How the Mines Are Made.—The contact mine.—This kind of a mine consists of a steel shell, or container, which holds the charge of high explosive, the trigger mechanism which explodes it when a ship strikes it, and the weights and cables needed to sink the mine to the right depth. Air chambers are also placed inside the container, to give the mine buoyancy; otherwise it would sink at once to the bottom of the sea.
FIG. 48. A SIMPLE CONTACT MINE.
In the contact mine the detonator is formed of an arm, or lever, called a striker, and this projects through the shell to the outside. When a ship strikes the arm it drives a firing pin against a percussion cap and explodes it, and this in turn fires the explosive charge in the mine. (See [Fig. 48].)
How the Contact Mine Works.—The way the mine works is like this: Before it is taken out of the compartment of the submarine it is adjusted to float at the proper depth.
When the mine is in the water a weight that it carries is released and sinks to the bottom; the cable which connects the weight and the mine together holds the mine in the right position, while the air tanks in the mine make it rise as high as the cable will let it go, as shown in [Fig. 49].
After the mine is planted, the submarine steals silently and invisibly away. When an enemy ship—or any other, for that matter, for the contact mine is no respecter of ships—strikes the trigger of the mine, it explodes the charge, and there is one less ship to sail the turquoise seas.
The Electric Controlled Mine.—To the end that a harbor can be planted with mines which will blow up enemy ships and yet be harmless to friendly ships, mines fired by electricity from the shore were invented.
