masses.

cles. When these are filled up with other mie dominates ; sometimes it is too small in quantity nerals, the rock passes into amygdaloid to be perceived. The size of the grains is no less

Amygdaloid is nothing more than this last subject to variation; when they are large the rock state of greenstone. The vesicles are filled up is sometimes called pudding stone. Of the old with calcareous spar, chalcedony, quartz, jasper red sandstone the grains are large. It is disagate, green earth, amethyst, &c., either com- tinctly stratified, and contains few ores. Cobalt, pletely or partially.

however, occurs in it; and it is often impregSometimes the transition greenstone, in this nated with copper. softened state, contains crystals 'of felspar co- 2. First flatz limestone.—Flætz limestone is lored green by the hornblende. It then consti- of a gray color; its fracture compact; has no tutes porphyritic transition trap.

lustre, and is only translucent on the edges. Globular trap is a fine granular hornblende Sometimes thin beds of granular foliated limerock of a loose texture, and tending very strongly stone occur in it; but they contajn petrifactions, to clay; of a liver brown color, and containing which distinguish thern from primitive limein it globular masses composed of concentric stone, Flætz limestone is wen characterised lamellar concretions, and containing a hard by the masses of hornstone and fint which it kernel.

contains. The transition trap rocks are only doubtfully The first flætz limestone is characterised by a stratified. They alternate with the other transi- bed of bituminous marl slate, containing copper. tion formations in beds, and sometimes compose This bed is always lowest, and therefore immewhole mountains. Common and lenticular clay diately contiguous to the sandstone. It contains ironstone occurs in it in beds.

but few petrifactions. They consist chiefly of 4. Transition flint slate. This formation con• fish. Various beds of marl occur in this forsists essentially of common flint slate and Ly- mation, and likewise a species of vesicular dian stone, which pass into each other. It is a limestone, known in Germany by the name of simple stone, but is characterised by containing rauch wacke. many veins of quartz. It is not stratified. 3. First flætz gypsum.-Gypsum, in general, When it constitutes rocks they are usually steep, may be considered as a simple rock; some and appear very much lacerated and worn times, however, it contains crystals of boracite, down by the weather. This is occasioned by arragonite, and quartz. Sulphur is likewise the numerous rents which this species of rock found in it

, both disseminated and in compact contains.

There are two formations of it. To this formation seems to belong riband jas- The first flætz gypsum lies immediately over per, which sometimes constitutes whole rocks. the first flætz limestone. It consists chiefly of It may possibly occur also in some of the sub- foliated and compact gypsum, together with a sequent formations.

good deal of selenite. It is in this formation To these formations may be added transition that swinestone occurs, either in beds or mixed gypsum, which Von Buch discovered, consti- with the gypsum. Rock salt also belongs to tuting a bed in greywacke slate, at Leogang in it, and appears to lie over it in short thick beds, Salzburg

being usually mixed with a species of saline

clay. Hence the saline springs, which obviously Class III.-Flretz FORMATIONS.

originate from rock salt, are likewise peculiar to The next grand class of formations have re- this formation. ceived the name of Nætz, because they lie 4. Variegated sandstone. This formation lies usually in beds much more nearly horizontal inmediately over the precediug. The rock than the preceding. When not covered by a which composes it consists of a fine granular succeeding formation, they form hills which do argillaceous sandstone, usually of a green, not rise to the same height as the primitive or brown, red, and white color. Several of these transition. They contain abundance of petri- colors alternate in stripes, which gives the stone factions; and these much more various in their a variegated appearance. Hence the name. It nature than those which occur in the transition often contains masses of a fat clay, of a greenish, formations, consisting of shells, fish, plants, &c. reddish, or yellowish color. indicating that they were formed at a period This formation is characterised by two species when urganised beings abounded. The fætz of rocks, which occur in it in beds. These formations lie immediately over the transition are, 1. The subspecies of limestone, described in the following order.

under the name of roestone; and, 2, Sandstone 1. Old red sandstone.—This formation lies slate. immediately over the transition, or, where they 3. Second flætz gypsum.—This formation lies are wanting, over the primitive rocks. Hence over the preceding in beds, and is sometimes, it is considered as the oldest of the flætz for- to a certain degree, mixed with it. It contains nations.

foliated gypsum, but scarcely any selenite, and Sandstone is composed of grains of quartz, or no swinestone; and is characterised by the some other siliceous stone, cemented together by fibrous gypsum, of which it is in a great measome basis, and can only be considered as a sure composed. It is of no great extent, and mechanical mixture. The cement is sometimes destitute of petrifactions. clay, sometimes quartz, lime, marl, &c., and the 6. Second flætz limestone, or shell limestone sandstone is named, in consequence, argillace- This formation is separated from the first floetz ous, siliceous, calcareous, marly, &c. This limestone by the beds of older gypsum, of vacement varies mucho iu quantity, but never pre- riegated sandstone, and of second gypsum,

a

ore.

