28 C. H. HITCHCOCK — GEOLOGY ON OAHU 



He states also that he lias ascertained the fact of the presence of ma- 

 rine salts in the artesian waters nearest the seashore. In addition, I 

 may say that I have ascertained from the engineer at the pumping sta- 

 tion on Be re tarda avenue that the amount of scale in the boilers left by 

 the evaporation of artesian water is greater than what he has seen com- 

 ing from spring water in other parts of the world, but the amount of the 

 deposit is not large. 



5. Most of the wells pass through considerable limestone, which is 

 usually supposed to be an ancient coral reef. Thus in the deep James 

 Campbell well " hard coral rock, like marble," was encountered between 

 320 and <S25 feet — that is, of a thickness of 505 feet. In King's well 

 number 2, less than half a mile from Campbell's, there is nearly as 

 much of the limestone below 150 feet, but mixed with clay for 100 feet 

 of the way. No other wells show so much limestone. In Goo Kim's 

 wells, a mile inland, there were 26 feet of limestone above 150'feet, and 

 194 feet above the level of 430 feet, including two intercalations of 20 

 feet of clay. In the three adjacent wells of G. N. Wilcox, Mrs Ward, 

 and the ice works (Kewalo), the limestone extends downward to 400 

 feet. At Thomas square, at the pumping station, and the Queen's hos- 

 pital the limestone occupies 200 feet in thickness at the surface. Other 

 wells show a less amount. At the Makiki reservoir no limestone was 

 encountered in two wells, 900 and 970 feet deep respectively, and the 

 water rises to 40 feet above sealevel. In Jaeger's well, Makiki, a log of 

 cocoanut wood was found at a depth of 245 feet beneath 150 feet of 

 limestone. It would seem proved that this limestone does not extend 

 beneath the Koolau basalt, and that it spreads over the underground 

 surface to the depth of 700 or 800 feet in Honolulu (1178 for "broken 

 corals") and to a similar depth in Ewa. I have been careful thus far 

 not to use the word coral reef, because the material has probably been 

 blown or drifted from its place of origin, and thus does not necessarily 

 imply a subsidence of the land for 800 feet. 



(>. This limestone is overlain by lava in quite a number of wells, as at 

 G. N. Wilcox; Marquez, at the mouth of Manoa valley; King's well 

 number 2, at Waikiki ; Pua, near Moiliili ; Wong Kim, at Waikiki ; three 

 at Kalihi, government building (old palace }'ard) ; T. R. Foster, and 

 others. I have observed basalt over the existing reef at several localities 

 to be mentioned later. 



7. Diamond head is of more recent origin than the limestone, because 

 270 feet of the peculiar tufa of this crater overlies the limestone in the 

 James Campbell well. At the Queen's hospital the record is, first, black 

 volcanic ash, 10 feet; "coral," 13 feet: tufa of Punchbowl, 47 feet; "coral," 



