The Romance of War Inventions / A Description of Warships, Guns, Tanks, Rifles, Bombs, and Other Instruments and Munitions of Warfare, How They Were Invented & How They Are Employed

by Thomas W. Corbin

Of the permanent mines whereby the entrances to important channels are protected arrangements are often made for firing by observation, that is to say, by the action of an observer ashore. Being laid by divers and securely anchored to heavy weights laying on the bottom, wires are carried from the mines to the observation station. The observer watches and fires the mines at the right moment by simply pressing a key thereby making the electrical circuit.

More often, however, mines are fired by contact. Observation mines have the advantage that while they may be exploded under an enemy they will allow a friendly ship to pass in perfect safety. Contact mines, on the other hand, will afford protection against attacks by night when enemy craft may attempt to creep in under cover of darkness.

An Italian Mine-layer.

This photograph was taken looking down upon the deck of the ship. The mines run upon rails, and are pushed by the men towards the stern, whence they are dropped one at a time into the water. The splash indicates that one has just fallen.

Contact mines are often fired electrically, sometimes

by batteries of their own inside their own cases, or else by current from the shore through wires, the circuit being completed by an automatic device of some sort actuated unwittingly by the unfortunate victim.

One of these contact devices will illustrate the general character of them all. Imagine a little vessel with mercury in it: it is, generally speaking, of some insulating material, but right at the bottom is a metal stud with which the mercury makes contact. The rim may likewise be of metal or a metal rod may project downwards into it: it matters not which, for we can see at once that it is quite easy so to arrange things that whereas, while upright, the mercury shall be well clear of the upper contact, it shall when the vessel is tilted flow on to it, thereby bridging from lower contact to upper contact and completing the circuit.

Of course, a mine must only go off when actually struck by a ship and not when it is gently swung to and fro by the action of tide or current in the water. That is easily arranged, for the vessel and contacts can be so shaped that contact is not made until an angle of tilt is reached which no tide or ordinary commotion of the water could bring about.