6, a Ganoid Fish.

1, 3, and 4, remains of curious Fish, from six to ten inches in length. 2 and 8, fossil Corals. 5 and 7, Trilobites, five or six inches in length. 9, the Plesiosaurus, a lizard-like marine reptile, from ten to fifteen feet in length. 10, the Ichthyosaurus, or fish-lizard, a kind of reptile whale, from twenty to thirty feet in length. portions could not be preserved in the drawing.]

[The relative pro

1. IN ascending from the Transition to the Secondary period, after passing the Devonian, which in North America exhibits no less than eleven distinct eras, we arrive at the Carboniferous system of rocks, which is so called from being the great depository of that important substance called coal. A new creation is here opened to view in the luxuriant tropical vegetation which distinguishes the Carboniferous epoch of our globe. The various kinds of coal are simply vegetable matter-the remains of ancient forests deposited in vast ravines or ocean beds, and deeply buried there, and changed to their present forms by chemical processes in Nature's own laboratory. The coal is often covered by layers of shale, or slaty coal, which consists of masses of leaves and stems closely pressed together, and indicating an intermediate stage in the coal formation. The appearance of the roof of one of the coal-mines of Bohemia having this shale or partially formed coal for its covering, is thus described by Dr. Buckland:

2. "The most elaborate imitations of living foliage on the painted ceilings of the Italian palaces bear no comparison with the beauteous profusion of extinct vegetable forms with which the galleries of these instructive coal-mines are overhung. The roof is covered as with a canopy of gorgeous tapestry, enriched with festoons of most graceful foliage, flung

* This seems to have been effected by exposure to heat and moisture, probably under great pressure, and in circumstances that excluded the air, and prevented the escape of the more volatile principles. Not only the various coals, but bitumen, amber, mineral oils, and even the diamond, were probably produced under various modifications of these circumstances.

in wild, irregular profusion over every portion of its surface. The effect is heightened by the contrast of the coal-black color of these vegetables with the light groundwork of the rock to which they are attached..

3. "The spectator feels transported, as if by enchantment, into the forests of another world; he beholds trees of form and character now unknown upon the surface of the earth, presented to his senses almost in the beauty and vigor of their primeval life; their scaly stems and bending branches, with their delicate apparatus of foliage, are all spread forth before him, little impaired by the lapse of indefinite ages, and bearing faithful records of extinct systems of vegetation, which began and terminated in times of which these relics are the infallible historians. Such are the grand natural herbaria wherein these most ancient remains of the vegetable kingdom are preserved in a state of integrity little short of their living perfection, under conditions of our planet which exist no more.

4. It is not only known that coal is of vegetable origin, but the kinds of plants which formed it have been accurately determined, to the number of more than three hundred species, but all different from any of the present age, although allied to existing types by common principles of organization. Of these fossil species, two thirds are related to the tree ferns and the higher orders of cryptogamous plants. The coniferous, or cone-bearing species, are also prominent; and there is little doubt that petroleum, and naphtha, and other mineral oils of coal regions, are nothing more than the turpentine oil of the pines of former ages. The internal heat of the earth has distilled it; and, after being buried for thousands of years, it is now discovered, to supply the wants of man. Remains of corals, shell-fish, a few insects, among which are several species of beetle, fishes of peculiar construction, the king-crab among Crustaceans, and in Pennsylvania the tracks of some Batrachian reptiles, have been found in the Carboniferous rocks. Here, also, are the last of the trilobites, which appear to have become extinct after the coal formations.

5. Ascending above the Carboniferous epoch, we pass successively, in this Secondary period, through three groups or systems of rocky strata, known as the Saliferous, or Red Sandstone, the Oolitic, and the Cretaceous. The first of these is comparatively scanty in organic remains; but in the other two, fossils are exceedingly abundant. Our existing islands and continents are principally composed of the spoils of this

period, whose history opens to us the fathomless depths of ancient seas, and vast marshes, with the remains of myriads of beings which lived and died in their waters.

6. The ocean then swarmed with sponges and other zoophytes, sea-weeds, and corals, and Crustaceans; even oysters were abundant, but different from existing species; remains of a shark-like fish are found here; smaller fish were numerous; and in almost every fragment of some of the flint formations their minute scales have been detected by the aid of the microscope. On the land were several species of spiders, and insects in considerable numbers. The tracks of gigantic birds have been detected-"footprints in the sands of time" -in the rocks of this period; but of the existence of any mammalia, the sole indications are the jaws of some small animals related to the opossum.

