ceous iron ore. 'A formation,' adds our author, 'that is at once the vehicle of two such valuable mineral productions as coal and iron, assumes a place of the first importance among the sources of benefit to mankind; and this benefit is the direct result of physical changes which affected the earth at those remote periods of time, when the first forms of vegetable life appeared upon its surface.'

Resting on the transition rocks, and therefore believed immediately to succeed them in the era of their deposition, come the rocks of what has been called the secondary epoch, during which, along with a distinct and peculiar vegetation, animals have existed, chiefly the inhabitants of the waters, or saurian reptiles, of gigantic forms, partly marine, partly amphibious, and partly terrestrial; and at the same period also, have lived mammalia of the marsupial order, and some testudinata and feathered tribes; as not only their petrified remains, but what is still more remarkable, the marks of their footsteps on sandstone have recently been found to testify. Dr. Buckland, in speaking of fossil Testudinata, says, ' The remains of land tortoises have been more rarely observed in a fossil state. Cuvier mentions but two examples, and these in very recent formations, at Aix, and in the Isle of France. Scotland has recently afforded evidence of the existence of more than one species of these terrestrial reptiles, during the period of the new red or variegated sandstone formation. The nature of this evidence is almost unique in the history of organic remains.' In a foot note he states that a discovery of fossil footmarks, similar to that made at Corncocklemuir, which was communicated by me in 1828, to the Edinburgh Royal Society, has recently been made in Saxony, at the village of Hessberg, near Hildburghausen, in several quarries of grey quartzose sandstone, alternating with beds of red sandstone, nearly of the same age with that of Dumfriesshire, of which notices have been given by Dr. Hohnbaum, Professor Caup, and Dr. Sickler. In another place he also mentions foot-marks of several extinct species of birds, having very lately been found by Professor Hitchcock, in the new red

sandstone of the Valley of Connecticut, one of them of a species of enormous dimensions, which took a stride of six feet. On the subject of these discoveries, with particular allusion to that in Corncocklemuir, Dr. Buckland has the following elegant observations: The historian or the antiquary may have traversed the fields of ancient or of modern battles, and may have pursued the line of march of triumphant conquerors, whose armies trampled down the most mighty kingdoms of the world. The winds and storms have utterly obliterated the ephemeral impressions of their course. Not a track remains of a single foot or a single hoof, of all the countless millions of men and beasts, whose progress spread desolation over the earth. But the reptiles that crawled upon the half-finished surface of our infant planet, have left memorials of their passage enduring and indelible. No history has recorded their creation or destruction; their very bones are found no more among the fossil relics of a former world. Centuries and thousands of years may have rolled away, between the time in which these footsteps were impressed by tortoises upon the sands of their native Scotland, and the hour when they are again laid bare, and exposed to our curious and admiring eyes. Yet we behold them stamped upon the rock, distinct as the track of the passing animal upon the recent snow; as if to show that thousands of years are but as nothing amidst eternity;-and, as it were, in mockery of the fleeting perishable course of the mightiest potentates among mankind.'

To the secondary period, again, is believed to have succeeded another epoch, during which rocks, of what is called the tertiary formation, have been deposited, and animals, as well as plants, of a larger and more perfect kind, and approaching nearer to those of our own era, have existed.

The tertiary epoch has recently been divided into four periods, founded on the proportions which their fossil shells bear to marine shells of existing species. During the first period, these productions exhibit but a small resemblance to our present orders, but this resemblance increases through

