CHAPTER III.

REMARKABLE COMETS.

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

THE

HE comets which might be included under the above head are so numerous as to make it impossible that all should receive proper attention. I must therefore limit myself to some few of the most interesting.

The comet of 1864 (ii), visible in August, had a head unusually large, scarcely less than 1 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 by no dissimilar to the planetary nebula in Virgo. There was a faint tail, but it presented no special feature of interest.

The comet of 1862 (iii), though not one of first-class brilliancy, was nevertheless a very interesting object, more particularly from its having presented a series of remarkable luminous jets, emanations ever changing, from its nucleus. Annexed are some views drawn by the Rev. J. Challis of Cambridge. It had also a tail, which, on Aug. 27, was 20° long.

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, prior to its perihelion passage, which took place on June 11. Passing from the southern hemisphere into the northern, it became visible in this country on June 29, though it was not generally seen till the

next evening. So many accounts of it were published that selection is difficult, but the following pages will be found to contain an epitome of the most noticeable features".

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 conspicuously visible on the 30th, 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 23-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 1st 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 2nd (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 of the Great Bear at least to 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 cometic 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, 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

By far the most complete account is that by the Rev. T. W. Webb in the Month. Not. R.A.S., vol. xxii. p. 305 et seq.