158 



cannot be regarded as a defensive weapon, might easily have been 

 overlooked, and the smoothness of the skin would give it a greater 

 resemblance to the horse than any other animal. 



This paper is accompanied by two plates, exhibiting the skull of 

 the African and of the fossil Siberian rhinoceros, and a fossil horn of 

 the latter. 



Extract of a Letter from Captain Basil Hall, R.N. F.R.S. to William 

 Hyde Wollaston, M.D. V.P.R.S. containing Observations of a Comet 

 seen at Valparaiso. Read January 10, 1822. [Phil. Trans. 1822, 

 p. 46.] 



The comet described in Captain Hall's letter was visible for 33 

 days in the months of April and May, 1821 . During the first week 

 its nucleus was bright and distinct ; but being then in the interior of 

 the country, he did not commence observing it till the 8th of April, 

 when its nucleus had become so indistinct as to render its measure- 

 ment by the micrometer uncertain. On its first appearance, the 

 comet appeared of a dull white, and its tail presented a dark streak 

 between its sides, giving it the appearance of being split. On the 

 second evening the tail subtended an angle of 7, reaching to p Ceti ; 

 on the seventh the nucleus was less bright, and the tail shorter, 

 arising, probably, from the increased distance of the comet. The tail 

 was at first nearly at right angles to the horizon, but each succeed- 

 ing night it inclined more to the south. Tables of the observations 

 and some sketches of the appearance of this comet accompany Cap- 

 tain Hall's communication. 



Elements of Captain Hall's Comet. By J. Brinkley, D.D. F.R.S. and 

 M.R.I. A. and Andrews Professor of Astronomy in the University of 

 Dublin. In a Letter addressed to W. H. Wollaston, M.D. V.P.R.S. 

 Read January 10, 1 822. [Phil. Trans. 1 822, p. 50.] 



Dr. Brinkley remarks that the comet observed by Captain Hall is 

 interesting to astronomers on account of its small perihelion distance, 

 for there are only three, out of 116, in M. Delambre's catalogue, 

 that pass nearer to the sun. On the 8th of April it was distant from 

 the earth T41, and on the 3rd of May, 2'64, the sun's distance from 

 the earth being unity. 



Dr. Brinkley also remarks that it is probably the same comet that 

 was observed in 1593; it agrees with that in its small perihelion 

 distance, and great inclination. Of that comet, the inclination was 

 88, and the perihelion distance '089 ; of this, the inclination is 106 

 44', and its perihelion distance '093. 



To the proximity of this comet to the sun, when on the north 

 side of the ecliptic, in February and March last, before it passed its 

 perihelion, Dr. Brinkley attributes its having escaped European ob- 

 servers. It was never more than a few degrees from the sun, and 

 therefore could not have been visible. The author then points out 



