angles to its body. This brings a sharp, thin edge
against the air, offering the least possible surface for
resistance, while at the same time a broad surface for
support is afforded by the flat, under side of the wings.
Identically the same thing is done in the construction of
the flying machine.

Note, for instance, the marked similarity in form as
shown in the illustration in Chapter II. Here A is the
bird, and B the general outline of the machine. The
thin edge of the plane in the latter is almost a duplicate
of that formed by the outstretched wings of the bird,
while the rudder plane in the rear serves the same purpose
as the bird's tail.



CHAPTER IV.

VARIOUS FORMS OF FLYING MACHINES.

There are three distinct and radically different forms
of flying machines. These are:

Aeroplanes, helicopters and ornithopers.

Of these the aeroplane takes precedence and is used
almost exclusively by successful aviators, the helicopters
and ornithopers having been tried and found lacking in
some vital features, while at the same time in some