264 Prof. Claudius on the Application of the Mechanical 



is to say, for a certain amount of imparted heat it famishes as 

 much work as, according to the mechanical theory of heat, is 

 possible at those temperatures. 



It is othei'wise, however, when those temperatures, instead of 

 being given, are also considered as a variable element, to be taken 

 into consideration in judging the machine. 



One uncompensated transformation not included in N, which, 

 with respect to the applicability of heat, causes a great loss, 

 arises from the fact that the liquid, during the processes of heating 

 and evaporation, has far lower temperatures than the fire, and 

 consequently the heat which is imparted to it must pass from a 

 higher to a lower temperature. The amount of work which can 

 be produced by the steam-engine from the quantity of heat 

 w,ri + Mc(Ti — To)=Qi, is, as may be seen from equation (27), 

 somewhat smaller than 



Qj t^-Tq 



A * T, ' 

 If, on the contrary, we could impart the same quantity of beat 

 Qi to a changeable body at the temperature of the fire, which 

 may be T', whilst the temperature during the abstraction of heat 

 remained Tq, as before, then by equation (4) the greatest possible 

 amount of work to be gained in such a case would be 



■M AT'- 



In order to compare the values of these expressions in a few 

 examples, let the temperature /q of the condenser be fixed at 

 50° C, and for the boiler let us assume the temperatures 110°, 

 150°, and 180° C, of which the two first correspond approxi- 

 mately to the low- and the ordinary high-pressure machines 

 respectively, and the last may be considered as the limit of the 

 temperatures hitherto employed in steam-engines. In these 

 cases the fraction dependent upon the temperatures has the fol- 

 lowing values : — 



whereas the corresponding value for the temperature of the fire 

 /', assuming the latter to be only 1000° C, is 0-746. - 



25. We may here easily discern, what has already been ex- 

 pressed by S. Carnot and several other authors, that in order to 

 render machines driven by heat more efficient, attention must be 

 particularly directed towards the enlargement of the interval of 

 temperature between Tj and Tq. 



