Fromtheidentityinmineralogicalnatureoftherocks，andfromCaptainBelcher’sminutedescriptionofthecoastbetweenLirguenandTome，thefossiliferousconcretionsatthislatterplacecertainlybelongtothesameformationwiththebedsexaminedbymyselfatLirguen;andtheseagainareundoubtedlythesamewiththestrataofQuiriquina;moreover;thethreefirstoftheshellsfromTome，thoughassociatedinthesameconcretionswiththeBaculite，areidenticalwiththespeciesfromQuiriquina。Henceallthesandstoneandlignitiferousbedsinthisneighbourhoodcertainlybelongtothesameformation。AlthoughthegenericcharacteroftheQuiriquinafossilsnaturallyledM。d’Orbignytoconceivethattheywereoftertiaryorigin，yetaswenowfindthemassociatedwiththeBaculitesvaginaandwithanAmmonite，wemust，intheopinionofM。d’Orbigny，andifweareguidedbytheanalogyofthenorthernhemisphere，rankthemintheCretaceoussystem。Moreover，theBaculitesvagina，whichisinatolerablestateofpreservation，appearstoProfessorE。Forbescertainlytobeidenticalwithaspecies，sonamedbyhim，fromPondicherryinIndia;
whereitisassociatedwithnumerousdecidedlycretaceousspecies，whichapproachmostnearlytoLowerGreensandorNeocomianforms：thisfact，consideringthevastdistancebetweenChileandIndia，istrulysurprising。
Again，theNautilusd’Orbignyanus，asfarasitsimperfectstateallowsofcomparison，resembles，asIaminformedbyProfessorForbes，bothinitsgeneralformandinthatofitschambers，twospeciesfromtheUpperGreensand。Itmaybeaddedthateveryoneoftheabove-namedgenerafromQuiriquina，whichhaveanapparentlytertiarycharacter，arefoundinthePondicherrystrata。Thereare，however，somedifficultiesonthisviewoftheformationsatConcepcionbeingcretaceous，whichIshallafterwardsalludeto;andIwillhereonlystatethattheCardiumaucaisfoundalsoatCoquimbo，thebedsatwhichplace，therecanbenodoubt，aretertiary。
NAVIDAD。(IwasguidedtothislocalitybytheReportonM。Gay’s“GeologicalResearches“inthe“AnnalesdesScienc。Nat。”1stseriestome28。)
TheConcepcionformationextendssomedistancenorthward，buthowfarI
knownot;forthenextpointatwhichIlandedwasatNavidad，160milesnorthofConcepcion，and60milessouthofValparaiso。Thecliffshereareabouteighthundredfeetinheight：theyconsist，whereverIcouldexaminethem，offine-grained，yellowish，earthysandstones，withferruginousveins，andwithconcretionsofhardcalcareoussandstone。Inonepart，thereweremanypebblesofthecommonmetamorphicporphyriesoftheCordillera：andnearthebaseofthecliff，Iobservedasingleroundedboulderofgreenstone，nearlyayardindiameter。Itracedthissandstoneformationbeneaththesuperficialcoveringofgravel，forsomedistanceinland：thestrataareslightlyinclinedfromtheseatowardstheCordillera，whichapparentlyhasbeencausedbytheirhavingbeenaccumulatedagainstorroundoutlyingmassesofgranite，ofwhichsomepointsprojectnearthecoast。Thesandstonecontainsfragmentsofwood，eitherinthestateofligniteorpartiallysilicified，sharks’teeth，andshellsingreatabundance，bothhighupandlowdownthesea-cliffs。
PectunculusandOlivaweremostnumerousinindividuals，andnexttothemTurritellaandFusus。Icollectedinashorttime，thoughsufferingfromillness，thefollowingthirty-onespecies，allofwhichareextinct，andseveralofthegeneradonotnowrange(asweshallhereaftershow)nearlysofarsouth：——
1。Gastridiumcepa，G。B。Sowerby。
2。Monoceros，fragmentsof，consideredbyM。d’Orbignyasanewspecies。
3。Volutaalta，G。B。Sowerby(consideredbyM。d’OrbignyasdistinctfromtheV。altaofSantaCruz)。
4。Volutatriplicata，G。B。Sowerby。
5。Olivadimidiata，G。B。Sowerby。
6。Pleurotomadiscors，G。B。Sowerby。
7。Pleurotomaturbinelloides，G。B。Sowerby。
8。Fusussubreflexus，G。B。Sowerby。
9。Fususpyruliformis，G。B。Sowerby。
10。Fusus，alliedtoF。regularis(consideredbyM。d’Orbignyasadistinctspecies)。
11。Turritellasuturalis，G。B。Sowerby。
12。TurritellaPatagonica，G。B。Sowerby(fragmentsof)。
13。Trochuslaevis，G。B。Sowerby。
14。Trochuscollaris，G。B。Sowerby(consideredbyM。d’OrbignyastheyoungoftheT。laevis)。
15。Cassismonilifer，G。B。Sowerby。
16。Pyruladistans，G。B。Sowerby。
17。Tritonverruculosus，G。B。Sowerby。
18。Sigaretussubglobosus，G。B。Sowerby。
19。Naticasolida，G。B。Sowerby。(ItisdoubtfulwhethertheNaticasolidaofS。Cruzisthesamespecieswiththis。)
20。Terebraundulifera，G。B。Sowerby。
21。Terebracostellata，G。B。Sowerby。
22。Bulla(fragmentsof)。
23。Dentaliumgiganteum，do。
24。Dentaliumsulcosum，do。
25。Corbis(？)laevigata，do。
26。Cardiummultiradiatum，do。
27。Venusmeridionalis，do。
28。Pectunculusdispar，(？)Desh。(consideredbyM。d’Orbignyasadistinctspecies)。
29，30。CytheraeaandMactra，fragmentsof(consideredbyM。d’Orbignyasnewspecies)。
31。Pecten，fragmentsof。
COQUIMBO。
(FIGURE21。SECTIONOFTHETERTIARYFORMATIONATCOQUIMBO。
>FromLevelofSeatoSurfaceofplain，252feetabovesea，throughlevelsF，E，DandC：
F——Lowersandstone，withconcretionsandsilicifiedbones，withfossilshells，all，ornearlyall，extinct。
E——Upperferruginoussandstone，withnumerousBalani，withfossilshells，all，ornearlyall，extinct。
CandD——Calcareousbedswithrecentshells。
A——Stratifiedsandinaravine，alsowithrecentshells。)
FormorethantwohundredmilesnorthwardofNavidad，thecoastconsistsofplutonicandmetamorphicrocks，withtheexceptionofsomequiteinsignificantsuperficialbedsofrecentorigin。AtTonguay，twenty-fivemilessouthofCoquimbo，tertiarybedsrecommence。IhavealreadyminutelydescribedintheSecondChapter，thestep-formedplainsofCoquimbo，andtheuppercalcareousbeds(fromtwentytothirtyfeetinthickness)
containingshellsofrecentspecies，butindifferentproportionsfromthoseonthebeach。Thereremainstobedescribedonlytheunderlyingancienttertiarybeds，representedinFigure21bythelettersFandE：——
IobtainedgoodsectionsofbedFonlyinHerraduraBay：itconsistsofsoftwhitishsandstone，withferruginousveins，somepebblesofgranite，andconcretionarylayersofhardcalcareoussandstone。Theseconcretionsareremarkablefromthegreatnumberoflargesilicifiedbones，apparentlyofcetaceousanimals，whichtheycontain;andlikewiseofashark’steeth，closelyresemblingthoseoftheCarchariasmegalodon。Shellsofthefollowingspecies，ofwhichthegiganticOysterandPernaarethemostconspicuous，arenumerouslyembeddedintheconcretions：——
1。Bullaambigua，d’Orbigny“Voyage“Pal。
2。MonocerosBlainvillii，d’Orbigny“Voyage“Pal。
3。Cardiumauca，d’Orbigny“Voyage“Pal。
4。PanopaeaCoquimbensis，d’Orbigny“Voyage“Pal。
5。PernaGaudichaudi，d’Orbigny“Voyage“Pal。
6。Artemisponderosa;Mr。SowerbycanfindnodistinguishingcharacterbetweenthisfossilandtherecentA。ponderosa;itiscertainlyanArtemis，asshownbythepallialimpression。
7。OstreaPatagonica(？);Mr。SowerbycanpointoutnodistinguishingcharacterbetweenthisspeciesandthatsoeminentlycharacteristicofthegreatPatagonianformation;buthewillnotpretendtoaffirmthattheyareidentical。
8。FragmentsofaVenusandNatica。
ThecliffsononesideofHerraduraBayarecappedbyamassofstratifiedshingle，containingalittlecalcareousmatter，andIdidnotdoubtthatitbelongedtothesamerecentformationwiththegravelonthesurroundingplains，alsocementedbycalcareousmatter，untiltomysurprise，Ifoundinthemidstofit，asinglethinlayeralmostentirelycomposedoftheabovegiganticoyster。
Atalittledistanceinland，IobtainedseveralsectionsofthebedE，which，thoughdifferentinappearancefromthelowerbedF，belongstothesameformation：itconsistsofahighlyferruginoussandymass，almostcomposed，likethelowestbedatPortS。Julian，offragmentsofBalanidae;
itincludessomepebbles，andlayersofyellowish-brownmudstone。Theembeddedshellsconsistof：——
1。MonocerosBlainvillii，d’Orbigny“Voyage“Pal。
2。Monocerosambiguus，G。B。Sowerby。
3。Anomiaalternans，G。B。Sowerby。
4。Pectenrudis，G。B。Sowerby。
5。PernaGaudichaudi，d’Orbigny“Voyage“Pal。
6。OstreaPatagonica(？)，d’Orbigny“Voyage“Pal。
7。Ostrea，smallspecies，inimperfectstate;itappearedtomelikeasmallkindnowlivingin，butveryrareinthebay。
8。MytilusChiloensis;Mr。Sowerbycanfindnodistinguishingcharacterbetweenthisfossil，asfarasitsnotveryperfectconditionallowsofcomparison，andtherecentspecies。
9。BalanusCoquimbensis，G。B。Sowerby。
