Whileat12milesthesustainingpowerisfiguredat230pounds，at24milesitisfourtimesasgreat，or920
　　pounds.
　　SupportingAreaofBirds.
　　Oneofthethingswhichallproducingaviatorsseektocopyisthemotivepowerofbirds，particularlyintheirrelationtotheareaofsupport.Closeinvestigationhasestablishedthefactthatthelargerthebirdthelessistherelativeareaofsupportrequiredtosecureagivenresult.Thisisshowninthefollowingtable：
　　SupportingWeightSurfaceHorseareaBirdinlbs.insq.feetpowerperlb.
　　Pigeon1.000.70.0120.7
　　WildGoose9.002.650.0260.2833
　　Buzzard5.005.030.0151.06
　　Condor17.009.850.0430.57
　　Sofarasknownthecondoristhelargestofmodernbirds.Ithasawingstretchof10feetfromtiptotip，asupportingareaofabout10squarefeet，andweighs17
　　pounds.It.iscapableofexertingperhaps1—30horsepower.
　　（Thesefiguresare，ofcourse，approximate.）
　　Comparingthecondorwiththebuzzardwithawingstretchof6feet，supportingareaof5squarefeet，andalittleover1—100horsepower，itmaybeseenthat，broadlyspeaking，thelargerthebirdthelesssurfacearea（relatively）
　　isneededforitssupportintheair.
　　ComparisonWithAeroplanes.
　　Ifwecomparethebirdfigureswiththosemadepossiblebythedevelopmentoftheaeroplaneitwillbereadilyseenthatmanhasmadeawonderfuladvanceinimitatingtheresultsproducedbynature.Herearethefigures：
　　SupportingWeightSurfaceHorseareaMachineinlbs.insq.feetpowerperlb.
　　Santos—Dumont350110.00300.314
　　Bleriot700150.00250.214
　　Antoinette1，200538.00500.448
　　Curtiss700258.00600.368
　　Wright[4]1，100538.00250.489
　　Farman1，200430.00500.358
　　Voisin1，200538.00500.448
　　[4]TheWrights’newmachineweighsonly900pounds.
　　Whiletheaveragesupportingsurfaceisinfavoroftheaeroplane，thisismorethanoverbalancedbythegreateramountofhorsepowerrequiredfortheweightlifted.Theaveragesupportingsurfaceinbirdsisaboutthree—quartersofasquarefootperpound.Intheaverageaeroplaneitisaboutone—halfsquarefootperpound.
　　Ontheotherhandtheaverageaeroplanehasaliftingcapacityof24poundsperhorsepower，whilethebuzzard，forinstance，lifts5poundswith15—100ofahorsepower.
　　IftheWrightmachine——whichhasaliftingpowerof50
　　poundsperhorsepower——shouldbealoneconsideredtheshowingwouldbemuchmorefavorabletotheaeroplane，butitwouldnotbeafaircomparison.
　　MoreSurface，LessPower.
　　Broadlyspeaking，thelargerthesupportingareathelesswillbethepowerrequired.Wright，bytheuseof538squarefeetofsupportingsurface，getsalongwithanengineof25horsepower.Curtiss，whousesonly258
　　squarefeetofsurface，findsanengineof50horsepowerisneeded.Otherthings，suchasframe，etc.，beingequal，itstandstoreasonthatareductionintheareaofsupportingsurfacewillcorrespondinglyreducetheweightofthemachine.ThuswehavetheCurtissmachinewithits258squarefeetofsurface，weighingonly600pounds（withoutoperator），butrequiringdoublethehorsepoweroftheWrightmachinewith538squarefeetofsurfaceandweighing1，100pounds.Thisdemonstratesinaforcefulwaythepropositionthatthelargerthesurfacethelesspowerwillbeneeded.
　　Butthereisalimit，onaccountofitsbulkandawkwardnessinhandling，beyondwhichthesurfaceareacannotbeenlarged.Otherwiseitmightbepossibletoequipandoperateaeroplanessatisfactorilywithenginesof15horsepower，orevenless.
　　TheFuelConsumptionProblem.
　　Fuelconsumptionisaprimefactorintheproductionofenginepower.Theveriestmechanicaltyroknowsinageneralwaythatthemorepowerissecuredthemorefuelmustbeconsumed，allowingthatthereisnodifferenceinthepower—producingqualitiesofthematerialused.Butfewofusunderstandjustwhattheratioofincreaseis，orhowitiscaused.Thispropositionisoneofkeeninterestinconnectionwithaviation.
　　Letusciteaproblemwhichwillillustratethepointquoted：Allowingthatittakesagivenamountofgasolenetopropelaflyingmachineagivendistance，halfthewaywiththewind，andhalfagainstit，thewindblowingatone—halfthespeedofthemachine，whatwillbetheincreaseinfuelconsumption？
　　IncreaseofThirtyPerCent.
　　Onthefaceofittherewouldseemtobenocallforanincreaseastheresistancemetwhengoingagainstthewindisapparentlyoffsetbythepropulsiveforceofthewindwhenthemachineistravellingwithit.This，however，iscalledfaultyreasoning.Theincreaseinfuelconsumption，asfiguredbyMr.F.W.Lanchester，oftheRoyalSocietyofArts，willbefully30percentovertheamountrequiredforasimilaroperationofthemachineinstillair.Ifthejourneyshouldbemadeatrightanglestothewindunderthesameconditionstheincreasewouldbe15percent.
　　InotherwordsMr.Lanchestermaintainsthattheworkdonebythemotorinmakingheadwayagainstthewindforacertaindistancecallsformoreengineenergy，andconsequentlymorefuelby30percent，thanissavedbythehelpingforceofthewindonthereturnjourney.
　　CHAPTERXIV.
　　ABOUTWINDCURRENTS，ETC.
　　Oneofthefirstdifficultieswhichthenovicewillencounteristheuncertaintyofthewindcurrents.Withalowvelocitythewind，somedistanceawayfromtheground，isordinarilysteady.Asthevelocityincreases，however，thewindgenerallybecomesgustyandfitfulinitsaction.This，itshouldberemembered，doesnotrefertothevelocityofthemachine，buttothatoftheairitself.
