The Distribution Of The Tenants Of This Archipelago Would
Not Be Nearly So Wonderful, If, For Instance, One Island Had
A mocking-thrush, and a second island some other quite distinct
genus, - if one island had its genus of lizard,
And a
second island another distinct genus, or none whatever; - or
if the different islands were inhabited, not by representative
species of the same genera of plants, but by totally different
genera, as does to a certain extent hold good: for, to give
one instance, a large berry-bearing tree at James Island has
no representative species in Charles Island. But it is the
circumstance, that several of the islands possess their own
species of the tortoise, mocking-thrush, finches, and numerous
plants, these species having the same general habits,
occupying analogous situations, and obviously filling the
same place in the natural economy of this archipelago, that
strikes me with wonder. It may be suspected that some of
these representative species, at least in the case of the
tortoise and of some of the birds, may hereafter prove to be
only well-marked races; but this would be of equally great
interest to the philosophical naturalist. I have said that most
of the islands are in sight of each other: I may specify that
Charles Island is fifty miles from the nearest part of Chatham
Island, and thirty-three miles from the nearest part of
Albemarle Island. Chatham Island is sixty miles from the
nearest part of James Island, but there are two intermediate
islands between them which were not visited by me. James
Island is only ten miles from the nearest part of Albemarle
Island, but the two points where the collections were made
are thirty-two miles apart. I must repeat, that neither the
nature of the soil, nor height of the land, nor the climate,
nor the general character of the associated beings, and
therefore their action one on another, can differ much in the
different islands. If there be any sensible difference in their
climates, it must be between the Windward group (namely,
Charles and Chatham Islands), and that to leeward; but
there seems to be no corresponding difference in the productions
of these two halves of the archipelago.
The only light which I can throw on this remarkable difference
in the inhabitants of the different islands, is, that
very strong currents of the sea running in a westerly and
W.N.W. direction must separate, as far as transportal by the
sea is concerned, the southern islands from the northern
ones; and between these northern islands a strong N.W. current
was observed, which must effectually separate James
and Albemarle Islands. As the archipelago is free to a
most remarkable degree from gales of wind, neither the
birds, insects, nor lighter seeds, would be blown from island
to island. And lastly, the profound depth of the ocean between
the islands, and their apparently recent (in a geological
sense) volcanic origin, render it highly unlikely that they
were ever united; and this, probably, is a far more important
consideration than any other, with respect to the geographical
distribution of their inhabitants.
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