first predicted apparition of £ Ida's comet.
193. Discovered by Dunlop, March 16.

195. An apparition of Encke's comet. Discovered by Boguslawski. July 30.

196. The second predicted return oi H alley's comet. It was visible to the naked
eye during the whole of October, with a tail from 20° to 30° long.

197. An apparition of Encke's comet. Discovered by Galle, Sept. 16. Perceptible
to the naked eye, Nov. 7.

202. An apparition of Encke's comet.

CHAP. VII.]

Catalogue. — No. I.

529

Calculator.

Date of
Discovery.

Discoverer.

Duration
of Visibility.

0-99927

Cliiver

1827, Aug. 2

Pons

10 weeks.

0-84462

Encke

1828, Oct. 13

Struve

15 weeks.

0-99938

Hadenkamp

1830, March 16

D'Abbadie

22 weeks.

and Mayer

I'O

Wolfers

1831, Jan. 7

Herapath

9 weeks.

0-84541

Encke

1832, June I

Mossotti

i-o

C. A. Peters

— July 19

Gambart

4 weeks.

0-75146

•+

Santini

— Aug. 25

Dumouchel

18 weeks.

I'O

C. A. Peters

1833, Oct. i

Dunlop

2 weeks.

Petersen

1834, March 8

Gambart

6 weeks.

W. Bessel

1835, April 20

Boguslawski

5 weeks.

0-84503

Encke

— July 22

Kreil

9 weeks.

0-96739

Westphalen

— Aug. 6

Dumouchel

41 weeks.

0-84517

Encke

1838, Aug. 14

Boguslawski

1 6 weeks.

1-OOO2O

Peters, Struve

1839, Vec. 3

Galle

10 weeks.

o'99323

Loomis

1840, Jan. 25

Galle

9 weeks.

Petersen

— March 6

Galle

3 weeks.

0-96985

Gotze

— Oct. 27

Bremiker

16 weeks.

0-84479

Encke

1842, Feb. 8

Galle

15 weeks.

Petersen

— Oct. 28

Laugier

4 weeks.

0-99989

Hubbard

1843, Feb. 28

Many observers.

7 weeks.

1-00017

Gotze

— May 2

Mauvais

21 weeks.

°'55596

Le Verrier

— Nov. 22

Faye

20 weeks.

198. Perceptible to the naked eye, Jan. 8.

199. An elliptic orbit ; period assigned, 2423 years. Plantamour, however, makes
it 13,864 years.

200. Probably a return of the comet of 1097. It had a tail 5° long.

201. An elliptic orbit ; period assigned, 344 years, subject to an uncertainty of
about 8 years. Possibly a return of the comet of 1490.

202. An apparition of Encke's comet.

203. Small and faint.

204. One of the finest comets of the present century. It had a tail 60° long.
The orbit is remarkable for its small perihelion distance. The period assigned is
376 years. This may be a return of the comet of 1668, but many others have
also been supposed to be identical with it. (See Cooper's Cometic Orbits, pp.
162-9.)

206. Usually known as Fayes comet. It had a very small tail. Period, 7'44
years.

M m

530

Comets.

[BOOK IV.

No.

Year.

PP.

207

(53?)

1844 i.

d. h.
Sept. a ii

0 /

343 30

o /

63 49

O I

* 54

1-1864

208

172

— ii.

Oct. 17 8

1 80 24

3i 39

48 36

0-8553

209

173

— iii.

Dec. 13 1 6

296 o

118 23

45 36

0-2512

2IO

174

1845 i.

Jan. 8 3

91 19

336 44

46 so

0-9051

211

175

— ii.

April 21 o

I92 33

347 6

56 23

1-2546

212

(44)

— iii.

June 5 i 6

262 i

337 48

48 41

0-4016

213

(105)

— iv.

Aug. 9 15

*57 44

334 19

13 7

0-3381

214

176

1846 i.

Jan. 22 2

89 6

in 8

47 26

1-4807

215

(92)

— ii.

Feb. 10 23

IO9 2

245 54

12 34

0-8564

216

177

— iii.

Feb. 25 7

116 28

102 37

30 57

0-6500

217

l?8

— iv.

March 512

90 27

77 33

85 6

0-6637

218

179

— v.

May 27 21

82 32

161 18

57 35

1-3/62

219

180

— vi.

June i 5

240 7

260 28

30 24

1-5287

22O

181

— Vii.

June 5 12

162 o

261 51

29 18

0-6334

221

182

— viii.

Oct. 29 I?

98 35

4 41

49 41

0-8306

222

183

1847 i.

March 30 6

276 2

21 42

48 39

0-0425

223

184

— ii.

June 4 i 8

In I 34

173 56

79 34

2-i 161

224

185

— iii.

Aug. 9 8

21 I7

76 43

32 38

1-4847

225

186

— iv.

Aug. 9 10

246 41

338 i?

83 27

1-7671

226

187

— v.

Sept. 9 13

79 I2

309 48

19 8

0-4879

227

188

— vi.

Nov. 14 9

274 14

190 50

/i 53

0-3291

228

189

1848 i.

Sept. 8 i

3io 34

211 32

84 24

0-3199

229

(105)

— ii.

Nov. a 6 2

157 47

334 22

13 8

0-3370

207. Visible to the naked eye. An elliptic orbit ; period assigned, 5*469 years.
It has not been observed since. Possibly identical with the comet of 1678.

208. Discovered by D'Arrest, July 9. Visible to the naked eye, Nov. 10. Period,
102,050 years, subject to an uncertainty of 3090 years.

209. First seen in the southern hemisphere. It had a tail 10° long.

211. Discovered by Faye, March 6.

212. Discovered by Richter, June 6. A fine comet. Visible to the naked eye,
with a tail 2^° long. A return of the comet of 1596. Period, 250 years.

213. An apparition of Encke's comet. Discovered by Di Vico, July 9, and by
Coffin, July 10.

214. An elliptic orbit; period assigned, 2721 years.

215. An apparition of Bielas comet. Discovered by Galle, Nov. 28. It was at
this return that the comet separated into 2 parts.

216. An elliptic orbit ; period assigned, 5-58 years.

CHAP. VII.]

Catalogue. — No. I.

531

Calculator.

Date of
Discovery.

Discoverer.

Duration
of Visibility.

0-61765

Briinnow

1844, Aug. 22

Di Vico

19 weeks.

0-99960

Plantamour

— July 7

Mauvais

35 weeks.

Hind

— Dec. 19

Wilmot

12 weeks.

i-o

Gotze

— Dec. 28

D'Arrest

13 weeks.

i-o

Faye

1845, Feb. 25

Di Vico

9 weeks.

0-98987

D' Arrest

— June 2

Colla

4 weeks.

0-84743

Encke

— July 4

Walker

IO days.

0-99240

Jelinek

1846, Jan. 24

Walker

14 weeks.

0-75700

Plantamour

1845, Nov. 26

Walker

21 weeks.

0-79446

Hind

1846, Feb. 26

Brorsen

8 weeks.

0-96224

Peirce

— Feb. 20

Di Vico

10 weeks.

Argelander

— July 29

Di Vico

II weeks.

0-72133

- .

C. H. Peters

— June 26

C. H. Peters

4 weeks.

0-98836

Wichmann

— April 30

Brorsen

6 weeks.

i-o

Hind

— Sept. 23

Di Vico

3 weeks.

0.99991

Hornstein

1847, Feb. 6

Hind

1 1 weeks.

I'O

Von Littrow

— May 7

Colla

30 weeks.

I'O

Schweizer

— Aug. 31

Schweizer

13 weeks.

I'O

Von Littrow

— July 4

Mauvais

41 weeks.

0-97256

D'Arrest

— July 20

Brorsen

8 weeks.

I'O

D'Arrest

— Oct. i

Miss Mitchell

13 weeks.

I'O

Sonntag and

1848, Aug. 7

Petersen

3 weeks.

Quirling

0-84782

Encke

— Aug. 27

G. P. Bond

13 weeks.

217. Discovered by G. P. Bond, Feb. 26.

218. Discovered by Hind, 2 hours later.

219. Discovered by Di Vico, July 2. An elliptic orbit ; period assigned, 12-8 years,
subject to an uncertainty of i year.

220. Discovered by Wichmann, May i. Visible to the naked eye, May 14. An
elliptic orbit ; period assigned, 400 years.

222. Visible in the daytime. It had a tail i|° long. The true elements are
probably elliptical. Hornstein has throughly discussed the orbit of this comet.

225. A parabolic orbit best satisfies the observations.

226. Period assigned, 75 years.

227. Discovered by Di Vico, Oct. 3 ; by Dawes, Oct. 7 ; and by Madame Riimker,
Oct. ii.

229. An apparition of Encke's comet. Discovered by Hind, Sept. 13. Perceptible
to the naked eye, Oct. 6. On Nov. 3 it had a tail more than i° long.

M m 2

532

Comets.

[BOOK IV.

No.

Year.

PP.

230

190

1849 i.

d. h.
Jan. 19 8

0 /

63 II

215 10

85 4

0-9599

231

191

— ii.

May 26 ii

235 43

202 33

67 9

I-I593

232

192

— iii.

June 8 4

267 3

30 31

66 59

0-8946

233

'93

1850 i.

July 23 12

273 24

92 53

68 12

1-0815

234

'94

— ii.

Oct. 19 8

89 20

206 o

40 6

0-5647

235

071)

1851 '•

April 3 ii

49 42

209 30

II 21

1-6999

236

J95

— ii.

July 9 o

324 10

149 19

I4 I4

1-1847

237

196

— iii.

Aug. 26 5

31° 58

223 40

38 9

0-9843

238

197

— iv.

Sept. 30 19

338 45

44 28

74 o

0-1410

239

(105)

1852 i.

March 14 18

157 51

334 23

13 7

0-3374

240

198

— ii.

April 19 13

280 o

317 8

48 52

0-9050

241

(92)

— iii.

Sept. 23 i

109 8

245 52

12 33

0-8606

243

199

— iv.

Oct. 12 15

43 12

346 i.l

40 58

1-2510

243

200

1853 i-

Feb. 24 6

153 21

69 49

20 19

1-0938

244

•201

— ii.

May 9 16

201 53

40 57

57 44

0-9044

245

202

— iii.

Sept. i 17

31° 56

140 31

61 31

0-3068

246

203

— iv.

Oct. 16 14

302 7

220 4

61 i

0-1725

?47

204

1854 i.

Jan. 4 6

55 57

227 3

66 7

I-2OO2

248

205

— ii.

March 24 o

213 47

3J5 26

82 22

0-2770

249

(13)

— iv.

June 22 2

272 58

347 48

71 8

0-6475

250

206

Oct. 27 9

94 20

324 34

40 59

O'SOOI

230. A parabolic orbit satisfies the observation, but a period of 382,801 years has
been assigned ! ! !

231. It had a small tail.

232. Discovered a few hours later by Bond, and by Graham April 14. Period,
8375 years.

233. Visible to the naked eye, with a tail. Carrington has assigned a period of
about 29,000 years.

234. Discovered by Brorsen, Sept. 5 ; by Mauvais and Robertson, Sept. 9 ; and by
Clausen, Sept. 14.

235. The first predicted apparition of Faye's comet.

236. Period, 6^441 years.

237. Discovered by Schweizer, Aug. 21. Period assigned, 5544 years.

238. It had a tail more than 1° long, and also a shorter one turned towards the Sun.

239. An apparition of Enckes comet.

240. Discovered by Petersen, May 17, and by G. P. Bond, May 19. It was very
email and faiut.

241. An apparition of Biela's comet. Theoretical elements.

CHAP. VII.]

Catalogue. — No. I.

533

Calculator.

Date of
Discovery.

Discoverer.

Duration
of Visibility.

I'O

Pogson

1848, Oct. 26

Petersen

20 weeks.

Goujon

1849, April 15

Goujon

24 weeks.

0-99783

D'Arrest

— April ii

Schweizer

20 weeks.

Villarceau

1850, May I

Petersen

17 weeks.

Reslhiiber

— Aug. 29

G. P. Bond

9 weeks.

0-55501

Le Verrier

— Nov. 28

Challis

14 weeks.

0-70001

D'Arrest

1851, June 27

D'Arrest

17 weeks.

0-99685

Brorsen

— Aug. i

Brorsen

8 weeks.

J. Breen

Oct. 22

Brorsen

4 weeks.

084767

Encke

1852, Jan. 9

Hind

8 weeks.

—

Sonntag

— May 15

Chacornac

3 weeks.

0-75625

Santini

— Aug. 25

Secchi

5 weeks.

0-92475

Marth

— June 27

Westphal

24 weeks.

D'Arrest

1853, March 6

Secchi

3 weeks.

Bruhns

— April 4

Schweizer

10 weeks.

1-00026

Krahl

— June 10

Klinkerfues

7 months.

I'O

Bruhns

— Sept. 1 1

Bruhns

II weeks.

Marth

— Nov. 25

Van Arsdale

12 weeks.

Hornstein

1854, March 23

Many observers

6 weeks.

Bruhns

— June 4

Klinkerfues

10 weeks.

Bruhns

— Sept. 1 1

Klinkerfues

11 weeks.

242. Discovered also by C. H. Peters. Visible to the naked eye early in October.
Period, 70 years.

243. Discovered by Schweitzer and C. W. Tuttle, March 8, and by Hartwig,
March 10. Elements resemble those of the comet of 1664.

244. Visible to the naked eye in the beginning of May, with a tail 3° long.

245. Visible in the daytime, Aug. 31 to Sept. 4. In the south of Europe, a tail
15° long was seen.

246. Perceptible to the naked eye about the middle of the month. Elements
resemble those of the comet of 1582.

247. Discovered by Klinkerfues, Dec. 2.

248. First seen in the south of France, when very conspicuous, with a tail 4° long.
Elements resemble those of the comet of 1 799 (ii).

249. Discovered also by Van Arsdale. At the time of the PP it was visible to
the naked eye. The elements strongly resemble those of the comets of 961 anil
1558.

250. Discovered also by several other observers. Probably a return of the comet
of 1845 (i).

534

Comets.

[BOOK IV.

No.

Year.

PP.

251

207

1854 vi.

d. h.
Dec. 15 17

0 I

165 9

0 /

238 7

o /

14 9

1-3575

252

208

1855 i-

Feb. 5 17

226 33

189 40

51 12

1-2195

253

(22)

— iii.

May 30 5

2.37 36

260 15

23 7

0-5678

254

(105)

— iv.

July I 5

157 53

334 26

13 8

o-337i

255

209

L- v

Nov. 25 15

85 21

52 2

10 16

1-2248

256

2IO

1857 i.

March 21 8

74 49

313 12

87 57

0-7721

257

(i/7)

— ii.

March 29 5

115 48

ioi 53

29 45

0-6202

258

211

— iii.

July 17 23

»49 37

23 4°

58 59

0-3675

259

212

— iv.

Aug. 24 o

21 46

200 49

32 46

0-7427

260

213

Sept. 30 19

250 21

14 46

56 18

0-5651

261

2I4

— vi.

Nov. 19 i

44 15

139 18

37 50

1-1009

262

(195)

— vii.

Dec. 33 o

323 3

148 27

13 56

1-1696

26.?

(III)

1858 i.

Feb. 23 8

115 29

268 54

54 32

1-0274

264

(Ml)

— ii.

May 2 i

275 38

H3 32

10 48

0-7689

265

215

— iii.

May 2 23

200 46 175 4

19 30

I-I493

266

216

— iv.

June 5 4

226 6

324 21

80 28

0-5462

267

(171)

Sept. 12 14

49 49

209 45

II 21 1-6999

268

217

— vi.

Sept. 29 23

36 13

165 19

63 I

0-5784

269

218

— vii.

Oct. 12 19

4 13

159 45

21 l6

1-4270

270

(105)

— viii.

Oct. 1 8 8

157 57

334 28

13 4

0-3407

271

219

1859 ii.

May 29 5

75 9

357 7

84 9

0-2O2O

272

2 2O

1860 L

Feb. 16 17

173 45

324 3

79 35 I-I973

251. Discovered by Winnecke and Dien, Jan. 15, 1855.

253. Discovered also by Dien and Klinkerfues. Probably a return of the comet
of 1362 (i). Period assigned, 493 years.

254. An apparition of Encke's comet.

255. Discovered also by Van Arsdale.

256. Discovered also by Van Arsdale. Orbit decidedly parabolic.
357. An apparition of Brorseris comet, 1846 (iii).

259. Discovered by Dien, July 28, and by Habicht, July 30. An elliptic orbit ;
period assigned, 234 years.

260. Faintly perceptible to the naked eye, Sept. 20. It had a short tail. Elements
resemble those of the comets of 1790 (iii) and 1625 (i). A period of 1618 years has
been assigned by Villarceau.

261. Discovered a few hours later by Van Arsdale.

262. An apparition of D'Arresd comet. Period, 2366 days. Lind and Villarceau
concur in dating the PP for Nov. 28.

CHAP. VII.]

Catalogue. — No. I.

535

Calculator.

Date of
Discovery.

Discoverer.

Duration
of Visibility.

0-98637

Elkin

1854, Dec. 24

Colla

1 6 weeks.

I'O

Winnecke

1855, April 1 1

Schweizer

5 weeks.

0-99090

Donati

— June 3

Donati

2 weeks.

0-84778

Encke

— July 13

Maclear

5 weeks.

I'O

—

G. Riimker

— Nov. 12

Bruhns

7 weeks.

1.0

Pape

1857, Feb. 22

D'Arrest

9 weeks.

0-80160

Bruhns

— Mar. 18

Bruhns

II weeks.

I'O

—

Pape

— - June 2 2

Klinkerfues

3 weeks.

0-98037

Moller

— July 25

C. H. Peters

5 weeks.

i-o

Bruhns

— Aug. 20

Klinkerfues

7 weeks.

I'O

Pape

— Nov. 10

Donati

5 weeks.

0-65985

Schulze

— Dec. 5

Maclear

6 weeks.

0-82961

Bruhns

1858, Jan. 4

H. P. Tuttle

9 weeks.

0-75467

Winnecke

— Mar. 8

Winnecke

12 weeks.

0-67368

Schulhof

— May 2

Tuttle

4 weeks.

I'O

Bruhns

— May 21

Bruhns

3 weeks.

0-55501

Bruhns

— Sept. 8

Bruhns

8 weeks.

0-99620

Von Asten

— June 2

Donati

7| months.

i-o

Weiss

— Sept. 5

H. P. Tuttle

8 weeks.

0-84639

Powalky

— Aug. 7

Forster

10 weeks.

i-o

Hall

1859, April 2

Tempel

1 2 weeks.

i-o

Liais

1860, Feb. 26

Liais

2 weeks.

263. Discovered by Bruhns, Jan. n. Probably a return of the comet of 179° (")•
Period assigned, 13-6 years.

264. An apparition of the comet of 1819 (iii), now called Winnecke's Comet.

266. Elements resemble those of the comet of 1799 (ii).

267. An apparition of Faye's comet.

268. One of the finest comets of the present centuiy. It became visible to the
naked eye early in September, and was very conspicuously seen in Europe for about
6 weeks, when, owing to its rapid passage to the southern hemisphere, it became
lost to view. It was seen at the Cape of Good Hope till March 4, 1859. During
the first week in October it had a tail nearly 40° long. An elliptic orbit ; period
assigned, 1879 years.

270. An apparition of Encke' s comet. It was very faint.

272. It does not appear that this comet was seen in Europe. Liais, who observed
it in Brazil, states that it had a double nebulosity, and conjectures it to be identical
with 1845 (ii), 1785 (i), and 1351.

536

Comets.

[BOOK IV.

No.

Year.

PP.

273

221

1860 ii.

d. li.
March 5 17

50 16

0 /

8 56

0 /

48 13

1-3083

274

222

— iii.

June i 6 2

161 32

84 40

79 18

0-2929

375

223

— iv.

Sept. 22 7

356 48

44 51

32 12

0-6827

276

224

1861 i.

June 3 8

243 22

29 55

79 45

0-9207

277

225

— ii.

June ii 12

249 4

278 58

85 26

0-8223

278

226

— iii.

Dec. 7 3

173 3°

MS 6

4i 57

0-8391

279

(105)

1862 i.

Feb. 6 4

158 o

334 30

13 5

0-3399

280

22?

— ii.

June 22 i

299 20

326 32

7 54

0-9813

281

228

— iii.

Aug. 22 22

344 4i

137 26

66 25

0-9626

282

229

— iv.

Dec. 28 3

125 9

355 44

42 22

0-8025

283

230

1863 i.

Feb. 3 12

191 22

"6 55

85 22

o-7947

284

231

— ii.

April 4 22

247 15

251 16

67 22

1-0682

285

232

— iii.

April 20 21

305 47

250 10

85 29

0-6288

286

233

— iv.

Nov. 9 12

94 43

97 29

/8 5

0-7066

287

(I29)

Dec. 26 14

59 13

3°4 57

63 35

0-7661

288

234

— vi.

Dec. 29 4

183 8

105 i

83 18

1-3131

289

235

1864 i.

July 37 21

190 10

175 ii

44 56

0-6140

290

236

— ii.

Aug. 15 14

3°4 13

95 12

i 52

0-9092

291

237

— iii.

Oct. 1 1 8

159 3°

3i 43

70 13

0-9338

292

238

— iv.

Dec. 22 ii

321 42

203 13

48 52

0-7709

293

239

— V.

Dec. 27 18

l62 22

34<> 53

17 7

I-II45

294

240

1865 i.

Jan. 14 7

I4I 15

253 3

87 32

0-0260

274. Suddenly became visible towards the end of June. On the 22nd it had a
tail 15° long. Liais has assigned a period of 1089 years.

375. Very faint, and only 4 observations obtained. Elements therefore very
uncertain.

276. Visible to the naked eye ; it had a faint diffused tail 3° long : an elliptic
orbit ; period assigned 415*4 years.

277. One of the most magnificent comets on record : on July 2 its tail was more
than 100° long. An elliptic orbit ; period assigned, 419 years.

279. An apparition of Encke's comet.

280. Discovered by Schmidt and Tempel on July 2 ; on July 4 it had a tail |°
long, and was then visible to the naked eye : between July 3rd and 4th it traversed
24° of a great circle.

281. Discovered by H. P. Tuttle and Simmons, July 18 ; by Pacinotti, July 22 ;
and by Rosa, July 25. Conspicuously visible to the naked eye for 2 or 3 weeks in

CHAP. VII.]

Catalogue. — No. I.

537

Calculator.

Date of
Discovery.

Discoverer.

Duration
of Visibility.

I'O

Seeling

1860, April 17

C. Riimker

7 weeks.

I'O

Moesta

— June 19

Several observers

8 weeks.

I'O

Kowalczyk

— Oct. 23

Tempel

3 days.

0-98345

Oppolzer

1861, April 4

Thatcher

8 weeks.

0-98532

Seeling

— May 13

Tebbutt

12 months.

I'D

—

Pape

— Dec. 28

H. P. Tuttle

8 weeks.

0-84670

Powalky

— Sept. 28

Forster

22 weeks.

I'O

Seeling

1862, July I

Valz

4 weeks.

0-96l27

Oppolzer

— July 15

Swift

13 weeks.

I'O

Engelman n

— Nov. 30

Bruhns

3 weeks.

I'O

Engelmann

— Nov. 27

Respighi

15 weeks.

I'O

Raschkoff

1863, April ii

Klinkerfues

6 months.

I'O

Frischauf

— April 1 2

Respighi

5 weeks.

I'O

Oppolzer

— Nov. 4

Tempel

1 6 weeks.

0-94590

Weiss

— Dec. 28

Respighi

8 weeks.

I'O

Engelmann

— Oct.. 9

Backer

7 months.

I'O

Celoria

1864, Sept. 9

Donati

4 weeks.

—

Kowalczyk

— July 4

Tempel

ii weeks.

I'O

Engelmann

— July 23

Donati

6 months.

I'O

Tietjen

— Dec. 15

Backer

7 weeks.

I'O

Engelmann

— Dec. 30

Bruhns

4 weeks.

I'O

—

Tebbutt

1865, Jan. 18

Moesta

10 weeks.

August — September; with a tail, on Aug. 27, as much as 25° long, according to
Schmidt. An elliptic orbit; period assigned, 123 jears.

283. Discovered by Bruhns, Nov. 30.

284. Visible to the naked eye in May: it had a faint tail 3° long.

285. Visible to the naked eye as a 5th mag. star.

286. Discovered independently by J. F. Schmidt, Nov. 12. Visible to the naked eye
as a star of the 4tn mag., with a tail 2° or more long.

287. Discovered also by Backer, Jan. I, 1864. Visible to the naked eye, with a
tail 2° long, at the end of January. Believed to be a return of the comet of 1810,
and possibly identical with that of 1490.

288. Discovered by Tempel, Oct. 14. Two computers make the orbit a hyperbola.
290. The same computer subsequently obtained an elliptic orbit with a period of

4754 years-

294.. Seen only in the southern hemisphere. On Jan. 18 it had a tail 25° long.

538

Comets.

[BOOK IV.

No.

Year.

PP.

295

(I°5)

1865 ii.

d. h.
May 27 22

O 1

158 4

o /
324 33

o /
!3 4

0-3410

296

241

1866 i.

Jan. ii 3

60 28

231 26

17 18

0-9765

2$6a

(171)

— ii.

Feb. 13 23

49 56

209 42

II 22

1-6822

297

242

1867 i.

Jan. 19 20 ! 75 52

78 35

18 12

I-5725

298

243

— ii.

May 23 22

236 9

101 10

6 24

I-5635

299

244

— iii.

Nov. 6 23

276 21

64 58

83 26

0-3304

300

(177)

1868 i.

April 20 23

116 2

101 14

29 22

0-5968

301

245

— ii.

June 25 23

287 7

53 4°

48 II

0-5823

302

(I°5)

— iii.

Sept. 14 1 6

158 10

334 3i

13 6

0-3339

3°3

(HO

1869 i.

June 10 23

275 55

"3 33

10 48

0.7815

304

246

— ii.

Oct. 9 1 8

123 24

311 29

68 23

1-2306

305

247

— iii.

Nov. 18 17

42 53

296 47

5 23

1-0630

306

248

] 870 i.

July 14 i

3°3 32

141 44

58 12

1-0087

307

249

— ii.

Sept. 2 12

i? 49

12 56

80 34

1-8171

308

C95)

— iii.

Sept. 22 16

318 41

146 25

15 39

1-2803

309

250

— iv.

Dec. 19 21

4 8

94 44

32 43

0-3892

310

251

1871 i.

June 10 14

141 49

279 18

87 36

o6543

252

— ii.

July 27 o

"5 43

211 56

78 o

1-0835

312

(III)

— iii.

Nov. 30 ii

116 5

269 17

54 17

1-0301

313

253

— iv.

Dec. 20 8

264 30

147 2

81 36

0-6944

3i4

(I°5)

Dec. 28 18

158 12

334 34

'3 8

0-3329

315

(243)

1873 i.

May 9 15

237 58

78 43

9 46

1-7720

316

254

— ii.

June 25 8

306 4

120 54

12 44

I-3436

317

(170

— iii.

July 18 ii

5° 5

209 41

II 22

1-6827

295. An apparition of Encke's comet. Perhaps seen as early as Jan. 25 by
D'Arrest.

296. An elliptic orbit ; period assigned, 33 years. Probably a meteor comet.
296 a. An apparition of Payees comet.

297. An elliptic orbit ; period assigned, 33-62 years.

298. Usually known as TempeVis I»t Periodical comet.

299. Discovered 4 hours later by Winnecke.

300. An apparition of Srorseiis comet. Tempel believes he sighted the comet as
early as March 22.

302. An apparition of Encke'x comet.

303. An apparition of Winnecke' 'g comet, (1819, iii).

305. A comet now known as TempeVs Illrd Periodical comet, or SivifCs comet.

CHAP. VII.]

Catalogue. — No. I.

539

Calculator.

Date of
Discovery.

Discoverer.

Duration
of Visibility.

0-84630

Von Asten

1 865, Feb. 13

Bruhns

5 months.

0.90541

Oppolzer

— Dec. 19

Tempel

7 weeks.

0-55754

Moller

Aug. 22

Thiele

20 weeks.

0-84905

Searle

1867, Jan. 28

Tempel

10 weeks.

0-50967

Sandberg

- April 3

Tempel

19 weeks.

I-O

Oppolzer

- Sept. 27

Backer

5 weeks.

0-80809

Brulms

1 868, April 1 1

Tempel

9 weeks.

I-O

—

W. E. Plummer

— June 13

Winnecke

5 weeks.

0-84916

Von Asten

- July 14

Winnecke

6 weeks.

0.75194

Oppolzer

1869, April 9

Winnecke

6 mouths.

I-O

Oppenheim-

- Oct. 1 1

Tempel

4 weeks.

0.65821

Zelbr

— Nov. 27

Tempel

5 weeks.

1-0

—

Dreyer

1870, May 29

Winnecke

6 weeks.

I-O

Hind

— Aug. 28

Coggia

17 weeks.

0-63490

Leveau

- Aug. 31

Winnecke

16 weeks.

I-O

Schulhof

— Nov. 23

Winnecke

i week.

0.99781

Holetschek.

1871, April 7

Winnecke

6 weeks.

I-O

Schulhof

— June 14

Tempel

13 weeks.

0-82105

Tischler

- Oct. 12

Borrelly

15 weeks.

I-O

Schulhof

— Nov. 3

Tempel

15 weeks.

0-84936

Glasenapp

— Sept. 19

Winnecke

1 1 weeks.

0-46308

. +

Gautier

1 873, April 3

Stephan

1 6 weeks.

0-54978

Schulhof

— July 3

Tempel

15 weeks.

0-55738

Moller

- Sept. 3

Stephan

16 weeks.

306. It had a very short tail.

308. An apparition of D' Arrest's comet.

310. Discovered by Borrelly on Apr. 13, and L. Swift on Apr. 15. It had a small
tail. An elliptic orbit; period assigned, 5188 years.

311. Thought to be a return of the comet of 1827 (i).

312. An apparition of Tuttle's comet, (1858, i).

314. An apparition of Encke"s comet. Guessed at, rather than certainly viewed on
Sept. 19. First fairly seen by Dune"r on Oct. 4, and by Hind on Oct. 8.

315. An apparition of Tempel' '« 1st Periodical comet.

316 An elliptic orbit ; period assigned, 5-158 years. Now known as TempeVs Ilnd
Periodical comet.

317. An apparition of Faye's comet.

540

Comets.

[BOOK IV.

No.

Year.

PP.

£3

3i8

255

1873 iv.

d. h.
Sept. 10 1 8

0 /

36 57

o /

230 38

o /

84 3

0-7948

319

256

Oct. i 1 8

302 58

i?6 43

58 30

0.3848

320

(177)

— vi.

Oct. IO 12

116 5

101 15

29 23

0-5935

321

(137?)

— vii.

Dec. 3 3

85 3°

248 37

26 29

0-7754

322

257

1874 i.

March 9 22

299 48

30 18

58 53

0-0445

323

258

— ii.

March 14 o

3°2 J5

274 7

3i 32

0-8861

259

— iii.

July 8 20

271 7

118 44

66 21

0-6757

325

260

— iv.

July 17 17

5 27

215 5i

34 8

1-6883

326

261

Aug. 26 21

344 8

251 29

4i 5°

0-9826

327

262

— vi.

Oct. 18 22

265 41

281 58

80 47

0-5083

328

(HO

1875 i-

March 12 2

276 38

in 29

ii 17

0-8289

329

(105)

— ii.

April 13 o

158 17

334 37

13 7

o-3329

330

263

1877 i.

Jan. 19 4

200 4

187 20

27 o

0-8074

33i

264

— ii.

April 17 15

253 29

3i6 37

58 51

0-9498

332

265

— iii.

April 26 19

102 52

346 4

77 9

1-0092

333

(195)

— iv.

May 10 8

3i9 9

146 9

15 43

1-3181

334

266

June 27 22

83 20

184 17

64 54

1-0231

335

267

— vi.

Sept. ii 10

107 37

250 58

77 42

1-5766

336

268

1878 i.

July 20 1 6

279 5«

102 15

78 10

1-3920

337

(105)

— ii.

July 26 3

158 20

334 39

13 7

0-3335

338

(254)

— iii.

Sept. 7 6

306 7

120 59

12 45

1-3393

339

(i77)

1879 i-

March 30 8

116 44

102 16

28 59

0-5855

34°

269

— ii.

April 28 i

42 44

44 57

72 45

0-8720

341

(243)

— iii.

May 6 23

238 ii

78 45

9 46

1-7694

342

270

— iv.

Aug. 24 6

308 12

32 22

72 15

0-9913

320. An apparition of Brorsens comet.

321. Discovered by Winnecke on Nov. ii. Probably identical with the comet of
1818 (i) ; but doubtful whether period is 55-8, 18-6, or 6-2 years ; Prof. Weiss thinks
the last-named the most probable.

324. An elliptic orbit; period assigned, 5711 years.
326. An elliptic orbit ; period assigned, 306 years.

328. An apparition of Winnecke'g comet, (1819, iii).

329. An apparition of Encke's comet. Discovered by Stephan, Jan. 27.

330. Discovered by Pechiile at Copenhagen, Feb. 9.

CHAP. VII.]

Catalogue. — No. I-

541

Calculator.

Date of
Discovery.

Discoverer.

Duration
of Visibility.

I-O

W. E. Plummer

1873, Aug. 20

Borrelly

4 weeks.

I-O

W. E. Plummer

— Aug. 23

Henry

1 6 weeks.

0-80890

W. E. Plummer

— Aug. 31

Stephen

8 weeks.

0-77032

Weiss

— Nov. 10

Coggia

I week.

1-0

Witts tein

1874, Feb. 20

Winnecke

i week.

I-O

Schur

— April 1 1

Winnecke

9 weeks.

0-99788

Seyboth

— April 17

Coggia

6 months.

0-96283

Holetschek

— Aug. 19

Coggia

1 2 weeks.

0-99865

Gruber

July 25

Borrelly

12 weeks.

I-O

Holetschek

- Dec. 7

Borrelly

4 weeks.

0-74101

Oppolzer

1875, Feb. i

Borrelly

i weeks.

0-84942

Von Asten

— Jan. 26

Holden

17 weeks.

I-O

Hartwig

1877, Feb. 8

Borrelly

12 weeks.

0-99770

—

Plath

- April 5

Winnecke

14 weeks.

I-O

Nichol

— April 1 1

Swift

7 weeks.

0-62780

Hind

- July 8

Coggia

8 weeks.

I-O

Schur

— Oct. 2

Tempel

2 weeks.

I-O

W. E. Plummer

- Sept. 13

Coggia

13 weeks.

I-O

Biittner

1878, July 7

Swift

2 weeks.

0-84917

Von Asten

— Aug. 3

Tebbutt

5 weeks.

0-55290

Schulhof

— July 19

Tempel

5 months.

0-81054

Wittstein

1879, Jan. 14

Tempel

17 weeks.

1-0

Abetti

— June 15

Swift

9 weeks.

0-46303

Gautier

- April 24

Tempel

10 weeks.

I-O

—

Hartwig

Aug. 24

Hartwig

4 weeks.

331. Visible to the naked eye for a few days. It had two small tails, one of them
turned towards the Sun. An elliptic orbit ; period assigned, 8393 years.

332. Discovered by Borrelly on April 14, and by Block on April 16. An elliptic
orbit, with a period of 28,000 (!) years has been assigned by Holetschek.

333. An apparition of D'ArresCs comet.

336. Elements uncertain ; comet observed only on 4 days.

337. An apparition of Encke's comet.

338. An apparition of TsmpeVs Ilnd Periodical comet.

339. An apparition of Brorsen's comet.

341. An apparition of Tempel 's 1st Periodical comet.

542

Comets.

[BOOK IV.

No:

Xo.

Year.

PP.

•a

343

271

1879 V.

d. h.
Oct. 4 1 6

0 /

2O2 27

0 /

87 7

0 >

77 6

0-9906

344

272

1880 i.

Jan. 27 10

278 23

356 i?

36 52

0-0059

345

273

— ii.

July i o

I 12 28

257 9

56 54

1-8186

346

274

— iii.

Sept. 6 21

82 23

45 12

38 6

0-3542

347

(247)

Nov. 7 14

43 o

296 41

5 3i

1-0692

348

275

— vi.

Nov. 8 19

184 2

257 35

5° 48

0-3866

349

276

— vii.

Nov. 9 10

261 5

249 22

60 42

0-6599

35°

070

1881 i.

Jan. 22 1 6

5° 50

209 36

1 1 20

I-7383

35i

277

— ii.

May 20 10

300 n

126 24

77 58

0-591 1

352

278

— iii.

June 1 6 10

265 13

270 57

63 25

0-7344

353

279

— iv.

Aug. 22 7

334 55

97 2

39 46

0-6335

354

280

Sept. 13 10

18 36

65 £2

6 50

0-7259

355

281

— vi.

Sept. 14 8

267 51

274 9

67 ii

0-4492

356

(•05)

— vii.

Nov. 15 i

158 3°

334 34

12 53

0-3430

357

282

— viii.

Nov. 19 17

63 27

181 19

35 i°

1-9261

358

283

1882 i.

June 10 13

53 55

2°4 55

73 48

0-0607

359

284

— iii.

Sept. 17 3

276 16

346 1 8

37 56

0-0082

360

285

— iv.

Sept. 24 2

232 21

354 5°

29 4i

0-0184

361

286

Nov. 1 3 o

354 48

249 7-

83 5i

0-9554

362

287

1883 i.

Feb. 18 22

29 o

278 7

78 4

o-7599

344. Seen only in the Southern Hemisphere. It was visible to the naked eye with
a not very bright tail 40° long. The elements closely resemble those of the great
comet of 1843.

346. Visible to the naked eye as a 5th mag. star with a tail 2° long. Perhaps
identical with the comets of 1382, 1444, 1506, and 1569, or some of them, in which
case Winnecke suggested a period of 62^ years, but the period of the orbit here given
is 1280 years.

347. An apparition of the comet of 1869 (iii) nowknownas Tempers IITrd Periodical
comet, or Swift's comet. Period, 6-00 years.

348. Observations, and therefore orbit, very uncertain. The whole thing probably
a fraud by one Cooper.

349. Visible to the naked eye on Dec. 18 with a tail -J° long. It had indeed 2
tails, one of which was seen by C. A. Young to be directed towards the sun.

350. An apparition of Fayes comet.

352. Visible to the naked eye in June with a tail 10° long. An elliptic orbit;
period assigned, 2954 years.

CHAP. VII.]

Catalogue. — No. I-

543

Calculator.

Date of
Discovery.

Discoverer.

Duration
of Visibility.

I-O

Zelbr

1879, Aug. 21

Falisa

9 weeks.

0-99947

W. Meyer

1 880, Feb. i

Many observers

3 weeks.

I-O

Schaberle

— April 6

Schaberle

5 months.

0-99701

[Bossert
Schulhof and

— Sept. 29

Hartwig

9 weeks.

0-67594

Upton

— Oct. 10

Swift

14 weeks.

I-O

—

Oppenheim

— Dec. 21

Cooper

4 days.

I-O

Oppenheim

— Dec. 1 6

Fechiile

15 weeks.

0-54902

Holler

— Aug. 2

Common

8 months.

1-0

Gruss

1 88 r, April 30

Swift

2 weeks.

0.99643

Dune"r

— May 22

Tebbutt

9 months.

I-O

—

Stechert

- July 13

Schaberle

14 weeks.

0-83041

W. E. Plummer

— Oct. 4

Denning

6 weeks.

I-O

- .

Millosevich

— Sept. 19

Barnard

6 weeks.

0-84550

Backlund

- Aug. 20

Hartwig

1 2 weeks.

I-O

Oppenheim

- Nov. 1 6

Swift

8 weeks.

I-O

Kreutz

1882, Mar. 17

Wells

5 months.

Q-99993

Tatlock

- Sept. 3

Many observers

9 months.

I-O

Hind

- Oct. 9

Schmidt

3 days.

I-O

—

Wolyncewicz

- Sept. 13

Barnard

12 weeks.

I-O

Chandler and
Wendell

1883, Feb. 23

Brooks

7 weeks.

353. Visible to the naked eye for 2 or 3 weeks in August with a tail which on
Aug. 21 was 10° long.

354. An elliptic orbit; period assigned, 8-86 years. Thought by Winnecke to be
a return of the comet of 1855 (ii).

356. An apparition of Encke's comet. Seen with the naked eye by Denning on
Oct. 29.

357. Elements resemble those of comet i. 1792.

358. Visible with a telescope on June 10 within 3° of the Sun. A period of about
400,000 years has been assigned by F. J. Parson (A. N., vol. cvii., 2550, Oct. 31, 1883).

359. 360. For important details connected with these comets see Bk. IV. ch. iii.
(ante). No. 359 is possibly a return of the comets of 370 B.C., and 1131 or 1132 A.n.,
but the period of the orbit here given is 1376 years. It is noteworthy that the comet
of 370 B.C. is said to have separated into 2 parts as No. 359 did. This comet was
last seen with the naked eye by Thome at Cordoba on March 7, 1883. Ravene found
the period to be 718 years.

362. Discovered a few hours later by Swift. It had a faint narrow tail about ^°
long.

544

Comets.

[BOOK IV

No.

Year.

PP.

•a

363

288

1883 ii.

d. h.
Dec. 25 7

o /

125 46

0 /

264 25

0 /

65 I

0-3097

364

(132)

1884 i.

Jan. 25 20

93 20

254 6

74 3

0-7751

365

289

— ii.

Aug. 16 ii

306 10

5 1°

5 27

'•2793

366

290

— iii.

Nov. 17 16

18 56

2O6 21

25 16

I-5736

367

(105)

1885 i.

Mar. 5 21

158 33

3 34

12 54

o-333o

368

291

— ii.

Aug. 5 16

270 47

92 17

80 37

2.5068

369

292

— iii.

Aug. 10 6

247 41

204 40

59 II

0-7508

37°

(III)

— iv.

Sept. 1 1 5

116 28

269 42

54 19

1-0260

371

293

Nov. 25 12

297 44

262 ii

42 26

i -0790

373

294

1886 i.

April 5 23

162 58

36 22

82 37

0-6423

373

295

— ii.

May 3 6

188 58

68 19

84 23

0-4790

374

296

— iii.

May 4 u

326 19

287 45

79 48

0-8419

375

297

— iv.

June 6 13

229 45

53 3

12 56

1-3370

376

298

June 7 9

33 55

192 42

87 44

0-2703

377

(HO

— vi.

Sept. 1 6 ii

276 4

101 56

14 27

0-8832

378

299

— vii.

Nov. 22 9

7 34

52 29

3 i

i-i7

379

300

— viii.

Nov. 28 9

290 4

258 ii

85 35

1-4800

380

3°I

— ix.

Dec. 16 12

223 43

137 21

78 20

0-6628

38i

302

1887 i.

Jan. ii 6

274 6

337 42

43 o

0-0054

382

3°3

— ii.

March 1 6 23

1 20 40

279 49

75 42

I-6333

383

304

— iii.

March 28 9

171 55

135 27

40 ii

i -0068

384

3°5

— iv.

June 16 16

260 19

245 12

i? 35

J-3949

385

(135)

Oct. 8 10

149 45

84 29

44 33

1-1996

386

306

1888 i.

March 17 o

245 i?

245 22

42 15

0-6987

387

(I05)

— ii.

June 28 o

158 36

334 39

12 53

0-3330

364. A return of Pons's comet of 1812.

365. An elliptic orbit ; period assigned, 5-36 years.

366. An elliptic orbit ; period assigned, 6-764 years.

367. A return of Endce's comet.

368. Perihelion distance greater than that of any other comet save 1729.
370. A return of Tattle's comet (1858, i).

372. At the end of April it reached mag. 2^, and had a tail 4° long.

373. It had a tail 3° long. Elements resemble those of the comet of 1785 (ii).
375. An elliptic orbit; period assigned, 6-30 years.

CHAP. VII.]

Catalogue. — No. I.

545

>>•

Calculator.

Date of
Discovery.

Discoverer.

Duration
of Visibility.

I-O

Oppenheim

1 884, Jan. 7

Ross

5 weeks.

0-95499

Schulhof and

1883, Sept. 2

Brooks

9 months.

Bossert

0-58247

Berberich

1 884, July 1 6

Barnard

17 weeks.

0-55988

Zelbr

— Sept. 17

Wolf

7 months.

0-84575

Backlund

— Dec. 13

Tempel

7 weeks.

I-O

Berberich

1885, July 7

Barnard

8 weeks.

0-98801

•f

Campbell

— Aug. 31

Brooks

5 weeks.

0-82154

Eahts

— Aug. 8

Perrotin

5 weeks.

I-O

Miiller

— Dec. 26

Brooks

9 weeks.

I-O

Svedstrup

— Dec. i

Fabry

8 months.

1-0

Hepperger

— Dec. 3

Barnard

8 months.

1-0

Celoria

1886, May I

Brooks (2)

5 weeks.

0-60810

Hind

— May 22

Brooks (3)

6 weeks.

I-O

Kruger

— April 27

Brooks (i)

13 weeks.

0-72677

Palisa

— Aug. 9

Finlay

14 weeks.

0-71819

Kruger

— Sept. 26

Finlay

6 months.

I-O

Egbert

1887, Jan. 23

Barnard

16 weeks.

1-0

Svedstrup

1886, Oct. 4

Barnard

14 weeks.

I-O

Chandler

1887, Jan. 18

Thome

i week.

I-O

Boss

— Jan. 2 2

Brooks

13 weeks.

I-O

Barnard

- Feb. 15

Barnard.

2 weeks.

I-O

Chandler

— May 12

Barnard.

3 months.

0-93108

Ginzel

— Aug. 24

Brooks.

2 months.

0-99493

Boss

1888, Feb. 1 8

Sawerthal

6 months.

0-84542

Backlund

— July 8

Tebbutt.

4 weeks.

377. A return of Winneckes comet. (Theoretical elements.)

378. An elliptic orbit ; period assigned, 6-67 years.

380. Visible to the naked eye as a star of mag. 2, with a tail 5° long, besides 2
secondary tails.

382. Probably an elliptic comet of long period.

385. A return of Gibers' s comet of 1815.

386. It had a tail which on April n was 5° long. An elliptic orbit: period
assigned 1615 years.

387. An apparition of Enc'ke's comet.

N n

546

Comets.

[Book IV

No.

Year.

PP.

i •

388
389
39°

307
(171)

308

1888 iii.
— iv.

d. h.
July 31 4
Aug. 19 12
Sept. 13 o

o /
1 60 40

50 56

68 35

o /
101 26
209 42
137 34

o /

74 ii

II 20

56 24

0-9025
1.7381
J-I532

391
392

309
310

1889 i.
— ii.

Jan. 31 6
June 13 8

1 6 56

73 3i

357 24
3io 35

1.1 38

16 12

1-8151
2-2493

ADDI'

riONAL

COMETS

37«
37J

26a
266

1457 i-
H57 »•

Jan. 17 23
Aug. 8 o

84 34
9 32

349 39

184 24

13 16

9 52

0-7035
0-7606

389. An apparition of Faye's comet.

CHAP. VII.]

Catalogue. — No. I.

Calculator.

Date ef
Discovery.

Discoverer.

Duration
of Visibility.

1-0

Wilson

1 888, Aug. 7

Brooks

ii weeks.

O-54QO2

— Aug. o

Perrotin

4 months.

1-0

Halm

— Oct. 30

Barnard

4 months or +

1-0

—

Berberich

— Sept. 2

Barnard

many months.

1-0

Kriiger

— Mar. 31

Barnard

4 weeks.

RECENT]

^Y C

ALCULATED.

1-0

Celoria

1457

Chinese obs.

I-O

Celoria

J457

Chinese obs.

