248 W. M. Davis — Shaler Memorial Study of Coral Beefs. 



out that the so-called "coral" is only the well-borers' offhand 

 name for any limestone fragments that have been brought to 

 the surface ; and that even if they were undoubtedly coral, 

 they might be talus fragments that had rolled down from a 

 surface reef; hence such records, until more fully studied, 

 prove little or nothing. 



In the above-mentioned review of various theories, under the 

 title of " The Home Study of Coral Reefs," published after my 

 departure on the Pacific voyage in January, 1914, the follow- 

 ing statements were made : — " Special attention should be called 

 to the unlike features presented between recently uplifted reefs 

 that had been previously formed by outgrowth arouud a still - 

 standing central island, and recently uplifted reefs that had 

 been previously formed by upgrowth around a subsiding central 

 island. Reefs of the first kind should contour around the 

 former shore line, but without entering any valleys that may 

 have been eroded with respect to the then sea level. . . Reefs of 

 the second kind, or their lagoon limestones, should enter every 

 valley, so as to extend inside of a line connecting the outer- 

 most outcrops of volcanic rocks in the spur ends at the for- 

 mer shore line " (Bull. Araer. Geogr. Soc, xliv, 1914, 726, 727). 

 The large-scale contour map of Oahu, prepared by the Engi- 

 neer Troops of the U. S. Army, 1909-1913, a manuscript 

 copy of which I had opportunity of seeing in Honolulu, made 

 it possible to select good localities for testing these deductions ; 

 and on my second day on the island I drove with Professor 

 W. A. Bryan, of the College of Hawaii, to Wailupe valley in 

 the younger volcanic mass of eastern Oahu, several miles east of 

 Honolulu, and immediately found the reef limestones with 

 abundant fossil corals several hundred yards inside of the 

 " line of volcanic outposts." A later excursion by rail to 

 the west coast of the island showed similar limestones in the 

 much larger valleys of the older volcanic mass of western Oahu, 

 especially in the great valley of Lualualei ; the breadth of 

 this valley in heavy lava beds represents a far greater 

 erosional work than could have been accomplished during 

 the glacial period. There seems to be no possible expla- 

 nation for these occurrences but the upgrowth of the reefs 

 during a considerable submergence of the island, after it 

 had long been standing higher than now ; the submerg- 

 ence being followed by a smaller emergence after the reefs 

 and their lagoon limestones had been formed. If the shore 

 line of the island were drawn for the period of maximum 

 submergence, it would be strongly embayed on the eastern, 

 southern and western coasts, but less so on the northern coast. 

 The embayments must have been longer than the inward 

 reach of the limestones now visible, for the innermost lime- 



