hence，duringthegradualwearofthehills，theyprojectabovethesurfaceoftheground。Secondly，almosteverylabourer，especiallyinthenorthernpartsofChile，understandssomethingabouttheappearanceofores。InthegreatminingprovincesofCoquimboandCopiapo，firewoodisveryscarce，andmensearchforitovereveryhillanddale；andbythismeansnearlyalltherichestmineshavetherebeendiscovered。Chanuncillo，fromwhichsilvertothevalueofmanyhundredthousandpoundshasbeenraisedinthecourseofafewyears，wasdiscoveredbyamanwhothrewastoneathisloadeddonkey，andthinkingthatitwasveryheavy，hepickeditup，andfounditfullofpuresilver：theveinoccurredatnogreatdistance，standinguplikeawedgeofmetal。Theminers，also，takingacrowbarwiththem，oftenwanderonSundaysoverthemountains。InthissouthpartofChile，themenwhodrivecattleintotheCordillera，andwhofrequenteveryravinewherethereisalittlepasture，aretheusualdiscoverers。
20th——Asweascendedthevalley，thevegetation，withtheexceptionofafewprettyalpineflowers，becameexceedinglyscanty，andofquadrupeds，birds，orinsects，scarcelyonecouldbeseen。Theloftymountains，theirsummitsmarkedwithafewpatchesofsnow，stoodwellseparatedfromeachother，thevalleysbeingfilledupwithanimmensethicknessofstratifiedalluvium。ThefeaturesinthesceneryoftheAndeswhichstruckmemost，ascontrastedwiththeothermountainchainswithwhichIamacquainted，were，——theflatfringessometimesexpandingintonarrowplainsoneachsideofthevalleys，——thebrightcolours，chieflyredandpurple，oftheutterlybareandprecipitoushillsofporphyry，thegrandandcontinuouswall-likedykes，——theplainly-dividedstratawhich，wherenearlyvertical，formedthepicturesqueandwildcentralpinnacles，butwherelessinclined，composedthegreatmassivemountainsontheoutskirtsoftherange，——
andlastly，thesmoothconicalpilesoffineandbrightlycoloureddetritus，whichslopedupatahighanglefromthebaseofthemountains，sometimestoaheightofmorethan2000feet。
Ifrequentlyobserved，bothinTierradelFuegoandwithintheAndes，thatwheretherockwascoveredduringthegreaterpartoftheyearwithsnow，itwasshiveredinaveryextraordinarymannerintosmallangularfragments。Scoresby[1]hasobservedthesamefactinSpitzbergen。Thecaseappearstomeratherobscure：forthatpartofthemountainwhichisprotectedbyamantleofsnow，mustbelesssubjecttorepeatedandgreatchangesoftemperaturethananyotherpart。Ihavesometimesthought，thattheearthandfragmentsofstoneonthesurface，wereperhapslesseffectuallyremovedbyslowlypercolatingsnow-water[2]thanbyrain，andthereforethattheappearanceofaquickerdisintegrationofthesolidrockunderthesnow，wasdeceptive。
Whateverthecausemaybe，thequantityofcrumblingstoneontheCordilleraisverygreat。Occasionallyinthespring，greatmassesofthisdetritusslidedownthemountains，andcoverthesnow-driftsinthevalleys，thusformingnaturalice-houses。Werodeoverone，theheightofwhichwasfarbelowthelimitofperpetualsnow。
Astheeveningdrewtoaclose，wereachedasingularbasin-likeplain，calledtheValledelYeso。Itwascoveredbyalittledrypasture，andwehadthepleasantsightofaherdofcattleamidstthesurroundingrockydeserts。ThevalleytakesitsnameofYesofromagreatbed，Ishouldthinkatleast2000feetthick，ofwhite，andinsomepartsquitepure，gypsum。
Wesleptwithapartyofmen，whowereemployedinloadingmuleswiththissubstance，whichisusedinthemanufactureofwine。Wesetoutearlyinthemorning(21st)，andcontinuedtofollowthecourseoftheriver，whichhadbecomeverysmall，tillwearrivedatthefootoftheridge，thatseparatesthewatersflowingintothePacificandAtlanticOceans。Theroad，whichasyethadbeengoodwithasteadybutverygradualascent，nowchangedintoasteepzigzagtrackupthegreatrange，dividingtherepublicsofChileandMendoza。
IwillheregiveaverybriefsketchofthegeologyoftheseveralparallellinesformingtheCordillera。Oftheselines，therearetwoconsiderablyhigherthantheothers；namely，ontheChilianside，thePeuquenesridge，which，wheretheroadcrossesit，is13，210feetabovethesea；andthePortilloridge，ontheMendozaside，whichis14，305feet。ThelowerbedsofthePeuquenesridge，andoftheseveralgreatlinestothewestwardofit，arecomposedofavastpile，manythousandfeetinthickness，ofporphyrieswhichhaveflowedassubmarinelavas，alternatingwithangularandroundedfragmentsofthesamerocks，thrownoutofthesubmarinecraters。
