The Cape Ann Museum is pleased to offer a tour of the new Fresnel Lens Gallery with Thacher Island Association President Paul St. Germain on Saturday, September 6.
The First Order Fresnel lens on display at the Museum is one of the original lamps from the twin lighthouses on Rockport’s Thatcher Island. The lens can now be seen in all its glory in a stunning new gallery, featuring audio-visual components about Thacher Island and the lighthouses that were constructed there, as well as related art and artifacts.
The massive Fresnel lens was made in Paris and installed in the south lighthouse tower on Thacher Island off Rockport in 1861. It takes its name from the French engineer Augustin Fresnel who invented the design in 1820. At nine feet, four inches in height and six feet, five inches in diameter, it is a “first order” lens meaning that it was the largest lens of its type available at the time. Its 286 prisms, precisely arranged in concentric circles, worked in concert to bend light emanating from inside the lens, focusing it into a single beam that could be seen 20 miles at sea. In addition to its powerful light, Fresnel designed his lenses to produce an array of different light patterns (called characteristics) allowing mariners to more easily distinguish one lighthouse from another.
The Thacher Island Lighthouse Towers are two of the oldest and most notable in North America. This particular lens sat atop the island’s south tower for nearly 120 years until it was decommissioned in the 1980s and removed to the U.S. Coast Guard Academy Museum in New London, Connecticut. Through the combined efforts of the Thacher Island Association, Cape Ann Museum and many generous supporters, the lens was returned to Cape Ann in 2013.
To make a reservation or for more information, call (978)283-0455 x16 or email info@capeannmuseum.org.