86 



THOUGHTS ON THE INFLUENCE OP ETHER 



ETHER. ITS RELATIONS TO COMETS. 



After the decline of the Peripatetic school of philosophy, few of the grand operations 

 of nature were ascribed to the agency of ether. The chief additions to its role prior to 

 the present century, were made by Huyghens and Sir Isaac Newton; the former giving 

 to ether a no less important function than the transmission of light, and the latter explain- 

 ing by its action, one of the phenomena of comets, still held by most astronomers to be a 

 profound mystery of nature. 



The views of Sir Isaac Newton on the influence of ether upon the tails of comets, may 

 be found in Book iii, Prop, xli, of the Principia. They accord with the theory I am en- 

 deavoring to explain, and are not the less interesting because of his failure to impress the 

 truth of his views upon the scientific world. He says, "Kepler ascribes the ascent of the 

 tails of the comets to the atmospheres of their heads; and the direction towards the parts 

 opposite to the sun, to the action of the rays of light, carrying along with them the matter 

 of the comets' tails; and, without any great incongruity, we may suppose that in so free 

 spaces, so fine a matter as that of the ether may yield to the action of the rays of the sun's 

 ligbt, though those rays are not able sensibly to move the gross substances in our parts, 

 which arc clogged with so palpable a resistance." 



"Another author thinks that there maybe a sort of particles of matter endowed with a 

 principle of levity, as well as others arc with a power of gravity; and that the matter of 

 the tails of comets may be of the former sort, and that its ascent from the sun may be 

 owing to its levity; but, considering that the gravity of terrestrial bodies is as the matter 

 of the bodies, and therefore can be neither more nor less in the same quantity of matter, 

 lam inclined to believe, that this ascent may rather proceed from the rarefaction of the matter 

 of the comets tails.'" 



■'The ascent of smoke in a chimney is owing to the impulse of the air with which it is 

 entangled. The air rarefied by beat ascends, because its specific gravity is diminished, 

 and in its ascent carries along with it the smoke with which it is engaged; and why may 

 not the tail of a comet rise from the sun after the same manner] For the sun's rays do 

 not act upon the mediums which they pervade, otherwise than by reflection and refraction; 

 and those reflecting particles heated by this action, heat the matter of the ether, which is 

 involved with them. This matter is rarefied by the heat which it acquires, and because 

 by this rarefaction the specific gravity with which it tended towards the sun before, is 

 diminished, it will ascend therefrom, and carry along with it the reflecting particles of 

 which the tail of the comet is composed." 

 «I have made this quotation from the Principia, because I find that M. Arago, from a 



