ps of sandhills, and when they were
sufficiently strong to use a rope for our motor and fly over one spot.
Our next work was to draw up the plans for a suitable machine. After
much study we finally concluded that tails were a source of trouble
rather than of assistance, and therefore we decided to dispense with
them altogether. It seemed reasonable that if the body of the operator
could be placed in a horizontal position instead of the upright, as in
the machines of Lilienthal, Pilcher, and Chanute, the wind resistance
could be very materially reduced, since only one square foot instead of
five would be exposed. As a full half horse-power would be saved by this
change, we arranged to try at least the horizontal position. Then the
method of control used by Lilienthal, which consisted in shifting the
body, did not seem quite as quick or effective as the case required; so,
after long study, we contrived a system consisting of two large surfaces
on the Chanute double-deck plan, and a smaller surface placed a short
distance in front of the main surfaces in such a position that the
action of the wind upon it would counterbalance the effect of the travel
of the centre of pressure on the main surfaces. Thus changes in the
direction and velocity of the wind would have little disturbing effect,
and the operator would be required to attend only to the steering of the
machine, which was to be effected by curving the forward surface up or
down. The lateral equilibrium and the steering to right or left was
to be attained by a peculiar torsion of the main surfaces which was
equivalent to presenting one end of the wings at a greater angle than
the other. In the main frame a few changes were also made in the details
of construction and trussing employed by Mr Chanute. The most important
of these were: (1) The moving of the forward main crosspiece of the
frame to the extreme front edge; (2) the encasing in the cloth of all
crosspieces and ribs of the surfaces; (3) a rearrangement of the wires
used in trussing the two surfaces together, which rendered it possible
to tighten all the wires by simply shortening two of them.'

The brothers intended originally to get 200 square feet of supporting
surface for their glider, but the impossibility of obtaining suitable
material compelled them to reduce the area to 165 square feet, which, by
the Lilienthal tables, admitted of support in a wind of about twenty-one
miles an hour at an angle of three d