The Portland daily press., 1898-03-23
AROUr SUBMARINE MINES.
Some of the Various Types Used for
Harb0r Defence.
The Chief Function of the Submarine Mine
Easily and Quickly Planted-The
Government Said to Have Large
Number.
(From the Baltimore Sun. }

Number.
(From the Baltimore Sum-
The use of submarine min and torpe-
does in conjunction with coast fortifica-
lions has given the engineers and ord
dnance officers almost as many difficult
problems to solve as were presented when
modern ordnance and disappearing gun
carriages were. first being evolved. Sub
marine mines are as much part OF the
Notifications scheme now being carried
out at all the great coast cities as the in
stallation of guns and mortar batteries.
The object of the mines and floating tor
pedo is to destroy any vessel that might
succeed in passing the forts. and II these
mines are as effective as the experts be-
Iieye. it should seem reasonably certain
that the most formidable feet could not
enter with safety any of the harbors on
the Atlantic included in the coast defence
plan.
Submarine mines are more practicable
and more efficient, of course, in narrow
entrances to harbors, or III channels
which all heavy draught vessels must
take in reaching port. Practically every
city now being. fortified, with the possible
exception of Baltimore, either has q
narrow entrance to it's waterway or
small channel up which the enemy's fleet
would have to pass. But it has been
shown to be ilnpracticable to block the
mouth of Chesapeake Bay owing to its
width between the capes, and as 1t would
be equally impracticable to plant torpe-
does in the bay south of the new fortl11oa-
lions at North Point and Hawkins Point,
whatever mines are planted for the pro-
lection of Baltimore must be in the chan
mel winding up by Fort Carroll. AT
Hawkins Point a mining casemate has
already been located and the entire chan
mel laid out into squares for the locat on
OF torpedoes to be placed there after q
feet enters the oapes.
Mining easements are nothing more,
practically, than well-proteoted magazine,
on shore, where the wires and instru-
ments, with the chart of the torpedoes
planted, are held. From this building
the field of torpedoas is operated, and as
each mine is directly connected by wire
leading to the switchboard any separate
mine or bunch of them may be exploited
at the will of the operator. Mines thus
operated contain each 400 or 500 pounds
Of high explosives, any one of which
would send easily to the bottom war
vessel the size of the Maine.
Submarine mines have been extensively
used in ell recent wars, and especially by
the Germans in preventing the French
fleet from bombarding their ports during
the Franco Prussian war. They were
used also by the Confederates. although
the system then developed was almost in
it's infancy compared to the progress in
this system of defence made by experts
in the past few years. Submarine mines
simplest ia that knownfas contact mine,
which explodes on impact with an object.
This consists of an iron case continuing
the explosives and cable attached to an
anchor, by which it is held in place.
This case has a number of projecting
points, on the end OF which are nring
nins. When snip hits one of these pi MS
the latter is driven in, exploding per-
cussion cap and thus bursting the charge.
In anchoring these mines, care must be
taken that they are not too near the sur
face when the tide is low. An INNER
sion OF at least ten feet is necessary to
give the charge sufficient force TO destroy
q heavy snip. As it has been shown that
a strong current reduces considerably the
efficiency of the contact mine, since 1t
NAV he forced down so far by the action
as to render it useless, some mines are
placed on the bottom. These are called
ground mines and are not so dangerous
as the contact mines. The- latter mine
is almost as dangerous to friena as to en-
envy, and if by cnanoe it should go adrlft
and strike some merchant vessel entering
the harbor the consequences would be
disastrous.
There is another kind of mine called
the electro contact mine, which is nred
by an electric cable leading from the
shore. When an enemy is in sight and
friendly ships are passing in and out Of
the harhor, the torpedo may be arranged
SO that if the mine Is struck it will not
explode. This is done by an arrange
nent of the firing pins on springs which
causes them to return to the proper posi-
ton in case they are accidentally driven
in.
Another type of mine is that known as
the observation mine, in which the firing
mechanism and mine proper are in gepa-
rate cases. Whenever the firing pins are
driven In, the signal circuit is closed and
bell rung at the shore station. Under
meath each bell is key for closing the
firing circuit The observer, standing Mt
a keyboard, on seeing certain bell ring,
knows that the buoy above the correspond
ing mine has been struck, and imue-