The Longitude Act, 1714

In 1707, Admiral Sir Clowdisley Shovel, with twenty-one ships of the Royal Navy, was returning from Gibraltar to England. On 22 October, having had observations for lati-

tude the previous day—here is one of the L's—and satisfied by soundings—here is the lead, another L—that they were at the mouth of the English Channel and clear of all danger, the fleet ran to the eastward in thick weather. At 7:30 that evening, five ships struck the rocks of the Gilstone Ledges in the Scilly Isles. This disaster—four ships were lost with nearly two thousand men—was a profound shock to the British public. And there had been several other maritime disasters recently, though none of the same magnitude.

In fact, the Shovel disaster was caused as much by bad charts as by bad navigation. Even if there had been a method of finding longitude, the shipwrecks would probably still have occurred. Nevertheless, the disaster's very magnitude made such an impression on the British public that they became more than ever receptive to any measure which might make navigation safer—and in the 1710s, "discovering the longitude" seemed to hold the key.

In 1714, a book called A New Method of Discovering the Longitude both at Sea and Land was published. In it the mathematicians William Whiston and Humphrey Ditton made a proposal that vessels should be moored in known positions at intervals along the trade routes, each fitted with a mortar which would, every midnight by Peak of Tenerife time, fire a projectile vertically which would burst at precisely 6,440 feet. Though the subject of great mirth among members of Swift and Pope's Scriblerus Club, this proposal was nevertheless taken seriously by some people and Whiston and Ditton presented a petition to Parliament asking for a reward. This was followed a month later by another petition, this time by sea captains and merchants, asking Parliament to give serious attention to the longitude problem.

Taking only a month to pass through all its parliamentary stages, "An Act for Providing a Publick Reward for such Persons or Persons as shall Discover the Longitude at Sea" was given the Royal Assent by Queen Anne on 20 July 1714, only twelve days before her death. Rewards of unprecedented magnitude were offered: £10,000 to the

discoverer of a method which determined the longitude to 60 geographical miles (96 kilometers), £15,000 if accurate to 40 miles (64 kilometers), £20,000 if accurate to 30 miles (48 kilometers). The method had to be proved to be "practicable and useful at sea" on a voyage to the West Indies. Commissioners—later to be called the Board of Longitude-were appointed to administer these provisions. The Astronomer Royal was ex officio a member of the board. The provisions were to apply to all who qualified, regardless of nationality.

Twenty thousand pounds of the 1720s is probably equivalent to a million pounds or more today—a prize indeed, which was to stimulate many advances in astronomy, navigation, mathematics, and horology over the next hundred years, just as Parliament hoped. The immediate effect was the publication of a welter of pamphlets by hopeful inventors, none of whom was successful and many of whom were cranks. Indeed, "finding the longitude," coupled with "squaring the circle" (for which the board received many suggestions quite unconnected with longitude), passed into the English language as expressing something which, if not downright impossible, was at least extremely difficult to achieve.