Nature has reared. In this inquiry, history and tradition cease to aid us. No longer circumscribed by these, we must push forward into the great ocean of Time, and explore by the light of analogy the new world that lies before us.

STRATIFIED ROCKS.

OUR observations have hitherto been confined to the earth's surface, we have now to penetrate into its interior, to examine the monuments of past ages which Nature has imbedded in the solid masonry of the vast superstructure of the globe, as if to supply the chronologist or historian in after times, with dates and facts for its history, and preserve a record of events which would have been lost in the oblivious stream of time; in the same manner as in great works of architecture, coins, medals, and inscriptions, are placed in some indestructible portion of the building, in order that posterity may identify the period and circumstances of its erection, should all other records be lost. As we have before seen, Nature has not piled Pelion upon Ossa, or Ossa upon Pelion indiscriminately, as we might from superficial observation infer, nor has she reared a rude edifice of unshapen materials like the Cyclopean masonry, but throughout the great fabric of the earth has preserved a symmetrical arrangement and a unity of design; and in no portion of her work has she omitted to enclose some memorial of the circumstances and events of the period when it was produced.

The principal agent employed in the formation of

the stratified masses, appears to have been the ocean, or other large bodies of water, in which the materials of the rocky strata have been suspended and quietly deposited, and the innumerable inhabitants of that element, whose remains form in many cases a considerable portion of the consolidated substance, lived and died. But this sedimentary process has not gone on uniformly from the beginning of time: the ocean has not always continued to deposit layer upon layer of earthy matter; its operations have been interrupted and for a time suspended, and again renewed under different circumstances, by convulsions in the interior of the earth, or changes upon its surface. Thus after a long series of ages, during which it may have deposited an immense mass of calcareous matter, the bed is perhaps upheaved, the sea is dispossessed of its dominion, and land animals and plants flourish on the oozy mass, where shells and fishes had before luxuriated.

It is this alternation, this succession of distinct operations, which has produced the series of stratified masses, which it is now our business to examine, and an enquiry attended with more interesting results never occupied the mind of man. For we soon discover that it is not merely the inorganic matter composing the earth's crust which has been remodelled in these geological changes, but that the animated creation has experienced still greater mutations, many species of animals being entombed in the strata which no longer exist upon the earth. Both sea and land appear to have been peopled with distinct races of inhabitants at successive periods, as every formation contains the remains of organic beings peculiar to itself. These organic relics

are not found in the same state as those of a more recent period-the elephants' tusks and bones of the diluvial gravel, and the osseous caves, which we have hitherto examined; but in all cases, the substances, whether animal or vegetable, have undergone petrifaction-the most delicate plant, the microscopic shell, and the hardest bone, being alike converted into the material of the rock in which they are preserved. How this metamorphosis was produced, by what process of transmutation the original elements were replaced, atom for atom, by matter in some cases so dissimilar-as for instance, vegetable matter converted into silex, or animal substance into sulphuret of iron-without destroying or in the least defacing their external configuration, is an interesting inquiry for the chemist, but it appears to be one of those secret operations conducted in Nature's laboratory, which we shall never perfectly understand. It is from these records, engraven upon stone, as it were by the finger of the Deity, that geologists have been enabled to frame a chronology of the earth, to assign certain periods to certain events, to trace the history of organized beings through a countless succession of ages, up to the period when the Omniscient fiat first said "Let there be life upon the earth," to ascend, in fact, the stream of time almost to its source. But in an inquiry so vast, involving a succession of events so complicated and remote, united by insensible gradations, where shall we commence and how measure our progress?

There being throughout the mineral masses a regular order of superposition, and an apparent gradation in the fossil organic remains which they contain, indicative of their respective ages, we ought in the

highest of the series to find the nearest approach in their organic contents, to the existing animals and vegetables of the countries in which they are situated. Now, were we to examine the bed of the ocean, we should find it filled with shells and other organic remains of animals, corresponding precisely with those which now inhabit it; but extending our observations to the elevated coast which skirts it, our eastern coast for instance, we discover a similar accumulation of sedimentary matter, (the English crag,) containing a large proportion of fossilized shells of the same species as those now existing in the sea below, but including also others, of which there is no existing types; and looking further inland, we see rising from beneath the crag another more extensive deposit, formed at an earlier period beneath the ocean, in which the number of shells corresponding with living species is considerably fewer, and as our observations are continued, the analogy ceases altogether, and the existing species entirely disappear. With the most recent of these formations, therefore, we commence our inquiry, and go back through these various gradations to the oldest and lowest in the series of fossiliferous rocks.

Until a recent period, the newest of the rock formations was supposed to be the chalk, but a most interesting series of beds,, which exhibit, in a remarkable manner, the retrogression in their organic contents to which we have just adverted, is known to geologists as the supracretaceous group, a term recently adopted, which expresses their position-supra upon, creta the chalk-they being invariably found resting upon that remarkable rock, which, previous to the deposition of