ng rammed by a
rapidly advancing steamer; our haste must be all the greater if the
conditions of visibility are impaired, as is often the case on the
high seas, for it takes time for the U-boat to submerge completely,
and during this process it is helplessly exposed to the fire of long
distance guns.

Calmly, but with great decision, the commander gives the general
orders to submerge. The internal combustion engines, the oil motors
which, during surface navigation are used to accelerate the speed of
the boat, are immediately disconnected, as they consume too much air
underseas, and electric motors are now quickly attached and set in
motion. They are supplied by a large storage battery, which consumes
no air and forms the motive power during subsurface navigation. Of
course electricity might be employed above water, but it uses up much
current which is far more expensive than oil, and would be wasted too
rapidly if not economized with care.

It would be convenient to employ the same oil motor for underseas
navigation, but such a machine has not yet been constructed, although
various futile attempts of this kind have been made. With only one
system of propulsion we should gain much coveted space and a more
evenly distributed weight; within the same dimensions new weapons of
attack could be inserted, and also effective weapons of defense. The
inventor of such a device would earn a large reward. Let him who wants
it, try for it!

Quickly, with deft hands, the outboard connections, which served as
exhausts for the oil motors, must be closed in such a way as to resist
at once the high water pressure. It is well known that for every ten
meters under water we oppose the pressure of one atmosphere--one
kilogram to the square centimeter--and we must be prepared to dive to
far greater depths.

When all these openings have been carefully closed and fastened, then
begins the maneuver of submersion. The sea water is admitted into big
open tanks. Powerful suction engines, in the central control of the
boat, draw out the air from these tanks so as to increase the rapid
inrush of the water. The chief engineer notifies the captain as soon
as the tanks are sufficiently filled and an even weight is established
so as to steer the boat to the proper depth for attack.
Notwithstanding the noise of the machinery, large, wide-open speaking
tubes facilitate the delivery of orders between the commander's turret
and the Central, and now is th