meteorology- 第7部分

water　it　contains　by　gradual　percolation　of　many　drops；　little　by



little；　and　that　this　is　how　the　sources　of　rivers　originate。　However；



there　is　nothing　impossible　about　the　existence　of　such　places



containing　a　quantity　of　water　like　lakes：　only　they　cannot　be　big



enough　to　produce　the　supposed　effect。　To　think　that　they　are　is



just　as　absurd　as　if　one　were　to　suppose　that　rivers　drew　all　their



water　from　the　sources　we　see　（for　most　rivers　do　flow　from



springs）。　So　it　is　no　more　reasonable　to　suppose　those　lakes　to



contain　the　whole　volume　of　water　than　these　springs。



　　That　there　exist　such　chasms　and　cavities　in　the　earth　we　are　taught



by　the　rivers　that　are　swallowed　up。　They　are　found　in　many　parts　of



the　earth：　in　the　Peloponnesus；　for　instance；　there　are　many　such



rivers　in　Arcadia。　The　reason　is　that　Arcadia　is　mountainous　and　there



are　no　channels　from　its　valleys　to　the　sea。　So　these　places　get



full　of　water；　and　this；　having　no　outlet；　under　the　pressure　of　the



water　that　is　added　above；　finds　a　way　out　for　itself　underground。



In　Greece　this　kind　of　thing　happens　on　quite　a　small　scale；　but　the



lake　at　the　foot　of　the　Caucasus；　which　the　inhabitants　of　these　parts



call　a　sea；　is　considerable。　Many　great　rivers　fall　into　it　and　it　has



no　visible　outlet　but　issues　below　the　earth　off　the　land　of　the



Coraxi　about　the　so…called　'deeps　of　Pontus'。　This　is　a　place　of



unfathomable　depth　in　the　sea：　at　any　rate　no　one　has　yet　been　able　to



find　bottom　there　by　sounding。　At　this　spot；　about　three　hundred



stadia　from　land；　there　comes　up　sweet　water　over　a　large　area；　not



all　of　it　together　but　in　three　places。　And　in　Liguria　a　river　equal



in　size　to　the　Rhodanus　is　swallowed　up　and　appears　again　elsewhere：



the　Rhodanus　being　a　navigable　river。







　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　14







　　The　same　parts　of　the　earth　are　not　always　moist　or　dry；　but　they



change　according　as　rivers　come　into　existence　and　dry　up。　And　so



the　relation　of　land　to　sea　changes　too　and　a　place　does　not　always



remain　land　or　sea　throughout　all　time；　but　where　there　was　dry　land



there　comes　to　be　sea；　and　where　there　is　now　sea；　there　one　day　comes



to　be　dry　land。　But　we　must　suppose　these　changes　to　follow　some　order



and　cycle。　The　principle　and　cause　of　these　changes　is　that　the



interior　of　the　earth　grows　and　decays；　like　the　bodies　of　plants



and　animals。　Only　in　the　case　of　these　latter　the　process　does　not



go　on　by　parts；　but　each　of　them　necessarily　grows　or　decays　as　a



whole；　whereas　it　does　go　on　by　parts　in　the　case　of　the　earth。　Here



the　causes　are　cold　and　heat；　which　increase　and　diminish　on　account



of　the　sun　and　its　course。　It　is　owing　to　them　that　the　parts　of　the



earth　come　to　have　a　different　character；　that　some　parts　remain　moist



for　a　certain　time；　and　then　dry　up　and　grow　old；　while　other　parts　in



their　turn　are　filled　with　life　and　moisture。　Now　when　places　become



drier　the　springs　necessarily　give　out；　and　when　this　happens　the



rivers　first　decrease　in　size　and　then　finally　become　dry；　and　when



rivers　change　and　disappear　in　one　part　and　come　into　existence



correspondingly　in　another；　the　sea　must　needs　be　affected。



　　If　the　sea　was　once　pushed　out　by　rivers　and　encroached　upon　the



land　anywhere；　it　necessarily　leaves　that　place　dry　when　it　recedes；



again；　if　the　dry　land　has　encroached　on　the　sea　at　all　by　a　process



of　silting　set　up　by　the　rivers　when　at　their　full；　the　time　must　come



when　this　place　will　be　flooded　again。



　　But　the　whole　vital　process　of　the　earth　takes　place　so　gradually



and　in　periods　of　time　which　are　so　immense　compared　with　the　length



of　our　life；　that　these　changes　are　not　observed；　and　before　their



course　can　be　recorded　from　beginning　to　end　whole　nations　perish



and　are　destroyed。　Of　such　destructions　the　most　utter　and　sudden



are　due　to　wars；　but　pestilence　or　famine　cause　them　too。　Famines；



again；　are　either　sudden　and　severe　or　else　gradual。　In　the　latter



case　the　disappearance　of　a　nation　is　not　noticed　because　some　leave



the　country　while　others　remain；　and　this　goes　on　until　the　land　is



unable　to　maintain　any　inhabitants　at　all。　So　a　long　period　of　time　is



likely　to　elapse　from　the　first　departure　to　the　last；　and　no　one



remembers　and　the　lapse　of　time　destroys　all　record　even　before　the



last　inhabitants　have　disappeared。　In　the　same　way　a　nation　must　be



supposed　to　lose　account　of　the　time　when　it　first　settled　in　a　land



that　was　changing　from　a　marshy　and　watery　state　and　becoming　dry。



Here；　too；　the　change　is　gradual　and　lasts　a　long　time　and　men　do



not　remember　who　came　first；　or　when；　or　what　the　land　was　like　when



they　came。　This　has　been　the　case　with　Egypt。　Here　it　is　obvious



that　the　land　is　continually　getting　drier　and　that　the　whole



country　is　a　deposit　of　the　river　Nile。　But　because　the　neighbouring



peoples　settled　in　the　land　gradually　as　the　marshes　dried；　the



lapse　of　time　has　hidden　the　beginning　of　the　process。　However；　all



the　mouths　of　the　Nile；　with　the　single　exception　of　that　at



Canopus；　are　obviously　artificial　and　not　natural。　And　Egypt　was



nothing　more　than　what　is　called　Thebes；　as　Homer；　too；　shows；



modern　though　he　is　in　relation　to　such　changes。　For　Thebes　is　the



place　that　he　mentions；　which　implies　that　Memphis　did　not　yet



exist；　or　at　any　rate　was　not　as　important　as　it　is　now。　That　this



should　be　so　is　natural；　since　the　lower　land　came　to　be　inhabited



later　than　that　which　lay　higher。　For　the　parts　that　lie　nearer　to　the



place　where　the　river　is　depositing　the　silt　are　necessarily　marshy



for　a　longer　time　since　the　water　always　lies　most　in　the　newly　formed



land。　But　in　time　this　land　changes　its　character；　and　in　its　turn



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；　stoppe