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much more whimsical even than these. As, for instance, that of De Marschall, who imagined that all the rocks and mountains are so many meteors which have fallen from the sky! To this we might add the theory of Demaillet, who says that the rocks were all made by shell-fish, and that all animals, man included, inhabited the sea, while the shell-fish were engaged in the construction of mountains high enough for our present land animals to stand upon! And last, though by no means least, in this catalogue of visions, let us not forget the happy thought of Kepler, who described the earth as being actually alive, with the waters for blood, and the rocks for bones!

These personages, however, and a great many of their disciples, we may leave to that oblivious repose which they have for some time enjoyed, and apply ourselves to the modern theories, among which that of Dr. Hutton, formerly Mathematical Professor at the Royal Military Academy of Woolwich, stands pre-eminent. He is what is called a Vulcanist, that is, he ascribes every thing to the immediate agency of fire. He sets out with imagining that before our globe was fashioned as we now find it, a great number of other globes must have formerly existed; that having been acted upon by the moist atmosphere, by rains, frosts, thaws, and tempests, those globes crumbled gradually away, and were carried by rivers, in the form of sand, clay, and gravel, to the sea, at the bottom of which they arranged themselves in beds, differing in thickness according to the circumstances by which they might be affected. Being thus disposed in beds, the Doctor next imagines that a great central fire exists in the interior of the earth, which found its way to the said beds, and fused them into rocks. The newly-formed rocks were next elevated above the sea by the expansion of the central fire, and thus assumed the character of continents, diversified by hill and valley, which in their turn are destined to be again crumbled into sand, and to be returned to the bottom of the sea, where they are to undergo a repetition of the process just described; and thus matters are to go on to the end of time. Dr. Hutton does not pretend to inform us what seas are particularly favourable to this vast chemical manufacture of continents and mountains. Nor does he at all explain how the sea-beds are operated upon by his central fire, without the interference of the element beneath which all this fusion is constantly going on. As to the cause of the expansive power of the fire ceasing as soon as its products are lifted to the pure atmosphere; or as to the sources whence his central fire is fed, the Doctor is discreetly silent. Professor Playfair, in his eloquent vindication of this system, compares the central fire to that of the sun, and maintains, that as the latter cannot be accounted for upon any principle with which we are acquainted, no questions should be asked about the former. If this reasoning be admissible, we are at liberty to imagine that the interior of the globe is inhabited, because the sun is said to be in a similar condition.

If, as Dr. Hutton insists, the rivers are constantly adding gravel, sand, and clay, to the bottom of the sea, sufficient to form new continents, how happens it that the waters of the sea are not continually rising and inundating the land already constructed? Some islands and cities, we know, have been overwhelmed in the ocean, but the instances are not at all sufficiently numerous to meet the question. Again, how were those globes manufactured, the ruin of which was necessary before our earth was composed? But in fact the objections to this theory are endless.

The next geological man of note is Werner. We shall give a description of his theory from the little work before us :

According to Werner, all the substances which now constitute rocks, mountains, and soil, on the earth's surface, were originally existing in a state of solution in the waters of the great chaos, which he supposes, at the beginning, to have surrounded the globe to a vast depth. The substances or materials of rocks, thus swimming in the primitive ocean, he conceives to have gradually fallen to the bottom, sometimes by chemical, sometimes by mechanical means, and sometimes by both together; and in this manner he thinks all the rocks have been formed which we now find, on digging into the earth. The inequalities of mountains and valleys on the surface of the earth, which were thus produced as soon as the waters began to subside (and this subsidence is an important point in the system), gradually rose out of the primitive sea, forming the first dry land. The rocks which were in this manner first formed, Werner calls the Original, or Primitive Formation; they consist of granite, gneiss, different species of slate, marble, and trap.

The formation of these rocks, however, did not, it seems, exhaust the materials floating in the waters, for the deposition went on, and a class of rocks were formed, consisting of gray wacké, limestone, and trap, which rested on the primitive, and are called by Werner the Intermediate or Transition Rocks; because, on their appearance above the water, the earth, he conceives, passed into a habitable state. After the formation of these primitive and transition rocks, Werner alleges that the waters suddenly rose over them to a great height, covering them in many places, as it again subsided, with a new formation of rocks, consisting of sandstone, conglomerates, limestone, gypsum, chalk, and rock salt, which he called Level or Floetz Rocks. Since that period, the wearing-down of the rocks, by the action of the weather and other causes, and the washing away of the worn materials by rains and streams of water, have formed soil, gravel, sand, peat, and the various other beds which are called Alluvial.'—pp. 58-60.

