ItisimpossibletoreflectonthechangedstateoftheAmericancontinentwithoutthedeepestastonishment。Formerlyitmusthaveswarmedwithgreatmonsters：nowwefindmerepigmies，comparedwiththeantecedent，alliedraces。IfBuffonhadknownofthegiganticslothandarmadillo-likeanimals，andofthelostPachydermata，hemighthavesaidwithagreatersemblanceoftruththatthecreativeforceinAmericahadlostitspower，ratherthanthatithadneverpossessedgreatvigour。Thegreaternumber，ifnotall，oftheseextinctquadrupedslivedatalateperiod，andwerethecontemporariesofmostoftheexistingsea-shells。Sincetheylived，noverygreatchangeintheformofthelandcanhavetakenplace。What，then，hasexterminatedsomanyspeciesandwholegenera？Themindatfirstisirresistiblyhurriedintothebeliefofsomegreatcatastrophe；butthustodestroyanimals，bothlargeandsmall，inSouthernPatagonia，inBrazil，ontheCordilleraofPeru，inNorthAmericauptoBehring’sStraits，wemustshaketheentireframeworkoftheglobe。Anexamination，moreover，ofthegeologyofLaPlataandPatagonia，leadstothebeliefthatallthefeaturesofthelandresultfromslowandgradualchanges。ItappearsfromthecharacterofthefossilsinEurope，Asia，Australia，andinNorthandSouthAmerica，thatthoseconditionswhichfavourthelifeofthe_larger_quadrupedswerelatelyco-extensivewiththeworld：whatthoseconditionswere，noonehasyetevenconjectured。Itcouldhardlyhavebeenachangeoftemperature，whichataboutthesametimedestroyedtheinhabitantsoftropical，temperate，andarcticlatitudesonbothsidesoftheglobe。InNorthAmericawepositivelyknowfromMr。Lyell，thatthelargequadrupedslivedsubsequentlytothatperiod，whenboulderswerebroughtintolatitudesatwhichicebergsnowneverarrive：fromconclusivebutindirectreasonswemayfeelsure，thatinthesouthernhemispheretheMacrauchenia，also，livedlongsubsequentlytotheice-transportingboulder-period。Didman，afterhisfirstinroadintoSouthAmerica，destroy，ashasbeensuggested，theunwieldyMegatheriumandtheotherEdentata？WemustatleastlooktosomeothercauseforthedestructionofthelittletucutucoatBahiaBlanca，andofthemanyfossilmiceandothersmallquadrupedsinBrazil。Noonewillimaginethatadrought，evenfarsevererthanthosewhichcausesuchlossesintheprovincesofLaPlata，coulddestroyeveryindividualofeveryspeciesfromSouthernPatagoniatoBehring’sStraits。Whatshallwesayoftheextinctionofthehorse？Didthoseplainsfailofpasture，whichhavesincebeenoverrunbythousandsandhundredsofthousandsofthedescendantsofthestockintroducedbytheSpaniards？Havethesubsequentlyintroducedspeciesconsumedthefoodofthegreatantecedentraces？CanwebelievethattheCapybarahastakenthefoodoftheToxodon，theGuanacooftheMacrauchenia，theexistingsmallEdentataoftheirnumerousgiganticprototypes？Certainly，nofactinthelonghistoryoftheworldissostartlingasthewideandrepeatedexterminationsofitsinhabitants。
　　Nevertheless，ifweconsiderthesubjectunderanotherpointofview，itwillappearlessperplexing。Wedonotsteadilybearinmind，howprofoundlyignorantweareoftheconditionsofexistenceofeveryanimal；nordowealwaysremember，thatsomecheckisconstantlypreventingthetoorapidincreaseofeveryorganizedbeingleftinastateofnature。Thesupplyoffood，onanaverage，remainsconstant，yetthetendencyineveryanimaltoincreasebypropagationisgeometrical；anditssurprisingeffectshavenowherebeenmoreastonishinglyshown，thaninthecaseoftheEuropeananimalsrunwildduringthelastfewcenturiesinAmerica。Everyanimalinastateofnatureregularlybreeds；yetinaspecieslongestablished，any_great_increaseinnumbersisobviouslyimpossible，andmustbecheckedbysomemeans。