For many years Ericsson had held faith in the theory of a hot-air engine in which heated air would produce the effect of steam, but with greater economy. With characteristic confidence he carried his experiments to their completion, and expended practically his entire capital on the necessary models and machines which the working-out of his plans required. Success crowned his efforts, and the hot-air, or caloric, engine was generally conceded to be a success. As the result of these experiments a number of New York capitalists supplied the necessary money to construct a large steamship, the paddle-wheels of which were operated by caloric engines designed by Ericsson. The vessel was named after the inventor and was a most novel and radical departure from any vessel up to that time designed. Her cost exceeded half a million dollars: an investment which showed the high esteem in which her designer was held. The Ericsson was launched in September, 1852, and made her trial trip on January 4, 1853. Never had so strong or fine a ship been built; the newspapers of the day were filled with praise, and her designer received from every quarter the most extravagant congratulations for the mechanical marvel which he had created. But unexpected disaster destroyed in a few seconds the product of these months of thought and energy. Within a few weeks of her launching the Ericsson encountered a tornado, and capsized and sank a few miles off New York Light. Although she was believed by many to mark the end of the use of steam-power and the beginning of a new era of hot-air dynamics, it is now recognized that this invention reached its maximum development in the Ericsson; and it is in connection with a later and far greater invention that history has accorded recognition to the designer’s great mechanical genius. Long before Ericsson left England he had thought out the plans for a strange kind of vessel, protected with iron, which would be able to fight and defeat any warship of any size. In 1854, the year in which he perfected the plan for his new type of warship, the navies of all the great nations were composed, in large part, of huge wooden vessels, usually sailing-ships, but a few combining sails and steam. For a number of years the use of iron-plating, or armor, on the sides of battleships had been discussed, and in 1845 R. L. Stevens, an American engineer, actually began the construction of a vessel, or “floating battery,” encased in metal. To France however, probably belongs the credit for the construction of the first ironclads, consisting of these floating batteries, the Lave, Devastation, and Tonnante, protected by 4.25-inch iron plates, which were used during the Crimean War. The following year France began the construction of four ironclad steam frigates, and England immediately followed, with the construction of a number of similar vessels.