‘It will be readily seen, that as soon as these fires commenced, all the young timber within their range must have been destroyed. The whole state of Illinois, being one vast plain, the fires kindled in different places, would sweep over the whole surface, with a few exceptions, of which we are now to speak. In the bottom-lands, and along the margins of streams, the grass and herbage remain green until late in the autumn, owing to the moisture of the soil. Here the fire would stop for want of fuel, and the shrubs would thus escape from year to year, and the outer bark acquire sufficient hardness to protect the inner and more vital parts of the tree. The margins of the streams would thus become fringed with thickets, which, by shading the ground, would destroy the grass, while it would prevent the moisture of the soil from being rapidly evaporated, so that even the fallen leaves would never become so thoroughly dry as the grass of the prairies, and the fire here would find comparatively little fuel. These thickets grow up into strips of forests, which continue to extend until they reach the high table-land of the prairie; and so true is this, in fact, that we see the timber now, not only covering all the bottom-lands and hill sides, skirting the streams, but wherever a ravine or hollow extends from the low grounds up into the plain, these are filled with young timber of more recent growth. But the moment we leave the level plane of the country, we see the evidences of a continual struggle between the forest and the prairie. At one place, where the fire has on some occasion burned with greater fierceness than usual, it has successfully assailed the edges of the forest, and made deep inroads; at another, the forest has pushed out long points or capes into the prairie. ‘It has been suggested that the prairies were caused by hurricanes, which had blown down the timber and left it in a condition to be consumed by fire, after it was dried by laying on the ground. A single glance at the immense region in which the prairie surface predominates, must refute this idea. Hurricanes are quite limited in their sphere of action. Although they sometimes extend for miles in length, their track is always narrow, and often but a few hundred yards in breadth. It is a well known fact, that wherever the timber has been thus prostrated, a dense and tangled thicket shoots up immediately, and, protected by the fallen trees, grows with uncommon vigor.