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 west-north-westerly
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 north-west 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. Reviewing the facts here given,
one is astonished at the amount of creative force, if such an
expression may be used, displayed on these small, barren, and rocky
islands; and still more so, at its diverse yet analogous action on
points so near each other. I have said that the Galapagos
Archipelago might be called a satellite attached to America, but it
should rather be called a group of satellites, physically similar,
organically distinct, yet intimately related to each other, and all
related in a marked though much lesser degree, to the great
American continent.