Absolution of y Rays, 



605 



In this equation I]/I 2 is the ratio of ionizations in the electro- 

 scope when thicknesses n\ and x 2 are used. The thicknesses 

 are given in the bottom row o£ the tables. 



Fig. 4. 



Fig. 5. 



10 12 



cms cf F&. 



As will be seen from the curves, the results may be sum- 

 marized as follows : — 



(1) The absorption coefficient in aluminium for the primarv 

 7 rays decreases gradually with increasing thickness up to 

 6'6 cm. aluminium, and is then practically constant up to 

 16 cm., while that in iron continually decreases with 

 increasing thickness. 



PJiil Mag. S. 6. Vol. 27. No. 160. April 1914. 2 S 