392. Very faint, say 12th mag. ; with a tail 15' long.

N n 2

548 Comets. [BOOK IV.

A SUMMARY OF THE PRECEDING CATALOGUE*.

TMROM an examination of the Catalogue just given we may
-•- obtain certain results which will here be analysed.

It appears that 394 comet apparitions have been subjected to
mathematical investigation, viz. : —

Known periodical comets ... 23

Subsequent returns 81

Elliptic comets not yet verified, and parabolic comets 284
Hyperbolic comets ... 6

394

Of known periodical comets, we have the following, as the
number of the apparitions of each : —

24 ... of Encke's.

17 ... ofHalley's.

8 ... ofFaye's.

6 ... ... ... ... ... of Biela's.

5 ofBrorsen's.

5 ... ... ... ... ... of Winnecke's.

4 of D' Arrest's.

4 ofTuttle's.

3 ... ... of Tempel's 1st.

2 of Tempel's Ilnd.

a of Tempel's Illrd.

Also 2 of each of the following : —
961: 1097: 1231: 1264: 13621: 1532: 1596: 1678: 1699!: i79oiii: 1810: 1812.

Elliptic orbits have been assigned in the Catalogue to various
comets, of which however no and 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 to warrant their being included in a list of
undoubted elliptic comets.

• This summary does not include comets discovered subsequently toDec. 31, 1888.

CHAP. VII.] Summary of Catalogue, No. I. 549

The following are the known hyperbolic comets : —

1729: 1771: 1774: 1840!: 1843!!: l853iii.

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: iSiSiii: i826ii: 1830!: 1843!; 1844^1: 1845!: 18451!
1849 iii: 185211: 1863 vi: 1886 ii.

The following are some of those comets which have been sup-
posed to be identical : —

1881 v. with 1855 ii.

1880 i. — 1843 i.

1880 iii. — 1569, 1506, 1444, or 1382.

1873 vii. — 1818 i.

1871 ii. — 1827 i.

1863 v. — 1490.

i86oi. — 1845 ii, 1785 i, and 1351.

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. I743i-

1819 iii. — 1766 ii.

1661 — 1532.

550 Comets. [BOOK IV.

CHAPTER VIII.

A CATALOGUE OF COMETS RECORDED, BUT NOT WITH SUFFICIENT
PRECISION TO ENABLE THEIR ORBITS TO BE CALCULATED".

IN the present day it does not often happen that a comet
becomes visible without its being observed sufficiently long
for at any rate some approximation to the elements of its orbit
to be deduced. Such however was not the case in olden times.
Observers were few, and till the I7th century observatories and
instruments can scarcely be said to have existed at all. There-
fore whatever astronomical information we possess antecedent
to A.D. 1600, we owe to the writings of historians and chroni-
clers, who seldom give more than bare statements, with few or
no details.

The first astronomer who made any systematic attempt to put
together the various allusions to comets which occur in the old
writers was Stanislaus Lubienitzki, whose Theatrum Cometicum in
2 folio volumes appeared at Amsterdam in 1668. The 2nJ volume
contains records of 415 comets or supposed comets up to 1665.
Hevelius gives a history of comets in the XIIth Book of his
Cometographia. Far more critical is Nicolas Struyck, who in his
Algemeene Geograp/iie, published at Amsterdam in 1740, and in
his Vervolg van de Beschryving cler Staartsterren, published at
Amsterdam in 1753, paved the way for the French astronomer
Pingre, who in 1783 published his celebrated Cometographie ; ou

* I should be glad to receive informa- journals, whether published or in MS.,

tion calculated to render this chapter of modern travellers and others, would

more complete. I cannot but believe bring to light many more comets than

that a diligent search through the these catalogued in this volume.

CHAP. VIII.] Introduction to Catalogue, No. II. 551

Traite historique et Iheoretique des Cometes. This work, which for
the industry and labour bestowed upon it has few equals, has been
from the period of its publication down to the present day the
astronomer's text-book on the subject of cometary history : it
has never been superseded, and is never likely to be, though
supplementary matter has of course been accumulated. E. Biot,
working from Chinese sources, followed up Pingre with great
industry. The following catalogue is based upon that of Pingre,
and includes recent results, especially those elaborated in a
valuable catalogue commenced by Hind in the Companion, to the
Almanac, 1859 and 1860, but remaining unfinished. Brevity
being essential to this work, I have been obliged to omit much
that was curious and interesting, and to confine my attention
chiefly to necessary facts and figures, with references only to the
most important authorities.

The Chinese observations, to which such constant reference is
made, were originally made known in Europe by MM. Couplet,
Gaubil, and De Mailla, Jesuit priests at Pekin, early in the i8th
century, who made very good use of their opportunities of bene-
fiting science. De Mailla's MSS. were published at Paris in the
last century, but those of Gaubil and Couplet remain in their
original form. E. Biot published in the Connaissance des Temps
a translation of some valuable Chinese catalogues of comets b,
which have been duly consulted ; and it is not improbable that
as our intercourse with that remarkable people becomes greater,
further sources of information may be opened to us.

Biot gives 2 supplementary catalogues of " extraordinary stars."
These are distinct in the originals from the comets strictly so
called ; but as there is little doubt that many of these objects
were genuine comets, though not treated as such by the Chinese,
a selection of them is inserted in this catalogue, an asterisk (*)
being appended either to the year or to M. Biot's name. The
remainder will be given in a catalogue of " New Stars," in a
later volume of this work, where will also be found some further
remarks on these objects.

b iS46, pp. 44-84.

552 Comets. [BOOK IV.

The most recent editor of Chinese comet observations is the
late Mr. J. Williams, whose catalogue published in 1871 is by
far the most elaborate work of its sort extant. Great use has
been made of that valuable compilation in the revision of the
pages which now follow.

It may be well to state that very great uncertainty hangs
over the earlier comets, hereinafter referred to, and to some
extent, too, over all. more especially as regards the positions in
which they were seen and the duration of their visibility.

The Chinese constellations are much more numerous than
ours, and where several Greek letters precede a Latin genitive
case, it is to be understood that the Chinese place the comet in
the group formed of those stars without specifying that it was in
juxtaposition with any one star in particular.

The Chinese reckon by moons, and as it rarely happens that
the whole of a lunation is comprised in a single Julian month,
it is requisite in many cases to couple 2 months together : thus,
May — June, which means that the comet appeared in the "moon"
which began on (say) May 18, and therefore ended on June 15.
In cases where the precise day of the lunation is recorded, the
exact Julian day can of course be deduced, and the expedient of
coupling together 2 months is superseded. The years B.C. are
reckoned in astronomical style.

One tchang equals 10° ; one die equals i°.

[i.] B.C. 1770. + St. Augustine has preserved the following extract from Varro : —
" There was seen a wonderful prodigy in the heavens with regard to the brilliant
star Venus, which Plautus and Homer, each in his own language, call the
' Evening Star.' Castor avers that this fine star changed colour, size, figure,
and path : that it was never seen before, and has never been seen since. Adrastus
of Cyzicus and Dion the Neapolitan refer the appearance of this great prodigy to the
reign of Ogyges." — (De Civitate, xxi. 8.) This description, such as it is, may be that
of a comet, but no further particulars have been preserved.

[2.] 1194. + We are told by Hyginus, a contemporary of Ovid, that "on the fall
of Troy, Electra, one of the Pleiads, quitted the company of her 6 sisters, and passed
along the heavens toward the Arctic Pole, where she remained visible in tears and
with dishevelled hair, to which the name of ' comet ' is applied." — (Freret, Acad. des
Inscriptions, x. 357-) What we are to understand by this is doubtful, but the
account might relate to a comet which passed from Taurus to the North Pole.

[3.] 1140. + At the time that Nebuchadnezzar overran Elam "a comet arose whose
body was bright like the day, while from its luminous body a tail extended, like the
sting of a scorpion." — (A. H. Sayce, Babylonian Inscriptions.}

CHAP. VIII.] Catalogue. — No. II. 553

[4.] 975. + "The Egyptians and the ^Ethiopians felt the dire effects of this comet,
to which Typhon, who reigned then, gave his name. It appeared all on fire, and was
twisted in the form of a wreath, and had a hideous aspect ; it was not so much a star
as a knot of fire." — (Pliny, Hist. Nat., ii. 25.) Date very uncertain.

[5.] 619 or 618. " We shall see in the W. a star such as is called a comet ; it will
announce to men war, famine, and the death of several distinguished leaders." —
(Sybill. Orac. iii.) Though given as a prophecy, Pingre" says he feels justified in
citing this passage as a historical record. He thinks moreover that the prophet
Jeremiah may refer to a comet, and it might be this comet, in Jer. i.

[6.] 611. In July a comet appeared among the 7 stars of Ursa Major. — (Confucius,
Tchun-tsieou, quoted by Ma-tuoan-lin.)

[7.] 532 or 531. At the winter solstice a comet appeared in the Western part of
Aquarius, or the tail of Capricornus. — (Gaubil.) Ma-tuoan-lin gives, from Confucius,
531 as the date, and the position a, a, r Scorpii. Pingre regards the description as
applying to one and the same comet.

[8.] 524-23. In the winter a comet passed from Scorpio to the Milky Way. —
(Gaubil ; De Mailla, Histoire Generale de la Chine, ii. 193.)

[9.] 515. In July a comet was seen near H Herculis. (Williams, i.) Monck
suggests that this should read rj Herculis.

[10.] 501. In December a comet was seen in the East. (Williams, i.)

[n.] 481. A comet appeared at the end of the year in the E. part of the
heavens. Its length was 2°, and it reached from the star Yng (?) to o Scorpii. —
(Gaubil; Ma-tuoan-lin; De Mailla, ii. 222.)

[12.] 479. At the time of the battle of Salamis a comet in the shape of a horn
was visible. — (Pliny, Hist. Nat., ii. 25.)

[13.] 465. + During a period of 75 days an extraordinary object appeared in the
sky, according to the testimony of several writers. — (Damachus; Pliny, Hist. Nat.,
ii. 58.) A comet may be referred to, but an Aurora Borealis would seem best to
reconcile the various European statements. Ma-tuoan-lin speaks of a comet in 466,
which Pingre" considers identical with the " extraordinary object " of the European
writers visible in January or February 465.

[14.] 432. It is certain that a comet appeared in this year. — (Couplet; De
Mailla, ii. 244; Ma-tuoan-lin.)

[15.] 426 or 402. At the time of the winter solstice, during the archonship of
Euclides, at Athens, a comet appeared near the North Pole. — (Aristot., Meteor., i. 6.)
There were 2 archons of this name, it is therefore impossible to fix the year of this
comet's apparition.

[16.] 360. A comet was seen in China and Japan in the W. — (Couplet; De
Mailla, ii. 267 ; Kaempfer, Histoire du Japan, ii. La Haie, 1729.)

[17.] 345 (?). A comet in the form of a mane was seen, which was afterwards
changed into that of a spear. — (Pliny, Hist. Nat., ii. 25.) Date very uncertain;
Pliny gives the double date of the Olympiad and A. U. C., which do not correspond,
so one or the other nrast be wrong. 345 above is from Pingre".

[18.] 344. " On the departure of the expedition of Tirnoleon from Corinth for
Sicily the gods announced his success and future greatness by an extraordinary
prodigy. A burning torch appeared in the heavens for an entire night, and went
before the fleet to Sicily." — (Diodorus Siculus, Sibliotheca Historica, xvi. ii ;
Plutarch, Timoleon.") Pingre1 remarks that it is easy to see that the comet
appeared in the W., and had a considerable N. declination.

[19.] 340. A comet was seen for a few days near the equinoctial circle. — (Aris-
totle, Meteor., i. 7.)

[20.] 304. A comet was seen in China. — (Ma-tuoan-lin ; De Mailla, ii. 306.)

[21.] 302. A comet was seen in China. — (Ma-tuoan-lin; De Mailla, ii. 306.)
The Chinese annalist expressly says that there were 2 comets in 2 years.

554 Comets. [BOOK IV.

[22.] 295. A comet was seen in China. — (Ma-tuoan-lin.)

[23.] 239. A comet was seen in China. It came from the E., and passed by the
N., and in the 5th moon (May) it was seen during 16 days in the W. — (Ma-tuoan-
lin ; Williams, 2.)

[24.] 237. In the pth year of Chi-hoang-ti a star appeared in the horizon. In
April it was seen in the W. ; it appeared then in the N., to the S. of the 7 stars of
Ursa Major, for 80 days. — (Ma-tuoan-lin ; Williams, 2.)

[25.] 233. In China a cornet was seen in January in the E. — (Ma-tuoan-lin.)
[26.] 232. Four comets were seen during 80 days. — (Williams, 3.)

[27.] 213. A brilliant star was seen in China to come from the W. — (Ma-tuoan-
lin ; De Mailla. ii. 399.) Probably a comet.

[28.] 203. A torch extended from E. to W. for 10 days in Aug. — Sept. It
appeared near Arcturus. — (Julius Obsequens, Prodigiorum Liber, 8vo. Amstelo-
dami, 1679, Supplement by Lycosthenes; Ma-tuoan-lin.)

[29.] 202. A burning torch was seen in the heavens.— (Julius Obsequens, Prodig. ^
Suppl.)

[30.] 171. A large comet with a tail was seen in China at the end of the sum-
mer.— (Couplet ; De Mailla, ii. 554.)

[31.] 168. A torch was seen in the heavens. — (Julius Obsequens, Prodig., Suppl.;
Livius, Historia, xliii. 13.)

[32.] 166. A burning torch was seen in the heavens. — (Julius Obsequens, Prodig.,
Suppl.)

[33.] 165. A torch was seen in the heavens. — (Julius Obsequens, Prodig., Suppl.)
We are further told that at one place the Sun was seen for several hours in the
night, so that if this object was a comet it must have been an extremely brilliant
one.

[34.] 156. In October (end of) a comet 10° long appeared in the W. It was
visible for 16 days, and traversed Aquarius and Equuleus to the neck of Pegasus. —
(Ma-tuoan-lin ; De Mailla, ii. 568.)

[35.] 154 (i). A comet came from the S. W. in January. — (Ma-tuoan-lin ; De
Mailla, ii. 569.)

[36.] 154 (ii). In July a comet appeared in the N. E. — (De Mailla, ii. 569 ;
Williams, 4.)

[37.] 153. In February a tailed star appeared in the W. — De Mailla, ii. 571 ;
Williams, 4.)

[38.] 147. A comet appeared in May in the N. W., and lasted 2 or 3 weeks. It
had the same R. A. as Orion. — (Ma-tuoan-lin ; De Mailla, ii. 588.)

[39.] 146 (i). On March 14 a comet 10 cubits long was seen at night in the N. W.,
probably in Orion. As it passed on it increased but little in size. After 1 5 days it
was no more seen. — (Williams, 4.)

[40.] 146 (ii). "After the death of Demetrius king of Syria, the father of Deme-
trius and Antiochus, a little before the war in Achaia, there appeared a comet as
large as the Sun. Its disc was at first red, and like fire, spreading sufficient light to
dissipate the darkness of night ; after a little while its size diminished, its brilliancy
became weakened, and at length it entirely disappeared." — (Seneca, Qucest. Nat.,
vii. 15.) It lasted 32 days. — (Julius Obsequens, Prodiyiorum Liber.) Probably
thi? account relates to the comet seen this year in China, August 6-} 6, and
which passed from the divisions Scorpio and Sagittarius to near £ Ophiuchi. The
size of the Chinese comet steadily decreased day by day. — (Williams, 4.)

[41.] 146 (iii). In October a comet was seen in the N. W. — (Williams, 5.)

[42.] 137 (i). " In the reign of Attalus a comet was seen which, small at first.
afterwards became much larger. It reached the equinoctial circle, and equalled in
length that part of the heavens which is called the Milky Way."— (Seneca, Q»(fst.

CHAP. VIII.] Catalogue. — No. II. 555

Nat., vii. 15.) It appeared in March — April, in the lower part of Hydra, and
passed through Leo — Virgo into the circmnpolar regions, arriving at length at the
Milky Way. — (Ma-tuoan-lin.)

[43.] 137 (ii). A comet appeared 2 months after the preceding; it passed from 0,
€ Herculis to a, «, C Lyrse.— (Ma-tuoan-lin.)

137 (iii). In August a comet was seen in the N. E. — (Williams, 5 ; Ma-tuoan-lin ;
De Mailla, iii. 9.)

The preceding 3 comets may in reality have been but one and the same ; one of
them, or else the comet of 134 (post}, is the comet which appears in the other
catalogue under the date of 136. {Therefore a number is dropped here.}

[44.] 136 (ii). In October a comet was seen in the N. E. — (Williams, 5.)

[45.] 134. At the birth of Mithridates a comet appeared and lasted 70 days ; the
heavens appeared all on fire ; the comet occupied the fourth part of the sky, and its
brilliancy was superior to that of the Sun ; it took 4 hours to rise and 4 to set. —
(Justinus, De Historicis Philippicis, xxxvii. 2.) There is very great uncertainty
about this comet of Mithridates, but Pingre', after weighing Ma-tuoan-lin's account,
considered that 134 was certainly the year. He also says that probably it appeared
in the W. in the middle of July ; before the end of August it would have been lost
for a few days in the Sun's rays, when probably the Perihelion Passage took place ;
it would then have re-appeared with increased brilliancy early in September in the
E. (for 30 days?), and so have passed away from the Sun. — (Cornet, i. 270, 578.)
Ma-tuoan-lin (Williams, 6) would have us consider the comet of September 1 34 to
be different from the comet of July 134, but this does not at all follow.

[46.] 127. A burning torch appeared in the heavens. — (Julius Obsequens, Prodig.
Suppl.)

[47.] 119. In the spring in China a comet was seen in the E. — (De Mailla, iii.
46.)

[48.] 118. When Mithridates ascended the throne there appeared during 70 days
a comet exactly resembling that which was seen at the birth of that monarch. —
(Justinus, De Historicis Philippicis, xxxvii. 2.) It came from the N. W. in May. —
(Ma-tuoan-lin; Williams, 6.)

[49.] 109 (i). In June a comet was seen in the feet of Gemini. — (Ma-tuoau-lin ;
De Mailla, iii. 61.)

[50.] 109 (ii). This comet appeared contemporaneously with the preceding : it was
in Ursa Major, near K, \, £. — (Ma-tuoan-lin ; De Mailla, iii. 61.)

[51.] 108. A comet appeared in the region lying between Procyon (a Canis
Minoris) and a and /3 Geminorum. — (Ma-tuoan-lin.) Or in the year 107 ; place
uncertain. — (Williams, 6.)

[52.] 102. + A comet was seen in China near 7 Bootis. — (Ma-tuoan-lin.)
[53.] 03. A torch appeared in the heavens. — (Julius Obsequens, Prodig.)
[54.] 91. A torch appeared in the heavens. — (Julius Obsequens, Prodig.)

[55.] 86. In August a comet was seen in the E. — (De Mailla, iii. 98 ; Williams,
7 ; Pliny, Hist. Nat., ii. 25.) Pliny's is merely an incidental notice. He says that
comets foretell bloodshed, and gives as an instance the one which appeared during
the consulate of Octavius.

[56.] 83. In March a comet was seen in the N. W. — (De Mailla, iii. 101 ;
Williams, 7.)

[57.] 75. "In the consulate of Cn. Octavius and C. Scribonius a spark was seen
to fall from a star; it grew larger as it approached the Earth, and became equal in
size to the Moon, and gave as much light as the Sun gives during the day-time when
the sky is entirely covered. On returning into the heavens it took the form of a
lampas [torch, one of Pliny's names for a class of comets]." — (Pliny, Hist. Nat., ii.
35.) The above is a rather obscure explanation, but in Pingre's estimation a comet
fairly meets it. In May a bright star was seen in the sidereal divisions of 0 Andro-
medae and 0 Arietis. — (Williams. 7.)

556 Comets. [BOOK IV.

[58.] 72. On May 10, early in the evening, a tailed star appeared to the W. of
the sidereal division of a, /3, &c. Orionis. — (Williams, 7.)

[59.] 71. On August 20 a comet appeared in the sidereal division of a Crateris. —
(Williams, 8.)

[60.] 69. On August 4 a comet appeared in the sidereal division of a Crateris ; it
passed near the Moon. — (Williams, 8.) Can this and the previous comet be one and
the same?

[6 1.] 68 (i). In January — February a comet was seen in the W. — (Williams, 8.)

[62.] 62. A burning beam stretched from the western horizon to the zenith. —
(Julius Obsequens, Prodig.} Torches ran from the W. to the middle of the sky. —
(Dion Cassius, Hist. Roman., xxxix.) A comet appeared in the E. in the 6th moon.
— (De Ma ilia, iii. 136.) Dion Cassius's allusion is very doubtful ; and whatever
may really have been the date of the burning beam, it is believed that De Mailla's
comet must be referred to 61, his dates invariably being i year behind. [But see
the next paragraph.]

[63.] 60. In July a comet was seen in the E. — (Williams, 8.) Perhaps this and
De Mailla's comet of 62 or 61 are identical.

[64.] 55. A torch appeared which advanced from the S, to the N. — (Dion Cassius,
Hist. Roman., xxxix.)

[65.] 52. A torch appeared, which passed from the S. to the E. — (Dion Cassius,
Hist. Roman., xl.)

[66.] 48. During the war between Csesar and Pompey " a comet, that terrible star
which upsets the powers of the Earth, shewed its portentous hair." — (Lucanus,
Pharsalia, i. 529.) In April a long comet was seen near £ Cassiopeise ; passing by t
in that constellation, it became lost in the circumpolar regions. — (De Mailla, iii. 155.)
In March an extraordinary star shewed itself about 9° to the N. E. of a, /3, 7, 77
Cassiopeise : it was 10° long, and pointed to the W, It passed by v, £, o, it Cassiopeiee,
and went towards the " blue palace " [circle of perpetual apparition at 34° lat. N.] —
(Biot.*)

[67.] 47.* In April — May an extraordinary star, as large as a scourge, was seen :
it was 4° or so to the E. of /* Sagittarii. — (Biot.)

[68.] 46. In June an extraordinary star was seen in the sidereal division of the
Pleiades, 5° E. of v Persei. Its tail was -&•$ of a cubit long. — (Biot* ; Williams, 9.)

[69.] 43 (i). In May — June a comet was seen in China, whose E. A. was the same
as that of Orion. — (De Mailla, iii. 162.) It was in the N. E., and its tail, which was
8 cubits long, and afterwards longer, pointed to the sidereal division of a, 0 Orionis. —
(Williams, 9.)

[70.] 43 (ii). A hairy star was seen for 7 days under the Great Bear during the
celebration of the games given by the Emperor Augustus in honour of Venus. It
rose at about 5 in the evening, was very brilliant, and was seen in all parts of the
Earth. The common people supposed that the star indicated the admission of the
soul of Julius Csesar into the ranks of the immortal gods. — (Suetonius, Vita Julii
Ccesaris, Ixxxvii.) It was visible therefore from Sept. 23 to Sept. 29. Dion Cassius
says, that, in addition to the comet, which appeared contemporaneously with the
Emperor's games, there was seen a burning torch, which traversed the heavens from
E. to W. ; and also an unknown star, which shone for many days. — (Hist. Roman.
xlv. 17.) Pingre" thinks that the "torch" was simply a meteor, but that the
" unknown star " was the preceding object which was seen in China, and there
recorded as a comet. — Cornet, i. 278.)

[71.] 42 and 44. Previous to the battle of Philippi comets appeared. — (Virgil,
Georgica, i. 488 ; Manilius, Astronomicon, i. 907.) Perhaps a comet in each year.

[72.] 31. A torch appeared for several days. — (Dion Cassius, Hist. Roman., 1.)
In February a comet 60 or 70 cubits (? degrees) long was seen in the sidereal
division of a Pegasi. — (De Mailla, iii. 178 ; Ma-tuoan-lin ; Williams, 9.)

CHAP. VIII.] Catalogue. — No. II. 557

[73.] 29. Before Egypt submitted to Augustus there appeared comets. — (Dion
Cassius, Hist. Roman., li.) Lubienitz says that a comet appeared for 95 days in Libra,
but he gives no authority.

[74.] 4. In March a comet appeared for 70 days in the sidereal division of a, 0, &c.
Capricorni. — De Mailla, iii. 214; Williams, 10.)

[75-] 3 B-c- In April or May a comet appeared near a and /3 Aquilae. — (De
Mailla, iii. 214; Williams, 10.)

[76.] 10 A.D. Several comets visible at the same time. — Dion Cassius, Hist. Roman.,
Ivi. 24.) Some modern cometographers state that a comet appeared in Aries for
32 days. — (Lubienitz.)

[77.] 14. Hairy stars of the colour of blood. — (Dion Cassius, Hist. Roman., Ivi. 29.)
A comet was seen in China for 20 days, either at the end of 13 or the beginning
of 14. — (De Mailla, iii. 140 ; Williams. 10.)

[78.] 19. A comet was seen in China. — (Couplet.)

[79.] 22. In November — December a comet was seen for 5 days. It was in the
sidereal division of «, A. Hydrse, and moved in a S. E. direction. — (De Mailla, iii. 251 ;
Ma-tuoan-lin ; Williams, 1 1 .)

[80.] 39. On March 13 a comet became visible in the Pleiades ; it moved in a
N. W. direction towards a, £ and A, /t Pegasi, and remained in sight for 40 days. —
(De Mailla, iii. 326 ; Ma-tuoan-lin; Williams, n.)

[8 1.] 54. In the autumn (?) a comet appeared for a long time. It was first seen
in the N. ; it moved to the zenith, and thence Eastwards, and day by day diminished
in brilliancy. — Dion Cassius, Hist. Roman., Ix. 35 ; Suetonius, Vita ClaudiiS) It
appeared in the circumpolar regions. — (De Mailla, iii. 345.) Probably De Mailla's
reference is to the next comet.

[82.] 55 (i). On June 4 a comet appeared ; the planet Mercury was about 20° in
the E. part of the sidereal division 7, e, &c. Geminorum. The comet pointed to
the S. E., was bright, and 10 cubits long. It went to the N. E., passing above
the W. boundary of the circle of perpetual apparition. It lasted 31 days. —
(Williams, II.)

[83.] 55 (ii). In November a comet appeared which remained visible for 16 weeks,
or till March 56. When first seen it was 2° long, and was then moving towards
the S. W. It disappeared on March 26, 6° N. E. of 7, S, n, 9 Cancri. — (Gaubil ;
Biot.*)

[84.] 60. On Aug. 9 a comet, with a tail 2 cubits long, appeared to the N. of
r), 7, a, S Persei. It remained visible for 19 weeks or more, and, passing South-
wards, disappeared S. of the feet of Virgo. — (Tacitus, Annales, xiv. 2 2 ; De Mailla, iii.
352; Ma-tuoan-lin; Williams, n.)

[85.] 61. On Sept. 27 a strange star was detected to the N. W. of p, S Bootis, with
a tail pointing towards Corona Borealis. After 1 7 days it quitted this position, but
we are not told whither it went. It was visible for 10 weeks altogether. — (Ma-tuoan-
lin ; Biot*; Seneca, Queest. Nat.,v\\. 28; Williams, 12.) It is uncertain whether
the comet seen in China is the same as that spoken of by Seneca.

[86.] 64 (i). On May 3 an extraordinary star, with a vapour 2° long, was seen to
the S. of 77 Virginis ; it lasted n weeks. — (Gaubil; Biot.*)

[87.] 64. (ii). At the end of the year, in the reign of Nero, a comet appeared for
6 months. It passed from the N. through the W. to the S. — (Seneca, Queest. Nat.,
vii. 21, 29 ; Tac., Ann., xv. 47 ; Suetonius, Vita Neronis.')

[87.] 65. On June 4 a great star was observed in the sidereal divisions of S and v
Hydrse ; it approached near a and 7 Leonis, and passing a, 7, 8 Persei arrived
in the vicinity of /3 Leonis. The vapour extended to t and K Ursae Majoris ; it
remained visible 8 weeks. — (Ma-tuoan-lin; Williams, 12.)

[89.] 69. Sometime between April and December a comet appeared. — (Dion
Cassius, Hist. Roman., Ixv. 8.) Possibly this may be the object referred to by
Josephus as having been seen suspended over Jerusalem before its destruction by
Titus. — (Bella Judceorum, vi. 5.)

558 Comets. [BOOK IV.

[90.] 70. In December 70 or January 71 a strange star appeared in a, 7, t, 17, £
Leonis for 7 weeks. — (Gaubil ; Biot.*)

[91.] 71. On March 6 a comet appeared in the sidereal division of the Pleiades ;
after 8 weeks it was seen near a, 7, &c. Leonis, and disappeared to the right of
the sidereal division of a Virginis. — (Gaubil; Biot*; Williams, 12.)

[92.] 75. On July 14 a comet was discovered in the sidereal division of a Hydrse ;
its tail was 3 cubits long. Moving to the S. of Coma Berenicis it passed to the
vicinity of /3 Leonis. — (De Mailla, iii. 375 ; Williams, 13.)

[93-] 76. On August 9 a comet, with a tail 2 or 3 cubits long, was seen between
a Herculis and a Ophiuchi, whence it passed to the sidereal division of a and 0
Capricorni. It remained visible for 6 weeks, and travelled slowly. — (De Mailla,
iii. 376 ; Ma-tuoan-lin ; Pliny, Hist. Nat., ii. 25 ; Williams, 13.)

[94.] 77. On Jan. 23 a comet, with a tail 8 or 9 cubits long, appeared in the E. A.
of Aries, whence it moved towards the tail of Draco and the N. Pole. It remained
visible for 1 5 weeks. — (Ma-tuoan-lin ; Gaubil ; Williams, 1 3.)

[95.] 79. In the spring (?) a comet was visible for a long time during the illness
of Vespasian. — (Dion Cassius, Hist. Roman., Ixvi. 1 7 ; Suetonius, Vita Vespasiani.)
[96.] 84. On May 25 an extraordinary star, 3 cubits long, appeared in the morning
in the Eastern heavens. It was in the 8th degree of the sidereal division of /x2
Scorpii. It traversed v, £, o, ir Cassiopeise into the circle of perpetual apparition,
remaining visible for 6 weeks. — (Biot* ; Williams, 13.) Williams places the comet
in the 8th degree of the division of a Muscse. These two divisions are in the original
Chinese represented by words of nearly identical sound : hence the uncertainty.

[97.] 102. On the evening of Jan. 7, a greenish white vapour, 30 cubits long, was
seen. It extended from t, K, x, $ Eridani towards /3 Canis Majoris, and was visible
for 10 days. — (Williams, 13 )

[98.] 104.* On June 10 anew star appeared in the circumpolar regions ; it passed
to the Pleiades, and vanished in the next moon. — (Biot.)

[99.] 108.* On July 25 an extraordinary star appeared in Ursa Major, with a
tail 2° long, which extended in a S.W. direction towards « and i of that constellation.
—(Biot.)

[100.] 110. In January a comet rose to the S. W. of 7, 8, « and f Eridani. It had
a bluish tail, 6 or 7 cubits long, pointing to the N. E., in which direction (?) it moved.
— (Ma-tuoan-lin ; Williams, 14.)

[101.] 115. On Nov. 16 an extraordinary star appeared in the W. On the 2ist it
was to the S. of /3 and a Aquarii, and afterwards moved to Musca and the Pleiades. —
(Biot.*) Gaubil erronously refers this comet to 117. — (Hind, Companion to the
Almanac, 1859, p. 12.) Pingre", following Gaubil, reads " /3 Aquarii and a Equulei."
[102.] 132. On January 29 a strange star, with a tail 2° long, pointing towards
the S.W., was observed. Its R. A. was 6° greater than that of /3 Capricorni ; it was
also seen near 8, \, <p Sagittarii, and moved near 0 Aquarii, a Equulei, and a
Aquarii, towards « and 0 Pegasi. — (Ma-tuoan-lin ; Biot * ; Williams, 14.) This
comet was seen in Europe in the time of Adrian, whose courtiers told him that the
soul of Antinous had been changed into a new star. — (Dion Cassius, Hist. Roman.,
Ixix.) Williams's date is 131 (no month), and his places less precise.

[103.] 133.* On February 8 an extraordinary star, with a vapour 50° long and 2°
broad, was seen to the S.W. of 7, 8, e, &c. Eridani. — (Biot.)

[104.] 149. On Oct 19 a comet, with a tail 5 cubits long, was observed in the
head of Hercules ; it was only seen for 3 days. — (De Mailla, iii. 441 ; Williams, 15.)
Gaubil dates its appearance for 148, and Ma-tuoan-lin for 147, but it can be shown
by an extraneous circumstance that 149 was really the year.

[105.3 161 (i). In February — March a comet was seen near a Scorpii. — (De Mailla,
iii. 459.)

[106.] 161 (ii). On June 14 an extraordinary star appeared in the sidereal division
of o Pegasi. It remained nearly stationary for some time, and then retrograded ; and
when it reached the R. A. of I4|h it threw out a tail 5 cubits long. — (Ma-tuoan-lin ;
Williams, 15.)

CHAP. VIII.] Catalogue. — No. II. 559

[107.] 180 (i). In Aug. — Sept. a comet was discovered near i, K, X, \i, v, £ Ursae
Majoris. It moved E. to the tail of Leo, and lasted 3 weeks. — (Ma-tuoan-lin.)

[108.] 180 (ii). A comet was visible in the winter of 180-1 for 2 or 3 months. It
came from the E. of Sirius, and moved towards «, v, X Hydrae, where it vanished. —
(De Mailla, iii. 506 ; Ma-tuoan-lin; Williams, 16.)

[109.] 182 (i). In February, March, or April, a comet was seen near 8 An-
dromedae. It tended towards the E., and entered the circle of perpetual apparition,
but left it again after 3 days. It was visible for nearly 9 weeks. — (Ma-tuoan-lin.)

[no.] 182 (ii). In August — September a comet appeared near t and K Ursae
Majoris, which was also seen in the vicinity of /3 Leonis. — (De Mailla, iii. 507 ;
Ma-tuoan-lin; Williams, 16.)

[in.] 188 (i). In March — April a comet was observed in the sidereal division of
/3 Andromedae. It went the contrary way and became circumpolar, and lasted about
8 weeks. — (De Mailla, iii. 520; Williams, 17.)

[112.] 188 (ii). On July 29 an extraordinary star appeared in Corona Borealis; it
moved to the S.W. to a Herculis and a Ophiuchi. It disappeared in the division of
I*2 Scorpii. — (Williams, 17.) Biot dates this comet for June 30, 182.

[113.] 190. + During the reign of Commodus a hairy star was seen. — (^Elius
Lampridius ; Herodianus, Historia, i.) No more exact date can be assigned.

[114.] 192. In September — October (or October — November) a grand comet 100
cubits long was seen to the S. of the sidereal divisions of a and * Virginis. — (Ma-
tuoan-lin ; Williams, 1 70

[115.] 193. In November — December a comet was seen near a and f Virginis,
moving towards the N. E. On arriving in the region near a Herculis and a
Ophiuchi it disappeared. — (Ma-tuoan-lin; Williams, 18.) Another authority places
it near a Herculis, &c. at its discovery. — (De Mailla, iii. 363.)

[116.] 200. On Nov. 7 a comet was observed near 8 Serpentis. — (De Mailla, iv.
35; Ma-tuoan-lin; Williams, 18.)

[117.] 204. In November — December a comet appeared in the sidereal division of
/t Geminorum, which passed by 0, 7, 8 Cancri, a, 7 Leonis, to the region lying around
0 Leonis. — (De Mailla, iv. 40 ; Ma-tuoan-lin ; Dion Cassiua, Hist. Roman., Ixxv.
16; Williams, 18.)

[118.] 206. In February a comet was observed in the square of Ursa Major:
the tail extended over the whole of the circle of perpetual apparition : it reached to
Ursa Minor. — (De Mailla, iv. 43 ; Ma-tuoan-lin ; Williams, 18.)

[119.] 207. On Nov. 10 a comet appeared in the sign of Leo (or Virgo). — (Ma-
tuoan-lin ; Couplet; Williams, 18.) De Mailla assigns this comet to the previous
year. — (Hist. Gin., iv. 45.)

[120.] 213. In January — February a comet appeared near 0, v, </> Geminorum. —
(De Mailla, iv. 63 ; Williams, 19.)

[121.] 222. On Nov. 4 a new star was observed between j3 Virginis and a Leonis.
— (Gaubil.) It is uncertain whether this was a comet or a temporary star. Either
will accord with the description. Between 77 and 7 Virgiuis.— (Biot* ; Williams,
20.)

[122.] 225. On Dec. 9 a comet was discovered near m Leonis; it passed by a, 7
Leonis. — (Ma-tuoan-lin ; Williams, 20.)

[123.] 232. On Dec. 4 a comet was seen near a Leonis. It approached £ Leonis.
— (Ma-tuoan-lin.) Near 7 Virginis. — (Williams, 20.)

[124.] 236 (i). On Nov. 30 a comet, with a tail 3 cubits long, was seen near
a Scorpii ; on Dec. i it (or another comet) was seen in the E. — (Ma-tuoan-lin; Gaubil ;
Williams, 20.)

[125.] 236 (ii). On Dec. 15 a comet was seen; it approached e, f Ophiuchi and
&, C Herculis. — (Ma-tuoan-lin ; Gaubil.) Williams treats this comet and the pre-
ceding as one, and it appears probable that such was the case.

560 Comets. [BOOK IV.

[126.] 238 (i). In September a comet, with a tail 3 cubits long, was discovered in
the sidereal division of «, A. Hydrae; it moved eastwards (?), and disappeared in 6
weeks. — (Gaubil ; Ma-tuoan-lin ; Williams, 21.)

[127.] 238 (ii). An extraordinary star was visible from Nov. 29 to Dec. 15. On
the former day it was between TT Cygni, * Andromedae, and X, /* (or r, v) Pegasi. On
Dec. 10 it passed near h, g Tauri Poniatowskii and 7 Ophiuchi. — (Gaubil; Biot* ;
Williams, 21.)

[128.] 245. On Sept. 18 a comet, with a tail 2 cubits long, appeared in the
sidereal division of a Hydrse ; it moved towards the division of v Hydrae ; it was
visible for 3 weeks. — (Gaubil ; Ma-tuoan-lin; Williams, 21.)

[129.] 247. On Jan. 16 a comet, with a tail i cubit long, was observed : it had the
same R.A. as Corvus, and was visible for 56 days. — (Ma-tuoan-lin.) One authority
states that the comet was visible for 156 days. — (Williams, 22.)

[130.] 248 (i). In April — May a comet was seen in the Pleiades. Its tail was
6 cubits long, and extended towards theS. W. — (Ma-tuoan-lin.)

[131.] 248 (ii). In August a comet appeared in the sidereal division of a Crateris ; it
moved towards that of 7 Corvi. The tail was 2° long, and the comet remained
visible for 6 weeks. — (Ma-tuoan-lin.) Williams (p. 22) treats the two preceding
comets as one.

[132.] 251. On Dec. 21 a comet appeared in the sidereal division of a and £
Pegasi. It moved westwards, and disappeared after 13 weeks. — (Ma-tuoan-lin;
Williams, 22.)

[133.] 252. On March 25 a comet was observed in the sidereal division of Musca,
with a tail 50 or 60 cubits stretching towards the S. in the direction of the cross of
Orion (5, e, &c.). The comet was seen for 3 weeks. — (Gaubil; Ma-tuoan-lin;
(Williams, 22.)

[134.] 253. In December a comet appeared near rj Virginis, 7, S, < Corvi, and
afterwards near /3 Leonis. The tail pointed to the S. W., and was fifty cubits long.
It remained visible for 6 months. — (Ma-tuoan-lin; Williams, 22.) Hind remarks
that probably the comet's motion was retrograde, and that therefore it receded from
the Sun's place towards the W. ; also that its path was no doubt more extensive than
Ma-tuoan-lin has set down. — (Companion to the Almanac, 1859, P- I9-)

[135.] 254. In December a vapour emerged from near 8 Sagittarii. Its length is
stated to have been very great. — (Ma-tuoan-lin.) Pingre' seems to doubt whether
this was a comet or not.

[136.] 255. In January — February a comet was seen near f, £ Aquilae, to the
N. W., near the horizon. — (Ma-tuoan-lin; Williams, 23.)

[137.] 257. In November or December a white comet was seen in the sidereal
division of a Virginis. — (Ma-tuoan-lin ; Williams, 23.)

[138.] 259. On November 23 a strange star was seen near 0 Leonis. It moved
towards the S. E., traversed the division of 7 Corvi, and disappeared in a week. —
(Biot* ; Williams, 23.)

[139.] 262. On Dec. 2 a comet, with a tail 50° long, appeared in the sidereal
division of K, i Virginis. It moved towards the N., and was visible for 6 weeks. —
(Gaubil.) Ma-tuoan-lin says that its tail was only 5 tsun dB0 of a cubit) long. —
(Williams, 23.)

[140.] 265. In June a comet was seen near a, 0, 77 Cassiopeiae. Its tail was 10
cubits long, and pointed to the S.E., and after 12 days it disappeared. — (Ma-tuoan-
lin; Williams, 23.)

(141.] 268. On Feb. 18 a comet was seen in the sidereal division of /3 Corvi. It
advanced to the N. W., and subsequently turned towards the E. (Ma-tuoan-lin ;
Williams, 24) ; which remark probably has reference only to the tail. — (Hind.)

[142.] 269. In October — November a comet was seen within the circle of perpetual
apparition. — (De Mailla, iv. 148.)

CHAP. VIII.] Catalogue. — No. II. 561

[143.] 275. In January — February a comet was discovered in the sidereal division
of li Corvi. — (Ma-tuoan-lin ; Williams, 24.)

[144.] 276. A comet was visible from June 23 to September. It moved from the
sidereal division of a Librae, by a Bootis to /3 Leonis, and passing through the
sidereal division of a Crateris, attained to the square of Ursa Major and i, K, \, (i
Ursae Majoris. — (Ma-tuoan-lin; Williams, 24.) Hind suggests that the Chinese
account may fairly be considered as applying to the motion of the head (which was
therefore retrograde) and the direction of the tail of one comet, though Ma-tucan-lin
states that there were three. " If Ma-tuoan-lin had been more precise in his dates,
we might have approximated to the elements of the real orbit." — (Companion to the
Almanac, 1859, p. 20.)

[145.] 277 (i). Ma-tuoan-lin (Williams, 24) says that in January — February there
was a comet in the W., and in April — May another in the sidereal division of
Musca, which two are probably identical. — (Hind, Companion to the Almanac, 1859,
p. 20.)

[146.] 277 (ii). Ma-tuoan-lin (Williams, 24) states that in May — June there was
a comet near TT Leonis, and another in June — July in the E. ; whilst De Mailla (iv.
162) speaks of a third within the circle of perpetual apparition in August — September.
Hind thinks that these three may easily have been but one. — (Companion to ths
Almanac, 1859, p. 20.) Pingre" points out that the New Moon fell nearly at the
time of the equinox, a circumstance which may have produced an error of one month
in the Chinese dates.

[147.] 278. In May — June a very large comet appeared in Gemini. It lasted till
the end of the year, or for 8 months (?). — (Ma-tuoan-lin ; Gaubil.)

[148.] 279. In April a comet was seen in the sidereal division of 8, € Hydras; in
May another (? the same) near IT Leonis. In July — August it was within the circle
of perpetual apparition. — (Ma-tuoan-lin ; Williams, 25.)

[149.] 281 (i). In September a comet appeared in the sidereal division of K, v, \
Hydrse. — (Ma-tuoan-lin; Williams, 25.)

[150.] 281 (ii). In December a comet appeared near 7 Leonis. — (Ma-tuoan-lin;
Williams, 25.) This might be the same as the preceding, and Hind appears to
favour this view of the matter.

[151.] 283. On April 2 2 a comet was seen in the S.W. — (Ma-tuoan-lin; Williams,
25-)

[152.] 287. In September a comet appeared in the sidereal division of <p Sagittarii
for 10 days.) Its tail was 10 tchang (100 cubits ?) long. — (Ma-tuoan-lin ; Williams,

250

[153.] 301 (i). In January a comet emerged to theW. of 0 Capricorni, with a tail
pointing towards the W. — (Ma-tuoan-lin; Williams, 26.)

[154.] 301 (ii). In April — May a comet was seen near either 01 Capricorni or
no Herculis. — (Ma-tuoan-lin; Pingre.) Near H Herculis. — (Williams, 26.)

[155.] 302. In May — June a comet was visible in the morning. — (Ma-tuoan-lin;
Williams, 26.)

[156.] 303. In April a Comet was seen in the Eastern heavens, pointing towards
t, K, \, p Ursse Majoris. — (Ma-tuoan-lin ; Williams, 27.)

[157.] 305 (i). In September — October a comet was seen in the sidereal division
of the Pleiades. — (Ma-tuoan-lin; Williams, 27.) Under the same date De Mailla
places a comet near the Pole. — (Hist Gen., iv. 248.) This is probably the comet of
Ma-tuoan-lin.

[158.] 305 (ii). On Nov. 22 a comet was seen in the square of Ursa Major, near
7 of that constellation. — (Ma-tuoan-lin; Williams, 27.) Hind identifies this with
the preceding, but not so Pingre".

[159.] 329. In August — September a comet appeared in the N.W. It entered the
sidereal division of </>, 5 Sagittarii, and was visible for 3 weeks. — (Ma-tuoan-lin;
Williams, 27.)

502 Conu't*. [BOOK IV.

[160.] 336. On Feb. 16 in the evening a comet was seen in the W. in the sidereal
division of 0 Andromedae. — (De Mailla, iv. 349 ; Williams, 27.) In Europe a comet
of extraordinary magnitude was seen for several days a year or more before the
death of Constantine, which happened on May 22, 337. — (Eutropius, Hist or in
Romanct, x. 8.) Pingre and Hind agree in considering these 2 comets as one, in which
case possibly it was visible for 2 or 3 months.

f 161.] 340. On March 5 or 25 a comet was seen in the vicinity of /3 Leonis. —
(Ma-tuoan-lin ; De Mailla, iv. 363 ; Williams, 28.)

[162.] 343. On Dec. 8 a comet was seen ; its K.A. exceeded that of K Virginis by
7°. — (Ganbil.) Williams (p. 28) simply says that it was in the sidereal division of
« Virginis, and was 7 cubits long.

[163.] 349. On November 23 a comet, with a tail 10 cubits long, and extending
Westwards, was discovered in the sidereal division of K Virginis. On Feb. 13, 350,
it was still visible, and in the same sidereal division. — (Gaubil ; Ma-tuoan-lin ;
Williams, 28.)

[164.] 358. On July i or 12 a comet was seen in the sidereal division of Musca,
near y, rj Persei. — (Williams, 28.)

[165.] 363. In August — September a comet appeared in the sidereal divisions of
o and K Virginis ; it subsequently passed to near a Hercnlis and o Ophiuci. —
(De Mailla, iv. 413; Williams, 28.) During the reign of Jovian, or towards the
end of the year, comets are said to have been visible in the daytime. — (Ammianus
Marcellinus, Eerum Gestarum, xxv.)

[166.] 373 (i). On March 9 a comet appeared. It traversed the following sidereal
divisions, i. e. its R.A. successively coincided with the following stars : — € Aquarii,
0 Aquarii, a Librae (April 7), a Virginis, K Virginis, 7 Corvi, a Crateris, and v
Hydrae. — (Ma-tuoan-lin; Williams, 29.) It is not impossible however that the comet
traversed the above constellations, in which case the inclination of its orbit must have
been very small.

[167.] 373 (ii). On Oct. 24 a comet appeared near a Herculis and a Ophiuchi. —
(Ma-tuoan-lin.) Hind thinks that this was probably Honey's comet, which may have
arrived at perihelion during the first week of November. — {Companion to the
Almanac, 1859, p. 23.) Williams (p. 29) identifies this comet with the preceding,
which is not a probable supposition. For Oct. 24 he gives Sept. 25.

