192 
SPECIFIC HEAT OF GASES. 
In this equation, A marks the excess of the temperature of 
the calorimeter over that of the surrounding air in the first in- 
stant of the experiment, and B that excess at the end of twenty 
minutes, supposing the calorimeter left to itself. In making 
the application to the experiments made on the air, we see, by 
by the first table, that A=lfi°/34, and from the preceding 
experiment A— B = 2“S87, and consequently B = i2oS47j 
v/hich gives S = S^-'lSyS. Another experiment, calculated in 
the same manner, gives for S = 3°2089. The medium of 
these two numbers is S = 3®19g2, which marks the degrees 
of coolness of the calorimeter in twenty minutes, if the rate 
of cooling had been during all that time the same as in the 
S 
first moment, we should have — = 1“5990 for the same de- 
2 
crease of heat in ten minutes. 
The current of hot air therefore communicated to the calo- 
rimeter in ten minutes a heat capable of raising its temperature 
to 1 5990. Now, the quantity of air which traversed the ca- 
lorimeter in ten minutes was, by this table, 35'99 litres, or 
46 800 grammes, and the loss of heat which this air expe- 
rienced to produce the effect of which, we have just spoken, 
was, from the same table, 72M15. Then, to raise 46" 8<50 
grammes of air through 72°415 requiresas rpuch heat as to raise 
the calorimeter or 590' 8 grammes of distilled water through 
1^5996 ; whence the specific heat of water being 1, that of the 
air is 0 2813. 
§ 
Third Method. 
The experiments we have made by following the process 
Third method. v^hich the labours of Count Rumford gave us an idea, gives 
us a method more simple and direct, and at the same time suffi- 
ciently exact to determine the porportion of the specific heat 
of water to that of air. 
In these experiments the calorimeter contained as much 
heat 
