In the autumn of 1707, Admiral Sir Cloudesley Shovell was leading a fleet of twenty-one Royal Navy ships back to England after a campaign in the Mediterranean. Foggy skies and fierce Atlantic storms obscured the sun and stars for days, making celestial navigation impossible. Left with no choice, the navigators relied on dead reckoning—a method of estimating position based on previously logged speeds, headings, and ocean currents.
In essence, it was a paper-based inventory system for tracking distance, and it went horribly wrong. Due to accumulated mathematical errors, poor ocean current estimates, and inaccurate logbook entries, every navigator in the fleet miscalculated their true position by tens of miles. A famous legend even claims a local sailor warned the Admiral of the discrepancy, only to be executed for mutiny on the spot.
On the night of October 22, believing they were safely entering the English Channel, the fleet sailed straight into the treacherous Gilstone Reef off the Isles of Scilly. Four ships—HMS Association, HMS Eagle, HMS Romney, and HMS Firebrand—struck the rocks and sank. Over 1,400 sailors perished, including Admiral Shovell himself, who reportedly washed ashore alive only to be murdered by a beachcomber for his emerald ring.
This horrific disaster shocked the British public and directly led to Parliament passing the famous Longitude Act of 1714, offering a massive financial prize for anyone who could invent a reliable way to accurately determine longitude at sea.