as they called their first aeroplane.
They could find no suitable engine and so proceeded to build for
themselves an internal combustion engine, which was designed to give
8 horse-power, but when completed actually developed about 12-15
horse-power and weighed 240 lbs. The complete machine weighed about
750 lbs. Further details of the first Wright aeroplane are difficult to
obtain, and even those here given should be received with some caution.
The first flight was made on December 17th 1903, and lasted 12 seconds.
Others followed immediately, and the fourth lasted 59 seconds, a
distance of 852 feet being covered against a 20-mile wind.

The following year they transferred operations to a field outside
Dayton, Ohio (their home), and there they flew a somewhat larger and
heavier machine with which on September 20th 1904, they completed the
first circle in the air. In this machine for the first time the pilot
had a seat; all the previous experiments having been carried out with
the operator lying prone on the lower wing. This was followed next
year by another still larger machine, and on it they carried out many
flights. During the course of these flights they satisfied themselves as
to the cause of a phenomenon which had puzzled them during the previous
year and caused them to fear that they had not solved the problem
of lateral control. They found that on occasions--always when on a
turn--the machine began to slide down towards the ground and that no
amount of warping could stop it. Finally it was found that if the nose
of the machine was tilted down a recovery could be effected; from which
they concluded that what actually happened was that the machine, 'owing
to the increased load caused by centrifugal force,' had insufficient
power to maintain itself in the air and therefore lost speed until a
point was reached at which the controls became inoperative. In other
words, this was the first experience of 'stalling on a turn,' which is a
danger against which all embryo pilots have to guard in the early stages
of their training.

The 1905 machine was, like its predecessors, a biplane with a biplane
elevator in front and a double vertical rudder in rear. The span was 40
feet, the chord of the wings being 6 feet and the gap between them about
the same. The total area was about 600 square feet which supported
a total weight of 925 lbs.; while the motor was 12 to 15 horse-power
driving two propellers on each side behind the