cles. When these are filled up with other minerals, the rock passes into amygdaloid Amygdaloid is nothing more than this last state of greenstone. The vesicles are filled up with calcareous spar, chalcedony, quartz, jasper agate, green earth, amethyst, &c., either completely or partially. Sometimes the transition greenstone, in this softened state, contains crystals of felspar colored green by the hornblende. It then constitutes porphyritic transition trap. Globular trap is a fine granular hornblende rock of a loose texture, and tending very strongly to clay; of a liver brown color, and containing in it globular masses composed of concentric lamellar concretions, and containing a hard kernel. The transition trap rocks are only doubtfully stratified. They alternate with the other transition formations in beds, and sometimes compose whole mountains. Common and lenticular clay ironstone occurs in it in beds. 4. Transition flint slate.-This formation consists essentially of common flint slate and Lydian stone, which pass into each other. It is a simple stone, but is characterised by containing many veins of quartz. It is not stratified. When it constitutes rocks they are usually steep, and appear very much lacerated and worn down by the weather. This is occasioned by the numerous rents which this species of rock contains. To this formation seems to belong riband jasper, which sometimes constitutes whole rocks. It may possibly occur also in some of the subsequent formations. To these formations may be added transition gypsum, which Von Buch discovered, constituting a bed in greywacke slate, at Leogang in Salzburg. CLASS III.-FLOETZ FORMATIONS. The next grand class of formations have received the name of flatz, because they lie usually in beds much more nearly horizontal than the preceding. When not covered by a succeeding formation, they form hills which do not rise to the same height as the primitive or transition. They contain abundance of petrifactions; and these much more various in their nature than those which occur in the transition formations, consisting of shells, fish, plants, &c. indicating that they were formed at a period when organised beings abounded. The floetz formations lie immediately over the transition in the following order. 1. Old red sandstone.-This formation lies immediately over the transition, or, where they are wanting, over the primitive rocks. Hence it is considered as the oldest of the flatz fornations. Sandstone is composed of grains of quartz, or some other siliceous stone, cemented together by some basis, and can only be considered as a mechanical mixture. The cement is sometimes clay, sometimes quartz, lime, marl, &c., and the sandstone is named, in consequence, argillaceous, siliceous, calcareous, marly, &c. This cement varies much in quantity, but never pre dominates; sometimes it is too small in quantity to be perceived. The size of the grains is no less subject to variation; when they are large the rock is sometimes called pudding stone. Of the old red sandstone the grains are large. It is distinctly stratified, and contains few ores. Cobalt, however, occurs in it; and it is often impregnated with copper. 2. First flatz limestone.-Flatz limestone is of a gray color; its fracture compact; has no lustre, and is only translucent on the edges. Sometimes thin beds of granular foliated limestone occur in it; but they contain petrifactions, which distinguish them from primitive limestone. Flatz limestone is well characterised by the masses of hornstone and flint which it contains. The first flatz limestone is characterised by a bed of bituminous marl slate, containing copper. This bed is always lowest, and therefore immediately contiguous to the sandstone. It contains but few petrifactions. They consist chiefly of fish. Various beds of marl occur in this formation, and likewise a species of vesicular limestone, known in Germany by the name of rauch wacke. 3. First flatz gypsum.-Gypsum, in general, may be considered as a simple rock; sometimes, however, it contains crystals of boracite, arragonite, and quartz. Sulphur is likewise found in it, both disseminated and in compact masses. There are two formations of it. The first flætz gypsum lies immediately over the first flætz limestone. It consists chiefly of foliated and compact gypsum, together with a good deal of selenite. It is in this formation that swinestone occurs, either in beds or mixed with the gypsum. Rock salt also belongs to it, and appears to lie over it in short thick beds, being usually mixed with a species of saline clay. Hence the saline springs, which obviously originate from rock salt, are likewise peculiar to this formation. 4. Variegated sandstone.-This formation lies inmediately over the preceding. The rock which composes it consists of a fine granular argillaceous sandstone, usually of a green, brown, red, and white color. Several of these colors alternate in stripes, which gives the stone a variegated appearance. Hence the name. often contains masses of a fat clay, of a greenish, reddish, or yellowish color. It This formation is characterised by two species of rocks, which occur in it in beds. These are, 1. The subspecies of limestone, described under the name of roestone; and, 2, Sandstone slate. 5. Second flatz gypsum.-This formation lies over the preceding in beds, and is sometimes, to a certain degree, mixed with it. It contains foliated gypsum, but scarcely any selenite, and no swinestone; and is characterised by the fibrous gypsum, of which it is in a great measure composed. It is of no great extent, and destitute of petrifactions. 6. Second flatz limestone, or shell limestone.