COMETS. 



the basis of the undulatory theory of light, would produce just 

 such a phenomenon, and accordingly the motion of this comet 

 is regarded as a strong evidence tending to convert that hypo- 

 thetical fluid into a real physical agent. 



It remains to be seen whether a like phenomenon will be 

 developed in the motion of other periodic comets. The discovery 

 of these bodies, and the observation of their motions, are as yet 

 too recent to enable astronomers, notwithstanding their greatly 

 multiplied number, to pronounce decisively upon it. 



23. If the existence of this resisting medium should be estab- 

 lished by its observed effects on comets in general, it will follow, 

 that, after the lapse of a certain time (many ages, it is true, but 

 still a definite interval), the comets will be successively absorbed 

 by the sun, unless, as is not improbable, they should be previously 

 vaporised by their near approach to the solar fires, and should 

 thus be incorporated with his atmosphere. 



In the efforts by which the human mind labours after truth, it 

 is curious to observe how often that desired object is stumbled upon 

 by accident, or arrived at by reasoning which is false. One of 

 Newton's conjectures respecting comets was, that they are "the 

 aliment by which suns are sustained ; " and he therefore con- 

 cluded that these bodies were in a state of progressive decline 

 upon the suns, round which they respectively swept; and that 

 into these suns they from time to time fell. This opinion appears- 

 to have been cherished by Newton to the latest hours of his life : 

 he not only consigned it to his immortal writings, but, at the age 

 of eighty-three, a conversation took place between him and his 

 nephew on this subject, which has come down to us. " I cannot 

 say," said Newton, "when the comet of 1680 will fall into the 

 sun ; possibly after five or six revolutions ; but whenever that 

 time shall arrive, the heat of the sun will be raised by it to such 

 a point, that our globe will be burnt, and all the animals upon it 

 will perish. The new stars observed by Hipparchus, Tycho, and 

 Kepler, must have proceeded from such a cause, for it is impos- 

 sible otherwise to explain their sudden splendour." His nephew 

 then asked him, " Why, when he stated in his writings that 

 comets would fall into the sun, did he not also state those vast fires 

 they must produce, as he supposed they had done in the stars ? " 

 "Because," replied the old man, "the conflagrations of the 

 sun concern us a little more directly. I have said, however," 

 added he, smiling, " enough to enable the world to collect my 

 opinion." 



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