Thisbedisremarkablefromcontainingmanyglobularandpear-shaped，externallyrustyballs，fromthesizeofanappletoaman’shead，ofverytough，slate-colouredporphyry，withimperfectcrystalsoffeldspar：inshapetheseballsdonotresemblepebbles，ANDIBELIEVETHATTHEYARE
SUBAQUEOUSVOLCANICBOMBS;theydifferfromSUBAERIALbombsonlyinnotbeingvesicular。Bed4;adullpurplish-red，hardconglomerate，withcrystallisedparticlesandveinsofcarbonateoflime，fromthreehundredtofourhundredfeetinthickness。Thepebblesareofclaystoneporphyriesofmanyvarieties;theyaretolerablywellrounded，andvaryinsizefromalargeappletoaman’shead。Thisbedincludesthreelayersofcoarse，black，calcareous，somewhatslatyrock：theupperpartpassesintoacompactredsandstone。
Inaformationsohighlyvariableinmineralogicalnature，anydivisionnotfoundedonfossilremains，mustbeextremelyarbitrary：nevertheless，thebedsbelowthelastconglomeratemay，inaccordancewithallthesectionshithertodescribed，beconsideredasbelongingtotheporphyriticconglomerate，andthoseaboveittothegypseousformation，marked[E]inthesection。ThepartofthevalleyinwhichthefollowingbedsareseenisnearPotreroSeco。Bed5，compact，fine-grained，palegreenish-grey，non-
calcareous，induratedmudstone，easilyfusibleintoapalegreenandwhiteglass。Bed6，purplish，coarse-grained，hardsandstone，withbrokencrystalsoffeldsparandcrystallisedparticlesofcarbonateoflime;itpossessesaslightlynodularstructure。Bed7，blackish-grey，muchindurated，calcareousmudstone，withextraneousparticlesofunequalsize;
thewholebeinginpartsfinelybrecciated。Inthismassthereisastratum，twentyfeetinthickness，ofimpuregypsum。Bed8，agreenishmudstone，withseverallayersofgypsum。Bed9，ahighlyindurated，easilyfusible，whitetuff，thicklymottledwithferruginousmatter，andincludingsomewhitesemi-porcellaniclayers，whichareinterlacedwithferruginousveins。ThisstonecloselyresemblessomeofthecommonestvarietiesintheUspallatachain。Bed10，athickbedofratherbrightgreen，induratedmudstoneortuff，withaconcretionarynodularstructuresostronglydevelopedthatthewholemassconsistsofballs。Iwillnotattempttoestimatethethicknessofthestratainthegypseousformationhithertodescribed，butitmustcertainlybeverymanyhundredfeet。Bed11isatleast800feetinthickness：itconsistsofthinlayersofwhitish，greenish，ormorecommonlybrown，fine-grained，induratedtuffs，whichcrumbleintoangularfragments：someofthelayersaresemi-porcellanic，manyofthemhighlyferruginous，andsomearealmostcomposedofcarbonateoflimeandironwithdrusycavitieslinedwithquartzf-crystals。Bed12，dullpurplishorgreenishordark-grey，verycompactandmuchinduratedmudstone：estimatedat1，500feetinthickness：insomepartsthisrockassumesthecharacterofanimperfectcoarseclay-slate;butviewedunderalens，thebasisalwayshasamottledappearance，withtheedgesoftheminutecomponentparticlesblendingtogether。Partsarecalcareous，andtherearenumerousveinsofhighlycrystallinecarbonateoflimechargedwithiron。Themasshasanodularstructure，andisdividedbyonlyafewplanesofstratification：thereare，however，twolayers，eachabouteighteeninchesthick，ofadarkbrown，finer-grainedstone，havingaconchoidal，semi-porcellanicfracture，whichcanbefollowedwiththeeyeforsomemilesacrossthecountry。
Ibelievethislastgreatbediscoveredbyothernearlysimilaralternations;butthesectionishereobscuredbyatiltfromthenextporphyriticchain，presentlytobedescribed。Ihavegiventhissectionindetail，asbeingillustrativeofthegeneralcharacterofthemountainsinthisneighbourhood;butitmustnotbesupposedthatanyonestratumlongpreservesthesamecharacter。Atadistanceofbetweenonlytwoandthreemilesthegreenmudstonesandwhiteinduratedtuffsaretoagreatextentreplacedbyredsandstoneandblackcalcareousshalyrocks，alternatingtogether。Thewhiteinduratedtuff，bed11，herecontainslittleornogypsum，whereasonthenorthernandoppositesideofthevalley，itisofmuchgreaterthicknessandaboundswithlayersofgypsum，someofthemalternatingwiththinseamsofcrystallinecarbonateoflime。Theuppermost，dark-coloured，hardmudstone，bed12，isinthisneighbourhoodthemostconstantstratum。Thewholeseriesdifferstoaconsiderableextent，especiallyinitsupperpart，fromthatmetwithat[BB]，inthelowerpartofthevalley;nevertheless，Idonotdoubtthattheyareequivalents。
FOURTHAXISOFELEVATION(VALLEYOFCOPIAPO)。
Thisaxisisformedofachainofmountains[F]，ofwhichthecentralmasses(nearLaPunta)consistofandesitecontaininggreenhornblendeandcopperymica，andtheoutermassesofgreenishandblackporphyries，togetherwithsomefinelilac-colouredclaystoneporphyry;alltheseporphyriesbeinginjectedandbrokenupbysmallhummocksofandesite。Thecentralgreatmassofthislatterrock，iscoveredontheeasternsidebyablack，fine-grained，highlymicaceousslate，which，togetherwiththesucceedingmountainsofporphyry，aretraversedbynumerouswhitedikes，branchingfromtheandesite，andsomeofthemextendinginstraightlines，toadistanceofatleasttwomiles。Themountainsofporphyryeastwardofthemicaceousschistsoon，butgradually，assume(asobservedinsomanyothercases)astratifiedstructure，andcanthenberecognisedasapartoftheporphyriticconglomerateformation。Thesestrata[G]areinclinedatahighangletotheS。E。andformamassfromfifteenhundredtotwothousandfeetinthickness。Thegypseousmassestothewestalreadydescribed，dipdirectlytowardsthisaxis，withthestrataonlyinafewplaces(oneofwhichisrepresentedinthesection)thrownfromit：hencethisfourthaxisismainlyuniclinaltowardstheS。E。andjustlikeourthirdaxis，onlylocallyanticlinal。
Theabovestrataofporphyriticconglomerate[G]withtheirsouth-eastwarddip，comeabruptlyupagainstbedsofthegypseousformation[H]，whicharegently，butirregularly，inclinedwestward：sothatthereishereasynclinalaxisandgreatfault。Furtherupthevalley，hererunningnearlynorthandsouth，thegypseousformationisprolongedforsomedistance;butthestratificationisunintelligible，thewholebeingbrokenupbyfaults，dikes，andmetalliferousveins。Thestrataconsistchieflyofredcalcareoussandstones，withnumerousveinsintheplaceoflayers，ofgypsum;thesandstoneisassociatedwithsomeblackcalcareousslate-rock，andwithgreenpseudo-honestones，passingintoporcelain-jasper。Stillfurtherupthevalley，nearLasAmolanas[I]，thegypseousstratabecomemoreregular，dippingatanangleofbetween30and40degreestoW。S。W。andconformablyoverlying，nearthemouthoftheravineofJolquera，strata[K]ofporphyriticconglomerate。Thewholeserieshasbeentiltedbyapartiallyconcealedaxis[L]，ofgranite，andesite，andagraniticmixtureofwhitefeldspar，quartz，andoxideofiron。
FIFTHAXISOFELEVATION(VALLEYOFCOPIAPO，NEARLOSAMOLANAS)。
Iwilldescribeinsomedetailthebeds[I]seenhere，which，asjuststated，diptoW。S。W。atanangleoffrom30to40degrees。Ihadnottimetoexaminetheunderlyingporphyriticconglomerate，ofwhichthelowestbeds，asseenatthemouthoftheJolquera，arehighlycompact，withcrystalsofredoxideofiron;andIamnotpreparedtosaywhethertheyarechieflyofvolcanicormetamorphicorigin。Onthesebedsthererestsacoarsepurplishconglomerate，verylittlemetamorphosed，composedofpebblesofporphyry，butremarkablefromcontainingonepebbleofgranite;——
ofwhichfactnoinstancehasoccurredinthesectionshithertodescribed。
Abovethisconglomerate，thereisablacksiliceousclaystone，andaboveitnumerousalternationsofdark-purplishandgreenporphyries，whichmaybeconsideredastheuppermostlimitoftheporphyriticconglomerateformation。
Abovetheseporphyriescomesacoarse，arenaceousconglomerate，thelowerhalfwhiteandtheupperhalfofapinkcolour，composedchieflyofpebblesofvariousporphyries，butwithsomeofredsandstoneandjasperyrocks。Insomeofthemorearenaceouspartsoftheconglomerate，therewasanobliqueorcurrentlamination;acircumstancewhichIdidnotelsewhereobserve。
