S/A' WILL1 'AM SIEMENS, F.K.S. 49 



used to effect a stroke of the engine could be wholly recovered, 

 except accidental losses, and that, theoretically, it involved the 

 accomplishment of a perpetual motion. Others, on the contrary, 

 contended that the regenerator was only an obstruction to the 

 passage of the air, and of no utility whatever. He had endea- 

 voured to prove in his paper, that neither the one extreme view, 

 nor the other was correct ; that, indeed, the respirator might be 

 usefully employed, to recover that portion of heat which presented 

 itself at the exhaust part of the engine, in the form of free, or 

 sensible heat, but that neither the respirator, nor any other 

 possible contrivance, could recover the heat that was lost in the 

 expansion of the air behind the working piston. He had adopted 

 the new " dynamical theory of heat " for his argument, because 

 that theory enabled him to calculate the absolute quantities of 

 heat, that must inevitably be sacrificed, to produce a given 

 mechanical effect, and to separate the same from the other and 

 much larger quantity, that served only to form the elastic 

 medium behind the working piston, and which might be 

 recovered, by means of a respirator, unless, as he had shown in 

 the paper, it was all converted into power, by the expansive 

 action being carried to its last (but impracticable) limits. 

 Ericsson himself seemed to incline to the idea, that he could 

 recover the whole of the heat by means of his " regenerator," for 

 it would be difficult otherwise to account for the extraordinary in- 

 sufficiency of heating surface he had provided. Mr. Siemens could 

 speak confidently as to the mechanical efficiency of action of the 

 respirator, having applied a precisely similar contrivance to a 

 steam-engine of his design, some years previously. 



Mr. Siemens agreed with Mr. Hawksley's proposition, that an 

 engine of his proportions could not give out any power. The 

 valve between the two cylinders in Ericsson's engine was as 

 necessary as it was between the boiler and cylinder of an ordinary 

 steam-engine, and could not be replaced by the regenerator, 

 which had a very different office to fulfil. Ericsson's engine 

 might indeed be compared to a steam-engine, in which the boiler 

 was represented by the air-chamber between the two cylinders, 

 and the feed-pump by Ericsson's pumping cylinder. Ericsson 

 had the disadvantage of sacrificing two-thirds of his power to 

 move the pump, but had the advantage of expending no latent 



VOL. I. E 



