STEAM ENGINE. 
air, and both cylinders filled with steam, 
the regulating valve whicli admits the steam 
into the inner cylinder is shut, and the 
other regulator which communicates with 
the condenser is opened, and the steam 
rushes into the vacuum of the condenser 
with violence : but there it comes into con- 
tact with the cold sides of the pumps and 
pipes, and meets a jet of Cold water, which 
was opened at the same time with the 
exhaustion regulator : these instantly de- 
prive it of its heat, and reduce it to water ; 
and the vacuum remaitiiug perfect, more 
steam continues to rush in, and is condensed 
till the inner cylinder is exhausted. Then 
the steam which is above the piston, ceasing 
to be counteracted by that which was be- 
low it, acts upon the piston with its whole 
elasticity, and forces it to descend to the 
bottom of the cylinder, and so raises the 
buckets of the puiiips, which are hung to 
the other end of the beam. The exhaustion 
regulator is now shut, and the steam one 
opened again ; wliich, by letting in the 
steam, allows the piston to be pulled up by 
the superior weight of the pump rods, and 
then the engine is ready for another stroke. 
Tile peculiar advantages that result from 
this construction are, that the cylinder be- 
ing surrounded with the steam from the 
boiler, is kept always uniformly as hot as 
the steam itself, and is, therefore, incapable 
of destroying any part of the steam which 
should fill it : and again, the condenser be- 
ing kept always as cold as water can be 
procured, the steam is perfectly condensed, 
and does not oppose the descent of the pis- 
ton; which is, therefore, forced down by 
the full power of the steam from the boiler, 
which is greater than that of the atmo- 
sphere. 
A steam-engine of tlie best construction, 
with a thirty inch cylinder, acts with the 
force of 40 horses; and since it acts with- 
out intermission, will perform the work of 
120 horses, or of 600 men; each square 
inch of the piston being nearly equivalent 
to a labourer. Tlie consumption of about 
8416. of good pit coal, will raise 43,000 cu- 
bical feet of water 10 feet higlf, which is 
equivalent to more than the daily labour of 
eight men : the value of this quantity of 
-coal is seldom so much as that of the work 
of a single labourer for a day; but the ex- 
pense of the machinery generally renders a 
steam-engine somewhat niore than half as 
expensive as the number of horses for which 
it is substituted. We shall now proceed to 
,a more particular description. 
Plates land II, Steam Engine, are draw- 
ings of a steam-engine of six-horses power, 
built by Mr. John Dixion, Maid Lane, 
Southwark, and used by him in his steam- 
engine manufactory, for turning lathes, &c. 
Plate I. is a general elevation of the whole 
engine; and Plate II. is a section on a 
larger scale of the cylinder steam pipes, 
condenser, &c. ; 6 6, Plate I. is the cylinder, 
the internal structure will be described 
hereafter ; a is the piston rod connected to 
the great working beam, B, by a system of 
levers called a parallel motion, the property 
of whicli is, that the rectilinear motion of 
the piston rod is preserved, though the end 
of the beam describes an arc of a circle; at 
the otherend of the beam, B, the connecting 
rod, I>, is jointed at its lower end ; it is also 
jointed to the crank, £,upou the axis of the 
great fly-w!ieel. When by the expansive force 
of the steam, the piston rod, o, is caused to 
ascend, it raises one end of the great beam 
and depresses the other, and by the connect- 
ing rod, ,D, turns the crank and fly wheel 
round. As soon as the piston rod arrives at 
the top of its stroke, it receives a new imr 
pulse, which brings it down again, and con- 
sequently raises the connected rod, D, and 
crank, E. The use of the fly wheel is to ac- 
quire an impetus, at the time When the 
crank is horizontal, and at which time the 
connecting rod exerts all tlie force of the 
engine upon the crank to turn it round, 
tin's momentum causes the wheel tc-turn, 
and the rest of the machinery, when the 
crank is at the top or bottom of its motion, 
being then in a line with the connecting 
rod, it has no tendency to turn it round. 
To describe the manner in which the. 
power is given to the piston rod, a, we 
must turn to Plate II. where 6666 is the 
cylinder of cast iron, and truly bored, it is 
closed at the top by an iron lid screwed on 
by a flanch at the top ; in the centre of the 
lid is a contrivance called a stuffing box, and 
is for holding a packing pf hemp, through 
which the piston rod, a a, passes perfectly 
air and .steam tight ; dd is the piston packed 
with hemp, round between its circumferesiije 
and the inside of the cylinder, so that it can 
move up and down in the cylinder easily, 
without allowing any steam to pass by it ; 
the piston is fitted to the rod, a,, and fast 
keyed in ; the cylinder has a flanch or pro- 
jecting ring round it, a little below the mid- 
dle, by which it is held into a jacket, ccc, 
which is constantly supplied with steam 
from the boiler, A ; Plate I. of the engine 
of the pipe, e ; ffy Plate II. is a pipe, cast 
