PROGRESS OF ELECTRICAL THEORY. 33 



lations, that when two electrized spheres are brought 

 near each other, the accumulation of the opposite 

 electricities on their nearest points increases with- 

 out limit as the spheres approach to contact; so that 

 before the contact takes place, the external resist- 

 ance will be overcome, and a spark will pass. 



Though the relations of non-conductors to elec- 

 tricity, and various other circumstances, leave many 

 facts imperfectly explained by the theory, yet we 

 may venture to say that, as a theory which gives 

 the laws of the phenomena, and which determines 

 the distribution of those elementary forces, on the 

 surface of electrized bodies, from which elementary 

 forces (whether arising from the presence of a fluid 

 or not,) the total effects result, the doctrine of 

 Dufay and Coulomb, as developed in the analysis of 

 Poisson, is securely and permanently established. 

 This part of the subject has been called statical 

 electricity. In the establishment of the theory of 

 this branch of science, we must, I conceive, allow 

 to Dufay more merit than is generally ascribed to 

 him; since he saw clearly, and enunciated in a 

 manner which showed that he duly appreciated 

 their capital character, the two chief principles, 

 the conditions of electrical attraction and repulsion, 

 and the apparent existence of two kinds ef elec- 

 tricity. His views of attraction are, indeed, partly 

 expressed in terms of the Cartesian hypothesis of 

 vortices, then prevalent in France ; but, at the time 

 when he wrote, these forms of speech indicated 

 VOL. in. D 



