But\"notsoincomprehensible，afterall，\"willbetheverdictofallwhocomparetheabovenarrativewiththeascentsgiveninaforegoingaccountofhowWisehadfaredmorethanoncewhenhisballoonhadburst。For，aswillbereadilyguessed，theballoonhadinthiscasealsoburst，owingtothereleaseoftheuppervalvebeingdelayedtoolong，andtheballoonhadinthenaturalwaytransformeditselfintoatrueparachute。
Moreover，thefall，which，byAlbertSmith’sownshowing，wasthatofaboutamileintwominutes，wasnotmoreexcessivethanonewhichwillpresentlyberecordedofMr。Glaisher，whoescapedwithnomaterialinjurybeyondafewbruises。
Onefacthastillnowbeenomittedwithregardtotheabovesensationalvoyage，namely，thenameofthepassengerwho，sittinginthering，wasthefirsttopointouttheimminentdangeroftheballoon。ThisindividualwasnoneotherthanMr。
HenryCoxwell，thesecond，indeed，ofthetwowhowerementionedintheopeningparagraphofthischapterasmarkingtheroadofprogresswhichitisthescopeofthesepagestotrace，andtowhomwemustnowformallyintroduceourreaders。
Thisjustlyfamousskypilot，whosepracticalacquaintancewithballooningextendsovermorethanfortyyears，wasthesonofanavalofficerresidingnearChatham，andinhisautobiographyhedescribesenthusiasticallyhow，aladofnineyearsold，hewatchedthroughaseatelescopeaballoon，pilotedbyCharlesGreen，ascendfromRochesterand，crossingtheThames，disappearindistanceovertheEssexflats。Hegoesontodescribehowtheincidentstartedhiminthoseearlydaysonboyishendeavourstoconstructfireballoonsandpaperparachutes。Someyearslaterhishome，onthedeathofhisfather，beingtransferredtoEltham，hecamewithinfrequentviewofsuchballoonsas，startingfromtheneighbourhoodofLondon，willthroughthesummerdriftwiththeprevailingwindsoverthatpartofKent。Anditwasherethat，erelong，hecameinatthedeathofanotherballoonofwhichGreenwasincharge。
Andfromthistimeonwardstheschoolboywiththestrangehobbywasconstantlyabletowitnesstheflightsandeventheinflationsofthoseshipsoftheair，which，hisfamilyassociationsnotwithstandingtookprecedenceofallboyishdiversions。
Hiselderbrother，nowanavalofficer，entirelyfailedtodiverthisaspirationsintootherchannels，anditwaswhentheboyhadcompletedsixteensummersthatanaeronauticenterpriseattractednotonlyhisown，butpublicattentionalso。ItwasthebuildingofamammothballoonatVauxhallunderthesuperintendenceofMr。Green。ThelaunchingofthishugecraftwhencompletedwasregardedassogreatanoccasionthattheyoungCoxwell，whohadbythistimeobtainedacommercialopeningabroad，wasallowed，athisearnestentreaty，tostaytilltheeventhadcomeoff，andfiftyyearsafterthehardenedskysailorisfounddescribingwithaboyishenthusiasmhowthirty—sixpolicemenwereneededroundthatballoon;howenormousweightswereattachedtothecordage，onlytobeliftedfeetabovetheground;whilethepolicewerecompelledtopasstheirstavesthroughthemeshestopreventthecordscuttingtheirhands。AtthisascentMr。Hollondwasapassenger，andbythemiddleofthefollowingNovemberallEuropewasringingwiththegreatNassauventure。
CommercialbusinessdidnotsuittheyoungCoxwell，andattheageofone—and—twentywefindhimtryinghishandattheprofessionofsurgeon—dentist，not，however，withanyprospectofitskeepinghimfromthelongingofhissoul，whichgrewstrongerandstrongeruponhim。Itwasnottillthesummerof1844thatMr。Hampton，givinganexhibitionfromtheWhiteConduitGardens，Pentonville，offeredtheyoungman，thentwenty—fiveyearsold，hisfirstascent。
