The Portland daily press., 1898-03-23

diately he touches the proper key, thus
closing the firing circuit and causing the
mine to explode. 1t Is not necessary in
using this type of mine for the observer
to see the enemy at all. The mining CASE
mate may be in bank on shore, where
it would not be possible, in fact, for the
observer to see the enemy. He simply
watches the keyboard and waits for
signal. From five to seven mines usually
constitute q group, and groups are placed
in two or more lines, as rule, so that
when a ship passes between the groups on
one line it must certainly pass over the
mines in the next lines. All mines are
located so that the explosion of one group
All these types Of mines described can
be effectively used only where the water
is not very deep and the currents are not
very strong, the rule being the greater
the depth the greater must be the amount
of the explosive used. Ground mines
have been used In water sixty-five feet
deep, and for this depth q charge of gun
cotton equivalents to 4, 800 pounds of pc W.
der was required The system by which
ground mines are fired is simple and in
genious. Two observers are employed to
determine when the enemy is directly over
the mine. Two !, stations are utilized,
with an observer on each, provided with
q telescope u4ou Oh VorOlCdA PlVoe, POI
hitting it to swing toward any point OF
the horizon. The instrument is SO ar
ran yed that when 1t points toward the
mine the break in the electric current at
that station will be closed. -
Submarine mines are loaded with such
high explosives as guncotton, dynamite
or explosive gelatine, all OF which are
superior to gunpowder in that they are
not affected by moisture. A mine Tuay
have hole in 1t and the explosive be-
come wet, still 1t is not rendered useless,
as ordinary gunpOwder would be. The
enormous pressure necessary to blow
hole through formid able war vessel has
been estimated to range from 5000 to IL,
600 pounds square inch. In case hole
sufficient in size is not blown in the ship
to cause her to founder, the shock would
be SO great as to throw all delicate ma
oh inery out of action, SO that she would
become a ready target for the guns on
shore. There is another danger to a ship
from the submarine mine, and that is
the possibility of setting off the high ex-
plosives ON the vessel by the submarine
shock.
The chief and main functions OF Ii sub
marine mine system are to check the early
advance of an enemy's feet. in order that
the defenders may have time to concen.
trate their ships for the attack. When
war is declared strategy would seem to
Gall lOr blt5 COuC0nGIuUlOu VI UuO ACdNlObt
fighting ships against o country's ports
where the coast defence system is weak.
There might be little time to prepare to
meet an attack, and it is not likely that
in an attack on our ports the navy will
learn exactly which one the enemy aims
to STRIKE until it's fleet is off the city. II
the comparatively small navy we now
have is massed at one poins, as the ships
are now at Key West, the enemy might
reach some OF our cities and do enormous
destruction before our vessels could reach
1t. Herein lies the value OF submarine
mines. They may keep the fleet we'll
beyond bombarding distance until our
squadron could reach the point asSa1led.
For example, several groups OF mines
placed in the narrow channels just out
side of Sandy Hook; at the entrance Of
Boston Harbor beyond the defensive sys-
tenn; at the mouth of the little river lead
ing to Portsmouth, N. H.; in the Della
ware, perhaps twenty miles below Will
mington, and in the main ship channel
near Fort Carroll, below which an
enemy's fleet could not successfully bonn
bard the city, could hold effectually a
powerful fleet Of vessels and possibly pre-
vent a single ship from passing the shore
line of defences.
In the Notifications system now being
rapidly completed progress in perfecting
the submarine mine problem is being
made at an equal pace. At all OF the To-
cations of new Notifications mining case.
mates have been erected on shore for
working the wires leading to the mines
anchored out in the streams. The loca-
ton OF these casemates is not always
known to the public, and for that matter
the War Department protects with the
utmost care all information relating not
only to the submarine mine system, but
practically everything connected with the
Notifications. 1t would be almost 1mpos-
sible for any one to learn where subma-,
rine mines will be placed in case of war,
or to what extent preparations have been
made in this direction.
With an ample supply of submarine
mines on hand, and it is believed that
the department has already great num-
Der, groups could be quickly laid in all
the harbors and connections made with
the classmates on shore. Reports have
been in circulation in tho past few weeks
to the erect that already torpedo mines
have been planted at various points nota-
bly, between the Virginia capes and at the
entrance to Hampton Roads. Nothing of
the sort has been done, however, for the
department has n intention of putting
these mines in place until war is practi
cally unavoidable. The submarine mines
entail no very great expense, but they
must be ready for instant use. There are
some ports. of course. which cannot he
defended ty mines owing to the fact that
they are too near the open sea, but gener-
ally in The entire perfect of coast defences
now being carried out by the War Depart
ment the submarine mine forms con-
spicuous and important feature.
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