_Fig. 13. Planes on Non-changing Body._

In Fig. 13 let the body of the aeroplane be horizontal,
and the sustaining planes B disposed at
the same angle, which we will assume to be 15
degrees, this being the imaginary angle for illustrative
purposes, with the power of the machine
to drive it along horizontally, as shown in position
1.

In position 2 the angles of both planes are now
at 10 degrees, and the speed 60 miles an hour,
which still drives the machine forward horizontally.

In position 3 the angle is still less, being now
only 5 degrees but the speed is increased to 80
miles per hour, but in each instance the body of
the machine is horizontal.

Now it is obvious that in order to ascend, in
either case, the changing of the planes to a greater
angle would raise the machine, but at the same
time keep the body on an even keel.

_Fig. 14. Descent with Non-changing Body._

DESCENDING POSITIONS BY POWER CONTROL.--In
Fig. 14 the planes are the same angles in the three
positions respectively, as in Fig. 13, but now the