THE CONQUEST OF NATURE 



and by Count Rumford and Humphry Davy and their 

 followers, and in due course the new doctrines of light 

 and heat were thoroughly established. In the light of the 

 new knowledge, the theory of the electric fluid or fluids 

 seemed, therefore, much less plausible. Whereas the 

 earlier physicists had merely disputed as to whether we 

 must assume the existence of two electrical fluids or 

 of only one, it now began to be questioned whether we 

 need assume the existence of any electrical fluid what- 

 ever. The physicists of about the middle of the nine- 

 teenth century developed the wonderful doctrine of 

 conservation of energy, according to which one form of 

 force may be transformed into another, but without the 

 possibility of adding to, or subtracting from, the orig- 

 inal sum total of energy in the universe. It became 

 evident that electrical force must conform to this law. 

 Finally, Clerk-Maxwell developed his wonderful elec- 

 tromagnetic theory, according to which waves of light 

 are of electrical origin. The work of Maxwell was 

 followed up by the German Hertz, whose experiments 

 produced those electromagnetic waves which, differing 

 in no respect except in their length from the waves of 

 light, have become familiar to everyone through their 

 use in wireless telegraphy. All these experiments 

 showed a close relation between electrical phenomena, 

 and the phenomena of light and of radiant heat, and a 

 long step seemed to be taken toward the explanation 

 of the nature of electricity. 



The new studies associated electricity with the ether, 

 rather than with the material substance of the electrified 

 body. Many experiments seemed to show that electric- 



[i54] 



