The lantern room was designed to accommodate a hyper-radial optic, the largest type of Fresnel lens available. Made up of six bullseye panels, and manufactured by F. Barbier, the optic was displayed at the Exposition Universelle of 1889 a world's fair held in Paris before being installed in the tower, the only hyper-radial lens to be used in a French lighthouse. To enable the optic to turn freely it was mounted upon a circular bath of mercury, known as a mercury float, providing an almost frictionless bearing. The rotation produced a white flash every 20 seconds, with a range of 31 miles. Originally lit with mineral oil and wick burners, the light source was converted to kerosene in 1905. In 1926, the lighthouse was electrified using diesel generators.