The Making of a Submarine Mine 



By John Randolph Rexford 



A battery of mines electrically exploded. Here is a fiercely graphic illustration of the de- 

 structive power which is contained in the comparatively small globe or cylinder of steel whose 

 sowing abroad in the sea is the first duty of the navy and coast defense when war breaks 



ORIGINALLY all forms of appa- 

 ratus designed to explode under 

 water to destroy ships were called tor- 

 pedoes, but this term is now applied only 

 to the well-known naval weapon. Sub- 

 marine mines may be divided into three 

 groups : 



1. Buoyant mines having a constant 

 depth of immersion. 



2. Ground mines which are used in 

 shallow waters and rest on the bottom. 



3. Floating mines. 



The mines belonging to the first and 

 second groups may be exploded either 

 from land by an electric current or by 

 automatic contact with a ship. 



Electrically controlled mines are em- 

 ployed only for the protection of har- 

 bors and channels and may be divided 

 into two classes : those which are entire- 

 ly and those which are partially con- 

 trolled from land. A mine consists gen- 

 erally of two perfectly watertight metal 

 casings made of suitable shape. One of 

 them is hollow and is intended to act 

 as a float to maintain the mine at the 

 required depth below the surface, while 

 the other one is filled with the charge, 

 which may be guncotton, trinitrotoluene 

 or any other suitable explosive, and the 

 detonator for firing the charge 



In coast defense work where electric 

 control is employed, mines are anchored 

 permanently in suitable positions, where 

 hostile vessels are likely to pass over 

 them, and are connected by means of 

 electric cables to the shore. Where 

 mines are entirely controlled from shore, 

 an observer on land can fire any mine 

 or groups of mines by closing the elec- 

 tric circuit the moment his optical in- 

 struments inform him that the enemy's 

 ship is over a mine. 



Firing an Electrical Mine 

 Mines which are partially controlled 

 from land are anchored only a few feet 

 below the surface of the water. When 

 a ship strikes such a mine an electric 

 contact is made which sends a signal to 

 the shore station. The ol)server can 

 then decide whether to fire the mine or 

 not. An advantage of electrically con- 

 trolled mines is that" neutral ships can be 

 allowed to pass over such mine fields in 

 perfect safety. The use of such mines 

 has, however, been considerably reduced, 

 chiefly because salt water is one of the 

 greatest enemies of electrical aj)paratus 

 and makes it very difficult to maintain 

 the electrical connections with the mine, 

 and also because the permanent location 



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