124 MOTIVE POWER OF HEAT. 



ever, that 1000 may be this limit, and we shall 

 certainly be below the truth. As to the tempera- 

 ture of the refrigerant, let us suppose it 0. We 

 estimated approximately (page 104) the quantity of 

 motive power that 1000 units of heat develop be- 

 tween 100 and 99. We found it to be 1. 112 units 

 of power, each equal to 1 metre of water raised to 

 a height of 1 metre. 



If the motive power were proportional to the 

 fall of caloric, if it were the same for each ther- 

 mometric degree, nothing would be easier than to 

 estimate it from 1000 to 0. Its value would be 



1.112 X 1000 = 1112. 



But as this law is only approximate, and as pos- 

 sibly it deviates much from the truth at high tem- 

 peratures, we can only make a very rough estimate. 

 We will suppose the number 1112 reduced one-half, 

 that is, to 560. 



Since a kilogram of carbon produces 7000 units 

 of heat, and since the number 560 is relatively 

 1000 units, it must be multiplied by 7, which gives 



7 X 560 = 3920. 



This is the motive power of 1 kilogram of carbon. 

 In order to compare this theoretical result with 



