the Radiation from Radioactive Bodies. 
543 
intensity as in the case of the a particles. The Curves III. 
and IT. correspond to I. and II. respectively as regards the 
intensity of the ionization currents. The Curve III. shows 
Fio:. 4. 
/ Z 3 «#• 5 
Time in Minutes. 
no oscillations at all, while IY. shows oscillations but com- 
paratively to a very slight extent. The fact that hardly any 
observable oscillations occurred in the case of ft radiation 
shows, independently of any theory, that the effect observed 
with « radiation is really due to the irregular nature of 
the a radiation, and not to a secondary effect. 
The difference in the shape of the curves is to be expected 
from simple theoretical considerations. It is known that 
the absolute average error in a large number of observations 
for two events P and Q is given by 
where N is the 
e = -+- \/ Npg, 
number of observations 
and p and q 
are the probabilities for the events P and Q respectively. 
If we apply this formula to radioactive changes, taking N 
as the number of atoms present, the number of atoms 
breaking up during a given time r (r being small compared 
202 
