CLASSIFICATION OF THE POSITIONS OF THE PERIHELIA AND

NODAL POINTS.

Taking the longitudes of the perihelia and of the ascending nodes of 209 comets (deducting 8 not certainly determined), we shall find that in every 100 they are distributed as follows:

An examination of the 2nd column shews,-That there is an evident tendency in the perihelia to crowd together in 2 opposite regions, between 60°-120° and 240°-300°. A uniform distribution would give 16.6 perihelia to every arc of 60°. Now, in the 1st case, we have 29.9, or 38 per cent. above the mean; and in the 2nd, 213, or 29 per cent. above the mean. A further examination will shew that the regions between 150°-180° and 330°—360° are correspondingly poor.

From the 3rd column it appears :-That there is an evident, though less marked, tendency in the nodes to come together in 2 regions (not, however, in this case exactly opposite) between 30°—90° and 180°— 240°. A uniform distribution would give 16·6 nodes to every arc of 60°. Now, in the 1st case we have 20.5, or 23 per cent. above the mean; and in the 2nd, 201, or 20 per cent. above the mean. With the nodes the poor region seems to be between 270°-300°.

CLASSIFICATION OF THE PERIHELION PASSAGES ACCORDING TO THE MONTHS OF THE YEAR.

Of the 292 known perihelion passages there occurred in:

:

The monthly average is therefore 24'3. April, September, October, November and December, are above the mean; all the others below. The minimum is in August, which only exhibits 18 o, or 33 per cent. below the average-a circumstance doubtless due to the long days and short nights which more or less prevail during the summer months. The quick rise in September is probably due less to the lengthening of the nights (and consequent increased opportunities for observation) than to the excellence of that month for astronomical purposes. The advantages afforded by the long winter nights are more or less neutralized by the frequent inclement weather. Thus it happens that all the winter months (December excepted) are below the average.

CHAPTER VII.

A CATALOGUE OF COMETS RECORDED, BUT NOT WITH SUFFICIENT PRECISION TO ENABLE THEIR ORBITS TO BE CALCULATED a.

IN

the present day it rarely happens that a comet becomes visible without its being observed, at any rate, sufficiently long for 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 17th century observatories and instruments can scarcely be said to have existed at all. For whatever information we possess we are therefore dependent on the writings of the historians and chroniclers, which seldom contain more than bare statements, with few or no details.

The first who made any systematic attempt to put together the various allusions to comets which occur in the old writers was the French astronomer Pingré, who in 1783 published his celebrated Cométographie; ou Traité historique et theoretique des Comètes. This work, which for the industry and labour bestowed upon it has few equals, has been the astronomers' text-book on the subject of cometary history from the period of its publication down to the present day it never has been superseded, and is never likely to be, though supplementary matter has of course been accumulated. E. Biot, working from Chinese sources, has followed up Pingré with great industry. The present catalogue is based upon that of Pingré, and includes recent results, especially those elaborated in a valuable catalogue commenced by Mr. Hind in the Companion to the Almanac, but remaining unfinished.

a I should be glad to receive information calculated to render this chapter more complete. I cannot but believe that a diligent search through the jour

Brevity being an essential

nals, whether published or in MS., of modern travellers and others, would bring to light many more comets than those catalogued in this volume.

pre-requisite, I have been obliged to omit much that was curious and interesting, confining 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 18th century, who made very good use of their opportunities of benefitting 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, some 20 years ago, published in the Connaissance des Temps a translation of some valuable Chinese catalogues of comets, 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, they are inserted in this catalogue, an asterisk (*) being appended either to the year or M. Biot's name. If any of these "extraordinary stars" were not comets, it may perhaps be assumed that they were what we call temporary stars. Anyhow, it is on the safe side to insert all of them.

It may be well to add that very great uncertainty hangs over the earlier comets, 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 very 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 juxta-position 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'

b 1846, pp. 44-84.

A a

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.

One tchang equals 10°; one che equals 1°.

B.C. 1770. +

[1] St. Augustine has preserved the following extract from Varro :“There was seen a wonderful prodigy in the heavens worthy to be compared with 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 presumed to be that of a comet, but no further particulars have been preserved.

1194. ±

[2] 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.”- (Fréret, Acad. des Inscriptions, x. 357.) What we are to understand by this is doubtful, but the account may relate to a comet which passed from Taurus to the North Pole.

975.±

[3.] “The Egyptians and the Æthiopians 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 spiral, and had a hideous aspect; it was not so much a star as a knot of fire."—(Pliny, Hist. Nat., ii. 23.) Date very uncertain.

[4.]

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, Pingré 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 possibly this comet, in Jer. i.