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 past changes which one of the most interesting
parts of the earth has undergone. It may be thought that the
facts and generalizations here given would have been more
appropriately placed at the end rather than at the beginning of a
narrative of the travels which supplied the facts. In some cases
this might be so, but I have found it impossible to give such an
account as I desire of the natural history of the numerous
islands and groups of islands in the Archipelago, without
constant reference to these generalizations which add so much to
their interest. Having given this general sketch of the subject,
I shall be able to show how the same principles can be applied to