. "ts construction at reasonable prices, and because in other cases the title to the said land is imperfect, or is vested in minors or persons non compos mentis, or in a feme covert, or in persons out of the District of Columbia; and whereas, it is necessary for the making of said aqueduct, reservoirs, dams, ponds, feeders, and other works, that a provision should be made for condemning a quantity of" . . . . .