<h2><SPAN name="CHAPTER_XIV" id="CHAPTER_XIV">CHAPTER XIV</SPAN><br/> <span class="subhead">"<span class="smcap">Devil's Eggs</span>"</span></h2>
<p class="drop-cap3"><span class="smcap1">In</span> modern warfare a duel between fixed forts
and floating forts is almost certain to end
in a draw. Because the former are fixed they
make good targets, while the war-ship, being
able to move about, can dodge the shell that are
fired against it. On the other hand, a fort on
land can stand a great deal of pounding and
each of its guns must be put out of action individually,
before it is subdued, while the fort
that is afloat runs the risk of being sunk with
a few well-directed shots.</p>
<p>But fortifications alone will not protect a
harbor from a determined enemy. They cannot
prevent hostile ships from creeping by them
under cover of darkness or a heavy fog. To
prevent this, the harbor must be mined, and this
must be done in such a way that friendly shipping
can be piloted through the mine-field,<span class="pagenum"><SPAN name="Page_277" id="Page_277">277</SPAN></span>
while hostile craft will be sure to strike the
mines and be destroyed.</p>
<p>The mines may be arranged to be fired by
electricity from shore stations, in which case
they are anchored at such a depth that ships
can sail over them without touching them. If a
hostile vessel tried to dash into the harbor, the
touch of a button on shore would sink it when
it passed over one of the mines. But the success
of electrically fired mines would depend
upon the "seeing." In a heavy fog they would
prove no protection.</p>
<p>Another way of using electric mines is to
have telltale devices which a ship would strike
and which would indicate to the operator on
shore that a vessel was riding over the mines
and would also let him know over which particular
mines it was at the moment passing.
No friendly vessel would undertake to enter
the harbor in a fog or after dark and the operator
would not hesitate to blow up the invader
even if he could not see him.</p>
<p>However, the ordinary method of mining a
harbor is to lay fields of anchored mines across
the channels and entrances to the harbor—sensitive
mines that will blow up at the slightest<span class="pagenum"><SPAN name="Page_278" id="Page_278">278</SPAN></span>
touch of a ship's hull—and leave tortuous
passages through the fields for friendly shipping.
Of course pilots have to guide the ships
through the passages and lest enemy spies learn
just where the openings are the mine-fields
must be shifted now and then.</p>
<p>The mines are, therefore, made so that they
can be taken up by friendly mine-sweepers who
know just how to handle them, and planted elsewhere.
These are defensive mines, but there
are other mines that are not intended to be
moved. They are planted in front of enemy
harbors to block enemy shipping and they are
made so sensitive or of such design that they
will surely explode if tampered with.</p>
<h3>THE MINE THAT DOES ITS OWN SOUNDING</h3>
<p>A favorite type of mine used during the war
was one which automatically adjusted itself to
sink to the desired depth. Submerged mines
are more dangerous to the enemy because they
cannot be seen and avoided. They should float
far enough under the surface to remain hidden
and yet not so deep that a shallow-draft ship
can pass over them without hitting them. As
the sea bottom may be very irregular, it is impossible<span class="pagenum"><SPAN name="Page_279" id="Page_279">279</SPAN></span>
to tell how long the anchor cable should
be without sounding the depth of the water at
every point at which a mine is planted. But
the automatic anchor takes care of this. Very
ingeniously it does its own sounding and holds
the mine down to the depth for which it is set.
The mine cable is wound up on a reel in the
anchor and the mine is held fast to the anchor
by a latch. The anchor is of box-shape or
cylindrical form, with perforations in it. At
first it sinks comparatively slowly, but as it
fills with water it goes down faster. Attached
to the anchor is a plummet or weight, connected
by a cord to the latch. The length of this cord
determines the depth at which the mine will
float.</p>
<div id="ip_279" class="figcenter" style="width: 340px;">
<ANTIMG src="images/i_280.jpg" width-obs="340" height-obs="268" alt="" /><br/>
<div class="captionl">Courtesy of the "Scientific American"</div>
<div class="caption0"><span class="smcap">Fig. 22.</span> How the mine automatically adjusts itself to various
depths of water</div>
</div>
<p>The operation of the mine is shown in <SPAN href="#ip_279">Fig. 22</SPAN>.
