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CORNELL 
 
 UNIVERSITY 
 
 LIBRARY 
 
 FROM THE LIBRARY 
 OP 
 
 PROFESSOR 
 
 RALPH S. TARR 
 
 1864-1911 
 
 GIFT OF 
 
 Russell Tarr 
 1939 
 
Cornell University Library 
 
 arV19368 
 
 The student's elements of geolo] 
 
 3 1924 031 249 166 
 olin,anx 
 
The original of tliis book is in 
 tine Cornell University Library. 
 
 There are no known copyright restrictions in 
 the United States on the use of the text. 
 
 http://www.archive.org/details/cu31 924031 2491 66 
 
TEETIAEY [l 
 
 or CAINOZOIC. 
 
 Nummulites laevigata. 
 
 SECONDARY 
 
 or MESOZOIC. 
 
 Ammonites 
 
 PEIMAEY 
 
 or PALEOZOIC. 
 
 Bronteusjldbellifer. 
 
THE STUDENT'S 
 
 ELEMENTS OF GEOLOGY. 
 
 By 6ie CHAKLES LYELL, Bakt., r.E.S., 
 
 AUTHOR OF "THE PKINCIPLES OB' GEOLOGY," "THE ANTIQUITY OF MAN," ETC. 
 
 Thecosmilia annularis. 
 
 WITH MORE THAW COO ILLUSTRATIONS ON WOOD. 
 
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PREFACE, 
 
 The last or sixth edition of my " Elements of Geology " 
 was already out of print before the end of 1868, in which 
 year I brought out the tenth edition of my " Principles of 
 Geology." 
 
 In writing the last-mentioned work I had been called upon 
 to pass in review almost all the leading points of specula- 
 tion and controversy to which the rapid advance of the sci- 
 ence had given rise, and when I proposed to bring out a 
 new edition of the " Elements " I was strongly urged by my 
 friends not to repeat these theoretical discussions, but to 
 confine myself in the new treatise to those parts of the "Ele- 
 ments " which were most indispensable to a beginner. This 
 was to revert, to a certain extent, to the original plan of 
 the first edition ; but I found, after omitting a great number 
 of subjects, that the necessity of bringing up to the day those 
 which remained, and adverting, however briefly, to new dis- 
 coveries, made it most difficult to confine the proposed 
 abridgment within moderate limits. Some chapters had to 
 be entirely recast, some additional illustrations to be intro- 
 duced, and figures of some organic remains to be replaced 
 by new ones from specimens more perfect than those which 
 had been at my command on former occasions. By these 
 changes the work assumed a form so difiTerent from the sixth 
 edition of the " Elements," that I resolved to give it a new 
 title and call it the " Student's Elements of Geology." 
 
 In executing this task I have found it very difficult to 
 meet the requirements of those who are entirely ignorant of 
 the science. It is only the adept who has already overcome 
 
xiv PREFACE. 
 
 the first steps as an observer, and is familiar with many of 
 the technical terms, who can profit by a brief and concise 
 manual. Beginners wish for a short and cheap book in 
 which they may find a full explanation of the leading facts 
 and principles of Geology. Their wants, I fear, somewhat 
 resemble those of the old woman in New England, who ask- 
 ed a bookseller to supply her with " the cheapest Bible in 
 the largest possible print." 
 
 But notwithstanding the difficulty of reconciling brevity 
 with the copiousness of illustration demanded by those who 
 have not yet mastered the rudiments of the science, I have 
 endeavored to abridge the work in the manner above hinted 
 at, so as to place it within the reach of many to whom it 
 was before inaccessible. 
 
 Chables Lyell, 
 
 73 Haklet Stkeet, London, 
 December, 1870. 
 
CONTENTS. 
 
 CHAPTER I. 
 
 ON THE DIFFEKENT CLASSES OF HOCKS. 
 
 Geology defined. — Successive formation of the Earth's Crust. — Classifica- 
 tx-Ti Oi Bocks according to their Origin and Age. — Aqueous Rocks. — Their 
 Stratification and imbedded Eossils. — ^Volcanic Rocks, with and without 
 Cones and Craters. — Plutonic Rocks, and their Relation to the Volcanic. — 
 Metamorphic Rocks, and their probable Origin. — The term Primitive, why 
 erroneously applied to the Crystalline Formations. — Leading Division of 
 the Work Page 25 
 
 CHAPTER II. 
 
 AQUEOUS ROCKS — THEIE COMPOSITION AND FORMS OF STRATIFICATION. 
 
 Mineral Composition of Strata. — Siliceous Rocks. — Argillaceous. — Calcare- 
 ous. — Gypsum. — Form's of Stratification. ^Original Horizontality. — Thin- 
 ning out. — Diagonal Arrangement. — Ripple-mark 35 
 
 CHAPTER III 
 
 ARRANGEMENT OF FOSSILS IN STRATA — FRESH-WATEK AND MARINE. 
 
 Successive Deposition indicated by Fossils. — Limestones formed of Corals 
 and Shells. — Proofs of gradual Increase of Strata derived from Fossils. — 
 Serpula attached to Spatangus. — Wood bored by Teredina. — Tiipoli form- 
 ed of Infusoria. — Chalk derived principally from Organic Bodies. — Dis- 
 tinction of Fresh-water from Marine Formations. — Genera of Fresh- water 
 and Land Shells. — Rules for recognizing Marine Testacea. — Gyrogonite 
 and Chara. — Fresh-water Fishes.^ — ^Alternation of Marine and Fresh-water 
 Deposits. — Lym-Fiord 47 
 
 CHAPTER IV. 
 
 CONSOLIDATION OF STRATA AND PETRIFACTION OF FOSSILS. 
 
 Chemical and Mechanical Deposits. — Cementing together of Particles. — 
 Hardening by Exposure to Air.- — Concretionary Kodules. — Consolidating 
 Effects of Pressure. — Mineralization of Organic Remains. — Impressions 
 and Casts : how formed. — Fossil Wood. — Goppert's Experiments. — Pre- 
 cipitation of Stony Matter most rapid where Putrefaction is going on. — 
 Sources of Lime and Silex in Solution 60 
 
xvi CONTENTS. 
 
 CHAPTER V. 
 
 ELEVATION OF STRATA ABOVE THE SEA. — HORIZONTAL AND INCLINED 
 STRATIFICATION. 
 
 Why the Position of Marine Strata, ahove the Level of the Sea, should be 
 referred to the rising up of the Land, not to the going down of the Sea. — 
 Strata of Deep-sea and Shallow-water Origin alternate.— Also Marine and 
 Fresh-water Beds and old Land Surfaces.— Vertical, inclined, and folded 
 Strata.— Anticlinal and Synclinal Curves.— Theories to explain Lateral 
 Movements. — Creeps in Coal-mines. — Dip and Strike. — Structure of the 
 Jura.— Various Torms of Outcrop.— Synclinal Strata forming Kidges. — 
 Connection of Fracture and Flexure of Eocks. — Inverted Strata. — Faults 
 described. — Superficial Signs of the same obliterated by Denudation. — 
 Great Faults the Result of repeated Movements. — AiTangement and Di- 
 rection of parallel Folds of Strata.— Unconformability.— Overiapping 
 Strata Page 70 
 
 CHAPTER VL 
 
 DENUDATION. 
 
 Denudation defined.^ — Its Amount more than equal to the entire Mass of strat- 
 ified Deposits in the Earth's Crust. — Subaerial Denudation. — Action of 
 the Wind. — Action of Running Water. — Alluvium defined. ^Different 
 Ages of Alluvium. — Denuding Power of Rivers affected by Rise or Fall of 
 Land. — Littoral Denudation. — Inland Sea-cliffs. — Escarpments. — Subma- 
 rine Denudation. — Dogger-bank. — Newfoundland Bank. — Denuding Pow- 
 er of the Ocean during Emergence of Land 96 
 
 CHAPTER VIL 
 
 JOINT ACTION OF DENDDATION, UPHEAVAL, AND SUBSIDENCE IN REMODEL- 
 LING THE earth's crust. 
 
 How we obtain an Insight at the Surface, of the Arrangement of Rocks at 
 great Depths. — Why the Height of the successive Strata in a given Region 
 is so disproportionate to their Thickness. — Computation of the average 
 annual Amount of subaerial Denudation. — Antagonism of Volcanic Force 
 to the Levelling Power of running Water. — How far the Transfer of Sed- 
 iment from the Land to a neighboring Sea-bottom may affect Subterranean 
 Movements. — Permanence of Continental and Oceanic Areas 108 
 
 CHAPTER VIIL 
 
 CHRONOLOGICAL CLASSIFICATION OF ROCKS. 
 
 Aqueous, plutonio, volcanic, and metamoi-phic Rocks considered chronologic- 
 ally. — Terms Primary, Secondary, and Tertiary ; Paleozoic, Mesozoic, 
 and Cainozoic explained. — On the different Ages of the aqueous Rocks. — 
 Three principal Tests of relative Age : Superposition, Mineral Character, 
 and Fossils. — Change of Mineral Character and Fossils in the same con- 
 tinuous Formation. — Proofs that distinct Species of Animals and Plants 
 have lived at successive Periods.— Distinct Provinces of indigenous Spe- 
 cies. — Great Extent of single Provinces. — Similar Laws prevailed at suc- 
 'cessive Geological Periods. ^ — Relative Importance of mineral and p.tteon- 
 
CONTENTS. xvii 
 
 tological Characters. — Test of Age by included Fragments. — Frequent 
 Absence of Strata of intervening Periods. — Tabular Views of fossiliferous 
 Strata .I'age 121 
 
 CHAPTER IX. 
 
 CLASSIFICATION OF TEETIAET FORMATIONS. 
 
 Order of Succession of Sedimentary Formations. — Frequent Unconformability 
 of Strata. — Imperfection of the Kecord. — Defectiveness of the Monuments 
 greater in Proportion to their Antiquity. — Reasons for studying the newer 
 Groups first. — Nomenclature of Formations. — Detached Tertiary Forma- 
 tions scattered over Europe. — Value of the Shell-bearing Mollusca in Class- 
 ification. — Classification of Tertiary Strata. — Eocene, Miocene, and Plio- 
 cene Terms explained 137 
 
 CHAPTER X. 
 
 KBCENT AND POST-PLIOCENE PERIODS. 
 
 Recent and Post-pliocene Periods. — Terms defined. — Formations of the 
 Recent Period. — Modern littoral Deposits containing Works of Art near 
 Naples.^Danish Peat and Shell-mounds. — Swiss Lake-dwellings. — Peri- 
 ods of Stone, Bronze, and Iron. — Post-pliocene Formations. — Coexistence 
 of Man with extinct Mammalia. — Reindeer Period of South of France. — 
 Alluvial Deposits of Paleolithic Age. — Higher and Lower-level Valley- 
 gravels.— -Loess or Inundation-mud of the Nile, Rhine, etc. — Origin of 
 Caverns. — Remains of Man and extinct Quadrupeds in Cavern Deposits. — 
 Cave of Kirkdale. — Australian Cave-breccias. — Geographical Relationship 
 of the Provinces of living Vertebrata and those of extinct Post-pliocene 
 Species. — Extinct struthious Birds of New Zealand. — Climate of the Post- 
 pliocene Period. — Comparative Longevity of Species in the Mammalia and 
 Testacea. — Teeth of Recent and Post-pliocene Mammalia 145 
 
 CHAPTER XL 
 
 POST-PLIOCENE PERIOD, CONTINUED. — GLACIAL CONDITIONS. 
 
 Geographical Distribution, Form, and Characters of Glacial Drift. — Funda- 
 mental Rocks, polished, grooved, and scratched. — ^Abrading and striating 
 Action of Glaciers. — Moraines, Erratic Blocks, and " Roches Moutonne'es." 
 — Alpine Blocks on the Jura. — Continental Ice of Greenland. — Ancient 
 Centres of the Dispersion of Erratics. — Transportation of Drift by floating 
 Icebergs. — Bed of the Sea furrowed and polished by the running aground 
 of floating Ice-islands 166 
 
 CHAPTER XIL 
 
 POST-PLIOCENE PERIOD, CONTINUED. — GLACIAL CONDITIONS, CONCLUDED. 
 
 Glaciation of Scandinavia and Russia. — Glaciation of Scotland. — Mammoth 
 in Scotch Till. — Marine Shells in Scotch Glacial Drift. — Their Arctic Char- 
 acter. — Rarity of Organic Remains in Glacial Deposits. — Contorted Strata 
 in Drift. — Glaciation of Wales, England, and Ireland. — Marine Shells of 
 Moel Tryfaen. — Erratics near Chichester. — Glacial Formations of North 
 America. — Many Species of Testacea and Quadrupeds survived the Glacial 
 
xviii CONTENTS. 
 
 Cold. — Connection of the Predominance of Lakes with Glacial Action. — 
 Action of Ice in preventing the silting up of Lake-basins. — Absence of 
 Lakes in the Caucasus. — Equatorial Lakes of Africa Page 174 
 
 CHAPTER XIII. 
 
 PLIOCENE PERIOD. 
 
 Glacial Foi-mations of Pliocene Age. — ^Bridlington Beds. — Glacial Drifts of 
 Ireland.— Drift of Norfolk Cliffs.— Cromer Eorest-bed.— Aldeby and Chil- 
 lesford Beds. — Norwich Crag. — Older Pliocene Strata. — Red Crag of Suf- 
 folk. — Coprolitic Bed of Red Crag. — ^White or Coralline Crag. — Relative 
 Age, Origin, and Climate of the Crag Deposits. — Antwerp Crag. — ^Newer 
 PUocene Strata of Sicily. — ^Newer Pliocene Strata of the Upper Val d'Ar- 
 no. — Older Pliocene of Italy. — Subapennine Strata. — Older Pliocene Flora 
 of Italy 189 
 
 CHAPTER XIV. 
 
 MIOCENE PEKIOD.^ — UPPER MIOCENE. 
 
 Upper Miocene Strata of France. — ^i'aluns of Touraine. — Tropical Climate 
 implied by Testacea. — Proportion of recent Species of Shell?. — Faluns 
 more ancient than the Suffolk Crag. — Upper Miocene of Bordeaux and 
 the South of France. — Upper Miocene of CEningen, in Switzerland. — Plants 
 of the Upper Fl-esh-water Molasse. — Fossil Fruit and Flowers as well as 
 Leaves. — Insects of the Upper Molasse.' — Middle or Marine Molasse of 
 Switzerland. — Upper Miocene Beds of the Bolderberg, in Belgium. — Vien- 
 na Basin.^ — Upper Miocene of Italy and Greece. — Upper Miocene of India ; 
 Siwalik Hills. — Older Pliocene and Miocene of the United States 211 
 
 CHAPTER XV. 
 
 LOWER MIOCENE. 
 
 Lower Miocene Strata of France. ^ — ^Line between Miocene and Eocene. — 
 Lacustrine Strata of Auvergne. — Fossil Mammalia of the Limagne d'Au- 
 vergne. — Lower Molasse of Switzerland. — Dense Conglomerates and Proofs 
 of Subsidence. ^Flora of the Lower Molasse. — American Character of the 
 Flora. — Theoiy of a Miocene Atlantis. — Lower Miocene of Belgium. — 
 Rupelian Clay of Hermsdorf near Berlin. — Mayence Basin. — Lower Mio- 
 cene of Croatia. — Oligocene Strata of Beyrich. — Lower Miocene of Italy. 
 — Lower Miocene of England. — Hempstead Beds. — Bovey Tracy Lignites 
 in Devonshire. — Isle of Mull Leaf-beds. — Arctic Miocene Flora. — Disco 
 Island. — ^Lower Miocene of United States. — Fossils of Nebraska 230 
 
 CHAPTER XVL 
 
 EOCENE FORMATIONS. 
 
 Eocene Areas of North of Europe. — Table of English and French Eocene 
 Strata. — Upper Eocene of England.- — Bembridge Beds. — Osborne or St. 
 Helen's Beds. — Headon Series. — Fossils of the Barton Sands and Clays. — 
 Middle Eocene of England. — Shells, Nummulites, Fish and Reptiles of the 
 Bracklesham Beds and Bagshot Sands. — Plants of Alum Bay and Bourne- 
 mouth. — Lower Eocene of England. — London Clay Fossils. — Woolwich 
 
CONTENTS. xix 
 
 and Reading Beds formerly called " Plastic Clay." — Fluviatile Beds under- 
 lying Deep-sea Strata. ^ — ^Thanet Sands.^ — Upper Eocene Strata of France. 
 — Gypseous Series of Montmartre and Extinct Quadrupeds. — Eossil Foot- 
 prints in Paris Gypsum. — Imperfection of the Record. — Caleaire Silicieux. 
 ■ — Grfes de Beauchamp. — Caleaire Grossier. — Miliolite Limestone. — Sois- 
 sonnais Sands. — Lower Eocene of France. — Nummulitic Formations of 
 Europe, Africa, and Asia. — Eocene Strata in the United States. — Gigantic 
 Cetacean .....Page 250 
 
 CHAPTER XVn. 
 
 UPPEK CKETACEOUS GROtTP. 
 
 Lapse of Time between Cretaceous and Eocene JPeriods. — Table of succes- 
 sive Cretaceous Formations. — Maestricht Beds. — Pisolitic Limestone of 
 Fi-ance. — Chalk of Faxoe. — Geographical Extent and Origin of the White 
 Chalk. — Chalky Matter now forming in the Bed of the Atlantic. — Marked 
 Difference between the Cretaceous and existing Fauna. — Chalk-flints. — 
 Pot-stones of Horstead.- — Vitreous Sponges in the Chalk. — ^Isolated Blocks 
 of Foreign Rocks in the White Chalk supposed to be ice-borne. — Distinct- 
 ness of Mineral Character in contemporaneous Rocks of the Cretaceous 
 Epoch. — Fossils of the White Chalk. — Lower White Chalk without Flints. 
 — Chalk Mail and its Fossils. — Chloritic Series or Upper Greensand. — 
 Coprolite Bed near Cambridge. — Fossils of the Chloritic Series. ^ — Gault. — 
 Connection between Upper and Lower Cretaceous Strata. — Blackdown 
 Beds. — Flora of the Upper Cretaceous Period. — Hippurite Limestone. — 
 Cretaceous Rocks in the United States.. 281 
 
 CHAPTER XVIIL 
 
 LOWER CRETACEOUS OR NEOCOMIAK FORMATION. 
 
 Classification of marine and fresh-water Strata. — Upper Neocomian. — Folke- 
 stone and Hythe Beds. — Atherfield Clay. — Similarity of Conditions causing 
 Reappearance of Species after short intervals. — Upper Speeton Clay. — 
 Middle Neocomian. — Tealby Series. — Middle Speeton Clay. — Lower Neo- 
 comian. — Lower Speeton Clay. — Wealden Formation.— Fresh- water Char- 
 acter of the Wealden. — Weald Clay. — Hastings Sands. — PunfieldBeds of 
 Purbeck, Dorsetshire. — Fossil Shells and Fish of the Wealden. — Area of 
 the Wealden. —Flora of the Wealden 308 
 
 CHAPTER XIX. 
 
 JTTKASSIG GROUP. — PURBECK BEDS AND OOLITE. 
 
 The Purbeck Beds a Member of the Jurassic Group. ^ — Subdivisions of that 
 Group. — Physical Geography of the Oolite in England and France. — Up- 
 per Oolite. — Purbeck Beds. — New Genera of fossil Mammalia in the 
 Middle Purbeck of Dorsetshire. — ^Dirt-bed or ancient Soil. — ^Fossils of 
 the Purbeck Beds. — Portland Stone and Fossils. — Kimmei-idge Clay. — 
 Lithographic Stone of Solenhofen. — Arcbseopteryx. — Middle Oolite. — Cor- 
 al Rag. — Nerinsea Limestone. — Oxford Clay, Ammonites and Belemnites. 
 — Kelloway Rock. — Lower, or Bath, Oolite. — Great Plants of the Oolite. 
 — Oolite and Bradford Clay. — Stonesfield Slate. — Fossil Mammalia. — 
 Fuller's Earth, — Inferior Oolite and Fossils. — Northamptonshire Slates. — 
 Yorkshire Oolitic Coal-field. — Brora Coal. — Palseontological Relations of 
 the several Subdivisions of the Oolitic group 321 
 
xi CONTENTS. 
 
 CHAPTER XX. 
 
 JURASSIC GKOUP — CONTINnED. — LIAS. 
 
 Mineral Character of Lias. — Numerous successive Zones in the Lias, marked 
 hy distinct Fossils, without Unconformity in the Stratification, or Change 
 in the Mineral Character of the Deposits.— Gryphite Limestone. — Shells 
 of the Lias.— Fish of the Lias.— Reptiles of the Lias.— Ich thy osaur and 
 Plesiosaur.— Marine Reptile of the Galapagos Islands.— Sudden Destruc- 
 tion and Burial of Fossil Animals in Lias. — Fluvio-marine Beds in Glou- 
 cestershire, and Insect Limestone. — Fossil Plants. — The Origin of the 
 Ootlie and Lias, and of alternating Calcareous and Argillaceous Foi-ma- 
 tions '. Page 353 
 
 CHAPTER XXI. 
 
 TKIAS, OR NEW RED SANDSTONE GROUP. 
 
 Beds of Passage between the Lias and Trias, Rhsetic Beds. — Triassic Mam- 
 mifer. — Triple Division of the Trias. — Keuper, or Upper Trias of England. 
 — Reptiles of the Upper Trias. — Foot-prints in the Bunter formation iii 
 England. — Dolomitic Conglomerate of Bristol. — Origin of Red Sandstone 
 and Rock-salt. — Precipitation of Salt from inland Lakes and Lagoons. — 
 Trias of Germany. — Keuper. — St. Cassian and Hallstadt Beds. — ^Peculiar- 
 ity of their Fauna. — Muschelkalk and its Fossils. — Trias of the United 
 States. — Fossil Foot-prints of Birds and Reptiles in the Valley of the Con- 
 necticut. — Triassic Mammifer of North Carolina. — Triassic Coal-field of 
 Richmond, Virginia. — Low Grade of early Mammals favorable to the The- 
 ory of Progressive Development 366 
 
 CHAPTER XXn. 
 
 PERMIAN OR MAGNESIAN LIMESTONE GROUP. 
 
 Line of Separation between Mesozoic and Palaeozoic Rocks. — Distinctness 
 of Triassic and Permian Fossils. — Term Permian. — Thickness of calcare- 
 ous and sedimentary Rocks in North of England. — ^Upper, Middle, and 
 Lower Permian. — Marine Shells and Corals of the English Magnesian 
 Limestone. — Reptiles and Fish of Permian Marl -slate. — Foot- prints of 
 Reptiles. — Angular Breccias in Lower Permian. — Permian Rocks of the 
 Continent. — Zechstein and Rothliegendes of Thuringia. — Permian Flora. 
 — Its generic Affinity to the Carboniferous...; 385 
 
 CHAPTER XXIIL 
 
 THE COAL OK CARBONIFEROUS GROUP. 
 
 Principal Subdivisions of the Carboniferous Group. — Different Thickness of 
 the sedimentary and calcareous Members in Scotland and the South of 
 England.^ — Coal-measures. — Terrestrial Nature of the Growth of Coal. — 
 Erect fossil Trees. — Uniting of many Coal-seams into one thick Bed. — 
 Purity of the Coal explained. — Conversion of Coal into Anthracite. — Ori- 
 gin of Clay-ironstone. — Marine and brackish-water Strata in Coal. — Fossil 
 Insects. ^ — Batrachian Reptiles. — Labyrinthodont Foot-prints in Coal-meas- 
 ures. — Nova Scotia Coal-measures with successive Growths of erect fossil 
 
CONTENTS. xxi 
 
 Trees. — Similarity of American and European Coal. — Air-breathers of the 
 American Coal.— Changes of Condition of Land and Sea indicated by the 
 Carboniferous Strata of Nova Scotia Page 394 
 
 CHAPTER XXIV. 
 
 FLORA AND FAUNA OF THE CARBONIFEKOnS PERIOD. 
 
 Vegetation ot the Coal Period. — Ferns, Lycopodiacese, Equisetacese, Sigilla- 
 risE, Stigmariae, Coniferse. — ^Angiosperms. — Climate of the Coal Period. — ■ 
 Mountain Limestone. — Marine Pauna of the Carboniferous Period. — Corals. 
 — Bryozoa, Crinoidqfi. — MoUusca.— Great Number of fossil Fish. — Fora- 
 minifera 420 
 
 CHAPTER XXV. 
 
 DEVONIAN OR OLD RED SANDSTONE GROUP. 
 
 Classification of the Old Red Sandstone in Scotland and in Devonshire. — 
 Upper Old Red Sandstone in Scotland, with Fish and Plants. — Middle 
 Old Red Sandstone. — Classification of the Ichthyolites of the Old Red, 
 and their Relation to Living Types. — Lower Old Red Sandstone, with 
 Cephalaspis and Pterygotus. — Marine or Devonian Type of Old Red Sand- 
 stone. — ^Table of Devonian Series. — Upper Devonian Rocks and Fossils. 
 — Middle. — Lower. — Eifel Limestone of Germany. — Devonian of Russia. 
 — Devonian Strata of the United States and Canada. — Devonian Plants 
 and Insects of Canada : 439 
 
 CHAPTER XXVL 
 
 SILURIAN GROUP. 
 
 Classification of the Silurian Rocks. — ^Ludlow Formation and Fossils. — Bone- 
 bed of the Upper Ludlow. — Lower Ludlow Shales with Pentamerm. — 
 Oldest known Remains of fossil Fish. — Table of the progressive Discovery 
 of Vertebrata in older Rocks. — Wenlock Formation, Corals, Cystideans 
 and Ti-ilobites. — Llandovery Group or Beds of Passage. — Lower Silurian 
 Rocks. — Caradoc and Bala Beds. — Brachiopoda. — Trilobites. — Cystideoe. 
 — Graptolites. — Llandeilo Flags. — ^Arenig or Stiper-stones Group. — For- 
 eign Silurian Equivalents in Europe. — Silurian Strata of the United States. 
 — Canadian Equivalents. — Amount of specific Agreement of Fossils with 
 those of Europe 458 
 
 CHAPTER XXVIL 
 
 CAMBRIAN AND LAURENTIAN GROUPS. 
 
 Classification of the Cambrian Group, and its Equivalent in Bohemia. — Up- 
 per Cambrian Rocks. — Tremadoc Slates and their Fossils. — Lingula Flags. 
 — Lower Cambrian Rocks. — Menevian Beds. — Longmynd Group. — Har- 
 lech Grits with large Trilobites. — Llanheris Slates. — Cambrian Rocks of 
 Bohemia. — ^Primordial Zone of Barrande. — Metamorphosis of Trilobites. 
 — Cambrian Rocks of Sweden and Norway. — Cambrian Rocks of tbe 
 United States and Canada. — Potsdam Sandstone. — Huronian Sei-ies. — 
 Laurentian Group, upper and lower. T—A'oaoon Canadense, oldest known 
 Fossil. — ^Fundamental Gneiss of Scotland 481 
 
xxii CONTENTS. 
 
 CHAPTER XXVIII. 
 
 VOLCANIC KOCKS. 
 
 External Form, Structure, and Origin of Volcanic Mountains. — Cones and 
 Craters. — Hypothesis of "Elevation Craters" considered. — Trap Kocks. — 
 Name whence derived. — Minerals most abundant in Volcanic Rocks. — ■ 
 Table of the Analysis of Minerals in the Volcanic and Hypogene Rocks. — 
 Similar Minerals in Meteorites. — Theory of Isomorphism. — Basaltic Rocks. 
 — Trachytic Rocks.— Special Forms of Structure.— The columnar and 
 globular Forms. — Trap Dikes and Veins. — Alteration of Rocks by vol- 
 canic Dikes. — Conversion of Chalk into Marble. — Intrusion of Trap be- 
 tween Strata. — Relation of trappean Rocks to the Products of active 
 Volcanoes , Page 494 
 
 CHAPTER XXIX. 
 
 ON THE AGES OF VOLCANIC KOCKS. 
 
 Tests of relative Age of Volcanic Rocks.- — Why ancient and modem Rocks 
 can not be identical. — Tests by Supei-position and Intrusion. — Test by Al- 
 teration of Rocks in Contact. — Test by Organic Remains. — Test of Ago by 
 Mineral Character. — Test by Included Fragments. — Recent and Post-plio- 
 cene volcanic Rocks. — Vesuvius, Auvergne, Puy de Come, and Puy de 
 Pariou. — Newer Pliocene volcanic Rocks. — Cyclopean Isles, Etna, Dikes 
 of Palagonia, Madeira. — Older Pliocene volcanic Rocks. — Italy. — Pliocene 
 Volcanoes of the Eifel. — Trass 520 
 
 CHAPTER XXX. 
 
 AGE OF VOLCANIC ROCKS — CONTINUED. 
 
 Volcanic Rocks of the Upper Miocene Period. — Madeira. — Grand Canary. — 
 Azores. — Lower Miocene Volcanic Rocks. — Isle of Mull. — Staffa and 
 Antrim. — The Eifel. — Upper and Lower Miocene Volcanic Rocks of 
 Auvergne. — Hill of Gergovia. — Eocene Volcanic Rocks of Monte Bolca. 
 — Trap of Cretaceous Period. — Oolitic Period. — Triassic Period. — Permi- 
 an Period. — Carboniferous Period. — Erect Trees buried in Volcanic Ash 
 in the Island of Arran. — Old Red Sandstone Period. — Silurian Period. — 
 Cambrian Period. — Laurentian Volcanic Rocks ,536 
 
 CHAPTER XXXI. 
 
 PLUTONIC KOCKS. 
 
 General Aspect of Plutonic Rocks. — Granite and its Varieties. — Decompos- 
 ing into Spherical Masses. — Rude columnar Structure. — Graphic Gran- 
 ite. — Mutual Penetration of Crystals of Qu&rtz and Feldspar. — Glass Cav- 
 ities in Quartz of Granite. — Porphyritic, talcose, and svenitic Granite.: 
 
 Schorlrock and Eurite.— Syenite.— Connection of the Granites and Sy- 
 enites with the Vplcanic Rocks. — ^Analogy in Composition of Trachyte and 
 Granite. — Granite Veins in Glen Tilt, Cape of Good Hope, and Corn- 
 
 _wall. — Metalliferous Veins in Strata near their Junction with Granite. 
 
 Quartz Veins. — Exposure of Plutonic Rocks at the Surface due to De- 
 nudation 55J 
 
CONTENTS. xxiii 
 
 CHAPTEB XXXII. 
 
 ON THE DIFFERENT AGES OP THE PLUTONIC ROCKS. 
 
 Difficulty in ascertaining the precise Age of a Platonic Rock. — Test of Age 
 by Relative Position. — Test by Intrusion and Alteration. — Test by Mineral 
 Composition. — Test by included Fragments. — Recent and Pliocene Plu- 
 tonic Rocks, why invisible. — Miocene Syenite of the Isle of Skye. — Eocene 
 Plutonic Rocks in the Andes. — Granite altering Cretaceous Rocks. — Granite 
 altering Lias in the Alps and in Skye. — Granite of Dartmoor altering Carbon- 
 iferous Strata. — Granite of the Old Red Sandstone Period. — Syenite altering 
 Silurian Strata in Norway. — Blending of the same with Gneiss. — ^Most an- 
 cient Plutonic Rocks. — Granite protruded in a solid Form Page 564 
 
 CHAPTER XXXIII. 
 
 METAM ORPHIC BOCKS. 
 
 General Character of Metamorphic Rocks. — Gneiss.- — Hornblende-schist. — 
 Serpentine. — Mica - schist. — Clay - slate. — Quartzite. — Chlorite - schist. — 
 Metamorphic Limestone. — Origin of the metamorphic Strata. — Their 
 Stratification. — Fossiliferous Strata near intrusive Masses of Granite con- 
 verted into Rocks identical with different Members of the metamorphic 
 Series. — Arguments hence derived as to the Nature of Plutonic Action. — 
 Hydrothermal Action, or the Influence of Steam and Gases in producing 
 Metamorphism. — Objections to the metamorphic Theory considered... 576 
 
 CHAPTER XXXIV. 
 
 METAMORPHIC ROCKS — CONTINUED. 
 
 Definition of slaty Cleavage and Joints. — Supposed Causes of these Struc- 
 tures. — Crystalline Theory of Cleavage. — Mechanical Theory of Cleavage. 
 — Condensation and Elongation of slate Rocks by lateral Pressure. — Lam- 
 ination of some volcanic Rocks due to Motion. — Whether the Foliation 
 of the crystalline Schists be usually parallel with the original Planes of 
 Stratification. — Examples in Norway and Scotland. — Causes of Irregular- 
 ity in the Planes of Foliation 588 
 
 CHAPTER XXXV. 
 
 ON THE DIFFERENT AGES OF THE METAMORPHIC ROCKS. 
 
 Difficulty of ascertaining the Age of metamoi-phic Strata.— Metamorphic 
 Strata of Eocene date in the Alps of Switzerland and Savoy. — Lime- 
 stone and Shale of Carrara. — Metamorphic Strata of older date than the 
 Silurian and Cambrian Bocks. — Order of Succession in metamorphic 
 Rocks. — Uniformity of mineral Character. — Supposed Azoic Period. — Con- 
 nection between the Absence of Organic Remains and the Scarcity of cal- 
 careous Matter in metamoi'phic Rocks 597 
 
 CHAPTER XXXVL 
 
 MINERAL VEINS. 
 
 Different Kinds of mineral Veins. — Ordinary metalliferous Veins or Lodes. 
 — Their frequent Coincidence with Faults. — Proofs that they originated 
 
xxiv CONTENTS. 
 
 in Fissures in solid Rock. — Veins shifting other Veins. — ^Polishing of their 
 Walls or " Slicken sides." — Shells and Pebbles in Lodes. — Evidence of the 
 successive Enlargement and Reopening of Veins. — Examples in Cornwall 
 and in Auvergne. — Dimensions of Veins. — Why some alternately swell 
 out and contract. — Filling of Lodes by Sublimation from below. ^Sup-^ 
 posed relative Age of the precious Metals. — Copper and lead Veins in Ire- 
 land older than Cornisli Tin. — Lead Vein in Lias, Glamorganshire. — Gold 
 in Russia, California, and Australia. — Connection of hot Springs and min- 
 eral Veins Page 605 
 
 Index 619 
 
STUDENT'S 
 ELEMENTS OF GEOLOGY. 
 
 CHAPTEK I. 
 
 ON THE DIFFEEENT CLASSES OF EOCKS. 
 
 Geology defined. — Successive Formation of the Earth's Crust. — Classifica- 
 tion of Rocks according to their Origin and Age. — Aqueous Rocks. — Their 
 Stratification and imbedded Fossils. — Volcanic Rocks, with and without 
 Cones and Craters. — Plutonic Rocks, and their Relation to the Volcanic. — 
 Metamorphic Rocks, and their probable Origin. — The term Primitive, why 
 erroneously applied to the Crystalline Formations. — Leading Division of 
 the Work. 
 
 Of what materials is the earth composed, and in what man- 
 ner are these materials arranged ? These are the first inqui- 
 ries with which Geology is occupied, a science which derives 
 its name from the Greek yrj, ge, the earth, and \oyoc, logos, a 
 discourse. Previously to experience we might have imagined 
 that investigations of this kind would relate exclusively to 
 the mineral kingdom, and to the various rocks, soils, and met- 
 als, which occur upon the surface of the earth, or at various 
 depths beneath it. But, in pursuing such researches, we soon 
 find ourselves led on to consider the successive changes 
 which have taken place in the former state of the earth's 
 surface and interior, and the causes which have given rise to 
 these changes ; and, what is still more singular and unex- 
 pected, we soon become engaged in researches into the his- 
 tory of the animate creation, or of the various tribes of ani- 
 mals and plants which have, at different periods of the past, 
 inhabited the globe. 
 
 All are aware that the solid parts of the earth consist of 
 distinct substances, such as clay, chalk, sand, limestone, coal, 
 slate, granite, and the like ; but previously to observation it is 
 commonly imagined that all these had remained from the 
 first in the state in which we now see them — that they were 
 created in their present form, and in their present position. 
 The geologist soon comes to a different conclusion, discoveu- 
 
 2 
 
26 ELEMENTS OF GEOLOGY. 
 
 ing proofs that the external parts of the earth were not all 
 produced in the beginning of things in the state in which 
 we now behold them, nor in an instant of time. On the con- 
 trary, he can show that they have acquired their actual con- 
 figuration and condition gradually, under a great variety of 
 circumstances, and at successive periods, during each of which 
 distinct races of living beings have flourished on the land 
 and in the waters, the remains of these creatures still lying 
 buried in the crust of the earth. 
 
 By the " earth's crust," is meant that small portion of the 
 exterior of our planet which is accessible to human observa- 
 tion. It comprises not merely all of which the structure is 
 laid open in mountain precipices, or in clifis overhanging a 
 river or the sea, or Avhatever the miner may reveal in arti- 
 ficiiil excavations ; but the whole of that outer covering of 
 the planet on which we are enabled to reason by observa- 
 tions made at or near the surface. These reasonings may 
 extend to a depth of several miles, perhaps ten miles ; and 
 even then it may be said, that such a thickness is no more 
 than -^ part of the distance from the surface to the centre. 
 The remark is just : but although the dimensions of such a 
 crust are, in truth, insignificant when compared to the entire 
 globe, yet they are vast, and of magnificent extent in relation 
 to man, and to the organic beings which people our globe. 
 Referring to this standard of magnitude, the geologist may 
 admire the ample limits of his domain, and admit, at the same 
 time, that not only the exterior of the planet, but the entire 
 earth, is but an atom in the midst of the countless worlds 
 surveyed by the astronomer. 
 
 The materials of this crust are not thrown together con- 
 fusedly ; but distinct mineral masses, called rocks, are found 
 to occupy definite spaces, and to exhibit a certain order of 
 arrangement. The term rock is applied indifierently by ge- 
 ologists to all these substances, whether they be soft or stony, 
 for clay and sand are included in the term, and some have 
 even brought peat under this denomination. Our old writers 
 endeavored to avoid offering such violence to our language, 
 by speaking of the component materials of the earth as con- 
 sisting of rocks and soils. But there is often so insensible a 
 passage from a soft and incoherent state to that of stone, 
 that geologists of all countries have found.it indispensable to 
 have one technical term to include both, and in this sense we 
 find roche applied in French, rocca in Italian, and felsart in 
 German. The beginner, however, must constantly bear in 
 mind that the term rock by no means implies that a mineral 
 mass is in an indurated or stony condition. 
 
AQUEOUS ROCKS, 27 
 
 The most natural and convenient mode of classifying the 
 various rocks which compose the earth's crust, is to I'efer, in 
 the first place, to their origin, and in the second to their rel- 
 ative age. I shall therefore begin by endeavoring briefly to 
 explain to the student how all rocks may be divided into 
 four great classes by reference to their different origin, or, in 
 other' words, by reference to the different circumstances and 
 causes by which they have been produced. 
 
 The first two divisions, which will at once be understood 
 as natural, are the aqueous and volcanic, or the products of 
 watery and those of igneous action at or near the surface. 
 
 Aqueous Rocks. — The aqueous ro(nis, sometimes called the 
 sedimentary, or fossiliferous, cover a larger part of the earth's 
 surface than any others. They consist chiefly of mechanical 
 deposits (pebbles, sand, and mud), but are partly of chemical 
 and some of them of organic origin, especially the limestones. 
 These rocks are stratified, or divided into distinct layers, or 
 strata. The term stratum means simply a bed, or any thing 
 spread out or strewed over a given surface ; and we infer that 
 these strata have been generally spread out by the action of 
 water, from what we daily see taking place near the mouths 
 of rivers, or on the land during temporary inundations. For, 
 whenever a running stream charged with mud or sand, has 
 its velocity checked, as when it enters a lake or sea, or over- 
 flows a plain, the sediment, previously held in suspension by 
 the motion of the water, sinks, by its own gravity to the 
 bottom. In this manner layers of mud and sand are thrown 
 down one upon another. 
 
 If we drain a lake which has been fed by a small stream, 
 we frequently find at the bottom a series of deposits, dis- 
 posed with considerable regularity, one above the other ; 
 the uppermost, perhaps, may be a stratum of peat, next be- 
 low a more dense and solid variety of the same material ; 
 still lower a bed of shell-marl, alternating with peat or sand, 
 and then other beds of marl, divided by layers of clay, 
 Now, if a second pit be sunk through the same continuous 
 lacustrine formation at some distance from the first, nearly 
 the same series of beds is commonly met with, yet with 
 slight variations ; some, for example, of the layers of sand, 
 clay, or marl, may be wanting, one or more of them having 
 thinned out and given place to others, or sometimes one of 
 the masses first examined is observed to increase in thick- 
 ness to the exclusion of other beds. 
 
 The term '■'■formation^'' which I have used in the above 
 explanation, expresses in geology any assemblage of rocks 
 which have some character in common, whether of origin, 
 
28 ELEMENTS OF GEOLOGY. 
 
 age, or composition. Thus we speak of stratified and unstrat- 
 ified, fresh-water and marine, aqueous and volcanic, ancient 
 and modern, metalliferous and non-metalliferous formations. 
 
 In the estuaries of large rivers, such as the Ganges and 
 the Mississippi, we may observe, at low water, phenomena 
 analogous to those of the drained lakes above menf^onedj 
 but on a grander scale, and extending over areas several 
 hundred miles in length and breadth. When the periodical 
 inundations subside, the river hollows out a channel to the 
 depth of many yards through horizontal beds of clay and 
 sand, the ends of which, are seen exposed in perpendicular 
 cliffs. These l)eds vary in their mineral composition, or col- 
 or, or in the fineness or coarseness of their particles, and 
 some of them are occasionally characterized by containing 
 drift-wood. At the junction of the river and the sea, espe- 
 cially in lagoons nearly separated by sand-bars from the 
 ocean, deposits are often formed in which brackish and salt- 
 water shells are included. 
 
 In Egypt, where the Nile is always adding to its delta by 
 filling up part of the Mediterranean with mud, the newly de- 
 posited sediment is stratified, the thin layer thrown down in 
 one season differing slightly in color from that of a previous 
 year, and being separable from it, as has been observed in 
 excavations at Cairo and other places.* 
 
 When beds of sand, clay, and marl, containing shells and 
 vegetable matter, are found arranged in a similar manner in 
 the interior of the earth, we ascribe to them a similar origin ; 
 and the more we examine their characters in minute detail, 
 the more exact do we find the resemblance. Thus, for exam- 
 ple, at various heights and depths in the earth, and often far 
 from seas, lakes, and rivers, we meet with layers of rounded 
 pebbles composed of flint, limestone, granite, or other rocks, 
 resembling the shingles of a sea-beach or the gravel in a tor- 
 rent's bed. Such layers of pebbles frequently alternate with 
 others formed of sand or fine sediment, just as we may see 
 in the channel of a river descending from hills bordering a 
 coast, where the current sweeps down at one season coarse 
 sand and grave!, while at another, when the waters are low 
 and less rapid, fine mud and sand alone are carried sea- 
 ward, f 
 
 If a stratified arrangement, and the rounded form of peb- 
 bles, are alone sufticient to lead us to the conclusion that 
 certain rocks originated under water, this opinion is farther 
 confirmed by the distinct and independent evidence of fos- 
 
 * See Erinciples of Geology, by the Author, Index, "Nile," "Elvers, "etc. 
 . t Seep. 44, Kg. 7. 
 
VOLCANIC ROCKS. 29 
 
 tils, so abundantly included in the earth's crust. By a fos- 
 sil is meant any body, or the traces of the existence of any 
 body, whether animal or vegetable, which has been buried 
 in the earth by natural causes. Now the remains of ani- 
 mals, especially of aquatic species, are found almost every- 
 where imbedded in stratified rocks, and sometimes, in the 
 case of limestone, they are in such abundance as to consti- 
 tute the entire mass of the rock itself Shells and corals are 
 the most fi-equent, and with them are often associated the 
 bones and teeth of fishes, fragments of wood, impressions of 
 leaves, and other organic substances. Fossil shells, of forms 
 such as now abound in the sea, are met with far inland, both 
 near the surface, and at great depths below it. They occur 
 at all heights above the level of the ocean, having been ob- 
 served at elevations of more than 8000 feet in the Pyrenees, 
 10,000 in the Alps, 13,000 in the Andes, and above 18,000 
 feet in the Himalaya.* 
 
 These shells belong mostly to marine testacea, but in some 
 places exclusively to forms characteristic of lakes and rivers. 
 Hence it is concluded that some ancient strata were deposit- 
 ed at the bottom of the sea, and others in lakes and estuaries. 
 ' We have now pointed out one great class of rocks, which, 
 however they may vary in mineral composition, color, grain, 
 or other characters, ex.ternal and internal, may nevertheless 
 be grouped together as having a common origin. They 
 have all been formed under water, in the same manner as 
 modern accumulations of sand, mud, shingle, banks of shells, 
 reefs of coral,and the like, and are all characterized by strati- 
 fication or fossils, or by both. 
 
 Volcanic Rocks. — The division of rocks which we may next 
 consider are the volcanic, or those which have been produced 
 at or near the surface whether in ancient or modern times, 
 not by water, but by the action of fire or subterranean heat. 
 These rocks are for the most part unstratified, and are de- 
 void of fossils.' They are more partially distributed than 
 aqueous formations, at least in respect to horizontal exten- 
 sion. Among those parts of Europe where they exhibit 
 characters not to be mistaken, I may mention not only Sici- 
 ly and the country round Naples, but Auvergne, Velay, and 
 Vivarais,now the departments of Puy de Dome, Haute Loire, 
 and Ardeche, towards the centre and south of France, in 
 which are several hundred conical hills having the forms of 
 modern volcanoes, with craters more or less perfect on many 
 of their summits. These cones are composed moreover of 
 
 * Col. E. J. Strachey found oolitic fossils 18,400 feet high in the Hima- 
 laya- 
 
30 ELEMENTS OE GEOLOGY. 
 
 lava, sand, and ashes, similar to those of active volcanoes. 
 Streams of lava may sometimes be traced from the cones 
 into the adjoining valleys, where they have choked up the 
 ancient channels of rivers with solid rock, in the same man- 
 ner as some modern flows of lava in Iceland have been 
 known to do, the rivers either flowing beneath or cutting 
 out a narrow passage on one side of the lava. Although 
 none of these French volcanoes have been in activity within 
 the period of history or tradition, their forms are often' very 
 perfect. Some, however, have been compared to the mere 
 skeletons of volcanoes, the rains and torrents having washed 
 their sides, and removed all the loose sand and scoriae, leav- 
 ing only the harder and more solid materials. By this ero- 
 sion, and by earthquakes, their intei'nal structure has occa- 
 sionally been laid open to view, in fissures and ravines ; and 
 we then behold not only many successive beds and masses 
 of porous lava, sand, and scoriag, but also perpendicular walls, 
 or dikes, as they are called, of volcanic rock, which have burst 
 through the other materials. Such dikes are also observed in 
 the structure of Vesuvius, Etna, and other active volcanoes. 
 They have been formed by the pouring of melted matter, 
 whether from above or below, into open fissures, and they 
 commonly traverse deposits oi volcanic tuff, a, substance pro- 
 duced by the showering down from the air, or incumbent 
 waters, of sand and cinders, first shot up from the interior of 
 the earth by the explosions of volcanic gases. 
 
 Besides the parts of France above alluded to, there are 
 other countries, as the north of Spain, the south of Sicily, 
 the Tuscan territory of Italy, the lower Rhenish provinces, 
 and Hungary, where spent volcanoes may be seen, still pre- 
 serving in many cases a conical form, and having craters and 
 often lava-streams connected with them. 
 
 There are also other rocks in England, Scotland, Ireland, 
 and almost every country in Europe, which we infer to be 
 of igneous origin, although they do not form hills with cones 
 and craters. Thus, for example, we feel assured that the 
 rock of Stafia, and that of the Giant's Causeway, called ba- 
 salt, is volcanic, because it agrees in its columnar structure 
 and mineral composition with streams of lava which we 
 know to have flowed from the craters of volcanoes. We find 
 also similar basaltic and other igneous rocks associated with 
 beds of tuf in various parts of the British Isles, and formiuEr 
 dikes, such as have been spoken of; and some of the strata 
 through which these dikes cut are occasionally altei-ed at 
 the point of contact, as if they had been exposed to the in- 
 tense heat of melted matter. 
 
PLUTONIC ROCKS. 31 
 
 The absence of cones and craters, and long narrow streams 
 of superficial lava, iiu England and many other countries, is 
 principally to be attributed to the eruptions having been 
 submarine, just as a considerable proportion of volcanoes in 
 our own times burst out beneath the sea. But this question 
 must be enlarged upon more fully in the chapters on Igne- 
 ous Rocks, in which it will also be shown, that as difierent 
 sedimentary formations, containing each their characteristic 
 fossils, have been deposited at successive periods, so also vol- 
 canic sand and scoriae have. been thrown out, And lavas have 
 flowed over the land or bed of the sea, at many difierent 
 epochs, or have been injected into fissures ; so that the igne- 
 ous as well as the aqueous rocks may be classed as a chrono- 
 logical series of monuments, throwing light on a succession 
 of events in the history of the earth. 
 
 Plutonic Bocks {Granite, etc). — We have now pointed out 
 the existence of two distinct orders of mineral masses, the 
 aqueous and the volcanic : but if we examine a large por- 
 tion of a continent, especially if it contain within it a lofty 
 mountain range, we rarely fail to discover two other classes 
 of rocks, very distinct from either of those above alluded to, 
 and which we can neither assimilate to deposits such as are 
 now accumulated in lakes or seas, nor to those generated by 
 ordinary volcanic action. The members of both these divis- 
 ions of rocks agree in being highly crystalline and desti- 
 tute of organic remains. The rocks of one division have 
 been called plutonic, comprehending all the granites and 
 certain porphyries, which are nearly allied in some of their 
 characters to volcanic formations. The members of the 
 other class are stratified and often slaty, and have been 
 called by some the crystalline schists, in which group are in- 
 cluded gneiss, micaceous-schist (or mica-slate), hornblende- 
 schist, statuary marble, the finer kinds of I'oofing slate, and 
 other rocks afterwards to be described. 
 
 As it is admitted that nothing strictly analogous to these 
 crystalline pvodu<!tioris can now be seen in the progress of 
 formation on the earth's surface, it will naturally be asked, 
 on what data we can find a place for them in a system of 
 classification founded on the origin of rocks. I can not, in 
 reply to this question, pretend to give the student, in a few 
 words, an intelligible account of the long chain of facts and 
 reasonings from which geologists have been led to infer the 
 nature of the rocks in question. The result, however, may 
 be briefly stated. All the various kinds of granites which 
 constitute the plutonic family are supposed to be of ig- 
 neous or aqueo-igneous origin, and to have been formed un- 
 
32 ELEMENTS OF GEOLOGY. 
 
 der great pressure, at a considerable depth in the earth, or 
 sometimes, perhaps, under a certain weight of incumbent 
 ocean. Like the lava of volcanoes, they have been melted, 
 and afterwards cooled and crystallized, but with extreme 
 slowness, and under conditions very different from those of 
 bodies cooling in the open air. Hence they differ from the 
 volcanic rocks, not only by their more crystalline texture, 
 but also by the absence of tuffs and breccias, which are the 
 products of eruptions at the earth's surface, or beneath seas 
 of inconsiderable depth. They differ also by the absence of 
 pores or cellular cavities, to which the expansion of the en- 
 tangled gases gives rise in ordinary lava. 
 
 Metamorphic, or Stratified Crystalline Rocks. — The fourth 
 and last great division of rocks are the crystalline strata 
 and slates, or schists, called gneiss, mica-schist, clay-slatei 
 chlorite-schist, marble, and the like, the origin of which is 
 more doubtful than that of the other three classes. They 
 contain no pebbles, or sand, or scoriae, or angular pieces of 
 imbedded stone,' and no traces of organic bodies, and they 
 are often as crystalline as granite, yet are divided into beds, 
 corresponding in form and arrangement to those of sediment* 
 ary formations, and are therefore said to be stratified. The 
 beds sometimes consist of an alternation of substances vary- 
 ing in color, composition, and thickness, precisely as we see 
 in stratified fossiliferous deposits. According to the Hut- 
 tonian theory, which I adopt as the most probable, and 
 which will be afterwards more fully explained, the materi- 
 als of these strata were originally deposited from water in 
 the usual form of sediment, but they were subsequently so 
 altered by subterranean heat, as to assume a new texture; 
 It is demonstrable, in some cases at least, that such a com* 
 plete conversion has actually taken place, fossiliferous strata 
 having exchanged an earthy for a highly crystalline texture 
 for a distance of a quarter of a mile from their contact with 
 granite. In some cases, dark limestones, I'eplete with shells 
 and corals, have been turned into white statuary marble ; 
 and hard clays, containing vegetable or other remains, into 
 slates called mica-schist or hornblende-schist, every vestige 
 of the organic bodies having been obliterated. 
 
 Although we are in a great degree ignorant of the precise 
 nature of the influence exerted in these cases, yet it evident- 
 ly bears some analogy to that which volcanic heat and gases 
 are known to produce ; and the action may be conveniently 
 called plutonic, because it appears to have been developed 
 in those regions where plutonic rocks are generated, and 
 under similar circumstances of pressure and depth in tli^ 
 
FOUR CLASSES OP ROCKS. 33 
 
 iearth. Intensely heated water or steam permeating strati- 
 fied masses under great pressure have no douht played 
 their part in producing the crystalline texture and other 
 changes, and it is clear that the transforming influence has 
 often pervaded entire mountain masses of strata. 
 
 In accordance with the hypothesis above alluded to, I pro- 
 posed in the first edition of the Principles of Geology (1833) 
 the term " Metamorphic " for the altered strata, a term de- 
 rived from fiETo., meta, trans, and fiopifi^), morphe, /brwa. 
 
 Hence there ai-e four great classes of rocks considered in 
 reference to their origin — the aqueous, the volcanic, the pin- 
 tonic, and the metamorphic. In the course of this work it 
 will be shown that portions of each of these four distinct 
 classes have originated at many successive periods. They 
 have all been produced contemporaneously, and may even 
 now be in the progress of formation on a large scale. It is 
 not true, as was formerly supposed, that all granites, togeth- 
 er with the crystalline or metamorphic strata, were first 
 formed, and therefore entitled to be called " primitive," and 
 that the aqueous and volcanic rocks were afterwards super- 
 imposed, and should, therefore, rank as secondary in the or- 
 der of time. This idea was adopted in the infancy of tlie 
 science, when all formations, whether stratified or unstrati- 
 fied, earthy or crystalline, with or without fossils, were alike 
 regarded as of aqueous origin. At that period it was nat- 
 urally argued that the foundation must be older than the 
 superstructure ; but it was afterwards discovered that this 
 opinion was by no means in every instance a legitimate de- 
 duction from facts ; for the inferior parts of the earth's crust 
 have often been modified, and even entirely changed, by the 
 influence of volcanic and other subterranean causes, while 
 superimposed formations have not been in the slightest de- 
 gree altered. In other words, the destroying and renovating 
 processes have given birth to new rocks below, while those 
 above, whether crystalline or fossiliferous, have remained in 
 their ancient condition. Even in cities, such as Venice aixd 
 Amsterdam, it can not be laid down as universally true, that 
 the upper parts of each edifice, whether of brick or marble, 
 ai'e more modern than the foundations on which they rest, 
 for these often consist of wooden piles, which may have rot- 
 ted and been replaced one after the other, without the least 
 injury to the buildings above ; meanwhile, these may have 
 required scarcely any repair; and may have been constantly 
 inhabited. So it is with the habitable surface of our globe, 
 in its relation to lai'ge masses of rock immediately below ; it 
 
 may continue the same for ages, while subjacent materials, at 
 
 2* " - 
 
34 ELEMENTS OE GEOLOGY. 
 
 a great depth, are passing from a solid to a fluid state, and 
 then reconsolidating, so as to acquire a new texture. 
 
 As all the crystalline rocks may, in some respects, be view- 
 ed as belonging to one great family, whether they be strati- 
 fied or unstratified, metamorphic or plutonic, it will often be 
 convenient to speak of them by one common name. It be- 
 ing now ascertained, as above stated, that they are of very 
 different ages, sometimes newer than the strata called sec- 
 ondary, the terms primitive and primary which were former- 
 ly used for the whole must be abandoned, as they would im- 
 ply a manifest contradiction. It is indispensable, therefore, 
 to find a new name, one which must not be of chronological 
 import, and must express, on the one hand, some peculiarity 
 equally attributable to granite and gneiss (to the plutonic as 
 well as the altered rocks), and, on the other, must have refer- 
 ence to characters in which those rocks difier, both from the 
 volcanic and from the unaltered sedimentary strata. I pro- 
 posed in the Principles of Geology (first edition, vol. iii.) the 
 term "hypogene" for this purpose, derived from imo, under, 
 and yivofiai,to be, or to be bom; a word implying the theory 
 that granite, gneiss, and the other crystalline formations are 
 alike netherformed rocks, or rocks which have not assumed 
 their present form and structure at the surface. They occu- 
 py the lowest place in the order of superposition. Even in 
 regions such as the Alps, where some masses of granite and 
 gneiss can be shown to be of comparatively modern date, be- 
 longing, for example, to the period hereafter to be described 
 as tertiary, they are still underlying rocks. They never re- 
 pose on the volcanic or trappean formations, nor on strata 
 containing organic remains. They are hypogene, as " being 
 under " all the rest. 
 
 From what has now been said, the reader will understand 
 that each of the four great classes of rocks may be studied 
 under two distinct points of view; first, they maybe studied 
 simply as mineral masses deriving their origin from particu- 
 lar causes, and having a certain composition, form, and posi- 
 tion in the earth's crust, or other characters both positive 
 and negative, such as the presence or absence of organic re- 
 mains. In the second place, the rocks of each class may be 
 viewed as a grand chronological series of monuments, attest- 
 ing a succession of events in the former history of the globe 
 and its living inhabitants. 
 
 I shall accordingly proceed to treat of each family of 
 rocks ; first, in reference to those characters which are not 
 chronological, and then in particular relation to the several 
 periods when they were formed, 
 
SILICEOUS AI!^D ARENACEOUS ROCKS. 35 
 
 CHAPTER n. 
 
 AQUEOUS EOCKS. — THEIB COMPOSITIOlSr AISTD POEMS OP STEATI- 
 
 PICATIOX. 
 
 Mineral Composition of Strata. — Siliceous Hocks. — Argillaceous. — Ca]cai%- 
 ous. — Gypsum. — Forms of Stratification. — ^Original Hori^ontality. — Thin- 
 ning out. — Diagonal Arrangement.— Eipple-mark. 
 
 In pursuance of the arrangement explained in the last 
 chapter, we shall begin by examining the aqueous or sedi- 
 mentary rocks, which are tor the most part distinctly strati- 
 fied, and contain fossils. We may first study them with 
 reference to their mineral composition, external appearance, 
 position, mode of origin, organic contents, and other charac- 
 ters which belong to them as aqueous formations, independ- 
 ently of their age, and we may afterwards consider them 
 chronologically or with reference to the successive geologic- 
 al periods when they originated. 
 
 I have already given an outline of the data which led to 
 the belief that the stratified and =fossiliferous rocks were 
 originally deposited under water ; but, before entering into 
 a more detailed investigation, it will be desirable to say 
 something of the ordinary materials of which such strata 
 are composed. These may be said to belong principally to 
 three divisions, the siliceous, the argillaceous, and the calca- 
 reous, which are formed, respectively of flint, clay, and car- 
 bonate of lime. Of these, the siliceous are chiefly made up 
 of, sand or flinty grains ; the argillaceous, or clayey, of a 
 mixture of siliceous matter with a certain proportion, about 
 a fourth in weight, of aluminous earth ; and, lastly, the cal- 
 careous rocks, or limestones, of carbonic acid and lime. 
 
 Siliceous and Arenaceous Rocks. — To speak first of the 
 sandy division : beds of loose sand are frequently met with, 
 of which the grains consist entirely of silex, which term 
 comprehends all purely siliceous minerals, as quartz and 
 common flint. Quartz is silex in its purest form. Flint 
 usually contains some admixture of alumina and oxide of 
 iron. The siliceous grains in sand are usually rounded, as 
 if by the action of running water. Sandstone is an aggre- 
 gate of such grains, which often cohere together without 
 any visible cement, but more commonly are bound together 
 
36 ELEMENTS OF GEOLOGY. 
 
 by a slight quantity of siliceous or calcareous matter, or by 
 oxide of iron or clay. 
 
 Pure siliceous rocks may be known by not effervescing 
 when a drop of nitric, sulphuric or other acid is applied to 
 them, or by the grains not being readily scratched or bro- 
 ken by ordinary pressure. In nature there is every inter- 
 mediate gradation, from perfectly loose sand to the hardest 
 sandstone. In micaceous sandstones mica is very abundant ; 
 and the thin silvery plates into which that mineral divides 
 are often arranged in layers parallel to the planes of stratifi- 
 cation, giving a slaty or laminated texture to the rock. 
 
 When sandstone is coarse-grained, it is usually called grit. 
 If the grains are rounded, and large enough to be called peb- 
 bles, it becomes a conglomerate or pudding-stone, which may 
 consist of pieces of one or of many different kinds of rock. 
 A conglomerate, therefore, is simply gravel bound together 
 by a cement. 
 
 Argillaceous Rocks. — Clay, strictly speaking, is a mixture 
 of silex or fliut with a large proportion, usually about one 
 fourth, of alumina, or argil ; but in common language, any 
 earth which possesses sufficient ductility, when kneaded up 
 with water, to be fashioned like paste by the hand, or by 
 the potter's lathe, is called a clay ; and such clays vary 
 greatly in their composition, and are, in general, nothing 
 more than mud derived from the decomposition or wearing 
 down of rocks. The purest clay found in nature is porce- 
 lain clay, or kaolin, which results from the decomposition of 
 a rock composed of feldspar and quartz, and it is almost al- 
 • ways mixed with quartz. The kaolin of China consists of 
 71'15 parts of silex, 15'86 of alumine, 1"92 of lime, and C'^S 
 of water;* but other porcelain clays differ materially, that 
 of Cornwall being composed, according to Boase, of nearly 
 equal parts of silica and alumine, with 1 per cenu of magne- 
 sia.f Shale has also the property, like clay, of becoming 
 plastic in water : it is a more solid form of clay, or argilla- 
 ceous matter, condensed by pressure. It always divides into 
 laminae more or less regular. 
 
 One general character of all ai'gillaceous rocks is to give 
 out a peculiar, earthy odor when breathed upon, which is 
 a test of the presence of alumine, although it does not be- 
 long to pure alumine, but, apparently, to the combination of 
 that substance with oxide of iron. J 
 
 Calcareous Rocks. — This division comprehends those rocks 
 which, like chalk, are composed chiefly of lime and carbonic 
 
 * W. Phillips, Mineralogy, p. 33. t Phil. Mag., vol. x., 1837. 
 
 X See W. Phillips's Mineialogy, "Alumine." 
 
OF STKATIFIED KOCKS. 31 
 
 acid. Shells and corals are also formed of the same ele- 
 ments, with the addition of animal matter. To obtain pure 
 lime it is necessary to calcine these calcareous substances, 
 that is to say, to expose them to heat of sufficient intensity 
 to drive off the carbonic acid, and other volatile matter. 
 White chalk is sometimes pure carbonate of lime ; and this 
 rock, although usually in a soft and earthy state, is occa- 
 sionally sufficiently solid to be used for building, and even 
 passes into a. compact stone, or a stone of which the sepa- 
 rate parts are so minute as not to be distinguishable from 
 each other by the naked eye. 
 
 Many limestones are made up entirely of minute frag- 
 ments of shells and coral, or of calcareous sand cemented to- 
 gether. These last might be called "calcareous sandstones;" 
 but that term is more properly applied to a rock in which 
 the grains are partly calcareous and partly siliceous, or to 
 quartzose sandstones, having a cement of carbonate of lime. 
 
 The variety of limestone called oolite is composed of nu- 
 mei-ous small egg-like grains, resembling the roe of a fish, 
 each of which has usually a small fragment of sand as a nu- 
 .cleus, around which concentric layers of calcareous matter 
 have accumulated. 
 
 Any limestone which is sufficiently hard to take a fine pol- 
 ish is called marble. Many of these are fossiliferous ; but 
 ^statuary marble, which is also called saccharoid limestone, as 
 having a texture resembling that of loaf-s.ugar, is devoid of 
 fossils', and is in many cases a member of the metamorphic 
 series. 
 
 Siliceous limestone is an intimate mixture of carbonate of 
 lime and flint, and is harder in proportion as the flinty mat- 
 ter predominates. 
 
 The presence of carbon ate of lime in a rock may be ascer- 
 tained by applying to the surface a small drop of diluted 
 sulphuric, nitric, or muriatic acid, or strong vinegar; for the 
 lime, having a greater chemical affinity for any one of these 
 acids, than for the carbonic, unites immediately with them, to 
 form new compounds, thereby becoming a sulphate, nitrate, 
 or muriate of lime. The carbonic acid, when thus liberated 
 from its union with the lime, escapes in a gaseous form, and 
 froths up or effervesces as it makes its way in small bubbles 
 through the drop of liquid.. This effervescence is brisk or 
 feeble in proportion as the limestone, is pure or impure, or, 
 in other words, according to the quantity of foreign matter 
 mixed with the carbonate of lime. Without the aid of this 
 test, the most experienced eye can not always detect the 
 presence of carbonate of lime, in rocks. , . .. _ , 
 
38 ELEMENTS OE GEOLOGY. 
 
 The above-mentioned three classes of rocks, the siliceous, 
 argillaceous, and calcareous, pass continually, into each oth- 
 er, and rarely occur in a perfectly separate and pure form. 
 Thus it is an exception to the general rule to meet with a 
 limestone as pure as ordinary white chalk, or with clay, as 
 aluminous as that used in Cornwall for porcelain, or with 
 sand so entirely composed of siliceous grains as the white 
 Band of Alum Bay, in the Isle of Wight, employed in the 
 manufacture of glass, or sandstone so pure as the grit of 
 Fontainebleau, used for pavement in France. More com- 
 monly we find sand and clay, or clay and marl, intermixed 
 in the same mass. When the sand and clay are each in con- 
 siderable quantity, the mixture is called loam. If there is 
 much calcareous matter in clay it is called marl; but this 
 term has unfortunately been used so vaguely, as often to be 
 very ambiguous. It has been applied to substances in which 
 there is no lime ; as, to that red loam usually called red mar/ 
 in certain parts of England. Agriculturists were in tht 
 habit of calling any soil a marl which, like true marl, fell to 
 pieces readily on exposure to the air. Hence arose the con- 
 fusion of using this name for soils which, consisting of loam, 
 were easily worked by the plough, though devoid of lime. 
 
 Marl slate bears the same relation to marl which shale 
 bears to clay, being a calcareous shale. It is very abundant 
 in some countries, as in the Swiss Alps. Argillaceous or 
 marly limestone is also of common occurrence. 
 
 There are few other kinds of rock which enter so largely 
 into the composition of sedimentary strata as to make it 
 necessary to dwell here on their characters. I may, how- 
 ever, mention two others — magnesian limestone or dolomite, 
 and gypsum. Magnesian limestone is composed of carbon- 
 ate of lime and carbonate of magnesia ; the proportion of 
 the latter amounting in some cases to nearly one half It 
 effervesces much more slowly and feebly with acids than 
 common limestone. In England this rock is generally of a 
 yellowish color ; but it varies greatly in mineralogical char- 
 acter, passing from an earthy state to a white compact stone 
 of great hardness. Dolomite, so common in many parts of 
 Germany and France, is also a variety of magnesian lime- 
 . stone, usually of a granular texture. 
 
 Gypsum is a rock composed of sulphuric acid, lime, and 
 water. It is usually a soft whitish-yellow rock, with a tex- 
 ture resembling that of loaf-sugar, but sometimes it is entire- 
 ly composed of lenticular ciystals. It is insoluble in acids, 
 and does not effervesce like chalk and dolomite, because it 
 does not contain carbonic acid gas, or fixed air, the lime be- 
 
FORMS OF STRATIFICATION. 39 
 
 ing already combined with sulphuric acid, for which it has a 
 stronger affinity than for any other. Anhydrous gypsum is 
 a rare variety, into which water does not enter as a compo- 
 nent part. Gypseous marl is a mixture of gypsum and 
 marl. Alabaster is a granular and compact variety of gyp- 
 sum found in masses large enough to be used in sculpture 
 and architecture. It is sometimes a pure snow-white sub- 
 stance, as that of Volterra in Tuscany, well known as being 
 carved for works of art in Florence and Leghorn. It is a 
 softer stone than marble, and more easily wrought. 
 
 Forms of Stratification. — A series of strata sometimes con- 
 sists of one of the above rocks, sometimes of two or more in 
 alternating beds. 
 
 Thus, in the coal districts of England, for example, we oft- 
 en pass through several beds of sandstone, some of finer, oth- 
 ers of coarser grain, some white, others of a dark color, and 
 below these, layers of shale and sandstone or beds of shale, 
 divisible into leaf-like laminae, and containing beautiful im- 
 pressions of plants. Then again we meet with beds of pui'e 
 and impure coal, alternating with shales and sandstones, and 
 underneath the whole, perhaps, are calcareous strata, or beds 
 of limestone, filled with corals and marine shells, each bed 
 distinguishable from another by certain fossils, or by the 
 abundance of particular species of shells or zoophytes. 
 
 This alternation of different kinds of rock produces the 
 most distinct stratification ; and we often find beds of lime- 
 stone and marl, conglomerate and sandstone, sand and clay, 
 recurring again and again, in nearly regular order, through- 
 out a series of many hundred strata. The causes which may 
 produce these phenomena are various, and have been fully 
 discussed in my treatise on the modern changes of the 
 earth's surface.* It is there seen that rivers flowing into 
 lakes and seas are charged with sediment, varying in quan- 
 tity, composition, color, and grain according to the seasons; 
 the waters are sometimes flooded and rapid, at other periods 
 low and feeble ; different tributaries, also, draining peculiar 
 countries and soils, and therefore charged with peculiar sed- 
 iment, are swollen at distinct periods. It was also shown 
 that the waves of the sea and currents undermine the cliffs 
 during wintry storms, and sweep away the materials into 
 the deep, after which a season of tranquillity succeeds, when 
 nothing but the finest mud is spread by the movements of 
 the ocean over the same submarine area. 
 
 It is not the object of the present work to give a desciip- 
 
 * Consult Index to Principles of Geology, "Stratification," "Currents," 
 ' ' Deltas, " ' ' Water, " etc. 
 
40 ELEMENTS OF GEOLOGY. 
 
 tion of these operations, repeated as they are, year after 
 year, and century after century ; but I may suggest an 
 explanation of the manner in which some micaceous sand- 
 stones have originated, namely, those in which we see innu- 
 merable thin layers of mica dividing layers of fine quartzose 
 sand. I observed the same arrangement of materials in re- 
 cent mud deposited in the estuary of La Roche St. Bernard 
 In Brittany, at the mouth of the Loire. The surrounding 
 rocks are of gneiss, which, by its waste, supplies the mud : 
 when this dries at low water, it is found to consist of brown 
 laminated clay, divided by thin seams of mica. The separa- 
 tion of the mica in this case, or in that of micaceous sand- 
 stones, may be thus understood. If we take a handful of 
 quartzose sand, mixed with mica, and throw it into a clear 
 running stream, we see the materials immediately sorted by 
 the water, the grains of quartz falling almost directly to the 
 bottom, while the plates of mica take a much longer time to 
 reach the bottom, and are cariied farther down the stream. 
 At the first instant the water is turbid, but immediately af- 
 ter the flat surfaces of the plates of mica are seen all alone, 
 reflecting a silvery light, as they descend slowly, to form a 
 distinct micaceous lamina. The mica is the heavier mineral 
 of the two; but it remains a longer time suspended in the 
 fluid, owing to its greater extent of surface. It is easy, 
 therefore, to perceive that where such mud is acted upon 
 by a river or tidal current, the thin plates of mica will be 
 carried farther, and not deposited in the same places as the 
 grains of quartz; and since the force and velopity of the 
 stream varies from time to time, layers of rnica or of sand 
 will be thrown down successively on the same area. 
 
 Original Horizontality. — It is said generally that the upper 
 and under surfaces of strata, oi- the "planes of stratification," 
 are parallel. Although this is not strictly true, they make 
 an approach to parallelism, for the same reason that sedi- 
 ment is usually deposited at first in nearly horizontal lay- 
 ■ ers. Such an arrangement can by no means be attributed 
 to an original evenness or horizontality in the bed of the 
 sea : for it is ascertained that in those places where no mat- 
 ter has been recently deposited, the bottom of the ocean is 
 often as uneven as that of the dry land, having in like man- 
 ner its hills, valleys, and ravines. Yet if the sea should go 
 down, or be removed from near the mouth of a large river 
 where a delta has been forming, we should see extensive 
 plains of mud and sand laid dry, which, to the eye, would 
 appear perfectly level, although, in reahty, they would slope 
 "gentjy from the land towards the sea. ... • 
 
HOEIZONTALITY OF STRATA. 
 
 41 
 
 This tendency in newly-formed strata to assume a horizon- 
 tal position arises principally from the motion of the watei', 
 which forces along particles of sand or mud at the bottom, 
 and causes them to settle in hollows or depressions where 
 they are less exposed to the force of a current than when 
 they are resting on elevated points. The velocity of the 
 curi'ent and the motion of the superficial waves diminish 
 from the surface downward, and are least in those depres- 
 sions where the water is deepest. 
 
 A good illustration of the principle here alluded to may 
 be sometimes seen in the neighborhood of a volcano, when a, 
 section, whether natural or artificial, has laid open to view a 
 succession of various-colored layers of sand and ashes, which 
 have fallen in showers upon uneven ground. Thus let A B 
 (Fig. 1) be two ridges, with an in- Fig. i. 
 
 tervening valley. These original 
 inequalities of the surface have 
 been gradually effaced by beds 
 of sand and ashes c,d, e, tlie sur- 
 face at e being quite level. It will be seen that, although the 
 materials of the first layers have accommodated themselves 
 in a great degree to the shape of the ground A B, yet each 
 bed is thickest at the bottom. At first a great many parti- 
 cles would be carried by their own gravity down the steep 
 sides of A and B, and others would afterwards be blown 
 by the wind as they fell off the ridges, and would settle in 
 the hollow, which would thus become more arid more effaced 
 as the strata accumulated from c to e. Now, waiter in mo- 
 tion can exert this levelling power on similar materials more 
 easily than air, for almost all stones lose in water more than 
 a third of the weight which they have in air, the specific 
 gravity of rocks being in general as 2^ when compared to 
 that of water, which is estimated at 1. But the buoyancy 
 of sand or mud would be still greater in the sea, as the den- 
 sity of salt-tvater exceeds that of fresh. 
 
 Yet, however uniform and horizontal may be the surface 
 of new deposits in general, thei-e are still la^nj disturbing 
 causes, siioh as eddies in the water, and currents moving first 
 in one and then in another direction, which frequently cause 
 
 
 Fig. 2. 
 
 ■- — — ,-,.—= ., 1 
 
 
 -_--.--.- - --r — ' — .■.■'.;.'■■■■■ ■: 
 
 
 
 —:r-s-7r^~^%. ° „ o ^ o°o^ "Js-S^Sa 
 
 [T- ■• •■ 
 
 
 Section of strata of sandstone, grit, and conglomerate. 
 
42 
 
 ELEMENTS OF GEOLOGY. 
 
 irregularities. We may sometimes follow a bed of lime- 
 stone, shale, or sandstone, for a distance of many hundred 
 yards continuously ; but we generally find at length that 
 each individual stratum thins out, and allows the beds which 
 were previously above and below it to meet. If the materi- 
 als are coarse, as in grits and conglomerates, the same beds 
 can rarely be traced many yards without varying in size, and 
 often coming to an end abruptly. (See Fig. 2.) 
 
 Diagonal or Cross Stratification. — There is also another phe- 
 nomenon of frequent occurrence. We find a series of larger 
 strata, each of which is composed of a number of minor lay- 
 ers placed obliquely to the general planes of stratification. 
 To this diagonal arrangement the name of " false or cross 
 bedding" has been given. Thus in the annexed section 
 (Fig. 3) we see seven or eight large beds of loose sand, yel- 
 low and brown, and the lines a, 5, c mark some of the princi- 
 pal planes of stratification, which are nearly horizontal. But 
 the greater part of the subordinate laminse do not conform 
 to these planes, but have often a steep slope, the inclination 
 
 Fig. 3. 
 
 Section of sand at Sandy Hill, near Biggleswade, Bedfordshire. 
 Height 20 ft. (Green-sand formation.) 
 
 being sometimes towards opposite points of the compass. 
 When the sand is loose and incoherent, as in the case here 
 represented, the deviation from parallelism of the slanting 
 laminse can not possibly be accounted for by any re-arrange- 
 ment of the particles acquired during the consolidation of 
 the rock. In what manner, then, can such irregularities be 
 
CAUSES OF DIAGONAL STRATIFICATION. 
 
 43 
 
 due to original deposition? We must suppose that at the 
 bottom of the sea, as well as in the beds of rivers, the mo- 
 tions of waves, currents, and eddies often cause mud, sand, 
 and gravel to be thrown down in heaps on particular spots, 
 instead of being spread out uniformly over a wide area. 
 Sometimes, when banks are thus formed, currents may cut 
 passages through them, just as a river forms its bed. Sup- 
 pose, the bank A (Fig. 4) to be thus formed with a steep 
 
 Fig. 4. 
 
 sloping side, and, the water being in a tranquil state, the lay- 
 er of sediment No. 1 is thrown down upon it, conforming 
 nearly to its surface. Afterwards the other layers, 2, 3, 4, 
 may be deposited in succession, so that the bank B C D is, 
 formed. If the current then increases in velocity, it may cut 
 away the upper portion of this mass down to the dotted line 
 e, and deposit the materials thus removed farther on, so as to 
 form the layers 5, 6, 7, 8. We have now the bank B C D E 
 (Fig. 5), of which the surface is almost level, and on which 
 
 Kg. 5. 
 
 the nearly horizontal layers, 9, 10, 11, may then accumulate. 
 It was shown in Fig. 3 that the diagonal layers of successive 
 strata may sometimes have an opposite slope. This is well 
 seen in some cliffs of loose Fig. 6. 
 
 sand on the Suffolk coast. A 
 portion of one of these is rep- 
 
 resented in Fig. 6, where the 
 layers, of which there are 
 about six in the thickness 
 of an inch, are composed of 
 quartzose grains. This ar- 
 rangement may have been 
 
 Cliff between Mismer and Dunwich. 
 
 duetto the altered direction of the tides and currents in the 
 same place. 
 
44 ELEMENTS OF GEOLOGY. 
 
 The description above given of the slanting position of 
 the minor layers constituting a single stratum is in certain 
 cases applicable on a much grander scale to masses' several 
 hundred feet thick, and many miles in extent. A fine exam- 
 ple may be seen at the base of the Maritime Alps near Nice. 
 The mountains here terminate abruptly in the sea, so that a 
 depth of one hundred fathoms is often found within a stone's 
 throw of the beach, and sometimes a depth of 3000 feet with- 
 in half a mile. But at certain points, strata of sand, marl, or 
 conglomerate intervene between the shore and the mount- 
 ains, as in the section (Fig. 7), where a vast succession of 
 slanting beds of gravel and sand may be traced from the sea 
 to Monte Calvo, a distance of no Jess than nine mile,s in a 
 straight linci The dip of these beds is remarkably uiiiform, 
 being always. south ward or towards the Mediterranean, at an 
 angle of about 25°. They are exposed to view in nearly ver- 
 tical precipices, varying from 200 to 600 feet in height, which 
 bound the valley through which the river Magnan flows. 
 
 Monte Calvo. Kg. 7. 
 
 Section from Monte Calvo to the sea by the valley of the Magnan, near Nice. 
 A. Dolomite and sandstone. (Green-sand formation ?) 
 o, 6, A. Beds of gravel and sand, 
 c. Fine marl and sand of Sto. Madeleine, with marine (Pliocene) shells. 
 
 Although, in a general view, the strata appear to be parallel 
 and uniform, they are nevertheless found, when examined 
 closely, to be wedge-shaped, and to thin out when followed 
 for a few hundred feet or yards, so that we may suppose 
 them to have been thrown down originally upon the side <s.f 
 a steep bank where a i-iver or Alpine torrent discharged it- 
 self into a deep and tranquil sea, and formed a delta,"which 
 advanced gradually from the base of Monte Calvo to a dis- 
 tance of nine miles from the original shore. If subsequently 
 this part of the Alps and bed of the sea were raised 700 feetj 
 the delta may have emerged, a deep channel may then have 
 been cut through it by the river, and the coast may at the 
 same time have acquired its present configuration. 
 
 It is well known that the torrents and streams which now 
 
CAUSES Oi" DIAGOKAi STRATIFICATION. 45 
 
 descend from the Alpine declivities to the shore, bring down 
 annually, when the snow melts, vast quantities of shingle and 
 sand, and then, as they subside, fine mud, while in summer 
 they are nearly or entirely dry; so that it may be safely as- 
 sumed that deposits like those of the valley of the Magnan, 
 consisting of coarse gravel alternating with tine sediment, 
 are still in progress at many points, as, for instance, at. the 
 mouth of the var. They must advance upon the Mediter- 
 ranean in the form of great shoals terminating in a steep 
 talus ; such being the original mode of accumulation of all 
 coarse materials conveyed into deep water, especially where 
 they are composed in great part of pebbles, which can not 
 be transported to indefinite distances by currents of mode- 
 rate velocity. By inattention to facts and inferences of this 
 kind, a very exaggerated estimate has sometimes been made 
 of the supposed depth of the ancient ocean. There can be 
 no doubt, for example, that the strata a, Fig. 7, or those neai- 
 est to Monte Calvo, are older than those indicated by h, and 
 these again were formed before c y but the vertical depth of 
 gravel and sand in any one place can not be proved to 
 amount even to 1000 feet, although it may perhaps be much 
 greater, yet probably never exceeding at any point 3000 or 
 4000 feet. But were we to assume that all the strata were 
 
 Fig. 8. 
 
 Slab of ripple-marked (New Eed) sandstone from Cheshire. 
 
 once horizontal, and that their present dip or inclination was 
 due to subsequent movements, we should then be forced to 
 conclude that a sea several miles deep had been filled up 
 with alternate layers of mud and pebbles thrown down one 
 upon another. 
 
46 ELEMENTS OF GEOLOGY. 
 
 In the locality now tinder consideration, situated a few 
 miles to the west of Nice, there are many geological data, 
 the details of which can not be given in this place, all lead- 
 ing to the opinion that, when the deposit of the Magnan was 
 formed, the shape and outline of the Alpine declivities and 
 the shore greatly resembled what we now behold at many 
 points in the neighborhood. That the beds a, b, c, d are of 
 comparatively modern date is proved by this fact, that in 
 seams of loamy marl intervening between the pebbly beds 
 are fossil shells, half of which belong to species now living 
 in the Mediterranean. 
 
 Ripple-mark. — The ripple-mark, so common on the surface 
 of sandstones of all ages (see Fig. 8), and which is so often 
 seen on the sea-shore at low tide, seems to originate in the 
 drifting of materials along the bottom of the water, in a 
 manner very similar to that which may explain the inclined 
 layers above described. This ripple is not entirely confined 
 to the beach between high and low water mark, but is also 
 produced on sands which are constantly covered by water. 
 Similar undulating ridges and furrows may also be some- 
 times seen on the surface of drift snow and blown sand. 
 
 The ripple-mark is usually an indication of a sea-beach, or 
 of water from six to ten feet deep, for the agitation caused 
 by waves even during storms extends to a very slight depth. 
 To this rule, however, there are some exceptions, and recent 
 ripple-marks have been observed at the depth of 60 or 10 
 feet. It has also been ascertained that currents or large 
 bodies of water in motion may disturb mud and sand at the 
 depth of 300 or even 450 feet.* Beach ripple, however, may 
 usually be distinguished ■ from current ripple by frequent 
 changes in its direction. In a slab of sandstone, not more 
 than an inch thick, the furrows or ridges of an ancient ripple 
 may often be seen in several successive laminae to run to- 
 wards different points of the compass. 
 
 • Darwin, Vole. Islands, p. 134. 
 
DEPOSITION INDICATED BY FOSSILS. 47 
 
 CHAPTER m. 
 
 ARHANGEMENT OF FOSSILS IN STEATA. — FEESH-WATBE AND 
 MARINE FOSSILS. 
 
 Successive Deposition indicated by Fossils. — Limestones foi-med of Corals 
 and Shells. — ^Proofs of gradual Increase of Strata derived from Fossils. — 
 Serpula attached to Spatangus. — Wood bored by Terediha, — Tripoli form- 
 ed of Infusoria. — Chalk derived principally from Organic Bodies. — Dis- 
 tinction of Fresh-water from Marine Formations. — Genera of Fresh- water 
 and Land Shells. ^Rules for recognizing Marine Testacea. — Gyrogonite 
 and Chara. — Fresh-water Fishes. — Alternation of Marine and Fresh- water 
 Deposits. — ^Lym-Fiord. 
 
 Having in the last chapter considered the forms of strati- 
 fication so far as they are determined by the arrangement 
 of inorganic matter, we may now turn our attention to the 
 manner in which organic remains are distributed through 
 stratified deposits. We should often be unable to detect 
 any signs of stratification or of successive deposition, if par- 
 ticular kinds of fossils did not occur here and there at cer- 
 tain depths in the mass. At one level, for example, univalve 
 shells of some one or more species predominate ; at another, 
 bivalve shells ; and at a third, corals ; while in some forma- 
 tions we find layers of vegetable matter, commonly derived 
 from land plants, separating strata. 
 
