meteorology-第7章

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enjoys　a　period　of　prosperity。　For　these　places　dry　up　and　come　to



be　in　good　condition　while　the　places　that　were　formerly　well…tempered



some　day　grow　excessively　dry　and　deteriorate。　This　happened　to　the



land　of　Argos　and　Mycenae　in　Greece。　In　the　time　of　the　Trojan　wars



the　Argive　land　was　marshy　and　could　only　support　a　small



population；　whereas　the　land　of　Mycenae　was　in　good　condition　（and　for



this　reason　Mycenae　was　the　superior）。　But　now　the　opposite　is　the



case；　for　the　reason　we　have　mentioned：　the　land　of　Mycenae　has　become



completely　dry　and　barren；　while　the　Argive　land　that　was　formerly



barren　owing　to　the　water　has　now　become　fruitful。　Now　the　same



process　that　has　taken　place　in　this　small　district　must　be　supposed



to　be　going　on　over　whole　countries　and　on　a　large　scale。



　　Men　whose　outlook　is　narrow　suppose　the　cause　of　such　events　to　be



change　in　the　universe；　in　the　sense　of　a　coming　to　be　of　the　world　as



a　whole。　Hence　they　say　that　the　sea　being　dried　up　and　is　growing



less；　because　this　is　observed　to　have　happened　in　more　places　now



than　formerly。　But　this　is　only　partially　true。　It　is　true　that　many



places　are　now　dry；　that　formerly　were　covered　with　water。　But　the



opposite　is　true　too：　for　if　they　look　they　will　find　that　there　are



many　places　where　the　sea　has　invaded　the　land。　But　we　must　not



suppose　that　the　cause　of　this　is　that　the　world　is　in　process　of



becoming。　For　it　is　absurd　to　make　the　universe　to　be　in　process



because　of　small　and　trifling　changes；　when　the　bulk　and　size　of　the



earth　are　surely　as　nothing　in　comparison　with　the　whole　world。　Rather



we　must　take　the　cause　of　all　these　changes　to　be　that；　just　as　winter



occurs　in　the　seasons　of　the　year；　so　in　determined　periods　there



comes　a　great　winter　of　a　great　year　and　with　it　excess　of　rain。　But



this　excess　does　not　always　occur　in　the　same　place。　The　deluge　in　the



time　of　Deucalion；　for　instance；　took　place　chiefly　in　the　Greek　world



and　in　it　especially　about　ancient　Hellas；　the　country　about　Dodona



and　the　Achelous；　a　river　which　has　often　changed　its　course。　Here　the



Selli　dwelt　and　those　who　were　formerly　called　Graeci　and　now



Hellenes。　When；　therefore；　such　an　excess　of　rain　occurs　we　must



suppose　that　it　suffices　for　a　long　time。　We　have　seen　that　some　say



that　the　size　of　the　subterranean　cavities　is　what　makes　some　rivers



perennial　and　others　not；　whereas　we　maintain　that　the　size　of　the



mountains　is　the　cause；　and　their　density　and　coldness；　for　great；



dense；　and　cold　mountains　catch　and　keep　and　create　most　water：



whereas　if　the　mountains　that　overhang　the　sources　of　rivers　are　small



or　porous　and　stony　and　clayey；　these　rivers　run　dry　earlier。　We



must　recognize　the　same　kind　of　thing　in　this　case　too。　Where　such



abundance　of　rain　falls　in　the　great　winter　it　tends　to　make　the



moisture　of　those　places　almost　everlasting。　But　as　time　goes　on



places　of　the　latter　type　dry　up　more；　while　those　of　the　former；



moist　type；　do　so　less：　until　at　last　the　beginning　of　the　same



cycle　returns。



　　Since　there　is　necessarily　some　change　in　the　whole　world；　but　not



in　the　way　of　coming　into　existence　or　perishing　（for　the　universe



is　permanent）；　it　must　be；　as　we　say；　that　the　same　places　are　not　for



ever　moist　through　the　presence　of　sea　and　rivers；　nor　for　ever　dry。



And　the　facts　prove　this。　The　whole　land　of　the　Egyptians；　whom　we



take　to　be　the　most　ancient　of　men；　has　evidently　gradually　come



into　existence　and　been　produced　by　the　river。　This　is　clear　from　an



