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the strata of the series a. But c appears to have been acted upon by two forces at distant points, when thrown out of its horizontal position; for the strata dip in opposite directions, forming a basin-shaped cavity, in which the serfes d was deposited. In like manner, after the disturbance of c, the series e was deposited, covering the ends of c; but the internal force, which raised the beds e from the depths of the sea to the summit of the mountain where they are now seen, appears to have acted in such a direction, as to have carried up the whole mass without disturbing the original horizontality of the structure. It is obvious, that all the interior strata must have partaken of this last disturbance. There are, besides, numerous proofs, that there have been not only frequent elevations of the strata, but also depressions; that the same strata, which had been at one time raised above the surface of the sea, had again sunk down, preserving an inclined position; that they had formed the ground, upon which new sediment was deposited, and had again been raised up, carrying along with them the more recently formed strata.
The subjects, which it is the province of the geologist to investigate, are by no means confined to questions concerning mineral substances, but embrace a wider field, involving many considerations intimately connected with the history of several tribes of animals and plants. It is not possible to give even a brief outline of the doctrines of geology without referring to the great orders, and classes, into which naturalists have divided the animal kingdom. It will be necessary, therefore, before proceeding to describe the divisions of the stratified rocks, which geologists have established, and which are founded mainly upon the
distinctive characters afforded by the remains of organized bodies contained in the different strata, to say a few words upon the classification of animals, in order to render the terms we must employ more intelligible to those who are unacquainted with the subject.
Animals are divided into four great branches, distinguished by the terms Vertebrated, Molluscous, Articulated, and Radiated. The FIRST includes all those animals which are provided with a backbone; and because the similar bones, or joints, of which it is composed, are called by anatomists vertebræ, (from a Latin word signifying to turn,) the individuals that belong to this division are called Vertebrated Animals. It is subdivided into four classes
; 1. Mammalia, comprehending man, land quadrupeds, and the whale tribe ; that is, all animals which give suck to their young; the term being derived from mamma, the Latin name of that part of the body, from which the milk is drawn. 2. Birds of all kinds. 3. All those animals called Reptiles by naturalists : the word means nothing more than that they creep, but it has in common language a far more extended sense than that to which it is restricted in natural history. Frogs, serpents, lizards, crocodiles, alligators, tortoises, and turtles, are reptiles, in the sense of the word as used by naturalists. 4. Fishes, of all kinds, except the whale tribe, which belongs to the class mammalia.
The SECOND DIVISION includes tribes of animals, which have no bones; and because their bodies contain no hard parts, they are called Molluscous Animals, from a Latin word signifying soft. But with a few exceptions, they have all a hard covering, or shell, to which they are either attached, or in which they can inclose themselves, and be preserved from injuries, to which, from their soft nature, they would otherwise be constantly exposed. There are six classes in this division, founded on certain peculiarities of anatomical structure in the animal, but these we shall not notice; for, without a much longer description than we can enter upon, it would be a useless enumeration of bard
It will answer our present purpose much better to say, that the animals belonging to this division may be classified according to differences in the forms of their hard covering or shells, for it is the hard parts of animals which furnish the records of their former existence; these only are preserved imbedded in the strata, all traces of the flesh or other soft parts, as far as form is concerned, having entirely disappeared. MOLLUSCOUS Animals, therefore, are divisible into, 1. Univalves, that is, animals armed with a shell or valve forming one continuous piece, such as snails and whelks. 2. Bivalves, or those having two shells united by a hinge, such as oysters, cockles, &c. 3. Multivalves, or - those having more than two shells, of which the common barnacle is an example.
The THIRD DIVISION is assigned to what are called Articulated Animals, these having a peculiar anatomical structure, called articulations, from articulus, Latin for a little joint. It is subdivided into four classes ; 1. Annelides, or those having a ringed structure, from annulus, Latin for ring : leeches and earth-worms are examples. 2. Crustacea, or those, which have their soft bodies and limbs protected by a hard coating or crust, which in common language we also call shell, such as lobsters, crabs, and prawns. 3. Spiders, which form a class by themselves. 4. Insects, such as flies, beetles, bees, and butterflies.
