按键盘上方向键 ← 或 → 可快速上下翻页，按键盘上的 Enter 键可回到本书目录页，按键盘上方向键 ↑ 可回到本页顶部！
————未阅读完？加入书签已便下次继续阅读！
constructed large mound； and in some cases from the summit of a low
tower。 The 〃birdman〃 would stand on the top of the mound； full to the
wind； and run quickly forward with outstretched wings。 When he thought
he had gained sufficient momentum he jumped into the air； and the wings
of the glider bore him through the air to the base of the mound。
To preserve the balance of his machinealways a most difficult feat
he swung his legs and hips to one side or the other； as occasion required；
and； after hundreds of glides had been made； he became so skilful in
maintaining the equilibrium of his machine that he was able to cover a
distance； downhill； of 300 yards。
Later on； Lilienthal abandoned the glider； or elementary form of
monoplane； and adopted a system of superposed planes； corresponding to
the modern biplane。 The promising career of this clever German was
brought to an untimely end in 1896； when； in attempting to glide from a
height of about 80 yards； his apparatus made a sudden downward swoop；
and he broke his neck。
Now that Lillenthal's experiments had proved conclusively the
efficiency of wings； or planes； as carrying surfaces； other engineers
followed in his footsteps； and tried to improve on his good work。 The first
〃birdman〃 to use a glider in this country was Mr。 Percy Pilcher who
carried out his experiments at Cardross in Scotland。 His glides were at first
made with a form of apparatus very similar to that employed by Lilienthal；
and in time he came to use much larger machines。 So cumbersome；
however； was his apparatusit weighed nearly 4 stonesthat with such a
52
… Page 53…
THE MASTERY OF THE AIR
great weight upon his shoulders he could not run forward quickly enough
to gain sufficient momentum to 〃carry off〃 from the hillside。 To assist him
in launching the apparatus the machine was towed by horses； and when
sufficient impetus had been gained the tow…rope was cast off。
Three years after Lilienthal's death Pilcher met with a similar accident。
While making a flight his glider was overturned； and the unfortunate
〃birdman 〃 was dashed to death。
In America there were at this time two or three 〃human birds〃； one of
the most famous being M。 Octave Chanute。 During the years 1895…7
Chanute made many flights in various types of gliding machines； some of
which had as many as half a dozen planes arranged one above another。 His
best results； however； were obtained by the two…plane machine；
resembling to a remarkable extent the modern biplane。
53
… Page 54…
THE MASTERY OF THE AIR
CHAPTER XVII The Aeroplane and the Bird
We have seen that the inventors of flying machines in the early days of
aviation modelled their various craft somewhat in the form of a bird； and
that many of them believed that if the conquest of the air was to be
achieved man must copy nature and provide himself with wings。
Let us closely examine a modern monoplane and discover in what way
it resembles the body of a bird in build。
First； there is the long and comparatively narrow body； or FUSELAGE；
at the end of which is the rudder； corresponding to the bird's tail。 The
chassis； or under carriage； consisting of wheels； skids； &c。； may well be
compared with the legs of a bird； and the planes are very similar in
construction to the bird's wings。 But here the resemblance ends： the
aeroplane does not fly； nor will it ever fly； as a bird flies。
If we carefully inspect the wing of a birdsay a large bird； such as the
crowwe shall find it curved or arched from front to back。 This curve；
however； is somewhat irregular。 At the front edge of the wing it is sharpest；
and there is a gradual dip or slope backwards and downwards。 There is a
special reason for this peculiar structure； as we shall see in a later chapter。
Now it is quite evident that the inventors of aeroplanes have
modelled the planes of their craft on the bird's wing。 Strictly speaking； the
word 〃plane〃 is a misnomer when applied to the supporting structure of an
aeroplane。 Euclid defines a plane； or a plane surface； as one in which； any
two points being taken； the straight line between them lies wholly in that
surface。 But the plane of a flying machine is curved； or CAMBERED； and
if one point were taken on the front of the so…called plane； and another on
the back； a straight line joining these two points could not possibly lie
wholly on the surface。
All planes are not cambered to the same extent： some have a very
small curvature； in others the curve is greatly pronounced。 Planes of the
former type are generally fitted to racing aeroplanes； because they offer
less resistance to the air than do deeply…cambered planes。 Indeed； it is in
the degree of camber that the various types of flying machine show their
chief diversity； just as the work of certain shipmasters is known by the
54
… Page 55…
THE MASTERY OF THE AIR
particular lines of the bow and stern of the vessels which are built in their
yards。
Birds fly by a flapping movement of their wings； or by soaring。 We are
quite familiar with both these actions： at one time the bird propels itself by
means of powerful muscles attached to its wings by means of which the
wings are flapped up and down； at another time the bird； with wings nicely
adjusted so as to take advantage of all the peculiarities of the air currents；
keeps them almost stationary； and soars or glides through the air。
The method of soaring alone has long since been proved to be
impracticable as a means of carrying a machine through the air； unless； of
course； one describes the natural glide of an aeroplane from a great height
down to earth as soaring。 But the flapping motion was not proved a failure
until numerous experiments by early aviators had been tried。
Probably the most successful attempt at propulsion by this method was
that of a French locksmith named Besnier。 Over two hundred years ago he
made for himself a pair of light wooden paddles； with blades at either end；
somewhat similar in