506 I»R0DUCT10N OP ELECTRICITY ftY fRlCTIOI^. 



that which is indicated hy the other, 3. The effect offrictioit 

 performed with one combination of dissimilar bodies is differ* 

 ent from that which is produced by any other combination, 

 4. The friction of two bodies^ similar in all respects to one 

 another, produces no excitement. 5. if the rubber of an elec- 

 trical machine be insulated, only a very slight charge can be 

 accumulated in the prime conductor ; and, under such circum-^ 

 These aeree staiices, the action of the machine soon ceases altogether. The 

 with the gene- agreement of the second, third, and fourth propositions with 

 ja! law. ^Y^e general law is too obvious to require being pointed out: 



and it will not be difficult to show a perfect agreement of 

 the first and last propositions with the same general law, and 

 in this manner to justify its application to the excitement of 

 bodies by friction. 

 Why one of |n the first place, let us consider, whence proceeds the ne- 

 must be an cessity of one of the bodies, employed to produce excitement 

 electric. by friction, being an electric. If one conductor be rubbed 



- on another, no evident excitement is produced; for in conse- 



quence of the free communication between all parts of a 

 conductor, and between conductors in contact, the charge 

 is removed from each set of particles, immediately as it is 

 excited in them; or, in other words, during the friction of 

 such bodies on one another, opposing powers operate; tbe 

 contact and separation of dissimilar bodies, tending to pro- 

 duce excitement; and the conducting quality, tending to 

 destroy excitement. If either of the bodies be connected 

 with the Earth, the electrical state of both must he precisely 

 the same as that of the Earth : if they be both insulated, 

 they must possess similar electrical states, as long as they 

 are in contact by the smallest physical points ; and conse- 

 quently there can be no excitement in either; for when ex- 

 tntement is produced by the contact and separation of two 

 insulated dissimilar bodies, one body assumes an electrical 

 state precisely opposite to that, which is acquired by the 

 other. When, therefore, the one conductor has been drawn 

 completely over the other, no more excitement can remain, 

 than what ife effected by the separation of the last particles, 

 which had been in contact ; a degree inconceivably small, 

 when shared with the whole of the bodies, to which the ex- 

 cited particles belong. As a confirmalion of this reasoning, 



1 



