Dava Sobel · 1995 · sea

Dava Sobel's 1995 book about the longitude problem. For centuries ships could not tell how far east or west they were, and fleets were lost because of it. Parliament offered a fortune for a solution, the astronomers expected to win it, and a Lincolnshire carpenter named John Harrison spent forty years building clocks that went to sea and kept time.

1. 1
   Barrow-on-Humber

   In a Lincolnshire village a self-taught carpenter builds wooden clocks that lose barely a second a month - and sets out to solve a problem the Astronomer Royal considers his own business rather than a joiner's.

2. 2
   Greenwich

   The Board of Longitude sits in London and the observatory at Greenwich pursues the rival lunar-distance method - and Harrison spends four decades submitting clocks to men with a professional interest in the other answer winning.

3. 3
   Port Royal

   H4 is sent to Jamaica in 1761 to be tested at sea, and arrives having lost five seconds in eighty-one days - an accuracy the Board finds so implausible that it asks for the trial to be done again.

4. 4
   Barbados

   The second trial to Barbados is supervised by the man most likely to lose by the result, and the watch performs better still - and Harrison, in his seventies, has to petition the King before Parliament will pay.