a

which constitute the third, fourth, and fifth for- minous shale, greenstone, and soft sandstone, and mations. It is characterised by the vast number is characterised by containing in it some metallic of shells which it contains in the state of petri- ores. These are ores of copper, iron, lead, and factions. Particles of galena are likewise found perhaps also mercury. The second is composer scattered chrough it.

of beds of indurated clay, marl, limestone, and 7. Third sandstone, or freestone. The relative porphyritic stone. It contains some pyrites, but position of this formation has not been well as- no other ore. The third, or newest, is composed certained, yet it is known to cover all the prece- of soft sandstone, conglomerate, and slate-clay, ding, and therefore to be much riewer than either and contains no ore. the first or second formations. It consists mostly The rocks belonging to this formation are very of a sandstone of a white color, well adapted for distinctly stratified. Abundance of vegetable building. It contains traces of coal, but no sand- petrifactions occur in it, especially in the sandstone, slate, nor roe-stone; and gypsum never stone and bituminous shale. occurs either immediately over or under it. It 10. Flætz trap.—The rocks of this formation is usually stratified, and contains natural rents or are very remarkable. They cover the other fætz seams, which cross each other at right angles; rocks, precisely as the newer porphyry and the one parallel to the stratification, the other sienite do the primitive. The level of the unco perpendicular to it, so that it can be easily quar- vered flætz formations becomes gradually lower, ried into large square blocks. This indeed is a in the order in which they have been described ; character that in some measure applies to all the but that of the flætz trap is high, as it covers sandstones. When not covered by any other them all, and often forms the summit of hills, formation it forms beautiful hills and romantic whose lower part consists of older formations. valleys.

The rocks belonging to the flætz-trap formations 8. Chalk.-Chalk is one of the newest flætz are of two kinds : namely, those which are pecurocks. It is always near the sea coast. It con- liar to it, and those which occur also in other fortains numerous heds of nodular flint, often full nations. The following are the rocks peculiar to of vesicles. Various petrifactions of echinites, this formation : wacke, iron-clay, basalt, pitchbelemnites, &c., occur in it. It is indistinctly stone, greenstone, porphyry slate, graystone, stratificd, and forms beautiful round knolls and amygdaloid, trap-tuff

. hills of very small height. Pyrites is some- Basalt, in many treatises, claims the first place, times found in it, but scarcely any other metallic as it characterises the Aætz formation ; but it is

now often referred to the volcanic formations. 9. Independent coal formation. This forma- It consists essentially of the mineral described in tion is deposited in detached patches, usually in another place under the name of basalt, for a valleys over the preceding flvetz rocks, or over basis, containing crystals of basaltic hornblende, the transition formation when the flætz rocks are augite, olivine, and iron-sand, which give it a wanting. These patches, in general, have no porphyritic structure. It contains also vesicles, connexion with each other. Hence the epithet which are filled with zeolite, calcareous spar, independent, by which the formation is distin- lithomarge, &c. The vesicles are sometimes guished: but they are found in considerable filled with water. Sometimes it passes into quantities in the most distant parts of the earth, wacke; sometimes into graystone; and sometimes, Europe, Ainerica, New Holland, and always si- though rarely, into porphyry slate. milarly situated with respect to the other forma- Wacke is sometimes the simple mineral detions. Coal occurs in it in great abundance; scribed already under that name. Sometimes it though in the preceding formations it is very contains basaltic hornblende and mica, which scarce, and indeed is only found in thin indivi- give it a porphyritic appearance: sometimes dual beds. Hence it is considered as character- it is spotted, from crystals which it contains. istic of this formation. The rocks of which this It passes sometimes into clay; sometimes into formation is composed (not reckoning the coal) basalt. The iron-clay likewise has been deare the following: sandstone, coarse conglome- scribed already. rate, slate-clay, bituminous shale, indurated clay, Pitchstone was first observed in this for nation limestone, marl, clay ironstone, porphyritic stone, by professor Jameson. It is distinguished from greenstone.

that which occurs in the older rocks by the folLayers of these rocks alternate a great many lowing circumstances: Its colors are usually times with each other, and in them the coal oc- black or green; it is composed of lamellar discurs in numerous beds, varying extremely in tinct concretions, and it contains crystals of glassy thickness. The subspecies of coal which occur felspar, or mionite as it is called. in this formation are coarse coal, foliated coal, Porphyry-slate is much less common than bacannel coal, slate coal, and a little pitch-coal. salt; but where it does occur it usually forms Professor Jameson has likewise discovered glance considerable hills. This rock is slaty in the coal in this formation.

