CORAL REEFS AND SUBMARINE BANKS 407 
A third inference is that, as the extra-tropical clift islands 
present no signs of a bench abraded in preglacial times at present 
sea-level, such a bench, if it ever existed, must have been com- 
pletely destroyed by the undercutting of the present bench; to 
be sure, no bench would have been cut if the islands had been 
surrounded by reefs in preglacial time; but in either case we may 
further infer that if the ocean could accomplish so much abrasion 
on these hard-rock extra-tropical islands as is indicated by their 
broad platforms, cliffs ought to have been cut on the spur ends of 
the hard-rock inter-tropical islands; thus the conclusion stated in 
an earlier section is confirmed. A fourth inference is that, inas- 
much as here again the marginal depths of the banks are about 4o 
fathoms, the recurrence of this measure indicates that the depths are 
not simply the work of abrasion by the lowered ocean, but of adjust- 
ment with respect to present sea-level between aggradation by 
inorganic and organic deposits and degradation by waves and 
currents. It is worth remembering in this connection that a 
number of soundings on the banks report “‘coral.”’ 
But the assumption that the islands here considered have not 
subsided is without support; the evidence given above that the 
island of Hawaii has suffered subrecent subsidence makes it not 
improbable that Bird and Necker islands also have subsided. In 
this case the fourth inference, just stated, would be of special 
importance; but the problem thus becomes so largely speculative 
that it need not be considered further at present. 
Bearing of submarine banks on the coral-reef problem.—In sum- 
marizing the considerations thus far presented, let me state 
explicitly that I do not wish to insist that the recent subsidence of 
the Ceram Sea basin demonstrates recent subsidence in the China 
Sea, which lies 1,500 miles to the northwest; nor that the geo- 
logically modern movements in the Philippines and other Australa- 
sian islands absolutely demand contemporaneous movements in 
the foundations of the Tizard and Macclesfield banks 200 or 300 
miles to the west of the Philippines; nor that subsidence of the 
foundations of these banks, if it should be proved, would fully 
certify to subsidence of the great banks in the Indian Ocean also; 
nor that the demonstrated subsidence of all these banks would 
unqualifiedly require the subsidence of all the atoll foundations in 
