Our geographical knowledge of the various branches of Missouri, is still more limited than respecting the Mississippi. Of the main stream, as high as the Man dan villages, our notices are tolerably ample. Lewis and Clarke, Stoddard, Brackenridge, Bradbury, and others, have enlarged the public stock of information on this interesting topic hut with all that has yet been published, a feeble light has been thrown upon those immense regions.
The greatest length of the basin of Missouri, is from the mouth of that stream to the head of Marias river, !200 miles ; its greatest breadth, from the sources of the Platte to a few miles south-east of the Mandan villages, 700 miles. The outline is too vaguely known to admit precision, as to the area of this vast extent ; it must, however, equal, if not exceed 500,000 square mulles, equal to 320,000,000 United States' acres.
General features.—Engrasping the whole valley of Missouri in one view, two remarkable features must comtnand pre-eminence ; the turbid muddy appearance of the water, and the very great difference in length and volume of the confluent streams from the right bank, when compared with those from the left bank of the main recipient. Whilst from the right, the Missouri receives such vast branches as the Yellow Stone, Chay enne, Quicourre, Platte, Kanses, and Osage; from the left, all the branches are of minor importance. This characteristic continues to distinguish the valley of the tower Mississippi below the mouth of Ohio; where, to the vast volumes of the White, Arkansaw, and Red rivers, are opposed the very inferior streams, the Yazoo, Big Black, and Homochitto.
It would appear that the Mississippi basin is divided into two immense inclined planes, falling from the two opposing chains of mountains, that of the Chippewan, and the Appalachian ; and that the two planes are in a very near ratio to the respective magnitude and elevation of the chains from which they decline. The line of contact between those planes is formed by the Illinois. and thence by the Mississippi, below the mouth of the former ; and if we extend our views beyond the Missis sippi basin, Lake Michigan is evidently the continuation of this line of depression to the north ; whilst to the south-east, the rivers entering the gulf of Mexico, as fa: as the Appalachicola inclusive, belong to the Appalachian plane ; and to the south-west, all streams flowing into the gulf of Mexico, as far the Rio Grande del Norte inclu sive, appertain to the plane of the Chippewan.
But to return to our particular subject, that of the Missouri valley. It would be useless to give a list of
the smaller rivers of this tract, the names of which are hardly known. A general outline is all that ought to be attempted. The Missouri valley is bounded on the west by the enormous chain of the Chippewan or Rocky mountains, from which flow the sources of the Missouri and most of its largest branches. The exact elevation of the Chippewan, or indeed any of its peaks within the domain of the United States, have never been determined, and the result made public. The general table land upon which those ridges rest must from the great length of the Missouri exceed 3000 feet ; perhaps about 5000 feet would be a safe estimate for the gneral elevation of the whole chain, particular peaks excepted.
The Chippewan partakes with the adjacent country the character of nakedness, timber being rare and of stunted growth. Like the Appalachian, and most other American mountains, the Chippewan is formed in col lateral ridges, with deep intervening valleys. The rivers rise in these valleys and pierce the ridges in their course., The sources of Missouri extend along the chain through near eight degrees of lititude, or upwards of 500 miles. In this region the main stream and most of its tributaries flow to north-east. The sources of Big Horn, a branch of the Yellow Stone river, rise at N. Lat. 41° 30', whilst Marias river has its most northern source above N. lat. 48° 30'. Some of the northern confluents of Missouri probably lie as far as N. lat. 50.
Missouri leaves the Chippewan by falling over con tinued ledges of rocks, in a distance of 18 miles ; after which, this overwhelming mass of water is augmented every few miles by large tributary waters, without falls or even shoals to its mouth. The channel is deep, and bounded by enormous precipices of rock. The imme diate margin of the streams only excepted, this almost interminable expanse is priarie, devoid of timber ; and except the deserts of Arabia, no part of the earth presents an equal surface, less inviting to civilized man, than the far greater part of the valley of Mis souri. Its asperities become more apparentas infor mation respecting its real features expand. The general character of this extensive valley may be com pleted in few words ; that, with some very partial ex ceptions, it is a wide and arid waste in summer, and over which in winter, the piercing winds of the north sweep without impediment, and on which a dense civil ized population can never exist.