Its a matter of time

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Its a matter of time
The quest for an accurate clock
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Accurate Clocks With the start of great voyages of discovery in the fifteenth century, and the establishment of a world-wide trade network, a means of accurately determining longitude at sea became increasingly urgent. This led the great maritime nations to offer substantial prizes for a practical solution to the problem: Spain offered 1000 crowns, the Netherlands 10,000 florins and the British Board of Longitude, following increased pressure from influential merchants and seamen for a solution to the longitude problem, the was formed by A British Government Act of 1714, and offered a top prize of £20,000 (equivalent to around £1 million today) for a successful measure of longitude to within half-a-degree. The Board of Longitude, who administered the award, was flooded with weird and wonderful suggestions. It was over half a century before a solution was found.. From the end of the fifteenth century, adventurers and merchants took to the sea in unprecedented numbers. These journeys were hazardous not only because of the inherent dangers but also because, once out of sight of land, sailors had no accurate means of knowing their exact position. One's position on the Earth is defined by two co-ordinates: latitude - the distance north or south of the equator, and longitude - the distance east or west from an agreed place. Latitude was easy to find by observation of the Sun at midday, or the pole star at night; but longitude had always been a problem. Since the earth revolves on its axis, longitude is a function of time. To find longitude at sea, one needs to know what time it is at some other known location on Earth - usually the home port. Then, by noting local time (which is relatively easy to do using the Sun or the stars), the difference between the two times measures the longitude. The real problem was how to discover the time at the home port. The obvious answer would be to take a portable clock, set to 'home' time. Such a clock would have to be both very accurate and unaffected by the violent movements of the ship and temperature changes. In 1700, almost no one believed such a clock could be made; even Isaac Newton considered it most unlikely. London was universally recognized as the world's most important centre for the manufacture of clocks and watches. Virtually all the important design improvements which shaped the modern mechanical clock were incorporated in English clocks by 1700. Only one real challenge remained to be met with an advance in clock design and it is no wonder the world looked to England for a solution. John Harrison (1693-1776) was born in Foulby, West Yorkshire. At the age of 20 he had taught himself the theory and practical skills of clockmaking. His father was a cabinet maker, and John was also a woodworker, and manufactured very accurate clocks, solely from wood. In the mid-1720's Harrison heard of the great longitude prize and set to work on a series of remarkable precision longcase clocks (regulators - jb: "grandfathers" of the grandfather clock), smaller versions of the turret clock, to see just how far they could push the capabilities of this fixed-clock design. Harrison also eliminated the significant error caused by expansion of the pendulum with heat with his gridiron rod pendulum which ensured a constant pendulum length. The early regulators achieved astonishing accuracy of one second per month, far exceeding the performance of the best London clocks of the day. To qualify for the main longitude prize, a timekeeper would have to keep time with a variation no greater than 2.8 seconds a day, but before 1750 even the best portable timepieces (ie watches) lost or gained at least a minute a day. The only timepieces capable of the required accuracy were large regulators, and so Harrison concluded he would have to make a portable clock on the scale of his precision regulator. Traditional pendulum clock designs, he knew, would not function properly on a ship at sea. In 1730, Harrison traveled to the Observatory with secret plans for a sea-clock to compete for the Longitude Prize. He received encouragement from the 2nd Astronomer Royal, Edmond Halley, and money from the world's leading clockmaker, George Graham. For the next six years Harrison worked to create his first marine timekeeper, today known as H1. Essentially a portable version of Harrison's precision wooden clocks, H1 ran for one day, not eight. Only the wheel work was made of wood (oak), the main frame and ancillaries being made of brass or other alloys. It was spring driven, with all moving parts counterbalanced and controlled by springs so that the machine was completely independent of gravity. The H1 H1's movement weighed 34 kg and stood 63 cms high. The pendulum would be useless in a rocking ship, so Harrison replaced it with two interlinked bar-balances, connected with crossed ribbons- an early type of frictionless gearing. Other refinements meant the clock required no lubrication, and was compensated for temperature changes. After preliminary testing on a barge in the Humber, H1 was brought to London, to Graham, and publicly displayed to the scientific community. It was widely regarded as one of the wonders of its age. The First Lord of the Admiralty arranged for Harrison and his timekeeper to be sent on board the warship Centurion to Lisbon in May 1736. In Lisbon, H1 was transferred to Orford, and on the long homeward journey Harrison used H1 to correct a misreading of the ship's longitude. On 30th June 1737 the Board of Longitude was convened, for the first time, to hear how H1's trial had gone and to inspect this model of 'high technology'. The news the Board received was evidence that, after all, a marine timekeeper (known nowadays as a 'marine chronometer') might just prove to be a practical solution to the longitude problem. Harrison was not entirely satisfied with H1's timekeeping, but requested financial assistance from the Board to make an improved version. They allocated him £250 there and then, with the promise of another £250 on completion. In agreeing to this support, the Commissioners were, in effect, instigating the very first Government-sponsored research and development project undertaken by a private contractor. The H2 Harrison immediately set to work on a second marine timekeeper, H2. Its design was still flawed, however, and after two years he moved onto a third. The H3 For 19 years Harrison obsessively built and rebuilt H3, supported by grants from the Board of Longitude and fees from other clock design work. In spite of including Harrison's unique inventions, the bimetallic strip, to provide compensation for changes in temperature and the almost frictionless ' caged roller bearing', H3 never went to sea, as by the time it was finished Harrison had created 'the most famous watch ever built', H4. The H4 Both externally, and to some extent internally, H4 looks like a very