117 
Steam Engine. 
As it is evident, from its constmction, that the whole 
of the steam is brought back again into the boiler, it af- 
fords the means of employing ardent spirit instead of wa- 
ter, and thus saving a great deal of fuel. 
This machine seems to be peculiarly applicable to pur- 
poses requiring only a small power, as it is not expensive, 
and occupies little room. 
It would far exceed the limits of this work, to enter in- 
to an examination of all the steam-engines invented by 
different persons. It is sufficient to mention, that no en- 
gine of this kind has been found, upon careful trial, to be 
superior to those of Mr. Watt. 
From this brief description of the steam engine, the 
reader will be enabled to perceive the nature, and appreci- 
ate the value, of Mr. Watt’s improvements. It had hith- 
erto been the practice to condense the steam in the cylin- 
der itself, by the injection of cold water ; but the water 
which is injected acquires a considerable degree of heat 
from the cylinder and being placed in air highly rarefied, 
part of it is converted into steam, which resists the piston, 
and diminishes the power of the engine. When the steam 
is next admitted, part of it is converted into water by 
coming in contact with the cylinder, which is of a lower 
temperature than the steam, in consequence of the de- 
struction of its heat by the injection- water. By conden- 
sing the steam, therefore, in the cylinder itself, the resist- 
ance to the piston is increased by a partial reproduction 
of this elastic vapour, and the impelling power is dimin- 
ished by a partial destruction of the steam which is next 
admitted. Both these inconveniences Mr. Watt has in 
a great measure avoided, by using a condenser separate 
from the cylinder, and encircled with cold water ; and by 
surrounding the cylinder with a wooden case, and inter- 
posing light wood-ashes in order to prevent its heat from 
I being abstracted by the ambient air. 
