148 BULLETIN OF THE 



He further says, 1 that the plain laud of Niihau, which comprises two 

 thirds of its surface, is composed of coral reef sand, and the detritus 

 washed from the mountains in successive layers. He also says that the 

 coral reef has been elevated from fifty to one hundred feet, and at the 

 southeast end of the island is quite level. This level portion is bare 

 and hard ; the coral structure is not evident, its fracture is conchoidal, 

 and it has a metallic ring. Opposite Kaula the reef is covered with sand 

 in round hills, which have a thiu crust of earth. 



Brigham has noticed that the limits of the coral reefs could readily 

 be traced by the marked change in color of the water of the fringing 

 reefs, which extend to a considerable distance from shore, usually re- 

 maining quite level as far as the outer edge, when they drop into deeper 

 water. 2 No detached coral reefs are known in any of the channels 

 between this island. This is very noticeable off Molokai, where there is 

 a fringing reef on the lee side, which can be plainly seen while steaming 

 along its shore. But whether the coral said to have been obtained 

 thei*e by Rev. Mr. Andrew at a height of three or four hundred feet above 

 the level of the sea is drift coral sand, or indicates a corresponding ele- 

 vation of the island, I am unable to state. 



Nowhere do the drift coral sands seem to play such an important 

 part as on the windward side of some of the Sandwich Islands. This 

 is due to their position in the belt of the trade winds, and to the im- 

 mediate proximity of the fringing reef to the shore. In some cases 

 the sands merely drift with the wind, forming irregular banks, which 

 become cemented together by the action of the rains into a more or less 

 friable sand rock. The sand rock consists of thin distinct layers, indi- 

 cating the successive duration of the winds which have driven the sand 

 in a given direction ; the successive layers are frequently separated by a 

 thin smooth crust, formed by the action of water on the exposed surface. 

 On the weather side of Oahu, all the way from Kahuku Point to Diamond 

 Head, we meet with such sand drifts (Plate II.). Where the hillsides 

 are more exposed to the full force of the trade winds in the range of an 

 old elevated reef which is pounding to pieces, as at Laie, the sands are 

 carried far inland towards Kahuku Point (Plate II.), where they form 

 well weathered pointed pinnacles of disintegrated sand rock, and assume 

 most fantastic shapes, reaching to a height of over two hundred feet 

 above the level of the sea, the material having been furnished by the drift 

 from the disintegration of the old reef; the loose sand is first swept in- 

 land by the trades, and banked up in layers, which are subsequently 

 » Ibid., p. 351. 2 Ibid., p. 352. 



