Progress of Foreign Science. 313 



(368.56 lbs, avoirdupois), supposing the steam generated un- 

 der the pressure of five atmospheres *. 



From these results the theoretic limits of the quantities of 

 action which it is possible to obtain in heating air, or water, 

 are nearly to each other in the proportion of 33 to ISO ; or of 

 1 to 5^. The difference is so considerable, that, notwithstand- 

 ing the uncertainty which may exist in some of the preceding 

 numerical values, the preference due to steam appears to be, in 

 no respect, doubtful. 



But steam engines present always a very considerable abate- 

 ment under the theoretic maximvm of effect, now computed. 

 It appears that the best steam engines, possessing the average 

 power of ten horses, consume 2^ kilogrammes (5^- lbs. 

 avoirdupois) of charcoal (coal?) to obtain a quantity of action, 

 equal to 28800 k. x m. Admitting that a kilogramme of 

 charcoal consumed in the calorimeter gives 7000° of heat, we 

 see that we obtain, for one degree of heat, only a quantity of 



action =28800 ^r>,^■^ . t i • e 

 = lb. 5 kilog. X met. ; which is very lar 



from the limit 180 k x m. found above. It would be im- 

 portant to investigate and to appreciate exactly the causes of 

 this considerable loss. We hope to see many of these import- 

 ant problems, referred to by M. Navier, treated in a clear and 

 conclusive manner, in M. Clement's new Treatise, Theoretical 

 and Practical, on Heat, and its applications to the Arts. 



We are indebted to M. Navier, also, for an ingenious me- 

 moir, in the same number of the Annales, on the variation of 

 temperatures, which accompanies the changes in the volume of 

 gases. His reasoning is founded on the experiments of M. M. 

 Clement and Desormes, Delaroche, and Berard. From his for- 

 mula; it appears, that on reducing the volume of air to A, so 

 that the pressure becomes 149.6 E inches, we can obtain an ele- 

 vation of temperature of about 237° C. (426.6 F.) 



It further appears, from his mode of research, that the rise 

 of temperature obtained by the condensation of atmospheric air, 

 is susceptible of a limit, somewhat confined. The formula gives 

 360° C. as the maximum effect. As to the cold producible by 

 the dilatation of air, the formula does not assign it any limit. 



M. Flaugergues, the astronomer, has made, at the Observa- 

 tory of Viviers, a scries of nice observations on the heat pro- 

 duced by the sun's rays, during the eclipse of this luminary, 



* The formulae for the maximum is, 

 „ ,^ n I + 0.0037.^ V , H 



'■ ' oIsF* TsTS ^^'TT' wl»ere"'='3568 k = the 



weight of the metre cube of mercury. The other formulary iii 

 n (.V100 + V — \"). 

 Vol. XII. Y 



