The first important attempt toward a scientific view of the character and relations of the strata in the United States was made by Mr.Maclure, but a short time previous to the year 1812. His work was small and general, but has proved a valuable guide to subsequent inquirers. In order to obtain a view of the general geological formation of the territory of the states, it will be well to recapitulate its chief geographical features; the Apalachian mountains on the east, with the slope to the Atlantic ocean; the Rocky mountains to the west, with the valleys intervening between them and the Pacific ocean; and the extended valley between these elevated ranges, with the Ozark mountains dividing it in the centre, and the Black mountains occupying its north-western angle.

The summits of the Rocky mountains are formed entirely of primitive rocks, chiefly of granite itself. Ared and saline sandstone rests on this granite, through the whole chain, as far as it has been explored. But few traces of that animal and vegetable life are found, which in other countries has reared mountains of limestone, clay-slate, and those other aggregates which are so often composed of the exuviÆ of living beings. The western boundary of this sandstone formation corresponds to the side of the easternmost granite ranges. From the Platte toward the south, the sandstone increases in width, and on the Canadian it extends more than half the distance from the sources of that river to its confluence with the Arkansas. It consists of two members; red sandstone, and argillaceous or gray sandstone. This formation was at one time probably horizontal and uniform; it is now found in a state of entire disruption and disorder. This tract abounds in scenery of an interesting and majestic character. The angle of inclination of the strata varies from forty-five to ninety degrees. Though not very recent, the sandstone along the base of the mountains contains the relics of marine animals and plants, and embraces extensive beds of pudding stone.

South of the Arkansas are rocks of basaltic origin, overlaying the red sandstone. By the vastness and broken character of their masses, and their dark color, they present a striking contrast to the light, smooth and fissile sandstone on which they rest. Sometimes they are compact and apparently homogeneous in their composition, and in many particulars of structure, form and hardness, more analogous to the primitive rock than to those recent secondary aggregates with which they are associated. In other instances, dark and irregular masses of porous and amygdaloidal substances are seen scattered about the plain, or gathered in conical heaps, but having no immediate connection with the strata on which they rest. Most of the rocks of this class were observed in the neighborhood of the sources of the Canadian; and may be distinguished into two kinds, referable to the two divisions called greenstone and amygdaloid.

The valley immediately east of the Rocky mountain range is composed of an extensive accumulation of sand, seemingly the debris of the mountains. To an unknown depth, the soil is made up of rounded fragments of granite, varying in dimension from a grain of sand to a six pound shot. This accumulation has evidently been washed from the mountains, and slopes gradually from their base. The small particles derived from the quartzose portions of the primitive aggregates, being least liable to decomposition, have been borne to the greatest distance, and of these the eastern margin of the great sandy desert is almost entirely composed; the central portions are of coarser sand, intermixed with particles of mica and feldspar; nearer the mountains, boulders and pebbles occur abundantly, and at length cover almost the entire surface of the country.

In many other respects besides geological structure, the Apalachian range of mountains differs from that we have just been considering. The whole of their eastern front is composed of primitive rocks, comprehending both the granitic family and its associated strata of clay-slate and limestone. In New England, rocks of this class constitute the seacoast, and with some exceptions extend inwards towards the St.Lawrence. South of the Hudson, the edge of the primitive follows the general contour of the mountains, at a variable distance from the sea to their termination, and until it meets more recent deposits at the extremity of the mountain range. The breadth of this primitive belt is very unequal. In passing through the states of Pennsylvania and Maryland, it occupies but a small part of the country; in Virginia it increases in breadth, and proportionably in height, composing the greatest mass as well as the most elevated points of the mountains in Georgia and North Carolina. Besides this range, there is a great mass of primitive on the west side of lake Champlain.

In general, the primitive rocks run from a north and south to a north-east and south-west direction, and dip generally to the south-east at an angle of more than forty-five degrees with the horizon; their highest elevation is towards their north-western limit. The mountains of this formation consist generally of detached masses, with rounded flat tops and a circular waving outline. Granite in large masses constitutes but a small part of this formation, and is found indifferently in the plains and on the tops of mountains. Gneiss extends perhaps over a half of this formation, and includes in a great many places beds from three to three hundred feet thick. These beds are mixed, and alternate occasionally in the same gneiss with the primitive limestone, the beds of hornblende and hornblende slate, serpentine, magnetic iron ore, and feldspar rocks. In short, there are scarcely any of the primitive rocks that may not occasionally be found included in the gneiss formation.

