Mechanical Philosophy. 25 



iiouses from the destructive effects of lightning, by 

 the use of metallic conductors. About the same 

 time. Dr. Frankhn's friend, Mr. Kinnersly, dis- 

 tinguished himself by rediscovering the apparently 

 contrary electricities of glass and resin, or sulphur, 

 which M. Du Fay had long before observed, but 

 with whose discovery he and Dr. Franklin were 

 both unacquainted. To solve the difficulty arising 

 from this fact, the Doctor, instead of recurring to 

 the supposition of two different kinds of electric 

 matter^ as the French philosopher had done, pro- 

 posed his celebrated theory oi positive ^iXid negative 

 electricity, or the plus and minus states of bodies 

 charged with that fluid: a theory which had been 

 before suggested by Dr. Watson, and which was 

 afterwards generally received throughout the scien- 

 tific world; and, though by no means without 

 opposition, still continues to hold a more exten- 

 sive influence than any other. 



Electricity seems to have been first applied to 

 viedical purposes, by Mr. Kratzenstein, Pro- 

 lessor of Medicine at Halle, in 1744. From that 

 period it gradually grew into notice, by means of 

 the experiments of the Abbe Nollet, Jallabert, 

 of Geneva, Sauvages, of Montpellier, Bohadscii,; 

 of Prague, Dr. Watson, before mentioned, Dr. 

 Franklin, and many others. The medical virtues 

 of this wonderful fluid soon excited attention and 

 inquiry throughout the scientific world. And al- 

 though the repetition of experiments, which has 

 been constantly going on from that period to the 

 present, has served to correct many errors into 

 which the enthusiastic fell in the beginning; yet 

 electricity, after undergoing many revolutions of 

 fashion, is now well established as an important 

 article of the Materia Medica. 



After the interesting discoveries of Dr. Frank- 

 lin^ the next great experimenters and discoverers 



E 



