WhenBiela’scometgavetheinhabitantsoftheearthsuchafrightin1832，itreallydidnotcomewithinfiftymillionsofmilesofus。Eventhegreatcometthroughwhosefilmytailtheearthpassedin1861wasitselffourteenmillionsofmilesaway。Theordinarymind，schooledtomeasurespacebythetinystretchesofapygmyplanet，cannotgrasptheimportofsuchdistances；yetthesearemereunitsofmeasurecomparedwiththevaststretchesofsiderealspace。Werethecometwhichhurtlespastusataspeedof，say，ahundredmilesasecondtocontinueitsmadflightuncheckedstraightintothevoidofspace，itmustflyonitsfrigidwayeightthousandyearsbeforeitcouldreachtheverynearestofourneighborstars；andeventhenitwouldhavepenetratedbutamerearm’s-lengthintothevistaswhereliethedozenorsoofsiderealresidentsthatarenextbeyond。Eventothetrainedmindsuchdistancesareonlyvaguelyimaginable。Yettheastronomerofourcenturyhasreachedoutacrossthisunthinkablevoidandbroughtbackmanyasecretwhichourpredecessorsthoughtforeverbeyondhumangrasp。
　　AtentativeassaultuponthisstrongholdofthestarswasbeingmadebyHerschelatthebeginningofthecentury。In1802thatgreatestofobservingastronomersannouncedtotheRoyalSocietyhisdiscoverythatcertaindoublestarshadchangedtheirrelativepositionstowardsoneanothersincehefirstcarefullychartedthemtwentyyearsbefore。Hithertoithadbeensupposedthatdoublestarsweremereopticaleffects。Nowitbecameclearthatsomeofthem，atanyrate，aretrue"binarysystems，"linkedtogetherpresumablybygravitationandrevolvingaboutoneanother。Halleyhadshown，three-quartersofacenturybefore，thatthestarshaveanactualor"proper"motioninspace；
　　Herschelhimselfhadprovedthatthesunsharesthismotionwiththeotherstars。Herewasanothershiftofplace，hithertoquiteunsuspected，tobereckonedwithbytheastronomerinfathomingsiderealsecrets。
　　DoubleStarsWhenJohnHerschel，theonlysonandtheworthysuccessorofthegreatastronomer，beganstar-gazinginearnest，aftergraduatingseniorwrangleratCambridge，andmakingtwoorthreetentativeprofessionalstartsinotherdirectionstowhichhisversatilegeniusimpelledhim，hisfirstextendedworkwastheobservationofhisfather’sdoublestars。Hisstudies，inwhichatfirsthehadthecollaborationofMr。JamesSouth，broughttolightscoresofhithertounrecognizedpairs，andgavefreshdataforthecalculationoftheorbitsofthoselongerknown。SoalsodidtheindependentresearchesofF。G。W。Struve，theenthusiasticobserverofthefamousRussianobservatoryattheuniversityofDorpat，andsubsequentlyatPulkowa。Utilizingdatagatheredbytheseobservers，M。Savary，ofParis，showed，in1827，thattheobservedellipticalorbitsofthedoublestarsareexplicablebytheordinarylawsofgravitation，thusconfirmingtheassumptionthatNewton’slawsapplytothesesiderealbodies。Henceforththerecouldbenoreasontodoubtthatthesameforcewhichholdsterrestrialobjectsonourglobepullsateachandeveryparticleofmatterthroughoutthevisibleuniverse。
　　Thepioneerexplorersofthedoublestarsearlyfoundthatthesystemsintowhichthestarsarelinkedarebynomeansconfinedtosinglepairs。Oftenthreeorfourstarsarefoundthuscloselyconnectedintogravitationsystems；indeed，thereareallgradationsbetweenbinarysystemsandgreatclusterscontaininghundredsoreventhousandsofmembers。Itisknown，forexample，thatthefamiliarclusterofthePleiadesisnotmerelyanopticalgrouping，aswasformerlysupposed，butanactualfederationofassociatedstars，sometwothousandfivehundredinnumber，onlyafewofwhicharevisibletotheunaidedeve。Andthemorecarefullythemotionsofthestarsarestudied，themoreevidentitbecomesthatwidelyseparatedstarsarelinkedtogetherintoinfinitelycomplexsystems，asyetbutlittleunderstood。Atthesametime，allinstrumentaladvancestendtoresolvemoreandmoreseeminglysinglestarsintoclosepairsandminorclusters。ThetwoHerschelsbetweenthemdiscoveredsomethousandsoftheseclosemultiplesystems；Struveandothersincreasedthelisttoabovetenthousand；andMr。S。W。
　　Burnham，oflateyearsthemostenthusiasticandsuccessfulofdouble-starpursuers，addedathousandnewdiscoverieswhilehewasstillanamateurinastronomy，andbyprofessionthestenographerofaChicagocourt。
　　Clearlytheactualnumberofmultiplestarsisbeyondallpresentestimate。
　　TheelderHerschel’searlystudiesofdoublestarswereundertakeninthehopethattheseobjectsmightaidhiminascertainingtheactualdistanceofastar，throughmeasurementofitsannualparallax——thatistosay，oftheanglewhichthediameteroftheearth’sorbitwouldsubtendasseenfromthestar。Theexpectationwasnotfulfilled。Theapparentshiftofpositionofastarasviewedfromoppositesidesoftheearth’sorbit，fromwhichtheparallaxmightbeestimated，issoextremelyminutethatitprovedutterlyinappreciable，eventothealmostpreternaturallyacutevisionofHerschel，withtheaidofanyinstrumentalmeansthenatcommand。Sotheproblemofstardistancealluredandeludedhimtotheend，andhediedin1822withoutseeingiteveninprospectofsolution。
　　Hisestimateoftheminimumdistanceoftheneareststar，basedthoughitwasonthefallacioustestofapparentbrilliancy，wasasingularlysagaciousone，butitwasatbestascientificguess，notascientificmeasurement。
　　TheDistanceoftheStarsJustaboutthistime，however，agreatopticiancametotheaidoftheastronomers。JosephFraunhoferperfectedtherefractingtelescope，asHerschelhadperfectedthereflector，andinventedawonderfullyaccurate"heliometer，"orsun-measurer。Withtheaidoftheseinstrumentstheoldandalmostinfinitelydifficultproblemofstardistancewassolved。In1838BesselannouncedfromtheKonigsbergobservatorythathehadsucceeded，aftermonthsofeffort，indetectingandmeasuringtheparallaxofastar。Similarclaimshadbeenmadeoftenenoughbefore，alwaystoprovefallaciouswhenputtofurthertest；butthistimetheannouncementcarriedtheauthorityofoneofthegreatestastronomersoftheage，andscepticismwassilenced。
　　NordidBessel’sachievementlongawaitcorroboration。
　　Indeed，assooftenhappensinfieldsofdiscovery，twootherworkershadalmostsimultaneouslysolvedthesameproblem——StruveatPulkowa，wherethegreatRussianobservatory，whichsolongheldthepalmoverallothers，hadnowbeenestablished；andThomasHenderson，thenworkingattheCapeofGoodHope，butafterwardstheAstronomerRoyalofScotland。
　　Henderson’sobservationshadactualprecedenceinpointoftime，butBessel’smeasurementsweresomuchmorenumerousandauthoritativethathehasbeenuniformlyconsideredasdeservingthechiefcreditofthediscovery，whichpriorityofpublicationsecuredhim。
　　Byanoddchance，thestaronwhichHenderson’sobservationsweremade，andconsequentlythefirststartheparallaxofwhichwasevermeasured，isournearestneighborinsiderealspace，being，indeed，sometenbillionsofmilesnearerthantheonenextbeyond。Yeteventhisneareststarismorethantwohundredthousandtimesasremotefromusasthesun。Thesun’slightflashestotheearthineightminutes，andtoNeptuneinaboutthreeandahalfhours，butitrequiresthreeandahalfyearstosignalAlphaCentauri。Andasforthegreatmajorityofthestars，hadtheybeenblottedoutofexistencebeforetheChristianera，weofto-dayshouldstillreceivetheirlightandseemtoseethemjustaswedo。Whenwelookuptothesky，westudyancienthistory；wedonotseethestarsastheyARE，butastheyWEREyears，centuries，evenmillenniaago。
　　Theinformationderivedfromtheparallaxofastarbynomeanshaltswiththedisclosureofthedistanceofthatbody。Distanceknown，thepropermotionofthestar，hithertoonlytobereckonedassomanysecondsofarc，mayreadilybetranslatedintoactualspeedofprogress；
