430 OHM ON THE GALVANIC CIRCUIT. 



2F' ui^clx dt, 

 ax 



and if we take, instead of the function F' dependent on the na- 

 ture of each single body, its value — , this expression, since «' 



is evidently here d <r, changes into 



^1 du , ^ 



2 k' u -r~ d t : 

 d X 



or if we reduce the moment of action x', referring to the magni- 

 tude of the section w, to the unit of surface, and at the same 

 time extend the action to the unit of time, into 



„ , du 



2 x' cou ^— , 



d X 



where the present x' represents the magnitude of the moment 

 of action reduced to the unit of surface. If we write this latter 

 expression thus : 



„ x' du 



2 X COM -y— , 



X d X 



in which x denotes the absolute power of conduction of the 



d tc 

 circuit ; and if we substitute for x w -j—, by which, according to 



the equation [b) in § 12, the magnitude of the electric current 



x' . . 

 is expressed, the sign S chosen for it, and i instead of—, it is 



changed into 



2iuS. 



We hence perceive that the force, with which the individual 

 discs in the circuit tend to move, is proportional, both to their 

 innate electroscopic force, and to the magnitude of the current; 

 and that this force alters its direction at that place of the cir- p 

 cuit. where the electricity passes from the one into the opposite 

 state. And here occurs the circumstance which must not be 

 overlooked, that this expi-ession still holds, even when the elec- 

 troscopic force u of the element M is changed in the moment 

 of action, by any causes whatsoever, into any other abnormal 

 U, while the electroscopic forces of the adjacent particles con- 

 tinue the same ; only that in this case the value U must be 

 substituted for u in the expression 2iuS. It must also be ob- 

 served, that the expression 2 iuS which we have found refers to 

 the whole extent of the section cu, which belongs to that part of 



