darwin and modern science- 第103部分

Darwin　has　related　how　his　theory　of　Coral…reefs　which　was　begun　in　a　more　〃deductive　spirit〃　than　any　of　his　other　work；　for　in　1834　or　1835　it　〃was　thought　out　on　the　west　coast　of　South　America；　before　I　had　seen　a　true　coral…reef。〃　　（〃L。L。〃　I。　page　70。）　　The　final　chapter　in　Lyell's　second　volume　of　the　〃Principles〃　was　devoted　to　the　subject　of　Coral…reefs；　and　a　theory　was　suggested　to　account　for　the　peculiar　phenomena　of　〃atolls。〃　Darwin　at　once　saw　the　difficulty　of　accepting　the　view　that　the　numerous　and　diverse　atolls　all　represent　submerged　volcanic　craters。　　His　own　work　had　for　two　years　been　devoted　to　the　evidence　of　land　movements　over　great　areas　in　South　America；　and　thus　he　was　led　to　announce　his　theory　of　subsidence　to　account　for　barrier　and　encircling　reefs　as　well　as　atolls。

Fortunately；　during　his　voyage　across　the　Pacific　and　Indian　Oceans；　in　his　visit　to　Australia　and　his　twelve　days'　hard　work　at　Keeling　Island；　he　had　opportunities　for　putting　his　theory　to　the　test　of　observation。

On　his　return　to　England；　Darwin　appears　to　have　been　greatly　surprised　at　the　amount　of　interest　that　his　new　theory　excited。　　Urged　by　Lyell；　he　read　to　the　Geological　Society　a　paper　on　the　subject；　as　we　have　seen；　with　as　little　delay　as　possible；　but　this　paper　was　〃withdrawn　by　permission　of　the　Council。〃　　An　abstract　of　three　pages　however　appeared　in　the　〃Proceedings　of　the　Geological　Society〃。　　（Vol。　II。　pages　552…554　（May　31；　1837）。）　　A　full　account　of　the　observations　and　the　theory　was　given　in　the　〃Journal〃　（1839）　in　the　40　pages　devoted　to　Keeling　Island　in　particular　and　to　Coral　formations　generally。　　（〃Journal　（1st　edition）；　pages　439…69。）

It　will　be　readily　understood　what　an　amount　of　labour　the　book　on　Coral　reefs　cost　Darwin　when　we　reflect　on　the　number　of　charts；　sailing　directions；　narratives　of　voyages　and　other　works　which；　with　the　friendly　assistance　of　the　authorities　at　the　Admiralty；　he　had　to　consult　before　he　could　draw　up　his　sketch　of　the　nature　and　distribution　of　the　reefs；　and　this　was　necessary　before　the　theory；　in　all　its　important　bearings；　could　be　clearly　enunciated。　　Very　pleasing　is　it　to　read　how　Darwin；　although　arriving　at　a　different　conclusion　to　Lyell；　shows；　by　quoting　a　very　suggestive　passage　in　the　〃Principles〃　（1st　edition　Vol。　II。　page　296。）；　how　the　latter　only　just　missed　the　true　solution。　　This　passage　is　cited；　both　in　the　〃Journal〃　and　the　volume　on　Coral…reefs。　　Lyell；　as　we　have　seen；　received　the　new　theory　not　merely　ungrudgingly；　but　with　the　utmost　enthusiasm。

In　1849　Darwin　was　gratified　by　receiving　the　support　of　Dana；　after　his　prolonged　investigation　in　connection　with　the　U。S。　Exploring　Expedition　（〃M。L。〃　II。　pages　226…8。）；　and　in　1874　he　prepared　a　second　edition　of　his　book；　in　which　some　objections　which　had　been　raised　to　the　theory　were　answered。　　A　third　edition；　edited　by　Professor　Bonney；　appeared　in　1880；　and　a　fourth　（a　reprint　of　the　first　edition；　with　introduction　by　myself）　in　1890。