Abovethisconglomerate，thereisavastthicknessofthinlystratified，pale-yellowish，siliceoussandstone，passingintoagranularquartz-rock，usedforgrindstones(hencethenameoftheplaceLasAmolanas)，andcertainlybelongingtothegypseousformation，asdoesprobablytheimmediatelyunderlyingconglomerate。Inthisyellowishsandstonetherearelayersofwhiteandpale-redsiliceousconglomerate;otherlayerswithsmall，well-roundedpebblesofwhitequartz，likethebedattheR。ClaroatCoquimbo;othersofagreenish，fine-grained，lesssiliceousstone，somewhatresemblingthepseudo-honestoneslowerdownthevalley;andlastly，othersofablackcalcareousshale-rock。Inoneofthelayersofconglomerate，therewasembeddedafragmentofmica-slate，ofwhichthisisthefirstinstance;henceperhaps，itisfromaformationofmica-slate，thatthenumeroussmallpebblesofquartz，bothhereandatCoquimbo，havebeenderived。Notonlydoesthesiliceoussandstoneincludelayersoftheblack，thinlystratified，notfissile，calcareousshale-rock，butinoneplacethewholemass，especiallytheupperpart，was，inamarvellouslyshorthorizontaldistance，afterfrequentalternations，replacedbyit。
Whenthisoccurred，amountain-mass，severalthousandfeetinthicknesswasthuscomposed;theblackcalcareousshale-rock，however，alwaysincludedsomelayersofthepale-yellowishsiliceoussandstone，oftheredconglomerate，andofthegreenishjasperyandpseudo-honestonevarieties。
Itlikewiseincludedthreeorfourwidelyseparatedlayersofabrownlimestone，aboundingwithshellsimmediatelytobedescribed。Thispileofstratawasinpartstraversedbymanyveinsofgypsum。Thecalcareousshale-rock，thoughwhenfreshlybrokenquiteblack，weathersintoanash-
colour：inwhichrespectandingeneralappearance，itperfectlyresemblesthosegreatfossiliferousbedsofthePeuquenesrange，alternatingwithgypsumandredsandstone，describedinthelastchapter。
Theshellsoutofthelayersofbrownlimestone，includedintheblackcalcareousshale-rock，whichlatter，asjuststated，replacesthewhitesiliceoussandstone，consistof：——
PectenDufreynoyi，d’Orbigny，“Voyage“PartPal。
TurritellaAndii，d’Orbigny，“Voyage“PartPal。
AstarteDarwinii，E。Forbes。
GryphaeaDarwinii，E。Forbes。
AnintermediateformbetweenG。giganteaandG。incurva。
Gryphaeanov。spec。？，E。Forbes。
PernaAmericana，E。Forbes。
Avicula，nov。spec。
ConsideredbyMr。G。B。SowerbyastheA。echinata，byM。d’Orbignyascertainlyanewanddistinctspecies，havingaJurassicaspect。Thespecimenhasbeenunfortunatelylost。
Terebratulaaenigma，d’Orbigny，(var。ofdo。E。Forbes。)
Thisisthesamevariety，withthatfromGuasco，consideredbyM。D’OrbignytobeadistinctspeciesfromhisT。aenigma，andrelatedtoT。obsoleta。
PlagiostomaandAmmonites，fragmentsof。
ThelowerlayersofthelimestonecontainedthousandsoftheGryphaea;andtheupperonesasmanyoftheTurritella，withtheGryphaea(nov。species)
andSerpulaeadheringtothem;inallthelayers，theTerebratulaandfragmentsofthePectenwereincluded。Itwasevident，fromthemannerinwhichspeciesweregroupedtogether，thattheyhadlivedwherenowembedded。Beforemakinganyfurtherremarks，Imaystate，thathigherupthissamevalleyweshallagainmeetwithasimilarassociationofshells;
andinthegreatDespobladoValley，whichbranchesoffnearthetownfromthatofCopiapo，thePectenDufreynoyi，someGryphites(IbelieveG。
Darwinii)，andtheTRUETerebratulaaenigmaofd’Orbignywerefoundtogetherinanequivalentformation，aswillbehereafterseen。Aspecimenalso，Imayadd，ofthetrueT。aenigma，wasgivenmefromtheneighbourhoodofthefamoussilverminesofChanuncillo，alittlesouthofthevalleyoftheCopiapo，andthesemines，fromtheirposition，Ihavenodoubt，liewithinthegreatgypseousformation：therocksclosetooneofthesilverveins，judgingfromfragmentsshownme，resemblethosesingularmetamorphoseddepositsfromtheminingdistrictofArquerosnearCoquimbo。
Iwillreiteratetheevidenceontheassociationoftheseseveralshellsintheseverallocalities。
COQUIMBO。
Inthesamebed，RioClaro：
PectenDufreynoyi。
Ostreahemispherica。
Terebratulaaenigma。
Spiriferlinguiferoides。
Samebed，nearArqueros：
HippuritesChilensis。
Gryphaeaorientalis。
CollectedbyM。Domeykofromthesamelocality，apparentlynearArqueros：
TerebratulaaenigmaandTerebratulaignaciana，insameblockoflimestone：
PectenDufreynoyi。
Ostreahemispherica。
HippuritesChilensis。
TurritellaAndii。
NautilusDomeykus。
GUASCO。
InacollectionfromtheCordillera，givenme：thespecimensallinthesamecondition：
PectenDufreynoyi。
TurritellaAndii。
Terebratulaignaciana。
Terebratulaaenigma，var。
SpiriferChilensis。
COPIAPO。
MingledtogetherinalternatingbedsinthemainvalleyofCopiaponearLasAmolanas，andlikewisehigherupthevalley：
PectenDufreynoyi。
TurritellaAndii。
Terebratulaaenigma，var。asatGuasco。
AstarteDarwinii。
GryphaeaDarwinii。
Gryphaeanov。species？
PernaAmericana。
Avicula，nov。species。
MainvalleyofCopiapo，apparentlysameformationwiththatofAmolanas：
Terebratulaaenigma(true)。
Inthesamebed，highupthegreatlateralvalleyoftheDespoblado，intheravineofMaricongo：
Terebratulaaenigma(true)。
PectenDufreynoyi。
GryphaeaDarwinii？
Consideringthistable，Ithinkitisimpossibletodoubtthatallthesefossilsbelongtothesameformation。If，however，thespeciesfromLasAmolanas，intheValleyofCopiapo，had，asinthecaseofthosefromGuasco，beenseparatelyexamined，theywouldprobablyhavebeenrankedasoolitic;for，althoughnoSpiriferswerefoundhere，alltheotherspecies，withtheexceptionofthePecten，Turritella，andAstarte，haveamoreancientaspectthancretaceousforms。Ontheotherhand，takingintoaccounttheevidencederivedfromthecretaceouscharacterofthesethreeshells，andoftheHippurites，Gryphaeaorientalis，andOstrea，fromCoquimbo，wearedrivenbacktotheprovisionalnamealreadyusedofcretaceo-oolitic。Fromgeologicalevidence，IbelievethisformationtobetheequivalentoftheNeocomianbedsoftheCordilleraofCentralChile。
ToreturntooursectionnearLasAmolanas：——Abovetheyellowsiliceoussandstone，ortheequivalentcalcareousslate-rock，withitsbandsoffossil-shells，accordingastheoneorotherprevails，thereisapileofstrata，whichcannotbelessthanfromtwotothreethousandfeetinthickness，inmainpartcomposedofacoarse，brightredconglomerate，withmanyintercalatedbedsofredsandstone，andsomeofgreenandothercolouredporcelain-jasperylayers。Theincludedpebblesarewell-rounded，varyingfromthesizeofaneggtothatofacricket-ball，withafewlarger;andtheyconsistchieflyofporphyries。Thebasisoftheconglomerate，aswellassomeofthealternatingthinbeds，areformedofared，ratherharsh，easilyfusiblesandstone，withcrystallinecalcareousparticles。Thiswholegreatpileisremarkablefromthethousandsofhuge，embedded，silicifiedtrunksoftrees，oneofwhichwaseightfeetlong，andanothereighteenfeetincircumference：howmarvellousitis，thateveryvesselinsothickamassofwoodshouldhavebeenconvertedintosilex！I
broughthomemanyspecimens，andallofthem，accordingtoMr。R。Brown，presentaconiferousstructure。
Abovethisgreatconglomerate，wehavefromtwotothreehundredfeetinthicknessofredsandstone;andabovethis，astratumofblackcalcareousslate-rock，likethatwhichalternateswithandreplacestheunderlyingyellowish-white，siliceoussandstone。Closetothejunctionbetweenthisupperblackslate-rockandtheupperredsandstone，IfoundtheGryphaeaDarwinii，theTurritellaAndii，andvastnumbersofabivalve，tooimperfecttoberecognised。Henceweseethat，asfarastheevidenceofthesetwoshellsserves——andtheTurritellaisaneminentlycharacteristicspecies——thewholethicknessofthisvastpileofstratabelongstothesameage。Again，abovethelast-mentionedupperredsandstone，therewereseveralalternationsoftheblack，calcareousslate-rock;butIwasunabletoascendtothem。Alltheseuppermoststrata，likethelowerones，varyextremelyincharacterinshorthorizontaldistances。Thegypseousformation，ashereseen，hasacoarser，moremechanicaltexture，andcontainsmuchmoresiliceousmatterthanthecorrespondingbedslowerdownthevalley。Itstotalthickness，togetherwiththeupperbedsoftheporphyriticconglomerate，Iestimatedatleastat8，000feet;andonlyasmallportionoftheporphyriticconglomerate，whichontheeasternflankofthefourthaxisofelevationappearedtobefromfifteenhundredtotwothousandfeetthick，ishereincluded。Ascorroborativeofthegreatthicknessofthegypseousformation，ImaymentionthatintheDespobladoValley(whichbranchesfromthemainvalleyalittleabovethetownofCopiapo)Ifoundacorrespondingpileofredandwhitesandstones，andofdark，calcareous，semi-jasperymudstones，risingfromanearlylevelsurfaceandthrownintoanabsolutelyverticalposition;sothat，bypacing，Iascertainedtheirthicknesstobenearlytwothousandsevenhundredfeet;takingthisasastandardofcomparison，IestimatedthethicknessofthestrataABOVEtheporphyriticconglomerateat7，000feet。
