Port Louis, Mauritius, August 1782. The French Indian Ocean colony—highly vulnerable to British attack at the height of the American Revolutionary War—is in a state of alert. The governor, Viscomte François de Souillac, has been warned that a flotilla of 11 ships is approaching his island. Fearing that this is the long-awaited invasion fleet, De Souillac orders a sloop-of-war out to reconnoiter. But before the vessel can report, the panic ends. De Souillac is informed that the fleet has altered course and is now steering away from Mauritius. A few days later, when the sloop returns, the governor gets confirmation: the ships were actually East Indiamen, British merchant vessels making for Fort William in India.
All this is remarkable chiefly for the source of De Souillac’s intelligence. The governor had his information not from signals made by ships sailing far offshore, nor from land-based lookouts armed with high-powered telescopes, but from a minor member of the local engineering corps, one Étienne Bottineau. And Bottineau was chiefly renowned in Mauritius (or “Île de France,” to give it its contemporary French name) as a man who won a lot of bets in waterfront taverns thanks to his uncanny ability to foresee the arrival of ships that were anywhere from 350 to 700 miles from the island when he announced their approach.