[168.] 374. In January — February a comet was visible in the sidereal division of
fjf Scorpii and y Sagittarii. — (De Mailla, iv. 437 ; Ma-tuoan-lin.) This position
would also apply to Halley's comet at this epoch, so that it is uncertain whether this
comet or the preceding one was that body. — (Hind.) Hind appears to give the
preference to the latter. Compare his memoir in Month. Not., vol. x. p. 57. Jan.
1850. Williams (p. 29) identifies this comet with 373 (i).

[169.] 375. A few days before the death of Valentinian, which occurred on Nov. 1 7,
comets were observed. — (Ammianus Marcellinus, Jierum Gestarum, xxx.)

[170.] 389. In August (probably) a splendid comet appeared. It rose in the N.,
at the hour of cock-ci owing. Resembling the morning star, it burned rather than
shone, and ceased to exist in 4 weeks. — (Marcellinus, Chronicon.~) It appeared in
the zodiacal region, but moving apparently on the left of the spectators, and rising
and setting with the morning star, it gradually advanced to Ursa Major and Minor.
It lasted for about 6 weeks, and vanished near the centre of the former constellation. —
(Philostorgius, Epitome Histories Ecdesiasticae, x. 9 ; Nicephoras, Historia Eccleni-
astica, xii. 37.)

[171.] 390. On Aug. 22 a comet was seen near a and/3 Geminorum. Passing the
vicinity of 0 Leonis, i, K, \, 0, and <f> Ursae Majoris, it entered the " square " of that
constellation; on Sept. 17 it arrived within the circle of perpetual apparition: its
tail was 100 cubits long. — (Ma-tuoan-lin ; Williams, 29.) It lasted 4 weeks. —
(Marcellinus, Chronicon.) It is certain that 2 large comets appeared in 2 successive
years, and, what is equally remarkable, that they both followed nearly the same path
from the zodiac to the Pole ; the first, seen, or at least rocorded, only in Europe ; the
latter seen both in Europe and China. Marcellinus distinctly records tuo comets.
One or other of them is probably the " new star" recorded by Cuspianinus.

CHAP. VIII.] Catalogue.— No. II. .">(>:'.

[172.] 392. A cornet appeared. — (Couplet.)

[173.] 395. A great comet appeared in August, which moved from € Sagittarii
towards 13 Aquarii and a Equulei.- — (De Mailla, iv. 496.)

[174.] 400. On March 19 a comet, 30° long, appeared in the sidereal division of
6 Andromedse. It rose to (, v, £ Cassiopeise, and stopped to the W. of the circle
of perpetual apparition ; it entered the square of Ursa Major, and arrived near
v, £, \, /j., i, K. In the next moon (commencing April ii) it passed by 0 Leonis
to 0 and 77 Virginis. — (Ma-tuoan-lin ; Williams, 30.) Gaubil adds that the comet
passed very near x Ursae Majoris. The most terrible comet on record. Its form was
that of a sword. — (Socrates Scholasticus, Hiatoria Ecclesittstica, vi. 6.)

[175.] 401. On January 2 a comet appeared in Corona Borealis and near a
Herculis and a, #, e, &c. Cygni. — (De Mailla, iv. 519 ; Williams, 30.)

[176.] 402-3. In November — December an extraordinary star appeared to the
W. of the region lying around 0 Leonis ; two moons later it was nearer that star. —
(Biot* ; Williams, 31.) " It first appeared in the E. towards that part of the heavens
where Cepheus and Cassiopeia shine. Passing then a little beyond the Great Bear,
it overpowered by [the brilliancy of] its wandering hair the beauty of the stars
of that constellation, till at length it languished, and finally dissipated itself in a very
feeble flarne." — (Claudianus, De Bella Getico, xxvi. 28 et seq.)

[177 and 178.] 415 or 416; (i and ii). On June 24 two comets were observed
near a Herculis and a Ophiuchi ; passing by the former star they were seen in the N.
of the sidereal divisions TT and a Scorpii. — (Ma-tuoan-lin ; Williams, 31 and 35.)
Probably this route applies to only one of the comets. From another Chinese
Chronicle it appears that on June 18, 416, two comets were visible. It is most
unlikely that in 2 consecutive years in the same moon and on the same day of
the moon [Chinese reckoning] 2 pairs of comets should have appeared, so (as Pingre
suggests) probably there was only i pair, one or the other of the 2 historians having
accelerated or retarded their appearance by one year.

[179.] 418 (i). On June 24 a comet was discovered in the middle of the square of
Ursa Major. — (Ma-tuoan-lin.) " Cette comete difierenecessaireinent de la suivante."
— (Pingr^ i. 599.)

[180.] 418 (ii). " On July 19, towards the 8th hour of the day, the Sun was so
eclipsed that even the stars were visible. But at the same time that the Sun was
thus hid, a light, in the form of a cone, was seen in the sky ; some ignorant people
called it a comet, but in this light we saw nothing that announced a comet, for it was
not terminated by a tail : it resembled the flame of a torch, subsisting by itself
without any star for its base. Its movement too was very different from that of
a comet. It was first seen to the E. of the equinoxes ; after that, having passed
through the last star in the Bear's tail [probably rj Ursae Majoris], it continued
slowly its journey towards the W. Having thus traversed the heavens, it at
length disappeared, having lasted more than 4 months. It first appeared about
the middle of the summer, and remained visible until nearly the end of autumn." —
(Philostorgius, Epitome Histories Ecclesiastics, xii. 8.) This description has been
taken by some to apply to the Zodiacal Light. (Boillot, Traite d' Astronomic, p. 257.)

In China this comet was -seen on Sept. 15 in Leo : it rcse above 5 or a Leonis, and
passed through the square of Ursa Major, the circle of perpetual apparition, and
near i and K (or A. and ft) Ursae Majoris. Its tail, short at first, increased to
i oo cubits or more. — (Ma-tuoan-lin ; Williams, 31.) It was first seen near 5 Cygni,
and was visible for 1 1 weeks. — (De Mailla, iv. 590.) Couplet states that it
appeared in November — December. If for appeared we could read disappeared,
Couplet's account would harmonise with those of the other observers.

[181.] 419. On Feb. 17 a comet appeared in the W. of the region lying around
/3 Leonis. — (Ma-tuoan-lin; Williams, 31.)

[182.] 420 or 421. In May a comet was seen. — (Couplet.) In Europe a wonder-
ful sign appeared in 421.— (Prosperus Tyronus, Clironicon.) Was this " sign " the
comet of the Chinese .'

002

564 Comets. [BOOK IV.

[183.] 422 (i). In March a star with a long white ray appeared for 10 nights
about the time of the cock-crowing. — (Chronicon Paschale. Parisiis, 1688.) On
March 16 it was in the sidereal divisions of a and 0 Aquarii. — (Gaubil.) Ma-tuoan-
lin dates its appearance for March 21. — (Williams, 32.)

[184.] 422 (ii). On Dec. 17 a comet was seen near a and ft Pegasi. — (Ma-tuoan-
lin ; Williams, 32.)

[185 ] 423 (i). On Feb. 13 a comet was seen in the eastern part of the sidereal
division of 7 Pegasi. — (Ma-tuoan-lin ; Williams, 32.) A comet was frequently seen
before the death of the emperor Honorius. — (Marcellinus, Chronicon.') This event
happened in August.

[186.] 423 (ii). On Oct. 15 a comet was seen in the sidereal division of a and 0
Librae. — ^Ma-tuoan-lin ; Williams, 32.) Hind gives the date as Dec. 14.

[187.] 432. A comet was seen near a and 7 Leonis; passing in the vicinity of 0
Leonis, it disappeared near a Bootis. — (Ma-tuoan-lin.) No moon given.

[188.] 436. On June 21 a comet was seen near ir Scorpii. — (Gaubil.)

[189.] 442. On Nov. i a comet without a tail was seen in the square of Ursa
Major. It soon threw out a tail, and passing 0, v Ursa Majoris, through Auriga,
p and it Tauri, carue to IT Ceti and 7, S, p Eridani. It disappeared in winter. —
(Ma-tuoan-lin; Biot* ; Williams, 32.) It appeared in December, and remained
visible for several months. — Marcellinus, Chronicon ; Idatius, Chronicon.)

[190.] 449. A comet appeared on Nov. ii in the vicinity of 0 Leonis. — (Ma-
tuoan-lin ; Williams, 33.)

[191.] 467. A comet resembling a trumpet was seen for periods of from 10 to 40
days in the evening sky. — (Chronicon Paschale ; Theophanes, Chronographia, p. 99,
Parisiis, 1655.)

[192.] 499. A comet appeared previous to the second invasion of Dlyria by the
Bulgarians.— (Zonaras, Annales, ii. 56. Parisiis, 1686.)

[T93-] 501. On Feb. 13 a tailed star appeared in the horizon. On March 2 a
grand comet was visible. — (Ma-tuoan-lin. Hind, Companion to the Almanac,
1860, p. 78.) For March 2, Williams (p. 33) reads April 14. Probably these notes
belong to one and the same object.

[194.] 504. A great and brilliant star, with along ray, appeared about the time of
the death of Ambrosius Aurelius. — (Galfredus, De Origine et gestis Reyum Britannia,
viii. 4. Heidelbergae, 1587.) It is just possible that this description may refer
to the preceding comet. Hind seems to be of this opinion.

[195.] 507. On Aug. 15 a comet was seen in the N. E. — (Gaubil.)

[196.] 519. A " fearful star," with a tail turned towards the W., was seen this
year, possibly between October and December. — (Theophanes, Chronographia, p. 142 ;
Malala, Historia Chronica, xvii. Venetiis, 1733.)

[197.] 520. On Oct. 7 a comet, bright like fire, was seen in the E. On Nov. 30 it
was observed in the morning. — (Gaubil.)

[198.] 524. A star was seen for 26 days and nights " above the gate of the
palace." — (Cedrenus, Compendium Hisloriarum, p. 365. Parisiis, 1647.)

[199.] 530 or 531. A great comet was observed in Europe and China, but accounts
differ as to the year, though probably it was 531. " It was a very large and fearful
comet," and was seen in the W. for 3 weeks. Its rays extended to the zenith. —
(Theophanes, Chronographia, p. 154; Malala, Historia Chronica, xviii.) It was
observed [? passed] in October from o Bootis to X, /i Ursae Majoris. — (De Mailla, v.
299.) Hind thinks that this was Halley's comet. If it arrived in perihelion at the
beginning of November it would have occupied the positions given by the historians,
and, in any case, it must have been near perihelion at this time. It is not im-
possible that there was a comet in each of the above years, a theory which might
perhaps remove some of the discrepancies which exist on the assumption that there
was only one.

CHAP. VIII.] Catalogue. — No. II. 565

[200.] 533. On March I a great star appeared. — (Ma tuoan-lin). There are no
further particulars, so it is uncertain whether this was a comet or a temporary star
(Hind). Williams (p. 33) gives, but with reserve, the date as January 6, 532. He
calls the object, however, a tailed star, in which case no doubt it was really a comet.

[201.] 534. A comet appeared in Leo and Virgo; passing v, £ Ursse Majoris, it
moved to the square of Pegasus. — (Gaubil.)

[202.] 556. In November a comet, in the form of a lance, extended from E. to W.,
or from N. to W. — (Malala, Histoiia Chronica, xviii.) Some writers date this
for 555.

[203.] 560. On Oct. 4 a comet, with a tail 4 cubits long, pointing towards the
S. W., was seen. — (Williams, 34 ; Gaubil.)

[204.] 563. A comet, like unto a sword, was seen for a whole year [? month]. — •
(Gregorius Turonensis, Hist or ia Francorum, iv.)

[205.] 565 (i). On April 21 a comet appeared. — (Ma-tuoan-lin.) Williams (p. 35)
thinks that there is some uncertainty about the year.

[206.] 568 (i). On July 20 a very brilliant comet was seen in the sidereal division
of IJL Geminorum. It moved towards the E., and stopped 8 "feet" [or degrees?]
N. of 6, rj Cancri on Aug. 18, and then disappeared. — (Ma-tuoan-lin; JBiot;
Williams, 36).

[207.] 575. On April 27 a comet was seen near Arcturus (a Bootis). — (Ma-tuoan-
lin ; Williams, 34.)

[208.] 581. On Jan. 20 a comet appeared in the S. W. — (Ma-tuoan-lin.) Williams
(p. 35) dates this comet for Jan. 26, 580.

[209.] 582. In the month of January many prodigies were seen. A comet
appeared, situate, as it were, in a sort of opening ; it shone in the midst of the
darkness, sparkled and spread out its tail. From the comet a ray of surprising
magnitude emanated, which appeared like the smoke of a conflagration as viewed at
a distance. The comet was visible in the W. from the first hour of the night. —
(Idatius, Chronicon, vi. 14.)

[210.] 584. A comet, like a column of fire suspended in the air, was observed, and
a great star appeared above it. — (Chronicon Turonense.}

[211.] 588. On Nov. 22 a comet appeared near & Capricorni. — (Ma-tuoan-lin;
Williams, 38.)

[212.] 591. A comet appeared for I month. — (Bonfinius, Herum Hungaricum, I.
viii., Hanoviae, 1606.)

[213.] 595. On Jan. 9 a comet was visible in the sidereal division of /3 Aquarii.
It moved through the sidereal division of a Aquarii and e Pegafi, towards those of
$ Andromedae and /3 Arietis. — (Gaubil; Ma-tuoan-lin; Simocatta, Historia, vii.,
Parisiis, 1647.) Williams (p. 38) dates this comet for Nov. 10, 594.

[214.] 602. A comet, like unto a sword, was seen in this year. — (Theophanes,
Chronographia, p. 240.)

[215.] About 605 (i). In April and May a comet was seen. — (Paulus Diaconus,
De Gestis Longobar<lorum,-iv. 33.)

[216.] About 605 (ii). In November and December a comet was seen. — (Paulus
Diaconus, iv. 34.)

[217.] 607 (i). On March 13 a comet was seen in the sidereal division of ^
Geminorum, and near v, <p Ursse Majoris ; it passed by K, T, 0 &c. Persei, a, /J, 0, x
Aurigse, a, £ Geminorum, the vicinity of 0 Leonis and a Herculis, and stopped after
14 weeks. (Ma-tuoan-lin ; Williams, 38.) Probably for Ti-tso (a Herculis) we
should read, as Hind suggests, Ou-ti-tso (# Leonis) ; and if we suppose the " v and <p
Ursae Majoris" to allude to the place to which the tail extended, this otherwise
inconceivable route will appear more reasonable.

On April 4 a tailed star appeared in the W. horizon. It traversed the sidereal
divisions of $ Andromedae, a and 0 Arietis, and a and « Virginia, and then disap-

Comets. [BOOK IV.

peared. — (Gaubil ; Williams, 39.) The Chinese account refers this to another comet,
but Hind thinks " it is more than probable that in the description of these so-called
first and second comets of this year, there is some confusion as regards the order in
which a single cornet may have passed through these sidereal divisions and con-
stellations ; or observations of the direction of the tail may be mixed up (as
occasionally happens) with the positions of the head." — (Companion to the Almanac,
1860, p. 85.)

[218.] 607 (ii). On Oct. 21 a comet appeared in "the Southern region;" it was
seen in the sidereal divisions of a and K Virginis and, passing in the vicinity of j8
Leonis, came to a Herculis : it entered most of the sidereal divisions, but not those of
a, fi, y, 5 Orionis or 7, t, n Geminorum ; in the beginning of the year 608 it disap-
peared. — (Williams, 39 ; Ma-tuoan-liu ; who declares this comet to be identical with
that of the 4th of April.) For o Herculis, Pingre read & Leouis, as above, and thinks
the "European comet or comets of 605 the same as the Chinese comet or comets of
607." — (Comttt. i. 327.) It is very difficult to decide from the Chinese observations
of comets in 607 how many comets really appeared in that year — whether there were
2 or 3, or even more than one.

[219.] 608. A comet emerged this year from a, /3 Aurigae, and passing v, <f> &c.
Ursae Majoris, came to /3, 8, tr, p Scorpii. — (Ma-tuoan-lin.) This is precisely the path
which Halleys comet follows when its PP. occurs in October, and as that comet was
due about this year, Hind thinks this was it.

[220.] 614. A comet appeared for i month during the occupation of Jerusalem by
Cosroes, king of Persia. — (Lubienitz, Theatram Cometicum, Lugd. Bat. 1681.) Date
very uncertain.

[221.] 615. In July a comet was seen to the S. E. of h, v, </>, 6 Ursse Majoris. It
was from 50° to 60° long, and its extremity had an undulatory motion. It moved to
the N. W. for some days, and when it had nearly reached the circle of perpetual
apparition it retrograded, and then disappeared. — (Gaubil; Ma-tuoan-lin.) The
dimensions assigned by the latter are 5 or 6 tsun (fo or -/^ of a cubit?). — Williams,
39-)

[222.] 616 (i). In July a comet, with a tail 3 or 4 cubits long, was seen near 0
Leonis ; after some days it disappeared. — (Ma-tuoan-lin ; Williams, p. 39). Hind
assigns this and the next comet to the year 617.

[223.] 616 (ii). In October a comet appeared in the sidereal division of a, 0
Pegasi. — (Ma-tuoan-lin ; Williams, 39,)

[224.] 622. A comet is recorded by several modern cometographers. — (Lubienitz.)

[225.] 626. In March an extremely brilliant star was seen in the W. after
sunset — (Chronicon Paschale.) On March 26 it was situated between the sidereal
divisions of the Pleiades and Musca. On March 30 it was near v, e, £ Persei. —
(Gaubil ; Williams, 40.)

[226.] 632. In May or June, or a little later, a sign appeared for 4 weeks in the
S. It was called a ''beam," and extended from S. to N. — (Cedrenus, Compendium
Jlistoriarum, p. 425. Parisiis, 1647.)

[227.] 633. A comet, in the form of a sword, was seen. — (J. A. Weber, Discursus
Curiosi, &c. Salisburgi, 1673.)

[228.] 634. On Sept. 22 a comet appeared in the sidereal divisions of 0 Aquarii
and a Aquarii ; it passed through the sign Aquarius, and on Oct. 3 was not visible. —
(Gaubil ; Williams, 40.)

[229.] 639. On April 30 a comet was seen in the sidereal divisions of a Tauri
and Pleiades. — (Ma-tuoan-lin; Williams, 40.) One Chinese authority makes the
year 638.

[230.] 641. On July 22 a comet was seen in the region near $ Leonis; it ap-
proached Coma Berenicis, and on Aug. 26 it had disappeared. — (Ma-tuoan-lin.) De
Mailla (vi. 93) dates this comet a month earlier, and Gaubil and Williams (p. 40)
say it was in the ft Leonis region on Aug. I.

CHAP. Mil.] Catalogue. — No. II. 567

[231.] 660. Some modern cometographers state that a comet was visible in Scorpio
for 12 days. — (Lubienitz.)

[232.] 663. On Sept. 27 a comet, 2 cubits long, was seen near o, TT, £ Bootis. On
Sept. 29 it had disappeared. — (Ma-tuoan-lin.) For Sept. 27 and 29 Williams (p. 41)
reads Sept. 29 and Oct. i.

[233-] 667. On May 24 a comet was seen in the N. E., near /?, 0 Aurigse, and 0
Tauri. — (Gaubil.) On June 12 it had disappeared. — (Ma-tuoan-lin ; Williams, 41.)

[234.] 668. In May or June a comet was seen for a few davs in Auriga. — (De
Mailla, vi. 145.) This is probably identical with the preceding with an error of one
year in the date.

[235.] 673. In the first year of Thierri of France a comet was observed. — ( Vita S.
Leodei/arii.} Several historians record a fire or extraordinary iris. Pingr£ suggests
that the whole may be reduced to an Aurora Borealis.

[236.] 674. According to some modern writers a great comet appeared. — •
(Lubienitz.)

[237.] 676 (i). On Jan. 3 a comet, 5 cubits long, was discovered to the S. of the
sidereal divisions of a and * Virginis. — (Ma-tuoan-lin ; Williams, 41.)

[238.] 676 (ii). " In the month of August a comet showed itself in the E. for 3
months, from the time of cock-crowing until morning. Its rays penetrated the
heavens ; all nations beheld with admiration its rising : at length, returning upon
itself, it disappeared." — (Anastasius, Historia Ecclesiastica, Parisiis, 1649; Paulus,
Diaconus, De Gestis Longobardorum, v. 31.) On Sept. 4 a comet appeared in the
sidereal division of p Geminorum ; it pointed towards a and 0 Geminorum ; it moved
towards the N.E. Its tail, at first 3 cubits long, afterwards increased to 30 cubits.
It [the comet — Pingre" ; or the tail — Hind] reached to \, /j. and 0, v, <£ Ursae Majoris.
On Nov. i the comet had disappeared. — (Ma-tuoan-lin; Gaubil.) For Sept. 4 and
Nov. i in this account, Williams (p. 41) reads July 7 and Sept. 3.

[239.] 681. On Oct. 17 a comet, 50° long, was near a Herculis ; gradually
diminishing in size, it moved towards a, 0, y Aquilae, and on Nov. 3 it had disappeared.

— (Gaubil ; Ma-tuoan-lin ; WTilliams, 42.)

[240.] 683. On April 20 a comet was seen to the N. of a, /3, 0, &c. Aurigse,
/3 Tauri. On May 15 it had disappeared. — (Ma-tuoan-lin; Williams, 42.)

[241.] 684 (i). On Sept. 6 a comet, 10° long, was seen in the evening towards
the W. On Oct. 9 it had disappeared. — (Gaubil.) Hind remarks that this single
account will tolerably well describe the position which Halley's cornet must have been
in at its return to perihelion in the year 684, so doubtless this was that celebrated body.
— (Companion to the Almanac, 1860, p. 88.) For Sept. 6 and Oct. 9 Williams (p.
42) reads July 8 and Aug. 10.

[242.] 684 (ii.) On Nov. n a star, like a half moon, was seen in the W. country.

— (Ma-tuoan-lin.) Hind says "in the n ort h" — apparently a misprint. For Nov. II
Pingre and Biot read Oct. u, and Williams (p. 42) Sept. 12. It seems doubtful
whether a comet is referred to.

[243.] 706. In the 3rd year of Ethelhard King of Wessex "Two comets appeared
...one in the evening, the other in the morning; one in the West, the other in the
East. They carried their fiery face towards the North, and appeared during the
month of January for almost a fortnight." — (Bartholomaei de Cotton, Historia Anglice.~)
This is no doubt one comet with a considerable North Declination.

[244.] 707. On Nov. 16 a comet appeared in the W. ; on Dec. 1 7 it had ceased to
be visible. — (Ma-tuoan-lin; Williams, 43.)

[245.] 708 (i). On March 30 a comet appeared between the sidereal divisions of
Musca and the Pleiades. — (Ma-tuoan-lin ; Williams, 43.)

[246.] 708 (ii). On Sept. 21 a comet appeared within the circle of perpetual
apparition. — (Ma-tuoan-lin ; Williams, 43.)

568 Comets. [BOOK IV.

[247.] 710 or 711. In the 92111! year of the Hegira a comet, endued with a sensible
motion, appeared for n days. — ',Haly, Liber Ptolemcel Comment. Venetii*, 1484.)
The year 92 of the Hegira commenced on Oct. 29, 710, and ended on Oct. 18, jrn.

[248.] 712. In August — September a comet emerged from the W., and passed
near j3 Leonis, &c. and thence to Arcturus. — (De Mailla, vi. 199.) Williams (p. 43)
sees a difficulty in assigning any more exact date than " between 710 and 7I3-"

[249.] 716. A comet of terrible aspect, with its tail directed towards the Pole, is
said to have been seen this year, but we have only a modern authority for the
statement. — (Sabellicus, Optra Omnia, Ennead. VIII. lib. vii. Basilese, 1560.)

[250.] 729. Several writers speak of 2 comets visible for 14 days in the month of
January, the one after sunset and the other before sunrise. — (Bede, Historia
Ecclesiastica, v. ; Monachus Herveldensis, Chronicon Histories Germaniee.} It is
easy to see that a single comet with a E.A. not greatly differing from that of the
Sun, but with a high North declination, would be seen after sunset and before
sunrise, and thus satisfy the statement of the Chroniclers. Donati's great comet of
1858 was so visible for several weeks in the month of September of that year.

[251.] 730. On Aug. 29 a comet was seen in Auriga: on Sept. 7 it was in the
sidereal divisions of a, 7 &c. Tauri and the Pleiades. — (Gaubil.) Ma-tuoan-lin
implies that the comet of Sept. 7 was not the same as that of Aug. 29. Williams's
dates are June 30 and July 9 (p. 43).

[252.] 738. On April i a comet was seen within the circle of perpetual apparition.
It traversed the square of Urea Major, and was observed for 10 days or more,
when clouds interfered.— (Ma- tuoan-lin.) Williams (p. 44) dates this comet for
739-

[253.] 744. A great comet was seen in Syria. — (Theophanes, p. 353.)

[254.] 749. " In his (Cuthrede's) time there appeared 2 biasing stars casting as
it were burning brands towards the North. — (Sfcowe, Chronicles.)

[255-l 762. A comet was seen in the E. like unto a beam. — (Theophanes, p. 363.)

[256.] 767- On Jan. 12 a comet I cubit long was seen near a, 0, 7, S Delphini.
It passed over f , i Delphini and was visible for 3 weeks. — (Ma-tuoan-lin ;- Williams,
p. 44.) For Jan. 12 Hind reads Jan. 22.

[257.] 773. On Jan. 173 tailed star was seen in the sidereal division of S Orionis.
— (Ma-tuoan-lin ; Williams, 45.)

[258.] 813. "On Aug. 4 a comet was seen which resembled 2 Moons joined
together ; they separated, and having taken different forms, at length appeared like a
man without a head." — (Theophanes, p. 423.) In spite of the strangeness of this
description, Pingre considers it to be really that of a comet, and thinks it possible to
find an explanation in the comet's peculiar position with regard to the Sun and the
Earth.— (Comet, i. 338.)

[259.] 815. In April — May a great comet appeared near 0 Leonis. — (Ma-tuoan-lin ;
Williams, 45.)

[260.] 817. On Feb. 5, at the second hour of the night, a monstrous comet was
seen in Sagittarius. — (Vita, Ludovici Pii in Bouquet's Collection, vi.) On Feb. 17
a comet was seen in the sidereal division of a, 7 Tauri. — (Ma-tuoan-lin; Williams,
45-)

[261.] 821 (i). On Feb. 27 a comet was seen in the sidereal division of a Crateris.
On March 7 it was near a Leonis. — (Ma-tuoan-lin ; Williams, 46.)

[262.] 821 (ii). In July a comet, with a tail 10 cubits long, was seen in the
sidereal division of the Pleiades. After 10 days it disappeared. — (Ma-tuoan-lin ;
Williams, 46.)

[263.] 828. On Sept. 3 a comet, with a ta:l 2 cubits long, was seen near r, v, 77
Bob'tis. — (Ma-tuoan-iin.) A comet in Libra. — (Georg'us Fabricius, lierum Germanice
. . . Memorabilium. L:psise, 1609.) Pingre, not then acquainted with Ma-tuoan-lin,
threw doubts on the value of the record for Sept. 3. Williams (p. 46) reads
JulyS.

CHAP. VIII.] Catalogue. — No. II. 569

[264.] 834. On Oct. 9 a comet, with a tail 10° long, was seen near /3 Leonis. It
went Northwards beyond Coina Berenicis. On Sept. 7 it had disappeared. — (Ma-
tuoan-lin ; Williams, 46.

[265.] 837 (ii). On Sept. 10 a comet was seen in the sidereal divisions of 0 and d
Aquarii. — (Ma-tuoan-lin ; Boethius, Scotorum Historia, x ; Williams, 48.)

[266.] 838 (i). On Nov. n a comet was seen in the sidereal divisions of £ Corvi
and 0 Cancri. It was 20 cubits long, and the tail gradually pointed to the W. —
(Ma-tuoan-lin ; Williams, 48.)

[267.] 838 (ii). On Nov. 21 a comet was seen in the E. country, in the sidereal
divisions fi* Scorpii and 7 Sagittarii. It extended in the heavens E. and W. On
Dec. 28 it had disappeared. — (Ma-tuoan-lin.) For Dec. 28, Williams (p. 49) reads
Dec. 8. Possibly this and the preceding account both relate to the same object.

[268.] 839 (i). On Jan. I a comet was seen in Aries. — (Annales Francorum
Fill-dense*, in Bouquet's Collection, vols. vii. and viii.) On Feb. 7 a comet was seen
near 8, r, x, $ Aquarii. — (Ma-tuoan-lin ; Williams, 49.) Pingre" thinks that the
latter could not have been the European comet of Jan. i. — (Comet, i. 614.)

[269.] 839 (ii). On March 12 a comet was seen to the N. W. of v, e, f, £Persei.
On April 14 it had disappeared. — (Ma-tuoan-lin ; Williams, 49.)

[270.] 840 (i). On March 20 a comet was seen between the sidereal divisions of
d and 7 Pegasi. After 3 weeks it disappeared. — (Ma-tuoan-lin ; Williams, 49.)

[271.] 840 (ii). On Dec. 3 a comet was seen in the E. country. — (Ma-tuoan-lin ;
WTilliams, 49.)

[272.] 841 (i). Before the battle of Fontenay, that is, before June 25, a comet
was seen in Sagittarius. — (Annales Francorum Fuldenses.') In July — August a comet
was seen near 8, r, x, ^ Aquarii and between 7 Pegasi and the E. of the sidereal
division of 7 Pegasi. — (Ma-tuoan-lin ; Williams, 49.)

[273.] 841 (ii). On Dec. 22 a comet was seen near a Piscis Australis ; it passed
through the wing of Pegasus into the circle of perpetual apparition. On Feb. 9, 842,
it had disappeared. — (Gaubil ; Williams, 50.) It was seen in the W. from Jan. 7
till Feb. 13. — (Chronicon Taronense.}

[274.] 852. In March — April a comet was seen in the sidereal divisions of A. and
8 Orionis. — (Ma-tuoan-lin ; Williams, 50.) Williams dates this comet for 851.

[275.] 855. A comet was seen in France for 3 weeks. — (Chronicon S. Maxeniii ;
in Bouquet's Collection, vols. vii. and ix.) Perhaps in the month of August.

[276.] 857. On Sept. 22 a comet, with a tail 3 cubits long, was seen in the
sidereal division of ir Scorpii. — (Ma-tuoan-lin.) Williams (p. 50) dates this comet
for Sept. 27, 856.

[277.] 858. At the time of the death of Pope Benedict III a comet appeared in
the E. ; its tail was turned towards the W. — (Ptolemaeus Lucensis, Historia Eccle-
siastica, xvi. 9, in Muratori's Collection, vol. xi.) Benedict died on April 8.

[278.] 864. On May i a comet was seen. — (Chronicon Floriacense.} On June
21 a comet was seen in the N. E. through an opening in the clouds for 15 minute?.
It was in the sidereal division of /3 Arietis, and had a tail 3 cubits long. — (Ma-tuoan-
lin ; Williams, 30.)

[279.] 866. Comets were seen before the death of Bardas. — (Constantinus Por-
phyrogenitus, Incerti Continuatoris, iv. p. 126.) Bardas was killed on April 21.

[280.] 868. About Jan. 29 a comet was seen for 17 days. It was under the tail
of the Little Bear and advanced to Triangulum. — (Annales Francorum Fuldeiisee.}
It was seen in China in the sidereal divisions of 0 Arietis and a Muscse. — (Ma-
tuoan-lin ; Williams, 51.) — This comet is probably identical withNos. 23 and 241 of
the other catalogue, all three objects being apparitions of what is now known as the
" November meteor comet." (See Hind, Month. Not. xxxiii. 48. Nov. 1872.)

570 Comets. [BOOK IV.

[281.] 860. A comet announced the death of Lotharius the Younger. — (Pontanus,
JJistoria Gelrica, v. Hardervici-Gelrorum, 1639.) Lotharius died on Aug. 8. In
September — October a comet was observed near x, «, 9, T, 3, p Persei. It went to
the N. E. — (Ma-tuoan-lin ; Williams, 51.)

[282.] 873. A comet was seen in France for 25 days. — (Chronicon Andegavense,
in Bouquet's Collection, vol. vii.)

[283.] 875. The death of the emperor Louis II. was announced by a burning star,
like a torch, which showed itself on June 7 in the N. It was seen also from June 6
in the N. E. at the first hour of the night. It was more brilliant than comets usually
are, and had a fine tail. This bright comet, with its long tail, was seen morning and
evening during the whole of June. (Breve Chronicon Andrece, in Bouquet's Collec-
tion, vol. vii.) After harmonising some discrepancies of dates, Pingre says the comet
would have appeared on June 3 in Aries ; having but little latitude, it would conse-
quently have risen a little after midnight, and would have been seen the same night.
The following days, as its longitude diminished and its N. latitude increased, it
would have been seen by June 6 or June 7, in the evening, towards the N. E. —
(Comet. i. 349.)

[284.] 877. " In the second year of the entrance of Charles the Bald into Italy a
comet was seen in the month of Mai-ch in the W., and in the sign Libra. It lasted
for 15 days, but was less bright than the preceding one [that of 875]. In the same
year the emperor Charles died." — (Chronicon Novalicicnse, in Muratori's Collection,
vol. ii.) Being in Libra, it was in opposition to the Sun, and therefore visible all
night, in the evening in the E. and in the morning in the W. — (Pingre, Comet., i.
350.) Ma-tuoan-lin says that it appeared in the 5th moon, or in June — July.
(Williams, 51.)

[285.] 882. On Jan. 18, at the ist hour of the night, a comet, with a prodigiously
long tail, was seen. — (Annales Francorum Fuldenses.}

[286.] 885. A comet was seen between A, p Persei and K Geminorum. — (Ma-
tuoan-lin; Williams, 51.)

[287.] 886. On June 13 a comet was seen in the sidereal divisions of /*2 Scorpii
and 7 Sagittarii. It passed a, /3, 7 Ursse Majoris, near to 6, it, $ or 17, ~r, v Bob'tis. —
(Ma-tuoan-lin ; Williams, 51.)

[288.] 800. About May 23. "Ging ein Comet mit haufenformiger Hiille auf ;
Spaterwurde die Hulle zum Schweife." (Tabari III. 2119, 10 : Ast. Nach.,~No. 2811.
vol. cxviii. Nov. 9, 1887.)

[289.] 891. On May 12 a comet, with a tail 100 cubits long, appeared near the
feet of Ursa Major ; it went towards the E. It passed by the vicinity of /3 Leonis to
a Bootis and Serpens, etc. On July 5 it had disappeared. — (Ma tuoan-lin ; Wil-
liams, 51 ; J. Asserius, Annales.')

[290.] 892 (i). A comet appeared this year in the tail of Scorpio. It lasted 12
weeks, and was followed by an extreme drought in April and May. — (Chronicon
A ndegavense.*)

[291.] 892 (ii). In June a comet, with a tail 2° long, appeared. — (Ma-tuoan-lin.)

[292.] 892 (iii). In November — December a comet appeared in the sidereal
divisions of <f> Sagittarii and £ Capricorni. — (Ma-tuoan-lin ; Williams, 52.)

[293.] 892 (iv). On Dec. 28 a comet came from the S. W. On Dec. 31, the sky
being cloudy, it was not seen. — (Ma-tuoan-lin.)

Possibly i. and ii. are identical, and also iii. and iv. ; and in that case there would
have been only 2 comets this year.

[294.] 893. After several months of very bad weather the clouds went away, and
on May 6 a comet was seen near t and K Urfse Majoris, with a tail 100° long. It went
towards the E., entered the region lying around /3 Leonis, and traversed Bootes, near
Arcturus passing into the region around a Herculis. It was visible for 6 weeks, and
its length gradually increased to 200° (?). The clouds then hid it. — (Ma-tuoan-lin.)
The length is incredible, though Gaubil gives the same. Gaubil's date is 895, but

CHAP. VIII.] Catalogue. — No. II. 571

Pingre is sure that 893 was the year. Williams (p. 52) pronounces in favour of 893,
but misquotes Pingre' in doing so.

[295.] 894. In February — March a comet was seen. It had the same R. A. as

Gemini or Cancer. — (Ma-tuoan-lin; Williams, 52.)

[296.] 896.* In this year there appeared 3 extraordinary stars, one large and two
smaller ones. They were between the divisions of /3 and a Aquarii. They travelled
together for 3 days. The little ones disappeared first, and then the large one. —
(Biot.)

[297.] 900. About February an extraordinary star appeared near e Herculis,
i Ophiuchi, W. of a Herculis. — (Biot.*) A comet appeared. — (Lubienitz.)

[298.] 902. About February an extraordinary star was seen below some stars in
Cainelopardus. After a little while it passed to \ Draconis. On March 2 a shooting
star touched it. On March 4 it returned to Camelopardus. — (Biot.*) A comet
appeared. — (Calvisius, Opus Ckronologicum. Francofurti-ad-Oderam, 1620.)

[299.) 904. At about the time of the birth of the Emperor Constantine Porphy-
rogenitus a brilliant comet showed its rays in the E. It lasted 40 days and 40 nights.
• — (Leo Grammaticus, Chronographia, p. 483.) Constantine was baptized on the
festival of the Epiphany, or on Jan. 6, 905 ; so the comet may be dated for November
and December 904.

[300.] 905. On May 22 a comet was seen near a, & Geminorum. It traversed
Ursa Major from 0, v, <f>, r past A, /x, towards v, £, The tail was 30 cubits long. On
June 12 the comet stretched from a and 7 Leonis towards Serpens: on June 13
clouds obscured the sky ; and on June 18 the comet had disappeared. — (Ma-tuoan-
lin; Williams, 52.) From the European account in the Chronicon Floriacense it
would rather seem that it was the head of the comet which was in Ursa Major, and
that the tail reached to the zodiacal region ; but the description is altogether very
vague. In all such cases the Chinese accounts are generally preferable.

[301.] 911. About June an extraordinary star appeared near a Herculis. —
(Biot.*) A comet appeared. — (Ordericus Vitalis, Historia Eccle*iastica, vii.)
Pingre", perhaps it may now be said without reason, refers this account of Ordericus
to the next comet.

[302.] 912. A comet appeared for 15 days in the W., like unto a sword. — (Leo
Grammaticus, Chronograp/iia, p. 487. Parisiis, 1655.) It lasted for 14 days in the
N. W. in March. — fHugo, Monachus Floriacensis, Chronicon, in Bouquet's Col-
lection, vol. viii.) On May 1 3 a comet was seen in the sidereal division of v Hydrse.
On May 15 it was near x Leonis. — (Ma-tuoan-lin; Williams, 53.) Probably
Jlalleys comet, the PP. occurring early in April. — (Hind, Month. Not. R.A.S., x. 55.
Jan. 1850.)

[303.] 912 or 913. A comet was seen in Egypt in the year 300 of the Hegira. —
(Haly, Liber Ptolemcei Comment.} That year commenced on Aug. 18,912, and ended
on Aug. 6, 913.

[304.] 916. In the I5th year of Edward, son of Alfred, a comet appeared. —
(Bartholornsei de Cotton, Hitstoria Anglice.}

[305.] 923. In November — December a comet was seen near 0, 7, 8 Cancri. — (De
Mailla, vii. 210.) Another authority ante- dates this comet i month.

[306.] 928. On Dec. 13 a comet was seen in the S. W. Its R. A. was 5°
greater than that of 0 Capricorni. Its tail was lo° long, and pointed to the S. E.
After 3 evenings it ceased to be visible. — (Ma-tuoan-lin.) For Dec. 13 Williams
(P- 53) reads Oct. 14.

[307.] 936. On Sept. 21 a comet appeared in the sidereal divisions of/? and a
Aquarii. It was i° long, and passed near f Aquarii and A, /^Capricorni. — (Ma-tuoan-
lin.) For Sept. 21 Williams (p. 54) reads Oct. 28.

[308.] 939. " There was seen in Italy, for 8 successive nights, a comet of
surprising grandeur : it threw out rays of extraordinary length." — (Luitprandi
Ticinensis, lieriim . . . Gestarum, V. i.; Possibly July was the month.

572 Comets. [BOOK IV.

[309.] 041. On Sept. 18 or Nov. 17 (it is not possible to say which, though the
former day seems the more likely, from the European account) a comet appeared in
the W. It swept Serpens and Hercules, and was 10 cubits long. — (Ma-tuoan-lin ;
Williams, 54.) It was seen in October for 3 weeks. — (Chronicon S. Flortntii, in
Bouquet's Collection, vols. vii. and ix.) Another Chinese account dates this comet for
Aug. 7. — (Williams, 64.)

[310.] 942. In October a comet appeared for 3 weeks in the W. : it had a long
tail, and advanced gradually Eastwards to the meridian. — (Chronicon Andegarense.)
Several authorities say that the comet appeared for only 2 weeks, from Oct. 18 to Nov.
I. — (Witichindus, Annalts. Francofurti, 1621.) All remark that a great mortality
amongst oxen occurred in the following year in consequence of the comet's ap-
parition [?].

[311.] 943. On Nov. 5 a comet appeared in the E. : its K. A. was greater than
that of a Virginis by 9°. Its tail was i cubit long, and pointed to the W. — Ma-tuoan-
lin; Williams, 54.) Comets were seen for 14 nights. — (Annalista Saxo; in Eccard'a
Corpus Historicum, Lipsise, 1723.)

[312.] 945. '"Theotilon, Bishop of Tours, set out from Laon to return to his dio-
cese, but was overtaken on the road by the malady of which he died. He had just
partaken of the Holy Sacrament, when a luminous sign was seen traversing the sky.
This sign was a cubit long. Its brilliancy was such that it gave light in the middle
of the night to those who were charged to conduct to Tours the body of the prelate by
a journey of 200 miles." — (Frodoardus, Chronicon.} Pingre considers that, apart from
other testimony, the duration determines this to have been " une veritable comete." —
(Comet, i. 356.)

[313.] 956. On March 13 a comet was seen in the cross of Orion. Its tail pointed
towards the S.W. — (Ma-tuoan-lin ; WTilliams, 54.) It is possible that " March 13 "
may not accurately represent the original, owing to a doubt attending the Chinese
method of computation.

[314.] 959. At the time of the death of the emperor Constantine Porphyro-
genitus a gloomy and obscure star appeared for some time. — (Constant. Porph.,
Incerti Continuatoria, p. 289.) Constantine died on Nov. 9. It was seen from Oct.
17 to Nov. i. — (Tackius, •Cee/t anomalon, id esf, de Cometis scriptum. Gissae-Has-
sorum, 1653.)

Biot has an extraordinary star in January, and another in'February, 962 : he
assumes these to be one and the same, and both to be identical with No. 13 of the
" calculated " comets.

[315.] 975 (i). In April a comet was seen in the E. — (Williams, 55.)

[316.] 975 (ii). A bearded comet was visible from August to October. — (Cedrenus,
Compendium Historiarum, p. 683.) It was first seen on Aug. 3 in the sidereal
division of 8 Hydrae, between 7 and 9 hours of the morning ; the tail was 40 cubits
long. The comet traversed Cancer and came to the sidereal division of 7 Pegasi,
and lasted altogether 12 weeks, during which time it passed through u sidereal
divisions. — (Gaubil.) It became visible on the 5th moon, which terminated on
July n. — (De Mailla, viii. 58.) There is much reason to believe that this comet is
identical with the celebrated ones of 1264 and 1556. Presuming the PP. to have
taken place at the end of July, the above accounts will all harmonise extremely
well. — (Pingre, i. 357.)

[317.] 981. A comet appeared in the autumn. — (Burkhardus, Monachus S. Galli,
Hisioria, i., in Goldastus's Alamannicarum Rerum. Francofurti, 1606.)

[318.] 983. On April 3 an extraordinary star appeared near /3 Leonis. More
precisely, it was between 0 and 77 Virginis : it approached v, £, -a Virginis, and went
to the N. — (Biot.*) A comet appeared. — (Lubienitz, &c.)

[319.] 985. A comet appeared during the pontificate of John XVI. — (Platinse,
De Vitis Summorvm Ponffficorum. Coloniae, 1540.)

[320.] 989 (i). On Feb. 10 a comet appeared to the N. of a and 0 Pegasi. It
was i° long, and lasted 14 days. — (Gaubil ; Annalista Saxo.) Pingre' seems to
question the value of Gaubil's citation. — (Cornet, i. 620.) Possibly the chronicle

CHAP. VIII.] Catalogue.— No. II. 573

cited above refers to the and comet of this year, the orbit of which has been cal-
culated by Burckhardt.

[321.] 990 (i).* On Feb. 2 an extraordinary star appeared in the division of
•y Corvi : it retrograded towards v, K, v, <p Hydrse and disappeared, having travelled
40° in 10 weeks. — (Biot.)

[322.] 990 (ii). A star, with a long tail, appeared in the N. After some
days it was in the W., and its tail extended to the E. — Romualdus Salernitanus,
Chronicon, in Muratori's Collection, vol. vii.) It was seen in August — September in
the W.— (Couplet.)

[323-] 995. On Aug. 10 a comet was seen. — (Hepidannus, Annalts, in Bouquet's
Collection, vol. vii ; Florentius Vigorniensis, Chronicon.)

[324.] 998. On Feb. 23 a comet, i cubit long, was seen to the N. of a and
/3 Pegasi. It lasted a fortnight. — (Couplet; De Mailla, viii. 131; Ma-tuoan-lin ;
Williams, 55.)

[325.] 1000. A comet appeared on Dec. 14 for 9 days. It frightened everybody.
— Iperius, Chronicon, xxxiii.) A meteor appeared at the same time, and the majority
of writers confound the one with the other. This may be the real explanation of
the fact that a slight doubt hangs over the year as to whether it was 999 or 1000.
Pingre thinks was clearly the latter.

[326.] 1003 (i). In February a comet was seen; it disappeared near the Sun, and
was only seen for a few days a little before the rising of that body. — (Hepidannus,
Annales.)

[327.] 1003 (ii). A comet appeared during the pontificate of John XVII. —
(Chronicon Nuremburgense.') It lasted a long time. — (Chronicon Stederburgense.)
It was discovered in China on Dec. 23, when it was situated in the sidereal divisions
of n Geminorum and 9 Cancri. It approached very near 0, r, t, v, ty Geminorum,
passed by a, /3 Aurigse, j8 Tauri, to the cross of Orion, and disappeared after 30 days.
Its tail was 4 cubits long, and like a vase in shape. — (Ma-tuoan-lin; Williams, 56.)
Some European writers refer to a comet in 1004, which is probably this one prolonged.
Pope John was elected on June 13, and lived only till Dec. 7. So can there have
been 2 comets between June 1003 and Dec. — Jan. 1003-4?

[328.] 1005. A comet was seen in the S. — (Alpertius, De Diversitate Temporum ;
in Eccard's Collection, vol. i.) It was in the W. in September, at the commencement
of the night, and lasted 3 months. It shone with great brilliancy, and did not set
till cock-crowing. — (Glaber Rudolphus, Annales, in Duchesne's Collection, vol. iv.)
It was seen in China in September — October, within the circle of perpetual apparition.
— De Mailla, viii. 158.) On Oct. 4 an extraordinary star appeared in the circuin-
polar regions near 0, y Draconis ; it passed by some little stars between ^ Draconis
and S Ursse Minoris to some little stars in Camel opardus, N. of Cassiopeia. It only
lasted ii days. — (Biot.*)

[329.] 1012. A comet of extraordinary grandeur was seen for 3 months in the
Southern part of the heavens. — (Hepidannus, Annales,*)

[330.] 1015. A comet was seen in February. — (Protospatas, Breve Chronicon,
in Muratori's Collection, vol. v.) In China on Feb. 10, 1014, a comet was seen
in the W. — (Williams, 64.) Probably one and the same comet, and some error
in the year.

