The extent of power attainable by this machine, consistently with its application to practical uses, is not yet precisely defined. Within the limit thus far given to it, its power is certain, uniform, and entirely sufficient. It is not attended with the numerous perils that make the steam-engine so uncomfortable a servant, but is absolutely free from danger. It requires no engineering supervision. It consumes a very small amount of fuel (about one-third of the amount required by the steam-engine) and requires no water. These peculiarities not only make it a very desirable substitute for the steam-engine, but render it available for many purposes to which the steam-engine would never be applied. In addition to his regular professional avocations, Ericsson was industriously occupied in devising new applications of the Calorie-Engine, when the attempted secession of the Southern States plunged the country into the existing war and struck a blow at all the arts of peace. Ills whole heart and mind were given at once to the support of the Union. Liberal in all his ideas, he is warmly attached to republican institutions, and has a hearty abhorrence of intolerance and oppression in all their forms. His early military education and his long study of the appliances of naval warfare increased the interest with which he watched the progress of events. The abandonment of the Norfolk navy-yard to the Rebels struck him as a disgrace that might have been avoided. He foresaw the danger of a formidable antagonist from that quarter in the steamship which we had so obligingly furnished them. The building of gun-boats with steam-machinery _above_ the water-line--where the first shot from an enemy might render it useless--seemed to him, in view of what he had done and was ready to do again, a very unnecessary error. Knowing thoroughly all the improvements made and making in the war-steamers of England and France, and feeling the liability of their interference in our affairs, he could not appreciate the wisdom of building new vessels according to old ideas. The blockade of the Potomac by Rebel batteries, in the very face of our navy, seemed to him an indignity which need not be endured, if the inventive genius of the North could have fair play.