MODERN THEORIES OP ELECTRICITY AND MATTER. 107 



coulombs i)er gram of ions, while an ion of valence, n, carries a charge 

 nq. There can not be conceived in electrolysis an isolated charge of 

 electricity less than that carried by a monovalent atom, such, for 

 example, as hydrogen in the ionic state. The atomic structure of 

 electricity is therefore an immediate and necessary consequence of the 

 atomic structure of matter. 



It is by no means evident, a priori, that this conception can be gen- 

 eralized and that the other known cases of conduction are susceptible 

 of an analogous interpretation; but this seems to be coming to pass. 

 The study of the electrical conductivity of gases has borrowed from 

 the theory of electrolysis the idea of charged ions, vehicles of the 

 current; and the phenomena are satisfactorily accounted for by the 

 hypothesis that the current in a gas is a current of convection. But 

 the vehicles of the current are not here the same as in an electrolyte. 

 It is believed that an ionized gas gives rise to two ions, of which one 

 is that minute thing which we call an electron, the other being the 

 remainder of the molecule deprived of the electron. By ingenious 

 methods the number of ions present in a given volume of gas has 

 been counted and the charge carried by each one determined. This 

 charge is equal to that transported by an atom of hydrogen in elec- 

 trolysis, and thus Ave find this presented to us the second time as the 

 smallest quantity of electricity which can be isolated. 



All the phenomena of conduction across a gas under the influence of 

 different forms of radiation or in the disruptive discharge at varying 

 tension appear to be susceptible to explanation by the theory of the 

 ionization of gases. 



Attempts have been made to explain the conduction of metals in a 

 similar way, and it is probable that this also may be considered as a 

 current of convection whose vehicles are the electrons set free in the 

 metal. Thus we arrive at the conclusion that electric currents through 

 all forms of matter are currents of convection, or, in other words, the 

 displacements of electric charges. Besides this it has been proved 

 that any such displacement gives rise to a magnetic field. 



The conception of the existence of atoms of electricity which is thus 

 brought before us in the phenomena of conduction plays an essen- 

 tial part in modern theories of electricity like that of Lorentz. This 

 theory retains the fundamental idea of Faraday and Maxwell, ac- 

 cording to which the electromagnetic actions are always transmitted 

 from place to place in a continuous medium with a finite velocity. 

 This medium is the ether of space, and the velocity is the velocity 

 of light. The laws of variation of an electromagnetic field in the 

 ether are expressed at each point by the equations of Maxwell, and 

 the causes wdiich produce the electromagnetic field are sought in the 

 existence of positive and negative atoms of electricity and in the 

 motions of these atoms. We are thus returning to a conception which 



