STEAM ENGINE. 
and condenses the steam, or cools it, and it 
instantly contracts into the same space it 
originally occupied when in the boiler, be- 
fore it was heated. As the valve, i, closes, 
it is evident that a vacuum will be caused 
in the condenser, as the small quantity of 
water produced from the steam, and tiie 
water injected into the condenser tailing 
down to the bottom, the air in the upper 
part of the cylinder will now expand itself 
into the condenser, through the pipe, jf, 
the cock, E, and p'pe, pp, and as it occu- 
pies move space tlian it did before, it will 
be considerably rarified ; the stream, press- 
ing with its full force against the lower side 
of the piston, will, perhaps, (now a rarefac- 
tion is made above il), overcome the re- 
sistance of the work and friction, and cause 
it to ascend, the air-pump rod and bucket 
moving with it, when the p'u, M, upon this 
rod, reaches the handle, K, it raises it up, 
and, by means of the rack and wheel shown 
in Plate I. turns the cock, E, one-fourth of 
a revolution, bringing its two passages into 
the position of fig. S, Plate II. 
The operation is now reversed, the steam 
from the boiler going above the piston, and 
that steam, mixed with atmospheric air, 
beneath it going to the condenser’, where 
the steam will be condensed, and a partial 
vacuum formed beneath tire piston ; the 
steam now presses it down, moving the 
beam fly-wheel and other machinery, it 
has to drive ; when the pin, L, on the air 
pump rod arrives at the handle, K, it presses 
it down, and brings the cock into the posi- 
tion of the figure I, in which the piston 
will be driven up again. At each stroke of 
the engine, when the piston rises, the valve, 
i, on the bucket of the air pump, will shut, 
and all the air and water contained above 
the bucket, will be lifted through the valves, 
m m, into the cistern, I, at the same time a 
vacuum being made beneath tire bucket, 
which is more perfect than that in fire con- 
denser, the valve, i, will be opened by the 
water and air in the condenser, which will 
enter the pump. On the ascent of the 
piston and the air pump bucket, the valves, 
m m and i, will shut, the pressure which 
opened them being removed, and the water 
and air in the pump pressing upon the valve, 
I, will open it, and get through as the 
bucket descends ; at its return it raises the 
water and air above it as before. In this 
manner, when the engine has made a few 
strokes, all the air contained in the engine 
at the commencement of the operalion will 
be pumped out; the operation of the en- 
gine is now milch more perfect. The instant 
the cock, E, is turned, so as to open a com- 
munication from the cylinder full of steam 
to the condenser ; the elasticity of the 
steam causes it to rush down the pipe, p p, 
into the condenser ; when it arrives there, 
it meets the stream of the injection water, 
which condeiises it, and the remaining 
steam in the cylinder follows it surprisingly 
quick, and in an instant an almost perfect 
vacuum is formed in the cylinder, so that 
the steam acts with its whole force upon the 
piston, all resistance upon the other side 
being removed. The air pump now has 
only to draw off from the condenser the 
water injected into it, the condensed steam, 
and a small quantity of gas, which goes 
from the boiler with the steam, and will 
not condense by the cold water ; these are 
delivered by the air pump into the cistern, 
I, from which the air escapes, the cover 
not being tight (as before mentioned), the 
water which still continues hot runs off, 
when at a certain level, by a waste pipe, o, 
Plate I. The water which is boiled off in 
steam from the boiler, is renewed fr om tliis 
cistern by means of a small pump, P, 
Plate I, which draws the water from it by 
a passage tinougli the cenlre of the cast 
iron column, Q, which stands upon the end 
of the condensing cistern, G G, and sup- 
ports the bearing for tlie main axis of the 
great beam, B, the water is conveyed to 
the bottom of the column by a short pipe, 
r, and after going tluough the pump, P, is 
carried by tire pipes, R R R, to a cis- 
tern on the top of the vertical pipe, S, 
which leads into the boiler. The top of S 
Ls closed by a valve in the cistern, whicli is 
raised by means of a lever, the other end 
of which has a wire, y, hooked to it, going 
through a small stuffing box into the boiler, 
where it has a stone hung on it ; tliis stone 
is balanced by a weight hung at the other 
end of the lever, so that when the stone is 
covered with water, the weight keeps the 
valve shut, and prevents any water getting 
down into the boiler: but as the water 
sinks in the boiler, the weight of the stone 
overcomes the weight, and opens the valve ; 
the water in the cistern now runs down the 
pipe, S, into the boiler, and raises the water 
and the stone until it closes the valve. 
It will be easily seen that by the conden- 
ser being constantly supplied with hot 
steam, which will give out its heat, and at 
lengtli vender the water surrounding it, ip 
the cistern, G, so hot, that it would con- 
dense no more ; to prevent this, it is cou- 
