CHARLESTON, SOUTH CAROLINA—Conservators working on the remains of H.L. Hunley, which sank in Charleston Bay in 1864 just after attacking the USS Housatonic, have discovered a piece of torpedo still attached to the submarine’s 20-foot spar. Eyewitness accounts put the sub 100 feet from the blast that eventually sank the Union ship, suggesting the crew remotely detonated its explosives. But the new discovery shows Hunley was still attached to the torpedo when it exploded, meaning the attack was far more risky than previously thought. “I would say this is the single-most important piece of evidence we have found from the attack,” said Maria Jacobsen, the Hunley project's senior archaeologist.