FortHillFig。5，p。39risesfromaneminenceoverlookingalittlerivercalledPaintCreek；thewallsvaryinheightfromeighttofifteenfeet，andexceedthirtyfeetinthickness。[234]Severaldoorsfacilitateentrance，andoneofthemleadstoasquareENCIENTE，thewallsofwhichhavebeenalmostentirelydestroyed。Thisenclosureprobablycontainedthehomesofthepeople，whichmayhavebeenmerecabinsofadobesorsun-burntbricks，orbutscoveredwithrushes，interlacedbranches，ortheskinsofanimals；onthispointwearereducedtoguesswork。Inthecentreoftheprincipalenclosurecanbemadeout，inalmosteverycase，severalmuchsmallerenclosures，eachcontainingintheirturnoneormoremounds。Somethinkthesewereconsecratedtoreligiousrites，butthisisamereconjecture，fornothingisreallyknownoftheformofgovernmentorofthereligionoftheMound-Builders。
　　Foresttreeshavegrownupontheseabandonedruins，succeedingothervegetablegrowths；thehugegirthofthedecayingtrunksprovingtheirlongevity。Man，impelledbymotiveswecannotfathom，hadabandonedthedistrictswhereeverythingbearswitnesstohispowerandintelligence，andthevigorousvegetationofnatureoncemorehasitallitsownway。
　　ThemostremarkablegroupofprehistoricfortificationsinNorthAmericaisperhapsthatnearNewark，inthevalleyoftheScioto。ItincludesanoctagonalENCEINTEeightyacresinarea，asquareENCEINTE
　　oftwentyacres，withtwoothers，onetwentytheotherthirtyacresinextent。Thewallsofthegreatcirclearestilltwelvefeethighbyfiftyfeetwideatthebase。Theyareprotectedbyaninteriorfossesevenfeetdeepbythirty-fivefeetwide。AccordingtomeasurementscarefullymadebyColonelWhittlesey，[235]thetotalareacoveredbytheseintrenchmentsisnolessthantwelvesquaremiles，andthelengthofthemoundsexceedstwomiles。Thelargeentrancesprotectedbymoundsthirty-fivefeethigh，theavenuesleadingtothemwhichareregularlabyrinths，thequaintlyshapedmounds——one，forinstance，representsthefootofagiganticbird——allcombinetostrikethevisitorwithastonishment。WegivearepresentationFig。86ofagroup，notunlikethatwehavejustdescribed，whichissituatedatLibertyOhio，andincludestwocirclesandonesquare。Thediameterofthegreatcircleis1，700feet，anditenclosesanareaoffortyacres，whilstthatofthesmallerENCEINTEIS500feet；theareaofthesquare，eachsideofwhichmeasures1，080feet，istwenty-sevenacres。Thewallsarenotstrengthenedbyanyditch，and，contrarytogeneralusage，theearthofwhichtheyaremadewasdugoutfromtheinsideoftheENCIENTEitself。WemayalsomentionOldFortGreenupCounty，Kentucky，successivelydescribedbyCalebAtwater，Squier，andJ。H。Lewis。Itissituatedfortyfeetabovetheriver，andthetotallengthofthewallsexceeds3，175feet。Sixentrancesgiveaccesstoit，andinthecentrerisesamoundrepresentingsomeanimal，abearprobably，measuringmorethan105feet。Severalsmallmounds，beneathwhichwerefoundhumanbones，clusteraboutthelargerone。
　　GroupatLibertyOhio。
　　TrenchesatJuigalpaNicaragua。
　　WemustnotomittonameanextraordinarysystemofintrenchmentsatJuigalpa，inNicaragua，whichsofarasIknowisquiteunique。ThisisaseriesoftrenchesextendingforseveralmilesFig。87，varyinginwidthfromnineandahalftothirteenfeet；atequaldistancesareovalreservoirs，thelongestaxisofwhichmeasuresasmuchasseventy-eightfeet。Ineachreservoiraretwoorfourmounds，probablyservingaswatch-towers。Weknownothingeitherofthepeoplewhoerectedthesesingularstructuresoroftheenemyfromwhomtheyformedaprotection。Norcananythingbeguessedastothewayinwhichthedefencewasconducted。Allisinvolvedinobscurity，andateveryturnwearecompelledtorepeatthatprehistoricstudiesareweightedwithuncertainty，longandarduousstudybeingnecessarytobringeversolittleorderintothechaosinwhicheverythingconnectedwiththemisinvolved。
　　Wemustcursorilyrefertosomeotherfortificationswhichreallyscarcelybelongtooursubject，thoughcertainarchaeologistsclaimforthemaprehistoricorigin。Werefertothevitrifiedforts，whicharestrangestructuresinwhichstones，suchasgraniteandgneiss，quartziteandbasalt，havebeensubjectedtoaheatsointenseastoproducevitrification。
　　ThesevitrifiedfortsareENCEINTES，generallyofroundorellipticalform，carefullyerectedwheretheyweremostneededfordefence，andprotectedbyoneormoreramparts。[236]Therampartsallbeartracesofvitrification，moreorlesscomplete，whichhas，sotospeak，cementedthemtogether。Thevitrificationisveryunequal，beingcompleteinsomepartsandscarcelynoticeableinothers。Itisevidentthatthebuildersdidnotknowhowtodirecttheirfireuniformly。
