To this hypothesis of Des Cartes, that of Leibnitz very nearly approaches ; he supposed the crust, of which we have just spoken, to have been of a vitreous nature, the minute fragments of which are the sand that is every where so abun dant. The affinity of our earth to the sun has been more strictly asserted by Buflon, who informs us, that the earth was origi nally separated from the sun, by the stroke which the sun received from the falling in of a comet ; that this fragment, during its cooling, acquired, from its ro tation, a spheroidal form, cavities being, at the same time, formed in its interior part, whilst its vapours condensed, and formed the waters of the ocean. Bieber entertained the o pinion, that there ex isted in the centre of the globe a cavity, which contained an accumulation of sul phurous, bituminous, and other mineral principles, which, raised in the state of va pours, by the internal heat, formed the va rious mineral substances which are con tained in the substance of the earth. This hypothesis, so little supported by probabi lity, has been nearly adopted in modern times, by Gensanne, in his "History of Lan guedoc ;" who imagines the existence of a central fire, by the influence of which nu. merous mineral principles are raised, in a state of vapour, through the different clefts of the earth, until they arrive near to its surface, where they enter into various combinations; the result of th?e is the production of the numerous mineral sub stances which the earth contains.
Besides these, who consider an inherent or central fire as necessary to the forma tion and continuation of this globe, there are others, who refer the particular modi fication of the form of its surface to the operation of subterraneous fires, acting partially by the incalescence of pyrites and volcanic eruptions, with accompany ing earthquakes ; amongst those who have adopted this opinion, may be mentioned Steno, Lazare, Moro, and Ray.
To produce the vast effects necessary to give form to a planet, or to modify its sur face anew, must of course require the most powerful physical agents. In the va rious systems, therefore, which human in genuity has devised, with the hope of pointing out the natural means which have been employed in these prodigious ope rations, the powerful agency of lire or of water has been generally referred to; and hence geologists have been rather whimsically named, according to the par ticular agency which they have supported in their discussions, Plutonists, and Nep tunists. The systems already here no ticed, it is obvious, are those in which fire has been adopted as almost the sole agent ; in those which next will engage our at tention, recourse has been bad to the combined powers of both agents.
Dr. Burnet, whose system manifests a considerable portion both of ingenuity and judgment, supposes the earth to have originally been a fluid mass, the compo nent parts of which became arranged ac cording to their gravity ; hence the hea viest matters were deposited at the cen tre, and above these were disposed, in concentric layers, the substances which were less and less heavy, and on the sur face was the earth, covered all round by the water, which was itself invested by an unctuous matter, around which existed the circumanibient air. By the subsequent in
tertnixture of the oily matte r and earth, and other arrangements of its several compo nent parts, the crust of earth acquired a smooth form, and obtained those qualities which were necessary for the existence of organized beings. At this period, the axis of the globe was supposed to be parallel with that of its orbit, the days and the nights to be equal in length, and a uniform season to have existed, resembling a perpetual spring ; but on the crust of the earth dry ing, from the ardency of the heat, it be came violently rent asunder, falling into, and giving openings for the vast abyss of waters beneath : hence the axis of the globe became inclined, occasioning those changes of the seasons, and of the length of the days and nights which now exist ; and thus also were produced the beds of the ocean, with the vallies and the nume rous mountainous elevations.
Mr. Winston conjectured, that the earth was originally a comet, which, at the pe riod mentioned in the Mosaic account as that of the creation of the world, had its orbit rendered nearly circular, and such an arrangement formed of its component parts, as made it fit for the existence of the vegetable and animal creation : having ex isted in this state its allotted time, he sup poses a comet to have passed so near to the earth, as to have involved it in the va pours fortning its tail, and which, being condensed, tell in torrents, and produced the deluge described by Moses ; the ac tion of the comet on the earth itself hav ing been sufficient to produce, at the same time, those irregularities of its sur face, which form chains of mountains and the vast beds of the ocean.
Mr. Pallas, having assumed the forma tion of the sea and the primitive rocks, supposed that, with the sand produced by their constant disintegration, the sea must have deposited such inflammable and fer ruginous matters, as, being disposed in beds on the granite, would form the fuel of volcanoes ; these, raising and bursting the solid beds under which they had ex isted, and which they must have altered by fusion or calcination, would raise up the mountains of schist and of lime-stone. The shores of the sea being gradually augmented, the sea being diminished and driven back, whilst its bed was raised in different parts by the power of volcanoes, the formation of the mountains containing petrifactions would take place. Lastly, he supposed, after the earth had been well stocked with vegetables and animals, that by some enormous eruptions at the bot tom of the sea, its waters may have been made to inundate the whole horizontal surface of the earth, and even those moun tains which have not exceeded one hun dred toises in height.