114 AURORA BOREALIS. 



latitude of 74° to 58° north, when it was observed that from the 

 latitude of 74° until 66°, the phenomenon was seen to the south- 

 ward, particularly at midnight ; but when the ship had passed to 

 the southward of the latitude of 66% it was seen to the northward. 

 In several instances the Aurora was distinctly observed to be 

 between the two ships, and also between the ships and the 

 icebergs; proving unquestionably that it could not be at that 

 time beyond the atmosphere of tlie earth. This indeed was 

 the only fact which I completely established during that voyage, 

 but which was a conclusion that led me to inquire how its 

 proximity to the earth was to be accounted for. Both at my 

 observatory in Scotland, and during my late and long-pro- 

 tracted residence in the Arctic Regions, my attention has been 

 particularly directed to this interesting subject, and my conclusions 

 are, that the splendid phenomenon, called the Aurora, is entirely 

 occasioned hy the action of the sun's rays upon the vast body of icy 

 and of snowy plains and mountains which surround the poles. 



The rays of the sun, in the first instance, are reflected, from 

 uneven, plain, or variegated surfaces, of the coloured, icy, or snow- 

 clad substances, which are presented to them at the point of 

 incidence by the rotation of the earth, and passing over the poles 

 reach and illuminate clouds which are only rendered visible to us 

 by such illumination, these clouds having positive, negative, and 

 reflecting qualities, possess the power of producing all the sur- 

 prising effects which have been observed by distributing the rays 

 they have received, and as they receive them, in every direction ; 

 and according to tlie state of the atmosphere, give additional 