— This formation is separated from the first floetz limestone by the beds of older gypsum, of variegated sandstone, and of second gypsum, which constitute the third, fourth, and fifth formations. It is characterised by the vast number of shells which it contains in the state of petrifactions. Particles of galena are likewise found scattered through it. 7. Third sandstone, or freestone.-The relative position of this formation has not been well ascertained, yet it is known to cover all the preceding, and therefore to be much newer than either the first or second formations. It consists mostly of a sandstone of a white color, well adapted for building. It contains traces of coal, but no sandstone, slate, nor roe-stone; and gypsum never occurs either immediately over or under it. It is usually stratified, and contains natural rents or seams, which cross each other at right angles; the one parallel to the stratification, the other perpendicular to it, so that it can be easily quarried into large square blocks. This indeed is a character that in some measure applies to all the sandstones. When not covered by any other formation it forms beautiful hills and romantic valleys. 8. Chalk.-Chalk is one of the newest fleetz rocks. It is always near the sea coast. It contains numerous beds of nodular flint, often full of vesicles. Various petrifactions of echinites, belemnites, &c., occur in it. It is indistinctly stratified, and forms beautiful round knolls and hills of very small height. Pyrites is sometimes found in it, but scarcely any other metallic ore. 9. Independent coal formation.-This formation is deposited in detached patches, usually in valleys over the preceding fleetz rocks, or over the transition formation when the fleetz rocks are wanting. These patches, in general, have no connexion with each other. Hence the epithet independent, by which the formation is distinguished but they are found in considerable quantities in the most distant parts of the earth, Europe, America, New Holland, and always similarly situated with respect to the other formations. Coal occurs in it in great abundance; though in the preceding formations it is very scarce, and indeed is only found in thin individual beds. Hence it is considered as characteristic of this formation. The rocks of which this formation is composed (not reckoning the coal) are the following: sandstone, coarse conglomerate, slate-clay, bituminous shale, indurated clay, limestone, marl, clay ironstone, porphyritic stone, greenstone. Layers of these rocks alternate a great many times with each other, and in them the coal occurs in numerous beds, varying extremely in thickness. The subspecies of coal which occur in this formation are coarse coal, foliated coal, cannel coal, slate coal, and a little pitch-coal. Professor Jameson has likewise discovered glance coal in this formation. All the different rocks of which this formation is composed seldom or never occur together. Hence it is presumed, that there are several subordinate formations belonging to the independent coal, which occupy determinate situations with respect to each other. Three such formations have been characterised. The oldest or lowest is composed of beds of indurated clay, limestone, marl, porphyritic stone, slate clay, bitu minous shale, greenstone, and soft sandstone, and is characterised by containing in it some metallic ores. These are ores of copper, iron, lead, and perhaps also mercury. The second is composed of beds of indurated clay, marl, limestone, and porphyritic stone. It contains some pyrites, but no other ore. The third, or newest, is composed of soft sandstone, conglomerate, and slate-clay, and contains no ore. The rocks belonging to this formation are very distinctly stratified. Abundance of vegetable petrifactions occur in it, especially in the sandstone and bituminous shale. 10. Flatz trap.-The rocks of this formation are very remarkable. They cover the other flatz rocks, precisely as the newer porphyry and sienite do the primitive. The level of the uncovered flatz formations becomes gradually lower, in the order in which they have been described; but that of the fleetz trap is high, as it covers them all, and often forms the summit of hills, whose lower part consists of older formations. The rocks belonging to the flatz-trap formations are of two kinds: namely, those which are peculiar to it, and those which occur also in other formations. The following are the rocks peculiar to this formation: wacke, iron-clay, basalt, pitchstone, greenstone, porphyry slate, graystone, amygdaloid, trap-tuff. Basalt, in many treatises, claims the first place, as it characterises the flatz formation; but it is now often referred to the volcanic formations. It consists essentially of the mineral described in another place under the name of basalt, for a basis, containing crystals of basaltic hornblende, augite, olivine, and iron-sand, which give it a porphyritic structure. It contains also vesicles, which are filled with zeolite, calcareous spar, lithomarge, &c. The vesicles are sometimes filled with water. Sometimes it passes into wacke; sometimes into graystone; and sometimes, though rarely, into porphyry slate. Wacke is sometimes the simple mineral described already under that name. Sometimes it contains basaltic hornblende and mica, which give it a porphyritic appearance: sometimes it is spotted, from crystals which it contains. It passes sometimes into clay; sometimes into basalt. The iron-clay likewise has been described already. Pitchstone was first observed in this formation by professor Jameson. It is distinguished from that which occurs in the older rocks by the following circumstances: