CHARLESTON, SOUTH CAROLINA—The Post and Courier reports that conservators have begun to scrape away the layer of sand and shell encasing the hull of the Confederate submarineH.L. Hunley, which went down in Charleston Harbor in 1864 just minutes after it sank the Union warshipUSS Housatonic. The layer, known as concretion, has obscured many of the specific features of the vessel that scientists are interested in studying, especially evidence of bullet holes or other damage that might reveal clues about why the submarine sank. "We have been waiting for this a long time," saysNestor Gonzalez,associate directorWarren Lasch Conservation Center, which is responsible for the project. "We will know if there was any damage to the submarine pre-sinking or post-sinking." The painstaking work, carried out using dental chisels and small hammers to remove concretion that is in some places a couple of inches thick, could take up to a year to complete.