[331.] 1017. A comet, like a large beam, was seen for 4 months. — (Sigebertus,
Chronographia, in Bouquet's collection, vol. iii; Gerbrandus, Chronicon Belgicum,
ix. 8.) Hevelius says that it appeared in Leo, but gives no authority for this
statement.

[332.] 1018. On Aug. 4 a comet appeared to the N. E. of (it would seem) f Ursse
Majoris ; its was 3 cubits long, and went Northwards. It passed by « and 6, v, </>
Ursae Majoris, and thence Southwards— (Ma-tuoan-lin ; Williams, 56) — by a route
which Pingre says must have been erroneously stated. However, it is certain that a
comet appeared this year in the Polar regions, and that it lasted about 6 weeks. —
(Ditmarus, Chronicon, viii.) It is less certain that its length increased to 30°, and
that passing Leo it disappeared in Hydra.

574 Comets. [BOOK IV.

An extraordinary star appeared on June 10 to the N.W. of K Leonis : it advanced
rapidly by a Leonis to the vicinity of /3 Leonis : it touched 0 Virginia, and passing
i Leonis (or 5 Virginis) caine to the N.W. of v, o, (, it Virginia. It lasted 1 1 weeks. —
(Biot.*)

[333-1 1023. A cornet appeared in Leo during the autumn. — (Ademarus,
Chronicon, in Bouquet's Collection, vol. x.) The original account contains much that
is certainly fictitious.

[334.] 1024. A comet appeared the year before the death of Boleslas I. king of
Poland. — (Dlugossus, Historia Polonica. Francofurti, 1711.)

[335.] 1032. On July 15 an extraordinary star appeared in the N. E. It ap-
proached /3 Leonis, and threw out a tail. On July 27 it disappeared. — (Biot.*)
Cedrenus speaks of a brilliant star having passed from S. to N. this year. — (Compen-
dium Historiarum, 730.)

[336.] 1033. A comet, 2° long, appeared on March 5 to " the E. of the N.
country" [N. E. ?].— (Ma-tuoan-lin.) It appeared on March 9 about the loth hour
of the night, and lasted till sunrise for 3 nights. — (Frugmentum Hi#tori<e Fran-
corum, i. and ii, in Bouquet's Collection, vol. viii.)

[337.] 1034. A column of fire was seen in the E. in September. Its summit in-
clined towards the S. — (Cedrenus, Compendium Historiarum, p. 737-) It appeared
between «, v, \, /*, <p Hydrse et Crateris. — (De Mailla, viii. 199 )

[338.] 1035 (i). On Sept. 15 a comet appeared in the sidereal divisions of v Hydras
and a Crateris. It was 7/^5- cubits long, and lasted 12 days. — (M;i-tuoan-lin ;
Williams, 56.) Possibly this is identical with the preceding. If 1035 is the right
year, probably the column of fire was a meteor.

[339.] 1035 (ii). On Nov. n a comet, with a faint tail, appeared near a, /3
Piscium. — (Ma-tuoan-lin.) For Nov. ii, 1035, Williams (p. 56) reads Jan. 15,
1036.

[340.] 1041. Comets appeared. — (Glycas, Annales, p. 316. Parisiis, 1660.)

[341.] 1042. On Oct. 6 a comet appeared. Its motion was from E. to W., and it
lasted through the month. — (Glycas, Annales, p. 319.)

[342.] 1046. A comet appeared in the isth year of Henry I. of France. — (Godellus,
Chronica, in Bouquet's Collection, vol. xi.)

[343.] 1049. On the morning of March 10, before sunrise, a comet was seen near
# Aquarii, and o Equulei ; it passed by the head of Orion, Musca, and the horns of
Aries, and lasted 16 weeks. — (Gaubil.) " La route qu'on assigne a cette comete n'est
pas naturelle."— (Pingre, i. 372.) Ma-tuoan-lin is scarcely more intelligible. Pingre
is disposed to think that Gaubil has made a mistranslation. The words rendered
"head of Orion" and "Musca," united into one word, closely resemble the word
standing for " the circumpolar region." This affords a certain amount of explanation
for the incongruity, and Williams seems to adopt it in saying (p. 56) that the comet
passed from the sidereal division of £ Aquarii through the circumpolar regions to the
sidereal division of /3 Arietis.

[344.] 1056. In July — August a comet appeared in the circumpolar regions. — (De
Mailla, viii. 245.) It seems to have passed southwards to Hydra, but Gaubil places
it in the head of Orion when first seen. Ma-tuoan-liu agrees with De Mailla. It
was 10 cubits long, and on Sept. 25 had disappeared. [N.B. The head of Orion is
Txoui, the other region Tee-ouey ; pronunciation nearly identical, hence possibly a
confusion. See note to No. 343, ante.~\ WTilliams's account (p. 57) is simply that
a comet was seen within the circle of perpetual apparition, and that it passed through
the " seven stars" [of Ursa Major?].

[345.] 1058. "The death of Casimir, king of Poland, was announced by a comet,
which appeared for several nights." (Hennenfeld, Annales Si1e*ice.} It lasted
the whole of Easter week. — (Morigia, Chronicon, i., in Muratori's Collection, vol.
xii.)

[346.] 1060. Shortly after the death of Henry, king of France, a comet with a
long tail appeared in the morning. — (Wilhelmus Malmesburiensis, De Gestis Regain,
') Henry died on Aug. 29.

CHAP. VIII.] Catalogue. — No. II. 575

[347.] 1067. A comet appeared at the death of Constantine Ducas. — (Chronicon
Andegavense.} This event happened in May.

[348.] 1069.* On July 12 an extraordinary star appeared in the sidereal division
of 72 Sagittarii : on July 23 it traversed 7, 8, «, A. Sagittarii. — (Biot.)

[349.] 1070.* On Dec. 25 an extraordinary star appeared in Aries, below Musca. —
(Biot.)

[350.] 1071-8. During the reign of Michael Parapinatius comets frequently
appeared. — (Curopalataa, Excerpta e Breviario Historico, p. 856. Parisiis, 1647.)

[351.] 1075 (i). A great comet was seen in Morocco, during July — August. (Ibn
Abi Zer'a, Annales Regum Maurit. : Aist.Nach.,No. 2811. vol. cxviii. Nov. 9, 1887.)

[352.] 1075 (ii). On Nov. 17 a comet, 3° long, appeared in the S. E. in the middle of
the sidereal division of 7 Corvi. The day following, the tail was bifid and curved.
On Nov. 19 its length was 5 cubits ; on Nov. 20, 7 cubits, and it pointed towards
T] Corvi. On Nov. 29 the comet entered the Hyades and disappeared. — (Ma-tuoan-
lin; De Mailla, viii. 285.) For " Hyades" Williams (p. 59) reads " the clouds."

[353.] 1080 (i). On Jan. 6 a comet passed over the sidereal division of p Scorpii. —
(Williams, 64.)

[354.] 1080 (ii). On Aug. 10 a comet, 10 cubits long, appeared to the S. of Coma
Berenicis : it was curved, and pointed to the S. E. Its R. A. exceeded that of 7 Corvi
by 8° or 9°. On Aug. 13 it moved towards the N. W. [Pingre does not understand
what is meant], and its R. A. exceeded that of a Crateris by 9°. On Aug. 15 it was
3 cubits long, and curved, and penetrated Coma Berenicis. On Aug. 20 the comet
passed very near a, 7 Leonis. On Aug. 24 it could not be seen. — (Ma-tuoan-lin ;
Williams, 59.)

[355.] 1080 (iii). On Aug. 27 a comet, which Ma-tuoan-lin regards as the pre-
ceding again visible, appeared in the middle of the sidereal division of v Hydrae ; it
lasted till Sept. 14. Pingre is the authority for disinguishing these comets. — (Comet.
i. 625.)

[356.] 1096. On Oct. 7 a comet like a sword appeared in the Southern part of the
heavens. — (Annalista Saxo.)

[357.] 1097 (ii)- On Dec. 6 a comet was seen in the W. — (Williams, 64.)

[358.] 1098. On June 3, "the night of the capture of Antioch," a comet shone
out with great brilliancy. — (Robertus, Historia Hierosolymitana, v.)

[359.] 1101. On Jan. 31 a large comet appeared in the W. after sunset. — •
(Monarchies Sinicce Synopsis Chronological)

[360.] 1106. A splendid comet appeared this year. It was first seen on Feb. 4,
within i£ feet of the Sun, between the 3rd and gth hours of the day. In Palestine
it became visible on Feb. 7, and in China 3 days later. On Feb. 7 it was in the
sidereal division of 0 Andromedae, and it passed through the sidereal divisions of
/3 Arietis, a Muscae, the Pleiades, and e Tauri. The comet remained visible for
7 or 8 weeks, and had a tail 63° long. — (Matthseus Paris, Historia Major ; Gaubil ;
Ma-tuoan-lin ; Williams, 60 ; and many others.) [Williams treats Ma-tuoan-lin's
account as pertaining to a meteor, but this is out of the question under the circum-
stances.]

[361.] 1109. In December a comet appeared near the Milky Way, with a tail
pointing towards the S. — (Hemingfort, Chronica, i. 33.)

[362.] 1110. On May 29 a comet, with a tail 6 cubits long, was seen in the
sidereal division of 0 Andromedae and 0 Arietis. It went Northwards towards
the Pole, and then became visible throughout the night, and ultimately disappeared
in the R. A. of about 4h. — (Chronica llegia IS. Pantaleonis ; Ma-tuoan-lin;
Williams, 60.)

[363.] 1113. A great comet appeared in May.— (Matthaeus Paris, Historia Major;

Matthseus Westmonasteriensis, Flores Hisloriarum.')

[364.] 1114. A cornet at the end of May. It lasted several nights, and had a long
tail. — (Henricus Huntingdoniensis, Hintoria ; Aiinale.i Waverleientes.)

576 Comets. [BOOK IV.

[365.] 1115. An extraordinary star in April — May, near a, B, 7 Leonis. It had a
long tail. — (De Mailla, viii. 377 ; Annales De Nargan ... a tempore S. Edwardi
Confess.} Probably a cornet, though no mention is made of movement.

[366.] 1125. A comet preceded the death of Uladislas, king of Bohemia. —
(Dubravius, Hisloria Bojemica, xi. HanovizE, 1602.)

[367.] 1126 (i). In June — July a large comet was seen within the circle of
perpetual apparition. It passed from a Herculis towards 6, </> Ursa Majoris. — (De
Mailla, viii. 443.) These Chinese positions will not harmonise with the statement of
the Latin historians (Sicardus, Chronicon, in Muratori's Collection, vol. vii.), unless
we suppose the cornet to have been in Ursa Major at the end of July, or even at the
beginning of August. — (Pingie, i. 392.) Williams (p. 61) dates this comet for May
20, and thinks the reading a Ursce Minoris to be preferred to a Herculis.

[368.] 1126 (ii). In the moon beginning on Dec. 15 a great comet was seen in
China, near the horizon. (De Mailla, viii. 447 ; Ma-tuoan-lin ; Williams, 61.)

[369.] 1131. In September — October a great star appeared. — (Ma-tuoan-lin; Wil-
liams, 61.)

[370.] 1132 (i). On Jan. 5 a comet was seen. — (Ma-tuoan-lin ; Williams, 61.)

[371.] 1132 (ii). On Oct. 2 a comet appeared; on Oct. 7 it was in the sidereal
division of a Muscse; on Oct. 27 it had disappeared. — (Ma-tuoan-lin; Florentius
Vigorniensis, Chronicon — continuation.) Williams (p. 61) makes this comet to have
been visible from Aug. 14 to Sept. 3.

[372.] 1133. On Sept. 29 a comet was seen near 0, v, <f> Ursse Majoris. — (Williams,
65-)

[373-1 H38. In August — September a comet appeared. — (De Mailla, viii. 524;
Biot.*)

[374.] 1142-3. In December — January a cornet appeared. — (Monarchic f-Hnicts
Synopsis Chronological)

[375.] 1145. On April 15 a comet appeared. — (Cat ndarius Ambrosiance Biblio-
theccB, in Muratori's Collection, vol. ii.) It is not easy to reconcile the conflicting
accounts of its course. In China it was first seen in the E. on April 24; on May 14
it was in the sidereal division of 5 Orionis [and must have had a considerable North
latitude, or it would not have been visible.— Pingre,] and had a tail, pointing to the
N. E., 10° long. On June 4 it was like a star ; on June 9 it was stationary between
a Hydrae et Crateris, and remained visible till July 14. — (Gaubil.) On April 26 it
came from the constellations of the E. country. [These are probably the first 7 of
the Chinese zodiac, commencing at o Virginis. — Pingre.] After 50 days it disappeared.
On July 13 it reappeared in the cross of Orion, and lasted 15 days. — Ma-tuoan-lin,
who adds that a comet was seen on June 4 [when the above was still visible].)
Hind considers the former to be certainly Halley's comet, and that it passed PP. on
April 29. Possibly Gaubil's " May 24" and the position assigned thereto is apocry-
phal. Pingre's note was made before Ma-tuoan-lin's account was in his possession :
he professes himself unable to decide. But the comet of July 15 might have been
different from the 5O-day one which disappeared on June 15 ; in which view of the
matter the latter might have been Ma-tuoan-lin's June 4 comet. Williams (p. 62) is
very brief.

[376.] 1146. A comet was seen for a long time in the W. — (Chronica Regia S.
Pantaleonis.)

[377.] 1147 (i). The emperor Conrad set out in May for Palestine ; his departure
was preceded by a cornet. — (Historia Episcoporum Virduncnsium.) On Feb. 8
a comet, 10° long, appeared in the E. for 15 days.- — (Gaubil.) On Jan. 6 (or ii) a
comet appeared in the S.W. of the sidereal division of a Aquarii and f, 0 Pegasi. —
(Ma-tuoau-lin.) This writer says that on Feb. 12 (or 17) another comet appeared in
the N. E. in the sidereal division of « Aquarii, and that on March 5 (or 7) it had
ceased to be visible.— (Williams, 62.)

[378.] 1147 (ii). About Aug. 20 in Japan a comet was seen. — (Kaempfer,
Ilistoire du Jupon, II. iv.)

CHAP. VIII.] Catalogue.— No. II. 577

[379.] 1152 or 1156. Ma-tuoan-lin, the former; Gaubil and the Great Annals of
China, the latter. On August 15 a comet was seen in the middle of Gemini ; the
next day it was like Jupiter, and 2°long. On the day Kouey-tcheow, or Aug. 22, H52>
a comet passed near 0, T, «, v, <p Geminorum. — (Ma-tuoan-lin.) On July 26 a comet,
10° long, was seen in the feet of Gemini. On the day Kouey-tcheou, or Aug. 2. 1156,
it was near 0 Geminorum. — (Gaubil.) Williams, (p. 62) renders Ma-tuoan-lin's year
as 1151, and some other difficulties occur in his account.

[380.] 1155. On May 5 a comet was seen. — (Chronicon Monusterii Admontensis.)
[381.] 1162. On Nov. 13 a great comet appeared in the square of Pegasus: it went
towards x and ^ Aquarii. Its tail was more than 10° long. — (Gaubil.)

[382.] 1165 (i and ii). Two comets appeared this year in August before sunrise ;
the one in the N., the other in the S. — (Chronica de Mailros.)

[383.] 1181. In July a comet was seen. — (Chronica de Mailros.} It appeared
shortly before the death of Pope Alexander III. — (Cavitellius, Annales Cremonenses.)
This happened on Aug. 30. Gaubil mentions a new star, seen on Aug. 1 1 , under the
footstool of Cassiopeia. It disappeared after 156 days. Nothing is said as to its
having had any movement. Between Aug. 6, 1181 and Feb. 6, 1182, an extra-
ordinary star was visible. From the division of £ Andromedse it passed over some
little stars in Camelopardus, N. of the head of Ursa Major. — (Biot.*)

[384.] 1188. A comet was seen all over England. It signified the death of
Henry the King. — (Annales Cambrics.)

[385.] 1198. In November a comet appeared for 1 5 days. It announced the death
of King Richard I. of England. — (Eadulphus Coggeshale, Chronicon Anglicanum.)
Richard died on April 6, 1 1 99.

[386.] 1204. In the year of the capture of Constantinople by the Latins a great
comet appeared. — (Sicardus, Chronicon.)

[387.] 1208. A comet appeared. — (ChroniconWeichenstephenense.} A brilliant star
like a fire appeared after sunset for 2 weeks ; the Jews regarded it as a sign of the
approach of the Messiah. — (Caesar Heisterbacensis, Excerpta Historiarum Memora-
bilium.}

[388.] 1211. In May a comet was seen for 18 days in Poland. — (M. Cromerus,
Polonia, vii. Colonise Agrippinae, 1589.)

[389.] 1214. In March two terrible comets were seen. — (Boethius, Scoiorum
Historia, xiii.) No doubt a single comet with a considerable North Declination,
which would accord with the statement of one comet preceding and the other
following the Sun. One author associates the comet with a solar eclipse which
happened in 1215.

[390]. 1217. " In the autumn, after sunset, we saw a beautiful sign ; a star which
soon sank below the horizon. This star was turned towards the South, pointing
a little Westwards. Its position faced the crown of Ariadne." — (Conradus, Abbas
Urspergensis, Chronicon.} Pingre" understands the above expression to mean that
the comet's azimuth was as much W. of S. as that of Corona Borealis was W. of N. —
(Cornet, i. 398.)

[391.] 1222. In the months of August and September a fine star of the Ist
magnitude, with a large tail, appeared. When first seen it was near the place where
the Sun sets in December. — (Annales Warerleienges, &c.) It was observed in
China between the feet of Virgo, Arcturus, and Coma Berenicis. It disappeared on
Oct 8. — (Gaubil.) On Sept. 25 it came from 77 Bootis. The tail was 30 cubits long.
The comet traversed the sidereal divisions of a, 0, &c. Librae, /3, 5, &c. a, a, &c.
Scorpii, and then perished, after remaining in sight for 2 months. — (Ma-tuoan-lin.)
With this comet we lose the invaluable guidance of this able Chinaman. For
" Sept. 25 " Williams (p. 63) reads " Sept. 15."

[392.] 1223. Early in July a comet appeared in the Western heavens in the
evening twilight. It was looked upon as the precursor of the death of Philip Augustus
King of France. — (Cltronique de France, MS.) Most probably Halley's comet.—-
(Hind.)

578 Comets. [BOOK IV.

[393.] 1226. On Sept. 13 a comet appeared between ij, T, v Bootis and Coma
Berenicis. It pointed towards a Bootis. On Sept. 12 (sic} it disappeared. —
(Williams, 65.)

[394.] 1227. A comet appeared. — (Matt. Paris., Abbrev. Chronic?)

[395-] 1230. A comet appeared. — (Dubravius, Historia Bojemica, xv.) On
Dec. 15 an extraordinary star appeared between Ophiuchus and Serpens below
the Stars Fand D in the head of Cerberus. On March 30, 1231, it had disappeared. —

(Biot.)

[396.] 1232. On Oct. 17 a comet, 10° long, was seen in the sidereal division of
a Virginia. On the I2th day of its apparition it was 20° long. On the i6th day
it was close to the Moon. On the 27th day, at the 5th watch, it reappeared in the
S.E., and was 40° long; it was finally lost sight of on Nov. 14. — (De Mailla, ix. 173 ;
Gaubil ; Williams, 63 ) It began to disappear on Dec. 2. — (Biot.) The date
Nov. 14 is determined by Pingre1, but it seems open to question. It must be added that
Biot states that it (the comet) was not seen on the " i6th day" during the moon-
shine: he likewise doubts whether the " I2th day" (and consequently the other days)
means that day of the moon or of the comet's apparition ; Pingre says the latter, ' ' sans
doute." Another entry by Williams (p. 65) assigns this comet to 1237, Sept. 21,
bnt the preponderance of testimony is in favour of 1232.

[397-] 1239. A comet was seen in February. — (Monarchies Sinicce Synopsis
Chronological) Shortly after the birth of Edward, son of Henry III. of England,
at the commencement of 1238, a splendid comet appeared for several days before
sunrise. — (Polydorus Vergilius, Anglica Historica, xvi.) Edward was certainly born
in 1239, so no doubt the Chinese date is the correct one.

[398.] 1240. On Jan. 25 a comet was seen ; at the end of that month it was
observed in the W. During February it continued to appear in the same quarter of
the heavens, its tail pointing to the E. — (Rolandinus, Chronicon, v. i, in Muratori's
Collection, vol. viii.) In China, on Jan. 31, a comet was seen near a Pegasi ; on
Feb. 23 it passed near a and /3 Cassiopeise. On March 31 it began to disappear. —
(Biot.)

[399-1 1250. A comet appeared in December, about the time of the death of the
Emperor Frederick II. — (Gesta Trerirensium Archiepiscoporum, No. 266.)

[400.] 1254. In November a comet appeared. — (Petrus Pictaviensis, Chronica,

MS.) '

[401.] 1262. A comet appeared for several months. — (Crusius, Annales Svevici,
III. ii. Francofurti, 1595.)

[482.] 1263. In July — August a comet was seen in the E. — (Gassarus, Annales
Augustlurgenses.) Of doubtful authenticity, the writer not being contemporary.

[403.] 1265. A comet appeared at the beginning of autumn and lasted till the
end of that season. It was visible from midnight. — (Chronicon Mellicense, in Pez's
Collection, Lipsiae, 1721.) It was first seen in September. — (Franciscus Pipinus,
Chronicon, in Muratori's Collection, vol. ix.) It is just possible that there were

2 comets this year ; one visible July — September, the other September — November.

[404.] 1266. In August, before daybreak, a comet was seen near the sign Taurus. —
(Gregoras, Historia Byzantina. Parisiis, 1/02.) A visibility of 3 months may be
inferred.

[405.] 1269. In the 2oth year of the reign of Alexander, King of Scotland, a
very fine comet appeared towards noon [sub meridiem]. — (Boethius, Scotorum
Historia, xiii.) "Towards the S." would be a good rendering. — (Pingre', i. 415.) It
was observed in the E. in August and September. — (Malvecius, Chronicon Srixiense,
VIII. Ixxviii, in Muratori's Collection, vol. xiv.)

[406.] 1273. On Dec. 5 a new star appeared in the Hyades. It moved through
Auriga, past 0, <t>, v Ursse Majoris, e, a, p Bootis to Arcturus, and remained visible

3 weeks. — (Gaubil.)

[407.] 1274. Three days before the death of Thomas Aquinas, a comet appeared. —
(Guillelmus De Thoco, Vita S. Thomce Aquinalis, x. 60.)

CHAP. VIII.] Catalogue, — No. II. 579

[408.] 1277. On March 9 a comet, 4° long, was seen in the N. E. — (Gaubil ;
Williams, 66.)

[409.] 1285. In this year a great comet appeared ; its tail pointed towards the
N. W. — (Ptolemseus Lucensis, Historia Ecclesiastica, XXIV. xvii.) On April 5
a very brilliant star was seen. — (Pontanus, Bohemia Pia, \. Francofurti, 1608.)

[410.] 1293 or 1294. In February 1293 or January 1294 a coniet was seen in the
circumpolar regions; it passed through the square of Urea Major. — (Couplet; Gaubil.)
On Nov. 7, 1293, a comet appeared as above. It was i cubit long, and lasted a
moon. — (Biot ; Williams, 67.)

[411.] 1298. Celestial signs announced the death of Beomond, Archbishop of
Treves [oh. Dec. 9, 1299]. In the preceding year a comet was seen, during 12 con-
secutive nights, at about the 3rd hour of the night. Its head was in the N. and its
tail trended Southwards. — (Gesta Trecirensium Arc/tiepiscorum.)

[412.] 1301 (ii). Before Christmas a comet was seen in the W. after sunset. It
set before midnight, and lasted 15 days. On Dec. I it was in Aquarius and Pisces. —
(Ricobaldus, Compilatio Chronological)

[413.] 1304. On Feb. 3 a comet was seen in the sidereal division of a Pegasi ; it
passed towards the circnmpolar regions, and by the tail of Cygnus and Cepheus ; it
lasted II weeks. — (Oe Mailla, ix. 483.) Its tail was more than I cubit long, and
pointed towards the S. E. when discovered ; afterwards it pointed towards the N. W.
On Feb. 3 it was ia the \ith degree of a Pegasi; it subsequently swept it Cygni,
X Andromedse, and entered the circumpolar regions. — (Biot ; Williams, 68.)

[414.] 1305. Three days before and 3 days after Easter, or from April 15 to
April 21, a long tail was seen. — (Botho, Chronica Brunsioicenses.}

[415.] 1313. From April 13 or 20 a comet was seen in the E. part of the sidereal
division of /i Geminorum. It remained visible a fortnight. — (Biot ; Gaubil ;
Williams, 68 ; Massatus, Ilisioria Augusta, xv. 4, in Muratori's Collection, vol. x.)

[416.] 1314. In October [?] a comet appeared in the latter part of [the sign?]
Virgo, towards the N. — (Paulus Cygnaeus, Chronicon Citizeiise.} The accounts are
very vague and contradictory. One writer dates its visibility from May I, and says
that it remained visible for 6 months. — (Pontanus, Ilisioria Gelrica, vi.)

[417.] 1315. On Oct. 29 a comet was discovered in the region lying around 3
Leonis. On Nov. 28 it was in the circumpolar regions. It then traversed 15 sidereal
divisions from that of 7 Corvi to that of 7 Pegasi. It remained in sight till March
n, 1316. — (Gaubil ; Biot ; Williams, 68.) European writers say that 2 comets were
visible from Dec. 1315 to Feb. 1316. The first was much larger than the second. —
(Hegecius, De Stelld Novd anni 1571, 4*cv The N. P. D. of the larger one, on Dec.
25, at i7h, was 18° 38'; on Jan. 15, at i/h,it was only 9° 49'. — (Massatus, De Gestis
Italicorum, vii. 14, in Muratori's Collection, vol. x.) Uhose who speak of the second
comet say that it appeared in the E. — (Chionicon Rotomageme.) Can it be that after
all there was only i comet ?

[418.] 1334. In August a comet, with a tail 7^ feet [degrees ?] long, was seen. —
(Monarchic Sinicce Synopsis Chronoloijica.'}

[419.] 1337 (ii). A comet was seen in Cancer during the visibility of the Great
Comet of this year. It lasted 2 months. — (Giovani Villani, Chroniche, XI. Ixvi, in
Muratori's Collection, vol. xiv.) The Great Comet was visible for 3 months or more,
from May. Chinete writers seem to speak of 2 comets. The lesser one passed from
a, 0, i] Cassiopeise to Corona Bcrcalis, and lasted from May 4 to July 31.

[420.] 1338. On April 15 a comet was discovered ; the Sun being then in Taurus,
the comet was in Gemini. Its movement was from W. to E. with a N. Declination.
It followed the Sun, and set about midnight. On April 17 it was in 24° of Gemini.
From a note by Friar Giles it appears that its latitude was then 17° or 18° N. It
remained in sight a fortnight or more. — (Chronicon Eotomagenxe.}

[421.] 1340. On March 24 a comet was discovered in the 7th degree of the
sidereal division it Scorpii. It went slowly to the N.W. " When first seen it was in
the latter part of Libra ; then it retrograded at the rate of 5° a day, till it came to

580 Cornet*. [BOOK IV.

Leo, where it disappeared." It was visible 32 days. — (De Mailla, ix. 576 ; Gaubil ;
Williams, 71 ; Gregoras, Histuria Byzantina, XI. vii. 5. Fol. Parisiis, 1702.) Biot's
chronicler states that this comet was in shape like a bale of cotton !

[422.] 1345. At the end of July a comet appeared near the head of Ursa
Major ; it advanced day by day to the zodiac, and when it reached the latter part of
the sign Leo, where the Sun was, it disappeared. — (Gregoras, Historia Byzantina,
XV. v. 6.)

[423.] 1347. In the reign of Louis of Bavaria a comet appeared for 2 months. In
Italy it was seen during 15 days in August in 16° of Taurus, and the head of Medusa.
— (Chronicon Nnremburgense.*)

[424.] 1356. On Sept. 21 a comet was seen precisely in the E. at 17° in the
sidereal division of v Hydrse ; it remained visible till Nov. 4. When discovered
it was near a Leonis, and had a tail i c,ubit long which pointed to the S. W. —
(Gaubil; Biot j Williams, 71.)

[425.] 1360. A comet was seen in the E. for a few days from March 25. —
(Chronicon Zvetlense, in Fez's Collection ; De Mailla, ix. 633.) For March 26
Williams (p. 71) reads March 12.

[426.] 1362 (ii). On June 29 a comet, with a tail i cubit long pointing to the
S. E., was seen in the circumpolar regions. Its R. A. was 2/^° greater than that of
/3 Capricorni [Biot, 9^%°]. It went to the S.W. On July 6 the luminous envelope
swept & Draconis ; on Aug. 2 the comet had disappeared, having lasted 5 weeks. —
(Gaubil ; Williams, 72.) De Mailla says that the comet appeared near a and /3
Capricorni, and that its tail was more than 100 feet long. — (Hist. G6n~ ix. 640.)
This account is altogether irreconcileable with Gaubil's. Can there have been
3 comets this year, or does not De Mailla rather refer to the first comet, the orbit of
which has been calculated, and therefore appears in Catalogue I. ?

[427.] 1363. On March 15 a comet appeared in the E. It was visible dm ing the
current moon. — (Biot ; Williams, 72.)

[428.] 1368. In February, March and April, a comet appeared in the evening in
the W. or N. W. to the N. of the Pleiades. — (Couplet ; Walsingham, Historia
Anglica.} On Feb. 7 a comet was seen in the sidereal divisions of the Pleiades and
e Tauri. On April 7 a comet was seen in the N.W. between T, K, p and a, 7, rj Persei ;
the tail was 8° long, and pointed towards 0, v, (p Ursae Majoris. It ultimately dis-
appeared to the N. of a and /3 Aurigse. — (Biot; Williams, 74.)

[429.] 1371. On Jan. 153 very great comet was seen in the N. Its tail was
directed towards the S. — (Bonincontrius, Annales, in Muratori's Collection, vol. xii.)

[430.] 1373. In April — May, three [?] comets entered the circle of perpetual
apparition. — (Biot.)

[431.] 1376. On June 22 a great comet appeared in Cetus near i, 0, 77; it tra-
versed S, t, n, v Piscium, v Persei, entered the circle of perpetual apparition, swept
9, v, <p Ursae Majoris, and directing itself towards S, «, it, p Draconis, entered the
sidereal division of v1 or 39 Hydrae. It disappeared on Aug. 8. — (Biot* ; Gaubil ;
Williams, 87.)

[432.] 1380. On Nov. 10 a comet appeared. — (Cygnaeus, Chronicon Citizense.}

[433."] 1382 (i). On March 30 a comet appeared. — (Botho, Chronicon Bruns-
wicenne!)

[434.] 1382 (ii). On Aug. 19 a comet appeared in that part of the heavens where
the Sun sets in June. It lasted for 15 days, and was seen 2 hours before sunrise,
though these two latter statements may be open to doubt. — (Annales Vicentini ; in
Muratori's Collection, vol. xiii.)

[435.] 1382 (iii). In December a comet appeared in the W. for more than a
fortnight. — (Walsingham, Higtoria Anglica.}

[436.] 1388. On March 29 a star appeared in the Eastern part of the sidereal
division of 7 Pegasi. — (Biot* ; Williams, 88.x

CHAP. VIII.] Catalogue.— No. II. 581

[437.] 1391. In May a small comet appeared near the stars of Ursa Major. Its
tail was not very bright. — (Annales Forolicienses ; in Muratori's collection, vol. xxii.)
Biot says that 2 comets appeared on the 23rd of this month ; one entered the circle
of perpetual apparition between a and t Draconis and passed to the S. of 0 Draconis,
and the other passed by the N. of Camelopardus and swept the Pole-star. —
(Williams, 74.)

[438.] 1399. In November a star of extraordinary brilliancy was seen ; its tail
was turned towards the W. ; it lasted only a week. — (F. E. Du Mezerai, Histoire de
France. Abridged ed., 4to. Paris, 1668.)

[439.] 1402 (i). About Feb. 8 a comet appeared, which afterwards became very
brilliant, so much so as to be visible in the daytime. It lasted till the middle of April.
It appears to have been in the S. W. when first seen, setting in the W. At the be-
ginning of March it was in Aries, and was seen from 2^h before till 3h after sunset, or
even later. Subsequently it was seen in the N.W. On Palm Sunday, March 19, its
size was prodigious. — (Walsingham, Historia Anglica ; Poggius. Historia Florentina,
in Muratori's Collection, vol. xx ; Ebendorff'erus, Chronicon Auslriacum, in Fez's
Collection.) The daylight visibility of this comet extended to 8 days, the longest
instance of the kind on record.

[440.] 1402 (ii). From June to September an immense comet was visible in the W.
— (Ducas, Historia Byzantina. Fol. Parisiis, 1649.) The descriptions are long, but
contain nothing of practical value. The comet was visible in the daytime, and
perhaps it attained its maximum brilliancy at the end of August. This or the pre-
ceding was regarded as the sign, by some even the cause, of the death of John
Gallius Visconti, Duke of Milan. — (Annales Forolivien$es.~)

[441.] 1406. Sometime between January and June a comet appeared in the W.
for several nights. — (Chronica Bremenses.}

[442.] 1407. On Dec. 15 a comet was seen. — (Biot ; Williams, 75.)

[443.] 1408. On Oct. 16 a comet, or something like one, was seen. — (Antonius
Petrus, Diarium Eomanum ; in Muratori's Collection, vol. xxiv.)

[444.] 1430 (i). A terrible comet appeared on Aug. 24. — (Kaempfer, Histoire
du Japan, II. v.) On Sept. 9 a great star appeared near a, /3 Canis Minoris. It
lasted 26 days.— (Biot* ; Williams, 88.)

[445.] 1430 (ii). On Nov. 14 an extraordinary star was seen to the S. of S, e, p, v
Piscium. It went to the S. E., passed near t, 0, 77 Ceti, and disappeared in 8 days. —
(Biot* ; Williams, 89.)

[446.] 1431. On May 15 or 27 a comet, 5 cubits long, was observed in the
Eastern part of the sidereal division of /i Geminorum. — (Gaubil ; Biot ; Williams,
75.) Is this identical with the " star " seen on Jan. 3 near /* Eridani which lasted
1 5 days ? — (Williams, 89.)

[447.] 1432. On Feb. 2 a comet, about 10° long, appeared in the E. It swept the
region near a Cygni, and went to the S. E. On Feb. 12 it began to disappear. On
Feb. 29 another comet [doubtless the same after its PP.] became visible for 17 days.
— (Biot ; Williams, 75.) It lasted 8 days, and its tail pointed from E. to N. —
(Michovius, Chronica Polonorum, IV. xlvii.) Williams has some doubt whether
for Feb. 29 we should 'not read Oct. 26, in which case there were 2 comets
in 1432.

[448.] 1436. James I. of Scotland was assassinated on Feb. 20, 1437. During the
previous autumn a comet was seen, — (Boethius, Historia Scot or um. xvii.)

[449.] 1439 (i). On March 25 a comet was seen in the sidereal division ofvHydrae,
It went to the W., and swept £, $, ca Leonis and K, £ Cancri. It then went to the N.,
and passed into the sidereal division of 6 Cancri. On April 2 it had a tail 5 cubits
long. — (Biot.) Williams (p. 76) makes the tail 50 cubits long.

[450.] 1439 (ii). On July 12 a comet, about 10° long, appeared near the Hyades
for 7 weeks. It pointed to the S. W. — (Biot; Williams, 76.) Perhaps the preceding,
after its PP. A comet, lasting i month, was seen this year in Poland, between the
W. and the S. — (Dlugossus, Historia Polotiica, xii.) In Japan also a comet was seen.
— (Kaempfer, Histoire dii Japon, II. v.)

582 Comets. [BOOK IV.

[451.] 1444. A comet appeared about the time of the summer solstice : on June
15, according to others. — (G. Fabricius, lierum Germaniee...Menwrabilium.} On
Aug. 6 a comet, 10° long, was seen to the E. of /3 Leonis. It became longer day by
day till Aug. 15, when it entered the sidereal division of a Virginia, and disappeared.
— (Biot; Williams, 76.)

[452.] 1452. In March — April a comet appeared near the Hyades. — (Gaubil.)
On March 5 a comet appeared in the sidereal division of t Tauri. — (Biot ; Williams,
77-)

[453.] 1453. On Jan. 4 an extraordinary star appeared near the nebula in Cancer.
It went slowly Westwards. — (Biot* ; Gaubil ; Williams, 89.)

[454.] 1454. In the summer a comet like a sword became visible in the evenings
after sunset. — (Phranza, Chronicon De Rebus Constaittinopolitanis, viii. Fol. Venetiis,
1 733-)

[455.] 1457 (i). At the commencement of the year a comet appeared. — (Pontanus,
Hiiftoria Gelrica, ix.) Between Jan. 14 and 23 a comet, j cubit and more long,
appeared in the sidereal division of t Tauri. It went to the S. E. — (Biot ; Williams.)
Celoria on the strength of some information given in a MS. by one Toscanelli pre-
served in the National Library at Florence calculated an orbit for this comet as
given at the end of Catalogue I., ante. — (Ast. Nach., vol. ex. No. 2627. Nov. 3,
1884.)

[456.] 1457 (ii). In June a comet appeared in the 2Oth degree of Pisces. —
(Chronicon Nuremburgenfe, and others.) The conclusion seems unavoidable that
there were 2 comets in June, and that this is not identical with the one computed by
Hind. This doubt has been confirmed by Celoria, who found in Toscanelli's MS.
materials for the orbit given at the end of Catalogue I., ante. (Ast. Nach., vol. ex.
No. 2627. Nov. 3, 1884.)

[457.] 1457 (iv). On October 26 a comet | cubit long appeared in the sidereal
division of a Virginis. It passed near £ and 6 Virginis. — (Williams, 78.)

[458.] 1458. On Dec. 24 a star appeared in the sidereal division of o Hydrae ; it
went to the W. till Dec. 27, when it became faint : it was near a, y, £, 77 Leonis.
On Dec. 31 it had a tail % cubit long ; it " attacked" A. (or </>) Cancri. On Jan. 12,
1459, it disappeared in the Eastern part of the sidereal division of /x Geminorum. —
(Biot * ; Williams, 89.)

[459.] 1458 or 1459. Probably the former. In June — July a comet appeared in
Taurus (?). — (De Mailla, x. 236 ; A. Rockenbackius, Exempla Cometarum.)

[460.] 1460. James II., King of Scotland, was killed on Aug. 3, 1460. The
evening before, a very brilliant comet with a long tail was seen. — (Boethius, Hiztoria
Scot rum, xviii.)

[461.] 1461. On July 30 a white star appeared near k, I, g Tauri Poniatowskii.
On Aug. 2 it transformed itself into a vapour, and disappeared. — (Biot *.) On Aug.
5, a comet was seen in the E. It pointed to the S. W. It entered the sidereal
division of /* Geminorum. On Sept. 2 it began to disappear. — (Williams, 79.) These
accounts do not seem reconcileable.

[462.] 1463. In this year (no month assigned) a comet was seen near T and v
Virginis. — (Gaubil.)

[463.] 1464. In the spring a comet was seen in Leo. — (Gaubil.)

[464.] 1465. In March and April a comet was seen, with a tail 30° long, in the
N. W. — (Biot ; Williams, 79 ; Kaempfer, Histoire du Japon, II. v.)

[465.] 1467. In October a comet was seen above Pisces, "as if it had been
formed in Cancer." Rainy weather prevented its being often seen. — (Chronicon !•>.
JEgidii Brunswicemis.) Pingre does not seem to attach much credibility to this
account.

[466.] 1468 (i). On Feb. 24 a comet was seen near Ursa Major. — (Gaubil.)
[467.] 1471. In the autumn, in Poland, a very great comet was seen. It rose

before sunrise. It was in the latter part of Virgo and in Libra, and lasted a month.

— (Michovius, Clironica Poloiiornnt, IV. Ixii.)

CHAP. VIII.] Catalogue. — No. II. 583

[468.] 1476. From Dec. 1476 to Jan. 5, 1477, a small comet was visible. —
(Ripamontius, Historic/, Urbis Mediolanensis, vi.)

[469.] 1477. In December a comet appeared. — (Chronica Bozsiana.}
[470.] 1478. In September a great comet appeared. — (Chronica Sossiana.}

[471.] 1495.* On Jan. 7 a star was seen near 0, p Ophiuchi ; it travelled with a
slow motion till Feb. 20, when it entered the division of a Aquarii. — (Biot.)

[472.] 1502.* On Nov. 28 a star appeared near Pyxis Nautica. From the
division of vl Hydrse it directed itself towards that of a Crateris. On Dec. 8 it dis-
appeared. — (Biot.)

[473.] 1503. At about the time of the Festival of the Assumption of the Virgin
Mary [Aug. 15] a comet was seen. Its tail pointed towards the E. — (Chronicon
Wa Idsassense. )

[474.] 1505. A comet was seen in Aries. It lasted only a few days. — (Mizaldus,
Cometographia. 4to. Parisiis, 1549.)

[475.] 1512. In March and April a comet appeared. — (Chronicon Magdebur-
gense.}

[476.] 1513. From Dec. 1513 to Feb. 21, 1514, a comet was visible. It passed
from the end of the sign Cancer to the end of that of Virgo, and was seen all night.
— (Vicomercatus, Commentarii in lib. Aristolel. Meteor., xlix.)

[477.] 1516. The death of Ferdinand the Catholic, King of Arragon (Jan. 23),
was announced by a comet, which lasted many days.— (P. Bizarus, Historia Qenuen-
sis, xix. 446.) Others say that the comet was only visible for a few days.

[478.] 1518. During the nights preceding April 6 a pale comet was seen above
the citadel of Cremona. — (Cavitellius, Annales Cremonenses.)

[479.] 1520. In February a comet appeared. — (Biot ; Williams, 82.)

[480.] 1521. In April a comet with a short tail appeared in the latter part of
Cancer. — (Vicomercatus, Comment, in Aristot. xlix ; Lubienitz.) Month and position
depend only on modern authority. On Feb. 7 a star appeared in the S. E. ; it was 6°
or 7° long : it went from E. to W., and divided itself. — (Biot.*) Gaubil alludes to
this, but his description was supposed by Pingre to belong to Jupiter.

[481.] 1522. A comet was seen in the W. — (Mizaldus, Cometographia, II. xi.)
No month given.

[482.] 1523. In July a comet was seen near a Ophiuchi. — (Biot ; Williams, 82.)

[483.] 1529. In February a long star traversed the sky. This phenomenon
renewed itself in August. — (Biot.*) European writers mention a comet in August,
but Pingre considers that their descriptions belong to an aurora. — (Comet., i. 486.)

[484.] 1530. On Nov. 30 a comet was seen. — (Conradus Urspergensis, Chronicon.
Fol. Argentorati, 1609.)

[485.] 1532. A comet appeared in the spring. — (Gaubil.) On March 9 a star
with a tail appeared in the S. E. After 19 days it disappeared. — (Biot* ; Williams,
920 ,

[486.] 1534. A comet appeared in July. — (Cavitellius, Annales Cremonenses.')
On June 12 a star was seen near ir Cygni, K Andromedae, &c. ; it passed by 9
Andromeda?, and entering v, £, o, IT Cassiopeise, disappeared after 24 days. — (Biot * ;
Williams, 92.)

[487.] 1536. On March 243 star was seen near /3, 7 Draconis. It went East-
wards, and, passing to the W. of 8, «, IT, f Draconis, came to the Milky Way, and
disappeared on April 27. — (Biot*; Williams, 92.)

[488.] 1538. On Jan 17 P. Apian saw a comet, with a tail 30° long, in 5° of
Pisces, with a latitude of 17° N. On the 22nd Gemma Frisius observed it in 9° of
Pisces, with a latitude of 11° N. — (Pingre1, Comet., i. 495.)

[489.] 1539. On April 30 a comet, with a tail 3° long, was seen. It remained
visible for 3 weeks, and swept a and y Leonis. — '^Biot ; Williams, 83.) On May 1 1 (?)

584 Comets. [BOOK IV.

Gemma Frisius observed it in 5° of Leo, with a latitude of J2° N. On May 17, at
ioh in the evening, its position, according to Apian's observations reduced by Pingre,
was 20° of Leo, with a latitude of 4^° S. — (Pingre, Comet., i. 500.)

[490.] 1545. A comet was seen for several days. No month is given. — (Aretius,
Srecis Cometarum Explicatio.} On Dec. 26 a comet appeared near 18, 7 Draconis ;
it entered the sidereal division of 8 Sagittarii, and returned to the N. E. It dis-
appeared at the end of the Moon. — (Biot* ; Williams, 92.)

[491.] 1554. On July 23 a comet was seen, which passed from 5 to 6, v, <f> Ursae
Majoris, and thence to a Serpentis. It lasted 4 weeks. — (Biot ; Williams, 83.)

[492.] 1557- In October, the Sun being in Libra, a comet was seen in the W., in
Sagittarius. — -(J. Camerarius, Coinetce. 8vo. Lipsiae, 1558.) On Oct. 22 it was seen
near A. Ophiucni ; it pointed to the N. E. It lasted till the next moon. — (Biot.) For
' Oct. 22 ' Williams reads ' Oct. 10,' and for ' N. E.' he reads ' N. W.'

[493.] 1560. In December a comet appeared for a month. — (J. A. Thuanus,
Historitz sui temporis, xxvii. u. Fol. London, 1733.)

[494.] 1569. In November a comet was seen in Ophiuchus and in the signs
Sagittarius and Capricornus. Its movement in longitude equalled the extent of these
2 signs, and it remained visible till Nov. 19. — (Kepler, He Cornells, 114.) It lasted
from Nov. 9 to Nov. 28. — (Biot ; Williams, 84.)

[495.] 1578. On Feb. 22 a star as large as the Sun appeared. — (Biot*; Williams,
92.) European writers mention a comet and a hairy star, the latter on April I. As
Tycho Brahe's comet of 1577 remained visible till January 1578, Pingre" thinks that
that is the object described as the comet of 1578 : the hairy star of April he con-
siders to have been a meteor.

[496.] 1579. " On the 10 of October (some say on 7) appeared a blazing star in
ye South, brushing towards ye East, which was nightly scene diminishing of his
brightness until ye 2ist of ye same month." — (Stowe, Chronicles.}

[497.] 1591. On April 3 a comet, i cubit long, was seen. It traversed the
sidereal divisions of a Aquarii, a Pegasi, and 7 Pegasi, increasing in length to 2°.
On April 13 it entered the sidereal division of £ Arietis. — (Biot; Williams, 85.)

[498.] 1604. On Sept. 30 a large star like a ball appeared in the sidereal division
of /*2 Scorpii. It vanished in the S. W. in November. On Jan. 14, 1605, it reap-
peared in the S. E. About March it became dim. — (Biot* ; Williams, 93.)

[499.] 1609. A great star appeared in the S. W. The tail had 4 rays. — (Biot* ;
Williams, 93.)

