Secondary y Radiation, 



235 



more secondary radiation than does a similar mass oi zinc ; 

 and this is in accordance with the results obtained for 



X rays. 



Fig. 4. 



The zinc radiators were increased in thickness from 0'5 cm. to 2 5 cm., 

 and the lead radiators from 0*085 to 1'6 cm. 



MASS Kfi owr ARt'A 



Electroscope in position K, 



