manned and loaded with passengers it is a _very
little above the level of the sea_. On this fact the acting of the
principle depends. Between the floor and the bottom of the boat--a
space of upwards of a foot in depth--there is some light ballast of cork
or of wood, and some parts of the space are left empty. The six holes
above-mentioned are tubes of six inches in diameter, which extend from
the floor through the bottom of the boat. Now, it is one of nature's
laws that water must find its level. For instance, take any boat and
bore large holes in its bottom, and suppose it to be supported in its
_ordinary_ floating position, so that it cannot sink even though water
runs freely into it through the holes. Then fill it suddenly quite full
of water. Of course the water inside will be considerably above the
level of the water outside, but it will continue to run out at the holes
until it is exactly on a level with the water outside. Now, water
poured into a lifeboat acts exactly in the same way; but when it has
reached the level of the water outside _it has also reached the floor_,
so that there is no more water to run out.

Such are the principal qualities of the splendid lifeboat now used on
our coasts, and of which it may be said that it has reached a state of
almost absolute perfection.

The accompanying sections of the lifeboat exhibit the position of the
air-cases and discharging tubes. In Figure 1 the _shaded_ parts give a
side view of the air-cases. The line A A indicates the deck or floor,
which lies a _little_ above the level of the water when the boat is
loaded; B B is the water-tight space containing ballast; C C C are three
of the six discharging holes or tubes; the dotted line D D shows the
level of the sea. Figure 2 gives a bird's-eye view of the boat. The
shaded parts indicate the air-cases; and the position of the six
discharging tubes is more clearly shown than in Figure 1. There are
three covered openings in the floor, which permit of a free circulation
of air when the boat is not in use, and in one of these is a small pump
to clear the ballast-space of leakage. It will be observed that the
boat draws little water; in fact, there is much more of her above than
below water, and she is dependent for stability on her great breadth of
beam and her heavy keel.

These four qualities in the lifeboat are illustrated every year by many
thrilling incidents of wreck and rescue. Let us glance at a f