But the death of the Merrimac was to follow close upon her birth; she was the portent of a few weeks only. For, during a short time past, there had been also rapidly building in a Connecticut yard the Northern marvel, the famous Monitor. When the ingenious Swede, John Ericsson, proposed his scheme for an impregnable floating battery, his hearers were divided between distrust and hope; but fortunately the President's favorable opinion secured the trial of the experiment. The work was zealously pushed, and the artisans actually went to sea with the craft in order to finish her as she made her voyage southward. It was well that such haste was made, for she came into Hampton Roads actually by the light of the burning Congress. On the next day, being Sunday, March 9, the Southern monster again steamed forth, intending this time to make the Minnesota her prey; but a little boat, that looked like a "cheese-box" afloat, pushed forward to interfere with this plan. Then occurred a duel which, in the annals of naval science, ranks as the most important engagement which ever took place. It did not actually result in the destruction of the Merrimac then and there, for, though much battered, she was able to make her way back to the friendly shelter of the Norfolk yard. But she was more than neutralized; it was evident that the Monitor was the better craft of the two, and that in a combat à outrance she would win. The significance of this day's work on the waters of Virginia cannot be exaggerated. By the armor-clad Merrimac and the Monitor there was accomplished in the course of an hour a revolution which differentiated the naval warfare of the past from that of the future by a chasm as great as that which separated the ancient Greek trireme from the flagship of Lord Nelson.