Beneath the Surface; or, the wonders of the underground world

Preface

. UP*?!®!^ t'le f°l'owing Pages an attempt is made to VÆ &J furnish the reader with a comprehensive and exact description of the structure of the Earth's crust, of the fossils enclosed within its various formations, of its metallic deposits, and its stores of mineral wealth. Special chapters are devoted to the interesting and sug gestive subjects of springs and fountains, and grottoes and caverns, the most remarkable of which are indicated, while their legends and associations are brought to gether. The salts and natural gases, fumeroles, and cha lybeate waters, as well as other remarkable features of the world " beneath the surface," are also duly noticed. The reader is conducted in turn to the coal-mines of Northumberland, the marble -quarries of Carrara, the sandstone - quarries of Fontainebleau, the tin-mines of Cornwall, the lead-mines of Allenhead, the oil-wells ot the United States and Canada ; and particulars are given VI

PREFACE.

. of the character and habits of the miner and quarryman, of the nature and extent of the important industries which depend upon their labours. Underground life has its perils, and these are recorded ; the underground world has its wonders, and these are put before the reader. It is believed that the information thus collected con tains much that is calculated to interest and astonish, and that to many it will supply an entirely novel idea of the treasures that lie " beneath the surface." The facts set forth have been carefully gathered from trustworthy sources ; but it is necessary to mention the writer's special indebtedness to Simonin's " Le Monde Souterrain," Tissandier's " La Houille," and Badin's "Les Grottes et Cavernes." Also, to Lubbock's " Pre historic Man," Lyell's " Principles of Geology," Nichol son's " Manual of Paleontology," and the works of Lar tet, Walter White, E. Hull, Tomlinson, Poulett Scrope, and Dr. Daubeny.

As an introduction to a valuable and interesting study, it is hoped this little volume will be found useful, while the general reader will probably find in its pages something that he could not easily find elsewhere. W. H. D. A. CONTENTS.

Chapter I. The Wokld On Which We Live

Compared to a house — Supposed sea or lake of fire — What are igneous rocks ? — The earth's crust examined — Its formations and periods — Successive developments of animal and vegetable life — Fossils, and theories about them — The " medals of creation" — The Maestricht cavern — Bone-caves — Something about Fossil Man — Proposed explorations " Beneath the Surface " 11

Chapter II. Prehistoric Man

A definition of " Fossil Man" — The earth an extinct sun, on which thc ■waters have built up continents, a?td life has undergone various evolutions — Fossil Man and Prehistoric Man considered — Researclies of the earlier geologists — Curious error as to the " Iwmo diluvii testis" — The Anthropolithes — Opinion of Cuvier — The Bone-caves and their treasures — Objections and objectors — M. Boucher de Perthes — Stone-hatchets of the valley of tlie Somme — The celebrated "jaw" discovered at Moulin-Quignon — A Scie?itific Congress — Yoi—Menchecourt — Fabricators of fUnt-weapojis — The miller Quignon~Discoveries of M. Lartet — Discoveries in Belgium, England, Germany, Italy, and America — Inferences deducible from well-authenticated fads 38

Chapter III. Underground

— METALLIC DEPOSITS AND THEIR FORMATIONS. Sedimentary a?ul eruptive rocks — Metamorphic rocks — Veins of metal — Theories of Descartes and Werner — Metallic deposits of thc Primary , Secondary , Ter- CONTENTS. tiary, and Quaternary rocks — Ribbon-tike veins — Veins of contact — Metal liferous strata — Eruptive veins — Deposits in the drift — The mine: Roof, walls, and galleries — Condition of the metallic ore in tlie veins — The metalliferous chain of tltc Andes — Discovery of the silver-mines of Spain and the gold-mines of Calif ornia — An unfortunate expedition — The commercial value of the Minerals and Metals — The Chinese — A Brilliant Transaction at Madagascar — How to secure a net prof t of five millions 59

