Today, we let nature do our work for us. 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.
What's the shape of a
falling raindrop? We like to sketch raindrops with
a tear-drop shape. Actually, they're spherical.
Once they've fallen far enough, surface tension has
pulled them into the shape with the least surface.
That's a sphere.
In 1782 an English plumber named William Watts saw
possibility in that. He realized that if he dropped
molten lead far enough through the air, it, too,
would form into spheres. The surface tension of
lead is a lot higher than that of water, so it
forms very perfect spheres indeed. He saw that he
had a new way to make buckshot.
Watts went back to his brick row house in Bristol
and began adding floors to it. It was already three
stories high. He doubled that. He put some
castle-like trim on the top and called the design
Gothic. He wanted his neighbors to like the
addition, but the real action was inside his
strange new home.
He knocked holes through each of the floors inside
and put a water tank at the bottom. At the top, he
poured lead into a sieve. The lead formed into
spheres as it fell six floors. By the time the
drops hit the water below, they'd started to
solidify. The water caught and cooled them the rest
of the way.
Up to then, most shot was cast. That was very
labor-intensive. Shot was also made by pouring lead
into a sieve over a barrel. That really did give
tear-shaped drops. Before Watts, no one had yet
realized that a much longer fall would give
spheres.
Watts saw how he might greatly cut the cost of
making high-quality shot. Then he gambled his home
that it would work. And it did. Shot towers like
his sprouted all over England and Europe. In 1808
Jefferson imposed the Embargo Act. That ended our
shot supply. So we, too, began
making shot towers.
Yet the process changed little. Shot makers added
an upflow of air, and they invented ways to sort
out deformed shot. Yet Watts's old patent still
gave a pretty good description of 20th-century
shot-making. In fact Watts's old house -- his
original shot tower -- kept producing shot until
1968.
Watts's invention teaches us the two essential
elements of good invention. The first is
perception. Watts gazed more closely at nature and
saw what other people had missed. The other element
is simplicity. Others had labored to control the
process with their own hands. Watts had the grace
to stand aside and let nature do the work for him.
The real beauty of this process is that, in the
end, there is no human process at all.
I'm John Lienhard, at the University of Houston,
where we're interested in the way inventive minds
work.
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