the mastery of the air(操纵空气)-第14节
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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
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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 shape to the double paddle of a canoe。 These he
placed over his shoulders； his feet being attached by ropes to the hindmost
paddles。 Jumping off from some high place in the face of a stiff breeze； he
violently worked his arms and legs； so that the paddles beat the air and
gave him support。 It is said that Besnier became so expert in the
management of his simple apparatus that he was able to raise himself from
the ground； and skim lightly over fields and rivers for a considerable
distance。
Now it has been shown that the enormous extent of wing required to
support a man of average weight would be much too large to be flapped by
man's arm muscles。 But in this； as with everything else； we have
succeeded in harnessing the forces of nature into our service as tools and
machinery。
And is not this； after all； one of the chief； distinctions between man
and the lower orders of creation？ The latter fulfil most of their bodily
requirements by muscular effort。 If a horse wants to get from one place to
another it walks； man can go on wheels。 None of the lower animals makes
a single tool to assist it in the various means of sustaining life； but man
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puts on his 〃thinking…cap〃； and invents useful machines and tools to
enable him to assist or dispense with muscular movement。
Thus we find that in aviation man has designed the propeller； which；
by its rapid revolutions derived from the motive power of the aerial engine；
cuts a spiral pathway through the air and drives the light craft rapidly
forward。 The chief use of the planes is for support to the machine； and the
chief duty of the pilot is to balance and steer the craft by the manipulation
of the rudder； elevation and warping controls。
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CHAPTER XVIII A Great British Inventor of
Aeroplanes
Though； as we have seen； most of the early attempts at aerial
navigation were made by foreign engineers； yet we are proud to number
among the ranks of the early inventors of heavier…than…air machines Sir
Hiram Maxim； who； though an American by birth； has spent most of his
life in Britain and may therefore be called a British inventor。
Perhaps to most of us this inventor's name is known more in
connection with the famous 〃Maxim〃 gun； which he designed； and which
was named after him。 But as early as 1894； when the construction of
aeroplanes was in a very backward state； Sir Hiram succeeded in making
an interesting and ingenious aeroplane； which he proposed to drive by a
particularly light steam…engine。
Sir Hiram's first machine； which was made in 1890； was designed to
be guided by a double set of rails； one set arranged below and the other
above its running wheels。 The intention was to make the machine raise
itself just off the ground rails； but yet be prevented from soaring by the set
of guard rails above the wheels； which acted as a check on it。 The motive
force was given by a very powerful steam…engine of over 300 horse…power；
and this drove two enormous propellers； some 17 feet in length。 The total
weight of the machine was 8000 pounds； but even with this enormous
weight the engine was capable of raising the machine from the ground。
For three or four years Sir Hiram made numerous experiments with his
aeroplane； but in 1894 it broke through the upper guard rail and turned
itself over among the surrounding trees； wrecking itself badly。
But though the Maxim aeroplane did not yield very practical results； it
proved that if a lighter but more powerful engine could be made； the chief
difficulty iii the way of aerial flight would be removed。 This was soon
forthcoming in the invention of the petrol motor。 In a lecture to the
Scottish Aeronautical Society； delivered in Glasgow in November； 1913；
Sir Hiram claimed to be the inventor of the first machine which actually
rose from the earth。 Before the distinguished inventor spoke of his own
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work in aviation he recalled experiments made by his father in 1856…7；
when Sir Hiram was sixteen years of age。 The flying machine designed by
the elder Maxim consisted of a small platform； which it was proposed to
lift directly into the air by the action of two screw…propellers revolving in
reverse directions。 For a motor the inventor intended to employ some kind
of explosive material； gunpowder preferred； but the lecturer distinctly
remembered that his father said that if an apparatus could be successfully
navigated through the air it would be of such inevitable value as a military
engine that no matter how much it might cost to run it would be used by
Governments。
Of his own claim as an inventor of air…craft it would be well to quote
Sir Hiram's actual words； as given by the Glasgow Herald； which
contained a full report of the lecture。
〃Some forty years ago； when I commenced to think of the subject； my
first idea was to lift my machint by vertical propellers； and I actually
commenced drawings and made calculations for a machine on that plan；
using an oil motor； or something like a Brayton engine； for motive power。
However； I was completely unable to work out any system which would
not be too heavy to lift itself directly into the air； and it was only when I
commenced to study the aeroplane system that it became apparent to me
that it would be possible to make a machine light enough and powerful
enough to raise itself without the agency of a balloon。 From the first I was
convinced that it would be quite out of the question to employ a balloon in
any form。 At that time the light high…speed petrol motor had no existence。
The only power available being steam…engines； I made all my calculations
with a view of using steam as the motive power。 While I was studying the
question of the possibility of making a flying machine that would actually
fly； I became convinced that there was but one system to work on； and that
was the aeroplane system。
