From Wikipedia, the free encyclopedia

The Board of Longitude was a British Government body formed in 1714 to solve the problem of finding longitude at sea. Its establishment was largely motivated by the 1707 grounding of Vice-Admiral Sir Cloudesley Shovell's fleet off the Isles of Scilly. The Board gathered the greatest scientific minds of its day to work on the problem, including Sir Isaac Newton, and also put up prizes for those who could demonstrate a working device, the longitude prize: the massive sums of 10,000 British pounds for a method that could determine longitude to within 60 nautical miles (111 km), 15,000 for one that could determine it within 40 nautical miles (74 km), and 20,000 pounds (equivalent to millions in today's currency) if the method could determine longitude within 30 nautical miles (56 km).

Even though many tried their hand at winning the prize, for decades none were able to come up with an efficient, practical and relatively economical solution to the problem. The board of longitude recognised that any serious attempt would be based on the recognition that the earth rotates through 15° of longitude every hour. The comparison of time between a known place (eg Greenwich) and the local time would determine longitude. This resulted in two different approaches. One relied on a purely astronomical approach requiring two observations. One to establish local time and the other based on a relatively fast moving astronomical body such as the moon. (The Lunar Distance Method)_ The difference in position of the fast moving astronomical body in comparison with the predicted position at a known place for a given time (eg Greenwich) would be proportional to the time difference between the two places. This could then be, with laborious calculations used to calculate the longitude. The other relied on a single astronomical observation for determining local time (the simplest one being local noon) and comparing it to a time piece set to the time at a known place. The concept of using a clock can be attributed to Gemma Frisius and attempts had been made on land with some success using pendulum clocks. However, many including Isaac Newton were pessimistic that a clock of required accuracy especially one which could withstand the rigours of ocean voyage could ever be developed.

In spite of this pessimism a small group felt that the answer lay in chronometry--developing a time piece that would work, even on extended voyages at sea. Most others believed that the ultimate solution was to be found in the heavens from a purely astronomical approach.

One member of the chronometry camp was a young clockmaker named John Harrison. Harrison thought that he was up to the enormous task presented by the Board of Longitude. He proceeded to try to create a timekeeper that would be accurate, even on the high seas.

His first product, which he dubbed H1, was extremely accurate but showed some anomalies under certain conditions. Both he and the Board determined that it was not accurate enough. Harrison was not deterred, though, and he devoted decades worth of work into improving his H1. This fostered the "improved" models of H2 and H3, but they were cumbersome and did not show a much greater percentage of accuracy than their predecessor. It should be noted that the Board was supportive of Harrison's efforts and forwarded several stipends of up to 500 pounds.

However, in the time that Harrison took to create H2 and H3 the Board had become heavy with astronomers who favoured the purely astronomical approach. Although unfair, it was in many ways predictable. Improved astronomical observations were required for the improved determination of latitude and for determining local time for longitude. Otherwise navigators were limited to using noon and the pole star, with the latter not being entirely accurate and not useful in determining local time. Furthermore early marine chronometers including Harrison's were not simply set and forget. The rate at which they gained or lost time required further calculations and these could be verified by using astronomical observations. While H1, H2 and H3 were all huge timekeepers, the realization of creating a smaller timekeeper dawned on him. He started work on the most accurate pocketwatch of the time. This proved to be a success. His son tested the clock on its first sea voyage, as Harrison was already too old at the time of his finishing his newest development. The watch lived up to its creator's expectations, and surpassed the highest standard expected by the board. However, Harrison received only a part and not the full prize from the Board of Longitude. They were doubtful that the solution to the longitude problem could be obtained by a mechanical means. The Board reasoned that a clock of such accuracy may not be able to be easily copied. Furthermore if the clock should fail then there was no way of determining longitude. They had been certain that the only resolution would be to find an astronomical clock through mathematics and the study of the heavenly bodies. The Board did not trust that this timekeeper was the answer.

Harrison was obviously upset with this turn of events and turned to King George III. He explained his situation to the King, who was moved by his years of hard work and dedication to his cause. He proclaimed that Harrison would be righted, and made certain that the clockmaker would receive his rightful prize from the Board of Longitude.

In spite of the obvious desirability of such a device by sailors, for many decades a sufficiently accurate chronometer was prohibitively expensive. The lunar distance method in spites of all of its shortcomings was often used by mariners either in conjunction with or instead of the marine chronometer.

However, with accurate clocks becoming commonplace Harrison showed that his method was the way of the future.

The Board of Longitude was dissolved in 1828.

[[1]]