on some of the leading Doctrines of Caloric, ce. 195 
Alcohol of 0-825 sp. gr. contains much water} specific 
gravity of its vapour .. oe ue a3 2°30 
That of water as before, unity a Ld oh 1-00 
The interstitial spaces in these three vapours will therefore be 
inversely as these numbers, or 
1 
230 
1 1 
— ther ; fora 1; — for water. 
a for ether ; or alcohol ; ied 
yan Bes acihyds ; 
Hence, ord of latent heat, existing in ethereal vapour, will oc— 
cupy a proportional space, be equally condensed or possess the 
same tension with aan in alcoholic, and rin in aqueous vapour. 
A small modification will no doubt be introduced by the dif- 
- ference of the thermometric tensions, or sensible heats, under the 
same elastic force. Common steam, for example, may be con- 
sidered as deriving its total elastic energy from the latent heat. 
multiplied into the specific gravity + the thermometric tension. 
~ Hence the elastic force of water, or 
E =970° x 1:004+212°=1182 
E. =302° x 3°55+112°=1184 
E ae: x 2°304+175°=1185 
Three equations which yield, according to my general propo- 
sition, equal quantities ; or of which the differences are incon- 
siderable, and undeserving of notice. 
Neither the specific heats nor specific gravities of the other 
vapours are ascertained with sufficient precision to enable us to 
subject them to calculation. 
General equation F—Txp+T=0:L, latent heat, D, density, 
T, temperature corresponding to F, 
When the elastic forces of vapours are doubled, or when they 
sustain a double pressure, their interstices are proportionally di- 
minished. We may consider them now as in the condition of 
vapours possessed of greater specific gravities. Hence, the se- 
cond portion of heat introduced to give double the elastic force’ 
need not be equal to the first, in order to produce the double’ 
tension. This view now given accords with the experiments of 
Mr. Watt, alluded to in the begiuning of this memoir. He found 
that ‘‘ the latent heat of steam is less when it is produced under 
a greater pressure or in a more dense state; and greater when it 
is produced under a less pressure or in a less dense state *.”” 
Berthollet thinks this fact so unaccountable, that he has been 
willing to diseard it altogether. Whether the view which I have 
just opened, of the relation subsisting between the elastic force, 
ce 
* Phil. Trans. vol. Ixxxiv. p. $35. 
N 2 density, 