10。Balanuspsittacus？King。ThisappearstoMr。Sowerbyandmyselfidenticalwithaverylargeandcommonspeciesnowlivingonthecoast。
Theuppermostlayersofthisferrugino-sandymassareconformablycoveredby，andimpregnatedtothedepthofseveralincheswith，thecalcareousmatterofthebedDcalledlosa：henceIatonetimeimaginedthattherewasagradualpassagebetweenthem;butasallthespeciesarerecentinthebedD，whilstthemostcharacteristicshellsoftheuppermostlayersofEaretheextinctPerna，Pecten，andMonoceros，IagreewithM。d’Orbigny，thatthisviewiserroneous，andthatthereisonlyamineralogicalpassagebetweenthem，andnogradualtransitioninthenatureoftheirorganicremains。Besidesthefourteenspeciesenumeratedfromthesetwolowerbeds，M。d’Orbignyhasdescribedtenotherspeciesgiventohimfromthislocality;namely：——
1。FususCleryanus，d’Orbigny“Voyage“Pal。
2。Fususpetitianus，d’Orbigny“Voyage“Pal。
3。Venushanetiana，d’Orbigny“Voyage“Pal。
4。Venusincerta(？)d’Orbigny“Voyage“Pal。
5。VenusCleryana，d’Orbigny“Voyage“Pal。
6。Venuspetitiana，d’Orbigny“Voyage“Pal。
7。VenusChilensis，d’Orbigny“Voyage“Pal。
8。Solecurtushanetianus，d’Orbigny“Voyage“Pal。
9。Mactraauca，d’Orbigny“Voyage“Pal。
10。Olivaserena，d’Orbigny“Voyage“Pal。
Ofthesetwenty-fourshells，allareextinct，except，accordingtoMr。
Sowerby，theArtemisponderosa，MytilusChiloensis，andprobablythegreatBalanus。
COQUIMBOTOCOPIAPO。
AfewmilesnorthofCoquimbo，Imetwiththeferruginous，balaniferousmassEwithmanysilicifiedbones;IwasinformedthatthesesilicifiedbonesoccuralsoatTonguay，southofCoquimbo：theirnumberiscertainlyremarkable，andtheyseemtotaketheplaceofthesilicifiedwood，socommononthecoast-formationsofSouthernChile。InthevalleyofChaneral，Iagainsawthissameformation，cappedwiththerecentcalcareousbeds。Ihereleftthecoast，anddidnotseeanymoreofthetertiaryformations，untildescendingtotheseaatCopiapo：hereinoneplaceIfoundvariouslycolouredlayersofsandandsoftsandstone，withseamsofgypsum，andinanotherplace，acomminutedshellymass，withlayersofrotten-stoneandseamsofgypsum，includingmanyoftheextinctgiganticoyster：bedswiththeseoystersaresaidtooccuratEnglishHarbour，afewmilesnorthofCopiapo。
COASTOFPERU。
Withtheexceptionofdepositscontainingrecentshellsandofquiteinsignificantdimensions，notertiaryformationshavebeenobservedonthiscoast，foraspaceoftwenty-twodegreesoflatitudenorthofCopiapo，untilcomingtoPayta，wherethereissaidtobeaconsiderablecalcareousdeposit：afewfossilshavebeendescribedbyM。d’Orbignyfromthisplace，namely：——
1。RostellariaGaudichaudi，d’Orbigny“Voyage“Pal。
2。PectunculusPaytensis，d’Orbigny“Voyage“Pal。
3。Venuspetitiana，d’Orbigny“Voyage“Pal。
4。OstreaPatagonica？Thisgreatoyster(ofwhichspecimenshavebeengivenme)cannotbedistinguishedbyMr。SowerbyfromsomeofthevarietiesfromPatagonia;thoughitwouldbehazardoustoassertitisthesamewiththatspecies，orwiththatfromCoquimbo。
CONCLUDINGREMARKS。
Theformationsdescribedinthischapter，have，inthecaseofChiloeandprobablyinthatofConcepcionandNavidad，apparentlybeenaccumulatedintroughsformedbysubmarineridgesextendingparalleltotheancientshoresofthecontinent;inthecaseoftheislandsofMochaandHuafoitishighlyprobable，andinthatofYpunandLemusalmostcertain，thattheywereaccumulatedroundisolatedrockycentresornuclei，inthesamemannerasmudandsandarenowcollectingroundtheoutlyingisletsandreefsintheWestIndianArchipelago。Hence，Imayremark，itdoesnotfollowthattheoutlyingtertiarymassesofMochaandHuafowereevercontinuouslyunitedatthesamelevelwiththeformationsonthemainland，thoughtheymayhavebeenofcontemporaneousorigin，andbeensubsequentlyupraisedtothesameheight。InthemorenorthernpartsofChile，thetertiarystrataseemtohavebeenseparatelyaccumulatedinbays，nowformingthemouthsofvalleys。
TherelationbetweentheseseveraldepositsontheshoresofthePacific，isnotnearlysoclearasinthecaseofthetertiaryformationsontheAtlantic。Judgingfromtheformandheightoftheland(evidencewhichI
feelsureisheremuchmoretrustworthythanitcaneverbeinsuchbrokencontinentsasthatofEurope)，fromtheidentityofmineralogicalcomposition，fromthepresenceoffragmentsofligniteandofsilicifiedwood，andfromtheintercalatedlayersofimperfectcoal，Imustbelievethatthecoast-formationsfromCentralChiloetoConcepcion，adistanceof400miles，areofthesameage：fromnearlysimilarreasons，IsuspectthatthebedsofMocha，Huafo，andYpun，belongalsotothesameperiod。ThecommonestshellinMochaandHuafoisthesamespeciesofTurritella;andI
believethesameCytheraeaisfoundontheislandsofHuafo，Chiloe，andYpun;butwiththesetriflingexceptions，thefeworganicremainsfoundattheseplacesaredistinct。ThenumerousshellsfromNavidad，withtheexceptionoftwo，namely，theSigaretusandTurritellafoundatYpun，arelikewisedistinctfromthosefoundinanyotherpartofthiscoast。
CoquimbohasCardiumaucaincommonwithConcepcion，andFususCleryanuswithHuafo;Imayadd，thatCoquimbohasVenuspetitiana，andagiganticoyster(saidbyM。d’OrbignyalsotobefoundalittlesouthofConcepcion)
incommonwithPayta，thoughthislatterplaceissituatedtwenty-twodegreesnorthwardoflatitude27degrees，towhichpointtheCoquimboformationextends。
>Fromthesefacts，andfromthegenericresemblanceofthefossilsfromthedifferentlocalities，Icannotavoidthesuspicionthattheyallbelongtonearlythesameepoch，whichepoch，asweshallimmediatelysee，mustbeaveryancienttertiaryone。ButastheBaculite，especiallyconsideringitsapparentidentitywiththeCretaceousPondicherryspecies，andthepresenceofanAmmonite，andtheresemblanceoftheNautilustotwouppergreensandspecies，togetheraffordverystrongevidencethattheformationofConcepcionisaSecondaryone;Iwill，inmyremarksonthefossilsfromtheotherlocalities，putononesidethosefromConcepcionandfromEasternChiloe，which，whatevertheiragemaybe，appeartometobelongtoonegroup。Imust，however，againcallattentiontothefactthattheCardiumaucaisfoundbothatConcepcionandintheundoubtedlytertiarystrataofCoquimbo：norshouldthepossibilitybeoverlooked，thatasTrigonia，thoughknowninthenorthernhemisphereonlyasaSecondarygenus，haslivingrepresentativesintheAustralianseas，soaBaculite，Ammonite，andTrigoniamayhavesurvivedinthisremotepartofthesouthernoceantoasomewhatlaterperiodthantothenorthoftheequator。
Beforepassinginreviewthefossilsfromtheotherlocalities，therearetwopoints，withrespecttotheformationsbetweenConcepcionandChiloe，whichdeservesomenotice。First，thatthoughthestrataaregenerallyhorizontal，theyhavebeenupheavedinChiloeinasetofparallelanticlinalanduniclinallinesrangingnorthandsouth，——inthedistrictnearP。Rumenabyeightorninefar-extended，mostsymmetrical，uniclinallinesrangingnearlyeastandwest，——andintheneighbourhoodofConcepcionbylessregularsinglelines，directedbothN。E。andS。W。andN。W。andS。E。Thisfactisofsomeinterest，asshowingthatwithinaperiodwhichcannotbeconsideredasveryancientinrelationtothehistoryofthecontinent，thestratabetweentheCordilleraandthePacifichavebeenbrokenupinthesamevariouslydirectedmannerashavetheoldplutonicandmetamorphicrocksinthissamedistrict。Thesecondpointis，thatthesandstonebetweenConcepcionandSouthernChiloeiseverywherelignitiferous，andincludesmuchsilicifiedwood;whereastheformationsinNorthernChiledonotincludebedsofligniteorcoal，andinplaceofthefragmentsofsilicifiedwoodtherearesilicifiedbones。Now，atthepresentday，fromCapeHorntonearConcepcion，thelandisentirelyconcealedbyforests，whichthinoutatConcepcion，andinCentralandNorthernChileentirelydisappear。Thiscoincidenceinthedistributionofthefossilwoodandthelivingforestsmaybequiteaccidental;butI
inclinetotakeadifferentviewofit;for，asthedifferenceinclimate，onwhichthepresenceofforestsdepends，ishereobviouslyinchiefpartduetotheformoftheland，andastheCordilleraundoubtedlyexistedwhenthelignitiferousbedswereaccumulating，Iconceiveitisnotimprobablethattheclimate，duringthelignitiferousperiod，variedondifferentpartsofthecoastinasomewhatsimilarmannerasitnowdoes。Lookingtoanearlierepoch，whenthestrataoftheCordilleraweredepositing，therewereislandswhicheveninthelatitudeofNorthernChile，wherenowallisirreclaimablydesert，supportedlargeconiferousforests。
