a history of science-1- 第41部分

STRABO　THE　GEOGRAPHER　The　earliest　of　these　workers　in　point　of　time　is　Strabo。　This　most　famous　of　ancient　geographers　was　born　in　Amasia；　Pontus；　about　63　B。C。；　and　lived　to　the　year　24　A。D。；　living；　therefore；　in　the　age　of　Caesar　and　Augustus；　during　which　the　final　transformation　in　the　political　position　of　the　kingdom　of　Egypt　was　effected。　The　name　of　Strabo　in　a　modified　form　has　become　popularized　through　a　curious　circumstance。　The　geographer；　it　appears；　was　afflicted　with　a　peculiar　squint　of　the　eyes；　hence　the　name　strabismus；　which　the　modern　oculist　applies　to　that　particular　infirmity。　Fortunately；　the　great　geographer　has　not　been　forced　to　depend　upon　hearsay　evidence　for　recognition。　His　comprehensive　work　on　geography　has　been　preserved　in　its　entirety；　being　one　of　the　few　expansive　classical　writings　of　which　this　is　true。　The　other　writings　of　Strabo；　however；　including　certain　histories　of　which　reports　have　come　down　to　us；　are　entirely　lost。　The　geography　is　in　many　ways　a　remarkable　book。　It　is　not；　however；　a　work　in　which　any　important　new　principles　are　involved。　Rather　is　it　typical　of　its　age　in　that　it　is　an　elaborate　compilation　and　a　critical　review　of　the　labors　of　Strabo's　predecessors。　Doubtless　it　contains　a　vast　deal　of　new　information　as　to　the　details　of　geographyprecise　areas　and　distance；　questions　of　geographical　locations　as　to　latitude　and　zones；　and　the　like。　But　however　important　these　details　may　have　been　from　a　contemporary　stand…point；　they；　of　course；　can　have　nothing　more　than　historical　interest　to　posterity。　The　value　of　the　work　from　our　present　stand…point　is　chiefly　due　to　the　criticisms　which　Strabo　passes　upon　his　forerunners；　and　to　the　incidental　historical　and　scientific　references　with　which　his　work　abounds。　Being　written　in　this　closing　period　of　ancient　progress；　and　summarizing；　as　it　does；　in　full　detail　the　geographical　knowledge　of　the　time；　it　serves　as　an　important　guide…mark　for　the　student　of　the　progress　of　scientific　thought。　We　cannot　do　better　than　briefly　to　follow　Strabo　in　his　estimates　and　criticisms　of　the　work　of　his　predecessors；　taking　note　thus　of　the　point　of　view　from　which　he　himself　looked　out　upon　the　world。　We　shall　thus　gain　a　clear　idea　as　to　the　state　of　scientific　geography　towards　the　close　of　the　classical　epoch。　〃If　the　scientific　investigation　of　any　subject　be　the　proper　avocation　of　the　philosopher；〃　says　Strabo；　〃geography；　the　science　of　which　we　propose　to　treat；　is　certainly　entitled　to　a　high　place；　and　this　is　evident　from　many　considerations。　They　who　first　undertook　to　handle　the　matter　were　distinguished　men。　Homer；　Anaximander　the　Milesian；　and　Hecaeus　（his　fellow…citizen　according　to　Eratosthenes）；　Democritus；　Eudoxus；　Dicaearchus；　and　Ephorus；　with　many　others；　and　after　these；　Eratosthenes；　Polybius；　and　Posidonius；　all　of　them　philosophers。　Nor　is　the　great　learning　through　which　alone　this　subject　can　be　approached　possessed　by　any　but　a　person　acquainted　with　both　human　and　divine　things；　and　these　attainments　constitute　what　is　called　philosophy。　In　addition　to　its　vast　importance　in　regard　to　social　life　and　the　art　of　government；　geography　unfolds　to　us　a　celestial　phenomena；　acquaints　us　with　the　occupants　of　the　land　and　ocean；　and　the　vegetation；　fruits；　and　peculiarities　of　the　various　quarters　of　the　earth；　a　knowledge　of　which　marks　him　who　cultivates　it　as　a　man　earnest　in　the　great　problem　of　life　and　happiness。