5 or 20-mile winds, we increased the area from 165 square feet, used in
1900, to 308 square feet--a size much larger than Lilienthal, Pilcher,
or Chanute had deemed safe. Upon trial, however, the lifting capacity
again fell very far short of calculation, so that the idea of securing
practice while flying as a kite had to be abandoned. Mr. Chanute, who
witnessed the experiments, told us that the trouble was not due to poor
construction of the machine. We saw only one other explanation--that the
tables of air-pressures in general use were incorrect.

[Illustration]

We then turned to gliding--coasting downhill on the air--as the only
method of getting the desired practice in balancing a machine. After
a few minutes' practice we were able to make glides of over 300 feet,
and in a few days were safely operating in 27-mile winds. In these
experiments we met with several unexpected phenomena. We found that,
contrary to the teachings of the books, the center of pressure on a
curved surface traveled backward when the surface was inclined, at small
angles, more and more edgewise to the wind. We also discovered that in
free flight, when the wing on one side of the machine was presented to
the wind at a greater angle than the one on the other side, the wing
with the greater angle descended, and the machine turned in a direction
just the reverse of what we were led to expect when flying the machine
as a kite. The larger angle gave more resistance to forward motion, and
reduced the speed of the wing on that side. The decrease in speed more
than counterbalanced the effect of the larger angle. The addition of a
fixed vertical vane in the rear increased the trouble, and made the
machine absolutely dangerous. It was some time before a remedy was
discovered. This consisted of movable rudders working in conjunction
with the twisting of the wings. The details of this arrangement are
given in specifications published several years ago.

The experiments of 1901 were far from encouraging. Although Mr. Chanute
assured us that, both in control and in weight carried per horse-power,
the results obtained were better than those of any of our predecessors,
yet we saw that the calculations upon which all flying machines had been
based were unreliable, and that all were simply groping in the dark.
Having set out with absolute faith in the existing scientific data, we
were driven to doubt one thing after another, till finally, after two
years of exp