lity, has been nearly adopted in modern times, by Gensanne, in his "History of Languedoc," who imagines the existence of a central fire, by the influence of which numerous 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 this is the production of the numerous mineral substances 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 modification of the form of its surface to the operation of subterraneous fires, acting partially by the incalescence of pyrites and volcanic eruptions, with accompanying 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 surface anew, must of course require the most powerful physical agents. In the various systems, therefore, which human ingenuity has devised, with the hope of pointing out the natural means which have been employed in these prodigious operations, the powerful agency of fire or of water has been generally referred to; and hence geologists have been rather whimsically named, according to the particular agency which they have supported in their discussions, Plutonists, and Neptunists. The systems already here noticed, it is obvious, are those in which fire has been adopted as almost the sole agent; in those which next will engage our attention, recourse has been had 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 component parts of which became arranged according to their gravity; hence the heaviest matters were deposited at the centre, and above these were disposed, in concentric layers, the substances which were less and less heavy, and on the surface was the earth, covered all round by the water, which was itself invested by an unctuous matter, around which existed the circumambient air. By the subsequent intermixture of the oily matter and earth, and other arrangements of its several component 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 drying, from the ardency of the heat, it became 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 numerous mountainous elevations.

Mr. Whiston conjectured, that the earth was originally a comet, which, at the period 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 existed in this state its allotted time, he supposes a comet to have passed so near to the earth, as to have involved it in the vapours forming its tail, and which, being condensed, fell in torrents, and produced the deluge described by Moses; the action of the comet on the earth itself having been sufficient to produce, at the same time, those irregularities of its surface, which form chains of mountains and the vast beds of the ocean.

Mr. Pallas, having assumed the formation 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 ferruginous 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 existed, 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 bottom of the sea, its waters may have been made to inundate the whole horizontal surface of the earth, and even those mountains which have not exceeded one hundred toises in height.

The system of Dr. Hutton resembles, in many points, that which has been just noticed; but its several parts are better connected, and it certainly possesses, als

though in its tendency it is highly exceptionable, a more prepossessing appear ance, since it ascribes the formation of continents, of mountains, vallies, &c. not to accidental occurrences, but to the operation of regular and uniform causes; making the decay of one part subservient to the restoration of another, by successive reproductions. Thus he supposes this globe to be regulated by a system of decay and renovation, and that these are effected by certain processes which bear a uniform relation to each other. The solid matter of the earth, especially of the rocks and high lands, he supposes to be perpetually separating by the reiterated action of air and water, and when thus detached, carried by the streams and rivers, and then deposited in the beds of the ocean. From these deposits, the various strata of our earth are supposed to be formed, obtaining their consolidation from the action of sub-marine fires; which, being placed at immense depths, must operate on these stratified depositions under the circumstance of vast pressure; by which volatilization must be prevented, and such changes produced, as would not otherwise be effected by the power of heat. The expansive power of subterraneous fire is called also in to explain, by the elevation of strata, their various positions. Thus, while the ocean is in one part removed by the accumulation and the elevation of strata, fresh receptacles are forming for it on other spots, where new strata will be deposited, rendered solid, and elevated.

According to this system, therefore, in the present world, which is made up of the fragments of those which preceded it, the materials are arranging for the formation of its successor; the system manifesting, as its author avowed, neither vestige of a beginning, nor prospect of an

end.

Having thus sketched the outlines of the most interesting of the systems, which suppose the formation of this globe to have chiefly depended on the agency of fire, we shall now proceed to take a view of those in which the same effect is described as having been produced by the influence of water.

Woodward, with too little attention to facts, well known at the period at which he wrote, supposed that the solid parts of the earth were arranged in strata, according to their degrees of specific gravity; the water which had held them in solution having afterwards retreated to the grand abyss, which he supposed to exist in the centre. After some time, God or.

dained that the crust should break and fall into the abyss, and that the water should cover the surface. By the great solvent powers of this water, he supposed that every thing was again dissolved, and that afterwards they were again precipitated in concentric layers. The surface was then supposed to have been again broken, by which the waters again reached the centre, and the broken surface yielded those inequalities which now exist.

