486 DONATl's COMET. 



DON ATI'S COMET. 



BY THE REV. JAMES WILLIAMSON, LL.D., 



PEOPESSOE OF MATHEMATICS, QtrEBN'S COLLEGE, KINGSTON. 



The appearance of Donati's Comet excited so much interest during 

 the whole period of its being visible in this latitude, that it may be 

 acceptable to the readers of the Canadian Journal, to be put in posses- 

 sion of some of the results of observations made with the aid of the fine 

 instruments in possession of the University of Queen's College, Kings- 

 ton. These observations have a further interest and value, from the 

 fact that they include an observation a day later than the last on which 

 a similar one was obtained in Britain, and which it may therefore he 

 not unimportant to place on record in our Canadian journal of 

 science. 



From the 7th September, when Donati's Comet was first observed 

 here by the naked eye, to the 12th, its tail rapidly increased in magni- 

 tude. On the 13th and 14th it pointed nearly in the direction of the 

 Pole-star, while the nucleus was as bright as a star of the first magnitude. 

 On the l7th the Comet was still in the southern part of Ursa Major, 

 with a tail of about 5^ in length, pointing between ;!^ and ^, but 

 nearer to the latter. On the 24th its tail had increased to 8° in length. 

 On the 26th it was a little south of Cor Caroli, with a tail of about 

 10°, pointing nearly through 8 of Ursa Major to the Polestar, and 

 a little concave towards the sun. On October 2nd the tail was 20° in 

 length, and on the 5th the head was about a degree southeast of 

 Arcturus, with a tail of about 32'^, which was nearly its maximum 

 length. On the 1 5th both the nucleus and the tail had rapidly de- 

 creased in brightness and the latter also in length, so that it was not 

 much more elongated than when it was first visible to the eye. On 

 the 18th it was scarcely distinguishable by the naked eye, even when 

 its place was known. Although its position, not far above a somewhat 

 hazy horizon, and the moonlight, impeded a distinct view of its appear- 

 ance through the telescope, it evidently now exhibited only traces of 

 the tail in the winged appearance of the head ; and the nvicleus, though 

 tolerably round and well defined, was still further diminished in 

 brightness. 



The tail was comparatively narrow at first, with the greatest bright- 

 ness in the centre, and not at the sides, but afterwards increased 

 greatly both in length and in breadth, while a darker portion in the 



