THE CONQUEST OF NATURE 



sarily some loss through dissipation of heat. Dr. 

 Stirling's practical engine had its uses, but could not 

 compete with the steam engine in the general field of 

 mechanical operations to which that apparatus is 

 applied. 



Another important practical experimenter in the con- 

 struction of hot-air engines was John Ericsson, who 

 in 1824 constructed an engine somewhat resembling 

 the early one of Cayley, and in 1852 built caloric engines 

 on such a scale as to be adapted to the propulsion of 

 ships. Notwithstanding the genius of Ericsson, how- 

 ever, engines of this type did not prove commercially 

 successful on a large scale, and in subsequent decades 

 the hot-air motors constructed for practical purposes 

 seldom exceeded one horse-power. Such small engines 

 as these are comparatively efficient and absolutely safe, 

 and they are thoroughly adapted for such domestic 

 purposes as light pumping. 



The great difficulty with all these engines operated 

 with heated air has been, as already suggested, that 

 their efficiency of action is limited by the difficulties 

 incident to applying high temperatures to large masses of 

 the gas. There is, however, no objection to the super- 

 heating of small quantities of gas, and it was early sug- 

 gested that this might be accomplished by exploding a 

 gaseous mixture within a cylinder. It was observed 

 by the experimenters of the seventeenth century that an 

 ordinary gun constitutes virtually an internal-com- 

 bustion engine; and such experimenters as the Dutch- 

 man Huyghens, and the Frenchmen Hautefeuille and 

 Papin, attempted to make practical use of the power set 



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