InafteryearsCoxwellreferredtohisfirstsensationsincharacteristiclanguage，contrastingthemwiththeexperiencesofthemountaineer。\"InAlpinetravels，\"hesays，\"theprocessissoslow，andcontactwiththecrustoftheearthsopalpable，thatthetravellerisgraduallypreparedforeachsuccessivephaseofviewasitpresentsitself。Butintheballoonsurvey，cities，villages，andvasttractsforobservationspringalmostmagicallybeforetheeye，andchangeinaspectandsizesopleasinglythatbewildermentfirstandthenunboundedadmirationissuretofollow。\"
Theicewasnowfairlybroken，and，notsufferingprofessionaldutiestobeanyhindrance，Coxwellbegantomakeaseriesofascentsundertheleadershipoftworivalballoonists，GaleandGypson。Onevoyagemadewiththelatterhedescribesasleadingtothemostperilousdescentintheannalsofaerostation。Thiswastheoccasion，givenabove，onwhichAlbertSmithwasapassenger，andwhichthattalentedwriterdescribesinhisownfashion。Hedoesnot，however，addthefact，worthyofbeingchronicled，thatexactlyaweekaftertheappallingadventureGypsonandCoxwell，accompaniedbyaCaptainwhosenamedoesnottranspire，andloadedwithtwicethepreviousweightoffireworks，madeaperfectlysuccessfulnightascentanddescentinthesameballoon。
ItisveryshortlyafterthisthatwefindCoxwellseducedintoundertakingforitsownerstheactualmanagementofaballoon，thepropertyofGale，andnowtobeknownasthe\"Sylph。\"Withthiscrafthepracticallybeganhiscareerasaprofessionalballoonist，andafterafewpreliminaryascentsmadeinEngland，wastoldofftocarryonengagementsinBelgium。
AlongseriesofascentswasnowmadeontheContinent，andinthetroubledstateofaffairssomestirringsceneswerevisited，notwithoutsomerealadventure。OneoccasionattendedwithimminentriskoccurredatBerlinin1851。
CoxwellrelatesthataPrussianlabourerwhomhehaddismissedforbadconduct，andwhoalmosttoomanifestlyharbouredrevenge，neverthelessbeggedhardforare—engagement，which，asthemanwasahandyfellow，Coxwellatlengthassentedto。
Hetookupthreepassengersbesidehimself，andatanelevationofsome3，000feetfounditnecessarytoopenthevalve，when，onpullingthecord，oneofthetopshuttersbrokeandremainedopen，leavingafreeapertureof26inchesby12inches，andoccasioningsuchacopiousdischargeofgasthatnothingshortofaprovidentiallandingcouldsavedisaster。Buttheprovidentiallandingcame，thepartyfallingintotheembraceofafruittreeinanorchard。Ittranspiredafterwardsthatthelabourerhadbeenseentotamperwiththevalve，theconnectinglinesofwhichhehadpartiallysevered。
ReturningtoEnglandin1852Coxwell，throughtheaccidentsinseparablefromhisprofession，foundhimselfvirtuallyinpossessionofthefield。Green，nowadvancedinyears，wasretiringfromthepubliclifeinwhichhehadwonsomuchfameandhonour。Galewasdead，killedinanascentatBordeaux。
Onlyoneaspirantcontestedtheplaceofpublicaeronaut——oneGoulston，whohadbeenGale’spatron。Beforemanymonths，however，hetoometwithaballoonist’sdeath，beingdashedagainstsomestonewallswhenascendingnearManchester。
ItwillnotbedifficulttoformanestimateofhowentirelythepopularityoftheballoonwasnowreestablishedinEngland，fromthemerefactthatbeforetheexpirationoftheyearCoxwellhadbeencalledupontomakethirty—sixvoyages。SomeofthesewerefromGlasgow，andhereacertaincoincidencetookplacewhichistoocurioustobeomitted。AdescenteffectednearMilngavietookplaceinthesamefieldinwhichSadler，twenty—nineyearsbefore，hadalsodescended，andthesamemanwhocaughttheropeofMr。Sadler’sballoonperformedthesameserviceonceagainforafreshvisitorfromtheskies。
