We may place between the isothermal lines of +5° and of 0° the limit where commences the territory which, in the northern hemisphere, merits the name of the Region of the Polar Deserts. Already, in effect, under this glacial latitude, the landscape assumes a sombre and desolate aspect, which seems to indicate the propinquity of the "funereal glaciers" of the Pole. The daring traveller who beards the Winter-king in his own realms meets no more with massive and lofty mountain-crests; a few only of the great chains of Europe and Asia--here the Scandinavian Alps, there the Oural Mountains; still further, at the easternmost extremity of Asia, some scattered summits, which we may consider as belonging to the elevation of the Altai, prolong even to the Arctic shores their cantled and snow-shrouded peaks. Everywhere, also, immense steppes, intersected by swamps and relieved with woods of fir and birch, spread for leagues upon leagues in the dull light of a wintry sky, until they merge into those rent and rocky plains, bare of all vegetation except a few lichens and mosses, which are almost always encrusted in glittering snow and ice, and mingle in the distance with the frost-bound waters of the Arctic Sea. It is in America that these icy deserts are most extensive; not only because that continent stretches much nearer the Pole than does the Old World, but because, owing to its geographical disposition and geological structure, it is much more exposed, even towards the south, to that combined action of the atmosphere, land, and water, whose effects constitute the Arctic climate.[190] This climate, then, prevails over nearly the whole of Danish America, the recently-acquired possessions of the United States, the Hudson's Bay Territory, and Labrador, down to that inconsiderable watershed which separates from the tributaries of Hudson's Bay, the three basins of the St. Lawrence, the five great lakes, and the Mississippi. This line of watershed undulates between the 52nd and 49th parallel of latitude, from Belle-Isle Strait to the sources of the Saskatchewan, in the Rocky Mountains, where it inflects towards the Pacific Ocean, skirting on the north the basin of the Columbia. "Thus circumscribed on the side of the south," say Messieurs Hervé and F. de Lanoye,[191] "the Arctic lands of America, including the archipelagoes of the north and north-east, cannot measure less than 560,000 square leagues. They therefore greatly exceed in superficies the mass of the European lands, estimated at about 490,000 square leagues."