How one of the greatest technical challenges of the 18th and 19th centuries was eventually solved.

Passed by the British government 300 years ago this July, the Longitude Act of 1714 sought to solve the problem of realising a ship’s east-west position at sea. Being able to determine longitude was key to dominating the world's oceans, and other countries – including Spain, the Netherlands and France – were offering similar financial rewards. For a maritime nation such as Britain, obtaining this information first was crucial.

The challenge was the talk of London’s 18th century coffee-houses and astronomers, artisans, politicians, seamen and satirists made attempts to scoop the Board of Longitude’s prize. And while John Harrison takes credit for making the all-important discovery, as this display suggests, the real story was far more complex.

While his marine sea-watch played a vital role, the inventions and research of Galileo, Isaac Newton, James Cook and William Bligh also had a profound influence. In fact, it was Nevil Maskelyne’s observations at the Royal Observatory in Greenwich – which demonstrated the complementary nature of astronomical and timekeeper methods – that ultimately lead to the determination of longitude at sea.

The display draws largely on artefacts from the Royal Observatory in Greenwich, which was founded in 1675 specifically 'to find out the so much desired longitude of places for the perfecting of the art of navigation'. Astronomers Royal became leading voices on the Board of Longitude, judging proposals and encouraging promising developments.

National Maritime Museum

Romney Road, Greenwich, London, Greater London, SE10 9NF

020 8312 6608


Opening times

Daily, 10am – 5pm. Closes 6pm during summer holidays. Closed 24 – 26 Dec

Free to all

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