through the air.

We may assume that the two brothers had closely studied the
engines patented by Daimler and Levassor, and, being of a
mechanical turn of mind themselves, they were able to build their
own motor, with which they could make experiments in power-driven
flight.

Before we study the gradual progress of these experiments it
would be well to describe the Wright biplane. The illustration
facing p. 96 shows a typical biplane, and though there are
certain modifications in most modern machines, the principles
upon which it was built apply to all aeroplanes.

The two main supporting planes, A, B, are made of canvas
stretched tightly across a light frame, and are slightly curved,
or arched, from front to back. This curve is technically known
as the CAMBER, and upon the camber depend the strength and speed
of the machine.

If you turn back to Chapter XVII you will see that the plane is
modelled after the wing of a bird. It has been found that the
lifting power of a plane gradually dwindles from the front edge--
or ENTERING EDGE, as it is called--backwards. For this reason it
is necessary to equip a machine with a very long, narrow plane,
rather than with a comparatively broad but short plane.

Perhaps a little example will make this clear. Suppose we had
two machines, one of which was fitted with planes 144 feet long
and 1 foot wide, and the other with planes 12 feet square. In