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National Aids to Navigation Museum

Museum The National Aids to Navigation Museum is also located in Canfield Hall and is home to one of the world's finest displays of Fresnel Lenses.  The lenses are the 1822 invention of French physicist Augustine Fresnel who invented the lens that would make his name commonplace along the seacoasts of Europe and North America.  Most lenses were handmade and shipped unassembled from France.  Others were made in England.  Early lens designs resembled a giant glass beehive, with a light at the center.
 

Museum
The lens could be as tall as 12 feet high with concentric rings of glass prism above and below a center drum section to bend the light into a narrow beam.  Later designs incorporated a bull's eye design into the center of the lens shaped like a magnifying glass, so the concentrated beam was even more powerful. Tests showed that while an open flame lost 97% of its light, and a flame with reflectors behind it lost 83% of its light, the Fresnel lens was able to capture all 17% of its light.  Because of its amazing efficiency, a Fresnel lens could easily throw it light 20 or more miles to the Horizon.

 

Last Modified 9/9/2008