You may be aware of John Harrison (1693 - 1776) as the genius horologist who after decades of work was awarded the British Admiralty’s Longitude Prize for his H4 clock. Harrison invented the precision marine chronometer and saved thousands of seaman's lives by enabling ships to navigate much more accurately.





Less well known though was that Harrison also designed and made a few pendulum clocks that he claimed were much more precise than the best available at the time. He was on the record as stating that his pendulum clocks were accurate to a one second per month, compared to a second per week of his competitors.

However, he outraged many reputed clockmakers of the time in claiming that he had designed a pendulum clock that he calculated would be accurate to one second in three months. This claim generated comments like "an incoherence and absurdity that was little short of the symptoms of insanity" and " “ …the ramblings of superannuated dotage.”



Unfortunately, Harrison died before making a pendulum clock with this then (and now) unparalleled level of precision so was unable to prove his critics wrong.



And that's how things stayed until 1975, when British artist and clockmaker Martin Burgess was commissioned to make a sculptural clock for the Gurney banking family of Norwich, England. Burgess took this as an opportunity to investigate Harrison's legacy. He began making two clocks based on Harrison’s principles, using modern materials where appropriate. Burgess completed Clock A in 1987, and it is now on display at The Castle Mall in Norwich.



Burgess never completed Clock B, and its components lay dormant in his workshop for over thirty years.



Then in 2009, a collector bought the uncompleted Clock B and commissioned English clockmakers Charles Frodsham & Co. to complete the work. Harrison's design called for a grasshopper escapement and did not require any lubrication.





The work took years, and when finally completed, after a few adjustments and regulation, the Clock B was found to be extremely stable, and capable of keeping a good rate.



An extremely good rate.

So good in fact that in 2015 Clock B was delivered to the Royal Observatory Greenwich where it underwent independent testing for 100 days after which it was out by just 0.625 of a second. This level of precision was not only completely unimaginable in Harrison's day; Clock B set a modern Guinness World Record for the "most accurate mechanical clock with a pendulum swinging in free air."





More than 250 years after he designed the clock, John Harrison was not only vindicated but has proved to the world that he was truly a horological genius and that H4 was no fluke.



