XXV. Account of Observations of HaUet/s Cornet. By R. W. Roth- 

 man, Esq., M.A. Fetlow of Trinity College. 



[Read December 11, 1837.] 



The accompanying observations of Halley's Comet were made on 

 the great tower of Trinity College, with a 30-inch achromatic tele- 

 scope, of 2f inches aperture, to which was adapted a ring-micrometer. 

 The power used with this micrometer was about 25 : the radius 

 of the inner ring was found by the transits of stars near the meri- 

 dian = 1258": of the outer = 1710". 



The observations here detailed form the whole of those that I was 

 able to make on this Comet: I saw it on the 18th of Sept. and 1st 

 of Nov., but was unable to get an observation. Whenever an ob- 

 servation lias been rejected, the circumstance has been noted in its 

 proper place and the reasons for doing so assigned. 



The time employed is Greenwich mean solar time. The seconds 

 watch I used was compared every evening with the clock by Moly- 

 neux in the Reading Room, and that again the next day with the transit- 

 clock at the Observatory. 



3u3 



