PROGRESS OF ELECTRICAL THEORY. 23 



over a large part of Europe, as the creator of the 

 science, and the terms 3 Franklinism, Franklinist, 

 Franklinian system, occur in almost every page of 

 continental publications on the subject. Yet the 

 electrical phenomena to the knowledge of which 

 Franklin added least, those of induction, were those 

 by which the progress of the theory was most pro- 

 moted. These, as we have already said, were at 

 first explained by the hypothesis of electrical atmo- 

 spheres. Lord Mahon wrote a treatise, in which 

 this hypothesis was mathematically treated; yet 

 the hypothesis was very untenable, for it would not 

 account for the most obvious cases of induction, 

 such as the Leyden jar, except the atmosphere was 

 supposed to penetrate glass. 



The phenomena of electricity by induction, when 

 fairly considered by a person of clear notions of 

 the relations of space and force, were seen to ac- 

 commodate themselves very generally to the con- 

 ception introduced by Dufay 4 ; of two electricities 

 each repelling itself and attracting the other. If 

 we suppose that there is only one fluid, which 

 repels itself and attracts all other matter, we obtain, 

 in many cases, the same general results as if we 

 suppose two fluids; thus, if an electrized body, 

 overcharged with the single fluid, act upon a ball, 

 it drives the electric fluid in the ball to the further 

 side by its repulsion, and then attracts the ball 

 by attracting the matter more than it repels the 



;! Priestley, p. 100. 4 Mem. A. P. 1733, p. 467> 