When it is thrown overboard (1) it immediately
turns over so that the buoyant mine
<i>A</i> floats on the surface (2). While the anchor
is slowly filling and sinking, the plummet <i>B</i>
runs out (3). If the mines are to float at a
depth of, say, ten feet, this cord must be ten
feet long. As soon as it runs out to its full
length (4) it springs a latch, <i>C</i>, releasing the
mine <i>A</i>. Then the mine cable <i>D</i> pays out, as<span class="pagenum"><SPAN name="Page_280" id="Page_280">280</SPAN></span>
the anchor <i>E</i> sinks, until the plummet <i>B</i> strikes
bottom (5). As soon as the plummet cord
slackens a spring-pressed pawl is released and
locks the mine-cable reel, so that as the anchor
continues to sink it draws the mine down with
it, until it touches bottom (6), and as the anchor
was ten feet from the bottom when the plummet
touched bottom and locked the reel, the mine<span class="pagenum"><SPAN name="Page_281" id="Page_281">281</SPAN></span>
must necessarily be dragged down to a depth
of ten feet below the surface.</p>
<p>The mine itself, or the "devil's egg" as it
is called, is usually a big buoyant sphere of
metal filled with TNT or some other powerful
explosive; and projecting from it are a
number of very fragile prongs which if broken
or even cracked will set off the mine. There
is a safety-lever or pin that makes the mine
harmless when it is being handled, and this
must be withdrawn just before the mine is to
be launched. In some mines the prongs are
little plungers that are withdrawn into the
mine-shell and held by a cement which softens
after the mine is submerged and lets the
plungers spring out. When the plungers are
broken, water enters and, coming in contact
with certain chemicals, produces enough heat to
set off a cartridge which fires the mine.</p>
<h3>PICKING INFERNAL MACHINES OUT OF THE SEA</h3>
<p>The enemy mine-fields were often located
by seaplanes and then mine-sweepers had to
undertake the extremely hazardous task of raising
the mines or destroying them. If they
were of the offensive type, it was much better<span class="pagenum"><SPAN name="Page_282" id="Page_282">282</SPAN></span>
to destroy them. But occasionally, when conditions
permitted, mine-sweepers undertook to
raise the mines and reclaim them for future use
against the enemy. The work of seizing a mine
and making it fast to the hoisting-cable of the
mine-sweeper was usually done from a small
rowboat. Raising the first mine was always
the most perilous undertaking, because no one
knew just what type of mine it was and how to
handle it with safety, or whether there was any
way in which it <i>could</i> be made harmless. There
were some mines, for instance, that contained
within them a small vial partly filled with
sulphuric acid. The mine carried no prongs,
but if it were tilted more than twenty degrees
the acid would spill out and blow up the mine.
Such a mine would be exceedingly difficult if
not impossible to handle from a boat that was
rocked about by the waves.</p>
<p>After the first mine of the field was raised
and its safety-mechanism studied, the task of
raising the rest was not so dangerous. A
water telescope was used to locate the mine and
to aid in hooking the hoisting-cable into the
shackle on the mine. The hook was screwed
to the end of a pole and after the mine was<span class="pagenum"><SPAN name="Page_283" id="Page_283">283</SPAN></span>
hooked, the pole was unscrewed and the cable
hauled in, bringing up the "devil's egg"
bristling with death. Care had to be taken to
keep the bobbing boat from touching the delicate
prongs until the safety-device could be
set.</p>
<p>However, this painstaking and careful
method of raising mines was not often employed.
Shallow-draft mine-sweepers would
run over the mine-field, dragging a cable between
them. The cable would be kept down by
means of hydrovanes or "water kites" deep
enough to foul the anchor cables of the mines.
The "water kites" were V-shaped structures
that were connected to the cable in such a way
that they would nose down as they were
dragged through the water and carry the cable
under. The action is just the reverse of a kite,
which is set to nose up into the wind and carry
the kite up when it is dragged through the air.
By means of the cable the anchor chain of the
mine was caught and then the mine with its
anchor was dragged up. If the mine broke
loose from its anchor it could be exploded with
a rifle-shot if it did not automatically explode
on fouling the cable.</p>
<p><span class="pagenum"><SPAN name="Page_284" id="Page_284">284</SPAN></span></p>
<h3>FLOATING MINES</h3>
<p>When England entered the war she mined her
harbors because, although she had the mastery
of the sea, she had to guard against raids of
enemy ships carried out in foggy and dark
weather. But the mines were no protection
against submarines. They would creep along
the bottom under the mines. Then cable nets
were stretched across the harbor channels to
bar the submarines, but the U-boats were
fitted with cutters which would tear through
the nets, and it became necessary to use mines
set at lower depths so that the submarines could
not pass under them; and nets were furnished
with bombs which would explode when fouled
by submarines. In fact, mines were set adrift
with nets stretched between them, to trap submarines.
