ELECTRIC INDUCTION. 477 



quencliable desire for longer lines, and one of 866 feet, is 

 successfully used; but Gray has seemingly satisfied him- 

 self on this subject, for, after several months' silence, he 

 reappears in June, 1731, with a host of new experiments, 

 depending mainly upon his discovery that it is possible to 

 insulate electrified bodies by placing them on cakes of 

 resin. This gives more employment for the Charterhouse 

 lads, who are hung up on hair lines and stood up on 

 blocks, and electrified tubes are applied to them in all 

 sorts of ways, which need not here be detailed. 



A year later, 1732, Godfrey and Wheler are both pressed 

 into service to aid him in making experiments to show in- 

 duction; and these lead him to the conclusion that "the 

 electric virtue may not only be carried from the tube by a 

 rod or line to distant bodies, but that the same rod or line 

 will communicate that virtue to another rod or line at a 

 distance from it, and by that other rod or line the attractive 

 force may be carried to other distant bodies." And thus 

 was proved for the first time that an electrified line could 

 induce a charge on another line; and, in fact, Gray found 

 that this induction would take place over distances as great 

 as a foot between the two lines. 



Gray's experiments had now extended over three years, 

 during which time, despite the attention which results so 

 novel and -unprecedented naturally excited, no one had 

 appeared to rival him. Dr. Desaguiliers, writing some 

 years after Gray's death, finds an explanation of this in 

 Gray's irascible temperament and intolerance of opposi- 

 tion, and gives as an excuse for the long withholding of 

 his own observations that their publication would probably 

 have caused Gray to abandon the research. Nevertheless, 

 when the field was entered, Gray welcomed the interloper, 

 and, so far from relaxing his efforts, continued them to the 

 end of his life with a pertinacity rivaling that of Hooke. 

 At all events, if such solicitude as Desaguiliers manifests 

 was sufficient to deter the English philosophers from in- 

 dependent investigation, it at least seems not to have ex- 



