which hitherto has been unoherved by "Philosophers. 189 



sphere. Now, it appears to me a sufficient argument to show the 

 fallacy of this opuiion, that a part of the coma or hair of the 

 comet, which is evidently of the same nature with the tail, is 

 going directly towards the sun in defiance to this rule ; and even 

 if we suppose this fluid, or effluvivm, on its first issuiiig from the 

 comet, to be too strong to be turned back by the force of the 

 sun's atmosphere, we should see the extremities of this coma 

 waving round on each side of the comet, in the same manner that 

 water docs when two streams meet, neither of which is strong 

 enough to turn back the other. Besides, as the comet's tail is 

 often visible when it is outside the earth's orbit, the sun's atmo- 

 sphere must therefore extend so far; and there would be a con- 

 stant resistance opposed to the velocity of the earth's annual and 

 diurnal motions, which in time must overcome them. Sir Isaac 

 Newton acknowledged this himself, with respect to the comets ; 

 and the laws of nature are general ; for he supposed thai the power 

 of the sun's attraction would increase so much upon the comet 

 in consequence of this loss of velocity, that in time it would be 

 drawn in to the sun and serve to supply him with fresh fuel. Now 

 as the sun was not meant to be eternal, it is a great deal more 

 likely that he was supplied with a sufficient quantity of light and 

 heat to last out his time, than that he should have to look for it 

 in the comets; which by the way, as they are not drawn plump 

 into the sun, but approach him very gradually if they do at all, 

 all that is combustible in thein would most likely be consumed; 

 and all they could supply him with would be a mass of ether 

 which would not burn. 



Those who suppose the tail of a comet to be an electric fluid, 

 are bound to show that electricity may be excited in bodies by 

 being simply placed in contact with the sun's rays; or, at least, 

 to show in what manner this electric matter may be excited. And 

 after all, for what purpose is this waste of fluid ? I know it will 

 be answered, To furnish the planets with a constant supply in re- 

 turn for what they are continually expending. But have we any 

 proof that the planets are continually expending it ? If they are, 

 why is it not visible in the planets, as well as in the comets ? 

 The comets, at all events, appear to be expending it much faster; 

 and it is more likely that they, who are so prodigal, would lie in 

 want of a supply, tiian that they should be able ro spare any to 

 the planets, w!io know so much better how to husband it. 



Upon the principle that God has made nothing in vain, I can- 

 not imagine a sufficient cause for the creation of comets, except 

 by supposing that, like the ])luncts, they are habitable worlds; and 

 then the pliaenomcnon of their extraordinary light is accounted 

 for rn the ncce:r*ity they have of possessing, in tlicniselvcs, a mo- 

 derate stock of light and heat, the want of which would be se- 

 verely 