Chapter IV. The Salts And Natural Gases

The great family of minerals — Old superstitions — The good old days of lit/tology — Tlie seven members of the minera I family — Ta rt played by each of them — The saline springs of tlie Carpathians and the Val-di-Cecina — The alum pits of Montioni — Fumeroles of boric acid — The Styx and Charon's boat — Sulphurous springs — Chalybeate springs — Petrifying waters and dropping wells ioo

Chapter V. Springs, Sources, And Fountains

Origin of Springs — From Lucretius — Phenomena of rain — Explanatory remarks — Capriciousness of rain — Statistics of the rainfall in different localities — Water and scenery — The Fountain of Arethusa— A legend — Talestine a "land of springs" — The course of streams — Springs in the granite forma tion— Fountain of Vaucluse— Fountain of Nimes— St. Winifred's Well— yets and wells — Fresh-water springs out at sea— Intermittent springs — Siloam — Mineral springs— Carlsbad— Kissingen — Vichy— Bareges— Aix-la-Chapelle— Spa — The German baths — Baths in the Pyrenees — Hot waters of Bath — Tunbridge Wells 166

Chapter VI. Grottoes And Caverns

Celebrated caverns— That of Trophonius— Description by Pausanias— Mystic ceremonies— The famous oracle— Livadhia— Grotto ofthe Cumean Sibyl— The Blue Grotto at Capri— Grotto of St. Rosalia— Grottoes with religious traditions— Caves always used as places of retreat and sanctuary— Grottoes of Spagari— Caverns in France— Grotto of Longara, in Italy— Grotto nf Camoens, at Macao— Salt-mine caverns of Wieliczka — FingaVs Cave- Grotto of tlie Cheeses— Cave of Petckabury— Grotto of Monsummano - Grottoof La Madeleine— Marine grottoes and caverns I— C aves of Crozou —Cave of Morgatte— Grottoes of Etretat— Grotto of Bonifacio— Grotto of CONTENTS. IX Torghatten — S. Michael' s Cavern — Scratchell's Cave — Grottoes of Tourane — Caves produced by subterranea?i currents : — The Devil's Hole — Grotto of Adelsberg — Grottoes of Sassenage — Sundry caverns excavated by subter ranean currents — Natural bridges — Stalactitic grottoes : — Antiparos — Grotto of La Bausne — Grottoes of Arcy — Grottoes of Osselles — Grotto of Han-sur-Lesse — Mammoth Caves of Kentucky— Alabaster cavern of Cali fornia — Grottoes and caverns with concretions not calcareous — Their origin — Ice-caves and natural glaciers — A t the abbey of Grace Dieu — Ice cave of Vergy — Artificial ice-cave of St. Ouen — Bone-caves : — In England — In France — In Belgium — Germany — Caverns in which human bones have been exhumed 207

Chapter VII. Coal And Coal-mines

Formation of coal— Growth of peat — Submarine forests — Reconstruction of the primeval 'world — Resemblance of tlie African forests to those of the ancient coal-?neasures — Deposit of coal — Development of the beds — Early history of coal as a combustible — Production of coal in Belgium — The United States — Coal in Great Britain — In Central Europe — In France — In Africa — In Hindustan — Some statistics — Coal-basins — Discovery of their position — Excavating a coal-mine — Working a coal-mine — Various systems in various countries — Life in the coal-mines — The miner: his labours, habits, and character — Perils " beneath the surface" — Choke-damp and fire-damp — A catastrophe at Mons — Landslips and floods — An anecdote — Tragedies in the coal-pits — The calamity at Lalle — A record of accidents — A liquid combustible — Petroleum — Oil-wells in the United States and Canada — ■ Their variable product — The story of Shaw, the American — A catastropkc at Idiona — Uses of Petroleum — Attempts to employ it as a combustible — Petroleum and steam navigation — The present and the future of coal — Diminution of the coal supplies of Great Britain — Probable discovery of a substitute for coal. 375

