ARTICLES 427 



the same altitude, but he overlooked the very variable amounts 

 of erosion that they have suffered, although these variations 

 indicate great differences in the dates of emergence ; and he 

 had an unwarranted confidence in the evidence afforded by 

 certain terraces for the almost universal emergence of conti- 

 nental shores by the same measure as the altitude of the high- 

 standing atolls. 



It is impossible to explain the facts now known regarding 

 elevated reefs by regarding them as having stood still while 

 the ocean surface sank, for the reefs stand at unequal heights 

 and have suffered very unlike amounts of erosion. 1 Moreover, 

 the unconformable sea-level and elevated reefs of certain archi- 

 pelagoes, such as the Fiji Islands, 8 demand a rather compli- 

 cated succession of unequal and non-synchronous submergences 

 and emergences for their production, and are not to be accounted 

 for by any universal and uniform rising and sinking of ocean 

 level ; they can be explained only by local and diverse uplifts 

 and subsidences of the islands themselves, the epochs of reef- 

 formation being the epochs of subsidence. I believe the same 

 statement will be shown true for the reefs of the Philippine and 

 Solomon Islands, when they are more closely studied. 



Darwin's theory alone gives a rational interpretation for 

 such reefs. Inasmuch as atolls occur in association with archi- 

 pelagoes where unconformable fringing and barrier reefs are 

 found both at sea-level and elevated above sea-level, the same 

 interpretation may be reasonably applied to the reefs of all 

 three kinds thus associated. As to archipelagoes of atolls alone, 

 no demonstration of origin can be given to-day ; but the 

 presumption is manifest that they can be best explained in 

 the same way as the atolls of barrier-reef archipelagoes ; 

 and this presumption is confirmed by the Funafuti boring. 



Origin of Elevated Reefs. — In this connection let it be noted 

 that the not infrequent explanation of elevated reefs as having 

 been formed during pauses in the elevation and emergence of 

 their foundation, and as therefore contradicting Darwin's 

 theory, is seriously defective, in that it does not consider 

 whether the reefs lie conformably or unconformably on their 



1 "The Structure of High-standing Atolls," Proc. Nat. Acad. Sci. iii. 1917, 



473-479- 



1 "Extinguished and Resurgent Coral Reefs," Proc. Nat. Acad. Sci. ii 1916, 

 466-471. 



