The Democratic advocate., 1878-09-21
How Birds Fly.

You will find, if you carefully examine
a birds wing, that all the bones and mus
cles are placed along the front edge, which
is thus made very stiff and strong. The
quill feathers are fastened in such a way
that they point backward, so that the hind
edge of the wing is not stiff like the front
edge, but is flexible and bends at the least
touch. As the air is not solid, but
gas, it has tendency to slide out from
under the wing when this is driven down.
ward, and, of course, it will do this at the
point where it can escape most easily.
Since the front edge of the wing is stiff
and strong, it retains its hollow shape,
and prevents the air from sliding out in
this direction, but the pressure of the air
is enough to bend up the thin, flexible
ends Of the feathers at the hinder border
Of the wing, so the air makes its escape
there, and slides out backward and up
ward. The weight of the bird is all the
time pulling it down toward the earth; so.
at the same time that the air slides out
upward and backward past the bent edge
Of the wing, the wing itself, and with it
the bird, slides forward and downward off
from the confined air. 1t is really its
weight which causes it to do this, SO that
the statement that bird flies BY its own
weight is strictly true.
This is true, also, of insects and bats.
They all have wings with stiff front edges,
and flexible hind edges which bend and al
low the air to pass out, so that flying is
nothing but sliding down hill made of
air. A bird rises by tapping its wings,
and it flies by falling back toward the
earth and sliding forward at the same
time. At the end of each stroke of its
wings it has raised itself enough to make
up for the distance it has fallen since the
last stroke, and accordingly it stays at the
same height and moves forward in SEEM
ingly straight line. But if you watch the
flight of those birds which flap their wings
slowly, such as the woOdpecker, you can
see them rise and fall, and will have no
trouble in seeing that their path is not
really straight line, but is made of curves;
although most birds flap their wings so
rapidly that they have no time to fall
through a space great enough to be seen.
Birds also make use of the wind to aid
them in fight, and by holding their wings
inclined like a kite, so that the wind shall
slide out under them, they can sail great
distances without tapping their wings ut
all. They are supported, as paper kite
is, by the wind, which is continually push
ing against their wings, and sliding out
backward and downward, thus lifting or
holding up the bird, and at the same time
driving it forward
The birds are not compelled to face the
wind while they are sailing, but by chang
ing the position of the wings little they
can 60 in whatever direction they wish,
much as boy changes his direction in
skating by leaning a little to one side or
the other. Some birds are very skillful
at this kind of sailing, and can even remain
stationary in the air for some minutes when
there is a strong wind; and they do this
without tapping their wings at all. It is
a difficult thing to do, and no birds except
the most skillfnl flyers can manage it.
Some hawks can do it, ard gulls and terms
may often be seen practicing it when a
gale of wind is blowing, and they seem to
take great delight in their power of fight.