14
　　Thesamepartsoftheeartharenotalwaysmoistordry，buttheychangeaccordingasriverscomeintoexistenceanddryup。Andsotherelationoflandtoseachangestooandaplacedoesnotalwaysremainlandorseathroughoutalltime，butwheretherewasdrylandtherecomestobesea，andwherethereisnowsea，thereonedaycomestobedryland。Butwemustsupposethesechangestofollowsomeorderandcycle。Theprincipleandcauseofthesechangesisthattheinterioroftheearthgrowsanddecays，likethebodiesofplantsandanimals。Onlyinthecaseoftheselattertheprocessdoesnotgoonbyparts，buteachofthemnecessarilygrowsordecaysasawhole，whereasitdoesgoonbypartsinthecaseoftheearth。Herethecausesarecoldandheat，whichincreaseanddiminishonaccountofthesunanditscourse。Itisowingtothemthatthepartsoftheearthcometohaveadifferentcharacter，thatsomepartsremainmoistforacertaintime，andthendryupandgrowold，whileotherpartsintheirturnarefilledwithlifeandmoisture。Nowwhenplacesbecomedrierthespringsnecessarilygiveout，andwhenthishappenstheriversfirstdecreaseinsizeandthenfinallybecomedry;andwhenriverschangeanddisappearinonepartandcomeintoexistencecorrespondinglyinanother，theseamustneedsbeaffected。
　　Iftheseawasoncepushedoutbyriversandencroacheduponthelandanywhere，itnecessarilyleavesthatplacedrywhenitrecedes;
　　again，ifthedrylandhasencroachedontheseaatallbyaprocessofsiltingsetupbytheriverswhenattheirfull，thetimemustcomewhenthisplacewillbefloodedagain。
　　Butthewholevitalprocessoftheearthtakesplacesograduallyandinperiodsoftimewhicharesoimmensecomparedwiththelengthofourlife，thatthesechangesarenotobserved，andbeforetheircoursecanberecordedfrombeginningtoendwholenationsperishandaredestroyed。Ofsuchdestructionsthemostutterandsuddenareduetowars;butpestilenceorfaminecausethemtoo。Famines，again，areeithersuddenandsevereorelsegradual。Inthelattercasethedisappearanceofanationisnotnoticedbecausesomeleavethecountrywhileothersremain;andthisgoesonuntilthelandisunabletomaintainanyinhabitantsatall。Soalongperiodoftimeislikelytoelapsefromthefirstdeparturetothelast，andnooneremembersandthelapseoftimedestroysallrecordevenbeforethelastinhabitantshavedisappeared。Inthesamewayanationmustbesupposedtoloseaccountofthetimewhenitfirstsettledinalandthatwaschangingfromamarshyandwaterystateandbecomingdry。
　　Here，too，thechangeisgradualandlastsalongtimeandmendonotrememberwhocamefirst，orwhen，orwhatthelandwaslikewhentheycame。ThishasbeenthecasewithEgypt。HereitisobviousthatthelandiscontinuallygettingdrierandthatthewholecountryisadepositoftheriverNile。Butbecausetheneighbouringpeoplessettledinthelandgraduallyasthemarshesdried，thelapseoftimehashiddenthebeginningoftheprocess。However，allthemouthsoftheNile，withthesingleexceptionofthatatCanopus，areobviouslyartificialandnotnatural。AndEgyptwasnothingmorethanwhatiscalledThebes，asHomer，too，shows，modernthoughheisinrelationtosuchchanges。ForThebesistheplacethathementions;whichimpliesthatMemphisdidnotyetexist，oratanyratewasnotasimportantasitisnow。Thatthisshouldbesoisnatural，sincethelowerlandcametobeinhabitedlaterthanthatwhichlayhigher。Forthepartsthatlienearertotheplacewheretheriverisdepositingthesiltarenecessarilymarshyforalongertimesincethewateralwaysliesmostinthenewlyformedland。Butintimethislandchangesitscharacter，andinitsturnenjoysaperiodofprosperity。Fortheseplacesdryupandcometobeingoodconditionwhiletheplacesthatwereformerlywell-temperedsomedaygrowexcessivelydryanddeteriorate。ThishappenedtothelandofArgosandMycenaeinGreece。InthetimeoftheTrojanwarstheArgivelandwasmarshyandcouldonlysupportasmallpopulation，whereasthelandofMycenaewasingoodcondition（andforthisreasonMycenaewasthesuperior）。Butnowtheoppositeisthecase，forthereasonwehavementioned：thelandofMycenaehasbecomecompletelydryandbarren，whiletheArgivelandthatwasformerlybarrenowingtothewaterhasnowbecomefruitful。Nowthesameprocessthathastakenplaceinthissmalldistrictmustbesupposedtobegoingonoverwholecountriesandonalargescale。
　　Menwhoseoutlookisnarrowsupposethecauseofsucheventstobechangeintheuniverse，inthesenseofacomingtobeoftheworldasawhole。Hencetheysaythattheseabeingdriedupandisgrowingless，becausethisisobservedtohavehappenedinmoreplacesnowthanformerly。Butthisisonlypartiallytrue。Itistruethatmanyplacesarenowdry，thatformerlywerecoveredwithwater。Buttheoppositeistruetoo：foriftheylooktheywillfindthattherearemanyplaceswheretheseahasinvadedtheland。Butwemustnotsupposethatthecauseofthisisthattheworldisinprocessofbecoming。Foritisabsurdtomaketheuniversetobeinprocessbecauseofsmallandtriflingchanges，whenthebulkandsizeoftheeartharesurelyasnothingincomparisonwiththewholeworld。Ratherwemusttakethecauseofallthesechangestobethat，justaswinteroccursintheseasonsoftheyear，soindeterminedperiodstherecomesagreatwinterofagreatyearandwithitexcessofrain。Butthisexcessdoesnotalwaysoccurinthesameplace。ThedelugeinthetimeofDeucalion，forinstance，tookplacechieflyintheGreekworldandinitespeciallyaboutancientHellas，thecountryaboutDodonaandtheAchelous，ariverwhichhasoftenchangeditscourse。HeretheSellidweltandthosewhowereformerlycalledGraeciandnowHellenes。When，therefore，suchanexcessofrainoccurswemustsupposethatitsufficesforalongtime。Wehaveseenthatsomesaythatthesizeofthesubterraneancavitiesiswhatmakessomeriversperennialandothersnot，whereaswemaintainthatthesizeofthemountainsisthecause，andtheirdensityandcoldness;forgreat，dense，andcoldmountainscatchandkeepandcreatemostwater：
　　whereasifthemountainsthatoverhangthesourcesofriversaresmallorporousandstonyandclayey，theseriversrundryearlier。Wemustrecognizethesamekindofthinginthiscasetoo。Wheresuchabundanceofrainfallsinthegreatwinterittendstomakethemoistureofthoseplacesalmosteverlasting。Butastimegoesonplacesofthelattertypedryupmore，whilethoseoftheformer，moisttype，dosoless：untilatlastthebeginningofthesamecyclereturns。
　　Sincethereisnecessarilysomechangeinthewholeworld，butnotinthewayofcomingintoexistenceorperishing（fortheuniverseispermanent），itmustbe，aswesay，thatthesameplacesarenotforevermoistthroughthepresenceofseaandrivers，norforeverdry。
　　Andthefactsprovethis。ThewholelandoftheEgyptians，whomwetaketobethemostancientofmen，hasevidentlygraduallycomeintoexistenceandbeenproducedbytheriver。Thisisclearfromanobservationofthecountry，andthefactsabouttheRedSeasufficetoproveittoo。Oneoftheirkingstriedtomakeacanaltoit（foritwouldhavebeenofnolittleadvantagetothemforthewholeregiontohavebecomenavigable;Sesostrisissaidtohavebeenthefirstoftheancientkingstotry），buthefoundthattheseawashigherthantheland。Sohefirst，andDariusafterwards，stoppedmakingthecanal，lesttheseashouldmixwiththeriverwaterandspoilit。Soitisclearthatallthispartwasonceunbrokensea。ForthesamereasonLibya-thecountryofAmmon-is，strangelyenough，lowerandhollowerthanthelandtotheseawardofit。Foritisclearthatabarrierofsiltwasformedandafteritlakesanddryland，butincourseoftimethewaterthatwasleftbehindinthelakesdriedupandisnowallgone。AgainthesiltingupofthelakeMaeotisbytherivershasadvancedsomuchthatthelimittothesizeoftheshipswhichcannowsailintoittotradeismuchlowerthanitwassixtyyearsago。Henceitiseasytoinferthatit，too，likemostlakes，wasoriginallyproducedbytheriversandthatitmustendbydryingupentirely。
