The How and Why of Submarine Mines 



At right: Dropping a mine. The 

 cable is wound on a dnim having 

 an escapement like that of a watch 



Below: Towing out electric cables 

 to the mines which are controlled 

 from the observatory en shore 



NOT the least important weapon for 

 defending our coasts and our har- 

 bors from the attacks of hostile war- 

 ships is the submarine mine. Though it is 

 perhaps the least ominous looking of naval 

 defenses, if it is once hit by an invading 

 warship, its tremendous explosive power 

 will sink the ship in less time than any 

 other weapon could. 



The shock of the striking vessel automat- 

 ically explodes the mine and the violently 

 expanding gases from the powder crush in 

 the hull of the ship in a twinkling. 



Submarine mines are made of an outer 

 casing of steel and an inner charge of 

 high explosive. A separate chamber, con- 

 taining nothing but air, gives the mine 

 buoyancy. The mines are carried in small 

 light-draft boats to the positions previous- 

 ly mapped out. The boat simply drops 

 the mines with their anchors overboard. 



When the cable is all 

 --»».' paid out, the buoyant 



mine will be floating about 

 ten feet below the water's 

 surface. 



V The mines lying far out- 



side of a harbor contain 

 their ignition system with- 

 in themselves. This may 

 be a number of percussion- 

 pins placed all around the 

 outside of the mine. When a ship strikes 

 one of these, the heat of the impact ignites 

 the powder instantly. Or, an internal igni- 

 tion system may be employed. When a ship 

 hits the mine it rolls it over. This releases 

 an iron ball which is ordinarily held in a 

 small cup in the center of the mine. The 

 ball falls out of the cup and pulls upon a 

 string, releasing a trigger and firing off 

 the charge. 



There is another type of mine in which 

 chlorate of potash is placed in the bottom 

 and an open vessel of acid is placed above 

 it. The mine is anchored well under the 

 water. Ordinary wave action does not 

 affect it. Disturbed by a passing ship, 

 however, the acid spills over upon the 

 chlorate causing a violent explosion. 



The mines which are near the land are 

 generally controlled from the shore through 

 an elertric cable from the observatory. 



689 



