2 THE VOYAGE OF H.M.S. CHALLENGER. 



out that region are mere traces. It was also believed that land existed to the south, 

 nearer the Equator, between South America and Africa. 1 But, as Sir Charles Lyell 

 rightly observes, 2 the speculations and theories of the zoologist or botanist as to the 

 manner in which these islands were peopled with living beings, must necessarily be most 

 imperfect, so long as we possess no accurate knowledge of their lithological structure and 

 composition. 



Now, the researches of the geologist tend to establish the fact that these islands, 

 formerly considered as united, are essentially of volcanic formation, and, moreover, the 

 authority just quoted affirms that nowhere among the Madeira and Canary Islands could 

 he detect any signs of subsidence, or even of the temporary emergence of old continental 

 surfaces. Do the rocks of St. Paul owe their origin to volcanic action, or must they be 

 classed among the rocks belonging to the crystalline schists ? Such is the question 

 they suggest, which is the more difficult to solve, because we have as our guide only the 

 examination of some specimens, and cannot take into account the relationship between 

 formations in the reefs of St. Paul and adjacent rocks. What still further increases the 

 difficulty is that the type to which the rocks of St. Paul belong appears in certain 

 cases with the characteristics of eruptive rocks, and in others with those of crystalline 

 schist. 



It is well known that in the hypothesis of an Atlantis, St. Paul is looked upon as 

 having belonged to that continent. 8 The position of the island in mid- Atlantic, together 

 with the aspect and lithological character of the rocks composing it, were calculated to 

 mislead as to its origin. At first sight the Eocks of St. Paul offer but little analogy 

 in their structure and mineralogical character to the volcanic material which, with coral 

 reefs, forms almost all the smaller oceanic islands ; and Darwin, to whom we are indebted 

 for so many important observations regarding the formation of oceanic islands, struck by 

 the peculiar character of this mineral mass, denied its volcanic origin. Speaking of St. 

 Paul, he says : " It is a remarkable fact, that all the many small islands in the Pacific, 

 Indian, and Atlantic Oceans, with the exception of the Seychelles and this little point of 

 rock, are, I believe, composed of coral or of erupted matter. The volcanic nature of 

 these oceanic islands is evidently an extension of that law, and the effects of the same 

 cause, whether chemical or mechanical, from which it results that a vast majority of the 

 volcanoes now in action stand either near the sea-coasts, or as islands in the midst of the 

 sea." ' Further, he has expounded his opinion in a formal manner when he says " St. 

 Paul is not of volcanic origin, and this circumstance, which is the most remarkable in its 

 history (as will hereafter be referred to), properly ought to exclude it from the present 



1 See Boue, Ueber die Eolle der Veranderungen des unorganischen iin grossen Maastabe in der Natur Sitzung- 

 berichte der wien. Akad. der Wiss., 1866, pp. 12-14. 



8 Lyell, Principles of Geology, llth ed., vol. ii. p. 406. 



s Cf. Boue, loc. cit., p. 14. 



4 Darwin, Voyage of a Naturalist, p. 8. 