　　relativebrightnessbecomesabsolutelustre，ascomparedwiththesun；andinthecaseofthedoublestarstheabsolutemassofthecomponentsmaybecomputedfromthelawsofgravitation。Itisfoundthatstarsdifferenormouslyamongthemselvesinalltheseregards。Astospeed，some，likeoursun，barelycreepthroughspace——compassingtenortwentymilesasecond，itistrue，yetevenatthatrateonlypassingthroughtheequivalentoftheirowndiameterinaday。
　　Attheotherextreme，amongmeasuredstars，isonethatmovestwohundredmilesasecond；yeteventhis"flyingstar，"asseenfromtheearth，seemstochangeitsplacebyonlyaboutthreeandahalflunardiametersinathousandyears。Inbrightness，somestarsyieldtothesun，whileotherssurpasshimasthearc-lightsurpassesacandle。Arcturus，thebrightestmeasuredstar，shinesliketwohundredsuns；andeventhisgiantorbisdimbesidethoseotherstarswhicharesodistantthattheirparallaxcannotbemeasured，yetwhichgreetoureyesatfirstmagnitude。Astoactualbulk，ofwhichapparentlustrefurnishesnoadequatetest，somestarsaresmallerthanthesun，whileothersexceedhimhundredsorperhapsthousandsoftimes。Yetoneandall，sodistantarethey，remainmeredisklikepointsoflightbeforetheutmostpowersofthemoderntelescope。
　　RevelationsoftheSpectroscopeAllthisseemswonderfulenough，butevengreaterthingswereinstore。In1859thespectroscopecameuponthescene，perfectedbyKirchhoffandBunsen，alonglinespointedoutbyFraunhoferalmosthalfacenturybefore。Thatmarvellousinstrument，byrevealingthetelltalelinessprinkledacrossaprismaticspectrum，disclosesthechemicalnatureandphysicalconditionofanysubstancewhoselightissubmittedtoit，tellingitsstoryequallywell，providedthelightbestrongenough，whethertheluminoussubstancebenearorfar——inthesameroomorattheconfinesofspace。
　　Clearlysuchaninstrumentmustproveaveritablemagicwandinthehandsoftheastronomer。
　　Verysooneagerastronomersallovertheworldwereputtingthespectroscopetothetest。Kirchhoffhimselfledtheway，andDonatiandFatherSecchiinItaly，HugginsandMillerinEngland，andRutherfurdinAmerica，werethechiefofhisimmediatefollowers。
　　Theresultsexceededthedreamsofthemostvisionary。
　　Attheveryoutset，in1860，itwasshownthatsuchcommonterrestrialsubstancesassodium，iron，calcium，magnesium，nickel，barium，copper，andzincexistintheformofglowingvaporsinthesun，andverysoonthestarsgaveupacorrespondingsecret。Sincethentheworkofsolarandsiderealanalysishasgoneonsteadilyinthehandsofamultitudeofworkersprominentamongwhom，inthiscountry，areProfessorYoungofPrinceton，ProfessorLangleyofWashington，andProfessorPickeringofHarvard，andmorethanhalftheknownterrestrialelementshavebeendefinitelylocatedinthesun，whilefreshdiscoveriesareinprospect。
　　Itistruethesunalsocontainssomeseemingelementsthatareunknownontheearth，butthisisnomatterforsurprise。Themodernchemistmakesnoclaimforhiselementsexceptthattheyhavethusfarresistedallhumaneffortstodissociatethem；itwouldbenothingstrangeifsomeofthem，whensubjectedtothecrucibleofthesun，whichisseentovaporizeiron，nickel，silicon，shouldfailtowithstandthetest。Butagain，chemistryhasbynomeansexhaustedtheresourcesoftheearth’ssupplyofrawmaterial，andthesubstancewhichsendsitsmessagefromastarmayexistundiscoveredinthedustwetreadorintheairwebreathe。Intheyear1895twonewterrestrialelementswerediscovered；butoneofthesehadforyearsbeenknowntotheastronomerasasolarandsuspectedasastellarelement，andnamedheliumbecauseofitsabundanceinthesun。Thespectroscopehadreachedoutmillionsofmilesintospaceandbroughtbackthisnewelement，andittookthechemistascoreofyearstodiscoverthathehadallalonghadsamplesofthesamesubstanceunrecognizedinhissublunarylaboratory。
　　Thereishardlyamorepicturesquefactthanthatintheentirehistoryofscience。
　　Buttheidentityinsubstanceofearthandsunandstarswasnotmoreclearlyshownthanthediversityoftheirexistingphysicalconditions。Itwasseenthatsunandstars，farfrombeingthecool，earthlike，habitablebodiesthatHerschelthoughtthemsurroundedbyglowingclouds，andprotectedfromundueheatbyotherclouds，areintruthseethingcaldronsoffieryliquid，orgasmadeviscidbycondensation，withluridenvelopesofbelchingflames。Itwassoonmadeclear，also，particularlybythestudiesofRutherfurdandofSecchi，thatstarsdifferamongthemselvesinexactconstitutionorcondition。TherearewhiteorSirianstars，whosespectrumrevelsinthelinesofhydrogen；yelloworsolarstarsoursunbeingthetype，showingvariousmetallicvapors；andsundryredstars，withbandedspectraindicativeofcarboncompounds；besidesthepurelygaseousstarsofmorerecentdiscovery，whichProfessorPickeringhadspeciallystudied。Zollner’sfamousinterpretationofthesediversities，asindicativeofvaryingstagesofcooling，hasbeencalledinquestionastotheexactsequenceitpostulates，butthegeneralpropositionthatstarsexistunderwidelyvaryingconditionsoftemperatureishardlyindispute。
　　Theassumptionthatdifferentstartypesmarkvaryingstagesofcoolinghasthefurthersupportofmodernphysics，whichhasbeenunabletodemonstrateanywayinwhichthesun’sradiatedenergymayberestored，orotherwisemadeperpetual，sincemeteoricimpacthasbeenshowntobe——underexistingconditions，atanyrate——inadequate。InaccordancewiththetheoryofHelmholtz，thechiefsupplyofsolarenergyisheldtobecontractionofthesolarmassitself；andplainlythismusthaveitslimits。Therefore，unlesssomemeansasyetunrecognizedisrestoringthelostenergytothestellarbodies，eachofthemmustgraduallyloseitslustre，andcometoaconditionofsolidification，seemingsterility，andfrigiddarkness。Inthecaseofourownparticularstar，accordingtotheestimateofLordKelvin，suchaculminationappearslikelytooccurwithinaperiodoffiveorsixmillionyears。
　　TheAstronomyoftheInvisibleButbyfarthestrongestsupportofsuchaforecastasthisisfurnishedbythosestellarbodieswhichevennowappeartohavecooledtothefinalstageofstardevelopmentandceasedtoshine。Ofthisclassexamplesinminiaturearefurnishedbytheearthandthesmallerofitscompanionplanets。Buttherearelargerbodiesofthesametypeoutinstellarspace——veritable"darkstars"——invisible，ofcourse，yetnowadaysclearlyrecognized。
　　Theopeningupofthis"astronomyoftheinvisible"
　　isanotherofthegreatachievementsofthenineteenthcentury，andagainitisBesseltowhomthehonorofdiscoveryisdue。Whiletestinghisstarsforparallax；
　　thatastuteobserverwasledtoinfer，fromcertainunexplainedaberrationsofmotion，thatvariousstars，Siriushimselfamongthenumber，areaccompaniedbyinvisiblecompanions，andin1840hedefinitelypredicatedtheexistenceofsuch"darkstars。"Thecorrectnessoftheinferencewasshowntwentyyearslater，whenAlvanClark，Jr。，theAmericanoptician，whiletestinganewlens，discoveredthecompanionofSirius，whichprovedthustobefaintlyluminous。
　　Sincethentheexistenceofotherandquiteinvisiblestarcompanionshasbeenprovedincontestably，notmerelybyrenewedtelescopicobservations，butbythecurioustestimonyoftheubiquitousspectroscope。
　　Oneofthemostsurprisingaccomplishmentsofthatinstrumentisthepowertorecordtheflightofaluminousobjectdirectlyinthelineofvision。Iftheluminousbodyapproachesswiftly，itsFraunhoferlinesareshiftedfromtheirnormalpositiontowardsthevioletendofthespectrum；ifitrecedes，thelinesshiftintheoppositedirection。Theactualmotionofstarswhosedistanceisunknownmaybemeasuredinthisway。
