contradiction. Borneo and New Guinea, as alike physically as two
distinct countries can be, are zoologically wide as the poles asunder;
while Australia, with its dry winds, its open plains, its stony deserts,
and its temperate climate, yet produces birds and quadrupeds which are
closely related to those inhabiting the hot damp luxuriant forests,
which everywhere clothe the plains and mountains of New Guinea.
In order to illustrate more clearly the means by which I suppose this
great contrast has been brought about, let us consider what would occur
if two strongly contrasted divisions of the earth were, by natural
means, brought into proximity. No two parts of the world differ so
radically in their productions as Asia and Australia, but the difference
between Africa and South America is also very great, and these two
regions will well serve to illustrate the question we are considering.
On the one side we have baboons, lions, elephants, buffaloes, and
giraffes; on the other spider-monkeys, pumas, tapirs, anteaters,
and sloths; while among birds, the hornbills, turacos, orioles, and
honeysuckers of Africa contrast strongly with the toucans, macaws,
chatterers, and hummingbirds of America.
Now let us endeavour to imagine (what it is very probable may occur in
future ages) that a slow upheaval of the bed of the Atlantic should take
place, while at the same time earthquake-shocks and volcanic action on
the land should cause increased volumes of sediment to be poured down
by the rivers, so that the two continents should gradually spread out by
the addition of newly-formed lands, and thus reduce the Atlantic which
now separates them, to an arm of the sea a few hundred miles wide. At
the same time we may suppose islands to be upheaved in mid-channel; and,
as the subterranean forces varied in intensity, and shifted their points
of greatest action, these islands would sometimes become connected with
the land on one side or other of the strait, and at other times again be
separated from it. Several islands would at one time be joined together,
at another would be broken up again, until at last, after many long ages
of such intermittent action, we might have an irregular archipelago
of islands filling up the ocean channel of the Atlantic, in whose
appearance and arrangement we could discover nothing to tell us which
had been connected with Africa and which with America. The animals and
plants inhabiting these islands would, however, certainly reveal this
portion of their former history. On those islands which had ever formed
a part of the South American continent, we should be sure to find such
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