A Barker's Mill is an apparatus based upon the principal of the hydraulic tourniquet. It consists of a vessel containing water and free to rotate about vertical axis. Near its base are provided outlet pipes through which the water is discharged horizontally, in a direction tangential to a circle having its centre at the axis of rotation of the vessel. The mill operates upon the reaction principle, the unbalanced pressures at the discharge orifices causing the vessel to rotate. A horizontal turbine wheel having curved outlet pipes around its periphery acts upon this principle. Research Barker's Mill