the height of the pole at Paris, going from thence directly northwards, till he came to the place where the height of the pole was one degree more than at that city. The length of the way was measured by the number of revolutions made by one of the wheels of his carriage; and, after proper allowances for the declivities and turnings of the road, he concluded that 68 Italian miles were equal to a degree on the earth. According to these methods, many other measurements of the earth's circumference have since that time been made, with much greater accuracy. See DEGREE and EARTH. Though the inaps of Eratosthenes were the best of his time, they were yet very imperfect and inaccurate. They contained little more than the states of Greece, and the dominions of the successors of Alexander, digested according to the sur veys above mentioned. He had indeed seen, and has quoted, the voyages of Pythias into the great Atlantic ocean, which gave him some faint idea of the western parts of Europe; but so imperfect, that they could not be realized into the outlines of a chart. Strabo says he was very ignorant of Gaul, Spain, Germany, and Britain; and he was equally ignorant of Italy, the coasts of the Adriatic, Pontus, and all the countries towards the north. Such was the state of geography, and the nature of the maps, before the time of Hipparchus. He made a closer connection between geography and astronomy, by determining the latitudes and longitudes from celestial observations. From his time nothing of any consequence to deserve recording occurs till about 150 years after Christ, when Ptolemy composed his system of geography. The chief materials he employed in composing this work, were the proportions of the gnomon to its shadow, taken by different astronomers at the times of the equinoxes and solstices; calculations founded on the length of the longest days; the measured or computed distances of the principal roads contained in the Roman itineraries and surveys; the various reports of travellers and navigators; and the works of preceding authors, particularly Strabo, who published under Augustus. All these were compared together, and digested into one uniform body or system. This system, however, was very imperfect, containing some great errors, which are pointed out in Blair's History of Geography: nevertheless it continued in vogue till the last three or four centuries, within which time, the great improvements in astronomy, the discoveries of new countries by navigators, and the progress of commerce and of arms, have contributed to a very great degree of perfection. From an observation of the diversity in the length of the days and nights, the rising and setting of the sun,with the other phenomena, the antient geographers divided the surface of the earth into certain districts, which they called climates; and instead of the method of describing the situation of places by their latitude and longitude as we do now, they contented themselves with men tioning the climate in which they were situated. This method of dividing the surface of the earth into climates, though now very much disused, has been adopted by several modern geographers. Some of these begin their climates at the equator, reckoning them by the increase of half an hour in the length of the day northward. Thus they go on till they come to the polar circles, where the longest day is 24 hours: betwixt these and the poles they count the climates by the increase of a natural day in the length of time that the sun conVOL. V. tinues above the horizon, until they come to one where the longest day is 15 of ours or half a month; and from this to the pole they count by the increase of half-months or whole months, the climates ending at the poles where the days are six months long. The climates betwixt the equator and the polar circles are called hour climates, and those between the polar circles and the poles are called month climates. In cominon language, however, we take the word climate in a very different sense; so that when two countries are said to be in different elimates, we understand only that the temperature of the air, seasons, &c. are different. See CLIMATE. From the difference in the length and positions of the shadows of terrestrial substances, ancient geographers have given different terms to the inhabitants of certain places of the earth; the rea. son of which will be easily understood from the following considerations: I. Since the sun in his apparent annual revolution never removes farther from the equator than 234 degrees, it follows, that none of those who live without that space, or beyond the tropics, can have the luminary vertical to them at any season of the year. 2. All who live between the tropics have the sun vertical twice a year, though not all at the same time. Thus, to those who live directly under the equator, he is directly vertical in March and September at the time of the equinox. If a place is in 10° north latitude, the sun is vertical when he has 10° north declination, and so of every other place. 