Thefossilsbeforeenumerated，fromthelimestone-layersinthewhitishsiliceoussandstone，arenowcovered，ontheleastcomputation，bystratafrom5，000to6，000feetinthickness。ProfessorE。Forbesthinksthattheseshellsprobablylivedatadepthoffromabout30to40fathoms，thatisfrom180to240feet;anyhow，itisimpossiblethattheycouldhavelivedatthedepthoffrom5，000to6，000feet。Henceinthiscase，asinthatofthePuentedelInca，wemaysafelyconcludethatthebottomoftheseaonwhichtheshellslived，subsided，soastoreceivethesuperincumbentsubmarinestrata：andthissubsidencemusthavetakenplaceduringtheexistenceoftheseshells;for，asIhaveshown，someofthemoccurhighupaswellaslowdownintheseries。Thatthebottomoftheseasubsided，isinharmonywiththepresenceofthelayersofcoarse，well-
roundedpebblesincludedthroughoutthiswholepileofstrata，aswellasofthegreatuppermassofconglomeratefrom2，000to3，000feetthick;forcoarsegravelcouldhardlyhavebeenformedorspreadoutattheprofounddepthsindicatedbythethicknessofthestrata。Thesubsidence，also，musthavebeenslowtohaveallowedofthisoften-recurrentspreadingoutofthepebbles。Moreover，weshallpresentlyseethatthesurfacesofsomeofthestreamsofporphyriticlavabeneaththegypseousformation，aresohighlyamygdaloidalthatitisscarcelypossibletobelievethattheyflowedunderthevastpressureofadeepocean。Theconclusionofagreatsubsidenceduringtheexistenceofthesecretaceo-ooliticfossils，may，Ibelieve，beextendedtothedistrictofCoquimbo，althoughowingtothefossiliferousbedstherenotbeingdirectlycoveredbytheuppergypseousstrata，whichinthesectionnorthofthevalleyareabout6，000feetinthickness，Ididnotthereinsistonthisconclusion。
Thepebblesintheaboveconglomerates，bothintheupperandlowerbeds，areallwellrounded，and，thoughchieflycomposedofvariousporphyries，therearesomeofredsandstoneandofajasperystone，bothliketherocksintercalatedinlayersinthissamegypseousformation;therewasonepebbleofmica-slateandsomeofquartz，togetherwithmanyparticlesofquartz。Intheserespectsthereisawidedifferencebetweenthegypseousconglomeratesandthoseoftheporphyritic-conglomerateformation，inwhichlatter，angularandroundedfragments，almostexclusivelycomposedofporphyries，aremingledtogether，andwhich，asalreadyoftenremarked，probablywereejectedfromcratersdeepunderthesea。FromthesefactsI
conclude，thatduringtheformationoftheconglomerates，landexistedintheneighbourhood，ontheshoresofwhichtheinnumerablepebbleswereroundedandthencedispersed，andonwhichtheconiferousforestsflourished——foritisimprobablethatsomanythousandlogsofwoodshouldhavedriftedfromanygreatdistance。Thisland，probablyislands，musthavebeenmainlyformedofporphyries，withsomemica-slate，whencethequartzwasderived，andwithsomeredsandstoneandjasperyrocks。Thislatterfactisimportant，asitshowsthatinthisdistrict，evenpreviouslytothedepositionofthelowergypseousorcretaceo-ooliticbeds，strataofananalogousnaturehadelsewhere，nodoubtinthemorecentralrangesoftheCordillera，beenelevated;thusrecallingtoourmindstherelationsoftheCumbreandUspallatachains。HavingalreadyreferredtothegreatlateralvalleyoftheDespoblado，Imaymentionthatabovethe2，700feetofredandwhitesandstoneanddarkmudstone，thereisavastmassofcoarse，hard，redconglomerate，somethousandfeetinthickness，whichcontainsmuchsilicifiedwood，andevidentlycorrespondswiththegreatupperconglomerateatLasAmolanas：here，however，theconglomerateconsistsalmostexclusivelyofpebblesofgranite，andofdisintegratedcrystalsofreddishfeldsparandquartzfirmlyrecementedtogether。Inthiscase，wemayconcludethatthelandwhencethepebbleswerederived，andonwhichthenowsilicifiedtreesonceflourished，wasformedofgranite。
ThemountainsnearLasAmolanas，composedofthecretaceo-ooliticstrata，areinterlacedwithdikeslikeaspider’sweb，toanextentwhichIhaveneverseenequalled，exceptinthedenudedinteriorofavolcaniccrater：
northandsouthlines，however，predominate。Thesedikesarecomposedofgreen，white，andblackishrocks，allporphyriticwithfeldspar，andoftenwithlargecrystalsofhornblende。Thewhitevarietiesapproachcloselyincharactertoandesite，whichcomposesaswehaveseen，theinjectedaxesofsomanyofthelinesofelevation。Someofthegreenvarietiesarefinelylaminated，paralleltothewallsofthedikes。
SIXTHAXISOFELEVATION(VALLEYOFCOPIAPO)。
Thisaxisconsistsofabroadmountainousmass[O]ofandesite，composedofalbite，brownmica，andchlorite，passingintoandesiticgranite，withquartz：onitswesternsideithasthrownoff，ataconsiderableangle，athickmassofstratifiedporphyries，includingmuchepidote[NN]，andremarkableonlyfrombeingdividedintoverythinbeds，ashighlyamygdaloidalontheirsurfacesassubaeriallava-streamsareoftenvesicular。Thisporphyriticformationisconformablycovered，asseensomewayuptheravineofJolquera，byamereremnantofthelowerpartofthecretaceo-ooliticformation[MM]，whichinonepartencases，asrepresentedinthecolouredsection，thefootoftheandesiticaxis[L]，ofthealreadydescribedfifthline，andinanotherpartentirelyconcealsit：inthislattercase，thegypseousorcretaceo-ooliticstratafalselyappearedtodipundertheporphyriticconglomerateofthefifthaxis。Thelowestbedofthegypseousformation，asseenhere[M]，isofyellowishsiliceoussandstone，preciselylikethatofAmolanas，interlacedinpartswithveinsofgypsum，andincludinglayersoftheblack，calcareous，non-fissileslate-rock：theTurritellaAndii，PectenDufreynoyi，Terebratulaaenigma，var。andsomeGryphiteswereembeddedintheselayers。Thesandstonevariesinthicknessfromonlytwentytoeightyfeet;andthisvariationiscausedbytheinequalitiesintheuppersurfaceofanunderlyingstreamofpurpleclaystoneporphyry。Hencetheabovefossilsherelieattheverybaseofthegypseousorcretaceo-ooliticformation，andhencetheywereprobablyoncecoveredupbystrataaboutseventhousandfeetinthickness：
itis，however，possible，thoughfromthenatureofalltheothersectionsinthisdistrictnotprobable，thattheporphyriticclaystonelavamayinthiscasehaveinvadedahigherlevelintheseries。Abovethesandstonethereisaconsiderablemassofmuchindurated，purplish-black，calcareousclaystone，alliedinnaturetotheoften-mentionedblackcalcareousslate-
rock。
Eastwardofthebroadandesiticaxisofthissixthline，andpenetratedbymanydikesfromit，thereisagreatformation[P]ofmica-schist，withitsusualvariations，andpassinginonepartintoaferruginousquartz-rock。
Thefoliaarecurvedandhighlyinclined，generallydippingeastward。Itisprobablethatthismica-schistisanoldformation，connectedwiththegraniticrocksandmetamorphicschistsnearthecoast;andthattheonefragmentofmica-slate，andthepebblesofquartzlowdowninthegypseousformationatLasAmolanas，havebeenderivedfromit。Themica-schistissucceededbystratifiedporphyriticconglomerate[Q]ofgreatthickness，dippingeastwardwithahighinclination：Ihaveincludedthislattermountain-massinthesameanticlinalaxiswiththeporphyriticstreams[NN];butIamfarfromsurethatthetwomassesmaynothavebeenindependentlyupheaved。
SEVENTHAXISOFELEVATION。
Proceedinguptheravine，wecometoanothermass[R]ofandesite;andbeyondthis，weagainhaveaverythick，stratifiedporphyriticformation[S]，dippingatasmallangleeastward，andformingthebasalpartofthemainCordillera。Ididnotascendtheravineanyhigher;buthere，nearCastano，Iexaminedseveralsections，ofwhichIwillnotgivethedetails，onlyobserving，thattheporphyriticbeds，orsubmarinelavas，preponderategreatlyinbulkoverthealternatingsedimentarylayers，whichhavebeenbutlittlemetamorphosed：theselatterconsistoffine-grainedredtuffsandofwhitishvolcanicgrit-stones，togetherwithmuchofasingular，compactrock，havinganalmostcrystallinebasis，finelybrecciatedwithredandgreenfragments，andoccasionallyincludingafewlargepebbles。
