SCIENCE AND TRAVEL 201 



When the Beagle left Devonport, December 27, 

 1831, the young naturalist was without any theory, 

 and when the ship entered Falmouth harbor, Octo- 

 ber 2, 1836, though he felt the need of a theory in 

 reference to the relations of the various species of 

 plants and animals, he had not formulated one. It 

 was not till 1859 that his famous work on the Or if/ In 

 of Species appeared. He went merely as a collector, 

 and frequently in the course of the voyage felt a 

 young man's misgivings as to whether his collections 

 would be of value to his Cambridge professors and 

 other mature scientists. 



Professor Henslow, the botanist, through whom 

 Darwin had been offered the opportunity to accom- 

 pany the expedition, had presented his pupil with 

 the first volume of Lyell's Principles of Geology. 

 (Perhaps, after Lyell, the most potent influence on 

 Darwin's mind at this time was that of Humboldt 

 and other renowned travelers, whose works he read 

 with avidity.) At the Cape Verde Islands he made 

 some interesting observations of a white calcareous 

 stratum which ran for miles along the coast at a 

 height of about forty-five feet above the water. It 

 rested on volcanic rocks and was itself covered with 

 basalt, that is, lava which had crystallized under the 

 sea. It was evident that subsequently to the forma- 

 tion of the basalt that portion of the coast contain- 

 ing the white stratum had been elevated. The shells 

 in the stratum were recent, that is, corresponded to 

 those still to be found on the neighboring coast. It 

 occurred to Darwin that the voyage might afford 

 material for a book on geology. Later in the voy- 

 age, having read portions of his Journal to Captain 



