s detailed. It appears that once power-driven flight had been
achieved, the brothers were not so willing to talk as before;
considering the amount of work that they put in, there could have been
little time for verbal description of that work--as already remarked,
their tables still stand for the designer and experimenter. The end of
the 1901 experiments left both brothers somewhat discouraged, though
they had accomplished more than any others. 'Having set out with
absolute faith in the existing scientific data, we ere driven to doubt
one thing after another, finally, after two years of experiment, we cast
it all aside, and decided to rely entirely on our own investigations.
Truth and error were everywhere so intimately mixed as to be
indistinguishable.... We had taken up aeronautics as a sport. We
reluctantly entered upon the scientific side of it.'

Yet, driven thus to the more serious aspect of the work, they found in
the step its own reward, for the work of itself drew them on and on, to
the construction of measuring machines for the avoidance of error, and
to the making of series after series of measurements, concerning which
Wilbur wrote in 1908 (in the Century Magazine) that 'after making
preliminary measurements on a great number of different shaped surfaces,
to secure a general understanding of the subject, we began systematic
measurements of standard surfaces, so varied in design as to bring
out the underlying causes of differences noted in their pressures.
Measurements were tabulated on nearly fifty of these at all angles from
zero to 45 degrees, at intervals of 2 1/2 degrees. Measurements were
also secured showing the effects on each other when surfaces are
superposed, or when they follow one another.

'Some strange results were obtained. One surface, with a heavy roll at
the front edge, showed the same lift for all angles from 7 1/2 to 45
degrees. This seemed so anomalous that we were almost ready to doubt our
own measurements, when a simple test was suggested. A weather vane, with
two planes attached to the pointer at an angle of 80 degrees with
each other, was made. According to our table, such a vane would be in
unstable equilibrium when pointing directly into the wind, for if by
chance the wind should happen to strike one plane at 39 degrees and the
other at 41 degrees, the plane with the smaller angle would have the
greater pressure and the pointer would be turned still farther out
of the course of th