the dominion of the air-第35章

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ss　than　half　a　foot　to　the　pound。　　He　next　proceeded　to　steam…driven　models　in　which　for　a　time　he　found　an　insuperable　difficulty　in　keeping　down　the　weight；　which；　in　practice；　always　exceeded　his　calculation；　and　it　was　not　till　the　end　of　1893　that　he　felt　himself　prepared　for　a　fair　trial。　　At　this　time　he　had　prepared　a　model　weighing　between　nine　and　ten　pounds；　and　he　needed　only　a　suitable　launching　apparatus　to　be　used　over　water。　　The　model　would；　like　a　bird；　require　an　initial　velocity　imparted　to　it；　and　the　discovery　of　a　suitable　apparatus　gave　him　great　trouble。　　For　the　rest　the　facilities　for　launching　were　supplied　by　a　houseboat　moored　on　the　Potomac。　　Foiled　again　and　again　by　many　difficulties；　it　was　not　till　after　repeated　failures　and　the　lapse　of　many　months；　when；　as　the　Professor　himself　puts　it；　hope　was　low；　that　success　finally　came。　　It　was　in　the　early　part　of　1896　that　a　successful　flight　was　accomplished　in　the　presence　of　Dr。　Bell；　of　telephone　fame；　and　the　following　is　a　brief　epitome　of　the　account　that　this　accomplished　scientist　contributed　to　the　columns　of　Nature：

〃The　flying　machine；　built；　apparently；　almost　entirely　of　metal；　was　driven　by　an　engine　said　to　weigh；　with　fuel　and　water；　about　25　lbs。；　the　supporting　surface　from　tip　to　tip　being　12　or　14　feet。　　Starting　from　a　platform　about　20　feet　high；　the　machine　rose　at　first　directly　in　the　face　of　the　wind；　moving　with　great　steadiness；　and　subsequently　wheeling　in　large　curves　until　steam　was　exhausted；　when；　from　a　height　of　80　or　100　feet；　it　shortly　settled　down。　　The　experiment　was　then　repeated　with　similar　results。　　Its　motion　was　so　steady　that　a　glass　of　water　might　have　remained　unspilled。　　The　actual　length　of　flight　each　time；　which　lasted　for　a　minute　and　a　half；　exceeded　half　a　mile；　while　the　velocity　was　between　twenty　and　twenty…five　miles　an　hour　in　a　course　that　was　constantly　taking　it　'up　hill。'　　A　yet　more　successful　flight　was　subsequently　made。〃

But　flight　of　another　nature　was　being　courageously　attempted　at　this　time。　　Otto　Lilienthal；　of　Berlin；　in　imitation　of　the　motion　of　birds；　constructed　a　flying　apparatus　which　he　operated　himself；　and　with　which　he　could　float　down　from　considerable　elevations。　　〃The　feat；〃　he　warns　tyros；　〃requires　practice。　　In　the　beginning　the　height　should　be　moderate；　and　the　wings　not　too　large；　or　the　wind　will　soon　show　that　it　is　not　to　be　trifled　with。〃　　The　inventor　commenced　with　all　due　caution；　making　his　first　attempt　over　a　grass　plot　from　a　spring　board　one　metre　high；　and　subsequently　increasing　this　height　to　two　and　a　half　metres；　from　which　elevation　he　could　safely　cross　the　entire　grass　plot。　　Later　he　launched　himself　from　the　lower　ridges　of　a　hill　250　feet　high；　when　he　sailed　to　a　distance　of　over　250　yards；　and　this　time　he　writes　enthusiastically　of　his　self…taught　accomplishment：

〃To　those　who；　from　a　modest　beginning　and　with　gradually　increased　extent　and　elevation　of　flight　have　gained　full　control　over　the　apparatus；　it　is　not　in　the　least　dangerous　to　cross　deep　and　broad　ravines。　　It　is　a　difficult　task　to　convey　to　one　who　has　never　enjoyed　aerial　flight　a　clear　perception　of　the　exhilarating　pleasure　of　this　elastic　motion。　　The　elevation　above　the　ground　loses　its　terrors；　because　we　have　learned　by　experience　what　sure　dependence　may　be　placed　upon　the　buoyancy　of　the　air。〃

