byThomasH。Huxley
INthelecturewhichIdeliveredlastMondayevening，Iendeavouredtosketchinaverybriefmanner，butaswellasthetimeatmydisposalwouldpermit，thepresentconditionoforganicnature，meaningbythatlargetitlesimplyanindicationofthegreat，broad，andgeneralprincipleswhicharetobediscoveredbythosewholookattentivelyatthephenomenaoforganicnatureasatpresentdisplayed。Thegeneralresultofourinvestigationsmightbesummedupthus：wefoundthatthemultiplicityoftheformsofanimallife，greatasthatmaybe，maybereducedtoacomparativelyfewprimitiveplansortypesofconstruction；
thatafurtherstudyofthedevelopmentofthosedifferentformsrevealedtousthattheywereagainreducible，untilweatlastbroughttheinfinitediversityofanimal，andevenvegetablelife，downtotheprimordialformofasinglecell。
Wefoundthatouranalysisoftheorganicworld，whetheranimalsorplants，showed，inthelongrun，thattheymightbothbereducedinto，andwere，infact，composedof，thesameconstituents。Andwesawthattheplantobtainedthematerialsconstitutingitssubstancebyapeculiarcombinationofmattersbelongingentirelytotheinorganicworld；that，then，theanimalwasconstantlyappropriatingthenitrogenousmattersoftheplanttoitsownnourishment，andreturningthembacktotheinorganicworld，inwhatwespokeofasitswaste；andthatfinally，whentheanimalceasedtoexist，theconstituentsofitsbodyweredissolvedandtransmittedtothatinorganicworldwhencetheyhadbeenatfirstabstracted。Thuswesawinboththebladeofgrassandthehorsebutthesameelementsdifferentlycombinedandarranged。
Wediscoveredacontinualcirculationgoingon，——theplantdrawingintheelementsofinorganicnatureandcombiningthemintofoodfortheanimalcreation；theanimalborrowingfromtheplantthematterforitsownsupport，givingoffduringitslifeproductswhichreturnedimmediatelytotheinorganicworld；andthat，eventually，theconstituentmaterialsofthewholestructureofbothanimalsandplantswerethusreturnedtotheiroriginalsource：therewasaconstantpassagefromonestateofexistencetoanother，andareturningbackagain。
Lastly，whenweendeavouredtoformsomenotionofthenatureoftheforcesexercisedbylivingbeings，wediscoveredthatthey——ifnotcapableofbeingsubjectedtothesameminuteanalysisastheconstituentsofthosebeingsthemselves——thattheywerecorrelativewith——thattheyweretheequivalentsoftheforcesofinorganicnature——thattheywere，inthesenseinwhichthetermisnowused，convertiblewiththem。Thatwasourgeneralresult。
Andnow，leavingthePresent，ImustendeavourinthesamemannertoputbeforeyouthefactsthataretobediscoveredinthePasthistoryofthelivingworld，inthepastconditionsoforganicnature。Wehave，to—night，todealwiththefactsofthathistory——ahistoryinvolvingperiodsoftimebeforewhichourmerehumanrecordssinkintoutterinsignificance——ahistorythevarietyandphysicalmagnitudeofwhoseeventscannotevenbeforeshadowedbythehistoryofhumanlifeandhumanphenomena——ahistoryofthemostvariedandcomplexcharacter。
Wemustdealwiththehistory，then，inthefirstplace，asweshoulddealwithallotherhistories。Thehistoricalstudentknowsthathisfirstbusinessshouldbetoinquireintothevalidityofhisevidence，andthenatureoftherecordinwhichtheevidenceiscontained，thathemaybeabletoformaproperestimateofthecorrectnessoftheconclusionswhichhavebeendrawnfromthatevidence。So，here，wemustpass，inthefirstplace，totheconsiderationofamatterwhichmayseemforeigntothequestionunderdiscussion。Wemustdwelluponthenatureoftherecords，andthecredibilityoftheevidencetheycontain；wemustlooktothecompletenessorincompletenessofthoserecordsthemselves，beforeweturntothatwhichtheycontainandreveal。Thequestionofthecredibilityofthehistory，happilyforus，willnotrequiremuchconsideration，for，inthishistory，unlikethoseofhumanorigin，therecanbenocavilling，nodifferencesastotherealityandtruthofthefactsofwhichitismadeup；thefactsstatethemselves，andarelaidoutclearlybeforeus。
But，althoughoneofthegreatestdifficultiesofthehistoricalstudentisclearedoutofourpath，thereareotherdifficulties——difficultiesinrightlyinterpretingthefactsastheyarepresentedtous——whichmaybecomparedwiththegreatestdifficultiesofanyotherkindsofhistoricalstudy。
