The waterwheel is an ancient technology that converts the energy of rushing water to human use. Mostly used for milling grain in ancient times, the simplest waterwheel has a series of submerged paddles fanning out from a vertical shaft. The moving water rotates the paddles and shaft, which passes through a fixed millstone and is fastened to a movable millstone on top. The more familiar traditional form employs a vertical wheel and horizontal shaft.

With the growing mechanization of the production process in the 1800s came an increasing demand for energy. Steam engines were feasible only where coal was cheap, and the old waterwheels did not make efficient use of available hydrological power. An urgent need to improve the efficiency of waterwheels was felt particularly in countries that had little or no coal. The first improvements were made by the Frenchman Jean Victor Poncelet (1788-1867), who...