346 Reflections on the Inadequacy of the [yrincipal Hypotheses 



might be adiiiitted. But Ijy admitting it, as much injury is 

 done to tlie Inpotliesis as i)y denying it. In either case nu- 

 merous incoiiipati'uilitics vvitli the other principles and with facts 

 occur, as has been and will further be seen. 



4. Under the examination of the fourth principle ^ve have to 

 consider the doctrine of plus and minus electricity. Franklin 

 states that in the charging of a Leydeii phial the following 

 changes take place. Su])pose that on each surface of the glass 

 are 20 particles, constituting the natural portion of electricity, 

 and that one surface will receive as much as the other loses and 

 no more. If 1 be added to the inside it will have 21, and the 

 outside only 19: and when the outside has lost all, the hisido 

 will have 40. Thus the phial when charged contains no nuive 

 than when not charged, except that the,(|uantity in the latter 

 case contained on both surfaces, is in the former case, con- 

 densed upon one. The e(|uilibrium cannot be obtained through 

 the glass : but when a conducting communication is established 

 between both surfaces, tlie excess of the one is eagerly recei\ed 

 by the other, and the equilibrium is restored v.ith violence. 

 Each surface now contains its natural 20 particles and every 

 thing remains in the same state as before charging. 



Tlie whole may be comprised in the three following positions. 



1. Electrics part with or receive no more electricity atone 

 surface than they can receive or j)art with at the other. 



2. When an electric is charged, one surface contains the 

 quantity of fluid which in the natural state is diffused on both ; 

 the other side is consequently vacant. 



3. After the dlschariic the equilibrium is restored, and both 

 surfaces cease to show electrical appearances, being preciselv in 

 the same state as before charging. With regard to the first posi- 

 tion, experiments do not seem to afford much support. Mr. 

 Wilson, having rubbed one surface of a large plane of glass in 

 the middle with his fmger, found l>oth surfaces electritied posi- 

 tively. If the rubbed side had been previously roughed, both 

 surfoces became negative. To these cases may be added the fol- 

 lowmg. Let a solid rod of rough glass l>e excited with a cat's-skiu 

 rubber; the rod will be negativelv electrified ail round. Never- 

 theless it i* probably a truth that one state of electricity cannot 

 be called into action without the other's existence, at least, in 

 some other body: but we must distinguish facts from hypotheses. 



Relating to the second position, namely, that of accumulation 

 and deficiency, I have made experiments which seem to oppose 

 this doctrine. According to Franklin a conijjlete charge in a 

 jar is obtained when its inside surface (if charged through the 

 ball) contains its own natural quantity with that of the outside. 

 In this case the outside is in an absolute state of deficiency, and 



as 



