When the rivers rise above their ordinary height, the waters of the smaller streams, which are backed up by the freshets of the former, break over their banks, and cover all the low grounds. Here they stand for a few days, or for many weeks, especially towards the bluffs; for it is a striking fact in the geology of the western country, that all the river bottoms are higher on the margins of the streams than at some distance back. Whenever increase of population shall create a demand for this species of soil, the most of it can be reclaimed at comparatively small expense. Its fertility will be inexhaustible, and if the waters from the rivers could be shut out by dykes or levees, the soil would be perfectly dry. Most of the small lakes on the American bottom disappear in the summer, and leave a deposit of vegetable matter undergoing decomposition, or a luxuriant coat of weeds and grass.
As our prairies mostly lie between the streams that drain the country, the interior of the large ones are usually level. Here are formed ponds and lakes after the winter and spring rains, which remain to be drawn off by evaporation, or absorbed by an adhesive soil. Hence the middle of our large, level prairies are wet, and for several weeks portions of them are covered with water. To remedy this inconvenience completely, and render all this portion of soil dry and productive, only requires a ditch or drain of two or three feet deep to be cut into the nearest ravine. In many instances, a single furrow with the plough, would drain many acres. At present, this species of inundated land offers no inconvenience to the people, except in the production of miasm, and even that, perhaps, becomes too much diluted with the atmosphere to produce mischief before it reaches the settlements on the borders of the prairie. Hence the inference is correct, that our inundated lands present fewer obstacles to the settlement and growth of the country, and can be reclaimed at much less expense, than the swamps and salt marshes of the Atlantic States.
2. _River Bottoms or Alluvion._ The surface of our alluvial bottoms is not entirely level. In some places it resembles alternate waves of the ocean, and looks as though the waters had left their deposit in ridges, and retired.