present the appearance of heaps of clay, great quantities of which, on the melting of the snows, and in heavy rains, are precipitated and carried to the principal river. This clay is of a grey color, extremely tenacious, being mixed with a large proportion of calcarious earth; the incumbent soil having been first carried away; the rock on which it reposed being laid bare to the frost and sun, and perhaps affected by the burning of coal banks near it, gradually crumbled and united with the clay. In taking up a handful, one may pick out pieces of gypsum, (sulphat of lime) some of half an ounce weight. Near these spots are usually found glaubers salt, (sulphat of soda) and common salt, oozing with water out of the ground, and crystallized {230} on the surface. The most remarkable fact, is the appearance on these heaps of clay, of the remains of trees, in a state of petrifaction, and some of enormous size. Fragments may be every where picked up, but stumps of four or five feet in height, perfectly turned to stone, and the trunks of tall trees, may be seen and traced. This is extraordinary in a country, where even in the richest alluvions the timber attains but a stinted growth.
From these facts an ingenious theorist might conjecture, that the Missouri has not always brought down in its channel, that astonishing quantity of earth which it does at the present day. It is probable that other causes, as in Tartary, might have operated in preventing the growth of woods, in a great proportion of this western region; but something of a different kind must have effected a change in this country, which apparently was once covered with trees. What immense quantities of the earth must have been carried off to form the great alluvions of the Mississippi, by means of the Arkansas, Red river, and chiefly from the Missouri, not to mention the vast quantities lost in the gulf of Mexico. The result of a {231} calcu-
