Abstract: A stream -or river-powered turbine consists of an elongated cylinder with radially-extending vanes, each vane having at its root a plurality of axially-spaced flap valves opening and closing corresponding openings therein. These valves open automatically as the vanes enter the tail wave to relieve the reverse pressure thereon, close while in the main stream to render the vanes fully effective, and open automatically as the vanes leave the stream to prevent the formation of vacuums on their trailing sides. The generator, which may be electric or hydraulic or pneumatic is mounted inside the cylinder and is driven as the result of relative rotation between an axial stationary torque tube and the cylinder via an oil lubricated chain that also serves to supply oil to other parts of the mechanism.