158 JAMES CLEIIK MAXWELL 



Meanwhile, during the same period, various 

 writers, Murphy, Plana, Charles, Sturm, and Gauss, 

 extended Poisson's work on electrostatics, treating the 

 questions which arose as problems in the distribution 

 of an attracting fluid, attracting or repelling according 

 to Newton's law, though here again the greatest 

 advances wero made by a self-taught Nottingham 

 shoemaker, George Green by name, in his paper " On 

 the Application of Mathematical Analysis to the 

 Theories of Electricity and Magnetism," 1828. 



Green's researches, Lord Kelvin writes, 4< have led to 

 the elementary proposition which must constitute the 

 legitimate foundation of every perfect mathematical 

 structure that is to be made from the materials fur- 

 nished by the experimental laws of Coulomb," 



Green, it may be remarked, was the inventor of 

 the term Potential. His essay, however, lay neglected 

 from 1828, until Lord Kelvin called attention to it in 

 1845. Meanwhile, some of its most important residts 

 had been re-discovered by Gauss and Charles and 

 Thomson himself. 



Until about 1845, the experimental work on which 

 these mathematical researches in electrostatics were 

 based was that of Coulomb. An electrified body is 

 supposed to have a charge of some imponderable fluid 

 41 electricity." Particles of electricity repel each other 

 according to a certain law, and the fluid distributes 

 itself in equilibrium over the surface of any charged 

 conductor in accordance with this law. There are on 

 this theory two opposite kinds of electric fluid, positive 

 and negative, two charges of the same kind repel, two 

 charges of opposite kinds attract; the repulsion or 



