"If we draw a line from the centre of Thibet, across Chinese Mongolia towards Ochotsk, and thence towards Cape Tchutscki, the eastern promontory of Asia, this line will in general coincide with a great chain of mountains which runs from the south-west to the north-east, and which every where descends rapidly towards the Indian and Pacific oceans, while on the contrary, it extends itself towards the Frozen ocean in high plains and secondary hills. It is probable that we may some day refer to the same rule the chain of Lapata, called the backbone of the world, in Africa; at any rate this chain runs from the Cape of Good Hope to that of Gardafui, in a direction south-east and north-west, and therefore in nearly the same direction as the great chain of Asia, but we are ignorant of the disposition of the slopes of these mountains. We may regard the mountains of the Happy Arabia, which are both steep and lofty, as the link that connects the mountains of Lapata with the table lands and mountains of Persia, which proceed from the mountains of Thibet."If we follow the western coasts of America, from Behring's straits, which hardly form a sensible interruption, to Cape Horn, we find an uninterrupted chain of mountains. From time to time this chain retires a little into the interior, but more frequently it immediately borders upon the great ocean, in immense cliffs, and often by frightful precipices. On the other side of it, the manner in which the lakes discharge themselves, and the direction of the great rivers, show sufficiently, that the surface of America inclines gently towards the Atlantic ocean."It results from a combination of these observations, that the greatest chains of mountains on our globe, are ranged in an arc of a circle around the great ocean, and the sea of India; that they seem to present rapid descents towards the immense basin they surround, and gentle slopes on their opposite sides; in fine, from the Cape of Good Hope to Behring's straits, and thence to Cape Horn, the eye of the most timid observer cannot fail to see some trace of an arrangement, as surprising from its uniformity, as from the vast extent of ground which it embraces."Let us pause for an instant to consider this great fact of physical geography. If we conceive ourselves placed in New South Wales, with our face turned towards the north, we have America on our right hand, Africa and Asia on our left. These continents, which we hardly before ventured to approach in our imagination, considered in this point of view, form a consistent system, whose structure, as far as we are acquainted with it, presents in its great features an astonishing symmetry. A chain of enormous mountains surrounds an enormous basin; this basin, divided into two by a vast collection of islands, often bathes with its waves the feet of this great primary chain of the earth."
"If we draw a line from the centre of Thibet, across Chinese Mongolia towards Ochotsk, and thence towards Cape Tchutscki, the eastern promontory of Asia, this line will in general coincide with a great chain of mountains which runs from the south-west to the north-east, and which every where descends rapidly towards the Indian and Pacific oceans, while on the contrary, it extends itself towards the Frozen ocean in high plains and secondary hills. It is probable that we may some day refer to the same rule the chain of Lapata, called the backbone of the world, in Africa; at any rate this chain runs from the Cape of Good Hope to that of Gardafui, in a direction south-east and north-west, and therefore in nearly the same direction as the great chain of Asia, but we are ignorant of the disposition of the slopes of these mountains. We may regard the mountains of the Happy Arabia, which are both steep and lofty, as the link that connects the mountains of Lapata with the table lands and mountains of Persia, which proceed from the mountains of Thibet.
"If we follow the western coasts of America, from Behring's straits, which hardly form a sensible interruption, to Cape Horn, we find an uninterrupted chain of mountains. From time to time this chain retires a little into the interior, but more frequently it immediately borders upon the great ocean, in immense cliffs, and often by frightful precipices. On the other side of it, the manner in which the lakes discharge themselves, and the direction of the great rivers, show sufficiently, that the surface of America inclines gently towards the Atlantic ocean.
"It results from a combination of these observations, that the greatest chains of mountains on our globe, are ranged in an arc of a circle around the great ocean, and the sea of India; that they seem to present rapid descents towards the immense basin they surround, and gentle slopes on their opposite sides; in fine, from the Cape of Good Hope to Behring's straits, and thence to Cape Horn, the eye of the most timid observer cannot fail to see some trace of an arrangement, as surprising from its uniformity, as from the vast extent of ground which it embraces.
"Let us pause for an instant to consider this great fact of physical geography. If we conceive ourselves placed in New South Wales, with our face turned towards the north, we have America on our right hand, Africa and Asia on our left. These continents, which we hardly before ventured to approach in our imagination, considered in this point of view, form a consistent system, whose structure, as far as we are acquainted with it, presents in its great features an astonishing symmetry. A chain of enormous mountains surrounds an enormous basin; this basin, divided into two by a vast collection of islands, often bathes with its waves the feet of this great primary chain of the earth."
In this chain lie the greatest mountains of the globe. One peak of the Himmalayah rises nearly five miles above the level of the sea; another has a height of 25,500 feet; and a third of 22,217 feet. In South America are Soratu, in height 25,250 feet.
Illimani,24,000Chimborazo,21,400
not to mention Antisana, Mauflos, Chillau, Cotopaxi, all of which exceed in height any mountains that do not lie in this great system. Nay, did not the great Volcano of Owyhee enter into the order with a height of 18,000 feet, the list of those surpassingthe other mountains of the globe, might be very much extended.
We shall have occasion hereafter to speak of the volcanic energies still exerted in this vast stony girdle, and shall therefore confine ourselves strictly to mere external form.
The arms and branches of mountain chains enclose as has been seen, basins marked by rivers which convey their surface waters to the ocean. The rains which fall on the sides of mountains and hills, unite in torrents and streams, which follow the lines of most rapid slope in their course to the sea.
The greater rivers mark the lowest part of a principal basin, on each side of which, at a greater or less distance, are to be found rising grounds, themselves hollowed out into lateral secondary basins, containing courses of water less considerable than the first, into which they cast themselves, and whose branches they are. The borders of these secondary basins are again hollowed out into basins of a third order, whose slopes also contain water courses less considerable than the preceding, into which they in turn discharge themselves. This ramification continues until we reach the smallest ravines of the boundary mountains, and the map appears, as it were, covered with a net work of rivers and lesser streams. The great valley of the Mississippi and Missouri, forms perhaps the most striking instance of this sort, upon the surface of our globe.