[500.] 1618 (ii). Between Nov. 10 and 26 a comet was seen by Figueroes at
Ispahan, coincidently with the apparition of comet iii. of this year. In consequence
of the comet's Southerly motion the head was not generally, if at all, seen in Europe
— only the tail. Kepler and Blancanus were the chief observers who saw the latter.
Kepler guessed that on Nov. 10 the nucleus was in 16° of Scorpio, with a latitude of
8° S. ; and that on Nov. 20 it was near the head of Centaur. At Rome the tail was
seen to be 40° long on Nov. 18. It was last seen on the 29th. The observers
(Jesuits) note that in 1 1 days the proper motion of the tail caused it to pass over 24°
from Crater towards a Hydras. — (Pingre", Comet., ii. 57.) On Nov. 24 a white vapour
20 cubits long was seen in the S. E. It extended across the sidereal division of
7 Corvi. It entered the sidereal division of a Crateris and disappeared after 19 days.
(Williams, 93.) The Chinese record "a star like a white flower" as being visible on
Dec. 5 of this year. It may be well to mention here that Cooper, in his Cometic
Orbits (p. 77)> appears to have fallen into a mistake relative to the comets of this
year, which others have copied. He gives the elements of the iiird comet, and
appends notes referring to the ii' d and iiird as if they were one and the same
object.

[501.] 1619. In February a comet was seen in the S. E. : it was 100 cubits long,
curved and pointed. — (Biot ; Williams, 87.)

[502.] 1625. From Jan. 26 to Feb. 12 a comet was observed by Schickhardt in
Eridanus and Cetus.— (Astronomische Nachrichten, vol. ii. No. 31. April 1823.) It
was Olbers who rescued this comet from oblivion.

CHAP. VIII.] Catalogue. — No. II. 585

[503.] 1628. A cornet appeared, mentioned by Ripamontius. — (Astronomische
Nachrichten, vol. xii. No. 277. April 29, 1835.)

[504.] 1630. A comet appeared ; also mentioned by Ripamontius, and by him
associated with a pestilence. — (Astronomische Nachrichten, vol. xii. No. 277. April
29> 1835.)

[505.] 1639. On Oct. 27 a comet with a small tail was seen in Canis Major by
Placidus de Titis. — (Astronomische Nachrichten, vol. viii. No. 171. January 1830.)
In the autumn a comet was seen in the sidereal division of 8 Orionis.— (Biot ;
Williams, 87.)

[506.] 1640. On Dec. 12 a comet was seen. — (Biot; Williams, 87.) Perhaps
it is to this comet that allusion is made by Evelyn, who speaking of the comet of
1680 says that one was seen about the trial of the Earl of Strafford in 1640. — (Diary,
ed. Bray, London, 1850, vol. ii. p. 154.)

[507.] 1647. On Sept. 29 a comet was seen soon after sunset in Coma Berenicis.
Its longitude was 188° and its latitude + 26°. It was 12° long and lasted one week,
traversing Bootes, Northwards of Arcturus, to Corona Borealis, in a line sensibly
parallel to the equator. — (Hevelius, Cometographia, p. 463.)

[508.] 1666. Robert Knox in a book on Ceylon published at Utrecht in 1692 says
that the tail of a comet was seen in Ceylon in 1666. — (Monatliche Correspondenz,
vol. xxviii. p. 428.)

[509.] 1699 (ii). On Oct. 26 Gottfried Kirch observed a faint comet in the poop
of Argo ; in longitude 122° 34', and latitude — 40° 38'. It was visible to the naked
eye, and its motion was sensibly Southwards. Kirch was unable to find it on any
subsequent night. — (Miscellanea Berolinensia, v. 50.)

[510.] 1702 (i). Numerous navigators in the Southern hemisphere report seeing
a comet between Feb. 20 and March i. On Feb. 28 the tail was 43° long. At
8 P.M., in latitude 15° 10' N., and. longitude 116° 45' E. of Teneriffe, the comet bore
S. of W. 20° 30', altitude 8° 40'. On all occasions it was seen in the evening, after
sunset. Maraldi at Rome saw the tail for several days at the end of February and
the beginning of March. — (Struyck, Vervolg van de Beschryving der Staarts Sternen.
4to. Amsterdam, 1753, p. 50.)

[511.] 1732. On Feb. 27 a comet was seen above Spica Virginis by Hanow, prob-
ably at Danzig. — (Monatliche Correspondenz, vol. xxviii. p. 430.)

[512.] 1733. On May 17 and 18 a comet was seen by several navigators off the
Cape of Good Hope, bearing N.W. \W. It was observed for more than an hour,
until it went below the horizon.- — (^ Struyck, Vervolg, p. 61.) Its place was R.A.,
6h 5m : Decl. + 18° 35'. The comets of 1807 and 1881 (iii.) cannot have been identical
with it. — (Oudemans, Copernicus, vol. i. p. 207.)

[513.] 1742 (ii). On April ii, in the morning, a comet was seen in the S.E. by
several Dutch navigators at sea in the Southern ocean. On April 14 the tail was
30° long.- — (Struyck, Vervolg.)

[514.] 1748 (iii). On April 24 a Dutch navigator, at the Cape of Good Hope,
saw a comet, at the beginning of Aries, rise in the E. JN.E. at 4h A.M. This is
probably the comet, rendered invisible at the Cape by a Northerly motion, which
Kindermanns saw on April 28, at 2h A.M., at an elevation of 8° above the horizon,
in a straight line with (it would seem) 5 and rj Trianguli and the brightest star
of Aries, in Longitude 80°, Latitude -t- 28°, and Declination + 50°. On May 3,
between nh and midnight, the comet was near Perseus, and circumpolar. — (Struyck,
Vervolg, p. 100.)

[515.] 1750. Between Jan. 21 and 25 Wargentin observed a comet below « and 0
Pegasi. — (Tables Astronomiqu.es de Berlin, i. 35.)

[516.] 1770. Returning from observing the Transit of Venus at Wardohrs, Hell
and Sainovics saw at Copenhagen on March 19, at II P.M., a comet in the North-
East. It was searched for in vain at the Copenhagen Observatory, March 20 to 26,
but, as pointed out by Olbers (Ast. Nuch., vol. xii., Nos. 273, 275, Feb. i f, March 7,

586 Comets. [BOOK IV.

1835), too early in the evening, as the comet was probably approaching the Sun and
would rise later every evening.

[517.] 1783 (ii). On Dec. 18, 1783, Sir W. Herschel observed a nebula i™ pre-
ceding 8 Ceti, and ^° N. of that star. He describes it as " small and cometic." In
his son's great Catalogue of Nebula, 1864, this object is set down as really a comet,
not having been since found, though looked for.

[518.] 1808 (i). On Feb. 6 Pons discovered a small faint comet between the neck
of Serpens and the needle pointer of Libra. It was only visible for 3 days, becoming
lost in the moonlight. Its movement was rapid and towards the S. — (Monatliche
Correspondenz, vol. xviii. p. 252. Sept. 1808: Ast. Nach., vol. vii. No. 149. Jan.
1829.)

[519.] 1808 (iv). On July 3 Pons discovered a comet in Camelopardus : it was
observed only on that night and July 5. Its position on July 3, at I5h 4™ 26s
Marseilles M.T., was R.A. 3" 10™ 10", and Decl. + 56° 36': on July 5 at I5h 8m 58'
the R.A. was 3h 31™ 46', and Decl. + 58° 19'. — (Monatliche Correspondenz, vol. xviii.
p. 249. Sept. 1808.)

[520.] 1839. On July 14 and 17 an extremely faint comet was seen at the
Homan College. It was in Draco, and appeared like a double nebula, or as if
divided into 2 branches. The following positions were taken: July i4d ioh im,
R.A. I2h 9m 41s, Decl. + 70° 28-6'; July I7d ioh 6m, R.A. nh 50™ 27', Decl. + 70°
39-3'. — (Memoria . . . Osservazioni fatte . . . in Collegia Romano, 1839, p. 38.)

[521.] 1846 (ix). On Oct. 18 Hind observed a comet in Coma Berenicis for more
than an hour. Its altitude was small, and being in the morning twilight it was
never seen again. Its exact position at i6h 15™ ii5 G.M.T. was R.A. nh 59™ 49s,
Decl. + 14° 59' 32". Its motion was increasing in R.A. at the rate of about 4™ a
day, and diminishing in Decl. at the rate of about n' a day. — (Month. Not., vii. 162.
Nov. 1846.)

[522.] 1849 (iv). On Nov. 15, at sea, in the S. Atlantic, a comet was seen from
the U. S. Ship Maryland, with a nucleus as bright as Mars, and with a tail, curved
and pointing to the S.W., nearly i° long. From the notes of Captain Homer, Mr.
Hind worked out the following position: at 9h 49™ G.M.T., R.A. 2oh 36-6™,
Decl. + 4° 18'. — (Month. Not., x. 122 and 192. March, &c., 1850.) „

[523.] 1854 (iii). On March 16 a bright nebulous object was seen by Brorsen.
Its position at 8h 15™ 34s Senftenburg M.T. was: R.A. 2h 30™ 12s, and Decl. + i°
11-2'. — (Ast. Nach., vol. xxxviii. No. 897. March 27, 1854.)

[524.] 1855 (ii). On May 16, whilst searching for Di Vico's comet, Goldschmidt at
Paris found a comet in R.A. 2ih 41™ 45*, Decl. — 15° 38', which he announced as
positively the missing comet (Ast. Nach., vol. xli. No. 978. Aug. 25, 1855). No
confirmation of the discovery was obtained, and astronomers, though they did not
doubt that a comet had been seen, decidedly doubted that it was the periodical comet
of Di Vico which Goldschmidt had found. Twelve years afterwards Winnecke
claimed to have cleared up the uncertainty by determining that the comet seen by
Goldschmidt was a prior return of comet ii. of 1867 (Ast. Nach., vol. Ixix. No. 1645.
June 20, 1867) : but this theory has been distinctly disproved by Von Asten (Ast.
Nach., vol. Ixxxii. No. 1962. Nov. 3, 1873.)

[525.] 1856 (i). In January a comet was seen in the N.W. fky at Panama. —
(Letter in the Morning Herald. Month. Not., vol. xvii. p. 114. Feb. 1857.)

[526.] 1856 (ii). On Aug. 7 an object, supposed to be a comet, was seen in
Virgo by E. J. Lowe. — (Month. Not., vol. xvii. p. 114. Feb. 1857.) ^ comet was
also seen at Arequipa, in Peru, for a fortnight previous to Aug. 21 for 2 hours after
sunset. — (Letter in the Times, Oct. 8, 1856.)

[527.] 1859 (i). In Feb. a very faint comet was seen by Slater, in R.A. i ih 48m :
Decl. + 19° 49'. He saw it again on May 7 and 22, when it had become fainter,
not being visible with any aperature below n£ inches. Its movement was very
slow, and seemed to be in a northerly direction. — (Month. Not., vol. xix. p. 291. June
1859.)

CHAP. VIII.] Catalogue. No. II. 587

[528.] I860 (v). On November 14, Tuttle at Cambridge U.S. observed a very
faint comet near the Pole-Star. It was not questioned till 8 years afterwards
but that this was identical with comet iv. of 1860. — (Ast. Nach., vol. Iv. No. 1301.
March 30, 1861 : ib., vol. Ixxiii. No. 1734. Jan. 16, 1869: ib., vol. Ixxiii. No. 1740.
Feb. 16, 1869: ib., vol. Ixxv. No. 1787. Jan. 12, 1870.)

[529.] 1865 (ii). Enckes comet. This object was discovered by Tebbutt at Windsor,
N.S.W., on June 24. It was very faint, and was seen only on that occasion and on
June 29. Its observed place on the 24th is noted to have differed very much from
that assigned by calculation. — (Ast. Nach., vol. Ixv. No. 1551. Oct. 6. 1865.)

[530 and 531.] 1865 iii. and iv. (?). On Aug. 27, two comets were seen by [E. J.]
Lowe at 8h 30™ P.M. The position of the first was, E. A. i5h 15'": Decl. — 3° 50'.
And of the second, R. A. 15'* om : Decl. — 7° 30'. "From an account I see in the
newspapers of a comet seen at 3h 45™ A.M. in the E. ' three days ago ' [no date given !]
I have little doubt this is one of the comets I saw in August." — (Month. Not., vol.
xxv. p. 278. Oct. 1865.) [This is a very slovenly record.]

[532.] 1871 (vi). On December 29, at 6h 15™ Milan M.T.,Tempel observed a faint
comet in R.A. I9h 51™ 32': Decl. + 29° 56'. — (Ast. Nach., vol. Ixxviii. No. 1872.
Jan. 3, 1872.)

[533-J 1872. On Dec. 2, Pogson at Madras, in consequence of a telegram from
Klinkerfues of Gottingen (in these words, "Biela touched Earth on Nov. 27 ; search
near 6 Centauri "), sought and found a comet. At i7h 31™ Madras M.T. its R.A. was
J4h 7™ 1 2s : Decl. — 34° 45'. It was " bright, circular, about 45" in diameter : a very
decided nucleus, but no tail discernible in strong twilight and cloudy sky." On the
following morning at i7h 3m the comet was seen again in R.A. 14'' 2im 55s : Decl.
— 35° 4'. The description was, " bright, round, and about 75" in diameter. A short
faint tail seen about 7^4' in length." Bad weather and the advance of twilight
rendered subsequent observations impossible. This was presumed to have been the
long-lost Biela's comet, but the idea has been disproved by Bruhns. — (Month. Not.,
vol. xxxiii. p. 116. Dec. 1872: Ast. Nach., vol. Ixxx. No. 1918. Jan. 16, 1873:
ib., vol. Ixxxiv. No. 2204. Aug. u, 1874: ib., vol. Ixxxvi. No. 2054. Sept. 10,
I875-)

[534.] 1880. On Aug. u, Mr. L. Swift at Rochester, State of New York, saw a
nebulous object in the field with the nebula y I 262. No motion could be detected
during the period of an hour. Bad weather followed, and the object, whatever it was,
was not seen again. Its position on Aug. II was somewhere about R.A. Iih 28™;
Decl. + 68°. — (Ast. Nach., vol. xcviii. No. 2334. Sept. n, 1880.)

[535-] 1881. On May 1 2 a faint comet was seen by Barnard at Nashville, Tennessee,
in R.A. 22'' 59'3m, Decl. + 14° 24' ; that is, in the field with and very near a Pegasi.
It was again seen on the following night, in R.A. 22h 58'9m, Decl. + 14° 36', but no
trace of it could be obtained subsequently. — (Ast. Nach., vol. c., No. 2384. July 26.
1881.)

[536.] 1883. On Dec. 25, and again on Dec. 27, a comet was seen with the naked
eye in Tasmania, according to testimony seemingly trustworthy. Kreutz by collating
the information given arrived at the following positions : —

L*>cal Time. R. A. «

h. m. h.

Dec. 24 ... 15 o ... ... 14-8 ... ... 6

26 ... 16 6 16-5 o

(Ast. Nach., vol. cviii. No. 2591, May 8, 1884; Tebbutt, Observatory, vol. vii. p.
116, April, 1884.)

[537.] 1882. On the occasion of the Eclipse of the Sun on May 16 a comet was seen
with the naked eye in Egypt near the Sun during the total phase by Trepied. Its
existence was also recorded on several photographs taken by Lockyer. It was distant
from the Sun about the amount of the Sun's diameter, and had a tail about ^° long-
It was never seen again. — (Ast. Nach., vol. cii. No. 2441, July 6, 1882 : Observatory,
vol. v. p. 209, July 1882 : Month. Not., vol. xliii. p. 206, Feb. 1883.)

[538.] 1884. On May 26, a faint object, assumed to have been a nebula, was found
at the Vienna Observatory with the great 26-inch refractor in R.A. 1 7h 40™ 48" ;

588 Comets.

Decl. + 35° 42'. It could not be found again on June 1 8, and may have been Tuttle's
comet (1858, iii.) due at that time and in about that position. — (Dun Edit Circular,
No. 84.) This last-named supposition seems to have been unfounded. (See p. 430,
ante.}

[539.] 1889. On Jan. 15, just before dawn, Brooks at Geneva, N.Y., found a
faint comet in E.A. i8h4m; Decl. —21° 20'. It had a rapid Westerly motion, and
could not be found on Jan. 20. — Month. Not., vol. xlix. p. 327.)

OBJECTS RECORDED AS NEBULA, BUT WHICH MAY POSSIBLY
HAVE BEEN COMETS.

614 H. R.A. for 1860 : 2h 44™ 6s : Decl. + 36° 557' : observed by Bessel. Looked
for and not found by D' Arrest, who supposes it to have been a comet. This is
assumed by Dreyer to have been a certain star, and not a nebula at all, much less a
comet. — (Notes to New Gen. Cat., p. 214.)

2094 H. R.A. for 1860: ioh 17™ 5s: Decl. + 27° 43-9' : observed by Sir J.
Herschel. Looked for 6 times and not found by Lord Rosse. "This then was a
comet or a lost nebula." Schulhof, possibly under some misconception of date, remarks
that at the time when this observation was made (but this is not stated in Sir J.
Herschel's O-. (?.) Tuttle's comet should have been very close to the place given for
the nebula, and that perhaps it was the comet which was seen on the occasion. —
(Ast. Nach., vol. cviii. No. 2592, May 13, 1884.) Dreyer thinks it was a nebula after
all, and identical with H 2095. — (Neto Gen. Cat., No. 3234.)

50 y III. On March 19, 1784, Sir W. Herschel observed an exceedingly faint
nebula, 3™ 15" following 45 Canum, and 4™ South. Sir J. Herschel stated that he
had found a memorandum that this nebula is lost, and was probably a comet. But
Dreyer identifies it with one found by Bigourdan. — (New Gen. Cat., No. 2661.)

3550 H. R.A. for 1860: I3h2imi3s: Decl. -)- 6° 43-4' : observed by D' Arrest, but
"not found again on Feb. 19, 1863. Sky perfectly clear. Perhaps a comet."—
(Dreyer, New Gen. Cat., No. 5160.)

Hevelius, in his Prodromus Astronomia (pp. 207 and 289), states that he once saw
in the head of Hercules, near a, a nebula. This was searched for unsuccessfully by
Messier. The nearest object is 901 JjJ II, but this would be quite beyond the reach
of the telescopes used in the time of Hevelius, so it must have been a comet that he
saw. — (Smyth, Cycle, ii. 385 : Lynn, Observatory, vol. ix. p. 164, April 1886.)

BOOK W

METEORIC ASTRONOMY.

CHAPTEK I.

AEROLITES.

Classification of the subject. — Aerolites. — Summary of the researches of Berzelius,
Rammelsberg, and others. — Celebrated Aerolites. — Summary of facts. — Catalogue
of Meteoric Stones. — Arago's Table of Apparitions. — The Aerolite of 1492. — Of
1627. — 0/1795. — The Meteoritic Shower of 1803. — The Aerolite of 1876 (Rowton).
—The Aerolite of 1881 (Hiddlesborough).—The Aerolite of 1887 (Soko Banjo).

rr> HE phenomena of which I am now about to speak form

a highly interesting and by no means unimportant branch

of descriptive astronomy. They may conveniently be treated

under 3 heads : —

1. Aerolites

2. Fireballs.

3. Shooting Stars,

Of all cosmical meteors those known as aerolites, meteorites,
or meteoric stones, are the rarest, but nevertheless they are not so
rare as to prevent satisfactory evidence being produced that such
occurrences have happened from time to time. It is to Chladni
that we owe much of our knowledge of this branch of the sub-
ject1'. Many of these meteoric stones, which have fallen or been

* This Book has been revised and added to a recent date will be found in An

to for this edition by Mr. W. F. Denning. Introduction to the Study of Meteorites,

b See his work 2X0 Ftuermeteore. A published by the British Museum

large amount of information brought up Trustees, 8vo. Lond., 1886.

590 Meteoric Astronomy. [BOOK V.

found in different parts of the world, have been subjected to
chemical analysis by Berzelius, Rammelsberg, and others, whose
deductions may be thus summed up : —

1. Meteoric stones are composed of elements all of which occur
in terrestrial minerals.

2. Of the 70 or more elementary substances now known, 24 have
been found in meteoric stones, namely: — oxygen, hydrogen, ni-
trogen, chlorine, sulphur, phosphorus, carbon, silicon, iron, nickel,
cobalt, chromium, manganese, copper, tin, antimony, aluminium,
magnesium, calcium, potassium, sodium, lithium, titanium, and
arsenic.

3. The produce of a meteoritic shower may be divided into
meteoric iron and meteoric stone.

4. Meteoric iron is an alloy that has not yet been certainly
found to exist among terrestrial minerals, and is composed of
iron with from 3 or 4 to 15 or 1 8 per cent, of nickel, and small
quantities of cobalt, manganese, magnesium, tin, copper, and
carbon.

5. Meteoric stone is composed of minerals found abundantly
in lavas and trap-rocks (and consequently of volcanic origin), a
variable proportion of meteoric iron being usually admixed.

The circumstances attending the fall of aerolites differ consider-
ably on different occasions. Not unfrequently the fall is attended
by a loud detonation ; but we must not therefore infer that every
detonating meteor is indeed an aerolite, without positive proof
to that effect. History records instances of considerable damage
having been done to life and property by the descent of these
bodies : as, for instance, from a Chinese catalogue we learn that
one which fell on Jan. 14, 616 B.C., broke several chariots and
killed ] o men. The chronicle of Frodoard informs us that in the
year 944 A.D. globes of fire traversed the atmosphere and burnt
several houses. More recently, on the evening of Nov. 13, 1835,
a brilliant meteor was seen in the department of Aisne (France).
It traversed the country in a north-easterly direction, and burst
near the castle of Lauseres, setting fire to a barn and the stables
burning the corn and cattle in a few minutes. A stony substance

CHAP. I.] Aerolites. 591

supposed to be an aerolite was found near the place after the
occurrence. On March 22, i 846, at 3 P.M., a luminous sheaf, which
traversed the air with great velocity and noise, fell on a barn in
a village in the department of Haute Garonne, which instantly
took fire and was destroyed, together with the stables adjoining
and the beasts therein contained c. It is related that the Emperor
Jehangir had a sword forged from a mass of meteoric iron which
fell at Jahlindu in the Punjab, in i62od. Some of these descrip-
tions doubtless relate to veritable aerolites, but other alleged
instances of falls of aerolites are, it may be supposed, merely
records of electrical discharges.

From the above and other similar observations we conclude : —

1. That the fact is undoubtedly established, that from time to
time masses of stone, of different sizes, and often of considerable
weight, pass through space, and are frequently precipitated upon
the Earth's surface.

2. That these bodies do not always strike the Earth in a ver-
tical or nearly vertical direction, but that they more often
fall in a direction very oblique to the plane of the horizon. This
is ascertained by an inspection of the manner in which they
penetrate the soil, which they often do to a considerable depth.

3. That they are originally endued with a very great velocity,
bearing indeed a finite proportion to the velocities which are
found to characterise the planetary members of the solar system.
This velocity they soon lose by the effects of atmospheric resist-
ance, and it is so much reduced by the time they reach the ground
that their speed scarcely exceeds that of bodies falling under the
influence of gravitation.

The Ancients seem to have been well aware of the phenomena
of which I am now treating, inasmuch as several objects are
mentioned by the classic writers as having fallen from heaven :
for instance, the Palladium of Troy, an " image " of Diana at

c See Arago, Ast. Pop., vol. iv.. pp. meteor catalogues are unfortunately left

224-29, French ed., where numerous out.

other instances are given. In the d Phil. Trans., vol. xciii. p. 200. 1830.
English edition this and other important

592

Meteoric Astronomy.

[BOOK V.

Ephesus6, and the sacred shield of Numa. The ideas of the
Ancients relative to the supposed celestial origin of these things
have often met with ridicule; but however fabulous the cases
referred to may have been, still the Moderns have been compelled,
though reluctantly, to admit the fact of the actual transmission
of stony substances from Space on to the surface of the Earth.
The following catalogue of some of the more important recorded
falls of meteoric stones is founded on one given in M. Izarn's
work f .

Substance. Period.

Showers of stones About 650 B.C.

Large stone 4658.0

Three large stones 452

Shower of stones 343

Place.
Eome.

Eiver Negos, Thrace.
In Thrace.
Rome.

54 Lucania.

Shower of iron

Shower of mercury Date unknown

Mass of iron of 14 quintals ,,

Large stone of 260 Ibs 1492 Nov. 7 ...

About 1 200 stones — I of 120 Ibs.,^

another of 60 Ibs [ *

Stoneofsglbs 1627 Nov. 27 ...

Sulphurous rain 1646

Sulphurous rain 1658

Shower of unknown matter ^95

Stone of 72 Ibs 1 706 January ...

Shower of fire 1717 Jan. 4 ...

Shower of sand for 1 5 hours 1 7 1 9 April 6 ...

Shower of sulphur 1721 October ...

Mass of stone 1750

Shower of stones 1 753 July 3 ...

Two stones weighing 20 Ibs J753 September

Two stones of 200 and 300 Ibs. ... 1762

A stone of 7 1 Ibs 1768 Sept. 13 ...

A stone 1768

Shower of stones 1789 July

Extensive shower of stones 1790 July 24 ...

About 12 stones 1794 July 16 ...

A stone of 56 Ibs 1795 Dec. 13 ...

A stone of i o Ibs 1796 Feb. 19 ...

A stone of 20 Ibs 1798 March 12

A stone of about 20 Ibs 1798 March 17

In Italy.

Abakauk, Siberia.
Ensisheim, Upper Rhine.

Padua, Italy.

Mont Vasia, Provence.

Copenhagen.

Duchy of Mansfeld.

Ireland.

Larissa, Macedonia.

Quesnoy.

In the Atlantic.

Brunswick.

Niort, Normandy.

Plaun, Bohemia.

Liponas, in Brest.

Near Verona.

Luce, Le Maine.

Aire, Artois.

Le Cotentin.

Barboutan, near Roquefort.

Near Agen.

Siena, Tuscany.

Wold Cottnge.Thwing, Yorks.

In Portugal.

Sules, near Ville Tranche.

Sale, Dep. of Rhone.

0 This no doubt was merely a stone of
no particular shape : certainly not a
Sculptured stone.

f Des Pierres Tonibtes du Ciel, ou
Lithologie Astronomiqne. Paris, 1803.

CHAP. I.]

Aerolites.

593

Substance. Period.

Shower of stones 1798 Dec. 19 .

Mass of iron, 70 cubic feet 1800 April 5

Many stones, the largest 8|lbs>. ... 1803 April 26 ,

Shower of stones 1807 Dec. 14 ,

A stone of 1653 Ibs 1810 ,

Shower of 200 stones ... 1812 May 22

A stone of 203 Ibs 1821 June 15

A large stone 1843 Sept. 1 6

Shower of stones 1864 May 15

Stone of 6 cwt. and 1000 smaller ones 1 866 June 9

Fragment of Iron weighing 7| Ibs. 1876 April 20

A stone of 3 Ibs. 8| oz 1881 Mar. 14

Place.
Benares.
America.

Near L'Aigle, Normandy.
Weston, Connecticut, U.S.
Santa Rosa, New Grenada.
Stannern, Bohemia.
Juvinas, Ardeche.
Kleinwenden, Thuringia.
Orgueil, France.
Knyahinya, Hungary.
Rowton, Shropshire.
Middlesborough, Yorkshire.

The 206 falls of aerolites, of which Arago knew the month of
occurrence, were, according to him, distributed in the following
manner through the i 2 months of the year : —

January ...

February...

March

April . ...

May

June

>-99

July
August
September .

.. 16

October
November . .
December . . .

. 18
20

From an inspection of the above table it appears that the
monthly average from December to June (16) is less than the
monthly average from July to November (18), and that, moreover,
the months of March, May, July, and November exhibit maximum
numbers : and we also learn this general fact — that the Earth,
in its annual course round the Sun, would seem to encounter a
greater number of aerolites in passing from aphelion to perihelion,
or between July and January, than in going from perihelion to
aphelion, or between January and July.

It has been asserted to be a general rule that the area over
which a shower of stones falls is oval, measuring from 6 to 10
miles in length by 2 or 3 in breadth, and, moreover, that the
largest stones may be expected to be found at one extremity of
the oval.

When found entire the stones are completely coated or glazed
over with a thin dark-coloured crust formed from the molten
substance of their surface fused by ignition in the fire-balls, the
part which travelled foremost being sometimes distinguishable

Q q

594 Meteoric Astronomy. [BOOK V.

from that which was in the rear. Freshly-fractured faces have
also been observed, and the pieces, 5 in number, of the well-
crusted meteorite weighing 32 Ibs. which fell at Butsura in India
in 1861 were without difficulty fitted together by Maskelyne after
an attentive consideration of the fractures. This is the more
noteworthy from the fact that the pieces were picked up at places
several miles apart. This instance of the disruption of a meteorite
perhaps throws some light upon the circumstance that large
fireballs are occasionally seen to break up into fragments as they
disappear.

The circumstances connected with the occurrence which stands
No. 8 in the catalogue (ante], are of more than ordinary interest,
especially from its having been long considered a poetical
romance of by-gone ages. The following narrative was drawn
up at the time by order of the Emperor Maximilian, and depo-
sited with the stone in the church at Ensisheim. " In the year
of the Lord 1492, on Wednesday, which was Martinmas Eve,
November 7, a singular miracle occurred ; for between 1 1 o'clock
and noon there was a loud clap of thunder, and a prolonged
confused noise, which was heard at a great distance ; and a stone
fell from the air, in the jurisdiction of Ensisheim, which weighed
260 pounds ; and the confused noise was, moreover, much louder
than here. There a child saw it strike on a field in the upper
jurisdiction, towards the Rhine and Jura, near the district of
Giscano, which was sown with wheat, and it did no harm, except
that it made a hole there ; and then they conveyed it from that
spot, and many pieces were broken from it, which the landvogt
forbade. They therefore caused it to be placed in the church,
with the intention of suspending it as a miracle ; and there came
here many people to see this stone. So there were remarkable
conversations about this stone ; but the learned said they knew
not what it was ; for it was beyond the ordinary course of nature
that such a large stone should smite the Earth, from the height of
the air, but that it was really a miracle of God ; for, before that
time, never anything was heard like it, nor seen, nor described.
When they found that stone, it had entered into the Earth to the

CHAP. I.] Aerolites. 595

depth of a man's stature, which everybody explained to be the
will of God that it should be found ; and the noise of it was heard
at Lucerne, at Vitting, and in many other places, so loud, that it
was believed that houses had been overturned : and as the King
Maximilian was here the Monday after St. Catherine's Day of
the same year, his Royal Excellency ordered the stone which had
fallen to be brought to the castle ; and after having conversed
a long time about it with the noblemen, he said that the people
of Ensisheim should take it, and order it to be hung up in the
church, and not to allow anybody to take anything from it. His
Excellency, however, took two pieces of it, of which he kept one,
and sent the other to Duke Sigismund of Austria ; and they spoke
a great deal about this stone, which they suspended in the choir,
where it still is ; and a great many people came to see it." This
relic remained in the church for 3 centuries, and then it was
temporarily removed, during the turmoil of the French Revolution,
to Colmar, but it has since been restored g. A fragment of it is
in the British Museum, and there is another piece at the Jardin
des Plantes, at Paris.

The fall of the aerolite of 1627 (No. 10) was witnessed by
the astronomer Gassendi : he states that when in the air it was
apparently surrounded by a halo of prismatic colours. This
being the only aerolite of the fall of which he had ever heard,
he supposed that it was the result of a volcanic eruption in some
one of the neighbouring mountains. Views similar to Gassendi's
of the origin of aerolites were maintained even recently by
Kesselmeyer, whose work on the geographical distribution of
aerolites supplied an excellent list, with maps, of such occur-
rences up to a very recent date. Such views, it will not be
necessary to remind the reader, cannot however now be held to
accord with the known cosinical origin of these bodies.

The aerolite of Dec. 13, 1795 (No. 28), is interesting from
the fact that it is one of the few instances recorded to have
taken place in this country. A loud explosion, followed by a

g Badeker says that this stone is now preserved in the Rathhaus. (Shine, gth
Eng. ed., p. 282, 1884.)

Q q 2

596 Meteoric Astronomy. [BOOK V.

hissing noise, was heard throughout a considerable portion of the
surrounding district ; a shock was also noticed, as if produced
by the falling to the Earth of some heavy body. A ploughman
saw the stone fall to the ground at a spot not far distant from
the place where he was standing ; it threw up mould on every
side, and, after passing through the soil, penetrated several
inches deep into the solid chalk rock. It fell on the afternoon
of a mild but hazy day, during which there was neither thunder
nor lightning h.

One of the most extensive falls of meteoric stones on record was
that which happened in Normandy on April 26, 1803 (No. 34).
It appears that at about i P.M. a very brilliant fire-ball was seen
traversing the country with great velocity ; and, some moments
afterwards, a violent explosion was heard, which was prolonged
for 5m or 6m. The noise seemed to proceed from a small cloud,
which remained motionless all the time but at a great elevation
in the atmosphere ; the detonation was followed by the fall of
an immense number of mineral fragments, nearly 3000 being
collected, the largest weighing 8| Ibs., according to Arago. The
sky was serene, and the air calm — an atmospheric condition that
has sometimes been noticed, as well as opposite states of the
weather, during the descent of aerolites '.

On April 20, 1876, a mass of meteoric iron weighing between
7 and 8 Ibs. fell at Rowton, a village near the Wrekin, in Shrop-
shire. Shortly before 4 P.M. a sound like that of thunder,
followed by reports as of cannon, shook the air, and was heard

h Howard, Phil. Trans., vol. xcii. p. supply a continuation of the list of

174. 1802. Buchner and of other compilers. The

1 A catalogue of 273 aerolites is given first such catalogue was formed by
in AT&go'sAst. Pop., vol. iv. pp. 184-204. Chladni, and a larger one by Kamtz
French ed. But larger numbers of aero- ( Meteor ologie). Subsequently Buchner
litic falls than this are now represented (DieMeteoriteninSammlunoen},T3.&idin-
by specimens of meteorites preserved in ger, Rammelsberg, Mrs. Sheppard, U.S.
the national museums of London, Paris, and others have furnished catalogues, a
and Vienna ; the British Museum alone collection and discussion of which by E.
possessing specimens of 370 different P. Greg will be found in the British
meteorites, of which about 240 were seen Association Report, 1860, with later sup-
to fall. An important series of articles plements and revised tables of frequency
by Dr. W. Flight, in the Geological of aerolites on different dates, in the
Magazine, 1875, 2nd Ser., vol. ii , volumes for 1867 (p. 414) and 1870 (p. 93 \

CHAP. I.]

Aerolites.

597

(during rain showers) for many miles in that neighbourhood,
but no fireball was observed. The iron mass was found nearly
an hour afterwards in a meadow where it had buried itself in
the earth to a depth of J 8 inches ; when dug out it was still
quite hot.

The meteorite which fell at Sako-Banja in Servia exhibits a
conglomerate structure or tufa resembling that presented by

Fig. 237.

METEORITE WHIC^ FELL AT SAKO-BANJA IN SERVIA, OCT. 13, 1877.

the ancient volcanos of Auvergne and of the valley of the
Rhine.

The circumstances connected with the fall of the meteorite of
March 14, 1881, near Middlesborough, were investigated by
Prof. A. S. Herschel. At 3h 35™ P.M., the air being calm and the
sun shining brightly, 4 railway platelayers heard a rushing or
roaring sound overhead, followed immediately by a thud on the
ground. On proceeding to the spot, less than 50 yards distant,

598 Meteoric Astronomy. [BOOK V.

they found a round vertical hole, into which one of them thrust
his arm and drew out the meteorite. The hole and also the
meteorite were felt to be slightly warm about 3 minutes after
the fall. Professor Herschel described the meteorite as of a low
pyramidal or shell-like shape, and measuring 5 inches by 6
inches, and about 3 inches high. The grey basaltic stone of
which it consisted was, as usual, completely enveloped in a thin
black molten crust, which hid from the eye its true stony
character, the latter being only visible here and there at its
frayed edges. It was remarkable for the unusual depth and
regularity of the indentations which its surface had received by
heat and fusion in its passage through the air. This meteorite
is now in the Library of the Literary and Philosophical Society
of Newcastle k.

This is only the eighth case where the actual fall of an aero-
siderite or mass of meteoric iron has been observed, although
many such masses have been found, some of them of large size,
as at Krasnojarsk in Siberia, Atacama in Chili, Melbourne in
Australia, and recently some colossal blocks on the Island of
Disco in Greenland. At least one such meteoric mass has been
discovered in this country ; this was a meteorite weighing about
32 Ibs., which was exhumed near Melrose in Scotland in the year
1827.

In addition to those mentioned above the following falls of
meteoric iron have been actually observed : — Agram, Croatia
(1751); Charlotte, Tenn., U.S. (1835); Braunau, Bohemia (1847);
Victoria West, S. Africa (1862); Nidigullam, Madras (1870);
Marysville, California (1873).

k Observatory, vol iv. p. 155. May 1881.

FIRST VIEW.

SECOND VIEW.

1783: Aug. 18. (Sanby and Robinson.}

1878 : June 7. (Denning.)

1863: Oct. 19. (Schmidt.)

FIREBALLS.

CHAP. II.] Fireballs. 601

CHAPTEK II.

FIREBALLS.

General Description of them. — Fireball of Nov. 12, 1861. — Monthly Table of ap-
paritions.— Dates of greatest frequency. — Results of calculations with reference
to these bodies.

FIREBALLS* may either represent the larger class of shooting
stars, or the aerolites described in the last chapter. There is
no doubt that meteor showers like the Perseids, Leonids and
many others, while yielding a considerable proportion of meteors
of the smallest visible types, yet occasionally furnish Fireballs
which are as brilliant and apparently as large as the Moon.
They appear suddenly, and are usually noiseless, though at times
a detonation is heard, and in these cases the phenomenon is
probably aerolitic. Their form is generally pear-shaped. The
slow-moving Fireballs usually evolve trains of sparks, but the
swifter class project streaks of phosphorescence upon the sky,
and these features (which may be taken to represent the con-
sumed material thrown off by the incandescent nucleus) some-
times linger for many minutes after the first appearance, assuming
irregular shapes and drifting slowly away from the place of
apparition by the action of wind-currents high in the atmo-
sphere.

Fireballs are occasionally of great brilliancy, and appear so
unexpectedly as to startle those who witness them. A good
description of one of these bodies which fell on Nov. 12, 1861,
is given by the Rev. T. W. Webb, and a part of his account

* The British Association Report for See also Month. Not., R. A.S., vol. xliv.
1878 contains full instructions to obser- p. 297, April 1884.
vers of Fireballs and kindred phenomena.

602

Meteoric Astronomy.

[BOOK V.

may be quoted as a typical example of what is to be seen from
time to time in connection with these objects:—

" About 5h 45™ G.M.T. (with an uncertainty of 5™ or more) we were walking,
a party of 3 persons, along a wide turnpike road, fully lighted by a moon 10 days
old, when we were surrounded and startled by an instantaneous illumination,

Fig. 242.

METEOR OF NOV. 12, i86i. (Webb.}

not like lightning, but rather
resembling the effect of moonlight
suddenly coming out from behind
a dark cloud on a windy night;
it faded very speedily, but on
looking up we all perceived at a
considerable altitude, perhaps 60°
or 70°, a superb mass of fire sweep-
ing onwards and falling slowly in a
curved path down the W.S.W.
sky. . . . Ruddy sparks, of the colour
of glowing coals, were left behind
at its smaller end, and its path was
marked bya long pale streak of little
permanency. Its termination, un-
fortunately, was concealed by boughs
of trees, among which, however, it
was traced till possibly some 10°
above the horizon, but it had pre-
viously undergone a great diminu-
tion. . . . The whole duration may
have been as much as 5 seconds. Its
aspect was decidedly that of a
liquefied and inflamed mass, and
the immediate impression was that
of rapid descent b."

Arago classified all the recorded instances of Fireballs ac-
cording to their dates, and found that they were distributed
as follows over the 12 months; a similar summary made up
to a more recent date (1879) is also added for comparison0: —

January
February
March
April . .
May . .
June ..

ARAGO.

• 55 -

• 57 •
48 .
53 -

• 5° -
43

Jan. to June = 305

TO 1879.

ARAGO.

TO 1879.

239

July

... 74 ...

... 287

!74

August

123

775

186

September . .

64 ...

373

234

October

... 77 ...

... 292

163

November .

... 90 ...

... 551

172

December ...

... 80 ...

... 289

1 168 July to Dec. = 508

2467

b Letter in the London Review, Novem- c Observatory, vol. iii. p. 127, Septem-
ber 16, 1861. her 1879.

CHAP. II.] Fireballs. 603

The numbers exhibit a great excess of these phenomena in
the last half of the year. The most prolific months are
August and November: the large number recorded in these
months is partly due to the circumstance that meteor observers
have devoted their chief attention to those months owing to the
occurrence of the Perseids, Leonids and Andromedes.

It is found that at certain definite epochs of the year Fireballs
are unusually numerous. The following appear to be the best
defined dates for their observation : —

Jan. 2, 21, 31.
Feb. 3, 7, 10.
March I, 2, 4.
April 11-12, 19-20.
May 2,4, 15, 31.
June 6-7, 12, 29-30.

July n, 20-21, 25-30.
Aug. 3, 5, 7-13, 15, 19-22.
Sept. 1-2, 6-7, 11-13, 25-
Oct. 13, 15, 17-18, 22, 24, 29.
Nov. 1-2, 4, 6-9, 11-15, 19, 27-
Dec. 8-9, 11-12, 21.

The dates printed in heavier type have proved especially rich
in Fireballs.

Though a very insignificant proportion of the observed Fire-
balls discharge aerolites upon the Earth's surface, it is probable
that the two phenomena are intimately associated. Aerolites
have occasionally been precipitated without any prior warning,
in the form of luminous exhalations; an instance occurred
on Sept. 1 6, 1 843, at the fall of the great aerolite of Klein wendend.
It is singular that during meteor storms, such as those of Nov. 13,
1866, and Nov. 27, 1872, none of the many thousands of fragments
which entered our atmosphere were observed to reach the earth.
This has been adduced as an argument against the theory of
affinity between aerolites and ordinary meteors. On Nov. 27,
1885, however, during the recurrence of the Biela meteor storm,
a piece of meteoric iron fell at Mazapil in Mexico ; and there
is strong evidence td show that this aerolite was a veritable
fragment of Biela's comet !

Many Fireballs have formed the subjects of computation as
to their distances, sizes, and velocities, but owing to the peculiar
nature of these phenomena, their unexpected appearance, and the

d Compt. Rend., vol. xxv. p. 627 (Nov. 2, 1847).

604

Meteoric Astronomy.

[BOOK V.

difficulty of securing perfectly accurate observations, the follow-
ing results must be considered as mere approximations.
J. As to the extreme heights during visibility : —

GREATEST KNOWN.

1868 Sept. 5
1844 Oct. 27
1718 Mar. 19

Mil.-,.
460-0
3I8.I
297-5

LEAST KNOWN.

1879 Feb- 22 ..
1879 Feb. 24 ..
1846 Mar. 21 ..

2. As to absolute diameter : —

GREATEST KNOWN.

1841 Aug. 1 8
1718 Mar. 19
1837 Jan- 4

Feet.

12,795
8,399
7,216

LEAST KNOWN.

1852 April 2
1846 July 23
1850 July 6

3. As to velocity per second : —

GREATEST KNOWN.

1850 July 6
1844 Oct. 27
1842 June 3

Miles.
47-22

44-74
44-74

LEAST KNOWN.

1718 March 19
1807 Dec. 14 ..
1676 Mar. 31 .,

Milea.
5-5
6-5

7-5

Feet.
105
321
705

Miles.
1.67

2-80

The average velocity of a considerable number of meteors
computed by Prof. A. S. Herschel is 35 miles per second.

The estimated diameters of Fireballs are usually much in
excess of the real values. The absolute dimensions attributed
to several large meteors in the above table must therefore be
received with caution. The nucleus of a Fireball during com-
bustion has a flaming aspect, and the glare invariably accompany-
ing it creates an exaggerated impression of its size. Their
velocities are also liable to considerable errors, as there are grave
difficulties in the way of determining the exact durations of their
flights, save in exceptional instances when the speed is slow and
the observer is sufficiently prepared for the event to be able
to time it carefully.

The average heights of Fireballs are less than the average
heights of shooting stars6. A comparison of many recorded
results gives the following relative figures : —

At appearance. At mid-course. At disappearance.

Fireballs 69 miles 49 £ miles 30 miles.

Shooting Stars ... 80 „ f 67 „ 54 miles.

e Month. Not., vol. xlviii. p. 113, January 1888.

CHAP. II.] Fireballs. 605

It is evident that the brighter forms of meteoric display occur
in a lower region of the atmosphere than that of the fainter
class of these phenomena.

There are certain meteor showers which apparently yield a
large proportion of Fireballs f.

As a very recent example of observations followed by com-
putation the following maybe cited. On Nov. 13, 1888, Denning
at Bristol and Backhouse at Sunderland each observed a fireball,
which on a comparison of the accounts proved to be one and

Fig. 243.

CUBIOUS FORM OF TRAIL LEFT BY THE FIREBALL OF OCTOBER 19, 1877.
i First effect. 2 Second effect (10 min. later).

the same object. Backhouse states that at i7h I9m he became
suddenly aware of a bright flash, and, a few seconds later, he
discovered an unusually intense Meteor-streak lying amongst the
stars of Bootes and about 5° below Arcturus. It was estimated
as 4° long at first, and proved very durable, for it remained in
sight for 9m, and exhibited during that time some alteration

' A table of the radiant points of these Pop., vol. iv. pp. 230-79, French Ed.

will be found in the Monthly Not., vol. See also some important summaries by

xliv. pp. 298-9, April 1884. A catalogue Greg in the B. A. Reports for 1860, 1867

of 584 Fireballs is given in Arago's Att. (p. "414), and 1870 (p. 93).

606 Meteoric Astronomy. [BOOK V.

both in shape and position. The places were carefully noted
and recorded. Denning's observations were so far less satisfactory
in that at Bristol the Meteor was seen much nearer the horizon,
but the salient features were so similar that there can be no
doubt about the identity of the two objects.

Fig. 244.

i7h 19™. i7h 22jm. i7h 28™.

TKA1L LEFT BY THE FIREBALL OF NOV. 13, 1 888.

The details of the observations need not be given, but a
summary of them yields the following results :—

Beginning of Meteor (Bristol) at 65 miles.

Beginning of Light Streak (Sunderland) at 57 miles.

End of Light Streak (Sunderland) at 45 miles.

End of Meteor (Bristol) at 37 miles.

Inclination to Mean horizon ... 57 degrees.

Entire length of observed real path (^ Bristol) 34 miles.

The Meteor's Earth-point was situated in about Lat. N., 55-6°,
Long. E., 3-3°, and its radiant at 149°, + 25°. The duration of its
flight was not estimated, so its velocity cannot be determined.
At Bristol however it was described as ' swift,' and the inference

CHAP. II.] Fireballs. 607

is that its motion probably accorded with the usual high rate
of speed attributed to the Leonid Meteors. The heights above
stated do not differ materially from the average of fireballs,
though the length of the path was decidedly shorter than
usual g.

g Denning, Month. Not., vol. xlix. p. 66, Dec. 1888.

608 Meteoric Astronomy. [BOOK V.

CHAPTER III.
SHOOTING STARS.

Have only recently attracted attention. — Are visible with greater or less frequency
every clear night. — Summaries of the monthly and horary rates of apparition
from observations by Coulvier- Gravier and Denning.— Number of known meteor
showers. — Their distribution amongst the constellations. — Monthly number of
meteors catalogued. — Early notices of great meteor showers. — The showers of
1799, 1831, 1832, 1833, 1866, and following years. — The shower of Aug. 10. —
Of Nov. 27, 1872, and Nov. 27, 1885. — Nomenclature of meteor systems. —
Views of Olbers. — Monthly summary of great meteoric displays.

