these reefs and islands have been subjected, and are liable" ("The
Structure and Distribution of Coral Reefs," page 107: London, 1842).)
This admission, I believe, is in no way fatal to the theory, though it is
so to certain few passages in my book.

In the areas where the large groups of atolls stand, and where likewise a
few scattered atolls stand between such groups, I always imagined that
there must have been great tracts of land, and that on such large tracts
there must have been mountains of immense altitudes. But not, it appears
to me, that one is only justified in supposing that groups of islands stood
there. There are (as I believe) many considerable islands and groups of
islands (Galapagos Islands, Great Britain, Falkland Islands, Marianas, and,
I believe, Viti groups), and likewise the majority of single scattered
islands, all of which a subsidence between 4,000 and 5,000 feet would
entirely submerge or would leave only one or two summits above water, and
hence they would produce either groups of nothing but atolls, or of atolls
with one or two encircled islands. I am far from wishing to say that the
islands of the great oceans have not subsided, or may not continue to
subside, any number of feet, but if the average duration (from all causes
of destruction) of reefs on the same spot is limited, then after this limit
has elapsed the reefs would perish, and if the subsidence continued they
would be carried down; and if the group consisted only of atolls, only open
ocean would be left; if it consisted partly or wholly of encircled islands,
these would be left naked and reefless, but should the area again become
favourable for growth of reefs, new barrier-reefs might be formed round
them. As an illustration of this notion of a certain average duration of
reefs on the same spot, compared with the average rate of subsidence, we
may take the case of Tahiti, an island of 7,000 feet high. Now here the
present barrier-reefs would never be continued upwards into an atoll,
although, should the subsidence continue at a period long after the death