Page:Transactions NZ Institute Volume 16.djvu/30

xxiv and a half years and seventy-six years respectively—the elements of the motion of others are not sufficiently known to admit of their return being predicted.

Those who recollect the great comet of 1843 confess that it hardly, if at all, surpassed the one of last year in brilliancy, although some maintain that it exceeded it in the apparent length of its tail as seen from the earth. The large majority of those now living, however, have never seen anything that can be compared to the magnificent comet of 1882. It was visible from all quarters of the globe, and so brilliant as to be seen with the naked eye at noon in a clear sky. On the 17th of September a unique observation was made at the Cape, where the comet was seen to pass right up to the sun's limb, after which it became invisible, not intercepting the faintest portion of the sun's light. The following morning it passed its perihelion passage so close as to be within the region beyond which the great solar jets of incandescent hydrogen (to which I will presently refer in another connection) are often seen to extend. It must, whilst in that position, have been exposed to a heat so intense, that rock-crystal, agate, or the most infusible substance we know of, would have been vapourized. The gigantic tail covered a space at least as long as the distance between the earth and the sun, and, although apparently of very small substantiality, several observers report that they saw distinctly in the sky the black shadow cast by the tail of the comet.

The question as to the relations between the comets of 18-13, 1880, and 1882 is one of great interest. According to Mr. Chandler, the orbit of the comet of last year is such as to be quite inconsistent with a short period of revolution, and, if so, it must be distinct from either of the earlier comets,—or from the earlier comet, supposing those of 1843 and 1880 to be identical.

Another view has lately been put forward in the "Observatory," from which I quote the following words:—"The physical appearance of the comet, which like that of 1843, and unlike that of 1880, showed at first a decided nucleus, together with the intimation of a period very considerably greater than that of the interval from the 27th January, 1880, the date of perihelion of the 1880 comet," to September, 1882, "suggest that perhaps the 1843 comet suffered disintegration when at its nearest approach, and that the 1880 comet was a portion of its less condensed material, whilst the body of the comet with the principal nucleus, suffering less retardation than the separated part, has taken two and a half years longer to perform a revolution."

The latest, and I understand the most accurate, calculations, however, attribute to the orbit of the comet of 1882 a period of 840 years, so that the last time it passed round the sun was about the year 1140, in the days of King Stephen.