Evening star. [volume] (Washington, D.C.) 1854-1972, 1891-05-23
HOW BIRDS FLY,
Mans Attsmpta ut Aerial volitation Are
Mistaken Ouee.

HOW BIRDS FLY,
Mans Attsmpta ut Aerial volitation Are
Mistaken Ones.
MECHANICAL PRINCIPLES usEp-rHr Law OF
GRAVITY n NOT IN THE wAr OF FLIGHT, BUT
ASSISTS rT-u BIRD WERE LIGHTER THAN AIR
IT COULD NOT rLr-THE MECHANISM EMPLOYED.
ssTNHE ART OF FLYING, IF TT Is EVER
L attained by man. viii be achieved by the
application of principles far different from
those by which investigators up to the present
time have tried to gain that end" said an ex-
pert ornithologist to writer for The STAR
In almost all human attempts to navigate the
air 1t has been sought first to acquire buoy
ancy by which the aerostas and its passenger
should be given lightness sufficient to enable
them to float in the atmosphere. This was
considered the essential thing, after which the
problems Of propulsion and steering were con-
sidered.
''This is the error that has done more than
all others put together to set at naught the
efforts Of experimenters in this direction up to
the present time. To, show how great a mis-
take it is take the birds for an example. Thew
are not lighter than the air, but enormously
might float, but they could not fiv. That il
just the difference between the bird and the
balloon. The latter is hghte than the atmos-
phere and floats upon it.; thus it cannot be di-
rected or propelled, because it contains no
force whercwith to resist the currents of air in
which 1t is immersed and no fulcrum to exert
force against. 1t becomes. as it were. a part
OF the atmosphere and must 20 wherever it
goes.
Solomon, who was credited with such un-
r114 -
eagle in the air that he knew it not:' but,
however mysterious may be the instinct by
which the bird makes use Of natural forces,
the mechanical principles it employs in fight
are no Longer mystery.
THE FORCE OF GRAVITY.
'The aeronauts first effort is directed to
overcoming the force of gravity, but that is
precisely the force upon which the bird most
Importantly depends for its powers of Volta
ton. Gravity to the fowl Of the air is what
the string IL to the kite; without it the animal
would at once keel over and fall futtering to
the ground. To make my meaning clear you
must realize that gravity is q steadily acting
force to be worked against. 1t gives the flying
creature fulcrum against which to ply its
wings. The wings are the levers: were the
fulcrum absent the wings would flap vainly
To overcome the force of gravity the bird de-
ponds upon the elasticity of the air, which,
like any other fluid, rebounds when struck
The winged animal strikes the atmosphere
downward and is upheld, even against gravita-
ton, by the rebound.
Few persons have any notion of the force
ordinarily expended by bird in the air. The
heron, remarkable for its slow and heavy flight
flaps its wings $50 times q minute No one
ever tried to count the volitative pulsations Of
the pigeon and the partridge. those Of the lat
ter being so swift as to leave only a blurred i'm
preston on the eye. 1t is interesting to OBJ
serve that the dimensions of a birds wing are
always in exact adjustment to the size and
weight Of the bird it is intended to lift.
CONSTRUCTION OF A BIRDS WING.
another provision made in the adaptation
Of the birds wing to the purpose in view is that
the feathers, composed Of such light though
strong material. are made to underlap each
other, so that in the downward flap the pressure
nected membrane, while in the upward stroke
they separate and let the air through with as
little resistance as possible.
You ask how it is that the bird is able to
move forward through the air. That is power
due merely to the structure of the wings, which
are rigid in front and extremely elastic toward
the ends, all the feathers pointing backward.
When the wing is tapped perpendicuarly,
the compressed and resistant air seeks escape
by the easiest way. 1t cannot go upward
through the wing, because the feathers are
closed; nor can it make its way out forward so
easily past the bent and rigid framework of
bones in front. But it finds ready exit back.
ward by lifting the elastic ends Of the feathers
in the rear of the wing thus communicating a
push forward to the body Of the bird. By this
mechanical contrivance the same volume of air
is made to do the double duty of sustaining the
BIRDS weight and Of communicating to it for
ward impulse. The creature therefore, has
only to repeat its perpendicular blows upon the
atmosphere in order to sustain and propel
itself. II you take in your hand the stretched
wing of heron which has been dried IN that
position and strike it quickly downward you
will find it very difficult to maintain the verti-
cal direction OF the stroke. and that if you do
not use much force to resist the tendency your
hand will be carried forward.
WEIGHT AND NOT BUoYANcY.
"1n all the beautiful evolutions of birds upon
the wing it is weight and not buoyancy which
makes these evolutions possible. True, one
often sees birds soaring with no motion of their
wings that is perceptible, but this they are en-
abled to do by using as a sustaining force the
breeze that strikes against the widespread
vanes extended from their bodies. 1t is the
principle of the kite. To bring these two forces
the wind and gravity-into the perfect bal
ance necessary for accomplishing this feat
called soaring, requires the most expert and
accomplished powers Of flying. such as few
birds possess. To perform it, the animal must
expand or contract its pinions exactly to the
right size and hold them precisely at the cor
kcCe nHSAe. 1uc sliRutest alteratlON IN these
adjustments produces instantly an upsetting
OF the balance. Fowls which seek their food
in the air have long and powerful wings and
their command of them is 30 perfect that they
can pick up flying gnat in the air while trav-
cling at the rate OF SO miles an hour. Such in
particular are the powers Of some species of the
swallow tribe.
SIN some birds the wing has to be adapted to
the double purpose of fight and diving. In
their case large area of pinion has to be dis
pcnsed with, because it could not be worked to
advantage under water. Thus you And that all
diving birds have very small wings and in some
OF them the wing is nothing more than q pow
erful fin for use in swimming and Of no utility
whatever for flight.
TAILS NOT Used AS RUDDERs.
at Is popularity imagined that birds tails
serve them rs rudders for steering purposes.
but thnt is not true II they had been designed
by nature with that object in view they would
have been set with their vanes vertical and not
The appendage, in fact il merely
intended for balance, and you will find that
all birds which possess great ease in evolution
through the air have largely developed tails
birds are perhaps the most remark
able examples known Of the machinery Of fly-
ing. Their power of posing themselves in the
air while searching the blossoms for insects, |
absolutely stationary, is extra
ordinary, depending not upon soaring but
upon the inconceivably rapid motion of their |
wings. as you may observe for yourself any
summer day.
The smaller birds wings in proportion to |
the weight Of its body the more rapidly it must |
flap them in order to sustain itself. The huge |