Theporphyriticlavasarehighlyamygdaloidal，bothontheirupperandlowersurfaces;theyconsistchieflyofclaystoneporphyry，butwithonecommonvariety，likesomeofthestreamsatthePuentedelInca，havingagreymottledbasis，aboundingwithcrystalsofredhydrousoxideofiron，greenonesapparentlyofepidote，andafewglassyonesoffeldspar。ThispileofstratadiffersconsiderablyfromthebasalstrataoftheCordillerainCentralChile，andmaypossiblybelongtotheupperandgypseousseries：
Isaw，however，inthebedofthevalley，onefragmentofporphyriticbreccia-conglomerate，exactlylikethosegreatmassesmetwithinthemoresouthernpartsofChile。
Finally，Imustobserve，thatthoughIhavedescribedbetweenthetownofCopiapoandthewesternflankofthemainCordillerasevenoreightaxesofelevation，extendingnearlynorthandsouth，itmustnotbesupposedthattheyallruncontinuouslyforgreatdistances。AswasstatedtobethecaseinoursectionsacrosstheCordilleraofCentralChile，soheremostofthelinesofelevation，withtheexceptionofthefirst，third，andfifth，areveryshort。Thestratificationiseverywheredisturbedandintricate;
nowherehaveIseenmorenumerousfaultsanddikes。Thewholedistrict，fromtheseatotheCordillera，ismoreorlessmetalliferous;andIheardofgold，silver，copper，lead，mercury，andironveins。Themetamorphicaction，eveninthelowerstrata，hascertainlybeenfarlessherethaninCentralChile。
VALLEYOFTHEDESPOBLADO。
Thisgreatbarrenvalley，whichhasalreadybeenalludedto，entersthemainvalleyofCopiapoalittleabovethetown：itrunsatfirstnortherly，thenN。E。andmoreeasterlyintotheCordillera;Ifolloweditsdrearycoursetothefootofthefirstmainridge。Iwillnotgiveadetailedsection，becauseitwouldbeessentiallysimilartothatalreadygiven，andbecausethestratificationisexceedinglycomplicated。Afterleavingtheplutonichillsnearthetown，Imetfirst，asinthemainvalley，withthegypseousformation，havingthesamediversifiedcharacterasbefore，andsoonafterwardswithmassesofporphyriticconglomerate，aboutonethousandfeetinthickness。Inthelowerpartofthisformationtherewereverythickbedscomposedoffragmentsofclaystoneporphyries，bothangularandrounded，withthesmalleronespartiallyblendedtogetherandthebasisrenderedporphyritic;thesebedsseparateddistinctstreams，fromsixtytoeightyfeetinthickness，ofclaystonelavas。NearPaipote，also，therewasmuchtrueporphyriticbreccia-conglomerate：nevertheless，fewofthesemassesweremetamorphosedtothesamedegreewiththecorrespondingformationinCentralChile。Ididnotmeetinthisvalleywithanytrueandesite，butonlywithimperfectandesiticporphyry，includinglargecrystalsofhornblende：numerousashavebeenthevarietiesofintrusiveporphyriesalreadymentioned，therewereheremountainscomposedofanewkind，havingacompact，smooth，cream-colouredbasis，includingonlyafewcrystalsoffeldspar，andmottledwithdendriticspotsofoxideofiron。
Therewerealsosomemountainsofaporphyrywithabrick-redbasis，containingirregular，oftenlens-shaped，patchesofcompactfeldspar，andcrystalsoffeldspar，whichlattertomysurpriseIfindtobeorthite。
AtthefootofthefirstridgeofthemainCordillera，intheravineofMaricongo，andatanelevationwhich，fromtheextremecoldnessandappearanceofthevegetation，Iestimatedatabouttenthousandfeet，I
foundbedsofwhitesandstoneandoflimestoneincludingthePectenDufreynoyi，Terebratulaaenigma，andsomeGryphites。ThisridgethrowsthewaterontheonehandintothePacific，andontheother，asIwasinformed，intoagreatgravel-covered，basin-likeplain，includingasalt-
lake，andwithoutanydrainage-exit。IncrossingtheCordillerabythisPass，itissaidthatthreeprincipalridgesmustbetraversed，insteadoftwo，oronlyoneasinCentralChile。
Thecrestofthisfirstmainridgeandthesurroundingmountains，withtheexceptionofafewloftypinnacles，arecappedbyagreatthicknessofahorizontallystratified，tufaceousdeposit。Thelowestbedisofapalepurplecolour，hard，fine-grained，andfullofbrokencrystalsoffeldsparandscalesofmica。Themiddlebediscoarser，andlesshard，andhenceweathersintoverysharppinnacles;itincludesverysmallfragmentsofgranite，andinnumerableonesofallsizesofgreyvesiculartrachyte，someofwhichweredistinctlyrounded。Theuppermostbedisabouttwohundredfeetinthickness，ofadarkercolourandapparentlyhard：butIhadnottimetoascendtoit。Thesethreehorizontalbedsmaybeseenforthedistanceofmanyleagues，especiallywestwardorinthedirectionofthePacific，cappingthesummitsofthemountains，andstandingontheoppositesidesoftheimmensevalleysatexactlycorrespondingheights。Ifunitedtheywouldformaplain，inclinedveryslightlytowardsthePacific;thebedsbecomethinnerinthisdirection，andthetuff(judgingfromonepointtowhichIascended，somewaydownthevalley)finer-grainedandoflessspecificgravity，thoughstillcompactandsonorousunderthehammer。Thegentlyinclined，almosthorizontalstratification，thepresenceofsomeroundedpebbles，andthecompactnessofthelowestbed，thoughrenderingitprobable，wouldnothaveconvincedmethatthismasshadbeenofsubaqueousorigin，foritisknownthatvolcanicashesfallingonlandandmoistenedbyrainoftenbecomehardandstratified;butbedsthusoriginating，andowingtheirconsolidationtoatmosphericmoisture，wouldhavecoveredalmostequallyeveryneighbouringsummit，highandlow，andwouldnothaveleftthoseaboveacertainexactlevelabsolutelybare;thiscircumstanceseemstometoprovethatthevolcanicejectionswerearrestedattheirpresent，widelyextended，equablelevel，andthereconsolidatedbysomeothermeansthansimpleatmosphericmoisture;andthisnodoubtmusthavebeenasheetofwater。Alakeatthisgreatheight，andwithoutabarrieronanyoneside，isoutofthequestion;consequentlywemustconcludethatthetufaceousmatterwasancientlydepositedbeneaththesea。Itwascertainlydepositedbeforetheexcavationofthevalleys，oratleastbeforetheirfinalenlargement(Ihaveendeavouredtoshowinmy“Journal“
etc。(2ndedition)page355，thatthisaridvalleywasleftbytheretreatingsea，asthelandslowlyrose，inthestateinwhichwenowseeit。);andImayadd，thatMr。Lambert，agentlemanwellacquaintedwiththiscountry，informsme，thatinascendingtheravineofSantandres(whichbranchesofffromtheDespoblado)hemetwithstreamsoflavaandmucheruptedmattercappingallthehillsofgraniteandporphyry，withtheexceptionofsomeprojectingpoints;healsoremarkedthatthevalleyshadbeenexcavatedsubsequentlytotheseeruptions。
Thisvolcanicformation，whichIaminformedbyMr。Lambertextendsfarnorthward，isofinterest，astypifyingwhathastakenplaceonagranderscaleonthecorrespondingwesternsideoftheCordilleraofPeru。Underanotherpointofview，however，itpossessesafarhigherinterest，asconfirmingthatconclusiondrawnfromthestructureofthefringesofstratifiedshinglewhichareprolongedfromtheplainsatthefootoftheCordillerafarupthevalleys，——namely，thatthisgreatrangehasbeenelevatedinmasstoaheightofbetweeneightandninethousandfeet(ImayherementionthatonthesouthsideofthemainvalleyofCopiapo，nearPotreroSeco，themountainsarecappedbyathickmassofhorizontallystratifiedshingle，ataheightwhichIestimatedatbetweenfifteenhundredandtwothousandfeetabovethebedofthevalley。Thisshingle，I
believe，formstheedgeofawideplain，whichstretchessouthwardsbetweentwomountainranges。);andnow，judgingfromthistufaceousdeposit，wemayconcludethatthehorizontalelevationhasbeeninthedistrictofCopiapoabouttenthousandfeet。
(FIGURE24。)
InthevalleyoftheDespoblado，thestratification，asbeforeremarkedhasbeenmuchdisturbed，andinsomepointstoagreaterdegreethanIhaveanywhereelseseen。Iwillgivetwocases：averythickmassofthinlystratifiedredsandstone，includingbedsofconglomerate，hasbeencrushedtogether(asrepresentedinFigure24)intoayokeorurn-formedtrough，sothatthestrataonbothsideshavebeenfoldedinwards：ontherighthandtheproperlyunderlyingporphyriticclaystoneconglomerateisseenoverlyingthesandstone，butitsoonbecomesvertical，andthenisinclinedtowardsthetrough，sothatthebedsradiatelikethespokesofawheel：onthelefthand，theinvertedporphyriticconglomeratealsoassumesadiptowardsthetrough，notgradually，asontherighthand，butbymeansofaverticalfaultandsynclinalbreak;andalittlestillfurtherontowardstheleft，thereisasecondgreatobliquefault(bothshownbythearrow-
