COMETS. 393 



fin the subtilty and nature of the materials of which 

 they were composed, and that there were sublunary 

 Comets ; that iftlwre were Comets amongst tJie 

 higher planets, it thpetv some light on the nature 

 of the matter of which those planets were com- 

 posed, as it shewed, that they possessed an atmos- 

 phere like our own, of a combustible nature ; 

 that it was probable their atmosphere was infi- 

 nitely rarer and purer ; and, consequently, that 

 the Comets subservient to the preservation of 

 ihe purity of their spheres, must move infinitely 

 more rapidly, and the lustre which they displayed 

 must be infinitely more brilliant, than those of a 

 sublunary nature. 



Destitute of facts, by which those conclu- 

 sions were founded, they could only be consi- 

 dered as unsupported assumptions from which 

 I had formed an hypothesis; I reasoned from the 

 necessity of the case, and not from any astrono- 

 mical knowledge which I possessed ; the late 

 Mr. GEORGE ADAMS, who was a good practical 

 astronomer, told me, in a conversation which I 

 had with him on physical subjects, that he had 

 been much struck with the deductions which I 

 had made, respecting the nature of Comets ; 

 for although it seemed as if I thought that nine 

 only existed, he could assure me, there were 

 many more ; and that M. MESSIER in particular, 

 of Paris, was nicnamed the Comet finder, in 

 consequence of the number of Comets which h<* 