　　Butincertaincasesthelightlinesareseentooscillateonthespectrumatregularintervals。Obviouslythestarsendingsuchlightisalternatelyapproachingandreceding，andtheinferencethatitisrevolvingaboutacompanionisunavoidable。Fromthisextraordinarytesttheorbitaldistance，relativemass，andactualspeedofrevolutionoftheabsolutelyinvisiblebodymaybedetermined。Thusthespectroscope，whichdealsonlywithlight，makesparadoxicalexcursionsintotherealmoftheinvisible。Whatsecretsmaythestarshopetoconcealwhenquestionedbyaninstrumentofsuchnecromanticpower？
　　Butthespectroscopeisnotaloneinthisaudaciousassaultuponthestrongholdsofnature。Ithasaworthycompanionandassistantinthephotographicfilm，whoseefficientaidhasbeeninvokedbytheastronomerevenmorerecently。Pioneerworkincelestialphotographywas，indeed，donebyAragoinFranceandbytheelderDraperinAmericain1839，buttheresultsthenachievedwereonlytentative，anditwasnottillfortyyearslaterthatthemethodassumedreallyimportantproportions。In1880，Dr。HenryDraper，atHastings-on-the-Hudson，madethefirstsuccessfulphotographofanebula。Soonafter，Dr。DavidGill，attheCapeobservatory，madefinephotographsofacomet，andtheflecksofstarlightonhisplatesfirstsuggestedthepossibilitiesofthismethodinchartingtheheavens。
　　Sincethenstar-chartingwiththefilmhascomevirtuallytosupersedetheoldmethod。Aconcertedeffortisbeingmadebyastronomersinvariouspartsoftheworldtomakeacompletechartoftheheavens，andbeforethecloseofourcenturythisworkwillbeaccomplished，somefiftyorsixtymillionsofvisiblestarsbeingplacedonrecordwithadegreeofaccuracyhithertounapproachable。Moreover，othermillionsofstarsarebroughttolightbythenegative，whicharetoodistantordimtobevisiblewithanytelescopicpowersyetattained——afactwhichwhollydiscreditsallpreviousinferencesastothelimitsofoursiderealsystem。
　　Hence，notwithstandingthewonderfulinstrumentaladvancesofthenineteenthcentury，knowledgeoftheexactformandextentofouruniverseseemsmoreunattainablethanitseemedacenturyago。
　　TheStructureofNebulaeYetthenewinstruments，whileleavingsomuchuntold，haverevealedsomevastlyimportantsecretsofcosmicstructure。Inparticular，theyhavesetatrestthelong-standingdoubtsastotherealstructureandpositionofthemysteriousnebulae——thoselazymasses，onlytwoorthreeofthemvisibletotheunaidedeye，whichthetelescoperevealsinalmostlimitlessabundance，scatteredeverywhereamongthestars，butgroupedinparticularaboutthepolesofthestellarstreamordiskwhichwecalltheMilkyWay。
　　Herschel’slaterview，whichheldthatsomeatleastofthenebulaearecomposedofa"shiningfluid，"inprocessofcondensationtoformstars，wasgenerallyacceptedforalmosthalfacentury。Butin1844，whenLordRosse’sgreatsix-footreflector——thelargesttelescopeeveryetconstructed——wasturnedonthenebulae，itmadethishypothesisseemverydoubtful。JustasGalileo’sfirstlenshadresolvedtheMilkyWayintostars，justasHerschelhadresolvednebulaethatresistedallinstrumentsbuthisown，soLordRosse’sevengreaterreflectorresolvedothersthatwouldnotyieldtoHerschel’slargestmirror。Itseemedafairinferencethatwithsufficientpower，perhapssomedaytobeattained，allnebulaewouldyield，hencethatallareinrealitywhatHerschelhadatfirstthoughtthem——
　　vastlydistant"islanduniverses，"composedofaggregationsofstars，comparabletoourowngalacticsystem。
　　Buttheinferencewaswrong；forwhenthespectroscopewasfirstappliedtoanebulain1864，byDr。Huggins，itclearlyshowedthespectrumnotofdiscretestars，butofagreatmassofglowinggases，hydrogenamongothers。Moreextendedstudiesshowed，itistrue，thatsomenebulaegivethecontinuousspectrumofsolidsorliquids，butthedifferenttypesintermingleandgradeintooneanother。Also，theclosestaffinityisshownbetweennebulaeandstars。Somenebulaearefoundtocontainstars，singlyoringroups，intheiractualmidst；certaincondensed"planetary"nebulaearescarcelytobedistinguishedfromstarsofthegaseoustype；andrecentlythephotographicfilmhasshownthepresenceofnebulousmatteraboutstarsthattotelescopicvisiondifferinnorespectfromthegeneralityoftheirfellowsinthegalaxy。ThefamiliarstarsofthePleiadescluster，forexample，appearonthenegativeimmersedinahazybluroflight。Allinall，theaccumulatedimpressionsofthephotographicfilmrevealaprodigalityofnebulousmatterinthestellarsystemnothithertoevenconjectured。
　　Andso，ofcourse，allquestionof"islanduniverses"
　　vanishes，andthenebulaearerelegatedtotheirtruepositionascomponentpartsoftheonestellarsystem——theoneuniverse——thatisopentopresenthumaninspection。
　　Andthesevastcloudsofworld-stuffhavebeenfoundbyProfessorKeeler，oftheLickobservatory，tobefloatingthroughspaceatthestarlikespeedoffromtentothirty-eightmilespersecond。
　　Thelinkingofnebulaewithstars，soclearlyevidencedbyallthesemodernobservations，is，afterall，onlythescientificcorroborationofwhattheelderHerschel’slatertheoriesaffirmed。Butthenebulaehaveotheraffinitiesnotuntilrecentlysuspected；forthespectraofsomeofthemarepracticallyidenticalwiththespectraofcertaincomets。Theconclusionseemswarrantedthatcometsareinpointoffactminornebulaethataredrawnintooursystem；or，puttingitotherwise，thatthetelescopicnebulaearesimplygiganticdistantcomets。
　　Lockyer’sMeteoricHypothesisFollowingupthesurprisingclewsthussuggested，SirNormanLockyer，ofLondon，hasinrecentyearselaboratedwhatisperhapsthemostcomprehensivecosmogonicguessthathaseverbeenattempted。Histheory，knownasthe"meteorichypothesis，"probablybearsthesamerelationtothespeculativethoughtofourtimethatthenebularhypothesisofLaplaceboretothatoftheeighteenthcentury。Outlinedinafewwords，itisanattempttoexplainallthemajorphenomenaoftheuniverseasdue，directlyorindirectly，tothegravitationalimpactofsuchmeteoricparticles，orspecksofcosmicdust，ascometsarecomposedof。Nebulaearevastcometaryclouds，withparticlesmoreorlesswidelyseparated，givingoffgasesthroughmeteoriccollisions，internalorexternal，andperhapsglowingalsowithelectricalorphosphorescentlight。Gravityeventuallybringsthenebularparticlesintocloseraggregations，andincreasedcollisionsfinallyvaporizetheentiremass，formingplanetarynebulaeandgaseousstars。
　　Continuedcondensationmaymakethestellarmasshotterandmoreluminousforatime，buteventuallyleadstoitsliquefaction，andultimateconsolidation——
　　theaforetimenebulaebecomingintheendadarkorplanetarystar。
　　TheexactcorrelationwhichLockyerattemptstopointoutbetweensuccessivestagesofmeteoriccondensationandthevarioustypesofobservedstellarbodiesdoesnotmeetwithunanimousacceptance。Mr。
　　Ranyard，forexample，suggeststhatthevisiblenebulaemaynotbenascentstars，butemanationsfromstars，andthatthetruepre-stellarnebulaeareinvisibleuntilcondensedtostellarproportions。Butsuchdetailsaside，thebroadgeneralhypothesisthatallthebodiesoftheuniverseare，sotospeak，ofasinglespecies——
　　thatnebulaeincludingcomets，starsofalltypes，andplanets，arebutvaryingstagesinthelifehistoryofasingleraceortypeofcosmicorganisms——isacceptedbythedominantthoughtofourtimeashavingthehighestwarrantofscientificprobability。
　　Allthis，clearly，isbutanamplificationofthatnebularhypothesiswhich，longbeforethespectroscopegaveuswarranttoaccuratelyjudgeoursiderealneighbors，hadboldlyimaginedthedevelopmentofstarsoutofnebulaeandofplanetsoutofstars。ButLockyer’shypothesisdoesnotstopwiththis。Havingtracedthedevelopmentalprocessfromthenebulartothedarkstar，itseesnocausetoabandonthisdarkstartoitsfatebyassuming，astheoriginalspeculationassumed，thatthisisaculminatingandfinalstageofcosmicexistence。
　　Forthedarkstar，thoughitsmolecularactivitieshavecometorelativestabilityandimpotence，stillretainstheenormouspotentialitiesofmolarmotion；
