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John Harrison |
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John Harrison |
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The Man who Solved the Longitude Problem
Early Life
John Harrison wan born in Foulby, Yorkshire in 1698. He was the son of a carpenter. He was interested in mechanics and clocks, and built his first clock when he was 20. Little did he know that his interest in clocks would make him famous the world over..............
The Problem
In the 16th and 17th Century thousands of sailors were dying at sea because they couldn't find their positions. In 1707 over 2000 men were lost when four ships run aground on the Sicily Isles. So the Government set up a committee to try and find the answer to the Longitude problem: a solution that can provide longitude to within ½º (half a degree), or 2 minutes of time! The reward? £20,000, or millions today.
Solving The Problem
In 1727 John Harrison had made a clock with a 'gridiron' pendulum, which consisted of nine alternating steel and brass rods to eliminate any effects of temperature changes. And in the years that followed, he used this mechanism to make four clocks each to rise to the challenge to solve the Longitude Problem...
H1 (1730-1735) H1 is a portable version of Harrison's wooden clocks. It's spring driven and only works for a day. The moving parts were counterbalanced and for the first time H1 was independent of the direction of gravity. The linked balance mechanism also makes sure that any change in motion with affects one of the balances is compensated for by the effect on the other balance.
In 1735 Harrison took H1 to London and showed it to the scientific community. Lots of scientists wanted to see the timekeeper.
A year later, Harrison and his timekeeper went to Lisbon aboard the ship Centurion to test the clock. and returned to the Oxford. H1 performed brilliantly in the test, keeping time accurately enough for Harrison to correct a misreading of the Oxford's longitude on the return voyage. Harrison did not ask for another test but he asked for money assistance from the Board of Longitude to make his next time keeper.......H2!
H2 (1737-1740) H2 was more or less the 'Homer Simpson' size H1, because it was larger and heavier, but had nearly the same design as H1. Harrison started H2 in 1737 but in 1740 realized H2 had some 'glitches' in his design, and asked for more money for....H3!
H3 (1740-1759) Harrison worked on H3 between 1740 and 1759. It incorporated two brand new inventions of his own; a bimetallic strip, to compensate the balance string for the effects of changes in the temperature, and the cage roller bearing, the ultimate version of his anti-friction devices. Both of these inventions are used in the present day!
But unfortunatly work on H3 went nowhere, but it's main job was to convince Harrison that the solution to the Longitude Problem was in a completly different design......H4.
H4 (1755-1759) In 1753, Harrison asked John Jefferys, a watchmaker from London, to make him a watch with Harrison's special designs. It was made for Harrison's personal use - to help with his clock testing. No one in the 1750s thought thought a simple pocket watch was a serious timekeeper, but Harrison discovered that if he improved certain parts on his clock, he could make a brilliant timekeeper.
So two years later, as well as asking for more support for the making of the doomed H3, he asked the Board of Longitude for support:
"...to make two watches, one of such size as may be worn in the pocket & thhe other bigger...having good reason to think from the performance of one already executed... that such small machines may be render'd capable of being of great service with respect to the Longitude at Sea... "
H4 was completely different from the other timekeepers. It was only 13cm in diameter and only weighing 1.45kg, it looks like a very nice, yet very large pocket watch. Harrison's son William set sail for the West Indies with H4, aboard Deptford on 18th November 1761. They
arrived in Jamaica on 19th January 1762, where the clock was only 5.1 seconds slow! It was a remarkable achievement, but it would be some time before the Board of Longitude were happy.
Another trail of H4 took place when William Harrison (John Harrison's son) set off for Barbados aboard the Tartar on 18 March 1764. Will used H4 to predict his arrival at Madeira with amazing accuracy. The watch's error was to be 39.2 seconds wrong in 47 days, which was three times as required for the £20,000 prize. But the Board of Longitude still weren't happy. They thought H4 was a fluke and would not be satisfied until others of the same kind could be made and tested. Harrison was to be paid £10,000 (only half of the full prize, but still a lot of money) as soon as his revealed his secrets and handed over his designs to the Astronomer Royal, and he got the rest of the money when the other timekeepers, accurate enough to find longitude to within 30 miles were made. Harrison had solved the Longitude problem.
Modern Interpretation of his Life
Cartoon version of John Harrison
In America, a tv/film company called a&e made a film based on the Longitude problem. The film starring Michael Gambon as John Harrison shows the extreme danger of being a sailor in the 1700's.
The Longitude movie starring Geremy Irons and Michael Gambon
"Two hundred fifty years ago, countless sea voyages ended in catastrophe because there was no technology to exact a ship's position on the vast ocean. Discovering a way to accurately measure longitude at sea was a top priority. So in 1714, England's Parliament offered a huge reward to seamen and scientists alike. While everyone looked to the stars for navigational guidance, one man saw a different route. John Harrison (Michael Gambon) dared to imagine a mechanical solution in the form of a clock. The world thought his ideas were preposterous, but John Harrison's dreams were as limitless as the seemingly infinite oceans before him."
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