Evening star. [volume] (Washington, D.C.) 1854-1972, 1896-02-15
FOR COAST DEFENSE
Practical Use for Great Magnets in
Modern Warfare.
EXPERIMENTS At WILLET'S POINT
Effect of BattIeship Entering /;
Harbor.
VIE VS. OF A SCIENTIST

| II w OF A SOLE II ST
So many people have been 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 experiments in
| this matter may be of interest
Out of what was at first mere idle Gu
riosity, 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, 1884, Col w. R. King, then
| commanding engineer at the United States
| engineering school at Wiliet's Point, on
| Long Island, tried to see how powerful a
magnet he could make, and of what use it
would be. He took the largest steel cannon
he had (of which it is unnecessary to give
the dimensions here, plugged up the muz-
Zie with soft metal then wrapped the bar
rel with copper wire, thereby making an in
strument that could be greatly magnetzed
by a current Of electricity. When the cur
rent was turned on, all small pieces of iron
lying near the cannon began to leave their
places and cling to the great magnet. A
man took dinner tray loaded with pieces
of scrap iron weighing from an ounce to
pound, and when he was within one hun
dred 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
We're through eating. Next a crowbar
| weighing twenty-five pounds was taken
near the cannon. 1t flew out of the man.
| hand and stuck with such force that two
| strong mel. were required to pull it away,
| and this could be done then only by sud
| den jerk.
| 1t was noticed also that the magnetic
| compasses in the immediate neighborhood
| We're appreciably depleted by this, the
| greatest magnet in the world. Some news
| paper reports at the time quoted Col. King
| as saying that a ships compass could be
| detected six miles at sea, but this was an
| injustice to the colonel, and herewith Is
! given an extract from private letter writ
| ten by him at the time. to show what was
| really done. After deprecating the wrong
statements by certain newspapers, Col.
King wrote:
| actly what the effect is on the needle, and
! this l had carefully tested just before your
| letter came, viz, at distance of 30, 100,
, 100 and 200 feet. In line nearly east and
west through the magnet, the reflections
| of the compass were So degrees, 16 degrees,
! 8 degrees and 21@ degrees, which shows the
rate at which the force tapers off, SO to
| speak.
You may also be interested in some pic
| lures recently taken, showing the magnet
holding up five 320-pound pr0jectiles, ami
now the force VIII pass through a man ana
| cause iron to stand out from his body,
like quilts upon the fretful porcupine.'
| The pictures show number of large
spikes attaching horizontally to the body of
! a man standing near the magnet.
What Might BE Done.
To illustrate the practical use of the
force in this great magnet, as it might be
applied to coast and harhor defenses at
New York and other places, shall give the
| sui of -oII- h
| the department of natural physics, Colunl-
| bia College, in relation to the effect that
| combination of these great magnets might
have upon battleShips approaching harbors
| and coasts. Prof. RaIlocil said:
| Il know OF Col. Kings great magnet.
| The magnetic power in it could not be
tran smitted through copper or any kind of
wiz, running out from the shore to small
| receiving magnets lying at the bottom OF
| the channel entrance to a harbor, because
! the currents slope eff, as it were, into air or
water as they proceed from the great mag
| net, thereby losing force. But ther- Is
nothing to hinder tine planting of Z. line OF
these great magnets across the entrance
| to a harbor several miles a sea, and mag
netting them through cables from the
| shore at short notice. They could be sunk
| to the bottom of the sea, and would CT Just
! as efficiently under water as on land.
For instance take the entrance to New
! York harb0r. The chart here, as you see
| shows that the channel is very narrow and
| that is one great advantage. If We should
| take few old cannon barrels and make
| magnets OF them, like Col Kings they
| could be dropped in a line across the cham
| mel few hundred feet apart, and here and
! t'lere around Sandy Hook, connecting them
| each with a powerful battery on shore
| The apparatus would be compare lively in
| expensive and simple. Each one would be
| what we call temporary magnet. that is
one which could be magnetized ternpora-
riiy by a current of electricity transmitted
| through the cable from the shore. A Der-
| manent magnet, or one retaining constant
| power, could hardly be made large enough
| to be efficient and if it Were its constant
| force would endanger all incoming vessels
| all the time. But a magnet or line Of n1a-r-
| nets like Col, Kings, could be magnetizai
| and made active in a minute, and the cur
rent could be shut off quickly. The
! power OF the magnet would depend upon
| the strength of the current received from
| the shore.
Eject IN :, BatHcsEfp.
| Now, suppose a battleship were coming
| up the channel .nto New York harbor. The
| ship is made a most entirely Of iron and
steel The line If great magnets lying un-
| der and across S Roadway could be pow
| erfully magnetized. When the ship APP
| preached within two hundred feet OF a
| magnet, the latter would leave its bed and
cling to the forward keel, and IL the shin
| should pass Directly over one of the mag
| nets, the depth of water below the keel is
! so slight that the magnet would come UP
| to the snip with great force. Having once
| touched the keel, the electric current from
the shore would either stop the ship or the
magnet would be dragged along the keel
| until 1t would strike the propelers. which
| would be done with such force as to crush
| them.
| IN case the first magnet should not be
| strong enough, and the ship should cross a
| second, the second would seek the end of
the ship opposite the first forming the two
| poles and magnetizing the entire ship
| Then it would be impossible for the ships
! steam power to overcome this force, while
| all movable iron would be stuck solid
"All this is very plausible and could be
! made practical OF course, what is done in
| New York harbor and along the immediate
| coasts could be done elsewhere. 1t would
| cost very little to try this first on one of
| our own battleships entering the harbor
and little harm could be done, for the cur
rent from the shore could be shut of i'm
media tely al a signal from the ship
| LAS to the detection of the compass of
| the ship, when one of these magnets should
| strike the keel, the compass could be made
to whirl like school boys top, for it would
be an almost direct ontact with the mag