CARNOT S THEORY OF THE MOTIVE POWER OF HEAT. 



565 



elusion, the actual methods of obtaining mechanical effect from heat are briefly 

 examined with reference to their economy. 



I. On the values of fx derived by Camot and Clapeyron from observations on Air, and on the 



Vapours of various liquids. 



43. In Caenot's work, p. 80-82, the mean value of /i between 0° and 1° is 

 derived from the experiments of Delaroche and Beraed on the specific heat of 

 gases, by a process approximately equivalent to the calculation of the value of 



f for the temperature \°. There are also, in the same work, determinations 

 dv 

 of the values of ^ from observations on the vapours of alcohol and water; but a 

 table given in M. Clapeyeon's paper, of the values of [x derived from the data 

 supplied by various experiments with reference to the vapours of ether, alcohol, 

 water, and oil of turpentine, at the respective boiling-points of these liquids, afford 

 us the means of comparison through a more extensive range of temperature. In 

 the cases of alcohol and water, these results ought of course to agree with those of 

 Caenot. There are, however, slight discrepancies which must be owing to the 

 uncertainty of the experimental data.* In the following table, Caenot's results 

 with reference to air, and Clapeyeon's results with reference to the four different 

 liquids, are exhibited, and compared with the values of fx which have been given 

 above (Table I.) for the same temperatures, as derived from Regnault's observa- 

 tions on the vapour of water. 



44. It may be observed that the discrepancies between the results founded on 

 the experimental data supplied by the different observers with reference to water 

 at the boiling-point, are greater than those which are presented between the re- 

 sults deduced from any of the other liquids, and water at the other tempera- 

 tm-es ; and we may therefore feel perfectly confident that the verification is com- 



* Thus, from Cabnot's calculations, we find, in the case of alcohol, 4-035 ; and in the case of 

 water, 3-648, instead of 3 963, and 3-658, which are Clapetiiow''s results in the same cases. 



VOL. XVI. PAET V. 7 G 



