CONTRIBUTIONS TO SCIENCE. 515 



conclusively, and in the best possible manner as far as the 

 instruments at his disposal would allow, that the attrac- 

 tion or repulsion between two small charged bodies varies 

 directly as the product of their charges, and inversely as 

 the square of the distance between them, so that the law of 

 electrical action is the same as Newton's law of gravitation, 

 except that the stress between similarly charged bodies is 

 repulsive, and that between dissimilarly charged bodies 

 attractive. After Cavendish's time comparatively little was 

 added to the theory of statical electricity, if we except the 

 elaborate mathematical investigations of particular problems 

 by Poisson, and the papers of George Green, which until 

 recently were read by few, and appreciated by only two or 

 three, until Faraday took up the subject. Most of Caven- 

 dish's work remained unpublished and unknown, and some 

 of his results were independently obtained by Faraday. It 

 is difficult to conceive what would have been the effect on 

 Faraday's mind of perusing Cavendish's " thoughts on 

 electricity," -as well as his own accounts of his experiments. 

 Perhaps it is best for the world that Faraday was left to work 

 and think on independent lines ; certainly it has been a 

 boon to Mathematicians and Physicists alike that Maxwell 

 has appeared to expound and develop, if not to perfect, the 

 work of both. 



The mathematical theory of attractions had, prior to the 

 time of Faraday, attained a very high degree of development 

 in the hands of Laplace, Lagrange, Poisson, and others, and 

 could be applied to the solution of many very interesting 

 problems in electricity. But Faraday was not satisfied with 

 the hypothesis of direct action at a distance between charges 

 of electricity, and held that there must be some mechanism 

 by which electric and electromagnetic actions can be com- 

 municated from point to point. Not all the arguments by 

 which he supported this view are conclusive, for the force 

 upon an electrified body and the induced electrification of 

 any conductor will be the same whether we adopt the 

 hypothesis of direct action at a distance or of the transmission 

 of electrical action in lines, straight or curved, through an 