 It may appear inconceivable to a beginner how mountains, 
 several thousand feet thick, can have become full of fossils 
 from top to bottom ; but the difficulty is removed, when he 
 reflects on the origin of stratification^ as explained in the 
 last chapter, and allows sufficient time for the accumulation 
 of Sediment. He must never lose sight of the fact that, dur- 
 ing the process of deposition, each separate layer was once 
 the uppermost, and immediately in contact with the water 
 in which aquatic animals lived. Each stratum, in fact, how- 
 ever far it may now lie beneath the surface, was once in the 
 state of shingle, or loose sand or soft mud at the bottom of 
 the sea, in which shells and other bodies easily became en- 
 veloped. 
 
 Bate of Deposition indicated by Fossils. — By attending to 
 the nature of these remains, we are often enabled to deter- 
 mine whether the deposition was slow or rapid, whether it 
 took place in a deep or shallow sea, near the shore or far 
 
48 
 
 ELEMENTS OF GEOLOGT. 
 
 Fig. ■9. 
 
 from land, and whethej; the water was salt,braokish, or fresh. 
 Some limestones consist almost exclusively of corals, and in 
 many cases it is evident that the present position of each 
 fossil zoophyte has been determined by the manner in which 
 it grew originally. The axis of the coral, for example, if its 
 natural growth is erect, still remains at right angles to the 
 plane of stratification; If the stratum be now horizontal, 
 the round spherical heads of certain species continue upper- 
 most, and their points of attachment are directed down- 
 ward. This arrangement is sometimes repeated throughout 
 
 a great succession of strata. 
 From what we know of the 
 growth of similar zoophytes 
 in modern reefs, we infer 
 that the rate luf increase was 
 extremely slow, and some of 
 the fossils must have flour- 
 ished for ages like forest- 
 trees, before they atta.ined 
 so large a size. Duiring 
 these ages, the water must 
 have been clear and trans- 
 parent, for such corals can 
 not live in turbid watei\ 
 
 In like manner, when we 
 see thousands of full-grown 
 shells dispersed everywhere 
 throughout a long series of 
 strata, we can not doiibt that 
 time was required for the 
 multiplication of successive 
 generations ; and the evi- 
 dence of slow accumulation 
 is rendered more striking 
 from the proofs, so often discovered, of fossil bodies having 
 lain for atime on the floor of the ocean after death before they 
 were imbedded in sediment. Nothing, for example, is more 
 common than to see fossil oysters in clay, with serpulse, or 
 barnacles (acorii-shells), or corals, and other creatures; at- 
 tached to the inside of the valves, so that the mollusk was 
 certainly not buried in argillaceous mud the moment it died. 
 There must have been an interval during which it was still 
 surrounded with clear water, when the creatures whose re- 
 mains now adhere to it grew from an embryonic to a mature 
 state. Attached shells which are merely external, like some 
 of the serpulae {a) in Fig. 9, may often have grown upon aij 
 
 Fossil GrypTima, covered both on the out- 
 side and inside with fossil serpulse. 
 
DEPOSITION INDICATED BY FOSSILS. 
 
 49 
 
 oyster or other shell while the animal within was still living ; 
 but if they are found on the inside, it c6uld only happen after 
 the death of the inhabitant of the shell which aifords the sup- 
 port. Thus, in Pi^. 9, it will be seen that two serpulse have 
 grown on the interior, one of them exactly on the place where- 
 the adductor muscle of the Gryphoea (a "kind of oyster) was 
 fixed. 
 
 Some fossil shells, even if simply attached to the outside 
 of others, bear full testimony to the conclusion above al- 
 luded to, namely, that an interval elapsed between the 
 death of the creature to whose shell they adhere, and the 
 burial of the sanie in mud or sand". The seai-urchins, or 
 Mchini, so abundant in white chalk, afford a good illustra- 
 tion. It is well known that these animals, when living, are 
 invariably covered with spines supported by rows of tuber- 
 des. These last are only seen after the death of the sea- 
 urchin, when the spines have dropped off. In Fig. 11a liv- 
 ing species of Spatangus, common on our coast, is represent- 
 ed with one-half of its shell stripped of the spines. In 
 Fig. 10a fossil of a similar and allied genus from the white 
 chalk of Ensfland shows the naked surface which the indi- 
 
 Fig.lO. 
 
 Fig. IL 
 
 Kg. 12. 
 
 Serpula attacliM to 
 a fossil Micraster 
 from the chalk. 
 
 Eecent Spatancjiis witli the spines 
 removed from one. side. 
 
 &. Spine and tubercles, natnral 
 size, 
 
 a. fhe same magnified. 
 
 a..Anaiu:hytea from the 
 .chajfe with lower 
 valve of Crania at- 
 tached. 
 
 6. tTpper valve of Cra- 
 nia detached. 
 
 viduals of this family exhibit when denuded of their bris- 
 tles. The fall-grown Serpula, therefore, which now adheres 
 externally, could not have begun to grow till the Micraster 
 had died', aiid the spines became detached; 
 
 Now the series of events here attested by a single fossil 
 may 1)6! can-ied a step farther. Thus, foi' example, we oft- 
 en meet with a sea-urchin {Ananchytes) in the cjialk (see 
 Fig. 12) which has fixed to it the lower valve of a Crania, 
 a genus of bivalve inollusca. The upper valve (6, Fig. 12) 
 is almpst invariably wanting, though occasionally found in 
 a perfect . state of preservation in white chalk at some dis- 
 tance.' In this case, we see clearly that the sea-urchin first 
 
 • •' - ' 3 ■ .. 
 
50 
 
 ELEMENTS 0¥ GEOLOGY. 
 
 lived from youtli to age, then died and lost its spines, which 
 were carried away. Then the young Crania adhered to the 
 hared shell, grew and perished in its turn ; after which the 
 upper valve was separated from the lower before the Anan- 
 chytes became enveloped in chalky mud. 
 
 It may be well to mention one more illustration of the 
 manner in which single fossils may sometimes throw light 
 on a former state of things, both in the bed of the ocean and 
 on some adjoining land. We meet with many fragments of 
 wood bored by ship-worms at various depths in the clay on 
 which London is built. Entii-e branches and stems of trees, 
 several feet in length, are sometimes found drilled all over 
 by the holes of these borers, the tubes and shells of the mol- 
 lusk still remaining in the cylindrical hollows. In Fig. 14, e, 
 
 Kg. 13; 
 
 Fossil ana recent wood drilled l)y perforating Mollusca. 
 
 Pig. 13. a. Fossil wood from London clay, bored by Teredina. 
 
 b. Shell and tnbe of Teredina persormta, the right-hand figure the ventral. 
 
 the left the dorsal view. 
 
 Fig. 14. e. Recent wood bored by Toredo. 
 
 d. Shell and tube of Teredo navalis, from the same. 
 
 c. Anterior and posterior view of the valves of same detached from the tube. 
 
 a representation is given of a piece of recent wood pierced 
 by the Teredo navalis, or common ship-worm, which destroys 
 wooden piles and ships. When the cylindrical tube d has 
 been extracted from the wood, the valves are seen at the 
 larger or anterior extremity, as shown at c. In like man- 
 ner, a piece of fossil wood (a, Fig. 13) has been perforated 
 by a kindred but extinct genus, the Teredina of Lamarck. 
 Ihe calcareous tube of this mollusk was united and, as it 
 were, soldered on to the valves of the shell (5), which there- 
 tore can not be detached from the tube, like the valves of 
 
IlfFUSORIA OF TKIPOLI. 51 
 
 the recent Teredo. The wood in this fossil specimen is now 
 converted into a stony mass, a mixture of clay and lime ; 
 but it must once have been buoyant and floating in the sea, 
 when the TeredinoB lived upon, and perforated it. Again, 
 before the infant colony settled upon the drift wood, part of 
 a tree must have been floated down to the sea by a river, 
 uprooted, perhaps, by a flood, or torn off and cast into the 
 waves by the wind: and thus our thoughts are carried 
 back to a prior period, when the tree grew for years on dry 
 land, enjoying a fit soil and climate. 
 
 Strata of Organic Origin.— It has been already remarked 
 that there are rocks in the interior of continents, at various 
 depths in the earth, and at great heights above the sea, al- 
 most entirely made up of the remains of zoophytes and tes- 
 tacea. Such masses may be compared to modern oyster- 
 beds and coral-reefs; and, like them, the rate of increase 
 must have been extremely gradual. But there are a varie- 
 ty of stope deposits in the earth's crust, now proved to have 
 been derived from plants* and animals of which the organic 
 origin was not suspected until of late years, even by natural- 
 ists. Great sui-prise was therefore created some years since 
 by the discovery of Professor Ehrenberg, of Berlin, that a 
 certain kind of siliceous stone, called tripoli, was entirely 
 composed of millions of the remains of organic beings, which 
 were formerly referred to microscopic Infusoria, but which 
 are now admitted to be plants. They abound in rivulets, 
 lakes, and ponds in England and other countries, and are 
 termed Diatomacese by those naturalists who believe in 
 their vegetable origin. The subject alluded to has long 
 been i well known in the arts, under the name of infusorial 
 earth or mountain meal, and is used in the form of powder 
 for polishing stones and metals. It has been procui-ed, 
 among other places, from the mud of a lake at Dolgelly, in 
 IS"orth Wales, and fi'om Bilin, in Bohemia, in which latter 
 place a single stratum, extending over a wide area, is no 
 less than fourteen feet thick. This stone, when examined 
 with a powei'ful microscope, is found to consist of the silic- 
 eous plates or frustules of the above-figured Diatomacese, 
 united together without any visible cement. It is difficult 
 to convey an idea of their extreme minuteness ; but Ehren- 
 berg estimates that in the Bilin tripoli there are 41,000 mil- 
 lions of individuals of the Gaittonella distans (see Fig. 16) in 
 every cubic inch (which weighs about 220 grains), or aboiit 
 1 8 7 millions in a single grain. At every stroke, therefore, that 
 we make with this polishing powder, several millions, perhaps 
 tens of millions, of perfect fossils are crushed to atoms. 
 
S2 ELEMENTS OF GEOLOGY. 
 
 Fig. 15. Fig. 10. Pig. IT. 
 
 :oj 
 
 o: 
 
 DjO 
 
 /IIITTTF1 ijJiMiiniliiiiiiin 
 ^' "" <^ 
 
 . wiiiiiilll I llli'lM I I lliiiiirB 
 
 6 
 
 Gaillonella . Gctillonella Bacillaria parodoxa. 
 
 /erruginm, Etib. disiam,'Bhh, a. Front view. 6. Side view. 
 
 A well-known substance, called bog-iron oi-e, often met 
 With in peat-mosses, has often been shown by Ehrenberg to 
 consist of innumerable articulated threads, of a yellow ochre 
 color, composed of silica, argillaceous matter, and peroxide 
 of iron. These threads are the cases of a minute microscop- 
 ic body, called Oaillonella ferruginea (Fig. 15), associated 
 with the siliceous frustules of other fresh- water algae. Lay- 
 ers of this iron ore occundng in Scotch peat bogs are often 
 called "the pan," and are sometimes of economical value. 
 
 It is clear that much time must have been required for the 
 accumulation of strata to which countless generations of Di- 
 atomacese have contributed their remains ; and these discov- 
 eries lead us naturally to suspect that other deposits, of 
 which the materials have been supposed to be inorganic, 
 may in reality be composed chiefly of microscopic oi-ganic 
 bodies. That this is the case with the white chalk, has oft- 
 en been imagined, and is now proved to be the fact. It has, 
 moreover, been lately discovered that the chambers into 
 which these Foraminifera are divided are actually often ■fill- 
 ed with thousands of well-pi-eserved organic bodieSj which 
 abound in every minute grain of chalk, and are especially 
 apparent in the white coating of flints, often accompanied 
 by innumerable needle-shaped spiculse of sponges (see Ohap. 
 
 The (lust we tread upon was once alive! — Btkon. 
 
 How faint an idea does this exclamation of the poet con- 
 vey of the real wonders of nature ! for here we discover 
 proofs that the calcareous and siliceous dust of which hills 
 are composed has not only been once alive, but almost every 
 particle, albeit invisible to the naked eye, still retains thje, or- 
 ganic structure which, at periods of time incalculably remote, 
 was impressed upon it by the powers of life. 
 
 Fresh-water and Marine Fossils.— Strata, whether deposited 
 in salt or fresh water, have the same forms ; but the imbed- 
 ded fossils are very different in the two cases, because the 
 aquatic animals which frequent lakes and rivers are distinct 
 from those inhabiting the sea. In the northern part of the 
 Isle of Wight formations of marl and limestone, more than 
 
FRESH-WATER AND MARINE FOSSIL 53 
 
 50 feet thick occur, in which the shells are of extinct species. 
 Yet we recognize their fresh-water origin, because they are 
 of the same genera as tliose now abounding in ponds, lakes, 
 and rivers, either in our own country; or in warmer latitudes. 
 
 In many parts of France — in Auvergne, for example — stra- 
 ta occur Off limestone, marl, and sandstone hundreds of feet 
 thick, which contain exclusively fresh-water and land shells, 
 together with the remains of terrestrial quadrupeds. The 
 number of land-shells scattered through some of these fresh- 
 water deposits is exceedingly great ; and there are districts 
 in Germany where the rocks scarcely contain any other fos- 
 sils except snail-shells (helices) ; as, for instance, the lime- 
 stone on the left bank of the Rhine, between Mayence and 
 Worms, at Oppenheim, Findheim, Budenheim, and other 
 places. In order to account for this phenomenon, the geol- 
 ogist has only to examine the small deltas of torrents which 
 enter the Swiss lakes when the waters are low, such as the 
 newly-formed plain Avhere the Kander enters the Lake of 
 Thun. He there sees sand and mud strewn over with innu- 
 merable dead land-shells, which have been brought down 
 from the valleys in the Alps in the preceding spring, during 
 the melting of the snows. Again, if we search the sands 
 on the borders of the Rhine, in the lower part of its course, 
 we find countless land-shells mixed with others of species 
 belonging to lakes, stagnant pools, and marshes. These in- 
 dividuals have been washed away from the alluvial plains 
 of the great river and its tributaries, some from mountain- 
 oiis regions, others from the low country. 
 
 Although fresh-water formations are often of great thick- 
 ness, yet they are usually very limited in area when com- 
 pared to marine deposits; just as lakes and estuaries are of 
 small dimensions in comparison with seas. 
 
 The absence of many fossil forms usually met with in ma- 
 rine strata, affords a useful negative indication of the fresh- 
 water origin of a formation. For example, there are no sea- 
 urchins, no corals, no chambered shells, such as the nautilus, 
 nor microscopic Foraminifera in lacustrine or fluviatile de- 
 posits. In distinguishing the latter from formations accu- 
 mulated in the sea, we are chiefly guided by the forms of 
 the mollusca. In a fresh-water deposit, the number of indi- 
 vidual shells is often as great as in a marine stratum, if not 
 greater; but there is a smaller variety of species and gen- 
 era. This might be anticipated, from the fact that the gen- 
 era and species of recent fresh-water and land shells are few 
 when contrasted with the marine. Thus, the genera of true 
 mollusca according to Woodward's system, excluding those 
 
54 
 
 ELEMENTS OF GEOLOGY. 
 Pig. 18. Fig. 19. 
 
 Oyrena oiovata, Sow. ; fossil. Hiints. 
 
 Cyrena {Corbicella) Jht/minalis, 
 Moll. ; fossil. Grays, Essex. 
 
 altogether extinct and those without shells, amount to 446 
 in number, of which the terrestrial and fresh-water genera 
 scarcely form more than a fifth.* 
 
 • Fig. 20 Fig. 21. Fig. 22. 
 
 Anodonta Cordierii; 
 D'Oi-b J fossil. Paris. 
 
 Anodonta laiimargincUa ; 
 recent. Bahin. 
 
 TTnio liUoralU ; Lam.; 
 recent. Auvergne. 
 
 Almost all bivalve shells, or those of acephalous moUusca, 
 are marine, about sixteen only out of 140 genera being fresh- 
 water. Among these last, the four most common forms, both 
 Pig, 23. recent and fossil, are Cyclas, Cyrena, 
 
 JJnio, and Anodonta (see figures) ; the 
 two first and two last of which are so 
 nearly allied as to pass into each other. 
 Lamarck divided the bivalve mol- 
 luscs into the Dimyary, or those having 
 two large muscular impressions in each 
 valve, as a 5 in the Cyclas, Fig. 18, and 
 Unio, Fig. 22, and the Monomyary, such 
 as the oyster and scallop, in which there 
 
 Gryphcm iru^rva, Sower.; ^^ O^Jy 0?^ of these impreSsionS as is 
 
 (c. areuata, Lam.) upper Seen in J^ig. 23. JJ^ow, as none of these 
 
 valve. Lias. ]^g^^ ^j. ^jj^ unimusoular bivalves, are 
 
 fresh-water,f we may at once presume a deposit containing 
 any of them to be marine. 
 
 * See Woodward's Manual of MoUusca, 1856. 
 
 t The fresh-water MuUeria, when young, forms a shigle exception to the 
 rule, as it then has two muscular impressions, but it has only one in the aduit 
 state. 
 
PRESH-WATER AND MARINE FORMATIONS. 55 
 
 I"ig- 24 Fig. 25. Fig. 20. 
 
 PlanmMseuomphalus, Sow. ; 
 fossil. Isle of Wight. 
 
 Bi'ong. ! fossil. Isle 
 of-mght. 
 
 Palwdina lento, Brand. ; 
 fossil. Isle of Wight. 
 
 The univalve shells most characteristic of fresh-water de- 
 posits are, Planorbis, Ziimncea, and Paludina. (See figures.) 
 
 Fig. 2T. Fig. 28. Fig. 29. Fig. 30. 
 
 =2^ 
 
 Succinea ainphihia, Ancylua velletia {A. 
 Drap. (S. putris, L.) ; elegans), Sow. ; fossil, 
 fossil. Loess, Rhiue. Isle of Wight 
 
 Valvata pisciTuir PhysahyjmO' 
 lie, Mull. ; fos- rum, Linae ; 
 
 sil. Grays, Es- recent. Isle 
 sex. of Wight. 
 
 But to these are occasionally added Physa, Succinea, Ancy- 
 lus, Valvata, Mblanopsis, Melania, PotamMes, and Neritina 
 (see figures), the four last being usually found in estuaries. 
 
 Fig. 31. Fig, 82. Fig. 33. 
 
 Pig. 34. 
 
 AuTieida; recent. Melania mquimda, Phym coliimnaris, Melanopais bucdnoidM, 
 Ava. Def. Paris basin. Desh. Paris basin. Feir. ; recent. Asia. 
 
 Some naturalists include NexitirM (Fig. 35) and the ma- 
 rine iVer* to (Fig. 36) in the same genus, it being scarcely 
 
 possible to dis- 
 tinguish the two 
 by good generic 
 characters. But, 
 as a general rule, 
 thefluviatilespe- 
 
 Fig. 36. 
 
 Fig. 36. 
 
 NetUina plobulus, Del 
 Fans basin. 
 
 Nerita gra/nulom, Desh. 
 Paris basin. 
 
56 
 
 ELEMENTS OF GEOLOGY. 
 
 Fig. 3T. cies are smaller, smoother, and more globular than 
 the marine ; and they have never, like the Neritm, 
 the inner margin of the outer lip toothed or crenu- 
 lated. (See Fig. 36.) 
 
 The Potamides inhabit the mouths of rivers in 
 warm latitudes, and are distinguishable from the 
 marine Cerithia by their orbicular and multispiral 
 opercula. The genus Auricula (Fig. 31) is amphib- 
 ious, frequenting swamps and marshes within the 
 influence of the tide. 
 
 The terrestrial shells are all univalves. The 
 most important genera among these, both in a re- 
 cent and fossil state, are Helix (Fig. 38), Cyclosto- 
 ma (Fig. 39), Fupa (Fig. 40), Clausilia (Fig. 41), 
 Bulimus (Fig. 42), Qlandina and Achatina. 
 
 AmpuUaria (Fig. 43) is another genus of shells 
 inhabiting rivers and ponds in hot countries. Many 
 fossil species formerly referred to this genus, and which have 
 bee» met with chiefly in marine formations, are now consid- 
 
 Fig. 38. 
 
 Fig. 39. 
 
 Fig. 40. ' Fig. 41. 
 
 Fig. 42. 
 
 Hdve Titronensis, Desh. ; Oycloetoma Ptipa Clausilia BuUmus lubrima, 
 
 Faluns, Tonraine. degans, tridem, bidens, Mull.; LoesB, 
 
 Mull. ; Drap. ; Drap. ; Rhine. 
 
 LoeBS. Loess. Loess. 
 
 ered by conchologists to belong to Natica and other marine 
 
 genera. 
 
 All univalve shells of land and fresh-water species, with 
 
 the exception of Melanopsis (Fig. 34), and Achatina, which 
 
 has a slight indentation, have entire mouths ; and this cir- 
 Fig.48. cumstance may often serve as a convenient 
 
 rule for distinguishing fresh-water from ma- 
 rine strata; since,. if any univalves occur of 
 which the mouths are not entire, we may 
 presume that the formation is marine. The 
 aperture is said to be entire in such shells 
 as the fresh-water Ampullaria and the land- 
 shells (Figs. 38-42), when its outline is not 
 
 "tom'the'jifiS"' ""te^'iipted by an indentation or notch, such 
 as that seen at b in Ancillaria (Fig. 45) ; or 
 
 is not prolonged into a canal, as that seen at a in Plmrotoma 
 
 (Fig. 44). 
 
FRESH-WATER AND MARINE FORMATIONS. 
 Mg.4*. Kg. 40. 
 
 51 
 
 PleurotoTim ex(yrta, Brand. 
 Upper and Middle Eocene. 
 Barton and Bracklesham. 
 
 ATicillaria »ubulata. Sow. 
 Barton clay. Eocene. 
 
 The mouths of a large proportion of the marine univalves 
 have these notches or canals, and almost all species are car- 
 nivorous; whereas neai'ly all testacea having entire mouths 
 are plant-eaters, whether the species be marine, fresh-water, 
 or terrestrial. 
 
 There is, however, one genus which aifords an occasion- 
 al exception to one of the above rules. The Potamides 
 (Fig. 37), a subgenus of Cerithium, although provided with 
 a short canal, comprises some species which inhabit salt, 
 others brackish, and others fresh water, and they are said to 
 be all plant-eaters. 
 
 Among the fossils very common in fresh-water deposits 
 are the shells of Gypris, a minute bivalve crustaceous ani- 
 mal.* Many minute living species of this genus swarm in 
 lakes and stagnant pools in Great Britain ; but their shells 
 are not, if considered separately, conclusive as to the fresh- 
 water origin of a deposit, because the majority of species in 
 another kindred genus of the. same order, the Cytherina of 
 Lamarck, inhabit salt-water; and, although the animal dif- 
 fers slightly, the shell is scarcely distinguishable from that 
 of the Cypris. 
 
 Fresh-water Fossil Plants. — ^The seed-vessels and stems of 
 Chara, a genus of aquatic plants, are very frequent in fresh- 
 water strata. These seed-vessels were called, before their 
 true nature was known, gyrogonites, and were supposed to 
 be foraminiferous shells. (See Fig. 46, a.) 
 
 The Gharae, inhabit the bottom of lakes and ponds, and 
 flourish mostly where the water is charged with carbonate 
 of lime. Their seed-vessels are covered with a very tough 
 integument, capable of resisting decomposition; to which 
 circumstance we may attribute their abundance in a fossil 
 * For figures of fossil species of Pnrbeck, see below, Chap. XIX. 
 3* 
 
58 
 
 ELEMENTS OF GEOLOGY. 
 
 State. The annexed figure (Fig. 47) represents a branch 
 of one of many new species found by Professor Amici in 
 the lakes of Northern Italy. The seed-vessel in this plant 
 is more globular than in the British CharcB, and therefore 
 more nearly resembles in form the extinct fossil species 
 found in England, France, and other countries. The stems, 
 as well as the seed-vessels, of these plants occur both in 
 modern shell-marl and in ancient fresh-water formations. 
 They are generally composed of a large central tube sur- 
 
 Fig. 46. 
 
 Fig. 47. 
 
 Chara Tnedicagimtla ; 
 
 fossil. Uppev Eocene, 
 
 IsleofWiglit. 
 
 u. Seed-vessel magniflefl 
 
 20 diameters. 
 b. Stem, magnified. 
 
 Chara elttstica ; recent. Italy. 
 
 a. Sessile seed-vessel between the divisions 
 
 of the leaves of the female plant. 
 
 b. Magnified transverse section of a branch, 
 
 with five seed-vessels, seen from below 
 upward. 
 
 rounded by smaller ones; the whole stem being divided at 
 certain intervals by transverse partitions or joints. (See 
 b, Fig. 46.) 
 
 It is not uncommon to meet with layers of vegetable mat- 
 ter, impressions of leaves, and branches of trees, in strata 
 containing fresh-water shells ; and we also find occasionally 
 the teeth and bones of land quadrupeds, of species now un- 
 known. The manner in which such remains are occasional- 
 ly carried by rivers into lakes, especially during floods, has 
 been fully treated of in the " Principles of Geology." 
 
 Fresh-water and Marine Fish. — The remains of fish are oc- 
 casionally useful in determining the fi-esh-water origin of 
 strata. Certain genera, such as carp, perch, pike, and loach 
 {Cyprinus, Perca, Esox, and Cohitis), a.« also Xiebias, being 
 peculiar to fresh water. Other genera contain some fresh- 
 water and some marine species, as Cotttos, Mugil, and An- 
 guilla, or eel. The rest are either common to rivers and the 
 sea, as the salmon; or are exclusively characteristic of salt 
 water. The above observations respecting fossil fishes are 
 applicable only to the more modern or tertiary deposits ; 
 
FRESH-WATER AND M4RINE FORMATIONS. 69 
 
 for in the more ancient rocks the forms depart so widely 
 from those of existing fishes, that it is very diJfBcult, at least 
 in the present state of science, to derive any positive infor- 
 mation from ichthyolites respecting the element in which 
 strata were deposited. 
 
 The alternation of marine and fi'esh-water formations, both 
 on a small and large scale, are facts well ascertained in ge- 
 ology. When it occurs on a small scale, it may have arisen 
 from the alternate occupation of certain spaces by river-wa- 
 ter and the sea ; for in the flood season the river forces back 
 the ocean and freshens it over a large area, depositing at the 
 same time its sediment ; after which the salt water again re- 
 turns, and, on resuming its former place, brings with it sand, 
 mud, and marine shells. 
 
 There are also lagoons at the mouth of many rivers, as the 
 Kile and Mississippi, which are divided off by bars of sand 
 from the sea, and which are filled with salt and fresh water 
 by turns. They often communicate exclusively with the 
 river for months, years, or even centuries ; and then a breach 
 being made in the bar of sand, they are for long periods filled 
 with salt-water. 
 
 Lym-Fiord. — The Lym-Fiord in Jutland offers an excellent 
 illustration of analogous changes ; for, in the course of the 
 last thousand years, the western extremity of this long frith, 
 which is 120 miles in length, including its windings, has been 
 four times fresh and four times salt, a bar of sand between it 
 and the ocean having been often formed and removed. The 
 last irruption of salt water happened in 1824, when the North 
 Sea entered, killing all the fresh-water shells, fish, and plants; 
 and from that time to the present, the sea-weed Fucus vesi- 
 eulosus, together with oysters and other marine mollusca, 
 have succeeded the Cyclaa, LymnoBa, Paludina, and Charm* 
 
 But changes like these in the Lyra-Fiord, and those before 
 mentioned as occurring at the mouths of great rivers, will 
 only account for some cases of marine deposits of partial ex- 
 tent resting on fresh-water strata. When we find, as in the 
 south-east of England (Chap. XVIII.), a great series of fresh- 
 water beds, 1000 feet in thickness, resting upon marine for- 
 mations and again covered by other rocks, such as the creta- 
 ceous, more than 1000 feet thick, and of deep-sea origin, we 
 shall find it necessary to seek for a different explanation of 
 the phenomena. 
 
 * See Principles, Index, "Lyra-Fiord." 
 
60 ' ELEMENTS OF GEOLOGY. 
 
 CHAPTER IV. 
 
 CONSOLIDATION OF STRATA AND PETRIFICATION OF FOSSILS. 
 
 Chemical and Mechanical Deposits.— Cementing together of Particles.— 
 Hardening by Exposure to Air. — Concretionary Nodules. — Consolidatinp; 
 Effects of Pressure: — Mineralization of Organic Remains. — Impressions 
 and Casts: how formed. — Fossil "Wood. — Goppert's Experiments.^-Pre- 
 cipitation of Stony Matter most rapid where Putrefaction is going on. — 
 Sources of Lime and Silex in Solution. 
 
 Having spoken in the preceding chapters of the characters 
 of sedimentary formations, both as dependent on the deposi- 
 tion of inorganic matter and the distribution of fossils, I may- 
 next treat of the consolidation of stratified rocks, and the pet- 
 rification of imbedded organic remains. 
 
 Chemical and Mechanical Deposits. — A distinction has been 
 made by geologists between deposits of a mechanical, and 
 those of a chemical, origin. By the name mechanical are 
 designated beds of mud, sand, or pebbles produced by the 
 action of running water, also accumulations of stones and 
 scorJsB thrown out by a volcano, which have fallen into their 
 present place by the force of gravitation. Bnt the matter 
 which forms a chemical deposit has not been mechanically 
 suspended in watei', but in a state of solution until separated 
 by chemical action. In this manner carboiiate of lime is oc- 
 casionally precipitated upon the bottom of lakes in a solid 
 form, as may be well seen in many parts of Italy, where min- 
 eral springs abound, and where the calcareous stone, called 
 travertin, is deposited. In these springs the lime is usually 
 held in solution by an excess of carbonic acid, or by heat if 
 it be a hot spring, until the water, on issuing from the earth, 
 cools or loses part of its acid. The calcareous matter then 
 falls down in a solid state, incrusting shells, fragments of 
 wood and leaves, and binding them together. 
 
 That similar travertin is formed at some points in the bed 
 of the sea where calcareous springs issue can not be doubt- 
 ed, but as a general rule the quantity of lime, according to 
 Bisehoff, spread through the waters of the ocean is very small, 
 the free carbonic acid gas in the same waters being five 
 times as much as is necessary to keep the lime in a fluid 
 state. Carbonate of lime, therefore, can rarely be precipita- 
 ted at the bottom of the sea- by chemical action alone, bnt 
 
CONSOLIDATION OF STRATA. 61 
 
 must be produced by vital agency as in the case of coral 
 reefs. 
 
 In such reefs, large masses of limestone are formed by the 
 stony skeletons of zoophytes ; and these, together with shells, 
 become cemented together by carbonate of lime, part of 
 which is probably furnished to the sea^water by the decom- 
 position of dead corals. Even shells, of which the animals 
 are stiU living on these reefs, are very commonly found to be 
 incrusted over with a hard coating of limestone. 
 
 If sand and pebbles are carried by a river into the sea, and 
 these are bound together immediately by carbonate of lime, 
 the deposit may be described as ©f a mixed origin, partly 
 chemical, and partly mechanical. 
 
 Now, the remarks ah-eady made in Chapter II. on the orig- 
 inal horizontality of strata are strictly applicable to mechan- 
 ical deposits, and only partially to those of a mixed nature. 
 Such as are purely chemical may be formed on a very steep 
 slope, or may even incrust the vertical walls of a fissure, and 
 be of equal thickness throughout ; but such deposits are of 
 small'extent, and for the most part confined to vein-stones. 
 
 Consolidation of Strata. — It is chiefly in the case of calca- 
 reous rocks that solidification takes place at the time of dep- 
 osition. But there are many deposits in which a cementing 
 process comes into operation long afterwards. We may 
 sometimes observe, where the water of ferruginous or calca- 
 reous springs has flowed through a bed of sand or gravel, 
 that iron or carbonate of lime has been deposited in the in- 
 terstices between the graiiis or pebbles, so that in certain 
 places the whole has been bound together into a stone, the 
 same set of strata remaining in other parts loose and inco^ 
 herent. 
 
 Proofs of a similar cementing action are seen in a rock at 
 Kelloway, in Wiltshire. A peculiar band of sandy strata be- 
 longing to the group called Oolite by geologists may be 
 traced through several counties, the sand being for the most 
 part loose and unconsolidated, but becoming stony near Kel- 
 loway. In this district there are numerous fossij shells which 
 have decomposed, having for the most part left only their 
 feasts. The calcareous matter hence derived has evidently 
 served, at some former period, as a cement to the siliceous 
 grains of sand, and thus a solid sandstone has been produced. 
 If we take fragments of many other argillaceous grits, re- 
 taining the casts of shells, and plunge them into dilute mu- 
 riatic or other acid, we see them imniediately changed into 
 common sand and mud ; the cement of lime, derived from the 
 shells, having been dissolved by the acid. 
 
62 ELEMENTS OF GEOLOGY. 
 
 Traces of impressions and casts are often extremely faint. 
 In some loose sands of recent date we meet with shells in so 
 advanced a stage of decomposition as to crumble into pow- 
 der when touched. It is clear that water percolating such 
 strata may soon remove the calcareous matter of the shell ; 
 and unless circumstances cause the carbonate of lime to be 
 again deposited, the grains of sand will not be cemented to- 
 gether; in which case no memorial of the fossil will remain. 
 
 In what manner silex and carbonate of lime may become 
 widely diffused in small quantities through the waters which 
 permeate the earth's crust will be spoken of presently, when 
 the petrifaction of fossil bodies is considered ; but I may re- 
 mark here that such waters are always passing in the case 
 of thermal springs from hotter to colder parts of the interior 
 of the earth; and, as often as the temperature of the solvent 
 is lowered, mineral matter has a tendency to separate from it 
 and solidify. Thus a stony cement is often supplied to sand, 
 pebbles, or any fragmentary mixture. In some conglorner- 
 ates, like the pudding-stone of Hertfordshire (a Lower Eo- 
 cene deposit), pebbles of flint and grains of sand are united 
 by a siliceous cement so firmly, that if a block be fractured, 
 the rent passes as readily through the pebbles as through 
 the cement. 
 
 It is probable that many strata became solid at the time 
 when they emerged from the waters in which they were de- 
 posited, and when they first formed a part of the dry land. 
 A well-known fact seems to confirm this idea : by far the 
 greater number of the stones used for building and road- 
 making are much softer when first taken from the quarry 
 than after they have been long exposed to the air; and 
 these, when once dried, may afterwards be immersed for 
 any length of time in water without becoming soft again. 
 Hence it is found desirable to shape the stones "which are to 
 be used in architecture while they are yet soft and wet, and 
 while they contain their " quarry- water," as it is called; 
 also to break up stone intended for roads when soft, and 
 then leave it to dry in the air for months that it may hard- 
 en. _ Such induration may perhaps be accounted for by sup- 
 posing the water, which penetrates the minutest pores of 
 rocks, to deposit, on evaporation, carbonate of lime, iron, si- 
 lex, and other minerals previously held in solution, and there- 
 by to fill up the pores partially. These particles, on crystal- 
 lizing, would not only be themselves deprived of freedom of 
 motion, but would also bind together other portions of the 
 rock which before were loosely aggregated. On the same 
 principle wet sand and mud become as hard as stone when 
 
CONSOLIDATION OF STKATA. 63 
 
 frozen ; because one ingredient of the mass, namely, the wa- 
 ter, has crystallized, so as to hold fiiinly together all the sep- 
 arate particles of which the loose mud and sand were com- 
 posed. 
 
 Dr. MacCuUoch mentions a sandstone in Skye, which may 
 be moulded like dough when first found; and some simple 
 minerals, which are rigid and as hard as glass in our cabin- _ 
 ets, are often flexible and soft in their native beds : this is 
 the case with asbestos, sahlite, tremolite, and chalcedony, 
 and it is reported also to hajjpeu in the case of the beryl.* 
 
 The marl recently deposited at the bottom of Lake Supe- 
 rior, in North America, is soft, and often filled with fresh- 
 water shells ; but if a piece be taken up and dried, it be- 
 comes so hard that it can only be broken by a smart blow 
 of the hammer. If the lake, therefore, was drained, such a 
 deposit would be found to consist of strata of marlstone, 
 like that observed in many ancient European formations, 
 and, like them, containing fresh-water shells. 
 
 Concretionary Structure. — It is probable that some of the 
 heterogeneous materials which rivers transport to the sea 
 may at once set under water, like the artificial mixture call- 
 ed pozzolana, which consists of fine volcanic sand charged 
 with about twenty per cent, of oxide of iron, and the addi- 
 tion of a small quantity of lime. This substance hardens, 
 and becomes a solid stone in water, and was used by the 
 Romans in constructing the foundations of buildings in the 
 sea. Consolidation in such cases is brought about by the ac- 
 tion of chemical aflSnity on finely comminuted matter previ- 
 ously suspended in water. After deposition similar particles 
 seeni often to exert a mutual attraction on each other, and 
 congregate together in particular spots, forming lumps, nod- 
 ules, and concretions. Thus in many argillaceous deposits 
 there are calcareous balls, or spherical concretions, ranged in 
 layers parallel to the general Fig. 48. 
 
 stratification; an arrangement 
 which took place after the 
 shale or marl had been thrown 
 down in successive laminse; for 
 
 these lammse are often trace- c.icaieons nodules in Lias, 
 
 able through the concretions, 
 remaining parallel to those of the surrounding unconsoli- 
 dated rock. (See Fig. 48.) Such nodules of limestone have 
 often a shell or other foreign body in the centre. 
 
 Among the most remarkable examples of concretionary 
 structure are those described by Professor Sedgwick as 
 * Dr. MacCuUoch, Syst. of Geol., vol. i., p. 123. 
 
64 ELEMENTS OF GEOLOGY. 
 
 abounding in the magne^ian limestone of the north of Eng- 
 land. The spherical balls are of various sizes, from that of a 
 pea to a diameter of several feet, and they have both a con- 
 centric and radiated structure, while at the same time the 
 laminffi of original deposition pass uninterruptedly through 
 them. In sorne cliffs this limestone resembles a great irreg- 
 ular pile of cannon-balls. Some of the globular masses have 
 their centre in one stratum, while a portion of their exterior 
 
 passes through to the stratum 
 '^" - 1 above or below. Thus the larger 
 
 spheroid in the annexed section 
 (Fig. 49) passes from the stratum 
 h upward into a. In this instance 
 we must suppose the deposition 
 
 Spheroidal concretiune in magneslan gf ^ series of minor layers, first 
 
 forming the stratum b, and aftei"- 
 wards the incumbent stratum a; then a movement of the 
 particles took place, and the carbonates of lime and magne- 
 sia separated from the more impure and mixed matter form- 
 ing the still unconsolidated parts of the stratum. Crystal- 
 ization, beginning at the centre, must have gone on forming 
 concentric coats around the original nucleus without intel^• 
 fering with the laminated strncture of the rock. 
 
 When the particles of rocks have been thus re-arranged 
 by chemical forces, it is sometimes difficult or impossible to 
 ascertain whether certain lines of division are due to original 
 Fig. 50. deposition or to the subsequent 
 
 aggregation of similar particles. 
 Thus suppose three strata of grit, 
 A, B, C, are charged unequally 
 with calcareous matter, and that 
 B is the most calcareous. If con- 
 solidation takes place in B, the concretionary action may 
 spread upward into a part of A, where the carbonate of lime 
 is more abundant than in the rest ; so that a mass, d e f, 
 forming a portion of the superior stratum, becomes united 
 with B into one solid mass of stone. The original line of 
 division, d e, being thus effaced, the line df would generally 
 be considered as the surface of the bed B, though not strictly 
 a true plane of stratification. 
 
 Pressure and Heat. — When sand and mud sink to the bot- 
 tom of a deep sea, the particles are not pressed down by the 
 enormous weight of the incumbent ocean ; for the water, 
 which becomes mingled with the sand and mud, resists press- 
 ure with a force equal to that of the column of fluid above. 
 The same happens in regard to organic remains which are 
 
 A 
 
 rf^^-r 
 
 
 r 1 1 II II 
 
 |I|'|B|I,(,' 
 
 lllllill 
 
 'l|l|i|i|i|,'l 
 
 C 
 
MINERALIZATION OF ORGANIC REMAINS. 65 
 
 filled with water under great pressure as they sink, other- 
 wise they would he immediately crushed to pieces and flat- 
 tened. ■• Nevertheless, if the materials of a stratum remain 
 in a yielding state, and do not set or solidify, they will be 
 gradually squeezed down by the weight of other materials 
 successively heaped upon them, just as soft clay or loose 
 sand on which a house is built may give way. By such 
 downward pressure particles of clay, sand, and marl may be- 
 conie packed into a smaller space, and be made to cohere to- 
 gether permanently. 
 
 . Analogous effects of condensation may arise when the 
 solid parts of the earth's crust are forced in various direc- 
 tions by those mechanical movements hereafter to be de- 
 scribed, by which strata have been bent, broken, and raised 
 above the level of the sea. Rocks of more yielding materi- 
 als must often have been forced against others previously 
 consolidated, and may thus by compression have acquired a 
 new structure. A recent discovery may help us to compre- 
 hend how fine sediment derived from the detritus of rocks 
 may be solidified by mere pressure. The graphite or " black 
 lead " of commei-ce having become very scarce, Mr. Brocke- 
 don contrived a method by which the dust of the. purer por- 
 tions of the mineral found in Borrowdale might be recom- 
 posed into a mass as dense and compact as native graphite. 
 The powder of graphite is first carefully prepared and freed 
 from air, and placed under a powerful preSs on a strong steel 
 die, with air-tight fittings. It is then struck several blows, 
 each of a power of 1000 tons; after which operation the 
 powder is so perfectly solidified that it can be cut for pen- 
 cils, and exhibits when broken the same texture as native 
 graphite. 
 
 But the action of heat at various depths in the earth is 
 probably the most po\*'erful of all causes iu hardening sedi- 
 mentary strata. To this subject I shall refer again when 
 treating of the metamorphi'c rocks, and of the slaty and joint- 
 ed structure. 
 
 Mineralization of Organic Remains. — ^The changes which 
 fossil organic bodies have undergone since they were first 
 imbedded in rocks, throw much light on the consolidation 
 of strata. Fossil shells in some modern deposits have been 
 scarcely altered in the course of centuries, having simply 
 lost a part of their animal matter. But in other cases the 
 shell has disappeared, and left an impression only of its ex- 
 terior, or, secondly, a cast of its ihterior'form, or, thirdly, a 
 cast of the shell itself, the original matter of which has been 
 removed. These different forms of fossilization may easily 
 
66 
 
 ELEMENTS OF GEOLOGY. 
 
 be understood if we examine the mud recently thrown out 
 from a pond or canal in which there are shells. If the mud 
 be argillaceous, it acquires consistency on drying, and on 
 breaking open a portion of it we find that each shell has 
 left impressions of its external form. If we then remove 
 the shell itself, we find within a solid nucleus of clay, hav- 
 ing the form of the interior of the shell. This form is often 
 ve°y different from that of the outer shell. Thus a cast 
 such as a, Fig. 51, commonly called a fossil screw, would 
 never be suspected by an inexperienced conchologist to he 
 the internal shape of the fossil univalve, b, Fig. 51. Nor 
 
 Fig. 51, 
 
 Fig. S2. 
 
 Phamanella Heddingtonenais, and cast 
 of the same. Coral Eag. 
 
 Pleurotomaria Anglica, 
 and cast. Lias. 
 
 should we have imagined at first sight that the shell a and 
 the cast b, Fig. 52, belong to one and the same fossil. The 
 reader will observe, in the last-mentioned figure {b, Fig. 52), , 
 that an empty space shaded dark, which the shell itself once 
 occupied, now intervenes between the enveloping stone and 
 the cast of the smooth interior of the whorls. In such cases 
 the shell has been dissolved and the component particles re- 
 moved by water percolating the rock. If the nucleus were 
 taken out, a hollow mould would remain, on which the ex- 
 ternal form of the shell with its tubercles and strise, as seen 
 in a, Fig. 52, would be seen embossed. Now if the space 
 alluded to between the nucleus and the impression, instead 
 of being left empty, has been filled up with calcareous spar, 
 flint, pyrites, or other mineral, we then obtain from the 
 mould an exact cast both of the external and internal form 
 of the original shell. In this manner silicified casts of shells 
 have been formed ; and if the mud or sand of the nucleus 
 happen to be incoherent, or soluble in acid, we can then pro- 
 cure in flint an empty shell, which in shape is the exact 
 counterpart of the original. This cast may be compared to 
 a bronze statue, representing merely the superficial form, 
 
MINERALIZATION OF OEGANIC REMAINS. 67 
 
 and not the internal organization ; but there is another de- 
 scription of petrifaction by no means uncommon, and of a 
 much more wonderful kind, which may be compared to cer- 
 tain anatomical models in wax, where not only the outward 
 forms and features, but the nerves, blood-vessels, and other 
 internal organs are also shown. Thus we find corals, origi- 
 nally calcareous, in which not only the general shape, but 
 also the minute and complicated internal organization is re- 
 tained in flint. 
 
 Such a process of petrification is still more remai'kably ex- 
 hibited in fossil wood, in which we often perceive not only 
 the rings of annual growth, but all the minute vessels and 
 medullary rays. Many of the minute cells and fibres of 
 plants, and even those spiral vessels which in the living veg' 
 etable can only be discovered by the microscope, are pre- 
 served. Among many instances, I may mention a fossil tree, 
 seventy-two feet in length, found at Gosforth, near New- 
 castle, in sandstone strata associated, with coal. By cutting 
 a transverse slice so thin as to transmit light, and magnify- 
 ing it about .fifty-five times, the texture, Pig.ss. 
 as seen in Fig. .53, is exhibited. A text- 
 ure equally minute and complicated has 
 been observed in the wood of large 
 trunks of fossil trees found in the Craig- 
 leith quarry near Edinburgh, where the 
 stone was not in the slightest degree 
 siliceous, but consisted chiefly of car- 
 bonate of lime, with oxide of iron, alu- Section of a tree tiom the 
 - ' _,, 11 , ' co»l-measnre8, magnifled 
 
 mina, and carbon. 1 he parallel rows (witham), showing text- 
 of vessels hei-e seen are the rings of an- "re of wood, 
 nual growth, but in one part they are imperfectly preserved, 
 the wood having probably decayed before the mineralizing 
 matter had penetrated to that portion of the tree. 
 
 In attempting to explain the process of petrifaction in 
 such cases, we may first assume that strata are very gener- 
 ally permeated by water charged with minute portions of 
 calcareous, siliceous, and other earths in solution. In what 
 manner they become so impregnated will be afterwards con- 
 sidered. If an organic substance is exposed in the open air 
 to the action of the sun and rain, it will in time putrefy, or be 
 dissolved into its component elements, consisting usually of 
 oxygen, hydrogen, nitrogen, and carbon. These will readily 
 be absorbed by the atmosphere or be washed away by rain, 
 so that all vestiges of the dead animal or plant disappear. 
 But if the same substances be submerged in water, they de- 
 compose more gradually ; and if buried in earth, still more 
 
 
68 ELEMENTS OF GEOLOGY. 
 
 slowly ; as in the familiar example of wooden piles or other 
 buried timber. Now, if as fast as each particle is set free by- 
 putrefaction in a -fluid or gaseous state, a particle equally mi- 
 nute of cai'bonate of lime, flint, or other mineral, is at hand 
 ready to be precipitated, we may imagine this inorganic mat- 
 ter to take the place just before left unoccupied by the or- 
 ganic molecule. In this manner a cast of the interior of cer- 
 tain vessels may first be taken, and afterwards the more sol- 
 id walls of the same may decay and suffer a like transmuta- 
 tion. Yet when the whole is lapidified, it may not form one 
 homogeneous mass of stone or metal. Some of the original 
 ligneous, osseous, or other organic elements may remain min- 
 gled in certain parts, or the lapidifying substance itself may 
 be differently colored at different times, or so crystallized as 
 to reflect light differently, and thus the texture of the orig- 
 inal body may be faithfully exhibited. 
 
 The student may perhaps ask whether, on chemical princi- 
 ples, we have any ground to expect that mineral matter will 
 be thrown down precisely in those spots where organic de- 
 composition is in progress ? The following curious experi- 
 ments may serve to illustrate this point : Professor Goppert 
 of Breslau, with a view of imitating the natural pi-ocess of 
 petrifaction, steeped a variety of animal and vegetable sub- 
 stances in waters, some holding siliceous, others calcareous, 
 others metallic matter in solution. He found that in the pe- 
 riod of a few weeks, or sometimes even days, the organic 
 bodies thus immersed were mineralized to a certain extent. 
 Thus, for example, thin vertical slices of deal, taken from the 
 Scotch fir {Pinus ■sylvestris), were immersed in a moderately 
 strong solution of sulphate of iron. When they had been 
 thoroughly soaked in the liquid for several days they were 
 dried and exposed to a red-heat until the vegetable matter 
 was burnt up and nothing remained but an oxide of iron, 
 which was found to have taken the form of the deal so ex- 
 actly that casts even of the dotted vessels peculiar to this 
 family of plants were distinctly visible under the microscope. 
 
 The late Dr. Turner observes, that when mineral matter is 
 in a " nascent state," that is to say, just liberated from a pre- 
 vious state of chemical combination, it is most ready to unite 
 with other matter, and form a new chemical compound. 
 Probably the particles or atoms just set free are of extreme 
 minuteness, and therefore move more freely, and are more 
 ready to obey any impulse of chemical affinity. Whatever 
 be the cause, it clearly follows, as before stated, that where 
 organic matter newly imbedded in sediment is decomposing, 
 there will chemical changes take place most actively. 
 
MINERALIZATION OF ORGANIC REMAINS. 69 
 
 An analysis was lately made of the water which was flow- 
 ing off from the rich mud deposited by the Hooghly River in 
 the Delta of the Gauges after the annual inundation. This 
 water was found to be highly charged with carbonic acid 
 holding lime in solution.* Now if newly-deposited mud is 
 thus proved to be peripeated by mineral matter in a state of 
 solution, it is not diffictilt to perceive that decomposing or- 
 ganic bodies, na,turaily imbedded in sediment, may as readily 
 become petrified as the substances artificially immersed by 
 Professor Goppert in various fluid mixtures. 
 
 It is well known that the watei-s of all springs are more or 
 less charged with earthy, alkaline, or metallic ingredients de- 
 rived from the rocks and mineral veins through which they 
 percolate. Silex is especially abundant in hot springs, and 
 carbonate of lime is almost always present in greater or less 
 quantity. The materials for the petrifaction of oi-ganic re- 
 mains are, therefore, usually at hand in a state of chemical 
 solution wherever organic remains are imbedded in new 
 strata. 
 
 * Piddington, Asiat. Research., vol. xTiii., p. 226. 
 
7Q ELEMENTS OF GEOLOGY. 
 
 CHAPTER V. 
 
 ELETATIOIT OF STRATA ABOVE THE SEA. — HOEIZONTAl AND 
 INCLINED STEATIFICATION. 
 
 Why the Position of Marine Strata, above the Level of the Sea, should be 
 referred to the rising up of the Land, not to the going down of the Sea.— 
 Strata of Deep-sea and Shallow-water Origin alternate.— Also Manne and 
 Fresh-water Beds and old Land Surfaces.— Vertical, incbned, and folded 
 Strata.— Anticlinal and Synclinal Cui-ves. —Theories to explain Lateral 
 Movements.— Creeps in Coal-mines.— Dip and Strike.— Structure of the 
 Jura.— Various Forms of Oatcrop.— Synclinal Strata forming Kidges.— 
 Connection of Fracture and Flexure of Rocks.— Inverted Strata.— Faults 
 described.— Supei-ficial Signs of the same obliterated by Denudation.— 
 Great Faults the Result of repeated Movements. — Arrangement and Di- 
 rection of parallel Folds of Strata.— Unconformability.— Overlapping 
 Strata. 
 
 Land has been raised, not the Sea lowered. — It has been al- 
 ready stated that the aqueous rocks containing marine fossils 
 extend over wide continental tracts, and are seen in mount- 
 ain chains rising to great heights above the level of the sea 
 (p. 29). Hence it follows, that what is now dry land was 
 once under water. But if we admit this conclusion, we 
 must imagine, either that there has been a genei-al lowering 
 of the waters of the ocean, or that the solid rocks, once cov- 
 ered by water, have been raised up bodily out of the sea, 
 and have thus become dry land. The earlier geologists, 
 finding themselves reduced to this alternative, embraced the 
 former opinion, assuming that the ocean was originally uni- 
 versal, and had gradually sunk down to its actual level, so 
 that the present islands and continents were left dry. It 
 seemed to them far easier to conceive that the water had 
 gone down, than that solid land had risen upward into its 
 present position. It was, however, impossible to invent any 
 satisfactory hypothesis to explain the disappearance of so 
 enormous a body of water throughout the globe, it being 
 necessary to infer that the ocean had once stood at what- 
 ever height marine shells might be detected. It moreover 
 appeared clear, as the science of geology advanced, that 
 certain spaces on the globe had been alternately sea, then 
 land, then estuary, then sea again, and, lastly, once more 
 habitable land, having remained in each of these states for 
 considerable periods. In order to account for such phenom- 
 
LAND RAISED, NOT THE SEA LOWERED. 71 
 
 ena without admitting any movement of the land itself, we 
 are required to imagine several retreats and returns of the 
 ocean ; and even then our theory applies merely to cases 
 where the marine strata composing the dry land are hori- 
 zontal, leaving unexplained those more common instances 
 where strata are inclined, curved, or placed on their edges, 
 and evidently not in the position in which they were first 
 deposited. 
 
 Geologists, therefore, were at last compelled to have re- 
 course to the doctrine that the solid land has been repeat- 
 edly moved upward or downward, so as permanently to 
 change its position relatively to the sea. There are several 
 distinct grounds for preferring this conclusion. First, it 
 will account equally for the position of those elevated mass- 
 es of marine origin in which the stratification remains hori- 
 zontal, and for those in which the strata are disturbed, 
 broken, inclined, or vertical. Secondly, it is consistent with 
 human experience that land should rise gradually in some 
 places and be depressed in others. Such changes have act- 
 ually occurred in our own days, and are now in progress, 
 having been accompanied in some cases by violent convul- 
 sions, while in others they have proceeded so insensibly as 
 to have been ascertainable only by the most careful scien- 
 tific observations, made at considerable intervals of time. 
 On the other hand, there is no evidence from human experi- 
 ence of a rising or lowering of the sea's level in any region, 
 and the ocean can not be raised or depressed in one place 
 without its level being changed all over the globe. 
 
 These preliminary remarks will prepare the reader to un- 
 derstand the great theoretical intei-est attached to all facts 
 connected with the position of strata, whether horizontal or 
 inclined, curved or vertical. 
 
 N"ow the first and most simple appearance is where strata 
 of marine origin occur above the level of the sea in horizon- 
 tal position. Such are the strata which we meet with in the 
 south of Sicily, filled with shells for the most part of the 
 same species as those now living in the Mediterranean. 
 Some of these rocks rise to the height of more than 2000 
 feet above the sea. Other mountain masses might be men- 
 tioned, composed of horizontal strata of high antiquity, 
 which contain fossil remains of animals wholly dissirnilar 
 from any now known to exist. In the south of Sweden, for 
 example, near Lake Wener, the beds of some of the oldest 
 fossiliferous deposits, called Silurian and Cambrian by geol- 
 ogists, occur in as level a position as if they had recently 
 formed part of the delta of a great river, and been left dry 
 
72 ELEMENTS OF GEOLOGY. 
 
 on the retiring of the annual floods. Aqueous rocks of 
 equal antiquity extend for hundreds of niiles over the lake- 
 district of North America, and exhibit in like manner a 
 stratification nearly undisturbed. The Table Mountain at 
 the Cape of Good Hope is another example of highly ele- 
 vated yet perfectly horizontal strata, no less than 3500 feet 
 in thickness, and consisting of sandstone of very ancient date. 
 
 Instead of imagining that such fossiliferous rocks were al- 
 ways at their present level, and that the sea was once high 
 enough to cover them, we suppose, them to have constituted 
 the ancient bed of the ocean, and to have been afterwards 
 uplifted to their present height. This idea, however start- 
 ling it may at first appear, is quite in accordance, as before 
 stated, with the analogy of changes now going on in certain 
 regions of the globe. Thus, in parts of Sweden, and the 
 shores and islands of the Gulf of Bothnia, proofs have been 
 obtained that the land is experiencing, and has experienced 
 for centuries, a slow upheaving movement.* 
 
 It appears from the observations of Mi-. Darwin and oth- 
 ers, that very extensive regions of the continent of South 
 America have been undergoing slow and gradual upheaval, 
 by which the level plains of Patagonia, covered with recent 
 marine shells, and the Pampas of Buenos Ayres, have been 
 raised above the level, of the sea. On the other hand, the 
 gradual sinking of the west coast of Greenland, for the space 
 of moi"e than 600 miles from north to south, during the last 
 four centuries, has been established by the observations of a 
 Danish naturalist, Dr. Pingel. And while these proofs of 
 continental elevation and subsidence, by slow and insensible 
 movenientSj'have been recently brought to light, the evi- 
 dence has been daily strengthened of continued cha,nges of 
 level efiected by violent convulsions in countries where earth- 
 quakes are frequent. There the rocks are rent from time to 
 time, and heaved up or thrown down several' feet at once, 
 and disturbed in such a manner as to show how entirely the 
 original position of strata may be modified in the course of 
 centuries. 
 
 Mr. Darwin has also inferred that, in those seas where cir- 
 cular coral islands and barrier reefs abound, there is a slow 
 and continued sinking of the submarine mountains on which 
 the masses of coral are based ; while there are other areas of 
 the South Sea where the land is on the rise, and where coral 
 has been upheaved far above the sea-leveL 
 
 Alternations of Marine and Fresh-water Strata.— It has been 
 shown in the third chapter that there is such, a difierence be- 
 * See " Principles of Geology," 1867, p. 314. 
 
VERTICAL STRATIFICATION. 
 
 73 
 
 tweeii land, fresh-water, and marine fossils as to enable the 
 geologist to determine whether particular groups of strata 
 were formed at the bottom of the ocean or in estuaries, riv- 
 ers, or lakes. If surprise was at first created by the discov- 
 ery of marine corals and shells at the height of several miles 
 above the sea-level, the imagination was afterwards not less 
 startled by observing that in the successive strata com- 
 posing the earth's crust, especially if their total thickness 
 amounted to thousands of feet, they comprised in some parts 
 formations of shallow-sea as well as of deep-sea origin ; also 
 beds of brackish or even of purely fresh- water formation, as 
 well as vegetable matter or coal accumulated on ancient land. 
 In these cases we as frequently find fresh-water beds below 
 a marine set or shallow-water under those of deep-sea ori- 
 gin as the reverse. Thus, if we bore an artesian well below 
 London, we pass through a marine clay, and there reach, at 
 the depth of several hundred feet, a shallow-water and flu- 
 viatile sand, beneath which comes the white chalk oiiginally 
 formed in a deep sea. Or if we bore vertically through the 
 chalk of the North Downs, we come, after traversing marine 
 chalky strata, upon a fresh-water formation many hundreds 
 of feet thick, called the Wealden, such as is seen in Kent and 
 Surrey, which is known in its turn to rest on purely marine 
 beds. In like manner, in various parts of Great Britain we 
 sink vertical shafts through marine deposits of great thick- 
 ness, and come upon coal which was formed by the growth 
 of plants on an ancient land-surface sometimes hundreds of 
 square miles in extent. 
 
 Vertical, Inclined, and Curved Strata. — It has been stated 
 that marine strata of different ages are sometimes found at a 
 considerable height above the sea, yet retaining their orig- 
 inal horizontality ; but this state of things is quite exception- 
 al. As a general rule, strata are 
 inclined or bent in such a manner 
 as to imply that their original po- 
 sition has been altered. 
 
 The most unequivocal evidence 
 of such a change is afforded by 
 their standing up vertically, show- 
 ing their edges, which is by no 
 means a rare phenomenon, espe- 
 cially in mountainous countries. 
 Thus we find in Scotland, on the southern skirts of the 
 Grampians, beds of pudding-stone alternating with thin 
 layers of fine sand, all placed vertically to the horizon. 
 When Saussure first observed certain conglomerates in a 
 
 4 
 
 Fig. 54. 
 
 Vertical conglomerate and sand- 
 stone. 
 
?4 
 
 ELEMENTS OF GEOLOGY. 
 
 [k 
 
 '■< 
 
 similar position in the Swiss Alps, he remarked that the 
 pebbles, being for the most part of an oval shape, had their 
 
 longer axes parallel to the planes 
 of stratification (see Fig. 54, on 
 the preceding page). From this 
 he inferred that such strata mustj 
 at first, have been horizontal, each 
 oval pebble having settled at the 
 bottom of the water, with its flat- 
 ter side parallel to the horizon, for 
 the same reason that an egg will 
 not stand on either end if unsup- 
 ported. Some few, indeed, of the 
 rounded stones in a conglomerate 
 occasionally afford an exception to 
 the above rule, for the same, reason 
 that in a river's bed, or on a shin- 
 ^ gle beach, some pebbles rest on 
 a a their ends or edges; these having 
 been shoved against or between 
 other stones by a wave or curi-ent, 
 so as to assume this position. 
 Anticlinal and Synclinal Curves. 
 ,^ — Vertical sti-ata, when they can 
 J 1° be traced continuously upward or 
 1 3 downward for some depth, are al- 
 g^ most invariably seen to be parts 
 &§ of great curves, which may have a 
 pjs diameter of a few yards, or of sev- 
 i eral miles. I shall first describe 
 : two curves of considerable regu- 
 • larity, which occur in Forfarshire, 
 I extending over a country twenty 
 ■ miles in' breadth, from the foot of 
 r the Grampians to the sea near Ar- 
 i broath. 
 
 ; The mass of strata here shown 
 
 j may be 2000 feet in thickness, con- 
 sisting of red and white sandstone, 
 and various colored shales, the 
 beds being distinguishable into 
 four principal groups, namely, No. 
 1, i-ed marl or shale; No. 2, red 
 sandstone, used for buildmg; No. 3, conglomerate; and No 4 
 gray pavmg-stone, and tile-stone, with green and reddish 
 shale, contaming peculiar organic remains. A glancfe at the 
 
 
 a to 
 
 or 
 
 *2 O 
 
CURVED STEATITICATION. 75 
 
 section will show that each of the formations 2, 3, 4 are re- 
 peated thrice at the surface, twice with a southerly, and once 
 with a northerly inclination or dip, and the beds in No. 1, 
 which are nearly horizontal, are still brought up twice by a 
 slight curvature to the surface, once on each side of A. Be- 
 ginning at the north-west extremity, the tile-stones and con- 
 glomerates, No. 4 and No. 3, are vertical, and they generally 
 form a ridge parallel to the southern skirts of the Grampi- 
 ans. The superior strata, Nos. 2 and 1, become less and less 
 inclined on descending to the valley of Strathmore, where 
 the strata, having a concave bend, are said by geologists to 
 lie in a "trough" or "basin." Through the centre of this 
 valley runs an imaginary line A, called technically a " syn- 
 clinal line," where the beds, which are tilted in opposite di- 
 rections, may be supposed to meet. It is most important for 
 the observer to mark such lines, for he will perceive by the 
 diagram that, in travelling from the north to the centre of 
 the basin, he is always passing from older to newer beds; 
 whereas, after crossing the line A, and pursuing his course in 
 the same southerly direction, he is continually leaving the 
 newer, and advancing upon older strata. All the deposits 
 which he had before examined begin then to recur in re- 
 versed order, until he arrives at the central axis of the Sid- 
 law hills, where the strata are seen to form an arch, or sad- 
 dle, having an anticlinal line, B, in the centre. On passing 
 this line, and continuing towards the S.E., the formations 4, 
 3, and 2, are again repeated, in the same relative order of 
 superposition, but with a southerly dip. At Whiteness (see 
 diagram) it will be seen that the inclined strata are covered 
 by a newer deposit, a, in horizontal beds. These are com- 
 posed of red conglomerate and sand, and are newer than any 
 of the groups, 1, 2, 3, 4, before described, and rest unconform- 
 ahly upon strata of the sandstone group. No. 2. 
 
 An example of curved strata, in which the bends or con- 
 volutions of the rock are sharper and far more numerous 
 within an equal space, has been well described by Sir James 
 Hall.* It occurs near St. Abb's Head, on the east coast of 
 Scotland, where the rocks consist principally of a bluish 
 slate, having frequently a ripple-marked surface. The un- 
 dulations of the beds reach from the top to the bottom of 
 cliffs from 200 to 300 feet in height, and there are sixteen 
 distinct bendings in the course of about six miles, the curva- 
 tures being alternately concave and convex upward. 
 
 Folding by Lateral Movement. — An experiment was made 
 by Sir James Hall, with a view of illustrating the manner in 
 * Edin. Trans., vol. vii., pi. 3. 
 
76 
 
 ELEMENTS OF GEOLOGY. 
 Fig. 56. 
 
 Curved strata of slate near St. Abb's Head, Berwickshive. (Sir J. Hall.) 
 
 ■which such strata, assuming them to have been originally 
 horizontal, may have been forced into their present position. 
 A set of layers of clay were placed under a weight, and their 
 opposite ends pressed towards each other with such force as 
 to cause them to approach more nearly together. On the 
 removal of the weight, the layers of clay were found to be 
 curved and folded, so as to bear a miniature resemblance to 
 the strata in the cliffs. We must, however, bear in mind 
 that in the natural section or sea-cliff we only see the fold- 
 ings imperfectly, one part being invisible beneath the sea, 
 and the other, or upper portion, being supposed to have 
 been carried away by denudation, or that action of water 
 which will be explained in the next chapter. The dark 
 lines in the accompanying plan (Fig. 57) represent what is 
 
 Fig. 5T. 
 
 actually seen of the strata in the line of cliff alluded to; the 
 fainter lines, that portion which is concealed beneath the sea- 
 level, as also that which is supposed to have once existed 
 above the present surface. 
 
CURVED STKATA. 77 
 
 We may still more easily illustrate the effects which a lat- 
 eral thrust might produce on flexible strata, by placing sev- 
 eral pieces of diflerently colored cloths upon a table, and 
 when they are spread out horizontally, cover them with a 
 book. Then apply other books to each end, and force them 
 
 Fig. SS. 
 
 towards each other. The folding of the cloths (see Fig. 58) 
 will imitate those of the bent strata ; the incumbent book 
 being slightly lifted up, and no longer touching the two vol- 
 umes on which it rested before, because it is supported by 
 the tops of the anticlinal ridges formed by the curved cloths. 
 In like manner there can be no doubt that the squeezed stra- 
 ta, although laterally condensed and more closely packed, 
 are yet elongated and made to rise upward, in a direction 
 perpendicular to the pressure. 
 
 Whether the analogous flexures in stratified rocks have 
 really been due to similar sideway movements is a question 
 which we can not decide by reference to our own observa- 
 tion. Our inability to explain the nature of the process is, 
 perhaps, not simply owing to the inaccessibility of the sub- 
 terranean regions where the mechanical force is exerted, but 
 to the extreme slowness of the movement. The changes 
 may sometimes be due to variation in the temperature of 
 mountain masses of rock causing them, while still solid, to 
 expand or contract; or melting them, and then again cool- 
 ing them and allowing them to crystallize. If such be the 
 case, we have scarcely more reason to expect to witness the 
 operation of the process within the limited periods of our 
 scientific observation than to see the swelling of the roots 
 of a tree, by which, in the course of years, a wall of solid 
 masonry may be lifted up, rent, or thrown down. In both 
 instances the force may be irresistible, but though adequate, 
 it need not be visible by us, provided the time required for 
 its development be very great. The lateral pressure arising 
 from the unequal expansion of rocks by heat may cause one 
 mass Iving in the same horizontal plane gradually to occupy 
 
78 ELEMENTS OF GEOLOGY. 
 
 a larger space, so as to press upon another rock, which, if flex- 
 ible, may be squeezed into a bent and folded form. It will 
 also appear, when the volcanic and granitic rocks are de- 
 scribed, that some of them have, when melted in the interior 
 of the earth's crust, been injected forcibly into fissures, and 
 after the solidification of such intruded matter, other sets of 
 rents, crossing the first, have been formed and in their turn 
 filled by melted rock. Such repeated injections imply a 
 stretching, and often upheaval, of the whole mass. 
 
 We also know, especially by the study of regions liable to 
 earthquakes, that there are causes at work in the interior of 
 the earth capable of producing a sinking in of the ground, 
 sometimes very local, but often extending over a wide area. 
 The continuance of such a downward movement, especially 
 if partial and confined to linear areas, may produce regular 
 folds in the strata. 
 
 Creeps in Coal-mines. — The " creeps," as they are called in 
 coal-mines, afford an excellent illustration of this fact. — 
 First, it may be stated generally, that the excavation of coal 
 at a considerable depth causes the mass of overlying strata 
 to sink down bodily, even when props are left to "support the 
 roof of the mine. " In Yorkshire," says Mr. Buddie, " three 
 distinct subsidences were perceptible at the surface, after the 
 clearing out of three seams of coal below, and innumerable 
 vertical cracks were caused in the incumbent mass of sand- 
 stone and shale which thus settled down."* The exact 
 amount of depression in these cases can only be accurately 
 measured where water accumulates on the surface, or a rail- 
 way traverses a coal-field. 
 
 When a bed of coal is worked out, pillars or rectangular 
 masses of coal are left at intervals as props to support the 
 roof, and protect the colliers. Thus in Fig. 59, page 79, rep- 
 resenting a section at Wallsend, Newcastle, the galleries 
 which have been excavated are represented by the white 
 spaces a, b, while the adjoining dark portions are parts of 
 the original coal-seam left as props, beds of sandy clay or 
 shale constituting the floor of the mine. When the props 
 have been reduced in size, they are pressed down by the 
 weight of overlying rocks (no less than 630 feet thick) upon 
 the shale below, which is thereby squeezed and forced up 
 into the open spaces. 
 
 _ Now it might have been expected that, instead of the floor 
 
 rising up, the ceiling would sink down, and this effect, called 
 
 a " thrust," does, in fact, take place where the pavement is 
 
 more solid than the roof. But it usually happens, in coal- 
 
 * Proceedings of Geo). Soc, vol. iii., p. 148. 
 
CEEEPS IN COAL-MINES. 
 
 79 
 
 mines, that the roof is composed of hard shale, or occasional- 
 ly of sandstone, more unyielding than the foundation, which 
 often consists of clay. Even where the ai'gillaceous substra- 
 ta ai'e hard at first, they soon become softened and reduced 
 to a plastic state when exposed to the contact of air and wa- 
 ter in the floor of a mine. 
 
 The first symptom of a " creep," says Mr. Buddie, is a 
 slight curvature at the bottom of each gallery, as at a, Fig. 
 59 : then the pavement, continuing to rise, begins to open 
 with a longitudinal crack, as at b; then the points of the 
 
 Fig. 69. 
 
 Section of carboniferous strata at Wallsend, Newcastle, showing " creeps." 
 (J. Buddie, Esq.) 
 
 Horizontal length of section 174 feet. The upper seam, or main coal, here worked 
 out, was 630 feet below the surface. 
 
 1. Main coal, 6 feet Inches. 2. Metal coal, 3 feet. 
 
 fractured ridge reach the roof, as at e; and, lastly, the up- 
 raised beds closfe up the whole gallery, and the broken por- 
 tions of the ridge are reunited and flattened at the top, ex- 
 hibiting the flexure seen at d. Meanwhile the coal in the 
 props has become crushed' and cracked by pressure. It is 
 also found that below the creeps a, b, c, d, an inferior stra- 
 tum, called the "metal coal," which is 3 feet thick, has been 
 fractured at the points e,f, g, h, and has risen, so as to prove 
 that_ the upward movement, caused by the working out of 
 tlie "main coal," has been propagated through a thickness 
 of 54 feet of argillaceous beds, which intervene between the 
 two coal-seams. This same displacement has also been 
 traced downward more than 150 feet below the metal coal, 
 but it grows continually less and less until it becomes im- 
 perceptible. 
 
 No part of the process above described is more deserv- 
 ing of our notice than the slowness with which the change 
 in the arrangement of the beds is brought about. Days, 
 
80 ELEMENTS OF GEOLOGY. 
 
 months, or even years, will sometimes elapse between the 
 first bending of the pavement and the time of its reaching 
 the roof Where the movement has been most rapid,_the 
 curvature of the beds is most regular, and the reunion of the 
 fractured ends most complete; whereas the signs of dis- 
 placement or violence are greatest in those creeps which 
 have required months or years for their entire accomplish- 
 ment. Hence we may conclude that similar changes may 
 have been wrought on a larger scale in the earth's crust by 
 partial and gradual subsidences, especially where the ground 
 has been undermined throughout long periods of time ; and 
 we must be on our guard against inferring sudden violence, 
 simply because the distortion of the beds is excessive. 
 
 Engineers are familiar with the fact that when they raise 
 the level of a railway by heaping stone or gravel on a foun- 
 dation of marsh, quicksand, or other yielding formation, the 
 new mound often sinks for a time as fast as they attempt to 
 elevate it; when they have persevered so as to overcome 
 this difficulty, they frequently find that some of the adjoin- 
 ing flexible ground has risen up in one or more parallel 
 arches or folds, showing that the vertical pressure ^of the 
 "sinking materials has given rise to a lateral foliJing'move- 
 ment. 
 
 In like manner, in the interior of the earth, the solid parts 
 of the earth's crust may sometimes, as before mentioned, be 
 made to exjjand by heat, or may be pressed by the force of 
 steam against flexible sti'ata loaded with a great weight of 
 incumbent rocks. In this ease the yielding mass, squeezed, 
 but unable to overcome the resistance which it meets with 
 in a vertical direction, may be gradually relieved by lateral 
 folding. 
 
 Dip and Strike. — In describing the manner in which strata 
 depart from their original horizontality,some technical terms, 
 such as "dip" and "strike," "anticlinal" and "synclinal" 
 line or axis, are used by geologists. I shall now proceed to 
 explain some of these to the student. If a stratum or bed 
 of rock, instead of being quite level, be inclined to one side, 
 j,,^ g„ it is said to dip; the point of 
 
 the compass to which it is in- 
 clined is called the point of 
 dip, and the degree of devia- 
 tion from a level or horizontal 
 line is called the amoxmt of 
 d,ip,ov the angle of dip. Thus, 
 m_ the annexed diagram (Fig. 60), a series of strata are in- 
 clined, and they dip to the north at an angle of forty-five 
 
DIP AND STRIKE. 81 
 
 degrees. The strike, or line of bearing, is the prolongation 
 or extension of the strata in a direction at right atigles to 
 the dip; and hence it is sometimes called the direction of 
 the strata. Thus, in the above instance of strata dipping 
 to the north, their strike must necessarily be east and west. 
 We have borrowed the word from the German geologists, 
 streichen signifying to extend, to have a certain" direction. 
 Dip and strike may be aptly illustrated by a row of houses 
 running east and west, the long ridge of the roof represent- 
 ing the strike of the stratum of slates, which dip on one side 
 to the north, and on the other to the south. 
 
 A stratum which is horizontal, or quite level in all direc- 
 tions, has neither dip nor strike. 
 
 It is always important for the geologist, who is endeavor- 
 ing to comprehend the structure of a country, to learn how 
 the beds dip in every part of the district ; but it requires 
 some practice to avoid being occasionally deceived, both as 
 to the point of dip and the amount of it. 
 
 If the upper surface of a hard stony stratum be uncovered, 
 whether artificially in a quarry, or by the waves at the foot 
 of a cliff, it is easy to determine towards Avhat point of the 
 compass the slope is steepest, or in what direction water 
 would flow if poured upon it. This is the true dip. But 
 the edges of highly inclined strata may give rise to perfectly 
 horizontal lines in the face of a vertical cliff, if the observer 
 see the strata in the line of their strike, the dip being inwai'd 
 from the face of the cliff. If, however, we come to a break 
 in the cliff, which exhibits a section exactly at right angles 
 to the line of the strike, we are then able to ascertain the 
 
 Fig. 61. 
 
 Apparent horizontality of inclined strata. 
 
 true dip. In the annexed drawing (Fig. 61), we may sup- 
 pose a headland, one side of which faces to the north, where 
 the beds would appear perfectly horizontal to a person in the 
 boat ; while in the other side facing the west, the true dip 
 
 4* 
 
82 
 
 ELEMENTS OF GEOLOGY. 
 
 Fig. 03. 
 
 would be seen by the jjeison on shore to be at a,n angle of 
 40°. If, therefore, our observations are confined to a vertical 
 precipice facing in one direction, we must endeavor to find a 
 ledge or portion of the plane of one of the beds projecting 
 bejrond the others, in order to ascertain the true dip. 
 
 If not provided with a clinometer, a most usef'il instru- 
 ment, when it is of consequence to determine with precision 
 
 the inclination of the strata, the ob- 
 server may measure the angle with- 
 in a few degrees by standing ex- 
 actly opposite to a cliff where the 
 true dip is exhibited, holding the 
 hands immediately before theeyes, 
 and placing the fingers of one in 
 a perpendicular, and of the other 
 in a horizontal position, as in Fig. 
 62. It is thus easy to discover 
 whether the lines of the inclined 
 beas bisect the angle of e*0°, form- 
 ed by the meeting of the hands, so 
 as to give an angle of 46°, or whether it would divide the 
 space into two equal or unequal portions. You have only to 
 change hands to get the line of dip on the upper side of the 
 horizontal hand. 
 
 It has been already seen, page 75, in describing the curved 
 siiata on the east coast of Scotland, in Forfarshire and Ber- 
 wickshire, that a series of concave and convex bendicgs ars 
 occasionally repeated several times. These usually form pari 
 of a series of parallel waves of strata, which are prolonged 
 in the same direction, throughout a considerable extent of 
 
 Section illustrating the structure of the Swiss Jariu 
 
 country. Thug, for example, in the Swiss Jura, that lofty 
 chain of mountains has been proved to consist of many par- 
 allel ridges, with intervening longitudinal valleys, as in Figi 
 63, the ridges being formed by curved fossiliferous strata, 
 
OUTCROP OF STRATA. 
 
 83 
 
 of which the nature and dip are occasionally displayed in 
 deep transverse gorges, called " cluses," caused by fractures 
 at right angles to the direction of the chain.* Now let us 
 suppose these ridges and parallel valleys to run north and 
 south, we should then say that the strike of the beds is north 
 and south, and the dip east and west. Lines drawn alon^ 
 the summits of the ridges, A, B, would be anticlinal line?, 
 and one following the bottom of the adjoining valleys a syn- 
 clinal line. 
 _ Outcrop of Strata.— It will be observed that some of these 
 ridges. A, B, are unbroken on the summit, whereas one of 
 them, C, has been fractured along the line of strike, and a 
 portion of it carried away by denudation, so that the ridges 
 of the beds in the formations a, b, c come out to the day, or, 
 as the miners say, crop 
 out, on the sides of a val- 
 ley. The ground-plan of 
 such a denuded ridge as 
 C, as given in a geological 
 map, may be expressed by 
 the diagram. Fig. 64, and 
 the cross - section of the 
 same by Fig. 66. The line 
 D E, .Fig. 64, is the anti- 
 
 Fig. 64. 
 
 Pig. 65. 
 
 'v:^>^ :-.■••. -.■■■. ■.••■. 
 
 D> > > > ^ •> > 
 
 
 Ground-plan oif the denuded vidge C, Fig. C3. 
 
 clinal line, on each side of which the dip is in opposite direc- 
 tions, as expressed by the arrows. The emergence of strata 
 at the surface is called by miners their outcrop, or basset. 
 
 If, instead of being folded into parallel ridges, the beds 
 form a boss or dome-shaped protuberance, and if we suppose 
 the summit of the dome carried off, the ground-plan would 
 exhibit the edges of the strata forming a succession of cir- 
 cles, or ellipses, round a common centre. These circles are 
 the lines of strike, and the dip being always at right angles 
 is inclined in the course of the circuit to eveiy point of the 
 compass, constituting what is termed a qua-quaversal dip — 
 that is, turning every way. 
 
 There are endless variation.^ in the figures described by 
 the basset-edges of the strata, according to the different in- 
 clination of the beds, and the mode in which they happen to 
 have been denuded. One of the simplest rules,with which ev- 
 ery geologist should be acquainted, relates to the Y-like form 
 of the beds as they crop out in an ordinary valley. First, 
 if the strata be horizontal, the V-like form will be also on a 
 level, and the rewest strata will appear at the gi-eatest heights. 
 
 * Thurmann. "Essai bi/v les ^onlfevemens Juj'assiques du Porrentruy." 
 Paris, 1883 
 
84 
 
 ELEMENTS OF GEOLOGY. 
 
 Slope of valley 40°, clip of strata 20'. 
 Fig. 6T. 
 
 Secondly, if the beds be inclined and intersected by a val- 
 ley sloping in the same direction, and the dip of the beds be 
 •''■=> less steep than the 
 
 i''g-66. slope of the valley, 
 
 then the V's, as they 
 are often termed by 
 miners, will point up- 
 ward (see Fig. 66), 
 those formed by the 
 newer beds appear- 
 ing in a superior po- 
 sition, and extending 
 highest up the valley, 
 as A is seen above B. 
 Thirdly, if the dip 
 of the beds be steep- 
 er than the slope of 
 the valley, then the 
 V's will point down- 
 ward (see Fig. 67), 
 and those formed of 
 the older beds will 
 now appear upper- 
 most, as B appears 
 above A. 
 
 Fourthly, in every 
 case where the strata 
 dip in a contrary di- 
 rection to the slope 
 of the valley, what- 
 ever be the angle of 
 inclination, the newer 
 beds will appear the 
 highest, as in the 
 first and second cases. 
 This is shown by the 
 drawing (Fig. 68), 
 which exhibits strata 
 rising at an angle of 
 20°, and crossed by a 
 valley, which declines 
 in an opposite direc- 
 tion at 20°. 
 
 These rules may 
 for the different de- 
 cases represented in 
 
 k' 
 
 Slope of valley 20°, dip of strata 50°. 
 Fig. 68. 
 
 Slope of 
 
 1 20°, in opposite 
 
 often be of great practical utility ; 
 grees of dip occurring in the two 
 
ANTICLINAI, AND STNCLINAIi LINES. 86 
 
 Figs. 66 and 67 may occasionally be encountered in follow- 
 ing the same line of flexure at points a few miles distant 
 from each other. A miner unacquainted with the rule, who 
 had first explored the valley Fig. 66, may have sunk a vert- 
 ical shaft below the coal-seam A, until he reached the inferior 
 bedjB. He might then pass to the valley, Fig. 67, and dis- 
 covei'ing there also the outcrop of two coal-seams, might be- 
 gin his workings in the uppermost in the expectation of com- 
 ing down to the other bed, A, which would be observed 
 cropping out lower down the valley. But a glance at the 
 section vill demonstrate the futility of such hopes.* 
 
 Synclinal Strata forming Ridges. — Although in many cases 
 an anticlinal axis forms a ridge, and a synclinal axis a valley, 
 as in A B, Fig. 63, p. 82, yet this can by no means be laid 
 down as a general rule, as the beds very often slope inward 
 
 Synclinal. Anticlinal. Synclinal. 
 
 Grits and shales. Mountain limestone. Grits and shales. 
 
 Section of carbonlferons rocks of Lancashire. (E. Hulht) 
 
 from either side of a mountain, as at a, 5, Fig. 69, while in 
 the intervening valley, c, they slope upward, forming an arch. 
 It would be natural to expect the fracture of solid rocks 
 to take place chiefly where the bending of the strata has 
 been sharpest, and such rending may produce ravines giving 
 access to running water and exposing the surface to atmos- 
 pheric waste. The entire absence, however, of such cracks 
 at points wliere the strain must have been greatest, as at a. 
 Fig. 63, is often very remarkable, and not always easy of ex- 
 planation. We must imagine that many strata of limestone, 
 chert, and other rocks which are now brittle, were pliant 
 when bent into their present position. They may have owed 
 their flexibility in part to the fluid matter which they con- 
 tained in their minute pores, as before described (p. 62), and 
 in part to the permeation of sea-water while they were yet 
 submerged. 
 
 * I am indebted to the kindness of T. Sopwith, Esq. , for three models which 
 I have copied in the above diagrams ; but the beginner may find it by no 
 means easy to understand such copies, although, if he were to examine and 
 handle the originals, turning them about in different ways, he would at once 
 comprehend their meaning, as well as the import of others fiir more compli- 
 cated, which the same engineer has constructed to illustrate /aW<s. 
 
 + Edward Hull, Quart. Geol. Journ., vol. xxiv., p. 324. 1868. 
 
Bt) 
 
 ELEMENTS OF GEOLOGY. 
 
 At the western extremity of the Pyrenees, great curva- 
 tures of the strata are seen in the sea-clifiFs, where the rocks 
 consist of marl, grit, and chert. At certain points, as at a, 
 Fig 70, some of the bendings of the flinty chert are so sharp 
 
 Fig. TO. 
 
 Fig. n. 
 
 Strata of chert, grit, and mar), near St. Jean de Luz. 
 
 that specimens might be broken off well fitted to serve as 
 ridge-tiles on the roof of a house. Although this chert coald 
 not have been brittle as now, when first folded into this shape, 
 it presents, nevertheless, here and there, at the points of great- 
 est flexure, small cracks, which show that it was solid, and 
 not wholly incapable of breaking at the period of its dis- 
 placement. The numerous rents alluded to are not empty, 
 but filled with chalcedony and quartz. 
 
 Between San Caterina and Castrogiovanni, in Sicily, bent 
 and undulating gypseous marls occur, with here and there 
 
 thin beds of solid gypsum inter- 
 stratified. Sometimes these solid 
 layers have been broken into de- 
 tached fragments, still preserving 
 their sharp edges {g,g, Fig. 11), 
 while the continuity of the more 
 pliable and ductile marls, m, m, 
 has not been interrupted. 
 
