Ship mill

A ship mill is a type of watermill. The milling and grinding technology and the drive (waterwheel) are built on a floating platform on this type of mill. Its first recorded use dates back to mid-6th century AD Italy.

Between barge and boat well is the undershot water wheel, which is driven by the flowing water of the current. There is also evidence of water mills for which both sides had a narrower water wheel, similar to an old paddle steamer. The floating platform is anchored at the most intense point in the current, to the bridge piers for easy access to the mill, or to the shore.

Floating allows the mill to operate with the same power despite changing water levels. The efficiency of the mill can at best match a standard undershot mill. Ship mills could potentially run full-time, good for tasks that demanded constant power.

Ship mills could be drawn when needed (due to shipping, rafting, ice) to shore. In central Europe ship mills were, as most water and wind mills, owned by lords or monasteries. Ship mills in Central Europe have not remained; after the advent of riverboat traffic, they became a hindrance. Ship mills last about fifty years.

A ship mill (drawing 1 after H.Ernst, 1805).

A ship mill (drawing 2 after H.Ernst, 1805).

There is historical evidence that the development of this type of mill dates back to the ingenious invention of Vitruvius, a Roman engineer of the 1st century BC. Vitruvius described a ship odometer working with a waterwheel attached to the ship hull.

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.

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