〃　Strabo　goes　on　to　say　that　in　common　with　other　critics；　including　Hipparchus；　he　regards　Homer　as　the　first　great　geographer。　He　has　much　to　say　on　the　geographical　knowledge　of　the　bard；　but　this　need　not　detain　us。　We　are　chiefly　concerned　with　his　comment　upon　his　more　recent　predecessors；　beginning　with　Eratosthenes。　The　constant　reference　to　this　worker　shows　the　important　position　which　he　held。　Strabo　appears　neither　as　detractor　nor　as　partisan；　but　as　one　who　earnestly　desires　the　truth。　Sometimes　he　seems　captious　in　his　criticisms　regarding　some　detail；　nor　is　he　always　correct　in　his　emendations　of　the　labors　of　others；　but；　on　the　whole；　his　work　is　marked　by　an　evident　attempt　at　fairness。　In　reading　his　book；　however；　one　is　forced　to　the　conclusion　that　Strabo　is　an　investigator　of　details；　not　an　original　thinker。　He　seems　more　concerned　with　precise　measurements　than　with　questionings　as　to　the　open　problems　of　his　science。　Whatever　he　accepts；　then；　may　be　taken　as　virtually　the　stock　doctrine　of　the　period。　〃As　the　size　of　the　earth；〃　he　says；　〃has　been　demonstrated　by　other　writers；　we　shall　here　take　for　granted　and　receive　as　accurate　what　they　have　advanced。　We　shall　also　assume　that　the　earth　is　spheroidal；　that　its　surface　is　likewise　spheroidal　and；　above　all；　that　bodies　have　a　tendency　towards　its　centre；　which　latter　point　is　clear　to　the　perception　of　the　most　average　understanding。　However；　we　may　show　summarily　that　the　earth　is　spheroidal；　from　the　consideration　that　all　things；　however　distant；　tend　to　its　centre；　and　that　every　body　is　attracted　towards　its　centre　by　gravity。　This　is　more　distinctly　proved　from　observations　of　the　sea　and　sky；　for　here　the　evidence　of　the　senses　and　common　observation　is　alone　requisite。　The　convexity　of　the　sea　is　a　further　proof　of　this　to　those　who　have　sailed；　for　they　cannot　perceive　lights　at　a　distance　when　placed　at　the　same　level　as　their　eyes；　and　if　raised　on　high　they　at　once　become　perceptible　to　vision　though　at　the　same　time　farther　removed。　So　when　the　eye　is　raised　it　sees　what　before　was　utterly　imperceptible。　Homer　speaks　of　this　when　he　says：

〃　'Lifted　up　on　the　vast　wave　he　quickly　beheld　afar。'　Sailors　as　they　approach　their　destination　behold　the　shore　continually　raising　itself　to　their　view；　and　objects　which　had　at　first　seemed　low　begin　to　lift　themselves。　Our　gnomons；　also；　are；　among　other　things；　evidence　of　the　revolution　of　the　heavenly　bodies；　and　common…sense　at　once　shows　us　that　if　the　depth　of　the　earth　were　infinite　such　a　revolution　could　not　take　place。〃＇1＇　Elsewhere　Strabo　criticises　Eratosthenes　for　having　entered　into　a　long　discussion　as　to　the　form　of　the　earth。　This　matter；　Strabo　thinks；　〃should　have　been　disposed　of　in　the　compass　of　a　few　words。〃　Obviously　this　doctrine　of　the　globe's　sphericity　had；　in　the　course　of　600　years；　become　so　firmly　established　among　the　Greek　thinkers　as　to　seem　almost　axiomatic。　We　shall　see　later　on　how　the　Western　world　made　a　curious　recession　from　this　seemingly　secure　position　under　stimulus　of　an　Oriental　misconception。　As　to　the　size　of　the　globe；　Strabo　is　disposed　to　accept　without　particular　comment　the　measurements　of　Eratosthenes。　He　speaks；　however；　of　〃more　recent　measurements；〃　referring　in　particular　to　that　adopted　by　Posidonius；　according　to　which　the　circumference　is　only　about　one　hundred　and　eighty　thousand　stadia。　