TABLE4。
Column1。Genera，withlivingandtertiaryspeciesonthewestcoastofSouthAmerica。(M。d’OrbignystatesthatthegenusNaticaisnotfoundonthecoastofChile;butMr。CumingfounditatValparaiso。ScalariawasfoundatValparaiso;Arca，atIquique，inlatitude20，byMr。Cuming;Arca，also，wasfoundbyCaptainKing，atJuanFernandez，inlatitude33degrees30’S。)
Column2。Latitudes，inwhichfoundfossilonthecoastsofChileandPeru。
(Indegreesandminutes。)
Column3。Southernmostlatitude，inwhichfoundlivingonthewestcoastofSouthAmerica。(Indegreesandminutes。)
Bulla：30to4330：12nearLima。
Cassis：34：137。
Pyrula：34(and3630atConcepcion)：5Payta。
Fusus：30and4330：23Mexillones;reappearsattheSt。ofMagellan。
Pleurotoma：34to4330：218St。Elena。
Terebra：34：5Payta。
Sigaretus：34to4430：12Lima。
Anomia：30：748。
Perna：30：123Xixappa。
Cardium：30to34(and3630atConcepcion)：5Payta。
Artemis：30：5Payta。
Voluta：34to4430：Mr。Cumingdoesnotknowofanyspecieslivingonthewestcoast，betweentheequatorandlatitude43south;fromthislatitudeaspeciesisfoundasfarsouthasTierradelFuego。
Seventy-ninespeciesoffossilshells，inatolerablyrecognisablecondition，fromthecoastofChileandPeru，aredescribedinthisvolume，andinthePalaeontologicalpartofM。d’Orbigny’s“Voyage“：ifweputononesidethetwentyspeciesexclusivelyfoundatConcepcionandChiloe，fifty-ninespeciesfromNavidadandtheotherspecifiedlocalitiesremain。
Ofthesefifty-ninespeciesonlyanArtemis，aMytilusandBalanus，allfromCoquimbo，are(intheopinionofMr。Sowerby，butnotinthatofM。
d’Orbigny)identicalwithlivingshells;anditwouldcertainlyrequireabetterseriesofspecimenstorenderthisconclusioncertain。OnlytheTurritellaChilensisfromHuafoandMocha，theT。PatagonicaandVenusmeridionalisfromNavidad，comeveryneartorecentSouthAmericanshells，namely，thetwoTurritellastoT。cingulata，andtheVenustoV。exalbida：
somefewotherspeciescomeratherlessnear;andsomefewresembleformsintheolderEuropeantertiarydeposits：noneofthespeciesresemblesecondaryforms。HenceIconceivetherecanbenodoubtthattheseformationsaretertiary，——apointnecessarytoconsider，afterthecaseofConcepcion。Thefifty-ninespeciesbelongtothirty-twogenera;ofthese，Gastridiumisextinct，andthreeorfourofthegenera(viz。Panopaea，Rostellaria，Corbis(？)，andIbelieveSolecurtus)arenotnowfoundonthewestcoastofSouthAmerica。Fifteenofthegenerahaveonthiscoastlivingrepresentativesinaboutthesamelatitudeswiththefossilspecies;
buttwelvegeneranowrangeverydifferentlytowhattheyformerlydid。TheideaofTable4，inwhichthedifferencebetweentheextensioninlatitudeofthefossilandexistingspeciesisshown，istakenfromM。d’Orbigny’swork;buttherangeofthelivingshellsisgivenontheauthorityofMr。
Cuming，whoselong-continuedresearchesontheconchologyofSouthAmericaarewell-known。
Whenweconsiderthatveryfew，ifany，ofthefifty-ninefossilshellsareidenticalwith，ormakeanycloseapproachto，livingspecies;whenweconsiderthatsomeofthegeneradonotnowexistonthewestcoastofSouthAmerica，andthatnolessthantwelvegeneraoutofthethirty-twoformerlyrangedverydifferentlyfromtheexistingspeciesofthesamegenera，wemustadmitthatthesedepositsareofconsiderableantiquity，andthattheyprobablyvergeonthecommencementofthetertiaryera。Maywenotventuretobelieve，thattheyareofnearlycontemporaneousoriginwiththeEoceneformationsofthenorthernhemisphere？
ComparingthefossilremainsfromthecoastofChile(leavingout，asbefore，ConcepcionandChiloe)withthosefromPatagonia，wemayconclude，fromtheirgenericresemblance，andfromthesmallnumberofthespecieswhichfromeithercoastapproachcloselytolivingforms，thattheformationsofbothbelongtonearlythesameepoch;andthisistheopinionofM。D’Orbigny。Hadnotasinglefossilshellbeencommontothetwocoasts，itcouldnothavebeenarguedthattheformationsbelongedtodifferentages;forMessrs。CumingandHindshavefound，onthecomparisonofnearlytwothousandlivingspeciesfromtheoppositesidesofSouthAmerica，onlyoneincommon，namely，thePurpuralapillusfrombothsidesoftheIsthmusofPanama：eventheshellscollectedbymyselfamongsttheChonosIslandsandonthecoastofPatagonia，aredissimilar，andwemustdescendtotheapexofthecontinent，toTierradelFuego，tofindthesetwogreatconchologicalprovincesunitedintoone。HenceitisremarkablethatfourorfiveofthefossilshellsfromNavidad，namely，Volutaalta，TurritellaPatagonica，Trochuscollaris，Venusmeridionalis，perhapsNaticasolida，andperhapsthelargeoysterfromCoquimbo，areconsideredbyMr。
SowerbyasidenticalwithspeciesfromSantaCruzandP。Desire。M。
d’Orbigny，however，admitstheperfectidentityonlyoftheTrochus。
ONTHETEMPERATUREOFTHETERTIARYPERIOD。
Asthenumberofthefossilspeciesandgenerafromthewesternandeasterncoastsisconsiderable，itwillbeinterestingtoconsidertheprobablenatureoftheclimateunderwhichtheylived。WewillfirsttakethecaseofNavidad，inlatitude34degrees，wherethirty-onespecieswerecollected，andwhich，asweshallpresentlysee，musthaveinhabitedshallowwater，andthereforewillnecessarilywellexhibittheeffectsoftemperature。ReferringtoTable4wefindthattheexistingspeciesofthegeneraCassis，Pyrula，Pleurotoma，Terebra，andSigaretus，whicharegenerally(thoughbynomeansinvariably)characteristicofwarmerlatitudes，donotatthepresentdayrangenearlysofarsouthonthislineofcoastasthefossilspeciesformerlydid。IncludingCoquimbo，wehavePernainthesamepredicament。Thefirstimpressionfromthisfactis，thattheclimatemustformerlyhavebeenwarmerthanitnowis;butwemustbeverycautiousinadmittingthis，forCardium，Bulla，andFusus(and，ifweincludeCoquimbo，AnomiaandArtemis)likewiseformerlyrangedfarthersouththantheynowdo;andasthesegeneraarefarfrombeingcharacteristicofhotclimates，theirformergreatersouthernrangemaywellhavebeenowingtocausesquitedistinctfromclimate：Voluta，again，thoughgenerallysotropicalagenus，isatpresentconfinedonthewestcoasttocolderormoresouthernlatitudesthanitwasduringthetertiaryperiod。TheTrochuscollaris，moreover，and，aswehavejustseenaccordingtoMr。Sowerby，twoorthreeotherspecies，formerlyrangedfromNavidadasfarsouthasSantaCruzinlatitude50degrees。If，insteadofcomparingthefossilsofNavidad，aswehavehithertodone，withtheshellsnowlivingonthewestcoastofSouthAmerica，wecomparethemwiththosefoundinotherpartsoftheworld，undernearlysimilarlatitudes;forinstance，inthesouthernpartsoftheMediterraneanorofAustralia，thereisnoevidencethattheseaoffNavidadwasformerlyhotterthanwhatmighthavebeenexpectedfromitslatitude，evenifitwassomewhatwarmerthanitnowiswhencooledbythegreatsouthernpolarcurrent。SeveralofthemosttropicalgenerahavenorepresentativefossilsatNavidad;andthereareonlysinglespeciesofCassis，Pyrula，andSigaretus，twoofPleurotomaandtwoofTerebra，butnoneofthesespeciesareofconspicuoussize。InPatagonia，thereisevenstilllessevidenceinthecharacterofthefossils，oftheclimatehavingbeenformerlywarmer。(ItmaybeworthwhiletomentionthattheshellslivingatthepresentdayonthiseasternsideofSouthAmerica，inlatitude40degrees，haveperhapsamoretropicalcharacterthanthoseincorrespondinglatitudesontheshoresofEurope：
foratBahiaBlancaandS。Blas，therearetwofinespeciesofVolutaandfourofOliva。)Asfromthevariousreasonsalreadyassigned，therecanbelittledoubtthattheformationsofPatagoniaandatleastofNavidadandCoquimboinChile，aretheequivalentsofanancientstageinthetertiaryformationsofthenorthernhemisphere，theconclusionthattheclimateofthesouthernseasatthisperiodwasnothotterthanwhatmighthavebeenexpectedfromthelatitudeofeachplace，appearstomehighlyimportant;
forwemustbelieve，inaccordancewiththeviewsofMr。Lyell，thatthecauseswhichgavetotheoldertertiaryproductionsofthequitetemperatezonesofEuropeatropicalcharacter，WEREOFALOCALCHARACTERANDDIDNOT
AFFECTTHEENTIREGLOBE。Ontheotherhand，Ihaveendeavouredtoshow，inthe“GeologicalTransactions，“that，atamuchlaterperiod，EuropeandNorthandSouthAmericawerenearlycontemporaneouslysubjectedtoice-
action，andconsequentlytoacolder，oratleastmoreequable，climatethanthatnowcharacteristicofthesamelatitudes。
