Sept. 27, 8h. A drawing which I took at this time exhibited a small fan-shaped centre, the broader part turned from the tail, and the brightness increasing towards the narrow part which had a small, circular, and very bright termination [which is properly the nucleus]. This central part was surrounded, except for about 90° on the side towards the tail, with a kind of hood or envelope, less bright and much larger than the central part, but bright enough to be in definite contrast with the coma which extended from it to a breadth about equal to its radius. The hood was more depressed towards the tail on the right side (as seen in the telescope) than on the left side. The right side of the tail was also considerably the brighter; the intermediate part was comparatively dark. A star of mag. 8, seen through this part at the distance of a few minutes from the nucleus, exhibited no unusual phenomena. By measurement with a position-circle the axis of the tail was inclined southward from the great circle through the pole by 8°.

66

Sept. 30, 7h-8h. In the finder a narrow dark band well defined was observable along the axis of the tail." My drawing represented the central brightness as larger and more oval than on Sept. 27, and having a round blunt termination at the lower or brightest part. Above the upper part was a less illumined space, increasing in brightness towards a luminous semicircular arch pretty definitely bounded on the outside, beyond which the coma was faintly visible to some extent. This arch descended towards the tail a little more on the right side than on the left. The tail appeared to stream both from the arch and from the exterior and interior coma, and the right-hand stream was considerably the brighter. By a drawing of the appearance to the naked eye, the curvature of the tail was now very considerable, the convexity turned southward, the convex side much the brightest, and the extremity of the tail broad and diffused. Its estimated length was 20°.

"Oct. 2, 74. About the very bright and small nucleus on the upper side was a bright fan or hood, and beyond this a larger hood, with a less illumined space between them. The coma was traceable beyond the second hood. Under the cusp

of the nucleus the space was remarkably dark, and a dark and rather broad band divided the tail into two parts which, at a considerable distance from the head, overlapped each other." A drawing represented the right-hand branch of the tail considerably the brighter, but the form and appearance of the head was now symmetrical about its axis. To the naked eye the tail was much more sharply defined on the southern than on the northern side, and was widely spread out at the extremity. Its length was 33°, as measured on a celestial globe, by reference to Arcturus, which was very close to the nucleus, and to stars of Ursa Major.

"Oct. 5, 7h. There were two dark openings in the space

included by the external arch, the larger on the left side of the nucleus, and the smaller above it. Also between the larger and the nucleus was a bright point, but not so bright as the nucleus." A sketch exhibited these openings as faint patches irregular in form and distribution of light, and the bright point as a small spot of light near the nucleus. The right-hand stream of the tail was the brighter; the nucleus and fan-shaped attachment appeared nearly as on Oct. 2. This evening I

looked at the light of the tail with a Nichol's prism and a tourmaline, and found that not far from the nucleus there was some polarisation.

"Oct. 6, 7h. The cusp of the nucleus not so sharp to-night; the left-hand irregular patch seen, but the one above scarcely discernible. There was much cloud about." A sketch exhibited the bright spot on the right-hand border of the irregular patch, and very near the nucleus.

"Oct. 8, 64h. Mottled appearance about the envelope [i. e. the space between the exterior arch and the bright central fan]. The left-hand patch seen, but not the bright spot. Apparently a greater divergence of the coma; the right-hand stream still the brighter." The central fan, as shown in a drawing, was spread out farther than on Oct. 6. To the naked eye the tail appeared more diffused than on Oct. 5, especially at its extremity. The greatest apparent curvature was at the distance from the nucleus of one-fourth its length. The length was but little diminished.

"Oct. 9, 7h. The angular divergence of the streams of coma greater, and the light more diffused; the comet altogether less bright. The bright part of the nucleus and the hood appeared smaller. Clouds about and the sky unfavourable. The axis of the cusp and nucleus not coincident with the axis of the tail." [This appearance was probably owing to the left side of the envelope being now extended farther than the right in the direction of the tail.] To the naked eye the tail was fainter and still more diffused than on Oct. 8, but nearly of the same length.

"Oct. 11, 61. Greater angular separation of the streams of the tail; the hood not so definitely bounded, the central brightness rounder, probably owing to the state of the atmosphere, the comet being low." A sketch exhibited a determination of the hood towards the left side, but the two streams of the tail of equal intensity. To the naked eye the tail was much spread out laterally, especially at the extreme part, and the nucleus was less bright. The length of the tail was judged by reference to stars to be 30°.

"Oct. 13, 6. Comet scarcely to be seen for mist. I endeavoured to estimate the radius of the exterior arch in the direction transverse to the axis of the tail. I think it was 6' of the micrometer, or 52′′. [This estimation is very uncertain.]

Oct. 15, 6. The length of the radius of the exterior arch in a direction inclined from its vertex by about 65° was found by measurement to be 4' of the micrometer, or 35′′. "The coma was distributed very unsymmetrically about the nucleus, being much more apparent on the lower, or northern side, than on the other. It was too faint on the latter side for measurement of the radius of the arch; there was a good deal of daylight. The boundary of the interior envelope was very definite: that of the exterior arch very indistinct and uncertain. The radius of the former on the apparent lower side was about one-third that of the other, or 12"." The nucleus and attached envelope presented in a sketch the form of an inverted comma. The interior boundaries of the two streams of the tail were confused, the coma spreading over the intermediate space. By measurement with a position circle the axis of the tail was inclined northward from the equatoreal direction by 4°.

