“Thenextpointtoberegardedwasamatteroffargreaterimportance。Fromindicationsaffordedbythebarometer，wefindthat，inascensionsfromthesurfaceoftheearthwehave，attheheightof1，000feet，leftbelowusaboutone-thirtiethoftheentiremassofatmosphericair，thatat10，600wehaveascendedthroughnearlyone-third；andthatat18，000，whichisnotfarfromtheelevationofCotopaxi，wehavesurmountedone-halfthematerial，or，atallevents，one-halftheponderable，bodyofairincumbentuponourglobe。Itisalsocalculatedthatatanaltitudenotexceedingthehundredthpartoftheearth’sdiameterthatis，notexceedingeightymilestherarefactionwouldbesoexcessivethatanimallifecouldinnomannerbesustained，and，moreover，thatthemostdelicatemeanswepossessofascertainingthepresenceoftheatmospherewouldbeinadequatetoassureusofitsexistence。ButI
　　didnotfailtoperceivethattheselattercalculationsarefoundedaltogetheronourexperimentalknowledgeofthepropertiesofair，andthemechanicallawsregulatingitsdilationandcompression，inwhatmaybecalled，comparativelyspeaking，theimmediatevicinityoftheearthitself；and，atthesametime，itistakenforgrantedthatanimallifeisandmustbeessentiallyincapableofmodificationatanygivenunattainabledistancefromthesurface。Now，allsuchreasoningandfromsuchdatamust，ofcourse，besimplyanalogical。
　　Thegreatestheighteverreachedbymanwasthatof25，000feet，attainedintheaeronauticexpeditionofMessieursGay-LussacandBiot。Thisisamoderatealtitude，evenwhencomparedwiththeeightymilesinquestion；andIcouldnothelpthinkingthatthesubjectadmittedroomfordoubtandgreatlatitudeforspeculation。
　　“But，inpointoffact，anascensionbeingmadetoanygivenaltitude，theponderablequantityofairsurmountedinanyfartherascensionisbynomeansinproportiontotheadditionalheightascendedasmaybeplainlyseenfromwhathasbeenstatedbefore，butinaratioconstantlydecreasing。Itisthereforeevidentthat，ascendashighaswemay，wecannot，literallyspeaking，arriveatalimitbeyondwhichnoatmosphereistobefound。Itmustexist，I
　　argued；althoughitmayexistinastateofinfiniterarefaction。
　　“Ontheotherhand，Iwasawarethatargumentshavenotbeenwantingtoprovetheexistenceofarealanddefinitelimittotheatmosphere，beyondwhichthereisabsolutelynoairwhatsoever。Butacircumstancewhichhasbeenleftoutofviewbythosewhocontendforsuchalimitseemedtome，althoughnopositiverefutationoftheircreed，stillapointworthyveryseriousinvestigation。OncomparingtheintervalsbetweenthesuccessivearrivalsofEncke’scometatitsperihelion，aftergivingcredit，inthemostexactmanner，forallthedisturbancesduetotheattractionsoftheplanets，itappearsthattheperiodsaregraduallydiminishing；thatistosay，themajoraxisofthecomet’sellipseisgrowingshorter，inaslowbutperfectlyregulardecrease。Now，thisispreciselywhatoughttobethecase，ifwesupposearesistanceexperiencedfromthecometfromanextremelyrareetherealmediumpervadingtheregionsofitsorbit。
　　Foritisevidentthatsuchamediummust，inretardingthecomet’svelocity，increaseitscentripetal，byweakeningitscentrifugalforce。Inotherwords，thesun’sattractionwouldbeconstantlyattaininggreaterpower，andthecometwouldbedrawnnearerateveryrevolution。Indeed，thereisnootherwayofaccountingforthevariationinquestion。Butagain。Therealdiameterofthesamecomet’snebulosityisobservedtocontractrapidlyasitapproachesthesun，anddilatewithequalrapidityinitsdeparturetowardsitsaphelion。WasInotjustifiableinsupposingwithM。Valz，thatthisapparentcondensationofvolumehasitsorigininthecompressionofthesameetherealmediumIhavespokenofbefore，andwhichisonlydenserinproportiontoitssolarvicinity？Thelenticular-shapedphenomenon，alsocalledthezodiacallight，wasamatterworthyofattention。Thisradiance，soapparentinthetropics，andwhichcannotbemistakenforanymeteoriclustre，extendsfromthehorizonobliquelyupward，andfollowsgenerallythedirectionofthesun’sequator。Itappearedtomeevidentlyinthenatureofarareatmosphereextendingfromthesunoutward，beyondtheorbitofVenusatleast，andIbelievedindefinitelyfarther。{*2}Indeed，thismediumIcouldnotsupposeconfinedtothepathofthecomet’sellipse，ortotheimmediateneighborhoodofthesun。Itwaseasy，onthecontrary，toimagineitpervadingtheentireregionsofourplanetarysystem，condensedintowhatwecallatmosphereattheplanetsthemselves，andperhapsatsomeofthemmodifiedbyconsiderations，sotospeak，purelygeological。
