arrangement; we shall only here generally remark, from the falling in of parts of the exterior crust that the occurrence of the most prominent circum- into the cavity beneath, the irregularities of the stances related in that account, has been repeatedly earth's surface were produced. inferred by the most learned writers, who have To this hypothesis of Des Cartes, that of Leibendeavored, from a view of the present state of nitz very nearly approaches. He supposed the the world, and of the various changes it has under-crust, of which we have just spoken, to have been gone, to form some conjectures with respect to its of a vitreous nature, the minute fragments of which original formation. are the sand which is every where so abundant. The affinity of the earth to the sun, has been more strictly asserted by Buffon, who informs us that the earth was originally 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 rotation, a spheroidal form, cavities being, at the same time, formed in its interior part, whilst its vapors condensed, and formed the waters of the ocean. Bicher entertained the opinion, that there existed in the centre of the globe a cavity, which contained an accumulation of sulphurous, bituminous, and other mineral principles, which, raised in the state of vapors, by the internal heat, formed the various mineral substances which are contained in the substance of the earth. This hypothesis, so little supported by probability, 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 vapor, through the different clefts of the earth, until they arrive near its surface, where they enter into various combinations; the result of this is the production of the numerous mineral substances which the earth contains.

From the very imperfect accounts which have reached us, of the doctrines of the Egyptian philosophers on this subject, we can only learn, that they were of opinion, that at the beginning the water had covered the whole surface of the world; and that this was proved by the remains of organized beings, which are so frequently seen in the substance of the earth. These waters, it was supposed, had retired to the interior cavities of the globe, remaining in this great abyss, ready to issue out and produce the most extensive inundations; to one of which it was supposed that some of their records referred. The axis of the globe, they believed to have been originally parallel with that of the plane of its orbit; and whilst it remained thus, they supposed that a perpetual spring existed; but that, on its inclining, an alteration of seasons took place.

The Chaldeans, like the Egyptians, are supposed by Diodorus Siculus, to have believed the earth to be hollow; and that in the early ages of its formation, a perpetual spring had existed. The Indians also believed in the existence of a vast abyss in the centre of the earth, for the reception of the waters which remained after the consolidation of the crus: of the earth: they also believed in a general deluge of the earth, and in a subsequent retiring of the

waters.

The opinions of the Epicureans, as delivered to us by Lucretius, appear to have been, that by the separation and appropriate reunion of accordant atoms, the different elements were formed, which, by the regulating influence of gravity, were separated from each other, and disposed in their allotted regions. One of the processes, which was thus performed, was the formation of the earth itself; which, being then variously acted upon, underwent those alterations of its surface, from which proceeded the vast cavities for the reception of the ocean, and those irregularities which divide its surface into hills and valleys.

Since several of the hypotheses of the formation of the world, and the changes which have brought it to its present state, deserve rather to be regarded as ingeniously devised allegories, than systems regularly deduced, it is not intended to do much more than specify those, the consideration of which will yield but little information. In agreement with this rule we shall only state, respecting the hypothesis of Des Cartes, that he conceived, that this globe might originally have been composed, like the sun, of the pure element (fire); but that by degrees, its less subtile parts had gradually collected together, and formed thick and obscure masses at its surface, similar to those accumulations which occasion the spots which we see on the sun. From the gradual, but, at length, complete incrustation thus formed, he supposed, that the whole planet, at length, became covered and obfuscated; that, in this manner, different crusts were formed, and that,

Besides these, who consider an inherent or central fire as necessary to the continuation and formation of this globe, there are others who refer the particular modifications 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; among 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 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 originally to have 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,

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, According to this system, therefore, in the presand such an arrangement formed of its component ent world, which is made up of the fragments of parts, as made it fit for the existence of the vegeta-those which preceded it, the materials are arranging ble and animal creation; having existed in this state its allotted time, he supposes a comet to have passed so near the earth as to have involved it in the vapors 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

which originated in, and proceeded from, the great Southern Ocean, below the equator, and which, rushing in to the northern hemisphere, descended southwards, and at length spread over the face of the whole earth.

of the thawed substances possessing less space | the primitive limestones. The level of the ancient than they did whilst frozen. The whole of the ocean becoming then lowered to the depth of nine crust, thus losing its support, sunk partially at dif- thousand feet, fish were created; and the various ferent periods, and the external water rushed in to stratified secondary mountains were formed within fill the cavities which existed, and thus caused a it during its retreat, and after the creation of fish. considerable diminution of the waters which cov-Soon after, the higher tracts of land being left unered the earth; whilst from the overturned frag- covered by the retreat of the sea to its bed, the land ments, arose the irregularities of the earth's present became supplied with vegetables and animals. surface. The deluge he considers as a miraculous effusion Led by the observation that the Alpine Moun-of water, both from the clouds and the great abyss, tains were frequently composed of strata, obliquely disposed, Saussure imagined that the surface of the globe, formed by successive depositions and crystallization, was originally covered by the ancient 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.

M. de la Metherie, who has investigated the subject with much attention, is of opinion, that all the mountains, valleys, 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 eighteen thousand 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 Patrin formed the opinion, that in the beginning which has disappeared since that period. Of this all the matters which now compose the exterior he imagines, that some part has escaped by evapopart of the globe were held in solution, or suspen-ration, and passed into other planets; but that by sion in a fluid, and that of these, some were depos- far the greatest part is buried in the immense cavited in a crystallized state, as the granite, &c. whilst erns which exist in the interior part of the globe. those which were not in a state of actual solution, On reviewing the systems which have been just formed the different schists and other earthy, saline, enumerated, it is obvious that some are so abundant and metallic strata, regularly and concentrically in fanciful conjecture, and so deficient of probabildisposed. Whilst thus existing in a soft and yield-ity, as not to require any farther remark; whilst in ing 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.

