"For the purpose intended, namely, the making of an improved low-water navigation, looking to a depth not exceeding two and one-half feet, the general plan designed, and in part executed, under the superintendence of Captain Sanders, was judicious; and if all the proposed dams had been finished in accordance with his plans there would have been a better navigation, especially for low-water craft, than there has been during the twenty-two years which have elapsed since the works were left, many of them, in a partly finished condition. Some of these wing dams, as might reasonably have been anticipated, have, in the course of years, been gradually injured by the action of floods, and in some cases portions of the stone have been removed by persons without authority, for their own private purposes. It is important to note the change which has taken place in the coal trade, not only on account of its great and increasing magnitude, but on account of the altered system upon which it is conducted. Formerly, and at the time when the riprap dams were constructed, the coal business was carried on by means of floating coal barges, drawing at most four feet water, which were not assisted in their descending navigation by steamers, and which never returned, but were sold as lumber at their point of destination. The increasing demand down the river for the Pittsburg coal, the increase in the value of lumber, and the general systematizing of the trade, all combine to revolutionize the mode of transportation. It is now [1866] carried on by means of large barges, each containing ten to twelve, some as high as sixteen thousand bushels of coal, which are arranged in fleets, generally of ten or twelve barges, towed by powerful steamers built and employed for that special purpose. Enough of these barges are owned by the coal operators to enable them to leave the loaded barges at their various points of coal delivery, down the Ohio, or on the Mississippi and other rivers, while they return to Pittsburg with a corresponding fleet of empty barges, to be again loaded, ready for the next coal-boat freshet. As these barges, when loaded draw from six feet to eight feet of water, it is obvious that they can only descend when there is what is now called a 'coal-boat rise' in the river--that is, a flood giving not less than eight feet water in the channels.