INTRODUCTION.

THAT part of natural history which treats of the internal structure of the earth, as far as we have been able to penetrate below its surface; of the arrangement of the materials of which it is composed, and of the changes which have taken place in these, is called GEOLOGY, from γη, the earth, and νέκτερ, a discourse. This science has been called by Werner, GEONOGY, and is by him defined to be that part of mineralogy which considering minerals as a part of our globe, treats chiefly of their bearings and positions with respect to each other (A). Till of late this department of literature was called physical geography, but at present the terms de Physique GEOLOGY and GEONOGY are generally adopted; of tom. iv. these we have preferred the former, as being equally expressive and more familiar; under this head we propose to include every thing that is usually comprehended under what have been called theories of the earth.

GEOLOGY differs from COSMOGONY as a part from the

(A) Werner has probably made this trifling change from a desire of novelty; and some of his admiring pupils have attempted to display in very pompous but puerile terms, that it is of great value and importance. the whole; the object of the latter is to give an account of the creation of the universe, while the former confines itself to the consideration of the planet which we inhabit.

Geology is intimately connected with mineralogy, and may indeed be said to depend on this as its very foundation. Werner, as we have seen, considers Geognosy as a part of Mineralogy; but we are disposed to concur with Mr Kirwan, who, speaking of mineralogy with respect to its relation to geology, calls it "the alphabet of the huge and mysterious volume of inanimate nature."

Geology may be divided into descriptive and speculative; the former giving a general account of the materials of which the globe is composed, and of their arrangement; while the latter is strictly confined to what may be called a theory of the earth, or an attempt to explain the manner in which the structure and arrangement have been brought about, and the changes that have taken place in the disposition of the component parts of the earth.

The science of geology is of considerable importance in many points of view.

1. The student of natural history cannot but derive a great fund of profit and advantage from a science, which makes him acquainted with so large a department of nature. Mineral bodies, whether we consider them as individuals of nature, or as collected into those masses which form the strata of the earth, and the mountains that rise above its surface, are peculiarly interesting to the naturalist, as well from the variety of form and beauty of appearance which some of them present, as the useful purposes to which many of them are applied. The other kingdoms of nature delight us with the display of order and design exhibited in their organization, or interest us from the intimate connexion which subsists between many of them and ourselves. These are objects of the beautiful; while the stupendous mountain, the awful volcano, the towering cliff, the gloomy mine, and the majestic cavern, are objects of the grand and the sublime.

2. To the miner, and all those who are employed in searching the bowels of the earth for the treasures which they contain, geology, as well as mineralogy, forms an essential qualification. Experience has shewn that certain minerals and metals are found more frequently attached to some of the stony materials of the earth than to others, and that a few of them are only found in particular strata. Examples of this kind will be given presently. We have also learned that the arrangement of the materials in the earth is so far regular and uniform, that when we know the particular materials near which certain metals and minerals are commonly found, and the usual disposition in these places; and when we find in another situation the same materials disposed in a similar manner, we are pretty certain that the metal or mineral of which we are in search is not far distant. We are therefore encouraged to prosecute the search with every probability of success. Those who undertake to direct an investigation of this kind, or to carry on the operations requisite for the obtaining what is sought would do well to inform themselves beforehand of such facts as are well established respecting the distribution of the materials of the earth, and the substances usually found connected with them. For want of this necessary information, we often see projectors impose on the credulity, and impoverish the finances, of gentlemen of landed property, who are led to suppose that they possess on some part of their estate a rich vein of metal, seam of coal, &c. the working of which will considerably improve their income.

3. The failure of undertakings of this kind, partly from the villany of the projector, and partly from the ignorance of his employer, shews the advantages that gentlemen of landed estates would derive from the study of geology. An acquaintance with this science would guard them against the artifices of designing men, and prevent them from embarking in uncertain and expensive projects, the issue of which is too often ruin and disappointment.

4. But the study of geology boasts a still higher advantage. Nothing has more contributed to demonstrate Christian truth of the divine writings, and to clear up many doubtful passages in them, than the discoveries that have lately been made in the structure and formation of the earth. The original state of the globe is so intimately connected with that which it at present exhibits, that we cannot properly understand the latter without referring to the former; and recent experience has shewn that the obscurity in which the philosophical knowledge of this subject was involved, has been highly favourable to those systems of atheism and infidelity which prevailed in the last age. Much of this obscurity is now removed; and the investigations of Whitehurst, Werner, Kirwan, Howard, and some other geologists, by proving that the supposition of a deluge is the only hypothesis on which we can account for the present state of our globe, have contributed as much to the advancement of true religion as of philosophical knowledge.

"So numerous indeed, and so luminous, have been the more modern geological researches, and so obviously connected with the object we have now in view, that since the obscuration or obliteration of the primitive traditions, strange as it may appear, no period has occurred so favourable to the illustration of the original state of the globe as the present, though so far removed from it. At no period has its surface been traversed in so many different directions, or its shape and extent under its different modifications of earth and water been so nearly ascertained, and the relative density of the whole so accurately determined, its solid constituent parts so exactly distinguished, their mutual relation, both as to position and composition, so clearly traced or pursued to such considerable depths, as within these last thirty years. Neither have the testimonies that relate to it been ever so critically examined and carefully weighed, nor consequently so well understood, as with the latter half of the 18th century."*

* Kirwan's Essays, Geol.

Geological researches seem at first view to be attended with almost insurmountable difficulty. It is evident that the part of the earth which it is in our power to examine, is infinitely small when compared to that which is entirely beyond our reach: and even much of the elevated parts, that appear above the surface, would seem to be so completely cut off from us by inaccessible precipices, and the ice and snow with which the summits mits of some of them are perpetually covered, that our knowledge of their structure and compositions must forever remain imperfect. Much of these difficulties, however, is rather apparent than real. It is true that our researches can extend but a very little way below the surface; but so far as our experience has yet taught us, any farther investigation would be rather a matter of curiosity than utility. Those metals and minerals which prove of most service to mankind, are found at no very great depth in the earth, and some of them almost on its surface; and when we have penetrated beyond these, the materials discovered are of a nature so uniform, and of a texture so firm and hard, that it is possible they may extend even to the centre. Again, the investigations of Saufure, De Luc, Dolomieu, and Humboldt, have proved that the most dangerous precipices, and the highest summits of those immense mountainous chains which traverse the earth in so many directions, oppose but feeble barriers to persevering industry and philosophic ardour.

The diversity which occurs in the structure and local arrangement of subterraneous substances, seems to throw another difficulty in the way of the geologist; but the farther his researches are extended, the more will this apparent diversity be diminished. The practical skill which some miners possess in many parts of the world, proves that the mazes of this labyrinth are not without a clue; and we may safely conclude, that when our knowledge of the structure of the earth, and the disposition of its materials, shall be still farther extended, the greater part of the obscurities under which the subject is now veiled, will be entirely removed. Multiplied observations of later years have enabled us to form certain general conclusions, and lay down certain general laws, which must materially assist future observers.

In the modern improvements of geology the Germans led the way, and Lehmann may be considered as the father of the science. Eminently skilled in general physics, practical mining, mineralogy, and chemistry, and fully acquainted with the circumstances attending the relative situation of most mineral bodies in very extensive tracts of different countries which he examined, he was enabled to deduce, from a long series of observations, some general conclusions, which have, with some exceptions, been since verified in every part of the world.

Lehmann was followed in his own country by Ferber, Gmelin, Born, and Werner; in Sweden by Bergman, Cronstedt, and Tilsa; in Italy by Arduino; in Switzerland, by Saufure and De Luc; in Russia, by Pallas; in France, by Delametherie, Saint Fond, Dolomieu, and Lavoisier; and in Britain, by Hutton and Kirwan, names which must ever be held in the highest estimation by the cultivators of this part of natural history.

Before entering on the study of geology, it is necessary to acquire a competent knowledge of chemistry, and a pretty extensive acquaintance with mineralogy, as these sciences form an essential introduction to the more general researches respecting the structure of the earth. The former supplies the means of ascertaining the nature of the substances met with; and the latter must be well understood, before we can arrange these substances under their proper heads, and before we can comprehend the terms employed by geological writers.

The study of this science, like that of some other parts of natural history, particularly botany, can be prosecuted with but little advantage in the closet. The student must examine the declivities of hills, the beds of rivers, the interior of caverns and of mines, the recesses of the ravine, and the utmost summits of the mountain, before he can obtain that degree of knowledge which is necessary to constitute a skilful and philosophic geologist. While making these personal observations, he should study the works of the best writers, and compare the facts related and described by them, with those which he himself has observed. The writings on this subject may be divided into two principal classes, one comprehending those works which contain a systematic account of the whole, or some part of the subject; such as Bergman's Physical Geography, the Geological Essays of Kirwan, the Theorie de la Terre of Delametherie, the writings of Werner, &c.; and the second comprising those works which treat of the geology of particular countries in the familiar style of travels; as Born's Travels in Hungary, Ferber's Travels through Italy, Saufure's Voyage dans les Alpes, Pallas's Travels, Jarl's Voyages Metallurgiques, Saint Fond's Travels in England and Scotland, &c. After having acquired a knowledge of the principles and general facts of the science from the former, the student will, by means of the latter increase his knowledge in the most familiar and agreeable way.

In the sketch of geology which we are to give in Arrangement, the following article, we shall consider the subject under four general heads, which will be the subject of as many chapters.

In the first chapter we shall describe the arrangement and distribution of the materials of which the earth is composed. Here, after giving some general notion of that arrangement, we shall consider each of the principal materials under a separate section, in which we shall first lay down those general marks by which each is distinguished, describe its general arrangement, and mention the places, especially in Britain, where the substance is found in greatest abundance, and those metallic or mineral bodies which are commonly found in connection with it.

After having briefly considered each substance, we shall, in the second chapter, bring the more general distribution of them under one view, still directing our attention to the arrangement of these materials in the British islands.

In the third chapter we shall give a brief outline of the most remarkable theories that have been framed in modern times, to account for the distribution of mineral bodies, and the manner in which we find them now arranged. In this chapter we shall dwell more particularly on the two rival theories which at present divide the geological world, and shall enumerate some of the objections which have been made to each.

In the fourth chapter we shall give some account of the derangement of the substances that compose our globe, so far as it has originated from known causes; and this will lead us to the consideration of EARTHQUAKES and VOLCANOES. CHAP. I. Of the Arrangement and Distribution of the Materials of which the Earth is Composed.

The materials of which the general mass of the earth is composed, are variously distributed in different parts. In some places they form irregular masses or blocks, either buried below the surface, or elevated to a greater or less height above it. In most places, however, the materials are arranged in a more regular manner; those of the same kind being collected into extensive masses, lying in layers or strata, above or below a similar mass of another kind, or these alternate with each other to a considerable depth. These strata are sometimes found arranged in a direction parallel to the horizon; at others they are vertical, or perpendicular to the horizon, appearing as if the horizontal strata had been lifted up, and laid upon their edges. More commonly the strata are arranged in a direction inclining to the horizon, when they are said to dip.

The uppermost stratum is in most places covered to a certain depth with mould that has evidently been formed from the decomposition of organized substances. In many parts of the earth this mould extends to a very considerable depth, and constitutes the soil; in other places it is barely sufficient to form a coating to the strata, and in others it is entirely wanting.

A good instance of horizontal strata occurs about two miles to the east of Balleycatle in the north of Ireland, of which we shall speak more particularly by and by. One of the most curious examples of vertical strata in Britain is found in the small island of Caldey, on the coast of Pembrokehire, where the strata of which the whole island is composed are placed in such a manner, that their edges are all exposed to view, and they may be successively examined from the one end of the island to the other. It is seldom that an opportunity offers of examining the arrangement of strata so easily as is afforded in this small island. In most cases it is necessary to penetrate to great depths before we can acquire an imperfect knowledge of the stratification of the earth; and in no instance have we yet proceeded a mile below the surface. In Caldey island, however, the strata may be examined to the extent of more than a mile, beginning at what may be supposed the uppermost stratum, which is not more than a foot thick, to that which may be called the lowest, at the opposite end of the island, being a mass of red stone of more than a mile in depth.

Sometimes the strata are continued in a regular arrangement, preserving the same inclination to a very considerable extent; but more commonly they appear in some parts separated, as if they had been broken asunder. These separations are usually in a perpendicular direction, and the cavities are found filled with various heterogeneous matters. Sometimes these are chiefly composed of fragments of the adjacent strata, but for the most part they consist of mineral or metallic substances of a different nature.

When these fissures are filled up with broken fragments or rubble, as it is called, it very commonly happens that they become the beds of brooks or rivers. Thus the river Derwent runs for a considerable extent in Derbyshire over a fissure of this kind. When the fissure is filled up with a solid stony matter, this forms what in Scotland is called a dyke. If a mass of mineral or metallic matters fill the fissure, or be infinatated between the strata, it forms what is called a vein, and these veins sometimes branch between the strata in various directions.

When a fracture has taken place in the stratified mass, one part of the mass sometimes preserves the same position as it had before, or still forms a continued line with the other parts of the mass, or is parallel to it; but more frequently one part is thrown out of its original position, and becomes more inclined to the horizon than before. Sometimes one side of the mass is more depressed than the other, as is commonly seen in many of the strata in Derbyshire; at others the two parts of the mass are so disturbed as to incline, towards each other, as if they had been broken upwards. When the edges of the strata on each side of the fissure are thus divided and disarranged, they are said by the miners to trap.

The chasms thus formed are sometimes of considerable width. Some are found in Cornwall nearly 20 feet across, and almost full of metallic and other mineral substances. It not unfrequently happens, that these fissures are empty, containing nothing but water in the bottom. A celebrated chasm of this kind is shewn at the Peak in Derbyshire; and if a stone be thrown in, it is heard to strike from side to side for a considerable time, till at length it seems lost in subterraneous water.

If the country in which the strata lie runs in a waving direction of hill and dale, the strata usually preserve the same waving direction, keeping pretty nearly parallel to each other. A curious example of this kind has been described by Gerhard, as occurring in the district of Mansfield in Germany. See fig. 1. In those places where some remarkable dislocation of the strata has not taken place, their distribution is in general extremely regular, certain materials lying above or below certain others in an uniform manner. The observations of later geologists have discovered pretty nearly the arrangement that takes place in most countries; and we shall presently give some examples of the stratification of several parts of Europe. Before we attempt this, however, we must mention some circumstances in which the materials composing the strata differ from each other.

The general observation of all modern geologists proves, that all these materials may be distributed under two general classes; one consisting of those substances which are found more or less connected with the remains of organized bodies, as the bones, teeth, and shells of animals, the trunks of trees, and other parts of vegetable bodies; and the other comprehending those in the substance of which these organic remains are never found. As it is now generally believed that the latter of these are of a formation prior to the former, we shall here adopt the general division of them into primary and secondary. We might go still farther in this division, by arranging them under more heads; one, for example, containing those in which organic remains are sparingly found, and others containing those substances which are found only in particular places; but as the first of these involves in it a particular theory which we shall notice fully hereafter, and the others allude to facts which will be mentioned when treating of the separate materials, we shall not here extend our division beyond the distribution of the materials into primary and secondary.

In the following short detail, many terms will occur which can be understood only by the mineralogist. They will be fully explained under the article MINERALOGY. The names which we shall give to the substances described will be such as have been most generally adopted in this country; but to prevent ambiguity, we shall, where it seems to be necessary, add the synonymous names that occur in the best geological writings.

A. Primitive Compounds.

SECT. I. Of Granite.

The name granite has long been applied to all stones which are composed of an aggregate of quartz, feldspar, and mica, distributed in such a manner as that each of them appear in a separate state; but as this definition has been considered as too loose, and comprehending too many varieties, the name is at present restricted to that kind of granitic stone in which the quartz, feldspar, and mica, are found in grains or crystals. Of the three substances, the feldspar is generally the most abundant, and the mica the least so.

Granite is found in the lowest and the highest situations of the earth that have yet been examined. It forms the basis of all the other strata; and though these are sometimes found below it, this situation seems to have been the consequence of some accident, by which the inferior substances were thrown below the granite. Many mountains seem almost entirely composed of granite, as Geforn one of the Rhaetian Alps; and there is a high hill of white granite about six miles to the west of Strontian in Scotland. Sometimes large masses of granite are found in a detached situation at some distance from the mountains to which they appear to belong; and these masses seem in some instances to have been broken off, and rolled down the mountain, and in others to have been carried away by irrefragible torrents, or dilogged by earthquakes. On the summits of the mountains near Port Sonnachin in Scotland, are found large quantities of detached pieces of granite, some of them of amazing size*.

Granite is most commonly found in vast blocks, separated from each other by rifts or chasms, irregularly disposed. This is the case in most mountains, especially in those which have high, pointed spires. The structure of these blocks is pretty uniform, there occurring seldom more than two varieties, one called porphyritic granite, in which the basis is of a fine grain, containing large crystals of feldspar. Of this variety many instances occur in the north of Scotland, and near Carlsbad in Bohemia. The other principal variety is that in which the granite is found in distinct globular concretions, composed of concentric lamellas. This variety was observed by Mr Jamefon, on the road between Dresden and Bautzen; and Mr Barrow, in his description of the Cape of Good Hope, mentions several globular concretions of immense size. The Isle of Arran in Scotland also affords instances of the same variety. Arrangement, &c. It is also found in Corlca, and is often called Corlca granite.

It has been doubted by some geologists, whether the true granite is ever found stratified; but numerous instances of its stratification have been lately adduced, that leave no room to doubt that this is sometimes the case. Pallas takes notice of some stratified granite on the banks of the river Berda, where he considered as perfect primitive granite, compactly crystallized, is disposed in layers of various degrees of thickness, some not exceeding one-eighth of an inch, and bounded both above and below by blocks of solid granite†. Again, Pallas's on the banks of the Gromoklea, he observed similar Trav. vol. layers of granite running in a direction from north to south, each bed being from one span to three feet six inches in breadth, and consisting of the most perfect primitive granite, which he considers as a continuation of that mineral tract which produces the cataracts of the Dnieper†. Mr Playfair mentions an example of stratified granite which he saw in Chorley forest in Lei.-p. 503. celftherie, where real granite is disposed in beds on the caftren border of the forest, especially near Mount Sorrel. Another instance of real granite disposed in regular beds, is also mentioned by Mr Playfair as occurring near the village of Priestlaw in Berwickshire‡. Mr Illustre- Jamefon observed the Riesengebirge, which separates Silefia from Bohemia, to be for 150 miles composed of granite disposed in horizontal strata, and he observed a similar stratification in Saxony and Lusatia §.

Granite constitutes the base of most of the British mountains, but is more commonly met with in the north and western parts of the island. There is a considerable mass of granite which runs longitudinally through Cornwall, from Dartmore to the Land's End*. Considerable masses are found in Scotland, but their extent has not been accurately ascertained. According to Mr Playfair, there is no mass of any magnitude in the southern parts, except that of Galloway, which occurs in two pretty large insulated tracts. Mr Playfair thinks that Dr Hutton greatly underrated the quantity of granite in Scotland, which, especially in the north, he considers as extending over a large district. If we suppose a line to be drawn from a few miles south of Aberdeen, to a few miles south of Fort William, it will, according to Mr Playfair, mark out the central chain of the Grampians, along which line there are many granite mountains, and large tracts in which granite is the prevailing rock†.

It is remarkable that in the mountainous regions of Peru, especially in the environs of the volcanoes, granite is found, except in very low situations, at the bottom of valleys‡.

Several varieties of granite are subject to decay, from Decay of the decomposition of the feldspar which they contain. This circumstance will probably explain a curious fact. It is found that the granite existing in the interior of mountains is much softer than that near the surface, probably from the decay of the feldspar in the latter, while it remains in its original state in the former (b).

(b) The decomposition of granite appears to go through several stages, from the solid rock to the loose sand. These Granite is by no means abundant in metallic and the richer mineral substances; it, however, contains a considerable variety, some of which have as yet been found in no other substance, especially molybdena. Iron ores are very commonly found in granite, especially the compact brown iron stone. It seems to be owing to the presence of iron that granite assumes that fine reddish colour with which we sometimes see it tinged. One of the most remarkable instances of this kind is afforded by the rocks to the south-east of the valley of Chamouni, at the foot of the Alps. These rocks, from their red appearance, are called Les Aiguilles Rouges, or the red needles. These rocks were mentioned by Sauflure, but he had not ascertained their composition. This has since been done by M. Berger, who found them to be composed of granite, with a considerable quantity of oxide of iron*. Bismuth, cobalt, blende, galena (an ore of lead), and several ores of copper, are also sometimes met with; but the metal most frequently found in granite is tin, especially in the great mining field in Cornwall.

Sect. II. Gneiss.

Gneiss, by some writers called kneift, is not unfrequently confounded with granite, from which it differs rather in the arrangement than in the nature of its component parts. The gneiss in gneiss are arranged in a schistose or flaty form, whereas in granite, they are in distinct grains or crystals, the layers being generally in the direction of the mica. It sometimes is intimately incorporated with masses of granite, but, in most instances, it reposes on the granite, being generally the second layer. In descending into the valley of Chamouni, Sauflure observed a fine bed of true granite incorporated with a rock of gneiss, which was arranged in very fine leaves†. Sometimes the gneiss lies entirely below the granite; but this is uncommon. More generally there is found a vertical mass of granite, with strata of gneiss on each side of it. Very frequently granite and gneiss alternate with each other.

Sometimes whole mountains are composed of gneiss. Thus, Ben Lomond scarcely contains any other substance, and the Schaw, which is the most northern point of the northernmost of the Shetland islands, is entirely gneiss. Mountains of this kind are, in general, neither so high nor so steep as those of granite, though Mount Rosa in Italy, and a few others, must be excepted. The summits of these mountains are also generally more rounded than those of granite mountains. The bases of all the Shetland islands seem chiefly composed of gneiss, and the middle part of the Pyrenees is almost wholly formed of this and granite.

It is curious that where gneiss is contiguous to granite, its quartz and feldspar are more apparent, and the mica less so; while, where it is more distant from granite, the contrary happens ‡.

Several metallic ores are found in gneiss, particularly those of iron, as the magnetic iron stone, and martial pyrites; lead ores, tin ores, blende, cobalt, copper, and arsenical pyrites, and not unfrequently silver ores.

Sect. III. Micaceous Schistus.

This is otherwise called schloese mica, and mica slate. It is also composed of the same materials with granite and gneiss, except that it contains little or no feldspar; schistus, the quartz and mica being arranged in layers as in gneiss.

This substance also is very abundant in most rocks and mountains. It generally composes the third layer or stratum, being immediately above or without the gneiss. It not uncommonly appears to be the only substance composing the hill or mountain, from the gneiss and granite being probably so completely covered as to be out of sight.

Micaceous schistus composes the rocks that are found immediately to the north of Duvekold in Scotland, and it is here penetrated in every direction by veins of quartz. The southern shores of Loch Tay, the mountains of Glen Lochy, the vale of Tumel between Loch Tumel and Loch Rannoch, contain much of the same substance; and the lower part of Glen Tilt is chiefly composed of it. In the western Highlands towards Ben Lomond, micaceous schistus also abounds, and some of it is found in the north of Argyleshire. The Shetland islands are mostly composed of micaceous schistus, in thick layers above the gneiss, with a few masses of granite interposed.

It not unfrequently happens that a bed of micaceous schistus is interlaced by veins of granite. Mr. Jameson observed an example of this in Glen Drummond in Ban- denoch, of which he has given a plate. The veins are very large, and run across the strata of schistus in a direction nearly parallel to each other*.

The metallic ores found in micaceous schistus, are chiefly those of iron, copper, tin, lead, cobalt, and antimony.

Sect. IV. Quartz.

Quartz is not unfrequently found distinct from feldspar and mica, and sometimes whole mountains are found composed of it. In particular, the mountain of Kultuc, at the south-east end of the lake of Baikal, among the Altaichan mountains, which is 4800 feet long, 350 high, and above 4000 broad, consists entirely of milk-white quartz; and the mountain of Flinzberg

These are thus marked by Mr. Jameson. In its beginning disintegration it splits into masses, having a greater or less tendency to the quadrangular form; but these masses have still a degree of connexion amongst themselves, as is the case upon the mountain top. The next step is the enlargement of the fissures, by which the masses are loosened from their connexion, and tumble down from their elevated situations, upon the summits of the neighbouring mountains, or are hurried with impetuous velocity down the mountain side, covering the bottom of the glens with their stupendous ruins. Lastly, these detached masses, by the action of the weather, are completely disintegrated, forming a loose sand, which is left upon the tops or sides of the mountains, or is carried in great quantities to the sea shore by the torrents. Jameson's Mineralogy of the Scottish Isles, vol. i. p. 82. berg in Luface, is almost wholly composed of it. There is also an extensive ridge of quartz, some miles long, in Bavaria, and Monnet mentions a rock of it 60 feet high. Mountains of it are also found in Thuringia, Silesia, and Saxony. It sometimes forms layers between gneis and micaceous schistus. A considerable body of granular quartz is found lying under micaceous schistus in the island of Ilay, see fig. 4, b. It is often found forming spires on the tops of mountains, and appearing like snow.

Quartz is found in several parts of Britain; but there is very little of it in the southern part of the island. Williams found it very common in the Highlands of Scotland, where he has seen it regularly stratified, with other regular strata immediately above and below it; and sometimes composing high mountains entirely of its own strata. These strata are sometimes moderately solid; but often are naturally broken into small irregular masses, with sharp angles, and of a uniformly fine granulated texture, resembling the finest loaf sugar.

There are large and high mountains of this stone in the thires of Rois and Inverness; and in a clear day these appear at a distance as white as snow, being quite bare of vegetation, except a little dry heath around the base of the hill*.

The mountain of Swetla Gera, one of the Uralian chain, consists of round grains of quartz, white and transparent, and of the size of a pea, united without any cement.

No metals are found in quartz, though it sometimes contains petroleum.

SECT. V. Argillaceous Schistus.

This stone, which is otherwise called clay slate, is the thonchiffer of Werner, and the argillite of Kirwan. It is of the same nature with gneis and micaceous schistus; but in this the stratification is still more complete, and all traces of crystallized granite entirely disappear. Doubts have arisen whether this stone is primitive; but these are now cleared up, as it is frequently found alternating with gneis and micaceous schistus, especially in Saxony, and with other primitive strata. It sometimes happens, too, that both gneis and granite rest upon it.

There are two varieties of this stone, one hard, and the other soft; but the hard often graduates into the softer.

Sometimes this stone is found forming whole mountains; but more commonly it enters into them only partially. In some, however, there are entire strata of it, as at Zillerthal, in the Tyrol. The famous mountains of Patosi consist entirely of argillaceous schistus, and Sauffure found it on the summit of Mont Blanc.

In Britain it is not very common; but is sometimes found on the higher parts of mountains. Thus it forms the summit of Skiddaw in Cumberland.

Argillaceous schistus, especially the softer variety, is remarkably rich in metals. We have said that it forms the greater part of Patosi, one of the richest silver mines. The ores of copper and lead, sulphur, pyrites, blende, and calamine, are also found in it. The great belly of copper ore in the Parys mountain in Anglesea, is found below this substance. It also sometimes contains antimonial and mercurial ores.

SECT. VI. Jasper.

It was supposed, by the earlier mineralogists of the last century, that jasper was only pure quartz, so much eroded, penetrated by a colouring metallic oxide as entirely to deprive it of its transparency; but Sauffure and Dolomieu, with their usual accuracy, discovered that it consists of flint, and not of pure quartz, having in combination a quantity of argillaceous matter, more or less mixed with oxide of iron.

Primitive jasper is always opaque. It is commonly found imbedded in other stony matters. In colour it varies from red to green, and frequently consists of alternate stripes of red and green, sometimes perfectly distinct, at others running together. There is a beautiful variety figured by Patrin, in which a dark-red ground is crossed in every direction with curved white lines, leaving here and there circular spaces of red surrounded with white, forming eyes.

Striped jasper is sometimes so abundant, as to be the chief material of some mountains, in which it is mixed with broken fragments of granite and other primary compounds (c). Mountains of red and green jasper also occur. Generally, however, it appears in strata, interposed between layers of micaceous schistus, or alternating, and sometimes mixed with compact red iron stone. It is found in the south of France, resting on granite; and in the Altaichan mountains, it sometimes lies below argillaceous schistus, but has there never been found in contact with granite. A coarse kind of jasper is sometimes found in the hills near Edinburgh; and some fine specimens are met with in the northern mountains.

SECT. VII. Hornstone.

This stone is considered by Mr Kirwan as the same Hornstone with petroflext, but Patrin and some others distinguish described them.

(c) There is often found interposed between the strata of rocks, or sometimes above the upper stratum, a bed of fragments that have been broken off from the principal strata. When these fragments chiefly consist of limestone and calcareous compounds, whether they be of an angular form, or confit of rounded pebbles, they are generally called by the name of breccia; but when the fragments are of a siliceous or quartzy nature, especially if they are agglutinated together, so as to form a solid mass, they have usually been called puddingstone. From the uncertain manner in which these terms were employed, much confusion arose, till Romé de l'Isle, and other later naturalists, have given the name of breccia to every stony mass that is composed of angular fragments, of whatever nature they be; and they call by the name of puddingstone every agglutinated mass that is composed of round pebbles, whether they be calcareous, quartzose, or of any other nature. These compounds will be spoken of presently in a separate section. them. According to Patrin, hornstone is a compound primitive rock, composed of the same elements with granite, in which felspar is very abundant, communicating to the stone a dull, gray, or sometimes blackish, colour, and containing a pretty large quantity of the argillaceous matter of mica. Petroflex, according to him, is purer than hornstone, and commonly of a grayish or greenish colour, semitransparent, and very hard, so as to give fire with itself. They are often found united, and sometimes form entire mountains, containing fragments of feldspar interposed. They are commonly found in large thick masses or blocks, though they are sometimes stratified like the schistose stones. Dolomieu is mistaken, when he affirms that petroflex is only found in primitive mountains, as it will appear hereafter, that it is sometimes a secondary compound. At Tuhumas, in the isle of Rona, Mr. Jamefon found a mass of rock chiefly composed of hornstone and quartz, from 12 to 15 feet wide, and of considerable length lying between two beds of gneiss.

SECT. VIII. Pitchstone.

The Germans have given the name of pitchstone, or pechstein, to a flinty matter, which is found in large masses of an irregular form, and of different colours, as yellow, brown, red, green, &c. have sometimes the appearance of rosin, and sometimes that of an enamel, or of glass imperfectly transparent. It is never crystallized.

It is found, either in large masses, or in veins. At Minia, it is found forming entire mountains; and in other countries there are mountains containing strata of pitchstone, sometimes alternating with granite, at others with porphyry. Mr. Jamefon describes a large vein of it of a green colour, several feet wide, traversing a mass of red argillaceous sandstone, at Tormore in the isle of Arran. This vein is extremely curious, and contains strata of different substances deposited in the same fissure *. Another curious vein of pitchstone is described by him as traversing a basaltic rock, together with a vein of hornstone, in the island of Eigg †. Mr. Jamefon considers this as the first example of pitchstone traversing basalt, discovered in Europe, though similar appearances have been found on the top of the peak of Teneriffe.

Pitchstone is only considered as a primitive rock, when it is nearly allied to porphyry.

SECT. IX. Hornblende, and Hornblende Slate.

Hornblende slate.

Hornblende is sometimes found existing separately from the compounds in which it usually occurs, as is the case in Siberia, where there are mountains of black hornblende. It is often found mixed with quartz, mica, feldspar, or felspar, of a greenish or black colour. More commonly, however, it occurs in immense strata, sometimes in layers of gneiss, argillaceous schistus, or primitive limestone. A stratum of it above primitive limestone has been found at Miltiz. It is sometimes seen below granite, or granite is even found imbedded in it. A rock of hornblende, reposing on granite, has been seen by Mr. Jamefon in the isle of Arran; * Ann. de Min. Nat. vol. iii. p. 400. † Min. of the Isles, vol. i. and on the side of Loch Fine he found it alternating with strata of micaceous schistus ‡.

The principal metallic substances found in hornblende slate, are native sulphuret of iron and copper ore.

SECT. X. Serpentine.

Serpentine is a stone of a similar nature with respect to its ingredients with those we have been describing. It takes its name from its appearance, being generally of a greenish ground, marked with white, yellow, brown, or reddish spots, so as to bear some resemblance to the skin of a snake. Its green colour is owing to a quantity of slightly oxidated iron which it contains. It is usually opaque; but sometimes parts of it are semi-transparent, and though not very hard, is capable of receiving a good polish.

Serpentine is by no means uncommon, and is often found in layers alternating with primitive limestone, or found below gneiss. The hill of Zobtenberg in Lower Silicia, consists almost entirely of serpentine, disposed in nearly vertical strata, with a little hornblende interperforated. Whole mountains of green serpentine are also found in Siberia, and near Geneva, where it is called gabbro or pulverezza. It is also found near the White Sea, and the mountain of Regelberg in Germany is chiefly composed of it. Rocks of it are found near the Lizard Point, on the coast of Cornwall; and hills of it occur in some of the Shetland islands.

Metals are seldom found in serpentine, except a magnetic ore of iron, which not unfrequently forms a part of the serpentine rocks, imparting to them its magnetic power. Veins of copper sometimes traverse it.

SECT. XI. Porphyry.

Porphyry generally consists of the same materials as granite, but in different proportions, and having altogether a different appearance; for instead of being crystallized as in granite, we find in the true porphyries an uniform compact mass, in which are disseminated small crystals of feldspar, and sometimes of felspar. There are, however, many varieties forming shades between granite and true porphyry, several of which are described by mineralogists.

Porphyry is very abundant in many situations, forming a considerable part of hills, and even mountains. It sometimes alternates with gneiss, and has been found below it. Gneiss has also been found in the midst of porphyry. It sometimes occurs in the midst of micaceous schistus, and sometimes forms an external covering to other primitive strata. Whole mountains of porphyry, arranged in immense strata, sometimes repose on a base of granite or gneiss. This stone is found in the greatest abundance in several places between the tropics, especially in South America, where it is sometimes met with at immense heights *.

Porphyry is very common in most parts of Scotland, and, in particular, forms a considerable stratum at the top of the Calton hill at Edinburgh, being in some places 12 or 15 yards thick, covering a bed of breccia.

Porphyry is found in considerable quantity between Newcastle and Wooler, and blocks of it of considerable size may be every where seen scattered about in the fields. The feldspar of these porphyries being less durable than the rest of the stone, is partly destroyed in some blocks, and appears corroded in others; from which circumstance the porphyries are so porous, as to appear as if they had been burnt. Porphyries of a familiar appearance are found in the mountain of Esterel in Provence, on the road from Frejus to Antibes*.

There is a variety of porphyry mentioned by Charpentier, a great part of whose composition is indurated clay, and nodules of clay of different colours are found in its substance. Specimens of a similar nature occur in the western islands of Scotland. There is also a species of porphyry nearly allied to hornstone.

The two varieties last mentioned are rich in metallic ores; in the former there being formed ores of silver, copper, iron, lead, and antimony; and, in the latter, sparry iron ore, native sulphuret of iron, galena, black blende, and ores of bismuth.

A stone of a porphyritic nature is described by Werner under the name of Schiffose porphyry, and is considered by Kirwan as the same with the horn slate of Charpentier. It is found among the primitive rocks of Altai, and on the borders of the lake of Baikal, in which latter place it is mixed with granite and hornblende. It is also found in Siberia, and in Bohemia. Sauflure found it near Pfaffenprung, intercepted between strata of gneiss.

SECT. XII. Puddingstone and Breccia.

The distinction between these two stony matters was mentioned in note c: they are both sufficiently common, consisting of different materials. The breccia usually lies in bodies, almost at the top of the other primitive strata, with some of which it sometimes alternates. Stratified breccias, consisting of fragments of flints and jasper, cemented by hardened clay, are frequently found in Siberia, and sometimes alternate strata of breccia, porphyry, jasper, and other primary compounds, compose a considerable part of mountains. Some mountains in the north of Scotland contain masses of breccia, composed of fragments of red granite, micaceous schistus, and quartz, in a base of sandstone. Mount Scurabien contains strata of this kind, surmounted by a rock of white quartz. Similar appearances take place at Cromarty, at Murray frith, and two or three miles to the south of Aberdeen; but in many of these instances the breccia must be considered as secondary. Much of the northern coast of Scotland abounds with breccia.

Puddingstone is also extremely common. A mountain of it is found in Siberia, near the rivulet of Tulat, being composed of fragments of jasper, chalcedony, aigue marine, and cornelian, cemented by a quartzose matter. Immense heaps, and even a mountain of puddingstone, are found at Meffenheim, in the Palatinate. Puddingstone is found in considerable abundance in passing from Loch Neis to Oban, in Scotland, and between Inverness and Dunella. Large detached rocks of puddingstone were seen by Pallas in the village of Temirdiki, in the Crimea. Some of these masses are seven or eight fathoms long, lying one above another†.

SECT. XIII. Syenite.

This name has been introduced by Werner, to denote a primary rock, essentially composed of grains of feldspar and hornblende, intimately blended together, in which the hornblende is generally most predominant. He first called it greenstone, but afterwards gave it the name of syenite, as he supposed it similar to a stone described by Pliny, as found at Syene in Upper Egypt, where it was dug in great quantities, and from thence carried to Rome; for the purpose of building public edifices.

Syenite sometimes contains a few grains of quartz and mica; but these seem to be accidental, and are always in very small quantity. This stone is not commonly stratified.

Syenite usually overlays most of the other primary rocks, and has often a bed of breccia interposed between it and the inferior strata. It is very commonly found reposing on porphyry.

It is found in Saxony, in the environs of Dresden; where at Meiffen in Thuringia; in Hungary, and in general found in almost all primitive chains of mountains, especially in the Alps. It is doubtless the same which Sauflure found in the summit of Mont Blanc, and which he calls granitelle.

Metallic veins are not unfrequently found in syenite. Metals in At Scharfenberg, veins of silver and lead are found in it; and it is said, that the veins of frontian in Argyleshire run in a similar rock.

SECT. XIV. Primitive or Granular Limestone.

It was long doubted whether limestone was ever to be found unmixed with organic remains, or primitive limestone; but the observations of late mineralogists and geologists have fully proved, that primitive limestone exists in considerable quantity. This stone is of granular structure, and of a whitish grey colour, though frequently of a dark iron gray, or reddish brown. It is sometimes fealy or lamellar; at others nearly compact, and is now and then found to have a splintery fracture. It is generally unmixed with other primary compounds; but sometimes particles of mica, quartz, hornblende, &c. occur in it.

This stone is always found alternating with the primary strata, especially with gneiss, micaceous, and argillaceous schistus. It sometimes forms whole mountains, as in Stiria, Carinthia, and Carniola, in Switzerland and in the Pyrenees, being often found seven or eight thousand feet high. Three mountains in Switzerland, all exceeding 10,000 feet in height, are chiefly composed of it. In these situations it commonly forms immense blocks, without any regular dip or direction; but it is sometimes stratified, as at Altenberg near the lake of Neuenberg. It is sometimes interposed between syenite and hornblende slate. One of the most singular mountains of granular limestone is that of Filabres in Spain, consisting of a block of white marble three miles in circumference, and 2000 feet high, without any mixture of other earths or stones, and with scarcely any fissure.

A considerable part of Mont Perdu in the Pyrenees is composed of alternate vertical bands of granite, porphyry, limestone, hornblende, and petroflex.

Granular limestone is found in various parts of Britain, especially in the north of Scotland. One of the most remarkable examples of it occurs in the island of Islay; Islay; the central part of which is formed of a compact bed of it of considerable extent. See fig. 4. d. It also occurs in some other of the Western isles.

Primitive limestone often contains veins of metallic ore, especially those of galena, magnetic ironore, blende, and pyrites.

Sect. XV. Primitive Trap.

Trap is a name that was long ago given by the Swedish mineralogists, to distinguish certain stones that are of a compact texture, and a dark colour, composing part of several mountains. The word originally signifies a staircafe, and was given to mountains containing this stone, because their strata retire one behind the other like the steps of a staircafe. But as many rocks of a very different kind, both in their nature and formation, have received the common name of trap, considerable confusion arose among mineralogists, with respect to what particular stones should receive this appellation. Most of the French mineralogists, as Saussure, Dolomieu, and Saintfond, make trap to signify a primitive rock, but they do not always mean the same rock. Other mineralogists, especially the Germans, understand by the name of trap, certain secondary rocks, and especially what are commonly called befaits.

Werner comprehends under the name of trap, several series of rocks, which are principally characterised by their containing hornblende, which is found almost pure in those which he considers as the most ancient, or what generally lie the lowest; and it degenerates gradually in the succeeding strata into a kind of blackish, ferruginous, hardened clay. He distinguishes three series or formations of traps; primitive traps, transition or intermediate traps, and stratiform or floetz traps. We shall here consider the first of these.

Primitive trap is almost wholly composed of hornblende, though it is sometimes mixed with feldspar, or more rarely with mica and some other substances. Under this general description Werner comprehends four stony substances; hornblende and hornblende slate, which we have already noticed in Section IX. primitive greenstone, and schistose greenstone.

Primitive greenstone is a mixture of hornblende and feldspar; under this there are several varieties, according as its texture is more or less granular, or compact. 1. Common greenstone, in which the hornblende and feldspar are intimately blended, is granular, and bears considerable resemblance to syenite, in which the hornblende is predominant. 2. A second variety has smaller grains, in which are imbedded crystals of feldspar, being of a structure between the granular and porphyritic. 3. A third variety has the grains of hornblende and feldspar extremely small, so as to be scarcely distinguishable. This stone loses its granular appearance, and becomes entirely porphyritic. 4. Lastly, when the mass becomes quite homogeneous, and of a complete green colour, it forms what was once called green porphyry, and constitutes the fourth variety*.

Schistose greenstone is composed of compact feldspar, hornblende, and a little mica, of which the hornblende and feldspar are nearly in equal quantity, and it now and then contains a little quartz. Its structure is schistose.

We have been thus particular in describing what Werner understands by primitive trap, as whatever may be thought of his theoretical opinions, his talent for mineralogical distinctions and characters cannot be called in question.

Mr Kirwan has given a long section on the distinguishing characters of trap, and its relation to basalt, &c. in his Geological Essays. He thinks that there might be formed a natural series of stones of a trap nature, taking in not only the composition, but also the texture, grain, and specific gravity, as something of this kind has been conceived and done by Werner.

Primitive trap is often found in vast strata in the midst of gneiss, and veins of it running through gneiss, have been found in Knobldorf in Silea, and in Bohemia. It is also sometimes found in granite, and it is found passing through granite and micaceous schistus in the Western isles of Scotland. Saintfond found it alternating with granite, near St Malo; and Charpentier, with gneiss. It sometimes forms entire mountains, as in the territory of Deux Ponts; and in Norway it is found reposing on granite. It sometimes alternates with argillaceous schistus, as at Leidenburgh.

Primitive trap frequently contains metals, especially the ores of iron and copper.

Sect. XVI. Topaz Rock.

This stone is composed of quartz, schorl, topaz, and Topazrock. Lithomarga, (a kind of hardened clay) the three former substances constituting small layers or plates alternating with each other. It sometimes contains cavities or geodes, lined on the inside with crystals of quartz and topazes. The texture of this stone is between the schistose and the granular; that is, it is composed of plates or laminae; but these laminae are of a granular structure.

Topaz rock is very rare. It forms part of a mountain near Averbach, in the metallic mountains of Saxony; but no metallic matter has hitherto been discovered in it.

Sect. XVII. Siliceous Schistus.

Siliceous schistus, or flinty slate, is the kiefelschiefer Siliceous of Werner; but there seems some dispute between his followers, whether it be a primitive or a secondary rock; on which account we have placed it last in the former series. Brochant does the fame; but Mr Jamefon, in his sketch of the Wernerian geognosy, places it among the transition formations, or those which immediately succeed the primitive. It is thus described by Mr Jamefon. Its colour is bluish gray; it is internally dull; its fracture in the great is imperfectly flaty; in the small, large splintery, passing into flat conchoidal; its fragments are indeterminately angular, and pretty sharp* Jamefon's edged; it is strongly translucent on the edges; it is Min. of hard and brittle, difficultly frangible, and not particularly heavy*.

An entire mountain formed of this stone is found in Where Lusatia, in which there are no petrifications. It is also found in the Alps, interposed between gneiss and hornstone. Schlendgenberg, a mountain in Saxony, is for the most part composed of it, mixed with hornblende and feldspar. Kirwan considers it as the same substance flance which Saufure calls palaiopetre, which is commonly considered as petroflex.

Flinty slate is described by Mr Jamefon as among the mineral substances found in Dumfriesshire. He particularly notices an immense rocky mass of it at the entrance of the valley at Leadhills, by which the metallic veins are completely interrupted*.

No metals have been found in it.

B. Secondary Compounds.

The substances which we are now to notice are distinguished from those which we have been describing, in containing more or less the remains of organized beings. As the inferior strata of these secondary compounds usually contain fewer organic remains than those above them, they are sometimes subdivided into two orders, one of which is considered to be intermediate between the primary and secondary strata. This is Werner's classification, of which we shall give an account in the next chapter.

SECT. XVIII. Secondary Limestone.

Under this title we shall comprehend what Werner calls transition limestone, floetz limestone, and limestone. Secondary limestone is a calcareous mass, sometimes granular, and sometimes compact, the former approaching to primitive limestone. Its fracture is scaly, and it is sometimes semitransparent. In colour it is very various, sometimes red, or rather blackish, with white veins, consisting of calcareous spar. It is often of a grayish cast. It sometimes forms vast blocks, without any appearance of stratification; at other times it is evidently stratified. It abounds with remains of marine animals, and often contains nodules of agate, and other similar stones.

A variety of calcareous stone is described by mineralogists under the name of swinestone. It is either compact, flatly, or porous, and is said in general to contain no petrifications, though some found in the mountain of Kinnecula contains many. It is considered by Kirwan as primeval limestone, impregnated with petroleum.

Limestone is sometimes found in oviform balls, commonly containing a grain of sand in them.

There is a variety of limestone that is very porous, and abounds in remains of vegetable matter, as impressions of leaves, &c.

Secondary limestone is very abundant in most parts of the world, forming a considerable part of many mountains, and being often the principal stratum to a considerable depth below the surface. The mountain Iberg, in the Hartz, is composed of vast masses of it, irregularly rifted; and mountains of a similar kind are found in Siberia and in the Vivarais. In some of those mountains vast caverns have been formed. Secondary limestone mountains always repose on some primitive stone; thus, in Siberia their base consists of granite, porphyry or hornblende; in Saxony, of granite, or granular limestone, and sometimes of argillaceous schistus; in Switzerland, these mountains repose on argillaceous schistus or gneiss, or sometimes on calcareous puddingstone. In the Crimea, there is an immense extent of secondary limestone, between Roslof and Perekop, which is minutely described by Pallas. Great part of the summit of Mont Perdu, the highest of the Pyrenees, is composed of secondary limestone, arranged in nearly vertical strata, and so full of the remains of marine animals as in some places to appear as if composed of nothing else. Here it seems to repose on granular limestone.

The base of Mount Ingleborough in Yorkshire, which is near 30 miles in circuit, consists entirely of limestone, containing vast quantities of sea shells. This stone also forms the principal inferior strata through the greater part of Derbyshire, being arranged in beds of various degrees of thickness, from a few inches to about 200 fathoms in some places, not having been perforated; and abounding with shells, and other marine remains.

It is found in many quarries in Scotland distinctly stratified. Mr Jamefon notices quarries of limestone at Clochburn, and Barjarg, and at Kelilhead in Dumfriesshire.

Secondary limestone often contains metallic veins, especially in Derbyshire, where it abounds with galena, found in it, blende, sulphur pyrites, and copper pyrites. Sulphur is also sometimes found in it. Kirwan remarks, that in the rest of Europe limestone is seldom metalliferous.

The stone commonly called alabaster, employed in making statues and ornaments, is properly a carbonated lime, nearly allied to marble; though it is usually supposed to be a variety of gypsum or platter stone. There is a gypsaceous alabaster that will be noticed presently.

Calcareous alabaster is not often white (though as white as alabaster is a common proverb), but generally tintured with iron of a yellow, brown, or reddish cast. It is semipeculucid, and usually so soft as to be scratched by the nail.

It is commonly found in blocks, in marble quarries, as in the island of Paros, and in several parts of Italy, particularly in the territory of Volterra in Tuscany, in Malta, &c. A variety is found in the form of stalactites of a conical or cylindrical form.

SECT. XIX. Gray Wacke.

Gray wacke is a stone composed of fragments of Gray quartz and argillaceous schistus, cemented by an argillaceous matter similar to the schistus, varying in size, ferbed, from that of a hen's egg, till they are so minute as to be no longer visible. It sometimes contains a matter similar to filiceous schistus.

There is a variety of this stone, called by Werner gray wacke slate, which is a simple flatly stone, which bears a considerable resemblance to argillaceous schistus. From this, however, it is to be distinguished, according to Mr Jamefon, by the following characters.

"It has seldom a greenish or light yellowish gray colour, as is the case with primitive slate, but is usually ash and smoke gray. It does not show the silvery continuous lustre of primitive clay slate, but is rather glimmering, which originates from intermixed scales of mica. Quartz scarcely occurs in it in layers, but usually traverses it in the form of veins. Further we do not find crystals of feldspar, schorl, talc, chlorite slate, or magnetic iron stone are to be observed in it. It contains petrifications, particularly those varieties that border on gray wacke. It alternates with gray wacke*."

These stones are distinctly stratified, but the direction of their strata is not parallel to that of the other rocks on which they lie. They are very commonly found covering limestone, especially at the foot of mountains.

Gray wacke is found in Erzgebirge, at Braunsdorf, Rieberg, and Averbach, in Vogtland, in Transylvania, on the banks of the Rhine, in Lautenthal, and some other places in Germany. It is also found in Britain; and Mr Jamefon notices it among the micurs of Dumfriesshire, where the gray wacke slate is found near Moffat, in the vicinity of Langholm, in the higher parts of the valley of Esk, and behind Burnswark. The strata found in these places yield a very good slate, nearly free from mechanical mixture, and well adapted to the roofing of houses.

