426 On the Determination of the [Dec. 



Article VI. 



Memoir on the Determination of the Specific Heat of the 

 different Gases. By MM. F. Delaroche, M. D. and J. E. 

 Berard. 



(Continued from p. 377.) 



Section VI. 



Determination of the Specific Heat of the Gases, that of JJater 

 being taken for Unity. 



We have already observed, that the principle upon which our 

 first set of experiments to determine the specific heat of the 

 gases, was founded, furnished us with two methods of ascertain- 

 ing the ratio between their specific heats and that of water, sup- 

 posing it unity. The second process, described in § 111., for 

 the basis of which we are indebted to C»ant Rumford, furnished 

 us with a third method of arriving at the same conclusions. We 

 will describe in succession the result of our experiments, accord- 

 ing to each of these three methods. 



§ I.— First Method. 



In determining the specific heat of the gases, we set out from 

 this principle, that this specific heat was proportional to the 

 maximum of the elevation of temperature in the calorimeter by 

 a current of hot gas. To compare these specific heats with those 

 of water, it was only necessary to compare the effect produced 

 upon the calorimeter by one of the gases, and by a current of 

 hot water moving so slowly that its effects should not be much 

 more considerable than those of the gas. This we did in the 

 following manner : — 



To get a constant and regular current of water, we made use of 

 a syphon of glass, C, (Plate X. fig. !),) one of the branches of 

 which passed through one of the mouths of a flagon with two 

 mouths almost filled with water. On the other mouth was placed 

 a globular vessel turned upside down, and full of water. The 

 neck of this vessel was of such a length as just to reach the sur- 

 face of the water in the flagon. Hence it is evident, that when- 

 ever the water ran out through the syphon so as to sink its sur- 

 face below the mouth of the globular vessel, the water which 

 filled that vessel would fall down and supply its place ; so that 

 the height of the water in the flagon would remain always nearly 

 the same, and of course the water would flow through the syphon 

 pretty equably. The bore of the syphon was capillary, in order 

 to make the current of water very slow. 



This current of water was heated in the same manner as the 



