height of the land. Bermuda seems to be an irregular, circular, flat bank,
encrusted with knolls and reefs of coral, with land formed on one side.
This land seems once to have been more extensive, as on some parts of the
bank farthest removed from the island there are little pinnacles of rock of
the same nature as that of the high larger islands. I cannot pretend to
form any precise notion how the foundation of so anomalous an island has
been produced, but its whole history must be very different from that of
the atolls of the Indian and Pacific oceans--though, as I have said, at
first glance of the charts there is a considerable resemblance.


LETTER 533. TO C. LYELL.
[1842.]

Considering the probability of subsidence in the middle of the great oceans
being very slow; considering in how many spaces, both large ones and small
ones (within areas favourable to the growth of corals), reefs are absent,
which shows that their presence is determined by peculiar conditions;
considering the possible chance of subsidence being more rapid than the
upward growth of the reefs; considering that reefs not very rarely perish
(as I cannot doubt) on part, or round the whole, of some encircled islands
and atolls: considering these things, I admit as very improbable that the
polypifers should continue living on and above the same reef during a
subsidence of very many thousand feet; and therefore that they should form
masses of enormous thickness, say at most above 5,000 feet. (533/1.
"...As we know that some inorganic causes are highly injurious to the
growth of coral, it cannot be expected that during the round of change to
which earth, air, and water are exposed, the reef-building polypifers
should keep alive for perpetuity in any one place; and still less can this
be expected during the progressive subsidences...to which by our theory