[EVE] SECONDARY y RAYS DUE TO THE y RAYS OF RADIUM C 13 



Hence, the secondary y rays due to the primary y rays, using lead, 

 iron or brick as secondary radiators, are absorbed to a degree approxi- 

 mating to that of the primary y rays of actinium. It would be inter- 

 esting to examine the secondary y rays due to the primary y rays of 

 actinium. These would probably be absorbed even more readily and 

 approximate more closely to the X rays. The effect would be dif- 

 ficult to obtain except with a considerable quantity of actinium. 



The reasons for considering the penetrating secondary raj's to be 

 of the y type, and not of the kathode, are as follows: — 



1 . There is a well marked bend in the absorption curves shown in 

 the diagrams. This change of character is also well marked when the 

 logarithms of the ordinates are plotted. 



2. The primary rays penetrate several centimetres in substances 

 such as brick or slate; some of the secondary rays emerge from that 

 depth and will then penetrate several millimetres of lead. 



3. The values of the coefficients of absorption by lead of these 

 penetrating rays equal about 4, or nearly the value of the coefficient of 

 absorption by lead of the primary X rays of actinium. 



4. If the secondary radiator, such as brick, be placed in a strong 

 magnetic field, the ionization current in the electroscope, due to the 

 penetrating secondary radiation from the brick, caused by a rays, is 

 unaffected by the absence or presence or direction of the magnetic field. 



The laws which govern the magnitudes of the secondary y radia- 

 tion are not j^et clear. 



If possible, further experiments will be made using different 

 screens, radiators and cylinders enclosing the radium. 