"Oct. 16, 6h The comet had nearly the same appearance as on the preceding evening; the comma form of the brightest part was seen in strong daylight; the boundary of the arch was still visible on the apparent lower side. By estimation from the teeth of the comb, its radius transverse to the axis was 4*7, or 41′′. According to a drawing, the radius of the brighter part was three-sevenths of this measure, or about 18′′. The axis of the tail was nearly in the equatoreal direction."

Professor Challis has appended to the foregoing observations a few explanatory notes, but as they will probably be published at full length in another form, we shall merely quote the following remark:

"In the course of the observations my attention was especially directed to the following particulars, respecting which I can speak with confidence. The brightness contiguous to the nucleus preponderated on the right side (as seen in the telescope) till October 2; and on October 9 the excess had passed to the left side. The excess of brightness of the right-hand stream of the tail above that of the other, attained its maximum about October 2; after which there was a gradual diminution, till, on October 11, 15, and 16, the two streams were not sensibly unequal. The dark band separating the two portions of the tail was of uniform width and definite boundary on September 30 and October 2; and in proportion as the boundaries afterwards became indefinite, and the intervening space was gradually filled with luminosity, the angular divergence of the two streams also increased."

The following additional details respecting the comet have been communicated:

Observed at Bradstones, near Liverpool, by W. Lassell, Esq.

The time of observation was 1858, September 12, from 8 to 9 P.M. The comet was first viewed with the 20-foot equatoreal, with a power of 155, having a field of 19'1 in diameter.

Nucleus estimated to be 10" diameter, remarkably well defined. Its appearance reminded me of the disk of the planet Uranus in this telescope with a power of 400 when the atmosphere was unfavourable enough to make the edge of the disk soft. A slight bifurcation was suspected at about 10' from the nucleus, but was not fully ascertained. Breadth of the tail about 12'. Edge of the tail on the side towards which the comet was advancing obviously brighter than the opposite edge.

The comet was also viewed with a refractor of 2.6 inches aperture and power 35, with a field of 76'. The tail was about twice the diameter of the field in length, or 2 degrees. The tail seemed narrower in proportion than in the 20-foot, but that might arise from the small portion of the tail visible at one time in the latter instrument. The substance of the tail appeared streaky in the direction of its length. It was almost exactly parallel from within a very short distance of the head and had a slight curvature, the convex side being that which, speaking relatively to the comet's motion, was the preceding side. The nucleus in this telescope seemed bright, but rather stellar than planetary.

Owing to the general cloudiness of the sky here I did not see this comet at all until the evening of the 11th September, and then only for a short time between clouds, too short to allow of placing the large telescope upon it.*

Observed at Tretire, Hereford, by the Rev. T. W. Webb.

Having lately received an object-glass from Mr. Alvan Clark, of 5 inches' clear aperture, of which he speaks highly, but which I have as yet had no opportunity of testing, I was anxious to turn it upon the recent magnificent comet; but а disappointment relative to the tube obliged me to content myself with a very rough temporary mounting, so that my observations were made under altogether unfavourable circumstances as to convenience; their results are, however, I believe, worthy of confidence.

1. The Nucleus. This appeared invariably circular, several seconds in diameter, of uniform light throughout; its definition decreasing with the increase of the power employed. As far

* The details of his subsequent observations of the comet may be expected from Mr. Lassell.-Editor.

as I could judge in the use of an excellent little 24-inch objectglass by Bardon, I think its distinctness on Oct. 11 had increased, as compared with its aspect on Sept. 21. Its colour was a clear yellow, not as deep as that of Arcturus.

2. The Envelope. This was of considerable extent, much fainter than the nucleus, but brighter than the exterior haze and train. Instead of being a hemispherical cap, serving as a base to the tail, as in the comet of 1811, its outline was distinctly continued through an arc of much more than 180°, round to the edges of the central darkness of the train. Sept. 30, when I perceived it on the first trial of the 5-inch object-glass, the portion next the sun was least luminous, and seemed to consist chiefly of a narrow are of light, indicating a hollow structure; this bright ring became more evident at a greater distance from the sun, so that the portions adjoining the central darkness were most conspicuous, especially, perhaps, that on the preceding side, according to the comet's orbital motion. Oct. 4, the whole circumference of the envelope, or photosphere, as it might in this case be termed, appeared entirely filled up with light, excepting where the central darkness cut out a large gap in it. Oct. 5, it was doubtful whether or not its outline was defined by a more luminous arc; but now its principal brightness was confined to about a hemisphere, not however symmetrically situated with respect to the general figure of the comet, but inclining a little backwards as though left behind in its movement, so that the faint sector which completed its form round to the central darkness on the antecedent side was considerably larger than the corresponding one in the subsequent direction: this was not very distinctly made out, but such was the prevailing impression. Oct. 11, when the comet had advanced beyond the range of the great telescope, the smaller one showed, though of course less evidently, a similar appearance; but the more luminous hemisphere now seemed to be inclined the other way, or partially to precede the nucleus in its course, its central radius making an angle of about 30° with the axis of the tail, as though there existed a kind of swinging motion, such as was perceived in the last return of the comet of Halley.

3. The Tail. This gave some intimation of its structure even to the naked eye; in the telescope its central darkness was very conspicuous; and as it advanced in its course the sides of the hollow paraboloid became more thin, and the angle included by them increased. Sept. 30, the proportion of the dusky streak to the whole breadth of the tail was estimated at it occupied perhaps on Oct. 11, while it seemed to have become rather more filled up with nebulous light: the clear and broad notch which it cut out of the photosphere, even up to immediate contact with the back of the nucleus, increasing, of course, in breadth in a similar way. Oct. 4, it was traced for a length of 2° or 21° before it was merged in