ONTHEABSENCEOFEXTENSIVEMODERNCONCHIFEROUSDEPOSITSINSOUTHAMERICA;
ANDONTHECONTEMPORANEOUSNESSOFTHEOLDERTERTIARYDEPOSITSATDISTANT
POINTSBEINGDUETOCONTEMPORANEOUSMOVEMENTSOFSUBSIDENCE。
KnowingfromtheresearchesofProfessorE。Forbes，thatmolluscousanimalschieflyaboundwithinadepthof100fathomsandunder，andbearinginmindhowmanythousandmilesofbothcoastsofSouthAmericahavebeenupraisedwithintherecentperiodbyaslow，long-continued，intermittentmovement，——
seeingthediversityinnatureoftheshoresandthenumberofshellsnowlivingonthem，——seeingalsothattheseaoffPatagoniaandoffmanypartsofChile，wasduringthetertiaryperiodhighlyfavourabletotheaccumulationofsediment，——theabsenceofextensivedepositsincludingrecentshellsoverthesevastspacesofcoastishighlyremarkable。TheconchiferouscalcareousbedsatCoquimbo，andatafewisolatedpointsnorthward，offerthemostmarkedexceptiontothisstatement;forthesebedsarefromtwentytothirtyfeetinthickness，andtheystretchforsomemilesalongshore，attaining，however，onlyaverytriflingbreadth。AtValdiviathereissomesandstonewithimperfectcastsofshells，whichPOSSIBLYmaybelongtotherecentperiod：partsoftheboulderformationandtheshingle-bedsonthelowerplainsofPatagoniaprobablybelongtothissameperiod，butneitherarefossiliferous：italsosohappensthatthegreatPampeanformationdoesnotinclude，withtheexceptionoftheAzara，anymollusca。TherecannotbethesmallestdoubtthattheupraisedshellsalongtheshoresoftheAtlanticandPacific，whetherlyingonthebaresurface，orembeddedinmouldorinsand-hillocks，willinthecourseofagesbedestroyedbyalluvialaction：thisprobablywillbethecaseevenwiththecalcareousbedsofCoquimbo，soliabletodissolutionbyrain-water。Ifwetakeintoconsiderationtheprobabilityofoscillationsoflevelandtheconsequentactionofthetidal-wavesatdifferentheights，theirdestructionwillappearalmostcertain。LookingtoanepochasfardistantinfuturityaswenowarefromthepastMioceneperiod，thereseemstomescarcelyachance，underexistingconditions，ofthenumerousshellsnowlivinginthosezonesofdepthsmostfertileinlife，andfoundexclusivelyonthewesternandsouth-easterncoastsofSouthAmerica，beingpreservedtothisimaginarydistantepoch。Awholeconchologicalserieswillintimebesweptaway，withnomemorialsoftheirexistencepreservedintheearth’scrust。
Cananylightbethrownonthisremarkableabsenceofrecentconchiferousdepositsonthesecoasts，onwhich，atanancienttertiaryepoch，strataaboundingwithorganicremainswereextensivelyaccumulated？Ithinktherecan，namely，byconsideringtheconditionsnecessaryforthepreservationofaformationtoadistantage。Lookingtotheenormousamountofdenudationwhichonallsidesofushasbeeneffected，——asevidencedbytheloftycliffscuttingoffonsomanycoastshorizontalandoncefar-extendedstrataofnogreatantiquity(asinthecaseofPatagonia)，——asevidencedbythelevelsurfaceofthegroundonbothsidesofgreatfaultsanddislocations，——byinlandlinesofescarpments，byoutliers，andnumberlessotherfacts，andbythatargumentofhighgeneralityadvancedbyMr。Lyell，namely，thateverySEDIMENTARYformation，whateveritsthicknessmaybe，andoverhowevermanyhundredsquaremilesitmayextend，istheresultandthemeasureofanequalamountofwearandtearofpre-existingformations;
consideringthesefacts，wemustconcludethat，asanordinaryrule，aformationtoresistsuchvastdestroyingpowers，andtolasttoadistantepoch，mustbeofwideextent，andeitherinitself，ortogetherwithsuperincumbentstrata，beofgreatthickness。Inthisdiscussion，weareconsideringonlyformationscontainingtheremainsofmarineanimals，which，asbeforementioned，live，withsomeexceptionswithin(mostofthemmuchwithin)depthsof100fathoms。How，then，canathickandwidelyextendedformationbeaccumulated，whichshallincludesuchorganicremains？First，letustakethecaseofthebedofthesealongremainingatastationarylevel：underthesecircumstancesitisevidentthatCONCHIFEROUSstratacanaccumulateonlytothesamethicknesswiththedepthatwhichtheshellscanlive;ongentlyinclinedcoastsalonecantheyaccumulatetoanyconsiderablewidth;andfromthewantofsuperincumbentpressure，itisprobablethatthesedimentarymatterwillseldombemuchconsolidated：suchformationshavenoverygoodchance，wheninthecourseoftimetheyareupraised，oflongresistingthepowersofdenudation。Thechancewillbelessifthesubmarinesurface，insteadofhavingremainedstationary，shallhavegoneonslowlyrisingduringthedepositionofthestrata，forinthiscasetheirtotalthicknessmustbeless，andeachpart，beforebeingconsolidatedorthicklycoveredupbysuperincumbentmatter，willhavehadsuccessivelytopassthroughtheordealofthebeach;andonmostcoasts，thewavesonthebeachtendtoweardownanddisperseeveryobjectexposedtotheiraction。Now，bothonthesouth-easternandwesternshoresofSouthAmerica，wehavehadclearproofsthatthelandhasbeenslowlyrising，andinthelonglinesofloftycliffs，wehaveseenthatthetendencyoftheseaisalmosteverywheretoeatintotheland。Consideringthesefacts，itceases，Ithink，tobesurprising，thatextensiverecentconchiferousdepositsareentirelyabsentonthesouthernandwesternshoresofAmerica。
Letustaketheoneremainingcase，ofthebedoftheseaslowlysubsidingduringalengthoftime，whilstsedimenthasgoneonbeingdeposited。Itisevidentthatstratamightthusaccumulatetoanythickness，eachstratumbeingdepositedinshallowwater，andconsequentlyaboundingwiththoseshellswhichcannotliveatgreatdepths：thepressure，also，Imayobserve，ofeachfreshbedwouldaidinconsolidatingallthelowerones。
Evenonarathersteepcoast，thoughsuchmusteverbeunfavourabletowidelyextendeddeposits，theformationswouldalwaystendtoincreaseinbreadthfromthewaterencroachingontheland。HencewemayadmitthatperiodsofslowsubsidencewillcommonlybemostfavourabletotheaccumulationofCONCHIFEROUSdeposits，ofsufficientthickness，extension，andhardness，toresisttheaveragepowersofdenudation。
Wehaveseenthatatanancienttertiaryepoch，fossiliferousdepositswereextensivelydepositedonthecoastsofSouthAmerica;anditisaveryinterestingfact，thatthereisevidencethattheseancienttertiarybedsweredepositedduringaperiodofsubsidence。Thus，atNavidad，thestrataareabouteighthundredfeetinthickness，andthefossilshellsareabundantbothattheleveloftheseaandsomewayupthecliffs;havingsentalistofthesefossilstoProfessorE。Forbes，hethinkstheymusthavelivedinwaterbetweenoneandtenfathomsindepth：hencethebottomoftheseaonwhichtheseshellsoncelivedmusthavesubsidedatleast700
feettoallowofthesuperincumbentmatterbeingdeposited。Imusthereremark，that，asalltheseandthefollowingfossilshellsareextinctspecies，ProfessorForbesnecessarilyjudgesofthedepthsatwhichtheylivedonlyfromtheirgenericcharacter，andfromtheanalogicaldistributionofshellsinthenorthernhemisphere;butthereisnojustcausefromthistodoubtthegeneralresults。AtHuafothestrataareaboutthesamethickness，namely，800feet，andProfessorForbesthinksthefossilsfoundtherecannothavelivedatagreaterdepththanfiftyfathoms，or300feet。Thesetwopoints，namely，NavidadandHuafo，are570
milesapart，butnearlyhalfwaybetweenthemliesMocha，anisland1，200
feetinheight，apparentlyformedoftertiarystratauptoitslevelsummit，andwithmanyshells，includingthesameTurritellawiththatfoundatHuafo，embeddedclosetothelevelofthesea。InPatagonia，shellsarenumerousatSantaCruz，atthefootofthe350feetplain，whichhascertainlybeenformedbythedenudationofthe840feetplain，andthereforewasoriginallycoveredbystratathatnumberoffeetinthickness，andtheseshells，accordingtoProfessorForbes，probablylivedatadepthofbetweensevenandfifteenfathoms：atPortS。Julian，sixtymilestothenorth，shellsarenumerousatthefootoftheninetyfeetplain(formedbythedenudationofthe950feetplain)，andlikewiseoccasionallyattheheightofseveralhundredfeetintheupperstrata;
theseshellsmusthavelivedinwatersomewherebetweenfiveandfiftyfathomsindepth。AlthoughinotherpartsofPatagoniaIhavenodirectevidenceofshoal-watershellshavingbeenburiedunderagreatthicknessofsuperincumbentsubmarinestrata，yetitshouldbeborneinmindthatthelowerfossiliferousstratawithseveralofthesamespeciesofMollusca，theuppertufaceousbeds，andthehighsummit-plain，stretchforaconsiderabledistancesouthward，andforhundredsofmilesnorthward;