Rivers and streams are constantly exerting a mechanical action on the surfaces over which they run; abrading and tearing off fragments even of the hardest rocks, they roll them in their course until the velocity becomes insufficient to transport them farther. At diminished velocities they move fragments of less size, down to the smallest pebbles; at still less velocities, they transport sand, and finally earthy matter, in the most minute division. These are deposited in succession in positions corresponding to the rapidity of the stream, and hence the beds of rivers present at each of their different sections, materials of magnitude and quality corresponding to the rate at which the stream usually flows. The increase in the magnitude of streams, due to violent rains and the melting of the snows, changes the position of the substances that compose their bed, and the more easily suspended materials are often held until the stream actually meets the ocean. In such sudden increases, the streams often overflow their usual banks, and make their deposits laterally, until the constant succession of such deposits raises the adjacent ground high enough to set bounds to the further spreading of the stream. This deposit is remarkable for its taking place in greatest quantity close to the usual bed of the stream; and thus it speedily opposes natural dykes to its own redundant waters. This action is most conspicuousat points where marked changes take place either permanently or periodically in the rapidity of running water: when streams descend from mountains into lines of less descent, a deposit uniformly takes place, formingflatsorintervals, as they are styled in the United States, of which we have such beautiful instances in the valleys of the Connecticut and Mohawk, and that part of the Hudson near Albany; again, where rivers meet the sea, they are interrupted in their course by the rise of the tides of the ocean, and here again deposits take place, sometimes forming shoals and banks in the ocean itself; at other times, bars and obstructions at their own mouths; and again, deltas of solid land, constantly encroaching upon the sea. This action, which is continually going forward, is called alluvial. The delta of greatest fame, and from which the others have derived their generic name, is that of the Nile; this we have evidence, almost historic, to prove to be wholly the gift of the river. And if it no longer increase as rapidly as in former ages, the cause is obvious, for the alluvion has been pushed so far forward as to meet a strong current that sweeps along the African coast, and must carry off much of the earth the Nile discharges into the Mediterranean. The great rivers of Asia and of America carry still greater quantities of solid matter, but we have not the same distant traditions to refer to for the amount of the increase they have caused; still, however, we know that the mouth of the Mississippi has been advanced into the Gulf of Mexico several leagues since the settlement of Louisiana; and that islands of great extent are frequently formed, in the course of a single year, by the deposits of the Ganges.
We however find traces of aqueous action far more extensive and powerful than those which are now taking place under our eyes by fluviatile action. There is no part of the globe that has been examined, which does not show that it has been subjected to the action of water, in floods far more powerful than any we now are in the habit of seeing. Every where, except in the case of rocky cliffs, and steep mountains, or where we see obvious evidence of a recent elevation, we find the surface strewn with the deposits of water: boulders of greater or less size, beds of gravel, sand, and clay, form the present outer coating of the greatest part of the land. These deposits were long confounded with the alluvial, but have at length been proved, by incontrovertible evidence, to be the results of an action, which if not contemporaneous, must have been universal. We have seen an able attempt to show that this species of deposit did not take place at one and the same period, but was merely the general consequence of similar causes acting at different epochs. Our impression, we must however confess to be, that the action was not only co-extensive with the globe, but contemporaneous. It at any rate exhibitsproofs the most satisfactory, that the last great and extensive change which our earth has undergone, was effected by the agency of water, in a state of rapid and violent motion. Ascribing this deposit to a single flood, it has been styled diluvial.
There are cases where alluvial deposits rest upon the diluvium, and from the depth of these it has been attempted to calculate the time that has elapsed since the former of these actions was resumed. The diluvium has also been found in caverns lying upon an ancient stalagmite, and covered again with a new formation of that modification of carbonate of lime. The thickness of the latter deposit has also been made the basis of a calculation, and although neither of these methods is to be considered as approaching to an accuracy more perfect than some hundreds of years, the two methods confirm each other in the general result, which is, that, at a date not more remote than fifty or sixty centuries, there must have taken place a total submersion of all the land, except, perhaps, the tops of high mountains, did they then exist. We have in the sacred volume, a record of such a catastrophe, the flood of Noah, and from that time to the present, no convulsion, equally extensive in its influence, has devastated the globe. Have not then the geologists who have seen in these indications the convincing evidence of that occurrence, been warranted in their inference, of the identity of an event pointed out by undeniable physical evidence, with one recorded in a history to which one of the most confirmed sceptics has recently admitted the merit of truth?
The diluvial deposits are found not only in the lower grounds, but on the tops and sides of lofty mountains; we have ourselves noted them distinctly characterized at high elevations upon the Kaatskills; they are found among the Alps at Valorsine, 6000 feet above the level of the sea, and in another place at more than 7000 feet. The excavations made in the extension of the city of New-York at Corlaer's Hook, have laid open a vast mass of diluvium, and afforded means for studying it with great facility. It in fact presented the appearance of a great cabinet of specimens of primitive and transition rocks, and it was possible in many cases to determine the very mountain whence the fragments had been torn. The most remarkable boulder, for instance, of a weight of at least an hundred tons, was distinctly recognisable as identical in every respect with the granitic syenite of Schooley's mountain, distant at least forty miles. Others had no known type nearer than Connecticut, in the opposite direction, while the gneiss and mica slate of the island of New-York, with their various embedded minerals, the serpentine and many of the magnesian minerals of Hoboken, with sandstone and trap of the Pallisadoc range, were distinctly recognisable. In this great excavation, where a region of a mile square was whollyremoved, to a depth, in many places, of thirty feet, no animal remains, as far as can be learnt, were detected; thus marking a most important difference between these deposits and those of the Old continent. Such is the remark of an intelligent geologist, whom we are proud to reckon as ourcollaborateur, and to whom that branch of Natural History is under no small obligations.
"Fragments of granite and other primitive rocks, cast here and there upon stratified formations, and interpersed in diluvium,[10]present a fact as certain as it is astonishing. All the chains of Mount Jura, all the mountains that precede the Alps, the hills and plains of Germany and Italy, are strewn with blocks of granite, often of a great dimension, and always of a composition as pure, and as perfect a crystallization, as the granites of the higher Alps. The same phenomenon is repeated in the plains of Russia, of Poland, of Prussia, of Denmark, and of Sweden. From Holstein to Eastern Prussia, diluvial[11]grounds, sand and clay, are covered with an immense number of blocks of granite. Near the island of Usedom, several points of granite rock rise from the bottom of the Baltic. We see in like manner, Scania and Jutland so filled with these fragments, that they construct of them enclosures, houses and churches. In the Lymfiord, a gulf of Jutland, and at some places on the western side of that peninsula, great points of granite rise from the bottom of the waters. But what is still more remarkable, is to see immense masses of granite lying on the tops of Rœduburg and Osmond, which are more than 6000 feet in height, and are therefore among the highest mountains in the North of Europe."
