Chapter XVIII: Introduction (1)

The Birmingham district, or that area of which Birmingham constitutes the natural capital and commercial centre, extends from Stafford on the north to Tewkesbury on the south, and from Wellington on the west to Leicester on the east, forming an area about 60 miles in length by 50 in breadth.

In no single district in Britain is the relation of the physiography of the country seen to be more strikingly dependent upon its geological structure than within the limits of the Birmingham district. Every hill, ridge, plain, and valley of any importance is a mere reflex of the underground geology. The local distribution and physical peculiarities of its rock formations afford a natural and complete explanation of all its special scenic peculiarities.

The dominant geological formation of this Midland area is the great Mesozoic formation of the _Triassic_ or New Red Sandstone, which stretches through Southern Britain in a continuous band from Hartlepool to Exeter, and divides the broken and contorted Paleozoic rocks of the west from the flat-lying Neozoics of the east. This great band of New Red Sandstone attains its widest extension in the north of the Birmingham district, between Eccleshall and Charnwood Forest, where its transverse diameter is about 50 miles. Within the limits of the Birmingham district, however, its diameter rapidly decreases, until in the extreme south, in the neighbourhood of Worcester and the Malverns, its breadth is reduced to about 10 miles.

The red rocks of this _Triassic_ formation not only form by far the most predominant and most conspicuous geological feature of the district at the present time, but not long since, geologically speaking, they must have extended over the entire area in one unbroken expanse. They now constitute a sheet of red sandstones and marls, through which protrude, in numerous bands and patches, the older Paleozoic rocks. Although nowhere very steeply inclined, these red beds of the _Triassic_ have been bent into several long low arches, or broad domes, whose longer axes range approximately north and south. The summits of many of these arches have been denuded, and the underlying older rocks have again been bared to-day. Four of these arches are especially conspicuous, those of the Wrekin, Malvern, Dudley, and Nuneaton. In each of these the underlying _Coal Measures_ are laid bare, forming the four coalfields of Coalbrookdale, Forest of Wyre, South Stafford, and Eastern Warwick, all of which shew round their outer margins a narrow band of the intermediate formation of the _Permian_. In each of these anticlinals, too, the denudation of the core of the arch has been sufficient to wear away the _Carboniferous_ from its centre, and to expose to view yet older formations--the _Old Red Sandstone_ in the Forest of Wyre, the _Silurian_ in South Staffordshire, the Malverns, and Coalbrookdale, and even the _Upper Cambrian_ and its underlying igneous rocks in the Wrekin, the Lickey, and near Nuneaton. With the exception of the _Silurian_ of Abberley and Dudley, and the recently discovered _Cambrian_ of Nuneaton, however, these _pre-Carboniferous_ rocks are comparatively inconspicuous, rising up merely in narrow bands in the cores of long wedge-shaped hills.

From the economical as well as from the structural point of view, by far the most important of these geological arches is that of South Staffordshire, which is the southward continuation of the Pennine chain, and part of the true backbone of Southern Britain. The central axis of this arch runs, as we have seen, through the Dudley Hills, and dies away in the complex of faults to the south of the Lickeys. On the natural consequences of the rise of this arch, all the physical, scenic, and economic peculiarities of the central parts of the district are essentially dependent. The hills and plains around Birmingham are all more or less related to this grand anticlinal--the hills marking the uplifted edges of the harder rocks, the limestones, sandstones, and pebble beds; and the plains, the position of the gently inclined soft shales and marls. It has brought within workable distance of the surface the coals and ironstones of South Staffordshire, and the valuable limestones of the Dudley Hills, and it has had its final effect in bringing together the overflowing population of the town and district.

The original simplicity of the geological structure of the floor of the Birmingham District is much complicated by fractures, faults, and unconformities. The Wrekin and the Malverns are both affected by profound dislocations. The South Staffordshire Coldfield is bounded both on the eastward and the westward by faults of more than ordinary magnitude, while a long straight fault more than 20 miles in length runs through the south-eastern part of Birmingham itself, and flings down the _Keuper marls_ of the Warwick plain against the older sandstones of the Birmingham plateau.

In the Birmingham District as everywhere in Britain, the _Triassic_ formation rests unconformably upon everything below. At the same time, its members overlap each other more or less irregularly, and shew a rapid diminution in thickness when followed from west to east. Thus it happens that not only do the _pre-Triassic_ rocks make their appearance in their expected positions along the main anticlinal lines, but many of the old ridges of Palæozoic rocks, which rose out of the Triassic waters, have had their enveloping pall of red sandstone removed from their flanks and summits, which have thus been bared once more to the light of day. Such are, in part, the ridges of the Wrekin, the Malverns, the Lickeys, and the Forest of Charnwood.

In the valley of the Severn, to the west of Birmingham, the strata run in narrow bands. The central portion of this valley lying between Coalbrookdale and Bridgnorth, to the west of the main anticlinal of the Birmingham district, owes all its striking beauty and variety to the rapid alternations of hard and soft strata which occur within its limits.

In the great Midland plain to the east of Birmingham, the strata are spread out in broad sheets. The plain is underlain in great part by the comparatively homogeneous flat lying Keuper marls, with their intercalated bands of harder sandstones. Its scenery is consequently less varied than that of the Severn valley, but it is rich in that sweet sylvan beauty which is almost peculiar to the English landscape, and it forms one broad expanse of gently rolling farmland and woodland, whose green crested waves sweep onward to the east and south, mile beyond mile, till they break against the long shore-like scarp of the harder Jurassics.

THE LOCAL ROCK FORMATIONS.

As will be apparent upon a study of the accompanying geological map, the geological formations exposed within thirty miles of Birmingham, include the entire stratigraphical succession between the _Cambrian_ and the middle portion of the _Jurassic_, with two notable exceptions. The two formations locally wanting are the _Ordovician_ and the _Old Red Sandstone_. The nearest known _Ordovician_ rocks occur in central Shropshire, to the east of Church Stretton; the nearest _Old Red Sandstone_ beds are met with to the south of the Forest of Wyre. The natural sequence of formations, and the localities where the several formations are most conspicuously displayed, are given in the following table:--

TABLE OF THE GEOLOGICAL FORMATIONS OF THE BIRMINGHAM DISTRICT.

MESOZOIC, OR SECONDARY ROCKS.

LIASSIC.
_Middle Lias_ (_Marlstone_)--Edge Hill, Fenny Compton.
_Lower Lias Clays_--Harbury, Rugby.

RHŒTIC.
_Marls and White Lias_--Harbury, Knowle, Wooten Wawen.

