Theories of Electricity 125 



When Franklin began his electrical experiments in 

 1746 the knowledge of electricity was of an extremely 

 fragmentary and elementary character. It was known 

 that a number of bodies, when rubbed, became elec- 

 trified and the repulsions and attractions of electrified 

 bodies had been observed. Dufay had shown that two 

 different kinds of electricity were developed by rubbing 

 glass and resin, which he termed " vitreous " and " res- 

 inous " electricity, respectively, or what we should now 

 term positive and negative. His work, however, was 

 very little known at the time, and it is very doubtful 

 whether Franklin in his earlier experiments was ac- 

 quainted with it. 



The fame of the shock produced by the accumulator 

 of electricity, or Leyden jar, discovered by Cunaeus of 

 Leyden in 1746, had immediately spread throughout 

 the civilized world, and there was an intense and wide- 

 spread interest in the properties of this " electrical fire," 

 as it was then called. At this period it was not difficult 

 for anyone to become rapidly acquainted with the work 

 already done in electrostatics, and the amateurs of sci- 

 ence were on an equal footing with their more profes- 

 sional brethren in the pursuit of further knowledge. 



It was at this period that Franklin became interested 

 in electrical experiments, mainly through the instrumen- 

 tality of Peter Collinson of Edinburgh, who had pre- 

 sented an electrical machine to the Library Company 



