Theories of Electricity 135 



was a purely experimental observation, and he appears 

 never to have put forward any definite electrical theory 

 to account for his results. 



From the point of view of the philosophers at that 

 time, the main defect of Franklin's theory lay in the fact 

 that it failed to offer any explanation why two bodies, 

 negatively electrified, should repel each other. To over- 

 come this objection John Symmer, an Englishman, put 

 forward in 1759 a modified form of Franklin's views, 

 now known as the " two fluid " theory. 



On this theory, a neutral body contains an equal 

 amount of two distinct electrical fluids which give rise 

 to positive and negative electricity respectively. Each 

 portion of the one fluid repels itself, but attracts the 

 other. On this view, positive and negative electricity 

 are two distinct entities instead of one as supposed by 

 Franklin. 



On account of its simplicity the theory of Franklin at 

 first met with general acceptance, for it offered a reason- 

 able explanation of the facts known at that time. As 

 electrical knowledge advanced, it began to be recog- 

 nized that Franklin's theory must be extended in order 

 to account fully for the observed facts. Aepinus, an 

 ardent advocate of Franklin's hypothesis, showed that it 

 was necessary to introduce the idea not only that the elec- 

 trical fluid repelled itself and attracted neutral matter, 

 but that the particles of matter repelled each other. 



