of Electricity through Gases exposed to Rontgen Rays. 405 



for the absolute values of the current in these gases is very 

 different, the saturation current in sulphuretted hydrogen 



Fig. 5. 



being in some cases three or four times that of air, while that 

 of chlorine is in some cases as much as ten times that of air. 



The value of the saturation current varies greatly in 

 different gases ; of the gases we have tried it is least in 

 hydrogen, greatest in mercury vapour, the saturation current 

 in mercury vapour being about 20 times that for air. It does 

 not seem to depend entirely on the density of the gas, as in 

 sulphuretted hydrogen it is three or four times what it is in 

 air, though the densities are nearly equal, while, though the 

 density of the vapour of CH 2 T 2 is greater than that of mercury 

 vapour, the saturation current in the former gas is only a 

 small fraction of its value for the latter. The gases which 

 have large saturation currents are those which contain the 

 elements which have an abnormally large specific inductive 

 capacity in comparison with their valency. 



We have made a large number of experiments with the 

 view to seeing whether there is any polarization when a 

 current of electricity passes through the gas; we have not, 

 however, been able to satisfy ourselves of the existence of this 

 effect. The absence of polarization implies, however, that the 

 ions are able to give up their charges to the metal electrodes. 

 Experiments on electrified gases show, however, that it is very 

 difficult to get a charge of electricity from a gas to a metal 

 unless the metal is exposed to radiation, either by the metal 

 being sufficiently hot to be luminous, or when it is exposed to 

 ultra-violet light. But in the case of the passage of electricity 

 through a gas which has been exposed to Rontgen rays the 



Phil. Mag. S. 5. Vol. 42. No. 258. Nov. 1896. 2 G 



