8 L. VEGARD. M.-N. Kl. 



buch der Spectroscopic. N. B. and P. B. mean negative and positive bands. 

 L. S. means line Spectrum. 



All somewhat strong lines in the ultraviolet found by means of the 

 quartz spectrograph are quite accurately determined, and the errors are less 

 than 1 A unit. The agreement between the auroral lines and the corre- 

 sponding N-lines is a very close one throughout the ultraviolet part. Also 

 the stronger lines of the visible part of the spectrum are quite accurately 

 determined, and the identification quite certain. 



The lines which are only determined by means of the small spectro- 

 graph may be somewhat less accurate, and there may be errors in the 

 wave length of 2 — 3 A, but still I think the identification also of these 

 lines is prety certain. 



We see that the auroral spectrum is almost entirely due to Nitrogen. 



The lines partly belong to the negative partly to the positive Band- 

 spectrum, and in the visible part also some lines appear, which in the 

 literature are arranged in the line spectrum. 



The grouping of these lines may be a more or less artifical one. 

 In the northlight spectrum, which corresponds to a fairly definite way of 

 production, they appear mixed together and with a quite tvpical intensity 

 distribution. In the northlight spectrum they may be said to form one 

 family of lines. 



In all 35 lines have been measured, out of these 29 lines have been 

 identified as belonging to Nitrogen and the two lines or bands 5925 and 

 6465 are probabh' N-Bands. Still, however, the tbllowing four lines — 

 the green line included — are not yet interpreted : 



5578,2 

 4182,5 

 3432,7 

 3208,3 



These lines are not found among the recorded lines of the N-spectrum. 

 They cannot be ascribed to Hydrogen, nor to Helium or Oxygen. I think 

 there is little doubt that also these lines are due to Nitrogen. This only 

 means that the auroral spectrum, is formed under conditions which are very 

 difficult to reproduce in the laboratory. Several facts go to support this 

 view, and I hope to gather some more knowledge through the continued 

 work on the auroral spectrum. 



A most important result of these observations of the auroral spectrum 

 is that no indication of either Hydrogen or Helium lines have been observed. 

 — This fact is the more remarkable because in some of the spectra the 

 stronger lines were greatly overexposed. 



During the last two years I have made experiments in my laborator}', 

 the object of which was to study the light exited by the bombardment of 