Its colors are usually black or green; it is composed of lamellar distinct concretions, and it contains crystals of glassy felspar, or mionite as it is called. Porphyry-slate is much less common than basalt; but where it does occur it usually forms considerable hills. This rock is slaty in the large, compact and splintery in the small. The basis of it consists of clinkstone; the crystals which it contains are of felspar and hornblende. It contains also zeolite, iron-sand, and some minerals not yet described. Greystone is still less common than porphyry slate. It appears to consist of an intimate mixture of much white felspar and a little black hornblende. This basis contains augite and olivine. Flatz greenstone is an intimate mixture of The pseudo-volcanic consist of minerals altered in consequence of the burning of beds of coal situated in their neighbourhood. Porcelain jas grains of felspar and hornblende. It is distinguished from primitive and transition greenstone by the more intimate mixture and less crystallised appearance of the constituents. It passes into per, earth slag, burnt clay, columnar clay-iron basalt. Amygdaloid has for its basis sometimes wacke; sometimes a fine granular greenstone, frequently already somewhat decomposed. The vesicles which it contains are filled with green earth, lithomarge, steatite, &c. Sometimes they remain empty; sometimes this basis contains crystals of hornblende, &c., which gives the rock both a porphyritic and amygdaloidal struc ture. Trap-tuff consists of fragments of floetz trap and other rocks, cemented by a basis of alluvial clay. The minerals which this formation contains, in common with others, are not so numerous as the preceding. They are the following: sand, quartzy sandstone, clay, limestone, coal. The grains of sand are of all degrees of magnitude. The clay sometimes contains schaum earth The coal consists chiefly of the following subspecies; common brown coal, bituminous wood, and pitch coal. Sometimes, though seldom, glance coal and columnar coal occur in this formation. It is chiefly in the beds of plaster that the great number of fossil bones of land animals have been found, for the description of which we are chiefly indebted to Cuvier. CLASS IV-ALLUVIAL FORMATIONS. The alluvial formations constitute the great mass of the earth's surface. They have been formed by the gradual action of rain and river water upon the other formations, and may be considered as very recent formations; or rather as deposites, the formation of which is still constantly going on. They may be divided into two kinds; namely, those deposited in the valleys of mountainous districts, or upon the elevated plains which often occur in mountains; and those deposited upon flat land. The first kind consists of sand, gravel, &c., which constituted the more solid parts of the neighbouring mountain; and which remained when the less solid parts were washed away. They sometimes contain ores (particularly gold and tin) which existed in the neighbouring mountains. Sometimes the alluvial soil is washed, in order to separate these ores. On mountain plains there occur also beds of loam. The second kind of alluvial deposite, or that which occupies the flat land, consists of loam, clay, sand, turf, and calctuff. Here also occur earth and brown coal (in this mineral amber is found), wood coal, bituminous wood, and bog iron ore. The sand contains some metals, among others gold. The calctuff is a chemical deposite, and extends widely. It contains plants, roots, moss, bones, &c., which it has encrusted. The clay and sand often contain petrified wood, and likewise skeletons of quadrupeds. CLASS V.-VOLCANIC FORMATIONS. The volcanic formations are of two kinds; namely, the pseudo-volcanic and the true volcanic. stone, and perhaps also polishing slate, are the minerals which have been altered. The real volcanic minerals are those which have been thrown out of the crater of a volcano. They are of three kinds; 1. Those substances which, having been thrown out from time to time, have formed the crater of the mount an: 2. Those which have been thrown out of the crater in a stream, and rolled down the mountain; they constitute lavas: 3. The water which is occasionally thrown out of volcanoes, containing ashes and other light substances, gradually evaporating, leaves the earthy matter behind it; this substance constitutes volcanic tuff. Of veins.-Veins are mineral repositories which cut through the strata or beds of which a mountain is composed, and which are filled with substances more or less different from the rocks through which they pass. We shall have a very distinct notion of veins, if we suppose that the mountains in which they occur were split by some means or other, and that the rifts thus formed were filled up by the matter which constitutes veins. They are distinguished from beds by their direction, which is either perpendicular to the stratifications, or at least forms an angle with it. Sometimes the strata through which veins pass are merely separated from each other; so that if we cut through the vein we find the same strata of the rock on both sides of it; but sometimes also the corresponding strata on one side are lower than on the other, as if the portion of the rock on one side of the vein had sunk a little, while the portion on the other side kept its original position. In such cases the side of the rock against which the vein leans, or the floor of the vein, has always its strata highest up; while the strata of the portion of rock which leans over the vein, or the roof of the vein, are always lowest. So that this is the portion which appears to have sunk. Such a change