260 W, M. Davis — Shaler Memorial Study of Coral Reefs. 



lower the ocean surface, lessen the effect of the uplift in rais- 

 ing it : but so specialized an arrangement of uplift and subsi- 

 dence is extremely improbable for an earth on which only a 

 quarter of the surface stands above the ocean, and on which 

 much of that quarter stands at a small altitude above sea level. 

 If, as is more probable, both areas were in part or entirely 

 beneath the ocean, as in the second section of fig. 8, the change 

 of ocean level would not be proportionate to either movement, 



Fig. 8. 



riTfiliniiiiif! )!]i)ilil 



iflllill 



*a 



II 



tDb 



lllll||||||!||!trn>J ; M Ml Hrif 



f-- T— !"t--r- 



|!PJ : !!!!J!I!!!I!1!!!|!!!!!!|!!!!!!III! 



Fig. 8. Submergence caused by rise of ocean surface (upper and middle 

 figures) and by subsidence (lower figure). 



but only to the failure of their compensation. If the two areas 

 were entirely beneath the ocean, and each movement included, 

 for example, one-twentieth of the whole ocean area, then a rise 

 of 300 feet in the ocean surface would demand enormous 

 movements of uplift and subsidence, such as 20,000 and 14,000 

 feet, in order that the failure of their compensation should be 

 6000 feet. Yet the thickness of certain reefs must be much 

 greater than 300 feet. On the east side of the island of 

 Wakaya, a tilted fault-block in the center of the Fiji group, 

 the reef is probably 1000 feet thick ; the uplifted reef's of the 

 Loyalty islands show 300 feet of limestone, and their total 

 thickness may well be several thousand feet ; certain elevated 

 reefs in Fiji expose 800 feet or more of limestone without 

 showing their foundation. Enormous measures of uplift else- 