Thesealternatingmassesarecoveredinthecentralparts，byagreatthicknessofredsandstone，conglomerate，andcalcareousclay-slate，associatedwith，andpassinginto，prodigiousbedsofgypsum。Intheseupperbedsshellsaretolerablyfrequent；andtheybelongtoabouttheperiodofthelowerchalkofEurope。Itisanoldstory，butnotthelesswonderful，tohearofshellswhichwereoncecrawlingonthebottomofthesea，nowstandingnearly14，000feetaboveitslevel。Thelowerbedsinthisgreatpileofstrata，havebeendislocated，baked，crystallizedandalmostblendedtogether，throughtheagencyofmountainmassesofapeculiarwhitesoda-graniticrock。
Theothermainline，namely，thatofthePortillo，isofatotallydifferentformation：itconsistschieflyofgrandbarepinnaclesofaredpotash-granite，whichlowdownonthewesternflankarecoveredbyasandstone，convertedbytheformerheatintoaquartz-rock。Onthequartz，thererestbedsofaconglomerateseveralthousandfeetinthickness，whichhavebeenupheavedbytheredgranite，anddipatanangleof45degs。towardsthePeuquenesline。Iwasastonishedtofindthatthisconglomeratewaspartlycomposedofpebbles，derivedfromtherocks，withtheirfossilshells，ofthePeuquenesrange；andpartlyofredpotash-granite，likethatofthePortillo。Hencewemustconclude，thatboththePeuquenesandPortillorangeswerepartiallyupheavedandexposedtowearandtear，whentheconglomeratewasforming；
butasthebedsoftheconglomeratehavebeenthrownoffatanangleof45degs。bytheredPortillogranite(withtheunderlyingsandstonebakedbyit)，wemayfeelsure，thatthegreaterpartoftheinjectionandupheavalofthealreadypartiallyformedPortilloline，tookplaceaftertheaccumulationoftheconglomerate，andlongaftertheelevationofthePeuquenesridge。
SothatthePortillo，theloftiestlineinthispartoftheCordillera，isnotsooldasthelessloftylineofthePeuquenes。EvidencederivedfromaninclinedstreamoflavaattheeasternbaseofthePortillo，mightbeadducedtoshow，thatitowespartofitsgreatheighttoelevationsofastilllaterdate。Lookingtoitsearliestorigin，theredgraniteseemstohavebeeninjectedonanancientpre-existinglineofwhitegraniteandmica-slate。Inmostparts，perhapsinallparts，oftheCordillera，itmaybeconcludedthateachlinehasbeenformedbyrepeatedupheavalsandinjections；andthattheseveralparallellinesareofdifferentages。
Onlythuscanwegaintime，atallsufficienttoexplainthetrulyastonishingamountofdenudation，whichthesegreat，thoughcomparativelywithmostotherrangesrecent，mountainshavesuffered。
Finally，theshellsinthePeuquenesoroldestridge，prove，asbeforeremarked，thatithasbeenupraised14，000feetsinceaSecondaryperiod，whichinEuropeweareaccustomedtoconsiderasfarfromancient；butsincetheseshellslivedinamoderatelydeepsea，itcanbeshownthattheareanowoccupiedbytheCordillera，musthavesubsidedseveralthousandfeet——innorthernChileasmuchas6000feet——soastohaveallowedthatamountofsubmarinestratatohavebeenheapedonthebedonwhichtheshellslived。Theproofisthesamewiththatbywhichitwasshown，thatatamuchlaterperiod，sincethetertiaryshellsofPatagonialived，theremusthavebeenthereasubsidenceofseveralhundredfeet，aswellasanensuingelevation。Dailyitisforcedhomeonthemindofthegeologist，thatnothing，noteventhewindthatblows，issounstableasthelevelofthecrustofthisearth。
Iwillmakeonlyoneothergeologicalremark：althoughthePortillochainisherehigherthanthePeuquenes，thewatersdrainingtheintermediatevalleys，haveburstthroughit。Thesamefact，onagranderscale，hasbeenremarkedintheeasternandloftiestlineoftheBolivianCordillera，throughwhichtheriverspass：analogousfactshavealsobeenobservedinotherquartersoftheworld。OnthesuppositionofthesubsequentandgradualelevationofthePortilloline，thiscanbeunderstood；forachainofisletswouldatfirstappear，and，asthesewereliftedup，thetideswouldbealwayswearingdeeperandbroaderchannelsbetweenthem。Atthepresentday，eveninthemostretiredSoundsonthecoastofTierradelFuego，thecurrentsinthetransversebreakswhichconnectthelongitudinalchannels，areverystrong，sothatinonetransversechannelevenasmallvesselundersailwaswhirledroundandround。
