ELKCTRIC EFFECTS OF FRICTION. Jl 



Exp. 5. In a piece of brass similar to the above, ^g". Exp. 5. 

 A, instead o? sealing wax, I placed a piece of Caoutc/ioucy f^^^^^''"'^'* 

 or Indian rubber of the same shape as the wax. This body 

 produced here a sinj^ulai' phenomenon (observed in other 

 <;a8es) which characterizes the manner in which yric/iow acts 

 in these phenomena; its effects changing, according to 

 circumstances foreign to the intrinsic nature of bodies. 

 Tills experiment is difficult, on account of the tendency of 

 the huUan rubber to stick to the glass cylinder, by which 

 the former is torn or disfigured if the pressure is too great, 

 or the motion too rapid : it is thei'elore necessary to fiad 

 th?^ proper degrc*e of both. Now, according to these (or 

 other unperceived circumstances) having repeated this ex- 

 periment on different days, sometimes the glass took off 

 some electric Jiuid from the Indian rubber, and made the 

 electroscope 11 diverge positively; at other times it was 

 the reverse; and in both cases the indian rubber was in the 

 state opposite to that of the glass cylinder, as shown by the 

 eKctroscope 19. 



Exp, 6. It has been seen in exp, 1, that a brass rubber, Exp. 6. 



applied to the D7rt55 cylinder, becomes weafa/iwe, the latter ?''^^^ ^"^ ^^^ 



' - , . . . . ing wax. 



becoming positive. I covered a similar glass cylinder with 



a thick coating of sealing wax, and applied to it a brass 

 rubber of the same breadth as the former, fitted to the 

 sealing ivax cylinder: it produced no sensible effect. I 

 suspected, that this rubber was too wide: because thus em* 

 bracing, in a great length, half the circumference of the 

 sealing wax cylinder, which constantly revolved against it, 

 the sealing icax lost and regained alternately electric jiuid 

 on too grfcat a surface; for the point 12, with which com- 

 municates the prime conductor, to preserve any sensible 

 change. With this idea, I reduced the breadth of the brass 

 rubber, in the part bearing on the sealing wax, to ^ of an 

 inch; placing the point 12 of the prime conductor, imraedi- 

 dteiy under and very near the extremity of the rubber. 

 Then the electroscope 11, communicating with the rubbed 

 sealing wax, diverged negatively, and the electroscope J 9, 

 communicating with the brass rubber, diverged positively* 



This experiment shows, in tlse first place, the errour of Distinction ©f 

 ^ distinction between bodies us electrics and anelictrics electrics i^r sc 



^electric '""'"''*'* 



