John Harrison

GP stock picture Sea Hawk II "To John Harrison" click on the picture to enlarge       Introduction "To John Harrison" is stated on the dial of the Sea Hawk II watches. Who was John Harrison ? Since I did not know or just vaguely, I did a small search and this is what I found. John Harrison (pictured left) was born on March 24, 1695 in Foulby, Yorkshire as the oldest of 5 children. About 4 years later, the whole family moves to Barrow, Lincolnshire. John is about 6 years old when he suffers from chickenpox. He stays in bed for a long time and, according to the story, in order to kill time, his parents give young, ill John a clock as a "ticking friend". Watches (or better clocks) in those days were large and apart from hearing the ticking you could see their works. Could this ticking companion be the basis for his later activities? His father Henry was an estate carpenter and John trained in his father's shop. He also mastered to tune bells and was an active member of the church choir during the Barrow period. John married in 1718, and his wife Elizabeth gave birth to a son (John) a few months later. By this time John was making clocks with the help of his youngest brother, James. He (they?) invented two novelties. One was the grid-iron pendulum which used linked rods of brass and steel for the pendulum, which have different rates of expansion thus keeping the length of the pendulum and the going rate of the clock even at all temperatures. By the way, this idea was later incorporated into the balance of his watches as a bimetallic strip, which is still used in thermostats. The other innovation was the grasshopper escapement. Not sure what that is though but it has very low friction and, as made by Harrison, it needed no lubrication at all. It is almost silent, since the pallets only contact the teeth of the escape wheel when the pendulum is nearly stopped close to the end of its swing. The main source of noise is the impact between the pallet and its rester after the pallet is released by the wheel.   Inventions and the accurate time Now to his biggest inventions. Although navigation on sea came a long way between Columbus's voyage and John's birth, calculating a ship's precise longitude was still a problem. Sure, It was possible and easy if you knew Greenwich Meridian time at the local noontime. But the huge problem was that there were no clocks at that time that could keep its accuracy well enough during months at sea. John was 21 (and just starting in the trade of clock making with James) when Parliament offered a prize of 20,000 pounds. In order to get this amount, one 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. In those days that challenge was almost impossible. But John decided to win the prize. John's first wife, Elizabeth, died in May 1726 and in November he married again. Another Elizabeth. Two more children were born, William, born 1728, and Elizabeth, born 1732. John, with his younger brother James, was now working on a clock (H1, see left picture) that could be used at sea and that could be submitted to the Board of Longitude to claim the prize, still unclaimed. On a test voyage with this clock in 1736 he navigated the HMS Oxford from Lisbon to London within 1 degrees: very impressive and the Board wanted to give John the prize but John did not accept it at that time because he was such a perfectionist that he thought the clock could be further improved......Only then he would accept the prize !!! The Board, wondering, gave John 250 pounds for further improvements! By the time John finished (1741) a second clock (H2, see left picture), England was at war with Spain. Therefore, England wouldn't let him test it at sea for fear the Spanish might capture it. John went on improving. That turned out to be a difficult task and John finished the H3 in 1759. As shown in the picture, the main improvement was the pendulum: now round and clearly visible on top of the clock. Another improvement was the application of a bi-metallic strip to minimize influences of temperature changes. The H3 is much smaller than its predecessors: 60 cm high and 30 cm broad. Because the war is not over yet, he is not able to test the clock. During the development of the H3, John was already working on the next step: the H4 (see right picture below). This clock ("pocketwatch") was based on a pocketwatch that John Jefferys (watchmaker and member of The Worshipful Company of Clockmakers) made for John (John has asked Jefferys to make a pocketwatch based on several of his ideas and improvements). John finishes the H4 in 1759 but shows it to the Board in 1760, who were amazed by this clock. No huge clock with lots of copper but a pocketwatch, a beautiful little 13 cm diameter masterpiece with jeweled action ! The H4 is handwound, runs for 30 hours, uses rubies and diamonds, and needs (in contrast to his earlier clocks) lubricant. John was now 68 and too old for another voyage, so he sent his son William 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 can't/won't believe that much of precision and gave him 1500 pounds of prize money, but the rest depended on a second trial. When the clock did even better, they gave him 1000 pounds more and withheld the other 10,000 pounds until he could deliver two more timepieces. Probably the main reason the Board acted this way was the fear that Harrison's inventions would fall into the hands of the French! Finally, after the aging Harrison produced a fifth, even more accurate, clock (H5), he asked King George III to test H5 in his own Observatory. The first tests were a disaster but after removal of some strong magnetic stones in the private collection of the king, the clock worked more than perfect. King George stepped in and told the Royal Society to give in. In june 1773, at the age of 80, John had finally won the prize, in parts! In the very same year, the Board made new rules for the Longitude Prize that were so absurd and timeconsuming, no one would ever have a go at it again !!! John Harrison died on March 24, 1776. Best regards, Mark   click on the picture to enlarge References: D. Sobel. Longitude (novel) Wilford, J.N., The Mapmakers. New York: Vintage Books, Random House, 1982, Chapter 9. John Lienhard, at the University of Houston, Clock pictures: (c) The National Maritime Museum, London

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