10 HISTORY OF ELECTRICITY. 



observed various of the effects of attraction and 

 repulsion upon threads hanging loosely. But the 

 person who appears to have first fully seized the 

 general law of these facts, is Dufay, whose experi- 

 ments appear in the Memoirs of the French Aca- 

 demy, in 1733, 1734, and 1737 1 . "I discovered," 

 he says, "a very simple principle, which accounts 

 for a great part of the irregularities, and, if I may 

 use the term, the caprices that seem to accompany 

 most of the experiments in electricity. This prin- 

 ciple is, that electric bodies attract all those that 

 are not so, and repel them as soon as they are 

 become electric by the vicinity or contact of the 

 electric body .... Upon applying this principle 

 to various experiments of electricity, any one will 

 be surprized at the number of obscure and puz- 

 zling facts which it clears up." By the help of 

 this principle, he endeavours to explain several of 

 Hawkesbee's experiments. 



A little anterior to Dufay's experiments were 

 those of Grey, who, in 1729, discovered the pro- 

 perties of conductors. He found that the attraction 

 and repulsion which appear in electric bodies are 

 exhibited also by other bodies in contact with the 

 electric. In this manner he found that an ivory 

 ball, connected with a glass tube by a stick, a wire, 

 or a packthread, attracted and repelled a feather, 

 as the glass itself would have done. He was then 



1 Priestley's History of Electricity, p. 45, and the Memoirs 

 quoted. 



