This river has a broad valley, bounded by bluffs from two to five hundred feet high, faced with rocky precipices near its source, and presenting abrupt declivities, intersected by numerous ravines lower down. It has a spacious bed, depressed but a few feet below the bottoms, and exhibiting one continued stratum of sand through the greater part of its length. It is the channel through which the water of a vast extent of country is carried off, yet, during most of the summer season, it is entirely destitute of running water throughout a large proportion of its extent, a circumstance in proof of the aridity of region drained by it. Fifty miles above its mouth, it receives at least two-thirds of its water from its principal tributary, denominated the North Fork. This fork rises between the Arkansa and Canadian, and has a meandering course of about seven hundred miles. Six miles above the fork just mentioned, another tributary enters the Canadian called the South Fork, about half as large as the other. Notwithstanding the supplies afforded by these two tributaries, the Canadian has not a sufficiency of water in summer to render it navigable even to their mouths. At the distance of twenty miles above its mouth, a chain of rocks (slaty sandstone) extends across the bed of the river, but occasions no considerable fall. A little above the entrance of the South Fork, is another of the same {232} description, forming rapids of moderate descent, not more than four hundred yards in length. With these exceptions, the bed of the river presents no rocky formations in place, for more than four hundred miles from its confluence with the Arkansa. About three hundred and fifty miles from that point, beds of gypsum, or plaster of Paris, begin to make their appearance in the bluffs fronting upon the river, and upon the declivities of the highland knobs. A great abundance of this article is to be met with, not only upon the Canadian, but also upon the upper part of the Arkansa. The hills, in which it is imbedded, are composed of ferruginous clay and fine sand of a deep red complexion. Hence the Arkansa derives the colouring matter that gives to its waters their reddish hue. The bottoms of the Canadian, in the neighbourhood of its mouth, are possessed of a soil exceedingly prolific; but, like those of the other rivers of this region, the more remote their situation from the mouth of the river, the more sandy and sterile is their appearance. Its valley is plentifully supplied with timber of an excellent quality, for a distance of about two hundred miles on the lower part of the river; and the high lands, for nearly the same distance, are agreeably diversified with prairies and woodlands. This portion of the river is situated eastward of the assumed meridian, and the country upon it has already been partially described in a former part of this report.