7 Rays from the CI, 



Products, 



255 



X is not a simple product but that it consists of two bodies, 

 viz. uranium X! and uranium X 2 . Uranium K^ has a period of 

 24*6 days and emits soft {3 rays, and uranium X 2 has a period 

 of 1*1 mins. and emits hard j3 rays. It is quite impossible 



Fig. 2, 



1-8 Q A 











i 6 \ 











1-4 



[ \Z° ■' 



'0-70 







Nl 



12 











i-o *** 











a 









\ 



12 3 4 



Thickness of Aluminium in cms. 



without using a very large amount of material to settle 

 definitely to which of the various products the various types 

 of 7 rays belong. Evidence on this point may be obtained, 

 however, by a consideration of the penetrating power of the 

 7 rays emitted by radium 13, radium C, thorium B, thorium 

 13, actinium B, and actinium D. Previous work has shown 

 that each of the B products emits three types of soft 

 7 rays, whilst radium C, thorium D, and actinium D each 

 emit only one single penetrating type. It has also been 

 pointed out that those bodies which emit soft 7 rays also in 

 general emit a soft ft radiation. 



It would appear therefore reasonable to suppose that 

 uranium X l emits those rays for which li = 21 and ll = 0*70, 

 since these groups correspond to two of the groups emitted 