Floating mines were also used by the
Germans for the destruction of surface vessels
and these were usually set adrift in pairs, with
a long cable connecting them, so that if a vessel
ran into the cable the mines would be dragged
in against its hull and blow it up.</p>
<p>The laws of war require that floating mines be<span class="pagenum"><SPAN name="Page_285" id="Page_285">285</SPAN></span>
of such a design that they will become inoperative
in a few hours; otherwise they might drift
about for weeks or months or years and be a
constant menace to shipping. Sometimes
anchored mines break away from their moorings
and are carried around by ocean currents
or are blown about by the winds. A year
after the Russo-Japanese War a ship was
blown up by striking a mine that had been torn
from its anchorage and had drifted far from
the field in which it was planted. No doubt
there are hundreds of mines afloat in the
Atlantic Ocean which for many years to come
will hold out the threat of sudden destruction
to ocean vessels; for the Germans knew no laws
of war and had no scruples against setting
adrift mines that would remain alive until they
were eaten up with rust.</p>
<div id="ip_285" class="figcenter" style="width: 339px;">
<ANTIMG src="images/i_286.jpg" width-obs="339" height-obs="285" alt="" /><br/>
<div class="captionl">Courtesy of the "Scientific American"</div>
<div class="caption0"><span class="smcap">Fig. 23.</span> Ocean currents of the North Atlantic showing the
probable path of drifting mines</div>
</div>
<p>The chart on the next page shows the course
of ocean currents in the North Atlantic as
plotted out by the Prince of Monaco, from which
it may be seen that German mines will probably
make a complete circuit of the North
Atlantic, drifting down the western coast of
Europe, across the Atlantic, around the Azores,<span class="pagenum"><SPAN name="Page_286" id="Page_286">286</SPAN></span>
and into the Gulf Stream, which will carry them
back to the North Sea, only to start all over.
(See <SPAN href="#ip_285">Fig. 23.</SPAN>) Some of them will run up into
the Arctic Ocean, where they will be blown up
by striking icebergs and many will be trapped
in the mass of floating
seaweed in the Sargasso
Sea. But many years
will pass before all danger
of mines will be removed.
In the meantime, the war has left a
tremendous amount of work to be done in raising
anchored mines and destroying them.</p>
<p><span class="pagenum"><SPAN name="Page_287" id="Page_287">287</SPAN></span></p>
<h3>EGG-LAYING SUBMARINES</h3>
<p>Early in the war the British were astonished
to find enemy mine-fields in their own waters,
far from any German ports. They could not
have been planted by surface mine-layers, unless
these had managed to creep up disguised
as peaceful trawlers. This seemed hardly
likely, because these fields appeared in places
that were well guarded. Then it was discovered
that German U-boats were doing this
work. Special mine-laying U-boats had been
built and one of them was captured with its
cargo of "devil's eggs."</p>
<p>A sectional view of the mine-laying U-boat
is shown opposite page <SPAN href="#Page_272">272</SPAN>. In the after part
of the boat were mine-chutes in each of which
three mines were stored. A mine-laying submarine
would carry about a score of mines.
These could be released one at a time. The
mine with its anchor would drop to the bottom.
As soon as it struck, anchor-arms would be
tripped and spread out to catch in the sand or
mud, while the mine cable would be released
and the mine would rise as far as the cable
would allow it. The U-boat commander would<span class="pagenum"><SPAN name="Page_288" id="Page_288">288</SPAN></span>
have to know the depth of water in which
the mines were to be laid and adjust the cables
to this depth in advance. This could not be
done while the U-boat was submerged. With
the mines all set for the depth at a certain spot,
the U-boat commander had to find that very
spot to lay his "eggs," otherwise they would
either lie too deep to do any harm to shipping,
or else they would reach up to the surface,
where they might be discovered by the Allied
patrols. As he had to do his navigating blindly,
by dead-reckoning, it was very difficult for him
to locate his mine-fields properly.</p>
<p>But the Germans did not have a monopoly
on submarine mine-laying. The British also
laid mines by submarine within German harbors
and channels, right under the guns of
Heligoland, and many a U-boat was destroyed
by such mines within its home waters.</p>
<div id="ip_288" class="figcenter" style="width: 511px;">
<ANTIMG src="images/i_288.jpg" width-obs="511" height-obs="359" alt="" /><br/>
<div class="captionl">(C) Press Illustrating Service</div>
<div class="caption0">A Dutch Mine-sweeper engaged in clearing the North Sea of German Mines</div>
</div>
<h3>PARAVANES</h3>
<p>On the other hand, the Allies had a way of
sailing right through fields of enemy mines
with little danger. Our ships were equipped
with "paravanes" which are something like
the "water kites" used by mine-sweepers, and<span class="pagenum"><SPAN name="Page_289" id="Page_289">289</SPAN></span>
they are still used in the waters of the war zone.