Chapter VIII. Quarries And Quarrymen

Mineral industry : its origin — Army of workers employed by it — Qitarrtes and quarrymen — Slate quarries — Quarries of alabaster and marble — Quarries at Volterra — Carrara and its marbles — Roman quarry at Polvaccio — Valley of Ravaccione — The Concha — A visit to the works — The saw-milt — Marble ivorks at Marseilles — Fils la — The Carrarese sculptors — 3Ianufacturers of imitations and copies — Academy of Carrara — Roman quarry at Colonnata — Historical details — Tlie quarries of Paris — Geological description — Gradual formation of the Paris basin — Its present character- CONTENTS. X Tin istics— Erratic blocks — Occurrence of a great natural revolution — Strata of tlie Paris basitt— Chalk— Clay— Shell limestone— Ancient history of the Parisian quarries— Used as Catacombs— Quarries now at work— Plaster of Paris: what U is — How it is worked — The American quarries and their marls — The Sandstones of Fontainebleau — The workmen of the quarries — An anecdote — A story from Ivry — The" Gouapeurs" — Conclusion 441

Chapter IX. The Great Mines

; TIN, LEAD, AND IRON. : its value as a metal — Tin-mines of Spain and Germany — In China — Tin in Great Britain— Antiquity ofthe tin trade— The Cornish tin-mines — Copper — The Botallack mine — The Cornish miners — Reduction of the tin ore — Gold as a metal — Gold in England — Gold extracted from lead — The lands of gold — Silver — The silver-mines — Lead — The lead-mines of Great Britain — A visit to Allenhead — Going down a lead-mine — The miners and their habits — Value of iron — The antiquity of this metal — Iron in Great Britain — Iron-mines of South Wales— An iwipressive scene — Description of a blastfurnace — Iron-producing districts — The end BENEATH THE SURFACE.

Chapter I. The World On Which We Live

Compared to a house — Supposed sea or lake of fire — What are igneous rocks* — The earth's crust exami*ied~-l ts formations and periods — Successive developments of animal and vegetable life — Fossils, and tlteories about them — The " medals of creation" — The Maestricht cavern — Bone-caves — Something about Fossil Man — Proposed explorations " beneath the surface." lKg*3l|T is necessary that we should introduce the feU SnJ rea^er to the underground world, the world BBgjgH "beneath the surface," before we attempt a description of its phenomena. It forms the lower stage ofthe earth which we inhabit; and the configuration and character of the upper work! are, to a certain extent, regulated by the physical economy of the under. Here are laid the foundations of the glorious palace which man is permitted to inhabit ; here are stored the materials which furnish him with so many comforts, luxuries, appliances.

It is the storehouse, or treasury, in which are accumulated the metals and minerals, the water-power, and the igneous action, which play so important a part in our human history. IGNEOUS AND AQUEOUS ROCKS. 12 On a sea or lake of sire, whose shores are composed of solid materials, rests the first continuous crust of the little sphere which carries on its surface Man and all his fortunes. This crust consists of the granites and other massive crystalline rocks, which geologists call igneous, because their formation is supposed to have been due to the agency of fire. Such is, at least, the hypothesis novi generally accepted. About a quarter of a century ago, it was the belief of all geologists that the granites were produced by igneous action, like those seething molten lavas which the vol canoes of the present age eject from the interior of the earth.

But a new geological school has arisen, which repudiates this theory, and asserts that water— though water, it is true, at a very high temperature — was the sole agent in their formation. This hypothesis, however, lacks the merit of novelty ; it was put forward, towards the close of the last century, by the German geologist Wer ner, and was then known as the distinctive principle of the Neptunian in opposition to the Plutonian theory. We recommend the reader to regard both theories as possessing elements of truth, and to adopt the classification of the most exact and least speculative geological authorities, who divide all the rocks entering into the stratification of the solid crust of the earth into two great classes : Igneous, and Aqueous. The igneous rocks are those formed within the body of the earth by the action of fire.

The aqueous, also called sedimentary, are those de posited on the terrestrial surface by the action of water. THEIR CHA RA C TER IS TICS. 13 The former are generally found lying in unstratified masses ; the latter, arranged in distinct strata, or layers, like courses of masonry. From the granites and porphyries, which form, as it were, the foundation and basement of our terrestrial habitation, we ascend to the first stage, where the sedimentary rocks begin. These, as we have said, are dis tinguished by their regular stratification ; by their disposition in distinct layers or strata. Such strata may be confined to a single material — as in a block of sandstone — or composed of more than one. When examined over a sufficient space, they invariably present a series of alternate layers of different mineral composition.

