Royal Astronomical Society. 22S 



its rate of increase of density towards the centre was rather more 

 rapid and decided than about the circumference, yet there was nothing 

 in the least entitled to the name of a nucleus. As no nebula exists 

 in that part of the heavens which could be confounded with an object 

 of this description, it was of course immediately recognised as the object 

 sought : but had I entertained any doubt of its identity, it would have 

 been dispelled by its motion, which, during an hour and a half, or 

 thereabouts, that I kept it in view, was very considerable. At the 

 commencement of my observation, it formed an irregular trapezium 

 with three pretty bright stars, A, B, C ; with two of which I measured 

 its angles of position, and, on repeating the measures after a short 

 interval, found them sensibly altered. The change of place speedily 

 became remarkable to the eye, and was such as to carry the comet 

 towards two or three other pretty bright stars, D, E, in a distant part 

 of the field. In approaching these, it passed directly over a small 

 cluster or knot of minute stars, of the 16th or 17th magnitude, which 

 occupied a space about a minute or two in diameter; and, when on 

 the cluster, it presented the appearance of a nebula resolvable, and 

 partly resolved, into stars, the stars of the cluster being visible through 

 the comet. 



" A more striking proof could not have been offered of the extreme 

 translucency of the matter of which this comet consists. The most 

 trifling fog would have entirely effaced this group of stars; yet they 

 continued visible through a thickness of the cometic matter, which, 

 calculating from its distance and apparent diameter, must have ex- 

 ceeded 50,000 miles, at least towards its central parts. That any 

 star of the cluster was centrally covered is, indeed, more than I can 

 assert ; but the general bulk of the comet may certainly be said to 

 have passed centrally over the group. 



" The reflector being at that time in a great measure dismantled, 

 for the purpose of making some changes in the sweeping apparatus, 

 I was unable to determine, as I could have wished, the place of the 

 comet by an extra-meridian sweep j I was, therefore, obliged to have 

 recourse to the 7-feet equatorial (aperture 5 inches), with which, at 

 best, I could only hope to procure an approximate place j and from 

 my knowledge of its comparative inefficiency in showing nebulae, I 

 had very slender expectation of being able to see it at all. However, 

 by carefully noting in the finder of the large instrument the exact 

 locality of the spot with respect to the stars 0, v, and r Auriga, I was 

 enabled, with no great difficulty, to find the telescopic constellation 

 consisting of the stars A, B, C, D, E, with which I had compared 

 the comet in the reflector ; and, after very long and careful attention 

 in a field totally dark, and without the smallest light in the observatory, 

 I succeeded in obtaining a sight of the comet in the place where, from 

 its motion during the interval, I expected to find it. Under such 

 circumstances, any determination of its place must be exceedingly 

 vague; and, in fact, on reducing three comparisons which I obtained, 

 directly and indirectly, of its place with that of Aurigce, it became 

 evident that in one of them I must have mistaken a retinal spectrum 

 produced by nervous excitement, for the comet. For their results 



