Disappointed in his ill success with inventions pertaining to locomotives, Ericsson now turned his attention to his early flame-engine, and the working model of a caloric engine of five-horse power soon attracted the attention of London. At first there seemed to be a great future for engines upon this principle, but after many years of experiments, at great expense, Ericsson found that the principle was useful only for purposes requiring small power. In 1851 he built a heat-engine for the ship Ericsson, a vessel two hundred and sixty feet in length, and tells the result as follows: "The ship after completion made a successful trip from New York to Washington and back during the winter season; but the average speed at sea proving insufficient for commercial purposes, the owners, with regret, acceded to my proposition to remove the costly machinery, although it had proved perfect as a mechanical combination. The resources of modern engineering having been exhausted in producing the motors of the caloric ship, the important question, Can heated air, as a mechanical motor, compete on a large scale with steam? has forever been set at rest. The commercial world is indebted to American enterprise for having settled a question of such vital importance. The marine engineer has thus been encouraged to renew his efforts to perfect the steam-engine without fear of rivalry from a motor depending on the dilation of atmospheric air by heat." [Illustration: Solar-engine Adapted to the Use of Hot Air. (Patented as a pumping-engine, 1880.)]