234 DALY. 



a nearly uniform rate, throughout the enormous area described. 

 Since all large-scale crustal movement, which has become well under- 

 stood, is differential — one part of a crust block moving faster than 

 other parts, the Darwin-Dana theory faces another strong antecedent 

 objection. Their postulate also fails to account for the approximate 

 equality of volumes characterizing the typical atoll crown and the 

 typical fringing reef, each volume being measured above the break of 

 slope at the platform. One can hardly assume that all coasts fringed 

 with reefs have sunk in recent geological time at the rate supposed to 

 explain the atolls; nor that most fringing reefs are located in rising 

 areas. Somewhere or other, an area of essential stability must exist 

 in the coral-sea region; and there, according to Darwin himself, the 

 breadth of the fringing reef should be much greater than that of a 

 normal atoll or barrier reef.^^ This consequence is not matched with 

 fact. 



Alleged Proofs of Current Subsidence. So far as the writer has been 

 able to cover the literature, no case is recorded where a region bearing 

 an atoll or barrier reef has been shown, beyond question, to be now 

 visibly sinking. At least some of the instances cited by Darwin and 

 others have not survived destructive criticism. This fact does not 

 disprove his theory, but it annuls one of the positive arguments put 

 forward in support of the theory. Even if local current subsidence 

 were demonstrated, the Darwin-Dana theory would not be specially 

 favored, for local sinking, like local uplift, is to be expected on any 

 theory. 



Darwin's related argument, derived from the "drowned" condition 

 of the Great Chagos and other atolls, has already been discussed 

 (page 213). It falls to the ground if the phenomenon is due to hurri- 

 cane action and mud-control. 



Permanence of the Pacific Basin. Dana was a leading advocate of 

 the antiquity of most of the depressions occupied by the present ocean. 

 Many specialists in geological dynamics favor that view, at least as 

 far as the Pacific basin is concerned. Assuming great antiquity for 

 the Pacific basin, the Darwin-Dana explanation of its reefs implies a 

 unique, or almost unique, behaviour of the intertropical part of the 

 basin in recent geological time. The narrowness of the atoll reefs is 

 interpreted as meaning relatively rapid sinking. According to each 

 of the two authors, the floor of the reef-covered Pacific has sunk 

 thousands of feet within a period which is probably not equal to 5 



66 C. Darwin, Coral Reefs, London, 3rd ed., p. 43 (1889). 