　　InthisconnectionMr.ArthurT.Atherholt，presidentoftheAeroClubofPennsylvania，inaddressingtheBostonSocietyofScientificResearch，said：
　　"ProbablythewhirlpoolsofNiagaracontainnomoreerraticcurrentsthanthestrataofairwhichisnowimmediatelyaboveus，afacthardtorealizeonaccountofitsinvisibility."
　　ChangesInWindCurrents.
　　WhileMr.Atherholt’sexperiencehasbeenmainlywithballoonsitisallthemorevaluableonthisaccount，astheballoonswereatthemercyofthewindandtheirvaryingdirectionsaffordedanindisputableguideastothechangingcourseoftheaircurrents.Inspeakingofthishesaid：
　　"Inthemanytripstaken，varyingindistancetraversedfromtwenty—fiveto900miles，itwasneverpossibleexceptinoneinstancetomaintainastraightcourse.
　　TheseuncertaincurrentsweremostnoticeableintheGordon—BennettracefromSt.Louisin1907.Ofthenineaerostatscompetinginthatevent，eightcoveredamoreorlessdirectcoursedueeastandsoutheast，whereasthewriter，withMajorHenryB.Hersey，firststartednorthwest，thennorth，northeast，east，eastbysouth，andwhenoverthecenterofLakeEriewereagainblownnorthwestnotwithstandingthatmorefavorablewindsweresoughtforataltitudesvaryingfrom100to3，000
　　meters，necessitatingafinishinCanadanearlynortheastofthestartingpoint.
　　"Thesenineballoons，makinglandingsextendingfromLakeOntario，Canada，toVirginia，allstartedfromonepointwithinthesamehour.
　　"ThesingleexceptiontotheserovingcurrentsoccurredonOctober21st，oflastyear（1909）when，startingfromPhiladelphia，thewindshiftedmorethaneightdegrees，thegreatestvariationbeingatthelowestaltitudes，yetatnotimewasaheightofoveramilereached.
　　"Throughouttheentiredaytheskywasovercast，withathermometervaryingfromfifty—sevendegreesat300
　　feettoforty—fourdegrees，Fahrenheitat5，000feet，atwhichaltitudethewindhadavelocityof43milesanhour，incloudsofacirro—cumulusnature，alandingfinallybeingmadenearTannersville，NewYork，intheCatskillmountains，afteravoyageoffiveandone—halfhours.
　　"Ihavenoknowledgeofarecordedtripofthisdistanceandduration，maintainedinpracticallyastraightlinefromstarttofinish."
　　Thiswinddisturbanceismorenoticeableandmoredifficulttocontendwithinaballoonthaninaflyingmachine，owingtothebulkandunwieldycharacteroftheformer.Atthesametimeitisnotconducivetopleasant，safeorsatisfactorysky—sailinginanaeroplane.
　　Thisisnotstatedwiththepurposeofdiscouragingaviation，butmerelythattheoperatormayknowwhattoexpectandbepreparedtomeetit.
　　Notonlydoesthewindchangeitshorizontalcourseabruptlyandwithoutnotice，butitalsoshiftsinaverticaldirection，onesecondblowingup，andanotherdown.Nomanhasasyetfathomedthewhyandwhereforeofthiserraticaction;itisonlyknownthatitexists.
　　Themoststablecurrentswillbefoundfrom50to100
　　feetfromtheearth，providedthewindisnotdivertedbysuchobjectsastrees，rocks，etc.Thatthereareequallystablecurrentshigherupistrue，buttheyaregenerallytobefoundatexcessivealtitudes.
　　HowaBirdMeetsCurrents.
　　Observeabirdinactiononawindydayandyouwillfinditcontinuallychangingthepositionofitswings.
　　Thisisdonetomeetthevaryinggustsandeddiesoftheairsothatsustentationmaybemaintainedandheadwaymade.Onesecondthebirdisbendingitswings，alteringtheangleofincidence;thenextitisliftingordepressingonewingatatime.Stillagainitwillextendonewingtipinadvanceoftheother，orbespreadingorfolding，loweringorraisingitstail.
　　Allthesemotionshaveameaning，apurpose.Theyassistthebirdinpreservingitsequilibrium.Withoutthemthebirdwouldbejustashelplessintheairasahumanbeingandcouldnotremainafloat.
　　Whenthewindisstill，orcomparativelyso，abird，havingsecuredthedesiredaltitudebyflightatanangle，maysailorsoarwithnowingactionbeyondanoccasionalstrokewhenitdesirestoadvance.But，inagusty，uncertainwinditmustuseitswingsoralightsomewhere.
　　TryingtoImitatetheBird.
　　Writingin_Fly_，Mr.WilliamE.Whitesays：
　　"Thebird’sflightsuggestsanumberofwaysinwhichtheequilibriumofamechanicalbirdmaybecontrolled.
　　Eachofthesemethodsofcontrolmaybeeffectedbyseveraldifferentformsofmechanism.
　　"Placingthetwowingsofanaeroplaneatanangleofthreetofivedegreestoeachotherisperhapstheoldestwayofsecuringlateralbalance.Thiswayreadilyoccurstoanyonewhowatchesaseagullsoaring.Thetheoryofthedihedralangleisthatwhenonewingisliftedbyagustofwind，theairisspilledfromunderit;
　　whiletheotherwing，beingcorrespondinglydepressed，presentsagreaterresistancetothegustandisliftedrestoringthebalance.Afixedangleofthreetofivedegrees，however，willonlybesufficientforverylightpuffsofwindandtomountthewingssothatthewholewingmaybemovedtochangethedihedralanglepresentsmechanicaldifficultieswhichwouldbebetteravoided.
　　"Theobjectionofmechanicalimpracticabilityappliestoanyplantopreservethebalancebyshiftingweightorballast.Thecenterofgravityshouldbelowerthanthecenterofthesupportingsurfaces，butcannotbemademuchlower.Itisacommonmistaketoassumethatcompletestabilitywillbesecuredbyhangingthecenterofgravityverylowontheprincipleoftheparachute.Anaeroplanedependsuponrapidhorizontalmotionforitssupport，andifthecenterofgravitybefarbelowthecenterofsupport，everychangeofspeedorwindpressurewillcausethemachinetoturnaboutitscenterofgravity，pitchingforwardandbackwarddangerously.
