An extensive series, comprising many isolated groups of marine and lacustrine deposits, containing fossil remains of animals and vegetables of all classes; the greater number of genera and species in the most ancient or lowermost beds belong to extinct types.

Subdivisions:—

1. The Pliocene[14] (more new, or recent.[15] Wond. p. 221); strata in which the shells are for the most part of recent species, having only about ten per cent of extinct forms. (Norwich Crag.)

2. The Miocene (less recent,[16] Wond. p. 221); containing about 20 per cent of recent species of shells. (Suffolk Crag.)

3. The Eocene (dawn of recent,[17] in allusion to the first appearance of recent species—Wond. p. 226); the most ancient tertiary strata contain but very few existing species of shells; not more than five per cent. (London, Hants, and Paris basins.)

Obs.—The marine are often associated with fresh-water deposits, and the general characters of the Tertiary system are alternations of marine and lacustrine strata. In England the most important Tertiary deposits are those of the London basin, the Isle of Sheppey, the south-western coasts of Sussex and Hampshire, the north of the Isle of Wight, and the eastern coasts of Essex, Norfolk, Suffolk. (Wond. p. 226.)

The Cretaceous or Chalk Formation. (Wond. p. 296). A marine formation, comprising a vast series of beds of limestone, sandstone, marl, and clay, &c.; characterized by remains of extinct zoophytes, mollusks, cephalopods, echinoderms, crustaceans, fishes, &c.; lacertians, crocodilians, chelonians, and other extinct reptiles; drifted coniferous and dicotyledonous wood and foliage, fuci, &c.

Subdivisions:—

1.	The Maestricht beds. Friable coralline and shelly limestones, with flints and chert.
2.	Upper Chalk, with flints	}	Craie blanche of the French geologists.
3.	Lower Chalk, without flints
4.	Chalk-marl		Craie tufeau.
5.	Firestone, Malm-rock, Upper Greensand, or Glauconite	}	Glauconie crayeuse.
6.	Galt, or Folkstone-marl		Glauconie sableuse.
7.	Shanklin,orLowerGreensand.	{	Formation nÉocomien; which is divided into N. supÉrieur, the English upper divisions of the Greensand or Kentish rag; and N. infÉrieur, the lower beds of sand and clay, of the southern shore of the Isle of Wight, at Atherfield.[18]

Obs.—The Maestricht beds are chiefly composed of fawn-coloured limestones of friable texture; containing peculiar species of corals, shells, fishes, reptiles, &c. The Chalk is generally white, but in some localities is of a deep red, in others of a yellow colour; nodules, layers, and veins of flint occur in the upper, but are seldom present in the lower chalk. The Marl is an argillaceous limestone, which generally prevails beneath the white chalk; it sometimes contains a large intermixture of green or chlorite sand, and then is called Firestone, or Glauconite. The Galt is a stiff, blue or blackish clay, abounding in shells which frequently retain their pearly lustre. The Greensand is a triple alternation of sands and sandstones with clays; and beds of cherty limestone called Kentish Rag.

The Wealden; a formation, whose fluviatile character was first observed and established by the researches of the author (Wond. p. 360). A series of clays, sands, sandstones and limestones, with layers of lignite, and extensive coal-fields; characterized by the remains of several peculiar terrestrial reptiles, namely, Iguanodon, HylÆosaurus, Pelorosaurus, Megalosaurus; Crocodilians and Chelonians; Enaliosaurians; Pterodactyles, &c.; Fishes of fluviatile and marine genera; Insects of several orders; fresh-water mollusks and crustaceans; conifers, cycads, ferns, &c.

Subdivisions:—

1.	Weald-clay, with Sussex or Petworth marbles.
2.	Tilgate-grit, and Hastings sands.
3.	Ashburnham clays, shales, and grey limestones.
4.	Purbeck beds; argillaceous and calcareous shales, and fresh-water limestones and marbles. Petrified forest, and layers of vegetable earth; with Cycads and Conifers.

