The first important change from this condition followed the departure of the Confederate ironclad _Virginia_ (_Merrimac_) carrying 10 guns and 300 men from the Norfolk Navy Yard on the 8th of March, 1862, and her sinking hardly two hours afterward the Union sloop of war _Cumberland_, carrying 24 guns and 376 men; and then destroying by fire the Union frigate _Congress_, carrying 50 guns and 434 men. The second step was taken on the following day, when the Union _Monitor_, 2 guns and 49 men, defeated the _Merrimac_. These two actions on two successive days are the most memorable naval actions in history from the standpoint of naval construction and naval ordnance, and perhaps of naval strategy; because they instituted a new era--the era of mechanism in naval war. The next step was the successful attack by the Confederate "fish-torpedo boat" _David_, on the Union ironclad _Housatonic_ in Charleston harbor on February 17, 1864; and the next was the sinking of the Confederate ironclad _Albemarle_ by a spar torpedo carried on a little steam-launch commanded by Lieutenant W. B. Cushing, U. S. N., on October 27, 1864. These four epochal events in our Civil War demonstrated the possibilities of mechanism in naval warfare, and led the way to the use of the highly specialized and scientific instruments that have played so important a part in the present war. During the half-century that has intervened since the _Monitor_ and _Merrimac_ ushered in the modern era, since the five brave crews of the _David_ lost their lives, and since Cushing made his amazing victory, a contest between the sailor and the scientist has been going on, as to which shall be deemed the ultimate master of the sea. As in many contests, the decision has gone unqualifiedly to neither; for he who sails the sea and braves its tempests, must be in heart and character a sailor--and yet he who fights the scientific war-craft of the present day cannot be merely a sailor, like him of the olden kind, but must be what the _New York Times_, a few years ago, laughingly declared to be a combination quite unthinkable, "a scientific person and a sailor." Each year since the fateful 8th of March, 1862, has seen some addition to the fighting machinery of navies. Some appliances have been developed gradually from their first beginnings, and are to-day substantially what they were at first--but of course improved; among these are the turret, the automobile torpedo, the telescope-sight, the submarine, and the gyrocompass. Many other appliances found favor for a while and then, having demonstrated the value of what they attempted and did perform, were gradually supplemented by improved devices, doing the same thing, but in better ways; in this class are many forms of interior-communication apparatus, especially electrical. Still other appliances are adaptations to ship and naval life of devices used in civil life--such as the telephone, electric light, and radio.