109 
Steam Engine* 
uniform, and trans]?arent, about half the gravity of atmo- 
spr^eric air, very much greater in bulk than the water of 
which it is composed, and capable of being again redu- 
ced to water when brought into contact with matter of a 
less degree of heat than itself. 
The pressure of the atmosphere, or any equivalent re- 
sistance, prevents the production of steam, until the wa- 
ter is heated to 212 degrees of Fahrenheit’s thermome- 
ter ; but when that pressure is removed, or the water is 
placed ill a vessel exhausted of air, steam is produced 
from it when it is colder than the human blood. On the 
contrary, if water is pressed upon by air or steam, which 
are more compressed than the atmosphere, a degree of 
heat above 212 degrees is necessary for the production of 
steam ; and the diiference of heats at which water boils 
under different pressures, increases in a less proportion 
than the pressures themselves ; so that a double pressure 
requires less than a double increase of sensible heat. 
The experiments which have been published concern- 
ing the bulk of w^ater when converted into steam, are er- 
roneous ; and the conclusions drawn from them make 
that bulk greater than it really is. It has been known 
for some time, that water would boil in an exhausted re- 
ceiver at a low degree of heat. 
If we consider the common steam-engine, we shall 
find it defective ; first, because the vacuum is produced 
by throwing cold water into the cylinder to condense the 
steam : that water becomes hot, and, being in a vessel par- 
tially exhausted, produces a steam, which in part resists 
the pressure of the atmosphere upon the piston, and les- 
sens the power of the engine. The second defect is the 
destruction of steam, which unavoidably happens upon at- 
tempting to fill a cold cylinder with that fluid ; for the 
injection-water, at the same time that it condenses the 
steam, not only cools the cylinder, but remains there un- 
til it is extruded at the eduction-pipe by the steam which 