TRIASSIC.
_Upper Trias or Keuper_:
(_a_) _New Red Marl_--Moseley, King’s Norton, &c., &c.
(_b_) _Lower Keuper or Waterstones_--Birmingham, Warwick.

_Lower Trias or Bunter_:
(_a_) _Upper Mottled Sandstone_--Harborne, Edgbaston, Hockley.
(_b_) _Pebble Beds and Conglomerate_--Sutton Park, Smethwick.
(_c_) _Lower Mottled Sandstone_--Clent Hills, Stourbridge.

PALÆOZOIC, OR PRIMARY ROCKS.

PERMIAN, OR DYASSIC.
(_a_) _Permian Breccia_--Clent Hills, Northfield.
(_b_) _Red Sandstones and Marls_--Halesowen, Enville, Rubery.

CARBONIFEROUS.
(_a_) _Upper Coal Measures with Spirarks Limestone,
&c._--Sandwell, Arley.
(_b_) _Lower Coal Measures_--Oldbury, Bilston, Hawkesbury.
(_c_) _Millstone Grit_--Absent near Birmingham, present near
Colebrookdale.
(_d_) _Carboniferous Limestone_--Absent.

OLD RED SANDSTONE OR DEVONIAN
Absent near Birmingham, present in Forest of Wyre.

SILURIAN.
(_a_) _Ludlow Shales and Limestones_--Sedgley Hill.
(_b_) _Wenlock Shales and Limestone_--Dudley Hill, Wren’s
Nest, Walsall.
(_c_) _Woolhope Beds_--Barr and Rubery.
(_d_) _Llandovery or Mayhill_--Rubery.

ORDOVICIAN.
Absent.

CAMBRIAN.
_Upper Cambrian_:
(_a_) _Tremadoc Beds and Lingula Flags._--Shineton, Nuneaton,
Lower Lickey, and Malverns.

FUNDAMENTAL, CRYSTALLINE AND IGNEOUS ROCKS.
(_a_) _Charnwood Volcanic Rocks_--Charnwood Forest, Caldecote
Hill, The Wrekin.
(_b_) _Malvern Crystalline Rocks_--North Hill, Hereford
Beacon, &c.

THE FUNDAMENTAL CRYSTALLINE AND VOLCANIC ROCKS OF THE MALVERNS, THE WREKIN, AND CHARNWOOD FOREST.

The rocks which undoubtedly occupy the lowest place in the geological formations of the Birmingham district are those crystalline and partly schistose masses which form the core of the Malvern Hills; and certain well-marked volcanic rocks which occur at the Wrekin and Nuneaton, and which appear to have their equivalents in the great igneous series of Charnwood Forest. That all these more or less crystalline rocks are of higher antiquity than the Upper Cambrian of Wales is demonstrated by the fact that fossiliferous rocks containing Cambrian fossils of this age overlie them, while the lowest recognisable zones of these overlying fossiliferous rocks (the Hollybush sandstone of the Malverns, the quartzite of the Wrekin, and the Hartshill quartzite of the neighbourhood of Nuneaton) are in part composed of their fragments. Whether, however, they belong in part to the Middle or Lower Cambrian, or wholly appertain to the earlier formations of the Archean, must as yet remain an open question.

(_a._) MALVERN HILLS.--The core of the Malvern Hills is composed of a coarse syenitic, and more or less gneissose rock, pierced by veins of quartzo-felspathic rock of igneous origin (Hereford Beacon, &c). The main mass which is coarsely crystalline, becomes occasionally distinctly gneissose and even schistose, and its mineral bands strike from north-west to south-east, _i.e._, transverse to the general trend of the Malvern Ridge. The basement beds of the Hollybush sandstones (Cambrian) and the Llandovery rest unconformably upon this rock, which has consequently been claimed by some geologists as distinctly of Archean age, representing in part the Laurentian of Logan.

The best localities for studying the essential characters of the Malvern rocks are the quarries of the North Hill and the Wych, and the eastern slopes of the hills between Malvern Wells and Herefordshire Beacon.

(_b._) THE WREKIN.--The core of the beautiful hill of the Wrekin is formed by a magnificent series of highly acidic volcanic rocks--rhyolitic lavas and ashes. As first pointed out by Dr. Callaway, they rise out unconformably from below fossiliferous rocks of Upper Cambrian age. (Hollybush Sandstone and Shineton Shales) and are believed by him to be of Archean age. The finest exhibitions of the volcanic ashes of the group are met with in quarries on the flanks of the Wrekin itself, while the rhyolitic lavas occur in scattered localities along the hill. A broad mound of the same igneous series rises out from below the Triassic to the south of Walcot Station, and a most beautiful and instructive section of banded and spherulitic rhyolites is shewn in the quarry at the locality known as the Lee Rock.

The truly volcanic nature of these remarkable rocks was first pointed out by Mr. S. Allport, F.G.S., and their original characteristics, and the changes they have undergone since their formation, have been described by him in a well-known series of memoirs. Their geological position, and their relation to the associated fossiliferous strata, and to the similar rhyolitic rocks of Caer Caradoc and Pontesbury have been fully discussed by Dr. C. Callaway, F.G.S.

(_c._) NUNEATON (CALDECOTE HILL).--A thin group of volcanic breccias and tuffs, with associated quartz-felsites, and diabase, rises out from below the Upper Cambrians of Nuneaton, in the Park of Caldecote Hill. The lowest zone of the overlying Cambrian Hartshill quartzite is in part composed of their fragments. The ashes are shewn in old cuttings to the north-west of Caldecote Lodge, the quartz-porphyries and diabase in an old quarry about a quarter of a mile to the southward, while the breccia composed of the fragments of these old rocks, in the base of the Cambrian quartzite is best shewn on the tramway still farther to the southward, leading down to the Coventry Canal.

(_d._) CHARNWOOD FOREST.--This district is formed of an island of ancient igneous and stratified rocks rising out from below the Upper Trias. The stratified rocks are almost wholly composed of materials of volcanic origin, and shade off on the one hand into coarse volcanic agglomerates, and on the other into fine green slates like those of the Borrowdale series in the Lake District, to which indeed the whole of the bedded Charnwood rocks bear a striking resemblance.

The stratified volcanic rocks are pierced by numerous igneous intrusions. The most conspicuous are those classed by Professor Bonney, F.R.S., as syenite. These are most conspicuous near Groby, Bradgate, and generally in the south eastern parts of the Charnwood area. A mass of beautiful hornblendic granite rises through the Trias immediately to the east of Charnwood Forest at Mount Sorrel, near Barrow on Soar. A few later dykes of altered andesite occur within the forest itself, and diorite in the outlier of Brazil Wood.

