shown　in　Fig。　30；　which　has　a　deep　concave　directly
  behind　the　forward　margin；　as　at　A；　so
  that　when　the　plane　is　at　an　angle　of　about　22
  degrees；　a　horizontal　line；　as　B；　passing　back　from
  the　nose；　touches　the　incurved　surface　of　the　plane
  at　a　point　about　one…third　of　its　measurement
  back　across　the　plane。
  _Fig。　30。　One　of　the　Monstrosities_
  This　form　is　an　exact　copy　of　the　wing　of　an
  actual　bird；　but　it　belongs；　not　to　the　soaring；
  but　to　the　class　which　depends　on　flapping　wings；
  and　as　such　it　cannot　be　understood　why　it　should
  be　used　for　soaring　machines；　as　all　aeroplanes
  are。
  The　foregoing　instances　of　construction　are
  cited　to　show　how　wildly　the　imagination　will
  roam　when　it　follows　wrong　ideals。
  THE　TAIL　AS　A　MONITOR。The　tendency　of　the
  center　of　pressure　to　change　necessitates　a　correctional
  means；　which　is　supplied　in　the　tail　of
  the　machine；　just　as　the　tail　of　a　kite　serves　to
  hold　it　at　a　correct　angle　with　respect　to　the　wind
  and　the　pull　of　the　supporting　string。
  CHAPTER　VII
  ABNORMAL　FLYING　STUNTS　AND　SPEEDS
  〃PEQUOD；　a　Frenchman；　yesterday　repeatedly
  performed　the　remarkable　feat　of　flying　with　the
  machine　upside　down。　This　exhibition　shows
  that　the　age　of　perfection　has　arrived　in　flying
  machines；　and　that　stability　is　an　accomplished
  fact。〃News　item。
  This　is　quoted　to　show　how　little　the　general
  public　knows　of　the　subject　of　aviation。　It　correctly
  represents　the　achievement　of　the　aviator；
  and　it　probably　voiced　the　sentiment　of　many
  scientific　men；　as　well　as　of　the　great　majority　of
  aviators。
  A　few　days　afterwards；　the　same　newspaper
  published　the　following：
  〃Lieutenant　；　while　experimenting　yesterday
  morning；　met　his　death　by　the　overturning
  of　his　machine　at　an　altitude　of　300　meters。
  Death　was　instantaneous；　and　the　machine　was
  completely　destroyed。〃
  The　machines　used　by　the　two　men　were　of　the
  same　manufacture；　as　Pequod　used　a　stock　machine
  which　was　strongly　braced　to　support　the
  inverted　weight；　but　otherwise　it　was　not　unlike
  the　well　known　type　of　monoplane。
  Beachy　has　since　repeated　the　experiment　with
  a　bi…plane；　and　it　is　a　feat　which　has　many　imitators；
  and　while　those　remarkable　exhibitions
  are　going　on；　one　catastrophe　follows　the　other
  with　the　same　regularity　as　in　the　past。
  Let　us　consider　this　phase　of　flying。　Are　they
  of　any　value；　and　wherein　do　they　teach　anything
  that　may　be　utilized；
  LACK　OF　IMPROVEMENTS　IN　MACHINES。It　is　remarkable
  that　not　one　single　forward　step　has
  been　taken　to　improve　the　type　of　flying　machines
  for　the　past　five　years。　They　possess　the　same
  shape；　their　stabilizing　qualities　and　mechanism
  for　assuring　stability　are　still　the　same。
  MEN　EXPEDITED；　AND　NOT　THE　MACHINE。The
  fact　is；　that　during　this　period　the　man　has　been
  exploited　and　not　the　machine。　Men　have　learned；
  some　few　of　them；　to　perform　peculiar　stunts；
  such　as　looping　the　loop；　the　side　glide；　the　drop；
  and　other　features；　which　look；　and　are；　hazardous；
  all　of　which　pander　to　the　sentiments　of　the　spectators。
  ABNORMAL　FLYING　OF　NO　VALUE。It　would　be
  too　broad　an　assertion　to　say　that　it　has　absolutely
  no　value；　because　everything　has　its　use
  in　a　certain　sense；　but　if　we　are　to　judge　from
  the　progress　of　inventions　in　other　directions；
  such　exhibitions　will　not　improve　the　art　of　building
  the　device；　or　make　a　fool…proof　machine。
  Indeed；　it　is　the　very　thing　which　serves　as　a
  deterrent；　rather　than　an　incentive。　If　machines
  can　be　handled　in　such　a　remarkable　manner；　they
  must　be；　indeed；　perfect！　Nothing　more　is
  needed！　They　must　represent　the　highest　structural
  type　of　mechanism！
  That　is　the　idea　sought　to　be　conveyed　in　the
  first　paragraph　quoted。　It　is　pernicious；　instead
  of　praiseworthy；　because　it　gives　a　false　impression；
  and　it　is　remarkable　that　even　certain　scientific
  journals　have　gravely　discussed　the　perfected
  （？）　type　of　flying　machine　as　demonstrated
  by　the　experiments　alluded　to。
  THE　ART　OF　JUGGLING。We　may；　occasionally；
  see　a　cyclist　who　understands　the　art　of　balancing
  so　well　that　he　can；　with　ease；　ride　a　machine
  which　has　only　a　single　wheel；　or　he　can；　with　a
  stock　bicycle；　ride　it　in　every　conceivable　attitude；
  and　make　it　perform　all　sorts　of　feats。
  It　merely　shows　that　man　has　become　an
  expert　at　juggling　with　a　machine；　the　same　as　he
