MOTIVE POWER OF HEAT. 181 



mensely to the experimental data available for this 

 object, by giving us the means of determining with 

 considerable accuracy the values of // within a very 

 wide range of temperature, and so affording a trust- 

 worthy standard for the comparison of isolated 

 results at different temperatures, derived from ob- 

 servations in various branches of physical science. 

 In the first section of this Appendix the theory 

 is tested, and shown to be confirmed by the com- 

 parison of the values of /* found above, with those 

 obtained by Carnot and Clapeyron from the obser- 

 vations of various experimenters on air, and the 

 vapors of different liquids. In the second and 

 third sections some striking confirmations of the 

 theory arising from observations by Dulong, on 

 the specific heat of gases, and from Mr. Joule's 

 experiments on the heat developed by the com- 

 pression of air, are pointed out ; and in conclu- 

 sion, the actual methods of obtaining mechanical 

 effect from heat are briefly examined with refer- 

 ence to their economy. 



I. On the values of ju derived by Carnot and 

 Clapeyron from observations on Air, and on 

 the Vapors of various liquids. 



43. In Carnot's work, pp. 80-82, the mean 

 value of * between and 1 is derived from the 



