Indeed, the facts known as to geysers, and those of half-drowned-out Volcanoes such as Stromboli--whose action is intermittent just as much as that of a geyser--show that this is not merely probable. There is, therefore, no need for the hypothesis of those who have supposed all the huge volumes of steam blown off from Volcanoes in eruption to come from vesicular water pre-existent in the minute cavities of crystalline or other rocks before their fusion into lava: a fact not proved for many classes of rock, and for none in sufficient quantity to account for the vast volume of steam required and for the irregularity of its issue. It is rather to anticipate, but I may state at once that, so far as the admission of superficial waters to the interior, and to any depth to which fissures or dislocation can extend, I believe no valid physical or mechanical difficulties exist, taking into account _all_ the conditions that may come into play together. Another set of views has been suggested and supported by various writers, which proposes to account for the rise of lava on purely hydrostatic principles. The solid crust, fractured into isolated fragments by tensions due to its own contraction, is supposed to sink into the sea of lava on which it floats; and much ingenuity has been expended in imagining the mechanism by which, in places, the liquid matter is supposed to rise _above_ the surface of the crust. I have no space for discussing these views further than to assert that, in the existing state of our globe, and even admitting a solid crust of only 60,000 metres thick, dislocation of the crust by _tension_ is not possible. The solid crust of our globe, as I hope we shall see further on, is not in a state of tension, and has not been so since it was extremely thin, a mere pellicle as compared with the liquid nucleus, but is, on the contrary, in a state of _tangential compression_. However tenable, in other respects, may be the volcanic theory which rests upon the assumption of a very _thin_ crust and a universal ocean of fused rock beneath, it fails wholly to explain many of the most important circumstances observable as to the distribution and movements of existing Volcanoes on our globe. It affords no adequate explanation of the configuration of the lines of Volcanoes, nor of their occurrence in the ocean bed, nor of their existence in high latitudes, near the Poles, where, no matter how or at what rate our globe cooled from liquidity, the crust must be thickest; nor of the independence of eruptive action of closely adjacent volcanic vents; nor of the non-periodicity, the sudden awakening-up to activity, the as sudden exhaustion, the long repose, the gradual decay of action at particular vents, and of much more that might be stated and sustained as difficulties left by that theory unexplained, or that are of a nature even opposed to it.