the dominion of the air-第44部分

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　experience　know　that　it　is　an　exceedingly　difficult　manoeuvre　to　keep　a　trail　rope　dragging　on　the　ground　if　it　is　desirable　to　prevent　contact　with　the　earth　on　the　one　hand；　or　on　the　other　to　avoid　loss　of　gas。　　A　slight　increase　of　temperature　or　drying　off　of　condensed　moisture　mayindeed；　is　sure　to　after　a　whilelift　the　rope　off　the　ground；　in　which　case　the　balloon；　rising　into　upper　levels；　may　be　borne　away　on　currents　which　may　be　of　almost　any　direction；　and　of　which　the　observer　below　may　know　nothing。　　As　to　the　actual　divergence　from　the　wind's　direction　which　a　trail　rope　and　side　sail　might　be　hoped　to　effect；　it　may　be　confidently　stated　that；　notwithstanding　some　wonderful　accounts　that　have　gone　abroad；　it　must　not　be　relied　on　as　commonly　amounting　to　much　more　than　one　or；　at　the　most；　two　points。

Although　it　is　to　be　feared　that　trustworthy　information　as　to　the　ultimate　destination　of　Andree's　balloon　may　never　be　gained；　yet　we　may　safely　state　that　his　ever　famous；　though　regrettable；　voyage　was　the　longest　in　duration　ever　attained。　　At　the　end　of　48　hours　his　vessel　would　seem　to　have　been　still　well　up　and　going　strong。　　The　only　other　previous　voyage　that　had　in　duration　of　travel　approached　this　record　was　that　made　by　M。　　Mallet；　in　1892；　and　maintained　for　36　hours。　　Next　we　may　mention　that　of　M。　Herve；　in　1886；　occupying　24　1/2　hours；　which　feat；　however；　was　almost　equal　led　by　the　great　Leipzig　balloon　in　1897；　which；　with　eight　people　in　the　car；　remained　up　for　24　1/4　hours；　and　did　not　touch　earth　till　1；032　miles　had　been　traversed。

The　fabric　of　Andree's　balloon　may　not　be　considered　to　have　been　the　best　for　such　an　exceptional　purpose。　　Dismissing　considerations　of　cost；　goldbeaters'　skin　would　doubtless　have　been　more　suitable。　　The　military　balloons　at　Aldershot　are　made　of　this；　and　one　such　balloon　has　been　known　to　remain　inflated　for　three　months　with　very　little　loss。　　It　is　conceivable；　therefore；　that　the　chances　of　the　voyagers；　whose　ultimate　safety　depended　so　largely　upon　the　staying　power　of　their　aerial　vessel；　might　have　been　considerably　increased。

One　other　expedient；　wholly　impracticable；　but　often　seriously　discussed；　may　be　briefly　referred　to；　namely；　the　idea　of　taking　up　apparatus　for　pumping　gas　into　metal　receivers　as　the　voyage　proceeds；　in　order　to　raise　or　lower　a　balloon；　and　in　this　way　to　prolong　its　life。　　Mr。　Wenham　has　investigated　the　point　with　his　usual　painstaking　care；　and　reduced　its　absurdity　to　a　simple　calculation；　which　should　serve　to　banish　for　good　such　a　mere　extravagant　theory。

Suppose；　he　says；　the　gas　were　compressed　to　one…twentieth　part　of　its　bulk；　which　would　mean　a　pressure　within　its　receiver　of　300　lbs。　per　square　inch；　and　that　each　receiver　had　a　capacity　of　1　cubic　foot；　while　for　safety　sake　it　was　made　of　steel　plates　one…twentieth　of　an　inch　thick；　then　each　receiver　would　weigh　10　lbs。；　and　to　liberate　1；000　feet　clearly　a　weight　of　500　lbs。　would　have　to　be　taken　up。　　Now；　when　it　is　considered　that　1；000　cubic　feet　of　hydrogen　will　only　lift　72　lbs。；　the　scheme　begins　to　look　hope　less　enough。　　But　when　the　question　of　the　pumping　apparatus；　to　be　worked　by　hand；　is　contemplated　the　difficulties　introduced　become　yet　more　insuperable。　　The　only　feasible　suggestion　with　respect　the　use　of　compressed　gas　is　that　of　taking　on　board　charged　cylinders　under　high　pressure；　which；　after　being　discharged　to　supply　the　leakage　of　the　balloon　could；　in　an　uninhabited　country；　be　cast　out　as　ballast　last。　　It　will　need　no　pointing　out；　however；　that　such　an　idea　would　be　practically　as　futile　as　another　which　has　gravely　been　recommended；　namely；　that　of　heating　the　gas　of　the　balloon　by　a　Davy　lamp；　so　as　to　increase　its　buoyancy　at　will。　　Major　Baden…Powell　has　aptly　described　this　as　resembling　〃an　attempt　to　warm　a　large　hall　with　a　small　spirit　lamp。'