Obs.—Clays and limestones, almost wholly composed of fresh-water snail-shells, and minute crustaceans, generally occupy the uppermost place in the series in Sussex; sands and sandstones, with shales, and lignite, prevail in the middle; while in the lowermost, argillaceous beds, with shelly marbles or limestones, again appear; and, buried beneath the whole, is a petrified pine-forest, with the trees still erect, and the vegetable mould undisturbed! The upper clay beds and marbles form the deep valleys or Wealds of Kent and Sussex, and the middle series constitutes the Forest-Ridge. The Purbeck strata are obscurely seen in some of the deepest valleys of eastern Sussex; they emerge on the Dorsetshire coast, form the Island or Peninsula whose name they bear, and surmount the northern brow of the Isle of Portland. On the southern coast of the Isle of Wight, the Wealden beds emerge from beneath the Greensand strata between Atherfield and Compton Bay on the western limit, and in Sandown Bay on the eastern; and their characteristic fossils are continually being washed up on the sea-shore.

The Jurassic or Oolitic Formation. (Wond. pp. 202, and 491). A marine formation of great extent and thickness, consisting of strata of limestone and clay, which abound in extinct species and genera of marine shells, Corals, Insects, Fishes, and terrestrial and marine Reptiles. Land plants of many peculiar types, and the remains of two genera of Mammalia.

Subdivisions:—

Upper Oolite of Portland, Wilts, Bucks, Berks, &c.

1.	Portland Oolite. Limestone of an oolitic structure, abounding in ammonites, trigoniÆ, &c. and other marine exuviÆ. Green and ferruginous sands—layers of chert.
2.	Kimmeridge clay. Blue clay, with septaria, and bands of sandy concretions—marine shells and other organic remains—ostrea deltoidea. Beds of lignite.

Middle Oolite of Oxford, Bucks, Yorkshire, &c.

1.	Coral oolite, or Coral rag. Limestone composed of corals, with shells and echinites.
2.	Oxford clay; with septaria and numerous fossils. Beds of calcareous grit, called Kelloway-rock swarming with organic remains.

Lower Oolite of Gloucestershire, Oxfordshire, and Northamptonshire.

1.	Cornbrash—a coarse shelly limestone.
2.	Forest marble; concretions of fissile arenaceous limestone—coarse shelly oolite—sand, grit, and blue clay.
3.	Great oolite—calcareous oolitic limestone and freestone; reptiles, corals, &c., upper beds full of shells.
Stonesfield slate;—terrestrial plants, insects, reptiles, Mammalia.
4.	Fullers earth beds;—marls and clays, with fuller's earth—sandy limestones and shells.
5.	Inferior oolite—coarse limestone—conglomerated masses of terebratulÆ and other shells—ferruginous sand, and concretionary blocks of sandy limestone, and shells.

Lower Oolite, of Brora in Scotland.

1.	Shelly Limestones—alternation of sandstones, shales, and ironstone; land-plants.
2.	Ferruginous limestone, with carbonized wood and shells.
3.	Sandstone and shale; with two beds of coal.

Lower Oolite of the Yorkshire coast.

1.	Cornbrash—a provincial term for a bluish grey rubbly limestone, with intervening layers of clay.
2.	Sandstones and clays, with land-plants, thin beds of coal and shale—calcareous sandstone and shelly limestone.
3.	Sandstone—often carbonaceous, with clays; coal-beds, and ironstone, with remains of vegetables.
4.	Limestone; ferruginous and concretionary sands.

Obs.—The difference observable between the lower beds of the Oolite in the midland counties, and those of Yorkshire and Scotland, is a fact of considerable interest. The fluvio-marine accumulations of vegetable matter in the state of coal, with the remains of land-plants at Scarborough and Brora, together with the presence of insects, fresh-water crustaceans, mammalia, and terrestrial plants, in the Stonesfield slate, attest the existence of neighbouring land, and the action of rivers and currents.

The Lias. (Wond. p. 521) A series of clays, shales, and limestones, with marine shells, cephalopoda, crinoidea , and fishes in great abundance; reptiles, (particularly of two extinct genera, Plesiosaurus, and Ichthyosaurus,) in immense numbers. Drifted wood and land plants: coniferÆ, cycadesÆ &c.

Subdivisions:—

1.	Upper Lias shale, full of saurian remains, belemnites, ammonites, &c. intercalated with the lowermost beds of the Oolite: nodules and beds of limestone.
2.	Lias marlstone; calcareous, sandy, and ferruginous strata, very rich in terebratulÆ and other marine shells.
3.	Lower Lias clay and shale, abounding in gryphea incurva, and other marine shells; intercalations of sands and clays, with nodules of limestone.
4.	Lias rock; a series of laminated limestones, with clay partings. Bone-bed, with numerous remains of fishes.