"Fragments of granite and other primitive rocks, cast here and there upon stratified formations, and interpersed in diluvium,[10]present a fact as certain as it is astonishing. All the chains of Mount Jura, all the mountains that precede the Alps, the hills and plains of Germany and Italy, are strewn with blocks of granite, often of a great dimension, and always of a composition as pure, and as perfect a crystallization, as the granites of the higher Alps. The same phenomenon is repeated in the plains of Russia, of Poland, of Prussia, of Denmark, and of Sweden. From Holstein to Eastern Prussia, diluvial[11]grounds, sand and clay, are covered with an immense number of blocks of granite. Near the island of Usedom, several points of granite rock rise from the bottom of the Baltic. We see in like manner, Scania and Jutland so filled with these fragments, that they construct of them enclosures, houses and churches. In the Lymfiord, a gulf of Jutland, and at some places on the western side of that peninsula, great points of granite rise from the bottom of the waters. But what is still more remarkable, is to see immense masses of granite lying on the tops of Rœduburg and Osmond, which are more than 6000 feet in height, and are therefore among the highest mountains in the North of Europe."
Beneath the diluvial deposit, we find beds and strata of substances of different character, and which appear on a cursory view to be involved in inextricable confusion. Long and careful examination has at length been efficient in ascertaining that in this apparent disorder are to be seen the traces of an order, as perfect as that of any other mechanism of nature, and of a succession of changes by which the earth has been finally fitted for the habitation of man. These strata have been finally arranged into five distinct classes, differing in their characters and position. These have been so fully described in a former article in this Journal, by the distinguished associate whom we have already quoted, that no more remains for us to say, than what is merely necessary to keep up the connexion of our subject.
These stratified rocks or formations are remarkable for the regular order in which they succeed and overlie each other, furnishing distinct and indisputable evidence of their having been formed in succession. The first set of strata, which are never covered by any of the others, and hence are conceived to be of most recent formation, lie inclined at a small angle to the horizon. In many cases they do not assume the character of rocks, but although distinctly stratified, are often soft and friable, presenting beds of marle and clay, and thick deposits of sand. In some cases their appearance is so similar to diluvial or even alluvialdeposits, that they might be mistaken for them, were it not for their more regular stratification. These are the tertiary formations of the German school, the superior order of Coneybeare and Philips.
Issuing from beneath these, and forming in their turn a considerable portion of the surface of the earth, rising occasionally into considerable hills, are strata of less uniform and regular inclination, forming basins and cavities in which the tertiary deposits are often found to lie, curved to conform to the bottoms of these basins.
The third and fourth series issue in their turn from beneath the preceding, as does the fifth from beneath the fourth. Each is marked in succession, by a greater degree of confusion or distortion in the stratification, until the last, which is apparently upheaved and thrown about without any regularity, its strata being occasionally found in positions almost vertical. Not only is the succession of the five different orders of rocks constant, but so is that in which the several rocks of each series overlie each other. This regularity of succession is, however, subject to this law; namely, that rocks of particular orders, or even the whole order itself, may be wanting in particular districts; thus, tertiary formations may be directly upon the lower order, and the second, third, and fourth, may not be present; or any one of the higher orders may lie directly upon any one of those we have stated to be inferior to it; but it has never been observed that the arrangement itself has been inverted, or that a rock which is in one place inferior, becomes, in its turn, superior in another.
The fifth, or inferior order, is uniformly found beneath one or all of the others; and, we may infer, that it in fact underlies the whole surface of the globe, forming not only the foundation of the solid land, but the original bottom on which the present bed of the sea is deposited. The rocks that compose this series are all highly crystalline in their character, are mostly composed of substances wholly or nearly insoluble in water, are wholly devoid of organic remains, and are in fact such substances as might be supposed to have been formed by slow cooling, from a state of igneous fusion. Is it then assuming too much to infer, that they are in fact the crust which has been first formed upon the surface of the earth, intensely heated by its own condensation, under the action of the gravitating force, that, communicated to it by the hand of the Creator, determined its figure, and still maintains its equilibrium. We do not include in this class, as is usually done, the crystalline rocks not stratified, as we conceive them to have been formed in another manner, to which we shall hereafter refer. All the four higher series of strata show, in the most evident manner, that their formation has beendue to the action of water; the grauwacke is, perhaps, the only rock that exists among them, in which the question could, even on simple inspection of specimens, appear doubtful; but this rock lies at the base of the old red sandstone, and upon the limestone of the submedial order, or transition, as it is styled by the Wernerians, and is equally regular in its stratification with either; we cannot, therefore, admit any other cause of its formation than what is common to them.
Some of these strata are obviously mechanical, others chemical deposits; thus, the sandstones and conglomerates are certainly the products of the disintegration of older rocks by a violent abrasion of running water, and have settled when the currents have ceased to flow; all calcareous rocks, except the limestones of the inferior or fifth order, the primitive of Werner, on the other hand, appear to have been products of chemical precipitation; while there are a few cases, as in the beds of rock salt, where the deposit must have been due to evaporation.
Of all these rocks and formations, the primitive, as has already been stated, and the sandstones, are wholly devoid of organic remains. And even the last rule is to be received as not wholly free from exception; for vegetable impressions have been found, as we are credibly informed, in sandstone, at Nyack on the Hudson, and near Belleville in New-Jersey, besides some other similar cases we shall hereafter note. All the other strata present a greater or less abundance of the traces of the organic kingdoms, from the slate, which lies lowest of the fourth order, to the most recent beds of the tertiary, and to so much of the diluvium as has been examined in the old continent. And although in the isolated case of the diluvium at New-York, no fossil remains have been found, we are yet unprepared to admit this as more than an exception, and are inclined to think that the remains of the mastodon, for instance, must be diluvian, or pre-diluvian. In this opinion, however, we know that we are opposed by high authority, and therefore do not express it without hesitation.
