(319.) Besides the rocks which carry this internal evidence of submarine deposition, are many which exhibit no such proofs, but on the contrary hold out every appearance of owing their origin to volcanoes or to some other mode of igneous action; and in every part of the world, and among strata of all ages, there occur evidences of such action so abundant, and on such a scale, as to point out the volcano and the earthquake as agents which may have been instrumental in the production of those changes of level, and those violent dislocations which we perceive to have taken place. (320.) At all events, in accounting for those changes, geologists have no longer recourse, as formerly, to causes purely hypothetical, such as a shifting of the earth’s axis of rotation, bringing the sea to overflow the land, by a change in the place of the longer and shorter diameters of the spheroidal figure, nor to tides produced by the attraction of comets suddenly approaching very near the earth, nor to any other fanciful and arbitrarily assumed hypotheses; but rather endeavour to confine themselves to a careful consideration of causes evidently in action at present, with a view to ascertain how far they, in the first instance, are capable of accounting for the facts observed, and thus legitimately bringing into view, as residual phenomena, those effects which cannot be so accounted for. When this shall have been in some measure accomplished, we shall be able to pronounce with greater security than at present respecting the necessity of admitting a long succession of tremendous and ravaging catastrophes and cataclysms,--epochs of terrific confusion and violence which many geologists (perhaps with justice) regard as indispensable to the explanation of the existing features of the world. We shall learn to distinguish between the effects which require for their production the sudden application of convulsive and fracturing efforts, and those, probably not less extensive, changes which may have been produced by forces equally or more powerful, but acting with less irregularity, and so distributed over time as to produce none of those _interregnums_ of chaotic anarchy which we are apt to think (perhaps erroneously) great disfigurements of an order so beautiful and harmonious as that of nature.