294 DISCOVERY CH. 



and reasoning, showed that the action took place along 

 curved lines, which he termed " lines of force." 



Faraday in his mind's eye saw lines of force traversing all 

 space, whereas the mathematicians saw centres of force attracting 

 at a distance ; Faraday saw a medium where they saw nothing 

 but distance ; Faraday sought the seat of the phenomena in 

 real actions going on in the medium ; they were satisfied that they 

 had found it in a power of action at a distance impressed on the 

 electric fluids. Clerk Maxwell. 



As the result of his analysis of Faraday's experi- 

 mental results, and the lines of force which he invoked 

 to explain them, Maxwell was able to prove that electro- 

 magnetic disturbances, and waves of light, are trans- 

 mitted by one and the same medium, and with the same 

 velocity. Thus, electro-magnetic and optical pheno- 

 mena are identical in kind, and differ only in the rapidity 

 of vibration of the medium the -universal ether which 

 transmits them. Sunlight comes to us across ninety- 

 three millions of miles of so-called empty space, and 

 starlight from distances hundreds of thousands of times 

 greater ; and they both reach us as waves which can 

 be measured, and their interference effects observed, 

 more easily than can those seen on the disturbed surface 

 of a lake or other sheet of water. A medium had to be 

 invented to account for the transmission of these waves ; 

 and this medium is appropriately termed the " ether," 

 signifying the sky the home of the gods. No one can 

 see the ether, or weigh it, or isolate any part of it, yet 

 it apparently pervades all space and permeates all 

 material things, as water does a wet sponge ; and through 

 it electro-magnetic waves, as well as waves of light and 

 heat, are propagated. 



In 1842, Joseph Henry arrived at the conclusion that 

 when an electric spark is produced by the sudden 



