as if the Isle of Man possessed a peculiar species of thrush and blackbird,
distinct from the birds which are common to England and Ireland.
These curious facts would indicate that Banca may have existed as a distinct
island even longer than Sumatra and Borneo, and there are some geological and
geographical facts which render this not so improbable as it would at first seem
to be. Although on the map Banca appears so close to Sumatra, this does not
arise from its having been recently separated from it; for the adjacent district of
Palembang is new land, being a great alluvial swamp formed by torrents from
the mountains a hundred miles distant.
Banca, on the other hand, agrees with Malacca, Singapore, and the intervening
island of Lingen, in being formed of granite and laterite; and these have all most
likely once formed an extension of the Malay peninsula. As the rivers of Borneo
and Sumatra have been for ages filling up the intervening sea, we may be sure
that its depth has recently been greater, and it is very probable that those large
islands were never directly connected with each other except through the Malay
peninsula. At that period the same species of squirrel and Pitta may have
inhabited all these countries; but when the subterranean disturbances occurred
which led to the elevation of the volcanoes of Sumatra, the small island of Banca
may have been separated first, and its productions being thus isolated might be
gradually modified before the separation of the larger islands had been
completed.
As the southern part of Sumatra extended eastward and formed the narrow
straits of Banca, many birds and insects and some Mammalia would cross from
one to the other, and thus produce a general similarity of productions, while a
few of the older inhabitants remained, to reveal by their distinct forms, their
different origin. Unless we suppose some such changes in physical geography to
have occurred, the presence of peculiar species of birds and mammals in such an
island as Banca is a hopeless puzzle; and I think I have shown that the changes
required are by no means so improbable as a mere glance at the map would lead
us to suppose.
For our next example let us take the great islands of Sumatra and Java. These
approach so closely together, and the chain of volcanoes that runs through them
gives such an air of unity to the two, that the idea of their having been recently
dissevered is immediately suggested. The natives of Java, however, go further
than this; for they actually have a tradition of the catastrophe which broke them
asunder, and fix its date at not much more than a thousand years ago. It becomes
interesting, therefore, to see what support is given to this view by the
comparison of their animal productions.