Comets and Meteors Part 4

What was thus proposed as theory has been since confirmed as undoubted facts. When the hypothesis was originally advanced, the data required for its mathematical demonstration were entirely wanting. The evidence, however, by which it was sustained was sufficient to give it a high degree of probability.

The existence of a divellent force by which comets near their perihelia have been separated into parts is clearly shown by the following facts.

Whether this force, as suggested by Schiaparelli, is simply the unequal attraction of the sun on different parts of the nebulous ma.s.s, or whether, in accordance with the views of other astronomers, it is to be regarded as a cosmical force of repulsion, is a question left for future discussion.

HISTORICAL FACTS.

1. Seneca informs us that Ephoras, a Greek writer of the fourth century before Christ had recorded the singular fact of a comet's separation into two distinct parts.[13] This statement was deemed incredible by the Roman philosopher, inasmuch as the occurrence was then without a parallel. More recent observations of similar phenomena leave no room to question the historian's veracity.

[13] "Quaest. Nat.," lib. vii., cap. xvi.

2. The head of the great comet of A.D. 389, according to the writers of that period, was "composed of several small stars." (Hind's "Comets," p.

103.)

3. On June 27, A.D. 416, two comets appeared in the constellation Hercules, and pursued nearly the same apparent path. Probably at a former epoch the pair had const.i.tuted a single comet.[14]

[14] Chambers' "Descr. Astr.," p. 374.

4. On August 4, 813, "a comet was seen which resembled two moons joined together." They subsequently separated, the fragments a.s.suming different forms.[15]

[15] Ibid., p. 383.

5. The Chinese annals record the appearance of three comets--one large and two smaller ones--at the same time, in the year 896 of our era.

"They traveled together for three days. The little ones disappeared first, and then the large one."[16] The bodies were probably fragments of a large comet which, on approaching the sun, had been separated into parts a short time previous to the date of their discovery.

[16] Ibid., p. 388.

6. _The third comet of 1618._--The great comet of 1618 exhibited decided symptoms of disintegration. When first observed (on November 30), its appearance was that of a lucid and nearly spherical ma.s.s. On the eighth day the process of division was distinctly noticed, and on the 20th of December it resembled a cl.u.s.ter of small stars.[17]

[17] Hevelius, "Cometographia," p. 341. See also Grant's "Hist.

of Phys. Astr.," p. 302.

7. _The comet of 1661._--The elements of the comets of 1532 and 1661 have a remarkable resemblance, and previous to the year 1790 astronomers regarded the bodies as identical. The similarity of the elements is seen at a glance in the following table:

Comet of 1532. Comet of 1661.

Longitude of perihelion 111 48' 115 16'

Longitude of ascending node 87 23 81 54 Inclination 32 36 33 1 Perihelion distance 0.5192 0.4427 Motion Direct. Direct.

The elements of the former are by Olbers; those of the latter by Mechain. The return of the comet about 1790, though generally expected, was looked for in vain. As a possible explanation of this fact, it is interesting to recur to an almost forgotten statement of Hevelius. This astronomer observed in the comet of 1661 an apparent breaking up of the body into separate fragments.[18] The case may be a.n.a.logous to that of Biela's comet.

[18] "Cometographia," p. 417.

8. The ident.i.ty of the comets of 1866 and 1366, first suggested by Professor H. A. Newton, is now unquestioned. The existence then of a meteoric swarm, moving in the same track, is not the only evidence of the original comet's partial dissolution. The comet of 1866 was invisible to the naked eye; that of 1366, seen under nearly similar circ.u.mstances, was a conspicuous object. The statement of the Chinese historian that "it appeared nearly as large as a tow measure,"[19]

though somewhat indefinite, certainly justifies the conclusion that its magnitude has greatly diminished during the last 500 years. The meteors moving in the same orbit are doubtless the products of this gradual separation.

[19] Williams' "Chinese Observations of Comets," p. 73.

9. The repart.i.tion of Biela's comet in 1845, as well as the non-appearance of the two fragments in 1865 and 1872,[20] were referred to in a previous chapter.

[20] One of the parts was seen at Madras, India, on the mornings of December 2 and 3, 1872.

The comet of Halley, if we may credit the descriptions given by ancient writers, has been decreasing in brilliancy from age to age. The same is true in regard to several others believed to be periodic. The comet of A.D. 1097 had a tail 50 long. At its return, in March, 1840, the length of its tail was only 5. The third comet of 1790 and the first of 1825 are supposed, from the similarity of their elements, to be identical.

Each perihelion pa.s.sage occurred in May, yet the tail at the former appearance was 4 in length, at the latter but 2-1/2. Other instances might be specified of this apparent gradual dissolution. It would seem, indeed, extremely improbable that the particles driven off from comets in their approach to the sun, forming tails extending millions of miles from the princ.i.p.al ma.s.s, should again be collected around the same nuclei.

