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ASTRONOMICAL PAPERS. 



H3 



however fiiiall they be, muft give them a cojifiderak mo- 

 menttim or impelling force, which muft be great in regions 

 near the Suu; by this force they repel the extremely fub- 

 tile and light "particles of air, and drive them off to fuch 

 a diftance behind the comet that their weight is hardly per- , 

 ccived on its furface. The atmofphere being thus repelled 

 by the Sun's rays, and thrown as it were into a fhelter be- 

 hind the planet, will be there extended longitudinally in 

 the form of a fhadow^ being very rare towards the top. 

 Every particle near the furface of this immcnfe ftream of 

 air muft be illuminated by the refradion and rciledion of 

 the Sun's rays, whence they will exhibit tlie faint appear- 

 ance of a blaze. Thus we are apt to imagine that a comet 

 is intenfely hot, and that a prodigious flame proceeds from 

 it, while we fee nothing elfe than its enlightened atmo- 

 fphere. 



As the inhabitants of comets are not prefled by day, 

 when they come near the Sun, with a thoufandth part of 

 the atmofphere which ufually furrounds them, and which 

 is doubtlefs the mediate and princij^al caufe of their per- 

 ceiving heat, we may eafUy fee how tHey may be tole- 

 rably cool at noon day, on their nearcft approach to the 

 Sun. 



If we might form any conjedurc concerning the life of 

 a cometarian, from the annual periods of the world which 

 he inhabits, we fliould apprehend that he far exceeds the 

 years of an antedeluvian. Or might we attempt to mea- 

 fure the continuance of this globe, from the length of time 

 which will be neceffary to bring the aftronomy of comets, 

 as well as every other fcience to that perfection at which 

 they muft doubtlefs arrive, we fhould infer that a fmall 



On which ever of thefe 

 for a few minutes, it 



t^ 



portion of that time is yet elapfed. ( 

 fubjeQs the mind is fuffered to ftray 



will find fufFicicut fubjed: of a plcafmg fpeculatiou. 



A letter 



