The fleet commander repeated his instructions, addressing his words particularly to Selfridge, who would be in command. The officers were told to avoid the channel where the mines were set. The tinclads were to move close to shore and, by using small boats, haul the infernal machines out and destroy them before proceeding upriver. The ram would follow immediately behind the tinclads, and the two gunboats would bring up the rear, shelling the banks whenever necessary. He concluded by advising that, if there was an apparent danger in the execution of these orders, the project was to be abandoned and they were to return until a better means of carrying it out could be found.
At 7:30 a.m. on December 12, the expedition proceeded up the Yazoo, with the vessels in the order designated. Here and there along the way sharpshooters fired from trees on shore, and an occasional shell was tossed in their direction.
Frequently on the way up, Selfridge displayed impatience. He would peremptorily shout orders to Capt. Edwin W. Sutherland, commander of the Queen of the West, moving directly ahead of the Cairo, to go faster. Other officers recognized that more speed imperiled the safety of the boats in advance, for, if they had been compelled by some unexpected danger to stop suddenly or to back up in the narrow, tortuous stream, they would have been inevitably run down by the ram.
Sometime after 10:30, the Marmora, moving 100 yards or so in advance, came in sight of the torpedoes and stopped, partially hidden by a bend in the river. Selfridge heard a heavy fire of musketry and supposed she was being attacked from shore. As the little fleet closed up, he saw that the firing was coming from the Marmora, then backing, and was aimed at a block of wood floating in the river.
“Why don’t you go ahead?” shouted Selfridge. Someone on the Marmora yelled back, “Here is where the torpedoes are!”
Selfridge ordered the firing stopped and a boat lowered to examine the object. At the same time, he directed that the right shore be bombarded and a boat sent out from his own vessel.
Men in the small boats recovered one infernal machine and debris from the torpedoes exploded the day before. In the meantime, the bow of the Cairo had turned toward shore. Selfridge, who seemed to have little fear of the Confederate torpedoes, backed out to proceed upstream and then ordered the Marmora to move ahead slowly. The Cairo took the lead and advanced into unreconnoitered waters. Her big wheel had made only a dozen revolutions when there were two explosions in quick succession, one close to her port quarter and the other under her port bow.
Opinions varied as to how long it took the Cairo to go down—8 to 15 minutes, the estimates ran. However long it was, the vessel was run in toward shore where she sank, leaving only her chimneys above water. The Queen of the West came to the aid of the Cairo’s crew, all of whom were rescued. Nothing was saved except a few hammocks and bags which floated away from the wreckage.
Before moving downstream, the Queen knocked down the stacks to keep the Southerners from finding the sunken ironclad. (This was an act that would have its benefits a century later, when an enterprising group of men, no longer taking sides between the North and South, sounded for the Cairo until they located her and then brought her to the surface to be restored.)
The Cairo’s value to the Union must be estimated in terms of disappointment. At the start, she failed to function properly. In addition, she fired a few shells at the riverbank at Eastport, took her share of guard duty at Fort Pillow, and played a rather inconspicuous part in the battle at Plum Point and later that at Memphis. She added little to the North’s offensive, and the records gave her very little mention. From a practical standpoint, her major contribution lies in what she took down below the waters with her when she sank in the Yazoo, for therein was preserved for future generations first-hand information on the type of fighting boat that fought along the inland rivers in the Civil War and the sort of life lived by the crewmen on board.