The　experimenter　learns；　after　many　attempts；
  that　gliding　is　a　matter　of　a　few　feet　only；　and　he
  anticipates　landing　too　soon；　and　the　moment　he
  leaps　from　the　ground　the　legs　are　swung　forwardly
  ready　to　alight。
  This　is　done　unconsciously；　just　as　a　jumper
  swings　his　legs　forwardly　in　the　act　of　alighting。
  Such　a　motion　naturally　disturbs　the　fore　and　aft
  stability　of　the　gliding　machine；　by　tilting　up　the
  forward　margin；　and　it　banks　against　the　air；
  instead　of　gliding。
  The　constant　fear　of　all　gliders　is；　that　the
  machine　will　point　downwardly；　and　his　motion；
  as　well　as　the　position　of　the　body；　tend　to　shoot
  it　upwardly；　instead。
  CHAPTER　IX
  AEROPLANE　CONSTRUCTION
  As　may　be　inferred　from　the　foregoing　statements；
  there　are　no　definite　rules　for　the　construction
  of　either　type　of　flying　machine；　as　the
  flying　models　vary　to　such　an　extent　that　it　is
  difficult　to　take　either　of　them　as　a　model　to　represent
  the　preferred　type　of　construction。
  LATERAL；　AND　FORE　AND　AFT。The　term　lateral
  should　be　understood；　as　applied　to　aeroplanes。
  It　is　always　used　to　designate　the　direction　at
  right　angles　to　the　movement　of　the　machine。
  Fore　and　aft　is　a　marine　term　meaning　lengthwise；
  or　from　front　to　rear；　hence　is　always　at　right
  angles　to　the　lateral　direction。
  The　term　transverse　is　equivalent　to　lateral；
  in　flying　machine　parlance；　but　there　is　this
  distinction：　Transverse　has　reference　to　a　machine
  or　object　which；　like　the　main　planes　of　an　aeroplane；
  are　broader；　（that　is；from　end　to　end）
  than　their　length；　（from　front　to　rear）。
  On　the　other　hand；　lateral　has　reference　to　side
  branches；　as；　for　instance；　the　monoplane　wings；
  which　branch　out　from　the　sides　of　the　fore　and
  aft　body。
  STABILITY　AND　STABILIZATION。These　terms　constantly
  appear　in　describing　machines　and　their
  operations。　If　the　flying　structure；　whatever　it
  may　be；　has　means　whereby　it　is　kept　from　rocking
  from　side　to　side；　it　has　stability；　which　is　usually
  designated　as　lateral　stability。　The　mechanism
  for　doing　this　is　called　a　stabilizer。
  THE　WRIGHT　SYSTEM。The　Wright　machine　has
  reference　solely　to　the　matter　of　laterally　controlling
  the　flying　structure；　and　does　not　pertain
  to　the　form　or　shape　of　the　planes。
  In　Fig。　49　A　designates　the　upper　and　lower
  planes　of　a　Wright　machine；　with　the　peculiar
  rounded　ends。　The　ends　of　the　planes　are　so
  arranged　that　the　rear　margins　may　be　raised　or
  lowered；　independently　of　the　other　portions　of
  the　planes；　which　are　rigid。　This　movement　is
  indicated　in　sketch　1；　where　the　movable　part　B
  is；　as　we　might　say；　hinged　along　the　line　C。
  The　dotted　line　D　on　the　right　hand　end；　shows
  how　the　section　is　depressed；　while　the　dotted
  lines　E　at　the　left　hand　end　shows　the　section
  raised。　It　is　obvious　that　the　downturned　ends；
  as　at　D；　will　give　a　positive　angle　at　one　end　of　the
  planes；　and　the　upturned　wings　E　at　the　other　end
  will　give　a　negative　angle；　and　thus　cause　the　right
  hand　end　to　raise；　and　the　other　end　to　move
  downwardly；　as　the　machine　moves　forwardly
  through　the　air。
  CONTROLLING　THE　WARPING　ENDS。Originally
  the　Wrights　controlled　these　warping　sections　by
  means　of　a　cradle　occupied　by　the　aviator；　so　that
  the　cradle　would　move　or　rock；　dependent　on　the
  tilt　of　the　machine。　This　was　what　was　termed
  automatic　control。　This　was　found　to　be　unsatisfactory；
  and　the　control　has　now　been　placed　so
  that　it　connects　with　a　lever　and　is　operated　by
  the　aviator；　and　is　called　Manually…operated　control。
  In　all　forms　of　control　the　wings　on　one　side　are
  depressed　on　one　side　and　correspondingly　elevated
  on　the　other。
  THE　CURTIS　WINGS。Curtis　has　small　wings；
  or　ailerons；　intermediate　the　supporting　surfaces；
  and　at　their　extremities；　as　shown　in　sketch　2。
  These　are　controlled　by　a　shoulder　rack　or　swinging
  frame　operated　by　the　driver；　so　that　the　body
  in　swinging　laterally　will　change　the　two　wings
  at　the　same　time；　but　with　angles　in　different
  directions。
  THE　FARMAN　AILERONS。Farman's　disposition
  is　somewhat　different；　as　shown　in　sketch　3。　The
  wings　are　hinged　to　the　upper　planes　at　their　rear
  edges；　and　near　the　extremities　of　the　planes。
  Operating　wires　lead　to　a　lever　within　reach　of　the
  aviator；　and；　by　this　means；　the　wings　are　held　at
  any　desired　angle；　or　changed　at　will。
  The　difficulty　of　using　any　particular　model；　is