To the south of Charnwood Forest, several remarkable points of syenitic rock protrude through the flat-lying Trias. The most conspicuous of these are the hills of Sapcote, Croft, and Enderby.

There is no direct evidence of the Cambrian or pre-Cambrian age of the Charnwood rocks, but strata identical with the fossiliferous Stockingford shales (Upper Cambrian) of Nuneaton, have been pierced in several borings through the Trias near Leicester, Market Bosworth, etc., and appear to rest at once upon the Charnwood rocks, as do the Nuneaton beds upon the Caldecote volcanic group.

CAMBRIAN ROCKS.

No fossiliferous strata unequivocally of Lower Cambrian age occur within the limits of the Birmingham District; but strata of Upper Cambrian age are met with in several localities. They were first recognised by Professor Phillips in the area of the Malvern Hills, and have been subsequently detected within the last few years at the Wrekin, at Nuneaton, and in the Lower Lickey Hills.

MALVERN HILLS.--The Upper Cambrian beds of the Malverns rest upon the crystalline rocks of the axis of the hills to the south of Herefordshire Beacon, along the slopes of Midsummer Hill and Keys Hill. The lowest zone is the _Hollybush Sandstone_, a light green micaceous rock, containing tubes of sea worms and _Kutorgina cingulata_.

The Hollybush Sandstone is succeeded by shivery shales, somewhat sandy below, and becoming darker and more carbonaceous above.

In their lower beds they yield:--_Obolella Salteri_, _Obolella sagittalis_, _Lingula pygmea_, _etc._ In their middle beds they afford _Pellura scarabeoides_, _Spheropthalmus alatus_, _Agnostis pisiformis_, _Agnostus trisectus_, etc., well-known fossils of the Upper Lingula Flags (Dolgelly) of North Wales.

Their highest beds contain _Dictyonema sociale_, a fossil which passes up into the succeeding Tremadoc Slates.

The rest of the local succession of the Cambrian rocks is hidden by the unconformable overlap of Silurian.

The Hollybush Sandstone and the overlying sandy shales contain numerous intercalated volcanic rocks, some of which are of the age of the surrounding strata, while others are intrusive.

NUNEATON DISTRICT.--In the neighbourhood of the town of Nuneaton in eastern Warwickshire, a strip of Cambrian rocks, about eight miles in length by one in breadth, has been detected within the last few years. The rocks consist of volcanic ashes, quartzites and thin-bedded shales, pierced by dioritic dykes. These strata were formerly mapped as altered Millstone Grit and Carboniferous shale, and their Cambrian age has only been recently demonstrated by the discoveries of Birmingham geologists. The complete succession is as follows:--

(1.) CALDECOTE VOLCANIC GROUP.--Well-bedded tuffs and volcanic ashes (see _ante_) with masses of Quartz-felsites and diabase.

(2.) HARTSHILL QUARTZITE.--Thick-bedded quartzites, with occasional layers of sandy shale.

(3.) STOCKINGFORD SHALES.--

(_a._) _Lower Division._--(_Obolella Beds_) Purple and green shales with _Obolella Salteri_, _Lingulella pygmea_, _Lingulella lepis_, _Acrotreta_, _Protospongia_, &c.

(_b._) _Upper Division._--(_Agnosias Beds_) Grey and black shales with _Agnostus pisiformis_. _Beyrichia Angelini_ and _Lingulella Nicholsoni_, in the lower zones, and _Spheropthalmus alatus_ and _Dictyonema_ in the upper zones.

These Cambrian rocks are overlain unconformably by the Coal measures to the west, and by the Keuper beds to the east; the boundary of the area is, however, locally defined by lines of fault.

The basement beds of the Hartshill Quartzite are locally composed of fragments of the underlying volcanic rocks (Caldecote Beds). The Quartzite itself, which forms the chief road metal of the neighbourhood, is laid bare in a long series of quarries between Nuneaton and Hartshill.

The overlying purple and green shales of the Stockingford Beds range from Marston Jabet, south of Chilvers Coton to Atherstone Outwoods. The best section is seen in Parley Park Lane near Atherstone, and the fossils have been obtained from this section, from Atherstone Oakwoods, Camp Hill, and Marston Jabet.

The best section of the succeeding grey and black Shales occurs in the cutting of the Midland Railway near Stockingford, which gives its name to the formation. Their fossils have been procured from the rocks of this section; from the cutting at Chilvers Coton, the banks of the Coventry Canal, from Oldbury reservoir, Mawbornes and Merevale Park.

The numerous intrusive dykes of volcanic rock form a conspicuous feature in the geology of these Cambrian strata. They are formed of coarse-grained diorites, much quarried for road metal, kerbs, and setts. Good sections occur in the quarries near Tuttle Hill, in the railway cuttings near Stockingford and Chilvers Coton, and in quarries near Oldbury Reservoir.

A small patch of these Nuneaton Cambrians is met with on the north-western margin of the East Warwickshire coalfield, at Dost Hill, to the south of Tamworth. It consists of the usual annelide-bearing Stockingford Shales, pierced by an intrusive mass of diorite.

LOWER LICKEY HILLS.--The core of the Lower Lickey Hills between Barnt Green and Rubery, about eight miles south of Birmingham, is formed of a mass of quartzite identical in all its main features with that of Hartshill, near Nuneaton.

At the village of Rubery, in an exposure on the roadside, it is seen to be unconformably overlain by fossiliferous Llandovery sandstone, the basement beds of which contain fragments of the underlying quartzite in abundance. At the south-western extremity of the Lower Lickey Range the quartzites contain fragments of igneous rocks, and appear to pass down into a series of felspathic grits, pierced by dioritic dykes similar to those of the Nuneaton District. Good sections of the quartzites are laid bare at Rubery Station, at the village of Rubery, and in a large quarry near the roadside, a mile northward from Kendall End. In the last-named locality the quartzites are seen greatly folded and faulted.

WREKIN DISTRICT.--In the Wrekin area the great volcanic series of the hills is immediately overlain by a quartzite similar to that of the Hartshill and the Lickey, the basement bed similarly containing fragments of the underlying volcanic rocks. The quartzite is succeeded by the Hollybush sandstone, with its characteristic fossil, _Kutorgina cingulata_.

