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followed by an apparent subsidence of the land caused by a rise 
of the sea-level, as Day imagines, -bas created the conditions neces- 
sary for the origin of many barrier reefs and atolls; in a still larger 
number of coral reefs it has equally certainly determined their present 
shape as well as that of the submarine platforms from which they 
rise, and finally it has had its share in the formation of all of them. 
Yet it appears to me not yet definitely proved that the “glacial 
control theory” is sufficient to explain the origin of all barrier reefs 
and atolls. | 
This theory gives no explanation of true or apparent subsidence 
of the land of considerably over 50 or 60 m., which must be 
admitted in order to explain the formation of several barrier reefs 
and atolls, e.g. of the numerous atolls which in the Pacific rise 
individually with very steep slopes from abysmal depths and do not 
stand connected with others on relatively shallow submarine plat- 
forms. True or apparent subsidence of the land of considerable amount 
is in my opinion indispensable for the explanation of the origin of those. 
In fact, for many islands surrounded by barrier reefs, a subsidence, 
certainly exceeding 60 m. must be inferred, with almost absolute 
certainty, according to Davis, from the occurrence and the shape 
of the “embayed valleys’. Also, on the Funafati atoll the well-known 
boring in the lagoon has proved a subsidence of at least 75 m. and 
the boring on the reef there has made a subsidence of + 340 m. 
probable. | 
To sum up I think we may conclude that the problem of the 
origin of the coral islands is at the present moment in this stage 
that it is pretty generally conceded that a subsidence of the ocean- 
bottom, either true or apparant, must be assumed for the regions 
where barrier reefs and atolls are found. Considerable uncertainty 
and diversion of opinion however still exists as to the amount and 
the cause of this subsidence. 
A glance at a map showing the geographical distribution of coral- 
reefs shows that they occur in regions so much varying in geological 
structure that we can hardly expect the causes of subsidence to 
have been the same in all cases. 
In fact subsidence of the land can be explained without much 
difficulty by crustal warping (or folding) where it is found to be 
restricted to the coasts of continents or to islands which are closely 
related to continents and rise from the same submarine platform 
as the continent does, as is the case in the southwestern part of the 
Pacific, which stands in close relation to the Australian continent. 
The name south-western part of the Pacific I use here in denoting 
