This position may be considered as the head of constant {35} navigation for the Mississippi. The Mississippi, from New Orleans to the Ohio, is navigable for boats of the largest size; and America may be considered as the head of constant as well as heavy navigation. Ice is seldom to be found in the Mississippi as low down as the mouth of the Ohio, and never in so large quantities as to oppose any serious obstruction to the navigation. The navigation of the Ohio has a serious impediment about four and a half miles above the town, occasioned by a limestone bar extending across the river, called the Grand Chain. This bar is impassable in the lowest stage of the water, and will not admit boats of any considerable burden, except in the higher stages. The Mississippi has, in like manner, two bars, called the Big and Little Chain, which appear to be a continuation of the same range of rocks as that in the Ohio, extending across the point of land situated between the two rivers. These bars are situated a little above the Tyawapatia Bottom, about thirty miles above the mouth of the Ohio, and in low water have but a moderate depth of water across them; which, added to the rapidity of the current, occasions a serious obstacle to the navigation. Boats suited to the navigation of both rivers above the bars here specified, should be of inferior size; those for the Mississippi not exceeding one hundred tons burden, and those for the Ohio from fifty to seventy-five tons. Any position on the Mississippi in the neighbourhood of the Ohio would be objectionable, for the following reasons:--First, The rapidity of the current, which renders it difficult to find a safe and commodious landing, there being no rocky-bound shore within thirty miles above and a far greater distance below the point. The Iron Banks,[052] seventeen miles below the mouth of the Ohio, have been thought by some an eligible position for the extensive business, {36} which, it is admitted by all, must centre in this neighbourhood. But at this place there is no safe landing; and besides, the banks are composed of layers of sand and clay alternating with each other, of an acclivity nearly perpendicular, and annually wearing away by the current of the river, which sets strongly against them. These banks are elevated about one hundred and thirty feet above the common level of the river, and are insurmountable, except by a circuitous route, leading from the river a considerable distance above and below them. Second, There are no positions on the Mississippi, except the Iron and Chalk Banks, for a great distance below the Ohio, secure from inundation. The bottom directly opposite the mouth of the Ohio, on the west side of the Mississippi is elevated a little above high water; but as it is an alluvial shore, having no permanent foundation, and the banks often falling in, it affords no conveniences or security as a place of business.