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Putting it upright should provide clues to the sinking.

Was it damaged by fire from the Housatonic or perhaps struck by a second Union ship coming to the aid of the blockade vessel? Were the Hunley sailors knocked out by the concussion of the explosion that sank the Housatonic?

The clues indicate the crew died of anoxia, a lack of oxygen that can overtake a person very quickly, and didn’t drown. The remains showed they were at their crank stations and that there was no rush for an escape hatch.

Mr. McConnell concedes he didn’t expect the project to take so long and thought it would have been in a museum by now.

“The Hunley is a very complex artifact, and we decided we had only one chance to do it and that was to do it right,” he said.

He estimates the Hunley could now be displayed in a museum by 2015.

Conservation of such artifacts often takes years, underwater archeologists say.

Frederick Hanselmann, a field archaeologist at the Institute of Nautical Archaeology at Texas A&M said the most painstaking part of conserving iron objects is removing the salts from years in seawater. Conserving a ship cannon alone can take three to four years, he said.