AURORA BOREALIS. 451 



ihey arrive at this line of reduced temperature, and leave the 

 region over the ice exposed to a bright sunshine. Indeed the 

 extraordinary effect of this large body of ice upon the atmos- 

 phere, particularly when the sea is deep and the temperature 

 of the ocean and its superstratum of air high, as between Spitz- 

 bergen and Greenland, will scarcely be credited by persons 

 who have not witnessed it. Mr. Scoresby has given some ex- 

 traordinary instances of this in his Arctic Voyages ; and to these 

 I will add one of many which fell under my own observation. 

 The ships of the first polar expedition were beset in the ice 

 about nine miles from the open sea. It was blowing a hard 

 gale upon the ice, and we could perceive a ship carrying off 

 under storm stay-sails only. There was nothing between us 

 and the ship to intercept the gale, and yet we were becalmed 

 during the whole of the day. The atmosphere over the open 

 sea was loaded with clouds (nimbi), while that over the ice 

 enjoyed a bright sunshine throughout. The limits of these 

 opposite states of the atmosphere, by seamen called the ice- 

 blink, were marked by a well-defined line, nearly perpendicular 

 over the margin of the ice. As the heavy clouds reached this 

 spot they were gradually condensed, the effect of which was 

 precisely similar to that which sometimes occurs about the 

 summits of high mountains, against which the clouds are suc- 

 cessively driven, without any being seen to depart, and with- 

 out any apparent increase. 



This remarkable disturbance of the equilibrium of the at- 

 mosphere being admitted, I would here merely suggest whe- 

 ther, under certain dispositions of the atmosphere, electricity 

 might not be induced and communicated to the surrounding 

 region, so as to occasion the Aurora Borealis, and to account 

 for its appearance in the before-mentioned directions in pre- 

 ference to others. 



I am not aware what would be the effect of the meeting of 

 two atmospheres, one influenced by a large body of ice, the 

 other by an extensive continent, such as that of America, and 

 particularly when the circumstances might be modified by large 

 frozen lakes. But it appears from Captain Franklin's obser- 

 vations at Great Bear Lake, that the Aurora arose in almost 



