60 MOTIVE POWER OF HEAT. 



temperature will be also indefinitely small and un- 

 important relatively to that which is necessary to 

 produce steam a quantity always limited. 



The proposition found elsewhere demonstrated 

 for the case in which the difference between the 

 temperatures of the two bodies is indefinitely small, 

 may be easily extended to the general case. In 

 fact, if it operated to produce motive power by the 

 passage of caloric from the body A to the body Z, 

 the temperature of this latter body being very dif- 

 ferent from that of the former, we should imagine 

 a series of bodies B, C, D . . . of temperatures 

 intermediate between those of the bodies A, Z, 

 and selected so that the differences from A to B, 

 from B to C, etc., may all be indefinitely small. 

 The caloric coming from A would not arrive at Z 

 till after it had passed through the bodies B, C, D, 

 etc., and after having developed in each of these 

 stages maximum motive power. The inverse 

 operations would here be entirely possible, and the 

 reasoning of page 52 would be strictly applicable. 



According to established principles at the present 

 time, we can compare with sufficient accuracy the 

 motive power of heat to that of a waterfall. Each 

 has a maximum that we cannot exceed, whatever 

 may be, on the one hand, the machine which is 

 acted upon by the water, and whatever, on the 



