IS 13.] Specific Heat of the different Gases. 371 



The principle upon winch these experiments depended was 

 such that -it would have heen requisite, in order to be applicable 

 to the object in view, that the gases during their passage through 

 the calorimeter should suffer the same diminution of tempera- 

 ture. As this could not actually take place exactly, we have 

 always by the rule of proportion brought the results obtained to 

 what they would have been if that had taken place. We took 

 for a measure of the cooling of the gases the difference between 

 the temperature of the gases when they entered the calorimeter, 

 and their temperature when they issued out, which we considered 

 as equal to that of the surrounding air. This last estimate could 

 not differ from the truth; for since the gas in passing through 

 the calorimeter assumed the temperature of the water in that 

 vessel, which during one-half of the experiment was below the 

 temperature of the air, and during the other half as much above 

 it, a compensation took place, which enabled us to take the tem- 

 perature of the air as the mean heat of the gas during the whole 

 process. 



The same compensation corrected another error, which might 

 have been occasioned by the condensation of aqueous vapour. 

 The gas saturated with vapour at the temperature of the air 

 would deposite a portion of it in its passage through the 

 serpentine during the first half of the experiment ; but as it 

 would take up nearly the same quantity during the second half 

 of the experiment, the general result would not be affected. 



We have observed already that we could not entirely prevent 

 the gas tube from communicating some heat to the calorimeter. 

 It was necessary to estimate the influence of this cause of error. 

 We ascertained, by two very correct experiments, that the quan- 

 tity of heat yielded in this manner to the calorimeter in ten mi- 

 nutes was capable of raising its temperature 0'342° Fahrenheit; 

 and as it was sensibly proportional to the time, nothing was 

 more easy than to allow for it. 



We now present the result of our experiments in the follow- 

 ing table, quite similar to the preceding one, and therefore 

 requiring no explanation : — 



2 a 2 



