common birds as chatterers and toucans and hummingbirds, and some of the
peculiar American quadrupeds; while on those which had been separated
from Africa, hornbills, orioles, and honeysuckers would as certainly be
found. Some portion of the upraised land might at different times have
had a temporary connection with both continents, and would then contain
a certain amount of mixture in its living inhabitants. Such seems to
have been the case with the islands of Celebes and the Philippines.
Other islands, again, though in such close proximity as Bali and
Lombock, might each exhibit an almost unmixed sample of the productions
of the continents of which they had directly or indirectly once formed a
part.
In the Malay Archipelago we have, I believe, a case exactly parallel
to that which I have here supposed. We have indications of a vast
continent, with a peculiar fauna and flora having been gradually and
irregularly broken up; the island of Celebes probably marking its
furthest westward extension, beyond which was a wide ocean. At the
same time Asia appears to have been extending its limits in a southeast
direction, first in an unbroken mass, then separated into islands as
we now see it, and almost coming into actual contact with the scattered
fragments of the great southern land.
From this outline of the subject, it will be evident how important an
adjunct Natural History is to Geology; not only in interpreting
the fragments of extinct animals found in the earth's crust, but in
determining past changes in the surface which have left no geological
record. It is certainly a wonderful and unexpected fact that an accurate
knowledge of the distribution of birds and insects should enable us to
map out lands and continents which disappeared beneath the ocean long
before the earliest traditions of the human race. Wherever the geologist
can explore the earth's surface, he can read much of its past history,
and can determine approximately its latest movements above and below the
sea-level; but wherever oceans and seas now extend, he can do nothing
but speculate on the very limited data afforded by the depth of the
waters. Here the naturalist steps in, and enables him to fill up this
great gap in the past history of the earth.
One of the chief objects of my travels was to obtain evidence of this
nature; and my search after such evidence has been rewarded by great
success, so that I have been able to trace out with some probability the
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