26 M‘CievLtanp—TZhe Energy of Secondary Radiation. 
heterogeneous as the experiments on their absorption by matter, made in the 
usual way, would indicate. Still, a comparison of the above table with the 
results of such experiments shows that after we have corrected for the error in 
the experiments introduced by the secondary effects, there is left a considerable 
decrease of the absorption coefficient as the thickness of the substance traversed 
increases. 
It is hoped to publish shortly further results on the passage of B radiation 
through matter. 
In conclusion, I have much pleasure in thanking Mr. F. E. Hackett, m.a., 
for valuable assistance in the work described in this paper. 
