The Portland daily press., 1896-02-22
FOR COAST DEFENSE.
Practical Use of Great Magnets in
in Modern Warfare.
Effect of Battleship Entering Harbor.

Effect of Battleship Entering HarbOr.
Washington Starr
So many people have heen talking and
thinking within the past few weeks. and
even nervous about the ways and means
of defending the coasts of the United
States against attacks by foreign power
that the progress of electrical expert
ments i'll this matter may be of interest.
Out of what was at first mere idle curl
osity. I took the trouble to find out how
far electricity can be relied upon as an
aid, or single factor in defending our
coasts and harbors, and the result is
here given.
In November, 1894, Col. W. r. King
then commanding engineer at the United
States engineering school at Willet's
Point, on Long Island, tried to see how
powerful magnet he could make, and
of what use il would be. He took the
largest steel damon he had (of which it
is unnecessary to give the dimensions
here). plugged up the muzzle with soft
metal, then wrapped the barrel with oop-
per wire, thereby making an instrument
that could be gIeatly magnetized by
current of electricity. When the current
was turned on, all small pieces of iron
lying near the cannon began to leave their
places and cling 10 the great magnet A
man took dinner tray loaded with
pieces of scrap iron weighing from an
ounce to a pound, and when he was with
in one hundred feet of the magnet the
pieces began to leave the tray and cling
to the cannon, and little nearer the
platter was as clean as that of Jack Sprat
and his wife after they were through
eating. Next crowbar weighing
twenty-five pounds was taken near the
cannon. 1t flew out of the mans hand
and stuck with such force that two
strong men weTe required to pull it away
and this could he done then only by q
sudden jerk.
1t was noticed also that the magnetic
oompasses in the immediate neighborhood
were appreoiably depleted by this, the
greatest magnet in the world. Some
newspaper reports at the time quoted
Col. King as Saying that ships COM
pass could be detected six miles at sea,
but this was an injustice to the colonel,
aud herewith isgiven an extract from a
time, to show what was really done.
After depreoatiDg the wrong statement
by certain newspapers, Col King
wrote:
sit may be Of interest to you to know
exactly what the effect is on the needle
anu this had carefully tested just be-
lore your letter came. viz, at a distance
of SO. 100, $50 and 200 feet. In q line
nearly east and vest through the mag
net, the defiections of the compass were
IS degrees, Is degrees, degrees and 2 Ia
degrees which shows the rate at which
the force tapers off, so to speak.
'sYou may also be interested in some
pictures recently taken, showing the
magnet holding up five 320-pound projec-
man and cause iron to stand out from
his body, ''like quilts upon the fretful
porcupine.
The pictures show mum Der OF large
spikes attaching horizontally to the body
of man standing near the mauget.
WHAT MIGHT BE DONE.
To illustrate the practical use Of the
force in this great magnet. as it might
be applied to coast and harbor defenses
as New York and other places, I shall
give the result of a talk with Prof. w.
Hallook of the department Of natural
physics, Columbia College, in relation to
the effect that combination of these
great magnets might have upon battle
ships approaching harbors and coasts.
Prof. Ha!lock said:
81 know of Col. Kings great mag
net. The magnetic power in it could not
kind of wire running out from the shore
to small receiving magnets lying at the
bottom of the channel entrance TO har-
Dor, because the currents slope off, as it
were, into air or water as they proceed
from the great magnet. thereby losing
force. But there is nothing TO hinder
the planting of line of these great mag
nets across the entrance to a harbor sew
eral miles at sea, and magnetizing them
through cables from the shore at short
notice. They could be sunk to the bot
tom of the sea, and would act just as eff
GENTLY under water as on land.
''For instance. take the entrance to
New York harbor. The charter, as you
see, shows that the channel is very mar
row, aud that is one great advantage. If
we should take a few old cannon barrels
and make magnets of them, like Col.
Kings, they could be dropped in a line
across the channel a few hundred feet
apart, and here and there around Sandy
Hook, connecting them each with u
powerful battery on shore. The apparatus
would be comparatively inexpensive and
simple. Each one would be what we call
a temporary magnet, that is, ons which
could be magnetized temporarily by a
current of electricity transmitted through
the cattle from the shore. A permanent
magnet, or one retaining constant power,
could hardly DO made large enough to be
efficient, and If it were, It's constant force
would endanger all incoming vessels all
the time. But magnet, or line of mag
nets like Col. Kings, could be magne-
tized and made active in q minute, and
the current could be shut off as quickly
The power of the magnet would depend
upon the strength of the current re-
ceived from the Shore
EFFECT ON A BATTLESHIP.
"Now suppose battleship were coming
up the channel into New York harbor
The ship is made almost entirely Of iron
and steel. The line of great magnets
lying under and across its Roadway
could be pqVerfully magnetized. When
the ship approached within two hundred