　　Eversince1777vitrifiedfortshavebeenknowninScotland，anduntil1837theyweresupposedtoexistnowhereelse。Aboutthattime，however，ProfessorZippecalledattentiontosimilarruinsinBohemia，andlateritwasannouncedthatdiscoveriesofthesamekindhadbeenmadeinvariouspartsofFrance，Denmark，andNorway。VirchowspeaksoftheSCHLAKENWALLE，orrampartsofvitrifiedscoria，nearKern[237]andSchaafhausen，andgaveanaccountofthematameetingofGermannaturalistsatRatisbon。Itwouldbeeasytomultiplyinstances。VitrifiedwallsareknowninthePuy-de-Dome，inwhichthefacingisofclay，anddraughtflues，forregulatingandfanningtheflames，havebeenmadeout。AtCastel-Sarrazinisacamprefugewithsimilardispositions，[238]andrecentlyDaubreepresentedtotheAcademiedesSciencesapieceofporphyryartificiallyvitrifiedfromtheprehistoricENCEINTEofHartmannswillerKopfinUpperAlsace。[239]
　　ItisinScotland，however，thataresituatedthemostremarkablevitrifiedforts。Afewyearsagonolessthanforty-fourwerecounted。ThemostcelebratedarethoseofBarryHillandCastleSpynieinInvernesshire，Top-O-NothinAberdeen，andasmallfortwhichrisesfromaloftyrockinthemidstoftheStraitofBute。VitrifiedcairnsalsooccurintheOrkneyIslands，notablyonthelittleisleofSanday，butthemostinterestingstructuresofthekindareCraigPhoedrickandOrdHillofKissock，whichriseuplikehugepillarsonthehillsattheentranceofMorayFirth，atadistanceofthreemilesfromeachother。[240]
　　CraigPhoedrickisnowcoveredwithaluxuriantvegetationofbroom，furze，andfern，withgrovesoffirsandlarches，amongstwhichtheexplorermakeshiswaywithdifficultytothefortifications，orrathertothepilesofmassiveblockstowhichthatnamehasbeengiven。Theseblocksformanacropolisofovalform，theupperpartofwhichisaflatterraceencirclingacentralbasinsomesixandahalftonineandahalffeetdeep，whichmaybecomparedtothecratersoftheextinctvolcanoesofAuvergne。Thesidesofthemoundarestrewnwithcyclopeanblocksofvitrifiedgranite，whichevidentlyoriginallyformedpartofthefortifications。Itisontheeasternside，overlookingthevalleyoftheNess，thatthebuildingsareofthegreatestimportance；
　　twoterracescanbemadeout，thelowerprojectingbeyondtheupper，formingadoubleseriesofalmostperpendicularfortifications，constructedofvitrifiedblockscementedtogetherwiththinlayersofmortar，spreadwithoutanyattemptatregularity。Theblocksform，withthemortar，aconglomeratesocompactthatwhenstruckwithahammertheybreakwithoutseparating。Examinationoffragmentsunderthemicroscopeprovethattheyhavegonethroughimportantmineralogicaltransformations，undertheinfluenceofwhatmusthavebeenanextremelyhightemperature。Theheatmusthavebeenindeedintensewhichcouldcausemicatodisappearentirely，andfeldspartomeltalmostcompletely。
　　ThehillknownasOrdHillofKissockiscrowned，asisCraigPhoedrick，withruinsstillstanding，butthevegetationaboutthemissodenseandthornythatitisdifficulttomakeouttheconditionoftheremains。Theruins，whichcanonlybeseenfromoneside，appearhowevertohaveformedpartoffortifications，datingfromthesametimeandservingthesamepurposeasthoseofCraigPhoedrick。Weretheyforts？Thereiscertainlynosignoftheirhavingbeenusedashabitations。Orwerethey，assomearchaeologistsaredisposedtothink，beaconhousesusedforwarningthepeopleoftheapproachoftheNormanpiratesorScandinavianVikings，whosedepredationswerenotdiscontinueduntiltheeighthcenturyoftheChristianera？Hypothesesarealwayseasy，butproofsofthesehypothesesaredifficulttofind，andweconfesswehavenonetobringforward。[241]
　　PassingtoFrance，wefindthegreaternumberofvitrifiedfortsintheDepartementdelaCreuse。AtChateauvieuxisanENCEINTEofovalform，416feetwideatitsbroadestpart。[242]Anearthwork，22feetwideatthebase，servesasfoundationtoawall，theouterandinnerportionsofwhichconsistofsmallgranitestones，arrangedinregularlayers。Thespacebetweenthetwoseriesofsmallstonesisfilledinwithasheetofmeltedgranite，sometwenty-fourincheswide，restingoncalcareoustufa。Thewholemassiscompletelyvitrified，andregulargeodesornoduleslinedwithcrystalsanddrapedwithpendentdropsofmeltedrockhavebeenproduced。
