372 On Lonzation produced in Gases by Rontgen Rays. 
In some of the experiments, especially with the harder rays, 
the intensity of the radiation, as measured by the standard 
apparatus, varied considerably ; ; but this variation of the 
intensity did not seem to affect the balance between the 
ionization in the two gases in the cylinders in any definite 
manner like the alteration of the pressure in the bulb did. 
The general results obtained from the experiments tended to 
show that this change of relative ionization is not a question 
of the intensity of the rays but of the type of rays. 
In considering the manner in which this variation of the 
relative ionization in the different gases with change of rays 
takes place, we observe that in all cases examined it always 
takes place in a definite direction. In the case of hydrogen 
and air, where the ionization in hydrogen is less than in air, it 
increases relatively to that in air, or the ionization in air 
decreases relatively to that in hy drogen, as the rays become 
harder. In the case of the other gases where the ionization 
is greater than in air, it decreases ‘relatively to that in air as 
the rays become harder. The tendency appears to ph there- 
fore, for the value of the ionization in the denser gas to 
approach the value of the ionization in the less deal one as 
the rays become more penetrating. The total relative ioniza- 
tion does not appear to be a function of the densities of the 
gases. In comparing oxygen and sulphur dioxide with air, 
the ratios for the relative ionization approached more nearly 
to the ratios for the densities the more penetrating the rays 
became ; but in the case of hydrogen and carbon dioxide, the 
more penetrating the rays became the farther from the ratios 
for the densities became the ratios for the relative ionization. 
This is easily seen by referring to Tables VI. and VII. The 
relative densities of the gases are given in Table VI. for 
convenient comparison. Mr. Hve* has shown a short time 
ago in anarticle in ‘ Nature,’ that for very penetrating rays the 
relative ionization in several gases was approximately 1 in the 
sume ratio as the densities of the gases. It is very probable, 
from the experiments described in this paper, that for 
extremely penetrating rays the ratios for the ionization in 
oxygen and sulphur dioxide compared with air would become 
approximately equal to the ratios of the densities of the gases. 
Hydrogen and carbon dioxide show, however, quite the 
opposite tendency. The general tendency shown by all the 
gases examined was for the amount of ionization in the 
denser gas to approach nearer to the amount of ionization in 
the less dense one as the rays become harder. 
* Nature, March 10th, 1904 (p. 436). 
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