3. All who live between the tropics have the sun at noon sometimes north and sometimes south of them. Thus those who live in a place situated in 20°north latitude have the sun at noon to the northward when he has more than 20 degrees north declination, and to the southward when he has less. 4. Such of the inhabitants of the earth as live without the tropics, if in the northern hemisphere, have the sun at noon to the southward of them, but to the northward if in the southern hemisphere.-1. Hence when the sun is in the zenith of any place, the shadow of a man or any upright objects falls directly upon the place where they stand and consequently is invisible; whence the inhabitants of such places were called Ascii, or without shadows. 2. Those who live between the tropics, and have the sun sometimes to the north and sometimes to the south of them, have of consequence their shadows projecting north at some seasons of the year, and south at others, whence they were called Amphisch, or having two kinds of shadows. 3. Those who live without the tropics have their noon-shadows always the same way, and are therefore called Heteroscii, that is, having only one kind of shadow. If they are in north latitude, the shadows are always turned towards the north, and if in the southern hemisphere, towards the south. 4 When a place is so far distant from the equator that the days are 24hours long, orlonger, the inhabitants were called Pericii, because their shadows turn round them. Names have likewise been imposed upon the inhabitants of different parts of the earth from the parallels of latitude under which they live, and their situation with regard to one another. 1. Those who lived at distant places, but under the same parallel, were colled Periæci, that is, living in the same circle. Some writers, however, by the name of Periæci distinguish those who live under opposite points of the same parallel, where the noon of one is the midnight of the other. 2. When two places lie under parallels equally distant from R the equator, but in opposite hemispheres, the inhabitants were called Autæci. These have a similar increase of days and nights, and similar seasons, but in opposite months of the year. According to some, the Antæci were such as lived under the same geographical meridian, and had day and night at the same time. 3. If two places are in parallels equally distant from the equator, and in opposite meridians, the inhabitants were called Antipodes, that is, having their feet opposite to one another. When two persons are Antipodes, the zenith of the one is the nadir of the other. They have a like elevation of the pole, but it is of different poles; they have also days and nights alike, and similar seasons of the year, but they have opposite hours of the day and night, as well as seasons of the year. Thus when it is midday with us, it is midnight with our Antipodes; when it is summer with us, it is winter with them, &c. From the various appearances of the sun, and the effects of his light and heat upon different parts of the earth, the division of it into zones has arisen. These are five in number. 1. The torrid zone, lying between the two tropics for the space of 47° of latitude. This is divided into two equal parts by the equator. 2. The two temperate zones lie between the polar circles and the tropics, containing a space of 43° of latitude. And, 3. The two frigid zones lie between the polar circles and the poles. In these last the longest day is never below 24 hours; in the temperate zones it is never quite so much, and in the torrid zone it is never above 14. The zones are named from the degree of heat they were supposed to be subjected to. The torrid zone was supposed by the ancients to be uninhabitable, on account of its heat; but this is now found to be a mistake, and many parts of the temperate zones are more intolerable in this respect than the torrid zone itself. Towards the polar circles also these zones are intolerably cold during the winter season. Only a small part of the northern frigid zone, and none of the southern, is inhabited. Some geographers reckoned six zones, dividing the torrid zone into two by the equator, The natural division of the surface of the globe is into sea andland; about three-fourths of the whole being occupied by water, although probably no where to a depth comparatively very considerable, at most, of a few miles on an average. The remaining fourth consists of lands, elevated more or less above the level of the sea, interspersed, in some parts, with smaller collections of water, at various heights, and in a few instances, somewhat lower than the general surface