Concentration on Geological Work 355 
had “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.” 
On arriving at the Cape of Good Hope in July, 1836, Darwin 
was greatly gratified by hearing that Sedgwick had spoken to his 
father in high terms of praise concerning the work done by him in 
South America. Referring to the news from home, when he reached 
Bahia once more, on the return voyage (August, 1836), he says : 
“The desert, volcanic rocks, and wild sea of Ascension. ..suddenly 
wore a pleasing aspect, and I set to work with a good-will at my old 
work of Geology.” Writing fifty years later, he says: “I clambered 
over the mountains of Ascension with a bounding step and made the 
volcanic rocks resound under my geological hammer? ! ” 
That his determination was now fixed to devote his own labours 
to the task of working out the geological results of the voyage, and 
that he was prepared to leave to more practised hands the study of 
his biological collections, is clear from the letters he sent home at 
this time. From St Helena he wrote to Henslow asking that he 
would propose him as a Fellow of the Geological Society; and his 
Certificate, in Henslow’s handwriting, is dated September 8th, 1836, 
being signed from personal knowledge by Henslow and Sedgwick. 
He was proposed on November 2nd and elected November 30th, 
being formally admitted to the Society by Lyell, who was then Presi- 
dent, on January 4th, 1837, on which date he also read his first 
paper. Darwin did not become a Fellow of the Linnean Society till 
eighteen years later (in 1854). 
An estimate of the value and importance of Darwin’s geological 
discoveries during the voyage of the Beagle can best be made when 
considering the various memoirs and books in which the author 
described them. He was too cautious to allow himself to write his 
first impressions in his Journal, and wisely waited till he could study 
his specimens under better conditions and with help from others on 
his return. The extracts published from his correspondence with 
Henslow and others, while he was still abroad, showed, nevertheless, 
how great was the mass of observation, how suggestive and pregnant 
with results were the reasonings of the young geologist. 
Two sets of these extracts from Darwin’s letters to Henslow 
were printed while he was still abroad. The first of these was the 
series of Geological Notes made during a survey of the East and 
West Coasts of South America, in the years 1832, 1833, 1834 and 
1835, with an account of a transverse section of the Cordilleras of 
the Andes between Valparaiso and Mendoza. Professor Sedgwick, 
who read these notes to the Geological Society on November 18th, 
1L. 1.1. p. 70. 21.1, 1 p. 265. 5 L, L. 1, p. 66, 
23—2 