ThefollowingautumnCoxwell，infulfillingoneoutofmanyengagements，foundhimselfinadilemmawhichboreresemblanceinaslightdegreetoafarmoreseriouspredicamentinwhichthewriterbecameinvolved，andwhichmustbetoldindueplace。Thepreparationsfortheascent，whichwasfromtheMileEndRoad，hadbeenhurried，andafterfinallygettingawayatalatehourintheevening，itwasfoundthatthevalvelinehadgotcaughtinafoldofthesilk，andcouldnotbeoperated。Inconsequence，theballoonwas，ofnecessity，lefttotakeitsownchancethroughthenight，and，afterrisingtoaconsiderableheight，itslowlylostbuoyancyduringthechillyhours，and，graduallysettling，cametoearthnearBasingstoke，wherethevoyager，failingtogethelporshelter，madehisbedwithinhisowncar，lyinginanopenfield，asotheraeronautshavehadtodoinlikecircumstances。
Coxwelltellsofastrikingphenomenonseenduringthatvoyage。
\"Asplendidmeteorwasbelowthecar，andapparentlyabout600
feetdistant。Itwasblueandyellow，movingrapidlyinaN。E。
direction，andbecameextinguishedwithoutnoiseorsparks。\"
CHAPTERXI。THEBALLOONINTHESERVICEOFSCIENCE。
Atthispointwemust，forabriefwhile，dropthehistoryofthefamousaeronautwhoseearlycareerwehavebeenbrieflysketchinginthelastchapter，andturnourattentiontoanewfeatureofEnglishballooning。Wehave，atlast，torecordsomegenuinelyscientificascents，whichourcountrynow，alltootardily，instituted。ItwastheBritishAssociationthattooktheinitiative，andthetwomentheychosefortheirpurposewerebothexceptionallyqualifiedforthetasktheyhadinhand。ThepracticalballoonistwasnoneotherthantheveteranCharlesGreen，nowinhissixty—seventhyear，butdestinedyettoenjoynearlytwentyyearsmoreoflife。ThescientificexpertwasMr。JohnWelsh，wellfittedfortheprojectedworkbylongtrainingatKewObservatory。Theballoonwhichtheyusedisitselfworthyofmention，beingthegreatNassauBalloonofoldenfame。
Welshwasquicktorealisemoreclearlythananyformerexperimentalistthatonaccountoftheabsenceofbreezeinafreeballoon，asalsoonaccountofgreatsolarradiation，theindicationsofthermometerswould，withoutspecialprecautions，befalsified。Hethereforeinventedaformofaspiratingthermometer，theearliesttobemetwith，andfarinadvanceofanythatweresubsequentlyusedbyotherscientists。Itconsistedofapolishedtube，inwhichthermometerswereenclosed，andthroughwhichastreamofairwasforcedbybellows。
Thedifficultyofobtainingreallyaccuratereadingswherethermometersarebeingquicklytransportedthroughvaryingtemperaturesisgenerallynotdulyappreciated。Inthecaseofinstrumentscarriedmaballoonitshouldberememberedthattheballoonitselfconveys，clingingaboutit，noinconsiderablequantityofair，broughtfromotherlevels，whilethetemperatureofitsownmasswillbeliabletoaffectanythermometerincloseneighbourhood。Moreover，anyordinaryformofthermometerisnecessarilysluggishinaction，asmaybereadilynoticed。If，forexample，onebecarriedfromawarmroomtoacoldpassage，orviceversaitwillbeseenthatthecolumnmovesverydeliberately，andquitealongintervalwillelapsebeforeitreachesitsfinalposition，thecausebeingthattheentireinstrument，withanystandormountingthatitmayhave，willhavetoadaptitselftothechangeoftemperaturebeforeatruerecordwillbeobtained。Thisdifficultyappliesunavoidablytoallthermometersinsomedegree，andtheskillofinstrumentmakershasbeentaxedtoreducetheerrorstoaminimum。Itisnecessary，inanycase，thataconstantstreamofsurroundingairshouldplayupontheinstrument，andthoughthisismostreadilyeffectedwheninstrumentsarecarriedaloftbykites，yeteventhusitisthoughtthatanintervalofsomeminuteshastoelapsebeforeanyformofthermometerwillfaithfullyrecordanydefinitechangeoftemperature。Itisonthisaccountthatsomeallowancemustbemadeforobservationswhichwill，indueplace，berecordedofscientificexplorers;thepointtobeborneinmindbeingthat，aswasmentionedinaformerchapter，suchobservationswillhavetoberegardedasgivingreadingswhicharesomewhattoohighinascentsandtoolowindescents。
