earning how to start and stop, to ascend and descend, the next
thing to master is the art of preserving equilibrium, the knack of
keeping the machine perfectly level in the air--on an "even keel," as
a sailor would say. This simile is particularly appropriate as all
aviators are in reality sailors, and much more daring ones than those
who course the seas. The latter are in craft which are kept afloat by
the buoyancy of the water, whether in motion or otherwise and, so long
as normal conditions prevail, will not sink. Aviators sail the air in
craft in which constant motion must be maintained in order to ensure
flotation.

The man who has ridden a bicycle or motorcycle around curves at anything
like high speed, will have a very good idea as to the principle of
maintaining equilibrium in an airship. He knows that in rounding curves
rapidly there is a marked tendency to change the direction of the motion
which will result in an upset unless he overcomes it by an inclination
of his body in an opposite direction. This is why we see racers lean
well over when taking the curves. It simply must be done to preserve the
equilibrium and avoid a spill.

How It Works In the Air.

If the equilibrium of an airship is disturbed to an extent which
completely overcomes the center of gravity it falls according to the
location of the displacement. If this displacement, for instance, is at
either end the apparatus falls endways; if it is to the front or rear,
the fall is in the corresponding direction.

Owing to uncertain air currents--the air is continually shifting and
eddying, especially within a hundred feet or so of the earth--the
equilibrium of an airship is almost constantly being disturbed to some
extent. Even if this disturbance is not serious enough to bring on
a fall it interferes with the progress of the machine, and should
be overcome at once. This is one of the things connected with aerial
navigation which calls for prompt, intelligent action.

Frequently, when the displacement is very slight, it may be overcome,
and the craft immediately righted by a mere shifting of the operator's
body. Take, for illustration, a case in which the extreme right end
of the machine becomes lowered a trifle from the normal level. It is
possible to bring it back into proper position by leaning over to the
left far enough to shift the weight to the counter-balancing point. The
same holds good as to minor front or rear displacements.

When Pl