As to their origin, a recent writer remarks that they are, for the most part, "derivative" rocks; in other words, they are derived from the attrition and trituration of pre-existent matter. Sometimes, however, they are the result of chemical or vital action ; and it is in this case that they are most accurately described as aqueous rocks. With reference to the mode of their deposit, it would seem that the materials composing them were formerly distributed through the agency of water; because a similar process is being worked out in our own dayat the mouths of tidal estuaries and great rivers, and, indeed, wherever water is in motion. Not a woodland stream, which poet has celebrated and fable hallowed, but, as it flows onward " for ever and for ever," carries with its cur rent a burden of mud, sand, and rounded pebble, "derived" FORMATION OF DEPOSITS. 14 from the incessant "wear and tear" of the rocks that form its channel.

This we may note for ourselves in almost every part of England or Scotland ; in the neighbourhood of the Thames or the Trent, the Tay or the Dee. The Adige of Italy bears along with its waters such a mass of refuse, that it has entirely filled up its ancient outlets to the ocean, and is now compelled to disembogue through new mouths. The Mississippi, in like manner, annually rolls down its turbid tide an im mense amount of muddy deposit. But when these materials cease to be carried onward by the moving waters, they necessarily sink to the bottom : the heaviest first ; then the lighter pebbles, gravel, and sand ; and, finally, the semi-liquid mud. And so, in course of time, every lake is converted into a basin or receptacle for a series of stratified rocks pro duced by the streams which pour their waters into it.

In different parts of the'lake these deposits will generally vary, for one stream will bring down one kind of material, and another stream another kind, according to the composition of the soil through which it makes its way; but in all cases the materials clearly show that they were produced, sifted, and deposited by the action of running water. It will be found that the finer marls and sands are arranged in layers or courses of varying thickness ; that in the gravel-beds every stone will be smooth or rounded, like the wave-wrought pebbles of the sea-beach. Similar results are brought about by great rivers in their "deltas;" and lastly, the sea itself is in cessantly preparing fresh stratified deposits by the force of its powerful continuous action. Is it not within the SEA AND LAND. 15 personal knowledge of many of our readers that at some points of the coast-line the sea is making great inroads upon the land, and that the spoils it thus acquires it deposits at other points in the form of new stratified DELTA OF THE NILE. accumulations .

It would be a grave error to suppose that Nature is at rest. The earth is incessantly under going changes of configuration, which necessitate corresponding changes in the relative position of the rock deposits. WASTE AND REPARATION. 16 In the neighbourhood of the North Foreland — the pro montory Acantium of the ancients, the 'Ak6.vtlov axpov of Ptolemy— the chalk cliffs undergo an annual average waste of two feet. At Reculver, in the Isle of Thanet, the ruined church now tottering on the edge of the crag, was, in the reign of Henry VIII., one mile inland. On the other hand, the fertile level of Romney Marsh has gained considerably; and at Dover, the sea, which once slowed up the valley of the Dour, has entirely receded. In Italy new land is being rapidly formed at the mouth of the Tiber by immense deposits of travertine ; and in EROSIVE ACTION OF THE SEA historic times the shore of the Adriatic, from the south of Ravenna to the head of the Gulf of Trieste, has en croached on the sea to a breadth varying from two to twenty miles.

The pine-woods between Ravenna and the Adriatic occupy an area of five miles, which was for merly a domain of waters : — " Ravenna's immemorial wood, Rooted where once the Adrian wave flowed o'er The Aqueous Rocks are generally arranged under two principal divisions, the Mechanical and the Chemical, according to the mode of their formation. The former are CHEMICAL ROCK'S. 17 those whose particles have been "mechanically" transported to their present position, and are sub-divisible into the Arenaceous or Silicious Hocks, such as sand and sandstones, grits, breccias, and conglomerates generally ; and into the Argillaceous or Aluminous, such as the marls, shales, clays, clay-slates, and flags or flag-stones. The " Chemical " rocks are those which have been SECTION OF MEUDON CHALK. created by chemical or vital agencies, and include the very important calcareous formations (chalk and limestone), as well as gypsum and coal.