SHOOTING stars, although noticed in ancient times, have
attracted special attention only during the present century.
This branch of the science may therefore be considered to be com-
paratively in its infancy. Though a vast number of observations
have now been accumulated and are available for discussion
we require many more, and a searching investigation of the
whole subject, before we can claim to have thoroughly mastered
its details and to have explained certain peculiarities which
are not quite in harmony with prevailing theories. The labours
of Heis and Schmidt, of A. S. Herschel and Greg, of Schiaparelli
and many others, have however so far smoothed the way to
a satisfactory conception of the movements and physical nature
of these objects that much of the former mystery concerning
them has been cleared away, and we have a substantial basis on
which to augment our knowledge a.

Shooting stars were long considered to have an atmospheric
origin and to be due to the combustion of inflammable gases ex-
haled by the earth. This theory is now rejected in favour of one
which is perfectly consistent with the observed features of these

a A pamphlet by T. Bredechin entitled Sur Vorigine des etoilesfilantes, published
at Moscow, 1888, may be mentioned in this connection.

CHAP. III.] Shooting Stars. 609

bodies. They are of celestial origin, pursuing orbits similar to
comets, and grouped into streams containing in many cases
an immense assemblage of particles. They become visible to
us on being inflamed by friction with our atmosphere, into which
they rush with planetary velocity and are instantly consumed
and reduced to imperceptible dust.

There is no clear night throughout the year on which a certain
number of shooting stars are not visible. When the air is trans-
parent, the moon absent, and the stars shining brightly, about
8 or 10 may be noticed every hour. The horary average will
be greater if the sky is watched in the morning hours during
the last half of the year. At such times it is often possible to
note 20 or 25 of these objects during an hour, though no par-
ticularly active shower may be in progress at the time. On
certain specific nights the numbers visible exhibit a great increase,
due to the recurrence of periodic showers. On ordinary nights
the shooting stars which are seen belong to a number of feeble
streams, and were formerly called sporadic meteors, but the term
has now lost much of its significance, for it has been proved that
as a rule the seemingly erratic members belong to definite systems
whose radiant points are capable of being discovered by pro-
longed and critical observation. Certain of these systems appear
to be of extreme tenuity, so that a single observer may only notice,
during an entire night, one or two meteors from each of them.
It is therefore found necessary to combine the records of several
consecutive nights of observation in order to ascertain their
radiant points.

There is a variation in the visible number of meteors, which is
regulated both by the season of the year and the hour of the
night. During the last six months of the year there are double
the number compared with the first six months. As to the
diurnal variation, it is found that the hourly rate increases up to
2 or 3 A.M., when the maximum is reached. From a large number
of observations by M. Coulvier-Gravier the following numbers
were derived b: —

b Recherche* sur tes Meteoren et hs lois qui leu rtgissent, Paris 1859, pp. 217-20.

R r

610

Me teoric A sti -onomy.

[BOOK V.

5
6

h.
to 6 even. ...

.. 7 ,>

Jan. t<> June.
... 8-5 ...
3- 1

July to Dec.

... 7-0 ...
... 6-<; ...

Whole year.

... 7-2
... 6-^

7
8

„ 8 „
„ o ,

.. 3-4 ..-

2-7

... 8-5 ...
8-4

7-0
6-1

„ 10 „

... 3-2 ...

... II-O ...

7-9

„ ii ,,

... 3-1

... I2-I

8.0

T T

,, 12 midnight

4-1

13-3

Q.C

„ I morn. ...

... <5-2 ...

I4-R

10-7

,, 2 ,,

.6-6

I7-O .

13-1

,, 3 ,,

... 8-1 ...

2O-4 ...

... 16-8

, 4

6-7

l8-7

15-6

„ 5 „

... 6-2 ...

... 184 ...

... 13-8

,, 6 „ ...

... 6-8 ...

1 8-4

IV7

, 7

6-i

17-2

i.VO

Below is added for comparison the horary number found from
observations at Bristol. About three-fourths of these were how-
ever obtained during the last half of the year, and the figures
(which show a good agreement with M. Coulvier-Gravier's) are
therefore rather higher than would be yielded by data equally
distributed over the first and last six months : —

h.
to 7 even.

10 ...

1 2 midnight

8.0
6-8
8-5
8-7

h.
12

2
3

1 morn.

2 ...

3 ...

4 ...

5 ...

6 .

12-9
15-3
J.5-3
15-0
16-3

As to the monthly mean of the hourly number of visible
shooting stars, the following values are given by MM. Coulvier-
Gravier and Saigey and by Denning : —

Month.

Jan
Feb. ...

Coulvier-Gravier
and Saigey.

... 3-6 ... .

3-7

Denning.

.. 8.0
5-8

Month.
July
Aug. .

Coulvier-Gravier
and Saigey.

... 7-0 ... .
... 8-<5 ... .

Denning.
.. I2-O
.. I2-Q

Mar. ...

2-7

6-!7

Sept

... 6-8 ... .

,. IO-Q

April
May
June

... 3-7 ... •
... 3-8 ... .
... 3-2 ... .

.. 7-0

• • 5-5
.. 5-0

Oct
Nov
Dec

... 9-1 ... .
... 9-5 ... .

... 7-2 ... .

.. 12-2
.. IO-9
0.6

Jan. to June

... 3-4 ••. •

6-3

July to Dec.

... 8-0 ... .

IL4

The two series of figures, though not agreeing amongst them-
selves, yet plainly indicate the great excess of shooting stars

CHAP. III.] Shooting Stars. 611

during the last half of the year. Aerolites and Fireballs, indeed
every form of meteoric phenomena, appear to attain their
maximum during the period from July to December. There
is a great increase in the horary numbers at about the middle of
July, and an equivalent decrease at the middle of December.
Though the earth is much nearer to the sun during the last half
of December and in January than in July and August, the rate of
meteoric apparitions during the former period is scarcely more
than one-third that of the latter. This circumstance is mentioned
by way of challenge to the idea that meteors are more densely
aggregated in regions nearer the sun. The systems of these
bodies annually encountered by the Earth evidently manifest
a peculiar distribution which further observations may elucidate.

Mr. Greg's last general catalogue0 of the radiant points of
shooting stars, published in 1876, was based on 850 radiants
deduced from 15,000 catalogued meteors. At the present time
we have more than 3000 radiants, derived from upwards of
82,000 meteors. These observations have been rapidly accumu-
lating in recent years. Of the 3000 radiants referred to as
having been now determined, a large proportion are dupli-
cate positions of identical showers, and it is probable that not
more than 500 distinct showers have been definitely ascertained.

Upon analysing all the positions, Denning finds that they
indicate a very uneven dispersion amongst the constellations,
a fact which is due partly to real differences and, in a less degree,
to the relatively excessive observations gathered in certain
favourable months of the year. In Right Ascension the radiant
points are situated as follows : —

R.A.

Radiants.

Per cent.

R.A.

Radiants.

Per cer

I tO

378

I2.4

181 to

2IO

147

4.8

31 „

449

I4-8

211 „

240

186

6.1

61 „

315

10-3 241 „

270

217

7-2

91 »,

I 2O

229

7.6 271 „

300

254

8-4

121 „

150

192

6-3

301 „

33°

243

8-0

151 „

1 80

142

4-7 33i „

283

9-3

c Brit. Assoc. Sep., 1876, p. 119. showers are from the Month. Not., vol.
These and the following notes with xlvii. pp. 35-39 (Nov. 1886).
reference to the distribution of meteor

R r 2

612 Meteoric Astronomy [BOOK V.

The meteor streams are found in greatest abundance between
i° and 60° of R.A. This is a fact irrespective of the cometary
showers of Andromedes (Nov. 27) and Perseids (Aug. 10), which
fall in this region, and might be supposed to have induced the
singular condensation referred to. The area, following it, from
61° to 90°, shows a great decline, notwithstanding it includes

.2 *

C i s a X q

o 3 c S .2 ;

•J E-5 hJ O O *

DISTRIBUTION OF METEOR STREAMS IN RIGHT ASCENSION.

•53 •£
fiH

<« S » > 'C a

« H

the Orionids (Oct. 17-20), and the mass of showers originating
in Auriga, Camelopardus, and the eastern quarter of Taurus.
And the area, 331° to o° preceding the area of maximum,
though rich in Aquariads, Pegasids, Lacertids, and Cepheids,
exhibits a great deficiency as compared with it. The excess, so
decided in character, between i° and 60° is distinctly to be

CHAP. III.] Shooting Stars. 613

attributed to the Cassiopeids, a, (B, and y Andromedes, Arietids,
Muscids, a and /3 Perseids, Taurids, &c., which, combined with
the cometary showers of Andromedes and Perseids, swell the
aggregate number to an abnormal figure.

The minimum proportion of showers is clearly between
151° and 210° R.A., and does not much exceed one- third of those
grouped between i° and 60°, the relative figures being 289 and
827.

In North Polar Distance the showers are placed as follows : —

X.P

Radiants.

Per cent.

.P.D

Radiants.

Per cei

o to

1-3

392

12-9

10 ,,

141

„

335

II-O

20 ,,

243

8-0

„

211

6.9

30 ,,

473

15-6

„

127

4-2

40 „

489

16.1

+ 99

170

5-6

5° ..

4'5

'3-7

The maximum obviously lies between 30° and 49° N.P.D., and
the minimum naturally occurs at the pole, inasmuch as the zone
o° to 9° includes a much smaller area than any other.

The distribution of the observed radiants in N.P.D. is affected
by the differences in the areas of the several zones and their
relative degrees of visibility. Though towards the pole the total
space included in the zones becomes less, yet this is in a large
measure compensated for by their more favourable position and
the persistency with which they are displayed to view. The
entire zones, from o° to 49° N.P.D., never fall below the horizon
in England, and such showers as they present are therefore
determinable at any period of the year or time of night. This
applies specially to English latitudes, but it also has a genera]
reference (with perhaps slight modifications in certain instances)
because nearly all our existing observations of shooting stars
have been made at stations having considerable (i.e. exceeding
35°) North latitude. The summary proves that while the two
zones embraced between the parallels of 30° and 49° N.P.D. have
the largest number of recorded streams, the three zones succeeding
towards the equator exhibit a gradual decline, though each re-
mains fairly prolific. The Andromedes, Perseids, and Quadrantids

614

Meteoric Astronomy.

[BOOK V.

are arranged between 30° and 49°, while the Geminids, Leonids,
and Lyrids, lie between 50° and 69° N.P.D. Considering all
the circumstances, there do not appear to be great inequalities
of grouping in North Polar Distance analogous to those which
undoubtedly occur in Right Ascension, but the point requires
further investigation.

In considering the distribution of meteor streams, several
important conditions must not be lost sight of. The bulk of the
observations have been effected in the summer months, whence it
necessarily follows that such constellations as are most favour-
ably visible at this period must certainly appear to exhibit a
predominance of showers. The comparative monthly numbers
of meteors registered (82,156 meteors in all) yield the following
result : —

Month.

Meteors
Catalogued.

Per cent.

Month.

Meteors
Catalogued.

Per cent.

January

2804

3-4

July

10670

12-1

February

1826

2-2

August

3'5l6

38-1

March

1764

2-1

September

43°4

5-i

April

5585

6-8

October

6840

8-3

May

2I2O

2-6

November

*3'9

"•3

June

2353

2-9

December

4°55

4-9

These numbers are derived from the catalogues of Corder,
Denning, Denza, Heis, Konkoly, Lucas, Sawyer, Schmidt, Tupman,
Weiss, Zezioli, and the Italian Meteoric Association, 1869, 1870,
and 1872, and some minor lists.

More than one-half the total number of observations were
obtained in July and August, and, in point of fact, are nearly all
embraced between the period from July 20 to August 15. The
majority of the observations have been secured before midnight,
and it is therefore certain that the region of 31° to 60° R.A.,
which is for the most part either below the horizon or low in the
North-East at the special epoch when the largest number of
meteors have been recorded, is not rendered rich solely by this
abundance of observations. Indeed the months of September,
October, and November appear to have furnished, relatively to
the number of meteors catalogued, by far the greatest number of
showers in this quarter of the sky. It seems, therefore, that the

CHAP. III.]

Shooting Stars.

615

great fertility in streams of the region about Andromeda. Aries,
and Perseus is a real fact, which cannot be explained away on the

Fig. 246.

RELATIVE NUMBER OV METEORS CATALOGUED DURING THE SEVERAL
MONTHS OF THE YEAR.

ground that it arises from excessive observations at special
periods, or that it is due to any conditions likely to induce a
misleading result.

I will now refer to the well-known and beautiful showers d of
shooting stars seen at certain epochs with such striking effect.

One of the earliest notices we find in history of this pheno-
menon is by Theophanes the Byzantine historian, who relates
that in November 472 A.D. the sky at Constantinople appeared
to be on fire with flying meteors. Conde, in his history of the
dominion of the Arabs, speaking of the year 902 A.D., states that
in the month of October, on the night of the death of King
Ibrahim-Ben-Ahmed, an immense number of falling stars were

d An interesting catalogue by Newton xxxvii. p. 377, vol. xxxviii. p. 53, May
will be found in Silliman's Journal, 2nd and July 1864.
Ser., vol. xxxvi. p. 145, July 1863: vol.

616 Meteoric Astronomy. [BOOK V.

seen to spread themselves over the face of the sky like rain, and
that the year in question was thenceforth called the "Year of
Stars." In some Eastern Annals of Cairo it is related that: "In
this year, in the month Redjeh [August 1029], many stars passed,
with a great noise, and brilliant light;" and in another passage it
says: "In the year 599, on Saturday night, in the last Mofiarrun
[Oct. 19, 1202], the stars appeared like waves upon the sky,
towards the east and west ; they flew about like grasshoppers,
and were dispersed from left to right ; this lasted till daybreak :
the people were alarmed." It is also recorded that a remark-
able display took place in England and France on April 4, 1 095.
The stars seemed " falling like a shower of rain from heaven
upon the Earth," and an eyewitness, having noticed where an
aerolite fell, " cast water upon it, which was raised in steam
with a great noise of boiling." In the Chronicle of Rheims we
read that the stars in heaven were driven like dust before the
wind, and Rastel says that : " By the report of the common
people in this kynge's time [William II] divers great wonders
were sene: and therefore the kynge was told by divers of his
familiars that God was not content with his ly vying; but he
was so wilful and proud of mind, that he regarded little their
saying."

In modern times, the earliest shower of falling stars of which
we have any detailed description is that of Nov. 13, 1799, which
was visible throughout nearly the whole of North and South
America: it was seen even in Greenland by the Moravian
missionaries. Humboldt, then, travelling with M. Bonpland, in
South America, says :—

"Towards the morning [of the 12th] the most extraordinary luminous meteors
were seen towards the E. . . Thousands of bolides and falling stars succeeded each
other during 4 hours. Their direction was very regularly from North to South. . . .
From the beginning of the phenomenon there was not a space in the firmament
equal in extent to 3 diameters of the Moon that was not filled every instant with
bolides and falling stars. . . . All these meteors left luminous traces from 5 to 10
degrees in length, as often happens in the equinoctial regions. The phosphorescence
of these traces lasted 7 or 8 seconds *.*'

0 Humboldt and Bonpland, Personal Narrative of Ti-arels, trans. Williams, vol.
iii. p. 331. Lond. 1881.

CHAP. III.] Shooting Stars. 617

Mr. Ellicott, an agent of the United States, at sea in the Gulf
of Mexico, thus describes the scene : —

"About 3 o'clock A.M. I was called up to see the shooting stars, as it is commonly
called. The phenomenon was grand and awful; the whole heaven appeared as
if illuminated with sky-rockets, which disappeared only by the light of the Sun after
daybreak. The meteors, which at any one instant of time appeared as numerous as
the stars, flew in all possible directions, except from the Earth, toward which they
all inclined more or less ; and some of them descended perpendicularly over the
vessel we were in, so that I was in constant expectation of their falling among usf. "

The same observer also states that his thermometer suddenly
fell 30°, and the wind changed from S. to N.W., whence it blew
with great violence g. for 3 days.

Meteoric showers were also witnessed in North America, in the
years 1814, 1818, and 1819.

Fine meteoric displays took place in 1831 and 1832, in both
cases on Nov. 13. Captain Hammond, of the ship Restitution,
then in the Red Sea, off Mocha, thus describes the latter: —

" From i o'clock A. M. till after daylight, there was a very unusual phenomenon in
the heavens. It appeared like meteors bursting in every direction. The sky at the
time was clear, the stars and Moon bright, with streaks of light and thin white clouds
interspersed in the sky. On landing in the morning, I inquired of the Arabs if they
had noticed the above. They said they had been observing it most of the night. I
asked if ever the like had appeared before. The oldest of them replied that it had not h."

This shower was seen from Arabia, westward to the Atlantic,
and from the Mauritius to Switzerland. Various descriptions of
it and of other star showers were collected by Arago in a Memoir
on shooting stars which will be alluded to again presently.

By far the most splendid display of shooting meteors on record
was that of Nov. 13, 1833, and one which served to point out the
periodicity of the phenomenon. It seems to have been visible
over nearly the whole of the Northern portion of the American
continent, or, more exactly, from the Canadian lakes nearly to the
equator. Over this immense area a sight of the most imposing
grandeur seems to have presented itself. The phenomenon
commenced at about midnight, and was at its height at about

' Trans.of the American Philosophical that windy and stormy weather was

Soc., vol. vi. p. 28. 1809. likely to occur.

* The prevalence of meteors was for- h SilUman's American Joitrn., istSer.,

merly considered an unfailing indication vol. xxvi. p. 136. 1834.

618 Meteoric Astronomy. [BOOK V.

5 A.M. Several of the meteors were of peculiar form and con-
siderable magnitude. One was especially remarked from its
remaining for some time in the zenith over the Falls of Niagara,
emitting radiant streams of light. In many parts of the country
the population were terror-stricken by the beauty and magni-
ficence of the spectacle before them. A planter of South Carolina
thus narrates the effect of the phenomenon on the minds of the
ignorant blacks : —

" I was suddenly awakened by the most distressing cries that ever fell on my ears.
Shrieks of horror and cries for mercy I could hear from most of the negroes of the
3 plantations, amounting in all to about 600 or 800. While earnestly listening for
the cause I heard a faint voice near the door, calling my name. I arose, and, taking
my sword, stood at the door. At this moment I heard the same voice still beseeching
me to rise, and saying, ' 0 my God, the world is on fire ! ' I then opened the door,
and it is difficult to say which excited me the most — the awfulness of the scene,
or the distressed cries of the negroes. Upwards of 100 lay prostrate on the ground —
some speechless, and some with the bitterest cries, but with their hands raised,
imploring God to save the world and them. The scene was truly awful ; for never
did rain fall much thicker than the meteors fell towards the Earth ; east, west, north,
and south, it was the same '."

The meteors of which the above shower was composed seem to
have been seen of 3 different kinds : —

1. Phosphoric lines, apparently described by a point. These
were the most abundant ; they passed along the sky with im-
mense velocity, as numerous as the flakes of a sharp snow-storm.

2. Large fireballs, which darted forth at intervals across the
sky, describing large arcs in a few seconds. Luminous trains
marked their paths, which remained in view for a number of
minutes, and in some cases for half an hour or more. The trains
were generally white, but the various prismatic colours oc-
casionally appeared, vividly and beautifully displayed. Some of
these fireballs were of enormous size ; indeed, one was seen
larger than the Moon when at its full.

3. Luminosities of irregular form, which remained stationary
for a considerable time. The one above mentioned as having
been seen at the Falls of Niagara was of this kind k.

' Quoted in Milner's Gallery of Nature. k Quoted in Milner's Gallery of Nature,
p. 140. p. 141 (abridged).

CHAP. III.] Shooting Stars. 619

Subsequently to 1833 the month of November was for some
years distinguished by an unusual number of shooting stars ; but
none of the showers equalled that which I have just described,
though those of 1866 and 1867 were extremely striking, the
former one, perhaps, especially so.

Fig. 247.

THE? METEOR RADIANT POINT IN LEO :
TRACKS OF METEORS SEEN AT GREENWICH, NOV. 13, 1 866.

The following letter, penned by Dawes, who observed the
meteors in Buckinghamshire, furnishes us with a brief and clear
description of most of the salient features of the shower of 1866,
which were attentively watched and very similarly described by
other competent observers : —

"Between midnight on the i3th and I4h 13"" ios (G.M.T.) 2800 meteors were
counted by myself and one assistant in the eastern hemisphere. Another assistant

620 Meteoric Astronomy. [BOOK V.

looking out to the West counted nearly 400 in an hour, but became so bewildered by
6 or 7 bursting out almost simultaneously, and this repeatedly, that the attempt to
count more was given up. I have no doubt from what I saw myself in the western
hemisphere, there must have been at least 700 visible in the 2\ hours. Adding to
these 75 which were seen before midnight, and we have upwards of 3500 in all, up to
about a quarter past 2 in the morning.

"Some were brighter than Venus ever is; but none were at all comparable to
several which appeared in 1832, Nov. 12, of which, however, I have never met with
any good or particular account V

Most of the reports of experienced observers who watched the
progress of the shower continuously, concur in placing at about
3000 or 4000 the total number that they saw, and which they
could have counted ; though it should be stated that the staff of
the Greenwich Observatory, as the result of a cleverly pre-arranged
subdivision of work, were able to count more than 8000.

The shower was at its height in England from about i 2h 45'"
to ih 45m A.M., when the radiant point in Leo had risen about 25°
above the Eastern horizon. The position of this radiant was in
R.A. 149°, Decl. + 23, corresponding very nearly with the place
given by Prof. Aiken for the shower of 1833 at R.A. 148°, Decl.
+ 24°. Before 4 A.M. the shower had almost ceased. Its display
was vertical over a meridian about 75° E. of Greenwich, and it was
accordingly confined to the Old World and quite invisible in
America. In 1867, 1868, and 1869 the shower recurred on the
same date, though declining each year, and was brilliantly visible
in America, though not comparable with the display of 1833.
Since 1872 this phenomenon has been feebly visible at its annual
returns, though re-observed at Bristol in 1876, 1877, 1879, 1885,
1887, and 1888. In 1879 and 1888, on the morning of Nov. 14,
the shower was rather conspicuous, and it furnished some brilliant
meteors from the same radiant as observed in 1 833 and 1 866.

Another meteor shower of great importance occurs annually on
Aug. i o. Public attention was first directed to that date by Ignace
Marie Thomas Forster, of Bruges m, and his diary even contained a
note of its annual character as early as the year 1 8 1 T . But it

1 Ast. Reg., vol. iv. p. 306. Dec. 1866. Nov. 12, 1832, in the Mem., R. A. S., vol.

In Ast. Reg., vol. xiii. p. 271, Nov. 1875, viii. p. 76. (Notes to a Star Catalogue.)

Mr. Webb drew attention to Dawes's m The Perennial Calendar, p. 400,

original observations of the meteors of Loud. 1824.

CHAP. III.] Shooting Stars. 621

was not until A. Quetelet constructed in 1836 the first general
catalogue of meteor showers, that the fact of its annual recur-
rence was fully recognised and established. The shower was
independently expected and successfully observed by E. C. Herrick
in the United States", and by Quetelet at Brussels, in the years
1836 and 1837; and it has since never failed to be annually
recorded. Years of maximum and minimum brightness have
occasionally been noticed, the year 1863 having been of the
former, and the years 1862, 1876, and 1888 of the latter class, but
meteors of this shower appear never to be entirely absent during
the nights of August 9-1 1 in each year. Herrick regarded
the position of the radiant-point as being near the cluster (x) in
the sword-hand of Perseus ; and another position at B, C, Camel-
opardi was also noted by Sir John Herschel at Slough in the
year 1840. The exact radiant point has more recently been
determined with great precision at R.A. 45°, Decl. + 57°, which
is a few degrees N.E. of the star 77 Persei. This stream is remark-
able for its extended duration, and for the obvious displacement
which occurs from night to night in the apparent position of its
radiant. The period of its visibility appears to cover the 43 nights
from July n to Aug. 22 inclusive, during which the centre of
radiation advances from R.A. 1 1°, Decl. + 48°, to R.A. 76°,Decl. + 57°,
according to the observations of Denning. The following are the
places successively taken up by the radiant on different nights: —

Date. R.A. Decl.

July ii ii +48 Aug. 10 46 +57

„ 18 18 +51 „ 15 ... ... 54 +57

„ 25 27 + 53 „ 19 67 +57

Aug. i , 35 +55 „ 22 76 +57

The displacement in the radiant0 is more rapid after the maxi-
mum on Aug. 10 than before it. This shower does not exhibit
great variations in its annual richness ; on the morning of Aug. 1 1
it usually yields from 60 to 80 meteors per hour for one
observer.

n Silliman's Journal, ist Ser., vol. and some other showers. In 1888 the

xxxiii. pp. 176 and 354. earliest indication of the Perseid shower

0 A displacement is also suspected in was seen on July 8 with radiant at

the diverging point of the April meteors K.A. 3°, Decl. + 49°, (see p. 641).

622 Meteoric Astronomy. [BOOK V.

Fig. 248 will convey a general idea as to the position of the
plane of the orbit of the shooting stars of August 10 relatively
to the plane of the orbit along which the earth travels round the
sun. It will also illustrate the annual encounter of the earth on
the day in question with these meteors, in numbers few or great,

Fig. 248.

INTERSECTION OP THE PLANE OF THE ORBIT OF THE EARTH BY THE SHOOTING
STARS OF AUGUST IO.

according to the circumstances of each year. The figures from
i to 12 represent the 12 months of the year.

Another meteor shower has in recent years become very
prominent. It occurred with imposing grandeur on November
27, 1872, and November 27, 1885, and was widely observed. The

CHAP. III.] Shooting Stars. 623

abundance of its meteors was remarkable on both occasions.
Mr. E. J. Lowe, who watched the display of 1872, computed that
58,660 meteors fell during the period from 5h 5om to ioh 30™ P.M.
At Moncalieri, 33,000 meteors were counted by Denza and
his assistants. Prof. Herschel collected and compared the
positions of the radiant as given by 90 observers. He found the
mean place at R.A. 25'i°, Decl. + 42*9° (closely N.W. of y Andro-
medae), from 35 of the best observations. This shower recurred
with equal splendour on Nov. 27, 1885. At Moncalieri, Denza
and 3 assistants observed nearly 40,000 meteors during the 4h
from 6 to 10 P.M. At many other stations, both in England and
abroad, the phenomenon was of similar intensity, and it was
watched with all the ardour that a great celestial event can
inspire. It was particularly noticed that the radiation was
diffused over 7° or more near the star y Andromedse, and Ranyard
considered it to have been elliptical, with its major axis North
and South, 12° or 15° long, and a minor axis of 6° or 8°.
Denning found the mean position of the radiant from 33 obser-
vations to be at K A. 237°, Decl. + 44-3°, which accords closely
with the centre assigned by Prof. Herschel for the shower of 1872.

These meteors are called Andromedes, from the fact that they
diverge from Andromeda. The shower of Nov. 14 is termed the
Leonids, and that of August 10 the Perseids. Some other con-
spicuous showers are distinguished by titles : thus we have the
Qiiadrantids of Jan. 2, the Lyrids of April 20, the Orionids of
Oct. 18-20, and the Geminids of Dec. 10-12, &c.

The annual recurrence of the January shower was noticed by
Wartmann at Geneva in 1 835-8, and its radiant-point was deter-
mined by Stillman Masters in America in January 1863. The
recurrence of the April and October showers was shown by
Herrick, in America, in 1 839, who also ascertained their radiant-
points. The November shower of Andromedes has appeared at
intervals since the close of the last century, and we owe to
Herrick in 1838, and subsequently to Heis and Schiaparelli, the
best observations of its radiant-point previously to one of its
cyclical returns in the year 1872. Like all the foregoing meteor

Meteoric Astronomy. | H.M.K v.

showers, except the last. the (triiiiniil* are also aininnl/i/ recurrent,
and this character was noticed and the radiant point of the
shower was determined simultaneously by Mr. (Jivy; in Kngland,
and by Professor Twining in America, on December i z, i S6 5.
Indications of periodicity and of early not ices of yearn of ma \ ima.
in these, appearances have been sought for, with some success, in
cat.aldi.Mirs ol meteor showers liy Prof. Newton1' and IVol. Kirk
wood with the prol)al>le result, announced by Kirkwood'1 that the
meteors of April, October, and December revolve in periods re-
spectively Of 28^, :;A, and .'.(> years, while the January meteor
ring has a suspected period of ahout I ; years.

Many of flu- astronoiuieal views concerning shooting stars
adopted before t lie first predicted return of the November meteors
in I H66 67 were due to a valuable memoir hy ()lhersr, in which in
the place of orhits approximately circular like those conceived \\\
I'-iot . and in the contemporaneous paper on shooting stars al>o\e
referred to, hy Arago, they were assumed to move rather in
comet-like or very elongated orhits. The .{.{-year cycle of the
November meteors wan pointed out and thus explained by
O I hers, who also ventured to predict a probable great return
of the November meteors about the year iM;, which prediction,
as well as the grounds upon which it rested, was verified by the
event.

Subdividing the recorded instances of great showers of shooting
stars according to the months of the year, we obtain the follow-
ing results : —

January

•Inly

•4

February .,

\utfiMt

ft6

Maroh

Sr (,(.•• in I..T

April

'**

Ootober ..

•">

May

November

,. 38

June ... ..

!l,

December

. 17,

We thus find, and it is worthy of especial remark, that the
coincidence to which I have already adverted in the case of ae'ro-

P Silliman't Journal, 2nd Her., vol. 1870, and vol. xiil. p. 501, Nov. at,

xxxvl. p. 145, July 1863. 1X7.1.

' Proowding* qf th« American I'/rifu- • Schumacher's Jain' \- :<>
Kophical Sorittif, vol. xi. p, 299, Maroh 4,

CHAP. III.

Shooting Star*.

025

lites, fireballs and other meteors also obtains with the showers
of shooting stars — namely, that the Earth encounters a larger
number of these bodies in passing from aphelion to perihelion,
or between July and January, than in passing from perihelion to
aphelion, or between January and July.

In concluding this chapter, brief reference may be made to the
apparent magnitudes of meteors •. From many thousands of
observations recorded in various published catalogues it would
appear that the following is something like the relative bright-
ness of these bodies :—

Star of—
> lit mug. = int. = and.

Percent. ... ... 3-0 10-6 18-4

Increase per cent. ... 7-6 7-8 7-8

The numbers show a definite increase of 7 '8 per cent. There
is an enormous excess of faint meteors as compared with the
more brilliant forms of these phenomena *.

4th mag. Total No.
= 3rd. and less, of Meteon.

26-3

41.8
15-6

3.V34

• An article in The Observatory, vol.
ii. p. jo (May 1878), may be consulted
for further details.

' A catalogue of 3 3 1 meteoric showers
is given in Arago's Ast. Pop., vol. iv.

pp. 393-314. Also a catalogue, extend-
ing from 538-1333 A.M., by Chasles, in

t 'inn ft. Itt ml., VOL i. pp. 499-5O9. 1841.

For an account of Quetelet's Catalogue
see p. 6aS, pott.

S S

626 Meteoric Astronomy. [BOOK V.

CHAPTEB IV.

THE THEORY OF METEORS.

Meteors are planetary todies. — Their periodicity. — Meteoric orbits. — Researches of
Neioton and Adams. — Orbit of the meteors of November 13. — Identity of the
orbit* of comets and meteors. — The meteor showers of Nov. 13 and 27. — Secent
progress of Meteoric Astronomy. — Table of the chief radiant points.

IT has been mentioned in a previous chapter that it is to some
extent doubtful whether aerolites, fireballs and shooting stars
are manifestations of identical phenomena or whether they belong
to distinct classes of bodies. There is much evidence to warrant
the assumption of identity, and it will be convenient to adopt this
view during our further consideration of the subject.

Many theories have been propounded to explain luminous
meteors, but they were usually based on few observations, and
later researches did not support them. But in recent years a
theory has been framed which so well accords with observed
facts that it has received universal recognition.

Meteors are diminutive planetary bodies revolving round the
sun in orbits similar to those pursued by comets. These orbits
intersect the annual path of the Earth, and hence it follows that
whenever the Earth passes through these points of intersection
there is a rencontre with the meteoric particles, which are there-
upon propelled into our atmosphere with great velocity and are
ignited by the friction generated by the force of impact. Fire-
balls of ordinary noiseless character and shooting stars are
entirely consumed and dissipated before reaching the lower
regions of the atmosphere, while aerolites are meteors which
succeed in penetrating completely through the air strata and
ultimately fall upon the Earth's surface.

CHAP. IV.] The Theory of Meteors. 627

With the meteors there prevails, as we have already seen, a
periodicity: this will be found on examination to countenance
the theory of their being planetary in their nature; and the well-
known experiment of igniting tinder by compressing air in a fire
syringe removes the notion of self-ignition from the domain of
fanciful speculation.

With reference to their periodicity, Sir J. Herschel says a : —

" It is impossible to attribute such a recurrence of identical
dates of very remarkable phenomena to accident. Annual period-
icity, irrespective of geographical position, refers us at once to
the place occupied by the Earth in its annual orbit, and leads
directly to the conclusion that at that place it incurs a liability
to frequent encounters or concurrences with a stream of meteors
in their progress of circulation around the Sun. Let us test this
idea, by pursuing it into some of its consequences. In the first
place, then, supposing the Earth to plunge in its yearly circuit
into a uniform ring of innumerable small meteoric planets, of
such breadth as would be traversed by it in one or two days ;
since, during this small time, the motions, whether of the Earth
or of each individual meteor, may be taken as uniform and rec-
tilinear, and those of all the latter (at the place and time) parallel,
or very nearly so, it will follow that the relative motion of the
meteors, referred to the Earth as at rest, will be also uniform,
rectilinear, and parallel. Viewed, therefore, from the centre of
the Earth (or from any point of the circumference, if we neglect
the diurnal velocity, as very small compared with the annual),
they will all appear to diverge from a common point, .fixed in re-
lation to the celestial sphere, as if emanating from a sidereal apex.

"Now this is precisely what happens. The meteors of the
1 2th- 1 4th of Nov., or at least the vast majority of them, describe
apparently arcs of great circles, passing through or near y Leonis.
No matter what the situation of that star, with respect to
the horizon or to its East and West points, may be at the time of
observation, the paths of the meteors all appear to diverge from
that star. On the Qth-i ith of August, the geometrical fact is the

* Outlines of Astronomy, nth Ed., p. 661.

S S 2

628 Meteoric Astronomy. [BOOK V.

same, the apex only differing ; B Camelopardi being for that
epoch the point of divergence. As we need not suppose the
meteoric ring coincident in its plane with the ecliptic, and as for
a ring of meteors we may substitute an elliptic annulus of any
reasonable eccentricity, so that both the velocity and direction of
each meteor may differ to any extent from the Earth's, there is
nothing in the great and obvious difference in latitude of these
apices at all militating against the conclusion.

" If the meteors be uniformly distributed in such a ring or
elliptic annulus, the Earth's encounter with them in every revo-
lution will be certain, if it occur once. But if the ring be broken
— if it be a succession of groups revolving in an ellipse in a period
not identical with that of the Earth, years may pass without a
rencontre ; and when such happen, they may differ to any extent
in their intensity of character, according as richer or poorer
groups have been encountered."

We wrill now consider the character of meteor orbits, and in
order to form a clear conception of the matter it may be neces-
sary to go back a few years and trace the developments leading
up to the present theory.

In November, 1833, ^nere was witnessed, as has already been
stated, a grand display of meteors b (" shooting stars "), a less grand
one in 1832, and 33 years before that, namely in 1799, another
very magnificent one. Availing himself of a comprehensive
catalogue of recorded appearances of meteor showers compiled by
A. Quetelet in 1836-39°, a learned American astronomer, Prof.
H. A. Newton, set himself the taskd of searching out all the
ancient records he could find of such displays : he found that more
than a dozen had been taken note of by historians, beginning
with 902 A.D., and that in all cases the intervals were either + i1*1

b In this chapter the word " meteors " Journal, 2nd Ser., vol. xxxvii. p. 377,

is intended to apply generally, to and vol. xxxviii. p. 53, May and July

aerolites, fireballs, and shooting stars ; 1 864. The periodic dates of the No-

in fact to all the allied, and probably vember and of some other annual meteor

identical, forms of meteoric apparitions. showers had been discussed in a previous

c Nouveaux Memoires de TAcademie paper in the same Journal, vol. xxxvi.

Eoyale des Scitnces, vol. xii. 1839. p. 145, July 1863.

d His papers appear in Silliman't

CHAP. IV.] The Theory of Meteors. 629

of a century or some multiple of that period. This was too im-
portant a fact to be neglected. By a course of reasoning, the
several steps of which I do not deem it necessary to reproduce,
Newton concluded that the + 33-year visible periodicity was
only reconcileable with an orbit whose period was either i8od,
j85'4d, 354'6d, 376-6d, or 33'25y. Why the true period must be
one of these 5 involves mathematical considerations unsuitable to
these pages. The period chosen by Newton himself as the most
probable was that of 354'6d, corresponding to an orbit nearly
circular ; but he pointed out that a certain retardation of the date
which had taken place could only be explained by assigning to
the meteor orbit that one of the 5 possible forms which would
account for the retardation, and that a proper mathematical
calculation undertaken for this purpose would finally decide
which of the five forms was the real one. With these remarks on
the orbit, and with a prediction that another great display would
occur on the morning of November 14, 1866, Newton terminated
his investigations.

In April, 1867, Prof. Adams presented to the Royal Astro-
nomical Society an outline of a very important investigation6
which, proceeding on Professor Newton's suggestion, he had
brought to a satisfactory conclusion. Availing himself of
Newton's labours, he sought to arrive at some more precise
knowledge of the orbit of the November meteors, taking ad-
vantage, of course, of the information furnished by the observa-
tions made in November 1 866. I should premise that Newton's
inquiries show that the display which in 1866 happened on
Nov. 13, in 902 happened on Oct. 12 (o. s.), indicating a pro-
gressive increase in the longitude of the points of intersection of
the orbits of the meteors and the Earth. The amount of this
motion is 102-6" annually with respect to the Equinox or of 52-6"
with respect to the stars, equal to 29' in 33^ years. Adams
calculated the extent of the progressive increase due to the
perturbing influence of the planets Venus, Jupiter, and the Earth.
He found that their conjoint effect, on the assumption that the

8 Month. Not., vol. xxvii. p. 247. April 1867.

630 Meteoric Astronomy. [BOOK V.

period of the meteors was i8od or i85d or 354"* or 37 7d, in no case
exceeded 12' in 33^ years, but that assuming 33^ years to be
the period, planetary influence (in this case caused by Jupiter,
Saturn, and Uranus) would produce an increase of 28'. The
near coincidence of this theoretical 28' with the observed 29'
places it almost beyond doubt that the true period is 33^ years.
Proceeding on this assumption, and having found that, according
to the mean of several determinations, the radiant-point of the
1 866 meteors was situated in : —

R.A. Decl.

h. in.

9 56 + 23 i

Adams proceeded to calculate elliptic elements of the orbit of the
meteors, and obtained the following set : —

Period ... = 33-25y (assumed)

Mean distance ... ... ... — 10-3402

Eccentricity ... = 0.9047

Perihelion distance = 0-9855

o /

Inclination ... = 16 46

Longitude of Node ... ... = 51 28

Distance of Perihelion from Node — 651

Heliocentric motion ... ... ... Retrograde.

Prof. Schiaparelli of Milan was also led at about the same time
to investigate the phenomena of meteors f. He observed the
Perseids on August 9, 10 and n, 1866, and assumed, from the
necessity of the conditions, that the orbit of these meteors must
JDC an elongated conic section, and employing the method of
Erman he computed parabolic elements for this system. It was
not long afterwards that he discovered a remarkable resemblance
between the meteoric orbit and the orbit of Comet iii. 1862, the
two sets of elements being as follow : —

August Meteors. Comet iii. 1862.

Perihelion Passage 1862, July 23 1862, August 22-9.

Long, of Perihelion 343 28 344 41

Ascending node 138 16 137 27

Inclination 64 3 66 25

Perihelion Distance 0-9643 0-9626

Period 105 years? 123-4 years

Motion Retrograde Retrograde.

1 Month. Not., vol. xxxii. pp. 194-9. February 1872.

CHAP. IV.] The Theory of Meteors. 631

The periods are doubtful. The generally close agreement
in the elements could only signify identity of the two orbits
and of the bodies describing them. And a similar coincidence
was found between the orbit of the November meteors (Leonids)
and that of Comet i. 1 866. The shower of April 20 (Lyrids) was
also shown by Galle and Weiss to match Comet i. 1861, while
the display of Nov. 27 (Andromedes) presented an equally close
accordance with the well-known periodical comet of Biela.

The expected return of Biela's comet in August and September,
1872, afforded an opportunity for verifying the presumed con-
nection ; and the appearance of an abundant star-shower agreeing
identically in the position of its radiant-point and in the date of
its appearance with those of a meteor-stream following directly
in the track of Biela's comet (about 12 weeks after the comet's
departure from the place), on November 27, 187-2*, corroborated
afresh an inference already drawn from the three previously
known examples of agreement, that a very rich assemblage
of the meteors revolving with a cometary body follows the
comet very closely in its orbit h. A somewhat different surmise
from this conjecture is however suggested by the showers of
Andromedes seen in the years 1798, 1830, and 1838, which
must have preceded Biela's comet at different distances between
jV and £ of a revolution along its track. A separate group
of the Leonids is also suspected to exist, preceding the prin-
cipal one about 12 years (or about \ of a revolution) in its
appearance. Notable star showers are recorded to have taken
place in 855-56, 1787, and 1818-23, and finally by Prof. D.
Kirkwood in 1852, Agreeing exactly with the principal cluster
in the day, and very closely also in the period of their returns *.
The original dismemberment of the comet, to which the ancient

B This display recurred with great Olmsted as far back as 1834. (Silliman's

brilliancy on Nov. 27, 1885, after the Amer. Journ., vol. xxvi. p. 172.) The

completion of two revolutions, of 6-5 period he assigned was i82d, which is in

years each, of the derivative comet. close agreement with one of the possible

h It seems to be often overlooked, or periods assigned by H. A. Newton many

not generally known, that the cometary years later.

character of the November shower of * Nature, vol. xi. p. 407, March 25,

Meteors was first suggested by Denison 1875 ; vol. xii. p. 85, June 3, 1875.

632 Meteoric Astronomy, [BOOK V.

record of this widely distant cluster points, must have been of
extraordinary antiquity, since the interval of 12 years between
the years 855-56 and the next principal Leonid display
in 868 differs very much from the distance still found to separate

Fig. 249.

ORBIT OF THE LEONIDS OF NOV. 13 RELATIVELY TO THE ORBITS
OF CERTAIN PLANETS.

the two clusters from the well-marked minor apparitions
of the years 1787, 1820, and 1822 compared with the modern
appearances of the chief cluster in 1799 and 1833. It is thus
that highly important consequences may be expected to be traced

CHAP. IV.] The Theory of Meteors. 633

from these and similar investigations and discussions ; indeed,
the subject may perhaps fairly be deemed an inexhaustible one,
for a few coincidences having been ascertained, more will be
sure to follow as observations multiply and research extends.

The orbit of Comet i. 1866, discovered by Tempel on Dec. 19,
1865, coincides with the Leonid meteor orbit given in Fig. 249.

Fig. 250.

POSITIONS OF BIEL4 8 COMET AT THE TIME OF THE METEOR SHOWEKS
OF 1798, 1838, AND 1872.

Prof. Newton, in a lecture delivered in 1874 at Yale College,
indicated the positions of Biela's comet in its orbit relatively to
the Earth at the times of occurrences of the greatest meteor-
showers known to have arisen from the Earth's approach to 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 the year 1798, at the time when the Earth encountered at

634 Meteoric Astronomy. [BOOK V.

that point the great meteor shower of Dec. 6 of that year,
observed by Brandes, Biela's comet was in the position marked
B, somewhat nearer to the earth than on the next occasion when
a similar display was witnessed in 1838. The comet was in the
latter year at the point marked A about 300 millions of miles
distant along its orbit from the earth. At the recurrence of this
great star shower on Nov. 27, 1872, the comet must have been
situated near C, or 200 millions of miles along the comet's
path from the node N. From this it appears that the meteoric
particles must be thickly distributed over at least 500 millions
of miles of the comet's orbit, preceding the comet 300 millions
and following it 200 millions of miles.

There is little doubt remaining that comets furnish the
numerous meteors which traverse the celestial spaces. The fact
of the intimate association of these phenomena is proved by the
identity of their orbits, and by other evidence gleaned from
observation which amply supports the views of Schiaparelli.
To him must be given the credit of first demonstrating the
connection, though the meritorious labours of several other
astronomers cleared the way and furnished many of the materials
the utilisation of which led to the actual discovery. Thus, several
years before Schiaparelli commenced his researches, Professor
Kirkwood broached the theory that " meteors and meteoric
rings are the debris of ancient but now disintegrated comets
whose matter has become distributed around their orbits k."
Earlier writers had also expressed ideas which do not differ
essentially from those now adopted, but unfortunately they
could not command the data required to give practical support
to their views, which were, in consequence, disregarded, as mere
speculations.

The two great meteor showers of November are more certain
in their cometary relations than the showers of April and August,
because in the former instances the periodical maximum returns
of the meteors have occurred at the predicted times and the
time of revolution of both comets and meteors are precisely the

k Danville Quarterly Review, December 1861.

CHAP. IV.] The Theory of Meteors. 635

same. But in the case of the April and August systems the
periods are open to considerable uncertainty, the orbits being
of far greater excentricity.

The meteors of November 13 may be expected to reappear
•with great brilliancy in 1899, and probably, for a year or two
both before and after that date, a large number of these bodies
will be seen at the middle of November. Possibly also there
will be fine showers from Biela's comet on Nov. 26 or 27,
in 1892 and 1898.

It is a noteworthy fact that the members of different meteor
showers exhibit visible features which in certain cases are quite
dissimilar. This arises from the circumstance that the various
showers encounter the earth at different angles, and their ap-
parent speed depends in a great measure upon this. Thus the
meteors of November 13 (Leonids) are moving in a direction
opposite to the Earth ; hence their velocity is very great, being
about 44 miles per second. But the meteors of Nov. 27 (Andromedei)
are moving in nearly the same direction as the Earth, and hence
have to overtake us, so that they apparently move very slowly,
their speed being only 1 1 miles per second. The Leonids above
referred to, together with the Perseids of Aug. 10 and the
Orionids of Oct. 18-20, are good examples of the swift-moving
meteors, and they are almost invariably accompanied by phos-
phorescent streaks. The slow meteors, of which the Andromedes
are a type, throw off trains of yellowish sparks.

Since the astronomical nature of meteors has been admitted
a large amount of attention has been given to this branch of the
science. A committee of the British Association was for many
years engaged in collecting and collating observations. Amongst
those who have exerted themselves to develope this branch of
astronomy must be mentioned the names of Adams, Challis,
Denning, Glaisher, Grant, Greg, A. S. Herschel, Lowe, Main, and
Tupman, in England ; and among the chief astronomers abroad,
who are either seeking or who have contributed to promote its
progress, Twining and Newton, Loomis, Kirkwood, B. V. Marsh,
Le Vender, E. Quetelet, Buchner, Von Boguslawski, Galle, Heis,

636 Meteoric Astronomy. [BOOK V.

Neumaycr, Schmidt, Weiss, Wolf, Schiaparelli, Denza, Secchi,
Serpieri, and Tacchini, with other observers, especially in Italy,
who watch nightly for shooting stars, and carry out with
unremitting zeal regular discussions of meteor tracks.