　　PreservingLongitudinalBalance.
　　"Thebirdsmaintainlongitudinal，orforeandaftbalance，byelevatingordepressingtheirtails.Whetherthisactionissecuredinanaeroplanebymeansofahorizontalrudderplacedintherear，orbydeflectingplanesplacedinfrontofthemainplanes，theprincipleisevidentlythesame.AhorizontalrudderplacedwelltotherearasintheAntoinette，BleriotorSantos—Dumontmonoplanes，willbeverymuchsaferandsteadierthanthedeflectingplanesinfront，asintheWrightorCurtissbiplanes，butnotsosensitiveorpromptinaction.
　　"Thenaturalforeandaftstabilityisverymuchstrengthenedbyplacingtheloadwellforward.Thecenterofgravitynearthefrontandatailorrudderstreamingtotherearsecuresstabilityasanarrowisbalancedbytheheadandfeathering.Theadoptionofthisprinciplemakesitalmostimpossiblefortheaeroplanetoturnover.
　　TheMatterofLateralBalance.
　　"Allsuccessfulaeroplanesthusfarhavemaintainedlateralbalancebytheprincipleofchangingtheangleofincidenceofthewings.
　　"Otherwaysofmaintainingthelateralbalance，suggestedbyobservationoftheflightofbirdsare——extendingthewingtipsandspillingtheairthroughthepinions;
　　or，whatisthesamething，varyingtheareaofthewingsattheirextremities.
　　"Extendingthewingtipsseemstobeasimpleandeffectivesolutionoftheproblem.Thetipsmaybemadetoswingoutwarduponaverticalaxisplacedatthefrontedgeofthemainplanes;ortheymaybehingedtotheendsofthemainplanesoastobeelevatedordepressedthroughsuitableconnectionsbytheaviator;ortheymaybesupportedfromahorizontalaxisparallelwiththeendsofthemainplanessothattheymayswingoutward，theaviatorcontrollingbothtipsthroughoneleversothatasonetipisextendedtheotherisretracted.
　　"Theelasticwingpinionsofabirdbendeasilybeforethewind，permittingtheguststoglanceoff，butpresentingalwaysanevenandefficientcurvaturetothesteadycurrentsoftheair."
　　HighWindsThreatenStability.
　　Toensureperfectstability，withoutcontrol，eitherhumanorautomatic，itisassertedthattheaeroplanemustmovefasterthanthewindisblowing.Solongasthewindisblowingattherateof30milesanhour，andthemachineistraveling40ormore，therewillbelittletroubleasregardsequilibriumsofaraswinddisturbancegoes，providedthewindblowsevenlyanddoesnotcomeingustsoreddyingcurrents.Butwhenconditionsarereversed——whenthemachinetravelsonly30milesanhourandthewindblowsattherateof50，lookoutforlossofequilibrium.
　　Oneofthemainreasonsforthisisthathighwindsarerarelysteady;theyseldomblowforanylengthoftimeatthesamespeed.Theyareusually"gusty，"thegustsbeingamomentarymovementatahigherspeed.
　　Tornadicgustsarealsoformedbythemeetingoftwoopposingcurrents，causingawhirlingmotion，whichmakesstabilityuncertain.Besides，itisnotunusualforwindofhighspeedtosuddenlychangeitsdirectionwithoutwarning.
　　TroubleWithVerticalColumns.
　　Verticalcurrents——columnsofascendingair——arefrequentlyencounteredinunexpectedplacesandhavemoreorlesstendency，accordingtotheirstrength，tomakeitdifficulttokeepthemachinewithinareasonabledistancefromtheground.
　　Theseverticalcurrentsaremostgenerallynoticeableinthevicinityofsteepcliffs，ordeepravines.Insuchinstancestheyareusuallyofconsiderablestrength，beingcausedbythedeflectionofstrongwindsblowingagainstthefaceofthecliffs.Thisdeflectionexertsabackpressurewhichisfeltquiteadistanceawayfromthepointoforigin，sothattheverticalcurrentexertsaninfluenceinforcingthemachineupwardlongbeforethecliffisreached.
　　CHAPTERXV.
　　THEELEMENTOFDANGER.
　　Thatthereisanelementofdangerinaviationisundeniable，butitisnowheresogreatasthepublicimagines.Menarekilledandinjuredintheoperationofflyingmachinesjustastheyarekilledandinjuredintheoperationofrailways.Consideringthecharacterofaviationthepercentageofcasualtiesissurprisinglysmall.
　　Thisisbecausetheresultsfollowingacollapseintheairareverymuchdifferentfromwhatmightbeimagined.
　　Insteadofdroppingtothegroundlikeabulletanaeroplane，underordinaryconditionswill，whenanythinggoeswrong，sailgentlydownwardlikeaparachute，particularlyiftheoperatoriscool—headedandnervyenoughtosomanipulatetheapparatusastopreserveitsequilibriumandkeepthemachineonanevenkeel.
　　TwoFieldsofSafety.
　　Atleastoneprominentaviatorhasdeclaredthattherearetwofieldsofsafety——oneclosetotheground，andtheotherwellupintheair.Inthefirst—namedthefallwillbeaslightonewithlittlechanceoftheoperatorbeingseriouslyhurt.Fromthefieldofhighaltitudethethedescentwillbegradual，asarule，theplanesofthemachineservingtobreaktheforceofthefall.Withacool—headedoperatorincontroltheaeroplanemaybeevenguidedatanangle（about1to8）initsdescentsoastotouchthegroundwithaglidingmotionandwithaminimumofimpact.
　　Suchanexperience，ofcourse，isfarfrompleasant，butitisbynomeanssodangerousasmightappear.
　　Thereismorerealdangerinfallingfromanelevationof75or100feetthanthereisfrom1，000feet，asintheformercasethereisnochanceforthemachinetoserveasaparachute——itscontactwiththegroundcomestooquickly.
　　LessoninRecentAccidents.
