Hello Lordbest:
Interesting topic...
According to Roger D. Hansen, http://www.waterhistory.org/histories/waterwheels/ , "There were at least 2 other multiple-wheeled
Roman mills, but neither was as ambitious as the one at Barbegal. One was at Chemtou in western Tunisia, where a combination bridge/dam spanned the Medjerda River. Three horizontal water wheels, side-by-side, were set into the bridge abutments. The other mill was in
Israel on a dam on the
Crocodile River near ancient
Caesarea, halfway between Haifa and
Tel Aviv. Here there were 2 horizontal wheels, each at the bottom of a penstock. According to Hodges (p. 111): "Neither installation has been fully studied, but together they remain the only known parallels to Barbegal." But he feels strongly that there are probably other
Roman mills that remain to be discovered. "Other Barbegals must surely await discovery in the more remote and less studied parts of the
Roman Empire. If this one could escape notice until 1940, what masterpieces may yet lie hidden in
Iraq and
North Africa, where desert sands now enshroud the remains of
Roman cities?"
Also according to Hansen, "Development occurred when
Rome was under siege by the Goths in 537 AD. Goths shut off the aqueducts whose water drove the city's gristmills, Belisarius, the Bzyantine general defending the city, ordered floating
mills installed close to the
Tiber bridges, whose piers constricted and accelerated the current. Two rows of boats were anchored with waterwheels suspended between them. The arrangement worked so well that cities all over Europe were soon copying it."
Vitruvius, an engineer of the Augustan Age (31 BC - 14 AD), who composed a 10 volume treatise on all aspects of
Roman engineering
Excerpt Vitruvius book X:
Chapter 4
1. I shall now explain the machines for raising water, and their various sorts. And first the
tympanum, which, though it raise not the water to a great height, yet lifts a large quantity in a small period of time. An
axis is prepared in the lathe, or at least made circular by hand, hooped with iron at the ends; round the middle whereof the
tympanum, formed of planks fitted together, is adjusted. This
axis rests on posts also cased with iron where the
axis touches them. In the hollow
part of the
tympanum are distributed eight diagonal pieces, going from the
axis to the circumference of the
tympanum, which are equidistant.
2. The horizontal
face of the wheel or
tympanum is close boarded, with apertures therein half a foot in size to admit the water. On the
axis also channels are cut for each bay. This machine, when moored like a ship, is turned round by mean walking a wheel attached to it, and, by receiving the water in the apertures which are in front of the wheel, brings it up through the channels on the axle into a trough, whence it is conducted in
abundance to water gardens, and dilute salt in pits.
3. If it be necessary to raise the water to a higher level, it must be differently adjusted. The wheel, in that case,
applied to the
axis must be of such
diameter that it shall correspond with the requisite height. Round the circumference of the wheel buckets, made tight with pitch and wax, are fixed; thus when the wheel is made to revolve by means of the persons treading in it, the buckets being carried to the top full of water, as they return downwards, discharge the water they bring up into a conduit. But if water is to be supplied to
still higher places, a double chain of iron is made to revolve on the
axis of the wheel, long enough to reach to the lower level; this is furnished with brazen buckets, each holding about a gallon. Then by turning the wheel, the chain also turns on the
axis, and brings the buckets to the top thereof, on passing which they are inverted, and pour into the conduits the water they have raised.
Chapter 5
1. Wheels on rivers are constructed upon the same principles as those just described. Round their circumference are fixed paddles, which, when acted upon by the force of the current, drive the wheel round, receive the water in the buckets, and carry it to the top with the aid of treading; thus by the mere impulse of the stream supplying what is required.
2. Water
mills are turned on the same principle, and are in all respects similar, except that at one end of the
axis they are provided with a drum-wheel, toothed and framed fast to the said
axis; this being placed vertically on the edge turns round with the wheel. Corresponding with the drum-wheel a larger horizontal toothed wheel is placed, working on an
axis whose upper
head is in the form of a dovetail, and is inserted into the mill-stone. Thus the teeth of the drum-wheel which is made fast to the
axis acting on the teeth of the horizontal wheel, produce the revolution of the mill-stones, and in the engine a suspended hopper supplying them with grain, in the same revolution the flour is produced.
Pax