﻿of the a Rays of Radiotliorium. 



87 



with the same preparation under exactly the same conditions. 

 The shape of the curve is very different. The first effect of 

 a. particles begins at a much greater distance, namely, about 

 8*6 centims. From previous work, it is known that this new 

 effect is due to the rays of thorium 0. Below 6 centims. 

 there is a change in the ionization curve, showing that the 

 particles of another product add their effect. The cc rays of 

 this product have less range than those of thorium (J, but 

 more than those of thorium B and radiotliorium. As there 



Fie. 2. 



10 



•J 6 



1 











. 



V 













U \ 















A\ 

















•*r~^*~~^ 













K 



\ 0/ 







^ 





c 















^o 



Ionization. 



is only the emanation and thorium X still unaccounted for, 

 we conclude that this range belongs to the a. particles of one 

 of these products. Since a greater part of the emanation 

 escaped from the preparation and was removed by the air- 

 current, it appears probable that the range of somewhat 

 below 6 centims. belongs to the a. particles of thorium X. 

 This conclusion is confirmed by later results. 



In the four days' interval, more than half of the maximum 

 amount of the thorium X is formed by the radiothorium. 

 The thorium X produces the emanation, which in turn gives 

 rise to thorium B and C. The ionization due to the latter 

 should, consequently, be observed, and this we have seen is 

 the case. 



There must, naturally, be the same amount of thorium B 



