OF GASES AND VAPOURS. 217 
ab ly aty 2 Pal 
Te igkiate ak(t, —¢,), 
or, with the above determined values of a, 6, « and k, 
BSG tA BE cris ips 
Soe 52°14 (¢, — 7), - - (7.) 
where the temperatures are reckoned from 0° Cent. 
41. If after this expansion the steam is condensed at ¢, degree, 
the duty thereby lost, as in No. 39, is equal to 
488000 . log Briggs 
5» (12300 + 52°L . ta), 
in which p, and p, hee forces of expansion of the steam of ¢, 
and ¢, degrees. From (5.), (7.), and this expression, finally the 
duty of the steam-engine with expansion and condensation for 
1 kilogramme of steam, is equal to 
12300 + 521. t, + 488000 . log 726 + 4 
236 + ty 
sa (12300 + 52°1.¢,) = 
st te ey ee 
oes + - oe 
For an engine in which the steam had ee ey pate 
rature 140° (34 atmospheres), then by expansion falls to 40°, 
and is also condensed at this temperature, we obtained the theo- 
retical duty for 1 kilogramme of the produced steam equal 
65450 kilometres. 
There has been obtained with high pressure with expansion 
and condensation the duty 19800*™ from 1 kilogramme of coals, 
therefore for 1 kil. steam about 3th of this, or 33000", which is 
somewhat more than the half of the theoretical maximum just 
calculated. But even this theoretical maximum is only the 
259400, or about the fourth part of the duty which the heat 
absorbed by the water should yield. 
A far greater portion of the motive force of the heat is likewise 
obtained with these engines on employing steam of very high 
temperature. 
= (12300 + 52°1 . t,) { oe Ba} + 488000 . log 7 