　　andclearly，wheremotionis，stasisisnot。Soonerorlater，initsceaselessflightthroughspace，thedarkstarmustcollidewithsomeotherstellarbody，asDr。
　　Crollimaginesofthedarkbodieswhichhis"pre-nebulartheory"postulates。Suchcollisionmaybelongdelayed；thedarkstarmaybedrawnincomet-likecircuitaboutthousandsofotherstellarmasses，andbehurtledonthousandsofdiverseparabolicorellipticalorbits，beforeitchancestocollide——butthatmattersnot:"billionsaretheunitsinthearithmeticofeternity，"
　　andsoonerorlater，wecanhardlydoubt，acollisionmustoccur。Thenwithoutquestionthemutualimpactmustshatterbothcollidingbodiesintovapor，orvaporcombinedwithmeteoricfragments；inshort，intoaveritablenebula，thematrixoffutureworlds。
　　Thusthedarkstar，whichisthelasttermofoneseriesofcosmicchanges，becomesthefirsttermofanotherseries——atonceapost-nebularandapre-nebularcondition；
　　andthenebularhypothesis，thusamplified，ceasestobeamerelinearscale，andisroundedouttoconnoteanunendingseriesofcosmiccycles，morenearlysatisfyingtheimagination。
　　Inthisextendedview，nebulaeandluminousstarsarebuttheinfantileandadolescentstagesofthelifehistoryofthecosmicindividual；thedarkstar，itsadultstage，ortimeoftruevirility。Orwemaythinkoftheshrunkendarkstarasthegerm-cell，thepollen-grain，ofthecosmicorganism。Reducedinsize，asbecomesagerm-cell，toamerefractionofthenebularbodyfromwhichitsprang，ityetretainswithinitsseeminglynon-
　　vitalbodyallthepotentialitiesoftheoriginalorganism，andrequiresonlytoblendwithafellow-celltobringanewgenerationintobeing。Thusmaythecosmicrace，whoseaggregatecensusmakesupthestellaruniverse，beperpetuated——individualsolarsystems，suchasours，beingborn，andgrowingold，anddyingtoliveagainintheirdescendants，whiletheuniverseasawholemaintainsitsunifiedintegritythroughoutalltheseinternalmutations——passingon，itmaybe，byinfinitesimalstages，toaculminationhopelesslybeyondhumancomprehension。
　　III。THENEWSCIENCEOFPALEONTOLOGY
　　WILLIAMSMITHANDFOSSILSHELLS
　　EversinceLeonardodaVincifirstrecognizedthetruecharacteroffossils，therehadbeenhereandthereamanwhorealizedthattheearth’srockycrustisonegiganticmausoleum。Hereandthereadilettantehadfilledhiscabinetswithrelicsfromthismonstercrypt；hereandthereaphilosopherhadponderedoverthem——questioningwhetherperchancetheyhadoncebeenalive，orwhethertheywerenotmereabortivesouvenirsofthattimewhenthefertilematrixoftheearthwassupposedtohave"teemedatabirthInnumerouslivingcreatures，perfectforms，Limbedandfullgrown。"
　　Somefewofthesephilosophers——asRobertHookeandStenointheseventeenthcentury，andMoro，Leibnitz，Buffon，Whitehurst，Werner，Hutton，andothersintheeighteenth——hadvaguelyconceivedtheimportanceoffossilsasrecordsoftheearth’sancienthistory，butthewisestofthemnomoresuspectedthefullimportofthestorywrittenintherocksthantheaveragestrollerinamodernmuseumsuspectsthemeaningofthehieroglyphsonthecaseofamummy。
　　Itwasnotthattherudimentsofthisstoryaresoveryhardtodecipher——thoughintruththeyarehardenough——butratherthatthemenwhomadetheattempthadallalongviewedthesubjectthroughanatmosphereofpreconception，whichgaveadistortedimage。Beforethisimagecouldbecorrecteditwasnecessarythatamanshouldappearwhocouldseewithoutprejudice，andapplysoundcommon-sensetowhathesaw。Andsuchamandidappeartowardsthecloseofthecentury，inthepersonofWilliamSmith，theEnglishsurveyor。Hewasaself-taughtman，andperhapsthemoreindependentforthat，andhehadthegift，besideshissharpeyesandreceptivemind，ofamosttenaciousmemory。Byexercisingthesefaculties，rareastheyarehomely，heledthewaytoasciencewhichwasdestined，initslaterdevelopments，toshakethestructureofestablishedthoughttoitsfoundations。
　　LittleenoughdidWilliamSmithsuspect，however，thatanysuchdireconsequencesweretocomeofhisactwhenhefirstbegannoticingthefossilshellsthathereandtherearetobefoundinthestratifiedrocksandsoilsoftheregionsoverwhichhissurveyor’sdutiesledhim。Nor，indeed，wasthereanythingofsuchapparentrevolutionarycharacterinthefactswhichheunearthed；yetintheirimplicationsthesefactswerethemostdisconcertingofanythathadbeenrevealedsincethedaysofCopernicusandGalileo。Initsbaldessence，Smith’sdiscoverywassimplythis:thatthefossilsintherocks，insteadofbeingscatteredhaphazard，arearrangedinregularsystems，sothatanygivenstratumofrockislabelledbyitsfossilpopulation；
　　andthattheorderofsuccessionofsuchgroupsoffossilsisalwaysthesameinanyverticalseriesofstratainwhichtheyoccur。Thatistosay，iffossilAunderliesfossilBinanygivenregion，itneveroverliesitinanyotherseries；thoughakindoffossilsfoundinonesetofstratamaybequiteomittedinanother。Moreover，afossiloncehavingdisappearedneverreappearsinanylaterstratum。
　　FromthesenovelfactsSmithdrewthecommonsenseinferencethattheearthhadhadsuccessivepopulationsofcreatures，eachofwhichinitsturnhadbecomeextinct。Hepartiallyverifiedthisinferencebycomparingthefossilshellswithexistingspeciesofsimilarorders，andfoundthatsuchasoccurinolderstrataoftherockshadnocounterpartsamonglivingspecies。But，onthewhole，beingeminentlyapracticalman，Smithtroubledhimselfbutlittleabouttheinferencesthatmightbedrawnfromhisfacts。HewaschieflyconcernedinusingthekeyhehaddiscoveredasanaidtotheconstructionofthefirstgeologicalmapofEnglandeverattempted，andhelefttootherstheuntanglingofanysnarlsofthoughtthatmightseemtoarisefromhisdiscoveryofthesuccessionofvaryingformsoflifeontheglobe。
　　Hedisseminatedhisviewsfarandwide，however，inthecourseofhisjourneyings——quitedisregardingthefactthatperipateticswentoutoffashionwhentheprinting-presscamein——andbythebeginningofthenineteenthcenturyhehadbeguntohaveafollowingamongthegeologistsofEngland。Itmustnotforamomentbesupposed，however，thathiscontentionregardingthesuccessionofstratametwithimmediateorgeneralacceptance。Onthecontrary，itwasmostbitterlyantagonized。Foralonggenerationafterthediscoverywasmade，thegeneralityofmen，proneasalwaystostrainatgnatsandswallowcamels，preferredtobelievethatthefossils，insteadofbeingdepositedinsuccessiveages，hadbeensweptallatonceintotheirpresentpositionsbythecurrentofamightyflood——andthatflood，needlesstosay，theNoachiandeluge。Justhowthenumberlesssuccessivestratacouldhavebeenlaiddowninorderlysequencetothedepthofseveralmilesinonesuchfellcataclysmwasindeedpuzzling，especiallyafteritcametobeadmittedthattheheaviestfossilswerenotfoundalwaysatthebottom；buttodoubtthatthishadbeendoneinsomewaywasrankheresyintheearlydaysofthenineteenthcentury。
　　CUVIERANDFOSSILVERTEBRATES
　　Butoncediscovered，WilliamSmith’suniquefactsastothesuccessionofformsintherockswouldnotdown。Therewasonemostvitalpoint，however，regardingwhichtheinferencesthatseemtofollowfromthesefactsneededverification——thequestion，namely，whetherthedisappearanceofafaunafromtheregisterintherocksreallyimpliestheextinctionofthatfauna。
　　Everythingreallydependedupontheanswertothatquestion，andnonebutanaccomplishednaturalistcouldansweritwithauthority。Fortunately，themostauthoritativenaturalistofthetime，GeorgeCuvier，tookthequestioninhand——not，indeed，withtheideaofverifyinganysuggestionofSmith’s，butinthecourseofhisownoriginalstudies——attheverybeginningofthecentury，whenSmith’sviewswereattractinggeneralattention。
　　CuvierandSmithwereexactcontemporaries，bothmenhavingbeenbornin1769，that"fertileyear"
