MINES
THE MINE SWEEPERS
“‘Ware mine!”
“Starboard your helm.”... “Full speed ahead!”
The squat craft duly swings--
A hand’s breadth off, a thing of dread
The sullen breaker flings.
Carefully, slowly, patiently,
The men of Grimsby Town
Grope their way on the rolling sea--
The storm-swept, treacherous, gray North Sea--
Keeping the death-rate down.
--H. INGAMELLS, in the “London Spectator.”
A mine is a torpedo that has no motive-power of its own but is either
anchored or set adrift in the supposed path of an enemy’s ship. We have
already seen how Bushnell used drifting mines at Philadelphia in 1777.
Anchored mines are among the many inventions of Robert Fulton. The
following description of the original type, illustrated by an engraving
made by himself, is taken from Fulton’s “Torpedo War and Submarine
Explosions.”
[Illustration: Fulton’s Anchored Torpedoes.]
“Plate II represents the anchored torpedo, so arranged as to blow
up a vessel which should run against it; _B_ is a copper case two
feet long, twelve inches diameter, capable of containing one hundred
pounds of powder. _A_ is a brass box, in which there is a lock similar
to a common gun lock, with a barrel two inches long, to contain a
musket charge of powder: the box, with the lock cocked and barrel
charged, is screwed to the copper case _B_. _H_ is a lever which has a
communication to the lock inside of the box, and in its present state
holds the lock cocked and ready to fire. _C_ is a deal box filled with
cork, and tied to the case _B_. The object of the cork is to render
the torpedo about fifteen or twenty pounds specifically lighter than
water, and give it a tendency to rise to the surface. It is held down
to any given depth under water by a weight of fifty or sixty pounds
as at _F_: there is also a small anchor _G_, to prevent a strong tide
moving it from its position. With torpedoes prepared, and knowing
the depth of water in all our bays and harbors, it is only necessary
to fix the weight _F_ at such a distance from the torpedo, as when
thrown into the water, _F_ will hold it ten, twelve, or fifteen feet
below the surface at low water, it will then be more or less below the
surface at high water, or at different times of the tide; but it should
never be so deep as the usual draft of a frigate or ship-of-the-line.
When anchored, it will, during the flood tide, stand in its present
position; at slack water it will stand perpendicular to the weight _F_,
as at _D_; during the ebb it will be at _E_. At ten feet under water
the waves, in boisterous weather, would have little or no tendency to
disturb the torpedo; for that if the hollow of a wave should sink ten
feet below what would be the calm surface, the wave would run twenty
feet high, which I believe is never the case in any of our bays and
harbors. All the experience which I have on this kind of torpedo is,
that in the month of October, 1805, I had one of them anchored nine
feet under water, in the British Channel near Dover; the weather was
severe, the waves ran high, it kept its position for twenty-four hours,
and, when taken up, the powder was dry and the lock in good order. The
torpedo thus anchored, it is obvious, that if a ship in sailing should
strike the lever _H_, the explosion would be instantaneous, and she
be immediately destroyed; hence, to defend our bays or harbors, let
a hundred, or more if necessary, of these engines be anchored in the
channel, as for example, the Narrows, to defend New York.
“The figure to the right of the plate is an end view of the torpedo.
_H-H_ shews its lever forked, to give the better chance of being struck.
“Having described this instrument in a way which I hope will be
understood,” continues Fulton, “I may be permitted to put the following
question to my reader, which is: Knowing that the explosion of one
hundred pounds of powder, or more if required, under the bottom of a
ship-of-the-line, would destroy her, and seeing, that if a ship in
sailing should strike the lever of an anchored torpedo, she would be
blown up, would he have the courage, or shall I say the temerity,
to sail into a channel where one or more hundred of such engines
were anchored? I rely on each gentleman’s sense of prudence and
self-preservation, to answer this question to my satisfaction. Should
the apprehension of danger become as strong on the minds of those who
investigate this subject as it is on mine, we may reasonably conclude
that the same regard to self-preservation will make an enemy cautious
in approaching waters where such engines are placed; for however brave
sailors may be, there is no danger so distressing to the mind of a
seaman, or so calculated to destroy his confidence, as that which is
invisible and instantaneous destruction.”
But Admiral Farragut at Mobile Bay, half a century later, did have the
“temerity to sail into a channel where one or more hundred of such
engines were anchored.” The monitor _Tecumseh_ struck and exploded a
mine that sent her to the bottom with almost her entire crew. The
rest of the fleet began to waver when, from the main-rigging of the
_Hartford_ Farragut shouted his immortal command:
“Full steam ahead! Damn the torpedoes!”
