CAUSES OF TRANSITION INVESTIGATED. 435 respond to, and are pictured in, the alternate strata of rocky detritus, and of organic exuvia, which compose the masonry of secondary formations. Each crisis of chemical deposit, and mechanical transformation, would occasion a sudden and very considerable abatement of terrestrial temperature. But we must present this important subject in a systematic form. The facts related in the preceding chapters of this work seem fully adequate to establish the four following propositions on sure grounds. 1. That a great portion of the present dry lands, more particularly the secondary strata which are replete with sea shells of the most delicate texture, distributed entire in regular beds, have lain for a long period at the bottom of the primeval ocean. 2. That within the schistose crust of the globe, explosive materials exist, which have given evidence of their convulsive and disruptive powers in all its terraqueous regions and in every age of the world from the protrusion of the primordial dry land, till the present day. 3. That the ocean at whose bottom many of our present earthy strata were deposited, has not been lessened by dissipation of its waters into celes flow from them; but they remain for many centuries inactive, and as it were asleep. Vesuvius had lain extinct from time immemorial, when starting all at once from its long lethargy, it suddenly rekindled its fires, under the reign of Titus, and buried the cities of Pompeii, Herculaneum, and Stabii, under its ejected products. It began to slumber once more at the end of the 15th century; so that in 1630, when it resumed an active state, its summit was inhabited, and covered with extensive forests. The inhabitants of Catania treated as fabulous what history related of the eruptions of Etna, when their city was ravaged, and partially destroyed by the fires of this volcano.-D'Aubuisson, vol. I. p. 163. tial space, or by their absorption into the bowels of the earth. 4. That, therefore, its channel must have been changed by transference of, a great portion at least, of its waters from their ancient to their present basin; an effect referrible to volcanic agency, which has operated by sinking the old lands, and upheaving the new. This transflux of the ocean mass could not be effected unquestionably, without the most violent fractures and dislocations of the terrestrial crust. Of the disorders and even metamorphoses of the earth's surface, coincident with these great changes of the sea channel, geology furnishes innumerable proofs, in mountain, valley, and plain. Many of these eruptive phenomena, indicate a succession of catastrophes an alternation of marine and freshwater floods, over no inconsiderable districts of the globe, at a period anterior to the penal cataclysm described by Moses; the last and greatest of that convulsive series. This flood was not partial like its predecessors, which left the contemporaneous breeds of animals alive, to be inhumed in the superior beds; it was manifestly universal, since all the animal remains buried in its detritus, belong to species now extinct, which, however closely allied to our existing genera, left no posterity on the earth. As we rise in the order of mineral superposition, or advance in geological time, we perceive a progressive approximation in the crasis, so to speak, as well as in the productions of the earth, to its modern condition in these respects. Thus in the lias and oolites, even up to the chalk, every thing organic H TERRAQUEOUS CONSTITUTION UNSTABLE. 437 speaks plainly of a fervid climate, actuating both the land and waters, of these high latitudes of ours. But the tertiary strata of England and France bear record to a marked abatement of heat, some time prior to the deluge. The organic exuvia which they contain, belong to a genial indeed, but not a torrid zone. In addition to the results of the successive interpositions of non-conducting media, between the ocean and its subjacent fires, in lowering the surface temperature of the globe, we must take the following phenomena into account. By each series of explosive dislocations of the terrestrial crust, the area of the "land standing out of the water" would be abridged, that of the sea would be amplified, with a proportionate diminution of its depth; or in other words, the cooling surface would be augmented, at the expense of the heating surface, while the ocean would come to repose as we have seen on a cooler bed, because more distant from the central heat of the earth. These propositions we shall endeavour to place in a clear and certain light by an ample induction of facts. In a revolving terraqueous sphere, deviating from the equilibrium form of rotation, by its elevated lands and deep ocean beds, at every considerable disruption and comminution of its surface, the gravitating powers will become effective on the shattered shell, and arrange its fragments, so as to make the crust approximate more nearly to the geometrical spheroid. The mountain and tableland masses will thus be strewn over the concave bottom of the seas, and cause a new distribution of the waters round the sphere; in which the area of the dry land will be diminished proportionally to the extent and duration of the disruptions. Supposing the earthquakes and consequent comminution of the shell, not partial and successive, but universal and synchronous, then the whole crust of the earth having its cohesion destroyed, for a season, would forthwith obey the gravitating forces on a revolving sphere, would assume the spheroidal figure of rotation, and remain universally circumfused with water, as under the primordial abyss. But a partial and successive series of disruptions of the crust, will cause only a partial approximation to that ultimate figure, accompanied with a transient deluge of greater or less extent over the surface. When the explosive commotions cease, the ocean undulations will subside, the sea will flow back into larger but shallower basins, and the dry land will again appear, furrowed, and strewed over with the detritus of the storm. This view of a diluvial transition, in my apprehension, can hardly be deemed hypothetical, resting as it does on the joint bases of geological facts and physical laws. The change in the globular figure, and terraqueous distribution, resulting from the fractured strata, may be illustrated by a simple experiment. If we hold a powerful magnet, a little way above a surface of iron filings, strewed upon a table, no change will ensue, because the friction between the solid plane, and the particles, is equivalent to a cohesive force, and prevents them from obeying the magnetical attraction. But if we momentarily suspend the counteracting force of friction by causing the table to vibrate with successive blows, SEA INCREASED AT THE EXPENSE OF LAND. 439 then the magnetical attraction will become effective, and the iron filings will arrange themselves in beautiful curves, accordant with the known laws of magnetism. In like manner the partial disruptions and tremors of the terrestrial strata, during its transition diluvial state, would permit a corresponding portion of its shattered surface to arrange itself, conformably to the centripetal and centrifugal powers under which it revolves, and cause a partial approximation in its figure, to the oblate spheroid of rotation. Indeed, without reference to any refined physical law, every one will see how in a bouleversement of mountain land, standing out of water, the debris would be distributed over the bottom, so as to spread the waters more widely. In considering the causes of these mighty revolutions, which have subverted the outer frame work of the ancient world, and which seem to have occasioned many unrecorded inundations, before the universal deluge, we must be careful to distinguish between the effect of a moderate expansive force acting within the crust of the earth, and that of a very great one; the former, like the late earthquakes in Chili to be presently described, sufficing merely to raise in an unbroken plain a large tract of land, while the latter would shatter the shell into fragments, and lay them prostrate under the equilibrating powers of gravitation in a revolving sphere. Thus to compare great things with small, a moderate blast of gunpowder, under a stratum of freestone, in a cliff, will be adequate merely to lift it along with its superjacent soil; but a greater explosion will break it into |