In order to prove the high prairies of the state of Ohio to have been once covered by the waters of Lake Erie, Mr. A. maintains, that the channel of the Niagara river has been worn down "several hundred feet" by the attrition of its waters. Mr. A. should have shown, that the banks of the Niagara are, at this time, several hundred feet high, or, like the Potomac, at Harper's Ferry, has broken through a mountain "several hundred feet" high; but neither the one nor the other is the fact; the face of the country, on either side of the river, is comparatively low and champaign; and were it possible for the waters of the lake to rise considerably above their present level, they would meet with no obstruction or impediment, for many miles on either side the river, but would be precipitated over the cataract, into Ontario, and down the St. Lawrence to the Atlantic. But supposing there had been a mountain running between Lakes Erie and Ontario of sufficient height to prevent the water of the former from passing into the latter, it must evidently have found other places through which to escape, and before it would rise high enough to overflow the elevated region of Madison and Fayette counties, in Ohio, it would have passed over into the heads of the Alleghany. But it is impossible to imagine this, unless we suppose the Atlantic to have been six or seven hundred feet higher than at present, which, according to Mr. A. would have made prairie of all the Atlantic states.
The fact of shells and other marine substances having been found in a few places, by digging in the prairies, proves nothing, or proves too much, for they are found in equal or greater quantities all over America, in the sides and near the summit of the Alleghany mountains; on the Andes, in South America, and the Alps, in Europe. The resemblance which the soil, in the low prairies, and not in the high, bears to the alluvial, can justly be attributed, it is presumed, to the leaves and other vegetables and light materials of which they are composed, having been washed by heavy rains, for ages past, from the higher to the lower places. This will also account for the circumstance of trees growing upon the summits of the hills of steep ascent: being thin and poor, the grass neither grows sufficiently long or thick to kill the timber when fired. They could not have been islands in this fairy lake; because their summits are frequently much lower than high prairie flats a few miles distant. These are facts which will be recollected by those who have ever travelled through a prairie country of any extent.
But suppose it to have been proved, that the waters of Lake Erie once overspread the state of Ohio, from its present shore to Chillicothe, (a supposition which I trust has however been shown to be visionary) does it follow that the prairies were occasioned by such overflowing? If the water, by covering the country, prevented the timber from growing, should we not naturally look for the largest timber on the higher grounds which would be first forsaken by the waters, and for small timber on the low grounds, where the water remained longest? If this be true, (and it is unquestionable) we should then look for prairies on the low grounds bordering on Lakes Erie, Huron, and Michigan; and the thickly timbered country would be on the high land, near the sources of the rivers. But the contrary is absolutely the fact: we find heavy timbered land, and no prairies, in the low countries north of the lakes, and none south, either in Michigan territory or elsewhere, until we arrive near the sources of the rivers. It is true, that the water standing in ponds will prevent the timber from growing; but the difference is readily observed between prairies, properly so called, and those bogs.
But to prove farther that water had no agency in bringing the prairies into existence, we may mention those on and near the summit of the Alleghany mountains, (principally in Alleghany County.[47]) Many of those prairies are ten or twelve miles in length, and three or four in width. Will it be pretended that the sides of those mountains were also lakes? Farther—the most extensive prairies known, are the very high plains immediately west of the Rocky Mountains, and east of the mountains near the sources of the Arkansaw and Missouri rivers, extending even on the spurs of those mountains; a country the highest perhaps in North America, with a great and continued descent to the Pacific on the one side, and to the Gulf of Mexico on the other.
The barrens, also, found in Kentucky, are another evidence that water had no agency in their formation—they are situate, it is believed, in the elevated parts of the country exclusively.
The writer of this, deeming it unnecessary to say more, or to produce more facts, (although much more may be said, and many more facts produced) to prove that prairies were not lakes, will now endeavour to prove that they were occasioned by the combustion of vegetables.
Prairies are found in those countries only that are congenial to the growth of grass, and only where the soil is sufficiently rich to produce it luxuriantly—they are found commonly on high plains, sufficiently drained to prevent water from remaining on them the whole year; for it is by no means necessary that they should be always dry; on the contrary, if they are sufficiently level to prevent the rains from running off immediately, the grass will grow thicker and higher—but they must be sufficiently dry to burn, at least once in two or three years, during the long, dry season, called Indian summer. It has been universally remarked, that these seasons are much longer as we proceed westerly—commencing usually in October, and continuing a month and a half or two months, during which the vegetation is killed by the frosts, and dried by the sun; the wet prairies are also dried, and before the season has expired, the grass is perfectly combustible.
The Indians, it is presumed, (and the writer, from a residence in their country and with them, is well acquainted with their customs) burn the woods, not ordinarily for the purpose of taking or catching game, as suggested by Mr. A. but for many other advantages attending that practice. If the woods be not burned as usual, the hunter finds it impossible to kill the game, which, alarmed at the great noise made in walking through the dry grass and leaves, flee in all directions at his approach. Also the Indians travel much during the winter, from one village to another, and to and from the various hunting grounds, which becomes extremely painful and laborious, from the quantity of briers, vines, grass, &c. To remedy these and many other inconveniences, even the woods were originally burned so as to cause prairies, and for the same and like reasons they continue to be burned towards the close of the Indian summer.
Woodland is not commonly changed to prairie by one burning, but by several successive conflagrations; the first will kill the undergrowth, which causing a greater opening, and admitting the sun and air more freely, increases the quantity of grass the ensuing season: the conflagration consequently increases, and is now sufficiently powerful to destroy the smaller timber; and on the third year you behold an open prairie.