With a mind thoroughly pervaded by this important principle, Siemens applied himself to the study of steam and caloric engines, and saw at once that there was an enormous difference between the theoretical and the actual power gained from the heat developed by the combustion of a given quantity of coal, and hence that there was a very large margin for improvement. He at once determined to try to utilise some of this wasted heat, and he conceived the idea (to which I invite your particular attention) of making a regenerator, or an accumulator, which should retain or store a limited quantity of heat, and be capable of yielding it up again when required for the performance of any work. In the factory of Mr. John Hicks, of Bolton, he first constructed an engine on this plan; the saving in fuel was great, but it was attended by mechanical difficulties which at that time he was unable to solve. The Society of Arts, however, recognised the value of the principle by awarding him a gold medal in 1850. Three years afterwards, his paper “On the Conversion of Heat into Mechanical Effect,” before the Institution of Civil Engineers, gained him the Telford premium (awarded only once in five years) and the medal of the Institution. In 1856 he gave a lecture upon his engine at the Royal Institution, considered as the result of ten years’ experimental work, and as the first practical application of the mechanical theory of heat; he then indicated the economic considerations which encouraged him to persevere in his experiments, pointing out that the total national expenditure for steam-coal alone amounted to eight millions sterling per year, of which at least two-thirds might be saved!