DISCHARGE OF NEGATIVE ELECTRICITY FROM HOT PLATINUM. 
255 
Temperature 1310° C. 
Pressure. 
Potential difference. 
Current. 
millims. 
volts 
amperes 
784 
784 
168xlO- 8 
385 
385 
83 x10-8 
183 
184 
35 x10-8 
71 
72 
26 xlO- 8 
46 
46 
26 xlO' 8 
23 
30 
16xlO" 8 
10 
20 
36x10-8 
0-85 
20 
78 xlO' 8 
0-45 
20 
60xlO” 8 
0-24 
20 
46 xlO” 8 
0-13 
20 
38 xlO" 8 
0-068 
20 
40 xlO" 8 
0-006 
20 
40 x10-s 
o-ooo 
20 
40xlO" 8 
It will be seen that below 200 millims. the current does not vary much with the 
pressure. The rise at 0’8 millim. is probably due to ionisation by collisions. In the 
previous paper the following results were obtained with new wires : — 
Temperature 1340° C. 
Pressure. 
Potential difference. 
Current. 
Current 
Pressure ’ - 
millims. 
volts 
amperes 
766 
40 
3 x 10“ 3 
3-9 x lO” 6 
450 
40 
1 • 5 x lO- 3 
3-3 x10- 6 
156 
40 
2-2 x10~ 4 
1-41x10“ 6 
14 
40 
6 x lO" 5 
4-3 xl0- c 
0-11 
40 
4 x lO" 6 
36 xlO- 6 
0-0013 
40 
5 x lO” 8 
39 xlO" 6 
It ought also to be said that the last two results in this table were obtained with a 
wire which had never been in hydrogen at more than a small fraction of a millimetre 
pressure. The first four results were obtained by letting hydrogen in, keeping the 
temperature constant. Comparing the two tables, we see that there is a surprising 
difference between them. The first table shows very little variation with the 
pressure, while the second shows that the leak increased 10 5 times when the pressure 
was increased 10 6 times. 
The difference between the old results and the new ones is so large that it was 
considered worth while to repeat the old experiments. A new wire was put up and 
heated in air, and was found to give a small current. The air was then pumped out 
