meaning bird wing, is applied to such
flying machines as depend on wing motion to support
them in the air.

Unquestionably, a support can be obtained by
beating on the air but to do so it is necessary to
adopt the principle employed by nature to secure
an upward propulsion. As pointed out elsewhere,
it cannot be the concaved type of wing,
or its shape, or relative size to the weight it must
carry.

As nature has furnished such a variety of data
on these points, all varying to such a remarkable
degree, we must look elsewhere to find the secret.
Only one other direction offers any opportunity,
and that is in the individual wing movement.

NATURE'S TYPE NOT UNIFORM.--When this is
examined, the same obscurity surrounds the issue.
Even the speeds vary to such an extent that when
it is tried to differentiate them, in comparison
with form, shape, and construction, the experimenter
finds himself wrapt in doubt and perplexity.

But birds do fly, notwithstanding this wonderful
array of contradictory exhibitions. Observation
has not enabled us to learn why these things
are so. High authorities, and men who are expert
aviators, tell us that the bird flies because