540 Onthe Constitution of mixed Gases, Bec. 
sidering of a ferruginous quality; but it will 
probably ever be beyond the reach of philoso= 
phical research to ascertain the nature of so 
subtile and distant a fluid. 
ESSAY II. 
- 
On the Force of Steam or Vapour from Water 
and various other Liquids, both in a Vacuum and 
an Air. 
SECTION Ie 
On Vapour in Vacuo. 
The term steam or vapour is equally applied to 
those elastic fluids which, by cold and pressure 
of certain known degrees, are reduced wholly 
or in part into a liquid state. Such are the elastic 
fluids arising from water, alkohol, ether, am- 
monia, mercury, &c. Other elastic fluids that 
cannot be reduced, or rather that have not yet 
been reduced, into a liquid state by the united 
agency of those two powers, are commonly 
denominated gases. There can scarcely be a 
doubt entertained respecting the reducibility of 
of all elastic fluids of whatever kind into liquids; 
and we ought not to despair of effecting it in 
low temperatures and by strong pressure exerted 
