In the
537 siege of Rome, supplies were interrupted by the
Goths from providing the population with vital flour from the surrounding water mills. Also, the aqueducts that supplied Rome with water and some cities which had water-driven mills could no longer work. The solution devised by the Eastern Roman general
Belisarius was the "reverse principle of a water mill" - the ship mills, which were anchored on the
Tiber river around Rome. It was a type of watermill powered by
water wheels mounted on the sides of vessels
moored in midstream, preferably close to bridges where the current is stronger. From then on, the ship mill spread to Europe, reaching
Paris (556),
Geneva (563) and
Dijon (c. 575). Ship mills were developed in the
Islamic world some time between the 8th and 10th centuries. They were employed along the
Tigris at
Mosul in 10th-century
Iraq, where large ship mills made of wood and iron could produce 10 tons of flour from corn daily for the granary in
Baghdad. In 1184,
Ibn Jubayr described ship mills in the same region on the
Khabur River. From the late 10th century onwards, there was an expansion of milling in Northern Europe. The
German terms
"Schiffsmühle" or
"Schiffmühle" are used according to local language preferences. ==Geographical spread of ship mills==