 We have already explained. Fig; 
 69, that stratified rocks have usu- 
 ally their strata bent into parallel folds forming anticlinal 
 and synclinal axes, a group of several of these folds hav- 
 ing often been subjected to a common movement, and having 
 acquired a uniform strike or direction. In some disturbed 
 regions these folds have been doubled back upon themselves 
 in such a manner that it is often difficult for an experienced 
 geologist to determine correctly the relative age of the beds 
 by superposition. Thus, if we 
 meet with the strata seen in the 
 section. Fig. 72, we should nat- 
 urally suppose that there were 
 twelve distinct beds, or sets of 
 beds, No. 1 being the newest, and No. 12 the oldest of the 
 series. But this section may perhaps exhibit merely six 
 
 g Gypsum. m Mjirl. 
 
 Fig. T2. 
 
FRACTURES OF THE STRATA AND FAULTS: 87 
 
 beds, which have been Fig. 78. 
 
 folded in the manner seen 
 in Fig. 73, so that each 
 of them is twice repeat- 
 ed, the position of one 
 half being reversed, and 
 part of No. 1, originally 
 the uppermost, having 
 now become the lowest 
 of the series. 
 
 These phenomena are 
 observable on a magnificent scale in certain regions in 
 Switzerland, in precipices often more than 2000 feet in per- 
 pendicular height, and there are flexures not inferior in di- 
 mensions in the Pyrenees. The upper part of the curves 
 seen in this diagram. Fig. 73, and expressed in fainter lines, 
 has been removed by what is called denudation, to be after- 
 wards explained. 
 
 Fractures of the Strata and Faults. — Numerous rents may 
 often be seen in rocks which appear to have been simply 
 broken, the fractured parts still remaining in contact ; but 
 we often find a fissure, several inches or yards wide, inter- 
 vening between the disunited portions. These fissures are 
 usually filled with fine earth and sand, or with angular frag- 
 ments of stone, evidently derived from the fracture of the 
 contiguous rocks. 
 
 The face of each wall of the fissure is often beautifully 
 polished, as if glazed, striated, or scored with parallel fur- 
 rows and ridges, such as would be produced by the contin- 
 ued rnbbrtig^ together of surfaces of unequal hardness. These 
 polished surfaces are called by miners " slickensides." It is 
 supposed that the lines of the striae indicate the direction 
 in which the rocks were moved. During one of the minor 
 earthquakes in Chili, in 1840, the brick walls of a building 
 were rent vertically in several places, and made to vibrate 
 for several minutes during each shock, after which they re- 
 mained uninjured, and without any opening, although the 
 line of each crack was still visible. When all movement 
 had ceased, there were seen on the floor of the house, at the 
 bottom of each rent, small heaps of fine brick-dust, evident- 
 ly produced by trituration. 
 
 It is not uncommon to find the mass of rock on one side 
 of a fissure thrown up above or down below the mass with 
 which it was once in contact on the other side. " This mode 
 of displacement is called a fault, shift, slip, or throw." " The 
 miner," says Playfair, describing a fault, " is often perplexed. 
 
88 
 
 ELEMENTS OF GEOLOGY. 
 
 in his subterraneous journey, by a derangement in the stra- 
 ta, which changes at once all tViose lines and bearings which 
 had hitherto directed his course. When his mine, reaches a 
 certain plane, which is sometimes perpendicular, as in_A B, 
 Fig. 74, sometimes oblique to the horizon (as in C D, ibid.), 
 he°finds the beds of rock broken asunder, those on the one 
 side of the plane having changed their place, by sliding in a 
 
 p;g. 74. 
 
 B 
 
 Faults. A B perpendicular, C D oblique to the horizon. 
 
 particular direction along the face of the others. In this 
 motion they have sometimes preserved their parallelism, as 
 in Fig. 74, so that the strata on each side of the faults A B, 
 C D, continue parallel to one another ; in other cases, the 
 strata on each side are inclined, as in a, h, c, d (Fig. 75), 
 
 Pig. 75. 
 
 F . rf C i 
 
 E F, fault or fissure filled with rubbish, on each side of which the shifted 
 strata are not parallel. 
 
 though their identity is still to be recognized by their pos- 
 sessing the same thickness and the same internal charac- 
 ters."* 
 
 In Coalbrook Dale, says Mr. Prestwich,f deposits of sand- 
 stone, shale, and coal, several thousand feet thick, a,nd occu- 
 pying an area of many miles, have been shivered into frag- 
 ments, and the broken remnants have been placed in very 
 discordant positions, often at levels differing several hun- 
 dred feet from each other. The sides of the faults^ when 
 perpendicular, are commonly several yards apart, and are 
 sometimes as much as 50 yards asunder, the interval being 
 filled with broken debris of the strata. In following the 
 
 * Playfair, lUust. of Hutt. Theory, § 42. 
 t Geol. Trans., second series, vol. v., p. 452. 
 
PAUXTS. 
 
 89 
 
 course of the same fault it is sometimes found to produce in 
 different places very unequal changes of level, the amount 
 of shift being in one place 300, and in another TOO feet, 
 which arises from the union of two or more faults. In oth- 
 er words, the disjointed strata have in certain districts been 
 subjected to renewed movements, which they have not suf- 
 fered elsewhere. 
 
 We may occasionally see exact counterparts of these slips, 
 on a small scale, in pits of loose sand and gravel, many of 
 which have doubtless been caused by the drying and shrink 
 ing of argillaceous and other beds, slight subsidences having 
 taken place from failure of support. Sometimes, however, 
 even these small slips may have been produced during earth- 
 quakes ; for land has been moved, and its level, relatively to 
 the sea, considerably altered, within the period when much 
 of the alluvial sand and gravel now covering the surface of 
 continents was deposited. 
 
 I have already stated that a geologist must be on his 
 guard, in a region of disturbed strata, against inferring re- 
 peated alternations of rocks, when, in fact, the same strata, 
 once continuous, have been bent round so as to I'ecur in the 
 same section, and with the same dip. A similar mistake 
 has often been occasioned by a series of faults. 
 
 If, for example, the dark line A H (Fig. 76) represent the 
 surface of a country on which the strata a, b, c frequently 
 
 Fig. T6. 
 
 :D 
 
 Apparent alternations of strata cansed by vertical fanlts. 
 
 crop out, an observer who is proceeding from H to A might 
 at first imagine tha<;. at every step he was approaching new 
 strata, whereas the repetition of the same beds has been 
 caused by vertical faults, or downthrows. Thus, suppose 
 the original mass. A, B, C, D, to have been a set of uniform- 
 ly inclined strata, and that the different masses under E F, 
 F G, and G D. sank down successively, so as to leave vacant 
 
90 ELEMENTS OF GEOLOGY. 
 
 the spaces marked in the diagram by dotted lines, and to 
 occupy those marked by the continuous lines, then let de- 
 nudation take place along the line A H, so that the protrud- 
 ing masses indicated by the fainter lines are swept away-- 
 a miner, who has not discovered the faults, finding the mass 
 
 a, which we will suppose to be a bed of coal four times re- 
 peated, might hope to find four beds, workable to an indefi- 
 nite depth, but first, on arriving at the fault G, he is stopped 
 suddenly in his workings, for he comes partly upon the shale 
 
 b, and partly on the sandstone c; the same result awaits 
 him at the fault F, and on reaching E he is again stopped 
 by a wall composed of the rock d. 
 
 The very different levels at which the separated parts of 
 the same strata are found on the difierent sides of the fis- 
 sure, in some faults, is truly astonishing. One of the most 
 celebrated in England is that called the "ninety-fathom 
 dike," in the coal-field of Newcastle. This name has been 
 given to it, because the same beds are ninety fathoms (540 
 feet) lower on the northern than they are on the southern 
 side. The fissure has been filled by a body of sand, which 
 is now in the state of sandstone, and is called the dike, which 
 is sometimes very narrow, but in other places more than 
 twenty yards wide.* The walls of the fissure are scored by 
 grooves,' such as would have been produced if the broken 
 ends of the rock had been rubbed along the plane of the 
 fault.f In the Tynedale and Craven faults, in the north of 
 England, the vertical displacement is still gi-eater, and the 
 fracture has extended in a horizontal direction for a distance 
 of thirty miles or more. 
 
 Great Faults the Eesult of repeated Movements. — It must 
 not, however, be supposed that faults generally consist of 
 single linear rents ; there are usually a number of faults 
 springing off from the main one, and sometimes a long strip 
 of country seems broken up into fragments by sets of paral- 
 lel and connecting transverse faults. Oftentimes a great 
 line of fault has been repeated, or the movements have been 
 continued through successive periods, so that, newer deposits 
 having covered the old line of displacement, the strata both 
 newer and older have given way along the old line of frac- 
 ture. Some geologists have considered it necessary to im- 
 agine that the upwai-d or downward movement in these 
 cases was accomplished at a single stroke, and not by a se- 
 ries of sudden but interrupted movements. They appear to 
 have derived this idea from a notion that the grooved walls 
 
 * Conybeare and. Phillips, Outlines, etc., p. 376. 
 t PhUlips, Geology, Lnrdner's Cyclop., p. 41. 
 
STRATIFIED ROCKS. 
 
 91 
 
 have merely been rubbed in one direction, which is far from 
 being a constant phenomenon. Not only are some sets of 
 strisB not parallel to others, but the clay and rubbish be- 
 tween the walls, when squeezed or rubbed,;bave been streak- 
 ed in different directions, the grooves which the harder min- 
 erals have impressed on the softer being frequently curved 
 and irregular. 
 
 The usual absence of protruding masses of rock forming 
 precipices or ridges along the lines of great faults has al- 
 ready been alluded to in explaining Fig. 76, p. 89, and the 
 same remarkable fact is well exemplified in every coal-field 
 which has been extensively worked. It is in such districts 
 that the former relation of the beds which have been shifted 
 is determinable with great accuracy. Thus in the coal-field 
 of Ashby de la Zouch, in Leicestershire (see Fig. 71), a fault 
 
 Fig. 77. 
 
 Faults and denuded coal-strata, Ashby de la Zouch. (Mammatt.) 
 
 occurs, on one side of which the Coal-beds a, b, c, d must once 
 have risen to the height of 500 feet above the corresponding 
 beds on the other side. But the uplifted strata do not stand 
 up 500 feet above the general surface ; on the contrary, the 
 outline of the country, as expressed by the line s z, is uni- 
 formly undulating, without any break, and the mass indi- 
 cated by the dotted outline must have been washed away.* 
 
 The student may refer to Mr. Hull's measurement of faults, 
 observed in the Lancashire coal-field, where the vertical dis- 
 placement has amounted to thousands of feet, and yet where 
 all the superficial inequalities which must have resulted from 
 such movements have been obliterated by subsequent denu- 
 dation. In the same memoir proofs are afforded of there 
 having been two periods of vertical movement in the same 
 fault — one, for example, before, and another after, the Trias- 
 sic epoch.f 
 
 The shifting of the beds by faults is often intimately con- 
 nected with those same foldings which constitute the anti- 
 
 ' * See Mamm.".tt's Geological pacts, etc., p. 90 and plate, 
 
 t Hull, Qnart. Geol. Journ., roi. xxiv., p. 318. 1868. 
 
92 ELEMENTS OF GEOLOGY. 
 
 clinal and synclinal axes before alluded to, and there is no 
 doubt that the subterranean causes of both forms of disturb- 
 ance are to a great extent the same. A fault in Virginia, 
 believed to imply a displacement of several thousand feet, 
 has been traced for more than eighty miles in the same di- 
 rection as the foldings of the Appalachian chain.* An hy- 
 pothesis which attributes such a change of position to a suc- 
 cession of movements, is far preferable to any theory which 
 assumes each fault to have been accomplished by a single 
 upcast or downthrow of several thousand feet. For we 
 know that there are operations now in progi-ess, at great 
 depths in the interior of the earth, by which both large and 
 small tracts of ground are made to rise above and sink be- 
 low their former level, some slowly and insensibly, others 
 suddenly and by starts, a few feet or yards at a time; where- 
 as there are no grounds for believing that, during the last 
 3000 years at least, any regions have been either upheaved 
 or depressed, at a single stroke, to the amount of several 
 hundred, much less several thousand feet. 
 
 It is certainly not easy to understand how in the subterra- 
 nean regions one mass of solid rock should have been folded 
 up by a continued series of movements, while another mass 
 in contact, or only separated by a line of fissure, has re- 
 mained stationary or has perhaps subsided. Uut every vol- 
 cano, by the intermittent action of the steam, gases, and 
 lava evolved during an eruption, helps us to form some idea 
 of the manner in which such operations take place. For 
 eruptions are repeated at uncertain intervals throughout the 
 whole or a large part of a geological period, some of the sur- 
 rounding and contiguous districts remaining quite undis- 
 turbed. And in most of the instances with which we are 
 best acquainted the emission of lava, scoria, and steam is 
 accompanied by the uplifting of the solid crust. Thus in 
 Vesuvius, Etna, the Madeiras, the Canary Islands, and the 
 Azores there is evidence of marine deposits of recent and 
 tertiary date having been elevated to the height of a thou- 
 sand feet, and sometimes more, since the commencement of 
 the volcanic explosions. There is, moreover, a general ten- 
 dency in contemporaneous volcanic vents to affect a linear 
 arrangement, extending in some instances, as in the Andes 
 01- the Indian Archipelago, to distances equalling half the 
 circumference of the globe. Where volcanic heat, there- 
 fore, operates at such a depth as not to obtain vent at the 
 surface, in the form of an eruption, it may nevertheless be 
 conceived to give rise to upheavals, foldings, and faults in 
 * H. D. Rogers, Geol. of Pennsylrania, p. 897. 
 
PABAiLEL FOLDS OF STRATA. 93 
 
 certain linear tracts. And marine denudation, to be treated 
 of in the next chapter, will help us to understand why that 
 which should be the protruding portion of the faulted rocks 
 is missing at the sui-face. 
 
 Arrangement and Direction of Parallel Folds of Strata. — ^The 
 possible causes of the folding of strata by lateral movements 
 have been considered in a, former part of this chapter. No 
 European chain of mountains affords so remarkable an illus- 
 tration of the persistency of such flexures for a great dis- 
 tance as the Appalachians before alluded to, and none has 
 been studied and described by many good observers with 
 more accuracy. The chain extends from north to south, or 
 rather N.KE. to S.S.W., for nearly 1500 miles, with a 
 breadth of 50 miles, throughout which the Palseozoic sti-ata 
 have been so bent as to form a series of parallel anticlinal 
 and synclinal ridges and troughs, comprising usually three 
 or four principal and many smaller plications, some of them 
 forming broad and gentle arches, others narrower and steep- 
 er ones, while some, where the bending has been greatest, 
 have the position of their beds inverted, as before shown in 
 Fig. 73, p. 81. 
 
 The strike of the parallel ridges, after continuing in a 
 straight line for many hundred miles, is then found to vary 
 for a more limited distance as much as 30°, the folds wheel- 
 ing round together in the new direction and continuing to 
 be parallel, as if they had all obeyed the same movement. 
 The date of the movements by which the great flexui-es 
 were brought about must, of course, be subsequent to the 
 formation of the uppermost part of the coal or the newest 
 of the bent rocks, but the disturbance must have ceased 
 before the Triassic strata were deposited on the denuded 
 edges of the folded beds. 
 
 The manner in which the numerous parallel folds, all si- 
 multaneously formed, assume a new direction common to the 
 whole of them, and sometimes varying at an angle of 30° 
 from the normal strike of the chain, shows what deviation 
 from an otherwise uniform strike of the beds may be experi- 
 enced when the geographical area through which they are 
 traced is on so vast a scale. 
 
 The disturbances in the case here adverted to occurred be- 
 tween the Carboniferous period and that of the Trias, and 
 this interval is so vast that they may have occupied a great 
 lapse of time, during which their parallelism was always 
 preserved. But, as a rule, wherever after a long geological 
 interval the recurrence of lateral movements gives rise to a 
 new set of folds, the strike of these last is different. Thus, 
 
94 
 
 ELEMENTS OF GEOLOGY. 
 
 for example, Mr. Hull has pointed out that three principal 
 lines of disturbance, all later than the Carboniferous period, 
 have affected the sti-atified rocks of Lancashire. The first 
 of these, having an E.N.E. direction, took place at the close 
 of the Carboniferous period. The next, running north and 
 south, at the close of the Permian, and the third, having a 
 N.N.W. direction, at the close of the Jurassic period.* 
 
 Unconfonnability of Strata. — Strata are said to be uncon- 
 formable when one series is so placed over another that the 
 planes of the superior repose on the edges of the inferior 
 (see Fig. 78). In this case it is evident that a period had 
 elapsed between the production of the two sets of strata, 
 
 Fig. T8. 
 
 Uncoufoi-mable junction of old red sandBtone and Silurian schist at the Siccar 
 Point, near St. Abb's Head, Berwickshire. 
 
 and that, during this interval, the older series had been tilt- 
 ed and disturbed. Afterwards the upper series was thrown 
 down in horizontal strata upon it. If these superior beds, 
 ^1 ^1 Fig. V8, are also inclined, it is plain that the lower 
 strata, a, a, have been twice displaced ; first, before the dep- 
 osition of the newer beds, d, d, and a second time when 
 these same strata were upraised out of the sea, and thrown 
 slightly out of the horizontal position. 
 _ It often happens that in the interval between the deposi- 
 tion of two sets of unconformable strata, the inferior rock 
 
 Junction of unoouformaWe strata near Mons, in Belgium. 
 
 has not only been denuded, but drilled by perforating shells. 
 Ihus, for example, at Autreppe and Gusigny, near Mons, 
 beds of an ancient (primary or palaeozoic) limestone, highly 
 inclined, and often bent, are covered with horizontal strata 
 * Edward Hull, Quart. Geol. Journ., vol. xxiv., p. 323. 
 
OVERLAPPING STRATA. 95 
 
 of greenish and whitish marls of the Cretaceous formation. 
 The lowest, and therefore the oldest, bed of the horizontal 
 series is usually the sand and conglomerate, a, in which are 
 rounded fragments of stone, from an inch to two feet in di- 
 ameter. These fragments have often adhering shells attach- 
 ed to them, and have been bored by perforating mollusca. 
 The solid surface of the inferior limestone has also been 
 bored, so as to exhibit cylindiical and pear-shaped cavities, 
 as at c, the work of saxicavous mollusca; and many rents, as 
 at h, which descend several feet or yards into the limestone, 
 have been filled with sand and shells, similar to those in the 
 stratum a. 
 
 Overlapping Strata. — Strata are sai3 , to overlap when an 
 upper bed extends beyond the limits of a lower one. This 
 may be produced in various ways ; as, for example, when al- 
 terations of physical geography cause the arms of a river or 
 channels of discharge to vary, so that sediment brought down 
 is deposited over a wider area than before, or when the sea- 
 bottom has been raised up and again depressed without dis- 
 turbing the horizontal position of the strata. In this case 
 the newer strata may rest for the most part conformably on 
 the older, but, extending farther, pass over their edges. Ev- 
 ery intermediate state between unconformable and over-lap- 
 ping beds may occur, because there may be every gradation 
 between a slight derangement of position, and a considerable 
 disturbance and denudation of the older formation before 
 the newer beds come on. 
 
ELEMENTS OF GEOLOGY. 
 
 CHAPTER VI. 
 
 DENUDATION. 
 
 Denudation defined. — Its Amount more than equal to the entire Mass of strat- 
 ified Deposits in the Earth's Cnist. — Subaerial Denudation. — Action of 
 the Wind. — Action of Running Water. — Alluvium defined. — Different 
 Ages of Alluvium. — Denuding Power of Rivers affected by Rise or Fall of 
 Land. — Littoral Denudation. — Inland Sea-cliffs. — Escarpments. — Subma- 
 rine Denudation. ^ — Dogger-bank. — Newfoundland Bank. — Denuding Pow- 
 er of the Ocean during Emergence of Land. 
 
 Denudation, which has been occasionally spoken of in the 
 preceding chapters, is the removal of solid matter by water 
 in motion, whether of rivers or of the waves and currents of 
 the sea, and the consequent laying bare of some inferior rock. 
 This operation has exerted an influence on the structure of 
 the earth's crust as universal and important as sedimentary 
 deposition itself; for denudation is the necessary antecedent 
 of the production of all new strata of mechanical origin. 
 The formation of every new deposit by the transport of sed- 
 iment and pebbles necessarily implies that there has been, 
 somewhere else, a grinding down of rock into rounded frag- 
 ments, sand, or mud, equal in quantity to the new strata- 
 All deposition, therefore, except in the case of a shower of 
 volcanic ashes, and the outflow of lava, and the growth of 
 certain organic formations, is the sign of superficial waste 
 going on contemporaneously, and to an equal amount, else- 
 where. The gain at one point is no more than sufficient to 
 balance the loss at some other. Here a lake has grown shal- 
 lower, there a ravine has been deepened. Here the depth 
 of the sea has been augmented by the removal of a sand- 
 bank during a storm, there its bottom has been raised and 
 shallowed by the accumulation in its bed of the same sand 
 transported from the bank. 
 
 When we see a stone building, we know that somewhere, 
 far or near, a quarry has been opened. The courses of stone 
 in the building maj be compared to successive strata, the 
 quarry to a ravine or valley which has sufiered denudation. 
 As the strata, like the courses of hewn stone, have been laid 
 one upon another gradually, so the excavation both of the 
 valley and quarry have been gradual. To pursue the com- 
 parison still farther, the superficial heaps of mud, sand, and 
 gravel, usually called alluvium, may be likened- to the'rub- 
 
SUBAERIAX DENUDATION. 97 
 
 biah of a quarry which has been rejected as useless by the 
 workmen, or has fallen upon the road between the quarry 
 and the building, so as to lie scattered at random over the 
 ground. 
 
 But we occasionally find in a conglomerate large rounded 
 pebbles of an older conglomerate, which had previously been 
 derived from a variety of different rocks. In such cases we 
 are reminded that, the same materials having been used over 
 and over again, it is not enough to aifirm that the entire mass 
 of stratified deposits in the earth's crust affords a monument 
 and measure of the denudation which has taken place, for in 
 truth the quantity of matter now extant in the form of strat- 
 ified rock represents but a fraction of the material removed- 
 by water and redeposited in past ages. 
 
 Subaerial Denudation. — Denudation may be divided into 
 subaerial, or the action of wind, rain, and rivers ; and sublna- 
 rine, or that effected by the waves of the sea, and its tides 
 and currents. With the operation of the first of these i we 
 are bedt acquainted, and it may be well to give it oar first 
 attention. 
 
 Action of the Wind. — In desert, regions where no rain falls, 
 or where, as in parts of the Sahara, the soil is so salt as to be 
 without any covering of vegetation, clouds of dust and sand 
 attest the power of the wind to cause the shifting of the un- 
 consolidated or disintegrated rock. 
 
 In examining volcanic countries I have been much struck 
 with the great supei-ficial changes brought about by this 
 power in the course of centuries. The highest peak of Ma- 
 deira is about 6050 feet above the sea, and consists of the 
 skeleton of a volcanic cone now 250 feet high, the beds of 
 which once dipped fi'om a centre in all directions at an an- 
 gle of more than 30°. The summit is formed of a dike of 
 basalt with much olivine, fifteen feet wide, apparently the 
 remains of a column of lava which once rose to the crater. 
 Nearly all the scoriae of the upper part of the cone have 
 been swept away, those portions only remaining which were 
 hardened by the contact or proximity of the dike. While I 
 was myself on this peak on January 25, 1854, 1 saw the wind, 
 though it was not stoi-my weather, removing sand and dust 
 derived from the decomposing scoriae. There had been frost 
 in the night, and some ice was still seen in the crevices of 
 the rock. 
 
 On the highest platform of the Grand Canary, at an eleva- 
 tion of 6000 feet, thei-e'is a cylindrical column of hard lava, 
 from which the softer matter has been carried away; and 
 other similar remnants of the dikes of cones of eruption at- 
 
 5 
 
98 ELEMENTS OF GEOLOGY. 
 
 test the denuding power of the wind at points where run- 
 ning water could never have exerted any influence. The 
 waste effected by wind aided by frost and snow, may not be 
 trifling, even in a single winter, and when multiplied by cen- 
 turies may become indefinitely great. 
 
 Action of Running Water. — There are different classes of 
 phenomena which attest in a most striking manner the vast 
 spaces left vacant by the erosive power of water. I may al- 
 lude, first, to those valleys on both sides of which the same 
 strata are seen following each other in the same order, and 
 having the same mineral composition and fossil contents. 
 We may observe, for example, several foi-mations, as Nos. 1, 
 2, 3, 4, in the accompanying diagram (Fig. 80) : No. 1, con- 
 
 Fig. 80. 
 a 
 
 ^ 
 
 a .,/?^^r-S>>^ 
 
 ^^^^^^^^ 
 
 a Older alluviam or drift. 6 Modern alluvimn. 
 
 glomerate, No. 2, clay. No. 3, grit, and No. 4, limestone, each 
 repeated in a series of hills separated by valleys varying in 
 depth. When we examine the subordinate parts of these 
 four formations, we find, in like manner, distinct beds in each, 
 corresponding, on the opposite sides of the valleys, both in 
 composition and order of position. No one can doubt that 
 the strata were originally continuous, and that some cause 
 has swept away the portions which once connected the 
 whole series. A torrent on the side of a mountain produces 
 similar interruptions; and when we make artificial cuts in 
 lowering roads, we expose, in like manner, corresponding 
 beds on either side. But in nature, these appearances occur 
 in mountains several thousand feet high, and separated by 
 intervals of many miles or leagues in extent. 
 
 In the " Memoirs of the Geological Survey of Great Brit- 
 ain" (vol. i.), Professor Eamsay has. shown that the missing 
 beds, removed from the summit of the Mendips, must have 
 been nearly a mile in thickness j and he has pointed out con- 
 siderable areas in South Wales and some of the adjacent 
 counties of England, where a series of primary (or palseozoic) 
 strata, not less than 11,000 feet in thickness, have been strip- 
 ped off. All these materials have of course been transport- 
 ed to new regions, and have entered into the composition of 
 more modern formations. On the other hand, it is shown by 
 
ALLUVIUM. 99 
 
 observations in the same " Survey," that the Palaeozoic strata 
 are from 20,000 to 30,000 feet thick. It is clear that such 
 rocks, formed of mud and sand, now for the most part con- 
 solidated, are the monuments of denuding operations, which 
 took place on a grand scale at a very remote period in the 
 earth's history. For, whatever has been given to one area 
 must always have been borrowed from another; a truth 
 which, obvious as it may seem when thus stated, must be re- 
 peatedly impressed on the student's mind, because in many 
 geological speculations it is taken for granted that the ex- 
 ternal crust of the earth has been always growing thicker 
 in consequence of the accumulation, period after period, of 
 sedimentary matter, as if the new strata were not always 
 produced at the expense of pre-existing rocks, stratified or 
 unstratified. By duly reflecting on the fact that all de- 
 posits of mechanical origin imply the transportation from 
 some other region, whether contiguous or remote, of an 
 equal amount of solid matter, we perceive that the stony ex- 
 terior of the planet must always have grown thinner in one 
 place, whenever, by accessions of new strata, it was acquir- 
 ing thickness in another. 
 
 It is well known that generally at the mouths of large riv- 
 ers, deltas are forming and the land is encroaching upon the 
 sea ; these deltas are monuments of recent denudation and 
 deposition ; and it is obvious that if the mud, sand, and 
 gravel were taken from them and restored to the continents 
 they would fill up a large part of the gullies and valleys 
 which are due to the excavating and transporting power of 
 torrents and rivers. 
 
 Alluvium. — Between the superficial covering of vegetable 
 mould and the subjacent rock there usually intervenes in 
 every district a deposit of loose gravel, sand, and mud, to 
 which when it occurs in valleys the name of alluvium has 
 been popularly applied. The term is derived from aUuvio, 
 an inundation, or alhto, to wash, because the pebbles and 
 sand commonly resemble those of a river's bed or the mud 
 and gravel washed over low lands by a flood. 
 
 In the course of those changes in physical geography 
 which may take place during the gradual emergence of the 
 bottom of the sea and its conversion into dry land, any spot 
 may either have been a sunken reef, or a bay, or estuary, or 
 sea-shore, or the bed of a river. The drainage, moreover, 
 may have been deranged again and again by earthquakes, 
 during which temporary lakes are caused by landslips, and 
 partial deluges occasioned by the bursting of the barriers of 
 such lakes. For this reason it would be unreasonable to 
 
200 ELEMENTS OF GEOLOGY. 
 
 hope that we should ever be able to account for all the allu- 
 vial phenomena of each particular country, seeing that the 
 causes of their origin are so various. Besides, the last opera- 
 tions of water have a tendency to disturb and confound to- 
 gether all pre-existing alluviums. Hence we are always in 
 danger of regarding as the work of a single era, and the 
 effect of one cause, what has in reality been the result of a 
 variety of distinct agents, during a long succession of geo- 
 logical epochs. Much useful instruction may therefore be 
 gained from the exploration of a country like Auvergne, 
 where the superficial gravel of very different eras happens 
 to have been preserved and kept separate by sheets of lava, 
 which were poured out one after the other at periods when 
 the denudation, and probably the upheaval, of rocks were in 
 progress. That region had already acquired in some degree 
 its present configuration before any volcanoes were in ac- 
 tivity, and before any igneous matter was superimposed 
 upon the granitic and fossiliferous formations. Ihe pebbles 
 therefore in the older gi-avels are exclusively constituted of 
 granite and other aboriginal rocks ; and afterwards, when 
 volcanic vents burst forth into eruption, those earlier alluvi- 
 ums were covered by streams of lava, which protected them 
 from intermixtm-e with gravel of subsequent date. In the 
 course of ages, a new system of valleys was excavated, so 
 that the rivers ran at lower levels than those at which the 
 first alluviums and sheets of lava were formed. When, 
 thereforcj fresh eruptions gave rise to new lava, the melted 
 matter was poured out over lower grounds ; and the gravel 
 of these plains differed from the first or upland alluvium, by 
 containing in it rounded fragments of various volcanic rocks, 
 and often fossil bones belonging to species' of land animals 
 different from those which had previously flourished in the 
 same country and been buried in older gravels. 
 
 The annexed drawing (Fig. 81) will explain the different 
 heights at which beds of lava and gravel, each distinct froni 
 the other in composition and age, are observed, some on the 
 flat tops of hills, 700 or 800 feet high, others on the slope of 
 
 Fig. 81. 
 
 Lavas of Auvergne resting ou allnviamB of diiferent 
 
DENUDING POWER OE RIVERS. 101 
 
 the same hills, and the newest of all in the channel of the ex- 
 isting river where there is usually gravel alone, although in 
 some cases a narrow strip of solid lava shares the bottom of 
 the valley with the river. 
 
 The proportion of extinct species of quadrupeds is more 
 numerous in the fossil remains of the gravel No. 1 than in 
 that indicated as No 2 ; and in No. 3 they agree more close- 
 ly, sometimes entirely, with those of the existing fauna. 
 The usual absence or rarity of organic remains in beds of 
 loose gravel and sand is partly owing to the friction which 
 originally ground down the rocks into small fragments, and 
 partly to the porous natui-e of alluvium, which allows the 
 free percola,tion through it of rain-water, and promotes the 
 decomposition and removal of fossil remains. 
 
 The loose transported matter on the surface of a large part 
 of the land now existing in the temperate and arctic regions 
 of the northern hemisphere, must be regai'de'd as being in a 
 somewhat exceptional state, in consequence of the important 
 part which ice has played in comparatively modern geologic- 
 al times. This subject will be more specially alluded to 
 when we describe, in the eleventh chapter, the deposits called 
 " glacial." 
 
 Denuding Power of Eivers affected by Rise or Pall of Land. — 
 It has long been a matter of common observation that most 
 rivers ai'e now cutting their channels through alluvial depos- 
 its of greater depth and extent than could ever have been 
 formed by the present streams. From this fact it has been 
 inferred that rivers in general have grown smaller, or be- 
 come less liable to be flooded than formerly. It may be true 
 that in the history .of almost every country the rivers have 
 been both larger and smaller than they are at the present 
 moment. ^ For the rainfall in particular regions varies ac- 
 cording to climate and physical geography, and is especially 
 governed by the' elevation of the land above the sea, or its 
 distance from it and other conditions equally fluctuating in 
 the course of time. But the phenomenon alluded to may 
 sometimes be accounted for by oscillations in the level of the 
 land, experienced since the existing valleys origina,ted, even 
 where no marked diminution in the quantity of rain and in 
 the size of the rivers has occurred. 
 
 We know that many large areas of land are rising and 
 others sinking, and unless it could be assumed that both the 
 upward and downward movements are everywhere uniform, 
 many of the existing hydrographical basins ought to have 
 the appearance of having been temporary lakes first filled 
 with fluviatile strata and then partially re-excavated. 
 
102 ELEMENTS OF GEOLOGY. 
 
 Suppose, foi example, part of a continent, comprising with- 
 in it a large hydi-ograpliical basin like that of the Mississippi, 
 to subside several inches or feet in a century, as the west 
 coast of Greenland, extending 600 miles north and south, has 
 been sinking for three or four centuries, between the lati- 
 tudes 60° and 69° N.* It will rarely happen that the rate of 
 subsidence will be everywhere equal, and in many cases the 
 amount of depression in the interior will regularly exceed 
 that of the region nearer the sea. Whenever this happens, 
 the fall of the waters flowing from the upland country will 
 be diminished, and each tributary stream will have less pow- 
 er to carry its sand and sediment into the main river, and the 
 main river less power to convey its annual burden of trans- 
 ported matter to the sea. All the rivers, therefore, will pro- 
 ceed to fill up partially their ancient channels, and, during 
 frequent inundations, will raise their alluvial plains by new 
 deposits. If then the same area of land be again upheaved 
 to its former height, the fall, and consequently the velocity, 
 of every river will begin to augment. Each of them will be 
 less given to overflow its alluvial plain ; and their power of 
 carrying earthy matter seaward, and of scouring out and 
 deepening their channels, will be sustained till, after a lapse 
 of many thousand years, each of them has eroded a new chan- 
 nel or valley through a fluviatile formation of comparatively 
 modern date. The surface of what was once the river-plain 
 at the period of greatest depression, will then remain fring- 
 ing the valley-sides in the form of a terrace apparently flat, 
 but in reality sloping down with the general inclination of 
 the river. Everywhere this terrace will present cliffs of grav- 
 el and sand, facing the river. That such a series of move- 
 ments has actually taken place in the main valley of the Mis- 
 sissippi and in its tributary valleys during oscillations of lev- 
 el, I have endeavored to show in my descrijDtion of that 
 country ;f and the fresh-water shells of existing species and 
 bones of land quadrupeds, partly of extinct races, preserved 
 in the terraces of fluviatile origin, attest the exclusion of the 
 sea during the whole process of filling up and partial re-ex- 
 cavation. 
 
 Littoral Denudation. — Part of the action of the waves be- 
 tween high and low water mark must be included in subae- 
 rial denudation, more especially as the undermining of cliffs 
 by the waves is facilitated, by land-springs, and these often 
 lead to the sliding down of great masses of land into the 
 sea. Along our coasts we find numerous submerged for- 
 
 * Principles of Geology, 7th ed., p. 506 ; 10th ed., vol. ii., p. 196. 
 t Second Visit to the United States, vol. i., chap, xxxiv. 
 
INLAND SEA-CLIFFS. 103 
 
 ests, only visible at low M'atier, having the trunks of the 
 trees erect and their, roots attached to them and still 
 spreading through, the ancient soil as when they were liv- 
 ing. They occur in too many places, and sometimes at too 
 great a depth, to be explained by a mere change in the level 
 of the tides, although as the coasts waste away and alter in 
 shape, the height to which the tides rise and fall is always 
 varying, and the level of high tide at any given point may, 
 in the course of many ages, differ by several feet or even 
 fathoms. It is this fluctuation in the height of the tides, 
 and the erosion and destruction of the sea-coast by the 
 waves, that makes it exceedingly difficult for us in a few 
 centuries, or even perhaps in a few thousand years, to de- 
 termine whether there is a change by subterranean move- 
 ment in the relative level of sea and land. 
 
 We often behold, as on the coasts of Devonshire and Pem- 
 brokeshire, facts which appear to lead to opposite conclu- 
 sions. In one place a raised beach with marine littoral 
 shells, and in another immediately adjoining a submerged 
 forest. These phenomena indicate oscillations of level, and 
 as the movements are very gradual, they must give repeat- 
 ed opportunities to the breakers to denude the land which 
 is thus again and again exposed to their fury, although it is 
 evident that the submergence is sometimes effected in such 
 a manner as toallpw the trees which border the coast not 
 to be carried away. 
 
 Inland Sea-cliffs.: — ^In countries where hai"d limestone rocks 
 abound, inland cliffs have often retained faithfully for ages 
 the characters which they acquired when they constituted 
 the boundary of land and sea. Thus, in the Morea, no less 
 than three or even four ranges of cliffs are well preserved, 
 rising one above the other at different distances from the 
 actual shore, the summit of the highest and oldest occasion- 
 ally attaining 1000 feet in elevation. A consolidated beach 
 with marine shells is usually found at the base of each cliff, 
 and a line of littoral caverns. These ranges of cliff probably 
 imply pauses in the process of upheaval when the waves and 
 currents had time to undermine and clear away considerable 
 masses of rock. 
 
 But the beginner should be warned not to expect to find 
 evidence of the former sojourn of the sea on all those lands 
 which we are nevertheless sure have been submerged at pe- 
 riods comparatively modern ; for notwithstanding the en- 
 during nature of the marks left by littoral action on some 
 rocks, especially limestones, we can by no means detect sea- 
 beaches and inland cliffs everywhere. On the contrary, thej 
 
104 ELEMENTS OF GEOLOGY. 
 
 are, upon the whole, extremely partial, and are often entire-' 
 ly wanting in districts composed of argillaceous and sandy 
 formations, which must, nevertheless, have been upheaved 
 at the same time, and by the same intermittent movements, 
 as the adjoining harder rocks. 
 
 Escarpments. — Besides the inland cliffs above alluded, to 
 which mark the ancient limits of the sea, there are other ab- 
 rupt terminations of rocks of various kinds which resemble 
 sea-cliffs, but which have in reality been due to subaerial de- 
 nudation. These have been called "escarpments," a term 
 which it is useful to confine to the outcrop of particular 
 formations having a scarped outline, as distinct from cliffs 
 due to marine action. 
 
 I formerly supposed that the steep line of cliff-like slopes 
 seen along the outcrop of the chalk, when we follow the edge 
 of the North or South Downs, was due to marine action; but 
 Professor Ramsay has shown* that the present outline of the 
 physical geographyis more in favor of the idea of the escarp- 
 ments having been due to gradual waste since the rocks were 
 exposed in the atmosphere to the action of rain and rivers. 
 
 Mr. Whittaker has given a good summary of the grounds 
 for ascribing these apparent sea-cliffs to waste in the open 
 air. 1. There is an absence of all signs of ancient sea-beach- 
 es or littoral deposits at the base of the escarpment. 2. 
 Great inequality is observed in the level of the base line. 
 3. The escarpments do not intersect, like sea-cliffs, a series 
 of distinct rocks, but are always confined to the boundary- 
 line of the same formation. 4. There are sometimes differ- 
 ent contiguous and parallel escarpments — those, for exam- 
 ple, of the greensand and chalk — which are so near each oth- 
 er, and occasionally so similar in altitude, that we can not 
 imagine any existing archipelago if converted into dry land 
 to present a like outline. 
 
 The above theory is by no means inconsistent with the 
 opinion that the limits of the outcrop of the chalk and 
 greensand which the escarpments now follow, were original- 
 ly determined by marine denudation. When the south-east 
 of England last emerged from beneath the level of the sea, 
 it was acted upon, no doubt, by the tide, waves, and cur- 
 rents, and the chalk would form from the first a mass pro- 
 jecting above the more destructible clay called gault. 
 Still the present escarpments so much resembling sea-cliffs 
 have no doubt, for reasons above stated, derived their most 
 characteristic features subsequently to emergence from sub- 
 aerial waste by rain and rivers. 
 
 * Physical Geography and Geology of Great Britain, p. 78. 1864. 
 
SUBMARINE DENUDATION. 105 
 
 Submarine Denudation. — When we attempt to estimate the 
 amount of submarine denudation, we become sensible of the 
 disadvantage under which we labor from our habitual inca- 
 pacity of observing the action of marine currents on the bed 
 of the sea. We know that the agitation of the waves, even 
 during storms, diminishes at a rapid rate, so as to become 
 very insignificant at the depth of a few fathoms, and is 
 quite imperceptible at the depth of about sixteen fathoms ; 
 but when large bodies of water are transferred by a current 
 from one part of the ocean to another, they are known to 
 maintain at great depths such a velocity as must enable 
 them to remove the finer, and sometimes even- the coarser, 
 materials of the rocks over which they flow. As the Missisr 
 sippi when more than 150 feet deep can keep open its chan- 
 nel and even carry down gravel and sand to its delta, the 
 surface velocity being not more^than two or three miles an 
 hour, so a gigantic current, like the Gulf Stream, equal in 
 volume to many hundred Mississippis, and having in parts 
 a surface velocity of more than three miles, may act as a 
 propelling and abrading power at still greater depths. But 
 the eflicaey of the sea as a denuding agent, geologically con- 
 sidered, is not dependent on the power of currents to pre- 
 serve at great depths a velocity sufficient to remove sand 
 and mud, because, even where the deposition or removal of 
 sediment is not in progress, the depth of water does not re- 
 main constant throughout geological time. Every page of 
 the geological record proves to us that the relative levels of 
 land and sea, and the position of the ocean and of continents 
 and islands, has been always varying, and we may feel sure 
 that some portions of the submarine area are now rising and 
 others sinking. The force of tidal and other currents and 
 of the waves during storms is sufiicient to prevent the 
 emergence of many lands, even though they may be under- 
 going continual upheaval. It is not an uncommon error to 
 imagine that the waste of sea-clifis afibrds the measure of 
 the amount of marine denudation of which it probably con- 
 stitutes an insignificant portion. 
 
 Dogger-bank. — That great shoal called the Dogger-bank, 
 about sixty miles east of the coast of Northumberland, and 
 occupying an area about as large as Wales, has nowhere a 
 depth of more than ninety feet, and in its shallower parts is 
 less than forty feet under water. It might contribute to- 
 wards the safety of the navigation of our seas to form an 
 artificial island, and to erect a light-house on this bank ; 
 but no engineer would be rash enough to attempt it, as he 
 would feel sure that the ocean in the first heavy gale -wfould 
 
 5* 
 
IQQ ELEMENTS OF GEOLOGY. 
 
 sweep it away as readily as it does every temporary shoal 
 that accumulates from time to time around a sunk vessel on 
 the same bank.* . . • . 
 
 No observed geographical changes in historical times en- 
 title us to assume that where upheaval may be in progress 
 it proceeds at a rapid rate. Three or four feet rather than 
 as many yards in a century may probably be as much as 
 we can reckon upon in our speculations ; and if such be the 
 case, the continuance of the upward movement might easily 
 be counteracted by the denuding force of such currents aid- 
 ed by such waves as, during a gale, are known to prevail in 
 the German Ocean. What' parts of the bed of the ocean are 
 stationary at present, and what areas may be i-ising or sink- 
 ing, is a matter of which we are very ignorant, as the tak- 
 ing of accurate soundings is but of recent date. 
 
 Newfoundland Bank. — The great bank of Newfoundland 
 may be compared in size to the whole of England. This 
 part of the bottom of the Atlantic is surrounded on three 
 sides by a rapidly deepening ocean, the bank itself being 
 from twenty to fifty fathoms (or from 120 to 300 feet) un- 
 der water. We are unable to determine by the comparison 
 of different charts made at distant periods, whether it is un- 
 dergoing any change of level, but if it be gradually rising 
 we can not anticipate on that account that it w^ill become 
 land, because the breakers in an open sea would exercise a 
 prodigious force even on solid rock brought up to within a 
 few yards of the surface. We know, for examjjle, that when 
 a new volcanic island rose in the Mediterranean in 1831, the 
 waves were capable in a few years of reducing it to a sunken 
 rock. 
 
 In the same way currents which flow over the Newfound- 
 land bank a great part of the year at the rate of two miles 
 an hour, and are known to retain a considerable velocity 
 to near the bottom, may carry away all loose sand and mud, 
 and make the emergence of the shoal impossible, in spite of 
 the accessions of mud, sand, and boulders derived occasion- 
 ally from melting icebergs which, coming from the northern 
 glaciers, are frequently stranded on various parts of the 
 bank. They must often leave at the bottom large erratic 
 blocks which the marine currents may be incapable of mov- 
 ing, but the same rocky fragments may be made to sink by 
 the undermining of beds consisting of finer matter on which 
 the blocks and gravel repose. In this way gravel and 
 boulders may continue to overspread a submarine bottom 
 after the latter has been lowered for hundreds of feet, the 
 * Principles; 10th ed., vol. i., p. 569. 
 
SUBMAKINE DENUDATION. 10^ 
 
 surface never having been able to emerge and become land. 
 It is by no means improbable that the annual removal of an 
 average thickness -of half an inch of rock might counteract 
 the ordinary upheaval -which large submarine areas are un- 
 dergoing; and the real enigma which the geologist has to 
 solve is not the extensive denudation of the white chalk or 
 of our tertiary sands and clays, but the fact that such inco- 
 herent materials have ever succeeded in lifting up their 
 beads above water in an open sea. Why were they not 
 swept away during storms into some adjoining abysses, the 
 highest parts of each shoal being always planed off down to 
 the depth of a few fathoms ? The hardness and toughness 
 of some rocks already exposed to windward and acting aS 
 breakwaters may perhaps have assisted; nor must we for- 
 get the protection afforded by a dense and unbroken cover- 
 ing of barnacles, limpets, and other creatures which flourish 
 •nost between high and low water and shelter some newly 
 risen coasts from the waves. 
 
J08 ELEMENTS Or GEOLOGY. 
 
 CHAPTER VII. 
 
 ■.'OINT ACTION OF DENTTDATIOlir, UPHEAVAL, AND SUBSIDENCE 
 
 IN bbm:odellin& the eaeth's ckust. 
 
 How we obtain an Insight at the Sm-face, of the Arrangement of Rocks at 
 great Depths. — -Why the Height of the successive Strata in a given Region 
 is so disproportionate to their Thickness. — Computation . of the average 
 annual Amount of subaerial Denudation. — Antagonism of Volcanic Force 
 to the Leyelling Power of running Water. — How far the Transfer of Sed- 
 iment from the Land to a neighboring Sea-bottom may affect Subterranean 
 Movements. — Permanence of Continental and Oceanic Areas. 
 
 How we obtain an Insight at the Surface of the Arrange- 
 ment of Rocks at great Depths.— The reader has been already- 
 informed that, in the structure of the earth's crust, we often 
 find proofs of the direct superposition of marine to fresh- 
 water strata, and also evidence of the alternation of deep-sea 
 and shallow-water formations. In order to explain how 
 such a series of rocks could be made to form our present 
 continents and islands, we have not only to assume that 
 there have been alternate upward and downward movements 
 of great vertical extent, but that the upheaval in the areas 
 which we at present inhabit has, in later geological times, 
 sufficiently predominated over subsidence to cause these por- 
 tions of the earth's crust to be land instead of sea. The sink- 
 ing down of a delta beneath the sea-level may cause strata 
 of fluviatile or even terrestrial origin, such as peat with trees 
 proper to marshes, to be covered by deposits of deep-sea ori- 
 gin. There is also no end to the thickness of mud and sand 
 which may accumulate in shallow water, provided that fresh 
 sediment is brought down from the wasting land at a rate 
 coiTesponding to that of the sinking of the bed of the sea. 
 The latter, again, may sometimes sink so fast that the earthy 
 matter, being intercepted in some new landward depression, 
 may never reach its former resting-place, where, the water 
 becoming clear may favor the growth of shells and corals, 
 and calcareous rocks of organic origin may thus be superim- 
 posed on mechanical deposits. 
 
 The succession of strata here alluded to would be consist- 
 ent with the occurrence of gradual downward and upward 
 movements of the land and bed of the sea without any disr 
 turbance of the horizontality of the several formations. But 
 
LATERAL COMPEESSION. 109 
 
 the arrangement of rocks Composing the earth's crust differs 
 materially from that which would result irom a mere series 
 of vertical movements. Had the v&lcanic forces been con- 
 fined to such movements, and had the, stratified rocks been 
 first formed beneath the sea and then, raised above it, with- 
 out any lateral compression, the geologist would never have 
 obtained an insight into the monuments of various ages, 
 some of extremely remote antiquity. 
 
 What we have said in Chapter V. of dip and strike, of the 
 folding and inversion of strata, of anticlinal and synclinal 
 flexures, and in Chapter VI. of denudation at different peri- 
 ods, whether subaerial or submarine, must be understood be- 
 fore the student can comprehend what may at first seem to 
 him an anomaly, but which it is his business particularly to 
 understand. I allude to the small height above the level of 
 the sea attained by strata often many miles in thickness, 
 and about the chronological succession of which, in one and 
 the same region, there is no doubt whatever. Had stratified 
 I'ocks in general remained horizontal, the waves of the sea 
 would have been enabled during oscillations of level to plane 
 off entirely the uppermost beds as they rose or sank during 
 the emergence or submergence of the land. But the occur- 
 rence of a series of formations of widely different ages, all 
 remaining horizontal and in conformable stratification, is ex- 
 ceptional, and for this reason the total annihilation of the 
 uppermost strata has rarely taken place. We owe, indeed, 
 to the sideway movements of lateral compression those an- 
 ticlinal and synclinal curves of the beds already described 
 (Fig. 55, p, 74), which, together with denudation, subaerial 
 and submarine, enable us to investigate the structure of the 
 earth's crust many miles below those points which the miner 
 can reach. I have already shown in Fig. 56, p. 76, how, at 
 St. Abb's Head, a series of strata of indefinite thickness may 
 become vertical, and then denuded, so that the edges of the 
 beds alone shall be exposed to view, the altitude of the up- 
 heaved ridges being reduced to a moderate height above 
 the sea-level ; and it may be observed that although the in- 
 cumbent strata of Old Red Sandstone are in that place near- 
 ly horizontal, yet these same newer beds will in other plafes 
 be found so folded as to present vertical strata, the edges of 
 which are abruptly cut off, as in 2, 3, 4 on the right-hand 
 side of the diagram, Fig. 55, p. 74. 
 
 Why the Height of the successive Strata in a given Re- 
 gion is so disproportionate to their Thickness. — We can not 
 too distinctly bear in mind how dependent we are on the 
 joint action of the volcanic and aqueous forces, the one in 
 
110 ELEMENTS OF GEOLOGY. 
 
 disturbing the original position of rocks, and the other in de- 
 stroying large portions of them, for our power of consulting 
 the different pages and volumes of those stony records of 
 which the crust of the globe is composed. Why, it may be 
 asked, if the ancient bed of the sea has been in many regions 
 uplifted to the height of two or three miles, and sometimes 
 twice that altitude, and if it can be proved that some single 
 formations are of themselves two or three miles thick, do we 
 so often find several important groups resting one upon the 
 other, yet attaining only the height of a few hundred feet 
 above the level of the sea ? 
 
 The American geologists, after carefully studying the Al- 
 leghany or Appalachian mountains, have ascertained that 
 the older fossiliferous rocks of that chain (from the Silurian 
 to the Carboniferous inclusive) are not' less than 42,000 feet 
 thick, and if they were now superimposed on each other in 
 the order in which they were thrown down, they ought to 
 equal in height the Himalayas with the Alps piled upon 
 them. Yet they rarely reach an altitude of 5000 feet, and 
 their loftiest peaks are no more than 7000 feet high. The 
 Carboniferous strata forming the highest member of the se- 
 ries, and containing beds of coal, can be shown to be of shal- 
 low-water origin, or even sometimes to have originated in 
 swamps in the open air. But what is more surprising, the 
 lowest part of this great Palasozoic series, instead of having 
 been thrown down at the bottom of an abyss more than 
 40,000 feet deep, consists of sediment (the Potsdam sand- 
 stone), evidently spread out on the bottom of a shallow sea, 
 on which ripple -marked sands were occasionally formed. 
 This vast thickness of 40,000 feet is not obtained by adding 
 together the maximum density attained by each formation 
 in distant parts of the chain, but by measuring the succes- 
 sive groups as they are exposed in a very limited area, and 
 where the denuded edges of the vertical strata forming the 
 parallel folds alluded to at p. 87 " crop out " at the suriaee. 
 Our attention has been called by Mr. James Hall, Paleon- 
 tologist of New York, to the fact that these Paleozoic rocks 
 of the Appalachian chain, which are of such enormous den' 
 sity, where they are almost entirely of mechanical origin, 
 thin out gradually as they are traced to the westward, 
 where evidently the contemporaneous seas allowed organic 
 rocks to be formed by corals, echinoderms, and encrinites in 
 clearer water, and where, although the same successive pe- 
 riods are represented, the total mass of strata from the Silu- 
 rian to the Carboniferous, instead of being 40,000 is onlv 
 4000 feet thick. ■' 
 
VAST THICKNESSES OE STRATA. m 
 
 A like phenomenon is exhibited in every mountainous 
 country, as, for example, in the European Alps ; but we need 
 not go farther than the north of England for its illustration. 
 Thus in Lancashire and central England the thickness of the 
 Cai'boniferous formation, including the Millstone Grit and 
 Yoredale beds, is computed to be more than 1 8,000 feet ; to 
 this we may add the Mountain Limestone, at least 2000 feet 
 in thickness, and the overlying Permian and Triassic forma- 
 tions, 3000 or 4000 feet thick. How then does it happen 
 that the loftiest hills of Yorkshire and Lancashire, instead 
 of being 24,000 feet high, never rise above 3000 feet ? For 
 heire, as before pointed out in the Alleghanies, all the great 
 tMcknesses are sometimes found in close approximation and 
 in a region only a few miles in diameter. It is true that 
 these same sets of strata do not preserve their full force 
 when followed for indefinite distances. Thus the 18,000 feet 
 of Carboniferous grits and shales in Lancashire, before al- 
 luded to, gradually thin out, as Mi-, Hull has shown, as they 
 extend southward, by attenuation or original deficiency of 
 sediment, and not in consequence of subsequent denudation, 
 so that when we have followed them for about 100 miles 
 into Leicestershire, they have dwindled away to a thickness 
 of only 3000 feet. In the same region the Carboniferous 
 limestone attains so unusual a thickness — namely, more than 
 4000 feet — as to appear to compensate in some measure for 
 the deficiency of contemporaneous sedimentary rock.* 
 
 It is adrnitted that when two formations are unconforma- 
 ble their fossil remains almost always diflTer considerably. 
 The break in the continuity of the organic forms seems con- 
 nected with a great lapse of time, and the same interval has 
 allowed extensive disturbance of the strata, and removal of 
 parts of them by denudation, to take place. The more we 
 extend our investigations the more numerous do the proofs 
 of these breaks become, and they extend to the most ancient 
 rocks yet discovered. The oldest examples yet brought to 
 light in the British Isles are on the borders of Rosshire and 
 Sutherlandshire, and have been well described by Sir Roder- 
 ick Murchison, by whom their chronological relations were 
 admirably worked out, and proved to be very difierent from 
 those which previous observers had imagined them to be. I 
 had an opportunity in the autumn of 1869 of verifying the 
 splendid section given in Fig. 82 by climbing in a few hours 
 from the banks of Loch Assynt to the summit of the moun- 
 tain called Queenaig, 2673 feet high. ^ ' 
 
 The formations 1, 2, 3, the Laurentian, Cambrian, and Si- 
 * Hull, Quart. Geol. Journ., vol. xxiv., p. 322. 1868. 
 
112 
 
 ELEMENTS OF GEOLOGY. 
 
 lurian, to be explained in Chapters XXV. and XXVI., not 
 only occur in succession in this one mountain, but their un- 
 confoi-mable junctions are distinctly exposed to view. 
 
 To begin with the oldest set of rocks. No. 1 ; they consist 
 chiefly of hornblendic' gneiss, and in the neighboring Heb- 
 rides form whole islands, attaining a thickness of thousands 
 of feet,. although they have sufiered such contortions and 
 denudation that they seldom rise more than a few hundred 
 feet above the sea-level. In discordant stratification upon 
 
 WNW 
 
 Fig. 82. 
 Qiieenaig (2673 feet). 
 
 ESE 
 
 1 2 
 
 Unconformable Paleozoic strata, Sntherlandshire (Muvchison). 
 
 1. Lanrentian gneiss. 2. Cambrian conglomerate and sandstone. 3, 8'. Qaartzose 
 Lower Silurian, with annelid burrows. 
 
 the edges of this gneiss reposes No. 2, a group of conglom- 
 erate and purple sandstone referable to the Cambrian (or 
 Longmynd) formation, which can elsewhere be shown to be 
 characterized by its peculiar organic remains. On this again 
 rests No. 3, a lower member of the important group called 
 Silurian, an outlier of which, 3', (?aps the summit of Queenaig, 
 attesting the removal by denudation of rocks of the same 
 age, which once extended from the great mass 3 to 3'. Al- 
 though this rock now consists of solid quartz, it is clear that 
 in its original state it was formed of fine sand, perforated by 
 numerous lob-worms or annelids, which left their burrows 
 in the shape of tubular hollows (see Chapter XXVI., figure 
 of Arefiicolites), hundreds, nay thousands, of which I saw as 
 I ascended the mountain. 
 
 In Queenaig we only behold this single quartzose mem- 
 ber of the Silurian series, but in the neighboring country 
 (see Fig. 83) it is seen to the eastward to be followed by 
 
 1 2 3 So 36 
 
 Diagrammatic section of the same groups near Queenaig (Mnrchieon). 
 
 1. Lanrentian gneiss. 2. Cambrian conglomerate and sandstone. 3^ 3'. Qnartzose 
 Lower Silurian, with annelid bnrrows. 3a. Fossiliferous Silurian limestone. 
 3&. Qaartzose, micaceous andgneissose rocks (altered Silurian). 
 
AMOUNT Ol? SUBAiiRIAL DENUDATION. 113 
 
 limestones, 3a, and schists, Sb, presenting numerous folds, 
 and becoming more and more metamorphic and crystalline, 
 until at length, although very diiferent in age and strike, 
 they much resemble in appearance the group No. 1. It is 
 very seldom that in the same country one continuous forma- 
 tion, such as the Silurian, is, as in this case, more fossiliferous 
 and less altered by volcanic heat in its older thaii ii its 
 newer strata, and still more rare to find an underlying and 
 unconformable group, like the Cambrian retaining its orig- 
 inal condition of a conglomerate and sandstone more per- 
 fectly than the overlying formation. Here, also we may-rer 
 mark in regard to the origin of these Cambrian rocks that 
 they were evidently produced at the expense of the underly- 
 ing Laurentian, for the rounded pebbles occurring in them 
 are identical in composition and texture. with that crystal- 
 line gneiss which constitutes the contorted beds of the in- 
 ferior formation No. 1. When the reader has studied the 
 chapter on metamorphism, and has become aware how much 
 modification by heat, pressure, and chemical action is rer 
 quired before the conversion of sedimentary into crystalline 
 strata can be brought about, he will appreciate the insight 
 which we thus gain into the date of the changes which had 
 ah'eady been effected in the Laurentian , rocks long before 
 the Cambi-ian pebbles of quartz and gneiss were derived 
 from them. The Laurentian is estimated by Sir William 
 Logan to amount in Canada to 30,000 feet in thickness. As 
 to the Cambrian, it is supposed by Sir Roderick Murchison 
 that the fragment left in Sutherlandshire is about 3500 feet 
 thick, and in Wales and the borders of Shropshire this forr 
 mation may equal 10,000 feet, while the Silurian strata No, 
 3, difficult as it may be to measure them in their various 
 foldings to the eastward, whex'e they have been invaded bj'' 
 intrusive masses of granite, are supposed many times to sur- 
 pass the Cambrian in volume and density. 
 
 But although we are dealing here with stratified rocks, 
 each of which would be several miles in thickness, if they 
 were fully i-epresented, the whole of them do not attain the 
 elevation of a single mile above the level of the sea. 
 
 Computation of the Average annual Amount of Subaerial 
 Denudation. — The geology of the district above alluded to 
 may assist our imagination in conceiving the extent to 
 which groups of ancient rocks, each of which may in their 
 turn have formed continents and oceanic basins, have been 
 disturbed, folded, and denuded even in the course of a few 
 out of many of those geological periods to which our im- 
 perfect records relate. It is not easy for us to overestimate 
 
114 ELEMENTS OF GEOLOGY. 
 
 the effects wnich causes in every-day action must prodnee 
 when the multiplying power of time is taken into account. 
 
 Attempts were made by Manfredi in 1736, and afterwards 
 by Playfair in 1802, to calculate the time which it would 
 require to enable the rivers to deliver over the whole of the 
 land into the basin of the ocean. The data were at first 
 too imperfect and vague to allow them even to approximate 
 to safe conclusions. But in our own time similar investiga- 
 tions have been renewed with more prospect of success, the 
 amount brought down by many large rivers to the sea hav- 
 ing been more accurately ascertained. Mr. Alfred Tylor, 
 in 1850, inferred that the quantity of detritus now being dis- 
 tributed over the sea-bottom would, at the end of 10,000 
 years, cause an elevation of* the sea-level to the extent of at 
 least three inches.* Subsequently Mr. Croll, in 1867, and 
 again, with more exactness, in 186S, deduced from the latest 
 measurement of the sediment transported by European and 
 American rivers the rate of subaerial denudation to which 
 the surface of large continents is exposed, taking especially 
 the hydrographical basin of the Mississippi as affording the 
 best available measure of the average waste of the land. 
 The conclusion arrived at in his able memoirf was that the 
 whole terrestrial surface is denuded at the rate of one foot 
 in 6000 years, and this opinion was simultaneously enforced 
 by his fellow-laborer, Mr. Geikie, who, being jointly engaged 
 in the same line of inquiry, published a luminous essay on 
 the subject in 1868. 
 
 The student, by referring to my " Pi-inciples of Geology ,?'! 
 may see that Messrs. Humphrey and Abbot, during their 
 survey of the Mississippi, attempted to make accurate meas- 
 urements of the proportion of sediment carried down annual- 
 ly to the sea by that river, including not only the mud held 
 in suspension, but also the sand and gravel forced along the 
 bottom. 
 
 It is evident that when we know the dimensions of the 
 area which is drained, and the annual quantity of earthy 
 matter taken from it and borne into the sea, we can affirm 
 how much on an average has been removed from the general 
 surface in one year, and there seems no danger of our over- 
 rating the mean rate of waste by selecting the Mississippi as 
 our example, for that river drains a country equal to more 
 than half the continent of Europe, extends through twenty 
 degrees of latitude, and therefore through regions enjoying 
 a great variety of climate, and some of its "tributaries de- 
 * Tylor, Phil. Mag., 4tli series, p. 268. 1850. 
 tCi-oU, Phil. Ma2.,1868, p. 381. t Vol. i., p. 442. 1867. 
 
VOLCAIJIC SOECE OPPOSED TO RUNNING WATEK. 115 
 
 scend from mountains of great height. The Mississippi is 
 also more likely to afford us a fair test of ordinary denuda- 
 tion, because, unlike the St. Lawrence and its tributaries, 
 there are no great lakes in which the fluviatile sediment is 
 thrown down and arrested in its way to the sea. In striking 
 a general average we have to remember that there are large 
 deserts in which there is scai-cely any rainfall, and tracts 
 which are as rainless as parts of Peru, and these must not be 
 neglected as counterbalancing others, in the tropics, where 
 the quantity of rain is in excess. If then, argues Mr. Geikie, 
 we assume that the Mississippi is lowering the surface of the 
 great basin which it drains at the rate of 1 foot in 6000 years, 
 10 feet in 60,000 years, 100 feet in 600,000 years, and 1000 
 feet in 6,000,000 years, it would not require more than about 
 4,500,000 years to wear away the whole of the North Amer- 
 ican continent if its mean height is correctly estimated by 
 Humboldt at 748 feet. And if the mean height of all the 
 land now above the sea throughout the globe is 1000 feet, 
 as some geograj)hers believe, it would only require six mil- 
 lion years to subject a mass of rock equal in volume to the 
 whole of the land to the action of subaiirial denudation. It 
 may be objected that the annual waste is partial, and not 
 equally derived from the general surface of the country, in- 
 asmuch as plains, water-sheds, and level ground at all heights 
 remain comparatively unaltered ; but this, as Mr. Geikie has 
 ■well pointed out, does not affect our estimate of the sum to- 
 tal of denudation. The amount remains the same, and if we 
 allow too little for the loss from the surface of table-lands 
 we only increase the proportion of the loss sustained by the 
 sides and bottoms of the valleys, and vice versa* 
 
 Antagonism of Volcanic Force to the Levelling Power of 
 Bunning Water. — In all these estimates it is assumed that 
 the entire quantity of land above the sea-level remains on 
 an average undiminished in spite of annual waste. Were it 
 otherwise the subaerial denudation would be continually less- 
 ened by the diminution of the height and dimensions of the 
 land exposed to waste. Unfortunately we have as yet no 
 accurate data enabling us to measure the action of that force 
 by which the inequalities of the surface of the earth's crust 
 may be restored, and the height of the continents and depth 
 of the seas made to continue unimpaired. I stated in 1 830 
 in the " Principles of GeoIogy,"f that running water and vol- 
 canic action are two antagonistic forces ; the one laboring 
 
 * Trans. Geol. Soc. Glasgow., vol. iii., p. 169. 
 
 + 1st ed., chap, x., p. 167, 1830; see also 10th ed., vol. i., chap, xv., p. 
 327. 1867. 
 
116 ELEMENTS OP GEOLOGY. 
 
 continually to reduce the whole of the land to the level of 
 the sea, the other to restore and maintain the inequalities of 
 the crust on which the very existence of islands and conti- 
 nents depends. I stated, however, that when we endeavor 
 to form some idea of the relation of these destroying and 
 renovating forces, we must always bear in mind that it is 
 not simply by upheaval that subterranean movements can 
 counteract the levelling force of running water. For where- 
 as the transportation of sediment from the land to the ocean 
 would raise the general sea-level, the subsidence of the sea- 
 bottom, by increasing its capacity, would check this rise and 
 prevent the submergence of the land. I have, indeed, en- 
 deavored to show that unless we assume that there is, on 
 the whole, more subsidence than upheaval, we must suppose 
 the diameter of the planet to be always increasing, by that 
 quantity of volcanic matter which is annually poured out in 
 the shape of lava or ashes, whether on the land or in the bed 
 of the sea, and which is derived from the interior of the earth. 
 The abstraction of this matter causes, no doubt, subterranean 
 vacuities and a corresponding giving way of the surface ; if 
 it were not so, the average density of parts of the interior 
 would be always lessening and the size of the planet increas- 
 ing.* 
 
 Our inability to estimate the aniount or direction of the 
 movements, due to volcanic power by no means renders its 
 efficacy as a land-preserving force in past times a mere mat- 
 ter of conjecture. The student will see in Chapter XXIV. 
 that we have proofs of Carboniferous forests hundreds of 
 miles in extent which grew on the lowlands or deltas near 
 the sea, and which subsided and gave place to other forests, 
 until in some regions fluviatile and shallow-water strata with 
 occasional seams of coal were piled one over the other, till 
 they attained a thickness of many thousand feet. Such ac- 
 cumulations, observed in Great Britain and America on opr 
 posite sides of the Atlantic, imply the long-continued exist- 
 ence of land vegetation, and of rivers draining a former con- 
 tinent placed where there is now deep sea. 
 
 It will be also seen in Chapter XXV. that we have evi- 
 dence of a rich terrestrial flora, the Devonian, even more an- 
 cient than the Carboniferous ; while on the other hand, the 
 later Triassic, Oolitic, Cretaceous, and successive Tertiary 
 periods have all supplied us with fossil plants, insects, or 
 terrestrial mammalia ; showing that, in spite of great oscilla- 
 tions of level and continued changes in the position of land 
 and sea, the volcanic forces have maintained a due propor- 
 *Principles, vol. ii.,p. 237; also lsted.,p. 447. 1830.. 
 
PEEMANENCE OF CONTINENTS AND OCEANH. 117 
 
 tion of dry land. We may appeal also to fresh-water forma- 
 tions, such as the Purbeck and Wealden, to prove that in the 
 Oolitic and Neocomian eras there were rivers draining an- 
 cient lands in Europe in times when we know that other 
 spaces, now above water, were submerged. 
 
 How far the Transfer of Sediment from the Land to a 
 neighboring Sea-bottom may affect Subterranean Movements. 
 — Little as we understand at present the laws which govern 
 the distribution of volcanic heat in the interior and crust of 
 the globe, by which mountain chains, high table-lands, and 
 the abysses of the ocean ai-e formed, it seems clear that this 
 heat is the prime mover on which all the grander features in 
 the external configuration of the planet depend. 
 
 It has been suggested that the stripping off by denuda- 
 tion of dense masses from one part of a continent and the 
 delivery of the same into the bed of the ocean must have a 
 decided effect in causing changes of temperature in the 
 earth's crust below, or, in other words, in causing the subter- 
 ranean isothermals to shift their position. If this be so, one 
 part of the crust may be made to rise, and another to sink, 
 by the expansion and contraction of the rocks, of which the 
 temperature is altered. 
 
 I can not, at present, discuss this subject, of which I have 
 treated more fully elsewhere,* but may state here that I be- 
 lieve this transfer of sediment to play a veiy subordinate 
 part in modifying those movements on which the configura- 
 tion of the earth's crust depends. In order that strata of 
 shallow-water origin should be able to attain a thickness of 
 several. thousand feetj and so come to exert a considerable 
 downward pressure, there must have been first some inde- 
 pendent and antecedent causes at work which have given 
 rise to the incipient shallow receptacle in which the sediment 
 began to accumulate. The same causes there continuing to 
 depress the sea-bottom, room would be made for fresh ac- 
 cessions of sediment, and it would only be by a long repe- 
 tition of the depositing process that the new matter could 
 acquire weight enough to affect the temperature of the rocks 
 far below, so as to increase or diminish their volume. 
 
 Permanence of Continental and Oceanic Areas. — If the 
 thickness of more than 40,000 feet of sedimentary strata be- 
 fore alluded to in the Appalachians proves a preponderance 
 of downward movements in Palaeozoic times in a district 
 now forming the eastei-n border of North America, it also 
 proves, as before hinted, the continued existence and waste 
 of some neighboring continent, probably formed of Lauren- 
 * Principles, vol. ii., p. 229. 1868. 
 
118 ELEMENTS OF GEOLOGY. 
 
 tian rocks, and situated where the Atlantic now prevails. 
 Such an hypothesis would be in perfect harmony with the 
 conclusions forced upon us by the study of the present con- 
 figuration of our continents, and the relation of their height 
 to the depth of the oceanic basins ; also to the considerable 
 elevation and extent sometimes reached by drift containing 
 shells of recent species, and still more by the fact of sedi- 
 mentary strata, several thousand feet thick, as those of cen- 
 tral Sicily, or such as flank the Alps and Apennines, contain- 
 ing fossil nioUusca sometimes almost wholly identical with 
 species still living. 
 
 I have remarked elsewhere* that upward and downward 
 movements of 1000 feet or more would turn much land into 
 sea and sea into land in the continental areas and their bor- 
 ders, whereas oscillations of equal magnitude would have no 
 corresponding eifect in the bed of the ocean generally, be- 
 lieved as it is to have a mean depth of 15,000 feet, and which, 
 whether this estimate be correct or not, is certainly of great 
 profundity. Subaerial denudation would not of itself lessen 
 the area of the land, but would tend to fill up with sediment 
 seas of moderate depth adjoining the coast. ■ The coarser 
 matter falls to the bottom near the shore in the first still 
 water which it reaches, and whenever the sea-bottom on 
 which this matter has been thrown is slightly elevated, it 
 becomes land, and an upheaval of a thousand feet causes it 
 to attain the mean elevation of continents in general. 
 
 Suppose, therefore, we had ascertained that the triturating 
 power of subaerial denudation might in a given time — in 
 three, or six, or a greater number of millions of years — pul- 
 verize a volume of rock equal in dimensions to all the pres- 
 ent land, we might yet find, could we revisit the earth at the 
 end of such a period, that the continents occupied very much 
 the same position which they held before ; we should find 
 the rivers employed in carrying down to the sea the very 
 same mud, sand, and pebbles with which they had been 
 charged in oar own time, the superficial alluvial matter as 
 well as a great thickness of sedimentary strata would inclose 
 shells, all or a great part of which we should recognize as 
 specifically identical with those already known to us as liv- 
 ing. Every geologist is aware that great as have been the 
 geographical changes in the northern hemisphere since the 
 commencement of the Glacial Period, there having been sub- 
 mergence and re-emergence of land to the extent of 1000 feet 
 vertically, and in the temperate latitudes great vicissitudes 
 of climate, the marine mollusca have not changed, and the 
 
 * Principles, vol. i.; p. 265. 1867. 
 
PERMANEjS'CE of continents and oceans. 119 
 
 same drift which had been carried down to the sea at the 
 beginning of the period is now undergoing a second trans- 
 portation in the same direction. 
 
 As when we have measured a fraction of time in an hour- 
 glass we have only to reverse the position of our chronom- 
 eter and we make the same sand measure over again the 
 duration of a second equal period, so when the volcanic force 
 has remoulded the form of a continent and the adjoining sea- 
 bottom, the same materials are made to do duty a second 
 time. It is true that at each oscillation of level the solid 
 rocks composing the original continent suffer some fresh 
 denudation, and do not remain unimpaired like the wooden 
 and glass iramework of the hour-glass, still the wear and 
 tear suffered by the larger area exposed to subaerial denu- 
 dation consists either of loose drift or of sedimentary strata, 
 which were thrown down in seas near the land, and subse- 
 quently upraised, the same continents and oceanic basins re- 
 maining in existence all the while. 
 
 From all that we know of the extreme slowness of the 
 upward and downward movements which bring about even 
 slight geographical changes, we may infer that it would re- 
 quire a long succession of geological periods to cause the 
 submarine and supramarine areas to change places, even if 
 the ascending movements in the one region and the descend- 
 ing in the other were continuously in one direction. But 
 we have only to appeal to the structui-e of the Alps, where 
 there are so many shallow and deep water formations of va- 
 rious ages crowded into a limited area, to convince ourselves 
 that mountain chains are the result of great oscillations of 
 level. High land is not produced simply by uniform up- 
 heaval, but by a predominance of elevatory over subsiding 
 movements. Where the ocean is extremely deep it is be- 
 cause the sinking of the bottom has been in excess, in spite 
 of interruptions by upheaval. 
 
 Yet persistent as may be the leading features of land and 
 sea on the globe, they are not immutable. Some of the 
 finest mud is doubtless carried to indefinite distances from 
 the coast by niariiie currents, and we are taught by deep-sea 
 dredgings that in clear water at depths equalling the height 
 of the Alps organic beings may flourish, and their spoils 
 slowly accumulate on the bottom. We also occasionally 
 obtain evidence that submarine volcanoes are pouring out 
 ashes and streams of lava in raid-ocean as well as on land 
 (see Principles, vol. ii., p. 64), and that wherever mountains 
 like Etna, Vesuvius, and the Canary Islands are now the site 
 of eruptions, there are signs of accompanying upheaval, by 
 
120 ELEMENTS OF GEOLOGY. 
 
 which beds of ashes full of recent marine shells have been 
 uplifted many hundred feet. We need not be surprised, 
 therefore, if we learn from geology that the continents and 
 oceans were not always placed where they now are, although 
 the imagination may well be overpowered when it endeav- 
 ors to contemplate the quantity of time required for such 
 revolutions. 
 
 We shall have gained a great step if we can approximate 
 to the number of millions of years in which the average 
 aqueous denudation going on upon the land would convey 
 seaward a quantity of matter equal to the average volume 
 of our continents, and this might give us a gauge of the 
 minimum of volcanic force necessary to counteract such lev- 
 elling power of running water; but to discover a illation 
 between these great agencies and the rate at which species 
 of organic beings vary, is at present wholly beyond the 
 reach of our computation, though perhaps it may not prove 
 eventually to transcend the powers of man. 
 
CHRONOLOGY OF BOCKS. 121 
 
 CHAPTER Vm 
 
 CHEONOLOGICAL CLASSIFICATION OF EOCKS. 
 
 Aqueous, plntonic, volcanic, aud metamoiphic Rocks considered chronologic- 
 ally. — Terms Primary, Secondary, and Tertiary; Palseozoic, Mesozoic, 
 and Cainozoic explained. — On the diflferent Ages of the aqueous Rocks. — 
 Three piincipal Tests of relative Age: Superposition, Mineral Character, 
 and Fossils. — Change of Mineral Character and Fossils in the same con- 
 tinuous Formation. — Proofs that distinct Species of Animals and Plants 
 have lived at successive Periods. — Distinct Provinces of indigenous Spe- 
 cies. — Great Extent of single Provinces. — Similar Laws prevailed at suc- 
 cessive Geological Periods. — Relative Importance of mineral and palseon- 
 tological Characters. — Test of Age by included Fragments. — Frequent 
 Absence of Strata of intervening Periods. — Tabular Views of fossiliferous 
 Strata. 
 
 Chronology of Rocks. — In the first chapter it was stated 
 that the four great classes of rocks, the aqueous, the volcan- 
 ic, the plutonie, and the metamorphic, would each be con- 
 sidered not only in reference to their mineral characters, and 
 mode of origin, but also to their relative age. In regard to 
 the aqueous rocks, we have already seen that they are strat- 
 ified, that some are calcareous, others argillaceous or silice- 
 ous, some made up of sand, others of pebbles ; that some con- 
 tain fresh-water, others marine fossils, and so forth ; but the 
 student has stUl to learn which rocks, exhibiting some or all 
 of these characters, have originated at one period of the 
 earth's history, and which at another. 
 
 To determine this point in reference to the fossiliferous 
 formations is more easy than in any other class, and it is 
 therefore the most convenient and natural method to begin 
 by establishing a chronology for these strata, and then to 
 refer as far as possible to the same divisions, the several 
 groups of plutonie, volcanic, and metamorphic rocks. Such 
 a system of classification is not only recommended by its 
 greater clearness and facility of application, but is also best 
 fitted to strike the imagination by bringing into one view 
 the contemporaneous revolutions of the inorganic and organ- 
 ic creations of former times. For the sedimentary forma- 
 tions are most readily distinguished by the difierent species 
 of fossil animals and plants which they inclose, and of which 
 one assemblage after another has flourished and then disap- 
 peared from the earth in succession. 
 
 6 
 
122 ELEMENTS OP GEOLOGY. 
 
 In the present work, therefore, the four great classes of 
 rocks, the aqueous, plutonic, volcanic, and metamorphic, will 
 form four parallel, or nearly parallel, columns in one chron- 
 ological table. They will be considered as four sets of mon- 
 uments relating to four contemporaneous, or nearly contem- 
 poraneous, series of events. I shall endeavoi-, in a subse- 
 quent chapter on the plutonic rocks, to explain the manner 
 in which certain masses belonging to each of the four classes 
 of rocks may have originated simultaneously at every geo- 
 logical period, and how the earth's crust may have been con- 
 tinually remodelled, above and below, by aqueous and igne- 
 ous causes, from times indefinitely remote. In the same 
 manner as aqueous and fossiliferous strata are now formed 
 in certain seas or lakes, while in other places volcanic rocks 
 break out at the surface, and are connected with reservoirs 
 of melted matter at vast depths in the bowels of the earth, 
 so, at every era of the past, fossiliferous deposits and su- 
 perficial igneous rocks were in progress contemporaneously 
 with others of subterranean and plutonic origin, and some 
 sedimentary strata were exposed to heat, and made to as- 
 sume a crystalline or metamorphic structure. 
 
 It can by no means be taken for granted, tliat during all 
 these changes the solid crust of the earth has been increasing 
 in thickness. It has been shown, that so far as aqueous ac- 
 tion is concerned, the gain by fresh deposits, and the loss by 
 denudation, must at each period have been equal (see above, 
 p. 96) ; and in like manner, in the inferior portion of the 
 earth's crust, the acquisition of new crystalline rocks, at each 
 successive era, may merely have counterbalanced the loss 
 sustained by the melting of materials previously consolidated. 
 As to the relative antiquity of the crystalline foundations of 
 the earth's crust, when compared to the fossiliferous and vol- 
 canic rocks which they support, I have already stated, in the 
 first chapter, that to pronounce an opinion on this matter is 
 as difficult as at once to decide which of the two, whether 
 the foundations or superstructure of an ancient city built on 
 wooden piles may be the oldest. We have seen that, to an- 
 swer this question, we must first be prepared to say whether 
 tlie work of decay and restoration had gone on most rapidly 
 above or below ; whether the average dui'ation of the piles 
 has exceeded that of the buildings, or the contrary. So also 
 in regard to the relative age of the superior and inferior por-, 
 tions of the earth's crust ; we can not hazard even a conjec- 
 ture on this point, until we know whether, upon an average, 
 the power of water above, or that of heat below, is most effi- 
 cacious in giving new forms to solid matter. 
 
PRIMARY, SECONDARY, TERTIARY. 123 
 
 The early geologists gave to all the crystalline and non- 
 fossiliferous rocks the name of Primitive or Primary, under 
 the idea that they were formed anterior to the appearance 
 of life upon the earth, while the aqueous or fossiliferous 
 strata were termed Secoudary, and alluviums or other super- 
 ficial deposits. Tertiary. The meaning of these terms has, 
 however, been gradually modified with advancing knowl- 
 edge, and they are now used to designate three great chron- 
 ological divisions under which all geological formations can 
 be classed, each of them being characterized by the presence 
 of distinctive groups of organic remains rather than by any 
 mechanical peculiarities of the strata themselves. If, there- 
 fore, we retain the term " primary," it must not be held to 
 designate a set of crystalline rocks some of which have been 
 proved to be even of Tertiary age, but must be applied to 
 all rocks older than the secondary formations. Some geolo- 
 gists, to avoid misapprehension, have introduced the term 
 Palaeozoic for primary, from TraXmov, " ancient," and ^wov, " an 
 organic being," still retaining the terms secondary and ter- 
 tiary ; Mr. Phillips, for the sake of uniformity, has proposed 
 Mesozoic, for secondary, from fiEaog, " middle," etc. ; and Cai- 
 nozoic, for tertiary, from caivoc, " recent," etc. ; but the terms 
 primary, secondary, and tertiary have the claim of priority 
 in their favor, and are of corresponding value. 
 
 It may perhaps be suggested that some metamorphic strata, 
 and some granites, may be anterior in date to the oldest of 
 the primary fossiliferous rocks. This opinion is doubtless 
 true, and will be discussed in future chapters ; but I may 
 here observe, that when we arrange the four classes of rocks 
 in four parallel columns in one table of chronology, it is by 
 no means assumed that these columns are all of equal length; 
 one may begin at an earlier period than the rest, and another 
 may come down to a later point of time, and we may not 
 be yet acquainted with the most ancient of the primary fos- 
 siliferous beds, or with the newest of the hypogene. 
 
 For reasons already stated, I proceed first to treat of the 
 aqueous or fossiliferous formations considered in chronolog- 
 ical order or in relation to the different periods at which they 
 have been deposited. 
 
 There are three principal tests by which we determine the 
 age of a given set of strata ; first, superposition ; secondly, 
 mineral character; and, thirdly, organic remains. Some aid 
 can occasionally be derived from a fourth kind of proof, 
 namely, the fact of one deposit including in it fragments of 
 a pre-existing rock, by which the relative ages of the two 
 may, even in the absence of all other evidence, be determined. 
 
124 ELEMENTS OF GEOLOGY. 
 
 Superposition. — The first and principal test of the age of 
 one aqueous deposit, as compared to another, is relative po- 
 sition. It has been already staled, that, where strata are 
 horizontal, the bed which lies uppermost is the newest of the 
 whole, and that which lies at the bottom the most ancient. 
 So, of a series of sedimentary formations, they are like vol- 
 umes of history, in which each writer has recorded the an- 
 nals of his own times, and then laid down the book, with the 
 last written page uppermost, upon the volume in which the 
 events of the ei-a immediately preceding were commemo- 
 rated. In this manner a lofty pile of chronicles is at length 
 accumulated ; and they are so arranged as to indicate, by 
 their position alone, the order in which the events recorded 
 in them have occurred. 
 
 In regard to the crust of the earth, however, there arc 
 some regions where, as the student has already been inform- 
 ed, the beds have been disturbed, and sometimes extensively 
 thrown over and turned upside down. (See pp. 73, 87.) But 
 an experienced geologist can rarely be deceived by these 
 exceptional cases. When he finds that the strata are frac- 
 tured, curved, inclined, or vertical, he knows that the origi- 
 nal order of superposition must be doubtful, and he then en- 
 deavors to find sections in some neighboring district where 
 the strata are horizontal, or only slightly inclined. Here, 
 the true order of sequence of the entire series of deposits 
 being ascertained, a key is furnished for settling the chronol- 
 ogy of those strata where the displacement is extreme. 
 
 Mineral Character. — The same rocks may often be ob- 
 served to retain for miles, or even hundreds of miles, the 
 same mineral peculiarities, if we follow the planes of strati- 
 fication, or trace the beds, if they be undisturbed, in a hori- 
 zontal direction. But if we pursue them vertically, or in 
 any direction transverse to the planes of stratification, this 
 uniformity ceases almost immediately. In that case we can 
 scarcely ever penetrate a stratified mass for a few hundred 
 yards without beholding a succession of extremely dissimilar 
 rooks, some of fine, others of coarse grain, some of mechan- 
 ical, others of chemical origin ; some calcareous, others argil- 
 laceous, and others siliceous. These phenomena lead to the 
 conclusion that rivers and currents have dispersed the same 
 sediment over wide areas at one period, but at successive 
 periods have been charged, in the same region, with very 
 dilferent kinds of matter. The first observers were so as- 
 tonished at the vast spaces over vsrhich they were able to 
 follow the same homogeneous rocks in a horizontal direc- 
 tion, that they came hastily to the opinion, that the whole 
 
TESTS OP THE AGES OS ROCKS, 126 
 
 globe had been environed by a succession of distinct aque- 
 ous formations, disposed round the nucleus of the planet, 
 like the concentric coats of an onion. But, although, in fact, 
 some formations may be continuous over districts as large 
 as half of Europe, or even more, yet most of them either ter- 
 minate wholly within narrower limits, or soon change their 
 lithological character. Sometimes they thin out gradually, 
 as if the supply of sediment had failed in that direction, or 
 they come abruptly to an end, as if we had. arrived at the 
 borders of the ancient sea or lake which seryed as their re- 
 ceptacle. It no less frequently happens that they vary in 
 mineral aspect and composition, as we pursue them horizon- 
 tally. For example, we trace a limestone for a hundred 
 miles, until it becomes more arenaceous, and finally passes 
 into sand, or sandstone. We may then follow this sand- 
 stone, already proved by its continuity to be of the same 
 age, throughout another district a hundred miles or more in 
 length. 
 
