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 mayhere 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 generallyresemble 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, I have carefully examined not a few of the fossil trees there existing. Among them I noticed 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 I have in my possession the perfect impression of the cassia and the tea leaf. Of ferns, I have beautiful impressions of the leaves, and of the bread-fruit tree flowers, fully expanded, fresh, and entire. I have 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, I ought 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. ‘I am 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 areno 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 I have 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, I know 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 togo 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.