　　AmongthemorerecentfatalitiesinaviationarethedeathsofAntonioFernandezandLeonDelagrange.Theformerwasthrowntothegroundbyasuddenstoppageofhismotor，theentiremachineseemingtocollapse.
　　Itisevidenttherewereradicaldefects，notonlyinthemotor，butintheaeroplaneframeworkaswell.AtthetimeofthestoppageitisestimatedthatFernandezwasupabout1，500feet，butthemachinegotnoopportunitytoexertaparachuteeffect，asitbrokeupimmediately.
　　Thiswouldindicateafatalweaknessinthestructurewhich，underpropertesting，couldprobablyhavebeendetectedbeforeitwasusedinflight.
　　Itishardtosayit，butDelagrangeappearstohavebeenculpabletogreatdegreeinoverloadinghismachinewithamotorequipmentmuchheavierthanitwasdesignedtosustain.Hewas65feetupintheairwhenthecollapseoccurred，resultinginhisdeath.AsinthecaseofFernandezcommon—senseprecautionwoulddoubtlesshavepreventedthefatality.
　　AviationNotExtraHazardous.
　　Alltoldtherehavebeen，uptothetimeofthiswriting（April，1910），justfivefatalitiesinthehistoryofpower—
　　drivenaviation.Thisissurprisinglylowwhenthenatureoftheexperiments，andthefactthatmostoftheoperatorswerefarfromhavingextendedexperience，istakenintoconsideration.MenliketheWrights，Curtiss，Bleriot，Farman，Paulhanandothers，arenowexperts，buttherewasatime，anditwasnotlongago，whentheywereunskilled.Thatthey，withnumerousotherslesswidelyknown，shouldhavecomesafelythroughtheirmanyexperimentswouldseemtodisprovetheprevailingideathataviationisanextrahazardouspursuit.
　　Inthehandsofcareful，quick—witted，nervymenthesailingofanairshipshouldbenomorehazardousthanthesailingofayacht.Avesselcaptainwithcommonsensewillnotgotoseainastorm，ornavigateaweak，unseaworthycraft.Neithershouldanaviatorattempttosailwhenthewindishighandgusty，norwithamachinewhichhasnotbeenthoroughlytestedandfoundtobestrongandsafe.
　　SaferThanRailroading.
　　Statisticsshowthatsome12，000peoplearekilledand72，000injuredeveryyearontherailroadsoftheUnitedStates.Cometothinkitoveritissmallwonderthatthelistoffatalitiesissolarge.Trainsarerunathighspeeds，dashingovercrossingsatwhichcollisionsareliabletooccur，andoverbridgeswhichoftencollapseoraresweptawaybyfloods.Still，whilethenumberofcasualtiesislarge，theactualpercentageissmallconsideringtheimmensenumberofpeopleinvolved.
　　Itissoinaviation.Thenumberofcasualtiesisremarkablysmallincomparisonwiththenumberofflightsmade.Inthehandsofcompetentmenthesailingofanairshipshouldbe，andis，freerfromriskofaccidentthantherunningofarailwaytrain.Therearenorailstospreadorbreak，nobridgestocollapse，nocrossingsatwhichcollisionsmayoccur，nochanceforsomesleepyoroverworkedemployeetomisunderstandthedispatcher’sordersandcauseawreck.
　　TwoMainCausesofTrouble.
　　Thetwomaincausesoftroubleinanairshipleadingtodisastermaybeattributedtothestoppageofthemotor，andtheaviatorbecomingrattledsothathelosescontrolofhismachine.Moderningenuityisfastdevelopingmotorsthatalmostdailybecomemoreandmorereliable，andexperienceismakingaviatorsmoreandmoreself—confidentintheirabilitytoactwiselyandpromptlyincasesofemergency.Besidesthisasatisfactorysystemofautomaticcontrolisinafairwayofbeingperfected.
　　Occasionallyeventhemostexperiencedandcompetentofmeninallcallingsbecomecarelessandbyfoolishactioninvitedisaster.Thisistrueofaviatorsthesameasitisofrailroaders，menwhoworkindynamitemills，etc.Butinnearlyeveryinstancetheresponsibilityrestswiththeindividual;notwiththesystem.Therearesomemenunfittedbynatureforaviation，justasthereareothersunfittedtoberailwayengineers.
　　CHAPTERXVI.
　　RADICALCHANGESBEINGMADE.
　　Changes，manyofthemextremelyradicalintheirnature，arecontinuallybeingmadebyprominentaviators，andparticularlythosewhohavewonthegreatestamountofsuccess.Wonderfulastheresultshavebeenfewoftheaviatorsarereallysatisfied.Theirsuccesseshavemerelyspurredthemontonewendeavors，theultimateendbeingthedevelopmentofanabsolutelyperfectaircraft.
　　AmongthemenwhohavebeenthusexperimentingaretheWrightBrothers，wholastyear（1909）broughtoutacrafttotallydifferentasregardsproportionsandweightfromtheoneusedtheprecedingyear.Onemarkedresultwasagainofabout31/2milesanhourinspeed.
　　Dimensionsof1908Machine.
　　The1908modelaeroplanewas40by29feetoverall.
　　Thecarryingsurfaces，thatis，thetwoaerocurves，were40by6feet，havingaparabolicalcurveofoneintwelve.
　　Withabout70squarefeetofsurfaceintherudders，thetotalsurfacegivenwasabout550squarefeet.Theengine，whichistheinventionoftheWrightbrothers，weighed，approximately，200pounds，andgaveabout25
　　horsepowerat1，400revolutionsperminute.Thetotalweightoftheaeroplane，exclusiveofpassenger，butinclusiveofengine，wasabout1，150pounds.Thisresultshowedaliftofafractionover21/4poundstothesquarefootofcarryingsurface.Thespeeddesiredwas40
　　milesanhour，butthemachinewasfoundtomakeonlyascant39milesanhour.Theuprightstrutswereabout7/8—inchthick，theskids，21/2by11/4inchesthick.
　　Dimensionsof1909Machine.
