Disappearance
After the attack, the H.L. Hunley failed to return to her base. There is evidence that the Hunley survived as long as one hour following the attack - at about 8:45 p.m. The commander of "Battery Marshall" reported on the day after the attack that he had received "the signals" from the submarine indicating it was returning to her base. The report did not state what manner of signals were observed. A postwar correspondent stated that "two blue lights" were the prearranged signals, and a lookout on the Housatonic reported that he saw a "blue light" on the water after his ship sank. "Blue light" in 1864 referred to a pyrotechnic signal in long use by the U.S. Navy. It has been falsely represented in published works as a blue lantern, even though the lantern found on the recovered H.L. Hunley had a clear, not a blue, lens. Pyrotechnic "blue light" can be seen easily over the four mile distance between Battery Marshall and the site of the Hunley's attack on the Housatonic.
After signaling, Dixon would have taken his submarine underwater to attempt to return to Sullivan's Island. What happened next is unclear. The finders of the Hunley suggested that she was unintentionally rammed by the USS Canandaigua when that warship was going to the aid of the crew of the Housatonic.
One possibility is that the torpedo was not detonated on command, but rather it malfunctioned because of some damage suffered during the underwater attack. The intention was that the torpedo would be detonated when the Hunley had retreated to about 150 feet (46 meters) away. However, witnesses aboard the Housatonic stated that the submarine was no more than about 100 feet (30 meters) away when her torpedo detonated.
In October 2008, scientists reported that they had found that the crew of the Hunley had not set her pump to remove water from the crew's compartment, and this might indicate that it was not being flooded. "It now really starts to point to a lack of oxygen making unconscious," the chairman of the South Carolina Hunley Commission said. "They may have been cranking and moving and it was a miscalculation as to how much oxygen they had."
Although there is no conclusive evidence as to the cause of the sinking of the H. L. Hunley, the head archeologist of Clemson University, Maria Jacobsen, and George Wunderlich, the executive director of the National Museum of Civil War Medicine, conducted experiments with modern castings of the forward conning tower of the H. L. Hunley. The original one had shown damage at one viewing port. The experiments used replica U.S. Navy firearms, and they showed that a .58 caliber Minie ball, fired from the U.S.S. Housatonic, could have penetrated at the viewing ports, hence producing a breach to let water enter. This result corresponds with the findings of Jaime Downs, an FBI forensic pathologist, which show variations in the preserved brain tissue from to forward to the aft crewmen of the Hunley. It has been conjectured that a ramming by the U.S.S. Canandaigua would have caused damage to the Hunley, but no such damage was found when the Hunley was raised from the bottom of the harbor.
Her crew perished, but the H.L. Hunley had earned a place in the history of undersea warfare by being the first submarine to sink any ship.
Read more about this topic: H. L. Hunley (submarine)