Electromotive Forces in Voltaic and Thermoelectric Piles. 263 



constants would have to be introduced, which I have left out 

 because they are unnecessary. 



The following is a sketch of the machine represented in the 

 act of solving the equation ^ 3 — 20,2? — 200 = 0. 



(One of these instruments is to be seen at the loan collec- 

 tion, South Kensington, where it will remain permanently.) 



XXXVII. On the Seat of the Electromotive Forces in Voltaic 

 and Thermoelectric Piles. Reply to Professors Ayrton and 

 Perry. By Dr. Olivek Lodge *. 



I AM glad that Professors Ayrton and Perry have reprinted 

 their criticism of my paper to the Society of Telegraph 

 Engineers at length in the Philosophical Magazine — with a 

 few emendations and additions doubtless, but with no sub- 

 stantial alterations ; for though I replied to the greater part 

 of it at the time, as reported in the ' Journal' of the Societyf, 

 there are one or two points which have been now brought 

 more prominently and distinctly forward, notably a more 

 precise statement of their thermoelectric views, first appended 

 by Prof. Perry as a footnote, by Prof. Ayrton as a descrip- 

 tion of experiments with hot and cold mercury, to their 

 respective communications in the Journal of the Society for 

 last year. The difference between our modes of regarding 

 electrical phenomena are so fundamental, and the smaller 

 points at issue so numerous, that it would be easy to carry on 

 the controversy by harassing each other in all manner of places 



* Communicated by the Author. 

 + April 1885. 



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