The St. Augustine Lighthouse and Fresnel Lens

    By Kathy Fleming

    The Fresnel lens was a major breakthrough in lighthouse equipment and helped to light Florida's Atlantic coast.

    Augustin-Jean Fresnel (1788-1827) was a French engineer recruited by the French Government as the commissioner of lighthouses in 1819. In 1822, after some experiments, Fresnel developed a multipart lens for lighthouses that made him world-famous. Not only would the Fresnel lens reflect and refract light, it also captured as much as 80 percent of the light from the light source and was visible 20 miles out to sea.

    The great majority of lighthouse lenses then used in the United States came from France, near Paris.  The Fresnel lens at the St. Augustine Lighthouse was nine feet tall. It was hand-blown in Paris specifically for the St. Augustine Lighthouse in 1874.

    In its Feb. 28, 1889 issue, The Saint Augustine Weekly News described the lens: “The lamp was a brass cylinder of 10 gallons capacity. Inside it has a heavy weight which governs the flow of oil to the burner. The burner has five wicks in concentric circles. A chimney leads to the roof. It has a damper which regulates the flame. The globe is a huge case of glass which revolves around the lamp every nine minutes. It makes a flash every three minutes when a big bulls-eye lines up between the lamp and the human eye. The cage weighs two tons. It revolves around a clock work. The machine is in the glass case directly below the lantern.”

    In 1936, the St. Augustine Lighthouse was the last lighthouse in Florida to be electrified.

    Today, only 16 original first-order Fresnel lenses remain inside lighthouse towers and in use in the United States. The St. Augustine Lighthouse and Museum owns and operates this historic optic. It was decommissioned and given to the museum by the United States Coast Guard and the National Park Service through the General Services Administration in July of 2002.