The invention that fixed lighthouses

It wasn’t the light. It was the lens.

The most important part of a lighthouse might be one of the beautiful tools hidden inside of it: the Fresnel lens, a breakthrough that changed seafaring and saved lives.

As the above video shows, these lenses satisfied a need for lighthouses that could shine farther and through dense layers of fog. The Fresnel lens, invented by Augustin-Jean Fresnel, helped do that by capturing all the light coming from a lamp, then magnifying and steering it in one direction. Suddenly, lighthouses became more useful and shipwrecks diminished.

Fresnel lenses are still in operation today. According to the US Lighthouse Society, more than 75 Fresnel lenses are in use in American lighthouses, and businesses such as Dan Spinella’s Artworks Florida craft replicas that capture the beauty — and functionality — of the 19th-century breakthrough.

Watch the video above to learn how these lenses work and how they saved lives.

Further reading:

• The United States Lighthouse Society’s history section is a great place to dig into the basics of lighthouse technology.
• Artworks Florida’s Dan Spinella offers a showcase of his Fresnel reproductions and useful videos about his process.
• Barnegat Light Museum curator Reilly Sharp’s article about the Barnegat Lighthouse captures the stakes behind the shift from primitive Lewis lamps to the Fresnel breakthrough.