But when we inquire whether aerial flight is possible in the
present state of our knowledge, whether, with such materials as we
possess, a combination of steel, cloth, and wire can be made
which, moved by the power of electricity or steam, shall form a
successful flying-machine, the outlook may be altogether
different. To judge it sanely, let us bear in mind the
difficulties which are encountered in any flying-machine. The
basic principle on which any such machine must be constructed is
that of the aeroplane. This, by itself, would be the simplest of
all flyers, and therefore the best if it could be put into
operation. The principle involved may be readily comprehended by
the accompanying figure. A M is the section of a flat plane
surface, say a thin sheet of metal or a cloth supported by wires.
It moves through the air, the latter being represented by the
horizontal rows of dots. The direction of the motion is that of
the horizontal line A P. The aeroplane has a slight inclination
measured by the proportion between the perpendicular M P and the
length A P. We may raise the edge M up or lower it at pleasure.
Now the interesting point, and that on which the hopes of
inventors are based, is that if we give the plane any given
inclination, even one so small that the perpendicular M P is only
two or three per cent of the length A M, we can also calculate a
certain speed of motion through the air which, if given to the
plane, will enable it to bear any required weight.
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