CHAPTER VIII.
DECK APPLIANCES AND APPARATUS.
Communication throughout a small ship is easily maintained by the
human voice, but the larger the ship the more difficult does it become
to maintain the rapid and effective transmission of imperative orders
from the navigating bridge to the various parts of the ship. The
engine and docking telegraphs, telephones and the various signalling
devices to indicate the position of watertight doors, the failure of
navigation lights, the overheating of a compartment or the outbreak
of fire, are installed in the wheelhouse which, in effect, is the nerve
centre of the vessel.
Mechanical Telegraphs.—Orders are transmitted from the bridge
to the engine-room by means of a wire and chain telegraph The dial
casing covers a sprocket wheel keyed to a horizontal axle; the end of the
axle projects through the centre of the dial and is firmly attached to a
hand lever. When the lever is moved the wheel turns through a
corresponding arc of a circle. The links of a flat chain, similar to the
driving chain of a bicycle, engage with the sprockets of the wheel and
the ends of the chain which hang down inside the pillar, are connected
by means of tightening screws to wires led in the most convenient
and direct way to a similar telegraph in the engine-room (Fig. 1).
In the event of the bridge and engine-room telegraphs not registering
the same command it would be necessary to unscrew the brass panel on
the pillar of the bridge telegraph, slacken back one of the connecting
screws and tighten the other one until the reply pointer and the command
pointer came together.
The dial is marked ahead and astern for "Slow," "Half," "Full!'
and also "Stand By," "Stop,35 "Finished with Engines." When the
lever is moved to half ahead the pointer on the engine-room telegraph
also moves to half ahead and a bell rings to attract attention. The
engineer then replies by moving the lever of his telegraph to half ahead
and by doing so operates the return pointer on the bridge telegraph
which rings a bell, thus indicating to the officer that the order has been
understood and is being executed.
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