of the pilot. The pilot's
feet, in a modern aeroplane, rest upon a bar working on a central
swivel, and this moves the rudder. To turn to the left, the left foot is
moved forward; to turn to the right the right foot.

But it was in the balancing control of their machine that the Wrights
showed such great ingenuity. Running from the edges of the lower plane
were some wires which met at a point where the pilot could control
them. The edges of the plane were flexible; that is, they could be bent
slightly either up or down, and this movement of the flexible plane is
known as WING WARPING.

You know that when a cyclist is going round a curve his machine leans
inwards. Perhaps some of you have seen motor races, such as those held
at Brooklands; if so, you must have noticed that the track is banked
very steeply at the corners, and when the motorist is going round these
corners at, say, 80 miles an hour, his motor makes a considerable
angle with the level ground, and looks as if it must topple over. The
aeroplane acts in a similar manner, and, unless some means are taken to
prevent it, it will turn over.

Let us now see how the pilot worked the "Wright" glider. Suppose the
machine tilted down on one side, while in the air, the pilot would pull
down, or warp, the edges of the planes on that side of the machine which
was the lower. By an ingenious contrivance, when one side was warped
down, the other was warped up, with the effect that the machine would
be brought back into a horizontal position. (As we shall return to
the subject of wing warping in a later chapter, we need not discuss it
further here.)

It must not be imagined that as soon as the Wrights had constructed
a glider fitted with this clever system of controlling mechanism they
could fly when and where they liked. They had to practise for two
or three years before they were satisfied with the results of their
experiments: neglecting no detail, profiting by their failures, and
moving logically from step to step. They never attempted an experiment
rashly: there was always a reason for what they did. In fact,
their success was due to systematic progress, achieved by wonderful
perseverance.

But now, for a short time, we must leave the pioneer work of the Wright
brothers, and turn to the invention of the petrol engine as applied
to the motor car, an invention which was destined to have far-reaching
results on the science of aviation.

CHAPTER XX. The Internal