June 01, 2009
One of the most dangerous places in Boston Harbor is the half-mile long shoal leading south from Nixes Mate, the famous shrinking island of the Boston Harbor Islands National Park. After its formation as a glacial drumlin 15,000 years ago, Nixes Mate has served as grazing land, quarry and gallows. It was, and remains, a significant hazard to navigation.
Piracy was a huge problem for the early Massachusetts Bay Colony, and it became the practice to execute captured pirates on the Islands adjacent to the main shipping channel and let their corpses hang as a warning for months, before burial in unmarked island graves. The primary sites for these displays were Bird Island (now beneath the runways of Logan Airport) and Nixes Mate. The most infamous hanging on Nixes Mate was William Fly, who led a mutiny on the Elizabeth, killing the Captain and First Mate.
Nixes Mate has been shrinking for 200 years. A likely cause of its diminution is removal of its most durable resource by generations of quarrymen. In the 1600s, its convenient location resulted in much rock being offloaded for ship ballast. Through the 1700s, the island was quarried for slate, to help support the booming Boston roofing industry. The fine glacial till left behind was no match for the strong winds and currents in this part of the harbor, resulting in the island’s gradual disappearance and the growth of the south bar. Nixes Mate and shoal became such a hazard to navigation that the Boston Marine Society built a copper-riveted masonry tower on the island remnant in 1802. This structure is still functioning today, and at high tide is the only part of the old island still above water. It is one of the few marine structures on the National Register of Historic Places.
This remarkable photo, taken from the air during an approach to Logan International Airport, coincident with an extreme low tide following a new Moon, shows the Nixes Mate marker, the remnant of the island, and the beautiful structure of the southerly shoal, defined by currents between adjacent Gallops, Lovells and Long Islands. At high tide, the only thing above the water is the marker itself.