The fact, then, that meteors move in the same orbits with comets is but a consequence of that disruptive process so clearly indicated by the phenomena described. In this view of the subject, comets--even such as move in elliptic orbits--are not to be regarded as permanent members of the solar system. Their _debris_ becomes gradually scattered around the orbit. Some parts of the nebulous ring will be more disturbed than others by planetary perturbation. Portions of such streams as nearly intersect the earth's path sometimes penetrate the atmosphere. Their rapid motion renders them luminous. If very minute, they are burnt up or dissipated without leaving any solid deposit; we then have the phenomena of _shooting-stars_. When, however, as is sometimes the case, they contain a considerable quant.i.ty of solid matter, they reach the earth's surface as _meteoric stones_.

II.

METEORS.

CHAPTER VII.

METEORIC STONES.

Although numerous instances of the fall of aerolites had been recorded, some of them apparently well authenticated, the occurrence long appeared too marvelous and improbable to gain credence with scientific men. Such a shower of rocky fragments occurred, however, on the 26th of April, 1803, at L'Aigle, in France, as forever to dissipate all doubt on the subject. Similar displays since that time have been frequently witnessed;--indeed scarcely a year pa.s.ses without the fall of meteoric stones in some part of the earth, either singly or in cl.u.s.ters. It would not comport with the design of the present treatise to give an extended list of these phenomena. The following account, however, includes the most important instances in which the fall of meteoric stones has been actually observed:

(1.) 1478 B.C.--According to the celebrated Parian chronicle, an aerolite, or _thunder-stone_, as it was called, fell in the island of Crete, about 1478 years before the Christian era. This is undoubtedly the most ancient stone-fall on record. Meteoric ma.s.ses have been _found_, however, the fall of which _probably_ occurred at an epoch still more ancient.

(2.) 1200 B.C.--A number of stones, which were anciently preserved in Orchomenos, a town of Boeotia, were said to have fallen from heaven about twelve centuries before our era.

(3.) 1168 B.C.--A ma.s.s of iron, as we learn from the Parian chronicle, was seen to descend upon Mount Ida, in Crete.

(4.) 654 B.C.--According to Livy, a number of meteoric stones fell on the Alban Hill, near Rome, about the year 654 B.C.

(5.) 616 B.C., _January_ 14.--It is related in the Chinese annals that on the 14th of January, 616 B.C., a meteoric stone-fall broke several chariots and killed ten men.

(6.) 466 B.C.--A ma.s.s of rock, described as "of the size of two millstones," fell at aegospotamos, in Thrace. An attempt to rediscover this meteoric ma.s.s, so celebrated in antiquity, was recently made, but without success. Notwithstanding this failure, Humboldt expressed the hope that, as such a body would be difficult to destroy, it may yet be found, "since the region in which it fell is now become so easy of access to European travelers."

(7.) 465 B.C.--The famous stone called the "Mother of the G.o.ds," and which is described or alluded to by many ancient writers, was said to have fallen from the skies. The poet Pindar was seated on a hill at the time of its descent, and the meteorite struck the earth near his feet.

The stone, as it fell, was _encircled by fire_. "It is said to have been of moderate dimensions, of a black hue, of an irregular, angular shape, and of a metallic aspect. An oracle had predicted that the Romans would continue to increase in prosperity if they were put in possession of this precious deposit; and Publius Scipio Nasico was accordingly deputed to Attalus, King of Pergamus, to obtain and receive the sacred idol, whose wors.h.i.+p was inst.i.tuted at Rome 204 years before the Christian era."--_Edinburgh Encyclopedia._

(8.) A.D. 921.--An immense aerolite fell into the river (a branch of the Tiber) at Narni, in Italy. It projected three or four feet above the surface of the water.

(9.) 1492, _November_ 7.--An aerolite, weighing 276 pounds, fell at Ensisheim, in Alsace, penetrating the earth to the depth of three feet.

This stone, or the greater part of it, may still be seen at Ensisheim.

(10.) 1511, _September_ 14.--At noon an almost total darkening of the heavens occurred at Crema. "During this midnight gloom," says a writer of that period, "unheard-of thunders, mingled with awful lightnings, resounded through the heavens.... On the plain of Crema, where never before was seen a stone the size of an egg, there fell pieces of rock of enormous dimensions and of immense weight. It is said that ten of these were found, weighing 100 pounds each." A monk was struck dead at Crema by one of these rocky fragments. This terrific display is said to have lasted two hours, and 1200 aerolites were subsequently found.

(11.) 1637, _November_ 29.--A stone, weighing 54 pounds, fell on Mount Vaison, in Provence.