302 Daly — Pleistocene Glaciation and Coral Reef Problem. 



12 3 4 5 



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fit U 01 _, 01 



rtO ^a<zi Sjato S-^oi SSSrrt 



i2 ©."S tSrtS xi-"a xp3 i^rtS. 

 a-SSi S.9ft W&5- W^S w-S-s; 



Mulaku, composite atoll 42 35 15 35 4 



. Kolumadulu, " " 45 40 24 27 4 



Suvadiva, " " 48 40 33 50 4 



Makiimidu, atoll 17 10 6 18 4 



Horsbuvgh, '• _ 23 20 4 9 4 



GahaFaro, " 22 20 4 7 4 



Easdu, " 28 18 4 5 4 



Wataru, " 21 18 3 4 4 



Addu, " 36 30 7 10 4 



Haddumati, " 42 38 13 20 4. 



Great Chagos Bank, 50 40 60 90 4 



Colnrans 3 and 4 give the respective extreme widths and 

 lenojths (in geographical miles) of atoll-bearing plateaus, and 

 the width of the plateaus surmounted by barrier-reefs. Column 

 5 states the approximate degree of exposure of each plateau to 

 marine erosion ; the coasts with barrier reefs being generally 

 exposed to waves from two quadrants ; and atoll-bearing pla- 

 teaus generally so exposed in all four quadrants. 



The average maximum depth of the lagoons and channels is 

 about 35 fathoms. The average depth of the great plateaus 

 which bear relatively small areas of reef-rock is about 45 

 fathoms. The diiference between the two averages, or 10 

 fathoms, may nearly represent the average depth to which the 

 lagoons have been tilled by calcareous matter since the existing 

 reefs began to grow. Removing from the plateaus their 

 veneers of solid reef-rock, coral detritus, and the exuviae of 

 algae, foraminifera, etc., we should have something like 45 to 

 50 fathoms of water on each of these vast platforms. The 

 relative nnifoi-mity of depth in each of the broader lagoons 

 and the striking lack of strong variation in the depths of 

 greater lagoons and barrier channels all ai'ound the world, 

 would be at least matched by the uniformity of depths on the 

 plateaus so uncapped. 



In explanation of the smoothness of the plateaus and of 

 their steady adherence to the average dejDth of about 45 

 fathoms, neither the Darwin-Dana hypothesis of prolonged 

 subsistence nor the Murray hypothesis of solution is adequate. 

 In his last volume Suess writes : " Notwithstanding the valu- 

 able investigations quite recently made, and notwithstanding 

 the objections which such distinguished investigators as 

 Semper, Murray, Agassiz, and so many others have raised to 

 the views of Darwin and Dana, it must still be admitted that 



