four¡¡cubic¡¡feet¡£
SHAPES¡¡OF¡¡THE¡¡PONTOONS¡£We¡¡are¡¡now¡¡ready
to¡¡design¡¡the¡¡shapes¡£¡¡Fig¡£¡¡75¡¡shows¡¡three¡¡general
types£»¡¡A¡¡being¡¡made¡¡rectangular¡¡in¡¡form£»
with¡¡a¡¡tapering¡¡forward¡¡end£»¡¡so¡¡constructed¡¡as¡¡to
ride¡¡up¡¡on¡¡the¡¡water¡£
The¡¡type¡¡B¡¡has¡¡a¡¡rounded¡¡under¡¡body£»¡¡the¡¡forward
end¡¡being¡¡also¡¡skiff¡shaped¡¡to¡¡decrease¡¡as
much¡¡as¡¡possible¡¡the¡¡resistance¡¡of¡¡the¡¡water¡¡impact¡£
_Fig¡£¡¡75¡£¡¡Hydroplane¡¡Floats¡£_
The¡¡third¡¡type¡¡C¡¡is¡¡made¡¡in¡¡the¡¡form¡¡of¡¡a
closed¡¡boat£»¡¡with¡¡both¡¡ends¡¡pointed£»¡¡and¡¡the¡¡bottom
rounded£»¡¡or¡¡provided¡¡with¡¡a¡¡keel¡£¡¡Or£»¡¡as¡¡in
some¡¡cases¡¡the¡¡body¡¡may¡¡be¡¡made¡¡triangular¡¡in
cross¡¡section¡¡so¡¡that¡¡as¡¡it¡¡is¡¡submerged¡¡its¡¡sustaining
weight¡¡will¡¡increase¡¡at¡¡a¡¡greater¡¡degree
as¡¡it¡¡is¡¡pressed¡¡down¡¡than¡¡its¡¡vertical¡¡measurement
indicates¡£
All¡¡this£»¡¡however£»¡¡is¡¡a¡¡matter¡¡left¡¡to¡¡the¡¡judgment
of¡¡the¡¡designer£»¡¡and¡¡is£»¡¡in¡¡a¡¡great¡¡degree£»
dependent¡¡on¡¡the¡¡character¡¡of¡¡the¡¡craft¡¡to¡¡which
it¡¡is¡¡to¡¡be¡¡applied¡£
CHAPTER¡¡XII
EXPERIMENTAL¡¡WORK¡¡IN¡¡FLYING
THE¡¡novice¡¡about¡¡to¡¡take¡¡his¡¡first¡¡trial¡¡trip¡¡in
an¡¡automobile¡¡will¡¡soon¡¡learn¡¡that¡¡the¡¡great¡¡task
in¡¡his¡¡mind¡¡is¡¡to¡¡properly¡¡start¡¡the¡¡machine¡£¡¡He
is¡¡conscious¡¡of¡¡one¡¡thing£»¡¡that¡¡it¡¡will¡¡be¡¡an¡¡easy
matter¡¡to¡¡stop¡¡it¡¡by¡¡cutting¡¡off¡¡the¡¡fuel¡¡supply
and¡¡applying¡¡the¡¡brakes¡£
CERTAIN¡¡CONDITIONS¡¡IN¡¡FLYING¡£In¡¡an¡¡aeroplane
conditions¡¡are¡¡reversed¡£¡¡Shutting¡¡off¡¡the
fuel¡¡supply¡¡and¡¡applying¡¡the¡¡brakes¡¡only¡¡bring
on¡¡the¡¡main¡¡difficulty¡£¡¡He¡¡must¡¡learn¡¡to¡¡stop¡¡the
machine¡¡after¡¡all¡¡this¡¡is¡¡done£»¡¡and¡¡this¡¡is¡¡the
great¡¡test¡¡of¡¡flying¡£¡¡It¡¡is¡¡not¡¡the¡¡launching£»
the¡¡ability¡¡to¡¡get¡¡into¡¡the¡¡air£»¡¡but¡¡the¡¡landing£»¡¡that
gives¡¡the¡¡pupil¡¡his¡¡first¡¡shock¡£
Man¡¡is¡¡so¡¡accustomed¡¡to¡¡the¡¡little¡¡swirls¡¡of¡¡air
all¡¡about¡¡him£»¡¡that¡¡he¡¡does¡¡not¡¡appreciate¡¡what
