These are some of the principal lines of work with which Ericsson occupied himself during the twenty-two years between 1839 and 1861. At the latter date came the supreme opportunity of his life, and his services in the art of naval construction during the remainder of the Civil War, which was then in progress, are a part of the history of that great struggle. Here, as with the propeller, volumes might be written in the attempt to give a full account of the inception, growth, and final vindication of Ericsson's ideas regarding naval offence and defence, as expressed by the means available in the engineering practice of the day. The leading points only can be summarized. The question of armored ships was in the air. The advantages of armor had been already demonstrated on the French ship "Gloire" and others in connection with the naval part of the Crimean War, and there was a feeling that ironclads of some kind were a necessity of the situation. These facts were perhaps more clearly realized at the South than at the North; and early in 1861 we find Mr. Stephen R. Mallory, the Confederate Secretary of the Navy, taking active steps to raise the "Merrimac," which had been sunken at the Norfolk Navy Yard, and convert her into an armor-clad. Information regarding this project naturally became known to the Federal authorities, and occasioned President Lincoln and the entire Cabinet the most serious anxiety. At length on August 3, 1861, the appointment of a Board was authorized, the duty of which it should be to examine into the question fully, obtain plans, and recommend the construction of such armor-clads as they should judge best suited to the demands of the situation.