uptions
through illness, Darwin estimated that it cost him twenty months of hard
work.

Darwin has related how his theory of Coral-reefs which was begun in a
more "deductive spirit" than any of his other work, for in 1834 or 1835
it "was thought out on the west coast of South America, before I had
seen a true coral-reef." ("L.L." I. page 70.) The final chapter in
Lyell's second volume of the "Principles" was devoted to the subject
of Coral-reefs, and a theory was suggested to account for the peculiar
phenomena of "atolls." Darwin at once saw the difficulty of accepting
the view that the numerous and diverse atolls all represent submerged
volcanic craters. His own work had for two years been devoted to the
evidence of land movements over great areas in South America, and thus
he was led to announce his theory of subsidence to account for barrier
and encircling reefs as well as atolls.

Fortunately, during his voyage across the Pacific and Indian Oceans, in
his visit to Australia and his twelve days' hard work at Keeling Island,
he had opportunities for putting his theory to the test of observation.

On his return to England, Darwin appears to have been greatly surprised
at the amount of interest that his new theory excited. Urged by Lyell,
he read to the Geological Society a paper on the subject, as we have
seen, with as little delay as possible, but this paper was "withdrawn by
permission of the Council." An abstract of three pages however appeared
in the "Proceedings of the Geological Society". (Vol. II. pages 552-554
(May 31, 1837).) A full account of the observations and the theory was
given in the "Journal" (1839) in the 40 pages devoted to Keeling
Island in particular and to Coral formations generally. ("Journal" (1st
edition), pages 439-69.)

It will be readily understood what an amount of labour the book on
Coral reefs cost Darwin when we reflect on the number of charts, sailing
directions, narratives of voyages and other works which, with the
friendly assistance of the authorities at the Admiralty, he had
to consult before he could draw up his sketch of the nature and
distribution of the reefs, and this was necessary before the theory, in
all its important bearings, could be clearly enunciated. Very pleasing
is it to read how Darwin, although arriving at a different conclusion to
Lyell, shows, by quoting a very suggestive passage in the "Principles"
(1st edition Vol. II. page 296.), how the latter only just