MOTIVE POWER OF HEAT. 201 



With reference to the cases (3), (4), (6), (7), the 

 hypothesis of Table B is probably in general nearer 

 the truth than that of Table A. In (4), (6), and 

 (7), especially upon hypothesis B, there is much 

 uncertainty as to the amount of evaporation that 

 will be actually produced by 1 Ib. of fuel. The 

 assumption on which the numbers in the second 

 column in Table B are calculated, is, that each 

 pound of coal will send the same number of units 

 of heat into the boiler, whether hypothesis A or 

 hypothesis B be followed. Hence, except in the 

 case of the French contract, in which the evapora- 

 tion, not the fuel, is specified, the numbers in the 

 third column are the same as those in the third 

 column of Table A. 



