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 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.
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