.382 Mr. W. K. Bridgman on the Theory of the Voltaic Pile. 



down, exerts only a trifling amount of force upon the secondary 

 metal ; but the instant the connexion is made through the elec- 

 trodes, the whole of the electrolyte enclosed between the metal 

 poles becomes electrolyzed and its ions separated, increasing the 

 electromotive force in like proportion. 



The contact of two dissimilar metals in air does not represent 

 the two dissimilar metals of the battery, but simply corresponds 

 with the two electric states of the primary metal alone. Scarcely 

 any two metals have an equal affinity for oxygen, and any two of 

 these placed together at once become polar and determine the 

 mixed gases of the atmosphere to their respective poles. The 

 combination which then takes place between the more oxidizable 

 metal and the oxygen evolves or induces a certain amount of elec- 

 trical force by which the combined metals and the adjacent por- 

 tions of air become charged respectively positive and negative. 



In the chemical action which takes place with the polarized 

 primary alone, it was stated that the greatest amount of chemical 

 action was found to occur near to the surfaces of air and acid in 

 contact. The determination of oxygen from the atmosphere to 

 the positive metal, combined with the electrolysis of the elec- 

 trolyte, was here exhibited in the greater extent of oxidation 

 and solution of the metal, and the less degree exhibited in the 

 metal which had been partly excluded from the atmosphere. 



That no current can be obtained from the contact of two me- 

 tals in air is due to the fact that the atmosphere is not an elec- 

 trolyte. It was distinctly defined by Faraday that no current is 

 obtainable from chemical action unless by the decomposition of 

 an electrolyte, the cation from which being absolutely indispen- 

 sable for creating the tension of the secondary metal. The 

 oxygen of the air having no cation to part with, is therefore un- 

 provided with the means of accomplishing it. 



The fact of this non-combination of the elements of the atmo- 

 sphere constitutes the means of initiating the action of the bat- 

 tery. The electrolyte of the battery being held together by a 

 combining force, cannot of its own accord separate itself into its 

 component elements, but requires the introduction of some anta- 

 gonistic force equivalent to or counterbalancing its cohesion, so 

 as to set its elements free — to repolarize them in fact ; this is 

 accomplished by the introduction of the polarized metal, which, 

 rendering the force equal on all sides, electrohjzes the water and 

 allows its elements to rearrange themselves according to the 

 polar influences then presented to them. 



Were the atmosphere an electrolyte, it would then require 

 some antecedent to effect its electrolysis, as the action must 

 begin by a non-combination of elements, or a condition requiring 

 no antecedent. 



Norwich, September 18(19. 