"Organized fossil remains belong to three different classes: the remains that have preserved their natural state, at least in part; petrifactions; and impressions."The remains of the first class are principally bones, and even entire skeletons, which, after having been stripped of the skin and flesh that covered them, have remained, some buried in the earth, others hidden in deep caverns. They are, sometimes, calcined in whole or in part, without having lost their configuration; they at others preserve, not only their texture, but even some traces of their hair and skin. They are also occasionally seen covered with a calcareous crust."Petrifactions, to use this word in its familiar sense, include all stony bodies that have the figure of an organized body. There are cases in which a strong solution has penetrated into a cavity formed by an organic body that has disappeared. Then the strong substance has occupied the cavity that has been left empty, and has taken the external form of the body that formerly existed there.If this body were, for instance, a branch or trunk of a tree, the stone will have at its surface its knots and asperities; but within, it will present all the characters of a true stone; it will be no more, to use the language of Hauy, than the statue of the substance that it has replaced."At other times, a vegetable or animal substance, while undergoing decomposition in a successive manner, and by obvious degrees, is pressed by the petrifying liquid that already surrounds it. As soon as an organic particle has disappeared, its place is occupied by one of stone.""Metallized bodies, and those which have been changed into bitumen or carbon, belong to this system of formation; thus, the turquoises, for instance, are the teeth of a great marine animal; a metallic substance has penetrated them, and has gradually replaced the softer parts of the bones."Impressions are often found between the plates of slaty rocks; they are relievos or intaglios representing the skeletons of animals, particularly fish, leaves, seeds, and entire plants, of which the most common kind belong to the forus."
"Organized fossil remains belong to three different classes: the remains that have preserved their natural state, at least in part; petrifactions; and impressions.
"The remains of the first class are principally bones, and even entire skeletons, which, after having been stripped of the skin and flesh that covered them, have remained, some buried in the earth, others hidden in deep caverns. They are, sometimes, calcined in whole or in part, without having lost their configuration; they at others preserve, not only their texture, but even some traces of their hair and skin. They are also occasionally seen covered with a calcareous crust.
"Petrifactions, to use this word in its familiar sense, include all stony bodies that have the figure of an organized body. There are cases in which a strong solution has penetrated into a cavity formed by an organic body that has disappeared. Then the strong substance has occupied the cavity that has been left empty, and has taken the external form of the body that formerly existed there.If this body were, for instance, a branch or trunk of a tree, the stone will have at its surface its knots and asperities; but within, it will present all the characters of a true stone; it will be no more, to use the language of Hauy, than the statue of the substance that it has replaced.
"At other times, a vegetable or animal substance, while undergoing decomposition in a successive manner, and by obvious degrees, is pressed by the petrifying liquid that already surrounds it. As soon as an organic particle has disappeared, its place is occupied by one of stone."
"Metallized bodies, and those which have been changed into bitumen or carbon, belong to this system of formation; thus, the turquoises, for instance, are the teeth of a great marine animal; a metallic substance has penetrated them, and has gradually replaced the softer parts of the bones.
"Impressions are often found between the plates of slaty rocks; they are relievos or intaglios representing the skeletons of animals, particularly fish, leaves, seeds, and entire plants, of which the most common kind belong to the forus."
The impressions of vegetables are most abundant in the shales that accompany coal formations; those of leaves and branches are the most common, but there are a few instances in which they retain the delicate structure of the flowers. All analogy leads to the inference, that those now found in temperate climates, are of such a character as could only exist in tropical regions; and when, as in some of the newer formations, the species are identical with those which now exist, the living type is only found within the torrid zone. A still more curious fact, is their identity in similar formations in different parts of the world. At the present day, the same soil in Pennsylvania and England produces plants of very different characters, and those which are native to each are of wholly distinct genera and species, while the fossils that accompany the coal in the two countries are precisely similar. But even those brought by Parry from the polar region of Melville island, are identical with those of England, and of course with those of this distant part of the same hemisphere in which the former are formed, although the character of the climate is so diverse. At the epoch of the coal formation, there existed plants, of genera, which, in temperate climates, at present rarely rise to more than a few inches in height, and which were at that remote period of enormous size. Thus, the forus must have attained the height of from fifty to sixty feet. At present, the forus assume the size of a tree only in the very warmest climates, and even there, are far inferior in magnitude to those of the coal formation. Now, it is well known, that the large size of the living species is due to great and constant heat, and copious moisture. Hence we may fairly infer that similar circumstances existed even at Melville island, where, at the present time, for the greater part of the year, the thermometer is below the freezing point.
As further instances of the same kind, we may quote the following facts. Faujas St. Fond found, in a marly slate, covered by lava, in France, the tree cotton, the liquid amber styrax, thecassia fistula, and other plants of tropical regions. The same observer found the fruit of the arcea palm near Cologne. The elastic bitumen of Derbyshire in England, is identical with the caoutchouc, which now grows only in the warmer parts of South America; and the amber of Prussia appears to be a fossil gum, similar to the Copal.
Among the more recent in formation of fossil vegetables, are the bituminized woods; these are often buried to great depths by diluvian action, but are never found in perfect rock. The most remarkable instance of this kind is at Bovey-Heathfield, in England, and beneath is found the retinasphaltum, that seems to be no more than the expressed viscorous juice of the trees. Coal is a similar formation, but due to a more ancient period. The mines of Pennsylvania occasionally furnish specimens, in which the fibre of the wood is as distinctly visible as in recently prepared charcoal. However these vast beds may have been formed, no doubt whatever can exist in respect to their vegetable origin.
Among animal remains found in the fossil state, shells and zoophytes are the most abundant. They form the principal parts of rocks which often occupy considerable districts. They are most frequent in calcareous strata, from the transition limestones to the highest of the marles. A remarkable fact is observed in respect to these shells, and the other fossils which accompany them; those which are found in the oldest, or transition formations, are more different from those that now exist, than those in the more modern deposits. Thus the transition limestones and slates contain terrebratulites, with encrinites, pentacrinites, and trilobites; in those of the submedial and medial series we find belemnites and the cornu ammonis; many of which are extinct genera, and some of which are of families that are no longer found living on our globe, while even where the genus is now to be met with, the species at least has become extinct; while in the latest of the tertiary or superior formations, we find ostracites, pectinites, buccinites, chamites, and many other genera that are still abundant, and even types of living species.
