The Malay archipelago : the land of the orang-utan ... - Wallace Online

I.] PHYSICAL GEOGRAPHY. 13does the ancient docti'ine—tliat difierences or similarities inthe various forms of life that inhabit different countries aredue to corresponding physical difierences or similarities in thecountries themselves—meet with so direct and palpable a contradiction.Borneo and Xew Guinea, as alike physically as twodistinct countries can be, are zoologically wide as the polesasunder ; while Australia, Avith its dry winds, its open plains,its stony deserts, and its temperate climate, yet produces birdsand quadrupeds which ai-e closely related to those inhabitingthe hot, damp, luxuriant forests which everywhere clothe theplains and mountains of New Guinea.In order to illustrate more clearly the means by which Isuppose this great contrast has been brought about, let usconsider what would occur if two strongly contrasted di\dsionsof the earth were, by natural means brought into proximity.No two parts of the world ditter so radically in their productionsas Asia and Australia, but the difference between Africa andSouth America is also very great, and these two regions willwell serve to illustrate the question we are considering. Onthe one side we have baboons, lions, elephants, buftaloes, andgiraffes ; on the other spider-monkeys, pumas, tapirs, ant-eaters,and sloths ;while among birds, the hornbills, tui'acos, orioles,and honeysuckers of Africa contrast strongly with the toucans,macaws, chatterers, and humming-birds of America.Now let us endeavour to imagine that a slow upheaval of thebed of the Altantic should take place, while at the same timeearthquake-shocks and volcanic action on the land should causeincreased volumes of sediment to be poured down by the river.s, sothat the two continents should gradually spread out by the additionof newlj^-formed lands, and thus reduce the Atlantic Avliichnow separates them to an arm of the sea a few hundred milesAt the same time we may suppose islands to be upheaved inwide.mid-channel ; and, as the subterranean forces varied in intensity,and shifted their points of greatest action, these islands Avouldsometimes become connected with the land on one side or otherof the strait, and at other times again be separated from it.Several islands would at one time be joined together, at anotherwould be broken up again, till at last, after many long ages ofsuch intermittent action, we might have an irregular archipelagoof islands tilling up the ocean channel of the Atlantic, in whoseappearance and arrangement we could discover nothing to tellus which had been connected with Africa and which withAmerica. The animals and plants inhabiting these islandswould, however, certainly reveal this portion of their formerhistory. On those islands which had ever formed a part of theSouth American continent we should be sure to tind such commonbirds as chatterers and toucans and humming-birds, andsome of the peculiar American quadrupeds ; while on thosewhich had been separated from Africa, hornbills, orioles, andhoneysuckers would as certainly be found. Some portion of