Land mines, which were developed in World War II, are buried just below the surface of the ground. They are of two kinds: antitank mines and antipersonnel mines. A land mine consists of a container made of metal, plastic or some other material with an explosive charge, a fuse and a detonator. Fuses are mostly of the type operated by the weight of a vehicle or a man

Naval mines are of mainly two types: moored mines which can be used in depths of water up to about 1300 ft. and ground mines. Moored mines are laid by vessels or by aircraft; Fig.1 shows a contact mine of this type. The casting of mine is usually spherical and contains the explosives charge with the detonator and firing mechanism. The mine is provided with an arming device which makes it operational only after it has been deposited from the mine laying craft and which also disarms the mine if it breaks loose from its mooring. The mine, attached to its anchor, is thrown in to the sea.

An auxiliary weight connected to a rope whose length is equal to the desired depth of the anchored mine below the surface of the sea is released and the mine is automatically detached from the anchor to which it remains connected by the mooring cable. The anchor is flooded with water, so that it sinks, unwinding the mooring cable as it descends. As soon as the auxiliary weight, suspended below the anchor, touches the bottom, the rope of the auxiliary weight slackens.

This causes the unwinding of the mooring cable to stop and the cable to be locked at the length it has then attained. The anchor continues to descend, pulling the down mine with it. Thus when the anchor reaches the bottom, the mine will be floating at the desired depth, attached to its cable. The pull on the cable now arms the mine by closing an electrical contact. Alternatively, the mine may be provided with a hydrostatic arming device which reacts to a predetermined depth of water.

The mine explodes when a vessel strikes one of the contact horns. This causes an electric current to actuate the firing mechanism, which in turn sends a strong current from a battery through the detonator. One type of contact horn contains an acid filled glass tube which fractures, allowing the acid to enter a zinc-carbon electric cell which then produces a current to energize the firing mechanism (Fig.2a). In another type (Fig.2b), contact is established by a spring-loaded contact piece, so that current from a battery can flow. These and other detonating systems are illustrated schematically in Fig.3.

The four in the top row are for contact mines. In the third diagram of that row is shown a system in which the impact causes sea water to enter an electric cell and thus produce the energizing current. In the hydrostatic detonating system the pressure of sea water admitted to the interior of the mine when the contact horn is struck causes the energizing circuit to be completed.

The systems illustrated in the bottom row relate to influence mines i.e., mines that are actuated not by contact but by the proximity of a ship. Ground mines are always of this kind. The magnetic mines are actuated by the change in the earth’s magnetic field, producing, when a steel vessel passes within a certain distance, a deflection of a magnetic needle. Actuation of the pressure mine is brought about by the change in water pressure under a vessel in relatively shallow water.

The mine contains a chamber divided into two parts, with one side of the chamber open to the sea. The deflection of the diaphragm establishes electrical contact. The acoustic mine is actuated by the sound of the ship’s engine or propellers, which is picked up by sensitive microphones. The last diagram in the bottom row illustrates a detonating system for a controlled mine detonated from an observation station on land.

Since the beginning of civilization people have used stone, ceramics and, later, metals found on or close to the Earth's surface. These were used to manufacture early tools and weapons. For example, high quality flint found in northern France and southern England were used to set fire and break rock. Flint mines have been found in chalk areas where seams of the stone were followed underground by shafts and galleries. The mines at Grimes Graves are especially famous, and like most other flint mines, are Neolithic in origin (ca 4000 BC-ca 3000 BC).