|Building Needed||Naval Board|
This watch keeps excellent time, enabling sailors to use it to calculate their longitude with some certainty.
While latitude is relatively easy to calculate for mariners, it is far harder to estimate longitude. Dead reckoning can put a ship many leagues out of position, making it incredibly risky to approach a possibly reef-strewn coast. Having a reliable "home" time, it is possible to compare local readings, and so calculate longitude.
In the 18th Century, poor navigation was a dangerous issue. Admiral Sir Cloudesley Shovell (1650-1707) and 1400 others in his Royal Navy squadron died when a fleet went a aground off the Scillies. Dead reckoning misplaced the fleet in a position of safety and, to add to the navigators' problems, no one could place the Scilly Islands on a map with any degree of accuracy either. Clearly, improvements were needed in navigational tools and the British Longitude Act of 1714 offered the immense fortune of £10,000 to anyone who could devise a method for successfully calculating that elementof a position. English clockmaker John Harrison (1693-1776) did eventually produce a chronometer that kept very accurate time, but spent more effort in trying to get the money out of a recalcitrant government committee!