The surviving papers of the Board of Longitude

The complete collection of surviving papers of the Board of Longitude 1714-1828
Cambridge Digital Library,

In 1707 four ships of the Royal Navy under the command of Vice Admiral Cloudesley Shovell ran aground off the Scilly Isles while returning from the Mediterranean.

More than 2,000 sailors died and Shovell’s reputation was ruined, all because no one at the time could properly calculate longitude. The Admiralty determined it would never happen again.

And so the Board of Longitude was born with a mission to find new ways to fix an east-west position at sea, a notoriously harder problem than finding latitude which can be determined from the position of the Sun.

The Board offered some extravagant prizes up to £20,000 - some $5 million today - for anyone who could locate a position with an accuracy of 30 nautical miles (56 km) accuracy.

It gave rise to some frankly crazy ideas. One hare-brained scheme was to position barges across the Atlantic, from which the crew would let off fireworks so sailors knew their position.

But the Board’s experts eventually settled on one basic concept which is still in use today - to contrast the time on the ship with the time at a fixed reference point. So if the time in the home port is 1 pm when the sun in your current location is at its midday zenith, then you now you are 15 degrees of longitude west of the port.

But how to know the time at home? Two different methods competed for many years. In one, astronomers calculated the moon’s position and its future movements, noted the findings in a nautical almanac that showed the moon’s relative position to other celestial bodies at any given longitude and comparing that to its position at home.

The other (ultimately successful) means, was more accurate clocks. Self-taught English clockmaker John Harrison spent 30 years on the problem ebfore his marine chronometer won. The story has been beautifully told by Dava Sobel with her 1997 book Longitude. But Harrison was not awarded the prize. In fact, the Board shamefully never awarded it to anyone.

With the problem solved, the Board was disbanded in 1828. Its history, preserved in the archives of the Royal Greenwich Observatory, has now been digitised and put online for everyone to access; part of a Cambridge University Library project to provide universal access to the greatest discoveries over the past two millennia.

There is a treasure trove of material here from the scientific journals of astronomers as well as maps and logs of voyages of discovery to the quirky, such as Captain William Bligh’s sheepish record of how mutineers stole his Admiralty-issue watch (pictured). Anyone who loves maps and navigation or revels in the fascinating history of the conquest of the sea, will be immersed for hours.

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