193 



Its peripd 

 haps 1900 



Elements < 

 ll\e last 21, 



ON COMETS. 



April, when his letter to me is dated. Mr. Bessel, the 

 coadjutor of Mr. Sehroeter, in his fine observatory at Lilien- 

 thal near Bremen, was able to follow it till the 24th of Fe- 

 bruary ; and by him were calculated the elements, that will 

 appear in this paper, from the observations made at Bremen 

 and Lilienthal. 

 er . He imagines, that he can determine the period of the re- 

 turn of this comet to its next perihelion. According to 

 him its revolution in its orbit is 1900 years : but Mr. Olbers 

 says, that we cannot depend on the accuracy of this deter- 

 mination. It is much to be wished, that he, or some other 

 astronomer, would collect at leisure all the accurate obser- 

 vations of this beautiful comet, made at different places, re- 

 vise these calculations, and endeavour to arrive at a pro- 

 bable result. The reappearances announced of two comets; 

 that of 1456, which has been seen four times, and that of 

 1532, which has been seen twice ; deuionfrrate the general 

 propositipn, that these returns may be predicted. If however 

 Mr. Bessel be near the truth with respect to the length of the 

 revolution of this comet, the approaches it may make dur- 

 ing so many centuries to the large gravitating bodies be- 

 longing to our system may occasion perturbations in its 

 course, of which no calculation con be formed. 



To finifh this article of comets, I (hall annex the elements 

 of the last twenty-one from Mr. Olbers. They are var 

 luabje, both because he himself has observed them, and 

 calculated several of their elements, namely, those marked 

 with a star; and because they determine with more precision 

 than the Comioissaiice des Temps one of the most essential 

 circumstances for the calculation of their periodical revolu- 

 tions, namely, the precise instant of their passing their pe- 

 rihelion. I set out with the numeration of Pingre in his 

 Cometographie, to indicate the number answering to each 

 of these last comets in the complete catalogue of those, the 

 orbits of which are calculated. 



glemmh 



