India, Sept. 6 -- In 1714, the British Parliament passed the Longitude Act. It offered £20,000, a fortune at the time, to anyone who could determine longitude at sea to within half a degree. The astronomers assumed the answer lay in the stars. John Harrison, a carpenter's son from Yorkshire who never saw the inside of a university, decided the answer was a clock. His H4 timekeeper lost about five seconds on a voyage to Jamaica in 1761. The Board of Longitude, dominated by astronomers, paid him in grudging instalments and kept revising the tests. He received a final £8,750 in 1773, at the age of eighty, and only after George III took a personal interest. (The Board never formally conceded that he had won.)

The purse mattered les...