Researches in Electricity 119 



In any consideration of his theory of electricity it must 

 be remembered that the doctrine of energy did not yet 

 exist, that fire was regarded as a subtile fluid penetrat- 

 ing the pores of bodies, and that Franklin in speaking 

 of " the electric fire " had in mind an analogous medium. 

 The mathematical concept of potential was yet to be 

 developed. Although Ellicott in 1746 and also Gralath 

 had attempted to determine electrostatic attractions by 

 means of the balance, and Nollet had used an electro- 

 scope with repelled threads of which he measured the 

 divergence, the science of electrical measurement was to 

 await the advent of Cavendish and Coulomb. 



Franklin contributed nothing of a quantitative char- 

 acter to the science of electricity, but he was an accurate 

 observer of phenomena. His fondness for speculation 

 was unbounded and he indulged it freely upon every 

 subject. 



Speculation is an essential feature of theory building, 

 particularly in the beginnings of a science. In Frank- 

 lin's case it was controlled by practical common sense, 

 sound logic and a rare definiteness of conception. After 

 any speculative flight the strongly utilitarian side of his 

 nature was sure to assert itself as in this characteristic 

 passage, which follows an attempt to explain the action 

 of points. " Nor is it of much importance to us to know 

 the manner in which nature executes her laws; 'tis 

 enough if we know the laws themselves. 'Tis of real ^. --■•—-„... 



