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