STRUCTURE AND FORMATION OF ICE. 479 



any of the large lakes, unless where it has drifted under the lee of piled-up 

 slabs of ice, or of rocks, islands, or other shelter. During winter, the ice 

 receives an increase of thickness from beneath, and at the same time eva- 

 porates above ; the latter process going on with a rapidity that would scarcely 

 be credible to one ignorant of the extreme dryness of the air*in an Arctic 

 winter. The ice acquires a thickness of from four to eight feet, according 

 to the severity of the season, the depth of the lake, and other modifying 

 circumstances; and I desire here to advert especially to the fact, that 

 although it is constructed of successive horizontal additions beneath, when 

 it decays in spring, it consists of vertical prisms, penetrating its whole 

 thickness, and standing side by side like the columns of a basaltic cliff. 

 . . . In this condition the ice may be strong enough to support a 

 considerable weight; and I have travelled over it with a large party on 

 several occasions, when the prisms on which the foot rested were depressed 

 at every step, and a pointed stick could be driven through the whole thick- 

 ness into the water beneath with as much ease as into a bank of snow. The 

 ice then, in fact, presents the physical characters of a semi-fluid mass, as 

 pointed out by Professor Forbes, its parts being movable on each other, 

 not only vertically, but, as in the case of travelling glaciers, capable of glid- 

 ing past one another horizontally." 



The extreme dryness of the air in an Arctic winter is attested by the 

 rapid evaporation of both snow and ice, long before these are thawed into 

 a liquid form by any action of the. sun. Of this fact Richardson gives 

 a familiar but striking illustration. " When a shirt, after being washed, is 

 exposed in the open air to a temperature of 40° or 50° below zero — say 70° 

 or 80° below the freezing point — it is instantly rigidly frozen, and may be 

 broken if violently bent. If agitated when in this condition by a strong 

 wind, it makes a rustling noise like theatrical thunder. In an hour or two, 

 however, or nearly as quickly as it would do if exposed to the sun in the 

 moist climate of England, it dries and becomes limber " — or flexible. . . . 

 " In consequence of the extreme dryness of the atmosphere in winter, most 

 articles of English manufacture made of wood, horn, or ivory, brought to 

 Rupert's Land, are shrivelled, bent, and broken. The handles of razors and 

 knives, combs, ivory scales, and various other things, kept in the warm 

 rooms, are damaged in this way. The human body also becomes visibly 

 electric from the dryness of the skin. One cold night I rose from my bed, 

 and, having lighted a lantern, was going out to observe the thermometer, with 

 no other clothing than my flannel night-dress, when, on approaching my hand 

 to the iron latch of the door, a distinct spark was elicitated! Friction of the 

 skin, at almost all times in winter, produced the electric odour." The lowiest 

 temperature registered during the winter was that of the l7th December, 

 when the minimum was -65°, or ninety-seven degrees below the freezing point. 



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