146 Couthouy on Coral Formations 



region of Polynesia. The islands of Maui, Molokai, Oahu, and 

 Kauai, abound in such evidences, of which I will specify here 

 only a few of the most striking. 



At Oahu on the south side, the whole plain on which the 

 town of Honolulu is situated, is an elevated coral reef, ex- 

 tending between three and four miles from east to west, and 

 varying from half a mile to a mile in breadth. The land- 

 ward side of this reef is highest, being, as well as I can re- 

 member, about twenty feet above the sea. In certain parts, 

 like that for instance on which the town is built, the reef is 

 covered to a depth of from two to five feet with ashes and 

 fine scoriaceous sand, which were probably ejected from the 

 now long extinct craters of Puiwa, just behind the town, and 

 Leahi* about four miles east of it on the coast, chiefly, how- 

 ever, from the former, at whose foot the plain terminates, about 

 a mile from the sea. Below this volcanic sand is sometimes 

 found a stratum of slightly cemented coral sand, containing 

 shells and Echinides of species identical with those now liv- 

 ing in the vicinity. In other places, as on the plain at the 

 entrance of the Manoa valley, between Honolulu and Waikiki, 

 the reef is entirely bare, with every hollow and guUey as dis- 

 tinctly defined as they are on the present shore reef A short 

 half mile west of Honolulu and half that distance from the 

 sea, at the mouth of a branch of the Nuuanu valley, a con- 

 siderable stream flows through a section of this elevated reef 

 some twenty feet deep. A mile and a half farther west there 

 is a similar section at the mouth of the Kalihi valley. These 

 appear to have been anciently passages in the reef, and show 

 that it is composed of the same genera of corals (principally 

 Porites) as constitute the mass of the recent reef In the dis- 

 trict of Ewa, fourteen miles west of Honolulu, on the left 

 bank of Pearl river a few rods from its mouth, there is a bed 

 of oyster shells, twelve feet in thickness and more than a hun- 

 dred yards in length, whose lowest portion is full five feet 

 above the sea. They are for the most part entire and in a 

 fine state of preservation, the internal polish yet uneflaced and 



* Puiwa is the " Punchbowl hill," and Leahi the " Diamond Head," of the 

 foreigners. 



