Today, rice and silk.
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.
Historian Roslyn Lee Hammers tells an intriguing
story of economic development in Medieval China. A minor official, Lou-Shu,
created a scroll in the mid-twelfth century -- in the Sung Dynasty. It
was a kind of technical manual, written for his emperor. It explained,
in detail, the laborious processes of producing rice and silk.
Rice and silk, it seems, were the coin in which farmers paid their taxes.
The scroll was a cloaked plea to the emperor that he be aware of the texture
of the toil that supported him. Maybe if he understood, he would show greater
respect to the farmer. Maybe he would bridle his more brutal and self-serving
The scroll consists of pictures and poems. Twenty-four detailed pictures show
the steps in producing both rice and silk. The poems refer only obliquely to
the pictures; and most describe the backbreaking toil required to satisfy tax
collectors. Yet they do so with a kind of bucolic sentimentality -- honorable
But Hammers is surprised by one image and its poem. Using typical metaphorical
Chinese language of those times, Lou-Shu describes a device that reduces
labor. He calls it a Crow's Tail. It's a treadmill-driven water pump --
a version of what we call a noria. The picture shows three men and
one woman. Their arms rest upon a bar while their bare feet walk the treadmill.
It drives a continuous chain of square plates in a square channel. The plates pick
up water and push it out through the rice paddies for irrigation. A woven mat above
their heads shades them from the sun.
Lou-Shu names the device by identifying the square plates with the squarish shape of
a crow's tail. He waxes lyrical as he writes:
How can it be that a crow's tail can hold water
And make it flow backwards, draining the pond?
Well, Hammers finds a dark side here. Lou-Shu's father seems to've installed a whole
array of these pumps and was using them, not only to irrigate existing fields, but also
to open up new ones.
Opening new fields got them a tax break; but draining the lake depleted the water supply
for the farmers on the other side. For them, all this had to be a disaster. No wonder
Lou-Shu includes this one high-tech labor-saver in his scroll. It helps justify his
village's action against the other farmers.
So the old drama of technology and change plays out here. New technology means trouble.
We like to scorn the Luddites for resisting new technology. The word Luddite
has become shorthand for the grim fact that technological change is disruptive. In the
end, Hammers is guardedly sympathetic to Lou-Shu because, in the long run, everyone's
better off when farmers no longer have to lug water buckets to their paddies. And
Lou-Shu puts it this way:
Now the rice dances in emerald waves,
Woven rush mats offer cool relief from the sunlight.
The setting sun shines on young willows,
The farmers with laughter and songs relax with young maidens.
I'm John Lienhard, at the University of Houston,
where we're interested in the way inventive minds
R. L. Hammers, "How Can It Be that a Crow's Tail Can Hold Water?" The Square-Pallet
Pump in Lou Shu's Pictures of Tilling and Weaving. Technology and Culture,
No. 1, Vol. 46, January 2005, pp. 132-136, and Cover.
The Engines of Our Ingenuity is
Copyright © 1988-2005 by John H.