1878.] 



Contact Theory of Voltaic Action. 



237 



the resistance of the ebonite being" very great, and the loss, therefore, 

 very slow even at high temperatures, and as the specific inductive 

 capacity of ebonite is unknown, we were compelled to make experi- 

 ments to determine the electric capacity of our arrangement. This 

 was very difficult on account of the small area, 45'6 square centims., of 

 the ebonite in contact with the platinum. The result, therefore, which 

 we obtained, and from which we deduced the specific inductive capa- 

 city of ebonite to be 1'7, must only be accepted as very rough, and 

 merely of use in giving us approximate values of the resistance at 

 various temperatures. The number 1*7 seems too small for a compo- 

 sition of india-rubber and sulphur. Consequently, all our calculated 

 values of x may be too large, and ought to be reduced in the ratio 

 of 1*7 to the true specific inductive capacity of ebonite. 



Temperature. — log — x 



r I E 2 ln megohms. 



Q 36° 0-0027 61030 x 10 6 



a 41° 0-0026 63390 x 10 6 



b 46° 0-0031 53160xl0 6 



c 48° -5 0-0038 43370 xlO 6 



d 53° 0-0045 36630 x 10 s 



e 57° 0-0048 34340 x10 s 



f 61° 0-0054 35020xl0 6 



g 64° 0-0057 28920 x 10 s 



h 67° 0-0077 21400xl0 6 



i 68° -5 0-0076 21690 x 10 6 



j 71° 0-0086 19160 x 10 6 



k 73° 0-0093 21560 x 10 6 



1 75° 0-0100 16480xl0 6 



m 77° 0-0112 14720 x10 s 



n 79° 0-0120 13740 x10 s 



o 80° -5 0-0124 13290xl0 6 



p 82° -3 0-0133 12400 x10 s 



q 84° 0-0140 11770 x10 s 



r 85° -6 0-0142 11610 x10 s 



s 87° -0 0-0147 11210 x10 s 



t 88° -6 -0152 10840 x 10 s 



u 90° 0-0153 10770 x10 s 



v 94° -4 0-0175 9419 x10 s 



R 96° -8 0-0170 9696 x10 s 



India- Rubber. 



The relation of conductivity to temperature of a chemically clean 

 piece of india-rubber containing sulphur is given in the curve ST. 

 As the loss was very slow we could not use the auxiliary condenser, 

 and, therefore, had to measure roughly the capacity of the arrange- 



R 2 