large, contemporary pocket watch, even to the extent of having pair cases (with an inner case for the movement and a protective outer case around it). Technically, however, it was different from an ordinary watch in a number of significant ways. Apart from being very finely constructed, its balance was much larger, although still relatively light, and of higher frequency: it oscillated five times a second. This means the balance had a great deal more energy stored in it when running, which rendered it much less vulnerable to physical disturbance. Temperature change was compensated for by using the bimetallic strip, a smaller version of H3's device. Harrison had made great progress with H4, but he was now not the only one coming closer to winning the longitude prize. In 1756, the Astronomer Royal himself, James Bradley (1693-1762), recommended that the Board of Longitude reconsider the potential of the lunar distance method for solving the longitude problem. At the Board's meeting on 18th July 1760, Harrison asked for a trial of H3 hoping that it would be possible to send 'the watch' (H4) as well, as it had far exceeded his expectations. In March 1761, the Board agreed and told John's son William (now in partnership with his father) to prepare for a trial voyage to Jamaica in charge of the timekeepers. After innumerable delays, on 18th November 1761 the Deptford sailed for the West Indies with William and H4 (in the event H3 was not sent with them). They arrived at Jamaica, the official end of the trial, on 19th January 1762. After ascertaining exact local time at Port Royal by equal altitudes, the error of the watch was calculated to be just 5.1 seconds slow! It was a remarkable achievement but was spoilt by one crucial oversight. There had been failure to discuss and agree the rate of the watch. Even very accurate, reliable, timekeepers do not usually keep exact time. It is extremely difficult to adjust a clock or watch so it does not gain or lose anything. As long as the amount is regular and predictable this does not really matter. If, for example, it gains 5 seconds per day (its 'rate') then one simply makes that much allowance every day and correct time can be deduced. However, for testing timekeepers this concept was entirely new and the trial was therefore next to useless. At the August meeting of the Board, Harrison reluctantly agreed to a second trial of H4 to the West Indies. When the Board met on 4th August 1763 to make the necessary arrangements, the first item on the agenda was the dreaded question of deciding H4's rate. It was finally agreed that Harrison should be allowed to provide his own statement of what the rate should be. William Harrison made his declaration of H4's rate (gaining 1 second a day) to the Admiralty on 24th March 1764, and he and Thomas Wyatt, a companion, departed with H4 in the Tartar from Spithead on the 28th. In the event, the trial was an astonishing success story for H4. The average computation put the watch's error at just 39.2 seconds after the voyage of 47 days. This was three times better than the performance needed to win the full £20,000 longitude prize. The Board consisted of a panel of six experts consisted of three well-respected practical watchmakers: Thomas Mudge (1717-94), William Matthews, and Larcum Kendall (1721-90); the Reverends William Ludlam (1717-88) and John Michell (1724-93) - both of Cambridge University; and the London instrument maker John Bird (1709-76). The meeting could scarcely have been a relaxed affair under these circumstances, but - to add to the tension - the Board appointed Nevil Maskelyne, the Astronomer Royal and an ardent supporter of the Lunar Distance method, to oversee the presentation. The Board of Longitude met again on 28th October 1765 and granted Harrison enough money to make up the first half of the full reward. In return, they insisted on taking H4 (which had become their property). They also asked Harrison to recommend someone suitable for copying the watch; he suggested Larcum Kendall, a leading London watchmaker. At last, Harrison had half the prize; but, for him, it was only the whole reward, and the recognition that went with it, that mattered. Harrison knew that, in order to qualify for the second part of the longitude prize, he had to make at least two other watches similar to H4 and have them tested. Knowing that he would not give up the challenge of winning the whole longitude prize, the Board decided to test all four of Harrison's timekeepers at Greenwich. Harrison and his son William began to make the first 'copy timekeeper' to qualify for the remaining prize money, while Kendall, one of the board members, made another. Kendall's watch (now known as K1) was completed in 1769 and inspected in early 1770 by the same panel that had seen H4. William Harrison was also present at the demonstration and admitted the copy was exceptional. (K1 was, in due course, to prove its worth with Captain Cook on his second (1772-75) and third (1776-80) voyages of discovery). Kendall's K1 The board decided not pay the rest of the fee, however, because Harrison did not produce both copies. Father and son had reached the end of the road, and desperate measures were now needed if further progress was to be made. As a last resort, John decided to appeal to the highest authority in the land, the King himself. An approach was made to George III on 31st January 1772, by letter, via the King's private astronomer at Richmond, Dr Stephen Demainbray (1710-82). William Harrison requested an opportunity for H5 to be put on trial by the King himself at his private observatory. He was summoned for interview at Windsor, and asked to expand on some of the details. At this point the King is said to have remarked: "...these people have been cruelly wronged...by God, Harrison, I will see you righted!" H5 went on trial at Richmond from May to July of that year. After a false start caused by leaving the watch too close to some magnets, H5 performed superbly. Its daily rate over the whole ten weeks averaged out at less than a third of a second per day. Both the King and Demainbray were very impressed and the Harrisons believed their own personal trial was nearing its end. Probably at the suggestion of the King himself, Harrison now formally approached the Prime Minister, Lord North, with the full story. The Harrisons' petition to Parliament eventually bore fruit and the Act of 13 George III, chapter 77, duly received Royal Assent. This awarded Harrison £8750 which, in addition to all the sums he had received from the Board before, including expenses, actually came to a bit more than the total £20,000. Harrison had, at last, won the great longitude prize. Perhaps more important to John, however, was that the award was seen to be his. Even though not all of it came from the Board of Longitude, here was public recognition that John Harrison had solved the longitude problem. Within three years, on 24th March 1776, Harrison died at Red Lion Square. It was his 83rd birthday.
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