Submarine Appliances And Their Uses
Deep Sea Diving, &c., &c.

SUBMARINE MINES FOR HARBOUR DEFENCE, &c. Submarine Mines are used both in defensive and offensive submarine warfare. Science of ■ T^e sc*ence defensive submarine warfare, as applied to the defence of harbours, con- Submarine s^s^s of the arrangement of stationary mines moored in such positions and so interspaced as to Warfare, practically prevent the possibility of a hostile vessel forcing a passage into a harbour without striking or coming within the destructive area of one or more of the mines. JJ“’ . r i Guncotton is the explosive now almost universally employed for submarine mining work. used°SlVe £reat safety with which it can be stored and manipulated in the wet state, and the im- portant fact that it can be and is employed in the wet state as an explosive, together with its insensitivity to sympathetic explosion when neighbouring mines arc fired, constitute its chief merits. By the new process of compression, blocks of guncotton can be produced mechanically true, and of a size and weight practically unlimited, at the same time a per- fectly uniform density is ensured throughout the block, with exact regulation and uniform distribution of the percentage of moisture. These points are of the highest importance in this description of charge, and for this reason, guncotton, as before stated, is almost exclu- sively employed. Explodin^ The mines are exploded by the detonation of fulminate of mercury in conjunction with Mines. small priming charges of dry guncotton, the fuses containing the fulminate being usually fired by electricity either from the shore or from a battery in the mine itself. tionsrof' The mines cases are usually made of mild steel in a spherical or cylindrical form; Mines. these shapes (especially the spherical) having been found by experiment to be the most capable of withstanding external pressure, and to offer the least resistance to tidal currents ; they are, therefore, the least liable to be affected by countermining, i.e., destruction through the explosion of neighbouring charges, or to be dragged from their moorings. The cases arc made as a rule of mild steel in various sizes for different charges, and the following are a few of the latest and most approved forms: — The spherical case shown in Fig. i is used as a small buoyant mine, containing a charge of 50 lbs. of guncotton, against boats or other small craft, or it may be employed as a ground mine, for which purpose it is provided with a cement lining and made to contain a 250 lbs. charge. It is also used as a case to contain the circuit closing arrangement over a ground or buoyant mine, which is reejuired to fire on contact, but where the charge is placed at too great a depth for a passing vessel to strike the mine itself. The spherical case shown in Fig. 2 is made to contain a 100 lbs. chargeas a buoyant mine or with a cement lining a charge of 500 lbs. as a ground mine. This form of mine is very suitable for the defence of a harbour. With the 500 lbs. charge it can be moored at the bottom m the centre of the defence, forming' a. fairway for the passage of friendly traffic in times of peace, and arranged to fire by observation from the shore , with the 100 lbs. charge it can be moored as a buoyant mine on the sides of such fair- way 01 channel, and arranged to fire either on contact with a ship or by observation from shore. Where the depth of water is too great to admit of the mine being moored at the bottom, similar cases of larger diameter, and containing 500 lbs. of guncotton, are used as buoyant mines, as shown in Fig. 4. Illustrations reproduced by courtesy of Messrs. SIEMENS BROS. & Co., Ltd. II4