they¡¡mean¡¡to¡¡a¡¡machine¡¡which¡¡is¡¡once¡¡free¡¡to
glide¡¡along¡¡in¡¡the¡¡little¡¡currents¡¡which¡¡are¡¡so¡¡unnoticeable
to¡¡him¡¡as¡¡a¡¡pedestrian¡£
The¡¡contour¡¡of¡¡the¡¡earth£»¡¡the¡¡fences£»¡¡trees£»¡¡little
elevations¡¡and¡¡other¡¡natural¡¡surroundings£»¡¡all
have¡¡their¡¡effect¡¡on¡¡a¡¡slight¡¡moving¡¡air¡¡current£»
and¡¡these¡¡inequalities¡¡affect¡¡the¡¡air¡¡and¡¡disturb
it¡¡to¡¡a¡¡still¡¡greater¡¡extent¡¡as¡¡the¡¡wind¡¡increases¡£
Even¡¡in¡¡a¡¡still¡¡air£»¡¡with¡¡the¡¡sun¡¡shining£»¡¡there¡¡are
air¡¡eddies£»¡¡caused¡¡by¡¡the¡¡uneven¡¡heating¡¡of¡¡the
air¡¡in¡¡space¡£
HEAT¡¡IN¡¡AIR¡£Heat¡¡is¡¡transmitted¡¡through¡¡the
air¡¡by¡¡what¡¡is¡¡called¡¡convection£»¡¡that¡¡is£»¡¡the¡¡particles
of¡¡the¡¡air¡¡transmit¡¡it¡¡from¡¡one¡¡point¡¡to¡¡the
next¡£¡¡If¡¡a¡¡room¡¡is¡¡closed¡¡up¡¡tight£»¡¡and¡¡a¡¡little
aperture¡¡provided¡¡so¡¡as¡¡to¡¡let¡¡in¡¡a¡¡streak¡¡of¡¡sunlight£»
it¡¡will¡¡give¡¡some¡¡idea¡¡of¡¡the¡¡unrest¡¡of¡¡the
atmosphere¡£¡¡This¡¡may¡¡be¡¡exhibited¡¡by¡¡smoke
along¡¡the¡¡line¡¡of¡¡the¡¡sun's¡¡rays£»¡¡which¡¡indicates
that¡¡the¡¡particles¡¡of¡¡air¡¡are¡¡constantly¡¡in¡¡motion£»
although¡¡there¡¡may¡¡be¡¡absolutely¡¡nothing¡¡in¡¡the
room¡¡to¡¡disturb¡¡it¡£
MOTION¡¡WHEN¡¡IN¡¡FLIGHT¡£If¡¡you¡¡can¡¡imagine
a¡¡small¡¡airship¡¡floating¡¡in¡¡that¡¡space£»¡¡you¡¡can
readily¡¡conceive¡¡that¡¡it¡¡will¡¡be¡¡hurled¡¡hither¡¡and
thither¡¡by¡¡the¡¡motion¡¡which¡¡is¡¡thus¡¡apparent¡¡to
the¡¡eye¡£
This¡¡motion¡¡is¡¡greatly¡¡accentuated¡¡by¡¡the¡¡surface
of¡¡the¡¡earth£»¡¡independently¡¡of¡¡its¡¡uneven¡¡contour¡£
If¡¡a¡¡ball¡¡is¡¡thrown¡¡through¡¡the¡¡air£»¡¡its
dynamic¡¡force¡¡is¡¡measured¡¡by¡¡its¡¡impact¡£¡¡So
with¡¡light£»¡¡and¡¡heat¡£¡¡In¡¡the¡¡space¡¡between¡¡the
planets¡¡it¡¡is¡¡very¡¡cold¡£¡¡The¡¡sunlight£»¡¡or¡¡the¡¡rays
from¡¡the¡¡sun¡¡are¡¡there£»¡¡just¡¡the¡¡same¡¡as¡¡on¡¡the
earth¡£
Unless¡¡the¡¡rays¡¡come¡¡into¡¡contact¡¡with¡¡something£»
they¡¡produce¡¡no¡¡effect¡£¡¡When¡¡the¡¡beams
