8.7

Precise Time on the High Seas

The “Longitude Act” was enacted in England on 8th July 1714. The one who could provide a method for finding geographic longitude with a deviation of, at most, one half of a degree would receive the prize of 20,000 pounds. The method was to be tested on a six-week sea voyage from England to the Caribbean. This meant that a clock would have to be accurate to within three seconds per day.

John Harrison (1693-1776) accomplished what others could only dream of. As from 1735, he developed several timekeepers, with each new one meeting the requirements of the “Longitude Act” more precisely. The drawings for his sea watch were published in 1767.

Harrison’s timekeepers were good. However, they were very elaborate and accordingly costly to make. John Arnold (1736-1799) developed a lower priced design which he patented in 1782. Arnold’s “chronometers” became the prototypes for the marine chronometers of the next 150 years.