On the Aurora Borealis. 263 , 



mist over that place, and is termed " frost smoke/' or " water 

 blink." The mass of ice filling Davis's Strait and Baffin's Bay- 

 is broken up by winds, tides, and currents, and spaces of water 

 appear among the fields of ice ; throughout the winter the air 

 in the neighbourhood of these spaces is always loaded with ex- 

 tremely minute spicuke of snow, recognizable as " frost smoke." 

 As the cold increases, the number and intensity of Auroras, seen 

 at any place on the Greenland coast, would be in proportion to 

 the proximity of the edge of the ice to that place, for, as a rule, 

 Auroras increase in brilliaucy as they approach the zone of the 

 line of winter ice. If we draw a meridian line passing through 

 the middle of North America, we find the annual number of 

 Auroras increase up to 62° N., where they appear in all parts 

 of the heavens ; farther north the number decreases, and the 

 display is seen more frequently in a southerly direction. The 

 same rule will hold good of a meridian passing up Davis's 

 Strait, only the maximum point of auroral intensity will be 

 situated several degrees to the northward of 62°. Still more so 

 will be the comparison for a meridian passing through Central 

 Europe. Early in the winter, at the northern posts of Green- 

 land, the Aurora is seen indefinitely higher up in the sky, and 

 nearer the zenith, than at a later period of the year, when, 

 after the sea has been, to a great extent, covered over with ice, 

 the Aurora locates itself towards the open water spaces. During 

 the first fifteen months of Dr. Kane's stay at Rensselaer Har- 

 bour, no Auroras were seen, or open water space noticed. At 

 the south of Greenland, where the ice of Davis's Strait edges 

 upon the waters of the Atlantic, a greater number of Auroras 

 is seen than in any other place along that coast line. Most of 

 the Auroras noticed during the last Arctic expedition were in 

 the direction of the open space of water seen during the day, 

 such spaces being, as usual, marked by the " frost smoke." 



Erom the above well-authenticated facts, I cannot but be- 

 lieve that these Auroras were connected with the vapour arising 

 from the open water spaces, and that they were caused by the 

 condensation and subsequent freezing of the particles of vapour ; 

 such particles evolving positive electricity, and by induction from 

 the surrounding atmosphere producing a light transmitted from 

 particle to particle, thus rendering the whole mass of vapour 

 luminous, the lower edges of the arch of the Aurora being the 

 place where first this condensation and freezing* takes place. 

 And if such be the cause of many of the Auroras near the 

 Arctic circle, I see no reason why the same effect should not 

 be produced elsewhere under similar circumstances. 



Whenever the temperature of a cloud, charged with parti- 

 cles of vapour, is lowered — either by changing its position, or 

 by the access of a colder atmosphere — and the particles become 