　　TheancientfortressofRibandelle，ofcircularform，risesabovetheCreuse，oppositeChateauvieux。ItwassuccessivelyoccupiedbytheCelts，theRomans，andtheVisigoths，butweareunabletofixthedateofitserectionorthenameofthepeoplewhobuiltit。Thereremainbutafewruinsatthepresentday，butwecanmakeoutinthemthesamemodeofconstructionasthatfollowedatChateauvieux。Thewallsarefacedwithunhewnstones，theoutersideofwhichstillretainsanaturalappearance，whiletheinneriscorrodedanddisintegrated。Inthewallitself，separatedfromthefacingsbybedsofpeatmould，aregreatblocksofvitrifiedgranite。Thetracesoftheactionoffirearespeciallynoticeableintheupperpartofthewalls，sothattheywereevidentlyfinishedwhenthefusiontookplace。
　　Thesiteofthefurnaceinthesefortsisdifficulttodetermine。Itwasevidentlynotsituatedunderanyoftheblocks，fortheearthworksonwhichtheyrestretainnotracesoftheactionoffire。Norwasitsituatedattheside，fortheouterfacingshaveretainedaliketheiroriginalformandconsistency。Norcanthefurnacehavebeenlitontheblocks，asheatexercisesitsactionbyradiatingineverydirection。Wearethereforeforcedtotheconclusionthatthefirewasspreadwiththeaidofspacesleftintheinsideoftheconstructionatvariouspoints，forthevitrifiedmassisdividedintoblocks，aboutnineandthreefourthsfeetlong，atveryshortdistancesfromeachother。
　　Thesefewexampleswillbeenoughtogivesomeideaofthestrangevitrifiedforts。ManyofthemretaintracesofRoman。occupation。TheGueretMuseumpossessesafragmentfromtheRibandellewallsinwhichaRomantileiscompletelyimbedded；andM。Thuotpickedupothertilesinasimilarconditionamongsttheruins。ThisisaverydecidedproofthatthevitrificationtookplaceafterthearrivaloftheconquerorsofGaul。Theweaponsandtoolsdiscoveredwouldappeartoconfirmthisidea，andtosuggestsimilarexplanationsofvitrificationelsewhere。Ifso，weshallhave。toadmitthatvitrifiedfortsdatefromtheearliestcenturiesoftheChristianera，andarenotprehistoricatall。Wehave，however，noticedthemhereonaccountofthegravedoubtsinthematter，andbecausetheyfurnishastrikingandvaluableillustrationoftherelationsexistingfromthemostremotetunesbetweenwidelyseparatedraces，andmaintaineduntilthepresenttime。InnootherwaycanweaccountforthepracticeoftheextremelydifficultandcomplicatedoperationofthevitrificationofbardrocksindistrictssofarapartasNorwayandScotland，GermanyandthemidlandsofFrance。
　　Themorewethinkofthedifficultiesvitrificationpresents，thegreaterisourastonishment。Howwasthefusionachievedofelementssorefractoryalikeintheirstructureandintheresistanceofferedbyaccumulatedmassesofmaterial？Bywhatprocesseswasheatbroughtuptothe1300degreesnecessaryforthefusionofgranite？Theincinerationandfusionofthematerialsofwhichthevitrifiedfortsaremade，especiallythegraniteonesofLaCreuseandtheCotesduNord，bearwitness，saysDaubree，toasurprisingskillandknowledgeofthemanagementoffireinthosewhoburnedthem，butthesequalitiesweremanifestedalsoinextremelyancientmetallurgicaloperations。Itisquiteimpossibletosupposethevitrificationtohavebeentheresultofaconflagration。Nofire，whetheraccidentalortheworkofanincendiary，couldbepowerfulenoughtoproducesuchresults。Theuseofpetroleuminthemostterribleconflagrationsofourowntime——thoseoftheCommunein1871，forinstance——didcalcineanddisintegratestone，butIknowofnocaseofvitrification。
　　TheKeramicMuseumofSevrescontainsseveralspecimenswhichpresentverynotabledifferencestoeachother。ThosefromChateau-Gontierareformedofveryclose-grainedquartzitegraniteofagreenishcolorstreakedwithblack。Theconglomerateweldingtheretogetherisavitrifiedscoriafullofverysmallbubblesmadebytheescapeofgaswhichhadnothadsufficientstrengthtogetout。TheblockfromSainte-SuzanneMayenneconsistsofquartzmixedwithhalfcalcinedgrainsoffeldspar，bleachedbytheactionoffusedglass，whichonceintroducedfilledupasitcongealedallthevacantspaceswithavitreoussubstanceoflightgreenish-whitecolor。Thefracturesaregreenandbright，andaredottedwithwhitepoints，whichareallthatisleftofthestonesaftertheirdisintegrationinthegripofaheatthatwasalikeintenseandrapidinitsaction。ThefragmentsbroughtfromScotlanddifferfromthosejustdescribed。Theyconsistofsmallpiecesofgranitecompletelymergedinathickpastewithwhichtheyformthemass，thewholebreakingtogetherwhenitdoesbreak；andthemeltedmatterseldomhasanybubblesinit。[243]