42G 
DE. IIAEOLD A. ^YILSOX OX THE 
The character of the relation between the current and temperature, however, was 
not sensildy affected Ijy this ageing of the tube. The results of the first series oi 
observations of this kind done are shown in diagram No, 6. The tube had then 
])een used at intervals for aljout a fortnight. 
The gradual falling off in the conductivity is shown by the numbers in the 
following table, which give the values of the currents at several temperatures 
obtained on different dates :— 
J uly G 
„ 10 
„ 30 
Current through Air in Amperes. 
E.M.F. 800 volts. 
Outer tube negative. 
Temperature 800°. 
. . 8 X 10“'^ 
OT 
900°. 
40 X lO-*^ 
11 
07 
1000 °. 
120 X 10“® 
50 
2-5 
1100 °. 
400 X 10-*^ 
140 
8 
Diao'ram No. 7 shows the results obtained with an E.M.F. of 240 volts, the outer 
O 
tube being the negative electrode. Date, July 29. 