Weare，nevertheless，seldomablewithcertaintytotellinanygivenspecies，atwhatperiodoflife，oratwhatperiodoftheyear，orwhetheronlyatlongintervals，thecheckfalls；or，again，whatistheprecisenatureofthecheck。Henceprobablyitis，thatwefeelsolittlesurpriseatone，oftwospeciescloselyalliedinhabits，beingrareandtheotherabundantinthesamedistrict；or，again，thatoneshouldbeabundantinonedistrict，andanother，fillingthesameplaceintheeconomyofnature，shouldbeabundantinaneighbouringdistrict，differingverylittleinitsconditions。Ifaskedhowthisis，oneimmediatelyrepliesthatitisdeterminedbysomeslightdifference，inclimate，food，orthenumberofenemies：yethowrarely，ifever，wecanpointouttheprecisecauseandmannerofactionofthecheck！Wearetherefore，driventotheconclusion，thatcausesgenerallyquiteinappreciablebyus，determinewhetheragivenspeciesshallbeabundantorscantyinnumbers。
　　Inthecaseswherewecantracetheextinctionofaspeciesthroughman，eitherwhollyorinonelimiteddistrict，weknowthatitbecomesrarerandrarer，andisthenlost：itwouldbedifficulttopointoutanyjustdistinction[13]betweenaspeciesdestroyedbymanorbytheincreaseofitsnaturalenemies。Theevidenceofrarityprecedingextinction，ismorestrikinginthesuccessivetertiarystrata，asremarkedbyseveralableobservers；ithasoftenbeenfoundthatashellverycommoninatertiarystratumisnowmostrare，andhasevenlongbeenthoughtextinct。Ifthen，asappearsprobable，speciesfirstbecomerareandthenextinct——ifthetoorapidincreaseofeveryspecies，eventhemostfavoured，issteadilychecked，aswemustadmit，thoughhowandwhenitishardtosay——andifwesee，withoutthesmallestsurprise，thoughunabletoassigntheprecisereason，onespeciesabundantandanothercloselyalliedspeciesrareinthesamedistrict——whyshouldwefeelsuchgreatastonishmentattheraritybeingcarriedonestepfurthertoextinction？
　　Anactiongoingon，oneverysideofus，andyetbarelyappreciable，mightsurelybecarriedalittlefurther，withoutexcitingourobservation。WhowouldfeelanygreatsurpriseathearingthattheMagalonyxwasformerlyrarecomparedwiththeMegatherium，orthatoneofthefossilmonkeyswasfewinnumbercomparedwithoneofthenowlivingmonkeys？andyetinthiscomparativerarity，weshouldhavetheplainestevidenceoflessfavourableconditionsfortheirexistence。Toadmitthatspeciesgenerallybecomerarebeforetheybecomeextinct——tofeelnosurpriseatthecomparativerarityofonespecieswithanother，andyettocallinsomeextraordinaryagentandtomarvelgreatlywhenaspeciesceasestoexist，appearstomemuchthesameastoadmitthatsicknessintheindividualisthepreludetodeath——tofeelnosurpriseatsickness——butwhenthesickmandiestowonder，andtobelievethathediedthroughviolence。[1]Mr。Waterhousehasdrawnupadetaileddescriptionofthishead，whichIhopehewillpublishinsomeJournal。
　　Anearlysimilarabnormal，butIdonotknowwhetherhereditary，structurehasbeenobservedinthecarp，andlikewiseinthecrocodileoftheGanges：HistoiredesAnomalies，parM。Isid。GeoffroySt。Hilaire，tom。i。p。244。
　　[M。A。d’Orbignyhasgivennearlyasimilaraccountofthesedogs，tom。i。p。
　　ImustexpressmyobligationstoMr。Keane，atwhosehouseIwasstayingontheBerquelo，andtoMr。LumbatBuenosAyres，forwithouttheirassistancethesevaluableremainswouldneverhavereachedEngland。
　　Lyell’sPrinciplesofGeology，vol。iii。p。
　　Theflieswhichfrequentlyaccompanyashipforsomedaysonitspassagefromharbourtoharbour，wanderingfromthevessel，aresoonlost，andalldisappear。
