of Gamma Rays from Radium B and Radium C. 727 



This will be shown to be due to the fact that two penetrating 

 types of radiation are present, the relative ionizations of 

 which differ in air and in methyl iodide. 



After passing through about 6 cm. of air, the absorption 

 curves, both for air and methyl iodide, became exponential 

 with a value of the absorption coefficient //, = 0*1 15, or 

 fju\D — 00424, where D is the density. This is practically 

 identical with the absorption coefficient found by Russell 

 and Sodtly for the 7 rays from radium C after passing 

 through 2 cm. of lead. The absorption curve of the 7 rays 

 for thicknesses of aluminium between *05 and 7 cm. is shown 

 in fig. 3, where the ionization itself is plotted as ordinates. 



Fig. 3. 

 52 



40 



32 



I 



^.24 



16 













































"*^. % . 



'*»*». 

















* r >v. 



"'*"""*= 



'"-^^g 



















"-**«««^-, 

















3 4-5 



CMS OF/lLUM/N/UM. 



After 6 cm. of aluminium the curve is exponential with a 

 value of /4 = *115. It will be shown later that the absorption 

 curve in aluminium of the 7 rays from, radium C is practi- 

 cally exponential from the beginning with a value of 

 //. = 0*115. Consequently, if the curve is produced back- 

 wards from a thickness of 6' cm. corresponding to radiations 

 for which yLt = *115, it gives the ionization duo to the 7 rays 

 from radium alone. This is shown in the dotted cur\e 

 fig. 3. If the difference between the ordinates of these 

 curves be plotted, it is found to be an exponential curve with 

 a value of /z, = 0*51 in aluminium. This radiation is un- 

 doubtedly due to radium B. A similar result was obtained 

 when air was used instead of methyl iodide, but the effect 

 due to this radiation is relatively smaller compared with that 

 from radium (J. 



3 D2 



