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The fresnel lens atop the Point Wilson Lighthouse in Port Townsend, Washington (state).

'In 1822 a French Physicist named Augustin Fresnel invented a lens that would make his name commonplace along the seacoasts of Europe and North America. It looked like a giant glass beehive, with a light at the center. The lens could be as tall as twelve feet, with concentric rings of glass prisms above and below to bend the light into a narrow beam.'

'By creating a lens that completely surrounded the light source with concentric rings of glass prisms, Fresnel designed a way to take a dispersed light source heading in multiple directions and redirect it through collected prisms by bending and redirecting the light beams. This 'bending' of the beams through a Fresnel lens pointed all of the light source in the same direction to create a very intense, focused and unified light beam that could be seen more than 20 miles out to sea using just a 1,000-watt light bulb!'

'These lenses were also made to spin on a pedestal, placed in the light tower, so that the different spacing placement of the multiple bull's-eyes on each lens would result in different intervals between their flashes - when the center of the bull's-eye on the lens lined up with the ship out at sea viewing the light. These flashes happening in different intervals, which were unique to each lighthouse, helping those at sea easily identify which lighthouse they were viewing and where they were along a coastline.'

Posted by Don Wiley on April 25th, 2007
Archived under: Washington (state) Coast/Puget Sound