ON THE ELECTRICAL PROPERTIES OF PURE SULPHUR, 
131 
4-942 X 10 13 ohms, and the corresponding specific resistance was 3'578 X 10 25 C.G.S. 
Voltage, 305 volts. The temperature was raised slowly to 96° C. and kept constant 
at this temperature. The resistance decreased very rapidly, and was observed to be 
R=3T98 X 10 10 (p = 2’315 X 10 23 ) before the spot went off the scale and the 
voltage had to be reduced. This is a reduction of, say, one hundred and sixty fold. 
The behaviour of the film was now curious. The temperature being allowed to rise 
from 96° C. to 100° C. in thirty minutes, the conductivity went on increasing so fast 
that the battery voltage required to be continually reduced at 100°, and after thirty 
minutes the conductivity had increased to one hundred times (say) its value at 96°. 
This increase of conductivity did not take place gradually, but by jumps—the 
galvanometer needle was thrown further and further out by sharp jerks which 
continually tailed off only to recommence. This effect went on till the temperature 
of 102° C. was reached, in fifteen minutes, after this the temperature was allowed to 
fall in order to discover whether the change in the sulphur would reverse. This it 
did immediately—the light spot coming back as markedly as it had previously 
moved off. An attempt was then made to reverse the change again, and the 
temperature was slowly raised to 105°, but the resistance still went on increasing. 
This suggested that the plates were coming apart, and on examination when all was 
cold this was found to be the case, for, though no sign of cracking was to be seen, 
the capacity was found, to vary when a tinfoil coated jar placed on the upper plate 
was filled with about 50 lbs. of mercury. The plates were therefore dismounted, and 
the upper one was found to be only held in position by the sulphur round its edges. 
We were pleased to find the capacity test so sensitive and positive. We looked 
carefully too see if there was any indication of a spark having passed, but could find 
no reason for supposing that this had taken place ; we do not think we could have 
missed it if such had been the case. 
The following table will sum up the resistance results. 
