As mentioned on the Marine Chronometer page, constructing a clock that functions on board a ship is difficult. Pendulum clocks were the most accurate timekeeping devices in the 1600s and early 1700s, but the rocking of a ship made the pendulum's motion unpredictable and the clock inaccurate.
John Harrison of the UK developed a chronometer that used a spring and balance wheel instead of a pendulum. This won him the Longitude Prize (worth about £3,000,000 in modern terms) and made ocean-going travel substantially safer.
Harrison's 1761 clock was actually his fourth model. The first three, using different methods for timekeeping, were less successful and less accurate. The beautiful photo above is of the H1 model, which was not sufficient to win the prize.
Related Instruments: Sand Glass, Marine Chronometer
Usage Dates: Invented in 1761. In use until modern electronic clocks prevailed in the mid to late 20th century.
H1 Harrison Clock
Harrison's first clock (the H1 model). Photo courtesy of user Metadata Deluxe on Flickr.
A schematic diagram of Harrison's fourth clock (the H4 model), which won the Longitude Prize.
H5 Harrison Clock
A photo of Harrison's later clock, the H5 model. Photo courtesy of Wikipedia user Racklever.
Wooden Harrison Clock
A wooden model of Harrison's H3 clock. The design of this pendulum clock was insufficient to keep precise time at sea, but its unique pendulum design helped it keep good time in different temperatures, where the length of the pendulum might change. Taken at the Harvard Museum of Historical Scientific Instruments.
A close-up on the gears of the same wooden Harrison Clock model.
A half-hour video from the Leeds Museum and the BBC entitled The Clock That Changed the World
Wikipedia's pages on John Harrison, Marine Chronometers, and the Longitude Prize.
The Royal Museums at Greenwich have a description of Harrison's Story
Harrison's later work, Clock B, is still being tested, as a more recent article from The Guardian attests.
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