It was stated also that a gull in its observed
maneuvers, rising up from a pile head on unflapping
wings, then plunging forward against the wind and
subsequently rising higher than his starting point, must
either time his ascents and descents exactly with the
variations in wind velocities, or must meet a wind billow
rotating on a horizontal axis and come to a poise on its
crest, thus availing of an ascending trend.
But the observations failed to demonstrate that the
variations of the wind gusts and the movements of the
bird were absolutely synchronous, and it was conjectured
that the peculiar shape of the soaring wing of certain
birds, as differentiated from the flapping wing, might,
when experimented upon, hereafter account for the performance.
Mystery to be Explained.
These computations, however satisfactory they were
for the speed of winds observed, failed to account for the
observed spiral soaring of buzzards in very light winds
and the writer was compelled to confess: "Now, this
spiral soaring in steady breezes of 5 to 10 miles per hour
which are apparently horizontal, and through which the
bird maintains an average speed of about 20 miles an
hour, is the mystery to be explained. It is not accounted
for, quantitatively, by any of the theories which have
been advanced, and it is the one performance which has
led some observers to claim that it was done through
'aspiration.
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