This species of stone is rich in metals; the greater part of the veins of lead and silver in the Hartz, especially those of Clausthal and Zellerfeld, are in gray wacke. In Transylvania, in Vorepath, it contains even rich mines of gold. The gray wacke strata on the banks of the Rhine are also traversed by some metallic veins, but those of Saxony contain nothing but blind coal.

SECT. XX. Secondary Trap.

Several varieties of trap occur among the secondary strata, and must be here enumerated. They all consist principally of greenstone, or that mixture of hornblende and feldspar, which constitutes the primitive traps, noticed in Section XV., but in the traps we are now to mention, the mixture is much more intimate, the grains considerably finer, and the mass appears homogeneous. We shall here notice only three principal varieties; the amygdaloid or toadstone, the globular trap, and the greenstone, called by the Wernerians transition greenstone.

1. The amygdaloid, called in Derbyshire toadstone, and sometimes cat dirt, appears to consist of hornblende flake in a state of decomposition, and appears very similar to a kind of wacke, of a very fine grain. It is of a blackish colour, and very hard, and often contains a number of bladder holes, which are sometimes entirely empty, at others are partially or wholly filled with spar.

It runs in immense fold beds, without any appearance of stratification or fissure, of unequal thickness, having been seen from 6 feet to 600 thick. It commonly alternates with the strata of secondary limestone, as in Derbyshire, and sometimes seems to penetrate the inferior stratum of limestone to a very considerable depth. It contains no metallic veins, and it is said entirely to intercept those which it passes in the limestone strata. Saintford affirms that lead ore is sometimes found in cat dirt; but he seems to have been deceived by the vagueness of the term, as the miners of Derbyshire give the same name to a greenish variety of limestone, which is sometimes traversed by veins of lead ore.

2. Globular trap. This is a schistose greenstone, partially decomposed, and also resembles a fine-grained wacke; but it appears in the form of large balls, composed of concentric layers, with a hard nucleus. It is found at Altenzulze in Vogtland, and some other places. It sometimes contains veins of copper and iron.

3. Greenstone. This is almost entirely composed of feldspar, usually of a pale flesh-red colour, having sometimes imbedded in it grains of grayish quartz, scales of iron, blackish mica, and crystals of pale flesh-coloured feldspar. This rock may be confounded with porphyry, or with feldspar; but is generally considered as different from both. Mr Jamefon found it in beds from three to twelve feet thick on the upper side of the Sufanna vein in the valley of Leadhills, and in the mountain between Wamphray and Ekdalemuir.

SECT. XXI. Sandstone, or Grit.

These terms, like many others which we meet with in mineralogy, are very vague and indefinite, and are used to denote three or four kinds of stone; a calcareous, an argillaceous, and a siliceous sandstone. We shall here consider only two of them, the argillaceous and the siliceous.

1. Argillaceous sandstone. This is the sandstein Argillaceus of Werner, and the argillaceous grit of the ordinary sand-miners. It is composed of grains of quartz, and sometimes of siliceous schifflus; more rarely of feldspar. These grains are of various sizes, and are cemented in an argillaceous matter, commonly containing iron: whence this stone is sometimes called ferruginous sandstone. From the coarseness or fineness of the grains, it receives the names of coarse and fine sandstone. There is a very coarse kind found in Derbyshire; containing a considerable quantity of quartz pebbles.

This species of sandstone is found in immense beds, sometimes above 100 yards thick.

It is very distinctly stratified, and is commonly divided by fissures, into the shape of parallelopipeds. It sometimes alternates with layers of compact limestone, and often lies above a stone which we are immediately to mention, bale or bliver.

Sandstone is sometimes formed into globular concretions, composed of concentric lamellae.

Sandstone is one of the most abundant products of nature, occurring in almost every country. In Britain it forms the uppermost stratum in many parts of Derbyshire; and in the isle of Arran there is an immense separate mass of it, forming what is called the cock *. In the same island it is found in Glenranza, reposing on secondary limestone.

The globular concretions of sandstone are uncommon. Mr Jamefon observed them in the isle of Skye, of the Min. of the Isles, vol. i. p. 76. Mineral. Min. of the Isles, vol. ii. p. 87. Mineral. Geograph. von Bobow. f. 46.

2. Siliceous sandstone. This is a stone of a similar nature with the last, except that the cementing mass is also of a siliceous nature. It is found in the ports of Dalmatia and Campara, in the isle of Arbe, and on the coast of Dalmatia, where it contains petrifications. The hill of Platinburg consists of sandstone, with a chalcedony cement. Some fine specimens of siliceous sandstone are found in Salisbury Craigs at Edinburgh, containing shells which have assumed the nature of chalcedony. It does not appear to contain metals.

SECT. XXII. Gypsum, or Plasterstone.

This is native sulphate of lime, and it appears in several forms. Six varieties are usually enumerated; com- G E O L O G Y.

mon gypsum, lenticular gypsum, crystallized gypsum, fibrous gypsum, stalactitic gypsum, and gypcrous alabaster.

1. Common gypsum is a compact, granulated stone, commonly of a grayish colour, and mixed with impurities, containing a considerable quantity of carbonate of lime. Its texture is seldom laminated, but it appears like coarse leaf sugar. This kind is very abundant, many hills being entirely formed of it. Of these the most remarkable are the plasterhills in the neighbourhood of Paris, those in the canton of Bern in Switzerland, and others among the Alps. Hills of gypsum occur also in Spain and Poland; near the White Sea; in Asia, where they are mostly in horizontal strata; in the north Archipelago, between Asia and America. Sauflure found a mountain in Switzerland composed of gypsum, sand, and clay*. This kind sometimes contains petrifactions, and often abounds with the impressions of animal and vegetable matters; some very curious examples of which will be mentioned in a future section. It contains few metals, although copper is sometimes found in it, as are rock-salt and sulphur.

2. Lenticular gypsum is a curious variety, which seems peculiar to Montmartre near Paris. In one of the banks in this mountain, specimens of it are found containing little lenticular bodies, distinct and disseminated through the stony matter, so as to form a great part of its mass. A specimen of this kind is figured by Patrin, in his natural history of minerals.

3. The crystalline d gypsum is also found chiefly in the environs of Paris, in crystals that are decedral, or sometimes like a rhomboidal octaedron, with the pyramids truncated near the base.

4. Fibrous gypsum, composed of short brittle threads disposed in bundles, is found in Derbyshire, and near Riom in Auvergne. A very beautiful variety, of a silky feel, and reticulated texture, is described by Patrin, as found in Poland, in the salt mines of Wielitka; in Ruffia, near the junction of the river Oka with the Wolga; in Spain; and in China.

A variety of gypsum with the appearance of vegetation is found in caverns near the baths at Matlock in Derbyshire. A beautiful specimen of it is figured by Patrin*.

5. Gypsum is sometimes found hanging from the sides and roof of caverns in the form of stalactites, a transverse section of which shows their internal structure to be radiated. This variety is commonly called selenite†.

6. Gypsous alabaster is very similar to true alabaster, except that it does not, like that, effervescce with acids, and is in general not so strong. It is found in great abundance in Derbyshire in large masses, filling up cavities in argillaceous grit. It never forms a stratum, but is generally attended with gravel, red clay, and shells. Mr Mawe represents the lower portions as being very strong and compact, so as to form columns and pilasters‡. This kind is also found in Franche of Derbyh. Comté, and on the Marne about six leagues from Paris, at Lagny.

Though from the ordinary form or situation of gypsum, and the organic remains so commonly found in it, there can be no doubt of its being in most cases a secondary rock; yet from its having been found mixed with mica in St Gothard, it is enumerated by some among the primary compounds.

SECT. XXIII. Fluor Spar.

This beautiful substance, which is native float of fluor time, is found either in large unformed masses or blocks, described, or crystallized in cubes or octaedrons. It is of different colours: but the most prevailing varieties are that in parallel zones or bands of green, blue, yellow, and white; and that in which a white ground is veined with a reddish brown. Some specimens are so shaded as to represent a geographical map; but these are very rare. It is so soft as to be easily turned in a lathe into those vases and other ornaments which are so commonly seen on chimneypieces.

Fluor spar is found in several countries of Europe, but especially in France and Britain. According to Patrin, there are mines of it in the primitive mountains of Gyromagny, in the Voiges, in the neighbourhood of Langecas, in Auvergne, and at Forez near Ambierle, that are inexhaustible §. It is also found in the mountain of Pilat not far from Lyons; among the rocks that skirt the valley of Chamouni in the Alps; in the Altaichan mountains of Asia; and in Greenland.

The most productive mines of this substance in Britain are in a mountain near Caffleton in Derbyshire. Here there are two mines producing the beautiful compact fluor, called Blue John, which is found in pipe veins running in various directions. The fluor commonly rests upon limestone, and it frequently has this stone for a nucleus, round which it appears to have crystallized. Frequently, however, the centre is hollow. In several parts of the mine the fluor is found in detached masses, in caves filled with clay and loose adventitious matter, having the appearance as if it had been broken off from the limestone on which it had been formed; for every piece, in one part or other, seems as if it had adhered to something, and been broken off.

Some of the pieces of fluor are a foot thick, and have four or five different veins or zones: such large pieces are, however, very rare, and generally they are only three or four inches thick*.

Saintfond, who has given an interesting account of the curiosities near Caffleton, says, that fluor spar would be the most beautiful substance in nature, if it were but a little harder.

It is also found in Northumberland, in a vein among the granite mountains of Aberdeenshire †, and in one of the Shetland isles, in a vein of basalt‡.

Fluor appears in some cases to be primitive. Thus it is found forming whole strata in the mountains of the forest of Thuringia, and in a vein of quartz in Upper Hungary.

SECT. XXIV. Chalk.

Chalk is too well known to require a description. It is not always white, but is frequently coloured. It is disposed in horizontal beds that are often many yards in thickness, and which always repose on layers of other calcareous stone of a harder structure. These beds are often of considerable extent, and very common- ly contain flints, oviform limestone, and vast quantities of shells.

Chalk, which is so abundant in some countries, is scarcely found in others. It is well known that the south and south-eastern parts of England, and the south and south-west of France contain vast cliffs and beds of it; much of it is also found in Zealand. It is, we believe, a rare production in Scotland, and in most mountainous tracts. It has been remarked by Pennant, that if a line be drawn from Dorchester in the county of Dorset, to the county of Norfolk, it would form the boundary of the great chalky stratum of England; no quantity having been found to the north or west of that line.

There is a mountain of chalk between Tor and Ilium on the banks of the Donetz in Russia, in which some Greek monks have excavated apartments to the length of fifty fathoms*.

No metals are found in chalk, though it is said that in France martial pyrites has been discovered in it.

SECT. XXV. Clay.

CLAY is found in various states with respect to hardness or solidity, from the soft ductile clay used by the potters and pipemakers to the perfect flate (clay flate, or argillaceous schistus) already described.

Soft clay is found in beds of various degrees of thickness, commonly not far below the surface, and alternating with harder clay, flates, sand, or limestone. It is generally very abundant, especially in those places where coal or rock-falt is found.

Clay of a harder consistence, commonly called indurated clay, or in the language of the miners clunch, is usually found below the softer clay, or there is sometimes a stratum of flate or similar argillaceous matter interposed. It often alternates with limestone, sandstone, or gypsum. Petrifications and shells are often found in it, as are quartz, sulphur pyrites, martial ochre, common salt, vitriol and alum.

A harder state of clay forms that substance which is called by mineralogists lithomarga (stone clay). This is found in beds or strata often alternating with the former, with flate or with limestone, especially in coal mines. It also forms nests or balls in sandstone and similar rock. It sometimes bears the impressions of reeds and other vegetable bodies.

The next degree of hardened clay, forms flate clay, (Schieferton of the Germans). This substance, however is not very hard, but is easily broken into angular tabular fragments. Its internal appearance is usually dull, but sometimes glimmering from a slight intermixture of scales of mica. Its colour is usually a yellowish gray, with spots or clouds of a pearl gray, or a cherry red, but sometimes it inclines to black. It usually lies between beds of sandstone, and almost always below the softer clays.

A kind of clay, of a still harder consistence, forms flate or schistus. This is usually of a dark brown or blackish colour, and a laminated texture. It lies in beds, sometimes of immense thickness, usually below sandstone, or alternating with this and limestone. It often contains impressions of organic remains, and there are sometimes found in it veins of lead ore. It is a very common stratum in the coal countries.

Nearly allied to this is what the miners call rubble stone, which is a common variety of flate found in familiar situations with flate, but often very rich in metallic ores, especially iron, galena, bismuth, and cobalt. It also abounds with petrifications. It is sometimes found in primitive rocks.

SECT. XXVI. Marl.

MARL is a substance chiefly composed of sand, clay, Marl, and calcareous matter, which is found in many places, and forms one of the most valuable natural manures used in agriculture. This is also found of various degrees of hardness, from a soft powder to a stony consistence, in which last state it forms what Kirwan calls marlstone. In colour it is usually of a reddish white, sometimes verging upon red, and it is not unfrequently found of a yellowish brown or blackish cast. Marl is usually disposed in considerable beds of various degrees of thickness, in valleys and other low lands, especially among the coal strata. Indurated marl occurs in the coal strata of Mid Lothian*, and it is also found in the island of Ilay. Powdery marl is seen in Skye.

Stony marl, or marlstone, is found in Bavaria, alternating with sand and sandstone. Hills of it occur in Carniola, Carinthia, and the Venetian territory. It is also found between strata of limestone and argillaceous schistus.

SECT. XXVII. Argillaceous Ironstone.

THIS is sometimes called metal stone, and is very common in the coal countries. It is very heavy and compact, and of various colours, from a dark brown to a blood red; the latter forms the haematites or bloodstone, one of the richest iron ores. It often contains in its spherical balls like iron bullets. It is disposed in strata alternating with indurated clay, flate clay, marl, or sandstone, seldom far below the surface. It seldom forms very extensive beds, but is often confined to particular spots.

Ironstone is found in great abundance in Cumberland, and in most parts of Scotland. It may be seen in the cliffs all along the coast of Fife, from Dysart to St Andrews.

SECT. XXVIII. Wacke and Basalt.

WE have already spoken of several stones under the Whinstone name of traps, that are found both among primitive and secondary compounds. The two substances which we are now to notice are nearly allied to the traps, and have been classed with them under the general name of whinstone. This is a favourite term among the mineralogists of Scotland, of whom Sir James Hall employs it as a generic name to denote trap, basalt, wacke, grunstein, and porphyry†. The term is convenient, but Professor Jamefon and others of the Wernerian school object to it as too vague and indefinite.

Wacke, or wacken, differs from trap only in being Wacke, more compact and of a finer grain. It is heavy and very hard, so as often to strike fire with steel; it is dull and opaque, and breaks with an even fracture. Its colour is usually a reddish brown or gray of various shades,

shades, and sometimes it has a greenish cast. It has usually an earthy smell, when breathed on. It is sometimes highly impregnated with iron, and often contains crystals of hornblende, and very commonly those of hexagonal black mica.

It often forms a considerable part of mountains, either in vast blocks, as in the hill on which Edinburgh cattle stands, or in strata lying above limestone or sandstone, or alternating with these. A great part of the Calton-hill, of Salisbury craigs, and Arthur's seat at Edinburgh, is composed of strata of this kind; and similar appearances take place in the bed of the water of Leith near the town, and in the cliffs on the coast of Fife, especially at St Andrews. To the eye of the volcanic Saintfond, all these beds appeared to be lava. We are disposed to think, with Mr Playfair, that the curious instance of alternate strata of basalt (as Saintfond calls it) and limestone, near Villeneuve de Berg, described and figured by that author, affords an example of whinstone alternating with limestone, such as are seen in Scotland. Several varieties of wacke are found in the hills near Edinburgh, and are described by Dr Townson. Mr Jamefon observed wacke alternating with porphyry in Skye.

Basalt has a finer grain, and is more compact, then even wacke, and is the most dense of all the whins or traps. It is found either in large blocks, covering the other strata, sometimes in the form of tables, or in regular prismatic columns, either straight or bended. We have already treated so fully of the nature, properties, and chief habitats of basalt (see BASALTES), that little remains to be added here.

It is principally distinguished from wacke, where it is not in regular prisms, by very rarely containing crystals of mica, which are so common in the latter.

Saintfond in his splendid work Sur les Volcans eteints du Vivarais, &c. has figured some examples of basaltic pillars which rival those of Staffa and the Giants Causeway. A more romantic situation is scarcely to be conceived than that drawn in his eleventh plate, of a village placed in the front of a bold hill covered with bundles of small pillars lying in every direction, and having detached perpendicular columns standing at each end, with a large cave directly behind the houses. Large masses of basalt are seen in the north of Shetland, standing insulated, and assuming a very grotesque appearance. Mr Jamefon describes one of these in the Isle of Jura, that forms a natural arch. We remember seeing two curious inflated rocks on the shore at the foot of Kinkeld braes at St Andrews, but do not recollect whether they are of a basaltic nature.

Several other substances, as sand, gravel, peat, &c. might here be noticed, but their structure and situation are too well known to render a particular notice necessary.

Many of the stones which we have described among the primitive rocks, are also sometimes found among the secondary strata, as argillaceous schistus, hornblende, hornblende, jasper, and especially puddingstone; but they are not so important as to require a second examination.

Before we conclude this general account of the materials which compose our globe, we must briefly notice two of the most valuable mineral productions, viz. rock salt and coal, and must say something of fossils and petrifications.

SECT. XXIX. Rock Salt.

Rock salt or sal gem, (the stein sal of the Germans) is the purest muriate of soda that is found in nature, it being much less impregnated with foreign matters than what is procured from sea water. It is very hard, and generally very transparent, being sometimes as clear as crystal. It is usually white, but often yellowish, blue, red, or violet, and now and then it is quite opaque. This salt forms in the bowels of the earth horizontal beds or banks, more or less thick, from a few inches to many hundred fathoms; and sometimes extending several miles round. It commonly alternates with clay or gypsum. The beds are sometimes without any break for a great extent. It is generally found a few fathoms below the surface, and in some places is found continued to the depth of 1000 feet.

It is found in some mountains; and in Algiers, near where the lake called Marks, there is a mountain almost wholly composed of it. The famous salt mine of Wielitka in Aultrian Poland, about eight miles to the south-east of Cracow, is in the northern extremity of a branch of the Carpathian mountains. The salt found here is of an iron gray colour, intermingled with white cubes; and sometimes large blocks of salt are found imbedded in marl. This famous mine has been worked ever since 1251, and it is pretended that its excavations extend more than a league from east to west*. About five leagues to the south-east of Cracow are the salt mines of Bofchnia, the depth of which * Torun. nearly equal to those of Wielitka (1000 feet); but the salt procured from them is less pure†. Mines of rock salt, in horizontal undulated beds, occur at Thorda in Tranfylvania, and in Upper Hungary. In the side of der Minen, a mountain, about two leagues from Halle, on the banks of the Inn, to the north-east of Inpruck, rock salt is found imbedded in layers of a flat rock; but there is one part of the mountain in which there occurs an immense body of salt, without any mixture of rock, to which they pass by a gallery 260 toles in length, closed at the end with a locked door. This salt is very impure†. There are three important salt mines in Spain; the first near Mingranelia, in a mountainous tract, between Valencia and Castile, imbedded in layers of gypsum; the second in Spanish Navarre, in a ridge of hills composed of limestone and gypsum; and the third that of Cardona in Catalonia, about 16 leagues to the north-east of Barcelona, which is one of the most curious natural productions with which we are acquainted. It consists of an immense solid rock of salt, elevated 500 feet above the earth, and extending to a depth that has not been ascertained. It is without crevices or clefts, and has no appearance of strata, and is near a league in circuit. There is no plaster or gypsum found in the neighbourhood, and the salt rock is as high as any of the adjacent hills||.

Rock salt in found is several places in England, particularly at Northwich in Cheshire, at Droitwich in North Worcestershire, and near Wefton in Staffordshire; but the mines in Northwich are the most productive. Salt mines, in this situation, were known to the Romans; but the principal mine that is at present wrought, was discovered in the beginning of last century. It forms immense quarries, extending over several acres, which, with their huge crystal pillars and glittering roof, present a most beautiful spectacle. The salt found here is of a dark-brown colour, like brown sugarcandy, and is so hard that it is blasted with gunpowder to get it from the mafs. It is disposed in beds, alternating with beds of clay, gypsum, and flaty stone. Salt is procured at the greatest depth hitherto explored; and wherever a shaft is sunk in the neighbourhood, there is a certainty of finding salt *.

Besides these extensive mines, rock salt is found in the canton of Berne in Switzerland, in Siberia, in Arabia, in Tibet, and even in New Holland. It is also found in many parts of America, at a great height in the mountains, especially those of Peru.

SECT. XXX. Coal.

We have already, in the articles COAL and COALERY, treated of the nature of this substance, of the strata that are usually found connected with it (according to the phraseology of the miners), and of the method of procuring it from the pits; and, in MINERALOGY, we shall give a particular account of the several varieties, and the distinguishing characters of each. A few observations respecting the principal collieries, with the appearance of the coal found in them, and the corresponding stratification, fall to be made in this place.

There are certain general circumstances that attend the depositions of coal in almost every place where it is found, and which we must mention before noticing the particular collieries. These are as follows.

1. The beds in which coal is disposed, usually have their extremities near the surface of the ground, from which they bend obliquely downwards, the middle part of the bed being nearly horizontal, so that a vertical section of the bed nearly resembles the keel of a boat. This figure is well expressed in the first and third plates to Mr Jameon's Mineralogy of Dumfries. The lowest part of the bed is usually the thickest (p).

2. A bed of coal is seldom found single; but, in general, several strata occur in the same place, of various thicknesses, the upper being usually very thin, and the lower very thick, with several stony strata between each two. Where there is only one bed, this is generally of very considerable thickness. At Whitehaven there are found at least 20 coal strata below the surface; and at Liege, in France, there are no less than 60.

3. The strata that separate the layers of coal are nearly the same in every colliery, and will be seen by referring to the table given under COALERY, and by those which will immediately be added. Those strata which are in immediate contact with the coal, are either whinstone, or more commonly an argillaceous flaty mafs; and near this is sandstone, in layers that are separated by flaty clay, mixed with particles of coal.

4. It is an observation which holds, almost without exception, that the flaty strata, and especially those next the coal, bear the impression of vegetables, and often of exotic or unknown plants.

Coal, in a greater or less quantity, but of very different qualities, has been found in most countries, and perhaps exists in all. It is found in France, Holland, Britain, Germany, Saxony, Portugal, Switzerland, and Sweden; in China, Japan, and in New Holland; and much of it is worked in Virginia in America. But France and Britain may be considered as the favourite seats of this invaluable commodity, which may justly be put in competition with the treasures of Potosi and Peru.

It is stated by Buffon, that there are no fewer than 400 collieries worked in France; and yet Saintford regrets that his countrymen are not so far advanced in the use of this mineral as the inhabitants of Britain *. The most considerable coal mines in France, are those fond's in the Lyonnais, at Forez, Burgundy, Auvergne, Travels, Languedoc, Franche Comté, and Liège.

The mines in the Lyonnais, and those of Forez, are among the most important in France. They are situated in a valley, extending from the Rhone to the Loire, in a direction from north-east to south-west, between two chains of primitive mountains, and they occupy in length a space of fix or seven leagues, from Rive-de-Gier to Firminy. In one part of the valley, in the neighbourhood of Saint-Etienne, the strata are nearly horizontal, and the medial thickness of the coal stratum is from three to fix feet; and near the Loire there are from 15 to 20 of these. At Rive-de-Gier the strata are almost vertical, and their thickness is very unequal, being seldom less than three feet, and sometimes amounting to 49 or even 60. All the coal produced by these mines is of an excellent quality, and its quantity is immense. Patrin states, on the most undoubted authority, that there are in the neighbourhood of Rive-de-Gier, no less than 40 mines at work, which produced in one year 1,600,000 quintals of coal †.

The next in importance are the coal mines of Liège. The beds of coal in that country have a direction from east to west; they commence about a league to the east of the town, and extend to about a league and a half to the west of it. Here, after meeting with some interruption, they extend for several leagues farther. Their breadth, from north to south, is about three-fourths of a league. At Verbais, which is to the north-west of the city, there are, according to Jars, more than 40 strata of coal, which are separated from each other by beds of different kinds of sandstone, of from 30 to 100 feet in thickness §. Gennete has counted 61 of these beds, placed one above another; and he is of opinion, that the lowest penetrates to the depth of 4000 feet perpendicularly. Though these mines have been wrought from the 12th century, they have not yet reached to more than the twenty-first bed, at the depth of a little more than 1000 English feet $.

(d) Saintfond, in the section which he has of the coal strata at Newcastle, describes them as if they were convex towards the upper surface. (See p. 134, of vol. i. of the English Translation of his Travels in England, &c.), Surely this is a mistake. The principal collieries of Britain are those of Newcastle and Whitehaven.

Newcastle is surrounded by collieries to the distance of fix or seven leagues, and may, perhaps, be considered as the richest coal district in the world. There are in several of the Newcastle mines not fewer than 16 beds of coal, two of which are considerably thicker than the rest, being each about a fathom in thickness. These are called the main coal, and are distinguished into the high main coal, and the low main coal, separated from each other by a considerable number of stony strata. Good coal, in sufficient quantity, is generally found at the depth of little more than 100 feet. The bed is five feet thick in some places, and less in others; but, in general, it is easily wrought, and large pieces are brought up. This last circumstance is of considerable advantage, as these pieces are most proper for chamber fires, and easily transported, which makes this kind of coal fell at a higher price. Where the bed of black and bituminous clay is penetrated, the coal is found adhering to it; but this is not always the case, for there are other mines in the neighbourhood where freestone is recovering, which, in the points of contact, is mixed with coal to the thickness of two or three inches; the latter running, as it were, in splinters into the stone, and having a lignaceous appearance, when attentively examined*.

At Whitehaven, the beds of coal lie in a direction parallel to each other. Their inclination or dip is nearly to the west, and is from one yard in eight, to one in twelve. The strata are frequently interrupted by large fissures, or dykes, some of which remove the strata upwards or downwards, 120 feet. The course of these fissures is almost east and west. In a depth from the surface of 165 and a half fathoms, there are, in these collieries, seven large beds of coal, and 18 thin beds, which cannot, at present, be rendered profitable.

The strata superincumbent on the large beds of coal are, 1st bed, Blue slate. 2d, Gray freestone. 3d, Hard, white freestone. 4th, Blue flate, flinted or speckled with freestone. 5th, Gray slate. 6th, Hard, white freestone.

The strata immediately beneath these large beds of coal, are from one and a half to fix inches thick, and consists of a species of argillaceous earth, or flake. As this earth is of a very soft or friable nature, the weight of the superincumbent strata presses the pillar of coal through it. If the pillar descends a few inches, the roof not equally yielding at the same time, crutches, or breaks into small pieces. When, under these circumstances, the thickness of the bed does not exceed fix feet, nor the depth 30 fathoms, the surface of the earth is sensibly affected*.

There appear to be two principal belts of coal in this island, extending from the eastern to the western coast; one from Newcastle to Whitehaven, the other from the east coast of Scotland, across the vale of Forth and Clyde, to Ayrshire. Coal is indeed found in many other parts of the island; but the quantity is very trifling.

The similarity of situation, and the similar nature of the coal at Whitehaven and Newcastle, would naturally lead us to infer, that the coal at both places is from the same seam. But this is placed beyond dispute, by a comparative examination of the strata in both situations. We shall here give two tabular views of the strata, one taken from Saintfond's Travels, and the other from Dr Joshua Dixon's account of the Whitehaven mines, in his literary life of Dr Brownrigg. Allowing for the different names given by different miners to the same substances, and Dr Dixon's greater minuteness, there is a wonderful similarity between the two tables.

<table> <tr> <th>N°</th> <th>Stratum.</th> <th>Fath.</th> <th>Feet.</th> <th>Inch.</th> </tr> <tr> <td>1</td> <td>Soil and clay,</td> <td></td> <td>5</td> <td>-</td> </tr> <tr> <td>2</td> <td>Brown freestone,</td> <td></td> <td>12</td> <td>-</td> </tr> <tr> <td>3</td> <td>Coal, I.</td> <td></td> <td>-</td> <td>6</td> </tr> <tr> <td>4</td> <td>Blue metalstone,</td> <td></td> <td>2</td> <td>5</td> </tr> <tr> <td>5</td> <td>White girdles,</td> <td></td> <td>2</td> <td>1</td> </tr> <tr> <td>6</td> <td>Coal, II.</td> <td></td> <td>-</td> <td>8</td> </tr> <tr> <td>7</td> <td>White and gray freestone,</td> <td></td> <td>6</td> <td>-</td> </tr> <tr> <td>8</td> <td>Soft blue metal stone,</td> <td></td> <td>5</td> <td>-</td> </tr> <tr> <td>9</td> <td>Coal, III.</td> <td></td> <td>-</td> <td>6</td> </tr> <tr> <td>10</td> <td>Freestone girdles,</td> <td></td> <td>3</td> <td>-</td> </tr> <tr> <td>11</td> <td>Whin,</td> <td></td> <td>1</td> <td>4</td> </tr> <tr> <td>12</td> <td>Strong freestone,</td> <td></td> <td>3</td> <td>1</td> </tr> <tr> <td>13</td> <td>Coal, IV.</td> <td></td> <td>-</td> <td>1</td> </tr> <tr> <td>14</td> <td>Soft blue thill,</td> <td></td> <td>1</td> <td>5</td> </tr> <tr> <td>15</td> <td>Soft girdles mixed with whin,</td> <td></td> <td>3</td> <td>5</td> </tr> <tr> <td>16</td> <td>Coal, V.</td> <td></td> <td>-</td> <td>6</td> </tr> <tr> <td>17</td> <td>Blue and black stone,</td> <td></td> <td>3</td> <td>4</td> </tr> <tr> <td>18</td> <td>Coal, VI.</td> <td></td> <td>-</td> <td>8</td> </tr> <tr> <td>19</td> <td>Strong freestone,</td> <td></td> <td>1</td> <td>3</td> </tr> <tr> <td>20</td> <td>Gray metalstone,</td> <td></td> <td>1</td> <td>4</td> </tr> </table>

TABLE I. Strata in Restoration Pit, St Anthon's Colliery, Newcastle, to the depth of 135 fathoms.—From Saintfond. <table> <tr> <th>N°</th> <th>Stratum.</th> <th>Fath.</th> <th>Feet.</th> <th>Inch.</th> </tr> <tr><td>21</td><td>Coal, VII.</td><td>-</td><td>-</td><td>8</td></tr> <tr><td>22</td><td>Gray poft mixed with whin,</td><td>4</td><td>1</td><td>-</td></tr> <tr><td>23</td><td>Gray girdles,</td><td>3</td><td>1</td><td>-</td></tr> <tr><td>24</td><td>Blue and black stone,</td><td>2</td><td>2</td><td>-</td></tr> <tr><td>25</td><td>Coal, VIII.</td><td>-</td><td>1</td><td>-</td></tr> <tr><td>26</td><td>Gray metalltone,</td><td>2</td><td>-</td><td>-</td></tr> <tr><td>27</td><td>Strong freestone.</td><td>6</td><td>-</td><td>-</td></tr> <tr><td>28</td><td>Black metalltone, with hard girdles,</td><td>3</td><td>-</td><td>-</td></tr> <tr><td>29</td><td>High main coal, IX.</td><td>1</td><td>-</td><td>-</td></tr> <tr><td>30</td><td>Gray metal,</td><td>4</td><td>3</td><td>-</td></tr> <tr><td>31</td><td>Poft girdles,</td><td>-</td><td>2</td><td>-</td></tr> <tr><td>32</td><td>Blue metal,</td><td>-</td><td>4</td><td>-</td></tr> <tr><td>33</td><td>Girdles,</td><td>-</td><td>1</td><td>2</td></tr> <tr><td>34</td><td>Blue metalltone,</td><td>5</td><td>-</td><td>-</td></tr> <tr><td>35</td><td>Poft,</td><td>-</td><td>1</td><td>-</td></tr> <tr><td>36</td><td>Blue metalltone,</td><td>3</td><td>-</td><td>-</td></tr> <tr><td>37</td><td>Whin and blue metal,</td><td>-</td><td>1</td><td>6</td></tr> <tr><td>38</td><td>Strong freestone,</td><td>3</td><td>3</td><td>-</td></tr> <tr><td>39</td><td>Brown poft with water,</td><td>-</td><td>7</td><td>-</td></tr> <tr><td>40</td><td>Blue metalltone with gray girdles,</td><td>2</td><td>2</td><td>-</td></tr> <tr><td>41</td><td>Coal, X.</td><td>-</td><td>3</td><td>-</td></tr> <tr><td>42</td><td>Blue metalltone,</td><td>3</td><td>-</td><td>3</td></tr> <tr><td>43</td><td>Freestone,</td><td>-</td><td>4</td><td>-</td></tr> <tr><td>44</td><td>Coal, XI.</td><td>-</td><td>6</td><td>-</td></tr> <tr><td>45</td><td>Strong gray metal, with poft girdles,</td><td>2</td><td>-</td><td>6</td></tr> <tr><td>46</td><td>Strong freestone,</td><td>1</td><td>1</td><td>-</td></tr> <tr><td>47</td><td>Whin,</td><td>-</td><td>1</td><td>-</td></tr> <tr><td>48</td><td>Blue metalltone,</td><td>1</td><td>2</td><td>7</td></tr> <tr><td>49</td><td>Gray metalltone, with poft girdles,</td><td>2</td><td>4</td><td>5</td></tr> <tr><td>50</td><td>Blue metalltone, with whin girdles,</td><td>1</td><td>4</td><td>3</td></tr> <tr><td>51</td><td>Coal, XII.</td><td>-</td><td>1</td><td>6</td></tr> <tr><td>52</td><td>Blue gray metal,</td><td>-</td><td>3</td><td>8</td></tr> <tr><td>53</td><td>Freestone,</td><td>2</td><td>-</td><td>7</td></tr> <tr><td>54</td><td>Freestone mixed with whin,</td><td>2</td><td>-</td><td>-</td></tr> <tr><td>55</td><td>Freestone,</td><td>1</td><td>2</td><td>-</td></tr> <tr><td>56</td><td>Dark blue metal,</td><td>-</td><td>2</td><td>2</td></tr> <tr><td>57</td><td>Gray metalltone and girdles,</td><td>2</td><td>2</td><td>-</td></tr> <tr><td>58</td><td>Freestone mixed with whin,</td><td>3</td><td>-</td><td>7</td></tr> <tr><td>59</td><td>Whin,</td><td>-</td><td>1</td><td>-</td></tr> <tr><td>60</td><td>Freestone mixed with whin,</td><td>1</td><td>-</td><td>6</td></tr> <tr><td>61</td><td>Coal, XIII.</td><td>-</td><td>3</td><td>3</td></tr> <tr><td>62</td><td>Dark gray metalltone,</td><td>-</td><td>3</td><td>6</td></tr> <tr><td>63</td><td>Gray metal and whin girdles,</td><td>1</td><td>4</td><td>10</td></tr> <tr><td>64</td><td>Gray metal and girdles,</td><td>1</td><td>3</td><td>-</td></tr> <tr><td>65</td><td>Freestone,</td><td>-</td><td>3</td><td>-</td></tr> <tr><td>66</td><td>Coal, XIV.</td><td>-</td><td>3</td><td>2</td></tr> <tr><td>67</td><td>Blue and gray metal,</td><td>-</td><td>4</td><td>2</td></tr> <tr><td>68</td><td>Coal, XV.</td><td>-</td><td>-</td><td>9</td></tr> <tr><td>69</td><td>Blue and gray metal,</td><td>2</td><td>-</td><td>-</td></tr> <tr><td>70</td><td>Freestone mixed with whin,</td><td>-</td><td>4</td><td>6</td></tr> <tr><td>71</td><td>Gray metal,</td><td>-</td><td>-</td><td>6</td></tr> <tr><td>72</td><td>Gray metal and girdles,</td><td>1</td><td>-</td><td>9</td></tr> <tr><td>73</td><td>Low main coal, XVI.</td><td>1</td><td>-</td><td>6</td></tr> </table>

TABLE TABLE II. Strata in Croft Pit at Preston-Hows near Whitehaven, to the depth of 107 Fathoms. From Dixon.

<table> <tr> <th>N°</th> <th>Stratum.</th> <th>Fath.</th> <th>Feet</th> <th>Inch.</th> </tr> <tr><td>1</td><td>Soil and clay,</td><td>1</td><td>1</td><td>-</td></tr> <tr><td>2</td><td>Brown soft limestone,</td><td>1</td><td>3</td><td>-</td></tr> <tr><td>3</td><td>Dark-coloured limestone, harder,</td><td>1</td><td>-</td><td>-</td></tr> <tr><td>4</td><td>Yellowish limestone mixed with spar,</td><td>-</td><td>4</td><td>-</td></tr> <tr><td>5</td><td>Reddish hard limestone,</td><td>-</td><td>3</td><td>6</td></tr> <tr><td>6</td><td>Hard dark-coloured limestone,</td><td>-</td><td>1</td><td>4</td></tr> <tr><td>7</td><td>Yellowish limestone mixed with spar,</td><td>-</td><td>4</td><td>-</td></tr> <tr><td>8</td><td>Soft brown limestone,</td><td>-</td><td>4</td><td>2</td></tr> <tr><td>9</td><td>Soft brown and yellow limestone mixed with freestone,</td><td>-</td><td>2</td><td>6</td></tr> <tr><td>10</td><td>Limestone mixed with yellow freestone,</td><td>-</td><td>2</td><td>-</td></tr> <tr><td>11</td><td>Reddish soft freestone,</td><td>-</td><td>1</td><td>6</td></tr> <tr><td>12</td><td>Red flate, striated with freestone in layers,</td><td>-</td><td>2</td><td>6</td></tr> <tr><td>13</td><td>Red freestone,</td><td>-</td><td>7</td><td>-</td></tr> <tr><td>14</td><td>Soft red stone,</td><td>-</td><td>-</td><td>6</td></tr> <tr><td>15</td><td>Red flate striated with red freestone,</td><td>-</td><td>4</td><td>1</td></tr> <tr><td>16</td><td>Red flate striated with freestone,</td><td>-</td><td>4</td><td>3</td></tr> <tr><td>17</td><td>Strong red freestone, rather grayish,</td><td>-</td><td>4</td><td>5</td></tr> <tr><td>18</td><td>Lumpy red freestone speckled with white freestone,</td><td>-</td><td>-</td><td>9</td></tr> <tr><td>19</td><td>Blue argillaceous schistus speckled with coal,</td><td>-</td><td>-</td><td>9</td></tr> <tr><td>20</td><td>Red foamy flate,</td><td>-</td><td>2</td><td>1</td></tr> <tr><td>21</td><td>Black flate with a small appearance of coal,</td><td>-</td><td>1</td><td>-</td></tr> <tr><td>22</td><td>Ath-coloured friable schistus,</td><td>-</td><td>4</td><td>6</td></tr> <tr><td>23</td><td>Purple-coloured flate,</td><td>-</td><td>3</td><td>5</td></tr> <tr><td>24</td><td>The fame, and under it black flate,</td><td>-</td><td>4</td><td>-</td></tr> <tr><td>25</td><td>Coal, I.</td><td>-</td><td>1</td><td>-</td></tr> <tr><td>26</td><td>Soft whitish freestone,</td><td>-</td><td>1</td><td>4</td></tr> <tr><td>27</td><td>Blackish flate, a little inclined to brown,</td><td>-</td><td>4</td><td>11</td></tr> <tr><td>28</td><td>Coal, II.</td><td>-</td><td>1</td><td>10</td></tr> <tr><td>29</td><td>Blackish flate intermixed with coal,</td><td>-</td><td>2</td><td>6</td></tr> <tr><td>30</td><td>Whitish freestone,</td><td>-</td><td>1</td><td>2</td></tr> <tr><td>31</td><td>Strong bluish flate mixed with freestone,</td><td>-</td><td>3</td><td>-</td></tr> <tr><td>32</td><td>White ironstone,</td><td>-</td><td>1</td><td>8</td></tr> <tr><td>33</td><td>Freestone striated with blue flate,</td><td>-</td><td>1</td><td>3</td></tr> <tr><td>34</td><td>White freestone in thin layers,</td><td>-</td><td>1</td><td>3</td></tr> <tr><td>35</td><td>Dark-blue flate,</td><td>-</td><td>2</td><td>1</td></tr> <tr><td>36</td><td>Coal, III.</td><td>-</td><td>-</td><td>9</td></tr> <tr><td>37</td><td>Dark gray shale,</td><td>-</td><td>-</td><td>5</td></tr> <tr><td>38</td><td>Coal, IV.</td><td>-</td><td>-</td><td>2</td></tr> <tr><td>39</td><td>Gray freestone mixed with ironstone,</td><td>-</td><td>1</td><td>2</td></tr> <tr><td>40</td><td>Hard white freestone,</td><td>-</td><td>2</td><td>3</td></tr> <tr><td>41</td><td>Coal, V.</td><td>-</td><td>1</td><td>-</td></tr> <tr><td>42</td><td>Shale mixed with freestone,</td><td>-</td><td>1</td><td>2</td></tr> <tr><td>43</td><td>Olive-coloured flate adhering to black flate superincumbent on coal,</td><td>-</td><td>2</td><td>4</td></tr> <tr><td>44</td><td>Coal, VI.</td><td>-</td><td>1</td><td>1</td></tr> <tr><td>45</td><td>Black flate mixed with freestone,</td><td>-</td><td>1</td><td>2</td></tr> <tr><td>46</td><td>White freestone mixed with flate,</td><td>-</td><td>1</td><td>2</td></tr> <tr><td>47</td><td>Dark-blue flate,</td><td>-</td><td>3</td><td>4</td></tr> <tr><td>48</td><td>Coal, VII.</td><td>-</td><td>1</td><td>3</td></tr> <tr><td>49</td><td>Black shale mixed with freestone,</td><td>-</td><td>1</td><td>1</td></tr> <tr><td>50</td><td>Strong white freestone,</td><td>-</td><td>1</td><td>-</td></tr> <tr><td>51</td><td>Brown ironstone,</td><td>-</td><td>3</td><td>-</td></tr> <tr><td>52</td><td>Dark-gray flate,</td><td>-</td><td>1</td><td>-</td></tr> <tr><td>53</td><td>Dark-gray shale with an intermixture of Coal, VIII.</td><td>-</td><td>5</td><td>6</td></tr> <tr><td>54</td><td>Light-coloured flate mixed with freestone,</td><td>-</td><td>5</td><td>6</td></tr> <tr><td>55</td><td>Blue flate striated with freestone,</td><td>-</td><td>1</td><td>4</td></tr> <tr><td>56</td><td>Strong white freestone a little tinged with iron.</td><td>-</td><td>2</td><td>6</td></tr> </table> <table> <tr> <th>No</th> <th>Stratum.</th> <th>Fath.</th> <th>Feet.</th> <th>Inch.</th> </tr> <tr><td>57</td><td>Very black thivery flate,</td><td></td><td>1</td><td>4</td><td>3</td></tr> <tr><td>58</td><td>Strong coal of a good quality, IX,</td><td></td><td></td><td>-</td><td>4</td></tr> <tr><td>59</td><td>Soft gray flate,</td><td></td><td></td><td>-</td><td>3</td></tr> <tr><td>60</td><td>Very black coal, X, burns well,</td><td></td><td></td><td>-</td><td>8</td></tr> <tr><td>61</td><td>Hard black flate,</td><td></td><td></td><td>1</td><td>7</td></tr> <tr><td>62</td><td>Coal mixed with pyrites, XI.</td><td></td><td></td><td>1</td><td>2</td></tr> <tr><td>63</td><td>Argillaceous schitus, gray and brittle,</td><td></td><td></td><td>3</td><td>-</td></tr> <tr><td>64</td><td>Blue rough argillaceous schitus,</td><td></td><td></td><td>4</td><td>6</td></tr> <tr><td>65</td><td>Fine blue flate,</td><td></td><td></td><td>3</td><td>-</td></tr> <tr><td>66</td><td>Freestone mixed with ironstone,</td><td></td><td></td><td>3</td><td>-</td></tr> <tr><td>67</td><td>Black thivery flate,</td><td></td><td></td><td>1</td><td>-</td></tr> <tr><td>68</td><td>Dark-blue flate, very fine,</td><td></td><td></td><td>5</td><td>6</td></tr> <tr><td>69</td><td>Dark-blue flate, very brittle,</td><td></td><td></td><td>6</td><td>6</td></tr> <tr><td>70</td><td>Coal, XII.</td><td></td><td></td><td>2</td><td>6</td></tr> <tr><td>71</td><td>Soft gray argillaceous schitus,</td><td></td><td></td><td>-</td><td>6</td></tr> <tr><td>72</td><td>Argillaceous schitus mixed with freestone,</td><td></td><td></td><td>2</td><td>-</td></tr> <tr><td>73</td><td>White freestone with fine particles,</td><td></td><td>1</td><td>1</td><td>-</td></tr> <tr><td>74</td><td>Blue flate striated with white freestone,</td><td></td><td></td><td>4</td><td>7</td></tr> <tr><td>75</td><td>Light-blue flate,</td><td></td><td></td><td>3</td><td>-</td></tr> <tr><td>76</td><td>Blue flate a little mixed with ironstone,</td><td></td><td>2</td><td>-</td><td>-</td></tr> <tr><td>77</td><td>Black thivery flate,</td><td></td><td></td><td>1</td><td>-</td></tr> <tr><td>78</td><td>Coal, XIII.</td><td></td><td></td><td>-</td><td>6</td></tr> <tr><td>79</td><td>Brownish hard flate,</td><td></td><td></td><td>1</td><td>3</td></tr> <tr><td>80</td><td>Strong blue flate tinged with ironstone,</td><td></td><td></td><td>4</td><td>6</td></tr> <tr><td>81</td><td>Dark-blue flate rather inclined to brown,</td><td></td><td></td><td>1</td><td>6</td></tr> <tr><td>82</td><td>Black thivery flate,</td><td></td><td></td><td>-</td><td>6</td></tr> <tr><td>83</td><td>Coal, XIV.</td><td></td><td></td><td>1</td><td>-</td></tr> <tr><td>84</td><td>Lighth-gray, brittle foamy schitus,</td><td></td><td></td><td>4</td><td>-</td></tr> <tr><td>85</td><td>Freestone striated with blue flate,</td><td></td><td></td><td>1</td><td>1</td></tr> <tr><td>86</td><td>Fine blue argillaceous schitus striated with freestone,</td><td></td><td></td><td>4</td><td>-</td></tr> <tr><td>87</td><td>Black flate, with hard, sharp, and fine particles,</td><td></td><td></td><td>3</td><td>-</td></tr> <tr><td>88</td><td>Very light blue flate, remarkably fine,</td><td></td><td></td><td>4</td><td>3</td></tr> <tr><td>89</td><td>Coal, XV.</td><td></td><td></td><td>5</td><td>4</td></tr> <tr><td>90</td><td>Soft gray argillaceous schitus,</td><td></td><td></td><td>4</td><td>3</td></tr> <tr><td>91</td><td>Black thivery flate,</td><td></td><td></td><td>2</td><td>2</td></tr> <tr><td>92</td><td>Coal, XVI.</td><td></td><td></td><td>1</td><td>3</td></tr> <tr><td>93</td><td>Strong lighth-coloured shale,</td><td></td><td></td><td>3</td><td>4</td></tr> <tr><td>94</td><td>Blue flate striated with white freestone,</td><td></td><td></td><td>3</td><td>4</td></tr> <tr><td>95</td><td>Ironstone,</td><td></td><td></td><td>-</td><td>4</td></tr> <tr><td>96</td><td>Gray flate,</td><td></td><td></td><td>3</td><td>9</td></tr> <tr><td>97</td><td>Strong white freestone,</td><td></td><td></td><td>5</td><td>6</td></tr> <tr><td>98</td><td>Freestone striated with blue flate,</td><td></td><td></td><td>10</td><td>-</td></tr> <tr><td>99</td><td>White freestone,</td><td></td><td></td><td>1</td><td>3</td></tr> <tr><td>100</td><td>Freestone striated with blue flate,</td><td></td><td></td><td>3</td><td>11</td></tr> <tr><td>101</td><td>Black flate,</td><td></td><td></td><td>-</td><td>5</td></tr> <tr><td>102</td><td>Freestone striated with blue flate,</td><td></td><td></td><td>1</td><td>4</td></tr> <tr><td>103</td><td>Strong white freestone,</td><td></td><td></td><td>-</td><td>4</td></tr> <tr><td>104</td><td>Freestone mixed with blue flate,</td><td></td><td></td><td>2</td><td>4</td></tr> <tr><td>105</td><td>Strong white freestone,</td><td></td><td></td><td>-</td><td>5</td></tr> <tr><td>106</td><td>Grayish flate of a thivery nature,</td><td></td><td></td><td>1</td><td>-</td></tr> <tr><td>107</td><td>Freestone mixed with blue flate,</td><td></td><td></td><td>4</td><td>-</td></tr> <tr><td>108</td><td>Very strong white freestone.</td><td></td><td></td><td>5</td><td>3</td></tr> <tr><td>109</td><td>Fine blue flate,</td><td></td><td></td><td>2</td><td>3</td></tr> <tr><td>110</td><td>White freestone striated with blue flate,</td><td></td><td></td><td>7</td><td>8</td></tr> <tr><td>111</td><td>Fine blue flate,</td><td></td><td></td><td>4</td><td>-</td></tr> <tr><td>112</td><td>White freestone,</td><td></td><td></td><td>2</td><td>1</td></tr> <tr><td>113</td><td>Freestone striated with blue flate,</td><td></td><td></td><td>10</td><td>-</td></tr> <tr><td>114</td><td>White freestone,</td><td></td><td></td><td>-</td><td>4</td></tr> <tr><td>115</td><td>White freestone in thin layers,</td><td></td><td></td><td>5</td><td>-</td></tr> <tr><td>116</td><td>Fine blue flate,</td><td></td><td></td><td>2</td><td>1</td></tr> <tr><td>117</td><td>Coal, XVII.</td><td></td><td></td><td>1</td><td>10</td></tr> </table> An interesting and valuable memoir on the subject of coal, written by M. Duhamel the younger, was presented a few years since to the Academy of Sciences at Paris, who adjudged it the prize that had been offered for the best essay on the subject. An ample abstract of this memoir appeared in the Journal des Mines, No. vii. In this paper is given a table of the number of veins, their direction and inclination, and the nature of the strata next the coal, and in the neighbourhood, in all the principal mines in Europe. For a fuller view of the natural history of coal, the readers may consult Dr Millar's edition of Williams's Mineral Kingdom, 1810.

