machine, as in starting from an elevated position or
by combination of these two things, and in either case the operation is
that of a soaring-machine, while power applied to the machine to propel
it positively forward will cause the air to support the machine in a
similar manner. In either case owing to the varying conditions to be
met there are numerous disturbing forces which tend to shift the machine
from the position which it should occupy to obtain the desired results.
It is the chief object of our invention to provide means for remedying
this difficulty, and we will now proceed to describe the construction by
means of which these results are accomplished.

In the accompanying drawing we have shown an apparatus embodying our
invention in one form. In this illustrative embodiment the machine is
shown as comprising two parallel superposed aeroplanes, 1 and 2, may be
embodied in a structure having a single aeroplane. Each aeroplane is of
considerably greater width from side to side than from front to rear.
The four corners of the upper aeroplane are indicated by the reference
letters a, b, c, and d, while the corresponding corners of the lower
aeroplane 2 are indicated by the reference letters e, f, g, and h. The
marginal lines ab and ef indicate the front edges of the aeroplanes, the
lateral margins of the upper aeroplane are indicated, respectively,
by the lines ad and bc, the lateral margins of the lower aeroplane are
indicated, respectively, by the lines eh and fg, while the rear margins
of the upper and lower aeroplanes are indicated, respectively, by the
lines cd and gh.

Before proceeding to a description of the fundamental theory of
operation of the structure we will first describe the preferred mode of
constructing the aeroplanes and those portions of the structure which
serve to connect the two aeroplanes.

Each aeroplane is formed by stretching cloth or other suitable fabric
over a frame composed of two parallel transverse spars 3, extending
from side to side of the machine, their ends being connected by bows 4
extending from front to rear of the machine. The front and rear spars
3 of each aeroplane are connected by a series of parallel ribs 5, which
preferably extend somewhat beyond the rear spar, as shown. These spars,
bows, and ribs are preferably constructed of wood having the necessary
strength, combined with lightness and flexibility. Upon this framework
the cloth which forms the supporting surfac