el electric motors and storage
batteries are employed exclusively. These vary, of course, in
detail. In principle, however, they are very much alike. Although
this combination of electric and oil power is largely responsible
for having made the submarine what it is to-day, it is far from
perfect. Mechanical complications of many kinds and difficulties of
varying degrees result from it. Up to comparatively recently these
were considered insurmountable obstacles. But engineers all over the
world are giving their most serious attention to the problem of
devising a way to remove these obstacles and continuous progress is
made by them.

As an immediate result of the development of motive power in the
submarine its speed both on and below the surface of the water as
well as its radius of action has been materially increased. To-day
submarines travel on the water with a speed which even a few years
ago would have been thought quite respectable for the most powerful
battleships or the swiftest passenger liners. And even under water,
submarines attain a velocity which is far superior to that of which
earlier submarines were capable on the surface of the water. How
immensely extended the radius of action of the submarine has become
in recent years, has impressed itself on the world especially in the
last few years. Both English and French submarines have travelled
without making any stops from their home ports to the Dardanelles
and back again. And used to, and satiated as we are with mechanical
wonders of all kinds the whole world was amazed when in 1916 German
submarines made successful trips from their home ports to ports in
the United States and returned with equal success. This meant a
minimum radius of action of 3500 miles. In the case of the German
U-boat which in 1916 appeared at Newport for a few hours, then
attacked and sank some merchantmen off the United States coast and
later was reported as having arrived safely in a German port, it has
never been established whether the boat renewed its supplies of food
and fuel on the way or carried enough to make the trip of some 7000
miles.

One other important feature without which submarines would have
found it impossible to score such accomplishments is the periscope.
In the beginning periscopes were rather crude appliances. They were
very weak and sprung leaks frequently. Moisture, formed by
condensation, made them practically useless. In certain positions
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