His relief arrived on the morning of December 4, and he set out for the mouth of the Yazoo immediately, arriving on the 8th. The fleet that gathered there ready to go upstream was under the command of Capt. Henry Walke, a Mexican War veteran, a fine artist, and a dauntless fighter.
The next 2 days were spent in recoaling. Then, on the 11th, plans for a reconnaissance up the Yazoo were carried out. This was done by the two tinclads, Marmora and Signal, light-draft stern-wheelers covered with 1¼ inches of iron that afforded protection against shells but not against heavier projectiles.
They ran up the river some 20 miles and prepared to round to, as the lookouts sighted several suspicious objects floating on the water. A man on board the Marmora fired a musket at one of them and touched off a tremendous explosion that shook the boat and threw water over a wide area. Another explosion occurred shortly afterward near the Signal. No damage was caused by either. However, it was recognized that contact had been made with some of the vaunted Confederate mines, more commonly referred to as “torpedoes.”
Back at the mouth of the river that night, the captains of the two tinclads told of their experience. They said the number of small scows and stationary floats they saw at the point where they had turned around indicated the presence of other torpedoes, but, if protected by one or two gunboats, they believed they could safely lift the “infernal machines” from the water and deactivate them.
Lt. Comdr. Thomas O. Selfridge.
Library of Congress
Selfridge requested permission to use the Cairo on such a venture, and Walke consented. He also designated the gunboat Pittsburg and the ram Queen of the West to go along.
The type of torpedo that sank the U.S.S. Cairo. From a sketch in the Official Records of the Union and Confederate Navies.
Wires to galvanic cell on shore Wood float 5-gallon glass demijohn filled with black powder Rope to shore Anchor