One of the largest improvements in lighthouses came with the development of the Fesnel lens. This lens, made up of multiple prisms which focused and amplified the light beam emitted from the lantern, revolutionized the lighthouse and increased its range and effectiveness for mariners.
The developer of the lens was an obscure French physicist, Augustine-Jean Fresnel (pronounced "Fraynel"), born in 1788. While assigned to civil engineering projects, such as roads and bridges, Fresnel developed an interest in light and began working on a method of focusing it.
Early lighthouses used a combination of a bulls-eye lens and a parabolic reflector to direct the light, an inefficient method that allowed light to escape at the top and sides. Later, refractive lenses were used to improve the light beam by bending it and directing it outward. Fresnel's design combined the best of both of these features into a single lens. Using a bulls-eye in the center, surrounded by concentric rings of prism lenses, the entire assembly sent a bright, concentrated beam of light outward.
Fresnel's lens was readily adopted in Europe, but was late coming to America because of resistance by the Lighthouse Service. Eventually, however, the lens became the standard for lighthouses around the world.