 Organic Remains. — This character must be used as a cri- 
 terion of the age of a formation, or of the contemporaneous 
 origin of two deposits in distant places, under very much 
 the same restrictions as the test of mineral composition. 
 
 First, the same fossils may be traced over widp regions, if 
 we examine strata in the direction of their planes, although 
 by no means for indefinite distances. Secondly, while the 
 same fossils prevail in a particular set of strata for hundreds 
 of miles in a horizontal direction, we seldom meet with the 
 same remains for many fathoms, and very rarely for several 
 hundred yards, in a vertical line, or a line transverse to the 
 strata. This fact has now been verified in almost all parts 
 of the globe, and has led to a conviction that at successive 
 periods of the past, the same area of land and water has 
 been inhabited by species of animals and plants even more 
 distinct than those which now people the antipodes, or 
 which now co-exist in the arctic, temperate, and tropical 
 zones. It appears that from the remotest periods there has 
 been ever a coming in of new organic forms, and an extinc- 
 tion of those which pre-existed on the earth ;■ some species 
 having endured for a longer, others for a shorter, time ; while 
 none have ever reappeared after once dying out. The law 
 which has governed the succession of species, whether we 
 adopt or reject the theory of transmutation, seems to be ex- 
 pressed in the verse of the poet — 
 
 Natura. il. fece, e poi ruppe la stampa. Aeiosto. 
 Nature made him, and then broke the die. 
 
126 ELEMENTS OF GEOLOGY. 
 
 And this circumstance it is, which confers on fossils their 
 highest value as chronological tests, giving to each of them, 
 in the eyes of the geologist, that authority which belongs to 
 contemporary medals in history. 
 
 The same can not be said of each peculiar variety of rock; 
 for some of these, as red marl and red sandstone, for exam- 
 ple, may occur at once at the top, bottom, and middle of the 
 entire sedimentary series ; exhibiting in each position so per- 
 fect an identity of mineral aspect as to be undistinguishable. 
 Such exact repetitions, however, of the same mixtures of 
 sediment have not often been produced, at distant periods, 
 in precisely the same parts of the globe ; and even where 
 this has happened, we are seldom in any danger of confound- 
 ing together the monuments of remote eras, when we have 
 studied their imbedded fossils and their relative position. 
 
 Zoological Provinces. — It was remarked that the same spe- 
 cies of organic remains can not be traced horizontally, or in 
 the direction of the planes of stratifications for indefinite dis- 
 tances. This might have been expected from analogy; for 
 when we inquire into the present distribution of living be- 
 ings, we find that the habitable surface of the sea and land 
 may be divided into a considerable number of distinct prov- 
 inces, each peopled by a peculiar assemblage of animals and 
 plants. In the " Principles of Geology," I have endeavored 
 to point out the extent and probable origin of these separate 
 divisions ; and it was shown that climate is only one of many 
 causes on which they depend, and that difierence of longi- 
 tude as well as latitude is generally accompanied by a dis- 
 similarity of indigenous species. 
 
 As different seas, therefore, and lakes are inhabited, at the 
 same period, by different aquatic animals and plants, and as 
 the lands adjoining these may be peopled by distinct terres- 
 trial species, it follows that distinct fossils will be imbedded 
 in contemporaneous deposits. If it were otherwise — if the 
 same species abounded in every climate, or in every part of 
 the globe where, so far as we can discover, a corresponding 
 temperature and other conditions favorable to their exist- 
 ence are found — the identification of mineral masses of the 
 same age, by means of their included organic contents, would 
 be a matter of still greater certainty. 
 
 Nevertheless, the extent of some single zoological prov- 
 inces, especially those of marine animals, is very great ; and 
 our geological researches have proved that the same laws 
 prevailed at remote periods ; for the fossils are often identical 
 throughout wide spaces, and in detached deposits, consisting 
 of rocks varying entirely in their mineral nature. ■ 
 
AGES OF AQUEOUS ROCKS. 127 
 
 The doctrine here laid down will be more readily under- 
 stood, if we reflect on what is now going on in the Mediter- 
 ranean. That entire sea may be considered as one zoological 
 province ; for although certain species of testacea and zo- 
 ophytes may be very local, and each region has probably 
 some species peculiar to it, still a considerable number are 
 common to the whole Mediterranean. If, therefore, at some 
 future period, the bed of this inland sea should be converted 
 into land, the geologist might be enabled, by reference to 
 organic remains, to prove the contemporaneous origin of 
 various mineral masses scattered over a space equal in area 
 to half of Europe. 
 
 Deposits, for example, are well known to be now in prog- 
 ress in this sea in the deltas of the Po, Rhone, Nile, and other 
 rivers, which differ as greatly from each other in the nature 
 of their sediment as does the composition of the mountains 
 which they drain. There are also other quarters of the Med- 
 iterranean, as off the coast of Campania, or near the base of 
 Etna, in Sicily, or in the Grecian Archipelago, whei-e another 
 class of rocks is now forming ; where showers of volcanic 
 ashes occasionally fall into the sea, and streams of lava over- 
 flow its bottom ; and where, in the intervals between vol- 
 canic eruptions, beds of sand and clay are frequently derived 
 from the waste of cliffs, or the turbid waters of rivers. 
 Limestones, moreover, such as the Italian travertins, ai-e here 
 and there precipitated from the waters of mineral springs, 
 some of which rise up from the bottom of the sea. In all 
 these detached formations, so diversified in their lithological 
 characters, the remains of the same shells, corals, Crustacea, 
 and fish are becoming inclosed ; or, at least, a sufficient num- 
 ber must be common to the different localities to enable the 
 zoologist to refer them all to one contemporaneous assem- 
 blage of species. 
 
 There are, however, certain combinations of geographical 
 circumstances which cause distinct provinces of animals and 
 plants to be separated from each other by very narrow lim- 
 its ; and hence it must happen that strata will be sometimes 
 formed in contiguous regions, differing widely both in min- 
 eral contents and organic remains. Thus, for example, the 
 testacea, zoophytes, and fish of the Red Sea are, as a group, 
 extremely distinct from those inhabiting the adjoining parts 
 of the Mediterranean, although the two seas are separated 
 only by the narrow isthmus of Suez. Calcareous formations 
 have accumulated on a great scale in the Red Sea in modern 
 times, and fossil shells of existing species are well preserved 
 therein ; and we know that at the mouth of the Nile large 
 
128 ELEMENTS OF GEOLOGY. 
 
 deposits of mud are amassed, including the remains of Med- 
 iterranean species. It follows, therefore, that if at some fu- 
 ture period the bed of the Red Sea should be laid dry, the 
 geologist might experience great difficulties in endeavoring 
 to ascertain the relative age of these formations, which, al' 
 though dissimilar both in organic and mineral characters, 
 were of synchronous origin. 
 
 But, on the other hand, we must not forget that the north- 
 western shores of the Arabian Gulf, the plains of Egyptj and 
 the Isthmus of Suez, are all parts of one province of terres- 
 trial species. Small streams, therefore, occasional land-floods, 
 and those winds which drift clouds of sand along the deserts, 
 might carry down into the Red Sea the same shells of flu- 
 viatile and land testacea which the Nile is sweeping into its 
 delta, together with some remains of terrestrial plants and 
 the bones of quadrupeds, whereby the groups of strata be- 
 fore alluded to might, notwithstanding the discrepancy of 
 their mineral composition and marine organic fossils, be 
 shown to have belonged to the same epoch. 
 
 Yet, while rivers may thus carry down the same fluviatile 
 and terrestrial spoils into two or more seas inhabited by dif- 
 ferent marine species, it will much more frequently happen 
 that the co-existence of terrestrial species of distinct zoolog- 
 ical and botanical provinces will be proved by the identity 
 of the marine beings which inhabited the intervening space. 
 Thus, for example, the land quadrupeds and shells of the val- 
 ley of the Mississippi, of central America, and of the West , 
 India islands differ very considerably, yet their remains are 
 all washed down by rivers flowing from these three zoolog- 
 ical provinces into the Gulf of Mexico. 
 
 In some parts of the globe, at the present period, the line 
 of demarkation between distinct provinces of animals and 
 plants is not very strongly marked, especially where the 
 change is determined by temperature, as it is in seas extend- 
 ing from the temperate to the tropical zone, or from the 
 temperate to the arctic regions. Here a gradual passage 
 takes place from one set of species to another. In like man- 
 ner the geologist, in studying particular formations of re- 
 mote periods, has sometimes been able to trace the grada- 
 tion from one ancient province to another, by observing 
 carefully the fossils of all the intermediate places. His suc- 
 cess in thus acquiring a knowledge of the zoological or bo- 
 tanical geogi-aphy of very distant eras has been mainly 
 owing to this circumstance, that the mineral character has 
 no tendency to be afiected by climate. A large river may 
 convey yellow or red mud into some part of the ocean, where 
 
CHE0N0L06Y OF FOSSILIFEROTJS STRATA. 129 
 
 it may be dispersed by a current over an area several hun- 
 dred leagues in length, so as to pass from the tropics into 
 the temperate zone. If the bottom of the sea be afterwards 
 upraised, the organic remains imbedded in such yellow or 
 red strata may indicate the different animals or plants which 
 once iiihabited at the same time the temperate and equato- 
 rial regions. 
 
 It may be true, as a general rule, that groups of the same 
 species of animals and plants may extend over wider areas 
 than deposits of homogeneous composition ; and if so, palseon- 
 tological characters will be of more importance in geological 
 classification than the test of mineral composition ; but it is 
 idle to discuss the relative value of these tests, as the aid of 
 both is indispensable, and it fortunately happens, that where 
 the one criterion fails, we can often avail ourselves of the other. 
 
 Test by included Fragments of older Rocks. — It was stated, 
 that proof may sometimes be obtained of the relative date 
 of two formations by fragments of an older rock being in- 
 cluded in a newer one. This evidence may sometimes- be 
 of great use, where a geologist is at a loss to determine the 
 relative age of two formations from want of clear sections 
 exhibiting their true oi-der of position, or because the strata 
 of each group are vertical. In such cases we sometimes dis- 
 cover that the more modern rock has been in part derived 
 from the degradation of the older. . Thus, for example, we 
 may find chalk in one part of a country, and in another strata 
 of clay, sand, and pebbles. If some of these pebbles consist 
 of that peculiar flint, of which layers more or less continu- 
 ous are characteristic of the chalk, and which include fossil 
 shells, sponges, and forarainifera of cretaceous species, we 
 may confidently infer that the chalk was the oldest of the 
 two formations. 
 
 ; Chronological Groups.^— The number of groups into which 
 the fossiliferous strata may be separated are more or less 
 numerous, according to the views of classification which dif- 
 ferent geologists entertain; but when we have adopted a 
 certain system of arrangement, we immediately find that a 
 few only of the entire series of groups occur one upon the 
 other in any single section or district. 
 
 The thinning out of individual strata was before described 
 (p. 42). But let the annexed diagram represent seven fosf- 
 siliferous groups, instead of as many strata. It will then be 
 seen that in the middle all the superimposed formations are 
 present ; but in consequence of some of them thinning out, 
 No. 2 and IHo. 5 are absent at one extremity of the section, 
 and No. 4 at the other. 
 
 6* 
 
130 
 
 ELEMENTS OE GEOLOGY. 
 
 Fig. 84. 
 
 In another diagram, Fig. 85, a real section of the geologic- 
 al formations in the neighborhood of Bristol and the Mendip 
 Hills is presented to the reader, as laid down on a true scale 
 by Professor Ramsay, where the newer groups 1, 2, 3, 4 rest 
 unconformably on the formations 5, 6, 1, and 8. At the 
 southern end of the line of section we meet with the beds 
 No. 3 (the New Red Sandstone) resting immediately on Nos. 
 7 and 8, while farther north, as at Dundry Hill in Somerset- 
 shire, we behold eight groups superimposed One upon the 
 other, comprising all the strata from the inferior oolite, No. 
 1, to the coal and carboniferous limestone. The limited hor- 
 
 Fig. 85. 
 Dundry Hilt. jj 
 
 Section South of Bristol. (A. C. Eamsay.) 
 
 Length of section 4 miles. a, 6. Level of the sea. 
 
 ]. Inferior Oolite. 2. Lias. 3. New Red Sandstone. 4. Dolomitic or magnesian con- 
 glomerate. S. Upper coal-measnres (shales, etc.). C. Pennant rock (sandstone). 
 7. Lower coal-measnres (shales, etc.). 8. Carboniferous or mountain limestone. 
 9. Old Eed Sandstone. 
 
 izontal extension of the groups 1 and 2 is owing to denuda- 
 tion, as these formations end abruptly, and have left outly- 
 ing paJiches to attest the fact of their having originally cov- 
 ei"ed a much wider area. 
 
 In order, therefore, to establish a chronological succession 
 of fossiliferous groups, a geologist must begin with a single 
 section in which several sets of strata lie one upon the other. 
 He must then trace these formations, by attention to their 
 mineral character and fossils, continuously, as far as possible, 
 from the starting-point. As often as he meets with new 
 groups, he must ascertain by superposition their age relative- 
 ly to those first examined, and thus learn how to intercalate 
 them in a tabular arrangement of the whole. 
 
 By this means the German, French, and English geologists 
 
GENERAL TABLE OF FOSSILIFEROUS STRATA. 131 
 
 have determined the succession of strata throughout a great 
 part of Europe, and have adopted pretty generally the fol- 
 lowing groups, almost all of which have their representatives 
 in the British Islands. 
 
 ABRIDGED GENERAL TABLE OF FOSSILIFEROUS STRATA. 
 1. EECENT. 
 
 2. POST-PLIOCENE. 
 
 3. NEWER PLIOCENE. 
 
 4. OLDER PLIOCENE. 
 B. UPPER MIOCENE. 
 6. LOWER MIOCENE. 
 T. UPPER EOCENE. 
 
 8. MIDDLE EOCENE. 
 
 9. LOWER EOCENE. 
 
 10. MAESTRICHT BEDS. 
 
 11. WHITE CHALK. 
 
 12. CHLORITIC SERIES. 
 
 13. GAULT. 
 
 14. NEOCOMIAN. 
 IB. WEALDEN. 
 
 16. PURBECK BEDS. 
 
 17. PORTLAND STONE. 
 
 18. KIMMERIDGE CLAY. 
 
 19. CORAL RAG. 
 
 20. OXFORD CLAY. 
 
 21. GREAT or BATH OOLITE. 
 
 22. INFERIOR OOLITE. 
 
 23. LIAS. 
 
 24 UPPER TRIAS. 
 
 25. MIDDLE TRIAS. 
 
 26. LOWER TRIAS. 
 
 27. PERMIAN. 
 
 28. COAL-MEASURES. 
 
 29. CARBONIFEROUS LIMESTONE. 
 
 30. UPPER "1 
 
 31. MIDDLE [devonian. 
 
 32. LOWER J 
 
 33. UPPER ) 
 
 34. LOWER |SILTJRIAN. 
 
 35. UPPER ) 
 
 „„ ^„„ S- CAMBRIAN. 
 86. LOWER j 
 
 37. UPPER ) 
 
 „„ ^^„r^^ ^LAUEENTIAN. 
 
 38. LOWER J 
 
 ^ POST -TERTIARY. 
 I PLIOCENE. 
 I MIOCENE. 
 
 I EOCENE. 
 
 CRETACEOUS. 
 
 JURASSIC. 
 
 y TRIASSIC. 
 PERMIAN. 
 i CARBONIFEROUS. 
 
 DEVONIAN. 
 
 SILURIAN. 
 
 CAMBRIAN. 
 
 LAURENTIAN. 
 
 o 
 
 I o 
 
 CQ 
 
 o 
 
 N 
 
132 
 
 TABULAB VIEW OF 
 
 TABULAE VIEW 
 OF 
 
 THE FOSSILIFEEOUS STRATA, 
 
 SHOWING THB OBDEE OP BTJPEEPOBITION OE CHECtNOLOGIOAL BTTOOKBSIOK OP THE PEIN- 
 OIPAL QEOUFB, WITH EEfEBKNOB TO TUB PAGES WHEEE THEY AEE DESOELBKD lu 
 IBIS Wote. 
 
 POST-TERTIAKT. 
 
 POST- 
 TERTIARY. 
 
 EECENT. 
 
 Sbella and mam- 
 malia, all nf 
 liTing Bpecies. 
 
 2. 
 POST- 
 PLIOCENE. 
 
 Shells, recent 
 mammalia in 
 part extinct. 
 
 EXAMPLES. 
 
 British — Clycle marine strata, with canoes (p. 146). 
 Foreign — Danish kitchen middens (p. 146). 
 Lacustrine mud, with remains of Swiss lake-dweK. 
 
 ings (p. 148). 
 Marine strata inclosing Temple of Serapis, at Puz- 
 zuoli (p. 146). 
 
 British— hoam of Brixham cave, with flint imple- 
 ments and bones of extinct and living quadru- 
 peds (p. 157). 
 
 Drift near Salisbury, with bones of mammoth, 
 Spermophilus, and stone implements (p. 161). 
 
 Glacial drift of Scotland, with marine shells and 
 remains of mammoth (p. 1T6). 
 
 Erratics of Pagham and Selsey Bill (p. 182). 
 
 Glacial drift of Wales, with marine fossil shells, 
 about 1400 feet high, on Moel Tryfaen (p. ,181). 
 Foreign — Dordogne caves of the reindeer period (p. 
 ISO). 
 
 Older valley-gravels of Amiens, with flint imple- 
 ments and bones of extinct mammalia (p. 162). 
 
 Loess of Rhine (p. 164). 
 
 Ancient Nile-mud forming river-terraces (p. 164). 
 
 Loam and breccia of Li6ge caverns, with human 
 remains (pp. 156, 157). 
 
 Australian cave breccias, with bones of extinct mar- 
 supials (p. 158). 
 
 Glacial drift of Northern Europe (pp. 166-188). 
 
 PLIOCENE. 
 
 TERTIARY OR CAINOZOIC. 
 
 \BrtYis7i — Bridlington beds, marine Arctic fauna (p. 
 
 189). 
 Glacial boulder formation of Norfolk clifiS (p. 190). 
 Forest-bed of Norfolk cliff's, with bones olMlepkas 
 
 meridionalis, etc. (p. 191). 
 Chillesford and Aideby beds, with marine shells, 
 
 chiefly Arctic <p. 192). 
 Norwich crag (p. 193). 
 Foreign— Eastern base of Mount Etna, with marine 
 
 shells (p. 204). 
 Sicilian calcareous and tnfaceons strata (pp. 206,206). 
 Lacustrine strata of Upper Val d'Arno (p. 207). 
 Madeira leaf-bed and land-shells (p. 532). 
 
 British— S.e& crag of Suffolk, marine shells, some of 
 northern forms (pp. 194, 195). 
 
 White or coralline crag of Suflblk (p. 197) 
 Foreign,— K-nivet^ crag (p. 204). 
 
 Snbapennine marls and sands (p. 208). 
 
 3. 
 
 NEWER 
 PLIOCENE. 
 
 Tile shells al- 
 most all of living 
 Bpecies. 
 
 4. 
 
 OLDER 
 
 PLIOCENE. 
 
 Extinct Bpecies 
 of shells forming 
 
THE FOSSILIFEEOUS STRATA. 
 
 133 
 
 MIOCENE. 
 
 EOCENE. 
 
 5. 
 
 T3PPBR 
 
 MIOCENE. 
 
 Minority of the 
 Bh«ll3 extinct. 
 
 6. 
 LOW'ER 
 
 MIOCENE. 
 
 Nearly all the 
 Bhella extinct. 
 
 7. 
 
 T7PPEH 
 
 EOCENE. 
 
 8. 
 MIDDLE 
 EOCENK 
 
 9. 
 LOWER 
 EOCENE. 
 
 EXAMPLES. 
 
 Bn'Msft— Wanting. 
 
 Foreign— Fi\\vins of Touvaine (p. 211). 
 Faluns, proper, of Bordeaux (p. 214). 
 Fresh^water strata of Gers (p. 215). 
 Swiss (Euingeu beds, ricli in plants and insects (pp. 
 
 216-223). ^^ 
 
 Marine Molasse, Switzerland (p. 223). 
 Bolderberg beds of Belgium (p. 224). 
 Vienna basin (p. 224). 
 Beds of the Superga,near Turin (p.22C). 
 Deposit at PilcermS, near Athens (p. 226). 
 Strata of the Siwalik hills, India (p. 226). 
 Marine strata of the Atlantic border in the United 
 
 States (p. 227). 
 Volcanic tuff and limestone of Madeira, the Cana- 
 ries, and the Azores (Chap. XSX.). 
 £ri<z8/i— Hempstead beds, marine and fresh- water 
 
 strata (p. 244). . 
 Lignites and clays of Bovey Tracev (p. 245). 
 Isle of Mull leaf-bed, volcanic tuff (p. 247). 
 Foreign — Calcaire de la Beauce, etc (p. 230). 
 Gr^s de Fontainebleau (p. 230). 
 Lacustrine strata of the Limagne d'Auvergne, and 
 
 the Cantal (p. 233). 
 Mayence basin (p. 242). 
 Radaboj beds of Croatia (p. 242). 
 Brown coal of Germany (p. 244). 
 Lower molasse of Switzerland, fresh-water and 
 
 brackish (pp. 235-239). 
 Rnpelmonde, Kleynspawen, aud Tongrian beds of 
 
 Belgium (pp. 241, 242). 
 Nebraska beds. United States (p. 248). 
 Lower Miocene beds of Italy (p. 244). 
 Miocene flora of North Greenland (p. 239). 
 British — Bembridge fluvio-marine strata (p. 252). 
 Osborne or St. Helen's series (p. 2B5). 
 Headon series, with marine and fresh-water shells 
 
 (P.25S). 
 Barton sands and clays (p. 268). 
 Foreign — Gypsum of Montmartre, fresh-water with 
 
 Palceotheriwm (p. 270). 
 Calcaire silicieux, or Travertin inferienr (p. 273). 
 Gr6s de Beauchamp, or Sables moyens (p. 2Z3). 
 British — Bracklesham beds and Bagshot sands (p. 
 
 259). 
 White clays of Alum Bay and Bournemouth (p. 
 
 262). 
 Foreign — Calcaire grossier, mlliolitic limestone (p. 
 
 274). 
 Soissonuais. sands, or Lits coquilliers, with Nwm- 
 
 Claiborne beds of the United States, with OrUUMea 
 and Zeuglodon (p, 279). 
 
 Nummulitic formation of Europe, Asia, etc. (p. 277). 
 British — ^London clay proper (p. 263). 
 ' Woolwich and Reading series, fluvio-marine (p. 
 
 . 267). 
 
 Thanet sands (p. 269). 
 ii'orej^— Argile de Londres, near Dunkirk (p. 262). 
 
 Areile plastique (p. 276). 
 
 Sables de Bracheux (p. 276). 
 
 CRETACE- 
 OUS. 
 
 SECONDARY OR MESOZOIC. 
 
 10. 
 UPPER 
 
 CRETACE- 
 OUS. 
 
 British — Upper white chalk, with flints (p. 290). 
 Lower white chalk, without flints (p. 298). 
 Chalk marl (p. 298). 
 Chloritic series (or Upper Greensand), flre-stone of 
 
 Surrey (p. 298). 
 Ganlt-(p. 300).. 
 Blackdown beds (p. 301). 
 
134 
 
 TABULAR VIEW OF 
 
 CRETACE- 
 OUS. 
 
 OOLITE. 
 
 LIAS. 
 
 TKIAS. 
 
 10. 
 
 UPPEE 
 
 CEETACB- 
 
 OUS. 
 
 11. 
 LOWER 
 CRETACE- 
 OUS 
 or 
 NEOCO- 
 MIAN. 
 
 12. 
 UPPER 
 OOLITE. 
 
 13. 
 MIDDLE 
 OOLITE. 
 
 14. 
 LOWER 
 OOLITE. 
 
 15. 
 LIAS. 
 
 16. 
 UPPEE 
 TRIAS. 
 
 IT. 
 MIDDLE 
 TRIAS. 
 
 18. 
 LOWBE 
 TEXAS. 
 
 EXAMPLES. 
 
 ■ Jibrciffn— Maestricht beds and Faxoe chalk (p. 283). 
 Pisolitic limestone of France (p. 285). 
 White chalk of Prance, Sweden, and Eussia (pp. 
 
 280, 28T). 
 PlSuer-kalk of Saxony (p. 293). 
 Sands and clays of Aix-la-Chapelle (p. 302). 
 Hippnrite limestone of SoDth of Prance (p. 305). 
 New Jersey, U. S., sands and marls (p. 307). 
 Bri*isft— Sands of Polkstone, Sandgate, and Hythe 
 (p. 308). ■ 
 Atherfleld clay, with Perna mulUti (p. 309). 
 Punlield marijie beds, with Vicarya Ivjana (p. 318). 
 Speeton clay of Flamborough Head and Tealby (p, 
 
 311). 
 Weald clay of Surrey, Kent, and Sussex, fresh-wa- 
 ter, with Cypriii (p. 313-315). 
 Hastings sands (p. 310-318). 
 Foreign — Neocomian of Neiifchatel, and Hils con- 
 
 W glomerate of North Germany (p. 312). 
 ealden beds of Hanover (p. 319). 
 British — Upper Purbeck beds, fresh-water (p. 323). 
 Middle Purbeck, with numerous marsupial quad- 
 rupeds, etc. (p. 324). 
 Lower Purbeck, fresh-water, with intercalated dirt- 
 bed (p. 330). 
 Portland stone and sand (p. 334). 
 Kimmeridge clay (p. 335). 
 i*'{weij7n— Marnes ^ gryph6es virgules of Argonne (p. 
 336). 
 Lithographic-stone of Solenhofen, with Arelueop- 
 teryx (p. 337). 
 British — Coral rag of Berkshire, Wilts, and Yorkshire 
 (p. 339). 
 Oxford clay, with belemnites and ammonite (p. 
 
 340). 
 Kelloway rock of Wilts and Yorkshire (p. 341). 
 Foreign — Nerinsean limestone of the Jura (p. 339). 
 British — Cornbrash and forest marble (p. 341), 
 Great or Bath oolite of Bradford (p. 342). 
 Stonesflcld slate, with marsupials and Araucaria 
 
 (p. 346). 
 Fuller's earth of Bath (p. 34S). 
 Inferior oolite (p. 349). 
 Upper lias, argillaceous, with Amnwnites striatw- 
 
 lits (p. 353). 
 Shale and limestone, with Ammonites bifrone (p. 
 
 353). 
 Middle lias or Marlstone series, with zones contain- 
 ing characteristic ammonites (p. 35.3). 
 Lower lias, also with zones characterized by pe- 
 culiar ammonites (p. 356). 
 British — ^Eboetic, Penarth or Avieula contorta beds 
 (beds of passage) (p. 366). 
 Keaper or Upper New Bed sandstone, etc. (p. 3C9). 
 Eed shales of Cheshke and Lancashire, with rock- 
 salt (p. 371). 
 Dolomite conglomerate of Bristol (p. 373). 
 J?orei(7»j— Keuper beds of Germany (p. 375). 
 St. Cassian or Hallstadt beds, with rich marine 
 
 fauna (p. 376). 
 Coal-field of Richmond, Virginia (p. 382). 
 Chatham coal-field, North Carolina (p. 383). 
 British — Wanting, 
 •j l^oreij^n— Maschelkalk of Germany (p. 378). 
 'British — Banter or Lower New Eed sandstone of 
 
 Lancashire and Cheshire (p. 372). 
 i^Vc^ffn— Bunter-sandstein of Gerniany (p. 380). 
 Eed sandstone of Connecticut Valley, with foot- 
 prints of birds and reptiles (p. 381). 
 
THE FOSSILITEKOUS STBATA. 
 
 135 
 
 PKIMART OR PALEOZOIC. 
 
 EXAMPLES. 
 
 PERMIAN. 
 
 CARBONIF- 
 EROUS. 
 
 DEVONIAN 
 
 or 
 
 Old Red 
 
 Sandstone. 
 
 SILURIAN. 
 
 19. 
 PERMIAN. 
 
 UPPER 
 CAHBONI- 
 FEKOUS. 
 
 21. 
 
 LOWER 
 
 CARBONI- 
 
 FEKOUS. 
 
 22. 
 UPPER 
 DEVO- 
 NIAN. 
 
 23. 
 MIDDLE 
 DEVO- 
 NIAN. 
 
 24. 
 LOWER 
 DEVO- 
 NIAN. 
 
 25. 
 
 UPPER 
 
 SILURIAN. 
 
 f British — Uppev Permian of St. Bees' Head, Cumber- 
 land (p. 386). 
 
 Middle Permian, magneaian limestone, and marl- 
 slate of Durham and Yorkshire, with Protoromu' 
 rm (387). 
 
 Lower Permian sandstones and hreccias of Penrith 
 and Dumfriesshire, intercalated (p. 390). 
 Foreign — Dark-colored shales of Thnringia (p. 392). 
 
 Zechstein or Dolomitic limestone (p. 392). 
 
 Mergel-Bchiefer or Kupfer-schiefer (p. 392). 
 
 Rotbliegendes of Thurmgia, v/ith Psaronius (p. 392). 
 
 Magnesian limestones, etc, of Russia (p. 393). 
 British — Coal-measnres of South Wales, with nnder- 
 clays inclosing Stigmaria (p. 397). 
 
 Coal-measures of north and central England (p. 
 395). 
 
 Millstone grit (p. 395). 
 
 Yoredale series of Yorkshire (p. 395). 
 
 Coal-fleld of Kilkenny, with Labyrinthodont (p. 407.) 
 Foreign — Coal-lield of Saarbruck,with Archegomurus 
 (p. 406). 
 
 Carboniferous strata of South Joggius, Nova Scotia 
 (p. 409). 
 
 Pennsylvania coal-field (p. 403). 
 British — ^Mountain limestone of Wales and South of 
 England (p. 480). 
 
 Same In Ireland (p. 437). 
 
 Carboniferous limestone of Scotland alternating 
 with coal-bearing sandstones (p. 396). 
 
 Erect trees in volcanic ash in the Island of Arran 
 (p. 546). 
 Foreign — ^Monntain limestone of Belgium (p. 436). 
 
 BW^ft— Yellow sandstone of Dura Den, with Holop- 
 tychiua, etc. (p. 440) ; and of Ireland \fllh Anodon 
 Jukesii (p. 441). 
 Sandstones of Forfarshire and Perthshire, with flb- 
 
 loptychiuB, etc. (p. 442). 
 Pilton group of North Devon (p. 449). 
 Petherwyn group of Cornwall, with Clymenia and 
 Cypridirui (p. 451). 
 Foreign — Clymenien-kalk and Cypridinen-schiefer of 
 
 Germany (p. 450). 
 \Bn'iisA— Bituminous schists of Gamrie, Caithness, 
 etc., with numerous tish (p. 443). 
 Ufracombe beds mth peculiar trilobites and corals 
 
 (p. 450). 
 Limestones of Torquay, with broad-winged Splri- 
 fers (p. 451). 
 Ji'oreisn— Eifel limestone, with nnderlyingschists con- 
 taining Calceola (p. 453). 
 Devonian strata of Russia (p. 454). 
 British — Arbroath paving-stones, with Ce^halaspis 
 and Pterygotus (p. 446). 
 Lower sandstones of Forfarshire, with Pterygotus 
 
 (p. 446). 
 Sandstones and slates of the Foreland and Linton 
 (p. 454). . 
 Foreign — Oriskany sandstone of Western Canada and 
 New York (p. 456); 
 Sandstones or Gaspe, with Cephalaspis (p. 455). 
 
 British — ^Uppcr Ludlow formation, Downton sand- 
 stone, with bone-bed (p. 469). 
 Lower Lndlow formation, with oldest known fish 
 remains (p. 461). 
 
136 
 
 TABULAR VIEW, ETC. 
 
 SILURIAN. 
 
 CAMBRIAN. 
 
 LAUREN- 
 TIAN. 
 
 25. 
 
 UPPER 
 
 SILUKIAN. 
 
 LOWER 
 SILURIAN. 
 
 2T. 
 
 UPPER 
 
 CAM- 
 
 BRLiN. 
 
 28. 
 LOWER 
 
 CAM- 
 BRIAN. 
 
 UPPER 
 
 LAUHEN- 
 
 TIAN. 
 
 30. 
 
 LOWER 
 
 LAUREN- 
 
 TIAN. 
 
 EXAMPLES. 
 
 Wenlock limestone and shale (p. 465). 
 Woolhope limestone and grit (p. 4(il). 
 Tarannon shales (p. 468). 
 
 Upper Llandovery, or May-hill") Beds of passage 
 sandstone, 'with- PentWmerusi between Upper 
 oblorwuSf etc. (p. 468). ( and Lower Si- 
 
 Lower Llandoverj slates (p. 469). ; Inrian. 
 Foreign— Niagara limestone, with Calymene, Homalo. 
 noUis, etc. (p. 479). 
 Clinton group of America, with Peniamems oUan- 
 
 gu8, etc. (p. 479). 
 Silarian strata of Rnssia, with Penianients (p. 477). 
 ' British— Bala and Caradoc beds (p. 470). 
 Llandeilo flags (p. 473). 
 
 -\renig or Stiper-stoues group (Lower Llandeilo of 
 Mnrchison) (p. 475). 
 Foreign— Vn^ulile or Obolns grit of Russia (p. 477). 
 Trenton limestone, and other Lower Silurian 
 
 groups of North America (p. 479). 
 Lower Silurian of Sweden (p. 477), 
 British — Tremadoc slates (p. 483). 
 
 Lingula flags, with Lingula Daviaii (p. 484). 
 Foreign — "Primordial" zone of Bohemia in part, 
 with trilobites of the genera Paradoxides, etc. (p. 
 
 487). 
 Alum schists of Sweden and Norway (p. 489). 
 Potsdam sandstone, with Dikelocephalus and Oho- 
 lella (p. 489). 
 British — Menevian beds of Wales, with Paradoxidei 
 Vavidis, etc. (p. 484). 
 Longraynd group, comprising the Harlech grits and 
 Llanoeris slates (p. 486). 
 Jibre^^n— Lower portion of Barrande's "Primordial" 
 zone in Bohemia (p. 486). 
 Fucoid sandstones of Sweden (p. 489). 
 Hnronian series of Canada? (p. 490). 
 \Bri«isft— .Fundamental gneiss of the Hebrides? (n. 
 493). 
 Hyperstheue rocks of Skye ? (p. 491). 
 Foreign — Labradorite series north of the river St 
 Lawrence in Canada (p. 491). 
 Adirondack mountains of New York (p. 491). 
 British — ^Wanting ? 
 
 Foreign— Be&s of gneiss and quartzite, with inter- 
 stratified limestones, in one of which, 1000 feet 
 thick, occurs a foraminifer, .Eto^oim Ccmadenae, the 
 oldest known fossil (p. 491). 
 
OEDEE OF STEATA. 
 
 137 
 
 CHAPTER IX. 
 
 CLASSIFICATION OP TEETIAET FOEMATIONS. 
 
 Order of Succession of Sedimentary Formations. — Frequent Unconformability 
 of Strata. — Imperfection of the Record. — Defectiveness of the Monuments 
 gi-eater in proportion to their Antiquity. — Reasons for studying the newer 
 (Groups first. — Nomenclature of Formations. — Detached Tertiary Forma- 
 tions scattered over Europe. — Value of the Shell-bearing MoUusca in Class- 
 ification. — Classification of Tertiary Strata. — Eocene, Miocene, and Plio- 
 cene Terms explained. 
 
 By reference to the tables g^iven at the end of the last 
 chapter the reader will see that when the fossiliferous rocks 
 are arranged chronologically, we have first to consider the 
 Post-tertiary and then the Tertiary or Cainozoic formations, 
 and afterwards to pass on to those of older date. 
 
 Order of Superposition. — The annexed diagram will show 
 the order of superposition of these deposits, assuming them 
 all to be visible in one continuous section. In nature, as be- 
 foi¥ hinted, page 107, we have never an opportunity of see- 
 Fig. 36. 
 
 ing the whole of them so displayed in a single region ; first, 
 because sedimentary deposition is confinedj during any one 
 geological period, to limited areas ; and, secondly, because 
 strata, after they have been formed, are liable to be utterly 
 annihilated over wide areas by denudation. But wherever 
 certain members of the series are present, they overlie one 
 another in the order indicated in the diagram, though not 
 always in the exact manner there represented, because some 
 of them repose occasionally in unconformable stratification 
 on others. This mode of superposition has been already ex- 
 plained at pp. 94, 111, where I pointed out that the discord- 
 ance which implies a considerable lapse of time between two 
 
138 ELEMENTS OP GEOLOGY. 
 
 formations in juxtaposition is almost invariably; accompanied 
 by a great dissimilarity in the species of organic remains. 
 
 Frequent Unconformability of Strata.— Where the widest 
 gaps appear in the sequence of the fossil forms, as between 
 the Permian and Triassic rocks, or between the Cretaceous 
 and Eocene, examples of such unconformability are very fre- 
 quent. But they are also met with in some part or other of 
 the world at the junction of almost all the other principal 
 formations, and sometimes the subordinate divisions of any 
 one of the leading groups may be found lying unconform- 
 ably on another subordinate member of the same — the Up- 
 per, for example, on the Lower Silurian, or the superior di- 
 vision of the Old Red Sandstone on a lower member of the 
 same, and so forth. Instances of such irregularities in the 
 mode of succession of the strata ai"e the more intelligible the 
 more we extend our survey of the fossiliferous formations, 
 for we are continually bringing to light deposits of interme- 
 diate date,. which have to be intercalated between those pre- 
 viously known, and which reveal to us a long series of events, 
 of which antecedently to such discoveries we had no knowl- 
 edge. 
 
 But while unconformability invariably bears testimony to 
 a lapse of unrepresented time, the conformability of two sets 
 of strata in contact by no rneans implies that the newer for- 
 mation immediately succeeded the older-one. It simply im- 
 plies that the ancient rocks were subjected to no movements 
 of such a nature as to tilt, bend, or break them before the 
 more modern formation was superimposed. It does not show 
 that the earth's crust was motionless in the region in ques- 
 tion, for there may have been a gradual sinking or rising, ex- 
 tending uniformly over a large surface, and yet, during siich 
 movement, the stratified rocks may have retained their orig- 
 inal horizontality of position. There may have been a con- 
 version of a wide area from sea into land and from land into 
 sea, and during these changes of level some strata may have 
 been slowly removed by aqueous action, and after this new 
 strata may be superimposed, differing perhaps in date by 
 thousands of years or centuries, and yet resting conformably 
 on the older set. There may even be a blending of the ma- 
 terials constituting the older deposit with those of the new- 
 er, so as to give rise to a passage in the minei-al character of 
 the one rock into the other as if there had been no break or 
 interruption in the depositing process. 
 
 Imperfection of the Eecord. — Although by the frequent dis- 
 covery of new sets of intermediate strata the transition from 
 one type of organic remains to another is becoming less and 
 
PRINCIPLES OF CLASSIFICATION. 139 
 
 less abrnpt, yet the entire series of records appears to the 
 geologists now living far more fragmentary and defective 
 than it seemed to their predecessors half a century ago. 
 The earlier inquirers, as often as they encountered a break 
 in the regular sequence of formatio js, connected it theoretic- 
 ally with a sudden and violent catastrophe, which had put 
 an end to the regular course of events that had been going 
 on uninterruptedly for ages, annihilating at the same time all 
 or nearly all the organic beings which had previously flour- 
 ished, after which, order being re-established, a new series of 
 events was initiated. In proportion as our faith in these 
 views grows weaker, and the phenomena of the organic or 
 inorganic world presented to us by geology seem explicable 
 on the hypothesis of gradual and insensible changes, varied 
 only by occasional convulsions, on a scale comparable to that 
 witnessed in historical times; and in proportion as it is 
 thought possible that former fluctuations in the organic world 
 may be due to the indefinite modifiability of species without 
 the necessity of assuming new and independent acts of cre- 
 ation, the number and magnitude of the gaps which still re- 
 main, or the extreme imperfection of the record, become more 
 and more striking, and what we possess of the ancient annals 
 of the earth's history appears as nothing when contrasted 
 with that which has been lost. 
 
 When we examine a large area such as Europe, the aver- 
 age as well as the extreme height above the sea attained by 
 the older formations is usually found to exceed that reached 
 by the more modern ones, the primary or palseozoic rising 
 higher than the secondary, and these in their turn than the 
 tertiary ; while in reference to the three divisions of the ter- 
 tiary, the lowest or Eocene group attains a higher summit- 
 level than the Miocene, and these again a greater height 
 than the Pliocene formations. Lastly, the post-tertiary de- 
 posits, such, at least, as are of marine origin, are most com- 
 monly restricted to much more moderate elevations above 
 the sea-level than the tertiary strata. 
 
 It is also observed that strata, in proportion as they are 
 of newer date, bear the nearest resemblance in mineral char- 
 acter to those which are now in the progress of formation in 
 seas or lakes, the newest of all consisting principally of soft 
 mud or loose sand, in some places full of shells, corals, or 
 other organic bodies, animal or vegetable, in others wholly 
 devoid of such remains. The farther we recede from the 
 present time, and the higher the antiquity of the formations 
 which we examine, the greater are the changes which the 
 sedimentary deposits have undergone. Time, as I have ex- 
 
140 ELEMENTS OP GEOLOGY. 
 
 plained in Chapters V., VI., and VII., has multiplied the ef. 
 fects of condensation by pressure and cementation, and the 
 modification produced by heat, fracture, contortion, upheaval, 
 and denudation. The organic remains also have sometimes 
 been obliterated entirely, or the mineral matter of which they 
 were composed has been removed and replaced by other sub- 
 stances. 
 
 Why newer Groups should be studied first.— We likewise 
 observe that the older the rocks the more widely do their 
 organic remains depart from the types of the living creation. 
 First, we find in the newer tertiary rocks a few species which 
 no longer exist, mixed with many living ones, and then, as 
 we go farther back, many genei'a and families at present un- 
 known make their appearance, until we come to sti-ata in 
 which the fossil relics of existing species are nowhere to be 
 detected, except a few of the lowest forms of invertebrate, 
 while some orders of animals and plants wholly unrepresent- 
 ed in the living world begin to be conspicuous. 
 
 When we study, therefore, the geological records of the 
 earth and its inhabitants, we find, as in human history, the 
 defectiveness and obscurity of the monuments always in- 
 creasing the remoter the era to which we refer, and the dif- 
 ficulty of determining the true chronological relations of 
 rocks is more and more enhanced, especially when we are 
 comparing those which were formed simultaneously in very 
 distant regions of the globe. Hence we advance with se- 
 curer steps when we begin with the study of the geological 
 records of later times, proceeding from the newer to the old- 
 er, or from the more to the less known. 
 
 In thus inverting what might at first seem to be the more 
 natural order of historical research, we must bear in mind 
 that each of the periods above enumerated, even the short- 
 est, such as the Post-tertiary, or the Pliocene, Miocene, or 
 Eocene, embrace a succession of events of vast extent, so that 
 to give a satisfactory account of what we already know of 
 any one of them would require many volumes. When, there- 
 foi'e, we approach one of the newer groups before endeavor- 
 ing to decipher the monuments of an older one, it is like en- 
 deavoring to master the history of our own country and that 
 of some contemporary nations, before we enter upon Roman . 
 History, or like investigating the annals of Ancient Italy and 
 Greece before we approach those of Egypt and Assyria. 
 
 Nomenclature. — The origin of the terms Primary and Sec- 
 ondary, and the synonymous terms Palaeozoic and Mespzoiti, 
 were explained in Chapter VHI., p. 123. 
 
 The Tertiary or Cainozoic strata (see p. 123) were so call- 
 
PRINCIPLES OF CLASSIFICATION. 141 
 
 .ed because they were all posterior in date to the Secondary 
 series, of which last the Chalk of Cretaceous, No. 9, Fig. 86, 
 constitutes the newest group. The whole of them were at 
 first confounded with the superficial alluviums of Europe; 
 and it was long before their real extent and thickness, and 
 the various ages to which they belong, were fully recognized. 
 They were observed to occur in patches, some of fresh-watei', 
 others of marine origin, their geographical area being usual- 
 ly small as compared to the secondary formations, and their 
 position often suggesting the idea of their having been de- 
 posited in different bays, lakes, estuaries, or inland seas, after 
 a large portion of the space now occupied by Europe had al- 
 ready been converted into dry land. 
 
 The first deposits of this class, of which the characters 
 were accurately determined, were those occurring in the 
 neighborhood of Paris, described in 1810 by MM. Cuvier and 
 Brongniart. They were ascertained to consist of successive 
 sets of strata, some of marine, others of fresh-water origin, 
 lying one upon the other. The fossil shells and corals were 
 perceived to be almost all of unknown species, and to have 
 in general a near affinity to those now inhabiting warmer 
 seas. The bones and skeletons of land animals, some of them 
 of large size, and belonging to more than forty distinct spe- 
 cies, were examined by Cuvier, and declared by him not to 
 agree specifically, nor most of them even generically, with 
 any hitherto observed in the living creation. 
 
 Strata were soon afterwards brought to light in the vicin- 
 ity of London, and in Hampshire, which, although dissimilar 
 in mineral composition, wei'e justly inferred by Mr. T. Web- 
 ster to be of the same age as those of Paris, because the 
 greater number of the fossil shells were specifically identi- 
 cal. For the same reason, rocks found on the Gironde, in 
 the South of France, and at certain points in the North of 
 Italy, were suspected to be of contemporaneous origin. 
 
 Another important discovery was soon afterwards made 
 by Brocchi in Italy, who investigated the argillaceous and 
 sandy deposits, replete with shells, which form a low range 
 of hills, flanking the Apennines on both sides, from the plains 
 of the Po to Calabria. These lower hills were called by him 
 the Snbapennines, and were formed of strata chiefly marine, 
 and newer than those of Paris and London. 
 
 Another tertiary group occarring in the neighborhood of 
 Bordeaux and Dax, in the South of France, was examined by 
 M. de Basterot in 1825, who described and figured several 
 hundred species of shells, which differed for the most part both 
 from the Parisian series and those of the Subapennine hills. 
 
142 ELEMENTS OF GEOLOGY. 
 
 It was soon, therefore, suspected that this fauna might be- 
 long to a period internaediate between that of the Parisian 
 and Subapennine strata, and it was not long before the evi- 
 dence of superposition was brought to bear in support of 
 this opinion ; for other strata, contemporaneous with those 
 of Bordeaux, were observed in one district (the Valley of the 
 Loire), to overlie the Parisian formation, and in another (in 
 Piedmont) to underlie the Subapennine beds. The first ex- 
 ample of these was pointed out in 1829 by M. Desrioyers, 
 who ascertained that the sand and marl of marine origin call- 
 ed Faluns, near Tours, in the basin of the Loire, full of sea- 
 shells and corals, rested upon a lacustrine formation, which 
 constitutes the uppermost subdivision of the Parisian group, 
 extending continuously throughout a great table-land inter- 
 vening between the basin of the Seine and that of the Loire. 
 The other example occurs in Italy, where strata containing 
 many fossils similar to those of Bordeaux were observed by 
 Bonelli and others in the environs of Turin, subjacent to 
 strata belonging to the Subapennine group of Brocchi. 
 
 Value of Testacean Fossils in Classification. — It will be ob- 
 served that in the foregoing allusions to organic i-emains, 
 the testacea or the shell-bearing moUusca are selected as 
 the most useful and convenient class for the purposes of gen- 
 eral classification. In the first place, they are more univer- 
 sally distributed through strata of every age than any other 
 organic bodies. Those families of fossils which are of rare 
 and casual occurrence are absolutely of no avail in estab- 
 lishing a chronological arrangement. If we have plants 
 alone in one group of strata and the bones of mammalia in 
 another, we can draw no conclusion respecting the affinity 
 or discordance of the organic beings of the two epochs com- 
 pared ; and the same may be said if we have plants and ver- 
 tebrated animals in one series and only shells in another. 
 Although corals are more abundant, in a fossil state, than 
 plants, reptiles, or fish, they are still rare when contrasted 
 with shells, because they are more dependent for their well- 
 being on the constant clearness of the water, and are, there- 
 fore, less likely to be included in rocks which endure in con- 
 sequence of their thickness and the copiousness of sediment 
 which prevailed when they originated. The utility of the 
 testacea is, moreover, enhanced by the circumstance that 
 some forms are proper to the sea, others to the land, and 
 others to fresh water. Rivers scarcely ever fail to cai-ry 
 down into their deltas some land-shells, together with spe- 
 cies which are at once fluviatile and lacustrine. By this 
 means we learn what terrestrial, fresh-water, and v-iarine spe- 
 
CLASSIFICATION OF TERTIARY STRATA. 143 
 
 cies coexisted at particular eras of the past : aud having 
 thus identified strata formed in seas with others which orig- 
 inated contemporaneously in inland lakes, we are then ena- 
 bled to advance a step farther, and show that certain quad- 
 rupeds or aquatic plants, found fossil in lacustrine forma- 
 tions, inhabited the globe at the same period when certain 
 fish, reptiles, and zoophytes lived in the ocean. 
 
 Among other characters of the molluscous animals, which 
 render them extremely valuable in settling chronological 
 questions in geology, may be mentioned, first, the wide geo- 
 graphical range of many species ; and, secondly, what is 
 probably a consequence of the former, the great duration of 
 species in this class, for they appear to have surpassed in 
 longevity the greater number of the mammalia and fish. 
 Had each species inhabited a very limited space, it could 
 never, when imbedded in strata, have enabled the geologist 
 to identify deposits at distant points ; or had they each last- 
 ed but for a brief period, they could have thrown no light 
 on the connection of rocks placed far from each other in the 
 chronological, or, as it is often termed, vertical series. 
 
 Classification of Tertiary Strata. — Many authors have di- 
 vided the European Tertiary strata into three groups — 
 lower, middle, and upper ; the lower comprising the oldest 
 formations of Paris and London before mentioned; the mid- 
 dle those of Bordeaux and Touraine; and the upper all those 
 newer than the middle group. 
 
 In the first edition of the Principles of Geology, I divided 
 the whole of the Tertiary formations into four groups, char- 
 acterized by the percentage of recent shells which they con- 
 tained. The lower tertiary strata of London and Paris were 
 thought by M. Deshayes to contain only 3-^ per cent, of re- 
 cent species, and were termed Eocene. The middle tertiary 
 of the Loire and Gironde had, according to the specific de- 
 terminations of the same conchologist, 17 per cent., and 
 formed the Miocene division. The Subapennine beds con- 
 tained 35 to 50 per cent., and were termed Older Pliocene, 
 while still more recent beds in Sicily, which had from 90 to 
 95 per cent, of species identical with those now living, were 
 called Newer Pliocene. The first of the above terms, Eocene, 
 is derived from t/wc, eos, dawn., and catvof, cainos, recent., be- 
 cause the fossil shells of this period contain an extremely 
 small proportion of living species, which may be looked upon 
 as indicating the dawn of the existing state of the testaceous 
 fauna, no recent species having been detected in the older or 
 secondary rocks. 
 
 The term Miocene (from juetov, meion, less., and KaivoQ, cainos, 
 
144 ELEMENTS OF GEOLOGY. 
 
 recent) is intended to expi-ess a minor proportion of recent 
 species (of testacea), the term Pliocene (from ■kXciov, pleion, 
 more, and kuivoq, cainos, recent) a comparative plurality of 
 the same. It may assist the memory of students to remind 
 them, that the Miocexie, contain a minor proportion, and Pli- 
 ocene a comparative plurality of recent species ; and that 
 the greater number of recent species always implies the more 
 modern origin of the strata. 
 
 It has sometimes been objected to this nomenclature that 
 certain species of infusoria found in the chalk are still exist- 
 ing, and, on the other hand, the Miocene and Older Pliocene 
 deposits often contain the' remains of mammalia, reptiles, 
 and fish, exclusively of extinct species. But the reader nmst 
 bear in mind that the terms Eocene, Miocene, and Pliocene 
 were originally invented with reference purely to concholog- 
 ical data, and in that sense have always been and are still 
 used by me. 
 
 Since the year 1830 the number of known shells, both re- 
 cent and fossil, has largely increased, and their identification 
 has been more accurately determined. Hence some modifi- 
 cations have been required in the classifications founded on 
 less perfect materials. The Eocene, Miocene, and Pliocene 
 periods have been made to compi-ehend certain sets of strata 
 of which the fossils do not always conform strictly in the 
 proportion of recent to extinct species with the definitions 
 first given by me, or which are implied in the etymology of 
 those terms. 
 
RECENT PERIOD. 145 
 
 CHAPTER X. 
 
 RECENT AND POST-PLIOCENE PERIODS. 
 
 Recent and Post-pliocene Periods. — Terms defined. — Eormations of the 
 Recent Period. — Modern littoral Deposits containing Works of Art near 
 Kaples. — Danish Peat and Shell-mounds. — Swiss Lake-dwellings, — Peri- 
 ods of Stone, Bronze, and Iron. — Post-pliocene Formations. — Coexistence 
 of Man with extinct Mammalia. — Reindeer Period of South of France. — 
 Alluvial Deposits of Paleolithic Age. — Higher and Lower-level Valley- 
 gravels. — Loess or Inundation-mud of the Nile, Rhine, etc. — Origin of 
 Caverns. — Remains of Man and extinct Quadrupeds in Cavern Deposits. — 
 Cave of Kirkdala. — Australian Cave-breccias. — Geographical Relationship 
 of the Provinces of living Vertebrata and those of extinct Post-pliocene 
 Species, — Extinct struthious Birds of New Zealand. — Climate of'the Post- 
 pliocene Period. — Comparative Longevity of Species in the Mammalia and 
 Testacea. — Teeth of Recent and Post-pliocene Mammalia. 
 
 We have seen in the last chapter that the uppermost or 
 newest strata ai-e called Post-tertiary, as being more modern 
 than the Tertiary. It will also be observed that the Post- 
 tertiary formations are divided into two subordinate groups : 
 the Recent, and Post-pliocene. In the former, or the Recent^ 
 the mammalia as well as the shells are identical with species 
 now living : whereas in the Post-pliocene, the shells being all 
 of living forms, a part, and often a considerable part; of the 
 mammalia belonged to extinct species. To this nomencla- 
 ture it may be objected that the term Post-pliocene should 
 in strictness include all geological monuments posterior in 
 date to the Pliocene ; but when I have occasion to speak of 
 the whole collectively, I shall call them Post-tertiary, and 
 reserve the term Post- pliocene for the older Post - tertiary 
 formations, while the IJpper or newer ones will be called 
 "Recent." 
 
 Cases will occur where it may be scarcely possible to draw 
 the boundary line between the Recent and Post-pliocene de- 
 posits ; and we must expect these difficulties to increase rath- 
 er than diminish with every advance in our knowledge, and 
 in proportion as gaps are filled up in the series of records. 
 
 RECENT PERIOD. 
 
 It was stated in the sixth chapter, when I treated of denu- 
 dation, that the dry land, or that part of the earth's surface 
 which is not covered by the waters of lakes or seas, is gen- 
 
 1 
 
146 ELEMENTS OF GEOLOGY. 
 
 erally wasting away by the incessant action of rain and riv- 
 ers, and in some cases by the undermining and removing 
 power of waves and tides on the sea-coast. But the rateof 
 waste is very unequal, since the level and gently sloping 
 lands, where they are protected by a continuous covering of 
 vegetation, escape nearly all wear and tear, so that they may 
 remain for ages in a stationary condition, while the removal 
 of matter is.constantly widening and deepening the inter- 
 vening ravines and valleys. 
 
 The materials, both fine and coarse, carried down annually 
 by rivers from the higher regions to the lower, and deposited 
 in successive strata in the basins of seas and lakes, must be 
 of enormous volume. We are always liable to underrate 
 their magnitude, because the accumulation of sti'ata is going 
 on out of sight. 
 
 There are, however, causes at work which, in the course 
 of centuries, tend to render visible these modern formations, 
 whether of marine or lacustrine origin. For a large portion 
 of the earth's crust is always undergoing a change of level, 
 some areas rising and others sinking at the rate of a few 
 inches, or a few feet, perhaps sometimes yards, in a century ; 
 so that spaces which were once subaqueous are gradually 
 converted into land, and others which were high and dry 
 become submerged. In consequence of such movements we 
 find in certain regions, as in Cashmere, for example, where- 
 the mountains are often shaken by earthquakes, deposits 
 which were formed in lakes in the historical period, but 
 through which rivers have now cut deep and wide channels. 
 In lacustrine strata thus intersected, works of art and fresh- 
 water shells are seen. In other districts on the borders of 
 the sea, usually at very moderate elevations above its level, 
 raised beaches occur, or marine littoral deposits, such as 
 those in which, on the borders of the Bay of Baise, near Na- 
 ples, the well-known temple of Serapis was imbedded. In 
 that case the date of the monument buried in the marine 
 strata is ascertainable, but in many other instances the ex- 
 act age of the remains of human workmanship is uncertain, 
 as in the estuary of the Clyde at Glasgow, where many ca- 
 noes have been exhumed, with other works of art, all assign- 
 able to some part of the Recent Period. 
 
 Danish Peat and Shell-mounds or Kitchen-middens. — Some- 
 times we obtain evidence, without the aid of a change of 
 level, of events which took place in pre-historic times. The 
 combined labors, for example, of the antiquary, zoologist, 
 and botanist have brought to light many monuments of the 
 early inhabitants buried in peat-mosses in Denmark. Their" 
 
DANISH SHELL MOUNDS. 147 
 
 geological age is determined by the fact that, not only the 
 contemporaneous fresh- water and land shells, but all the 
 quadrupeds, found in the peat, agree specifically with those 
 now inhabiting the same districts, or which are known to 
 have been indigenous in Denmark within the memory of 
 man. In the lower beds of peat (a deposit varying from 20 
 to 30 feet in thickness), weapons of stone accompany trunks 
 of the Scotch fir, Plnus sylvestris. This peat may be refer- 
 red to that part of the stone period for which Sir John Lub- 
 bock proposed the name of " Neolithic "* in contradistinction 
 to a still older era, termed by him " Paleolithic," and which 
 will be described in the sequel. In the higher portions of 
 the same Danish bogs, bronze implements ai-e associated 
 with trunks and acorns of the common oak. It appears that 
 the pine has never been a native of Denmark in historical 
 times, and it seems to have given place to the oak about the 
 time when articles and instruments of bronze superseded 
 those of stone. It also appears that, at a still later period, 
 the oak itself became scarce, and was nearly supplanted by 
 the beach, a tree which now flourishes luxuriantly in Den- 
 mai-k. Again, at the still later epoch when the beech-tree 
 abounded, tools of iron were introduced, and were gradually 
 substituted for those of bronze. 
 
 On the coasts of the Danish islands in the Baltic, certain 
 mounds, called in those countries " Kjokken-modding," or 
 "kitchen-middens," occur, consisting chiefly of the castaway 
 shells of the oyster, cockle, periwinkle, and other eatable 
 kinds of moUusks. The mounds are from three to ten feet 
 high, and from 100 to 1000 feet in their longest diameter. 
 They greatly resemble heaps of shells formed by the Red 
 Indians of North America along the eastern shores of the 
 United States. In the old refuse-heaps, recently studied by 
 the Danish antiquaries and naturalists with gi-eat skill and 
 diligence, no implements of metal have ever, been detected. 
 All the knives, hatchets, and other tools, are of stone, horn, 
 bone, or wood. With them are often intermixed fragments 
 of rude pottery, charcoal and cinders, and the bones of 
 quadrupeds on which the rude j)eople fed. These bones be- 
 long to wild species still living in Europe, though some of 
 them, like the beaver, have long been extirpated in Den- 
 mark. The only animal which they seem to have domesti- 
 cated was the dog. 
 
 As there is an entire absence of metallic tools, these i-efuse- 
 heaps are referi-ed to the Neolithic division of the age of 
 stone, which immediately preceded in Denmark the age of 
 * Sir John Lubbock, Pre-historic Times, p. 3. 1865. 
 
148 ELEMENTS OF GEOLOGY. 
 
 bronze. It appears that a race more advanced in civiliza- 
 tion, armed with weapons of that mixed metal, invaded Scan- 
 dinavia, and ousted the aborigines. 
 
 Lacustrine Habitations of Switzerland.— In Switzerland a 
 different class of monuments, illustrating the successive ages 
 of stone, bronze, and iron, has been of late years investigated 
 with great success, and especially since 1854, in which year 
 Dr. P. Keller explored near the shore at Meilen, in the bot- 
 tom of the lake of Zurich, the ruins of an old village, origi- 
 nally built on numerous wooden piles, driven, at some un- 
 known period, into the muddy bed of the lake. Since then 
 a great many other localities, more than a hundred and fifty 
 in all, have been detected of similar pile-dwellings, situated 
 near the borders of the Swiss lakes, at points where the depth 
 of water does not exceed 15 feet.* The superficial mud in 
 such cases is filled with various articles, many hundreds of 
 them being often dredged up from' a very limited area. 
 Thousands^of piles, decayed at their upper extremities, are 
 often met with still firmly fixed in the mud. 
 
 As the ages of stone, bronze, and iron merely indicate suc- 
 cessive stages of civilization, they may all have coexisted at 
 once in different parts of the globe, and even in contiguous 
 regions, among nations having little intercourse with each 
 other. To make out, therefore, a distinct chronological se- 
 ries of monuments is only possible when our observations are 
 confined to a limited district, such as Switzerland. 
 
 The relative antiquity of the pile-dwellings, which belong 
 respectively to the ages of stone and bronze, is clearly illus- 
 trated by the associations of the tools with certain groups of 
 animal remains. Where the tools are of stone, the castaway 
 bones which served for the food of the ancient people are 
 those of deer, the wild boar, and wild ox, which abounded 
 when society was in the hunter state. But the bones of the 
 later or bronze epoch were chiefly those of the domestic ox, 
 goat, and pig, indicating progress in civilization. Some vil- 
 lages of the stone age are of later date than others, and ex- 
 hibit signs of an improved state of the arts. Among their 
 relics are discovei-ed carbonized grains of wheat and barley, 
 and pieces of bread, proving that the cultivation of cereals 
 had begun. In the same settlements, also, cloth, made of 
 woven flax and straw, has been detected. 
 
 The pottery of the bronze age in Switzerland is of a finer 
 texture, and more elegant in form, than that of the age of 
 stone. At Nidau, on the lake of Bienne, articles of iron have 
 
 * Bulletin de la Societe Vaudoise des Sci. Nal. , t. vi. , Lausanne, 1860 ; and 
 Antiquity of Man, by the author, ch. ii. 
 
POST-PLIOCENE PERIOD. I49 
 
 also been discovered, so that this settlement was evidently 
 not abandoned till that metal had come into use. 
 
 At La Thene, in the northern angle of the lake of Neufcha- 
 tel, a gi'eat many articles of iron have been obtained, which 
 in form and ornamentation are entirely different- both from 
 those of the bronze period and from those used by the Ro^ 
 rnans. Gaulish and Celtic coins have also been found there 
 by MM. Schwab and Desor. They agree in character with 
 remains, including many iron swords, which have been found 
 at Tiefenau, near Berne, in ground supposed to have been a 
 battle-field ; and their date appears to have been anterior to 
 the great Roman invasion of Northern Europe, though per- 
 haps not long before, that event.* Coins, whicli sometimes 
 occur in deposits of the age of iron, have never yet been 
 found in formations of the ages of bronze or stone. 
 
 The period of bronze must have been one of foreign com- 
 merce, as tin, which enters into this metallic mixture in the 
 proportion of about ten per cent, to the copper, was obtain- 
 ed by the ancients chiefly from Cornwall.f Very few hu- 
 man bones of the bronze period have been met with in the 
 Danish peat, or in the Swiss lake-dwellings, and this scarcity 
 is generally attributed by ai-chseologists to the custom of 
 burning the dead, which prevailed in the age of bronze. 
 
 POST-PLIOCENE PERIOD. 
 
 From the foregoing observations we may infer that the 
 ages of iron and bronze in Northern and Central Europe 
 were preceded by a stone age, the Neolithic, referable to that 
 division of the post-tertiary epoch which I have called Re- 
 cent, when the mammalia as well as the other organic re- 
 mains accompanying the stone implements were of living 
 species. But memorials have of late been brought to light 
 of a still older age of stone, for which, as above stated, the 
 name Paleolithic has been proposed, when man was contem- 
 porary in Europe with the elephant and rhinoceros, and va- 
 rious other animals, of which many of the most conspicuous 
 have long since died out. 
 
 Reindeer Period in South of France. — In the larger number 
 of the caves of Europe, as for example in those of England, 
 Belgium, Germany, and many parts of France, the animal re- 
 mains agree specifically with the fauna of this oldest division 
 of the age of stone, or that to which belongs the drift of 
 Amiens and Abbeville presently to be mentioned, containing 
 
 * Sir J. Lubbock's Lecture, Royal Institution, Feb. 27th, 1863. 
 t Diodorus, v., 21, 22, and Sir H. James, Note on Block of Tin dredged 
 up in Falmouth Harbor. Royal Institution of Cornwall, 1863. 
 
150 ELEMENTS OF GEOLOGY. 
 
 flint implements of a very antique type. But there are some 
 caves in the departments of Dordogne, Aude, and other parts 
 of the south of France, which are believed by M. Lartet to be 
 of intermediate date between the Paleolithic and Neolithic 
 periods. To this inteismediate era M. Lartet gave, in 1863, 
 the name of the " reindeer period," because vast quantities 
 of the bones and horns of that deer have been met with in 
 the French caverns. In some cases seJDarate plates of molars 
 of the mammoth, and several teeth of the great Irish deer, 
 CervvjS megaceros, and of the cave-lion, JFhlis spelcea, have been 
 found mixed up with cut and carved bones of reindeer. On 
 one of these sculptured bones in the cave of Perigord, a rude 
 representation of the mammoth, with its long curved tusks 
 and covering of wool, occurs, which is regarded by M. Lartet 
 as placing beyond all doubt the fact that the early inhabit- 
 ants of these caves must have seen this species of elephant 
 still living in France. The presence of the marmot, as well 
 as the reindeer and some other northern animals, in these 
 caverns seems to imply a colder climate than that of the 
 Swiss lake-dwellings, in which no remains of reindeer have 
 as yet been discovered. The absence of this last in the old 
 lacustrine habitations of Switzerland is the moi-e significant, 
 because in a cave in the neighborhood of the lake of Geneva, 
 namely, that of Mont Salfeve, bones of the reindeer occur with 
 flint implements similar to those of the caverns of Dordogne 
 arid Perigord. 
 
 The state of the arts, as exemplified by the instruments 
 found in these caverns of the reindeer period, is somewhat 
 more advanced than that which chai-acterizes the tools of 
 the Amiens drift, but is nevertheless more rude than that of 
 the Swiss lake-dwellings. No metallic articles occur, and 
 the stone hatchets are not ground after the fashion of celts ; 
 the needles of bone are shaped in a workmanlike style, hav- 
 ing their eyes diilled with consummate skill. 
 
 The formations above alluded to, which are as yet but im- 
 perfectly known, may be classed as belonging to the close 
 of the Paleolithic era, of the monuments of which I am now 
 about to treat. 
 
 , Alluvial Deposits of the Paleolithic Age. — The alluvial and 
 marine deposits of the Paleolithic age, the earliest to which 
 any vestiges of man have yet been traced back, belong to a 
 time when the physical geography of Europe differed in a 
 marked degree from that now prevailing. In the Neolithic 
 period, the valleys and rivers coincided almost entirely with 
 those by which the present drainage of the land is efffected, 
 and the peat-mosses were the same as those now growing. 
 
EECENT.AND POST-PLIOCENE DEPOSITS. 151 
 
 The situation of the shell-mounds and lake-dwellings above 
 alluded to is such as to imply that the topography of the 
 districts where they are observed has not subsequently un- 
 dergone any material alteration. Whereas we no sooner ex- 
 amine the Post-pliocene formations, in which the remains of 
 so many extinct mammalia are found, than we at once per- 
 ceive a more decided discrepancy between the former and 
 present outline of the surface. Since those deposits origi- 
 nated, changes. of considerable magnitude have been eflfect- 
 ed in the depth and width of many valleys, as also in the di- 
 rection of the superficial and subterranean drainage, and, as 
 is manifest near .the sea-coast, in the relative position of land 
 and water. In the annexed diagram (Fig. 87) an ideal sec- 
 Fig. 87. 
 
 Eeceut and Post-pliocene alluvial deposits. 
 1. Peat of the recent period. 2. Gravel of modem river. 2'. Loam of brick-earth 
 : (loess) of same age as 2, formed hy inundations of the river. 3. Lower-level 
 
 valley-gravel with extinct mammalia (Post-pliocene). 3'. Loam of same age. 
 
 4. Higner-level valley-gravel (Post-pliocene). 4'. Loam of same age. 6. Upland 
 
 fravel'of various kinds and periods, consisting in some places of uustratiHed 
 balder clay or glacial drift. 6. Older rocks. 
 
 tion is given, illustrating the different position which the 
 Recent and Post-pliocene alluvial deposits occupy in many 
 European valleys. . 
 
 The peat, No. 1, has been formed in a low part of the mod- 
 ern alluvial plain, in parts of which gravel No. 2 of the re- 
 cent period is seen. Over this gravel the loam or fine sedi' 
 ment 2' has in many places been. deposited by the river dur- 
 ing floods which covered nearly the whole alluvial plain. 
 
 No. 3 represents an older alluvium, composed of sand and 
 gravel, formed before the valley had been excavated to its 
 .present depth. It contains the remains of fluviatile shells 
 of living species associated with the bones of mammalia, in 
 part of recent, and in part of extinct species. Among the 
 latter, the mammoth {E. primigenius) and the Siberian rhi- 
 noceros {R. tichorhinus) are the most common in Europe. 
 No. 3' is a remnant of the loam or brick-earth by. which No. 
 3 was overspread. No. 4 is a still older and more elevated 
 terrace, similar in its composition and organic remains to 
 No. 3, and covered in like manner with its iriundation-mujdi 
 
152 ELEMENTS OF GEOLOGY. 
 
 4'. Sometimes the valley-gravels of older date are entirely 
 missing, or there is only one, and occasionally there are more 
 than two, marking as many successive stages in the excava- 
 tion of the valley. They usually occur at heights varying 
 from 10 to 100 feet, sometimes on the right and sometimes 
 on the left side of the existing river-plain, but rarely in great 
 strength on exactly opposite sides of the valley. 
 
 Among the genera of extinct quadrupeds most frequently 
 met with in England, France, Germany, and other parts of 
 Europe, are the elephant, rhinoceros, hippopotamus, horse, 
 great Irish deer, bear, tiger, and hysena. In the peat, No. 1 
 (Fig. 87), and in the more modern gravel and silt (No. 2), 
 works of art of the ages of iron and bronze, and of the later 
 or Neolithic stone period, already described, are met with. 
 In the more ancient or Paleolithic gravels, 3 arid 4, there 
 have been found of late years in several valleys in France 
 and England — as, for example, in those of the Seine and 
 Somme, and of the Thames and Ouse, near Bedford — stone 
 implements of a rude type, showing that man coexisted in 
 those districts with the mammoth and other extinct quadru- 
 peds of the genera above enumerated. In 1847, M. Boucher 
 _de Perthes observed in an ancient alluvium at Abbeville, in 
 Picardy, the bones of extinct mammalia associated in such a 
 manner with flint implements of a rude type as to lead him 
 to infer that both the organic remains and the works of art 
 were referable to one and the same period. This inference 
 was soon after confirmed by Mr. Prestwich, who found in 
 1859 a flint tool in situ ih the same stratum at Amiens that 
 contained the remains of extinct mammalia. 
 
 The flint implements found at Abbeville and Amiens are 
 most of them considered to be hatchets and spear-heads, and 
 are different from those commonly called "celts." These 
 celts, so often found in the recent formations, have a more 
 regular oblong shape, the result of grinding, by which also 
 a sharp edge has been given to them. The Abbeville tools 
 found in gravel at different levels, as in Nos. 3 and 4, Fig. 
 87, in which bones of the elephant, rhinoceros, and other 
 extinct mammalia occur, are always unground, having evi- 
 dently been brought into their present form simply by the 
 chipping off" of fragments of flint by repeated blows, such as 
 could be given by a stone hammer. 
 
 Some of them are oval, others of a spear-headed form, 
 no two exactly alike, and yet the greater number of each 
 kind are obviously fashioned after the same general pattern. 
 Their outer surface is often white, the original black flint 
 having been discolored and bleached by exposure to the air, 
 
DISCOVEEIES AT AMIENS. 153 
 
 or by the action of acids, as they lay in the gravel. They 
 are most commonly stained of the same ochreous color as 
 the flints of the gravel in which they are imbedded. Occa- 
 sionally their antiquity is indicated not only by their color 
 but by superficial incrustations of carbonate of lime, or by 
 dendrites formed of oxide of iron and manganese. The edges 
 also of most of them are worn, sometimes by having been 
 used as tools, or sometimes by having been rolled in the old 
 river's bed. They are met with not only in the lower-level 
 gravels, as in No. 3, Fig. 87, but also in No. 4, or the higher 
 gravels, as at St. Acheul, in the suburbs of Amiens, where 
 the old alluvium lies at an elevation of about 100 feet above 
 the level of the river Somme. At both levels fluviatile and 
 land-shells are met with in the loam as well as in the gravel, 
 but there are no marine shells associated, except at Abbe- 
 ville, in the lowest part of the gravel^near the sea, and a few 
 feet only above the present high-water mark. Here v/ith 
 fossil shells of living species are mingled the bones of JSle- 
 phas primigenius and JE. antiquus, Rhinoceros tichorhinus. 
 Hippopotamus, Felis spelcea, Hycena spelc^a, reindeer, and 
 many others, the bones accompanying the flint implements 
 in such a manner. as to show that both were buried in the 
 old alluvium at the same period. 
 
 Nearly the entire skeleton of a rhinoceros was found at 
 one point, namely, in the Menchecourt drift at Abbeville, 
 the bones being in such juxtaposition as to show that the 
 cartilage must have held them together at the time of their 
 inhumation. 
 
 The general absence here and elsewhere of human bones 
 from gravel and sand in which flint tools are discovered, 
 may in some degree be due to the present limited extent of 
 our rfesearches. But it may also be presumed that when a 
 hunter population, always scanty in numbers, ranged over 
 this region, they were too wary to allow themselves to be 
 overtaken by the floods which swept away many herbivor- 
 ous animals from the low river-plains where they may have 
 been pasturing or sleeping. Beasts of prey prowling about 
 the same alluvial flats in search of food may also have been 
 surprised more readily than the human tenant of the same 
 region, to whom the signs of a coming tempest were better 
 known. 
 
 Inundation^mud of Rivers.— Brick-earth.— Fluviatile Loam, 
 or Loess. — As a general rule, the fluviatile alluvia of differ- 
 ent ages (Nos. 2, 3, 4, Fig. 87) are severally made up of coarse 
 materials in their lower portions, and of fine silt or loam in 
 their upper parts. For rivers are constantly shifting their 
 
154 ELEMENTS OF GEOLOGY. 
 
 position in the valley-plain, encroaching gradually on one 
 bank, near which there is deep water, and deserting the oth- 
 er or opposite side, where the channel is growing shallower, 
 being destined eventually to be converted into land. Where 
 the current runs strongest, coarse gravel is swept along, and 
 where its velocity is slackened, first sand, and then only the 
 finest mud, is thrown down. A thin film of this fine sed- 
 iment is spread, during floods, over a wide area, on one, or 
 sometimes on both sides, of the main stream, often reaching 
 as far as the base of the blufis or higher grounds which bound 
 the valley. Of such a description are the well-known annual 
 deposits of the Nile, to which Egypt owes its fertility. So 
 thin are they, that the aggregate amount accumulated in a 
 century is said rarely to exceed five inches, although in the 
 course of thousands of years it has attained a vast thickness, 
 the bottom not having been reached by borings extending 
 to a depth of 60 feet towards the central parts of the valley. 
 Everywhere it consists of the same homogeneous mud, des- 
 titute of stratification — the only signs of successive accumu- 
 lation being where the Nile has silted up its channel, or 
 where the blown sands of the Libyan desert have invaded 
 the plain, and given rise to alternate layers of sand and 
 mud. 
 
 In European river-loams we occasionally observe isolated 
 pebbles and angular pieces of stone which have been floated 
 by ice to the places where they now occur ; but no such 
 coarse materials are met with in the plains of Egypt. 
 
 In some parts of the valley of the Rhine the accumulation 
 of similar loam, called in Germany " loess," has taken place 
 on an enormous scale. Its color is yellowish-gray, and very 
 homogeneous ; and Professor Bischoff has ascertained, by 
 analysis, that it agrees in composition with the mud of the 
 Nile. Although for the most part unstratified, it betrays in 
 some places marks of stratification, especially where it con- 
 tains calcareous concretions, or in its lower part where it 
 rests on subjacent gravel and sand which alternate with 
 each other near the junction. About a sixth part of the 
 whole mass is composed of carbonate of lime, and there is 
 usually an intermixture of fine quartzose and micaceous 
 sand. 
 
 Although this loam of the Rhine is unsolidified, it usually 
 terminates where it has been undermined by running water 
 in a vertical cliff", from the face of which shells of terrestrial, 
 fresh-water and amphibious mollusks project in relief These 
 shells do not imply the permanent sojourn of a body of fresh 
 water on the spot, for the most aquatic of them, the Succi- 
 
LOESS OR INUNDATION-MUD. 155 
 
 Kg. 88. Fig. 89. Hg. 90.. 
 
 Hi 1 1 
 
 Suceinea elongata. Pupa muscorum (Lmn.), Helia> hiapida ijj^mi.) {plebeia). 
 
 nea, inhabits marshes and wet grassy meadows. The Suo- 
 cinea elongata (or S. oblongata), Fig. 88, is very characteris- 
 tic both of the loess of the Rhine and of some other Europe- 
 an river-loams. 
 
 Among the land-shells of the Rhenish loess, Helix hispida, 
 Fig. 90, and Pupa museorum, Fig. 89, are very common. 
 Both the terrestrial and aquatic shells are of most fl-agile 
 and delicate structure, and yet they are alnaost invariably 
 perfect and uninjured. They must have been broken to 
 pieces had they been swept along by a violent inundation. 
 Even the color of some of the land-shells, as that of Helix 
 nemoralis, is occasionally preserved. 
 
 In parts of the valley of the Rhine, between Bingen and 
 Basle, the fluviatile loam or loess now under consideration 
 is several hundred feet thick, and contains here and there 
 throughout that thickness land and amphibious shells. As 
 it is seen in masses fringing both sides of the great plain, 
 and as occasionally remnants of it occur in the centre of the 
 valley, forming hills several hundred feet in height, it seems 
 necessary to suppose, first, a time when it slowly accumu- 
 lated ; and secondly, a later period, when large portions of 
 it were removed, or when the original valley, which had 
 been partially filled up with it, was re-excavated. 
 
 Such changes may have been brought about by a great 
 movement of oscillation, consisting first of a general depres- 
 sion of the land, and then of a gradual re-elevation of the 
 same. The amount of continental depression which first 
 took place in the interior, must be imagined to have exceed- 
 ed that of the region near the sea, in which case: the higher 
 part of the great valley would have its alluvial plain grad- 
 ually raised by an accumulation of sediment, which would 
 only cease when the subsidence of the land was at an end. 
 If the direction of the movement was then reversed^ and, 
 during the ire-elevation of the continent, the inland region 
 nearest the mountains should rise more rapidly than that 
 near the coast, the river would acquire a denuding power 
 sufficient to enable it to sweep away gradually nearly all 
 the loam and gravel with which parts of its basin had been 
 filled up. Terraces and hillocks of mud a,nd sand ' would 
 then alone remain to attest the various -levels at- which -the 
 
156 ELEMENTS OF GEOLOGY. 
 
 rivei- had thrown down and afterwards removed alluvial 
 matter. 
 
 Cavern Deposits containing Human Remains and Bones of 
 Extinct Animals. — In England, and in almost all countries 
 where limestone rocks abound, caverns are found, usually- 
 consisting of cavities of large dimensions, connected together 
 by low, narrow, and sometimes tortuous galleries or tunnels. 
 These subterranean vaults are usually filled in part with 
 mud, pebbles, and breccia, in which bones occur belonging 
 to the same assemblage of animals as those characterizing 
 the Post-pliocene alluvia above desciibed. Some of these 
 bones are referable to extinct and others to living species, 
 and they are occasionally intermingled, as in the valley- 
 gravels, with implements of one or other of the great divi- 
 sions of the stone age, and these are not unfi-equently accom- 
 panied by human bones, which are much more common in 
 cavern deposits than in valley-alluvium. 
 
 Each suite of caverns, and the passages by which they com- 
 municate the one with the other, afford memorials to the ge- 
 ologist of successive phases through which they must have 
 passed. First, there was a period when the carbonate, of 
 lime was carried out gradually by springs ; secondly, an era 
 when engulfed rivers or occasional floods swept organic and 
 inorganic debris into the subterranean hollows previously 
 formed; and thirdly, there were such changes in the configu- 
 ration of the region as caused the engulfed rivers to be turn- 
 ed into new channels, and springs to be dried up, after which 
 the cave-mud, breccia, gravel, and fossil bones would bear the 
 same kind of relation to the existing drainage of the country 
 as the older valley-drifts with their extinct mammalian re- 
 mains and works of art bear to the present rivers and allu- 
 vial plains. 
 
 The quarrying away of large masses of Carboniferous and 
 Devonian limestone, near Liege, in Belgium, has afforded the 
 geologist magnificent sections of some of these caverns, and 
 the former communication of cavities in the interior of the 
 rocks with the old surface of the country by means of ver- 
 tical or oblique fissures, has been demonstrated in places 
 where it would not otherwise have been suspected, so com- 
 pletely have the upper extremities of these fissures been 
 concealed by superficial drift, while their lower ends, which 
 extended into the roofs of the caves, are masked by stalac- 
 titic incrustations. 
 
 The origin of the stalactite is thus explained by the emi- 
 nent chemist Liebig. Mould or humus, being acted on by 
 moisture and air, evolves carbonic acid, which is dissolved 
 
CAVES AT ENGIHdUL AND BRIXHAM. 157 
 
 by rain. The rain-water, thus impregnated, permeates the 
 porous limestone, dissolves a portion of it, and afterwards, 
 when the excess of carbonic acid evaporates in the caverns, 
 parts with the calcareous matter, and forms stalactite. Even 
 while caverns are still liable to be occasionally flooded such 
 calcareous incrustations accumulate, but it is generally when 
 they are no longer in the line of drainage that a solid floor 
 of hard stalagmite is formed on the bottom. 
 
 The late Dr. Schmerling examined forty caves near Liege, 
 and found in all of them the remains of the same fauna, com- 
 prising the mammoth, tichorhine rhinoceros, cave-bear, cave- 
 hysena, cave-lion, and many others, some of extinct and some 
 of living species, and in all of them flint implements. In four 
 or five caves only parts of human skeletons were met with, 
 comprising sometimes skulls with a few other bones, some- 
 times nearly every part of the skeleton except the skull. In 
 one of the caves, that of Engihoul, where Schmerting had 
 found the remains of at least three human individuals, they 
 were xningled in such a manner with bones of extinct mam- 
 malia, as to leave no doubt on his mind (in 1833) of man 
 having co-existed with them. 
 
 In 1860, Professor Malaise, of Liege, explored with me this 
 same cave of Engihoul, and beneath a hard floor of stalag- 
 mite we found mud full of the bones of extinct and recent 
 animals, such as Schmerling had desci-ibed, and my compan- 
 ion, persevering in his researches after I had returned to 
 England, extracted fi-om the same deposit two human lower 
 jaw-bones retaining their teeth. The skulls from these Bel- 
 gian caverns display no marked deviation from the normal 
 European type of the present day. 
 
 The careful investigations carried on by Dr. Falconer, Mr. 
 Pengelly, and others, in the Brixham cave near Torquay, in 
 1858, demonstrated that flint knives were there imbedded in 
 such a manner in loam underlying a floor of stalagmite as to 
 prove that man had been an inhabitant of that region when 
 the cave-bear and other members of the ancient post-pliocene 
 fauna were also in existence. 
 
 The absence of gnajs'ed bones had led Dr. Schmerling to 
 infer that none of the Belgian caves which he explored had 
 served as<the dens of wild beasts; but there are many caves 
 in Germany and England which have certainly been so in- 
 habited, especially by the extinct hysena and bear. 
 
 A fine example of a hyaena's den was afibrded by the cave 
 of Kirkdale, so well described by the late Dr. Buckland in 
 his BeliquicB JDiluviance. In that cave, above twenty -five 
 miles N.N.E. of York, the remains of about 300 hyaenas, be- 
 
158 
 
 ELEMENTS OF GEOLOGY. 
 
 longing to individuals of every age, were detected. The 
 species {Hyaena speloea) has been considered by palseontolo- 
 gists as extinct ; it was larger than the fierce Hycena crocuta 
 of South Africa, which it closely resembled, and of which it 
 is regarded by Mr. Boyd Dawkins as a variety. Dr. Buck- 
 land, after carefully examining the spot, proved that the hy- 
 £enas must have lived there ; a fact attested by the quantity 
 of their dung, which, as in the case of the living hyaena, is of 
 nearly the same composition as bone, and almost as durable. 
 In the cave were found the remains of the ox, young ele- 
 phant, hippopotamus, rhinoceros, horse, bear, wolf, hare, 
 water-rat, and several birds. All the bones have the ap- 
 pearance of having been broken and gnawed by the teeth 
 of the hyaenas; and they occur confusedly mixed in loani 
 or mud, or dispersed through a crust of stalagmite which 
 covers it. In these and many other cases it is supposed that 
 portions of herbivorous quadrupeds have been dragged into 
 caverns by beasts of prey, and have served as their food — 
 an opinion quite consistent with the known habits of the liv- 
 ing hyaena. 
 
