Mechanical Theory of Heat to the Steam Engine. 27 
which contributes to increase the difference, namely: that we do 
not offer to the steam the shortest and widest possible channel 
for its passage into the atmosphere, but conduct it into the chim- 
ney, and there let it flow out through a somewhat narrow tube 
in order to produce in this way an artificial draught. 
In this case an accurate determination of the difference is im- 
portant for the reliability of the result. We must also consider 
in a term affected by the factor ¢, and therefore exerts a very 
slight influence on the value of the work, we may without fear 
put ior p, the value which is most probable for p’,. 
he pressure which takes place in the injurious space p”, de- 
pends as already mentioned upon whether the cutting off from 
the condenser takes place before or after the end of the motion 
of the piston, and may therefore vary greatly. But this pres- 
sure also, and the quantities which depend upon it, occur in equay 
fons (xtv) only in such terms as are affected with small factors 
namely, with « and w, so that we may satisfy ourselves with an 
4pproximate estimate and omit an accurate determination of this 
Pressure, In such cases, where no particular circumstances lead 
these quantities. This value may then simply be denoted by p,; 
oy the introduction of these simplifications, equations (XIV) pass 
W=* Emr —Mm,r 4+ Me(T,-Ts) + #07. -"¢(T,- 7) ] 
A 1, Mee 
: : + m,%3(P3-Po) 
(xv). Mor =m 7, +Me(T,-To) +o? o—C( T2-T 9) + Allg" o( Pa —Py) 
: + AMo(p,-p2). 
Mae _Mo"s | yt u)elog 22. 
T, = 7, + +e)elog 7 
