104 MOTIVE POWER OF HEAT. 



have found it equal to 550, or, to speak more 

 exactly, to 550 of our units of heat. 



Thus 0.611 units of motive power result from 

 the employment of 550 units of heat. The quan- 

 tity of motive power resulting from 1000 units of 

 heat will be given by the proportion 



550 1000 611 



whence x = -- = 1.112. 



0.611 x 550 



Thus 1000 units of heat transported from one 

 body kept at 100 degrees to another kept at 99 

 degrees will produce, acting upon vapor of water, 

 1.112 units of motive power. 



The number 1.112 differs by about J from the 

 number 1.395 previously found for the value of the 

 motive power developed by 1000 units of heat acting 

 upon the air ; but it should be observed that in this 

 case the temperatures of the bodies A and B were 

 1 degree and zero, while here they are 100 degrees 

 and 99 degrees. The difference is much the same ; 

 but it is not found at the same height in the ther- 

 mometric scale. To make an exact comparison, it 

 would have been necessary to estimate the motive 

 power developed by the steam formed at 1 degree 

 and condensed at zero. It would also have been 

 necessary to know the quantity of heat contained 

 in the steam formed at one degree. 