Although　Professor　Semper；　in　his　account　of　the　Pelew　Islands；　had　suggested　difficulties　in　the　acceptance　of　Darwin's　theory；　it　was　not　till　after　the　return　of　the　〃Challenger〃　expedition　in　1875　that　a　rival　theory　was　propounded；　and　somewhat　heated　discussions　were　raised　as　to　the　respective　merits　of　the　two　theories。　　While　geologists　have；　nearly　without　exception；　strongly　supported　Darwin's　views；　the　notes　of　dissent　have　come　almost　entirely　from　zoologists。　　At　the　height　of　the　controversy　unfounded　charges　of　unfairness　were　made　against　Darwin's　supporters　and　the　authorities　of　the　Geological　Society；　but　this　unpleasant　subject　has　been　disposed　of；　once　for　all；　by　Huxley。　　（〃Essays　upon　some　Controverted　Questions〃；　London；　1892；　pages　314…328　and　623…　625。）

Darwin's　final　and　very　characteristic　utterance　on　the　coral…reef　controversy　is　found　in　a　letter　which　he　wrote　to　Professor　Alexander　Agassiz；　May　5th；　1881：　　less　than　a　year　before　his　death：　　〃If　I　am　wrong；　the　sooner　I　am　knocked　on　the　head　and　annihilated　so　much　the　better。　　It　still　seems　to　me　a　marvellous　thing　that　there　should　not　have　been　much；　and　long…continued；　subsidence　in　the　beds　of　the　great　oceans。　I　wish　that　some　doubly　rich　millionaire　would　take　it　into　his　head　to　have　borings　made　in　some　of　the　Pacific　and　Indian　atolls；　and　bring　home　cores　for　slicing　from　a　depth　of　500　or　600　feet。〃　　（〃L。L。〃　III。　page　184。）

Though　the　〃doubly　rich　millionaire〃　has　not　been　forthcoming；　the　energy；　in　England；　of　Professor　Sollas；　and　in　New　South　Wales　of　Professor　Anderson　Stuart　served　to　set　on　foot　a　project；　which；　aided　at　first　by　the　British　Association　for　the　Advancement　of　Science；　and　afterwards　taken　up　jointly　by　the　Royal　Society；　the　New　South　Wales　Government；　and　the　Admiralty；　has　led　to　the　most　definite　and　conclusive　results。

The　Committee　appointed　by　the　Royal　Society　to　carry　out　the　undertaking　included　representatives　of　all　the　views　that　had　been　put　forward　on　the　subject。　　The　place　for　the　experiment　was；　with　the　consent　of　every　member　of　the　Committee；　selected　by　the　late　Admiral　Sir　W。J。　Whartonwho　was　not　himself　an　adherent　of　Darwin's　viewsand　no　one　has　ventured　to　suggest　that　his　selection；　the　splendid　atoll　of　Funafuti；　was　not　a　most　judicious　one。

By　the　pluck　and　perseverance　of　Professor　Sollas　in　the　preliminary　expedition；　and　of　Professor　T。　Edgeworth　David　and　his　pupils；　in　subsequent　investigations　of　the　island；　the　rather　difficult　piece　of　work　was　brought　to　a　highly　satisfactory　conclusion。　　The　New　South　Wales　Government　lent　boring　apparatus　and　workmen；　and　the　Admiralty　carried　the　expedition　to　its　destination　in　a　surveying　ship　which；　under　Captain　（now　Admiral）　A。　Mostyn　Field；　made　the　most　complete　survey　of　the　atoll　and　its　surrounding　seas　that　has　ever　been　undertaken　in　the　case　of　a　coral　formation。

After　some　failures　and　many　interruptions；　the　boring　was　carried　to　the　depth　of　1114　feet；　and　the　cores　obtained　were　sent　to　England。　　Here　the　examination　of　the　materials　was　fortunately　undertaken　by　a　zoologist　of　the　highest　repute；　Dr　G。J。　Hindewho　has　a　wide　experience　in　the　study　of　organisms　by　sectionsand　he　was　aided　at　all　points　by　specialists　in　the　British　Museum　of　Natural　History　and　by　other　naturalists。　　Nor　were　the　chemical　and　other　problems　neglected。

The　verdict　arrived　at；　after　this　most　exhaustive　study　of　a　series　of　cores　obtained　from　depths　twice　as　great　as　that　thought　necessary　by　Darwin；　was　as　follows：〃The　whole　of　the　cores　are　found　to　be　built　up　of　those　organisms　which　are　seen　forming　coral…reefs　near　the　surface　of　the　oceanmany　of　them　evidently　in　situ；　and　not　the　slightest　indication　could　be　detected；　by　chemical　or　microscopic　means；　which　suggested　the　proximity　of　non…calcareous　rocks；　even　in　the　lowest　portions　brought　up。〃

