Saturday, April 28, 2012

Gristmill


Grinding mechanism in an old Swedish flour mill

The Greek geographer Strabo reports in his Geography a water-powered grain-mill to have existed near the palace of king Mithradates VI Eupator at Cabira, Asia Minor, before 71 BC.

The early mills had horizontal paddle wheels, an arrangement which later became known as the "Norse wheel", as many were found in Scandinavia. The paddle wheel was attached to a shaft which was, in turn, attached to the centre of the millstone called the "runner stone". The turning force produced by the water on the paddles was transferred directly to the runner stone, causing it to grind against a stationary "bed", a stone of a similar size and shape. This simple arrangement required no gears, but had the disadvantage that the speed of rotation of the stone was dependent on the volume and flow of water available and was, therefore, only suitable for use in mountainous regions with fast-flowing streams. This dependence on the volume and speed of flow of the water also meant that the speed of rotation of the stone was highly variable and the optimum grinding speed could not always be maintained.

Vertical wheels were in use in the Roman Empire by the end of the first century BC, and these were described by Vitruvius. The peak of Roman technology is probably the Barbegal aqueduct and mill where water with a 19-metre fall drove sixteen water wheels, giving a grinding capacity estimated at 2.4 to 3.2 tonnes per hour. Water mills seem to have remained in use during the post-Roman period, and by 1000 AD, mills in Europe were rarely more than a few miles apart.

In England, the Domesday survey of 1086 gives a precise count of England's water-powered flour mills: There were 5,624, or about one for every 300 inhabitants, and this was probably typical throughout western and southern Europe. From this time onward, water wheels began to be used for purposes other than grist milling. In England, the number of mills in operation followed population growth, and peaked around 17,000 by 1300.

Limited extant examples of gristmills can be found in Europe from the High Middle Ages. An extant well-preserved waterwheel and gristmill on the Ebro River in Spain is associated with the Real Monasterio de Nuestra Senora de Rueda, built by the Cistercian monks in 1202. The Cistercians were known for their use of this technology in Western Europe in the period 1100 to 1350.

Geared gristmills were also built in the medieval Near East and North Africa, which were used for grinding grain and other seeds to produce meals. Gristmills in the Islamic world were powered by both water and wind. The first wind-powered gristmills were built in the 9th and 10th centuries in what are now Afghanistan, Pakistan and Iran.[


“I commenced plowing this morning but about 10 O’clock it commenced raining and I quit.  It rained until nearly night.  I helped Lettie a little about fixing some things in our room and put up a grist of corn and barley to take to mill.”
Leesah

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