Sect. XXXI. Of Fossils and Petrifications.

Those organic remains of vegetable and animal matter which are found below the surface of the earth, mixed with the stony matters which are properly the component parts of the earth, are generally called fossils, or extraneous fossils. If they have entirely lost all traces of vegetable or animal matter, and have assumed a stony earthy nature, they are called petrifications.

Some of these organic remains, particularly those of the vegetable kind, are found penetrated with a bituminous substance, so as to be rendered highly inflammable. One of the most curious circumstances attending these fossil bodies is, that they are very commonly natives of a different country from that in which they are found, or are the remains of species that are now no longer known.

We may properly divide these substances into those of the vegetable and those of the animal kingdom.

1. Vegetable fossils. Almost every part of vegetables, the trunks, branches, leaves, and fruits, have been found in a fossil state, or impressions of some of them are seen in various mineral substances, especially in the flinty stone which accompanies coal.

Fig. 6. represents a curious example of this, that was found in the mines at Saint Etienne in France.

A, is a fruit resembling that of coffee. B, is a portion of an unknown vegetable, apparently of the verticillate tribe. C, is a species of fern, which is very remarkable, as it is furnished with fructifications. D, is part of a plant with verticillate leaves, probably a species of gallium. E, is some exotic fruit.

Whole trees are often found below the surface of the earth, especially in bogs and moors, sometimes retaining much of their vegetable nature, but more commonly either impregnated with bitumen or completely petrified. Subterranean trees are frequently dug up in the Isle of Anglesea; and in the Isle of Man there is a marsh six miles long and three broad, in which fir trees are found in great quantities; and though they are 18 or 20 feet below the surface, they appear as if standing firmly upon their roots. Subterranean trees, in various states, are frequently found in Ireland, especially in the neighbourhood of Lough Neagh. Much has been written on the subject of these petrifications of Lough Neagh, by Dr Boate, in his Natural History of Ireland; by Mr Molyneux, in the Philosophical Transactions, No. clviii. and Dr Barton in his Lectures on Natural Philosophy. Some of these trees are represented as of an immense size*. One of the most curious instances of vegetable fossils, is that related by Raimazzini, as seen by him at Modena in Italy. At the bottom of wells, that are dug there below stony masses, which appear to have been the foundation of a former city, at the depth of near 30 feet, they find heaps of wheat entire, filbert trees, with their nuts, briars, &c. They find, likewise, every fix feet, a layer of earth, alternating with branches and leaves of trees.

At the depth of 28 feet, or thereabouts, they find a chalk that cuts very easily. It is mixed with shells of several sorts, and makes a bed of about 11 feet. After this they find a bed of marly earth, of about two feet, mixed with rushes, leaves, and branches. After this bed comes another chalk bed, of nearly the same thickness with the former, which ends at the depth of 49 feet.

That is followed by another bed of marly earth like the former; after which comes a new chalk bed; and these successive beds are always found in the same order. The ager sometimes finds great trees, which give the workmen much trouble. They see also sometimes at the bottom of these wells, great bones, coals, flints, and pieces of iron †.

The vegetable fossils are generally of a flinty structure, being sometimes rough and sandy; at others so fine and compact as to admit of a fine polish. Some beautiful specimens of petrified wood, of the appearance of agate, are to be seen in cabinets of natural history. That of Beffon at Paris contains two examples of this kind, which are figured at fig. 7. and 8. Fig. 7. is a transverse section of a piece of agatized wood, in which the ligneous texture is most completely preserved. Fig. 8. is another, more compact, and which has the additional singularity of containing several worms. The white oval spots are supposed to have been eggs, from which the worms had issued. In Dr Millar's Mineralogical Cabinet there is a similar specimen containing worms and their ova from Siberia, as well as many beautiful specimens of agatized wood from Siberia and Germany.

Among the bituminous vegetable fossils, none have attracted more attention than what is called bovey coal, a substance of an intermediate nature between wood and pitcoal, which is dug up in a common near Chudleigh in Devonshire. It is of a laminated texture, of a chocolate, or sometimes of a shining black colour, like deal boards that had been half charred. It burns heavily, and confines to light gray ashes. It is regularly stratified among beds of sand and clay, and the beds of coal are sometimes of considerable thickness. Mr Parkin* has collected much information respecting the remains, former and present state of this coal, in his entertaining work on fossils ‡.

2. Animal fossils. Fossils of animal matters are still more common than those of vegetables. Shells and fish bones are found in almost every bed of limestone, and in almost every country, at the bottom of the deepest valleys, and at the tops of very considerable mountains.

In the limestone strata in Derbyshire are found many of those fossils, which are called star-fishes and screw-fishes, which appear to be the remains of marine animals called encrinii. These are described by Whitehurst, who has given figures of similar animals brought entire from the West Indies §. Fig. 9. represents one of these fishes.

The isle of Cherea in Dalmatia contains caverns in chap. xvi. which are found prodigious quantities of fossil bones of oxen, oxen, horses, and sheep. Similar examples occur in many places; but human bones are, we believe, never found in a fossil state.

Fossil shells are found on the Alps, on the top of Mount Cenis, on the Appennines, on the mountains of Genoa, and in most of the quarries of stone and marble in Italy; in most parts of Germany and Hungary, and indeed generally in all the elevated places in Europe. We also find them in the flunes whereof the most ancient edifices of the Romans were constructed.

In Switzerland, Asia, and Africa, travellers have observed petrified fish in many places; for instance, on the mountains of Caftravan, there is a bed of white laminated stone, and each lamina contains a great number and diversity of fishes; they are, for the most part, very flat, and extremely compressed, in the manner of fossil ferns; yet they are so well preserved, that the minutest marks of their fins and scales are distinguishable, and every other part, whereby one species of fish is known from another.

There are likewise many echinites and petrified fish between Iver and Cairo, and on all the hills and heights of Barbary, most of which exactly correspond with the like species taken in the Red sea.

The long chain of mountains which extend from east to west, from the lower part of Portugal to the most eastern parts of China, those which stretch collaterally to the north and south of them, together with the mountains of Africa and America, which are now known to us, all contain strata of earth and stone, full of shells.

The islands of Europe, Asia, and America, wherein Europeans have had occasion to dig, whether in mountains or plains, all furnish us with shells, and convince us that they have this particular in common with their adjacent continents.

The gryphopetra, or the teeth of sharks and other fishes, are found in the jaws, polished and worn smooth at the extremities, consequently must have been made use of during the animal's life; and in shells the very pearls are found, which the living animals of the same kind produce.

It is well known that the purpura and pholades have a long-pointed proboscis, which serves them as a kind of gimlet or drill, to pierce the shells of living fish, on whose flesh they feed. Now, shells thus pierced are found in the earth, which is another incontrovertible proof that they heretofore inclosed living fish, and that these fish inhabited places where the purpura and pholades preyed on them.

In Holland sea shells are found 100 feet below the surface; at Marly-la-Ville, fix leagues from Paris, at 75; and in the Alps and Pyrenean mountains they are found under beds of stone of 100, nay even 1000 feet.

Shells are likewise found in the mountains of Spain, France, and England, in all the marble quarries of Flanders, in the mountains of Guelders, in all the hills round Paris, in those of Burgundy and Champagne; and, in short, in all places where the basis of the soil is neither freestone nor sandstone.

By shells we would be understood to mean, not only those which are merely tefaceous, but the relics of the crustaceous fishes also; and even all other marine productions; and we can venture to assert, that, in the generality of marbles, there is so great a quantity of marine productions, that they appear to surpass in bulk the matter where by they are united.

Among the many instances of the multiplicity of oysters, there are few more extraordinary than that immense bed which M. de Reaumur gives an account of, which contains 139,632,000 cubic fathoms. This vast mass of marine fossils is in Touraine in France, at upwards of 36 leagues from the sea. Some of these shells are found to entire, that their different species are very distinguishable.

Some of the same species are found recent on the coast of Poitou, and others are known to be natives of more distant parts of the world. Among them are likewise blended some fragments of the more strong parts of sea plants, such as mudriporae, fungi marini, &c. The caution of Touraine contains full nine square leagues in surface, and furnishes these fragments of shells wherever you dig.

Near Reading in Berkshire, a continued body of oyster shells has been found; they lie in a stratum of greenish sand, about two feet in thickness, and extend over five or six acres of ground; they are covered by strata of sand and clay, upwards of 14 feet deep. Several whole oysters are found with both their valves or shells lying together, as oysters before they are opened; the shells are very brittle; and in digging them up, one of the valves will frequently drop from its fellow. Several are dug out entire; nay, some double oysters with their valves united.

In a quarry at the cast end of Broughton in Lincolnshire, innumerable fragments of the shells of shell fish, of various sorts, are found under a stratum of stone imbedded in clay, with pieces of coral, and sometimes whole shell fish, with their natural shells and colours: some are most miserably cracked, bruised, and broken; others totally squeezed flat by the incumbent weight of earth.

Sharks teeth are dug up in the isle of Sheppey, retaining their natural colour, not petrified.

The teeth of sharks have likewise been taken out of a rock in Henderthelf park, near Malton in Yorkshire.

In the isle of Caldey, and elsewhere about Tenby in Pembrokehire, marine fossils have been found in solid marble, on the face of the broken sea cliffs, 200 fathoms below the upper surface of the rocks. Nor were they only observed upon the face of these rocks, but even more or less throughout the whole mass or extent of them. This is manifest from divers rocks hewn down by workmen for making of lime, and other pieces casually fallen from the cliffs.

Thousands of fossil teeth, exactly answering to those of divers sorts of sea fish, have been found in quarries and gravel pits about Oxford.

At Tame in Oxfordshire, the belemnites, or thunderbolt stones, are found in a stratum of blue clay, which still retain their native shelly substance.

The belemnites found in gravel pits, have suffered much, by their being rubbed against each other in the fluctuation of waters.

The nautili and belemnites are frequently found at Goring near Oxford*.

One of the most extraordinary collections of shells is Trans. vol. that liv. p. 5. that lately discovered by Ramond on the summit of Mont Perdu, the highest of the Pyrenées, where there are found vast quantities of sea shells and other marine spoils, and even skeletons of animals in a fossil state.

Whole skeletons of very large animals have been discovered in a fossil state. Those of elephants have been found buried in the plains of Siberia; and bones of the rhinoceros, the hippopotamus, and the tapir, have been found in other places. A very large skeleton, nearly complete, of an immense animal, similar to the rhinoceros, is preserved in the cabinet of Madrid. It was dug up at Paraguay in South America, at the depth of 100 feet, in a sandy bed, on the banks of the river de la Plata. A description and engraving of it are given by Cuvier, in the Annals of the National Museum, No. 29. It appears to be at least 12 feet long, and the bones are of an immense size.

A prodigious quantity of fossils, both of marine animals, and of quadrupeds, are found in the platter hills of Montmartre near Paris. An account of these has lately appeared in several numbers of the Annals of the National Museum, by M. Lamarck, accompanied with the anatomical illustrations of Cuvier. These papers are extremely curious, and contain engravings of most of the fossils described, some of which are the remains of unknown animals. Our limits do not permit us to present our readers with even an abstract of these accounts. We shall therefore select only one example.

Fig. 10. represents a block of gypsum, on the surface of which is the skeleton of an animal resembling a moufe, or, according to Cuvier, one of the opossum tribe. The skeleton is nearly entire, and the head, the neck, the spine, the pelvis, one of the fore and hind legs, and part of the tail, are very distinct. There were two pieces of gypsum found together, which appear to have divided the skeleton between them. The animal seems to have been crushed or imbedded in his natural situation*.

We have now enumerated the principal materials that compose the external crust of our earth, and have mentioned some of the most material circumstances respecting each. The metallic ores still remain to be considered, and they shall be noticed in describing metallic veins.

CHAP. II. General Distribution of the Materials of the Earth.

The uppermost stratum of the earth, in low situations, is, for the most part, composed of sand or clay, or a mixture of these, forming beds that are either composed of the same mixture, or of alternate layers of the two substances. These beds vary in thickness, in different places; but, in the same place, they usually preserve nearly the same thickness for a considerable extent. Sometimes these beds of clay, sand, and earth, with shells, extend to the depth of some hundred feet. See the annexed table, I. (E).

This table exhibits a view of the arrangement of strata in several countries of Europe; and, with the tables of coal strata, in the last chapter, will give the reader more information on this subject than an elaborate detailed account.

(e) The following works are referred to in the table of strata.

* Varenii Geogr. Gener. lib. i. prop. vii. † Buffon, Nat. Hist. vol. i. act. vii. ‡ Bergman, Descript. Phyl. de Terre, sect. viii. || Kirwan, Geolog. Essays, p. 259. § Guettard, Atlas Mineral. de la France. ¶ Whitehurst's Theory of the Earth, sect. xvi. ** Ib. sect. xix. TABLE of the order of Strata in Various Parts of Europe.

<table> <tr> <th rowspan="2">No of Strata.</th> <th colspan="3">1*</th> <th colspan="3">2†</th> <th colspan="3">3‡</th> <th colspan="3">4||</th> <th colspan="3">5§</th> <th colspan="3">6¶</th> <th colspan="3">7**</th> </tr> <tr> <th>Strata at Amsterdam.</th> <th>Ft. Feet.</th> <th>Ft. In.</th> <th>At Marly la Ville, France.</th> <th>Ft. In.</th> <th>Gravefend in Kent.</th> <th>Ft. In.</th> <th>Mansfield in Germany.</th> <th>Ft. In.</th> <th>Hills near Etampes in France.</th> <th>Ft. In.</th> <th>Strata of Derbyshire.</th> <th>Ft. In.</th> <th>At Balleycattle, Ireland.</th> <th>Ft. In.</th> </tr> <tr> <td>1</td> <td>Soil,</td> <td>7</td> <td>Earth, mud & sand, 13</td> <td></td> <td>Sand and flints, 1</td> <td>3</td> <td>Vegetable earth,</td> <td></td> <td>Vegetable earth, 4</td> <td></td> <td>Coarse fandstone,</td> <td>360</td> <td>Whinstone,</td> <td></td> </tr> <tr> <td>2</td> <td>Turf,</td> <td>9</td> <td>Earth and gravel,</td> <td>2</td> <td>Red sand,</td> <td>0</td> <td>Swinefetone,</td> <td>36</td> <td>Marl and turf cut by dykes, 135</td> <td></td> <td>Slate clay,</td> <td>360</td> <td>Firestone,</td> <td></td> </tr> <tr> <td>3</td> <td>Soft clay,</td> <td>9</td> <td>Mud and sand</td> <td>3</td> <td>Sand and flints, 1</td> <td>8</td> <td>Gypsum, 24—180</td> <td></td> <td>Of freestone, marl, and shells, 12</td> <td></td> <td>Shelly limestone,</td> <td>150</td> <td>Shale,</td> <td></td> </tr> <tr> <td>4</td> <td>Sand,</td> <td>8</td> <td>Hard marl,</td> <td>2</td> <td>Red sand,</td> <td>0</td> <td>Clay, chalk, and sand, 72—120</td> <td></td> <td>Brown pebbles, 4</td> <td></td> <td>Amygdaloid,</td> <td>48</td> <td>Stony clay,</td> <td></td> </tr> <tr> <td>5</td> <td>Earth,</td> <td>4</td> <td>Marly stone,</td> <td>4</td> <td>Sand and flints, 2</td> <td>6</td> <td>Compact limestone, 12</td> <td></td> <td>Marl and shells, 0</td> <td></td> <td>Compact limestone,</td> <td>150</td> <td>Shale,</td> <td></td> </tr> <tr> <td>6</td> <td>Clay,</td> <td>10</td> <td>Powdery marl with sand,</td> <td>5</td> <td>Pure sand in beds, 1</td> <td>8</td> <td>Argilliferous limestone,</td> <td></td> <td>Sand and grit, 45</td> <td></td> <td>Amygdaloid</td> <td>138</td> <td>Freestone,</td> <td></td> </tr> <tr> <td>7</td> <td>Earth,</td> <td>4</td> <td>Sand,</td> <td>1</td> <td>Blackish clay,</td> <td>0</td> <td>Indurated clay,</td> <td>3</td> <td>Sand and rounded pebbles, 18</td> <td></td> <td>Lamellar limestone,</td> <td>180</td> <td>Stony clay,</td> <td></td> </tr> <tr> <td>8</td> <td>Sand,</td> <td>10</td> <td>Marl and sand,</td> <td>3</td> <td>Chalk and flints, 1</td> <td>6</td> <td>Calciferous clay,</td> <td>4</td> <td>Sand and shells, 6</td> <td></td> <td>Amygdaloid,</td> <td>66</td> <td>Shale,</td> <td></td> </tr> <tr> <td>9</td> <td>Clay,</td> <td>2</td> <td>Hard marl and flint,</td> <td>3</td> <td>Clay, sand, flints, and shells,</td> <td>1</td> <td>Clay flate,</td> <td>1</td> <td>Sand & gravel, 16</td> <td></td> <td>Limestone not cut through,</td> <td></td> <td>Limestone,</td> <td></td> </tr> <tr> <td>10</td> <td>White sand,</td> <td>4</td> <td>Gravel or marl in powder,</td> <td>1</td> <td>Fine yellow sand, 4</td> <td>5</td> <td>Marlite,</td> <td>1</td> <td>Tuf and shells, 4</td> <td></td> <td>Coal,</td> <td></td> <td></td> <td></td> </tr> <tr> <td>11</td> <td>Earth,</td> <td>6</td> <td>Eglantine,</td> <td>1</td> <td></td> <td></td> <td>Saand,</td> <td>0</td> <td>Soft shale,</td> <td>4</td> <td></td> <td></td> <td>Indurated clay,</td> <td></td> </tr> <tr> <td>12</td> <td>Sand,</td> <td>14</td> <td>Marly gravel,</td> <td>1</td> <td></td> <td></td> <td>Gravel,</td> <td>3</td> <td>Marly clay,</td> <td>8</td> <td></td> <td></td> <td>Stony clay,</td> <td></td> </tr> <tr> <td>13</td> <td>Clay and fand,</td> <td>8</td> <td>Stony marl,</td> <td>4</td> <td></td> <td></td> <td>Blue clay,</td> <td>2 in. to 8</td> <td></td> <td></td> <td></td> <td></td> <td>Not ascertained,</td> <td></td> </tr> <tr> <td>14</td> <td>Sand & shells,</td> <td>4</td> <td>Sand and shells,</td> <td>1</td> <td></td> <td></td> <td>Sandstone, clay, & mica,</td> <td>6</td> <td></td> <td></td> <td></td> <td></td> <td>Coarse fandstone,</td> <td></td> </tr> <tr> <td>15</td> <td>Clay,</td> <td>102</td> <td>Gravel,</td> <td>2</td> <td></td> <td></td> <td>Red femiprotolite, 360</td> <td></td> <td></td> <td></td> <td></td> <td></td> <td>See fig. 1.</td> <td></td> </tr> <tr> <td>16</td> <td>Sand,</td> <td>31</td> <td>Stony marl,</td> <td>3</td> <td></td> <td></td> <td>Siliceous fandtone, 96</td> <td></td> <td></td> <td></td> <td></td> <td></td> <td></td> <td></td> </tr> <tr> <td>17</td> <td></td> <td></td> <td>Powder marl,</td> <td>1</td> <td></td> <td></td> <td>Cragg-flone,</td> <td>10</td> <td></td> <td></td> <td></td> <td></td> <td></td> <td></td> </tr> <tr> <td>18</td> <td></td> <td></td> <td>Hard stone,</td> <td>1</td> <td></td> <td></td> <td>Wacken,</td> <td>156</td> <td></td> <td></td> <td></td> <td></td> <td></td> <td></td> </tr> <tr> <td>19</td> <td></td> <td></td> <td>Sand and shells,</td> <td>18</td> <td></td> <td></td> <td>Clay flate,</td> <td>4</td> <td></td> <td></td> <td></td> <td></td> <td></td> <td></td> </tr> <tr> <td>20</td> <td></td> <td></td> <td>Brown freestone,</td> <td>3</td> <td></td> <td></td> <td>Coal,</td> <td>4</td> <td></td> <td></td> <td></td> <td></td> <td></td> <td></td> </tr> <tr> <td>21</td> <td></td> <td></td> <td>Sand,</td> <td>22</td> <td></td> <td></td> <td>Clay flate,</td> <td>3</td> <td></td> <td></td> <td></td> <td></td> <td></td> <td></td> </tr> <tr> <td>22</td> <td></td> <td></td> <td></td> <td></td> <td></td> <td></td> <td>Slaty trap,</td> <td>90</td> <td></td> <td></td> <td></td> <td></td> <td></td> <td></td> </tr> <tr> <td>23</td> <td></td> <td></td> <td></td> <td></td> <td></td> <td></td> <td>Red femiprotolite, 180</td> <td></td> <td></td> <td></td> <td></td> <td></td> <td></td> <td></td> </tr> <tr> <td>24</td> <td></td> <td></td> <td></td> <td></td> <td></td> <td></td> <td>Primitive rock,</td> <td>0</td> <td></td> <td></td> <td></td> <td></td> <td></td> <td></td> </tr> <tr> <td colspan="3">Total No of Feet.</td> <td>232</td> <td>100</td> <td>15</td> <td></td> <td></td> <td>256</td> <td>6</td> <td></td> <td></td> <td></td> <td></td> <td></td> </tr> </table> In our subsequent view of the distribution of the stony matters that compose the earth, we shall consider, 1. The nature, disposition, and structure, of mountains. 2. The nature, direction, &c. of dykes. 3. The nature, direction, &c. of metallic veins.

SECT. I. Of Mountains.

There are no objects on the surface of the earth which are so well calculated to excite the attention of mankind in general, and that of geologists in particular, as those stupendous elevated masses which we call mountains. The term mountain has in general been applied to those parts of the earth which are elevated to a very considerable height above the level surface; and a mountain is in common language distinguished from a hill only by its superior elevation. But as it is found necessary in a scientific point of view to render this distinction more accurate and precise, various geologists have given more correct definitions. By Pini and Mitterpacher every elevation whose declivity makes with the horizon an angle of at least 13°, and whose perpendicular height is not less than one-fifth of the declivity, is called a mountain. Werner distinguishes mountains according to their height, into high, middle-sized, and low. A high mountain according to him is that whose perpendicular height exceeds 6000 feet; when the height is not above 6000 nor below 3000 he calls it middle-sized; and when its height is below 3000 feet, he calls it low.

Mountains are either single or in groups; and these groups either consist of several mountains standing near each other so as to occupy nearly the centre of a certain space of ground, or they follow each other so as to form a ridge or chain, running across a country, or along its shores. Sometimes these chains run in a longitudinal direction, as is the case with Mount Caucasus and the Uralian mountains in Asia, the Cordilleras in South America, &c. but often they run in a curvilinear direction like a crescent, as the Carpathian mountains, which separate Hungary from the rest of the Austrian territories. It has been supposed by some theoretic writers, that chains of mountains always run in nearly the same direction, which has been conceived to be from east to west; but this is by no means exact, as later observations have shewn that they assume different directions according to the form of the country where they are situated. Some writers have laid it down as a general rule, that chains of mountains always extend in a direction nearly parallel to the length of the country; but to this there are also many exceptions. Thus the Uralian mountains, the Carpathians, the Pyrenees, the Grampians in Scotland, and many others, run rather across the country. It often happens that mountains occupy nearly the central parts of a country; and the land generally slopes with a gentle declivity towards one side of the chain, while towards the other it is considerably steeper. This circumstance of one side of a chain of mountains being steeper than the other, has been lately extended to mountains and hills in general; and Dr Kirwan has written an excellent paper on the subject, from which we shall here extract the most important observations.

"That one part of almost every high mountain or hill is steeper than another, could not have escaped the notice of any person who had traversed such mountains; but that nature in the formation of such declivities had any regard to different aspects or points of the compass, seems to have been first remarked by the celebrated Swedish geologist Mr Tilas, in the 22d vol. of the Memoirs of Stockholm for 1760. Neither Varrenius, Lulolph, nor Buffon in his natural history published in 1748, have noticed this remarkable circumstance.

"The observation of Tilas, however, relates only to the extreme ends, and not to the flanks of mountains; The flency with respect to the former, he remarked that the steep fides eft declivity always faces that part of the country where the land lies lowest; and the gentlest, that part of the country where the land lies highest; and that in the southern and eastern parts of Sweden they consequently face the east and south-east; and in the northern the west. The essential part of this observation extends therefore only to the general elevation or depression of the country, and not to the bearings of their declivities.

"The discovery that the different declivities of the western flanks of mountains bear an invariable relation to their different aspects, seems to have been first published by steepest. Mr Bergman in his Physical Description of the Earth, of which the second edition appeared in 1773. He there remarked, that in mountains that extend from north to south, the western flank is the steepest, and the eastern the gentlest. And that in mountains which run east and west the southern declivity is the steepest, and the northern the gentlest. Vol. II. § 187.

"This affection he grounds on the observations related in his 1st vol. § 32, namely, that in Scandinavia, the Suevoberg mountains that run north and south, separating Sweden from Norway, the western or Norwegian fides are the steepest, and the eastern or Swedish, the most moderate; the verticality or steepness of the former being to that of the latter as 40 or 50 to 4 or 2.

"That the Alps are steeper on their western and southern fides than on the eastern and northern.

"That in America the Cordilleras are steeper on the western fide, which faces the Pacific ocean, than on the eastern. But he does not notice a few exceptions to this rule in particular cases which will hereafter be mentioned.

"Buffon, in the first volume of his Epochs of Nature, published in 1778, p. 185, is the next who notices the general prevalence of this phenomenon, as far as relates to the eastern and western sides of the mountains that extend from north to south; but he is silent with respect to the north and south fides of the mountains that run from east to west; nay, he does not seem to have had a just comprehension of this phenomenon; for he considers it conjointly with the general dip of the regions in which these mountains exist. Thus he tells us, vol. i. p. 185, that in all continents the general declivity, taking it from the summit of mountains, is always more rapid on the western than on the eastern fide; thus the summit of the chain of the Cordilleras is much nearer to the western shore than to the eastern; the chain which divides the whole length of Africa, from the Cape of Good Hope, to the mountains of the Moon, General Moon, is nearer, he says, to the western than to the eastern seas; of this, however, he must have been ignorant, as that tract of country is still unknown.

"The mountains which run from Cape Comorin through the peninsula of India are, he says, much nearer to the sea on the east than on the west; he probably meant the contrary, as the fact is evidently so, and fo he states it in vol. ii. p. 295; the fame he tells us may be observed in islands and peninsulas, and in mountains.

"This remarkable circumstance of mountains was notwithstanding fo little noticed, that in 1792 the author of an excellent account of the territory of Carlsbad in Bohemia, tells us he had made an observation, which he had never met with in any physical description of the earth, namely, that the southern declivity of all mountains was much steeper than the northern, which he proves by inferring the Erzgebirge of Saxony, the Pyrenees, the mountains of Switzerland, Savoy, Carinthia, Tyrole, Moravia, the Carpathian and Mount Haemus in Turkey. 2. Bergm. Journ. 1792. p. 385. in the note.

"Herman in his geology, published in 1787, p. 90. has at least partially mentioned this circumstance; for he says that the eastern declivities of all mountains are much gentler and more thickly covered with secondary strata, and to a greater height than the western flanks, which he instances in the Swedish and Norwegian mountains, the Alps, the Caucasian, the Appenine, and Ouralian mountains; but the declivities bearing a southern or northern aspect he does not mention.

"Lamethier, in vol. iv. of his Theory of the Earth, of which the second edition appeared in 1797, a work which abounds in excellent observations, p. 381. produces numerous instances of the inequality of the eastern and western declivities, but scarce any of the northern and southern, whose difference he does not seem to have noticed; but he makes a remark which I have not seen elsewhere, that the coasts of different countries present similar declivities.

"With regard to eastern and western aspects, he thinks that a different law has obtained in Africa from that which has been observed in other countries; for in that vast peninsula he imagines the eastern declivities of mountains are the steepest, and the western the gentlest. Of this, however, he adduces no other proof, but that the greatest rivers are found on the western side: this proof seems insufficient, as, if mountains be situated far inland, great rivers may flow indiscriminately from any side of them, and sometimes few rivers flow even from the side whose descent is most moderate; for instance, from the eastern side of the mountains of Syria. The Elbe and the Oder, two of the greatest rivers in Germany, take their course from the western sides, the first of the Bohemian and the other of the Moravian mountains, which yet are the steepest. Many originate from lakes, as the Shannon with us; many take such a winding course, that from a bare knowledge of the place of their disemboguement it is impossible to judge from what side of a mountain they issue, if from any; their course at most discovers the depression of the general level of the country.

"In 1798, the celebrated traveller and circumnavigator, John Reinhold Forster, published a geological tract which merits so much more attention, as all the facts were either observed by himself, or related to him by the immediate observers. In this he states as a fact universally observed, that the south and south-east sides of almost every mountain are steep, but that the north and north-west sides are gently covered and connected with secondary strata, in which organic remains abound, which he illustrates by various instances, some of which have been already, and others will presently be mentioned.

"At present this fact attracts the greatest attention, being obviously connected with the original structure of the globe, and clearly proving that mountains are not merely fortuitous eruptions unconnected with translations on the surface of the earth, as has of late been confidently advanced.

"I shall now state the principal observations relative to this object, that have been made in different parts of the world.

In Europe.

1. The mountains that separate Sweden from Norway extend from north to south, their western sides are steep, and the eastern gentle. 1. Berg. Erde Beschreib. p. 157. 2. The Carpathian mountains run from east to west; their southern sides towards Hungary are steep, their northern towards Poland moderate. Foster, § 46. 3. Dr Walker, professor of natural history at Edinburgh, observed that the coasts and hills of Scotland are steeper and higher on the western side than on the eastern. Jameton's Mineralogy of Scotland, p. 3. However, Jameton observed, that the south side of the Isle of Arran is the lowest, and the north side the highest, p. 51. 4. The mountains of Wales are gentle on the eastern and steep on the western side. 5. The mountains of Parthry, in the county of Mayo, are steep on the western side. 6. The mountains which separate Saxony from Bohemia, defend gently on the Saxon or northern side, but are steep on the Bohemian or southern side. Charpentier, p. 75. The southern declivity is to the northern as six to two. Bergm. Journ. 1792, p. 384. and 385. 7. The mountains which separate Silesia from Bohemia run nearly from east to west, yet are steeper on the northern or Silesian side than on the opposite Bohemian. Affermann Silesia, 335. Such branches as run from north-east to south-west, have their western covered with primordial strata, and consequently less steep. 4. New Roz. p. 157. 8. The Meißener in Hesse is steeper on the north and east sides, which face the Warra, than on the south and western. 1. Bergm. Journ. 1789, p. 272. 9. The mountains of the Harz and Habichtswald are steep on the south, and gentle on the northern sides. Foster, § 46. 10. The Pyrenees, which run from east to west, are steeper on the southern or Spanish side. Carbonieres, xiii. 11. The mountains of Crim Tartary are gentle on the northern, and steep on the southern sides. Foster, ibid. 12. The Oursals, which stretch from north to south, are far steeper on the western than on the southern sides. Herman Geologic, p. 93; and, 2. Ural Befchreib, p. 380.

13. The mountain of Armenia, to the west of the Oursals, is steep on its east and north sides; but gentle on the southern and western. 1. Pallas Voy. p. 277.

14. The Altaichan mountains are steep on their southern and western sides, but gentle on the northern and eastern. Fosser, ibid. and Herman. 2. Ural Befschreib, p. 392, in the note.

15. So also are the mountains of Caucæus. 3. Schrift. Berl. Gelafch. 471.

16. The mountains of Kamtschatka are steep on the eastern sides. Pallas, 1. Afl. Petropol. 1777. p. 43.

17. The Ghauts in the Indian peninsula are steep on the western side.

18. The mountains of Syria, which run from north to south, skirting the Mediterranean, are said to be steeper on the western side, facing the Mediterranean. 4. La Metherie, p. 380.

In America.

"The Cordilleras run from north to south; their western flanks towards the Pacific are steep, their eastern descend gradually.

"In Guiana there is a chain of mountains that run from east to west; their southern flanks are steep, their northern gentle. Voyages de Condamine, p. 140."*

The theory according to which Mr Kirwan attempts to explain the appearances of mountains which are enumerated above, will be given in the next chapter.

We have already, under the article Barometer, No. 44, shewn the method of computing the height of mountains by means of that instrument. The following table shews the height of the principal mountains in the globe, chiefly according to this computation.

In this table the second column shews the height as estimated by the barometer, and the third the same by geometrical calculation. Where the numbers are placed in the middle of these two spaces, it denotes an uncertainty by what method the computation has been made.

<table> <tr> <th>Mountains.</th> <th>Height by Barom.</th> <th>Height by Geometry.</th> <th>Mountains.</th> <th>Height by Barom.</th> <th>Height by Geometry.</th> </tr> <tr> <td>In Britain.</td> <td></td> <td></td> <td>Pyrenees.</td> <td></td> <td></td> </tr> <tr> <td>Ben Nevis,</td> <td>435°</td> <td></td> <td>Mont Perdu,</td> <td>11,000</td> <td></td> </tr> <tr> <td>Whirn,</td> <td>405°</td> <td></td> <td>Canigou,</td> <td>9,000</td> <td></td> </tr> <tr> <td>Ben Lawers,</td> <td>4015</td> <td></td> <td></td> <td></td> <td></td> </tr> <tr> <td>Ingleborough,</td> <td>3987</td> <td></td> <td></td> <td></td> <td></td> </tr> <tr> <td>Do.</td> <td>2377</td> <td>2380</td> <td></td> <td></td> <td></td> </tr> <tr> <td>Ben More,</td> <td>3993</td> <td></td> <td></td> <td></td> <td></td> </tr> <tr> <td>Pennygent,</td> <td>3930</td> <td></td> <td></td> <td></td> <td></td> </tr> <tr> <td>Crosthwaite,</td> <td>3839</td> <td></td> <td></td> <td></td> <td></td> </tr> <tr> <td>Skiddaw,</td> <td>3380</td> <td>3530</td> <td></td> <td></td> <td></td> </tr> <tr> <td>Snowden,</td> <td>3456</td> <td></td> <td></td> <td></td> <td></td> </tr> <tr> <td>Mount Battock,</td> <td>3465</td> <td></td> <td></td> <td></td> <td></td> </tr> <tr> <td>Pendlehill,</td> <td>3411</td> <td></td> <td></td> <td></td> <td></td> </tr> <tr> <td>Schehallion,</td> <td>3564</td> <td></td> <td></td> <td></td> <td></td> </tr> <tr> <td>Helvellyn,</td> <td>3324</td> <td></td> <td></td> <td></td> <td></td> </tr> <tr> <td>Hartfell,</td> <td>3300</td> <td></td> <td></td> <td></td> <td></td> </tr> <tr> <td>Ben Wevis,</td> <td>3700</td> <td></td> <td></td> <td></td> <td></td> </tr> <tr> <td>Ben Lomond,</td> <td>3240</td> <td></td> <td></td> <td></td> <td></td> </tr> <tr> <td>Saddleback,</td> <td>3048</td> <td></td> <td></td> <td></td> <td></td> </tr> <tr> <td>Ben Ledy,</td> <td>3099</td> <td></td> <td></td> <td></td> <td></td> </tr> <tr> <td>In Ireland.</td> <td></td> <td></td> <td></td> <td></td> <td></td> </tr> <tr> <td>Slieve Donard,</td> <td>3150</td> <td></td> <td></td> <td></td> <td></td> </tr> <tr> <td>Croagh Patrick,</td> <td>2666</td> <td></td> <td></td> <td></td> <td></td> </tr> <tr> <td>Nephin,</td> <td>2640</td> <td></td> <td></td> <td></td> <td></td> </tr> <tr> <td>Knock Meledown,</td> <td>2700</td> <td></td> <td></td> <td></td> <td></td> </tr> <tr> <td>Mangerton,</td> <td>2160</td> <td>2500</td> <td></td> <td></td> <td></td> </tr> <tr> <td>Cumeragh,</td> <td></td> <td></td> <td></td> <td></td> <td></td> </tr> <tr> <td>In France.</td> <td></td> <td></td> <td>Alps.</td> <td></td> <td></td> </tr> <tr> <td>Puy de Sanfi,</td> <td>6300</td> <td></td> <td>Mont Blanc,</td> <td>15,662</td> <td></td> </tr> <tr> <td>Plomb de Cantal,</td> <td>6200</td> <td></td> <td>Schreckhorn,</td> <td>13,000+</td> <td></td> </tr> <tr> <td>Puy de Dome,</td> <td>5000</td> <td></td> <td>Finsteraar,</td> <td>12,000+</td> <td></td> </tr> <tr> <td></td> <td></td> <td></td> <td>Mount Titlis,</td> <td>10,818</td> <td></td> </tr> <tr> <td></td> <td></td> <td></td> <td>Mont Rofa,</td> <td>15,000</td> <td></td> </tr> <tr> <td></td> <td></td> <td></td> <td>Mont Cenis,</td> <td>9,760</td> <td></td> </tr> <tr> <td></td> <td></td> <td></td> <td>In the Tyrole.</td> <td></td> <td></td> </tr> <tr> <td></td> <td></td> <td></td> <td>Glochner,</td> <td>11,500 Fr.</td> <td></td> </tr> <tr> <td></td> <td></td> <td></td> <td>Ortele,</td> <td>13,000 Fr.</td> <td></td> </tr> <tr> <td></td> <td></td> <td></td> <td>Plaley Kogel,</td> <td>9,748 Fr.</td> <td></td> </tr> <tr> <td></td> <td></td> <td></td> <td>Germany.</td> <td></td> <td></td> </tr> <tr> <td></td> <td></td> <td></td> <td>Stuben,</td> <td>4692</td> <td></td> </tr> <tr> <td></td> <td></td> <td></td> <td>Brenner,</td> <td>5109</td> <td></td> </tr> <tr> <td></td> <td></td> <td></td> <td>Lomnitz peak,</td> <td>8640</td> <td></td> </tr> <tr> <td></td> <td></td> <td></td> <td>Kefmark peak,</td> <td>8508</td> <td></td> </tr> <tr> <td></td> <td></td> <td></td> <td>Krivan,</td> <td>8343</td> <td></td> </tr> <tr> <td></td> <td></td> <td></td> <td>Carpath.</td> <td></td> <td></td> </tr> <tr> <td></td> <td></td> <td></td> <td>Sicily.</td> <td></td> <td></td> </tr> <tr> <td></td> <td></td> <td></td> <td>Ætna,</td> <td>10,032</td> <td></td> </tr> <tr> <td></td> <td></td> <td></td> <td>In Denmark, Norway, and Sweden.</td> <td></td> <td></td> </tr> <tr> <td></td> <td></td> <td></td> <td>Swukku,</td> <td>9000</td> <td></td> </tr> <tr> <td></td> <td></td> <td></td> <td>Arefkutan,</td> <td>6162</td> <td></td> </tr> <tr> <td></td> <td></td> <td></td> <td>Kinneculla,</td> <td>931</td> <td></td> </tr> <tr> <td></td> <td></td> <td></td> <td>Røtack,</td> <td>6000</td> <td></td> </tr> </table>

TABLE GEOLOGY.

TABLE of the Heights of Mountains, Continued.

<table> <tr> <th>Mountains.</th> <th>Height by Barom.</th> <th>Height by Geometry</th> <th>Mountains.</th> <th>Height by Barom.</th> <th>Height by Geometry</th> </tr> <tr> <td>In Russia.<br>Pauda,</td> <td>Fect.</td> <td>4512</td> <td>South America.<br>Chimborazo,<br>Do.</td> <td>Fect.</td> <td>20,280</td> </tr> <tr> <td>Canary Islands.<br>Peak of Teneriffe,</td> <td></td> <td>11,424</td> <td>Cotopaxi,<br>Tunguragas,</td> <td></td> <td>18,600</td> </tr> <tr> <td>In North America.<br>Stony Mountains,<br>White Mountains,<br>Blue Mountains,</td> <td>3000<br>4000<br>2000</td> <td></td> <td>In Jamaica.<br>Blue Mountains,</td> <td></td> <td>7431</td> </tr> </table>

The course of mountains is that direction of their length in which they descend and grow lower; or if a river runs parallel to them, they are said to have their course in the direction of the stream of the river. The course of mountains is seldom uniform. It has been laid down as a general maxim by Buffon, that when there are two parallel chains of mountains, the salient angle of one of the chains always corresponds with the internal angle of the other; but later geologists have ascertained that this circumstance does not generally hold, except when a river runs between the two chains.

It generally happens, that one particular mountain, or chain of mountains is composed of those stony materials which we have denominated primitive; while the rest is made up of the secondary compounds. The primitive substances occupy the base and central parts of the mountain, and often extend to its very summit; the secondary cover these, and are generally found on the flanks or sides of the mountain, though sometimes they cover the top of the mountain. In a chain of mountains there are commonly three, and often five parallel ridges, of which the central ridge is composed of primitive compounds, and those on each side of it, chiefly or entirely of secondary compounds. Hence mountains are usually divided into primary or primeval, and secondary or epizootic; the latter term being given to the secondary mountains from their being replete with shells and other remains of animal beings. The secondary mountains are also sometimes divided into original and derivative, for a reason that will appear hereafter.

The primary mountains, besides their being in the centre, and destitute, or nearly so, of organic remains, may generally be distinguished by the ruggedness and angular appearances arising from the different nature and hardness of the substances of which they are composed; the quartz and harder granite resisting the attacks of the air and weather, while the other substances being softer, gradually decay, and leave the harder in the form of spires and angles. Where, however, the primitive compounds have been completely covered with secondary strata, these angular appearances seldom take place; and the mountain is only to be distinguished by its position and the structure of its internal parts. The secondary mountains generally have their tops round, and much smoother than those of the primary mountains.

In some cases a number of mountains appear united at their tops into an extensive plain or platform, from which they seem to diverge and branch in every direction. The most remarkable instance of this kind occurs in Tibet. (See GEOGRAPHY, No 41.)

It is difficult to acquire a knowledge of the interior structure of mountains. The greater part of them is hid from our view, and nature only exposes them in a few points by means of fissures, caverns, and intermediate valleys.

"The materials of which mountains consist are deposited either in irregular heaps, or piles variously interlaced by rifts, or in beds or strata separated from each other by rifts, often horizontal, or varying from that direction by an angle of from 5 to 40 degrees, and sometimes much more considerably, approaching even to a vertical position. The strata of mountains are most frequently in the direction of their declivity, yet sometimes their course is directly opposite, or countercurrent: the best manner of determining the angles of their course is by discovering that of their rifts. It chiefly depends on the unevenness of the fundamental ground that supports them. According to M. Sauff, 502, most of the elevated granitic mountains in Switzerland are formed of immense vertical pyramidal laminae, parallel to each other, that is, piles somewhat inclining from the unequal distribution of their weight, a disposition that may well be expected from collateral crystallizations; but this disposition is not universal, for they have been found in Saxony, and in the Pyrenees, horizontally stratified; much less can it be said, that this vertical position is general, for the strata of gneiss are generally horizontal, and commonly very regular discovering no traces of a violent shock. Mount Rofa, next to Mount Blanc, the highest in Europe, consists also of gneiss, which M. Sauffire found horizontally stratified.

"Shangin, who lately (1786) travelled over the Altaishan mountains, being consulted by Pallas, whether he found any vertical layers or strata therein, answered, he had not; but that he found them perfectly horizontal on the banks of the river Tchary.

"Mountains of primitive limestone are frequently in irregular piles, but often also horizontally stratified. Siliceous schistus is also often horizontally stratified." Many argillites, particularly roof slates, are generally said to have nearly a vertical position; but Voight has shewn that it is only their lamellae that are so situated; their horizontal seams, and their walls, discovering their true position; their verticality arising only from the drain of the water, and, consequently, their contraction in that direction: hence those that are most solicited, as they contract less, discover less verticality. Sometimes horizontal strata overlap on both sides. Sometimes they are flanked on both sides with vertical strata.

"Much confusion prevails in the structure of the Pyrenees, and of the Grifon mountains, and those on the borders of the Baikal, and other great lakes.

"The perturbed state of the strata often proceeds from the decomposition of internal beds of pyrites, to which water has had access; this appears to be the cause of the alterations observed in the mountain of Rannenberg, on the frontiers of Saxony. In this mountain a double direction of the strata of gneiss is observed; between both the strata are vertical, and a large intermediate space is filled with iron ore: but this mountain contains beds of pyrites and vast swallowes; most probably then the pyrites swoll, uplifted the whole, and the diffused iron flowed into the vacuity, from which the water afterwards drained off on the sides.

"In secondary mountains, particularly the calcareous, the greatest disorder often prevails, though in general their stratification is horizontal.

"The calcareous mountains of Savoy are often arch'd like a lambda, probably from the sinking of the intermediate strata, the intermediate remaining horizontal. Sometimes they assume the form of the letters Z. S. C. or of a disjointed O, the convexities facing each other. So also in the Pyrenees, they sometimes overlap, from an unequal distribution in their original formation, and bend various ways. They assume a spiral form, or that of a horse-shoe placed horizontally.

"According to Lehman, most secondary strata present hollows or moulds, (as they are called,) from internal depression. But sometimes also elevations, from an original elevation in the fundamental stone.

"In Scotland, all the secondary strata in the vicinity of primeval mountains, are nearly vertical; but at a greater distance they approach more to an horizontal direction.*"

We shall now trace the course of the principal mountainous chains on the globe, and in accompanying us, the reader may have before him a good map of the world.

M. Buache places the most elevated points of the great chains of mountains under the equatorial line: but, according to Pallas, the fullest and most continuous lands, and perhaps likewise the most elevated, are to be found at a distance from the equator, and towards the temperate zones. If, in fact, we survey the globe's surface, we shall not be able to perceive that chain of mountains, which running from east to west, and dividing the earth into two portions, ought again to meet. On the contrary, extensive plains seem to accompany the line through almost its whole extent. In Africa, the deserts of Nigritia and those of Upper Ethiopia are on the one side of the line; and on the other are the fandy plains of Nicoco, Cafraria, Monemugi, and Zanguebar. From the caftren shores of Africa to the Sunda islands, is a space of 1500 leagues of sea with almost no islands, except the Laccadive and Maldive islands; most part of which have little elevation, and which run from north to south. From the Molucca islands and New Guinea, to the western borders of America, the sea occupies a space of 3000 leagues. Though Chimborazo and Pichincha in America, the two highest mountains which have been measured, are near and even under the line, yet from this no conclusion can be drawn; because on one side these mountains run in a direction not parallel to the equator; the Andes or Cordilleras attain a greater elevation as they remove from the equator towards the poles; and a vast plain is found exactly under the line, between the Oroonoko and the river of the Amazons. Besides, the latter river, which takes its rise in the province of Lima about the 11th degree of south latitude, after crossing the whole of South America from west to east, falls into the ocean exactly under the equator. This shows that there is a deficient for the space of 12 degrees or 300 leagues. From the mouth of the river of the Amazons, to the western shores of Africa, the sea forms another plain of more than 50 degrees.

From the few certain facts and accurate observations which we have received from well informed travellers, we might almost affirm that the most elevated land on our globe is situated without the tropics in the northern and southern hemispheres. By examining the course of the great rivers, we in fact find that they are in general discharged into three great reservoirs, the one under the line, and the other two towards the poles. This, however, we do not mean to lay down as universally 'true; for it is allowed, that, besides the two elevated belts, the whole surface of the earth is covered with innumerable mountains, either detached from one another or in a continued chain. In America, the Oroonoko and the river of the Amazons run towards the line, while the river St Lawrence runs towards the 45th degree of north latitude, and the river de la Plata towards the 40th degree of south latitude. We are still too little acquainted with Africa, which is almost all contained within the tropics, to form any accurate conclusions concerning this subject. Europe and Asia, which form only one great mass, appear to be divided by a more elevated belt, which extends from the most westerly shores of France to the most easterly of China, and to the island of Sagaleen or Anga-hata, following pretty nearly the 50th degree of north latitude. In the new continent, therefore, we may consider that chain where the Mississippi, the river St Lawrence, the Ohio, and the river de los Estrechos, take their rise, as the most elevated situation in North America; whence the Mississippi flows towards the equator, the river St Lawrence towards the north-east, and the rest towards the north-west. In the old continent, the belt formerly mentioned, and to which we may assign about 10 degrees of breadth, may be reckoned from the 45th to the 55th degree of north latitude: for in Europe the Tagus, the Danube, the Dnieper, the Don and the Volga, and in Asia the Indus, the Ganges, the Meran, the Mecon, the Hoang-ho, and the Yang-tse-Kiang, defending as it were from this elevation, fall into the great reservoir between the tropics; whilst towards the General north the Rhine, the Elbe, the Oder, the Vistula, the Oby, the Jenišci, the Lena, the Indigirka, and the Kowyma, are discharged into the northern reservoir.