Twoformsofthermometersatextremelysimpleconstruction，yetpossessedofgreatsensibility，willbediscussedinlaterchapters。
ThethermometersthatWelshusedwereundoubtedIyfarsuperiortoanythatweredevisedbeforehistimeanditismuchtoberegrettedthattheywereallowedtofallintodisuse。Perhapsthemostimportantstrictureontheobservationsthatwillhavetoberecordedisthattheobserverswerenotprovidedwithabasestation，onwhichaccountthevalueofresultswasimpaired。Itwasnotrealisedthatitwasnecessarytomakeobservationsonthegroundtocomparewiththosethatwerebeingmadeathighaltitudes。
Welshmade，inall，fourascentsinthesummerandautumnof1852andinhisreportheiscarefultogivethehighestpraisetohiscolleague，Green，whosecontroloverhisballoonhedescribesas\"socompletethatnonewhoaccompaniedhimcanbeotherwisethanrelievedfromallapprehension，andfreetodevoteattentioncalmlytotheworkbeforehim。\"
Thefirstascentwasmadeat3。49p。m。onAugustthe17th，underasouthwindandwithcloudscoveringsomethree—quartersofthesky。Welsh’sfirstremarksignificant，andwillbeappreciatedbyanyonewhohasattemptedobservationalworkinaballoon。Hestatesnaivelythat\"ashorttimewaslostatfirstinanattempttoputtheinstrumentsintomoreconvenientorder，andalsofromthenoveltyofthesituation。\"Thenhementionsanobservationwhich，intheexperienceofthewriter，isacommonone。Thelowestclouds，whichwereabout2，500feethighandnotneartheballoon，werepassedwithoutbeingnoticed;othercloudswerepassedatdifferentheights;and，finally，afewstar—shapedcrystalsofsnow;butthesunshonealmostconstantly。Littlevariationoccurredinthedirectionoftravel，whichaveragedthirty—eightmilesanhour，andthedescenttookplaceat5。20p。m。atSwavesey，nearCambridge。
Thesecondascenttookplaceat4。43p。m。onAugust26th，underagentleeastwindandapartiallyobscuredsky。Thecloudswereagainpassedwithoutbeingperceived。Thiswasattheheightof3，000feet，beyondwhichwasveryclearskyofdeepblue。Theaircurrentsuptothelimitsof12，000feetsetfromvaryingdirections。ThedescentoccurrednearCheshamat7。45p。m。
Thethirdascent，at2。35p。m。onOctoberthe21stwasmadeintoaskycoveredwithdensecloudmasseslyingwithin3，000
and3，700feet。Thesunwasthenseenshiningthroughcirrusfarup。Theshadowoftheballoonwasalsoseenonthecloud，fringedwithaglory，andaboutthistimetherewasseen\"stretchingforaconsiderablelengthinaserpentinecourse，overthesurfaceofthecloud，awell—definedbelt，havingtheappearanceofabroadroad。\"
Beingnowat12，000feet，Greenthoughtitprudenttoreconnoitrehisposition，and，findingtheywerenearthesea，descendedat4。20p。m。atRayleigh，inEssex。Someimportantnotesonthepolarisationofthecloudsweremade。
Thefourthandfinalvoyagewasmadeinafastwindaveragingfiftyknotsfromthenorth—east。Thinscudwasmetat1，900
feet，andanupperstratumat4，500feet，beyondwhichwasbrightsun。Themainshiftofwindtookplacejustastheuppersurfaceofthefirststratumwasreached。InthisascentWelshreachedhisgreatestelevation，22，930feet，whenbothGreenandhimselfexperiencedconsiderabledifficultyinrespirationandmuchfatigue。Theseabeingnowperceivedrapidlyapproaching，ahastydescentwasmade，andmanyoftheinstrumentswerebroken。
InsummarisinghisresultsWelshstatesthat\"thetemperatureoftheairdecreasesuniformlywithheightabovetheearth’ssurfaceuntilatacertainelevation，varyingondifferentdays，decreaseisarrested，andforthespaceof2，000or3，000