of the main ocean. Thus the Caspian Sea is said to be about three hundred feet lower than the ocean; and in the interior parts of Africa there is probably a lake equally de pressed. Hence arise the following technical terms: A continent is a large portion of the earth, which comprehends several countries that are not separated by any sea; such are Europe, Asia, Africa, and America. An island is a part of the earth which is entirely surrounded by water; as Great Britain. A peninsula is a tract of land almost surrounded with water, and is joined to a contiient only by a narrow slip or neck; such is the Morea in Greece. An isthinus, or neck of Jand, is that part by which a peninsula is joined to a continent, or two continents together; as the isthmus of Suez, which joins Africa to Asia. A promontory, or cape, is a high part of land which *retches into the sea; thus the Cape of Good Hope is a promontory. An ocean is a vast col lection of waters surrounding a considerable part of the continent; as the Atlantic. A sea is a smaller collection of waters; as the Black Sea. A gulf is a part of the sea which is nearly surrounded with land; as the gulf of Venice. A bay has a wider entrance than a gulf; as the Bay of Biscay. A strait is a narrow passage that joins two seas; as the Strait of Gibraltar, which joins the Mediterranean to the Atlantic. A lake is a large collection of water entirely surrounded by land, having no visible communication with the sea; as the Caspian Lake in Asia. A river is a stream of water that has its source from a spring, which keeps continually running till it falls into some other river, or into the sea. The ancients considered the globe under the three grand divisions of Asia, Europe, and Africa. Here the distinctions were arbitrary, as they often included Egypt under Asia, and they had not discovered the limits of Europe towards the N. EModern discoveries have added a fourth division, that of America, which exceeding even Asia in size, might have been admitted under two grand and distinct denominations, limited by the ischinus of Darien. Till within these last thirty years it was supposed that a vast continent existed in the south of the globe; but the second navigation of captain Cook dispelled the idea, and demonstrated that if any continent existed there, it must be in the uninhabitable ice of the south pole. The vast extent of New Holland rewarded the views of the enterprize; this, which seems too large to be ranked among islands, and too small for a continent, eludes the petty distinctions of man: and while geographers hesitate whether to ascribe it to Asia, or to denominate it a fifth specific division of the earth, it is not improbable that the popular division of four quarters will still predominate over all speculative discussions. Of the grand divisions of the earth, Asia bas ever been esteemed the most populous; and is supposed to contain five hundred millions of souls, if China, as has been averred by the latest writers, comprizes three hundred and thirty millions. The population of Africa may be estimated at thirty millions, of America at twenty millions, and one hundred and fifty millions may perhaps be assigned to Europe. We cannot observe any general symmetry in the distribution of the earth's surface; excepting that the two large continents of Africa and South America have some slight resemblance in their forms, and that each of them is terminated to the eastward by a collection of numerous islands. The large capes projecting to the southward have also a similarity with respect to their form, and the islands near them; to the west the continents are excavated into large bays, and the islands are to the east: thus Cape Horn has the Falkland Islands; the Cape of Good Hope, Madagascar ; and Cape Comorin, Ceylon to the east. The great continent, composed of Europe, Asia, and Africa, constitutes about a seventh of the whole surface of the earth; America about a sixteenth; and Australasia, or New South Wales, about a fiftieth; or in hundredth parts of the whole, Europe contains two; Asia, seven; Africa, six; America, six; and Australasia, two; the remaining seventy-seven being sea; although some authors assign seventy-two parts only out of one hundred to the sea, and twenty-eight to the land. These proportions may be ascertained with tolerable accuracy, by weighing the paper made for covering a globe, first entire, and then cut out according to the terminations of the different countries; or, if still greater precision were required, the greater parts of the continents might be divided into known portions of the whole spherical surface, and the remaining irregular portions only weighed. The general inclinations and levels of the continents are discovered by the course of their rivers. Of these the principal are, the rivers of the Amazons, the