Such impounding has successful inauguration in five small reservoirs now in operation on the headwaters of the Mississippi out of forty-two planned. An ambitious plan for controlling the turbulent Ohio by a system of from seventeen to forty-three reservoirs at an estimated cost of from twenty to thirty-four millions of dollars has been suggested by Mr. M. O. Leighton of the United States Geological Survey, and received indorsement from the Pittsburgh Flood Commission, the Dayton Flood Commission, and the National Waterways Commission. These would suffice to keep the lawless waters within temperate bounds in the spring and to give more generous navigable currents in the summer and autumn. Against the great expense of such a project is set the tremendous possibilities in the development of water-power. Of the theoretical sixty millions of horse-power in the current of the Mississippi, it is estimated that about six and a half millions can be economically developed throughout the year, while twelve millions could be developed during six months or more without storage reservoirs. An adequate system of reservoirs might double or treble these totals, while a million or two would be immediately available to begin the payment of the debt, and more of the strength would be harnessed to that purpose in time. So, it is urged, the river would be made to meet the expense of its own conquest. [Footnote: See reports of the National Conservation Commission in 1909; National Waterways Commission, 1912; Report Commissioner of Corporations on Water-Power Development in the United States, 1912; J. L. Mathews "Remaking the Mississippi," Boston, 1909.] And once that is done the river may be straightened, shortened, deepened, leveed, and made a docile, reliable carrier of commerce. It may then be compelled to a respect for cities and government signals and wharfs and mills. And the astute suggestion of the practical Joliet for the canalization of its waters, may be realized in the safe passage not merely of boats but of stately, giant, ocean-sized vessels from the Great Lakes to the gulf.