Some interesting experiments were also carried out in February 1863 with a steamer called the _Edith_, built by Dudgeon with a view to testing further, for the benefit of the Admiralty, whose representatives were present, the advantages of the twin-screw for naval manœuvring purposes. This vessel was not constructed for the Navy, however, but for commercial service across the Atlantic. She was rather larger than the _Experiment_, being 175 feet in length, 25 feet in breadth, and drawing 9 feet aft and 6 feet 6 inches forward. The twin-screws, each driven by its own engine, were three-bladed and had a diameter of 8 feet 6 inches, and a pitch of 16 feet. On her trial run down the river with the Admiralty officials on board, a speed was attained of nearly 12 knots against the tide, and nearly 15 knots with the tide, the engines averaging 100 revolutions a minute under 28 lb. steam-pressure. The vessel turned a complete circle in 3 minutes 29 seconds with her own centre as a pivot, and then the action of both screws was suddenly reversed. Their action upon the vessel was instantaneous, the revolving motion of the ship being changed to the opposite direction with the greatest ease. The manœuvre was repeated several times, and the vessel thus represented a revolving battery mounted with heavy ordnance, too heavy for training upon any given object by ordinary appliances. The hull became the carriage for such heavy guns, and trained them upon any given point by revolving under the action of the screws alone. [Illustration: _Photo. G. West & Son._ THE “KOENIG WILHELM,” GERMAN NAVY.] [Illustration: _Photo. G. West & Son._ THE “BADEN,” GERMAN NAVY.] The American Navy up to the time of the Civil War was not taken into very serious consideration by the other nations, but in that momentous struggle the Federals awoke to the need of thoroughly effective vessels and built them quickly. They were the last to take to iron ships of war but they more than made up for the delay. In scarcely a year after the launch of Ericsson’s _Monitor_, the first ship of its class possessed by the Federal Government, there were built, or building, close upon twenty of these vessels. Various modifications were introduced but the principle was the same. This was the turret on the deck, where the armament of the vessel was placed, it being sought to construct an effective battery for defensive operations rather than to build a sea-going ship. The contest between the Confederate iron protected _Merrimac_ and the Federal wooden warships, which ended disastrously for the latter, and the battle between the _Monitor_ and the _Merrimac_ proved that the old wooden three-deckers had become obsolete and that they would be perfectly useless against a steam ram like the _Merrimac_ and harmless against an ironclad ram like the _Monitor_.