large, compact and splintery in the small. . The All the different rocks of which this formation basis of it consists of clinkstone; the crystals is composed seldom or never occur together. which it contains are of felspar and hornblende. Hence it is presumed, that there are several sub- It contains also zeolite, iron-sand, and some miordinate formations belonging to the indepen- nerals not yet described. dent coal, which occupy determinate situations Greystone is still less common than porphyry with respect to each other. Three such forma- slate. It appears to consist of an intiniate mixtions have been characterised. The oldest or ture of much white felspar and a little black lowest is composed of beds of indurated clay, hornblende. This hasis contains augite and olivine. limestone, marl, porphyritic stone, slate clay, bitu- Flætz greenstone is an intimate mixture of grains of felspar and hornblende. It is distin- The pseudo-volcanic consist of minerals altered guished from priunitive and transition greenstone in consequence of the burning of beds of coal by the more intimate mixture and less crystallised situated in their neighbourhood. Porcelain jasappearance of the constituents. It passes into per, earth slag, burnt clay, columnar clay-iron basalt.

stone, and perhaps also polishing slate, are the Amygdaloid has for its basis sometimes wacke; minerals which have been altered. sometimes a fine granular greenstone, frequently The real volcanic minerals are those which already somewhat decomposed. The vesicles have been thrown out of the crater of a volcano. which it contains are filled with green earth, li- They are of three kinds ; 1. Those substances thomarge, steatite, &c. Sometimes they re- which, having been thrown out from time to time, main empty; sometimes this basis contains have formed the crater of the mount:an: 2. crystals of hornblende, &c., which gives the Those which have been thrown out of the crater rock both a porphyritic and amygdaloidal struc- in a stream, and rolled down the inountain ; they ture.

constitute lavas : 3. The water which is occasionTrap-tuff consists of fragments of flætz trapally thrown out of volcanoes, containing ashes and other rocks, cemented by a basis of alluvial and other light substances, gradually evaporating, clay. The minerals which this formation con- leaves the earthy matter behind it; this substance tains, in common with others, are not so numer- constitutes volcanic tuff. ous as the preceding. They are the following : Of veins. – Veins are mineral repositories sand, quartzy sandstone, clay, limestone, coal. which cut through the strata or beds of which a

The grains of sand are of all degrees of mag- mountain is composed, and which are filled with nitude. The clay sometimes contains schaum substances more or less different from the rocks earth The coal consists chiefly of the following through which they pass. We shall have a very subspecies; common brown coal, bituminous distinct notion of veins, if we suppose that the wood, and pitch coal. Sometimes, though sel- mountains in which they occur were split by doin, glance coal and columnnar coal occur in some means or other, and that the rifts thus this formation.

formed were filled up by the matter which conIt is chiefly in the beds of plaster that the stitutes veins. They are distinguished from beds great number of fossil bones of land animals by their direction, which is either perpendicular have been found, for the description of which to the stratifications, or at least forms an angle we are chiefly indebted to Cuvier.

with it.

Sometimes the strata through which veins Class IV.-ALLUVIAL FORMATIONS.

pass are merely separated from each other; so The alluvial formations constitute the great that if we cut through the vein we find the same mass of the earth's surface. They have been strata of the rock on both sides of it; but someformed by the gradual action of rain and river times also the corresponding strata on one side water upon the other formations, and may be are lower than on the other, as if the portion of considered as very recent formations ; or rather the rock on one side of the vein had sunk a litas deposites, the formation of which is still con- tle, while the portion on the other side kept its stantly going on. They may be divided into two original position. In such cases the side of the kinds; namely, those deposited in the valleys of rock against which the vein leans, or the floor of mountainous districts, or upon the elevated plains the vein, has always its strata highest up; while which often occur in mountains; and those de- the strata of the portion of rock which leans posited upon flat land.

over the vein, or the roof of the vein, are always The first kind consists of sand, gravel, &c., lowest. So that this is the portion which appears which constituted the more solid parts of the to have sunk. Such a change of position in the neighbouring mountain; and which remained strata is known in this country by the name of when the less solid parts were washed away. a shift. They sometimes contain ores (particularly gold In considering veins, there are two circuinand tin) which existed in the neighbouring stances which claim our attention ; namely, 1. mountains. Sounetimes the alluvial soil is wash- The shape of veins; and, 2, The substances with ed, in order to separate these ores. On moun- which they are filled. tain plains there occur also beds of loam.