observation　of　the　country；　and　the　facts　about　the　Red　Sea　suffice　to



prove　it　too。　One　of　their　kings　tried　to　make　a　canal　to　it　（for　it



would　have　been　of　no　little　advantage　to　them　for　the　whole　region　to



have　become　navigable；　Sesostris　is　said　to　have　been　the　first　of　the



ancient　kings　to　try）；　but　he　found　that　the　sea　was　higher　than　the



land。　So　he　first；　and　Darius　afterwards；　stopped　making　the　canal；



lest　the　sea　should　mix　with　the　river　water　and　spoil　it。　So　it　is



clear　that　all　this　part　was　once　unbroken　sea。　For　the　same　reason



Libya…the　country　of　Ammon…is；　strangely　enough；　lower　and　hollower



than　the　land　to　the　seaward　of　it。　For　it　is　clear　that　a　barrier



of　silt　was　formed　and　after　it　lakes　and　dry　land；　but　in　course　of



time　the　water　that　was　left　behind　in　the　lakes　dried　up　and　is　now



all　gone。　Again　the　silting　up　of　the　lake　Maeotis　by　the　rivers　has



advanced　so　much　that　the　limit　to　the　size　of　the　ships　which　can　now



sail　into　it　to　trade　is　much　lower　than　it　was　sixty　years　ago。　Hence



it　is　easy　to　infer　that　it；　too；　like　most　lakes；　was　originally



produced　by　the　rivers　and　that　it　must　end　by　drying　up　entirely。



　　Again；　this　process　of　silting　up　causes　a　continuous　current



through　the　Bosporus；　and　in　this　case　we　can　directly　observe　the



nature　of　the　process。　Whenever　the　current　from　the　Asiatic　shore



threw　up　a　sandbank；　there　first　formed　a　small　lake　behind　it。



Later　it　dried　up　and　a　second　sandbank　formed　in　front　of　the　first



and　a　second　lake。　This　process　went　on　uniformly　and　without



interruption。　Now　when　this　has　been　repeated　often　enough；　in　the



course　of　time　the　strait　must　become　like　a　river；　and　in　the　end　the



river　itself　must　dry　up。



　　So　it　is　clear；　since　there　will　be　no　end　to　time　and　the　world



is　eternal；　that　neither　the　Tanais　nor　the　Nile　has　always　been



flowing；　but　that　the　region　whence　they　flow　was　once　dry：　for



their　effect　may　be　fulfilled；　but　time　cannot。　And　this　will　be



equally　true　of　all　other　rivers。　But　if　rivers　come　into　existence



and　perish　and　the　same　parts　of　the　earth　were　not　always　moist；



the　sea　must　needs　change　correspondingly。　And　if　the　sea　is　always



advancing　in　one　place　and　receding　in　another　it　is　clear　that　the



same　parts　of　the　whole　earth　are　not　always　either　sea　or　land；　but



that　all　this　changes　in　course　of　time。



　　So　we　have　explained　that　the　same　parts　of　the　earth　are　not　always



land　or　sea　and　why　that　is　so：　and　also　why　some　rivers　are　perennial



and　others　not。



　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　Book　II



　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　1







　　LET　us　explain　the　nature　of　the　sea　and　the　reason　why　such　a　large



mass　of　water　is　salt　and　the　way　in　which　it　originally　came　to　be。



　　The　old　writers　who　invented　theogonies　say　that　the　sea　has



springs；　for　they　want　earth　and　sea　to　have　foundations　and　roots



of　their　own。　Presumably　they　thought　that　this　view　was　grander　and



more　impressive　as　implying　that　our　earth　was　an　important　part　of



the　universe。　For　they　believed　that　the　whole　world　had　been　built　up



round　our　earth　and　for　its　sake；　and　that　the　earth　was　the　most



important　and　primary　part　of　it。　Others；　wiser　in　human　knowledge；



give　an　account　of　its　origin。　At　first；　they　say；　the　earth　was



surrounded　by　moisture。　Then　the　sun　began　to　dry　it　up；　part　of　it



evaporated　and　is　the　cause　of　winds　and　the　turnings　back　of　the



sun　and　the　moon；　while　the　remainder　forms　the　sea。　So　the　sea　is