seeingthisuniformityofstructure，IconceiveitmaybefairlyconcludedthatthesubsidencebywhichtheshellsatSantaCruzandS。Julianwerecarrieddownandcoveredup，wasnotconfinedtothesetwopoints，butwasco-extensivewithaconsiderableportionofthePatagoniantertiaryformation。Inasucceedingchapteritwillbeseen，thatweareledtoasimilarconclusionwithrespecttothesecondaryfossiliferousstrataoftheCordillera，namely，thattheyalsoweredepositedduringalong-
continuedandgreatperiodofsubsidence。
>Fromtheforegoingreasoning，andfromthefactsjustgiven，Ithinkwemustadmittheprobabilityofthefollowingproposition：namely，thatwhenthebedoftheseaiseitherstationaryorrising，circumstancesarefarlessfavourable，thanwhenthelevelissinking，totheaccumulationofCONCHIFEROUSdepositsofsufficientthicknessandextensiontoresist，whenupheaved，theaveragevastamountofdenudation。Thisresultappearstome，inseveralrespects，veryinteresting：everyoneisatfirstinclinedtobelievethatatinnumerablepoints，whereverthereisasupplyofsediment，fossiliferousstrataarenowforming，whichatsomefuturedistantepochwillbeupheavedandpreserved;butontheviewsabovegiven，wemustconcludethatthisisfarfrombeingthecase;onthecontrary，werequire(1st)，along-continuedsupplyofsediment;(2nd)，anextensiveshallowarea;and(3rd)，thatthisareashallslowlysubsidetoagreatdepth，soastoadmittheaccumulationofawidelyextendedthickmassofsuperincumbentstrata。Inhowfewpartsoftheworld，probably，dotheseconditionsatthepresentdayconcur！Wecanthus，also，understandthegeneralwantofthatclosesequenceinfossiliferousformationswhichwemighttheoreticallyhaveanticipated;for，withoutwesupposeasubsidingmovementtogoonatthesamespotduringanenormousperiod，fromonegeologicaleratoanother，andduringthewholeofthisperiodsedimenttoaccumulateattheproperrate，sothatthedepthshouldnotbecometoogreatforthecontinuedexistenceofmolluscousanimals，itisscarcelypossiblethatthereshouldbeaperfectsequenceatthesamespotinthefossilshellsofthetwogeologicalformations。(ProfessorH。D。Rogers，inhisexcellentaddresstotheAssociationofAmericanGeologists(“Silliman’sJournal“volume47page277)makesthefollowingremark：“I
questionifweareatallawarehowCOMPLETELYthewholehistoryofalldepartedtimeliesindeliblyrecordedwiththeamplestminutenessofdetailinthesuccessivesedimentsoftheglobe，howeffectually，inotherwords，everyperiodoftimeHASWRITTENITSOWNHISTORY，carefullypreservingeverycreatedformandeverytraceofaction。”Ithinkthecorrectnessofsuchremarksismorethandoubtful，evenifweexcept(asIsupposehewould)allthosenumerousorganicformswhichcontainnohardparts。)Sofarfromaverylong-continuedsubsidencebeingprobable，manyfactsleadtothebeliefthattheearth’ssurfaceoscillatesupanddown;andwehaveseenthatduringtheelevatorymovementsthereisbutasmallchanceofDURABLEfossiliferousdepositsaccumulating。
Lastly，thesesameconsiderationsappeartothrowsomelightonthefactthatcertainperiodsappeartohavebeenfavourabletothedeposition，oratleasttothepreservation，ofcontemporaneousformationsatverydistantpoints。WehaveseenthatinSouthAmericaanenormousareahasbeenrisingwithintherecentperiod;andinotherquartersoftheglobeimmensespacesappeartohaverisencontemporaneously。Frommyexaminationofthecoral-
reefsofthegreatoceans，Ihavebeenledtoconcludethatthebedoftheseahasgoneonslowlysinkingwithinthepresentera，overtrulyvastareas：this，indeed，isinitselfprobable，fromthesimplefactoftherisingareashavingbeensolarge。InSouthAmericawehavedistinctevidencethatatnearlythesametertiaryperiod，thebedoftheseaoffpartsofthecoastofChileandoffPatagoniawassinking，thoughtheseregionsareveryremotefromeachother。If，then，itholdsgood，asageneralrule，thatinthesamequarteroftheglobetheearth’scrusttendstosinkandrisecontemporaneouslyovervastspaces，wecanatoncesee，thatwehaveatdistantpoints，atthesameperiod，thoseveryconditionswhichappeartoberequisitefortheaccumulationoffossiliferousmassesofsufficientextension，thickness，andhardness，toresistdenudation，andconsequentlytolastuntoanepochdistantinfuturity。(ProfessorForbeshassomeadmirableremarksonthissubject，inhis“ReportontheShellsoftheAegeanSea。”InalettertoMr。Maclaren(“EdinburghNewPhilosophicalJournal“January1843)，Ipartiallyenteredintothisdiscussion，andendeavouredtoshowthatitwashighlyimprobable，thatupraisedatollsorbarrier-reefs，thoughofgreatthickness，should，owingtotheirsmallextensionorbreadth，bepreservedtoadistantfutureperiod。)
CHAPTERVI。PLUTONICANDMETAMORPHICROCKS：——CLEAVAGEANDFOLIATION。
Brazil，Bahia，gneisswithdisjointedmetamorphoseddikes。
Strikeoffoliation。
RiodeJaneiro，gneiss-granite，embeddedfragmentin，decompositionof。
LaPlata，metamorphicandoldvolcanicrocksof。
S。Ventana。
ClaystoneporphyryformationofPatagonia;singularmetamorphicrocks;
pseudo-dikes。
FalklandIslands，Palaeozoicfossilsof。
TierradelFuego，clay-slateformation，cretaceousfossilsof;cleavageandfoliation;formofland。
ChonosArchipelago，mica-schists，foliationdisturbedbygraniticaxis;
dikes。
Chiloe。
Concepcion，dikes，successiveformationof。
CentralandNorthernChile。
Concludingremarksoncleavageandfoliation。
Theircloseanalogyandsimilarorigin。
Stratificationofmetamorphicschists。
Foliationofintrusiverocks。
Relationofcleavageandfoliationtothelinesoftensionduringmetamorphosis。
Themetamorphicandplutonicformationsoftheseveraldistrictsvisitedbythe“Beagle“willbeherechieflytreatedof，butonlysuchcasesasappeartomenew，orofsomespecialinterest，willbedescribedindetail;attheendofthechapterIwillsumupallthefactsoncleavageandfoliation，——
towhichIparticularlyattended。
BAHIA，BRAZIL：latitude13degreessouth。
Theprevailingrockisgneiss，oftenpassing，bythedisappearanceofthequartzandmica，andbythefeldsparlosingitsredcolour，intoabrilliantlygreyprimitivegreenstone。Notunfrequentlyquartzandhornblendearearrangedinlayersinalmostamorphousfeldspar。Thereissomefine-grainedsyeniticgranite，orbicularlymarkedbyferruginouslines，andweatheringintovertical，cylindricalholes，almosttouchingeachother。Inthegneiss，concretionsofgranularfeldsparandothersofgarnetswithmicaoccur。Thegneissistraversedbynumerousdikescomposedofblack，finelycrystallised，hornblendicrock，containingalittleglassyfeldsparandsometimesmica，andvaryinginthicknessfrommerethreadstotenfeet：thesethreads，whichareoftencurvilinear，couldsometimesbetracedrunningintothelargerdikes。Oneofthesedikeswasremarkablefromhavingbeenintwoorthreeplaceslaterallydisjointed，withunbrokengneissinterposedbetweenthebrokenends，andinonepartwithaportionofthegneissdriven，apparentlywhilstinasoftenedstate，intoitssideorwall。Inseveralneighbouringplaces，thegneissincludedangular，well-
defined，sometimesbent，massesofhornblenderock，quitelike，exceptinbeingmoreperfectlycrystallised，thatformingthedikes，and，atleastinoneinstance，containing(asdeterminedbyProfessorMiller)augiteaswellashornblende。Inoneortwocasestheseangularmasses，thoughnowquiteseparatefromeachotherbythesolidgneiss，had，fromtheirexactcorrespondenceinsizeandshape，evidentlyoncebeenunited;henceI
cannotdoubtthatmostorallofthefragmentshavebeenderivedfromthebreakingupofthedikes，ofwhichweseethefirststageintheabove-
mentionedlaterallydisjointedone。Thegneissclosetothefragmentsgenerallycontainedmanylargecrystalsofhornblende，whichareentirelyabsentorrareinotherparts：itsfoliaorlaminaeweregentlybentroundthefragments，inthesamemannerastheysometimesareroundconcretions。
Hencethegneisshascertainlybeensoftened，itscompositionmodified，anditsfoliaarranged，subsequentlytothebreakingupofthedikes，theselatteralsohavingbeenatthesametimebentandsoftened。(ProfessorHitchcock“GeologyofMassachusetts“volume2page673，givesacloselysimilarcaseofagreenstonedikeinsyenite。)
Imustheretaketheopportunityofpremising，thatbythetermCLEAVAGEI
