30 
PROF. 0. W. RICHARDSON ON THE EMISSION OF ELECTRONS 
paper. This experiment leaves little doubt as to the reality of the gradual approach 
to the voltage axis in the case of the chemical effect. It is the more convincing because, 
during the determination of the two points at 0 and — 0-5 volts, the standard current 
at — 3 volts was increased to about 450 divisions per two minutes (cap. 0 -01 mfd.); 
whereas, during the determination of the rest of the points in fig. 15, the standard 
current varied between 20 and 30 divisions per two minutes, with the same capacity. 
Notwithstanding this very great change in the absolute value of the standard current, 
the two end points are seen to fall on the same curve as the rest. The actual numerical 
values may be of interest and are given in the next table:— 
Table VII. — Chlorine. 
Applied volts (voltmeter 
readings). 
2-5 
2-0 
1-6 
1-3 
1-0 
0-8 
0-5 
0 
Chemical effect currents 
(scale divs. per 2 mins.) 
18 
11 
6 
3 
2 
1 
8 
2 
Relative chemical currents 
0-78 
0-43 
0-24 
0-116 
0-068 
0-05 
0-025 
0-004 
Relative photo-electric 
currents . 
0-51 
0-16 
0-00 
0-00 
0-00 
0-00 
0-00 
The sensitiveness of the electrometer was 570 divisions per volt, the added capacity 
0 -01 mfd., making the total capacity equal to 0 -01012 mfd. ; the pressure was 0 -002 mm. 
throughout and the pump running continuously in this experiment. 