In　any　future　attempt　to　reach　the　Pole　by　balloon　it　is　not　unreasonable　to　suppose　that　wireless　telegraphy　will　be　put　in　practice　to　maintain　communication　with　the　base。　　The　writer's　personal　experience　of　the　possibilities　afforded　by　this　mode　of　communication；　yet　in　its　infancy；　will　be　given。



CHAPTER　XXV。　　THE　MODERN　AIRSHIPIN　SEARCH　OF　THE　LEONIDS。


In　the　autumn　of　1898　the　aeronautical　world　was　interested　to　hear　that　a　young　Brazilian；　M。　Santos　Dumont；　had　completed　a　somewhat　novel　dirigible　balloon；　cylindrical　in　shape；　with　conical　ends；　83　feet　long　by　12　feet　in　diameter；　holding　6；500　cubic　feet　of　gas；　and　having　a　small　compensating　balloon　of　880　cubic　feet　capacity。　　For　a　net　was　substituted　a　simple　contrivance；　consisting　of　two　side　pockets；　running　the　length　of　the　balloon；　and　containing　battens　of　wood；　to　which　were　affixed　the　suspension　cords；　bands　being　also　sewn　over　the　upper　part　of　the　balloon　connecting　the　two　pockets。　　The　most　important　novelty；　however；　was　the　introduction　of　a　small　petroleum　motor　similar　to　those　used　for　motor　tricycles。

The　inventor　ascended　in　this　balloon；　inflated　with　pure　hydrogen；　from　the　Jardin　d'Acclimatation；　Paris；　and　circled　several　times　round　the　large　captive　balloon　in　the　Gardens；　after　which；　moving　towards　the　Bois　de　Boulogne；　he　made　several　sweeps　of　100　yards　radius。　　Then　the　pump　of　the　compensator　caused　the　engine　to　stop；　and　the　machine；　partially　collapsing；　fell　to　the　ground。　　Santos　Dumont　was　somewhat　shaken；　but　announced　his　intention　of　making　other　trials。　　In　this　bold　and　successful　attempt　there　was　clear　indication　of　a　fresh　phase　in　the　construction　of　the　airship；　consisting　in　the　happy　adoption　of　the　modern　type　of　petroleum　motor。　　Two　other　hying　machines　were　heard　of　about　this　date；　one　by　Professor　Giampietre；　of　Pavia；　cigar…shaped；　driven　by　screws；　and　rigged　with　masts　and　sails。　　The　other；　which　had　been　constructed　and　tested　in　strict　privacy；　was　the　invention　of　a　French　engineer；　M。　Ader；　and　was　imagined　to　imitate　the　essential　structure　of　a　bird。　　Two　steam　motors　of　20…horse　power　supplied　the　power。　　It　was　started　by　being　run　on　the　ground　on　small　wheels　attached　to　it；　and　it　was　claimed　that　before　a　breakdown　occurred　the　machine　had　actually　raised　itself　into　the　air。

Of　Santos　Dumont　the　world　was　presently　to　know　more；　and　the　same　must　be　said　of　another　inventor；　Dr。　Barton；　of　Beckenham；　who　shortly　completed　an　airship　model　carrying　aeroplanes　and　operated　by　clockwork。　　In　an　early　experiment　this　model　travelled　four　miles　in　twenty…three　minutes。

