OHM ON THE GALVANIC CIRCUIT. 465 



changes to the extent of the entire tension situated at that 

 place. 

 b. If any single place of the circuit is induced by any circum- 

 stance whatsoever to change its electric condition, all the 

 other places of the circuit change theirs at the same time, 

 and the same amount. 

 The constant c is in the rule determined by ascertaining the 

 electroscopic force at any place of the circuit. If, for instance, 

 we designate by t/ the electroscopic force at a place of the circuit, 

 the reduced abscissa of which is y', then, in accordance with the 

 general equation above stated, 



where O' represents the sum of the tensions abruptly passed 

 over by the abscissa y'. If we now subtract this equation, valid 

 for a certain place of the circuit, from the previous one belong- 

 ing in the same manner to all places, we obtain 



u-u' = ^{y-y')-{0-0'), 



in which nothing more remains to be determined. 



If the circuit, during its production, is exposed to no external 

 deduction or adduction, the constant c must be sought for in 

 the circumstance that the sum of all the electricity in the cir- 

 cuit must be zero. This determination is founded on the fun- 

 damental position, that, from a previously indifferent state, 

 both electricities constantly originate at the same time and in 

 hke quantity. To illustrate, by an example, the mode in which 

 the constant c is found in such a case, we will again consider the 

 case treated of in § 16. In the portion P of that circuit, u is 



generally = ^ y + c, where y = — , and in the portion P' we 



have constantly m = ^ y — a' + c, where y = — j — ^ + A. Since 



now the magnitude of the element, in the portion P, is aid x 

 or xeo^ dy, but in the portion P' is co' d x or x! eo'^ dy, we ob- 

 tain for the quantity of electricity contained in an element of 

 the first portion 



and for the quantity contained in an clement of the second 

 portion 



