XX. 



On the Orbit of the Comet of 1819. 



By ALEXANDER M. FISHER, A. M 



PROFESSOK OF MATHEMATICS AXD NATUPvAL PHILOSOPHY IN YALE 



COLLEGE. 



Comrminicated in a letter to the Hon. J\*athaniel Bowditdu 



T 



HIS body was first observed, in the United States, on the 

 evening of the second of July : in riglit ascension 10:^% declina- 

 tion 43° N. Its lustre was nearly equal to that of a star of the first 

 magnitude^ when viewed at no greater distance from the horizon. 

 The length of the tail, on the morning of July 6lh, the moon he- 

 ing helowthe horizon and the air perfectly clear, was judged to 

 be somewhat greater than that between the two Stars a and ^ 



Aurigse. The direction was marked on the evening of July 18th, 



as being towards a point between e and ^ Ursse Minoris : hence 

 it must have pointed, as usual, nearly opposite to the sun. Near 

 the body of the comet it was unusually narrow and well defined; 

 bat its boundaries soon diverged, and became indistinct. The 

 head, as viewed with telescopes of different powers, presented a 

 disk of very sensible magnitude, but too ill defined to admit of 

 exact measurement. With a Gregorian reflector of five inches 

 aperture and a magnifying power of about 70? the light was vexy 

 perceptible on the evening of the 13th, through a diameter of two 



minutes ; and the utmost extent of the visible coma was perhaps 



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