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.' i, e., that a bird acted upon by a current,
actually
drew forward into that current against its exact
direction of motion."
