lo Hemsalech, spectrum of the Glow Discharge. 



Origin of the Radium Glow. 



Comparing the luminous glow of radium with that of 

 the glow discharge in air we find, according to the 

 observations of Sir William and Lady Huggins, that the 

 two phenomena are very similar. 



The glow of radium is confined to the surface only, 

 and does not extend into the air. The spectrum of this 

 glow is the same as that of the glow discharge in air. On 

 heating radium, the luminosity of its glow is increased. 

 We do not, however, know the cause of the spontaneous 

 emission of electrons, nor exactly how the ionisation on 

 its surface is effected. But very probably the emission 

 of electrons, and their breaking through a thin layer of 

 ionised air, is the direct cause of the glow. 



Let us suppose that radium possesses the property of 

 absorbing negative ions of nitrogen ; then, as these diffuse 

 into the radium, they will encounter at the boundary 

 surface the stream of electrons moving outwards. The 

 collisions which will ensue will give rise to the glow giving 

 the negative band spectrum. Now supposing that these 

 negative ions in diffusing into the radium are being 

 deprived of not only one, but of several of their electrons, 

 such that they pass through the neutral state into that of 

 positive ions, then the number of free electrons and of 

 positive ions in the radium would increase. Now as more 

 and more negative ions are being absorbed, the electrons 

 and positive ions will be driven out again, and thus give 

 rise to two different kinds of radiations : one consisting of 

 electrons and constituting the |3 rays, and another one 

 consisting of positive nitrogen ions, and forming the a 

 rays of radium. The a rays on their way out will encounter 

 the in-going negative ions, and thus give rise to the positive 

 bands of nitrogen in the radium glow. The highly 

 penetrative 7 rays could perhaps be explained by assum- 



