Evening star. [volume] (Washington, D.C.) 1854-1972, 1902-09-18
SECRET OF BIRD SOARING.
a Naturalist Who Thinks He Has
Found It Inside the Quills.

From Chambers Journal
what is the motive power of a quiescent
bird that moves 1t through air resistance
and Keeps Its heavy body from falling? We
are absolutely baff1ed when confronted with
the problem of a soaring bird. It does not
move Its wings when 1t has once got well
started: its moving parts seem to be Of use
merely to get 1t off some unknown dead
center: 1t has infinite capacity for taking
advantage of balance, and all this is done
while violating every known mechanical
law, holding up a heavy body In the air,
and overcoming strong atmospheric resist
ance at rapid rate without discoverable
expenditure of energy.
Yet weight is absolutely necessary for
hight, and the relative area of wing ex-
panse diminishes as the weight of the bird
increases. For example, gnat, which pos
sesses very light, fairy-like body, has
swallow in proportion to the weight of
each l have been trying to discover the
exact structure of birds surfaces which
enables 1t to get the soaring force from the
air pressure under its wings for the past
fifteen years. The task seemed hopeless
until accident settled the case. 1 had To-
Gated in the foothills Of the Flat Top noun
tains of Colorado. in the dry air of that
yellow tailed hawks. that were admirable
soaring birds, were abundant
A precipitous cliff 1000 feet high was
near, from which 1 floated all sorts Of sur
races, and year after year the quest went
on. A furious forest fire had filled the air
with smoke and ashes, and the odor of
burning wood was in evidence for months
l had killed large hawk and, was exam
lining Its feathers, when stain was detect
ed on the sides of the quill between the
spcules that was not before seen. A small
magnifier gave it the appearance of dis
colorations about the throat of a dust ex-
haust in planning mill.
A microscope was at once procured, with
an outfit of detectives from 60 to 100 dame
tiers, and in an hours time / knew more
about bird flights than twenty-five years of
study had given me- The discolorations ex-
tended along eacn spicule between the
plates. The downy filaments filing the
double-wall structure of the wings were
stained in the same unusual manner This
stain, when scraped off and examined re-
sembled SCOT from a stovepipe, showing
that the air had been going through the
wing In an incessant stream, carrying the
smoke and carbon particles of the fire with
ideas >''->N' -
And this brings me to the device that
scars the bird. What is a feather? 1t is
an air engine, and the bird surfaces are
made of them. They have been looked
on as a light, flexible material for making
an extended surface impervious to air that
would readily fold upon itself, and their
exquisite mechanical structure has been
overlooked They consist of quill and two
vanes made up of spicules, between which
are the plates. The plates cross channel
about one-fortieth of an inch wide. made
by the spcules. There are about 1000 of
them to the inch, being practically in
Vulnerable, and they are located at the
outer surface, filling about one-fifth part
of the depth of the channel. They are
about the twenty-thousandth part of an
inch thick, as nearly an amateur with a
microscope could determine, so that nine
teen-tWentieths of the space of the chan
nels Is open to the passage of air.
The mechanical service Of the plates is
obvious. The curve impinges against the
air current through the feathers and drives
the bird to the front. Pressure produced
by the normal factor of weight is thus
made to serve the motive power of
flight.