Ionization of Gases and the Absorjjtion of Bontgen Bays. 321 
X-rays. As we pass from the absorber Sn (50) to absorber Pt (79) (no 
intermediate absorbers are given) the constant of proportion of Kw to 
falls in the ratio of 4- 81 : 1. 
We therefore have 
nr. 4- + • • 
4-81. 
= 3-81. 
> 3-81, 
" n^^ 
and from the order of the quantities involved — 
'^<4-81. 
If we assume that for an absorber whose atomic number is 78, its L radia- 
tion would have been excited, whilst the absorber Pt (79) had only its 
M radiation excited by the Ni X-rays, we obtain 
»„ ^ (I - p) - 7-4)' 
(i4:)(N-21-8)^ 
where N is 78. 
. ^=4-52, 
a result agreeing well with Barkla's figures. There seems to be every 
likelihood, therefore, that the theory I have outlined is not far from the 
truth. 
Summary. 
An attempt is made to co-ordinate the known processes of ionization in 
gases during the passage of a beam of homogeneous X-rays with absorption 
phenomena generally in solids. 
The basis of the theoretical considerations is the experimental fact that 
for a given wave-length of the primary rays the number of /3 particles pro- 
duced in a gas varies as the fourth power of the atomic number of the 
absorbing element (Moore, Proc. Eoy. Soc. (A), xci, p. 337), whilst the 
absorption per atom during the passage of X-rays through solids also varies 
as the fourth power of the atomic number of the absorber (Bragg, Phil. 
Mag. (6), xxviii, p. 627). It is assumed, therefore, that all absorption in 
solids is due to a direct interchange of energy between the ether waves and 
the /3 particles which are liberated throughout the solid. 
The amount of energy absorbed from the primary wave per particle 
produced 
= I m^K^ + Jin^ + JiUl + • . . 