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 Mr.mountains and valleys 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 nuinerously on one spot than on another. Particular currents may 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 seems 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

That respectable and excellent mineralogist, Kirwan, has zealously endeavored 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 crytallization of the contents of this solution, the various metallic substances, the different earths, &c. were deposited, in various combinations, forming, according to the predominant proportion of the ingredients, granite, gneiss, porphyry, 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

in solution. It has been objected against this mountains themselves, Werner discovered the system of crystallization of rocks, &c. that nature strongest proofs of the diminution of the original seems to form nothing of that kind at the present waters of the globe. He ascertained, 1st. That the period; but were this the fact, the objection would outgoings (the upper extremities as they appear at not possess much force, since a most satisfactory the surface of the earth) of the newer strata are answer might be given, by asserting that the opera- generally lower than the outgoings of the older, tion has ceased, in consequence of the task being from granite downward to the alluvial depositions, accomplished; and, speaking with respect to the and this, not in particular spots, but around the granitic and porphyry rocks, all the materials being whole globe. 2d. That the primitive part of the employed. The formation of stone by crystalliza-earth is entirely composed of chemical precipitation 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.

fire cause of this mixture, we are referred to the later formation than any of the preceding classes. period of their formation, that at which the sum- These deposites may be divided into, first, Those mits of the primitive mountains just appeared which are formed in mountainous countries, and are above the waters, when, by the attrition excited by found in valleys, being composed of rolled masses, the motion of the waves, and which we are re-gravel, sand, and sometimes loam, fragments of minded extends to no great depth, particles of the ores, and different kinds of precious stones. Second, original mountains were worn off and deposited. Those which occur in low and flat countries, being As the height of the level of the ocean diminish- peat, sand, loam, bog-iron ore, nagel flech, calced, so would the surface on which its waves acted tuff, and calc-sinter: the three latter being better increase, and of course the quantity of the me-known by the names breccia, tufa, and stalactite. chanical depositions. Hence these are much more In this ingenious system, in which so much abundant in the rocks of the next formation, which knowledge of the subject prevails, and in which are denominated floetz rocks, on account of their the marks of long and patient investigation are being generally disposed in horizontal or flat strata. evident, a very close accordance with geological In these, petrifactions are very abundantly found, facts is generally observable. Some few difficul having been formed whilst vegetables and animals ties, however, occur, particularly, it seems, with existed in great numbers. These rocks are gener- respect to the new trap-formation, since although ally of very wide extent, and commonly placed at the appearances which this is intended to explain the feet of primitive mountains. They are seldom do not better agree with any other supposition, still of very great height, from whence it may be in- the rising of the waters whilst they yet covered the ferred, that the water had considerably subsided at summits of the primitive mountains, has much the the time of their formation, and did not then cover appearance of a supposition made up for this parthe whole face of the earth. Countries composed ticular purpose; and as it appears to be warranted of these rocks are not so rugged in their appearance by no other phenomena, it seems to require further nor so marked by rapid inequalities, as those in consideration before it is fully admitted. which the primitive and transition rocks prevail. The formations of this class are supposed to be first, first or old red sand-stone; second, first or oldest floetz limestone; third, first or oldest floetz gypsum; fourth, second or variegated sand-stone; The instruments used in geometry, are the scale fifth, second floetz gypsum; sixth, second floetz, and the compass: the scale, to draw and measure or shell limestone; seventh, third floetz sand stone; lines; the compass, to describe circles, of which eighth, rock-salt formation; ninth, chalk formation; the use is the measurement of angles. The scale tenth, floetz trap-formation; eleventh, independent is usually divided into feet, inches, and lines: the coal-formation; twelfth, newest floetz trap-forma

tion.

Most of the rocks which have been just enumerated are covered by a great formation, which is named the newest floetz trap. 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 deposites, such as clay, sand, and gravel. The remains both of vegetables and animals also occur very abundantly in these deposites. 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 found in other floetz 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 appearances observed in these rocks, it is concluded, that the waters in which they were formed had risen with great rapidity, and had afterwards settled into a state of considerable calmness.

The collections and deposites derived from the materials of pre-existing masses, worn down by the powerful agency of air and water, and afterwards deposited on the land or on the sea coasts, are termed alluvial, and are, of course, of much

GEOMETRY. The art of measuring quantity of every kind; whether length, breadth, height, or depth.

circle is divided into three hundred and sixty parts or degrees; and when an angle of teu, twenty, or any other number of degrees, are mentioned, ten, twenty, or the specific number of parts of a circle, divided into three hundred and sixty degrees, is intended.

The origin of this science is always attributed to Egypt, where it is said to have been produced by the necessity of ascertaining the boundaries of landed property, which are every year effaced by the inundations of the Nile.

From the time of Euclid, who died three hundred years before the Christian era, to that of Purbach and Müller, who died in the fifteenth century, geometry was neglected. Since its revival, it has benefited by the illustrious labors of Nepper, Des Cartes, Newton, and Leibnitz.

GEORGIC. A poetical composition upon the subject of husbandry, containing rules therein, put into a pleasing dress, and set off with all the beauties and embellishments of poetry.

GERANIUM. A genus of plants, containing a vast number of species, many of which are cultivated on account of the elegance of their flowers. The calyx is persistent, of five leaves; the petals are five, alternate with the calyx leaves; the stamens are ten, more or less connected at the base; the style single, terminating in five stigmas. The species are herbaceous or saffruticose, with the younger stems articulate. Most of the cultivated species belong to the subgenus pelargonium, and are natives of Southern Africa, where they are ex