Whatisthisrecordofthepasthistoryoftheglobe，andwhatarethequestionswhichareinvolvedinaninquiryintoitscompletenessorincompleteness？Thatrecordiscomposedofmud；andthequestionwhichwehavetoinvestigatethiseveningresolvesitselfintoaquestionoftheformationofmud。Youmaythink，perhaps，thatthisisavaststep——ofalmostfromthesublimetotheridiculous——fromthecontemplationofthehistoryofthepastagesoftheworld’sexistencetotheconsiderationofthehistoryoftheformationofmud！But，innature，thereisnothingmeanandunworthyofattention；thereisnothingridiculousorcontemptibleinanyofherworks；andthisinquiry，youwillsoonsee，Ihope，takesustotheveryrootandfoundationsofoursubject。
How，then，ismudformed？Always，withsometriflingexception，whichI
neednotconsidernow——always，astheresultoftheactionofwater，wearingdownanddisintegratingthesurfaceoftheearthandrockswithwhichitcomesincontact——poundingandgrindingitdown，andcarryingtheparticlesawaytoplaceswheretheyceasetobedisturbedbythismechanicalaction，andwheretheycansubsideandrest。Fortheocean，urgedbywinds，washes，asweknow，alongextentofcoast，andeverywave，loadedasitiswithparticlesofsandandgravelasitbreaksupontheshore，doessomethingtowardsthedisintegratingprocess。Andthus，slowlybutsurely，thehardestrocksaregraduallygrounddowntoapowderysubstance；andthemudthusformed，coarserorfiner，asthecasemaybe，iscarriedbytherushofthetides，orcurrents，tillitreachesthecomparativelydeeperpartsoftheocean，inwhichitcansinktothebottom，thatis，topartswherethereisadepthofaboutfourteenorfifteenfathoms，adepthatwhichthewateris，usually，nearlymotionless，andinwhich，ofcourse，thefinerparticlesofthisdetritus，ormudaswecallit，sinkstothebottom。
Or，again，ifyoutakeariver，rushingdownfromitsmountainsources，brawlingoverthestonesandrocksthatintersectitspath，loosening，removing，andcarryingwithitinitsdownwardcoursethepebblesandlightermattersfromitsbanks，itcrushesandpoundsdowntherocksandearthsinpreciselythesamewayasthewearingactionoftheseawaves。Themattersformingthedepositaretornfromthemountain—sideandwhirledimpetuouslyintothevalley，moreslowlyovertheplain，thenceintotheestuary，andfromtheestuarytheyaresweptintothesea。Thecoarserandheavierfragmentsareobviouslydepositedfirst，thatis，assoonasthecurrentbeginstoloseitsforcebybecomingamalgamatedwiththestillerdepthsoftheocean，butthefinerandlighterparticlesarecarriedfurtheron，andeventuallydepositedinadeeperandstillerportionoftheocean。
Itclearlyfollowsfromthisthatmudgivesusachronology；foritisevidentthatsupposingthis，whichInowsketch，tobetheseabottom，andsupposingthistobeacoast—line；fromthewashingactionoftheseaupontherock，wearingandgrindingitdownintoasedimentofmud，themudwillbecarrieddown，andatlength，depositedinthedeeperpartsofthisseabottom，whereitwillformalayer；andthen，whilethatfirstlayerishardening，othermudwhichiscomingfromthesamesourcewill，ofcourse，becarriedtothesameplace；and，asitisquiteimpossibleforittogetbeneaththelayeralreadythere，itdepositsitselfaboveit，andformsanotherlayer，andinthatwayyougraduallyhavelayersofmudconstantlyformingandhardeningoneabovetheother，andconveyingarecordoftime。
Itisanecessaryresultoftheoperationofthelawofgravitationthattheuppermostlayershallbetheyoungestandthelowesttheoldest，andthatthedifferentbedsshallbeolderatanyparticularpointorspotinexactlytheratiooftheirdepthfromthesurface。Sothatiftheywereupheavedafterwards，andyouhadaseriesofthesedifferentlayersofmud，convertedintosandstone，orlimestone，asthecasemightbe，youmightbesurethatthebottomlayerwasdepositedfirst，andthattheupperlayerswereformedafterwards。Here，yousee，isthefirststepinthehistory——theselayersofmudgiveusanideaoftime。