Obs.—The Lias is the grand depository of those tribes of marine reptiles, the Ichthyosauri and Plesiosauri, whose remarkable forms, structure, and state of preservation, have excited the attention even of the most incurious. The collection of these remains in the British Museum, principally formed by Mr. Hawkins, is unrivalled.[19]

The Trias; or New Red Sandstone Formation,[20] (Wond. p. 533). This group of rocks consists of variegated marls, sandstones, and conglomerates, frequently of a red colour, with marine shells, crinoideans, fishes, and reptiles; marine and terrestrial plants. This series contains extensive deposits of rock-salt, and brine-springs.

This formation comprises the Trias, or triple group, viz. the Keuper, Muschelkalk, and Upper Bunter Sandstein, of the German geologists.

Subdivisions:—

1.	Variegated red, blue, and white marls, and shales, with gypsum and beds of rock-salt. (Marnes irisÉes of the French.)
2.	Variegated red and white sandstones.
3.	Conglomerates formed of the detritus of the older rocks.
4.	Bed mottled sandstone, and marls. (GrÈs bigarrÉ of the French.)

Obs.—To this formation belong the principal deposits in Leicestershire and other midland counties of England. Fossils are not generally abundant, but some localities yield highly interesting remains. The shelly limestone of Germany, called Muschelkalk, which contains the Lily Encrinite, &c. does not occur in England. Remains of Conifers allied to the Yew and Araucaria, are found near Coventry; and peculiar reptiles (Labyrinthodons) near Warwick.

The Permian Formation. (Wond. p. 533). The separation of the strata now termed Permian from the Triassic, with which they were formerly classed, was first proposed by Sir Roderick Murchison, and is based on the fact that the fossils hitherto discovered are entirely distinct from any that occur in the Trias and subsequent formations; it is, therefore, inferred, that after the deposition of the so-called Permian strata, a complete change took place in the faunas and floras of the lands and seas, and the Trias is at present regarded as the dawn of a new system of organic beings.

The strata comprised in this group are variegated blue and red marls and sandstones, like those of the Triassic; magnesian or dolomitic limestones; and conglomerates more or less coloured with peroxide of iron.

Subdivisions:—

1.	Red and white marls.
2.	Yellow magnesian limestones, and dolomitic conglomerates of Yorkshire and Durham.
3.	Marl-slate in thin layers, containing reptiles and fishes. The Keuper schiefer or copper-schist of Mansfeld.
4.	Marls and variegated sandstones, sands, and clays.

Obs.—This group includes the Lower Bunter, Zechstein, and Rothliegendes[21] of the German geologists. The Permian comprises all the deposits that intervene between the Triassic above, and the Carboniferous below; and it is believed that this formation contains but one type of animal and vegetable life.

The Carboniferous, or Coal Formation. (Wond. pp. 660-748). Sandstones, grits, shales, layers of ironstone, and clay, with immense beds of coal; fresh-water limestones sparingly; marine limestones abundantly.

Subdivisions:—

1.	The Coal Measures.—Sandstones, shales, and grits, with numerous beds and seams of Coal; ironstone nodules. Land plants in profusion. Intercalations of bands of limestone with fresh-water bivalves and crustaceans in some districts; and with marine shells in others.
2.	Millstone Grit.—Sandstones, shales, and quartzose conglomerates and grit, (provincially, Millstone-grit): with shales and thin seams of coal, and plants of the coal-measures in some localities. The conglomerates and grits have evidently resulted from the destruction of granitic rocks.
3.	Carboniferous, or Mountain Limestone.—A series, nearly 1,000 feet in thickness, of limestones and flagstones, abounding in crinoideans, corals, and marine shells and crustaceans; with layers and nodules of chert. Ores of lead, zinc, copper, barytes; fluor spar, &c. Limestones, with innumerable shells of the genera Productus, Spirifer, Goniatites, Orthocera, Bellerophon, &c. Several varieties of black, bluish grey, and variegated marbles. Coal occurs in the mountain limestone of some parts of Russia.