 Australian Cave-breccias. — Ossiferous breccias are not con- 
 fined to Europe, but occur in all parts of the globe; and 
 those discovered in fissui-es and caverns in Australia corre- 
 spond closely in character with what has been called the 
 bony breccia of the Mediterranean, in which the fragments 
 of bone and rock are firmly bound together by a red ochre- 
 ous cement. 
 
 Some of these caves were examined by the late Sir T. 
 Mitchell in the Wellington Valley, about 210 miles west of 
 
 Fig. 91. 
 
 Part oflower jaw otMcuropus atlas. Owen. A yonng individnal of an extinct species. 
 a. Permanent false molar, in the alveolus. 
 
AUSTRALIAN CAVE-BRECCIAS. 
 
 159 
 
 Sidney, on the river Bell, one of the principal sources of the 
 Macquai'ie, and on the Macquarie itself. The caverns often 
 branch off in different directions through the rock, widening 
 and contracting their dimensions, and the roofs and floors 
 are covered with stalactite. The bones are often broken, but 
 do not seem to be water- worn. In some places they lie imbed- 
 ded in loose earth, but they are usually included in a breccia. 
 
 The remains belong to marsupial animals. Among the 
 most abundant are those of the kangaroo, of which there are 
 four species, while others belong to the genera Phascolomys, 
 the wombat ; Dasyurus, the ursine opossum ; Phalang'ihta, 
 the vulpine opossum ; and Hypsiprymnus, the kangaroo-rat. 
 
 In the fossils above enumerated, several species are larger 
 than the largest living ones of the same genera now known 
 in Australia. The preceding figure of the right side of a 
 lower jaw of a kangaroo {Macropus atlas, Owen) will at once 
 be seen to exceed in magnitude the corresponding ' part of 
 the largest living kangaroo, which is represented in Fig. 92. 
 
 Fig. 92. 
 
 Lower Jaw of largest living species of kangaroo. (Maeropua major.) 
 
 In both these specimens part of the substance of the jaw has 
 been broken open, so as to show the permanent false molar 
 (a, Fig. 91), concealed in the socket. From the fact of this 
 molar not having been cut, we learn that the individual was 
 young, and had not shed its first teeth. 
 
 The reader will observe that all these extinct quadrupeds 
 of Australia belong to the marsupial family, or, in other 
 words, that they are referable to the same peculiar type of 
 organization which now distinguishes the Australian mam- 
 malia from those of other parts of the globe. This fact is 
 one of many pointing to a general law deducible from the 
 fossil vertebrate and invertebrate animals of times imme- 
 diately antecedent to our own, namely, that the present geo- 
 graphical distribution of organic /ojtos dates back to a peri- 
 od anterior to the origin of existing species; in other words, 
 
IQQ ELEMENTS OF GEOLOGY. 
 
 the limitation of particular genera or families of quadrupeds, 
 moUusca, etc., to certain existing provinces of land and sea, 
 began before the larger part of the species now contempora- 
 ry with man had been introduced into the earth. 
 
 Professor Owen, in his excellent "History of British Fos- 
 sil Mammals," has called attention to this law, remarking 
 that the fossil quadrupeds of Europe and Asia differ from 
 those of Australia or South America. We do_ not find, for 
 example, in the Eui-opaeo-Asiatic province fossil kangaroos, 
 or armadillos, but the elephant, rhinoceros, horse, bear, hy- 
 sena, beaver, hare, mole, and others, which still characterize 
 the same continent. 
 
 In like manner, in the Pampas of South America the skele- 
 tons of Megatherium, Megalonyx, Glyptodon, Mylodon, Tox- 
 odon, Macrauchenia, and other extinct forms, are analogous 
 to the living sloth, armadillo, cavy, capybara, and llama. 
 Tiie fossil quadrumana, also associated with some of these 
 forms in the Brazilian caves, belong to the Platyrrhine fam- 
 ily of monkeys, now peculiar to South America. That the 
 extinct fauna of Buenos Ayres and Brazil was very modern 
 has been shown by its relation to deposits of marine shells, 
 agreeing with those now inhabiting the Atlantic. 
 
 The law of geographical relationship above alluded to, be- 
 tween the living vertebrata of every great zoological prov- 
 ince and the fossils of the period immediately antecedent, 
 even where the fossil species are extinct, is by no means con- 
 fined to the mammalia. New Zealand, when first examined 
 by Europeans, was found to contain no indigenous land quad- 
 rupeds', no kangaroos, or opossums, like Australia; but a 
 wingless bird abounded there, the smallest living represent- 
 ative of the ostrich family, called the Kiwi by the natives 
 {Apteryx). In the fossils of the Post-pliocene period in this 
 same island, there is the like absence of kangaroos, opos- 
 sums, wombats, and the rest ; but in their place a prodigious 
 number of well-preserved specimens of gigantic birds of the 
 struthious order, called by Owen Dinornis and Palapteryst, 
 which are entombed in superficial deposits. These genera 
 comprehended many species, some of whicli were four, some 
 seven, others nine, and others eleven feet in height ! It seems 
 doubtful whether any contemporary mammalia shared the 
 land with this population of gigantic feathered bipeds. 
 
 Mr. Darwin, when describing the recent and fossil mam- 
 malia of South America, has dwelt much on the wonderful 
 relationship of the extinct to the living types in that part 
 of the world, inferring from such geographical phenomena 
 that the existing species are all related to the extinct ones 
 which preceded them by a bond of common desoent. 
 
CLIMATE OF POST-PLIOCENE PERIOD. 161 
 
 . Climate of the Post-pliocene Period.— The evidence as to 
 the climate of Europe during this epoch is somewhat con- 
 flicting. The fluviatile and land-sliells are all of existing 
 species, but their geographical range has not always been 
 the same as at present. Some, for example, which then lived 
 in Britain are now only found in Norway and Finland, prob- 
 ably implying that the Post-pliocene climate of Britain was 
 colder, especially in the winter. So also the reindeer and 
 the, musk-ox {Ovibos masehatus), now inhabitants of the 
 Arctic regions, occur fossil in the valleys of the Thames and 
 Avon, and also in France and Germany, accompanied in 
 most places by the mammoth and the woolly rhinoceros. 
 At Grays in Essex, on the other hand, another species both 
 of .elephant and rhinoceros occurs, together with a hippopot- 
 amus and the Cyrena fluminalis, a shell now extinct in Eu- 
 rope but still an inhabitant of the Nile and some Asiatic 
 rivers. With it occurs the Unio littoralis, now living in the 
 Seine and Loire. In the valley of the Somme flint tools have 
 been found associated with Hippopotamus major and Oyrena 
 fluminoMs in the lower-level Post-pliocene gravels ; while in 
 the highei'-level (and moi-e ancient) gravels similar tools are 
 more abundant, and are associated with the bones of the 
 mammoth and other Post-pliocene quadrupeds indicative of 
 a colder climate. 
 
 It is possible that we may here have evidence of summer 
 and winter migrations rather than of a general change of 
 temperature. Instead of imagining that the hippopotamus 
 lived all the year round with the musk-ox and lemming, we 
 we may rather suppose that the apparently conflicting evi- 
 dence may be due to the place of our observations being 
 near the boundary line of a northern and southern fauna, 
 either of which may have advanced or receded during com- 
 paratively slight and temporary fluctuations of climate. 
 There may then have been a continuous land communication 
 between England and the North of Siberia, as well as in an op- 
 posite direction with Africa, then united to Southern Europe. 
 
 In drift at Fisherton, near Salisbury, thirty feet above the 
 river Wiley, the Greenland lemming and a new species of 
 the Ai'ctic genus Spermophilus have been found, along with 
 the mammoth, reindeer, cave-hysena, and other mammalia 
 suited to a cold climate. A flint implement was taken out 
 from beneath the bones of the mammoth. In a higher and 
 older deposit in the vicinity, flint tools like those of Amiens 
 have been discovered. Nearly all the known Post-pliocene 
 quadrupeds have now been found accompanying flint knives 
 or hatchets in such a way as to imply their coexistence with 
 
162 ELEMENTS OF GEOLOGY. 
 
 man ; and we have thus the concui-rent testimony of several 
 classes of geological facts to the vast antiquity of the human 
 race. In the first place, the disappearance of a great variety 
 of species of wild animals from every part of a wide conti- 
 nent must have required a vast period for its accomplish- 
 ment ; yet tliis took place while man existed upon the earthy 
 and was completed before that early period when the Dan- 
 ish shell-mounds were formed or the oldest of the Swiss lake- 
 dwellings constructed. Secondly, the deepening and widen- 
 ing of valleys, indicated by the position of the river gravels 
 at various heights, implies an amount of change of. which 
 that which has occurred during the historical period foi-ms a 
 scarcely perceptible part. Thirdly, the change in the course 
 of rivers which once flowed through caves now removed 
 from any line of drainage, and the formation of solid floors 
 of stalagmite, must have required a great lapse of time. 
 Lastly, ages must have been required to change the climate 
 of wide regions to such an extent as completely to alter the ge- 
 ographical distribution of many mammalia as well as land and 
 fresh-water shells. The 3000 or 4000 years of the historical 
 period does not furnish us with any appreciable measure for 
 calculating the number of centuries which would suffice for 
 such a series of changes, which are by no means of a local char- 
 acter, but have operated over a considerable part of Europe. 
 Belative Longevity of Species In the Mammalia and Testacea. 
 — I called attention in 1830* to the fact, which had not at 
 that time attracted notice, that the association in the Post- 
 pliocene deposits of shells, exclusively of living species, with 
 many extinct quadrupeds betokened a longevity of species 
 in the testacea far exceeding that in the mammalia. Subse- 
 quent researches seem to show that this greater duration of 
 the same specific forms in the class mollusca is dependent on 
 a still more general law, namely, that the lower the grade of 
 animals, or the greater the simplicity of their structure, the 
 more persistent are they in genei-al in their specific charac- 
 ters throughout vast periods of time. Not only have the in- 
 vertebrata, as shown by geological data, altered at a less rap- 
 id rate than the vertebrata, but if we take one of the classes 
 of the former, as for example the mollusca, we find those of 
 more simple structure to have varied at a slower rate than 
 those of a higher and more complex organization ; the brach- 
 iopoda, for example, more slowly than the lamellibranchiate 
 bivalves, while the latter have been more persistent than the 
 univalves, whether gasteropoda or cephalopoda. In like man- 
 ner the specific identity of the characters of the foraminifera, 
 * Principles of Geology, 1st ed., vol. lii., p. 140. 
 
TEETH or EXTINCT MAMMALIA. 
 
 163 
 
 which are among the lowest types of the invertebrata, has 
 outlasted that of the mollusca in an equally decided manner. 
 
 Teeth of Post-pliocene Mammalia. — To those who have nev- 
 er studied comparative anatomy, it may seem scarcely cred- 
 ible that a single bone taken from any part of the skeleton 
 may enable a skillful osteologist to distinguish, in many 
 cases, the genus, and sometimes the species, of quadrupeds to 
 which it belonged. Although few geologists can aspire to 
 such knowledge, which must be the result of long practice 
 and study, they will nevertheless derive great advantage 
 from learning, what is comparatively an easy task, to distin- 
 guish the principal divisions of the mammalia by the forms 
 and characters of their teeth. 
 
 The annexed figures represent the teeth of some of the 
 more common species and gehei'a found in alluvial and cav- 
 ern deposits. 
 
 Fig. 93. 
 
 Elephaa primigenius (or Mammoth) ; molar of npper jaw, right side ; oiie-thi-d of 
 
 uataral size. Post-pliocene. 
 
 u. Grinding surface. 6. Side view. 
 
 Fig. 94. 
 
 Elephas antigwus. Falconer. Pennltimate molar, one-third of natural size. 
 " Fost-pliocene and Pliocene. 
 
164 
 
 ELEMENTS OP GEOLOGY. 
 
 Fig. 95. 
 
 Elepftas merUionalU, Nesti. Peuultimato molai', one-third of uatnral size. 
 Post-pliocene and Pliocene. 
 
 Fig 9T. 
 
 Fig. 98. 
 
 Rhinoceros leptorhinua. On- Rhinoceros tichorhinus ; pe- Hippopotamtis ; from cave 
 
 vier — Rhin. Tnegarhimtti, 
 Christol; fossil from 
 fresli-waterbeds of Grays, 
 Essex (see p. 161) ; pe- 
 unltimate molar, lower 
 jaw, left side ; two-thirds 
 of nat. size. Post-plio- 
 cene audNewer pliocene. 
 
 Pig. 99. 
 
 nnllimate molar, lower 
 jaVv, left side ; two-thirda 
 of nat. size. Post-plio- 
 cene. 
 
 near Palermo; molar 
 tooth; two-thirds of nat. 
 size. Fost-plioceue. 
 
 Fig. 100. 
 
 Horse. 
 Equns cabdllm, L. (common horse) ; 
 from the shell-marl, Forfarshire ; sec- 
 ond molar, lower jaw. Recent, 
 w. Grinding surface, two-thirds nat. size. 
 b. Side view of same, half nat. size. 
 
 Deer. 
 
 Moose {Cervus alcee, L.) ; recent; molar 
 
 of upper jaw. 
 
 a. Grinding surface, h. Side view, two- 
 thirds of nat. size. 
 
TEETH OF EXTINCT MAMMALIA. 
 
 ^'K- 101- Pig. 102. 
 
 165 
 
 Ox. 
 
 Ox, common, from Bhell-mail, Forfar- 
 shire ; true molar, upper jaw ; two- 
 thirds nat. size. Kecent. 
 
 c. Grinding surface, d. Side view, 
 fangs uppermost. 
 
 Fig. 103. 
 
 Bear. 
 
 a. Canine tooth or tusk of bear (ITrsua 
 spelcBus); from cave near Li6ge, 
 &. Molar of left side, upper jaw ; 
 one-third of nat. size. - Post-plio- 
 cene. 
 
 Fig. 104. 
 
 Tiger. 
 
 e. Canine tooth of tiger (Felis tigris) ; 
 recent d. Outside view of pos- 
 , iterior molar, lower jaw; one- 
 third of nat. size. Becent. 
 
 Hyoma spelcea, Goldf. (variety of H. crocuta) ; 
 lower jaw. Kent's Hole, Torquay, Devon- 
 shire ; one-third nat. size. Post-pliocene. 
 
 v/«m> 
 
 Teeth of a new species of Arvicola, field-mouse ; from the Norwich Crag. 
 ■ Newer pliocene. 
 
 a. Grinding surface, i. Side view of the same, c Nat. size of a and t. 
 
 On comparing the grinding surfaces of the corresponding 
 molars of the three species of elephants, Figs. 93, 94, 95, it 
 will be seen that the folds of enamel are most numerous in 
 the mammoth, fewer and wider, or more open, in M antiquus y 
 and most open and fewest in E. meridionalis. It will be also 
 seen that the enamel in the molar of the Rhinoceros tioho- 
 rhinus (Fig. 97), is much thicker than in that of the Rhinoc- 
 eros Uptorhinus (Fig. 96). 
 
166 ELEMENTS OF GEOLOGY. 
 
 CHAPTER XI. 
 
 POST-PLIOCENB PEEIOD, CONTINUED. — GLACIAL CONDITIONS.* 
 
 Geographical Distribution, Form, and Characters of Glacial Drift. — Funda- 
 mental Kocks, polished, grooved, and scratched. — ^Abrading and striating 
 Action of Glaciers.— Moraines, En-atic Blocks, and "Eoches Moutonne'es." 
 — Alpine Blocks on the Jura. — Continental Ice of Greenland. — Ancient 
 Centres of the Dispersion of Erratics. — Transportation of Drift by floating 
 Icebergs. — Bed of the Sea furrowed and polished by the running aground, 
 of floating Ice-islands. 
 
 Character and Distribution of Glacial Drift. — In speaking of 
 the loose transportedmatter commonly found on the surface 
 of the land in all parts of the globe, I alluded to the excep- 
 tional character of what has been called the boulder forma- 
 tion in the temperate and Arctic latitudes of the northern 
 hemisphere. The peculiarity of its form in Europe north of 
 the 50th, and in North America north of the 40th parallel of 
 latitude, is now universally attributed to the action of ice, 
 and the difference of opinion respecting it is now chiefly re- 
 stricted to the question whether land-ice or floating icebergs 
 have played the chief part in its distribution. It is wanting 
 in the warmer and equatorial regions, and reappears when 
 we examine the lands which lie south of the 40th. and 50th 
 parallels in the southern hemisphere, as, for example, in Pata-* 
 gonia. Terra del Fuego, and New Zealand. It consists of 
 sand and clay, sometimes stratified, but often wholly devoid 
 of stratification for a depth of 50, 100, or even, a greater num- 
 ber of feet. To this unstratified form of the deposit the name 
 of till has long been applied in Scotland. It generally con- 
 tains a mixture of angular and rounded fragments of rock, 
 some of large size, having occasionally one or more of their 
 sides flattened and smoothed, or even highly polished. The 
 smoothed surfaces usually exhibit many scratches parallel to 
 each other, one set of which often crosses an older set. The 
 till is almost everywhere wholly devoid of organic remains,, 
 except those washed into it from older formations, though iri' 
 some places it contains marine shells, usually of northern or 
 
 * As to the former excess of cold, whether brought about by modifications ■ 
 in the height and distribution of the land or by altered astronomical condi-. 
 tions, see Trinciples, vol. i. (10th ed., 1867), chaps, xii. and xiii., " Vicissi- 
 tudes of Climate." 
 
CHARACTERISTICS OF GLACIAL DRIFT. J 67 
 
 Arctic species, and frequently in a fragmentary-state. The 
 bulk of the till has usually been derived from the grinding 
 down into mud of rocks in the immediate neighborhood, so 
 that it is red in a region of Red Sandstone, as in Strathmore 
 in Forfarshire ; gray or black in a district of coal and bitu- 
 minous shale, as around Edinburgh ; and white in a chalk 
 country, as in parts of Norfolk and Denmark. The stony 
 fragments dispersed irregularly through the till usually be- 
 . long, especially in mountainous countries, to rocks found in 
 some part of the same hydrographical basin ; but there are 
 regions where the whole of the boulder clay has come from 
 a distance, and huge blocks, or " erratics," as they have been 
 called, many feet in diameter, have not unfrequently travelled 
 hundreds of miles from their point of departure, or from the 
 parent rocks from which they have evidently been detached. 
 These are commonly angular, and have often one or more of 
 their sides polished and furrowed. 
 
 The rock on which the boulder formation reposes, if it con- 
 sists of granite, gneiss, mai'ble, or other hard stone, capable 
 of permanently retaining any superficial markings which may 
 have been imprinted upon it, is usually smoothed or polish- 
 ed, like the erratics above described, and exhibits parallel 
 striae and furrows having a determinate direction. This di- 
 rection, both in Europe and North America, agrees generally 
 in a marked manner with the course taken by the erratic 
 blocks in the same district. The boulder clay, when it was 
 first studied, seemed in many of its characters so singular and 
 anomalous, that geologists despaired of ever being able to 
 interpret the phenomena by reference to causes now in ac- 
 tion. In those exceptional cases where marine shells of the 
 same date as the boulder clay were found, nearly all of them 
 were recognized as living species — a fact conspiring with the 
 superficial position of the drift to, indicate a comparatively 
 modern origin. 
 
 The term " diluvium " was for a time the most' popular 
 name of the boulder formation, because it was referred by 
 many to the deluge of Noah, while others retained the name 
 as expressive of their opinion that a. series of diluvial waves 
 raised by hurricanes and storms, or by earthquakes, or by* the 
 sudden upheaval of land from the bed of the sea, had swept 
 over the continents, carrying with them vast masses of mud 
 and heavy stones, and forcing these stones over rocky sur- 
 faces so as to polish and imprint upon them long furrows and 
 striae. But geologists were not long in seeing that the boul- 
 der formation was characteristic of high latitudes, and that 
 on the whole the size and number of erratic blocks increases 
 
168 
 
 ELEMENTS OF GEOLOGY. 
 
 as we travel towards the Arctic regions. They could tiot; 
 fail to be struck with the contrast which the countries bor- 
 dering the Baltic presented when compared with those sur- 
 rounding the Mediterranean. The multitude of travelled 
 blocks and striated rocks in the one region, and the absence 
 of such appearances in the other, were too obvious to be over- 
 looked. Even the great development of the boulder forma- 
 tion, with large erratics so far south as thie Alps, offered an 
 exception to the general rule favorable to the hypothesis 
 that there was some intimate connection between it and ac- 
 cumulations of snow and ice. 
 
 Transporting and abrading Power of Glaciers. — I have de- 
 scribed elsewhere ("Principles," vol. i., chap, xvi., 1867) the 
 manner in which the snow of the Alpine heights is prevent- 
 ed from accumulating indefinitely in thickness by the con- 
 stant descent of a large portion of it by gravitation. ' Be- 
 coming converted into ice it forms what are termed glaciers, 
 which glide down the principal valleys. On their surface 
 are seen mounds of rubbish or large heaps of sand and mud, 
 
 Fig. 106. 
 
 Limestone, polished, fuvrowecl, and scratched by the glacier of Bosenlan In 
 Switzerland. (Agassiz.) 
 
 a a. White streaks or scratches, cansed by small grains of flint frozen into the ica 
 6 6, Furrows. 
 
 with angular fragments of rock which fall from the steep 
 slopes or precipices bounding the glaciers. When a glacier, 
 
ALPINE BLOCKS ON THE JURA. 169 
 
 thus laden, descends so far as to reach a region about 3500 
 feet above the level of the sea, the warnath of the air is such 
 that it melts rapidly in summer, and all the mud, sand, and 
 pieces of rock are slowly deposited at its lower end, forming 
 a confused heap of unstratified rubbish called a moraine, and 
 resembling the till before described (p. 166). 
 
 Besides the blocks thus carried down on the top of the 
 glacier, many fall through fissures in the ice to the bottom, 
 where some of them become firmly frozen into the mass, and 
 are pushed along the base of the glacier, abrading, polishing, 
 and grooving the rocky floor below, as a diamond cuts glassj 
 or as emery -powder polishes steel. The striae which are 
 made, and the deep grooves which are scooped out by this 
 action, are rectilinear and parallel to an extent never seen 
 in those produced on loose stones or rocks, where shingle is 
 hurried along by a torrent, or by the waves on a sea-beach. 
 In addition to these polished, striated, and grooved surfaces 
 of rock, another mark of the former action of a glacier is 
 the " roche moutonnee." Projecting eminences of rock so 
 called have been smoothed and worn into the shape of flat- 
 tened domes by the glacier as it passed over them. They 
 have been traced in the Alps to great heights above the pres- 
 ent glaciers, and to great horizontal distances beyond them. 
 
 Alpine Blocks on the Jura. — The moraines, erratics, pol- 
 ished surfaces, domes, and striae, above described, are ob- 
 served in the great valley of Switzerland, fifty miles broad ; 
 and almost everywhere on the Jura, a chain which lies to 
 the north of this valley. The average height of the Jura is 
 about one-third that of the Alps, and it is now entirely des- 
 titute of glaciers; yet it presents almost everywhere similar 
 moraines, and the same polished and grooved surfaces. The 
 erratics, moreover, which cover it, present a phenomenon 
 which has astonished and perplexed the geologist for more 
 than half a century. No conclusion can be more incontest- 
 able than that these angular blocks of granite, gneiss, and 
 other crystalline formations came from the Alps, and that 
 they have been brought for a distance of fifty miles and up- 
 ward across one of the widest and deepest valleys, in the 
 world ; so that they are now lodged on a chain composed 
 of limestone and other formations, altogether distinct from 
 those of the Alps. Their great size and angularity, after a 
 journey of so many leagues, has justly excited wonder; for 
 hundreds of them are as large as cottages; and one in par- 
 ticular, composed of gneiss, celebrated under the name of 
 Pierre h, Bot, rests on the side of a hill about 900 feet above 
 the lake of Neufchatel, and is no less than 40 feet in diameter. 
 
 8' 
 
1^70 ELEMENTS OF GEOLOGY. 
 
 In the year 1821, M; Venetz first announced his opinion 
 that the Alpine glaciers must formerly have extended far 
 beyond their present limits, and the proofs appealed to by 
 him in confirmation of this doctrine were acknowledged by 
 all subsequent observers, and greatly strengthened by new 
 observations and arguments. M. Charpentier supposed that 
 when the glaciers extended continuously from the Alps to 
 the Jura, the former mountains were 2000 or 3000 feet high- 
 er than at present. Other writers, on the contrary, conjec- 
 tured that the' whole country had been submerged, and the 
 moraines and erratic blocks transported on floating icebergs ; 
 but a careful study of the distribution of the travelled mass- 
 es, and the total absence of marine shells from the old gla- 
 cial drift of Switzerland, have entirely disproved this last 
 hypothesis. In addition to the many evidences of the ac- 
 tion of ice in the northern parts of Europe which we have 
 already mentioned, there occur here and there in some of 
 these countries, what are wanting in Switzerland, deposits 
 of marine fossil shells, which exhibit so arctic a character 
 that they must have led the geologist to infer tlie former 
 prevalence of a much colder climate, even had he not en- 
 countered so many accompanying signs of ice-action. The 
 same marine shells demonstrate the submergence of large 
 areas in Scandinavia and the British Isles, during the gla- 
 cial cold. 
 
 A characteristic feature of the deposits under -considera- 
 tion in all these countries is the occurrence of large erratic 
 blocks, and sometimes of moraine matter, in situations re- 
 mote from lofty mountains, and separated from the nearest 
 points where the parent rocks appear at the surface by 
 great intervening valleys, or arms of the sea. We also oft- 
 en observe strisa and furrows, as in Norway, Sweden, and 
 Scotland, which deviate from the direction which they ought 
 to follow if they had been connected with the present line 
 of drainage, and they, therefore, imply the prevalence of a 
 very distinct condition of things at the time when the cold 
 was most intense. The actual state of North Greenland 
 seems to afford the best explanation of such abnormal gla- 
 cial markings, 
 
 Greenland Continental Ice. — Greenland is a vast unex- 
 plored continent, buried under one continuous and colossal 
 mass of ice that is always moving seaward, a very small 
 part of it in an easterly direction, and all the rest westward^ 
 or towards Bafiin's Bay. All the minor ridges and Valleys 
 are levelled and concealed under a general eovering'of snow, 
 but here and there some steep mountains protrude abruptly 
 
CONTINENTAL ICE OF GREENLAND. 171 
 
 from the icy slope, and a fe-w superficial lines of stones or 
 moraines are visible at certain seasons, when no snow has 
 fallen for many months, and when evaporation, promoted by 
 the wind and sun, has caused much of the upper snow to 
 disappear. The height of this continent is unknown, but it 
 must be very great, as the most elevated lands of the out- 
 skirts, which are described as comparatively low, attain alti- 
 tudes of 4000 to 6000 feet. The icy slope gradually lowers 
 itself towards the outskirts, and then terminates abruptly in 
 a mass about 2000 feet in thickness, the great discharge of 
 ice taking place through certain large friths, which, at their 
 Upper ends,- are usually about four miles across. Down 
 these friths the ice is protruded in huge masses, several miles 
 wide, which continue their course — grating along the rocky 
 bottom like ordinary glaciers long after they have reached 
 the salt water. When at last they arrive at parts of Baffin's 
 Bay deep enough to buoy up icebergs from 1000 to 1500 
 feet in vertical thickness, broken masses of them float ofij 
 carrying with them on their surface not only fine mud and 
 sand but lai-ge stones. These fragments of rock are often 
 polished and scored on one or more sides, and as the ice 
 melts, they drop down to the bottom of the sea, where large 
 quantities of mud are deposited, and this muddy bottom is 
 inhabited by many raollusca. ^ 
 
 Although the direction of the ice-streams in Greenland 
 may coincide in the main with that which separate glaciers 
 would take if there were no more ice than there is now in the 
 Swiss Alps, yet the stiiation of the surface of the rocks on 
 an ice-clad continent would, on the whole, vary considerably 
 in its minor details from that which would be imprinted on 
 rocks constituting a region of separate glaciers. For where 
 there is a universal covering of ice there will be a genwal 
 outward movement from the higher and more central re- 
 gions towards the circumference and lower country, and this 
 movement will be, to a certain extent, independent of' the 
 minor inequalities of hill and valley, when these are Till re- 
 duced to one level by the snow. The moving ice may some- 
 times cross even at right angles deep narrow ravines, or the 
 crests of buried ridges, on which last it may afterwards seem 
 sti-ange to detect glacial sti-ise and polishing after Ihe lique- 
 faction of the snow and ice has taken place. 
 
 Rink mentions that in North Greenland powerful springs 
 of clayey water escape in winter from under the ice, where 
 it descends to " the outskirts," and where, as already stated, 
 it is often 2000 feet thick — a fact showing how much grind- 
 ing action is going on upon the surface of the subjacent 
 
172 ELEMENTS OF GEOLOGY. 
 
 rocks. I also learn from Dr. Torell that there are large 
 areas in the outskirts, now no longer covered with perma- 
 nent snow or glaciers, which exhibit on their surface un- 
 mistakable signs of ancient ice-action, so that, vast as is the 
 power now exerted by ice in Greenland, it must once have 
 operated on a still grander scale. The land, though now 
 very elevated, may perhaps have been formerly much higher. 
 It is well known that the south coast of Greenland, from lati- 
 tude 60° to about 70° IST., has for the last four centuries been 
 sinking at the rate of several feet in a century. By this 
 means a surface of rock, Avell scored and polished by ice, is 
 now slowly subsiding beneath the sea, and. is becoming 
 strewed over, as the icebergs melt, with impalpable mud 
 and smoothed and scratched stones. It is not precisely 
 known how far north this downward movement extends. 
 
 Drift carried hy Icebergs. — An account was given so long 
 ago as the year 1822, by Scoresby, of icebergs seen by him 
 in the Arctic seas drifting along in latitudes 69° and 10° N., 
 which rose above the surface from 100 to 200 feet, and some 
 of which measured a mile in circumference. Many of them 
 were loaded with beds of earth and rock, of such thickness 
 that the weight was conjectured to be from 50,000 to 100,000 
 tons. A similar transportation of rocks is known to be in 
 p?~ogress in the southern hemisphere, where boulders included 
 in ice are far more frequent than in the north. One of these 
 it'cbergs was encountered in 1839, in mid-ocean, in the ant- 
 arctic regions, many hundred miles from any known land, 
 sailing northward, with a large erratic block firmly frozen 
 into it. Many of them, carefully measured by the officers of 
 the French exploring expedition of the Astrolabe, were be- 
 tween 100 and 225 feet high above water, and from two to 
 five miles in length. Captain d'Urville ascertained one of 
 them which he saw floating in the Southern Ocean to be 13 
 miles long and 100 feet high, with walls perfectly vertical. 
 The submerged portions of such islands must, according to 
 the weight of ice relatively to sea-water, be from six to eight 
 times more considerable than the part which is visible, so 
 that when they are once fairly set in motion, the mechanical 
 force which they might exert against any obstacle standing 
 in their way would be prodigious. 
 
 We learn, therefore, from a study both of the arctic and 
 antarctic regions, that a great extent of land may be. entire- 
 ly covered throughout the whole year by snow and ice, from 
 the summits of the loftiest mountains to the sea-coast, and 
 may yet send down angular erratics to the ocean. We may 
 also conclude that such land will become in the course of 
 
DISPERSION OF EKEATICS. 113 
 
 ages almost everywhere scored and polished like the rocks 
 which underlie a glacier. The discharge of ice into the sur- 
 rounding sea will take place principally through the main 
 valleys, although these are hidden from our sight. Erratic 
 blocks and moraine matter will be dispersed somewhat irreg- 
 ularly after reaching the sea, for not only will prevailing 
 winds and marine currents govern the distribution of the 
 drift, but the shape of the submerged area will have its influ- 
 ence ; inasmuch as floating ice, laden with stones, will pass 
 freely through deep water, while it will run aground where 
 there are reefs and shallows. Some icebergs in Baffin's Bay 
 have been seen stranded on a bottom 1000 or even 1500 feet 
 deep. In the course of ages such a sea-bed may become 
 densely covered with .transported matter, from which some 
 of the adjoining greater depths may be free. If, as in "West 
 Greenland, the land is slowly sinking, a large extent of the 
 bottom of the ocean will consist of rock polished and striated 
 by land-ice, and then overspread by mud and boulders de- 
 tached from melting bergs. 
 
 The mud, sand, and boulders thus let fall in still water 
 must be exactly like the moraines of terrestrial glaciers, de- 
 void of stratification and organic remains. But occasional- 
 ly, on the outer side of such packs of stranded bergs, the 
 waves and currents may cause the detached earthy and stony 
 materials to be sorted according to size and weight before 
 they reach the bottom, and to acquire a stratified arrange- 
 ment. 
 
 I have already alluded (p. 1V2) to the large quantity of 
 ice, containing great blocks of stone, which is sometimes seen 
 floating far from land, in the southern or Antarctic seas. 
 After the emergence, therefore, of such a submarine area, 
 the superficial detritus will have no necessary relation to the 
 hills, valleys, and river-plains over which it will be scattered. 
 Many a water-shed may intervene between the starting-point 
 of each erratic or pebble and its final resting-place, and the 
 only means of discovering the country from which it took 
 its departure will consist in a careful comparison of its min- 
 eral or fossil contents with those of the parent rocks. 
 
174 ELEMENTS OF GEOLOGY. 
 
 CHAPTER Xn. 
 
 POST-PLIOCENE PERIOD, CONTINUED. — GLACIAL CONDITIONS, 
 CONCLUDED. 
 
 Glaciation of Scandinayia and Russia. — Glaciatioii of Scotland. — Mammoth 
 in Scotch Till. — Marine Shells in Scotch Glacial Drift.— Their Arctic Char- 
 acter. — Rarity of Organic Remains in Glacial Deposits. — Contorted Strata 
 in "Drift. —Glaciation of Wales, England, and Ireland. — Marine Shells of 
 Moel Tryfaen. — Erratics near Chichester. — Glacial Formations of North 
 America. — Many Species of Testacea and Quadrupeds survived the Glacial 
 Cold. — Connection of the Predominance of Lakes with Glacial Action. — 
 Action of Ice in preventing the silting up of Lake-basins. — Absence of 
 Lakes in the Caucasus. — Equatorial Lakes of Africa. 
 
 Glaciation of Scandinavia and Eussia. — lu large tracts of 
 Norway and Sweden, where there have been no glaciers in 
 historical times, the signs of ice-action have been traced as 
 high as 6000 feet above the level of the sea. These signs 
 consist chieily of polished and furrowed rock-surfaces, of 
 moraines and erratic blocks. The direction of the erratics, 
 like- that of the furrows, has usually been conformable to the 
 course of the principal valleys ; but the lines of both some- 
 times radiate outward in all directions from the highest 
 land, in a manner which is only explicable by the hypothesis 
 above alluded to of a general envelope of continental ice, 
 like that of Greenland (p. 1 VO). Some of the far-transported 
 blocks have been carried from the central parts of Scandina- 
 via towards the Polar regions ; others southward to Den- 
 mark ; some south-westward, to the coast of Norfolk in Eng- 
 land ; others south-eastward, to Germany, Poland, and Rus- 
 sia. 
 
 In the immediate neighborhood of TJpsala, in Sweden, I 
 had observed, in 1834, a ridge of stratified sand and gravel, 
 in the midst of which occurs a layer of marl, evidently form- 
 ed originally at the bottom of the Baltic, by the slow growth 
 of the mussel, cockle, and other marine shells of living spe- 
 cies, intermixed with some proper to fresh water. The ma- 
 rine shells are all of dwarfish size, like those now inhabiting 
 the brackish waters of the Baltic; and the marl, in which 
 many of them are imbedded, is now raised more than 100 
 feet above the level of the Gulf of Bothnia. Upon the top of 
 this ridge repose several huge erratics, consisting of gneiss for 
 the vr%t part unrounded, from nine to sixteen feet in diame- 
 
GLACIATION OF SCOTLAJJD, 1^5 
 
 tei-, and which must have been brought into their present po- 
 sition since the time when the neighboring gulf was already 
 characterized by its peculiar fauna. Here, therefore, we have 
 proof that the transport of erratics continued to take place, 
 not merely when the sea was inhabited by the existing tes- 
 tacea, but when the north of Europe had already assumed 
 that remarkable feature of its physical geography which 
 • separates the Baltic from the North Sea, and causes the Gulf 
 of Bothnia to have only one-fourth of the aaltness belonging 
 to the_ ocean. In Denmark, also, recent shells have been 
 found in stratified beds, closely associated with the boulder 
 clay. 
 
 Gladation of Scotland. — Mr. T. F. Jamieson, in 1858, ad- 
 duced a great body of facts to prove that the Grampians 
 once sent down glaciers from the central regions in all di- 
 rections towards the sea. "The glacial grooves," he ob- 
 served, " radiate outward from the central heights towards 
 all points of the compass, although they do not always strict- 
 ly conform to the actual shape and contour of the minor val- 
 leys and ridges." 
 
 These facts and other chai-acteristics of the Scotch drift 
 lead us to the inference that when the glacial cold first set 
 in, Scotland stood higher above the sea than at present, and 
 was covered for the most part with snow and ice, as Green- 
 land is now. This sheet of land-ice sliding down to lower 
 levels, ground down and polished the subjacent rocks, sweep- 
 ing off- nearly all superficial deposits of older date, and leav- 
 ing only till and boulders in their place. To this continent- 
 al state succeeded a period of depression and partial sub- 
 mergence. The sea advanced over the lower lands, and Scot- 
 land was converted into an archipelago, some marine sand 
 with shells being spread over the bottom of the sea. On this 
 sand a great mass of boulder clay usually quite devoid of 
 fossils was accumulated. Lastly, the land re-emerged from 
 the water, and, reaching a level somewhat above its present 
 height, became connected with the continent of Europe, gla- 
 ciers being formed once more in the higher regions, though 
 the ice probably never regained its former extension.* Af- 
 ter all these changes, there were some minor oscillations in 
 the level of the land, on which, although they have had im- 
 portant geographical consequences, separating Ireland from 
 England, for example, and England from the Continent, we 
 need not here enlarge. 
 
 Mammoth in Scotch TiU, — Almost all remains of the ter- 
 restrial fauna of the Continent which preceded the period of 
 * Jamieson, Quart. Geol. Journ., 1860, vol. xvi., p. 370. 
 
176 
 
 ELEMENTS OF GEOLOGY. 
 
 submergence have been lost ; but a few patches of estuarine 
 and fresh-water formations escaped denudation by submer- 
 gence. To these belong the peaty clay from which several 
 mammoths' tusks and horns of reindeer were obtained at Kil- 
 maurs, in Ayrshire, as long ago as 1816. Mr. Bryce in 1865 
 ascertained that the fresh-water formation containing these 
 fossils rests on carboniferous sandstone, and is covered, first 
 by a bed of marine sand with arctic shells, and then with a 
 great mass of till with glaciated boulders.* Still more re- 
 cent explorations in the neighborhood of Kilmaurs have 
 shown that the fresh-water formation contains the seed of 
 the pond-weed Potamogeton and the aquatic Ranunculus; 
 and Mr. Young of the Glasgow Museum washed the mud ad- 
 hering to the reindeer horns of Kilmaurs and that which fill- 
 ed the cracks of the associated elephants' tusks, and detect- 
 ed in these fossils (which had been in the Glasgow Museum 
 for half a century) abundance of the same seeds. 
 
 All doubts, therefore, as to the true position of the remains 
 of the mammoth, a fossil so rare in Scotland, have been set 
 at rest, and it serves to prove that part of the ancient conti- 
 nent sank beneath the sea at a period of great cold, as the 
 shells of the overlying sand attest. The incumbent till or 
 boulder clay is about 40 feet thick, but it often attains much 
 greater thickness in the same part of Scotland. 
 
 Fig. lOT. 
 
 Fig. 108. 
 
 Fig. 109. 
 
 AstarU borealiSf Cliem. ; {A. 
 arctica, Moll.; A. com- 
 presm^ Mont.) 
 
 Fig. 110. 
 
 Leda lanceokda (06- 
 longa). Sow. 
 
 Kg. 111. 
 
 Saaicava ruf/osa, 
 Penn. 
 
 Fig. 112. 
 
 Pecten islamiicns, Natica clausa, Trophon clathra- 
 
 Moll. Bred. tvm, Liiin^. 
 
 Northern ehells common in the drift of the Clyde, in Scotland. 
 
 Marine Shells of Scotch Drift— The greatest height to 
 which marine shells have yet been traced in this boulder 
 * Bryce, Quart. Geol. Joum., vol. xxi., p. 217. 1865. 
 
MARINE SHELLS OE SCOTCH DEIET. 
 
 Ill 
 
 clay is at Airdrie, in Lanarkshire, ten miles east of Glasgow, 
 524 feet above the level of the sea. At that spot they were 
 found imbedded in stratified clays with till above and below 
 them. There appears no doubt that the overlying deposit 
 was true glacial till, as some boulders of granite were ob- 
 served in it, which must have come from distances of sixty 
 miles at the least. 
 
 The shells above figured are only a few out of a large 
 assemblage of living species, which, taken as a whole, bear 
 testimony to conditions far more arctic than those now pre- 
 vailing in the Scottish seas. But a group of marine shells, 
 indicating a still greater excess of cold, has been brought to 
 light since 1860 by the Rev. Thomas Brown, from glacial 
 drift or clay on the borders of the estuaries of the Forth 
 and Tay. This clay occurs at Elie, in Fife, and at Errol, in 
 
 Fig. 113. 
 
 Fig. 114. 
 
 Leda truncata. 
 
 a. Exterior of left valve. 6. Interior 
 of same. 
 
 Tdlina calcarea^ Cliem. {Tdlina proximal 
 Brown.) 
 
 «. Outside of left valve, b. Interior 
 of same. 
 
 Perthshire ; and has already aflForded about 35 shells, all of 
 living species, and now inhabitants of arctic regions, such as 
 Zieda truncata, Tellina proxima (see Figs. 113, 114), Pecten 
 Choenlandiem, Crenella Imvigata, CreneUa nigra, and others, 
 some of them first brought by Captain Sir E. Parry from 
 the coast of Melville Island, latitude 76° N. These were all 
 identified in 1863 by Dr. Torell, who had just returned from 
 a survey of the seas around Spitzbergen, where he had col- 
 lected no less than 150 species of mollusea, living chiefly on 
 a bottom of fine mud derived from the moraines of melting 
 glaciers which there protrude into the sea. He informed 
 me that the fossil fauna of this Scotch glacial deposit exhib- 
 its not only the species but also the peculiar varieties of 
 mollusea now characteristic of very high latitudes. Their 
 large size implies that they formerly enjoyed a colder, oi-, 
 what was to them a more genial climate, than that now pre- 
 vailing in the latitude where the fossils occur. Marine shells 
 have also been found in the glacial drift of Caithness and 
 Aberdeenshire at heights of 250 feet, and in Banff of 350 
 feet, and stratified drift continuous with the above ascends 
 to heights of 500 feet. Already 75 species are enumerated 
 
1>J8 ELEMENTS OF GEOLOGY. 
 
 from Caithness, and the same number from Aberdeenshire 
 and Banff, and in both cases all but six are arctic species. 
 
 I formerly suggested that the absence of all signs of or- 
 ganic life in the Scotch drift might be connected with the 
 severity of the cold, and also in some places with the depth 
 qf the sea during the period of extreme submergence ; but 
 my faith in such an hypothesis has been shaken by modern 
 investigations, an exuberance of life having been observed 
 both in arctic and antarctic seas of great depth, and where 
 floating ice abounds; The difficulty, moreover, of accounting 
 for the entire dearth of marine shells in till is removed when 
 once we have adopted the theory of this boulder clay being 
 the product of land-ice. For glaciers coming down from a 
 continental ice-sheet like that which covers Greenland may 
 fill friths many hundred feet below the sea-level, and even 
 invade parts of a bay a thousand feet deep, before they find 
 water enough to float off their terminal portions in the form 
 of icebei'gs. In such a case till without marine shells may 
 first accumulate, and then, if the climate becomes warmer 
 and the ice melts, a marine deposit may be superimposed on 
 the till without any change of level being required. 
 
 Another curious phenomenon bearing on this subject was 
 styled by the late Hugh Miller the " striated pavements " 
 of the boulder clay. Where portions of the till have been 
 removed by the sea on the shores of the Forth, or in the in- 
 terior by railway cuttings, the boulders embedded in what 
 remains of the drift are seen to have been all subjected to a 
 process of abrasion and striation, the striae and furrows be- 
 ing parallel and persistent across them all, exactly as if a 
 glacier or iceberg had passed over them and scored them 
 in a manner similar to that so often undergone by the solid 
 rocks below the glacial drift. It is possible, as Mr. Geikie 
 conjectures, that this second striation of the boulders may 
 be referable to floating ice.* 
 
 Contorted Strata in Drift.— In Scotland the till is often 
 covered with stratified gravel, sand, and clay, the beds of 
 which are sometimes horizontal and sometimes contorted for 
 a thickness of several feet. Such contortions are not uncom- 
 mon in Forfarshire, where I observed them, among other 
 places, in a vertical cutting made in 1840 near the left bank 
 of the South Esk, east of the bridge of Cortachie. The con- 
 volutions of the beds of fine and coarse sand, gravel, and 
 loam, extend through a thickness of no less than 25 feet ver- 
 tical, or from b to c, Fig. 115, the horizontal stratification 
 bemg resumed very abruptly at a short distance, as to the 
 * Geikie, Trans. Geol. Soc. Glasgow, vol. i., part ii., p. 68. 1863. 
 
Gravel and a 
 eand. i 
 
 Contorted 
 drift. 
 
 CONTORTED STRATA IN DRIFT. 
 
 Fig. 115. 
 
 179 
 
 Till. 
 
 Section of contorted drift overlying till, seen on left bank of South Esk, near 
 Cortachie, in 1S40. Height of section seen, from a to d, about 60 feet. 
 
 right of/, g. The overlying coarse gravel and sand, a, is in 
 some places horizontal, in others it exhibits cross bedding, 
 and does not partake of the disturbances which the strata b, 
 c, have undergone. The underlying till is exposed for a 
 depth of about 20 feet ; and we may infer from sections in 
 the neighborhood that it is considerably thicker. 
 
 In some cases I have seen fragments of stratified clays and 
 sands, bent iu like manner, in the middle of a great mass of 
 till. Mr. Trimmer has suggested, in explanation of such phe- 
 nomena, the intercalation in the glacial period of large irreg- 
 ular masses of snow or ice between layers of sand and grav- 
 el. Some of the cliffs near Behring's Straits, in which the 
 remains of elephants occur, consist of ice mixed with mud 
 and stones ; and Middendorf describes the occurrence in Si- 
 beria of masses of ice, found at various depths from the sur- 
 face after digging through drift. Whenever the intercala- 
 tion of snow and ice with drift, whether stratified or unstrat- 
 ified, has taken place, the melting of the ice will cause such 
 a failure of support as may give rise to flexures, and some- 
 times to the most complicated foldings. But in many cases 
 the strata may have been bent and deranged by the mechan- 
 ical pressure of an advancing glacier, or by the sideway 
 thrust of huge islands of ice running aground against sand- 
 banks ; in which case, the position of the beds forming the 
 foundation of the banks may not be at all disturbed by the 
 shock. 
 
 There a,re indeed many signs in Scotland of the action of 
 floating ice, as might have been expected where proofs of 
 submergence in the Glacial Period are not wanting. Amdng 
 these are the occurrence of large erratic blocks, frequent- 
 ly in clusters at or near the tops of hills or ridges, places 
 which may have formed islets or shallows in the sea where 
 floatuig ice would mostly ground and discharge its cargo on 
 
180 ELEMENTS OF GEOLOGY. 
 
 melting. Glaciers or land-ice would, on the contrary, chief- 
 ly discharge their cargoes at the bottom of valleys. Traces 
 of an earlier and independent glaciation have also been ob- 
 served in some regions where the striation, apparently pro- 
 duced by ice proceeding from the north-west, is not explica- 
 ble by the radiation of land-ice from a central mountainous 
 region.* 
 
 Glaciation of Wales and England. — The mountains of 
 North Wales were recognized, in 1842, by Dr. Buckland, as 
 having been an independent centre of the dispersion of errat- 
 ics — great glaciers, long since extinct, having radiated from 
 the Snowdonian heights in Carnarvonshire, through seven 
 principal valleys towards as many points of the compass, 
 carrying with them large stony fragments, and grooving the 
 subjacent rocks in as many directions. 
 
 Besides this evidence of land-glaciers, Mr. Trimmer had 
 previously, in 1831, detected the signs of a great submerg- 
 ence in Wales in the Post-pliocene period. He had observed 
 stratified drift, from which he obtained about a dozen spe- 
 cies of marine shells, near the summit of Moel Tryfaen, a hill 
 1400 feet high, on the south side of the Menai' Straits. I 
 had an opportunity of examining in the summer of 1 863, to- 
 gether with the Rev. W. S. Symonds, a long and deep cut- 
 ting made through this drift by the Alexandra Mining Com- 
 pany in search of slates. At the top of the hill above-men- 
 tioned we saw a stratified mass of incoherent sand and grav- 
 el 35 feet thick, from which no less than 54 species of mol- 
 lusca, besides three characteristic arctic varieties — in all 51 
 forms — have been obtained by Mr. Darbishire. They be- 
 long without exception to species still living in British or 
 more northern seas ; eleven of them being exclusively arctic, 
 four common to the arctic and British seas, and a large pro- 
 portion of the remainder having a northward range, or, if 
 found at all in the southern seas of Britain, being compara- 
 tively less abundant. In the lowest beds of the drift were 
 large heavy boulders of far-transported rocks, glacially pol- 
 ished and scratched on more than one side. "Underneath 
 the whole we saw the edges of vertical slates exposed to 
 view, which here, like the rocks in other parts of Wales, 
 both at greater and less elevations, exhibit beneath the drift 
 ui(equivocal marks of prolonged glaciation. The whole de- 
 posit has much the appearance of an accumulation in shal- 
 low water or on a beach, and it probably acquired its thick- 
 ness during the gradual subsidence of the coast— an hypoth- 
 esis which would require us to ascribe to it a high antiquity, 
 * Milne Home, Trans. Eoyal Soc. Edinburgh, vol. xxv., 1868-9. 
 
ERRATICS NEAR CHICHESTER. 181 
 
 since we must allow time, first for its sinking, and then for 
 its re-elevation. 
 
 The height reached by these fossil shells on Moel Tryfaen 
 is no less than 1300 feet — a most important fact when we 
 consider how very few instances we have on record beyond 
 the limits of Wales, whether in Europe or North America, 
 of marine shells having been found in glacial drift at half 
 the height above indicated. A marine molluscous fauna, 
 however, agreeing in character with that of Moel Tryfaen, 
 and comprising as many species, has been found in drift at 
 Macclesfield and other places in central England, sometimes 
 reaching an elevation of 1200 feet. 
 
 Professor Ramsay* estimated the probable amount of sub- 
 mergence during some part of the glacial period at about 
 2300 feet ; for he was unable to distinguish the supei-ficial 
 sands and gravel which reached that high elevation from 
 the drift which, at Moel Tryfaen and at lower points, con- 
 tains shells of living species. The evidence of the marine 
 origin of the highest drift is no doubt inconclusive in the 
 absence of shells, so great is the resemblance of the gravel 
 and sand of a sea beach and of a river's bed, when organic 
 remains are wanting ; but, on the other hand, when we con- 
 sider the general rarity of shells in drift which we know to 
 be of marine origin, we can not suppose that, in the shelly 
 sands of Moel Tryfaen, we have hit upon the exact upper- 
 most limit of marine deposition, or, in other words, a precise 
 measure of the submergence of the land beneath the sea 
 during the glacial period. 
 
 We are gradually obtaining proofs of the larger part of 
 England, north of a line drawn from the mouth of the Thames 
 to the Bristol Channel, having been under the sea and trav- 
 ersed by floating ice since the commencement of the glacial 
 epoch. Among recent observations illustrative of this point, 
 I may allude to the discovery, by Mr. J. F. Bateman, near 
 Blackpool, in Lancashire, fifty miles from the sea, and at the 
 height of 568 feet above its level, of till containing rounded 
 and angular stones and marine shells, such as Turritdla com- 
 munis, Purpura lapiUus, Cardium edule, and others, among 
 which Trophon clathratvm {=Fumjis Bamffius), though still 
 surviving in North British seas, indicates a cold climate. 
 
 Erratics near Chichester. — The most southern memorials 
 of ice-action and of a Post-pliocene fauna in Great Britain is 
 on the coast of the county of Sussex, about 25 miles west of 
 Brighton, and 15 south of Chichester. A marine deposit ex- 
 posed between high and low tide occurs on both sides of the 
 * Quart. Geol. Joum., 1852, Tol. viii., p. 372. 
 
182 ELEMENTS OE GEOLOGY. 
 
 promontory called Selsea Bill, in which Mr. Godwin-Austen 
 found thirty-eight species of shells, and the number has since 
 been raised-to seventy. 
 
 This assemblage is interesting because on the whole, while 
 all the species are recent, they have a somewhat more southr 
 em aspect than those of the present British Channel. It is 
 true that about forty of them range from British to high 
 northern. latitudes ; but several of them, as, for example, Lu- 
 traria rugosa and Pecten polymorphns, which are abundant, 
 are not known at present to range farther north than the 
 coast of Portugal, and seem to indicate a warmer tempera- 
 ture than now prevails on the coast where we find them fos- 
 sil. What renders this curious is the fact that the sandy 
 loam in which they occur is overlaid by yellow clayey gravel 
 with large erratic blocks which must have been drifted into 
 their present position by ice when the climate had become 
 much colder. These transported fragments of granite, syen- 
 ite, and greenstone, as well as of Devonian and Silurian rocks, 
 may have come from the coast of Normandy and Brittany^ 
 and are many of them of such large size that we must sup- 
 pose them to have been drifted into their present site by 
 coast-ice. I measured one of granite, at Pagham, 21 feet in 
 circumference. In the gravel of this drift with erratics are 
 a few littoral shells of living species, indicating an ancient 
 coast-line. 
 
 Glacial Formations in North America. — In the western 
 hemisphere, both in Canada and as far south as the 40th 
 and even 38th parallel of latitude in the United States^ we 
 meet with a repetition of all the peculiarities which distin- 
 guish the European boulder formation. Fragments of rock 
 have travelled for great distances, especially from north to 
 south : the surface of the subjacent rock is smoothed, striar 
 ted, and fluted; unstratified mud or till containing boulders 
 is associated with strata of loam, sand, and clay, usually de- 
 void of fossils. Where shells ai-e present, they are of spe- 
 cies still living in northern seas, and not a few of them iden- 
 tical with those belonging to European drift, including most 
 of those already figured, p. 176. The fauna also of the gla- 
 cial epoch in North America is less rich in species than that 
 now inhabiting the adjacent sea, whether in the Gulf of St. 
 Lawrence, or off the shores of Maine, or in the Bay of Mas- 
 sachusetts. 
 
 The extension on the American continent of the range of 
 erratics during the Post-pliocene period to lower latitudes 
 than they reached in Europe, agrees well with the present 
 southward deflection of the isothermal lines, or rather the 
 
GLACIAL FORMATIONS IN NORTH AMERICA. 183 
 
 lines of equal winter temperature. It seems that formerly, 
 as now, a more extreme climate and a more abundant sup- 
 ply of ice prevailed on the western side of the Atlantic. An- 
 other resemblance between the distribution of the drift fos- 
 sils in Europe and North America has yet to be pointed out. 
 In Canada and the United States, as in Europe, the marine 
 shells are generally confined to very moderate elevations 
 above the sea (between 100 and 100 feet), while the erratic 
 blocks and the grooved and polished surfaces of rock extend 
 tQ elevations of several thousand feet. 
 
 I have already mentioned that in Europe several quadru- 
 peds of living, as well as extinct, species were common to 
 pre-glacial and post-glacial times. In like manner there is 
 reason to suppose that in North America much of the an- 
 cient mammalian fauna, together with nearly all the inverte^ 
 brata, lived through the ages of intense cold. That in the 
 United States the Mastodon giganteus was very abundant 
 after the drift period, is evident from the fact that entire 
 skeletons of this animal are met with in bogs and lacustrine 
 deposits occupying hollows in the glacial drift. They some- 
 times occur in the bottom even of small ponds recently 
 drained by the agriculturist for the sake of the shell-marl. 
 In 1845 no less than six skeletons of the same species of 
 Mastodon were found in Warren couijty. New Jersey, six 
 feet below the surface, by a farmer who was digging out the 
 rich mud from a small pond which he had drained. Five 
 of these skeletons were lying together, and a large part of 
 the bones crumbled to pieces as soon as they were exposed 
 to the air. 
 
 It would be rash, however, to infer from such data that 
 these quadrupeds were mired in, modem times, unless we 
 use that term strictly in a, geological sense. I have shown 
 that there is a fluyiatile deposit in the valley of the Niagara, 
 containing shells of the genera Mdania, Lymiiea, Planorbis, 
 Valvata, Cyelaz, Vhio, Helix, etc., all of recent species, from 
 which the bones of the great Mastodon have been taken in 
 a very perfect state. Yet the whole excavation of the ra- 
 vine, for many miles below the Falls, has been slowly effect- 
 ed since that fluviatile deposit was thrown down. Other 
 extinct animals accompany the Mastodon giganteus in the 
 post-glacial deposits of the United States, and this, taken 
 with the fact that so few of the mollusca, even of the com- 
 mencement of the cold period, differ from species now living, 
 is important, as refuting the hypothesis, for which some have 
 contended, that the intensity of the glacial cold annihilated, 
 all the species in temperate and arctic latitudes. 
 
184 ELEMENTS OF GEOLOGY. 
 
 Connection of the Predominance of Lakes with Glacial Ac- 
 tion.— It was first pointed out by Professor Ramsay m 1862, 
 that lakes are exceedingly numerous in those countiies where 
 erratics, striated blocks, and other signs of ice-action abound; 
 and that they are comparatively rare in tropical and sub- 
 tropical regions. Generally in countries where the winter 
 cold is intense, such as Canada, Scandinavia, and Finland, 
 even the plains and lowlands are thickly strewn with innu- 
 merable ponds and small lakes, together with some others 
 of a larger size ; while in more temperate regions, such as 
 Great Britain, Central and Southern Europe, the United 
 States, and New Zealand, lake districts occur in all such 
 mountainous tracts as can be proved to have been glaciated 
 in times comparatively modern or since the geographical 
 configuration of the surface bore a considerable resemblance 
 to that now prevailing. In the same countries, beyond the 
 glaciated regions, lakes abruptly cease, and in warmer and 
 tropical countries are either entirely absent, or consist, as 
 in equatorial Africa, of large sheets of water unaccom- 
 panied so far as we yet know by numerous smaller ponds 
 and tarns. 
 
 The southern limits of the lake districts of the Northern 
 Hemisphere are found at about 40° N. latitude on the Amer- 
 ican continent, and about 50° in Europe, or where the Alps 
 intervene four degrees farther south. A large proportion of 
 the smaller lakes are dammed up by barriers of unstratified 
 drift, having the exact character of the moraines of glaciers, 
 and are termed by geologists " morainic," but some of them 
 are true rock-basins, and would hold water even if all the 
 loose drift now resting on their margins were removed. 
 
 In a paper read before the Geological Society of London in 
 1862, Professor Ramsay maintained that the first formation 
 of most existing lakes took place during the glacial epoch, 
 and was due, not to elevation or subsidence, but to actual 
 erosion of their basins by glaciers. M. Mortillet in the same 
 year advanced the theory that after the Alpine lake-basins 
 had been filled up with loose fluviatile deposits, they were 
 re-excavated by the great glaciers which passed down the 
 valleys at the time of the greatest cold, a doctrine which 
 would attribute to moving ice almost as great a capacity of 
 erosion as that which assumed that the original basins were 
 scooped out of solid rock by glaciers. It is impossible to 
 deny that the mere geographical distribution of lakes points 
 to the intimate connection of their origin with the abun- 
 dance of ice during a former excess of cold, but how far the 
 erosive action of moving ice has been the sole or even the 
 
LAKES CONNECTED WITH GLACIAL ACTION. 185 
 
 principal cause of lake-basins, is a question still open to dis- 
 cussion. 
 
 The lakes of Switzerland and the noi-th of Italy are some 
 of them twenty and thirty miles in length, and so deep that 
 their bottoms are in some cases from 1000 to 2000 feet be- 
 neath the level of the sea. It is admitted on all hands that 
 they were once filled with ice, and as the existing glaciers 
 polish and grind down, as before stated, the surface of the 
 rocks, we are prepared to find that every lake-basin in coun- 
 tries once covered by ice should bear the marks of super- 
 ficial glaciation, and also that the ice during its advance and 
 retreat should have left behind it much transported matter 
 as well as some evidence of its having enlarged the pre-ex- 
 isting cavity. But much more than this is demanded by the 
 advocates of glacial erosion. They suggest that as the old 
 extinct glaciers were several thousand feet thick, they were 
 able in some places gradually to scoop out of the solid rock 
 cavities twenty or thirty miles in length, and as in the case 
 of Lago Maggiore from a thousand to two thousand six hun- 
 dred feet below the previous level of the river-channel, and 
 also that the ice had the power to remove from the cavity 
 formed by its grinding action all the materials of the miss- 
 ing rocks. A constant supply, it is argued, of fine mud is- 
 sues from the termination of every glacier in the stream 
 which is produced by the melting of the ice, and this result 
 of friction is exhibited both during winter and summer, af- 
 fording evidence of the continual deepening and widening of 
 the valleys through which glaciers pass. As the fine mud is 
 carried away by a river from the deep pool which is formed 
 from the base of every cataract, so it seems to be imagined 
 that lake-basins may be gradually emptied of the mud form- 
 eel by abrasion during the glacial period. 
 
 I am by no means disposed to object to this theory on the 
 ground of the insufficiency of the time during which the ex- 
 treme cold endured, but we must carefully consider whether 
 that same time is not so vast as to make it probable that 
 other forces, besides the motion of glaciers, must have co- 
 operated in converting some parts of the ancient valley 
 courses into lake-basins. They who have formed the most 
 exalted conceptions of the erosive energy of moving ice do 
 not deny that during the period termed " Glacial " there have 
 been movements of the earth's crust sufiicieut to produce os- 
 cillations of level in Europe amounting to 1000 feet or more 
 in both directions. M. Charpentier, indeed, attributed some 
 of the principal changes of climate in Switzerland, during the 
 glacial period, to a depression of the central Alps to the ex- 
 
186 ELEMENTS OF GEOLOGY. 
 
 tent of 3000 feet, and Swiss geologists have long been accus 
 tomed to attribute their lake basins, in part, to those con- 
 vulsions by which the shape and course of the valleys may 
 have been modified. Our experience, in the lifetime of the 
 present generation, of the changes of level witnessed in New 
 Zealand during great earthquakes is entirely opposed to the 
 notion that the movements,, whether, up ward or downward, 
 are uniform in amount or direction throughout areas of indefi- 
 nite extent. On the contrary, the land has been permanently 
 raised in one region several feet or yards, and the rise has been 
 found gradually to die out, so as to be imperceptible at a disT 
 tance of. twenty miles, and in some areas is even exchanged 
 for a simultaneous downward movement of several feet. 
 
 But, it is asked, if such inequality of movement can have 
 contributed towards the production of lake basins, does it 
 not leave unexplained the comparative rarity of lakes in tropr 
 ical and subtropical countries. . In reply to this question it 
 may be observed that in our endeavor to estimate the efiects 
 of subterranean movements in modifying the superficial ge- 
 ography of a country we must remember that each convul- 
 sion effects a very slight change. If.it interferes with the 
 drainage, whether by raising the lower or sinking the high- 
 er portion of a hydrographical basin, the upheaval or de- 
 pression will only amount to a few feet at a time, and there 
 may be an interval of years or centuries before any further 
 movement takes place in the same region. In the mean 
 time an incipient lake if produced may be filled up with 
 sediment, and the recently-formed barrier will then be cut 
 through by the river, whereas in a country where glacial 
 conditions prevail no such obliteration of the tempoi-ary lake- 
 basin would take place ; for however deep it- became by re- 
 peated sinking of the upjjer or rising of the lower extremity, 
 being always filled with ice it might remain, throughout the 
 greater part of its extent, free from sediment or drifl until 
 the ice melted at the close of the glacial period. 
 
 One of the most serious objections to the exclusive origin 
 by ice-erosion of wide and deep lake-basins arises from their 
 capricious distribution, as for example in Piedmont, both to 
 the eastward and westward of Turin, where great lakes are 
 wanting,* although some of the largest extinct glaciers de- 
 scending from Mont Blanc and Monte Rosa came down from 
 the Alps, leaving their gigantic moraines in the low country. 
 Here, therefore, we might have expected to find lakes of the 
 first magnitude rivalling the contiguous Lago Maggiore in 
 importance. 
 
 * Antiquity of Man, p. 313. 
 
LAKES CONNECTED WITH GLACIAL ACTION. 187 
 
 A still more stiiking illustration of the same absence of 
 lakes where large glaciers abound is afforded by the Cauca- 
 sus, a chain more than 300 miles long, and the loftiest peaks of 
 which attainheights from 16,000 to 18,000 feet. This great- 
 est altitude is reached by Elbruz, a mountain in lat. 43° N. 
 three degrees south of Mont Blanc, but on the other hand 
 3000 feet higher. The present Caucasian glaciers are equal 
 or superior in dimensions to those of Switzerland, and like 
 them give rise occasionally to temporary lakes by obstruct- 
 ing the course of rivers, and causing great floods when the 
 icy barriers give way. Mr. Freshfield, a careful observer, 
 writing in 1869, says:* "A total absence of lakes on both 
 sides of the chains is the most marked feature. Not only 
 are there no gi-eat subalpine sheets of water, like Como or 
 Geneva, but mountain tarns, such as the Dauben See on the 
 Gemmi, or the Klonthal See near Glarus, are equally want- 
 ing." The same author states on the authority of the emi- 
 nent Swiss geologist, Mons. E. Favre, who also explored the 
 Caucasus in 1868, that moraines of great height and huge er- 
 ratics of gi-anite and other rocks " justify the assertion that 
 the present glaciers of the Caucasus, like those of the Alps, 
 are only the shadows of their former selves." 
 
 It seems safe to assume that the chain of lakes, of which 
 the Albert Nyanza forms one in equatorial Africa, was due 
 to causes other than glacial. Yet if we could imagine a 
 glacial period to visit that region filling the lakes with ice 
 and scoring the rocks which form their sides and bottoms, 
 we should be unable to decide how much the capacity of the 
 basins had been enlarged and the surface modified by glacial 
 erosion. The same may be true of the Lago Maggiore and 
 Lake Superior, although the present basins of both of them 
 afford abundant superficial markings due to ice-action. 
 
 But to whatever combination of causes we attribute the 
 great Alpine lakes one thing is clear, namely, that they are, 
 geologically speaking, of modern origin. Every one must 
 admit that the upper valley of the Rhone has been chiefly 
 caused by fluviatile denudation, and it is obvious that the 
 quantity of matter removed from that valley previous to the 
 glacial period would have been amply sufficient to fill up 
 with sediment the basin of the Lake of Geneva, supposing it 
 to have been in existence, even if its capacity had been many 
 times greater than it is now.f 
 
 On the whole, it appears to me, in accordance with the 
 views of Professor Ramsay, M. Mortillet, Mr. Geikie, and oth- 
 
 * Travels in Central Caucasus, 1869, p. 452. 
 t See Principles, vol. i., p. 420, 10th ed. 1867. 
 
188 ELEMENTS OF GEOLOGY. 
 
 ers, that the abrading action of ice has formed some mount- 
 ain tarns and many morainic lakes ; but when it is a question 
 of the origin of larger and deeper lakes, like those of Swit- 
 zerland or the north of Italy, or inland fresh-water seas, like 
 those of Canada, it will probably be found that ice has play- 
 ed a subordinate part in comparison with those movements 
 by which changes of level in the earth's crust ar<3 gtadually 
 brought about. 
 
BRIDLINGTON DEIFT. ]89 
 
 TERTIARY OR CAINOZOIC PERIOD. 
 
 CHAPTER XIII. 
 
 PLIOCENE PEEIOD. 
 
 Glacial Formations of Pliocene Age. — Bridlington Beds.— Glacial Drifts of 
 Ireland. — Drift of Norfolk Cliffs. — Cromer Forest-bed. — Aldeby and Chil- 
 lesford Beds. — Norwich Crag. — Older Pliocene Strata. — lied Crag of Suf- 
 folk. — Coprolitic Bed of lied Crag. — White or Coralline Crag.— Relative 
 Age, Origin, and Climate of the Crag Deposits. — Antwerp Crag. — Newer 
 Pliocene Strata of Sicily. — Newer Pliocene Strata of the Upper Val d'Ar- 
 no. — Older Pliocene of Italy. — Subapennine Strata.— Older PUocene Flora 
 of Italy. 
 
 It will be seen in the description given in the last chapter 
 of the Post-pliocene formations of the British Isles that they 
 comprise a large proportion of those commonly termed gla- 
 cial, characterized by shells which, although referable to liv- 
 ing species, usually indicate a colder climate than that now 
 belonging to the latitudes where they occur fossil. But in 
 parts of England, more especially in Yorkshire, Norfolk, and 
 Suffolk, there are superficial formations of clay with glaci- 
 ated boulders, and of sand and pebbles, containing occasion- 
 al, though rare, patches of shells, in which the marine fauna 
 begins to depart from that now inhabiting the neighboring 
 sea, and comprises some species of moUusca not yet known 
 as living, as well as extinct varieties of others, entitling us 
 to class them as Newer Pliocene, although belonging to the 
 close of that period and chronologically on the verge of the 
 later or Post-pliocene epoch. 
 
 Bridlington Drift. — To this era belongs the well-known 
 locality of Bridlington, near the mouth of the Humber, in 
 Yorkshire, where about seventy species or well-marked vari- 
 eties of shells have been found on the coast, near the sea-lev- 
 el, in a bed of sand several feet thick resting on glacial clay 
 with much chalk debris, and covered by a deposit of purple 
 clay with glaciated boulders. More than a third of the spe- 
 cies in this drift are now inhabitants of arctic regions, none 
 of them extending southward to the British seas ; which is 
 the more remarkable as Bridlington is situated in lat. 54° 
 
190 ELEMENTS OF GEOLOGY. 
 
 north. Fifteen species are British and Arctic, a very few 
 belong to those species which range south of our British 
 seas. Five species or well-marked varieties are not known 
 living, namely, the variety of Astarte borealis (called A. 
 Withami) ; A. mictabilis ; the sinistral form of Tritonium 
 carinatmn, Cardita anaUs, and Tellina obliqua, Fig. 120, p. 
 194. Mr. Searles Wood also inclines to consider Nucula 
 Cobholdice, Fig. 119, p. 194, now absent from the European 
 seas and the Atlantic, as specifically distinct from a closely- 
 allied shell now living in the seas surrounding Vancouver's 
 Island, which some conchologists regard as a variety. Tel- 
 lina obliqua also approaches very near to a shell now living 
 in Japan. 
 
 Glacial Drift of Ireland. — Marine drift containing the last- 
 mentioned Nucvla and other glacial shells reaches a height 
 of from 1000 to 1200 feet in the county of Wexford, south 
 of Dublin. More than eighty species have already been ob- 
 tained from this formation, of which two, Conovulics pyra- 
 midalis and Nassa monensis, are not known as living ; while 
 Turritella incrassata and Cyprcea lucida no longer inhabit 
 the British seas, but occur in the Mediterranean. The great 
 elevation of these shells, and the still , greater height to 
 which the surface of the rocks in the mountainous regions 
 of Ireland have been smoothed and striated by ice-action, 
 has led geologists to the opinion that that island, like the 
 greater part of England and Scotland, after having been 
 United with the continent of Europe, from whence it re- 
 ceived the plants and animals now inhabiting it,. was in 
 great part submerged. The conversion of this and other 
 parts of Great Britain into an archipelago was followed by 
 a re-elevation of land and a second continental period. M- 
 ter all these changes the final separation of Ireland from 
 Great Britain took place, and this event has been supposed 
 to have preceded the opening of the straits of Dover.* 
 
 Drift of Norfolk Cliffs.— There are deposits of boulder clay 
 
 and till in the Norfolk cliffs principally made up of the waste 
 
 v'^te,^ Fi 116 ^^ white chalk and 
 
 ^^^^^^r ^^^^^,^^ ^''^' "^'^ ^^^^^ *^^° *^® 
 
 Tellina baithica (r. eo!ia«Za). Contain a larger pro- 
 
 portion of shells com- 
 mon to the Norwich and Red Crag, including a certain num- 
 * See Antiquity of Man, oliap. xiv. 
 
CROMER FOREST-BED. 191 
 
 ber of extinct forms, but also abounding in Tellina halthica 
 {T. solidula, Fig. 116), which is found fossil at Bridlitigton, 
 and living in our British seas, but wanting in all the forma- 
 tions, even the newest, afterwards to be described as Crag. 
 As the greater part of these drifts are barren of organic re- 
 mains, their classification is at present a matter of great un- 
 certainty. 
 
 They can nowhere be so advantageously studied as on 
 the coast between Happisburgh and Cromer. Hei-e we may 
 see vertical cliffs, sometimes 300 feet and more in height, ex- 
 posed for a distance of fifty miles, at the base of which the 
 chalk with flints crops out in nearly horizontal strata. Beds 
 of gravel and sand repose on this undisturbed chalk. They 
 are often strangely contorted, and envelop huge masses or 
 erratics of chalk with layers of vertical flint. I measured 
 one of these fragments in 1839 at Sheri'ingham, and found it 
 to be eighty feet in its longest diameter. It has been since 
 entirely removed by the waves of the sea. In the floor of 
 th6 chalk beneath it the layers of flint were horizontal. Such 
 erratics have evidently been moved bodily from their orig- 
 inal site, probably by the same glacial action which has pol- 
 ished and striated some of the accompanying granitic and 
 other boulders, occasionally six feet in diameter, which are 
 imbedded in the drift. . 
 
 Cromer Forest-bed. — Intervening between these glacial 
 formations and the subjacent chalk lies what has been call- 
 ed the Cromer Forest -bed. This buried forest has been 
 traced from Cromer to near Kessingland, a distance of more 
 than forty miles, being exposed at certain seasons between 
 high and low water mark. It is the remains of an old land 
 and estuarine deposit, containing the submerged stumps of 
 trees standing erect with their roots in the ancient soil. As- 
 sociated with the stumps and overlying them, are lignite 
 beds with fresh-water shells of recent species, and laminated 
 clay without fossils. Through the lignite and forest-bed are 
 scattered cones of the Scotch and spruce firs Avith the seeds 
 of recent plants, and the bones of at least twenty species of 
 terrestrial mammalia. Among these are two species of ele- 
 phant, M meridionalis, Nesti, and E. antiqwus, the former 
 found in the Newer Pliocene beds of the Val d'Arno, near 
 Florence. In the same bed occiir Hippopotamus major, Rhi- 
 Koeeros etrusGiis,hoih>of them also Val d'Arno species, many 
 species of deer considered by Mr. Boyd Dawkins to be char- 
 acteristic of warmer countries, and also a horse, beaver, and 
 field-mouse. Half of these mammalia are extinct, and; the 
 rest still survive in Europe. The vegetation taken alone 
 
19ij ELEMENTS OF GEOLOGY. 
 
 does not imply a temperature higher than that now prevail- 
 ing in the British Isles. There must have been a subsid- 
 ence of the forest to the amount of 400 or 500 feet, and a re- 
 elevation of the same to an equal extent in order to allow 
 the ancient surface of the chalk or covering of soil, on which 
 the forest grew, to be first covered with several hundred feet 
 of drift, and then upheaved so that the trees should reach 
 their present level. Although the relative antiquity of the 
 forest-bed to the overlying glacial till is clear, there is some 
 difference of opinion as to its relation to the crag presently 
 to be described. 
 
 Chillesford and Aldeby Beds. — It is in the counties of Nor- 
 folk, Suffolk, and Essex, that we obtain our most valuable 
 information respecting the British Pliocene strata, whether 
 newer or older. They have obtained in those counties the 
 provincial name of "Crag," applied particularly to masses 
 of shelly sand which have long been used in agriculture to 
 fertilize soils deficient in calcareous matter. At Chillesford, 
 between Woodbridge and Aldborough in Suffolk, and Alde- 
 by, near Beccles, in the sam^ county, there occur stratified 
 deposits, apparently older than any of the preceding drifts 
 of Yorkshire, Norfolk, and Suffolk. They are composed at 
 Chillesford of yellow sands and clays, with much mica, form- 
 ing horizontal beds about twenty feet thick. Messrs. Prest- 
 wich and Searles Wood, senior, who first described these 
 beds, point out that the shells indicate on the whole a cold- 
 er climate than the Red Crag ; two-thirds of them being 
 characteristic of high latitudes. Among these are Gardium 
 Ghoenlandicum, Leda limatula, Tritonium caritiatum, and 
 Scalaria Grcenlandica. In the upper part of the laminated 
 clays a skeleton of a whale was found associated with casts 
 of the characteristic shells, Nucula Cobboldioe and Tellina 
 oUiqua, already referred to as no longer inhabiting our seas, 
 Fi".iiT. ^"'^ ^^ being extinct varieties if not species. 
 The same shells occur in a perfect state in the 
 lower part of the formation. Natica helicoides 
 (Fig. 117) is an example of a species formerly 
 known only as fossil, but which has now been 
 found living in our seas. 
 _ At Aldeby, where beds occur decidedly simi- 
 
 Natica iwiicoides, lar in mineral character as well as fossil re- 
 JohnaoD. mains, Messrs. Crowfoot and Dowson have now 
 obtained sixty-six species of mollusca, comprising the Chilles- 
 ford species and some others. Of these about nine-tenths 
 are recent. They are in a perfect state, clearly indicating a 
 cold climate; as two-thirds of them are now met with in arc- 
 
NORWICH CRAG. 193 
 
 tic regions. As a rule, the lamellibranchiate molluscs have 
 both valves united, and many of them, such as Mya arena- 
 ria, stand with the siphonal end upward, as when in a living 
 state. 2'eUina balthioa, before mentioned (Fig. 116) as so 
 characteristic of the glacial beds, including the drift of Brid- 
 lington, has not yet been found in deposits of Chillesford and 
 Aldeby age, whether at Sudbourn, East Bavent, Horstead, 
 Coltishall, Burgh, or in the highest beds overlying the Nor- 
 wich Crag proper at Bramerton and Thorpe. 
 
 Norwich or Fluvio-marine Crag. — The beds above alluded 
 to ought, perhaps, to be regarded as beds of passage be- 
 tween the glacial formations and those called from a pro- 
 vincial name " Crag," the newest member of which has been 
 commonly called the "Norwich Crag." It is chiefly seen 
 in the neighborhood of Norwich, and consists of beds of in- 
 coherent sand, loam, and gravel, which are exposed to view 
 on both banks of the Yare, as at Bramerton and Thorpe. 
 As they contain a mixture of marine, land, and fresh-water 
 shells, with bones of fish and mammalia, it is clear that these 
 beds have been accumulated at the bottom of a sea near the 
 mouth of a river. They form patches rarely exceeding twen- 
 ty feet in thickness, resting on white chalk. At their junc- 
 tion with the chalk there invariably intervenes a bed called 
 the " Stone-bed," composed of unrolled chalk-flints, common- 
 Fig, lis. 
 
 Jtraatodon arvernensis, third milk molar, left side, upper jaw ; grinding surface, naturnl 
 size. Norwich Crag, Postwick, also found in Ked Crag, see p. 19T. 
 
 ly of large size, mingled with the remains of a land fauna 
 comprising Mastodon arvernensis, JElephas meridionalis, and 
 an extinct species of deer. The mastodon, which is a spe- 
 cies characteristic of the Pliocene strata of Italy and France, 
 is the most abundant fossil, and one not found in the Cro- 
 
 9 
 
194 ELEMENTS OF GEOLOGY. 
 
 mer forest before mentioned. When these flints, probably- 
 long exposed in the atmosphere, became submerged, they 
 were covered with barnacles, and the surface of the chalk 
 became perforated by the Pholas crispata, each fossil shell 
 still remaining at the bottom of its cylindrical cavity, now- 
 filled up with loose sand from the incumbent crag. This 
 species of Pholas still exists, and drills the rocks between 
 high and low water on the British coast. The name of 
 " Fluvio-marine " has often been given to this formation, as 
 no less than twenty species of land and fresh-water shells 
 have been found in it. They are all of living species ; at 
 least only one univalve, Paludina lenta, has any, and that a 
 very doubtful, claim to be regarded as extinct. 
 
 Of the marine shells, 124 in number, about ]8 per cent, 
 are extinct, according to the latest estimate given me by 
 Mr. Searles Wood ; but, for reasons presently to be men- 
 tioned, this percentage must be only regarded as provision- 
 al. It must also be borne in mind that the proportion of 
 recent shells would be augmented if the uppermost beds at 
 Bramerton, near Norwich, which belong to the most mod- 
 ern or Chillesford division of the Crag, had been included, as 
 they were formerly, by Mr. Woodward and myself, in the 
 Norwich series. Arctic shells, which foi-med so large a pro- 
 portion in the Chillesford and Aldeby beds, are more rare 
 in the Norwich Crag, though many northern species — such 
 as Rhynchonella psittacea, Scalaria Grcenlandica,Astarte bo- 
 
 Fig. 119. Fig. 120. 
 
 Nucula CobbolditB. Tellina dbliqua. 
 
 realis, PanopcBa Nbrvegica, and others — still occur. The 
 Nucula GobboldioB and Tellina obliqua,'P\gs. 119 and 120, 
 before mentioned, p. 194, are frequent in these beds, as are 
 also Littorina littorea, Cdrdium edule, and Turritella commu- 
 nis, of our seas, proving the littoral origin of the beds. 
 
 OLDER PLIOCENE STRATA. 
 
 Red Crag. — Among the English Pliocene beds the next in 
 antiquity is the Red Crag, which often rests immediately on 
 the London clay, as in the county of Essex, illustrated in the 
 accompanying diagram. 
 
EED CEAG. 195 
 
 Fig. 121. 
 
 London Clay. Chalk. 
 
 It is chiefly in the county of Suffolk that it is found, rare- 
 ly exceeding twenty feet in thickness, and sometimes over- 
 lying another Pliocene deposit, the Coralline Crag, to be 
 mentioned in the sequel. It has yielded — exclusive of 25 
 species regarded by Mr. Wood as derivative — 256 species of 
 mollusca, of which 65, or 25 per cent., are extinct. Thus, 
 apart from its order of superposition, its greater antiquity 
 than the Norwich and glacial beds, already described, is 
 proved by the greater departure from the fauna of our seas. 
 It may also be observed that in most of the deposits of this 
 Red Crag, the northern forms of the Norwich Crag, and of 
 such glacial formations as Bridlington, are less numerous, 
 while those having a more southern aspect begin to make 
 their appeai-ance. Both the quartzose sand, of which it 
 chiefly consists, and the included shells, are most commonly 
 distinguished by a deep ferruginous or ochreous color, whence 
 its name. The shells are often rolled, sometimes comminu- 
 ted, and the beds have much the appearance of having been 
 shifting sand-banks, like those now forming on the Dogger- 
 bank, in the sea, sixty miles east of the coast of Northum- 
 berland. Cross stratification is almost always present, the 
 planes of the strata being sometimes directed towards one 
 point of the compass, sometimes to the opposite, in beds im- 
 mediately ovei'lying. That such a structure is not decep- 
 tive or due to any subsequent concretionary rearrangement 
 of particles, or to mere bands of color produced by the iron, 
 is proved by each bed being made up of flat pieces of shell 
 which lie parallel to the planes of the smaller strata. 
 
 It has long been suspected that the different patches of 
 Red Crag are not all of the same age, although their chro- 
 nological relation can not be decided by superposition. Sep- 
 arate masses are characterized by shells specifically distinct 
 or greatly varying in relative abundance, in a manner imply- 
 ing that the deposits containing them were separated by in- 
 tervals of time. At Butley, Tunstall, Sudbourn, and in the 
 Red Crag of Chillesford, the mollusca appear to assume their 
 most modern aspect when the climate was colder than when 
 the earliest deposits of the same period were formed. At 
 Butley, Nucula Cohholdim, so common in the Norwich and 
 certain glacial beds, is found, and Purpura tetragona (Fig. 
 122) is very abundant. On the other hand, at Walton-cm- 
 
196 
 
 ELEMENTS OE GEOLOGY. 
 
 Fig. 122. the-Naze, in Essex, we seem to have an ex- 
 hibition of the oldest phase of the Red Crag ; 
 and a warmer climate seems indicated, not 
 only by the absence of many northern forms, 
 but alsff by the abundance of some now liv- 
 ing in the British seas and the Mediterranean. 
 Voluta JLamberti (see Figs. 123 and 124), an 
 extinct form, which seems to have flourished 
 chiefly in the antecedent Coralline Crag pe^ 
 riod, is still represented here by individuals 
 of every age. 
 
 The reversed whelk (Fig. 125) is com- 
 ^S^T^Tsfzr mon at Walton, where the dextral form of 
 that shell is unknown. Here also we find 
 most frequently specimens of lamellibranchiate molluscs, 
 with both the valves united, showing that they belonged 
 to this sea of the Upper Crag, and were not washed in 
 from an older bed, such as the Coralline, in which case the 
 
 Fig. 123., 
 
 Fig. 124. 
 
