SPECIFIC HEAT OP GASES. 
spect to its mass, it diminishes in proportion as the density in- 
creases, but yet pursuing a less rapid progression. 
The absorption or the disengagement of caloric, which is 
disengaged when the air is dilated or compressed, has been 
attributed to a change which was supposed to operate on the 
specific heat of tlieair; but that explanation rested on a sim- 
ple supposition, which our experiments, if they are exact, 
have now changed into a certainty. 
3d, For equal volumes, the specific heat of the gases is al- 
most null with respect to that of bodies solid or liquid, 
4th. The little specific heat of the air induces us to think, 
that it might be of advantage, with respect to the economy of 
combustibles, to make use of machines in which we might 
employ the dilatation of air instead of that of water re- 
duced to vapour j and the more we raised the temperature of 
the air, the more advantageous it would be to make use of it. 
5th. We have discovered that aqueous vapour has a spe- 
cific heat less than that of water. This extraordina>‘y result 
has been furnished by an experiment very delicate and very 
difficult to make. Whence, notwithstanding all the attention we 
paid to it, we dare not affirm it to be correct. It will shew' how 
highly interesting it would be to make more numerous expe- 
riments on these subjects. 
6ih. Again, it appears from our experiments, that we cannot 
admit the relation which some philosophers have thought 
4 
they perceived betw’een the specific heat of the contponent 
part*!, nJ of the body which they form. We know that 
Dr. Irw’in piesented a theory, in which he sought to ex- 
plain the heat disengaged in the combination of two bodies by 
the less specili:: heat of the composed body. But Irom our 
experiments, water presents an objection against this theory, 
which appears to us to be impossible to refute. In fact, we 
find, from the table which we have inserted, that a mixture of 
oxigeii and hydrogen, in a proper proportion to form water, has 
a specific heat represented by O 0,3, w'hile the specific heat of the 
water formed by this mi.xtun;, would be 1. Besides, we know 
the enormous quantity of heat which is disengaged in the com- 
bination 
