The design of these facts, is not merely to satisfy the curiosity of the reader, but as will be seen in the sequel, to account for phenomena which the earth presents, by showing an analogy between the effects of known and unknown causes. Thus the earth almost every where indicates, by the position of its strata, that its crust has been disturbed · by subterranean forces; and marine remains, shew that a great proportion of the dry land has once been under the That these changes have been effected by the same cause which elevates islands from the sea at the present day, we shall endeavor to show in another place.

sea.

Temple of Jupiter Serapis. In a few instances, it is known that portions of land have several times changed their level, with respect to that of the sea; and of which the following is an interesting and curious example.

The temple of Serapis, a celebrated monument of antiquity, is situated on the little bay, called Baiæ, within the bay of Naples.

A geological examination of the coast of Puzzuoli, along this bay, shows that the land has been elevated about twenty feet at a period not very remote, so that without the evidence presented by the temple, there is sufficient proof that the land in the vicinity has changed its level.

If the coast along the shore, between Naples and Puz zuoli be examined, it will be seen that the tract of fertile land which intervenes between the present shore, and the high rocky cliffs, was evidently once under the water, and that the ancient shore was near these cliffs.

The inland cliff near Puzzuoli, is in many places about eighty feet high, and quite perpendicular. At its base, the new deposite attains the height of twenty feet above the sea. This consists of sedimentary matter, mixed with marine shells showing that it was formed under the water.

The annexed cut, fig. 10, from Mr. Lyell, will explain the situation of this coast in 1828. a, on the right, shows the situation of antiquities, on a hill south of Puzzuoli; b, ancient cliff, now inland; c, terrace composed of marine deposites of recent date. a, on the left, represents the remains of Cicero's villa, at the north of Puzzuoli; b, ancient cliff, now inland; c, terrace composed of recent marine deposites; d, temple of Serapis.

The soil of these level deposites, is considered so valuable, that a wall has been built for its protection against the washing of the sea; but in some places, the wall has been thrown down, so that the strata are exposed. These consist of alternate layers of mud and pumice, enclosing abundance of marine shells. One stratum contains large quantities of the remains of ancient art, as tiles, and pieces of Mosaic pavement.*

The remains of the works of art are found below, as well as above the marine shells. Among the shells, are the Cardium, Donax, Buccinum, and Östrea. (These will be found, figured and described, towards the close of this volume.)

Now there are no tides in the Mediterranean, by which these shells could have been cast upon the shore; and the remains of ancient buildings at other places, show that there has been no change in the level of this sea, for the last two thousand years; hence we must conclude, that the land along this coast has been elevated about twenty feet above its former level.

But in addition to the above evidence, the remains of the temple of Serapis, show that that edifice has undergone several changes of level, when compared with the

sea.

With respect to this temple, Mr. Lyell, who has lately visited the spot, says, "It appears, from the most authentic accounts, that the three pillars, now standing erect, continued down to the middle of the last century, half buried in the new marine strata above described. The upper parts of the columns being concealed by bushes,

* Ancient Mosaic pavement consists of small pieces of stone, generally marble, of different colors, arranged in figures, sometimes representing groups of men and animals, in commemoration of some historical event. These are cemented so as to form a continuous solid mass. The floors of ancient churches and temples were often thus made.

had not been discovered, until 1750, when they were seen to form part of a splendid edifice. On examination, the pavement was found, still entire, and upon it lay a number of magnificent columns, a part of which were of African breccia,* and a part of granite. The original plan of the building could be traced distinctly: it was of a quadrangular form, seventy feet in diameter, and the roof had been supported by forty-six noble columns, twenty-four of which were of granite, and the rest of brecciated marble. The large court had been surrounded by apartments, supposed to have been used as bathing rooms; for a thermal spring, still employed for medicinal purposes. continues to flow from just behind the ruins, and the water of this spring, it is said, was conveyed to the chambers by marble conductors." Lyell, vol. i. p. 453.

Since the discovery of these remains, many antiquaries have entered into elaborate discussions, on the question to what deity this edifice was consecrated; but from its situation, and construction, there is more reason to suppose that it was a bathing house, than a heathen temple. But our object will be to show what geological changes these antiquities indicate.

