26 Mechanical PIiilosopHt/. 



in electricity were Mr. Canton, of Great-Britain^ 

 Signor Beccaria, of Italy, and Mr. Wilcke, of 

 Germany, who considerably enlarged the sphere 

 of our knowledge respecting the conducting powers 

 of different substances; and threw farther light on 

 the plus and viinus- states of electrics. The doc- 

 trine of Franklin, that these two states arise from 

 a redundancy or deficiency of the same matter, 

 was but little opposed, until 1759, when Mr. 

 Symmer, an English' philosopher, revived the ideas 

 of Du Fay, with- some new modifications of his 

 own . He taught the existence of two electric Jluids, 

 not independent, but always co~existent, and coun- 

 teracting one another. In this opinion he has been^ 

 followed by some gentlemen of very respectable 

 character, in Great-BHtain, and on the continent 

 of Europe ; though by far the greater number of 

 the learned appear still- to be in favour of the Frank* 

 linian theory.'^ 



The progressive improvements of electrical ma^- 

 chines, and of the various instruments for exhibiting^ 

 the phenomen^i^^ of this science, have generally 

 kept pace with the gradual developement of its= 

 principles. H-ence the honour of these improve- 

 ments is, in general, due to the gentlemen already 

 named. Beside these, several artists of respec- 

 table character have done much to forward the 

 mechanical part of this branch of philosophy. 



Soon after the grand discoveries of Franklin , Mr. 

 iEpiNus, a philosopher of high character in the 

 Imperial Academy of St. Petersburgh, assuming 

 his principles, offered to the world some new and 

 interesting views on this branch of science . Struck 

 with the resemblance between the phenomena of 

 electricity and magnetism, and believing that the 



h The above stated facts relating to the rise and progrees of electricity, 

 are chiefly taken fr«m Dr. Priestlet's Hhtory of Ekttrmt^t 1794, LoE» 

 €k)»| 4to. 



