674 



POPULAR SCIENCE MONTHLY. 



The lowland between rises gradually to a watershed 888 feet above 

 the sea. Each range represents an elongated dome composed of 

 basaltic layers gently inclined outwards in every direction (quaqua- 

 versal). The Kaala dome originated first in igneous ejections out- 

 pouring at the bottom of the ocean ; they were constantly renewed, and 

 finally emerged above the waters. It was then exposed to the erosive 

 influences of the rains brought by the trade-winds. The streams ex- 

 cavated canons in the basalt upon both sides of the island, eating 

 away more of the rock in certain portions than in others. After a 



Fig 1. Map of Oahu. 



long period a similar but longer island developed upon the eastern 

 side, becoming the Koolau range, with more marked erosion upon the 

 windward side, and very little upon the northern half of the leeward 

 side. The Koolau lava poured itself out profusely, and covered up 

 some of the earlier formed canons upon the Kaala range. 



The character of the erosion is shown in Figure 2 upon the Waianae 

 side of the Kaala range. The canon has been enlarged to an alcove and 

 the precipitous side — called a Pali by the Hawaiians — presents a curious 

 escalloped surface, or what might almost be called the ribs of the 

 mountain side. Precisely similar waves appear upon the pali at the 

 eastern side of the Koolau range. The most interesting point is at 

 a wind-gap, 1,205 feet above the sea, the only place in the whole range 

 where a road has been cut through from Honolulu by way of Nuuanu 

 Valley to Kaneohe Bay. Tip this valley for about eight miles about 

 a hundred years ago King Kamehameha drove an army of his enemies, 



