n 



a fair statement, for the tendency of the errors hi that apparatus is 

 to diminish the result. Dalton's trial was jnade by a very inarti- 

 ficial method, and therefore is entitled to less confidence. Reck- 

 oning the caloric which is absorbed in the fiision of ice to be = 140°. 

 C t =14000, N and P are known by the experiments of Laroche 

 and Berard, (e) and C though with less certainty, by a mean of the 

 numbers of Crawford and Gadolin, the first makes it .27, the other 

 .39, .3 may be taken as a fair average, and our equation will give U3 

 S=4575". If the fire were blown by pure oxygen as N n disap- 

 jjears from the denominator, it would be 6 times as great. ( /") 



Two objections may be urged against this determination, one de- 

 rived from theory and one from observation, the first is that I have 

 supposed the capacities permanent, while there is every reason to 

 suppose that they cliange with the temperature. Admitting to a cer- 

 tain degree the truth of this, it does not affect my conclusion, for 

 the numerator of the fraction 6 is independent of the temperature, 

 it being tlie quantity of caloric evolved during the combustion of an 

 atom of charcoal : now this must be invariable, for the proportion 



(e) According to these sble experimenters N=r 2754 and P=r. 221. 

 {/) If tlie combustible were Hydrogen, burnt with pure oxygen, the circumstances are jn 

 some degree different, tlie mixture is at the temperature of the atmosphere, and all the libe- 



rated caloric is found In the steam resulting from the combustion, therefore » now 



1132 

 C'*' is by a mean of Lavoisier and Dalton, 42000°, s ~ — — and S by Laroche and Berard 



=r.S5 therefore 8=5738, or about J more than the utmost heat of furnaces and much inferior 

 to the heat of charcoal blown by oxygen. I am aware that the reverse is commonly sup- 

 posed to be true, but if we consider that in the experiments which have been made with char- 

 coal the bodies experimented on are cooled by the blast of oxygen, while in the other case, 

 the flame is impelled on them in the most advantageous manner, and leas heat is lost by radi- 

 ation, we shall not be surprised at the superiority of its effects. 



