First rotating light in a lighthouse

The first rotating reflector in a lighthouse lantern was installed in Marstrand Lighthouse (formerly part of the 17th-century Carlsten Fortress) on the island of Marstrand in western Sweden in 1781. It was devised by the Swedish engineer Jonas Norberg (aka Johan Nordqvist) of the State Model Museum in Stockholm and comprised three wick lamps, each with two reflectors, placed on a stand that revolved with a clockwork mechanism.

This wasn't Norberg's first foray into lighthouse optics: in 1757, he installed the first flashing light into a lighthouse at Korsö Tower on Sweden's eastern Baltic coast.

The notion of intermittent light emitted by a lighthouse, particularly a regular cycle afforded by a rotating lantern, was groundbreaking as it meant mariners were far less likely to confuse the landmark with lights from other buildings on shore or those on other ships.