SUBMARINE MINES. The anese and the European wars demonstrated that the most deadly weapons of seacoast and naval warfare are the submarine mine and tor pedo. A single submarine mine exploded at the proper time will disable or sink the largest battleship. The Turkish Coast artillery in clos ing and keeping closed the Dardanelles was pitted against the persistent and combined at tack of the Allied fleets of Great Britain, France and Russia. Submarine mines are prin cipally in defensive operations within harbors, whereas torpedoes are primarily an element of offensive warfare by warships. Mines are generally classed as fixed and float ing. The .fixed or stationary submarine mine is fired by contact, electricity, timing device or fuse. Such mines, which are extensively used by all navies, are rugged in design and may contain large charges of explosives. They are placed in position by submarines and other es pecially equipped mine-laying vessels. Such mines are provided with anchoring devices and are deposited, if possible, in harbors and chan nels of the enemy or in the paths of ocean travel. Floating mines differ from fixed mine;; in that they are unanchored, and unless guard boats arc at hand to warn friendly vessels of their proximity, may be as dangerous to friend as to foe. Such mines must be, according to the laws of war, designed to become inoperative within a few hours after being set adrift. The German floating mines were often cast adrift in pairs, connected by a line about 100 feet long. If a ship runs between the two mines they are drawn alongside the ship and exploded. Con tact depth mines, which rise to the surface if failing to contact, are sometimes used with tell ing effect. The essence of the depth charge is that it explodes in the vicinity of the submarine or other craft, in case it fails to strike the boat itself. The use of the contact depth mine pre supposes the necessary accuracy to strike the target. The high-explosive mines used by the Germans and other belligerent powers, known as submerged contact mines, when first put in place were so anchored that they were held at a certain distance below the surface of the water. It was intended that they should re main invisible and be exploded when struck by any vessel that might come in contact with them. Such mines may be removed by various methods of dragging or sweeping, such as by sinking a long cable, each end of which is at to a tug, and thus dragging a suspected locality.
Submarine mines, fixed and floating, are of three different kinds: (1) Observation mines, fired from shore, when a ship is judged to be within effective range of the explosion; (2) Au tomatic mines, which are self-firing when struck by a ship; (3) Electrical contact mines, which, on being struck by a ship, give notice to an operator on shore, who, by the throw of a switch, fires the mines. As a rule the sub
marine mine consists of a metal case, filled with high explosives and fitted with a fuse that may be fired automatically, or at will by an operator located at some distant point. In shallow water the mine is laid on the bottom and is known as a ground mine. When the depth is so great as to interfere with the de structive force of the explosion, the explosive is carried in a buoyant cylinder or sphere, which is anchored to the bottom by a length of cable which causes it to float at the proper depth to be struck by a passing ship. The mines (the type in general use being the electro contact mine) are usually planted in rows across the channel to be defended, the mines in suc cessive rows being °staggered," so that if a vessel should pass through the first row it must inevitably strike one or more in the later rows. They are planted in what is known as "grand groups," which consist of 21 mines in groups of three. Some distance in the rear of the line of mines there lies on the bottom of the channel a grand junction box, from which seven cables spread, each leading to a triple junction box, which in turn controls its small group of three mines. From the grand junc tion box, also, the multiple cable winds its way to the switchboard connection in the oper ating-room on shore. The grand junction box is placed at the centre of the line of mines and about 100 feet to the rear. The triple junction boxes are laid in a straight line at intervals of 300 feet ; from each of these boxes separate cables lead to each of three mines, the mines, 21 in all, being spaced 100 feet apart, in a line which extends for 2,000 feet across the channel. Each mine is anchored by a cable to an anchor, the length of the cables being such that each mine will float at a depth of 10 or 12 feet below the surface of the water. By an ingenious arrangement, one, three or the whole grand group of mines can be fired, either from the operating-room ashore, or by contact with a ship, all at the will of the operator. No mine field is complete, or can ever be thoroughly effective, unless it is protected by rapid-fire guns. It is possible for small boats, launches, etc., to be sent forward ahead of the ships, and set off the mines by exploding large charges of dynamite in the mine field. If the mines are within the °sympathetic radius" of the explo sions, they will be exploded by the shock. The most effective protection against such counter mining, as it is called, is by flanking the field with batteries of rapid-fire guns.