　　whichgavetheworldalsoChateaubriand，VonHumboldt，Wellington，andNapoleon。ButtheFrenchnaturalistwasofverydifferentantecedentsfromtheEnglishsurveyor。Hewasbrilliantlyeducated，hadearlygainedrecognitionasascientist，andwhileyetayoungmanhadcometobeknownastheforemostcomparativeanatomistofhistime。Itwastheanatomicalstudiesthatledhimintotherealmoffossils。Somebonesdugoutoftherocksbyworkmeninaquarrywerebroughttohisnotice，andatoncehistrainedeyetoldhimthattheyweredifferentfromanythinghehadseenbefore。Hithertosuchbones，whennotentirelyignored，hadbeenforthemostpartascribedtogiantsofformerdays，oreventofallenangels。Cuviersoonshowedthatneithergiantsnorangelswereinquestion，butelephantsofanunrecognizedspecies。Continuinghisstudies，particularlywithmaterialgatheredfromgypsumbedsnearParis，hehadaccumulated，bythebeginningofthenineteenthcentury，bonesofabouttwenty-fivespeciesofanimalsthathebelievedtobedifferentfromanynowlivingontheglobe。
　　Thefameofthesestudieswentabroad，andpresentlyfossilbonespouredinfromallsides，andCuvier’sconvictionthatextinctformsofanimalsarerepresentedamongthefossilswassustainedbytheevidenceofmanystrangeandanomalousforms，someofthemofgiganticsize。In1816thefamousOssementsFossiles，describingthesenovelobjects，waspublished，andvertebratepaleontologybecameascience。Amongotherthingsofgreatpopularinterestthebookcontainedthefirstauthoritativedescriptionofthehairyelephant，namedbyCuvierthemammoth，theremainsofwhichbadbeenfoundembeddedinamassoficeinSiberiain1802，sowonderfullypreservedthatthedogsoftheTungusianfishermenactuallyateitsflesh。BonesofthesamespecieshadbeenfoundinSiberiaseveralyearsbeforebythenaturalistPallas，whohadalsofoundthecarcassofarhinocerosthere，frozeninamud-bank；butnoonethensuspectedthattheseweremembersofanextinctpopulation——theyweresupposedtobemerelytransportedrelicsoftheflood。
　　Cuvier，ontheotherhand，assertedthattheseandtheothercreatureshedescribedhadlivedanddiedintheregionwheretheirremainswerefound，andthatmostofthemhavenolivingrepresentativesupontheglobe。
　　This，tobesure，wasnothingmorethanWilliamSmithhadtriedallalongtoestablishregardinglowerformsoflife；butfleshandbloodmonstersappealtotheimaginationinawayquitebeyondthepowerofmereshells；
　　sotheannouncementofCuvier’sdiscoveriesarousedtheinterestoftheentireworld，andtheOssementsFossileswasaccordedapopularreceptionseldomgivenaworkoftechnicalscience——areceptioninwhichtheenthusiasticapprovalofprogressivegeologistswasmingledwiththebitterprotestsoftheconservatives。
　　"Naturalistscertainlyhaveneitherexploredallthecontinents，"saidCuvier，"nordotheyasyetevenknowallthequadrupedsofthosepartswhichhavebeenexplored。
　　Newspeciesofthisclassarediscoveredfromtimetotime；andthosewhohavenotexaminedwithattentionallthecircumstancesbelongingtothesediscoveriesmayallegealsothattheunknownquadrupeds，whosefossilboneshavebeenfoundinthestrataoftheearth，havehithertoremainedconcealedinsomeislandsnotyetdiscoveredbynavigators，orinsomeofthevastdesertswhichoccupythemiddleofAfrica，Asia，thetwoAmericas，andNewHolland。
　　"Butifwecarefullyattendtothekindofquadrupedsthathavebeenrecentlydiscovered，andtothecircumstancesoftheirdiscovery，weshalleasilyperceivethatthereisverylittlechanceindeedofoureverfindingalivethosewhichhaveonlybeenseeninafossilstate。
　　"Islandsofmoderatesize，andataconsiderabledistancefromthelargecontinents，haveveryfewquadrupeds。
　　Thesemusthavebeencarriedtothemfromothercountries。CookandBougainvillefoundnootherquadrupedsbesideshogsanddogsintheSouthSeaIslands；andthelargestquadrupedoftheWestIndiaIslands，whenfirstdiscovered，wastheagouti，aspeciesofthecavy，ananimalapparentlybetweentheratandtherabbit。
　　"Itistruethatthegreatcontinents，asAsia，Africa，thetwoAmericas，andNewHolland，havelargequadrupeds，and，generallyspeaking，containspeciescommontoeach；insomuch，thatupondiscoveringcountrieswhichareisolatedfromtherestoftheworld，theanimalstheycontainoftheclassofquadrupedwerefoundentirelydifferentfromthosewhichexistedinothercountries。Thus，whentheSpaniardsfirstpenetratedintoSouthAmerica，theydidnotfindittocontainasinglequadrupedexactlythesamewiththoseofEurope，Asia，andAfrica。Thepuma，thejaguar，thetapir，thecapybara，thellama，orglama，andvicuna，andthewholetribeofsapajous，weretothementirelynewanimals，ofwhichtheyhadnotthesmallestidea……
　　"Iftherestillremainedanygreatcontinenttobediscovered，wemightperhapsexpecttobemadeacquaintedwithnewspeciesoflargequadrupeds，amongwhichsomemightbefoundmoreorlesssimilartothoseofwhichwefindtheexuviaeinthebowelsoftheearth。
　　Butitismerelysufficienttoglancetheeyeoverthemapsoftheworldandobservetheinnumerabledirectionsinwhichnavigatorshavetraversedtheocean，inordertobesatisfiedthattheredoesnotremainanylargelandtobediscovered，unlessitmaybesituatedtowardstheAntarcticPole，whereeternalicenecessarilyforbidstheexistenceofanimallife。"[1]
　　CuvierthenpointsoutthattheancientswerewellacquaintedwithpracticallyalltheanimalsonthecontinentsofEurope，Asia，andAfricanowknowntoscientists。Hefindslittlegrounds，therefore，forbeliefinthetheorythatatonetimethereweremonstrousanimalsontheearthwhichitwasnecessarytodestroyinorderthatthepresentfaunaandmenmightflourish。
　　Afterreviewingthesetheoriesandbeliefsindetail，hetakesuphisInquiryRespectingtheFabulousAnimalsoftheAncients。"Itiseasy，"hesays，"toreplytotheforegoingobjections，byexaminingthedescriptionsthatareleftusbytheancientsofthoseunknownanimals，andbyinquiringintotheirorigins。Nowthatthegreaternumberoftheseanimalshaveanorigin，thedescriptionsgivenofthembearthemostunequivocalmarks；asinalmostallofthemweseemerelythedifferentpartsofknownanimalsunitedbyanunbridledimagination，andincontradictiontoeveryestablishedlawofnature。"[2]
　　Havingshownhowthefabulousmonstersofancienttimesandofforeignnations，suchastheChinese，weresimplyproductsoftheimagination，havingnoprototypesinnature，Cuviertakesuptheconsiderationofthedifficultyofdistinguishingthefossilbonesofquadrupeds。
　　WeshallhaveoccasiontoreverttothispartofCuvier’spaperinanotherconnection。Hereitsufficestopassatoncetothefinalconclusionthatthefossilbonesinquestionaretheremainsofanextinctfauna，thelikeofwhichhasnopresent-dayrepresentationontheearth。Whateveritsimplications，thisconclusionnowseemedtoCuviertobefullyestablished。
　　InEnglandtheinterestthusarousedwassenttofever-heatin1821bythediscoveryofabundantbedsoffossilbonesinthestalagmite-coveredfloorofacaveatKirkdale，YorkshirewhichwenttoshowthatEngland，too，hadoncehadhershareofgiganticbeasts。
　　Dr。Buckland，theincumbentofthechairofgeologyatOxford，andthemostauthoritativeEnglishgeologistofhisday，tookthesefindsinhandandshowedthatthebonesbelongedtoanumberofspecies，includingsuchalienformsaselephants，rhinoceroses，hippopotami，andhyenas。HemaintainedthatallofthesecreatureshadactuallylivedinBritain，andthatthecavesinwhichtheirboneswerefoundhadbeenthedensofhyenas。
　　Theclaimwashotlydisputed，asamatterofcourse。
　　Aslateas1827bookswerepublisheddenouncingBuckland，doctorofdivinitythoughhewas，asonewhohadjoinedinan"unhallowedcause，"andreiteratingtheoldcrythatthefossilswereonlyremainsoftropicalspecieswashedthitherbythedeluge。Thattheywerefoundinsolidrocksorincavesofferednodifficulty，atleastnottothefertileimaginationofGranvillePenn，theleaderoftheconservatives，whoclungtotheoldideaofWoodwardandCattcutthatthedelugehaddissolvedtheentirecrustoftheearthtoapaste，intowhichtherelicsnowcalledfossilshadsettled。Thecaves，saidMr。Penn，aremerelytheresultofgasesgivenoffbythecarcassesduringdecomposition——
