Today, we marry architecture to engineering and
move an obelisk. 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.
The emperor Caligula brought
a great stone obelisk from Egypt to the Circus Nero
in Rome. It was a 327-ton monolith, 83 feet long.
1500 years later, in 1586, it lay half-buried in
dirt, not far from the Vatican. A few years before,
Pope Sixtus V had told the young architect Domenico Fontana: \
"Too many Christians have been martyred in the shadow of that stone. St. Peter himself died there."
Now Sixtus ordered the obelisk moved to the
Piazza where St. Peter's Basilica was going up.
Renaissance engineers had to do what the ancients
had done before them; but they had to use less
labor-intensive means. The obelisk had to travel
only 275 yards. But picking it up and laying it
down were the hardest part. They might just as well
have been shipping it across the sea.
The Vatican solicited proposals for the work.
Fontana bid on it, but he had little hope. He was
already working on St. Peter's dome, and he was
younger than the other bidders. Yet he had the best
plan for doing a terribly difficult job. In the end
he did the job. Later, he wrote a fine illustrated
book about it. The book reveals him as a new and
more sophisticated kind of engineer and as a superb
organizer.
The move took 6 months to plan. The obelisk was as
fragile as it was immense. Human and animal power
had to be carefully focused. Fontana built timber
towers on either side and strengthened the obelisk
itself with metal bands and wooden beams. He wound
three-inch ropes on forty huge capstans -- each one
powered by four horses. He planned to lift the
obelisk between the towers, turn it on its side,
lower it onto rollers for the trip to St. Peter's,
and then reverse the process.
All this took the precision of close-order drill
and absolute silence. Fontana allowed only two
sounds: a trumpet blast to begin a movement, and a
bell to end it. Two hundred years later, writers
began spinning yarn around that part. We read that
he built a gallows on the site to punish any
disturbance. When the ropes jammed, a sailor was
supposed to have broken silence to suggest wetting
them down. The story says he was saved from hanging
when the ropes came free at the last moment.
And so Fontana's feat grew larger in its legends.
Yet he was a great engineer -- among the first to
use the title Civil Engineer. To move the obelisk,
he took the use of block and tackle to a new level.
Egyptians may have moved the same stone, but
Fontana did more. He transformed the field of
architecture by wedding it to the new techniques of
analytical mechanics.
I'm John Lienhard, at the University of Houston,
where we're interested in the way inventive minds
work.
(Theme music)
Dibner, B., Moving the Obelisks.
Cambridge, MA: MIT Press, 1970.
Clark, R. W., Works of Man. New York:
Viking Press, 1985, p. 57.
Image from Moving the
Obelisks, courtesy of the Burndy Library,
Dibner Institute for the History of Science and
Technology
Fontana raising the obelisk
The obelisk, as it was shown standing before St.
Peter's Church in Rome, in the 1911
Encyclopaedia Britannica
The Engines of Our Ingenuity is
Copyright © 1988-2004 by John H.
Lienhard.