[Illustration: Sinking of the U. S. S. _Tecumseh_, by a Confederate
mine, in Mobile Bay.]
As the flagship led the way through the mine-field, those on board
heard mine after mine bump against her bottom, but though the levers
were struck and the primers snapped, the powder-charges failed to
explode. Hastily improvised out of beer-kegs and other receptacles,
with tin or iron covers that became rusty and useless soon after they
were placed under water, many of the Confederate mines were in this
respect inferior to the well-built copper torpedoes of Fulton. Yet
crude as they were, they destroyed more than forty Northern warships,
transports, and supply vessels.
[Illustration:
From Scharf’s History of the Confederate States Navy.
A Confederate “Keg-Torpedo.”]
Percussion-caps instead of flintlocks were now used to explode contact
mines. A new type of anchored torpedo, set off by an electric spark
through a wire running to an operator on shore, was also a favorite
with the Confederates. Because they are exploded not by contact with
the ship’s hull but by the closing of the circuit by the operator
when he observes an enemy’s vessel to be above one of them, these are
called “observation mines.” In the Civil War, many effective mines
of this sort were made out of whisky demijohns. One of these blew up
the gunboat _Cairo_, in the Yazoo River, in the autumn of 1862. The
double-ended, river gunboat _Commodore Jones_ was blown to pieces by an
observation mine, whose operator was subsequently captured and tied to
the cut-water of another Federal gunboat as a warning and a hostage.
During the bombardment of Fort Sumter by the United States fleet in
1863, the _New Ironsides_ lay for an hour directly above an observation
mine made of boiler iron and containing a ton of gunpowder but which
failed to explode despite all the efforts of the operator. He was
naturally accused of treachery and it would have gone hard with him had
it not been discovered, soon after the _New Ironsides_ ceased firing
and stood out to sea, that the shore end of the wire had been severed
by the wheel of an ammunition wagon.
[Illustration: U. S. IRON-CLAD “CAIRO” (BLOWN UP BY CONFEDERATE
TORPEDO).
From Scharf’s History of the Confederate States Navy.
First Warship Destroyed by a Mine.]
During the Franco-Prussian War, the powerful French fleet blockaded the
German coast but did not attack the shore batteries, which were well
protected by mines. After peace was declared the foreign consuls at one
of the North German seaports congratulated the burgomaster on having
planted and taken up so many mines without a single accident. Unknown
to any one, the prudent burgomaster had unloaded them first, and they
kept the French away just as well.
In the Spanish-American War, Admiral Dewey was able to enter Manila
Bay and destroy the Spanish squadron there because its commander “had
repeatedly asked for torpedoes (mines) from Madrid, but had received
none and his attempts to make them had been failures.”[20] It was the
mine-fields and not the feeble shore batteries that kept Sampson’s
fleet out of Havana and Santiago. At Guantanamo, now a United States
naval station, the _Texas_ and the _Marblehead_ each “struck her
propeller against a contact mine, which failed to explode only because
it was incrusted with a thick growth of barnacles. Gratitude for the
vessels’ escape may fairly be divided between divine care to which the
gallant and devout Captain Philip attributed it in his report, and the
Spaniards’ neglect to maintain a proper inspection of these defenses.
A number of these torpedoes, which were of French manufacture, and
contained forty-six and a half kilograms (one hundred and two pounds)
of guncotton, were afterward dragged up in the channel.”[21]
[Illustration:
From Scharf’s History of the Confederate States Navy.
A Confederate “Buoyant Torpedo” or Contact-mine.]
At the siege of Port Arthur in 1904, the Japanese fleet planted mines
outside the harbor to keep the Russians in, and the Russians came out
and planted mines of their own to entrap the blockaders. While engaged
in this work, the Russian mine-layer _Yenisei_ had a mine which
had just been lowered through her specially constructed sternports
thrown by a wave against her rudder, and was blown to atoms by the
consequent explosion of three hundred more in her hold. The flagship
_Petropavlosk_, returning from a sortie on April 13, struck a Japanese
contact-mine and went down with the loss of six hundred men, including
Vereshchagin, the famous painter of war-scenes, and Admiral Makaroff,
who was not only the commander but the heart and soul of the Russian
fleet.[22] A month later, another mine cost the Japanese their finest
battleship, the _Hatsuse_. Nor was the loss confined either to the
belligerents or to the duration of the war. Nearly one hundred Chinese
and other neutral merchant vessels were sunk by some of the many mines
torn loose from their anchors by storms to drift, the least noticeable
and most terrible of derelicts, over all the seas of the Far East, long
after peace was declared.
