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. A red 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. A grand 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. A region
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, 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 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 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 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 I have 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. ‘I have
before me,’ says Professor Eaton, ‘several of the shells from which
the workmen took the animals, fried and ate them. I have 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? I was 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. I think I am 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?’
GENERAL REMARKS ON GEOLOGY.
Geological researches are made with much greater facility in
America than in Europe, especially in the region of the secondary
strata. The immense extent over which they can be traced, the
undisturbed condition in which they are found, and their generally
horizontal position, afford great facility for efforts of system
and generalization. The absence of the newest floetz-trap rocks,
and of the effects of the violent convulsions, so frequent in
the vicinity of this disputed formation, unquestionably assist
geological research. A second and more efficient cause is found in
the extent of the changes that have been wrought in the different
classes of rocks on the European continent since their original
formation, by the effect of water, and the continual action of
rivers wearing deep beds, and exposing the subordinate strata.
Rivers also in North America have not generally cut so deep
into the different strata, either in the mountains, or during
their course in the level country, as materially to derange the
stratifications. Broken masses of one formation covering the
tops of mountains, whose foundations are composed of rocks of a
different class, seldom occur. A third cause of the facility of
geological observation in this continent is found in the fact
that the whole continent east of the Mississippi follows the
arrangement of one great chain of mountains. Europe, on the
contrary, is intersected by five or six distinct ranges, which
follow different laws of stratification, and frequently interrupt
each other.
The effect of opening this new field of observation has been
striking and important. It has been to confound every previous
effort at the determination and arrangement of general strata.
European geologists themselves have acknowledged that the general
strata must be determined in America. The absence of the chalk
forcibly illustrates this; the chalk being not only a very
prominent feature in the geological structure of Europe, but
the grand point of division between the secondary and tertiary
formations. The English oolite is not found in this country. It
has been affirmed by Professor Eaton that the old red sandstone
is not a general stratum, and even the existence of primitive
clay-slate is questioned; while Mr. Maclure informs us that though
the primitive formation contains all the variety of rocks contained
in the mountains of Europe, yet neither their relative situation
in the order of succession, nor their relative heights in the
range of mountains, correspond with European observations. The
order of succession from the clay-slate to the granite, as well as
the gradually diminishing height of the strata, from the granite
through the gneiss, mica slate, and hornblende rock, down to
the clay-slate, is so often inverted and mixed, as to render the
arrangement of any regular series impracticable.
It is of course out of the question in these remarks to present a
detailed account of the general science of geology. For valuable
and well-digested treatises on this subject, we refer to Cuvier’s
_Theory of the Earth_, and _Lyell’s Principles of Geology_. The
volumes of Silliman’s Journal, and Professor Cleaveland’s works,
abound in important matter on the geology of our continent.