GEOLOGICAL REMAINS OF ANIMALS OF THE UPPER SECONDARY PERIOD. 1, a Crinoidea. These are sparingly found in this period. 2, 6, and 9 are remains of Echinites, or Sea-urchins. 3, 8, and 12 are Cretacean shells. The fish here represented are from one to three feet in length. 5 is the Pterodactyl, or flying reptile, having the head and neck of a bird, the jaws and teeth of a crocodile, the wings of a bat, and the body and tail of a mammal. It is believed that the spread of its wings was not less than twenty-five feet. 13 is the restored figure of the Iguanodon, as drawn by Martin, and found in Mantell's Geology. In making a complete drawing of such an animal from its fossil remains, much of its external appearance must be left to the imagination. It is certain, however, that the iguanodon was a monster reptile, thirty or forty feet in length. From the form of its teeth, and the vegetable matter found in connection with its skeleton, it is known to have been herbivorous.

7. The remains of turtles, the earliest clear indications of the reptile tribe, occur in the Saliferous period; and above them, and later in point of time, but still in this Secondary era, are the remains of the crocodile. But what especially mark this as the Age of Reptiles are the numerous species of monster Saurians, bearing such uncouth names as the ichthyosau'rus, plesiosau'rus, megalosau'rus, and the iguan'odon, with the pterodac'tyls, or flying reptiles. In the island or peninsula of Portland, England, a petrified forest has been discovered in the upper formations of the Secondary period, and therefore contemporary with the monster reptiles whose

names we have given. We have represented the forms and dimensions of some of these monsters of a by-gone age as they have been pictured and described by geologists.

8. In closing our sketch of this Secondary period, we would remark, in the language of Hugh Miller, that at this period in the history of our country, "at the close of the Cretaceous system, there existed no species of plant or animal that exists at the present time. We know that it is appointed for all individuals once to die, whatever their tribe or family, because hitherto all individuals have died; and geology, by extending our experience, shows us that the same fate awaits on species as on the individuals that compose them." Of the several periods of existence which measure animated nature, the briefest is allotted to individuals: species live longergenera longer still; while above them are orders and classes, the latter the most comprehensive of all.

of formations which link together the present and the past. We have evidences of numerous changes in the earth's crust in the beginnings of this epoch, of volcanic action of great extent and frequency, and of alternations of ocean beds with those of vast fresh-water lakes. The alternating strata of this period have been divided into three principal groups, characterized by the proportion of shells, allied to existing species, which they contain. Thus the lowest group, the eocene, signifying the dawn of the recent, contains not more than three or four per cent. of fossil shells allied to those of recent species; the next, the miocene, about twenty per cent.; and the upper, the pliocene, about eighty per cent.*

2. But besides the marine and fresh-water shells which abound in this period, imbedded in vast layers of limestone rocks, the fossils of crabs, lobsters, and other Crustaceans are numerous; there have also been found the teeth of unknown sharks, and the remains of many genera of fishes, vast quantities of the remains of leaves, fruits, stems of plants, and trunks of trees perforated by the borer, together with the fossils of birds related to existing species. But what especially characterize the older Tertiary deposits are the numerous fossil remains of a class of pachydermata, of species now unknown, but bearing an affinity to the tapir, the rhinoceros, and the hippopotamus. Such are the numerous species of the palæotherium and the anoplotherium, some of which are represented in the engraving at the head of this lesson.

3. In the middle division of this period the seas became the habitation of numbers of marine mammalia, consisting of dolphins, whales, seals, and the manatee, although none of them were of the same species as those which exist at present. Here, also, are found the remains of the gigantic dinotherium —an animal not less than fifteen feet in height, with the proboscis of an elephant, and tusks curved downward as in the walrus. He seems to have formed a connecting link between

It may be regarded as a singular coincidence that the capitals of Great Britain and France are located on strata of the same geological epoch in the Tertiary period. Both Paris and London are situated on a vast alternation of marine and fresh-water beds, lying in basins of the chalk formation, the uppermost of the Secondary period. The annexed cut illustrates the geological formation of the two cities. These ancient basins or gulfs

London.

Paris.

1

were evidently open to the sea on one side, while on the other they were supplied by riv. ers charged with the spoils of the country through which they flowed, and carrying down the remains of animals and plants, with land and river shells. Changes in the relative level of the land and sea took place, and, lastly, the country was elevated to its present altitude above the sea.-MANTELL.