The chief discovery that has been positively made is, that lumi-
nous meteors are much more regular in their movements than
was formerly supposed. The known "radiant points" are no
longer confined to the constellations Leo and Camelopardus,

Fig. 251.

alar

RADIANT POINT OF GEM1NIDS (DEC. 12) ON NOV. 28-DEC. Q, 1864.

as they were when Sir J. Herschel wrote the passage which
I have quoted on a previous page, but have been found to exist
in every quarter of the heavens. A vast number of these systems
of meteors must cross the annual path of the Earth, though only
a few of these are well known. The observations of a single
night have yielded evidence of 50 or 60 different showers in pro-
gress at the same time.

A list of the more important radiant points will be found on
p. 640, et seq. It is based upon a large number of recent observa-

CHAP. IV.]

TJie Theory of Meteors.

637

tions obtained at Bristol, and the positions will be found fairly
accurate, every precaution having been taken to ensure precision.
Observers in the Southern hemisphere are much needed, for the
Southern Heavens remain comparatively unexplored as regards
meteoric Astronomy.

Figs. 251-2 (on pp. 636-7) represent the paths of certain
meteors observed at the specified dates. Projected, after the
manner of a surveyor's plan, to form a meteor chart, the fact
that the meteors really are thrown off from determinate

Fig. 252.

RADIANT POINT OP ORIONIDS (OCT. 1 8-2 1 j ON OCT. 2O, 1865.

centres becomes strikingly apparent. It is unfortunate for the
sake of Science that the suddenness with which all these objects
appear and the shortness of their duration usually take observers
aback, and impair the certainty of their mental impressions,
making it often difficult to obtain exactness. The plan of the
projection used is that of a plane perspective view, in which the
meteor-tracks observed can be represented by straight lines.
It should be the chief aim of future observers to obtain evidence

638 Meteoric Astronomy. [BOOK V.

as to the duration of certain meteor showers, and to determine
whether their radiant points are variable or stationary in position.
Many of the radiant points are apparently fixed relatively to the
adjoining stars, and it is important to determine at successive
epochs whether these positions are really permanent. If small
differences are observable, and such as cannot be attributed to the
unavoidable errors of observation, then the nearly accordant
radiants are merely due to accidental grouping. But there is a
good deal of evidence1 in support of the opinion that certain
radiants are more or less permanent both in activity and position,
though this peculiarity, being one which is strongly opposed by
theoretical considerations, cannot be definitely accepted until it
has been submitted to the most rigorous tests that can be
applied.

1 Month. Not., vol. xlv. p. 93 (Dec. 1884). Sidereal Messenger, vol. v. p. 167 (June

CHAP. V.] Radiant Points. 639

CHAPTER V.

RADIANT POINTS.

Explanation of Reference Letters in the List of Radiant Points.
(pp. 640-643.)

The references in column 7 are — " G.," Greg's General Cata-
logue published in the British Association Report for 1876; " T.,"
Tupman's Catalogue printed in the Monthly Notices, vol. xxxiii.
p. 298, March 1873 ; " S.Z.," Schiaparelli's Catalogue derived
from Zezioli's Observations, British Association Report for 1878;
and "C.j" Corder's Catalogue in the Monthly Notices, vol. xl.
p. 131, Jan. 1880.

640

Meteoric Astronomy. [BOOK V.

LIST OF THE CHIEF RADIANT POINTS

Ref.
No.

Date of
Shower.

Position of Radiant.

Meridional Position of Radiant
by the Stars.

No. in
other Catalogues.

R. A.

Decl.

In time.

In deg.

b. m.

Jan. 2

15 20

230

+ 53

Quadrans, 12° N.N.E. of /3 Bootis

G. 6.

2
3

Jan. 5
Jan. 9
Jan. 17
Feb. 15

9 20
14 44

19 40
15 44

140

221

295
236

+ 57
+ 42

+ 53
+ ii

Ursa Major, 5° N. of 0 . . . .
Bootis, 3° W. of 0

Heis (M. i>.

SZ. 10.

Cvemus, 4° E. of Y

Heis (F. 10).
T. 10.

Serpens, 8° N. of o

Feb. 20

12 4

181

+ 34

Canes Venatici, ioj° E.S.E. of a .

G. ii, T. 4.

Feb. 20

17 32

263

+ 36

Hercules, 3° S.E. of p- . . . .

March 14

II 40

175

+ 10

Virgo, 5° S. of # Leonis ....

G. 28.

March 14

18 40

280

-14

Scutum, 10° S.S.W. of X Aquil* .

G. 22.

10
ii

12
13

March 24
March 27
March 28
April 1 8
April 19

10 44
15 16
17 32
i5 24
15 16

161
229
263
231
229

+ 58
+ 32
+ 62
+ 17

— 2

Ursa Major, 2° N.W. of £ . . .
Corona, 2° W. of 0

Heis (M. 8).
S.Z. 48, C. 12.

G. 53 a.
G. 53, T. 32.

Draco, 6° S.E. of £ . .
Serpens 4° W. of /3

Near Libra, 7° N. of 0 . . . .

April 20

18 o

270

+ 33

E. of Lyra, 8|° S.W. of a . . .

G. 51, C. 20.

I?
18

April 25
May I
May 6

18 8
15 56

22 32

272

239
338

+ 21
+ 46
— 2

Cerberus, 3° W. of * 1 09 . . . .
Hercules, 3° W. of T

G.5o.
G. 71, S.Z. 71.
G. 6i,T. 33.

Aquarius, 1 |° S.E. of 17 . . . .

May 7

16 16

244

+ 7

Ophiuchus, 5° N.N.W. of X . .

20
21
22

23
24

May 15
May 30
June 7
June 13
June 1 5

19 40

22 12

16 28

>2O 40

19 o

295
333
247

31°

285

± °

+ 27

-25
+ 61

+ 23

Aquila, i£° W.S.W. of 17 . . .
Pegasus 10° W. of /3

T. 35-

G.6?.
G. 77, C. 30.
Sa. 6 ( i* Cat.).

Scorpio, 2° N.E. of o

Cepheus close to 17 ...

Anser, 8° W.S.W. of 0 Cygni . .

25
26

27
28
29

June i 8
June 20

July 5

July 20
July 22

20 8
22 2O
I 24
17 56
1 4

302
335

21
269

+ 24

+ 57
+ 23

+ 49
+ 3i

Vulpecula, close to *24 .
Cepheus close to 8

C. 74, C. 24.

S.Z. 121.

Near Aries, 6° N.W. of/3 . . .
Draco, 2° S. of 7

Andromeda, 3° S. of/3 . . . .

July 23

22 2O

335

+ 49

Lacerta, 8° S. of S Cephei . . .

G. 68.

July 25

3 12

+ 43

Perseus, 4° N.E. of/3 . .

S.Z. 137.

July 28

22 36

339

— 12

Aquarius, 5° N.N.W. of 5 . . .

G. 109, T. 43.

Aug. 4

2 O

+ 36 Triangulum. 3° N. of 3 . . .

G. 100, S.Z. 12=;.

Aug. 10

3 4

+ 57 Perseus, 4° N.E. of ij . .

G. 108, C. 39.

Aug. 1 6

4 4

61 +48

Perseus, very close to /x . . . .

G. 114, C. 47.

JHAP. V.] Radiant Points. 641

OF METEOR SHOWERS. (From the observations of W.F. DENNING, F.R.A.S.)

NOTES.

A rich annual shower. Well observed in 1864. Probable duration Dec. 28 to
Jan. 4.

Meteors swift with short paths. A very definite shower observed in 1 886.

A morning shower. Meteors swift with streaks. Observed in 1869 and 1877.
f Meteors slow and bright. Observed in 1877. Showers here also in Aug. and
\ autumnal months.

Radiant sharply defined. Meteors swift with streaks. Observed in 1869 and 1877.

A shower of swift, rather bright meteors observed in 1877. Perhaps different

.t?T4'
Visible only in the morning hours. Meteors swift with streaks. Observed in 1877.

Meteors slow and brilliant. A radiant of swift meteors here in Feb. and Nov.-Dec.

Meteors swift with streaks. Showers of slow meteors from here in July and Aug.

Well-defined shower of swift meteors in 1887. Radiants here in Nov. and Dec.

Meteors small and swift. Seen in 1887. Radiant sharply defined.

Meteors of moderate speed. Many other showers here in May, Aug., Oct., etc.
JA shower contemporary with the Lyrids. Meteors short and quick. Observed in
\ 1885 and 1887.

Meteors slow with long paths. Several observers have determined this radiant.
[Lyrids. Meteors swift, the brighter ones leave streaks. Rich display = Comet
1 I, 1861.

(Meteors short and swift. Observed also by Herschel 1864, April 13, and by Greg,
\ 1872, April 20.

Meteors small and short. Well-defined shower in 1886.

Rich shower visible before sunrise. Discovered by Tupman. = Halley's comet.

Meteors slow. Rad*ant not very certain. More observations required.
(Meteors swift with streaks and long paths. Obsei'ved in 1877. Radiant here
1 in July '(

Radiant of swift, streak -leaving meteors, well-defined. Shower here in July.

A radiant of slow-moving fireballs. Several seen in 1878.

Meteors very swift with streaks. Perhaps connected with Comet I, 1850.

Meteors rather slow. Well observed in 1887. A shower here also in April.
/There are apparently many, other showers from this point in the spring and
1 summer.

Meteors swift. The radiant seems prolonged in July and September.

Meteors very swift with streaks. Observed in 1886. More observations required.

Observed in 1873 and 1887. Active radiation from this place in other months.

Meteors brilliant with streaks. Centre sharply defined. Observed in 1887.

Seen by many observers. Meteors very swift and short. Lacertidg.

Meteors bright, swift and leaving streaks. Rich shower 1884. ? = Comet of 1764.

Aqnariflg. Very active display of slowish, long meteors recurring annually.

Well-defined shower of swift meteors with streaks. Seen also in Sept. and Oct.
(Perseids. Very rich annual shower. Whole duration July 8 to Aug. 22. Meteors
•j swift, bright and leaving streaks. Radiant shifts from 3° + 49° to 76° +57°.
= Comet III, 1862.

Meteors swift with streaks. Active, definite shower in 1877.

642

Meteoric Astronomy. [BOOK V

LIST OF THE CHIEF RADIANT POINT!

Ref.
No.

Date of
Shower.

Position of Radiant.

Meridional Position of Radiant
by the Stars.

No. in

otlier Catalogues.

R. A.

Decl.

n time.

ndeg.

h. m.

36
37

39
40

42
43

Aug. 21
Aug. 22

Aug. 25
ept. 3
Sept. 4
Sept. 7
Sept. 19
Sept. 20

4 52
19 24
o 20
23 36

23 4
4 8

•

12 48

73
291

5
354
346
62

75
192

+ 41
+ 60
+ II

+ 38

~f~ O

+ 37
+ 15
+ 79

Auriga, 5° S.W. of a
Draco, 4° E. of o

T. 66.

G. 78, T. 58.
G. in, T. 49.
Schmidt v 354° +43°]
T. 73, C. 51.
T. 64, S.Z. 147.
G. 134, T. 72.

Pisces, 4° S.E. of 7 Pegasi . . .
Andromeda, 12° N.N.W. of a . .

Pisces, 3° S.W. of 7
Perseus, 4° S.E. of e . . . .

Taurus, 8° E. of a

Near Ursa Minor, 8° N.W. of /3 .

44
45
46

Sept. 21
Sept. 22
Sept. 30

2 4
4 12

I 40

+ 19

+ 22

+ 71

Aries, 3° S. of o
Taurus, 4° N.N.W. of e . . . .

C. 70.

Gustos Messium, close to *f. . .

Oct. 2

15 0

225

+ 52

Quadrans, n°N. of /3 Bootis .

48
49
5°

Oct. 4
Oct. 8
Oct. 8

8 52

2 48

5 8

133
42

+ 79

+ 55

Camelopardus, 3° E.S.E. of «H 28 .
Perseus, |° E. of 77

Heis (N. 15).
G. 168.
T.83.

Taurus, 3^° N.N.W. of /3 ...

51
52
53
54

Oct. 1 1
Oct. 14
Oct. 14
Oct. 1 8

o 52

2 40

9 °
6 8

i35
92

+ 6

+ 20

+ 68

+ 15

Pisces, i° S.W. of e
Aries, 3° W. of «

Backhouse (14°, + «
G. 195.

G. 157, T. 79.

Ursa Major, 13° W.N.W. of a . .

Orion, 2° E. of v

55
56
57
58

Oct. 20
Nov. i
Nov. 2
Nov. 13

7 4
2 52

3 4°
10 o

106
43

55
150

+ 12
+ 22

+ 9

+ 22

Canis Major, 5° N.W. of /3 . . .
Aries, i° N. of e

G. 153, T. 82.
G. 195-
T. 91, C. 87.
G. i7i,T. 100.

Taurus, close to *e

Leo, 3° W.N.W. of 7

Nov. 1 6

10 16

154

+ 4I

Ursa Major, i° S. of p . . . .

T-97-

60
6
6
6

Nov. 1 7
Nov. 20
Nov. 27
Nov. 30

3 32
4 8
i 40

12 40

53
62
25
190

+ 71
+ 23

+ 44

+ 58

Camelopardus, close to *H 5 . .
Taurus, 5° N.N.W. of e . . . .

G. 156.
G. 172, C. 90.
G. 179.

Andromeda, 4° N.W. of 7 . . .
Ursa Major, 2° N.W. of e . . .

Dec. 4

7 20

+ 25

Gemini, 5° S.W. of/3

G. 178, C. 93.

6
6
6

Dec. 6
Dec. 8
Dec. 8

5 20
9 40
13 57

80
20?

+ 23

+ 7
+ 71

Taurus, 3° N.W. of f
Leo, 8° S.W. of a

G. 210, C. 95.
Backhouse(i43°, +9'
G. i79b, C. 92.

Draco, 6° N. of a

Dec. 10

7 22

+ 33

Gemini, 3° W.N.W. of a . . .

G. 178,0.94.

Dec. 10
Dec. 22

7 48

12 56

117

194

+ 32

Gemini, 8|° S.S.E. of0 . . . .
Draco, 7° W of a . . .

Backhouse(ii3°, + 3

CHAP. V.] Radiant Points. 643

OF METEOR SHOWERS.

No.

NOTES.

(Radiant sharply defined. Meteors swift with streaks. Showers here in Sept.

I and Oct.

I A very rich shower of bright slow meteors seen in 1879 and not observed since

[ that year.

Meteors very short and slow. Radiants are also here in July and September.

Meteors very swift and faint. The chief shower visible in Sept. 1885.

Meteors slow and bright with long paths. Radiation from here in earlier months.

Well-defined and active display of swift, streak-leaving meteors in 1877, 1885, etc.

Meteors very swift with streaks. A morning shower. Also Aug. 25 and Sept. 9.
(Meteors slow. Observed in 1879. Radiant of swift meteors here, Nov. 29-30,
1 1886.

{Active shower of slow meteors seen in 1879. Radiation from here in Aug.
\ and Oct.

Meteors very swift with streaks. Observable in the morning hours.

Meteors small and short. Many radiants cluster here in July, Aug., Nov., etc.

A shower of very brilliant slow meteors in 1877. Further observat;ons are needed.
[Radiant sharply defined in 1877. Meteors swift with streaks. ?= Comet II,
I .1825.

Meteors slow, sometimes trained. Observed in 1885. Shower here in Dec.

Meteors swift with streaks. Two fireballs in 1877. Visible also in Nov. and Dec.

Well-defined shower of slow bright meteors 1887. Seen also on Sept. 13, 1885.

Very active radiant in 1887. ? = No. 56. Meteors rather swift.
jRadiant sharply defined in 1887. Meteors swift with streaks. Further obser-
\ vations required.

f Orionids. A very rich shower occurring every year. Whole duration from Oct. 9
1 to 29. Radiant stationary. Meteors swift with streaks.

Meteors very swift with long paths and streaks. A shower here in Dec.

An abundant display in 1877. Meteors brilliant and rather slow.

Yielded many fine meteors in 1886. Distinct from Taurids of Nov. 20 (No. 61).
(Leonids. Period 33! years. Grand displays in 1799, 1833 and 1866, and will
< reappear in 1899. Furnishes a slight shower every year. Meteors swift with
( streaks. = Comet I, 1866. The shower continues from Nov. 9 to 17.
(Meteors very swift and streak-leaving, similar to the Leonids. Well observed
\ in 1885. A rich shower seen here by Booth, Jan. 3, 1889.

Well-defined shower in 1886. Radiation also from here in Aug., Sept., Oct.
[ Taurids. A well-known shower. Meteors slow. Furnished several fireballs in

I 1876-7.

[ A ndromedes. Period about 6| years. Grand displays in 1872 and 1885. May
| reappear in 1892 or 1898. Meteors very slow with trains. = Biela's comet.

Radiant diffuse.

Meteors very swift with streaks. Radiant sharply defined. Observed in 1886.
[Perhaps connected with the Geminids of Dec. 10, though the radiant is evidently

8° South.

[A well-defined and active shower of slow meteors observed in 1876 and subse-
[ quent years.

Meteors very swift with streaks. Sharply defined. Observed in 1877.
Meteors rather swift. Further observations required. Possibly = Pons's comet

of 1812.

' Geminids. A rich annual shower of swift short meteors. Radiant well defined.
[ Duration from Dec. I to 14.

Distinct from preceding, though situated only 8° E. of it and visible at same epoch.
Meteors swift with streaks. The most active radiant seen in Dec. 1886.

644 Meteoric Astronomy. [BOOK V.

CHAPTER VI.

TELESCOPIC METEORS.

Our knowledge of them limited. — Observations. — Probable heights in the atmosphere. —
Showers of telescopic meteors. — Summary of Prof. Safarik's observations and
deductions. — Fireball observed in a telescope on Oct. 19, 1863.

WE have now to consider types of meteoric phenomena
smaller and probably more distant than the imposing
forms visible to the unaided eye. But though generally more
minute, they are no doubt identical in character with the con-
spicuous meteors such as fireballs and ordinary shooting stars.

The observation of telescopic meteors commenced with the
invention of that instrument nearly 300 years ago, yet our
knowledge of these bodies is very limited. We find occasional
references to them in scientific publications, but no one seems to
have pursued this particular subject with that method and
assiduity which it requires. Those who search for comets or are
engaged in observing variable stars frequently notice telescopic
meteors, the low powers and large fields usually employed in
such cases being suitable for their observation, and it is to be
hoped that in future years a special effort will be directed towards
gathering more information about them.

In 1795 Schroter saw with his reflecting telescope of 2o-inches
aperture, a shooting star the height of which he estimated at
more than four millions of miles ! This is, of course, an enor-
mous exaggeration of the real distance. In 1839, between
August i and 10, Mason observed 50 telescopic meteors with a
reflecting telescope armed with a power of 80. He noticed

CHAP. VI.] Telescopic Meteors. 645

that their angular velocity was not greater than that of ordinary
naked-eye meteors, and he concluded from this that they were
situated at great elevations in the atmosphere ; in certain
instances probably more than 1200 miles. Professor Schiaparellia
mentions that he is inclined to believe that the relatively slow
velocity is the result of their small mass being unable to overcome
the atmospheric resistance, but he does not deny that some falling
stars first become visible at least 400 miles above the earth's
surface.

Dr. J. F. J. Schmidt stated that during 10 years he recorded
146 telescopic meteors ranging between the 7th and nth mag-
nitudes. Heis, Hartwig, Luther and others have also observed
many of these objects. In the year 1854 Prof. Winnecke re-
corded no less than 105 on 32 evenings in a 3-inch finder magni-
fying 15 times and with a field of 3°. Denning has also noticed a
considerable number of these small meteors while comet-seeking.
He was surprised at the comparative slowness of motion of these
bodies. They travel with sufficient leisure across the field to be
easily followed by the eye, and their appearance is such as to
give the impression of great distance. He concludes that their
diminutive size and slow courses are attributable to their re-
moteness, and computes that they are more numerous than the
naked-eye meteors in the proportion of 22 to I. On Oct. 4, 1881,
he noticed a telescopic meteor of the 8th magnitude, which left,
for fully 65 seconds, a beautiful narrow streak, showing minute
irregularities and reminding one forcibly of a spider's line on a
frosty morning b.

One of the best and • most recent observations of these bodies
is thus related by Mr. W. R. Brooks : —

" While sweeping on the evening of Nov. 28 [1883] it was my pleasure to observe
a wonderful shower or flight of telescopic meteors about 10° above the horizon and
near the sunset point. They were very small, none of them visible to the naked eye,
most of them leaving a faint train visible in the telescope for I or 2 sees. The motion
of most of them was to the northward, with an occasional group to the South of the
Sun moving southward. . . . The instrument used was my 9-in. reflector, with comet

a Theory of Meteors, ch. i. § 2, note.

b Observatory, vol. vi. p. 123. April, 1883.

646

Meteoric Astronomy.

[BOOK V.

eye-piece, giving field of i^0 . . . The faithful comet-seeker frequently in a single
night's work encounters numerous telescopic meteors singly, very rarely two at once ;
but this flight is quite unprecedented in my experience c."

Fig. 253.

FLIGHT OP TELESCOPIC METEORS. (Brooks.}

Mr. Barnard of Nashville confirms the above remarks,
and says that on Dec. 15, 1883, he saw with his telescope small
bright bodies close to the Sun. " They were visible at the rate of
5 or 6 per minute, and all moving to the North of East quite
rapidly. Occasionally a larger body was seen to flash across the
field, blurred by being out of focus. Generally they looked like
little stars, many as bright as those of the Ist magnitude."
It does not seem to be the case that when naked-eye meteors are
frequent, telescopic meteors are also to be seen in proportionate
numbers. On Dec. 12, 1877, Prof. Lewis Swiftd witnessed an
abundant display of naked-eye meteors [probably Geminids].
He estimated that one observer might have counted 50 per hour
between 2h 3om A.M. and daybreak. "He was comet-seeking at
the time, and noticed a remarkable paucity of telescopic meteors,
as during 4^ hours of sweeping he only saw 2 certainly, and one

c Sidereal Mewenger, vol. ii. p. 294.
Jan. 1884.

d Science Observer (Boston), vol. 5. p. 46.
Feb. 1878.

CHAP. VI.] Telescopic Meteors. 647

other suspected, cross the field of his glass, whereas they are
generally of frequent occurrence."

Prof. Safarik, the variable-star observer, of Prague, has given
a valuable and interesting account of the telescopic meteors he
has observed6. Writing in 1885 he says: —

" Since 1879 1 have been engaged almost exclusively in observations of variable stars,
and in that time I have seen hundreds of meteors of every magnitude, from the 2nd
down to the 1 2th, passing through the field of my -6|in. reflector (ordinary power 32,
field 54') or its I |-in. finder. To me they are so common that it would be difficult to pass
a night at a low-power telescope of large aperture without having caught sight of a
couple of them. On Aug. 30, 1880, I noted in my observing book : 'It would be
difficult to tell the number of telescopic meteors which passed to-night (between 9h
and I5b) the field of my telescope or its finder; I think more than 50, if not nearly
100.' And on the subsequent night (9* to I4h) : 'To-night also numerous telescopic
and some naked-eye meteors seen ; less than last night, about 20, many of them only
diffused luminosities.' I had no time to register the tracks in the Bonn Star Maps,
though I am sure that after a little practice it might be done with considerable
accuracy."

Prof. Safarik classifies telescopic meteors as follows : —

(i.) Well-defined star-like objects of very small diameter,
round, or of no recognisable shape, sometimes with smoky
luminous trails of cometary aspect — i.e. widening as they recede
from the principal body.

(2.) Large luminous bodies of some minutes of arc in diameter,
round or ovoid, sometimes pretty well defined, ordinarily diffused
and smoky, with wedge-shaped tails, fading as they recede from
the body.

(3.) Well-defined discs of a very perceptible diameter, almost
invariably brighter at the border than at the centre, which
gives them the aspect of hollow transparent shells, or luminous
bubbles. When they happen to travel slowly across the field
in an horizontal direction they look very much like soap-bubbles
driven by wind.

(4.) Faint diffused nebulous masses of irregular shape, con-
siderable size, and different colours.

In Class i. Safarik places an object of very peculiar character,
which he saw on April 24, 1874, at about 3^h P.M. He was

6 Astronomical Register, vol. xxiii. pp. 205-6. Sept. 1885.'

048 Meteoric Astronomy. [BOOK V.

observing the moon (nearly illuminated |th8) in bright sunshine,
with a 4-inch refractor, when he was surprised by the appa-
rition, on the disc of the moon, of a dazzling white star, which
travelled slowly from E.S.E. to W.N.W., and after leaving
the bright disc shone on the deep blue sky like Sirius or Vega
in daylight and fine air. It is well known that luminous
star-like objects are seen in summer time near the Sun. Schwabe
gave much attention to them, and called them " Lichtflocken." It
is generally admitted now that they are partly the pappus of
various seeds, partly convolutions of the Gossamer, floating high
in the air and brilliantly illuminated by the Sun when nearly in
the line between the Sun and the eye. Schrb'ter saw something of
the kind at night (Oct. 15, 1789), when scrutinising the un-
illuminated part of the Moon with his 7ft reflector, power 161.
Suddenly a " splash of light," as he calls it, consisting of small
sharp sparks of light, was formed on the disc of the Moon, and
crossed the rest of the disc and field in 2 sees. ; and before it had
left the field, there was formed another splash nearly at the
same place and which left the field in the same direction.
Numerous telescopic bodies of very small diameter and moving
rapidly across the Moon, or near it, were also seen by the Abbo
Lamey in 1864 and i873f.

Safarik gives numerous examples of the various classes of
telescopic meteors, and concludes with the following remarks : —
"In our mineralogical museums hundreds of meteoric stones
are preserved and have been thoroughly studied in modern
times. They present a great variety of types, from pure compact
iron through hard crystalline silicate rocks to porous friable
masses easily broken with the fingers. The identity of falling
stars and meteorites has been doubted by some physicists, but
Schiaparelli regards their arguments against identity as in-
sufficient, and so we may admit that the matter which con-
stitutes falling stars is similar to that of bolides. Now if we
try to establish a relation between the different known classes

1 Le* Monde*, Nov. 20, 1873.

CHAP. VI. Telescopic Meteors. 649

of meteorites and our four classes of telescopic meteorites we
may describe it thus : —

" I. Solid bodies, small, very compact and refractory, not
easily disaggregated by the enormous pressure they suffer
on entering the terrestrial atmosphere ; little or no occulted
gases ; the smoke accompanying part of them may consist
of the superficial melted layer torn off and dispersed by the
friction of the atmosphere ; (hard stony meteorites).

"II. Bodies larger than Class I., of a less compact material,
which is easily melted and torn off by the mighty current of air
produced by their rapid flight ; another part of their envelope
and trail may consist of vapours and gases ; (tufaceous and
conglomeratic stony meteorites).

" III. Small very compact and refractory masses, rich in occulted
gas, which is expelled by their sudden enormous calefaction, and
expands almost equally in every direction, presenting thus the
appearance of a ball ; (siderites).

" IV. Clouds of cosmical dust or meteorites, so soft and friable
that they are crushed and converted into dust as soon as the
pressure of the atmosphere begins to act upon them."

These deductions are interesting, and will doubtless be tested
by new observations which can hardly fail to throw some
further light on the subject. Prof. Herschel has also called
attention to the desirability of ascertaining whether telescopic
meteors are principally seen only at low apparent altitudes
and moderate real heights, or whether they appear with equal
frequency at all angular altitudes above the horizon, and there-
fore at all possible heights above the earth's surface to which
the use of astronomical telescopes enables us to extend our
sight8.

The showers of telescopic meteors witnessed by Brooks and
Barnard in March and December, 1883, were very noteworthy,
and Denning has suggested that they were connected with the
remarkable sun-glows which attracted so much attention at that

e Report of the Luminous Meteor Committee of the British Association, 1878,
p. 116.

650 Meteoric Astronomy.

period ; but this idea seems to me at variance with what we
know otherwise as to the cause of these glows.

Perhaps the most striking observation ever recorded of a
meteor seen by means of a telescope was by Schmidt on Oct. 19,
1863, when he followed a fireball for 14 seconds. This meteor
was double-headed, and was closely attended by a number of
smaller meteors advancing together with parallel motions.
[See Fig. 241, Plate XXXVI.] Though not a telescopic meteor
properly so called, it merits description from its curious, multiple
character, and the inference suggested, that could instrumental
observations of bolides be greatly increased, we might often find
that, instead of a solitary compact mass, the nucleus is really
composed of a number of bodies revolving closely together in
concentric orbits.

BOOK VI.

TABLES OF THE PLANETS.

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Tables of the Planets.

[BOOK VI.

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The Major Planets.

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[BOOK VI.

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Chacornac . . .
Luther

Marseilles . . .
Bilk...

302 48

236 2 1;

214 16

42 ee

21 36

3 S^

(*D

Euterpe

— Nov. 8

Hind

London

87 so

Q3 El

i 36

Bellona .....

1854, March i

Luther

Bilk

124 *>

144 4O

0 21

Amphi trite

- March i

Marth...

London .

K.6 23

3K.6 41

6 7

(3°)

Urania

-- July 22

Hind

London

ai CQ

308 e;

2 6

Euphrosyne
Pomona

— Sept. i
- Oct. 26

Ferguson
Goldschmidt

Washington
Paris

9248

193 22

3' 4°
220 43

26 29

= 2Q

CH/

Polyhymnia

- Oct. 28

Chacornac . . .

Paris . . .

3,43, 26

0 14

I t>^

Circe

1855, April 6

Chacornac . .

Paris

141 18

184 47

6 27

(W)

Leucothea

— April IQ

Luther

Bilk

2OI 30

3C£ C2

8 12

BOOK VI.]

The Minor Planets.

655

'eriod.

Semi-
axis,
Major.

Diameter.!

App.
opp.
Star
Mag.

Epoch.
Berlin M. T.

Calculator.

Years.

®'S=I.

Miles

0-0790

771

4-60

2-767

196

7-4

1887, Sept. 3O-O...

Godward.

0-2405

77°

4-61

2-769

171

8-0

1888, Dec. 5-0 ...

Farley.

0-2563

814

4-36

2-669

I24

8-7

1887, Sept. 30-0 ...

Hind.

0-0883

978

3-63

2-362

2I4

6-5

i888,^Sept. 24-0...

Farley.

0-1880

857

4-14

2-577

9.9

— Jan. 27-0 ...

Farley.

0-2025

940

3-78

2-425

8-5

— Jan. 17-0 ...

R. Luther.

0-2309

963

3-69

2.386

8-4

1850, Jan. o-o

Briinnow.

0-1567

1086

3-27

2-201

8-9

1848, Jan. i-o

Briinnow.

0-1233

962

3-69

2-387

8-9

1858, June 30-0..

Lesser.

0-1175

639

5-58

3-137

103

9-5

1888, Mar. 27-0...

E. Becker.

O-IOO2

924

3-84

2-453

9-5

1888, Jan. 17-0 ...

R. Luther.

O-2I7O

995

3-57

2-334

9-7

1831, Jan. o-o

Briinnow.

0-0872

858

4-14

2-576

9-7

1850, Jan. o-o

Hansen.

O-I874.

852

82*

4-17

4-3O

2-589

2 '6J.4.

f\1t

9-7
8-6

1888, Feb. 1 6-0 ...
1854, Jan. o-o

Maywald.
Schubert.

w u / T1
0-1357

"*;)

709

4-99

2-925

9.6

1888, May 25-0 ...

Schubert.

O-I299

913

3-89

2-472

5°

1 0-1

- July 25-0 ...

Maywald.

O-2I76

1020

3-48

2-296

9-3

1854, Jan. o-o

Schubert.

0.1596

930

3-82

2-442

9.8

1887, Dec. 1 8.0 ...

Berberich.

0.1432

948

3-74

2-410

9-2

1888, May 25-0 ...

Kiistner.

0.1627

934

3-80

2-436

IO-I

1853, Jan. 2-0

Lesser.

0-I03I

715

4.96

2-909

9.8

1888, Jan. 7-0

Berberich.

0.2309

832

4-27

2-630

10-5

Apr. 15 o ..

Schubert.

0-1337

641

5-55

3.129

10.8

— Nov. 2-0 ..

Kruger.

O-254O

954

3-72

2-400

10-5

1887, Sept. 29-0..

Berberich.

O-O874

820

4-33

2-656

10.5

1853, June ii-o..

Hoek.

0-1739

987

3.60

2-347

9-7

1873, Jan. 5-0

Hoppe.

0.1510

767

4-63

2-777

IO-I

1 888, July 25-0 ..

Bruhns.

0.074I

869

4-08

2-555

9-0

1855, Jan. o-o.. ..

Becker.

0-I282

976

3-64

2-365

9-9

1889, Mar. 2-0 ..

Gunther.

O-2238

635

5-59

3-H7

II-O

1888, Dec. ii-o ..

Schubert.

0-083I

853

4-16

2-587

10-6

1855, Jan. o-o

Lesser.

0-3333

729

4-84

2-871

n-8

1888, Nov. i-o ..

Schubert.

0-1094

806

4.40

2-686

1 1-5

Nov. 2-0 ..

Auwers.

0.2247

686

5-i7

2-992

12-2

— Sept. 22-0 ..

Schubert.

65G

Tables of the Planets.

[BOOK VI.

Discovered

fc»

Atalanta .

1855, Oct. 5

Goldschmidt

Paris

0 /
43 Q

o /
3SQ E

1 8 40

f^\

Fides

— Oct. T

Luther

Bilk.. .

66 36

8 18

a 6

Leda ...

1856, Jan. 12

Chacornac . . .

Paris

ioo 27

296 28

6 j;8

Feb 8

Chacornac

Paris

I S1? 23

IO 22

(V)

Harmon! a

- March 3 1

Luther

Bilk

O !>4

Q3 3C

4 l6

(Z)

Daphne

— May 2 2

Goldschmidt

Paris

221 21

178 «;o

I- cc

VZV

Isis

— May 23

Pogson

Oxford

3.18 4

84 27

8 35

rrr>

Ariadne

18^7. April if,

Pogson...,

Oxford

278 17

264 4.0

3 28

^•y

Nysa

— May 27

Goldschmidt

Paris

III n4

131 8

3 42

v*jy

Eugenia

— June 28

Goldschmidt

Paris

2^2 }I

148 4

6 35

(7>

— Auff. 16

Pogson

Oxford

3KA I 2

181 30

2 18

\±y
O

Melete

— Sept. Q

Goldschmidt

Paris

201; ii

104 O

8 a.

vjy

C*v

Ai'laia

— Sept. 1 «

Luther

Bilk

ill 3O

1 58

c I

Doris

— Sept. io

Goldschmidt

Paris

72 2

185 2

6 30

V2y

Pales

— Sept. IQ

Goldschmidt

Paris

51 4Q

2QO 3,0

3 8

kS/

0
(*\

Virginia
Nemausa ...
Europa

- Oct. 4
1858, Jan. 22
— Feb. 6

Ferguson
Laurent
Goldschmidt

Washington
Nismes
Paris

io 29

174 27

106 2.

17339
17545
I 2Q 42

2 49

957
7 26

\S/

Calypso . . .

— April 4

Luther

Bilk

02 ^3.

144 1

5 7

VSf^

Alexandra

— Sept. io

Goldschmidt

Paris

20; an

aia 41

II 48

v5>
®

Pandora

— Sept. io

Searle

Albany, U.S.

II 44

IO ^7

7 1^

Mnemosyne

1859, Sept. 22

Luther

Bilk

K.2 a

2OO O

1^ 12

Concordia .

1860, March 24

Luther

Bilk

189 io

161 20

X 2

Danae
Olvm.fElpis}

— Sept. 9
— Sept. 1 2

Goldschmidt
Chacornac . . .

Chatillon
Paris

343 57
18 40

334 9

17O 41

18 16
8 37

Erato

— Sept. 14

Forster

Berlin

}8 5Q

I2S 46

2 12

Echo . . .

— Sept. 14

Ferguson

Washington

QQ IE

IQ1 ^8

T 4^

(5)

Ausonia

i86i,Feb. io

De Gasparis

Naples

2 TO 4O

22^ c;7

c 47

Angelina ...

— March 4

Tempel .

Marseilles ...

I 24 S7

^10 <;6

I 10

Cybele

— March 8

Tempel ... .

Marseilles . . .

2 so e

i $8 s.o

^ 2O

Maia
Asia

- April 9
- April 17

H. P. Tuttle
Pogsoii .

Cambridge ,17 .S.
Madras

48 0
306 23

8 25
202 so

3 5
5 59

Hesperia ...

- April 29

Schiaparelli

Milan

no 19

1 86 44

8 31

Leto

- April 29

Luther

Bilk

^46 4

j: O

7 58

Panopea . . .

— Mays

Goldschmidt

Chatillon

30939

4814

1138

BOOK VI.]

The Minor Planets.

657

Period.

Semi-
axis,
Major.

Diameter.!

App.
opp.
Star
Mag.

Epoch.
Berlin M. T.

Calculator.

O-3OO2

780

Years.

4-KK

®'B«=I.
2-746

Miles.
18

I2-O

i889,Mar. i-o

Schubert.

0-1762

825

T *J *J

4-3°

2-645

10-4

1888, May 25-0 ...

Schubert.

0-1544

782

4-54

2-741

1 1-4

1886, Oct. 24-0 ...

Berberich.

0-1144

771

4'63

2-767

9-5

1888, Jan. 27-0 ...

Tietjen.

0-0465

1039

3-4i

2-267

9-2

1863, Jan. o-o

Schubert.

0-266l

771

4-62

2-767

10-5

1888, Feb. 16-0...

Berberich.

0-2227

93°

3-81

2-441

10-4

1887, Aug. 20-0...

L. Becker.

0-1679

1085

3-27

2-203

IO-O

1889, Jan. j-o

Prey.

0-I530

942

3-77

2-421

9-8

1888, Aug. 14-0...

Powalky.

0-0825

79i

4-49

2.721

10-7

— Apr. 16-0 ...

Richter.

0-1659

884

4-01

2'525

10-6

1888, May 6-0 ...

Karlinski.

0-2340

847

4-18

2-599

1 1-7

1887, Dec. 28-o ...

R. Luther.

0-1328

726

4-88

2-880

II-2

1889, Feb. 10-0 ...

Powalky.

0-0628

645

5-52

3-II5

IO-9

1888, Apr. 16-0...

Powalky.

0-2289

652

5-44

3-094

II-O

1887, Mar. 2-0 ...

Powalky.

0-2882

823

4-32

2-649

11-7

1889, Feb. I o-o ...

Powalky.

0-0674

975

3-64

2-365

9-8

1888, July 25-0 ...

Berberich.

0-"35

652

5-44

3-093

10-3

— Sept. 23-0 ...

Murmann.

0-2048

837

4-24

2-620

"-5

— Mar. 7-0 ...

Tietjen.

o-i 999

796

4-47

2-710

10-9

1884, Aug. 15-0...

Schultz.

0-1446

774

4-58

2-759

10-8

1885, Jan. 22-0 ...

Moeller.

0-1175

635

5-59

3-150

10-7

1888, Dec. 12-0 ...

Adolph.

0-0425

800

4-43

2-704

ii-6

1865, Jan. 7-0

Oppolzer.

0-1662

689

5-15

2-982

II-O

1888, Jan. 17-0 ...

R. Luther.

0-1172

794

4-47

2-713

10-9

1865, Jan. 7-0

OppoJzer.

0-1757

643

5-53

3.124

12-3

1877, Sept. 21-0...

Oppoker.

0-1825

958

3-70

2-394

II-I

1888, Feb. 16-0 ...

C. H. F. Peters.

0-1253

957

3-71

2-395

9-9

— July 25-0 ...

Tietjen.

0-1242

808

4-39

2-682

10-5

1887, Jan. 12-0 ...

Oppolzer.

0-1031

558

6-36

3-430

II-O

1888, Aug. 14-0...

Fritsche.

0-1728

823

4-3i

2-648

12-2

1887, April 2-0 ...

Maywald.

0-1865

942

3-77

2-420

II-2

1888, Aug. 14-0...

Frischauf.

0-1645

689

5-i5

2-983

10-7

1880, Mar. 29-0 ...

Kowalczyk.

0-1851

764

4.64

2-783

10-5

1879, May 14-0 ...

• T. Wolff.

0-1814

839

4-23

2-615

10-9

1874, Jan. o-o

DuneV.

u u

658

Tables of tic I'll t. nets.

[BOOK VI.

Discovered

Feronia ...
Niobe

1 86 1, May 29

— Aug. 13

C.H. F.Peters
Luther

Clinton, U.S....
Bilk

o /
3°8 25

207 50
316 19

o /

r -'4
23 17

(V)

Clytie

1862, April 7

Tuttle

Cambridge, U.S.

CT IO

7 4.2

2 24

Galatea ...

— Aug. 3.0

Tempel

Marseilles

8 ii

10,7 50

(77)

Eurydice...

Freia
Frieda

— Sept. 22

— Oct. 21

— Nov. 15

C.H. F.Peters

D' Arrest
C.H. F.Peters

Clinton, U.S....

Copenhagen ...
Clinton, U.S...

335 33
9043

SO AO

35959

212 12
211

2 3
2 28

Diana

1863, March 15

Luther

Bilk

121 42

333 58

8 40

Eurynome

— Sept. 14

Watson

AnnArbor.U.S

2O6 4!

4 3.7

Sappho . . .

1864, May 2

Pogson

Madras

3SS 32

218 36

8 3.8

Terpsichore

— Sept. 30

Tempel

Marseilles

2 23

7 55

(5)

Alcmene . . .

— Nov. 27

Luther

Bilk

131 AO

26 58

2 51

/><

Beatrix . . .

1865, April 26

De Gasparis

Naples

27 34.

C?*)

Clio . . .

— Au£T. 25

Luther

Bilk

33O KS

3.27 26

921

— Sept. IQ

C.H.F. Peters

Clinton, U.S...

3.23 57

2O3 3Q

I I 54

Semele

1866, Jan. 4

Tietjen....

Berlin

28 55

I 87 51

4. 47

Sylvia

— Mav 17

Pogson

Madras

33A I I

75 53.

IO 55

(5)

Thisbe
Julia

— June 15
— Aug. 6

C.H.F. Peters
Stephan

Clinton, U.S...
Marseilles

309 10

353 5Q

277 36

311 4.4.

5 »5

16 1 2

Antiope . . .

— Oct. i

Luther .

Bilk

3OI I 2

i ?! 25

217

(V)

jEgina

— Nov. 4

Stephan

Marseilles

81 28

IO 57

2 8

fe)

Undina ...
Minerva

1867, July 7
— Aug. 24

C.H. F.Peters

Watson

Clinton, U.S...
AnnArbor,U.S

32747
276 39

102 53

956

8 3.5

(w)

Aurora ...

— Sept. 6

Watson

AnnArbor,U.S

4.5 30

4 17

8 4

(95)

Arethusa ..

— Nov. 23

Luther

Bilk

3.4 3.3

244 3,

12 56

JEsle .,

1868, Feb. 17

Cosreia. . . ,

Marseilles

161 46

3.22 57

16 6

Gy
©

Clotho
lanthe
Dike

— Feb. 17
— April 18
— Mav 20

Tempel
C.H.F. Peters
Borrelly . . .

Marseilles
Clinton, U.S...

65 33
14843

16043

354 IB

ii 46
1532

ja £2

Hecate

Helena
Miriam . .
Hera
Clymene . .
Artemis ..

— July 1 i
— Aug. 15

Aug. 22

— Sept. 7
— Sept. 13
— Sept. 1 6

Watson

Watson
C.H.F.Peters
Watson
Watson
Watson

AnnArbor,U.!:

AnnArbor,U.S
Clinton, U.S...
AnnArbor,U.S
AnnArbor,U.S
AnnArbor,U.S

306 18

327 o

35442
32055

60 21
242 46

128 14

343 39

211 4,5

136 13

43 39
188 6

6 23

10 10

5 5
5 24
2 54

21 31

BOOK VI.]

The Minor Planets.

659

Period.

Semi-
axis,
Major.

App.
opp.
Star
Mag.

Epoch.
Berlin M.T.

Calculator.

Years.

©'s =i.

O-I2O2

1040

3-41

2-266

II-2

1886, Oct. 24.0 ...

C. H. F. Peters.

0-1768

776

4-57

2-754

IO-7

1888, July 5-0 ...

E. Becker.

0-0442

816

4-35

2-665

I2-O

1886, Nov. 13-0 ...

Powalky.

0-2383

766

4-63

2-778

u-8

1888, May 26-0 ...

Maywald.

0-3029

811

4-37

2-674

n-6

— Aug. 14-0 ...

Stockwell.

0-1688

562

6-32

3-418

12-0

1889, Jan. 21-0 ...

Murmann.

0-I33I

814

4-37

2-668

II-I

1888, Sept. 3-0 ...

Plath.

0-2088

837

4.24

2-619

10-6

1882, Sept. 15-0 ...

Dubjago.

0-1934

928

3-82

2-444

10-5

1886, Oct. 22-0 ...

Lachmann.

O-2OO8

IO2O

3-48

2-296

10-6

1888, June 15-0...

A. Leman.

0-2102

736

4-83

2-854

11-8

1888, Sept. 3-0 ...

Maywald.

O-22I8

772

4-59

2-764

11-7

1887, Nov. 28-0...

W. Luther.

0-0848

936

3-78

2-432

"•3

1888, May 26-0 ...

E. Becker.

0-2354

977

3-63

2-362

"•3

1889, Feb- IO-° •••

Maywald.

0-1934

821

4-32

2-654

10-9

1887, Nov. 28-0...

Groeben.

O-22OI

650

5-46

3-101

12-4

1889, Feb. i o-o ...

Maywald.

0-0947

546

6-50

3.481

1 1-9

1888, Nov. 22-0...

Plath.

0-1642

77!

4-60

2-766

10-8

1883, Oct. 20-0 ...

Kowalczyk.

0-1803

871

4-07

2-551

10- I

— Dec. 19-0 ...

T. Wolff.

0-l6l3

636

5-58

3-147

11-6

1888, Aug. 14-0...

Maywald.

0-1083

852

4-16

2-589

"•3

1889, Apr. n-o ...

Maywald.

O-IOII

623

5-7o

3-188

10-9

1884, Dec. I3-° •••

Anderson.

0-1409

776

4-57

2-755

10.8

1886, Nov. 13-0...

Lehmann.

0-0825

631

5-62

3-163

M-3

1883, July 12-0 ...

Leppig.

0-1492

66 1

5-37

3-067

"•3

1888, Aug. 14-0...

Schur.

0-1363

665

5-33

3-052

11.4

1887, Nov. 8-0 ...

Schulhof.

0-2571

814

4-35

2-669

10-6

1888, Nov. 2-0 ...

Maywald.

0-1917

806

4.40

2-686

ii.6

NOV. 22-O ...

C. H. F. Peters.

0-2385

759

4-68

2-797

14-0

1868, June 5-0 ...

Lowy & Tisserand.

0-1673

654

5-44

3-087

11-9

1888, Mar. 7-0 ...

Stark.

0-1392

854

4-15

2-585

10-7

— June 15-0 ...

Watson.

0-2529

818

4-34

2-660

12-6

— May 6-0 . . .

C. H. F. Peters.

0-0814

799

4-44

2-701

TO*2

— Feb. 16-0 ...

Leveau.

0-1556

633

5-60

3-156

12-2

— May 6-0 . . .

Watson.

0-1759

971

3-66

2-372

II-I

1889, Feb. 10-0 ...

A. Leman.

<)60

2'ables of tic l}l«nets.

[BOOK VI.

Discovered

(3)

Dione

1868, Oct. 10

Watson

AnnArbor, U.S.

O 1

26 8

o /
63 20

o /

4 38

(Zft

Camilla

— Nov. 17

Pogson

Madras

III 2

175 59

O 52

v_y

(rofi)

Hecuba . . .

1869, April 2

Luther

Bilk

169 58

352 2I

4 24

Felicitas ...
Lydia ..