As　a　commentary　to　the　above　we　extract　the　following：〃We　have　to　record　the　death　of　Otto　Lilienthal；　whose　soaring　machine；　during　a　gliding　flight；　suddenly　tilted　over　at　a　height　of　about　60　feet；　by　which　mishap　he　met　an　untimely　death　on　August　9th；　1896。〃　　Mr。　O。　Chanute；　C。E。　of　Chicago；　took　up　the　study　of　gliding　flight　at　the　point　where　Lilienthal　left　it；　and；　later；　Professor　Fitzgerald　and　others。　　Besides　that　invented　by　Penaud；　other　aero…plane　models　demanding　mention　had　been　produced　by　Tatin；　Moy；　Stringfellow；　and　Lawrence　Hargrave；　of　Australia；　the　subsequent　inventor　of　the　well…known　cellular　kite。　　These　models；　for　the　most　part；　aim　at　the　mechanical　solution　of　the　problem　connected　with　the　soaring　flight　of　a　bird。

The　theoretical　solution　of　the　same　problem　had　been　attacked　by　Professor　Langley　in　a　masterly　monograph；　entitled　〃The　Internal　Work　of　the　Wind。〃　　By　painstaking　experiment　with　delicate　instruments；　specially　constructed；　the　Professor　shows　that　wind　in　general；　so　far　from　being；　as　was　commonly　assumed；　mere　air　put　in　motion　with　an　approximately　uniform　velocity　in　the　same　strata；　is；　in　reality；　variable　and　irregular　in　its　movements　beyond　anything　which　had　been　anticipated；　being　made　up；　in　fact；　of　a　succession　of　brief　pulsations　in　different　directions；　and　of　great　complexity。　　　These　pulsations；　he　argues；　if　of　sufficient　amplitude　and　frequency；　would　be　capable；　by　reason　of　their　own　〃internal　work；〃　of　sustaining　or　even　raising　a　suitably　curved　surface　which　was　being　carried　along　by　the　main　mean　air　stream。　　This　would　account　for　the　phenomenon　of　〃soaring。〃　　Lord　Rayleigh；　discussing　the　same　problem；　premises　that　when　a　bird　is　soaring　the　air　cannot　be　moving　uniformly　and　horizontally。　　Then　comes　the　natural　question；　Is　it　moving　in　ascending　currents？　　Lord　Rayleigh　has　frequently　noticed　such　currents；　particularly　above　a　cliff　facing　the　wind。　　Again；　to　quote　another　eminent　authority；　Major　Baden…Powell；　on　an　occasion　when　flying　one　of　his　own　kites；　found　it　getting　to　so　high　an　angle　that　it　presently　rose　absolutely　overhead；　with　the　string　perpendicular。　　He　then　took　up　a　heavy　piece　of　wood；　which；　when　tied　to　the　string；　began　to　rise　in　the　air。　　He　satisfied　himself　that　this　curious　result　was　solely　due　to　a　strong　uptake　of　the　air。

But；　again；　Lord　Rayleigh；　lending　support　to　Professor　Langley's　argument；　points　out　that　the　apparent　cause　of　soaring　may　be　the　non…uniformity　of　the　wind。　　The　upper　currents　are　generally　stronger　than　the　lower；　and　it　is　mechanically　possible　for　a　bird；　taking　advantage　of　two　adjacent　air　streams；　different　in　velocity；　to　maintain　itself　in　air　without　effort　on　its　own　part。

Lord　Rayleigh；　proceeding　to　give　his　views　on　artificial　flight；　declares　the　main　problem　of　the　flying　machine　to　be　the　problem　of　the　aerial　plane。　　He　states　the　case　thus：　〃Supposing　a　plane　surface　to　be　falling　vertically　at　the　rate　of　four　miles　an　hour；　and　also　moving　horizontally　at　the　rate　of　twenty　miles　an　hour；　it　might　have　been　supposed　that　the　horizontal　motion　would　make　no　difference　to　the　pressure　on　its　under　surface　which　the　falling　plane　must　experience。　　We　are　told；　however；　that　in　actual　trial　the　horizontal　motion　much　increases　the　pressure　under　the　falling　plane；　and　it　is　this　fact　on　which　the　possibility　of　natural　and　artificial　flight　depends。

Ere　this　opinion　had　been　stated　by　Lord　Rayleigh　in　his　discourse　on　〃Flight；〃　at　the　Royal　Institution；　there　were　already　at　work　upon　the　aero…plane　a　small　army　of　inventors；　of　whom　it　will　be　only　possible　in　a　future　chapter　to　mention　some。　Due　reference；　however；　should　here　be　made　to　Mr。　W。　F。　Wenham；　of　Boston；　U。S。A。；　who　had　been　at　work　on　artificial　flight　for　many　years；　and　to　whose　labours　in　determining　whether　man's　power　is　sufficient　to　raise　his　own　weight　Lord　Rayleigh　paid　a　high　tribute。　　As　far　back　as　1866　Mr。　Wenham　had　published　a　paper　on　aerial　locomotion；　in　which　he　shows　that　any　imitation　by　man　of　the　far…extended　wings　of　a　bird　might　be　impracticable；　the　alternative　being　to　arrange　the　necessary　length　of　wing　as　a　series　of　aero…planes；　a　conception　far　in　advance　of　many　theorists　of　his　time。