Judging from those mountains the height of which has been calculated, and from the immense chains with which we are acquainted, we may infer that the highest mountains are to be found in this elevated belt. The Alps of Switzerland and Savoy extend through the 45th, the 46th, and the 47th degrees. Among them we find St Gothard, Furca, Brunig, Rus, Whiggis, Scheidek, Gunggels, Galanda, and lastly, that branch of the Swiss Alps which reaches Tirol by the name of Arlenberg and Arula. In Savoy, we meet with Mont Blanc, the Peak of Argentiere, Cornero, Great and Little St Bernard, Great and Little Cenis, Couppeline, Servin, and that branch of the Savoyard Alps which proceeds towards Italy through the duchy of Aost and Montferrat. In this vast heap of elevated peaks, Mont Blanc and St Gothard are particularly distinguished. The Alps, leaving Switzerland and Savoy, and passing through Tirol and Carniola, traverse Saltzbourg, Stiria, and Austria, and extend their branches through Moravia and Bohemia, as far as Poland and Prussia.—Between the 47th and 48th degrees, we meet with Grimming the highest mountain of Stiria, and Priel which is the highest in Austria. Between the 46th and 47th degrees, the Bacher and the Reinichnicken, form two remarkable chains. The upper one, which traverses the counties of Trenesin, Arrava, Scopus, and the Kreyna, separates Upper Hungary from Silesia, Little Poland, and Red Russia; the inferior one traverses Upper Croatia, Bosnia, Servia, and Transylvania, separates Lower Hungary from Turkey in Europe, and meets the upper chain behind Moldavia, on the confines of Little Tartary. In these mountains are situated the rich mines of Schemnitz.

To form a general idea of the great height of this Alpine belt, it is necessary only to remark, that the greatest depth of the wells at Schemnitz is 200 toises; and yet it appears, from the barometrical calculations of the learned M. Noda, that the greatest depth of these mines is 286 toises higher than the city of Vienna. The granite-argillaceous mountains of Schemnitz, and of the whole of this metallic district, are inferior, however, to the Carpathian mountains. Mount Krivany in the county of Arrava, and the Carpathian mountains between Red Russia and the Kreyna, appear by their great elevation to rule over the whole of the upper Alpine chain. In the inferior chain we likewise meet with mountains of an extraordinary height; among others, Mount Medvednik, which gives its name to a chain extending far into Bosnia; and Mount Hemus, celebrated even among the ancients. In short, this extensive chain reaches into Asia, and is there confounded with another chain no less famous, which, following exactly the 50th degree of latitude, runs through the whole of Asia. This chain of mountains is described by Dr Pallas in the work above mentioned; and we shall now trace its course in company with this intelligent observer.

This author places the head of the mountains of Oural, between the sources of the Yaik and the Bie-lala, about the 53d degree of latitude, and the 47th of longitude. Here the European Alps, after having traversed Europe, and sent off various branches which we shall afterwards examine, lose their name, which is changed into that of the Ouralic or Uralian mountains, and begin their course in Asia. This lofty chain, which separates Great Bulgaria from the deserts of Ichimika, proceeds through the country of the Eleuths, follows the course of the river Iris, approaches the lake Telekskaia, and afterwards forms a part of the same system of mountains with the Altaic chain. There they give rise to the Oby, the Iris, and the Jenišci, which begin their course about the 50th degree of north latitude, and fall into the Frozen ocean.

The Altaic chain, after having embraced and united Altaic all the rivers which supply the Jenišci, is continued chain under the name of Saianet, without the smallest interruption, as far as the Baikal lake. The extension of this chain to the south forms that immense and elevated plain which is lost in Chinese Tartary, which may be compared with the only plain in Quito, and which is called Gobi or Chamo. The Altaic afterwards interposing between the source of the Tchikoi and of the rivers which supply the Amur or Sagaleen, rises towards the Lena, approaches the city Jakuck beyond the 60th degree of latitude, runs from that to the sea of Kamtchatka, turns round the Ochockoi and Penfuk gulfs, joins the great marine chain of the Kurile isles near Japan, and forms the steep shores of Kamtchatka, between the 55th and 60th degrees of latitude. After running in the same parallel, and giving rise to the Ohio, the Riviere Longue, the river St Lawrence, and the Mississippi, they are lost in Canada. From the eastern shores of America to the western shores of Europe, we find a vast interruption.

The European Alps produce three principal chains, which run towards the equator, and some smaller ones chain running towards the pole. The first southern chain is sent out through Dauphine; traverses Vivarais, Languedoc, Auvergne, Cevennes, and Languedoc; and, after joining the Pyrenees, enters Spain. There it divides into two or three ramifications, one of which runs through Navarre, Biscay, Arragon, Castile, Marche, and Sierra Morena, and extends into Portugal. The other, after traversing Andalusia and the kingdom of Granada, and there forming a number of mountains, again makes its appearance, beyond the straits of Gibraltar, in Africa, and coasts along its northern shores, under the name of Mount Atlas.—The second principal chain of the Alps passes out through Savoy and Piedmont; spreads its roughnesses over the states of Genoa and Parma; forms the belt of the Appennines; and after frequently changing its name, and dividing Italy into two parts, terminates in the kingdom of Naples and in Sicily, producing volcanoes in every part of its course. The third chain is sent off from Hungary, and scatters innumerable mountains over all Turkey in Europe, as far as the Morea and the Archipelago at the bottom of the Mediterranean sea. The northern branches, though smaller at first, are no less clearly defined; and some of them even extend their ramifications as far as the Frozen ocean. An Alpine branch, issuing from Savoy through the country of Gex, proceeds through Franche Comté, Suntgaw, Alsace, the Palatinate, and Veterabia.— Another rises from the territory of Saltzbourg, passes along Bohemia, enters Poland, sends off a ramification into Prussia towards the deserts of Waldow, and after having passed through Ruffia is lost in the government of Archangel.

The Altic Alps sent forth in like manner several branches both to the south and north. The Ouralic mountains, between the sources of the Biclaia and the Jaik, produce three principal branches; the first of which, including the Caspian sea in one of its divisions, enters Circassia through the government of Atraean, passes through Georgia under the name of Caucacus, sends a vast number of ramifications to the west into Asiatic Turkey, and there produces the mountains, Tichilder, Ararat, Taurus, Argée, and many others in the three Arabie; while the other division, passing between the Caspian sea and the lake Aral, penetrates through Chorafan into Persia. The second branch, taking a more easterly direction, leaves the country of the Eleuths; reaches Little Bueharia; and forms the ramparts of Gog and Magog, and the celebrated mountains, formerly known by the name of Caf, which M. Bailly has made the seat of the war between the Dives and the Peris*. It traverses the kingdoms of Cafgar and Turkestan, enters through that of Lahor into the Mogul territory, and, after giving rise to the elevated desert of Chamo, forms the western peninsula of India. While these two branches run towards the south, the third branch of the Ouralic chain rises towards the north, following almost the 79th degree of longitude, and forms a natural boundary between Europe and Asia; without, however, bounding the immense empire of Russia. This chain, after coming opposite to Nova Zembla, divides into two considerable branches. The one, running to the north-east, passes along the Arctic shores; the other, proceeding towards the north-west, meets the northern European chain, traverses Scandinavia in the shape of a horfe floe, covers the low lands of Finland with rocks; and, as is observed by Dr Pallas, appears to be continued from the North Cape of Norway through the marine chain of Spitzbergen, flattening islands and shelves perhaps throughout the northern ocean, that, passing through the pole, it may join the northern and eastern points of Asia and North America.

The Ouralic, which, in the country of the Mongols, becomes the Altaic chain, proceeds towards the equator. After forming the mountains and caverns wherein, as we are told, the ashes of the Mongol emperors of the race of Gengis-Kan are deposited, together with the vast plain of Chamo, consisting of arid sand, and the frightful rocks and precipices of Thibet, which form the mysterious and desert retreats of the Grand Lama, it crosses the rivers Ava and Menan; contains in its subdivisions the kingdoms of Ava, Pegu, Laos, Tonquin, Cochin-China, and Siam; supports the peninsula of Malacca; and overpreads the Indian ocean with the isles of Sunda, the Moluccas, and the Philippines. From the borders of the Baikal lake and of the province of Selinginkoy, a branch is detached, which spreads over Chinese Tartary and China, is continued into Corea, and gives rise to the islands of Japan.

The great chain having extended to the north, near the city of Jakuck, upon the banks of the Lena, sends off one of its branches to the north-west, which, passing between the two Tunguita, is lost in marshy grounds lying in the northern parts of the province of Jenneliefskoy. The same chain, after it has reached the eastern part of Asia, is lost in the icy regions of the north about Nos-Tchatalatfokoy, or the Icy Promontory, and Cape Czuczenskoy.

It will be more difficult, perhaps, to trace the elevated belt in the southern hemisphere beyond the tropic of Capricorn, than it has been to distinguish that towards the north. An immense extent of ocean seems to occupy the whole Antarctic part of the globe.—The greatest south latitude of the old continent is not more than 34 degrees, and South America scarcely extends to the 55th degree. In vain has the enterprising Cook attempted to discover regions towards the pole: his progress was constantly interrupted by tremendous mountains and fields of ice. Beyond the 50th degree no land and no habitations are to be found. The islands of New Zealand are the farthest land in these desert seas; and yet the south cape of Taral-Poennamoo extends only to the 48th degree: We do not mention Sandwich land, which is situated in the 58th degree, because it is too small and too low. It must be recollected, however, that, according to the declarations of travellers, the Cordilleras become higher as they advance southward to the straits of Magellan; and that Tierra del Fuego, which lies in the latitude of 55, is nothing but a mass of rocks of prodigious elevation. America, however, exhibits to our view elevated points, whence chains of mountains are distributed in different directions over the whole surface of the new continent. There must likewise be great reservoirs, where the most remarkable rivers take their rise, and from which they necessarily descend towards their mouths. In the southern hemisphere, this elevated belt is nearer the equator; and though it does not extend to the 50th degree, it is evidently to be met with, and may be accurately traced, between the 20th and 30th degrees. The high mountains of Tucuman and of Paraguay, which intersect South America about the 25th degree of latitude, may be considered as the American Alps. If we look into the map of the world, we shall be able to distinguish an elevated belt all along this parallel. In Africa, Monomotapa, and Cafraria, are covered with very high mountains, from which pretty large rivers descend. In the Pacific ocean, we find New Holland, New Caledonia, the New Hebrides, and the Friendly and the Society islands, under the same parallel. We may, therefore, with sufficient propriety, distinguish this parallel by the name of the Southern Alps, as we have already distinguished the elevated belt of the 50th degree of north latitude by that of the Northern Alps. In America, the Rio de la Plata, which, after a course of 500 leagues, falls into the ocean at the 35th degree of south latitude; the Pavana, which rises from the mountains of the Arapés, and falls into the Plata at Corriente; the great number of rivers which flow into that of the Amazons, such as the Pará, which receives in its course the tribute of more than 30 other rivers; the Madera, the Cuchirara, the Ucayal, &c. &c. all descend from these southern Alps. From these Alps likewise three considerable branches of mountains are detached, which General Distribution of the Materials of the Earth.

go by the common name of Andes or Cordilleras.—The first branch, which extends towards the south, and passes out from Paraguay through Tucuman, separates Chili from these provinces and from Chinito, and is continued through Terra Magellonica as far as Terra del Fuego. The second branch, directing its course towards the equator, traverses Peru, in vain endeavouring to conceal treasures which the avarice of men has taught them to discover in its bowels; bounds the Spanish Missions; enters Terra Firma through Popayan; and unites South and North America by the isthmus of Panama. The third division, issuing from Paraguay through Guayra and the territory of Saint Vincent, traverses Brazil, distributes ramifications into Portuguese, French, and Dutch Guiana, crosses the Orinoco, forms the mountains of Venezuela, and near Cartagena meets the second branch coming from Popayan.

We have already supposed, that the elevated belt of North America was situated about the 45th degree of north latitude; and there we imagined we recognized the continuation of the northern Alps of the old continent. This chain likewise sends forth considerable branches on both sides. One of them is detached across the sources of the Mississippi, the Belle Riviere, and the Missouri, and at the entrance of New Mexico divides, in order to form California to the west, and the Apalachian mountains to the east.—Thence proceeding through New Biscay, the audience of Guadalaxara, Old Mexico, and Guatemala, it meets at Panama the southern branch, which is part of the Alps of Paraguay. The second branch, following the course of the Mississippi, separates Louisiana from Virginia; serves as a bulwark to the United States of America; forms the Apalachian mountains in Carolina; and at last, traversing East Florida, encloses the gulf of Mexico with the Great and Little Antilles. In the north, we can trace the branches of the elevated belt; on one side observe them proceeding towards Canada, directing their course through Labrador to Hudson's Straits, and at length confounded with the rocks of Greenland, which are covered with eternal snow and ice. On the other side, we see them rising through the country of the Altiplano and the Kritinos, as far as Michinipis and the northern Archipelago.

In tracing the course and direction of the British mountains, we shall begin with the central chain, which runs through the southern part of the island from north to south, commencing at Geltidale, about 14 miles to the south-east of Carlisle, and ending at Land's End in Cornwall, or rather in the Scilly Isles to the west of this. This chain passes from Geltidale forest through the western districts of Durham and Yorkshire, forming the hills called Kelton Fell, Stanmore, Widehill Fell, Wildbore Fell, Bow Fell, Home Fell, Bun Hill, &c. A little to the west of the chain stand several detached mountains, the principal of which is Skiddaw in Cumberland. Passing through Yorkshire we find Craven, Whurnside, Ingleborough, and Penygynt; and on the east of Lancaster is Pendle. In this course there are several miles of coal and lead. The chain next proceeds through Derbyshire, and in this part of the ridge a great variety of valuable minerals are found, especially lead, copper, gypsum, fluor, barytic earths, martial pyrites, iron ore, manganese, and several ores of zinc. About this point the ridge stretches a little into Cheshire, and seems to terminate; a central chain of somewhat less elevation may, however, still be traced, proceeding in a waving direction towards Salisbury, and having three irregular branches, two to the east, and another running to the south-west into Cornwall. The first eastern branch proceeds towards Norfolk, and to this belong some considerable hills, especially those of Gog Magog in Cambridgeshire. The second branch passes into Kent, and diverges a little into Surrey and Hampshire. The continuation of this chain is afforded by the hills of Mendip, Polden, Ledgemoor, and Blackdown in Somersetshire; the Torcs and Wilds of Dartmore in Devonshire, and the upland Downs of Cornwall. Malvern hills in Worcestershire deviate a little from the chain, but those of Cotswold in Gloucestershire appear to be a continuation of it. The principal mineral found in this ridge of mountains, after leaving Derbyshire, is the tin ore of Cornwall.

Wales contains many mountains, especially in its northern part, where Snowdon is celebrated for its height and classical fame. The top of this mountain is formed almost into a point, and commands an extensive view, not only of the neighbouring counties, but of part of Scotland and Ireland, and the isles of Mann and Anglesey. A line of mountains proceeds from Snowden along the western coast to Plinlimmon; and in this line lie Urrou Seth, Caerdris, and Moyle Vadian. A few hills of little elevation proceed towards Shropshire, among which the Wrekin is the most remarkable. Another small chain proceeds south towards Cardiff, but contains no hills of any eminence.

Leaving England, and proceeding towards the north, Scotch we find the Cheviot Hills, so celebrated in the history mountains, of the border skirmishes. These form a regular ridge, running from south-west to north-east, where they join the hills of Galloway. In this part of Scotland there are several mountainous ridges running in various directions, generally north and south according to the course of the rivers; but there is, properly speaking, no uniform chain. Dumfriesshire contains several mountains, some of which are of a considerable height, especially Hartfell in Annandale, from which proceeds the celebrated chalybeate spring; Lowther near Leadhills; Blacklaw on the borders of Ayrshire; Etrick Pen, in Eskdale moor; Carnkinnow near Drumlanrigg; and Queensberry hill, which gives the title to the dukedom of that name. Proceeding towards the north, we find Pentland hills, a little to the south-west of Edinburgh, and the romantic hills of Arthur's seat and Salisbury Craigs, in the immediate vicinity of that city. On the eastern coast, before crossing the Forth, is North Berwick Law, which must be considered as closing the list of southern hills in Scotland. The principal part of these southern hills consists of calcareous earth, and argillaceous schistus; and except in those of Galloway, granite and other primitive rocks are very sparing. In the Lothian hills the calcareous strata are surmounted by vast blocks of trap, wacke, and basalt.

On the north of the Forth are the hills of Ochil, of little elevation, but celebrated for affording large quantities of agates and chalcedonies. The hills of Kinoul and Dunfman in the eastern part of Perthshire, are generally considered the last of the lowland hills. The principal northern chain of British mountains is that of the Grampian hills, extending from Loch Lomond to Stonehaven, and forming the southern boundary of the Highlands; and rising by a gradual transition from the Sidlaw hills on the east, the Campsye hills on the west, and the Ochils in the middle. The principal mountains of this chain are Ben Lawers, Ben More, Schehallion, Ben Vorlich, Ben Lomond, and Ben Ledy. Near Ben Lawers is Ben Nevis, the highest mountain in Britain, and to the north-west of this, near Fort Augustus, is the long hill of Corri Allok. About 30 miles to the east of this is the high mountain of Cairngorm, famous for the specimens of quartzose stones found there. Numerous mountains lie in the second divisions of the Highlands, beyond Loch Linne, and Loch Nefs, especially on the western shore, which is crowded with hills. Few of these are considerable. To the west of Rossshire are several hills, among which Ben Chat, Ben Chalker, and Ben Golich are the most remarkable. More inland stands the high mountain of Ben Wevis, nearly equal to Ben Nevis. In most of these mountains the primitive rocks prevail, and granite is often very abundant. Few minerals, however, except iron ore, are found.

Ireland contains but few mountains, and none of any considerable importance. They generally form short lines, or appear in detached groups, one of the highest of which is that on the west and south of the lake of Killarney, in which is the mountain of Mangerton. A small line of hills called Shockey mountains runs on the north-west of Bantry Bay, passing towards the east. To the northward of this stands Slilboghler and Nagles, and towards the east are the hills of Knockemdown. In the county of Leinster is a mountain of the same name, and to the south of Dublin are the Wicklow hills, from which there were lately such great expectations of golden treasure. In Ulster stand the mountains of Mourne, the highest of which, Donard, is said to be nearly the height of Mangerton. The most mountainous part of Ireland is the western peninsula of that island, towards which, in the county of Mayo, stands Nephin, one of the highest in the kingdom. On the south-east of Clewbay is the mountain of Croagh Patrick, also in the county of Mayo, which is the last Irish hill of any importance.

We cannot here with propriety enter on the theory of the formation of mountains. The hypothesis of the principal geological writers with respect to this subject, will be seen from the general view of the theories to be given in the next chapter. We may in this place only remark, that all the systems which have been constructed, to explain the formation of the primitive mountains, with respect to which there is the most dispute, may be reduced to three.

In the first of these, mountains are supposed to have been formed such as we now see them, except that they have suffered some degradations and modifications, from certain accidents posterior to their original formation, and that these mountains owed their elevation above the places which surround them, to one single accidental accumulation of more materials in one place than in another; an accumulation which might have taken place without that great precipitation which preceded and occasioned the consolidation of the crust of our globe.

In the second hypothesis, all the primitive mountains, are supposed to have been raised by one cause, and in one certain manner; and the materials which compose them, to have been thrown out of their natural position. It is with respect to this raising or displacement that geologists have imagined so many different hypotheses.

In the third general theory, these mountains are supposed to have become pre-eminent from the accidental lowering or removal of the materials which originally surrounded them, whether this happened from the materials composing these mountainous situations having suffered no displacement, or that they had been themselves removed.

M. Dolomieu is of opinion, that there are mountains whose situation and structure favour each of these three hypotheses*.

SECT. II. Of Dykes.

We have described dykes (No 15.) to be those interruptions of the strata which are formed by perpendicular fissures filled with stony substances. As these stony matters are frequently of that kind called whinstone, these dykes are commonly called whin dykes, and the history of these is very important, as they form one of the principal subjects in the principal theories of the earth.

Dykes have received different denominations, descriptive, in some measure, of the nature of the substances of which they are composed; or of the seeming effects they have produced on the intersected horizontal strata. They are called basaltic veins, trap dykes, whin dykes; and in the coal countries of Scotland they are called gowr, from the idea that they have occasioned the separation of the coal, and contiguous strata, through which they run.

These dykes have been more attentively observed in coal countries, than where they occur elsewhere; because on the accurate knowledge of their course, inclination, and thickness, depend, in a great measure, the judicious and successful operations of the miner, when his workings approach the dike, or render it necessary to cut through it to reach the strata of coal on the other side. But, though less attended to, they have been observed and traced in other places, where a great extent of the horizontal strata has been exposed in the beds of rivers, as in the bed of the Water of Leith, above St Bernard's Well, near Edinburgh, and on the sea shore, especially on the western coasts of Scotland, where the rocks are more abrupt and precipitous, and where the violence of the Atlantic ocean has removed part of the horizontal strata, and left the vertical strata remaining, like immense walls or dykes. Hence probably the origin of the name; and as they often consist of that species of stone called whinstone, this epithet has been added.

The course, however, of the greater number which course we have had the opportunity of examining, generally lies between the points of the compass S. and S. E. and N. and N. W. This is most frequently the course of the whin dykes of Ilray and Jura; it is the course of a remarkable dyke which traverses the coal strata at the village of Stevenfon, near Saltcoats, in Ayrshire; part of which is seen on the surface, not many hundred yards to the north of the west end of that village; lage; and it is the course of two dykes, still more remarkable, in the island of Great Cumbrey, in the frith of Clyde.

Geologists, who have treated this subject, do not seem to have marked, with much attention, the course of the dykes. They have mentioned in general terms, that they follow all directions. More extensive observation may probably shew, that the most frequent directions of the principal dykes, is from north to south, or a few points deviation from that course. And if this be established, by a fuller and more accurate history of dykes, the analogy between them and metallic veins will be more complete; for it is observed of the latter, that the most powerful, that is, the most productive, run from north to south.

Dykes do not always run in a straight line. In their course they form certain flexuositie. But, in this winding course, the deviations are usually so small, as to have little effect on the general direction of the dyke, which, upon the whole, may be considered as nearly the same.

The continuity of dykes is sometimes interrupted, exactly in the same manner as frequently happens to the horizontal strata, and which, in technical language, is termed a slip.

In the island of Islay we have observed two dykes of this description, the one on the south side of Lochindal, near the point of Laggan; the other on the shore of the south-east part of the island, a little to the south of the house of Ardmore. In both these dykes, the extent of the separation of the slip was just equal to the thickness of the dyke. The opposite sides were brought exactly into the same line.

After this separation, these dykes, in so far as they could be traced, preserve the same thickness, course, and inclination as formerly.

A very remarkable dyke has been discovered, in the coal field, in the district of Boulogne in France. It runs in the form of a crescent from north to west.

The direction of dykes downwards is seldom perpendicular. This deviation from a line perpendicular to the horizon is called their inclination. The inclination of a dyke is usually denominated the hade or hading. See the article Coalery.

The inclination of different dykes, and even of the same dyke, is various, sometimes approaching to, and sometimes deviating from the perpendicular. The extent of dykes downwards, we believe, has not been ascertained with any degree of accuracy, and the termination of very few has yet been detected. The depth to which researches of this kind can be carried, is comparatively small. With all the ardour, ingenuity, and power of man, investigations to determine this point, will probably always be limited by the extent of his mining operations. The recent-formed dyke just mentioned, which occurs in a coal-field in the district of Boulogne in France, which consists of a species of marble, found in several quarries in the vicinity, has been traced to the perpendicular depth of 600 feet, where it is succeeded by a schistus rock, which latter, with the same course and inclination, continues to intersect the horizontal strata.

The extent of dykes in length has not been accurately determined. Indeed, it must be extremely difficult to trace them with any degree of certainty. For those which are observed on the sea coast, where they are most conspicuous, soon disappear in the mountains, on the one hand, or on the other lose themselves in the sea. And, as the extent of the same coal field rarely exceeds a few miles, they have seldom been followed beyond its limits. In many cases, the change in the nature and arrangement of the strata, renders it almost impossible. Some, however, have been traced to a very great extent; one in particular, on the banks of the river Meuse in the Netherlands, has been followed in its direct course, to the distance of four leagues; and of this dyke it is observed, if pursued through all its windings, the extent is not less than six leagues.

The thickness of dykes is various. Sometimes they are observed no thicker than a few inches. From that they increase to one foot, five feet, and very often are found from 10 to 20 feet. There is one in the island of Ilay, of the enormous thickness of 69 feet. This immense dyke accompanies a lead vein, about a foot thick, which is included between it and the limestone strata. In this mining field, two whin dykes, one of them 10 feet thick, have been discovered, crossing the metallic veins.

In going downwards, dykes are said to decrease in thickness. This is particularly observed of dykes of smaller magnitude. Of smaller dykes it is also said, that they diminish in thickness towards the extremities.

In one respect, some whin dykes are exactly analogous to metallic veins, in having branches, or in the miners' phrase, rings going off and traversing the contiguous strata, and forming in the course they take, an acute angle with the principal dyke. A whin dyke of this description has been observed in the island of Jura, on the shore of the sound. The diverging branch terminated in a point among the horizontal strata, at the distance of a few feet from the great dyke, assuming altogether a wedge-like form.

If we include metallic veins in the account, the vertical strata may be said to be composed of every kind of mineral substance, but almost always different from the intersected horizontal strata. By this last circumstance their occurrence is at once recognized. In general, the dykes that are found in Scotland, whether in the coal countries, or in the western coasts and islands, where they are so frequent, are of that species of stone which comes under the denomination of trap or whinstone. Dykes, consisting of other species of stone, have also been found in Scotland. On the Mull of Kinouth, which forms the southern headland, at the entrance of Lochindal, in Ilay, we observed a small dyke of granite, crossing the headland, which is of granular quartz. There are some vertical strata of granite in the island of Icolmkill, of pitchstone in the island of Arran, and of serpentine at Portfoy in Banffshire.

Bergman, in his Physical Geography, supposes that granite was never found to be a component part of vertical strata. What has been already mentioned proves the contrary. Granite dykes have also been discovered in other places. Beffon has observed dykes of this description on the great road between Limoges and Cahors in France, traversing horizontal strata of argillaceous schistus, a species of stone which has generally been considered of later formation than granite. These dykes, he observes, are from an inch to six feet in thickness, and the quartz, feldspar, and mica, are of larger size than are usually found in the granite of mountains. Dolomieu has made a similar observation, and considers it as a discriminative character, by which the granite of mountains and that found in vertical strata may be easily distinguished. But this is not always to be admitted as a characteristic mark of distinction. The granite dyke which has been already mentioned, crossing the granular quartz, on the Mull of Kinouth in Ilay, is small grained, and others of this latter description have been observed in other places.

There is a very singular dyke on the coast of Ayrshire, between Weems bay and Largs, near the house of Kelly. It is about ten feet thick, traverses the horizontal strata, which consist of plumb-pudding rock, whose cement is sandstone of a red colour, from north-east to south-west, and crosses a larger dyke of the whinstone of this country, nearly at right angles. This dyke is composed of different materials. Part is of the common whinstone, and part of a plumb-pudding rock, cemented by the matter of the dyke; and these alternate with each other, both in the thickness of the dyke, and lengthwise. On one side, there are four feet thick of whinstone; immediately in contact with this there is plumb-pudding stone three feet thick, and so on alternately, across the whole line, there is found a few yards of whinstone, which is succeeded by a few yards of plumb-pudding stone, and this is again succeeded by the whinstone.

But, for the general view which is here proposed, it is not requisite to give a full account of all the mineral substances which enter into the composition of vertical strata, or even a minute enumeration of all the varieties that are found in whin dykes.

One of the most singular circumstances respecting structure of whin dykes, which seems to have been entirely overlooked by geologists, still remains to be considered. This is the peculiar structure or arrangement of the parts of which they are composed. Of this peculiar arrangement it may be observed in general, that it is in all respects the reverse of what takes place in the horizontal strata.

When the dyke is of small magnitude, it is pretty compact in all its parts; but if an attempt be made to break or separate any part of it, the fracture will be found to run most readily in the perpendicular direction. But when the dyke is of more considerable thickness, it usually forms several divisions, marked by perpendicular fissures, and there is often very great variety in the nature and qualities of the several divisions of the same dyke. The exterior division of one side sometimes, and sometimes the exterior division of both sides, are of a softer texture than the intermediate division; and often contain, in great proportion, specks of radiated zeolite and calcareous spar, while the middle divisions, as well as being harder, are also more homogeneous. In other cases, the reverse of this appears. The middle parts of the dyke are the softest and least compact, exhibiting the greatest variety of heterogeneous substances.

Some whin dykes have a great tendency to affume, when broken, the prismatic form. This is the case with many, even of the most compact texture. In others, where the side of the dyke is exposed to view, and minutely examined, fissures may be traced, discovering the ends of pretty regular prisms. But in some dykes in the island of Jura, the prismatic columns are entirely separated, and lying loose, are four, five, or six-sided, jointed; the perpendicular fissures forming the joints, and in all respects similar to the perpendicular baltic columns, except being in the horizontal position. In one of the dykes in the island of Jura, the columns are from 12 to 18 inches in diameter. In some others on the sea shore, near the house of Mr Campbell of Jura, and at the harbour of the small isles, in the same island, there are columns of the enormous size of 10 and 12 feet diameter.

A dyke which traverses the baltic strata of the Giants Causeway in the north of Ireland, exhibits still more remarkably this peculiarity of structure. The smallest masses detached from it assume the columnar form, and most of them are perfectly regular. The fracture invariably runs in the horizontal direction; the columns consequently lie in the same position, are three, four, five, and fix-sided, and are generally of small size. Observations on Vertical Strata, by Dr Millar, Scots Mag. vol. lxiv.

Sect. III. Of Metallic Veins.

The history of metallic veins, although far from being so full and satisfactory as could be wished, is more complete than that of whin dykes. The latter have excited no farther attention than as objects of curiosity to the geologist, or as singular facts in establishing a theory, and when they come in the way of the operations of the miner, to discover their connexion with the contiguous strata; while the wants and luxuries of man have roused ingenuity and exertion in exploring the former, on account of the precious and useful metals with which they are stored. Thus, the splendour and beauty of some metallic substances, and the utility of others, have made them in all ages be esteemed and valued by mankind; and consequently they have been the constant objects of pursuit and investigation. It is obvious that the beauty and utility of metals, on account of which they are so much valued and fought after, excite greater interest in procuring them; on the one hand, the researches and observations of the philosopher in furnishing the history and general principles, and, on the other, the immediate application of this knowledge, and of these principles, in the practice and operations of the miner.

The history of whin dykes is, in general, quite analogous to metallic veins; but, of the latter, from what has been stated, we can speak with more certainty and precision.

Three different kinds of metallic veins have been described by geological writers; the perpendicular vein, the pipe vein, and the flat or dilated vein. We shall consider each of these in their order.

1. Of the perpendicular vein.—This kind of metallic vein occurs most frequently. As may be expected, it is various in its course or direction, thickness, and inclination. Metallic veins are found running in every direction; but, in general, the most powerful veins, that is, the most productive, are observed to run from north to south, or at least a few points deviation from that course; and when any deviation happens, it is usually to the east of north, and to the west of south.

The course or direction of a vein is called in technical cal language its bearing. The extent of a vein in the line of bearing, we believe rarely exceeds the range of mountains in which it is discovered. This is the case with the principal vein at Leadhills. It is limited to the chain of mountains in which the operations are now carried on; and although the mines of Wanlockhead are not a mile distant, new veins appear with galena or lead ore, of quite a different quality, and all the accompanying minerals, whether forming part of the vein, or found in cavities, are also quite different from the lead ore and other minerals found in the veins at Leadhills.

The inclination of veins is various. Sometimes they are nearly perpendicular; sometimes they deviate considerably from a perpendicular line; sometimes the same vein in its course downward, inclines to one side; sometimes it is perpendicular, and sometimes it inclines to the other side. When the deviation from the perpendicular does not exceed 10°, the vein is still considered as a perpendicular or vertical vein. When a vein is inclined, the two sides which include the metallic substances are in very different positions, and have consequently received from the miners different names. That side which supports the metallic ore, or on which it seems to lean, is called the ledger side, or simply the ledger. The opposite side which covers the ore, or which overhangs it, is denominated the hanging side, or simply the hanger. From the inclination of the vein being varied in its course downwards, it must appear that the same fides, according as the inclination varies, must change their position and denomination. This will perhaps be more intelligible by the section at fig. 5, in which AA represents the vein ; BB, CC, DD, EE, the strata intersected by it ; 1. the hanger ; 2. the ledger ; 3. the hanger ; and, 4. the ledger.

The thickness of veins, and indeed of the same vein, is also extremely various. Sometimes they are only a few inches thick. From this they increase to the thickness of several feet. The veins which were wrought at Leadhills, about seven years ago, were from two to six feet within the sides; but some years before that time the principal vein in those mines, by the addition of two strings or small veins, assumed the extraordinary thickness of 14 feet of pure ore. This unusual appearance, both on account of its richness and grandeur, excited so much attention and admiration, that the counts of Hopetoun undertook a journey to these inferior regions, not less than 150 fathoms below the surface of the earth, to witness the splendour and brilliancy of this subterraneous apartment. The uncommon thickness and abundant riches of this vein are still talked of at Leadhills with enthusiasm. But a thicker vein was once wrought at Llangunog in Wales. Fifteen feet of clean ore were for some time dug out of this vein. These are, however, far exceeded by the copper veins in the Parys mountain in Anglesea, which are described by Mr Pennant in his Welsh tour. The thickness of one of these veins is 21 feet, and of another 66 feet.

The broadest metallic vein, of which we have any account, is, we believe, that of the Eton copper mine, in Derbyshire. In this mine there was worked, at one time, a heap of ore, of the astonishing extent of 70 yards

The extent of veins downwards has in many cases been ascertained. To the regret and disappointment of the miner, they have been frequently intercepted and entirely cut off by the horizontal strata. The rich vein of lead ore at Llangunog in Wales, which we have already mentioned, was intercepted in this manner by a stratum of black schistus or thiver, the nature of which is not described by Williams, who states the fact*. Their researches to recover their lost wealth, which were prosecuted for several years, proved altogether fruit-les. The smallest trace of this unusually productive vein was never afterwards discovered.

Two kinds of perpendicular mineral veins have been observed and described. In the one case the relative perpendicu- lar veins, or the strata which contain the metallic substances is exactly similar to that of the coal strata when they are intersected by a whin dyke. On one side of the vein the strata are elevated or depressed from their former plane. This is illustrated by fig. 5, where the letters BB, CC, DD, EE, mark the corresponding strata which have been deranged or displaced. In the other kind of vein the mineral substances containing the metallic ores are merely separated without any elevation or depression; for each side of the fissure still remaining in its former plane, the opposite sides of the divided strata exactly correspond to each other. The mines at Strontian in Argylshire are of this latter description.

Veins of this kind have frequently smaller veins, or, as they are called in the language of the miners, fringes, which run off at an acute angle, preserve their course for some distance, not, in general, very great, gradually diminishing in thickness, and at last are entirely lost among the contiguous strata. At the place of junction the principal vein is always thicker, as has been already noticed with regard to the unusual thickness of the principal vein at Leadhills.

To this account of perpendicular veins we may add, that some veins are found crossing each other, and that whin dykes have also been discovered intersecting metallic veins. Examples of the latter occur in the island of Islay.

2. Of the pipe vein.—The perpendicular vein last de- scribed, intersected or cut the strata across. What has been denominated the pipe vein is extremely limited in the line of bearing, but having the same inclination as the strata which include it. It may be considered as in some measure of a circular form, extremely irregular, and always following the course of the strata between which it is included, like the perpendicular veins; sometimes as it dips downwards, it is enlarged; sometimes it is diminished, and sometimes it is so much contracted, that the including strata come into close contact. In a word, this kind of vein is subject to all the irregularities of the veins formerly described, only that its inclination is invariably the same with the accompa- nying strata.

3. The flat or dilated vein.—This kind of metallic Flat vein, after what has been said with regard to other veins, will require but a short description. It is exactly similar to the pipe vein, only that it is more extend- ed in the line of bearing. It is included between the horizontal strata; and therefore its inclination or dip must be the same as the including strata. A vein of this kind might with more propriety and accuracy be regarded as a metallic horizontal stratum, were it not that it is always found varying in its dimensions, and equally irregular as the perpendicular veins which intersect the horizontal strata.

It is almost needless to add, that the flat or horizontal veins are subject to the same derangement as the coal strata, when they are intersected by a whin dyke. The vein, along with the including strata, is either elevated or depressed, and the same thing takes place when they are traversed by a metallic vein. M.S. by Dr Millar.

To finish the sketch of the history of metallic veins, we have only to enumerate the different metallic ores that occur in them, and to mention the places where these are found in greatest abundance. In this enumeration we shall follow the arrangement of metals given by Brochant, in the second volume of his Traité Élémentaire de Mineralogie.

In naming the several species, we shall adopt the nomenclature of Kirwan, adding the French and German synonyms to each. As it would far exceed our limits to give even a cursory description of the several species, we refer the reader for that to the article MINERALOGY in this work, or to the elementary treatises of Kirwan or Brochant, or the more extensive treatise of Haüy.

I. PLATINA

Has been found hitherto only in its metallic or native state, and it has as yet only been met with in South America, especially at Choco in New Grenada. It is found in the land of rivulets, and probably comes from the primitive mountains.

II. GOLD.

Native gold.—This is found principally in primitive mountains, sometimes in veins, and sometimes disseminated through the felsy matter. The substances which most commonly accompany it are quartz, feldspar, calcareous spar, heavy spar, pyrites, red silver ore and vitreous silver ore, and galena. Gold is still more commonly met with in the sand washed from certain rivers. The countries where gold is chiefly found in rocky substances, are Hungary, Transylvania, Peru, Mexico, Siberia, and Sweden. It has also been found in France, near the town of Offans, in the department of the Hère; but not in sufficient abundance to render the working of the mine profitable. Among the rivers whose sands furnish gold, we may enumerate the Rhine, the Danube, and the Aranitch in Transylvania.

Gold has been found in several parts of the British dominions, especially at Silsloe in Bedfordshire, in the Wicklow hills in Ireland, and in the neighbourhood of Leadhills in Lanarkshire. It is said that a jeweller, who died lately in Dublin, often declared that gold, to the value of 30,000l., had passed through his hands, which was brought from the Wicklow hills. This mine is now in the hands of government, but we believe does not answer the expectation that was first formed as to its produce. General Diron informs us, that in the reign of James V. of Scotland, 300 men were employed for several summers in washing the sand near Leadhills, for gold of which they are said to have collected to the amount of 100,000l. sterling. It is said that pieces of gold, an ounce in weight, have been found at Leadhills, and that Lord Hopetoun has a piece still larger in his possession*.

III. MERCURY.

Species 1. Native Mercury, or Quicksilver. Le Mercure natif. Gredigen Quecksilber.—This is found at Idria in the Austrian territories; at Almaden in Spain; in the Palatinate, and a few other places. We are told by Mr Jamclon, that a quantity of quicksilver was discovered some years ago in a peat moss, in the island of Islay, and he thinks it probable that veins of it exist there†; but there seems no ground whatever for such expectations.

Species 2. Natural Amalgama. L'Amalgame naturel. Naturlicher Amalgam.—This consists of mercury and silver, in very variable proportions. It is found at Sahlberg in Sweden; at Rofencau in Hungary, and especially at Mofchellandberg in the duchy of Deux Ponts, where it is found mixed with common ferruginous clay, and with other ores of mercury.

Species 3. Mercury Mineralized by the Sulphuric and Muriatic Acids. Mercure Corné ou Muriaté. Quecksilber Hornzer.—This species was discovered about 90 years ago, in the mines of Mofchellandberg, and at Morefeld, in the duchy of Deux Ponts, by M. Woulfe, mixed with ferruginous clay, quartz, lithomarga, native quicksilver, and cinnabar. It has also been found at Almaden in Spain, and at Herfowitz in Bohemia; but it is very rare.

Species 4. Native Cinnabar. Le Cinnabre. Zinnber.—This usually forms a gangart for the other ores of mercury. It occurs in the stratiformed mountains, pretty near the surface. This ore is found in a great many parts of Europe, especially at Almaden in Spain, Idria in the Austrian territories, at Mofchellandberg, in Bohemia, in Saxony, in Hungary, in Transylvania, in the Palatinate, and in France; but in this last it is found but in small quantity.

IV. SILVER.

Species 1. Native Silver.—A particular variety of this species, mixed with gold, is very rare. It is principally found in Conigberg in Norway, and Schlangenberg in Siberia. In the former of these places it is found disseminated through calcareous spar, fluor spar, and rock crystal, in a vein running through a rock of hornblende slate, and accompanied with blende, galena, and pyrites. That of Siberia is found distributed through a mass of heavy spar.

Common native silver is found in considerable quantity in Mexico and Peru. It is also met with in Siberia, Saxony, France, Sweden, Norway, in the Hartz, and in Bohemia. It is principally found in the primitive mountains, distributed through masses of heavy spar, quartz, calcareous spar, fluor spar, pyrites, blende, cobalt, galena, red silver ore, and vitreous silver ore.

Silver has been found in several parts of Britain, especially near Alva in Scotland. It is confidently affirmed, that a mass of capillary silver, weighing 16 oz. was found in the lead mines at Garthoncel in the isle of Islay, mixed with galena†.

Species 2. Antimoniated Native Silver. L'Argent Antimonial. Spiegglas Silber.—This species has hitherto been only found in the mine at St Wencelas at Altwolfach, and in the duchy of Wurttemberg, in a vein mixed with calcareous spar, heavy spar, native silver, and quartz. Species 3. Arseniated Native Silver. L'Argent Arsenical. Arlenik Silber.—This is also rare, having been found only at Andreasberg, in the Hartz, and at Kaffala in Spain. In the Hartz it is mixed with native arsenic, red silver ore, galena, blende, and calcareous spar. Considerable quantities of silver, probably of this species of ore, are obtained from the lead ore of Leadhills.

Species 4. Corneous Silver Ore, or Muriated Silver. L'Argent Cornée ou Muriaté. Horn Erz.—This has been found in Peru, Mexico, Saxony, France, Siberia, and, as is affirmed, in Cornwall in England.

Species 5. Soapy Silver Ore. L'Argent Noir. Silberfuchswärze.—This is found in Saxony, France, and Hungary, mixed with other ores of silver, and sometimes with native silver.

Species 6. Vitreous Silver Ore. L'Argent Vitreux. Silberglaszer.—This is found in Bohemia, Saxony, Norway, Swabia, Siberia, and in Hungary, mixed with other silver ores, and usually accompanying calcareous spar, heavy spar, and fluor spar.

Species 7. Red Silver Ore. L'Argent Rouge. Rothgiltezer.—This is found in the Hartz, Bohemia, Saxony, France, Swabia, and in Hungary, accompanying native arsenic, realgar, vitreous silver ore, galena, calcareous spar, and heavy spar.

V. COPPER.

Species 1. Native Copper.—This is met with in Siberia, the Uralian and Altaichian mountains, Kamtschatka, Japan, Saxony, France, Sweden, Hungary, Palatinate, and near Redruth in Cornwall, in England. It usually accompanies other ores of copper, especially malachite and copper azure.

Species 2. Vitreous Copper Ore. Le Cuivre Vitreux. Kupferglas.—This is found in Siberia, Hungary, Sweden, Norway, Russia, Saxony, Silesia, Hesse, and in Cornwall.

Species 3. Purple Copper Ore. La Mine de Cuivre Violette. Buntkupfererz.—This is always found in the neighbourhood of other copper ores, especially with the species last mentioned, and with copper pyrites. It is found in Saxony, Bohemia, the Banat in Transylvania, the Hartz, Norway, Russia, Sweden, Hungary, Hesse, and in Derbyshire in England, especially in the famous Ecton copper mine.

Species 4. Yellow Pyrites, or Yellow Copper Ore. La Pyrite Cuivreuse. Kupferkies.—This is the most common species of copper ore, and is found both in primitive and secondary mountains, sometimes in beds, and sometimes in veins. It occurs most abundantly in Bohemia, Saxony, Hungary, Sweden, France, Spain, and especially in Britain, where it forms one of the principal varieties of copper ores, found in the famous Parys mine in the Isle of Anglesea.

Species 5. White Copper Ore. La Mine de Cuivre Blanche. Weißkupfererz.—This species is very rare, but it has been found in Saxony in the mines of Freyberg, in Hesse, in Württemberg, and in Siberia, with other copper ores.

Species 6. Gray Copper Ore. Le Cuivre Gris. Fahlzer.—This again is a very common species, and is found in all those countries that possess mines of copper.

Species 7. Black Copper Ore. Le Cuivre Noir. Kupferschwärze.—This is found mixed with malachite and with green and blue copper ores in Saxony, Hungary, in the Banat, in Silesia, in Norway, in Russia, in Swabia, in Sweden, and in Siberia. It also occurs in the Parys mine of Anglesea.

Species 8. Florid Red Copper Ore. Mine de Cuivre Rouge. Roth-Kupfererz.—This usually accompanies native copper, malachite, and brown earthy iron ore. It is met with in Saxony, in the Banat, in the Hartz, in Norway, in Siberia, near Cologne, and in Cornwall.

Species 9. Brick-red Copper Ore. Le Mine de Cuivre couleur de Brique. Ziegelzer.—Found in similar situations with the preceding.

Species 10. Blue Calciform Copper Ore. L'Azur de Cuivre. Kupferlazur.—Found in the Banat, in Hesse, in Salzburg, in Poland, in Siberia, in Thuringia, and in the Tyrolce. It is usually imbedded in flinty marl, or in sandstone, not far below the surface of the earth.

Species 11. Malachite.—This is always found mixed with other copper ores, and occurs in most of the copper mines that have been enumerated.

Species 12. Mountain Green. Le Vert de Cuivre. Kupfergrün.—This commonly accompanies species 4, 6, 9, 10, and 11. It is found in Saxony, in the Hartz, in Norway, Silesia, Siberia, Hungary, Württemberg, and Britain, as at Leadhills and in Derbyshire.

Species 13. Olive Copper Ore. Mine de couleur Olive. Olivenerz.—This species is extremely rare. It has been found chiefly near Karrarah in Cornwall, where it is accompanied by species 11 and 12, and brown iron ore in a gangart of yellow lithomarga mixed with quartz. It is said to have been found also at Jonfbach near Ruffeltstadt in Silesia.

VI. IRON.

Species 1. Native Iron.—This species is very uncommon; but it has been met with in several places, especially at Kamtschad and Eibesstock in Saxony, at Kranj-najark in Jenisei in Siberia, at Olumba near St Jago in South America, and Oulle near Grenoble in France. The two most remarkable specimens of native iron are those found in South America and in Siberia. The former of these forms a mass weighing at least 300 quintals, or 15 tons. It is soft and malleable, and in every respect like the purest iron. That of Siberia is a spheroidal mass, weighing about 14 quintals, resting on the surface of the earth, near the summit of a mountain. Its texture is cellular, and its cavities are filled with a transparent, greenish, vitreous matter. No mines or veins of iron are in the neighbourhood of either.

Species 2. Martial Pyrites. Pyrite Martiale. Schweifelkies.—This species is one of the most common ores of iron, and is found abundantly in every country where there are any other ores of iron. There are three varieties of it described by Brochant, which are less common, but these are also found in many places.

Species 3. Magnetic Pyrites. La Pyrite Magnétique. Magnetkies.—This has been found only in primitive rocks, especially in micaceous schistus, accompanied by quartz, hornblende, &c. and usually lying in beds mixed with other pyrites, galena, and magnetic iron. stone. It is found in Saxony, Bavaria, Norway, and Silegia.

Species 4. Magnetic Ironstone. Le Fer Magnétique. Magnetischer Eisenstein.—Of this there are three varieties, the common magnetic ore, which is very common in primitive mountains, especially those that are composed of gneiss and micaceous schistus. It is often in great abundance, forming large beds, or even whole mountains. It is found in greatest quantity in Saxony, Bohemia, Italy, Corsica, Silesia, Siberia, Norway, and especially in Sweden. The second variety, called fibrous magnetic ironstone, is uncommon, but is found at Bibsburg in Sweden. The third, which Kirwan calls magnetic sand, is found in the banks of some rivers, particularly of the Elbe, as also in Sweden and Italy.

Species 5. Specular Iron-ore. Le Fer Speculaire. Eifenglanz.—This is found in many places, often in considerable quantity, especially in Saxony, Bohemia, France, Normandy, Prussia, Sweden, Siberia, Hungary, Corsica, and the island of Elba. It is generally found only in primitive mountains, sometimes in beds, sometimes in veins, accompanied with quartz, hornblende, martial pyrites, and magnetic iron ore.

Species 6. Red Feely Iron Ore. La Mine de Fer Rouge. Roth-Eisenstein.—This is rather rare, but is found in several parts of Saxony, in the Hartz, in Nassau, in Thuringia and Hungary. Another variety of the same species, the compact red ironstone of Kirwan, is much more common, being found in Saxony, Bohemia, the Hartz, Heilé, Siberia, and in France, sometimes in veins, and sometimes in beds, commonly mixed with the two following species, and with argillaceous ironstone, quartz, hornblende, and calcareous spar.

A third variety, the common hematites or bloodstone, which is one of the most productive iron ores, is always found accompanying the last variety, and is of course met with in most of the situations above enumerated. It is procured in abundance in several parts of England, as in Derbyshire, but more especially at Ulverston in Lancashire, where there is one perpendicular vein of it 30 yards wide, in a rock of limestone. Large quantities of it are carried to Carron, where it is smelted with the common Carron ironstone.

Species 7. Brown Iron ore. La Mine de Fer Brune. Braun-eisenstein.—Of this there are several varieties, of which the compact brown ironstone, and the brown haematites, are very common; but the brown feely iron ore is rather rare. The last is found at Kampdorf in Saxony, at Klauffel, in the Hartz, at Lauterick in the Palatinate, and at Naïla in the principality of Bareith.

Species 8. Calcareous Iron Ore. Le Fer Spathique. Spathiger-eisenstein.—This is found both in primary and secondary mountains, and there are few veins of iron which do not contain it in greater or less quantity.