By far the greater part of the animals whose remains are found in the older strata are aquatic, and the vast extents over which they are distributed, show, that the waters must at one time have covered a very great proportion of what is now dry land. Nor has this change been produced by any gradual subsidence, for we find no coincidence in the levels of those portions of the land that contain similar fossils; some for instance are still lower than the level of the present ocean; others, again, of similar character, rest upon the tops or sides of the highest mountains. In Europe, the tops of the highest of the Pyrenees, rising 11000 feet above the level of the sea, are of limestone, containing numerousfossil remains, while Humboldt found a rock, similarly characterized, among the Andes, at the height of 14000 feet.
The ancient philosophers, who, in other departments of physical science, were far behind the moderns, seem in this alone to have pursued a process of inductive reasoning, which led to results far more accurate than any attained by the moderns, until within a very few years. The dogmatism which determined to find in every fossil aquatic remain a proof of the particular Noachic deluge, and the timidity of those whose researches had made them better informed, left the world wholly in the dark as to the real inferences to be drawn from a study of the structure of the earth; but what modern geologist could better express what are now admitted opinions, than the words which the Roman poet puts in the mouth of Pythagoras.
"Vidi ego, quod quondam fuerat solidissima tellus,Esse Fretum. Vidi factas ex æquore terras:Et procul a pelago conchæ jacuere marinæ;Et vetus inventa est in montibus anchora summis.Quodque fuit campus, vallem decursus aquarumFecit: et eluvie mons est deductus in æquor:Eque paludosa siccis humus aret arenis;Quæque sitim tulerant, stagnata paludibus hument.Hic fontes Natura novos emisit, at illieClausit: et antiquis concussa tremoribus orbisFlumina prosiliunt; aut exæcata resident."
"Vidi ego, quod quondam fuerat solidissima tellus,Esse Fretum. Vidi factas ex æquore terras:Et procul a pelago conchæ jacuere marinæ;Et vetus inventa est in montibus anchora summis.Quodque fuit campus, vallem decursus aquarumFecit: et eluvie mons est deductus in æquor:Eque paludosa siccis humus aret arenis;Quæque sitim tulerant, stagnata paludibus hument.Hic fontes Natura novos emisit, at illieClausit: et antiquis concussa tremoribus orbisFlumina prosiliunt; aut exæcata resident."
The order in which fossil remains are found to succeed each other in the successive formations that are to be traced from the oldest rocks to the diluvial deposit, are well illustrated in the words of a late distinguished philosopher, whom we shall quote.
"In those strata which are deepest, and which must consequently be supposed to be the earliest deposited, forms, even of vegetable life, are rare; shells and vegetable remains are found the next in order; the bones of fishes and oviparous reptiles exist in the following class; the remains of birds, with those of the same genera mentioned before, in the next order; those of quadrupeds of extinct species in a still more recent class; and it is only in the loose and slightly consolidated strata of gravel and sand, and which are usually called diluvial formations, that the remains of animals such as now people the globe are found, with others of extinct species. But in none of these formations, whether called secondary, tertiary, or diluvial, have the remains of man, or any of his works, been discovered: and whoever dwells upon this subject, must be convinced that the present order of things, and the comparatively recent existence of man as the master of the globe, are as certain as the destruction of a former and different order, and the extinction of a number of living forms, which have types in being. In the oldest secondary strata there are no remains of such animals as now belong to the surface; and in the rocks which may be regarded as most recently deposited, these remains occur but rarely, and with abundance of distinct species;—there seems, as it were, a gradual approach to the present system of things, and a succession of destructions and creations preparatory to the existence of man."
"In those strata which are deepest, and which must consequently be supposed to be the earliest deposited, forms, even of vegetable life, are rare; shells and vegetable remains are found the next in order; the bones of fishes and oviparous reptiles exist in the following class; the remains of birds, with those of the same genera mentioned before, in the next order; those of quadrupeds of extinct species in a still more recent class; and it is only in the loose and slightly consolidated strata of gravel and sand, and which are usually called diluvial formations, that the remains of animals such as now people the globe are found, with others of extinct species. But in none of these formations, whether called secondary, tertiary, or diluvial, have the remains of man, or any of his works, been discovered: and whoever dwells upon this subject, must be convinced that the present order of things, and the comparatively recent existence of man as the master of the globe, are as certain as the destruction of a former and different order, and the extinction of a number of living forms, which have types in being. In the oldest secondary strata there are no remains of such animals as now belong to the surface; and in the rocks which may be regarded as most recently deposited, these remains occur but rarely, and with abundance of distinct species;—there seems, as it were, a gradual approach to the present system of things, and a succession of destructions and creations preparatory to the existence of man."
We have stated that the zoophytes and shell-fish have left the most numerous fossil remains. Those of other families are not however rare. Fish, for instance, are found in great abundance,near Glarus in Switzerland, in clay slate; in Germany, at Papenheim, in a slaty marle, in the cupriferous slate of Eisleben, in the fetid limestone of Oehningen. They are also found in Egypt, and we have specimens of the same sort from Lyria, in a limestone apparently belonging to the oolitic or Jura formation. China and the coast of Coromandel have also fossils of this sort, but by far the greatest quantity have been procured from Mount Bolea, near Verona. A splendid suite from the last locality are to be seen in the Gibbs' Cabinet at New-Haven. Besides the impressions of entire fish, separate portions are very abundant, and perhaps the most frequent of these are the teeth of sharks, which are sometimes of a magnitude vastly greater than those of any living species. Animals of the class of amphibia appear not to have existed until after the æra that gave birth to fish. The oldest are probably the tortoises, of which a specimen has been found in sandstone near Berlingen. They have also been found in England, in the Netherlands near Brussels, at Aix in Provence, and in the quarries near Paris. The most remarkable fossils of this class belong, however, to the lizard family. Of these the most remarkable are the plesiosaurus, the megalosaurus, the iguanodon, and the crocodile of Maestricht, all belonging to extinct species.
