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the h。p。
Hargrave's Kite Experiments。
After experimenting with very many models and
building no less than eighteen monoplane flying model
machines； actuated by rubber； by compressed air and by
steam； Mr。 Lawrence Hargrave； of Sydney； New South
Wales； invented the cellular kite which bears his name
and made it known in a paper contributed to the Chicago
Conference on Aerial Navigation in 1893； describing
several varieties。 The modern construction is well
known； and consists of two cells； each of superposed surfaces
with vertical side fins； placed one behind the other
and connected by a rod or frame。 This flies with great
steadiness without a tail。 Mr。 Hargrave's idea was to
use a team of these kites； below which he proposed to
suspend a motor and propeller from which a line would
be carried to an anchor in the ground。 Then by actuating
the propeller the whole apparatus would move
forward； pick up the anchor and fly away。 He said：
〃The next step is clear enough； namely； that a flying
machine with acres of surface can be safely got under
way or anchored and hauled to the ground by means of
the string of kites。〃
The first tentative experiments did not result well and
emphasized the necessity for a light motor； so that Mr。
Hargrave has since been engaged in developing one； not
having convenient access to those which have been produced
by the automobile designers and builders。
Experiments With Glider Model。
And here a curious reminiscence may be indulged in。
In 1888 the present writer experimented with a two…cell
gliding model； precisely similar to a Hargrave kite； as
will be confirmed by Mr。 Herring。 It was frequently
tested by launching from the top of a three…story house
and glided downward very steadily in all sorts of breezes；
but the angle of descent was much steeper than that of
birds； and the weight sustained per square foot was less
than with single cells； in consequence of the lesser support
afforded by the rear cell； which operated upon air
already set in motion downward by the front cell； so
nothing more was done with it； for it never occurred to
the writer to try it as a kite and he thus missed the
distinction which attaches to Hargrave's name。
Sir Hiram Maxim also introduced fore and aft superposed
surfaces in his wondrous flying machine of 1893；
but he relied chiefly for the lift upon his main large surface
and this necessitated so many guys； to prevent distortion；
as greatly to increase the head resistance and
this； together with the unstable equilibrium； made it
evident that the design of the machine would have to
be changed。
How Lilienthal Was Killed。
In 1895； Otto Lilienthal； the father of modern aviation；
the man to whose method of experimenting almost all
present successes are due； after making something like
two thousand glides with monoplanes； added a superposed
surface to his apparatus and found the control of
it much improved。 The two surfaces were kept apart
by two struts or vertical posts with a few guy wires； but
the connecting joints were weak and there was nothing
like trussing。 This eventually cost his most useful life。
Two weeks before that distressing loss to science； Herr
Wilhelm Kress； the distinguished and veteran aviator
of Vienna； witnessed a number of glides by Lilienthal
with his double…decked apparatus。 He noticed that it
was much wracked and wobbly and wrote to me after
the accident： 〃The connection of the wings and the
steering arrangement were very bad and unreliable。 I
warned Herr Lilienthal very seriously。 He promised
me that he would soon put it in order； but I fear that he
did not attend to it immediately。〃
In point of fact； Lilienthal had built a new machine；
upon a different principle； from which he expected great
results； and intended to make but very few more flights
with the old apparatus。 He unwisely made one too
many and； like Pilcher； was the victim of a distorted
apparatus。 Probably one of the joints of the struts
gave way； the upper surface blew back and Lilienthal；
who was well forward on the lower surface； was pitched
headlong to destruction。
Experiments by the Writer。
In 1896； assisted by Mr。 Herring and Mr。 Avery； I
experimented with several full sized gliding machines；
carrying a man。 The first was a Lilienthal monoplane
which was deemed so cranky that it was discarded after
making about one hundred glides； six weeks before
Lilienthal's accident。 The second was known as the
multiple winged machine and finally developed into five
pairs of pivoted wings； trussed together at the front and
one pair in the rear。 It glided at angles of descent of
10 or 11 degrees or of one in five； and this was deemed
too steep。 Then Mr。 Herring and myself made computations
to analyze the resistances。 We attributed much
of them to the five front spars of the wings and on a
sheet of cross…barred paper I at once drew the design for
a new three…decked machine to be built by Mr。 Herring。
Being a builder of bridges； I trussed these surfaces
together； in order to obtain strength and stiffness。 When
tested in gliding flight the lower surface was found too
near the ground。 It was taken off and the remaining
apparatus now consisted of two surfaces connected together
by a girder composed of vertical posts and diagonal
ties； specifically known as a 〃Pratt truss。〃 Then
Mr。 Herring and Mr。 Avery together devised and put
on an elastic attachment to the tail。 This machine
proved a success； it being safe and manageable。 Over
700 glides were made with it at angles of descent of 8
to 10 degrees； or one in six to one in seven。
First Proposed by Wenham。
The elastic tail attachment and the trussing of the
connecting frame of the superposed wings were the only
novelties in this machine； for the superposing of the
surfaces had first been proposed by Wenham； but in
accordance with the popular perception； which bestows
all the credit upon the man who adds the last touch
making for success to the labors of his predecessors； the
machine has since been known by many persons as the
〃Chanute type〃 of gliders； much to my personal gratification。
It has since been improved in many ways。 Wright
Brothers； disregarding the fashion which prevails among
birds； have placed the tail in front of their apparatus and
called it a front rudder； besides placing the operator in
horizontal position instead of upright； as I did； and also
providing a method of warping the wings to preserve
equilibrium。 Farman and Delagrange； under the very
able guidance and constructive work of Voisin brothers；
then substituted many details； including a box tail for
the dart…like tail which I used。 This may have increased
the resistance； but it adds to the steadiness。 Now the
tendency in France seems to be to go back to the monoplane。
Monoplane Idea Wrong。
The advocates of the single supporting surface are