Species 9. Black Ironstone. La Mine de Fer Noire. Schwarz-eisenstein.—This is found in the principality of Bareith, in the Hartz, Saxony, Hesse, and Palatinate.

The common argillaceous iron ore of Kirwan, is ranked by Brochant as a variety of this. It is very common in most iron countries, and much of it is found in Britain, especially in Colebrook-dale, Shropshire, and in Dean forest in Gloucestershire. The Carron ore is principally of this kind.

Species 10. Lowland Iron Ore. La Mine de Fer de Gazon. Reaen-eisenstein.—There are several varieties of this, all of which are found in low, humid situations, in very extensive beds, alternating with sandstone, clay, &c. This species is much more abundant in the north than in the south of Europe, especially in the duchy of Brandenburg, in Courland, Lithuania, Livonia, Prussia, Prussian Poland, and Lusatia.

Species 11. Blue Martial Earth. Le Fer Terreux bleu. Blaue-eisenerde.—This is found imbedded in clay and similar earths, and often accompanies the last species. It occurs in Saxony, Silesia, Swabia, Bavaria, Poland, Siberia, and the Palatinate.

Species 12. Green Martial Earth. Le Fer Terreux Vert. Grun-eisenerde.—This species is uncommon, having been found only at Braundorf, and Schneeburg in Saxony, in veins, accompanying quartz and sulphur pyrites.

Species 13. Emery. L'Emeril. Schmirgel.—This is found in Saxony, distributed in a bed of hardened felsites, in sandstone. It is also found in Italy, Spain, Peru, the isle of Naxos in the Archipelago, where there is a cave called by the Italians, Copo Smeriglio, or the Emery Cape. It is often mixed with particles of magnetic iron ore, whence some have supposed the emery to be magnetic.

VII. LEAD.

Species 1. La Galén Commune. Gemeiner-Blei-Lead. glanz.—This is the most common and abundant ore of lead, and is found both in primitive and secondary strata, in beds and veins, accompanied with quartz, fluor spar, calcareous spar, sparry iron ore, barytic earths, blende, pyrites, and several ores of silver. It is found in great abundance at Leadhills and at Wanlockhead in Dumfriesshire, in Derbyshire, Strontian in Scotland, and in the Mendip hills in Somersetshire. A variety of this, called compact galena, is found in the same situations, especially in Derbyshire. It has often been confounded with graphite, or plumbago.

Werner enumerates nearly 20 formations, as he calls them, of galena, but Mr Jameón thinks the galena formation in Dumfriesshire is different from any of these.

Species 2. Blue Lead Ore. La Mine de Plomb Bleue. Blau-bleierz.—This species has as yet been found only at Zichopau in Saxony, accompanying fluor spar, barytic spar, white and black lead, and malachite.

Species 3. Brown Lead Ore. La Mine de Plomb Brune. Braun bleierz.—This species is also very rare, but is found at the same place with the last, and also in Bohemia, Brittany, and Hungary.

Species 4. Black Lead Ore. La Mine de Plomb Noire. Schwarz-bleierz.—This is found in Saxony, at Freyberg, at Zichopau, in Cumberland, in some parts of Scotland, in Poland, and Siberia.

Species 5. White Lead Ore. La Mine de Plomb Blanche. Weißs-bleierz.—This is not a very abundant species, but it is found in several lead mines, especially in Bohemia, Saxony, the Hartz, France, Siberia, Hungary, Carinthia, and in some of the British lead mines, especially at Leadhills.

Species 6. Green Lead Ore. Phosphorated lead ore of Kirwan. La Mine de Plomb Vert. Green-bleierz.—This is found in veins, more commonly in the primitive mountains. It is met with in Bohemia, Saxony, Chap. II.

G E O L O G Y.

General Distribution of the Materials of the Earth.

Bavaria, Siberia, Brilgau, France, Peru, and at Leadhills in Scotland.

Species 7. Red Lead Spar. Le Plomb Rouge. Rothesbleierz.—This is one of the rarest ores of lead, being as yet only found at Ekatharenburg in Siberia.

Species 8. Yellow Lead Spar. Le Plomb jaune. Gelbes-bleierz.—This has been known only for a few years. It has been found at Bleiberg in Carinthia, in a gangart of calcareous stone. It has also been found near Freyberg in Saxony, at Annaberg in Austria, and at Reczbanya in Hungary.

Species 9. Native Vitriol of Lead. Le Vitriol de Plomb natif. Naturlicher-blei-vitriol.—This is found in the ille of Anglesea, in a vein of brown iron ore, mixed with copper pyrites. It is also found at Leadhills in Scotland.

Species 10. Earthy Lead Ore.—Of this there are two varieties, the friable and the indurated. The former is found in Saxony, in Lorraine, in Poland, and Sibereia, Bohemia, and Silesia: The latter is found in most lead mines. Mr. Janseon notices two varieties of lead earth, which he calls white-lead earth, and friable lead earth, as met with at Leadhills.

VIII. Tin.

Species 1. Tin Pyrites. La Pyrite d'Etain. Zinnkies. This species is very rare, and is, we believe, found only in Cornwall, at Wheal rock, among copper pyrites.

Species 2. Common Tinstone. La Pierre d'Etain. Zinnstein.—This is found chiefly in primitive rocks, as in granite, gneiss, micaceous schistus, and porphyry, both in masses and veins. It is the common ore of Cornwall, and is found also in Saxony, Bohemia, and the East Indies.

Species 3. Wood Tin Ore. L'Etain grenu. Zinnerz.—This is found in Cornwall, in the parishes of Colomb, St Denis and Roach, accompanying the former.

IX. Bismuth.

Species 1. Native Bismuth.—Bismuth is a very rare metal, but is most commonly found in its native state. It is usually in a gangart of quartz, calcareous spar, and barytic spar. It occurs in Bohemia, in Saxony, in the territory of Hainault, in Swabia, in Sweden, and in France, in the mines of Brittany.

Species 2. Sulphurated Bismuth. La Galène de Bismuth. Wismuth Glanz.—This is very rare. It commonly accompanies the former, and is found at Joachimsthal, in Bohemia, at Johann-Georgen-stadt, Schwarzenberg, and Altenberg in Saxony, and at Ridderyttan in Sweden.

Species 3. Bismuth Ochre. L'Ochre de Bismuth. Wismuth Okker.—This is still more rare than the last, and is chiefly found near Schneeberg in Saxony, and at Joachimsthal in Bohemia.

X. Zinc.

Species 1. Blende. This is sulphurated zinc, and is one of the most common ores of that metal. There are three varieties; the brown, the yellow, and the black. Of these the yellow is the most rare, and is found in Saxony, in Bohemia, in the Hartz, in Norway, Tranfylvania, and Hungary. The brown and the black are found in most of these places, and besides in France and England, especially in Derbyshire.

Species 2. Calamine. La Calamine. Galmel.—Of this there are two varieties, compact and friolated. Both occur only in particular stratiform rocks, often forming entire beds with indurated clay, and calcareous spar. The latter is usually found in the cavities of the former. Both occur in Bohemia, in Carinthia, and in most of the German lead mines. They are also found in Britain, especially at Leadhills, Wanlock-head, and in Derbyshire.

XI. Antimony.

Species 1. Native Antimony.—This is very rare. It was discovered at Sahlberg in Sweden, in the year 1748, ores in a gangart of some calcareous stone, and it was also found some years ago at Allemont in France, accompanying other ores of antimony and of cobalt.

Species 2. Sulphurated Antimony. L'Antimoine Gris. Grau-fpsis glas-erz.—There are several varieties of this, as the compact sulphurated antimony, found at Braunsdorf in Saxony; at Goldgronach in the principality of Bareith; at Maguria in Hungary, and Auvergne in France: foliated sulphurated antimony, found at Braunsdorf and Goldgronach, and in the Hartz, and Tranfylvania: friolated sulphurated antimony, found in Saxony, Hungary, France, Swabia, Tuscany, Sweden, the Hartz, Spain, and in England: plumose antimonial ore, found at Freyberg in Saxony, at Braunsdorf and Stahlberg, and at Chemnitz in Hungary. All these varieties are usually found in a quartzose rock.

Species 3. Red Antimonial Ore. L'Antimoine Rouge. Roth-fpsis glas-erz.—This is found at Braunsdorf, at Malafka and Kremnitz, in Hungary, and at Allemont in France. It usually accompanies the first and second species, especially at Allemont, or the next species, which is the cafe at Braunsdorf.

Species 4. Muriated Antimony. Antimoine blanc. Weies-fpsis glas-erz.—White antimony is extremely rare; it is principally found at Przibran in Bohemia, in quadrangular, shining tables, disposed in bundles upon galena. It is said also to have been found at Braunsdorf and Malafka.

Species 5. Antimonial Ochre. L'Ocre d'Antimoine. Spies glas-okker.—This species is also very rare; it is found at Braunsdorf, near Freyberg, and in Hungary, always accompanying the second and third species.

XII. Cobalt.

Species 1. White Cobalt Ore. Le Cobalt blanc. Weisser fepsis-kobolt.—This is found in Norway, Sweden, at Anaberg in Saxony, in Swabia and Stiria; but it is very rare. In Saxony and Norway, it occurs in beds of micaceous schistus, along with the 7th species, and with quartz, hornblende, and pyrites.

Species 2. Dull Gray Cobalt Ore. Le Cobalt gris. Grauer-fpsis-kobolt.—This is found in Saxony, Bohemia, France, Norway, Swabia, Hungary, Stiria, and in a few mines in England. It is sometimes mixed with ores of silver.

Species 3. Bright White Cobalt Ore. Le Cobalt Elatant. Glanz-kobolt.—This is the most common of all the ores of cobalt, and almost always accompanies the ores of nickel, and of silver. It is found in Bo- General Distribution of the Materials of the Earth.

Species 4. Black Cobalt Ochre. Le Cobalt Terreux noir. Schwarzer-erd-kobolt.—This is found in Saxony, in Thuringia, Swabia, Hesse, the Palatinate, Salzburg, and in the Tyrol, accompanying other ores of cobalt, and several ores of silver, copper, and iron.

Species 5. Brown Cobalt Ochre. Le Cobalt Terreux brun. Brauner-erd-kobolt.—This is found in considerable quantity at Saalfeld in Thuringia; at Kamsdorf in Saxony, and at Alperfach in Wirtemberg, accompanying other ores of cobalt.

Species 6. Yellow Cobalt Ochre. Le Cobalt Terreux jaunne. Geber-erd-kobolt.—This is one of the rarest ores of cobalt. It is found at Saalfeld in Thuringia, at Alperfach in Wirtemberg, and at Allemont in Dauphiné in France.

Species 7. Red Cobalt Ore. Le Cobalt Terreux rouge. Rother-erd-kobolt. This is found in Saxony, Thuringia, Hesse, Swabia, Bohemia, Allemont in France, and in Norway.

XIII. NICKEL.

Species 1. Sulphurated Nickel. Le Kupfer Nikel. KupferNikkel.—This is found in veins, both in primitive and secondary mountains, almost always accompanying some of the ores of cobalt, to which it seems to bear some geological relation. It is also found in some silver mines. It is met with in Bohemia, Saxony, Thuringia, the Hartz, in Swabia, Hesse, Allemont in France, Stiria, and in some parts of Britain. Its usual gangart is quartz, barytic and calcareous spar.

Species 2. Nickel Ochre. L'Ocre de Nikel. Nikkel-okker.—This is found in the same situations with the last, from a decomposition of which it appears to be produced.

XIV. MANGANESE.

Species 1. Gray Ore of Manganese. Le Manganec. Grau-braunstein-erz.—There are several varieties of this, but they are all commonly found near each other, in veins or in masses, commonly in the primitive mountains.

They are found in considerable quantity in many mines in Saxony, Bohemia, Bavaria, and Hungary. They are also met with in France, and in several parts in Britain, as in Derbyshire, Leadhills, and Wanlockhead; in the Mendip hills, and the Isle of Jura.

Species 2. Red Manganese Ore. Le Manganec rouge. Roth-Cronflein-erz.—This is very rare, but is found at Katnick, Offenbanya, and especially at Nagyag in Transylvania, at which last place it is found in a gold mine.

XV. MOLYBDENA.

Le Molybdene sulphure. Wasserbley.—This is found in Bohemia; at several places in Saxony; in Sweden; at Tillot in France, and at Chamouni at the foot of Mont Blanc. It is commonly found in primitive rocks, especially in tin mines.

XVI. ARSENIC.

Species 1. Native Arsenic.—This is found in Bohemia, Saxony, Silesia, the Hartz, Hesse, Sweden, Swabia, Norway, Stiria, Spain, Thuringia, and in England. It is found in beds in the primitive rocks, and in veins in the secondary.

Species 2. Arsenical Pyrites, or Marcosite. La Pyrite Arsenicale. Arsenik-kies.—This is found in Bohemia, Saxony, and Silesia, accompanying the common tin stone, and galena, with some other minerals.

Species 3. Realgar. Le Realgar. Rauchgelb.—This is found in the Bannat, Bohemia, Saxony, Swabia, the Hartz, the Tyrol, Hungary, and in the neighbourhood of volcanoes, especially Etna and Vesuvius.

Orpiment, which Brochant makes a variety of realgar, is found in several of the above places, and also in Natolia, in Servia, Transylvania, and Wallachia, usually accompanying quartz and clay.

Species 4. Native calx of Arsenic. L'Arsenic oxidé natif. Naturlechur arsenik-kalk.—This is very rare, but is found in a small quantity in Bohemia and Joachimthal, in Saxony, at Racheau, at Salatna, in Transylvania, and in Hungary.

XVII. TUNGSTEN.

Species 1. Tungsten. Le Tungstène. Schiverstein. Tungsten—This is a very rare mineral, but is found at Schlack-ores, enwald in Bohemia, at Ehrenfriedersdorf in Saxony, and at Riddarkytten, Bisburg in Sweden, usually accompanying quartz, mica, talc, and tin ore.

Species 2. Wolfram.—This is also pretty rare, but is found in Bohemia, Saxony, and at Poldice in Cornwall.

XVIII. URANIUM.

Species 1. Sulphurated Uranite. L'Uranie noir. Pe-Uranium cherz.—This is found at Joachimthal in Bohemia, and ores. at Johann-Georgen-Stadt, and Schneiberg in Saxony, accompanying the two following species, and lead and copper ores.

Species 2. Micaceous Uranitic Ore. L'Uranie Micacé. Uran-glimmer.—This is found in the Bannat, Saxony, Wirtemberg; near Autun in France, and near Karra-rach in Cornwall.

Species 3. Uranitic Ochre. L'Ocre d'Uranie Uran-okerh.—This has been found at Joachimthal in Bohemia, and at Johann-Georgen-Stadt in Saxony, but it is uncommon.

XIX. TITANIUM.

Species 1. Menakanite.—This has been found chiefly Titanium near Menakan in Cornwall.

Species 2. Titanite. Le Ruthile. Ruthil.—This is found at Bojnik and Rhonitz in Hungary; in New Castile in Spain; at Aschaffenburg in Franconia; at St Yreux in France, and in Mount St Gothard, and some other places in the Alps.

Species 3. Titanitic Siliceous Ore. Le Nigrine. Nigrin.—This has been found near St Gothard in the Alps, at Ohlapien in Transylvania, &c.

XX. TELLURIUM.

Species 1. Sylvanite. Le Sylvane natif. Gedie-Tellurium gen Sylvan.—This is found chiefly at Fatzeborg in Transylvania, but is now become extremely rare. It occurs in Chap. III.

G E O L O G Y.

Theories of in beds of gray wacke and secondary (or transition) limestone.

Species 2. — Le Sylvane graphique. Shrifterz. — This is found at Offenbanya in Transylvania, in a bed of porphyritic fycnite, and granular limestone.

Species 3. — Le Sylvane blanc. Weiß-Sylvanerz.—This was brought to Brochant from Freyberg in Saxony.

Chap. III. Of the most Remarkable Theories of the Earth.

A late writer considers the proper object of a theory of the earth, to be the tracing the series of those revolutions which have taken place on the surface of the earth; to explain their causes, and thus to connect together all the indications of change that are found in the mineral kingdom. He justly observes, that the formation of such a theory requires an accurate and extensive examination of the phenomena of geology, and that it is inconsistent with any, but a very advanced state of the physical sciences. There is perhaps no research in those sciences more arduous than this; none where the subject is so complex, where the appearances are so diversified, or so widely scattered; and where the causes that have operated are so remote from the sphere of ordinary observation*.

With such requisites, and under such difficulties, it is not surprising that so many who have aimed at constructing theories of the earth, have failed in the attempt. It certainly requires a prodigious accumulation of facts, together with a talent for observation, and for arrangement, which are seldom found united. We shall presently see how far those theories which have hitherto been framed to account for the changes that the earth has undergone, have been successful.

It is not, however, to be supposed, that a correct theory of the earth is impossible, though some may think it an arrogant, if not a presumptuous undertaking, to attempt explaining how the present state of the globe and the revolutions which it has undergone, were brought about. The time is perhaps not far distant when the present prevailing hypotheses will be improved into a rational, and so far as is consistent with the knowledge and acquirements of man, a perfect system.

Mr Kirwan has laid down certain laws of reasoning; which should be adhered to inviolably in investigations of this kind. The first is, that no effect should be attributed to a cause whose known properties are inadequate to its production. The second is, that no cause should be adduced, whose existence is not proved either by actual experience or approved testimony. Many natural phenomena have arisen or do arise, in times or places so distant, that well conditioned testimony concerning them cannot, without manifest absurdity, be rejected. Thus the inhabitants of the northern parts of Europe, who have never felt earthquakes, nor seen volcanoes, must nevertheless admit, from mere testimony, that the first have been, and that the second do actually exist. The third is, that no powers should be ascribed to an alleged cause, but those that it is known by actual observation to possess in appropriated circumstances.

Sect. I. Theory of Burnet.

The first who formed this amusement of earth-making Theory of into a system, was the celebrated Thomas Burnet; a Burnett man of polite learning, and rapid imagination. His sacred theory, as he calls it, describing the changes which the earth has undergone, or shall hereafter undergo, is well known for the warmth with which it is imagined, and the weakness with which it is reasoned; for the elegance of its style, and the neatness of its philosophy. The earth, says he, before the deluge, was very differently formed from what it is at present; it was at first a fluid mass; a chaos composed of various substances, differing both in density and figure; those which were heaviest sunk to the centre, and formed in the middle of our globe a hard solid body; those of a lighter nature remained next; and the waters, which were lighter still, swam upon its surface, and covered the earth on every side. The air, and all those fluids which were lighter than water, floated upon this also, and in the same manner encompassed the globe; so that between the surrounding body of waters, and the circumambient air, there was formed a coat of oil, and other unctuous substances, lighter than water. However, as the air was still extremely impure, and must have carried up with it many of those earthy particles with which it once was intimately blended, it soon began to defecate, and to deposit these particles upon the oily surface already mentioned, which soon uniting, the earth and oil formed that crust which soon became an habitable surface, giving life to vegetation, and dwelling to animals.

This imaginary antediluvian abode was very different from what we see it at present. The earth was light and rich, and formed of a substance entirely adapted to the feeble state of incipient vegetation; it was a uniform plain, everywhere covered with verdure, without mountains, without seas, or the smallest inequalities. It had no difference of seasons, for its equator was in the plane of the ecliptic, or, in other words, it turned directly opposite to the sun, so that it enjoyed one perpetual and luxuriant spring. However, this delightful face of nature did not long continue in the same state, for, after a time, it began to crack and open in fissures; a circumstance which always succeeds when the sun exhales the moisture from rich or marshy situations. The crimes of mankind had been for some time preparing to draw down the wrath of heaven; and they at length induced the deity to deter repairing those breaches in nature. Thus the chasms of the earth every day became wider, and, at length, they penetrated to the great abyss of waters, and the whole earth in a manner fell in. Then ensued a total disorder in the uniform beauty of the first creation, the terrae surface being broken down; as it sunk, the waters gushed out in its place; the deluge became universal; all mankind, except eight persons, were destroyed, and their posterity condemned to toil upon the ruins of desolated nature.

It remains to mention the manner in which he relieves the earth from this universal wreck, which would seem to be as difficult as even its first formation. These great malices of earth falling into the abyss, drew down with them vast quantities of air; and by dashing against each other, and breaking into small parts by Theories of by the violence of the shock, they at length left between them large cavities filled with nothing but air. These cavities naturally offered a bed to receive the influent waters; and in proportion as they filled, the face of the earth became once more visible. The higher parts of its broken surface, now become the tops of mountains, were the first that appeared; the plains soon after came forward, and at length the whole globe was delivered from the waters, except the places in the lowest situations; so that the ocean and the seas are still a part of the ancient abyss that have not had a place to return to. Islands and rocks are fragments of the earth's former crust; kingdoms and continents are larger masses of its broken substance; and all the inequalities that are to be found on the surface of the present earth, are owing to the accidental confusion into which both earth and waters were then thrown.

Sect. II. Theory of Woodward.

The next who attempted a theory of the earth was Mr Woodward, who in his essay towards a natural history of the earth, endeavoured to give what he considered as a more rational account of its appearances than had been given by any preceding writer. He was indeed much better qualified for such an undertaking than any of his predecessors, as he was one of the most industrious naturalists of his time. Hence though his system must be considered as weak and untenable, his work contains many important facts relating to natural history.

Woodward sets out by asserting that all terrestrial substances are disposed in beds of various natures, lying horizontally, one over the other, like the coats of an onion, and that they are replete with shells and other marine productions; these shells being found in the deepest cavities, and on the tops of the highest mountains. From these observations, which were warranted by the experience of naturalists at that time, but which we now know not to be universally correct, he proceeds to remark that these shells and extraneous fossils are not productions of the earth, but are all actual remains of those animals which they are known to resemble; that all the beds of the earth lie below each other in the order of their specific gravities, and that they are disposed as if they had been left in this situation by subduing waters. All this is affirmed with much earnestness, although many of the circumstances are contradicted by daily experience. Thus, we not unfrequently meet with layers of stone above the lightest soils, and find the softest earth below a stratum of hard stone. Woodward, however, having taken for granted, that all the strata of the earth are arranged in the order of their specific gravities, the lightest at the top, and the heaviest near the centre, he deduces as a natural consequence, that all the substances of which the earth is composed were once in an actual state of solution. This universal solution he conceives to have happened at the time of the flood. He supposes that at that time a body of water, which was then in the centre of the earth, uniting with that which was found on the surface, so far separated the terrae parts as to mix all together in one fluid mass; the contents of which afterwards sinking according to their respective gravities, produced the present appearances of the earth. Being aware, however, that an objection that solid substances are not found dissolved, he exempts them from this universal dissolution, and for that purpose, endeavours to show that the parts of animals have a stronger cohesion than those of minerals; and that, while even the hardest rocks may be dissolved, bones and shells may still continue entire.

Sect. III. Theory of Whiston.

Or all the theories of the earth that have been formed, previous to those of Hutton and Werner, none has been more applauded or more opposed than that of Whiston. Nor is this surprising; for this theory being supported with all the parade of mathematical calculation, confounded the ignorant, and produced the approbation of such as desired to be thought learned, since it implied a considerable knowledge of abstract science, even to be capable of comprehending what the writer aimed at. It is not easy to divest this theory of its mathematical garb, but the result of our philosopher's reasoning appears to be as follows.

He supposes the earth to have been originally a comet, and he considers the history of the creation, as given us in scripture, to have its commencement just when it was, by the hand of the Creator, more regularly placed as a planet in our solar system. Before that time, he supposes it to have been a globe without beauty or proportion; a world in disorder, subject to all the vicissitudes which comets endure; some of which have been found, at different times, a thousand times hotter than melted iron; at others, a thousand times colder than ice. These alternations of heat and cold, continually melting and freezing the surface of the earth, he supposes to have produced, to a certain depth, a chaos entirely resembling that described by the poets, surrounding the solid contents of the earth, which still continued unchanged in the midst, making a great burning globe of more than two thousand leagues in diameter. This surrounding chaos, however, was far from being solid: he compares it to a dense though fluid atmosphere, composed of substances mingled, agitated, and shocked against each other; and in this disorder he describes the earth to have been just at the eve of creation.

But upon its orbit being then changed, when it was more regularly wheeled round the sun, every thing took its proper place, every part of the surrounding fluid then fell into a situation, in proportion as it was light or heavy. The middle or central part, which always remained unchanged, still continued so, retaining a part of that heat which it received, in its primeval approaches towards the sun; which heat he calculates, may continue for about fix thousand years. Next to this fell the heavier parts of the chaotic atmosphere, which serve to sustain the lighter; but as in descending they could not entirely be separated from many watery parts with which they were intimately mixed, they drew down a part of these also with them; and these could not mount again after the surface of the earth was consolidated; they therefore surrounded the heavy first descending parts, in the same manner as these surround the central globe. Thus, the entire body of the earth is composed internally of a great burning globe, next which is placed a heavy terrane substance that encoun- Theories of passes it, round which also is circumfused a body of water. Upon this body of water, the crust of the earth on which we dwell is placed, so that, according to him, the globe is composed of a number of coats, or shells, one within the other, all of different densities. The body of the earth being thus formed, the air, which is the lightest substance of all, surrounded its surface, and the beams of the sun darting through, produced that light which, we are told, first obeyed the Creator's command.

The whole economy of the creation being thus adjusted, it only remained to account for the risings and depressions on the surface of the earth, with the other seeming irregularities of its present appearance. The hills and valleys are considered by him as formed by their prelling upon the internal fluid, which sustains the outward shell of earth with greater or less weight; those parts of the earth which are heaviest, sink into the subjacent fluid more deeply, and become valleys; those that are lighter, rise highest upon the earth's surface, and are called mountains.

Such was the face of nature before the deluge; the earth was then more fertile and populous than it is at present; the life of man and animals was extended to ten times its present duration; and all those advantages arose from the superior heat of the central globe, which ever since has been cooling. As its heat was then in full power, the genial principle was also much greater than at present; vegetation and animal increase were carried on with more vigour; and all nature seemed teeming with the seeds of life. But these physical advantages were only productive of moral evil; the warmth which invigorated the body, increased the passions and appetites of the mind; and as man became more powerful, he grew less innocent. It was found necessary to punish this depravity; and all living creatures were overwhelmed by the deluge in universal destruction.

This deluge, which simple believers are willing to ascribe to a miracle, philosophers have been long desirous to account for by natural causes. They have proved that the earth could never supply from any reservoir towards its centre, nor the atmosphere by any discharge from above, such a quantity of water as would cover the surface of the globe to a certain depth over the tops of our highest mountains. Where, therefore, was all this water to be found? Whiston has found enough, and more than a sufficiency, in the tail of a comet: for he seems to allot comets a very active part in the great operations of nature.

He calculates with great seeming precision, the year, the month, and the day of the week on which this comet (which has paid the earth some visits since, though at a kinder distance) involved our globe in its tail. The tail he supposed to be a vaporous fluid substance, exhaled from the body of the comet, by the extreme heat of the sun, and increasing in proportion as it approached that great luminary. It was in this that our globe was involved at the time of the deluge; and as the earth still acted by its natural attraction, it drew to itself all the watery vapours which were in the comet's tail; and the internal waters being also at the same time let loose, in a very short space the tops of the highest mountains were laid under the deep.

The punishment of the deluge being thus completed and all the guilty destroyed, the earth, which had been broken by the eruption of the internal waters, was also enlarged by it; so that upon the comet's recess, there was found room sufficient in the internal abyss for the recess of the superfluous waters, whither they all retired, and left the earth uncovered, but in some respect changed, particularly in its figure, which, from being round, was now become oblate. In this universal wreck of nature Noah survived, by a variety of happy caules, to repeople the earth, and to give birth to a race of men flow in believing ill-imagined theories of the earth.

Sect. IV. Theory of Buffon.

Less abstracted and more popular than the theory of Whiston, but equally fanciful and pompous, was the hypothesis of Buffon. This system, which was received with great admiration, depends principally on two facts which, though generally true, were by Buffon extended much too far.

It had been long observed, that such flinty or silicious bodies as form a part of the composition of glass, are among the most abundant materials which compose the earth, and that many of them nearly resemble glass in colour, transparency, lustre, hardness, and specific gravity. As glass is produced by fusion in a strong heat, it was inferred by Buffon, that the flinty bodies found on the earth derived their origin from a similar fusion; and as no heat sufficient to produce to great an effect, could be found on our globe, the author has recourse to the sun as its source. He supposes the planets, and the earth among the number, to have originally formed a part of the body of the sun. In this situation a comet falling in on that great body, might have given it such a shock, and so shaken its whole frame, that some of its particles might have been driven off, like streaming sparkles from red-hot iron; and each of these streams of fire, though very small in comparison of the sun, might have been large enough to form a planet much greater than our earth, or any other of the planetary system. In this manner the planets, together with the globe which we inhabit, might have been driven off from the body of the sun by impulsion; and in this way they would have continued to recede from it for ever, had they not been arrested by the superior power of attraction, exerted on them by the sun; and thus, by the combination of the centrifugal and centripetal forces, they were whirled round in the orbits which they now describe.

After giving a number of reasons for the credibility, or at least possibility, of the foregoing supposition, the author concludes that it is evident, that the earth assumed its present figure when in a melted state. It is natural to think, says he, that the earth, when it issued from the sun, had no other form but that of a torrent of melted and inflamed matter; that this torrent, by the mutual attraction of its parts, took on a globular figure, which its diurnal motion changed into a spheroid; that, when the earth cooled, the vapours, which were expanded like the tail of a comet, gradually condensed, and fell down in the form of water upon the surface, depositing at the same time a flimsy substance mixed with sulphur and salts, part of which was carried by the motion of the waters into the perpendicular fissures of the strata, and produced metals, and the rest remained on the surface, and gave rise to the vegetable mould which abounds in different places, with more or less of animal or vegetable particles, the organization of which is not obvious to the senses.

Thus the interior parts of the globe were originally composed of vitrified matter, and probably they are so at present. Above this were placed those bodies which had been reduced by the heat to the finestest particles, as sand, which are only portions of glads, and above these pumice stones, and the scoriae of melted matter, from which were afterwards produced the several kinds of clay. The whole mass was covered with water to the depth of five or six hundred feet, arising from the condensation of the vapours when the earth began to cool. This water deposited a stratum of mud, mixed with all those substances which were capable of being sublimed, or exhaled by fire; and the air was formed of the most subtle vapours, which, from their small specific gravity, floated above the water.

Such was the condition of the earth, when the tides, the winds, and the heat of the sun, began to introduce changes on its surface. The diurnal motion of the earth, and that of the tides, elevated the waters in the equatorial regions, and necessarily transported thither great quantities of lime, clay, and sand; and by thus elevating those parts of the earth, they perhaps sunk those under the poles about two leagues, or a 230th part of the whole; for the waters would easily reduce into powder pumice stones, and other spongy parts of the vitrified matter upon the surface; and by this means excavate some places and elevate others, which, in time, would produce islands and continents, and all those inequalities on the surface, which are more considerable towards the equator than towards the poles. The highest mountains lie between the tropics and the middle of the temperate zones, and the lowest from the polar circles towards the poles. Indeed, both the land and sea have most inequalities between the tropics, as is evident from the incredible number of islands peculiar to these regions.

The other circumstance which forms a principal part of the basis of this theory, is derived from the composition of sea shells. It is well known that these shells consist chiefly of an earth like that which constitutes the principal part of limestone or marble; and it was hence inferred that, after a series of ages, these shells being broken down into minute particles, produced those immense masses of calcareous substances which are now found either in vast mountains, or in stratified plains, in almost every part of the earth.

Buffon conceives very naturally, that the surface of the earth must, at the beginning, have been much less solid than it is at present, and consequently the same causes which at this day produce but slight changes, must then, on so yielding a body, have been attended with very considerable effects. There is, he thinks, every reason to suppose, that the earth was at that time covered with the waters of the sea; and that these waters were above the tops of our highest mountains, since, even in such elevated situations, we find shells and other marine productions in very great abundance. It appears also that the sea continued for a considerable time upon the face of the earth; for as these layers of shells are found so very frequently at such great depths, and in such prodigious quantities, it seems impossible for such numbers to have been supported all alive at one time; so that they must have been brought there by successive depositions. These shells also are found in the bodies of the hardest rocks, where they could not have been deposited all at once, at the time of the deluge, or at any such instant revolution; since that would be to suppose, that all the rocks in which they are found were, at that instant, in a state of dissolution, which would be absurd to assert. The sea, therefore, deposited them wherever they are now to be found, and that by flow and successive degrees.

"It will appear also, that the sea covered the whole earth, from the appearance of its layers, which lying regularly one above the other, seem all to resemble the sediment formed at different times by the ocean. Hence, by the irregular force of its waves and its currents, driving the bottom into sand-banks, mountains must have been gradually formed within this universal covering of waters; and these successively raising their heads above its surface, must, in time, have formed the highest ridges of mountains upon land, together with continents, islands, and low grounds, all in their turns. This opinion will receive additional weight by considering, that in those parts of the earth, where the power of the ocean is greatest, the inequalities on the surface of the earth are highest; the ocean's power is greatest at the equator, where its winds and tides are most confluent; and in fact, the mountains at the equator are found to be higher than in any other parts of the world. (Vid. No 129.). The sea, therefore, has produced the principal changes in our earth; rivers, volcanoes, earthquakes, storms, and rain, having made but slight alterations, and only such as have affected the globe to very inconsiderable depths."

"In the formation of this theory, says Mr Kirwan, genius (I mean genius in its primitive sense, the sublime talent of fascinating invention, and not the energetic power of patient, profound, and fagacious investigation), unhappily prefixed. Yet dazzled by the splendid but delusive scenery, presented by an ardent imagination roaring to the source of light, and rendering from its flaming orb the planetary masses that surround it; then marking with daring and overweening confidence, fancied successive epochs of the consolidated fabric of the terraqueous globe; the public attention was long arrested by the magical representation, and the understanding nearly betrayed into a partial, if not a total, assent to it.

"This proud gigantic theory was, however, like another Goliath, soon demolished by a common flint or pebble, the very substance it sprung from. Common glads essentially contains an alkaline salt, to which alone it owes its fusibility; siliceous substances contain none, and are absolutely infusible when unassociated with any. Macquer found them infusible not only in furnaces, but in the still incomparably superior heat of inflamed oxygen. Hence the hypothesis grounded on the assumed identity of these substances and common glads, vanished like the unembodied visions of the night. With respect to limestone, the other pillar on which this theory rests, Cronstedt, Ferber, Born, Arduini, and Bergman, demonstrated the existence of numerous and immense mountains, in which not only no vestiges of shells could be traced, but whose internal structure of Theories of position was incompatible with the supposition of an origin "the Earth, gination thence derived."*

* Kitson's Geological Effects.

Theory of Whitehurst.

The first person who founded a theory of the earth on accurate and industrious observation was the late Mr John Whitehurst, who, in an inquiry into the original state and formation of the earth, has advanced opinions which differ considerably from those of preceding naturalists, and in some measures resemble those which are at present in greatest repute.

Mr Whitehurst sets out with stating his opinions, that the terraqueous globe, which we now inhabit, was originally in a fluid state, and this, not from any solvent principle or subsequent solution, but owing to the first assemblage of its component parts; whence he presumes that the earth had a beginning, and has not existed from eternity. He rests his proof of this original fluid state of the earth on its spheroidal form, which a fluid globe in its revolution would naturally acquire, but which could not easily be produced in a solid body. The fluidity of the earth and the infinite divisibility of matter, an opinion which generally prevailed at that time, prove, according to him, that the component parts of the elements were uniformly blended together, none being heavier or lighter than another; hence they composed a uniform mass of equal consistence throughout, from the surface to the centre, and consequently the new formed globe was not adapted to the support of animal or vegetable life. It would therefore be absurd to suppose, that organized bodies were created during the chaotic state of the earth; and there is a great presumption that mankind were not created till the earth was become suitable to the nature of their existence.

The component parts of the chaos were heterogeneous, and endowed with peculiar chemical affinities, whereby similar substances were disposed to unite and form several bodies of various denominations, and thus the chaos was progressively formed into a habitable world.

The first operation of nature which presents itself to our consideration is the production of the spheroidal figure of the earth, acquired from its diurnal rotation, and the laws of gravity, fluidity, and centrifugal force. When this form was once completed, the component parts began to act on each other according to their affinities: hence the particles of earth, air, and water, united to those of their own kind, and with their union commenced their specific gravities; and the uniform suspension which had hitherto prevailed throughout the whole of the chaotic mass, was destroyed.

"On the component parts separating into homogeneous masses, those of the greatest density began to approach towards the centre of gravity, and those of the greatest levity ascended towards the surface. As the specific gravity of air is so much less than that of water, it is presumed that the former escaped from the general mass sooner than the latter, and formed an impure atmosphere surrounding the newly-formed globe. Water being next in levity, succeeded the air, and formed one vast ocean about the earth. In process of time these elements became perfectly pure, and fit for the preservation of animal and vegetable life.

When the component parts of the chaos had been thus progressively separated, and collected into distinct masses, the following consequences are supposed to have ensued. The folds could not uniformly subside from every part of the surface, and be equally covered by water; for, as the sun and moon were coeval with the chaos, in proportion as the separation of the folds and fluids increased, so, by the action of those bodies on the sea, the tides became greater, and removed the folds from place to place, without any order or regularity. Hence the sea became unequally deep; and those inequalities daily increasing, dry land gradually appeared, and divided the waters which had hitherto been universally diffused over the earth. The primitive islands being thus formed, gradually became firm and dry, and fit for the reception of animals and vegetables.

The atmosphere, the sea, and the land, being thus formed, Mr Whitehurst proceeds to consider the order in which animal and vegetable bodies were severally created. He first supposes that, as the ocean became pure, and fit for animal life, before the formation of the primitive islands, fish were the first animals produced, and he supports this opinion by many ingenious arguments and facts. He observes, that in every instance upon record, the fragments of sea-shells are infinitely more numerous than the bones and teeth of fish. The latter, too, are but rarely deposited in any other matter than in beds of sand and gravel, and not in the solid substance of limestone, as the shells of fish generally are, even to the depth of many hundred yards, and dispersed throughout the whole extent of the secondary strata. Hence it is probable, that shell-fish were produced in prodigious quantities, sooner than any other kind of animal. The ocean being thus stocked with inhabitants, previous to the formation of the primitive islands, many of them became enveloped, and were buried in the mud by the action of the tides; and this would happen more particularly to the shell-fish, as they were less able to extricate themselves. Since the remains of marine animals are thus imbedded at various depths in the earth, there is sufficient proof that these marine bodies were entombed at successive periods of time, and that they were likewise created before the primitive islands, and consequently before any terrestrial islands.

That the earth has, at different times, suffered very violent convulsions, producing extensive ruptures of its solid parts, may reasonably be concluded from the rugged and uncouth appearance of many of the mountainous parts of the world. We see rocks in some places torn asunder, or appearing as if cut with a saw, and we find, in various parts, substances both mineral and organized, which are not generally met with, except in very distant regions. Most of the irregularities of the earth's surface are attributed by Mr Whitehurst to the general deluge. This would, in some instances, have the effect of reducing large masses of matter to a second state of solution; many eminences would be levelled, and some of the valleys would be filled up, while some parts which were before covered with water, might receive such an accession of matter as to fill up their cavities, and on the subsiding of the waters become a vast level plain. On the other hand, those elevated regions which were chiefly composed of the hardest stones, by having the lighter portions of earth washed away Theories of away from their basis, would appear considerably increased in height. Mr Whitehurst attributes the production of pit coal also to the deluge, as it is difficult to account for the deposition of such a quantity of vegetable matter (supposing pit-coal to be of vegetable origin) below the surface of the earth, on any other hypothesis. The animal matters found in a fossil state, especially those remains of animals which are not now found upon the earth, can only be accounted for, on the supposition of a deluge.

Mr Whitehurst, however, is not content with attributing to the deluge most of the changes which have taken place on the surface of the earth, but he derives from the same source the curtailed longevity of man, and many of the evils incident to mankind. "At that dreadful era, says he, and not before, the year became divided into summer and winter, spring and autumn, and the spontaneous products of the earth no longer sufficed the calls of human nature without art and labour; wherefore he who would expect to reap, and he who built an hut for his protection, would naturally expect to enjoy the fruits of his own labour; necessity, therefore, was the parent of property, and property created a thousand imaginary wants, which its possessors endeavoured to gratify, and their example excited similar ideas in those who had it not, but nevertheless studiously endeavoured to gratify their artificial wants by unjustifiable means. Hence the necessity of laws, dominion, and subordination, which had no existence in the antediluvian world.

"To that great revolution in the natural world, we may therefore ascribe many of the evils incident to mankind; for experience shews, that men who are born in rude and savage climates are naturally of a ferocious disposition; and that a fertile soil, which leaves nothing to wish for, softens their manners, and inclines them to humanity."

The above is a general outline of Mr Whitehurst's theory, some parts of which are very ingenious, and are corroborated by observation, while others are not a little fanciful and improbable. In his supposition that the earth was originally in a fluid state, he agrees with most other theorists, as this is a circumstance which admits of little doubt; though, as Kirwan has shewn, it is not necessary to suppose that the whole mass of the earth was fluid, but only those parts of it which are near the surface. In his play of affinities, and consequent separation of the materials of the earth into homogeneous masses, Whitehurst has been followed by Mr Kirwan, who has framed a beautiful and ingenious speculation on the successive changes that took place from the action of the materials on each other †.

Mr Whitehurst has been betrayed by his fondness for a favourite theory, into several errors respecting the stratification of the earth, which require to be mentioned. Thus, though the arrangement of the strata, especially where it has not been disturbed by some evident and violent cause, is extremely uniform; he has, however, extended this regularity farther than it really obtains. He tells us that the strata invariably follow each other, as if it were in an alphabetical order, or a series of numbers, whatever be their denomination. Not that they are alike in all the different regions of the earth, either in quality or in thickness, but that their order in each particular part, however they may differ in quality; yet they follow each other in regular succession, both as to thickness and quality, inso much, that by knowing the incumbent stratum, together with the arrangement thereof in any particular part of the earth, we may come to a perfect knowledge of all the inferior beds, so far as they have been previously discovered in the adjacent country. With respect to the strata that accompany coal, some instances are apparently, but not really, contradictory to this rule.

We now know, however, that Mr Whitehurst's observations do not universally apply. In the old mines in the valley of Planen, in Saxony, the strata, though they are near each other, vary considerably in thickness, from that of a few inches to several feet, and the stratum of coal, in particular, varies from two to thirty-two feet. Again, in Mount Salive, the strata of coal, though in a calcareous mountain, vary considerably; and Mr Whitehurst himself informs us, that at Benfai moor, those strata which are in other places the lowest, are found at the surface. Even in Derbyshire, to which Mr Whitehurst's observations chiefly apply, we are informed that even when the arrangement is the same, the thickness of the strata varies considerably.

SECT. VI. Theory of Dr Hutton.

THE next theory which we have to consider, is that proposed by Dr James Hutton, which has become so much the object of inquiry and debate, as to give name to one of the two principal sects into which geologists are now divided.

The leading principles of the Huttonian theory, as concisely laid down by one of its greatest admirers and supporters, are the following:

1. The first circumstance which Dr Hutton has considered as a general fact is, that by far the greater part of the bodies which compose the exterior crust of our globe, bear the marks of being formed of the materials of mineral and organized bodies, of more ancient date. The spoils or the wreck of an older world are, he thinks, everywhere visible in the present, and though not found in every piece of rock, they are diffused so generally as to leave no doubt that the strata which now compose our continents are all formed out of strata more ancient than themselves.

2. The present rocks, with the exception of such as are not stratified, having all existed in the form of loose materials collected at the bottom of the sea, must have been consolidated and converted into stone by virtue of some very powerful and general agent. The consolidating cause which he points out is subterraneous heat, and the objections to this hypothesis have been attempted to be removed, by the introduction of a principle new and peculiar to himself. This principle is the compression which must have prevailed in that region where the consolidation of mineral substances was accomplished. Under the weight of a superincumbent ocean, heat, however intense, might be unable to volatilize any part of those substances which, at the surface, and under the lighter pressure of our atmosphere, it can entirely consume. The same pressure, by forcing those substances to remain united, which at the surface are easily separated, might occasion the fusion of some bodies which in our fires are only calcined. 3. The third general circumstance which this theory is founded on is, that the stratified rocks, instead of being either horizontal or nearly so, as they no doubt were originally, are now found polishing all degrees of elevation, and some of them were perpendicular to the horizon; to which we must add, that those strata which were once at the bottom of the sea, are now raised up, many of them several thousand feet above its surface. From this, as well as from the inflexions, the breaking and separation of the strata, it is inferred, that they have been raised by the action of some expansive force placed under them. This force, which has burst in pieces the solid pavement on which the ocean rests, and has raised up rocks from the bottom of the sea into mountains 15,000 feet above its surface, exceeds any which we feel actually exerted, but seems to come nearer to the cause of the volcano or the earthquake than to any other, of which the effects are directly observed. The immense disturbance, therefore, of the strata, is in this theory ascribed to heat acting with an expansive power, and elevating these rocks which it had before consolidated.

4. Among the marks of disturbance in which the mineral kingdom abounds, those great breaches among rocks, which are filled with materials different from the rock on either side, are among the most conspicuous. These are the veins, and comprehend not only the metallic veins, but also those of whinstone, of porphyry, and of granite, all of them substances more or less crystallized, and none of them containing the remains of organized bodies. These are of posterior formation to the strata which they intersect, and in general also they carry with them the marks of the violence with which they have come into their place, and of the disturbances which they have produced on the rocks already formed. The materials of all these veins, Dr Hutton concludes to have been melted by subterraneous heat, and while in fusion, injected among the fissures and openings of rocks already formed, but thus disturbed, and moved from their original place.

This conclusion he extends to all the masses of whinstone, porphyry, and granite, which are interposed among the strata, or raised up in pyramids, as they often appear to be, through the midst of them. Thus, in the fusion and injection of the unstratified rocks, we have the third and last great operation which subterraneous heat has performed on mineral substances.

5. From this Dr Hutton proceeds to consider the changes to which mineral bodies are subject when raised into the atmosphere. Here he finds, without any exception, that they are all going to decay; that, from the shore of the sea to the top of the mountain, from the softest clay to the hardest quartz, all are wasting and undergoing a separation of their parts. The bodies thus resolved into their elements, whether chemical or mechanical, are carried down by the rivers to the sea, and are there deposited. Nothing is exempted from this general law; among the highest mountains and the hardest rocks, its effects are most clearly discerned; and it is on the objects which appear the most durable and fixed, that the characters of revolution are most deeply imprinted*.

It is not surprising that this theory should have met with many advocates among the more superficial observers of nature. The production of a man in whom genius, observation, and industry, were united, and who passed a considerable part of a long life in chemical and geological researches, was calculated to dazzle the imagination by the grandeur of its design, and to captivate the judgment by its appearance of regularity and consistence. It has been considered as a peculiar excellence of this theory, that it ascribes to the phenomena of geology an order similar to that which exists in the provinces of nature with which we are best acquainted; that it produces seas and continents, not by accident, but by the operation of regular and uniform causes; that it makes the decay of one part subservient to the restoration of another, and that it gives stability to the whole, not by perpetuating individuals, but by reproducing them in succession*.

An hypothesis with such pretensions could not fail of being minutely examined and severely criticized by the more enlightened part of geologists, and accordingly the very serious objections have been made to it by Kirwan and others. We shall state a few of what appear to us to be the most convincing arguments against Dr Hutton's theory, referring those who wish to see a more detailed refutation of it to the geological writings of Kirwan, and A Comparative View of the Huttonian and Neptunian Theories.

Some of the strongest arguments against this theory are drawn from the nature of caloric, and what we know of its action on other bodies. We know that caloric is of so diffusible a nature, that it is always communicated, from that body or set of bodies, in which it is most abundant, to that in which it is least, till an equilibrium of temperature is produced. But Dr Hutton's theory supposes a subterraneous heat as constantly existing, capable of fusing the most obdurate rocks, and of raising them by its expansibility from the bottom of the ocean, and yet incapable of extending its influence through the superincumbent strata at all times, so as to fuse or evaporate superior bodies, and gradually expand itself, so as to acquire that equilibrium which is one of its natural effects. Again, supposing such a subterraneous heat to exist, it is surely extraordinary, that substances which we are incapable of fusing by the strongest heat that we can excite, even in the greatest state of division, though, by this subterraneous heat be so completely fused, and in such vast masses, as to have assumed the appearance under which they now present themselves. If the solar rays, in the utmost state of concentration, if a united stream of inflamed hydrogenous and oxygenous gases from the tube of a blow-pipe or gazometer, cannot melt the smallest visible portion of calcareous spar or rock crystal, how can we conceive that the immense mountains of limestone and of quartz which are met with in so many places could have been fused into a state of perfect fluidity? Or even if they could be fused, how is it possible that the carbonic acid of the limestone should not have been diffused by so strong a heat? If we suppose with Dr Hutton, that this subterraneous heat acts with the affluence of immense prelude from the superincumbent strata and waters of the ocean, hence preventing the dissipation of volatile matters, still it should act uniformly, and should fuse all those bodies which come in its way, that are capable of fusion. Now, we know that feldspar, schorl, mica, and chlorite, are much more fusible than quartz, and of course, when a mass compounded of these comes Theories of under the influence of this heat, all these more fusible substances should be melted as well as the quartz. But in some stones in which most of these ingredients meet, as in the granite of Portfoy, there is every reason to suppose that some of them have been in a fluid state, while the others were solid or less fluid, as crystals of the latter are impressed on a bed of the former, viz. in the instance cited, crystals of feldspar in a mass of quartz. As it is certain, according to the advocates of the Huttonian theory, that at least the quartz was fluid when it was moulded on the feldspar, how happened it that this comparatively fusible stone was not also melted, and blended in one compact mass with the quartz? We also frequently find crystals of quartz penetrated by felspar and chlorite, which is a proof that the latter must have been hard while the former was in a fluid state. Hence it is evident that these appearances could not have been the effect of fusion by heat. Again, we find seams of coal penetrated by thin laminae and crystals of quartz, an effect which, according to this theory, must have taken place while the quartz was in a state of fusion. But, in this case, the strata of shale above and below the coal should also have been fused (shale being much more fusible than quartz), and thus the whole should have acquired a flaty texture; and besides in this intense heat, the coal should have been entirely charred and lost all its vegetable impre- sions.