Thewholesurfaceoftheearth，——Ispeakbroadly，andleaveoutminorqualifications，——ismadeupofsuchlayersofmud，sohard，themajorityofthem，thatwecallthemrockwhetherlimestoneorsandstone，orothervarietiesofrock。And，seeingthateverypartofthecrustoftheearthismadeupinthisway，youmightthinkthatthedeterminationofthechronology，thefixingofthetimewhichithastakentoformthiscrustisacomparativelysimplematter。Takeabroadaverage，ascertainhowfastthemudisdepositeduponthebottomofthesea，orintheestuaryofrivers；takeittobeaninch，ortwo，orthreeinchesayear，orwhateveryoumayroughlyestimateitat；
thentakethetotalthicknessofthewholeseriesofstratifiedrocks，whichgeologistsestimateattwelveorthirteenmiles，oraboutseventythousandfeet，makeasuminshortdivision，dividethetotalthicknessbythatofthequantitydepositedinoneyear，andtheresultwill，ofcourse，giveyouthenumberofyearswhichthecrusthastakentoform。
Truly，thatlooksaverysimpleprocess！Itwouldbesoexceptforcertaindifficulties，theveryfirstofwhichisthatoffindinghowrapidlysedimentsaredeposited；butthemaindifficulty——adifficultywhichrendersanycertaincalculationsofsuchamatteroutofthequestion——isthis，thesea—bottomonwhichthedeposittakesplaceiscontinuallyshifting。
Insteadofthesurfaceoftheearthbeingthatstable，fixedthingthatitispopularlybelievedtobe，being，incommonparlance，theveryemblemoffixityitself，itisincessantlymoving，andis，infact，asunstableasthesurfaceofthesea，exceptthatitsundulationsareinfinitelyslowerandenormouslyhigheranddeeper。
Now，whatistheeffectofthisoscillation？TakethecasetowhichI
havepreviouslyreferred。Thefinerorcoarsersedimentsthatarecarrieddownbythecurrentoftheriver，willonlybecarriedoutacertaindistance，andeventually，aswehavealreadyseen，onreachingthestillerpartoftheocean，willbedepositedatthebottom。
LetCy（Fig。4）bethesea—bottom，yDtheshore，xythesea—level，thenthecoarserdepositwillsubsideovertheregionB，thefineroverA，whilebeyondAtherewillbenodepositatall；and，consequently，norecordwillbekept，simplybecausenodepositisgoingon。Now，supposethatthewholeland，C，D，whichwehaveregardedasstationary，goesdown，asitdoesso，bothAandBgofurtheroutfromtheshore，whichwillbeatyl；x1，y1，beingthenewsea—level。Theconsequencewillbethatthelayerofmud（A），beingnow，forthemostpart，furtherthantheforceofthecurrentisstrongenoughtoconveyeventhefinest’debris’，will，ofcourse，receivenomoredeposits，andhavingattainedacertainthicknesswillnowgrownothicker。
Weshouldbemisledintakingthethicknessofthatlayer，wheneveritmaybeexposedtoourview，asarecordoftimeinthemannerinwhichwearenowregardingthissubject，asitwouldgiveusonlyanimperfectandpartialrecord：itwouldseemtorepresenttooshortaperiodoftime。
Fig。4。
Suppose，ontheotherhand，thattheland（CD）hadgoneonrisingslowlyandgradually——sayaninchortwoinchesinthecourseofacentury，——whatwouldbethepracticaleffectofthatmovement？Why，thatthesedimentAandBwhichhasbeenalreadydeposited，wouldeventuallybebroughtnearertotheshore—level，andagainsubjectedtothewearandtearofthesea；anddirectlytheseabeginstoactuponit，itwouldofcoursesooncutupandcarryitaway，toagreaterorlessextent，tobere—depositedfurtherout。
Well，asthereis，inallprobability，notonesinglespotonthewholesurfaceoftheearth，whichhasnotbeenupanddowninthiswayagreatmanytimes，itfollowsthatthethicknessofthedepositsformedatanyparticularspotcannotbetaken（evensupposingwehadatfirstobtainedcorrectdataastotherateatwhichtheytookplace）asaffordingreliableinformationastotheperiodoftimeoccupiedinitsdeposit。Sothatyouseeitisabsolutelynecessaryfromthesefacts，seeingthatourrecordentirelyconsistsofaccumulationsofmud，superimposedoneontheother；seeinginthenextplacethatanyparticularspotsonwhichaccumulationshaveoccurred，havebeenconstantlymovingupanddown，andsometimesoutofthereachofadeposit，andatothertimesitsowndepositbrokenupandcarriedaway，itfollowsthatourrecordmustbeinthehighestdegreeimperfect，andwehavehardlyatraceleftofthickdeposits，oranydefiniteknowledgeoftheareathattheyoccupied，inagreatmanycases。Andmarkthis！Thatsupposingeventhatthewholesurfaceoftheearthhadbeenaccessibletothegeologist，——thatmanhadhadaccesstoeverypartoftheearth，andhadmadesectionsofthewhole，andputthemalltogether，——eventhenhisrecordmustofnecessitybeimperfect。
