he complete and automatic devices for
operating the watertight doors which connect them, a full explanation
has already been given in the description of the Titanic's physical
features, to which the reader is referred. A wise precaution usually
taken in the case of twin and triple screw ships is to arrange the
bulkheads so that each engine is in a separate compartment, as is also
each boiler or bank of boilers and each coal bunker.

SUBMARINE SIGNALS

Then there are submarine signals to tell of near-by vessels or shores.
This signal arrangement includes a small tank on either side of the
vessel, just below the water line. Within each is a microphone with
wires leading to the bridge. If the vessel is near any other or
approaching shore, the sounds; conveyed through the water from the
distant object are heard through the receiver of the microphone. These
arrangements are called the ship's ears, and whether the sounds come
from one side of the vessel or the other, the officers can tell the
location of the shore or ship near by. If both ears record, the object
is ahead.

LIFEBOATS AND RAFTS

The construction of life-boats adapts them for very rough weather.
The chief essentials, of course, are ease in launching, strength in
withstanding rough water and bumping when beached; also strength to
withstand striking against wreckage or a ship's side; carrying capacity
and lightness. Those carried on board ship are lighter than those used
in life-saving service on shore. Safety is provided by air-tight tanks
which insure buoyancy in case the boat is filled with water. They
have also self-righting power in case of being overturned; likewise
self-emptying power. Life-boats are usually of the whaleboat type, with
copper air-tight tanks along the side beneath the thwarts, and in the
ends.

Life-boats range from twenty-four to thirty feet in length and carry
from thirty to sixty persons. The rafts carry from twenty to forty
persons. The old-fashioned round bar davits can be got for $100 to $150
a set. The new style davits, quick launchers in type, come as low as
$400 a set.

According to some naval constructors, an ocean steamship can carry in
davits enough boats to take care of all the passengers and crew, it
being simply a question as to whether the steamship owners are willing
to take up that much deck room which otherwise would be used for
lounging chairs or for a promenade.

Nowadays all life-boats are equipped with a