　　The1909aeroplanewasbuiltprimarilyforgreaterspeed，andrelativelyheavier;tobelessatthemercyofthewind.Thisresultwasobtainedasfollows：Theaerocurves，orcarryingsurfaces，werereducedindimensionsfrom40by6feetto36by51/2feet，thecurveremainingthesame，oneintwelve.Theuprightstrutswerecutfromseven—eighthsinchtofive—eighthsinch，andtheskidsfromtwoandone—halfbyoneandone—quartertotwoandone—quarterbyoneandthree—eighthsinches.
　　Thisresultshowsthatthereweresome81squarefeetofcarryingsurfacemissingoverthatoflastyear’smodel.andsome25poundslossofweight.Relatively，though，the1909modelaeroplane，whileactually25
　　poundslighter，isreallysome150poundsheavierintheairthanthe1908model，owingtothelessersquarefeetofcarryingsurface.
　　SomeoftheResultsObtained.
　　Reducingthecarryingsurfacesfrom6to51/2feetgavetworesults——first，lesscarryingcapacity;and，second，lesshead—onresistance，owingtothefactthattheextentoftheparaboliccurveinthecarryingsurfaceswasshortened.The"head—on"resistanceistheretardancetheaeroplanemeetsinpassingthroughtheair，andiscountedinsquarefeet.Inthe1908modelthecurvebeingoneintwelveand6feetdeep，gave6inchesofhead—onresistance.Theplanebeing40feetspread，gave6inchesby40feet，or20squarefeetofhead—onresistance.Increasingthisfigurebyalikeamountforeachplane，andaddingapproximately10squarefeetforstruts，skidsandwiring，wehaveatotalofapproximately，50squarefeetofsurfacefor"head—on"resistance.
　　Inthe1909aeroplane，shorteningthecurve6inchesattheparabolicendofthecurvetookoff1inchofhead—onresistance.Shorteningthespreadoftheplanestookoffbetween3and4squarefeetofhead—onresistance.
　　Addtothisthetotalof7squarefeet，lesscurvesurfaceandabout1squarefoot，lesswireandwoodworkresistance，andwehaveagrandtotalof，approximately，12squarefeetofless"head—on"resistanceoverthe1908model.
　　ChangesinEngineAction.
　　Theengineusedin1909wasthesameoneusedin1908，thoughsomeminorchangesweremadeasimprovements;forinstance，amakeandbreaksparkwasused，andanine—tooth，insteadofaten—toothmagnetogear—wheelwasused.Thisincreasedtheenginerevolutionsperminutefrom1，200to1，400，andthepropellerrevolutionsperminutefrom350to371，givingapropellerthrustof，approximately，170footpoundsinsteadof153，aswashadlastyear.
　　MoreSpeedandSameCapacity.
　　Oneunsatisfactoryfeatureofthe1909modeloverthatof1908，apparently，wasthelackofinherentlateralstability.Thiswascausedbythelessersurfaceandlesserextentofcurvaturesattheportionsoftheaeroplanewhichwerewarped.ThisdefectdidnotshowsoplainlyafterMr.OrvilleWrighthadbecomefullyproficientinthehandlingofthenewmachine，andwithskillfulmanagement，the1909modelaeroplanewillbejustassafeandsecureastheotherthoughitwilltakealittlemorepracticetogetthatsamedegreeofskill.
　　Tosumup：Theaeroplaneusedin1909was25
　　poundslighter，butreallyabout150poundsheavierintheair，hadlesshead—onresistance，andgreaterpropellerthrust.Thespeedwasincreasedfromabout39
　　milesperhourto421/2milesperhour.Theliftingcapacityremainedaboutthesame，about450poundscapacitypassenger—weight，withthe1908machine.Inthisrespect，thelossofcarryingsurfacewascompensatedforbytheincreasedspeed.
　　Duringthefirstfewflightsitwasplainlydemonstratedthatitwouldneedthehighestskilltoproperlyhandletheaeroplane，asfirstoneendandthentheotherwoulddipandstriketheground，andeithertearthecanvasorslewtheaeroplanearoundandbreakaskid.
　　WrightsAdoptWheeledGears.
　　InstillanotherimportantrespecttheWrights，sofarastheoutputofoneoftheircompaniesgoes，havemadearadicalchange.AlltheaeroplanesturnedoutbytheDeutschWrightGesellschaft，accordingtotheGermanpublication，_Automobil—Welt_，willhereafterbeequippedwithwheeledrunninggearsandtails.Theplanofthisnewmachineisshownintheillustrationonpage145.
　　Thewheelsarethreeinnumber，andareattachedonetoeachofthetwoskids，justunderthefrontedgeoftheplanes，andoneforwardofthese，attachedtoacross—
　　member.Itisassertedthatwiththesewheelstheteachingofpurchaserstooperatethemachinesismuchsimplified，asthebeginnerscanmakeshortflightsontheirownaccountwithoutusingthestartingderrick.
　　ThisisabigconcessionfortheWrightstomake，astheyhavehithertoadheredstoutlytotheskidgear.
　　WhileitistruetheydonotcontroltheGermancompanyproducingtheiraeroplanes，yetthenatureoftheirconnectionwiththeenterpriseissuchthatitmaybetakenforgrantednoradicalchangesinconstructionwouldbemadewithouttheirapprovalandconsent.
　　OnlyThreeDangerousRivals.
　　Officialtrialswiththe1909modelsmashedmanyrecordsandleavetheWrightbrotherswithonlythreedangerousrivalsinthefield，andwithbasicpatentswhichcoverthecurve，warpandwing—tipdevicesfoundonalltheothermakesofaeroplanes.ThesethreerivalsaretheCurtissandVoisinbiplanetypeandtheBleriotmonoplanepattern.
　　TheBleriotmonoplaneisprobablythemostdangerousrival，asthismakeofmachinehasarecordof54
　　milesperhour，hascrossedtheEnglishchannel，andhasliftedtwopassengersbesidestheoperator.Thelatesttypeofthismachineonlyweighs771.61poundscomplete，withoutpassengers，andwillliftatotalpassengerweightof462.97pounds，whichisaliftof5.21poundstothesquarefoot.ThisisabetterresultthanthosepublishedbytheWrightbrothers，thebestnotedbeing4.25poundspersquarefoot.
　　OtherAviatorsatWork.
