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  • Lynda Paterson

The marine chronometer - the most perfect machine


"The marine chronometer must rank as one of the most perfect machines ever devised."

John Cronin - The Marine Chronometer Its History and Development

Maritime navigation, out of sight of land, was a treacherous undertaking before the invention of the chronometer in the middle of the 18th century.


The problem was an inability to accurately measure longitude, the distance of a location east or west of the Greenwich meridian, while at sea. Early navigators relied on measuring latitude, the distance north or south of the equator, which could be determined by observing the altitude of the sun and/or the location of other celestial objects. The danger and increased risk of this early navigation is evident in the countless records of shipwreck and lives lost at sea in world maritime history.


Dutch scientist, Gemma Frisius, first proposed the use of super accurate clock to determine longitude in 1530 but the search for a solution didn’t begin in earnest until 1714. The British government, motivated by a significant number of maritime disasters, established the Board of Longitude in that year. They founded the Longitude Prize to be awarded to whoever discovered a practical and reliable method for determining longitude at sea. The prize sparked bitter rivalry between advocates for a mechanical maritime navigation tool and supporters of the lunar method of navigation.


The first successful sea clock, the H1, was trialed in 1736 by the British Admiralty on a short voyage from Spithead to Lisbon. The clock maker was Englishman John Harrison who persisted in his bid to win the Longitude Prize, continually improving his sea clock design for the next 66 years. His last design, known as H5, was completed in 1772. However, it was a duplicate of Harrison’s H4 model, known as K1, made in 1769 by Larcum Kendall that tipped the scales in favour of the chronometer.


K1 was entrusted to Captain James Cook on his second voyage to the South Seas in 1772. Cook had navigated his first voyage (1768-1771) using the lunar method. Therefore on his return, to England, in 1775 Cook was in an incontestable position to objectively compare the two methods of navigation and he was a convert to the chronometer. In his log of the voyage, Cook wrote ‘our trusty friend the watch … our never failing guide’, high praise indeed from one of the age’s greatest navigators.


The chronometer continued to be developed by European clock makers. The clock Captain William Bligh purchased in 1791 for his second voyage to the South Seas was made by another Englishman, Thomas Earnshaw. Earnshaw did more than any other of the early makers to bring English chronometers to full development and his design soon came to dominate.


It is a tribute to these early craftsmen that, despite two centuries of continuous experimentation, no significant improvements were made to their chronometer design until the use of modern electronics. It has been estimated that in 200 years of English and American production about 100,000 chronometers were made. Marine history enthusiasts and clock collectors regard these early marine chronometers as prized possessions. They will always be rare and precious objects.

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