MECHANICAL BIRD ACTION

In order to understand the theory of the modern flying
machine one must also understand bird action and wind
action. In this connection the following simple experiment
will be of interest:

Take a circular-shaped bit of cardboard, like the lid of
a hat box, and remove the bent-over portion so as to
have a perfectly flat surface with a clean, sharp edge.
Holding the cardboard at arm's length, withdraw your
hand, leaving the cardboard without support. What is
the result? The cardboard, being heavier than air, and
having nothing to sustain it, will fall to the ground.
Pick it up and throw it, with considerable force, against
the wind edgewise. What happens? Instead of falling
to the ground, the cardboard sails along on the wind,
remaining afloat so long as it is in motion. It seeks
the ground, by gravity, only as the motion ceases, and
then by easy stages, instead of dropping abruptly as in
the first instance.

Here we have a homely, but accurate illustration of
the action of the flying machine. The motor does for
the latter what the force of your arm does for the cardboard--
imparts a motion which keeps it afloat. The
only real difference is that the motion given by the
motor is continuous and much more powerful than that
given by your arm. The action of the latter is limited
and the end of its propulsive force is reached within a