Nor are there evidences wanting, in existing volcanoes, of the intensity of the fires which still glow within the interior of our earth. There are at present more than TWO HUNDRED volcanoes in active operation; these are not confined to any particular zone, but are distributed like those of the older families through the different quarters of the world. The greater centers of action are situated in the mountain-ranges of South America, along the western coast of North America, and in the numerous islands of the Southern Pacific; but at the same time there is scarcely a portion of the earth’s crust that is not subjected to the shock of volcanic influence and the movement of earthquakes. There are two theories by which all volcanic phenomena are attempted to be explained. The more prevailing one among geologists is that which connects them with one great source of central heat—interior lakes of molten stone—the residue of that incandescent condition in which the globe originally appeared, and out of which the primary crystalline strata were formed. The other mode of explanation is that which supposes the internal heat to be the result of chemical and galvanic action among the materials composing the earth’s crust. The metallic and earthy bases, upon contact with water, everywhere transmitted through fissures and apertures on the surface, burn, melt, and are converted into lavaform matter, and which acting again as fuel, serve to fuse the rocks among which they occur. Hence various gases will be generated sufficient to occasion much local disturbance; though certainly not upon a scale to correspond with the magnitude, universality, and perpetuity of those changes that have resulted in the igneous products of the primary, secondary, or even tertiary formations.