76 
Steam Eyigine. 
precise dis]_x)sition of the parts as they are usually put to- 
gether : but in fig, 1, of the plate, this deviation is very 
little, and represents a single engine, A the cylinder in 
which the piston moves, B the steam-pipe, D the conden- 
ser, E the discharging-pump, F a bottom common to the 
pump and condenser, in which is an occasional commu-. 
nication by a hanging valve at F : ^ is a valve to be lifted 
"by the engine at every stroke, for the purpose of conden- 
sing the steam ; A is a valve placed outside the cistern (of 
which X X xxis a section on purpose to shew the con- 
tents), but communicates only with the condenser by a 
pipe passing through the side of the cistern,, and is insert- 
ed at the side of the condenser ; f is a valve to be lifted by 
the engine, and opens a communication between the cy- 
linder and the condenser ; A" is a valve to be lifted by the 
engine, and opens a communication between the lower 
part of the cylinder and the steam-pipe ; and / is also a 
valve of the same kind, opening a passage from the boiler 
to all parts of the engine. 
The piston-rod, which is here broken off at m, is con^- 
nected by a drain to the lever or beam, which is supported 
on a wail of good masonry, with proper pivot-blocks for 
support to the gudgeons ; and as this kind of engine is 
usually employed for pumping water, another set of chains 
at the other end of the beam is appropriated to connect 
to the pump-rods. 
Then to set the engine to work, the first thing is to lift 
the three valves i, k, and / (for which there are apparatus 
too minute to lay down on this scale) ; these being open- 
ed, the steam occupies every cavity and crevice of the 
engine, and in a little while displaces ail the air in the cy- 
linder, condenser, 8^c. which is discharged at the valve h: 
this valve is always covered with water in a small cis- 
tern attached to the side of the large one ; for it is hardly 
in the power of art to fit it to that degree of accuracy as to 