implythoseplanesofdivisionwhichrenderarock，appearingtotheeyequiteornearlyhomogeneous，fissile。BythetermFOLIATION，Irefertothelayersorplatesofdifferentmineralogicalnatureofwhichmostmetamorphicschistsarecomposed;thereare，also，oftenincludedinsuchmasses，alternating，homogeneous，fissilelayersorfolia，andinthiscasetherockisbothfoliatedandhasacleavage。BySTRATIFICATION，asappliedtotheseformations，Imeanthosealternate，parallel，largemassesofdifferentcomposition，whicharethemselvesfrequentlyeitherfoliatedorfissile，——suchasthealternatingso-calledstrataofmica-slate，gneiss，glossyclay-slate，andmarble。
ThefoliaofthegneisswithinafewmilesroundBahiagenerallystrikeirregularly，andareoftencurvilinear，dippinginalldirectionsatvariousangles：butwherebestdefined，theyextendedmostfrequentlyinaN。E。byN。(orEast50degreesN。)andS。W。byS。line，correspondingnearlywiththecoast-linenorthwardsofthebay。ImayaddthatMr。
GardnerfoundinseveralpartsoftheprovinceofCeara，whichliesbetweenfourandfivehundredmilesnorthofBahia，gneisswiththefoliaextendingE。45degreesN。;andinGuyanaaccordingtoSirR。Schomburgk，thesamerockstrikesE。57degreesN。Again，Humboldtdescribesthegneiss-graniteoveranimmenseareainVenezuelaandeveninColombia，asstrikingE。50
degreesN。anddippingtotheN。W。atanangleoffiftydegrees。(Gardner“GeologicalSectionoftheBritishAssociation“1840。ForSirR。
Schomburgk’sobservationssee“GeographicalJournal“1842page190。SeealsoHumboldt’sdiscussiononLoxodrisminthe“PersonalNarrative。”)Hencealltheobservationshithertomadetendtoshowthatthegneissicrocksoverthewholeofthispartofthecontinenthavetheirfoliaextendinggenerallywithinalmostapointofthecompassofthesamedirection。(I
landedatonlyoneplacenorthofBahia，namely，atPernambuco。Ifoundthereonlysoft，horizontallystratifiedmatter，formedfromdisintegratedgraniticrocks，andsomeyellowishimpurelimestone，probablyofatertiaryepoch。Ihavedescribedamostsingularnaturalbarofhardsandstone，whichprotectstheharbour，inthe19thvolume1841page258ofthe“LondonandEdinburghPhilosophicalMagazine。”
ABROLHOSISLETS，Latitude18degreesS。offthecoastofBrazil。
Althoughnotstrictlyinplace，IdonotknowwhereIcanmoreconvenientlydescribethislittlegroupofsmallislands。Thelowestbedisasandstonewithferruginousveins;itweathersintoanextraordinaryhoneycombedmass;
aboveitthereisadark-colouredargillaceousshale;abovethisacoarsersandstone——makingatotalthicknessofaboutsixtyfeet;andlastly，abovethesesedimentarybeds，thereisafineconformablemassofgreenstone，insomepartshavingacolumnarstructure。Allthestrata，aswellasthesurfaceoftheland，dipatanangleofabout12degreestoN。byW。Someoftheisletsarecomposedentirelyofthesedimentary，othersofthetrappeanrocks，generally，however，withthesandstone，croppingoutonthesouthernshores。)
RIODEJANEIRO。
Thiswholedistrictisalmostexclusivelyformedofgneiss，aboundingwithgarnets，andporphyriticwithlargecrystals，eventhreeandfourinchesinlength，oforthoclasefeldspar：inthesecrystalsmicaandgarnetsareoftenenclosed。AtthewesternbaseoftheCorcovado，thereissomeferruginouscariousquartz-rock;andintheTijeukarange，muchfine-
grainedgranite。Iobservedbouldersofgreenstoneinseveralplaces;andontheisletofVillegagnon，andlikewiseonthecoastsomemilesnorthward，twolargetrappeandikes。Theporphyriticgneiss，orgneiss-
graniteasithasbeencalledbyHumboldt，isonlysofarfoliatedthattheconstituentmineralsarearrangedwithacertaindegreeofregularity，andmaybesaidtohavea“GRAIN，“buttheyarenotseparatedintodistinctfoliaorlaminae。Thereare，however，severalothervarietiesofgneissregularlyfoliated，andalternatingwitheachotherinso-calledstrata。
Thestratificationandfoliationoftheordinarygneisses，andthefoliationor“grain“ofthegneiss-granite，areparalleltoeachother，andgenerallystrikewithinapointofN。E。andS。W。dippingatahighangle(between50and60degrees)generallytoS。E。：sothathereagainwemeetwiththestrikesoprevalentoverthemorenorthernpartsofthiscontinent。Themountainsofgneiss-granitearetoaremarkabledegreeabruptlyconical，whichseemscausedbytherocktendingtoexfoliateinthick，conicallyconcentriclayers：thesepeaksresembleinshapethoseofphonoliteandotherinjectedrocksonvolcanicislands;noristhegrainorfoliation(asweshallafterwardssee)anydifficultyontheideaofthegneiss-granitehavingbeenanintrusiveratherthanametamorphicformation。Thelinesofmountains，butnotalwayseachseparatehill，rangenearlyinthesamedirectionwiththefoliationandso-calledstratification，butrathermoreeasterly。
(FIGURE22。FRAGMENTOFGNEISSEMBEDDEDINANOTHERVARIETYOFTHESAME
ROCK。)
OnabaregentlyinclinedsurfaceoftheporphyriticgneissinBotofogoBay，IobservedtheappearancerepresentedinFigure22。
Afragmentsevenyardslongandtwoinwidth，withangularanddistinctlydefinededges，composedofapeculiarvarietyofgneisswithdarklayersofmicaandgarnets，issurroundedonallsidesbytheordinarygneiss-
granite;bothhavingbeendislocatedbyagraniticvein。ThefoliainthefragmentandinthesurroundingrockstrikeinthesameN。N。E。andS。S。W。
line;butinthefragmenttheyarevertical，whereasinthegneiss-granitetheydipatasmallangle，asshownbythearrows，toS。S。E。Thisfragment，consideringitsgreatsize，itssolitaryposition，anditsfoliatedstructureparalleltothatofthesurroundingrock，is，asfarasIknow，auniquecase：andIwillnotattemptanyexplanationofitsorigin。
Thenumeroustravellersinthiscountry，haveallbeengreatlysurprisedatthedepthtowhichthegneissandothergraniticrocks，aswellasthetalcoseslatesoftheinterior，havebeendecomposed。(SpixandMartiushavecollectedinanAppendixtotheir“Travels，“thelargestbodyoffactsonthissubject。SeealsosomeremarksbyM。LundinhiscommunicationstotheAcademyatCopenhagen;andothersbyM。GaudichaudinFreycinet“Voyage。”)NearRio，everymineralexceptthequartzhasbeencompletelysoftened，insomeplacestoadepthlittlelessthanonehundredfeet。(Dr。
Benzadescribesgraniticrock，“MadrasJournalofLiterature“etc。October183？page246)，intheNeelgherries，decomposedtoadepthoffortyfeet。)
Themineralsretaintheirpositionsinfoliarangingintheusualdirection;andfracturedquartzveinsmaybetracedfromthesolidrock，runningforsomedistanceintothesoftened，mottled，highlycoloured，argillaceousmass。Itissaidthatthesedecomposedrocksaboundwithgemsofvariouskinds，ofteninafracturedstate，owing，assomehavesupposed，tothecollapseofgeodes，andthattheycontaingoldanddiamonds。AtRio，itappearedtomethatthegneisshadbeensoftenedbeforetheexcavation(nodoubtbythesea)oftheexisting，broad，flat-bottomedvalleys;forthedepthofdecompositiondidnotappearatallconformablewiththepresentundulationsofthesurface。Theporphyriticgneiss，wherenowexposedtotheair，seemstowithstanddecompositionremarkablywell;andI
couldseenosignsofanytendencytotheproductionofargillaceousmasseslikethoseheredescribed。Iwasalsostruckwiththefact，thatwhereabaresurfaceofthisrockslopedintooneofthequietbays，therewerenomarksoferosionatthelevelofthewater，andthepartsbothbeneathandaboveitpreservedauniformcurve。AtBahia，thegneissrocksaresimilarlydecomposed，withtheupperpartsinsensiblylosingtheirfoliation，andpassing，withoutanydistinctlineofseparation，intoabrightredargillaceousearth，includingpartiallyroundedfragmentsofquartzandgranite。Fromthiscircumstance，andfromtherocksappearingtohavesuffereddecompositionbeforetheexcavationofthevalleys，Isuspectthathere，asatRio，thedecompositiontookplaceunderthesea。Thesubjectappearedtomeacuriousone，andwouldprobablywellrepaycarefulexaminationbyanablemineralogist。
THENORTHERNPROVINCESOFLAPLATA。
AccordingtosomeobservationscommunicatedtomebyMr。Fox，thecoastfromRiodeJaneirotothemouthofthePlataseemseverywheretobegranitic，withafewtrappeandikes。AtPortAlegre，neartheboundaryofBrazil，thereareporphyriesanddiorites。(M。Isabelle“VoyageaBuenosAyres“page479。)AtthemouthofthePlata，Iexaminedthecountryfortwenty-fivemileswest，andforaboutseventymilesnorthofMaldonado：
