p@rsons_world of John Harrison

Written by Heather and Mervyn Hobden and reproduced here with their permission.

The Brocklesby Clock

John Harrison (1693-1776)

An original essay [Feb 2000] - Heather and Mervyn Hobden,
authors of John Harrison and the Problem of Longitude.

John Harrison is famous as the inventor of the first chronometer - a clock for finding time at sea, and for the reluctance of the Board of Longitude to award his prize.

John Harrison was born in Foulby, near Wakefield, but the family moved to Barrow-on-Humber soon after. John's father was a joiner, and he was also churchwarden and parish clerk. John was not only trained in his father's shop, he learned about the tuning of bells and sang in the choir. His interest in music was to be influential in the development of his scientific ideas.

He was married in 1718, and his son John was born a few months later. By this time he was specializing in making clocks, helped by his youngest brother, James. Two innovations date from this time. 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. Later he was to incorporate this idea into his watches as a bimetallic strip, which is still used in thermostats. The other innovation was the grasshopper escapement, which can be seen in the clock he made for the stables at Brocklesby Park, which is still in good working order.

John's first wife died in May 1726 and in November he married again. They moved to a house on the Barton Road and had two more children, William, born 1728, and Elizabeth, born 1732. By this time John was working on a clock that could be used at sea, that could be submitted to the Board of Longitude to claim the prize of £20,000 set up by the Act of 1714 and still unclaimed. John took his designs to the Astronomer Royal, Halley, who sent him to George Graham. In 1736 his first sea-clock (H.1.) was sent for official trials to Lisbon.

"Troublesome, tedious, difficult"

The results were good enough for further funding, and John moved to London to work on his second machine (H.2). This was finished in 1737 but did not do well in tests. He began a third machine (H.3). It was not ready for trials until 1761, but by then Harrison had made a deck watch (H.4) that had much better performance.

This was taken by William for the trial. By this time, the Rev. Nevil Maskelyne, who was soon to become Astronomer Royal, was also a candidate for the longitude prize, with the Lunar Distance Method of finding longitude, using new tables by Tobias Mayer. As a result the Board of Longitude put every obstacle they could think of to prevent a "mechanic" like Harrison claiming the award. Even after a second successful trial watched by Maskelyne in Barbados in 1764. Harrison had to produce detailed drawings, and make two more watches. One of these, H.5 was tested by King George III himself in his Observatory at Kew. Eventually Harrison was paid the money owing to him, not by the Board of Longitude but by a special Act of Parliament.


"Besmear'd or bespatter'd"

In 1775, when he was 82, John Harrison wrote an account of his life's work. His book is called "A Description Concerning Such mechanism As Will Afford a Nice, or True Mensuration of Time; Together With Some Account of the Attempts for the Discovery of the Longitude by the Moon: As Also An Account of the Discovery of the Scale of Music, by John Harrison, Inventer of the Time-Keeper For The Longitude At Sea." In it he gives his opinion of the Board of Longitude, "Whiston was pissed on, and Ditton shit on, but surely these Men ought to be besmear'd or bespatter'd with both, who, after the Longitude was had by a good and easy Way, wanted to have it from a very troublesome, tedious, difficult, and uncertain endless Method!"


More Information....

More information on Harrison's life and work can be found in: John Harrison and the Problem of Longitude, by Heather and Mervyn Hobden, 7th edition, ISBN 1 871443 25 3, price £10, published by The Cosmic Elk, which is on sale at Jews Court, Steep Hill, Lincoln and other places. This also gives information on sources and further reading. The BHI has Harrison's book and other relevant work in its library, Upton Hall, (near Newark). Harrison's drawings and H.5 are at the Guildhall Library and Museum, London. H.1, H.2, H.3, H.4 and its copy, K.1 are in the National Maritime Museum, Greenwich. H.6 is missing.

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