91 



6. 



Luminous phenomena of the same kind as the 

 auroral light, natural and artificial. 



During journey in the polar-regions peculiar luminous 

 phenomena, besides easily discerned auroras, have been 

 observed near the earths surface, the origin of which can 

 be regarded as doubtful. 



Already during our first journey in the polar-regions, 

 as partaker in the Svedish polar-expedition 1868, we had 

 the occasion to observe such luminous phenomena. They 

 appeared as feeble flames around mountain tops and moun- 

 tain ranges, especially when these vvere surrounded by fog. 

 On this expedition we found in the spectroseope an exellent 

 mean to determinate the nature of the phenomenon. The 

 polarlight gives in the spectroseope several luminous rays, 

 which all, but one, appeer only by high intensity. This, 

 ray has the wave-length l =5569.10~ 7 and is, because it 

 has been observed hitherto only in case of auroras, as 

 characterizing for the polarlight that we can say: every 

 time a luminous phenomenon shows this ray, it is of the 

 nature of polarlight. It is not said hereby that all luminous 

 phenomena of polarlight nature must give this ray, for 1 

 have some times observed luminous phenomena, which I 

 suspected as of auroral nature, but they have not given the 

 yellow ray *). We will, for brevety call this ray y. r. By 

 aid of the spectroseope we continued the studies afterwards 



*J The colour of the line is lying in the spectre, more in the 

 green than in the yellow, but to my eyes is seems more yellow thaa 

 green. By the kindness of the prof. Ramsay 1 have seen the spectre 

 of the new gas with same wave-leDght as the auroral line, but 

 there it was more green than yellow. 



