The Kilauean magma column consists of (1) hypomagma below, in which gases are still in solution, which grades upward into (2) pyromagma (making up the lava lakes), in which gases are separating, causing vesiculation; and (3) epimagma (the "bench magma" surrounding and underlying the lakes), which consists of incandescent but semisolid material in which gases are no longer expanding. Two convections exist, one caused by vesiculation in the pyromagma, the other by sinking of masses of epimagma. Tumescence of the hypomagma is propagated in directions of least loading wherever vesiculation can occur. Linear expansion of the perilith, the solid rock surrounding the magma column, by gas heating, may contribute to tumescence. Tumescence is associated with harmonic tremor and causes tilt of the surface away from the volcanic center during several weeks preceding eruption. Lowering of the magma surface is accompanied by a reverse tilt and is often preceded by earthquakes from the Mauna Loa rifts. In addition to the effects of magmatic activity, tilting of the ground occurs from diurnal heating and from solar and lunar effects seen as quasi-rhythmic quarterly and monthly patterns. Lava movements show similar rhythms; culminations of lava rise lag a little after equinox, and lava troughs appear to be reactions following the equinox effect and occurring somewhat after solstice. Jaggar notes that local earthquakes occur less frequently but have higher magnitudes when lava level is low and constant; earthquake counts increase but maximum magnitudes are lower during periods of inflation or deflation. Jaggar discusses the mechanism of formation of pahoehoe and aa, and he describes all the major Hawaiian mountains. The Kohala cliff is due to faulting, and the whole block back to the head of Waipio Valley has moved downward. Kilauea and Hualalai are regarded as older than Mauna Loa. This is an important reference for modern study of the Kilauea magma system. Jaggar realized the importance of lava lake observation in defining the character of the Kilauea plumbing system. His interpretations, using different terminology than we would today, are not altogether consistent with modern observation. Yet the observations are given in sufficient detail to make a positive contribution to our current understanding of the processes of magma accumulation, eruption, and subsequent flow.