Ordinarily these outlets are along cracks or rifts in the slope of the mountain, where they are seen to break out in gassy fountains 500 feet high, and often to flow along the crack to a cavity where they cascade downward when less foamy and heavier. A lava flow is always solving a problem of foaming and liquefying, just as does champagne or beer. There still remains the unsolved problems of how much of the deep lava is gas and whether it is mere pressure which holds the gases in solution, as in soda water. The alternative is for the deeper magma to be entirely gas, oozing up cracks in the globe, and reacting with oxygen from the air and solid rock, percolating from the core of the earth upward, and melting its walls. In a sense, the entire decade to 1920 was an experiment. The results of that decade showed that the mountain swells and shrinks in tides with the passages of the sun and moon, but that Kilauea Mountain and Mauna Loa Mountain are all parts of what might be called Hawaii Island Mountain. The island of Hawaii is above an old ocean bottom 18,000 feet deep and is only the end of a ridge 1,700 miles long, which even at its lowest end, Midway and Ocean Islands, is still 12,000 feet high above the smooth mud-over-rock ball of the Pacific Ocean bottom. All the evidence shows the ridge to be a pile of lava flows over a crack, with a veneer of coral. If, then, the relatively small Kilauea dome is swelling and shrinking in sympathy with the sun, the long Hawaiian ridge is doing the same thing to a much greater degree. Michelson has shown that the solid rock of the globe rises and falls in a tide about one foot every half day. As I have said, our daily measurements in 1912 showed that the lava in Halemaumau had a daily tide and that the larger movements reached maxima in June and December and minima in the intervening months, which proved it must be a solar effect. This was very exciting information and suggested a long train of experiments, which were to be successful in the next decade, based on the idea that the whole mountain swells as shown by leveling. This extends out to a radius of twenty miles from Kilauea Crater, and probably extends all the way to the seashore. The actual measurement of a lava tide in Halemaumau was done during July and August 1919. R. H. Finch had just come from Washington to be my assistant. Oliver Emerson of Honolulu was another assistant, and two Harvard youths, Sumner Roberts and Charles Thorndike, who had been on war missions in submarine chasers, sent word through their parents that they were anxious to do something dangerous around an active volcano. I jumped at the chance to employ them to help me measure the lava tide.