148 Dr. G. Gore on the Relations of Surface- resistance 



The electrodes faced each other at about 5*0 cm. apart in the 

 respective liquids in a glass cup, the one which was positive 

 in the thermo-couple being used as the anode ; and the 

 strengths of current employed were the same as the thermo- 

 electric ones, because I have found that an alteration of strength 

 of current affects the amount of " transfer- resistance/' One 

 terminal of a Thomson's reflecting-galvanometer of 3040 ohms 

 resistance was connected with the slider ; and the other con- 

 nected, first to the anode (or cathode), and then to a vertical 

 platinum wire (or idle electrode) immersed in the liquid close 

 to the anode (or cathode) but not touching it ; a balance being 

 obtained in each case by moving the slider. 



In the dilute nitric acid, with a current of '00004 ampere, 





At 14° C. 



At 95° C. 



At the anode . 



. 49266 ohms. 



531 ohms 



At the cathode 



. 29784 „ 



494 „ 



By a rise of temperature, therefore, of one of the pieces of 

 platinum of the thermoelectric couple 81 Centigrade degrees, 

 the amount of " surface-resistance " of that piece was reduced, 

 as a cathode or in the direction of the thermoelectric current, 

 98*34 per cent., and in the opposite direction, or as an anode, 

 98*92 per cent.; and the total "surface-resistance" in the 

 circuit was also reduced 37*05 per cent, in the direction of 

 that current, and 61*65 per cent, in the opposite one. 



The results also show that the cold platinum offered 39 '55 

 per cent., and the hot platinum 6*97 per cent., less amount 

 of " surface-resistance "as a cathode than as an anode ; also 

 that the total amount of such " resistance " in the two 

 directions in the circuit, when one of the junctions was heated 

 to 94° C, was 64*14 per cent, greater in the direction of the 

 thermoelectric current produced than in the opposite one. 



In the dilute sulphuric acid, with a current of *00001 

 ampere, the amounts of " surface-resistance " were : — 



At 14° C. At 95° C. 



At the anode . . . 63500 ohms. 3848 ohms. 



At the cathode . . 18350 „ 2152 „ 



By a rise of temperature, therefore, of one of the pieces of 

 platinum of the thermoelectric couple 81 C. degrees, the 

 amount of ** surface-resistance " of that piece was reduced in 

 the direction of the thermoelectric current, or as a cathode, 

 88*27 per cent., and in the opposite direction, or as an anode, 

 93*94 per cent.; and the total "surface-resistance" in the 

 circuit was also reduced 19*79 per cent, in the direction of 

 that current, and 72*88 per cent, in the opposite one. 