　　r。Blackwall，inhisResearchesinZoology，hasmanyexcellentobservationsonthehabitsofspiders。
　　AnabstractisgiveninNo。IV。oftheMagazineofZoologyandBotany。
　　Ifoundhereaspeciesofcactus，describedbyProfessorHenslow，underthenameofOpuntiaDarwiniiMagazineofZoologyandBotany，vol。i。p。466，whichwasremarkablefortheirritabilityofthestamens，whenIinsertedeitherapieceofstickortheendofmyfingerintheflower。Thesegmentsoftheperianthalsoclosedonthepistil，butmoreslowlythanthestamens。Plantsofthisfamily，generallyconsideredastropical，occurinNorthAmericaLewisandClarke’sTravels，p。221，inthesamehighlatitudeashere，namely，inbothcases，in47degs。
　　[10]Theseinsectswerenotuncommonbeneathstones。
　　Ifoundonecannibalscorpionquietlydevouringanother。
　　[11]Shelley，LinesonMt。Blanc。
　　[12]IhavelatelyheardthatCapt。Sulivan，R。N。，hasfoundnumerousfossilbones，embeddedinregularstrata，onthebanksoftheR。Gallegos，inlat。51degs。4’。Someofthebonesarelarge；othersaresmall，andappeartohavebelongedtoanarmadillo。Thisisamostinterestingandimportantdiscovery。
　　[13]SeetheexcellentremarksonthissubjectbyMr。Lyell，inhisPrinciplesofGeology。PreviousChapterNextChapterTheVoyageoftheBeagle-Chapter9TheVoyageoftheBeaglebyCharlesDarwinPreviousChapterNextChapterChapter9-SantaCruz，Patagonia，andtheFalklandIslandsAPRIL13，1834——TheBeagleanchoredwithinthemouthoftheSantaCruz。ThisriverissituatedaboutsixtymilessouthofPortSt。Julian。
　　DuringthelastvoyageCaptainStokesproceededthirtymilesupit，butthen，fromthewantofprovisions，wasobligedtoreturn。Exceptingwhatwasdiscoveredatthattime，scarcelyanythingwasknownaboutthislargeriver。CaptainFitzRoynowdeterminedtofollowitscourseasfarastimewouldallow。Onthe18ththreewhale-boatsstarted，carryingthreeweeks’
　　provisions；andthepartyconsistedoftwenty-fivesouls——aforcewhichwouldhavebeensufficienttohavedefiedahostofIndians。Withastrongflood-tideandafinedaywemadeagoodrun，soondranksomeofthefreshwater，andwereatnightnearlyabovethetidalinfluence。
　　Theriverhereassumedasizeandappearancewhich，evenatthehighestpointweultimatelyreached，wasscarcelydiminished。Itwasgenerallyfromthreetofourhundredyardsbroad，andinthemiddleaboutseventeenfeetdeep。Therapidityofthecurrent，whichinitswholecourserunsattherateoffromfourtosixknotsanhour，isperhapsitsmostremarkablefeature。Thewaterisofafinebluecolour，butwithaslightmilkytinge，andnotsotransparentasatfirstsightwouldhavebeenexpected。Itflowsoverabedofpebbles，likethosewhichcomposethebeachandthesurroundingplains。Itrunsinawindingcoursethroughavalley，whichextendsinadirectlinewestward。Thisvalleyvariesfromfivetotenmilesinbreadth；
　　itisboundedbystep-formedterraces，whichriseinmostparts，oneabovetheother，totheheightoffivehundredfeet，andhaveontheoppositesidesaremarkablecorrespondence。
　　April19th——Againstsostrongacurrentitwas，ofcourse，quiteimpossibletoroworsail：consequentlythethreeboatswerefastenedtogetherheadandstern，twohandsleftineach，andtherestcameonshoretotrack。
　　AsthegeneralarrangementsmadebyCaptainFitzRoywereverygoodforfacilitatingtheworkofall，andasallhadashareinit，Iwilldescribethesystem。Thepartyincludingeveryone，wasdividedintotwospells，eachofwhichhauledatthetrackinglinealternatelyforanhourandahalf。Theofficersofeachboatlivedwith，atethesamefood，andsleptinthesametentwiththeircrew，sothateachboatwasquiteindependentoftheothers。Aftersunsetthefirstlevelspotwhereanybushesweregrowing，waschosenforournight’slodging。Eachofthecrewtookitinturnstobecook。Immediatelytheboatwashauledup，thecookmadehisfire；twootherspitchedthetent；thecoxswainhandedthethingsoutoftheboat；therestcarriedthemuptothetentsandcollectedfirewood。
