The Quest for Longitude

Author: W.J.H. Andrewes

437 pages, 2nd edition.

With the increase in exploration, colonization, and trade during the sixteenth and seventeenth centuries that was stimulated by the discoveries of the wealth of the New World, the problems of ocean navigation, in particular finding longitude at sea, became of growing concern to the major seafaring nations of Europe.

When a ship was swept off course by winds, tides, or currents, its latitude could be determined with reasonable accuracy, but there was no method for finding its longitude. To compound the problems of navigation, knowledge of the locations of land and the shapes of coastlines remained sparse and inaccurate until a reliable method of determining longitude on land was developed.
For more than two centuries the cost - in lives, as well as money - increased, many ingenious, but unsuccessful attempts were made to solve the problem of finding longitude at sea.

The foundation of observatories to improve knowledge of astronomy and the establishment of large reward to encourage participation of individuals from all walks of life eventually produced results.

Two of the earliest methods proposed - one requiring knowledge of the Moon's motion and measurement of its angular distance from a star, the other dependent on an accurate timekeeper - proved to be the most practicable solutions. But by 1760, when John Harrison finally perfected a timekeeper of sufficient accuracy, improvements in the lunar-distance method threatened to deny him the British government's enormous prize of £20,000.!!