s as great as in the
latter, and the lifting power would necessarily be much greater. Thus,
though both machines have planes of the same area, each plane having
a surface of 144 square feet, yet there is a great difference in the
"lift" of the two.

But it is not to be concluded that the back portion of a plane
is altogether wasted. Numerous experiments have taught aeroplane
constructors that if the plane were slightly curved from front to back
the rear portion of the plane also exercised a "lift"; thus, instead of
the air being simply cut by the entering edge of the plane, it is driven
against the arched back of the plane, and helps to lift the machine into
the air, and support it when in flight.

There is also a secondary lifting impulse derived from this simple
curve. We have seen that the air which has been cut by the front edge of
the plane pushes up from below, and is arrested by the top of the arch,
but the downward dip of the rear portion of the plane is of service in
actually DRAWING THE AIR FROM ABOVE. The rapid air stream which has been
cut by the entering edge passes above the top of the curve, and "sucks
up", as it were, so that the whole wing is pulled upwards. Thus there
are two lifting impulses: one pushing up from below, the other sucking
up from above.

It naturally follows that when the camber is very pronounced the machine
will fly much slower, but will bear a greater weight than a machine
equipped with planes having little or no camber. On high-speed machines,
which are used chiefly for racing purposes, the planes have very little
camber. This was particularly noticeable in the monoplane piloted by Mr.
Hamel in the Aerial Derby of 1913: the wings of this machine seemed to
be quite flat, and it was chiefly because of this that the pilot was
able to maintain such marvellous speed.

The scientific study of the wing lift of planes has proceeded so far
that the actual "lift" can now be measured, providing the speed of the
machine is known, together with the superficial area of the planes. The
designer can calculate what weight each square foot of the planes will
support in the air. Thus some machines have a "lift" of 9 or 10 pounds
to each square foot of wing surface, while others are reduced to 3 or 4
pounds per square foot.

CHAPTER XXV. The Wright Biplane (Cont.)

The under part of the frame of the Wright biplane, technically known as
the CHASSIS, resembled a pair of long "runner" skates, s