A broad area, lying between the Hollybush sandstone and the unconformably overlying Silurian rocks of Buildwas, is occupied by a series of Upper Cambrian rocks, denominated by Dr. Callaway the Shineton Shales, and characterised by the forms:--_Olenus Salteri_, _Sphæropthalmus_, _Asaphellus Homfrayi_, _&c._, _Bryograptus Callavei_, _&c._, allying them with the Tremadoc Beds of North Wales.

SILURIAN ROCKS.

The rocks of the Silurian System are fully developed within the limits of the Birmingham District, under their most typical aspect. The well known localities of Dudley and Barr have been famous in the geological world since the publication of Murchison’s great work, the Silurian System; and the abundance and beauty of the fossils of the limestone rocks of the district place it next to the typical area of Central Shropshire as the representative country of the Silurian rocks.

The Silurian strata are all of the well-known Salopian type, shewing several thick-bedded limestones, occurring on distinct horizons in a great thickness of dark blue or grey nodular shales and mudstones. They make their appearance in sharp anticlinal arches in the South Staffordshire coalfield, and along its faulted margins. Four of these exposures occur along the crest of the Lickey-Dudley anticlinal--at Rubery, Dudley Castle Hill, the Wren’s Nest, and Sedgley. The largest continuous exposure is that near the town of Walsall, on the eastern margin of the coalfield.

All the Silurian formations from the Mayhill Sandstone to the Ludlow (Aymestry) Limestone are recognisable, but the terminal Downton sandstone is lost below the unconformably overlying Carboniferous. None of the localities, however, shew the complete consecutive series, which is made out by piecing together the sections occurring in the several areas.

(1.) LOWER LICKEY HILLS.--

(_a._) _Landovery or Mayhill Rocks._--The usual red and grey _Pentamerus_ sandstone of the Mayhill formation is exposed along the north-west flank of the Lower Lickey Hills. It may be seen resting unconformably upon the Cambrian quartzite in the village of Rubery, and at Leach Heath. Casts of fossils are abundant in some of the sandstones a few feet above the base of the formation, and include the well known forms:--_Pentamerus oblongus_, _Pentamerus lens_, _Strophomena expansa_, _Attrypa reticularis_, _etc._--These may be collected from the rocks at the village of Rubery, and from the fragments of sandstone scattered over the fields between the Asylum and Leach Heath.

(_b._) _Woolhope or Barr Limestone._--The Llandovery sandstone is followed (in a stream section below the Asylum) by pale blue shales and mudstones containing a bed of hard calcareous rock, affording examples of _Illenus Barriensis_, _Atrypa reticularis_, _Encrinurus punctatus_, _Rhynchonella Lewisii_; but the section is a poor one, and is covered up almost immediately by the overlying Carboniferous.

(2.) WALSALL AND BARR.--This is the typical area for the well known Barr Trilobite _Illenus Barriensis_. The quarries of the Woolhope Limestone which afford it are now disused, but a good section of the fossiliferous shales above is displayed in the railway cutting between Aldridge and Walsall. The overlying Wenlock or Dudley Limestones are mined at the town of Walsall itself, but good fossils are now comparatively rare.

(3.) DUDLEY AND THE WREN’S NEST.--By far the most notable and interesting of the Silurian exposures are those of the neighbourhood of Dudley. In the three exposures of Dudley Castle, the Wren’s Nest, and Sedgley Hill, the Silurian limestone rises up in steep dome-like forms. This limestone, which is that of the Wenlock of Siluria, is here composed of two calcareous bands--the higher about 28 feet in thickness, and the lower about 42 feet--separated from each other by an intermediate zone of about 90 feet of gray shales. The limestone has been worked for centuries as a flux for the ironstones of the coalfield. The hills have been mined to a great depth, and all the best limestone rock extracted. The intervening and enveloping shales have been allowed to remain, and the present structure of the hills is that of a central dome surrounded by two enveloping shells, separated from each other by two more or less empty spaces. Where the dip of the rock is high, and these excavated parts are exposed, they form deep moat-like hollows, bounded by walls of shale. Where the dip is low, and the overhanging rocks are supported by the vast pillars left by the workmen, these excavations form magnificent caverns of peculiar weirdness and beauty. In the heart of the hill at greater depths they form damp gloomy chasms of enormous extent, which can only be seen to perfection when lit up by artificial light.

The Dudley limestone bands and the surrounding calcareous shales have long been famous for the abundance and beauty of their included fossils. Many of the type species of Murchison’s Silurian System came from this locality; but since the superficial limestones have been worked out, good specimens are exceedingly rare. An excellent collection of the fossils of these beds is laid out in the Dudley Museum, and another in the Geological Museum of the Mason College. Many good collections are in the possession of private individuals in Dudley and elsewhere.

The best localities for fossils at present are the shaly slopes on the flanks of the Wren’s Nest, where the usual Wenlock Brachiopods and Corals are abundant, but the beautiful Trilobites of the formation are but rarely met with.

The Wenlock limestone occurs both in the Dudley Castle Hill and in the Wren’s Nest. The Aymestry limestone is only met with in a single locality on the flanks of Sedgley Hill, where it yields occasional specimens of its characteristic fossil, the _Pentamerus Knightii_.

CARBONIFEROUS ROCKS.

Rocks of Carboniferous age make their appearance at four distinct localities within the limits of the Birmingham District, viz., in the coal fields of Coalbrookdale, the Forest of Wyre, South Staffordshire, and East Warwickshire. The strata exposed on the last three of these coalfields are those of the upper Carboniferous or Coal measures; neither the Carboniferous limestone nor the Millstone grit being met with outside the limits of the coalfield of Coalbrookdale.

In the Forest of Wyre the Coal measures rest upon the Old Red Sandstone, in the South Staffordshire Coalfield upon the various members of the Silurian, and in the East Warwickshire upon the Upper Cambrian rocks. In these three coalfields a two-fold division of the Carboniferous is recognisable:--

(_a._) _The Lower Coal Measures_ proper, consisting of grey sandstones and shales with occasional coal seams, some of which are of remarkable thickness.

(_b._) _Upper Coal Measures_, or Halesowen grey and red sandstones, brick clays and marls, with occasional coal-seams, none, however, of commercial value.

In the South Staffordshire and East Warwickshire coalfields, the well known “_Spirorbis Limestone_” of the Upper Coal Measures occurs in its normal place near the summit of the Carboniferous series.

