A water wheel is a machine for converting the energy of free-
flowing or falling water into useful forms of power, often in a
watermill. A water wheel consists of a large wooden or metal
wheel, with a number of blades or buckets arranged on the
outside rim forming the driving surface. Most commonly, the
wheel is mounted vertically on a horizontal axle, but the tub or
Norse wheel is mounted horizontally on a vertical shaft.
Vertical wheels can transmit power either through the axle or
via a ring gear and typically drive belts or gears; horizontal
wheels usually directly drive their load. Water wheels were
still in commercial use well into the 20th century, but they are
no longer in common use. Prior uses of water wheels include
milling flour in gristmills and grinding wood into pulp for
papermaking, but other uses include hammering wrought iron,
machining, ore crushing and pounding fiber for use in the
manufacture of cloth. Some water wheels are fed by water from a
mill pond, which is formed when a flowing stre