　　Again，thisprocessofsiltingupcausesacontinuouscurrentthroughtheBosporus;andinthiscasewecandirectlyobservethenatureoftheprocess。WheneverthecurrentfromtheAsiaticshorethrewupasandbank，therefirstformedasmalllakebehindit。
　　Lateritdriedupandasecondsandbankformedinfrontofthefirstandasecondlake。Thisprocesswentonuniformlyandwithoutinterruption。Nowwhenthishasbeenrepeatedoftenenough，inthecourseoftimethestraitmustbecomelikeariver，andintheendtheriveritselfmustdryup。
　　Soitisclear，sincetherewillbenoendtotimeandtheworldiseternal，thatneithertheTanaisnortheNilehasalwaysbeenflowing，butthattheregionwhencetheyflowwasoncedry：fortheireffectmaybefulfilled，buttimecannot。Andthiswillbeequallytrueofallotherrivers。Butifriverscomeintoexistenceandperishandthesamepartsoftheearthwerenotalwaysmoist，theseamustneedschangecorrespondingly。Andiftheseaisalwaysadvancinginoneplaceandrecedinginanotheritisclearthatthesamepartsofthewholeeartharenotalwayseitherseaorland，butthatallthischangesincourseoftime。
　　Sowehaveexplainedthatthesamepartsoftheeartharenotalwayslandorseaandwhythatisso：andalsowhysomeriversareperennialandothersnot。
　　BookII
　　1
　　LETusexplainthenatureoftheseaandthereasonwhysuchalargemassofwaterissaltandthewayinwhichitoriginallycametobe。
　　Theoldwriterswhoinventedtheogoniessaythattheseahassprings，fortheywantearthandseatohavefoundationsandrootsoftheirown。Presumablytheythoughtthatthisviewwasgranderandmoreimpressiveasimplyingthatourearthwasanimportantpartoftheuniverse。Fortheybelievedthatthewholeworldhadbeenbuiltuproundourearthandforitssake，andthattheearthwasthemostimportantandprimarypartofit。Others，wiserinhumanknowledge，giveanaccountofitsorigin。Atfirst，theysay，theearthwassurroundedbymoisture。Thenthesunbegantodryitup，partofitevaporatedandisthecauseofwindsandtheturningsbackofthesunandthemoon，whiletheremainderformsthesea。Sotheseaisbeingdriedupandisgrowingless，andwillendbybeingsomedayentirelydriedup。Otherssaythattheseaisakindofsweatexudedbytheearthwhenthesunheatsit，andthatthisexplainsitssaltness：forallsweatissalt。Otherssaythatthesaltnessisduetotheearth。Justaswaterstrainedthroughashesbecomessalt，sotheseaowesitssaltnesstotheadmixtureofearthwithsimilarproperties。
　　Wemustnowconsiderthefactswhichprovethattheseacannotpossiblyhavesprings。Thewaterswefindontheeartheitherfloworarestationary。Allflowingwaterhassprings。（Byaspring，aswehaveexplainedabove，wemustnotunderstandasourcefromwhichwatersareladledasitwerefromavessel，butafirstpointatwhichthewaterwhichiscontinuallyformingandpercolatinggathers。）
　　Stationarywateriseitherthatwhichhascollectedandhasbeenleftstanding，marshypools，forinstance，andlakes，whichdiffermerelyinsize，orelseitcomesfromsprings。Inthiscaseitisalwaysartificial，Imeanasinthecaseofwells，otherwisethespringwouldhavetobeabovetheoutlet。Hencethewaterfromfountainsandriversflowsofitself，whereaswellsneedtobeworkedartificially。Allthewatersthatexistbelongtooneorotheroftheseclasses。
　　Onthebasisofthisdivisionwecansecthattheseacannothavesprings。Foritfallsunderneitherofthetwoclasses;itdoesnotflowanditisnotartificial;whereasallwaterfromspringsmustbelongtooneorotherofthem。Naturalstandingwaterfromspringsisneverfoundonsuchalargescale。
　　Again，thereareseveralseasthathavenocommunicationwithoneanotheratall。TheRedSea，forinstance，communicatesbutslightlywiththeoceanoutsidethestraits，andtheHyrcanianandCaspianseasaredistinctfromthisoceanandpeopledwellallroundthem。Hence，iftheseseashadhadanyspringsanywheretheymusthavebeendiscovered。
　　Itistruethatinstraits，wherethelandoneithersidecontractsanopenseaintoasmallspace，theseaappearstoflow。Butthisisbecauseitisswingingtoandfro。Intheopenseathismotionisnotobserved，butwherethelandnarrowsandcontractstheseathemotionthatwasimperceptibleintheopennecessarilystrikestheattention。
　　ThewholeoftheMediterraneandoesactuallyflow。Thedirectionofthisflowisdeterminedbythedepthofthebasinsandbythenumberofrivers。MaeotisflowsintoPontusandPontusintotheAegean。Afterthattheflowoftheremainingseasisnotsoeasytoobserve。ThecurrentofMaeotisandPontusisduetothenumberofrivers（moreriversflowintotheEuxineandMaeotisthanintothewholeMediterraneanwithitsmuchlargerbasin），andtotheirownshallowness。Forwefindtheseagettingdeeperanddeeper。PontusisdeeperthanMaeotis，theAegeanthanPontus，theSicilianseathantheAegean;theSardinianandTyrrhenicbeingthedeepestofall。
　　（OutsidethepillarsofHeraclestheseaisshallowowingtothemud，butcalm，foritliesinahollow。）Wesee，then，thatjustassingleriversflowfrommountains，soitiswiththeearthasawhole：
　　thegreatestvolumeofwaterflowsfromthehigherregionsinthenorth。Theiralluviummakesthenorthernseasshallow，whiletheouterseasaredeeper。Somefurtherevidenceoftheheightofthenorthernregionsoftheearthisaffordedbytheviewofmanyoftheancientmeteorologists。Theybelievedthatthesundidnotpassbelowtheearth，butrounditsnorthernpart，andthatitwastheheightofthiswhichobscuredthesunandcausednight。
　　Somuchtoprovethattherecannotbesourcesoftheseaandtoexplainitsobservedflow。
　　2
　　Wemustnowdiscusstheoriginofthesea，ifithasanorigin，andthecauseofitssaltandbittertaste。
　　Whatmadeearlierwritersconsidertheseatobetheoriginalandmainbodyofwateristhis。Itseemsreasonabletosupposethattobethecaseontheanalogyoftheotherelements。Eachofthemhasamainbulkwhichbyreasonofitsmassistheoriginofthatelement，andanypartswhichchangeandmixwiththeotherelementscomefromit。Thusthemainbodyoffireisintheupperregion;thatofairoccupiestheplacenextinsidetheregionoffire;whilethemassoftheearthisthatroundwhichtherestoftheelementsareseentolie。Sowemustclearlylookforsomethinganalogousinthecaseofwater。Butherewecanfindnosuchsinglemass，asinthecaseoftheotherelements，exceptthesea。Riverwaterisnotaunity，norisitstable，butisseentobeinacontinuousprocessofbecomingfromdaytoday。Itwasthisdifficultywhichmadepeopleregardtheseaastheoriginandsourceofmoistureandofallwater。Andsowefinditmaintainedthatriversnotonlyflowintotheseabutoriginatefromit，thesaltwaterbecomingsweetbyfiltration。
　　Butthisviewinvolvesanotherdifficulty。Ifthisbodyofwateristheoriginandsourceofallwater，whyisitsaltandnotsweet？
　　Thereasonforthis，besidesansweringthisquestion，willensureourhavingarightfirstconceptionofthenatureofthesea。
