OUTLINES OF GEOLOGY.

THE term GEOLOGY comes from the Greek ge, the "earth," and logos, "reason," or "discourse," and signifies the doctrine, or science of the Earth.

The object of Geology is to investigate the phenomena of the external and internal parts of the earth-to inquire into the modifications and changes which have taken place in the crust of the globe since its creation, and to account for these phenomena in a rational and scientific manner.

This science, though of very recent date, has already been the means of offering to the consideration of the world, most important information, both of a physical and moral nature. Many important geological facts, it is true, have been long known; but in attempting to account for them, theorists have indulged themselves, until recently, in the wildest imaginations, and the most unfounded and singular fancies.

No subject of importance has come down to the philosophers of the present age, so incumbered with false theories, false reasonings, and whimsical vagaries, as Geology.

It is true, that a few writers of early date have reasoned correctly from the facts then known, but the great mass of authors on this subject, seem to have had no other object in view, but to establish theories founded on plausibilities, without the aid of facts, or observations.

From the earliest antiquity men have been inquisitive in relation to the origin and duration of the earth; and the mutations which it has undergone already, or is likely to undergo in future times. In the absence of knowledge concerning the Earth's structure, or of observations on the phenomena which its surface exhibits, it was easier to found theories, and reason for the ignorance then existing, than to undertake long excursions in order to observe facts, from which to reason correctly, and draw just conclusions.

It appears from the remotest records of profane history, that philosophy had assigned to this Earth a perpetual series of mutations, either by fire, or water, or by both.

Some supposed that this fair world was occasionally, or periodically destroyed, and again renovated under a new aspect; and that a new creation of men and animals took place after every such renovation. The ancient Egyptians believed that this world was subject to occasional deluges and conflagrations, and that the gods by such awful judgments arrested the career of human wickedness, and purified the habitation of man from his own guilt. It was supposed that all the wicked were destroyed by such disasters, and that the few who escaped, were the wise, virtuous, and happy, but that their descendants gradually became wicked, and were in like manner swept away by the wrath of the gods.

Baron Humboldt states, that after the destruction of a large portion of the inhabitants of Cumana, in South America, by an earthquake, in 1766, an extraordinary fertility ensued, in consequence of the rain which had accompanied the convulsion. On this occasion says he, the Indians celebrated, in conformity to an ancient superstition, by festivals and dancing, the destruction of the world, and the approaching epoch of its renovation.

The Egyptian priests assigned certain periods of time for the destruction and renovation of the world. According to Pritchard, in his Egyptian Mythology, the cycles, or periods of these catastrophes were variously estimated. Orpheus supposed their duration to be 120,000 years; Cassander, 300,000 years, &c. The Greek philosophers and stoics also believed that the Earth was liable to be afflicted by periodical catastrophes, both by flood and fire. The first, they supposed destroyed the whole human race, and annihilated all animal and vegetable productions, and that the second dissolved the Earth itself, but that this was afterwards renovated, or re-produced.

The connection between the doctrine of successive catastrophes, and repeated deteriorations in the moral character of the human race, is more intimate and natural to the minds of men than might at first be imagined. For in a rude state of society, all great calamities are regarded by the people as the immediate judgments of God on the wickedness of man. Thus says Mr. Lyell in our own times, the priests persuaded a large part of the population of Chili, and perhaps believed themselves, that the great earthquake of 1322, which convulsed that country was

a sign of the wrath of heaven on them, for the great political revolution just then commencing in South America.

We may observe from the accounts of travellers, and voyagers among barbarous tribes in the South Sea Islands, and in India, that earthquakes are almost universally considered among these people as judgments sent by a supreme, or superior being, on the wickedness of men. In countries not subject to earthquakes, as among the Egyptians, there are still traditions, or forebodings of conflagrations, as we have already seen; and so far as is known, all nations and tribes, whether civilized or barbarous, are not without their notions, however vague, of a flood of water which destroyed at least most of the inhabitants of their own country. Were it not most probable that this idea has been handed down by tradition from the time of Noah, it would often appear as though it were an innate moral sentiment, designed by divine authority to impress all mankind with the fear of punitive justice.

This subject will come under consideration when we come to treat of the Deluge, and we will only remark further at present, that it is believed, neither the ancient philosophers, nor modern barbarians ever entertained any idea of the final destruction of the Earth, this belief being derived exclusively from the sacred scriptures. We have seen that several ancient nations held to the doctrine of perpetual changes, consisting of the alternate destruction and renovation of the Earth. A similar doctrine is said to have been taught by the Gerbanites, a sect of astronomers who flourished before the Christian era. They believed that after every period of 36,000 years, there were produced twenty-five pair of every species of animals, male and female; and that these multiply and spread over the face of this lower world. But that when a circulation of the heavenly orbs was completed, which is finished in the above named space of time, then other species of animals are created, together with new plants and other things, and so it goes on forever and ever.

It is the light of revelation alone, to which we are indebted, at the present day, for that knowledge and understanding which places us above a belief in the false doctrines of heathen philosophy. Civilization and experience never yet corrected the speculative philosophy, or the religious opinions of heathenism.

With respect to the knowledge which the ancients possessed of geology, nothing of importance can be said. The Greek naturalists, and the Arabian physicians and philosophers have recorded some few geological facts, and several Latin writers have noticed phenomena connected with earthquakes and volcanoes, especially the rising of islands out of the sea. But the geologist will search in vain, for any facts or speculations concerning the history of the Earth, worthy his notice, until the beginning of the 16th century; when some shells dug out of the Earth at Verona, in Italy, became the subject of a controversy which may be considered as having laid the foundation of geological knowledge.

These fossil, or petrified shells were found in 1517, in consequence of some excavations which were made for the purpose of repairing some part of the city of Verona. Such remains it is true, had long before been discovered in various places; but no persons of learning or judgment seem previously to have troubled themselves about such matters. The idea seems to have prevailed, that these were the products of what was then termed "plastic nature;" that is, that shells, and other organic remains, found in the solid earth, above the sea, were not the exuviæ of animals, but were formed in the rocks where they were discovered, and that they were nothing more than imitations of real shells and bones. This idea was probably suggested, for the purpose of accounting for the appearance of shells in places where it was supposed impossible the sea should ever have been; the idea that the sea had changed its bed, or that the strata had been elevated by subterranean forces, being then entirely unknown. At present, such phenomena are readily accounted for on the hypothesis that many parts of the earth, have been thrown up from the bottom of the sea by volcanic force.

The shells at Verona furnished matter for much speculation, and many writers gave their opinions concerning them, as well as of other fossils found in similar situations. Among these, one writer named Fracastoro, gave it as his settled conviction that these and other fossil shells, wherever they were found, had once belonged to living animals, and at the same time ridiculed the notion that the "plastic force" of nature ever formed them, or any other such like productions. He also maintained that these belonged to animals which grew and multiplied in the places