Buttohowmuchhasmanreallyaccess？IfyouwilllookatthisMapyouwillseethatitrepresentstheproportionoftheseatotheearth：
thiscolouredpartindicatesallthedryland，andthisotherportionisthewater。Youwillnoticeatoncethatthewatercoversthree—fifthsofthewholesurfaceoftheglobe，andhascovereditinthesamemannereversincemanhaskeptanyrecordofhisownobservations，tosaynothingoftheminuteperiodduringwhichhehascultivatedgeologicalinquiry。Sothatthree—fifthsofthesurfaceoftheearthisshutoutfromusbecauseitisunderthesea。Letuslookattheothertwo—fifths，andseewhatarethecountriesinwhichanythingthatmaybetermedsearchinggeologicalinquiryhasbeencarriedout：agooddealofFrance，Germany，andGreatBritainandIreland，bitsofSpain，ofItaly，andofRussia，havebeenexamined，butofthewholegreatmassofAfrica，exceptpartsofthesouthernextremity，weknownexttonothing；littlebitsofIndia，butofthegreaterpartoftheAsiaticcontinentnothing；bitsoftheNorthernAmericanStatesandofCanada，butofthegreaterpartofthecontinentofNorthAmerica，andinstilllargerproportion，ofSouthAmerica，nothing！
Underthesecircumstances，itfollowsthatevenwithreferencetothatkindofimperfectinformationwhichwecanpossess，itisonlyofabouttheten—thousandthpartoftheaccessiblepartsoftheearththathasbeenexaminedproperly。Therefore，itiswithjusticethatthemostthoughtfulofthosewhoareconcernedintheseinquiriesinsistcontinuallyupontheimperfectionofthegeologicalrecord；for，I
repeat，itisabsolutelynecessary，fromthenatureofthings，thatthatrecordshouldbeofthemostfragmentaryandimperfectcharacter。
Unfortunatelythiscircumstancehasbeenconstantlyforgotten。Menofscience，likeyoungcoltsinafreshpasture，areapttobeexhilaratedonbeingturnedintoanewfieldofinquiry，togooffatahand—gallop，intotaldisregardofhedgesandditches，losingsightofthereallimitationoftheirinquiries，andtoforgettheextremeimperfectionofwhatisreallyknown。Geologistshaveimaginedthattheycouldtelluswhatwasgoingonatallpartsoftheearth’ssurfaceduringagivenepoch；theyhavetalkedofthisdepositbeingcontemporaneouswiththatdeposit，until，fromourlittlelocalhistoriesofthechangesatlimitedspotsoftheearth’ssurface，theyhaveconstructedauniversalhistoryoftheglobeasfullofwondersandportentsasanyotherstoryofantiquity。
Butwhatdoesthisattempttoconstructauniversalhistoryoftheglobeimply？Itimpliesthatweshallnotonlyhaveapreciseknowledgeoftheeventswhichhaveoccurredatanyparticularpoint，butthatweshallbeabletosaywhatevents，atanyonespot，tookplaceatthesametimewiththoseatotherspots。
Letusseehowfarthatisinthenatureofthingspracticable。SupposethathereImakeasectionoftheLakeofKillarney，andherethesectionofanotherlake——thatofLochLomondinScotlandforinstance。
Theriversthatflowintothemareconstantlycarryingdowndepositsofmud，andbeds，orstrata，arebeingasconstantlyformed，oneabovetheother，atthebottomofthoselakes。Now，thereisnotashadowofdoubtthatinthesetwolakesthelowerbedsareallolderthantheupper——thereisnodoubtaboutthat；butwhatdoes’this’tellusabouttheageofanygivenbedinLochLomond，ascomparedwiththatofanygivenbedintheLakeofKillarney？Itis，indeed，obviousthatifanytwosetsofdepositsareseparatedanddiscontinuous，thereisabsolutelynomeanswhatevergivenyoubythenatureofthedepositofsayingwhetheroneismuchyoungerorolderthantheother；butyoumaysay，asmanyhavesaidandthink，thatthecaseisverymuchalteredifthebedswhichwearecomparingarecontinuous。Supposetwobedsofmudhardenedintorock，——AandB—areseeninsection。（Fig。5。）
[Fig。5。]
Well，yousay，itisadmittedthatthelowermostbedisalwaystheolder。Verywell；B，therefore，isolderthanA。Nodoubt，’asawhole’，itisso；orifanypartsofthetwobedswhichareinthesameverticallinearecompared，itisso。Butsupposeyoutakewhatseemsaverynaturalstepfurther，andsaythatthepart’a’ofthebedAisyoungerthanthepart’b’ofthebedB。Isthissoundreasoning？Ifyoufindanyrecordofchangestakingplaceat’b’，didtheyoccurbeforeanyeventswhichtookplacewhile’a’wasbeingdeposited？Itlooksallveryplainsailing，indeed，tosaythattheydid；andyetthereisnoproofofanythingofthekind。AstheformerDirectorofthisInstitution，SirH。DelaBeche，longagoshowed，thisreasoningmayinvolveanentirefallacy。Itisextremelypossiblethat’a’mayhavebeendepositedagesbefore’b’。Itisveryeasytounderstandhowthatcanbe。ToreturntoFig。4；whenAandBweredeposited，theywere’substantially’contemporaneous；Abeingsimplythefinerdeposit，andBthecoarserofthesamedetritusorwasteofland。Nowsupposethatthatsea—bottomgoesdown（asshowninFig。4），sothatthefirstdepositiscarriednofartherthan’a’，formingthebedAl，andthecoarsenofartherthan’b’，formingthebedB1，theresultwillbetheformationoftwocontinuousbeds，oneoffinesediment（AA1）
