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Show GEOLOGICAL CONFORMATION----BOTANY. 329 in the immediate vicinity of Fort Clarke, not even lime. On the other hand, the strata of black, bituminous coal appear in the hills for many hundred miles. This coal ignites easily, with a strong sulphureous smell, but it does not emit sufficient heat to serve as fuel or for the forge. In many places it may be evidently seen that these strata have been on fire. The surrounding clay is frequently burnt red, and the shards are perfectly coloured, hard and sonorous, like our bricks and Dutch clinkers. About Fort Clarke they know nothing of such fires, but they have frequently occurred lower down the Missouri. The red clay, which we have so often spoken of, appears to have been elevated by the action of fire. On the banks, extremely light, porous, cellular, red brown scoriae are everywhere found, which the people here call pumice stone, though they are totally different from the fossil usually so called, and of which extensive strata are found on the banks of the Rhine. Petrifactions of animals and plants are to be looked for only on the banks of the rivers, though they doubtless are as frequent in the chains of hills, where they are concealed by the greensward from the eye of the passing observer. I was told that, in the prairie, about twenty miles distant from Fort Clarke, there are places in the hills where the organic remains of the antediluvian world lie exposed on the surface, but that country can be visited only for short intervals of time, and that, too, attended with great danger, on account of the hostile Indians. Entire petrified trunks of trees, such as we had observed on the banks of the Missouri, are said to be there, and impressions of crabs, or similar Crustacea, have been found. The Indians speak of a petrified man, at the distance of three or four days' journey, whose head is round, and lies detached from the body. The story about the head is, probably, incorrect, as they pretend to be able to discern the countenance; but the rest of the skeleton is said plainly and distinctly to be seen. These are, doubtless, the remains of some antediluvian animal. It is much to be regretted that it is impracticable to explore, without much risk, a country so abounding with remains of this nature. The extensive prairies, and their hills, certainly produce a great variety of plants, of which a part only have been described. Bradbury collected many plants about the Mandan villages, which were described by Pursh; and Nuttall's works likewise contain many; but there is, undoubtedly, much remaining to be done, especially in the chain of the Black Hills. The country, about the Missouri, has its peculiar botanical characters. The tongues of land at the bends of the river are generally covered with wood ; other parts of the banks more rarely so; the species of trees and shrubs which occur here have already been mentioned. There are no pines in the vicinity of Fort Clarke ; but they are found higher up the river; nor are there any birch trees; indeed, I did not meet with one on the whole course of the Missouri. These do not grow, except on the tributaries of the Upper Missouri, for instance, Knife River. At the distance of three days' journey from the mouth, at the foot of the mountains which are improperly called La Cote Noire, though they join the Black Hills, of which they are a branch, the latter form 2 u |