realizing the Advantages of the Air-Engine. 31 



site supply of air at the ordinary atmospheric pressure, and 

 the engine was consequently of enormous bulk and weight as 

 compared with its power. 



To proceed to the process D : It consisted in compressing 

 the air with which the compressing cylinder had been filled to 

 about two-thirds of its original volume, and forcing it into a 

 receiver or magazine for compressed air. There was no pro- 

 vision in the compressing cylinder for abstracting the heat 

 produced by the compression, and a certain waste of power 

 must have arisen from this cause, which will be again referred 

 to in its order. 



The process A consisted in opening the induction-valve of the 

 expanding cylinder, and filling that cylinder about two-thirds 

 full of the compressed air. In the act of entering the ex- 

 panding cylinder, the air passed through the regenerator 

 which was fixed in the nozzle, and, receiving the heat stored 

 up there, had its temperature elevated. On the admission of 

 the proper quantity of air, the induction-valve was closed. 



The process B consisted in the expansion of the air in the 

 expanding cylinder, the latent heat being supplied from a 

 furnace placed directly beneath the bottom of that cylinder. 



The process C was then recommenced by opening the educ- 

 tion-valve, to allow the hot air to escape through the regene- 

 rator, and so on, as before. 



23. Efficiency of Ericsson's Engine of 1852. — In calcu- 

 lating the efficiency of this engine, I have been guided chiefly 

 by data contained in the report of Professor Norton (regarding 

 him as a neutral inquirer). As nearly as I can judge, the ef- 

 ficiency of a theoretically perfect engine, working between the 

 same temperatures, would be 0-404, corresponding to a con- 

 sumption of 0*82 lb. of coal per horse-power per hour. Ac- 

 cording to Professor Norton, the actual consumption was 1*87 

 lb. of anthracite, being equivalent to 2-8 of bituminous coal, if 

 3 lb. of bituminous coal of the quality specified in this paper 

 be taken as equivalent to 2 lb. of anthracite. This is about 

 3-4 times the consumption of a theoretically perfect engine, 

 and corresponds to an actual efficiency of 0*118, being less 

 than the maximum theoretical efficiency in the ratio of 0*295 

 to 1. The waste of heat and power, therefore, in Ericsson's 



