Longitude Act

Discovery of Longitude at Sea Act 1713

Act of Parliament
Parliament of Great Britain
Long title	An Act for Providing a Publick Reward for such Person or Persons as shall Discover the Longitude at Sea.
Citation	13 Ann. c. 14 12 Ann. St. 2. c. 15
Dates
Royal assent	9 July 1714
Commencement	16 February 1714
Repealed	8 May 1818
Other legislation Amended by Discovery of Longitude at Sea Act 1753 Discovery of Longitude at Sea Act 1762 Discovery of Longitude at Sea (John Harrison) Act 1763 Discovery of Longitude at Sea Act 1774 Repealed by Discovery of Longitude at Sea, etc. Act 1818 Relates to Discovery of Longitude at Sea, etc. Act 1821 Nautical Almanack Act 1828
Status: Repealed
Text of statute as originally enacted

The Longitude Act 1714 (13 Ann. c. 14), also known as the Discovery of Longitude at Sea Act 1713, was an act of the Parliament of Great Britain passed in July 1714 at the end of the reign of Queen Anne. It established the Board of Longitude and established a inducement prize contest (the longitude rewards) for anyone who could find a simple and practical method for the precise determination of a ship's longitude. The 1714 act was followed by a series of other Longitude Acts that revised or replaced the original.

Background

As transoceanic travel became ever more relevant, so did the importance of accurate and reliable navigation at sea. Scientists and navigators had been working on the problem of measuring longitude for a long time. While determining latitude was relatively easy, early ocean navigators had to rely on dead reckoning to find longitude. This was particularly inaccurate on long voyages without sight of land and could sometimes lead to tragedy, as during the Scilly naval disaster of 1707, which claimed the lives of nearly 2,000 sailors. This brought the problem of measuring longitude at sea into sharp focus once more. Following the Merchants and Seamen Petition, which called for finding an adequate solution and was presented to Parliament in May 1714, the Longitude Act was passed in July 1714.

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

The rewards

The act offered a series of rewards, rather than a single prize. The rewards increased with the accuracy achieved: £10,000 (worth over £1.69 million in 2025) for anyone who could find a practical way of determining longitude at sea with an error of not greater than one degree of longitude (equates to 60 nautical miles (110 km; 69 mi) at the equator). The reward was to be increased to £15,000 if the error was not greater than 40 minutes, and further enhanced to £20,000 (equivalent to £3.97 million in 2025) if it was not greater than half a degree. Other rewards were on offer for those who presented methods that worked within 80 geographical miles of the coast (being the most treacherous part of voyages) and for those with promising ideas who needed help to bring them to readiness for trial. Many rewards were paid out over the 114 years of the Board of Longitude's existence. John Harrison received more money than any other individual, with several rewards from the 1730s–1750s, and £10,000 in 1765.

Later Acts

Discovery of Longitude at Sea, etc. Act 1818
Act of Parliament
Parliament of the United Kingdom
Long title	An Act for more effectually discovering the Longitude at Sea, and encouraging Attempts to find a Northern Passage between the Atlantic and Pacific Oceans, and to approach the Northern Pole.
Citation	58 Geo. 3. c. 20
Territorial extent	United Kingdom
Dates
Royal assent	8 May 1818
Commencement	8 May 1818
Repealed	15 July 1828
Other legislation Repeals/revokes Discovery of Longitude at Sea Act 1713 Discovery of North-West Passage Act 1744 Discovery of Longitude at Sea Act 1753 Discovery of Northern Passage Act 1776 Discovery of Longitude at Sea Act 1790 Amended by Discovery of Longitude at Sea, etc. Act 1821 Repealed by Nautical Almanack Act 1828
Status: Repealed
Text of statute as originally enacted

Discovery of Longitude at Sea, etc. Act 1821
Act of Parliament
Parliament of the United Kingdom
Long title	An Act to amend an Act of the Fifty-eighth Year of His late Majesty, for more effectually discovering the Longitude at Sea, and encouraging Attempts to find a Northern Passage between the Atlantic and Pacific Oceans, and to approach the Northern Pole.
Citation	1 & 2 Geo. 4. c. 20
Territorial extent	United Kingdom
Dates
Royal assent	23 February 1821
Commencement	23 February 1821
Repealed	15 July 1828
Other legislation Amends Discovery of Longitude at Sea, etc. Act 1818 Repealed by Nautical Almanack Act 1828 Relates to Discovery of Longitude at Sea Act 1713 Discovery of North-West Passage Act 1744 Discovery of Longitude at Sea Act 1753 Discovery of Northern Passage Act 1776 Discovery of Longitude at Sea Act 1790 Discovery of Longitude at Sea Act 1774
Status: Repealed
Text of statute as originally enacted

Subsequent Longitude Acts offered different rewards. The act of Parliament^[which?] of 1767 held out £5,000 for improvements to Tobias Mayer's lunar tables.

