Fog cannon at Brewster Light is oldest artifact in the Coast Guard

METRO - 16lighthouse - Little Brewster Island, MA -- 6/15/2012 Located on Little Brewster Island within the Boston Harbor, Boston Light was the first lighthouse established in what was to become the United States. The wooden parts of the lighthouse were burned by American troops during the revolutionary war to prevent the British from using it. A woman walks along the shore of Wollaston Beach in Quincy on Thursday afternoon. Ten beaches on the South Shore have been closed because of bacteria contamination, including Wollaston Beach. (Tamir Kalifa for The Boston Globe)
Boston Light
Tamir Kalifa for The Boston Globe

LITTLE BREWSTER ISLAND – Last summer, a Coast Guard officer was taking a tour of Boston Light, when a particular artifact caught his eye.

There are a lot of old things at Boston Light – home of the nation’s first and oldest light station, built in 1716 a mile off the coast of Hull – but one artifact seemed particularly old in a particular way.

The item in question was a 293-year-old fog cannon, which for the first 150 years of its life was fired every 30 minutes during periods when poor visibility limited the reach of the light. The officer, Captain James McPherson, wondered if it might just be the oldest artifact in the entire Coast Guard.

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Thus began a historical mystery hunt, as Coast Guard historians and archivists worked to answer that question and others, such as making sure the long black cannon on display was the original, and that it had always been owned by one of the entities that would form into the Coast Guard.

After a few months of work, it was determined that McPherson’s hunch was right. The signal cannon was purchased by the Lighthouse Service, which later became part of the Coast Guard, in 1719, making it the oldest known artifact by several decades. The lighthouse itself is older by three years, but was torched by the British as they left town on what is now known as Evacuation Day, March 17, 1776.

“Sometimes maritime historians have a lot of debate over firsts and lasts and whens, but there was quick concurrence from everyone involved in this,” said Lt. Joe Klinker,the public affairs officer for the First Coast Guard District.

On Friday, Rear Admiral Daniel Abel, First Coast Guard District commander, visited Boston Light to see the cannon and present a commendation to Sally Snowman, the 70th lighthouse keeper at Boston Light and the first female.

Snowman said the fog cannon was the brainchild of the third lighthouse keeper, who noted that the bright light was of little use if no one could see it. He asked for, and was granted, permission to buy a cannon.

Today the lighthouse uses an automated system that measures the thickness of the fog and releases bursts from an air horn at intervals that indicate that thickness to mariners.