Steam Engine, B.l 
doming from the cylinder either above or below the piston^ 
and its operation is as follows : 
When the air is blown out of the engine, and the pis- 
ton happens to be in its upper situation^ the valve v on 
the steam side is lifted, and the valve r on the exhausting 
side is opened : the exhausting- valve r takes the steam 
from below the piston, while the steam by the valve v en- 
ters on the upper surface^ and a stroke is made ; and at the 
instant the piston comes to its place at the bottom of the 
cylinder, these valves are both shut, and the valves w and 
t are opened, and the upward stroke commences, and so 
on alternately. 
It must be observed here that, whereas the piston in the 
single engine is pendant on the lever by the chains lying 
in the arch of the inner end, this must be Connected by 
a mode that shall render the rod rigid in its action up- 
ward ; for which purpose there is a system of transverse 
joints which compel the rod to a motion parallel to itselfo 
At the other end of the beam or lever is a rod which con- 
nects the motion of the engine to a fly ; and Mr. Watt has 
chosen to do this by a very ingenious application of one 
wheel fixed on the axis of the fly, and another fixed on 
the rod that is connected to the lever, by which means 
the fly makes one entire revolution, while the engine makes 
but one stroke ; and thus the fly makes as many revolu- 
tions as the eno-ine does strokes ; but we are inclined to 
give the preference to a simple crank with a fly of such 
weight as shall have the desired momentum with less ve- 
locity, simplicity being ever a desideratum in the construc^i 
tion of maciiinery. 
CMTtwrighfs Engine^,^ A steam engine has been in- 
tented by Mr. Edmund Cartwright, which has as much 
merit as can possibly be attributed to a gentleman engaged 
m the pursuit of jnechanical studies for his own amuse- 
ment. Mr, Cartwriffht has two very important desiderata 
Vol, IL ' ^ L 
