414 Dr. Faraday *s Experimeyital Researches in Electricity, 



be made to pass through the instrument for given portions of 

 time in succession. The whole of the battery evolved 0*9 of 

 a cubic inch of oxygen and hydrogen in half a minute; the 

 forty plates evolved 4*6 cubic inches in the same time, the 

 whole then evolved 1 cubic inch in the half minute; the ten 

 weakly charged evolved 0*4 of a cubic inch in the time given : 

 and finally the whole evolved 1*15 cubic inch in the standard 

 time. The order of the observations was that given : the results 

 sufficiently show the extremely injurious effect produced by 

 the mixture of strong and weak charges in the same battery*. 



1045. In the same manner associations oi strong and *meak 

 pairs of plates should be carefully avoided. A pair of copper 

 and platina plates arranged in accordance with a pair of zinc 

 and platina plates in dilute sulphuric acid, were found to stop 

 the action of the latter, or even of two pairs of the latter, as 

 effectually almost as an interposed plate of platina (1011.), or 

 as if the copper itself had been platina. It, in fact, became 

 an interposed decomposing plate, and therefore a retarding 

 instead of an assisting pair. 



1046. The reversal^ by accident or otherwise, of the plates 

 in a battery has an exceedingly injurious effect. It is not 

 merely the counter action of the current which the reversed 

 plates can produce, but their effect also in retarding even as 

 indifferent plates, and requiring decomposition to be effected 

 upon their surface, in accordance with the course of the cur- 

 rent, before the latter can pass. They oppose the current, 

 therefore, in the first place, as platina interposed plates would 

 do (1011 — 101 S.); and to this they add a force of opposition 

 as counter- voltaic plates. I find that, in a series of four pairs of 

 zinc and platina plates in dilute sulphuric acid, if one pair be 

 reversed, it very nearly neutralizes the power of the whole. 



1047. There are many other causes of reaction, retarda- 

 tion, and irregularity in the voltaic battery. Amongst them 

 is the not unusual one of precipitation of copper upon the zinc 

 in the cells, the injurious effect of which has before been ad- 

 verted to (1006.). But their interest is not perhaps sufficient 

 to justify any increase of the length of this paper, which is 

 rather intended to be an investigation of the theory of the 

 voltaic pile than a particular account of its practical applica- 

 tion. 



liJote, — Many of the views and experiments in this Series 

 of my Experimental Researches will be seen at once to be cor- 



•♦ The gradual increase in the action of the whole fifty pairs of plates 

 was due to ihe elevation of temperature in the weakly charged trough by 

 the passage of the current, in consequence of which the exciting energies 

 of the fluid within were increased. 



