Having sunk the Cumberland, the Merrimac next turned her attention to the Congress, which had meanwhile run into shoal water and grounded where the rebel vessel could not follow.  But the Merrimac, being herself apparently proof against shot and shell by her iron plating, took up a raking position two cables’ length away, and during an hour’s firing deliberately reduced the Congress to helplessness and to surrender—­her commander being killed and the vessel set on fire.  The approach, the manoeuvering, and the two successive combats consumed the afternoon, and toward nightfall the Merrimac and her three small consorts that had taken little part in the action withdrew to the rebel batteries on the Virginia shore:  not alone because of the approaching darkness and the fatigue of the crew, but because the rebel ship had really suffered considerable damage in ramming the Cumberland, as well as from one or two chance shots that entered her port-holes.

That same night, while the burning Congress yet lighted up the waters of Hampton Roads, a little ship, as strange-looking and as new to marine warfare as the rebel turtleback herself, arrived by sea in tow from New York, and receiving orders to proceed at once to the scene of conflict, stationed herself near the grounded Minnesota.  This was Ericsson’s “cheese-box on a raft,” named by him the Monitor.  The Union officers who had witnessed the day’s events with dismay, and were filled with gloomy forebodings for the morrow, while welcoming this providential reinforcement, were by no means reassured.  The Monitor was only half the size of her antagonist, and had only two guns to the other’s ten.  But this very disparity proved an essential advantage.  With only ten feet draft to the Merrimac’s twenty-two, she not only possessed superior mobility, but might run where the Merrimac could not follow.  When, therefore, at eight o’clock on Sunday, March 9, the Merrimac again came into Hampton Roads to complete her victory, Lieutenant John L. Worden, commanding the Monitor, steamed boldly out to meet her.

Then ensued a three hours’ naval conflict which held the breathless attention of the active participants and the spectators on ship and shore, and for many weeks excited the wonderment of the reading world.  If the Monitor’s solid eleven-inch balls bounded without apparent effect from the sloping roof of the Merrimac, so, in turn, the Merrimac’s broadsides passed harmlessly over the low deck of the Monitor, or rebounded from the round sides of her iron turret.  When the unwieldy rebel turtleback, with her slow, awkward movement, tried to ram the pointed raft that carried the cheese-box, the little vessel, obedient to her rudder, easily glided out of the line of direct impact.