538 
MR. 0. W. RICHARDSON ON THE ELECTRICAL CONDUCTIVITY 
down to ampere. In that case it was found that the leak increased less rapidly 
with the temperature below than above about 180°, so that presumably the ionisation 
present below 180° is not due to the emission of corpuscles from the metal surface. 
In the series of experiments which gave the numbers in the following table the 
pressure of the gas was about 1 '5 millims. 
Reading of 
thermocouple. 
Tempercature, 
centigrade. 
Current, 
amperes. 
Reading of 
thermocouple. 
Temperature, 
centigrade. 
Current, 
amperes. 
170 
o 
427 
1-39 X10-2 
139 
o 
334 
5■14X10-5 
165 
410 
8-34 X10-3 
136 
327 
3-06 X10-5 
160 
393 
8-34 X10-^ 
132 
317 
1-53X10-6 
158 
387 
3-61X10-^ 
129 
310 
5-56 X10-" 
156 
381 
1-65 X10-^ 
123 
296 
l-39x 10-' 
152 
370 
6 •34X10-5 
122 
284 
6-25 X10-s 
145 
350 
l-39x 10-5 
102 
248 
9-72X10-5 
143 
345 
1 -11X10-5 
89 
217 
1-8 xlO-5 
140 
337 
7-0 xl0-« 
— 
— 
— 
Corresponding values of current and temperature have been plotted on the 
accompanying curve (fig. 20) in order to facilitate comparison with the results 
obtained for carbon and platinum. It will be seen that the general appearance of 
the curves is much the same as before. The unit of current is successively multiplied 
by ten as we pass to the right from one curve to the next. 
