ELECTRICITY OF THE ATMOSPHERE AND AURORA BOREALIS.229 



"west-soutbwest. In a few moments the cloud of mist passed the mount- 

 ain and the rays disappeared, but the crest of the mountain continued 

 to be illuminated by a pale wandering light, which floated along the 

 mountain, and of which it was not easy to determine the character; still 

 I was in no doubt, for the spectral analysis very clearly disi)layed the 

 yellow ray discovered in polar light by M. Angstrom. I continued to 

 observ^e the crest of the mountain, over which foggy vajiors were pass- 

 ing, allowing to appear from time to time the pale light I have described. 



At 11 o'clock 30 minutes the npjjer part of the fog, which presented 

 very much the appearance of a cloud with serrated edges, became illu- 

 miuated with a yellowish white light, in the course of a moment con- 

 verted into yellowish and reddish rays, which extended with an undula- 

 tory motion alqng the edges of the fog, following the irregularities in 

 their minutest detail. The fog rose in the form of an arch about 10"^ 

 above the mountain, and the rays attained a height of from 10° to 15°, 

 which gives for the whole phenomenon an elevation of from 20° to 25° 

 above the horizon. At the same time there began to appear at the 

 north an indistinct combination of the brilliant edges of clouds, among 

 which I clearly distinguished one, from which proceeded a distinctly- 

 marked yellow ray, seeming in appearance to connect this cloud with 

 another. The rest of the sky was' covered with fillets or bands of light 

 clouds, passing over the zenith from the east to the west and allowing 

 the stars to appear at intervals. 



The day following, the 2Gth of September, having observed the crest 

 of the mountain with attention, I found it was almost entirely covered 

 with snow, except at one or two j)laces, which seemed to be those at 

 which the night before the light had appeared with least intensity. 

 The evening of the same day the phenomenon was again manifested, 

 but with some modifications. A little below the horizon to the south- 

 west, almost opposite the promontory or headland which terminates the 

 mountain, appeared a series of clouds whose upper edges were strongly illu- 

 minated with a diffuse yellow and white light, which was very intense 

 on the edge of the cloud at the extreme western end of the series, but di- 

 minished in brilliancy along the edges of the clouds until at the eastern 

 end, where the last cloud seemed to melt into the headland, it was 

 hardly perceptible. Very soon rays appeared, similar to those observed 

 the night before, which seemed to proceed from a mist lying along the 

 crest of the mountain, but somewhat back of it. This time the i)he- 

 uomenon seemed to take place at a much greater distance than during 

 the preceding observations, but the form and color of the rays were the 

 same ; and I again, with the spectroscope, obtained the yellow ray as 

 well from the light emanating from the edge of the clouds as from that 

 proceeding from the rays themselves. 



On the 27th of September, after having observed in the mornicg a 

 radiation of yellowish-white light proceeding from one edge of a cloud 

 which stood out prominently from a wall of clouds, I perceived in the 



