John Harrison

From Academic Kids

For the recipients of the Victoria Cross, see either John Harrison (VC 1857) or John Harrison (VC 1917)

See also the author M. John Harrison; John Harrison Mayor of North Tyneside

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John Harrison.

John Harrison (March 24 1693March 24 1776) was an English clock designer, who developed and built the world's first successful maritime clock, one whose accuracy was great enough to allow the determination of longitude over long distances.

Harrison was born at Foulby in Yorkshire, the eldest son of a carpenter. A carpenter by initial trade, Harrison built and repaired clocks in his spare time. Legend has it that he was given a watch when he was six to amuse him while in bed with smallpox, spending hours listening to it and studying its moving parts. As clocks and watches of all kinds were rare and expensive at the time, and Harrison came from a family of fairly modest means, it is likely the legend is false or the timepiece was broken enough to be worth little.

He was a man of many skills and used these to improve on the way clocks were built. For example, he developed the gridiron pendulum, consisting of alternating brass and steel rods assembled so that the different expansion and contraction rates cancelled each other out. Another example of his inventive genius was the grasshopper escapement—a control device for the step-by-step release of a clock's driving power. Being almost frictionless, it required no oiling.

In 1728 Harrison packed up full scale models of his inventions and drawings for a proposed marine clock to compete for the Longitude Prize and headed for London seeking financial assistance. He met with Edmond Halley, the Astronomer Royal, and presented his ideas. Halley sent him to meet George Graham, the country's foremost horologist (clockmaker). He must have been impressed with Harrison, for Graham personally loaned him money and told him to build a model of his marine clock.

It took Harrison seven years to build Harrison Number One or H1. He presented it to members of the Royal Society who spoke on its behalf to the Board of Longitude. The board was so skeptical of any such design, after 14 years of failures, that they demanded a sea trial. Harrison boarded a small ship to Lisbon and back, and on their return the captain and navigator both praised the design. The navigator noted that his own calculations estimated they were 90 miles offshore on their return to Britain, but the H1 put them just offshore right when the shoreline appeared.

This was not the transatlantic voyage demanded by the Board of Longitude, but the Board was impressed enough to grant Harrison 500 pounds for continued work. Harrison moved on to develop a more rugged version, H2. H2 was ready in 1741 after three years of building and two of on-land testing, but Britain was at war with Spain at the time in the War of Austrian Succession and the mechanism was deemed too important to risk it falling into Spanish hands. He was granted another 500 by the Board while waiting for the war to end, and he used it to work on H3. Five years later he abandoned it, unhappy with its performance.

He then proposed to build two new designs, H4 and H5. It was H4 that would become the masterpiece Harrison's designs are known as today. All of his early designs were heavy instruments needing to be slung from a beam in a ship and all were designed to keep time in a ship rolling and pitching in the worst storm. H4 was an instrument of beauty, being of the shape of a large pocketwatch.

H4 took 13 years to construct, and Harrison, now 68 years old, sent it on its transatlantic trial in the care of his son, William, in 1761. When the ship reached Jamaica it was only two miles in error. When the ship returned Harrison waited for the 20,000 prize, but the Board refused to believe the accuracy was not just luck, and demanded another trial. The Harrisons were outraged and demanded their prize, a matter that eventually worked its way to Parliament, which offered 5000 for the design. They refused and planned another trip, to the Caribbean city of Bridgetown, on the island of Barbados to settle the matter.

At the time of the trial, another method for measuring longitude was being developed to the point where it was ready for testing, the Method of Lunar Distances. The moon moves fast enough, almost 15 degrees a day, to easily measure the movement from day to day. By comparing the angle between the moon and the sun for today and when you left Britain (or more typically over Greenwich), the "proper position" of the moon could be calculated. By then comparing this with the angle of the moon over the horizon, the longitude could be calculated.

On Harrison's second H4 trial, the Reverend Nevil Maskelyne was asked to accompany the ship and test the Lunar Distances system. Once again H4 proved almost astonishingly accurate, measuring Bridgetown to within 10 miles. Maskelyne's measures were also fairly good, at 30 miles, but required considerable work and calculation in order to use. At a meeting of the Board in 1765 the results were presented, and once again they couldn't believe it wasn't just luck. Once again the matter reached Parliament, which offered 10,000 up front, and the other half once he turned over the design to other watchmakers to duplicate. In the meantime H4 would have to be turned over to the Astronomer Royal for long-term on-land testing.

Unfortunately, Nevil Maskelyne had been appointed Astronomer Royal on his return from Barbados, and was therefore also placed on the Board of Longitude. He returned a report of the H4 that was negative, claiming that the "drift rate" of the clock, the amount of time it gained or lost per day, was actually an inaccuracy, and refused to allow it to be factored out when measuring longitude. This made the H4 fail the needs of the Board, even though in reality it had already proven itself twice.

Harrison started work on his H5 while the testing was continuing, with H4 being sent around the world (and even the arctic). After three years of this he had had enough—Harrison felt "extremely ill used by the gentlemen who I might have expected better treatment from" and decided to enlist the aid of King George III. He asked for and was granted an audience with the King, who became extremely annoyed with the Board. King George tested H5 himself at the palace and when it had lost only four and a half seconds in ten days he was outraged and raged "By God Harrison, I'll see you righted!", and told Harrison to petition Parliament for the full prize after threatening to appear in person to dress them down. So in 1773, Harrison finally received his reward.

James Cook used one of the copies of H4 on his voyages, although the cost of the clocks was so high that the Lunar Distances method would also go on to be widely used for the next hundred years.

After World War I, Harrison's timepieces were found in a storeroom at the Royal Greenwich Observatory, in a highly decrepit state, by retired Naval officer Rupert Gould, who spent several years repairing and restoring them. It was Gould, not Harrison, who gave them the designations H1 through H5.

Today, the restored H1, H2, H3 and H4 can be seen on display in the National Maritime Museum at Greenwich Observatory. The H5 is owned by the Worshipful Company of Clockmakers of London and is on display at the Clockmakers' Museum in the Guildhall, London, as part of the Company's collection.

In the final years of his life, John Harrison wrote about his research into musical tuning, and manufacturing methods for bells. His tuning system (a meantone system derived from pi), is described in his book "Concerning Such Mechanism ........ (CSM)". This system challenges the traditional view that "harmonics" occur at integer frequency ratios, and in consequence all music using this tuning produces low frequency beating.

Dava Sobel wrote a 1995 book chronicling the history of John Harrison's invention, titled, Longitude: The true story of a lone genius who solved the greatest scientific problem of his time. An illustrated volume co-written with William J. H. Andrewes was produced in 1998: "The Illustrated Longitude" (ISBN 0-8027-1344-0). The account was dramatised in the 2000 film Longitude starring Michael Gambon as Harrison and Jeremy Irons as Gould.

Harrison's home was located on Red Lion Square in London, a short walk from the Holborn Tube. There is a plaque on Summit House which is located at the South side of the square.

See also

External links

fr:John Harrison pl:John Harrison sl:John Harrison


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