ETHER AND PONDERABLE MATTER 



thought, however, presents few difficulties to the mind 

 accustomed to philosophical speculation. But the 

 question early arose in the mind of Fresnel whether 

 the ether is not considerably affected by contact with 

 the particles of solids. Some of his experiments led 

 him to believe that a portion of the ether which pene- 

 trates among the molecules of tangible matter is held 

 captive, so to speak, and made to move along with 

 these particles. He spoke of such portions of the ether 

 as "bound" ether, in contradistinction to the great 

 mass of "free" ether. Half a century after Fresnel's 

 death, when the ether hypothesis had become an ac- 

 cepted tenet of science, experiments were undertaken 

 by Fizeau in France, and by Clerk-Maxwell in Eng- 

 land, to ascertain whether any portion of ether is 

 really thus bound to particles of matter; but the re- 

 sults of the experiments were negative, and the ques- 

 tion is still undetermined. 



While the undulatory theory of light was still fighting 

 its way, another kind of evidence favoring the existence 

 of an ether was put forward by Michael Faraday, who, 

 in the course of his experiments in electrical and mag- 

 netic induction, was led more and more to perceive def- 

 inite lines or channels of force in the medium subject to 

 electro-magnetic influence. Faraday's mind, like that 

 of Newton and many other philosophers, rejected I he 

 idea of action at a distance, and he felt convinced that 

 the phenomena of magnetism and of electric induction 

 told strongly for the existence <>f an invisible plenum 

 everywhere in space, \\lik h might very probably be 

 the same plenum that carries the undulations of light 

 and radiant heat. 



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