Page:Popular Science Monthly Volume 23.djvu/486

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if not the why, of all things terrestrial. Here is a corner of the world in which the evidences of change—of transition are—so patent that a glance reveals them to the dullest beholder. It is as if Nature were here trying to impress upon her children a great object-lesson, as if the universal Dame had said: "Behold! Look! Here have I stripped all the hills and laid bare all the valleys, that you might learn my time honored methods, and once for all see something of how worlds are made." No man would say, as he looks for the first time out over these naked hills: "Such have they ever been; such shall they always be." By no means. These, at least, are not the "everlasting hills." Here is transition. Now, transition is to the student a word of magic sound—echoing the past, prefiguring the future. Let him but behold any of Nature's processes in intermediate stage, and mystery as to mode and method vanishes; the solution is easy.

But, now that our object-lesson is before us, what can we learn about it? Let us look again from the top of the butte, this time for instruction rather than for pleasure. See, there the river winds—a silver thread, shut in by long lines of banded bluffs. Into the river valley principal ravines debouch, others into these, and so on to the very base of the bluff on which we stand. And now, you say, the problem is solved; the river is the outlet, and all these strange phenomena are due to surface-drainage. Here is the water-system, and here are its effects. But this answer can be but part of the truth, else why are no Bad Lands seen along the Desmoines or the Tennessee? Why are they not of universal occurrence? Besides, the beds of all these ravines are, for the most part, flat and level as a floor, scantily covered with short grass, or white with sage-brush (Artemisia). Only here and there a gully without water, or perchance, in some larger ravine, we may find a tiny, scarcely flowing streamlet, brown with alkali. Manifestly the river-system accounts for the general features of the country, but not for that which is peculiar. But let us look at the problem in another way. Let us begin at the bottom of these hillocks, at least as low down as we may come, and study for a moment the hillocks themselves.

We have already incidentally noticed the uniform stratification which characterizes the whole country, and is revealed by the banded appearance of the hills. At the base of one of these hills we may find (Fig. 1) a stratum of pale, yellowish clay. Just above, and perfectly conformable, is a layer of lignitic coal, inferior to soft coal, of a deep-brown color, rapidly crumbling on exposure to the air, and even, when in sufficient mass, liable to spontaneous ignition. Overlying the coal is another bed of clay of an ashy hue, containing more or less sand in composition. Next comes a layer in which sand predominates, a distinct gray in color; then a bed of clay of a bluish tint, another layer of coal, a layer of yellow clay, a stratum of very soft sandstone, another bed of clay, and then a foot or two of reddish-