466 The Faraday Centenary. [June 17, 



monly described as dependent upon the mutual induction between 

 two distinct circuits, one being that primarily excited by a battery or 

 other source of electricity, while the other occurred in a detached 

 circuit. Many surprising effects, however, depended on the reactions 

 ■which took ])lace at different parts of the same circuit. One of these 

 he illustrated by the decomposition of water under the influence of 

 self-induction. 



About the time the experiments of which he had been speaking 

 were made, Faraday evidently felt uneasiness as to the soundness of 

 the views about electricity held bj his contemporaries, and to some 

 extent shared by himself, and he made elaborate experiments to 

 remove all doubt from his mind. He re-proved the complete 

 identity of the electricity of lightning and of the electricity of the 

 voltaic cell. He evidently w^as in terror of being misled by words 

 which might convey a meaning beyond what facts justified. Much 

 use was made of the term " poles " of the galvanic battery. Faraday 

 was afraid of the meaning which might be attached to the word 

 "pole," and he introduced a term since generally substituted, 

 *' electrode," which meant nothing more than the way or path by 

 which the electricity was led in. " Electric fluid " was a term 

 which Faraday considered dangerous, as meaning more than they 

 really knew about the nature of electricity, and as was remarked 

 by Maxwell, Faraday succeeded in banishing the term " electric 

 fluid " to the region of newspaper paragraphs. 



Diamaguetism was a subject upon which Faraday worked, but it 

 would take him too long to go into that subject, though he must say a 

 word or two. Faraday found that whereas a ball of iron or nickel or 

 cobalt, when placed near a magnet or combination of magnets, would be 

 attracted to the place where the magnetic force was the greatest, the 

 contrary occurred if for the iron was substituted a corresponding mass 

 of bismuth or of many other substances. The experiments in diamag- 

 netism were of a microscopic character, but he would like to 

 illustrate one position of Faraday's, developed years afterwards by 

 Sir Wm. Thomson, and illustrated by him in many beautiful experi- 

 ments, only one of which he now proposed to bring before them. 

 Supposing they had two magnetic poles, a north pole and a south 

 pole, with an iron ball between them, free to move along a line 

 perpendicular to that joining the poles, then, according to the rule he 

 had stated, the iron ball would seek an intermediate position, the 

 place at which the magnetic force was the greatest. Consequently, 

 if the iron ball be given such a position, they would find it tended 

 with considerable force to a central position of equilibrium ; but if, 

 instead of using opposite poles, they used two north poles, they would 

 find that the iron ball did not tend to the central position, because 

 that was not the place in which the magnetic force was the greatest. 

 At that place there was no magnetic force, for the one pole com- 

 pletely neutralised the action of the other. The greatest force 

 would be a little way out, and that, according to Faraday's observa- 