Chalk and limestone have originated in the deposit of the shells of foramini fera, molluscs, sea-urchins, sea-mosses, and other marine organisms. The nummulitic limestone, almost wholly composed of fossil nummulites, frequently attain a thickness of many thousand feet; and extends in Europe from .601) FORMATION OF THE EARTH'S CRUST. 18 the Alps to the Carpathians, while in Northern Africa it may be traced from Egypt to Algeria. Gypsum, on the other hand, has been chemically compound ed of sulphuric acid, lime, and water ; while coal, as everybody knows, consists of vegetable mat ter solidified at a high tempera ture and under immense pressure. NCMMUI.ITK. We now return to our terrestrial habitation, with the view of pointing out the order in which its several stages, or "formations," as the geologist calls them, are super imposed on one another.

Beginning with the most ancient, which are necessarily the lowest, and ascending towards the surface, we count the following principal sub-divisions : — IN THE PRIMARY PERIOD. a. Laurentian and Huronian. A Cambrian. c. Silurian. ti. Devonian (or Old Red Sandstone). e. Carboniferous. /. Permian (or New Red Sand stone). THE SECONDARY PERIOD. g. Triassic (or New Red Sanrlstonr). //. Jurassic (or Oolilic). i. Cretaceous. THE TERTIARY PERIOD. /. Pliocene. m. Post-Pliocene. / Eocene. k. Miocene Section of the Terrestrial Crust> 5Jb^jwmgtl\eI)i_rerentToTTXiations from the MOST RECENT TO THE MOST ANCIENT FORMATION OF THE EARTH'S CRUST. 20 The first six of these "formations" are referred to the geological period known as Primary or Palacozotc. The animals and plants which they preserve in a fossil condi tion, differ entirely from any now existing upon the globe.

The next three (g, h, i, Triassic, Jurassic, Cretaceous), belong to the Secondary or Mesozoic period ; so called because its organic remains are intermediate (/xccros anil far)) between those of the Palaeozoic period and those of more recent strata. The last four (/, k, I, m, Eocene, Miocene, Pliocene, and Post -Pliocene), are grouped together under the head of Tertiary or Kainozoic («au<os and &D.7), because they are latest in point of time, their organic remains approaching very nearly in character to those now exist ing on the globe. I. PRIMARY OR PALAEOZOIC PERIOD. a. Laurcntian. — The rocks of this formation are ar ranged in two sub groups, the Lower and Upper Lauren tian. The former is wholly wanting in Great Britain, but is found in Canada with a total thickness of about 20,000 feet.

It includes gneiss, mica-schist, quartzite, and lime stones. Tlie Upper Laurentian rocks (gneiss) are found in the Hebrides and the Isle of Skye. Huronian. — This, too, is not a British formation. As its name implies, its rocks, which rest upon the Lauren tian series, are found in the vicinity of Lake Huron and the other great inland seas of Canada. Total thickness, about 18,000 feet. They consist of quartzites, silicious strata, conglomerates, and limestones. CAMBRIAN FORMATION. 21 b. Cambrian. — The name " Cambrian " is derived from the fact that these strata are the lowest rocks visible in North Wales and its borders, the ancient Cambria. In Great Britain the Lower Cambrian rocks are well seen in the Longmynd Hills of Shropshire, where they consist of about 25,000 feet of variously-coloured sand stones, grits, and shales, often rippled by waves that ebbed and flowed, and marked by rains that fell from cloudy skies, tens of thousands of years ago.

