At six feet tall, this first order Fresnel Lens is the largest Fresnel Lens ever made. Using a clockwork mechanism it provided a double flash every six seconds. That mechanism which turned the lens was lubricated by liquid mercury. Since mercury is now considered a hazardous waste, that mechanism will not be reactivated.
Lenses such as these were used in lighthouses all along the California coast to warn ships of the unsuspecting rocky shoreline. Roughly 90 miles north of San Francisco, this stretch of the Mendocino coast is home to one of the tallest lighthouse towers in the west. Dramatically perched on a narrow peninsula, the Point Arena Lighthouse tower is 115 feet tall. Erected in 1870, destroyed by the 1906 earthquake and rebuilt the following year, it was the first lighthouse to be made of steel and concrete.
The original Fresnel Lens was removed in 2008 and now resides in a museum at the base of the lighthouse.
Looking down from atop the Point Arena lighthouse, look in the upper right hand corner of this photo. That small white looking wave is actually water breaking over a tall rock formation called Arena Rock. Arena Rock is a mile long and a mere six feet under water. This point is difficult to navigate due to its currents, reefs and below the surface rocks. Thus a reason for lighthouses along this coast.
View of the copper roof looking up inside the lighthouse.
The Point Arena tower is the only Pacific west coast lighthouse of significant height you can climb all the way to the top. Narrow, spiral, see-through metal...did I mention spiral and narrow...steps lead you to the top. Once there the views are unrivaled. Plus for extra views, you can walk outside around the edge. The railing keeps you from falling. The wind buffets you against the walls.
See the whale bones in the museum's yard?
More spectacular downward views.
The current lens.