As might be expected, this era was marked by vast and violent convulsions; volcanoes raged and threw up molten granite, earthquakes heaved and uplifted continents, seas were displaced and inundated the land, and still the earth was enveloped in vapor and mist, arising from the high temperature, and the light most probably penetrated only sufficiently to produce a sickly twilight, while the sun shot lurid rays through the dense and foggy atmosphere. Such a world must have been incompatible with either animal or vegetable life, and we accordingly find no remains of either in the rocks which belong to this early period; their principal characteristic is a highly crystalline appearance, giving strong presumptive evidence of the presence of great heat.
After this era of desolation and gloom, we enter upon what is technically termed the "Transition period," and here we begin to mark the gradual preparation of the globe for the reception of its destined inhabitants. The change is, however, at first very slight, and there is evidence of frequent convulsions and of a high degree of temperature; but the action of fire appears to have declined in force, and aqueous agencies are exerting themselves. The earlier portion of this formation is rendered peculiarly interesting by the fact, that during it the most ancient forms of life sprang into existence. It is true that merely a few species of shell-fish, with some corals, inhabited the depths of the ocean, while the dry land still remained untenanted; nevertheless, humble and scanty as they were, we can not fail to look with interest on the earliest types of that existence, which has subsequently reached such perfection in ourselves.
The presence of corals shows, that although the transition seas had lost their high temperature, yet they retained a sufficient degree of heat to encourage the development of animals requiring warmth. These minute animals possess the remarkable property of extracting from the elementary bodies held in solution in the waters, the materials for forming new rocks. To the coral animalcule or polype we owe much of the vast limestone beds which are found in every part of the world, and many a vessel laden with the riches and productions of the earth finds a grave on the sunken reefs that are the fruit of its labors.