The breadth of the transition district, like that of the primitive, is variable. Narrow towards the gulf of Mexico, it gradually widens towards the north-east, till it reaches the river Hudson. From its upper portion it sends off a considerable arm, which penetrates for several hundred miles into the granitic region, overlaying it, but running parallel with the principal body. After the primitive, it forms some of the highest mountains in the range, and seems to be both higher and wider to the west in Pennsylvania, Maryland and part of Virginia, where the primitive is least extended and lowest in height. It contains all the varieties of rocks found in the same formation in Europe.

It varies in breadth from twenty to one hundred miles. In the limestone of this formation there are many and extensive caves, some of which extend for miles under ground, and contain the bones of animals. It is the lowest, and is considered the most ancient of the rocks containing organized remains, which are those of cryptogamous plants, and animals without sight. The graywacke has been observed to contain impressions of organized remains, but they are usually those of zoophytic animals, and are exceedingly unlike those found so abundantly in the coal formations. Its colors are variable; it is, however, most commonly bluish, black, or dark brown. The graywacke seems to form the connecting link between the clay-slate and a rock which has been called the old red sandstone, and is usually found intimately blended either with the one or the other. This sandstone occurs throughout the whole extent of the transition formation, and evidently belongs to the oldest depositions of that rock. It is for the most part distinctly stratified, and in all cases its stratification is inclined.

Of the rocks thus described, the limestone occurs extensively all along the north-western side of the primitive strata. It is probable that transition limestone is the foundation through their whole extent of the Alleghany mountains of Pennsylvania, Maryland and the western parts of Virginia, on a level with the surface at the base of their eastern declivities. The clay-slate occurs in the central portions of that extensive field of transition, which skirts the western margin of the primitive of New York and New England, and forms the great body of the Catskill mountains. The old red sandstone in the transition district, along the whole range of mountains, is perhaps more abundant than any other aggregate. This region has also a considerable mixture of trap. Various large bodies of transition rock are thrown to a considerable distance into the primitive region; while in many instances, secondary rocks are found running along the valleys far into the bosom of the mountains.

With the edge of the transition strata, we approach the western summits of the Apalachian mountains, or the line from whence they begin to fall toward the Mississippi valley. Along this line commences a series of secondary rocks, stretching westward to an immense extent towards the Mississippi and the lakes, and constituting one of the most interesting and important geological formations in the United States. This secondary region extends unbroken across the whole country to the shores of the lakes, being bounded on the west probably by the river Wabash, and in descending the Mississippi by the more recent formations through which that river flows. It consists generally of various strata of sandstone, limestone and clay. Immense beds of secondary limestone, of all shades from light blue to black, sometimes intercepted by extensive tracts of sandstone and other secondary aggregates, appear to constitute the foundation of this formation, which extends from the head waters of the Ohio, with some interruptions, all the way to the waters of the Tombigbee, accompanied by slaty clay and freestone with vegetable impressions; but in no instance yet ascertained, covered by or alternating with any rock resembling basalt, or indeed any of those called the newest floetz trap formation. Agrand peculiarity of this secondary region is the uniform, horizontal direction of the strata.

We will now briefly examine the region which occupies the centre of the Mississippi valley. The Ozark mountains consist chiefly of secondary and transition rocks; but there are two points at which the primitive makes its appearance. About fifteen miles south-east from the hot springs, near the Washita, granite is found in situ. It is very soft, and disintegrates rapidly when exposed to the air. It is compounded of greyish-white quartz, yellowish-white feldspar, and an unusually large proportion of mica in variously and brilliantly-colored masses. This granite, if of secondary formation, is much more extensive than any of the kind hitherto known. ‘We are ignorant,’ says Dr.James, ‘of the manner of its connection with any other rock, nor do we know of any formation of primitive granite from which it could, by the action of water, have been derived: one can have no hesitation, however, in considering the Ozark mountains as a separate system within themselves, and having no immediate connection with either the Apalachian or the Chippewayan mountains.’ Mr.Schoolcraft mentions another granite region as occurring in the north-eastern extremity of the Ozark range, in the mining district of Potosi.