nearthistown，thereissomecommongneiss，andmuch，inallpartsofthecountry，ofacoarse-grainedmixtureofquartzandreddishfeldspar，often，however，assumingalittledark-greenimperfecthornblende，andthenimmediatelybecomingfoliated。Theabrupthillocksthuscomposed，aswellasthehighlyinclinedfoliaofthecommonvarietiesofgneiss，strikeN。N。E。oralittlemoreeasterly，andS。S。W。Clay-slateisoccasionallymetwith，andneartheL。delPotrero，thereiswhitemarble，renderedfissilefromthepresenceofhornblende，mica，andasbestus;thecleavageoftheserocksandtheirstratification，thatisthealternatingmassesthuscomposed，strikeN。N。E。andS。S。W。likethefoliatedgneisses，andhaveanalmostverticaldip。TheSierraLarga，alowrangefivemileswestofMaldonado，consistsofquartzite，oftenferruginous，havinganarenaceousfeel，anddividedintoexcessivelythin，almostverticallaminaeorfoliabymicroscopicallyminutescales，apparentlyofmica，andstrikingintheusualN。N。E。andS。S。W。direction。Therangeitselfisformedofoneprincipallinewithsomesubordinateones;anditextendswithremarkableuniformityfarnorthward(itissaideventotheconfinesofBrazil)，inthesamelinewiththeverticallyribbonedquartzrockofwhichitiscomposed。TheS。deLasAnimasisthehighestrangeinthecountry;I
estimateditat1，000feet;itrunsnorthandsouth，andisformedoffeldspathicporphyry;nearitsbasethereisaN。N。W。andS。S。E。ridgeofaconglomerateinahighlyporphyriticbasis。
NorthwardofMaldonado，andsouthofLasMinas，thereisanE。andW。hillybandofcountry，somemilesinwidth，formedofsiliceousclay-slate，withsomequartz，rock，andlimestone，havingatortuousirregularcleavage，generallyrangingeastandwest。E。andS。E。ofLasMinasthereisaconfuseddistrictofimperfectgneissandlaminatedquartz，withthehillsranginginvariousdirections，butwitheachseparatehillgenerallyrunninginthesamelinewiththefoliaoftherocksofwhichitiscomposed：thisconfusionappearstohavebeencausedbytheintersectionofthe[E。andW。]and[N。N。E。andS。S。W。]strikes。NorthwardofLasMinas，themoreregularnortherlyrangespredominate：fromthisplacetonearPolanco，wemeetwiththecoarse-grainedmixtureofquartzandfeldspar，oftenwiththeimperfecthornblende，andthenbecomingfoliatedinaN。andS。line——withimperfectclay-slate，includinglaminaeofredcrystallisedfeldspar——withwhiteorblackmarble，sometimescontainingasbestusandcrystalsofgypsum——withquartz-rock——withsyenite——andlastly，withmuchgranite。Themarbleandgranitealternaterepeatedlyinapparentlyverticalmasses：somemilesnorthwardofthePolanco，awidedistrictissaidtobeentirelycomposedofmarble。Itisremarkable，howraremicaisinthewholerangeofcountrynorthandwestwardofMaldonado。Throughoutthisdistrict，thecleavageoftheclay-slateandmarble——thefoliationofthegneissandthequartz——thestratificationoralternatingmassesoftheseseveralrocks——andtherangeofthehills，allcoincideindirection;andalthoughthecountryisonlyhilly，theplanesofdivisionarealmosteverywhereveryhighlyinclinedorvertical。
Someancientsubmarinevolcanicrocksareworthmentioning，fromtheirrarityonthiseasternsideofthecontinent。InthevalleyoftheTapas(fiftyorsixtymilesN。ofMaldonado)thereisatractthreeorfourmilesinlength，composedofvarioustrappeanrockswithglassyfeldspar——ofapparentlymetamorphosedgrit-stones——ofpurplishamygdaloidswithlargekernelsofcarbonateoflime(NearthePandeAzucarthereissomegreenishporphyry，inoneplaceamygdaloidalwithagate。)——andmuchofaharshishrockwithglassyfeldsparintermediateincharacterbetweenclaystoneporphyryandtrachyte。Thislatterrockwasinonespotremarkablefrombeingfullofdrusycavities，linedwithquartzcrystals，andarrangedinplanes，dippingatanangleof50degreestotheeast，andstrikingparalleltothefoliationofanadjoininghillcomposedofthecommonmixtureofquartz，feldspar，andimperfecthornblende：thisfactperhapsindicatesthatthesevolcanicrockshavebeenmetamorphosed，andtheirconstituentpartsrearranged，atthesametimeandaccordingtothesamelaws，withthegraniticandmetamorphicformationsofthiswholeregion。InthevalleyoftheMarmaraya，afewmilessouthoftheTapas，abandoftrappeanandamygdaloidalrockisinterposedbetweenahillofgraniteandanextensivesurroundingformationofredconglomerate，which(likethatatthefootoftheS。Animas)hasitsbasisporphyriticwithcrystalsoffeldspar，andwhichhencehascertainlysufferedmetamorphosis。
MONTEVIDEO。
Therockshereconsistofseveralvarietiesofgneiss，withthefeldsparoftenyellowish，granularandimperfectlycrystallised，alternatingwith，andpassinginsensiblyinto，beds，fromafewyardstonearlyamileinthickness，offineorcoarsegrained，dark-greenhornblendicslate;thisagainoftenpassingintochloriticschist。Thesepassagesseemchieflyduetochangesinthemica，anditsreplacementbyotherminerals。AtRatIslandIexaminedamassofchloriticschist，onlyafewyardssquare，irregularlysurroundedonallsidesbythegneiss，andintricatelypenetratedbymanycurvilinearveinsofquartz，whichgraduallyBLENDintothegneiss：thecleavageofthechloriticschistandthefoliationofthegneisswereexactlyparallel。Eastwardofthecitythereismuchfine-
grained，dark-colouredgneiss，almostassumingthecharacterofhornblende-
slate，whichalternatesinthinlaminaewithlaminaeofquartz，thewholemassbeingtransverselyintersectedbynumerouslargeveinsofquartz：I
particularlyobservedthattheseveinswereabsolutelycontinuouswiththealternatinglaminaeofquartz。InthiscaseandatRatIsland，thepassageofthegneissintoimperfecthornblendicorintochloriticslate，seemedtobeconnectedwiththesegregationoftheveinsofquartz。(Mr。Greenoughpage78“CriticalExamination“etc。observesthatquartzinmica-slatesometimesappearsinbedsandsometimesinveins。VonBuchalsoinhis“TravelsinNorway“page236，remarksonalternatinglaminaeofquartzandhornblende-slatereplacingmica-schist。)
TheMount，ahillbelievedtobe450feetinheight，fromwhichtheplacetakesitsname，ismuchthehighestlandinthisneighbourhood：itconsistsofhornblendicslate，which(exceptontheeasternanddisturbedbase)hasaneastandwestnearlyverticalcleavage;thelongeraxisofthehillalsorangesinthissameline。Nearthesummitthehornblende-slategraduallybecomesmoreandmorecoarselycrystallised，andlessplainlylaminated，untilitpassesintoaheavy，sonorousgreenstone，withaslatyconchoidalfracture;thelaminaeonthenorthandsouthsidesnearthesummitdipinwards，asifthisupperparthadexpandedorbulgedoutwards。Thisgreenstonemust，Iconceive，beconsideredasmetamorphosedhornblende-
slate。TheCerrito，thenexthighest，butmuchlesselevatedpoint，isalmostsimilarlycomposed。Inthemorewesternpartsoftheprovince，besidesgneiss，thereisquartz-rock，syenite，andgranite;andatColla，I
heardofmarble。
NearM。Video，thespacewhichImoreaccuratelyexaminedwasaboutfifteenmilesinaneastandwestline，andhereIfoundthefoliationofthegneissandthecleavageoftheslatesgenerallywelldeveloped，andextendingparalleltothealternatingstratacomposedofthegneiss，hornblendicandchloriticschists。Theseplanesofdivisionallrangewithinonepointofeastandwest，frequentlyeastbysouthandwestbynorth;theirdipisgenerallyalmostvertical，andscarcelyanywhereunder45degrees：thisfact，consideringhowslightlyundulatorythesurfaceofthecountryis，deservesattention。WestwardofM。Video，towardstheUruguay，whereverthegneissisexposed，thehighlyinclinedfoliaareseenstrikinginthesamedirection;ImustexceptonespotwherethestrikewasN。W。byW。ThelittleSierradeS。Juan，formedofgneissandlaminatedquartz，mustalsobeexcepted，foritrangesbetween[N。toN。E。]and[S。
toS。W。]andseemstobelongtothesamesystemwiththehillsintheMaldonadodistrict。Finally，wehaveseenthat，formanymilesnorthwardofMaldonadoandfortwenty-fivemileswestwardofit，asfarastheS。delasAnimas，thefoliation，cleavage，so-calledstratificationandlinesofhills，allrangeN。N。E。andS。S。W。whichisnearlycoincidentwiththeadjoiningcoastoftheAtlantic。WestwardoftheS。delasAnimas，asfaraseventheUruguay，thefoliation，cleavage，andstratification(butnotlinesofhills，fortherearenodefinedones)allrangeaboutE。byS。andW。byN。whichisnearlycoincidentwiththedirectionofthenorthernshoreofthePlata;intheconfusedcountrynearLasMinas，wherethesetwogreatsystemsappeartointersecteachother，thecleavage，foliation，andstratificationruninvariousdirections，butgenerallycoincidewiththelineofeachseparatehill。
