354 Darwin and Geology 



is the most southern point where there is much geological interest, 

 as there the modern beds end. The Captain then talks of crossing 

 the Pacific ; but I think we shall persuade him to finish the coast of 

 Peru, where the climate is delightful, the country hideously sterile, 

 but abounding with the highest interest to the geologist....! have 

 long been grieved and most sorry at the interminable length of the 

 voyage (though I never would have quitted it).... I could not make up 

 my mind to return. I could not give up all the geological castles in 

 the air I had been building up for the last two years 1 ." 



In April, 1835, he wrote to another sister: "I returned a week 

 ago from my excursion across the Andes to Mendoza. Since leaving 

 England I have never made so successful a journey... how deeply 

 I have enjoyed it ; it was something more than enjoyment ; I cannot 

 express the delight which I felt at such a famous winding-up of all 

 my geology in South America. I literally could hardly sleep at 

 nights for thinking over my day's work. The scenery was so new, 

 and so majestic ; everything at an elevation of 12,000 feet bears so 

 different an aspect from that in the lower country.... To a geologist, 

 also, there are such manifest proofs of excessive violence ; the 

 strata of the highest pinnacles are tossed about like the crust of 

 a broken pie 2 ." 



Darwin anticipated with intense pleasure his visit to the Galapagos 

 Islands. On July 12th, 1835, he wrote to Henslow : "In a few days' time 

 the Beagle will sail for the Galapagos Islands. I look forward with 

 joy and interest to this, both as being somewhat nearer to England 

 and for the sake of having a good look at an active volcano. Although 

 we have seen lava in abundance, I have never yet beheld the crater 3 ." 

 He could little anticipate, as he wrote these lines, the important aid 

 in the solution of the "species question" that would ever after 

 make his visit to the Galapagos Islands so memorable. In 1832, as 

 we have seen, the great discovery of the relations of living to extinct 

 mammals in the same area had dawned upon his mind ; in 1835 he 

 was to find a second key for opening up the great mystery, by 

 recognising the variations of similar types in adjoining islands among 

 the Galapagos. 



The final chapter in the second volume of the Principles had 

 aroused in Darwin's mind a desire to study coral-reefs, which was 

 gratified during his voyage across the Pacific and Indian Oceans. 

 His theory on the subject was suggested about the end of 1834 or 

 the beginning of 1835, as he himself tells us, before he had seen 

 a coral-reef, and resulted from his work during two years in which he 



1 L. L. i. pp. 25758. 2 L. L. I. pp. 25960. 



3 M. L. i. p. 26. 



