458 Royal Society : — Prof. Faraday on the Voltaic Pile. 



gives, cause that no action take place, unless a current be formed and 

 the hydrogen be transferred to a distance, whilst the forces circulate 

 in what is called the electric current. Placing the origin of the cur- 

 rent in the chemical action, which yet could be thus virtually restrained 

 unless the circuit was completed, the author expected to find a state 

 of tension in the chemical or electrical forces before metallic contact 

 was made or the circuit perfect, and was able at last to prove this most 

 fully by obtaining an electric spark between two plates of different 

 metals immersed in acid before they came in contact. This fact, with 

 the former one of decomposition, fully proved that contact was not 

 necessary to the production of the electricity in the voltaic pile. 



The second part of this memoir contains an investigation of the fol- 

 lowing important points : namely, whether electrolytes could resist 

 the action of an electric current if below a certain intensity ; whether 

 the intensity at which an electric current might cease to act would be 

 the same for all bodies ; and also whether the electrolytes, when thus 

 resisting decomposition, would conduct the electricity as a metal or 

 charcoal does, after they ceased to conduct as electrolytes, or would 

 act as insulators. It is first proved with regard to water, that a cur- 

 rent of a certain intensity is necessary for its decomposition, but that 

 a current of a lower intensity is conducted by it j and that with such 

 feeble currents, pure water conducts as well as acidulated water or 

 saline solutions. The same condition of a certain necessary intensity 

 of current was found to hold good also with sulphate of soda in solu- 

 tion, with fused chloride of lead and other bodies, and is considered 

 by analogy as extending to all electrolytes. 



In the third part of the paper, associated voltaic circles, or the 

 voltaic battery, is examined. From the principles and facts stated in 

 the preceding parts, it appears evident that the association of many 

 pairs of plates, equal in size, nature and force, cannot by any possi- 

 bility increase the quantity of electricity above that which any single 

 pair in the series could produce, taking the quantity of zinc oxidized 

 at any one plate as the standard of development. It is easy, by using 

 amalgamated zinc, to construct a battery in which no action shall 

 take place on the metals, except the extremities be in communication. 

 If a battery of ten pairs of plates be thus communicated, there is of 

 course oxidation of each zinc plate, and a current of electricity cir- 

 culates. If the contact of the extremities be continued until a cer- 

 tain quantity of zinc has been dissolved at any one plate, it will be 

 found that an exactly equal quantity has been dissolved at each of the 

 other plates ; and that a certain quantity of electricity has passed, 

 which can be taken cognizance of by the volta-electrometer. But 

 should nine of the pairs of plates be removed and the battery be re- 

 duced to a single pair, yet when the given quantity of zinc had been 

 dissolved there, as much electricity would have gone round the circuit 

 as with the whole number of ten pairs, and during the evolution of 

 which ten times the quantity of zinc had been oxidized. 



This result, already proved by electro-magnetic experiments, is 

 shown to be a necessary consequence of the construction of the pile 

 and the manner in which its forces act. The electricity evolved by 



