Federals had not placed obstructions or taken other measures, as done on the Stono River, to deter Confederate attacks. And the USS Memphis, a former blockade runner herself, operated in the North Edisto. Acting Master Robert O. Patterson commanded the Memphis.
With the Hunley gone, the Confederates employed the CSS David torpedo-boat. The David employed a spar torpedo much like that successfully used on the Hunley. But the David could not submerge, and relied on a low profile to avoid detection during an attack.
In late February the David transited the backwaters to reach Church Flats. On the night of March 4, First Assistant Engineer James H. Tomb skippered the David downriver to within sight of the Memphis. But the torpedo-boat's pumps failed and Tomb abandoned the attack. The following night, Tomb again moved the David downriver. And again the pumps failed. But this time the crew managed to resolve the problem. Tomb then proceeded to attack the Memphis:
About 12:30 a.m. [March 6], as we came within hailing distance, they hailed us, but we paid no attention to their hail, and the next moment they opened on us with small arms, the shot striking the steel cover did no harm. The next moment the "David" struck her on the port quarter about 8 feet below the surface. The blow was a good one, but the torpedo failed to explode.Patterson reported his men first hailed the David around 1 a.m. as it approached, at a distance of fifty yards.
We immediately beat to quarters and slipped the chain; in an instant the torpedo was under our port quarter, and we could not bring a gun to bear on her. The watch being armed at the time, we were enabled to concentrate a rapid fire with muskets, revolvers, and pistols drawn up on her, and into what looked like a hatchway, nearly in the center; the rapid firing seemed to stop her progress....Tomb then angled for a second attack:
We then made a turn to port and came back at her, striking her on the starboard quarter. At this time the Memphis was going through the water at good speed and the blow was a glancing one, passing under her counter, taking a portion of our stack away, but the torpedo failed again to explode.Tomb then turned back upriver, with the Memphis firing on, but not hitting, the David.
When we reached Church Flats and made an examination of the torpedo we found the first blow was a good one, as the tube or cap on that side was mashed perfectly flat, and the glass tube containing the acid was broken, but being a defective tube it failed to explode. The second blow as not a good one, as the tube was slightly bent and the glass tube not broken. The expedition was a failure, caused by a defective tube. The torpedo held 95 pounds of rifle powder.Captain Francis D. Lee, Chief of Engineers at Charleston and designer of the torpedo used, explained this failure:
As this occurrence may disturb the confidence heretofore felt in the torpedoes prepared by me, I deem it due to myself to state that about ten days since I saw Engineer Tomb, and in the presence of Mr. Theodore Stoney distinctly told him that the torpedo then on the "David" could not be relied upon, it having been exposed for the last six months to every vicissitude of weather and climate.Lee suggested a new torpedo for the David, but Tomb departed without following up. Thus an opportunity to sink a second Federal steamer during the winter of 1864 eluded the Confederates. In response to the attack, Captain Stephen C. Rowan, then acting commander of the South Atlantic Blockading Squadron, cautioned Patterson to take measures preventing another attack. Those recommendations indicate, as did the precautions ordered by Rear-Admiral John Dahlgren earlier in January, the Federals were well acquainted to the threat:
You will, if practicable, obtain from the shore suitable spars for outriggers, and take your studding sail booms and other spare spars for that purpose. Having prepared your outriggers with 6 or 7 inch hawser, and nets to hang some 8 feet below the surface of the water, you will be protected from torpedo boats, but you must use great vigilance, row guard, and keep your people at or near their guns, giving them rest during the day.Those simple practices offered countermeasures against the feared spar torpedo in 1864.
(Citations from ORN, Series I, Volume 15, pages 356-9.)