　　greatair-bubbles，sotospeak，inthepastymass，becomingcavernswhenthewatersrecededandthepastehardenedtorockyconsistency。
　　Buttheseandsuch-likefancifulviewsweredoomedeveninthedayoftheirutterance。Alreadyin1823
　　othergiganticcreatures，christenedichthyosaurusandplesiosaurusbyConybeare，hadbeenfoundindeeperstrataofBritishrocks；andthese，aswellasothermonsterswhoseremainswereunearthedinvariouspartsoftheworld，boresuchstrangeformsthateventhemostscepticalcouldscarcelyhopetofindtheircounterpartsamonglivingcreatures。Cuvier’scontentionthatallthelargervertebratesoftheexistingageareknowntonaturalistswasborneoutbyrecentexplorations，andthereseemednorefugefromtheconclusionthatthefossilrecordstellofpopulationsactuallyextinct。
　　Butifthiswereadmitted，thenSmith’sviewthattherehavebeensuccessiverotationsofpopulationcouldnolongerbedenied。Norcoulditbeindoubtthatthesuccessivefaunas，whoseindividualremainshavebeenpreservedinmyriads，representingextinctspeciesbythousandsandtensofthousands，musthaverequiredvastperiodsoftimefortheproductionandgrowthoftheircountlessgenerations。
　　Asthesefactscametobegenerallyknown，andasitcametobeunderstoodinadditionthattheverymatrixoftherockinwhichfossilsareimbeddedisinmanycasesonegiganticfossil，composedoftheremainsofmicroscopicformsoflife，common-sense，which，afterall，isthefinaltribunal，cametotheaidofbelaboredscience。Itwasconcededthattheonlytenableinterpretationoftherecordintherocksisthatnumerouspopulationsofcreatures，distinctfromoneanotherandfrompresentforms，haverisenandpassedaway；andthatthegeologicagesinwhichthesecreatureslivedwereofinconceivablelength。Therankandfilecamethus，withtheaidoffossilrecords，torealizetheimportofanideawhichJamesHutton，andhereandthereanotherthinker，hadconceivedwiththeswiftintuitionofgeniuslongbeforethescienceofpaleontologycameintoexistence。TheHuttonianpropositionthattimeislonghadbeenabundantlyestablished，andbyaboutthecloseofthefirstthirdofthelastcenturygeologistshadbeguntospeakof"ages"and"untoldaeonsoftime"withafamiliaritywhichtheirpredecessorshadreservedfordaysanddecades。
　　CHARLESLYELLCOMBATSCATASTROPHISM
　　Andnowanewquestionpressedforsolution。Iftheearthhasbeeninhabitedbysuccessivepopulationsofbeingsnowextinct，howhaveallthesecreaturesbeendestroyed？Thatquestion，however，seemedtopresentnodifficulties。Itwasansweredoutofhandbytheapplicationofanoldidea。Alldownthecenturies，whatevertheirvaryingphasesofcosmogonicthought，therehadbeeneverpresenttheideathatpasttimeswerenotasrecenttimes；thatinremoteepochstheearthhadbeenthesceneofawfulcatastrophesthathavenoparallelin"thesedegeneratedays。"Naturallyenough，thisthought，embalmedineverycosmogonicspeculationofwhateverorigin，wasappealedtoinexplanationofthedestructionofthesehithertounimaginedhosts，whichnow，thankstoscience，rosefromtheirabysmalslumberasincontestable，butalsoassilentandasthought-provocative，asSphinxorpyramid。
　　Theseancienthosts，itwassaid，havebeenexterminatedatintervalsofoddmillionsofyearsbytherecurrenceofcatastrophesofwhichtheMosaicdelugeisthelatest，butperhapsnotthelast。
　　Thisexplanationhadfullestwarrantofscientificauthority。
　　CuvierhadprefacedhisclassicalworkwithaspeculativedisquisitionwhoseverytitleDiscourssurlesRevolutionsduGlobeisominousofcatastrophism，andwhosetextfullysustainstheaugury。
　　AndBuckland，Cuvier’sforemostfolloweracrosstheChannel，hadgoneevenbeyondthemaster，namingtheworkinwhichhedescribedtheKirkdalefossils，ReliquiaeDiluvianae，orProofsofaUniversalDeluge。
　　Boththeseauthoritiessupposedthecreatureswhoseremainstheystudiedtohaveperishedsuddenlyinthemightyfloodwhoseawfulcurrent，astheysupposed，gougedoutthemodernvalleysandhurledgreatblocksofgranitebroadcastovertheland。Andtheyinvokedsimilarfloodsfortheexterminationofpreviouspopulations。
　　Itistruethesescientificcitationshadmetwithonlyqualifiedapprovalatthetimeoftheirutterance，becausethentheconservativemajorityofmankinddidnotconcedethattherehadbeenapluralityofpopulationsorrevolutions；butnowthatthebeliefinpastgeologicageshadceasedtobeaheresy，therecurringcatastrophesofthegreatpaleontologistswereacceptedwithacclaim。Forthemomentscienceandtraditionwereatone，andtherewasatrucetocontroversy，exceptindeedinthoseoutlyingskirmish-linesofthoughtwhithernewsfromheadquartersdoesnotpermeatetillithasbecomeancienthistoryatitssource。
　　Thetruce，however，wasnotforlong。Hardlyhadcontemporarythoughtbeguntoadjustitselftotheconceptionofpastagesofincomprehensibleextent，eachterminatedbyacatastropheoftheNoachiantype，whenamanappearedwhomadetheutterlybewilderingassertionthatthegeologicalrecord，insteadofprovingnumerouscatastrophicrevolutionsintheearth’spasthistory，givesnowarranttothepretensionsofanyuniversalcatastrophewhatever，nearorremote。
　　ThisiconoclastwasCharlesLyell，theScotchman，whowassoontobefamousasthegreatestgeologistofhistime。AsayoungmanhehadbecomeimbuedwiththeforceoftheHuttonianproposition，thatpresentcausesareonewiththosethatproducedthepastchangesoftheglobe，andhecarriedthatideatowhatheconceivedtobeitslogicalconclusion。Tohismindthisexcludedthethoughtofcatastrophicchangesineitherinorganicororganicworlds。
　　Buttodenycatastrophismwastosuggestarevolutionincurrentthought。Needlesstosay，suchrevolutioncouldnotbeeffectedwithoutalongcontest。Forascoreofyearsthematterwasarguedproandcon。，oftenwithmostunscientificardor。Amereoutlineofthecontroversywouldfillavolume；yettheessentialfactswithwhichLyellatlastestablishedhisproposition，initsbearingsontheorganicworld，maybeepitomizedinafewwords。Theevidencewhichseemstotellofpastrevolutionsistheapparentlysuddenchangeoffossilsfromonestratumtoanotheroftherocks。ButLyellshowedthatthischangeisnotalwayscomplete。
　　Somespeciesliveonfromoneallegedepochintothenext。Bynomeansallthecontemporariesofthemammothareextinct，andnumerousmarineformsvastlymoreancientstillhavelivingrepresentatives。
　　Moreover，theblanksbetweenstratainanyparticularverticalseriesareamplyfilledinwithrecordsintheformofthickstratainsomegeographicallydistantseries。Forexample，insomeregionsSilurianrocksaredirectlyoverlaidbythecoalmeasures；butelsewherethissuddenbreakisfilledinwiththeDevonianrocksthattellofagreat"ageoffishes。"Socommonlyarebreaksinthestratainoneregionfilledupinanotherthatweareforcedtoconcludethattherecordshownbyanysingleverticalseriesisofbutlocalsignificance——
　　telling，perhaps，ofatimewhenthatparticularsea-bedoscillatedabovethewater-line，andsoceasedtoreceivesedimentuntilsomefutureagewhenithadoscillatedbackagain。Butifthisbetherealsignificanceoftheseeminglysuddenchangefromstratumtostratum，thenthewholecaseforcatastrophismishopelesslylost；
　　forsuchbreaksinthestratafurnishtheonlysuggestiongeologycanofferofsuddenandcatastrophicchangesofwideextent。
　　LetusseehowLyellelaboratestheseideas，particularlywithreferencetotherotationofspecies。[2]
　　"Ihavededucedasacorollary，"hesays，"thatthespeciesexistingatanyparticularperiodmust，inthecourseofages，becomeextinct，oneaftertheother。
