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The boat submergence in the water is practically
the same； whether going ten or twenty miles an
hour。 The head resistance is the same； substantially；
at all times in the case of the boat； with the
flying machine the resistance of its sustaining
surfaces decreases。
Without going into a too technical description
of the reasoning which led to the discovery of the
law of air pressures； let us try and understand
it by examining the diagram； Fig。 7。
A represents a plane at an angle of 45 degrees；
moving forwardly into the atmosphere in the
direction of the arrows B。 The measurement
across the plane vertically； along the line B；
which is called the sine of the angle； represents
the surface impact of air against the plane。
In Fig。 8 the plane is at an angle of 27 degrees；
which makes the distance in height across the line
C just one…half the length of the line B of Fig。 7；
hence the surface impact of the air is one…half that
of Fig。 7； and the drift is correspondingly decreased。
_Fig。 7。 Equal Lift and Drift in Flight。_
_Fig。 8。 Unequal Lift and Drift。_
MOVING PLANES VS。 WINDS。In this way Boisset；
Duchemin； Langley； and others； determined
the comparative drift； and those results have been
largely relied upon by aviators； and assumed to
be correct when applied to flying machines。
That they are not correct has been proven by
the Wrights and others； the only explanation being
that some errors had been made in the calculations；
or that aviators were liable to commit errors
in observing the true angle of the planes
while in flight。
MOMENTUM NOT CONSIDERED。The great factor
of momentum has been entirely ignored； and it is
our desire to press the important point on those
who begin to study the question of flying machines。
THE FLIGHT OF BIRDS。Volumes have been
written concerning observations on the flight of
birds。 The marvel has been why do soaring birds
maintain themselves in space without flapping
their wings。 In fact； it is a much more remarkable
thing to contemplate why birds which depend
on flapping wings can fly。
THE DOWNWARD BEAT。It is argued that the
downward beat of the wings is so much more
rapid than the upward motion； that it gets an action
on the air so as to force the body upwardly。
This is disposed of by the wing motion of many
birds； notoriously the crow； whose lazily…flapping
wings can be readily followed by the eye； and the
difference in movement； if any； is not perceptible。
THE CONCAVED WING。It is also urged that the
concave on the under side of the wing gives the
quality of lift。 Certain kinds of beetles； and particularly
the common house fly； disprove that theory；
as their wings are perfectly flat。
FEATHER STRUCTURE CONSIDERED。Then the
feather argument is advanced； which seeks to
show that as each wing is made up of a plurality
of feathers； overlapping each other； they form a
sort of a valved surface； opening so as to permit
air to pass through them during the period of
their upward movement； and closing up as the
wing descends。
It is difficult to perform this experiment with
wings； so as to show such an individual feather
movement。 It is certain that there is nothing in
the structure of the wing bone and the feather
connection which points to any individual feather
movement； and our observation is； that each
feather is entirely too rigid to permit of such an
opening up between them。
It is obvious that the wing is built up in that
way for an entirely different reason。 Soaring
birds； which do not depend on the flapping motion；
have the same overlapping feather formation。
WEBBED WINGS。Furthermore； there are numerous
flying creatures which do not have
feathered wings； but web…like structures； or like the
house fly； in one continuous and unbroken
plane。
That birds which fly with flapping wings derive
their support from the air； is undoubtedly true；
and that the lift produced is due； not to the form；
or shape； or area of the wing； is also beyond question。
The records show that every conceivable
type of outlined structure is used by nature； the
material and texture of the wings themselves differ
to such a degree that there is absolutely no
similarity； some have concaved under surfaces；
and others have not； some fly with rapidly beating
wings； and others with slow and measured
movements； many of them fly with equal facility
without flapping movements； and the proportions
of weight to wing surface vary to such an extent
that it is utterly impossible to use such data as a
guide in calculating what the proper surface
should be for a correct flying machine。
THE ANGLE OF MOVEMENT。How； then； it may
be asked； do they get their support？ There must
be something； in all this variety and diversity of
form； of motion； and of characteristics； which
supplies the true answer。 The answer lies in the
angle of movement of every wing motion； which
is at the control of the bird； and if this is examined
it will be found that it supplies the correct
answer to every type of wing which nature has
made。
AN INITIAL IMPULSE OR MOVEMENT NECESSARY。
Let A； Fig。 9； represent the section of a bird's
wing。 All birds； whether of the soaring or the
flapping kind； must have an initial forward movement
in order to attain flight。 This impulse is
acquired either by running along the ground； or
by a leap； or in dropping from a perch。 Soaring
birds cannot； by any possibility； begin flight；
unless there is such a movement to change from a
position of rest to one of motion。
_Fig。 9。 Wing Movement in Flight。_
In the diagram； therefore； the bird； in moving
forwardly； while raising the wing upwardly； depresses
the rear edge of the wing； as in position
1； and when the wing beats downwardly the rear
margin is raised； in relation to its front margin；
as shown in position 2。
A WEDGING MOTION。Thus the bird； by a
wedge…like motion； gives a forwardly…propelling
action； and as the rear margin has more or less
flexure； its action against the air is less during its
upward beat； and this also adds to the upward lift
of the body of the bird。
NO MYSTERY IN THE WAVE MOTION。There is
no mystery in the effect of such a wave…like motion；
and it must be obvious that the humming
bird； and like flyers； which poise at one spot； are
able to do so because； instead of moving forwardly；
or changing the position of its body horizontally；
in performing the undulatory motion of
the wing； it causes the body to rock； so that at the
point where the wing joins the body； an elliptical
motion is produced。
_Fig。 10。 Evolution of Humming…Bird's Wing。_
HOW BIRDS POISE WITH FLAPPING WINGS。This
is shown in Fig。 10； in which eight successive positions
of the wing are shown； and wherein four
of the position； namely； 1； 2； 3； and 4； represent
the downward movement； and 6； 7； 8；