 Fig. 125. 
 
 Voluta IjamiberUi Sow. Va- 
 riety characteristic of Snf- 
 follt Crag. Pliocene. 
 
 Voluta Lamherti, yoimg 
 individual, Cor. and 
 Eed Crag. 
 
 Frophon antiquum, Mu.l. 
 {Fttaus amtrariua) half 
 nat. size. 
 
 ligament would not have held together the valves in strata 
 so often showing signs of the boisterous action of the waves. 
 No less than forty species of lamellibranchiate molluscs, with 
 double valves, have been collected by Mr. Bell from the vari- 
 ous localities of the Red Crag. 
 At and near the base of the Red Crag is a loose bed of 
 
WHITE OB CORALLINE CRAG. 197 
 
 bfown nodules, first noticed by Professor Henslow as con- 
 taining a large percentage of earthy phosphates. This bed 
 of coprolites (as it is called, because they were originally 
 supposed to be the faeces of animals) does not always occur 
 at one level, but is generally in largest quantity at the junc- 
 tion of the Crag and the underlying formation. In thick- 
 ness it usually varies from six to eighteen inches, and in some 
 rare cases amounts to many feet. It has been much used in 
 agriculture for manure, as not only the nodules, but many of 
 the separate bones associated with them, are largely impreg- 
 nated with phosphate of lime, of which there is sometimes 
 as much as sixty per cent. They are not unfrequently cov- 
 ered with barnacles, showing that they were not formed as 
 concretions in the stratum where they now lie buried, but 
 bad been previously consolidated. The phosphatic nodules 
 often include fossil crabs and fishes from the London clay, 
 together with the teeth of gigantic sharks. In the same bed 
 have been found many eai'-bones of whales, and the teeth of 
 Mastodon arvernensis, Rhinoceros 8chleiermacheri, Tapirus 
 priseus, and Hipparion (a quadruped of the horse family), 
 and antlers of a stag, Cerous anoceros. Organic remains also 
 of the older chalk and lias are met with, showing how great 
 was the denudation of previous formations during the Plio- 
 cene period. As the older White Crag, presently to be men- 
 tioned, contains similar phosphatic nodules near its base, those 
 of the Red Crag may be partly derived from this source. 
 
 White or Coralliue Crag.— The lower or Coralline Crag is 
 of very limited extent, ranging over an area about twenty 
 miles in length, and three or four in breadth, between the 
 rivers Stour and Aide, in Sufiblk. It is generally calcareous 
 and marly — often a mass of comminuted shells, and the re- 
 mains of bryozoa* (or polyzoa), passing occasionally into a 
 soft building-stone. At Sudbourn and Gedgrave, near Or- 
 ford, this building-stone has been largely quarried. At some 
 places in the neighborhood the softer mass is divided by thin 
 flags of hard limestone, and bryozoa placed in the upright 
 position in which they grew. From the abundance of these 
 coralloid moUusca the lowest or White Crag obtained its 
 popular name, but true corals, as now defined, or zoantharia, 
 ai'e very rare in this formation. 
 
 * Ehrenberg proposed in 1831 the term Bryozoum, or " Moss-animal," for 
 the molluscous or ascidian form of polyp, characterized by having two open- 
 ings to the digestive sack, as in Eschara, Flustra, Retepora, and other zo- 
 ophytes popularly included in the corals, but now classed by naturalists as 
 mollusca. The term Polyzoum, synonymous with Bryozoum, was, it seems, 
 proposed in 1830, or the year before, by Mr. J. O. Thompson. 
 
198 ELEMENTS OF GEOLOGY. 
 
 The Coralline Crag rarely, if ever, attains a thickness of 
 thirty feet in any one section. Mr. Prestwich imagines that 
 if the beds found at different localities were united in the 
 probable order of their succession, they might exceed eighty 
 feet in thickness, but Mr. Searles Wood does not believe in 
 the possibility of establishing such a chronological succession 
 by aid of the organic remains, and questions whether proof 
 could be obtained of more than forty feet. I was unable to 
 come to any satisfactory opinion on the subject, although at 
 Orford, especially at Gedgrave, in the neighborhood of that 
 place, I saw many sections in pits, where this crag is cut 
 through. These pits are so unconnected, and of such limit- 
 ed extent, that no continuous section of any length can be 
 obtained, so that speculations as to the thickness of the whole 
 deposit must be very vague. At the base of the formation 
 at Sutton a bed of phosphatic nodules, very similar to that 
 before alluded to in the Red Crag, with remains of mamma- 
 lia, has been met with. 
 
 Whenever the Red and Coralline Crag occur in the same 
 district, the Red Crag lies uppermost ; and in some cases, as 
 in the section represented in Fig. 126, which I had an oppor- 
 
 Sutton. Shottisham Eamsholt. 
 
 Section near Woodbridge, in Suffolk. 
 a. Eed Crag. 6. Coralline Crag, a London clay. 
 
 tunity of seeing exposed to view in 1839, it is clear that the 
 older deposit, or Coralline Crag, b, had suffered denudation, 
 before the newer formation, a, was thrown down upon it. At 
 D there was not only seen a distinct cliff, eight or ten feet 
 high, of Coralline Crag, running in a direction N.E. and S.W., 
 against which the Red Crag abuts with its horizontal layers, 
 but this cliff occasionally overhangs. The rock composing 
 it is drilled everywhere by Pholacles, the holes which they 
 perforated having been afterwards filled with sand, and cov- 
 ered over when the newer beds were thrown down. The 
 older formation is shown by its fossils to have accumulated 
 in a deeper sea, and contains none of those littoral forms such 
 as the limpet. Patella, found in the Red Crag. So great an 
 amount of denudation could scarcely take place, in such inco- 
 herent materials, without some of the fossils of the inferior 
 beds becoming mixed up with the overlying crag, so that 
 considerable difficulty must be occasionally experienced by 
 
WHITE OR CORALLINE CRAG. 
 
 199 
 
 the palaeontologist in deciding which species belong several- 
 ly to each group. 
 
 Mr. Searles Wood estimates the total number of marine 
 testaceous mollusca of the Coralline Crag at 350, of which 
 110 are not known as living, being in the proportion of 
 thirty-one per cent, extinct. No less than 130 species of bry- 
 ozoa have been found in the Coralline Crag, and some be- 
 long to genera unknown in the living creation, and of a very 
 peculiar structure ; as, for example, that represented in the 
 annexed figure (127), which is one of several species having 
 
 Fig. 127. 
 
 Fascicularia av/rantiwrn, Milne Edwards. Family, Tvhvliporid^^ of same author. 
 Bryozoan of extinct genus, from the inferior or Coralline Crag, Suffolk. 
 
 0, Exterior. 6. Vertical section of interior, e. Portion of exterior magnified, d. Por- 
 tion of interior magnified, showing that it is made up of long, thin, straight 
 tubes, nnited in conical bundles. 
 
 a globular form. Among the testacea the genus Astarte (see 
 Fig. 128) is largely represented, no less than fourteen species 
 
 Fig. 128. 
 
 Asiarte, Omalii, Laj.; species common to Upper and Lower Crag. 
 
 being known, and many of these being rich in individuals. 
 There is an absence of genera peculiar to hot climates, such 
 as Conus, Oliva, Fasciolaria, Crassatella, and others. The 
 absence also of large cowries {Cypred), those found belong- 
 
200 ELEMENTS OF GEOLOGY. 
 
 ing exclusively to the section Trivia, is remarkable. The 
 lai'ge volute, called Valuta Lamberti (Fig. 123, p. 196), may 
 seem an exception ; but it differs in form from the volutes 
 of the torrid zone, and, like the living Voluta Magdktnica, 
 must have been fitted for an extra-tropical climate. 
 
 The occurrence of a species of Lingula at Sutton (see Fig. 
 129) is worthy of remark, as these Brachiopoda seem now 
 confined to more equatorial latitudes ; and the same may be 
 said still more decidedly of a species oi Pyi-ula, supposed by 
 Mr. Wood to be identical with P. reticulata (Fig. 130), now 
 living in the Indian Ocean. A genus also of echinoderms, 
 called by Professor Forbes Temnechinus (Fig. 131), occurs 
 
 Fig. 129. Fig. 130. Fig. 131. 
 
 Limjula Ihimm-tieri, Pyrvla reticulata, Lam. ; Temnechinus excavatus, Forbes ; 
 Nyst ; Suffolk aud Coralline Crag, Earn- !remru>pleurusexcavatus,'Wooi; 
 
 Antwerp Crag. Bholt. Cor. Crag, Eamsholt. 
 
 in the Red and Coralline Crag of Suffolk, and until lately 
 was unknown in a living state, but it has been brought to 
 light as an existing form by the deep-sea dredgings, both 
 of the United States survey, off Florida, at a depth of from 
 180 to 480 feet, and more recently (1869), in the British seas, 
 during the explorations of the "Porcupine." 
 
 Climate of the Crag Deposits. — One of the most interesting 
 conclusions deduced from a careful comparison of the shells 
 of the British Pliocene strata and the fauna of our present 
 seas has been pointed out by Professor E. Forbes. It ap- 
 pears that, during the Glacial period, a period intermediate, 
 as we have seen, between that of the Crag and our own 
 time, many shells, previously established in the temperate 
 zone, retreated southward to avoid an uncongenial climate, 
 and they have been found fossil in the Newer Pliocene strata 
 of Sicily, Southern Italy, and the Grecian Archipelago, where 
 they may have enjoyed, during the era of floating icebergs, 
 a climate resembling that now prevailing in higher Europe- 
 an latitudes.* The Professor gave a list of fifty shells which 
 inhabited the British seas while the Coralline and Red Crag 
 were forming, and which, though now living in our seas, 
 * E. Forbes, Mem. Geol. Survey Gt. Brit., vol. i., p. 386. 
 
PAUNA OF THE CRAG. 201 
 
 were wanting, as far as was then known, in the glacial de- 
 posits. Some few of these species have subsequently been 
 found in the glacial drift, but the general conclusion of 
 Forbes remains unshaken. 
 
 The transport of blocks by ice, when the Red Crag was 
 being deposited, appears to me evident from the large size 
 of some huge, irregular, quite unrounded chalk fliDts,"retain- 
 ing their white coating, and 2 feet long by 18 inches broad, 
 in beds worked for pliosphatic nodules at Foxhall, four miles 
 south-east of Ipswich. These must have been tranquilly 
 drifted to the spot by floating ice. Mr. Prestwich also men- 
 tions the occurrence of a large block of porphyry in the base 
 of the Coralline Crag at Sutton, which would imply that the 
 ice-action had begun in our seas even in this older period. 
 The cold seems to have gone on increasing from the time 
 of the Coralline to that of the Norwich Crag, and became 
 more and more severe, not perhaps without some oscillations 
 of temperature, until it reached its maximum in what has 
 been called the Glacial period, or at the close of the Newer 
 Pliocene, and in the Post-pliocene periods. 
 
 Belation of the Fauna of the Crag to that of the recent 
 Seas. — By far the greater number of the recent maiine spe- 
 cies occurring in the several Crag formations are still inhab- 
 itants of the British seas ; but even these differ considerably 
 in their relative abundance, some of the commonest of the 
 Crag shells being now extremely scarce — as, for example, 
 Buccinum Dalei — while others, rarely met with in a fossil 
 state, are now very common, as Murex erinaceus and Car- 
 dium echinatum. Some of the species also, the identity 
 of which with the living would not be disputed by any 
 conchologist, are nevertheless distinguishable as varieties, 
 whether by slight deviations in form or a difference in aver- 
 age dimensions. Since Mr. Searles Wood fivst described the 
 marine testacea of the Crags, the additions made to that fos- 
 sil fauna have not been considerable, whereas we have made 
 in the same period immense progress in our knowledge of 
 the living testacea of the British and arctic seas, and of the 
 Mediterranean. By this means the naturalist has been en- 
 abled to identify with existing species many forms previous- 
 ly supposed to be extinct. 
 
 In the forthcoming supplement to the invaluable mono- 
 graph communicated by Mr. Wood to the Palseontographi- 
 cal Society, in which he has completed his figures an^ de- 
 scriptions of the British crag shells of every age, lists will 
 be found of all the fossil shells, of which a summary is given 
 in the annexed table, p. 202. 
 
202 
 
 ELEMENTS OF GEOLOGY. 
 
 To begin with the uppermost or Chillesford beds, it will 
 be seen that about 9 per cent, only are extinct, or not 
 known as living, whereas in the Norwich, which succeeds in 
 the descending order, seventeen in a hundred are extinct. 
 Formerly, when the Norwich or Fluvio-marine Crag was 
 spoken of, both these formations were included under the 
 same head, for both at Bramerton and Thorpe, the chief lo- 
 calities where the Norwich Crag was studied, an overlying 
 deposit occurs referable to the Chillesford age. If now the 
 two were fused together as of old, their shells would, ac- 
 cording to Mr. Wood, yield a percentage of iifteen in a hun- 
 dred of species extinct or not known as living. 
 
 NUMBER OF KNOWN 
 
 SPECIES OF MARINE TESTACEA IN 
 THE CRAG. 
 
 CHILLESFORD AND ALDEET BEDS. 
 
 Total Number. 
 
 Bivalves . 
 UnivalveB 
 Brachiopods 
 
 Bivalves . 
 Univalves 
 Brachiopods 
 
 Bivalves . 
 Univalves 
 Brachiopods 
 
 Bivalves . 
 Univalves 
 Brachiopods 
 
 61 
 
 33 
 
 
 
 Not known as 
 liviDg. 
 
 4 
 5 
 
 
 NORVl'ICH OR rLUTIO-MARINE CRAG. 
 
 61 
 
 64 
 
 1 
 
 10 
 
 12 
 
 
 
 Percentage of 
 
 Shells not known 
 
 as living. 
 
 9-5 
 
 17-5 
 
 RED CRAG. 
 (Exclusive of many derivative shells.') 
 
 128 
 
 127 
 
 1 
 
 31 
 
 33 
 
 1 
 
 CORALLINE CRAG. 
 
 161 
 
 47 
 
 184 
 
 60 
 
 5 
 
 3 
 
 25-0 
 
 31-5 
 
 To come next to the Red Crag, the reader will observe 
 that a percentage of 25 is given of shells unknown as living, 
 and this increases to 31 in the antecedent Coralline Crag. 
 But the gap between these two stages of our Pliocene de- 
 posits is really wider than these numbers would indicate, for 
 several reasons. In the first place, the Coralline Crag is 
 more strictly the product of a single period, the Red Crag, 
 as we have seen, consisting of separate and independent 
 patches, slightly varying in age, of which the newest. is 
 probably not much anterior to the Norwich Crag. Second- 
 ly, there was a great change of conditions, both as to the 
 
FAUNA OF THE CEAG. 203 
 
 depth of the sea and climate, between the periods of the 
 Coralline and Red Crag, causing the fauna in each to differ 
 far more widely than would appear from the. above numer- 
 ical results. 
 
 The value of the analysis given in the above table of the 
 shells of the Red and Coralline Crags is in no small degree 
 enhanced by the fact that they were all either collected by 
 Mr. Wood himself, or obtained by him direct from their dis- 
 coverers, so that he was enabled in each case to test their 
 authenticity, and as far as possible to avoid those errors 
 which arise from confounding together shells belonging to 
 the sea of a newer deposit, and those washed into it from a 
 formation of older date. The danger of this confusion may 
 be conceived when we remember that the number of species 
 rejected from the Red Crag as derivative by Mr. Wood is no 
 less than 25. Some geologists have held that on the same 
 grounds it is necessary to exclude as spurious some of the 
 species found in the Norwich Crag proper; but Mr. Wood 
 does not entertain this view, believing that the spurious 
 shells which have sometimes found their way into the lists 
 of this crag have been introduced by want of care from 
 strata of Red Crag. 
 
 There can be no doubt, on the other hand, that concholo- 
 gists have occasionally rejected from the Red arid Norwich 
 Crags, as derivative, shells which really belonged to the seas 
 of those periods, because they were extinct or unknown as 
 living, which in their eyes afforded sufficient ground for sus- 
 pecting them to be intruders. The derivative origin of a 
 species may sometimes be indicated by the extreme scarcity 
 of the individuals, their color, and worn condition; whereas 
 an opposite conclusion may be arrived at by the integrity 
 of the shells, especially when they are of delicate and ten- 
 der structure, or their abundance, and, in the case of the 
 lamellibranchiata, by their being held together by the liga- 
 ment, which often happens when the shells have been so 
 broken that little more than the hinges of the two valves 
 ai'e preserved. As to the univalves, I have seen from a pit 
 of Red Crag, near Woodbridge, a large individual of the ex- 
 tinct Voluta JLamberti, seven inches in length, of which the 
 lip, then perfect, had in former stages of its growth been 
 frequently broken, and as often repaired. It had evidently 
 lived in the sea of the Red Crag, where it had been exposed 
 to rough usage, and sustained injuries like those_ which the 
 reversed whelk, Trophon antiquum, so characteristic of the 
 same formation, often exhibits. Additional proofs, howev- 
 er, have lately been obtained by Mr. Searles Wood that this 
 
204 ELEMENTS OF GEOLOGY. 
 
 shell had not died out in the era of the Red Crag by the dis- 
 covery of the same fossil near Southwold, in beds of the later 
 Norwich Crag. , tj j j 
 
 Antwerp Crag.— Strata of the same age as the Ked and 
 Coralline Crag of Suffolk have been long known in the coun- 
 try round Antwerp, and on the banks of the Scheldt, below 
 that city; and the lowest division, or Black Crag, there 
 found is shown by the shells to be somewhat more ancient 
 than any. of our British series, and probably forms the first 
 links of a downward passage from the strata of the Pliocene 
 to those of the Upper Miocene period. 
 
 Newer Pliocene Strata of Sicily.— At several points north 
 of Catania, on the eastern sea-coast of Sicily — as at Aei-Cas- 
 tello, for example, Trezza, and Nizzeti— marine strata, assor 
 ciated with volcanic tuffs and basaltic lavas, are seen, wrhich 
 belong to a period when the first igneous eruptions of Mount 
 Etna were taking place in a shallow bay of the Mediterra- 
 nean. They contain numerous fossil shells, and 
 Fig. 132. out of 142 species that have been collected all 
 but eleven are identical with species now liv- 
 ing. Some few of these eleven shells may pos- 
 sibly still linger in the depths of the Mediterra- 
 nean, like Murex. vaginatus, see Fig. 132. The 
 last-mentioned shell had already become rare 
 when the associated marine and volcanic strata 
 above alluded to were formed. On the whole, 
 the modern character of the testaceous fauna 
 under consideration is expressed not only by 
 the small proportion of extinct species, but by 
 ■"^"m* piai™^ the relative number of individuals by which 
 most of the other species are represented, for 
 the propoi'tion agrees with that observed in the present fauna 
 of the Mediterranean. The rarity of individuals in the ex- 
 tinct species is such as to imply that they were already on 
 the point of dying out, having flourished chiefly in the earlier 
 Pliocene times, when the Subapennine strata were in prog- 
 ress. 
 
 Yet since the accumulation of these Newer Pliocene sands 
 and clays, the whole cone of Etna, 11,000 feet in height and 
 about 90 miles in circumference at its base, has been slowly 
 built up ; an operation requiring many tens of thousands of 
 years for its accomplishment, and to estimate the magnitude 
 of which it is necessary to study in detail the internal struc- 
 ture of the mountain, and to see the proofs of its double axis, 
 or the evidence of the lavas of the present great centre of 
 eruption having gradually overwhelmed and enveloped a 
 
NEWER PLIOCENE OF SICILY. 205 
 
 move ancient cone, situated 3-J- miles to the east of the pres- 
 ent one.* 
 
 It appears that while Etna was increasing in bulk by a 
 series of eruptions, its whole mass, comprising the founda- 
 tions of subaqueous origin above alluded to, was undergoing 
 a slow upheaval, by which those marine strata were raised 
 to the height of 1200 feet above the sea, as seen at Catera, 
 and pei-haps to greater heights, for we can not trace their 
 extension westward, owing to the dense and continuous cov- 
 ering of modern lava under which they are buried. During 
 the gradual rise of these Newer Pliocene formations (consist- 
 ing of clays, sands, and basalts) other strata of Post-pliocene 
 date, marine as well as fluviatile, accumulated round the base 
 of the mountain, and these, in their turn, partook of the up- 
 ward movement, so that several inland cliffs and terraces at 
 low levels, due partly to the action of the sea and partly to 
 the river Simeto, originated in succession. Fossil remains 
 of the elephant, and other extinct quadrupeds, have been 
 found in these Post-pliocene strata, associated with recent 
 shells. 
 
 There is probably no part of Europe where the Newer Pli- 
 ocene formations enter so largely into the structure of the 
 earth's crust, or rise to such heights above the level of the 
 sea, as Sicily. They cover nearly half the island, and near 
 its centre, at Castrogiovanni, reach an elevation of 3000 feet. 
 They consist principally of two divisions, the upper calcare- 
 ous and the lower argillaceous, both of which may be seen 
 at Syracuse, Girgenti, and Castrogiovanni. According to 
 Philippi, to whom we are indebted for the best account of 
 the tertiary shells of this island, thirty-five species out of one 
 hundred and twenty-four obtained from the beds in central 
 Sicily are extinct. 
 
 A geologist, accustomed to see nearly all the Newer Pli- 
 ocene foyraations in the north of Europe occupying low 
 grounds' and very incoherent in texture, is naturally surprised 
 to behold formations of the same age so solid and stony, of 
 such thickness, and attaining so great an elevation above 
 the level of the sea. The upper or calcareous member of 
 this group in Sicily consists in some places of a yellowish- 
 white stone, like the Calcaire Grossier of Paris ; in others, 
 of a rock nearly as compact as marble. Its aggregate thick- 
 ness amounts sometimes to IQO or 800 feet. It usually oc- 
 curs in regular horizontal beds, and is occasionally intersect- 
 ed by deep valleys, such as those of Sortino and Pentalica, 
 
 * See a Memoir on the Lavas and Mode of Origin of Mount Etna, by the 
 Author, Phil. Trans., 1858. 
 
206 
 
 ELEMENTS OF GEOLOGY. 
 
 in which are numerous caverns. The fossils are in every 
 stage of preservation, from shells retaining portions of their 
 animal matter and color to others which are mere casts. 
 The limestone passes downward into a sandstone and con- 
 glomerate, below which is clay and blue marl, from which 
 perfect shells and corals may be disengaged. The clay some- 
 times alternates with yellow sand. 
 
 South of the plain of Catania is a region in which the ter- 
 tiary beds are intermixed wi'th volcanic matter, which has 
 been for the most part the product of submarine eruptions. 
 It appears that, while the clay, sand, and yellow limestone 
 before mentioned were in course of deposition at the bottom 
 of the sea, volcanoes burst out beneath the waters, like that 
 of Graham Island, in 1831, and these explosions recurred 
 again and again at distant intervals of time. Volcanic ashes 
 and sand were showered down and spread by the waves and 
 currents so as to form strata of tuff, which ai-e found inter- 
 calated between beds of limestone and clay containing ma- 
 rine shells, the thickness of the whole mass exceeding 2000 
 feet. The fissures through which the lava rose may be seen 
 in many places, forming what are called dikes. 
 
 No shell is more conspicuous in these Sicilian strata than 
 the great scallop, Pecten jacobceus (Fig. 133), now so common 
 in the neighboring seas. The more we reflect on the pre- 
 ponderating number of this and other recent shells, the more 
 
 Kg. 133. 
 
 Pecten jacoiceue; half natural size. 
 
PLIOCENE STKATA OF ITALY. 207 
 
 we are surprised at the great thickness, solidity, and height 
 above the sea of the rocky masses in which they are en- 
 tombed, and the vast amount of geographical change which 
 has taken place since their origin. It must be remembered 
 that, before they began to emerge, the uppermost strata of 
 the whole must have been deposited under water. In oi-der, 
 therefore, to form a just conception of their antiquity, we 
 must first examine singly the innumerable minute parts of 
 which the whole is made up, the successive beds of shells, 
 corals, volcanic ashes, conglomerates, and sheets of lava ; and 
 we must afterwards contemplate the time required for the 
 gradual upheaval of the rocks, and the excavation of the val- 
 leys. The historical period seems scarcely to form an appre- 
 ciable unit in this computation, for we find ancient Greek 
 temples, like those of Girgenti (Agrigentum), built of the 
 modern limestone of which we are speaking, and resting on 
 a hill composed of the same ; the site having remained to 
 all appearances unaltei-ed since the Greeks first colonized the 
 island. 
 
 It follows, from the modern geological date of these rocks, 
 that the fauna and flora of a large part of Sicily are of high- 
 er antiquity than the country itself The greater part of 
 the island has been raised above the sea since the epoch of 
 existing species, and the animals and plants now inhabiting 
 it must have migrated from adjacent countries, with whose 
 productions the species are now identical. The average du- 
 ration of species would seem to be so great that they are 
 destined to outlive many important changes in the config- 
 uration of the earth's surface, and hence the necessity for 
 those innumerable contrivances by which they are enabled 
 to extend their range to new lands as they are formed, and 
 to escape from those which sink beneath the sea. 
 
 Newer Pliocene Strata of the Upper Val d'Arno. — When 
 we ascend the Arno for about ten miles above Florence, we 
 arrive at a deep narrow valley called the Upper Val d'Arno, 
 which appears once to have been a lake, at a time when the 
 valley below Florence was an arm of the sea. The horizon- 
 tal lacustrine strata of this upper basin are twelve miles long 
 and two broad. The depression which they fill has been 
 excavated out of Eocene and Cretaceous rocks, which form 
 everywhere ,the sides of the valley in highly inclined strati- 
 fication. The thickness of the more modern and unconform- 
 able beds is about 750 feet, of which the upper 200 feet con- 
 sist of Newer Pliocene strata, while the lower are Older Pli- 
 ocene. The newer series are made up of sands and a con- 
 glomerate called "sansino." Among the imbedded fossil 
 
208 ELEMENTS OF GEOLOGY. 
 
 mammalia are Mastodon arvernensis, Elephas meridionalis, 
 Rhinoceros etruscus, Hippopotamus major, and remains of the 
 genera bear, hyaena, and felis, nearly all of which occur in 
 the Cromer forest-bed (see p. 191). 
 
 In the same upper strata are found, according to M. Gau- 
 din, the leaves and cones of Glyptostrobus europoeus, a plant 
 closely allied to G. lieterophyUus, now inhabiting the north 
 of China and Japan. This conifer had a wide range in time, 
 having been traced back to the Lower Miocene strata of 
 Switzerland, and being common at CEningen in the Upper 
 Miocene, as we shall see in the sequel (p. 218). 
 
 Older Pliocene of Italy.— Subapennine Strata. — The Apen- 
 nines, it is well known, are composed chiefly yof Secondai'y 
 or Mesozoic rocks, forming a chain which branches off from 
 the Ligurian Alps and passes down the middle of the Italian 
 peninsula. At the foot of these mountains, on the side both 
 of the Adriatic and the Mediterranean, are found a series of 
 tertiary strata, which form, for the most part, a line of low 
 hills occupying the space between the older chain and the 
 sea. Brocchi was the first Italian geologist who described 
 this newer group in detail, giving it the name of the Subap- 
 ennine. Though chiefly composed of Older Pliocene strata, 
 it belongs, nevertheless, in part, both to older and newer 
 members of the tertiary series. The sti-ata, for example, of 
 the Superga, near Turin, are Miocene; those of Asti and Par- 
 ma Older Pliocene, as is the blue marl of Sienna; while the 
 shells of the incumbent yellow sand of tlie same territory 
 approach more nearly to ,the recent fauna of the Mediterra- 
 nean, and may be Newer Pliocene. 
 
 We have seen that most of the fossil shells of the Older 
 Pliocene strata of Suffolk which are of recent species are 
 identical with testacea now living in British seas, yet some 
 of them belong to Mediterranean species, and a few even of 
 the genera are those of warmer climates. We might there- 
 fore expect, in studying the fossils of corresponding age in 
 countries bordering the Mediterranean, to find among them 
 some species and genera of warmer latitudes. Accordingly, 
 in the marls belonging to this period at Asti, Parma, Sienna, 
 and parts of the Tuscan and Roman territories, we observe 
 the genera Oonus, Cyprma, Strombus, Pyrula, Mitra, Faseio- 
 laria, Sigaretus, Delphinula, AncUlaria, Oliva, TerebeUum, 
 Terebi-a, Perna, PUcatula, and Corbis, some characteristic of 
 tropical seas, others represented by species more numerous 
 or of larger size than those now proper to the Mediterranean. 
 
 Older Pliocene Flora of Italy.— I have already alluded to 
 the Newer Pliocene deposits of the Upper Val d'Arno above 
 
OLDER PLIOCENE FLORA OF ITALY. 
 
 209 
 
 Florence, and stated that below those sands and conglomer- 
 ates, contaii}ing the remains of the Elephas meridionalis and 
 other associated quadrupeds, lie an older horizontal and con- 
 formable series of beds, which may be classed as Older Plio- 
 cene. They consist of blue clays with some subordinate 
 layers of lignite, and exhibit a richer flora than the overly- 
 ing Newer Pliocene beds, and one receding farther from the 
 existing vegetation of Europe. They also comprise more 
 species common to the antecedent Miocene period. Among 
 the genera of flowering plants, M. Gaudin enumerates pine, 
 oak, evergreen oak, plum, plane, alder, elm, fig, laurel, maple, 
 walnut, birch, buckthorn, hickory, sumach, sarsaparilla, sassa- 
 fras, cinnamon, Glyptostrobus, Taxodium, Sequoia, Persea, 
 Qreodaphne (Fig. 134), Cassia, and Psoralea, and some oth- 
 ers. This assemblage of plants indicates a warm climate, 
 but not so subtropical an one as that of the Upper Miocene 
 period, which will presently be considered. 
 
 M. Gaudin, jointly with the Marquis Strozzi, has thrown 
 much light on the botany of beds of the same age in another 
 
 Fig. 134. 
 
 Fig. 135. 
 
 Oreodaphne Heerii. 
 Leaf balf uaL size.* 
 
 Liquidambar ewopcewn, var. trilobatwm, A. Br. (sometimes 
 four-lobed, and more commonly flve-lobed). 
 
 a. Lent, halt nat. size, 
 nat. size. 
 
 h. Part of same, nat. size. 
 d. Seed, do. (Eningen. 
 
 Fmit, 
 
 part of Tuscany, at a place called Montajone, between the 
 rivers Elsa and Evola, where, among other plants, is found 
 the Oreodaphne merii. Gaud, (see Fig. 134), which is prob- 
 ably only a variety of Oreodaphne /ceteris, or the laurel called 
 * Feuilles fossiles de la Toscane. 
 
210 . ELEMENTS OF GEOLOGY. 
 
 the Til in Madeira, where, as in the Canaries, it constitutes a 
 large portion of the native woods, but can not now endure 
 the climate of Europe. In the fossil specimens the same 
 glands or protuberances are preserved* (see Fig. 134) as 
 those which are seen in the axils of the primary veins of the 
 leaves in the recent Til. Another plant also indicating a 
 warmer climate is the lAquidanibar europceum, Brong. {see 
 Fig.. 135), a species nearly allied to JL. styracifluum, L., which 
 flourishes in most places in the Southern States of North 
 America, on the borders of the Gulf of Mexico. 
 
 * Contributions a la Elore fossile Italienne. Gaudin and Strozzi. Plate 
 11, Fig. 3. Gaudin, p. 22. 
 
PALimS OF TOUKAINE. 211 
 
 CHAPTER XIV. 
 
 MIOCENE PERIOD — UPPEE MIOCENE. 
 
 Upper Miocene Strata of France. — ^Faluns of Touraine. — Tropical Climate 
 implied by Testacea. — Proportion of recent Species of Shells. — Faluns 
 more ancient than the Suffolk Crag. — Upper Miocene of Bordeaux and 
 the South of France. — Upper Miocene of OEningen, in Switzerland. — Plants 
 "f the Upper Fresh-water Molasse. — Fossil Fruit and Flowers as well as 
 Leaves. — Insects of the Upper Molasse. — Middle or Marine Molasse of 
 Swi'aHerland. — Upper Miocene Beds of the Bolderberg, in Belgium. — Vien- 
 na Basin. — Upper Miocene of Italy and Greece. — Upper Miocene of India ; 
 Siwalik Hills. — Older Pliocene and Miocene of the United States. 
 
 Tipper Miocene Strata of France — Faluns of Touraine. — 
 The strata which we meet with next in the descending order 
 are those called by many geologists " Middle^ertiai-y," for 
 which in 1833 I proposed the name of Miocene, selecting the 
 " faluns " of the valley of the Loire, in France, as my example 
 or type. I shall now call these falimian deposits Upper Mi- 
 ocene, to distinguish them from others to which the name of 
 Lower Miocene will be given. 
 
 No British strata have a distinct claim to be regarded 
 as Upper Miocene, and as the Lower Miocene are also but 
 feebly represented in the British Isles, we must refer to for- 
 eign examples in illustration of this important period in the 
 earth's history. The term "faluns" is given provincially by 
 French agriculturists to shelly sand and marl spread over 
 the land in Touraine, just as similar shelly deposits were for- 
 merly, much used in Suffolk to fertilize the soil, before the 
 coprolitic or phosphatic nodules came into use. Isolated 
 masses of such faluns occur from near the mouth of the Loire, 
 in the neighborhood of Nantes, to as far inland as a district 
 south of Tours. They are also found at Pontlevoy, on the 
 Cher, about seventy miles above the junction of that river 
 with the Loire, and thirty miles south-east of Tours. De- 
 posits of the same age also appear under new mineral con- 
 ditions near the towns of Dinan and Rennes, in Brittany. I 
 have visited all the localities above enumerated, and found 
 the beds on the Loire to consist principally of sand and marl, 
 in which are shells and^ corals, some entire, some rolled, and 
 others in minute fragments. In certain districts, as at Done, 
 in the Department of Maine and Loife, ten miles south-west 
 
212 ELEMENTS OF GEOLOGY. 
 
 of Saumur, they form a soft building-stone, chiefly composed 
 of an aggregate of broken shells, bryozoa, corals, and echino- 
 derms, united by a calcareous cement ; the whole mass being 
 very like the Coralline Crag near Aldborough, and Sudbourn 
 in Suffolk. The scattered patches of faluns are of slight 
 thickness, rarely exceeding fifty feet ; and between the dis- 
 trict called Sologne and the sea they repose on a great va- 
 riety of older rocks ; being seen to rest successively upon 
 gneiss, clay-slate, various secondary formations, including 
 the chalk ; and, lastly, upon the upper fresh-water limestone 
 of the Parisian tertiary series, which, as before mentioned (p. 
 142), stretches continuously from the basin of the Seine to 
 that of the Loire. 
 
 At some points, as at Louans, south of Tours, the shells 
 are stained of a ferruginous color, not unlike that of the Red 
 Crag of Suffolk. The species are, for the most part, marine, 
 but a few of them belong to land and fluviatile genera. 
 j,j J35 Among the former, Helix turonen- 
 
 sis (Fig. 38, p. 56) is the most abun- 
 dant. Remains of terrestrial quad- 
 rupeds are here and there inter- 
 mixed, b-elonging to the genera 
 Dinotherium (Fig. 136), Mastodon, 
 Rhinoceros, Hippopotamus, Chae- 
 ropotamus Dichobune, Deer, and 
 others, and these are accompanied 
 by cetacea, such as the Lamantin, 
 Morse, Sea-calf, and Dolphin, all of 
 extinct species. 
 
 The fossil testacea of the faluns 
 of the Loire imply, according to 
 
 mnoa<^iur^ gig^nte.^, iL^^^. f'^ ^^^'^ Edward Forbes, that the 
 beds were formed partly on the 
 shore itself at the level of low water, and partly at very 
 moderate depths, not exceeding ten fathoms below that 
 level. The molluscan fauna is, on the whole, much more lit- 
 toral than that of the Pliocene Red and Coralline Crag of 
 Suffolk, and implies a shallower sea. It is, moreover, con- 
 trasted with the Suffolk Crag by the indications it affords of 
 an extra-European climate. Thus it contains seven species 
 of Cyprma, some larger than any existing cowry of the Med- 
 iterranean, several species of OUva, Ancillaria, Mitra, Tere- 
 bra, Pyrula, Fasciolaria, and Gonus. Of the cones there are 
 no less than eight species, some very large, whereas the only 
 i^uropean cone now living is of diminutive size. The genus 
 JStenta, and many others, are also represented by individuals 
 
COMPABISONS OF CRAG AND FALUNS. 213 
 
 of a type now characteristic of equatorial seas, and wholly 
 unlike any Mediterranean forms. These proofs of a more 
 elevated temperature seem to imply the higher antiquity of 
 the faluns as compared with the Suffolk Crag, and are in per- 
 fect accordance with the fact of the smaller proportion of 
 testacea of recent species found in the faluns. 
 
 Out of 290 species of shells, collected by myself in 1840 at 
 Pontlevoy, Louans, Bossee, and other villages twenty miles 
 south of Tours, and at Savigne, about fifteen miles north-west 
 of that place, seventy-two only could be identified with re- 
 cent species, which is in the proportion of twenty-iive per 
 cent. A large number of the 290 species are common to all 
 the localities, those peculiar to each not being more numer- 
 ous than we might expect to find in different bays of the 
 same sea. 
 
 The total number of species of testaceous mollusca from 
 the faluns in my possession is 302, of which forty-five only, or 
 fourteen per cent., were found by Mr. Wood to be common 
 to the Sufiblk Crag. The number of corals, including bryo- 
 zoa and zoantharia, obtained by me at Done and other lo- 
 calities before adverted to, amounts to forty-three, as deter- 
 mined by Mr. Lonsdale, of which seven (one of them a zoan- 
 tharian) agree specifically with those of the Suffolk Crag. 
 Some of the genera occurring fossil in Touraine, as the corals 
 Astrea and bendrophyUia,, and the bryozoan LunuUtes, have 
 not been found in European seas north of the Mediterranean ; 
 nevertheless, the zoantharia of the faluns do not seem to in- 
 dicate, on the whole, so warm a climate as would be inferred 
 from the shells. 
 
 It was stated that, on comparing about 300 species of Tou- 
 raine shells with about 450 from the Suffolk Crag, forty-five 
 only were found to be common to both, which is in the pi'o- 
 portion of only fifteen per cent. The same small amount of 
 agreement is found in the corals also. I formerly endeavored 
 to reconcile this marked difference in species with the sup- 
 posed co-existence of the two faunas, by imagining them to 
 have severally belonged to distinct zoological provinces or 
 two seas, the one opening to the north and the other to the 
 south, with a barrier of land between them, like the Isthmus 
 of Suez, now separating the Red Sea and the Mediterranean. 
 But I now abandon that idea for several reasons ; among 
 others, because I succeeded in 1841 in tracing the Crag fauna 
 southward in Normandy to within seventy miles of the Fa- 
 lunian type, near Dinan, yet found that both assemblages of 
 fossils retained their distinctive characters, showing no signs 
 of any blendiag of species or transition of climate. 
 
214 
 
 ELEMENTS OF GEOLOGY. 
 
 The principal grounds, however, for referring the English 
 Crag to the older Pliocene and the French faluns to the Up- 
 per Miocene epochs, consist in the predominance of fossil 
 shells in the British strata identifiable with species not only- 
 still living, but which are now inhabitants of neighboring 
 seas, while the accompanying extinct species are of genera 
 such as characterize Europe. In the faluns, on the contrary, 
 the recent species are in a decided minority ; and most of 
 them are now inhabitants of the Medi- 
 terranean, the coast of Africa, and the 
 Indian Ocean ; in a word, less northern in 
 character, and pointing to the prevalence 
 of a warmer climate. They indicate a 
 state of things receding farther from the 
 present condition of Central Europe in 
 physical geography and climate, and 
 doubtless, thei'efbre, receding farther 
 from our era in time. 
 
 Among the conspicuous fossils common 
 to the faluns of the Loire and the Sufiblk 
 Crag is a variety of the Voluta Lamberti, 
 a shell already alluded to (p. 196, Fig. 
 123). The specimens of this shell which 
 I have myself collected in Touraine, or 
 have seen in museums, are thicker and 
 Variety characteristic of heavier than British individuals of the 
 MunB of Touraine. Mi- game species, and shorter in proportion 
 to their width, and have the folds on the 
 columella less oblique, as represented in the annexed figure. 
 Upper Miocene Strata of Bordeaux and South of France.— 
 A great extent of country between the. Pyrenees and the 
 Gironde is overspread by tertiary deposits of various ages, 
 and chiefly of Miocene date. Some of these, near Bordeaux, 
 coincide in age with the faluns of Touraine, already men- 
 tioned, but many of the species of shells are peculiar to the 
 south. The succession of beds in the basin of the Gironde 
 implies several oscillations of level by which the same wide 
 area was alternately converted into sea and land and into 
 brackish-water lagoons, and finally into fresh - water ponds 
 and lakes. 
 
 Among the fresh-water strata of ttis age near the base of 
 the Pyrenees are marls, limestones and sands, in which the 
 eminent comparative anatomist, M. Lartet, has obtained a 
 great number of fossil mammalia common to the faluns of 
 the Loire and the Upper Miocene beds of Switzerland, such 
 as Dmotheritim giganteum and Mastodon angustidens ; also 
 
 Voluta Lamiberti, Sow. 
 
UPPER MIOCENE OF SWITZERLAND. 215 
 
 tbe_ bones of quadrumana, or of the ape and monkey tribe, 
 which were discovered in 1837, the first of that order of 
 quadrupeds detected in Eui-ope. They were found near 
 Auch, in the Department of Gers, in latitude 43° 39' N. 
 about forty miles west of Toulouse. They were referred by 
 MM. Lartet and Blainville to a genus closely allied to the 
 Gibbon, to which they gave the name of Pliopithecus. Sub- 
 sequently, in 1856, M. Lartet described another species of 
 the same family of long-armed apes {Hylohates), which he 
 obtained from strata of the same age at Saint-Gaudens, in 
 the Haute Garonne. The fossil remains of this animal con- 
 sisted of a portion of a lower jaw with teeth and the shaft 
 of a humerus. It is supposed to have been a tree-climbing 
 frugivorous ape, equalling man in stature. As the trunks 
 of oaks are common in the lignite beds in which it lay, it 
 has received the generic name of Dryopitheeus. The angle 
 formed by the ascending ramus of the jaw and the alveolar 
 border is less open, and therefore more like the human sub- 
 ject, than in the Chimpanzee, and what is still more remark- 
 able, the fossil, a young but adult individual, had all its milk 
 teeth replaced by the second set, while its last true molar 
 (or wisdom-tooth) was still undeveloped, or only existed as 
 a germ in the jaw-bone. In the mode, therefore, of the suc- 
 cession of its teeth (which, as in all the Old-World apes, ex- 
 actly agree in number with those in man) it diifered from 
 the Gorilla and Chimpanzee, and corresponded with the hu- 
 man species. 
 
 Upper Miocene Beds of (Eningen, in Switzerland. — The fa- 
 luns of the Loire first served, as already stated (page 211), 
 as the type of the Miocene formations in Europe. They 
 yielded a plentiful harvest of marine fossil shells and corals, 
 but were entirely barren of plants and insects. In Switzer- 
 land, on the other hand, deposits of the same age have been 
 discovered, remarkable for their botanical and entomological 
 treasures. "We are indebted to Professor Heer, of Zurich, for 
 the description, restoration, and classification of several hun- 
 dred species and varieties of these fossil plants, the whole of 
 which he has illustrated by excellent figures in his " Flora 
 Tertiaria Helvetise." This great work, and those of Adolphe 
 Brongniart, linger, Goeppert and others, show that this class 
 of fossils is beginning to play the same important part in 
 the classification of the tertiary strata containing lignite or 
 brown coal as an older flora has long played in enabling us 
 to understand the ancient coal or carboniferous formation. 
 No small skepticism has always prevailed among botanists 
 as to whether the leaves alone and the wood of plants could 
 
216 ELEMENTS OF GEOLOGY. 
 
 ever aflford sufficient data for determining even genera and 
 families in the vegetable kingdom. In truth, before such 
 remains could be rendered available a new science had to 
 be created. It was necessary to study the outlines, nerva- 
 tion, and microscopic structure of the leaves, with a degree 
 of care which had never been called for in the classification 
 of living plants, where the flower and fruit aflforded charac- 
 ters so much more definite and satisfactory. As geologists, 
 we can not be too grateful to those who, instead of despair- 
 ing when so difficult a task was presented to them, or being 
 discouraged when men of the highest scientific attainments 
 treated the fossil leaves as worthless, entered with full faith 
 and enthusiasm into this new and unexplored field. That 
 they should frequently have fallen into errors was unavoid- 
 able, but it is remarkable, especially if we inquire into the 
 history of Professor Heer's researches, how often eai'ly cou- 
 jectui'es as to the genus and family founded on the leaves 
 alone were afterwards confirmed when fuller information 
 was obtained. As examples to be found on comparing 
 Heer's earlier and later works, I may instance the chestnut, 
 elm, maple, cinnamon, magnolia, buckbean or Menyanthes, 
 vine, buckthorn {Rhamnus), Andromeda and Myrica, and 
 among the conifers Sequoia and Taxodium. In all these 
 cases the plants were first recognized by their leaves, and 
 the accuracy of the determination was afterwards confirmed 
 when the fruit, and in some instances both fruit and flower, 
 were found attached to the same stem as the leaves. 
 
 But let us suppose that no fruit, seed, or flower had ever 
 been met with in a fossil state, we should still have been in- 
 debted to the persevering labors of botanical palsBontologists 
 for one of the grandest scientific discoveries for which the 
 present century is ]-eraarkable — namely, the proofs noW es- 
 tablished of the prevalence of a mild climate and a rich ar- 
 borescent flora in the arctic regions in that Miocene epoch 
 on the history of which we are now entering. It may be 
 useful if I endeavor to give the reader in a few words some 
 idea of the nature of the evidence of these important conclu- 
 sions, to show how far they may be safely based on fossil 
 leaves alone. When we begin by studying the fossils of the 
 Newer Pliocene deposits, such as those of the Upper Val 
 d'Arno, before alluded to, we perceive that the fossil foliage 
 agrees almost entirely with the trees and shrubs of a mod- 
 ern European forest. In the plants of the Older Pliocene 
 strata of the same region we observe a larger proportion of 
 species and genera which, although they may agree with 
 well-known Asiatic or other foreign types, are at present 
 
UPPER FRESH-WATER MOLASSH. 217 
 
 wanting in Italy. If we then examine the Miocene forma- 
 tions of the same country, exotic forms become more abun- 
 dant, especially the palms, whether they belong to the Eu- 
 ropean or American fan-palms, Cliamcerops and Sabal, or to 
 the more tropical family of the date-palms or .Phoenicites, 
 which last are conspicuous in the Lower Miocene beds of 
 Central Europe. Although we have not found the fruit or 
 flower of these palms in a fossil state, the leaves are so char- 
 acteristic that no one doubts the family to which they be- 
 long, or hesitates to accept them as indications of a warm 
 and sub-tropical climate. 
 
 When the Miocene formations are traced to the north- 
 ward of the 50th degree ot latitude, the fossil palms fail us, 
 but the greater proportion of the leaves, whether identical 
 with those of existing European trees or of forms now un- 
 known in Europe, which had accompanied the Miocene palms, 
 still continue to characterize rocks of the same age, until we 
 meet with them not only in Iceland, but in Greenland, in lat- 
 itude 70° N., and in Spitzbergen, lat. 78° 56', or within about 
 11 degrees of the pole, and under circumstances which clear- 
 ly show them to have been indigenous in those regions, and 
 not to havcbeen drifted from the south (see p. 240). Not only, 
 therefore, has the botanist afforded the geologist much pa- 
 Iseontological assistance in identifying distinct tertiary for- 
 mations in distant places by his power of accurately discrim- 
 inating the forms, veining, and microscopic structure of leaves 
 or wood, but, independently of that exact knowledge deriv- 
 able from the organs of fructification, we are indebted to 
 him for one of the most novel, unexpected results of modern 
 scientific inquiry. 
 
 The Miocene formations of Switzerland have been called 
 Molasse, a terra derived from the French mol, and applied to 
 a soft, incoherent, greenish sandstone, occupying the country 
 between the Alps and the Jura. This molasse comprises 
 ^hree divisions, of which the middle one is marine, and being 
 closely related by its shells to the faluns of Touraine, may 
 be classed as Upper Miocene. The two others are fresh-wa- 
 ter, the upper of which may be also grouped with the faluns, 
 while the lower must be referred to the Lower Miocene, as 
 defined in the next chapter. 
 
 Tipper Fresh-water Molasse. — This formation is best seen 
 at CEningen, in the valley of the Rhine, between Constance 
 and Schaffhausen, a locality celebrated for having produced 
 in the year 1700 the supposed human skeleton called by 
 Scheuchzer " homo diluvii testis," a fossil afterwards demon- 
 strated by Cuvier to be a reptile, or aquatic salamander, of 
 
 10 
 
218 ELEMENTS OF GEOLOGY. 
 
 larger dimensions than even its great living representative, 
 the salamander of Japan. 
 
 The OEningen strata consist of a series of marls and lime- 
 stones, many of them thinly laminated, and which appear to 
 have slowly accumulated in a lake probably fed by springs 
 molding carbonate of lime in solution. The elliptical area 
 over which this fresh-water formation has been traced ex- 
 tends, according to Sir Roderick Murchison, for a distance of 
 ten miles east and west from Berlingen, on the right bank of 
 the river to Wangen, and to CEningen, near Stein, on the left 
 bank. The organic remains have been chiefly derived from 
 two quarries, the lower of which is about 550 feet above the 
 level of the Lake of Constance, while the upper quarry is 150 
 feet higher. In this last, a section thirty feet deep displays 
 a great succession of beds, most of them splitting into slabs 
 and some into very thin laminae. Twenty-one beds are enu- 
 merated by Professor Heer, the uppermost a bluish-gray marl 
 seven feet thick, with organic remains, resting on a limestone 
 with fossil plants, including leaves of poplar, cinnamon, and 
 pond-weed {Potamogeton), together with some insects ; while 
 in the bed No. 4, below, is a bituminous rock, in which the 
 Mastodon tapiroides, a characteristic Upper Miocene quadru- 
 ped, has been met with. The 5th bed, two or three inches 
 thick, contains fossil fish, e. g., Leuciscus (roach), and the larvae 
 of dragon-flies, with plants such as the elm ( Ulnvus), and the 
 aquatic Chara. Below this are other plant-beds ; and then, 
 in No. 9, the stone in which the great salamander {Andrias 
 Scheuchzeri) and some fish were found. Below this other 
 strata occur with fish, tortoises, the great salamander before 
 alluded to, fresh-water mussels, and plants. In No. 16 the 
 fossil fox of CEningen, Gahcynus (Ening0nsis,OyfGn,-<fii[.%6h- 
 tained by Sir R. Murchison. To this succeed other beds with 
 mammalia {Lagomys), reptiles (Emys), fish, and plants, such 
 as walnut, maple, and poplar. In the 19th bed are numerous 
 fish, insects, and plants, below which are marls of a blue in- 
 digo color. 
 
 In the lower quarry eleven beds are mentioned, in which, 
 as in the upper, both land and fresh-water plants and many 
 insects occur. In the 6th, reckoning from the top, many 
 plants have been obtained, such as Liquidambar, Daphnogmie, 
 Podogonium, and Ulmus, together with tortoises, besides the 
 bones and teeth of a ruminant quadruped, named by H. von 
 Meyer PakBonwryx eminens. No. 9 is called the insect-bed, 
 a layer only a few inches thick, which, when exposed to the 
 frost, splits into leaves as thin as paper. In these thin laminae 
 plants such as Liquidambar, Daphnogene, and Glyptostrohm, 
 
UPPER MIOCENE OP SWITZERLAND. 
 
 219 
 
 occur, with innumerable insects in a wonderful state of pres- 
 ervation, usually found singly. Below this is an indigo-blue 
 marl, like that at the bottom of the higher quarry, resting on 
 yellow marl ascertained to be at least thirty feet thick. 
 
 All the above fossil-bearing strata were evidently formed 
 with extreme slowness. Although the fossiliferous beds are, 
 in the aggregate, not more than a few yards in thickness, and 
 have only been examined in the small area comprised in the 
 two quarries just alluded to, they give us an insight into the 
 state of animal and vegetable life in part of the Upper Mio- 
 cene period, such as no other region in the world has else- 
 where supplied. In the year 1859, Prof. Heer had ah-eady 
 determined no less than 475 species of plants and more than 
 800 insects from these CEningen beds. He supposes that a 
 river entering a lake floated into it some of the leaves and 
 land insects, together with the carcasses of quadrupeds, 
 among others a great Mastodon. Occasionally, during tem- 
 pests, twigs and even boughs of trees with their leaves were 
 torn off and carried for some distance so as to reach the lake. 
 Springs, containing carbonate of lime, seem at some points to 
 have supplied calcareous matter in solution, giving origin lo- 
 cally to a kind of travertin, in which organic bodies sinking 
 to the bottom became hermetically sealed Up. The laminae, 
 says Heer, which immediately succeed each other were not 
 all formed at the same season, for it can be shown that, when 
 some of them Originated, certain plants were in flower, where- 
 as, when the next of these layers was produced, the same 
 plants had ripened their fruit. This infer- 
 Fig. 138. ence is confirmed by independent proofs de- 
 
 rived from insects. The principal insect-bed 
 is rarely two inches thick, and is composed, 
 says Heer, of about 250 leaf-like laminae, some 
 of which were deposited in the spring, when 
 the Cinnamomum polymorphum (Fig. 138) 
 was inflower, others in 
 summer, when winged 
 ants were numerous, 
 and when the poplar 
 and willow had ma- 
 tured their seed; oth- 
 ers, again, in autumn, 
 when the same Giwiia- 
 momum polymorphum 
 (Fig. 138) was in fruit; 
 as well as the liquid- 
 ambar, oak, clematis, 
 
 Upper 
 
 Cinnamummm polymorphwm, Ad. Bi'ong. 
 and Lower Miocene. 
 
 a. Leaf. b. Flower, nat. size ; Heer, P1.93, Fig. 28. 
 c. Einc frnit of CinrMmomwmpolyrnorpTiwn, from 
 (Eningen ; Heer, PI. 94, Fig. 14. d. Frmt of recent 
 Cimiamomum camphonem of Japan ; ueer, ri. 
 1S2, Fig. 18. 
 
220 ELEMENTS OP GEOLOGY. 
 
 and many other plants. The ancient lake seems to have 
 had a belt of poplars and willows round its borders, count- 
 less leaves of which were imbedded in mud, and together 
 with them, at some points, a species of reed, Arundo, which 
 was very common. 
 
 One of the most characteristic shrubs is a papilionaceous 
 and leguminous plant of an extinct genus, called by Heer 
 JPodogoniufn, of which two species are known. Entire twigs 
 have been found with flowers, and always without leaves, as 
 the flowers evidently came out, as in the poplar and willow 
 tribe, before any leaves made their appearance. Other spec- 
 imens have been obtained with ripe fruits accompanied by 
 leaves, which resemble those of the tamarind, to which it 
 was evidently allied, being of the family CsBsalpineae, now 
 proper to warmer regions. 
 
 The Upper Miocene flora of CEningen is peculiarly impor- 
 tant, in consequence of the number of genera of which not 
 merely the leaves, but, as in the case of the Podogfonium ^ust 
 mentioned, the fruit also and even the flower are known. 
 Thus there are nineteen species of maple, ten of which have 
 
 Fig. 139. '^l.^'eady . been found 
 
 with iruit. Although 
 in no one region of the 
 globe do so many ma- 
 ples now flourish, we 
 need not suspect Pro- 
 fessor Heer of having 
 made too many species 
 in this genus when we 
 consider the manner in 
 which he has dealt with 
 one of them, Acer trilo- 
 batum, Figs. 139, 140. 
 Of this plant the num- 
 ber of marked varieties 
 figured and named is 
 very great, and no less 
 
 /loer trilohatvmi, normal form; Heer, Flora Tert. than three of them had 
 Helv., PI. 114, Fig. 2. Size i aiam. (Part only of i, „ •-, ■■ j- 
 
 thelongstalkofflieorigiiialfosailspecimeuishere "^^en Considered aS QIS- 
 
 !?owSm7oS^/S^S.^'"=^''°'''"°'*'^ *'°°t ?Pe«ies by other 
 
 botanists, while six of 
 the others might have laid claim, with nearly equal proprie- 
 ty, to a like distinction. The common form, called Acer tri- 
 lobatum. Fig. 139, may be taken as a normal representative 
 of the CEningen fossil, and Fig. 140, as one of the most diver- 
 gent varieties, having almost four lobes in the leaf instead 
 of three. 
 
MIOCENE STEATA OF SWITZERLAND. 
 
 *"jg. 140. 
 
 221 
 
 Acer trihiatum. 
 
 a. Abnonnal variety of leaf; Heer, PI. 110, Fig. 16. b. Mower and bracts, norma] 
 form J Heer, PI. 1l1, Fig. 21. c. Half a seed-vessel ; Heer, PI. Ill, Fig. 6. 
 
 Among the conspicuous genera which abounded in the 
 Miocene period in Europe is the plane-tree, Platanm, the 
 fossil species being considered by 
 Heer to come nearer to the American ^'^" ^*'' 
 
 P. occidentalis than to P. orientalis of 
 Greece and Asia Minor. In some of 
 the fossil specimens the male flowers 
 are preserved. Among other points 
 of resemblance with the living plane- 
 trees, as we see them in the parks 
 and squares of London, fossil frag- 
 ments of the trunk are met with, hav- 
 ing pieces of their bark peeling off. 
 
 The vine of CEningen, Vitis teuton- 
 tea. Ad. Brong., is of a North Ameri- p;ato™«MeroMc«,a>pp.; Heer, 
 
 ' -r. .7 .1 1 1 T PI. 88, Figs. 5-S. Sizefdiam. 
 
 can type. JtSOth the leaves and seeds upper Miocene, CEningen. 
 
 have been found at CEningen, and a. leaf. ft. The core of a bundle 
 bunches of compressed grapes of the peSpTSurai si"^'^ '™'' "' 
 same species have been met with in 
 
 the brown coal of Wetteravia in Germany. No less than 
 eight species of smilax, a monocotyledonous genus, occur at 
 CEningen and in other Upper Miocene localities, the flowers 
 of some of them, as well as the leaves, being preserved ; as in 
 the case of the very common fossil, 8. sagittifera. Fig. 142, a. 
 Leaves of plants supposed to belong to the order Proteaceae 
 have been obtained partly from CEningen and partly from the 
 lacustrine formation of the same age at Lode in the Jura. 
 They have been referred to the genera Banksia, Grevillea, 
 Sakea, and Persoonia. Of Hakea there is the impression of 
 a supposed seed-vessel, with its characteristic thick stalk and 
 seeds, but as the fruit is without structure, and has not yet 
 
222 
 
 ELEMENTS OF GEOLOGY. 
 
 Smilax sagiUifera; Heer, PI. 30, flg. 7. 
 i diameter. 
 
 Size 
 
 Fig. 142. been found attached to the 
 
 same stem as the leaf, the 
 proof is incomplete. 
 
 To whatever family the 
 foliage hitherto regarded as 
 proteaceous by many able 
 palaeontologists may even- 
 tually be shown to belong, 
 we must be careful not to 
 question their affinity to 
 that order of plants on those 
 geographical considerations 
 which have influenced some 
 botanists. The nearest liv- 
 
 a. Leaf. 6. Flower magnified, one of tlie ing Proteacese now flourish 
 six petals wanting at 3. TJpper Miocene, ■ ° k-< • • • i . n„o xr 
 
 (Eningen. c. St^Uax owXvoHa; B.eer, m Abyssmia m lat. 20 JSI., 
 
 Sinin-'S^' "' "*'■ ^"^' ^''''*' *'''"=^°^' but the greatest number are 
 
 confined to the Cape and 
 Australia. The ancestors, however, of the CEningen fossils 
 ought not to be look- 
 ed for in such distant '^" 
 regions,but from that 
 European land which 
 in Lower Miocene 
 times bore trees with 
 similar foliage, and 
 these had doubtless 
 an Eocene source, for 
 cones admitted by all 
 botanists to be pro- 
 teaceous have been 
 met with in one di- 
 vision of that older 
 Tertiary group (see 
 Fig. 206, p. 265). The source of these last, again, must not be 
 sought in the antipodes, for in the white chalk of Aix-la-Cha- 
 pelle leaves like those of Grevillea and other proteaceous 
 genera have been found in abundance, and as we shall see 
 (p. 304) in a most perfect state of preservation. All geolo- 
 gists agree that the distribution of the cretaceous land and 
 sea had scarcely any connection with the present geography 
 of the globe. 
 
 In the same beds with the supposed Proteacese there oc- 
 curs at Locle a fan-palm of the American type Sabal (for ge- 
 nus see Fig. 151), a genus which ranges throughout the low 
 country near the sea from the Carolinas to Florida and Lou- 
 
 Fruit of the fossil and recent species of Haken, a genns 
 of Proteacese. 
 
 a Leaf of fossil species, Hakm salicirui. Upper Mio- 
 cene, CEningen ; Heer, PI. 97, Fig. 29. i diara. ft. Im- 
 pression of woody frnit of same, showing thick stalk. 
 i diam. c. Seed of same, nat. size. d. Fruit of 
 living Australian species, Hakea ealigna, K. Brown. 
 i diam. e. Seed of same, uat. size. 
 
MIOCENE STBATA OE SWITZERLAND. 223 
 
 isiana. Among the Coniferse of Upper Kg. 144. 
 
 Miocene age is found a deciduous cypress 
 
 nearly allied to the Taxodium disticlmm 
 
 of North America, and a Glyptostrobus 
 
 (Fig. ] 44), very like the Japanese G. het- 
 
 erophyllus, now common in our shrub- 
 
 beiies. 
 
 Before the appearance of Heer's work 
 on the Miocene Flora of Switzerland, 
 Unger and Goppert had already pointed 
 out the large proportion of living North ''t^^^^.^^XTm:, 
 American genera which distinguished the Heer, Pi. 20, Fig. 1. Up. 
 vegetation of the Miocene period in Cen- P"' ^""'°'' *^°"^™- 
 tral Europe. Next in number, says Heer, to these American 
 forms at CEningen the European genera preponderate, the 
 Asiatic ranking in the third, the African in the fourth, and 
 the Australian in the fifth degree. The American forms are 
 more numerous than in the Italian Pliocene flora, and the 
 whole vegetation indicates a warmer climate than the Plio- 
 cene, though not so high a temperature as that of the older 
 or Lower Miocene period. 
 
 The conclusions drawn from the insects are for the most 
 part in perfect harmony with those derived from the plants, 
 but they have a somewhat less tropical and less American 
 aspect, the South European types being more numerous. 
 Oa the whole, the insect fauna is richer than that now inhab- 
 iting any part of Europe. No less than 844 species are reck- 
 oned by Heer from the CEningen beds alone, the number of 
 specimens which he has examined being 5080. The entire list 
 of Swiss species from the Upper and Lower Miocene together 
 amount to 1322. Almost all the living families of Coleoptera 
 are represented, but, as we might have anticipated from the 
 preponderance of arborescent and ligneous plants, the wood- 
 eating beetles play the most conspicuous part, the Buprestidse 
 and other long-horned beetles being particularly abundant. 
 
 The patterns and some remains of the colors both of Cole- 
 optera and Semiptera are preserved at CEningen, as, for ex- 
 ample, in the annexed figure of Sarpactor, in which the an- 
 tennae, one of the eyes, and the legs and wings are retained. 
 The characters, indeed, of many of the insects are so well 
 defined as to incline us to believe that if this class of the 
 invertebrata were not so rare and local, they might be more 
 useful than even the plants and shells in settling chronolog- 
 ical points in geology. 
 
 Middle or Marine Molasse (Upper Miocene) of Switzerland.— 
 It was before stated that the Miocene formation of Switzer- 
 
224 
 
 ELEMENTS OF GEOLOGY. 
 
 Harpactor tnacuUpea^ Hecr. 
 Miocene, (Euingen, 
 
 Upper 
 
 Fig. 14B. land consisted of, 1st, the upper 
 
 fresh -water molasse, comprising 
 the lacustrine marls of CEningen ; 
 2dly, the marine molasse, corre- 
 sponding in age to the faluns of 
 Touraine ; and 3dly, the lower 
 fresh-water molasse. Some of the 
 beds of the marine or middle series 
 reach a height of 2470 feet above 
 the sea. A large number of the 
 shells are common to the faluns 
 of Touraine, the Vienna basin, and 
 other Upper Miocene localities. 
 The terrestrial plants play a sub- 
 ordinate part in the fossiliferous 
 beds, yet more than ninety of them 
 are enumerated by Heer as belong- 
 ing to this falunian division, and of 
 these more than half are common 
 to subjacent Lower Miocene beds, while a proportion of about 
 forty-five in one hundred are common to the overlying CEnin- 
 gen flora. Twenty-six of the ninety-two species are peculiar. 
 Upper Miocene of the Bolderberg, in Belgium. — In a small 
 hill or ridge called the Bolderberg, which I visited in 1851, 
 situated near Hasselt, about forty miles E.N.E. of Brussels, 
 strata of sand and gravel occur, to which M. Dumont first 
 called attention as appearing to constitute a northern repre- 
 sentative of the faluns of Touraine. On the whole, they are 
 very distinct in their fossils from the two upper divisions of 
 the Antwerp Crag before mentioned (p. 
 204), and contain shells of the genera Oliva, 
 Conits, AncUlaria, Pleurotomd, and Cancel- 
 laria in abundance. The most common 
 shell is an Olive (Fig. 146), called by Nyst 
 Oliva Dufresnii; and constituting, as M. 
 Bosquet observes, a smaller and shorter va- 
 riety of the Bordeaux species. 
 
 So far as the shells of the Bolderberg are 
 known, the proportion of recent species 
 agrees with that in the faluns of Touraine, 
 and the climate must have been warmer than that of the Cor- 
 alline Crag of England. 
 
 Upper Miocene Beds of the Vienna Basin. — In South Ger- 
 many the general resemblance of the shells of the Vienna 
 tertiary basin with those of the faluns of Touraine has long 
 been acknowledged. In the late Dr. Hornes's excellent work 
 
 Fig. 146. 
 
 Oliva Dufresnii, Bast 
 Bolderberg, Belginiii ; 
 natural size. a,_ front 
 view ; b, back view. 
 
UPPER MIOCENE BEDS, VIENNA. 225 
 
 on the fossil mollusca of that formation, we see accurate fig- 
 ures of many shells, clearly of the same species as those 
 found in the falunian sands of Touraine. 
 
 According to Professor Suess, the most ancient and purely 
 marine of the Miocene strata in this basin consist of sands, 
 conglomerates, limestones, and clays, and they are inclined 
 inwardj or from the borders of the trough towards the cen- 
 tre, their outcropping edges rising much higher than the new- 
 er beds, whether Miocene or Pliocene, which overlie them, 
 and which occupy a smaller area at an inferior elevation 
 above the sea. M. Homes has described no less than 500 
 species of gasteropods, of which he identifies one-fifth with 
 living species of the Mediterranean, Indian, or African seas, 
 but the proportion of existing species among the lamelli- 
 branchiate bivalves exceeds this average. Among many 
 univalves agreeing with those of Africa on the eastern side 
 of the Atlantic are Cyprcea sanguinolenta, Buccinum lyra- 
 turn, and Oliva flammulata. In the lowest marine beds of 
 the Vienna basin the remains of several mammalia have been 
 found, and among them a species of Dinotherium, a Masto- 
 don of the Trilophodon family, a Rhinoceros (allied to R. 
 ■megarhimts, Christol), also an animal of the hog tribe, iis^n- 
 odon. Von Meyer, and a carnivorous animal of the canine 
 family. The JSelix twonensis (Fig. 38, p. 56), the most com- 
 mon land shell of the French faluns, accompanies the above 
 land animals. In a higher member of the Vienna Miocene 
 series are found Dlnotherium giganteum (Fig. 136, p. 212), 
 Mastodon longirostris, Rhinoceros Schleiermacheri, Acerothe- 
 rium incisivuni, and Hippotheriwm gracile, all of them equally 
 characteristic of an Upper Miocene deposit occurring at Ep- 
 pelsheim, in Hesse Darmstadt ; a locality also remarkable as 
 having furnished in latitude 49° 60' N. the bone of a large 
 ape of the Gibbon kind, the most north- _,. . 
 
 erly example yet "discovered of a quadru- 
 manous animal. 
 
 M. Alcide d'Orbigny has shown that 
 the foraminifera of the Vienna basin dif- 
 fer alike from the Eocene and Pliocene 
 species, and agi'ee with those of the fa- 
 luns, so far as the latter are known. 
 
 Among the Vienna foraminifera, the ge- Amphintegina Hauenna, 
 nus Amphistegina (Fig. 1 47) is very char- S^"vi?n?.a."""*"^ 
 acteristic, and is supposed by d'Archiac to 
 take the same place among the Rhizopods of the Upper Mio- 
 cene era which the Nummulites occupy in the Eocene period. 
 
 The flora of the Vienna basin exhibits some species which 
 
 10* 
 
226 ELEMENTS OF GEOLOGY. 
 
 have a general range through the whole Miocene period, such 
 as Ginnamomum polymorphum (Fig. 138), and G. Schmchzeri, 
 also Flanera Bichardi, Mich., Liquidambar europcmm (Fig. 
 185, p. 209), Juglans bilinica, Gassia ambigua, and C. lignir 
 turn. Among the plants common to the Upper Miocene beds 
 of CEningen, in Switzerland, are Platanus aceroides (Fig. 141, 
 p. 221), Myrica vindobonensis, and others. 
 
 Upper Miocene Strata of Italy. — We are indebted to Sign^ 
 or Michelotti for a valuable work on the Miocene shells of 
 Iforthern Italy. Those found in the hill called th,e Superga, 
 near Turin, have long been known to correspond in age with 
 the faluns of Touraine, and they contain so many species com- 
 mon to the Upper Miocene strata of Bordeaux as to lead to 
 the conclusion that there was a free communication between 
 the northern part of the Mediterranean and the Bay of Bis- 
 cay in the Upper Miocene period. 
 
 Upper Miocene Formations of Greece. — At Pikerme, near 
 Athens, MM. Wagner and Roth have described a deposit in 
 which they found the remains of the genera Mastodon, Di- 
 notherium, Hipparion, two species of Giraffe, Antelope, and 
 others, some living and some extinct. With them were also 
 associated fossil bones of the Semnopithecus, shovfing that 
 here, as in the south of France, the quadnimana were char- 
 acteristic of this period. The whole fauna attests the former 
 extension of a vast expanse of grassy plains where we have 
 now the broken and mountainous country of Greece ;; plains, 
 which were probably united with Asia Minor, spreading over 
 the area where the deep ^gean Sea and its numerous islands 
 are now situated. We are indebted to M. Gaudry, who vis- 
 ited Pikerm6, for a treatise on these fossil bones, showing 
 how many data they contribute to the theory of a transition 
 from the mammalia of the Upper Miocene through the Plio- 
 cene and Post-pliocene forms to those of living genera and 
 species. 
 
 Upper Miocene of India. Siwalik Hills.— The Siw^lik Hills 
 lie at the southern foot of the Himalayan chain, rising to the 
 height of 2000 and 3000 feet. Between the Jumna and the 
 Ganges they consist of inclined strata of sandstone, shingle, 
 clay, and marl. We are indebted to the indefatigable re- 
 searches of Dr. Falconer and Sir Proby Cautley, continued 
 for fifteen years, for the discovery in these marls and sand- 
 stones of a great variety of fossil mammalia and reptiles, to- 
 gether with many fresh-water shells. Out of fifteen species 
 of shells of the genera Paludina, Melania, Ampidlaria, and 
 Unio, all are extinct or unknown species with the exception, 
 of four, which are still inhabitants of Indian rivers. Such a 
 
UPPER MIOCENE OF INDIA. 227 
 
 proportion of living to extinct mollusca agrees well with the 
 usual character of an Upper Miocene or Falunian fauna, as 
 observed in Touraine, or in the basin of Vienna and else-; 
 where. 
 
 The genera of mammalia point in the same direction. One 
 of them, of the genus Chalicotherium (or Anisodon of Lar- 
 tet), is a pachyderm intermediate between the Rhinoceros 
 and Anoplothere, and characteristic of the Upper Miocene 
 strata of Eppelsheim, and of the south of France. With it 
 occurs also an extinct form of Hippopotamus, called Hexa- 
 protodon, and a species of Hippotheriuni and pig, also two 
 species of Mastodon-, two of elephant, and three other ele- 
 phantine proboscidians ; none of them agreeing with any fos- 
 sil forms of Europe, and being intermediate between the gen- 
 era Elephas and Mastodon, constituting the sub-genus Stego- 
 don of Falconer. With these are associated a monkey, al- 
 lied to the Semnopithecus entelius, now living in the Himalaya, 
 and many ruminants. Among these last, besides the giraife, 
 camel, antelope, stag, and others, we find a remarkable new 
 type, the Sivatherium, like a gigantic four-horned , deer. 
 There are also new forms of carniyora, both feline and canine, 
 the Machairodus among the former, also hyaenas, and a sub- 
 ursine form called the Hymnarctos, and a genus allied to the 
 otter {Enhydriodon), of formidable size. 
 
 The giraffe, camel, and a large ostrich ma,y be cited as 
 proofs that there were formerly extensive plains where now 
 a steep chain of hills, with deep ravines, runs for many hun- 
 dred miles east and west. Among the accompanying reptiles 
 are several crocodiles, some of huge dimensions, and one not 
 distinguishable, says Dr. Falconer, from a species now living 
 in the Ganges (C. Gangetims) ; and there is still another sau- 
 rian which the same anatomist has identified with a species 
 now inhabiting India. There was also an extinct species of 
 tortoise of gigantic proportions {Colossochelys Atlas), the 
 curved shell of which was twelve feet three inches long and 
 eight feet in diameter, the entire length of the animal being 
 estimated at eighteen feet, and its probable height seven feet. 
 
 Numerous fossils of the Siwalik type have also been found 
 in Perim Island, in the Gulf of Cambay, and_ among these a 
 species of Dinotherium, a genus so characteristic of the Up- 
 per Miocene period in Europe. tt -j. j 
 
 Older Pliocene and Miocene rormations m the Unitett 
 States.— Between the Alleghany Mountains, formed of older 
 rocks, and the Atlantic, tliere intervenes, in the United States, 
 a low region occupied principally by beds of marl, clay, and 
 sand consisting of the cretaceous and tertiary formations, 
 
228 ELEMENTS OE GEOLOGY. 
 
 and chiefly of the latter. The general elevation of this plain 
 bordei-inff the Atlantic does not exceed 100 feet.although it 
 is sometimes several hundred feet high. Its width" in the 
 middle and southern states is very commonly from 100 to 
 150 miles. It consists, in the South, as in Georgia, Alabama, 
 and South Carolina, almost exclusively of Eocene deposits; 
 but in North Carolina, Maryland, Virginia, Delaware more 
 modern strata predominate, of the age of the English Crag 
 and faluns of Touraine.* 
 
 Fig. 148. 
 
 Fig. 149. 
 
 FvXgur ca-naliculatv^. Maryland. 
 
 }*\mts quadri£08tatuSy Say, Maryland. 
 
 In the Virginian sands, we find in great abundance a spe- 
 cies of Astarte {A. undulata, Conrad), which resembles close- 
 ly, and may possibly be a variety of, one of the commonest 
 fossils of the Suffolk Crag {A. Omalii) ; the other shells also, 
 of the genera JVatica, Fissurdla, Artemis, Ijucina, Chama, Pec- 
 tunculus, and Pecten, are analogous to shells both of the Eng- 
 lish Crag and French faluns, although the species are almost 
 all distinct. Out of 14*7 of these American fossils I could 
 only find thirteen species common to Europe, and these occur 
 partly in the Suffolk Crag, and partly in the faluns of Tou- 
 raine ; but it is an important characteristic of the American 
 group, that it not only contains many peculiar extinct forms, 
 such as Fusus quadricostatus, Say (see Fig. 149), and Venus 
 tridaenoides, abundant in these same formations, but also some 
 shells which, like Fulgur carica of Say and F. canaMculatus 
 (see Fig. 148), Galyptroea costata, Venus mercenaria, Lam., 
 Mbdiola glaniktla, Totten, and Pecten magellanicus, Lam., 
 are recent species, yet of forms now confined to the western 
 side of the Atlantic — a fact implying that some traces of the 
 beginning of the present geographical distribution of mollus- 
 * Proceed, of the Geol. Soc, vol. iv., pt. iii., 1845, p. 547. 
 
MIOCENE STRATA OF VIRGINIA. 
 
 229 
 
 ca date back to a period as remote as that of the Miocene 
 strata. 
 
 Of ten species of corals which I procured on the hanks of 
 the James River, one agrees generically with a coral now 
 living on the coast of the United States. Mr. Lonsdale re- 
 garded these corals as indicating a temperature exceeding 
 that of the Mediterranean, and the 
 shells would lead to similar conclu- 
 sions. Those occurring on the James 
 River are in the 37th degree of N. lat- 
 itude, while the French faluns are in 
 the 4'7th ; yet the forms of the Amer- 
 ican fossils would scarcely imply so 
 warm a climate as must have prevailed 
 in France when the Miocene strata of 
 Touraine originated. 
 
 Among the remains of fish in these Astramjia Uneata, Lonsdale. 
 
 post-eocene strata of the United States f^Sijf^'s^rgfv^iniT'"'^ 
 are several large teeth of the shark 
 
 family, not distinguishable specifically from fossils of the fa- 
 luns of Touraine. 
 
230 ELEMENTS OF GEOLOGY. 
 
 CHAPTER XV. 
 
 LOWER MIOCENE.* 
 
 Lower Miocene Strata of France. — Line between Miocene and Eocene. — 
 Lacustrine Strata of Auvergne. — Fossil Mammalia of the Limagne d'An- 
 vergne. — Lower Molasse of Switzerland. — Dense Conglomerates and Proofs 
 of Subsidence, — Flora of the Lower Molasse. — American Charactef of the 
 Flora. — Theory of a Miocene Atlantis. — Lower Miocene of Belgium. — 
 Rupelian Clay of Hermsdorf near Berlin. — Mayence Basin. — Lower Mio- 
 cene of Croatia. — Oligocene Strata of Beyrich. — Lower Miocene of Italy. 
 — Lower Miocene of Jlngland. — Hempstead Beds. — Bovey Tracy Lignites 
 in Devonshire. — Isle of Mnll Leaf-beds.— Arctic Miocene Flora. — ^Distio 
 Island. — Lower Miocene of United States. — Fossils of Nebraska. 
 
 Line between Miocene and Eocene Tormations. — The marine 
 faluns of the valley of the Loire have been already described 
 as resting in some places on a fresh-water tertiary limestone, 
 fragments of which have been broken off and rolled on the 
 shores and in the bed of the Miocene sea. Such pebbles are 
 frequent at Pontlevoy on the Cher, with hollows drilled in 
 them in which the perforating marine shells of the Falunian 
 period still remain. Such a mode of superposition implies 
 an interval of time between the origin of the fresh-water 
 limestone and its submergence beneath the waters of the Up- 
 per Miocene sea. The limestone in question forms a part of 
 the formation called the Calcaire de la Beauce, which consti- 
 tutes a large table-land between the basins of the Loire and 
 the Seine. It is associated with marls and other deposits, 
 such as may have been formed in marshes and shallow lakes 
 in the newest part of a great delta. Beds of flint, continuous 
 or in nodules, accumulated in these lakes, and aquatic plants 
 called Charae, left their stems and seed-vessels imbedded 
 both in the marl and flint, together with fresh-water and 
 land shells. Some of the siliceous rocks of this formation are 
 used extensively for mill-stones. The flat summits or plat- 
 forms of the hills round Paris, and large areas in the forest 
 of Fontainebleau, as well as the Plateau de la Beauce, already 
 alluded to, are chiefly composed of these fresh-water strata. 
 Next to these in the descending order are marine sands and 
 sandstone, commonly called the Gr^s de Fontainebleau, from 
 which a considerable number of shells, very distinct from 
 those of the faluns, have been obtained at Etampes, south of 
 
 * Oligocene of Beyrich. 
 
LOWEE MIOCENE OF CENTRAL FRANCE. 231 
 
 Paris,. and at Montmartre and other hills in Paris itself, or in 
 its suburbs. At the bottom of these sands a green clay oc- 
 curs, containing a small oyster, Ostrea eyathxda, Lam., whichj 
 although of slight thickness, is spread over a wide area. 
 This clay rests immediately on the Paris gypsum, or that se- 
 ries of beds of gypsum and gypseous marl from which Guvier 
 first obtained several species of Paleotherium and other ex- 
 tinct mammalia.* 
 
 At this junction of the clay and the gypsum the majority 
 of French geologists have always drawn the line between 
 the Middle and Lower Tertiary, or between the Miocene and 
 Eocene formations, regarding the Fontainebleau sands and 
 the Ostrea cyathrda clay as the base of the Miocene, and the 
 gypsum, with its mammalia, as the top of the Eocene group; 
 I formerly dissented from this division, but I now find that I 
 must admit it to be the only one which will agree with the 
 distribution of the Miocene mammalia, while even the mollus- 
 ca of the Fontainebleau sands, which were formerly supposed 
 to present a preponderance of affinities to an Eocene fauna, 
 have since been shown to agree more closely with the fessils 
 of certain deposits always regarded as Middle Tertiary at 
 Mayence and in Belgium. Li fact, we are now arriving at 
 that stage of progress when the line, wherever it be drawn 
 between Miocene and Eocene, will be an arbitrary one, or one 
 of mere convenience, as I shall have an opportunity of show- 
 ing when the Upper Eocene formations in the Isle of Wight 
 are described in the sixteenth chapter. 
 
 Lower Miocene of Central France. — Lacustrine strata, be- 
 longing, for the most part, to the same Miocene system as the 
 Calcaire de la Beauce, are again met with farther south in 
 Auvergne, Cantal, and Velay. They appear to be the mon- 
 uments of ancient lakes, which, like some of those now exist- 
 ing in Switzerland, once occupied the depressions in a mount- 
 ainous region, and have been each fed by one or more rivers 
 and torrents. The country where they occur is almost en- 
 tirely composed of granite and different varieties of granitic 
 schist, with here and there a few patches of Secondary strata, 
 much dislocated, and which have suffered great denudation. 
 There are also some vast piles of volcanic matter, the great- 
 er part of which is newer than the fresh-water strata, and is 
 sometimes seen to rest upon them, while a small part has ev- 
 idently been of contemporaneous origin. Of these igneous 
 rocks I shall treat more particularly in the sequel. 
 
 The study of these regions possesses a peculiar interest 
 very distinct in kind from that derivable from the investiga- 
 * Bulletin, 1856, Jonrn., vol. xii., p. 768. 
 
232 ELEMENTS OF GEOLOGY. 
 
 tion either of the Parisian or English tertiary- areas. Fol 
 •we are presented in Auvergne with the evidence of a series 
 of events of astonishing magnitude and grandeur, by which 
 the original form and features of the country have been 
 greatly changed, yet never so far obliterated but that they 
 may still, in part at least, be restored in imagination. Great 
 lakes have disappeared — lofty mountains have been formed, 
 by the reiterated emission of lava, preceded and followed by 
 showers of sand and scoriae — deep valleys have been subse- 
 quently furrowed out through masses of lacustrine and vol- 
 canic origin — at a still later date, new cones have bcec 
 thrown up in these valleys — new lakes have been formed by 
 the damming up of rivers — and more than one assemblage 
 of quadrupeds, birds, and plants, Eocene, Miocene, and Plio- 
 cene, have followed in succession ; yet the region has pre- 
 served from first to last its geographical identity ; and we 
 can still recall to our thoughts its external condition and 
 physical structure before these wonderful vicissitudes began, 
 or while a part only of the whole had been completed. 
 There was first a period when the spacious lakes, of which 
 we still may trace the boundaries, lay at the foot of mount- 
 ains of moderate elevation, unbroken by the bold peaks and 
 precipices of Mont Dor, and unadorned by the picturesque 
 outline of the Puy de Dome, or of the volcanic cones and cra- 
 ters now covering the granitic platform. During this ear- 
 lier scene of I'epose deltas were slowly formed ; beds of marl 
 and sand, several hundred feet thick, deposited ; siliceous and 
 calcai'eous rocks precipitated from the waters of mineral 
 springs ; shells and insects imbedded, together with the re- 
 mains of the crocodile and tortoise, the eggs and bones of 
 water-birds, and the skeletons of quadrupeds, most of them 
 of genera and species characteristic of the Miocene period. 
 To this tranquil condition of the surface succeeded the era of 
 volcanic eruptions, when the lakes were drained, and when 
 the fertility of the mountainous district was probably en- 
 hanced by the igneous matter ejected from below, and pour- 
 ed down upon the more sterile granite. During these erup- 
 tions, which appear to have taken place towards the close of 
 the Miocene epoch, and which continued during the Pliocene, 
 various assemblages of quadrupeds successively inhabited the 
 district, among which are found the genera mastodon, rhi- 
 noceros, elephant, tapir, hippopotamus, together with the ox, 
 various kinds of deer, the bear, hysena, and many beasts of 
 prey which ranged the forest or pastured on the plain, and 
 were occasionally overtaken by a fall of burning cinders, or 
 buried in flows of mud, such as accompany volcanic ernp- 
 
LOWER MIOCENE OF CENTRAL FRANCE. 233 
 
 tions. Lastly, these quadrupeds became extinct, and gave 
 place in their turn to the species now existing. There are 
 no signs, during the whole time required for this series of 
 events, of the sea having intervened, nor of any denudation 
 which may not have been accomplished by currents in the 
 diflerent lakes, or by rivers and floods accompanying repeat- 
 ed earthquakes, or subterranean movements, during which 
 the levels of the district have in some places been material- 
 ly modified, and perhaps the whole upraised relatively to the 
 surrounding parts of France. 
 