　　Theearthissurroundedbywater，justasthatisbythesphereofair，andthatagainbythespherecalledthatoffire（whichistheoutermostbothonthecommonviewandonours）。Nowthesun，movingasitdoes，setsupprocessesofchangeandbecominganddecay，andbyitsagencythefinestandsweetestwateriseverydaycarriedupandisdissolvedintovapourandrisestotheupperregion，whereitiscondensedagainbythecoldandsoreturnstotheearth。This，aswehavesaidbefore，istheregularcourseofnature。
　　Henceallmypredecessorswhosupposedthatthesunwasnourishedbymoistureareabsurdlymistaken。Somegoontosaythatthesolsticesareduetothis，thereasonbeingthatthesameplacescannotalwayssupplythesunwithnourishmentandthatwithoutithemustperish。
　　Forthefirewearefamiliarwithlivesaslongasitisfed，andtheonlyfoodforfireismoisture。Asifthemoisturethatisraisedcouldreachthesun！orthisascentwerereallylikethatperformedbyflameasitcomesintobeing，andtowhichtheysupposedthecaseofthesuntobeanalogous！Reallythereisnosimilarity。Aflameisaprocessofbecoming，involvingaconstantinterchangeofmoistanddry。Itcannotbesaidtobenourishedsinceitscarcelypersistsasoneandthesameforamoment。Thiscannotbetrueofthesun;forifitwerenourishedlikethat，astheysayitis，weshouldobviouslynotonlyhaveanewsuneveryday，asHeraclitussays，butanewsuneverymoment。Again，whenthesuncausesthemoisturetorise，thisislikefireheatingwater。So，asthefireisnotfedbythewateraboveit，itisabsurdtosupposethatthesunfeedsonthatmoisture，evenifitsheatmadeallthewaterintheworldevaporate。Again，itisabsurd，consideringthenumberandsizeofthestars，thatthesethinkersshouldconsiderthesunonlyandoverlookthequestionhowtherestoftheheavenlybodiessubsist。Again，theyaremetbythesamedifficultyasthosewhosaythatatfirsttheearthitselfwasmoistandtheworldroundtheearthwaswarmedbythesun，andsoairwasgeneratedandthewholefirmamentgrew，andtheaircausedwindsandsolstices。Theobjectionisthatwealwaysplainlyseethewaterthathasbeencarriedupcomingdownagain。Evenifthesameamountdoesnotcomebackinayearorinagivencountry，yetinacertainperiodallthathasbeencarriedupisreturned。Thisimpliesthatthecelestialbodiesdonotfeedonit，andthatwecannotdistinguishbetweensomeairwhichpreservesitscharacteronceitisgeneratedandsomeotherwhichisgeneratedbutbecomeswateragainandsoperishes;onthecontrary，allthemoisturealikeisdissolvedandallofitcondensedbackintowater。
　　Thedrinkable，sweetwater，then，islightandisallofitdrawnup：thesaltwaterisheavyandremainsbehind，butnotinitsnaturalplace。Forthisisaquestionwhichhasbeensufficientlydiscussed（I
　　meanaboutthenaturalplacethatwater，liketheotherelements，mustinreasonhave），andtheansweristhis。Theplacewhichweseetheseafillingisnotitsnaturalplacebutthatofwater。Itseemstobelongtotheseabecausetheweightofthesaltwatermakesitremainthere，whilethesweet，drinkablewaterwhichislightiscarriedup。Thesamethinghappensinanimalbodies。Here，too，thefoodwhenitentersthebodyissweet，yettheresiduumanddregsofliquidfoodarefoundtobebitterandsalt。Thisisbecausethesweetanddrinkablepartofithasbeendrawnawaybythenaturalanimalheatandhaspassedintothefleshandtheotherpartsofthebodyaccordingtotheirseveralnatures。Nowjustashereitwouldbewrongforanyonetorefusetocallthebellytheplaceofliquidfoodbecausethatdisappearsfromitsoon，andtocallittheplaceoftheresiduumbecausethisisseentoremain，sointhecaseofourpresentsubject。Thisplace，wesay，istheplaceofwater。Henceallriversandallthewaterthatisgeneratedflowintoit：forwaterflowsintothedeepestplace，andthedeepestpartoftheearthisfilledbythesea。Onlyallthelightandsweetpartofitisquicklycarriedoffbythesun，whileherestremainsforthereasonwehaveexplained。Itisquitenaturalthatsomepeopleshouldhavebeenpuzzledbytheoldquestionwhysuchamassofwaterleavesnotraceanywhere（fortheseadoesnotincreasethoughinnumerableandvastriversareflowingintoiteveryday。）Butifoneconsidersthematterthesolutioniseasy。Thesameamountofwaterdoesnottakeaslongtodryupwhenitisspreadoutaswhenitisgatheredinabody，andindeedthedifferenceissogreatthatintheonecaseitmightpersistthewholedaylongwhileintheotheritmightalldisappearinamoment-asforinstanceifoneweretospreadoutacupofwateroveralargetable。Thisisthecasewiththerivers：allthetimetheyareflowingtheirwaterformsacompactmass，butwhenitarrivesatavastwideplaceitquicklyandimperceptiblyevaporates。
　　ButthetheoryofthePhaedoaboutriversandtheseaisimpossible。
　　ThereitissaidthattheearthispiercedbyintercommunicatingchannelsandthattheoriginalheadandsourceofallwatersiswhatiscalledTartarus-amassofwateraboutthecentre，fromwhichallwaters，flowingandstanding，arederived。Thisprimaryandoriginalwaterisalwayssurgingtoandfro，andsoitcausestheriverstoflowonthissideoftheearth’scentreandonthat;forithasnofixedseatbutisalwaysoscillatingaboutthecentre。Itsmotionupanddowniswhatfillsrivers。Manyoftheseformlakesinvariousplaces（ourseaisaninstanceofoneofthese），butallofthemcomeroundagaininacircletotheoriginalsourceoftheirflow，manyatthesamepoint，butsomeatapointoppositetothatfromwhichtheyissued;forinstance，iftheystartedfromtheothersideoftheearth’scentre，theymightreturnfromthissideofit。Theydescendonlyasfarasthecentre，forafterthatallmotionisupwards。Watergetsitstastesandcoloursfromthekindofearththerivershappenedtoflowthrough。
　　Butonthistheoryriversdonotalwaysflowinthesamesense。
　　Forsincetheyflowtothecentrefromwhichtheyissueforththeywillnotbeflowingdownanymorethanup，butinwhateverdirectionthesurgingofTartarusinclinesto。Butatthisrateweshallgettheproverbialriversflowingupwards，whichisimpossible。Again，whereisthewaterthatisgeneratedandwhatgoesupagainasvapourtocomefrom？Forthismustallofitsimplybeignored，sincethequantityofwaterisalwaysthesameandallthewaterthatflowsoutfromtheoriginalsourceflowsbacktoitagain。Thisitselfisnottrue，sinceallriversareseentoendintheseaexceptwhereoneflowsintoanother。Notoneofthemendsintheearth，butevenwhenoneisswallowedupitcomestothesurfaceagain。Andthoseriversarelargewhichflowforalongdistancethroughalowyingcountry，forbytheirsituationandlengththeycutoffthecourseofmanyothersandswallowthemup。ThisiswhytheIstrusandtheNilearethegreatestoftheriverswhichflowintooursea。Indeed，somanyriversfallintothemthatthereisdisagreementastothesourcesofthemboth。Allofwhichisplainlyimpossibleonthetheory，andthemoresoasitderivestheseafromTartarus。
　　Enoughhasbeensaidtoprovethatthisisthenaturalplaceofwaterandnotofthesea，andtoexplainwhysweetwaterisonlyfoundinrivers，whilesaltwaterisstationary，andtoshowthattheseaistheendratherthanthesourceofwater，analogoustotheresidualmatterofallfood，andespeciallyliquidfood，inanimalbodies。
　　3
　　Wemustnowexplainwhytheseaissalt，andaskwhetheriteternallyexistsasidenticallythesamebody，orwhetheritdidnotexistatallonceandsomedaywillexistnolonger，butwilldryupassomepeoplethink。
