MR HAYCRAFT on the Specific Heat of the Gases. 215 



ing in a ratio equal to the temperature acquired, the absorption 

 of caloric is lessened, and a greater proportion of the heat of com- 

 bustion is rendered free. Thus, although the total quantity of 

 caloric evolved at, and consequently to combustion, may be in a 

 direct ratio of the quantity of fuel consumed ; yet the intensity 

 of the thermometrical heat at the moment, and at the place of 

 combustion, will be greater in a compound ratio, directly as the 

 pressure of the atmosphere, and inversely as the times of expan- 

 sion of the air employed in the blast. These times are, of course, 

 inversely as the intensity of the blast. The thermometrical heat, 

 then, at the moment and place of combustion, will be in a com- 

 pound ratio of the quantities of fuel consumed, the weight of the 

 atmosphere, and the quantity of air employed in the blast in a 

 given time. The same rule will hold even in what are called 

 Chimney Furnaces ; and it is ascertained by experience, that 

 those furnaces of steam-engines through which a greater quan- 

 tity of air passes in a given time, consume a proportionally less 

 quantity of fuel to produce the same effect. Probably blast- 

 furnaces might be advantageously employed in lessening the 

 quantity of fuel used for those valuable machines. 



Although, according to the foregoing experiment, it appears 

 contrary to my original expectation, that, by volume, oxygen gas 

 has the same specific heat as carbonic acid, it by no means follows 

 that caloric should not be evolved during the formation of the 

 latter by combustion. This formation does not consist of a con- 

 version of oxygen into carbonic acid, but of a union of two in- 

 gredients into a compound, having an absolute capacity for calo- 

 ric equal to one of the ingredients only, namely, the oxygen gas ; 

 consequently the whole absolute heat of the carbon is rendered 

 free. 



The direct results of these experiments shew, that the speci- 

 fic heats of all the Gases experimented upon, are to each other 