The same thing on a larger scale will doubtless take place as a result
of the present European War. From the Baltic to the Dardanelles, both
sides have sown the waters thick with contact mines, hundreds of which
have already broken loose and been cast up on the shores of Denmark,
Holland, and other neutral lands. How many more have been picked up
on the coasts of the different belligerent countries, the military
censors have naturally kept a close secret; how many of these infernal
machines are now drifting about the North Sea, the North Atlantic, and
the Mediterranean it is impossible to compute. Scarcely a week passes
without the publication of such news items as the following extracts
from “Current events in Norway,” in the “American-Scandinavian Review”
for July-August, 1915:
“One hundred and fifty mines had been brought into Bergen up to April
12. The steamer _Caprivi_ of Bergen, which sank after being struck
by a mine off the coast of Ireland, was on its way from Baltimore
with a cargo of 4150 tons of grain, the property of the Norwegian
government.... The German government has declared its willingness to
comply with the demand of the Norwegian government for compensation for
the _Belridge_, provided it be proved that the sinking of the steamer
was the result of a German torpedo. The pieces of the shell found in
the side of the vessel are to be sent to the German government, and
in case there should be any disagreement about the facts they will be
submitted to arbitration.”
Unfortunately in most cases where a neutral ship is so sunk, the
exploding mine automatically destroys all evidence of its own origin,
and each belligerent promptly and positively declares that it must have
been planted, if not deliberately set adrift, by the other side. The
neutral is left to get what satisfaction he can out of the ruling of
the last Hague Conference that all contact mines must be so constructed
as to become harmless after breaking loose from their moorings. There
is nothing mechanically difficult about installing such a safety
device, and all the great powers now at war with each other solemnly
pledged themselves to do so. But the temptation of perhaps destroying a
hostile battleship as the _Hatsuse_ was destroyed, by a drifting mine,
has apparently been too great.
Premature explosion of the mine during handling and planting, such
as caused the destruction of the _Yenisei_ is, of course, carefully
guarded against. One of the simplest and most effective safety devices
is that used in the British navy, where the external parts of the
exploding apparatus are sealed with a thick layer of sugar, which is
dissolved by the sea-water after being submerged for a few minutes.
By then the mine-laying vessel has had time to get safely out of the
neighborhood.
Modern mines are of various shapes and sizes but are as a rule either
spherical or shaped like a pear with the stem down. The anchor is a
hollow, flat-bottomed cylinder, containing its own anchor cable wound
on a windlass, and making a convenient base or stand for the explosive
chamber or mine proper, so that the whole apparatus can be stood or
trundled about the deck of a mine-layer like a barrel. Once placed in
the water either by being dropped through the overhanging stern-ports
of a large sea-going mine-planter like the U.S.S. _San Francisco_, or
lowered over the side of a smaller craft by a derrick boom, the weight
of its anchor causes the mine to assume an upright position. This
releases a small weight or plummet at the end of a short line attached
to a spring that keeps the windlass inside the anchor from revolving.
When the plummet has sunk to the end of its cord, its weight pulls
down the spring, and the windlass begins to revolve and unreel the
cable, the end of which is, of course, made fast to the bottom of the
mine. This causes the anchor, which has been held up by the buoyancy
of the mine, to sink, and follows the plummet till the latter touches
the bottom. Freed of the plummet’s weight, the spring now flies up and
stops the windlass. But the hollow anchor is now filled with water,
whose additional weight drags the mine under. When the anchor rests on
the bottom, the mine will be at the same distance beneath the surface
of the water as the anchor had to sink after the windlass stopped, or
the length of the plummet’s line. By regulating that, a mine can be
made automatically to set itself at any desired depth.
[Illustration:
(Redrawn from the London Sphere.)
Modern Contact-Mine.
A, Mine-Planter; B, Mine being dropped overboard; C, Plummet-line
extended; D, Anchor sinking; E, Plummet touching bottom; F, Mine
submerged and anchored; G, Battleship striking mine; 1, The
“Striker”; 2, Charge of Explosives; 3, Air-space, for Buoyancy;
4, Mine-case; 5, Anchor; 6, Plummet.