　　Everyoneadmitsthis，thatifthewholeworldoriginatedtheseadidtoo;fortheymakethemcomeintobeingatthesametime。Itfollowsthatiftheuniverseiseternalthesamemustbetrueofthesea。AnyonewhothinkslikeDemocritusthattheseaisdiminishingandwilldisappearintheendremindsusofAesop’stales。HisstorywasthatCharybdishadtwicesuckedinthesea：thefirsttimeshemadethemountainsvisible;thesecondtimetheislands;andwhenshesucksitinforthelasttimeshewilldryitupentirely。SuchataleisappropriateenoughtoAesopinaragewiththeferryman，butnottoseriousinquirers。Whatevermadethesearemainatfirst，whetheritwasitsweight，assomeevenofthosewhoholdtheseviewssay（foritiseasytoseethecausehere），orsomeotherreason-clearlythesamethingmustmakeitpersistforever。Theymusteitherdenythatthewaterraisedbythesunwillreturnatall，or，ifitdoes，theymustadmitthattheseapersistsforeveroraslongasthisprocessgoeson，andagain，thatforthesameperiodoftimethatsweetwatermusthavebeencarriedupbeforehand。Sotheseawillneverdryup：forbeforethatcanhappenthewaterthathasgoneupbeforehandwillreturntoit：forifyousaythatthishappensonceyoumustadmititsrecurrence。Ifyoustopthesun’scoursethereisnodryingagency。Ifyouletitgoonitwilldrawupthesweetwateraswehavesaidwheneveritapproaches，andletitdescendagainwhenitrecedes。Thisnotionabouttheseaisderivedfromthefactthatmanyplacesarefoundtobedriernowthantheyoncewere。Whythisissowehaveexplained。Thephenomenonisduetotemporaryexcessofrainandnottoanyprocessofbecominginwhichtheuniverseoritspartsareinvolved。Somedaytheoppositewilltakeplaceandafterthattheearthwillgrowdryonceagain。Wemustrecognizethatthisprocessalwaysgoesonthusinacycle，forthatismoresatisfactorythantosupposeachangeinthewholeworldinordertoexplainthesefacts。Butwehavedweltlongeronthispointthanitdeserves。
　　Toreturntothesaltnessofthesea：thosewhocreatetheseaonceforall，orindeedgenerateitatall，cannotaccountforitssaltness。Itmakesnodifferencewhethertheseaistheresidueofallthemoisturethatisabouttheearthandhasbeendrawnupbythesun，orwhetheralltheflavourexistinginthewholemassofsweetwaterisduetotheadmixtureofacertainkindofearth。Sincethetotalvolumeoftheseaisthesameoncethewaterthatevaporatedhasreturned，itfollowsthatitmusteitherhavebeensaltatfirsttoo，or，ifnotatfirst，thennotnoweither。Ifitwassaltfromtheverybeginning，thenwewanttoknowwhythatwasso;andwhy，ifsaltwaterwasdrawnupthen，thatisnotthecasenow。
　　Again，ifitismaintainedthatanadmixtureofearthmakestheseasalt（fortheysaythatearthhasmanyflavoursandiswasheddownbytheriversandsomakestheseasaltbyitsadmixture），itisstrangethatriversshouldnotbesalttoo。Howcantheadmixtureofthisearthhavesuchastrikingeffectinagreatquantityofwaterandnotineachriversingly？Forthesea，differinginnothingfromriversbutinbeingsalt，isevidentlysimplythetotalityofriverwater，andtheriversarethevehicleinwhichthatearthiscarriedtotheircommondestination。
　　Itisequallyabsurdtosupposethatanythinghasbeenexplainedbycallingthesea’thesweatoftheearth’，likeEmpedicles。
　　Metaphorsarepoeticalandsothatexpressionofhismaysatisfytherequirementsofapoem，butasascientifictheoryitisunsatisfactory。Eveninthecaseofthebodyitisaquestionhowthesweetliquiddrunkbecomessaltsweatwhetheritismerelybythedepartureofsomeelementinitwhichissweetest，orbytheadmixtureofsomething，aswhenwaterisstrainedthroughashes。
　　Actuallythesaltnessseemstobeduetothesamecauseasinthecaseoftheresidualliquidthatgathersinthebladder。That，too，becomesbitterandsaltthoughtheliquidwedrinkandthatcontainedinourfoodissweet。Ifthenthebitternessisdueinthesecases（aswiththewaterstrainedthroughlye）tothepresenceofacertainsortofstuffthatiscarriedalongbytheurine（asindeedweactuallyfindasaltdepositsettlinginchamber-pots）andissecretedfromthefleshinsweat（asifthedepartingmoisturewerewashingthestuffoutofthebody），thennodoubttheadmixtureofsomethingearthywiththewateriswhatmakestheseasalt。
　　Nowinthebodystuffofthiskind，viz。thesedimentoffood，isduetofailuretodigest：buthowtherecametobeanysuchthingintheearthrequiresexplanation。Besides，howcanthedryingandwarmingoftheearthcausethesecretionsuchagreatquantityofwater;especiallyasthatmustbeamerefragmentofwhatisleftintheearth？Again，waivingthequestionofquantity，whydoesnottheearthsweatnowwhenithappenstobeinprocessofdrying？Ifitdidsothen，itoughttodosonow。Butitdoesnot：onthecontrary，whenitisdryitgrawsmoist，butwhenitismoistitdoesnotsecreteanythingatall。Howthenwasitpossiblefortheearthatthebeginningwhenitwasmoisttosweatasitgrewdry？
　　Indeed，thetheorythatmaintainsthatmostofthemoisturedepartedandwasdrawnupbythesunandthatwhatwasleftoveristheseaismorereasonable;butfortheearthtosweatwhenitismoistisimpossible。
　　Sincealltheattemptstoaccountforthesaltnessoftheseaseemunsuccessfulletusexplainitbythehelpoftheprinciplewehaveusedalready。
　　Sincewerecognizetwokindsofevaporation，onemoist，theotherdry，itisclearthatthelattermustberecognizedasthesourceofphenomenalikethoseweareconcernedwith。
　　Butthereisaquestionwhichwemustdiscussfirst。Doestheseaalwaysremainnumericallyoneandconsistingofthesameparts，orisit，too，oneinformandvolumewhileitspartsareincontinualchange，likeairandsweetwaterandfire？Alloftheseareinaconstantstateofchange，buttheformandthequantityofeachofthemarefixed，justastheyareinthecaseofaflowingriveroraburningflame。Theanswerisclear，andthereisnodoubtthatthesameaccountholdsgoodofallthesethingsalike。Theydifferinthatsomeofthemchangemorerapidlyormoreslowlythanothers;andtheyallareinvolvedinaprocessofperishingandbecomingwhichyetaffectsthemallinaregularcourse。
　　Thisbeingsowemustgoontotrytoexplainwhytheseaissalt。
　　Therearemanyfactswhichmakeitclearthatthistasteisduetotheadmixtureofsomething。First，inanimalbodieswhatisleastdigested，theresidueofliquidfood，issaltandbitter，aswesaidbefore。Allanimalexcretaareundigested，butespeciallythatwhichgathersinthebladder（itsextremelightnessprovesthis;foreverythingthatisdigestediscondensed），andalsosweat;inthesethenisexcreted（alongwithothermatter）anidenticalsubstancetowhichthisflavourisdue。Thecaseofthingsburntisanalogous。Whatheatfailstoassimilatebecomestheexcrementaryresidueinanimalbodies，and，inthingsburnt，ashes。Thatiswhysomepeoplesaythatitwasburntearththatmadetheseasalt。Tosaythatitwasburntearthisabsurd;buttosaythatitwassomethinglikeburntearthistrue。Wemustsupposethatjustasinthecaseswehavedescribed，sointheworldasawhole，everythingthatgrowsandisnaturallygeneratedalwaysleavesanundigestedresidue，likethatofthingsburnt，consistingofthissortofearth。Alltheearthystuffinthedryexhalationisofthisnature，anditisthedryexhalationwhichaccountsforitsgreatquantity。Nowsince，aswehavesaid，themoistandthedryevaporationsaremixed，somequantityofthisstuffmustalwaysbeincludedinthecloudsandthewaterthatareformedbycondensation，andmustredescendtotheearthinrain。
　　Thisprocessmustalwaysgoonwithsuchregularityasthesublunaryworldadmitsof。anditistheanswertothequestionhowtheseacomestobesalt。
