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December 11, 2012

Museum, island group want to return lighthouse lens to Cape Ann

Museum, island group want to return lighthouse lens to Cape Ann

A mammoth lighthouse lens, which served as a beacon for mariners for more than 120 years, is now the focus of an effort to bring this piece of history back to Cape Ann.

The Cape Ann Museum and the Thacher Island Association have teamed up to return a Fresnel lens, which is 10 feet tall and 6 feet in diameter, and oversee its restoration and house it permanently at the museum.

The one-ton lens was made in Paris in 1860 and is comprised of more than 1,000 glass prisms set in a bronze frame. The lens was once housed in Thacher Island’s South Tower and later called Cape Ann Light. The 50-acre Thacher Island is home to twin lighthouses, of which there are only a few remaining in the country. The lighthouses themselves pre-date the Revolutionary War, having been erected in 1771.

The light was fueled first by whale oil, then by lard oil, and eventually kerosene. In 1860, work began to rebuild the towers to accommodate and support the newest in lighting technology with the installment of the first-order Fresnel lens.

“During the 1850s most of America’s lighthouses received Fresnel lenses that improved their efficiency tremendously,” according to the Thacher Island Association’s website. “It was decided that new, taller towers were needed ... Twin towers, 124 feet high, were built. The twin lighthouses were fitted with enormous first-order Fresnel lenses, which cost $10,000 each. The new towers were first illuminated on October 1, 1861.”

Invented in the early 1820s by French physicist Augustine-Jean Fresnel, a Fresnel lens could cast a much greater beam of light than previous lenses. “On Thacher Island, this meant the light could be seen 22 miles at sea, triple the distance of earlier lights,” according to a museum press release.

The lens was electrified in 1932 and ultimately removed by the Coast Guard in 1980, after which it was on display at the U.S. Coast Guard Academy Museum in New London, Conn. A few years ago it was placed in storage in Maryland and an offer was made to return it to its original home.

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