The Portland daily press., 1891-05-27
ARRANGING FOR OUR DEFENCE.
The Board of Engineers INSPECT the
Harbor.
Picking Out Locations for Big Guns
and Torpedo Stations.

General Henry l.. Abbott, General Cyrus
FL. Comstock, Colonel David c. Houston and
Lieutenant Colonel George L. Gillespie of
the Board of Engineers Of the United States
Army, yesterday forenoon were taken in
charge by Lieutenant Colonel Jared A.
Smith, the district engineer. and left on the
steam launch Leo, for a tour of the govern
ment reservations on the main land and on
the islands in the harbor.
They examined the site of the battery at
Portland Head Cow Island, which the gov
ernment owns, and on which at some future
date 1t is proposed to establish Notifications
for the defence of Hussey's Sound, where
the water is very deep; the spurs on each
side OF Diamond Cove. and Forts Preble,
Scammell and Gorges, besides other locali-
ties and elevations which appeared to be de-
sirable points and elevations best calculated
to defend the city with guns of the heaviest
calibre, rifles and mOrtarS, together with the
system of torpedo defence. The board will
submit their report as soon as possible to the
Secretary of War. and it is understood that
these officers are very favorably impressed
with Portland as strategic point.
Next month Colonel Smith will commence
the construction of casemate, or operating
room, and gallery for torpedoes, in connec-
ton with the battery for Portland Head.
The locality selected is rocky cliff, and in
order tor the casemate to be we'll protected
II VIII be sunk into the ledge. The gallery,
In which Is laid the cable communicating
with torpedoes in mid channel, and the case
mate and machinery will cost $4,000. The
of 90
gress, and 1t is expected that this sum will
ne granted by tho mont Csns.esss to bo OK
pended in fortifying Portland harbor. The
present plan of defence advocated by this
board In regard to Portland, aims at the
erection of batteries on the outermost points
of land bounding the harbor, for the defence
OF the harbor channels. The torpedo station
at Portland Head will be very effectual
method of defence, and will be capable of do
Ing great harm to an invading vessel of war.
The system of torpedo or mine warfare
which will be used at Portland Head, is a
very ingenious one. 1t is operated from the
electric batteries on shore. Electrical mines
have the advantage over the mechanical, that
by the removal of the firing battery the pas
sage OF ship is rendered perfectly safe, and
that the condition of the mine can be ascer
tained by electrical tests. Gun cotton and
dynamite are the explosives generally used
in mines, the charges varying from 80 to 500
pounds, according to the description of the
mines. In all mines the charge is exploded
by means of detonator, containing fulmi.
nate of mercury
The electrical circuit of all electrical mines
Is very similar. A voltaic battery ashore has
one pole put permanently to the earth, and
the other pole Joined to the electric cable
leading to the mine out in the channel. This
cable passes into the mine case, through
water-tight joint. and is connected up to one
pole of the electric detonator, the other pole
OF the detonator being connected to the
mouth-piece of the mine and consequently
to earth. The current is closed by means of
firing key, and in this way the mine or tor
pedo is exploded.
The government officers left for New York
yesterday afternoon.