On the Ohio, the rapids are chiefly caused by bars, or as they are termed “chains of rock,” extending across the river, which, when the water is low, impede navigation and sometimes stop it altogether. Artificial means have, however, in some instances been adopted whereby a greatly increased volume of water is thrown into a single channel, but hitherto these schemes have not been of much practical utility, though the money expended in the removal of “snags” and other temporary obstructions has tended to render the navigation of the Ohio, as well as of the Mississippi, Missouri, and Red River, comparatively safe and easy to what it was when steam-boats were for the first time despatched upon these mighty streams. [Sidenote: Peculiar description of wharves and levees.] In consequence of the great fluctuations in the depth of the western rivers, no regular wharves or jetties can be formed alongside of which the boats engaged in the traffic can land their passengers and goods. In lieu of these, therefore, the banks of the river opposite to the towns, or where landing-places are necessary, are sloped off at a considerable inclination and paved with ordinary paving-stones. At intervals along the shore, and, also, at different distances up the bank, piles are driven with large ringbolts attached to their heads for the purpose of mooring the boats. Owing, also, to the same cause, and the ever varying strength of the currents of the rivers, it is necessary that the boats employed on them should be as light as possible combined with the requisite strength, of small draught of water, and of great power, so as to be able to pass over the sandbanks and make headway against the currents. [Sidenote: Description of steamers employed.] In order that the boats may land passengers without difficulty at these sloping banks or “levees,” as they are termed, and also discharge and take in freight and passengers, their bows have a very long rake, so that when they strike the bank the bow gradually rises out of the water till it has sufficient hold upon the bank to maintain its position while landing the cargo, without any material assistance from the warps attached to the mooring post. To facilitate the operation of landing, the forecastle deck carries its width in most cases right to the stem, so as to furnish the necessary platform for discharging and loading cargo. In order, also, to meet the frequent occurrence of very shallow water during the summer months, a class of boats has been constructed termed light-water steamers. They differ from the ordinary description of boats, in that they are built in the lightest possible manner and with a comparatively small engine power, so that their speed seldom exceeds from 6 to 7 miles per hour; they have, however, the advantage of being able to navigate rivers the ordinary boat could not traverse, their draught of water ranging from 12 to not more than 18 inches when laden with cargo and passengers.