[OSMH] Sunken Treasure in Boston Harbor
Mar. 22nd, 2007 05:13 pm![[personal profile]](https://www.dreamwidth.org/img/silk/identity/user.png){kind=small}
magidToday's lecture continued March's maritime history theme with a talk by Allen Gontz, assistant professor in environmental earth and ocean studies at UMASS Boston titled "What Lies Beneath: sunken Treasure in Boston Harbor".
The tools used for underwater exploration include direct observation and first-hand accounts, sidescan sonar (scans show the reflectivity of the sea floor), subbottom profiling, marine magnetometry (metal detectors), and remotely operated vehicles.
We got to see rather ideal sidescan sonar images from the wreck of the Portland, a ship that used to go between Boston and Portland, ME, until it was lost in a storm. It sank so deep, 500 feet, than when it was found, the sonar images were pretty amazingly clear, even for someone who'd never seen them before.
The wrecks that have happened in Boston harbor aren't nearly so clear. The water is much shallower (trickier to navigate, easier to defend), so wrecks are subjected to more interference from waves, currents, and storms. Also, the harbor itself has changed over the years, with some islands being annexed to the mainland, or severely eroded, or enhanced by landfill, or changed by storms or rising sea levels, so it can be difficult to find where wrecks went down even with contemporary descriptions. So it's a bit of a treasure hunt, trying to find what's left.
There were two examples discussed. The first was the case of the French ship Le Magnifique, a French ship of the line that was part of the French support during the Revolution. It was large enough to carry 74 cannon. Unfortunately, despite having a local navigator board to guide the ship through the harbor, it ran aground on the shoals of Lovell's Island. Everyone was saved, and the French were able to strip it of pretty much anything of use, but the ship itself sank there. Lovell's Island is exposed to the northeast, prone to erosion from storms, so it's not obvious where the ship went down. Since the ship was stripped, there wasn't much metal left, but there was enough in the nails and such that the manetometer showed some anomalies, on the order of 8 nanoteslas or so. The sonar didn't show anything that was clearly the ship, however.
(One consequence of the loss of the Magnifique: the American government, wanting to keep the French friendly, offered a replacement ship, the first major ship built, the America. However, this was to have been the flagship of the naval commander, John Paul Jones, who resigned his post in protest and ended up working for Catherine the Great.)
The other ship that they've been investigating this year was the USS Niagara. It was first launched 23 February 1856, 328 feet long, a steam/sail frigate with 55 foot beam and 5540 tons, the largest wooden ship of the time. It was used to lay transAtlantic cable from Newfoundland to Ireland, served in the Civil War, and was employed on a number of political missions. It was sold for scrap in 1889, stripped of all its fittings, and burned to the waterline off Grape Island. Obviously, there wouldn't be a traditional ship visible on the sonar, but there were magnetometer anomalies to the order of 200-300 nanotesla. When they overlaid this on the sonar scan, it showed the most likely places to search. Then there was a subbottom profile, which didn't look like anything particular to me (the others had), but seemed to confirm to the lecturer the placces most likely to have remains.
As of now, this is where the searches stand, with neither of them definitive.
The last part of the talk was about the treasure, which is not of the gold dubloon variety, but of history. He'd like to get these sites status as underwater protected preserves, so everyone could dive and appreciate them. He also noted that in cases where there's more of the structure left, they're good diving sites both for history and for the marine life around it; the structures become a habitat for all kinds of things.
This is the first lecture I remember that hasn't been by some kind of historian; it was an interesting change. Also, I didn't know that MA even had a Board of Underwater Archaeological Resources.
I'm behind on these, with notes for at least two others needing to be typed up.
The tools used for underwater exploration include direct observation and first-hand accounts, sidescan sonar (scans show the reflectivity of the sea floor), subbottom profiling, marine magnetometry (metal detectors), and remotely operated vehicles.
We got to see rather ideal sidescan sonar images from the wreck of the Portland, a ship that used to go between Boston and Portland, ME, until it was lost in a storm. It sank so deep, 500 feet, than when it was found, the sonar images were pretty amazingly clear, even for someone who'd never seen them before.
The wrecks that have happened in Boston harbor aren't nearly so clear. The water is much shallower (trickier to navigate, easier to defend), so wrecks are subjected to more interference from waves, currents, and storms. Also, the harbor itself has changed over the years, with some islands being annexed to the mainland, or severely eroded, or enhanced by landfill, or changed by storms or rising sea levels, so it can be difficult to find where wrecks went down even with contemporary descriptions. So it's a bit of a treasure hunt, trying to find what's left.
There were two examples discussed. The first was the case of the French ship Le Magnifique, a French ship of the line that was part of the French support during the Revolution. It was large enough to carry 74 cannon. Unfortunately, despite having a local navigator board to guide the ship through the harbor, it ran aground on the shoals of Lovell's Island. Everyone was saved, and the French were able to strip it of pretty much anything of use, but the ship itself sank there. Lovell's Island is exposed to the northeast, prone to erosion from storms, so it's not obvious where the ship went down. Since the ship was stripped, there wasn't much metal left, but there was enough in the nails and such that the manetometer showed some anomalies, on the order of 8 nanoteslas or so. The sonar didn't show anything that was clearly the ship, however.
(One consequence of the loss of the Magnifique: the American government, wanting to keep the French friendly, offered a replacement ship, the first major ship built, the America. However, this was to have been the flagship of the naval commander, John Paul Jones, who resigned his post in protest and ended up working for Catherine the Great.)
The other ship that they've been investigating this year was the USS Niagara. It was first launched 23 February 1856, 328 feet long, a steam/sail frigate with 55 foot beam and 5540 tons, the largest wooden ship of the time. It was used to lay transAtlantic cable from Newfoundland to Ireland, served in the Civil War, and was employed on a number of political missions. It was sold for scrap in 1889, stripped of all its fittings, and burned to the waterline off Grape Island. Obviously, there wouldn't be a traditional ship visible on the sonar, but there were magnetometer anomalies to the order of 200-300 nanotesla. When they overlaid this on the sonar scan, it showed the most likely places to search. Then there was a subbottom profile, which didn't look like anything particular to me (the others had), but seemed to confirm to the lecturer the placces most likely to have remains.
As of now, this is where the searches stand, with neither of them definitive.
The last part of the talk was about the treasure, which is not of the gold dubloon variety, but of history. He'd like to get these sites status as underwater protected preserves, so everyone could dive and appreciate them. He also noted that in cases where there's more of the structure left, they're good diving sites both for history and for the marine life around it; the structures become a habitat for all kinds of things.
This is the first lecture I remember that hasn't been by some kind of historian; it was an interesting change. Also, I didn't know that MA even had a Board of Underwater Archaeological Resources.
I'm behind on these, with notes for at least two others needing to be typed up.