2ÔO                                FLYING  MACHINES.
its several elements, and each element considered as a
separate problem, it will be seen that the mechanical diffi-
culties are very great ; but it will be discerned also that
none ot them can now be said to be insuperable, and that
material progress has recently been achieved toward their
solution.
The resistance and supporting power of air are approxi-
mately known, the motor and the propelling instrument
are probably sufficiently worked out to make a beginning ;
we know in a general way the kind of apparatus to adopt,
its approximate extent and required texture of sustaining
surfaces, and there remain to solve the problems of the
maintenance of the equilibrium, the guidance, the starting
up, and the alighting, as well as the final combination of
these several solutions into one homogeneous design.
In spite, therefore, of the continued failures herein re-
corded, it is my own judgment, as the result ot this inves-
tigation into the "progress in flying machines," more
particularly the progress of late years, and into the recent
studies of the principles and problems which are involved,
that, once the problem of equilibrium is solved, man may
hope to navigate the air, and that this will probably be
accomplished (perhaps at no very distant day), with some
form of aeroplane provided with fixed concavo-convex sur-
faces, which will at first utilize the wind as a motive
power, and eventually be provided with an artificial motor.
The conclusion that important progress may be achieved
without an artificial motor was little expected when this
investigation was begun ; but the study of the various ex-
periments which have been passed in review, the percep-
tion of the partial successes which have been accomplished
with soaring devices, and the general consideration of the
subject, have led to the conclusion that the first problem
which it is needful to solve is that of the equilibrium, and
that in working this out the wind may furnish an adequate
motive power.
Preliminary experiments will, of course, be tried upon
a small scale, but no experiment with a model can be
deemed quite conclusive until the same principles have
been extended to a full-sized apparatus capable of sus-
taining a man, and until this has been exposed to all the
vicissitudes of actual flight. It will readily be discerned
that a less achievement than this would not prove an ade-
quate performance, and that no matter how well a model
might behave in still air, there would still remain the
questions as to how it would behave in a wind, and how
it was to solve the problems of starting up and of alighting.
It would seem, therefore, that the first problem to solve
is that of the maintenance of the equilibrium at all the