214 MR HAYCRAFT on the Specific Heat of the Gases. 



been proved to have a greater specific heat than the ingredients 

 of that composition, the phenomenon of heat being produced 

 during that combustion should not be urged as an objection to 

 the hypothesis of BLACK and CRAWFORD. Indeed it appears 

 very probable, from the inspection of the Table of Specific Heats 

 of Different Bodies, that those elastic products have a less capa- 

 city than the ingredients of gunpowder, from which they are 

 produced. For example, azote, which composes two-thirds of 

 the elastic products, has a capacity of 2669, and carbonic acid, 

 comprising one-third of the products, if my experiments are to 

 be trusted to, has a capacity of only 1751, water being 10000. 

 Nitric acid of a specific gravity of 1,1854, has a capacity of 

 5760. The azote, therefore, and oxygen, which is produced from 

 the decomposition of one of the ingredients forming the elastic 

 products of not half the specific heat of that ingredient, should, 

 according to the hypothesis of BLACK* evolve heat. This might 

 take place even if we make allowance for the lesser capacity which 

 nitric acid has in its state of one of the ingredients of the nitrate 

 of potash. 



The same condition of potential compression may also con- 

 tribute to the intense heat which takes place in a blast-furnace. 

 This heat is known by all conversant with the phenomenon to 

 be, not in a ratio of the fuel consumed, but of some compound 

 ratio. This may be explained in the following manner : 1st, A 

 quantity of air is forced into contact with the coals in a state of 

 ignition, and its temperature is suddenly raised extremely high. 

 2d, In this condition, were it not for the pressure of the atmo- 

 sphere, it would become as suddenly expanded. 3d, Had this 

 expansion taken place, it would have acquired an increased ca- 

 pacity, and would consequently have absorbed a considerable 

 portion of the caloric evolved by the combustion, tending there- 

 by to lessen the capacity of the heat. 4th, But the heated air 

 being prevented by the pressure of the atmosphere from expand- 



