S12 Progress of Foreign Science. 



kilogramme of air, of which the volume, which was w at the 

 temperature 0°C., under the atmospheric pressure O^TS,^ 

 (29.92 English inches), has become 0, he represents by the 

 following formula : — 



0-26 ^0.76 ^ + 0.24 



By means of these results, he seeks to establish a relation 

 between the quantity of action (power) which it is possible to 

 obtain, in heating and dilating the air, and the quantity of 

 heat which is consumed. When the volume of the atmospheric 

 air is thus made to vary, the quantities of heat, which it ab- 

 sorbs or disengages, are proportional to the variation of the 

 specific heat. So that, calling C the primitive specific heat, 

 c the specific heat after the change of volume, we have for the 

 quantity absorbed ; a, (c C), a being a constant co-effi- 

 cient, whose value in round numbers may be stated at 1200°. 

 After a train of algebraic formulae which we cannot here insert, 

 he concludes, that in expending a degree of heat to warm the 

 air, we cannot obtain a quantity of action which surpasses the 

 elevation of a weight of 33 kilogrammes (72.8 libs.) to. 

 the height of one metre ; considering always 500° C. (= 

 932° F.) as the highest temperature to which it can be car- 

 ried. In treating of the comparative powers of heat, whea 

 employed in the vapour of water, he endeavours to shew, that 

 there is an advantage in producing the vapour at the highest 

 possible temperature. Supposing the vapour produced under 

 the pressure of 5 atmospheres; that is, let H (the elastic force 

 of the vapour) =r 3"". 8 (149.6 E inches), and V (corresponding 

 temperature =^165° C. or 329 F *. The value in this case 

 most suitable to V Ctemperature of the condensed water), as 

 may be found by calculation, would be less than 10° C. (50° F.). 

 which has been adopted for the exterior temperature v. Sup- 

 pose, however, that V =r 10° C. and of consequence H' (the 

 elastic force of vapour corresponding to^V or 10° C.) = O^.OOQS. 

 our formula will then give for the 7naximum of the quantity 

 of action which it is possible to obtain, 



123300 n kilogrammes x metres; and for the minitmim 

 of the corresponding expenditure of heat ; 685 degrees. 

 The ratio of these two numbers being 1 80, we see that by expend- 

 ing a degree of heat to produce aqueous vapour, the limit of 

 the quantity of action which it is possible to obtain, is the ele- 

 vation to one metre in height, of a weight of 180 kilogrammes 



* This temperature seems to be calculated from some erroneous for- 

 mula of the force of steam. The temperature corresponding to five atmo- 

 spheres, by Dr. Ure's experiments, is only 30b F., or 151.fa"C. 



