The Sun.
London, England, 1851-08-26 00:00:00

When the visitor to the Exhibition contemplates
the stupendous machines which he will find placed
upon the railway, which, entering the western ex-
tremity of the building, is conducted along the north-
ern side of the western aisle, he cannot fail to be
struck with the extraordinary progress made in the
art of inland transport within a brief period of 20
years, especially if he compares these machines with
the engines which were first used on the Liverpool
and Manchester Railway, the first line on which the
locomotive engine was applied to the swift transport
of passengers.
It will not be uninteresting or uninstructive to
take here a brief retrospect of the progress which this
great agent of inter-communication has undergone,
the more especially as the main features which distin-
guished the original locomotive are preserved in the
present machines.
That part of the locomotive engine employed to
generate steam consists of three principal parts—the
boiler, the firebox, and the smokebox. The boiler
having a cylindrical form, the length of which is
three or four times its diameter, is placed with its
axis horizontal and parallel to the rails; behind it is
the firebox, and before it the smokebox, so that as
the machine progresses the boiler is preceded by the
latter and followed by the former; the whole is sup-
ported on four or more wheels. The" firebox con-
sists of a hollow casing of metal, in the bottom of
which are placed the grate bars, and under them the
ash-pit; this casing is filled with water to a level
above its roof, and the grate-bars are placed below the
bottom of the boiler.
The boiler is traversed longitudinally by a number
of tubes, through which the flame and heated air
proceeding from the furnace are conducted to the
smokebox. Over the smokebox is erected the
smoke-funnel, or chimney, up which the heated air,
which has thus traversed the tubes, is conducted, and
from which it escapes into the atmosphere.
A vehicle called the tender, supported on four or
more wheels, which carries a certain supply of fuel
for the furnace and a tank containing a supply of
water for the boiler, is attached to the boiler. A
pipe of communication, having a flexible joint capable
of accommodating itself to the irregularities inci-
dental to the motion, connects this water tank with
the boiler, a force pump being applied in such pipe
of communication, by means of which the water is
driven from the tank into the boiler. This force
pump, or feed pump, as it is called, can be put in
operation or suspended, as occasion requires, by
the engine-driver. Behind the firebox is a stage
which is flush with the floor of the tender, so that
the engine-driver and fireman can pass freely from
the one to the other. In the back of the firebox
is a small door, through which the firebox is fed with
coke.
If the visitor to the Exhibition mount upon the
stage just described, on any of the engines exhibited,
he will observe several appendages, the use of which
it may be interesting to indicate. At the back of
the firebox is usually attached a glass water gauge,
the purpose of which is to enable the engineer to see
the level of the water in the boiler. This is accom-
plished in the following manner :—lt will be ob-
served that the glass tube is attached to the fire-
box in a vertical position, and communicates at its
lowest and highest points with the interior by pipes
governed by stopcocks. Now, the position of this
gauge is so regulated that when the right quantity
of water is in the boiler its level should be below
the top and above the bottom of the glass tube, and
as the water in the tube must stand at the same
level as the water in the boiler, the engineer will
know when the boiler requires feeding, by observing
the water to fall in the tube to its lower extremity,
and he will know when the feed has been sufficiently
supplied by observing the level of the water in the
tube rise somewhat above its middle point.
As these tubes are liable to accidental fracture,
stopcocks are provided in rectangular brass tubes,
which connect them at top and bottom with the
boiler, which being closed the fracture of the glass
tube produces no other inconvenience than that of de-
priving the engine of the gauge.
But even in this case provision is made by other
means, which will be seen upon any of the engines
exhibited.
Small pipes of discharge, furnished with stopcocks,
will be observed issuing from the boiler at different
levels. The engineer on opening these stopcocks,
severally, may at any time ascertain the position of
the level of the water in the boiler by reference to the
points at which these tubes severally enter it. If, on
opening either of these cocks, steam escapes, it shows
that the level of the water is below that of the cock ;
if water escapes, it is above it ; and as these cocks are
placed at several different levels, the engineer is able
to feel, as it were, by severally opening them, where
the level of the water lies, and he acts accordingly in
feeding the boiler.
