£32 Prof. Barkla and Mr. Philpot : Ionization in Gases and 



not certain. Their structure is so unlike that of other 

 nitrogen bands that, in spite of the series relationships indi- 

 cated by the results of Strutt and Fowler, it is hard to believe 

 that they are due to nitrogen alone. 



It seems clear from these experiments and the photographs 

 previously published in the ' Astrophysical Journal,' that the 

 second group of bands belong exclusively to the discharge, 

 not to the afterglow ; while the third and /5 groups are 

 relatively more intense in the afterglow. The former are 

 associated with the period of dissociation, the latter with the 

 period of recombination. Of course these effects are super- 

 imposed in the uninterrupted discharge. 



In closing this paper my attention has been called to an 

 article by Konig and Elod in the Physikalische Zeitschrift for 

 February 15, 1913. They are of the opinion that the after- 

 glow is a property of pure nitrogen. This may well be the 

 case, but I doubt whether it has been proven. It seems 

 certain that the nitrogen used by me and by Strutt was not 

 free from oxygen, and I am not convinced that anyone has 

 ever worked with nitrogen free from oxygen. 



Berkeley, Cal., 

 March 11, 1913. 



LXXXVII. Ionization in Gases and Gaseous Mixtures by 

 Rontgen and Corpuscular [Electronic) Radiations. By 

 C. G. Barkla, F.R.S., Wheat stoixe Professor of Physics, 

 and A. J. Philpot, B.Sc, Layton Research Scholar, 

 King's College, London *. 



A STUDY of the ionization produced in gases and in 

 mixtures of gases and vapours by corpuscular radia- 

 tions and by Rontgen radiations furnishes valuable information 

 regarding the processes taking place during the transmission 

 of these rays through matter. The investigations on this 

 subject described in the following paper will be considered 

 under several headings. 



Total Ionization by Corpuscular {Electronic) Radiation 



in Gases. 



The relative ionizations produced in several gases by the 

 complete absorption of corpuscular radiations set up by 

 Rontgen radiation were investigated by Kleeman f, and 

 important conclusions were drawn from the results obtained. 



* 'Communicated by the Authors. 



t Proc. Roy. Soc. A. lxxxiv. pp. 16-24 (1910). 



