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.