lines)，withthestratadippingtoadirectlyoppositepoint;thesemountainsareintersectedbyinfinitelynumerousdikes，someofwhichcanbeseentorisefromhummocksofgreenstone，andcanbetracedforthousandsoffeet。Inthesecondcase，twolowridgestrendtogetheranduniteattheheadofalittlewedge-shapedvalley：throughouttheright-
handridge，thestratadipat45degreestotheeast;intheleft-handridge，wehavetheverysamestrataandatfirstwithexactlythesamedip;
butinfollowingthisridgeupthevalley，thestrataareseenveryregularlytobecomemoreandmoreinclineduntiltheystandvertical，theythengraduallyfallover(thebassetedgesformingsymmetricalserpentinelinesalongthecrest)，tillattheveryheadofthevalleytheyarereversedatanangleof45degrees：sothatatthispointthebedshavebeenturnedthroughanangleof135degrees;andherethereisakindofanticlinalaxis，withthestrataonbothsidesdippingtooppositepointsatanangleof45degrees，butthoseonthelefthandupsidedown。
ONTHEERUPTIVESOURCESOFTHEPORPHYRITICCLAYSTONEANDGREENSTONELAVAS。
InCentralChile，fromtheextrememetamorphicaction，itisinmostpartsdifficulttodistinguishbetweenthestreamsofporphyriticlavaandtheporphyriticbreccia-conglomerate，buthere，atCopiapo，theyaregenerallyperfectlydistinct，andintheDespoblado，Isawforthefirsttime，twogreatstrataofpurpleclaystoneporphyry，afterhavingbeenforaconsiderablespacecloselyunitedtogether，oneabovetheother，becomeseparatedbyamassoffragmentarymatter，andthenboththinout;——theloweronemorerapidlythantheupperandgreaterstream。Consideringthenumberandthicknessofthestreamsofporphyriticlava，andthegreatthicknessofthebedsofbreccia-conglomerate，therecanbelittledoubtthatthesourcesoferuptionmustoriginallyhavebeennumerous：
nevertheless，itisnowmostdifficulteventoconjecturetheprecisepointofanyoneoftheancientsubmarinecraters。Ihaverepeatedlyobservedmountainsofporphyries，moreorlessdistinctlystratifiedtowardstheirsummitsorontheirflanks，withoutatraceofstratificationintheircentralandbasalparts：inmostcases，Ibelievethisissimplydueeithertotheobliteratingeffectsofmetamorphicaction，ortosuchpartshavingbeenmainlyformedofintrusiveporphyries，ortobothcausesconjoined;insomeinstances，however，itappearedtomeveryprobablethatthegreatcentralunstratifiedmassesofporphyrywerethenowpartiallydenudednucleioftheoldsubmarinevolcanoes，andthatthestratifiedpartsmarkedthepointswhencethestreamsflowed。Inonecasealone，anditwasinthisValleyoftheDespoblado，Iwasableactuallytotraceathickstratumofpurplishporphyry，whichforaspaceofsomemilesconformablyoverlaytheusualalternatingbedsofbreccia-conglomeratesandclaystonelavas，untilitbecameunitedwith，andblendedinto，amountainousmassofvariousunstratifiedporphyries。
Thedifficultyoftracingthestreamsofporphyriestotheirancientanddoubtlessnumerouseruptivesources，maybepartlyexplainedbytheverygeneraldisturbancewhichtheCordillerainmostpartshassuffered;butI
stronglysuspectthatthereisamorespecificcause，namely，THATTHE
ORIGINALPOINTSOFERUPTIONTENDTOBECOMETHEPOINTSOFINJECTION。Thisinitselfdoesnotseemimprobable;forwheretheearth’scrusthasonceyielded，itwouldbeliabletoyieldagain，thoughtheliquifiedintrusivemattermightnotbeanylongerenabledtoreachthesubmarinesurfaceandflowaslava。Ihavebeenledtothisconclusion，fromhavingsofrequentlyobservedthat，wherepartofanunstratifiedmountain-massresembledinmineralogicalcharactertheadjoiningstreamsorstrata，therewereseveralotherkindsofintrusiveporphyriesandandesiticrocksinjectedintothesamepoint。Astheseintrusivemountain-massesformmostoftheaxes-linesintheCordillera，whetheranticlinal，uniclinal，orsynclinal，andasthemainvalleyshavegenerallybeenhollowedoutalongtheselines，theintrusivemasseshavegenerallysufferedmuchdenudation。Hencetheyareapttostandinsomedegreeisolated，andtobesituatedatthepointswherethevalleysabruptlybend，orwherethemaintributariesenter。Onthisviewoftherebeingatendencyintheoldpointsoferuptiontobecomethepointsofsubsequentinjectionanddisturbance，andconsequentlyofdenudation，itceasestobesurprisingthatthestreamsoflavaintheporphyriticclaystoneconglomerateformation，andinotheranalogouscases，shouldmostrarelybetraceabletotheiractualsources。
IQUIQUE，SOUTHERNPERU。
DifferentlyfromwhatwehaveseenthroughoutChile，thecoasthereisformednotbythegraniticseries，butbyanescarpmentoftheporphyriticconglomerateformation，betweentwoandthreethousandfeetinheight。(Thelowestpoint，wheretheroadcrossesthecoast-escarpment，is1，900feetbythebarometerabovethelevelofthesea。)Ihadtimeonlyforaveryshortexamination;thechiefpartoftheescarpmentappearstobecomposedofvariousreddishandpurple，sometimeslaminated，porphyries，resemblingthoseofChile;andIsawsomeoftheporphyriticbreccia-conglomerate;thestratificationappearedbutlittleinclined。Theuppermostpart，judgingfromtherocksnearthefamoussilvermineofHuantajaya，consistsoflaminated，impure，argillaceous，purplish-greylimestone，associated，I
believe，withsomepurplesandstone。(Mr。Bollaerthasdescribed“GeologicalProceedings“volume2page598，asingularmassofstratifieddetritus，gravel，andsand，eighty-oneyardsinthickness，overlyingthelimestone，andaboundingwithloosemassesofsilverore。Theminersbelievethattheycanattributethesemassestotheirproperveins。)Inthelimestoneshellsarefound：thethreefollowingspeciesweregivenme：——
LucinaAmericana，E。Forbes。
Terebratulainca，E。Forbes。
Terebratulaaenigma，D’Orbigny。
Thislatterspecieswehaveseenassociatedwiththefossilsofwhichlistshavebeengiveninthischapter，intwoplacesinthevalleyofCoquimbo，andintheravineofMaricongoatCopiapo。Consideringthisfact，andthesuperpositionofthesebedsontheporphyriticconglomerateformation;and，asweshallimmediatelysee，fromtheircontainingmuchgypsum，andfromtheirotherwiseclosegeneralresemblanceinmineralogicalnaturewiththestratadescribedinthevalleyofCopiapo，IhavelittledoubtthatthesefossiliferousbedsofIquiquebelongtothegreatcretaceo-ooliticformationofNorthernChile。IquiqueissituatedsevendegreeslatitudenorthofCopiapo;andImayheremention，thatanAmmonites，nov。species，andanAstarte，nov。species，weregivenmefromtheCerroPasco，abouttendegreesoflatitudenorthofIquique，andM。D’OrbignythinksthattheyprobablyindicateaNeocomianformation。Again，fifteendegreesoflatitudenorthward，inColombia，thereisagrandfossiliferousdeposit，nowwellknownfromthelaboursofVonBuch，Lea，d’Orbigny，andForbes，whichbelongstotheearlierstagesofthecretaceoussystem。Hence，bearinginmindthecharacterofthefewfossilsfromTierradelFuego，thereissomeevidencethatagreatportionofthestratifieddepositsofthewholevastrangeoftheSouthAmericanCordillerabelongstoaboutthesamegeologicalepoch。
Proceedingfromthecoastescarpmentinwards，Icrossed，inaspaceofaboutthirtymiles，anelevatedundulatorydistrict，withthebedsdippinginvariousdirections。Therocksareofmanykinds，——whitelaminated，sometimessiliceoussandstone，——purpleandredsandstone，sometimessohighlycalcareousastohaveacrystallinefracture，——argillaceouslimestone，——blackcalcareousslate-rock，likethatsooftendescribedatCopiapoandotherplaces，——thinlylaminated，fine-grained，greenish，indurated，sedimentary，fusiblerocks，approachingincharactertotheso-