In connection with the granite of the Washita is found a stratum of clay-slate, and another of transition sandstone, but neither of them of great extent. The hot springs of the Washita issue from the clay-slate, and it is supposed that a very large mass of clay-slate is interposed between the surface of the granite and the point at which the springs rise. The slate-rock about the hot springs is highly inclined, often flinty in its composition, and, as far as it has been hitherto examined, contains no organic remains. It is traversed by large upright veins, usually filled with white quartz. The mountains contain vast beds of secondary limestone, which from its peculiar crystalline appearance might be easily mistaken for the primitive. These vast beds of sparry limestone, almost exclusively made up of deposits from chemical solution, would seem to have been formed during periods of great tranquillity in the waters. The sandstones of this small group of mountains appear under almost every variety of character. Aregion similar in mineralogical character to the Ozark mountains extends northward from the confluence of the Missouri, to the Ouisconsin and Ontonagon rivers of lake Superior. The sandstones, limestones and other rocks have a striking resemblance. Of the Black mountains in the north-western part of the Mississippi valley, but little is known; they appear to be composed of sandstone lying horizontally, and to be destitute of valuable minerals. Between these mountains and the central district, is a wide alluvial tract containing the course of the Missouri. The same appellation has been given by Dr.James to a space between the Ozark mountains and the Chippewayan sands, and to the country on both sides of the lower Mississippi.

We must now turn our attention to the region which lies to the eastward of the Apalachian mountains. The eastern front of this range is composed of primitive rocks, which reach the sea as far south as the Hudson; from this point they take an inland course, and leave a considerable tract of land between them and the ocean all the way to the Mississippi. On this side, there is no appearance of any rocks of the transition class; the primitive terminates abruptly, and is skirted through its whole length by an extensive series of beds of shell-limestone, marl, clay, sand and gravel, constituting what has been described as the Atlantic slope. This class of strata begins at Long island, and gradually widens in its extent through the middle and southern states, forms the whole of Florida, and crossing the Mississippi, meets the secondary formation of that valley, and sends up a tongue for a considerable distance along the sides of that river. We may here notice one of the most peculiar features of our geology. This is the ridge of granite which forms the boundary between the primitive and secondary regions, and is conjectured to have been the ancient line of the seacoast. It commences in Georgia and extends as far north as New York, whence it seems to pass into Long island and under the sound into Connecticut.

The entire region to the eastward of the primitive was long considered as alluvial; but it has been found to comprehend secondary, as well as a large extent of tertiary formations. Decisive evidence of this fact has been furnished by the investigations of Dr.Morton of Philadelphia. The secondary strata are not, however, calcareous, but consist of beds of sand and clay analogous to the iron sand, green sand, and chalk marl or galt of England. Dr.Morton calls it the ferruginous sand formation. In Maryland commences a vast deposit of sand and clay, extending along the coast to the Mississippi; this tract abounds with tertiary fossils, which appear chiefly to belong to the upper marine formation of European geologists. The secondary strata are occasionally met with beneath it, and sometimes approach so near the surface as to be readily identified by their fossils. It is therefore reasonable to suppose, that the beds of ferruginous sand extend nearly the whole length of the Atlantic frontiers, of the states south of Long island. One of the most abundant mineral productions of these beds is lignite, which is found at the deep cut of the Chesapeak and Delaware canal, in almost every variety, from charred wood to well-characterized jet. It sometimes occurs in small fragments, and sometimes in large masses, presenting the trunks and limbs of trees thirty feet in length.

Though occurring largely on the Atlantic slope, the tertiary formations are by no means confined to it; they overlay the secondary strata to a great extent on both sides of the mountain chains. Of all visible strata, marly clay is one of the most universal; it is the common clay of all North America. In this clay, sulphate of magnesia frequently occurs, and sometimes muriate of soda. Bagshot sand and crag are next in extent to the marly clay, and generally overlie it. The plastic clay formation is stated to appear very distinctly on the west side of lake Champlain, and at various points from Martha’s Vineyard to the eastward of Long island, to Florida and the Mississippi. The silicious limestone of Georgia is asserted to be decidedly contemporaneous with the calcaire silicieuse of the Paris basin. In Virginia, the marly or London clay is found, and the sands of the upper marine formation are conceived to occur in the same state and in Staten island.

Of the geology of the region west of the Chippewayan mountains, nothing certain is known. The chains which stretch nearer to the Pacific are lofty, and are presumed to be primitive. Mr.Scrope represents the mountains which border the Pacific ocean as volcanic.

From the importance which fossil remains have recently assumed in geological science, much interest is naturally attached to those contained in the strata of the western world. It will be long before so vast a field of inquiry is fully explored, and with Mr.Maclure in 1812, we may still say that it has not yet been examined with that accuracy of discrimination necessary to form just conclusions. We derive such knowledge as is possessed on the subject from various sources. The fossils of the transition strata consist of the ancient coralline and encrinital families, and generally resemble those of similar rocks in other parts of the globe. Organic remains in the coal formations are found at Westfield, Connecticut; at Sunderland, Massachusetts; and it is said also in some other places. At Westfield they were found, in exploring for coal, lying upon bituminous shale.

