"Every fountain and river, from the inch-deep streamlet that crosses the village lane in trembling clearness, to the massy and silent march of the everlasting multitude of waters in Amazon or Ganges, owe their play and purity and power to the ordained elevations of the earth. Gentle or steep, extended or abrupt, some determined slope of the earth's surface is of course necessary before any wave can so much as overtake one sedge in its pilgrimage; and how seldom do we enough consider, as we walk beside the margins of our pleasant brooks, how beautiful and wonderful is that ordinance, of which every blade of grass that waves in their clear waters is a perpetual sign,--that the dew and rain fallen on the face of the earth shall find no resting-place; shall find, on the contrary, fixed channels traced for them from the ravines of the central crests down which they roar in sudden ranks of foam to the dark hollows beneath the banks of lowland pasture, round which they must circle slowly among the stems and beneath the leaves of the lilies; paths prepared for them by which, at some appointed rate of journey, they must evermore descend, sometimes slow, and sometimes swift, but never pausing; the daily portion of the earth they have to glide over marked for them at each successive sunrise; the place which has known them knowing them no more; and the gateways of guarding mountains opened for them in cleft and chasm, none letting them in their pilgrimage, and from afar off the great heart of the sea calling them to itself: 'Deep calleth unto deep.'" Geologists, however, do not in these days teach that the present paths of rivers were made for them, but rather that the rivers have carved out their own valleys for themselves. The old teaching before the days of Lyell and Hutton, the founders of modern geology, was that valleys were rents in the rocks of the earth's crust formed by some wonderful convulsion of Nature, whereby they were cracked, torn asunder, and upheaved. But a careful study of rivers and their valleys for many years has shown that there is no evidence of such sudden convulsions. The world is very old indeed, and rivers have been flowing much as we see them for ages and ages. A few thousand years is to the geologist but a short space of time; and there can be no doubt that a stream can in the course of time carve out for itself a valley. The operations of Nature seem slow to us because our lives are so short, and we can see so little change even in a generation; but the effects of these changes mount up enormously when continued through a long space of time. Nature works slowly; but then she has unlimited time, and never seems in a hurry. It is like the old story of the hare and the tortoise; and the river, working on steadily and quietly for hundreds or thousands of years, accomplishes far more in the end than sudden floods or violent catastrophes of any sort.