Illustration: MAST HOUSE.
The masts of a “ship” are three in number, a “schooner” has two, and
a “sloop” but one. These masts pass right down through the decks,
and rest upon the keelson. In small vessels each division is made of
one piece, but in larger ships they are made up of a central piece,
with others fastened round it so as to enlarge and strengthen it.
The first or lower division of the central mast is called the “main”
mast, and that above it the “maintop” mast; the fore mast is divided
into “fore” mast and “foretop” mast, and the after mast is called the
“mizen” and “mizentop” mast, and the pieces above these the “foretop
gallant” mast, “maintop gallant” mast, and “mizentop gallant” mast.
These masts are made, and raised by cranes in a building called a
mast-house, and placed in the right position in the ship floating
beneath.
The outside of ships, as high as the “water-line,” is covered with
a sheathing of copper to defend it from the action of the “worm”
(_Teredo navalis_), which bores into and destroys the wood exposed to
its ravages; the copper also presents a smooth surface to the water,
and facilitates the motion of the vessel. At the stern of the ship
is placed the “rudder,” a wooden construction turning like a door on
fastenings, and which, by being moved on one side, presents a greater
amount of resistance to the water, and consequently tends to turn the
stern of the ship away from that side, thus altering its course. The
decks of a ship are like the floors of a house, running across from
side to side, and supported on strong beams bolted into the sides;
they are slightly arched, to increase their strength, as they have in
ships of war to support the weight of the guns, &c. A section of the
decks and other parts of a ship is shown at fig. 3. where the general
figure and the different parts described may be seen; the section is
through the middle, from side to side. Most ships of any considerable
size carry several boats with them, either on deck or suspended
between the masts, to serve as a means of escape in case of fire, or
any other accident requiring the crew to leave the ship, also as a
means of keeping up communication with the shore. Ships of war are
named according to the number of guns they carry, as a seventy-four,
a hundred-and-twenty-gun ship, &c.
Illustration: REPAIRING DOCK.
When ships have to be repaired they are brought into the repairing
dock, which has a pair of gates shutting it off from the river; when
they are closed (at low water) the water is pumped out from the dock,
and the repairs done; when finished the water is let in, and the ship
floats out. In small vessels it is sometimes sufficient to haul them
on shore at high tide, so that when the tide is down they may be
left high and dry and repaired, and when the tide is at the highest,
hauled off again. Steam ships are constructed to be propelled either
by paddle wheels having flat boards fixed to their circumferences,
which on being turned round, take a great hold in the water, and so
cause the motion of the ship; or by the screw-propeller, which has
been described.
Illustration: PADDLE AND SAILING SHIP.
Illustration: BREAKING UP.
The iron ships, which of late have almost superseded those of wood,
are made of plates of wrought iron, rolled, while red hot, between
rollers to the thickness required, which is generally half-an-inch;
these plates have holes punched all round them by machinery, and
are united by rivets placed in the holes red-hot and rivetted by
heavy hammers. The most magnificent specimen of iron shipbuilding
ever attempted is the Leviathan. This ship is 680 feet long, and is
not made of one thickness or case of iron plates, but is upon a new
principle called the “cellular,” consisting of an outer and inner
casing of iron plates held together by partitions of iron so as to
separate them into square compartments or “cells.” The objects gained
by this arrangement are greater strength, and greater safety, for
in case of injury to the outer portion, the water would enter only
between the two in that compartment where the injury happened to be,
and so fill only that small portion with water. The whole ship is
also divided into compartments by means of double screens of iron,
making it like a fire-proof box, and even if a fire should occur in
one of these, the others would be preserved from its effects. The
masts and yards of this great ship are also of hollow wrought iron
plates rivetted together, and are both stronger and lighter than
they would be of wood. A machine is placed at the lower part of each
mast which by compressing, can crush it up, and cause it to break
off and fall over the side of the vessel in case such a thing should
be required, as in a very violent storm; and the standing rigging,
which is of wire-rope, can be let loose in a few minutes so as to
completely free the ship of the mast. This great ship is constructed
to be propelled both by screw and paddles; the screw engines are four
in number, and are each of 1,600 horse power, the paddle engines are
also four, of 1000 horse power each, being 10,800 altogether. They
will require about 180 tons of coal a day to work them; 12,000 tons
of which are capable of being carried. The Leviathan will have six
masts, and be able to spread 6,500 yards of sail, will accommodate
4000 passengers, and when ready to sail, with all on board, will
weigh about 25,000 tons.