(more about that presently). Thence it runs
along a spout, and falls—a mass of blazing
splashing, red-hot liquid iron—into the mould
we have spoken of, which bears, as will be
remembered, the impression of the model cannon.
The liquid iron, of course, fills up this impression
with perfect exactness. It is then allowed
to cool, the joints of the drain are unfastened,
the mould breaks up, and there is a solid mass
of iron, the exact shape and size required, and
almost ready to be bored.

It is conveyed into another building, where
its "dead head" is cut off. This "dead head"
is a large mass of iron which renders the cannon
when it comes out of the mould, about one-third
longer than is required. The gun is made
with this addition, because it is found that
the worst part of the iron, or its scum, rises
to the surface: so that in a casting, the uppermost
portion of the iron is less dense and strong
than that below. If, therefore, the gun were
cast the right length at once, the iron at the
cannon's mouth (which it will be remembered
was uppermost as the mould stood in the pit)
would be porous and imperfect, whereas, by this
plan, the porous and imperfect portion is cut off,
and the iron below is even improved by the
condensation effected by this superincumbent
weight.

This overplus of iron being removed, the
next process the cannon goes through, is called
being "centred." That is to say, the centre
of the section left by the removal of the
dead head is found, and in it a small hole is
bored. At the other end of the gun there is, as
most of our readers know, a sort of nob or projection.
The use of this, and of the hole just
mentioned, become now apparent: for, in every
machine through whose rough handling the
gun has now got to pass, there is a socket
into which the nob will fit at one end, and at
the other a steel point which fits into the hole.
Supported, then, at each end by these means, the
gun revolves with perfect ease in spite of its
immense weight; a capability which is of great
importance, as the whole finishing and boring
process makes this facility of revolving the
most indispensable of qualities. The gun revolves
now, more or less, till it is done. It revolves
while the superfluous iron is being pared
from off its outside: being scraped as it turns by
steel edges, which peel off the supererogatory
iron as easily as a sharp chisel deals with soft
pine-wood. It revolves while its outside shape
is being completed, and the refinements of taper
and polish are imparted to it, and it revolves
lastly while it is being bored. For, in this
last operation, the gigantic gimlet, which gouges
with slow persistence a hole some six or eight
inches in diameter, does not turn itself, but
simply advances, forced onward by a dread
pressure of wheels and machinery. The gun
it is that turns, and not the instrument. This
boring, which is a long process, being
accomplished, and the lock adjusted, the gun
has only to be proved and it is ready for use
—ready to break down a rampart, to destroy
a dozen lives, to make a hole in a ship's side, to
carry death with one charge, and to announce a
prince's birth with another.

There is, in the museum attached to the Gun
Factories, a very curious register kept of the
history of each gun, and how it has stood the
proof. In this register, which your Eye-witness
was permitted to see, the guns which fail under
the test are recorded, as well as those which are
pronounced fit for service. The register goes into
the minutest details, and even the state of the
weather at the time of the gun's casting, the degrees
of temperature, the quarter of the wind,
the pedigree of the iron of which the gun was
made, where it came from, and by whom it was
supplied, all these things are put down most
carefully, and form a register of immense value
and interest. In this museum, too, is an extraordinary
machine by which the iron is tested
before it is used at all, and the degree of pressure
which it will bear accurately ascertained.
Your Eye-witness saw this machine made use of
in a manner he could hardly have conceived possible.
The iron to be tested in this case was
tried by weight: the question being, how much
pressure it would take to tear it asunder.

The E. W. was much interested in this experiment.
To him it seemed impossible that a
piece of iron could be pulled in two. The thing
appears almost impracticable, even with wood.
Let the reader take a lucifer match, which is
about the slightest piece of wood one can think
of, and let him, taking hold of each end, try to
pull it asunder. He can snap it across, of course,
almost by a thought, but he may pull for ever,
and it will not come apart.

The piece of iron to which the writer saw this
extraordinary test applied, was shaped something
like a dice-box, large at the two ends and small
in the middle. Each of the ends (having a
shoulder to prevent its slipping) was firmly
grasped in the vice-like claw of the machine and
screwed immovably tight. One of these claws is
a fixture; the other, is connected by means of a
lever with the steel bar, at the end of which the
weights used in the test are placed; and the
machinery is so constructed that every added
ounce tends to pull this claw further from the
other. They are kept from flying asunder, simply
by the piece of iron which is to be tried, and the
degree of pull upon this, augments, of course, as
the different weights are added at the end of the
lever. It is the last hair that breaks the camel's
back, and it is the last pound that pulls the iron
in two. It was at a pressure of about twenty-eight
thousand pounds that the iron parted with
a mighty crash, leaving an end in each of the
claws of this remorseless machine.

Among the many objects of interest in this
museum, a new method of firing large guns by
electricity ranks conspicuously. It is an immense
improvement on the old system, as an
anecdote related to your Eye-witness by the
superintendent will show. The guns used formerly
to be fired by means of a fuse, and it was
the custom of the gunners to ignite several of
them at once, along a whole row of guns, and