368 Prof. R. B. Clifton on the Difference of Potential 



The unsatisfactory nature of the explanation of voltaic action 

 given in modern treatises on electricity has induced Profes- 

 sors Ayrton and Perry to undertake the investigation to 

 which they draw attention in their letter ; and the same cir- 

 cumstance led me to give special attention to the subject; 

 we even refer to the same passage in the textbook by Pro- 

 fessor Fleeming Jenkin as an instance of statements requiring 

 further explanation. It is therefore not extraordinary that 

 there should be a great resemblance between the series of 

 metals and liquids selected for examination by the two Profes- 

 sors and by myself; but as they were working perfectly inde- 

 pendent of me, and I of them ; the claim of priority seems to 

 be devoid of meaning. 



I shall not attempt to discuss the question of priority ; it is 

 a matter in which I do not feel the slightest interest ; but as 

 Professors Ayrton and Perry state that I appear to have com- 

 menced my earliest experiments on the subject several months 

 after the Meeting of the British Association at Glasgow in 

 1876, I think it better, in order to avoid any difficulty in the 

 future, to mention that I began to give special attention to 

 this subject in 1874; and although frequent interruptions 

 prevented me from making much progress, all the principal 

 results communicated in my paper were obtained before the 

 summer of 1876, and were introduced into my lectures deli- 

 vered during Michaelmas Term 1876, and Hilary Term 1877. 

 In my paper I have only given some of the latest quantitative 

 determinations which I made — partly because I considered 

 them the best, but more especially because I had, in making 

 them, employed Clark's standard cell, to the variation of 

 which I wished to draw attention. In my earlier experiments 

 I had used a Daniell's cell. 



The method of investigating the difference of potential 

 arising from the contact of different substances, employed by 

 Professors Ayrton and Perry, is quite distinct from that which 

 I adopted, so far at least as I am able to judge from the 

 description without the drawing, which I have not yet seen. 



Their method, which seems to me both ingenious and novel, 

 possesses the great advantage of permitting two liquids to be 

 treated in the same way as two solids, or as a solid and a 

 liquid. The method which I adopted is essentially the same 

 as that employed by Kohlrausch in the case of two metals ; 

 but the condenser was furnished with horizontal plates, for one 

 of which a vessel of liquid could be substituted. The only 

 changes which I introduced consist in the arrangements for 

 adjusting and moving the opposed plates, in the mode of in- 

 sulating, and in the form of kev used with the condenser. 



