Today, we look for the first mechanical clock. 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.
In other programs, we talk
about what a fool's errand it is to name the
first inventor of
anything. But since the exception really does
prove the rule, let's raise yet another priority
question; let's ask when the first mechanical
clock was invented.
Mechanical clocks replaced the old water clocks,
which, by the 13th century, had been around for
millennia. Water flowed steadily into a vertical
tank and the rising water level indicated the time
of day. That's simple enough, but, like mechanical
clocks, water clocks had become ornate structures
with gears and dials. Like mechanical clocks, they
tolled the hours and displayed the planets.
What makes a mechanical clock is a mechanism called
an escapement -- the balance wheel on a watch or
the pendulum on a grandfather's clock. An
escapement ticks in a steady rhythm and lets the
gears move forward in a series of little equal
jumps.
The first
escapement was the verge and foliot
mechanism (see the full image below). The foliot is
a horizontal bar with weights on either end. It
sits on a vertical rod, called a verge. The verge
has pallets to engage and release the main gear
which is turned by a heavy stone on the end of a
cable.
The verge nudges
the foliot back and forth in an inertial rhythm,
and that determines the pace of the gear train. It
was complex and very creative, but when did it come
about? We don't really know because its importance
wasn't apparent at first. People who wrote about
early clocks couldn't see that the escapement was
not just an incremental improvement on the water
clock. Rather, it was a whole new technology and a
whole new metaphor.
French architect Villard de
Honnecourt described the first escapement we
know about in AD 1250; but he didn't yet use it to
control a clock. Instead, he built a kind of
almost-clock -- a gadget that steadily
pointed at the sun as it moved across the sky.
After that, monastery records mention the bells,
gearing, and towers that went with either kind of
clock, while they ignore the heartbeat of the
clock. The first clear drawing of an escapement was
given by Jacopo di Dondi and his son in 1364.
They'd probably been building clocks for twenty
years by then. So we can only guess that the first
mechanical clocks were made in the late 1200s.
It's strange that so great a change can be that
invisible. The best water-clock accuracy was about
fifteen minutes a day, and that's about as well as
the first mechanical clocks did. But now, engineers
began to cut that error in
half every thirty years, right up into the 20th
century. It wasn't long before mechanical clocks
swept the imagination of the Western world and
created new standards of precision in instruments
and ultimately in thought itself.
The defining technology of an age might not be the
most obvious one. Great changes often come in on
little cat feet. That's what the mechanical clock
did in the thirteenth century. And we might well
wonder what technology is doing just that, today.
I'm John Lienhard, at the University of Houston,
where we're interested in the way inventive minds
work.
(Theme music)
