Today, we try to make sense of an old Roman power
plant. The University of Houston's College of
Engineering presents this series about the machines
that make our civilization run, and the people
whose ingenuity created them.
Anyone who's ever studied
the history of technology has seen a drawing of 16
Roman water wheels, two abreast, arranged in
stair-steps down a hillside. Historians have
isolated that one mill like a sore. The common
wisdom says that the Romans, who kept slaves, had
no need of water power. This must be a lone oddity.
But the Romans were different people over many
centuries and many lands they occupied. This mill
was built just after 300 AD in a place called
Barbegal near Arles in Southern France. In those
days the emperor Constantine was in residence at
Arles. Arles was far from Rome and it was also far
from any reliable supply of barbarian tribes --
whom the Romans liked to enslave.
Power-generating water wheels had been around for
about 600 years by then and they occasionally turn
up in old writings and old ruins. But this Barbegal
mill was a colossus among water mills.
An aqueduct brought water into a catch basin at the
top of a small hill. From there it flowed through
one pair of water wheels after another. The 16
mills ground enough grain to feed over 12,000
people -- roughly the entire population of
4th-century Arles.
The great stone foundations of the Barbegal mill
still march down that hill. But they were covered
by dirt, and not discovered until 1940. If Barbegal
could stay hidden from history, what about smaller
mills? So many mills, especially smaller ones,
easily could've passed into dust.
We know water wheels were all over medieval Europe
later on, when slaves weren't used at all. After
1066, William the Conqueror's Doomsday book listed
nearly 6000 mills in England alone.
Trevor Hodge looks at that record and asks, "Where
are all those English mills today?" Almost none of
those 900-year-old mills have stood up. That means
there had to be more of the really old Roman mills
than we know about. And Barbegal was clearly a
well-developed, well-understood technology.
Still, far fewer mills turn up in the Roman
literature than in medieval documents. The Romans
clearly didn't exploit mills fully and we wonder
why. Hodge points to a matter beyond slavery.
Horses hadn't yet been harnessed for hauling goods.
It was still hard to move grain to and from central
mills. A few big cities like Arles might've had
mills. But it didn't yet pay to build grain mills
where the population was sparse.
So the Barbegal mill is an important reminder that
the offer of an effective new technology is not
always easy to accept. The true usefulness of new
technology depends on more factors than are ever
obvious. By 1000 AD horses, stronger and faster
than oxen, were now hauling goods. It was only then
that the water wheel could complete its
transformation of the human condition.
I'm John Lienhard, at the University of Houston,
where we're interested in the way inventive minds
work.
(Theme music)
Hodge, T., A Roman Factory. Scientific
American, November 1990, pp. 106-111.
Singer, C., Holmyard, E.J., Hall, A.R., Williams,
T.I., A History of Technology, Vol.
II. New York: Oxford University Press, 1956,
Chapter 17, Power.
The Engines of Our Ingenuity is
Copyright © 1988-1997 by John H.
Lienhard.
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