Blue plaque for clockmaker John Harrison in Harrow
Inventor of marine chronometer that revolutionised navigation to be commemorated.
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The headline uses mild sensationalism by referring to the 'world's most important clock' and a 'millionaire' inventor.
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A blue plaque will commemorate John Harrison, the self-taught clockmaker whose invention of the marine chronometer revolutionised maritime navigation. Harrison, who died in 1776, solved the centuries-old challenge of determining longitude at sea, enabling sailors to accurately calculate their east-west position.
The ability to accurately determine longitude was a national obsession in the 18th century, driven by the urgent need to prevent maritime disasters. A significant event that highlighted this need was the 1707 wreck of four Royal Navy ships off the Isles of Scilly, which resulted in the loss of at least 1,400 lives, including Admiral Sir Cloudesley Shovell. This tragedy prompted Parliament to offer a £20,000 prize for a reliable naval chronometer.
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Harrison dedicated decades to developing a timepiece accurate enough to maintain Greenwich Mean Time despite the fluctuating conditions of sea voyages. He completed his first marine timekeeper, the H1, in 1735. By 1759, his H4 model met the stringent requirements of the Longitude Act, remaining accurate under challenging sea conditions. Some historians consider the H4 to be the world's most important timepiece and it is now displayed at the Royal Observatory in Greenwich.
Beyond his work on marine chronometers, Harrison's innovations include the bimetallic strip, used in thermostats and fire safety devices, and the caged roller bearing, a key component in modern machinery. His contribution to navigation was famously depicted in the 1996 Only Fools and Horses episode 'Time on Our Hands', where a Harrison timepiece made the Trotter brothers millionaires.
John Harrison died on his 83rd birthday in 1776 and is buried in Hampstead parish churchyard. His former home in Red Lion Square, Holborn, also bears a commemorative plaque.
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Questions this report answers
+What did John Harrison invent?
John Harrison invented a marine chronometer that revolutionised navigation by solving the centuries-old problem of calculating longitude at sea. He also invented the bimetallic strip and the caged roller bearing.
+Why was John Harrison's invention important?
Harrison's marine chronometer made ocean voyages safer and more accurate. It enabled sailors to determine their position more precisely, preventing the loss of ships and lives that had been common due to navigational errors.
+Where can John Harrison's work be seen?
Harrison's H4 marine chronometer, considered by some historians to be the world's most important timepiece, is displayed at the Royal Observatory in Greenwich. His former home in Red Lion Square, Holborn, also has a commemorative plaque.
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