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 require--evidence 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 the islands, and in some cases there seems also to have
been time for a change of species to have taken place. Birds and
insects illustrate the same view, for every family and almost
every genus of these groups found in any of the islands occurs
also on the Asiatic continent, and in a great number of cases the
species are exactly identical. Birds offer us one of the best
means of determining the law of distribution; for though at first