A lever will be observed attached to the tender,
which governs the feed, so as to throw the feed-
pump in or out of action at the will of the engineer.
If the visitor direct his attention to the roof of the
firebox, generally on the left side as he looks for-
ward, he will see a lever held down by a spring con-
nected with an index and graduated scale. This
spring governs the safety valve, which is fixed upon
the roof of the firebox, and the apparatus is, in fact, a
spring steelyard which measures the pressure of the
steam in the boiler in pounds per square inch. A
screw will be observed in connexion with this steel-
yard, by which it may be so adjusted that the pres-
sure of the steam will open the valve when it attasns
any proposed amount per square inch thus the screw
may be so adjusted that whenever the steam acts
upon the valve with a pressure exceeding 601 b. per
square inch the valve will be opened and the steam
will blow off.
When a train stops, as it does at the several sta-
tions along the road, the boiler continues to produese
steam, which, accumulating, would soon attain a
pressure that would open the safety valve, and it
would escape into the atmosphere. An ingenious
means is provided by which this waste of steam is
saved. Instead of allowing it to escape into the at-
mosphere it is made to pass into a pipe, by which it
is conveyed to the tank upon the tender containing the
water intended to feed the boiler. The moment it
enters the tank it is condensed by the cold water, and,
mixing with it, raises its temperature. A gallon of
water, in the form of steam, which thus enters the
tank, is capable of imparting to nearly seven gsllous
of water contained in the tank enough of beat to raise
this quantity to the boiling point.
Every one who has travelled by railways will re-
collect that when the train stops at a station for any
length of time he frequently hears a peculiar rattling
noise produced in or near the engine, and that the
noise immediately ceases when the engine begins to
move. This noise is produced by the sudden con-
densation of the steam escaping from the safety valve
and entering the tank.
It will also be observed that standing on the stage
of the firebox, and looking forward, two levers are
placed on the right of the engine. These levers are
what are called way bars, the purpose of which is to
start the engine. When at rest they invest the engi-
neer with a power of moving the valves two or three
times successively, so as to conduct the steam alter-
nately to each end of the cylinder, and thus to cause
the motion of the piston to commence. After the
motion of the piston has once commenced, the inertia
of the machinery and the self-acting mechanism will
cause its continuance.
Attached to the back of the firebox will also be
observed a lever which is usually made to move upon
a graduated arc. This lever governs a valve which is
placed in the pipe of communication between the
boiler and the cylinder. This valve is so constructed
that it may be opened or closed in a greater or lesa
degree so as to admit the steam to the cylinder in
greater or less quantity, and thus regulate the motion
of the engine.
The extraordinary speed attained upon the rail-
ways, and the not less extraordinary loads which
are transported at those speeds, will excite a natural
curiosity to know the physical principles upon which
such velocities can be imparted to such weights. It
happens that these principles are extremely simple and
such as may be made perfectly intelligible to any
commonly well-informed person. Let us take the
case of an engine moved with a speed of 70 miles an
hour, whose driving wheels are 7 feet in diameter,
and consequently measuring about 21 feet or 7 yards
in circumference ; as a speed of 70 miles an hour is,
in round numbers, 105 feet per second, it follows that
when moving at this rate the driving wheels of the
dimensions above mentioned would revolve at the
rate of five times per second. Now, to produce one
revolution of such wheels, each piston must once
pass backwards and forwards in the cylinder, and
its motion, therefore, must divide a second into ten
equal parts. On arriving at each end of the cylin-
der, at the moment it is about to change the direc-
tion of its motion and to return, a valve must he
shifted by which steam may be admitted at one side
of the piston and withdrawn from the other side.
This valve must, therefore, be moved ten times per
second, and must complete its motion so rapidly as to
form but a small fraction of the entire stroke of the