1923- ^<'^ 



TKE AURORAL SPECTRUM AND THE ATMOSPHERE. 



Table I. 

 spectrograph ur. I. (Quartz). 



Photographic Plates : "Imperial Eclipse". 



The spark s{>ectrum 01' Cd used for comparison. 



Afterwards an Imperial Eclipse plate was put in and developed after 

 18 hours of exposure. Only the 6 strongest lines in blue and violet were 

 visible. — The He-comparison spectrum was over exposed and in conse- 

 quence the accuracy of the wave length determination may be somewhat 

 reduced. 



The measurements cave the foUowine results: 



470S.7 

 4651.1 

 4277,9 

 4266.8 

 4236.3 

 3913.3 



The last line was wery faint so it could hardh* be seen in the micro- 

 scope. These are mainly the same lines as those which I obser^•ed in the 

 vear 1912 — 13. There is onlv the differences that now I get a faint diffuse 