feetthetemperatureremainsnearlyconstant，orevenincreases，theregulardiminutionbeingagainresumedandgenerallymaintainedatarateslightlylessrapidthaninthelowerpartoftheatmosphere，andcommencingfromahighertemperaturethanwouldhaveexistedbutfortheinterruptionnoticed。\"Theanalysisoftheupperairshowedtheproportionofoxygenandnitrogentovaryscarcelymorethanatdifferentspotsontheearth。
AsitisnecessaryatthispointtotakeleaveoftheveteranGreenasapracticalaeronaut，wemayhererefertooneortwonoteworthyfactsandincidentsrelatingtohiseventfulcareer。
In1850M。Poitevinissaidtohaveattracted140，000peopletoParistolookatanexhibitionofhimselfascendinginaballoonseatedonhorseback，afterwhichMadamePoitevinascendedfromCremorneGardensinthesamemanner，theexhibitionbeingintendedasarepresentationof\"EuropaonaBull。\"This，however，wasdiscountenancedbytheauthoritiesandwithdrawn。Thefeatswere，inreality，merelytherepetitionsofonethathadbeenconceivedandextremelywellcarriedoutbyGreenmanyyearsbefore——aslongago，infact，as1828，whenhearrangedtomakeanascentfromtheEagleTavern，CityRoad，seatedonapony。Tocarryouthisintention，hediscardedtheordinarycar，replacingitwithasmallplatform，whichwasprovidedwithplacestoreceivethepony’sfeet;whilestrapsattachedtothehoopwerepassedundertheanimal’sbody，preventingitfromlyingdownorfrommakinganyviolentmovement。Thisthecreatureseemedinnowaydisposedtoattempt，andwhenallhadbeensuccessfullycarriedoutandaneasydescenteffectedatBeckenham，theponywasdiscoveredeatingamealofbeanswithwhichithadbeensupplied。
SeveralinterestingobservationshavebeenrecordedbyGreenondifferentoccasions，someofwhicharehighlyinstructivefromapracticalorscientificpointofview。OnanascentfromVauxhall，inwhichhewasaccompaniedbyhisfriendSpencerandMr。Rush，herecordedhow，asheconstantlyandsomewhatrapidlyrose，thewindchangeditsdirectionfromN。W。throughN。toN。E。，whileheremainedoverthemetropolis，theballoonallthewhilerotatingonitsaxis。ThiscontinualswingingorrevolvingoftheballoonGreenconsidersanaccompanimentofeitherarapidascentordescent，butitmaybequestionedwhetheritisnotmerelyaconsequenceofchangingcurrents，or，sometimes，ofaninitialspingiveninadvertentlytotheballoonatthemomentofitsbeingliberated。Thephenomenonofmarkedchangewhichhedescribesintheuppercurrentsishighlyinteresting，andtallieswithwhatthewriterhasfrequentlyexperiencedoverLondonproper。Suchhighercurrentsmaybeduetonaturalenvironment，andtoconditionsnecessarilyprevailingoversovastandvariedacity，andtheymaybeabletoplayanall—importantpartinthedispersalofLondonsmokeorfog。Thispointwillbetouchedonlater。InthisparticularvoyageGreenrecordsthatashewasrisingatthemomentwhenhisbarometerreached19inches，thethermometerhecarriedregistered46degrees，whileoncomingdown，whenthebarometeragainmarked19inches，thesamethermometerrecordedonly22degrees。Itwillnotfailtoberecognisedthatthereisdoubtlesshereanexampleoftheerrorsalludedtoabove，inseparablefromreadingstakeninascentanddescent。
AcalculationmadebyGreeninhisearlieryearshasacertainvalue。Bythetimehehadaccomplished200ascentshewasatpainstocomputethathehadtravelledacrosscountrysome6，000miles，whichhadbeentraversedin240hours。Fromthisitwouldfollowthatthemeanrateoftravelinaerialvoyageswillbeabouttwenty—fivemilesperhour。TowardstheendofhiscareerwefinditstatedbyLieutenantG。Grover，R。E。，that\"theMessrs。Green，FatherandSon，havemadebetweenthemsome930ascents，innoneofwhichhavetheymetwithanymaterialaccidentorfailure。\"Thisiswonderfultestimony，indeed，andwemayhereaddthefactthatthefathertookuphisownfather，thenattheageofeighty—three，inaballoonascentof1845，withoutanyseriousconsequences。Butitistimethatsomeaccountshouldbegivenofaparticularoccasionwhichatleastprovidedthefamousaeronautwithanadventurespicedwithnosmallamountofrisk。Itwasonthe5thofJuly，1850，thatGreenascended，withRushashiscompanion，fromVauxhall，atthesomewhatlatehourof7。50p。m。，using，asalways，thegreatNassauballoon。Therateofrisemusthavebeenveryconsiderable，andtheypresentlyrecordanaltitudeofnolessthan20，000feet，andatemperatureof12
