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made between those intended to explode retaliation of his own guns—in other by direction from an observation station words, to hold him at arm's length, and ashore, and those that are fired automat to cripple him beyond thought of further ically upon contact with the bottom of an enemy's ship.

It has become axiomatic in military circles that "the defensive can only avoid defeat; it cannot win victory." Such, in substance, is the mission of all our fortified seaports. The batteries there can only repel the foe; they cannot go forth as a fleet, and wring victory from the

Single enemy: at most, they can prevent a de

Disconnecto termined naval antagonist from running by at all hazard to reach the cities lying

Multiple back of these bulwarks. The prime object, then, is to prevent this; and to that end, the aim is so to limit and obstruct

Disconnector

Group Cuble

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JUNCTION-Box OF MINE SYSTEM.

venture. The second line of mine defense is to detain the enemy still further, and to hold him in the face of the combined attack of all the guns—slow and rapid-fire—and effectually to check the

-CIRCUIT

CLOSER

PEDESTAL

OBSERVATION MINE.

the approach of a foe that he shall be

CHARGET

PRIMER forced to make a frontal attack in line with the heaviest and the most powerful of the defending ordnance.

First and Second Lines To accomplish this, submarine mines of various sorts are planted throughout the waters leading to a fortified position. By thus covertly guarding the flanking avenues of approach, it is possible to bring to bear upon an enemy a superior

ELECTRO-CONTACT MINE. force at the point of attack. To this Held in position by anchor chain. Circuit can be broken

from shore at will, to avoid danger to friendly end, the navigable waters leading to a

vessels. When circuit is closed, collision fortified position would be planted with a double line of mine defenses, the first smaller and more elusive of an attacking line seaward, or distant from the heavy fleet that might slip through the slower gun emplacements, about 3,500 yards. At

fire of the heaviest guns. that range, the most powerful of the guns should be able to pierce the heaviest of

How Mines are Guarded the enemy's armor, and, before he could To insure the effective working of the come closer, the aim would be to destroy mine fields, they must be guarded against his stability, injure his maneuvering the counter-mining efforts of an active powers, and thus prevent the successful enemy; and for this purpose lighter bat

with mine causes explosion.

teries of rapid-fire guns and searchlights an enemy's approach. For this reason, are installed to sweep all avenues of ap the mines planted in a harbor-way or the proach, and effectually to repel the small navigable waters of seaboard ports, are craft, to whom such work is generally placed deeper than the type designed intrusted by the foe. The aim is not only commonly to explode on contact; and, to to destroy all vessels attempting this make them effective, they carry a much work, but to hold such craft at a distance larger explosive charge, must be strucso that they shall not be able even to turally stronger to withstand the water

pressure at the greater depths, and are, in consequence, very heavy. In fact, the large, modern observation mines weigh quite half a ton, and their proper planting involves a deal of careful handling and a wealth of special facilities that cannot be enumerated in a brief sketch of the subject. Let us dwell, instead, upon the principal features of the mines themselves, which, while differing in minor details in most countries—the secrets of which are sooner or later known to all military experts—are fundamentally the same, for the fields of employment remain identical and fairly constant.

[graphic]
[graphic]

EXPLOSION OF Contact MINE LOADED with 75 Pounds
OF GUN-COTTON.

ELECTRO-MECHANICAL MINE. locate the position of the mine fields; for

Observation Mines it is in the secret, hidden nature of such defenses that their moral force lies, even Taking the mines in their order of more than in their applied destructive relative safety to those planting them, power.

the Observation mine naturally comes

first. This type of mine is shown in acSystems of Planting

companying diagram(p. 139). The casing The work of planting a mine field in is of steel, and large enough to be buoyvolves no little preparation, for, as must ant when loaded with 500 pounds of wet be understood, the modern mine is rather gun-cotton, packed in a copper vessel complex in its installation in the fairways with perforations permitting the entrance of commerce; and, of course, the idea to of sea water. In the lower center is the day is to provide an efficient defense primer of dry gun-cotton, and the detowhile still leaving the channels of traffic nator of fulminate of mercury. The area open to free passage during daylight and of destruction of such a mine is a circle at such other times as may be secure from with a 60-foot diameter. These mines

are generally planted in groups of 3, 5, suggest, and may be either spherical or or 7, with battery connections leading cylindrical, as shown in the diagram. back to a single junction-box containing Being intended to explode only when in as many disconnectors as there are sepa actual contact with the bottom of a vesrate mines. The purpose of this is, first, sel, they lie nearer the surface, and carry to centralize the connections of the mines, a moderate charge of 75 pounds of gunand then, by the separate disconnectors, cotton. No craft has yet been fashioned to prevent the discharge of a single mine that can resist the under-water attack of from short-circuiting and cutting out the such a weapon.

These mines differ rest of the group from subsequent con radically from the observation mine in trol. The main multiple cable is led their method of firing. Within a pedestal from the junction-box shoreward to the in their upper half, they carry the bared observation station, where each mine has ends of the firing circuit-one at the top

and one at the bottom. This pedestal is partly filled with mercury, which, when the mine is tipped about seventy degrees, bathes both of the bared ends of the firing

circuit, thus forming a continuous metal-DISCONNECTOR lic connection, and closing the circuit.

The circuit so closed heats a platinum filament which fires a primer similar

that in the observation mine. JUNCTION BOX

ON

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are stationed at A and B.

GROUPS OF CONTACT Mines, Plan View. its button on an elaborate keyboard. These mines can be exploded either singly or in groups.