The following information is furnished in an article by Mr.Caleb Atwater. ‘In the vicinity of the Ohio river, and on the waters of the Muskingum, Ihave carefully examined not a few of the fossil trees there existing. Among them Inoticed the following, viz. black oak, black walnut, sycamore or button wood, white birch, sugar maple, the date or bread-fruit tree, cocoanut-bearing palm, the bamboo and the dogwood; and Ihave in my possession the perfect impression of the cassia and the tea leaf. Of ferns, Ihave beautiful impressions of the leaves, and of the bread-fruit tree flowers, fully expanded, fresh, and entire. Ihave specimens so perfect, and so faithful to nature, as to dispel all doubts as to what they once were. The larger trees are found mostly in sandstone, although the bark of the date tree, much flattened, Iought to say perfectly so, is found in shale covering coal. The date is a large tree, not very tall, and having numerous wide-spreading branches. Nine miles west of Zanesville, the body of a bread-fruit tree, now turned to sandstone, may be seen; it is exactly such sandstone as that in which M.Brongniart found tropical plants imbedded in France. It contains a considerable quantity of mica in its composition. The cassia was found in such sandstone in the Zanesville canal. The bamboo is mostly impressed upon ironstone, especially the roots, and the trunk and leaves are found in the micaceous sandstone. The ironstone is sometimes apparently made of bamboo leaves, the leaves of fern, and bamboo roots. It happens frequently that the trunks of small trees and plants are flattened by pressure, and the bark of them partially turned into coal. Thus the shale often contains a bark, now become coal, and a stratum of shale in succession, alternately, for several inches in thickness.’

Some further interesting particulars respecting fossil and other remains will be found in the following description of them by Mr.Atwater, as occurring in the state of Ohio. ‘Iam credibly informed, that in digging a well at Cincinnati, in this state, an arrow-head was found more than ninety feet below the surface. At Pickaway plains, while several persons were digging a well several years since, a human skeleton was found seventeen feet six inches below the surface. This skeleton was seen by several persons, and among others, by Doct.Daniel Turney, an eminent surgeon; they all concurred in the belief, that it belonged to a human being. Pickaway plains are, or rather were, a large prairie, before the land was improved by its present inhabitants. This tract is alluvial to a great depth; greater, probably, than the earth has ever been perforated, certainly than it ever has been by the hand of man. The surface of the plain is at least one hundred feet above the highest freshet of the Scioto river, near which it lies. On the surface is a black vegetable mould, from three, to six, and nine feet in depth; then we find pebbles, and shells imbedded among them: the pebbles are evidently rounded and smoothed by attrition in water, exactly such as we now see at the bottom of rivers, ponds, and lakes.

‘I have examined the spot where this skeleton was found, and am persuaded that it was not deposited there by the hand of man, for there are no marks of any grave, or of any of the works of man; but the earth and pebbles appear to lie in the very position in which they were deposited by the water. On the north side of a small stream, called Hargus creek, which at this place empties itself into the Scioto, in digging through a hill composed of such pebbles as Ihave described in Pickaway plains, at least nine feet below the surface, several human skeletons were discovered, perfect in every limb. These skeletons were promiscuously scattered about, and parts of skeletons were sometimes found at different depths below the surface. This hill is at least fifty feet above the highest freshets in the Scioto, and is a very ancient alluvion, where every stratum of sand, clay, and pebbles has been deposited by the waters of some stream. Other skulls have been taken out of the same hill, by persons who, in order to make a road through it, were engaged in taking it away. These bones are very similar to those found in our mounds, and probably belonged to the same race of men; a people short and thick, not exceeding generally five feet in height, and very possibly they were not more than four feet six inches. The skeletons, when first exposed to the atmosphere, are quite perfect, but afterwards moulder and fall into pieces. Whether they were overwhelmed by the deluge of Noah, or by some other, Iknow not; but one thing appears certain, namely: that water has deposited them here, together with the hill in which, for so many ages, they have reposed. Indeed, this whole country appears to have been once, and for a considerable period, covered with water, which has made it one vast cemetery of the beings of former ages. Fragments of antique pottery, and even entire pots of coarse earthen ware, have been found likewise in the excavations of the Illinois salt-works, at the depth of eighty feet and more from the surface. One of these was ascertained to hold from eight to ten gallons, and some were alleged to be of much greater capacity. This fossil pottery is stated not to differ materially from that which frequently occurs in the mounds supposed to have been formed by the aboriginal Indians.’