　　Italsoexplainswhyrainthatcomesfromthesouth，andthefirstrainsofautumn，arebrackish。Thesouthisthewarmestofwindsanditblowsfromdryandhotregions。Henceitcarrieslittlemoistvapourandthatiswhyitishot。（Itmakesnodifferenceevenifthisisnotitstruecharacteranditisoriginallyacoldwind，foritbecomeswarmonitswaybyincorporatingwithitselfagreatquantityofdryevaporationfromtheplacesitpassesover。）Thenorthwind，ontheotherhand，combingfrommoistregions，isfullofvapourandthereforecold。Itisdryinourpartoftheworldbecauseitdrivesthecloudsawaybeforeit，butinthesouthitisrainy;justasthesouthisadrywindinLibya。Sothesouthwindchargestherainthatfallswithagreatquantityofthisstuff。
　　Autumnrainisbrackishbecausetheheaviestwatermustfallfirst;sothatthatwhichcontainsthegreatestquantityofthiskindofearthdescendsquickest。
　　This，too，iswhytheseaiswarm。Everythingthathasbeenexposedtofirecontainsheatpotentially，asweseeinthecaseoflyeandashesandthedryandliquidexcretaofanimals。Indeedthoseanimalswhicharehottestinthebellyhavethehottestexcreta。
　　Theactionofthiscauseiscontinuallymakingtheseamoresalt，butsomepartofitssaltnessisalwaysbeingdrawnupwiththesweetwater。Thisislessthanthesweetwaterinthesameratioinwhichthesaltandbrackishelementinrainislessthanthesweet，andsothesaltnessofthesearemainsconstantonthewhole。Saltwaterwhenitturnsintovapourbecomessweet，andthevapourdoesnotformsaltwaterwhenitcondensesagain。ThisIknowbyexperiment。
　　Thesamethingistrueineverycaseofthekind：wineandallfluidsthatevaporateandcondensebackintoaliquidstatebecomewater。Theyallarewatermodifiedbyacertainadmixture，thenatureofwhichdeterminestheirflavour。Butthissubjectmustbeconsideredonanothermoresuitableoccasion。
　　Forthepresentletussaythis。Theseaisthereandsomeofitiscontinuallybeingdrawnupandbecomingsweet;thisreturnsfromabovewiththerain。Butitisnowdifferentfromwhatitwaswhenitwasdrawnup，anditsweightmakesitsinkbelowthesweetwater。
　　Thisprocesspreventsthesea，asitdoesrivers，fromdryingupexceptfromlocalcauses（thismusthappentoseaandriversalike）。
　　Ontheotherhandthepartsneitheroftheearthnorofthesearemainconstantbutonlytheirwholebulk。Forthesamethingistrueoftheearthasofthesea：someofitiscarriedupandsomecomesdownwiththerain，andboththatwhichremainsonthesurfaceandthatwhichcomesdownagainchangetheirsituations。
　　Thereismoreevidencetoprovethatsaltnessisduetotheadmixtureofsomesubstance，besidesthatwhichwehaveadduced。
　　Makeavesselofwaxandputitinthesea，fasteningitsmouthinsuchawayastopreventanywatergettingin。Thenthewaterthatpercolatesthroughthewaxsidesofthevesselissweet，theearthystuff，theadmixtureofwhichmakesthewatersalt，beingseparatedoffasitwerebyafilter。Itisthisstuffwhichmakesaltwaterheavy（itweighsmorethanfreshwater）andthick。Thedifferenceinconsistencyissuchthatshipswiththesamecargoverynearlysinkinariverwhentheyarequitefittonavigateinthesea。Thiscircumstancehasbeforenowcausedlosstoshippersfreightingtheirshipsinariver。Thatthethickerconsistencyisduetoanadmixtureofsomethingisprovedbythefactthatifyoumakestrongbrinebytheadmixtureofsalt，eggs，evenwhentheyarefull，floatinit。Italmostbecomeslikemud;suchaquantityofearthymatteristhereinthesea。Thesamethingisdoneinsaltingfish。
　　Againif，asisfabled，thereisalakeinPalestine，suchthatifyoubindamanorbeastandthrowitinitfloatsanddoesnotsink，thiswouldbearoutwhatwehavesaid。Theysaythatthislakeissobitterandsaltthatnofishliveinitandthatifyousoakclothesinitandshakethemitcleansthem。Thefollowingfactsallofthemsupportourtheorythatitissomeearthystuffinthewaterwhichmakesitsalt。InChaoniathereisaspringofbrackishwaterthatflowsintoaneighbouringriverwhichissweetbutcontainsnofish。
　　ThelocalstoryisthatwhenHeraclescamefromErytheiadrivingtheoxenandgavetheinhabitantsthechoice，theychosesaltinpreferencetofish。Theygetthesaltfromthespring。Theyboiloffsomeofthewaterandletthereststand;whenithascooledandtheheatandmoisturehaveevaporatedtogetheritgivesthemsalt，notinlumpsbutlooseandlightlikesnow。Itisweakerthanordinarysaltandaddedfreelygivesasweettaste，anditisnotaswhiteassaltgenerallyis。AnotherinstanceofthisisfoundinUmbria。
　　Thereisaplacetherewherereedsandrushesgrow。Theyburnsomeofthese，puttheashesintowaterandboilitoff。Whenalittlewaterisleftandhascooleditgivesaquantityofsalt。
　　Mostsaltriversandspringsmustoncehavebeenhot。Thentheoriginalfireinthemwasextinguishedbuttheearththroughwhichtheypercolatepreservesthecharacteroflyeorashes。Springsandriverswithallkindsofflavoursarefoundinmanyplaces。Theseflavoursmustineverycasebeduetothefirethatisorwasinthem，forifyouexposeearthtodifferentdegreesofheatitassumesvariouskindsandshadesofflavour。Itbecomesfullofalumandlyeandotherthingsofthekind，andthefreshwaterpercolatesthroughtheseandchangesitscharacter。SometimesitbecomesacidasinSicania，apartofSicily。Theretheygetasaltandacidwaterwhichtheyuseasvinegartoseasonsomeoftheirdishes。IntheneighbourhoodofLyncus，too，thereisaspringofacidwater，andinScythiaabitterspring。Thewaterfromthismakesthewholeoftheriverintowhichitflowsbitter。Thesedifferencesareexplainedbyaknowledgeoftheparticularmixturesthatdeterminedifferentsavours。
　　Butthesehavebeenexplainedinanothertreatise。
　　Wehavenowgivenanaccountofwatersandthesea，whytheypersist，howtheychange，whattheirnatureis，andhaveexplainedmostoftheirnaturaloperationsandaffections。
　　4
　　Letusproceedtothetheoryofwinds。Itsbasisisadistinctionwehavealreadymade。Werecognizetwokindsofevaporation，onemoist，theotherdry。Theformeriscalledvapour：fortheotherthereisnogeneralnamebutwemustcallitasortofsmoke，applyingtothewholeofitawordthatispropertooneofitsforms。Themoistcannotexistwithoutthedrynorthedrywithoutthemoist：wheneverwespeakofeitherwemeanthatitpredominates。Nowwhenthesuninitscircularcourseapproaches，itdrawsupbyitsheatthemoistevaporation：whenitrecedesthecoldmakesthevapourthathadbeenraisedcondensebackintowaterwhichfallsandisdistributedthroughtheearth。（Thisexplainswhythereismoreraininwinterandmorebynightthanbyday：thoughthefactisnotrecognizedbecauserainbynightismoreapttoescapeobservationthanbyday。）Butthereisagreatquantityoffireandheatintheearth，andthesunnotonlydrawsupthemoisturethatliesonthesurfaceofit，butwarmsanddriestheearthitself。Consequently，sincetherearetwokindsofevaporation，aswehavesaid，onelikevapour，theotherlikesmoke，bothofthemarenecessarilygenerated。Thatinwhichmoisturepredominatesisthesourceofrain，asweexplainedbefore，whilethedryevaporationisthesourceandsubstanceofallwinds。Thatthingsmustnecessarilytakethiscourseisclearfromtheresultingphenomenathemselves，fortheevaporationthatistoproducethemmustnecessarilydiffer;andthesunandthewarmthintheearthnotonlycanbutmustproducetheseevaporations。