of position in the strata is known in this country by the name of a shift. In considering veins, there are two circuinstances which claim our attention; namely, 1. The shape of veins; and, 2, The substances with which they are filled. All those mineralogists who have had the best opportunity of examining the shone of veins with correctness, agree in representing them as widest above, and as gradually diminishing in size as they deepen, till at last they terminate in a point, exactly as if they had been originally fissures. Sometimes, indeed, veins widen in different parts of their course, and afterwards contract again to their former size; but more commonly they continue diminishing gradually to their extremity. Sometimes these veins are either partially or entirely empty. In that case they are denominated fissures, but most commonly they are filled with a matter more or less different from the rock through which they pass. Sometimes the vein is filled up with one species of mineral. Thus we have veins of calcareous spar, of quartz, &c.; but, when it is of any size, we frequently find a variety of substances; these are disposed in regular layers always parallel to the sides of the vein, and they follow in their position a very regular order. One species of mineral constitutes the centre of the vein; on each side of this central bed the very same layers occur in the same order from the centre to the side of the vein. Almost every mineral substance which occurs in the mass of rocks has been found in veins. Veins of course, according to our theory, are newer than the rocks in which they occur; and, when two veins cross, that is obviously the newest wnich traverses the other without interruption, as the fissures constituting the second vein must have been formed after the first vein was filled up. But when different veins contain the same minerals, arranged in the same order, Werner conceives that they were filled at the same time, and says that such veins belong to the same formation. A general Synoptical Table of Geology was a desideratum in this science to a very late period. Dr. Aime Boué supplies us with the following: professing it to be his design to exhibit the science reduced to its most simple terms, and to enable every one to contemplate at a glance the principal geognostical facts ascertained by the labors of geologists. For the more clearly following the details in the synoptical table, he gives the following sketch of his theoretical views. 1. All geologists who have had opportunities of examining burning and extinct volcanoes, agree in admitting the existence of extinct volcanoes, or of very anciently volcanised countries. 2. The greater number of geologists, and especially those who have visited extinct volcanoes, believe in the igneous origin of tertiary basalt, in the form of streams (coulées), beds, cones, and veins, and also that of trachyte. 3. A good many distinguished geologists agree in consider ing it as probable, that the secondary or floetz trap rocks are of igneous origin, because these rocks agree in nature, position, and accidents, with basalt and trachyte. 4, And lastly, The intimate connexion of the porphyries with gra nite, syenite, and other unstratified rocks, not only in nature, but also in position, has induced some geologists to consider these also as of igneous formation. 'All the stratified rocks, with the exception of those of the hit class, called primitive, are generally admitted to be of Neptunian origin. These rocks are distinguished by their peculiar texture, and by 'he imbedded crystalline minerals they contain, and which are foreign to stratified rocks. Although the stratified primitive rocks are placed under the head Neptunian, I consider them as Neptunian rocks which have been brought to their present state by the agency of heat, and that the imbedded minerals they contain were introduced among them by the action of some igneous power, as stated in the Edinburgh Philosophical Journal for July 1823, and Annales des Sciences Naturelles 1824. These stratified primitive rocks, then, are partly of Neptunian, partly of igneous formation. The tufaceous or conglomerated productions of ancient and modern volcanoes are more appropriately placed immediately after the igneous rocks, from which they are derived, than amongst the Neptunian rocks. Although the salt and gypsum deposites probably owe their origin to submarine solfataras, we have not separated them from the Neptunian series, because they were deposited by water. If these were removed from the Neptunian series, for the same reason we should be obliged also to separate from it masses of iron ore, and of other ores, certain salts, &c. 'My theoretical ideas have induced me to separate from the Neptunian series the metalliferous veins, because their contents are more easily traced to Plutonic than to Neptunian agents. The alterations occasioned in Neptunian rocks, by their proximity to those of igneous origin, are stated in the table only in a cursory way, although phenomena of high interest. 'The synoptical table also presents the most striking zoological characters of each formation, the different periods of the appearance and disappearance of the different classes of vegetables and of animals, and a proper selection of synonyms of the different denominations given to the rock formations.' Great masses of Weiss tein, or Whitestone. UNSTRATIFIED CRYSTALLINE OR Granitic rocks, in dome-like or imbedded masses Greenstone or Diabase, especially as short beds These rocks are intimately connected with the following formation, by innumerable and well known transitions, (Alps, Pyrenees, Scotland, Germany). |