The people in Pittsburgh, and the western country along the waters of the Ohio, draw their supplies from Philadelphia and Baltimore; but they send the productions of the country, which would be too bulky for land carriage, down the Ohio and Mississippi to New Orleans. From Pittsburgh to New Orleans the distance is two thousand one hundred and eighty-three miles. On an average it takes about twenty-eight days to go down there with the stream; but to return by water it takes from sixty days to three months. The passage back is very laborious as well as tedious; on which account they seldom think of bringing back boats which are sent down from Pittsburgh, but on arriving at New Orleans they are broken up, and the plank sold. These boats are built on the cheapest construction, and expressly for the purpose of going down stream. The men get back the best way they can, generally in ships bound from New Orleans to the southern states, and from thence home by land. Now, if the passage from the Ohio to the Patowmac is opened, it cannot be supposed that the people in Pittsburgh and the vicinity will continue thus to send the produce down to Orleans, from whence they cannot bring any thing in return; they will naturally send to the federal city, from whence they can draw the supplies they are in want of, and which is so much nearer to them, that when the navigation is perfected it will be possible to go there and back again in the same time that it requires merely to go down to New Orleans. [Sidenote: FLOODS AND EDDIES.] But although the people of that country which borders upon the Ohio and its waters, in the vicinage of Pittsburgh, may have an interest in trading to the federal city, yet those who live towards the mouth of that river will find an interest equally great in trading to New Orleans, for the Ohio River is no less than eleven hundred and eighty-three miles in length. How far down upon the Ohio a commercial intercourse will be kept up with the city, will most probably be determined by other circumstances than that of distance alone; it may depend upon the demand there may be at one or other port for particular articles, &c. &c.; it may also depend upon the season; for at regular periods there are floods in the Mississippi, and also in the Ohio, which make a great difference in the time of ascending and descending these rivers. The floods in the Mississippi are occasioned by the dissolution of the immense bodies of snow and ice accumulated during winter in those northern regions through which the river passes; they are also very regular, beginning in the month of March and subsiding in July. Those in the Ohio take place between Christmas and May; but they are not regular and steady like those of the Mississippi, for the water rises and falls many times in the course of the season. These floods are occasioned by heavy falls of rain in the beginning of winter, as well as by the thawing of the ice.