ss, and to one long and serious illness.
The greater part of my time, when I could do anything, was devoted to
my work on 'Coral Reefs,' which I had begun before my marriage, and of
which the last proof-sheet was corrected on May 6th, 1842. 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. It
was thought highly of by scientific men, and the theory therein given
is, I think, now well established.

No other work of mine was begun in so deductive a spirit as this, for
the whole theory was thought out on the west coast of South America,
before I had seen a true coral reef. I had therefore only to verify and
extend my views by a careful examination of living reefs. But it should
be observed that I had during the two previous years been incessantly
attending to the effects on the shores of South America of the
intermittent elevation of the land, together with denudation and the
deposition of sediment. This necessarily led me to reflect much on the
effects of subsidence, and it was easy to replace in imagination the
continued deposition of sediment by the upward growth of corals. To do
this was to form my theory of the formation of barrier-reefs and atolls.

Besides my work on coral-reefs, during my residence in London, I read
before the Geological Society papers on the Erratic Boulders of South
America ('Geolog. Soc. Proc.' iii. 1842.), on Earthquakes ('Geolog.
Trans. v. 1840.), and on the Formation by the Agency of Earth-worms of
Mould. ('Geolog. Soc. Proc. ii. 1838.) I also continued to superintend
the publication of the 'Zoology of the Voyage of the "Beagle".' Nor did
I ever intermit collecting facts bearing on the origin of species; and I
could sometimes do this when I could do nothing else from illness.

In the summer of 1842 I was stronger than I had been for some time, and
took a little tour by myself in North Wales, for the sake of observing
the effects of the old glaciers which formerly filled all the larger
valleys. I published a short account of what I saw in the 'Philosophical
Magazine.' ('Philosophical Magazine,' 1842.) This excursion interested
me greatly, and it was the last time I was ever strong enough to climb
mountains or to take long walks such as are necessary for geological
work.

During the early part of our life in London, I was strong enough to go
into general society, and saw a good deal of sever