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XVIII. On the Moving Force of Heat, and the Laws regarding 

 the Nature of Heat itself which are deducible therefrom. 

 By R. Clausius. 



[Concluded from p. 21.] 



CARNOT, as already mentioned, has regarded the production 

 of work as tiie equivalent of a mere transmission of heat 

 from a warm body to a cold one, the quantity of heat being thereby 

 undiminished. 



The latter portion of this assumption, that the quantity of 

 heat is undiminished, contradicts our maxim, and must there- 

 fore, if the latter be retained, be rejected. The former portion, 

 however, may remain substantially as it is. For although we 

 have no need of a peculiar equivalent for the produced work, 

 after we have assumed as such an actual consumption of heat, it 

 is nevertheless possible that the said transmission may take place 

 contemporaneously with the consumption, and may likewise stand 

 in a certain definite relation to the produced work. It remains 

 therefore to be investigated whether this assumption, besides 

 being possible, has a sufficient degree of probability to recom- 

 mend it. 



A transmission of heat from a warm body to a cold one cer- 

 tainly takes place in those cases where work is produced by heat, 

 and the condition fulfilled that the body in action is in the same 

 state at the end of the operation as at the commencement. In 

 the processes described above, and represented geometrically in 

 figs. 1 and 3, we have seen that the gas and the evaporating water^ 

 while the volume was increasing, received heat from the body A, 

 and during the diminution of the volume yielded up heat to the 

 body B, a certain quantity of heat being thus transmitted fi'om 

 A to B j and this quantity was so great in comparison with that 

 which we assumed to be expended, that, in the infinitely small 

 alterations represented in figs. 2 and 4, the latter was a difi*er- 

 ential of the second order, while the former was a differential of 

 the first order. In order, however, to bring the transmitted 

 heat into proper relation with .the work, one limitation is still 

 necessaiy. As a transmission of heat may take place by con- 

 duction without producing any mechanical effect when a warm 

 body is in contact with a cold one, if we wish to obtain the 

 greatest possible amount of work from the passage of heat be- 

 tween two bodies, say of the temperatures t and t, the matter 

 must be so arranged that two substances of different tempep- 

 tures shall never come in contact with each other. l 



It is this maximum of work that must be compared with the 

 transmission of the heat ; and we hereby find that it may reason- 