calledpseudo-honestoneofChile，includingthincontemporaneousveinsofgypsum，——andlastly，muchcalcareous，laminatedporcelainjasper，ofagreencolour，withredspots，andofextremelyeasyfusibility：Inoticedoneconformablestratumofafreckled-brown，feldspathiclava。ImayherementionthatIheardofgreatbedsofgypsumintheCordillera。Theonlynovelpointinthisformation，isthepresenceofinnumerablethinlayersofrock-salt，alternatingwiththelaminatedandhard，butsometimesearthy，yellowish，orbrightredandferruginoussandstones。Thethickestlayerofsaltwasonlytwoinches，anditthinnedoutatbothends。OnoneofthesesaliferousmassesInoticedastratumabouttwelvefeetthick，ofdark-brown，hardbrecciated，easilyfusiblerock，containinggrainsofquartzandofblackoxideofiron，togetherwithnumerousimperfectfragmentsofshells。Theproblemoftheoriginofsaltissoobscure，thateveryfact，evengeographicalposition，isworthrecording。(ItiswellknownthatstratifiedsaltisfoundinseveralplacesontheshoresofPeru。TheislandofSanLorenzo，offLima，iscomposedofapileofthinstrata，abouteighthundredfeetinthickness，composedofyellowishandpurplish，hardsiliceous，orearthysandstones，alternatingwiththinlayersofshale，whichinplacespassesintoagreenish，semi-porcellanic，fusiblerock。Therearesomethinbedsofreddishmudstone，andsoftferruginousrotten-stones，withlayersofgypsum。Innearlyallthesevarieties，especiallyinthesoftersandstones，therearenumerousthinseamsofrock-salt：Iwasinformedthatonelayerhasbeenfoundtwoinchesinthickness。Themannerinwhichtheminutestfissuresofthedislocatedbedshavebeenpenetratedbythesalt，apparentlybysubsequentinfiltration，isverycurious。Onthesouthsideoftheisland，layersofcoalandofimpurelimestonehavebeendiscovered。Henceweherehavesalt，gypsum，andcoalassociatedtogether。Thestrataincludeveinsofquartz，carbonateoflime，andironpyrites;theyhavebeendislocatedbyaninjectedmassofgreenish-brownfeldspathictrap。NotonlyissaltabundantontheextremewesternlimitsofthedistrictbetweentheCordilleraandthePacific，but，accordingtoHelms，itisfoundintheoutlyinglowhillsontheeasternflankoftheCordillera。Thesefactsappeartomeopposedtothetheory，thatrock-saltisduetothesinkingofwater，chargedwithsalt，inmediterraneanspacesoftheocean。Thegeneralcharacterofthegeologyofthesecountrieswouldratherleadtotheopinion，thatitsoriginisinsomewayconnectedwithvolcanicheatatthebottomofthesea：seeonthissubjectSirR。Murchison“AnniversaryAddresstotheGeologicalSociety“1843page65。)Withtheexceptionofthesesaliferousbeds，mostoftherocksasalreadyremarked，presentastrikinggeneralresemblancewiththeupperpartsofthegypseousorcretaceo-ooliticformationofChile。
METALLIFEROUSVEINS。
Ihaveonlyafewremarkstomakeonthissubject：innineminingdistricts，someofthemofconsiderableextent，whichIvisitedinCENTRAL
Chile，IfoundthePRINCIPALveinsrunningfrombetween[N。andN。W。]to[S。andS。E。](TheseminingdistrictsareYaquilnearNancagua，wherethedirectionofthechiefveins，towhichonlyinallcasesIrefer，isnorthandsouth;intheUspallatarange，theprevailinglineisN。N。W。andS。S。E。;intheC。dePrado，itisN。N。W。andS。S。E。;nearIllapel，itisN。
byW。andS。byE。;atLosHornosthedirectionvariesfrombetween[N。andN。W。]to[S。andS。E。];attheC。delosHornos(furthernorthward)，itisN。N。W。andS。S。E。;atPanuncillo，itisN。N。W。andS。S。E。;and，lastly，atArqueros，thedirectionisN。W。andS。E。)：insomeotherplaces，however，theircoursesappearedquiteirregular，asissaidtobegenerallythecaseinthewholevalleyofCopiapo：atTambillos，southofCoquimbo，Isawonelargecopperveinextendingeastandwest。Itisworthyofnotice，thatthefoliationofthegneissandmica-slate，wheresuchrocksoccur，certainlytendtorunlikethemetalliferousveins，thoughoftenirregularly，inadirectionalittlewestwardofnorth。AtYaquil，IobservedthattheprincipalauriferousveinsrannearlyparalleltothegrainorimperfectcleavageofthesurroundingGRANITICrocks。Withrespecttothedistributionofthedifferentmetals，copper，gold，andironaregenerallyassociatedtogether，andaremostfrequentlyfound(butwithmanyexceptions，asweshallpresentlysee)intherocksofthelowerseries，betweentheCordilleraandthePacific，namely，ingranite，syenite，alteredfeldspathicclay-slate，gneiss，andasnearGuascomica-schist。Thecopper-oresconsistofsulphurets，oxides，andcarbonates，sometimeswithlaminaeofnativemetal：Iwasassuredthatinsomecases(asatPanuncilloS。E。ofCoquimbo)，theupperpartofthesameveincontainsoxides，andthelowerpartsulphuretsofcopper。(ThesamefacthasbeenobservedbyMr。
TaylorinCuba：“LondonPhilosophicalJournal“volume11page21。)Goldoccursinitsnativeform;itisbelievedthat，inmanycases，theupperpartoftheveinisthemostproductivepart：thisfactprobablyisconnectedwiththeabundanceofthismetalinthestratifieddetritusofChile，whichmusthavebeenchieflyderivedfromthedegradationoftheupperportionsoftherocks。Thesesuperficialbedsofwell-roundedgravelandsand，containinggold，appearedtometohavebeenformedundertheseaclosetothebeach，duringtheslowelevationoftheland：SchmidtmeyerremarksthatinChilegoldissoughtforinshelvingbanksattheheightofsomefeetonthesidesofthestreams，andnotintheirbeds，aswouldhavebeenthecasehadthismetalbeendepositedbycommonalluvialaction。
(“TravelsinChile“page29。)Veryfrequentlythecopper-ores，includingsomegold，areassociatedwithabundantmicaceousspeculariron。Goldisoftenfoundiniron-pyrites：attwogoldminesatYaquil(nearNancagua)，I
wasinformedbytheproprietorthatinonethegoldwasalwaysassociatedwithcopper-pyrites，andintheotherwithiron-pyrites：inthislattercase，itissaidthatiftheveinceasestocontainiron-pyrites，itisyetworthwhiletocontinuethesearch，butiftheiron-pyrites，whenitreappears，isnotauriferous，itisbetteratoncetogiveupworkingthevein。AlthoughIbelievecopperandgoldaremostfrequentlyfoundinthelowergraniticandmetamorphicschistoseseries，yetthesemetalsoccurbothintheporphyriticconglomerateformation(asontheflanksoftheBellofQuillotaandatJajuel)，andinthesuperincumbentstrata。AtJajuelIwasinformedthatthecopper-ore，withsomegold，isfoundonlyinthegreenstonesandalteredfeldspathicclay-slate，whichalternatewiththepurpleporphyriticconglomerate。Severalgoldveinsandsomeofcopper-
oreareworkedinseveralpartsoftheUspallatarange，bothinthemetamorphosedstrata，whichhavebeenshowntohavebeenofprobablysubsequentorigintotheNeocomianorgypseousformationofthemainCordillera，andintheintrusiveandesiticrocksofthatrange。AtLosHornos(N。E。ofIllapel)，likewise，therearenumerousveinsofcopper-
pyritesandofgold，bothinthestrataofthegypseousformationandintheinjectedhillsofandesiteandvariousporphyries。
Silver，intheformofachloride，sulphuret，oranamalgam，orinitsnativestate，andassociatedwithleadandothermetals，andatArqueroswithpurenativecopper，occurschieflyintheuppergreatgypseousorcretaceo-ooliticformationwhichformsprobablytherichestmassinChile。
WemayinstancetheminingdistrictsofArquerosnearCoquimbo，andofnearlythewholevalleyofCopiapo，andofIquique(wheretheprincipalveinsrunN。E。byE。andS。W。byW。)，inPeru。HencecomesMolina’sremark，thatsilverisborninthecoldandsolitarydesertsoftheUpperCordillera。Thereare，however，exceptionstothisrule：atParal(S。E。ofCoquimbo)silverisfoundintheporphyriticconglomerateformation;asI
suspectislikewisethecaseatS。PedrodeNolaskointhePeuquenesPass。
Richargentiferousleadisfoundintheclay-slateoftheUspallatarange;
andIsawanoldsilver-mineinahillofsyeniteatthefootoftheBellofQuillota：IwasalsoassuredthatsilverhasbeenfoundintheandesiticandporphyriticregionbetweenthetownofCopiapoandthePacific。Ihavestatedinapreviouspartofthischapter，thatintwoneighbouringminesatArquerostheveinsinonewereproductivewhentheytraversedthesingulargreensedimentarybeds，andunproductivewhencrossingthereddishbeds;whereasattheothermineexactlythereversetakesplace;Ihavealsodescribedthesingularandrarecaseofnumerousparticlesofnativesilverandofthechloridebeingdisseminatedinthegreenrockatthedistanceofayardfromthevein。MercuryoccurswithsilverbothatArquerosandatCopiapo：atthebaseofC。delosHornos(S。E。ofCoquimbo，adifferentplacefromLosHornos，beforementioned)Isawinasyeniticrocknumerousquartzoseveins，containingalittlecinnabarinnests：therewerehereotherparallelveinsofcopperandofaferrugino-auriferousore。