The effectiveness of the observation mine depends upon accuracy in locating the enemy over them. This is done by cross-bearings, which, however, may be more or less indistinct or invisible by

A. Mine System on Single Cable across Harbor Entrance. reason of atmospheric conditions. The

Line of sight between mark buoys indicates vulnerable act of discharge is effected by an electric position of passing vessel. current, which, heating a platinum fila B. Observers, with telescopes trained at a certain angle,

When vessel E comes into ment in the primer, ignites the fulminate

view of both observers, she is directly over mine C, and of mercury, which sets the explosive closing of circuit will cause explosion. chain in motion. In principle of firing,

These mines also are planted in groups, the observation mine is not unlike the explosive sequence in the Whitehead tor

and have junction-boxes and disconnectpedo. Until the firing key is pressed,

ors, as do the observation mines. Until the observation mine is pre-eminently

their battery connections are made safe and will stand a lot of rough hand

ashore, they are of course harmless even ling, for the primer is pretty securely

when struck by a passing vessel. By housed within the mass of the insensitive plugging a

plugging a diagrammatic keyboard, wet gun-cotton.

single mines or groups are made either

operative or inoperative as the case may Electro-Contact Mines

be; but, when once the battery connecThe Electro-Contact mine is made tions are made, the mine becomes its own either of iron or of steel, as conditions lookout, and should an enemy's ship

make the fatal mistake of bumping operative until they have been properly against it, the mine will do its deadly planted—for all mines must be anchored work without further aid.

at certain depths, varying accordingly as

the mines differ—there is a circuitAutomatic Mines

breaker consisting of a composition of The Electro-Mechanical, Electro- sugar and powdered chalk (good nonChemical, or Automatic mine, as it is conductors), which separates the ends of variously styled, is by long odds the most the wires in the mercury cup. This comdangerous to handle. Once laid, they position is poured in and allowed to crysbecome a common menace to friend and tallize long before the two small batteries foe alike. They are complete unto them are put in place. In a brief while after selves, and entirely independent of ex the mines are placed in the water, this traneous control other than the unfor- composition melts and the weapons are

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Mines are distributed in groups and electrically controlled from shore. Vessels avoiding one group will certainly pass over another. Whole field is swept by battery fire, and illuminated by

searchlights at night, to prevent counter-mining.

tunate bumping of a doomed craft. Such ready for instant service. The electrowere the mines the Japanese planted out

chemical mine is similar in principle, side of Port Arthur; and such, too, were differing only in the nature of the mathe mines with which the Russians in terial of the circuit-closer. An acid is turn caught the Japanese battleship Hat set free by the tilting, which, by coming suse.

in contact with the two elements of a In construction, the automatic mine is battery attached to the ends of the firingsubstantially similar to the electro-con circuit wires, creates a current strong tact mine, the difference being that the enough to heat the platinum filament of firing battery is contained in the mine the primer. itself, and is of power sufficient to heat

Naval Defense Mines the delicate platinum wire passing There is a form of electro-contact through the middle of the detonating mine now carried by the heavy fighting fuse. This mine, too, has a mercurial ships of a number of nations, called the circuit-closer, and it must be tipped over "Naval Defense” mine. These mines are to an angle of seventy degrees to cause intended to protect a hastily established it to explode. To make these mines in naval base on the enemy's coast or at

some point not otherwise defended. They

Counter-Mining differ from the ordinary electro-contact Counter-mining is the work of rendermines only in the absence of a shore-bat- ing an enemy's mine fields ineffective, tery connection. After these mines are either by cutting his electric cable conplanted and the mine-laying vessel or nections or by exploding the mines by the boat is at a safe distance, a small battery, shock of counter-mines fired in their in a water-tight case and connected by a neighborhood. This work involves a number of yards of small, insulated great deal of risk, is very hazardous, and cable, is thrown overboard ; and then must be carried out under cover of night and then only—the mine becomes dan or fog and with the utmost deliberation. gerous to any craft hitting it. To recover The chances of its success are reduced to these mines in safety, the battery-boxes a minimum in the face of the powerful are swept for, raised, and disconnected, electric lights and the rapid-fire guns that after which the mines themselves may be should always command the approaches recovered without danger. Mines of this to the mine fields. Men there are in sort can be laid and recovered very plenty who can be found at all times to rapidly, even during the heat of action; undertake the tasks of such forlorn hopes, and, by an ingenious arrangement, they and in that readiness we see how little are made self-anchoring at a prede- the awfulness of modern weapons of war termined depth.

will halt a gallant and persistent foe.

Automatic Appliances for Handling

Coal and Iron Ore

A Description of Some of the Most Important Modern Adjuncts of the

Lake and Railway Carrying Trade

By WALDON FAWCETT

I:

T IS SAFE TO SAY that in no twentieth century find practically the en

other one division of the commercial tire movement from mine to market acand industrial world has the past complished solely by mechanical means.

quarter of a century witnessed the Surpassing as the achievements of the rapid, continuous, and truly phenomenal past score and a half of years have been development which has characterized the in labor-saving, and consequently in the evolution of means and methods for hand cost of handling iron ore and coal, they ling coal and iron ore in the transit of have not been more wonderful than the these most important of raw materials economies of time effected by the more from mine to furnace, or, in other words, rapid handling of the world's two most from Mother Earth to the finished prod- important minerals. It is indeed a far uct. To so high a state of perfection cry from the old method of trundling have the utilities employed in the hand small loads of the bulk material back and ling of these bulk commodities been forth in wheelbarrows, to the new plan brought, that the dawning years of the of transferring a carload of coal per

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