When Navy divers and NOAA archaeologists recovered the USS Monitor steam engine from the Atlantic in 2001, the pioneering Civil War propulsion unit was enshrouded in a thick layer of marine concretion.
Sand, mud and corrosion combined with minerals in the deep Cape Hatteras, N.C., waters to cloak every feature of Swedish-American inventor John Ericsson’s ingenious machine, and they continued to envelop the 30-ton artifact after nine years of desalination treatment.
Just this past week, however, conservators at The Mariners’ Museum and its USS Monitor Center drained the 35,000-gallon solution in which the massive engine was submerged and began removing the 2- to 3-inch-thick layer of concretion with hammers, chisels and other hand tools.
Working slowly and carefully to avoiding harming the engine’s original surface, they stripped off more than 2 tons of encrustation in their first week of work alone, gradually revealing the details of a naval milestone that had not been seen since the historic Union ironclad sank in a December 1862 storm.
“This is a technological marvel. It was cutting edge in its day. But what’s really neat is revealing all the wheels, oil cups, valves and other parts that the Monitor’s crew used to operate the engine,” said conservation project manager Dave Krop.
“If you consider that it spent nearly 139 years underwater, it’s in outstanding shape — though some of the wrought iron has seen better days. And there are some copper alloy parts that look brand new when they’re first uncovered — like they just came off the shelf.”
Smaller, more compact, yet just as capable as other steam engines of its day, the Monitor’s vibrating side-lever engine was the ideal match for Ericsson’s revolutionary warship.
Its long, low, horizontal cylinder enabled the engineer to place it below the vessel’s waterline as well as behind a thick armor belt — and that well-protected position virtually eliminated the vulnerability associated with the much larger and more easily targeted engines of the day, most of which towered above the ships’ decks.
So confident was Ericsson in his engine’s capabilities that he ignored orders to equip the vessel with masts and rigging.
And it astounded Union and Confederate observers alike with the way it performed in its historic clash with the rebel warship Virginia — also known as the Merrimac — in the March 8, 1862 Battle of Hampton Roads.
“If the turret and the guns were the Monitor’s muscle, this steam engine was its heart,” Monitor National Marine Sanctuary historian Jeff Johnston said.
“And it was the heart of the first naval vessel to be 100 percent machine.”
Once the concretion is gone — probably by the end of the coming week — the engine will be submerged in a new solution of purified water and sodium hydroxide. It also will be exposed to a low-level electrical current that speeds up the release of potentially damaging chlorides through a process called electrolytic reduction.
Sometime in the spring, conservators hope to begin a lengthy disassembly process involving thousands of parts. Each element will then be individually treated and documented — and the most seriously corroded ones replaced by carefully crafted replicas — before the giant artifact is reassembled and placed on exhibit in the museum.
“The reason this disassembly is so important is that you have to gain access to each interior space and each part in order to conserve them and make them stable,” Krop said.
“Realistically, we’re talking about another 15 years of work before all is said and done.”
Conservation of the USS Monitor steam engine
Where: The Mariners’ Museum, 100 Museum Drive, Newport News
When: 10 a.m.-5 p.m. Wednesday-Thursday and 10 a.m.-3 p.m. Friday through Dec. 17
Cost: $12 adults, $7 children 6-12
Online: Go to
to see a video of the project. You can also go to