All those mineralogists who have had the best The second kind of alluvial deposite, or that opportunity of examining the shone of veins which occupies the flat land, consists of loam, with correctness, agree in representing them as clay, sand, turf, and calctuff. Here also occur widest above, and as gradually diminishiug in earth and brown coal (in this mineral amber is size as they deepen, till at last they terminate in found), wood coal, bituminous wood, and bog a point, exactly as if they had been originally iron ore. The sand contains some metals, among fissures. Sometimes, indeed, veins widen in others gold. The calctuff is a chemical deposite, different parts of their course, and afterwards and extends widely. It contains plants, roots, contract again to their former size; but more moss, bones, &c., which it has encrusted. The commonly they continue diminishing gradually clay and sand often contain petrified wood, and to their extremity. likewise skeletons of quadrupeds.

Sometimes these veins are either partially or CLASS V.-VOLCANIC FORMATIONS.

entirely empty. In that case they are denomin

ated fissures, but most commonly they are filled The volcanic formations are of two kinds; with a matter more or less different from the namely, the pseudo-volcanic and the true vol rock through which they pass. Sometimes the canic.

vein is filled up with one species of mineral. Thus we have veins of calcareous spar, of quartz, nite, syenite, and other unstratified rocks, not &c.; but, when it is of any size, we frequently only in nature, but also in position, has induced find a variety of substances; these are disposed some geologists to consider these also as of igin regular layers always parallel to the sides of neous formation. the vein, and they follow in their position a very *All the stratified rocks, with the exception of regular order. One species of mineral constitutes those of the hist class, called primitive, are gethe centre of the vein; on each side of this cen- perally admitted to be of Neptunian origin. tral bed the very same layers occur in the same These rocks are distinguished by their peculiar order from the centre to the side of the vein. texture, and by .he imbedded crystalline mineAlmost every mineral substance which occurs in rals they contain, and which are foreign to strathe mass of rocks has been found in veins. tified rocks. Although the stratified primitive

Veins of course, according to our theory, are rocks are placed under the head Neptunian, I newer than the rocks in which they occur; and, consider them as Neptunian rocks which have when two veins cross, that is obriously the news been brought to their present state by the agency est wnich traverses the other without interrup- of heat, and that the imbedded minerals they tion, as the fissures constituting the second vein contain were introduced among them by the acmust have been formed after the first vein was tion of some igneous power, as stated in the filled

up. But when different veins contain the Edinburgh Philosophical Journal for July 1823, same minerals, arranged in the same order, Wer- and Annales des Sciences Naturelles 1824. ner conceives that they were filled at the same These stratified primitive rocks, then, are partly time, and says that such veins belong to the same of Neptunian, partly of igneous formation. formation.

The tufaceous or conglomerated productions of A general Synoptical Table of Geology was ancient and modern volcanoes are more approa desideratum in this science to a very late pe- priately placed immediately after the igneous riod. Dr. Aime Boué supplies us with the rocks, from which they are derived, than amongst following: professing it to be his design to ex- the Neptunian rocks. Although the salt and hibit the science reduced to its most simple gypsum deposites probably owe their origin to terms, and to enable every one to contemplate submarine solfataras, we have not separated them at a glance the principal geognostical facts from the Neptunian series, because they were ascertained by the labors of geologists. For deposited by water. If these were removed from the more clearly following the details in the the Neptunian series, for the same reason we synoptical table, he gives the following sketch should be obliged also to separate from it masses of his theoretical views.

of iron ore, and of other ores, certain salts, &c. ‘1. All geologists who have had opportunities • My theoretical ideas have induced me to sepaof examining burning and extinct volcanoes, rate from the Neptunian series the metalliferous agree in admitting the existence of extinct vol- veins, because their contents are more easily canoes, or of very anciently volcanised countries. traced to Plutonic than to Neptunian agents. 2. The greater number of geologists, and espe- The alterations occasioned in Neptunian rocks, cially those who have visited extinct volcanoes, by their proximity to those of igneous origin, are believe in the igneous origin of tertiary basalt, stated in the table only in a cursory way, although in the form of streams (coulées), beds, cunes, phenomena of high interest. and veins, and also that of trachyte. 3. A good * The synoptical table also presents the most many distinguished geologists agree in consider- striking zoological characters of each formation, ing it as probable, that the secondary or flætz the different periods of the appearance and distrap rocks are of igneous origin, because these appearance of the different classes of vegetables rocks agree in nature, position, and accidents, and of animals, and a proper selection of synowith basalt and trachyte. 4, And lastly, The nyms of the different denominations given to the intimate connexion of the porphyries with gra- rock formations.'

These rocks are intimately connected with the following formation, by innumerable and well known transitions, (Alps, Pyrenees, Scotland, Germany).