“Before showing you over the vessel, let me say that there were three possible points of weakness in the _Monitor_, two of which might have been guarded against in her construction, if there had been more time to perfect her plans. One of them was in the turret, which, as you see, is constructed of eight plates of inch iron--on the side of the ports, nine--set on end so as to break joints, and firmly bolted together, making a hollow cylinder eight inches thick. It rests on a metal ring on a vertical shaft, which is revolved by power from the boilers. If a projectile struck the turret at an acute angle, it was expected to glance off without doing damage. But what would happen if it was fired in a straight line to the centre of the turret, which in that case would receive the whole force of the blow? It might break off the bolt-heads on the interior, which, flying across, would kill the men at the guns; it might disarrange the revolving mechanism, and then we would be wholly disabled. “I laid the _Monitor_ close alongside the _Merrimac_, and gave her a shot. She returned our compliment by a shell, weighing one hundred and fifty pounds, fired when we were close together, which struck the turret so squarely that it received the whole force. Here you see the scar, two and a half inches deep in the wrought iron, a perfect mould of the shell. If anything could test the turret, it was that shot. It did not start a rivet-head or a nut! It stunned the two men who were nearest where the ball struck, and that was all. I touched the lever--the turret revolved as smoothly as before. The turret had stood the test; I could mark that point of weakness off my list forever. “You notice that the deck is joined to the side of the hull by a right angle, at what sailors call the ‘plank-shear.’ If a projectile struck that angle, what would happen? It would not be deflected; its whole force would be expended there. It might open a seam in the hull below the water-line, or pierce the wooden hull, and sink us. Here was our second point of weakness.