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.
‘Some have imagined that our prairies have been lakes; but this hypothesis is not tenable. If the whole state of Illinois is imagined to have been one lake, it ought to be shown that it has a general concavity of surface. But so far from this being true, the contrary is the fact; the highest parts of the state are in its centre. If we suppose, as some assert, that each prairie was once a lake, we are met by the same objection; as a general rule, the prairies are highest in the middle, and have a gradual declivity towards the sides; and when we reach the timber, instead of finding banks corresponding with the shores of a lake, we almost invariably find valleys, ravines, and water-courses depressed considerably below the general level of the plain.
‘Wherever hills are found rising above the common plane of the country, they are clothed with timber; and the same fact is true of all broken lands. This fact affords additional evidence in support of our theory. Most of the land in such situations is poor; the grass would be short, and if burned at all, would occasion but little heat. In other spots, the progress of the fire would be checked by rocks and ravines; and in no case would there be that accumulation of dry material which is found on the fertile plain, nor that broad, unbroken surface, and free exposure, which are necessary to afford full scope to the devouring element.
‘By those who have never seen this region, a very tolerable idea may be formed of the manner in which the prairie and forest alternate, by drawing a colored line of irregular thickness, along the edges of all the water-courses laid down on the map. This border would generally vary from one to five or six miles, and often extend to twelve. As the streams approach each other, these borders would approach or come in contact; and all the intermediate spaces not thus colored would be prairie. It would be seen that in the point formed by the junction of the Ohio and Mississippi, the forest would cover all the ground; and that, as these rivers diverge, and their tributaries spread out, the prairies would predominate.’
Between the Platte river, and the head-waters of the Colorado and Sabine rivers, there is an extensive desert tract, which has been called the Great American Desert, stretching from the Ozark Mountains to the Chippewan. Over this desert the members of Long’s expedition travelled nearly a thousand miles. The intense reflection of light and heat, from this tract, added much to the fatigue and suffering of their journey. ‘We often met with extensive districts covered entirely with loose and fine sand, blown from the adjacent hills. In the low plains along the river where the soil is permanent, it is highly impregnated with saline substances, and too sterile to produce any thing except a few stinted carices and rushes. As we approached the mountains, we felt or fancied a very manifest change in the character of the weather, and the temperature of the air. Mornings and evenings were usually calm, and the heat more oppressive than in the middle of the day. Early in the forenoon, a light and refreshing breeze often sprung up, blowing from the west or south-west, which again subsided on the approach of night. This phenomenon was so often observed, that we were induced to attribute it to the operation of the same local cause, which in the neighborhood of the sea produces a diurnal change in the winds, which blow alternately to and from the shore. The Rocky Mountains may be considered as forming the shore of that sea of sand, which is traversed by the Platte, and extends northward to the Missouri above the great bend. The rarefaction of the air over this great plain, by the reverberation of the sun’s rays during the day, causes an ascending current, which is supplied by the rushing down of the condensed air from the mountains. * * * * For several days the sky had been clear, and in the morning we had observed an unusual degree of transparency in every part of the atmosphere. As the day advanced, and the heat of the sun began to be felt, such quantities of vapor were seen to ascend from every part of the plain, that all objects at a little distance appeared magnified, and variously distorted. An undulating and tremulous motion in ascending lines was manifest over every part of the surface. Commencing soon after sunrise it continued to increase in quantity until the afternoon, when it diminished gradually, keeping an even pace with the intensity of the sun’s heat. The density of the vapor was often such as to produce the perfect image of a pool of water in every valley upon which we could look down at an angle of about ten degrees. This aspect was several times seen so perfect and beautiful as to deceive almost every one of our party. A herd of bisons, at the distance of a mile, seemed to be standing in a pool of water, and what appeared to us the reflected image was as distinctly seen as the animal itself.4 Illusions of this kind are common in the African and Asiatic deserts, as we learn from travellers and from the language of poets.’
The Pine Plains are a district of sandy alluvion, bounded by the gravelly soil of Guilderland and Duanesburgh on the south-west, and by the river alluvions of Niskayuna and Watervliet, on the north-east, and covering an area of about seventy square miles. This tract is included in a triangle formed by the junction of the Mohawk with the Hudson, and of which the Helleberg, a lofty chain of highlands, visible from the plains at the distance of twenty miles, forms the south-western boundary. Situated near the centre of a state, computed at forty thousand square miles, and containing a population of nearly two million souls, this tract presents the topographical novelty of an unreclaimed desert, in the heart of one of the oldest counties in the state, and in the midst of a people characterized for enterprise and public spirit. Several attempts have lately been made to bring this tract into cultivation, and from the success which has attended the introduction of gypsum, and other improved modes of agriculture, it is probable the whole will, at some future period, be devoted to the cultivation of the various species of grasses, fruit trees, and esculent roots; three branches of agriculture to which its sandy soil seems admirably adapted.
GENERAL REMARKS ON PLAINS AND PRAIRIES.
Plains like valleys are of two classes; the high plains, which are found between two chains of mountains, are frequently of great extent, and are placed as it were upon the shoulders of secondary mountains; such are the elevated plains of Tartary, of Persia, and probably of the interior of Africa. The plains of Quito are twelve thousand feet above the level of the sea; those of Karakorum, in Chinese Mongolia, are probably as elevated. The low plains, whose soil is composed of sand, gravel and shells, seem formerly to have been the basins of interior
