achine oscillating;
and second, its usefulness was restricted to calm air.

In a slightly modified form the same system was applied to the
fore-and-aft balance. The main aeroplane was set at a positive angle,
and a horizontal tail at a negative angle, while the center of gravity
was placed far forward. As in the case of lateral control, there was a
tendency to constant undulation, and the very forces which caused a
restoration of balance in calms caused a disturbance of the balance in
winds. Notwithstanding the known limitations of this principle, it had
been embodied in almost every prominent flying machine which had been
built.

After considering the practical effect of the dihedral principle, we
reached the conclusion that a flyer founded upon it might be of interest
from a scientific point of view, but could be of no value in a practical
way. We therefore resolved to try a fundamentally different principle.
We would arrange the machine so that it would not tend to right itself.
We would make it as inert as possible to the effects of change of
direction or speed, and thus reduce the effects of wind-gusts to a
minimum. We would do this in the fore-and-aft stability by giving the
aeroplanes a peculiar shape; and in the lateral balance by arching the
surfaces from tip to tip, just the reverse of what our predecessors had
done. Then by some suitable contrivance, actuated by the operator,
forces should be brought into play to regulate the balance.

Lilienthal and Chanute had guided and balanced their machines, by
shifting the weight of the operator's body. But this method seemed
to us incapable of expansion to meet large conditions, because the
weight to be moved and the distance of possible motion were limited,
while the disturbing forces steadily increased, both with wing area
and with wind velocity. In order to meet the needs of large machines,
we wished to employ some system whereby the operator could vary at
will the inclination of different parts of the wings, and thus obtain
from the wind forces to restore the balance which the wind itself had
disturbed. This could easily be done by using wings capable of being
warped, and by supplementary adjustable surfaces in the shape of
rudders. As the forces obtainable for control would necessarily
increase in the same ratio as the disturbing forces, the method
seemed capable of expansion to an almost unlimited extent. A
happy device was discovered whereby the apparently r