and the planes are very similar in construction to the bird's
wings. But here the resemblance ends: the aeroplane does not
fly, nor will it ever fly, as a bird flies.

If we carefully inspect the wing of a bird--say a large bird,
such as the crow--we shall find it curved or arched from front to
back. This curve, however, is somewhat irregular. At the front
edge of the wing it is sharpest, and there is a gradual dip or
slope backwards and downwards. There is a special reason for
this peculiar structure, as we shall see in a later chapter.

Now it is quite evident that the inventors of aeroplanes have
modelled the planes of their craft on the bird's wing. Strictly
speaking, the word "plane" is a misnomer when applied to the
supporting structure of an aeroplane. Euclid defines a plane, or
a plane surface, as one in which, any two points being taken, the
straight line between them lies wholly in that surface. But the
plane of a flying machine is curved, or CAMBERED, and if one
point were taken on the front of the so-called plane, and another
on the back, a straight line joining these two points could not
possibly lie wholly on the surface.

All planes are not cambered to the same extent: some have a very
small curvature; in others the curve is greatly pronounced.
Planes of the former type are generally fitted to racing
aeroplanes, because they offer less resistance to the air than do
deeply-cambered planes. Indeed, it is in the degree of camber
that the various types of flying machine show their chief
diversity, just as the work of certain shipmasters is known by
the particular lines of the bow and stern of the vessels which