Lighting Boston Harbor for 150 years

by Sally Snowman – Lighthouse keeper, Boston Light
Photo by Petty Officer 3rd Class Connie Terrell

One-hundred and fifty-years ago, at sunset on the winter solstice, Boston Light’s newly installed second order classical Fresnel lens was lit for the first time on the country’s first lighthouse.

The lighthouse, situated on Little Brewster Island at the entrance of Boston Harbor, was built in 1716 to guide ships in safely transiting into the outer harbor. With technological advancements, the most effective lamp device available in the world was installed at Boston Light in 1859. It’s a flashing mechanism is comprised of 4,000 pounds of brass and glass rotating on a clock-works mechanism.

The inventor credited for revolutionizing illumination optics in the 1820’s was Augustin Fresnel from France. This technology was adopted for use in lighthouses and the U.S. began importing these lenses in the 1840’s.

Boston Light’s entire assembly is 11 feet tall comprising of 336 individual prisms with 12 bullseyes. Today, the illuminate in the center of the lens is a 1,000 watt lamp, magnifying the light 2,000,000 candle power that’s visible for 27 nautical miles on a clear night.

The lighting characteristic is distinguishable from other lights in the harbor with its one flash every 10 seconds. The lamp appears to only flash, but in actuality, the rotation of the lens mechanism allows the bullesyes to capture the light from the 1,000 watt lamp, sending 12 beams of light across the bay appearing as one solid flash of light.

Today the 150 year old lens is fully automated and one of the few remaining classical lenses functioning as an active aid to navigation. It no longer needs vigils during the night to keep the light burning. However, Boston Light is very unique in that it remains the last Coast Guard lighthouse in the country with a lighthouse keeper. Due to it being the first established lighthouse in colonial America, congressional law has proclaimed it is remain “manned”.

Little Brewster Island is also included in the Boston Harbor Islands National Park Area with tours of the island offered by the Park Service during the summer months.

Little Brewster Island is also included in the Boston Harbor Islands National Park Area with tours of the island offered by the Park Service during the summer months.

Little Brewster Island is also included in the Boston Harbor Islands National Park Area with tours of the island offered by the Park Service during the summer months.

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