Justification of the Contact Theory of Galvanism, 367 



(1198. 1207.)» it is evident that the one just receiving? its half 

 charge must fall faster in its tension than the other. For sup- 

 pose app. i. first charged, and app. ii. used to divide with it; 

 though both may actually lose alike, yet app. i., which has 

 been diminished one half^ will be sustained by a certain de- 

 gree of return action or charge (1234.), whilst app. ii. will 

 sink the more rapidly from the coming on of the particular 

 state. I have endeavoured to avoid this interference by per- 

 forming the whole process of comparison as quickly as pos- 

 sible, and taking the force of app. ii. immediately after the di- 

 vision, before any sensible diminution of the tension arising 

 from the assumption of the peculiar state could be produced ; 

 and I have assumed that as about three minutes pass between 

 the first charge of app. i. and the division, and three minutes 

 between the division and discharge, when the force of the 

 non-transferable electricity is measured, the contrary ten- 

 dencies for those periods would keep that apparatus in a mo- 

 derately steady and uniform condition for the latter portion 

 of time. 



1251. The particular action described occurs in the shell- 

 lac of the stems, as well as in the dielectric used within the 

 apparatus. It therefore constitutes a cause by which the out- 

 side of the stems may in some operations become charged 

 with electricity, independent of the action of dust or carrying 

 particles (1203.). 



[To be continued.] 



XLIX. Justification of the Contact Theory of Galvanism. 

 By G. Th. Fechner. 



[Continued from p. 21 7-] 



II. Facts 'which relate to the closed circuit. 



1. TT appears according to the theory of contact as if iron, 

 ■"^ which when brought into contact with copper in water 

 or diluted acids exhibits positive electricity, must on the con- 

 trary be positive in all other fluids ; it acts however, never- 

 theless, negatively in a solution of sulphuret of potassium 

 [Sch'iscefelleber). Other examples may be placed by the side 

 of this, in which also the electromotive condition of the metals 

 changes with the consistence of the intermediate fluid, for in- 

 stance, that of tin and copper is in solution of ammonia the 

 reverse of what it is in pure water, and that of copper and 

 lead, in concentrated nitric acid, is the opposite of that in di- 

 luted nitric acid, which immediately obviates the objection, 