Paravanes are steel floats with torpedo-shaped
bodies and a horizontal plane near the forward
end. At the tail of the paravane, there
are horizontal and vertical rudders which can be
set to make the device run out from the side of
the vessel that is towing it, and at the desired
depth below the surface. Two paravanes are
used, one at each side of the ship, and the towing-cables
lead from the bow of the vessel.
Thus there are two taut cables that run out
from the ship in the form of a V and at such a
depth that they will foul the mooring-cable of
any mine that might be encountered. The mine
cable slides along the paravane cable and in
this way is carried clear of the ship's hull.
When it reaches the paravane it is caught in a
sharp-toothed jaw which cuts the mine cable and
lets the mine bob up to the surface. The mine
is then exploded by rifle or machine-gun fire.</p>
<div id="ip_289" class="figcenter" style="width: 364px;">
<ANTIMG src="images/i_289.jpg" width-obs="364" height-obs="493" alt="" /><br/>
<div class="captionl">Courtesy of "Scientific American"</div>
<div class="caption0">Hooking Up Enemy Anchored Mines</div>
</div>
<p>In some forms of paravane there is a hinged
jaw which is operated from the ship to shear the
cable. The jaw is repeatedly opened and
closed by a line that runs to a winch on the ship.
This winch winds up the line until it is taut
and then the line is permitted to slip, letting<span class="pagenum"><SPAN name="Page_290" id="Page_290">290</SPAN></span>
the jaw open, only to close again as the winch
keeps on turning and winding up the line.</p>
<p>Guarded by steel sharks on each side, their
jaws constantly working, a ship can plow right
through a field of anchored mines with little
danger. To be sure, the bow might chance to
hit a mine, when, of course, there would be an
explosion; but the ship could stand damage here
better than anywhere else and unless the bow
actually hit the mine, one or other of the paravanes
would take care of it and keep it from
being dragged in against the hull of the vessel.</p>
<h3>PENNING IN THE U-BOATS</h3>
<p>According to German testimony, mines were
responsible for the failure of the U-boat. However,
it was not merely the scattered mine-fields
sown in German waters that brought the
U-boat to terms, but an enormous mine-field
stretching across the North Sea from the Orkney
Islands to the coast of Norway. Early in the
war, U-boats had been prevented from entering
the English Channel by nets and mines stretched
across the Straits of Dover. As the submarine
menace grew, it was urged that a similar net
be stretched across the North Sea to pen the<span class="pagenum"><SPAN name="Page_291" id="Page_291">291</SPAN></span>
U-boats in. But it seemed like a stupendous
task. The distance across at the narrowest
point is nearly two hundred and fifty miles.
It would not have been necessary to have the
net come to the surface. It could just as well
have been anchored so that its upper edge
would be covered with thirty feet of water.
Surface vessels could then have sailed over it
without trouble and submarines could not have
passed over it without showing themselves to
patrolling destroyers. It would not have been
necessary to carry the net to the bottom of the
sea. A belt of netting a hundred and fifty feet
wide would have made an effective bar to the
passage of U-boats. As U-boats might cut their
way through the net, it was proposed to mount
bombs or mines on them which would explode on
contact and destroy any submarine that tried to
pass. However, laying a net two hundred feet
long even when it is laid in sections, is no small
job, but when the net is loaded with contact
mines, the difficulty of the work may be well
imagined.</p>
<p>And yet had it been thought that the net would
be a success it would have been laid anyhow,
but it was argued that seaweed would clog the<span class="pagenum"><SPAN name="Page_292" id="Page_292">292</SPAN></span>
meshes of the net and ocean currents would tear
gaps in it. Even if it had not been torn away,
the tidal currents would have swept it down and
borne it under so far that U-boats could have
passed over it in safety without coming to the
surface.</p>
<h3>A WALL OF MINES</h3>
<p>When America entered the war, we were very
insistent that something must be done to block
the North Sea, and we proposed that a barrage
of anchored mines be stretched across the sea
and that these mines be set at different levels
so as to make a "wall" that submarines could
not dive under. This would do away with all
the drawbacks of a net. Ocean currents and
masses of seaweed could not affect individual
mines as they would a net. Furthermore, an
American inventor had devised a new type of
mine which was peculiarly adapted to the proposed
mine barrage. It had a firing-mechanism
that was very sensitive and the mine
had twice the reach of any other.</p>
<p>At length the British mine-laying forces were
prevailed upon to join with us in laying this
enormous mine. It was one of the biggest and<span class="pagenum"><SPAN name="Page_293" id="Page_293">293</SPAN></span>
most successful undertakings of the war. It
was to be two hundred and thirty miles long
and twelve miles wide on the average, reaching
from the rocky shores of the Orkney Islands
to Norway. There was plenty of deep water
close to the coast of Norway and it was against
international law to lay mines within three miles
of the shores of a neutral nation, so that the U-boats
might have had a clear passage around the
end of the barrage. But as it was also against
the law for the U-boats to sail through neutral
waters, Norway laid a mine-field off its coast
to enforce neutrality, and this was to join with
that which the British and we were to lay.