Senegal, the Nile, the river St. Lawrence, the Hoangho, the river La Plata, the Jenisei, the Mississippi, the Volga, the Oby, the Amur, the Oronooko, the Ganges, the Euphrates, the Danube, the Don, the Indus, the Dnieper, and the Dwina; and this is said to be nearly the order of their magnitudes. But if we class them according to the length of the country through which they run, the order will, according to Major Rennel's calculation, be somewhat different; taking the length of the Thames for unity, he estimates that of the river of Amazons, at 154; the Kian Kew, in China, 15; the Hoango, 13; the Nile, 12; the Lena, 1; the Amur, 11; the Oby, 10; the Jenisei, 10; the Ganges, its companion the Burrampooter, the river of Ava, and the Volga, each 9; the Euphrates, 81; the Mississippi, 8; the Danube, 7; the Indus, 54; and the Rhine, 54 We may form a tolerably accurate idea of the levels of the ancient continent, by tracing a line across it in such a direction as to pass no river, which will obviously indicate a tract of country higher than most of the neighbouring parts. Beginning at Cape Finisterre, we soon arrive at the Pyrennees, keeping to the south of the Garronne, and the Loire. After taking a long turn northwards, to avoid the Rhine, we come to Swisserland, and we may approach very near to the Mediterranean in the state of Genoa, taking care not to cross the branches of the Po. We make a circuit in Swisserland, and pass between the sources of the Danube, and of the branches of the Rhine, in Swabia. Crossing Franconia, we leave Bohemia to the north, in order to avoid the Elbe; and coming near to the borders of Austria, follow those of Hungary to the south of the Vistula. The Dnieper then obliges us to go northwards through Lithuania, leaving the Don wholly to the right; and the Volga, to pass still further north, between Petersburg and Moscow, a little above Bjelosero. We may then go eastwards to the boundary of Asia, and thence northwards to Nova Zembla. Hence we descend to the west of the Oby, and thence to the east of the branches of the Volga, and the other inland rivers flowing into the lake Aral and the Caspian Sea. Here we are situated on the widely-extended elevation of India, in the neigh bourhood of the sources of the Indus; and, lastly, in our way from hence towards Kamschatka, we leave the Jenisei and Lena on the left, and the Ganges, Kiang Kew, the Hoangho, and the Amur, to the right. The direction of the most conspicuous mountains is, however, a little different from this; the principal chain first constitutes the Pyrennees, and divides Spain from France, then passes through the Vivarais and Auvergne, to join the Alps, and through the South of Germany to Dalmatia, Albania, and Macedonia; it is found again beyond the Euxine, under the names of Taurus, Caucasus, and Imaus, and goes on to Tartary, and to Kamschetka. The peninsula of India is divided from north to south by the mountains of Gute, extend ing from the extremity of Caucasus, to Cape Comorin. In Africa, Mount Atlas extends from Fez to Egypt, and the mountains of the Moon run nearly in the same direction: there is also a considerable elevation between the Nile and the Red Sea. In the new world, the neighbourhood of the western coast is the most elevated; in North America, the Blue Mountains, or Stony Mountains, are the most considerable; and the mountains of Mexico join the Andes or Cordeliers, which are continued along the whole of the west coast of South America. There are several points in both hemispheres, from which we may observe rivers separating to run to different seas; such are Swisserland, Bjelosero, Tartary, Little Tibet, Nigritia or Guinea, and Quito. The highest mountains are Chimboraçao, and some others of the Cordeliers in Peru, or perhaps Descabesado in Chili, Mont Blanc, and the Peak of Teneriffe. Chimboraçao is about seven thousand yards, or nearly four miles, above the level of the sea; Mont Blanc, five thousand, or nearly three miles; the Peak of Teneriffe about four thousand, or two miles and a quarter; Ophir, in Sumatra, is said to be five or six hundred feet higher. It has, however, been asserted, that some of the snowy mountains to the north of Bengal are higher than any of those of South America. The plains of Quito, in Peru, are so much elevated, that the barometer stands at the height of fifteen inches only, and the air is reduced to half its usual density. But none of these heights is equal to a thousandth part of the earth's semi-diameter, and the greatest of them might be represented on a sixinch globe by a single additional thickness of the paper with which it is covered. Mount Sinai, in Japan, Mount Caucasus, Etna, the Southern Pyrenees, St. George among the Azores, Mount Adam in Ceylon, Atlas, Olympus, and Taurus, are also high mountains; and there are some very considerable