Today, we build a cathedral and pay the piper for
it. 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.
We read of the great
constructions of ancient Egypt -- the Pyramids,
Karnak, endless burial monuments -- each one
grander than the one before it. All that stone! The
Great Pyramid alone is made from forty million
cubic feet of rock.
Now here's a startling statistic. The limestone
quarries of Northern France produced more stone
during 300 years in the High Middle Ages than was
used in all of ancient Egypt. Those magnificent
Gothic cathedrals and other late medieval buildings
ate an enormous amount of rock. Some of the
cathedrals were almost as tall as the Great
Pyramid, and so many were built! So much stone!
Furthermore, the blood of the Battle of Hastings
was hardly dry when William the Conqueror exported
stone to England to build a Battle Chapel. After
that we find huge quantities of rock moving across
the Channel: stone for Canterbury Cathedral, stone
for Westminster Abbey, stone for Winchester Castle,
stone for Norwich Cathedral ...
Some of this rock came from open pits and some from
underground mines. 800 years later, dirt has filled
in most of the old open pits, and grass has grown
over them. The underground stone quarries are a
different matter. They remain. Some have been
sealed off. Some are now used to grow mushrooms.
Some, like the one at Saint-Leu d'Esserent, north
of Paris, are still in use. It reaches so far into
a hill that stone has to be hauled through a mile
of tunnel. Here and there its caverns open into
workshop areas where stone is shaped before it's
taken out. The Germans used these areas to
manufacture rocket engines, safe from allied bombs,
during WW-II.
Paris itself sits on limestone, and the earth
beneath it is a rabbit-warren of tunnels. The famed
Paris Metro has 190 kilometers of underground
lines, but the quarries crisscrossing under the
city run twice that distance. Parisians keep a
close eye on those caverns -- not out of
archaeological or historical interest, but out of
an ongoing concern for the structural safety of the
city above.
These tunnels remind us that our works have been
altering the face of the earth for a long time. The
flight of imagination that propelled the
magnificent Gothic cathedrals into the sky was
rooted deep in the earth. Many of those glorious
buildings remain, but so, too, do the empty cocoons
from which they were taken. They remind us of a
natural balance of payments that we can never
escape when we build things.
I'm John Lienhard, at the University of Houston,
where we're interested in the way inventive minds
work.
(Theme music)