Posidonius；　we　may　note　in　passing；　was　a　contemporary　and　friend　of　Cicero；　and　hence　lived　shortly　before　the　time　of　Strabo。　His　measurement　of　the　earth　was　based　on　observations　of　a　star　which　barely　rose　above　the　southern　horizon　at　Rhodes　as　compared　with　the　height　of　the　same　star　when　observed　at　Alexandria。　This　measurement　of　Posidonius；　together　with　the　even　more　famous　measurement　of　Eratosthenes；　appears　to　have　been　practically　the　sole　guide　as　to　the　size　of　the　earth　throughout　the　later　periods　of　antiquity；　and；　indeed；　until　the　later　Middle　Ages。　As　becomes　a　writer　who　is　primarily　geographer　and　historian　rather　than　astronomer；　Strabo　shows　a　much　keener　interest　in　the　habitable　portions　of　the　globe　than　in　the　globe　as　a　whole。　He　assures　us　that　this　habitable　portion　of　the　earth　is　a　great　island；　〃since　wherever　men　have　approached　the　termination　of　the　land；　the　sea；　which　we　designate　ocean；　has　been　met　with；　and　reason　assures　us　of　the　similarity　of　this　place　which　our　senses　have　not　been　tempted　to　survey。〃　He　points　out　that　whereas　sailors　have　not　circumnavigated　the　globe；　that　they　had　not　been　prevented　from　doing　so　by　any　continent；　and　it　seems　to　him　altogether　unlikely　that　the　Atlantic　Ocean　is　divided　into　two　seas　by　narrow　isthmuses　so　placed　as　to　prevent　circumnavigation。　〃How　much　more　probable　that　it　is　confluent　and　uninterrupted。　This　theory；〃　he　adds；　〃goes　better　with　the　ebb　and　flow　of　the　ocean。　Moreover　（and　here　his　reasoning　becomes　more　fanciful）；　the　greater　the　amount　of　moisture　surrounding　the　earth；　the　easier　would　the　heavenly　bodies　be　supplied　with　vapor　from　thence。〃　Yet　he　is　disposed　to　believe；　following　Plato；　that　the　tradition　〃concerning　the　island　of　Atlantos　might　be　received　as　something　more　than　idle　fiction；　it　having　been　related　by　Solon；　on　the　authority　of　the　Egyptian　priests；　that　this　island；　almost　as　large　as　a　continent；　was　formerly　in　existence　although　now　it　had　disappeared。〃＇2＇　In　a　word；　then；　Strabo　entertains　no　doubt　whatever　that　it　would　be　possible　to　sail　around　the　globe　from　Spain　to　India。　Indeed；　so　matter…of…fact　an　inference　was　this　that　the　feat　of　Columbus　would　have　seemed　less　surprising　in　the　first　century　of　our　era　than　it　did　when　actually　performed　in　the　fifteenth　century。　The　terrors　of　the　great　ocean　held　the　mariner　back；　rather　than　any　doubt　as　to　where　he　would　arrive　at　the　end　of　the　voyage。　Coupled　with　the　idea　that　the　habitable　portion　of　the　earth　is　an　island；　there　was　linked　a　tolerably　definite　notion　as　to　the　shape　of　this　island。　This　shape　Strabo　likens　to　a　military　cloak。　The　comparison　does　not　seem　peculiarly　apt　when　we　are　told　presently　that　the　length　of　the　habitable　earth　is　more　than　twice　its　breadth。　This　idea；　Strabo　assures　us；　accords　with　the　most　accurate　observations　〃both　ancient　and　modern。〃　These　observations　seemed　to　show　that　it　is　not　possible　to　live　in　the　region　close　to　the　equator；　and　that；　on　the　other　hand；　the　cold　temperature　sharply　limits　the　habitability　of　the　globe　towards　the　north。　All　the　civilization　of　antiquity　clustered　about　the　Mediterranean；　or　extended　off　towards　the　east　at　about　the　same　latitude。　Hence　geographers　came　to　think　of　the　habitable　globe　as　having　the　somewhat　lenticular　shape　which　a　crude