to one of these spaces, at either end of the ship,
the other end of the vessel would rise steadily upwards. In nearly
every case, even the largest steamer, just before sinking, tilts
abruptly its bow or stern straight up out of the sea, until the water
rushing into the hold draws the vessel downwards, and with a mighty
roar it plunges forever into the deep. We have repeatedly noticed at
this moment that the air within the boat escapes with a shrill whistle
from every possible aperture, and the sound resembles the shriek of a
steam siren. This is a wonderful spectacle to behold!

The velocity with which a ship sinks depends on the size of the hold,
and its distance from the ship's center of gravity, for the suction
occurs more rapidly if the ship is struck at either end than if the
blow is delivered amidships.

We are seldom concerned with ships having empty holds; those we pursue
usually carry heavy cargoes, and therefore the water can only
penetrate within, where space and air exist; whatever air is left
around loosely packed bales and boxes must be driven out before the
water can stream in; certain exceptional cargoes, like wool and
cereals, absorb a given amount of water, but these can be discounted.

[Illustration: _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]

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