　　TheWrights，however，arenotaloneintheireffortstopromotetheefficiencyoftheflyingmachine.Othercompetentinventiveaviators，notablyCurtiss，Voisin，BleriotandFarman，arecloseafterthem.TheWrights，asstated，haveamarkedadvantageinthepossessionofpatentscoveringsurfaceplanedeviceswhichhavethusfarbeenfoundindispensableinflyingmachineconstruction.
　　Numerouslawsuitsgrowingoutofallegedinfringementsofthesepatentshavebeenstarted，andothersarethreatened.Whateffecttheseactionswillhaveindeterringaviatorsingeneralfromproceedingwiththeirexperimentsremainstobeseen.
　　Inthemeantimethefourmennamed——Curtiss，Voisin，BleriotandFarman——aregoingaheadregardlessofconsequences，andtheinventivegeniusofeachissostrongthatitisreasonabletoexpectsomeremarkabledevelopmentsinthenearfuture.
　　SmallestofFlyingMachines.
　　ToSantosDumontmustbegiventhecreditofproducingthesmallestpracticalflyingmachineyetconstructed.
　　True，hehasdonenothingremarkablewithitinthelineofspeed，buthehasdemonstratedthefactthatalargesupportingsurfaceisnotanessentialfeature.
　　Thismachineisnamed"LaDemoiselle."Itisamonoplaneofthedihedraltype，withamainplaneoneachsideofthecenter.Thesemainplanesareof18footspread，andnearly61/2feetindepth，givingapproximately115feetofsurfacearea.Thetotalweightis242pounds，whichis358poundslessthananyothermachinewhichhasbeensuccessfullyused.Thetotaldepthfromfronttorearis26feet.
　　Theframeworkisofbamboo，strengthenedandheldtautwithwireguys.
　　HaveOneRuleinMind.
　　Inthisstruggleformasteryinflyingmachineefficiencyallthecontestantskeeponeruleinmind，andthisis：
　　"Thecarryingcapacityofanaeroplaneisgovernedbytheperipheralcurveofitscarryingsurfaces，plusthespeed;andthespeedisgovernedbythethrustofthepropellers，lessthe’head—on’resistance."
　　Theirideasastothepropermeansofapproachingthepropositionmay，andundoubtedlyare，atvariance，buttheoneruleinsolvingtheproblemofobtainingthegreatestcarryingcapacitycombinedwiththegreatestspeed，obtainsinallinstances.
　　CHAPTERXVII.
　　SOMEOFTHENEWDESIGNS.
　　Spurredonbythesuccessattainedbythemoreexperiencedandbetterknownaviatorsnumerousinventorsoflesserfamearealmostdailyproducingpracticalflyingmachinesvaryingradicallyinconstructionfromthosenowingeneraluse.
　　OneofthesecomparativelynewdesignsistheVanAndenbiplane，madebyFrankVanAndenofIslip，LongIsland，amemberoftheNewYorkAeronauticSociety.Whilehismachineiswhollyexperimental，manysuccessfulshortflightsweremadewithitlastfall（1909）.Oneflight，madeOctober19th，1909，isofparticularinterestasshowingthepracticabilityofanautomaticstabilizingdeviceinstalledbytheinventor.Themachinewascaughtinasuddenseveregustofwindandkeeledover，butalmostimmediatelyrighteditself，thusdemonstratinginamostsatisfactorymannerthevalueofonenewattachment.
　　FeaturesofVanAndenModel.
　　Insizethesurfacesofthemainbiplaneare26feetinspread，and4feetindepthfromfronttorear.Theupperandlowerplanesare4feetapart.Silkolenecoatedwithvarnishisusedforthecoverings.Ribs（spruce）arecurvedoneinchtothefoot，thedeepestpartofthecurve（4inches）beingonefootbackfromthefrontedgeofthehorizontalbeam.Struts（alsoofspruce，asisalltheframework）areellipticalinshape.
　　Themainbeamsareinthreesections，nearlyhalfroundinform，andjoinedbymetalsleeves.
　　Thereisatwo—surfacehorizontalrudder，2x2x4feet，infront.Thisispivotedatitslateralcenter8feetfromthefrontedgeofthemainplanes.Intherearisanothertwo—surfacehorizontalrudder2x2x21/2feet，pivotedinthesamemannerasthefrontone，15feetfromtherearedgesofthemainplanes.
　　Hingedtotherearcentralstrutoftherearrudderisaverticalrudder2feethighby3feetinlength.
　　TheMethodofControl.
　　Intheoperationoftheserudders——bothfrontandrear——andtheelevationanddepressionofthemainplanes，theCurtisssystemisemployed.Pushingthesteering—
　　wheelpostoutwarddepressesthefrontedgesoftheplanes，andbringsthemachinedownward;pullingthesteering—wheelpostinwardelevatesthefrontedgesoftheplanesandcausesthemachinetoascend.
　　Turningthesteeringwheelitselftotherightswingsthetailruddertotheleft，andthemachine，obeyingthislikeaboat，turnsinthesamedirectionasthewheelisturned.Bylikecauseturningthewheeltotheleftturnsthemachinetotheleft.
　　AutomaticControlofWings.
　　Therearetwowingtips，eachof6feetspread（length）
　　and2feetfromfronttorear.Thesearehingedhalfwaybetweenthemainsurfacestothetwooutermostrearstruts.Cablesrunfromthesetoanautomaticdeviceworkingwithpowerfromtheengine，whichautomaticallyoperatesthetipswiththetiltingofthemachine.Normallythewingtipsareheldhorizontalbystiffspringsintroducedinthecablesoutsideofthedevice.
　　ItwasthesuccessfulworkingofthisdevicewhichrightedtheVanAndencraftwhenitwasoverturnedinthesquallofOctober19th，1909.PrevioustothatoccurrenceMr.VanAndenhadlookeduponthedeviceaspurelyexperimental，andhadadmittedthathehadgraveuncertaintyastohowitwouldoperateintimeofemergency.Heisnowquotedasbeingthoroughlysatisfiedwithitspracticability.ItisthisautomaticdevicewhichgivestheVanAndenmachineatleastonedistinctivelynewfeature.
