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Scilly's human history really started in 4000 BC, during the Stone Age, when the first nomadic hunter-gatherers visited the Islands. Prehistoric graves are left from these peoples , most are simply mounds of earth. But the Scilly's are probably best known indirectly for the creation of accurate mobile clocks.
1707 was a tragic year for the Islands as it was in this year that a large proportion of the British Navy fleet were wrecked off Scilly. As the fleet was returning home victorious, the fleets’ longitude was misjudged and in bad visibility, the flagship Association along with others of the fleet were wrecked on the western approaches. This incident spurred the British government to establish The Longitude Act of 1714.
1714–1775 AD – The Longitude Problem
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The lack of an accurate, reliable, and practical method of determining longitude had serious consequences for sailors. Maritime disasters were numerous, and a major tragedy occurred in 1707. In a shipwreck of four British warships off the Scilly Islands, near southwest England, two thousand men perished. The Scilly Island incident spurred the British government to establish The Longitude Act of 1714.
Newton's Doubts
The British government consulted their leading scientists: Sir Isaac Newton, Edmund Halley, and Robert Hooke. Newton didn't think any of the current methods for calculating longitude could work! Telescopes would be too long and a ship's motion too rough to accurately use Jupiter's satellites. Research of the moon was not advanced enough for the lunar-distance method. An accurate timekeeper would be the ideal answer, but such factors as the ship's motion, changing temperature, and variations between wet and dry environments appeared overwhelming for the development of a reliable, seaworthy clock.Board of Longitude
However, Parliament was desperate for a solution. They established an official Board of Longitude and offered a prize of 20,000 pounds (equivalent today to millions of dollars) to whomever could come up with a method for determining longitude within a distance of 30 nautical miles during a voyage from England to the West Indies. A marine timekeeper would have to be accurate to within a total of two minutes for the outward journey. Given the state of clock-making technology at this time, this seemed a nearly impossible standard to achieve.John Harrison (1693-1776) thought he could do it and spent nearly 50 years proving himself right. His exceptionally accurate timepiece is also called a chronometer, from the Greek words for time (chrono) and measure (metron).
Hadley's Quadrant
John Hadley invented a new quadrant in 1731. Hadley's quadrant, also called an octant, had an arc which measured one-eight of a circle and two mirrors which allowed the Sun (or another star) and the sea horizon to be seen simultaneously. This allowed for much more accurate measurements at sea and easier observations of the lunar-distance method. The quadrant was further advanced by John Bird who invented the sextant in 1757.Captain Cook's Second Voyage
During his second voyage to the Pacific from 1772-1775, Captain James Cook carried with him a copy of John Harrison's chronometer which he was able to use to figure his longitude. Cook greatly appreciated the reliability of the watch and its simplicity over the lunar-distance method.