20 



JO 



/^ = 2J.5 



IQ 



« = July 3 

 o - Jult^ 5 



J _1_ 



J I 



,0/ 



.03 OS 



cm. oluminiurn 



.07 



Fig. 1. Absorption of radiations from radium by aluminium measured by their 

 effect upon the egg of Nereis. Thickness of aluminium measured in cm. along 

 the abscissa. Per cent of transmitted radiation measured logarithmically along 

 the ordinate. The dotted line indicates the absorption of 7-rays. 



27 