These are succeeded by a great series of micaceous flagstones, slates, and shales, which vary in thickness from 2000 to 6000 feet, and belong to the Upper Cambrian age. Cambrian rocks occur in other parts of Great Britain, and the following table will bring the reader acquainted with their principal members : — {a.) Lower Cambrian. 1. Longmynd beds (25,000 feet). 2. Llanteris slates (3000 feet). 3. Harlech grits (6000 feet). 4. Oldhamia slates of Ireland. (b.) Upper Cambrian. 5. Lingula Hags of Wales. 6. Tremadoc slates of North Wales (2000 feet). 7. Skiddaw slates of the North of England (7000 feet). The Cambrian beds are found also in Sweden, Nor way, and Bohemia ; and in the State of New York, in North America. c. Silurian. — This designation was suggested by the late eminent geologist, Sir Roderick Murchison, for a large series of strata lying underneath the Old Red Sand- SILURIAN FORMA TION. 22 stone, and occupying those parts of Wales and England which, in the old historic times, were inhabited by the Silures, a tribe of ancient Britons.

The Silurian rocks are extensively distributed over Wales, Northern England, Scotland, Ireland ; in Bohemia, Saxony, Sweden, and Russia ; and in North America. The entire series may be subdivided into two groups, or sections, the Lower and Upper Silurian ; and each of these is again subdivided into smaller sections, which take their names from the localities where they were first explored, or where they occur in full development. Thus, in our own island, they are classified as follows, beginning with the lowest : — (a). Ltnver Llandeilo : flags, slates, sandstones. (b.) Upper Llandeilo : micaceous flags, shales, grits. (e.) Bala, Caradoc, or Coniston : slates, grits, sandstones. (d.) Lower Llandniery : slates, sandstones, conglomerate. (e.) Upper Llandovery : limestones, shales, conglomerates, slates.

(/) Wenlock: shale, flag-stone, limestone. (g.) Ludlow: shale, limestone, sandstone. The first four groups belong to the Lower Silurian, and the last three to the Upper Silurian. d. Devonian. — The Silurian rocks are succeeded, as we mount upward, by a very important and interesting system, to which the name of "Old Red Sandstone" was at one time applied. The strata belonging to this period are largely found in Devonshire, and hence they are frequently known as Devonian. But it is more than probable that, as Professor Nicholson suggests, the De vonian rocks represent a portion only of the Old Red OLD RED SANDSTONE. 23 Sandstone, and are not to be regarded, therefore, as the full equivalent of that formation as it occurs in other regions. With this limitation, however, the term "Devon ian " may be usefully employed as a general designation for those strata which intervene between the Silurian system and the great formation of the Coal Measures.

The Old Red Sandstone in Great Britain has formed the subject of a picturesque monograph by Hugh Miller. It is divisible into three groups, Lower, Middle, and Upper Old Red. The Lower "Old Red" repose with admirable con- FOSSIL FISH (PTERICUTHYS) OF THE OLD RED SANDSTONE. formity on the highest beds of the Upper Silurian, the two formations appearing to pass into one another by an inter mediate series of so-called "passage-beds," which contain large specimens of the crustacean family of the Euryp terida. This section consists mainly of massive con glomerates, with sandstones, shales, and concretionary limestones. Its organic remains are almost exclusively confined to plants, crustaceans, and fishes. In the Middle " Old Red " of Scotland we meet with dark gray flag-stones, bituminous flaggy shales, and con glomerates ; not infrequently accompanied by shales in which irregular calcareous nodules are embedded.

The OLD RED SANDSTONE. 24 fossil remains are those of fishes, with a few plants and a solitary crustacean. The Upper " Old Red" of Scotland consists of pebbly conglomerates, sandstones, and shales. Fossil fishes are abundant ; there are several undoubted land-plants, and numerous fragments of supposed fuci and other sea-weed. Underlying the carboniferous rocks, in Devonshire, is found a great series of strata, which has been regarded as the equivalent of the Old Red Sandstone. To this period, indeed, it unquestionably belongs, but yet it is FOSSIL FISH (CEPHALASPIS) OF THE OLD RED SANDSTONE. by no means apparent that the Devonian rocks can be regarded as the equivalent of the Old Red Sandstone of Scotland. They are largely represented, however, on the continent of Europe ; and they are fossiliferous to a remarkable extent, though containing none of the charac teristic crustaceans, and only one or two genuine repre sentatives of the characteristic fishes of the Scotch Old Red.

