426 SCIENCE PROGRESS 



about 600 ft., but this is not its full measure, for it is continued 

 to an unknown depth below sea level. This example has been 

 confirmed a year after my visit of 1914 by Foye, who reports 

 an unconformable elevated reef on Lakemba also, in the same 

 group, with a minimum vertical measure of 320 ft. 1 On Efate, 

 in the New Hebrides group, I saw terraces of unconformable 

 elevated reefs up to 800 ft. 



A few observers have called attention to the unconformable 

 contacts of elevated reefs on their foundations. Nearly thirty 

 years ago Walther recorded the occurrence of unconformable 

 elevated reefs on the Sinai peninsula. 3 Some years afterwards 

 Becker, 8 and, later, Smith, 4 announced the unconformable con- 

 tact of a series of elevated reefs on Cebii in the Philippine Islands, 

 where the highest reefs stand at an altitude of 2,362 ft. Wanner 

 states that quaternary coral limestone lies unconformably on 

 inclined conglomerates at an altitude of 400 metres in the 

 east arm of Celebes. 6 Other geological studies in the East 

 Indies give similar information. But in many accounts of 

 elevated reefs the important question of unconformity is not 

 mentioned : thus Levesey reports that " on top of a hill [in 

 British New Guinea], judged to be over 3000 ft. high, ... a 

 large coral reef . . . stood out so clean cut, and so hard and 

 solid, it appeared as if it had only emerged from the sea a 

 short time previously " 8 ; but the relation of the reef lime- 

 stones to their foundation is not announced. 



It seems as impossible to explain unconformable reefs with- 

 out deep erosion before their formation and strong subsidence 

 during their formation, as to explain their present altitude 

 without uplift after their formation. True, Suess believed that 

 the present altitude of elevated atolls in the Pacific was not 

 due to their uplift, but to a lowering of the ocean surface ; for 

 he not only thought that all high-standing atolls had essentially 



1 W. G. Foye, "The Geology of the Lau Islands (Fiji)," Amer. Journ. Set. xliii. 



IOI7, 344-350- 



1 J. Walther, "Die Korallenriffe der Sinai-Halbinsel," Abh. k. Sachs. Ces. 

 Wiss., Math. Phys. CI. xiv. 1888, 439-506. 



3 G. F. Becker, " Geology of the Philippines," 21 Ann. Rep. U.S. Geol. Surv. 



* W. D. Smith, "Contributions to the Geology of the Philippine Islands: 

 I. Cebii Island," Phil. Journ. Set. i. 1906, 1043-1057. 



* J. Wanner, "Beitrage zur Geologie des Ostarms der Insel Celebes," N. Jahrb. 

 f. Min. 29 Beilageband, 1910, 739-778 ; see p. 770. 



6 Geogr. Journ. xii. 1899, 436. 



