26 R. Clausius on the Application of the 
of the steam from the cylinder into the condenser and include 
this in VN. By this calculation, which I will not here actually 
execute, we arrive completely at the expression given in (XIV) 
for the work. 
40. In order now to be able to apply the equations (XIV) to a 
numerical calculation, it is first necessary to determine more 
nearly the quantities p’,, p’, and p”,. ; 
No generally valid law can be established as to the manner 1n 
which the pressure changes in the cylinder during the influx, 
because the opening and closing of the steam pipe takes place 
in different machines in different ways. 
a 
_ If, however, we do not restrict ourselves to bring into calcula- 
tion precisely the end of the time necessary for closing, as the 
moment of the cut-off, but allow some liberty in fixing this mo- 
We may therefore accept this modification of Pambour’s assump- 
tion that p’,=p,, whereby, however, it remains reserved for es- 
pecial consideration for each particular case, to determine cor- 
rectly the period of the cut-off, with reference to the prevailing © 
circumstances of the case. 
41. With respect to the counter pressure p’, which takes place 
during the return of the piston, the difference p’,—p, is evi- 
dently smaller under otherwise equal circumstances, the smaller 
p, is. It will therefore be smaller in machines with condensers 
than in machines without condensers in which p, is equal to one 
atmosphere. In the most important machines without condens- 
ers, the locomotives, a particular circumstance u occurs 