degreesbelowfreezing。Theywerenowabovetheclouds，whereallviewofearthwaslost，and，notventuringtoremainlonginthissituation，theycommencedarapiddescent，andonemergingbelowfoundthemselvessailingdownSeaReachinthedirectionofNoreSands，whentheyobservedavessel。Theirchanceofmakinglandwas，tosaytheleast，uncertain，andGreen，consideringthathissafetylayinbespeakingthevessel’sassistance，openedthevalveandbroughtthecardowninthewatersometwomilesnorthofSheerness，thehourbeing8。45，andonlyfifty—fiveminutessincethestart。Thewindwasblowingstiffly，and，catchingthehollowofthehalf—inflatedballoon，carriedthevoyagersrapidlydowntheriver，toofast，indeed，toallowofthevessel’sovertakingthem。Thisbeingsoonapparent，Greencastouthisanchor，andnotwithoutresult，foritshortlybecameentangledinasunkenwreck，andtheballoonwaspromptly\"broughtup，\"thoughstrugglingandtossinginthebrokenwater。Aneighbouringbargeatonceputoffaboattotherescue，andotherboatsweredespatchedbyH。M。cutterFly，underCommanderGurling。GreenandRushwerespeedilyrescued，buttheballoonitselfwastoorestiveanddangerousanobjecttoapproachwithsafety。AtGreen’ssuggestion，therefore，avolleyofmusketrywasfiredintothesilk’afterwhichitbecamepossibletopassaropearounditandexpelthegas。Greensubsequentlyrelateshowittookafortnighttorestorethedamage，consistingofsixty—twobulletrentsandnineteentorngores。
Green’snamewillalwaysbefamous，ifonlyforthefactthatitwashewhofirstadoptedtheuseofcoalgasinhiscalling。
This，itwillberemembered，wasin1821，anditshouldbeborneinmindthatatthattimehouseholdgashadonlyrecentlybeenintroduced。Inpointoffact，itfirstlightedPallMallin1805，anditwasnotusedforthegenerallightingofLondontill1814。
Wearenotsurprisedtofindthatthegreataeronautatonetimeturnedhisattentiontotheconstructionofmodels，andthiswithnoinconsiderablesuccess。Amodelofhiswasexhibitedin1840atthePolytechnicInstitution，andisdescribedintheTimesasconsistingofaminiatureballoonofthreefeetdiameter，inflatedwithcoalgas。Itwasactedonbyfans，whichwereoperatedbymechanismplacedinthecar。A
seriesofthreeexperimentswasexhibited。First，theballoonbeingweightedsoastoremainpoisedinthestillairofthebuilding，themechanismwasstarted，andthemachinerosesteadilytotheceiling。Thefanswerethenreversed，whenthemodel，equallygracefully，descendedtothefloor。Lastly，theballoon，withaweightedtrailrope，beingoncemorebalancedinmid—air，thefanswereappliedlaterally，whenthemachinewouldtakeahorizontalflight，pullingthetrailropeafterit，withanattachedweightdraggingalongtheflooruntilthemechanismhadrundown，whenitagainremainedstationary。ThecorrespondentoftheTimescontinues，\"Mr。GreenstatesthatbythesesimplemeansavoyageacrosstheAtlanticmaybeperformedinthreeorfourdays，aseasilyasfromVauxhallGardenstoNassau。\"
