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



of the receiver had acquired a temperature of nearly 54°, and 

 the water not so much. This experiment shows, that though 

 heat is evolved in the combustion of gunpowder, its quantity 

 is not nearly so great as has been imagined. Again, if we 

 consider that the products of the combustion of gunpowder 

 have not, by direct experiment, been proved to have a greater 

 specific heat than the ingredients of that composition, the phe- 

 nomenon 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 capacity than the in- 

 gredients of gunpowder, from which they are produced. For 

 example, azote, which composes two-thirds of the elastic pro- 

 ducts, 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 J , 1354- 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 : 1 st, 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 

 capacity, and would consequently have absorbed a considerable 

 portion of the caloric evolved by the combustion, tending 

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

 air being prevented by the pressure of the atmosphere from 

 expanding in a ratio equal to the temperature acquired, the 

 absorption of caloric is lessened, and a greater proportion of 

 the heat of combustion is rendered free. Thus, although the 

 total quantity of caloric evolved at, and consequently to com- 

 bustion, may be in a direct ratio of the quantity of fuel con- 

 sumed ; yet the intensity of the thermometrical heat at the mo- 

 ment, 



