rine possesses the most reliable type of compass available. At
night when the periscope is practically useless or in very rough
weather, or in case the periscope has been damaged or destroyed,
steering is done exclusively by means of the compass. The latest
type in use now on submarines is called the gyroscope compass which
is a highly efficient and reliable instrument.

[Illustration: Permission of _Scientific American_.

_The Exterior of First German Submarine._]

In the matter of ventilation the modern submarine also has reached a
high state of perfection. The fresh air supply is provided and
regulated in such a manner that most of the discomforts suffered by
submarine crews in times past have been eliminated. The grave danger
which formerly existed as a result of the poisonous fumes, emanating
from the storage batteries and accumulators, has been reduced to a
minimum. In every respect, except that of space, conditions of life
in a submarine have been brought to a point where they can be
favourably compared with those of boats navigated on the surface of
the water. Of course, even at the best, living quarters in a
submarine will always be cramped. However, it is so important that
submarine crews should be continuously kept on a high plane of
efficiency that they are supplied with every conceivable comfort
permitted by the natural limitations of submarine construction.

[Illustration: Permission of _Scientific American_.

_The Interior of First German Submarine. Showing Appliances for
Man-Power._]

Submarine boats so far have been used almost exclusively as
instruments of warfare. One of their most important features,
therefore, naturally is their armament. We have already heard
something about the use of torpedoes by submarines. The early
submarines had as a rule only one torpedo tube and were incapable of
carrying more than two or three torpedoes. Gradually, however, both
the number of torpedo tubes and of torpedoes was increased. The
latest types have as many as eight or ten tubes and carry enough
torpedoes to permit them to stay away from their base for several
weeks. In recent years submarines have also been armed with guns.
Naturally these have to be of light weight and small calibre. They
are usually mounted so that they can be used at a high angle. This
is done in order to make it possible for submarines to defend
themselves against attacks from airships. The mountings of these
guns are constructed in