the malay archipelago-1-第4章

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　south…east　monsoon；　which　lasts　for　about　two…thirds　of　the　year　（from　March　to　November）；　blowing　over　the　northern　parts　of　that　country；　produces　a　degree　of　heat　and　dryness　which　assimilates　the　vegetation　and　physical　aspect　of　the　adjacent　islands　to　its　own。　A　little　further　eastward　in　Timor　and　the　Ke　Islands；　a　moister　climate　prevails；　the　southeast　winds　blowing　from　the　Pacific　through　Torres　Straits　and　over　the　damp　forests　of　New　Guinea；　and　as　a　consequence；　every　rocky　islet　is　clothed　with　verdure　to　its　very　summit。　Further　west　again；　as　the　same　dry　winds　blow　over　a　wider　and　wider　extent　of　ocean；　they　have　time　to　absorb　fresh　moisture；　and　we　accordingly　find　the　island　of　Java　possessing　a　less　and　less　arid　climate；　until　in　the　extreme　west　near　Batavia；　rain　occurs　more　or　less　all　the　year　round；　and　the　mountains　are　everywhere　clothed　with　forests　of　unexampled　luxuriance。

Contrasts　in　Depth　of　Sea。It　was　first　pointed　out　by　Mr。　George　Windsor　Earl；　in　a　paper　read　before　the　Royal　Geographical　Society　in　1845；　and　subsequently　in　a　pamphlet　〃On　the　Physical　Geography　of　South…Eastern　Asia　and　Australia〃；　dated　1855；　that　a　shallow　sea　connected　the　great　islands　of　Sumatra；　Java；　and　Borneo　with　the　Asiatic　continent；　with　which　their　natural　productions　generally　agreed；　while　a　similar　shallow　sea　connected　New　Guinea　and　some　of　the　adjacent　islands　to　Australia；　all　being　characterised　by　the　presence　of　marsupials。

We　have　here　a　clue　to　the　most　radical　contrast　in　the　Archipelago；　and　by　following　it　out　in　detail　I　have　arrived　at　the　conclusion　that　we　can　draw　a　line　among　the　islands；　which　shall　so　divide　them　that　one…half　shall　truly　belong　to　Asia；　while　the　other　shall　no　less　certainly　be　allied　to　Australia。　I　term　these　respectively　the　Indo…Malayan　and　the　Austro…Malayan　divisions　of　the　Archipelago。

On　referring　to　pages　12；　13；　and　36　of　Mr。　Earl's　pamphlet；　it　will　be　seen　that　he　maintains　the　former　connection　of　Asia　and　Australia　as　an　important　part　of　his　view；　whereas；　I　dwell　mainly　on　their　long　continued　separation。　Notwithstanding　this　and　other　important　differences　between　us；　to　him　undoubtedly　belongs　the　merit　of　first　indicating　the　division　of　the　Archipelago　into　an　Australian　and　an　Asiatic　region；　which　it　has　been　my　good　fortune　to　establish　by　more　detailed　observations。

Contrasts　in　Natural　Productions。To　understand　the　importance　of　this　class　of　facts；　and　its　bearing　upon　the　former　distribution　of　land　and　sea；　it　is　necessary　to　consider　the　results　arrived　at　by　geologists　and　naturalists　in　other　parts　of　the　world。

It　is　now　generally　admitted　that　the　present　distribution　of　living　things　on　the　surface　of　the　earth　is　mainly　the　result　of　the　last　series　of　changes　that　it　has　undergone。　Geology　teaches　us　that　the　surface　of　the　land；　and　the　distribution　of　land　and　water；　is　everywhere　slowly　changing。　It　further　teaches　us　that　the　forms　of　life　which　inhabit　that　surface　have；　during　every　period　of　which　we　possess　any　record；　been　also　slowly　changing。

It　is　not　now　necessary　to　say　anything　about　how　either　of　those　changes　took　place；　as　to　that；　opinions　may　differ；　but　as　to　the　fact　that　the　changes　themselves　have　occurred；　from　the　earliest　geological　ages　down　to　the　present　day；　and　are　still　going　on；　there　is　no　difference　of　opinion。　Every　successive　stratum　of　sedimentary　rock；　sand；　or　gravel；　is　a　proof　that　changes　of　level　have　taken　place；　and　the　different　species　of　animals　and　plants；　whose　remains　are　found　in　these　deposits；　prove　that　corresponding　changes　did　occur　in　the　organic　world。

Taking；　therefore；　these　two　series　of　changes　for　granted；　most　of　the　present　peculiarities　and　anomalies　in　the　distribution　of　species　may　be　directly　traced　to　them。　In　our　own　islands；　with　a　very　few　trifling　exceptions；　every　quadruped；　bird；　reptile；　insect；　and　plant；　is　found　also　on　the　adjacent　continent。　In　the　small　islands　of　Sardinia　and　Corsica；　there　are　some　quadrupeds　and　insects；　and　many　plants；　quite　peculiar。　In　Ceylon；　more　closely　connected　to　India　than　Britain　is　to　Europe；　many　animals　and　plants　are　different　from　those　found　in　India；　and　peculiar　to　the　island。　In　the　Galapagos　Islands；　almost　every　indigenous　living　thing　is　peculiar　to　them；　though　closely　resembling　other　kinds　found　in　the　nearest　parts　of　the　American　continent。

