Sea-power kept the North in affluence while it starved the South. Sea-power held Maryland in its relentless grip and did more than land-power to keep her in the Union. Sea-power was the chief factor in saving Washington. Seapower enabled the North to hold such points of vantage as Fortress Monroe right on the flank of the South. And sea-power likewise enabled the North to take or retake other points of similar importance: for instance, Hatteras Island. In a couple of days at the end of August, 1861, the Confederate forts at Hatteras Inlet, North Carolina, were compelled to surrender to a joint naval and military expedition under Flag-Officer Stringham and Major-General B. F. Butler. The immediate result, besides the capture of seven hundred men, was the control of the best entrance to North Carolina waters, which entailed the stoppage of many oversea supplies for the Confederate army. The ulterior result was the securing of a base from which a further invasion could be made with great advantage. The naval campaign of the following year was truly epoch-making; for the duel between the _Monitor_ and _Merrimac_ in Hampton Roads on March 9, 1862, was the first action ever fought between ironclad steam men-of-war. Eleven months earlier the Federal Government had suddenly abandoned the Norfolk Navy Yard; though their strongest garrison was at Fortress Monroe, only twelve miles north along a waterway which was under the absolute control of their navy, and though the Confederates' had nothing but an inadequate little untrained force on the spot. Among the spoils of war falling into Confederate hands were twelve hundred guns and the _Merrimac_, a forty-gun steam frigate. The _Merrimac_, though fired and scuttled by the Federals, was hove up, cut down, plated over, and renamed the _Virginia_. (History, however, knows her only as the _Merrimac_.) John L. Porter, Naval Constructor to the Confederate States, had made a model of an ironclad at Pittsburgh fifteen years before; and he now applied this model to the rebuilding of the _Merrimac_. He first cut down everything above the water line, except the gun deck, which he converted into a regular citadel with flat top, sides sloping at thirty-five degrees, and ends stopping short of the ship's own ends by seventy feet fore and aft. The effect, therefore, was that of an ironclad citadel built on the midships of a submerged frigate's hull. The four-inch iron plating of the citadel knuckled over the wooden sides two feet under water. The engines, which the South had no means of replacing, were the old ones which had been condemned before being sunk. A four-foot castiron ram was clamped on to the bow. Ten guns were mounted: six nine-inch smooth-bores, with two six-inch and two seven-inch rifles. Commodore Franklin Buchanan took command and had magnificent professional officers under him. But the crew, three hundred strong, were mostly landsmen; for, as in the case