SUBMARINE MINE 



5605 



SUBMARINE MINE 



Electro-Contact Mines. These mines are 

 made either of iron or steel, and contain a 

 charge of seventy-five pounds of guncotton, 

 which is sufficient to destroy the biggest ship 

 afloat. They lie nearer the surface than obser- 

 vation mines, as they are intended to explode 

 when actually in contact with the bottom of 

 a vessel. Running through the explosive charge 

 is an electric wire called the firing circuit. To 

 complete the circuit the mine must be tipped 

 over to an angle of seventy degrees. At this 

 angle mercury, placed in the pedestal carrying 

 the electric wire, also tilts and bathes both ends 

 of the wire, completing the circuit and causing 

 the explosion. The electric current is supplied 



The position must be carefully studied and 

 the depth beneath the surface accurately calcu- 

 lated, as also must be the localities where the 

 effect will be greatest. In mines to be ex- 

 ploded by electric current from the shore the 

 laying of cables is a work requiring care, and 

 the wires connecting the mines to the cable and 

 the shore battery must be sufficiently strong to 

 anchor the mine, and of a sufficient length to 

 keep the explosive at such a depth that it 

 will be out of the path of vessels allowed to 

 enter or leave harbor. 



Searching for Mines. The accompanying illus- 

 tration clearly shows the principal method of 

 searching the sea for suspected mines. The 



SEARCHING FOR MINES IN A MINE FIELD 



from a shore battery, and all that is needed to 

 make these mines harmless is to turn off the 

 current. 



Automatic Mines. These are the most dan- 

 gerous to handle, as they contain within them- 

 selves all that is necessary for explosion, and do 

 not depend on an electric spark flashed from 

 the shore. The firing battery is in the shell 

 itself. In appearance and construction these 

 mines are similar to the other two varieties, 

 and are either spherical or cylindrical in shape. 

 They are absolutely beyond control when once 

 laid, and a fishing boat is as liable to destruc- 

 tion as a warship. Friend and foe are equally 

 in danger, unless the exact location is known; 

 when anchored by weights they are carefully 

 charted for the benefit of friendly and neutral 

 shipping. Automatic mines, when scattered in- 

 discriminately over the sea, are called floating 

 mines. Drifting according to wind, tide and 

 currents, they are a menace to all shipping. 



Mine Laying. The proper placing and laying 

 of mines is a complicated operation. Mines 

 cannot be dropped haphazard into the sea. 



work involves great difficulty and danger, as 

 the mines can be located only after the vessels 

 have successfully passed over the zone of dan- 

 ger. The two vessels are connected by a 

 heavily-weighted cable, which they drag be- 

 tween them. Mines thus caught are destroyed. 

 If an electrical cable is caught in the net it is 

 at once cut, rendering all mines connected with 

 that cable ineffective. Areas of mined waters 

 may be rendered safe also by countermining, 

 that is, by exploding mines in the suspected 

 area. The explosions would cause all pre- 

 viously laid automatic mines to explode and 

 might force adrift mines attached to electric 

 cables and render them harmless. 



In the War of the Nations. Numerous war- 

 ships, destroyers, passenger steamers and other 

 vessels were destroyed by mines during the 

 great war. These instruments of destruction 

 were laid principally in the North Sea, the 

 English Channel and the Mediterranean Sea, 

 but other waters traversed by ocean craft were 

 not entirely free. Both the British and the 

 German naval departments put forth special 



