418 THE CANADIAN NATURALIST. [Vol. viii. 



sists of three varieties : common floe ice, hummocky ice, and 

 floe-berg ice. To form "old hummocky ice," as described by 

 Captain Sir George Nares, a large area of sea water is required, 

 for this kind of ice is produced by the over-riding and piling up 

 of ordinary floes, which are then cemented together by wintry 

 frost. Floes are piled on floes, but the areas the over-riding 

 floes occupied are frozen again. 



Floe-berg ice is from 80 to 100 feet thick. A full description 

 of it and its vast extent will be found in the journals and pro- 

 ceedings of the Arctic Expedition. This floe-berg ice and the 

 " hummocky ice " are constantly streaming down from the north. 

 Many floes associated with icebergs, finally appear in the seas 

 washing the coasts of Labrador and Newfoundland, which they 

 reach via the Hudson Straits, the Davis Straits, and the East 

 Greenland Currents, the last named sweeping round Cape Fare- 

 well, and all uniting to form the Labrador Current. 



Subjoined is a rough estimate of the area occupied by these 

 three varieties of ice within the limits of the 4,000,000 square 

 miles : — 



I. Floe Ice. — Appproximate area formed each year, 2,000,000 

 square miles. Thickness, 3|- to 5J feet : mean thickness, 4J- feet. 

 Average elevation of this ice above the level of the sea, five 

 inches, or one-tenth of its volume. Reduced to a uniform thick- 

 ness of one foot, this area would be equivalent to 833,330 square 

 miles. 



II. " Hummocky Ice." — Estimated area. 1,000,000 square 

 miles. Estimated average winter increase above water line, one 

 foot. 



III. Floe-berg Ice. — Estimated average area in polar waters, 

 500,000 square miles. Estimated average winter increase above 

 floatation line, one foot. 



RECAPITULATION. 



Ice above the Surface of the Sea reduced to a Mean Thickness of One Foot. 



Ordinary Floe Ice - - - 833,330 sq. miles. 

 Hummocky Ice - - - 1,000.000 



Floe-ben? Ice ... 500,000 



Total - - - 2,333,330 sq. miles. 



This area, one foot thick, is equal to 382 cubic miles of ice. 

 We arrive at nearly the same result if we assume that the mean 



