THE 



EDINBURGH NEW 



PHILOSOPHICAL JOURNAL. 



On the Means of realizing the Advantages of the Air-Engine. 

 By William John Macquorn Eankine, Civil Engineer, 

 F.R.SS. Lond. and Edin., &c* 



Section I. Summary of the Laws of the Mutual Relations 

 of Heat and Mechanical Power, and of the Theoretical 

 Efficiency of Thermo-Dynamic Engines. 



1. The principal object of this paper is to explain the ad- 

 vantages of certain improvements in air-engines, and the 

 reasons for believing that, with these improvements, such 

 engines will be found to be the most economical means of 

 developing motive power by the agency of heat. For this 

 purpose, it is necessary, in the first place, to state briefly the 

 general principles which have been established by the joint 

 agency of reasoning and experiment respecting the mutual 

 relations of heat and motive power, and which are applicable 

 to steam, air, and all substances whatsoever. 



It is a matter of ordinary observation, that heat, by ex- 

 panding bodies, is a source of mechanical power ; and con- 

 versely, that mechanical power, being expended either in 

 compressing bodies, or in producing friction, is a source of 

 heat. 



* Read to the British Association for the Advancement of Science, Section G, 

 at Liverpool, September 1854. 



VOL. I. NO. I. — JAN. 1855. A 