　　’Theymustdieout，’toborrowanemphaticexpressionfromBuffon，’becauseTimefightsagainstthem。’IftheviewswhichIhavetakenarejust，therewillbenodifficultyinexplainingwhythehabitationsofsomanyspeciesarenowrestrainedwithinexceedingnarrowlimits。Everylocalrevolutiontendstocircumscribetherangeofsomespecies，whileitenlargesthatofothers；andifweareledtoinferthatnewspeciesoriginateinonespotonly，eachmustrequiretimetodiffuseitselfoverawidearea。Itwillfollow，therefore，fromtheadoptionofourhypothesisthattherecentoriginofsomespeciesandthehighantiquityofothersareequallyconsistentwiththegeneralfactoftheirlimiteddistribution，somebeinglocalbecausetheyhavenotexistedlongenoughtoadmitoftheirwidedissemination；
　　others，becausecircumstancesintheanimateorinanimateworldhaveoccurredtorestricttherangewithinwhichtheymayoncehaveobtained……
　　"Ifthereadershouldinfer，fromthefactslaidbeforehim，thatthesuccessiveextinctionofanimalsandplantsmaybepartoftheconstantandregularcourseofnature，hewillnaturallyinquirewhetherthereareanymeansprovidedfortherepairoftheselosses？Isitpossibleasapartoftheeconomyofoursystemthatthehabitableglobeshouldtoacertainextentbecomedepopulated，bothintheoceanandontheland，orthatthevarietyofspeciesshoulddiminishuntilsomeneweraarriveswhenanewandextraordinaryeffortofcreativeenergyistobedisplayed？Orisitpossiblethatnewspeciescanbecalledintobeingfromtimetotime，andyetthatsoastonishingaphenomenoncanescapethenaturalist？
　　"Inthefirstplace，itisobviouslymoreeasytoprovethataspeciesoncenumerouslyrepresentedinagivendistricthasceasedtobethanthatsomeotherwhichdidnotpre-existhadmadeitsappearance——assumingalways，forreasonsbeforestated，thatsinglestocksonlyofeachanimalandplantareoriginallycreated，andthatindividualsofnewspeciesdidnotsuddenlystartupinmanydifferentplacesatonce。
　　"Soimperfecthasthescienceofnaturalhistoryremaineddowntoourowntimesthat，withinthememoryofpersonsnowliving，thenumbersofknownanimalsandplantshavedoubled，orevenquadrupled，inmanyclasses。Newandoftenconspicuousspeciesareannuallydiscoveredinpartsoftheoldcontinentlonginhabitedbythemostcivilizednations。Conscious，therefore，ofthelimitedextentofourinformation，wealwaysinfer，whensuchdiscoveriesaremade，thatthebeingsinquestionbadpreviouslyeludedourresearch，orhadatleastexistedelsewhere，andonlymigratedatarecentperiodintotheterritorieswherewenowfindthem。
　　"Whatkindofproofs，therefore，couldwereasonablyexpecttofindoftheoriginataparticularperiodofanewspecies？
　　"Perhaps，itmaybesaidinreply，thatwithinthelasttwoorthreecenturiessomeforesttreeornewquadrupedmighthavebeenobservedtoappearsuddenlyinthosepartsofEnglandorFrancewhichhadbeenmostthoroughlyinvestigated——thatnaturalistsmighthavebeenabletoshowthatnosuchbeinginhabitedanyotherregionoftheglobe，andthattherewasnotraditionofanythingsimilarhavingbeenobservedinthedistrictwhereithadmadeitsappearance。
　　"Now，althoughthisobjectionmayseemplausible，yetitsforcewillbefoundtodependentirelyontherateoffluctuationwhichwesupposetoprevailintheanimalworld，andontheproportionswhichsuchconspicuoussubjectsoftheanimalandvegetablekingdomsbeartothosewhicharelessknownandescapeourobservation。Thereareperhapsmorethanamillionspeciesofplantsandanimals，exclusiveofthemicroscopicandinfusoryanimalcules，nowinhabitingtheterraqueousglobe，sothatifonlyoneoftheseweretobecomeextinctannually，andonenewoneweretobeeveryyearcalledintobeing，muchmorethanamillionofyearsmightberequiredtobringaboutacompleterevolutionoforganiclife。
　　"Iamnothazardingatpresentanyhypothesisastotheprobablerateofchange，butnonewilldenythatwhentheannualbirthandtheannualdeathofonespeciesontheglobeisproposedasamerespeculation，this，atleast，istoimaginenoslightdegreeofinstabilityintheanimatecreation。Ifwedividethesurfaceoftheearthintotwentyregionsofequalarea，oneofthesemightcomprehendaspaceoflandandwateraboutequalindimensionstoEurope，andmightcontainatwentiethpartofthemillionofspecieswhichmaybeassumedtoexistintheanimalkingdom。Inthisregiononespeciesonlycould，accordingtotherateofmortalitybeforeassumed，perishintwentyyears，oronlyfiveoutoffiftythousandinthecourseofacentury。Butasaconsiderableportionofthewholeworldbelongstotheaquaticclasses，withwhichwehaveaveryimperfectacquaintance，wemustexcludethemfromourconsideration，and，iftheyconstitutehalfoftheentirenumber，thenonespeciesonlymightbelostinfortyyearsamongtheterrestrialtribes。
　　Nowthemammalia，whetherterrestrialoraquatic，bearsosmallaproportiontootherclassesofanimals，formingless，perhaps，thanathousandthpartofawhole，that，ifthelongevityofspeciesinthedifferentorderswereequal，avastperiodmustelapsebeforeitwouldcometotheturnofthisconspicuousclasstoloseoneoftheirnumber。Ifonespeciesonlyofthewholeanimalkingdomdiedoutinfortyyears，nomorethanonemammifermightdisappearinfortythousandyears，inaregionofthedimensionsofEurope。
　　"Itiseasy，therefore，toseethatinasmallportionofsuchanarea，incountries，forexample，ofthesizeofEnglandandFrance，periodsofmuchgreaterdurationmustelapsebeforeitwouldbepossibletoauthenticatethefirstappearanceofoneofthelargerplantsoranimals，assumingtheannualbirthanddeathofonespeciestobetherateofvicissitudeintheanimalcreationthroughouttheworld。"[3]
　　Inaword，then，saidLyell，itbecomesclearthatthenumberlessspeciesthathavebeenexterminatedinthepasthavediedoutonebyone，justasindividualsofaspeciesdie，notinvastshoals；ifwholepopulationshavepassedaway，ithasbeennotbyinstantaneousextermination，butbytheeliminationofaspeciesnowhere，nowthere，muchasonegenerationsucceedsanotherinthelifehistoryofanysinglespecies。Thecauseswhichhavebroughtaboutsuchgradualexterminations，andinthelonglapseofageshaveresultedinrotationsofpopulation，arethesamenaturalcausesthatarestillinoperation。Specieshavediedoutinthepastastheyaredyingoutinthepresent，underinfluenceofchangedsurroundings，suchasalteredclimate，orthemigrationintotheirterritoryofmoremasterfulspecies。Pastandpresentcausesareone——naturallawischangelessandeternal。
　　SuchwastheessenceoftheHuttoniandoctrine，whichLyelladoptedandextended，andwithwhichhisnamewillalwaysbeassociated。Largelythroughhisefforts，thoughofcoursenotwithouttheaidofmanyotherworkersafteratime，thisidea——thedoctrineofuniformitarianism，itcametobecalled——becametheaccepteddogmaofthegeologicworldnotlongafterthemiddleofthenineteenthcentury。Thecatastrophists，afterclingingmadlytotheirphantomforageneration，atlastcapitulatedwithoutterms:theoldheresybecametheneworthodoxy，andthewaywaspavedforafreshcontroversy。
　　THEORIGINOFSPECIES
　　Thefreshcontroversyfollowedquiteasamatterofcourse。Fortheideaofcatastrophismhadnotconcernedthedestructionofspeciesmerely，buttheirintroductionaswell。Ifwholefaunashadbeenextirpatedsuddenly，newfaunashadpresumablybeenintroducedwithequalsuddennessbyspecialcreation；
　　butifspeciesdieoutgradually，theintroductionofnewspeciesmaybepresumedtobecorrespondinglygradual。
　　Thenmaynotthenewspeciesofalatergeologicalepochbethemodifiedlinealdescendantsoftheextinctpopulationofanearlierepoch？
　　Theideathatsuchmightbethecasewasnotnew。
