Adapted from Submarines from The Story of Great Inventions
by Elmer Ellsworth Burns
Successful navigation beneath the surface of the water,
though not carried to the extent imagined by Jules Verne, was a
reality at the beginning of the twentieth century. Instead of
twenty thousand leagues under the sea, less than a hundred
leagues had been accomplished, but no one can foretell what
the future may have in store.
The submarine is primarily utilized in wars. The weapon used
by the submarine is the torpedo. The torpedo is itself a small
submarine able to propel itself, and if started in the water
toward a certain object, to go under water straight to the mark.
It carries a heavy charge, either of guncotton or dynamite,
which explodes when the torpedo strikes a solid object, such as
a battle-ship. It would be very difficult for one submarine to fight another
submarine, for the submarine when completely submerged is
blind. It could not see in the water to find its enemy. The
torpedo-boat-destroyer is able to destroy a submarine by
torpedoes, shells full of high explosives, or quick-firing guns.
Advantage must be taken of the moment when the submarine
comes to the surface to get a view of her enemy.
One of the great enemies of the submarine will probably be
the air-ship, for while the submarine when under water cannot
be seen from a ship on the surface, it can, under favorable
conditions, be seen from a certain height in the air.
The rising and sinking of the submarine depend on the
principle of Archimedes. The upward push of the water is just
equal to the weight of the water displaced. If the water
displaced weighs more than the boat, then the upward push of
the water is greater than the weight of the boat and the boat
rises. However, the boat can be made to dive when its weight is
just a little less than the weight of the water displaced. This is
done by means of horizontal rudders which may be inclined so
as to cause the boat to glide downward as its propeller drives it
forward. For every boat, there is a depth beyond which it must not go.
The penalty for going beyond this depth is a battered vessel, for
the pressure increases with the depth. Every time the depth is
increased thirty-two feet, the pressure is increased fifteen
pounds on every square inch. Beyond a certain depth, the
vessel cannot resist the pressure. Submarines have been made
strong enough to withstand the pressure at a depth of five
thousand feet, or nearly a mile. Most submarines, however,
cannot go deeper than a hundred and fifty feet.
Air is supplied to the occupants of the boat either from
reservoirs containing compressed air or oxygen, or by means of
chemicals which absorb the carbon dioxide produced in
breathing and restore the needed quantity of oxygen to the air. Create a summary of the passage by placing the four most important points in the correct order. A. Sometimes submarines can be seen from an airplane. B. All submarines must be sure not to descend too far underwater. C. Submarines either rise or Supmerge by displacing water. D. Most of submarines are created solely for military purposes. E. Certain submarines have a special chamber for diverse. F. Some submarines are used for oceanic exploration.