- Oct. 9
1870, April 10

C. H.F.Peters
Borrelly

Clinton, U.S....
Marseilles

5653
336 19

433
57 X4

8 i
6 o

Ate

— Aug. 14

C. H.F.Peters

Clinton, U.S.. .

no 13

306 23

4 ^6

(^!

Iphigenia
Amaltbcea

— Sept. 19
1871, March 12

C. H.F.Peters
Luther

Clinton, U.S....
Bilk

338 3
200 i

324 2

123 8

2 37

S 2

V_x

Cassandra
Thyra

— July 23
— Aug. 6

C. H.F.Peters
Watson

Clinton, U.S....
AnnArbor, U.S.

15324

43 O

164 25
309 ii

454
II 35

(3)

Sirona
Loiuia

— Sept. 8
— Sept. 12

C. H.F.Peters
Borrelly

Clinton, U.S....
Marseilles

'5M7

48 6

6425
349 33

3 35
1458 j

(§)

Peitho

1872, March 15

Luther

Bilk

78 33

47 32

7 47 I

C120)

Althaea . . .
Lachesis ...

Hermione

— April 3
— April 10

— May 12

Watson
Borrelly

Watson

AnnArbor,U.S.
Marseilles ......

Ann Arbor,U .S.

ii 26
223 o

3S7 17

203 56
34240

76 55

5 44
6 59

7 36

0 J

Gerda

— July 31

C. H.F.Peters

Clinton, U.S. ..

2OO 46

178 52

i 36

(123)
(124)

Brunhilda
Alceste. . .
Liberatrix

— July 31
— Aug. 23
— Sept. ii

C. H.F.Peters
C. H.F.Peters
ProsperHenry

Clinton, U.S....
Clinton, U.S....
Paris

69 13

247 3°

276 8

3°8 31
18823
169 26

625
256
4 38

(S)

Velleda ...

Nov. 5

Paul Henry

Paris

34.8 43

23 19

2 56

^27)

Johanna . . .

— Nov. 5

ProsperHenry

Paris

119 58

31 49

8 16

(132)
(•33)

Nemesis ...
Antigone. . .
Electra . . .

Vala
^Ethra ...
Cyrene .

— Nov. 25
1873, Feb. 5
- Feb. 17

— May 24
— June 13
— Aug. 1 6

Watson
C. H.F.Peters
C. H.F.Peters

C. H.F.Peters
Watson
Watson

AnnArbor, U.S.
Clinton, U.S....
Clinton, U.S....

Clinton, U.S....
AnnArbor,U.S.
AnnArbor,U.S.

1547
242 13
20 2S

220 39
152 45

24.1 32

7638
13744
H6 5

65 25
25953

321 12

6 16

12 10

22 57

458

2457

7 *4

Sophrosyne

— Sept. 27

Luther

Bilk

67 2O

346 24

II 36

(S)

Hertha ...
Austria . . .

1874, Feb. 18
— March i

C. H.F.Peters
Palisa

Clinton,U.S. ...
Pola

320 32

316 is

344 °
186 15

2 IS

9 33

(5)

Melibcea ...

— April 21

Palisa

Pola

300 35

203 43

13 21

(139)

Tolosa
Juewa

— May 19
— Oct. 10

Perrotin
Watson

Toulouse
Pekin

310 I
164 31

544s

352 27

3 M

10 57

Siwa

— Oct. 13

Palisa

Pola

300 7

107 6

3 I2

BOOK VI.]

The Minor Planets.

661

t>-

Period.

Semi-
axis,
Major.

App.
opp.
Star
Mag.

Epoch.
Berlin M. T.

Calculatoi

„

Years.

®'s = i.

0-1754

629

5'64

3-I67

"•3

1888, May 6-0 ...

Tietjen.

0-0692

544

6-53

3-49 i

II-2

1887, Feb. 21-0 ...

Matthiessen.

0-1048

618

5-74

3-206

ii. 7

1888, Aug. 14-0...

Schulhof.

0-2977

802

4-43

2-696

I2-O

1887, Dec. 1 8-0 ...

Groeben.

0-0808

786

4-5i

2-732

10-5

1888, Feb. 16-0 ...

H. Oppenheim.

0-1045

850

4-17

2-593

"•3

1887, Sept. 9-0 ...

Holetschek.

0-1282

934

3-80

2-435

1 1-5

1888, July 25-0...

Tietjen.

0-0866

969

3-66

2-376

II-O

— Jan. 17-0 ...

W. Luther.

0-1374

810

4-38

2-677

n-i

— July 5-0 ...

Anton.

0-1934

966

3-67

2-380

10-4

1886, May 26-0 ...

Watson.

0-1412

770

4-62

2-769

10-7

1880, Sept. 25-0 ...

H. Oppenheim.

0-0294

686

5-17

2-991

n-4

1887, Nov. 28-0...

Tietjen.

0-1610

931

3-8 1

2-439

10-8

1888, May 26-0 ...

Holetschek.

0-0825

856

4-'5

2-580

10-6

— Jan. 27-0 ...

Berberich.

0-0541

645

5-50

3-118

11.7

- Feb. 17-0 ...

Plath.

0-1262

552

6-42

3-456

II- 2

1887, Nov. 8-0 ...

Berberich.

0-0451

614

5-78

3.221

"•5

1888, May 6-0 ...

Lange.

0-1219

802

4-43

2-694

11.8

— March 7-0- ••

Berberich.

0-0779

832

4-27

2-629

10-3

— March 27-0

Hall.

0-0787

781

4-54

2-743

112

— Jan. 27-0 ...

Lange.

0-1054

932

3-82

2-439

"•5

1887, Sept. 9-0 ...

Groeben.

0-0645

776

4-57

2-756

10-5

1888, Mar. 27-0...

Maywald.

0-1288

777

4-56

2-752

10-6

1886, Dec. 23-0 ...

A. Palisa.

0-2136

731

4-87

2-866

10-3

1888, Mar. 7-0 ...

Austin.

0-2142

645

5-50

3'"5

10-6

NOV. 22.O ...

Powalky.

0.0686

936

3-77

2-432

12-2

— May 6-0 ...

Berberich.

0-3832

846

4-19

2-600

II. I

1881, Jan. 3-0 ...

Watson.

0-1418

663

5-35

3-061

"•3

1888, May 26-0 ...

Maywald.

0-1161

864

4-12

2-565

u-i

— May 6-0 ...

Maywald.

0-2039

938

3-78

2-428

10-5

1889, Feb. i o-o ...

Maywald.

0-0848

1026

3-46

2-286

11-2

1879, Dec. 10-0 ...

H. Oppenheim.

0-2142

643

5-53

3-124

11-8

1887, Nov. 28-0...

Tietjen.

0-1619

926

3-83

2-449

1 1-8

1 888, Feb. 6-0 ...

Plath.

0-1777

766

4-63

2-780

10-9

— Dec. 12-0 ...

Berberich.

0-2162

786

4-5i

2-731

11-4

1883, Oct. 20-0 ..

Maywald.

662

Tables of the Planets.

[BOOK VI.

Discovered

Lumen

Paul Henry. . .

Paris

o /
ra A°7

0 /

I I -S

(MI)

Pol ana

Jan 28

Palisa

Pola

16 47

ox9 X3

(142)

A dria

TVb 2 1

Palisa

Pola

"JP" 0

2 14

(us)

Vibilia

— June 3

C.H.F.Peters

Clinton, U.S.

7 2Q

233 49
76 46

4 48

(ui)

Adeona

June 3

C.H.F.Peters

Clinton, U.S.

1 18 ?o

77 A1

Lu cilia . .

June 8

Borrelly

Marseilles

22*7 21

84 16

T3 6

Protogeneia

July 10

Schulhof

Vienna

21 34

lo °

Gallia ..

ProsperHenry

Paris

16 6

r^c 8

1 54

(MS)

Medusa

Sept 2 i

Perrotin

Toulouse

M5 °

•*S I9

i 6

(^49)

Nuwa

Oct. 19

Watson

AnnArbor.U.S

35K 27

2 8

(g)

Abundantia

Nov i

Palisa .

Pola

164 46

38 r A

6 28

Atala

Nov 2

Paul Henry

Paris

82 21

o° 34

(S)

Hilda

Nov 2

Palisa .

Pola

284 3s

41 33

228 23

7 t 3

Bertha

— Nov. 6

ProsperHenry

Paris

IQO ^0

37 3A

2O SO

\*°)
^~\

Scylla

Nov. 8

Palisa

Pola

82 14

(s)

Xantippe . . .

NOV. 22

Palisa ..

Pola

I c6 Q

4o 4

Dejanira . . .

Dec. i

Borrelly

Marseilles

IO7 32

62 38

12 2

vjsj/

Coronis

1876 Jan 4

TCnorrfi

Berlin

61 58

280 s;

I O

Emilia

— Jan. 26

Paul Henry..

Paris

101 32

«X* 33

ias 8

6 4

(^59)

Una

Feb. 20

C.H.F.Peters

Clinton, U.S.

E7 IQ

912

3 KI

/^N

Athor

April 18

Watson

AnnArbor,U . S.

3IO A2

18 1C.

vi!>

Laurentia ...

April 21

ProsperHenry

Paris

IJE ii

38 6

6 t;

Erigone
Eva

— April 26
July 12

Perrotin
Paul Henry

Toulouse
Paris .. .

9358

3CQ 2O

I59H

77 36

441

2.1 25

(«sjj

Loreley

— AUET. 10

C.H.F.Peters

Clinton, U.S.

270 «;6

1OA C

II 11

Khodope . . .
Urda

— Aug. 10
— Aug 28

C.H.F.Peters
C.H.F Peters

Clinton, U.S.
Clinton, U.S.

3032

2OC O

129 34

12 0

/i6?)

Sibylla

— Sept. 27

Watson

AnnArbor,U.S

17 lo

2OO 2A.

4 34

Zelia

— Sept. 28

ProsperHenry

Paris ...

327 I

c 31

Maria or
Myrrha

Ophelia .

1877, Jan. 10
— Jan. 13

Perrotin
Borrelly

Toulouse
Marseilles

9640
144 40

301 22

101 16

1423
2 34

Baucis
Ino

- Feb. 5
— Aug. 2

Borrelly
Borrelly . ..

Marseilles
Marseilles

329 2
1 a ja

33i 57

14.8 3Q

10 2
14 l6

(174)

Phaedra
Andromache

- Sept. 3
— Oct. i

Watson
Watson

AnnArbor.U.S.
AnnArbor.U.S.

25346

293 8

328 53
23 42

12 8

347

BOOK VI.]

The Minor Planets.

003

I'-

Period.

Semi-
axia,
Major.

App.
opp.
Star
Mag.

Epoch.
Berlin M. T.

Calculator.

Years.

® 's = I .

0-2136.

816

4-35

2-664

n-4

1888, Feb. 1 6-0 ...

Berberich.

0-1331

943

3-76

2-419

12-2

1885, Dec. 28-0 ..

L. Becker,

0-0724

773

4-57

2-762

12-4

1880, Mar. 29.0 ...

Haerdol.

0-2329

819

4-33

2-657

10-7

1888, July 1 8-0 ...

Powalky.

0-1438

4-38

2-6/5

"•3

May 6-0 ...

Tietjen.

0-0663

792

4.48

2-719

II-I

Apr. 16-0 ...

Berberich.

0-0308

639

5-54

3-137

12-5

— Dec. 12-0 ...

L. Becker.

0-1834

768

4-62

2-773

II-O

— July 25-0 ...

L. Becker.

0-1193

"39

3-12

2-133

12-9

Sept. 30-5 ...

Tietjen.

0-1305

690

5-i5

2-980

u-6

1884, May 25-5 ...

H. Oppenheim.

0-0369

851

4.17

2-591

ii. 7

1887, Sept. 9-0 ..

Knopf.

0-0814

638

5-54

3-139

12-2

1888, Jan. 7-0 ..

Lange.

0-1676

449

7-90

3-968

12-6

— June 15-0 ...

Kiihnert.

0-0787

621

5-7i

3-197

II-2

1887, Dec. 18-0 ...

Anton.

0-2557

4-97

2-913

13-5

1875, Nov. 8-5 ...

Schulhof.

0-2636

670

5-29

3-038

11-9

— Nov. 27-5 ...

A. Schmidt.

0-2105

855

4-i5

2-583

147

— Dec. 27-5 ...

A. Leman.

0-0541

73i

4-86

2-868

12-3

1888, July 25-0 ...

Maywald,

O-IO22

648

5-48

3-107

12-3

— Mar. 7-0 ...

Berberich.

O-O68O

788

4-52

2-728

n-8

— Nov. 22-0 ...

Neugebauer.

0-1377

967

3-67

2-379

II-O

Sept. 3-0 ...

Tietjen.

O-lSig

676

5'25

3-019

12-3

1887, June i-o ...

Tietjen.

0-1567

981

3-6i

2-356

12-O

1876, May 26-5 ...

A. Leman.

0-3464

831

4-27

2-633

"•5

1888, Apr. 16-0 ...

Richter.

0-0703

640

5-54

3-132

II-I

— Nov. 2-0 ...

Samter.

O-2IIO

805

440

2-687

I2'5

May 26-0 ...

Richter.

0-0340

737

4-82

2-852

13-0

1889, Apr. ii-o ...

Lange.

0-0753

573

6-2O

3-372

11-6

1888, Sept. 3-0 ...

Groeben.

0-I302

980

3-62

2-358

"•3

1887, Nov. 8-0 ...

Richter.

0-0648

870

4-08

2-554

11-7

1888, Dec. 12-0 ...

A. Leman.

0-1161

636

5-58

3-145

I2-I

— Jan. 7-0 ...

Berberich.

0-1141

967

3-67

2-379

IO-4

— Feb. 16-0 ...

Berberich.

0-2073

782

4-54

2-742

I 1-0

— Apr. 16-0 ...

Becka.

o- 1 4.06

733

4-84

2861

11-6

1886, June 26-5...

H. Oppenheim.

0-3478

54° ! 6-57

3-5°7

II-2

1883, July 12-0 ...

Watson.

6(54

Tables of the Planets.

[BOOK VI.

Discovered

txS

(if*)

Idunna

1877, Oct. 14

C.H. F.Peters

Clinton, U.S.

o /
22 48

0 /

201 8

0 /

22 3,7

Imia

— Nov. 5

Paul Henry

Paris

22 4O

3.4Q IQ

I 27

Belisana

Nov. 6

Palisa

Pola

262 40

ZQ 51

it;

(179)

Clytetnnestra
Garumna . . .

— Nov. 12
1878, Jan. 29

Watson
Perrotin

AnnArbor,U.S.
Toulouse

355 4°

124 21

253 '3
314 38

747
o si

(181)

Eucharis

— Feb. 2

Cottenot

Marseilles

QC I1?

144 5.1

18 3.6

(182)

Elsa

— Feb. 7

Palisa

Pola

=4. =n

1 06 36

2 IO

/iSm

Istria

— Feb. 8

Palisa

Pola

4.C a

142 46

26 31

Deiopeia

— Feb. 28

Palisa

Pola ..

171 30

3.35 44

I 12

Eunike

— March i

C.H. F.Peters

Clinton, U.S.

15 4

1^3 51

23. 14

Celuta

— April 6

ProsperHenry

Paris

227 5^

14 3,7

Mil

(i8?)

Lamberta ...

— April 1 1

Coggia

Marseilles

214 Q

22 2O

IO 4^

(*V

Menippe . . .
Phthia

— June 1 8
- Sept 9

C.H.F.Peters
C.H.F.Peters

Clinton, U.S.
Clinton, U.S.

30948

q 47

241 55

2O3. 25

II 21

; q

Ismene

— Sept. 22

C.H. F.Peters

Clinton, U.S.

106 27

177 5

6 7

n?y

Kolga
Nausikaa ...

— Sept. 30
1879, Feb. 17

C.H.F.Peters
Palisa

Clinton, U.S.
Pola

2451
10 58

15955

3.43 17

n 29
652

Ambrosia . .

— Feb. 28

Coggia . . .

Marseilles

71 IO

ici 24

I I ^6

Prokne

— Mar. 21

C.H.F.Peters

Clinton, U.S.

310 18

159 25

18 23

Eurykleia

— April 2 2

Palisa

Pola

118 21

7 S3

7 o

Philomela . . .
Arete

— May 14
— May 21

C.H.F.Peters
Palisa

Clinton, U.S.
Pola

309 26

314 I S

7324
82 4

7 16
8 50

Ampella . . .
Byblis .

— June 13
— July o

Borrelly
C.H.F.Peters

Marseilles
Clinton, U.S.

355 29
261 40

26838
QO O

9 20
15 23

C200)

Dynamene
Penelope . .

— July 27
— Aug. 7

C.H.F.Peters
Palisa

Clinton, U.S.
Pola

48 2
3ar 6

32518

157 8

655
5 43

(5)

Chryseis . . .
Pompeia . . .
Callisto

— Sept. ii
- Sept. 25
— Oct. 8

C.H.F.Peters
C.H.F.Peters
Palisa

Clinton, U.S.
Clinton, U.S.
Pola

132 9

444°

256 so

137 Si
34841
205 46

848
3 12
8*17

Martha

Oct. 13

Palisa

Pola

24 27

212 17

10 40

(*v

Hersilia

— Oct. 13

C.H.F.Peter8

Clinton, U.S.

8s 4i

145 16

3 46

Hedda

— Oct. 17

Palisa

Pola

218 J$7

28 56

3 49

Lacrimosa . . .

— Oct. 21

Palisa

Pola ..

127 40

5 22

i 47

Dido

— Oct. 22

C.H F.Peters

Clinton, U.S.

255 55

2 "5

7 ]4

Isabella

— Nov. 12

Palisa

Pola

44 8

32 ^8

5 l8

v^y

BOOK VI.]

Tlie Minor Planets.

6G5

Period.

Semi-
axis,
Major.

App.
opp.
Star
Mag.

Epoch.
Berlin M. T.

Calculator.

Years.

®'s=i.

0.1683

625

5-68

3-183

I2-I

1888, Aug. 140...

Neugebauer.

0-2363

770

4-60

2-769

12-4

— Jan. 7.0 ...

Richter.

0-0430

919

3-86

2-461

12.0

1887, Apr. 22-0 ...

Berberich.

0-1132

693

5.12

2.971

"•5

1886, June 26-5 ...

H. Oppenheim.

0-1672

789

4-5i

2-725

13-3

1888, May 26-0 ...

Groeben.

0.2193

644

5-5»

3-I2I

n-5

1887, Oct. 19-0 ...

De Ball.

0-1884

945

3-76

2-416

II-O

1888, NOV. 22-0...

Sarnter.

o-35"

757

4.69

2-801

12-6

1878, Mar. 2-5 ...

Douner.

0-0680

624

5-69

3-186

12.4

1885, June n-o...

Thraen.

0-1255

782

4-53

2-740

10-4

1888, May 26-0 ...

Groeben.

0-1503

978

3-63

2-362

1 1-4

— Jan. 7-0 ...

Tietjen.

0-2405

788

4-52

2-727

11.4

1887, Apr. 2-0 ...

A. Leman.

0-2173

749

4-74

2-821

13.0

1878, July 5.5 ...

A. Leman.

0-0369

925

3-84

2.451

"•5

1885, July 1-5 ...

H. Oppenheim.

0-1622

453

7-83

3-944

1 2-O

1887, Dec. 18-0 ...

Kiistner.

0-0863

719

4-94

2-898

I2-O

1886. Apr. 7-0 ...

L. Becker.

0-2447

952

3-73

2-403

9-3

1888, July 25-0...

Lange.

0-2854

858

4-14

2-576

12-2

1879, Mar- 25-5 •••

A. Leman.

0-2375

838

4-23

2-618

10-5

1888, June 15-0...

Tietjen.

0-0417

727

4-89

2-878

12-3

— Feb. 16-0 ...

Tietjen.

0-0125

645

5-50

3-1 16

10-3

1887, Oct. 19-0 ...

Tietjen.

0-1617

783

4-53

2-739

12-7

— Feb. 21-0 ...

Lange.

0-2261

920

3-86

2-460

II. I

1888, NOV. 22-0...

A. Leman.

o- 1 704

626

6-67

3-179

12-4

1887, Dec. 18-0 ...

Tietjen.

0-1337

784

4-53

2-737

1 1-0

1888, July 25-0...

Groeben.

0-1785

809

4-39

2-679

11-9

— Nov. 2-0 ...

Richter.

0-0964

657

5-40

3-078

10-7

— May 6-0 . . .

Berberich.

0-0593

784

4-53

2-736

n-7

— Sept. 23-0 ...

Berberich.

0-1719

812

4-38

2-672

I2-O

1886, Feb. 26-0...

A. Palisa.

0-0334

766

4-63

2-779

12-7

— Feb. 26-0 ...

Kiistner.

0-0407

782

4-53

2-740

I2-O

1887, June 21-0...

Stechert.

0-0288

1028

3-45

2-284

11-8

1888, Apr. 16-0 ...

Richter.

0-0160

722

4-91

2-891

I2-I

— Aug. 14-0 ...

Berberich.

0-0659

636

5-58

3-144

n-6

— Apr. 16-0 ...

Groeben.

0-1239

790

4-50

2-722

12-5

— Nov. 2-0 ...

Berberich.

Tables of the Planets.

[BOOK VI.

Discovered

(£)

Isolda

1870, Dec. 10

Palisa

Pola

O 1

7S 28

o /
26^ 14.

0 1
3 IT

Medea

1880, Feb. 6

Palisa

Pola

c6 47

31^ 6

4 IT

Lilaea

Feb 1 6

C H F Peters

Clinton U S

282 «

6 4-7

A sch era

— March i

Palisa

Pola

108 17

342 33

u 4^
1 27

CEnone

— April 7

Knorre

Berlin

341 27

2^ 2O

I 41

(p)

Cleopatra ...

— April 10

Palisa

Pola

12 4

21 c £2

13 2

§5

Eudora

— Aug. 10

Coggia . . .

Marseilles

•3,14 24

164. I

10 17

(***)

Bianca

— Sept. 4

Palisa

Pola

23O Q

1*70 Z.6

IS 12

Thusnelda...

— Sept. 30

Palisa

Pola

140 27

2OO ^2

JO 47

Stephania ...

1881, May 19

Palisa

Vienna

111 is

258 26

7 14

V221)

Eos

1882, Jan. 1 8

Palisa

Vienna

ISO 14

142 3O

10 51

Ci22y

Lucia

— Feb. Q

Palisa

Vienna

2S7 12

80 1 7

211

Rosa

— March 9

Palisa .,

Vienna

IO4 1

4O K

i ;q

Oceana

— Mar. 30

Vienna

260 10

1^1 24

S S2

Henrietta ...

— April 19

Palisa

Vienna . . .

200 36

2OO 46

20 41

(226)

Weringia ...

— July 19

Palisa

Vienna

28s 10

1 IS 24

is 40

6*27)

Philosophia

— AUET. 12

Paul Henry. . .

Paris

22n :;:,

no s6

Q IS

(?*y

Agathe ...

Palisa

Vienna

120 23

in 18

2 23

Adelinda ...

— Aug 22

Palisa

Vienna ....

111 17

10 48

2 IO

Athamaiitis

- Scot i

De Ball

Bothkamp

l6 44

25Q 4O

0 26

Vindobona

— Sept 10

Palisa

Vienna ....

2S3 22

1^2 SI

5 IO

(*9n

Russia

1883 Jan 31

Palisa

Vienna ....

2OO 25

IS2 14

6 4

Asterope . . .

— May T i

Borrelly

Marseilles ... .

144 22

222 29

7 39

Barbara

A net I 2

C H.F.Peters

Clinton U.S.

111 ^1

144 12

IS 21

Carolina . . .

— Nov. 28

Palisa

Vienna

260 4O

66 33

9 4

Honoria

1884, April 26

Palisa

Vienna . .

3=;6 e;8

1 86 29

7 37

C«)elestina ...

— June 27

Palisa . ...

Vienna . .

281 e;=;

84 36

9 47

(23^

Hypatia

- July i

Knorre

Berlin

20 12

184 12

12 22

Adrastea . . .

— Auar. 1 8

Palisa

Vienna . . .

26 5

181 40

6 8

Vanadis . . .

— AUJJ. 27

Borrelly

Marseilles . . .

CI K.A

IIS O

C241)

Gennauia ...

- Sept. 12

Luther

Diisseldorf

*41 O

272 21

5 31

(242)

Kriemhild. . .

— Sept. 22

Palisa

Vienna

123 2

207 s8

ii 17

Ida

— Sept. 29

Palisa

Vienna

"72 41

326 20

I 10

Sita

— Oct. 14

Palisa

Vienna

13 6

208 37

Vera

1885, Feb. 6

Pogson...

Madras

27 M

62 12

;..

BOOK VI.]

The Minor Planets

m>7

/x Period.

Semi-
axis,
Major.

App.
opp.
Star
Mag.

Epoch.
Berlin M. T.

Calculator.

Tears.

®s' = i.

0-1564

666 5-32

3-049

"•5

1887, July i i-o ...

A. Palisa.

0-II08

646

5-49

3-II2

12-2

1888, Aug. 14-0...

L. Becker.

0-1438

776

4-57

2-754

ii. 7

1887, Dec. 1 8.0 ...

A. Lenian.

0-0317

841 4-22

2-612

I2-I

1886, Sept. 14-0...

L. Becker.

0-0359

771 4-60

2-766

12-8

1888, Jan. 7-0 ...

Groeben.

0-2507

760 4-67

2-794

IO-I

1886, June 26-0...

Knopf.

0-3093

730

4-86

2-868

13-1

1888, Mar. 7-0 ...

Richter.

0-1164

814

4-37

2-667

"•3

— May 26-0 . . .

Groeben.

0-2241

983 3-61

2-354

II-2

1884, Nov. 23-0...

Danner.

0-257I

985 3-60

2-350

13-6

1887, Jan> °-5 •••

Bidschof.

O-IO28

6?9 5-23

3.011

II-2

1888, Apr. 1 6-0 ...

Groeben.

0-1475

642 5-54

3-127

I2«9

— Apr. 16-0...

Berberich.

0-1179

65i 5-45

3-098

13-3

— May 6-0 ...

Groeben.

0-0425

825

4-30

2-644

n-7

1887, July ii-o ...

S. Oppenheim.

0-2650

566

6-27

3-398

12-7

1884, Dec. 16-5 ...

Cerulli.

O-2O22

793

4-47

2-7I5

13-0

1887, Nov. 28-0...

Kreutz.

0-2099

639

5-53

3-137

12-9

1888, Sept. 23-0...

Lange.

0-2405

1087

3-26

2-201

14.7

1882, Aug. 24.5...

Kreutz.

O.I5I8

564

6-29

3-406

!3-5

1888, July 5-0 ...

Berberich.

0-1659

965

3-68

2-382

10-3

— Mar. 7-0 ...

Richter.

0.1507

710

4-94

2-922

12-4

1887, July 31-0 ...

Lange.

0.1747

870

4-08

2-552

'3-4

Apr. 2.5 ...

Herz.

0-0996

817

4-34

2-662

"•3

— Apr. 2-0 ...

Knopf.

0-2428

962

3-69

2-386

11.7

— Nov. 8-0 ...

Tietjen.

0-0572

725

4-89

2-882

12-2

— Aug. 20-0...

Tietjen.

0-1893

758

4-68

2-799

1 1-4

1885, July 22-5 ...

Bidschof.

0-0742

773

4-59

2-763

12-8

1887, Jan. 12-0 ...

Oppolzer.

0-0863

4-97

2-911

u-7

1888, May 26-0 ...

Berberich.

0-2284

689

5-i5

2-981

14-2

— May 6-0 ...

Berberich.

0-2065

815

4-36

2-666

12-5

1884, Nov. 10 5 ...

Saint-Blancat.

0-0999

665

5-33

3-053

u-4

1888, May 6.0 ...

W. Luther.

0-1218

733

4-84

2-863

12-6

1884, Sept. 26-5...

Herz.

0-0430

733

4-84

2-862

13-3

1887, Jan. 1-5 ...

Herz.

0-1374

1106

3-21

2-175

13-7

— Sept. 9-0 ...

Berberich.

0-1960

649

5-47

3-104

12-5

— May 2-0 ...

Saint-Blancat.

Tables of tlic Planets.

[BOOK VI,

Discovered

* j

(*w

Asporina ...

1885, Mar. 6

Borrelly ..,

Marseilles

0 /

256 6

O 1

162 35

0 / j

is 38

Eukrate

— Mar. 14

Luther .

Dusseldorf.

53 4O

o 20

2S O

Lameia

— June «.

Palisa

Vienna

24.Q 6

246 V7

Use

— Aug. 1 6

C.H.F.Peters

Clinton, U.S.

lie1?

214 48

0 41

Bettina

— Sept. 3

Palisa

Vienna

88 7

26 Q

12 S.7

Sophia ...

— Oct. 4

Palisa

Vienna

77 47

ij;7 20

JO 26

Oct. ii

Perrotin

Nice

5.S6 2

IO I

\^y

Mathilde

— Nov. 1 2

Palisa

Vienna ....

5.25. A_2

180 6

6 3.7

(253)

1886 Mar. 31

Palisa

Vienna

28 IT.

" o/

45.T

(254)

Mar. 31

Palisa

Vienna ...

162 8

14 6

\Valpurga

— At>r. ^

Palisa

Vienna

228 48

183 A-i

T 5 16

Silesia

— Apr. c,

Palisa

Vienna

6s, 16

4S 5O

3 AQ

Tyche

— May 4

Luther

Diisseldorf.

5£Q 27

20*7 LI

14 14

fe)

Aletheia . . .
Hubert a

— June 28
Oct. 3

C.H.F.Peters
Palisa

Clinton, U.S.
Vienna

23949
556 17

8834

1 68 47

1043

6 16

(**)

Prymno
Valda

— Oct. 31
Nov. 3

C.H.F.Peters
Palisa

Clinton, U.S.
Vie^iTifv ....

25948
60 29

96 20

ag 43

338
7 41?

Dresda

— Nov. 3

Palisa

Vienna

II 4O

2I1? 55

I 17

(5)
(2)

Libnssa
Anna

— Dec. 17
1887, Feb. 27

C.H.F.Peters
Palisa

Clinton, U.S.
Vienna

2429

226 8

50 8

551 2Q

I027

2S 4S

(§)

Aline '

— • May 17

Palisa

Vienna

23. SI

216 1 8

I 3 2O

Tirza ...;

— • May 27

Charlois ,

Nice

264 67

74 8

6 2

Adorea'

— June 9

Borrelly

Marseilles

l84 40

121 40

2 25

jgj

Justitia

— Sept. 21

Palisa

Vienna

275 2,8

I R"7 2O

t; 2^

(27°)

Anabita
Penthesilea

— Oct. 8
— Oct. 13

C.H. F.Peters
Knorre

Clinton, U.S.
Berlin

335 50

28 3,2

25443

237 7

2 20
3 35

Antonia

1888, Feb. 4

Charlois

Nice

A tropes

— Mar. 8

Palisa

Vipnna. ^

284 58

is.8 so

2O 4n

Philagoria

April 3

Palisa

Vienna

212 48

Q5 3.8

3 41

Sapientia . .

— April 15

Palisa

Vienna ... .-.

l62 52

I 3.4 5.6

448
1 1

(?t)

Adelheid . . .

— April 17

Palisa

Vienna

T2O ^

211 3O

21 4.4

Elvira

— May 3,

Charlois

Nice

(278)

Paulina

— May 17

Palisa

Vienna .

224 48

62 24

7 20

Thule

— Oct. 25

Palisa

Vienna

2O8 4Q

75 12

2 23

Philia

— Oct. 29

Palisa

Vienna ..

06 ^6

10 56

7 22

BOOK VI.]

The Minor Planets,

669

Period.

Semi-
axis,
Major.

App.
opp.
Star
Mag.

Epoch.
Berlin M.T.

Calculator.

Years.

®'s=i.

0-1050

802

4-43

2-695

11-7

1885, Apr. 18-5 ...

A doyer.

0-2406

782

4-53

2-740

II-O

1887, Sept. 29-0...

Lange.

0-0657

914

3-89

2-471

13-0

1888, Jan. 27-0 ...

Berberich.

0-2161

967

3-66

2-379

13-6

— May 6-0 ...

Berberich.

0-1285

634

5-60

3-153

11.7

1885, Dec. 8-0 ...

Monnichmeyer.

0-1071

645

5-47

3-ii5

13.6

— Nov. 10-5...

Knopf.

0-0834

634

5.60

3-153

13-0

— Oct. 30-5 ...

Tietjen.

0-2620

824

4-3i

2-647

13-4

1888, Jan. 7-0 ...

Lebeuf.

0-1161

1086

3-27

2-202

13-4

1886, Apr. 2-5 ...

Schwarz.

0-0830

779

4-55

2-748

13-8

— Mar. 31-5...

Berberich.

0-0740

680

5-22

3-010

13-2

— June 1-5 ...

Berberich.

0-1217

644

5-52

3-"9

12-8

— Apr. 5-5

Berberich.

0-2062

837

4.24

2-620

Il-I

1887, July 31-0...

Stechert.

0-1170

638

5-54

3-139

I2-I

1886, July 1-5 ...

Tietjen.

0-1103

548

6-48

3-475

13-9

- Oct. 4-5

Berberich.

0-0897

997

3-56

2-331

n-9

1887, Jan. 12-0 ...

Lange.

0-2133

873

4-06

2-547

14-1

1886, Nov. 6-5 ...

Berberich.

0-0814

724

4-90

2-885

13-3

— Nov. 13-0 ...

Lange.

0-1580

771

4-61

2-767

12- 1

1887, Jan. 1-5 ...

Millosevich.

0-2616

942

3-77

2-421

13-8

Apr. 17-5 ...

Berberich.

0-1573

754

4-75

2-808

13-5

May 17-5 ...

Lange.

0-0978

768

4-62

2-774

14-0

— June 25-5...

Charlois.

0-1279

655

5-42

3-085

12-5

1888, Aug. 14-0...

Parrish.

0-2023

838

4-23

2-617

13-0

1887, Nov. 12-5...

Berberich.

0-1441

1096

3-24

2-188

II-I

— Oct. 11-5 ...

Lange.

0-1032 682

5-26

3004

12-7

— Nov. 14-0...

Knopf.

13-5

0-1446 974

3-64

2.368

1888, Mar. 9-5 ...

Lange.

0-1254 668

5-3i

3-043

12-8

Apr. 3.5 ...

Lange.

0-1655 769

4-61

2-771

11.5

— Apr. 15-5 ...

Lange.

0-0651 644

5-51

3-120

ii-8

— Apr. 17-5...

Lange.

13-0

0-1106 786

4-52

2-732

"•3

— May 16-5 ...

Lange.

0-1080 405

8-76

4-247

I2-O

— Oct. 25-5 ...

Lange.

0-1374 692

5-i3

2.972

14-0

— Oct. 29-5 ...

Lange.

670

Tables of the Planets.

[BOOK VI.

Discovered.

1 0 /

o /

o , 1

Lucretia . . .

1888, Oct. 31

Palisa

Vienna

4.S c6

3* o

5 *9

1889, Jan. 28

Charlois

Nice

— Feb. 8

Charlois ....

Nice

•

BOOK VI.]

The Minor Planets.

671

Period.

0-1328

1096

3-24

Semi-
axis,
Major.

& 8=1.

2-188

App.
opp.
Star
Mag.

Epoch.
Berlin M.T.

Calculator.

1888, Oct. 31-5

Lange.

INDEX.

*% This Index is designed fur me in connexion with the Table of Contents.
It is not complete by itself.

Aberration of light, page 380.
Acceleration, secular, of the Moon's mean

motion, 121.
Aerolites, 589.
JSthra, 165.

Agathocles, eclipse of, 324.
Almanac (Nautical), 355.
Anagram on Venus, 105.
Anahita, 165.
Andromache, 165.
Annual Equation of the Moon, 121.
Annular eclipses of the Sun, 262 ; of

March 1858, 291.
Aphelion, 57, 61.

Aphelion distances of comets, 57, 282.
Apsides of the Earth's orbit, their annual

motion, no.

Areas, equal, Kepler's law of, 57, 58.
Ariel, 247.

Aristarchus (Lunar mountain), 126.
Ascending node : of planetary orbits, 57;

of cometary orbits, 282.
Asteroids. See Minor Planets, 164.
Atmosphere, refraction of, 272 ; lunar,

128.
Aurora Borealis, and spots on the Sun,

31* 35 » vibrations in comets' tails re-
sembling, 412.

Baily's beads, 277.

Barnard's Comet, 427.

Barometer, use of, in determining refrac-
tion, 389.

Belgrade, siege of, 331.

Belts of Jupiter, 174; of Saturn, 205.

Bergeron's experiment, 1 25.

Bestiary, 1 16.

Bible^allusions to comets, conjectured,
333"

Bible, references to —

Gen. viii. 22 374

Lev. xvii. 7 490

Isaiah xiv. 12 .... 490

Jer. i 553

S. Jude 13 490

Kev. xii. 3 490

Biela's comet, 408, 430, 631.

Bode's (so-called) law of planetary dis-
tances, 67.

Bore (tidal phenomenon), 371.

Brorsen's comet, 425.

Burmese enumeration of the planets,
246.

Callisto, 185.

Calorific rays of the Sun, 7 ; of the Moon,

138-

Camilla, 1 66.
Catalogue of aerolites, 592 : of calculated

comets, 511 ; of recorded comets, 550;

of eclipses, 334.
Ceres, 165, 166, 167.
Charts of the Moon, 1 39.
Chepstow, tides at, 368.
Chromosphere, 52.
Coma of a comet, 399.
Comets, 395; periodicals; remarkable,

446 ; statistics of, 482 ; historical

notices, 487 ; catalogues of, 511, 550.
Comparative sizes of the Sun and planets,

63, 64, 65.

Conjunction of the planets, 68.
Constant of aberration, 381.
Copernican system, 72.
Copernicus and Mercury, 91.
Copernicus (Lunar mountain) , 1 28.
Corona in eclipses of the Sun, 53, 280,

30.5, 3°9> 3"-

X X

674

Index.

D' Arrest's comet, 427.

Day, length of, 115.

Denning's comet, 430.

Density of the Sun, 5 ; of the planets, 68.

See also the several planets.
Diameter of Sun and planets, 652. See

also the several planets.
Digit, explanation of, 266.
Dike, 1 66.

Dione, 233, 234, 235.
Diurnal inequality of the tides, 365.
Di Vice's comet, 433.
Donati's great comet, 57, 64, 448.
Draconic period, 264.

Earth, 3, 107.

Earth-shine, 135.

Eclipses, general outlines, 260; Catalogue

°f> 334 ; °f tne Sun, 261, 270 ; of July

1851, 286, 312 ; of March 1858, 291 ;

of July 1860, 295, 312; of Aug. 1868,

304 ; of Aug. 1869, 307, 312 ; of Dec.

1870, 308, 313 ; of Dec. 1871, 309, 313;

of April 1874,315; of April 1 875, 315;

of July 1878, 316; of May 1882, 317;

of May 1883, 318; of Sept. 1885, 318;

of Aug. 1886, 319; of Aug. 1887,320;

historical notices, 321; of the Moon,

326; of Jupiter's satellites, 186.
Ecliptic, Obliquity of, 109 ; variation in,

374-

Egyptian system, 72.
Elements of a planetary orbit, 58 ; general

summaries and tables of, 65 1 et seq. ; of

a cometary orbit, 403.
Ellipse, 6 1, 401.
Elongation of planets, 55.
Enceladus, 232, 233, 234.
Encke's comet, 64, 89, 416.
Ensisheim aerolite, 594.
Equation, Annual of the Moon, 121.
Equinoxes, 109; precession of, 374.
Establishment of the port, 364.
Europa ^satellite of Jupiter), 185.
Evection of the Moon, 1 20.

Faculse, solar, 45.

Faye's comet, 429.

Fides, 1 66.

Finlay's comet, 428.

Fireballs, 601.

Flames, Red, 282. See Red Flames.

Foucault's Pendulum experiment, 112.

Ganymede, 185.

Georgium Sidus, name proposed for
Uranus, 243.

"Girdle of the sky," 116.

Granules, solar, 50.

Gresham College, Hooke's place of obser-
vation, 383.

Halley's comet, 437.

Harvest Moon, 135.

Heat rays on the Moon, 138.

Hencke's search for Minor Planets, 168.

Hilda, 165, 166.

Hindu astronomy, 207, 271.

— celebration of an eclipse, 271.
Horizon, 383.

Horizontal parallax, 384.
Hunter's Moon, 136.
Hygre (tidal phenomenon), 371.
Hyperbola, properties of, 281, 283.
Hyperbolic comets, 368.
Hyperion, 233, 234.

lapetus, 233, 257.

Inclination of the ecliptic, 374.

Indian astronomy, 271.

Inequality, parallactic, of the Moon, 1 20 ;

diurnal, of the tides, 365.
Inferior planets, 54.
Intra-Mercurial planets, 81.
lo (satellite of Jupiter), 185.
Iron, meteoric, 590.
Ismene, 165.

Juno, 166, 167.

Jupiter, 173.

Jupiter's influence on comets, 401, 429.

Kepler's laws, 57 ; the Illrd, 59, 77.

— Rudolphine Tables, 345.
Kirkwood's coincidences with respect to

the satellites of Saturn, 238.

" Ladye's way," 117.

Lagging of the tides, 365.

Larissa, eclipse of, 322.

Le Verrier's investigations into the

theories of the Planets, 3.
Lexell's comet, 400.
Libration of the Moon, 119, 137.
Light, aberration of, 380 ; progressive

transmission of, 197 ; velocity of, 380.

Index.

675

Limits, ecliptic, 263.

Logogriphes on Venus, 105 ; Saturn, 207.

Luculi, solar, 46.

Lumiere cendree on the Moon, 135; on

Venus, 101.
Lydia, 166.

Magnetism, terrestrial and solar spot*, 28.

Magnitude of the solar system, 63.

Maia (minor planet), 166.

Maps, Berlin Star, 168.

Mars, 2, 3, 148.

— observations of, for solar parallax, 2.

Masses of the Sun, 5 ; of the planets, 652 ;

of comets, 400. See the several planets.
Massilia, 165.
Medium, resisting, 419.
Medusa, 165.
Mercury, 86.

Meteoric Astronomy, 589.
Mimas, 232, 233, 237.
Minor planets, 164; table of, 654.
Moon, 1 1 8.

Moonlight, brightness of, 138.
Motions of the planets, 54.
Mountains, suspected, on Venus, 99 ; on

the Moon, 124; suspected on Saturn's

ring, 228.

Napoleon Buonaparte, 97, 489.

Neptune, 252.

Nodes, of the Moon's orbit, 264.

Nodical revolutions of the Moon, 264.

Noonstede circle, 117-

Nucleus of a comet, 396.

Nutation, 377.

Oberon, 247.

Obliquity of the ecliptic, 109, 374.

Occupations, 355; of Jupiter's satellites,

187.

Olbers's Periodical comet, 437.
Orbits of planets and their elements, 58 ;

of comets and their elements, 401.

Pacific ocean, tides in, 368.

Pallas, 165, 166, 167.

Parallactic inequality of the Moon, 120.

Parallax, 383 ; horizontal, of the Moon,

384; solar, 2, 385.
Pendulum experiments, 112.
Penumbra (of a solar spot), 8.
Perigee solar, its motion, no.

Perihelion, longitude of, 58, 403 ; dis-
tances of comets, 484.

Periodic comets, 415.

Periodicity of shooting stars, 640.

— of fireballs, 613.

Periods of the planets, 651; of comets,
400.

Perturbations of Uranus by Neptune, 256.

Phases, of an inferior planet, 55 ; of Mer-
cury, 86 ; of Venus, 94 ; of the Moon,
119; of Mars, 149; of Jupiter, 174;
of Saturn's rings, 217, 226 ; of a comet,
409.

Philomela, 165.

Photometry of the Sun and Moon, 7, 8.

Photosphere, 52.

Planetoids, 164. See Minor Planets.

Planets, 54. See the several planets.

Pliny's opinions on the Tides, 373.

Plymouth breakwater, curious occurrence
at, 7.

Polarisation of a comet's light, 467.

Poles of Mars, snow at the, 156.

Pons's Periodical comet, 435.

Precession of the equinoxes, 374.

Priming and lagging of the tides, 365.

Projection of stars on the Moon's limb in
occupations, 356.

Prominences, solar, 282.

Radiant points of meteors, 640.

Range of the tides, 364.

Red Flames in eclipses of the Sun, 1 7,

282.

Red spot on Jupiter, 178.
Resisting medium, 419.
Rhea, 233, 234, 237.
Rice grains on the Sun, 49.
Rings of Saturn, 206.
Rotation of the Sun, 14; of the planets,

68. See also the several planets.
Rotundity of the Earth, in.

Salamis, Battle of, 323.

Sani (Hindu deity), 207.

Saros, 265.

Satellites, of Mars, 59, 159; of Jupiter,

60, 183 ; Saturn, 60, 231 ; Uranus, 60,

247 ; Neptune, 258.
Saturn, 200, 651.

Schwabe's observations on Sun-spots, 25.
Scylla, 166.
Seas, Lunar, 124.

676

Index.

Seasons, no.

Secular acceleration of the Moon's mean

motion, 121.
Shadow cast by Venus, 94 ; by Jupiter,

182.

Shooting stars, 608.
Sirona, 166.
Sita, 165.

Snow on Mar?, 156.
Solstices, 109.
Spectrum analysis, 53.
Spherical form of the Earth, proofs of, 1 1 1 .
Spots on the Sun, 8 ; on Jupiter, 176.
Stones, meteoric, 589. See Aerolites.
Summary of facts concerning the planets,

67 ; concerning the calculated comets,

482.

Sun, I ; statistics relating to, 5.
Sun-dials made by Sir I. Newton, 74.
Superior planets, 56.
Surfaces of the Sun and planets, 652.
Swift's comet, 426.

— alleged intra-mercurial planets, 83.
Sylvia, 166.
Synodical revolutions of the planets, 65 1 ;

of the lunar nodes, 122.
Systems of the universe, 71.

Tables, of the major planets, 651 ; of
the Moon, 140.

Tails of comets, 410.

Telescopic meteors, 644.

Tempel's Periodical comets, 424, 426.

Tethys, 232, 233, 237.

Thales, eclipse of, 321.

Theory of Meteors, 626.

Thermometer, use of in determining re-
fractions, 389.

Thule, 165.

Thwart circle, 116.

Tides, 360.

Titan, 233, 234, 237.

Titania (satellite of Uranus), 247.

Total eclipses of the Sun, 273, 286, 295,

3°3-

Trabes, 144.

Trans-Neptunian planet (supposed), 260.

Transits, of interior planets, 337 ; of Mer-
cury, 340; of Venus, 340, 345; of
Jupiter's satellites, 1 88 ; of shadow of
Saturn's satellite Titan, 238.

Tuttle's comet, 430.

Twilight, 1 1 6, 392.

Tycho (Lunar mountain), 123.

Tychonic system, 73.

Umbriel, 247.
Uranus, 242.

Variation of the Moon, 1 20.

Velocity of tidal wave, 369 ; of light,

380.

Venus, 2, 93, 651.
Vernal equinox, 109.
Vesta, 165, 1 66, 167.
Volume of the Sun, 5 ; of the planets,

652. See also the several planets.
Vulcan, 75.

Watson's alleged intra-mercurial planets,

82.
Weather influences imputed to the Moon,

140.

" Willow-leaves," 46.
Winnecke's comet, 424.
Wolfs comet, 429.

Zodiacal light, 142.

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Old Class

Astron Chambers, George F.

C Handbook of descriptive

vol.1 and practical astronomy.

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