M.^IR,.' Ciausius on the Moving Force of Heai. 103 



ably be assumed_, with Carnot, that the work depends solely upon 

 the quantity of heat transmitted^ on the temperatures t and t of 

 both bodies A and B, and not upon the nature of the substance 

 which transmits it. This maximum has the property, that, by its 

 consumption, a quantity of heat may be carried from the cold body 

 B to the warm one A equal to that which passed from A to B during 

 its production. We can easily convince ourselves of this by con- 

 ceiving the processes above described to be conducted in a reverse 

 manner ; for example, that in the first case the gas shall be per- 

 mitted to expand of itself until its temperature is lowered from 

 t to T, the expansion being then continued in connexion with B ; 

 afterwards compressed by itself until its temperature is again t, 

 and the final compression eff'ected in connexion with A. The 

 amount of work expended during the compression will be thus 

 greater than that produced by the expansion, so that on the 

 whole a loss of work will take place exactly equal to the gain 

 which accrued from the former process. Further, the same 

 quantity of heat will be here taken away from the body B as in 

 the former case was imparted to it, and to the body A the same 

 amount will be imparted as by the former proceeding was taken 

 away from it ; from which we may infer, both that the quantity 

 of heat formerly consumed is here produced, and also that the 

 quantity which formerly passed from A to B now passes from 

 # to A. 



"^ Let us suppose that there are two substances, one of which is 

 able to produce more work by the transmission of a certain 

 amount of heat, or what is the same, that in the performance of 

 a certain work requires a less amount of heat to be carried from 

 A to B than the other; both these substances might be applied 

 alternately ; by the first work might be produced according to 

 the process above described, and then the second might be applied 

 to consume this work by a reversal of the process. At the end 

 both bodies would be again in their original state ; further, the 

 work expended and the work produced would exactly annul each 

 other, and thus, in agreement with our maxim also, the quantity 

 of heat would neither be increased nor diminished. Only with 

 regard to the distribution of the heat would a diff'erence occur, as 

 more heat would be brought from B to A than from A to B, and 

 thus on the whole a transmission from B to A would take place. 

 Hence by repeating both these alternating processes, without 

 expenditure of force or other alteration whatever, any quantity 

 of heat might be transmitted from a cold body to a warm one ; 

 and this contradicts the general deportment of heat, which every- 

 where exhibits the tendency to annul differences of temperature, 

 and therefore to pass from a warmer body to a colder one. 

 From this it would appear that we are theoretically/ justified in 



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