However rapid may be the growth of population in North America, however great the rapidity--shall we say the avidity?--of the American _squatters_ in their conquest and appropriation of the soil, the Desert still occupies, principally in "the far West" and the North--that is to say, in the angle comprised between the line of the great lakes and the Rocky Mountains--an area almost equal to the whole of Continental Europe. There we find, as Mr. Johnstone points out, the largest plains in the world. One such, for example, is that immense basin which extends from the mouths of the Mackenzie, in the icy Arctic Sea, even to the remote Delta of the Mississippi, and from the huge chain of the Rocky Mountains, with their piny recesses and snowy peaks, to the less rugged and more pastoral range of the Alleghanies; a total area of 4,400,000,000 square yards (3,245,000 square miles). A table-land of gentle elevation, nowhere above 1500 feet, and rarely more than 700 feet high, separates this territory into two secondary basins. The _north-east_, which pours its waters into the Arctic Ocean, Hudson's Bay, and through the Canadian lakes and River St. Lawrence, into the Atlantic; and, The _south_ basin, of the Missouri-Mississippi, whose mighty waters flow into the Gulf of Mexico. It is in the latter that the traveller encounters the great grassy plains of the _Prairies_ or _Savannahs_ which are so remarkable a feature of North America, and which chiefly lie along the western bank of the Mississippi. "There are no prairies," says Sir J. Richardson, "to the north of Peace River, and the level lands which border the Rocky Mountains do not extend beyond the Great Salt Lake." Under so wide a range of latitude the plain necessarily embraces a great variety of soil, climate, and productions; but being almost in a state of nature, it is characterized in its central and southern parts by interminable grassy savannahs and enormous forests, and in the far north by deserts not less dreary than those of Siberia.[90]