  true；　also；　of　the　arrangement　of　the　fore　and　aft
  control；　as　well　as　the　means　for　laterally　stabilizing
  it。　In　view　of　this　we　shall　submit　a　general
  form；　which　may　be　departed　from　at　will。
  FEATURES　WELL　DEVELOPED。Certain　features
  are　fairly　well　developed；　however。　One　is　the
  angle　of　the　supporting　plane；　with　reference　to
  the　frame　itself；　and　the　other　is　the　height　at
  which　the　tail　and　rudder　should　be　placed　above
  the　surface　of　the　ground　when　the　machine　is　at
  rest。
  DEPRESSING　THE　REAR　END。This　latter　is　a
  matter　which　must　be　taken　into　consideration；
  because　in　initiating　flight　the　rear　end　of　the
  frame　is　depressed　in　order　to　give　a　sufficient
  angle　to　the　supporting　planes　so　as　to　be　able　to
  inaugurate　flight。
  In　order　to　commence　building　we　should　have
  some　definite　idea　with　respect　to　the　power；　as
  this　will；　in　a　measure；　determine　the　area　of　the
  supporting　surfaces；　as　a　whole；　and　from　this
  the　sizes　of　the　different　planes　may　be　determined。
  DETERMINING　THE　SIZE。Suppose　we　decide　on
  300　square　feet　of　sustaining　surface。　This　may
  require　a　30；　a　40　or　a　50　horse　power　motor；
  dependent　on　the　speed　required；　and　much　higher
  power　has　been　used　on　that　area。
  However；　let　us　assume　that　a　forty　horse　power
  motor　is　available；　our　300　square　feet　of　surface
  may　be　put　into　two　planes；　each　having　150　square
  feet　of　surface；　which　would　make　each　5'　by　30'
  in　size；　or；　it　may　be　decided　to　make　the　planes
  narrower；　and　proportionally　longer。　This　is　immaterial。
  The　shorter　the　planes　transversely；
  the　greater　will　be　the　stability；　and　the　wider　the
  planes　the　less　will　be　the　lift；　comparatively。
  RULE　FOR　PLACING　THE　PLANES。The　rule　for
  placing　the　planes　is　to　place　them　apart　a　distance
  equal　to　the　width　of　the　planes　themselves；
  so　that　if　we　decide　on　making　them　five　feet　wide；
  they　should　be　placed　at　least　five　feet　apart。
  This　rule；　while　it　is　an　admirable　one　for　slow
  movements　or　when　starting　flight；　is　not　of　any
  advantage　while　in　rapid　flight。
  If　the　machine　is　made　with　front　and　rear
  horizontally…disposed　rudders；　or　elevators；　they
  also　serve　as　sustaining　surfaces；　which；　for　the
  present　will　be　disregarded。
  Lay　off　a　square　A；　Fig。　49a；　in　which　the　vertical
  lines　B；　B；　and　the　horizontal　lines　C；　C；　are
  5'　long；　and　draw　a　cross　D　within　this；　the　lines
  running　diagonally　from　the　corners。
  Now　step　off　from　the　center　cross　line　D；　three
  spaces；　each　five　feet　long；　to　a　point　E；　and　join
  this　point　by　means　of　upper　and　lower　bars　F；
  G；　with　the　upper　and　lower　planes；　so　as　to　form
  the　tail　frame。
  _Fig。　49a。　Rule　for　spacing　Planes。_
  As　shown　in　Fig。　50；　the　planes　should　now　be
  indicated；　and　placed　at　an　angle　of　about　8　degrees
  angle；　which　are　illustrated；　H　being　the
  upper　and　I　the　lower　plane。　Midway　between　the
  forward　edges　of　the　two　planes；　is　a　horizontal
  line　J；　extending　forwardly；　and　by　stepping　off
  the　width　of　two　planes；　a　point　K　is　made；　which
  forms　the　apex　of　a　frame　L；　the　rear　ends　of　the
  bars　being　attached　to　the　respective　planes　H；　I；
  at　their　forward　edges。
  _Fig。　50。　Frame　of　Control　Planes。_
  _Fig。　51。　and　Fig。　52。_
  ELEVATING　PLANES。We　must　now　have　the　general
  side　elevation　of　the　frame；　the　planes；　their
  angles；　the　tail　and　the　rudder　support；　and　the
  frame　for　the　forward　elevator。
  To　this　may　be　added　the　forward　elevating
  plane　L；　the　rear　elevator；　or　tail　M；　and　the　vertical
  steering　rudder　N。
  The　frame　which　supports　the　structure　thus
  described；　may　be　made　in　a　variety　of　ways；　the
  object　being　to　provide　a　resilient　connection　for
  the　rear　wheel　O。
  Fig。　52　shows　a　frame　which　is　simple　in　construction
  and　easily　attached。　The　lower　fore
  and　aft　side　bars　P　have　the　single　front　wheel
  axle　at　the　forward　end；　and　the　aft　double　wheels
  at　the　rear　end；　a　flexible　bar　Q；　running　from　the
  rear　wheel　axle　to　the　forward　end　of　the　lower
  plane。
  A　compression　spring　R　is　also　mounted　between
  the　bar　and　rear　end　of　the　lower　plane　to
  take　the　shock　of　landing。　The　forward　end　of
  the　bar　P　has　a　brace　S　extending　up　to　the　front
  edge　of　the　lower　plane；　and　another　brace　T　connects
  the　bars　P；　S；　with　the　end　of　the　forwardly…
  projecting　frame。
  _Fig。　53。　Plan　view。_
  The　full　page　view；　Fig。　53；　represents　a