De Luc conceived, that in the beginning the sun did not exist in a luminous state, and that the earth, not feeling its influence, was frozen; but that, as the sun diffused its rays, the ice on the earth's surface became thawed, and penetrating inwards, dissolved the earth and other frozen matters to the depth of several leagues below the surface. But the thaw having reached this point, he supposes that the dissolved substances became either crystallized or precipitated, and that as they solidified they formed the primitive crust of the earth. After this, orga nized beings were created, many of which became involved in new strata, (the secondary) which were now formed at the bottom of the ocean; and the thawing of the internal parts of the globe continuing, cavities were formed, in consequence of the thawed substances possessing less space than they did whilst frozen. The whole of the crust, thus losing its support, sunk partially, at different periods, and the external water rushed in to fill the cavities which existed, and thus caused a considerable diminution of the waters which covered the earth; whilst, from the overturned fragments, arose the irregularities of the earth's present surface.

Led by the observation that the Alpine Mountains were frequently composed of strata obliquely disposed, Saussure imagined that the surface of the globe, formed by successive depositions and crystallizations, was originally covered by the an cient ocean; but that the crust bursting by the expansive force of heat, or of elastic fluids, the interior or primitive parts of the crust were turned outwards, and supported by those of secondary formation. By the rapid retreat of the waters into the cavities thus formed, he accounts for the enormous blocks, now lying in plains far distant from the rocks from which they were separated. After this retreat of the waters, he supposes that plants and animals were formed; and that since that period several immense currents have been caused by the opening of fresh gulfs, into which the waters have retreated at different periods; the last of

which being that which reduced the waters to their present level.

Patrin formed the opinion, that in the beginning all the matters which now compose the exterior part of the globe were held in solution, or suspension in a fluid; and that of these, some were deposited in a crytallized state, as the granite, &c. whilst those that were not in a state of actual solution formed the different schists, and other earthy, saline, and metallic strata, regularly and concentrically disposed. Whilst thus existing in a soft and yielding state, the different substances, by acting on each other, he supposes to have passed into a state of fermentation, necessarily productive of a swelling or raising up, which taking place first of all in the granitic and saline pasty masses, these were elevated, carrying with them, or bursting through the other strata, thus forming the rocks and mountains now existing on the face of the earth.

That respectable and excellent mineralogist, Mr. Kirwan, has zealously endea voured to form a system which may accord with the Mosaic account of the creation. He supposes the superficial parts of the globe to have been in a fluid state, being held in solution by water considerably heated. From the coalescing and crystallization of the contents of this solu tion, the various metallic substances, the different earths, &c. were deposited in various combinations, forming, according to the predominant proportion of the ingredients, granite, gneiss, phorphyry, and the other primeval rocks. By the crystallization of these immense masses,a prodigious quantity of heat was generated, even to incandescence, and the oxygen uniting with inflammable air occasioned a stupendous conflagration; by this the solid basis on which the chaotic fluid rested was rent to a great extent. From the extrication, by this heat, of the oxygen and nitrogen gases, the atmosphere was formed and from the union of the oxygen with ignited carbon, carbonic acid proceeded, which, being absorbed by calcareous earth, was precipitated in combination with it, forming the primitive lime stones. The level of the ancient ocean becoming then lowered to the depth of 9000 feet, fish were created; and the various stratified secondary mountains were formed within it during its retreat, and after the creation of fish. Soon after, the higher tracts of land being left uncovered by the retreat of the sea to its bed, the land became supplied with vegetables and animals. The deluge he considers as a miraculous effusion of water, both

from the clouds and from the great abyss which originated in, and proceeded from, the great southern ocean below the equator, and which, rushing into the northern hemisphere, descended southwards, and at length spread over the face of the whole earth.

M. de la Metherie, who has investigated the subject with much attention, is of opinion, that all the mountains, vallies, and plains, composing the crust of the earth, were formed nearly in the state in which they now exist, by crystallization of the mass of water which surrounded the earth. The matters composing the highest mountains, he shows, have evidently been held in solution: the water, therefore, must have reached above their summits, and of course have stood 18,000 feet, at least, above its present level. But this being admitted, it becomes necessary to determine what has become of the immense quantity of water which has disappeared since that period. Of this he imagines that some part has escaped by evaporation, and passed into other planets, but that by far the greatest part is buried in the immense caverns which exist in the interior part of the globe.