elevations in the island of Owyhee. Ben Nevis, in Scotland, is the loftiest of the British hills, but its height is considerably less than a mile. The most elevated mountains, excepting the summit of volcanos, consist of rocks, more or less mixed, without regular order, and commonly of granite or porphyry. These are called primary mountains; they run generally from east to west in the old world, and from north to south in the new; and many of them are observed to be of easier ascent on the east than the west side. The secondary mountains accompany them in the same direction; they consist of strata, mostly calcareous and argillaceous, that is, of the nature of lime-stone and clay, with a few animal and ve getable remains, in an obscure form, together with sait, coals, and sulphur, The tertiary mountains are still smaller; and in these, the animal and ve getable remains are very abundant; they consist chiefly of lime-stone, marble, alabaster, buildingstone, mill-stone, and chalk, with beds of flint. Where the secondary and tertiary mountains are intersected by valleys, the opposite strata often correspond at equal heights, as if the valleys had been cut or washed from between them; but sometimes the mountains have their strata disposed as if they had been elevated by an internal force, and their summits had afterwards crumbled away, the strata which are lowest in the plains being highest in the mountains. The strata of these mountains are often intermixed with veins of metal, running in all possible directions, and occupying vacuities which appear to be of somewhat later date than the original formation of the mountains. The volcanic mountains interrupt those of every other description, without any regularity, as if their origin were totally independent of all the rest. The internal constitution of the earth is very little known from actual observation, for the depths to which we have penetrated are comparatively very inconsiderable, the deepest mine scarcely descending half a mile perpendicularly. It appears that the strata are more commonly in a direction nearly horizontal, than in any other; and their thickness is usually almost equable for some distance; but they are not disposed in the order of their specific gravity, and the opinion of their following each other in a similar series, throughout the greater part of the globe, appears to rest on very slight foundations. Among the moderns, the chief authors on the subject of Geography are Johannes de Sacrobosco, or John Hallifax, who wrote a Treatise on the sphere: Sebastian Munster, in his Cosmographia Universalis, in 1559; Clavius, on the sphere of Sacrobosco; Piccioli's Geographia et Hydrographia Reformata; Weigelius's Speculum Terra; De Chales's Geography, in his Mundus Mathematicus; Cellarius's Geography; Cluverius's Introductio in Universam Geographiam; Leibnecht's Elementa Geographiæ Generalis; Stevenius's Compendium Geographicum; Wolfius's Geographia, in his Elementa Matheseos; Busching's New System of Geography; Gordon's, Salmon's, and Guthrie's Grammars; Adams's Geography, ancient and modern; and Pilkington's Geography, lately published in two vols. 4to., with an introduction by Mr. Vince. But, as an excellent scientific work, we must not omit Varenius's Geographia Generalis, with Jurin's additions: we really wish some gentleman of talents would publish a new edition of this admirable work, suited to the present state of the science. Dr. Playfair has recently published a system of Geography, which is, in many respects, a valuable performance. In studying particular Geography, recourse must be had to voyages and travels: the collections of Mavor, and that by Pinkerton now publishing, may be safely recominended. We must also mention Pennant's Tours in Britain. Young's Tours in the British Isles. Spallanzani's Travels in the Two Sicilies. Porter's in Do. Pallas's Travels in the Russian Empire. of Travels. Staunton's Account of China. Percival's Account of Ceylon. Symes's Embassy to Ava. Collins's Account of New South Wales. Park's Travels in the Interior of Africa. The Moravian accounts of their Mission in the interior of America: with the Voyages of Ansons Byron, Cooke, Phipps, Bligh, Wilson, Walis, La Peyrouse, Perron, &c. (Blair, Gregory, Hutton, Nicholson, Pinkerton). GEOLOGICAL. a. (from geology.) Relating to the subject of geology. GEOLOGY. (from the earth, and λoyos, a discourse, or treatise.) That part of natural philosophy which treats of the structure of the earth, in regard to the origin, composition, and decomposition of its solid contents. Thus explained, mineralogy should seem to be a branch of geology: but the former term has of late years been carried to such an extent by the most popular mineralogist of his day, M. Werner, as te include not only geology, properly so called, but every thing immediately