28 R. Clausius on the Application of the 
42. It is assumed in these equations that beside the masses ¥, 
and m,, of which the first two must be known by direct 
observation, and the last two can be determined approximately 
from the magnitude of the injurious space, the four pressures 
Pir Pos Pas Pos or What is the same, the four temperatures Pi 
T,, T,, T,, are given. This condition 4 is however only partially 
fulfilled for the cases which occur in practice, and we must 
therefore take other data to assist us in the calculation. 
Only two of these four pressure-forces are to be supposed as 
known, namely p, and p,, the first of which is given immedi- 
ately by the boiler pressure-guage, and the last may be inferred, 
at ideas approximately, from the sadioxtions of the condenser- 
guage. ‘lhe two others, p, an , are not given, but instead 
of them we know the dimensions of the cylinder, and at what 
ition of the piston the cut-off from the boiler takes place. 
Goon this we may deduce the volumes which the steam in the 
cylinder takes up at the moment of the cut-off and at the end of 
the expansion, and these two volumes oor therefore take the 
place, as data, of the pressure-forces p, >, 
e have now to bring the e ectionne! into such a form that 
we on execute the calculation by means of these data. ; 
et us again denote, as in setting forth Pambour’s theory, 
the whole space which becom es free in the cylinder during one 
stroke, Pon ey the injurious space, by v’, the space which be- 
comes free up to the cutting-off from the boiler, by cv’, and the 
peanrichy sai by ev’. Then we have, according to what has 
y been naif the equations 
ma © ‘at (M+u)o = ev" 
mata t(ItH) 0 
oMotee= ew: 
The quantities wif’ o are both so small that we may neglect 
their product, so that we have 
My Uy —ev’ —Mo 
(45) mt. — 
‘a hoa 
Furthermore, according to equation (v1) we have 
Tug, 
if we omens the letter g for the differential co-efficient 77, sf 
tions by wu, and u,. on the sgilies m, and m, occur only in 
the products Ms, u. ea m, u,, and for for these us may stake 