 Auvergne. — The most northern of the fresh-water groups 
 is situated in the valleyrplain of the Allier, which lies within 
 the department of the Puy de Dome, being the tract which 
 •went formerly by the name of the Limagne d'Auvergne. 
 The average breadth of this tract is about twenty miles ; 
 and it is for the most part composed of nearly horizontal 
 strata of sand, sandstone, calcareous marl, clay, and lime- 
 stone, none of which observe a fixed and invariable order 
 of supei'position. The ancient borders of the lake wherein 
 the fresh-water strata were accumulated may generally be 
 traced with precision, the granite and other ancient rocks 
 rising up boldly from the level country. The actual junc- 
 tion, however, of the lacustrine beds and the granite is rare- 
 ly seen, as a small valley usually intervenes between them. 
 The fresh-water strata may sometimes be seen to retain their 
 hoi'izontality within a very slight distance of the border- 
 rocks, while in some places they are inclined, and in few in- 
 stances vertical. The principal divisions into which the la- 
 custrine series may be separated are the following: — 1st, 
 Sandstone, grit, and conglomerate, including red marl and 
 red sandstone ; 2dly, Green and white foliated marls ; 3dly, 
 Limestone, or travertin, often oolitic in structure; 4thly, 
 Gypseous mai'ls. 
 
 The relations of these different groups can not be learnt 
 by the study of any one section ; and the geologist who sets 
 out with the expectation of finding a fixed order of succes- 
 sion may perhaps complain that the different parts of the 
 basin give contradictory results. The arenaceous division, 
 the marls, and the limestone may all be seen in some places 
 to alternate with each other; yet it can by no means be af- 
 firmed that there is no order of arrangement. The sands, 
 sandstone, and conglomerate constitute in general a littoral 
 group ; the foliated white and green marl, a contemporane- 
 ous central deposit more than 700 feet thick, and thinly foli- 
 ated, a character which often arises from the innumerable 
 thin shells or carapace valves shed by the small crustacean 
 
234 ELEMENTS OF GEOLOGY. 
 
 called Cypris in the ancient lakes of Auvergne ; and lastly 
 the limestone is for the most part subordinate to the newer 
 portions of both the above formations. 
 
 It seems that, when the ancient lake of the Limagne first 
 began to be filled with sediment, no volcanic action had yet 
 produced lava and scoriae on any part of the surface of Au- 
 vergne. No pebbles, therefore, of lava were transported into 
 the lake— no fragments of volcanic rocks imbedded in the 
 conglomerate. But at a later period, when a considerable 
 thickness of sandstone and marl had accumulated, eruptions 
 broke out, and lava and tuff were deposited, at some spots, 
 alternately with the lacustrine strata. It is not improbable 
 that cold and thermal springs, holding different mineral in- 
 gredients in solution, became more numerous during the suc- 
 cessive convulsions attending this development of volcanic 
 agency, and thus deposits of carbonate and sulphate of lime, 
 silex, and other minerals were produced. Hence these min- 
 erals predominate in the uppermost strata. The subterra- 
 nean movements may then have continued until they altered 
 the relative levels of the country, and caused the waters of 
 the lakes to be drained off, and the further accumulation of 
 regular fresh-water strata to cease. 
 
 Lower Miocene Mammalia of the Limagne. — It is scarcely 
 possible to determine the age of the oldest part of the fresh- 
 water series of the Limagne, large masses both of the sandy 
 and marly strata being devoid of fossils. Some of the lowest 
 beds may be of Upper Eocene date, although, according to 
 M. Pomel, only one bone of a Paleotherium has been discov- 
 ered in Auvergne. But in Velay, in strata containing some 
 species of fossil mammalia common to the Limagne, no less 
 than four species of Paleothere have been found by M. Ay- 
 mard, and one of these is generally supposed to be identical 
 with Paleotherium magnum, an undoubted Upper Eocene fos- 
 sil, of the Paris gypsum, the other three being peculiar. 
 
 Not a few of the other mammalia of the Limagne belong 
 undoubtedly to genera and species elsewhere proper to the 
 Lower Miocene. Thus, for example, the Cainotherium of 
 Bravard, a genus not far removed from the Anoplotheiium, 
 is represented by several species, one of which, as I learn 
 from Mr. Waterhouse, agrees with Microtherium Renggeri of 
 the Mayence basin. In like manner, the Amphit/raguius ele- 
 gans of Pomel, an Auvei-gne fossil, is identified by -Water- 
 house with Dorcatherium nanum of Kaup, a Rhenish species 
 from "Weissenau, near Mayence. A small species, also, of 
 rodent, of the genus Titanomys of H. von Meyer, is common 
 to the Lower Miocene of Mayence and the Limagne d'Au- 
 
LOWEK MOLASSE OF SWITZERLAND. 235 
 
 vergne, and there are many other points of agreement which 
 the discordance of nomenclature tends to conceal. A re- 
 markable carnivorous genus, the Hyaenodon of Laizer, is 
 represented by more than one species. The same genus has 
 also been found in the Upper Eocene marls of Hordwell Cliff, 
 Hampshire, just below the level of the Bembridge Limestone, 
 and therefore a formation older than the Gypsum of Paris. 
 Several species of opossum {Didelphis) are met with in the 
 same strata of the Limagne. The total num,ber of mamma- 
 lia enumerated by M. Pomel as appertaining to the Lower 
 Miocene fauna of the Limagne and Velay falls little short 
 of a hundred, and with them are associated some large croc- 
 odiles and tortoises, and some Ophidian and Batrachian rep- 
 tiles. 
 
 Lower Molasse of Switzerland,— The two upper divisions 
 of the Swiss Molasse — the one fresh-water, the other marine 
 — ^have already been described in the preceding chapter. I 
 shall now proceed to treat of the third division, which is of 
 Lower Miocene age. Nearly the whole of this Lower Mo- 
 lasse is fresh-water, yet some of the inferior beds contain a 
 m.ixture of marine and fluviatile shells, the Gerithiwm mar- 
 garitaceum, a well-known Lower Miocene fossil, being one of 
 the marine species. Notwithstanding,, therefore, that some 
 of these Lower Miocene strata consist of old shingle-beds 
 several thousand feet in thickness, as in the Rigi, near Lu- 
 cerne, and in the Speer, near Wesen, mountains 5000 and 
 7000 feet above' the sea, the deposition of the whole series 
 must have begun at or below the sea-level. 
 
 The conglomerates, as might be expected, ai'e often very 
 unequal in thickness, in closely adjoining districts, since in a 
 littoral formation accumulations of pebbles would swell out 
 in certain jilaces where rivers entered the sea, and would thin 
 out to comparatively small dimensions where no streams or 
 only small ones came down to the coast. For ages, in spite 
 of a gradual depression of the land and adjacent sea-bottom, 
 the rivers continued to cover the sinking area with their 
 deltas ; until finally, the subsidence being in excess, the sea 
 of the Middle Molasse gained upon the land, and marine 
 beds were thrown down over the dense mass of fresh-water 
 and brackish^water deposit, called the Lower Molasse, which 
 had previously accumulated. 
 
 Plora of the Lower Molasse. — In part of the Swiss Molasse, 
 which belongs exclusively to the Lower Miocene period, the 
 number of plants has been estimated at more than 500 species, 
 somewhat exceeding those which were before enumerated as 
 occurring in the two upper divisions. The Swiss Lower Mio- 
 
236 ELEMENTS OE GEOLOGY. 
 
 cene may best be studied on tlie northern borders of the 
 Lake of Geneva, between Lausanne and Vevay, where the 
 contiguous villages of Monod and Rivaz are situated. The 
 strata there, which I have myself examined, consist of al- 
 ternations of conglomerate, sandstone, and finely laminated 
 marls with fossil plants. A small stream falls in a succes- 
 sion of cascades over the harder beds of pudding-stone, which 
 resist, while the sandstone and plant-bearing shales and marls 
 give way. From the latter no less than 193 species of plants 
 have been obtained by the exei'tions of MM. Heer and Gau- 
 diii, and they are considered to afford a true type of the 
 vegetation of the Lower Miocene formations of Switzerland — 
 a vegetation departing farther in its character from that now 
 flourishing in Europe than any of the higher members of the 
 series before alluded to, and yet displaying so much affinity 
 to the flora of CEuingen as to make it natural for the bota- 
 nist to refer the whole to one and the same Miocene period. 
 There are, indeed, no less than 81 species of these Older Mio- 
 cene plants which pass up into the flora of (Eningen. 
 
 This fact is important as bearing on the propriety of clas- 
 sifying the Lower Molasse of Switzerland as belonging to the 
 Miocene rather than to the latter part of the Eocene period. 
 There are, indeed, so many types among the fossils, both spe- 
 cific and generic, which have a wide range through the whole 
 of the Molasse, that a unity of character is thereby stamped 
 on the whole flora, in spite of the contrast between the plants 
 of the uppermost and lowest formations, or between CEnin- 
 gen and Monod. The proofs of a warmer climate, and the ex- 
 cess of arborescent over herbaceous plants, and of evergreen 
 trees over deciduous species, are characters common to the 
 whole flora, but which are intensified as we descend to the 
 inferior deposits. 
 
 Nearly all the plants at Monod are contained in three lay- 
 ers of marl separated by two of soft sandstone. The thick- 
 ness of the marls is ten feet, and vegetable matter predom- 
 inates so much in some layers as to form an imperfect lig- 
 nite. One bed is filled with large leaves of a species of fig 
 {Ficus populina), and of a hornbeam ( Carpinus grandis), the 
 strength of the wind having probably been great when they 
 were blown into the lake ; whereas another contiguous lay- 
 er contains almost exclusively smaller leaves, indicating, ap- 
 parently, a diminished strength in the wind. Some of the 
 upper beds at Monod abound in leaves of Proteaceae, Cype- 
 raceae, and ferns, while in some of the lower ones Sequoia, 
 Cinnamomum, and Sparganium are common. In one bed 
 of sandstone the trunk of a large palm-tree was found unac- 
 
LOWER MOLASSE OF SWITZERLAND. 237 
 
 companied by other fossils, and near Vevay, in the same se- 
 ries of Lower Miocene strata, the leaves of a palm of the ge- 
 nus Sabcd (Fig. 151), a genus now proper to America, were 
 obtained. 
 
 Among other genera of the same class is a Flabellaria oc- 
 curring near Lausanne, and a magnificent Phoenicites allied 
 to the date palm. When these j,.„ jgj 
 
 plants flourished the climate must 
 have been much hotter than now. vIi\MMmIA,w//. 
 
 The Alps were no doubt much 
 lower, and the palms now found \ ^ 
 
 fossil in strata elevated 2000 feet ^ \ \\ M ^ 
 
 above the sea grew nearly at the | ^ ^ 
 
 sea-level, as is demonstrated by the | ^ "^ * *> / ^ : 
 
 brackish-water character of some 3 ><*^ — " 
 
 of the beds into which they were ^^^^^^^^^^^^p 
 carried by winds or rivers from "^^^^^—^ y ^^-^^^^ 
 the adjoining coast. II 
 
 In the same plant-bearing depos- (I 
 
 its of the Lower Molasse in Swit- Sdbal major, Unger sp. Vevay. 
 zerland leaves have been found Lower kiocene = Heer, Pl. «. 
 
 which have been ascribed to the order Proteacese already 
 spoken of as well represented in the QSningen beds (see p. 
 221). The Proteas and other plants of this family now 
 flourish at the Cape of Good Hope ; while the Banksias, and 
 a set of genera distinct from those of Africa, grow most lux- 
 uriantly in the southern and temperate parts of Australia. 
 They were probably inhabitants, says Heer, of dry hilly 
 ground, and the stiff leathery character of their leaves must 
 have been favorable to their preservation, allowing them to 
 float on a river for gi-eat distances without being injured, and 
 then to sink, when water-logged, to the bottom. It has been 
 objected that the fruit of the Proteacese is of so tough and 
 enduring a texture that it ought to have been more com- 
 monly met with ; but in the first place we must not forget 
 the numerous cones found in the Eocene strata of Sheppey, 
 which all admit to be proteaceous and to belong to at least 
 two species (see p. 222). Secondly, besides the fruit of Ha- 
 kea before mentioned (p. 221), Heer found associated with 
 fossil leaves, having the exact form and nervation of Bank-- 
 sia, fruit precisely such as may have come from a cone of 
 that plant, and lately he has received another similar fruit 
 from the Lower Miocene strata of Lucerne. They may have 
 fallen out of a decayed cone in the same way as often hap- 
 pens to the seeds of the spruce fir, Pinus dbies, found scat- 
 tered over the ground in our woods. It is a known fact 
 
238 
 
 ELEMENTS OF GEOLOGY. 
 
 that among the living ProteacesB the cones are very firmly 
 attached to the branches, so that the seeds drop out without 
 the cone itself falling to the ground, and this may perhaps 
 be the reason why, in some instances in which fossil seeds 
 have been found, no traces of the cone have been observed. 
 
 Pig. 152. 
 
 Fig. 153. 
 
 Tn 1 ^ , ., « , Sequoia Langadorfii. Ad. Brong., i Eatnral 
 
 "•^T '.,"., &^*!'?*5?^'''- size. Eivaz, near Lausanne ; Heer, PI. 
 
 6. Leaf of BankBiaDeek- ^1, Kg. ,4. Upper and Lower Miocene 
 
 '*'^*- and Lower Pliocene, Val d'Arno. 
 
 a. Branch with leaves. K Young cone. 
 
 Among the Coniferse the Sequoia, here figured is common 
 at Rivaz, and is one of the most universal plants in the Low- 
 est Miocene of Switzerland, while it also characterizes the 
 Miocene Brown Coals of Germany and certain beds of the 
 Val d'Arno, which I have called Older Pliocene, p. 208. 
 Among the ferns met with in profusion at Monod is the 
 
 Iiastroea stiriaca, Unger, 
 ^'^■^^ which has a wide range 
 
 in the Miocene period 
 from strata of the age of 
 CEningen to the lowest 
 part of the Swiss Mo- 
 lasse. In some speci- 
 mens, as shown in Figure 
 154, the fructification is 
 distinctly seen. 
 
 Among the laurels sev- 
 eral species of Ginnamo- 
 mum are very conspicu- 
 
 Lastfcm stiriaca, Ung.; Beer's Plo7a, PI 143 ^^^- I^^sides the C. poll/- 
 
 Fig. 8. Natural size. Lower and Upper Mlo- morphum, before fiffUred, 
 
 cene, Switzerland. „ onr^ ii_ ■ 
 
 ». Specimen from Monod, showing the position P" ^^^' another speCieS 
 
 of the Bori on the middle of the tertiary alSO ranges from the 
 
 nerves. 6. More cominon appearance, where T.owpr tn tlio TTr>,-.<:.v Mn 
 
 the son remam and the nerves are obliter- •'-'"Wer 10 ine U pper iVlO- 
 
 *'*^- lasse of Switzerland, and 
 
ARCTIC MIOCENE FLORA. 
 
 339 
 
 Fig. 156. 
 
 Cinrumiomum Roasmdsslen, Heer. 
 Daphnogene cinna/momi/oliaj Uii' 
 — Upper and Lower Miocene, 
 i-lai ' 
 
 is very characteristic of different 
 deposits of Brown Coal in Ger- 
 many. It has been called Cinna- 
 momum Mossmassleri by Heer (see 
 Fig. 155). The leaves are easily 
 recognized as having two side 
 veins, which run up uninterrupt- 
 edly to their point. 
 
 American Character of the Flora. 
 — If we consider not merely the 
 number of species but those plants 
 which constitute the mass of the 
 Lower Miocene vegetation, we find 
 the European part of the fossil 
 flora very much less prominent 
 than in the (Eningen beds, while 
 the foreground is occupied by 
 American forms, by evergreen 
 oaks, maples, poplars, planes, Liq- 
 uidambar, Robinia, Seqnoia, Tax- 
 odium, and ternate-leaved pines. 
 
 There is also a much gl-eater fu- Switzerldnd and Germany. 
 
 sion of the characters now belonging to distinct botanical 
 provinces than in the Upper Miocene flora, and we shall 
 find this fusion still more strikingly exemplified as we go 
 back to the antecedent Eocene and Cretaceous periods. 
 
 Professor Heer has advocated the doctrine, first advanced 
 by linger to explain the large number of American genera 
 in the Miocene flora of Europe, that the present basin of the 
 Atlantic was occupied by land over which the Miocene flora 
 could pass freely. But other able botanists have shown that 
 it is far more pi-obable that the American plants came from 
 the east and not from the west, and instead of reaching 
 Europe by the shortest route over an imaginary Atlantis, 
 migrated in an opposite direction, crossing the whole of 
 Asia. 
 
 Arctic Miocene Flora. ^But when we indnlge in specula- 
 tions as to the geographical origin of the Miocene plants of 
 Central Europe, we must take into account the discoveries 
 recently made of a rich terrestrial flora having flourished in 
 the Arctic Regions in the Miocene period from which many 
 species may have migrated from a common centre so as to 
 reach the present continents of Europe, Asia, and America. 
 Professor Heer has examined the v.arious collections of fossil 
 plants that have been obtained in N. Greenland (lat. 70°), 
 Iceland, Spitzbergen, and other parts of the Arctic regions, 
 
240 ELEMENTS OF GEOLOGY. 
 
 and has determined that they are of Miocene age and indi- 
 cate a temperate climate.* Including the collections recent- 
 ly brought from Greenland by Mr. Whymper, the Arctic 
 Miocene flora now comprises 194 species, and that of Green- 
 land 137 species, of which 46, or exactly one-third, are iden- 
 tical with plants found in the Miocene beds of Central Eu- 
 rope. Considerably more than half the number are trees, 
 which is the more remarkable since, at the present day, 
 trees do not exist in any part of Greenland even 10° farther 
 south. 
 
 More than thirty species of Coniferse have been found, in- 
 cluding several Sequoias (allied to the gigantic Wellingtonia 
 of California), with species of Thujopsis and Salisburia now 
 peculiar to Japan. There are also beeches, oaks, planes, pop- 
 lars, maples, walnuts, limes, and even a magnolia, two cones 
 of which have recently been obtained, proving that this 
 splendid evergreen not only lived but ripened its fruit within 
 the Arctic circle. Many of the limes, planes, and oaks were 
 large-leaved species, and both flowers and fruit, besides im- 
 mense quantities of leaves, are in many cases preserved. 
 Among the shrubs were many evergreens, as Andromeda, 
 and two extinct genera, Daphnogene and M' Clintockia, with 
 fine leathery leaves, together with hazel, blackthorn, holly, 
 logwood, and hawthorn. A species of Zamia (Zamites) grew 
 in the swamps, with Potamogeton, Sparganium, and Menyan- 
 thes, while ivy and vines twined around the forest trees and 
 broad-leaved ferns grew beneath their shade. Even in Spitz- 
 bergen, as far north as lat. 78° 56', no less than ninety-five 
 species of fossil plants have been obtained, including Taxo- 
 dium of two species, hazel, poplar, alder, tjeech,. plane-tree, 
 and lime. Such a vigorous growth of trees within 12° of the 
 pole, where now a dwarf willow and a few herbaceous plants 
 form the only vegetation, and where the ground is covered 
 with almost perpetual snow and ice, is truly remarkable. 
 
 The identity of so many of the fossils with Miocene species 
 of Central Europe and Italy not only pi-oves that the climate 
 of Greenland was much warmer than it is now, but also ren- 
 ders it probable that a much more uniform climate prevailed 
 over the entire northern hemisphere. This is also indicated 
 by the whole character of the Upper Miocene flora of Central 
 Europe, which does not necessitate a mean temperature very 
 much greater than exists at present, if we suppose such ab- 
 sence of winter cold as is proper to insular climates. Pro- 
 fessor Heer believes that the mean temperature of North 
 Greenland must have been at least 30° higher than at pres- 
 * Heer, ' ' Miocene baltische Flora, " and ' ' Fossil-flora von Alaska," 1869. 
 
LOWER MIOCENE, BELGIUM. 241 
 
 ent, while an addition of 10° to the mean temperature of 
 Central Europe would probably be as much as was required. 
 The chief locality where this wonderful flora is preserved is 
 at Atanekerdluk in North Greenland (lat. '70°), on a hill at an 
 elevation of about 1200 feet above the sea. There is here a 
 considerable succession of sedimentary strata pierced by vol- 
 canic rocks. Fossil plants occur in all the beds, and the erect 
 trunks as thick as a man's body which are sometimes found, 
 together with the abundance of specimens of flowers and 
 fruit in good preservation, sufficiently prove that the plants 
 grew Avhere they are now found. At Disco island and other 
 localities on the same part of the coast, good coal is abun- 
 dant, interstratified with beds of sandstone, in some of which 
 fossil plants have also been found, similar to those at Atan- 
 ekerdluk. 
 
 Lower Miocene, Belgium. — The Upper Miocene Bolderberg 
 beds, mentioned at p. 224, rest on a Lower Miocene forma- 
 tion called the Rupelian of Dumont. This formation is best 
 seen at the villages of Rupelmonde and Boom, ten miles south 
 of Antwerp, on the banks of the Scheldt and near the junc- 
 tion with it of a small stream called the Rupel. A stiff" clay 
 abounding in fossils is extensively worked at the above lo- 
 calities for making tiles. It attains a thickness of about 100 
 feet, and though very different in age, much i-esembles in 
 mineral character the " London clay," containing, like it, sep- 
 taria or concretions of argillaceous limestone traversed by 
 cracks in the interior, which are filled with calc-spar. The 
 shells, referable to about forty species, have been described 
 by MM. Nyst and De Koninck. Among them l,eda (or Ific- 
 cula) DeshayesiaTia pjg jgg 
 
 (see Fig. 156) is by 
 far the most abun- 
 dant; a fossil un- 
 known as yet in the 
 
 English tertiaiy "'^^^^^Jrw ^ X^' 
 strata, but when ^ , '"", , „ . ~. « i 
 
 ' , Leia (Nucula) veshayesiana, Nyst. 
 
 young much resem- 
 bling Z,eda amygdaloides of the London Clay proper (sec 
 Fig. 213, p. 266). Among other characteristic shells are 
 Pecten Soeninghausii, and a species of Cassidaria, and sev- 
 eral of the genus Pleurotoma. Not a few of these testacea 
 ao-ree with Eno-lish Eocene species, such as Actmon simulatus, 
 Sow., Cancdlaria evulsa, Brander, Corbula ^nsum (Fig. 157), 
 and JVautilus {Aturia) ziczac. . They are accompanied by 
 many teeth of sharks, as Lamna contortidem, Ag., Oxyrhi- 
 naxiphodon, Ag., Carcharodon angustidens (see Figure 1 96, 
 
242 
 
 ELEMENTS OF GEOLOGY. 
 
 J). 262), Ag., and other fish, some of them common to the 
 Middle Eocene strata. 
 
 Kleyn Spawen beds. — The succession of the Lower Miocene 
 strata of Belgium can be best studied in the environs of 
 Kleyn Spawen, a village situated about seven miles_ west of 
 Maestricht, in the old province of Limburg in Belgium. In 
 that region, about 200 species of testacea, marine and fresh- 
 watei-, have been obtained, with many foraminifera and re- 
 mains of fish. In none of the Belgian Lower Miocene strata 
 could I find any nummulites ; and M. d'Archiac had pre- 
 viously observed that these foraminifera characterize his 
 " Lower Tertiary Series," as contrasted with the Middle, and 
 they therefore serve as a good test of age between Eocene 
 and Miocene, at least in Belgium and the North of France.* 
 Between the Bolderberg beds and the Rupelian clay there is 
 a great gap in Belgium, which seems, according to M. Bey- 
 rich, to be filled up in the North of Germany by what he 
 calls the Sternberg beds, and which, had Dumont found them 
 in Belgium, he might probably have termed Upper Rupelian. 
 
 Lower Miocene of Germany. — Eupelian Clay of Hermsdorf, 
 near Berlin. — Professor Beyrich has described a mass of clay, 
 used for making tiles, within seven miles of the gates of Ber- 
 lin, near the village of Hermsdorf, rising up from beneath 
 the sands with which that country is chiefly overspread. 
 This clay is more than forty feet thick, of a dark bluish- 
 gray color, and, like that of Rupelmbnde, contains septaria. 
 Among other shells, the Leda Deshayesiana, before mention- 
 ed (Fig. 156), abounds, together with many species of Pfettr 
 rotoma, Voluta, etc., a certain proportion of the fossils being 
 identical in species with those of Rupelmonde. 
 
 Mayence Basin. — An elaborate description has been pub- 
 lished by Dr. F. Sandberger of the Mayence tertiary area, 
 which occupies a tract from five to twelve miles in breadth, 
 extending for a great distance along the left bank of the 
 Rhine from Mayence to the neighboi-hood of Manheim, and 
 which is also found to the east, north, and south-west of 
 Frankfort. M. de Koninck, of Liege, first pointed out to me 
 that the purely marine portion of the deposit contained many 
 species of shells common to the Kleyn Spawen beds, and to 
 the clay of Rupelmonde, near Antwerp. Among these he 
 mentioned Cassidaria depressa, Tritonium anjivtum, Bran- 
 der (T. Jlandricitm,T>e Koninck), TornateUa simulata, Apor- 
 rhais Smoerbyi, Zfeda Deshayesiana (Fig. 156), Corbiilapisiim', 
 (Fig. 158, p. 245), and others. 
 
 Lower Miocene Beds of Croatia. — The Brown Coal of Rada- 
 
 * D'Archiac, Monogr., pp. 79, 100, 
 
LOWER MIOCENE OE GERMANY. 
 
 243 
 
 boj, near Angram in Croatia, not far from the borders of 
 Styria, is covered, says Von Buch, by beds containing the 
 marine shells of the Vienna basin, or, in other words, by Up- 
 per Miocene or Falunian strata. They appear to correspond 
 in age to the Mayence basin, or to the Rupelian strata of 
 Belgium. They have yielded more than 200 species of fossil 
 plants, described by the late Professor linger. These plants 
 are well preserved in a hard marlstone, and contain several 
 palms ; among them the Sabal, Fig. 151, p. 237, and another 
 genus allied to the date-palm Phcenicites spectabilis. The 
 only abundant plant among the Radaboj fossils which is 
 characteristic of the Upper Miocene period is the Populua 
 mutabilis, whereas no less than fifty of the Radaboj species 
 are common to the more ancient flora of the Lower Molasse 
 of Switzerland. 
 
 The insect fauna is very rich, and, like the plants, indicates 
 a more tropical climate than do the fossils of CEningen pres- 
 ently to be mentioned. There are ten species of Termites, 
 or white ants, some of gigantic size, and large dragon-flies 
 with speckled wings, like those of the Southern States in 
 North America ; there are also grasshoppers of considerable 
 size, and even the Lepidoptera are not unrepresented. In 
 one instance, the pattern of a butterfly's wing has escaped 
 
 Fig. 15T. 
 
 Vanessa Pluto; nat. size. Lower Miocene, Badaboj, Croatia. 
 
 obliteration in the marl-stone of Radaboj ; and when we re- 
 flect on the remoteness of the time from which it has been 
 fliithfully transmitted to us, this fact may inspire the reader 
 with some confidence as to the -reliable nature of the charac- 
 ters which other insects of a more durable texture, such as 
 the beetles, may afibrd for specific determination. The Va- 
 nessa above figured retains, says Heer, some of its colors, and 
 corresponds with V. Sadena of India. 
 
244 ELEMENTS OF GEOLOGY. 
 
 Professor Beyrich has made known to us the existence of 
 a long succession of marine strata in North Germany, which 
 lead "by an almost gradual transition from beds of Upper 
 Miocene age to others of the age of the base of the Lower 
 Miocene. Although some of the German lignites called 
 Brown Coal belong to the upper parts of this series, the most 
 important of them ai-e of Lower Miocene date, as, for exam- 
 ple, those of the Siebengebirge, near Bonn, which are associa- 
 ted with volcanic rocks. 
 
 Professor Beyrich confines the term " Miocene " to those 
 strata which agree in age with the faluus of Touraine, and 
 he has proposed the term " Oligocene " for those older for- 
 mations called Lower Miocene in this work. 
 
 Lower Miocene of Italy. — In the hills of which the Superga 
 forms a part there is a great series of Tertiary strata which 
 pass downward into the Lower Miocene. Even in the Su- 
 perga itself there are some fossil plants which, according to 
 Heer, have never been found in Switzerland so high as the 
 marine Molasse, such as jBanksia longifolia, and Carpinus 
 grandis. In several parts of the Ligurian Apennines, as at 
 Dego and Carcare, the Lower Miocene appears, containing 
 some nummulites, and at Cadibona, north of Savona, fresh- 
 water strata of the same age occur, with dense beds of lig- 
 nite inclosing remains of the Anthracotherium magnum and 
 A. minimum, besides other mammalia enumerated by Gas- 
 taldi. In these beds a great number of the Lower Miocene 
 plants of Switzerland have been discovered. 
 
 Lower Miocene of England— Hempstead Beds. — We have 
 already stated that the Upper Miocene formation is nowhere 
 represented in the British Isles; but strata referable to the 
 Lower Miocene period are found both in England, Scotland, 
 and Ireland. In the Hampshire basin these occupy a very 
 small superficial area, having been discovered by the late 
 Edward Forbes at Hempstead near Yarmouth, in "the north- 
 ern part of tlie Isle of Wight, where they are 170 feet thick, 
 and rich in characteristic marine shells. They overlie the 
 uppermost of an extensive series of Eocene deposits of ma- 
 rine, brackish, and fresh-water formations, which rest on the 
 Chalk and terminate upward in strata corresponding in age 
 to the Paris gypsum, and containing the same extinct gen- 
 era of quadrupeds, Paloeotherium,, Anoplotherium, and others 
 which Cavier first described. The following is the succes- 
 sion of these Lower MioCene strata, most of them exposed 
 in a clifi" east of Yarmouth : 
 
 1. The uppermost or Corbula beds, consisting of marine 
 sands and clays, contain Valuta Mathieri, a chai-acteristio 
 
LOWER MIOCENK OF ENGLAND. 
 
 246 
 
 Lower Miocene shell; Corbula pisum (Fig. 158), a species 
 common to the Upper Eocene clay of Barton ; Cyrena semi- 
 striata (Fig. 159), several Cerithia, and other shells peculiar 
 to this series,. 
 
 Fig. 158. 
 
 Corbula pisiim. Hempstead Beds, 
 Isle of Wight. 
 
 Cwrema semistriata. 
 Hempstead Beds. 
 
 2. Next below are fresh-water and estuary marls and car- 
 bonaceous clays in the brackish-water portion of which are 
 Fig. 160. Fig. 161. found abundantly Gerithium 
 
 plicatum, Lam. (Fig. 160), 0. 
 elegans (Fig. 161), and C. tri- 
 cinctum ; also Missoa Chaste- 
 lii (Fig. 162), a very common 
 Kleyn Spawen shell, and which 
 occurs in each of the four sub- 
 divisions of the Hempstead se- 
 ries down to its base, where 
 it passes into the Bembridge 
 beds. In the fresh-water por- 
 tion of the same beds Paludina 
 
 Cerithium elegaiia. Unta (Fig. 163) OCCUrs ; a shell 
 
 Hempstead. identified by some concholo- 
 gists with a species now living, P. unicolor ; also several 
 species of Lymneus, Planorbis, and Unio. 
 
 Cerithium plieatUTn, 
 Lam., Hempstead. 
 
 Fig. 163. 
 
 3. The next series, or mid 
 die fresh - water and estuary 
 marls, are distinguished by the 
 presence of Melania fasciata, 
 Paludina lenta, and clays with 
 Cypris ; the lowest bed con- 
 tains Cyrena semistriata (Fig. 
 159),nlingled with Cerithia and 
 a Panopcea. 
 
 4. The lower fresh-water and estuary marls contam Mela 
 nia costata, Sow., Melanopsis, etc. The bottom bed is car- 
 bonaceous, and called the " Black band," in which Rissom 
 Chastelii (Fig. 162), before alluded to, is common. This bed 
 contains a mixture of Hempstead shells with those of the 
 Underlying Tipper Eocene or Bembridge series. The mam- 
 
 Rissoa Chasteliij ^jst, 
 Sp. Hempi 
 of Wight. 
 
 Sp. Hempstead, Isle 
 
 Paliutina lenta. 
 Hempstead 
 Bed. 
 
246 ELEMEISTS OF GEOLOGY. 
 
 irialia, among which is Hyapotamus iovinus, differ, so far as 
 they are known, from those of the Bembrid^e beds. Among: 
 the plants, Professor Heer has recognized four species com- 
 mon to the lignite of Bovey Tracey, a lower Miocene forma- 
 tion presently to be described: namely, Sequoia Gouttsice, 
 Heer; Andromeda reticulata, ^Urngs.; Nelumbium {Nym- 
 phoea) doris, Heer ; and CarpoUthes Websteri, Brong.* The 
 seed-vessels of Chara medieaginula, Brong., and C. helicteres 
 are characteristic of the Hempstead beds generally. 
 
 The Hyopotamus belongs to the hog tribe, or the same 
 family as the Anthracotherium, of which seven species, vary- 
 ing in size from the hippopotamus to the wild boar, liavo 
 been found in Italy and other parts of Europe associated 
 with the lignites of the Lower Miocene period. 
 
 Lignites and Clays of Bovey Tracey, Devonshire. — Surround-' 
 ed by the granite and other rocks of the Dartmoor hills in 
 Devonshire, is a formation of clay, sand, and lignite, long 
 known to geologists as the Bovey Coal formation, respecting 
 the age of which, until the year 1861, opinions were very un- 
 settled. This deposit is situated at Bovey Tracey, a village 
 distant eleven miles from Exeter in a south-west, and about 
 as far from Torquay in a north-west direction. The strata 
 extend over a plain nine miles long, and they consist of the 
 materials of decomposed and worn-down granite and vege- 
 table matter, and have evidently filled up an ancient hollow 
 or lake-like expansion of the valleys of the Bovey and Teign. 
 
 The lignite is of bad quality for economical purposes, as 
 there is a great admixture in it of iron pyrites, and it emits, 
 a sulphurous odor, but it has been successfully applied to 
 the baking of pottery, for which some of the fine clays are 
 well adapted. Mr. Pengelly has confirmed Sir H. De la 
 Beche's opinion that much of the upper portion of this old 
 lacustrine formation has been removed by denudation. f 
 
 At the surface is a dense covering of clay and gravel with; 
 angular stones probably of the Post-pliocene period, for la 
 the clay are three species of willow and the dwarf bircL. 
 Betida nana, indicating a climate colder than that of Devoii 
 shire at the present day. 
 
 Below this are Lower Miocene strata about 300 feet in 
 thickness, in the upper part of which are twenty-six beds of 
 lignite, clay, and sand, and at their base a ferruginous quart- 
 zose sand, varying in thickness from two to twenty-seven 
 
 * Pengelly, preface to The Lignite Formation of Bovey Tracer, p. xvii., 
 fioudon, 18G3. 
 
 t Philos. Trans., 18G3. Paper by W. Pengelly, F. K. S., and LV. Oswald' 
 Heer. 
 
LEAF-BEDS OF MULL, IN SCOTLAND. 247 
 
 feet. Below this sand are forty-five teds of alternating lig; 
 nite and clay. No shells or bones of mammalia, and no in- 
 sect, with the exception of one fragment of a beetle {Bupres' 
 tis) ; in a word, no organic remains, except plants, have as 
 yet been found. These plants occur in foui-teen of the beds^— 
 namely, in two of the clays, and the rest in the lignites.. 
 One of the beds is a perfect mat of the debris of a eonifei'ous 
 tree, called by Heer Sequoia Gouttsice, intermixed with leaves 
 of ferns. The same Sequoia (before mentioned as a Hemp- 
 stead fossil, p. 246) is spread through all parts of the forma- 
 tion, its cones, and seeds, and branches of every age being 
 pi'eserved. It is a species supplying a link between S. 
 JLangsdorfii (see Fig. 153, p. 238) and S. Sternbergi, the wide- 
 ly spread fossil representatives of the two living trees 8. sem- 
 pervirens and B. gigantea (or Wellingtonia), both now con- 
 fined to California. Another bed is full of the large rhizomes 
 of ferns, while two others are rich in dicotyledonous leaves. 
 In all. Professor Heer enumerates forty-nine species of plants, 
 twenty of which are common to the Miocene beds of the 
 Continent, a majority of them being characteristic of the 
 Lower Miocene. The new species, also of Bovey, are allied 
 to plants of the older Miocene deposits of Switzerland, Ger- 
 many, and other Continental countries. The grape-stones of 
 two species of vine occur in the clays, and leaves of the fig 
 and seeds of a water-lily. The oak and laurel have supplied, 
 many leaves. Of the triple-nerved laurels several are refer- 
 red to Cinnamomum. There are leaves also of a palm of 
 which the genus is not determined. Leaves also of protea- 
 ceous forms, like some of the Continental fossils before men- 
 tioned, occur, and ferns like the well-known Lastrcea stiriaca 
 (Fig. 154, p. 238), displaying at Bovey, as in Switzerland, its 
 fructification. 
 
 The croziers of some of the young ferns are very perfect, 
 and were at first mistaken by collectors for shells of the ge- 
 nus Planorhis. On the whole, the vegetation of Bovey im- 
 plies the existence of a sub-tropical climate in Devonshire, in 
 the Lower Miocene period. 
 
 Scotland : Isle of Mull. — In the sea-elifTs forming the head- 
 land of Ardtun, on the west coast of Mull, in the Hebrides, 
 several bands of tertiary sti-ata containing leaves of dicoty- 
 ledonous plants were discovered in 1851 by the Duke of Ar- 
 gyll.* From his description it appears that there are three 
 leaf-beds, varying in thickness from \\ to 5^ feet, which are 
 interstratified with volcanic tufi" and trap, the whole mass 
 being about 130 feet in thickness. A sheet of basalt 40 feet 
 * -Quart. Geol. Journal, 1851, p. 19. 
 
248 ELEMENTS OF GEOLOGY. 
 
 thick covers the whole ; and another columnar bed of the 
 same rock, ten feet thick, is* exposed at the bottom of the cliff. 
 One of the leaf-beds consists of a compressed mass of leaves 
 unaccompanied by any stems, as if they had been blown into 
 a marsh where a species of Equisetum grew, of which the re- 
 mains are plentifully imbedded in clay. 
 
 It is supposed by the Duke of Argyll that this formation 
 was accumulated in a shallow lake or marsh in the neighbor- 
 hood of a volcano, which emitted showers of ashes and 
 streams of lava. The tufaceous envelope of the fossils may 
 liave fallen into the lake from the air as volcanic dust, or 
 have been washed down into it as mud from the adjoining 
 land. Even without the aid of organic remains we might 
 have decided that the deposit was newer than the chalk, for 
 chalk-flints containing cretaceous fossils were detected by 
 the duke in the principal mass of volcanic ashes or tufi".* 
 
 The late Edward Forbes observed that some of the plants 
 of this formation resembled those of Croatia, described by 
 Unger, and his opinion has been confirmed by Professor 
 Heer, who found that the conifer most prevalent was the 
 Sequoia Langsdorfii (Fig. 153, p. 238), also Corylus grosse- 
 dentata, a Lower Miocene species of Switzerland and of 
 Menat in Auvergne. There is likewise a plane-tree, the 
 leaves of which seem to agree with those of Platanus ace- 
 roides (Fig. 141, p. 221), and a fern which is as yet peculiar 
 to Mull, Filicites liebridica, Forbes. 
 
 These interesting discoveries in Mull led geologists to sus- 
 pect that the basalt of Antrim, in Ireland, and of the cele- 
 brated Giant's Causeway, might be of the same age. The 
 volcanic rocks that overlie the chalk, and some of the strata 
 associated with and interstratified between masses of basalt, 
 contain leaves of dicotyledonous plants, somewhat imperfect, 
 but resembling the beech, oak, and plane, and also some co- 
 niferse of the genera pine and Sequoia. The general dearth 
 of strata in the British Isles, intermediate in age between the 
 formation of the Eocene and Pliocene periods, may arise, says 
 Professor Forbes, from the extent of dry land which pre- 
 vailed in that vast interval of time. If land predominated, 
 the only monuments we are likely ever to find of Miocene 
 date are those of lacustrine and volcanic origin, such as the 
 Bovey Coal in Devonshire, the Avdtun beds in Mull, or the 
 lignites and associated basalts in Antrim. 
 
 Lower Miocene, United States : Nebraska. — In the territory 
 of Nebraska, on the Upper Missouri, near the Platte River, 
 lat. 42° N., a tertiary formation occurs, consisting of white 
 * Quart. Geol. Journal, 1851, p. 90. 
 
LOWER MIOCKNE, UNITED STATES. 249 
 
 limestone, mai-ls, and siliceous clay, described by Dr. D. 
 Dale Owen,* in which many bones of extinct quadrupeds, 
 and of chelonians of land or fresh-water foi-ms, are met with. 
 Among these. Dr. Leidy describes a gigantic quadruped, 
 called by him Titanotherium, nearly allied to the PaloBothe- 
 Hum, but larger than any of the species found in the Paris 
 gypsum. With these are several species of the genus Ore- 
 odon, Leidy, uniting the characters of pachyderms and rumi- 
 nants also ; £/ucrotaphus, another new genus of the same 
 mixed character ; two species of rhinoceros of the sub-genus 
 Acerotherium, a Lower Miocene form of Europe before men- 
 tioned ; two species of Archceotherium, a pachyderm allied 
 to Chmropotamus and Hyracotherium ; also Pmbrotherium, 
 an extinct ruminant allied to Dorcatherium, Kaup; also 
 Agriochcerus, of Leidy, a ruminant allied to Merycopotamus 
 of Falconer and Cautley ; and, lastly, a large carnivorous 
 animal of the genus Machairodus, the most ancient example 
 of which in Europe occurs in the Lower Miocene strata of 
 Auvergne, but of which some species are found in Pliocene 
 deposits. The turtles are referred to the genus Testudo, but 
 have some affinity to Emys. On the whole, the Nebraska 
 formation is probably newer than the Paris gypsum, and 
 referable to the Lower Miocene pei-iod, as above defined. 
 * David Dale Owen, Geol. Survey of Wisconsin, etc. ; Fhilad., 1852. 
 
 11* 
 
250 
 
 ELEMENTS. OF GEOLOGY. 
 
 CHAPTER XVI. 
 
 EOCENE rORMATIONS. 
 
 Eocene Areas of North of Europe. — Table of English and French Eocene 
 Strata. — Upper Eocene of England. — Bembridge Beds. — Osbonie or St. 
 Helen's Beds. — Headon Series. — Fossils of the Barton Sands and Clays. — 
 Middle Eocene of England. — Shells, Nummulites, Fish and Reptiles of the 
 Bracklesham Beds and Bagshot Sands. — Plants of Alum Bay and Bourne- 
 mouth. — Lower Eocene of England.- — London Clay Fossils. — Woolwich 
 a.nd Beading Beds formerly called "Plastic Clay. " — Fluviatile Beds under- 
 lying Deep-sea Strata. — Thanet Sands. — Upper Eocene Strata of France. 
 -rGypseous Series of Montmartre and Extinct Quadrupeds. — Fossil Foot- 
 prints in Paris Gypsum. — Imperfection of the Record. — Calcaire Silicieiix. 
 — Grfes de Beauchamp. — Calcaire Grossier. — Miliolite Limestone. — Sois- 
 sonnais Sands. — Lower Eocene of France.— Nummulitic Foi-mations of 
 Europe, Africa, and Asia. — Eocene Strata in the United States. — Gigantic 
 Cetacean. 
 
 Eocene Areas of the North of Europe. — The strata next in 
 order in the descending series are those which I term Eoceee. 
 
 Fig. 164. 
 Map of the principal Eocene areas of North-western Europe. 
 
 ><.' ■' "' 
 
 ^P^ 
 
 .<<: 
 
 fc;^.;j Hypogene rocks and strata older 
 ' than the Bevouian. 
 
 N.B.. 
 
 ^3 Eocene for- 
 — rnations. 
 -The space left blank is occupied by fossiliferous formations from the Devo- 
 nian to the chalk inclusive. 
 
 In the accompanying map, the position of several Eocene 
 areas in the north of Europe is pointed out. When this 
 map was constructed I classed as the newer part of the Eo- 
 
EOCENE. -AEEAS OF NORTH OF EUEOPE. 251 
 
 cene those Tertiary strata which have been described in the 
 last chapter as Lower Miocene, and to which M. Beyrich has 
 given the name of Oligocene. None of these occur in the 
 London Basin, and they occupy in that of Hampshire, as we 
 have seen at p. 244, too insignificant a superficial area to be 
 noticed in a map on this scale. They fill a larger space in 
 the Paris Basin between the Seine and the Loire, and con- 
 stitute also part of the northern limits of the ai"ea of the 
 Netherlands which are shaded in the map. 
 
 It is in the northern part of the Isle of Wight that. we 
 have the uppermost beds of the true Eocene best exhibited 
 — namely, those which correspond in their fossils with the 
 celebrated gypsum of the Paris basin before alluded to, p. 
 231 (see Table, p. 252). That gypsum has been selected by 
 almost all Continental geologists as affording the best line 
 of demarkation between the Middle and Lower Tertiary, or, 
 in other words, between the Lower Miocene and Eocene for- 
 mations. 
 
 In reference to the annexed table I may observe, that the 
 correlation of the Prench and English subdivisions here laid 
 down is often a matter of great doubt and difficulty, not- 
 withstanding their geographical proximity. This arises from 
 various cii'cumstances, partly from the former prevalence of 
 marine conditions in one basin simultaneously with fluviatile 
 or lacustrine in the other, and sometimes from the existence 
 of land in one area causing a break or absence of all records 
 during a period when deposits may have been in progress 
 in the other basin. As bearing on this subject, it may be 
 stated that we have unquestionable evidence of oscillations 
 of level shown by the superposition of salt or brackish-water 
 strata to fluviatile beds; and those of deep-sea origin to 
 strata formed in shallow water. Even if the upward and 
 downward movements were uniform in amount and direc- 
 tion, which is very improbable, their effect in producing the 
 conversion of sea into land or land into sea would be differ- 
 ent, according to the previous shape and varying elevation 
 of the land and bottom of the sea. Lastly, denudation, ma- 
 rine and subaerial, has frequently caused the absence of de- 
 posits in one basin of corresponding age to those in the oth- 
 er, apd this destructive agency has been more than ordina- 
 rily effective on account of the loose and unconsolidated na- 
 ture of the sands and clays. 
 
252 ELEMENTS OF GEOLOGY. 
 
 TABLE OF ENGLISH AND FRENCH EOCENE STRATA. 
 
 UPPEK EOCENE. 
 
 English subcUvisionB. French equivalents. 
 
 A. 1. Bembiidge series, Isle of Wight, A. 1. Gypseous series of Montmartre, 
 
 p. 252. P- 270. 
 
 A. 2. Osborne or St. Helen's series, A. 2 and 3. Calcaire silicenx, or Tra- 
 
 Isle of Wight, p. 255. vertin Infe'rienr, p. 273. 
 A. 3. Headon series. Isle of Wight, 
 p. 255. 
 
 A. 4. Bai-ton series. Sands and clays A. 4. Gres de Beauchamp, or Sables 
 of Barton CliflF, Hants, p. 258. Moyens, p. 27a 
 
 MIBDLE EOCENE. 
 
 B. 1. Bracklesham series, p. 259. B. 1. Calcaire Grossier, p. 274. 
 B. 2. Alum Bay and Bournemouth B. 2. Wantmg m France ? 
 
 beds, p. 259. . „ n -r ■ ^ 
 
 B. 2. Wanting in England ? B. 2. Soissonnais Sands, or Lits Co. 
 
 quilliers, p. 275. 
 
 LOWER EOCENE. 
 
 C. 1. London Clay, p. 263. C. 1. Argile de Londres, Cassel, near 
 
 Dunkirk. 
 C. 2. Woolwich and Reading series, C. 2. Argile plastique and lignite, p. 
 
 p. 267. 276. 
 
 C. 3. Thanet sands, p. 269. C. 3. Sables de Bracheux, p. 276. 
 
 UPPER EOCENE, ENGLAND. 
 
 Bembridge Series, A. 1. — These beds are about 120 feet 
 thick, and, as before stated (p. 245), lie immediately under 
 the Hempstead beds, near Yarmouth, in the Isle of Wight, 
 being conformable with those Lower Miocene strata. They 
 consist of marls, clays, and limestones of fresh-water, brack- 
 ish, and marine origin. Some of the most abundant shells, 
 as Cyreiia semistriata var., and Paludina lenta, Fig. 163, p. 
 245, are common to this and to the overlying Hempstead 
 series ; but the majority of the species are distinct. The 
 following are the subdivisions described by the late Profess- 
 or Forbes : 
 
 a. Upper marls, distinguished by the abundance of Me- 
 lania turritissitna,Y orhes (Fig. 165). 
 
 i. Lower marls, characterized by Cerithium mutabile, Gy- 
 rena pulchra, etc., and by the remains of Trionyx (see Fig. 
 166). 
 
 c. Green marls, often abounding in a peculiar species of 
 oyster, and accompanied by Cerithium^ Mytilus, Area, Nu- 
 eula, etc. 
 
 d. Bembridge limestones, compact cream-colored lime- 
 stones alternating with shales and marls, in all of which 
 land-shells are common, especially at Sconce, near Yarmouth, 
 
UPPER EOCENE FORMATIONS. 
 
 253 
 
 as described by Mr. F. Edwards. The Bvlimus ellipticus. 
 Fig. 167, and Hdix occlusa. Fig. 168, are among its best 
 known land-shells. Paludina orbieidaris,Fig. 169, is also of 
 
 Fig. 105. 
 
 Fig. 166. 
 
 Melania turritissinui, Forbes. 
 Bembridge. 
 
 Fig. 16T. 
 
 Fragment of Carapace of Trionyx; 
 Bembridge Beds, Isle of Wight. 
 
 Fig. 188. 
 
 Fig. 169. 
 
 BuUrrms ellipticim, Sow. 
 Bembridge Limestone. 
 } nat. size. 
 
 Fig. 170. 
 
 Hdix occlusa, Edwards. 
 Bembridge Limestone, 
 Isle of Wight. 
 
 Fig. 171. 
 
 Palwtina orbicularis, 
 Bembridge, 
 
 Plarunrhig ditetts, Edwards. 
 Bembridge. i diam. 
 
 Fig. 172. 
 
 ( longiscata, Brand. 
 Nat. size. 
 
 Ckara tuberculata^ 
 seed-vessel. Bern- 
 bridge Limestone, 
 Isle of Wight 
 
 frequent occurrence. One of the bands is filled with a lit- 
 tle globular Paludina. Among the fresh-water pulmonifera, 
 Lymnea longiscata (Fig. 171) and Planorbis discus (Fig. 170) 
 
254 
 
 ELEMEKTS OF GEOLOGY. 
 
 Fig. 173. 
 
 are the most generally distributed : the latter represents or 
 takes the place of the Planorbis momphalus (see Fig. 1 '75) 
 of the more ancient Headon series. Chara tuberculata (Fig. 
 172) is the characteristic Bembridge gyrogonite or seed- 
 vessel. 
 
 From this formation on the shores of Whitecliff Bay, Dr. 
 Mantell obtained a fine specimen of a fan palm, Flabellaria 
 Lamanonis, Brong., a plant first obtained from beds of cor- 
 responding age in the subui'bs of Paris. The well-known 
 building-stone of Binstead, near Ryde, a 
 limestone with numerous hollows caused 
 by Cyrense which have disappeared and 
 left the jnoulds of their shells, belongs to 
 this subdivision of the Bembridge series. 
 In the same Binstead stone Mr. Pratt and 
 the Rev. Darwin Fox first discovered the 
 remains of mammalia characteristic of the 
 gypseous series of Paris, as Palceotherium Lower mote tooth, nat. 
 magnum (Fig. 174), P. nieclmm, P. m,inus, Ampiotherium. 
 P. minimum, P. curtutn, P. crassum/ also 
 Anoplotherium, commune (Fig. 173),^. se- 
 cundarium, Dichobune cervinum, and Chmropotamus Ouvieri. 
 The Paleothere above alluded to resembled the living tapir 
 ill the form of the head, and in having a short proboscis, but 
 
 Fig. 1T4. 
 
 com- 
 mune. BiBstead, Isle 
 of Wight. 
 
 Palceotheriwn ma^itm,' Cnvier. 
 
 its molar teeth were more like those of the rhinoceros. Pa- 
 Imotherium mxignum was of tHe size of a horse, three or four 
 feet high. The annexed woodcut. Fig. 1 Y4, is one of the 
 restorations which Cuvier attempted of the outline of the 
 living animal, derived from the study of the entire skeleton. 
 
UPPER EOCENE FORMATIONS. 255 
 
 As the vertical range of particular species of quadrupeds, so 
 far as our knowledge extends, is far more limited than that 
 of the testacea, the occurrence of so many species at Bin- 
 Stead, agreeing with fossils of the Paris gj'psum, strengthens 
 the evidence derived, from shells and plants of the synchro- 
 nism of the two formations. 
 
 Osborne or St. Helen's Series, A. 2.— This group is of fiesh 
 and brackish-water origin, and very variable in mineral char- 
 acter and thickness. Near Ryde, it supplies a freestone much 
 used for building, and called by Pi'ofessor Forbes the Nettle- 
 stone grit. In one part ripple-marked flagstones occur, and 
 rocks with fucoidal markings. The Osborne beds are distin- 
 guished by peculiar species of Paludhia, Melania, apd Me- 
 lanopsis, as also of Cypris and the seeds of Chara. 
 
 Headon Series, A. 3. — These beds are seen both in White- 
 cliff Bay, Headon Hill, and Alum Bay, or at the east and 
 west extremities of the Isle of Wight. The upper and lower 
 portions are fresh-water, and the middle of mixed origin, 
 sometimes brackish and marine. Everywhere Planorhis ett- 
 omphalus, Fig. 115, characterizes the fresh-water deposits, 
 just as the allied form, P. discus. Fig. 170, does the Bem- 
 bridge limestone. The brackish-water beds contain Pota- 
 momya plana, Cerithium nvutahile, and Potainides cinctus 
 (Fig. 37, p. 56), and the marine beds Venus (or Cytherea) in- 
 crassata, a species common to the Limburg beds and Gres de 
 Kg. its. 
 
 Fig. 1T6. 
 
 ' * ' ■ i 
 
 Plaiwrbis momphalws. Sow. Helix labjfrinihica, Say. Headon Hill, Isle of Wight; 
 Headou Hill, i diam. and Hordwell CJiff, Hants— also recent. 
 
 Fontainebleau, or the Lower Miocene series. The prevalence 
 of salt-water remains is most conspicuous in some of the cen- 
 tral parts of the formation. 
 
 Among the shells which are widely distributed through 
 the Headon series are JVeritina concava (Fig. ^.^ ^^^ 
 i'J'7),Zymnea oaudata (Fig. 178), and Cerithi- 
 um concavum :(Fig. 179). JTelix labyrinthica. 
 Say (Fiff. 176), a land-shell now inhabiting the 
 United States, was discovered in this series by ^^l^j^'^HeadZar 
 Mr. Searles Wood in Hordwell Cliff. It is also ries. 
 
256 ELEMENTS OF GEOLOGY. 
 
 Fig. ITS. Fig. 1T9. met with in Headon 
 
 Hill, in the same beds. 
 At Sconce, in the Isle 
 of Wight, it occurs in 
 the Bembridge series, 
 and affords a rare ex- 
 ample of an Eocene fos- 
 sil of a species still liv- 
 ing, though, as usual 
 
 l/ymnea cavdata, Edw. Cerithium conmrnim, Sow. in SUch CaseS, having 
 Headon .eries. Headon series. ^^ j^^^j Connection 
 
 with the actual geographical range of the species. The lower 
 and middle portion of the Headon series is also met with in 
 Hordwell Cliff (or Hordle, as it is often spelt), near Lyming- 
 ton, Hants. Among the shells which abound in this cliff are 
 Paludina lenta and various species of Lymnea^ Planorbis, 
 Melania, Cyclas, Unio, Potamomya, Dreissena, etc. 
 
 Among the chelonians we find a species of Emys; and no 
 less than six species of Trionyx ; among the saurians an al- 
 ligator and a crocodile ; among the ophidians two species of 
 land-snakes (Paferyx, Owen) ; and among the fish Sir P. Eger- 
 ton and Mr. Wood have found the jaws, teeth, and hard shin- 
 ing scales of the genus Lepidosteiis, or bony pike of the Amer- 
 ican rivers. This same genus of fresh-water ganoids has also 
 been met with in the Hempstead beds in the Isle of Wight. 
 The bones of several birds have been obtained from Hord- 
 well, and the remains of quadrupeds of the genera Paloeothe- 
 rinm {P. rninus),Anoplotherium.,Anthracotheriurn,Dichoc[on, 
 Dichobune, Spalacodon, and JSyoenodon. The latter offers, I 
 believe, the oldest known example of a true carnivorous ani- 
 mal in the series of British fossils, although I attach very 
 little theoretical importance to the fact, because herbivorous 
 species are those most easily met with in a fossil state in all 
 save cavern deposits. In another point of view, however, 
 this fauna deserves notice. Its geological position is consid- 
 erably lower than that of the Bembiidge or Montmartre 
 beds, from which it differs almost as much in species as it 
 does from the still more ancient fauna of the Lower Eocene 
 beds to be mentioned in the sequel. It therefore teaches us 
 what a grand succession of distinct assemblages of mamma- 
 lia flourished on the earth during the Eocene period. 
 
 Many of the marine shells of the brackish-water beds of 
 the above series, both in the Isle of Wight and Hordwell 
 Cliff, are common to the underlying Barton Clay : and, on 
 the other hand, there are some fresh-water shells, such as Gy- 
 rena obovata, which are common to the Bembridge beds, not- 
 
UPPER EOCENE FOBMATIONS. 257 
 
 Withstanding the intervention of the St. Helen's series. The 
 white and green marls of the Headon series, and some of the 
 accompanying limestones, often resemble the Eocene strata 
 of France in mineral character and color in so striking a 
 manner as to suggest the idea that the sediment was derived 
 from the same region or produced contemporaneously under 
 very similar geographical circumstances. 
 
 At Brockenhurst, near Lyridhurst, in the New Forest, ma- 
 rine strata have recently been found containing fifty-nine 
 shells, of which many have been described by Mr. Edwards. 
 These beds rest on the Lower Headon, and are considered as 
 the equivalent of the middle part of the Headon series, many 
 of the shells being common to the brackish-water or Middle 
 Headon beds of Colwell and White- 
 cliff" Bays, such as Cancellaria mu- ^ ■^'^" ^^"^ 
 ricata. Sow., Fusus labiatus, Sow., 
 etc. In these beds at Brocken- 
 hurst, corals, ably described by Dr. 
 Duncan, have recently been found 
 in abundance and perfection ; see 
 Fig. 180, Solenastroea cellulosa. 
 
 Baron Von Konen* has pointed 
 out that no less than forty-six out 
 of the fifty-nine Bi-ockenhurst shell s, 
 
 or a pi-oportion of 78 per cent., agree Solenastr<Ea cellulosa, Dune. 
 
 With species occurring m Dumont s 
 
 Lower Tongrian formation in Belgium. This being the case, 
 we might fairly expect that if we had a marine equivalent 
 of the Bembridge series or of the contemporaneous Paris 
 gypsum, we should find it to contain a still greater number 
 of shells common to the Tongrian beds of Belgium, but the 
 exact correlation of these fresh-water groups of France, Bel- 
 gium, and Britain has not yet been fully made out. It is 
 possible that the Tongrian of Dumont may be newer than 
 the Bembridge series, and therefore referable to the Lower 
 Miocene. If ever the whole series should be complete, we 
 must be prepared to find the marine equivalent of the Bem- 
 bridge beds, or the uppermost Eocene, passing by impercepti- 
 ble shades into the inferior beds of the overlying Miocene 
 strata. 
 
 Among the fossils found in the Middle Headon are Uythe- 
 rea incrassata and Cerithiicm plicatum (Fig. 160, p. 245). 
 These shells, especially the latter, are very characteristic of 
 the Lower Miocene, and their occurrence in the Headon se- 
 ries has been cited as an objection to the line proposed to be 
 * Quart. Geol. Journal, vol. xx., p. 97. 1864. 
 
258 ELEMENTS OF GEOLOGY. 
 
 drawn between Miocene and Eocene. But if we were to at- 
 tach importance to such occasional passages, we should soon 
 find that no lines of division could be drawn anywhere, for 
 in the present state of our knowledge of the Tertiary series 
 there will always be species common to beds above and be- 
 low our boundary-lines. 
 
 Barton Series [Sands and Clays), A. 4, Table, p. 252. — 
 Both in the Isle of Wight, and in Hordwell Cliff, Hants, the 
 Headon beds, above-mentioned, rest on white sands usually 
 devoid of fossils, and used in the Isle of Wight for making 
 glass. In one of these sands Dr. Wright found Chama squor 
 mosa, a Barton Clay shell, in great plenty, and certain im- 
 pressions of marine shells have been found in 
 sands supposed to be of the same age in White- 
 cliff Bay. These sands have been called Upper 
 Bagshot in the maps of our Government Survey, 
 but this identification of a fossiliferous series in 
 the Isle of Wight with an unfossiliferous forma- 
 tion in the London Basin can scarcely be de- 
 pended upon. The Barton Clay, which imrae- 
 «a,Eichw. Bar- diately underlies these sands, is seen vertical in 
 '°"- Alum Bay, Isle of Wight, and nearly horizontal 
 
 in the cliffs of the mainland near Lymington. This clay, to- 
 gether with the Brackleshani beds, presently to be described, 
 has been termed Middle Bagshot by the Survey. In Barton 
 Cliff, where it attains a thickness of about 300 feet, it is rich 
 in marine fossils. 
 
 It was formerly confounded with the London Clay, an old- 
 er Eocene deposit of very similar mineral character, to be 
 mentioned below, p. 263, which contains many shells in com- 
 mon, but not more than one-fourth of the whole. In other 
 words, there are known at present 247 species in the London 
 Clay and 321 in that of Barton, and only VO common to the 
 two formations. Fifty-six of these have been found in the 
 intermediate Bracklesham beds, and the reappearance of the 
 other 14 may imply a return of similar conditions, whether 
 of temperature or depth or of a muddy argillaceous bottom, 
 common to the two periods of the London and Barton Clays. 
 According to M. Hebert, the most characteristic Barton Clay 
 fossils correspond to those of the Gres de Beauchamp, or Sa- 
 bles Moyens, of the Paris Basin, but it also contains many 
 common to the older Calcaire Grossier. 
 
 SHELLS OF THE BAETON CLAY. 
 
 Certain foraminifera called Nummulites begin, when we- 
 study the Tertiary formations in a descending order, to make 
 
MIDDLE EOCENE, ENGLAND. 
 Mg. 182. ■ Fig. 1S3. Pig. 184. 
 
 259: 
 
 Mitra scabra, Sow. Valuta ambigua, Sol. Typhis pungens, BraDd. 
 
 their first appearance in these beds. A small species called 
 Mimmulites variolaria, Fig. 190, is found both on the Hamp- 
 
 Fig. 185. 
 
 Kg. 180. 
 
 Fig. 18T. 
 
 Volwta athleta, Sol. Barton 
 and Bracklesham. 
 
 Terebellumfusiforms, Lam. 
 Barton and Bracklesham. 
 
 Terebellwm sopita-^ 
 Brand. 
 
 shire coast land in beds of the same age in Whiteeliff Bay, 
 in the Isle of Wight. Several marine shells, such as Gorbida 
 
 Pig. 188. 
 
 Pig. 189. 
 
 Cardita mlcata, Brand. 
 Barton. 
 
 Crassatella sulcata, Sow. 
 Bracklesham and Barton. 
 
 Kwmmvlites variolaria^ 
 Lam. Var. of N. radi- 
 ata, Sow. Mid. Eocene^ 
 Brackleshain Bay. 
 
 ft.Nat.eize; &. magnified. 
 
 pisum (Fig. 158, p. 246), are common to the Barton beds and 
 the Hempstead or Lower Miocene series, and a still greater 
 number, as before stated, are common to the Headon series. 
 
 MIDDLE EOCENE, ENGLAND. 
 
 Bracklesham Beds and Bagshot Sands (B. 1, Table, p. 252). 
 Beneath the Barton Clay we find in the north of the Isle of 
 Wight, both in Alum and Whiteeliff Bays, a great series of 
 various colored sands and clays for -the most part unfossilif- 
 
260 
 
 ELEMENTS OF GEOLOGY. 
 
 erous, and probably of estuarine origin. As some of these 
 beds contain Gardita planicosta (Fig. 191) they have been 
 
 Fig. 191. 
 
 Cardita {Veiwncardia) planicosta, Lam. 
 
 identified with the marine beds much richer in fossils seen 
 in the coast section in Braclcleshani Bay near Chichester in 
 Sussex, where the strata consist chiefly of green clayey sands 
 with some lignite. Among the Bracklesham fossils besides 
 the Cardita, the huge Gerithium giganteum is seen, so con- 
 spicuous in the Calcaire Grossier of Paris, where it is some- 
 times two feet in length. The Nummulites losvigata (see 
 
 Fig. 192. 
 
 Nummulites {Nummularia) Iceoiijata. Bracklesham. Dixon's Fossils 
 ofSussex, PI. 8. 
 
 It. Section of the nummulite. i>. Group, with an individual showing the exterior 
 of the shell. 
 
 Fig. 192), SO characteristic of the lower beds of the Calcaire 
 Grossier in France, where it sometimes forms stony layers, 
 as near Compifegne, is very common in these beds, together 
 with N. scabra and If. variolaria. Out of 1 93 species of tes- 
 taeea procured from the Bagshot and Bracklesham beds in 
 England, 126 occur in the Calcaire Grossier in France. It 
 was clearly, therefore, coeval with that part of the Parisian 
 series more nearly than with any other. 
 
 According to tables compiled from the best authorities by 
 Mr. Etheridge, the number of moUusca now known from the 
 Bracklesham beds in Great Britain is 393, of which no less 
 
MIDDLE EOCENE, ENGLAND. 
 
 Fig. 193. 
 
 261 
 
 Paleeophis typhteus, Owen ; an Eocene sea-serpent. Bracklesham. 
 
 a, 6. Vertebra, with long neural spine preserved, c. Two vertebrae articulated 
 
 together. 
 
 than 240 are peculiar to this subdivision of the British Eo- 
 cene series, while 70 are common to the Older London Clay, 
 
 Fig. 194 
 
 Fig. 196. 
 
 Defensive spine of OBtracion. Bracklesham. 
 
 and 140 to the Newer Bai-ton Clay. The volutes and cow- 
 ries of this formation, as well as the lunulites and corals, fa- 
 vor the idea of a wai-m climate 
 having prevailed, which is borne 
 out by the discovery of a ser- 
 pent, Paleeophis typhoeus (see Fig. 
 193),exceeding,according toPro- 
 fessorOwenjtwentyfeetinlength, 
 and allied in its osteology to the 
 Boa, Python, Coluber, and Hy- ^^ 
 
 drus. The compressed form and j,^„,^, ^^^^Mylv,Wl^mv^ria. 
 
 diminutive size OI certain caudal Bracklesham Bay. 
 
 veilebrae indicate so much anal- Pixon-s Fossils of Sussex, Pi. 8. 
 ogy with Hydrus as to induce Professor Owen to pronounce 
 this extinct ophidian to have been marine.* Among the 
 companions of the sea-snake of Bracklesham was an extinct 
 crocodile {Gavialis Dixoni, Owen), and numerous fish, such 
 as now frequent the seas of warm latitudes, as the Ostracion 
 of the family Balistidse, of which a dorsal spine is figured 
 ^see Fig. 194), and gigantic rays of the genus Myliobates 
 (see Fig. 195). 
 
 The teeth of sharks also, of the genera Garcharodon, Oto- 
 dus, Lamna, Galeocerdo, and others, are abundant. (See 
 Figs. 196, 197, 198, 199.) 
 
 * PalseoBt. Soc. Monograph. Kept., pt. ii., p. 61. 
 
262 
 
 ELEMENTS OF GEOLOGY. 
 Fig. 196. Fig.l9T. 
 
 Fig. 198. 
 
 Carcharodon anryuatUens, Agass. Otodua obliguue, Agiiss. Galeocerdo- latidens, 
 
 AgasB.^ 
 Teetli of Sharks from Braclclesham Beds. 
 
 MARINE SHELLS OP BKACKLBSHAM BEDS. 
 
 Alum Bay and Bournemouth Beds (Lower Bagshot ofEng-^ 
 lish Survey), B. 2, Table, p. 252. To that great series of 
 sands and clays which intervene between the equivalents of 
 the Bracklesham Beds and the London Clay or Lower ^Eo- 
 cene, our Government Survey has given the name of the 
 Lower Bagshot sands, for they are supposed to agree in age 
 with the inferior unfossiliferous sands of the country rOund 
 
 Fig. 200. 
 
 Fig. 201. 
 
 Fig. 202. 
 
 Fig. 203. 
 
 Fie;. 204. 
 
 Pleurotoma Valuta 
 
 attenuatay Selse^ensis, 
 
 Sow. Edwards. 
 
 Titrritella 
 
 multieulcatat 
 
 Lain. 
 
 jAKina serrata. Sow 
 Magnified. 
 
 Coavm 
 
 depffrdittls, 
 
 Bmg. 
 
 Bagshot in the London Basin. This part of the series is 
 finely exposed in the vertical beds of Alum Bay, in the Isle 
 of Wight,' and east and west of Bournemouth, on the south 
 coast of Hampshire. In some of the close and white com- 
 pact clays of this locality, there are not only dicotyledonous 
 leaves, but numerous fronds of ferns allied to Gleichenia 
 which are well preserved with their fruit. 
 
 None of the beds are of great horizontal extent, and there 
 is much cross-stratification in the -sands, and in some places 
 
LOWER EOCENE, ENGLAND. 263 
 
 black carbonaceous seams and lignite. In the midst of these 
 leaf-beds in Studland Bay, Purbeck shells of the genus Unio 
 attest the fresh- water origin of the white clay. 
 
 No less than forty species of plants are mentioned by MM. 
 de la Harpe and Gaudin from this formation in Hampshire, 
 among which the Proteacese {Ih'yandra, etc.) and the lig 
 tribe are abundant, as well as the cinnamon and several oth- 
 er laurineae, with some papilionaceous plants. On the whole, 
 they remind the botanist of the types of subtropical India 
 and Australia.* 
 
 Heer has mentioned several species which are common to 
 this Alum Bay flora and that of Monte Bolca, near Verona, 
 so celebrated for its fossil fish, and where the strata contain 
 nummulites and other Middle Eocene fossils. He has par- 
 ticularly alluded to Aralia primigenia (of which genus a 
 fruit has since been found by Mr. Mitchell at Bournemouth), 
 Daphnogene Veronensis, and Ficus granadilla, as among the 
 species common to and characteristic of the Isle of Wight 
 and Italian Eocene beds ; and he observes that in the flora 
 of this period those forms of a temperate climate which con- 
 stitute a marked feature in the European Miocene forma- 
 tions, such as the willow, poplar, birch, alder, elm, hornbeam, 
 oak, fir, and pine, are wanting. The American types are also 
 absent, or much more feebly represented than in the Mio- 
 cene period, although fine specimens of the fan-palm {Sabal) 
 have been found in these Eocene clays at Studland. The 
 number of exotic forms which are common to the Eocene 
 and Miocene strata of Europe, like those to be alluded to in 
 the sequel which are common to the Eocene and Cretaceous 
 fauna, demonstrate the remoteness of the times in which the 
 geographical distribution of living plants originated. A 
 great majority of the Eocene genera have disappeared from 
 our temperate climates, but not the whole of them ; and they 
 must all have exerted some influence on the assemblages of 
 species which succeeded them; Many of these last occur- 
 ring in the Upper Miocene are indeed so closely allied to 
 the flora now surviving as to make it questionable, even in 
 the opinion of naturalists opposed to the doctrine of trans- 
 mutation, whether thev are not genealogically related the 
 one to the other. 
 
 LOWER EOCENE FOEMATIOlSrS, ENGLAND. 
 
 London Clay (C. 1, Table, p. 252).— This formation under- 
 lies the preceding, and sometimes attains a thickness of 500 
 feet. It consists of tenacious brown and bluish-gray clay, 
 * Heer, Climat et Vegetation du Pays Tertiaire', p. 172. 
 
264 
 
 ELEMENTS OF GEOLOGY. 
 
 with layers of concretions called septaria, which abound chief- 
 ly in the brown clay, and are obtained in sufficient numbers 
 from sea-cliffs near Harwich, and from shoals off the coast 
 of Essex and the Isle of Sheppey, to be used for making Ro- 
 man cement. The total number of British fossil moUnsca 
 known at present (January, 1870) in this formation are 264, 
 of which 166 are peculiar, or not found in other Eocene beds 
 in this country. The principal localities of fossils in the Lon- 
 don clay are Highgate Hill, near London, the Island of Shep- 
 pey at the mouth of the Thames, and Bognor on the Sussex 
 coast. Out of 133 fossil shells, Mr. Prestwich found only 20 
 to be common to the Calcaire Grossier (from which 600 spe- 
 cies have been obtained), while 33 are common to the " Lits 
 Coquilliers" (p. 2T5), in which 200 species are known in 
 France. 
 
 In the Island of Sheppey near the mouth of the Thames, 
 the thickness of the London Clay is estimated by Mr. Prest- 
 wich to be more than 500 feet, and it is in the uppermost 50 
 feet that a great number of fossil fruits were obtained, being 
 chiefly found on the beach when the sea has washed away 
 the clay of the rapidly wasting cliffs. 
 
 Pig. 205. Mr. Bowerbank, in a valuable 
 
 publication on these fossil fruits 
 and seeds, has described no less 
 than thirteen fruits of palms of the 
 recent type Nipa, now only found 
 in the Molucca and Philippine Isl- 
 ands, and in Bengal (see Fig. 206). 
 In the delta of the Ganges, Dr. 
 Hooker observed the large nuts of 
 Nipa fruticans floating in such 
 numbers in the various arms of that 
 great river, as to obstruct the pad- 
 NipadUes eUipiiem, Bow. dle-wheels of Steamboats. These 
 
 Fossil fruit of palm, from Sheppey. , , 1 1 . , , 
 
 plants are allied to the cocoanut 
 tribe on the one side, and on the other to the Pandanus, 
 or screw-pine. There are also met with three species of 
 Anona, or custard - apple ; and cucurbitaceous fruits (of 
 the gourd and melon family), and fruits of various species 
 of Acacia. 
 
 Besides fir-cones or fruit of true Coniferse there are cones 
 of Proteacese in abundance, and the celebrated botanist the 
 late Robert Brown pointed out the affinity of these to the 
 New Holland types Petrophila and Isopogon. Of the first 
 there are about fifty, and of the second thirty described spe^ 
 oies now living in Australia. 
 
LOWER EOCENE, ENGLAND. 265 
 
 Ettirigsnausen remarked in 1851 rig. 206. 
 
 that five of the fossil species from 
 Sheppey, named by Bowerbank,* '^A 
 were specimens of the same fruit 
 (see Fig. 206), in difiFerent states 
 of preservation ; and Mr. Carru- 
 thers, having examined the origi- 
 nal specimens now in the British 
 Museum, tells me that all these 
 cones from Sheppey may be re- „ „ , „ ., 
 
 J J] . . r^ .•' 1 ■ i 1 EoceDe Proteaceons Pruit. 
 
 duced to two species, which have PetrophHoide, EieMrds<mi. London 
 an undoubted aflinity to the two Clay, Sheppey. Natural size. 
 
 existing Australian genera above »• Cone. 6. section of cone Bhow- 
 
 i ■ J ij.1, i,^i_ • J? J. IIS tbe position of the seeds. 
 
 mentioned, although their perfect 
 identity in structure can not be made out. 
 
 The contiguity of land may be inferred not only from these 
 vegetable productions, but also from the teeth and bones of 
 crocodiles and turtles, since these creatures, as Dean Cony- 
 beare remarked, must have resorted to some shore to lay 
 their eggs. Of turtles there were numerous species referred 
 to extinct genera. These are, for the most part, not equal in 
 size to the largest living tropical turtles. A sea-snake, which 
 must have been thirteen feet long, of the genus FaMophis 
 before mentioned (p. 261), has also been described by Pro- 
 fessor Owen from Sheppey, of a different species from that 
 of Bracklesham, and called P. toliapicus. A true crocodile, 
 also, Crocodilus toliapicus, and another saurian more nearly 
 allied to the gavial, accompany the above fossils ; also the 
 relics of several birds and quadrupeds. One of these last 
 belongs to the new genus Syracotherium of Owen, of the 
 hog tribe, allied to Chseropotamus; another is a, Lophiodon ; 
 a third a pachyderm called Coryphodon eoccenus by Owen, 
 larger than any existing tapir. All these animals seem to 
 have inhabited the banks of the great river which floated 
 down the Sheppey fruits. They imply the existence of a 
 mammiferous fauna antecedent to the period when nummu- 
 lites flourished in Europe and Asia, and therefore before the 
 Alps, Pyrenees, and other mountain-chains now forming the 
 backbones of great continents, were raised from the deep ; 
 nay, even before a part of the constituent rocky masses now 
 entering into the central ridges of these chains had been de- 
 posited in the sea. 
 
 The marine shells of the London clay confirm the infer- 
 ence derivable from the plants and reptiles in /avor of a 
 hio-h temperature. Thus many species of Conus and Voltita 
 
 * Bowerbank Fossil Fruits and Seeds of London Clay, Plates ix. and x. 
 
 12 
 
266 
 
 ELEMENTS OF GEOLOGY. 
 
 occur, a large Gyproea, G. oviformis,ayerj large Rostettmia 
 (Fig. 209), a species of Cancellaria, six species of Nautilus 
 (Fig. 211), besides other Cepbalopoda of extinct genera, one 
 of the most remarkable of which is the Belosepia (Fig. 21 2)^ 
 
 rig. 207. 
 
 SHELLS OF THE LONDON CLAY. 
 
 Fig. 20». 
 
 Fig. 20S. 
 
 VohiXa nodosa, 
 Sow. Highgate. 
 
 Phorus extensue. 
 Sow. Higligate. 
 
 Fig. 210. 
 
 Nautilus eentraliSj Sow. Highgate. 
 Fig. 211. 
 
 Aturia ziczae, Bronn. Syn. NautUu^ 
 eiczac, Sow. London clay. ' Sheppey. 
 
 Boetellaria {mppocren^) ampla, Brnn- 
 der. i of nat. size; also found in 
 the Barton clay. 
 
 Fig. 212. 
 
 Belosepia eepioidetfiTie Blainv. 
 London clay. Sheppey. 
 
 Fig. 213. 
 
 Lt _^^dtdoides, 
 
 Sow. Highgate. 
 
 Fig. 214. 
 
 Cyptodon {Axinus) an- 
 flulatUTn^ Sow. Lou- 
 don clay, Hornsey. 
 
 Fig. 215. 
 
 Astropeaten crispatue, E. 
 Forbes. ' Sheppey. 
 
WOOLWICH AND READING SERIES. 261 
 
 Among many characteristic bivalve shells are Zeda amyg- 
 daloides (Fig. 213) and Gryptodon angulatum (Fig. 214), 
 and among the Eadiata a stai--fish, Astropeoten (Fig. 215). 
 
 These fossils are accompanied by a sword-fish {Tetrapterus 
 prisaus, Agassiz), about eight feet long, and a saw-fish \Pris- 
 tis bisiilcatus, Ag.), about ten feet in length; genera now 
 foreign to the British seas. On the whole, about eighty 
 species of fish have been described by M. Agassiz from these 
 beds of Sheppey, and they indicate, in his opinion, a warm 
 climate. 
 
 In the lower part of the London clay at Kyson, a few 
 miles east of Woodbridge, the remains of mammalia have 
 been detected. Some of these have been referred by Pro- 
 fessor Owen to an opossum, and others to the genus Hyra- 
 cotherium. The teeth of this last- mentioned pachyderm 
 were at first, in 1 840, supposed to belong to a monkey, an 
 opinion afterwards abandoned by Owen when more ample 
 materials for comparison were obtained. 
 
 Woolwich and Reading Series (C 2, Table, p. 252). — This 
 formation was formerly called the Plastic Clay, as it agrees 
 with a similar clay used in pottei-y which occupies the same 
 position in the French series, and it has been used for the 
 like purposes in England.* 
 
 No formations can be moi"e dissimilar, on the whole, in 
 mineral character than the Eocene deposits of England and 
 Paris ; those of our own island being almost exclusively of 
 mechanical origin — accumulations of mud, sand, and pebbles ; 
 while in the neighborhood of Paris we find a great succes- 
 sion of strata composed of limestones, some of them siliceous, 
 and of crystalline gypsum and siliceous sandstone, and some- 
 times of pure flint used for millstones. Hence it is often im- 
 possible, as before stated, to institute an exact comparison 
 between the various members of the English and French 
 series, and to settle their respective ages. But in regai'd to 
 the division which we have now under consideration, wheth- 
 er we study it in the basins of London, Hampshire, or Paris, 
 we recognize as a general rule the same mineral character, 
 the beds consisting over a large area of mottled clays and 
 sand, with' lignite, and with some strata of well-rolled flint 
 pebbles, derived from the chalk, varying in size, but occa- 
 sionally several inches in diameter. These strata may be 
 seen in the Isle of Wight in contact with the chalk, or in 
 the London basin, at Reading, Blackheath, and Woolwich. 
 In some of the lowest of them, banks of oysters ai-e observed, 
 consisting of Ostrea bellovacina, so common in France in the 
 * Prestwich. Quart. Geo). Journ,, vol. x. 
 
268 
 
 ELEMENTS OF GEOLOGY. 
 
 same relative position. In these beds at Bromley, Dr. Buck- 
 land found a large pebble to whicli live full-grown oysters 
 were affixed, in such a manner as to show that they had 
 commenced their first growth upon it, and remained attach- 
 ed to it through life. 
 
 In several places, as at Woolwich on the Thames, at New- 
 haven in Sussex, and elsewhere, a mixture of marme and 
 fresh-water testacea distinguishes this member of the series. 
 Among the latter, Gyrena cuneiformis (see Fig. 216) and Me- 
 lania inqidnata (see Fig. 217) are very common, as in beds 
 
 Fig. 210. 
 
 Fig. 21T. 
 
 Cyrena cuneiformis, Sow. Natural size. Melania {Melcmatria) in- 
 
 Woolwich clays. gninata, Des. Syn. 
 
 C&i-ithiwni ruelanmaes. 
 Sow. Woolwichclays. 
 
 of corresponding age in France. They clearly indicate 
 points where rivers entered the Eocene sea. Usually there 
 is a mixture of brackish, fresh-water, and marine shells, and 
 sometimes, as at Woolwich, proofs of the river and the sea 
 having successively prevailed on the same spot. At New 
 Charlton, in the suburbs of Woolwich, Mr. de la Condamine 
 discovered in 1849, and pointed out to me, a layer of sand 
 associated with well-rounded flint pebbles in which numer- 
 ous individuals of the Cyrena tellinella were seen standing 
 endwise with both their valves united, the siphonal extrem- 
 ity of each shell being uppermost, as would happen if the 
 mollusks had died in their natural position. I have de- 
 scribed* a bank of sandy mud, in the delta of the Alabama 
 River at Mobile, on the borders of the Gulf of Mexico, where 
 in 1846 I dug oat at low tide specimens of living species of 
 Cyrena and of a Gnathodon, which were similarly placed 
 with their shells erect, or in a posture which enables the an- 
 imal to protrude its siphon upward, and draw in or reject 
 water at pleasure. The water at Mobile is usually fresh, 
 * Second Visit to the United States, vol. ii., p. 104. 
 
WOOLWICH AND READING SERIES. 269 
 
 but sometimes brackish. At Woolwich a body of river-wa- 
 ter must have flowed permanently into the sea where the 
 CyrenxB lived, and they may have been killed suddenly by 
 an influx of pure salt-water, which invaded the spot when 
 the river was low, or when a subsidence of land took place. 
 Traced in one direction, or eastward towards Heme Bay, 
 the Woolwich beds assume more and more of a marine char- 
 acter ; while in an opposite, or south-western direction, they 
 become, as near Chelsea and other places, more fresh-water, 
 and contain Unio, Paluclina, and layers of lignite, so that 
 the land drained by the ancient river seems clearly to have 
 been to the south-west of the present site of the metropolis. 
 
 Fluviaiile jBeds underlying Deep-sea Strata. — Before the 
 minds of geologists had become familiar with the theory of 
 the gradual sinking of land, and its conversion into sea at 
 difierent periods, and the consequent change from shallow 
 to deep water, the fluviatile and littoral character of this 
 inferior group appeared strange and anomalous. After pass- 
 ing through hundreds of feet of London clay, proved by its 
 fossils to have been deposited in deep salt-water, we arrive 
 at beds of fluviatile origin, and associated with them masses 
 of shingle, attaining at Blackheath, near London, a thickness 
 of 50 feet. These shingle banks are probably of marine ori- 
 gin, but they indicate the proximity of land, and the exist- 
 ence of a shore where the flints of the chalk were rolled into 
 sand and pebbles, and spread over a wide space. We have, 
 therefore, flrst, as before stated (p. 268), evidence of oscilla- 
 tions of level during the accumulation of the Woolwich se- 
 ries, then of a great submergence, which allowed a marine 
 deposit 500 feet thick to be laid over the antecedent beds 
 of fresh and brackish water origin. 
 
