NAVAL MINES. Naval mining is logic ally divided as follows: (1) Coastal mining, which denies to an enemy suitable ports, unde fended or nearly so; (2) advance base min ing; (3) off-shore or strategical mining; (4) battle or tactical mining, during an engagement between fleets. Coastal mining, outside of areas which are defended by coast fortification guns, does not require large or speedy vessels. Tugs, trawlers and light draught vessels, with naval reserve crews may be advantageously employed for this purpose. These vessels are provided with searchlights and suitable guns in order that they may properly guard their own mine fields. Advance base mining is the log ical or legitimate duty of the active naval force. For this purpose an organized unit is supplied, consisting generally of several mine ships, six or more seagoing tugs, and two net layers. The mining ships are armed with a sufficient num ber of guns of proper calibre to defeat any attempt of raiding cruisers from interfering with the work establishing the advance base ashore and the laying of mines for the protec tion of the harbor. These ships are provided with all facilities to lay and pick up mine fields. The tugs are employed for sweeping areas which are to be used for fleet manoeuvres or to sweep a channel to insure that hostile mines have not been planted. The sweeps, made of wire hawsers and chain, are hung between two tugs so that the bight of the sweep is dragged across the area to be swept. When the sweep fouls a mine it drags it from its moorings and explodes it. The net layers are used for laying submarine entangling nets across the entrance of a harbor or about a fleet when at anchor in an open roadstead. In mining the channels of an advanced base, mines are laid in the principal channels and as a rule are distantly controlled or exploded by observers ashore, when an enemy ship is sufficiently near them. Off-shore or strategical mining is done for the purpose of refusing or denying certain waters to the enemy. A sufficient number of mines are laid to make a venture by an enemy fleet extremely hazardous. For this mining, mine-laying ves sels of considerable size and good speed are required, being accompanied by a mine depot ship and tugs. When occasion demands very high speed, scout cruisers or even destroyers should be used. High speed can be given min ing vessels only by sacrificing mine capacity. In strategical mining a supporting force should always accompany the mine force to protect it from interference by enemy fast cruisers which might arrive before the mining has been com pleted. All hostile obstructions should be
guarded against continuously. Battle or tacti cal mining. during an engagement between fleets, is accomplished by vessels of very high speed with characteristics on the order of scout cruisers, hut with decks arranged to carry sev eral hundred mines. The mines are laid in such localities during the progress of the battle that may be in the line of advance or retreat of the enemy. When an area is properly mined, one of the principal aims of the fleet is to force the enemy over the mine field. Battle mines may be either fixed or floating; but when off soundings, floating mines only can be used.
The United States has two mining branches. One branch is under the coast artillery and is employed as an element in the fixed defenses of the coast and the mine fields are covered by guns in fixed positions. The other branch is under the navy and forms a part of the active fleet. The control of the fixed mine defense belongs with the control of the fortifications and the control of the fixed land defenses and mine fields belong to the navy in order to in sure complete co-operation between the mobile and fixed defenses of the coast. The fleet for its own safety should dictate the location of mine fields. As a rule the navies of Europe control the coast fortifications and the fixed mine fields.
Generally speaking, there are two types of mines — fixed and floating. The fixed or sta tionary submarine mine is fired by contact, elec tricity, timing device or fuse. Such mines are rugged in design and may contain large charges of explosives. They are placed in position by submarines and other especially equipped mine laying vessels. Such mines are provided with anchoring devices and are deposited, if possi ble, in harbors and channels of the enemy or in the paths of ocean travel. Floating mines differ from fixed mines in that they are unan chored, and unless guard boats are at hand to warn friendly vessels of their proximity, may be as dangerous to friend as to foe. Such mines must be, according to laws of war, de signed to become inoperative within a few hours or days—after being set adrift. They are often cast adrift in pairs, connected by a line about 100 feet long. If a ship runs be tween the two mines they are drawn alongside the ship, and exploded. See SUBMARINE