Clockmaker vindicated 250 years after he was derided for accuracy claims


Clock B, made to John Harrison's design, was as accurate as he claimed it would be.
NATIONAL MARITIME MUSEUM

British clockmaker John Harrison, who was derided for his claims to having designed the most accurate pendulum timepiece in history, has been vindicated 250 years later.

Harrison's marine chronometers revolutionised navigation in the 18th century, but critics said his claim to make a clock accurate to within a second over a 100-day period was simply impossible.

But, as Robin McKie reports in the The Observer newspaper, the last laugh lies with Harrison.

One of Guinness World Records’ more unusual awards was presented at the National Maritime Museum yesterday. After a 100-day trial, the timepiece known as Clock B – which had been sealed in a clear plastic box to prevent tampering – was officially declared, by Guinness, to be the world’s “most accurate mechanical clock with a pendulum swinging in free air”.

The clock was built to the clockmaker’s exact specifications had run for 100 days during official tests and had lost only five-eighths of a second in that period.

“It is a quite extraordinary achievement and a complete vindication of Harrison, who suffered ridicule over his claim to be able to achieve such accuracy,” said Rory McEvoy, curator of horology at the Royal Museums Greenwich. “This is a wonderful device.”

Harrison was a self-educated carpenter as well as clockmaker and was the subject of the fascinating book Longitude by Dava Sobel. You can also see a review of the Cambridge Digital Library collection of surviving papers of the Board of Longitude 1714-1828 here.

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Bill Condie is publisher of Cosmos.
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