Lecture 18: Milling Grain with Water
Understanding Greek and Roman Technology: From the Catapult to the Pantheon
Dr Stephen Ressler (2013)
Water in ancient Greece and Rome was mainly used to mill grans, which provided 70-75% of the average person’s calories. Nevertheless archeologists have discovered a water powered sawmill (used to cut marble) in ancient Gaul. During the late empire, there is also evidence of using water power to knead dough, cleaning wool and lifting hammers to crush mineral ores.
To process grain into flour, the husk must be broken so it can be ground into a fine powder. Prior to the classical age, the saddle quern (below) was the main tool used to grind wheat and other grains. The residue was passed through a sieve to remove the chaff. With this method, it took three hours to produce enough flour for one household for one day.
In the 5th century BC, the Greeks invented the hopper mill, consisting of a concave lower stone, a convex upper stone and a hopper in the middle.By adding a lever, the hopper mill provided mechanical advantage. It also saved time because the flour fell into the hopper as it was produced.
In the 3rd century BC, the rotary quern became the first mill to be operated by animal. Used in commercial bakeries, it consisted of a moveable cone shaped hopper that rotated on top of a lower stone fixed to the base. The former rotated on a wooden spindle connected to two wooden capstans. The miler only had to load the hopper and collect the flour. One or two donkeys would be yoked to the capstan arms.
Introduced around the 3rd century BC, water mills were widely adopted by the 1st century BC. Ressler describes three types of water mills: the undershot wheel (described by Vetruvius in De Architectura), the overshot wheel and the vertical shaft wheel.
With the undershot wheel, the grinding surface turns on a vertical axis, connecting to the water wheel via right angle gearing.
The overshot wheel supplied water to the top of the wheel via a head race and carried it away via a tail race. It, too, connected to the mill stones via right angle gearing. It was 30 times more efficient than the undershot wheel.
The gearing systems used in these water mills and elsewhere were developed in Alexandria during the third century BC.
Vertical shaft mills were much less common. They employed a horizontally oriented wheel to drive a vertical shaft. Developed during the 3rd century BC, it was the simplest, with water driving the mill shaft directly. Although it was probably too slow for effective milling, it was the world’s first true turbine, very similar to the turbines used in modern hydroelectric plants.
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