　　WhileonthissubjectitwillnotbeamisstoaddthatMr.Curtissdoesnotlookkindlyonautomaticcontrol.
　　"Iwouldrathertrusttomyownactionthanthatofamachine，"hesays.ThisisundoubtedlygoodlogicsofarasMr.Curtissisconcerned，butallaviatorsarenotsocool—headedandresourceful.
　　MotivePowerofVanAnden.
　　A50—horsepower"H—F"watercooledmotordrivesalaminatedwoodpropeller6feetindiameter，witha17
　　degreepitchattheextremities，increasingtowardthehub.Therearendofthemotorisabout6inchesbackfromthereartransversebeamandtheengineshaftisinadirectlinewiththeaxesofthetwohorizontalrudders.
　　AnR.I.V.ballbearingcarriestheshaftatthispoint.Flying，themotorturnsatabout800revolutionsperminute，delivering180poundspull.Atestofthemotorrunningat1，200showedapullof250poundsonthescales.
　　StillAnotherNewAeroplane.
　　AnothernewaeroplaneisthatproducedbyA.M.
　　Herring（anold—timer）andW.S.Burgess，underthenameoftheHerring—Burgess.Thisisalsoequippedwithanautomaticstabilitydeviceformaintainingthebalancetransversely.Thecurvatureoftheplanesisalsolaidoutonnewlines.Thatthisnewplaniseffectiveisevidencedbythefactthatthemachinehasbeenelevatedtoanaltitudeof40feetbyusingone—halfthepowerofthe30—horsepowermotor.
　　Thesystemofrudderandelevationcontrolisverysimple.Theaviatorsitsinfrontofthelowerplane，andextendinghisarms，graspstwosupportswhichextenddowndiagonallyinfront.Ontheundersideofthesesupportsjustbeneathhisfingersarethecontrolswhichoperatetheverticalrudder，intherear.Thus，ifhewishestoturntotheright，hepressesthecontrolunderthefingersofhisrighthand;iftotheleft，thatunderthefingersofhislefthand.Theelevatingrudderisoperatedbytheaviator’srightfoot，thecontrolbeingplacedonafoot—rest.
　　MotorIsExtremelyLight.
　　Nottheleastnotablefeatureofthecraftisitsmotor.
　　Althoughdeveloping，underload，30—horsepower，orthatofanordinaryautomobile，itweighs，complete，hardly100pounds.Havingoccasiontomoveitalittledistanceforinspection，Mr.Burgesspickeditupandwalkedoffwithit——cylinders，pistons，crankcaseandall，eventhemagneto，beingattached.Therearenotmany30—
　　horsepowerengineswhichcanbesohandled.Everythingaboutitisreducedtoitslowesttermsofsimplicity，andhence，ofweight.Asinglecamshaftoperatesnotonlyalloftheinletandexhaustvalves，butthemagnetoandgearwaterpump，aswell.Themotorisplaceddirectlybehindtheoperator，andthepropellerisdirectlymountedonthecrankshaft.
　　Thisweightoflessthan100pounds，itmustberemembered，isnotforthemotoralone;itincludestheentirepowerplantequipment.
　　The"thrust"ofthepropellerisalsoextraordinary，beingbetween250and260pounds.Theforceofthewinddisplacementisstrongenoughtoknockdownagood—sizedboyasoneyoungsterascertainedwhenhegotbehindthepropellerasitwasbeingtested.Hewasnotonlyknockeddownbutdrivenforsomedistanceawayfromthemachine.Thepropellerhasfourbladeswhicharebutlittlewiderthanalath.
　　MachineBuiltbyStudents.
　　StudentsattheUniversityofPennsylvania，headedbyLaurenceJ.Lesh，aprotegeofOctaveChanute，haveconstructedapracticalaeroplaneofordinarymaximumsize，inwhichisincorporatedmanynewideas.Themostuniqueoftheseistobefoundinthesteeringgear，andtheprovisionmadefortheaccommodationofapupilwhiletakinglessonsunderanexperiencedaviator.
　　Immediatelybackoftheaviatorisanextraseatandanextrasteeringwheelwhichworksintandemstylewiththefrontwheel.Bythisarrangementabeginnermaybeeasilyandquicklytaughttohaveperfectcontrolofthemachine.Thesetandemwheelsarealsohandyforpassengerswhomaywishtooperatethecarindependentlyofoneanother，itbeingunderstood，ofcourse，thattherewillbenoconflictofaction.
　　FrameSizeandEnginePower.
　　Theframehas36feetspreadandmeasures35feetfromthefrontedgetotheendofthetailintherear.ItisequippedwithtworearpropellersoperatedbyaRamsey8—cylindermotorof50horsepower，placedhorizontallyacrossthelowerplane，withthecrankshaftrunningclearthroughtheengine.
　　The"PennsylvaniaI"isthefirsttwo—propellerbiplanechainlesscar，thisschemehavingbeenadoptedinordertoavoidthecrossingofchains.ThelateralcontrolisbyanewinventionbyOctaveChanuteandLaurenceJ.
　　Lesh，forwhichLeshisnowapplyingforapatent.ThedevicewasworkedoutbeforetheWrightbrothers’suitwasbegun，andissaidtobesuperiortotheWrightwarpingortheCurtissailerons.Thelandingdeviceisalsonewindesign.Thisaeroplanewillweighabout1，500pounds，andwillcarryfuelforaflightof150miles，anditisexpectedtoattainaspeedofatleast45milesanhour.
　　Thereareothers，lotsofthem，toonumerousinfacttoadmitofmentioninabookofthissize.
　　CHAPTERXVIII.
　　DEMANDFORFLYINGMACHINES.
　　Asacommercialpropositionthemanufactureandsaleofmotor—equippedaeroplanesismakingmuchmorerapidadvancethanatfirstobtainedinthesimilarhandlingoftheautomobile.Great，andevenphenomenal，aswasthecommercialdevelopmentofthemotorcar，thatoftheflyingmachineisevengreater.Thisisastartlingstatement，butitisfullywarrantedbythefacts.
