HOW RESISTANCE AFFECTS THE SHAPE.--It is because
of this counterforce, resistance, that shape
becomes important in a flying object. The metal
ball may be flattened out into a thin disk, and now,
when the same force is applied, to project it forwardly,
it will go as much farther as the difference
in the air impact against the two forms.

MASS AND RESISTANCE.--Owing to the fact that
resistance acts with such a retarding force on an
object of small mass, and it is difficult to set up a
rapid motion in an object of great density, lightness
in flying machine structures has been considered,
in the past, the principal thing necessary.

THE EARLY TENDENCY TO ELIMINATE MOMENTUM.--
Builders of flying machines, for several
years, sought to eliminate the very thing
which gives energy to a horizontally-movable
body, namely, momentum.

Instead of momentum, something had to be
substituted. This was found in so arranging the
machine that its weight, or a portion of it, would
be sustained in space by the very element which
seeks to retard its flight, namely, the atmosphere.

If there should be no material substance, like
air, then the only way in which a heavier-than-air
machine could ever fly, would be by propelling it