1774

Discovery of Longitude at Sea Act 1774

Act of Parliament
Parliament of Great Britain
Long title	An Act for the Repeal of all former Acts concerning the Longitude at Sea, except so much thereof as relates to the Appointment and Authority of the Commissioners thereby constituted, and also such Clauses as relate to the constructing, printing, publishing, vending, and licensing of Nautical Almanacks, and other useful Tables; and for the more effectual Encouragement and Reward of such Person and Persons as shall discover a Method for finding the same, or shall make useful Discoveries in Navigation; and for the better making Experiments relating thereto.
Citation	14 Geo. 3. c. 66
Territorial extent	Great Britain
Dates
Royal assent	2 June 1774
Commencement	24 June 1774
Repealed	21 August 1871
Other legislation Repeals/revokes See § Repealed enactments Amended by Finding of the Longitude at Sea Act 1776 Repealed by Statute Law Revision Act 1871 Relates to Discovery of Longitude at Sea, etc. Act 1818 Discovery of Longitude at Sea, etc. Act 1821 Nautical Almanack Act 1828
Status: Repealed
Text of statute as originally enacted

The Discovery of Longitude at Sea Act 1774 (14 Geo. 3. c. 66) halved the amount offered for any method or instrument achieving the degrees of precision outlined in the original act (i.e. £5,000 for a degree, £7,500 for 2⁄3 of a degree or £10,000 for 1⁄2 a degree). The act repealed the earlier legislation providing rewards for the discovery of a method of finding the longitude at sea, saving the provisions constituting the Commissioners for the Discovery of the Longitude (the Board of Longitude) and those relating to the Nautical Almanac, and made new and reduced provision for such rewards.

Section 1 of the act repealed 8 enactments, listed in that section, except so far as they related to the appointment and authority of the commissioners thereby constituted, or to the constructing, printing, publishing, vending, and licensing of nautical almanacks and other useful tables.

Citation	Short title	Description	Extent of repeal
13 Ann. c. 14 12 Ann. St. 2. c. 15	Discovery of Longitude at Sea Act 1713	An Act for Providing a Publick Reward for such Person or Persons as shall Discover the Longitude at Sea.	The whole act, except so far as it relates to the appointment and authority of the commissioners thereby constituted, and except such clauses as relate to the constructing, printing, publishing, vending, and licensing of nautical almanacks and other useful tables.
14 Geo. 2. c. 39	Longitude and Latitude Act 1740	An Act for surveying the Chief Ports and Head Lands, on the Coasts of Great Britain and Ireland, and the Islands and Plantations thereto belonging, in order to the more exact Determination of the Longitude and Latitude thereof.
26 Geo. 2. c. 25	Discovery of Longitude at Sea Act 1753	An Act to render more effectual an Act made in the Twelfth Year of the Reign of Her late Majesty Queen Anne, intituled, "An Act for providing a publick Reward for such Person or Persons as shall discover the Longitude at Sea," with regard to the making Experiments of Proposals made for discovering the Longitude; and to enlarge the Number of Commissioners for putting in Execution the said Act.
2 Geo. 3. c. 18	Discovery of Longitude at Sea Act 1762	An Act for rendering more effectual an Act, made in the Twelfth Year of the Reign of Her late Majesty Queen Anne, intituled, "An Act for providing a Publick Reward for such Person or Persons as shall discover the Longitude at Sea," with regard to the making Experiments of Proposals made for discovering the Longitude.
3 Geo. 3. c. 14	Discovery of Longitude at Sea (John Harrison) Act 1763	An Act for the Encouragement of John Harrison to publish and make known his Invention of a Machine, or Watch, for the Discovery of the Longitude at Sea.
5 Geo. 3. c. 11	Discovery of Longitude at Sea Act 1765	An Act for rendering more effectual an Act made in the Twelfth Year of the Reign of Her late Majesty Queen Anne, intituled, "An Act for providing a publick Reward for such Person or Persons as shall discover the Longitude at Sea," with regard to the making Experiments of Proposals made for discovering the Longitude.
5 Geo. 3. c. 20	Discovery of Longitude at Sea (No. 2) Act 1765	An Act for explaining and rendering more effectual Two Acts, One, made in the Twelfth Year of the Reign of Queen Anne, intituled, "An Act for providing a publick Reward for such Person or Persons as shall discover the Longitude at Sea;" and the other, in the Twenty-sixth Year of the Reign of King George the Second, intituled, "An Act to render more effectual an Act made in the Twelfth Year of the Reign of Her late Majesty Queen Anne, intituled, 'An Act for providing a publick Reward for such Person or Persons as shall discover the Longitude at Sea,' with regard to the making Experiments of Proposals made for discovering the Longitude; and to enlarge the Number of Commissioners for putting in Execution the said Act."
10 Geo. 3. c. 34	Discovery of Longitude at Sea Act 1770	An Act for rendering more effectual several Acts for providing a Publick Reward for discovering the Longitude at Sea; for improving the Lunar Tables constructed by the late Professor Mayer; and for encouraging Discoveries and Improvements useful to Navigation.

Notes

References

Further reading

• Alexi Baker (July 2013), Longitude Acts, Board of Longitude project, University of Cambridge Digital Library
• Image of the original act from the Parliamentary Archives
• Transcript of the 1774 act, from Transcripts of the 23 Longitude Acts, Royal Observatory Greenwich