The largest and most interesting fossils of this country are the remains of the mastodon, an enormous creature of an extinct race, nearly allied to the elephant, and long considered identical with it, but now allotted to a distinct genus under the name of mastodon. For a minute and detailed account of these remains, we must refer our readers to the valuable work of Godman. The size of the living animal may be conjectured when it is stated, that the head at the posterior part is thirty-two inches across, the lower jaw two feet ten inches long, and the tusks ten feet seven inches long, and seven inches and three fourths in diameter at the base. It is wonderful to reflect that but for the accidental preservation of a few bones, we should never have known the existence of an animal so huge in its dimensions, and necessarily of such vast strength and power.

We know not where, better than in the present connection, to introduce a circumstance hitherto unexplained, if not altogether inexplicable. There have been found, it appears beyond all question, in naked limestone of the elder secondary formation, close on the western margin of the Mississippi at St.Louis, the prints of human feet. The prints are those of a man standing erect, with his heels drawn in, and his toes turned outward, which is the most natural position. They are not the impressions of feet accustomed to a tight shoe, the toes being very much spread, and the foot flattened in the manner that happens to those who have been habituated to go a great length of time without shoes. The prints are strikingly natural, exhibiting every muscular impression and swell of the heel and toes, with great precision and faithfulness to nature. The length of each foot, as indicated by the prints, is ten inches and a half, and the width across the spread of the toes, four inches, which diminishes to two inches and a half at the swell of the heels, indicating, as it is thought, a stature of the common size.

Every appearance seems to warrant the conclusion that these impressions were made at a time when the rock was soft enough to receive them by pressure, and that the marks of feet are natural and genuine. ‘Such was the opinion of Governor Cass and myself,’ says Mr.Schoolcraft, ‘formed upon the spot, and there is nothing that Ihave subsequently seen to alter this view: on the contrary, there are some corroborating facts calculated to strengthen and confirm it.’ At Herculaneum, in the same neighborhood, similar marks have been found, as well as on some of the spurs of the Cumberland mountains, always in similar limestone. In the latter case it is stated that the impressions are elongated, as of persons slipping in ascending a slimy steep. Opinions are much divided as to the origin and import of these impressions. Should similar observations multiply, important inferences may perhaps be drawn from them; at present it seems impossible to speak respecting them decisively or satisfactorily.

The following extraordinary facts, respecting what may be termed living fossils, appear to be well authenticated. During the construction of the Erie canal, while the workmen were cutting through a ridge of gravel, they found several hundred of live molluscous animals. ‘Ihave before me,’ says Professor Eaton, ‘several of the shells from which the workmen took the animals, fried and ate them. Ihave received satisfactory assurances that the animals were taken alive from the depth of forty-two feet.’ In addition to this discovery in diluvial deposits, mention is made of a similar one in a much older formation. In laying the foundation of a house at Whitesborough, the workmen had occasion to split a large stone from the millstone grit. ‘It was perfectly close-grained and compact. On opening it, they discovered a black, or dark brown spherical mass, about three inches in diameter, in a cavity which it filled. On examining it particularly, they found it to be a toad, much larger than the common species and of a darker color. It was perfectly torpid. It was laid upon a stone, and soon began to give signs of life. In a few hours, it would hop moderately on being disturbed. They saw it in the yard, moving about slowly for several days; but it was not watched by them any longer, and no one observed its farther movements. They laid one half of the stone in the wall, so that the cavity may still be seen.

‘The millstone grit,’ says Professor Eaton, who gives this account, ‘in which this toad was found, is the oldest of the secondary rocks. It must have been formed many years before the deluge. Was this toad more than four thousand years old? or was it from an egg introduced, through a minute and undiscovered cleavage, into this cavity or geode, made precisely to fit the size and form of a toad? Iwas particular in my inquiry, and learned that the whole stone was perfectly compact, without any open cleavage which would admit an egg. Besides, it is well known that the millstone grit is neither porous nor geodiferous. If this rock stratum was deposited upon the toad, it must have been in aqueous, not in igneous solution, and the toad must have been full grown at the time. Toads are often found in compact, hard, gravelly diluvial deposits, in situations which demonstrate that they must have lived from the time of the deluge. Ithink Iam warranted in saying this without citing authorities, as it is a common occurrence. Then why may they not have lived a few centuries longer, if we admit them a life of at least three thousand years?’