[Illustration: Fig. 1. THE SOLAR SYSTEM.
_Frontispiece._]
COMETS AND METEORS:
THEIR PHENOMENA IN ALL AGES;
THEIR MUTUAL RELATIONS;
AND THE
THEORY OF THEIR ORIGIN.
BY
DANIEL KIRKWOOD, LL.D.,
PROFESSOR OF MATHEMATICS IN INDIANA UNIVERSITY,
AND AUTHOR OF "METEORIC ASTRONOMY."
[Illustration]
PHILADELPHIA:
J. B. LIPPINCOTT & CO.
1873.
Entered according to Act of Congress, in the year 1873, by
DANIEL KIRKWOOD, LL.D.,
In the Office of the Librarian of Congress at Washington.
PREFACE.
The origin of meteoric astronomy, as a science, dates from the memorable
star-shower of 1833. Soon after that brilliant display it was found that
similar phenomena had been witnessed, at nearly regular intervals, in
former times. This discovery led at once to another no less important,
viz.: that the nebulous masses from which such showers are derived
revolve about the sun in paths intersecting the earth's orbit. The
theory that these meteor-clouds are but the scattered fragments of
disintegrated comets was announced by several astronomers in 1867:--a
theory confirmed in a remarkable manner by the shower of meteors from
the _débris_ of Biela's comet on the 27th of November, 1872.
To gratify the interest awakened in the public mind by the discoveries
here named, is the main design of the following work. Among the subjects
considered are, cometary astronomy; aerolites, with the phenomena
attending their fall; the most brilliant star-showers of all ages; and
the origin of comets, aerolites, and falling stars.
It may be proper to remark that the language used by the writer in a
volume[1] published several years since, and now nearly out of print,
has been occasionally adopted in the following treatise.
BLOOMINGTON, INDIANA, April, 1873.
[1] Meteoric Astronomy.
CONTENTS.
PAGE.
PREFACE 3
CHAPTER I.
A GENERAL VIEW OF THE SOLAR SYSTEM 9
CHAPTER II.
COMETS 13
COMETS VISIBLE IN THE DAY-TIME 15
PERIODIC COMETS 18
CHAPTER III.
COMETS WHOSE ELEMENTS INDICATE PERIODICITY, BUT
WHOSE RETURNS HAVE NOT BEEN RECOGNIZED 31
CHAPTER IV.
OTHER REMARKABLE COMETS 39
CHAPTER V.
THE POSITION AND ARRANGEMENT OF COMETARY ORBITS 43
CHAPTER VI.
THE DISINTEGRATION OF COMETS 49
CHAPTER VII.
METEORIC STONES 57
CHAPTER VIII.
SHOOTING-STARS--METEORS OF NOVEMBER 14 69
CHAPTER IX.
OTHER METEORIC STREAMS 82
CHAPTER X.
THE ORIGIN OF COMETS AND METEORS 94
I.
COMETS.
COMETS AND METEORS.
CHAPTER I.
A GENERAL VIEW OF THE SOLAR SYSTEM.
A descriptive treatise on COMETS and METEORS may properly be preceded by
a brief general view of the _planetary_ system to which these bodies are
related, and by which their motions, in direction and extent, are
largely influenced.
THE SOLAR SYSTEM consists of the sun, together with the planets, comets,
and meteors which revolve around it as the centre of their motions. The
sun is the great controlling orb of this system, and the source of light
and heat to its various members. Its magnitude is one million three
hundred thousand times greater than that of the earth, and it contains
more than seven hundred times as much matter as all the planets put
together.
Mercury is the nearest planet to the sun; its mean distance being about
35,400,000 miles. Its diameter is 3000 miles, and it completes its
orbital revolution in 88 days.
Venus, the next member of the system, is sometimes our morning and
sometimes our evening star. Its magnitude is almost exactly the same as
that of the earth. It revolves round the sun in 225 days.
The earth is the third planet from the sun in the order of distance; the
radius of its orbit being about 92,000,000 miles. It is attended by one
satellite,--the moon,--the diameter of which is 2160 miles.
Mars is the first planet exterior to the earth's orbit. It is
considerably smaller than the earth, and has no satellite. It revolves
round the sun in 687 days.
_The Asteroids._--Since the commencement of the present century a
remarkable zone of telescopic planets has been discovered immediately
exterior to the orbit of Mars. These bodies are extremely small; some of
them probably containing less matter than the largest mountains on the
earth's surface. 131 members of the group are known at present, and the
number is annually increasing.
Jupiter, the first planet exterior to the asteroids, is nearly
500,000,000 miles from the sun, and revolves round it in a little less
than 12 years. This planet is 86,000 miles in diameter, and contains
more than twice as much matter as all the other planets, primary and
secondary, put together. Jupiter is attended by four moons or
satellites.
Saturn is the sixth of the principal planets in the order of distance.
Its orbit is about 400,000,000 miles beyond that of Jupiter. This planet
is attended by eight satellites, and is surrounded by three broad flat
rings. Saturn is 73,000 miles in diameter, and its mass or quantity of
matter is more than that of all the other planets except Jupiter.
Uranus is at double the distance of Saturn, or nineteen times that of
the earth. Its diameter is about 34,000 miles, and its period of
revolution 84 years. It is attended by at least four satellites.
Neptune is the most remote known member of the system; its distance
being 2,800,000,000 miles. It is somewhat larger than Uranus; has
certainly one satellite, and probably several more. Its period is about
165 years. A cannon-ball flying outward from the sun at the uniform
velocity of 500 miles per hour would not reach the orbit of Neptune in
less than 639 years.
These planets all move round the sun in the same direction,--from west
to east. Their motions are nearly circular, and also nearly in the same
plane. Their orbits, except that of Neptune, are represented in the
frontispiece. It is proper to remark, however, that all representations
of the solar system by maps and planetariums must give an exceedingly
erroneous view either of the magnitudes or distances of its various
members. If the earth, for instance, be denoted by a ball half an inch
in diameter, the diameter of the sun, according to the same scale
(16,000 miles to the inch), will be between four and five feet; that of
the earth's orbit, about 1000 feet; while that of Neptune's orbit will
be nearly six miles. To give an accurate representation of the solar
system at a single view is therefore plainly impracticable.
THE ZODIACAL LIGHT.--This term was first applied by Dominic Cassini, in
1683, to a faint nebulous aurora, somewhat resembling the milky way,
apparently of a conical or lenticular form, having its base toward the
sun and its axis nearly in the direction of the ecliptic. The most
favorable time for observing it is when its axis is most nearly
perpendicular to the horizon. This, in our latitudes, occurs in March,
for the evening, and in October, for the morning. The angular distance
of its vertex from the sun is frequently seventy or eighty degrees,
while sometimes, though rarely (except within the tropics), it exceeds
even one hundred degrees. It was noticed in the latter part of the 16th
century by Tycho Brahe. The first accurate description of the phenomenon
was given, however, by Cassini. This astronomer supposed the appearance
to be produced by the blended light of innumerable bodies too small to
be separately observed,--a theory still very generally accepted. In
other words, the zodiacal light is probably a swarm of infinitesimal
planets; the greater part of the cluster being interior to Mercury's
orbit.
The distances between the different members of our planetary system,
vast as they may seem, sink into insignificance when compared with the
intervals which separate us from the so-called fixed stars. _Alpha
Centauri_, the nearest of those twinkling luminaries, is 7000 times more
distant than Neptune from the sun. Even light itself, which moves
185,000 miles in a second, is more than three years in traversing the
mighty interval.