Our Sea

Part 10 - Water Wheels

The oxen or donkey powered sāqiyah was a big improvement over the Shaduf. It could lift water from a depth of 10 to 20 metres from a well, with buckets attached to a wheel or a continuous loop of rope, without human effort. An Egyptian tomb painting from the 2nd century BCE shows a pair of yoked oxen driving a water-lifting wheel for irrigation but there is evidence that these were used much earlier.

Sometime in 4th century BCE India, farmers realized that, where water wheels could be driven by the flow of a river or stream, they didn't need the oxen. So they invented the undershot water wheel. They also realized that it could be used for purposes other than raising water.

For the first time in history, they had a source of power that did not depend on human or animal muscles. It was a revolutionary product of early engineering as important as the much later invention of the steam engine.

There was a small problem of efficiency. The undershot wheel was driven by the flow of water but its rotation was impeded as the paddles entered and left the water so inventors quickly developed the overshot wheel. This was had twice the efficiency of the undershot wheel as the water was delivered to the top of the wheel so that the weight of water drove the wheel until it spilled out as the buckets reached the bottom of the wheel. This required a dam or mill pond with a surface higher than the outflow from the wheel. (The difference in height is known as the head).

The water wheel was quickly adapted to grind seeds of wheat or other cereals and this required shafts and gearing to connect the horizontal drive shaft from the waterwheel to the vertical shaft o the grinding stones. Early drive shafts and gears were typical made from wood as metal was either too expensive or not available.

Later developments included the use of a crank driven saw to cut timber, stone or marble and trip hammers lifted by cams to crush gold bearing rock or for fulling (cleansing and thickening woolen cloth) or for metal working.

The technology quickly spread throughout the Roman empire. In the 1st century CE at Arelate, in southern France, 16 watermills, driven by overshot waterwheels, produced about 4.5 tons of flour a day for the 12,500 inhabitants.

The Romans also used boats anchored or moored in fast flowing rivers as floating, undershot water wheels which permitted them to use the power of tidal currents.

The breast shot waterwheel was invented in the 4th century CE as a way to use a small head of water not high enough for an overshot wheel. It had and efficiency between an undershot and an overshot wheel.

The earliest water reaction turbines were designed in modern-day Tunisia, between the 4th and 3th century CE. They used two helical-turbines with angled blades, on a vertical shaft, installed at the bottom of water-filled, circular housing. Water entered the housing tangentially, creating a swirling water column which turned the fully submerged wheel.

The Roman encyclopedist Pliny mentions water-powered trip hammers operating in Italy in 70 CE and a fulling mill in 74 CE Antioch, Roman Syria.

In the 2nd century CE the mill complex of Barbegal in southern France had 16 overshot waterwheels driving 16 flour mills producing 4.5 tons of flour per day to supply bread for the 12,500 inhabitants of Arelate.

The 3rd century CE Hierapolis water-powered stone sawmill is the earliest known machine to incorporate a crank and connecting rod mechanism.

Waterwheel driven trip hammers and piston bellows, used to smelt iron, appeared in China about 30 CE. In 488 CE, Emperor Wu of Southern Qi inspected a watermill built by engineer Zu Chongzhi, and hundreds of them were in use by the 6th century.

The Tang Dynasty (618–907 CE) Department of Waterways issued an ordinance in 737 CE that watermills should not interfere with river transport and many water mills were demolished in consequence.

Islamic engineers improved the output of undershot watermills by building them between the piers of bridges where the restriction increased the speed of the water flow. They also built ship-mills with water wheels mounted on the sides of ships moored in midstream. This technique was used along the Tigris and Euphrates rivers in 10th-century CE Iraq, to produce 10 tons of wheat flour per day for Baghdad.

The British Domesday Book (1086 CE), listed 5,624 watermills in England alone. By 1300 CE, this number had risen to between 10,000 and 15,000.

European countries expanded the use of watermills for various industrial purposes between 770 and 1443 CE . These included the production of : - malt, hemp and paper and for cloth fulling, leather tanning, tool sharpening, sawing timber and stone, ore crushing, forging, cutting and slitting metals and for industrial bellows and blast furnaces used to make iron and steel.

Until the age of steam power, water mills were use for a wide variety of other industrial purposes including: - 

Carding, spinning, weaving and fulling machines as textile and carpet industries became more mechanized. (Early steam engines were used to pump water up to mill ponds so that the water wheels could continue when there was no rain).  Wood working machines such as saws, lathes and routers.   Spoke mills turning lumber into spokes for carriage wheels.

Gristmills, corn mills, or other seeds ground into flour. Crushers for oil seeds. Gunpowder mills.  Stamp mills for crushing ore.  Rolling mills to shape metal by passing it between rollers.  Slitting mills used to slit bars of iron into rods, for nail making.  Polishing mills for needles.  Paper mills used water not only for power, but also for the manufacturing process.

This is the end of book 4 of  'Who the Hell are We?'  

The series continues in book 5.