The very existence of such a subterraneous heat, that constantly maintains itself without fuel, ready to act on any emergency, when a quantity of the old world has been abraded and translated, sufficient to furnish the materials of a new one, is avowedly hypothetical, as we have no proof that it exists. Nay, we have direct proof, as far as rational induction can carry us, to the contrary. It was long ago observed, by Irving and Foster, that the heat of the sea diminishes in proportion to the depth to which we proceed in examining it, and the same has been more lately proved by Peron, by *Journ. de various trials in many different latitudes*. Now the contrary of this ought certainly to happen, (unless this subterraneous heat is entirely unlike common heat) if there constantly existed in the bowels of the earth a heat capable of fusing quartz and limestone.

The structure of whin dykes, detailed in Section II. of last Chapter, affords additional arguments in opposition to the Huttonian theory.

The evidence which Dr Hutton has adduced to prove the subterraneous eruption of dykes, is drawn from the apparent derangement of the horizontal strata at a place where they are intercepted by a dyke, and the peculiar appearance of the coal in their immediate vicinity, which he supposes to be in a state of calcination, from having been in contact with the ejected matter of the dyke in fusion. Let us first attend to the effect of this eruption of a dyke, the apparent derangement of the strata; and let us consider for a moment, what must be the mechanical operation of a mass of this liquid matter bursting upwards through the coal strata. Suppose a coal field of a mile square in extent; suppose that the coal and concomitant strata are perfectly regular, having a moderate dip or inclination to the south; and suppose that this coal field is to be intersected by a dyke, ejected in a state of fusion from the bowels of the earth. Considering the nature of the strata which usually accompany coal, such as sandstone, lime, flint, ironstone, &c. which are very hard and compact, we must allow, that the resistance from such substances would be very great. In this previous state of circumstances, then, what would be the effect of the eruption of a dyke in the middle of the field, in a direction from north to south? Can it even be imagined, that this liquid mass in its progress upwards through the superincumbent strata to the surface of the earth, would merely destroy the continuity of these strata, and not in its irresistible course, carry along with it part of all the substances composing that strata through which it passed? But farther, one of the most obvious consequences of such an eruption, would be the elevation of part of the whole range of the strata on both sides of the dyke, and the extent of this elevation will be in proportion to the power or thickness of the dyke; and, not only is it natural to expect this elevation of the strata to a certain extent, but from the operation of an agent so tremendous and irresistible, that the whole strata should be broken, disjointed, and confused. But does this statement correspond with the phenomena? From the history of dykes traversing coal strata, we know that it does not. On the contrary, the whole of the strata, in most cases, preserve the same thickness, the same parallelism, and the same inclination to the horizon on both sides of the dyke. It is true, the half mile of coal field, intersected by a dyke, as we have supposed above, will on one side of it be elevated or depressed. If the dyke, which runs north and south in its course upwards, inclines to the west, the western division will be elevated. But this is not a partial elevation only in the immediate vicinity of the dyke. It extends over the whole field on the west side of the dyke, and the strata continue fair and regular, in all respects corresponding to those from which they have been detached, till they are intersected by another dyke.

From this reasoning, we think the conclusion fair and obvious, that dykes intersecting coal strata have not been formed by subterraneous eruption, and therefore, that the elevation or depression of the strata is not owing to this cause. Dr Hutton's theory, in this respect, is opposed by the facts which it professes to explain, and consequently it is untenable.

Let us now consider the argument drawn from the supposed calcination of the coal which has been in contact with the matter of the dyke in a state of fusion. Here Dr Hutton seems to have overleaped the bounds of his own theory, and lost sight of his own principles, which suppose, that all the strata and stony matters of which the globe is composed, have been consolidated by means of heat; that the exhibition of the common or ordinary phenomena of heat is not to be looked for in the grand processes of nature; because these operations have taken place at great depths in the bowels of the earth, or under immense pressure at the bottom of the sea; and this is the reason that coal, and lime strata, for instance, which have been subjected to this intense degree of heat discover no marks of calcination, the one being deprived of its carbonic acid, and the other of its bitumen. Now, granting this hypothetical argument to be well founded, what is the reason that the coal, which is in contact with a dyke, has undergone the processes of calcination, when this coal is at as great a depth in the bowels of the earth, under as immense pressure, and as much Chap. III.

Theories of much excluded from atmospheric air, as any coal at its original formation. But all the coal in contact with a dyke, is not in this state. Clean coal is sometimes found in immediate contact; and, in many places, clean coal is also found intercepted between regular ranges of bafalic columns, and this coal discovers not the smallest mark of calcination. On the other hand, coal in this supposed state of calcination, has been frequently discovered, at a great distance from any dyke or bafalic substance whatever. Masses of this foul coal often occur, to the regret and disappointment of the miner, in the midst of strata otherwise perfectly clean and regular. This last fact shows us, that we must look for the cause of this singular phenomenon elsewhere than in the circumstance of the coal having been in contact with a dyke while in fusion; for it appears that the effect does not always follow in the same circumstances, and that the same effect is produced in very different circumstances.

These observations are probably sufficient to show that the above argument in proof of the subterraneous eruption of dykes, is equally unsatisfactory in explaining the phenomena, and consequently equally untenable with the former. Both, therefore, must fall to the ground.

The wedge-like form of dykes might be adduced as another argument against their formation by subterraneous eruption; for it is not easy to conceive that a dyke in a state of fusion should, in its eruptive progress towards the surface of the earth, enlarge and become thicker.

The history of metallic veins furnishes us with stronger objections against Dr. Hutton's theory. If, according to this theory, metallic veins have been formed by the substances they contain being ignited in a state of fusion from the bowels of the earth, it will naturally follow, that the veins thus formed might be traced to the greatest depths, and even to the subterraneous furnace from which they issued. But we know that the fact is quite otherwise. The termination of many veins downwards has been discovered. Even the most powerful and productive have been unexpectedly cut off by the horizontal strata, and no vestige of them could ever be traced. This was the case with the rich vein of lead ore at Llangunog in Wales. It is the case also with many veins in their course downwards, to diminish gradually in form of a wedge, and then they are lost forever. Now, this certainly could never have happened, had they been formed by subterraneous eruption. Some trace of their progress, some mark of their course through the intersected strata, would still have remained. But no such indications, no such traces, are found. We must therefore conclude, that metallic veins have not been formed in this way, and that this theory, which appears to be so much at variance with facts, will not account in a satisfactory manner for their formation.

The masses of stone of the same species with the neighbouring superior strata, sometimes rounded and worn by the action of water, which are found at great depths in mineral veins, and organized substances, petrifications of vegetables and animals, present us with another objection to this theory, equally strong and insurmountable. These substances are the productions of the surface of the earth; and even supposing them to have existed in the bowels of the earth, it is conceivable that they should have retained their primitive form after they were subjected to so high a temperature as is necessary to hold metals in a state of fusion.

SECT. VII. Theory of Werner.

The latest, and perhaps most celebrated, theory that has yet appeared, is that of Professor Werner of Frey-Werlberg, with an account of which, and some observations on Mr Kirwan's opinions, we shall close this chapter.

We have said already, (No 1.) that the subject of which we are now treating is called by Werner geognosy, and his pupils are commonly called geognosts.

Werner is of opinion, that our knowledge is already sufficiently advanced to form a rational theory respecting the formation of the exterior crust of our globe; for he does not deny that we cannot reason with respect to what is below this, since we have no fact which can give us the least notion with respect to it. We are only certain that some part of our globe has been in a fluid state, as is proved by its spherical form. The crystalline form of granite and other rocky substances which constitute the base of that part of the earth with which we are acquainted, are, according to Werner, sufficient proofs that this part at least has been in a state of minute dilution. Again, the stratified appearance of most mountains and rocks shew that they are an accumulation of precipitates or sediments which have been deposited one over another. The numerous remains of marine animals which are found imbedded in many rocks, and of which some species are still found in our seas, allow us to believe that this solution was aqueous; that it was a vast ocean which has covered our globe to a very considerable height. The exterior part of the globe, then, has been entirely dissolved by the waters which surrounded it, and from this solution certain chemical precipitations took place, which have formed the crust that we now see.

In framing his theory, Werner professes to banish every thing that is hypothetical, and only to draw from general facts such immediate consequences as he believes it impossible not to deduce from them, and on these alone he founds his geognosy. The object of this theory, according to one of his disciples (the translator of his book on metallic veins), is to acquire a knowledge of the structure of the solid crust of the terraqueous globe, and the relative disposition of the materials which compose it; the means of doing this are to be derived from observation. Werner sets out with stating, that the chemical precipitates that took place from the chaotic fluid, did not form a regular surface, but that they collected here and there so as to produce the primitive mountains. These mountains he calls chaotic, because, says he, they have been formed during the period when the surface of the earth was a sort of chaos. After the retreat of the waters, these elevated parts were first discovered. They were exposed to the destructive action of the elements, and the shock of tides and torrents. The valleys were hollowed out, and the mountains acquired nearly the form in which we now see them.

Observation has shewn that the strata of which the earth is composed, may be divided into a certain number of congeries, each of which is composed of a certain tain set of minerals that are nearly the same in whatever part of the world the congeries is found. To these congeries Werner has given the name of formations, of which he distinguishes fix kinds or classes, four universal, being found all over the globe, and two partial, found only in particular districts. These formations he has arranged according to the order in which he conceives them to have been produced, beginning with that formation which lies next the solid nucleus of the earth, and which may therefore be conceived to be the oldest, and ending with the most superficial, which is considered as the newest formation.

The first of these classes is called by Werner that of primitive formations, which consist of a number of formations lying above each other, being those which are supposed the oldest, as in these no organic remains have been discovered. The substances constituting this class are granite, gneiss, micaceous schistus, argillaceous schistus, primitive limestone, primitive trap, fensite, and porphyry. Of these the granite is the lowest, and therefore is considered as the oldest; and next this follow the others in the order in which we have enumerated them, except that the primitive limestone, and primitive trap, are found in an uncertain order, alternating with gneiss, argillaceous schistus, or micaceous schistus; and are therefore considered as subordinate to these formations.

When the waters had subsided, and the summits of the primitive mountains had been uncovered, organized bodies were produced; and part of these being intercepted among the chemical precipitations which were still going on, and the mechanical precipitations which now began to take place, were carried with these to the flanks of the primitive mountains, and the valleys between them. Hence were produced a second series of formations, which are called by Werner transition formations, or rocks of transition, as he considered them to be deposited during the period when the earth was passing from an uninhabited to an inhabited state. Among these formations, however, the organic remains are but few. The substances composing this class, are transition limestone, gray wacke, gray wacke flate, transition trap, siliceous schistus. Of these the two last are subordinate, alternating with gray wacke and gray wacke flate.

The third formation is what Werner calls floetz formation, or that, in which the beds or strata lie nearly horizontal, appearing as if they had been deposited from water. This formation comprehends most of what are usually called secondary strata. It is divided by Werner into three subformations, named from the variety or situation of the sandstone, which forms a principal part of each; as, 1. Old red sandstone formation, composed of floetz limestone, old red sandstone, and foliated gypsum. 2. Second sandstone formation, composed of sandstone, floetz limestone, and fibrous gypsum.

3. Third sandstone formation, composed of sandstone, limestone, and chalk, &c. Of these, as before, the first mentioned is the oldest; and in this, somewhere near the gypsum, there is usually found salt or sulphur. In this formation, organic remains are first seen in any great quantities.

The fourth formation is called independent coal formation, because in this coal is first found, and because it is not universally spread over the earth as the three preceding, but is collected in insulated masses, independent of each other. This is also divided into three, each successively more recent than the preceding. The first series of strata consists of flate clay, limestone, marl, soft sandstone, greenstone, argillaceous ironstone, flate, and coal; the second of inundated clay, marl, limestone, porphyritic stone, and coal; and the third of loose sandstone, conglomerate, (a variety of sandstone), flate clay, and coal.

The fifth is called floetz trap formation, so called because the beds of which it is composed, consist of materials that are mostly of the nature of trap, or whin-rone. The substances that compose this formation are gravel, sandstone, siliceous sandstone, clay, wacke, basalt, greenstone, schistose porphyry, pitchstone, and graystone. Coal is also found in this formation, somewhere among the beds of siliceous sandstone, clay, wacke, and basalt, to which it is therefore considered as subordinate (F).

The sixth and last formation is the alluvial formation, or that which has arisen from the action of lakes and rivers, washing down part of the older strata. This is divided into two series of strata; the first being those that have arisen from the action of lakes newly drained, comprehending marl, sand, clay, and coal; and the second, those which have been produced from the action of rivers, comprehending mud, ironstone, sand, peat, &c. This formation is the most recent of any, but, like the fourth, it is only partial.

The above is an outline of Werner's geognosy, which is considered as an improvement of what is called the Neptunian theory, or that which explains geological appearances by the action of water, in opposition to what is called the volcanic theory, or that which attributes these appearances to an igneous origin.

One of the principal objections to the Neptunian theory is drawn from the insolubility in water of many of the substances which compose our globe; but this theory of the Neptunians endeavour to explain, by supposing that, at the very commencement of their existence these substances were in that state of minute division which aqueous solutions require, but which no known existing quantity would be able to effect, after the substances had acquired their utmost consolidation, as it is well known, that a solid substance may be kept in solution, at least for a short time, in a less quantity of fluid than was originally requisite to dissolve it.

(f) We may here notice Werner's opinion with respect to the formation and situation of basalt; as this is the only theory of importance respecting it, that has not been mentioned under the article Basaltes. "I am perfectly convinced (says Werner in a late memoir) that all the varieties of basalt have been produced in the humid way, and that they are of a very recent formation; that they formerly composed a great bed of immense extent, covering both the primitive and secondary strata; that time has anew destroyed a considerable part, and has left only the basaltic eminences which we now see." Vid. Jameson's Mineralogy of Dumfries, p. 184. A second objection is derived from the difficulty of supposing that these substances could have been consolidated below water, or that the water could completely shut up the pores of a body, to the entire exclusion of itself; so that had the mineral substances been consolidated as here supposed, the solvent ought either to remain within them in a liquid state, or, if evaporated, should have left the pores empty, and the body pervious to water.

Mr Playfair argues strenuously against the notion of these substances being precipitated from the chaotic fluid, which has been so ingeniously supported by Kirwan, who ascribes the solution of all substances in the chaotic fluid to their being finely pulverized, or created in a state of the most minute division; and the solvent being then insufficient in quantity, he supposes that, on that account, the precipitation took place the more rapidly.

"If, says Mr Playfair, he means by this to say, that a precipitation without solution would take place the sooner, the more inadequate the menstruum was to dissolve the whole, the proposition may be true, but will be of no use to explain the crystallization of minerals, the very object he has in view; because to crystallization it is not a bare subsidence of particles suspended in a fluid, but it is a passage from chemical solution to non-solution, or insolvability, that is required.

"If on the other hand he means to say, that the solution actually took place more quickly, and was more immediately followed by precipitation, because the quantity of the menstruum was insufficient, this is to assert that the weaker the cause, the more instantaneous will be its effect*."

Werner's theory of dykes and veins requires a more particular consideration.

This theory supposes, that the spaces which are now occupied by vertical strata, or dykes, including also metallic veins, were originally fissures, formed by the operation of different causes.

1. The unequal height and density of mountains, are considered as the most general causes of fissures. When the mountains were in a soft and humid state, that side which was least supported not only separated by its own weight, but the whole strata of the side gave way, and sunk below their former plain. This also seems to be the opinion of Saufure, with regard to the formation of fissures. It is not to be expected, that events of this kind should be of frequent occurrence, now that mountains have acquired sufficient firmness and stability to resist the force of gravity, operating in consequence of the inequality of weight and diversity of the materials of which they are composed. Instances, however, of the operation of such causes are not altogether wanting, even in modern times. After a season of excessive rains, in the year 1767, similar fissures were formed in mountains in Bohemia and Lusatia.

2. When the waters covered the surface of the earth, the unequal weight of the mountains was supported by their pressure; but when the waters retreated, this pressure was removed, the equilibrium was destroyed, the unsupported side of the mountain separated and sunk; and in this manner a fissure was formed.

3. The evaporation of the moisture, after the retreat of the waters, and the consequent diminution of bulk by contraction of the substances which enter into the composition of mountains, are also considered as the causes of fissures.

4. Fissures, too, derive their origin from other local and accidental causes, and especially from earthquakes. In the year 1783, when Calabria was afflicted with this most dreadful of all calamities which visit the earth, mountains were separated, exhibiting fissures similar to those which are now occupied by vertical strata.

The second part of the theory is employed in proving that the empty spaces, occasioned by the operation of one or other of the causes which have been enumerated, were filled from above; that the different substances, of which the vertical strata are composed, were held in solution by the waters which covered the earth; and that they were precipitated, by different chemical agents, according to the order of chemical affinity, and deposited in the places which they now occupy. In support of the opinion, that these fissures were filled from above, Werner adduces facts of angular and rounded fragments of stones of various species, and organized bodies, as marine shells and vegetables, having been found in vertical strata, at the immense depth of 150 and 200 fathoms. It may be doubted, on good grounds, whether this theory, supported by all the ingenuity and experience of its author, will account in a satisfactory manner, for that regularity of position and arrangement which are discovered in the vertical strata; for, notwithstanding the seeming disorder which a superficial vein may exhibit, they are not less regular and uniform than the horizontal strata. And when our researches are extended beyond the narrow bounds within which they are at present limited, when we are better acquainted with their relative positions and connexions, this uniformity and regularity will become more conspicuous. It may be doubted whether the fortuitous operation of such causes as have been stated, be equal to the effect of the formation of the vertical strata, as they now appear.

But, supposing that fissures were produced by some of the causes which have been mentioned, few of these causes could operate till the retreat of the waters left the mountains uncovered. It was only then that the mountains, by the inequality of height and density, being left unsupported, separated, and sunk from their former situation; it was then only that the process of evaporation could take place, succeeded by diminution of bulk and consequent contraction. In short, none of the causes which have been stated, could have any effect before the waters had retreated, excepting earthquakes; of the operation of which there is no proof previous to that period. The materials which compose the vertical strata, it is said, were formed by deposition from the waters which covered the mountains, holding them in solution. But before the fissures could be formed to receive these materials by precipitation and deposition, the waters had retired. A second delay must therefore have happened, from the waters of which the various substances which enter into the composition of vertical strata have been deposited. This the theory does not suppose to have taken place; and, without such a supposition, it seems to be attended with considerable difficulty. But another difficulty still remains. It does not appear how the peculiarity of Theories of structure, which was mentioned in our account of whin dykes, Sect. II. of the last chapter, can be accounted for by the principles of this theory. If it be granted, that the horizontal strata were formed in the humid way, the materials of which they are composed must have been precipitated from the waters which held them in solution, by the laws of chemical affinity. But the vertical strata are supposed to have been formed in the same manner, and according to the same process. Now, this being the case, What is the reason that the vertical strata should exhibit a peculiarity of structure and arrangement, different from the horizontal strata? Some of the whin dykes which have been already described, are very remarkable for this singular structure, especially those which assume the form of prismatic columns. These columns are in the horizontal position; and, excepting the latter circumstance, these dykes, in every respect, resemble a basaltic stratum, in which the columns are perpendicular.

More arguments might be adduced in opposition to the theory of Werner; but we must hafien to conclude this chapter, with mentioning a few of Mr Kirwan's peculiar opinions.

Among these, the manner in which he accounts for the unequal declivities of the fides of mountains, forms one of the most conspicuous objects; and to this we shall principally confine ourselves, and shall give it in his own words, as extracted from his essay on the declivities of mountains, to which we were obliged in the first section of Chap. II.

"To assign the causes of this almost universal allotment of unequal declivities to opposite points, and why the greatest are directed to the west and south, and the gentlest, on the contrary, to the east and north, it is necessary to consider,

"1. That all mountains were formed while covered with water.

"2. That the earth was universally covered with water at two different eras, that of the creation, and that of the Noachian deluge.

"3. That in the first era we must distinguish two different periods, that which preceded the appearance of dry land, and that which succeeded the creation of fish, but before the sea had been reduced nearly to its present level. During the former, the primeval mountains were formed; and during the latter, most of the secondary mountains and strata were formed.

"4. That all mountains extend either from east to west, or from north to south, or in some intermediate direction between these cardinal points, which need not be particularly mentioned here, as the same species of reasoning must be applied to them, as to those to whose aspect they approach most.

"These preliminary circumstances being noticed, we are next to observe that, during the first era, this vast mass of water moved in two general directions, at right angles with each other, the one from east to west, which needs not to be proved, being the course of tides which still continue, but were in that ocean necessarily stronger and higher than at present; the other from north to south, the water tending to these vast abysses then formed in the vicinity of the south pole, as shewn in my former essays. Before either motion could be propagated, a considerable time must have elapsed.

"Now the primeval mountains formed at the commencement of the first era, and before this double direction of the waters took place, must have opposed a considerable obstacle to the motion of that fluid in the sense that crossed that of the direction of these mountains. Thus the mountains that stretch from north to south must have opposed the motion of the waters from east to west; this opposition diminishing the motion of that fluid, disposed it to suffer the earthy particles with which in those early periods it must have been impregnated, to crystallize or be deposited on these eastern flanks, and particularly on those of the highest mountains, for over the lower it could easily pass; these depositions being incessantly repeated at heights gradually diminishing as the level of the waters gradually lowered, must have rendered the eastern declivities or fides, gentle, gradual, and moderate, while the western fides receiving no such accretions from depositions, must have remained steep and craggy.

"Again, the primeval mountains that run from east to west, by opposing a similar resistance to the course of the waters from north to south, must have occasioned similar depositions on the northern fides of these mountains, against which these waters impinged, and thus smoothed them.

"Where mountains intersect each other in an oblique direction, the north-east side of one range being continuous to the south-west flanks of another range, there the influx of adventitious particles on the north-east side of the one, must have frequently extended to the south-west side of the other, particularly if that influx were strong and copious; thus the Erzgebirge of Saxony, which run from west to east, have their north-east sides contiguous to the south-west side of the Riegengebirge that separate Silesia from Bohemia, and hence these latter are covered with the same beds of gneiss, &c. as the northern fides of the Saxon, and thereby are rendered smooth and gentle, comparatively to the opposite fide, which, being sheltered, remains steep and abrupt, which explains the seventh observation.

"The causes here assigned explain why the covering of adventitious strata on the highest mountains is generally thinnest at the greatest height, and thickest towards the foot of the mountain; for the bulk of the water that contained the adventitious particles being proportioned to its depth, and the mass of earthy particles with which it was charged being proportioned to the bulk of the water that contained them, it is plain, that as the height of water gradually decreased, the depositions from it on the higher parts of the mountains must have been less copious than on the lower, where they must have been often repeated.

"Hence, 2. granite mountains, generally the most ancient, frequently have their northern or eastern fides covered with strata of gneiss or micaceous schistus, and this often with argillite or primeval sandstone, or limestone, these being either of somewhat later formation, or longer suspensible in water.

"Hence, 3. different species of stone are often found at different heights of the same flank of a mountain, according as the water which conveyed these species, happened to be differently impregnated at different heights. During the first era its depositions formed the primitive stony masses; after which the creation of fish, limestone, sandstone, (puddingstone) and secondary argillites, in which pifcine remains are found, were deposit. Theories of ted. But during the second era, that of the Noahian deluge, by reason of the violence and irregularity of its aggreption, the depositions were more miscellaneous, and are found at the greatest heights; yet in general they may well be distinguished by the remains of land animals, or of vegetables, or of both, which they present in their strata (or at least by the imprestions of vegetables which they bear) as these must have been conveyed after the earth had been inhabited. But mountains regularly stratified bearing such remains, for instance the carboniferous, cannot be deemed to have been formed in a period so tumultuous. During this deluge the waters also held a different course, proceeding at first from south to north, and afterwards in both opposite directions, as shewn in treating of that catastrophe in my second essay.

"Hence, and from various contingent local causes, as partial inundations, earthquakes, volcanoes, the erosion of rivers, the elaption of strata, disintegration, the disruption of the lofty mounds by which many lakes were anciently hemmed in, several changes were produced in particular countries, that may at first sight appear, though in reality they are not, exceptions to the operations of the general causes already stated.

"Thus the mountains of Kamtchatka had their eastern flanks torn and rendered abrupt by the irruption of the general deluge, probably accompanied by earthquakes. And thus the Meissen had its east and north flanks undermined by the river Warre, as Werner has shewn; thus the eighth and sixteenth observations are accounted for, as is the thirteenth by the vast inundations so frequent in this country, (1. Pallas, p. 172.), which undermined or corroded its east side, while the western were smoothed by the calcareous depositions from the numerous rivers in its vicinity.

"Hence, 4. we see why on different sides of lofty mountains different species of stones are found, as Pallas and Sauflure have observed (2. Sauff. § 981.), a circumstance which Sauflure imagined almost inexplicable, but which Dolomieu has since happily explained, by showing that the current which conveyed the calcareous substances to the northern, eastern, and north-eastern sides of the Alps, for instance, was stopped by the height of these mountains, and thus prevented from conveying them to the southern sides, and thus the north-eastern sides were rendered more gentle than the opposite, (3. New Rox. p. 423.), conformably to the theory here given.

"Hence, 5. where several lofty ridges run parallel to each other, it must frequently happen that the external should intercept the depositions that do not surround them, and thus leave the internal ridges steep on both sides.

"Hence, 6. low granitic or other primitive hills are frequently uncovered by adventitious strata on all sides, as at Phanet in the county of Donegal, or are covered on all sides; the impregnated waters either easily pafling over them, or stagnating upon them, according to the greater or less rapidity of its course, and the obstacles it met with."

Mr Kirwan's theory of the formation of whin dykes, is as follows.

He supposes that the dyke existed in the spot where it is found previous to the formation of the horizontal strata; that, during the formation of the latter by de-

position, their equal extension on each side of the dyke was obstructed by its height preventing the passage of the current of waters; that the strata on that side of the dyke which were first formed, occasioned a much more considerable prelure than on the side on which the strata of latter formation repose, and must have pulled the upper and more moveable extremity of the lip gradually towards the side on which there was least prelure; on that side it must therefore overhang: this prelure being of earlier date than on the opposite side, must have had a more considerable effect in depressing each particular stratum, and forcing their integrant particles into closer contact, than could have been produced in those of later formation; and consequently the strata must be lower. The ingenious author has added, with good reason, that he is not satisfied with this explanation. It is undoubtedly quite incompatible with the phenomena which it attempts to explain. For it has been already observed, that the coal and contiguous strata are, in every respect, the same on both sides of a dyke, to whatever distance they may have been elevated or depressed, which demonstrates clearly, that their formation must have been coeval. But, besides, the same derangement takes place in a slip where there is merely a solution of contiguity of the horizontal strata, one side being only elevated or depressed above or below the corresponding side from which it has been detached without having a vertical stratum or dyke interposed.

Chap. IV. Of Earthquakes and Volcanoes.

In the preceding chapters we have given a short account of the materials which constitute the globe of the earth; we have taken a view of the relative position and connexion which subsist among these materials, so far as they are known, and we have considered some of the changes which are supposed to have taken place in their arrangement and distribution, and some of the theories which have been propounded to account for these changes. We have hitherto contemplated nature in a state of seeming repose, conducting her operations by a gradual and silent process, and accomplishing the most beneficial and wonderful effects, unheeded and unobserved. We are now to take a view of those more terrible and sudden changes which are exhibited in the devastation and ruin which accompany the earthquake and the volcano;—changes awful in the contemplation, but dreadful and terrible in their tremendous effects.

Many of the phenomena which accompany earthquakes and volcanoes, are common to both. Earthquakes are frequently the forerunners, and sometimes the attendants, of volcanic eruptions; but earthquakes have often existed, and their terrible effects have been feverely felt, where no volcano was ever known.

In the present chapter, we propose to consider the phenomena, history, and causes of earthquakes and volcanoes, which will form the subjects of the two following sections. In the first we shall treat of earthquakes, and in the second of volcanoes.

Sect. I. Of the Phenomena and History of Earthquakes.

Earthquakes have been felt in most countries of the world. There are, however, particular places where earthquakes prevail. which seem to be more subject to this dreadful calamity than others; and this does not seem to depend on any local circumstances, with regard to particular regions of the earth. It may be observed in general, that earthquakes are more frequent within the tropics; but there are places within the torrid zone, which are more rarely visited by earthquakes than some of the more temperate, or even the colder regions of the earth. In the islands of the West Indies, and in some parts of the American continent which lie between the tropics, the earthquake is more frequently felt than in most other regions of the earth. But the northern shores of the Mediterranean, the kingdom of Portugal, and some other places without the tropics, have been oftener the scene of desolation, by the effects of the earthquake, than many of the islands and extensive continents within the torrid zone. From this circumstance in the history of earthquakes, it would appear that they are not limited to particular regions, on account of proximity to the equator or distance from it, on account of insular situation or extent of continent. Particular islands, however, and particular parts of continents, have undoubtedly been oftener visited by earthquakes than others. Of all the islands of the West Indies, Jamaica has most frequently experienced their dreadful effects. Indeed, scarcely a year passes, without several shocks of an earthquake being felt in that island. Mexico and Peru in South America, are more subject to earthquakes than the other regions of the American continent. Portugal has been often shaken to the very foundations, by terrible earthquakes, while Spain, immediately adjoining, or it may be said, including it, is, comparatively, almost exempted from their effects. It has been observed, that earthquakes have been less destructive in Italy than in Sicily, which are in the immediate vicinity of each other, and are both volcanic countries.

Observations on phenomena so awful and terrible, can scarcely be expected to be very numerous. The operation of the causes which produce them is too rapid, the effects are too sudden and unexpected, to be rendered the subject of accurate or attentive philosophical investigation; or, perhaps, we might acknowledge at once, that they are too extensive and too obscure for the powers of man. They are beyond the grasp of the human mind.

It has been already observed, that earthquakes are more frequent in volcanic countries than in any others. In these regions they are oftener dreaded and expected than in other places. Where a volcano exists, and when it has ceased to throw out flame and smoke for any long period, shocks of earthquakes begin to be dreaded. This has been very generally the case with the principal volcanoes of the world, the events of whose history have been recorded. An earthquake is often the forerunner of an eruption, and the very first warning of its approach.

Earthquakes are often preceded by long droughts. The earthquake, however, does not immediately succeed the cessation of the drought, or the fall of rain. Some electrical appearances are observed to take place in the air, before the earthquake comes on. The aurora borealis is frequent and brilliant, and bright meteors are often seen darting from one region of the heavens to another, or from the atmosphere to the earth.

Before the shock comes on, the waters of the ocean appear to be unusually troubled; without the effect of wind, or any perceptible cause, it swells up with great noise. Fountains and springs are also greatly disturbed, and their waters are agitated, and become muddy. The air at the time of the shock has been observed to be remarkably calm and serene, but afterwards it becomes dark and cloudy.

The noise which accompanies the shock of an earthquake is sometimes like that of a number of carriages, driving along the pavement of a street with great rapidity. Sometimes it is like a rushing noise, similar to that of wind, and sometimes it resembles the explosions occasioned by the firing of artillery. The noise which accompanied the earthquake, which was pretty generally felt over Scotland about three years ago, we recollect, resembled that of a heavy person walking rapidly, and barefooted, through an adjoining room.

The effect of earthquakes on the surface of the earth is various. Sometimes it is instantaneously heaved up in a perpendicular direction; and sometimes assumes a kind of rolling motion, from side to side. Sometimes the shock commences with the perpendicular motion, and terminates with the other.

Great openings or fissures are made in the earth by the shock, and these in general throw out vast quantities of water, but sometimes smoke and flame are also emitted. Flame and smoke are often seen issuing through the surface of the earth, even where no chasm or fissure has been produced.

The effects of an earthquake on the ocean are not less terrible than those on land. The sea swells up to a great height; its waters sometimes seem to be entirely separated, and from the place of separation, currents of air, smoke, and flame, are discharged. Similar effects have been observed to take place in lakes, ponds, and rivers. Their waters are thrown into great agitation, and are sometimes swelled up. Places in which there was a considerable body of water, have become dry land, and dry land has been converted into an extensive lake by the shock of an earthquake.

The most terrible earthquake that has yet visited the earth, has never been felt over its whole surface. Their effects, however, extend to very distant regions, from the centre or principal scene of desolation. The existence of an earthquake is indicated much more extensively by water than by land. Where its effects have not been at all perceived on dry land, the agitation produced on the waters in the ocean, or in lakes and rivers, has been often communicated to a very great distance.

The duration of the shock of an earthquake rarely exceeds a minute, and perhaps very few continue for near that length of time. But the shocks are sometimes repeated in rapid succession; and perhaps from the effect on the fenées, and the dread and alarm which are, thus occasioned, it is supposed that their duration is much longer than it really is.

But as no general account of the phenomena which accompany an earthquake, from the difficulty or scantiness of observation, can be complete, it will be rendered much more intelligible and interesting, if we enter a little little more into the detail of the history of particular earthquakes; and in the account of some of them which we propose to lay before our readers, it will be found that most of the appearances and effects which have been enumerated, were observed.

The first earthquake, the history of which we shall now detail, happened in Calabria, in the year 1638. This earthquake is rather to be considered as an exception to what was said with regard to their not taking place in the neighbourhood of a volcano, soon after an eruption. The volcanoes in that vicinity had experienced violent eruptions a very short time before. Five years before, there had been an eruption of Mount Vesuvius, and two years only had elapsed from the time that a similar event had befallen Etna. This mountain, indeed, at the very time, threw out a great body of smoke, which seemed to cover the whole island, and entirely concealed the shores from view. The air over the sea at a little distance was calm and serene, and the surface of the water was perfectly smooth. Seemingly without any cause, it began to be slightly agitated, as happens to the surface of water in a heavy shower of rain. A dreadful noise succeeded, and the smell of sulphureous vapours was perceived. The noise, like the rattling of chariots, grew more frequent and loud, and the shock at last was terribly felt, when the earth was heaved up, or rolled in the form of waves.

This earthquake is particularly described by the celebrated father Kircher. "On the 24th of March, (says he), we departed in a small boat from the harbour of Messina in Sicily, and the same day arrived at the promontory of Pelorus. Our destination was for the city of Euphemia in Calabria, but unfavourable weather obliged us to remain at Pelorus three days. Weary at length with delay, we determined to proceed on our voyage, and although the sea seemed unusually agitated, yet it did not deter us from embarking. As we approached the gulf of Charybdis, the waters seemed whirled round with such violence, as to form a large hollow in the centre of the vortex. Turning my eyes to Mount Etna, I saw it throw out huge volumes of smoke, which entirely covered the island. This awful appearance, with the dreadful noise, and the sulphureous smell which accompanied it, filled me with strong apprehensions that some terrible calamity was approaching. The sea itself exhibited a very unusual appearance, its agitation resembling that of the waters of a lake which is covered with bubbles in a violent shower of rain. My surprise was still increased by the calmness and serenity of the weather; not a breeze stirred, not a cloud obscured the face of the sky, which might be supposed to produce these dreadful commotions. I therefore warned my companions, that the unusual phenomena which we observed, were the forerunners of an earthquake. Soon after we stood in for the shore, and landed at Tropæa; but we had scarcely arrived at the Jesuits college in that city, when a horrid sound, which resembled the rattling wheels of an infinite number of chariots, driven furiously along, stunned our ears. Soon after a terrible shaking of the earth began; the ground on which we stood seemed to vibrate, as if we were in the scale of a balance, which continued waving. The motion soon grew more violent; I could no longer keep my legs, but was thrown prostrate upon the ground. After some time had elapsed, when I had recovered from the conflagration; and finding that I was unhurt amidst the general crash, I resolved to make the best of my way to a place of safety, and running as fast as I could, I reached the shore. I soon found the boat in which I had landed, as well as my companions; and leaving this scene of desolation, we prosecuted our voyage along the coast. Next day we arrived at Rochetta, where we landed, although the earth still continued in violent commotion. But we had scarcely reached the inn when we were again obliged to return to the boat. In about half an hour we saw the greatest part of the town, as well as the inn where we had stopped, levelled with the ground, and most of the inhabitants buried in its ruins. As we proceeded onward, we landed at Lopezium, which is a cattic about half way between Tropæa and Euphemia, to which we were bound; and here, wherever I looked, nothing but scenes of ruin and horror presented themselves. Towns and castles were levelled with the ground, and Stromboli at the distance of 60 miles threw out an immense body of flames, accompanied with a noise which could be distinctly heard. But our attention was quickly drawn from more remote to present danger. The rattling sound which immediately precedes an earthquake, again alarmed us; every moment it seemed to grow louder and louder, and to approach nearer the place on which we stood. A dreadful shaking of the earth now began, so that being unable to stand, my companions and I caught hold of whatever shrub was next to us, to support ourselves. After some time the violent commotion ceased, and we stood up, and proposed to prosecute our voyage to Euphemia, which lay within sight; but in the meantime, while we were preparing ourselves, I turned my eyes towards the city, but could see nothing but a thick, black cloud, which seemed to rest on the place. This appeared an extraordinary circumstance, as the sky all round was calm and serene. We waited till the cloud passed away, and then turning to look for the city, it was totally sunk, and where it formerly stood, nothing remained but a dismal and putrid lake."

In the year 1693, an earthquake happened in Sicily, in which not only shook the whole island, but also reached Naples and Malta. Previous to the shock, a black cloud was seen hovering over the city of Catania, which was destroyed at this time. The sea began to be violently agitated; the shocks succeeded like the discharge of a great number of artillery; the motion of the earth was so violent, that no persons could keep their legs. Even those who lay on the ground were tossed from side to side, as on a rolling billow; high walls were razed from their foundations, and were thrown to the distance of several paces. Almost every building in the countries which it visited was thrown down; 54 cities and towns, besides a great number of villages, were either greatly damaged, or totally destroyed. Among those which we have already mentioned, was the city of Catania, one of the most ancient and flourishing in the kingdom. After the thick cloud which remained after the earthquake had diffused, no remains of this magnificent city could be seen. Of 18,000 inhabitants, not fewer than 18,000 perished by this dreadful calamity.

The terrible earthquake which visited the island of Jamaica in 1692, affords us another example of almost in 1692. the whole of the phenomena which were enumerated as the forerunners or attendants of earthquakes. It was on the 7th of June, in that year, that this dreadful calamity, which in two minutes totally destroyed the town of Port Royal, on the south side of Jamaica, and at that time the capital of the island, took place. The effect of the shock on the surface was immediately preceded by a hollow rattling noise, like that of thunder. The streets were heaved up like waves of the sea, and then instantly thrown down into deep pits. All the wells discharged their waters with prodigious agitation; the sea burst its bounds, and deluged a small part of the town which was not entirely overwhelmed. The fissures produced in the earth were so great, that one of the streets seemed twice as broad as formerly, and in some places the earth opened and closed again for some time. A great many of these openings were seen at once. In some of them, the houses and inhabitants, and every thing that was near, were swallowed up. Some persons were swallowed up in one of these chasms, and what will appear most extraordinary, and indeed almost incredible, were thrown out alive from another. Whole streets sunk in some, and from others an immense body of water was projected high into the air. Smells which were extremely offensive now succeeded; nothing but the distant noise of falling mountains was heard, and the sky, which before the shock was still and serene, assumed a dull red colour.

The effects of this earthquake were not limited to this spot. It was severely felt through the whole island, which in many places sustained very material damage. Indeed there were few houses which were not either injured or thrown down. In some places the inhabitants, houses, trees, and whole surface, were swallowed up in the same chasm; and what was formerly dry land was left a pool of water. The wells in almost every corner of the island, whatever was their depth, threw out their water with great violence. The rivers were either entirely stopped, or ceased to flow for 24 hours; and many of them formed to themselves new channels. At the distance of 12 miles from the sea, an immense body of water spouted out from a gap which was formed in the earth, and was projected to a great height in the air. Such was the violence of the shock, that many persons were thrown down on their faces, even in places where the surface of the ground remained unbroken. It was observed that the shock was most severely felt in the immediate vicinity of the mountains. Could this arise from the greater preasure, and consequently the greater resistance, or was it because the force which produced these terrible effects existed near them?

After the great shock which destroyed the town of Port Royal, the inhabitants who escaped went on board ships in the harbour, where many of them remained for two months, during which time the shocks were repeated, and were so frequent, that there were sometimes two or three in the course of an hour. These were still accompanied with the same rattling noise, like that of thunder, or like the rushing noise occasioned by a current of air in rapid motion. They were also attended with what are called brimstone blasts. These, it is probable, were sulphureous vapours which issued from the openings made by the earthquake. The atmosphere, however, seemed to be loaded with noisome vapours, for a very general sickness soon succeeded, which in a short time swept off not fewer than 3000 persons.

But of all the earthquakes, the history of which is on record, that which happened at Lisbon, in the year 1755, was by far the most extensive in its effects, and, at Lisbon from its recent occurrence, will probably be deemed the most interesting. In the year 1759, several shocks of earthquakes had been sensibly felt. The four following years were remarkable for excessive drought. The springs which formerly yielded abundance of water, were totally dried up and lost; the winds which chiefly prevailed were from the north and north-east. During this period also there were slight tremors of the earth; the seasons in 1755, were unusually wet, and the summer, as the consequence of this, proved unusually cold. But for the space of 40 days before the earthquake happened, the sky was more clear and serene. On the last day of October the face of the sun was considerably obscured, and a general gloom prevailed over the atmosphere. The day following (the 1st of November) a thick fog arose, but it was soon dissipated by the heat of the sun. Not a breath of wind was stirring; the sea was perfectly calm, and the heat of the weather was equal to that of June or July in this country. At 35 minutes after nine in the morning, without any previous warning, excepting the rattling noise resembling that of distant thunder, the earthquake came on with short, quick vibrations, and shook the very foundation of the city, so that many of the houses instantly fell. A pause, which was indeed just perceptible, succeeded, and the motion changed. The houses were then tossed from side to side, like the motion of a wagon driven violently over rugged stones. It was this second shock which laid great part of the city in ruin, and, as might be expected, great numbers of the inhabitants were destroyed at the same time. The whole duration of the earthquake did not exceed six minutes. When it began, some persons in a boat, at the distance of a mile from the city, and in deep water, thought the boat had struck on a rock, in consequence of the motion which was communicated to it. At the same time they perceived the houses falling on both sides of the river. The bed of the Tagus was in many places raised to the very surface of the water; ships were driven from their anchors or moorings, and were tossed about with great violence; and the persons on board did not for some time know whether they were afloat or aground. A large new pier with several hundreds of people upon it, sunk to an unfathomable depth, and not one of the dead bodies was ever found. The bar of the river was at one time seen dry from side to side; but suddenly the sea came rolling in like a mountain, and in one part of the river the water rose in an instant to the extraordinary height of 50 feet. At noon another shock happened; the walls of some houses that remained were seen to open from top to bottom, near a foot wide, and were afterwards so exactly cloed, that scarcely any mark of this injury remained.

But what was the most singular circumstance attending this earthquake was, the prodigious extent to which its effects reached. At Colares, 20 miles from Lisbon, and two miles from the sea, the weather was uncommonly warm for the season, on the last day of October. About four o'clock in the afternoon, a fog arose which, proceeding proceeding from the sea, covered the valleys. This was an unusual occurrence at that season of the year; but soon after the wind shifting, the fog returned to the sea, collected over its surface, and became very thick and dark; and as the fog dispersed, the sea was violently agitated, and with great noise. On the first of November, at the dawn of day, the sky was fair and serene; about nine o'clock the sun was overclouded, and became dim. Half an hour after, the rattling noise like that of chariots was heard; and this soon increased to such a degree, that it resembled the explosions of the largest artillery. The shock of an earthquake was immediately felt, and was quickly succeeded by a second and a third. In these shocks it was observed, that the walls of buildings moved from east to west. From some of the mountains flames were seen issuing, somewhat resembling the kindling of charcoal accompanied with a great deal of thick black smoke. The smoke which arose from one mountain was at the same time accompanied with noise, which increased with the quantity of smoke. When the place from which the smoke issued was afterwards examined, no signs of fire could be perceived.

At Oporto, near the mouth of the river Douro, the earthquake began at 40 minutes past nine. The sky was quite serene when the hollow rattling noise was heard, and it was immediately attended with a commotion of the earth. In the space of a minute or two, the river rose and fell five or six feet, and continued this motion for four hours. In some places it seemed to open, and discharge great quantities of air. The sea was also violently agitated, and indeed the agitation was so great, to the distance of a league beyond the bar, that it was supposed the discharge of air from that place must also have been very considerable.

St Ubes, a sea-port town twenty miles south of Lisbon, was entirely swallowed up by the repeated shocks of this earthquake, and the immense surf of the sea which was produced. Large masses of rock were detached from the promontory at the extremity of the town. This promontory consists of a chain of mountains composed of a very hard stone.

The same earthquake was felt in almost every part of Spain. The only places which escaped from its effects were the provinces of Arragon, Catalonia, and Valencia. At Ayamonte, which is near the place where the Guadiana falls into the bay of Cadiz, the earthquake was not felt till a little before ten o'clock. It was here also preceded by the hollow rattling noise. The shocks continued with intervals, for 14 or 15 minutes, and did very considerable damage. Searcely half an hour had elapsed from the time that the commotion first began, when the sea, the river, and canals, rose violently over their banks, and laid every place near them under water. The sea rolled in in huge mountains, and carried everything before it.

The earthquake began at Cadiz some minutes after nine in the morning, and lasted about five minutes. The water in the cisterns under ground was so much agitated, that it rose in the form of froth. About ten minutes after eleven, a huge wave was seen coming from the sea, at the distance of eight miles, which was supposed not to be less than 60 feet high, and burst in upon the city. The water returned with the same violence with which it approached, and places which were deep at low water were left quite dry. Similar waves continued, but gradually lessening till the evening.

The earthquake was not felt at Gibraltar till after ten o'clock. There it began with a tremulous motion of the earth, which continued for about half a minute. A violent shock then followed; the tremulous motion again commenced, and continued for five or fix seconds, and then succeeded a second shock, but less violent than the first. The whole time did not exceed two minutes; the earth had an undulating motion; some of the guns on the batteries were seen to rise, and others to sink. Many people, seized with sickness and giddiness, fell down. Some who were walking or riding, felt no shock, but were attacked with sickness. The sea had an extraordinary flux and reflux; it ebbed and flowed every 15 minutes; it rose fix feet, and then fell suddenly so low, that a great many fish and small boats were left on the shore.

The shock was felt at Madrid nearly at the same time as at Gibraltar. It continued for fix minutes, and the same sickness and giddiness prevailed. It was not felt by those who walked quietly, or who were in carriages, and no accident happened excepting two persons who were killed by the fall of a stone eros from the porch of a church.

Malaga, a sea-port town on the Mediterranean, experienced a violent shock; the bells were set a ringing in the steeples, and the water of the wells overflowed, and as suddenly retired. St Lucar, at the mouth of the Guadalquivir, suffered much from a similar shock, as well as from an inundation of the sea, which broke in, and did great damage. At Seville, 16 leagues above this, a number of houses was thrown down; the celebrated tower of the cathedral, called La Giralda, opened in the four sides; the waters were thrown into violent agitation, and the vessels in the river were driven on shore.

In Africa this earthquake was felt nearly as severely as in Europe. Great part of the city of Algiers was destroyed. This happened about ten in the morning. About the same time at Arzila, a town in the kingdom of Fez, the sea suddenly rose with such impetuosity, that it lifted up a vessel in the bay, and forced it on shore with such violence that it was broken to pieces. A boat was also found within land, at the distance of two musket shots from the sea. At Fez and Mequinez, many houses were thrown down, and numbers of persons were buried in the ruins.

Many people were destroyed at Morocco by the falling of houses. Eight leagues from the city the earth opened, and swallowed up a village with all its inhabitants, to the number of 8,000 or 10,000, as well as all their cattle. Soon after the earth closed, and they were seen no more. The town of Sallee also suffered greatly; a third part of the houses were thrown down; the waters rushed into the streets with great violence, and when they retired, they left behind them a large quantity of fish. The earthquake began at Tangier at ten in the morning; its whole duration was about ten or twelve minutes. The sea came up to the walls with great violence, and retired immediately with the same rapidity, leaving behind a great quantity of fish. This agitation of the water was repeated no less than 18 times, and continued till about fix o'clock in the evening. It began at the same time at Tetuan, but its du- ration was only about seven or eight minutes. Three of the shocks were so violent as to excite great apprehensions that the city would be destroyed. Similar effects were produced by the same earthquake at different places along the African shore of the Mediterranean.

At the town of Funchal in Madeira, the first shock of this earthquake was felt at 38 minutes past nine. It was preceded by the rattling noise, which seemed to be produced in the air; the shock, it was supposed, continued for more than a minute; the earth moved with a vibratory, undulating motion, and some of the vibrations increased greatly in force. The noise in the air which accompanied the shocks, lasted some seconds after the motion of the earth had ceased. At three quarters past eleven, the day being calm and serene, the sea retired suddenly, then, without the least noise, rose with a great swell, overflowed the shore, and entered the city. It rose 15 feet perpendicular above high-water mark. Having thus fluctuated four or five times, it at last subsided, and resumed its former stillness. In the northern part of the island, the inundation was still more violent. It first retired to the distance of 100 paces, and suddenly returning, overflowed the shore, broke down walls of magazines and store-houses, and left behind it great quantities of fish in the streets of a village. At this place the sea rose only once beyond the high-water mark, although it continued to fluctuate much longer before it entirely subsided than at Funchal.