connected with it: the situation of the materials constituting the solid contents of the earth, so far as we have been able to examine them, as well as their mode of origin, and the veins by which they are intersected. And hence, in the Wernerian system, geology becomes a branch of mineralogy; and, in order to prevent coufusion, from the subjection of what has hitherto been regarded as a classific term to an ordinal station, the word geognosy has been invented to supply its place. See MINERALOGY. The object of geology, then, is to unfold the structure of the globe; to discover by what causes its parts have been arranged; from what operations have originated the general stratification of its materials, the inequalities with which its surface is diversified, and the immense number of different substances of which it is composed. It is In pursuing this investigation, many difficulties occur to us. The bare surface or mere crust of the solid substance of the earth is the whole that we are capable of boring into, or of acquiring a knowledge of, even by the deepest clefts of volcanoes, or the bottoms of the deepest seas. not often, however, that we have a possibility of examining either seas or volcanoes at their bottom: the inhabitable part of the globe bears but a small portion to the uninhabitable, and the civilized an infinitely smaller proportion still. Hence, our experience must be necessarily extremely limited; a thousand facts may be readily conceived to be unfolded that we are incapable of accounting for, and a variety of systems that shall, nevertheless, aim at an explanation. So far as the superficies of the earth has been laid open to us by ravines, rivers, mines, &c. we find it composed of stony masses, sometimes simple, as lime-stone, serpentine, or quartz; but more frequently compound, or composed of two or more sin.ple materials, variously mixed and united to gether, as granite, which is a composition of quartz, felspar, and mica. These stony masses, or rocks, are numerous, and they appear to be laid one over the other, so that a rock of one kind of stone is covered by another species of rock, and this by a third, and so on. In this superposition of rocks, it is easily observable, that their situation is not arbitrary: every stratum occupies a determinate place, so that they follow each other in regular order from the deepest part of the earth's crust, which has been examined, to the very surface. Thus there are two things respecting rocks, that peculiarly claim our attention; their composition and their relative situation. But, besides the rocks which constitute the earth's crust, there are other masses which must also be considered. These traverse the rocks in a different direction, and are known by the name of veins, as if the rocks had split asunder in different places from top to bottom, and the chasins had been afterwards filled up with the matter which constitutes the vein. Independently of the substances thus presented to us, we meet with facts that prove most decisively that the general mass has undergone various revolutions at various times, and revolutions not only of great antiquity, but of universal extent. We have the most unexampled proof, that its whole surface has been covered with ocean, and that every part of it has suffered change; mountains have been raised, plains levelled, islands separated from a continent, and the waters collected so as to leave an elevated land. We find it dif ficult to conceive causes adequate to the production of such effects; and operations so immense seem too remote from any means of investigation which we possess, to admit of being explained. One point, however, in the midst of all the intricacy that surrounds us still remains decided, that the shell of the globe has, at some period or other, been in a state of fluidity, and that from this circumstance has arisen its present arrangement. Now the only two causes that can enter into the mind of man as being competent to such an effect are the operation of fire or of some solvent: and hence our researches become in some degree limited to the inquiry by which of these means this effect has been induced. If a solvent have been the cause, that solvent must have been water, for there is no other fluid in nature in sufficient abundance to have acted the part of a solvent upon a scale so prodigious. Hence, then, two distinct theories arise, which appear to have been agitated with considerable warmth in former times, but with a much greater degree of warmth, and much deeper view of the subject, in the present day. Is the present structure of the solid contents of the earth, so far as it is capable of examination, the result of igneous fusion, or of aqueous solution? Is the Plutonic or the Neptunian system founded on the strongest basis? In ancient times Heraclitus took the lead * to the former: and Thales, or rather, perhaps, Epicurus, as to the latter. In our own day, though the Plutonic theory was first started by M. Buffon, its defenders are now chiefly confined to our own country, and consist of Dr. Hutton, professor Playfair, and very lately of sir James Hall; names unquestionably highly respectable, and entit ed to every deference, but most power fully opposed by the respectable authorities of Werner, de Saussure, and Kirwan, not to mention that the general voice of geologists is very considerably in favour of the Neptunian theory, or that entertained by the last-mentioned philosophers. Plutonic Theory.