.V7A' \V1LUAM SIEMENS, F.R.S. 197 



" When I examined the apparatus I found the speed to average 

 fifteen revolutions per minute, and the following are the mean 

 ;tvs and horse-power indicated upon the three cylinders, 

 viz.: 



MEAN HORSE 



PBESSUBE. POWER. 



The steam cylinder according to data 



obtained from Mr. Blake . . 8'8 Ibs. 32 



Comiiressing cylinder . . . . 26'75 37'85 



Expanding cylinder with injection . 18*25 ., 2T1 



Kxpanding cylinder without injec- 

 tion 14-22 16-5 



" Theory. Before entering into a consideration of the merits 

 and defects of the apparatus in its actual condition, it will be of 

 advantage to establish generally the principles whereon its effect 

 depends. The heat which it is purposed to abstract from the 

 water is communicated to expanding air, or, in the language of 

 modern science, is converted into mechanical effect, and it can be 

 proved philosophically that a caloric engine may be devised which 

 derives its power from the latent heat of water in causing it to 

 congeal. In fact, the heat communicated by the injected solution 

 to the expanding air is a source of power to the machine, which 

 would yield both effective power and ice but for the compressing 

 cylinder, which in the arrangement described has to be worked by 

 an engine. The power expended in compressing the air produces, 

 however, its equivalent of heat, which heat would be sufficient, in 

 a philosophically perfect arrangement, to reproduce the power 

 necessarily expended by the engine, and a surplus of effective 

 power proportionate to the heat abstracted from the water would 

 be realised. 



" This view of the principle involved in your machine is novel, 

 I believe, and somewhat startling ; but I am confident it will 

 be acquiesced in by those conversant with the dynamic theory 

 of heat, and although the conditions of the ideal machine will 

 probably never be realised, it is important for our purpose to 

 know that the production of ice does not necessarily involve an 

 expenditure of power. 



" Starting, then, with the admission that the heat produced in 