But　there　had　been　developments　in　aerostation　in　other　lines；　and　it　is　time　to　turn　from　the　somewhat　tedious　technicalities　of　mechanical　flight　and　the　theory　or　practice　of　soaring；　to　another　important　means　for　traversing　the　airthe　parachute。　This　aerial　machine；　long　laid　aside；　was　to　lend　its　aid　to　the　navigation　of　the　air　with　a　reliability　never　before　realised。　　Professor　Baldwin；　as　he　was　termed；　an　American　aeronaut；　arrived　in　England　in　the　summer　of　1888；　and　commenced　giving　a　series　of　exhibitions　from　the　Alexandra　Palace　with　a　parachute　of　his　own　invention；　which；　in　actual　performance；　seems　to　have　been　the　most　perfect　instrument　of　the　kind　up　to　that　time　devised。　　It　was　said　to　be　about　18　feet　in　diameter；　whereas　that　of　Garnerin；　already　mentioned；　had　a　diameter　of　some　30　feet；　and　was　distinctly　top…heavy；　owing　to　its　being　thus　inadequately　ballasted；　for　it　was　calculated　that　its　enormous　size　would　have　served　for　the　safe　descent；　not　of　one　man；　but　of　four　or　five。　　Baldwin's　parachute；　on　the　contrary；　was　reckoned　to　give　safe　descent　to　250　lbs。；　which　would　include　weight　of　man　and　apparatus；　and　reduce　the　ultimate　fall　to　one　not　exceeding　8　feet。　The　parachute　was　attached　to　the　ring　of　a　small　balloon　of　12；000　cubic　feet；　and　the　Professor　ascended；　sitting　on　a　mere　sling　of　rope；　which　did　duty　for　a　car。

Mr。　Thomas　Moy；　who　investigated　the　mechanics　of　the　contrivance；　estimated　that　after　a　drop　of　16　feet；　the　upward　pressure；　amounting　to　over　2　lb。　per　square　foot；　would　act　on　a　surface　of　not　less　than　254　square　feet。　　There　was；　at　the　time；　much　foolish　comment　on　the　great　distance　which　the　parachute　fell　before　it　opened；　a　complete　delusion　due　to　the　fact　that　observers　failed　to　see　that　at　the　moment　of　separation　the　balloon　itself　sprang　upward。



CHAPTER　XXII。　　THE　STORY　OF　THE　SPENCERS。


It　has　been　in　the　hands　of　the　Spencers　that　the　parachute；　as　also　many　other　practical　details　of　aeronautics；　has　been　perfected；　and　some　due　sketch　of　the　career　of　this　family　of　eminent　aeronauts　must　be　no　longer　delayed。

Charles　Green　had　stood　godfather　to　the　youngest　son　of　his　friend　and　colleague；　Mr。　Edward　Spencer；　and　in　later　years；　as　though　to　vindicate　the　fact；　this　same　son　took　up　the　science　of　aeronautics　at　the　point　where　his　father　had　left　it。　　We　find　his　name　in　the　records　of　the　Patent　Office　of　1868　as　the　inventor　of　a　manumetric　flying　machine；　and　there　are　accounts　of　the　flying　leaps　of　several　hundred　feet　which　he　was　enabled　to　take　by　means　of　the　machine　he　constructed。　　Again；　in　1882　we　find　him　an　inventor；　this　time　of　the　patent　asbestos　fire　balloon；　by　means　of　which　the　principal　danger　to　such　balloons　was　overcome。

At　this　point　it　is　needful　to　make　mention　of　the　third　generationthe　several　sons　who　early　showed　their　zeal　and　aptitude　for　perpetuating　the　family　tradition。　　It　was　from　his　school　playground　that　the　eldest　son；　Percival；　witnessed　with　intense　interest　what　appeared　like　a　drop　floating　in　the　sky　at　an　immense　altitude。　　This　proved　to　be　Simmons's　balloon；　which　had　just　risen　to　a　vast　elevation　over　Cremorne　Gardens；　after　having　liberated　the　unfortunate　De　Groof；　as　mentioned　in　a　former　chapter。　　And　one　may　be　sure　that　the　terrible　reality　of　the　disaster　that　had　happened　was　not　lost　on　the　young　schoolboy。　　But　his　wish　was　to　become　an　aeronauts；　and　from　this　desire　nothing　deterred　him；　so　that　school　days　were　scarcely　over　before　he　began　to　accom