　　Sincethetwoevaporationsarespecificallydistinct，windandrainobviouslydifferandtheirsubstanceisnotthesame，asthosesaywhomaintainthatoneandthesameairwheninmotioniswind，butwhenitcondensesagainiswater。Air，aswehaveexplainedinanearlierbook，ismadeupoftheseasconstituents。Vapourismoistandcold（foritsfluidityisduetoitsmoistness，andbecauseitderivesfromwateritisnaturallycold，likewaterthathasnotbeenwarmed）：whereasthesmokyevaporationishotanddry。Henceeachcontributesapart，andairismoistandhot。Itisabsurdthatthisairthatsurroundsusshouldbecomewindwheninmotion，whateverbethesourceofitsmotiononthecontrarythecaseofwindsislikethatofrivers。Wedonotcallwaterthatflowsanyhowariver，evenifthereisagreatquantityofit，butonlyiftheflowcomesfromaspring。Sotoowiththewinds;agreatquantityofairmightbemovedbythefallofsomelargeobjectwithoutflowingfromanysourceorspring。
　　Thefactsbearoutourtheory。Itisbecausetheevaporationtakesplaceuninterruptedlybutdiffersindegreeandquantitythatcloudsandwindsappearintheirnaturalproportionaccordingtotheseason;anditisbecausethereisnowagreatexcessofthevaporous，nowofthedryandsmokyexhalation，thatsomeyearsarerainyandwet，otherswindyanddry。Sometimesthereismuchdroughtorrain，anditprevailsoveragreatandcontinuousstretchofcountry。Atothertimesitislocal;thesurroundingcountryoftengettingseasonableorevenexcessiverainswhilethereisdroughtinacertainpart;or，contrariwise，allthesurroundingcountrygetslittleorevennorainwhileacertainpartgetsraininabundance。Thereasonforallthisisthatwhilethesameaffectionisgenerallyapttoprevailoveraconsiderabledistrictbecauseadjacentplaces（unlessthereissomethingspecialtodifferentiatethem）standinthesamerelationtothesun，yetonoccasionthedryevaporationwillprevailinonepartandthemoistinanother，orconversely。Againthereasonforthislatteristhateachevaporationgoesovertothatoftheneighbouringdistrict：forinstance，thedryevaporationcirculatesinitsownplacewhilethemoistmigratestothenextdistrictorisevendrivenbywindstosomedistantplace：orelsethemoistevaporationremainsandthedrymovesaway。Justasinthecaseofthebodywhenthestomachisdrythelowerbellyisofteninthecontrarystate，andwhenitisdrythestomachismoistandcold，soitoftenhappensthattheevaporationsreciprocallytakeoneanother’splaceandinterchange。
　　Further，afterrainwindgenerallyrisesinthoseplaceswheretherainfell，andwhenrainhascomeonthewindceases。Thesearenecessaryeffectsoftheprincipleswehaveexplained。Afterraintheearthisbeingdriedbyitsownheatandthatfromaboveandgivesofftheevaporationwhichwesawtobethematerialcauseof。wind。
　　Again，supposethissecretionispresentandwindprevails;theheatiscontinuallybeingthrownoff，risingtotheupperregion，andsothewindceases;thenthefallintemperaturemakesvapourformandcondenseintowater。Wateralsoformsandcoolsthedryevaporationwhenthecloudsaredriventogetherandthecoldconcentratedinthem。
　　Thesearethecausesthatmakewindceaseontheadventofrain，andrainfallonthecessationofwind。
　　Thecauseofthepredominanceofwindsfromthenorthandfromthesouthisthesame。（Mostwinds，asamatteroffact，arenorthwindsorsouthwinds。）Thesearetheonlyregionswhichthesundoesnotvisit：itapproachesthemandrecedesfromthem，butitscourseisalwaysoverthe-westandtheeast。Hencecloudscollectoneitherside，andwhenthesunapproachesitprovokesthemoistevaporation，andwhenitrecedestotheoppositesidetherearestormsandrain。Sosummerandwinterareduetothesun’smotiontoandfromthesolstices，andwaterascendsandfallsagainforthesamereason。
　　Nowsincemostrainfallsinthoseregionstowardswhichandfromwhichthesunturnsandthesearethenorthandthesouth，andsincemostevaporationmusttakeplacewherethereisthegreatestrainfall，justasgreenwoodgivesmostsmoke，andsincethisevaporationiswind，itisnaturalthatthemostandmostimportantwindsshouldcomefromthesequarters。（ThewindsfromthenortharecalledBoreae，thosefromthesouthNoti。）
　　Thecourseofwindsisoblique：forthoughtheevaporationrisesstraightupfromtheearth，theyblowrounditbecauseallthesurroundingairfollowsthemotionoftheheavens。Hencethequestionmightbeaskedwhetherwindsoriginatefromaboveorfrombelow。Themotioncomesfromabove：beforewefeelthewindblowingtheairbetraysitspresenceiftherearecloudsoramist，fortheirmotionshowsthatthewindhasbeguntoblowbeforeithasactuallyreachedus;andthisimpliesthatthesourceofwindsisabove。Butsincewindisdefinedas’aquantityofdryevaporationfromtheearthmovingroundtheearth’，itisclearthatwhiletheoriginofthemotionisfromabove，thematterandthegenerationofwindcomefrombelow。Theobliquemovementoftherisingevaporationiscausedfromabove：forthemotionoftheheavensdeterminestheprocessesthatareatadistancefromtheearth，andthemotionfrombelowisverticalandeverycauseismoreactivewhereitisnearesttotheeffect;butinitsgenerationandoriginwindplainlyderivesfromtheearth。
　　Thefactsbearouttheviewthatwindsareformedbythegradualunionofmanyevaporationsjustasriversderivetheirsourcesfromthewaterthatoozesfromtheearth。Everywindisweakestinthespotfromwhichitblows;astheyproceedandleavetheirsourceatadistancetheygatherstrength。Thusthewinterinthenorthiswindlessandcalm：thatis，inthenorthitself;but，thebreezethatblowsfromtheresogentlyastoescapeobservationbecomesagreatwindasitpasseson。
　　Wehaveexplainedthenatureandoriginofwind，theoccurrenceofdroughtandrains，thereasonwhyrainstopswindandwindrisesafterrain，theprevalenceofnorthandsouthwindsandalsowhywindmovesinthewayitdoes。
　　5
　　Thesunbothcheckstheformationofwindsandstimulatesit。Whentheevaporationissmallinamountandfaintthesunwastesitanddissipatesbyitsgreaterheatthelesserheatcontainedintheevaporation。Italsodriesuptheearth，thesourceoftheevaporation，beforethelatterhasappearedinbulk：justas，whenyouthrowalittlefuelintoagreatfire，itisoftenburntupbeforegivingoffanysmoke。Inthesewaysthesuncheckswindsandpreventsthemfromrisingatall：itchecksthembywastingtheevaporation，andpreventstheirrisingbydryinguptheearthquickly。
　　HencecalmisveryapttoprevailabouttherisingofOrionandlastsuntilthecomingoftheEtesiaeandtheir’forerunners’。
　　Calmisduetotwocauses。Eithercoldquenchestheevaporation，forinstanceasharpfrost：orexcessiveheatwastesit。Intheintermediateperiods，too，thecausesaregenerallyeitherthattheevaporationhasnothadtimetodeveloporthatithaspassedawayandthereisnoneasyettoreplaceit。
　　BoththesettingandtherisingofOrionareconsideredtobetreacherousandstormy，becausetheyplaceatachangeofseason（namelyofsummerorwinter;andbecausethesizeoftheconstellationmakesitsriselastovermanydays）andastateofchangeisalwaysindefiniteandthereforeliabletodisturbance。
　　TheEtesiaeblowafterthesummersolsticeandtherisingofthedog-star：notatthetimewhenthesunisclosestnorwhenitisdistant;andtheyblowbydayandceaseatnight。Thereasonisthatwhenthesunisnearitdriesuptheearthbeforeevaporationhastakenplace，butwhenithasrecededalittleitsheatandtheevaporationarepresentintherightproportion;sotheicemeltsandtheearth，driedbyitsownheatandthatofthesun，smokesandvapours。Theyabateatnightbecausethecoldpfthenightschecksthemeltingoftheice。Whatisfrozengivesoffnoevaporation，nordoesthatwhichcontainsnodrynessatall：itisonlywheresomethingdrycontainsmoisturethatitgivesoffevaporationundertheinfluenceofheat。