Most of the mine-laying was to be done by the
United States and we were to furnish the mines.</p>
<p>The order to proceed with the work was given
in October, 1917, and it was a big order. A
hundred thousand mines were to be made and to
preserve secrecy, as well as to hurry the work
as much as possible, it was divided among five
hundred contractors and subcontractors. The
parts were put together in one plant and then
sent to another, where each mine was filled with
three hundred pounds of molten TNT. To
carry them across the ocean small steamers<span class="pagenum"><SPAN name="Page_294" id="Page_294">294</SPAN></span>
were used, so that if one should be blown up
by a submarine the loss of mines would not be
very great. There were twenty-four of these
steamers, each carrying from twelve hundred to
eighteen hundred mines and only one of them
was destroyed by a submarine. The steamers
delivered their loads on the west coast of Scotland
and the mines were taken across to the
east coast by rail and motor canal-boats. Here
the mines were finally assembled, ready for
planting. Seventy thousand mines were
planted, four fifths of them by American mine-layers
and the rest by the British.</p>
<h3>MINE RAILROADS ON SHIPS</h3>
<p>To handle the mines the ships were specially
fitted with miniature railroads for transporting
the mines to the launching-point, so that they
could be dropped at regular intervals without
interruption. Each anchor mine was provided
with flanged wheels that ran on rails. The
mines were carried on three decks and each
deck was covered with a network of rails,
switches, and turn-tables, while elevators were
provided to carry the mines from one deck to
another. The mines, like miniature railroad<span class="pagenum"><SPAN name="Page_295" id="Page_295">295</SPAN></span>
cars, were coupled up in trains of thirty or forty
and as each mine weighed fourteen hundred
pounds, steam winches had to be used to haul
them. At the launching-point the tracks ran out
over the stern of the boat and here a trap was
provided which would hold only one mine at a
time. By the pulling of a lever the jaws of the
trap would open and the mine would slide off the
rails and plunge into the sea.</p>
<p>The mines were dropped every three hundred
feet in lines five hundred feet apart, as it was
unsafe for the mine-layers to steam any closer
to one another than that. The mines were of
the type shown in <SPAN href="#ip_279">Fig. 22</SPAN> and automatically
adjusted themselves to various depths. The
depth of the water ran down to twelve hundred
feet near the Norwegian coast. Never before
had mines been planted at anywhere near that
depth.</p>
<p>It was dangerous work, because the enemy
knew where the mines were being planted, as
neutral shipping had to be warned months in advance.
The mine-layers were in constant
danger of submarine attack, although they were
convoyed by destroyers to take care of the
U-boats. There was even danger of a surface<span class="pagenum"><SPAN name="Page_296" id="Page_296">296</SPAN></span>
attack and so battle-cruisers were assigned the
job of guarding the mine-layers. The mine-layers
steamed in line abreast, and had one of
them been blown up, the shock would probably
have been enough to blow up the others as well.
Enemy mines were sown in the path of the
mine-layers, so the latter had to be preceded by
mine-sweepers. Navigation buoys had to be
planted at the ends of the lines of mines and the
enemy had a habit of planting mines near the
buoys or of moving the buoys whenever he had
a chance. But despite all risks the work was
carried through.</p>
<p>The barrier was not an impassable one. With
the mines three hundred feet apart, a submarine
might get through, even though the field was
twenty-five miles broad, but the hazards were
serious. Before the first lines of mines had been
extended half-way across, its value was demonstrated
by the destruction of several U-boats,
and as the safety-lane was narrowed down the
losses increased. It is said that altogether
twenty-three German submarines met their
doom in the great mine barrage. U-boat commanders
balked at running through it, and
U-boat warfare virtually came to a standstill.<span class="pagenum"><SPAN name="Page_297" id="Page_297">297</SPAN></span>
According to Captain Bartenbach, commander
of submarine bases in Flanders, three U-boats
were sunk by anchored mines for every one that
was destroyed by a depth bomb.</p>
<hr />
<p><span class="pagenum"><SPAN name="Page_298" id="Page_298">298</SPAN></span></p>
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