232 THE INFLUENCE OF INANIMATE SUREOtTNDINGS. 



a process of elevation still going on. He does so, indeed, with 

 the full understanding that his theories would be undermined 

 if he were to accept Dana's views ; for it is clear that no theory 

 of upheaval or subsidence, strictly speaking, could then come 

 under discussion. According to Dana's views we may assume 

 that, in regions of general subsidence, local upheavals may 

 occur ; and, vice versd, that local subsidence may occur in regions 

 of general upheaval. From this, however, it follows that the 

 structure of the reef itself can give no certain evidence what- 

 ever, as the basis of an assertion that this or that region is at 

 a given moment undergoing upheaval or subsidence. Thus 

 to settle this question we must avail ourselves of other argu- 

 ments than those used by Darwin to establish his theory ; 

 Dana in fact seeks for such, and his investigations led him to 

 the conclusion that the whole of the Pacific Ocean is a region of 

 subsidence, while Darwin recognises in it certain distinct 

 regions of subsidence and others of upheaval. Dana further 

 assumes that the West Indian Ocean is at present sinking, 

 while Darwin, on the contrary, regards it as rising, since the 

 reefs occurring in it belong almost exclusively to the group 

 which, according to his theory, ought to prove a condition of 

 upheaval. 



Now it might perhaps be objected that, with regard to the 

 formation of atolls and barrier-reefs, both writers perfectly 

 agree, and that the possibility granted by Darwin of the occur- 

 rence of fringing reefs on steep and subsiding coasts certainly 

 affords no ai-gument against the view that atolls and barrier- 

 reefs can under any circumstances be formed only during subsi- 

 dence. This must of coui-se be admitted ; but I must never- 

 theless maintain my opinion that Dana's and Darwin's theories 

 do contradict each other, and that if, as Dana says, all kinds of 

 I'eefs may originate during subsidence, the structure of the reef 

 itself is of no importance in investigating the question as to 

 whether in any given spot subsidence or upheaval is taking 

 place or has taken place. 



Hence it seems to me allowable to ignoi'e Dana's views 

 when the matter in point— as in this place — is to establish in 

 what way the form of the reef has been determined or altered 



