CONDUCTION THROUGH GASES 127 



A similar supposition has been adopted to explain 

 the conductivity of gases, although it will be clear 

 that, in many respects, the ions in the case of 

 electric discharge through gases must be endowed 

 with properties different from those which pertain 

 to the ions of liquid solutions. 



After a period of activity on the part of 

 some ionizing agency, such as Rontgen rays, 

 the resultant conductivity does not cease simulta- 

 neously with the action of the rays. It persists 

 for some little time ; it can be blown about with 

 currents of air ; and in all respects acts as though 

 it were due to the presence of material particles, 

 formed somehow in the gas through which the 

 rays had passed. The conductivity is destroyed 

 if the gas be passed through a plug of glass wool 

 or bubbled through water ; it is also removed if 

 the gas be subjected to the action of an electric 

 field. Such experiments, and many others of 

 somewhat similar nature, are readily explained 

 by the conception of charged particles, which, 

 produced in some way by the action of the 

 ionizing agency on the molecules of the gas, are 

 afterwards driven through the gas by an electric 

 force, just as the ions of a salt solution are driven 

 through the liquid. Unlike the ions of liquids, 

 however, those of gases do not long persist after 

 the cessation of the outside ionizing agency. 

 Left to themselves, the ions gradually disappear. 

 Such a disappearance might be anticipated on 

 the view that the opposite ions recombine and 

 neutralise each other, and also on the assumption 

 that they give up their charges to the solid objects 

 with which they come in contact as they move 

 about under their own motions of diffusion, and 



