MODELS OF POSITIVE ION 313 



tion to those given by the ordinary laws of electro- 

 statics. It would make the attraction between a 

 positively charged oxygen atom and a negatively 

 charged hydrogen atom less than that between a 

 negatively charged oxygen atom and a positively 

 charged hydrogen one. It is to these unstable or 

 nascent ions that we may once more attribute the 

 stored-up energy which in suitable conditions can 

 be given up as phosphorescent light. 



If the energy stored up be great there is very 

 little chance of these ions recombining, and the 

 two forces, those brought into play by the condi- 

 tions of the wrong charges and the electrostatic 

 ones, may neutralise each other, or perhaps actually 

 be repelled. 



This would enable them to maintain their separate 

 existence for a very long time, until the conditions 

 are such that condensation occurs on the walls of the 

 vacuum tube, when the interchange, according to 

 the theory, must take place, and as a consequence 

 of which luminosity will be the visible manifesta- 

 tion. 



The identity between the spectrum of the " pres- 

 sure glow " and that of the negative glow in oxygen 

 suggests that something similar occurs beyond the 

 boundary of the dark space. 



The passage of a discharge through a gas must 

 give rise to both the stable and unstable ions, and 

 when the latter come within the path of the cathode 

 rays they will act as nuclei which will facilitate the 

 interchange of carriers, during which new molecules 