Obs.—The strata comprised in the carboniferous (coal-hearing) system, consist of sandstones more or less felspathic, and of dark bituminous shales with innumerable ferns, and other vascular cryptogamiÆ, and coniferÆ, &c. The uppermost group is composed of numerous alternations of coal, clay, shale, ironstone, and sandstone; the middle, of sandstones, shales, clays, and quartzose conglomerates, generally of a dull red colour; and the lowermost, of crystalline limestones with occasional layers of chert, abounding in marine shells, corals, crinoidea, and other exuviÆ. These lower limestones are the principal repositories of the lead ores of Derbyshire.

The Devonian or Old Red Formation. (Wond. pp. 204 and 751). Conglomerates, quartzose grits, sandstones, marls , and limestones; the prevailing colour is a dull red. Shells, corals, and ganoid fishes, of a very peculiar type. Reptiles, (Telerpeton; Batrachians? Chelonians?); the most ancient reptilian remains hitherto discovered. Ferns, Lepidodendrons, and other trees of the carboniferous flora; fluviatile plants with batrachian ova(?).

Subdivisions:—

1.	Sandstone, quartzose conglomerates, and shale, with but few fossils.
2.	Flagstones, marls, and concretionary limestones; provincially termed corn-stones; laminated reddish and greenish micaceous sandstones (prov. tilestones). Peculiar genera of fish; orthocerata, and many species of marine shells.

Obs.—The term Devonian, by which the series of strata comprehended in this formation is now generally distinguished by geologists, was first proposed by Sir R. Murchison, as being more precise than the name formerly applied to this group. In Scotland, where the formation is of vast extent, it was first characterized by its peculiar ganoid fishes (Pterichthys, Coccosteus, Cephalaspis), and will probably always there retain the original name of Old Red.[22] In Devonshire it is marked by the presence of shells of a character intermediate between those of the Silurian and Carboniferous systems.

The sandstones are in various states of induration, and when slaty, are employed for roofing. The red colour predominates in the marls, and is derived from peroxide of iron. The formation of these rocks has manifestly resulted from the waste of ancient slate rocks, the detritus of which is cemented together into coarse conglomerates. In South Devonshire (at Torquay, Babbicombe, &c.), beautiful coralline marbles occur in this formation.

The Silurian System. (Wond. p. 765). Marine limestones, sandstones, shales, and calcareous flagstones, characterized by peculiar types of corals, crinoideans, mollusks, and crustaceans, constitute this important and extensive system of rocks; the GrauwackÉ, or Transition series of the earlier geologists.

Subdivisions:—

UPPER SILURIAN.

1.	Ludlow rocks;—slightly micaceous grey-coloured sandstones. Blue and grey argillaceous limestones. Dark-coloured shales and flagstones, with concretions of earthy limestone, containing marine shells, Orthocerata, Spirifers, and Trilobites. Fishes.
2.	Wenlock, or Dudley limestone;—sub-crystalline blue and grey limestone, abounding in Trilobites, Crinoidea, Polyparia, Spirifers, Orthocerata, &c.
3.	Wenlock shale;—dark grey argillaceous shale, with nodules of sandstone.

LOWER SILURIAN.

1.	Caradoc sandstone;—shelly limestones, and finely laminated, slightly micaceous, greenish sandstones. Corals, Shells, Trilobites.
2.	Llandeilo flags and limestones. Freestone, conglomerates, grits, and limestones. Dark-coloured flags. Beds of schist with abundance of Trilobites and shells. The lowermost beds are full of small bivalves, termed LingulÆ.

Obs.—The Silurian System, (so named by Sir R. Murchison, from the Silures, the ancient Britons who inhabited those parts of our island in which the geological relations of these strata were first recognised by him,) occupies the border counties of England and Wales, and spreads over a vast area of both North and South Wales, intervening between the Carboniferous series and the Cambrian or ancient slate-rocks of that country.[23] The strata are entirely of marine origin, and many of the beds (as the well-known Dudley or Wenlock limestone) are composed of shells, corals, crinoideans, and remains of that remarkable family of crustaceans termed Trilobites, cemented together by carbonate of lime. A few remains of Fishes occur: Reptiles are unknown. No vegetable relics, excepting Fuci, have been found in Britain below the Devonian or Old Red formation.[24]

The Cambrian Formation. This term is applied to a largely developed series of unfossiliferous slate-rocks and conglomerates, many thousand yards in thickness.