　　Havingadoptedthisviewofthesubject，Ihadlittlefurtherhesitation。GrantingthatonmypassageIshouldmeetwithatmosphereessentiallythesameasatthesurfaceoftheearth，Iconceivedthat，bymeansoftheveryingeniousapparatusofM。Grimm，Ishouldreadilybeenabledtocondenseitinsufficientquantityforthepurposesofrespiration。Thiswouldremovethechiefobstacleinajourneytothemoon。Ihadindeedspentsomemoneyandgreatlaborinadaptingtheapparatustotheobjectintended，andconfidentlylookedforwardtoitssuccessfulapplication，ifIcouldmanagetocompletethevoyagewithinanyreasonableperiod。Thisbringsmebacktotherateatwhichitmightbepossibletotravel。
　　“Itistruethatballoons，inthefirststageoftheirascensionsfromtheearth，areknowntorisewithavelocitycomparativelymoderate。Now，thepowerofelevationliesaltogetherinthesuperiorlightnessofthegasintheballooncomparedwiththeatmosphericair；and，atfirstsight，itdoesnotappearprobablethat，astheballoonacquiresaltitude，andconsequentlyarrivessuccessivelyinatmosphericstrataofdensitiesrapidlydiminishingIsay，itdoesnotappearatallreasonablethat，inthisitsprogressupwards，theoriginalvelocityshouldbeaccelerated。Ontheotherhand，Iwasnotawarethat，inanyrecordedascension，adiminutionwasapparentintheabsoluterateofascent；althoughsuchshouldhavebeenthecase，ifonaccountofnothingelse，onaccountoftheescapeofgasthroughballoonsill-constructed，andvarnishedwithnobettermaterialthantheordinaryvarnish。Itseemed，therefore，thattheeffectofsuchescapewasonlysufficienttocounterbalancetheeffectofsomeacceleratingpower。Inowconsideredthat，providedinmypassageIfoundthemediumIhadimagined，andprovidedthatitshouldprovetobeactuallyandessentiallywhatwedenominateatmosphericair，itcouldmakecomparativelylittledifferenceatwhatextremestateofrarefactionIshoulddiscoveritthatistosay，inregardtomypowerofascendingforthegasintheballoonwouldnotonlybeitselfsubjecttorarefactionpartiallysimilarinproportiontotheoccurrenceofwhich，Icouldsufferanescapeofsomuchaswouldberequisitetopreventexplosion，but，beingwhatitwas，would，atallevents，continuespecificallylighterthananycompoundwhateverofmerenitrogenandoxygen。Inthemeantime，theforceofgravitationwouldbeconstantlydiminishing，inproportiontothesquaresofthedistances，andthus，withavelocityprodigiouslyaccelerating，Ishouldatlengtharriveinthosedistantregionswheretheforceoftheearth’sattractionwouldbesupersededbythatofthemoon。Inaccordancewiththeseideas，Ididnotthinkitworthwhiletoencumbermyselfwithmoreprovisionsthanwouldbesufficientforaperiodoffortydays。
　　“Therewasstill，however，anotherdifficulty，whichoccasionedmesomelittledisquietude。Ithasbeenobserved，that，inballoonascensionstoanyconsiderableheight，besidesthepainattendingrespiration，greatuneasinessisexperiencedabouttheheadandbody，oftenaccompaniedwithbleedingatthenose，andothersymptomsofanalarmingkind，andgrowingmoreandmoreinconvenientinproportiontothealtitudeattained。{*3}Thiswasareflectionofanaturesomewhatstartling。Wasitnotprobablethatthesesymptomswouldincreaseindefinitely，oratleastuntilterminatedbydeathitself？
　　Ifinallythoughtnot。Theiroriginwastobelookedforintheprogressiveremovalofthecustomaryatmosphericpressureuponthesurfaceofthebody，andconsequentdistentionofthesuperficialblood-vesselsnotinanypositivedisorganizationoftheanimalsystem，asinthecaseofdifficultyinbreathing，wheretheatmosphericdensityischemicallyinsufficientfortheduerenovationofbloodinaventricleoftheheart。Unlessfordefaultofthisrenovation，Icouldseenoreason，therefore，whylifecouldnotbesustainedeveninavacuum；fortheexpansionandcompressionofchest，commonlycalledbreathing，isactionpurelymuscular，andthecause，nottheeffect，ofrespiration。Inaword，Iconceivedthat，asthebodyshouldbecomehabituatedtothewantofatmosphericpressure，thesensationsofpainwouldgraduallydiminishandtoendurethemwhiletheycontinued，Ireliedwithconfidenceupontheironhardihoodofmyconstitution。
