412 Dr. Faraday's Experimental Researches in Electricity, 



cells, and how influential in diminishing the force of the bat- 

 tery this effect must be. 



1039. In the ordinary voltaic pile, the influence of this 

 effect will occur in all variety of degrees. The extremities of 

 a trough of twenty pairs of plates ot Wollaston's construction 

 were connected with the volta-electrometer, fig. 11. (711.), of 

 the Seventh Series of these Researches*, and after five minutes 

 the number of bubbles of gas issuing from the extremity of 

 the tube, in consequence of the decomposition of the water, 

 [was] noted. Without moving the plates, the acid between the 

 copper and zinc was agitated by the introduction of a feather. 

 The bubbles were immediately evolved more rapidly, above 

 twice the number being produced in the same portion of time 

 as before. In this instance it is very evident that agitation 

 by a feather must have been a very imperfect mode of restor- 

 ing the acid in the cells against the plates towards its first 

 equal condition ; and yet imperfect as the means were, they 

 more than doubled the power of the battery. The first effect 

 of a battery, which is known to be so superior to the action 

 which the battery can sustain, is almost entirely due to the 

 favourable condition of the acid in contact with the plates. 



1 04-0. A second cause of diminution in the force of the voltaic 

 battery, consequent upon its own action, is that extraordinary 

 state of the surfaces of the metals (969.) which was first de- 

 scribed, I believe, by Ritter -]-, to which he refers the powers 

 of his secondary piles, and which has been so well experi- 

 mented upon by Marianini, and also by A. De la Rive. If 

 the apparatus, fig. 31. (1036.), be left in action for an hour 

 or two, with the wire 3 in contact with the plate jp, so as to 

 allow a free passage for the current, then, though the contact 

 be broken for ten or twelve minutes, still, upon its renewal, 

 only a feeble current will pass, not at all equal in force to 

 what might be expected. Further, if P* and P^ be connected 

 by a metal wire, a powerful momentary current will pass from 

 P^ to P^ through the acid, and therefore in the reverse direc- 

 tion to that produced by the action of the zinc in the arrange- 

 ment; and after this has happened, the general current can 

 pass through the whole of the system as at first, but by its 

 passage again restores the plates P^ and P' into the former 

 opposing condition. This, generally, is the fact described by 

 Ritter, Marianini, and De la Rive. It has great opposing 

 influence on the action of a pile, especially if the latter consist 

 of but a small number of alternations, and has to pass its cur- 

 rent through many interpositions. It varies with the solution 



[* Lond. and Edinb. Phil. Mag., 1834.— Edit.] 

 t Journal de PhysiquCy Ivii. p. 349. 



