will better please it; and even if it is banked up and forced to keep to the old one, it will not deepen, but do all it can to raise it, and leap out of it. And although, wherever water has a steep fail, it will swiftly cut itself a bed deep into the rock or ground, it will not, when the rock is hard, cut a wider channel than it actually needs; so that if the existing river beds, through ranges of mountain, had in reality been cut by the streams, they would be found, wherever the rocks are hard, only in the form of narrow and profound ravines,--like the well-known channel of the Niagara, below the fall; not in that of extended valleys. And the actual work of true mountain rivers, though often much greater in proportion to their body of water than that of the Niagara, is quite insignificant when compared with the area and depth of the valleys through which they flow; so that, although in many cases it appears that those larger valleys have been excavated at earlier periods by more powerful streams, or by the existing stream in a more powerful condition, still the great fact remains always equally plain, and equally admirable, that, whatever the nature and duration of the agencies employed, the earth was so shaped at first as to direct the currents of its rivers in the manner most healthy and convenient for man. The valley of the Rhone may, though it is not likely, have been in great part excavated in early time by torrents a thousand times larger than the Rhone; but it could not have been excavated at all, unless the mountains had been thrown at first into two chains, between which the torrents were set to work in a given direction. And it is easy to conceive how, under any less beneficent dispositions of their masses of hill, the continents of the earth might either have been covered with enormous lakes, as parts of North America actually are covered; or have become wildernesses of pestiferous marsh; or lifeless plains, upon which the water would have dried as it fell, leaving them for great part of the year desert. Such districts do exist, and exist in vastness: the _whole_ earth is not prepared for the habitation of man; only certain small portions are prepared for him,--the houses, as it were, of the human race, from which they are to look abroad upon the rest of the world, not to wonder or complain that it is not all house, but to be grateful for the kindness of the admirable building, in the house itself, as compared with the rest. It would be as absurd to think it an evil that all the world is not fit for us to inhabit, as to think it an evil that the globe is no larger than it is. As much as we shall ever need is evidently assigned to us for our dwelling-place; the rest, covered with rolling waves or drifting sands, fretted with ice or crested with fire, is set before us for contemplation in an uninhabitable magnificence; and that part which we are enabled to inhabit owes its fitness for human life chiefly to its mountain ranges,