Copyright by Underwood & Underwood, N.Y.
BRITISH HOSPITAL SHIP GLOUCESTER CASTLE, SHOWING RED CROSS ON BOW,
SUNK IN THE ENGLISH CHANNEL BY A GERMAN SUBMARINE[ToList]
Accordingly the air must escape through existing holes, as the water pouring in drives the air into the hold; the pressure with which the water comes in is equal to the air pressure in the hold. It is quite conceivable that a cargo may be so closely packed that there will be no space left for air to escape, but this is hardly ever the case; frequently, however, the cross-sections of the air vents are so small that the air escapes only very slowly, and the water enters very slowly in the same ratio; under these conditions it would take a long time for a ship to sink. This undoubtedly is very desirable in peace time, but in time of war this is not at all agreeable to our purpose; first, if the foundering of the vessel is prolonged we are prevented from accomplishing other work, and secondly, warships may come to the assistance of a sinking steamer.
Whenever possible we found it expedient to break open with an axe big holes in the lockers in case the hatch could not be quickly enough removed; or, if circumstances did not permit of our doing this, we shot holes with our cannon into the upper part of the steamer, above the hold, so that the air might conveniently escape and the water rush in. We employed, with excellent results, this method in the sinking of many steamers which otherwise would have settled too slowly.
It happens sometimes that a ship may carry a cargo that floats and that is not porous, such as wood. It is impossible to sink a vessel with such a cargo by admitting water into the hold. Shots therefore must be fired at the engine and boiler rooms to force this kind of a steamer to sink. In general this is a safe rule to follow, for these are always the most vulnerable portions of every heavily laden vessel, and this mode of attack is nearly invariably successful.
A warship is usually equipped with cross or lateral bulkheads, in addition to the longitudinal bulkhead that runs from stem to stern through the middle of the ship, dividing it into halves, and other bulkheads separate these two longitudinal sections into further subdivisions. With the exception of the great fast passenger steamers, these divisions by means of longitudinal bulkheads seldom exist on vessels of commerce, although exceptions are to be found.
The sinking of a steamer with a multitude of partitions is effected by its gradually listing more and more on the side in which the water is penetrating, until it capsizes completely and founders with the keel uppermost. A ship can also roll over on its side as it plunges downwards with stem or stern erect.
Theoretically a vessel might sink on a parallel keel, descending horizontally deeper and deeper into the sea; but it never occurs in reality. This hypothesis assumes that a ship has taken in at the bow exactly the same amount of water as at the stern, at exactly the same distance from the center of gravity; this, of course, is impossible; besides the holes through which the water is pouring in must also be at precisely the same level, or else the water pressure would be greater at one end than at the other, and the slightest alteration of level would occasion a greater intake of water and upset the equilibrium of the boat.