over—lappinganotherofcoarsesediment（BBl）。Nowsupposethewholesea—bottomisraisedup，andasectionexposedaboutthepointAl；nodoubt，’atthisspot’，theupperbedisyoungerthanthelower。ButweshouldobviouslygreatlyerrifweconcludedthatthemassoftheupperbedatAwasyoungerthanthelowerbedatB；forwehavejustseenthattheyarecontemporaneousdeposits。StillmoreshouldwebeinerrorifwesupposedtheupperbedatAtobeyoungerthanthecontinuationofthelowerbedatBl；forAwasdepositedlongbeforeB1。Infine，if，insteadofcomparingimmediatelyadjacentpartsoftwobeds，oneofwhichliesuponanother，wecomparedistantparts，itisquitepossiblethattheuppermaybeanynumberofyearsolderthantheunder，andtheunderanynumberofyearsyoungerthantheupper。
NowyoumustnotsupposethatIputthisbeforeyouforthepurposeofraisingaparadoxicaldifficulty；thefactis，thatthegreatmassofdepositshavetakenplaceinsea—bottomswhicharegraduallysinking，andhavebeenformedundertheveryconditionsIamheresupposing。
DonotrunawaywiththenotionthatthissubvertstheprincipleIlaiddownatfirst。Theerrorliesinextendingaprinciplewhichisperfectlyapplicabletodepositsinthesameverticallinetodepositswhicharenotinthatrelationtooneanother。
Itisinconsequenceofcircumstancesofthiskind，andofothersthatI
mightmentiontoyou，thatourconclusionsonandinterpretationsoftherecordarereallyandstrictlyonlyvalidsolongasweconfineourselvestooneverticalsection。Idonotmeantotellyouthattherearenoqualifyingcircumstances，sothat，eveninveryconsiderableareas，wemaysafelyspeakofconformablysuperimposedbedsbeingolderoryoungerthanothersatmanydifferentpoints。Butwecanneverbequitesureincomingtothatconclusion，andespeciallywecannothesureifthereisanybreakintheircontinuity，oranyverygreatdistancebetweenthepointstobecompared。
Wellnow，somuchfortherecorditself，——somuchforitsimperfections，——somuchfortheconditionstobeobservedininterpretingit，anditschronologicalindications，themomentwepassbeyondthelimitsofaverticallinearsection。
Nowletuspassfromtherecordtothatwhichitcontains，——fromthebookitselftothewritingandthefiguresonitspages。Thiswritingandthesefiguresconsistofremainsofanimalsandplantswhich，inthegreatmajorityofcases，havelivedanddiedintheveryspotinwhichwenowfindthem，oratleastintheimmediatevicinity。Youmustallofyoubeaware——andIreferredtothefactinmylastlecture——thattherearevastnumbersofcreatureslivingatthebottomofthesea。Thesecreatures，likeallothers，soonerorlaterdie，andtheirshellsandhardpartslieatthebottom；andthenthefinemudwhichisbeingconstantlybroughtdownbyriversandtheactionofthewearandtearofthesea，coversthemoverandprotectsthemfromanyfurtherchangeoralteration；and，ofcourse，asinprocessoftimethemudbecomeshardenedandsolidified，theshellsoftheseanimalsarepreservedandfirmlyimbeddedinthelimestoneorsandstonewhichisbeingthusformed。YoumayseeinthegalleriesoftheMuseumupstairsspecimensoflimestonesinwhichsuchfossilremainsofexistinganimalsareimbedded。Therearesomespecimensinwhichturtles’eggshavebeenimbeddedincalcareoussand，andbeforethesunhadhatchedtheyoungturtles，theybecamecoveredoverwithcalcareousmud，andthushavebeenpreservedandfossilized。
