The Ohio is formed by the junction of the Alleghany and Monongahela rivers at Pittsburg, that town being seated in the fork--its breadth there, is between eight and nine hundred yards. From the mouths of those two rivers it narrows and deepens for some distance; but afterwards, from the accession of the many tributary streams by which it is supplied, gradually becomes wider and deeper, until it empties itself into the Mississippi. The length of the Ohio, following its meanders, is about 950 miles, and it may be said to be navigable almost the entire year, as the water must be unusually low when the smaller steam-boats cannot ply to Pittsburg. The character of this river is somewhat peculiar. But for the improvements on the banks, when you have seen six or eight miles of this stream, you are acquainted with the remainder as far as the Falls--that is to say, any variety that may be in the scenery will occur in any given six miles from Pittsburg to that point. Below Louisville there are one or two rocky bluffs, and the face of the country is somewhat different. The channel of the Upper Ohio lies between hills, which frequently approach the _mamélle_ form, and are covered with a heavy growth of timber. Where the hills or bluffs do not rise immediately from the river, but recede some distance, the space between the river and the hill is called bottom land, from the circumstance of its being overflown annually; or having at some former period formed part of the river's bed, which is indicated by the nature of the soil. The bluffs and bottoms invariably alternate; and when you have bluffs on one side, you are sure to have bottom on the other. The windings are extremely uniform, with few exceptions, curving in a serpentine form in so regular a manner, that the Indians always calculated the distance by the number of bends. "The Falls" are improperly so termed, as this obstruction is nothing more than a gradual descent for a distance of about a mile and a half, where the water, forcing its way over a rugged rocky bottom, presents the appearance of a rapid. Below this the country is of various aspects--hills, bottom-land, and high rocky bluffs; and towards the mouth, cotton-wood trees, (_populus angulata_), and cane brakes, are interspersed along the banks. The junction of these two noble rivers, the Ohio and Mississippi, is really a splendid sight--the scenery is picturesque, and the water at the point of union is fully two miles broad.