144* 0N TWO CELESTIAL BODIES. 



numerous obfervations of comets, it is exprefsly remarked, that 

 they had none that could be feen. Befides, what I have called 

 a nucleus, would Hill be far from what I now fhould have mea- 

 I'ured as a difk ; to conftitute which, a more determined outline 

 is required. 



In the fecond article, their motions differ much from that of 

 comets ; for, fo far as we have at prefent an account of the 

 orbits of thefe new ftars, they move in ellipfes which are not 

 very excentric. 



Nor are the fituations of the planes of their orbits fo much 

 unlike thofe of the planets, that we mould think it necetTary 

 to bring them under the third article of comets, which leaves 

 them quite unlimited. 



In the fourth article, relating to the direction of their motion, 

 thefe ftars agree with planets, rather than with comets. 



The fifth article, which refers to the atmofphere of comets, 

 feems to point out thefe ftars as belonging to that clafs ; it 

 will, however, on a more particular examination, appear that 

 the difference is far too confiderable to allow us to call them 

 comets. 

 Account of the The following account of the fize of the comas of the fmalleft 

 comets. ' comets I have obferved, will fhew that they are beyond com- 



parifon larger than thofe of our new ftars. 



Nov. 22, 1781. Mr. Pigott's comet had a coma of 5 or 6' 

 in diameter. 



Nov. 29, 1783. Another of Mr. Pigott's comets had a coma 

 of 8' in diameter. 



Dec. 22, 1788. My filter's comet had a coma of 5 or &' in 

 diameter. 



Jan. 9, 1790. Another of her comets was furrounded by 

 hazinefs of 5 or 6' in diameter. 



Jan. 1 8, 1790. Mr. Mechain's comet had a coma of 5 or 6' 

 in diameter. 



Nov. 7, 1795. My filler's comet had a coma of 5 or 6' in 

 diameter. 



Sept. 8, 1799. Mr. Stephen Lee's comet had a coma of not 

 lefs l-lian 10' in diameter, and alfo a fmall tail of 15' in length. 



From thefe obfervations, which give us the dimenfions of 

 the comas of the fmalleft comets that have been obferved with 

 good inftruments, we conclude, that the comas of thefe new 

 ftars, which at moft amount only to a few times the diameter 



of 



