The Longitude Act

The History of Parliament gives its title as An Act for Providing a Publick Reward for such Person or Persons as shall Discover the Longitude at Sea.⁵

It followed a campaign begun in 1713 by the mathematicians William Whiston and Humphry Ditton and a petition to Parliament in May 1714; Isaac Newton gave evidence.^2, 5

Royal Museums Greenwich ties the background to the loss of Shovell’s fleet on the Isles of Scilly in 1707, but says there was no public outcry and credits the mathematicians’ lobbying instead.¹

Royal assent came on 9 July 1714, under Queen Anne. The Act is dated 1713 because the session began in February 1714 in the old-style year.^1, 2

£10,000 for a method accurate to one degree of longitude, £15,000 to forty minutes and £20,000 to half a degree. Royal Museums Greenwich says the top prize would be worth at least £1.5 million today.^1, 2, 5

Half a reward was payable once a method was judged able to bring ships within eighty miles of the coast, the other half after a successful voyage to the West Indies. Up to £2,000 could be spent on trials, and smaller rewards given for useful methods, according to the History of Parliament.⁵

The Act named twenty-four Commissioners, by name or by office, from Parliament, the Navy, astronomy and mathematics. They became known as the Board of Longitude.^3, 5

They did not meet together until 1737, when John Harrison’s sea clock H1 brought them together; on 30 June that year they agreed £500 towards an improved clock.^3, 5, 6

The Board paid many smaller awards: £3,000 to the widow of Tobias Mayer for his lunar tables, £300 to Leonhard Euler, and sums to chronometer makers, among them Thomas Earnshaw and John Roger Arnold in 1805.^3, 7, 8

A new Act of 10 May 1765 set the Board’s terms for Harrison: £10,000 at once, the rest when other makers could reproduce his timekeeper. He never received the full prize; Parliament paid him £8,750 in 1773 outside the Board’s scheme.^2, 6, 9

According to Wikipedia’s account of the Act, an Act of 1774 halved the rewards, to £5,000, £7,500 and £10,000, and an Act of 1818 turned the Board towards navigation in general, with prizes for the Northwest Passage, and repealed the Act of 1714.²

Parliament abolished the Board in 1828, replacing it with three advisers to the Admiralty: Thomas Young, Michael Faraday and Edward Sabine. Its papers, 1737 to 1828, are at Cambridge University Library and have been digitised.^{2, 3, 10, 11}