Notonlydoesthisprocessofimbeddingandfossilizationoccurwithmarineandotheraquaticanimalsandplants，butitaffectsthoselandanimalsandplantswhicharedriftedawaytosea，orbecomeburiedinbogsormorasses；andtheanimalswhichhavebeentroddendownbytheirfellowsandcrushedinthemudattheriver’sbank，astheherdhavecometodrink。Inanyofthesecases，theorganismsmaybecrushedorbemutilated，beforeorafterputrefaction，insuchamannerthatperhapsonlyapartwillbeleftintheforminwhichitreachesus。Itis，indeed，amostremarkablefact，thatitisquiteanexceptionalcasetofindaskeletonofanyoneofallthethousandsofwildlandanimalsthatweknowareconstantlybeingkilled，ordyinginthecourseofnature：theyarepreyedonanddevouredbyotheranimalsordieinplaceswheretheirbodiesarenotafterwardsprotectedbymud。
Thereareotheranimalsexistinginthesea，theshellsofwhichformexceedinglylargedeposits。YouareprobablyawarethatbeforetheattemptwasmadetolaytheAtlantictelegraphiccable，theGovernmentemployedvesselsinmakingaseriesofverycarefulobservationsandsoundingsofthebottomoftheAtlantic；andalthough，aswemustallregret，uptothepresenttimethatprojecthasnotsucceeded，wehavethesatisfactionofknowingthatityieldedsomemostremarkableresultstoscience。TheAtlanticOceanhadtobesoundedrightacross，todepthsofseveralmilesinsomeplaces，andthenatureofitsbottomwascarefullyascertained。Well，now，aspaceofabout1，000mileswidefromeasttowest，andIdonotexactlyknowhowmanyfromnorthtosouth，butatanyrate600or700miles，wascarefullyexamined，anditwasfoundthatoverthewholeofthatimmenseareaanexcessivelyfinechalkymudisbeingdeposited；andthisdepositisentirelymadeupofanimalswhosehardpartsaredepositedinthispartoftheocean，andaredoubtlessgraduallyacquiringsolidityandbecomingmetamorphosedintoachalkylimestone。Thus，yousee，itisquitepossibleinthiswaytopreserveunmistakablerecordsofanimalandvegetablelife。
Wheneverthesea—bottom，bysomeofthoseundulationsoftheearth’scrustthatIhavereferredto，becomesupheaved，andsectionsorboringsaremade，orpitsaredug，thenwebecomeabletoexaminethecontentsandconstituentsoftheseancientsea—bottoms，andfindoutwhatmannerofanimalslivedatthatperiod。
Nowitisaveryimportantconsiderationinitsbearingonthecompletenessoftherecord，toinquirehowfartheremainscontainedinthesefossiliferouslimestonesareabletoconveyanythinglikeanaccurateorcompleteaccountoftheanimalswhichwereinexistenceatthetimeofitsformation。Uponthatpointwecanformaveryclearjudgment，andoneinwhichthereisnopossibleroomforanymistake。
Thereareofcourseagreatnumberofanimals——suchasjelly—fishes，andotheranimals——withoutanyhardparts，ofwhichwecannotreasonablyexpecttofindanytraceswhatever：thereisnothingofthemtopreserve。Withinaveryshorttime，youwillhavenoticed，aftertheyareremovedfromthewater，theydryuptoamerenothing；
certainlytheyarenotofanaturetoleaveanyveryvisibletracesoftheirexistenceonsuchbodiesaschalkormud。Thenagain，lookatlandanimals；itis，asIhavesaid，averyuncommonthingtofindalandanimalentireafterdeath。Insectsandothercarnivorousanimalsveryspeedilypullthemtopieces，putrefactiontakesplace，andso，outofthehundredsofthousandsthatareknowntodieeveryyear，itistherarestthingintheworldtoseeoneimbeddedinsuchawaythatitsremainswouldbepreservedforalengthenedperiod。Notonlyisthisthecase，butevenwhenanimalremainshavebeensafelyimbedded，certainnaturalagentsmaywhollydestroyandremovethem。
Almostallthehardpartsofanimals——thebonesandsoon——arecomposedchieflyofphosphateoflimeandcarbonateoflime。Someyearsago，I
hadtomakeaninquiryintothenatureofsomeverycuriousfossilssenttomefromtheNorthofScotland。FossilsareusuallyhardbonystructuresthathavebecomeimbeddedinthewayIhavedescribed，andhavegraduallyacquiredthenatureandsolidityofthebodywithwhichtheyareassociated；butinthiscaseIhadaseriesof’holes’insomepiecesofrock，andnothingelse。Thoseholes，however，hadacertaindefiniteshapeaboutthem，andwhenIgotaskilfulworkmantomakecastingsoftheinterioroftheseholes，Ifoundthattheyweretheimpressionsofthejointsofabackboneandofthearmourofagreatreptile，twelveormorefeetlong。Thisgreatbeasthaddiedandgotburiedinthesand；thesandhadgraduallyhardenedoverthebones，butremainedporous。Waterhadtrickledthroughit，andthatwaterbeingprobablychargedwithasuperfluityofcarbonicacid，haddissolvedallthephosphateandcarbonateoflime，andthebonesthemselveshadthusdecayedandentirelydisappeared；butasthesandstonehappenedtohaveconsolidatedbythattime，thepreciseshapeoftheboneswasretained。
