Phosphorescent Glow in Gases. 457 



show, at first sight, that it is not the glow which conducts, 

 and that the conductivity is in the gas itself quite distinct 

 from the glowing particles ; but the glowing particles may 

 consist of groups of ions so close together — which Professor 

 Fitz Gerald has suggested to me as a possible hypothesis — 

 that they can protect each other in diffusing through the 

 metal tubing, and thus enable themselves to make their way 

 through the wire-gauzes without being finally broken up by 

 the electromotive force between these electrodes. 



There is, further, a difficulty in explaining the conductivity 

 of the gas by the passage of the phosphorescent molecules 

 through it, as their velocity is so very small ; but there is no 

 need to suppose that the conductivity is in the gas alone as 

 distinct from the phosphorescent particles. Since the condition 

 of the gas when the glow takes place, as has been pointed out, 

 appears to be that o£ a semi-chemical mixture ; and if wo 

 bear in mind the part played by oxygen, both in the after- 

 glow and in the negative glow, in which the conductivity is 

 likewise considerable, it seems plausible to regard the con- 

 ductivity in the glow as being of an electrolytic nature, due to 

 the formation of large groups of molecules ; and this view of 

 the matter is further strengthened by the fact that the con- 

 ductivity is retained after the passage of the glowing particles 

 through the wire-gauze electrodes with an electromotive force 

 between them, and also perhaps by the fact that the glow 

 presents a somewhat dirty or semi-opaque appearance. 



The semi-opacity resembles that accompanying the pheno- 

 menon of fluorescence of uranium glass. (See also Newall, 

 loc. cit.) 



Thus we may be led to regard the phenomenon of phospho- 

 rescence as due to the formation of large and probably com- 

 plicated molecular groups, which are gradually broken up by 

 molecular impacts of a certain frequency. The destruction 

 of these molecular groups may also be effected, as has been 

 shown, by negative ions of sufficient penetrating power. The 

 radiation from the phosphorescent molecules must produce, 

 at molecular distances, a considerable repulsion, which should 

 diminish considerably the violence of the bombardment from 

 other molecules, and possibly ionize the latter. 



(15) The capacity that, as has already been stated, a gas 

 possesses of storing up energy from a spark which has been 

 tent through it, and then of emitting this energy under 

 suitable conditions in the form of phosphorescent light, is 

 somewhat analogous to the phenomenon of thermo-lumines- 

 cence, with this exception, that whereas in the case of tho 

 former the phosphorescence is dependent solely upon the 

 pressure of the gas, and independent as to whether this pressure 



Phil. Mag. S. 6. Vol. 1. No. 4. April 1901. 2 H 



