250 Dr. Gr. Gore on "Resistance" at the Surfaces 



I have further shown by experiments that, with a thermoelec- 

 tric couple composed of a hot and cold sheet of platinum in 

 dilute nitric or dilute sulphuric acid, " in each of these two 

 couples the total amount of ' surface-resistance ' in the cir- 

 cuit, when one of the junctions was heated, was very much 

 greater in the direction of the current produced than in the 

 opposite one ;" and I inferred that the direction of current 

 was not due to those differences of resistance. And I further 

 stated that several of the results of experiments described in 

 that paper "agree with the conclusion that differences of 

 transfer-resistance are incapable of producing a current, and 

 are essentially unlike differences of electric potential ;" also 

 "that heat decreases such resistance whilst increasing contact- 

 potential in various metal-electrolyte thermoelectric couples.''' 



Lest it should still be supposed that the phenomena to which 

 I have ventured to apply the term " transfer-resistance " are 

 not really of the nature of " resistance," but are effects due to 

 polarization, some kind of counter electromotive force, or 

 other form of opposing difference of electric potential, I have 

 further examined, by means of the following experiments, the 

 question whether the phenomenon I have found can exist 

 independently of such difference. 



A single conclusive adverse fact is sufficient to upset the 

 most fixed theory : if the phenomena termed " transfer-resist- 

 ance " are really due to some form of opposing difference of 

 electric potential, they ought to disappear wherever such 

 difference is absent. 



I have tested this point in the following manner : — By the 

 aid of some tables of " Chemico-electric relations of Metals in 

 Solutions of Salts of Potassium" (Proc, Roy. Soc. 1877, 

 No. 200), and in another on " Some Relations of Heat" &c. 

 (ibid. 1884, No. 233), I selected cases in which two different 

 metals in an electrolyte produced no voltaic current, and 

 examined those combinations of metals and liquid for any 

 differences of " surface-resistance." 



I nearly filled a glass trough, 10*0 centim. long, 2*5 centim. 

 wide, and 3'0 centim. deep, with a solution consisting of 

 about 3 grammes of potassic cyanide (of 92*1 per cent.) and 

 100 cubic centim. of water. In this solution was immersed, 

 near the opposite ends of the trough, at 8*0 centim. apart, a 

 sheet of nickel and one of pure gold, each being l'Oxl'0 

 centim., not varnished on the back, and connected with a 

 graded, dead-beat, Despretz d'Arsonval galvanometer (see 

 i Nature/ vol. xxxi. p. 86), having a resistance of about 150 

 ohms, and I altered the strength of the liquid until all signs 

 of difference of potential ceased. (The sensitiveness of the 



