19th, Augustin-Jean, california, century, french, Fresnel, lens, lighthouse, pigeon, point
This past November, we were extremely lucky to be at Pigeon Point Lighthouse Hostel on the exact day they took the lens down from the top of the lighthouse for the first time since it was installed in 1872, a hundred and forty years ago.
The Pigeon Point lens is a traditional Fresnel lens, designed in 1823 by French physicist Augustin-Jean Fresnel for use in lighthouses, and characterized by many thin layers of glass which form a prism, allowing the lens to capture more oblique light from a light source and make lighthouses more visible over much greater distances.
It consists of 1008 separate lenses and prisms, and weighs over 8000 pounds.
You can see the lens stored at ground level in the Fog Signal House at the hostel as they complete repairs on the lighthouse. Read history of the lighthouse here.