132 ON CORAL REEFS AND ISLANDS. 



islands, with barriers, and the others are low coral. Rotuma, 

 (177° 15' E., and 12° 30' N.,) is another high island, to the west 

 of Wallis's. It has encircling reefs, but we know nothing as to 

 its changes of level. 



k. Sandwich Islands. — Oahu affords decided proof of an ele- 

 vation of twenty-five or thirty feet. There is an impression at 

 Honolulu, derived from a supposed increasing height in the reef 

 off the harbor, that the island is slowly rising. Upon this point 

 I can offer nothing decisive. The present height of the reef is 

 not sufficiently above the level to which it might be raised by 

 the tides, to render it certain, from this kind of evidence, that 

 the suspected elevation is in progress. 



Kauai presents us with no evidence that the island, at the pres- 

 ent time, is at a higher level than when the coral reefs begun : 

 or at the most, no elevation is indicated beyond a foot or two. 

 The drift sand rock of Koloa appears to be a proof of elevation, 

 from its resemblance to those of Northern Oahu : but if so, there 

 must have been a subsidence since, as it now forms a cliff on the 

 shore that is gradually wearing away. 



Molokai, according to information from the Rev. Mr. Andrews, 

 has coral upon its declivities three hundred feet above the sea. 

 The same gentleman informed us that on the western peninsula 

 of Maui, coral occurs in some places eight hundred feet above 

 the sea; and specimens of well defined coral were obtained at a 

 height of five hundred feet. These islands were not visited by 

 the writer. 



With regard to Molokai, Mr. Andrews informed the author 

 that the coral occurs " upon the acclivity of the eastern or highest 

 part of the island, over a surface of more than twenty or thirty 

 acres, and extends almost to the sea. We had no means of 

 accurately measuring the height ; but the specimens were ob- 

 tained at least three hundred feet above the level of the sea, 

 and probably four hundred. The specimens have distinctly the 

 structure of coral. The distance from the sea was two to three 

 miles." 



Mr. Andrews, who appears to doubt the connection of the sup- 

 posed coral on Maui with reefs, writes to the author as follows : 

 " In no case have I seen the coral in a rocky ledge ; it is gen- 

 erally mixed with the lava rock, to which it adheres. It has 

 usually the appearance of burnt lime j and thus, large stones and 

 rocks seem as though they had been whitewashed several times 

 over, and sometimes it amounts to an inch in thickness, or an 

 inch and a half. At other times the whitewash has found its 

 way into cracks in the stones. Sometimes only one side of a 

 stone is whitened by it, or only a corner of it. It is sometimes 

 soft and crumbly, and at other times quite hard ; and again it is 

 mixed with the earth." From this description it appears to re- 



