OHM ON THE GALVANIC CIRCUIT. 477 



and that it at last entirely vanishes ; the permanent state of the 

 circuit has then occurred. This moment can, as is evident from 

 the form of the expression, be retarded by a diminished power of 

 conduction, and in a far greater degree by an increased length of 

 the circuit. 



This expression found for u, however, holds perfectly only 

 so long as the circuit, which we have supposed, is not induced 

 by any external disturbance to change its natural state. If 

 the circuit is at any time compelled by any external cause, for 

 instance, by deductive contact at any place, to approximate to 

 an altered permanent state, the above method has to undergo 

 some changes, w hich I intend to develope on another occasion. 

 I will, moreover, observe, that it is in this last class of galvanic 

 circuits, in which the peculiar phaenomena of dry piles, and, in 

 general, of circuits of unusually great length, have to be sought 

 for ; to which class likewise belong the circuits of very great 

 length employed in the experiments of Basse, Erman, and Aldini, 

 if the influence of their great length be not annulled by an in- 

 creased goodness of conduction, or by an increased section. 



C. Phaenomena of the Electric Current. 



24. According to what was advanced in paragraph 1 2, the 

 magnitude of the electric current, in a prismatic body, will in 

 general be expressed for each of its places by tht equation 



where S denotes the magnitude of the current, and u the elec- 

 troscopic force at that place of the circuit whose abscissa is x, 

 while o) represents the section of the prismatic body, and x its 

 power of conduction at the same place. To connect this equa- 

 tion with the general equation found in § 18 for any circuit, 

 composed of any number of parts, we write it thus: 

 c, du dy 



ay ax 



and substitute for ~j~ the value -p resulting from that general 



equation, and for -r^ the value — easily deducible from the 

 ax X CO 



same paragraph, both which values are valid for each place. 



