Darwin's verifications of his theory 491 



reefs, and atolls finds a simply and rational explanation in the processes 

 that the theory of subsidence involves, and thus gave to the theory the 

 recommendation of bringing reasonable order out of unexplained confu- 

 sion. This evidence is of the same kind that he employed some 20 years 

 later when he wrote in the "Origin of Species" : "I believe in the doctrine 

 of descent with modification, notwithstanding that this or that particular 

 change of structure can not be accounted for, because this doctrine groups 

 together and explains . . . many general phenomena of nature." 



ACCORDANT DISTRIBUTION OF DIFFERENT KINDS OF REEFS 



Darwin showed further that coral reefs, as known in 1840, were dis- 

 tributed in such a way as to associate barrier reefs and atolls in certain 

 large regions, and fringing reefs in certain other large regions; and as 

 on the one hand the reefs of barriers and atolls were taken to indicate 

 subsidence, and on the other hand fringing reefs were, as a rule, taken 

 to indicate upheaval, the occurrence of the two groups of reefs in* sepa- 

 rate large regions was regarded as accordant with the manner in which 

 subsidence and upheaval were supposed to operate in deforming the ocean 

 floor. "We may, therefore, conclude," Darwin wrote, "that the proximity 

 in the same areas of the two classes of reefs [barriers and atolls], which 

 owe their origin to the subsidence of the earth's crust, and their sepa- 

 ration from those [fringes] formed during its stationary or uprising 

 condition, holds good to the full extent which might have been anticipated 

 by our theory" (1842, 125). 



The distribution of reefs, as known today, does not bear out this con- 

 clusion, for reefs of different kinds are found to be intermingled in a 

 much more intimate manner than Darwin believed ; and many fringing 

 reefs occur in areas of strong and recent subsidence, where they appear 

 to have been formed in a manner which Darwin clearly recognized, al- 

 though he thought it exceptional, as will be shov^n below. But it may be 

 added at once that, as far as detailed studies such as those of Foye in Fiji 

 (1917) have been made in recent years, they show that, even in regions 

 of complicated movement, reef formation has been associated with sub- 

 sidence; thus confirmation has been found recently for Darwin's theory 

 precisely in those regions which have been thought to contradict it. 



DEEP LAGOONS INCLOSED BY BARRIER REEFS 



Darwin also pointed out that the occurrence of barrier reefs, "in some 

 cases steep on both sides like a wall, at a distance of two, three or more 

 miles from the shore, leaving a channel [lagoon] often between 200 and 

 300 feet deep," is inconsistent with their formation on stationary foun- 



