John Harrison

Harrison was a carpenter by trade and taught himself clockmaking. The Science Museum dates his earliest clock to 1713, made almost entirely of wood, and wooden clocks of 1713 and 1715 survive.^{1, 2, 4, 7}

He developed the gridiron pendulum, which kept its length as the temperature changed, and the grasshopper escapement.^2, 5

Royal Museums Greenwich says his precision longcase clocks of the mid-1720s kept time to about one second a month.¹

Seeking the reward of the Longitude Act, he went to London, where Edmond Halley sent him to the clockmaker George Graham.^1, 2

He built H1 at Barrow upon Humber, probably with his brother James, and brought it to London in 1735. On a voyage to Lisbon in 1736 it let him correct the ship’s reckoning, and in 1737 the Commissioners agreed £500 for an improved clock.^1, 8

H2 was never tried at sea, because of a flaw in its balances. H3 took him from 1740 for about two decades; its lasting results were the bimetallic strip and the caged roller bearing.^1, 2

His watch H4 was completed in 1759, building on ideas tried earlier in a watch the London maker John Jefferys made to his design.^1, 9

His son William carried H4 to Jamaica in 1761–62 and to Barbados in 1764. Under the Act of 1765 the Board awarded Harrison £10,000 but required him to disclose his design and show it could be copied; he felt the rules had been changed against him.^1, 2

Wikipedia’s biography records that he wrote he had been extremely ill used.²

King George III tested Harrison’s fifth timekeeper, H5, himself. Parliament paid Harrison £8,750 in 1773; with earlier sums he received about £23,065, but never the official prize.^2, 5, 6

According to Wikipedia’s biography, in 1775 he published a description of his mechanism and of a land clock he said would keep time to a second in a hundred days, a claim ridiculed at the time; he was buried at St John-at-Hampstead.²

In the 1920s Lieutenant Commander Rupert Gould found Harrison’s timekeepers at the Royal Observatory in poor condition and restored them between 1923 and 1939.^2, 10

Wikipedia’s biography says a well-known story, that he was given a watch as a sick child, is probably untrue.²