of　which　is　a　right…angled　triangle。
  _Fig。　44。　and　45。　Deltoid　Formation。_
  The　peculiarity　of　this　formation　is；　that　it　has
  remarkable　stability　when　used　as　a　kite；　with
  either　end　foremost。　If　a　small　weight　is　placed
  at　the　pointed　end；　and　it　is　projected　through　the
  air；　it　will　fly　straight；　and　is　but　little　affected
  by　cross　currents。
  THE　DUNNE　FLYING　MACHINE。A　top　view　of
  this　biplane　is　shown　in　Fig。　46。　The　A…shaped
  disposition　of　the　planes；　gives　it　good　lateral
  stability；　but　it　has　the　disadvantage　under　which
  all　aeroplanes　labor；　that　the　entire　body　of　the
  machine　must　move　on　a　fore　and　aft　vertical
  plan　in　order　to　ascend　or　descend。
  _Fig。　46。　The　Dunne　Bi…plane。_
  This　is　a　true　deltoid　formation；　as　the　angle　of
  incidence　of　the　planes　is　so　disposed　that　when
  the　planes　are　horizontal　from　end　to　end；　the　inclination
  is　such　as　to　make　it　similar　to　the　deltoid
  kite　referred　to。
  ROTATING　KITE。A　type　of　kite　unlike　the
  others　illustrated　is　a　rotating　structure；　which
  gives　great　stability；　due　to　the　gyroscopic　action
  on　the　supporting　surfaces。
  Fig。　47　shows　a　side　view　with　the　top　in　section。
  The　supporting　surface　is　umbrella…shaped。
  In　fact；　the　ordinary　umbrella　will　answer　if　not
  dished　too　much。　An　angularly…bent　piece　of　wire
  A；　provided　with　loops　B；　B；　at　the　ends；　serve　as
  bearings　for　the　handle　of　the　umbrella。
  At　the　bend　of　the　wire　loop　C；　the　cord　D　is
  attached。　The　lower　side　of　the　umbrella　top　has
  cup…shaped　pockets　E；　near　the　margin；　so　arranged
  that　their　open　ends　project　in　the　same
  direction；　and　the　wind　catching　them　rotates　the
  circular　plane。
  _Fig。　47。　Rotable　Umbrella　Kite。_
  KITE　PRINCIPLES。A　careful　study　of　the　examples
  here　given；　will　impress　the　novice　with
  one　important　fact；　which；　in　its　effect　has　a　more
  important　bearing　on　successful　flight；　than　all
  the　bird　study　and　speculations　concerning　its
  mysteries。
  This　fact；　in　essence；　is；　that　the　angle　of　the
  kite　is　the　great　factor　in　flight　next　to　the　power
  necessary　to　hold　it。　Aside　from　this；　the
  comparison　between　kites　and　aeroplanes　is　of　no
  practical　value。
  Disregarding　the　element　of　momentum；　the
  drift　of　a　machine　against　a　wind；　is　the　same；
  dynamically；　as　a　plane　at　rest　with　the　wind
  moving　past　it。　But　there　is　this　pronounced
  difference：　The　cord　which　supports　the　kite
  holds　it　so　that　the　power　is　in　one　direction　only。
  When　a　side　gust　of　wind　strikes　the　kite　it
  is　moved　laterally；　in　sympathy　with　the　kite；
  hence　the　problem　of　lateral　displacement　is　not
  the　same　as　with　the　aeroplane。
  LATERAL　STABILITY　IN　KITES。In　the　latter　the
  power　is　definitely　fixed　with　relation　to　the　machine
  itself；　and　if　we　should　assume　that　a　plane
  with　a　power　on　it　sufficient　to　maintain　a　flight
  of　40　miles　an　hour；　should　meet　a　wind　moving
  at　the　same　speed；　the　machine　would　be　stationary
  in　space。
  Such　a　condition　would　be　the　same；　so　far　as
  the　angles　of　the　planes　are　concerned；　with　a
  kite　held　by　a　string；　but　there　all　similarity　in
  action　ends。
  The　stabilizing　quality　of　the　kite　may　be　perfect；
  as　the　wind　varies　from　side　to　side；　but　the
  aeroplane；　being　free；　moves　to　the　right　or　to
  the　left；　and　does　not　adjust　itself　by　means　of　a
  fixed　point；　but　by　a　movable　one。
  SIMILARITY　OF　FORE　AND　AFT　CONTROL。Fore
  and　aft；　however；　the　kite　and　aeroplane　act　the
  same。　Fig。　48　shows　a　diagram　which　illustrates
  the　forces　which　act　on　the　kite；　and　by　means
  of　which　it　adjusts　its　angle　automatically。
  Let　us　assume　that　the　kite　A　is　flown　from
  a　cord　B；　so　that　its　angle　is　22　1/2　degrees；　the
  wind　being　15　miles　per　hour　to　maintain　the
  cord　B　at　that　angle。　When　the　wind　increases
  to　20　miles　an　hour　there　is　a　correspondingly
  greater　lift　against　the　kite。
  _Fig。　48。　Action　of　Wind　forces　on　Kite。_
  As　its　angle　is　fixed　by　means　of　the　loop　C；
  it　cannot　change　its　angle　with　reference　to　the
  cord；　or　independently　of　it；　and　its　only　course
  is　to　move　up　higher　and　assume　the　position
  shown　by　the　figure　at　D；　and　the　angle　of　incidence
  of　the　kite　is　therefore　changed　to　15　degrees；
  or　even　to　10　degrees。
  In　the　case　of　the　aeroplane　the　effect　is　similar
  from　the　standpoint　of　power　and　disposition
  of　the　planes。　If　it　has　sufficient　power；　and　the
  angle　of　the　planes　is　not　changed；　it　will　ascend；
