The islander. [volume] (Friday Harbor, Wash.) 1891-1899, 1895-05-16
AS THE BIRDS SOAR,
THEY POINT TO NOVEL IDEAS OF ME-
cHANIcAL IMPORTANCE.

Testimony
sonian Institution.
1t has long been observed that certain
species of birds maintain themselves in
definitely in the air by soaring, without
any Tapping of the wing or any motion
other than slight rocking of the body,
and this although the body in question
is many hundred times denser than the
air in which it seems to float with an
undulating movement as on the waves
of an invisible stream.
No satisfactory mechanical explana-
ton of this anomaly has been given,
and none would be offered in this con-
nection by the writer were he not salts
fed that it involves much more than an
pathological problem, and that it
points to novel conclusions of mechan-
ical and unitarian Importance. They
are paradoxical at first sight, since they
imply that under certain specified con-
ditions very heavy bodies entirely de-
tached from the earth, immersed in and
free to move in the air, can be sustained
there indefinitely without any expendi-
ture of energy from within.
These bodies may be entirely of me-
chanical construction, but for the pres
ent we will continue to consider the
character of the invisible support of the
soaring bird and to study its motions,
though only as pregnant instance Of
fered by nature, to show that rational
solution of the mechanical problem is
possible.
1t is frequently suggested by those
who know these facts only from books
that there must be some quivering OF
the wings so rapid as to escape obser-
walton. Those who do know them from
observation are aware that it is abso-
lutely certain that nothing of the kind
takes place, and that the birds sustain
themselves on pinions which are quite
rigid and motionless, except for rock
ing or balancing movement, involving
little energy.
To the writer, who has himself been
attracted from his earliest years to the
mystery which has surrounded this &C
ton of the soaring bird, it has been
subject of continual surprise that it has
attracted so little attention from ply
sicists. That nearly inert bodies,
weighing from five to ten and even
more pounds, and many hundred times
denser than the air, should be visibly
suspended in it above our heads, some
times for hours at time, and without
falling-this, it might seem, is, without
misuse of language, to be called phys
ical miracle, and yet the fact that
those whose province it is to investigate
nature have hitherto seldom thought it
deserving attention is perhaps the
greater wonder.
The writer will not attempt any gen
eral description of his own observations,
but as an illustration of what can some
times be seen will give single one, to
whose exactness he can personally wit
ness. The common turkey buzzard
(Cathartes aura) is so plentiful around
the environs of Washington that there
is rarely time when some of them may
not be seen in the sky, gliding in curves
over some attractive point or-more
rarely-moving in nearly straight lines
on rigid wings, if there be a moderate
wind. On the only occasion when the
motion of one near at hand could be
studied in very high wind, the author
was crossing the long aqueduct bridge
over the Potomac in an usually violent
November gale, the velocity of the wind
being probably over 35 miles an hour.
About one-third of the distance from
the right bank of the river, and imme-
diately over the right parapet of the
bridge, at height of not over 20 yards,
was one of these buzzards, which, for
some object which was not evident,
chose to keep over this spot, where the
gale, undisturbed by any surface irreg-
ularities, swept directly up the river
with unchecked violence. In this aerial
torrent, and apparently Indifferent to
it, the bird hung, gliding in the usual
m amer of its species, round and round,
in small oval curve, whose major axis
which seemed toward the wind-was
not longer than twice its height from
the water. The bird was therefore at
all times in close view. He swung
around repeatedly, rising and falling
slightly in its course, while keeping, as
whole, on one level and over the same
place, moving with slight swaying,
both in front and lateral direction, but
in such an effortless way as suggested
lazy yielding of itself to the rocking of
some invisible wave.
1t may be asserted that there was not
only no flap of the wing, but not the
culver of a wing feather visible to the
closest scrutiny during the considerable
time the bird was under observation.
and during which the gale continued
A record of this time was not kept
but it at any rate lasted until the
writer, chilled by the cold blast, gave
up watching and moved away, leaving
the bird still floating about at the same
height in the torrent of air, in nearly
the same circle and with the same as
pect of indolent repose.
1t the wind is such body as it is
commonly supposed to be, it is abso-
lutely impossible that the sustentation
could have taken place in a horizontal
current any more than in calm, and
yet that the ability to soar is in some
way connected with the presence of the
wind became to the writer as certain
as any fact of observation could be, and
at first the difficulty of reconciling such
facts-tO him ndoubted-with accept
ed laws of motion seemed quite insu-
perable. Professor Langley.