HISTORY AND PROGRESS. 6 



substance by an electrified body, it had been observed by 

 Grey that the former was repelled from the moment that 

 it was itself electrified by contact. It was further remarked 

 that when the electrified body was a rod of glass, the light 

 body would be strongly attracted by a stick of resin also 

 electrified by friction. It is not a settled question whether 

 Symner it was, or Dufay, who in 1733 concluded, from the 

 combination of these facts, the existence of two electricities. 

 It was supposed that all bodies in their natural state con- 

 tained an equal amount of each of these electricities in 

 equilibrium ; but that from the moment this equilibrium 

 was upset, and until it was re-established, the elements 

 would divide themselves between the rubber and the rubbed 

 body those identical with the electricity of a glass rod 

 showing themselves in some bodies, and, in others, those of 

 the same nature as the electricity of a piece of resin. This 

 occasioned the former to be called vitreous electricity, and the 

 latter resinous electricity. 



6. Benjamin Franklin believed, however, in the existence 

 of only a single fluid, and explained the phenomena by sup- 

 posing that on exciting any substance till the equilibrium 

 of the electricity was destroyed, an excess of it would be 

 deposited on one side, and a deficiency, necessarily to the 

 same amount, would occur on the other. Hence he gave 

 the name of positive electricity to that which Dufay had 

 called vitreous, and negative to that called resinous. 



Dufay, without the remotest idea of the transmission of 

 signals for practical purposes, and with the pure curiosity of 

 a physical experiment, made some capital attempts to ascer- 

 tain the distance to which the electric attraction could be 

 observed in an insulated wire. 



7. Winckler, in Leipsic, and Lemonnier of Paris, in 

 1746, and Dr. Watson, Bishop of Landaff, in 1747, took up 

 the same inquiry. 



8. The discovery of the Leyden jar by Muschenbrceck, of 

 Leyden, in 1746, came very opportunely for the experi- 

 menters in the transmission of electric power. 



Muschenbrceck, struck by the escape of electricity into the 



B 2 



