This works by pressure, and may be drowned or connected to a suction tube. It is an axial or parallel-flow turbine, the water passing through the motor in directions parallel with the central shaft. The water enters a fixed wheel, and is guided into the movable wheel keyed to the shaft, which rotates on a pivot bearing. To regulate the power of the turbine, a number of the guide passages are closed by a special casting, carrying a segmental rack worked by a worm. The efficiency of the Jonval turbine increases with the load.