The ultimate champion of longitude was an unlikely candidate.  John Harrison was a carpenter’s son with no formal education, a self-taught craftsman who began building clocks as a youngster.  He worked for six years on his first attempt to win the prize.  Now called H1, the three-foot-high clock, with opposing interconnected vertical balance springs in the place of a pendulum, took a test run on a round-trip journey to Lisbon.  Harrison was so sick during most of the five-week voyage that he never went to sea again.  H1, however, fared better-accurate probably to within ten seconds a day.  That was not enough to win Harrison the longitude prize, which required a daily accuracy of 2.8 seconds or less.  But it did earn him a small stipend from the Board of Longitude and provided the encouragement he needed to try again.

            Harrison had been working on his second clock for more than two years when he discovered a fatal flaw: an unexpected violent jolt, such as might occur on a ship, threw it slightly out of whack.  Without a backward glance, he put aside H2 and began building a third clock.

            While working on H3, Harrison wondered if he could miniaturize the temperature-compensating features of his seagoing clocks into a pocket watch for his personal use.  He designed the watch on paper, carefully specifying materials and dimensions, then commissioned John Jefferys, a London watchmaker, to build it for him.

            The performance of the new watch astounded even Harrison, outperforming anything he had envisioned so far.  “He suddenly realized he’d been following the wrong path all those years,” states Betts.  “He now knew he should have been concentrating on a watch-type timepiece, not a large clock.” Throwing away 19 years of labor on H3, Harrison one more started over.  The result was H4.  Five inches in diameter and three pounds in weight, it represented a revolutionary departure from his earlier attempts.

            During a 6½-week voyage Harrison’s son made from Britain to Jamaica in 1761-62, H4 lost only five seconds.  It was an astonishing feat, but a reluctant Board of Longitude refused to award Harrison the prize.  “They were entirely attuned to astronomical solutions,” explains Betts.  “They simply couldn’t believe that a mechanical timekeeper that looked like a large pocket watch, albeit a beautiful one, could do what it had done, in spite of what they had witnessed.”

            “Maybe this is merely a fluke,” argued members of the longitude board.  Harrison and the board bickered incessantly over procedures for testing and producing the watch.  At last, after a second test voyage, the board relinquished one-half of the prize money, or  £10,000.

            Exasperated, in 1772 Harrison’s son pleaded for an audience with King George III.  After the king heard his tale, he pounded his fist on the table and shouted, “By God, Harrison, I shall see you righted.” It had taken 45 years of painstaking effort and persistence, but John Harrison, by then 80 years old, finally received another £10,000, plus expenses-and his place in horological history.

            Other clockmakers followed his lead, making further refinements on H4, and by the 19^th century, chronomenters, as they came to be called, were standard equipment on all oceangoing vessels.  Navigation was now accurate to within a few miles-all thanks to the self-taught son of a country carpenter, who solved a technological problem that had baffled sailors and scientists for centuries.  Claims Sir George White, “H4 was the technological triumph that paved the way for the British Empire.”

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