The marine animals that are met with in a fossil state, are in great part foreign to the climates in which they are found buried. It has been shown that the fish of Bolea have their nearest living prototypes in the seas of Otaheite. The perpites of Gothland have been supposed to be petrifactions of the medusæ of India. The madrepores, so abundant in Russia and in the frozen deserts of Siberia, only live now in seas within the tropics. Shells analogous to a great part of those found fossil in England, are only to be seen in the Atlantic, in a living state, on the coasts of Florida and Cuba. A shell-formed fossil at Havre is only to be met with recent at Amboyna.
Of the shells found in Italy, fossil in the sub Appenine hills, many are common to the Mediterranean and the Indian oceans. But while those in the fossil slate and the recent specimens from the tropics correspond in size, individuals of the same species from the Mediterranean are dwarfish and degenerate.
Thus then the remains of aquatic and amphibious animals appear to confirm the conclusion drawn from vegetable fossils, that a climate of temperature as elevated as that now found in the tropics, once extended into high northern latitudes. It has been seen that the fossil remains and impressions of shells have been found at great heights upon the sides, and even upon the tops of mountains; and that in the older of the strata no trace is to be found of any but aquatic animals. Thus before our existing mountains and the minerals they contain had arisenabove the general surface; before diluvial and alluvial deposits, or even the great formations of sandstone and conglomerate had arisen from their disintegration, the globe was covered, in a great degree, and as it appears from considerations we have not space to enter into, by various successive eruptions, with waters, sometimes fresh, sometimes saline. These waters have, it could be readily made to appear, often rested long on the surface in a quiet state, after having been in violent agitation; and long ages of tranquillity have been succeeded and closed by convulsions of the most violent character.
In all the regularly stratified formations, animals of the mammiferous or cetaceous classes are wholly wanting; at least we have no proof that can be relied upon of any having been found in formations which took place prior to the last great deluge, that covered so much of the land with diluvium. In this last formation, however, they are often found in great abundance. Some of them are of recent, others of extinct species. Among the most remarkable of the latter are, the palæotherium, and anoplotherium, found near Paris; the megalonyx, an animal of the sloth genus, but of the size of an ox, found in Virginia; a still larger sloth, called the megatherium, found near Buenos Ayres; the fossil elephant, as different from the living elephants of India or Africa, as the horse is from the ass, and which has been found in Europe, in Asia, and in America. The mastodon, of which several species have been discovered on the banks of the Hudson, in Kentucky, in Louisiana, in the plains of Quito, in France, and finally on the borders of the Irrawaddy.
The bones of rhinoceroses, bears, elephants, and hyænas, have been found mixed in confusion in caverns; and it has been shown by Buckland that the latter animal had inhabited these caverns, and drawn thither the carcasses of the others as his prey, in one of the most perfect inductive arguments which has been produced, since Bacon propounded the rules of that species of reasoning.
"The moveable earths that fill the bottoms of valleys, and which cover the surface of great plains, have furnished us in the above two orders, of pachidermata and elephants, the bones of twelve species, to wit: one rhinoceros, two hippopotami, two tapirs, an elephant, and six mastodons. All these twelve species are now absolutely extinct in the climates in which their bones are found. The mastodons alone may be considered as forming a separate genus, now unknown, but closely approaching to the elephant. All the others belong to genera now existing in the torrid zone. Three of these living genera are now found only in the ancient continent, to wit: the rhinoceros, the hippopotami, and the elephant; the fourth, that of the tapirs, only exist in the new. The distribution of the fossil species is different; the tapirs have been found only upon the old continent, while elephants have been discovered in the new."
"The moveable earths that fill the bottoms of valleys, and which cover the surface of great plains, have furnished us in the above two orders, of pachidermata and elephants, the bones of twelve species, to wit: one rhinoceros, two hippopotami, two tapirs, an elephant, and six mastodons. All these twelve species are now absolutely extinct in the climates in which their bones are found. The mastodons alone may be considered as forming a separate genus, now unknown, but closely approaching to the elephant. All the others belong to genera now existing in the torrid zone. Three of these living genera are now found only in the ancient continent, to wit: the rhinoceros, the hippopotami, and the elephant; the fourth, that of the tapirs, only exist in the new. The distribution of the fossil species is different; the tapirs have been found only upon the old continent, while elephants have been discovered in the new."
The fossil species, although belonging to known and existinggenera, are essentially different inspeciesfrom those which now live upon the earth. The former are not mere varieties, but have marked specific differences. This at least is beyond alldoubt in respect to the smaller of the hippopotami, and the gigantic tapir, as well as the fossil rhinoceros, and is extremely probable in respect to the elephant and the smaller tapir. If there be any question of the fact, it is only in respect to the greater hippopotamus.
"These different bones are buried in all different places in beds that resemble each other. They are often mixed indiscriminately with those of other animals, identical with those which exist at present. These beds are generally moveable, sandy, or marly, and always within a short distance of the surface. It is therefore probable that these bones have been enveloped by the last catastrophe of the globe. In a great number of places, they are accompanied by the accumulated spoils of marine animals; in other places, but these are less numerous, the remains of marine animals are not found, and sometimes the sand or marle that covers them contains only fresh-water shells. Although a small number of shells attached to fossil bones indicate that, they have remained some time under water, yet is there no authentic account of their having been found covered with regular stony beds, filled with marine remains, nor, in consequence, is there any proof of the sea having made a long and peaceable stay above them."The catastrophe that has covered them, would appear then to have been a great marine inundation, of no long duration, were it not that they are found upon the tops of high mountains, whither the waters of our present ocean could never have reached in their most violent agitations. On the other hand, these bones presenting no appearance of having been rolled, being occasionally only fractured, as the remains of our present domestic animals may occasionally be, and being sometimes found in entire skeletons, and accumulated as if in a common cemetery, demonstrate that the living beings to which they have belonged, must have met their fate in the very parts of the globe in which we now find the fossil monuments of their existence."
"These different bones are buried in all different places in beds that resemble each other. They are often mixed indiscriminately with those of other animals, identical with those which exist at present. These beds are generally moveable, sandy, or marly, and always within a short distance of the surface. It is therefore probable that these bones have been enveloped by the last catastrophe of the globe. In a great number of places, they are accompanied by the accumulated spoils of marine animals; in other places, but these are less numerous, the remains of marine animals are not found, and sometimes the sand or marle that covers them contains only fresh-water shells. Although a small number of shells attached to fossil bones indicate that, they have remained some time under water, yet is there no authentic account of their having been found covered with regular stony beds, filled with marine remains, nor, in consequence, is there any proof of the sea having made a long and peaceable stay above them.
