438 SCIENCE PROGRESS 



to have gained acceptance more because of its simplicity and 

 apparent sufficiency than because of the verification which its 

 capacity to correlate various kinds of reefs provided for it. 

 Geology was a more exacting science in 1880, and yet in the 

 following twenty years many a geologist seems to have been 

 indifferent, as far as the origin of coral reefs is concerned, to 

 the need of the kind of verification for his beliefs that comes 

 from the success of the unforeseen consequences of a theory 

 in matching previously unobserved or uncorrelated facts ; for it 

 is otherwise impossible to explain the inattention to the verifi- 

 cation provided by the shoreline embayments of reef-encircled 

 islands and reef-bordered coasts ; and to the further and larger 

 verification provided by the unconformable contacts of reef 

 limestones on their foundations. 



Principles so well established and so pertinent as those 

 involved in the embayments of shorelines and in the uncon- 

 formable contact of marine limestones upon foundations that 

 have suffered subaerial erosion, should no longer be overlooked 

 in the indoor discussion of coral reefs, and much less in their 

 outdoor observation. Reports and text-books which omit the 

 consideration of these principles from the pages in which coral 

 reefs are treated must be regarded as still representing the 

 nineteenth-century phase of the discussion, and as having failed 

 to reach the twentieth-century phase. 



The Reefs of the Seychelles. — The reefs of the Seychelles 

 Islands in the southern Indian Ocean may be briefly considered 

 as a concrete illustration of the importance of embayed shore- 

 lines and unconformable contacts in the coral-reef problem. 

 The central members of this remarkable group are small granitic 

 islands which rise in mountain-like forms from a vast submarine 

 bank, 200 by 80 miles across, with a maximum depth of forty 

 fathoms near its centre. The margin of the bank is somewhat 

 shallower than the centre, especially on its northern side, where 

 several atolls reach the sea surface. The largest of the granitic 

 islands is Mahe, 17 miles in length and 2,993 ft. in height ; its 

 shoreline is indented with well-marked embayments, which are 

 separated by tapering points fringed with narrow reefs. Keller l 

 and Chun ' have reported the occurrence of an elevated reef 

 80 ft. above sea-level. The same authors, and Gardiner also, 



1 C. Keller, Die Ostafrikanischen Inseln, Berlin, 1898 ; see p. 158. 

 1 C. Chun, Aus den Tieftn des Weltmeeves, Jena, 1900 ; see p. 426. 





