Clearing a Passage through the Torpedo Defences of an Enemy.—The subject of clearing a passage through the torpedo defences of an enemy is one fraught with innumerable difficulties, on account of the varied nature and impracticability of obtaining accurate and certain information of such defences, and thus it is impossible to lay down any fixed rule or plan for carrying out such an operation.
In fact, it will be only under the most favourable circumstances that such a service will be successfully accomplished, that is to say, in the case of a harbour or river defended by submarine mines but unsupported by guns, or guard boats, or where the electric light is used.
Numerous methods have been devised from time to time to effect the destruction of an enemy's submarine defences, among which are the following:—
- 1.—Projecting frames, &c., from the bows of a vessel.
- 2.—Creeping and sweeping by boats.
- 3.—Countermining.
Projecting Frames, &c., from the Bows of a Vessel.—This method was adopted by the Federals during the American civil war of 1861-5, and in many instances it was the means of saving their ships when proceeding up rivers which had been torpedoed by the Confederates, though notwithstanding this precaution several vessels were sunk. The submarine mines against which this mode of defence was used, were in nine cases out of ten mechanical ones, and therefore the framework defence afforded a better means of protection then, than would be the case now that electrical ground mines and circuit closers are used, as the framework would catch the circuit closer only, and the vessel would probably be over the mine when the explosion took place. The Americans moor their circuit closers in rear of their mines, so that a vessel fitted with a bow frame or not, coming in contact with the former must be right over the charge at the instant of explosion.
Against ground electrical mines fired at will, the bow net, &c., is no protection whatever, still under certain circumstances it would be found extremely useful.
Sweeping for Submarine Mines.—This method of clearing a channel of submarine mines could not possibly be carried out under artillery fire, but in waters not so defended it would prove of some value.
Where only buoyant mines, or ground mines with circuit closers are to be cleared away, two or more boats dragging a hawser between them would be sufficient to discover them, and so lead to their destruction; but where dummy mines and inverted creepers are moored in addition, another method of sweeping must be resorted to, viz., that of bringing an explosive charge of gun-cotton to act on the obstruction grappled, and thus destroy it. This is effected by lashing a charge to each end of the sweep, so that whatever is grappled may slide along it, until caught by hooks, which are attached for this purpose to the centre of the charge. On grappling an obstruction, the two boats drop their anchors, one hauling in, the other veering out the sweep, until the charge is hooked by the obstruction; this being effected, the boats move out of range, and the charge is fired.
Creeping for Electrical Cables, &c.—Creeping is the method employed for picking up the electric cables of the enemy's submarine mines, and is effected by boats towing an ordinary grappling iron, or specially prepared creeper on the ground.
In both sweeping and creeping it would be found necessary to employ a diver, who would ascertain the nature of the grappled obstructions which could not be easily raised by the boats.