　　Itisbarelymorethanayearago（1909）thatattentionwasseriouslyattractedtothemotor—equippedaeroplaneasavehiclepossibleofmanipulationbyothersthanprofessionalaviators.Uptothattimesuchactualflightsasweremadewerealmostexclusivelywiththesolepurposeofdemonstratingthepracticabilityofthemachine，andthemeritsoftheideasastoshape，enginepower，etc.，ofthevariousproducers.
　　ResultsofBleriot’sDaring.
　　ItwasnotuntilBleriotflewacrossthestraitsofDoveronJuly25th，1909，thatthegeneralpublicawoketoafullrealizationofthefactthatitwaspossibleforothersthanprofessionalaviatorstoindulgeinaviation.
　　Bleriot’sfeatwasacceptedasproofthatatlastanabsolutelynewmeansofsport，pleasureandresearch，hadbeenpracticallydeveloped，andwaswithinthereachofallwhohadtheinclination，nerveandfinancialmeanstoadoptit.
　　Fromthiseventmaybedatedthebirthofthemodernflyingmachineintotheworldofbusiness.Theautomobilewastakenupbythegeneralpublicfromtheverystartbecauseitwasapropositioncomparativelyeasyofdemonstration.Therewasnothingmysteriousoruncannyinthefactthatawheeledvehiclecouldbepropelledonsolid，substantialroadsbymeansofenginepower.Andyetittook（comparativelyspeaking）alongtimetoreallypopularizethemotorcar.
　　WonderfulResultsinaYear.
　　Menoflargefinancialmeansengagedinthemanufactureofautomobiles，andexpendedfortunesinattractingpublicattentiontothemthroughthemediumofadvertisements，speedandroadcontests，etc.Bythesemeansamammothbusinesshasbeenbuiltup，butbringingthisbusinesstoitspresentproportionsrequiredyearsofpatientindustryandindomitablepluck.
　　Atthiswriting，lessthanayearfromthedaywhenBleriotcrossedthechannel，theactualsalesofflyingmachinesoutnumbertheactualsalesofautomobilesinthefirstyearoftheircommercialdevelopment.Thismayappearincredible，butitisafactasstatisticswillshow.
　　Inthisconnectionweshouldtakeintoconsiderationthefactthatuptoayearagotherewasnoseriousintentionofputtingflyingmachinesonthemarket;nopreparationshadbeenmadetoproducethemonacommercialscale;nomoneyhadbeenexpendedinadvertisementswithaviewtosellingthem.
　　SomeoftheActualResults.
　　Todayflyingmachinesarebeingproducedonacommercialbasis，andthereisabigdemandforthem.Thepeoplemakingthemareovercrowdedwithorders.Someoftheproducersarealreadymakingarrangementstoenlargetheirplantsandadvertisetheirproductforsalethesameasisbeingdonewithautomobiles，whileanumberofflyingmachinemotormakersarealreadypromotingthesaleoftheirwaresinthisway.
　　HereareafewactualfiguresofflyingmachinesalesmadebythemoreprominentproducerssinceJuly25th，1909.
　　SantosDumont，90machines;Bleriot，200;Farman，130;Clemenceau—Wright，80;Voisin，100;Antoinette，100.Manyoftheseordershavebeenfilledbydeliveryofthemachines，andinotherstheconstructionworkisunderway.
　　Theforegoingareallofforeignmake.InthiscountryCurtissandtheWrightsareengagedinsimilarwork，butnoactualfiguresoftheiroutputareobtainable.
　　LargerPlantsAreNecessary.
　　Andthissituationexistsdespitethefactthatnoneoftheproducersarereallyequippedwithadequateplantsforturningouttheirmachinesonamodern，business—
　　likebasis.Thedemandwassosuddenandunexpectedthatitfoundthempoorlypreparedtomeetit.This，however，isnowbeingremediedbytheerectionofspecialplants，theenlargementofothers，andtheintroductionofnewmachineryandotherlabor—savingconveniences.
　　Companies，withlargecapitalization，toengageintheexclusiveproductionofairshipsarebeingorganizedinmanypartsoftheworld.Onenotableinstanceofthisnatureisworthquotingasillustrativeofthemannerinwhichtheproductionofflyingmachinesisbeingcommercialized.ThisistheformationatFrankfort，Germany，oftheFlugmaschineWright，G.m.b.H.，withacapitalof$119，000，theKrupps，ofEssen，beinginterested.
　　PricesatWhichMachinesSell.
　　Thiswonderfuldemandfromthepublichascomenotwithstandingthefactthatthemachines，owingtolackoffacilitiesforwholesaleproduction，arefarfrombeingcheap.Suchdefinitequotationsasaremadeareonthefollowingbasis：
　　SantosDumont——Listprice$1，000，butowingtotherushofordersagentsarereadilygettingfrom$1，300to$1，500.Thisisthesmallestmachinemade.
　　Bleriot——Listprice$2，500.Thisisforthecross—
　　channeltype，withAnzanimotor.
　　Antoinette——Listpricefrom$4，000to$5，000，accordingtosize.
　　Wright——Listprice$5，600.
　　Curtiss——Listprice$5，000.
　　Thereis，however，nostabilityinpricesaspurchasersarealmostinvariablyreadytopayaconsiderablepremiumtofacilitatedelivery.
　　Themotoristhemostexpensivepartoftheflyingmachine.Motorpricesrangefrom$500to$2，000，thislatteramountbeingaskedfortheCurtissengine.
　　SystematicInstructionofAmateurs.
　　Inadditiontotheproductionofflyingmachinesmanyoftheexperiencedaviatorsaremakingabusinessoftheinstructionofamateurs.CurtissandtheWrightsinthiscountryhaveanumberofpupils，ashavealsotheprominentforeigners.Schoolsofinstructionarebeingopenedinvariouspartsoftheworld，notaloneasprivatemoney—makingventures，butinconnectionwithpubliceducationalinstitutions.OneoftheselatteristobefoundattheUniversityofBarcelona，Spain.
　　Theflyingmachineagent，themanwhohandlesthemachinesonacommission，hasalsobecomeaknownquantity，andwillsoonbeasnumerousashisbrotheroftheautomobile.Thesign"JohnBird，agentforSkimmer’sFlyingMachine，"isnolongeracuriosity.