Fig. 11.

The annexed cut, fig. 11, represents Serapis, as it now appears, reduced from the drawing of Mr. Lyell. These pillars are forty-two feet in height, and their surfaces are smooth and entire to the height of about twelve feet above the pedestal, the reason of which will appear directly. Above this, is a zone, twelve feet in length, where the marble has been pierced by a marine perforating shell fish, called by Cuvier, Lithodomus. It is a species of the Mytilus of Linnæus, and the Modiola of Lamarck.

* Breccia is a rock composed of broken, angular pieces of stone, generally of various colors, cemented by the hand of nature. The pillars of the capitol, at Washington, are of this kind of marble.

These animals enter the stone by a small orifice, which they make themselves when quite young, and as they increase in size they enlarge their habitations in proportion. They are nourished by the sea water, which is admitted through the small aperture. These animals have not the power, or perhaps inclination to leave their cells, hence their houses during life, become their tombs at death.

The limestones on the shores of the Mediterranean, are frequently full of the excavations of these animals. The genus Pholas, also contains some species which penetrate rocks. Both are figured under the articles "Multivalves" and "Bivalves," towards the end of this volume. These animals cannot pierce silicious rocks, such as granite.

As these animals cannot live, except when immersed in salt water, we must infer that these pillars were for a long time submerged, and that during part of that period, their lower portions were covered up by the rubbish already mentioned, while their upper ends reached above the water. This accounts for the reason why their middle portions only, are peforated by these animals. On the pavement of the temple lie several columns, broken in pieces. These are perforated on their fractured ends, as well as on other parts, showing that they had lain under water for a long time after they were broken.

The platform of the temple is at present just under the water, and the upper part of the perforations on the standing columns is at least twenty-three feet above the water, from which it is clear that these columns must have continued for a long time immersed in the water, while in an erect position, after which they must have been raised, by the rising of the ground to their present elevation.

Thus it appears, that the temple of Serapis was first depressed by the sinking down of the ground where it stands, so that the water of the sea surrounded these pillars about twenty feet above its present level; after which, it was again raised to its present situation, by the elevation of the coast. It is hardly necessary to say, that the cause of these changes, was undoubtedly the same which has produced the elevation of islands, and the sinking down of the ground in other places.

SEAT AND THEORY OF VOLCANOES.

It was formerly believed that the seat of volcanoes was superficial, and that the heat which fused the rocks, and sent them forth in the form of lava from the mouths of volcanoes, was owing to the combustion of mineral coal. It is a sufficient refutation of this hypothesis, that were the whole interior of the earth composed of coal, it must have long since been exhausted in the vicinity of ancient burning mountains. Also, that no geologist ever supposed coal to exist below granite mountains, which are often pierced by volcanic apertures.

The cause of volcanoes has also been attributed to the spontaneous ignition of pyrites, or metallic sulphurets.

With respect to this theory, in the first place, there is no evidence that the interior of the earth is composed of the sulphurets of the metals, nor is this in the least degree probable; and second, were this ascertained to be the case, and could the theorist contrive to perpetuate its ignition, or to make it occasional, as circumstances required, still it would fail to account for the phenomena of earthquakes and volcanoes. But lastly, the products of volcanoes are not such as would result from the ignition of the sulphurets of the metals. This is sufficient.

Since the great discovery of Sir H. Davy, that the earths and alkalies are the oxides of metallic substances, it has been proposed to account for volcanoes and earthquakes, by the admission of water to these metallic elements.

This theory may be thus stated. If pure potash or soda be deprived of its oxygen, there remains a brilliant silver-white metal, so light as to swim on the surface of water.

These metals have an affinity of oxygen so strong, that when thrown on water, the fluid is decomposed, the oxygen being absorbed by the metal so rapidly as to occasion a degree of heat, which sets the hydrogen on fire. Thus by throwing these metals on water, combustion is excited, and the oxides of potassium, and sodium, or in other words, pure potash or soda is formed.

Now if we suppose that at the creation, the elements of things were formed in a distinct and separate state, and that the condition of the earth's surface at the present time is owing to the exercise of chemical affinities, then we might