In the first weeks of the war inventors had besieged the United States Navy Department with proposals for the construction of ironclad warships. The Department was still leisurely debating as to what policy should be adopted, when news came that the "Merrimac," half-burnt at Norfolk Yard, was being reconstructed as an armoured ram, and it became urgent to provide an adversary to meet her on something like equal terms. It was at this moment that John Ericsson came forward with his offer to construct an armoured light-draught turret-ship, which could be very rapidly built and put in commission. This last point was of cardinal importance, for report said that work on the "Merrimac" was far advanced, and no ship could be built on ordinary lines, of sufficient power to meet her, in the time now available. The vessel must be of light draught to work in the shallow coast waters, creeks, and river mouths of the Southern States. She might have to fight in narrow channels, where there would not be room for manoeuvring to bring broadside guns to bear. Ericsson, therefore, proposed that her armament should be a pair of heavy guns mounted in a turret, which could be revolved so as to point them in any direction, independently of the position of the ship herself. The hull was to be formed of two portions, a kind of barge-like structure or lower hull, built of iron, and mostly under water when the ship was afloat, and fixed over this the upper hull, a raft-like structure, wider and longer, and with overhanging armoured sides and lighter deck-armour. The dimensions were-- Upper part of hull, length 172 feet, beam 41 feet. Lower hull, length 122 feet, beam 34 feet. Depth, underside of deck to keel-plate, 11 feet 2 inches. Draught of water, 10 feet. Engines and boilers were aft, and the long overhang of the armoured deck astern protected the under-water rudder and screw propeller. In the overhang at the bow there was a well, in which the anchor hung under water. Forward, near the bow, there was a small armoured pilot-house, or, as we now call it, "conning-tower." Amidships, in an armoured turret, were mounted two heavy smooth-bore guns, of large calibre, and throwing a round, solid shot. The conning-tower was built of solid iron blocks, nine inches thick. The sight-holes were narrow, elongated slits. This was the helmsman's station.