The Fresnel Lens

On September 7, 1873, the lighthouse supply ship “Haze” delivered a new lens to the Pointe aux Barques Lighthouse.  The lens was a sixteen-panel Fresnel lens, named after French physicist Augustin-Jean Fresnel.  The 16 panels were assembled at the top of the 89 foot tower, the lamp was lit, and the lens went into service rotated by a weight system similar to that used in a grandfather clock.

The Pointe aux Barques Fresnel lens is a 3rd order lens, with 1st order being the largest and 6th order being the smallest. The lens is almost 43 inches in diameter, 5½ feet high, and weighs approximately 1,400 pounds.  The upper and lower sections of each panel are called catadioptrics – they use both reflection and refraction to direct the light from the oil lamp into horizontal rays.  The dioptrics – lenses – are located above and below the “Bull’s eye” and accomplish the same purpose using only refraction.  The “bull’s eye” is a simple lens that focuses light out to the horizon.   The Henry-Lepaute Company of Paris manufactured nine Fresnel lenses for Great Lakes lighthouses.  Five of the lenses were stationary; four were rotating.  The four that rotated had four, eight, twelve and sixteen panels, respectively. The Pointe aux Barques lens is the only sixteen panel, 3rd order lens ever installed on the Great Lakes.   The new Fresnel lens, like the simpler lens that had been used before it, continually warned mariners of the dangerous rock ledge stretching two miles into Lake Huron from Pointe aux Barques.  The lens was in service for almost 100 years, finally being removed from the tower in 1969 and replaced by an electric beacon.  Upon decommissioning, it was not feasible to display this artifact at Point aux Barques because no museum or other suitable facility then existed.  Thus, the lens was originally stored in a Coast Guard warehouse in Detroit.  In 1970, the lens was moved to Harbor Beach and displayed in the City’s office.  Soon thereafter, it was moved to the Grice Museum in Harbor Beach where it could be more readily seen by the public.  In 1987, the Lens was moved to Huron City Museums, midway between Port Hope and Port Austin, where it could be viewed as part of a tour of the museums.  On June 1, 2013 the lens was removed from Huron City and moved to Coast Guard Station Harbor Beach.  In early August, lampist Kurt Fosburg began restoration and cleaning of the lens, and on  August 23rd, the lens was returned to its original home at the lighthouse.  Harbor Beach resident and Society member Scott Richardson and Society member Larry Becker assisted Mr. Fosburg with moving and reassembly of the lens.