Different Types of Beta Rays. 149 



a way that the pencils of rays from the radium were directed 

 straight into the ionizing-chamber. The saturation currents 

 for magnetic fields in both directions, when the 8 '14 mms. of 

 aluminium alone covered the chamber, were then measured. 

 From the values of these currents, which are recorded in 

 Table XX., it will be seen that the ionization corresponding 



Table XX. 



Thickness of aluminium over the top of chamber = 8' 14 mms. 

 Radium vertically above chamber. 



j8 rays deflected towards 



j f3 rays deflected away from 



chamber. 



chamber. 



Current 





Current 



1 



through 



Satm-ation 



through 



Saturation 



magnet 



Current. 



magnet 



Current. 



(amperes). 





(amperes). 





o-o 



15-69 



00 



15-37 



2-5 



15-31 



3-0 



15-31 



4-3 



1515 



4-5 



15-23 



6-4 



14-97 



6-3 



14-78 



100 



14-81 



100 14-66 



150 



14-89 



150 14-82 



22-5 



14-72 



22-5 



14-74 



to any selected field-intensity was the same for both directions 

 of the field. Since the disposition of the apparatus in this 

 experiment was symmetrical, it follows that the effect noted 

 with the previous arrangement was not only connected with 

 some special property of the secondary radiation excited in 

 the aluminium by the 7 rays, but it also was due evidently to 

 a non-symmetrical configuration of these secondary rays in 

 the ionizing chamber. 



The following is offered as an explanation of the foregoing 

 experiments : — 



In fig. 17 (p. 150), A represents the ionization-chamber, B 

 the electrode, CD the aluminium screen, and R the position of 

 the radium in the non-symmetrical arrangement. From a 

 consideration of the figure, it is evident that the line RA, 

 which is the axis of a pencil of 7 rays entering the chamber, 

 will mark the line of greatest intensity of these rays ; since 

 for all other rays the metal path traversed is longer, and con- 

 sequently the absorption is greater. It follows then that RA 

 will also represent the direction of the axis of the pencil of 

 secondary rays of greatest intensity issuing from the back of 



