546 
Dr. Hans G-eiger on the Irregularities in 
5*8 sec. is thus ±68 a particles or transformed into divisions 
= ± aK = +3'1 divisions. 
The figures in the following table are all calculated in the 
same way as indicated in the above example. The difference 
between the theoretical and experimental error is about 
15 per cent. 
Intensity of 
the radiation. 
Absolute error determined. 
Theoretically. 
Experimentally. 
4500^ 
mm. 
2700 „ 
1100 ... 
500 „ 
100 „ 
6-4 div. 
4-9 „ 
3-1 ,, 
2-1 „ 
09 „ 
5'4 div. 
44 „ 
2-9 „ 
2-1 „ 
13 „ 
The agreement is better than one would expect considering 
the conditions of the experiment and the uncertainty of the 
data from which the number of a particles is deduced. A 
slight correction ought also to be made since the electrometer 
needle was not quite dead-beat. The agreement between 
theory and experiment is quite as close if the error is deter- 
mined by measuring the magnitude of the oscillations of the 
electrometer-needle for any convenient time, for example, 
each half minute, instead of the time of swing of the 
electrometer, viz. 5'8 seconds. 
Kohlrausch (loc. cit.) did not find a numerical agreement 
between the theory and his experiments, but this seems to be 
due to an incorrect use of the formula, since on calculating 
the error as above from his data, quite a close agreement 
(10 per cent.) is obtained for saturation currents. If the 
current is not saturated, as was the case in some of Kohl- 
rausch's experiments, the above formula cannot be applied. 
For if the current is only half saturated, half of the ions 
produced from each a particle are lost by recombination ; 
consequently each a particle produces only one half of its 
effect under ordinary conditions of saturation. Taking this 
fact into consideration, a close agreement between theory and 
experiment was also found by calculating the data given by 
Kohlrausch for non-saturated currents. 