Ifthatsandstonehadremainedsoftalittlelonger，weshouldhaveknownnothingwhatsoeveroftheexistenceofthereptilewhosebonesithadencased。
Howcertainitisthatavastnumberofanimalswhichhaveexistedatoneperiodonthisearthhaveentirelyperished，andleftnotracewhateveroftheirforms，maybeprovedtoyoubyotherconsiderations。
Therearelargetractsofsandstoneinvariouspartsoftheworld，inwhichnobodyhasyetfoundanythingbutfootsteps。Notaboneofanydescription，butanenormousnumberoftracesoffootsteps。Thereisnoquestionaboutthem。ThereisawholevalleyinConnecticutcoveredwiththesefootsteps，andnotasinglefragmentoftheanimalswhichmadethemhasyetbeenfound。Letmementionanothercasewhileuponthatmatter，whichisevenmoresurprisingthanthosetowhichIhaveyetreferred。ThereisalimestoneformationnearOxford，ataplacecalledStonesfield，whichhasyieldedtheremainsofcertainveryinterestingmammaliananimals，anduptothistime，ifIrecollectrightly，therehavebeenfoundsevenspecimensofitslowerjaws，andnotabitofanythingelse，neitherlimb—bonesnorskull，oranypartwhatever；notafragmentofthewholesystem！Ofcourse，itwouldbepreposteroustoimaginethatthebeastshadnothingelsebutalowerjaw！Theprobabilityis，asDr。Bucklandshowed，astheresultofhisobservationsondeaddogsintheriverThames，thatthelowerjaw，notbeingsecuredbyveryfirmligamentstothebonesofthehead，andbeingaweightyaffair，wouldeasilybeknockedoff，ormightdropawayfromthebodyasitfloatedinwaterinastateofdecomposition。Thejawwouldthusbedepositedimmediately，whiletherestofthebodywouldfloatanddriftawayaltogether，ultimatelyreachingthesea，andperhapsbecomingdestroyed。Thejawbecomescoveredupandpreservedintheriversilt，andthusitcomesthatwehavesuchacuriouscircumstanceasthatofthelowerjawsintheStonesfieldslates。Sothat，yousee，faultyastheselayersofstoneintheearth’scrustare，defectiveastheynecessarilyareasarecord，theaccountofcontemporaneousvitalphenomenapresentedbythemis，bythenecessityofthecase，infinitelymoredefectiveandfragmentary。
ItwasnecessarythatIshouldputallthisverystronglybeforeyou，because，otherwise，youmighthavebeenledtothinkdifferentlyofthecompletenessofourknowledgebythenextfactsIshallstatetoyou。
Theresearchesofthelastthree—quartersofacenturyhave，intruth，revealedawonderfulrichnessoforganiclifeinthoserocks。Certainlynotfewerthanthirtyorfortythousanddifferentspeciesoffossilshavebeendiscovered。Youhavenomoregroundfordoubtingthatthesecreaturesreallylivedanddiedatorneartheplacesinwhichwefindthemthanyouhaveforlikescepticismaboutashellonthesea—shore。
Theevidenceisasgoodintheonecaseasintheother。
Ournextbusinessistolookatthegeneralcharacterofthesefossilremains，anditisasubjectwhichitwillberequisitetoconsidercarefully；andthefirstpointforusistoexaminehowmuchtheextinct’Flora’and’Fauna’asa’whole’——disregardingaltogetherthe’succession’oftheirconstituents，ofwhichIshallspeakafterwards——differfromthe’Flora’and’Fauna’ofthepresentday；——howfartheydifferinwhatwe’do’knowaboutthem，leavingaltogetheroutofconsiderationspeculationsbaseduponwhatwe’donot’know。
Istronglyimaginethatifitwerenotforthepeculiarappearancethatfossilisedanimalshave，anyofyoumightreadilywalkthroughamuseumwhichcontainsfossilremainsmixedupwiththoseofthepresentformsoflife，andIdoubtverymuchwhetheryouruninstructedeyeswouldleadyoutoseeanyvastorwonderfuldifferencebetweenthetwo。Ifyoulookedclosely，youwouldnotice，inthefirstplace，agreatmanythingsverylikeanimalswithwhichyouareacquaintednow：youwouldseedifferencesofshapeandproportion，butonthewholeaclosesimilarity。
IexplainedwhatImeantbyORDERStheotherday，whenIdescribedtheanimalkingdomasbeingdividedinsub—kingdoms，classesandorders。Ifyoudividetheanimalkingdomintoorders，youwillfindthatthereareaboutonehundredandtwenty。Thenumbermayvaryononesideortheother，butthisisafairestimate。Thatisthesumtotaloftheordersofalltheanimalswhichweknownow，andwhichhavebeenknowninpasttimes，andleftremainsbehind。