SOUTH STAFFORDSHIRE COALFIELD.--The Carboniferous rocks of South Staffordshire are arranged in a broad dome about 23 miles in length by 6 in breadth. Their basement beds rest unconformably upon the Silurian around the flanks of the Dudley Hills, and in the neighbourhood of Walsall. Their highest beds dip conformably below the Permian rocks at the southern extremity of the coalfield south of Halesowen, and are overlapped unconformably by the Triassic pebble beds at its northern extremity, in the district of Cannock Chase. The eastern and western boundaries of the coalfield are formed by lines of fault, which have flung down against the Coal Measures the various members of the Permian and the Triassic. The total thickness of the Carboniferous beds is about 1,300 feet, and the normal succession in the central and highest part of the coalfield is as follows:--

_Upper Coal Measures._--

_2a._ Halesowen Sandstone Group, 600 to 800 feet.

_2b._ Red Coal Measure Clays.

_Lower Coal Measures_, 500 to 600 feet, containing several excellent coal seams, of which the following are the most important:--

(_a._) Brooch Coal, 4 feet.

(_b._) Thick Coal, 30 feet.

(_c._) Heathen Coal, 3 feet.

(_d._) New Mine Coal, 2 to 11 feet.

(_e._) Fire Clay Coal, 1 to 14 feet.

(_f._) Bottom Coal, five feet and above.

These measures include several zones of workable ironstone, of which the most important are:--

(1.) The Pins and Pennyearth ironstones, below the Brooch coal.

(2.) The Whittery and Gubbin ironstones, below the Thick coal.

(3.) The Blue Flats, Silver Threads and Diamond Ironstones, below the Bottom coal.

For its size the South Staffordshire coalfield has proved itself the richest mineral area in Britain. Thick coal seams, rich bands of ironstone, and great thicknesses of Silurian limestone, all occur within a short distance of each other, and all within easy reach of the miner. The natural result has been that the South Staffordshire coalfield and its immediate neighbourhood has been the great coal and iron mart of Central Britain, and the abundance and cheapness of its material it has afforded, have rendered Birmingham and the “Black Country” the hardware workshop of the world.

Almost all the available coal seams and ironstone beds within easy reach have been long since practically worked out, but there is still much excellent coal and iron to be obtained at greater depths, especially in the northern part of the coalfield. Of late years the Triassic rocks which surround the coalfield have been pierced in order to reach the Coal measures beneath. An entirely new coalfield has been developed in this manner in the district of Cannock Chase; and two most remarkable collieries, those of Sandwell Park, and Hamstead, have been opened in the neighbourhood of Birmingham itself.

The area immediately underlain by the Coal measures constitutes the district of the “Black Country,” which extends from the western margin of Birmingham to the fringe of Cannock Chase. It includes within its limits, the large towns of Dudley, Walsall, Wolverhampton, Bilston, and others of scarcely less note.

The most remarkable seam of the South Staffordshire coalfield is that known as the Ten yard or Thick coal, a continuous bed of workable coal from 25 to 30 feet in thickness. This underlies all the south central part of the field in the area enclosed by Smethwick, Oldbury, Dudley, Walsall and Bilston. To the southward near Halesowen it thins out and becomes mixed with shaly material. It is in reality composed of 13 or 14 superimposed coal seams, which form an apparently unbroken mass, but are easily distinguished individually by the practised Thick coal miner. As we pass northward from the typical Thick coal area towards Walsall and Cannock Chase, the component seams become separated by intercalated sandstones and shales, so that eventually in the district of Essington and Pelsall the Thick coal is represented by 14 distinct coals occurring at intervals in a mass of sandy rock, between 500 and 600 feet in total thickness. The Thick coal is known to extend far to the eastward, beyond the present margin of the South Staffordshire coalfield. The first attempt to reach it through the red ground (Permian) was made under the bold and skilful guidance of the late Mr. Henry Johnson, C.E., of Dudley, at the locality of Sandwell Park. The coal was reached in 1873 at a depth of 1,250 feet and found to be of its original thickness, and of excellent quality. The next attempt which was made at Hamstead Hall, about three miles outside the limit of the coalfield, was even bolder and more hazardous, but it was eventually crowned with equal success; the Thick coal being reached at a depth of 1,800 feet. As the demand for coal increases, other collieries will doubtless be started at fresh localities outside the limits of the coalfield, for there can be no question that the Thick coal extends far to the eastward, under and beyond the town of Birmingham itself.

The strata of the South Staffordshire Coalfield afford the usual fossils of the British Coal Measures. The roofs of the coal seams, and the layers of carbonaceous shale, locally furnish well preserved examples of _Lepidodendron_, _Sigillaria_, _Calamites_, _Annularia_, _Pecopteris_, _Neuropteris_, etc., often associated with abundant specimens of the peculiar _Unio_-like shell, _Anthracosia_: while the ironstone nodules occasionally yield fragmentary _Crustaceans_ and _Insects_. Marine fossils are principally confined to the lower beds of the series, below the Thick coal. Owing to the absence of true limestone beds in the coalfield, the characteristic corals, &c., of the Carboniferous are absent, but the following marine forms are not uncommon in the lower ironstones:--

_Lingula elliptica_, _Discina nitida_, _Producta scrabicula_, _Conularia quadrisulcata_, _Aviculopecten scalaris_, _Gyracanthus farmosus_, _Megalichthys Hibberti_, _Pœcilodus angustus_.

These have been met with at several localities near Walsall, Oldbury, Old Hill, Kingswinford, and Oldswinford, etc.

The rocks of the South Staffordshire coalfield are pierced locally by sheets of igneous rock. The most important of these is a mass of dolerite about two miles and a half in length, which caps the long ridge of Rowley Regis. It is traversed by several mining shafts, which pass through the dolerite into the workable coals below. Other igneous masses occur near Dudley, and at Pouk Hill, near Walsall.

THE EAST WARWICKSHIRE COALFIELD.--The rocks of this coalfield form a narrow strip about 15 miles in length, ranging from Tamworth on the north to Bedworth on the South. The coalbearing strata rest unconformably upon the Cambrian below, and pass up conformably into the Permian above. The sequence of the beds is practically identical with that of South Staffordshire--the richer coal measures being all confined to the lower part of the Carboniferous series, and passing up through a group of coloured clays into a final group of barren sandstones. In the north of the coalfield five workable seams of coal occur, separated by many feet of barren measures. As they pass to the southward the intermediate strata thin out, and the coal-beds practically come together at Hawkesbury to form one Main coal seam, as do the corresponding members of the Thick coal of South Staffordshire. It is probable that the two coalfields were formed in the same general area of deposition, and except for the possibility of its destruction by erosion prior to the deposition of the Triassic, it might be suggested with safety that the Thick coal of South Staffordshire extends in a continuous sheet under the red rocks of Northern Warwickshire from Smethwick to Hawkesbury.