The Devonian rocks of Devonshire consist essentially of greenish slates, alternating with sandstones, conglomerates, and well-developed bands of blue crystalline limestone and calcareous strata. The Devonian strata are extensively developed in the United States of North America. THE COAL-MEASURES. 25 e. Carboniferous. — In this formation the workable coal beds most commonly occur. They are found intercalated, in comparatively thin strata, between deposits of shales, sandstones, and limestones. In Great Britain, if we allow for the limited area, we must regard their de velopment as unusually extensive. They are abundant also in Australia, North America, and on the continent of Europe. Generally, they may be divided into the following group, of which the first lies lowest :— (a.) The Carboniferous Slates and Mountain Limestone, which are mainly calcareous.

(b. ) The Millstone Grit, chiefly arenaceous and conglomeratic. ( c. ) The Coal- Measures proper, consisting of alternate shales, sandstones, and other strata, with workable beds of coal. f. Permian. — These rocks, the uppermost ofthe Palaeo zoic formations, are so named from the province of Perm, in Russia, where they abound, and where Sir Roderick Murchison investigated their nature. Formerly they were included, with the superimposed strata of the Trias, under the common name of New Red Sandstone ; but this application of the term is now almost obsolete. They may be arranged under three divisions : the Lower, the Middle, and the Upper Permians ; and are found in Russia, Germany, Britain, and North America. g. Triassic. — The Triassic rocks form the base of the Mesozoic, or secondary series, and are identical with the upper beds of the New Red Sandstone of the earlier geologists.

They are subdivisible into three groups : the Lower, corresponding to the Bunter Sandstein (or "varie- JURASSIC FORMA TION. gated sandstone") of the Germans, and consisting of red and white sandstones, red clays, and thin limestones, with a total thickness of about 1500 feet ; the Middle, or Muschelkalk (" mussel limestone") of Germany, consisting of compact gray or yellowish limestones, with beds of rock-salt and gypsum ; and the Upper or Keuper (" copper"), consisting of white sandstones, brown sand stones, red marls, red clays, rock-salt, and gypsum. The Middle Trias is not found in Great Britain. //. Jurassic. — The rocks included in this group are some times termed Oolitic, because they generally contain oolitic limestones, or limestones made up of granulated particles, oval, like eggs (Gk. wov and XiÆos) ; and some times Jurassic, because they are extensively developed in the noble mountain -range of the Jura, on the western borders of Switzerland.

They occupy a considerable area in Great Britain, where their component parts are generally found in the following order : — (a.) Lias. (b. ) Lower Oolites : consisting of the inferior oolites, fuller's earth, great oolite, Stonessield slate. (c.) Middle Oolites : Oxford clay and coral rag; and ((/.) Upper Oolites, or Kimmeridge clay, Portland stone, and Purbeck beds. i. Cretaceous. — This formation derives its name from the prevalence of chalk (creta) among its principal rocks. It is well known in the south and south-east of England, from Portland Bill to the North Foreland. The usual arrangement is as follows : — CRETACEOUS FORMATION. 27 (a.) Wealden: so named after the Weald (wold, or forest wilderness), a part of Surrey, Kent, and Sussex, where it is spread over a very considerable area.

A characteristic of this district is its undulating ranges of chalky downs, covered with crisp and fragrant turf, and sheltering in their recesses the most picturesque combes or hollows. Springs are abundant. (b.) Lower Greensand, or Neocomian: the latter term derived, for a similar reason, from Neufchatel (Lat Neocomnm), a town in Switzerland. These groups, a and b, form the Lower Cretaceous. (_•.) Gault (from a provincial term). (d.) Upper Greensand. (_■.) Chalk proper: which may be traced from the north oflreland to the Crimea, and, in an opposite direction, from the south of Sweden to Bordeaux, or 1 140 by 840 geographical miles. With or without flints, it occupies a considerable area of south-east England, rising on the sea-coast into lofty cliffs of a romantic configuration. When flints occur, they are generally disposed in their layers at some distance apart ; so that a chalk cliff, from a distance, seems scored with horizontal black lines, as if they had been mechanically ruled.