and in the Condensation of Vapours. 411 



Upon examining the subject attentively, we shall 

 find, however, reasons for thinking that the capacity of 

 steam for heat ought necessarily to be diminished with 

 the increase of its temperature. The following calcula- 

 tions may serve to elucidate this subject. 



In order to determine the highest degree of tempera- 

 ture which can exist in the midst of the greatest fire 

 when pure hydrogen is the only combustible employed 

 and when the fire is fed by atmospheric air, it is necessary 

 to remark that, as oxygen and nitrogen are intimately 

 mixed in the atmosphere, the heat which results from 

 the combustion of hydrogen ought to be immediately 

 divided between the vapour which results from the 

 union of the hydrogen with the oxygen, and the ni-tro- 

 gen which is found necessarily mixed with this vapour. 



In order to simplify our inquiry, we shall commence 

 by supposing that all the oxygen which exists in the 

 atmospheric air is employed. 



In this case, as it requires 7.3333 pounds of oxy- 

 gen to be united to i pound of hydrogen in order to 

 compose 8.3333 pounds of steam, and as the atmos- 

 pheric air is composed of 21 pounds of oxygen gas 

 mixed with 79 pounds of nitrogen, the 7.3333 pounds 

 of oxygen which are united to i pound of hydrogen in 

 order to form 8.3333 pounds of steam, ought to be 

 found mixed with 27.587 pounds of nitrogen ; conse- 

 quently the heat developed in the combustion of i 

 pound of hydrogen ought to be also divided between 

 8.3333 pounds of steam and 27.587 pounds of nitro-' 

 gen ; and this partition ought to take place in the 

 direct ratio of the weights of these two fluids, and 

 of their capacity for heat. 



The capacity of the steam being to that of nitrogen 



