342 DARWINISM 



and that during the course of known geological time the 

 continents and great oceans had again and again changed 

 places with each other. Sir Charles Lyell, in the last edition 

 of his Principles of Geology (1872), said: "Continents, there- 

 fore, although permanent for whole geological epochs, shift 

 their positions entirely in the course of ages ; " and this may 

 be said to have been the orthodox opinion down to the very 

 recent period when, by means of deep-sea soundings, the nature 

 of the ocean bottom was made known. The first person to 

 throw doubt on this view appears to have been the veteran 

 American geologist, Professor Dana. In 1849, in the Eeport 

 of Wilke's Exploring Expedition, he adduced the argument 

 against a former continent in the Pacific during the Tertiary 

 period, from the absence of all native quadrupeds. In 1856, 

 in articles in the American Journal, he discussed the develop- 

 ment of the American continent, and argued for its general 

 permanence ; and in his Manual of Geology in 1863 and later 

 editions, the same views were more fully enforced and were 

 latterly applied to all continents. Darwin, in his Journal of 

 Researches, published in 1845, called attention to the fact that 

 all the small islands far from land in the Pacific, Indian, and 

 Atlantic Oceans are either of coralline or volcanic formation. 

 He excepted, however, Rodriguez and St. Paul's rocks; but 

 the former has since been shown to be no exception, as 

 it consists entirely of coral rock; and although Darwin 

 himself spent a few hours on St. Paul's rocks on his outward 

 voyage in the Beagle, and believed he had found some 

 portions of them to be of a " cherty," and others of a 

 " felspathic " nature, this also has been shown to be erroneous, 

 and the careful examination of the rocks by the Abbe Eenard 

 clearly proves them to be wholly of volcanic origin. 1 We 

 have, therefore, at the present time, absolutely no exception 

 whatever to the remarkable fact that all the oceanic islands of 

 the globe are either of volcanic or coral formation ; and there 

 is, further, good reason to believe that those of the latter class 

 in every case rest upon a volcanic foundation. 



In his Origin of Species, Darwin further showed that no 

 true oceanic island had any native mammals or batrachia 



1 See A. Agassiz, Three Cruises of the Blake (Cambridge, Mass., 1888), 

 vol. i. p. 127, footnote. 



