This year we celebrate the ingenious work of John Harrison (1693 – 1776). Craftsman, inventor, materials technologist and musician.
John Harrison was born in Wakefield West Yorkshire and his systematic analytical prowess led him to provide numerous solutions to chronology. He invented the gridiron pendulum, consisting of alternating brass and iron rods assembled so that the swing of the pendulum would not be influenced by thermal expansion. The grasshopper escapement solved, in an elegant way, the step-by-step release of a clock’s driving power. Being almost entirely free of friction, it required no lubrication. He subsequently went on to invent the bi-metallic strip and the caged roller bearing. Harrison is however perhaps most widely recognised as the man who was never given due credit and reward for solving one of the most intractable and difficult problems of his time, determining Longitude whilst at sea.
In today’s world where clocks are everywhere the problem of recording time seems quite a simple one. In the days of sea fairing, recording time was seen as impossible. When one considers the enormity of the problem of producing a mechanical clock that could maintain accurate time on a lengthy, rough sea voyage with widely varying conditions of temperature, pressure and humidity, it is no wonder that many leading scientists including Newton and Huygens doubted that such a clock could ever be built. It was for this reason that so many academics of the time looked for solutions to the problem in astronomical observation.
The measurement of longitude was a problem that came into sharp focus as people began making transoceanic voyages. The Board of Longitude was set up to invite and judge the competitors.
The main longitude prizes were:
* 10,000 for a method that could determine longitude within 60 nautical miles
* 15,000 for a method that could determine longitude within 40 nautical miles
* 20,000 for a method that could determine longitude within 30 nautical miles
It was H4(pictured above)measuring some five and a quarter inches diameter that was to be his masterpiece — an instrument of beauty. H4 took six years to construct and Harrison, by then 68 years old, sent it on its transatlantic trial in the care of his son William in 1761. When HMS Deptford reached Jamaica the watch was 5 seconds slow, corresponding to an error in longitude of 1.25 minutes or approximately one nautical mile. It was this design that was removed from him by the Board of longitude for tests that went on for years. It was during the third year that he resolved to embark upon his fifth design. Harrison felt “extremely ill used by the gentlemen who I might have expected better treatment from” and so secured an audience with the then King George III who sympathised and expressed his anger to the Board.
11 years later King George tested H5 himself at the palace and after ten weeks of daily observations between May and July in 1772, found it to be accurate to within one third of one second per day. King George then advised Harrison to petition Parliament for the full prize after threatening to appear in person to dress them down. In 1773 when he was 80 years old, Harrison received a monetary award to the tune of £8,750 from Parliament for his achievements, however he never received the official award which was never awarded to anyone. John Harrison was to survive for just three more years.
In the final years of his life, John Harrison wrote about his research into musical tuning and manufacturing methods for bells. His tuning system, (a meantone system derived from pi) is described in his book “Concerning Such Mechanism. This system challenges the traditional view that harmonics occur at integer frequency ratios and in consequence all music using this tuning produces low frequency beating. In 2002 Harrison’s last manuscript, a true and (“short, but” – crossed out) full Account of the Foundation of Musick, or, as principally therein, of the Existence of the Natural Notes of Melody, was rediscovered in the US Library of Congress. His theories on the mathematics of bell manufacturing, using “Radical Numbers”, are to this day not clearly understood.
Dava Sobel’s 1996 bestseller Longitude (ISBN 0-14-025879-5) recounts Harrison’s story. A film adaptation of Longitude was released by Granada Productions and A&E in 2000 starring Michael Gambon as Harrison and Jeremy Irons as Rupert Gould.
H3 is pictured above
H1,2,3 and 4 are on display at the Greeenwich Maritime Museum London.
