Today, a parable about the origin of ideas. 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 steam engine was 70
years old in 1769. Then James Watt filed the patent
that changed it utterly. Before Watt, you squirted
cold water into a cylinder to condense the steam.
That made a vacuum. It sucked the piston down in a
working stroke. But it also cooled the cylinder.
You wasted more steam reheating the cylinder than
you used to refill it.
In one ingenious leap, Watt got around the problem.
He exhausted the steam into a separate condenser.
The condenser was always cool and it always held a
vacuum. The cylinder stayed hot and the condenser
stayed cold. That doubled steam engine
Watt was an instrument maker at the University of
Glasgow. The great chemist Joseph Black taught
there. He was a friend to Watt. They would talk
together. Black had just found out about latent
heat. He showed that water absorbs a huge lot of
energy, without changing temperature, when you boil
it. We like to believe that science leads
technology. So we've presumed that Black gave Watt
the key idea he needed to invent the separate
One of Black's students fed that notion after Black
died. He wrote up Black's lecture notes and
published them as a textbook. He dedicated the book
to Watt. He called him, "Black's most illustrious pupil."
He said Watt owed his invention to
"the instructions ... you received from Dr. Black."
All that supported our belief that science gives
birth to technology. But in the last few years
we've learned it's not really what happened at all.
Watt worked six years giving birth to his new
engine. He spent part of that time in his lab,
experimenting with steam. He learned -- on his own
-- that the heat from just one pound of steam will
bring six pounds of water to its boiling point.
Then he told Black what he'd done. So Black
answered that his result was because of latent
heat. Later, Watt wrote,
Thus I stumbled upon one of the material facts
by which [Black's] beautiful theory is
This is not a story about a fight for
priority. There was no argument between Watt and
Black. New ideas do suddenly well up among many
people. Watt came upon latent heat one way -- Black
another. Watt used the concept to change our world
before he'd seen it formalized. And that's really no
surprise. After all, it's in the nature of invention
that it must, one way or another, precede
I'm John Lienhard, at the University of Houston,
where we're interested in the way inventive minds