IbelievetinhasneverbeenfoundinChile。
>FrominformationgivenmebyMr。NixonofYaquil(AttheDuraznomine，thegoldisassociatedwithcopper-pyrites，andtheveinscontainlargeprismsofplumbago。CrystallisedcarbonateoflimeisoneofthecommonestmineralsinthematrixoftheChileanveins。)，andbyothers，itappearsthatinChilethoseveinsaregenerallymostpermanentlyproductive，which，consistingofvariousminerals(sometimesdifferingbutslightlyfromthesurroundingrocks)，includeparallelstringsRICHinmetals;suchaveiniscalledavetareal。Morecommonlytheminesareworkedonlywhereone，two，ormorethinveinsorstringsrunninginadifferentdirection，intersectaPOOR“vetareal：“itisunanimouslybelievedthatatsuchpointsofintersection(cruceros)，thequantityofmetalismuchgreaterthanthatcontainedinotherpartsoftheintersectingveins。Insomecrucerosorpointsofintersection，themetalsextendevenbeyondthewallsofthemain，broad，stonyvein。Itissaidthatthegreatertheangleofintersection，thegreatertheproduce;andthatnearlyparallelstringsattracteachother;intheUspallatarange，Iobservedthatnumerousthinauri-ferruginousveinsrepeatedlyranintoknots，andthenbranchedoutagain。IhavealreadydescribedtheremarkablemannerinwhichrocksoftheUspallatarangeareinduratedandblackened(asifbyablastofgunpowder)
toaconsiderabledistancefromthemetallicveins。
Finally，Imayobserve，thatthepresenceofmetallicveinsseemsobviouslyconnectedwiththepresenceofintrusiverocks，andwiththedegreeofmetamorphicactionwhichthedifferentdistrictsofChilehaveundergone。
(SirR。MurchisonandhisfellowtravellershavegivensomestrikingfactsonthissubjectintheiraccountoftheUralMountains(“GeologicalProceedings“volume3page748。)Suchmetamorphosedareasaregenerallyaccompaniedbynumerousdikesandinjectedmassesofandesiteandvariousporphyries：Ihaveinseveralplacestracedthemetalliferousveinsfromtheintrusivemassesintotheencasingstrata。Knowingthattheporphyriticconglomerateformationconsistsofalternatestreamsofsubmarinelavasandofthedebrisofancientlyeruptedrocks，andthatthestrataoftheuppergypseousformationsometimesincludesubmarinelavas，andarecomposedoftuffs，mudstones，andmineralsubstances，probablyduetovolcanicexhalations，——therichnessofthesestrataishighlyremarkablewhencomparedwiththeeruptedbeds，oftenofsubmarineorigin，butNOT
METAMORPHOSED，whichcomposethenumerousislandsinthePacific，Indian，andAtlanticOceans;forintheseislandsmetalsareentirelyabsent，andtheirnatureevenunknowntotheaborigines。
SUMMARYOFTHEGEOLOGICALHISTORYOFTHECHILEANCORDILLERA，ANDOFTHE
SOUTHERNPARTSOFSOUTHAMERICA。
WehaveseenthattheshoresofthePacific，foraspaceof1，200milesfromTresMontestoCopiapo，andIbelieveforaverymuchgreaterdistance，arecomposed，withtheexceptionofthetertiarybasins，ofmetamorphicschists，plutonicrocks，andmoreorlessalteredclay-slate。
Ontheflooroftheoceanthusconstituted，vaststreamsofvariouspurplishclaystoneandgreenstoneporphyrieswerepouredforth，togetherwithgreatalternatingpilesofangularandroundedfragmentsofsimilarrocksejectedfromthesubmarinecraters。Fromthecompactnessofthestreamsandfragments，itisprobablethat，withtheexceptionofsomedistrictsinNorthernChile，theeruptionstookplaceinprofoundlydeepwater。Theorificesoferuptionappeartohavebeenstuddedoverabreadth，withsomeoutliers，offromfiftytoonehundredmiles：andcloselyenoughtogether，bothnorthandsouth，andeastandwest，fortheejectedmattertoformacontinuousmass，whichinCentralChileismorethanamileinthickness。Itracedthismould-likemass，foronly450miles;butjudgingfromwhatIsawatIquique，fromspecimens，andfrompublishedaccounts，itappearstohaveamanifoldgreaterlength。Inthebasalpartsoftheseries，andespeciallytowardstheflanksoftherange，mud，sinceconvertedintoafeldspathicslatyrock，andsometimesintogreenstone，wasoccasionallydepositedbetweenthebedsoferuptedmatter：withthisexceptiontheuniformityoftheporphyriticrocksisveryremarkable。
Attheperiodwhentheclaystoneandgreenstoneporphyriesnearlyorquiteceasedbeingerupted，thatgreatpileofstratawhich，fromoftenaboundingwithgypsum，Ihavegenerallycalledthegypseousformationwasdeposited，andfeldspathiclavas，togetherwithothersingularvolcanicrocks，wereoccasionallypouredforth：Iamfarfrompretendingthatanydistinctlineofdemarcationcanbedrawnbetweenthisformationandtheunderlyingporphyriesandporphyriticconglomerate，butinamassofsuchgreatthickness，andbetweenbedsofsuchwidelydifferentmineralogicalnature，somedivisionwasnecessary。Ataboutthecommencementofthegypseousperiod，thebottomoftheseahereseemsfirsttohavebeenpeopledbyshells，notmanyinkind，butaboundinginindividuals。AttheP。delIncathefossilsareembeddednearthebaseoftheformation;inthePeuquenesrange，atdifferentlevels，halfwayup，andevenhigherintheseries;
hence，inthesesections，thewholepileofstratabelongstothesameperiod：thesameremarkisapplicabletothebedsatCopiapo，whichattainathicknessofbetweensevenandeightthousandfeet。ThefossilshellsintheCordilleraofCentralChile，intheopinionofallthepalaeontologistswhohaveexaminedthem，belongtotheearlierstagesofthecretaceoussystem;whilstinNorthernChilethereisamostsingularmixtureofcretaceousandooliticforms：fromthegeologicalrelations，however，ofthesetwodistricts，Icannotbutthinkthattheyallbelongtonearlythesameepoch，whichIhaveprovisionallycalledcretaceo-oolitic。
Thestratainthisformation，composedofblackcalcareousshaly-rocksofredandwhite，andsometimessiliceoussandstone，ofcoarseconglomerates，limestones，tuffs，darkmudstones，andthosesingularfine-grainedrockswhichIhavecalledpseudo-honestones，vastbedsofgypsum，andmanyotherjasperyandscarcelydescribablevarieties，varyandreplaceeachotherinshorthorizontaldistances，toanextent，Ibelieve，unequalledeveninanytertiarybasin。Mostofthesesubstancesareeasilyfusible，andhaveapparentlybeenderivedeitherfromvolcanoesstillinquietaction，orfromtheattritionofvolcanicproducts。Ifwepicturetoourselvesthebottomofthesea，rendereduneveninanextremedegree，withnumerouscraters，somefewoccasionallyineruption，butthegreaternumberinthestateofsolfataras，dischargingcalcareous，siliceous，ferruginousmatters，andgypsumorsulphuricacidtoanamountsurpassing，perhaps，eventheexistingsulphureousvolcanoesofJava(VonBuch’s“DescriptionPhysiquedesIlesCanaries“page428。)，weshallprobablyunderstandthecircumstancesunderwhichthissingularpileofvaryingstratawasaccumulated。Theshellsappeartohavelivedatthequiescentperiodswhenonlylimestoneorcalcareo-argillaceousmatterwasdepositing。FromDr。
Gillies’account，thisgypseousorcretaceo-ooliticformationextendsasfarsouthasthePassofPlanchon，andIfolloweditnorthwardatintervalsfor500miles：judgingfromthecharacterofthebedswiththeTerebratulaaenigma，atIquique，itextendsfromfourtofivehundredmilesfurther：
andperhapsevenfortendegreesoflatitudenorthofIquiquetotheCerroPasco，notfarfromLima：again，weknowthatacretaceousformation，aboundingwithfossils，islargelydevelopednorthoftheequator，inColombia：inTierradelFuego，ataboutthissameperiod，awidedistrictofclay-slatewasdeposited，whichinitsmineralogicalcharactersandexternalfeatures，mightbecomparedtotheSilurianregionsofNorthWales。Thegypseousformation，likethatoftheporphyriticbreccia-
conglomerateonwhichitrests，isofinconsiderablebreadth;thoughofgreaterbreadthinNorthernthaninCentralChile。
Asthefossilshellsinthisformationarecovered，inthePeuquenesridge，byagreatthicknessofstrata;atthePuentedelInca，byatleastfivethousandfeet;atCoquimbo，thoughthesuperpositionthereislessplainlyseen，byaboutsixthousandfeet;andatCopiapo，certainlybyfiveorsixthousand，andprobablybyseventhousandfeet(thesamespeciesthererecurringintheupperandlowerpartsoftheseries)，wemayfeelconfidentthatthebottomoftheseasubsidedduringthiscretaceo-ooliticperiod，soastoallowoftheaccumulationofthesuperincumbentsubmarinestrata。Thisconclusionisconfirmedby，orperhapsratherexplains，thepresenceofthemanybedsatmanylevelsofcoarseconglomerate，thewell-
