100 MOTIVE POWER OF HEAT. 



If we carry out the indicated multiplications, we 

 find the value of the product to be 0.000000372. 



Let us endeavor now to estimate the quantity of 

 heat employed to give this result ; that is, the 

 quantity of heat passed from the body A to the 

 body B. 



The body A furnishes : 



(1) The heat required to carry the temperature 

 of one kilogram of air from zero to 0.001; 



(2) The quantity necessary to maintain at this 

 temperature the temperature of the air when it 

 experiences a dilatation of 



TTTT ~T 



The first of these quantities of heat being very 

 small in comparison with the second, we may dis- 

 regard it. The second is, according to the rea- 

 soning on page 74, equal to that which would be 

 necessary to increase one degree the temperature 

 of one kilogram of air subjected to atmospheric 

 pressure. 



According to the experiments of MM. Delaroche 

 and Berard on the specific heat of gases, that of 

 air is, for equal weights, 0.267 that of water. If, 

 then, we take for the unit of heat the quantity 

 necessary to raise 1 kilogram of water 1 degree, 



