SIR WILLIAM SIEMENS, F.R.S. 1 7 



that it would only be necessary for the condenser to work quick 

 enough to condense one cylinder-full of steam before the next 

 cylinder-full was discharged ; and this he thought would easily be 

 effected by widening the plates of the condenser to a proportionate 

 size, and shortening the stroke of the condenser piston, so as to 

 reduce its velocity as far as might be required. The condensed 

 steam would then return to the tender in pipes, between which air 

 was caused to circulate by means of the rapid motion of the 

 engine. He expected the condensing water would be cooled down 

 to about 100 before it was returned to the tender, by the process 

 of passing through the pipes of the refrigerator, from the rapid 

 motion of the engine through the air ; and the water was not re- 

 quired to be so cold as in the ordinary condenser, since only the 

 last portion of the steam was condensed by injection. 



Mr. Siemens showed by a comparative indicator diagram that 

 with the application of the condenser to a locomotive engine the 

 steam might be cut off at about one-third of the stroke, instead of 

 at two-thirds as usual, and thereby a saving of one-half the steam 

 would be effected with the same power. 



ON THE EXPANSION OF ISOLATED STEAM, AND 

 THE TOTAL HEAT OF STEAM. 



BY MB. CHAKLES "W. SIEMENS, of LONDON.* 



THE object of this paper is to lay before the members the 

 results of certain experiments on steam, purporting, in the first 

 place, to corroborate Regnault's disproval of Watt's law, "that 

 the sum of latent and sensible heat in steam of various pressures 

 is the same ; " in the second place, to prove the rate of expansion 

 by heat of isolated steam ; and, in the third place, to illustrate 

 the immediate practical results of those experiments in working 

 steam engines expansively. 



* Excerpt Minutes of Proceedings of the Institution of Mechanical Engineers, 

 1852, pp. 131141. 



VOL. I. C 



