40 Electric and Magnetic Science 



He found, in fact, that when gold-leaf which had been 

 electrified by contact with excited glass was brought near to an 

 excited piece of copal,* an attraction was manifested between 

 them. " I had expected," he writes, " quite the opposite effect, 

 since, according to my reasoning, the copal and gold-leaf, which 

 were both electrified, should have repelled each other." 

 Proceeding with his experiments he found that the gold-leaf, 

 when electrified and repelled by glass, was attracted by all 

 electrified resinous substances, and that when repelled by the 

 latter it was attracted by the glass. " We see, then," he continues, 

 " that there are two electricities of a totally different nature 

 namely, that of transparent solids, such as glass, crystal, &c., 

 and that of bituminous or resinous bodies, such as amber, copal, 

 sealing-wax, &c. Each of them repels bodies which have 

 contracted an electricity of the same nature as its own, and 

 attracts those whose electricity is of the contrary nature. We 

 see even that bodies which are not themselves electrics can 

 acquire either of these electricities, and that then their effects 

 are similar to those of the bodies which have communicated it 

 to them." 



To the two kinds of electricity whose existence was thus 

 demonstrated, du Fay gave the names vitreous and resinous, by 

 which they have ever since been known. 



An interest in electrical experiments seems to have spread 

 from du Fay to other members of the Court circle of Louis XV ; 

 and from 1745 onwards the Memoirs of the Academy contain a 

 series of papers on the subject by the Abbe Jean-Antoine Nollet 

 {&. 1700, d. 1770), afterwards preceptor in natural philosophy 

 to the Koyal Family. Nollet attributed electric phenomena to 

 the movement in opposite directions of two currents of a fluid, 

 " very subtle and inflammable," which he supposed to be present 

 in all bodies under all circumstances.f When an electric is 

 excited by friction, part of this fluid escapes from its pores, 

 forming an effluent stream; and this loss is repaired by an 



* A hard transparent resin, used in the preparation of varnish. 

 t Cf. Nollet' s lieeherchet, 1749, p. 245. 



