New Presque Isle Light - Fresnel Lens

Fresnel Lens

A third-order Fresnel lens, which stood six feet in height—manufactured by Henry LePaute Cie. of Paris—was used for the lamp. This lens was invented by a Frenchman of the same name, and it quickly became popular in towers across the country. Its strong, efficient lens was able to cast light much farther than previous techniques: open flame, light fueled by whale oil, or small wicks. The Fresnel lens system was a great improvement over previous lenses in lighthouses, but it was not until the 1850s that it was commonly adopted in the United States and on the Great Lakes. The lens allowed only a small amount of light to “escape” – that is, disperse and not shine directly to the water and incoming vessels. Fresnel was able to do this by creating various concentric rings surrounding the lens that would bend the light, ultimately focusing it in one direction. A very intense light could thus be seen by boats on the Lakes several miles away. This advantage would be very valuable for the lake freighters or passenger steamers lost in a storm or dangerous weather that is prone to occur on the Lakes.

It also had advantage over a previous system of lenses – the Lewis system. With this system, designed by a former sea captain named Winslow Lewis, a parabolic reflector directed light emitted from a hollow-tube wick. This wick was intensified by a draft of air that would flow over it, creating the light of six or seven candles. Even with the reflectors, the lens still could not produce nearly enough light as the Fresnel lens system. Furthermore, it was difficult to clean and maintain, resulting in constant repair, adjustment, and other maintenance. Clearly, the Fresnel lens system was the optimum choice for the Lighthouse Service and for the Presque Isle Harbor lighthouse.

The light at Presque Isle was not installed with any sort of flashing system, though the option was left available. Often, boats are able to distinguish between two different lights by a Flashing beacon. Either the beacon itself would rotate, and thus illuminate 360° around the lighthouse, or a blinder with only a small portion unshielded would rotate around the lamp, exposing the bright light for only a few seconds. The rotation was controlled by heavy weights that would slowly sink due to gravity. Every few hours the lightkeeper would “wind up” the rotating beacon or blinder. However, Presque Isle's light was a steady beacon.