JFH Jewels is a new Irish business owned by my brother John Harrison that is built on and continues the Harrison family tradition in the watch and jewellery industries in both the UK and Ireland. John Harrison senior, a gemmologist and diamond specialist who studied his craft, trained and worked in Hatton Garden and elsewhere in London, had many jewellery shops in Ireland, the most recent were J W Harrisons, Jon Louise and JWH in Limerick City.
This tradition began with our direct ancestor John Harrison who was the subject of Dava Sobel’s 1995 best-selling book, Longitude: The True Story of a Lone Genius Who Solved the Greatest Scientific Problem of His Time, The book was made into a television series entitled Longitude broadcast on Channel 4 in 2000 starring Michael Gambon as John Harrison and Jeremy Irons as horologist Rupert Gould.
Born in Yorkshire in 1693, John a carpenter and clockmaker, invented the first marine chronometer which enabled navigators to determine longitude at sea, a task which some of the most respected scientists of the time, including Isaac Newton, thought an impossible task. This was an important development in navigation and was a device that helped to establish the longitude of a ship at sea which made long distance sea travel safer.
Dava Sobel explains that in order to know longitude at sea, you need to know what time it is aboard a ship and also the time at the home port or another place of known longitude at that very same moment. The two clock times enable the navigator to convert the hour difference into geographical separation. Every day at sea, when the navigator resets his ship’s clock to local noon when the sun reaches its highest point in the sky, and then consults the home port clock, every hour’s discrepancy between them translates into another fifteen degrees of longitude. One degree of longitude equals four minutes of time. Precise knowledge of the hour in two different places at once was unattainable up to the era of pendulum clocks. On the deck of a rolling ship such clocks would slow down, or speed up, or stop running altogether. Changes of temperature while travelling at sea thinned or thickened a clocks lubricating oil and made its metal parts expand or contract. A rise or fall in barometer pressure, variations in the Earth’s gravity from one latitude to another, could also cause a clock to gain or lose time.
John Harrison spent four decades perfecting a watch that earned him compensation from Parliament thanks to the recognition and influence of King George III of England and became a wealthy man for the last few years of his life.
In 1772 Captain James Cook used the K1 chronometer on his second and third voyages to the South Pacific Ocean and praised it’s accuracy. K1 made by Larcum Kendall was an accurate copy of John Harrison’s successful H4 chronometer, but cost a fraction of the price.