from¡¡the¡¡sun¡¡come¡¡into¡¡contact¡¡with¡¡the¡¡atmosphere
a¡¡dynamic¡¡force¡¡is¡¡exerted£»¡¡just¡¡the¡¡same
as¡¡when¡¡the¡¡ball¡¡struck¡¡an¡¡object¡£¡¡When¡¡the¡¡rays
reach¡¡the¡¡earth£»¡¡reflection¡¡takes¡¡place£»¡¡and¡¡these
reflected¡¡beams¡¡act¡¡on¡¡the¡¡air¡¡under¡¡different¡¡conditions¡£
CHANGING¡¡ATMOSPHERE¡£If¡¡the¡¡air¡¡is¡¡full¡¡of
moisture£»¡¡as¡¡it¡¡may¡¡be¡¡at¡¡some¡¡places£»¡¡while
comparatively¡¡dry¡¡at¡¡other¡¡points£»¡¡the¡¡reflection
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the¡¡dry¡¡places£»¡¡hence¡¡evaporation¡¡will¡¡take¡¡place
and¡¡whenever¡¡a¡¡liquid¡¡vaporizes¡¡it¡¡means¡¡heat¡£
On¡¡the¡¡other¡¡hand£»¡¡when¡¡the¡¡vapor¡¡is¡¡turning
to¡¡a¡¡liquid£»¡¡condensation¡¡takes¡¡place£»¡¡and¡¡that
means¡¡cooling¡£¡¡If¡¡the¡¡air¡¡should¡¡be¡¡of¡¡the¡¡same
degree¡¡of¡¡saturation¡¡throughout£»that¡¡is£»¡¡have
the¡¡same¡¡amount¡¡of¡¡moisture¡¡everywhere£»¡¡there
would¡¡be¡¡few¡¡winds¡£¡¡These¡¡remarks¡¡apply¡¡to
conditions¡¡which¡¡exist¡¡over¡¡low¡¡altitudes¡¡all¡¡over
the¡¡earth¡£
But¡¡at¡¡high¡¡altitudes¡¡the¡¡conditions¡¡are¡¡entirely
different¡£¡¡As¡¡we¡¡ascend¡¡the¡¡air¡¡becomes¡¡rarer¡£
It¡¡has¡¡less¡¡moisture£»¡¡because¡¡a¡¡wet¡¡atmosphere£»
being¡¡heavier£»¡¡lies¡¡nearer¡¡the¡¡surface¡¡of¡¡the¡¡earth¡£
Being¡¡rarer¡¡the¡¡action¡¡of¡¡sunlight¡¡on¡¡the¡¡particles
is¡¡less¡¡intense¡£¡¡Reflection¡¡and¡¡refraction¡¡of¡¡the
rays¡¡acting¡¡on¡¡the¡¡light¡¡atmosphere¡¡do¡¡not¡¡produce
such¡¡a¡¡powerful¡¡effect¡¡as¡¡on¡¡the¡¡air¡¡near¡¡the
ground¡£
All¡¡these¡¡conditionsthe¡¡contour¡¡of¡¡the¡¡earth£»
the¡¡uneven¡¡character¡¡of¡¡the¡¡moisture¡¡in¡¡the¡¡air£»
the¡¡inequalities¡¡of¡¡the¡¡convection¡¡currents£»¡¡and
the¡¡unstable£»¡¡tenuous£»¡¡elastic¡¡nature¡¡of¡¡the¡¡atmosphere£»
make¡¡the¡¡trials¡¡of¡¡the¡¡aviator¡¡a¡¡hazardous
one£»¡¡and¡¡it¡¡has¡¡brought¡¡out¡¡numerous¡¡theories
connected¡¡with¡¡bird¡¡flight¡£¡¡One¡¡of¡¡these¡¡assumes
that¡¡the¡¡bird£»¡¡by¡¡means¡¡of¡¡its¡¡finely¡¡organized
sense£»¡¡is¡¡able¡¡to¡¡detect¡¡rising¡¡air¡¡currents£»¡¡and¡¡it
