528 Miss Jadwiga Szmidt on Distribution of Energy in 



the assumption is not true the relative total ionization will 

 not be the same for the different types. The difficulty arises 

 in practice to obtain strong enough sources of homogeneous 

 or practically homogeneous 7 radiation of different penetrating 

 powers. The experiments which could be carried out in this 

 direction are therefore limited ; their description is given in 

 Part I. of the paper, which deals with the passage of 7 rays 

 through gases in general. The second part of the paper 

 (Part II.) deals with the direct question under investigation, 

 and describes experiments to determine the relative energies 

 of the different types of 7 rays from radium B, C, and D. 



Part I. 



Absorption and Ionization of Gases by y Rays. 



The experiments deal mainly with tw 7 o types of 7 rays, the 

 soft 7 rays from radium D (yu = 45 cm. -1 Al) and the hard 

 rays of radium C (//,= 0*115 cm. -1 Al), since both were 

 found sufficiently homogeneous for the purpose. Some ioni- 

 zation measurements were also carried out with the hard rays 

 of radium D (^ = 0*99 cm. -1 Al). The gases used were air, 

 carbon dioxide, sulphur dioxide, and sulphuretted hydrogen. 

 All are easily obtained in a pure state, and consist of elements 

 for which no appreciable characteristic radiation has been 

 detected. We will first consider the absorption of 7 rays by 

 the various gases. 



Fiff. 1. 



The source R — a fairly strong preparation of radium D, 

 in equilibrium with its product radium E, on filter-paper — 

 was permanently fixed at one end of the cylinder A, placed 

 between the poles of an electromagnet, as shown in fig. %y 



