LONGITUDE. -- An Act for Providing a Publick Reward for such Person or Persons as shall Discover the Longitude at Sea. London: John Baskett, and the the assigns of Thomas Newcomb and Henry Hills, deceased, 1714.
2 (300 x 195mm). 3 leaves (verso of final leaf blank). General title (verso blank), 3pp. text with drophead title. Stitched, uncut.
Longitude: 'Distance east or west on the earth's surface, measured by the angle which the meridian of a particular place makes with a standard meridian, as that of Greenwich. It is reckoned to 180 east or west, and is expressed either in degrees, etc. or in time (15 being equivalent to 1 hour)' (OED). As the horizons of trade and empire expanded, long-distance navigation (which depended on accurate measurements of longitude) became increasingly important.
An excellent unsophisticated copy of the act which led to the creation of the 'Commissioners for the Discovery of the Longitude at Sea'. They were empowered to award up to 2000 for any theoretical scheme that proved worthy of further investigation. Then, depending on the accuracy of the device or method, they were instructed to award between 10,000 and 20,000 to the maker or makers of the successful device. To qualify for the highest level of prize-money the device had to be accurate to within 30 miles after a voyage 'from Great Britain to any such Port in the West-Indies, as those Commissioners.. shall choose'.
The large prize remained unpaid until 1773 when, after a petition to the House of Commons, the Board of Longitude was forced to award the final part of the prize to John Harrison (1693-1776). Harrison's successful device (a large watch) had its roots in his manuscript proposals of June 1730. In conjunction with his brother he built a cumbersome marine clock which in 1737 proved accurate enough to qualify them for a grant of 500 towards further experimentation. Harrison built two more machines: the second proved unsatisfactory and was never tested at sea, the third was tested in 1757, but was still bulky. 'Next Harrison conceived of a radically different timekeeper in the form of a large watch - although. of course, with an entirely different escapement. As accurate as the third machine and far more convenient in size, it alone was tested on a voyage to Jamaica in 1761. On arrival, more than nine weeks later, it was only five seconds slow, about 1,25 minutes of arc, well within the 30 minutes of arc or longitude required.' (PMM p.130). Harrison received 10,000 (half of the prize offered) after a second trial in 1764, but encountered numerous obstacles before the balance was paid in 1773.