Among his numerous observations and discoveries during the voyage, those which appear to stand out in his mind so that he quotes them in his “Autobiography” are--the explanation of the forms of coral islands, the geological structure of St. Helena and other islands, and the relations between the animals and plants of the several Galapagos islands to each other and to those of South America. His letters and the collections which he sent home attracted much attention; and Sedgwick told Dr. Darwin that his son would take a place among the leading scientific men. When Darwin heard this from his sisters, he says, “I clambered over the mountains of Ascension with a bounding step, and made the volcanic rocks resound under my geological hammer.” His letters during the voyage are full of enthusiasm and of longing to return to his family and friends. There was the same conflict between the naval and scientific departments of the _Beagle_ on the untidiness of the decks which was afterwards repeated on the _Challenger_, where I have been told that one of the naval authorities used to say, with resigned disgust, “Oh, no, we’re not a man-of-war, we’re only a ---- dredger!” In the course of the voyage the following countries and islands were visited in the order given:--The Cape de Verde Islands, St. Paul’s Rocks, Fernando Noronha, South America (including the Galapagos Archipelago, the Falkland Islands, and Tierra del Fuego), Tahiti, New Zealand, Australia, Tasmania, Keeling Island, Maldive Coral Atolls, Mauritius, St. Helena, Ascension. Brazil was then visited again for a short time, the _Beagle_ touching at the Cape de Verde Islands and the Azores on the voyage home. Darwin says, concerning the intellectual effect of his work during the voyage:-- “That my mind became developed through my pursuits during the voyage is rendered probable by a remark made by my father, who was the most acute observer whom I ever saw, of a sceptical disposition, and far from being a believer in phrenology; for on first seeing me after the voyage he turned round to my sisters, and exclaimed, ‘Why the shape of his head is quite altered!’” (_l. c._, pp. 63, 64). CHAPTER IV. CAMBRIDGE--LONDON--WORK UPON THE COLLECTIONS--MARRIAGE--GEOLOGICAL WORK--JOURNAL OF THE VOYAGE--CORAL REEFS--FIRST RECORDED THOUGHTS ON EVOLUTION (1837–42).