Rather than seek an explanation from agencies exogenous to our earth, we might perhaps with advantage appeal to the endogenous phenomena of our planet. When the barometer falls, which we have shown corresponds to an upward motion of the earth’s crust, we know, from the results of experiments, that microseismic motions are particularly noticeable. As a pictorial illustration of what this really means, we may imagine ourselves to be residing on the loosely fitting lid of a large cauldron, the relief of the external pressure over which increases the activity of its internal ebullition—the jars attendant on which are gradually propagated from their endogenous source to the exterior of our planet. This travelling outwards would take place much in the same way that the vibrations consequent to the rattle and jar of a large factory slowly spread themselves farther and farther from the point where they were produced. Admitting an action of this description to take place, it would then follow that this extra liberation of gaseous material beneath the earth’s crust would result in an increased upward pressure from within, and a tendency on the part of the earth’s crust to elevation. If we accept this as an explanation of the increased activity of a tremor indicator, then such an instrument may be regarded as a barometer, measuring by its motions the variations in the internal pressure of our planet. The relief of external pressure and the increase of internal pressure, it will be observed, both tend in the same direction—namely, to an elevation of the earth’s crust. This explanation of the increased activity of earth tremors, which has also been suggested by M. S. di Rossi, is here only advanced as a speculation, more probable perhaps than many others.