grain mill | structure for grinding cereals | Britannica
grain mill, structure for grinding cereal. Waterwheels were first exploited for such tasks. Geared mills turning grindstones (see gear) were used in the Roman Empire, but their fullest development occurred in medieval Europe, in, for example, the great grain mill near Arles, France, which, with its 16 cascaded overshot wheels, each 7 feet (2 metres) in diameter, and wooden gearing,