　　Ithadbeensuggestedwhenfossilsfirstbegantoattractconspicuousattention；andsuchsagaciousthinkersasBuffonandKantandGoetheandErasmusDarwinhadbeendisposedtoacceptitintheclosingdaysoftheeighteenthcentury。Then，in1809，ithadbeencontendedforbyoneoftheearlyworkersinsystematicpaleontology——JeanBaptisteLamarck，whohadstudiedthefossilshellsaboutPariswhileCuvierstudiedthevertebrates，andwhohadbeenledbythesestudiestoconcludethattherehadbeennotmerelyarotationbutaprogressionoflifeontheglobe。Hefoundthefossilshells——thefossilsofinvertebrates，ashehimselfhadchristenedthem——indeeperstratathanCuvier’svertebrates；
　　andhebelievedthattherehadbeenlongageswhennohigherformsthanthesewereinexistence，andthatinsuccessiveagesfishes，andthenreptiles，hadbeenthehighestofanimatecreatures，beforemammals，includingman，appeared。Lookingbeyondthepaleofhisbarefacts，asgeniussometimeswill，hehadinsistedthattheseprogressivepopulationshaddevelopedonefromanother，underinfluenceofchangedsurroundings，inunbrokenseries。
　　Ofcoursesuchathoughtasthiswashopelesslymisplacedinagenerationthatdoubtedtheexistenceofextinctspecies，andhardlylesssointhegenerationthatacceptedcatastrophism；butithadbeenkeptalivebyhereandthereanadvocatelikeGeoffreySaint-Hilaire，andnowthebanishmentofcatastrophismopenedthewayforitsmorerespectfulconsideration。RespectfulconsiderationwasgivenitbyLyellineachrecurringeditionofhisPrinciples，butsuchconsiderationledtoitsunqualifiedrejection。InitsplaceLyellputforwardamodifiedhypothesisofspecialcreation。Heassumedthatfromtimetotime，astheextirpationofaspecieshadleftroom，sotospeak，foranewspecies，suchnewspecieshadbeencreateddenovo；andhesupposedthatsuchintermittent，spasmodicimpulsesofcreationmanifestthemselvesnowadaysquiteasfrequentlyasatanytimeinthepast。Hedidnotsayinsomanywordsthatnooneneedbesurprisedto-daywerehetoseeanewspeciesofdeer，forexample，comeupoutofthegroundbeforehim，"pawingtogetfree，"likeMilton’slion，buthistheoryimpliedasmuch。Andthattheory，letitbenoted，wasnotthetheoryofLyellalone，butofnearlyallhisassociatesinthegeologicworld。Thereisperhapsnootherfactthatwillbringhometoonesovividlytheadvanceinthoughtofourowngenerationastherecollectionthatsocrude，soalmostunthinkableaconceptioncouldhavebeenthecurrentdoctrineofsciencelessthanhalfacenturyago。
　　Thistheoryofspecialcreation，moreover，excludedthecurrentdoctrineofuniformitarianismasnightexcludesday，thoughmostthinkersofthetimedidnotseemtobeawareoftheincompatibilityofthetwoideas。ItmaybedoubtedwhetherevenLyellhimselffullyrealizedit。Ifhedid，hesawnoescapefromthedilemma，foritseemedtohimthattherecordintherocksclearlydisprovedthealternativeLamarckianhypothesis。
　　Andalmostwithoneaccordthepaleontologistsofthetimesustainedtheverdict。Owen，Agassiz，Falconer，Barrande，Pictet，Forbes，repudiatedtheideaasunqualifiedlyastheirgreatpredecessorCuvierhaddoneintheearliergeneration。Someofthemdid，indeed，cometobelievethatthereisevidenceofaprogressivedevelopmentoflifeinthesuccessiveages，butnosuchgradedseriesoffossilshadbeendiscoveredaswouldgivecountenancetotheideathatonespecieshadeverbeentransformedintoanother。Andtonearlyeveryonethisobjectionseemedinsuperable。
　　Butin1859appearedabookwhich，thoughnotdealingprimarilywithpaleontology，yetcontainedachapterthatrevealedthegeologicalrecordinanaltogethernewlight。ThebookwasCharlesDarwin’sOriginofSpecies，thechapterthatwonderfulcitationofthe"ImperfectionsoftheGeologicalRecord。"Inthisepoch-makingchapterDarwinshowswhatconditionsmustprevailinanygivenplaceinorderthatfossilsshallbeformed，howunusualsuchconditionsare，andhowprobableitisthatfossilsonceimbeddedinsedimentofasea-bedwillbedestroyedbymetamorphosisoftherocks，orbydenudationwhenthestrataareraisedabovethewater-level。Addtothisthefactthatonlysmallterritoriesoftheearthhavebeenexploredgeologically，hesays，anditbecomesclearthatthepaleontologicalrecordaswenowpossessitshowsbutamerefragmentofthepasthistoryoforganismsontheearth。Itisahistory"imperfectlykeptandwritteninachangingdialect。Ofthishistorywepossessthelastvolumealone，relatingonlytotwoorthreecountries。
　　Ofthisvolumeonlyhereandthereashortchapterhasbeenpreserved，andofeachpageonlyhereandthereafewlines。"Forapaleontologisttodogmatizefromsucharecordwouldbeasrash，hethinks，as"foranaturalisttolandforfiveminutesonabarrenpointofAustraliaandthendiscussthenumberandrangeofitsproductions。"
　　Thiscitationofobservations，whichwhenoncepointedoutseemedalmostself-evident，cameasarevelationtothegeologicalworld。Intheclarifiedviewnowpossibleoldfactstookonanewmeaning。ItwasrecalledthatCuvierhadbeenobligedtoestablishaneworderforsomeofthefirstfossilcreaturesheexamined，andthatBucklandhadnotedthatthenondescriptformswereintermediateinstructurebetweenalliedexistingorders。Morerecentlysuchintermediateformshadbeendiscoveredoverandover；sothat，tonamebutoneexample，Owenhadbeenable，withtheaidofextinctspecies，to"dissolvebygradationstheapparentlywideintervalbetweenthepigandthecamel。"
　　Owen，moreover，hadbeenledtospeakrepeatedlyofthe"generalizedforms"ofextinctanimals，andAgassizhadcalledthem"syntheticorprophetictypes，"thesetermsclearlyimplying"thatsuchformsareinfactintermediateorconnectinglinks。"Darwinhimselfhadshownsomeyearsbeforethatthefossilanimalsofanycontinentarecloselyrelatedtotheexistinganimalsofthatcontinent——edentatespredominating，forexample，inSouthAmerica，andmarsupialsinAustralia。
　　Manyobservershadnotedthatrecentstrataeverywhereshowafossilfaunamorenearlyliketheexistingonethandomoreancientstrata；andthatfossilsfromanytwoconsecutivestrataarefarmorecloselyrelatedtoeachotherthanarethefossilsoftworemoteformations，thefaunaofeachgeologicalformationbeing，indeed，inawideview，intermediatebetweenprecedingandsucceedingfaunas。
　　SosuggestivewerealltheseobservationsthatLyell，theadmittedleaderofthegeologicalworld，afterreadingDarwin’scitations，feltabletodrophisowncrassexplanationoftheintroductionofspeciesandadoptthetransmutationhypothesis，thusroundingoutthedoctrineofuniformitarianismtothefullproportionsinwhichLamarckhadconceivedithalfacenturybefore。
　　Notallpaleontologistscouldfollowhimatonce，ofcourse；theproofwasnotyetsufficientlydemonstrativeforthat；butallwereshakenintheseemingsecurityoftheirformerposition，whichisalwaysanecessarystageintheprogressofthought。Andpopularinterestinthematterwasraisedtowhiteheatinatwinkling。
　　So，forthethirdtimeinthisfirstcenturyofitsexistence，paleontologywascalledupontoplayaleadingroleinacontroversywhoseinterestextendedfarbeyondtheboundsofstaidtruth-seekingscience。Andthecontroversywagedovertheageoftheearthhadnotbeenmorebitter，thatovercatastrophismnotmoreacrimonious，thanthatwhichnowragedoverthequestionofthetransmutationofspecies。Thequestionhadimplicationsfarbeyondtheboundsofpaleontology，ofcourse。Themainevidenceyetpresentedhadbeendrawnfromquiteotherfields，butbycommonconsenttherecordintherocksmightfurnishacrucialtestofthetruthorfalsityofthehypothesis。"Hewhorejectsthisviewoftheimperfectionsofthegeologicalrecord，"saidDarwin，"willrightlyrejectthewholetheory。"
　　Withsomethingmorethanmerescientificzeal，therefore，paleontologiststurnedanewtotherecordsintherocks，toinquirewhatevidenceinprooforrefutationmightbefoundinunreadpagesofthe"greatstonebook。"And，asmighthavebeenexpected，manymindsbeingthuspreparedtoreceivenewevidence，suchevidencewasnotlongwithheld。