　　Thequestionissometimesasked：whydothenorthwindswhichwecalltheEtesiaeblowcontinuouslyafterthesummersolstice，whentherearenocorrespondingsouthwindsafterthewintersolstice？
　　Thefactsarereasonableenough：fortheso-called’whitesouthwinds’
　　doblowatthecorrespondingseason，thoughtheyarenotequallycontinuousandsoescapeobservationandgiverisetothisinquiry。
　　ThereasonforthisisthatthenorthwindIfromthearcticregionswhicharefullofwaterandsnow。ThesunthawsthemandsotheEtesiaeblow：afterratherthanatthesummersolstice。（Forthegreatestheatisdevelopednotwhenthesunisnearesttothenorth，butwhenitsheathasbeenfeltforaconsiderableperiodandithasnotyetrecededfar。The’birdwinds’blowinthesamewayafterthewintersolstice。They，too，areweakEtesiae，buttheyblowlessandlaterthantheEtesiae。Theybegintoblowonlyontheseventiethdaybecausethesunisdistantandthereforeweaker。Theydonotblowsocontinuouslybecauseonlythingsonthesurfaceoftheearthandofferinglittleresistanceevaporatethen，thethoroughlyfrozenpartsrequiringgreaterheattomeltthem。SotheyblowintermittentlytillthetrueEtesiaecomeonagainatthesummersolstice：forfromthattimeonwardsthewindtendstoblowcontinuously。）ButthesouthwindblowsfromthetropicofCancerandnotfromtheantarcticregion。
　　Therearetwoinhabitablesectionsoftheearth：onenearourupper，ornothernpole，theotherneartheotherorsouthernpole;andtheirshapeislikethatofatambourine。Ifyoudrawlinesfromthecentreoftheearththeycutoutadrum-shapedfigure。Thelinesformtwocones;thebaseoftheoneisthetropic，oftheothertheevervisiblecircle，theirvertexisatthecentreoftheearth。Twootherconestowardsthesouthpolegivecorrespondingsegmentsoftheearth。Thesesectionsalonearehabitable。Beyondthetropicsnoonecanlive：fortheretheshadewouldnotfalltothenorth，whereastheearthisknowntobeuninhabitablebeforethesunisinthezenithortheshadeisthrowntothesouth：andtheregionsbelowtheBearareuninhabitablebecauseofthecold。
　　（TheCrown，too，movesoverthisregion：foritisinthezenithwhenitisonourmeridian。）
　　Soweseethatthewayinwhichtheynowdescribethegeographyoftheearthisridiculous。Theydepicttheinhabitedearthasround，butbothascertainedfactsandgeneralconsiderationsshowthistobeimpossible。Ifwereflectweseethattheinhabitedregionislimitedinbreadth，whiletheclimateadmitsofitsextendingallroundtheearth。Forwemeetwithnoexcessiveheatorcoldinthedirectionofitslengthbutonlyinthatofitsbreadth;sothatthereisnothingtopreventourtravellingroundtheearthunlesstheextentoftheseapresentsanobstacleanywhere。Therecordsofjourneysbyseaandlandbearthisout。Theymakethelengthfargreaterthanthebreadth。IfwecomputethesevoyagesandjourneysthedistancefromthePillarsofHeraclestoIndiaexceedsthatfromAethiopiatoMaeotisandthenorthernmostScythiansbyaratioofmorethan5to3，asfarassuchmattersadmitofaccuratestatement。Yetweknowthewholebreadthoftheregionwedwellinuptotheuninhabitedparts：
　　inonedirectionnoonelivesbecauseofthecold，intheotherbecauseoftheheat。
　　ButitistheseawhichdividesasitseemsthepartsbeyondIndiafromthosebeyondthePillarsofHeraclesandpreventstheearthfrombeinginhabitedallround。
　　Nowsincetheremustbearegionbearingthesamerelationtothesouthernpoleastheplaceweliveinbearstoourpole，itwillclearlycorrespondintheorderingofitswindsaswellasinotherthings。Sojustaswehaveanorthwindhere，theymusthaveacorrespondingwindfromtheantarctic。Thiswindcannotreachussinceourownnorthwindislikealandbreezeanddoesnotevenreachthelimitsoftheregionwelivein。Theprevalenceofnorthwindshereisduetoourlyingnearthenorth。Yetevenheretheygiveoutandfailtopenetratefar：inthesouthernseabeyondLibyaeastandwestwindsarealwaysblowingalternately，likenorthandsouthwindswithus。Soitisclearthatthesouthwindisnotthewindthatblowsfromthesouthpole。Itisneitherthatnorthewindfromthewintertropic。Forsymmetrywouldrequireanotherwindblowingfromthesummertropic，whichthereisnot，sinceweknowthatonlyonewindblowsfromthatquarter。Sothesouthwindclearlyblowsfromthetorridregion。Nowthesunissoneartothatregionthatithasnowater，orsnowwhichmightmeltandcauseEtesiae。Butbecausethatplaceisfarmoreextensiveandopenthesouthwindisgreaterandstrongerandwarmerthanthenorthandpenetratesfarthertothenorththanthenorthwinddoestothesouth。
　　Theoriginofthesewindsandtheirrelationtooneanotherhasnowbeenexplained。
　　6
　　Letusnowexplainthepositionofthewinds，theiroppositions，whichcanblowsimultaneouslywithwhich，andwhichcannot，theirnamesandnumber，andanyotheroftheiraffectionsthathavenotbeentreatedinthe’particularquestions’。Whatwesayabouttheirpositionmustbefollowedwiththehelpofthefigure。Forclearness’sakewehavedrawnthecircleofthehorizon，whichisround，butitrepresentsthezoneinwhichwelive;forthatcanbedividedinthesameway。Letusalsobeginbylayingdownthatthosethingsarelocallycontrarywhicharelocallymostdistantfromoneanother，justasthingsspecificallymostremotefromoneanotherarespecificcontraries。Nowthingsthatfaceoneanotherfromoppositeendsofadiameterarelocallymostdistantfromoneanother。
　　（Seediagram。）
　　LetAbethepointwherethesunsetsattheequinoxandB，thepointopposite，theplacewhereitrisesattheequinox。Lettherebeanotherdiametercuttingthisatrightangles，andletthepointHonitbethenorthanditsdiametricaloppositeOthesouth。LetZ
　　betherisingofthesunatthesummersolsticeandEitssettingatthesummersolstice;Ditsrisingatthewintersolstice，andGitssettingatthewintersolstice。DrawadiameterfromZtoGfromD
　　toE。Thensincethosethingsarelocallycontrarywhicharemostdistantfromoneanotherinspace，andpointsdiametricallyoppositearemostdistantfromoneanother，thosewindsmustnecessarilybecontrarytooneanotherthatblowfromoppositeendsofadiameter。
　　Thenamesofthewindsaccordingtotheirpositionarethese。
　　ZephyrusisthewindthatblowsfromA，thisbeingthepointwherethesunsetsattheequinox。ItscontraryisApeliotesblowingfromB
　　thepointwherethesunrisesattheequinox。ThewindblowingfromH，thenorth，isthetruenorthwind，calledAparctias：whileNotusblowingfromOisitscontrary;forthispointisthesouthandOiscontrarytoH，beingdiametricallyoppositetoit。CaeciasblowsfromZ，wherethesunrisesatthesummersolstice。ItscontraryisnotthewindblowingfromEbutLipsblowingfromG。ForLipsblowsfromthepointwherethesunsetsatthewintersolsticeandisdiametricallyoppositetoCaecias：soitisitscontrary。EurusblowsfromD，comingfromthepointwherethesunrisesatthewintersolstice。ItbordersonNotus，andsoweoftenfindthatpeoplespeakof’Euro-Noti’。ItscontraryisnotLipsblowingfromGbutthewindthatblowsfromEwhichsomecallArgestes，someOlympias，andsomeSciron。Thisblowsfromthepointwherethesunsetsatthesummersolstice，andistheonlywindthatisdiametricallyoppositetoEurus。Thesearethewindsthatarediametricallyoppositetooneanotherandtheircontraries。
　　Thereareotherwindswhichhavenocontraries。ThewindtheycallThrascias，whichliesbetweenArgestesandAparctias，blowsfromI;
