But the greatest improvement of all in the direction of safety is the system of bulkheads and double bottoms introduced by the builders of the City of New York and the City of Paris. For many years past it has been the custom to divide all steamers by transverse bulkheads into so-called water-tight compartments, the purpose of which is to increase their buoyancy and stability in case of collision. The Etruria, the Umbria, the Britannic, the Germanic, and the Arizona have nine compartments each. Excellent as the theory is, the feeling of everybody acquainted with the subject has been distrustful of the manner of its application, the chief objection being the inadequacy of the number of subdivisions. Sometimes, as when the Arizona ran into the iceberg, the bulkheads have saved the ship, but in other cases they have been of little or no use, as in the case of the Oregon. The Oregon was divided into ten compartments, but she sank in a few hours after her collision with a coal schooner off Fire Island light. The compartments have invariably proved useless when the ship has been struck amidships with sufficient force to open her engine and boilers to the sea, though when the weather has been calm and the injury forward or astern, they have kept her afloat.
The insufficiency of their number in proportion to the size of the ships has not been their only defect, moreover. In order to give an unobstructed passage along the decks it has been the custom to cut doors in the bulkheads, and it has frequently happened that in the confusion following a collision these have been left open, allowing the sea to rush from compartment to compartment, either because they were forgotten or because they refused to work.
The Deep-sea Sounding Machine at Work.
In the newest type of ship, as represented by the City of Paris and the City of New York, there are no fewer than twenty water-tight compartments separated by solid transverse bulkheads, which rise from the keel to the saloon deck, eighteen feet above the waterline, and which have no doors or openings of any kind whatever. A few feet from the stem there is a collision bulkhead of extraordinary strength to protect the ship, should she run “bow-on” against any obstacle—a reef, a derelict, or a vessel attempting to cross her path; next, aft of this come three compartments for steerage passengers or cargo; then two compartments for saloon passengers; then four compartments for boilers, coal bunkers, kitchens, and machinery; two more for saloon passengers; one for second-cabin passengers, and two, those farthest aft of all, for steerage passengers or cargo. Each compartment is thus isolated, and only by a blow in the line of the dividing bulkhead could two compartments be flooded at once; the bulkheads also serve in case of fire to prevent the flames from spreading.
Still another safeguard becomes possible through the adoption of the twin screw. The propellers are worked by two complete and entirely independent sets of boilers and engines, and these are separated by a longitudinal bulkhead in addition to the transverse bulkheads already described. In a single-screw ship this longitudinal bulkhead is impossible, and the space in which her engine and boilers are situated is her most vulnerable point; if she is struck there with sufficient force to make a fissure large enough to admit any considerable quantity of water, nothing will save her from sinking. In the case of the twin-screw ship, however, we have had the best of evidence, within the past two years, that with one of her engine-rooms flooded and open to the sea, she will still float and be navigable.
For many years past the value of the twin screw has been debated by the builders, the managers, the captains, and the engineers of the great transatlantic lines, to whom it did not commend itself so readily as to the Admiralty. It was adopted for war-ships several years before any of the well-known passenger lines ventured to use it, and its first appearance in this service was in the City of New York, four years ago. Since then it has been adopted by the White Star and the Hamburg-American lines, and though the North German Lloyd has not yet applied it to the recent accessions to its fleet, its advantages over the single screw for passenger vessels, as well as for war-ships, are more generally conceded now than ever before. The Admiralty adopted it for the security it afforded, and for its superior capacity for rapid manœuvring. Another feature which recommends it is that, should one of the two sets of engines become disabled from the breaking of the shaft, or any other cause, the opposite engine would be equal to taking the ship into port; while a similar accident on a single-screw ship would compel her to make port under sail (a very difficult feat with the modern type of ocean steamers), or to wait for another steamer to take her in tow.
Off Fire Island, New York.
