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 card-board—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
second or two after it is exerted, while the action of the motor is
prolonged.