The Wernerians do not pretend to account for the existence of their great chaotic ocean; in this respect they claim the same freedom of hypothesis as Dr. Hutton insists upon for his original globes. They argue, however, in this way. In every part of the earth great masses of rocks are met with, the origin and formation of which can only be explained by supposing them to have been deposited from a solution of their materials in water. But it is chemically impossible that so extensive a solution could have existed

without a vast quantity of water; therefore the chaotic ocean must have existed. Conceding this conclusion to be true, we may ask, what became of this chaotic ocean? Whither has it retired? To a great central abyss, say the Wernerians, or hollow in the centre of the earth, formed by impenetrable walls of granite! But how were these walls formed? Supposing them, however, to exist, how could the ocean, which first contained the whole earth, be subsequently contained within it? Others say, that the earth was sent to afford a retreat to the waters of this sea, when they were no longer necessary; and others again maintain that the waters in question were decomposed, and that its component parts were disposed of in the atmosphere. A conjecture more simple and more satisfactory than any of those just mentioned is this, that a sufficient number of Leviathans rose to the surface of this superfluous ocean, and drank it all up. This is a strong conjecture we grant, but not more untenable than any that we have enumerated.

There are chemical objections to Werner's hypothesis, of an ocean holding so many substances in a state of solution, which leave it, in our apprehension, without even the appearance of plausibility. Besides, he seems to have imagined that all the rocks in the world were like those of Saxony, which is as much as saying that all the porcelain in the world is like that of Dresden.

But although we may be dissatisfied with the theories which make a great central fire, or a chaotic ocean the universal agent, we cannot deny that the deep produces rocks, and those, too, of the most solid description; nor yet that, as the volcanic islands prove, there are powerful subterraneous fires constantly in operation. But both of these phenomena stand well authenticated by the reports of different voyagers. The former are the work of the coral animalculæ minute and delicate creatures, which seem to have the power of encasing themselves in a hard crust, for the purpose of protection. They are described as more like a snail, or a shell-fish, than an insect. Colonies of them abound in the seas between New Holland, New Caledonia, and New Guinea, where they have erected large coral reefs. Indeed, one coral barrier is said to run three hundred and fifty miles in a straight line, opening into the sea. This reef is connected with others, so as altogether to make an extent of nearly one thousand miles in length, and from twenty to fifty miles in breadth. The process by which the coral is made seems to resemble that by which the snail forms its shell. The sea water always contains lime; the coral snail produces by its breathing carbonic acid gas, which, uniting with the lime, forms the basis of the coral rocks; and this being cemented and strengthened by the slime of the animal, becomes that durable substance which the sailor often fears to meet amid the waves, and which we often see dangling from a lady's ear.

The intelligence with which the coral snails combine their operations, is as wonderful a chapter in natural history, as that which

describes the economy of the bees. The mere creation of the coral rocks seems to be little more than the result of a chemical process; but the manner in which they assist each other, in order to produce a firm compact wall, from the bottom to the surface of the sea, is surprising. But it is still more so to observe that these reefs are generally constructed in the form of a crescent, or of a circle, with the convex side to the waves, as if the little masons were perfectly apprised of all the qualities of the arch in resisting the force of the waves. If the barrier consist only of a segment of a circle, the strength of the arch is always sure to be nicely placed in that quarter from which the storm most frequently blows. The description given by Captain Flinders, of the operations of the coral snails, is singularly interesting.

"It seems to me, that, when the coral animalcules cease to live, their structures adhere to each other, by virtue either of the glutinous remains within, or of some propensity in the salt water; and, the interstices being gradually filled up with sand and broken pieces of coral washed by the sea, which also adhere, a mass of rock is at length formed. Future races of these animalcules erect their habitations upon the rising banks, and die in their turns, to increase, but principally to elevate, this monument of their wonderful labours.