FOREST OF WYRE.--Unlike the strata of the other coalfields, the Carboniferous rocks of the coalfield of the Forest of Wyre are comparatively barren of good coal seams. The best, which is locally known as the _Main_ coal, is about seven-and a-half feet in thickness, and occurs at an average depth of 300 feet.

COALBROOKDALE.--This coalfield, which lies to the east of the Wrekin, covers an area of about 28 square miles. It originally contained about 28 coal seams, but the majority of these are now practically worked out. The succession includes the Carboniferous limestone, the Millstone grit, and the Lower coal-measures in conformable sequence. The Upper coal-measures rest in a hollow eroded out of the Lower coal-measures beneath, forming what is locally known as the “Symon Fault.”

PERMIAN OR DYASSIC.

The Permian rocks of the Birmingham District are totally distinct in their petrological characters from those of the typical area of Yorkshire and Durham. No true limestones are present, and the formation is wholly made up of red sandstones, marls and beds of angular breccia.

The lowest zones of the Permian repose conformably upon the Upper Coal Measures of the South Staffordshire Coalfield in the slopes of the hills to the south of Halesowen, and its strata are seen in corresponding relation to the Carboniferous on the east of the Coalfields of the Forest of Wyre and Coalbrookdale, and to the west of the Coalfield of Eastern Warwickshire.

The Permian is everywhere covered up unconformably, or locally overlapped, by the various members of the Triassic formation; all the subdivisions of the Triassic series being found resting immediately upon it in turns as they are followed from the valley of the Severn to the neighbourhood of Charnwood Forest.

In the neighbourhood of Enville and the Forest of Wyre, three divisions are recognisable in the Permian, viz.:--

(1.) _Lower Red Sandstones and Marls_, with bands of calcareous conglomerate.

(2.) _Coarse Breccia._

(3.) _Upper Red Sandstones and Marls._

Round the South Staffordshire Coalfield the Breccia is the highest division exposed, and this only occurs in force to the south of the coalfield.

Between Tamworth and Kenilworth, to the east of Birmingham, the Permian strata floor a wide tract of country, and lie almost horizontal. Red sandstones, marls and beds of breccia occur in association, but the divisions named above are not individually recognisable.

By far the most striking local member of the Permian formation is the so-called _Volcanic or Permian Breccia_. It is found in scattered patches over an area of about 500 square miles, extending from the Malverns to Enville, Stourbridge, and the Lickey Hills. It is made up of angular fragments of volcanic rocks, tuffs, altered shales, grits, and slabs of fossiliferous sandstone and limestones, all embedded in paste of bright red marl or pebbly sandstone. It is usually both underlain and overlain by red sandstones and marls, but sometimes, as at Stagbury and Woodbury Hills, &c., in the Valley of the Severn, it reposes at once upon pre-Permian rock.

This peculiar Breccia is well displayed in the Clent Hills, between Hagley and Halesowen. It there reposes upon the Lower Permian Sandstones with calcareous grit bands--(which may be seen above the little Church of St. Kenelm)--and forms all the highest points of the Clent Hills, passing unconformably to the southward under the pebble beds of the New Red Sandstone. In this locality the angular fragments composing the Breccia are mainly volcanic:--rhyolites, porphyrites, ashes, and volcanic grits, embedded in a coarse matrix formed of similar materials. Other sections are seen in the Bromsgrove Lickey Hills, and in the neighbourhood of Northfield. In the last-named locality an excellent section is exposed in a lane leading from the Bell Inn to Bangham Pit. In this exposure the breccia, which shows the usual preponderance of volcanic materials, contains in addition fragments of Silurian limestone (crowded with characteristic fossils), and pieces of Landovery grit and shale.

According to Sir Andrew Ramsay,[60] this Permian breccia is probably of glacial origin, its materials having been brought down by ice in Permian times from the neighbourhood of the Longmynd in central Shropshire, where all the formations represented in its derived rock fragments occur at present in natural juxtaposition. According to Professor Jukes,[61] the fragments of the Northfield breccia, at any rate, “may have been derived from adjacent rocks, now concealed under the Permian and New Red Sandstone.”

The Triassic Rocks.

BY W. JEROME HARRISON, F.G.S.

A considerable portion of the Midland Counties of England is composed of red sandstones and marls. The town of Birmingham stands upon, and is surrounded by rocks of this character. They form the Triassic System of geologists, the first of the four grand members of the Mesozoic series.

Strictly speaking, the title _Trias_ is a misnomer as applied to the English development of the rocks of this system. The central member of the typical German succession, the _Muschelkalk_, is wanting in Britain; and only the upper and lower divisions, the so-called Keuper and Bunter, are represented. The _Bunter_ or lower Trias, consists in the Midland areas of a mass of pebble beds or conglomerate, usually underlain and overlain by variegated sandstones. The _Keuper_ is formed of a great thickness of red marly strata, with a thick sandstone (_Waterstones_) at the base.

The following table shews the subdivisions of the Trias which have been recognised in England, together with (_a_) their maximum thickness, and (_b_) their thickness in the neighbourhood of Birmingham.

CLASSIFICATION OF THE TRIASSIC STRATA--

Thickness Thickness near
in Cheshire. Birmingham.
Feet. Feet.
KEUPER RED MARLS (with the Upper
Keuper Sandstone) f. 6. 3,000 700
LOWER KEUPER SANDSTONE, f. 5. 450 200
_Muschelkalk_ (wanting in England).
UPPER MOTTLED SANDSTONE, f. 3. 500 200
PEBBLE BEDS, _or Bunter
Conglomerate_, f. 2. 600 400
LOWER MOTTLED SANDSTONE, f. 1. 400 (wanting.)

The Trias enters England on the south coast, between Torbay and Exmouth. At the little watering-place of Budleigh Salterton there is a bed of quartzite pebbles in the Trias 100 feet thick which is worthy of study in connection with the great numbers of similar pebbles that occur in the same strata round Birmingham. In West Somerset and Devon, the Triassic strata are 3,500 feet in thickness. Their subdivisions cannot be correlated with those of the Midlands, for they appear to have been deposited in a separate basin, of which the Mendips, &c., still mark the northern boundary.

Crossing into Gloucestershire, we find the vale of the Severn composed of Triassic marls, and thence northwards the “red rocks” broaden till they form the plains of Cheshire and South Lancashire on the west, and extend eastward to Warwick, Leicester, and Derby. From this great central plain of our island a long strip of Triassic sandstones and marls runs northwards, forming the Vale of Trent and the Vale of York, until finally it reaches the coast between Redcar and Hartlepool. Along the main line of outcrop--from the Malvern Hills to the mouth of the Tees--the Triassic strata incline gently, or dip, to the south-east, at from two to five degrees.

