Mr. Haycraft on the Specific Heat of the Gases. 269 



ment, and at the place of combustion, will be greater in a com- 

 pound ratio, directly as the pressure of the atmosphere, and 

 inversely as the times of expansion 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 compound ratio of the 

 quantity 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 Fur- 

 naces ; and it is ascertained by experience, that those furnaces 

 of steam-engines through which a greater quantity 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 forma- 

 tion of the latter by combustion. This formation does not 

 consist of a conversion of oxygen into carbonic acid, but of a 

 union of two ingredients into a compound, having an absolute 

 capacity for caloric 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 show, that the spe- 

 cific heats of all the gases experimented upon are to each other 

 inversely as their specific gravities ; and, 2dly, That different 

 states of combinations of the gases with aqueous and other 

 vapours, affect the capacities of the gases, and that probably, 

 in some instances, in a regular arithmetical progression, cor- 

 responding with the arithmetical rate of expansive force of the 

 gases in different states of combination with vapour. The 

 most interesting result to the physiologist is, that the air of 

 respiration, at a temperature of between 100^° and 95°, has a 

 less specific heat than atmospherical air. Many experiments 

 were made which are not here detailed, which showed that 

 the air of respiration, at the temperature of 102° and upwards, 

 and of 91° and downwards, had a capacity the same as that 

 of atmospherical air. I should feel a hesitation in stating 

 these results, had not experiments, very often repeated, during 

 a course of several months, warranted me in my conclusions. 



XLV. An 



