494 OHM ON THE GALVANIC CIRCUIT. 



In both cases a positive value of the expression shows that 

 the pressure takes place in an opposite direction to that of the 

 abscissae ; a negative value, on the contrary, indicates that the 

 pressure is exerted in the direction of the abscissae. To deduce 

 from these individual tendencies of the constituents the force 

 with which both endeavour to separate from each other, we 

 must remember that this force is given by the twofold differ- 

 ence between the quantities of motion which each constituent 

 would of itself assume, were it associated to the other by no 

 coherence, and those quantities of motion which each con- 

 stituent must assume were it strongly combined to the other. 

 We thus readily find for the decomposing force of the cii-cuit 

 the following expression : 



. , mji — na 



4t. z (l — z) . -^^-r, -^ . o, 



^ ' a.z + j3 {1 —z) ' 



from which we learn that the decomposing force of the circuit 

 is proportional to the electric current, and also to a coeffi- 

 cient dependent on the chemical nature of each place of the 

 circuit.. 



If this expression has a positive value, it indicates that the 

 separation of the constituent A takes place in a contrary di- 

 rection to that of the abscissas, that of the constituent B in the 

 direction of the abscissae ; but if this expression has a negative 

 value, it denotes a separation in the reverse direction. It is 

 besides evident, at first sight, that the decomposing force of 

 the circuit is constantly determined by the absolute value of the 

 expression. 



If « = /3, the decomposing force of the circuit changes into 



4i .z {l—z) {m — n) .S. 



1{ m z + n [l — z) = 0, i. e. if the latent electroscopic forces, 

 existing in the united constituents, are equal and opposed ; or, 

 what is the same, if the body, situated in the disc M, is per- 

 fectly neutral, in which case m and n have constantly opposite 

 values, we obtain, for the decomposing force of the circuit, the 

 following expression : 



4 ^ . . S. 



m —n 



The form of the general expression found for the decompos- 

 ing force of the circuit shows that this force disappears ; first, 

 when S = 0, i. e. when no electric current exists ; secondly, 



