I J ELECTRIC EFFXCTS OF FllICTION. 



(electric ;>e'r se, and electric A// commnuicatioyh as they have 

 been also calie<l); considering /ric/iow as the test between 

 these two classes of bodies, and placing metals foremost 

 among^ the anclectr'tcs. But it is seen in the above experi- 

 ments, that there is no such distinction, since brass under- 

 goes, by friction, changes in its electric state, as well as 

 resinous bodies and ^/aw. only these changes, in conduct- 

 ing bodies, cannot be manifested without insulation ; and 

 the want of this condition in the experiments of former 

 electricians was the cause of the errour. 

 Np'ther are The same experiments show also, that brass (as a metal) 



kinds of elec- becomes eitherpo5i/i6"^ or ne^o/ir^, according to the body with 

 tricity. which it undergoes/ric/ion. In the above experiment the brass 



rubber was made positive^ because it took off some electric 

 Jluid from sealing-ivax ; hut mexper, 1 it was made iiegO' 

 tive, because it lost some of the Jlvid to glass. But this 

 ditference in the electric state of the same body, by the 

 ^ difference of those with which it undergoes friction, ex- 



tends farther ; and the following experiment will show the 

 errour of the distinction between two electricities, in which 

 one is called resinous and the other vitreous ; and in general 

 between two Jiuids, or two electric properties in different 

 bodies. 



Exper. 7. Exper. 7. It has been seen in the last experiment, that 



dealing wax .i ,. i- i i • i i • ,, , 



•nd india ^"^' sealing-wax cy under was made negative, by being rubbed 



rubber. with brass. To the same cylinder I applied the Indian 



rubber ; and with the smallest pressure (to prevent adhesion) > 

 and a very slow motion of the winch, the gold leaves struck 

 so rapidly in both electroscopes, that, in order to try the 

 kinds of divergences produced, I was obliged to stop at one 

 part only of a revolution: then I found constantly, that 

 the sealing'Wax, which in the above experiment was ren» 

 dered negative by brass, now became positive ; and that the 

 indian rubber, which in exper, 5 became sometimes 

 positivf with the glass cylinder, was here constantly nega- 

 tive. Therefore sealing-wax itself either loses or gains some 

 electric fluid, according to the body which exercisesyWc/io^ 

 upon it, and the rubbing bodijijs always experience tji'^, 

 contrary effect. 



I ha*e 