Now，howmanyofthoseareabsolutelyextinct？Thatistosay，howmanyoftheseordersofanimalshavelivedataformerperiodoftheworld’shistory，buthaveatpresentnorepresentatives？ThatisthesenseinwhichImeanttousetheword\"extinct。\"Imeanthatthoseanimalsdidliveonthisearthatonetime，buthaveleftnooneoftheirkindwithusatthepresentmoment。Sothatestimatingthenumberofextinctanimalsisasortofwayofcomparingthepastcreationasawholewiththepresentasawhole。Amongthemammaliaandbirdstherearenoneextinct；butwhenwecometothereptilesthereisamostwonderfulthing：outoftheeightorders，orthereabouts，whichyoucanmakeamongreptiles，one—halfareextinct。Thesediagramsoftheplesiosaurus，theichthyosaurus，thepterodactyle，giveyouanotionofsomeoftheseextinctreptiles。Andhereisacastofthepterodactyleandbonesoftheichthyosaurusandtheplesiosaurus，justasfreshasifithadbeenrecentlydugupinachurchyard。Thus，inthereptileclass，therearenolessthanhalfoftheorderswhichareabsolutelyextinct。Ifweturntothe’Amphibia’，therewasoneextinctorder，theLabyrinthodonts，typifiedbythelargesalamander—likebeastshowninthisdiagram。
Noorderoffishesisknowntobeextinct。Everyfishthatwefindinthestrata——towhichIhavebeenreferring——canbeidentifiedandplacedinoneoftheorderswhichexistatthepresentday。Thereisnotknowntobeasingleordinalformofinsectextinct。Thereareonlytwoordersextinctamongthe’Crustacea’。Thereisnotknowntobeanextinctorderofthesecreatures，theparasiticandotherworms；
buttherearetwo，nottosaythree，absolutelyextinctordersofthisclass，the’Echinodermata’；outofalltheordersofthe’Coelenterata’
and’Protozoa’onlyone，theRugoseCorals。
Sothat，yousee，outofsomewhereabout120ordersofanimals，takingthemaltogether，youwillnot，attheoutsideestimate，findabovetenoradozenextinct。Summingupalltheordersofanimalswhichhaveleftremainsbehindthem，youwillnotfindabovetenoradozenwhichcannotbearrangedwiththoseofthepresentday；thatistosay，thatthedifferencedoesnotamounttomuchmorethantenpercent。：andtheproportionofextinctordersofplantsisstillsmaller。Ithinkthatthatisaveryastounding，amostastonishingfact，seeingtheenormousepochsoftimewhichhaveelapsedduringtheconstitutionofthesurfaceoftheearthasitatpresentexists；itis，indeed，amostastoundingthingthattheproportionofextinctordinaltypesshouldbesoexceedinglysmall。
Butnow，thereisanotherpointofviewinwhichwemustlookatthispastcreation。Supposethatweweretosinkaverticalpitthroughthefloorbeneathus，andthatIcouldsucceedinmakingasectionrightthroughinthedirectionofNewZealand，IshouldfindineachofthedifferentbedsthroughwhichIpassedtheremainsofanimalswhichI
shouldfindinthatstratumandnotintheothers。First，Ishouldcomeuponbedsofgravelordriftcontainingthebonesoflargeanimals，suchastheelephant，rhinoceros，andcavetiger。RathercuriousthingstofallacrossinPiccadilly！IfIshoulddiglowerstill，IshouldcomeuponabedofwhatwecalltheLondonclay，andinthis，asyouwillseeinourgalleriesupstairs，arefoundremainsofstrangecattle，remainsofturtles，palms，andlargetropicalfruits；
withshell—fishsuchasyouseethelikeofnowonlyintropicalregions。IfIwentbelowthat，Ishouldcomeuponthechalk，andthereIshouldfindsomethingaltogetherdifferent，theremainsofichthyosauriandpterodactyles，andammonites，andsoforth。
IdonotknowwhatMr。GodwinAustinwouldsaycomesnext，butprobablyrockscontainingmoreammonites，andmoreichthyosauriandplesiosauri，withavastnumberofotherthings；andunderthatIshouldmeetwithyetolderrocks，containingnumbersofstrangeshellsandfishes；andinthuspassingfromthesurfacetothelowestdepthsoftheearth’scrust，theformsofanimallifeandvegetablelifewhichIshouldmeetwithinthesuccessivebedswould，lookingatthembroadly，bethemoredifferentthefurtherthatIwentdown。Or，inotherwords，inasmuchaswestartedwiththeclearprinciple，thatinaseriesofnaturally—disposedmudbedsthelowestaretheoldest，weshouldcometothisresult，thatthefurtherwegobackintimethemoredifferenceexistsbetweentheanimalandvegetablelifeofanepochandthatwhichnowexists。ThatwastheconclusiontowhichIwishedtobringyouattheendofthisLecture。