202 ELECTRICAL EFFECTS PRODUGBD BY fRl«TIO». 



gold leaf electrometer, the riband which has moved is found 

 • positive, and the other negative. I must observe, that this ex- 



periment cannot succeed, but when the air is very dry, com- 

 monly in winter, at the time that a divergence produced in th« 

 gold leaves by any cause is long preserved j else the effects pro- 

 duced on the ribands is soon dissipated, 

 with glass, 12.1 have produced the same effect by the friclion between 



other bodies absolutely similar to one another, namely, glass 

 and glass ; as may be seen in Exp. 3 of the same paper. The 

 revolving body was a glass cylinder, and the rubber a piece of 

 the same glass. Now, the revolving glass, as the riband 

 which passed in length over the other, carried off some electric 

 Jluid from the immovable rubber, and immediately transmitted 

 it to the prime conductor of the small machine j so that, at 

 every revolution, the gold-leaves connected with it increased in 

 divergence, and at last diverged much as positive. *- 



and with dis8l- 13^ ^11 the experiments related in that paper demonstrate 



miiflr sub" 



stances, the same theory concerning the effects of friction ; but 1 shall 



only indicate them shortly, as the details may be seen in the 

 paper itself. In Exper. 1, a brass rubber acting on a glass 

 revolving cylinder, the brass became negative, and the glasi 

 was made positive. This is the same effect produced by a me- 

 tallic amalgama laid on the rubber of the electric machine. 

 In Exper. 4, a sealing wax rubber applied on the same re- 

 volving glass cylinder, the sealing wax becomes negative, and 

 the glass is positive. The latter, as being a better conductor, 

 carries off a greater part of the agitated electric Jluid. In 

 Exper, 5 is seen a very singular case. Having used for rubber 

 a piece of India-rubber, on the same revolving glass cylinder, 

 according to the degree of pressure, sometimes the glass be- 

 came positive, and the rubber then was negative; at other 

 times the former was negative, and the latter positive. This 

 case shows, that, between the same bodies, when they have a 

 disposition to adhere to each other, friction may have inverted 

 electrical tffects, according to the degree, or parts, that the 

 adhesion takes place. 

 A metal, when 14^ I come now to very remarkable changes in the electrical 

 dered either * effects of friction, according to other circumstances. It has 

 positive orne- been seen above, in Exper. l, that a iraw rubber, applied to 

 ding to cir-"'^' *^ revolving ghss tylinder, became negative, and the glan 

 cumstance*. wat 



