_Entering the Water._
Instructors should never force young swimmers reluctantly to leap into
the water. It would be advisable for delicate persons, especially
when they intend to plunge in, to put a little cotton steeped in oil,
and afterwards pressed, in their ears, before entering the water.
This precaution will prevent irritation of the organ of hearing. In
entering, the head should be wetted first, either by plunging in head
foremost, or by pouring water on it, in order to prevent the pressure
of the water driving up the blood into it too quickly, and increasing
congestion. The swimmer should next advance, by a clear shelving shore
or bank, where he has ascertained the depth by plumbing or otherwise,
till the water reaches his breast; should turn towards the place of
entrance; and, having inflated his breast, lay it upon the water,
suffering that to rise to his chin, the lips being closed.
_Buoyancy in the Water._
The head alone is specifically heavier than salt water. Even the legs
and arms are specifically lighter; and the trunk is still more so. Thus
the body cannot sink in salt water, even if the lungs were filled,
except owing to the excessive specific gravity of the head.
Not only the head, but the legs and arms, are specifically heavier than
fresh water; but still the hollowness of the trunk renders the body
altogether too light to sink wholly under water, so that some part
remains above until the lungs become filled. In general, when the human
body is immersed, one-eleventh of its weight remains above the surface
in fresh water, and one-tenth in salt water.
In salt water, therefore, a person throwing himself on his back, and
extending his arms, may easily lie so as to keep his mouth and nostrils
free for breathing; and, by a small motion of the hand, may prevent
turning, if he perceive any tendency to it. In fresh water, a man
cannot long continue in that situation, except by the action of his
hands; and if no such action be employed, the legs and lower part of
the body will gradually sink into an upright position, the hollow of
the breast keeping the head uppermost. If, however, in this position,
the head be kept upright above the shoulders, as in standing on the
ground, the immersion, owing to the weight of the part of the head out
of the water, will reach above the mouth and nostrils, perhaps a little
above the eyes. On the contrary, in the same position, if the head be
leaned back, so that the face is turned upwards, the back part of the
head has its weight supported by the water, and the face will rise
an inch higher at every inspiration, and will sink as much at every
expiration, but never so low that the water can come over the mouth.
For all these reasons, though the impetus given by the fall of the
body into water occasions its sinking to a depth proportioned to the
force of the descent, its natural buoyancy soon impels it again to the
surface, where, after a few oscillations up and down, it settles with
the head free.
Unfortunately, ignorant people stretch the arms out to grasp at
anything or nothing, and thereby keep the head under; for the arms and
head, together exceeding in weight one-tenth of the body, cannot remain
above the surface at the same time. The buoyancy of the trunk, then and
then only, occasions the head and shoulders to sink, the ridge of the
bent back becoming the portion exposed; and, in this attitude, water
is swallowed, by which the specific gravity is increased, and the body
settles to the bottom. It is, therefore, most important to the safety
of the inexperienced to be firmly convinced that the body naturally
floats.
To satisfy the beginner of the truth of this, Dr. Franklin advises him
to choose a place where clear water deepens gradually, to walk into
it till it is up to his breast, to turn his face to the shore, and to
throw an egg into the water between him and it--so deep that he cannot
fetch it up but by diving. To encourage him to take it up, he must
reflect that his progress will be from deep to shallow water, and that
at any time he may, by bringing his legs under him, and standing on the
bottom, raise his head far above the water. He must then plunge under
it, having his eyes open, before as well as after going under; throw
himself towards the egg, and endeavour, by the action of his hands and
feet against the water, to get forward till within reach of it. In
this attempt, he will find that the water brings him up against his
inclination, that it is not so easy to sink as he imagined, and that he
cannot, but by force, get down to the egg. Thus he feels the power of
water to support him, and learns to confide in that power; while his
endeavours to overcome it, and reach the egg, teach him the manner of
acting on the water with his feet and hands, as he afterwards must in
swimming, in order to support his head higher above the water, or to go
forward through it.
If, then, any person, however unacquainted with swimming, will hold
himself perfectly still and upright, as if standing with his head
somewhat thrown back so as to rest on the surface, his face will remain
above the water, and he will enjoy full freedom of breathing. To do
this most effectually, the head must be so far thrown back that the
chin is higher than the forehead, the breast inflated, the back quite
hollow, and the hands and arms kept under water. If these directions be
carefully observed, the face will float above the water, and the body
will settle in a diagonal direction. (Plate XXIII. fig. 1.)
In this case, the only difficulty is to preserve the balance of the
body. This is secured, as described by Bernardi, by extending the arms
laterally under the surface of the water, with the legs separated,
the one to the front and the other behind: thus presenting resistance
to any tendency of the body to incline to either side, forward or
backward. This posture may be preserved any length of time. (Plate
XXIII. fig. 2.)
The Abbé Paul Moccia, who lived in Naples in 1760, perceived, at the
age of fifty, that he could never entirely cover himself in the water.
He weighed three hundred pounds (Italian weight), but being very fat,
he lost at least thirty pounds in the water. Robertson had just made
his experiments on the specific weight of man; and everybody was then
occupied with the Abbé, who could walk in the water with nearly half
his body out of it.
[Illustration: _Plate XXIII_
_Page 90._
Swimming--Buoyancy in Water.