THE 



AMERICAN JOURNAL OF SCIENCE 



[FOURTH SERIES.] 



Art. VI. — The Coral-reef Problem and the Evidence of the 

 Funafuti Borings; by Ernest W. Skeats, Geological 

 Department, University of Melbourne. 



Introduction. 



Interest in the vexed problem of the origin of atolls and 

 barrier reefs has been again stimulated during the last few 

 years by the writings of the two Harvard geologists, Professors 

 W. M. Davis and R. A. Daly. Davis* has reinforced Darwin's 

 view of the origin of atolls in a series of papers, by amplify- 

 ing and elaborating the evidence, first recorded by Dana, in 

 favor of the subsidence theoiw which is yielded by the presence 

 of drowned valleys and embayed coasts in many of the central 

 islands surrounded by barrier reefs. 



Daly,f elaborating and adding to the earlier work of Belt;}; 

 and Penck,§ among others has propounded the "glacial-control 

 theory of coral reefs," claiming that the Pleistocene glaciation 

 by means of Polar ice caps locked up so much water that a 

 lowering of level of the tropical seas of 50-100 meters occurred. 

 The lowering of temperature is pictured as killing most of the 

 corals, while prolonged abrasion of oceanic islands during the 

 period of lowered sea level led to the development of wave- 

 cut "reef platforms" which served as the ' foundations on 

 which the existing atolls were built up when sea temperatures 

 and sea level subsequently rose. The phenomena of drowned 



* Davis. W. M., this Journal, xxxv, pp. 173-188, 1913 ; ibid., xl, pp. 223- 

 271, 1915; Bull. Am. Geogr. Soc, xlvi, pp. 561-739, 1914 ; Proc. Acad. Sci., 

 Washington, pp. 146-152, March 1915. 



fDaly, E. A., this Journal, xxx, pp. 297-308, 1910; Proc. Amer. Acad. 

 Sci.,li, pp. 157-251, Xov. 1915; this Journal, xli, pp. 153-186, 1916; Nat. 

 Acad. Sci., pp. 664-670, Dec. 1916. 



X Belt, Quart. Journ. Science, xi, p. 450, 1874. 



S Penck, Jahr. Geogr. Ges. Munichen, vi, p. 76, 1881. Penek, Morpholo- 

 gie der Erdolurfliische, Stuttgart, ii, p. 660, 1894. 



Am. Jour. Sci.— Fourth Series, Vol. XLV, No. 266.— February, 1918. 

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