ON the occasion of the centenary of the Franklin Institute in 1924, Dr. A. L. Day delivered an address on volcanic activity, which appears in the journal of the Institute for August 1925. It is well known that the crater of Mauna Loa is 10,000 feet higher than the lava lake of Kilauea. Since more lava emerges from the higher vent than the lower, and eruptions rarely occur simultaneously, it is clear that the two vents cannot be connected with a continuous liquid interior. The changes of level of the lava of Kilauea would show periodic tidal effects if there were a molten cauldron underneath, but they fail to do so. Moreover, the lava lake was recently drained to a depth of 1500 feet, and a solid relatively cold bottom was exposed. A number of channels leading in from below were detected on the side walls.