Many delays from ill-health and the interruption of other work,
caused the progress to be slow, and his journal speaks of "recommencing"
the subject in February 1839, shortly after his marriage, and again in
October of the same year. In July 1841, he states that he began once more
"after more than thirteen month's interval," and the last proof-sheet of
the book was not corrected till May 6th, 1842. Darwin writes in his
autobiography, "This book, though a small one, cost me twenty months of
hard work, as I had to read every work on the islands of the Pacific, and
to consult many charts." The task of elaborating and writing out his books
was, with Darwin, always a very slow and laborious one; but it is clear
that in accomplishing the work now under consideration, there was a long
and constant struggle with the lethargy and weakness resulting from the sad
condition of his health at that time.

Lyell's anticipation that the theory of coral-reefs would be slow in
meeting with general acceptance was certainly not justified by the actual
facts. On the contrary the new book was at once received with general
assent among both geologists and zoologists, and even attracted a
considerable amount of attention from the general public.

It was not long before the coral-reef theory of Darwin found an able
exponent and sturdy champion in the person of the great American
naturalist, Professor James D. Dana. Two years after the return of the
"Beagle" to England, the ships of the United States Exploring Expedition
set sail upon their four years' cruise, under the command of Captain
Wilkes, and Dana was a member of the scientific staff. When, in 1839, the
expedition arrived at Sydney, a newspaper paragraph was found which gave
the American naturalist the first intimation of Darwin's new theory of the
origin of atolls and barrier-reefs. Writing in 1872, Dana describes the
effect produced on his mind by reading this passage:--"The paragraph threw