On reviewing the systems which have been just enumerated, it is obvious that some are so abundant in fanciful conjecture, and so deficient of probability, as not to require any further remark; whilst in others of a more specious appearance, there are some points which cannot be allowed to their ingenious authors. On these particular doubtful points, it is thought best to offer a few remarks, rather than separately examine each system. With respect to crystallization from an aqueous solution, a supposition which has not yet been generally adopted, it may be remarked, that the primitive mountains and vallies give exactly that irregularity of appearance, from lofty needle-like forms shooting up in some parts, and extensive plains existing in others, which are observable in cases of crystallization on the small scale. It has been objected, that the secondary mountains do not every where cover the primary on which they rest; this circumstance must, in all probability, have depended on particular local circumstances, and especially on such as would, as in ordinary cases of crystallization, direct the formation of crystals more numerously on one spot than on another. Particular currents may perhaps be considered among the causes which assisted in producing these effects, as well as in forming particular chains: whilst to the action of contrary currents

may be attributed the formation of separate mountains. The formation of secondary mountains seem also to concur with what is generally observed in the ordinary progress of crystallization, where it is observed, that after one series of crystals are formed of the least soluble matters, others are then formed of those substances which the fluid was able to hold still longer in solution. It has been objected against the system of crystallization of rocks, &c. that nature seems to perform nothing of that kind at the present period; but were this the fact, the objection would not possess much force, since a most satisfactory answer might be yielded, by asserting that the operation has ceased, in consequence of the task being accomplished; and, speaking with respect to the granitic and phorphyry rocks, all the materials being employed. The formation of stone by crystallization is, however, carrying on in various situations at the present moment; the incrustations formed in certain springs, and the various stalactitic formations which take place daily, are instances of this kind.

The unfitness of water to hold the substances forming the primitive rocks in solution has been considered as a powerful objection: but it is to be considered, that the menstruum cannot be supposed to have been simple water, but, as Mr. Kirwan observes, this primitive fluid must have contained all the various simple saline substances, and indeed every simple substance, variously distributed, "forming, upon the whole, a more complex menstruum than any that has since existed, and consequently endued with properties very different from any with which we have been since acquainted." Geological Essays, P. II.

Considerable difficulty must, however, continue, in adapting any system which confines the production of the various geological phenomena, which present themselves to our observation, to too few and to too limited causes; since, however necessary it may be to refer the general phenomena to the operation of one particularly powerful agent, it still must be necessary to take into the reckoning the sinking and the raising of particular spots from subterraneous submarine fires; as well as the changes produced by the subversion of lofty mountains, rapid and violent currents of water, and various other powerful causes.

By the preceding sketch of the numerous systems which have been advanced, and by these cursory remarks on some of

the objections which have been made against those which appear to possess the greatest share of probability, the mind becomes better prepared to attend to the system of the celebrated Werner, to whom, in the opinion of his learned and zealous annotator, we owe almost every thing that is truly valuable in this import. ant branch of knowledge. For the purpose of conveying some notion of this ingenious system, the following sketch is taken from the view of it, given in the "Elements of Geognosy," by Professor

Jameson.

Agreeable to this system, the earth is supposed to have existed originally in a state of aqueous fluidity, which is inferred from its spheroidal form, and from the highest mountains being composed of rocks, possessing a structure exactly resembling that of those fossils, which have as it were, under the eye, been formed by water. From this circumstance it also follows, that the ocean must have formerly stood very high over these mountains; and as these appear to have been formed during the same period of time, it follows, that the ocean must have formerly covered the whole earth at the same time.Contemplating the formations of the mountains themselves, Werner discovered the strongest proofs of the diminution of the original waters of the globe. He ascertained, 1st, that the outgoings (the upper extremities as they appear at the surface of the earth) of the newer strata are generally lower than the outgoings of the older, from granite downwards to the alluvial depositions, and this, not in particular spots, but around the whole globe. 2d. That the primitive part of the earth is entirely composed of chemical precipitations, and that mechanical depositions only appear in those of a later period, that is, in the transition class, and thence they continue increasing, through all the succeeding classes of rocks. This evidence of the vast diminution of the volume of water which stood so high over the whole earth is assumed to be perfectly satisfactory, although we can form no correct idea of what has become of it.