being　dried　up　and　is　growing　less；　and　will　end　by　being　some　day



entirely　dried　up。　Others　say　that　the　sea　is　a　kind　of　sweat　exuded



by　the　earth　when　the　sun　heats　it；　and　that　this　explains　its



saltness：　for　all　sweat　is　salt。　Others　say　that　the　saltness　is　due



to　the　earth。　Just　as　water　strained　through　ashes　becomes　salt；　so



the　sea　owes　its　saltness　to　the　admixture　of　earth　with　similar



properties。



　　We　must　now　consider　the　facts　which　prove　that　the　sea　cannot



possibly　have　springs。　The　waters　we　find　on　the　earth　either　flow



or　are　stationary。　All　flowing　water　has　springs。　（By　a　spring；　as



we　have　explained　above；　we　must　not　understand　a　source　from　which



waters　are　ladled　as　it　were　from　a　vessel；　but　a　first　point　at　which



the　water　which　is　continually　forming　and　percolating　gathers。）



Stationary　water　is　either　that　which　has　collected　and　has　been



left　standing；　marshy　pools；　for　instance；　and　lakes；　which　differ



merely　in　size；　or　else　it　comes　from　springs。　In　this　case　it　is



always　artificial；　I　mean　as　in　the　case　of　wells；　otherwise　the



spring　would　have　to　be　above　the　outlet。　Hence　the　water　from



fountains　and　rivers　flows　of　itself；　whereas　wells　need　to　be



worked　artificially。　All　the　waters　that　exist　belong　to　one　or



other　of　these　classes。



　　On　the　basis　of　this　division　we　can　sec　that　the　sea　cannot　have



springs。　For　it　falls　under　neither　of　the　two　classes；　it　does　not



flow　and　it　is　not　artificial；　whereas　all　water　from　springs　must



belong　to　one　or　other　of　them。　Natural　standing　water　from　springs　is



never　found　on　such　a　large　scale。



　　Again；　there　are　several　seas　that　have　no　communication　with　one



another　at　all。　The　Red　Sea；　for　instance；　communicates　but　slightly



with　the　ocean　outside　the　straits；　and　the　Hyrcanian　and　Caspian　seas



are　distinct　from　this　ocean　and　people　dwell　all　round　them。　Hence；



if　these　seas　had　had　any　springs　anywhere　they　must　have　been



discovered。



　　It　is　true　that　in　straits；　where　the　land　on　either　side



contracts　an　open　sea　into　a　small　space；　the　sea　appears　to　flow。　But



this　is　because　it　is　swinging　to　and　fro。　In　the　open　sea　this　motion



is　not　observed；　but　where　the　land　narrows　and　contracts　the　sea



the　motion　that　was　imperceptible　in　the　open　necessarily　strikes



the　attention。



　　The　whole　of　the　Mediterranean　does　actually　flow。　The　direction



of　this　flow　is　determined　by　the　depth　of　the　basins　and　by　the



number　of　rivers。　Maeotis　flows　into　Pontus　and　Pontus　into　the



Aegean。　After　that　the　flow　of　the　remaining　seas　is　not　so　easy　to



observe。　The　current　of　Maeotis　and　Pontus　is　due　to　the　number　of



rivers　（more　rivers　flow　into　the　Euxine　and　Maeotis　than　into　the



whole　Mediterranean　with　its　much　larger　basin）；　and　to　their　own



shallowness。　For　we　find　the　sea　getting　deeper　and　deeper。　Pontus



is　deeper　than　Maeotis；　the　Aegean　than　Pontus；　the　Sicilian　sea



than　the　Aegean；　the　Sardinian　and　Tyrrhenic　being　the　deepest　of　all。



（Outside　the　pillars　of　Heracles　the　sea　is　shallow　owing　to　the



mud；　but　calm；　for　it　lies　in　a　hollow。）　We　see；　then；　that　just　as



single　rivers　flow　from　mountains；　so　it　is　with　the　earth　as　a　whole：



the　greatest　volume　of　water　flows　from　the　higher　regions　in　the



north。　Their　alluvium　makes　the　northern　seas　shallow；　while　the　outer



seas　are　deeper。　Some　further　evidence　of　the　height　of　the　northern



regions　of　the　earth　is　afforded　by　the　view　of　many　of　the　ancient



meteorologists。　They　believed　that　the　sun　did　not　pass　below　the



earth；　but　round　its　northern