154 BULLETIN OF THE 



inferred from the borings of the artesian wells, as well as from what we 

 see going on in the harbor of Kaneohe along its shore line, along the 

 shore line at Diamond Head and other parts of the fringing reefs east 

 and west of Honolulu, as well as in certain portions of the islands where 

 coral sand rock is intercalated between beds of lava of greater or less 

 thickness. 



The great thickness of the coral rock can be accounted for by the 

 extension seaward of a growing reef, active only within narrow limits near 

 the surface, which is constantly pushing its way seaward upon the talus 

 formed below the living edge. This talus may be of any thickness, and 

 the older the reef, the greater its height would be, as nothing indicates 

 that in the Hawaiian district there has been any subsidence to account 

 for such a thickness of coral rock in its fringing reef. 



Dana thinks that the western coral islands beyond Bird Island, in the 

 Hawaiian range, indicate participation in the general subsidence, which 

 he traces over a large part of the Pacific Ocean, as indicated by atolls 

 and barrier reefs. Yet he himself describes the fringing reefs of Kaui 

 and Oahu, and mentions their width as being considerable. 



There appears to be no evidence that there has been any considerable 

 elevation in the Hawaiian Islands, twenty to twenty-five feet being prob- 

 ably the extreme ; while the existence of cinder cones with their base 

 close to the present sea level would indicate also that there had been no 

 special subsidence. There is, however, some evidence of subsidence on 

 the southern shore of Hawaii. At Kalapanu is a sunken plain about 

 a mile wide and two miles long, where there has evidently been a sub- 

 sidence of about fifty feet ; and the raised coral reef extending along a 

 part of the shore would indicate another change of level in former times. 

 Brigham has given a sketch plan of the plain in Fig. 27, on page 373 

 of his " Notes on the Volcanoes of the Hawaiian Islands." * Plate XIII. 

 shows the position of the sunken beach at Kaimu. 



From the recent examination of the islands of the Hawaiian group, 

 and the explanations given by Dutton of the causes determining their 

 present physiognomy, it would be more natural to suppose that the 

 gradual building up of the various islands by overflows and eruptions had 

 overwhelmed such reefs as existed (if any did exist) during the period of 

 great volcanic activity of the islands. There have been as yet no sunken 

 reefs discovered in any of the channels between the islands, and as far as 

 we know the reefs are all littoral formations of the present shore lines. 



The greatest depth in the channel between Oahu and Molokai is 317 



i Mem. Bost. Nat. Hist. Soc, Vol. I. Part III. 



