of eagles' feathers, which he fixed to his body and launched
himself into the air. As might be expected, he fell and broke
his legs.

But although the muscles of man are of insufficient strength to
bear him in the air, it has been found possible, by using a motor
engine, to give to man the power of flight which his natural
weakness denied him.

Scientists estimate that to raise a man of about 12 stone in the
air and enable him to fly there would be required an immense pair
of wings over 20 feet in span. In comparison with the weight of
a man a bird's weight is remarkably small--the largest bird does
not weigh much more than 20 pounds--but its wing muscles are
infinitely stronger in proportion than the shoulder and arm
muscles of a man.

As we shall see in a succeeding chapter, the "wing" theory was
persevered with for many years some two or three centuries ago,
and later on it was of much use in providing data for the gradual
development of the modern aeroplane.



CHAPTER XV
A Pioneer in Aviation

Hitherto we have traced the gradual development of the balloon
right from the early days of aeronautics, when the brothers
Montgolfier constructed their hot-air balloon, down to the most