  if　the　planes　are　changed　to　15　degrees　to　correspond
  with　the　kite　angle　it　will　remain　stationary。
  GLIDING　FLIGHT。The　earliest　attempt　to　fly
  by　gliding　is　attributed　to　Oliver；　a　Monk　of
  Malmesbury　who；　in　1065　prepared　artificial
  wings；　and　with　them　jumped　from　a　tower；　being
  injured　in　the　experiment。
  Nearly　700　years　later；　in　1801；　Resnier；　a
  Frenchman；　conducted　experiments　with　varying
  results；　followed　by　Berblinger；　in　1842；　and
  LeBris；　a　French　sailor；　in　1856。
  In　1884；　J。　J。　Montgomery；　of　California；　designed
  a　successful　glider；　and　in　1889　Otto　and
  Gustav　Lilienthal　made　the　most　extended　tests；
  in　Germany；　and　became　experts　in　handling
  gliders。
  Pilcher；　in　England；　was　the　next　to　take　up　the
  subject；　and　in　1893　made　many　successful　glides；
  all　of　the　foregoing　machines　being　single　plane
  surfaces；　similar　to　the　monoplane。
  Long　prior　to　1896　Octave　Chanute；　an
  engineer；　gave　the　subject　much　study；　and　in　that
  year　made　many　remarkable　flights；　developing
  the　double　plane；　now　known　as　the　biplane。
  He　was　an　ardent　believer　in　the　ability　of　man
  to　fly　by　soaring　means；　and　without　using　power
  for　the　purpose。
  It　is　doubtful　whether　gliders　contributed　much
  to　the　art　in　the　direction　of　laterally　stabilizing
  aeroplanes。　They　taught　useful　lessons　with　respect
  to　area　and　fore　and　aft　control。
  The　kite　gave　the　first　impulse　to　seek　out　a
  means　for　giving　equilibrium　to　planes；　and
  Montgomery　made　a　kite　with　warping　wings　as
  early　as　1884。
  Penaud；　a　Frenchman；　in　1872；　made　a　model
  aeroplane　which　had　the　stabilizing　means　in　the
  tail。　All　these　grew　out　of　kite　experiments；　and
  all　gliders　followed　the　kite　construction；　or　the
  principles　involved　in　them；　so　that；　really；　there
  is　but　one　intervening　step　between　the　kite　and
  the　flying　machine；　as　we　know　it；　the　latter　being
  merely　kites　with　power　attached；　as　substitutes
  for　the　cords。
  ONE　OF　THE　USES　OF　GLIDER　EXPERIMENTS。
  There　is　one　direction　in　which　gliders　are　valuable
  to　the　boy　and　to　the　novice　who　are　interested
  in　aviation。　He　may　spend　a　lifetime　in
  gliding　and　not　advance　in　the　art。　It　is
  questionable　whether　in　a　scientific　way　it　will　be　of
  any　service　to　him；　but　experiments　of　this　character
  give　confidence；　the　ability　to　quickly　grasp
  a　situation；　and　it　will　thus　teach　self　reliance　in
  emergencies。
  When　in　a　glider　quick　thinking　is　necessary。
  The　ability　to　shift　from　one　position　to　another；
  to　apply　the　weight　where　required　instantaneously；
  to　be　able　during　the　brief　exciting　moment
  of　flight　to　know　just　what　to　do；　requires　alertness。
  Some　are　so　wedded　to　the　earth　that　slight
  elevation　disturbs　them。　The　sensation　in　a
  glider　while　in　flight　is　unlike　any　other　experience。
  It　is　like　riding　a　lot　of　tense　springs；　and　the
  exhilaration　in　gliding　down　the　side　of　a　hill；
  with　the　feet　free　and　body　suspended；　is　quite
  different　from　riding　in　an　aeroplane　with　power
  attached。
  HINTS　IN　GLIDING。It　seems　to　be　a　difficult
  matter　to　give　any　advice　in　the　art　of　gliding。　It
  is　a　feat　which　seems　to　necessitate　experiment
  from　first　to　last。　During　the　hundreds　of　tests
  personally　made；　and　after　witnessing　thousands
  of　attempts；　there　seems　to　be　only　a　few　suggestions
  or　possible　directions　in　which　caution　might
  be　offered。
  First；　in　respect　to　the　position　of　the　body　at
  the　moment　of　launching。　The　glider　is　usually
  so　made　that　in　carrying　it；　preparatory　to　making
  the　run　and　the　leap　required　to　glide；　it　is　held
  so　that　it　balances　in　the　hands。
  Now　the　center　of　air　pressure　in　gliding　may
  not　be　at　the　same　point　as　its　sustaining　weight
  when　held　by　the　hand；　and　furthermore；　as　the
  arm…pits；　by　which　the　body　of　the　experimenter
  are　held　while　gliding；　are　not　at　the　same　point；
  but　to　the　rear　of　the　hands；　the　moment　the　glider
  is　launched　too　great　a　weight　is　brought　to　the
  rear　margin　of　the　planes；　hence　its　forward　end
  lifts　up。
  This　condition　will　soon　manifest　itself；　and　be
  corrected　by　the　experimenter；　but　there　is　another
  difficulty　which　is　not　so　easy　to　discover
  and　so　quick　to　remedy；　and　that　is　the　swing　of
  the　legs　the　moment　the　operator　leaves　the
  ground。
  The　experimenter　learns；　after　many　attempts；
  that　gliding　is　a　matter　of　a　few　feet　only；　and　he
  a