A compass in the conning-tower enables the navigator to steer a true course whether above or below the surface. This conning-tower, only six feet high, rises above the centre of the living quarters, and is of steel with small windows in the upper part. Encircling it to about three-quarters of its height is a reservoir for gasolene, which feeds into a smaller tank within the boat for consumption. The compressed air is stored in two Mannesmann steel reservoirs which have been tested to a pressure of 4000 lbs. per square inch. This renews the air-supply for the crew when the Argonaut is long below, and also enables the diving operations to be carried on.
The maximum speed at which the Argonaut travels submerged is five knots an hour, and when she has arrived at her destination—say a sunken coal steamer—the working party pass into the “intermediate” chamber, whose air-tight doors are then closed. A current of compressed air is then turned on until the air is equal in pressure to that in the divers’ room. The doors of this close over india rubber to be air and water-tight; one communicates with the “intermediate,” the other is a trap which opens downwards into the sea. Through three windows in the prow those remaining in the room can watch operations outside within a radius varying according to the clearness of the water. The divers assume their suits, to the helmets of which a telephone is attached, so arranged that they are able to talk to each other as well as to those in the boat. They are also provided with electric lamps, and a brilliant flood of light streams upon them from the bows of the vessel. The derrick can be used with ease under water, and the powerful suction-pump will “retrieve” coal from a submerged vessel into a barge above at the rate of sixty tons per hour.
It will thus be seen how valuable a boat of this kind may be for salvage operations, as well as for surveying the bottom of harbours, river mouths, sea coasts, and so on. In war time it can lay or examine submarine mines for harbour defence, or, if employed offensively, can enter the enemy’s harbour with no chance of detection, and there destroy his mines or blow up his ships with perfect impunity.
To return the Argonaut to the surface it is only necessary to force compressed air into the space below the deck and the four tanks in the hold. Her buoyancy being thus gradually restored she rises slowly and steadily till she is again afloat upon the water, and steams for land.
We have now glanced briefly at some of the most interesting attempts—out of many dozens—to produce a practicable submarine vessel in bygone days; and have inquired more closely into the construction of several modern designs; among these the Holland has received especial attention, as that is the model adopted by our Admiralty, and our own new boats only differ in detail from their American prototype. But before quitting this subject it will be well to consider what is required from the navigating engineer, and how far present invention has supplied the demand.
The “Holland” Submarine in the last stages of submersion.
The perfect submarine of fiction was introduced by Jules Verne, whose Nautilus remains a masterpiece of scientific imagination. This marvellous vessel ploughed the seas with equal power and safety, whether on the surface or deeply sunk beneath the waves, bearing the pressure of many atmospheres. It would rest upon the ocean floor while its inmates, clad in diving suits, issued forth to stroll amid aquatic forests and scale marine mountains. It gathered fabulous treasures from pearl beds and sunken galleons; and could ram and sink an offending ship a thousand times its size without dinting or loosening a plate on its own hull. No weather deflected its compass, no movement disturbed its equilibrium. Its crew followed peacefully and cheerfully in their spacious cabins a daily round of duties which electric power and automatic gear reduced to a minimum. Save for the misadventure of a shortened air-supply when exploring the Polar pack, and the clash of human passions, Captain Nemo’s guests would have voyaged in a floating paradise.
Compare with this entrancing creation the most practical vessels of actual experiment. They are small, blind craft, groping their way perilously when below the surface, the steel and electrical machinery sadly interfering with any trustworthy working of their compass, and the best form of periscope hitherto introduced forming a very imperfect substitute for ordinary vision.
Their speed, never very fast upon the surface, is reduced by submersion to that of the oldest and slowest gunboats. Their radius of action is also circumscribed—that is, they cannot carry supplies sufficient to go a long distance, deal with a hostile fleet, and then return to headquarters without replenishment.