1813.] « Specific Heat of the different Gases. 429 



current of air, we find that the maximum of temperature at 

 which it would have maintained the calorimeter would have been 

 11 5*241° above the surrounding air. The specific heats being 

 proportional to the effects of the currents, it follows that if the 

 specific heat of water be 1, that of air is 0-2460. A second 

 experiment gave us 0-2536. . The mean of the two is 0*2498. 



§ II. — Second Method. 

 The second method of knowing the ratio between the specific 

 heats of water and air, consists in determining by calculation 

 the quantity of heat given out in a certain time by the calori- 

 meter, when the current of hot air has rendered its temperature 

 stationary. We have shown that, when it reaches this point, it 

 abandons as much heat to the ambient air as it receives from the 

 hot gas. The bases of this calculation are as follows : — 



Our calorimeter contained 8586-8 grains of distilled water. 

 The brass of which it was composed and the worm weighed 

 5065 6 grains. Now as the specific heat of this metal is 0-112,* 

 this quantity of brass corresponds with 566-80 grains of distilled 

 water. There was besides 1652-5 grains of solder, the specific 

 heat of which being a mean between that of tin and lead,f may 

 be reckoned at 0038. Hence the solder is equivalent to 6270 

 grains of water. Therefore the whole calorimeter, with its 

 contents, contained as much heat as 9217 grains of distilled 

 water. 



Let us recapitulate here the result of our experiment upon 

 atmospherical air under the pressure of 29-922 inches of mer- 

 cury, and at the temperature of 32°. A current of air of 2196*4 

 cubic inches in ten minutes, by cooling 130-347°, lost a quantity 

 of heat sufficient to keep the calorimeter 28*321° above the 

 temperature of the surrounding air. Hence it furnished it in a 

 given time with as much heat as it lost during that time : but 

 it results from an experiment of which we shall give an account 

 immediately, that if the quantity of heat which it lost in ten 

 minutes under these circumstance? had not been supplied, its 

 temperature would have sunk 2-8793° ; or, which comes to the 

 same thing, the quantity of heat abandoned by the current was 

 sufficient to elevate the temperature of the calorimeter 2*8793°. 



The air which passed through the calorimeter in ten minutes 

 weighed 72371 grains. This quantity, in suffering a diminution 

 of temperature amounting to 130*347°, lost as much heat as was 

 sufficient to raise 9217 grains of water 2*8793°; or, which 

 comes to the same thing, to heat 203-60 grains of water, 



♦ Crawford. Thomson 1 * Chemiltr*f, ii. 227, Frr-nrh trausl. 

 + '1 ho ipeclfc lira's of IcaJ aud tio are. IfckeA from the Mtmoirs of Lavoi- 

 sier, i. iao. 



