1813.] Specific Heat of the different Gases. 439 



experiments liable to error, we cannot draw from it a positive 

 objection against the law: but the fifth case exhibits an example 

 which appears to us perfectly decisive. The specific heat of 

 water by calculation ought to be only O'GSS.'i, while in reality it 

 is roOOO. The only part of this determination against which 

 any doubts can be raised, is the specific heat of oxygen and 

 hydrogen ga>es : but we conceive that the methods which we 

 employed were such that we could not fall into an error with 

 respect to these gases nearly so great as would be necessary to 

 make the difference between experiment and calculation disap- 

 pear; still less that the difference should be on the other side, as 

 would be necessary to make our results agree with the law of 

 Irvine. Supposing all the causes of error to have acted the same 

 way, and supposing them to exceed the limits which it is reason- 

 able to assign them, we could not raise the specific heat of water 

 by calculation higher than 0*800. It is necessary, therefore, 

 unless we deceive ourselves, to abandon the hypothesis which 

 ascribes the evolution of heat in cases of combination to a dimi- 

 nution of the specific heat in the bodies combined, and admit, 

 with Black, Lavoisier, and Laplace, and many other philoso3 

 phcrs, the existence of caloric in a state of combination in 

 bodies. The knowledge of the specific heat of oxygen alone 

 would be sufficient to induce us to adopt this opinion : for it is 

 so small that it is almost impossible for us to account for the 

 great quantity of heat disengaged during the combustion of the 

 greatest number of bodies, unless we suppose that this heat pre- 

 viously existed in a state of combination. Accordingly, when 

 the opposite hypothesis was adopted, philosophers were obliged 

 to suppose the specific heat of this gas fifteen times greater than 

 it is in reality. 



We must not suppose, however, that there exists no relation 

 between the specific heats of compounds and that of their con- 

 stituents. Too many facts prove this relation to make it possible 

 to deny it. Water, in this respect, constitutes the greatest 

 deviation which has been observed ; yet it does not exceed -!-d of 

 the specific heat of this fluid. In general, we may say that the 

 constituents of a body communicate to it their specific heat. 

 This is very observable in the combinations of hydrogen, which 

 has the highest specific heat of all known bodies. The com- 

 pounds which it forms have a much greater specific heat than 

 other bodies. Hence the great specific heat of water, of defiant 

 gas, and of animal and vegetable substances. 



Note 1st. 



We employed, to determine the quantity of beat communicated 

 to the calorimeter by the vapour tube which served to heat the 



