
iw) 
=I 
i) 
DYNAMICAL THEORY OF HEAT. 
39. Supplementary Table of the Motive Powers of Heat. 





Til. IV. VG VI. 
Range of Temperatures. buy Quantit 
uanti 3 
Duty of a Unit Tee Bee Quantity 



of Heat through | feat sup- || converted of Heat 
IL the whole range. plied from || into mecha- wasted. 
the source, || nical effect. 
8 
Ss T fe mal ae Ww e==)R) R 
Ft.-lbs. Ft.-lbs. 


coooococo So 





40. Taking the range 30° to 140° as an example suitable to the circumstances 
of some of the best steam-engines that have yet been made (See Appendix to 
Account of Carnot’s Theory, sec. v.), we find in Col. III. of the supplementary 
Table, 377 ft.-lbs. as the corresponding duty of a unit of heat instead of 440, 
shewn in Col. HI., which is Carnor’s theoretical duty. We conclude that the 
recorded performance of the Fowey-Consols engine in 1845, instead of being only 
574 per cent. amounted really to 67 per cent., or 2 of the duty of a perfect engine 
with the same range of temperature ; and this duty being ‘271 (rather more than 
4) of the whole equivalent of the heat used; we conclude farther, that a or 18 
per cent. of the whole heat supplied, was actually converted into mechanical 
effect by that steam-engine. 
41. The numbers in the lower part of the supplementary Table shew the great 
advantage that may be anticipated from the perfecting of the air-engine, or any 
other kind of thermodynamic engine in which the range of the temperature can 
be increased much beyond the limits actually attainable in steam-engines. Thus 
an air-engine, with its hot part at 600°, and its cold part at 0° cent., working with 
perfect economy, would convert 76 per cent. of the whole heat used into mechani- 
eal effect; or working with such economy as has been estimated for the Fowey- 
Consols engine, that is, producing 67 per cent. of the theoretical duty correspond- 
ing to its range of temperature, would convert 51 per cent. of all the heat used 
into mechanical effect. 
42. It was suggested tome by Mr Joute, in a letter dated December 9, 1848, 
