4 Physico-Geognostic Sketch of the Island of Oahu^ 



these rise by a regular gradation from Raena to Monna Raala, 

 and descend with nearly equal regularity to Laaloa. Raala, a 

 mountain with a table-shaped summit about half a mile in 

 length, extended in the direction of the chain, is not in its mid- 

 dle but about one-third of its length from Raena, and two-thirds 

 from Laaloa ; it is elevated 3850 feet above the level of the sea, 

 being the highest summit in the island, Ronahuanui perhaps ex- 

 cepted. The total length of this chain is about twenty-three miles. 

 From its sides are given off very regular lateral chains, which 

 descend gradually from the lofty summits, till they are lost in 

 the plains, enclosing deep and narrow valleys which terminate 

 in the precipitous rocky walls of the central chain. The only 

 means of ascending the central chain is by following the crest of 

 one of these lateral ridges, in consequence of the tremendous 

 precipices which bound the valleys both at their head and sides. 

 This applies more especially to the ridges descending from the 

 summit of Raala. On the north-east, the denticulated summits 

 of the central ridge generally correspond to the point of junction 

 of one of the lateral ridges, and the intervening passes to the 

 head of one of the valleys. 



The general direction of the highest part of the chain forms 

 nearly the same angle with the meridian as that of Ronahuanui. 

 The chain was not examined on the west side, that of Wainae ; 

 a view of this side was only obtained at sea, at the distance of 

 from twelve to fifteen miles. The eastern acclivity of the chain 

 is of unequal height, in consequence of the varying elevation of 

 the base from which it rises. The northern portion as far as 

 Raala rises almost immediately from the level of the sea. The 

 base of Mouna Raala itself, which is about three miles from the 

 sea, is 312 feet above its level. Five miles of the chain south 

 of Raala rise from the plains of Eva, the elevation of which an 

 accident which happened to my barometer prevented me ascer- 

 taining, but upon a rough estimate is from 300 to 400 feet above 

 the sea. 



The lateral ridges are in some places so steep, that even on 

 them it is impossible to ascend the central ridge, to which all ac- 

 cess is then prevented by inaccessible precipices. 



The valleys of the island are of two kinds, either those de- 

 scending between two lateral ridges from the central ridge of 