　　“Thus，mayitpleaseyourExcellencies，Ihavedetailedsome，thoughbynomeansall，theconsiderationswhichledmetoformtheprojectofalunarvoyage。Ishallnowproceedtolaybeforeyoutheresultofanattemptsoapparentlyaudaciousinconception，and，atallevents，soutterlyunparalleledintheannalsofmankind。
　　“Havingattainedthealtitudebeforementioned，thatistosaythreemilesandthree-quarters，Ithrewoutfromthecaraquantityoffeathers，andfoundthatIstillascendedwithsufficientrapidity；
　　therewas，therefore，nonecessityfordischarginganyballast。Iwasgladofthis，forIwishedtoretainwithmeasmuchweightasI
　　couldcarry，forreasonswhichwillbeexplainedinthesequel。Iasyetsufferednobodilyinconvenience，breathingwithgreatfreedom，andfeelingnopainwhateverinthehead。Thecatwaslyingverydemurelyuponmycoat，whichIhadtakenoff，andeyeingthepigeonswithanairofnonchalance。Theselatterbeingtiedbytheleg，topreventtheirescape，werebusilyemployedinpickingupsomegrainsofricescatteredfortheminthebottomofthecar。
　　“Attwentyminutespastsixo’clock，thebarometershowedanelevationof26，400feet，orfivemilestoafraction。Theprospectseemedunbounded。Indeed，itisveryeasilycalculatedbymeansofsphericalgeometry，whatagreatextentoftheearth’sareaIbeheld。
　　Theconvexsurfaceofanysegmentofasphereis，totheentiresurfaceofthesphereitself，astheversedsineofthesegmenttothediameterofthesphere。Now，inmycase，theversedsinethatistosay，thethicknessofthesegmentbeneathmewasaboutequaltomyelevation，ortheelevationofthepointofsightabovethesurface。“Asfivemiles，then，toeightthousand。”wouldexpresstheproportionoftheearth’sareaseenbyme。Inotherwords，Ibeheldasmuchasasixteen-hundredthpartofthewholesurfaceoftheglobe。Theseaappearedunruffledasamirror，although，bymeansofthespy-glass，Icouldperceiveittobeinastateofviolentagitation。Theshipwasnolongervisible，havingdriftedaway，apparentlytotheeastward。Inowbegantoexperience，atintervals，severepaininthehead，especiallyabouttheearsstill，however，breathingwithtolerablefreedom。Thecatandpigeonsseemedtosuffernoinconveniencewhatsoever。
　　“Attwentyminutesbeforeseven，theballoonenteredalongseriesofdensecloud，whichputmetogreattrouble，bydamagingmycondensingapparatusandwettingmetotheskin。Thiswas，tobesure，asingularrecontre，forIhadnotbelieveditpossiblethatacloudofthisnaturecouldbesustainedatsogreatanelevation。Ithoughtitbest，however，tothrowouttwofive-poundpiecesofballast，reservingstillaweightofonehundredandsixty-fivepounds。Uponsodoing，Isoonroseabovethedifficulty，andperceivedimmediately，thatIhadobtainedagreatincreaseinmyrateofascent。Inafewsecondsaftermyleavingthecloud，aflashofvividlightningshotfromoneendofittotheother，andcausedittokindleup，throughoutitsvastextent，likeamassofignitedandglowingcharcoal。This，itmustberemembered，wasinthebroadlightofday。Nofancymaypicturethesublimitywhichmighthavebeenexhibitedbyasimilarphenomenontakingplaceamidthedarknessofthenight。Hellitselfmighthavebeenfoundafittingimage。Evenasitwas，myhairstoodonend，whileIgazedafardownwithintheyawningabysses，lettingimaginationdescend，asitwere，andstalkaboutinthestrangevaultedhalls，andruddygulfs，andredghastlychasmsofthehideousandunfathomablefire。Ihadindeedmadeanarrowescape。Hadtheballoonremainedaveryshortwhilelongerwithinthecloudthatistosayhadnottheinconvenienceofgettingwet，determinedmetodischargetheballast，inevitableruinwouldhavebeentheconsequence。Suchperils，althoughlittleconsidered，areperhapsthegreatestwhichmustbeencounteredinballoons。Ihadbythistime，however，attainedtoogreatanelevationtobeanylongeruneasyonthishead。