The FOURTH DIVISION comprehends a great variety of animals, which have an anatomical structure like an assemblage of rays diverging from a common point, and from which they are called Radiated Animals, radius being Latin for ray.
It contains five classes, but as three of these are animals without hard parts, we may pass them over: of the remaining two, the one contains the echini or sea urchins; the other, the very numerous tribe called zoöphites, from two Greek words signifying animal and plant, because the animal is fixed to the ground, and builds its strong habitation in the form of a shrub, or branch, or leafy plant. Corals and sponges belong to this class; and among all the different animal renains, that are found in the
strata, there is no class, which bears any proportion, in point either of frequency of occurrence, or in quantity, to this last.
The great divisions of animals, so far as the remains of species found in the strata are concerned, or, as it is termed, in a fossil state, are therefore briefly these :
I. Vertebrated Animals; Classes-Mammalia, Birds, Reptiles, Fishes.
II. Molluscous Animals; Classes-Univalve, Bivalve, Multivalve Shells.
III. Articulated Animals; Classes-Crustacea, Insects.
IV. Radiated Animals; Classes-Eehini, Zoöphites.
Each class is farther divisible into several families ; each family into several genera ; each genus into several species, according as greater or minor points of resemblance and difference bring individuals near to each other. There are certain other great distinctions, which it is necessary to mention, 'viz. that some animals eat animal food, the Carnivorous; others vegetable food, the Graminivorous; some can live both in the air and in water, the Amphibious Among fishes, molluscæ, and crustacea, some live in the sea, some in fresh water, some in both; and of those inhabiting fresh water, some are peculiar to rivers, others to lakes. There are also land-shells, such as the common garden-snail. It is scarcely necessary to remind our readers, that certain species are peculiar to particular regions of the earth, being adapted by their nature to the different temperature and other peculiarities, that exist in different countries.
The number of distinguishable genera and species of fossil plants bears but a small proportion to that of fossil animal remains.
The lowest members in the order, in which the stratified rocks are placed one above another, are distinguished by the great predominance of hard slaty rocks, having a crystalline or compact texture, but chiefly by this circumstance, that they have not been found to contain any fragments of pre-existing rocks,
or the' remains of organized bodies. On this account they have been called the PRIMARY STRATA, as if formed prior to the existence of animal life, and as containing no evidence of other rocks having existed before them. That we cannot now discover animal remains in these strata is, however, no proof that they had not previously existed, because we meet with rocks containing organic remains, which are so altered by the action of heat in those parts, where they happen to have come in contact with a mass of granite or whinstone, that all traces of the organic remains are obliterated, those parts of the rocks acquiring a crystalline character analogous to what prevails in the primary strata. These last may have contained the remains of animals ; 'but being nearest to the action of volcanic heat, they may have been so changed as to obliterate the shells and corals, by their being melted, as it were, into the substance of the crystalline rock. The absence of the fragments of pre-existing rock is a less questionable ground of distinction. From whence the materials composing these primary strata were derived, is a question, that it is not very likely any geological researches will enable us to solve ; that they were in a state of minute division, were suspended in, and gradually deposited from, a fluid in a horizontal arrangement, and that they were subsequently elevated, broken, and contorted by some powerful force, prior to the deposition of the strata that lie over them, is beyond all doubt. There may also be beds of rock of great thickness, in which neither fragment nor organic remain has been found throughout a great extent of country, which nevertheless may not be primary; for if in any part of the same mass a single pebble or a single shell should afterwards be discovered, indubitably imbedded in it, one such occurrence would be as conclusive as a thousand, that a prior state of things had existed. It follows, therefore, that until the whole of an extensive district of such rocks were carefully examined, we could never be sure, that they might not one day be discovered to be of secondary origin; there is nothing in the mineral