"The catastrophe that has covered them, would appear then to have been a great marine inundation, of no long duration, were it not that they are found upon the tops of high mountains, whither the waters of our present ocean could never have reached in their most violent agitations. On the other hand, these bones presenting no appearance of having been rolled, being occasionally only fractured, as the remains of our present domestic animals may occasionally be, and being sometimes found in entire skeletons, and accumulated as if in a common cemetery, demonstrate that the living beings to which they have belonged, must have met their fate in the very parts of the globe in which we now find the fossil monuments of their existence."
All the animals of which we have particularly spoken, are of genera now only found in the torrid zone, and the abundance of food which their great size would have caused them to require, renders their existence in numbers only possible in a warm climate. Their remains are, however, found in almost polar regions, whence we obtain a third link in the chain of evidence, that before the last great catastrophe to which the globe was subjected, its surface must have been warmer than at present.
We have seen in a former place, that such a change of temperature may have gradually occurred in consequence of a cooling of the external surface of the globe by an excess of its radiation above the quantity of heat received from the sun. The final cooling of its solid crust, down to the mean temperature at which we now find it, might, as is obvious, have been effected by a great irruption of waters, like that of which we have distinct evidence in the diluvial deposits, and the animal remains upon its surface. From that time, a state of equilibrium in the action of solar and terrestrial radiation having been attained, while the mean temperature still continues to depend upon the internal structure and nature of the globe, the distribution of heat upon the surface, and the vicissitudes of the seasons, have been solely influenced by the varying relation between these two radiations, which if equal to each other in their total amounts, differ in everydifferent latitude, for every successive day in the year, and during each varying hour of the day.
It has been attempted to explain this change that has unquestionably taken place in the temperature of climate, by conceiving a change in the situation of the earth's axis. This hypothesis, however, is shown to be untenable by the calculations of physical astronomy: no other cause then remains but an actual change in the condition of the earth itself.
The most remarkable of all the phenomena which the earth presents, are the great changes of weight that have taken place in identical formations which must have arisen from the prevalence of water, and therefore nearly if not exactly upon the same level. The primitive or lowest stratified rocks, probably had not water for their cause; still, however, they must have been in the fluid state, and these are not only found beneath all other rocks, and in the lowest places to which the industry of man has penetrated, but they also rise and form the greatest part in bulk of many of the highest mountains; indeed, if we except volcanic mountains, of all the more elevated masses. The transition and secondary formations are subject to similar although less changes of level, rising, as has been seen, to the tops of the Pyrenees, and to even a greater height on the sides of the Andes. The tertiary or superior formations are found in Italy and Sicily, forming mountains several thousand feet in height, while the latest of all, the diluvial with its embedded mammalia, exists in the lofty table land of Quito. The inference is irresistible, that we do not now find these deposits at the levels where they were left by the ocean, as in the case of the primitive rocks by their own crystallization from a fluid state, but that they have been altered in their positions by actions of a character totally distinct from that by which they were originally formed.
This inference is still further confirmed by the great and sudden changes of level that are frequently to be seen in similar strata, faults, as they are styled by miners, in which the same bed has its level sometimes changed hundreds, nay even thousands of feet. These faults, if in greatest abundance in the more ancient rocks, are to be found even in the newest, and sometimes affect several formations incumbent on each other, of ages the most different. Thus, then, we have distinct and conclusive evidence, that as we inferred from theory, the solid crust of the globe has been shattered and fractured repeatedly, and at all the different epochs of its history. This fracturing and cracking we have shown, must, in conformity with strict mechanical laws, have been attended with the rise of the molten liquid from beneath, which ought in some cases to have formed veins and dykes, in the places where the fractures occurred. It is however possible, that the rise of the fluid from beneath, may not have takenplace where the pressure occurred; but it would then have been compelled by hydrostatic pressure, to issue at some other point, breaking and tearing the weaker parts of the solid crust, in order to afford itself a vent.
The latter class of phenomena are still in action, and we have evident traces of their occurrence in all the different stages of the world's existence; of the former it will also be seen there is conclusive evidence.
The visible effects of a subterranean heat, are most frequently met with at the present day in the form of volcanoes. Of these, there are not only a great number in activity, but there are still more that have been certainly active since the last great change that the surface of the earth has undergone.
That part of the great group of mountains which we have before described, which lies in the new continent, contains many active volcanoes, and others but recently extinct. Terra del Fuego, as its very name imports, is the seat of many; Chili has several; in Peru are to be noted Arequipa, Pichinca, and Cotapaxi; while Chimborazo is obviously one that has become extinct at a period not remote. Passing the Isthmus of Panama, we find the volcanoes of Guatimala and Nicaragua almost infinite in number. In Mexico, are Orezaba, Popocatepetl, and Jorullo; the last of which first rose from beneath the surface in 1759. California has five active volcanoes; and we know, from the observations of La Perouse and Cook, that they also exist along the north-western coast of America. Mount St. Elias, in particular, was seen in a state of eruption. These mountains connect those of Mexico with the volcanoes of the Aleutian islands and of the peninsula of Alaska, which continue the system towards Kamtschatka, in which peninsula there are three of great violence. We have seen some proofs, that there are active volcanoes to the north-west of China, but none now exist in Thibet; and the action that once took place there has sought new vents, in regions more near to the present bed of the ocean. Thus, Japan has eight volcanoes, Formosa several, and, in proceeding to the south, the land of volcanic action widens, and becomes of immense extent. It embraces the Philippine, Marian, and Molucca islands, Java, Sumatra, Queen Charlotte's islands, and the New-Hebrides. The active volcanoes of Europe and western Asia are few in number; but those that are extinct form a great system, in which the active ones are included, and which seems to spread in the form of a belt, from the Caspian sea to the Atlantic. Volcanic action still occurs on the shores of the Caspian. In the chain of Elburg is a lofty mountain that still emits smoke, and around whose base are several distinct craters. Syria and Palestine abound in volcanic appearances, of which the great crater that has swallowedup the waters of the Jordan, and forms the Dead sea, is the most remarkable. Greece and the Grecian Archipelago have been, almost within historic times, the seat of a volcanic action, of great extent and violence, and which has not wholly exhausted itself. In Sicily, Ætna has burnt for 3300 years, and is yet surrounded by extinct craters of more ancient date. The Lipari islands are wholly volcanic. Vesuvius, that had long before intermitted its eruptions, and broke forth again in the great one that destroyed Herculaneum and Pompeii, is not the only volcanic mountain of Naples. An extinct one of much greater size is to be found near Roccafina. The catacombs of Rome are excavated in lava, and Tuscany contains strong evidences of volcanic action. Volcanic indications can be traced near Padua, Verona, and Vicenza, extending into Dalmatia. A district of Hungary was suspected of containing the seeds of subterranean fire, and the suspicion has been confirmed by an actual eruption. Germany and Bohemia contain a great number of extinct volcanoes, as does the south of France, and particularly Auvergne. In Spain, too, the proofs of a volcanic agency are clear and decisive.
