Geology of South America 373 
Darwin landed in South America than two sets of phenomena power- 
fully arrested his attention. The first of these was the occurrence of 
great masses of red mud containing bones and shells, which afforded 
striking evidence that the whole continent had shared in a series of 
slow and gradual but often interrupted movements. The second 
related to the great masses of crystalline rocks which, underlying 
the muds, cover so great a part of the continent. Darwin, almost as 
soon as he landed, was struck by the circumstance that the direction, 
as shown by his compass, of the prominent features of these great 
crystalline rock-masses—their cleavage, master-joints, foliation and 
pegmatite veins—was the same as the orientation described by 
Humboldt (whose works he had so carefully studied) on the west 
of the same great continent. 
The first five chapters of the book on South America were devoted 
to formations of recent date and to the evidence collected on the 
east and west coasts of the continent in regard to those grand earth- 
movements, some of which could be shown to have been accompanied 
by earthquake-shocks. The fossil bones, which had given him the 
first hint concerning the mutability of species, had by this time been 
studied and described by comparative anatomists, and Darwin was 
able to elaborate much more fully the important conclusion that the 
existing fauna of South America has a close analogy with that of the 
period immediately preceding our own. 
The remaining three chapters of the book dealt with ‘the meta- 
morphic and plutonic rocks, and in them Darwin announced his 
important conclusions concerning the relations of cleavage and folia- 
tion, and on the close analogy of the latter structure with the banding 
found in rock-masses of igneous origin. With respect to the first of 
these conclusions, he received the powerful support of Daniel Sharpe, 
who in the years 1852 and 1854 published two papers on the 
structure of the Scottish Highlands, supplying striking confirmation 
of the correctness of Darwin’s views. Although Darwin’s and Sharpe’s 
conclusions were contested by Murchison and other geologists, they 
are now universally accepted. In his theory concerning the origin 
of foliation, Darwin had been to some extent anticipated by Scrope, 
but he supplied many facts and illustrations leading to the gradual 
acceptance of a doctrine which, when first enunciated, was treated 
with neglect, if not with contempt. 
The whole of this volume on South American geology is crowded 
with the records of patient observations and suggestions of the 
greatest value; but, as Darwin himself saw, it was a book for the 
working geologist and “caviare to the general.” Its author, indeed, 
frequently expressed his sense of the “dryness” of the book; he 
even says “I long hesitated whether I would publish it or not, ” and 
