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210 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