It was once thought that watermills only began to be used on an industrial scale in medieval times. But in 1937 a Roman complex with 16 water wheels was found in Barbegal in southern France – the largest ancient water-powered factory found anywhere in the world.
Now it has been shown that the Barbegal factory probably specialised in producing flour for making ship biscuits, rather than for supplying the nearby Roman city of Arelate as previously assumed.
During excavations of the site in 1937 archaeologists discovered thick limescale deposits that had built up on the wooden wheels as they churned through the water.
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“They have impressions of the woodwork,” says geologist Cees Passchier of the Johannes Gutenberg University in Germany. “The wood itself has rotted away.”
Summer holiday
His team’s isotopic analyses show the limescale was not deposited continuously throughout the year and suggests the mills stopped operating in late summer and autumn.
This doesn’t make sense if the mills were producing flour for normal use. Flour was milled throughout the year as needed, because it does not store as well as grain. “For a major city you need a supply all year round,” says Passchier.
Roman shipping was strongly seasonal, though, with few ships sailing the Mediterranean in winter because of the risk of storms. So the archaeologists on the team think the mill complex was used from winter to late summer to produce flour for the nearby ports of Arles and Fossae Marianae. There it would have been double baked to create long-lasting ship biscuits similar to the “hardtack” used in later times.
The crystalline structure of the deposits also shows that they were deposited in the dark by rapidly flowing water. That suggests that the water wheels were actually inside the buildings, rather than outside as assumed.
Ancient civilisations from Egypt to China used water wheels for powering machinery like mills and for lifting water, but the Barbegal site, with its 16 water wheels arranged in two rows down a hillside, is unique. However, Passchier thinks we may yet discover similar complexes elsewhere.
Water power remains important today. Hydropower supplies around a fifth of electricity globally, and 70 per cent of all electricity from renewable sources.
Science Advances
