In the 1820s, a new kind of lens saved ships

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The oldest operating lighthouse in France (construction began in the 16th Century, but beacons had existed there hundreds of years prior) and the world’s first to be built in the open sea, this imposing sentinel of white stone is a Renaissance masterpiece. Whale oil was replaced in the early 18th Century by coal, which proved a difficult lighting system to maintain as keepers had to routinely haul fuel to the top of the lighthouse and stoke the fire day and night. By the 1860s, thousands of lighthouses had been fitted with Fresnel lenses, from small harbour lanterns to great sea lights.

Source: www.bbc.com