74 
mr. j. c. Mclennan on electrical conductivity in cases 
Table X. 
Gases examined. 
Column 1. 
Column 11. 
Densities (sbown above 
to be proportional to 
ionization by cathode 
rays), air = 1. 
Ionization by 
Rontgen rays. 
Ionization of air taken 
as unity. 
Air. 
1-00 
TOO 
Oxygen . 
1T06 
1-1 
Nitrogen .... 
•97 
•89 
Carbon dioxide . 
1-53 
1-4 
Hydrogen .... 
•069 
•33 
Nitrons oxide. 
1-52 
D47 
The numbers, with the exception of those for hydrogen, present an agreement 
which is very striking, and show that although the two forms of radiation are so very 
different, still the products of their action upon the gases cited are practically the 
same. 
While the difference in the numbers for hydrogen is very large, there seems to he 
some doubt as to the proper value to he assigned to the conductivity produced by 
Itontgen rays in this gas. The conductivities under Rontgen rays in the gases 
named have been measured by a number of experimenters, and while their values for 
the other gases differ but little, a very wide divergence exists in their numbers for 
hydrogen. Rutherford* gives the value '5, while Perrin f has obtained the 
number ‘026 by a method entirely different from that of any of the others. 
Though we have been thus led to conclude that the density of a gas should 
determine its conductivity under cathode rays, strong evidence exists against adopt¬ 
ing any such general conclusion regarding the conductivity produced by Itontgen 
rays, notwithstanding the general agreement indicated above for the gases cited. 
With such gases as HC1, CL, S0 2 , and H 2 S, J. J. Thomson, Rutherford, and 
Perrin have found the conductivities given in Table XI. 
From an examination of these values and a comparison with those of Table X., it 
is evident that it is quite impossible to deduce any such relation between the densities 
of the gases and their conductivities under this radiation. 
* ‘ Phil. Mag.,’ April, 1S97, p. 254 
f ‘ These presentee a la Faculte des Sciences de Paris,’ 1897, p. 46. 
