MOTIONS OF ELECTRONS 191 



photographic plate (since the pulses will affect it much 

 the same way as does light). 



The mechanism of the ether whereby energy may 

 thus be transmitted through space from one electron to 

 another is not as yet known, although we know many 

 important quantitative laws as to such transmission. 

 We have considered the unexplained realities which 

 the physicist meets to be matter (i.e., electricity) and 

 energy. The ether is sometimes taken as a third real- 

 ity, but its explanation will probably be included in 

 that of the other two. Thus, when we know why an 

 electron and an atom which has lost an electron con- 

 stitute a system the potential energy of which tends to 

 decrease as the parts tractate, we shall probably know 

 also the mechanism of the transfer of energy through 

 space. 



The fact that the motion of an electron anywhere 

 in space may affect the motion of any other electron hi 

 space, except in so far as the energy which the first is 

 transmitting is absorbed by intervening electrons, is 

 the basis of all so-called " electromagnetic radiation " 

 whether manifested to us as heat, light, X-rays, wire- 

 less telegraph radiations, or obscured to us because of 

 our insufficient scientific knowledge and hence awaiting 

 detection by future scientists. There is also another 

 whole field of effects which moving electrons produce 

 upon other electrons in their immediate neighborhood. 

 These are the basis of the dynamos, motors, and trans- 

 formers with which the electrical engineer deals. They 

 are, however, but special cases of the more general 

 phenomenon of the effect of an electron in motion upon 

 other electrons. 



