4 A letter to Prof. Faraday. 



But I am unable to imagine any change which can admit of 

 gradations of intensity, iticreasing with remoteness. I cannot 

 fignre to myself any reaction which increase of distance would 

 not lessen. Much less can I conceive that such extremes of in- 

 tensity can be thus created, as those of which you consider the 

 existence as demonstrated. It may be suggested that the change 

 of polarity produced in particles by electrical inductions, may 

 arise from the forced approximation of reciprocally repellent poles, 

 so that the intensity of the inductive force, and of their effort to 

 return to their previous situation, may be susceptible of the gra- 

 dation which your electrical doctrines require. But could the 

 existence of such a repellent force be consistent with the mutual 

 cohesion which appears almost universally to be a property of pon- 

 derable particles ? I am aware that, agreeably to the ingenious hy- 

 pothesis of MossoUi, repulsion is an inherent property of the parti- 

 cles which we call ponderable ; but then he assumes the existence 

 of an imponderable fluid to account for cohesion ; and for the 

 necessity of such a fluid to account for induction it is my ultimate 

 object to contend. I would suggest that it can hardly be expe- 

 dient to ascribe the phenomena of electricity to the polarization 

 of ponderable panicles, unless it can be shown that if admitted, 

 it would be competent to produce all the known varieties of elec- 

 tric excitement, whether as to its nature or energy. 



If I comprehend your theory, the opposite electrical state in- 

 duced on one side of a coated pane, when the other is directly 

 electrified, arises from an aflection of the intervening vitreous 

 particles, by which a certain polar slate caused on one side of 

 the pane, induces an opposite state on the other side. Each vit- 

 reous particle having its poles severally in opposite states, they 

 are arranged as magnetized iron filings in lines ; so that alternately 

 opposite poles are presented in such a manner that all of one kind 

 are exposed at one surface, and all of the other kind at the other 

 surface. Agreeably to this or any other imaginable view of the 

 subject, I cannot avoid considering it inevitable that each particle 

 must have at least two poles. It seems to me that the idea of 

 polarity requires that there shall be in any body possessing it, 

 two opposite poles. Hence you correctly allege that agreeably 

 to your views it is impossible to charge a portion of matter with 

 one electric force without the other. (See par. 1177.) But if all 

 this be true, how can there be a " positively excited particle ?" 



