The evening times., 1898-07-16
TUE POT0MAC MINE FIELDS
Fear That Their Explosion May
Impair the Channel.
PLANS FOR THEIR REMOVAL
The Method Of Cleaxing the River
of Gum lotion VIII BE Left to
the Engineers at Fort Washing
ton and sheridan Point-How
Mines Are Controlled.

Although vessel owners have been
granted permission to pass through the
mine fields of the Potomac River at any
hour. no order for the removal of the
mines has as yet been sent to the engin-
GERS at Forts Washington and Sheridan.
The manner In which the mines will be
removed will be left entirely to the en-
gineers. They might be raised without
danger, but to unload the torpedoes of
their charge of dynamite would involve
risk In exploding them the possibility
of injuting the channel is a consideration.
While the explosions would create holes,
they might also create Jumps, which
would lessen the depth of water in places.
Each mine is charged with go pounds of
dynamite and the movement of key on
the electrical switchboard in the case
mates of the forts would create the nee
essary spark to explode the charge. Any
vessel within forty feet of the mine would
be a victim of this force. OF If none
were around huge column of water
would be thrown high in the air. As the
mines are anchored on the river bed by
their own weight, the force exerted in all
directions by the explosion would make
a hole in the bed.
There are two fields of mines. so that
should vessel of the enemy escape one
she must encounter the other before en-
tering the harbor. These fields are in the
vicinity of Forts Washington and Sheri-
dan. and control the passage of the chan
nel which would have to be used by
warShip.
There are two classes of mines. one
known as Judgment mines, which are
fired from the classmates. and the other
contact mines, which can be set from
the classmates TO go off when struck by
a ship. The mines are connected in
groups of three at distance of seventy
five feet. SO that they can be exploded
together TO make sure of the destructive
work for which they are intended. Let
vessel of the enemy get in or near this
triangle and her destruction is sure If a
judgment set fails TO do the work the
contact mines are counted upon TO per-
form IL. Both classes of mines are under
control of the operator in the casemate,
and in an instant can be changed from
one class 10 the other.
The shells containing the charge of
dynamite is of heavy galvinized boiler
iron and is shaped like a mushroom. Its
base is about three feet wide and the |
altitude in the center is about two feet.
small stick of dynamite of higher eX-
plosive nature than the charge is fixed |
So that an electric spark sets it off, and
this in turn expiodes a detonating cap !
which eXpiodes the charge.
The completion OF the circuit which |
sends the death-dealing current into the |
mine Is done by simply moving a key on |
the switchboard. Wires leading to the .
mines are thoroughly insulated and in
closed in a heavy armored cable TO pre-
vent injury if struck by vessels. A ball |
Of galvanized iron floats a few feet be-
low the surface of the water, and is con-
nected to the mine by a cable which also
carries the electrical connection. An in
suated ring divides this ball and the !
sections are connected TO the poles of the
electrical battery which supplies the cur
rent. The insulated ring keeps the cir
cult open, and to create the spark that
explodes the mine ii is necessary to close
the circuit. To accomplish this brass
ball is placed in the bottom of the cham.
Der. and when a vessel strikes the cylin-
der inclOSipg it the jar throws the bail
around and as it rolls over ths insulated
ring il has contact with the metal on
either side completing the circuit through |
he bail. If the switchboard in the case
mate At the Tort is set for a contact ex-
Dlosion the mine goes off. but If Ii is not ,
SO Set there will be no explosion. A num-
Der of vessels have struck these cylin-
iers. and even dragged the mines out of |
n ,
NE operator in the easement that no ,
lamage was done
An interesting feature of the method in
Shich the mines are controlled is tine .
means employed in locating vessel and ! .
exploding the right group of mines to .
estroy her. base line has been estab- q
shed along the Fort Washington side
win an expert stationed at either end
no telephone COMMUNICATION between |
nem- Each Is provided with chart of @
ne mine helds and plat of the shore
ne. When vessel appears each man
axes a sight with the proper instru-
rents and the result is shown on the |
mart As the vessel moves between the h
NO stations the intersection of the two C
o.nts of sight locates her position.
ther sights are taken ana the speed of :,
lie vessel noted. so that the osition of |
he vessel Is shown with mathematical | d
;uracy. reference is then made to the ! n
lart of the mine fields and the group of p
ineS nearest to the vessel Is shown | NJ
n order 10 get ready 10 explode the | -
roup goes over the telephone to the man | :"
the switchboard. and at the moment
hen :he vessel is over or near the pt
cups the explosion occurs n,
Men used to handling high explosives Is
ere secured to do the work, and the
ay in which they handled dynamite ~
artled those who were around when the
DIX was going on. Two fabricated boards T,
ere used on the scow where the torpe- y,
es were charged, along which the load :,
torDedoes were slid to the end of the =,
ow. One day men were showing load ~
torpedoeS along these boards but in oe
Herent directions, and not watching =
cir movements the shells came toyeth- .r
with crash. The officer in charge of II,
e scow turned pale and those around ~
re speechiess as the possibility of an a.,
plosion flashed across their minds ~ ~
hen the: recovered their conposure A,
men heard some words that were al on
Isl not enough 10 set off the torpedoes. II
--- ity
Tide Table. sp
Foday-Low tide at $40 a. m and e.,5 tn
M; hiS! tide. 1927 a. m. cla