GEOMORPHY 25 



the drainage forced to the base of Kaala from Koolau, and the later 

 excavation of comparatively small canyons. This view does not force 

 us to believe in the existence of climatic conditions different from those 

 now prevailing, and it enables us to interpret what has happened from 

 the varied topography.* 



This view is confirmed by observing a more decided contrast on the 

 adjacent double island of Maui. The smaller, older mass of Eeka, in 

 West Maui, has suffered much greater erosion than Kaala, and has also 

 its wind gap, while the gigantic Haleakala, which has poured out sheets 

 of lava almost in historic times, presents only the modern type of small 

 canyon erosion on its windward side, and the leeward side has not been 

 affected. The contrast between the two parts of Maui is more marked 

 than upon Oahu, but it is the same in kind and may illustrate the sim- 

 ilar sequence of Kaala and Koolau. 



Artesian Wells 



About 20 years ago it was discovered that good water could be ob- 

 tained by sinking artesian wells near the seashore. By 1884 no less 

 than 96 had been bored, nearly all of which yielded water. A list of 

 them in Thrum's Annual for 1884 shows 53 in Honolulu district, 19 in 

 Ewa, 21 in Waialua, and 3 in Koolau, at the northeast end of the island. 

 Since that time the number has doubled. I have the records of many 

 of these wells, and will state what general conclusions ma}' be drawn 

 from them. 



1. The water-bearing stratum comes from a vesicular basalt situated 

 deep down the Kaala and Koolau series. The rains soak through the 

 permeable layers till this particular rock is reached. 



2. Flowing water shows itself only in a narrow belt of territory adjacent 

 to the seashore. At Honolulu the highest altitude reached by the flow 

 is 42 feet. In the Ewa district the limit is 32 feet; in Waialua 21 feet, 

 and near Kahuku 26 feet. Now that the number of wells has greatly 

 increased, this limit is lowered to the amount of 7 feet at Punahou, but 

 the exact figures for other localities have not been ascertained. Professor 

 C. J. Lyons says the artesian well level about Honolulu fell during the 

 month of July, 1899, from 35.1 feet to 34.6 feet, because of the semi- 

 annual flooding of the rice fields. Wells sunk above the limit of flowing 



*After writing the above, I find a somewhat similar statement of some of the facts by Professor 

 Dana. He says, " That the volcano of East Oahn was in fall action long after the extinction of the 

 western cone is shown " [in 1840 and 1887] " by the encroachment of the eastern lava streams over 

 its base and the burial in part of the valleys." " The depth of burial by the East Oahu lavas was 

 probably some hundreds of feet." A figure shows the steep east wall of Kaala just behind the 

 newly encroaching lavas. Characteristics of Volcanoes, p. 301. 