　　andthewindcalledMeses，whichliesbetweenCaeciasandAparctias，fromK。（ThelineIKnearlycoincideswiththeevervisiblecircle，butnotquite。）Thesewindshavenocontraries。Meseshasnot，orelsetherewouldbeawindblowingfromthepointMwhichisdiametricallyopposite。ThrasciascorrespondingtothepointIhasnot，forthentherewouldbeawindblowingfromN，thepointwhichisdiametricallyopposite。（ButperhapsalocalwindwhichtheinhabitantsofthosepartscallPhoeniciasblowsfromthatpoint。）
　　Thesearethemostimportantanddefinitewindsandthesetheirplaces。
　　Therearemorewindsfromthenorththanfromthesouth。Thereasonforthisisthattheregioninwhichweliveliesnearertothenorth。Also，muchmorewaterandsnowispushedasideintothisquarterbecausetheotherliesunderthesunanditscourse。Whenthisthawsandsoaksintotheearthandisexposedtotheheatofthesunandtheearthitnecessarilycausesevaporationtoriseingreaterquantitiesandoveragreaterspace。
　　OfthewindswehavedescribedAparctiasisthenorthwindinthestrictsense。ThrasciasandMesesarenorthwindstoo。（Caeciasishalfnorthandhalfeast。）SoutharethatwhichblowsfromduesouthandLips。East，thewindfromtherisingofthesunattheequinoxandEurus。Phoeniciasishalfsouthandhalfeast。West，thewindfromthetruewestandthatcalledArgestes。Moregenerallythesewindsareclassifiedasnortherlyorsoutherly。Thewestwindsarecountedasnortherly，fortheyblowfromtheplaceofsunsetandarethereforecolder;theeastwindsassoutherly，fortheyarewarmerbecausetheyblowfromtheplaceofsunrise。Sothedistinctionofcoldandhotorwarmisthebasisforthedivisionofthewindsintonortherlyandsoutherly。Eastwindsarewarmerthanwestwindsbecausethesunshinesontheeastlonger，whereasitleavesthewestsoonerandreachesitlater。
　　Sincethisisthedistributionofthewindsitisclearthatcontrarywindscannotblowsimultaneously。Theyarediametricallyoppositetooneanotherandoneofthetwomustbeoverpoweredandcease。Windsthatarenotdiametricallyoppositetooneanothermayblowsimultaneously：forinstancethewindsfromZandfromD。Henceitsometimeshappensthatbothofthem，thoughdifferentwindsandblowingfromdifferentquarters，arefavourabletosailorsmakingforthesamepoint。
　　Contrarywindscommonlyblowatoppositeseasons。ThusCaeciasandingeneralthewindsnorthofthesummersolsticeblowaboutthetimeofthespringequinox，butabouttheautumnequinoxLips;andZephyrusaboutthesummersolstice，butaboutthewintersolsticeEurus。
　　Aparctias，Thrascias，andArgestesarethewindsthatfallonothersmostandstopthem。Theirsourceissoclosetousthattheyaregreaterandstrongerthanotherwinds。Theybringfairweathermostofallwindsforthesamereason，for，blowingastheydo，fromcloseathand，theyoverpowertheotherwindsandstopthem;theyalsoblowawaythecloudsthatareformingandleaveaclearsky-unlesstheyhappentobeverycold。Thentheydonotbringfairweather，butbeingcolderthantheyarestrongtheycondensethecloudsbeforedrivingthemaway。
　　Caeciasdoesnotbringfairweatherbecauseitreturnsuponitself。Hencethesaying：’BringingitonhimselfasCaeciasdoesclouds。’
　　Whentheycease，windsaresucceededbytheirneighboursinthedirectionofthemovementofthesun。Foraneffectismostapttobeproducedintheneighbourhoodofitscause，andthecauseofwindsmoveswiththesun。
　　Contrarywindshaveeitherthesameorcontraryeffects。ThusLipsandCaecias，sometimescalledHellespontias，arebothrainygestesandEurusaredry：thelatterbeingdryatfirstandrainyafterwards。
　　MesesandAparctiasarecoldestandbringmostsnow。Aparctias，Thrascias，andArgestesbringhail。Notus，Zephyrus，andEurusarehot。Caeciascoverstheskywithheavyclouds，Lipswithlighterones。
　　CaeciasdoesthisbecauseitreturnsuponitselfandcombinesthequalitiesofBoreasandEurus。Bybeingcolditcondensesandgathersthevaporousair，andbecauseitiseasterlyitcarrieswithitanddrivesbeforeitagreatquantityofsuchmatter。Aparctias，Thrascias，andArgestesbringfairweatherforthereasonwehaveexplainedbefore。ThesewindsandMesesaremostcommonlyaccompaniedbylightning。Theyarecoldbecausetheyblowfromthenorth，andlightningisduetocold，beingejectedwhenthecloudscontract。Someofthesesamebringhailwiththemforthesamereason;
　　namely，thattheycauseasuddencondensation。
　　Hurricanesarecommonestinautumn，andnextinspring：Aparctias，Thrascias，andArgestesgiverisetothemmost。Thisisbecausehurricanesaregenerallyformedwhensomewindsareblowingandothersfallonthem;andthesearethewindswhicharemostapttofallonothersthatareblowing;thereasonforwhich，too，wehaveexplainedbefore。
　　TheEtesiaeveerround：theybeginfromthenorth，andbecomefordwellersinthewestThrasciae，Argestae，andZephyrus（forZephyrusbelongstothenorth）。FordwellersintheeasttheyveerroundasfarasApeliotes。
　　Somuchforthewinds，theiroriginandnatureandthepropertiescommontothemallorpeculiartoeach。
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　　Wemustgoontodiscussearthquakesnext，fortheircauseisakintoourlastsubject。
　　Thetheoriesthathavebeenputforwarduptothepresentdatearethree，andtheirauthorsthreemen，AnaxagorasofClazomenae，andbeforehimAnaximenesofMiletus，andlaterDemocritusofAbdera。
　　Anaxagorassaysthattheether，whichnaturallymovesupwards，iscaughtinhollowsbelowtheearthandsoshakesit，forthoughtheearthisreallyallofitequallyporous，itssurfaceiscloggedupbyrain。Thisimpliesthatpartofthewholesphereis’above’andpart’below’：’above’beingthepartonwhichwelive，’below’theother。
　　Thistheoryisperhapstooprimitivetorequirerefutation。Itisabsurdtothinkofupanddownotherwisethanasmeaningthatheavybodiesmovetotheearthfromeveryquarter，andlightones，suchasfire，awayfromit;especiallyasweseethat，asfarasourknowledgeoftheearthgoes，thehorizonalwayschangeswithachangeinourposition，whichprovesthattheearthisconvexandspherical。Itisabsurd，too，tomaintainthattheearthrestsontheairbecauseofitssize，andthentosaythatimpactupwardsfrombelowshakesitrightthrough。Besideshegivesnoaccountofthecircumstancesattendantonearthquakes：fornoteverycountryoreveryseasonissubjecttothem。
　　Democritussaysthattheearthisfullofwaterandthatwhenaquantityofrain-waterisaddedtothisanearthquakeistheresult。
　　Thehollowsintheearthbeingunabletoadmittheexcessofwateritforcesitswayinandsocausesanearthquake。Oragain，theearthasitdriesdrawsthewaterfromthefullertotheemptierparts，andtheinrushofthewaterasitchangesitsplacecausestheearthquake。
　　Anaximenessaysthattheearthbreaksupwhenitgrowswetordry，andearthquakesareduetothefallofthesemassesastheybreakaway。Henceearthquakestakeplaceintimesofdroughtandagainofheavyrain，since，aswehaveexplained，theearthgrowsdryintimeofdroughtandbreaksup，whereastherainmakesitsoddenanddestroysitscohesion。
　　Butifthiswerethecasetheearthoughttobefoundtobesinkinginmanyplaces。Again，whydoearthquakesfrequentlyoccurinplaceswhicharenotexcessivelysubjecttodroughtorrain，astheyoughttobeonthetheory？Besides，onthisview，earthquakesoughtalwaystobegettingfewer，andshouldcometoanendentirelysomeday：thenotionofcontractionbypackingtogetherimpliesthis。Sothisisimpossiblethetheorymustbeimpossibletoo。