208 Geological Society. 



that postulate a fixed relation between reef -formation and ocean- 

 level are disproved, and are probably inapplicable to the case of 

 atolls. It appears certain that reef -upgrowth is intimately associated 

 with submergence wherever the matter can be tested. The solution 

 of the coral-reef problem turns, at present, upon some means of 

 discriminating between a submergence caused by subsidence, and a 

 submergence caused either by a general rise of the ocean -level due 

 to the uplift of the ocean-floor beyond the coral-reef region, or to 

 the melting of the Pleistocene ice-sheets. Although no means of 

 such discrimination are known, the author presents reasons that 

 lead him to regard changes in ocean -level as of secondary importance,, 

 and that have caused him to attribute the submergence demanded 

 by self -encircled islands to local subsidence, in accordance with the 

 views of Darwin and Dana. He regards the theory that pre- 

 supposes the raising of the ocean -level by uplift as extravagant in 

 its demands, and he finds the theory of ' Glacial Control ' inadequate 

 when applied to barrier-reefs and encircled islands. 



Stress is laid on the highly-significant unconformable relationship 

 that exists between reef- and lagoon -limestones and their foundations 

 — a feature that presents the strongest testimony for subsidence. 

 In such a case the foundations must have suffered erosion for a 

 considerable period before they were submerged, in preparation for 

 the unconformable deposition of reef -limestones upon them. From 

 a consideration of such unconformable relations it is concluded that 

 fringing-reefs do not mark stationary or rising islands so generally 

 as Darwin supposed. 



With regard to elevated reefs, the author demonstrates the 

 impossibility of explaining their features by regarding them as 

 having been stationary while the ocean -surface was lowered, and 

 holds that they must be due to local and diverse uplift affecting 

 the islands themselves, following on epochs of subsidence which 

 were the epochs of reef -formation. The theory that such reefs 

 were formed during pauses in the elevation and emergence is 

 considered to be seriously defective, and is contrary to Darwin's 

 views. 



The author discusses the studies of Semper on the reefs of the 

 Pelew Islands, the origin of atolls as propounded by Rein, the views 

 of Murray on barrier-reefs and atolls, and of Wharton on the 

 truncation of atoll-foundations ; but forms the opinion that the 

 geological evidence for subsidence has been overlooked by these 

 investigators, who paid no attention to the evidence afforded by 

 unconformable contacts or embayed shore-lines. 



The author feels that scientific opinion in regard to the origin 

 of coral-reefs has been guided rather by subjective preference than 

 by objective logic. He considers that Darwin's theory of inter- 

 mittent subsidence is the most competent to explain the facts, and 

 while he holds that other theories than Darwin's deserve cordial 

 consideration, he feels that the burden of proof should be laid upon 

 those who assume that reef -foundations have not subsided. 



