ELECTRICITY. 



that the conducting power of the packthread used in the experiments of Grey 

 depended on the moisture contained in it, and that the conducting power \vas 

 considerably increased by wetting it. By this expedient he transmitted elec- 

 tricity along a cord to the distance of about thirteen hundred feet. 



It had been previously ascertained that when any substance charged with 

 electricity communicated the electric principle to another body near it, but not 

 in contact with it, the electricity passed from the one body to the other in the 

 form of a spark, accompanied by a snapping or cracking noise, like that of a 

 slight explosion. It had also been discovered by Grey and Wheeler that the 

 bodies of men and animals would become charged with electricity if placed in 

 the usual manner in contact with an excited glass tube, provided they were 

 suspended by silk cords, so as to prevent the escape of the electricity. Du- 

 faye, therefore, reasoned that a man being so suspended by silk cords, the 

 electricity imparted to his person could not escape ; and being charged by the 

 excited glass tube, sparks of fire ought to issue from his body, if any body ca- 

 pable of receiving the electricity were presented to it. To reduce this to the 

 immediate test of experiment, Dufaye suspended his own person by silk lines ; 

 and being electrified, the Abbe Noflet, who assisted him in these experiments, 

 presented his hand to his body, when immediately a spark of fire issued from 

 the person of the one philosopher and entered the body of the other. Although 

 such a result had been predicted as a consequence of the arrangement, the as- 

 tonishment was not the less great at its occurrence. Nollet states that he can 

 never forget the surprise of both Dufaye and himself when they witnessed the 

 first explosion from the body of the former. 



The celebrity of Dufaye rests, however, not on his experiments, but on the 

 sagacity which led him to evolve natural laws of a high degree of generality 

 from his own experiments, and from those of the philosophers who preceded 

 him. He reproduced in a more definite form the principles of attraction and 

 subsequent repulsion, which had previously been announced by Otto Guericke. 

 " I discovered," says Dufaye, " 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 principle 

 was, first, that excited electrics attract all bodies in their natural state ; second, 

 that after a body is so attracted, and has touched the excited electric, then such 

 body is repelled by the excited electric ; third, that if, after being so repelled, 

 such body touches any other, it will be again attracted, and again repelled by 

 the excited electric, and so on. 



But a discovery of a much higher order was due to Dufaye. " Chance," 

 says he, " threw in my way another principle more universal and remarkable 

 than the preceding one, and which casts a new light upon the subject of elec- 

 tricity. The principle is, that there are^vo distinct kinds of electricity, very 

 difierent from one another ; one of which I shall call vitreous, and the other 

 resinous electricity. The first is that of glass, rock-crystal, precious stones, 

 hair of animals, wool, and many other bodies. The second is that of amber, 

 copal, gum-lac, silk-thread, paper, and a vast number of other substances. The 

 characteristic of these two electricities is, that they repel themselves and at- 

 tract each other. Thus a body of the vitreous electricity repels all other 

 bodies possessed of the vitreous, and, on the contrary, attracts all those of the 

 resinous electricity. The resinous also repels the resinous, and attracts the 

 vitreous. From this principle one may easily deduce the explanation of a 

 great number of other phenomena, and it is probable that this truth will lead 

 us to the discovery of many other things." 



This was a discovery of the highest order, and in its consequences fully 

 justified the anticipation that " it would lead to the discovery of many other 



