Longitude is the dramatic human story of an epic scientific quest. The "longitude problem" was the thorniest dilemma of the eighteenth century. Lacking the ability to measure longitude, sailors throughout the great ages of exploration had been literally lost at sea. At the heart of Dava Sobel's fascinating brief history of astronomy, navigation and horology stands the figure of John Harrison, self-taught Yorkshire clockmaker, and his forty-year obsession with building the perfect timekeeper. Battling against the establishment, Harrison stood alone in pursuit of his solution and the £20,000 reward offered by Parliament.