AboutnoonwebeganthetediousascentofthePeuquenesridge，andthenforthefirsttimeexperiencedsomelittledifficultyinourrespiration。
Themuleswouldhalteveryfiftyyards，andafterrestingforafewsecondsthepoorwillinganimalsstartedoftheirownaccordagain。TheshortbreathingfromtherarefiedatmosphereiscalledbytheChilenos“puna；“andtheyhavemostridiculousnotionsconcerningitsorigin。Somesay“allthewatersherehavepuna；“othersthat“wherethereissnowthereispuna；“——andthisnodoubtistrue。TheonlysensationIexperiencedwasaslighttightnessacrosstheheadandchest，likethatfeltonleavingawarmroomandrunningquicklyinfrostyweather。Therewassomeimaginationeveninthis；foruponfindingfossilshellsonthehighestridge，Ientirelyforgotthepunainmydelight。Certainlytheexertionofwalkingwasextremelygreat，andtherespirationbecamedeepandlaborious：IamtoldthatinPotosi(about13，000feetabovethesea)strangersdonotbecomethoroughlyaccustomedtotheatmosphereforanentireyear。Theinhabitantsallrecommendonionsforthepuna；asthisvegetablehassometimesbeengiveninEuropeforpectoralcomplaints，itmaypossiblybeofrealservice：——formypartIfoundnothingsogoodasthefossilshells！
Whenabouthalf-wayupwemetalargepartywithseventyloadedmules。
Itwasinterestingtohearthewildcriesofthemuleteers，andtowatchthelongdescendingstringoftheanimals；theyappearedsodiminutive，therebeingnothingbuttheblackmountainswithwhichtheycouldbecompared。
Whennearthesummit，thewind，asgenerallyhappens，wasimpetuousandextremelycold。Oneachsideoftheridge，wehadtopassoverbroadbandsofperpetualsnow，whichwerenowsoontobecoveredbyafreshlayer。
Whenwereachedthecrestandlookedbackwards，agloriousviewwaspresented。
Theatmosphereresplendentlyclear；theskyanintenseblue；theprofoundvalleys；thewildbrokenforms：theheapsofruins，piledupduringthelapseofages；thebright-colouredrocks，contrastedwiththequietmountainsofsnow，allthesetogetherproducedascenenoonecouldhaveimagined。
Neitherplantnorbird，exceptingafewcondorswheelingaroundthehigherpinnacles，distractedmyattentionfromtheinanimatemass。IfeltgladthatIwasalone：itwaslikewatchingathunderstorm，orhearinginfullorchestraachorusoftheMessiah。
OnseveralpatchesofthesnowIfoundtheProtococcusnivalis，orredsnow，sowellknownfromtheaccountsofArcticnavigators。Myattentionwascalledtoit，byobservingthefootstepsofthemulesstainedapalered，asiftheirhoofshadbeenslightlybloody。Iatfirstthoughtthatitwasowingtodustblownfromthesurroundingmountainsofredporphyry；
forfromthemagnifyingpowerofthecrystalsofsnow，thegroupsofthesemicroscopicalplantsappearedlikecoarseparticles。Thesnowwascolouredonlywhereithadthawedveryrapidly，orhadbeenaccidentallycrushed。
Alittlerubbedonpapergaveitafaintrosetingemingledwithalittlebrick-red。Iafterwardsscrapedsomeoffthepaper，andfoundthatitconsistedofgroupsoflittlespheresincolourlesscases，eachofthethousandthpartofaninchindiameter。
ThewindonthecrestofthePeuquenes，asjustremarked，isgenerallyimpetuousandverycold：itissaid[3]toblowsteadilyfromthewestwardorPacificside。Astheobservationshavebeenchieflymadeinsummer，thiswindmustbeanupperandreturncurrent。ThePeakofTeneriffe，withalesselevation，andsituatedinlat。28degs。，inlikemannerfallswithinanupperreturnstream。Atfirstitappearsrathersurprising，thatthetrade-windalongthenorthernpartsofChileandonthecoastofPeru，shouldblowinsoverysoutherlyadirectionasitdoes；
butwhenwereflectthattheCordillera，runninginanorthandsouthline，intercepts，likeagreatwall，theentiredepthoftheloweratmosphericcurrent，wecaneasilyseethatthetrade-windmustbedrawnnorthward，followingthelineofmountains，towardstheequatorialregions，andthuslosepartofthateasterlymovementwhichitotherwisewouldhavegainedfromtheearth’srotation。AtMendoza，ontheeasternfootoftheAndes，theclimateissaidtobesubjecttolongcalms，andtofrequentthoughfalseappearancesofgatheringrain-storms：wemayimaginethatthewind，whichcomingfromtheeastwardisthusbankedupbythelineofmountains，wouldbecomestagnantandirregularinitsmovements。