selects¡¡them¡¡in¡¡its¡¡flight£»¡¡and¡¡by¡¡that¡¡means¡¡is¡¡enabled
to¡¡continue¡¡in¡¡flight¡¡indefinitely£»¡¡by¡¡soaring£»
or¡¡by¡¡flapping¡¡its¡¡wings¡£
ASCENDING¡¡CURRENTS¡£It¡¡has¡¡not¡¡been¡¡explained
how¡¡it¡¡happens¡¡that¡¡these¡¡particular¡¡¡¨ascending
currents¡¨¡¡always¡¡appear¡¡directly¡¡in¡¡the¡¡line¡¡of
the¡¡bird¡¡flight£»¡¡or¡¡why¡¡it¡¡is¡¡that¡¡when£»¡¡for¡¡instance£»
a¡¡flock¡¡of¡¡wild¡¡geese¡¡which¡¡always¡¡fly¡¡through
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ascending¡¡air¡¡currents¡¡over¡¡the¡¡wide¡¡scope¡¡of¡¡space
they¡¡cover¡£
ASPIRATE¡¡CURRENTS¡£Some¡¡years¡¡ago£»¡¡in¡¡making
experiments¡¡with¡¡the¡¡outstretched¡¡wings¡¡of
one¡¡of¡¡the¡¡large¡¡soaring¡¡birds£»¡¡a¡¡French¡¡sailor
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when¡¡the¡¡bird's¡¡wings¡¡were¡¡held¡¡at¡¡a¡¡certain
angle£»¡¡so¡¡that¡¡the¡¡air¡¡actually¡¡seemed¡¡to¡¡draw¡¡it
into¡¡the¡¡teeth¡¡of¡¡the¡¡current¡£
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string£»¡¡and¡¡a¡¡jet¡¡of¡¡air¡¡is¡¡directed¡¡against¡¡it£»¡¡in
a¡¡particular¡¡way£»¡¡the¡¡ball¡¡will¡¡move¡¡toward¡¡the
jet£»¡¡instead¡¡of¡¡being¡¡driven¡¡away¡¡from¡¡it¡£¡¡A¡¡well
known¡¡spraying¡¡device£»¡¡called¡¡the¡¡¡¨ball¡¡nozzle£»¡¨
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was¡¡propounded£»¡¡namely£»¡¡that¡¡birds¡¡flew¡¡because
of¡¡the¡¡aspirated¡¡action¡¡of¡¡the¡¡air£»¡¡and¡¡the¡¡wings
and¡¡body¡¡were¡¡so¡¡made¡¡as¡¡to¡¡cause¡¡the¡¡moving¡¡air
current¡¡to¡¡act¡¡on¡¡it£»¡¡and¡¡draw¡¡it¡¡forwardly¡£
OUTSTRETCHED¡¡WINGS¡£This¡¡only¡¡added¡¡to¡¡the
¡¨bird¡¡wing¡¨¡¡theory¡¡a¡¡new¡¡argument¡¡that¡¡all¡¡flying
things¡¡must¡¡have¡¡outstretched¡¡wings£»¡¡in¡¡order
to¡¡fly£»¡¡forgetting¡¡that¡¡the¡¡ball£»¡¡which¡¡has¡¡no
outstretched¡¡wings£»¡¡has¡¡also¡¡the¡¡same¡¡¡¨aspirate¡¨
movement¡¡attributed¡¡to¡¡the¡¡wings¡¡of¡¡the¡¡bird¡£
The¡¡foregoing¡¡remarks¡¡are¡¡made¡¡in¡¡order¡¡to¡¡impress
on¡¡the¡¡novice¡¡that¡¡theories¡¡do¡¡not¡¡make
