Not a medieval invention, but a medieval spread
The waterwheel did not begin in the Middle Ages. Water-powered grain mills were known in the Roman world, and descriptions from the first century BCE onward mention them. What changed in medieval Europe was the scale. By the eleventh century, mills had become common across much of the continent, and by the later Middle Ages they were driving machines for many tasks other than grinding grain.
The earlier history of water-powered machinery, including Roman examples, is covered in the article on water mills. This article follows what happened afterward.
A mill in nearly every village
One of the clearest pieces of evidence comes from England. The Domesday survey of 1086 records thousands of mills, commonly summarized as roughly 6,000, spread across many settlements. The figure is approximate and the survey did not intend to count everything, but it indicates that water mills had become a normal part of the landscape within a generation or two of the Norman conquest. Similar growth is documented in France, Italy, Germany and elsewhere.
Before mills, grain was usually ground by hand with a stone quern, a slow and tiring task. A mill took over much of that work. Historians have long debated how large the labor savings were and who benefited, but there is general agreement that milling by water displaced a great deal of hand grinding.
Types of wheel
Medieval wheels were built in a few main forms.
- Horizontal wheel. The wheel lies flat, with its axle vertical, so that it can turn a millstone directly without gears. It suits small, fast streams and was simple to build.
- Undershot wheel. A vertical wheel, turned by water flowing beneath it. It works on flat rivers but is relatively inefficient.
- Overshot wheel. Water arrives at the top, filling buckets and turning the wheel by weight as well as flow. This usually gets more from the water, but needs a drop in height, often created by a dam or a channel called a leat.
- Breastshot wheel. A middle form, with water entering around the level of the axle.
Gearing connected a vertical wheel to the horizontal millstones. A large wheel on the axle drove a smaller gear, speeding up the stones. Millwrights built these from wood, often with iron fittings, and the craft of the millwright became a skilled trade.
Ponds, weirs and tide mills
A mill needs a steady supply of water, so builders dug ponds, built weirs across rivers and cut channels. These works changed local waterways and sometimes caused disputes over fishing, navigation and flooding. In places on the coast, tide mills used the rise and fall of the sea, trapping water in a pond at high tide and releasing it through a wheel as the tide went out.
Beyond grain
Once a river could turn a shaft, the shaft could be linked to other machines. The most important medieval uses were these.
- Fulling. After weaving, wool cloth was pounded in water to shrink and thicken it. Mills equipped with wooden hammers did this work, replacing the older practice of trampling cloth by foot. Fulling mills are recorded from the twelfth century in parts of Europe and became important in wool-producing regions.
- Iron working. Water-driven hammers could forge iron, and water-driven bellows could raise furnace temperatures. By the later Middle Ages these were used in some ironworks, forerunners of the blast furnace operations.
- Sawing, tanning, mining and paper. Waterwheels powered saws for timber, bark-crushing for tanning, pumps and hoists in mines, and in Italy and Spain, from the thirteenth century, the stamping mills used to make paper.
Many of these applications used a camshaft, a rod with projecting pegs that lifts a hammer and lets it fall. The cam turned rotary motion into repeated up-and-down motion, a basic mechanical idea of lasting importance.
Who owned the mill
Mills were expensive to build and maintain, and in much of feudal Europe they belonged to lords or religious houses. Tenants were often required to grind their grain at the lord’s mill and pay a share, a system sometimes called milling monopoly. Resentment of mill dues is recorded in many places, and the miller had a reputation, fair or not, for taking too much.
Monasteries, especially Cistercian houses, are often noted for their use of water power for many tasks. How far they led technical innovation, versus using what existed, is debated.
Was it an industrial revolution?
Some historians have described the spread of mills as a medieval industrial revolution. That phrase is contested. Waterpower in the Middle Ages was limited by rivers, seasons and the power of a single wheel, which was small compared with later steam engines. Mills were also scattered, small and mostly local. Even so, they showed that machinery driven by natural power could be a normal part of an economy, a pattern that later factories followed, as in the water frame and other early cotton mills.
Competition and decline
Windmills appeared in Europe in the twelfth century and offered power where rivers were weak, as with grain-grinding windmills across flat regions. Waterwheels remained important well into the nineteenth century, and improved designs, including iron wheels and later turbines, extended their life. Eventually, steam and electric power replaced most of them, though some mills operated into the twentieth century.