But　another　airship；　a　true　leviathan；　had　been　growing　into　stately　and　graceful　proportions　on　the　shores　of　the　Bodenzee　in　Wurtemberg；　and　was　already　on　the　eve　of　completion。　　Count　Zeppelin；　a　lieut。…general　in　the　German　Army；　who　had　seen　service　in　the　Franco…German　War；　had　for　some　years　devoted　his　fortune　and　energy　to　the　practical　study　of　aerial　navigation；　and　had　prosecuted　experiments　on　a　large　scale。　　Eventually；　having　formed　a　company　with　a　large　capital；　he　was　enabled　to　construct　an　airship　which　in　size　has　been　compared　to　a　British　man…of…war。　　Cigar…shaped；　its　length　was　no　less　than　420　feet；　and　diameter　40　feet；　while　its　weight　amounted　to　no　more　than　7；250　lbs。　　The　framework；　which　for　lightness　had　been　made　of　aluminium；　was；　with　the　object　of　preventing　all　the　gas　collecting　at　one　end　of　its　elongated　form；　subdivided　into　seventeen　compartments；　each　of　these　compartments　containing　a　completely　fitted　gas　balloon；　made　of　oiled　cotton　and　marvellously　gas　tight。　　A　steering　apparatus　was　placed　both　fore　and　aft；　and　at　a　safe　distance　below　the　main　structure　were　fixed；　also　forward　and　aft；　on　aluminium　platforms；　two　Daimler　motor　engines　of　16…horse　power；　working　aluminium　propellers　of　four　blades　at　the　rate　of　1；000　revolutions　a　minute。　　Finally；　firmly　attached　to　the　inner　framework　by　rods　of　aluminium；　were　two　cars　of　the　same　metal；　furnished　with　buffer　springs　to　break　the　force　of　a　fall。　　The　trial　trip　was　not　made　till　the　summer　followingJune；　1900and；　in　the　meanwhile；　experiments　had　gone　forward　with　another　mode　of　flight；　terminating；　unhappily；　in　the　death　of　one　of　the　most　expert　and　ingenious　of　mechanical　aeronauts。

Mr。　Percy　S。　　Pilcher；　now　thirty…three　years　of　age；　having　received　his　early　training　in　the　Navy；　retired　from　the　Service　to　become　a　civil　engineer；　and　had　been　for　some　time　a　partner　in　the　firm　of　Wilson　and　Pilcher。　　For　four　or　five　years　he　had　been　experimenting　in　soaring　flight；　using　a　Lilienthal　machine；　which　he　improved　to　suit　his　own　methods。　　Among　these　was　the　device　of　rising　off　the　ground　by　being　rapidly　towed　by　a　line　against　the　wind。

At　the　end　of　September　he　gave　an　exhibition　at　Stamford　Park　before　Lord　Bray　and　a　select　party　of　friendsthis　in　spite　of　an　unsuitable　afternoon　of　unsteady　wind　and　occasional　showers。　　A　long　towing　line　was　provided；　which；　being　passed　round　pulley　blocks　and　dragged　by　a　couple　of　horses；　was　capable　of　being　hauled　in　at　high　speed。　　The　first　trial；　though　ending　in　an　accident；　was　eminently　satisfactory。　　The　apparatus；　running　against　the　wind；　had　risen　some　distance；　when　the　line　broke；　yet　the　inventor　descended　slowly　and　safely　with　outstretched　wings。　　The　next　trial　also　commenced　well；　with　an　easy　rise　to　a　height　of　some　thirty　feet。　　At　that　point；　however；　the　tail　broke　with　a　snap；　and　the　machine；　pitching　over；　fell　a　complete　wreck。　　Mr。　Pilcher　was　found　insensible；　with　his　thigh　broken；　and　though　no　other　serious　injury　was　apparent；　he　succumbed　two　days　afterwards　without　recovering　consciousness。　　It　was　surmised　that　shrinkage　of　the　canvas　of　the　tail；　through　getting　wet；　had　strained　and　broken　its　bamboo　stretcher。

This　autumn　died　Gaston　Tissandier；　at　the　age　of　fifty…six；　and　in　the　month　of　December；　at　a　ripe　old　age；　while　still　in　full　possession　of　intellectual　vigour；　Mr。　Coxwell　somewhat　suddenly　passed　away。　　Always　keenly　interested　in　the　progress　of　aeronautics；　he　had　but　recently；　in　a　letter　to　the　Standard；　proposed　a　well…considered　and　practical　method　of　employing　Montgolfier　reconnoitring　balloons；　portable；　readily　inflated；