each successive period, till the greater proportion of the fossil species come to bear a distinctly marked affinity to present existences. A similar remark may be made with regard to the inhabitants of the land. By far the greater proportion of the genera which existed during the earliest period of this epoch, are now extinct, while the terrestrial animals of the latest period have very generally antitypes in the living species of our own era. 'It appears,' says Dr. Buckland, 'that at this epoch the whole surface of Europe was densely peopled by various orders of Mammalia, that the numbers of the herbivora were maintained in due proportion by the controlling influence of carnivora; and that the individuals of every species were constructed in a manner fitting each to its own enjoyment of the pleasures of existence, and placing it in due and useful relations to the animal and vegetable kingdoms by which it was surrounded.' He then concludes his obser vations on the tertiary series with the following just and striking remarks :-'Every comparative anatomist is familiar with the beautiful examples of mechanical contrivance and compensations which adapt existing species of herbivora and carnivora, to their own peculiar place and state of life. Such contrivances began not with living species. The geologist demonstrates their prior existence in the extinct forms of the same genera, which he discovers beneath the surface of the earth; and he claims for the Author of these fossil forms, under which the first types of such mechanisms were embodied, the same high attributes of wisdom and goodness, the demonstration of which exalts and sanctifies the labours of science, in her investigations of the organizations of the living world.'

This latter period is believed to have immediately preceded the Mosaic creation, and to have ended in some universal catastrophe, which entirely broke up and deranged the whole face of the earth, destroying all vegetable and animal life, and reducing the whole materials of the globe to that state of chaos which the sacred historian so briefly, but emphatically describes, when he says, that 'the earth

was without form and void, and darkness was on the face of the deep.'

It would be inconsistent with my plan to enter, with any minuteness, into a detail of the arguments by which geologists maintain the truth of these views; but I may mention, in a single sentence, that the rocks called primary, obtain this name, because, though they frequently are found to have burst through all the other strata of which the crust of the earth is composed, and even to overtop them all, forming our most elevated mountain ranges, yet they uniformly dip deeper down below the earth's surface than all the rest, and form the substratum on which the others recline. Immediately above these, lies the transition deposit, then the secondary, and then the tertiary formations. The obvious conclusion is, that, if we may at all suppose successive periods of deposit, these periods must have occurred in the order we have described; and the existence of peculiar forms of organized beings, connected respectively with these periods, while it strangely excites curiosity, and gives a very deep and mysterious interest to the subject, by opening up, as it were, a glimpse into former worlds, cannot readily be accounted for in any other way than by the hypothesis of successive epochs. and successive creations. If, indeed, the plants and animals of one formation were found intermingled with those of another, there might be some ground for hesitation. But this is not the case; and, what is particularly worthy of remark, it appears that the whole individuals of the organized beings, which existed during those primeval periods, had been des troyed before the era of the Mosaic creation, none of such species being in existence at the present day.

What a surprising, and at the same time consistent, view does this unfold, of the operations of the Eternal Mind. We have been accustomed to think of the Self-existing Being as only beginning to exert his creative energies, within the last six thousand years, when our globe was brought out of a state of chaos, and the human race was formed. But it is natural for the inquiring mind to ask, if it be indeed true that

an eternity had passed before the Almighty displayed his perfections, by calling worlds into existence, and exercising over them that paternal care which is so conspicuous and so endearing in the present state of things. This inquiry we may not be able satisfactorily to answer; but it is undoubtedly a step towards the solution of the question, to discover, that the materials of which the present earth is composed, have been employed by the Creator, in previous periods of unknown but vast duration, in the formation of other worlds, of which other beings, strangers to the existing earth, were denizens; and we seem to acquire a more sublime idea of the Divine perfections, when we think of those primeval times, in which plants and flowers, now totally unknown, adorned the face of nature, and rose to luxuriance under warmer suns; in which animals of different forms and species, roamed the woods and forests; and in which the ocean rolled its billows, and the finny tribes found food and enjoyment, where now fertile fields wave with grain, and the lofty trees of the forest throw their boughs towards heaven, and man and beast tread the solid ground.'*

THIRTEENTH WEEK-TUESDAY.

III. GEOLOGY.-SUCCESSIVE PERIODS OF ORGANIZED EXIS

TENCES.

If the view of our modern geologists, which I have adopted, be correct, there is something- exceedingly interesting, and certainly, as I have already observed, not inconsistent with the character of the Creator, as we read it inscribed on His works, in the gradual development of the powers of nature, and in the adaptation of living beings to the progress of that development. 'In the beginning,' the earth was, according to this hypothesis, created a mass of inert matter, perhaps in a liquid state from excessive heat, but crystallizing

* Study of Nature, p. 202.