By the earliest separations from the chaotic mass, which are discoverable in the crust of the globe, was formed a class of rocks, which are therefore termed primitive rocks, being chiefly composed of silex, alumina, and magnesia, constitut ing, by their various intermixtures, 1, granite; 2, gneiss; 3, mica-slate; 4, clayslate; 5, primitive lime-stone; 6, primi

tive-trap; 7, serpentine; 8, porphyry; 9, sienite; 10, topaz rock; 11, quartz rock; 12, primitive flinty slate; 13, primitive gypsum; 14, white stone. The circumstances which chiefly mark the high antiquity of these rocks are, that they form the fundamental rock of the other classes; and that the outgoings of their strata are generally higher than those of the other classes. Having been formed in the uninhabitable state of the globe, they contain no petrifactions; and, excepting the small portions which sometimes accompany those which will be next mentioned, they contain no mechanical deposits, but are throughout pure chemical productions. Small portions of carbonaceous matter occur only in the newer members of the class.

Before the summits of the mountains appeared above the level of the ocean, and before the creation of vegetables and animals, a rising of the waters is supposed to have taken place, during which that class of rocks which are said to be of the second porphyry and sienite formation was deposited. The rocks of this formation are of clay-porphyry, pearl-stone porphyry, obsidian porphyry, sienite, and pitch-stone. They contain very little mechanical depositions, are of complete chemical formation, and contain little or no carbonaceous matter, and never any petrifactions.

On the appearance of land, or during the transition of the earth from its chaotic to its habitable state, rocks, which, from this circumstance, are denominated transition rocks, were formed. In these rocks the first slight traces of petrifactions, and of mechanical depositions, are to be found. The species of rocks which come under this class are, the transition lime-stone, transition-trap, gray-wacke, and flinty slate. The petrifactions are, corallites, encrinites, pentacrinites, entrochites, and trochites. The lime-stone of Derbyshire is said to be of this kind. As the former class of rocks were purely of chemical formation, so the contents of these are chiefly chemical productions, mingled with a small proportion of mechanical depositions. To explain the cause of this mixture we are referred to the period of their formation, that at which the summits of the primitive mountains just appeared above the waters, when, by the attrition excited by the motion of the waves, and which we are reminded extends to no great depth, particles of the original mountains were worn off and deposited.

As the height of the level of the ocean diminished, so would the surface on which its waves acted increase, and of course the quantity of the mechanical depositions. Hence these are much more abundant in the rocks of the next formation, which are denominated flatz rocks, on account of their being generally disposed in horizontal or flat strata. In these, petrifactions are very abundantly found, having been formed whilst vegetables and animals existed in great numbers. These. rocks are generally of very wide extent, and commonly placed at the feet of primitive mountains. They are seldom of very great height, from whence it may be inferred, that the water had considerably subsided at the time of their formation, and did not then cover the whole face of the earth. Countries composed of these rocks are not so rugged in their appearance, nor so marked by rapid inequalities, as those in which the primitive and transition rocks prevail. The formations of this class are supposed to be, 1, first or old red sand-stone; 2, first or oldest flætz lime-stone; 3, first or oldest flatz gypsum; 4, second or variegated sand-stone; 5, second flatz gypsum; 6, second flatz or shell lime-stone; 7, third flatz sandstone; 8, rock-salt formation; 9, chalk formation; 10, flatz-trap formation; 11, independent coal formation; 12, newest flatz-trap formation.

Most of the rocks which have been just enumerated are covered by a great for mation, which is named the newest flœtztrap. This formation also covers many of the high primitive mountains: it has but little continuity, but is very widely distributed. It contains considerable quantities of mechanical deposits, such as clay, sand, and gravel. The remains both of vegetables and animals also occur very abundantly in these deposits. Heaps of trees and of parts of plants, and an abundance of shells and other marine productions, with the horns of stags, and great beds of bituminous fossils, point out the lateness of the period when this formation was deposited. In this formation several rocks occur, which are also met with in other flatz formations; but the following are supposed to be peculiar to this class, basalt, wacke, gray-stone, porphyry, slate, and trap tuff. These rocks are said to have been formed during the settling of the water consequent to a vast deluge, which is supposed to have taken place when the surface of the earth was covered with animals and vegetables, and when much dry land existed. From various ap