Of the two great divisions of the Trias, the lower (Bunter) is mainly sandy; while the upper (Keuper) is chiefly a stiff marl or clay. One result of this is that while the outcrop of the former is usually barren, forming much heath or waste land, as Sherwood Forest, the Keuper marls produce a rich soil, well fitted for the plough.

Owing to the soft nature of the strata, valleys are usually hollowed out in the Lower and Upper Mottled Sandstones, while the Keuper marls form an undulating plain. On the other hand the harder nature of the Bunter pebble bed, and the Lower Keuper Sandstone, causes these two rocks to form escarpments or lines of hills, parallel to each other; the abrupt face generally looking west or north-west, while the gentle slope is to the east or south-east, agreeing with the average dip.

THE LOWER RED AND MOTTLED SANDSTONE.--Round Bridgenorth this division rests unconformably on Permian strata, and is about 650 feet thick. It is a homogeneous sandstone, of reddish-brown, yellow, and bright red colours, entirely devoid of pebbles. As we follow this stratum to the east it decreases in thickness, being only 200 feet near Stourbridge. East of the South Staffordshire field, the Lower Mottled Sandstone is entirely absent, and the Bunter pebble beds repose directly upon the Permian rocks. Geologists desirous of examining the “Lower Mottled” should visit Kinver Edge, west of Stourbridge, where this rock is well seen underlying the Bunter conglomerate. Its upper portion has here been hardened by calcareous matter, and projects beyond the pebble beds above. Caves, or “rock-houses,” have been excavated in the Edge, and in a detached mass of sandstone called the Holy Austen Rock. The Lower Mottled Sandstone is again visible on Whittington Common, between Kinver and Stourbridge. It is everywhere quite unfossiliferous. “False bedding” is especially characteristic of this division, but it is common in all the Midland Triassic sandstones.

THE BUNTER CONGLOMERATE OR PEBBLE-BED occupies the surface of the Birmingham area, along a line running from south-west to north-east. It extends from Worcester, by Bridgnorth, Stourbridge, Cannock Chase, and Sutton Park to Lichfield. At all these places it is seen as a remarkable mass of rounded pebbles--mostly yellow, brown, or liver-coloured quartzites--and attains a thickness of 300 feet at Cannock Chase. West of Stourbridge the Conglomerate forms the “Ridge,” and caps Kinver Edge, dipping east or south-east at from five to eight degrees. Thence it is traceable northward by Upper Penn and Bushbury to Cannock Chase, where it forms a wide undulating heathy moorland, six miles in breadth from Bednall on the west to Rugeley on the east, and is exposed in many gravel pits and other excavations. The Staffordshire Coalfield lies like a great wedge between the Trias on its western and eastern sides. Crossing over from Stourbridge, we again find the Bunter Conglomerate or Pebble-beds extending between Harborne and Smethwick, and thence it runs northward in a broad band across the western suburbs of Birmingham, by Winson Green, Handsworth, Perry Barr, and Perry, to Sutton Park (where its outcrop is 3½ miles wide), and on to Aldridge, Wreford, Hopwas Wood, and Lichfield Racecourse. All along this line the Pebble-beds rest on Permian marls, and their thickness at Barr Beacon is about 400 feet. Good sections of the pebble-beds are rare on the south-west or west of Birmingham, but in the north-west they are well seen in a quarry south of Great Barr Station, and in one or two sections near the Beacon. At Sutton, exposures along the new railway lines to Lichfield and to Walsall have been numerous and good, and the Quarry in the Park, close to Blackroot Pool, gives a vertical section of thirty feet. Each section shows a mass of well-rounded hard pebbles, which have been so pressed together during the earth-movements that have taken place since their deposition that many are cracked, while all bear white indentations. The Bunter Conglomerate contains no fossils of contemporaneous age, but many species of shells have been obtained from the hard, rounded lumps of rock of which it is composed. These fossils being of necessity of the age of the rock-fragments in which they are included, they furnish a clue to the sources from which the pebble-beds were derived. The following list of these derivative fossils will give some idea of the results which have already been obtained:--

ORDOVICIAN (in quartzite pebbles).--(_Arenig Beds._) _Lingula
Lesueurii._ (This interesting brachiopod shell has not yet been
found in its parent rock in England, though it is not uncommon
in the _Gres Armoricain_ of Brittany, a quartzite on the same
horizon as the Stiper stones); various lamellibranchs such as
_Modiolopsis_, _Palaearca_, and _Lyrodesma_ occur.

(_Caradoc and Bala Beds._)--Seven or eight species of
brachiopods, of which the commonest is _Orthis Budleighensis_;
a crinoid (_Glyptocrinus basalis_), &c.

(_May Hill Sandstone._)--Lumps of coarse sandstone, identical
lithologically with the rock which flanks the Lickey Hills,
occur commonly; they contain numerous casts of _Stricklandinia
lirata_, &c.

DEVONIAN.--Nine or ten species of brachiopods (especially
_Spirifera Verneuilii_). Remains of trilobites, such as
_Phacops_ and _Homalonotus_ are not unfrequent.

MOUNTAIN LIMESTONE.--Mr. Molyneux enumerates twenty-two species
of mountain limestone fossils--brachiopods, corals, crinoids,
&c.--which he obtained from the Bunter pebble-beds of Trentham.
Near Birmingham, fragments of partly decomposed chert, in which
the stems of crinoids are beautifully shown, are common in the
same strata.

THE UPPER RED AND MOTTLED SANDSTONE.--Stourbridge stands on the bright red sands of this division, which extend northward through Kingswinford to Trysall and Tettenhall. South of Birmingham we find the same strata at Harborne Heath and Mill--there is a good exposure underneath the drift in Flavel’s brick pit at “California”--from which point we can trace the “Upper Mottled” across the western part of Birmingham, by Rotton Park Reservoir and the Botanical Gardens; the beautiful soft red sandstone forming a strip about a mile in width between Spring Hill, Hockley Brook, Aston Villa, and Birchfields on the west, to the foot of Snow Hill, and Aston Park on the east. In the cemetery adjoining the Great Western Station at Hockley, there is a grand section, forty feet in height, where the incoherent sand is largely worked for moulding and foundry purposes. It is also exposed in and round Aston Park.

THE LOWER KEUPER SANDSTONE.--The lower member of the Keuper is the most consolidated part of the Triassic formation, being best known as a tolerably hard sandstone, white or pink in colour, which often yields good building stone.