]
Mines are almost never laid singly but in groups, the area of water so
planted being called a “mine field.” A secret, zigzag channel is often
left clear for the benefit of friendly craft. The rows of mines are
usually “staggered” or placed like the men on a checker-board, so that
if a hostile vessel passes through an opening in the first row she will
strike a mine in the second. Another device is to couple together the
mooring cables of two or more mines so that a ship passing between them
will draw them in against her sides.
Contact may cause explosion in any one of several different ways. The
head or sides of the mine may be studded with projecting rods like the
striker on the nose of a Whitehead, to be either driven directly in
against a detonating charge of fulminate or else open the jaws of a
clutch and release the spring of a firing-pin. Such external movable
parts, however, are too prone to become overgrown and clogged with
barnacles and the like. A more modern way is to have the shock of the
collision with the ship’s hull dislodge a heavy ball held in a cup
inside the mine. The fall of this weight sets in motion machinery which
fires the detonating charge. Or the device may not be mechanical but
electrical, as in the type of mine that, when drawn far enough over
to one side by a vessel passing over it, spills a cupful of mercury.
This stream of liquid metal closes an electric circuit, so that an
electric current passes through a piece of platinum wire embedded in
fulminate and heats it red-hot, with obvious results. This current may
be obtained either from a storage-battery carried in the mine itself,
or through a wire running down the mooring cable and over the bottom
to the shore. Most shore-control mines are so designed that they can
either be fired by observation, or else turned into electro-contact
mines of the above-mentioned type by arranging the switches in the
controlling station. It is also possible to have the contact serve
to warn the operator on shore by ringing a bell and indicating the
position of the intruding ship in the mine-field.
Just as barbed-wire entanglements on land are blown out of the way by
small charges of high explosives, so mined areas of the sea can be
cleared by “counter-mining.” One or more strings of linked-together
mines, of a small, easily-handled type, are carefully placed by
light-draft vessels in the waters already planted by the enemy.
When these are exploded together, the concussion is enough to
destroy any anchored mines near at hand, either by setting off their
exploding-devices or causing their cases to leak, so that they will be
filled with water and sink harmlessly to the bottom. Or a channel may
be cleared by “sweeping” it with a drag-rope towed along the bottom
by two small steamers, exploding the mines or tearing them up by the
roots. Very effective work of this kind has been done by the small
steam-trawlers used by the North Sea fishermen, and if anything of the
sort is ever necessary in American waters we may be thankful for the
powerful sea-going tugs now towing strings of barges up and down our
coasts.
[Illustration: U. S. Mine-planter _San Francisco_.]
But even a light field-piece on shore can shell and sink the sort
of small, unarmored craft that must be used for mine-sweeping. When
a fleet attacks a channel or harbor entrance properly defended by
both mine-fields and batteries, each supporting the other, there
comes a time when the naval forces must wait till troops can be
landed to drive away the forces protecting the rear of the batteries,
so that the mine-sweepers can advance and clear a channel for the
superdreadnoughts. The most striking example of this is the holding of
the Allied fleet by the Turks at the Dardanelles.
There, too, effective use is being made of the latest, which is an
adaptation of the oldest type of torpedo: the drifting mine.[23] This
twentieth-century improvement on Bushnell’s “kegs charged with powder”
floats upright, with a vertical-acting propeller on top and another on
its bottom, and a hydrostatic valve set to maintain it at any desired
depth. Should it rise or sink, the change in pressure will cause the
valve to act on the principle already explained in connection with
the Whitehead torpedo (see page 44). Controlled by the valve, the
little compressed-air motor attached to the vertical propellers will
cause them to make a few revolutions, just enough to keep the mine
at a constant depth beneath the surface of the Dardanelles, as the
four-mile-an-hour current carries it down against the Anglo-French
fleet. Within a few hours of each other, during the furious bombardment
of the forts on March 18, 1915, the French battleship _Bouvet_ was
struck by one of these drifting mines and went down stern-foremost,
then H.M.S. _Ocean_ was sunk by another, and the _Irresistible_ forced
to run ashore to escape sinking, only to be pounded to pieces by the
guns of the forts. A feature of this type of mine is that its size and
shape enable it to be launched through a torpedo tube, either from a
surface craft or from a submarine.
Ordinary contact-mines, without anchors and attached to floats that
held them a few feet below the surface of the water, are sometimes
dropped overboard from a vessel closely pursued by an enemy. A small
mine so dropped by a German light cruiser returning from an attempted
raid on the English coast, early in the war, was struck by the pursuing
British submarine _D-5_ and sent her to the bottom. The _D-5_ was
running awash at the time and only two officers and two seamen were
saved.