　　Bythisorder，inhalfanhoureverythingwasreadyforthenight。Awatchoftwomenandanofficerwasalwayskept，whosedutyitwastolookaftertheboats，keepupthefire，andguardagainstIndians。Eachinthepartyhadhisonehoureverynight。
　　Duringthisdaywetrackedbutashortdistance，forthereweremanyislets，coveredbythornybushes，andthechannelsbetweenthemwereshallow。
　　April20th——Wepassedtheislandsandsettowork。Ourregularday’smarch，althoughitwashardenough，carriedusonanaverageonlytenmilesinastraightline，andperhapsfifteenortwentyaltogether。Beyondtheplacewherewesleptlastnight，thecountryiscompletely_terraincognita_，foritwastherethatCaptainStokesturnedback。Wesawinthedistanceagreatsmoke，andfoundtheskeletonofahorse，soweknewthatIndianswereintheneighbourhood。Onthenextmorning21sttracksofapartyofhorse，andmarksleftbythetrailingofthechuzos，orlongspears，wereobservedontheground。ItwasgenerallythoughtthattheIndianshadreconnoitredusduringthenight。Shortlyafterwardswecametoaspotwhere，fromthefreshfootstepsofmen，children，andhorses，itwasevidentthatthepartyhadcrossedtheriver。
　　April22nd——Thecountryremainedthesame，andwasextremelyuninteresting。
　　ThecompletesimilarityoftheproductionsthroughoutPatagoniaisoneofitsmoststrikingcharacters。Thelevelplainsofaridshinglesupportthesamestuntedanddwarfplants；andinthevalleysthesamethorn-bearingbushesgrow。Everywhereweseethesamebirdsandinsects。Eventheverybanksoftheriverandoftheclearstreamletswhichenteredit，werescarcelyenlivenedbyabrightertintofgreen。Thecurseofsterilityisontheland，andthewaterflowingoverabedofpebblespartakesofthesamecurse。Hencethenumberofwaterfowlisveryscanty；forthereisnothingtosupportlifeinthestreamofthisbarrenriver。
　　Patagonia，poorassheisinsomerespects，canhoweverboastofagreaterstockofsmallrodents[1]thanperhapsanyothercountryintheworld。Severalspeciesofmiceareexternallycharacterizedbylargethinearsandaveryfinefur。Theselittleanimalsswarmamongstthethicketsinthevalleys，wheretheycannotformonthstogethertasteadropofwaterexceptingthedew。Theyallseemtobecannibals；fornosoonerwasamousecaughtinoneofmytrapsthanitwasdevouredbyothers。
　　Asmallanddelicatelyshapedfox，whichislikewiseveryabundant，probablyderivesitsentiresupportfromthesesmallanimals。Theguanacoisalsoinhisproperdistrict，herdsoffiftyorahundredwerecommon；and，asIhavestated，wesawonewhichmusthavecontainedatleastfivehundred。
　　Thepuma，withthecondorandothercarrion-hawksinitstrain，followsandpreysupontheseanimals。Thefootstepsofthepumaweretobeseenalmosteverywhereonthebanksoftheriver；andtheremainsofseveralguanacos，withtheirnecksdislocatedandbonesbroken，showedhowtheyhadmettheirdeath。
　　April24th——Likethenavigatorsofoldwhenapproachinganunknownland，weexaminedandwatchedforthemosttrivialsignofachange。Thedriftedtrunkofatree，oraboulderofprimitiverock，washailedwithjoy，asifwehadseenaforestgrowingontheflanksoftheCordillera。
　　Thetop，however，ofaheavybankofclouds，whichremainedalmostconstantlyinoneposition，wasthemostpromisingsign，andeventuallyturnedoutatrueharbinger。Atfirstthecloudsweremistakenforthemountainsthemselves，insteadofthemassesofvapourcondensedbytheiricysummits。