  manipulates　balls；　and　wheels；　and　other　artifices；
  by　his　dexterity。
  PRACTICAL　USES　THE　BEST　TEST。The　bicycle
  did　not　require　such　displays　to　bring　it　to　perfection。
  It　has　been　the　history　of　every　invention
  that　improvements　were　brought　about；　not
  by　abnormal　experiments；　but　by　practical　uses
  and　by　normal　developments。
  The　ability　of　an　aviator　to　fly　with　the　machine
  in　an　inverted　position　is　no　test　of　the　machine's
  stability；　nor　does　it　in　any　manner　prove　that
  it　is　correctly　built。　It　is　simply　and　solely　a
  juggling　featsomething　in　the　capacity　of　a　certain
  man　to　perform；　and　attract　attention　because
  they　are　out　of　the　ordinary。
  CONCAVED　AND　COXVEX　PLANES：They　were　performed
  as　exhibition　features；　and　intended　as
  such；　and　none　of　the　exponents　of　that　kind　of
  flying　have　the　effrontery　to　claim　that　they　prove
  anything　of　value　in　the　machine　itself；　except
  that　it　incidentally　has　destroyed　the　largely
  vaunted　claim　that　concaved　wings　for　supporting
  surfaces　are　necessary。
  HOW　MOMENTUM　IS　A　FACTOR　IN　INVERTED　FLYING。
  When　flying　〃upside　down；〃　the　convex
  side　of　the　plane　takes　the　pressure　of　the　air；
  and　maintains；　so　it　is　asserted；　the　weight　of　the
  machine。　This　is　true　during　that　period　when
  the　loop　is　being　made。　The　evolution　is　made
  by　first　darting　down；　as　shown　in　Fig。　31；　from
  the　horizontal　position；　1；　to　the　position　2；　where
  the　turn　begins。
  _Fig。　31。　Flying　upside　down。_
  TURNING　MOVEMENT。Now　note　the　characteristic
  angles　of　the　tail；　which　is　the　controlling
  factor。　In　position　1　the　tail　is　practically
  horizontal。　In　fact；　in　all　machines；　at
  high　flight；　the　tail　is　elevated　so　as　to　give　little
  positive　angle　of　incidence　to　the　supporting
  planes。
  In　position　No。　2；　the　tail　is　turned　to　an　angle
  of　incidence　to　make　the　downward　plunge；　and
  when　the　machine　has　assumed　the　vertical；　as　in
  position　3；　the　tail　is　again　reversed　to　assume
  the　angle；　as　in　1；　when　flying　horizontally。
  At　the　lower　turn；　position　4；　the　tail　is　turned
  similar　to　the　angle　of　position　2；　which　throws
  the　rear　end　of　the　machine　down；　and　as　the
  horizontal　line　of　flight　is　resumed；　in　an　inverted
  position；　as　in　position　4；　the　tail　has　the　same
  angle；　with　relation　to　the　frame；　as　the　supporting
  planes。
  During　this　evolution　the　engine　is　running；　and
  the　downward　plunge　develops　a　tremendous
  speed；　and　the　great　momentum　thus　acquired；
  together　with　the　pulling　power　of　the　propeller
  while　thus　in　flight；　is　sufficient　to　propel　it　along
  horizontally；　whatever　the　plane　surface　curve；　or
  formation　may　be。
  It　is　the　momentum　which　sustains　it　in　space；
  not　the　air　pressure　beneath　the　wings；　for
  reasons　which　we　have　heretofore　explained。
  Flights　of　sufficient　duration　have　thus　been　made
  to　prove　that　convex；　as　well　as　concave　surfaces
  are　efficient；　nevertheless；　in　its　proper　place　we
  have　given　an　exposition　of　the　reasoning　which
  led　to　the　adoption　of　the　concaved　supporting
  surfaces。
  WHEN　CONCAVED　PLANES　ARE　DESIRABLE。
  Unquestionably；　for　slow　speeds　the　concaved　wing
  is　desirable；　as　will　be　explained；　but　for　high
  speeds；　surface　formation　has　no　value。　That　is
  shown　by　Pequod's　feat。
  THE　SPEED　MANIA。This　is　a　type　of　mania
  which　pervades　every　field　of　activity　in　the　building
  of　aeroplanes。　Speed　contests　are　of　more
  importance　to　the　spectators　on　exhibition
  grounds　than　stability　or　durability。　Builders
  pander　to　this；　hence　machines　are　built　on　lines
  which　disregard　every　consideration　of　safety
  while　at　normal　flight。
  USES　OF　FLYING　MACHINES。The　machine　as
  now　constructed　is　of　little　use　commercially。
  Within　certain　limitations　it　is　valuable　for　scouting
  purposes；　and　attempts　have　been　made　to
  use　it　commercially。　But　the　unreliable　character
  of　its　performances；　due　to　the　many　elements
  which　are　necessary　to　its　proper　working；　have
  operated　against　it。
  PERFECTION　IN　MACHINES　MUST　COME　BEFORE
  SPEED。Contrary　to　every　precept　in　the　building
  of　a　new　article；　the　attempt　is　made　to　make
  a　machine　with　high　speed；　which；　in　the　very
  nature　of　things；　operates　against　its　improvement。
  The　opposite　lack　of　speedis　of　far
  greater　utility　at　this　stage　of　its　development。
  THE　RANGE　OF　ITS　USE。The　subject　might　be
  illustrated　by　assuming　that　we　have　a　line　running
  from　A