The skipper still remains horizontal, so that as
it moves toward the earth its flat surface, which
is now exposed to the action of the air, meets
with a resistance, and this changes the angle of
the disk, so that it will not be horizontal. Instead
it assumes the position as indicated at D,
and this impinging effect against the air causes
the skipper to move upwardly along the line E,
and having reached a certain limit, as at, say E,
it automatically again changes its angle and moves
downwardly along the path F, and thus continues
to undulate, more or less, dependent on the combined
action of the power and weight, or momentum,
until it reaches the earth.

It is, therefore, clear that the atmosphere has
an action on a plane surface, and that the extent
of the action, to sustain it in flight, depends on two
things, surface and speed.

Furthermore, the greater the speed the less the
necessity for surface, and that for gliding purposes
speed may be sacrificed, in a large measure,
where there is a large surface.

This very action of the skipper is utilized by
the aviator in volplaning,--that is, where the
power of the engine is cut off, either by accident,
or designedly, and the machine descends to the
earth, whether in a long straight glide, or in a