WecanhardlyattributethisstatementseriouslytoonewhoknewaswellasdidGreenhowficklearethewinds，andhowutterlydifferentaretheconditionsbetweenthestillairofaroomandthoseoftheopensky。Hisinsightintothedifficultiesoftheproblemcannothavebeenlessthanthatofhissuccessor，Coxwell，who，astheresultofhisownequallywideexperience，statespositively，\"Icouldneverimagineamotivepowerofsufficientforcetodirectandguideaballoon，muchlesstoenableamanoramachinetofly。\"Evenwhenmoderninventionhadproducedamotivepowerundreamedofinthedayswearenowconsidering，Coxwelldeclareshisconvictionthatinherentdifficultieswouldnotbeovercome\"unlesstheairshouldinvariablyremaininacalmstate。\"
Itwouldbetediousandscarcelyinstructivetoinquireintothevariousformsofflyingmachinesthatwereelaboratedatthisperiod;butonethatwasdesignedinAmericabyMr。
Henson，andwithwhichitwasseriouslycontemplatedtoattempttocrosstheAtlantic，maybebrieflydescribed。Intheoryitwassupposedtobecapableofbeingsustainedintheairbyvirtueofthespeedmechanicallyimpartedtoit，andoftheangleatwhichitsadvancingundersurfacewouldmeettheair。
Theinventorclaimedtohaveproducedasteamengineofextremelightnessaswellasefficiency，andfortheresthismachineconsistedofahugeaero—planepropelledbyfanswithobliquevanes，whileatailsomewhatresemblingthatofabirdwasadded，asalsoarudder，thefunctionsofwhichweretodirectthecraftverticallyandhorizontallyrespectively。BeithererecordedthatthemachinedidnotcrosstheAtlantic。
Onewordastotheinstrumentsuseduptothistimefordeterminingaltitudes。Thesewere，ingeneral，ordinarymercurialbarometers，protectedinvariousways。Greenencasedhisinstrumentinasimplemetaltube，whichadmittedofthecolumnofmercurybeingeasilyread。Thisinstrument，whichisgenerallytobeseenheldinhishandinGreen’soldportraits，mightbemistakenforamariner’stelescope。ItisnowinthepossessionofthefamilyofSpencers，thegrandchildrenofhisoldaeronauticalfriendandcolleague，anditisstatedthatwithallhiscaretheglasswasnotinfrequentlybrokeninadescent。
Wise，withcharacteristicingenuity，devisedarough—and—readyheightinstrument，whichheclaimstohaveansweredwell。Itconsistedsimplyofacommonporterbottle，totheneckofwhichwasjoinedabladderofthesamecapacity。Thebottlebeingfilledwithairofthedensityofthatontheground，andthebladdertiedoninacollapsedstate，theexpansionoftheairinthebottlewouldgraduallyfillthebladderasitroseintotherarerregionsoftheatmosphere。Experiencewouldthenbetrustedtoenabletheaeronauttojudgehisheightfromtheamountofinflationnoticeableinthebladder。
CHAPTERXII。HENRYCOXWELLANDHISCONTEMPORARIES。
Mentionshouldbemadeinthesepagesofanightsailofahundredmiles，boldlycarriedoutin1849byM。Arban，whichtookthevoyagerfromMarseillestoTurinfairlyovertheAlps。
Themainsummitwasreachedat11p。m。，whenthe\"snow，cascades，andriverswereallsparklingunderthemoon，andtheravinesandrocksproducedmassesofdarknesswhichservedasshadowstothegiganticpicture。\"ArbanwasatonetimeonalevelwiththehighestpointofMontBlanc，thetopofwhich，standingoutwellabovetheclouds，resembled\"animmenseblockofcrystalsparklingwithathousandfires。\"
InLondon，intheyearoftheGreatExhibition，andwhilethebuildingwasstillstandinginHydePark，thereoccurredaballoonincidentsmallinitself，butsufficienttocausemuchsensationatthecrowdedspotwhereittookplace。TheascentwasmadefromtheHippodromebyMr。andMrs。Grahaminveryboisterousweather，and，onbeingliberated，theballoonseemstohavefouledamast，sufferingaconsiderablerent。AfterthistheaeronautssucceededinclearingthetreesinKensingtonGardens，andindescendingfairlyinthePark，but，stillatthemercyofthewinds，theywerecarriedontotheroofofahouseinArlingtonStreet，andthenceontoanotherinParkPlace，where，becominglodgedagainstastackofchimneys，theywereeventuallyrescuedbythepolicewithoutanymaterialdamagehavingbeendone。