Such were the effects of this earthquake, in those places where it was accompanied with considerable damage. It was, however, perceptibly felt to a great distance in every direction, either by a slight motion of the earth, or by the agitation of the waters. At the island of Antigua the sea rose to such a height as had never been before known, and afterwards the water at the wharfs which used to be six feet deep, was not more than two inches. About two in the afternoon, the sea ebbed and flowed at Barbadoes in a very unusual manner. It overflowed the wharfs, and rushed into the streets. This flux and reflux continued till 10 at night.

Shocks were distinctly felt in different parts of France, as at Bayonne, Bourdeaux, and Lyons. The waters were also observed to be agitated in different places, as at Angouleme, and Havre de Grace, but with a less degree of violence than some which have been mentioned. At Angouleme, a subterraneous noise like thunder was heard, and soon after a torrent of water, mixed with red sand, was discharged from an opening in the earth. Most of the springs in the neighbourhood sank, and continued dry for some time.

The effects of this earthquake were also very perceptible in many places of Germany. Throughout the duchy of Holstein, the waters were greatly agitated, particularly the Elbe and Trave. The water of a lake, called Lihsee, in Brandenburg, ebbed and flowed six times in half an hour, and although the weather was then perfectly calm, this motion was accompanied with a great noise. A similar agitation took place in the waters of the lakes called Mypelgulf and Neeso, but here there was also emitted a most offensive smell.

The sea was greatly agitated round the island of Corsica, and many of the rivers of the island overflowed their banks. The same earthquake was felt in the city of Milan in Italy, and its neighbourhood. Turin in Savoy experienced a very smart shock.

Many of the rivers of Switzerland became all at once muddy, although there had been no rain. The lake of Neuchatel rose to the height of two feet above its usual level, and continued at this height for a few hours. The waters of the lake of Zurich were also greatly agitated.

The commotion of the waters in Holland was still more remarkable. In the afternoon of the 1st of November, the waters of the Rhine at Alphen, between Leyden and Woerden, were so violently agitated, that the buoys were broken from their chains, large vessels parted from their cables, and smaller ones were thrown upon the dry land. At 11 in the forenoon at Amsterdam, when the air was perfectly calm, the waters in the canals were thrown into great commotion, so that boats broke loose from their moorings, chandeliers were observed to vibrate in the churches, although it is said no motion of the earth was perceptible. In the forenoon, at Haarlem, not only the water in the rivers, canals, &c. but, it is asserted, smaller quantities of fluids contained in vessels, were greatly agitated, and sometimes dashed over the sides of the vessels. This continued for about four minutes. Between 10 and 11 in the forenoon, in some of the canals at Leyden, the waters rose suddenly, and produced very perceptible undulations.

The effects of this earthquake extended as far north as Norway and Sweden: many of the rivers and lakes in Norway were greatly agitated; shocks were felt in several of the provinces in Sweden, and commotions of the waters, with the rivers and lakes, especially in Dalecarlia, were observed. The river Dala suddenly overflowed its banks, and as suddenly retired; and at the same time, a lake which is a league distant from it, bubbled up with great violence. Several smart shocks were felt at Fahlun, a town in Dalecarlia.

In many places of Great Britain and Ireland, the agitation of the waters was very perceptible. At Eaton bridge in Kent, near a pond of an acre in extent, some persons heard a sudden noise, which they supposed was occasioned by something falling into the pond, for it was then a dead calm, and ran to the spot, where they saw the pond open in the middle, while the water dashed over a perpendicular bank two feet high. This motion was repeated several times, and still accompanied with a great noise.

At Cobham in Surrey, between 10 and 11 o'clock A.M. a person was watering a horse at a pond, the waters of which were derived from springs. At the moment the animal was drinking, the waters retired from his mouth, and left the bottom of the pond dry. It then returned with great violence, and when it retired, its progress was towards the south. About the same time at Bulbridge, in the same county, while the weather was remarkably calm, the waters of a canal 700 feet long and 38 broad, were greatly agitated, and this was accompanied with an unusual noise. The waters rose between two and three feet above the usual level, in the form of a heap or ridge, extending 30 yards in length. This ridge then heeled towards the north side, and flowed with great impetuosity over the grass walk; it then returned to the canal, again heaped up in the middle, and then heeled to the south side with with still greater violence, flowing over the grass walk, and leaving several feet at the bottom of the canal on the north side perfectly dry. These motions continued for 15 minutes, after which the waters resumed their former tranquillity. During the agitation of the waters, the sand and mud at the bottom were thrown up, and mixed with them.

In Suffolk, the water of a pond at Dunfalt rose gradually for several minutes in the form of a pyramid, and then fell down like a water-fount. In other ponds in the same neighbourhood, the waters of which were less agitated, there was a smooth flux and reflux from the one extremity to the other.

At Earlycourt in Berkshire, about 11 o'clock, a person standing near a fish pond, felt a violent trembling of the earth, which continued for about a minute. He observed immediately after, the water move from the south to the north end of the pond, leaving the bottom of the fourth end quite dry, to the extent of five feet. It then returned, flowed at the fourth end, rose three feet up the bank, and immediately after returned to the north bank, where it rose to the same height. Between the flux and reflux the waters formed a ridge in the middle of the pond, 20 inches higher than the level on each side, and boiled up with great violence.

Similar phenomena were observed about half after ten, near Durham. A person was alarmed with a sudden rushing noise, which seemed to proceed from a pond. The water rose gradually up without any fluctuating motion, stood some inches higher than the usual level; it then subsided and swelled again, and continued in this manner rising and falling for the space of six or seven minutes, rising four or five times in a minute.

The effects of this earthquake in Derbyshire excited considerable alarm. At Barlborough, between 11 and 12 o'clock, in a boat-house on the west side of a large body of water, called Pibley dam, which is supposed to cover not less than 30 acres of land, there was heard a sudden and terrible noise; a swell of water proceeding from the south, rose two feet on the flope dam head at the north end. It then subsided, but immediately returned. The water continued thus agitated for 45 minutes, but became gradually less violent. At Eyam bridge in the Peak, an overseer of the lead mines, fitting in his room about 11 o'clock, felt a sudden shock, by which the chair on which he sat was suddenly raised, and some pieces of plaster were broken off from the sides of the room. The commotion was so great that he thought the engine shaft had fallen together, and he ran out to see what was the matter, and found every thing in safety. Some miners employed at the time in a drift 120 yards deep, were greatly alarmed first with one shock, and then with a second, which seemed to be so violent as to make the rocks grind upon one another. Three other shocks succeeded the two first at intervals of a few minutes, and became gradually weaker.

A little after 10 o'clock in the morning, the water in a moat which surrounds Shireburn castle in Oxfordshire, exhibited a very unusual appearance. A thick fog prevailed, the air was perfectly still, and the surface of the water quite smooth. At one corner it was observed to flow towards the shore, and then again to retire; and this flux and reflux continued for some time quite regular. Every flux began slowly; but increased in its velocity till near its full height, when it rushed with great impetuosity; and having remained for a short time stationary, it then retired, at first slowly, but at last it sunk with great rapidity. What will appear most singular in this commotion of the water is, that it was limited to one part of the moat. At a different corner about 25 yards distant no motion could be perceived. But in that part of the moat directly opposite to the place where the motion of the water was first observed, the water rose towards the shore at the same time as at the other side. In a pond at a little distance the waters were agitated in a similar manner, but the risings and sinkings took place at different times from those in the moat.

On the evening of the same day, about three quarters after fix, and about the time of two hours ebb of the tide, at White rock in Glamorganshire, a great body of water rushed up accompanied with great noise. It was in such quantity that it floated two vessels not less than 200 tons burden each, drove them from their moorings, and carried them across the river. The whole length of time of the rise and fall of this body of water did not exceed 10 minutes, so that it seemed to have burst from the earth at the spot where it appeared. It seems singular, if the account of it be correct, that on this spot the effects of the earthquake should be felt at the distance of seven or eight hours from the time it was felt in other parts of the island.

The waters of the lakes in Scotland were also greatly agitated from the same cause. Half an hour after nine in the morning, without the least breath of wind, the water in Loch Lomond rose suddenly and violently against its banks. It immediately fell very low, again returned to the shore, and in five minutes rose as high as at first. This commotion continued till 15 minutes after 10, with an alternate flux and reflux every five minutes. From this time, till 11 o'clock, the height to which the water rose gradually diminished, till it returned its former tranquillity. But each flux and reflux continued for a period of five minutes as at first. Here the violence of the shock was such, that a large stone lying at some distance from the shore in shallow water, was moved from its place and carried to dry land, leaving a deep furrow in the ground along which it had moved.

About the same time the waters of Loch Ness in the north of Scotland exhibited also a very unusual agitation. About ten o'clock the river Oich, which falls into the head of the loch, swelled very much, and ran upwards from the loch with a high wave two or three feet above its usual level. The motion of the wave was in a direction contrary to that of the wind, and it proceeded with great rapidity up the river for the space of 200 yards, broke on a shallow, and overflowed the banks. It then returned gently to the loch. This ebbing and flowing continued for about an hour, the height of the waves gradually diminishing, till, about 11 o'clock, a wave higher than any of the former broke with such violence on the bank on the side of the river, that it ran upwards of 30 feet from the bank.

Between two and three o'clock in the afternoon, at Kinfaile in Ireland, when the weather was perfectly calm, and the tide nearly full, a great body of water suddenly burst into the harbour, and with such vio- lence, that it broke the cables of two vessels, each moored with two anchors, and of several boats which lay near the town. The vessels were whirled round several times by an eddy formed in the water, and then hurried back again with the same rapidity as before. These motions were repeated different times; and while the current rushed up along one side of the harbour, it ran down with the same violence along the other. The muddy bottom of the harbour was greatly altered; the mud was removed from some places and deposited in others. At one place the height of the water, where it was measured, was found to be five feet and a half; in other places it is said to have been much higher, particularly where it flowed into the market-place with such rapidity, that many persons had not time to escape, but were immersed, knee deep, in the water. These commotions extended several miles up the river, and were most perceptible in shallow places. The alternate elevation and depression of the water continued about ten minutes, when the tide returned to its usual level. In the evening, between six and seven, the water rose again, but with less violence than before, and continued to ebb and flow till three next morning. The rise of the waters was not at first gradual, but, accompanied with a hollow note, rose fix or seven feet in a minute, and rushed in like a deluge, after which it as suddenly subsided. The water, too, became thick and muddy, emitting at the same time a most offensive smell. Similar agitations of the waters were observed all along the coast to the westward of Kinsale.

Such were the phenomena of this earthquake, as they were observed on land in the different places which have been mentioned. Its effects were also severely felt at sea. A frigate off St Lucar received so violent a shock, that it was supposed the had struck the ground. Another vessel in N. Lat. 36°.24., between nine and ten in the morning, was so much shaken and strained as if she had struck upon a rock. The scam of the deck opened, and the compass was overturned. The sensation experienced by some persons on board of another vessel, which was then in N. Lat. 29°. W. Long. 40°, were such as if she had been suddenly raised up and suspended by a rope. One person looking out at the cabin window, thought he saw land about a mile distant; but when he reached the deck, no land was to be seen. A strong current was observed crossing the ship's way to leeward. The current returned in about a minute with great violence; and, at the distance of about a league, three craggy pointed rocks were seen throwing up water of various colours, and seemingly resembling fire. This appearance terminated in a thick black cloud, which arose heavily in the atmosphere. Between nine and ten in the morning another ship, 40 leagues off St Vincent, received so violent a shock, that the men on deck were thrown a foot and a half above its surface, and the anchors, although they were lashed down, bounced up. Immediately after the flip funk in the water so low as the main chains. On having the lead a great depth of water was found, and the line was of a yellow colour, and gave out the smell of sulphur. The first shock was the most violent; but smaller ones were repeated for 24 hours.

The effects of this earthquake on springs were very remarkable. On the afternoon of the 31st of October, the water of a fountain at Colares was observed to be greatly diminished. On the morning of the 1st of November, the day on which the earthquake happened, it became thick and muddy, but afterwards recovered its usual quantity and limpidity. In some places springs appeared where there had been formerly no water, and continued afterwards to flow. At Varge, on the river Macaas, many springs of water burst forth at the time of the earthquake, and some threw up their waters mixed with sand of various colours, to the height of 18 or 20 feet. In Barbary, a stream of water, which was as red as blood, burst forth from a mountain, which was split in two. At Tangier all the fountains were dried up during the whole of the day on which the earthquake happened. The mineral waters of Toplitz, a village in Bohemia, which have been celebrated since the year 1762, experienced a very remarkable change. The principal hot spring had continued to flow from the time it was discovered, of the same temperature and the same in quantity. On the morning of the earthquake, between 11 and 12 o'clock, the waters of this spring increased so much in quantity, that all the baths ran over in the space of half an hour. A short time before the water increased, it flowed from the spring thick and muddy; and then having entirely stopped for about a minute, it burst out with great violence, carrying before it a great quantity of reddish ochre. It afterwards became limpid, and flowed as formerly; but in larger quantity, and of a higher temperature. At Angouleme in France the earth opened in one place, and discharged a great body of water, which was mixed with reddish sand. Most of the springs in the neighbourhood sunk to low, that for some time it was supposed they had become quite dry.

Such were the extraordinary effects of this terrible earthquake, which extended over a space not less than four millions of square miles. Other earthquakes, although of more limited extent, have produced effects not less destructive, and particularly some of the earthquakes which have visited Italy and Sicily in modern times; accounts of which have been drawn up with accuracy and attention. Some of these we shall now detail.

One of the most calamitous earthquakes was that which befel Calabria in the year 1783. Of this earthquake Sir William Hamilton, who, soon after the earthquake happened, visited the scenes of defolation, which it left behind, has drawn up a particular account. He observes, that "if on a map of Italy, and with your compass on the scale of Italian miles, you were to measure off 22, and then fixing the central point on the city of Oppido, which seemed to be the spot where the earthquake had exerted its greatest force, form a circle, the radius of which will be 22 miles, you will then include all the towns, villages, &c. that have been utterly ruined, and the spots where the greatest mortality happened, and where there have been the most visible alterations on the face of the earth. Then extend your compass in the same scale to 72 miles, preserving the same centre, and form another circle, you will include the whole country that has any mark of having been affected by the earthquake. A gradation was plainly observed in the damage done to the the buildings, as also in the degree of mortality, in proportion as the countries were more or less distant from this supposed centre of the evil."

This earthquake, it has been remarked, differed very considerably from others in one circumstance, which was this. Where it happened that two towns were situated at the same distance from the centre, one of which was placed on a hill, and the other on a plain, it was found that the town on the lowest situation always sustained the greatest damage from the shocks of the earthquakes which are alluded to above.

That part of Calabria which most severely felt this dreadful calamity, lies between the 38th and 39th degrees of latitude, and the force of the earthquake extended from the foot of the Appenines called Monte Dijo, Monte Sacro, and Monte Caulene, as far to the westward as the Tyrrhenian sea. By the shock of the 5th of February, every town, village, and farm-house near to the mountains, whether situated on some part of the elevated ground or on the plain, was left a heap of ruins. In proportion to the distance from the centre, as has been already hinted, the damage sustained was more or less considerable. But even the more distant towns and villages suffered greatly from the shocks which happened on the 7th, 26th, and 28th of February, and on the 1st of March. From the time the first shock came on, the earth continued in a constant tremor; the shocks were felt with different degrees of force in different parts of the provinces which were the scene of this terrible calamity; and the motion was either in a whirling direction, as in a vortex, or horizontal, or pulsatory, the beatings proceeding from the bottom upwards. The apprehensions and alarms of the miserable inhabitants were terribly increased by this variety of changing motions, dreading that every moment the earth would open under their feet and swallow them up. That part of Calabria which suffered from this earthquake, was also drenched with long continued and heavy rains, accompanied with frequent and furious squalls of wind. These rains prevailed particularly on the western side, where many fissures had appeared in the mountains. Some mountains had been lowered greatly, and others had been entirely swallowed up. The roads were rendered impassable by the deep chasms which were left by the shock; valleys were filled up by the parts of mountains which were split asunder; the course of rivers was changed; springs were dried up, and new springs burst out where none existed before.

At Laureana in Farther Calabria, two houses, surrounded with extensive plantations of olive and mulberry trees, situated in a valley, were removed by the force of the earthquake, with all their trees, and carried to the distance of a mile; and on the spot where they formerly stood, hot water burst from the earth, and was projected to a considerable height into the air. The water was mixed with sand of a reddish colour. Some countrymen and shepherds, who were employed in rural affairs near this spot, were swallowed up, with their teams of oxen, and their whole flocks of goats and sheep. The number of inhabitants who lost their lives in this calamity, exceeded, according to some calculations, 32,000; but it is supposed by others, that, including strangers, the number was not less than 40,000.

The inhabitants of the town of Scilla, on the east coast of the earthquake on the 5th of February, laid hold along with their prince to the sea shore for safety, and remained either on the strand or in boats near the shore. In the night time a tremendous wave overflowed the land to the distance of three miles from the shore, and, in its return, swept off near 32000 of the inhabitants, among whom was the prince. This water was said by some to have been boiling hot, so that many of the people were supposed to have been scalded with it. A mountain, it is asserted, of 500 palms in height, and 1300 palms in circumference at its base, was detached from the place where it stood, and carried to the distance of four miles. It was about the same time that the hill on which the town of Oppido stood, and which extended three miles in length, was split in two, and filled up on each side the bed of a river. Two great lakes were formed by the current of the rivers being stopped; and, as they increased in extent, infected the air with their putrid and noisome exhalations.

Sir William Hamilton, who was then resident at Naples as ambassador from Britain, was indefatigable in obtaining every kind of information with regard to the effects of this earthquake. With this view he made an extensive tour over these parts of the country which had been visited by this calamity. Some of the accounts which were first published seem to have been somewhat exaggerated, either from the love of the marvellous in those who framed them, or from the excessive alarms of the surviving sufferers. On the 2d of May following Sir William landed on the coast of Higher Calabria. The effects of the earthquake were first perceived at Cedraro. The inhabitants had quitted their houses, but it did not appear that the town had sustained any material damage. Most of the inhabitants of St. Lucido were then living in barracks, and the baron's palace, as well as the church steeple, had suffered greatly. He afterwards landed at the town of Pizzo in Farther Calabria. This town stood on volcanic tufa. It sustained great injury from the shock of the 5th February, but was completely destroyed by that of the 28th. Here he was informed, that Stromboli, a volcanic mountain which is nearly opposite, and in full view, but 50 miles distant, had ejected much less matter, and had thrown up less smoke, during the time of the earthquakes, than it had done for many years before. Even at this time slight shocks of earthquakes were occasionally felt. One indeed happened the same night. The boat in which he slept received a smart shock, and seemed to be lifted out of the water; but this shock was unaccompanied with noise.

The town of Monteleone is situated on a hill which overlooks some fine rich plains and the sea below. These plains, formerly covered with numerous towns and villages, now exhibited a gloomy scene of utter desolation. The town of Monteleone itself had not suffered materially from the first shock on the 5th of February; but it was considerably damaged by some of those which took place afterwards. It was generally observed, that the shocks of the earthquake came on with a rattling noise, which seemed to proceed from the westward. They usually began with a horizontal motion, and terminated with a whirling motion, during which most of the buildings in the province were thrown down. It was generally observed too, that previous to a shock the clouds seemed to be unusually still and motionless, and that a shock quickly succeeded a heavy shower of rain.

Approaching the plain, it was observed, according to the general remark made above, that the towns and villages were more or less defoliated in proportion to their vicinity to the plain. Of the town of Mileto, which stood in a bottom, not a house remained. Soriano and the noble Dominican convent presented a heap of ruins. According to the same general remark, all the buildings which stood upon the high grounds, the soil of which is a gritty sandstone, sustained less damage than those situated in the plain, for the latter were universally thrown down. The soil of the plain is a sandy clay of various colours, and full of sea shells. It is frequently intersected by rivers and torrents which have formed wide and deep ravines. Passing through St Pietro, a town in ruins, Sicily was seen and the summit of Mount Etna, which at this time threw out a considerable quantity of smoke. In a swampy plain through which he passed, Sir William examined a number of small holes in the earth, of the shape of an inverted cone. These holes were covered with sand as well as the surrounding soil. During the earthquake of the 5th of February, water mixed with sand spouted up to a considerable height from each of these openings. The river, it was observed, before these fountains burst out, was dried up; but soon after the waters returned, and overflowed their banks. It appeared from more extensive observation, that the same thing had uniformly happened to all the other rivers in the plain during the shock of the 5th of February. This has been ascribed to the first impulse of the earthquake proceeding from the bottom upwards, and this seemed to be the general opinion. The surface of the plain then rising suddenly, the rivers which are shallow naturally disappeared; and the plain returning with violence to its former level, the rivers returned and overflowed from the sudden depression of the boggy grounds, which would naturally force out the water under their surface.

The town of Rolarno, and the duke of Monteleone's palace, was a heap of ruins; fix feet high of the walls only remained. It was somewhat singular, that the only building which escaped uninjured was the public jail. At Laureana Sir William ascertained the truth of the circumstance of the two tenements which were said to have been removed from their situations. These flood in a valley surrounded with high grounds. In the same valley were observed hollows in the form of inverted cones similar to those which he had formerly examined. Between this place and the town of Polistene he did not see a single house, after travelling four days through a rich and beautiful country. Every thing presented the most indescribable misery: the violence of the earthquake was so great that all the inhabitants were buried in an instant alive or dead in the ruins of their houses. This town was situated between two rivers that were occasionally subject to overflow their banks. Of six thousand inhabitants, more than two thousand lost their lives by the shock on the 5th of February.

The princess Gerace Grimaldi, with four thousand of her subjects, perished at Cafal Nuova on the same day; some persons who were dug alive out of the ruins observed, that they felt their houses fairly lifted up without any previous warning. An inhabitant of this town, being at that moment on a hill which overlooked the plain, when he felt the shock turned round towards the town, but he could see nothing excepting a thick white cloud of dust. So completely was this town destroyed, that no vestige of house or street remained; all lay in the same confused heap of ruins. Other towns had suffered in the same manner, and now exhibited the same scene of desolation.

Terra Nuova suffered severely from the same earthquake. It is situated between two rivers which had formed deep and wide ravines in their course; one of these was not less than 500 feet deep, and three quarters of a mile broad. In consequence of the great depth of this ravine, and the violent motion of the earth, two large masses of the soil on which a great part of the town, consisting of some hundred houses, had been thrown into the ravine at the distance of half a mile from the place where they formerly stood. Many of the inhabitants who had been carried along with their houses, were dug out of the ruins alive, and even some of them escaped unhurt. Of 1600 inhabitants, 400 only remained alive. In other places in the same neighbourhood, great tracts of land had been removed and carried to a considerable distance, with all their plantations and crops, which continued to grow and thrive in their new situation as well as formerly. The river here disappeared at the moment of the earthquake; but soon after returned, and covered the bottom of the ravine to the depth of three feet. This water was observed to be salt like that of the sea.

The whole town of Molochi di Sotto had been thrown into the ravine, and a vineyard of many acres lay near it in an inclined situation, but had not suffered any other injury. In several parts of the plain, the soil, with all its trees and crops of corn, to the extent of many acres, had sunk eight and ten feet below the level of the plain; and in other places it had risen the same height. The soil of this plain, it is to be observed, is composed of clay mixed with sand, which readily assumes any form.

Sir William next proceeded to Oppido, which, it will be recollected, was considered as the central point on which the greatest force of the earthquake was exerted. This city stands on a mountain of grittone of a reddish colour. It is surrounded by two rivers, which run in a deep ravine. It had been reported, that the mountain on which the city stands, had been split in two, and stopped up the course of the rivers; but it appeared on examination, that huge masses of the plain on the edge of the ravine, had been detached into it, and had so far filled it up, as to stop the course of the rivers, the waters of which were collecting, and forming lakes to a great extent. Part of the rock, it was found, on which the city stood, was separated, and with several houses upon it, was thrown into the ravine. Great tracts of land, with plantations of vines and olives, were transported from one side of the ravine to the other, to a distance exceeding half a mile.

"Having walked, (says Sir William), over the ruins of Oppido, I descended into the ravine, and examined carefully the whole of it. Here I saw, indeed, the wonderful force of the earthquake, which has produced exactly the same effects as those described in the ravine at Terra Nuova, but on a scale infinitely greater. The enormous masses of the plain detached from each side, of the ravine, lie sometimes in confused heaps, forming real mountains, and having stopped the course of two rivers (one of which is very considerable), great lakes are already formed; and if not afflited by nature or art so as to give the rivers their due course, must infallibly be the cause of a general infection in the neighbourhood. Sometimes I met with a detached piece of the surface of the plain (of many acres in extent) with the large oaks and olive trees, with corn or lupins under them, growing as well and in as good order at the bottom of the ravine, as their companions from whence they were separated do on their native soil, at least 500 feet higher, and at the distance of about three quarters of a mile. I met with whole vineyards in the same order in the bottom, that had likewise taken the same journey. As the banks of the ravine from whence these pieces came are now bare and perpendicular, I perceived that the upper foil was a reddish earth, and the under one a sandy white clay, very compact, and like a soft stone. The impulse these huge masses received, either from the violent motion of the earth alone, or that afflited with the additional one of the volcanic exhalations set at liberty, seems to have acted with greater force on the lower and more compact stratum than on the upper cultivated crust: for I constantly observed, where these cultivated lands lay, the under stratum of compact clay had been driven some hundred yards farther, and lay in confused blocks; and, as I observed, many of these blocks were in a cubical form. The under foil, having had a greater impulse, and leaving the upper in its flight, naturally accounts for the order in which the trees, vineyards, and vegetation fell, and remain at present in the bottom of the ravine.

"In another part of the bottom of the ravine there is a mountain composed of the same clay foil, and which was probably a piece of the plain detached by an earthquake at some former period: it is about 250 feet high, and 400 feet diameter at its basis. This mountain, as is well attested, has travelled down the ravine near four miles; having been put in motion by the earthquake of the 5th of February. The abundance of rain which fell at that time, the great weight of the fresh detached pieces of the plain which I saw heaped up at the back of it, the nature of the foil of which it is composed, and particularly its situation on a declivity, account well for this phenomenon; whereas the reports which came to Naples of a mountain having leaped four miles, had rather the appearance of a miracle. I found some single timber trees also with a lump of their native foil at their roots, standing upright in the bottom of the ravine, and which had been detached from the bottom of the plain above mentioned. I observed also, that many confused heaps of the loose foil, detached by the earthquake from the plains on each side of the ravine, had actually run like a volcanic lava (having probably been afflited by the heavy rain), and produced many effects much resembling those of lava during their course down a great part of the ravine. At Santa Christina, near Oppido, the like phenomena have been exhibited, and the great force of the earthquake of the 5th of February seems to have been exerted on these parts, and at Cafal Nuova, and Terra Nuova.

The next places which were visited were the towns of Seminara and Palmi. Palmi is nearer the sea, and Earth had suffered most; not fewer than 1400 of the inhabitants having been destroyed. In the course of his tour in this part of the country, he was informed that the sea was observed to be hot, and fire was seen issuing from the earth.

At Reggio, although the shock had been much less violent than in other places, no house was yet habitable. During the earthquakes which visited this place in 1773 and 1780, near 17,000 inhabitants lived for several months encamped in the fields, or in barracks.

Having examined the different places on the Calabrian coast, which had suffered from this terrible earthquake, Sir William Hamilton failed for Messina in Sicily, to be informed of its effects there. He found that the shock had been very violent, but far less so than on the opposite shores. Many of the houses, even in the lower part of the town, were standing, and some of them had sustained little damage; but in the more elevated situations the shocks seemed to have had scarcely any effect. This still corresponds with the general remark, which was already made. A striking instance of this appeared in two convents, which are situated on elevated places, and had suffered nothing from the earthquakes which had afflicted the country for four months. It was said that fire had been seen issuing from fissures of the earth near the shore. The shock of the earthquake on the 5th of February, seemed to proceed from the bottom upwards; but the succeeding shocks came on with a horizontal or whirling motion.

A remarkable circumstance with regard to fish, was taken notice of at Messina, and indeed the same thing was observed along the coast of Calabria, where the effects of the earthquake had been most severe. A small fish, somewhat larger than the English white bait, but resembling it, and which usually lives at the bottom of the sea, buried in sand, had remained for several months after the commencement of the earthquakes, near the surface, and was taken in great abundance to be the common food of poor people. Before the earthquake, this fish was extremely rare, and was considered as a great delicacy. After the earthquake, indeed, it was observed, that fish of all kinds were found in greater abundance.

These earthquakes, of which we have now given so detailed an account, continued for many months afterwards; tremulous motions of the earth continued to be felt, and they were not perfectly settled even in the year 1784.

The southern continent of America is often visited by earthquakes. In the year 1797, Peru was afflicted with this dreadful calamity, which perhaps in the extent of surface which experienced the dreadful shock, exceeds that of any earthquake, the history of which is on record. The following is a short account of this earthquake by M. Cavanilles. "In the midst, (says he), of the most profound calm, there is frequently heard a dreadful bellowing noise, the forerunner of earthquakes, to which this part of the world is often exposed. After the year 1791, this noise was frequently heard in the neighbourhood of the mountain of Tunguragua. Antonio Pineda and Née, the two naturalists employed in the expedition round the world, when examining the declivity of this volcano, the lava of which had been hardened more by the internal fire than by the ardour of the sun, were struck with terror by the horrible sound which they heard, and the heat which they experienced. Pineda, that valuable member of society, whose premature death is still deplored by the friends of science, foretold that a terrible eruption was preparing in the mountain of Tunguragüa; and his conjectures were confirmed by the event. On the 4th of February 1797, at three quarters past seven in the morning, the summit of the volcano was more free from vapours than usual; the interior part of the mountain was agitated by frequent shocks, and the adjacent chains burst in such a manner, that in the space of four minutes an immense tract of country was convulsed by an undulating movement. Never did history relate the effects of an earthquake to extraordinary, and never did any phenomenon of nature produce more misfortunes, or destroy a greater number of human beings. A number of towns and villages were destroyed in a moment: some of them, such as Riobamba, Quero, Polileo, Patate, Pillaro, were buried under the ruins of the neighbouring mountains; and others in the jurisdictions of Harrabata, Latacunga, Guaranda, Riobamba, and Alauji, were entirely overthrown. Some sustained prodigious loss by the gulfs which were formed, and by the reflux of rivers intercepted in their course by mounds of earth; and others, though in part saved, were in such a shattered state as to threaten their total ruin. The number of persons who perished during the first and succeeding shocks is estimated at 16,000. At ten o'clock in the morning, and four in the afternoon, the same day, (February 4,) after a dreadful noise, the earth was again agitated with great violence, and it did not cease to shake, though faintly, for the whole months of February and March; but, at three quarters past two in the morning of the 5th of April, the villages already ruined were again exposed to such violent shocks as would have been sufficient to destroy them. This extraordinary phenomenon was felt throughout the extent of 140 leagues from east to west, from the sea as far as the river Napo; and without doubt farther, for we are little acquainted with these districts which are inhabited by the savages. The distance north-east and south-west between Popayan and Piura, is reckoned to be 175 leagues; but in the centre of that district, 1 degree 16.6 from these places, is situated the part totally destroyed, and which comprehends 40 leagues from north to south between Guaramdam and Machache, and twenty leagues from east to west. But, as if an earthquake alone had not been sufficient to ruin this fertile and populous country, another misfortune, hitherto unknown, was added. The earth opened, and formed immense gulfs; the summits of the mountains tumbled down into the valleys, and from the fissures in their sides there issued an immense quantity of fetid water, which in a little time filled up valleys a thousand feet in depth and fix hundred in breadth. It covered the villages, buildings, and inhabitants; choked up the sources of the purest springs, and being condensed by desiccation, in the course of a few days into an earthy and hard paste, it intercepted the course of rivers, made them flow backwards for the space of 87 days, and converted whole districts of dry land into lakes. Very extraordinary phenomena, which will doubtless be one day mentioned in history, occurred during these earthquakes; I shall, however, content myself with mentioning only two of them. At the same moment that the earth shook, the lake of Quirotoa, near the village of Infiolo, in the jurisdiction of Latacunga, took fire, and the vapour which rose from it suffocated the cattle and flocks that were feeding in the neighbourhood. Near the village of Pelileo, a large mountain named Moya, which was overturned in an instant, threw out a prodigious stream of the before-mentioned thick fetid matter, which destroyed and covered the miserable remains of that city. Naturalists will one day find, in these ravaged countries, objects worthy of their researches. Fragments of the minerals and earths of Tunguragua are about to be transported to Spain: but it is not in such fragments that we ought to search for the cause of these surprising phenomena; we must visit the country itself, where this conflict of the elements took place, and where the ruins it occasioned are still to be seen (c).

To the history of earthquakes now given, we shall In Scots only add the following account of the earthquakes which have taken place at Comrie in Perthshire, in Scotland, which was communicated to the Royal Society of Edinburgh, by Dr Finlayson, in a letter from Mr Taylor.

"The earthquakes which have lately (January 1790) taken place at Comrie (h) and its neighbourhood, are certainly very deserving of attention. I shall therefore cheerfully comply with your request, and give you as particular a description as I can of such of them as have been most remarkable. To give a particular account of all the nifts or concussions which, during the last half year, have been heard or felt at Comrie, and within a short distance to the north, east, and west of that village, is beyond my power, and would indeed be of little use. With regard to these small concussions, it will be sufficient to say, that many of them have sometimes been observed to succeed one another in the space of a few hours; that they take place in all kinds of weather; that they are thought by some people to proceed from north-west to south-east, and by others from north-east to south-west; that they have not been observed to affect the barometer; that they do not extend in any direction above three or four miles from Comrie; and that towards the south they are bounded by the Earn, which is in the immediate vicinity of the village. The same person, though bestowing the minutest attention, is often uncertain whether they proceed from the earth

(c) The volcano of Tunguragua occasioned an earthquake in 1557. (h) Comrie is a village about 22 miles west of Perth, situated in the valley of Strathearn, and on the north side of the river Earn, about four miles below the place where it issues from the lake. The remains of a Roman camp on the opposite side of the river, have made the name of this village very well known to Scottish antiquaries. earth or from the air, sometimes believing them to come from the one, and sometimes from the other; neither do all agree with respect to the seat of any one of them.

"After the strictest enquiry, I find it impossible to determine with accuracy the date of any of the concussions which took place before the 2d of September last. Some people in the neighbourhood of Killin assert positively, that they heard unusual rumbling noises in the month of May; but the impression which these noises made was so faint, that they would probably have been soon forgotten altogether, had they not been succeeded by concussions of a less equivocal nature. Towards the end of August, two or three shocks are said to have been felt at Dundurn, Dunira Lodge and Comrie; but I have not been able to learn the precise day or hour on which any of them happened. The truth is, the concussions hitherto observed were feeble, and the minds of the people seem not to have been roused to particular attention till the 2d of September. About eleven o'clock that evening, a smart shock was felt at Comrie. I myself heard here, for the first time, a rumbling noise, which I took for that of a large table, dragged along the floor above stairs, and which I probably would never have thought of again, unless my attention had been turned to it by the alarm which it had excited in the neighbourhood. Many other feeble noises or concussions are said to have been observed in Glen Leadnach and about Comrie during the months of September and October. At that time, however, I confess I was disposed to doubt the numerous reports of earthquakes with which the country was filled, and to ascribe them to the workings of an imagination, on which the alarm of the 2d of September still continued to be impressed.

"On the 5th of November, a concussion took place two or three minutes before six o'clock P. M. which was too violent to be mistaken. Some compared the noise which accompanied it to that of heavy loaded waggons, dragged with great velocity along a hard road or pavement, and thought that it passed under their feet. To me it seemed as if an enormous weight had fallen from the roof of the house, and rolled with impetuosity along the floor of the rooms above; and it must have made a familiar impression on the servants, for some of them instantly ran up stairs to discover what had happened. Others were sensible of a tremulous motion in the earth, perceived the flames of the candles to vibrate, and observed the mirrors and kitchen utensils placed along the walls to shake and clatter. There is also reason to believe that the waters in the loch of Monivaird, in the near neighbourhood of Ochtertyre, suffered unusual agitation, as the wild fowl then upon the loch were heard to scream and flutter. The noise on this occasion, as far as I can judge, did not last above ten or twelve seconds. During the course of the day, the mercury in the barometer rose and fell several times, and at fix o'clock it stood at 28 1/2 inches. The sky was then perfectly serene, and hardly a breath of wind was to be felt; but next morning, about fix o'clock, a violent tempest rose, which raged without intermission for 24 hours.

"At Glen Leadnach, Comrie and Lawers, this concussion was much more violent, and the noise that accompanied it much more alarming. The inhabitants of these places, and of Aberuchill and Dunira, declare, that they perceived distinctly the earth heaving under them, and the motion communicated to their chairs, and other furniture. They imagined that the slates and stones were tumbling from their houses, and many of them ran out in the greatest trepidation, from the notion, that the roofs were falling in. Even the domestic animals were alarmed, and contributed, by their howls and forebears, to increase the terrors of the people. Though I have not been able to discover whether Loch Earn was ever agitated by these concussions, there is little doubt, that the river near Comrie was affected on this occasion, as two men then on its banks heard the dashing of its waters. This great shock was succeeded by a number of those lighter rumbling noises which have been already mentioned. Not less than 30 of them were counted in the space of two hours after it happened; but they did not extend above two miles to the east, north, and west of Comrie.

"On the 10th of November, at three o'clock P. M. we had here another shock of much the same length, violence, and extent, as that on the 5th. The mercury in the barometer on this day was more stationary than on the former, and at the time of the earthquake was 29 inches high. The weather was calm and hazy. It was a market-day at Comrie; and the people, who were assembled from all parts of the country, felt as if the mountains were to tumble instantly upon their heads. The hard-ware exposed for sale in the shops and booths shook and clattered, and the horses crowded together with signs of unusual terror.

"About one o'clock P. M. of the 29th December, we had another pretty smart shock, during a violent storm of wind and rain, which continued the whole day, and which was at its height during the time of the earthquake. Indeed, as has been remarked already, these concussions seem to have no dependence on the weather. According to the accounts of those who live nearest to the centre of the phenomena, rumbling noises, like those above described, may be heard in all states of the atmosphere.

"Though I mention no more of these earthquakes, you are not to conclude, that many more have not taken place, and some of them perhaps equally violent with those of the 5th and 10th of November. Several shocks have happened during the stillness of the night, which, even at this distance from Comrie, where their centre seems to be, have been abundantly terrifying. But the great resemblance, or rather the perfect similarity of their effects, and of the impression they make on our minds, renders it unnecessary for me to trouble you with a particular description of each of them.

"The direction of all the noises or concussions I have observed, great as well as small, appeared to be in the same line from N. W. to S. E. Others describe them as sometimes proceeding in that direction, and sometimes as coming from N. E. to S. W. I have not heard any other line of direction ascribed to them.

"Upon the fullest enquiry, I find, that these earthquakes have been very limited in point of extent. The greater shocks have been feebly felt at Loch Earn head, about Killin, and at Ardonich, on the southern bank of Loch Tay. They do not appear to have extended farther eastward on that lake; and, what is more remarkable, they have not been felt in Glen Almond, mond, or the small glen through which the military road from Crieff to Tay-bridge passes. The farmer at Auchkraine, (which lies at the head of Glen Almond,) and is separated from Glen Leadnach only by the mountain Benecheon, over the northern side of which his shepherds daily travel,) has assured me, that neither he, nor any of his people, have been at any time sensible of the least extraordinary noise or concussion. Towards the east, the two first great shocks extended to Monzie, Cultoukhey and Dollar, about seven miles distant from Comrie. The shock of the 6th of November reached till farther, and was felt, though but faintly, at Ardoch and Drummond Castle towards the S. E. In the direction of the south, however, the banks of the Earn seem to be its general boundary, as the noise of the most violent concussions was heard but faintly at the manse of Comrie, and along the strath on the south side of the river. The limits of the lesser concussions, I am confident, do not extend above three miles in any direction from their centre. They are commonly observed at Lawers on the east; throughout the whole of Glen Leadnach, at Dunira, Dalchonzie and Aberkichill, on the north and west; and do not reach so far as the manse, which is about three quarters of a mile on the south of Comrie (1.)

In another communication, dated in 1793, from the same gentleman, he observes, that "there is no reason to believe that these phenomena are yet come to an end. After temporary intermissions, sometimes of several months, they have returned, ever since their first appearance in 1789, without any apparent difference in their extent or force." The rumbling noises or lighter concussions, as usual, are observed at Comrie, in Glen Leadnach, and the places in their near neighbourhood; the more violent extend to much the same distance as formerly described. Having been only occasionally in that country since February 1791, I have not been able to ascertain dates. On the 2d of September 1791, at five minutes past five in the afternoon, a slight shock was felt at Oechtyre. The barometer was not in order, on which account the weight of the atmosphere could not be ascertained. Its electrical state was tried by Sauflure's electrometer, but no indication of anything uncommon was perceived. Since that period, shocks have been observed at different times till within these few weeks past.

"From this account, it will be observed, that all the greater shocks have taken place in the season of autumn or the beginning of winter; that this has been now repeated for more than four years; and that those greater shocks have been succeeded at short intervals by rumbling noises or more feebleconcussions. It has also been remarked, that they have in general been preceded or followed by great rains or boisterous weather; but variations in the weather take place so frequently in our climate at that season of the year, that the connection between them and the phenomena above described, is probably altogether accidental."

After the view which we have given of the pheno-mena and history of earthquakes, we now proceed to consider the consideration of the causes, by the operation of"quakes, which, according to the speculations of philosophers, these terrible convulsions of nature, which spread ruin and desolation in some of the fairest portions of the earth, are to be accounted for. Various opinions have been formed, and various hypotheses have been proposed, for the explanation of these dreaded phenomena. According to some of the ancient philosophers, subterraneous clouds existed in the internal cavities of the earth, and these bursting into lightning, shook and demolished the vaults which contained them. This was the opinion of Anaxagoras. It was supposed by others, according that earthquakes were owing to the filling up of immeme archèd roofs, which confined subterraneous fires; and the vaults or arches being weakened by the constant burning of these fires. Some ascribed earthquakes to the vapour of water which was produced, and greatly rarefied, by means of internal fires, while others, among whom was Epicurus and some of the peripatetic philosophers, fought for the explanation of the phenomena of earthquakes, in the explosion of certain inflammable balsamates, which were exhaled from the internal cavities of the earth.

Some of the modern philosophers, as Gassendi, Kircher, Varenius, Des Cartes, and others, have adopted eatns the last hypothesis, according to which it is supposed, that there are immense cavities in the earth, communicating with each other. Some of these cavities contain water, and others contain vapours and exhalations, arising from bituminous, sulphureous, and other inflammable balsamates. These combustible materials being kindled by some subterraneous spark, or by some actual flame, proceeding through narrow fissures from without, or by the heat evolved during the mixture of different substances, and the formation of new ones, produce commotions on the surface of the earth, according to the extent of the cavities, and the quantity and active nature of the inflamed matter. Those who support this hypothesis think, that it receives illustration from a common experiment of mixing together iron filings and sulphur, and burying them in the earth; and in consequence of the chemical action of these substances on each other, and the elastic vapours thus produced, the shaking of the earth is effected.

A different hypothesis has been proposed by Dr Woodward. According to this hypothesis, water is continually raised by means of subterraneous heat, from the abyss which he supposes to occupy the centre of the earth, to furnish rain and dew. Obstructions may take place in this process of nature, and whenever this happens, a swelling and commotion are occasioned by the heat in the waters of the abyss. This force is at the same time exerted against the incumbent fluids, and thus the agitation and concussion, with the other phenomena which accompany earthquakes, are produced.

Another hypothesis, different from any of these, has been proposed by M. Amontons, of which the following explanation is given. The atmosphere being taken at 45 miles high, and the density of the air increasing in proportion to the absolute height of the superincumbent column of fluid, it is shewn that at the depth of 43,528 fathoms below the surface of the earth, the air is but one-fourth lighter than mercury. But this depth is only about one seventy-fourth of the semidiameter of the earth. The immense sphere beyond this depth, the diameter of which is 6,451,528 fathoms, may perhaps be only filled with air: this air must be here greatly condensed, and heavier than the heaviest bodies with which we are at present acquainted. It is found by experiment, that the more air is compressed, the more do equal degrees of heat increase its elastic force, and the more capable it becomes of producing violent effects. As, for instance, the temperature of boiling water increases the elasticity of the air beyond its natural force in temperate climates, by a quantity equal to one-third of the weight with which it is pressed. Hence it is concluded, that a degree of heat which on the surface of the earth produces only a moderate effect, may occasion violent convulsions by the rarefaction of the denser air at great depths; but if it be considered that this condensed air may be exposed to much higher degrees of heat than that of boiling water, the elastic force of the air thus produced, and assisted by the great weight of a high column, may be more than sufficient to convulse and break up the solid orb of 43,528 fathoms, the weight of which, comparing it with that of the included air, would be trifling.

These hypotheses, however insufficient they may appear for explaining in a satisfactory manner the phenomena of earthquakes, were generally adopted till about the middle of the 18th century, when the knowledge of electricity began to be cultivated and extended. This principle was applied successively in the explanation of many natural phenomena, and, among others, the phenomena of earthquakes were ascribed to the same principle. An earthquake which was felt at London in the month of March 1749, directed the attention of philosophers to this explanation. The first who made this attempt, we believe, was Dr Stukeley, who had been much occupied about that time with electrical experiments. The consideration of the phenomena which accompanied this earthquake, led him to suppose that it could not be occasioned by vapours generated in the cavities of the earth, or by any process like fermentation, in which elastic fluids are formed and disengaged, to which such effects could be ascribed. He is of opinion, that no evidence has yet been brought to establish the probability of the existence of extensive cavities within the earth. On the contrary, he thinks there is good reason to presume, that it is in a great measure solid, so that there is little space for those changes which are supposed to be effected within the cavities, to take place. Coal pits, he adds, which have been frequently known to be on fire, and for a great length of time, never exhibited any of the phenomena which accompany an earthquake on the surface of the ground above.

The earthquake which visited London and other places of Britain, in March 1749, was felt in a circuit of 30 miles diameter; but there was no eruption of fire or vapour, and it was unattended with smoke or smell. From this consideration alone, of the extent of surface which felt the effects of the earthquake, he supposes that it could not be ascribed to the expansive force of subterraneous vapours; for, he observes, small fire-balls which are exploded in the air, emit a sulphureous smell to the distance of several miles. Now, it cannot be imagined, that so prodigious a force, acting instantaneously, on so great an extent of ground, should neither break the surface, nor indicate its presence either by the sight or smell. But if this effect is to be ascribed to fermentation, this process is not instantaneous; it continues many days, and the evaporation of such a quantity of inflammable matter would require a long space of time. Such an effect, therefore, can only be accounted for on electrical principles, the operation of which is always instantaneous.

If earthquakes were occasioned by vapours and subterraneous fermentations, explosions and eruptions, such processes would entirely destroy springs and fountains, wherever they had once existed. This, however, is contrary to what happens, for although springs are stopped, or otherwise changed, previous to an earthquake, or about the time it happens, they very often recover their former state. In the great earthquake which happened A.D. 17, in Asia Minor, and which shook a mass of earth 300 miles in diameter, and destroyed 13 great cities, neither the springs nor the face of the country received any injury.

If it be considered, that a subterraneous power capable of moving 30 miles in diameter, as in the earthquake mentioned above, which happened at London, must exist and operate at least 15 or 20 miles under the surface, the hypothesis of earthquakes being occasioned by the force of vapours will be found totally inapplicable, because this force must move an inverted cone of solid earth, the base of which is 30 miles in diameter, and the axis 15 or 20. This is an effect which is impossible to any known natural power, excepting that of electricity.

But besides, no subterraneous explosion can account for the singular effects of an earthquake on ships that are far out in the ocean. It has been already observed, that they seem as if they struck on a rock, or as if some solid body struck against their bottom. Even fishes, it is found, are particularly affected by the shock of an earthquake; but a subterraneous explosion could only produce on the water a gradual swell. It could not communicate to it that impulse by which it produces effects, as if it were a stone projected with great force against solid bodies.

From the consideration of all these circumstances, Dr Stukeley is of opinion, that the phenomena of earthquakes can only be satisfactorily explained on electrical principles. He was particularly led to this opinion by directing his attention to the phenomena which accompanied the earthquakes which took place in England in 1749 and 1750. For five or six months previous to this time, the weather had been unusually warm; the wind was from the south and south-west, and there had been no rain, so that the earth was particularly prepared to receive an electrical shock. The flat country of Lincolshire had suffered greatly from extreme drought, and hence, as dry weather is favourable to electricity, earthquakes and other similar phenomena are more frequent in southern regions of the world. Before the earthquake at London, all vegetables had been unusually premature, and it is well known how much electricity quickens vegetation. About the same time the aurora borealis had been very frequent. A very short time before the earthquake, it had exhibited unusual colours, and its motions were to the south, contrary to the ordinary direction. From these circumstances an earthquake was predicted by Italians and others who had been accustomed to the appearances which precede them. During this year, too, meteors of different kinds, as fire-balls, lightnings, and corufations, had been common; and particularly it was observed in the night preceding the earthquake, and early in the morning on the day on which it happened, that corufations were very frequent. In these circumstances nothing was wanting to produce an earthquake, according to this hypothesis, but the touch of a non-electric body. This body must be derived from the air or atmosphere; hence it is inferred, that if a non-electric could discharge its contents upon any part of the earth, in this prepared and highly electrical state, a violent commotion or earthquake must be produced; and as the discharge from an excited tube produces a shock on the human body, so the discharge of electric matter from an extent of many miles of solid earth, must produce an earthquake. The rattling, uncouth noise which attends it, is to be ascribed to the snap which is occasioned by the contact.

