elevatory movements and corresponding depressions were continued incessantly at intervals to a very recent period, (and, indeed, there is evidence that they have not yet ceased in our own latitudes in Europe,) while, on the other hand, very few instances are known of extensive dislocation affecting the beds newer than the magnesian limestone in the British islands, at any period except that one marked by the commencement of the tertiary series of deposits.

There are no means whatever by which we can at present determine how long a time elapsed between the conclusion of the first great series of deposits in England and the commencement of the next; nor is it for us to assert that the wild and chaotic confusion resulting in all those violent dislocations of the hardest strata, which we so readily observe, was in any way inconsistent with the existence of life in many other parts of the world, now, perhaps, covered with hundreds of fathoms of salt water. But I would not dwell on this possibility, for I wish only to speak of what is known; nor can it be necessary to wander into the field of conjecture or romance, in order to obtain a striking picture of a former state of existence which shall exhibit all the charm of novelty, both in the outline and colouring. Without any such conjectures, of one thing at least we are certain: that during this interval, whatever it may have been, and however it may have been occupied in various parts of the world, every species of animal, and almost every vegetable, seems to have been replaced by some new one, not differing much perhaps from the former, or performing another office, but yet different,-exhibiting an instance of the rich variety of nature, and an effect

of that law of universal dissolution which appears to influence species, as well as individuals, allotting to each its appointed time, and causing each to pass through the different phases of imperfect development, full growth and vigour, and then gradual but certain decay and death.

Little as the transition from the rocks of the older to those of the secondary period is marked by mineral changes in the strata, this total difference in the nature of the organic remains is far too important to be passed by without notice. Both the upper part of the magnesian limestone series, and the strata that are superimposed, consist of sands often loosely aggregated, but sometimes hardened into stone by the infiltration of oxide of iron or some other cementing medium. Neither of these beds is prolific in fossils, but each contains a few; and this is the case as well in England as on the Continent, where the development is much more remarkable, and where the beds contain many more fossils. The difference between the organic remains of the two beds is, however, total, and in fishes is carried even into a point of structure which seems to be connected, though in an obscure way, with the whole organization of the class.* The vegetation, too, of the newer period is distinct; and the introduction of reptilian animals in great abund

* In the fishes met with in the older rocks the vertebral column is invariably continued to the extremity of the tail (fig. 42); and the upper lobe of the tail-fin, into which the back-bone extends, is larger than the other. In the rocks of the secondary period, the vertebral column does not extend into the tail, but the tail-fin is generally unsymmetrical, the upper lobe being the largest. In more modern fishes the tail-fin is perfectly symmetrical in every respect (fig. 43).

ance, and of large size, offers a characteristic of considerable interest.

I have been the more anxious to mark the existence of this break in the general continuity of the various strata, because, unlike that occurring after the deposit of the chalk, it is by no means distinctly visible to every one, nor is it altogether understood even by many Geologists. It is, however, almost equally important with respect to the great standard of comparison, that of organic life, and its conditions have been worked out carefully, although they have only lately been so satisfactorily proved as to admit of confident and direct assertion. One reason of this may perhaps be, that of the disturbances ultimately so effective we see in some cases the first small commencement, and are enabled to trace the gradual change in the general character of the deposits, and perceive the mineral structure of the beds insensibly adapted to the new state of things. Another reason undoubtedly is, that the changes produced on the older rocks after the deposit of the carboniferous sys

tem, are very much hidden and covered up, in consequence of their long exposure to aqueous action, and perhaps also to the atmosphere, during the countless ages that have elapsed since the commencement of the secondary epoch of creation.

We pass on now from the consideration of this chapter in the world's history. We have seen, first of all, how the earth lay buried in the dark obscurity of its early state, when the only rocks of mechanical origin consisted of huge masses of decomposed and pounded granite, broken into fragments by the disruption of the first thin shell of solid matter; and in these deposits no evidence has yet been obtained of any created thing having existed, either animal or vegetable. We have traced the history from this time through the period when a few worms crawled on the mud and sand of the newly-made shores of the ocean, when to these were added other lower forms of animal existence, and when marine vegetables first contributed to the subsistence of its inhabitants. We have watched the appearance of its denizens, as they, one after another, or in groups, present themselves, and have seen how different were these from the present tenants of the sea, and yet how like them, and how evidently and admirably adapted to perform the part assigned them; and we have thus gazed upon the first doubtful and misty appearance of light and life, as they have become visible in the morning of creation by slow degrees, and through a long twilight. Trilobites, brachiopods, shell-fish of various kinds, are seen to abound; and the cuttle-fish, or creatures nearly allied and not so highly organized, reign for a time undisputed lord of the sea. At length their reign terminated; other

animals, of higher and more complicated functions, succeeded, and the waters, after a long preparation, became fit for the presence of fishes. These, at first of small size and comparatively powerless, soon increased rapidly, both in number and dimensions, and, encased in their impenetrable armour, seem to have delighted in the troubled ocean where the coarse conglomerate of the old red sandstone was being accumulated; and for a long while these less perfect species of the class were predominant. In time, however, other fishes sprung up, the old ones were displaced, and a new, vigorous, and powerful group of animals came into the field, endowed with exuberant life, and darting with speed and with almost irresistible force through the water. Land, also, richly clothed with vegetation, even to the water's edge, contributed to support this abundant flow of life; and some few land animals of high organization appear to have been associated with the insects and the fresh-water animals whose remains have been preserved. But few, indeed, were the tenants of the land, so far as we can judge, when compared with those of the ocean; and while we have in so many parts of the world a rich supply of the vegetable remains of that period, there are only to be quoted the fragments of a scorpion, one or two foot-marks, and such like indications that nature was not inactive, though the conditions for preserving any terrestrial animal remains were so eminently unfavourable, that there is only just sufficient evidence to satisfy us of the fact.

The conditions of aqueous deposit were, however, more advantageous, so far as marine animals were concerned; and during this period, and especially towards