34 AUTOBIOGRAPHY. [ch. ii. 



worked as hard as I possibly could, than during any other 

 equal length of time in my life. This was owing to fre- 

 quently recurring unwellness, and to one long and serious 

 illness. The greater part of my time, when I could do any- 

 thing, 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 ob- 

 served that I had during the two previous years been inces- 

 santly attending to the effects on the shores of South Amer- 

 ica 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,* on Earthquakes,! and 

 on the Formation by the Agency of Earth-worms of Mould. J 

 I also continued to superintend the publication of the Zo- 

 ology 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* 

 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. 



* Geolog. Soc. Proc. iii. 1842. X Geolog. Soc. Proa ii. 1838. 



t Geolog. Trans, v. 1840. # Philosophical Magazine, 1842. 



