The vessels employed on the Mississippi vary in size from 150 to 1500 tons burden, and in some cases more. It is necessary, too, that these should be built so to draw as little water as possible, the largest not exceeding when loaded from 7 to 8 feet, as this great river is also impeded by bars or “chains” extending across it, though not to the same extent as the Ohio and other smaller rivers. At New Orleans, the _levee_ or quay is from four to five miles in extent, with an average breadth of 100 feet. It is 15 feet above low-water mark, or that condition of the river when its waters retire within their natural bed, and is 6 feet above the level of the city, to which it is graduated by an easy descent. It is constructed of the alluvial soil brought down from the north, and deposited in the vicinity by the waters of the Mississippi. [Sidenote: Boats of the Mississippi.] Prior to the general introduction of steam navigation, the trade carried on by flat boats occupied a great space in this now important emporium of commerce. Hundreds of long, narrow, black, dirty-looking, crocodile-like craft lay sluggishly without moorings, upon the soft _batture_,[154]—a heterogeneous compound produced from the territories of the Upper Mississippi and its numerous tributaries, while they poured out their contents upon the quay. These rafts, or flat boats as they are technically called, which frequently had on board cargo to the value of from 3000_l._ to 5000_l._, are covered with a raised work or scantling, giving them the appearance of long, narrow cabins, built for the purpose of habitation, but really designed to protect their contents from the weather. They are guided by an oar at the stern, aided with an occasional dip of two huge pieces of timber, which move on each side like fins (rude imitations of the leeboards to be found in Dutch galiots or Thames barges), and float with the stream at the rate of 3 miles the hour. Such were the means of carriage of the up-country’s products on the Mississippi about half a century ago, and steam-boat navigation has not diminished the number of these flat boats. They are so natural, simple, and cheap a mode of transporting produce down the stream, that as long as the Mississippi passes with such rapidity from its source to its embouchure in the gulf, the traveller will be sure to meet with these unsightly masses floating on its bosom; swayed to and fro by its currents, countercurrents, and eddies, often shifting end for end like some species of shell-fish, and not unfrequently resembling the crab, preferring the oblique to the forward movement. [Sidenote: Boatmen.]