12 HISTORY OF ELECTRICITY. 



universal and remarkable than the preceding one, 

 and which casts a new light upon the subject of 

 electricity. The principle is, that there are two 

 distinct kinds of electricity, very different from one 

 another ; one of which I call vitreous, the other 

 resinous, electricity. The first is that of glass, 

 gems, hair, wool, &c. ; the second is that of amber, 

 gum lac, silk, &c. The characteristic of these two 

 electricities is, that they repel themselves and at- 

 tract each other." This discovery does not, how- 

 ever, appear to have drawn so much attention as 

 it deserved. It was published in 1735 ; (in the 

 Memoirs of the Academy for 1733;) and yet in 

 1747, Franklin and his friends at Philadelphia, 

 who had been supplied with electrical apparatus 

 and information by persons in England well ac- 

 quainted with the then present state of the subject, 

 imagined that they were making observations un- 

 known to European science, when they were led to 

 assert two conditions of bodies, which were in fact 

 the opposite electricities of Dufay, though the 

 American experimenters referred them to a single 

 element, of which electrized bodies might have 

 either excess or defect. " Hence," Franklin says, 

 "have arisen some new terms among us: we say 

 B," who receives a spark from glass, "and bodies 

 in like circumstances, is electrized positively; A," 

 who communicates his electricity to glass, " nega- 

 tively ; or rather B is electrized plus, A minus." 

 Dr. (afterwards Sir William) Watson had, about 