SOUTHERNLAPLATA。
Thefirstridge，southofthePlata，whichprojectsthroughthePampeanformation，istheSierraTapalguenandVulcan，situated200milessouthwardofthedistrictjustdescribed。Thisridgeisonlyafewhundredfeetinheight，andrunsfromC。CorrientesinaW。N。W。lineforatleast150milesintotheinterior：atTapalguen，itiscomposedofunstratifiedgranularquartz，remarkablefromformingtabularmassesandsmallplains，surroundedbyprecipitouscliffs：otherpartsoftherangearesaidtoconsistofgranite：andmarbleisfoundattheS。Tinta。ItappearsfromM。
Parchappe’sobservations，thatatTandilthereisarangeofquartzosegneiss，veryliketherocksoftheS。LarganearMaldonado，runninginthesameN。N。E。andS。S。W。direction;sothattheframeworkofthecountryhereisverysimilartothatonthenorthernshoreofthePlata。(M。d’Orbigny’s“Voyage“Part。Geolog。page46。IhavegivenashortaccountofthepeculiarformsofthequartzhillsofTapalguen，sounusualinametamorphicformation，inmy“JournalofResearches“2ndeditionpage116。)
TheSierraGuitru-gueyuissituatedsixtymilessouthoftheS。Tapalguen：
itconsistsofnumerousparallel，sometimesblendedtogetherridges，abouttwenty-threemilesinwidth，andfivehundredfeetinheightabovetheplain，andextendinginaN。W。andS。E。direction。SkirtingroundtheextremeS。E。termination，Iascendedonlyafewpoints，whichwerecomposedofafine-grainedgneiss，almostcomposedoffeldsparwithalittlemica，andpassingintheupperpartsofthehillsintoarathercompactpurplishclay-slate。Thecleavagewasnearlyvertical，strikinginaN。W。byW。andS。E。byE。line，nearly，thoughnotquite，coincidentwiththedirectionoftheparallelridges。
TheSierraVentanaliesclosesouthofthatofGuitru-gueyu;itisremarkablefromattainingaheight，veryunusualonthissideofthecontinent，of3，340feet。Itconsistsuptoitssummit，ofquartz，generallypureandwhite，butsometimesreddish，anddividedintothicklaminaeorstrata：inonepartthereisalittleglossyclay-slatewithatortuouscleavage。ThethicklayersofquartzstrikeinaW。30degreesN。
line，dippingsoutherlyatanangleof45degreesandupwards。Theprincipallineofmountains，withsomequitesubordinateparallelridges，rangeaboutW。45degreesN。：butattheirS。E。termination，onlyW。25
degreesN。ThisSierraissaidtoextendbetweentwentyandthirtyleaguesintotheinterior。
PATAGONIA。
WiththeexceptionperhapsofthehillofS。Antonio(600feethigh)intheGulfofS。Matias，whichhasneverbeenvisitedbyageologist，crystallinerocksarenotmetwithonthecoastofPatagoniaforaspaceof380milessouthoftheS。Ventana。Atthispoint(latitude43degrees50minutes)，atPointsUnionandTombo，plutonicrocksaresaidtoappear，andarefound，atratherwideintervals，beneaththePatagoniantertiaryformationforaspaceofaboutthreehundredmilessouthward，tonearBirdIsland，inlatitude48degrees56minutes。JudgingfromspecimenskindlycollectedformebyMr。Stokes，theprevailingrockatPortsSt。Elena，Camerones，Malaspina，andasfarsouthasthePapsofPineda，isapurplish-pinkorbrownishclaystoneporphyry，sometimeslaminated，sometimesslightlyvesicular，withcrystalsofopaquefeldsparandwithafewgrainsofquartz;hencetheseporphyriesresemblethoseimmediatelytobedescribedatPortDesire，andlikewiseaserieswhichIhaveseenfromP。AlegreonthesouthernconfinesofBrazil。ThisporphyriticformationfurtherresemblesinasingularlyclosemannertheloweststratifiedformationoftheCordilleraofChile，which，asweshallhereaftersee，hasavastrange，andattainsagreatthickness。AtthebottomoftheGulfofSt。
George，onlytertiarydepositsappeartobepresent。AtCapeBlanco，thereisquartzrock，verylikethatoftheFalklandIslands，andsomehard，bluesiliceousclay-slate。
AtPortDesirethereisanextensiveformationoftheclaystoneporphyry，stretchingatleasttwenty-fivemilesintotheinterior：ithasbeendenudedanddeeplywornintogulliesbeforebeingcoveredupbythetertiarydeposits，throughwhichithereandthereprojectsinhills;thosenorthofthebaybeing440feetinheight。Thestratahaveinseveralplacesbeentiltedatsmallangles，generallyeithertoN。N。W。orS。S。E。Bygradualpassagesandalternations，theporphyrieschangeincessantlyinnature。Iwilldescribeonlysomeoftheprincipalmineralogicalchanges，whicharehighlyinstructive，andwhichIcarefullyexamined。Theprevailingrockhasacompactpurplishbase，withcrystalsofearthyoropaquefeldspar，andoftenwithgrainsofquartz。Thereareothervarieties，withanalmosttrulytrachyticbase，fulloflittleangularvesiclesandcrystalsofglassyfeldspar;andtherearebedsofblackperfectpitchstone，aswellasofaconcretionaryimperfectvariety。Onacasualinspection，thewholeserieswouldbethoughttobeofthesameplutonicorvolcanicnaturewiththetrachyticvarietiesandpitchstone;
butthisisfarfrombeingthecase，asmuchoftheporphyryiscertainlyofmetamorphicorigin。Besidesthetrueporphyries，therearemanybedsofearthy，quitewhiteoryellowish，friable，easilyfusiblematter，resemblingchalk，whichunderthemicroscopeisseentoconsistofminutebrokencrystals，andwhich，asremarkedinaformerchapter，singularlyresemblestheuppertufaceousbedsofthePatagoniantertiaryformation。
Thisearthysubstanceoftenbecomescoarser，andcontainsminuteroundedfragmentsofporphyriesandroundedgrainsofquartz，andinonecasesomanyofthelatterastoresembleacommonsandstone。Thesebedsaresometimesmarkedwithtruelinesofaqueousdeposition，separatingparticlesofdifferentdegreesofcoarseness;inothercasesthereareparallelferruginouslinesnotoftruedeposition，asshownbythearrangementoftheparticles，thoughsingularlyresemblingthem。Themoreinduratedvarietiesoftenincludemanysmallandsomelargerangularcavities，whichappearduetotheremovalofearthymatter：somevarietiescontainmica。Alltheseearthyandgenerallywhitestonesinsensiblypassintomoreinduratedsonorousvarieties，breakingwithaconchoidalfracture，yetofsmallspecificgravity;manyoftheselattervarietiesassumeapalepurpletint，beingsingularlybandedandveinedwithdifferentshades，andoftenbecomeplainlyporphyriticwithcrystalsoffeldspar。Theformationofthesecrystalscouldbemostclearlytracedbyminuteangularandoftenpartiallyhollowpatchesofearthymatter，firstassumingaFIBROUSSTRUCTURE，thenpassingintoopaqueimperfectlyshapedcrystals，andlastly，intoperfectglassycrystals。Whenthesecrystalshaveappeared，andwhenthebasishasbecomecompact，therockinmanyplacescouldnotbedistinguishedfromatrueclaystoneporphyrywithoutatraceofmechanicalstructure。
Insomeparts，theseearthyortufaceousbedspassintojasperyandintobeautifullymottledandbandedporcelainrocks，whichbreakintosplinters，translucentattheiredges，hardenoughtoscratchglass，andfusibleintowhitetransparentbeads：grainsofquartzincludedintheporcelainousvarietiescanbeseenmeltingintothesurroundingpaste。Inotherparts，theearthyortufaceousbedseitherinsensiblypassinto，oralternatewith，brecciascomposedoflargeandsmallfragmentsofvariouspurplishporphyries，withthematrixgenerallyporphyritic：thesebreccias，thoughtheirsubaqueousoriginisinmanyplacesshownbothbythearrangementoftheirsmallerparticlesandbyanobliqueorcurrentlamination，alsopassintoporphyries，inwhicheverytraceofmechanicaloriginandstratificationhasbeenobliterated。
Somehighlyporphyriticthoughcoarse-grainedmasses，evidentlyofsedimentaryorigin，anddividedintothinlayers，differingfromeachotherchieflyinthenumberofembeddedgrainsofquartz，interestedmemuchfromthepeculiarmannerinwhichhereandtheresomeofthelayersterminatedinabruptpoints，quiteunlikethoseproducedbyalayerofsedimentnaturallythinningout，andapparentlytheresultofasubsequentprocessofmetamorphicaggregation。Inanothercommonvarietyofafinertexture，theaggregatingprocesshadgonefurther，forthewholemassconsistedofquiteshort，parallel，oftenslightlycurvedlayersorpatches，ofwhitishorreddishfinelygranulo-crystallinefeldspathicmatter，generallyterminatingatbothendsinbluntpoints;theselayersorpatchesfurthertendedtopassintowedgeoralmond-shapedlittlemasses，andthesefinallyintotruecrystalsoffeldspar，withtheircentresoftenslightlydrusy。
