Engines of Our Ingenuity

No. 235:
HARRISON'S TIMEPIECE

by John H. Lienhard

Click here for audio of Episode 235.

Today, we spend a lifetime making a 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.

John Harrison was born in Yorkshire in 1693. When he came down with smallpox at the age of six, his parents put a watch on his pillow to keep him company. 17th-century watches were large and not very accurate, but you could see their works and relate the loud ticking to mechanical action. That odd monosyllabic companion awakened young John's imagination.

Navigation came a long way between Columbus's voyage and John's birth. But calculating a ship's precise longitude was still a nasty problem. It was easy enough if you knew Greenwich Meridian time (or Greenwich noontime) at the local noontime. The trouble was, no clock held its accuracy well enough during months at sea.

Harrison was 21 and just starting in the trade of clockmaking, when Parliament offered a prize of 20,000 pounds. To win it you had to invent a clock that could hold a ship within half a degree of longitude on a trip all the way to the West Indies. 20,000 pounds was an enormous sum, because in 1714 the challenge looked impossible.

Harrison decided to win the prize. He invented a new escapement mechanism and a bimetallic temperature compensator. In 1728 he went to London and found financial backing to make a seagoing model. On a test voyage in 1735 he navigated from Lisbon to London within 1½ degrees -- very impressive but not enough to win the prize.

When Harrison finished a second clock, England -- now at war with Spain -- wouldn't let him test it at sea for fear the Spanish might capture it. So he went on improving. His third clock was a fine instrument, but he saw how to make it still better. He built a fourth clock -- a beautiful little four-inch-diameter masterpiece with jeweled action. He was now 68 and had, in his words, put into it:

... fifty years of self-denial, unremitting toil, and ceaseless concentration.
He went on to say,
I think I may make bold to say that there is neither any other Mechanism or Mathematical thing in the World that is more beautiful or curious in texture than this my [longitude] Time-keeper.
Harrison was too old for another voyage, so he sent his son off to the West Indies in 1761. The clock lost 5 seconds on the trip and placed them within 1-1/4 minutes of longitude at Jamaica.

Now the Royal Society began to waffle. They gave him 2,500 pounds of prize money, but the rest depended on a second trial. When the clock did even better, they gave him 7,500 pounds more and withheld the other 10,000 pounds until he could deliver two more time-pieces. Finally, after the aging Harrison produced a fifth, even more accurate, clock, King George stepped in and told the Royal Society to give in. Harrison had finally won the prize at the age of 80.

Harrison had devoted his entire life to adding one really beautiful and lasting thing to this world. It was a hard bargain, but in the end it was a bargain we all might envy.

I'm John Lienhard, at the University of Houston, where we're interested in the way inventive minds work.

(Theme music)


Wilford, J.N., The Mapmakers. New York: Vintage Books, Random House, 1982, Chapter 9.



Image from the Edinburgh Encyclopaedia

One of Harrison's escapement mechanisms



The Engines of Our Ingenuity is Copyright © 1988-1997 by John H. Lienhard.


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