Obs.—Certain beds of dark-coloured schists containing a few corals, fuci, and shells, are referred to the uppermost part of this formation by some eminent geologists, but it is more consonant to the established system of classification to regard these fossiliferous beds as the lowermost of the Silurian rocks. The fineness of grain, general aspect, hardness, and texture of these strata, are well known, from the general employment of slate for economical purposes. These rocks extend over a great part of Cumberland, Westmoreland, and Lancashire, reaching to elevations of 3,000 feet, and giving rise to the grand scenery of the Lakes, and of North Wales.

Hypogene Rocks.

(Wond. p. 806.)

Non-fossiliferous.

Metamorphic (transformed) or stratified crystalline rocks.

Subdivisions.—

1.	Mica-schist System. (Wond. p. 843.) Probably sedimentary rocks altered by high temperature. Mica-slate, Quartz-rock, Crystalline limestone, Hornblende schist, &c.
2.	Gneiss System. Layers of Gneiss, Sienite and Quartz-rock, alternating with Clay-slate, Mica-schist, &c.

Plutonic Rocks; unstratified crystalline masses.

Granitic System. (Wond. p. 844.) Granite—a rock composed of mica, quartz, and felspar; Porphyry; Serpentine; Trap. These rocks occur in amorphous or shapeless masses, and in dykes and veins.

>Obs.—No fossils have been detected in these rocks: but the intense igneous action which the masses appear to have undergone, may have obliterated all evidence of animal and vegetable structures, should any have been present, as well as the lines of stratification. By the aid of the microscope, we may yet perhaps solve the mystery which shrouds the origin of these rocks, and the student may take up the investigation with the certainty of obtaining much valuable information, even should the search for organic structures prove abortive. It is not, however, improbable that the siliceous frustules of diatomaceÆ may have escaped destruction, and remain to reward the researches of some skillful and patient observer.

Volcanic Rocks.

(Wond. p. 806.)

The products of subterranean fire or heat, erupted from profound depths through fissures in the Earth's crust, whether in ancient or modern times.

Subdivisions.—

1.	Trap, Basalt, Toadstone, Volcanic-tuff; the erupted materials of ancient extinct volcanoes.
2.	Lavas, ScoriÆ, Pumice, Ashes; ejected by modern volcanoes.

Obs.—These igneous products are of all ages, and they traverse alike the hypogene rocks and the older and newer sedimentary deposits. Their characters, and the effects they have produced, are considered in the work to which reference is made.

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By a reference to the geological map of England (Wond. pl. i. vol. i.), it will be seen, that the several formations appear on the surface in a somewhat chronological order, as we pass from the eastern or south-eastern part of the Island to the west or north-west. Thus the principal Tertiary deposits are situated in the eastern and south-eastern parts; and proceeding towards the north-west, we traverse successively the Secondary—the Chalk, Oolite, Lias and Trias; then the PalÆozoic—Permian, Carboniferous, and Devonian; next the Silurian and Cambrian; and at length metamorphic and primary rocks appear. It is this distribution of the strata of the respective formations that has determined the characters of the physical geography of England. The Alpine or mountainous districts, which extend north and south along the western portion of England and Wales, from Cornwall to Cumberland, are formed by the elevated masses of the Silurian, Cambrian, and Metamorphic rocks. These are succeeded by a band of the Carboniferous and Triassic deposits, with a few intrusions of metamorphic and plutonic rocks, that stretches from the coast of Devonshire, through the midland counties, by Leicestershire and Derbyshire, to Newcastle. On the south-east of this tract, the Oolite and Cretaceous formations, chiefly made up of argillaceous and calcareous strata, constitute a diversified agricultural district, extending from the southern shores of Hants and Dorset to the coast of Yorkshire. The Wealden occupies the country lying between the Chalk Downs of Sussex, Hants, Surrey, and Kent. The Tertiary deposits lie in basins or depressions of the upper cretaceous rocks in the south-eastern and eastern maritime districts, and on an extensive area of these beds stands the metropolis of England; lastly, irregular accumulations of Drift, containing mammalian remains in some localities, are spread over the surface of the ancient formations, and form the immediate subsoil of the most fertile regions.

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