Page:Popular Science Monthly Volume 67.djvu/684

676 which lifted the water about sixty feet. Later the wells are a foot in diameter in groups of ten for each pump. The water is forced through steel pipes twenty-four and thirty inches in diameter to a maximum elevation of four hundred feet. From various points ditches are dug which carry the water to every field of the plantation. The photograph, Figure 3, shows one of these pumping stations where there are twenty wells, each a foot in diameter. Though the pumps act without cessation, the water never fails; 5,000 acres of land are irrigated from these wells. The water here rises to the height of 22 feet above sea level.

5. These wells at Ewa are found to be slightly affected by the brine

of the sea. The natural waters of the island contain .0073 per cent, of salt according to Dr. Walter Maxwell; Pacific water holds 2.921 per cent, of the same. One hundred grains to the gallon of water represents 0.14 per cent. The analyst of the Ewa company found that the chlorine present (sodium chloride) was more abundant in the wells nearest the ocean. At station No. 1 the chlorine amounted to 17.61 grains in a gallon. At stations Nos. 2 and 3, farther inland, the chlorine had diminished to 8.18 and 11.97 grains to the gallon. By experiment at several localities it has been found that the salinity increases when the pumping becomes excessive. At Ewa it is stated that vegetation is not at all affected when the number of grains per