“The care taken to work perpendicularly in the early stages, would mark a surprising instinct in these diminutive creatures. Their wall of coral, for the most part built in situations where the winds are constant, being arrived at the surface, affords a shelter, to leeward of which their infant colonies may be safely sent forth; and to this, their instinctive foresight, it seems to be owing, that the windward side of a coral reef, exposed to the open sea, is generally, if not always, the highest part, rising almost perpendicularly, sometimes from the depth of two hundred, and perhaps many more, fathoms.

To be constantly covered with water seems necessary to the existence of the animalcules, for they do not work, except in holes upon the reef, beyond low-water mark: but the coral sand, and other broken remnants thrown up by the sea, adhere to the rock, and form a solid mass with it, as high as the common tide reaches. That elevation surpassed, the future ones, being scarcely covered, lose their adhesive property, and, remaining in a loose state, form what is usually called a key, upon the top of the reef.

"The new bank is not long in being visited by sea-birds; salt plants take root upon it, and a soil begins to be formed; a cocoa-nut, or the berry of a pandanus, is thrown on shore; land birds visit it, and deposit the seeds of plants, shrubs, and trees; every high tide, and still more every gale, adds something to the bank; the form of an island is gradually assumed; and, last of all, comes man to take possession.

"Half-way Island is well advanced in the above progressive state; having been many years, probably some ages, above the reach of the highest spring tides, or the wash of the surf in the heaviest gales. I distinguished, however, in the rock which forms its basis, the sand, coral, and shells formerly thrown up, in a more or less perfect state of cohesion. Small pieces of wood, pumice-stone, and other extraneous bodies, which

chance had mixed with the calcareous substances when the cohesion began, were inclosed in the rock.”—pp. 153—155.

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This island will probably be fit for habitation before the end of the present century. Captain Cooke says that the coral reefs are most probably the origin of all the tropical low isles over the whole South Sea." Here, therefore, is a natural cause producing rocks and islands from the deep, though not exactly in the way that Werner and his disciples would be most happy to discover.

On the other hand, Dr. Hutton's theory of the agency of a central fire is partially countenanced by the fact, that islands have been occasionally thrown up to the surface of the sea by volcanos. The instances, however, of these eruptions are too few to establish a general conclusion in favour of his hypothesis. The island of Teneriffe is supposed to have been produced by an eruption of this kind. According to Mr. Barrow, eighteen small islands appeared above the surface of the sea, near the Azores, at the termination of a great earthquake, but they gradually sunk again, and vanished from the view. Professor Pallas gives us a curious account of an island that appeared in 1790, in the sea of Azoph, after loud thunder and subterraneous noises.

"Then," he says, “after an explosion ĺike that of a cannon, an island, about the size of a large antient tumulus, rose from out of the sea, which in that part was from twenty-five to thirty feet deep. The island was about six hundred feet in circumference, appeared to raise itself, to break into chasms, and to throw out mud and stones, till smoke and flame at length broke forth; the perpendicular height of the island was about twelve feet. There was an amazing swell of the sea during the whole process, which lasted two hours; and, in the course of the day, two earthquakes were felt at the distance of fifty leagues. The final dimensions of the island were four hundred and thirty feet in length, two hundred and eighty-eight in breadth, and seven in height; but the following year the island disappeared."—pp. 158, 159.

So, also, an island which in 1811 rose from the bottom of the sea, in view of his Majesty's ship Sabrina, and called by that name, was engulphed again in a few months after; whence it would appear that these volcanic islands are very unstable in their duration. Teneriffe, however, is an example to the contrary; as is also the island of Erini, in the bay of that name, about twenty-eight leagues to the north of Crete. Ševeral other similar occurrences might be mentioned. Volcanos have also produced mountains on land, in some few instances, and not more than three or four years ago, we all remember that the shore of the Pacific, to the north of Valparaiso, was raised two or three feet by an earthquake-an alteration which it still retains. But Dr. Hutton's theory applies only to rocks and mountains raised from the sea, and we rather fear that, however ingenious may be his speculations, he can hardly muster a sufficient number of facts to support them.

It is time for us now to proceed to Mr. Granville Penn's geolo

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