Greenland and Iceland present a third group of volcanoes; in the latter island, a single volcano was in a state of continuous eruption for five or six years. The Azores, the Canaries and Madeiras, also contain numerous volcanoes, both active and extinct, as do the Caribbean islands.
In comparing together volcanoes that are in present activity, and others in which the crater and the streams of emitted lava are too distinct to permit a doubt of their having arisen from the same cause, differences are observed that only have arisen from great differences in the circumstances under which the eruption has taken place. In many of the ancient volcanoes, we find the emitted streams are arranged in prismatic forms, constituting basalt, and frequently passing into what under other circumstances would be styledtrapby the Wernerians. Now, we know that when streams of lava enter the sea, they spontaneously assume the prismatic structure. Hence we may infer, that these ancient volcanoes originally gave vent to their craters beneath the level of the sea, at a time when the rocks through which they penetrated, and over which their streams have passed, were beds of the primitive ocean. The trap rocks themselves may have been formed in a similar manner, by upward pressure of the igneous fluid beneath, through the veins and fissures formed on the breaking of the solid crust. Trap traverses, in dykes of unknown depth, many formations, and is occasionally seen forming beds between successive strata. It frequently occurs in faults, and sometimes in extensive overlying masses. Close observation, and a just course of analogy, lead to the irresistibleconclusion, that all the trap rocks, however situated or arranged, grow out of the same great cause, the rising of the liquid interior of the earth to its surface. An action sometimes taking place through veins and fissures in the solid crust, and sometimes by the eruption of volcanoes, both occurring during the pressure of water upon the surface. One of the most extensive groups of trap-rocks is to be seen in the north-eastern part of the state of New-Jersey. The Hudson is bordered for nearly forty miles by a great ridge of columnar rock, lying upon sandstone. When this is surveyed with an eye to its analogy to volcanic action, it appears as if it were the outpourings of a crater, whose basin is now occupied by the lake in which the Hackensack river takes its rise, and whence a great stream of lava has run over the sandstone rock, as far as the strait that separates Staten Island from the main land. The two Newark mountains are ridges of the same description, of even greater extent; other smaller ridges of the same kind are also distinctly visible, and the whole of this last system appears to have proceeded from a crater now filled by the alluvion of the Passaic, but which is bordered by a ridge still occupying two-thirds of a circle, and showing conclusive marks of igneous action, that goes by the name of the Hook mountain. The phenomenon of a dyke of trap is well exhibited in the quarries near Hartford in Connecticut, where this rock has been laid bare for a considerable depth, as it rises through a sandstone rock, instead of overlying it, as it is seen to do on the Hudson.
The trap-rocks, which are, generally speaking, of the character called by mineralogists greenstone, vary in this district of New-Jersey, from a compact basalt of homogeneous structure, to one of regular and distinct crystallization, not distinguishable in hand specimens from primitive syenite. A rock of this last character is to be found in the mountain that extends from Morristown to Mount Kemble, which is columnar in its structure, but almost identical, in mere external characters, with stratified rocks of gneiss containing hornblende, that are found in the primitive ridges within a few miles.
Thus then the older volcanic rocks gradually pass in character into those which, under the general name of granitic, form the apparent nucleus of gneiss and mica slate mountains, and penetrate them, and the primitive limestones, in veins. One of the best instances of veins of granite with which we are acquainted, are those which occur in the quarries of white marble at Kingsbridge, which are traversed in every direction by thin veins of a rock, principally composed of a white fetid felspar, mixed with spangles of silvery mica, and small grains of quartz, interspersed with occasional masses of tourmaline. The famous locality of chrysoberyl, beryl, and other interesting minerals, at Haddam,in Connecticut, is said to occur in a granitic vein passing through strata of gneiss.
In all these cases we cannot fail to see evidence of igneous eruptions, taking place, however, under circumstances widely different from those of our present terrestrial volcanoes, or of the submarine craters of more remote dates, but which can be readily explained by supposing, either that the penetration took place when the surface of the earth was so intensely heated as to admit of the injected veins being slowly cooled, and therefore more perfectly crystallized; or that the issuing mass was so great as to retain its heat for a great length of time.
It might at first sight appear difficult to explain how volcanic energies should still continue in activity, now that the mean temperature of the earth has become constant, and the outer crust can be no longer subject to the shrinking, and consequent cracking which it must have undergone while cooling. The phenomena that attend volcanic eruptions furnish a full explanation of this, for they are attended in almost all cases with the evolution of great quantities of gaseous matters, and steam, which must therefore exist in a state of intense compression, and at elevated temperatures, in the mass whence the volcanic flood issues. Their elastic energies are sufficient to account for all the striking effects that attend the action of volcanoes.
The earthquake is a phenomenon connected with volcanic eruptions, and arising from the same great cause; but while the latter are confined to certain mountains, and restricted within narrow limits at the present day, an earthquake is sometimes found to prevail over a very large portion of the earth's surface. To omit the more usual phenomena of earthquakes, we shall speak of but one, which has in some cases been observed, that throws a great light upon the manner in which the stratified rocks have had their levels changed, and been dislocated and distorted in the manner we now find them. We allude to the sudden raising of countries of greater or less extent. Of this we shall quote three several instances from a paper of Arago's.