Title:
Fresnel Lighthouse Lens from Tree Point Light Station, 1904-1963
Description:
This fourth-order Fresnel lens came from the Tree Point Light Station, which was located at the entrance to Revillagigedo Channel, about 40 miles southwest of Ketchikan. The U.S. Lighthouse Service opened the station in 1904. The lens, manufactured in France, uses both refraction and reflection to concentrate light into a horizontal beam. It was originally illuminated by a kerosene vapor lamp.
A clockwork mechanism, activated by weights suspended through the center of the lighthouse, made the lens rotate once each minute. Every six seconds, one of the lens's ten bulls-eyes aligned with the viewer's eye, creating a flash. The light and rotating mechanism were electrified in 1939. In 1963, the lens was replaced with a rotating beacon. The station was manned by the Coast Guard until 1970 when automation made the personnel unnecessary.
A clockwork mechanism, activated by weights suspended through the center of the lighthouse, made the lens rotate once each minute. Every six seconds, one of the lens's ten bulls-eyes aligned with the viewer's eye, creating a flash. The light and rotating mechanism were electrified in 1939. In 1963, the lens was replaced with a rotating beacon. The station was manned by the Coast Guard until 1970 when automation made the personnel unnecessary.
Collection:
Ketchikan Museums: Tongass Historical Society Collection, THS 97.1.1.1
Click to Enlarge
Fresnel lighthouse lens on display
Postcard of fresnel lighthouse lens
Fresnel lighthouse lens on display
Postcard of fresnel lighthouse lens