m 
Steam Engine, 
under the receiver of an air-pump and producing volatili- 
'sation solely by taking off a part of the pressure of the at- 
mosphere. See Chymie^ tome I. pa, 9. And we know 
by many expriments of M. DeLuc and others, that water 
boils the more speedily as it is less pressed by the 
weight of the atmosphere. 
Lavoisier notices a curious consequence of what has 
been here said ; which is, that if our planet revolved upon 
its axis, with such a velocity as to lessen the pressure of 
the atmosphere, or if the temperature of the air were rais- 
ed, then several fluids which we now see under a liquid 
state would only exist in the aeriform state ; for example, 
if under the temperature of summer the pressure of the at- 
mosphere were only equivalent to 20 or 24 inches of the 
barometrical tube, that pressure would not retain Ether in 
the fluid state, it would be changed into gas ; and the like 
would happen, if while the pressure of the air was equiva- 
lent to 28 or 30 inches of the mercury the habitual tem- 
perature were 105 or 110 degrees on Fahrenheit’s scale. 
The principles which have been here exhibited are suf- 
ficient for the undestanding of all which relates to the ac- 
tion of water or other fluids reduced to vapour. Now, it 
has appeared from frequent experiments that water heated 
in common air volatilises at BO*’ of Reaumur’s thermome- 
ter, or 212 of Fahrenheit’s, the height of the barometer 
being 28 French, or 29“ 9 English inches : and spirits of 
wine under a like pressure volatilises at between 63® and 
64°of Reaumur, or nearly 175® of Fahrenheit. The ex» 
pansive force of .he vapour must, therefore, in both these 
cases, according to the principles just explained, be mea- 
sured by a column of mercury of 28 French, or 29“ 9 Eng- 
lish inches, in like manner as such a column measures 
the pressure of the atmosphere, or the ealasticity of com- 
mon air. And at any more elevated temperatures the 
Mastic force of the vapour will surpass the pressure of tl\e 
