102 Prof. Norton on Molecular Physics. ■ 



tides to the next should be equal to the quantity received by 

 the surface ; for the determining cause of the electric wave of 

 translation lies in the fact that the force of tension of the propa- 

 gated electricity urges this quantity between the surface and the 

 first layer of the medium. 



The tension of the electricity received results from the com- 

 pression produced by the expansive action of the charge, which 

 is ultimately in equilibrium with the force by which the dis- 

 turbed atmospheres of the medium tend to return to their ori- 

 ginal condition. The tendency of the free electricity to escape 

 between and around the polarized molecules of the medium is 

 counteracted, as will soon be seen, by a resistance developed by 

 the polarization. 



This we conceive to be the true process of induction. It will 

 be readily perceived that it is in entire conformity with the expe- 

 rimental results obtained by Faraday, and in accordance with 

 his theoretical ideas of the general nature of the process. 



We have supposed the electrized surface to be surrounded by 

 a single dielectric medium extending indefinitely ; but the result 

 would be essentially the same if the waves were propagated 

 through several such media, as air, glass, &c. If we suppose the 

 first medium to be replaced by another, while the entire quan- 

 tity of electricity propagated by it, as the polarization of the 

 medium goes on, should remain the same, as Faraday has shown 

 that it actually does, it does not follow that the final degree of 

 polarization received will be the same as before. In this respect 

 substances may differ, or they may have different " specific in- 

 ductive capacities," as maintained by Faraday. It is in fact just 

 this difference of property that constitutes the difference between 

 conduction and non- conduction, or between the different degrees 

 of conduction or of non-conduction. 



So long as the charge of electricity on the surface S, fig. 6, 

 remains the same, the degree of polarization of the surrounding 

 medium or media will continue the same ; but if the charge be 

 drawn off, waves of decreasing polarization will be propagated 

 outward from S, which will be accompanied by electric waves of 

 translation flowing inward toward S. The entire process that 

 went on within the medium while the body was receiving its 

 charge will now be exactly reversed. 



If we suppose a body to receive a charge of negative electri- 

 city, the process will also be reversed, as when a charge of posi- 

 tive electricity is withdrawn. The final result will be that the 

 particles of the surrounding dielectric medium will be positively 

 polarized on the side toward the electrized surface, and there 

 will be a deficiency of electric aether between the surface and the 

 first layer of the particles of the medium. 



