OF GASES AND VAPOURS. 207 
number of degrees. The quantity of heat in 1‘ steam of the 
presures 0°0521 is 
9 
qg=A +1687. Ets ae log Graco 
=A + 2:060.¢+4 0373. 
and the quantity of heat given off in al, 56° equals 2° 060. 56 
— Lilet oF 
The density of this steam is to that of air of the same force 
of expansion at the temperature 30°, about 3, and to air under 
5 0°0521 
8 °0°7075 
only OKi-0460 steam is cooled; the heat which is given off is 
therefore 
the pressure 0™:7075 equal — = 0°0460, with 1) air 
15°29 + 0°0460 x 115°36 = 20°57. 
In an experiment with dry air this was cooled 56°9; it like- 
wise stood under the pressure 07596; the quantity of heat 
given off by 1* of this air is 0°267 x 56°9 = 15°18. This air 
0°7596 
0°7075 
ment; consequently if the velocity of the air in both had been 
the same, there would have passed through the pipe during the 
0°7596 
0°7075 
would have given off 1:074 x 15°18 = 16°30 heat. 
According to this calculation the increments of heat should 
stand in the two experiments in the proportion 20°57 : 16°30, or 
9°5 : 7°52; but the observed were 9°5 and 8°6; the difference 
amounts to 1°08, and is more considerable than can be explained 
from the uncertainty of the numbers here employed for the cal- 
culation. But assuredly the sources of error in this experiment 
are far more considerable than in the other experiments of De 
la Roche and Bérard, and the appearance of so great a difference 
will be explained from their consideration, combined with the 
accuracy above noticed of the numbers employed by me. 
was in the proportion denser than that in the first experi- 
= 1ki-974, and 
time, in the one, 1+ dry air, in the other, 
§ 4. Specific Heat and Elasticity of other Vapours. 
23. The formula (2.) in No. 15 furnishes in hke manner the 
elasticity of other vapours, if B and S are determined for these 
Q 2 