The “basement beds” of the Keuper are certain coarse sandstones and chocolate coloured marls seen in a pit at “California,” near Harborne. Above these come massively-bedded sandstones, of which there is a good exposure in the now disused quarry at Weoley Castle.

Commencing at Edgbaston, we can trace the Lower Keuper Sandstone by the Five Ways, and across the central highest part of Birmingham to Nechells, Gravelly Hill, and Erdington. Its lower boundary line, where it reposes on the Bunter, may be indicated by a line drawn from the junction of Monument Road with Hagley Road to the bottom of Snow Hill, and thence to Aston Station. From this point it extends eastward, for from one mile (Edgbaston) to half-a-mile (Aston). The ridge on which stands the Town Hall, St. Philip’s Church, &c., (475 feet above sea-level) is formed by the Lower Keuper Sandstone, and deep excavations for foundations in the centre of the town, frequently disclose the thin-bedded, dull-coloured, pinkish sandstones (known to workmen as “skerry”) which constitute the upper portion of this rock. Its thickness under Birmingham may be estimated at 200 feet. The average dip is from three to five degrees south-east. Similar beds are exposed in the cutting at Bromsgrove Railway Station, and it was from a quarry here (now closed) that the remarkable fossil fish was obtained, which was described by Sir Philip Egerton as _Dipteronotus cyphus_. From quarries at Coton End, Guy’s Cliff, Cubbington and Blakedown Hill, near Warwick, bones and teeth of four species of the _Labyrinthodon_ have been obtained, and foot-prints of the same creature have been found in the Lower Keuper Sandstone in many localities.

THE KEUPER RED MARL is the uppermost member of the Trias. Near Birmingham it is abruptly separated from the Lower Keuper Sandstone by a line of _fault_, which can be traced from Selly Oak northwards to the junction of the Rea with the Tame. East of this line of fault, the red marls extend for ten or twelve miles forming an undulating fertile plain, on which stand Moseley, Smallheath, and Castle Bromwich, Coleshill and Whitacre. The thickness of the Keuper Marls is considerable. A boring in Smallheath Park was made to a depth of 440 feet entirely in such strata; but quite lately another boring at King’s Heath has been continued to a depth of 700 feet. Gypsum is plentiful in the red marls, occurring in white fibrous layers, but not of sufficient thickness to be of any value in this district. At Droitwich (eighteen miles south-west of Birmingham) the Keuper Marls contain a thick bed of rock salt, which yields an inexhaustible supply of _brine_.

_The Upper Keuper Sandstone_ is a thin band of sandstone, not exceeding thirty feet in thickness, which occurs irregularly in the upper part of the Keuper Marls. It is well exposed at the entrance to the canal tunnel at Shrewley Common, and in a small quarry at Rowington (thirteen miles south-east of Birmingham), and also crops out on the hill sides at many points in South Warwickshire. From this thin stratum, the Rev. P. B. Brodie, F.G.S., has obtained a fossil fish (_Palæoniscus superstes_), and the crustacean (_Estheria minuta_). Specimens of these may be seen in the Warwick Museum, which contains the finest collection of Triassic fossils possessed by any provincial museum.

HOW THE TRIASSIC ROCKS WERE FORMED.--According to the writer’s views, the area now occupied by central England, alternated in condition during the Carboniferous epoch, between a low plain and a shallow sea. In the Permian period, land conditions prevailed, except in the North and North Midland Counties, where a brackish sea somewhat like the Baltic, it may be--occupied a shallow depression. In Triassic times this central sea appears to have been completely cut off from the open ocean, and to have formed a large inland lake, comparable to the Caspian or the Dead Sea of our own day. The southern boundary of this inland sea was formed by a ridge of old rocks which extended from Charnwood by Hartshill and the Lickey to the Wrekin and Malvern Hills. In the basin north of this axial ridge, all the subdivisions of the Bunter and the Keuper were in turn deposited; and the cliffs and reefs of the Palæozoic rocks of which this coastline was composed, yielded large contributions to the pebble-beds, sands and marls, which constitute the Trias. According to a theory originally advanced by Professor Hull, and ably supported by Professor Bonney, the pebbles of the Bunter were mainly derived from the Paleozoic Rocks of the N.W. and N.E., some being possibly furnished by the ancient strata of N.W. Scotland.

The waters of the Triassic sea were so overcharged with salts of iron, that every grain of sand was encrusted, before its deposition, with a pellicle of peroxide of iron: of chloride of sodium (common salt) and sulphate of sodium (gypsum), there was also an excess, so that much was deposited on the sea-floor, producing beds of rock-salt and of gypsum, of considerable thickness. The presence of these mineral substances in the water was prejudicial to life, so that--as in the Dead Sea, and in Lake Utah to-day--few living creatures could inhabit the Triassic sea, and fossils are consequently of extreme rarity in strata of this age.

_The Trias as a source of Water Supply._--The Triassic strata are so porous, that they absorb a large proportion of the rain which falls upon them, and they consequently form an underground reservoir which, when tapped by wells or boreholes, is capable of yielding an almost inexhaustible supply of good, though somewhat hard water. In this way Birmingham receives three-fourths of its water from three deep wells--two on the north-east of the town, at Aston and at Perry respectively, and one on the south-west, near Selly Oak. These wells extend to depths of 400 feet, passing through the Upper Mottled Sandstone, and piercing the pebble beds, and the average supply of water from each is three million gallons per day. The hardness varies from nine to fifteen degrees. There are many other deep wells in and round the West of Birmingham, and at Stourbridge, Wolverhampton, etc., which derive their water from the same source.

Liassic and Rhætic.

BY REV. P. B. BRODIE, M.A., F.G.S.

The Lias occupies a large area in the south and east of the Birmingham District, and consists for the most part of the middle and lower divisions. The highest position of the Lias is seen on the south and south-eastern division of Warwickshire, the middle Lias forms the hills projecting in spurs to the north-west, and the lower division extending in the same direction, at a lower level, up to the southern edge of the Trias.

UPPER LIAS.--The Upper Lias is chiefly represented by a thin bed of clay, with some characteristic fossils. It occurs on the hills of Fenny Compton and elsewhere, and there is evidence to show that it formerly capped the range of the Edge Hills adjacent, occupying its natural position above the marlstone, or Middle Lias, of which they are mainly composed. From Fenny Compton to Harbury, a good descending section may be obtained from the marlstone (rock bed), through the underlying clays and marly beds, through the “Lima Beds” and White Lias, to the New Red Marls at Harbury.