But　this　was　not　all。　　Professor　David　succeeded　in　obtaining　the　aid　of　a　very　skilful　engineer　from　Australia；　while　the　Admiralty　allowed　Commander　F。C。D。　Sturdee　to　take　a　surveying　ship　into　the　lagoon　for　further　investigations。　　By　very　ingenious　methods；　and　with　great　perseverance；　two　borings　were　put　down　in　the　midst　of　the　lagoon　to　the　depth　of　nearly　200　feet。　　The　bottom　of　the　lagoon；　at　the　depth　of　101　1/2　feet　from　sea…　level；　was　found　to　be　covered　with　remains　of　the　calcareous；　green　sea…　weed　Halimeda；　mingled　with　many　foraminifera；　but　at　a　depth　of　163　feet　from　the　surface　of　the　lagoon　the　boring　tools　encountered　great　masses　of　coral；　which　were　proved　from　the　fragments　brought　up　to　belong　to　species　that　live　within　AT　MOST　120　feet　from　the　surface　of　the　ocean；　as　admitted　by　all　zoologists。　　（〃The　Atoll　of　Funafuti；　Report　of　the　Coral　Reef　Committee　of　the　Royal　Society〃；　London；　1904。）

Darwin's　theory；　as　is　well　known；　is　based　on　the　fact　that　the　temperature　of　the　ocean　at　any　considerable　depth　does　not　permit　of　the　existence　and　luxuriant　growth　of　the　organisms　that　form　the　reefs。　　He　himself　estimated　this　limit　of　depth　to　be　from　120　to　130　feet；　Dana；　as　an　extreme；　150　feet；　while　the　recent　very　prolonged　and　successful　investigations　of　Professor　Alexander　Agassiz　in　the　Pacific　and　Indian　Oceans　lead　him　also　to　assign　a　limiting　depth　of　150　feet；　the　EFFECTIVE；　REEF…FORMING　CORALS；　however；　flourishing　at　a　much　smaller　depth。　　Mr　Stanley　Gardiner　gives　for　the　most　important　reef…forming　corals　depths　between　30　and　90　feet；　while　a　few　are　found　as　low　as　120　feet　or　even　180　feet。

It　will　thus　be　seen　that　the　verdict　of　Funafuti　is　clearly　and　unmistakeably　in　favour　of　Darwin's　theory。　　It　is　true　that　some　zoologists　find　a　difficulty　in　realising　a　slow　sinking　of　parts　of　the　ocean　floor；　and　have　suggested　new　and　alternative　explanations：　　but　geologists　generally；　accepting　the　proofs　of　slow　upheaval　in　some　areas　as　shown　by　the　admirable　researches　of　Alexander　Agassizconsider　that　it　is　absolutely　necessary　to　admit　that　this　elevation　is　balanced　by　subsidence　in　other　areas。　　If　atolls　and　barrier…reefs　did　not　exist　we　should　indeed　be　at　a　great　loss　to　frame　a　theory　to　account　for　their　absence。

After　finishing　his　book　on　Coral…reefs；　Darwin　made　his　summer　excursion　to　North　Wales；　and　prepared　his　important　memoir　on　the　glaciers　of　that　district：　　but　by　October　（1842）　we　find　him　fairly　settled　at　work　upon　the　second　volume　of　his　〃Geology　of　the　'Beagle'Geological　Observations　on　the　Volcanic　Islands；　visited　during　the　Voyage　of　H。M。S。　'Beagle'〃。　　The　whole　of　the　year　1843　was　devoted　to　this　work；　but　he　tells　his　friend　Fox　that　he　could　〃manage　only　a　couple　of　hours　per　day；　and　that　not　very　regularly。〃　　（〃L。L。〃　I。　page　321。）　　Darwin's　work　on　the　various　volcanic　islands　examined　by　him　had　given　him　the　most　intense　pleasure；　but　the　work　of　writing　the　book　by　the　aid　of　his　notes　and　specimens　he　found　〃uphill　work；〃　especially　as　he　feared　the　book　would　not　be　read；　〃even　by　geologists。〃　　（Loc。　cit。）

As　a　matter　of　fact　the　work　is　full　of　the　most　interesting　observations　and　valuable　suggestions；　and　the　three　editions　（or　reprints）　which　have　appeared　have　proved　a　most