roundedpebblesinwhichwecannotbelieveweretransportedinverydeepwater。EventheunderlyingporphyriesatCopiapo。withtheirhighlyamygdaloidalsurfaces，donotappeartohaveflowedundergreatpressure。
Thegreatsinkingmovementthusplainlyindicated，musthaveextendedinanorthandsouthlineforatleastfourhundredmiles，andprobablywasco-
extensivewiththegypseousformation。
Thebedsofconglomeratejustreferredto，andtheextraordinarilynumeroussilicifiedtrunksoffir-treesatLosHornos，perhapsatCoquimboandattwodistantpointsinthevalleyofCopiapo，indicatethatlandexistedatthisperiodintheneighbourhood。Thisland，orislands，inthenorthernpartofthedistrictofCopiapo，musthavebeenalmostexclusivelycomposed，judgingfromthenatureofthepebblesofgranite：inthesouthernpartsofCopiapo，itmusthavebeenmainlyformedofclaystoneporphyries，withsomemica-schist，andwithmuchsandstoneandjasperyrocksexactlyliketherocksinthegypseousformation，andnodoubtbelongingtoitsbasalseries。Inseveralotherplacesalso，duringtheaccumulationofthegypseousformation，itsbasalpartsandtheunderlyingporphyriticconglomeratemustlikewisehavebeenalreadypartiallyupheavedandexposedtowearandtear;nearthePuentedelIncaandatCoquimbo，theremusthaveexistedmassesofmica-schistorsomesuchrock，whencewerederivedthemanysmallpebblesofopaquequartz。Itfollowsfromthesefacts，thatinsomepartsoftheCordilleratheupperbedsofthegypseousformationmustlieunconformablyonthelowerbeds;andthewholegypseousformation，inparts，unconformablyontheporphyriticconglomerate;
althoughIsawnosuchcases，yetinmanyplacesthegypseousformationisentirelyabsent;andthis，althoughnodoubtgenerallycausedbyquitesubsequentdenudation，mayinothersbeduetotheunderlyingporphyriticconglomeratehavingbeenlocallyupheavedbeforethedepositionofthegypseousstrata，andthushavingbecomethesourceofthepebblesofporphyryembeddedinthem。Intheporphyriticconglomerateformation，initslowerandmiddleparts，thereisveryrarelyanyevidence，withtheexceptionofthesmallquartzpebblesatJajuelnearAconcagua，andofthesinglepebbleofgraniteatCopiapo，oftheexistenceofneighbouringland：
intheupperparts，however，andespeciallyinthedistrictofCopiapo，thenumberofthoroughlywell-roundedpebblesofcompactporphyriesmakemebelieve，that，asduringtheprolongedaccumulationofthegypseousformationthelowerbedshadalreadybeenlocallyupheavedandexposedtowearandtear，soitwaswiththeporphyriticconglomerate。HenceinfollowingthusfarthegeologicalhistoryoftheCordillera，itmaybeinferredthatthebedofadeepandopen，ornearlyopen，oceanwasfilledupbyporphyriticeruptions，aidedprobablybysomegeneralandsomelocalelevations，tothatcomparativelyshallowlevelatwhichthecretaceo-
ooliticshellsfirstlived。Atthisperiod，thesubmarinecratersyieldedatintervalsaprodigioussupplyofgypsumandothermineralexhalations，andoccasionally，incertainplacespouredforthlavas，chieflyofafeldspathicnature：atthisperiod，islandsclothedwithfir-treesandcomposedofporphyries，primaryrocks，andthelowergypseousstratahadalreadybeenlocallyupheaved，andexposedtotheactionofthewaves;——thegeneralmovement，however，atthistimehavingbeenoveraverywidearea，oneofslowsubsidence，prolongedtillthebedoftheseasankseveralthousandfeet。
InCentralChile，afterthedepositionofagreatthicknessofthegypseousstrata，andaftertheirupheaval，bywhichtheCumbreandadjoiningrangeswereformed，avastpileoftufaceousmatterandsubmarinelavawasaccumulated，wheretheUspallatachainnowstands;alsoafterthedepositionandupheavaloftheequivalentgypseousstrataofthePeuquenesrange，thegreatthickmassofconglomerateinthevalleyofTenuyanwasaccumulated：duringthedepositionoftheUspallatastrata，weknowabsolutely，fromtheburiedverticaltrees，thattherewasasubsidenceofsomethousandfeet;andwemayinferfromthenatureoftheconglomerateinthevalleyofTenuyan，thatasimilarandperhapscontemporaneousmovementtheretookplace。Wehave，then，evidenceofasecondgreatperiodofsubsidence;and，asinthecaseofthesubsidencewhichaccompaniedtheaccumulationofthecretaceo-ooliticstrata，sothislattersubsidenceappearstohavebeencomplicatedbyalternateorlocalelevatorymovement——
fortheverticaltrees，buriedinthemidstoftheUspallatastrata，musthavegrownondryland，formedbytheupheavalofthelowersubmarinebeds。
PresentlyIshallhavetorecapitulatethefacts，showingthatatastilllaterperiod，namely，atnearlythecommencementoftheoldtertiarydepositsofPatagoniaandofChile，thecontinentstoodatnearlyitspresentlevel，andthen，forthethirdtime，slowlysubsidedtotheamountofseveralhundredfeet，andwasafterwardsslowlyre-upliftedtoitspresentlevel。
ThehighestpeaksoftheCordilleraappeartoconsistofactiveormorecommonlydormantvolcanoes，——suchasTupungato，Maypu，andAconcagua，whichlatterstands23，000feetabovethelevelofthesea，andmanyothers。Thenexthighestpeaksareformedofthegypseousandporphyriticstrata，thrownintoverticalorhighlyinclinedpositions。Besidestheelevationthusgainedbyangulardisplacements，Iinfer，withoutanyhesitation——fromthestratifiedgravel-fringeswhichgentlyslopeupthevalleysoftheCordillerafromthegravel-cappedplainsattheirbase，whichlatterareconnectedwiththeplains，stillcoveredwithrecentshellsonthecoast——
thatthisgreatrangehasbeenupheavedinmassbyaslowmovement，toanamountofatleast8，000feet。IntheDespobladoValley，northofCopiapo，thehorizontalelevation，judgingfromthecompact，stratifiedtufaceousdeposit，cappingthedistantmountainsatcorrespondingheights，wasabouttenthousandfeet。Itisverypossible，orratherprobable，thatthiselevationinmassmaynothavebeenstrictlyhorizontal，butmoreenergeticundertheCordillera，thantowardsthecoastoneitherside;nevertheless，movementsofthiskindmaybeconvenientlydistinguishedfromthosebywhichstratahavebeenabruptlybrokenandupturned。WhenviewingtheCordillera，beforehavingreadMr。Hopkins’sprofound“ResearchesonPhysicalGeology，“theconvictionwasimpressedonme，thattheangulardislocations，howeverviolent，werequitesubordinateinimportancetothegreatupwardmovementinmass，andthattheyhadbeencausedbytheedgesofthewidefissures，whichnecessarilyresultedfromthetensionoftheelevatedarea，havingyieldedtotheinwardrushoffluidifiedrock，andhavingthusbeenupturned。
Theridgesformedbytheangularlyupheavedstrataareseldomofgreatlength：inthecentralpartsoftheCordilleratheyaregenerallyparalleltoeachother，andruninnorthandsouthlines;buttowardstheflankstheyoftenextendmoreorlessobliquely。TheangulardisplacementhasbeenmuchmoreviolentinthecentralthanintheexteriorMAINlines;butithaslikewisebeenviolentinsomeoftheMINORlinesontheextremeflanks。
Theviolencehasbeenveryunequalonthesameshortlines;thecrusthavingapparentlytendedtoyieldoncertainpointsalongthelinesoffissures。Thesepoints，Ihaveendeavouredtoshow，wereprobablyfirstfocioferuption，andafterwardsofinjectedmassesofporphyryandandesite。(SirR。Murchisonandhiscompanionsstate“GeologicalProceedings“volume3page747，thatnotruegraniteappearsinthehigherUralMountains;butthatsyeniticgreenstone——arockcloselyanalogoustoourandesite——isfarthemostabundantoftheintrusivemasses。)Theclosesimilarityoftheandesiticgranitesandporphyries，throughoutChile，TierradelFuego，andeveninPeru，isveryremarkable。Theprevalenceoffeldsparcleavinglikealbite，iscommonnotonlytotheandesites，but(asIinferfromthehighauthorityofProfessorG。Rose，aswellasfrommyownmeasurements)tothevariousclaystoneandgreenstoneporphyries，andtothetrachyticlavasoftheCordillera。Theandesiticrockshaveinmostcasesbeenthelastinjectedones，andtheyprobablyformacontinuousdomeunderthisgreatrange：theystandinintimaterelationshipwiththemodernlavas;andtheyseemtohavebeentheimmediateagentinmetamorphosingtheporphyriticconglomerateformation，andoftenlikewisethegypseousstrata，totheextraordinaryextenttowhichtheyhavesuffered。