flying¡¡machines£»¡¡and¡¡that¡¡speculations£»¡¡or¡¡analogies
of¡¡what¡¡we¡¡see¡¡all¡¡about¡¡us£»¡¡will¡¡not¡¡make¡¡an
aviator¡£¡¡A¡¡flying¡¡machine¡¡is¡¡a¡¡question¡¡of
dynamics£»¡¡just¡¡as¡¡surely¡¡as¡¡the¡¡action¡¡of¡¡the¡¡sun¡¡on
the¡¡air£»¡¡and¡¡the¡¡movements¡¡of¡¡the¡¡currents£»¡¡and
the¡¡knowledge¡¡of¡¡applying¡¡those¡¡forces¡¡in¡¡the¡¡flying
machine¡¡makes¡¡the¡¡aviator¡£
THE¡¡STARTING¡¡POINT¡£Before¡¡the¡¡uninitiated
should¡¡attempt¡¡to¡¡even¡¡mount¡¡a¡¡machine¡¡he¡¡should
know¡¡what¡¡it¡¡is¡¡composed¡¡of£»¡¡and¡¡how¡¡it¡¡is¡¡made¡£
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what¡¡is¡¡the¡¡duty¡¡of¡¡each¡¡strut£»¡¡or¡¡brace¡¡or¡¡wire
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the¡¡life¡¡of¡¡the¡¡machine¡¡itself£»¡¡should¡¡be¡¡like¡¡a
book¡¡to¡¡him¡£¡¡It¡¡is¡¡not¡¡required¡¡that¡¡he¡¡should
know¡¡all¡¡the¡¡theories¡¡which¡¡is¡¡necessary¡¡in¡¡the
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of¡¡the¡¡carbureter£»¡¡its¡¡mechanism¡¡and¡¡construction£»
the¡¡propeller¡¡should¡¡be¡¡studied£»¡¡and¡¡its¡¡action
at¡¡various¡¡speeds¡£
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conditions£»¡¡as¡¡well¡£
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rate¡¡of¡¡ten¡¡miles¡¡an¡¡hour£»¡¡and¡¡the¡¡chauffeur¡¡turns
the¡¡steering¡¡wheel¡¡ten¡¡degrees¡£¡¡He¡¡can¡¡do¡¡so¡¡with
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and¡¡it¡¡may¡¡mean¡¡an¡¡accident¡£¡¡In¡¡one¡¡case¡¡the
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angle¡¡of¡¡flight£»¡¡he¡¡must¡¡study¡¡its¡¡arrangement£»
and¡¡note¡¡how¡¡far¡¡it¡¡must¡¡be¡¡moved¡¡to¡¡assume
the¡¡proper¡¡elevating¡¡angle¡£¡¡Then¡¡come¡¡the¡¡means
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All¡¡these¡¡features¡¡should¡¡be¡¡considered¡¡and¡¡studied
over¡¡and¡¡over£»¡¡until¡¡you¡¡have¡¡made¡¡them¡¡your
friends¡£
While¡¡thus¡¡engaged£»¡¡you¡¡are¡¡perfectly¡¡sure¡¡that
you¡¡can¡¡remember¡¡and¡¡act¡¡on¡¡a¡¡s
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