1906-7.] Photo-Electric Discharge from Platinum. 
125 
Time, 
7th March. 
Photo-electric current in 
Heating 
current 
in amperes. 
Temperature 
arbitrary units. 
in °C. 
2.30 p.m. 
56 57 58 
} 0 
15° 
to 2.50 p.m. 
57 58 58 
2.51 
Heating current switched on. 
) 1 
( 
2.52 
65 
2.55 
66 
7 
78° 
2.58 
66 
i 
3.1 
65 
) 
3.2 
Heating current increased. 
3.3 
70 
3.6 
3.8 
69 
70 
10 
160° 
3.11 
69 
3.13 
69 
■ 
3.14 
Heating current increased. 
N 
3.15 
64 
3.174 
56 
3.20" 
53 
3.22 
50 
3.25 
48 
3.27 
3.32 
46 
43 
- 13 
250° 
3.35 
40 
3.51 
35 
3.53 
31 
3.56 
29 
4.16 
28 
4.18 
29 
4.19 
1 Heating current switched off. 
\ 
4.20 
35 
4.23 
4.26 
39 
39 
.25° to 16° 
4.42 
44 
0 
4.45 
45 
8th Mar., 
4.10 p.m. 
1 60 
l 15° 
4.13 
) 60 
> 
J 
The gradual diminution in the photo-electric current with time at 250° 
is also shown by the curve in fig. 4. 
This curve is a logarithmic curve, and can be represented by the equation 
C-27 = 69e-°-° 54i 
where C is the photo-electric current in the above arbitrary units, and t is 
the time in minutes. 
If log (C — 27) is plotted against t, a straight line is obtained — shown in 
fig. 4a. 