-1. According to this system there is in the substance either of the entire globe, or throughout the entire crust of it with which we are acquainted, a regular series of decay and renovation, and the processes by which these are affected have an uniform relation to each other. The hardest rocks are worn down by air and water, causes which, however slowly they may operate, are constant in their action, and which, therefore, in indefinite time, must be equal to the production of the greatest effect. From the figure of the surface of the earth, the decayed materials must be carried towards the ocean, and ultimately deposited in its bed. This transportation may be impeded by local causes, or may, in general, be extremely slow, yet from the declivity of the land it must necessarily take place, and may, therefore, be admitted as an uniformly operating cause. 2. It is further assumed, that at certain depths in the mineral regions an immense heat is constantly present; a heat which operates in the fusion and consolidation of the substances deposited in these regions. To the action of this subterraneous fire the formation of all our strata is attributed, for by this they are again sublimed, and exposed to view in different states of combination and perfection. These strata, therefore, consist of the wrecks of a former world, which have been more or less completely fused by this agent, and by subsequent cooling have been consolidated. The subterraneous fire to which these effects are ascribed is conceived to operate under the modification of compression, in consequence of which, from various facts appealed to, and to a certain extent confirmed by some very valuable experiments by sir James Hall, (provided those experiments should bear the test of farther enquiry) it seems pretty clearly ascertained, that when certain gasses appertaining to the fusible substance, as carbonic acid for example, are rendered incapable of flying off, a much less quantity of actual heat is sufficient for the purpose of fusion, than when such gasses, freed from a heavy superincumbent pressure, have a possibility of escaping. Now the subterraneous fire being placed at immense depths, the substances on which it operates must be enormously compressed; which compression will prevent their volatilization in whole or in part: and from this circumstance it is possible, we are told, to explain appearances and qualities in minerals, and to answer various objections, which would otherwise weigh heavy against the hypothesis. -3. The elevation of the strata is in like manner the result of this same subterraneous heat: and it is contended that nothing but the extensive and forcible power which is hereby produced can be fairly conceived adequate to such an effect. The first of these positions is not very objectionable, and as far as relates to its general principle, separated from the positions with which it is connected, may be admitted. It may be allowed by the Neptunian as well as by the Plutonic geologist, that the strata of the earth are liable to waste, and that the materials are carried forward to the sea: but the appearance of lime-stones and marbles containing shells, in which the sparry structure is as perfect as it is in the primary limestone, and in which are distributed veins of crystallized carbonat of lime, this, and a variety of facts like this, must at all times militate fatally against the agency of fire in the production of such sparry structure, and such veins of crystallization; for in every instance in which it is found sufficient to produce such a structure, it must necessarily have destroyed every vestige of the structure of the shells, and have altogether dissipated the carbonic acid, necessary for the veins of crystallized carbonat of lime. Against the second position the objections are indeed strong, and, if we mistakenot, insuperable. "It is not fire, says Mr. Playfair, in the usual sense of the word, but heat, which is required for this purpose: and there is nothing chimerical in supposing that nature has the means of producing heat, even in a very great degree, without the assistance of fuel, or of vital air. Friction is a source of heat, unlimited, for what we know, in |