Board of Longitude

The Board of Longitude was the popular name for the Commissioners for the Discovery of the Longitude at Sea. It was a British Government body formed in 1714 to administer a scheme of prizes intended to encourage innovators to solve the problem of finding longitude at sea.

Origins

Navigators and scientists had been working on the problem of not knowing a ship's longitude. The establishment of the Board of Longitude was motivated by this problem and by the 1707 grounding of four ships of Vice-Admiral Sir Cloudesley Shovell's fleet off the Isles of Scilly, resulting in heavy loss of life. Established by Queen Anne the Longitude Act 1714 named 24 Commissioners of Longitude, key figures from politics, the Navy, astronomy and mathematics.^[1] However, the Board did not meet until at least 1737^[2] when interest grew in John Harrison's marine timekeeper.

The Board administered prizes for those who could demonstrate a working device or method. The main longitude prizes were:

• £10,000 for a method that could determine longitude within 60 nautical miles (111 km)
• £15,000 for a method that could determine longitude within 40 nautical miles (74 km)
• £20,000 for a method that could determine longitude within 30 nautical miles (56 km).

In addition, the Board had the discretion to make awards to persons who were making significant contributions to the effort or to provide financial support to those who were working towards a solution. The Board could also make advances of up to £2,000 for experimental work deemed promising.^[3] Under this heading, the Board made many lesser awards, including some awards in total £5,000 made to John Harrison before he received his main prize, an award of £3,000 to the widow of Tobias Mayer, whose lunar tables were the basis of the lunar data in the early decades of the Nautical Almanac, £300 to Leonhard Euler for his (assumed) contribution to the work of Mayer, £50 each to Richard Dunthorne and Israel Lyons for contributing methods to shorten the calculations connected with lunar distances, and awards made to the designers of improvements in chronometers.

Even though many tried their hand at winning the main prize, for decades none was able to come up with a practical solution to the problem. The Board 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 (e.g., Greenwich) and the local time would determine longitude. Since local apparent time could be determined with some ease, the problem centred on finding a means of determining the time at a known place.

For details of the efforts towards determining the longitude, see History of longitude.

End of the Board's mandate

For many decades a sufficiently accurate chronometer was prohibitively expensive. The lunar distance method was used by mariners either in conjunction with or instead of the marine chronometer. However, with the expectation that accurate clocks would eventually become commonplace, John Harrison showed that his method was the way of the future. However the board, to its discredit, never awarded the prize to Harrison, nor anyone else.

With the significant problems considered as solved, the Board of Longitude was abolished by Act of Parliament in 1828.

References

External links

• National Maritime Museum, UK.
• Cambridge Digital Library presents digitised works from the archive of the Royal Greenwich Observatory, held at Cambridge University Library.