Manchester Memoirs, Vol. xlviii. (1904), No. 10. 7 



Spectrum of the Glow Discharge in Hydrogen. 



The spectrum consists of lines of both the elementary 

 and the compound line spectra of hydrogen ; the lines 

 are very sharp, just as they are obtained in Geissler tubes, 

 they are sharper even than the lines of the oscillatory 

 spark^ itself for an equal value of self-induction. Besides 

 these hydrogen lines, there are also visible lines of the 

 metal constituting the wire ; and with a platinum wire 

 the edges of the two negative bands of nitrogen, X = 4278 

 and X = 39i4, stand out very prominently. When a 

 copper wire was used, these bands were barely seen and 

 it seems probable that their presence is due to the well- 

 known fact that platinum absorbs nitrogen and gives it 

 off on heating. A photograph of the hydrogen glow 

 spectrum is reproduced in Fig. 3 of Plate VI. 



4. — Glow Discharge in Oxygen. 

 To produce the glow the platinum wire needs to be 

 heated very little and only at the beginning, the wire soon 

 afterwards becoming red hot and remaining so throughout 

 the duration of the sparking. The presence of the glow 

 can only be revealed by the spectroscope on account of 

 the red or even white heat of the wire. The spectrum is 

 that of the elementary line spectrum of oxygen with the 

 most intense line atX = 44i5"3A. Of other conspicuous lines 

 are to be noted the edges of the negative bands of nitrogen 

 at X = 4278 and X=39I4, their presence being due to the 

 absorption of this gas by the platinum. The spectrum of 

 the oxygen glow is reproduced in Fig. 4 of Plate VI. 



Behaviour of the Calcium lines in the Glow Discharge. 

 These lines have attracted much attention of late years 

 and it seemed useful to just record their behaviour under 

 ^Hemsalech, Comptes Rendus, t. 129, p. 288, 1899. 



