El Paso herald. (El Paso, Tex.) 1901-1931, 1914-11-21

WASHINGTON, d. c., Nov. I'll
M Although IL is only recently
w and with reluctance that Eng
land, fonr the protection of her shores
and ships, has Gin imitation Of the
GCImaus) resOrted to the eXpedient OF
sowing the Straits OF Dover and the
North Sea with contact Mines all the
harbors of the British Isles have been
planted with submarine explosive con-
irlvances ever since the beginning of
the war. And the same may be said
Of the HORRORS Of Germany.
But these cOntrlvances for harbor
defence, while much more formidable
and dangerous to an enemy, are harm
less to friendly ships. They are what
are known as observation mines and,
being connected by wire with the
shore, are set off by the sending of
an electric spark at the moment when
a hostile vessel may happen to be
within range of their tremendous ex-
plosive activities.
All the navigable channels Of the
harbor OF Portsmouth for example, are
at this moment guarded by an elabor-
ate system Of mine fields" which are
protected by rapid fire guns on shore.
A. night they are under constant
watch, as wen as by day, being swept
by huge searchlights.
Have Heavy Charge.
Such mines are hollow spheres OF
galvanized iron three feet in diameter
each containing 500 pounds of gun
that they can float They are an
chored a few feet below the surface
IN a series Of lines across a channel,
about so feet apart in each line. If
an enemy's ship were to succeed by
good luck in getting through one line
without being blown up, she could
hardly pass another.
The area of water surface covered
by a mine field is laid off (by careful
survey in a checkerbOard of imagin-
airy squares This checkerbOard is re-
produced on a small scale on table
in an underground casemate on shore,
which is part Of a fort suppose a
hostile vessel to approach Two tele-
scopes are aimed at her from points on
shore some hundreds OF yards apart
their lines of sight crossing, of course,
AT the spot where she floats. The tele-
scopes are electrically connected with
tv o pointers that move on the table.
Moving with the telescopes the ends
OF the pointers meet on the square
corresponding to the one where lover
the mine field the vessel actually Is.
A button marked with the number Of
that square is touched, and bang!-she
Is blown skyhlgh.
Small steamers specially equipped
for the purpose are used in the bust
ness of planting these mines, and, the
work being of such great Importance,
the men who undertake it are highly
trained Theirs is branch Of the
coast artillery which does it's fight
iHE literally under water, and, apart
trCm the mechanical details OF their
employment, they must have fairly
expert acquaintance with electricity
and the chemistry of explosives.
Depths Are Measured.
A part of the preliminary work Of
establishing mine field consists IN
ma king sOundings. The depths all
over the surveyed area having been
asCertained. wire ropes are measured
off into corresponding lengths, heavy
leaden sinker Cor another being at
tached to one end of each, and a mine
to the other end. BY this simple means
the sphere Of galva nized iron is made
TO float just as many feet below the
surface as may be desired. Recently.
however, an ingenious automatic
anchor" has been contrived by which
no matter what the depth, exactly
the required submergence for each sub
marine mine may be obtained off
hand