BLBCTRICAL EFFECTS PRODUCED BT FRICTION. 199 



5. 1 shall first observe, that, had Dr. Maycock read my paper Errour in the 

 on the effects of friction, to which I shall here refer on many i^^^^^ dec-^" 

 points, he would have seen the errour of the first electricians in tries and con- 

 their distinction of bodies, which he continues to admit, that of '^"^^°"' 

 electrics opposed to conductors ; as if the former only had the 

 faculty to be electrified by friction. With respect to electricity, all bodies con- 

 there is no other distinction than that of more or less conductors, o" Tes"s^ '""^^ 

 which explains all the phenomena. From the property of ah- b^ q^ some 

 solute nonconductors, as are resinous bodies, whatever change the efFects are 

 >is produced in the electrical state of their surface, either by ^^^^ propag*' 

 friction, or by communication with an electrified body, it is not 

 propagated on them ; and this is their only distinctive property 

 with respect to e/ec/n'ca/ phenomena. The difference, there- 

 fore, between these bodies, and the imperfect nonconductors, 

 is this ; that the changes produced on some points of the latter, 

 either by friction, or by communication with an eltctrified body, 

 are propagated on their surface, slowly on some, as glass., or 

 almost instantly on the best conductors, such as metals. 



6. From this determination of the effects of the different Motion of tht 



conducting faculties of bodies, united with that of the nature electric fluid 



° along dlfFejent 



of the electric fluid, which Dr. Maycock has not thought ne- bodies. 



cessary to investigate, I derived in the same paper (pp. 3 and 4) 



the following theory of the effects of friction, which is to be 



compared with the phenomena. " The electric fluid resides 



** on all terrestrial bodies, every particle of air included ; being 



*' retained upon them by a mutual attraction, which, however, 



" differs in degree ; some attract the electric fiuid only when it 



*' comes into contact with them 5 but then it adheres strongly 



"*' to the parts which receive it, or moves but very slowly along 



" their surface -y which therefore are nonconductors : others 



*' receive it at more or less distance, and it is propagated more 



** or less rapidly along their surface. Glass, though absolutely 



*' impermealle to the electric fluid, permits it to move with a 



" sensible progress along its surface." 



7. After these definitions of the nature of the electric fluid, Theory of the 

 and of its motions along different bodies, I thus define the effects of fric 

 effects o{ friction, connected with these premises. " Friction 



** excited between two bodies, has no other effect than that of 

 ** disturbing the natural equilibrium of the electric fluid, which 

 " equilibrium tends always to be produced among all bodies, 



accord- 



