Theories of Electricity 143 



impossible to obtain any quantity of electricity which is 

 a fraction of this unit. 



The term " electron " was applied by Johnstone Stoney 

 an a convenient name for this " atom " of electricity. 

 We have already seen how this point of view at once 

 gives a deep physical significance to the results observed 

 by Faraday. The possibilities of this new hypothesis 

 were quickly recognized by the mathematical physicists, 

 Larmor and Lorentz, as affording a probable explana- 

 tion of many of the more recondite relations that existed 

 between electricity and matter. 



The electronic theories developed by them supposed 

 that the atom of matter consisted in an aggregation of 

 positive and negative ions or electrons in rapid motion, 

 forming, as it were, a miniature planetary system. 



It was recognized that a charged particle in motion 

 always radiated energy when its motion was hastened 

 or retarded. Since a charged particle moving, for ex- 

 ample, in a small circular orbit is constantly and strongly 

 accelerated towards its center, it must act as a powerful 

 radiator of energy. This at once suggested that the 

 electron rotating within the atom was the mechanism 

 which gave rise to light. This conception was devel- 

 oped notably by Lorentz, who predicted that the period 

 of vibrations of the electrons must be altered by exposing 

 the radiant source in a magnetic field. This prediction 

 was verified a few years later by the experiments of 



