Monday, September 27, 2010

WTC Ship Gives Up Lucky Coin

As Nichole Doub -- Head Conservator at the Maryland Archaeological Conservation Laboratory -- was helping extract the remains of an 18th century ship from the mud of the World Trade Center construction site, she was asked a familiar question:

While we’re out on the site, we have all these construction workers coming up and one of the most common questions asked any archaeologist on a site is: Have you found the gold yet? It’s kind of the question that everyone asks. And normally you go “No, no.”

But in this case there’s a chance we could find gold. And that’s if we found one of the lucky coins.

Lucky coin? Ever since the 2nd century B.C. -- not long after Romans began minting coins -- shipbuilders have been slipping a coin into the structure of their ships. It’s a tradition that continues today. In fact, the USS New York - made partially from steel recovered from the World Trade Center towers - did it as well (see "What is Stepping the Mast?").

For the ancient Romans it was likely a continuation of religious customs. Now it's just a tradition and done for good luck.

So we didn’t find it during the five days we were actually excavating it. However, one of my curators did find it between the stern knee and the stern post while we were cleaning the timbers.

Here's what they found:

It’s only a copper alloy coin. I think it’s of George II, a half penny.

Originally they thought they were working on the front of the ship. Not so -- upon closer inspection they've discovered they've got the stern of the ship.

Doub also says signs continue to point to the ship being a coastal vessel, most likely involved in commerce.

As for the mysteries surrounding the ship? Answers are forthcoming.

As of last week, all the researchers who required access to the timbers had taken their samples and measurements and returned to their respective laboratories for analysis. That means we'll soon know:

-- the species of the tree the wood came from;

-- the region where the wood was grown;

-- what year the tree was cut down;

-- the origins of the woodworm remains found in the timbers (which tells you where the ship sailed).

Doub estimates it'll take several months for that analysis to finish up.

In the meantime, it's her job to battle against the natural process of deterioration to ensure the timbers remain intact and in the good condition they arrived in. That fight includes keeping the waterlogged timbers waterlogged. Letting them dry out would cause the timbers -- even on a molecular level -- to break down. You can see what that would look like [here]. Broken cells = not pretty.

In order to keep the submerged wood from rotting away, she has to make sure there are no organisms in the lab's wet tanks, where the timbers are kept. The reason the back part of the ship remained preserved while the front of the ship disappeared was that the stern was buried in mud so dense there wasn't enough oxygen for the wood bores and wood-hungry microbes to survive. Instead, those bugs stayed above the mud and ate what they could, which turned out to be the bow of the ship.

In the tanks, the water does contain plenty of oxygen, but the water is finely filtered to keep the bugs out.

One other bad guy for the marine archaeologist: salt.

This has been an ocean-going vessel, or at least traveled in brackish water, so it has a lot of salt retained in it. And salt, when it's wet, when it's in its soluble form, it's fine. It's completely stable, it's neutral, it kind of floats through the cellular structure of the ship, no problem.

But we've all seen salt crystallize. It grows. And if that salt crystal is trapped in one of those cell walls as it expands, it's going to burst through. And it's another means of cracking and warping and distortion. The pressure exerted by a single salt crystal on a single cell wall -- and if you have that times millions and billions -- you get a lot of damage.

I asked Nichole if anything about the project stood out for her personally:

Being able to work on a shipwreck on land. It's very unusual to be able to work on a terrestrial excavation of a ship.

Visit the website to see the rest of the pictures

See another story about the World Trade Centre ship:
Mysteries abound in wtc ship remains


Williams, James. 2010. "WTC Ship Gives Up Lucky Coin". Discovery News. Posted: September 10, 2010. Available online:

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