Forces in Voltaic and Thermoelectric Piles. 267 



inductively, is monarch of all it surveys, including the whole 

 of electrochemistry and thermoelectricity under its sway. 

 If Ayrton and Perry believe all this, or rather since they 

 believe all this, their energy in experimenting on it, and the 

 importance they have attached to questions of priority in 

 connection with it, are no longer surprising. 



It will be understood, then, that my first contention is that 

 the function fit), characteristic of a thermoelectric circuit, has 

 no relation whatever to the Volta-effect. The function f(t) is 

 something connected with the properties of the metals them- 

 selves : the Volta-effect is caused by an action between each 

 metal and the medium surrounding it. The one is physical, 

 the other is chemical. This, of course, is as yet an open 

 question ; but any way it is plain that, before one can legiti- 

 mately assert a connection between such apparently distinct 

 things, he should be prepared with full and satisfactory proof. 

 I am not aware that Profs. Ayrton and Perry have attempted 

 any proof; it would seem rather that they have been deceived 

 by a jingle of names, as thus : — f(t) is a potential function cha- 

 racteristic of two metals, the Volta-effect is a difference of 

 electrical potential in the air near two metals, hence f(t) and 

 the Volta-effect are identical. If they have any stronger basis 

 for their assumption than this singular syllogism I shall be 

 glad to hear it. Till then I must regard it as a baseless con- 

 jecture ; and I believe that with as much right they might 

 say that/(£) meant the specific gravity, or elasticity, or thermal 

 conductivity of the two metals, as assert that it means their 

 Volta-effect, at the specified temperature. 



Nevertheless, although the Volta-effect is some hundred or 

 thousand times greater than any concerned in thermoelec- 

 tricity*, though it has no relation with bismuth and antimony 

 or the thermoelectric order of metals, though it is plainly 

 related to the affinities of metals for the oxygen in which they 

 are immersed, being demonstrably connected with their che- 

 mical properties and calculable very approximately from them; 

 notwithstanding all this, Profs. Ayrton and Perry, and those 

 who think with them, believe that a thermoelectric current is 

 propelled solely by the difference of two forces at the junc- 

 tions, and that these forces are the same as those which Volta 

 and Kohlrausch and Ayrton and Perry have observed and 

 measured electrostatically in the air near metals in contact. 



* Profs. Ayrton and Perry will reply that the constant a is indepen- 

 dent of thermoelectricity and may have any value they like, however 

 great. So it may as a matter of mathematics ; "but what proof is there 

 that the value they like is its correct value ? The "burden of proof assu- 

 redly rests with them. 



