MOMENTUM NOT CONSIDERED.--The great factor
of momentum has been entirely ignored, and it is
our desire to press the important point on those
who begin to study the question of flying machines.

THE FLIGHT OF BIRDS.--Volumes have been
written concerning observations on the flight of
birds. The marvel has been why do soaring birds
maintain themselves in space without flapping
their wings. In fact, it is a much more remarkable
thing to contemplate why birds which depend
on flapping wings can fly.

THE DOWNWARD BEAT.--It is argued that the
downward beat of the wings is so much more
rapid than the upward motion, that it gets an action
on the air so as to force the body upwardly.
This is disposed of by the wing motion of many
birds, notoriously the crow, whose lazily-flapping
wings can be readily followed by the eye, and the
difference in movement, if any, is not perceptible.

THE CONCAVED WING.--It is also urged that the
concave on the under side of the wing gives the
quality of lift. Certain kinds of beetles, and particularly
the common house fly, disprove that theory,
as their wings are perfectly flat.

FEATHER STRUCTURE CONSIDERED.--Then the
feather argument is advanced, which seeks to