ELECTRICAL AND MAGNETIC DISCOVERIES OF FARADAY 645 



Faraday now took up an analogous subject the source of the elec- 

 tricity in the voltaic battery. He showed that the current from the 

 battery was proportional to the amount of zinc dissolved, and that the 

 direction of the current depended on the direction of the chomical 

 action. 



The theory of Volta, that the contact of two metals was the source of 

 electricity, was thus effectually disposed of, so that even the recent at- 

 tempt to revive that ancient theory could only have met with the disas- 

 ter which befell it. 



It is impossible for me, in a few minutes, to give account of all that 

 Faraday did on these subjects of electrolysis and the theory of the voltaic 

 battery. His work is a perfect mine of results not haphazard and dis- 

 connected, but each designed to elucidate some point in theory or dem- 

 onstrate some law, and his name must forever be associated with this 

 subject. His law of the definite chemical action of the current will 

 always form an enduring monument to his fame. 



Every discovery that Faraday made only served as a guide to him in 

 making fresh ones. 



We have seen that Faraday found that when an electrolyte was in the 

 solid state it no longer conducted the current. To most observers this 

 would only have been an interesting, but disconnected, fact. But the 

 far-sighted mind of Faraday perceived in this an explanation of no less 

 a subject than that of electric induction. As in the electrolyte, he con- 

 ceived the particles to be arranged in certain directions, decomposing 

 and recomposing along lines in the direction of the electric currents, so 

 in the solidified electrolyte there was some arrangement along the lines 

 in which the current wished to pass, that is, of electric force. Hence his 

 theory of the nature of electric induction and of electric force. It was 

 not action at a distance, but the action of contiguous particles on each 

 other. As in magnetism, so in electricity, the action was carried to a 

 distance by a medium. 



Not content with merely giving the theory, he proceeded to prove 

 it. If it were true, then the nature of the medium should affect the 

 amount of the induction. We all know his beautiful apparatus for test- 

 ing this the two globular Leyden jars which could be filled with 

 air, glass, oil of turpentine, gases, etc., how he divided the charge of 

 one between the two and measured it on a Coulomb electrometer, and 

 thus discovered that his inference was correct, that each substance had 

 a specific inductive capacity, and that the charge of a condenser de- 

 pended not only on the area of the surface and the thickness of the 



