Rocky Ford enterprise., 1915-02-05

-0z- OF the war. ANA the same may
be said OF the harbors of Germany.
But these contrivances for harbor defense, while
much more formidable and dangerous to an enemy.
harmless to friendly ships. They what
known as Conservation mnes and being con-
nected by wire with the shore. are set off by the
sending of an electric spark at moment when a
hostile vessel may happen to be within range OF
their tremendous explosive activities.
All the navigable channels of the harbor of
Portsmouth for example. at this moment
guarded by an elaborate system OF mime fields"
which protected by rapid-fire guns on shore.
At night they under constant watch, well
by day, being swept by huge search!ights.
Such mines hollow spheres OF galvanized
iron three feet In diameter each containing 500
pounds of guncotton. which Is lighter than water.
that they float. They are anchored few
feet below the surface In series of lines across
channel, about eighty feet apart In each line.
II an enemys 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 mine
field is laid off (by careful survey in a checker.
board of imaginary squares. This checkerboard is
reproduced n small scale table in
derground casemate on shore. which is part of
fort. Suppose a hostile vessel to approach Two
telescopes 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 telescopes electrically connected with two
pointers that move on the table. Moving with the
telescopes. the ends of the pointers meet on tho
square corresponding to the where lover the
mine field the vessel actually is. button mark
ed with the number of that square is touched. and
bang,-she is blown sky-high.
Small steamers especially equipped for the pur-
pose are used in the business of planting these
mines and the work being of such great import.
ance the men who undertake 1t are highly trained
Theirs is branch of the coast artillery which
does its fighting literally under water and apart
from the mechanical details of their employment.
they n ust have fairly expert acquaintance with
electricity and the chemistry of explosive.
a part of the preliminary work OF establishing
a mine field consists in making soundings. The
depths all over the surveyed having been
ascertained, wire ropes are measured OFF into cor
responding lengths, heavy leaden sinker Tor
anchor) being attached to end of each. and
mine to the other end. BY this simple means the
sphere of galvanized iron is made to float just as
many feet below the surface as may be desired
Recently, however. an ingenious automatic an
Choir has been contrved. by which. no matte:
what the DEPTH exactly the required submergences
for each submarine may be obtained offhand.
As yet experience in actual warfare has not
afforded practical demonstration of the usefulness
of such observation mines. But of their destruc-
tive power there be question. Many ex-
periments have been made with them in the blow
ing up of old hulks. and this side of the water.
not long ago. a miniature ship of war was scat
tered in smithereens at Fort Totten, n. Y. by
mine of corresponding size gnited by an electric
spark from a distance of mile and quarter.
From such trials the conclusion has been drawn
that the explosion of mine containing 500 pounds
of guncotton would at least disable the stoutest
battleship within radius of 60 feet, IL 1t did not
sink her In a field defending a harbor channel.
each row OF galvanized iron spheres is strung
along electric cable. which Is attached TO the
sinkers (or anchors) and runs along the bottom
The rows are connected together by a main cleo
trio cable to which each mine is Joined by
branch cable that meets it Just above the anchor
Thus every mine IN the field" is under direct
control by the apparatus in the casemate on shore
The casemate is underground room, lined
,nst, al tI,o phnn SIM
for controlling the mine system. 1t is connected
by telephone and otherwise electrically. with the
two observing stations. in which are mounted the
telescopes already mentioned for watching hostile
ships
Sometimes for the protection of harbors, what
are called "electro-contact" mines are used. They
are much smaller in size. and are commonly ar
ranged In groups OF five or SIX which are con