Before the earthquake alluded to came on, a black cloud suddenly covered the atmosphere to a great extent; the discharge of a shower, according to this hypothesis, probably occasioned the shock; and as the electrical snap precedes the shock, a sound was observed to roll from the Thames towards Temple-bar, before the motion of the houses ceased. This noise, which is generally the forerunner of earthquakes, it is supposed can only be accounted for on the principles of electricity. The contrary to this would take place, were these phenomena owing to subterraneous eruptions. The flames and sulphureous smells which accompany earthquakes, might, it is thought, be more easily accounted for on the same principles, than by eruptions from the bowels of the earth. The sudden concussion, too, seems to be produced by a motion which could only be excited by electricity, not proceeding from any convulsion in the interior parts of the earth, but from a uniform vibration along its surface, like that of a musical string, or like the vibratory motion of a glass, when the edge is rubbed with the finger. From the circumstance that earthquakes are chiefly fatal to places near the sea coasts, along the course of rivers, and elevated situations, a farther proof is derived, that they depend on the operation of electricity. The course or direction which the earthquake above alluded to took, affords an illustration of this point. Another argument in favour of the electrical hypothesis is drawn from the effects of the earthquake, or the state of the weather at the time, on persons of weak or nervous constitutions. To some these disorders proved at that time fatal; and its effects, in general, were similar to those of artificial electricity.

A similar hypothesis was proposed by Beccaria, to account for the phenomena of earthquakes. He supposes that the electric matter to which these phenomena are owing, is lodged deep in the earth, and that it is this matter discharged from the earth, to restore the equilibrium or deficiency which the clouds in the atmosphere have sustained during thunder storms, by giving out their electrical matter to another part of the earth. This, he supposes, is confirmed by the noise resembling thunder, and the flashes of lightning which are perceived during earthquakes.

Dr Priestley proposes to construct, on the principles of Stukeley and Beccaria, an hypothesis which he thinks will explain the phenomena in a more satisfactory manner. For this purpose he supposes the electric matter to be some way or other accumulated on one part of the surface of the earth, and on account of the dryness of the season, not easily to diffuse itself. It may, as Beccaria supposes, force its way into the higher regions of the air, forming clouds in its passage out of the vapours which float in the atmosphere, and occasion a sudden shower, which may farther promote the passage of the fluid. The whole surface thus unloaded will receive a concussion like any other conducting substance, on parting with or receiving a quantity of the electric fluid. The rushing noise will likewise sweep over the whole extent of the country; and upon this supposition also, the fluid, in its discharge from the country, will naturally follow the course of the rivers, and also take the advantage of any eminences, to facilitate its ascent into the higher regions of the air. In making some experiments on the passage of the electrical fluid over water, he observed that it produced a tumultuous motion, and therefore he concludes that it must receive a concussion resembling that which is given to the waves of the sea by an earthquake. To try this still farther, he immersed his hands in water, while an electrical flash passed over its surface, and he felt a sudden concussion, like that which is supposed to affect ships at sea during an earthquake. The impulse, which was felt in different parts of the water, was strongest near the place where the explosion was made.

"Pleased with this resemblance of the earthquake, he observes, I endeavoured to imitate that great natural phenomenon in other respects; and it being frosty weather, I took a plate of ice, and placed two sticks about three inches high on their ends, so that they would just stand with ease; and upon another part of the ice I placed a bottle, from the cork of which was suspended a brass ball with a fine thread. Then making the electrical flash pass over the surface of the ice, which it did with a very loud report, the nearer pillar fell down, while the more remote stood, and the ball which had hung nearly full, immediately began to make vibrations, about an inch in length, and nearly in a right line from the place of the flash.

"I afterwards diversified this apparatus, erecting more pillars, and suspending more pendulums, sometimes upon bladders stretched on the mouth of open vellies, and at other times on wet boards swimming in a vellie of water. This last method seemed to answer the best of any; for the board representing the earth, and the water the sea, the phenomena of them both during an earthquake may be imitated at the same time; pillars, &c. being erected on the board, and the electric flash being made to pass, either over the board, over the water, or over them both *."

The ingenious Dolomieu proposes to account for these phenomena on different principles. On this subject he makes the following observations with regard to the earthquakes which defoliated Calabria in 1783, and the causes by which they were produced. "The sea, says he, during the earthquakes of 1783, had little share in the shocks on the main land. The masts of water experienced no general movement, or fluctuation, or oscillation; the waves did not rise above their ordinary limits. Those which on the night of the 5th February beat against the coast of Sicily, and which afterwards covered the point of the Faro of Messina, were only the effects of a particular cause. The fall of a mountain into the sea raised the waters, which received an undulating motion, as happens always in similar cases. The undulation reached from the point of Sicily beyond the cape of Rofacolmo, extending in length along the coast which runs to the south; but always with a decrease in elevation as it was more remote from Sicily. Whatever inquiries the author has made, he has not been able to discover, in all the details which have been given him, any proofs of the existence of electrical phenomena; no spark, no disengagement of the electrical fluid, which the Neapolitan naturalists wish to assign as the cause of earthquakes.

"The state of the atmosphere was not the same in the whole range of earthquakes. While the tempests and the rain seemed to have confounded with them for the destruction of Messina, the interior part of Calabria enjoyed very fine weather. A little rain fell in the plain in the morning of the 5th of February; but the sky was clear during the rest of the day. This month and that of March were not only pretty serene, but likewise warm. There were some storms and rain; but they were the natural attendants of the season.

"The moving force seems to have resided under Calabria itself, since the sea which surrounds it had no share in the oscillations or vibrations of the continent. This force seems also to have advanced along the ridge of the Apennines in ascending from the south to the north. But what power in nature is capable of producing such effects? I exclude electricity, which cannot accumulate continually during the course of a year, in a country surrounded with water, where every thing confines to place this fluid in equilibrium. Fire remains to be considered. This element, by acting directly upon the solids, can only dilate them; then their expansion is progressive, and cannot produce violent and instantaneous movements. When fire acts upon fluids, such as air and water, it gives them an astonishing expansion; and we know that then their elastic force is capable of overcoming the greatest resistances. These appear the only means which nature could employ to operate the effects we speak of: but in all Calabria there is no vestige of a volcano; nothing to point out any interior combustion; no fire concealed in the centre of mountains, or under their base; a fire which could not exist without some external signs. The vapours dilated, the air rarefied by a heat constantly active, must have escaped through some of the crevices or clefts formed in the soil; they must there have formed currents. Both flame and smoke must have issued by some one or other of these passages. These once opened, the prelude would have ceased; the force not meeting with any more resistance, would have lost its effect; and the earthquakes could have no longer continued. None of these phenomena took place: we must then renounce the supposition of a combustion acting directly under Calabria. Let us see whether, having recourse to a fire at some distance from this province, and acting upon it only as an occasional cause, we shall be able to explain all the phenomena which have accompanied the shocks. Let us take for example Etna in Sicily, and suppose large cavities under the mountains of Calabria; a supposition which cannot be refuted. It is certain that immense subterranean cavities do exist, since Etna, in elevating itself by the accumulation of its explosions, must leave in the heart of the earth cavities proportioned to the greatness of the masts.

"The autumn of 1782 and the winter of 1783 were very rainy. The interior waters, augmented by those of the surface, may have run into those caverns which form the focus of Etna: there they must have been converted into vapour capable of the highest degree of expansion, and must have pressed forcibly against everything which opposed their dilatation. If they found canals to conduct them into the cavities of Calabria, they could not fail to occasion there all the calamities of which I have given the description.

"If the first cavity is separated from the second by a wall (so to speak) or some slight division, and this separation is broken down by the force of the elastic vapour, the whole force will act against the bottom and sides of the second. The focus of the shocks will appear to have changed place, and become weaker in the space which was agitated most violently by the first earthquake.

"The plain, which was undoubtedly the most slender part of the vault, yielded most easily. The city of Messina, placed upon low ground, experienced a shock which the buildings on higher grounds did not. The moving force ceased at once as suddenly as it acted violently. When, at the periods of the 7th of February and the 28th of March, the focus appeared changed, the plain scarcely suffered anything. The subterraneous noise, which preceded and accompanied the shocks, appeared always to come from the south-west, in the direction of Messina. It seemed like thunder under ground, which resounded beneath vaults.

"If Etna, then has been the occasional cause of the earthquakes, it has also prepared, for some time, the misfortunes of Calabria, by gradually opening a passage along the coast of Sicily to the foot of the Neptu- nian mountains: for during the earthquakes of 1780, which disturbed Messina the whole summer, they felt, for the whole length of that coast, from Taormina even to the Faro, considerable shocks; but near the villages of Alli and Fiume de Nif, which are situated about the middle of that line, shocks so violent were experienced, that they dreaded lest the mouth of a volcano should open. Each shock resembled the effort of a mine that had not strength to make an explosion. It appears, that then the volcano opened a free passage for the expansion of its vapours, and that they have since circulated without restraint; since in the year 1783 the earthquake was almost nothing upon that part of Sicily, at the time that Messina buried under its ruins the half of its inhabitants."

By others the phenomena of earthquakes have been ascribed to the force of vapour or steam, which, no doubt, is an agent sufficiently powerful, if it is confined so, that its prodigious elastic force may be exerted; but it is denied by those who oppose this hypothesis, that earthquakes, though very frequent in regions where subterranean fires are really known to exist, as in volcanic countries, always happen in such places, and therefore water cannot be converted into vapour. But, besides, it is well known, that this vapour, even admitting the possibility of its production in subterranean cavities would be re-converted into water, the moment it came in contact with a cold body, which would deprive it of the principle of heat, in combination with which water assumes the form of vapour.

Many objections might have been made to the hypotheses which have been proposed to account for earthquakes. Many of these will probably occur to the attentive reader, who is a little acquainted with the nature and properties of the agents by which they are supposed to be produced; but whatever may be the cause of these extraordinary phenomena, it appears that it is very far from being clearly ascertained. Perhaps all the agents which have been stated as the cause of earthquakes, may have some influence in contributing to the effect, and many operate at different times, and in different circumstances.

SECT. II. Of Volcanoes.

Volcanoes exist in almost every part of the world, from the north to the south pole. Hecla in Iceland, and a volcano which has been observed in Terra del Fuego, at the termination of the southern continent of America, nearly comprehend the extremities of the globe; and having mentioned these boundaries, it is unnecessary to observe, that they exist in all climates.

The number of volcanoes at present known, is not less than 100. The volcanoes of Europe are well known: these are Vesuvius in Italy, Etna in Sicily, and Hecla in Iceland. To these may be added the volcanoes in the Aeolian or Lipari islands on the coast of Italy, of which Stromboli is remarkable for having thrown out flames, without the eruption of other volcanic matter, for more than 2000 years. In Asia there is a volcano in Mount Taurus; five in Kamtchatka, 10 in the islands of Japan; one in the peak of Adam in the island of Ceylon; four which have been observed in Sumatra; and some others in different parts of the Asiatic continent or islands. There are also some volcanoes on the African continent, as well as in some of the islands. Volcanoes exist also in the American continent, and in many of the islands which have been discovered in the South seas.

Almost all volcanoes are in the immediate vicinity of the sea. Mount Taurus, in the interior of Asia, and some of the volcanoes in the Andes, are the only exceptions to this.

Another general remark which may be made with regard to volcanoes is, that they always occupy the tops of mountains. No volcano was ever found burrowing out in plains. The existence of volcanoes at the bottom of the ocean seems to be an exception; but it is to be observed, that these are also in the peaks of mountains, which have been raised up from great depths at the bottom of the ocean.

The first symptom of an approaching eruption is an increase of the smoke, if smoke has been emitted, in fair of an eruption. This smoke is of a whitish colour; but, after some time, black smoke is observed to shoot up in the midst of the column of white smoke. These appearances are usually accompanied with explosions. The black smoke is then followed, at a shorter or longer distance of time, by a reddish-coloured flame. Showers of stones are afterwards thrown out, and some of them are projected to great heights in the air, which shews that the force by which they are impelled is very great. Along with these, ashes are likewise ejected. These phenomena, which daily increase in frequency and violence, are also usually preceded and accompanied by earthquakes, and hollow noises from the bowels of the earth, something like those that precede earthquakes unaccompanied with volcanic eruptions. The smoke, flame, and the quantity of stones and ashes, increase, and the stones are at last thrown out red hot.

The smoke which issues from the crater has been observed to be sometimes in a highly electrified state. The ashes are strongly attracted, and carried up along with the smoke to great heights in the atmosphere, forming a dense black column of vast height and size. Flashes of lightning are seen darting in a zig-zag direction, through the column of smoke and ashes; and this lightning is sometimes attended with thunder. But from some observations which have been made, this thunder and lightning are seemingly less intense than atmospheric electricity. When these terrible appearances have continued for four or five months, or for a longer or shorter time, according to the nature of the eruption, the lava begins to flow. This is a current of melted matter, which sometimes boils over the top, and sometimes, when the mountain is high, as is the case with Etna, bursts out at the side, and makes a passage for itself. The period of the duration of the eruption is very different. Sometimes it continues to flow, at intervals, for the space of several weeks.

The matters ejected from volcanoes are lavas, which are either more or less consolidated; ashes, flags of different kinds, and stones which have undergone little or no fusion. For an account of the nature and properties of volcanic productions, see MINERALOGY. Stones have been projected into the air from Mount Etna, to the height of 7000 feet. A stone which was ejected from Vesuvius, measured 12 feet long, and 45 feet in circumference; and even larger masses have been thrown out from Etna.

Water has been frequently ejected from volcanoes. This water is sometimes cold, and sometimes hot. Eruptions of water have taken place, both from Vesuvius and Aetna. At one time salt water was ejected from Mount Vettius. Different opinions have been held concerning the origin of this water, or its connexion with the volcano. This is founded on the circumstance already taken notice of in the general remark which was made, that almost all volcanoes are in the vicinity of the sea.

It seems to be a singular circumstance in the history of volcanoes, that when once eruptions have commenced, they follow each other in rapid succession; and at other times that they cease for a long period. From the year 1447, Aetna ceased to throw out any fire till the year 1536, when a terrible eruption took place, accompanied with smoke, flame, ashes, and burning stones. This conflagration continued to rage with great violence for many weeks. The following year a river swelled and overflowed its banks to a great distance; furious squalls of wind succeeded, after which there was a terrible eruption from Aetna. The torrents of flaming and fused matter which flowed out, destroyed towns, villages, and vineyards, to a great extent. After the conflagration, the summit of the mountain fell in with a dreadful crash. For 100 years after this period, the eruptions seemed to observe some kind of regularity, returning periodically every 25 and 30 years. From the year 1686 to 1755, the same year on which the earthquake at Lisbon happened, for more than half a century, Aetna enjoyed profound repose.

The first considerable eruption of Vesuvius, the account of which is recorded in history, happened in the year 79 of the Christian era. It was this eruption which destroyed Herculaneum and Pompeii; but this was not the first eruption of this mountain, for the streets of these cities have been since discovered to be paved with lava. Since that time, 30 different eruptions have taken place. There was a very remarkable one in 1538.

It would appear that volcanoes seem to become quite extinct, and are rekindled. Some of the Roman writers, as Diodorus Siculus, Vitruvius, and others, speak of Vesuvius only as having been a volcano. After this period it burnt for 1000 years, and again became extinct, from 1136 to 1506. Pools of water had collected in the crater, and woods were growing on its sides, and even in the crater itself. Vesuvius has now burnt for three centuries past, as furiously as ever; but particularly, during the 18th century. Of 29 eruptions which have taken place from Vesuvius, since the reign of Titus, half of the number have happened in the 18th century.

Beside the volcanoes, the history of which we have now briefly detailed, volcanoes are known to exist at the bottom of the ocean. These are distinguished by the name of submarine volcanoes. Excepting in situation, so far as the history of submarine volcanoes is known, they resemble the volcanoes on land. It would appear that they exist in the tops of mountains at the bottom of the ocean, and eject immense burning masses of matter in whirlwinds of ashes and pumice, with prodigious torrents of lava. Submarine volcanoes are either very few in number, or the places where they exist have not been ascertained. Those that are certainly known are at Santorin, the Azores, and Ice-land. The island of Santorin, formerly called Thera Earth- and St Irene, was denominated by the Greeks, in allusion to its origin, Kavouni, or "burnt." According to Pliny, there is a tradition, that it arose out of the sea, at a very remote but unknown period.

Without going far back into history, to inquire concerning the early eruptions of this volcano, we shall mention some of a later date, the existence of which is better ascertained. In 1457, an eruption took place, at which time ashes and red-hot rocks were ejected, with a great quantity of lava. This event, with the date of it, is recorded on a marble stone, erected near the gate of Fort Scarus, in Santorin. An eruption also took place in 1570. This produced a new island, called the Little Kaminoi. In 1650, the agitations of the volcanoes continued for the greater part of a year. Smyrna and Constantinople were inclosed with the ashes, which rushed from the ocean in whirlwinds of flame. The same volcano opened again in 1707. The Little Kaminoi, mentioned, was increased, and it is now more than three leagues in circumference. A violent eruption took place in 1767, which shook the earth greatly for some days, and raised the sea in such a manner, as to excite apprehensions of the destruction of the islands in the neighbourhood. A thick black smoke darkened the air, which was so infected with a strong smell of sulphur, that many persons and animals were suffocated by it. Black ashes resembling gunpowder were dispersed around, and torrents of flame issuing from the sea, and waving above it, to the height of several feet, lighted, at intervals, the horrid scene. At the end of 10 or 12 days the eruption began to be more moderate; and a new island which had been thrown up was discovered. When it was examined, many parts of it were still burning; but the next day, those whom curiosity had drawn to the spot, were compelled to betake themselves to flight. They felt the new soil moving; in some parts it rose, and sunk in others. The earth, sea, and sky, soon resumed their formidable appearance; the boiling sea changed colour; flames in rapid succession issued as from a furnace, but accompanied with ashes and pumice. The frightful noise of subterranean thunders was heard; it seemed as if enormous rocks, darting from the bottom of the abyss, beat against the vaults above it, and were alternately repelled and thrown up again. The repetition of their blows seemed to be distinctly heard. Some of them finding a passage, were seen flying up red hot into the air, and again falling into the sea from which they had been ejected. Masses were produced, held together for some days, and then disappeared. In this general disorder, large portions of the Little Kaminoi were swallowed up. Meanwhile the labour of the volcano took a larger surface. Its ejections became prodigiously abundant, and a new island was seen forming. By successive additions continued for near four months, it made a junction with that produced in June. From the colour of its soil it was named the Black Island. It is larger than the Little Kaminoi, and is separated from it by a narrow strait. After frequent alarms for several months, the volcano opened again on the 15th of April in the following year; but the eruption was only for a moment, when it threw out a multitude of burning rocks, which fell at the distance of two miles. Similar submarine volcanoes have been observed near the island of St Michael, one of the Azores or Western islands in the Atlantic ocean. In the year 1638, near the island of St Michael, where the sea was known to be 120 feet deep, there arose, after an agitation of several weeks, an island about six miles round. It was again swallowed up in about the same space of time that had elapsed during its formation. In the year 1691, this volcano was in great agitation for a month. It convolved the whole island of St Michael, and by the heat and violent commotion of the sea, as well as by the eruption of flames, ashes, and pumice, occasioned great damage; but in this case no island appeared. Similar eruptions were known in 1720, and in 1757. During the latter eruption, some of the islands were shaken to their foundations.

After this account of submarine volcanoes, of their effects, and of the islands formed by them, it would be unnecessary to enter into any detail of the submarine volcano which threw up an island off the coast of Iceland, in the year 1783. This island, the existence of which seemed to be fully ascertained, was again swallowed up in the ocean, and was seen no more.

Volcanoes of a very different kind have been described. The volcanoes to which we allude, have received the name of mud volcanoes, from ejecting a great quantity of mud. These, however, are similar to those which have been already described, in having volcanic motions and convulsive eruptions. The first volcano of this kind which was discovered is in the island of Sicily, near a place called Macalouba, between Aragona and Girgenti. It is in a hill of a conical shape, truncated at the top, and 150 feet high. The summit is a plain, half a mile round, and the whole surface is covered with thick mud. The depth of the mud, which is supposed to be immense, is unknown. There is not the slightest appearance of vegetation upon it. In the rainy season the mud is much softened; the surface is even, and there is a general ebullition over it, which is accompanied with a very sensible rumbling noise. In the dry season, the mud acquires greater consistency, but without ceasing its motion. The plain assumes a form somewhat convex; a number of little cones are thrown up, which rarely rise to the height of two feet. Each of them has a crater, where a black mud is seen in constant agitation, and incessantly emitting bubbles of air. With these the latter insensibly rises, and as soon as the crater is full of it, it disgorges. The residue sinks, and the cone has a free crater until a new emission.

This hill is sometimes subject to alarming convulsions. Earthquakes are felt at the distance of two or three miles, accompanied with internal noises, resembling thunder. These increase for several days, and terminate in an eruption of a prodigious spout of mud, earth, and stones, which rises two or three hundred feet into the air. This explosion is repeated twice or thrice in the course of 24 hours. Some years pass over without any eruption, but it generally happens that the eruptions continue yearly for five years successively. An eruption from this mud volcano took place in 1777.

Phenomena somewhat similar have been described by Pallas, which he observed partly in the peninsula of the Kercha, the boundary of Europe to the south-east of Little Tartary, now Taurida, and partly in the island of Taman, which is separated from Kercha only by one of the mouths of the river Cuban. The island of Taman is situated in Asia. These places, he observes, are in flat countries where there are few hills, and those very little raised above the level of the sea. The whole is covered with beds of flint, mixed with sand, with some beds of marl and sea-shells. From this he concludes that no real volcanic pit can exist here. Copious springs of petroleum are found in several places, and also pools or typhons of various dimensions, through most of which a briny mud is disgorged in bubbles. Pallas observed several of these pools, both in the peninsula and in Taman. The last eruption which took place, he observes, was in 1794. This was the greatest and most copious that had been known. It proceeded from the top of a hill at the north point of Taman. The place where the new gulf opened was a pool, where the snow and rain water usually remained for a long time. The explosion came on with a noise like that of thunder, and with the appearance of a mass of fire in the form of a sheaf. This lasted only for about half an hour, and it was accompanied with a thick smoke; but the ebullition which threw up part of the liquid mud, continued till the next day, after which the mud ran slowly in streams down the hill. The mud discharged was of a soft clay, of a bluish ash colour, every where of the same nature, and mixed with brilliant sparks of mica, with a small quantity of marl, calcareous and sandy fragments of schistus, which seemed to have been torn from their beds.

Pallas supposes that a very deep coal mine had been for ages on fire, under Kercha and Taman, and that the sea having accidentally broken into the burning cavities of the mine, the expansion produced by the water converted into steam, and the struggle of the different aeriform substances to get free, forced the upper beds, broke them in pieces, and formed a passage to themselves. The vapours, as they escaped, carried the mud along with them. But others have supposed that these phenomena are not produced by fire; that the appearance of the sheaf of fire mud have been extraneous, or that it was only a quantity of inflammable air, which exploded when it came to the surface; or, perhaps it was altogether an illusion, from the appearances of the vapours which were emitted.

An account is given of a singular phenomenon, somewhat similar to the above, which was observed in 1711, at Bofely, near Wenlock, in Shropshire. After a great hurricane, the inhabitants were awakened in the middle of the night by commotions of the earth, which were accompanied with noise. Some persons went to an eminence from which the noise proceeded, and they saw water oozing through the turf, while at the same time inflammable air was emitted. The water was not hot. This continued for some time, but at last it ceased to throw out any inflammable air for some years, previous to the year 1746, when a second eruption took place, attended with similar circumstances.

We shall not dwell longer on the history of volcanoes. For a particular account of the most remarkable eruptions of the principal volcanoes in the world, the reader is referred to the history given under Etna, Hecula, and Vesuvius. We shall now proceed to state some of the opinions and conjectures of philosophers, phers, with regard to the cause of these extraordinary phenomena.

Volcanic eruptions have been ascribed to the action of the waters of the sea, bursting in upon an immense quantity of fused or burning matter; to the action of central fires, and to the decomposition of different substances, by which a great quantity of heat and inflammable fubstances is produced.

Water, according to some philosophers, is absolutely necessary for the formation of volcanoes. This opinion is supported by the circumstance of almost all volcanoes being near the sea. According to this opinion, they were all formed under the surface of the waters of the ocean. The first explosion at the formation of a volcano, it is supposed, was preceded by an earthquake. The first eruptions would be extremely violent, and immense quantities of matter would be ejected. Torrents of lava would continue to be discharged for a long series of ages, and thus the foundations of the burning mountain are laid in the bottom of the ocean. But it becomes a question, in what way the internal fire was preserved from extinction by the incumbent waters of the ocean? To this M. Houel replies, that the fire having difused the fubstances in fusion to make an eruption, next laid open the earth, and emitted as much matter as it could discharge, with a force sufficient to overcome the resistance of the column of water, which would oppose its ascent; but as the strength of the fire diminished, the matter discharged was no longer expelled beyond the mouth; but, by accumulating there, soon closed up the orifice. Thus, only small orifices would be left sufficient for giving vent to the vapours of the volcano, and from which only small bubbles of air could ascend to the surface of the water, until new circumstances, such as originally gave occasion to the eruption of the volcano, again took place in the bowels of the earth, and produced new eruptions, either through the same or other mouths. The appearance of the sea over the new formed volcano, in its state of tranquillity, would then be similar to what it is betwixt the islands of Bafilizzo and Pariaria. Columns of air bubbles are there ascending at the depth of more than 30 feet, and burst on their arriving at the surface. This air would continue to difengage itself with little disturbance as long as it issues forth only in small quantity, until, at the very instant of explosion, when prodigious quantities, generated in the burning focus, would make their way at once, and the same phenomena which originally took place would again make their appearance.

A volcano, while under water, cannot act precisely as it does in the open air. Its eruptions, though equally strong, cannot extend to so great a distance. The lava accumulates in greater quantity round the crater; the sand, ashes, and pozzolana are not carried away by the winds, but are deposited around its edges, and prevent the marine substances which are driven that way by the waters from entering. Thus they agglomerate with these bodies, and thus a pyramidal mount is formed of all the materials together.

In this manner M. Houel supposes that the mountain was gradually raised out of the sea by the accumulation of lava, &c. at every eruption, and that the cavern of the volcano was gradually enlarged, the lava being driven down into the bottom of the cavern by the continued action of the stones which the volcano is constantly throwing up; that it was there fused, and at last thrown out at the top of the mountain to accumulate on its sides. M. Houel's opinion about the volcanic fire we shall give in his own words.

"We cannot form any idea of fire subsisting alone, without any pabulum, and unconnected with any other principle. We never behold it but in conjunction with some other body, which nourishes and is consumed by it. The matter in fusion, which issues from the focus, is but the incomputable part of that which nourishes the fire, and into the bosom of which that active principle penetrates in search of pabulum. But as the fire acts only in proportion to the facility with which it can difuse and evaporate, I am of opinion, that it is only the bottom of the volcano on which it acts; and that its action extends no farther than to keep these substances which it has melted in a constant state of ebullition. That fusible matter being discharged from the mouth of the volcano, and hardening as it is gradually cooled by the action of the air, produces that species of stones which are distinguished by the name of lavas. This lava, even when in the focus, and in a state of fluidity, must also possess a certain degree of solidity, on account of the gravity and density of its particles. It therefore opposes the fire with a degree of resistance which irritates it, and requires, to put it into a state of ebullition, a power proportioned to the bulk of the mass.

"That quantity of matter, when difused by the action of the fire, must constantly resemble any other thick substance in a state of ebullition. Small explosions are produced in various parts over the surface of every such substance while in a state of ebullition; and, by the bursting of these bubbles, a great number of small particles are scattered around. This is the very process carried on in the focus of a volcano, though on a scale immensely more large; and the vast explosions there produced expel every body which lies in their way with the utmost violence; nor is there any piece of lava which falls down from the upper part of the arch, of weight sufficient to resist this violent centrifugal force.

"The pabulum by which the internal fire is supported, M. Houel thinks to be substances contained in the mountain itself, together with bitumen, sulphur, and other inflammable materials, which may from time to time flow into the focus of the volcano in a melted state through the subterraneous ducts, and the explosions he ascribes to water making its way in the same manner. The water is converted into steam, which fills the cavern and pushes the melted lava out at the crater; this opinion is corroborated by the copious smoke which always precedes an eruption. But, combined with the water, there is always a quantity of other substances, whose effects precede, accompany, or follow the eruptions, and produce all the various phenomena which they display. The eruption of water from Aetna in the year 1775 proceeded undoubtedly from this cause. The sea, or some of the reservoirs in Aetna or the adjacent mountains, by some means discharged a vast quantity of water into the focus of the volcano. That water was instantly resolved into vapour, which filled the whole crater, and issued from the mouth of the crater. As soon as it made its way into the open atmosphere, it was condensed again into water, which streamed down the sides of the mountain in a dreadful and destructive torrent."

Others have attempted to account for the existence of volcanic fire, on the supposition that it is derived from central fires, and to these it is supposed that volcanoes act the part of chimneys; while others are of opinion that they are owing to the chemical decomposition of different substances, by which inflammable matters are evolved, with a great deal of heat, and by means of the latter the combustible materials are kindled, and exhibit the phenomena which are thus proposed to be accounted for.

M. Patrin is one of the latest naturalists who, with the assistance of modern chemistry, has attempted to account for the phenomena of volcanoes on the principles of this science. For a full view of his theory, or rather of his fanciful conjectures on this subject, we must refer the reader to the work itself*. But the following is a recapitulation of the principles on which he gives this explanation. All volcanoes, he observes, in a state of activity, are in the vicinity of the sea, and are never found but in those places where sea salt is abundant. The volcanoes of the Mediterranean abstract the salt which the waters of the ocean hold in solution, and are constantly pouring in by the straits of Gibraltar. The strata of primitive schistus are the great laboratories in which volcanic matters are prepared, by a constant circulation of different fluids; but according to this theory, these strata contribute no part of their own substance. They suffer no waste in the process.

The sphere of the activity of volcanoes may be far extended in these strata, but they have no other outlet beside spiracles, by which the gaseous substances escape, of which one part is dissipated in the atmosphere, and the other becomes concrete by its combination with oxygen. The concretion of these fluids is supposed to be analogous to the concretion of the primitive matters of the globe, according to the theory of La Place; and the elective attractions determine, in the same way, the formation of stony crystals.

Volcanic eruptions are proportioned, in regard to their violence and duration, to the extent of the strata of schistus in which the volcanic fluids are accumulated. These fluids are,

1. Muriatic acid, which carries off the oxygen from the metallic oxides of the schistus.

2. The oxygen of the atmosphere, which constantly replaces in the metals that which was carried off by the muriatic acid.

3. Carbonic acid gas, which the water absorbs from the atmosphere, and conveys to the schistus, which always abounds in carbone.

4. Hydrogen, which proceeds from the decomposition of water. A part of this hydrogen is inflamed by electric explosions; the other united to carbonic acid forms oil, which becomes petroleum by its combination with sulphuric acid; and it is to this petroleum that the bitterness of sea water is owing.

5. The electric fluid, which is attracted from the atmosphere by the metals contained in the schistus. Sulphur seems to be the most homogeneous portion of this fluid, which has become concrete. Phosphorus is a modification of it, and it contributes to the fixation of oxygen. The sulphur formed in the schistus by means of the electric fluid, combines with the oxygen, and forms sulphuric acid, which decomposes the sea salt.

6. The metalliferous fluid. This forms the iron in lavas. It is the origin of metallic veins, and the colouring principle of organized bodies. This substance in its undecomposed state affords iron, but by decomposition it produces other metals. It is conjectured to be one of the principles of muriatic acid, and it contributes, along with phosphorus, to fix oxygen under an earthy form.

7. The last of the volcanic fluids is exotic gas. To this gas is owing the formation of the marls of carbonate of lime which are ejected by Vesuvius, and of the calcareous earth contained in lavas.

Such are the materials with which the author proposes to form the different substances which are produced in volcanoes, and by the operation of which he proposes to explain the phenomena of volcanic eruptions. Our readers will probably agree with us in thinking, that the present state of chemical science, even with the assistance of such hypothetical substances as the metalliferous fluids, is yet inadequate to give any degree of support to such opinions, even in the form of conjecture.* We shall therefore dismiss it without farther remark.

We shall now conclude this subject with some interesting observations by M. de Luc, on the nature of the strata in which volcanic fires exist.

"Volcanoes, he observes, have been more numerous on the surface of our continents, when they were under the waters of the ancient sea; and as this clas of mountains, raised by subterranean fires, manifest themselves still on the shores of the present sea, and in the middle of its waters, it is of importance to geology and the philosophy of the earth to obtain as just ideas of them as possible.

"I have attended a great deal to this subject from my own observations; and I have shewn, at different times, the errors into which several geologists and naturalists, in treating of it, have fallen.

"This clas of mountains, in particular, requires that we should see them, that we should behold them during their eruptions, that we should have traced the progress of their lava, and have observed closely their explosions; that we should have made a numerous collection of the matters which they throw up under their different circumstances, that we might afterwards be able to study them in the cabinet, and to judge of their composition according to the phenomena which have been observed on the spot.

"This study is highly necessary when we apply it to geology and the philosophy of the earth, in order that we may avoid falling into those mistakes which make us ascribe to subterranean fires what does not belong to them, or which leads us to refute them what really belongs to them.

"We read in the Journal de Physique for January 1804, under the title, On the Cause of Volcanoes, the following assertions:

'What is the nature of the matters which maintain these subterranean fires? We have seen that Chimborazo, all these enormous volcanoes of Peru, and the Peak of Teneriffe, are composed of porphyry.

'The Puy-de-Dôme is also composed of porphyry, as well as the Mont d'Or and the Cantal.

'Ætna, 'Ætna, Solfatara, and Vesuvius, are also of the porphyry kind.

'These facts prove that the most considerable volcanoes with which we are acquainted are of porphyry.'

'This opinion, that the fires of volcanoes have their centres in such or such a rock, and that their lavas are produced from these rocks, has always appeared to me not to be founded on any certain data. Opinions also on this subject have varied; some having placed the origin of lava in horn rock, others in granite or schist, and at present it is assigned to porphyry.

'I have always been of opinion that nothing certain could be determined in regard to this point. It ever remains uncertain whether the seat of the matters of which lava is formed be in compact rocks, or in strata in the state of softness, pulverulent, and muddy.

'Those who see lava issue from a volcano in its state of fusion and incandescence, and in its cooling, are convinced that the nature of every thing is changed, that it exhibits a paste in which nothing can be known, except the substances which the volcanic fires have not reduced to fusion.

'But these substances contained in the paste of lava, and those which are the most numerous, show us, that the strata from which they proceed cannot be similar to those exposed to the view, nor even to the most profound strata to which we can penetrate.

'Admitting the hypothesis, that the strata from which the lavas proceed are in a pulverulent and muddy state, containing elements of all these small crystals, one may conceive how they are formed there, inflated, grouped, or solitary, and are found then in the lava in that state of infolution.

'The fragments of natural rocks thrown up by Vesuvius are not of the same kind as the matters of which the lava is composed. Most of these fragments are micaceous rocks, with laminae of greater or less size, and of a kind of granite called syenite. I have found some composed of white quartzy rock; it is found sometimes of calcareous rock.

'The most probable idea that can be formed in regard to the origin of these fragments is, that they have been carried from the borders of the strata through which the lava, that comes from great depths, has opened for itself a passage. These fragments are carried to the surface of the lava as far as the bottom of the chimney of the crater, whence they have been thrown out by explosions, mixed with fragments separated, or rather torn, from the lava; for it is not by the lava that they have been brought forth to view, but by explosions.

'Some of these fragments of natural rocks have not been attacked by the fire; others have more or less; which depends, no doubt, on the place which they occupied in the volcano, and on the time which they remained in it. The most of the latter have retained at their surface a crust of lava, and this crust contains substances which are not the same as that of the fragment it covers.

'On Vesuvius the strata pierced by eruptions are lower than the surface of the soil; in Auvergne and several places of Germany they are above; for this reason there are seen there in their place schists or granites, which the eruptions have broken to form for themselves a passage.

'No volcano rests on natural strata: they sometimes show themselves on the exterior; but they have been opened by eruptions, and their edges have remained in their place.

'The focus of no volcano exists or has existed in the cone which appears above the surface of the ground. They have been raised by eruptions, which, proceeding from great depths, have thrown them up through the upper strata. When it is said, therefore, that the volcanic mountains of Auvergne rest on granite, this is a mistake, and an incorrect expression has been used by those who have not formed a just idea of the phenomenon. Lava may have flowed upon granite or any other rock, and rested upon it; but this is never the case with the volcano itself: its bases are below all the rocks visible.

'It is from the bosom even of the lava, when in a state of fusion in the interior of the volcano, that all the explosions proceed. In that state of fusion they contain all the matters which produce fermentations, and the disengagement of expansible fluids.

'I have been enabled to ascertain this on Vesuvius as far as was possible. The continual noise which was heard through the two interior mouths of the crater which I had before my eyes, was that of an ebullition, accompanied with inflammable vapours, and the gerbes of burning matters which they threw up at intervals were separated pieces of the lava in its state of fusion. I saw several of them in the air change their form, and sometimes become flat on the bodies which they struck or embraced in falling. And among the most apparent of these fragments there are always a multitude of small ones of the size of peas and nuts, and still smaller ones, which flow at their surface, by their aperities, all the characters of laceration.

'The name of scoria has been given to these fragments, to distinguish them from compact lava, though their composition be the same as that of the hardest lava; and it is for want of reflecting properly on this point that it has been said that it is the compact part only that we must observe, in order to judge of their nature. The pieces which I took from the flowing lava with an iron hook, have at their surface the same lacerations and the same aperities as the fragments thrown up by explosions, and both contain the same substances.

'This separation, by tearing off the parcels of the lava, effected by fermentations and explosions which proceed from their bosom, serves to explain those columns, sometimes prodigious, of volcanic sand, which rise from the principal crater. When seen with a magnifying glass, this sand exhibits nothing but lava reduced very small, the particles of which, rough with inequalities, have the bright black colour and the varnish of recent lava.

'Parcels of substances which exist in our strata, such as fragments of quartz, scales of mica, and crystals of feldspar, are found sometimes in lava. Similar matters must no doubt be disseminated in the composition of our globe, without there being reason to conclude that the strata from which they proceed are the same as the exterior strata. It is neither in the granites, the porphy- ries, nor the horn rock, and still less in the schists and calcarceous rocks, that the ehorls of volcanoes, the leucites, and perhaps olivins, will be found. These small crystals are brought to view by the lava, otherwise they would be unknown to us.

"These lavas contain a great deal of iron, which they acquire neither from the granite nor porphyries. Might not one see in the ferruginous sand which is found in abundance on the borders of the sea near Naples, and in the environs of Rome, specimens of that kind of pulverulent strata from which lava proceeds?

"I have here offered enough to prove that it cannot be determined that lava proceeds from strata similar to those with which we are acquainted. The operations of volcanoes, those vast laboratories of nature, will always remain unknown to us, and on this subject our conjectures will always be very uncertain.

"What is the nature of that mixture which gives birth to these eruptions, that produce lava and throw up mountains? What we observe as certain is, that the introduction of the water of the sea is necessary to excite these fermentations, as containing marine acid, and other salts, which, united to the sulphuric acid, the bases of which are contained in abundance in the subterranean strata, determine these fermentations, which produce the disengagement of fire and other fluids, and all the grand effects that are the consequence.

"Several naturalists have believed, and still believe, that fresh or rain water is sufficient for this purpose; but they are mistaken: this opinion is contradicted by every fact known. To be convinced of this, nothing is necessary but to take a short view of them. I have done it several times, as it is necessary to consider them often. I shall here enumerate the principal ones:—No burning mountain exists in the interior part of the earth; and all those which still burn are, without exception, in the neighbourhood of the sea, or surrounded by its waters. Among the deliquescent salts deposited by the smoke of volcanoes, we distinguish chiefly the marine salt, united to different bases. Several of the volcanoes of Iceland, and Hecla itself, sometimes throw up eruptions of water, which deposit marine salt in abundance. No extent of fresh water, however vast, gives birth to a volcano. These facts are sufficient to prove that the concurrence of sea-water is absolutely necessary to excite those fermentations which produce volcanoes.

"I shall here repeat the distinction I have already made between burnt-out volcanoes and the ancient volcanoes, that I may range them in two separate classes.

"When we simply give the name of burnt-out or extinguished volcanoes to volcanic mountains which are in the middle of the continents, it is to represent them as having burnt while the land was dry, and inhabited as it is at present; which is not a just idea. These volcanoes have burnt when the land on which they are raised was under the waters of the ancient sea, and none of them have burnt since our continents became dry. It is even very apparent that most of them were extinct before the retreat of the sea, as we find by numerous examples in the present sea.

"Those which I denominate extinct volcanoes are such as no longer burn, though surrounded by the sea, or placed on the borders of it. They would still burn, were not the inflammable matters by which they were raised really exhausted and consumed. Of this kind is the volcano of Agde, in Languedoc. Of this kind also are many of the volcanic islands which have not thrown up fire since time immemorial.

"M. Humboldt, in his letters written from Peru, speaks of the volcanoes which he visited, but what he says is not sufficiently precise to enable us to form a just idea of them. He represents Chimborazo as being composed of porphyry from its bottom to its summit, and adds, that the porphyry is 1900 toises in thickness; afterwards, he remarks, that it is almost improbable that Chimborazo, as well as Pichincha and Antilana, should be of a volcanic nature: 'The place by which we ascended,' (says he), 'is composed of burnt and scorified rock, mixed with pumicestone, which resembles all the currents of lava in this country.'

"Here are two characters very different. If Chimborazo be porphyry from the top to the bottom, it is not composed of burnt and scorified rocks, mixed with pumicestone; and if it be composed of burnt rocks, it cannot be porphyry. This expression, burnt and scorified rocks, is not even exact, because it excites the idea of natural rocks, altered in their place by fire, and they are certainly lava which has been thrown up by the volcano. But the truth must be, that Chimborazo, and all the other volcanoes of Peru, are composed of volcanic matters, from their base at the level of the sea to the summit.

"I have just read in the Annales du Muséum d'Historie Naturelle*, a letter of the same traveller, written from Mexico, on his return from Peru, where, speaking of the volcanoes of Popayan, Paito, Quito, and the other parts of the Andes, he says, 'Great masses of this fossil (obsidian) have issued from the craters; and the sides of these gulfs, which we closely examined, consist of porphyry, the base of which holds a mean between obsidian and pitchstone (pechtlein).' M. Humboldt therefore considers obsidian, or black compact glass, as a natural fossil or rock, and not as volcanic glass†."

* Journ. de Mines, N° 95.

PLATE CCXXXVIII.

Fig. 1.

Fig. 2. Siende Breccia Prim. Mica Slate Gneiss Granite Gneiss Mica Primit Slate

Fig. 3.

Fig. 4. a Sea Granite Granite Granular Quartz Granular Quartz Sea

Fig. 5. A B C D E F W. Archibald sculp. Fig. 6. GEOLOGY. Fig. 7. PLATE CCXXXIX. Fig. 8.

Fig. 10. Fig. 9. INDEX.

A. Alabaster described, No 67 gypsaceous, 85 Amonton's theory of earthquakes, 229 Amygdaloid described, 72 Antimony, ores of, enumerated, 170 Arsenic, ores of, enumerated, 173

B. Basalt described, 100 Werner's opinion respecting, Note (r) p. 600. Beccaria's theory of earthquakes, 231 Bismuth, ores of, enumerated, 168 Breccia described, Note (c) p. 556. examples of, 49 Buffon's remarks on mountains, 117 theory of the earth, 184 objections to, 185 Burnet's theory of the earth, 181

C. Chalk, 88 where found, 89 Clay, indurated, 90 flate, described, 91 Coal, general circumstances attending, 104 where found, 106 mines of France, 107 England, 108 strata at Newcastle, table of, p. 566 Whitehaven, table of, 568 bovey, described, No 110 Cobalt, ores of, enumerated, 171 Copper, ores of, enumerated, 164

D. Delametherie's remarks on the declivities of mountains, 119 Dolomieu's theory of earthquakes, 233 Dykes, account of, 142 names of, 143 course of, 144 inclination of, 145 extent of, 146 thickness of, 147 materials of, 148 whin, peculiar structure of, 149

E. Earthquakes, account of, 198 where most prevalent, 199 phenomena preceding and accompanying, 200 at Calabria, in 1635; relation of, 201 in Sicily, 202 Earthquakes, in Jamaica, at Lilbon, 203 felt at Colares, 204 at Oporto, 205 destroys St Ubes, 206 felt in Spain, 207 in Africa, 208 in Madecira, 209 in France, 210 in Germany, 211 in Switzerland, 212 in Holland, 213 in Norway, 214 in Britain, 215 effects of, at sea, 216 in Calabria, in 1783; destruction of Op-pido, by, 217 in Peru, 218 in Scotland, 219 causes of, according to the ancients, 220 according to the moderns, 221 theory of, by Woodward, 222 by Amontons, 223 by Stukeley, 224 by Beccaria, 225 by Priestley, 226 by Dolomieu, 227 ascribed to the force of steam, 228

F. Fluor spar described, 86 where found, 87 Fossils, vegetable, animal, 109

G. Geognosy, definition of, 1 Geology, definition and object of, 2 division of, 3 importance of, 4 to naturalists, 5 miners, 6 landed proprietors, 7 Christians, 8 difficulties attending the study of, not insurmountable, 9 principal improvers of, method of studying, 10 Gneiss described, where found, 24 metals found in, 25 Gold, ores of, enumerated, 161 Granite described, its different states, 19

N° 203 Granite, stratified, instances of, where found, 21 decay of, 22 metals found in, 23 Gray wacke described, flate described, ib. where found, 69 rich in metals, 70 Greenstone described, 74 Gypsum described, 79 common, 81 lenticular, ib. crystallized, 82 fibrous, 83 stalactitic, 84

H. Herman's remarks on mountains, 118 Hornblende flate described, 40 metals found in, 41 Hornstone described, 37 Houel's theory of volcanoes, 244 Hutton's theory of the earth, 188 objections to, 189

I. Jasper described, 35 where found, 36 Iron, ores of, enumerated, 165 Ironstone, argillaceous, described, 97 Islands formed by submarine volcanoes, 242

K. Kirwan's remarks on the declivities of mountains, 114—124 theory of do. of dykes, 196

L. Lead, ores of, enumerated, 166 Limestone, granular, described, 54 where found, 55 metals found in, 56 secondary, described, 64 where found, 65 metals found in, 66 Lithomarga, 92 Luc's (de) observations on the strata in the neighbourhood of volcanoes, 245

M. Manganese, ores of, enumerated, 173 Marl described, 96 Materials composing the earth, general distribution of, 12 division of, 17 Mercury, ores of, enumerated, 162 Molybdena, where found, 174 Mountains, definition of, No 112 chains of, 113 declivities of, 124 Kirwan's observations on, 114 sloep side of, faces the low country, 115 western side of, steepest, 116 remarks on by Buffon, 117 by Herman, 118 by Delametherie, 119 south and south-east sides of, the steepest, 120 account of, in Europe, 122 in Asia, 123 in America, 124 height of, table of, p. 576 course of, No 126 structure of, 127 primary and secondary, how distinguished, 128 equatorial, not the highest, 129 Uralian, course of, 131 Altaic, course of, 132 Alpine, 133 Afiatic, 134 southern, 136 of North America, 137 England, 138 Scotland, 140 Ireland, 141

Nickel, ores of, enumerated, 172 Northwich, salt mines at, 193

Ores, metallic, enumerated, 159—179 of platina, 160 gold, 161 mercury, 162 silver, 163 copper, 164 iron, 165 lead, 166 tin, 167 bismuth, 168 zinc, 169 antimony, 170 cobalt, 171 nickel, 172 manganese, 173 molybdena, 174 arsenic, 175 tungsten, 176 uranium, 177 titanium, 178 tellurium, 179

P. Patrin's theory of volcanoes, No 244 Pitchstone described, 38 where found, 39 Platina, where found, 160 Porphyry described, 44 where found, 45 metals found in, 46 schifrose, 47 Priestley's theory of earthquakes, 232 Puddingstone, 30

Q. Quartz described, 32 where found, 33 no metals found in,

S. Salt rock described, 101 where found, 102 mines at Northwich, 103 Sandstone described, 75 argillaceous, 76 where found, 77 filiceous, 78 Schiflus, micaceous, described, 27 where found, 28 metals found in, 29 argillaceous, described, 32 where found, 33 metals found in, 34 filiceous, described, 61 where found, 62 Syenite described, 51 where found, 52 metals found in, 53 Silver, ores of, enumerated, 163 Slate, 94 clay, 93 Strata of the earth, horizontal and vertical, 14 derangement of, 15 in general regular, 16 in various parts of Europe, table of, p. 573 Stukeley's theory of earthquakes, No 230

T. Tellurium, ores of, enumerated, 179 Theories of the earth, object of, 180 of Burnet, 181 of Woodward, 182 of Whiston, 183 of Buffon, 184 objections to, 185 of Whitehurst, 186 objections to, 187

Theory of Hutton, objections to, 188 of Werner, 189 Tin, ores of, enumerated, 193 Titanium, ores of, enumerated, 167 Toadflone described, 72 Topaz rock described, 60 Trup, primitive, described, 37 where found, 58 metals found in, 59 secondary, described, 71—74 globular, 72 Tungsten, ores of, enumerated, 176

U. Uranium, ores of, enumerated, 177

V. Veins metallic, account of, 150 definition of, 151 perpendicular, 152 two kinds of, 156 course of, 153 inclination of, 154 thickness of, 155 pipe, described, 157 flat, described, 158 Volcanic fluids, 244 Volcanoes exist almost in every part of the world, 235 number of, 236 all near the sea, 237 all on the tops of mountains, 238 symptoms of the eruption of, 239 matters thrown out by, 240 become extinct, and are rekindled, 241 submarine, 242 of mud, 243 causes of, discussed, 244

W. Wacke described, 99 Werner's theory of the earth, 193 objections to, 194 opinion on the formation of basalt, Note (r) p. 660. theory of veins, 195 Whinstone, 98 Whiston's theory of the earth, 183 Whitehurst's theory of the earth, 186 objections to, 187 Woodward's theory of the earth, 182

Z. Zinc, ores of, enumerated, 169