Aeroplanes and Dirigibles of War | Page 7

the machine that its weight, or a portion of it, would be
sustained in space by the very element which seeks to retard its flight,
namely, the atmosphere.
If there should be no material substance, like air, then the only way in
which a heavier-than-air machine could ever fly, would be by
propelling it through space, like the ball was thrown, or by some sort of
impulse or reaction mechanism on the air-ship itself. It could get no
support from the atmosphere.
LIGHT MACHINES UNSTABLE.--Gradually the question of weight
is solving itself. Aviators are beginning to realize that momentum is a
wonderful property, and a most important element in flying. The safest
machines are those which have weight. The light, willowy machines
are subject to every caprice of the wind. They are notoriously unstable
in flight, and are dangerous even in the hands of experts.
THE APPLICATION OF POWER.--The thing now to consider is not
form, or shape, or the distribution of the supporting surfaces, but HOW
to apply the power so that it will rapidly transfer a machine at rest to
one in motion, and thereby get the proper support on the atmosphere to
hold it in flight.
THE SUPPORTING SURFACES.--This brings us to the consideration
of one of the first great problems in flying machines, namely, the
supporting surfaces,--not its form, shape or arrangement, (which will be
taken up in their proper places), but the area, the dimensions, and the
angle necessary for flight.
AREA NOT THE ESSENTIAL THING.--The history of flying

machines, short as it is, furnishes many examples of one striking fact:
That area has but little to do with sustaining an aeroplane when once in
flight. The first Wright flyer weighed 741 pounds, had about 400
square feet of plane surface, and was maintained in the air with a 12
horse power engine.
True, that machine was shot into the air by a catapult. Motion having
once been imparted to it, the only thing necessary for the motor was to
maintain the speed.
There are many instances to show that when once in flight, one horse
power will sustain over 100 pounds, and each square foot of supporting
surface will maintain 90 pounds in flight.
THE LAW OF GRAVITY.--As the effort to fly may be considered in
the light of a struggle to avoid the laws of nature with respect to matter,
it may be well to consider this great force as a fitting prelude to the
study of our subject.
Proper understanding, and use of terms is very desirable, so that we
must not confuse them. Thus, weight and mass are not the same.
Weight varies with the latitude, and it is different at various altitudes;
but mass is always the same.
If projected through space, a certain mass would move so as to produce
momentum, which would be equal at all places on the earth's surface,
or at any altitude.
Gravity has been called weight, and weight gravity. The real difference
is plain if gravity is considered as the attraction of mass for mass.
Gravity is generally known and considered as a force which seeks to
draw things to the earth. This is too narrow.
Gravity acts in all directions. Two balls suspended from strings and
hung in close proximity to each other will mutually attract each other.
If one has double the mass it will have twice the attractive power. If
one is doubled and the other tripled, the attraction would be increased
six times. But if the distance should be doubled the attraction would be

reduced to one-fourth; and if the distance should be tripled then the pull
would be only one-ninth.
The foregoing is the substance of the law, namely, that all bodies attract
all other bodies with a force directly in proportion to their mass, and
inversely as the square of their distance from one another.
To explain this we cite the following illustration: Two bodies, each
having a mass of 4 pounds, and one inch apart, are attracted toward
each other, so they touch. If one has twice the mass of the other, the
smaller will draw the larger only one-quarter of an inch, and the large
one will draw the other three-quarters of an inch, thus confirming the
law that two bodies will attract each other in proportion to their mass.
Suppose, now, that these balls are placed two inches apart,--that is,
twice the distance. As each is, we shall say, four pounds in weight, the
square of each would be 16. This does not mean that there would be
sixteen times the attraction, but, as the law says, inversely as the square
of the distance, so that at two inches there is only one-sixteenth the
attraction as at one inch.
If the cord of one of the balls