While he was making all these machines he was also experimenting with designs for a caloric engine. His researches in this direction were begun with the “flame engine” already mentioned. He contributed a paper on the subject to the English Institution of Civil Engineers in 1826; built three engines in 1827 based on the principle of the expansion of air; brought out a completed caloric engine in 1833, to which he applied improvements as his investigations continued; received the Rumford medal in 1856 for his researches into the nature of heat; and, according to Mr. Church, spent in thirty years, including the engines for his caloric ship, more than a quarter of a million dollars in building twenty-seven experimental engines. The caloric system was not successful when applied to the propulsion of large vessels like the Ericsson, although that vessel registered a speed of eight and attained at one time a speed of eleven miles an hour, but for lighter work it has proved very practicable and efficient; the smaller machines have been extensively used, and the inventor derived large profits from them.
The first experiment with the screw propeller was made in 1836 by Captain Ericsson, in conjunction with his friend Francis B. Ogden, of New Jersey, United States consul at Liverpool. A model of the apparatus was built and tested in a public bath. Then a boat forty feet long, propelled by a double screw, attained a speed of ten miles an hour on the Thames. The Lords of the Admiralty were passengers on the trial trip; but seeing was not believing with them, and, while they witnessed the successful performance of the craft, they declared that no vessel could be steered if the power was applied at the stern, and would have nothing to do with it. Captain Robert J. Stockton, of New Jersey, afterward United States Senator, was visiting England at the time on business connected with the Delaware and Raritan Canal, and, witnessing the performance of the propeller vessel, ordered one built for himself and named after him. It was sent across the Atlantic, and when it reached New York the freedom of the city was given to its captain. This vessel was employed for many years in the waters of the United States, and, passing into the possession of the Messrs. Stevens, of Hoboken, N. J., was known as the tug New Jersey till 1866, when, or about that time, it was broken up.
On the invitation of Captain Stockton, Captain Ericsson resigned, in 1839, the position of Superintending Engineer of the Eastern Counties Railroad in England, and removed to the United States. By the aid of Captain Stockton's influence he obtained a commission to build a steam-propeller frigate, the Princeton, for the United States Navy. Before this vessel was finished, in 1844, his screw had been placed in forty-one commercial vessels of the