It is, in fact, the old bed of seas and lakes, which has been so gradually elevated as to have suffered little disturbance. Consistently with its level surface, its soils have not been carried away by rain and flood, but rather cover it with a deep and widespread mantle. This is the great source of its wealth in Nature's creations of vegetable and animal life, and from it will be drawn the wealth of its future inhabitants. On this account its products have a character of uniformity; but viewed from the stand-point of the political philosopher, so long as peace and steam bind the natural sections of our country together, so long will the plains be an important element in a varied economy of continental extent. But they are not entirely uninterrupted. The natural drainage has worn channels, and the streams flow below the general level. The ancient sea and lake deposits have neither been pressed into very hard rock beneath piles of later sediment, nor have they been roasted and crystallized by internal heat. Although limestone rock, they easily yield to the action of water, and so the side drainage into the creeks and rivers has removed their high banks to from many rods to many miles from their original positions. In many cases these banks or bluffs have retained their original steepness, and have increased in elevation as the breaking-down of the rock encroached on higher land. In other cases the rain-channels have cut in without removing the intervening rocks at once, and formed deep gorges or canyons, which sometimes extend to great distances. They frequently communicate in every direction, forming curious labyrinths, and when the intervening masses are cut away at various levels, or left standing like monuments, we have the characteristic peculiarities of "bad lands" or _mauvaises terres_. In portions of Kansas tracts of this kind are scattered over the country along the margins of the river and creek valleys and ravines. The upper stratum of the rock is a yellow chalk; the lower, bluish, and the brilliancy of the color increases the picturesque effect. From elevated points the plains appear to be dotted with ruined villages and towns, whose avenues are lined with painted walls of fortifications, churches, and towers, while side alleys pass beneath natural bridges or expand into small pockets and caverns, smoothed by the action of the wind, carrying hard mineral particles. But this is the least interesting of the peculiarities presented by these rocks. On the level surfaces, denuded of soil, lie huge oyster-shells, some opened and others with both valves together, like remnants of a half-finished meal of some titanic race, who had been frightened from the board, never to return. These shells are not thickened like most of those of past periods, but contained an animal which would have served as a meal for a large party of men. One of them measured twenty-six inches across.