SEMI-SUBMERGIBLE WRECKING APPARATUS
The submergible tube has the diver's operating compartment shut off from the rest of the apparatus by means of an air lock which permits passage from the surface vessel and normal air pressure to the diver's compartment, where the air is under pressure equal to the compartment's depth of submergence, when the diver's exit door is open. The above illustration shows divers "breaking" the cargo out of the hold of a sunken ship and sending it to the surface.
The general method of operating upon a submerged wreck is as follows: The vessel carrying the tube is brought to the place of operation; it may be carried there either by towing or by its own power. The carrying vessel is moored over the wreck by quartering lines; anchor lines connect with anchors run out abeam on each side of the vessel. These lines are controlled from within the operating chamber, when once the anchors are planted, so that the lower end of the tube, when submerged, may be swung through the arc of a circle within the pivotal point at the buoyant end attached to the surface vessel.
The operating chamber and tube are lighted electrically, and electricity also supplies power control within the chamber. Compressed air is led into this compartment to supply the chamber when operating under pressure and also to supply any divers sent out therefrom at such times.
The surface vessel being properly moored, the ballast compartments are flooded and the working end of the apparatus allowed to settle near enough to the wreck to permit of inspection through the "aquascope," or the bottom door may be opened and divers sent out for more intimate inspection, and instructions may then be telephoned to the surface vessel so to change her position that the working compartment may be located in the place most convenient to act as a base for carrying on the operations of recovering cargo, making repairs, etc., as the occasion may demand.
The position of the operating chamber may be over the hatchway of a ship, or, in the case of an old and worthless hulk, the decks may be blown off and the working end of the apparatus lowered right down through and on to the cargo itself. Sufficient additional water ballast may now be introduced to hold the working chamber securely to the bottom, or it may be held fast to the hulk itself, if that course be preferable. It will thus be seen that communication is now established between the surface and the submerged vessel at the point where it is desired to carry on the operations, and it will be realized that this can be accomplished without the use of divers and in absolute safety throughout the range or reach of the apparatus. The operators are protected by a strong steel tube, which now forms a sheltered passageway to and from the surface under normal atmospheric pressure, and no more skill is required to go down within working reach of the sunken ship than that required to go up or down a flight of stairs. It will also be seen, by referring to the sketch, that the operators are where they are protected from the currents, and even quite a severe storm on the surface would not interfere with work below, so long as the surface vessel could be held to her moorings.
The illustration shows a wrecking plant of the "Lake" design as it appears when operating on a sunken steamship. The case taken for illustration is that of a vessel that had been sunk for some time and where it had been considered advisable to blow away the decks in order to enable the operating compartment of the tube to be lowered right down into the cargo hold. The ship's hold is lighted up electrically, and the work of removing the material follows. A light down-haul line leads from the lower block of each set of derrick falls, and is led through a block secured conveniently to the diver's station. This line is handled by an electric winch in the operating compartment. Its purpose is to return the hoisting line with its sling to the divers after each load has been discharged upon the surface craft. As the divers operate only a few feet from the working chamber, they are protected from the surge of the surface boat, with its attendant pull on air-hose and life-line, and also from possible aggravation by currents; and, as the handling of all lines is done by mechanical power, work of recovery may be carried on in a very expeditious manner with a minimum of stress upon the operator.
THE "CAVIAR MAP" OF SHIPPING'S GREATEST GRAVE-YARD
(The little circles represent wrecks.)