Most　naturalists　now　admit　that　these　facts　can　only　be　explained　by　the　greater　or　less　lapse　of　time　since　the　islands　were　upraised　from　beneath　the　ocean；　or　were　separated　from　the　nearest　land；　and　this　will　be　generally　（though　not　always）　indicated　by　the　depth　of　the　intervening　sea。　The　enormous　thickness　of　many　marine　deposits　through　wide　areas　shows　that　subsidence　has　often　continued　（with　intermitting　periods　of　repose）　during　epochs　of　immense　duration。　The　depth　of　sea　produced　by　such　subsidence　will　therefore　generally　be　a　measure　of　time；　and　in　like　manner；　the　change　which　organic　forms　have　undergone　is　a　measure　of　time。　When　we　make　proper　allowance　for　the　continued　introduction　of　new　animals　and　plants　from　surrounding　countries　by　those　natural　means　of　dispersal　which　have　been　so　well　explained　by　Sir　Charles　Lyell　and　Mr。　Darwin；　it　is　remarkable　how　closely　these　two　measures　correspond。　Britain　is　separated　from　the　continent　by　a　very　shallow　sea；　and　only　in　a　very　few　cases　have　our　animals　or　plants　begun　to　show　a　difference　from　the　corresponding　continental　species。　Corsica　and　Sardinia；　divided　from　Italy　by　a　much　deeper　sea；　present　a　much　greater　difference　in　their　organic　forms。　Cuba；　separated　from　Yucatan　by　a　wider　and　deeper　strait；　differs　more　markedly；　so　that　most　of　its　productions　are　of　distinct　and　peculiar　species；　while　Madagascar；　divided　from　Africa　by　a　deep　channel　three　hundred　miles　wide；　possesses　so　many　peculiar　features　as　to　indicate　separation　at　a　very　remote　antiquity；　or　even　to　render　it　doubtful　whether　the　two　countries　have　ever　been　absolutely　united。

Returning　now　to　the　Malay　Archipelago；　we　find　that　all　the　wide　expanse　of　sea　which　divides　Java；　Sumatra；　and　Borneo　from　each　other；　and　from　Malacca　and　Siam；　is　so　shallow　that　ships　can　anchor　in　any　part　of　it；　since　it　rarely　exceeds　forty　fathoms　in　depth；　and　if　we　go　as　far　as　the　line　of　a　hundred　fathoms；　we　shall　include　the　Philippine　Islands　and　Bali；　east　of　Java。　If；　therefore；　these　islands　have　been　separated　from　each　other　and　the　continent　by　subsidence　of　the　intervening　tracts　of　land；　we　should　conclude　that　the　separation　has　been　comparatively　recent；　since　the　depth　to　which　the　land　has　subsided　is　so　small。　It　is　also　to　be　remarked　that　the　great　chain　of　active　volcanoes　in　Sumatra　and　Java　furnishes　us　with　a　sufficient　cause　for　such　subsidence；　since　the　enormous　masses　of　matter　they　have　thrown　out　would　take　away　the　foundations　of　the　surrounding　district；　and　this　may　be　the　true　explanation　of　the　often…noticed　fact　that　volcanoes　and　volcanic　chains　are　always　near　the　sea。　The　subsidence　they　produce　around　them　will；　in　time；　make　a　sea；　if　one　does　not　already　exist。

But；　it　is　when　we　examine　the　zoology　of　these　countries　that　we　find　what　we　most　requireevidence　of　a　very　striking　character　that　these　great　islands　must　have　once　formed　a　part　of　the　continent；　and　could　only　have　been　separated　at　a　very　recent　geological　epoch。　The　elephant　and　tapir　of　Sumatra　and　Borneo；　the　rhinoceros　of　Sumatra　and　the　allied　species　of　Java；　the　wild　cattle　of　Borneo　and　the　kind　long　supposed　to　be　peculiar　to　Java；　are　now　all　known　to　inhabit　some　part　or　other　of　Southern　Asia。　None　of　these　large　animals　could　possibly　have　passed　over　the　arms　of　the　sea　which　now　separate　these　countries；　and　their　presence　plainly　indicates　that　a　land　communication　must　have　existed　since　the　origin　of　the　species。　Among　the　smaller　mammals；　a　considerable　portion　are　common　to　each　island　and　the　continent；　but　the　vast　physical　changes　that　must　have　occurred　during　the　breaking　up　and　subsidence　of　such　extensive　regions　have　led　to　the　extinction　of　some　in　one　or　more　of