From all the facts available, the conclusion seems warranted that the underground waters descend to the seas from the high lands and remain free from admixture till the pressure of the ocean exceeds that of the descending stream, when a commingling of the two liquids results. When the ocean pressure becomes greater, because of excessive pumping, the brine will increase in amount. In a smaller island the ocean water will force itself inland quite conspicuously. Molokai illustrates this proposition. Our information is derived from a report of Waldemar Lindgren in the Water Supply and Irrigation Papers No. 77. The springs there are of three classes, of which only the first calls for sideration here, (I) those very near the shore, (2) those break ing forth up to the height of 2,000 feet, (3) running streams still higher.
Shallow wells near the shore show the following degrees of salinity or number of grains per gallon, 238, 403, 15o, 126, 109, 86, 102, 86; of deeper wells the first gave eighty-six grains at the surface and became ocean water at fifty feet. The second became ocean water at one hundred and twenty-five feet. At Naiwa there are ninety grains of salinity at seventy feet. At Kalamaula several deep wells gave one hundred and two and one hundred and four grains and pure ocean water. The American Sugar Company sank several deep wells at Kaunakakai, of which the first five had one hundred and fifty grains per gallon ; others ranged from two hundred and seventy to four hundred and eighty five grains. The Risdon wells yielded seventy to seventy-nine grains per gallon. Better results appeared in nine wells sunk at Kawela, many of them showing less than fifty grains of salinity.
The fresh water is contaminated up to four or five feet above the sea level. None of the underground streams can be more than eight miles in length, and many do not exceed three. It is also probable that no impervious layer protects the underground water as in Oahu.
6. There are springs of fresh water near the sea shore in Oahu which correspond to the artesian fountains. One is the famous Kamehameha Bath near Punahou, a second is near the railroad station at Honolulu, and a third gladdens the thirsty soul at Waialua near the Haleiwa Hotel. Another is at Niu, west of Koko Head. It would seem that the underground water finds its way to the surface through some crevice, after the usual manner of springs, and that it is powerful enough to prevent the com mingling of the ocean water with it.
The theory of the subterranean stream from the summits to sea level has been further tested practically by the driving of tunnels to reach the water near its source. Thus derived the water is free from any possible saline contamination, and being delivered by means of a ditch sloping downwards, the expense of sinking artesian wells and the subsequent pumping is saved. In this wa) a copious daily flow has been obtained from the Waianae side of Kaala, utilized to run a dynamo, besides irrigating several planta tions. A second is to be found upon the Oahu plantation. On Maui near Lahaina, a six-million-gallon daily flow is derived from the altitude of 2,60o feet through a tunnel of the same length. There are no springs nor other signs of underground water along the route. It must be permanent, as the flow has been constant for the past two years. Other examples could be cited.