﻿122 M. F. Zollner on the Spectrum of the Aurora borealis. 



direction, and its effect would be to make the eastward forces 

 preponderate ; so that although the ocean should be supposed to 

 be at rest at the first, it would ultimately be dragged round by 

 the earth. 



Letterkenny, Ireland. 



XVII. On the Spectrum of the Aurora borealis. 

 By F. Zollner*. 



/""\N the 25th instant I observed, by means of a Browning's 

 ^-^ miniature-spectroscope, the spectrum of the aurora borealis 

 as shown in the annexed engraving. To obtain sufficient bright- 

 ness, the slit was opened rather wide. 



With an alcohol-flame, the wick of which was impregnated 

 with sodium- and lithium- salts, the lines of lithium and sodium 

 were at the same time produced ; and their position was used for 

 the approximate determination of the lines of the aurora borealis. 

 The line in the green part of the spectrum is, in all probability, the 

 one first observed and approximately determined by Angstrom f. 

 On the contrary, the above-represented red line has not, to my 

 knowledge, till now been observed. Certainly this line occurs 

 with sufficient intensity only in those parts of the sky which 

 even to the naked eye appear intensely reddened. But the 

 green line also was always present in these spots, and, indeed, 

 so intense that very seldom did the red line produce an equally 

 strong optical impression. In the blue portion of the spectrum 

 there only sometimes occurred faint band-like streaks, among 

 which a broad dark band on a brighter ground was the most 

 striking. 



Dr. Vogel had the goodness to send me the drawing of the spec- 

 trum of an aurora observed by him in conjunction with Dr. Lohse, 

 about the same time, at the observatory of Chamberlain von 

 Billow at Bothcamp, near Kiel. It showed the bright lines in 

 the green part, and flutings on both sides very quickly diminish- 

 ing in intensity, similar to the light-maximum of a diffraction- 

 spectrum ; but the red line was not present. 



It was not till after the aurora had vanished that I was able 



* Translated from the Berichte der Kon. Sachs. Gesellschaft der Wis- 

 senschaften, math.-phys. Classe, Oct. 31, 1870. 



t Compare Angstrom's Recherches sur le Spectre solaire, p. 41. Berlin, 

 1869. 



