(2) The tundra or region of intensely cold winters, forbidding tree-growth, where mosses and lichens cover most of the ground when unfrozen, and shrubs occur of species which in other conditions are trees, here stunted to the height of a few inches.
During the rapid formation of ice the still unfrozen brine is often imprisoned between the little plates of frozen water; hence without some special treatment sea-ice is not suitable as a source of drinking water.
In January the northern water areas of the continent are frozen and snow-covered; Hudson Bay becomes unduly cold, and the greatest southward bending of the isotherms is somewhat east of the continental axis, with an extension of its effects out upon the Atlantic; but the southward bending isotherms are somewhat looped back about the unfrozen waters of the lower Great Lakes.
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