 Thanet Sands (C 3, p. 252).— The Woolwich or plastic clay 
 above described may often be seen in the Hampshire basin 
 in actual contact with the chalk, constituting in such places 
 the lowest member of the British Eocene series. But at 
 other points another formation of marine origin, character- 
 ized by a somewhat difierent assemblage of organic remains, 
 has been shown by Mr. Prestwich to intervene between the 
 chalk and the Woolwich series. For these beds he has pro- 
 posed the name of " Thanet Sands," because they are well 
 seen in the Isle of Thanet, in the northern part of Kent, 
 and on the sea-coast between Heme Bay and the Keculvers, 
 where they consist of sands with a few concretionary masses 
 of sandstone, and contain, among other fossils, Pholadomya m- 
 neata, Cyprina Morrisii, Gorhula longirostris, Scalaria Bower- 
 hanJcii, etc. The greatest thickness of these beds is 90 feet. 
 
270 ELEMENTS OF GEOLOGY. 
 
 UPPER EOCENE FOEMATIONS OF FEANCB. 
 
 The tertiary formations in the neighborhood of Paris con- 
 sist of a series of marine and fresh-water strata, alternating 
 with each other, and filling up a depression in the chalk. 
 The area which they occupy has teen called the Paris Basin, 
 and is about 180 miles in its gi-eatest length from north to 
 south, and about 90 miles in breadth from east to west. MM. 
 Cuvier and Brongniart attempted, in 1810, to distinguish 
 five diiferent groups, comprising three fresh- water and two 
 marine, which were supposed to imply that the waters of 
 the ocean, and of rivers and lakes, had been by turns admit- 
 ted into and excluded from the same area. Investigations 
 since made in the Hampshire and London basins have rather 
 tended to confirm these views, at least so far as to show that 
 since the commencement of the Eocene period there have 
 been great movements of the bed of the sea, and of the ad- 
 joining lands, and that the superposition of deep-sea to shal- 
 low-water deposits (the London clay, for example, to the 
 Woolwich beds) can only be explained by referring to such 
 movements. It appears, notwithstanding, from the research- 
 es of M. Constant Prevost, that some of the minor alternations 
 and intermixtures of fresh-water and marine deposits, in the 
 Paris basin, may be accounted for without such changes of 
 level, by imagining both to have been simultaneously in 
 progress, in the same bay of the same sea, or a gulf into 
 which many rivers entered. 
 
 Gypseous Series of Montmartre (A. 1, Table, p. 252).— To 
 enlarge on the numerous subdivisions of the Parisian strata 
 would lead me beyond ray present limits ; I shall therefore 
 give some examples only of the most important formations. 
 Beneath the Gres de Fontainebleau, belonging to the Lower 
 Miocene period, as before stated, we find, in" the neighbor- 
 hood of Paris, a series of white and green marls, with subor- 
 dinate beds of gypsum. These are most largely developed 
 in the central parts of the Paris basin, and, among other 
 places, in the hill of Montmartre, where its fossils were first 
 studied by Cuvier. 
 
 The gypsum qnan-ied there for the manufacture of plaster 
 of Paris occurs as .a granular crystalline rock, and, together 
 with the associated marls, contains land and fluviatile shells, 
 together with the bones and skeletons of birds and quadru- 
 peds. Several land-plants are also met with, among which 
 are fine specimens of the fan-palm or palmetto tribe {FlabellOr 
 ria). The remains also of fresh-water fish, and of crocodiles 
 and other reptiles, occur in the gypsum. The skeletons of 
 
UPPER EOCENE. STRATA OF FRANCE. 
 
 271 
 
 mammalia ai-e usually isolated, often entire, the most deli- 
 cate extremities being preserved ; as if the carcasses, clothed 
 with their flesh and skin, had been floated down soon after 
 death, and while they were still swollen by the gases gene- 
 rated by their first decomposition. The few accompanying 
 shells are of those light kinds which frequently float on the 
 surface of rivers, together with wood. 
 
 In this formation the relies of about fifty species of quad- 
 rupeds, including the genera PalcBOtherium (see Fig. 174, p. 
 254), Anoplothermm (see Fig. 218), and others, have been 
 found, all extinct, and neai'ly four-fifths of them belonging 
 to the Perissodactyle or odd-toed division of the order Pdch- 
 ydermata, which now contains only four living genera, 
 namely, rhinoceros, tapir, horsfe, and hyrax. With them a 
 few carnivorous animals are associated, among which are 
 the HycEnodon dasyuroides, a species of dog, Canis Parisierir 
 sis, and a weasel, Gynodon Parisiensis. Of the Poderitia 
 are found a squirrel ; of the Cheiroptera, a bat ; while the 
 Marsupialia (an order now confined to America, Australia, 
 and some contiguous islands) are represented by an opossum. 
 
 Of birds, about ten species have been ascertained, the skel- 
 etons of some of which are entire. None of them are refer- 
 able to existing species.* The same remark, according to 
 MM. Cuvier and Agassiz, applies both to the reptiles and 
 fish. Among the last are crocodiles and tortoises of the gen- 
 era Mnys and Trionyx. 
 
 The tribe of land quadrupeds most abundant in this for- 
 mation is such as now inhabits alluvial plains and marshes, 
 and the banks of rivers 
 
 and lakes, a class most ^'S- ^^^• 
 
 exposed to suffer by riv- 
 er inundations. Among 
 these were several spe- 
 cies oi Palae,othe,rium,& 
 genus before alluded to 
 fp. 254). These were 
 associated with the An- 
 oplotherium, a tribe 
 intermediate between 
 pachyderms and rumi- 
 nants. One of the three 
 divisions of this family 
 was called by Cuvier 
 Xiphodon. Their forms 
 were slender and ele- 
 
 Xiphodan gracile, m Anoplotherium gracile, Cuvier. 
 Restored outline. 
 
 * Cuvier, Oss. Foss., torn, iii., p. 255. 
 
272 ELEMENTS OF GEOLOGY. 
 
 gant, and one, named Xiphodon gracile (Fig. 218), was about 
 the size of tbe chamois ; and Ciivier inferred from the skele- 
 ton that it was as light, graceful, and agile as the gazelle. 
 
 Fossil Foot-prints. — There are three superimposed masses 
 of gypsum in the neighborhood of Paris, separated by inter- 
 vening deposits of laminated marl. In the uppermost of the 
 three, in the valley of Montmorency, M. Desnoyers discovered 
 in 1859 many foot-prints of animals occurring at no less than 
 six different levels.* The gypsum to which they belong 
 varies from thirty to fifty leet in thickness, and is that 
 which has yielded to the naturalist the largest number of 
 bones and skeletons of mammalia, birds, and reptiles. I 
 visited the quarries, soon after the discovery was made 
 known, with M. Desnoyers, who also showed me large slabs 
 in the Museum at Paris, where, on the upper planes of strat- 
 ification, the indented foot-marks were seen, while corre- 
 sponding casts in relief appeared on the lower surfaces of 
 the strata of gypsum which were immediately superim- 
 posed. A thin film of marl, which before it was dried and 
 condensed by pressure must have represented a much thick- 
 er layer of soft mud, intervened between the beds of solid 
 gypsum. On this mud the animals had trodden, and made 
 impressions which had penetrated to the gypseous mass 
 below, then evidently unconsolidated. Tracks of the Ano- 
 plotherium with its bisnlcate hoof, and the trilobed foot-prints 
 of Palmotherium, were seen of different sizes, corresponding 
 to those of several species of these genera which Cuvier had 
 reconstructed, while in the same beds were foot-marks of 
 carnivorous mammalia. The tracks also of fluviatile, lacus- 
 trine, and terrestial tortoises [Einys, Trionyx, etc.) were 
 discovered, also those of crocodiles, iguanas, geckos, and 
 great batrachians, and the foot-prints of a huge bird, appar- 
 ently a wader, of the size of the gastornis, to be mentioned 
 in the sequel. There were likewise the impressions of the 
 feet of other creatures, some of them clearly distinguishable 
 from any of the fifty extinct types of mammalia of which 
 the bones have been found in the Paris gypsum. The whole 
 assemblage, says Desnoyers, indicate the shores of a lake, or 
 several small lakes communicating with each other, on the 
 borders of which many species of pachyderms wandered, 
 and beasts of prey which occasionally devoured them. The 
 tooth-marks of these last had been detected by paleontolo- 
 gists long before on the bones. and skulls of Faleotheres en- 
 tombed in the gypsum. 
 
 * Sur des Empreintes de Pas d'Animaux, par M. J. Desnoyers. Compte 
 rendu de I'lnstitut, 1859. 
 
UPPER EOCENE STRATA OF FRANCE. 273 
 
 Imperfection of the Record. — These foot-marks have re- 
 vealed to us new and unexpected proofs that the air-breath- 
 ing fauna of the Upper Eocene period in Europe far surpassed 
 in the number and variety of its species the largest estimate 
 which had previously been formed of it. We may now feel 
 sure that the mammalia, reptiles, and birds which have left 
 portions of their skeletons as memorials of their existence in 
 the solid gypsum constituted but a part of the then living 
 creation. Similar inferences may be drawn from the study 
 of the whole succession of geological records. In each dis- 
 trict the monuments of periods embracing thousands, and 
 pi'obably in some instances hundreds «f thousands of years, 
 are totally wanting. Even in the volumes which are extant 
 the greater number of the pages are missing in any given 
 region, and where they are found they contain but few and 
 casual entries of the physical events or living beings of the 
 times to which they relate. It may also be remarked that 
 the subordinate formations met with in two neighboring 
 countries, such as France and England (the minor Tertiary 
 groups above enumerated), commonly classed as equivalents 
 and referred to corresponding periods, may nevertheless have 
 been by no means strictly coincident in date. Though call- 
 ed contemporaneous, it is probable that they were often sep- 
 arated by intervals of many thousands of years. We may 
 compai'e them to double stars, which appear single to the 
 naked eye because seen from a vast distance in space, and 
 which really belong to one and the same stellar system, 
 though occupying places in space extremely remote if esti- 
 mated by our ordinary standard of terrestrial measurements. 
 
 Calcaire siliceux,or Travertin inferieur (A. 2 and 3, p. 262). 
 — This compact siliceous limestone extends over a wide area. 
 It resembles a precipitate from the waters of mineral springs, 
 and is often traversed by small empty sinuous cavities. It 
 is, for the most part, devoid of organic remains, but in some 
 places contains fresh-water and land species, and never any 
 marine fossils. The calcaire siliceux and the calcaire gros- 
 sier usually occupy distinct parts of the Paris basin, the one 
 attaining its fullest development in those places where the 
 other is of slight thickness. They are described by some 
 writers as alternating with each other towards the centre 
 of the basin, as at Sergy and Osny. 
 
 The gypsum, with its associated marls before described, is 
 in greatest force towards the centre of the basin, where the 
 calcaire drossier and calcaire siliceux are less fully developed. 
 
 Grfes de Beauchamp, or Sables Moyens (A. 4, p. 252). — In 
 some parts of the Paris basin, sands and marls, called the 
 ^ 12* 
 
2Y4 ELEMENTS OF GEOLOGY. 
 
 Gi-6s de Beauehamp, or Sables moyens, divide the gypseous 
 beds from the calcaire gi-ossier proper. These sands, in 
 which a small nummulite {JV. variolaria) is very abundant, 
 contain more than 300 species of marine shells, many of them 
 peculiar, but others common to the next division. 
 
 MIDDLE EOCENE EOEMATIONS OF FKANCE. 
 
 Calcaire Grossier, upper and middle (B. l, p. 252). — The up- 
 per division of this group consists in great part of beds of 
 compact, fragile limestone, with some intercalated green 
 marls. The shells in some parts are a mixture of Oerithium, 
 Gyelostoma, and Gorbula; in others Limnea, Cerithium, Pa- 
 ludina, etc. In the latter, the bones of reptiles and mamma- 
 lia, Paloeotherium and Lophiodon, have been found. The 
 middle division, or calcaire grossier proper, consists of a coarse 
 limestone, often passing into sand. It contains the greater 
 number of the fossil shells which characterize the Paris ba- 
 sin. No less than 400 distinct species have been procured 
 from a single spot near Grignon, where they are imbedded 
 in a calcareous sand, chiefly formed of comminuted shells, in 
 which, nevertheless, individuals in a perfect state of preser- 
 vation, both of marine, terrestrial, and fresh- water species, are 
 mingled together. Some of the marine shells may have lived 
 on the spot ; but the Cyclostoma and Ijimnea, being land and 
 fresh-water shells, must have been brought thither by rivers 
 and currents, and the quantity of triturated shells implies 
 considerable movement in the waters. 
 
 Nothing is more striking in this assemblage of fossil testa- 
 cea than the great proportion of species referable to the ge- 
 nus Cerithium (see Figures, p. 245). There occur no less than 
 IS"? species of this genus in the Paris basin, and almost all of 
 them in the calcaire grossiei'. Most of the living Gerithia 
 inhabit the sea near the mouths of rivers, where the waters 
 are brackish ; so that their abundance in the marine strata 
 now under consideration is in harmony with the hypothesis 
 that the Paris basin formed a gulf into which several rivers 
 flowed. 
 
 In some parts of the calcaire grossier round Paris, certain 
 beds occur of a stone used in building, and called by the 
 French geologists "Miliolite limestone." It is almost entire- 
 ly made up of millions of microscopic shells, of the size of 
 minute grains of sand, which all belong to the class Foram- 
 inifera. Figures of some of these are given in the annexed 
 wood-cut. As this miliolitic stone never occurs in the Fa- 
 luns, or Upper Miocene strata of Brittany and Touraine, it 
 often furnishes the geologist with a useful criterion for dis- 
 
MIDDLE EOCENE STRATA OE ERANCE. 
 
 275 
 
 tinguishing the detached Eocene and Upper Miocene for- 
 mations scattered over those and other adjoining provinces 
 The discovery of the remains of Paleeotheriun? and other 
 mammalia in some of the upper beds of the calcaire grossier 
 
 EOCENE FOEAMINIEEEA. 
 
 Fig. 220. Pig. 221. 
 
 h 
 
 Calcarina rarispina, Spirolina stenostoma, FrilocuUna inflata, 
 
 Desh. Desh. Deeh. 
 
 a. Natural size. 6. Magnified. 
 
 shows that these land animals began to exist before the dep- 
 osition of the overlying gypseous series had cbmmenced. 
 
 Lower Calcaire grossier, or Glauconie grossiere (B. l,p. 252). 
 — -The lower part of the calcaire grossier, which often con- 
 tains much green earth, is characterized at Auvers, near Pon- 
 toise, to the north of Paris, and still more in the environs 
 of _Corapi6gne, by the abundance of nummulites, consisting 
 chiefly of JV. IcBvigata, JV. scabra, and JV. Zamarcki, which 
 constitute a large proportion of some of the stony strata, 
 though these same foraminifera are wanting in beds of sim- 
 ilar age in the immediate environs of Paris. 
 
 Soissounais sands, or Lits coquilliers (B. 2, p. 252). — Below 
 the preceding formation, shelly sands are seen, of consider- 
 able thickness, especially at Cuisse-Lamotte, near Compifegne, 
 and other localities in the Soissonnais, about fifty miles N.E. 
 of Paris, from which about 300 species of shells have been 
 obtained, many of them common 
 to the calcaire grossier and the 
 Bracklesham beds of England, alnd 
 inany peculiar. Th6 Nummvlites 
 planulata is very abundant, and the 
 most characteristic shell is the Ne- 
 
 rita conoidea. Lam., a fossil which ^^"- ^- **™*«'»'^. Chemnitz, 
 has a very wide geographical range ; for, as M. d'Archiac re- 
 marks, it accompanies the nnmmulitic formation from Europe 
 to India, having been found in Cutch, near the mouths of the 
 Indus, associated with Nummulites scabra. No less than 33 
 shells of this group are said to be identical with shells of the 
 London clay proper, yet, after visiting Cuisse-Lamotte and 
 
 Pig. 222. 
 
 Nerita conoidea^ Lam. 
 
276 ELEMENTS OF GEOLOGY. 
 
 other localities of the " Sables inferieurs " of Archiac, I agree 
 with Mr. Prestwich, that the latter are probably newer than 
 the London clay, and perhaps older than the Bracklesham 
 beds of England. The London clay seems to be unrepre- 
 sented in the Paris basin, unless partially so, by these sands.* 
 
 LOWER EOCElfE FORMATIONS OF FRANCE. 
 
 Argile Plastique (C. 2, p. 252). — At the base of the tertiary 
 system in France are extensive deposits of sands, with occa- 
 sional beds of clay used for pottery, and called " argile plas- 
 tique." Fossil oysters {Ostrea bellovacina) abound in some 
 places, and in others there is a mixture of fluviatile shells, 
 such as Gyrena cuneiformis (Fig. 216, p. 2Q%), Melania in- 
 quinata (Fig. 217), and others, frequently met with in beds 
 occupying the same position in the London Basin. Layers 
 of lignite also accompany the infeidor clays and sands. 
 
 Immediately upon the chalk at the bottom of all the ter- 
 tiary strata in France there generally is a conglomerate or 
 breccia of rolled and angular chalk-flints, cemented by sili- 
 ceous sand. These beds appear to be of littoral origin, and 
 imply the previous emergence of the chalk, and its waste 
 by denudation. In the year 1 855, the tibia and femur of a 
 large bird equalling at least the ostrich in size were found at 
 Meudon, near Paris, at the base of the Plastic clay. This 
 bird, to which the name of Gastornis Parisiensis has been 
 assigned, appears, from the Memoirs of MM. Hebert, Lartet, 
 and Owen, to belong to an extinct genus. Professor Owen 
 refers it to the class of wading land birds rather than to an 
 aquatic species.f 
 
 That a formation so much explored for economical pur- 
 poses as the Argile plastique around Paris, and the clays 
 and sands of corresponding age near London, should never 
 have afforded any vestige of a feathered biped previously to 
 the year 1855, shows what diligent search and what skill in 
 osteological interpretation are required before the existence 
 of birds of remote ages can be established. 
 
 Sables de Bracheux (C. 3, p. 252). — The marine sands call- 
 ed the Sables de Bracheux (a place near Beauvais), are con- 
 sidered by M. Hebert to be older than the Lignites and 
 Plastic clay, and to coincide in age with the Thanet Sands 
 of England. At La F6re, in the Department of Aisne, in a 
 deposit of this age, a fossil skull has been found of a quad- 
 ruped called by Blainville Arctocyon primcevus, and sup 
 
 * D'Archiac, Bulletin, torn, x.; and Prestwich, Quart. Geo!. Jouni., 1847, 
 p. 377. 
 
 t Quart. Geol. Journ., vol. xii., p. 204. 1856. 
 
NUMMULITIC FOEMATION. 211 
 
 posed by him to be related both to the bear and to the Kin- 
 kajou {Uercoleptes). This creature appears to be the oldest 
 known tertiary mammifer. 
 
 Nummulitic Formation of Europe, Asia, etc. — Of all the 
 rocks of the Eocene period, no formations are of such great 
 geographical importance as the Upper and Middle Eocene, 
 as above defined, assuming that the older tertiary formation, 
 commonly called nummulitic, is correctly ascribed to this 
 group. It appears that of more than fifty species of these 
 foraminifera described by D'Archiac, one or two species only 
 are found in other tertiary formations whether of older or 
 newer date. Nitnimulites intermedia, a Middle Eocene form, 
 ascends into the Lower Miocene, but it seems doubtful 
 whether any species descends to the level of the London 
 clay, still less to the Argile plastique or Woolwich beds. 
 Separate groups of strata are often characterized by distinct 
 species of nummulite ; thus the beds between the lower Mio- 
 cene and the lower Eocene may be divided into three sec- 
 tions, distinguished by three difierent species of nummu- 
 lites, JV. variolaria in the upper, N. laevigata in the middle, 
 and ]Sr. planulata in the lower beds. The nummulitic lime- 
 stone of the Swiss Alps rises to more than 10,000 feet above 
 the level of the sea, and attains here and in other mountain 
 chains a thickness of several thousand feet. It may be said 
 to play a far more conspicuous part than any other tertiary 
 group in the solid framework of the earth's crust, whether 
 in Europe, Asia, or Africa. It occurs in Algeria and Moroc- 
 co, and has been traced from Egypt, where it was largely 
 quarried of old for the building of the Pyramids, into Asia 
 Minor, and across Persia by Bagdad to the mouths of the 
 Indns. It has been observed not only in Cutch, but in the 
 mountain i-anges which separate Scinde from Persia, and 
 which form the passes leading to Caboul ; and it has been 
 followed still farther eastward into India, as far as eastern 
 Bengal and the frontiers of China. 
 
 Dr. T. Thompson found nunimulites at an elevation of no 
 less than 16,500 feet above the level of the sea, in Western 
 Thibet. One of the species, which I myself found very 
 abundant on the flanks of the Pyrenees, in a compact crys- 
 talline marble (Fig. 223) is called by M. d'Archiac Nummu- 
 lites Puschi. The same is also very common in rocks of the 
 same age in the Carpathians. In many distant countries, in 
 Cutch, for example, some of the same shells, such as Nerita 
 conoidea (Fig. 222), accompany the nummulites, as in France. 
 The opinion of many observers, that the Nummulitic forma- 
 tion belongs partly to the cretaceous era, seems chiefly to 
 
278 
 
 ELEMENTS OF GEOLOGY. 
 
 have arisen from, confounding an allied genus, Orbitoidesi 
 with the true Nummulite. 
 
 Fig. .223. ' 
 
 Nummulites Puschi^ D'Archiac. Peyrehorade, Pyrenees. 
 
 a. External surface of one of the unmmiilites, of which longitndinal sectiooB 
 are seen in the limestone. 6. Transverse section of same. 
 
 When we have once arrived at the conviction that the 
 nummulitic formation occupies a middle and upper place in 
 the Eocene series, we are struck with the comparatively 
 modern date to which some of the greatest revolutions in the 
 physical geography of Europe, Asia, and Northern Africa 
 must be referred. All the mountain-chains, such as the Alps, 
 Pyrenees, Carpathians, and Himalayas, into the composition 
 of whose central and loftiest parts the nummulitic strata 
 enter bodily, could have had no existence till after the Mid- 
 dle Eocene period. During that period the sea prevailed 
 where these chains now rise, for nummulites and their ac- 
 companying testacea were unquestionably inhabitants of salt 
 water. Before these events, comprising the conversion of a 
 wide area from a sea to a continent, England had been peo- 
 pled, as I before pointed out (p. 267), by various quadrupeds, 
 by herbivorous pachyderms, by insectivorous bats, and by 
 opossums. 
 
 Almost all the volcanoes which preserve any remains of 
 their original form, or from the craters of which lava streams 
 can be traced, are more modern than the Eocene fauna now 
 under consideration ; and besides these supei'ficial monu- 
 ments of the action of heat, Plutonic influences have worked 
 vast changes in the texture of rocks within the same period. 
 Some members of the nummulitic and overlying tertiary 
 strata called flysch have actually been converted in the cen- 
 tral Alps into crystalline rocks, and transformed into marble, 
 quartz-rock, micha-schist, and gneiss.* 
 
 Eocene Strata in the United States. — In North America 
 the Eocene formations occupy a large area bordering the At- 
 
 * Murchison, Quart. Journ. of Geol. Soc, vol. v., and Lyell, vol. vi. 1850 
 Anniversary Address. 
 
EOCENE STRATA, UNITED STATES. 279 
 
 Ian tic, which increases in breadth and importance as it is 
 traced southward from Delaware and Maryland to Georgia 
 and Alabama. They also occur in Louisiana and other States 
 both east and west of the valley of the Mississippi. At Clai- 
 borne, in Alabama, no less than 400 species of marine shells, 
 with many echinoderms and teeth of fish, characterize one 
 member of this system. Among the shells, the Cardita pla- 
 nicosta, before mentioned (Fig. 191, p. 260), is in abundance; 
 and this fossil and some others identical with European spe- 
 cies, or very nearly allied to them, make it highly probable 
 that the Claiborne beds agree in age with the central or 
 Bracklesham group of England, and with the calcaire gros^ 
 siere of Paris.* 
 
 Higher in the series is a remarkable calcareous rock, for- 
 merly called " the nummulite limestone," from the great 
 number of discoid bodies resembling nummulites which it 
 contains, fossils now referred by A. C'Orbigny to the genus 
 Orbitoides, which has been demonstrated by Dr. Carpenter 
 to belong to the foraminifera.f That naturalist, moreover, 
 is of opinion that the Orbitoides alluded to ( 0. Mantelli) is 
 of the same species as one found in Cutch, in the Middle 
 Eocene or nummulitic formation of India. 
 
 Above the orbitoidal limestone is a white limestone, some- 
 times soft and argillaceous, but in parts very compact and 
 calcareous. It contains several peculiar corals, and a large 
 Nautilus allied to N. ziczac ; also in its upper bed a gigantic 
 cetacean, called Zeuglodon by Owen. J 
 
 The colossal bones of this cetacean are so plentiful in the 
 interior of Clarke County, Alabama, as to be characteristic 
 of the formation. The vertebral column of one skeleton 
 found by Dr. Buckley at a spot visited by me, extended to 
 the length of nearly seventy feet, and not far off part of an- 
 other backbone nearly fifty feet long was dug up. I ob- 
 tained evidence, during a short excursion, of so many locali- 
 ties of this fossil animal within a distance of ten miles, as to 
 lead me to conclude that they must have belonged to at least 
 forty distinct individuals. 
 
 Prof Owen first pointed out that this huge animal was not 
 reptilian, since each tooth was furnished with double roots 
 (Fio-. 224), implanted in corresponding double sockets ; and 
 his opinion of the cetacean nature of the fossil was afterwards 
 
 * See paper by the Author, Quart. Joum. Geol. Soe., vol. iv., p. 12 ; and 
 Second Visit to the United States, vol. ii., p. 59. 
 
 t Quart. Journ. Geol. Soc, vol. vi., p. 32. 
 
 X See Memoir by K. W. Gibbes, Journ. of Acad. Nat. Sci. Philad., vol. i. 
 1847. 
 
280 ELEMENTS OF GEOLOGY. 
 
 Fig. 234. Fig. 225. 
 
 Zeuglodon cetoides, Owcd. JBaaUosaurus, Harlan. 
 Molar tooth, natural size. Vertebra, reduced. 
 
 confirmed by Dr. Wyman and Dr. R. W. Gibbes. That it 
 was an extinct mammal of the whale tribe has since been 
 placed beyond all doubt by discovery of the entire skull of 
 another fossil species of the same family, having the double 
 occipital condyles only met with in mammals, and the con- 
 voluted tympanic bones which are characteristic of cetaceans. 
 
CRETACEOUS PERIOD. 281 
 
 SECONDARY OR MESOZOIC SERIES. 
 
 CHAPTER XVII. 
 
 trPPEE CRETACEOUS GROUP. 
 
 Lapse of Time between Cretaceous and Eocene Periods. — Table of succes- 
 sive Cretaceous Eormations. — Maestricht Beds. — Pisolitic Limestone of 
 France.— Chalk of Paxoe. — Geographical Extent and Origin of the White 
 Chalk. — Chalky Matter now forming in the Bed of the Atlantic. — Marked 
 Difference between the Cretaceous and existing Fauna. — Chalk-flints. — 
 Pot-stones of Horstead. — Vitreous Sponges in the Chalk. — Isolated Blocks 
 of Foreign Rocks in the White Chalk supposed to be ice-borne. — Distinct- 
 ness of Mineral Character in contemporaneous Rocks of the Cretaceous 
 Epoch.— Fossils of the White Chalk. — Lower White Chalk without Flints. 
 — Chalk Marl and its Fossils. — Chloritic Series or Upper Greensand. — 
 Coprolite Bed near Cambridge. ^ — Fossils of the Chloritic Series. — Gault. — 
 Connection between Upper and Lower Cretaceous Strata. — Blackdown 
 Beds. — Flora of the Upper Cretaceous Period. — Hippurite Limestone. — 
 Cretaceous Rocks in the United States. 
 
 We have treated in the preceding chapters of the Tertiary 
 or Cainozoic strata, and have next to speak of the Second- 
 ary or Mesozoic formations. The uppermost of these last is 
 commonly called the chalk or the cretaceous formation, from 
 creta, the Latin name for that remarkable white earthy lime- 
 stone, which constitutes an upper member of the group in 
 those parts of Europe where it was first studied. The mark- 
 ed discordance in the fossils, of the tertiary, as compared 
 with the cretaceous formations, has long induced many ge- 
 ologists to suspect that an indefinite series of ages elapsed 
 between the respective periods of their origin. Measured, 
 indeed, by such a standard, that is to say, by the amount of 
 change in the Fauna and Flora of the earth effected in the 
 interval, the time between the Cretaceous and Eocene may 
 have been as great as that between the Eocene and Recent 
 periods, to the history of which the last seven chapters have 
 been devoted. Several deposits have been met with here 
 and there, in the course of the last half century, of an age in- 
 termediate between the white chalk and the plastic clays 
 and sands of the Paris and London districts, monuments 
 
282 ELEMENTS OP GEOLOGY. 
 
 which have the same kind of interest to a geologist which 
 certain mediaeval records excite when we study the history 
 of nations. For both of them throw light on ages of dark- 
 ness, preceded and followed by others of which the annals 
 are comparatively well known to us. But these newly-dis- 
 covered records do not fill up the wide gap, some of them 
 being closely allied to the Eocene, and others to the Creta- 
 ceous type, while none appear as yet to possess so distinct 
 and characteristic a fauna as may entitle them to hold an 
 independent place in the great chronological series. 
 
 Among the formations alluded to, the Thanet Sands of 
 Prestwich have been sufficiently described in the last chap- 
 ter, and classed as Lower Eocene. To the same tertiary 
 series belong the Belgian formations, called by Professor 
 Dumont, Landenian. On the other hand, the Maestricht 
 and Faxoe limestones are very closely connected with the 
 chalk, to which also the Pisolitic limestone of France is refer- 
 able. 
 
 Classification of the Cretaceous Eocks. — The cretaceous 
 group has generally been divided into an Upper and a Low- 
 er series, the Upper called familiarly the chalk, and the Low- 
 er the greensand; the one deriving its name from the pre- 
 dominance of white earthy limestone and marl, of which it 
 consists in a great part of France and England, the other or 
 lower series from the plentiful mixture of green or chloritic 
 grains contained in some of the sands and cherts of which it 
 largely consists in the same countries. But these mineral 
 characters often fail, even when we attempt to follow out 
 the same continuous subdivisions throughout a small portion 
 of the north of Europe, and are worse than valueless when 
 we desire to apply them to more distant regions. It is only 
 by aid of the organic remains which characterize the suc- 
 cessive marine subdivisions of the formation that we are able 
 to recognize in remote countries, such as the south of Europe 
 or ISTorth America, the formations which were there contem 
 poraneously in progress. To the English student of geology 
 it will be sufiicient to begin by enumerating those groups 
 which characterize the series in this country and others im- 
 mediately contiguous, alluding but slightly to those of more 
 distant regions. In the annexed table it will be seen that I 
 have used the term Neocomian for that commonly called 
 "Lower Greensand ;" as this latter term is peculiarly objec- 
 tionable, since the green grains are an exception to the rule 
 in many of the members of this group even in districts where 
 it was first studied and named. 
 
MAESTRICHT BEDS. 
 
 283 
 
 Fig. 226. 
 
 UPPER CKETACEOUS OK CHALK PEKIOD. 
 
 1. Maestricht Beds and Faxoe Limestone. 
 
 2. Upper White Clialk, with flints. 
 
 3. Lower White Chalk, without flints. 
 
 4. ChalliMarl. 
 
 5. Chloritic series (or Upper Greensand). 
 
 6. Gault. 
 
 LOWER CKETACEOUS OR NEOOOMIAW. 
 
 Marine. Freph-v;ate. 
 
 1. Upper Neocomian, see p. 308.) 
 
 2. Middle Neocomian, see p. 312. [ Wealden Beds (apper part). 
 
 3. Lower Neocomian, see p. 312.) 
 
 Maestricht Heels. — Ou tbe Lp-nks of the Meuse, at Maes- 
 tricht, reposing ou ordinary white 'jh-^lk with flints, we find 
 an upper calcareous formntion about 
 100 feet thick, the fossils of which are, 
 on the wholejvevy peculiar, and all dis- 
 tinct from tevtiavy species. Some few 
 are of species common to the inferior 
 white chaUi, among which may be men- 
 tioned JBeiemnitella mucronata (Fig. 
 226) and Pecten quadricostatus, a shell 
 regarded by many as a mere variety 
 of P. qumqvscostatus (see Fig. 270, 
 p. 300). Besides the Belemnite there 
 are other genera, such as Baculites and 
 ilamites, never found in strata newer 
 than the cretaceous, but frequently 
 met with in these Maestricht beds. 
 On the other hand, Volitta, Fasciola- 
 ria, and other genera of univalve 
 shells, usually met with only in ter- 
 tiary strata, occur. 
 
 The upper part- of the rock, about 20 feet thick, as seen in 
 St. Peter's Mount, in the suburbs of Maestricht, abounds in 
 corals and Bryozoa, often detachable from the matrix ; and 
 these beds are succeeded by a soft yellowish limestone 50 
 feet thick, extensively quarried from time immemorial for 
 building. The stone below is whiter, and contains occasion- 
 al nodules of gray chert or chalcedony. 
 
 M. Bosquet, with whom I examined this formation (Au- 
 gust, 1850), pointed out to me a layer of chalk from two to 
 four inches thick, containing green earth and numerous en- 
 crinital stems, which forms the line of demarkation between 
 the strata containing the fossils peculiar to Maestricht and 
 * For particulars of structure, seep. 318. 
 
 Belemnitdla mucronata-, 
 Maestricht, Faxoe, and 
 White Challj. 
 
 o. Entire specimen, showing 
 vascular impression on out- 
 er surface, and characteris- 
 tic slit, b. Section of same, 
 showing place of phragmo- 
 coue.* 
 
284 
 
 ELEMENTS OF GEOLOGY. 
 
 the white chalk below. The latter is distinguished by reg- 
 ular layers of black flint in nodules, and by several shells, 
 such as Terebratula carnea (see Fig. 246, p. 294), wholly want- 
 ing in beds higher than the green band. Some of the or- 
 ganic remains, however, for which St. Peter's Mount is cele- 
 brated, occur both above and below that parting layer, and, 
 among others, the great marine reptile called Mosasaurus 
 
 Mosamurus Camperi. Oiiginal more than three feet long. 
 
 (see Fig. 227), a saurian supposed to have been 24 feet in 
 length, of which the entire skull and a great part of the skel- 
 eton have been found. Such remains' are chiefly met with 
 in the soft freestone, the principal member of the Maestricht 
 beds. Among the fossils common to the Maestricht and 
 white chalk may be instanced the echinodern, Fig. 228. 
 I saw proofs of the previous denudation of the white chalk 
 exhibited in the lower bed of the 
 Maestricht formation in Belgium, 
 about 30 miles S.W. of Maestricht, 
 at the village of Jendrain, where the 
 base of the newer deposit consisted 
 chiefly of a layer of well-rolled, black 
 chalk-flint pebbles, in the midst of 
 which perfect specimens of Theci- 
 deapapillata and BelemniteUa rmwro- 
 nata are imbedded. To a geologist 
 accustomed in England to regard 
 rolled pebbles of chalk-flint as a com- 
 mon and distinctive feature of tertiary beds of different ages, 
 it is a new and surprising phenomenon to behold strata made 
 up of such materials, and yet to feel no doubt that they were 
 
 Hemip7iemtes radiatus, Ag. 
 
 SpatangiM radiatus, Lam. 
 
 Chalk of Maestricht and white 
 
 chalk. 
 
CHALK OF FAXOE. 285 
 
 accumulated in a sea in which the belemnite and other cre- 
 taceous mollusca flourished. 
 
 Pisolitic Limestone of France. — Geologists were for many 
 years at variance respecting the chronological relations of 
 this rock, which is met with in the neighborhood of Paris, 
 and at places north, south, east, and west of that metropolis, 
 as between Vertus and Laversines, Meudon and Montereau. 
 By many able palaeontologists the species of fossils, moi-e than 
 fifty in number, were declared to be more Eocene in their ap- 
 pearance than Cretaceous. But M. H6bert found in this for- 
 mation at Montereau, near Paris, the Pecten quadricostatvs, 
 a well-known Cretaceous species, together with some other 
 fossils common to the Maestricht chalk and to the Baculite 
 limestone of the Cotentin, in Normandy. He therefore, as 
 well as M. Alcide d'Orbigny, who had carefully studied the 
 fossils, came to the opinion that it was an upper member of 
 the Cretaceous group. It is usually in the form of a coarse 
 yellowish or whitish limestone, and the total thickness of the 
 series of beds already known is about 100 feet. Its geograph- 
 ical range, according to M. Hebert, is not less than 45 leagues 
 from east to west, and 35 from north to south. Within these 
 limits it occurs in small patches only, resting unconformably 
 on the white chalk. 
 
 The Nautilus Danicus, Fig. 230, and two or three other 
 species found in this rock, are frequent in that of Faxoe, in 
 Denmark, but as yet no Ammonites, Hamites, Scaphites, Tur- 
 rilites, Baculites, or Hippurites have been met with. The 
 proportion of peculiar species, many of them of tertiary as- 
 pect, is confessedly large ; and great aqueous erosion suffered 
 by the white chalk, before the pisolitic limestone was formed, 
 affords an additional indication of the two deposits being 
 widely separated in time. The pisolitic formation, therefore, 
 may eventually prove to be somewhat more intermediate in 
 date between the secondary and tertiary epochs than the 
 Maestricht rock. 
 
 Chalk of Faxoe. — In the island of Seeland, in Denmark, the 
 newest member of the chalk series, seen in the sea-cliffs at 
 Stevensklint resting on white chalk with flints, is a yellow 
 limestone, a portion of which, at Faxoe, where it is used as a 
 building-stone, is composed of corals, even more conspicuous- 
 ly than is usually observed in recent coral reefs. It lias been 
 quarried to the depth of more than 40 feet, but its thickness 
 is unknown. The imbedded shells are chiefly casts, many of 
 them of univalve mollusca, which are usually very rare in 
 the white chalk of Europe. Thus, there are two species of 
 Oyproea, one of Oliva, two of Mitra, four of the genus Cm- 
 
286 
 
 ELEMENTS OF GEOLOGY. 
 
 Fig. 229. 
 
 Portion of Baculites Faujaaii. 
 
 Maestricht and Faxoe beds 
 and white chalk. 
 
 thium, six of Misus, two of Trochus, one of Patella, one of 
 Emargimda, etc. ; on the whole, more than thirty univalves, 
 spiral or patelliform. At the- same time, some of the accom- 
 panying bivalve shells, echinoderms, 
 and zoophytes, are specifically, identi- 
 cal with fossils of the true Cretaceious 
 gjaries. Among the cephalopoda of 
 Faxoe may be mentioned jBaculites 
 Faiijasii (Fig. 229), and Jielemnitella 
 mucronata (¥ig. 226, p. 283), shells of 
 the white chalk. The JVautilus Dani- 
 cits (see Fig. 230) is characteristic of 
 this formation; and it also occurs in 
 France in the calcaire pisolitique of Laversin (JDepartment of 
 
 Oise). The claws and 
 entii;e skull of a small 
 crab, Brachyurm nt- 
 ffoms (Schlott.), are 
 scattered through the 
 Faxoe stone, i-emind- 
 ing us of similar crus- 
 taceans inclosed in the 
 rocks of modern coral 
 reefs. Some small por- 
 tions of this coralline 
 formation consist of 
 white earthy chalk, , 
 
 Composition, Extent, 
 highest beds of chalk 
 pure, white, calcareous 
 
 Fig. 230. 
 
 NauMua Danictis, Schl. Faxoe, DenmaA. 
 
 -The 
 
 and Origin of the White Chalk, 
 in England and France consist of a 
 
 mass, usually too soft for a building-stone, but sometimes 
 passing into a more solid state. It consists, almost purely, 
 of carbonate of lime ; the stratification is often obscure, ex- 
 cept where rendered distinct by interstratified layers of flint, 
 a few inches thick, occasionally in continuous beds, but often- 
 er in nodules, and recurring at intervals generally from two 
 to four feet distant from each other. This upper chalk is 
 usually succeeded, in the descending order, by a great mass 
 of white chalk without flints, below which comes the chalk 
 marl, in which there is a slight admixture of argillaceous 
 matter. The united thickness of the three divisions in the 
 south of England equals, in some places, 1000 feet. The sec- 
 tion on the opposite page will show the manner in which the 
 white chalk extends fi-om England into France, covered by 
 the tertiary strata described in former chapters, and reposing 
 on lower cretaceous beds. 
 
WHITE CHALK. 
 
 287 
 
 The area over which the white ojialk preserves a neai'ly 
 homogeneous aspect is so vast, that the earlier geologists de- 
 spaired of discovering any analogous deposits 
 
 of recent date. Pure chalk, of nearly uniform 
 aspect and composition, is met with in a north- 
 west and south-east direction, from the north 
 of Ireland to the Crimea, a distance of about 
 1140 geographical miles, and in an opposite 
 direction it extends from the south of Sweden 
 to the south of Bordeaux, a distance of about 
 840 geographical miles. In Southern Russia, 
 according to Sir R. Murchison, it is sometimes 
 600 feet thick, and retains the same mineral 
 character as in France and England,. with the 
 same fossils, including Inoceramus Cuvieri, 
 JBelemnitella mucrotiata, and Ostrea vesicula- 
 ris (Fig. 251, p. 295). 
 
 Great light has recently been thi'own upon 
 the origin of the unconsolidated white chalk 
 by the deep soundings made in the North At- 
 lantic, previous to laying down, in 1858, the 
 electric telegraph between Ireland and New- 
 foundland. At depths sometimes exceeding 
 two miles, the mud forming the floor of the 
 ocean was found, by Pi'ofessor Huxley, to be 
 almost entirely composed (more than nineteen- 
 twentieths of the whole) of minute Rhizopods, 
 or foraminiferous shells of the, genus Glohige- 
 rina, especially the species (Mohigerina bul- 
 loides (see Fig. 232). The organic bodies 
 next in quantity were the siliceous shells 
 called PolycystinecB, and next to them the 
 siliceous skeletons of plants called Diatoma- 
 cecB (Figs. 233, 234, 235), and occasionally 
 some siliceous spiculae of sponges (Fig. 236) 
 were intermixed. These were connected by 
 a mass of living gelatinous matter to which 
 he has given the name of JBathyiius,^ and 
 which contains abundance of very minute 
 bodies, termed Coccoliths and Coccospheres, 
 which have also been detected fossil in chalk. 
 
 Sir Leopold MacClintock and Dr. Wallich 
 have ascertained that 95 per cent, of the mud 
 of a large part of the North Atlantic consists 
 of G-lobigerina shells. But Capt. Bullock, R. N., lately 
 brought up from the enormous depth of 16,860 feet a white, 
 
 
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288 
 
 ELEMENTS OF GEOLOGY. 
 
 Fig 232. 
 
 Fig. 234. Fig. 235. Pig. 236. 
 
 Fig. 238. 
 
 Organic bodies forming the ooze of the bed of the Atlantic at great depths. 
 Fig. 232. Glotigerina iulloides. Calcareous Rhizopod. 
 " 233. Actinoirijclus. ) 
 
 " 234. Pinrmlaria. i- Siliceous Diatomaceee, 
 " 235. Eunotia Mdens.) 
 " 230. Spicula of sponge. Siliceous sponge. 
 
 Tiscid, chalky mud, wholly devoid of Globigerinse. This mud 
 was perfectly homogeneous in composition, and contained no 
 organic remains visible to the naked eye. Mr. Etheridge, 
 however, has ascertained by microscopical examination that 
 it is made up of CoccoUths, Discoliths, and other minute fos- 
 sils like those of the Chalk classed by Huxley as JBathybiw, 
 when this terra is used in its widest sense. This mud, more 
 than three miles deep, was dredged up in lat. 20° 19' N., 
 long. 4° 36' E., or about midway between Madeira and the 
 Cape of Good Hope. 
 
 The recent deep-sea dredgings in the Atlantic conducted 
 by Dr. Wy ville Thomson, Dr. Carpenter, Mr. Gwyn Jeffreys, 
 and others, have shown that on the same white mud there 
 sometimes flourish Mollusca, Crustacea, and Echinoderms, be- 
 sides abundance of siliceous sponges, forming, on the whole, 
 a marine fauna bearing a striking resemblance in its general 
 character to that of the ancient chalk. 
 
 Popular Error as to the Geological Continuity of the Creta- 
 ceous Period. — We must be careful, however, not to overrate 
 the points of resemblance which the deep-sea investigations 
 have placed in a strong light. They have been supposed by 
 some naturalists to warrant a conclusion expressed in these 
 words: "We are still living in the Cretaceous epoch;" a 
 doctrine which has led to much popular delusion as to the 
 bearing of the new facts on geological reasoning and classi- 
 fication. The reader should be reminded that in geology 
 we have been in the habit of founding our great chronolog- 
 ical divisions, not on forarainifera and sponges, nor even on 
 echinoderms and corals, but on the remains of the most 
 highly organized beings available to us, such as the mollus- 
 ca; these being met with, as above explained (p. 142), in 
 stratified rocks of .ilmost every age. In dealing with the 
 mollusca, it is those of the highest or most specialized organ- 
 ization which aiford us the best cliaractei-s in proportion as 
 their vertical range is the most limited. Thus the Cephalo- 
 
THE CRKTACi:r>US PERIOD. 289 
 
 poda are the most vuln.ible, as having a more restricted 
 range in time than the Gasteropoda ; and these, again, are 
 more characteristic of the particular stratigraphical subdi- 
 visions than are the Lamellibranchiate Bivalves, while these 
 last, again, are more serviceable in classification than the 
 Brachiopoda, a still lower class of shell-fish, which are the 
 most enduring of all. 
 
 When told that the new dredgings prove, that "we are 
 still living in the Chalk Period," we naturally ask whether 
 some cuttle-fish has been found with a Belemnite forming 
 part of its internal frame-work ; or have Ammonites, Bacu- 
 lites, Hamites, Turrilites, with four or five other Cephalopo- 
 dous genera characteristic of the chalk and unknown as ter- 
 tiary, been met with in the abysses of the ocean ? Or, in the 
 absence of these long-extinct forms, has a single spiral uni- 
 valve, or species of Cretaceous Gasteropod, been found liv- 
 ing ? Or, to descend still lower in the scale, has some char- 
 acteristic Cretaceous genus of Lamellibranchiate Bivalve, 
 such as the Inoceramus, or Hipj)urite, foreign to the Tei'tiary 
 seas, been proved to have survived down to our time ? Or, 
 of the numerous genera of lamellibranchiates common to the 
 Cretaceous and Recent seas, has one species been found liv- 
 ing? The answer to all these questions is — not one has 
 been found. Even of the humblest shell-fish, the Brachio- 
 pods, no new species common to the cretaceous and recent 
 seas has yet been met with. It has been very generally ad- 
 mitted by conchologists that out of a hundred species of this 
 tribe occurring fossil in the Upper Chalk — one, and one only, 
 Terebratulina striata, is still living, being thought to be iden- 
 tical with Terebratula caput-serpentis. Although this iden- 
 tity is still questioned by some naturalists of authority, it 
 would certainly not surprise us if another lamp-shell of equal 
 antiquity should be met with in the deep sea. 
 
 Had it been declared that we are living in the Eocene 
 epoch, the idea would not be so extravagant, for the great 
 reptiles of the Upper Chalk, the Mososaurus, Pliosaurus, and 
 Pterodactyle, and many others, as well as so many genera 
 of chambered univalves, had already disappeared from the 
 earth, and the marine fauna had made a greater approach to 
 our own by nearly the entire difference which separates it 
 from the fauna of the Cretaceous seas. The Eocene num- 
 mnlitic limestone of Egypt is a rock mainly composed, like 
 the more ancient white chalk, of globigerine mud ; and if 
 the reader will refer to what we have said of the extent to 
 which the nummulitic marine strata, formed originally at 
 the bottom of the sea, now enter into the frame-work of 
 
 13 
 
290 ELEMENTS OF GEOLOGY. 
 
 mountain chains of the principal continents, he will at onco 
 perceive that the present Atlantic, Pacific, and Indian Oceans 
 are geographical terms, which must he wholly without mean- 
 ing when applied to the Eocene, and still more to the Creta- 
 ceous Period ; so that to talk of the chalk having been un- 
 interruptedly forming in the Atlantic from the Cretaceous 
 Period to our own, is as inadmissible in a geographical as in 
 a geological sense. 
 
 Chalk-flints. — The origin of the layers of flint, whether 
 in the form of nodules, or continuous sheets, or in veins or 
 cracks not parallel to the stratification, has always been 
 more difiicult to explain than that of the white chalk. But 
 here, again, the late deep-sea soundings have suggested a 
 possible source of such mineral matter. During the cruise 
 of the "Bulldog," already alluded to, it was ascertained that 
 while the calcareous GloMgerince had almost exclusive pos- 
 session of certain tracts of the sea-bottom, they were wholly 
 wanting in others, as between Greenland and Labrador. Ac- 
 cording to Dr. Wallich, they may flourish in those spaces 
 where they derive nutriment from organic and other matter, 
 brought from the south by the warm waters of the Gulf 
 Stream, and they may be absent where the effects of that 
 great current are not felt. Now, in several of the spaces 
 wliere the calcareous Rhizopods are wanting, certain micro- 
 scopic plants, called Diatomacece, above mentioned (Figs. 
 233-235), the solid parts of which are siliceous, monopolize 
 the ground at a depth of nearly 400 fathoms, or 2400 feet. 
 
 The large quantities of silex in solution required for the 
 formation of these plants may probably arise from the disin- 
 tegration of feldspathic rocks, which are universally distrib- 
 uted. As more than half of their bulk is formed of siliceous 
 earth, they may afford an endless supply of silica to all the 
 great rivers which flow into the ocean. We may imagine 
 that, after a lapse of many years or centuries, changes took 
 place in the direction of the marine currents, favoring at 
 one time a supply in the same area of siliceous, and at an- 
 other of calcareous matter in excess, giving rise in the one 
 case to a preponderance of Globigerinae, and in the other of 
 Diatomaceae. These last, and certain sponges, may by their 
 decomposition have furnished the silex, which, separating 
 from the chalky mud, collected round organic bodies, or 
 formed nodules, or filled shrinkage cracks. 
 
 Pot-stones. — A more difficult enigma is presented by the 
 occurrence of certain huge flints, or pot-stones, as they are 
 called in Norfolk, occurring singly, or arranged in nearly 
 continuous columns at right angles to the ordinary and hor- 
 
POT-STONES OF HOESTEAD. 291 
 
 izontal layers of small flints. I visited in the year 1825 an 
 extensive range of quarries then open on the river Bure, near 
 Horstead, about six miles from Norwich, which afforded a 
 continuous section, a quarter of a mile in length, of white 
 chalk, exposed to the depth of about twenty-six feet, and 
 covered by a bed of gravel. The pot-stones, many of them 
 pear-shaped, were usually about three feet in height and one 
 foot in their transverse diameter, placed in vertical rows, 
 like pillars, at irregular distances from each other, but usu- 
 ally from twenty to thirty feet apart, though sometimes 
 
 Fig. 23T. 
 
 From a drawing by Mrs. Gnnn. 
 
 View of a chalk-pit at Horstead, near Norwich, showing the position of the 
 
 pot^stones. 
 
 nearer together, as in the above sketch. These rows di«l 
 not terminate downward in any instance which I could ex- 
 amine, nor upward, except at the point where they were cut 
 off abruptly by the bed of gravel. On breaking open the 
 pot-stones, I found an internal cylindrical nucleus of pure 
 chalk, much harder than the ordinary surrounding chalk, 
 and not crumbling to pieces like it, when exposed to the 
 winter's frost. At the distance of half a mile, the vertical 
 piles of pot-stones were much farther apart from each other. 
 Dr. Buckland has described very similar phenomena as char- 
 acterizing the white chalk on the north coast of Antrim, in 
 Ireland.* 
 
 Vitreous Sponges of the Chalk. — These pear-shaped masses 
 of flint often resemble in shape and size the large sponges 
 * Geol. Trans., 1st Series, vol. iv., p. 413. 
 
292 
 
 ELEMENTS OF GEOLOGY. 
 
 called Neptune's Cups [Spongia patera^ Hardw,), which grow 
 in the seas of Sumatra; and if we could suppose a series of 
 such gigantic sponges to be separated from each other, like 
 trees in a forest, and the individuals of each successive gen- 
 eration to grow on the exact spot where the j)arent sponge 
 died and was enveloped in calcareous mud, so that they 
 should become piled one above the other in a vertical col- 
 umn, their growth keeping pace with the accumulation of 
 the enveloping calcareous mud, a counterpart of the phe- 
 nomena of the Horstead pot-stonesmight be obtained. 
 
 Professor Wyville Thomson, describing the modern sound- 
 ings in 1869 off the north coast of Scotland, speaks of the 
 ooze or chalk mud brought from a depth of about 3000 feet, 
 and states that at' one haul they obtained 
 forty specimens of vitreous sponges buried 
 in the mud. He suggests that the Ven- 
 triculites of the chalk wei'e nearly allied 
 to these sponges, and that when the silica 
 of their spicules was removed, and was 
 dissolved out of the calcareous matrix, it 
 set into flint. 
 
 Boulders and Groups of Pebbles in Chalk. 
 — The occurrence here and there, in the 
 white chalk of the south of England, of 
 isolated pebbles of quartz and green schist 
 has justly excited much wonder. It was 
 at first supposed that they had been drop- 
 ped from the roots of some floating tree, 
 by which means stones are carried to some 
 ^MaS!%y;;"^1te!: of tJie small coral islands of the Pacific. 
 imiaradiata. D'Orb. But the discovcry in 1857 of a group of 
 stones in the white chalk near Croydon, 
 the largest of which was syenite and weighed about forty 
 pounds, accompanied by pebbles and fine sand like that of a 
 beach, has been shown by Mr. Godwin Austen to be inex- 
 plicable except by the agency of floating ice. If we consid- 
 er that icebergs now reach 40° north latitude in the Atlan- 
 tic, and several degrees nearer the equator in the southern 
 hemisphere, we can the more easily believe that even during 
 the Cretaceous epoch, assuming that the climate was milder, 
 fragments of coast ice may have floated occasionally as far 
 as the south of England. 
 
 Distinctness of Mineral Character in Contemporaneous Rocks 
 of the Cretaceous Period. — But we must not imagine that be- 
 cause pebbles are so rare in the white chalk of England and 
 Prance there are no proofs of sand, shingle, and clay having 
 
FOSSILS or THE WHITE CHALK. 293 
 
 been accumulated contemporaneously even in European seas. 
 The siliceous sandstone called " upper quader " by the Ger- 
 mans overlies white argillaceous chalk or " planer-kalk," a 
 deposit resembling in composition and organic remains the 
 chalk marl of the English series. This sandstone contains 
 as many fossil shells common to our white chalk as could be 
 expected in a sea-bottom formed of such different materials. 
 It sometimes attains a thickness of 600 feet, and, by its 
 jointed structure and vertical precipices, plays a conspicu- 
 ous part in the picturesque scenery of Saxon Switzerland, 
 near Dresden. It demonstrates that in the Cretaceous sea, 
 as in our own, distinct mineral deposits were simultaneously 
 in progress. The quartzose sandstone alluded to, derived 
 from the detritus of the neighboring granite, is absolutely 
 devoid of carbonate of lime, yet it was formed at the dis- 
 tance only of four hundred miles from a sea-bottom now con- 
 stituting part of France, where the purely calcareous white 
 chalk was forming. In the North American continent, oil 
 the other hand, where the Upper Ci-etaceous formations are 
 so widely developed, true white chalk, in the ordinary sense 
 of that term, does not exist. 
 
 Fossils of the White Chalk. — Among the fossils of the 
 white chalk, echinoderms are very numerous ; and some of 
 the genera, like Ananchytes (see Fig. 239), are exclusively 
 
 Fig. 239. 
 
 Ananchytes ovatus, Leske. White chalk, upper and lower. 
 
 a. Side view. 6. Base of the shell, on which both the oral and anal apertnres are 
 
 placed ; the anal being more round, and at the smaller end. 
 
 cretaceous. Among the Crinoidea, the Marsupites (ITig. 242) 
 is a characteristic genus. Among the moUusca, the cepha- 
 lopoda are represented by Ammonites, Baculites (Fig. 229, 
 p. 286), and Belemnites (Fig. 226, p. 283). Although there 
 are eight or more species of Ammonites and six of them pe- 
 culiar to it, this genus is much less fully represented than 
 in each of the other subdivisions of the Upper Cretaceous 
 
 group. 
 
 Among the brachiopoda in the white chalk, the Terebra- 
 tMloB are very abundant (see Figs. 243- 247). With these 
 
294 
 
 ELEMKNTS OF GEOLOGY. 
 
 iire associated some forms of oyster (see Fig. 251), and other 
 bivalves (Figs. 249, 250). 
 
 Fig. 240. Pig. 241. Fig. 242. 
 
 Micraster cfyr-antjuw/wm, 
 Leske. VFhite chalk. 
 
 Galerites dlhogaleirus, Lnm. 
 Wliite chalk. 
 
 MarsupUes Millffri, 
 Maut. White chalk; 
 
 Among the bivalve mollusea, no form marks the Creta- 
 ceous era in Europe, America, and India in a more striking 
 
 Fig. 243. Fig. 244 Fig. 245. Fig. 246. 
 
 Terebratulina striata^ 
 Wablenh. Upper 
 • white chalk. 
 
 Rhynehonella oc- 
 toplicata, Sow. 
 (Var. of jR. pli- 
 catilis). Upper 
 white chalk. 
 
 Mat/as puraila. 
 Sow. Upper 
 white ch'^lk 
 
 Terebratula camea, 
 Sow. Upper white 
 chalk. 
 
 manner than the extinct genus InoceramiM ( Catillus of Lam.; 
 see Fig. 252), the shells of which are distinguished by a 
 
 Fig. 24T. 
 
 Fig. 248. 
 
 Fig. 249. 
 
 Pig. 250. 
 
 Terebratulahip- Crania Parisien- PC'CtenBeaverijSow. 
 Hcata, Brocch, sis, Duf. Infe- Reduced to one- 
 Upper creta- rior or attached third diameter, 
 ceous. valve. Upper Lowerwhite chalk LiiTia spinosa, aow. Syn. 
 
 white chalk. and chalk marl. Spmwiylue spinosus. Up- 
 
 Maidstone. per white chalk. 
 
 fibi-ous texture, and are often met Avith in fragments, having 
 probably been extremely friable. 
 
 Of the singular family called Rudistes by Lamarck, here- 
 after to be mentioned as extremely characteristic of the chalk 
 
FOSSILS OF THE WHITE CHALK. 
 
 Fig. 251. Pig. 252. 
 
 295 
 
 Ostrea venicularis. Syn. Grijpkcea 
 convexa. Upper chalk and Upper 
 green sand. 
 
 Inoceramits Lamarckii. Syn. Crt- 
 tilhts Lamarckii. White chalk 
 (Dixon'a Geol. Sussex, Tab. 28, 
 Pig. 29). 
 
 of southern Europe, a single representative only (Fio-. 253) 
 has been discovered in the white chalk of England. 
 
 Fig. 254. 
 
 RadialiUs Mnrtoni^'iS.ixateW, Houghton, Sussex. White chalk. Diameter 
 
 one-seventh natural size. 
 
 Fig. 353. Two individuals deprived of their upper valves, adhering together.— Fig. 
 
 254. Same seen from above.— Fig. 255. Transverse section of part of the wall of 
 
 the Shell, magnified to show the strncture.— Fig. 286. Vertical section of the same. 
 
 On the side where the shell is thinnest, there is one external furrow and corre- 
 
 oponding interaal ridge, a, ft, Figs. 253, 254 ; but they are usually less prominent 
 
 , than in these figures. The upper or opercular valve is wanting. 
 
 The general absence of univalve mollusca in the white 
 chalk is very marked. Of bryozoa there is an abundance, 
 such as Eschara and Eseharina (Figs. 257, 258). These and 
 other organic bodies, especially sponges, such as Ventriculites 
 
296 
 
 ELEMENTS OF GEOLOGY. 
 
 Fig. 25r. 
 
 Fig. 25S. 
 
 Eachara dislicha. Wliite chalk. 
 a. Natural size. 6. Povtion magnified. 
 
 (Fig. 238, p. 292), are dispersed indifferently through the 
 soft chalk and hard flint, and some of the flinty nodules owe 
 
 their irregular forms to inclosed 
 sponges, such as Fig. 25 9, a, where 
 the hollows in the exterior are 
 caused by the branches of a 
 sponge (Fig. 259, b), seen on 
 breaking open the flint. 
 
 The remains of fishes of the 
 Upper Cretaceous formations 
 consist chieflj' of teeth belong- 
 ing to the shark family. Some 
 of the genera are common to the 
 Tertiary formations, and some 
 are distinct. To the latter be- 
 longs the genus Ptychodus (Fig. 260), which is allied to the 
 livjng Port Jackson shai-k, Cestracion Phillippi, the anterior 
 
 6 Fig. 259. 
 
 EscTiarina oceani. 
 
 o Natural size. 6 Part of the same 
 
 magnified. White chalk. 
 
 A branching sponge in a flint, from the white chalk. From the collection 
 of Mr. Bowerhank. 
 
 teeth of which (see Fig. 261, a) are sharp and cutting, while 
 the posterior or palatal teeth (b) are flat (Fig. 260). But we 
 meet with no bones of land-animals, nor any terrestrial or 
 fluviatile shells, nor any plants, except sea-weeds, and here 
 and there a piece of drift-wood. All the appearances concur 
 
FOSSILS OF THE WHITE CHALK. 
 
 297 
 
 Fig. 2C1. 
 
 Fig. 260. in leading us to conclude that the white chalk 
 
 was the product of an open sea of considera- 
 ble depth. 
 
 The existence of turtles and oviparous sau- 
 rian s, and of a Pterodactyl or winged lizard, 
 found in the white chalk of Maidstone, im- 
 ^ikofus°"d'ecurr'2: pli^s, no doubt, some neighboring land; but 
 Lower white chalk, a few Small islets in mid-ocean, like Ascen- 
 sion, formerly so much frequented by mi- 
 gratory droves of turtle, might perhaps have afforded the 
 required retreat 
 where these crea- 
 tures laid their 
 eggs in the sand, 
 or from which the 
 flying species may 
 have been blown 
 out to sea. Of the 
 vegetation of such 
 islands we have 
 scarcely any indi- 
 cation, but it con- 
 sisted partly of cy- 
 cadaceous plants ; 
 for a fragment of 
 of these 
 
 one 
 
 was 
 
 fUt^ 
 
 found by Capt. lb- Cestradon Phillippi; lecent. Port Jackson. Backland, 
 betSOn in the Chalk Brldgewater Treatise, pi. 2T, d. 
 
 Marl of the Isle of Wight, and is referred by A. Brongniart 
 to Clathraria Lyellii, Mantell, a species common to the 
 antecedent Wealden period. The fossil plants, however, 
 of beds corresponding in age tg the white chalk at Aix- 
 la-Chapelle, presently to be described, like the sandy beds of 
 Saxony, before alluded to (p. 293), afford such evidence of 
 land as to prove how vague must be any efforts of ours to 
 restore the geography of that period. 
 
 The Pterodactyl of the Kentish chalk, above alluded to, 
 was of gigantic dimensions, measuring 16 feet 6 inches from 
 tip to tip of its outstretched wings. Some of its elongated 
 bones were at first mistaken by able anatomists for those of 
 birds ; of which class no osseous remains have as yet been 
 derived from the white chalk, although they have been found 
 (as will be seen at page 299) in the Chloritic sand. 
 
 The collector of fossils from the white chalk was former- 
 ly puzzled by meeting with certain bodies which they call 
 larch-cones, which were afterwards recognized by Dr. Buck- 
 
 13* 
 
298 
 
 KLEMENTcJ OF GEOLOGY. 
 
 Fig. 263. land to be the excrement of fish (see 
 
 Fig. 262). They are composed in great 
 part of phosphate of lime. 
 
 Lower White Chalk. — The Lower 
 White Chalk, which is several hundred 
 feet thick, without flints, has yielded 25 
 species of Ammonites, of which half are 
 peculiar to it. The genera Baculite, 
 Hamite, Scaphite, Turrilite, Nautilus, 
 copruiites offish, from the Belemnite, and Belemnitella, are also 
 
 chalk. 't 
 
 represented. 
 Chalk Marl. — The lower chalk without flints passes grad- 
 ually downward, in the south of England, into an argilla- 
 
 Fig. 263. 
 
 ;>T T---'-'V-"-'^'^^^™'''^"''' '-''g"^^ 
 
 Baeuliies arwepa, Lam. Lower chalk. 
 
 ceous limestone, " the chalk marl," already alluded to (p. 
 286). It contains 32 species of Ammonites, seven of which 
 are peculiar to it, while eleven pass up^into the overlying 
 
 lower "white chalk. A. 
 ^' ^^' Mhotomagensis is charac- 
 
 teristic of this formation. 
 Among the British cephal- 
 opods of other genera may 
 be mentioned Scaphites 
 CBqualis (Fig. 266) and 
 Turrilites costatus (Fig. 
 265). 
 
 Chloritic Series (or Tipper 
 Greensand). — According 
 to the old nomenclature, 
 this subdivision of the 
 chalk was called Tipper 
 Greensand, in order to distinguish it from those members of 
 the Neocomian or Lower Cretaceous series below the Gault 
 to which the name of Greensand had been applied. Besides 
 the reasons before given (p. 282) for abandoning this nomen- 
 clature, it is objectionable in this instance as leading the un- 
 initiated to suppose that the divisions thus named Upper 
 and Lower Greensand are of co-ordinate value, instead of 
 which the chloritic sand is quite a subordinate member of 
 the Upper Cretaceous group, and the term Greensand has 
 very commonly been used for the whole of the Lower Creta- 
 ceous rocks, which are almost comparable in importance to 
 
 Awmwniteft Rhotomagensis. Chalk marl. 
 Back aud side view. 
 
THE CHLORIXIC SERIES. 
 
 299 
 
 Pig. 265. 
 
 Fig. 266. 
 
 ScapMtes ceqvalis. CfilDvitio mar' 
 and saud, Doisetshire. 
 
 'rii.rrUiteiicostatwi,'La,m. Lower chalk and challcmarl. 
 a. SectioD, showing the foliated border of the su- 
 tures of the chambers. 
 
 the entire Upper Cre- 
 taceous series. The 
 higher portion of the 
 Chloritic series in 
 some districts has 
 been called chloritic 
 marl, from its consist- 
 ing of a chalky marl 
 with chloritic grains. 
 In parts of Surrey, 
 where calcareous mat- 
 ter is largely inter- 
 mixed with sand, it 
 forms a stone called 
 malm -rock or fire- 
 stone. In the cliffs 
 of the southern coast 
 of the Isle of Wight 
 it contains bands of 
 calcareous limestone with nodules of chert. 
 
 CoproUte Bed. — The so-called coprolite bed, found near 
 Farnham, in Surrey, and near Cambridge, contains nodules 
 of phosphate of lime in such abundance as to be largely 
 worked for the manufacture of artificial manure. It belongs 
 to the upper part of the Chloritic series, and is doubtless 
 chiefly of animal origin, and may perhaps be partly copro- 
 litic, derived from the excrement of fish and i-eptiles. The 
 late Mr. Barrett discovered in it, near Cambridge, in 1858, 
 the remains of a bird, which was rather larger than the com- 
 mon pigeon, and probably of the order Natatores, and which, 
 like most of the Gull tribe, had well-developed wings. Por- 
 tions of the metacarpus, metatarsus, tibia, and femur have 
 been detected, and the determinations of Mr. Barrett have 
 been confirmed by Professor Owen. 
 
 This phosphatic bed in the suburbs of Cambridge musi 
 have been formed partly by the denudation of pre-existing 
 rocks, mostly of Cretaceous age. The fossil shells and bonei 
 of animals washed out of these denuded strata, now forming 
 a layer only a few feet thick, have yielded a rich harvest to 
 the collector. A large Rudist of the genus Radiolite, no less 
 than two feet in height, may be seen in the Cambridge Mu- 
 seum, obtained from this bed. The number of reptilian re- 
 mains, all apparently of Cretaceous age, is truly surprising ; 
 more than ten species of Pterodactyl, five or six of Ichthy- 
 osaurus, one of Pliosaurus, one of Uinosaurus, eight of Che- 
 lonians, besides other forms, having been recognized. 
 
300 
 
 I'LEMENTd Oi^ GEOLOGY. 
 
 The cbloritic sand is regarded by many geologists as a 
 littoral deposit of the Chalk Ocean, and therefore contempo- 
 raneous with part of the chalk marl, and even, perhaps, with 
 some part of the white chalk. For, as the land went on sink- 
 ing, and the cretaceous sea widened its area, white mud and 
 chloritic sand were always foi-ming somewhere, but the line 
 of sea-shore was perpetually shifting its position. Hence, 
 though both sand and mud originated simultaneously, the 
 
 Fig. 20T. 
 
 Fig. 26S. 
 
 Ostrea columba. Syii. 
 Gryphcen columba. 
 Cliloritic sand. 
 
 Ostrea carinata. Chalk marl aud chloritic saud. 
 Neocomiau. 
 
 one near the land, the other far from it, the sands in every 
 locality where a shore became submerged might constitute 
 the underlying deposit. 
 
 Among the characteristic mollusca of the chloritic sand 
 may be mentioned Terebrirostra lyra (Fig. 269), Plagiostoma 
 
 Fig. 269. 
 
 Fig. 2T0. 
 
 Fig. 271. 
 
 Terebrirostra lyra, Sow. 
 Chloritic sand. 
 
 Peeten S-costatus. White 
 chalk and chloritic 
 saud. Neocomian. 
 
 Plagiostoma Hoperi, Sow. 
 Syn. Lima Hoperi. White 
 chalk and cbloritic sand. 
 
 Hoperi (Fig. 2'71), Pecten qidnqm-costatus (Pig. 270), and 
 Ostrea columha (Fig. 267). 
 
 The cephalopoda are abundant, among which 40 species of 
 Ammonites are now known, 10 being peculiar to this sub- 
 division, and the rest common to the beds immediately above 
 or below. 
 
 Gault.— The lowest member of the Upper Cretaceous group, 
 
GAULT— BLACKDOWN BEDS. 801 
 
 usually about 100 feet Kg. 272. 
 
 thick in the S.E. of 
 England, is provincially 
 termed Gault. It con- 
 sists of a dark blue marl, 
 sometimes intermixed 
 with green sand. Many 
 peculiar forms of ceph- 
 alopoda, such as the 
 Hamite (Fig. 272), and 
 Scaphite, with other 
 
 fn«<!il!! rlmrnpf-pviyp this -A-ncVloceraa epinigemm, D'Orb. SyD. HamUes 
 lObbllh, ouaracieiize mis spmi^er, Sow. Near Folkestone. Gault. 
 
 formation, which, small 
 
 as is its thickness, can be traced by its organic remains to 
 
 distant parts of Europe, as, for example, to the Alps. 
 
 Twenty-one species of British Ammonites are recorded as 
 found in the Gault, of which only eight are peculiar to it, ten 
 being common to the overlying Chloritic series. 
 
 Connection between Upper and Lower Cretaceous Strata— 
 Blackdown Beds. — Tlie break between the Upper and Lower 
 Cretaceous formations will be appreciated when it is stated 
 that, although the Neocomian contains 31 species of Am- 
 monite, and the Gault, as we have seen, 21, there are only 3 
 of those common to both divisions. Nevertheless, we may 
 expect the discovery in England, and still more when we 
 extend our survey to the Continent, of beds of passage inter- 
 mediate between the Upper and Lower Cretaceous. Even 
 now the Blackdown beds in Devonshire, which rest imme- 
 diately on Triassic strata, and which evidently belong to 
 some part of the Cretaceous series, have been referred by 
 some geologists to the Upper group, by others to the Lower 
 or Neocomian. They resemble the Folkestone beds of the 
 latter series in mineral character, and 59 out of 156 of their 
 fossil mollusca are common to them; but they have also 16 
 species common to the Gault, and 20 to the overlying Chlo- 
 ritic series; and what is very important, out of seven Am- 
 monites six are found also in the Gault and Chloritic series, 
 only one being peculiar to the Blackdown beds. 
 
 Professor Ramsay has remarked that there is a strati- 
 graphical break; for in Kent, Surrey, and Sussex, at those 
 few points where there are exposures of junctions of the 
 Gault and Neocomian, the surface of the latter has been 
 much eroded or denuded, while to the westward of the great 
 chalk escarpment the unconforraability of the two groups 
 is equally striking. At Blackdown this unconformability is 
 still moi-e marked, for though distant only 100 miles from 
 
302 ELEMENTS OF GEOLOGY. 
 
 Kent and Surrey, no formation intervenes between these 
 beds and the Trias; all intermediate groups, such as the 
 Lower Neocomian and Oolite, having either not been depos- 
 ited or destroyed by denudation. 
 
 riora of the Upper Cretaceous Period.— As the Upper Cre- 
 taceous rocks of Europe are, for the most part, of purely ma- 
 rine origin, and formed in deep water usually far from the 
 nearest shore, land-plants of this period, as we might natu- 
 rally have anticipated, are very rarely met with. In the 
 neighborhood of Aix-la-Ohaijelle, however, an important ex- 
 ception occurs, for there certain white sands and laminated 
 clays, 400 feet in thickness, contain the remains of terrestrial 
 plants in a beautiful state of preservation. These beds are 
 the equivalents of the white chalk and chalk marl of Eng- 
 land, or Senonien of D'Orbigny, although the white siliceous 
 sands of the lower beds, and the green grains in the upper 
 part of the formation, cause it to differ in mineral character 
 from our white chalk. 
 
 Beds of fine clay, with fossil plants, and with seams of lig- 
 nite, and even perfect coal, are intercalated. Floating wood, 
 containing perforating shells, such as Pholas and Gastrochoe- 
 na, occur. There ai-e ' likewise a few beds of a yellowish- 
 brown limestone, with marine shells, which enable us to prove 
 that the lowest and highest plant-beds belong to one group. 
 Among these shells are Pecten qiiadricostatus, and several 
 others which are common to the upper and lower part of the 
 series, and Trigonia limbata, D'Orbigny, a shell of the white 
 chalk. On the whole, the organic remains and the geologi- 
 cal position of the strata prove distinctly that in the neigh- 
 borhood of Aix-la-Chapelle a gulf of the ancient Cretaceous 
 sea was bounded by land composed of Devonian rocks. 
 These rocks consisted of quartzose and schistose beds, the 
 first of which supplied white sand and the other argillaceous 
 mud to a river which entered the sea at this point, carrying 
 down in its turbid waters much drift-wood and the leaves 
 of plants. Occasionally, when the force of the river abated, 
 marine shells of the genera Trigonia, Turritella, Pecten, etc., 
 established themselves in the same area, and plants allied to 
 Zostera and Micus grew on the bottom. 
 
 The fossil plants of this member of the upper chalk at Aix 
 have been diligently collected and studied by Dr. Debey, 
 and as they afford the only example yet known of a terres- 
 trial flora older than the Eocene, in which the great divis- 
 ions of the vegetable kingdom are represented in nearly the 
 same proBortions as in our own times, they deserve particu- 
 lar attention. Dr. Debey estimates the number of species 
 
FLORA OF THE UPPER CHALK. 303 
 
 as amounting to more than two hundred, of which sixty-sev- 
 en are cryptogamous, chiefly ferns, twenty species of which 
 can be well determined, most of them being in fructification. 
 The scars on the bark of one or two are supposed to indicate 
 tree-ferns. Of thirteen genera three are still existing, name- 
 ly, Gleichenia, now inhabiting the Cape of Good Hope and 
 '^ew Holland ; Lygodium, now spread extensively through 
 tropical regions, but having some species which live in Ja- 
 pan and North America ; and Asplenium., a cosmopolite 
 form. Among the phtenogamous plants, the Conifers are 
 abundant, the most common belonging to a genus called 
 Cycadopteris by Debey, and hardly separable from Sequoia 
 (or Wellingtonia), of which both the cones and branches are 
 preserved. When I visited Aix, I found the silicified wood 
 of this plant very plentifully dispersed through the white 
 sands in the pits near that city. In one silicified trunk 200 
 rings of annual growth could be counted. Species of Arau- 
 caria like those of Australia are also found. Cycads are ex- 
 tremely rare, and of Monocotyledons there are but few. No 
 palms have been recognized with certainty, but the genus 
 Pandanus, or screw pine, has been distinctly made out. 
 The number of the Dicotyledonous Angiosperms is the most 
 striking feature in so ancient a flora.* 
 
 Among them we find the familiar forms of the Oak, Fig, 
 and Walnut ( Quercus, Fictis, and Juglans), of the last both 
 the nuts and leaves ; also several genera of the Myrtaceae. 
 But the predominant order is the Proteacese, of which there 
 ai"e between sixty and seventy supposed species, many of 
 extinct genera, but some referred to the following living 
 forms — Dryandra, Grevillea, Hakea, Banksia, Persoonia — all 
 
 * In this and subsequent remarks on fossil plants I shall often use Dr. 
 Lindley's terms, as most familiar in this country ; but as those of M. A. 
 Biongniart are much cited, it may be n.'efal to geologists to give a table 
 explaining the corresponding names of groups so much spoken of in 
 pal£eontology. 
 
 Brongniiirt. Lindley. 
 
 1. Cryptogamous am-"> 
 phigens, or cellu- > Thallogens. Lichens, sea-weeds, fungi, 
 lar cryptogamic. ) 
 
 2. Cryptogamous aero- Acrogens. Mosses, equisetums, ferns, lyco- 
 gens. podiums — Lepidodendra. 
 
 '3. Dicotyledonous gym- Gymnogens. Conifers and Cycads. 
 
 nosperms. 
 4. Dicot. angiosperms. Exogens. Compositje, leguminosse, umbel 
 
 IjferiB, crucifera!, heaths, etc. 
 All native European trees ex- 
 cept conifers. 
 Monocotyledons. Endogens. Palms, lilies, aloes, rushes, grass- 
 
 es, etc. 
 
304 ELEMENTS OF GEOLOGY. 
 
 now belonging to Australia, and Leucospermum, species of 
 which form small bushes at the Cape. 
 
 The epidermis of the leaves of many of these Aix plants, 
 especially of the Proteacese, is so perfectly preserved in an 
 envelope of fine clay, that under the microscope the stomata, 
 or polygonal cellules, can be detected, and their peculiar ar- 
 rangement is identical with that known to characterize some 
 living Proteacese (Grevillea, for example). Although this 
 peculiarity of the structure of stomata is also found in plants 
 of widely distant orders, it is, on the whole, but rarely met 
 with, and being thus observed to characterize a foliage pre- 
 viously suspected to be proteaceous, it adds to the proba- 
 bility that the botanical evidence had been correctly inter- 
 preted. 
 
 An occasional admixture at Aix-la-Chapelleof Fucoids and 
 Zosterites attests, like the shells, the presence of salt-water. 
 Of insects. Dr. Debey has obtained about ten species of the 
 families Curculionidse and Carabidae. 
 
 The resemblance of the flora of Aix-la-Chapelle to the ter- 
 tiary and living floras in the proportional number of dicoty- 
 ledonous angiosperms as compared to the gymnogens, is a 
 subject of no small theoretical interest, because we can now 
 afiirm that these Aix plants flourished before the rich reptil- 
 ian fauna of the secondary rocks had ceased to exist. The 
 Ichthyosaurus, Pterodactyl, and Mosasaurus were of coeval 
 date with the oak, the walnut, and the fig. Speculations 
 have often been hazarded respecting a connection between 
 the rarity of Exogens in the older rocks and a peculiar state 
 of the atmosphere. A denser air, it was suggested, had in 
 earlier times been alike adverse to the well-being of the high- 
 er order of flowering plants, and of the quick-breathing ani- 
 mals, such as mammalia and birds, while it was favorable to 
 a cryptogamic and gymnospermous flora, and to a predomi- 
 nance of reptile life. But we now learn that there is no in- 
 compatibility in the co-existence of a vegetation like that of 
 the present globe, and some of the most remarkable forms 
 of the extinct reptiles of the age of gymnosj)erms. 
 
 If the passage seem at present to be somewhat sudden 
 from the flora of the Lower or Neoeomian to that of the 
 Upper Cretaceous period, the abruptness of the change will 
 probably disappear when we are better acquainted with the 
 fossil vegetation of the uppermost beds of the Neocomian 
 and that of the lowest strata of the Gault or true Cretaceous 
 series. 
 
 Hippurite Limestone. — Difference between the Chalk of the 
 JVorth and South of Mtrope. By the aid of the three tests, 
 
HIPPUEITE LIMESTONE. 
 
 305 
 
 Fig. m. 
 
 superposition, mineral character, 
 and fossils, the geologist has been 
 enabled to refer to the same Cre- 
 taceous period certain rocks in 
 the north and south of Europe, 
 wliich differ greatly both in their 
 fossil contents and in their miner- 
 al composition and structure. 
 
 If we attempt to trace the cre- 
 taceous deposits from England 
 and France to the countries bor- 
 dering the Mediterranean, we per- 
 ceive, in the first place, that in 
 the neighborhood of London and 
 Paris they form one great contin- 
 uous mass, the Straits of Dover 
 being a trifling interruption, a, 
 mere valley with chalk cliffs on 
 both sides. We then observe 
 that the main body of the chalk 
 which surrounds Paris stretches 
 from Tours to near Poitiers (see 
 the annexed map. Fig. 273, in which the shaded part repre- 
 sents chalk). 
 
 Betw^een Poitiers and La Rochelle, the space marked A 
 on the map separates two regions of chalk. This space is oc- 
 cupied by the Oolite and^certain other formations older than 
 the Chalk and Neocomian, and has been supposed by M. E. 
 de Beaumont to have formed an island in the Cretaceous sea. 
 South of this space we again meet with rocks which we at 
 once recognize to be cretaceous, partly from the chalky ma- 
 trix and partly from the fossils being very similar to those 
 
 Fig. 2T4. 
 
 Fig. 2T6. 
 
 a. RadioUtM ratlwaa, D'Orb. 
 b. TJppei" valve of same. 
 White cliallc of France. 
 
 BatUolitee falioMvx, D'Orb. 
 SyD. Sptuei-ulites Ugariei- 
 forrais, Blainv, 
 White challc of France. 
 
 of the white chalk of the north : especially certain species of 
 the genera Spatangus, Aiianchytes, Cidarites, NuciCla, Ostrea, 
 
306 
 
 ELEMENTS OF GEOLOGY. 
 
 Gryphwa {Mcogyra), Pecten, Plagiostoma {Lima), Trigonia, 
 Catillus (Inoeeramus), and llrebratula* But Ammonites, 
 as M. d'Ai'chiac observes, of which so many species are met 
 with in the chalk of the north of E'rance, are scarcely ever 
 found in the southern region; while the genera Ifaniite, 
 Turrilite, and Scaphite, and perhaps Belemnite, are entirely 
 wanting. 
 
 On the other hand, certain forms are common in the south 
 which are rare or wholly unknown in the north of France. 
 Among these may be mentioned many Hippurites, Sphoeru- 
 lites, and other members of that great family of mollusca 
 called Mudistes by Lamarck, to which nothing analogous has 
 been discovered in the living creation, but which is quite 
 . characteristic of rocks 
 
 '^' of the Cretaceous era 
 
 in the south of France, 
 Spain, Sicily, Greece, 
 and other countries 
 bordering the Mediter- 
 ranean. The species 
 called Hippurites or- 
 ganisans (Fig. 276) is 
 more abundant than 
 any other in the south 
 of Europe; and the 
 geologist should make 
 himself well acquaint- 
 ed with the cast of the 
 b interior, d, which is oft- 
 en the only part pre- 
 served in many com- 
 pact marbles of the 
 tipper Cretaceous pe- 
 riod. The flutings on 
 
 BippuHtea organwaiw,Tiefmnn\ms. Upper chalk-— the interior of the Hip- 
 
 chiilk marl of Pyrenees ?t nnn'tp wViicli !iVP rpiv 
 
 a. Young individual; when fi,ll grown they occnv in P"'''^^' y^lCll aie lep 
 
 groups adhering laterally to each other, b. Upper resented On the Cast bv 
 
 side ofthe upper valve, showing a reticulated struc- amnotVi Tniinrlpil Inn- 
 turo in those parts, 6, where tSe external coating ^^OOin, lOUnaea 1011 
 
 isAvorn off. c. Upper end or opening of the lower gltudinal nbs, and m 
 
 fhf ioTv'efco,ucarvaL. "^ ''"' "' '"' """■'"• "' some individuals at- 
 
 tain a great size and 
 length, are wholly unlike the markings on the exterior of 
 the shell. 
 
 * D'Arehiac. Siir la Form. Cre'tacee du S.-O. de la France, Mdm. de la 
 hoc. Geol. de France, torn. ii. 
 + D'Orbigny's Pale'outologie fran^aise, pi. 533. 
 
CRETACEOUS ROCKS OF AMERICA. 30'? 
 
 Cretaceous Rocks in the United States. — If we pass to the 
 American continent, we find in the State of New Jersey a 
 series of sandy and argillaceous beds wholly unlike in min- 
 eral character to our Upper Cretaceous system ; which we 
 can, nevertheless, recognize as referable, palseontologically, 
 to the same division. 
 
 That they were about the same age generally as the Euro- 
 pean chalk and Neocomian, was the conclusion to which Gi: 
 Morton and Mr. Conrad came after their investigation of the 
 fossils in 1834. The strata consist chiefly of green sand and 
 green marl, with an overlying coralline limestone of a pale 
 yellow color, and the fossils, on the whole, agree most nearly 
 with those of the Upper European series, from the Maestricht 
 beds to the Gault inclusive. I collected sixty shells from the 
 New Jersey deposits in 1841, five of which were identical 
 with European species — Ostrea larva, 0. vesicularis, Gryphoea 
 costata, Pecten quinque-costatus, J3elemnitella mucronata. As 
 some of these have the greatest vertical range in Europe, 
 they might be expected more than any others to recur in 
 distant parts of the globe. Even where the species were 
 different, the generic forms, such as the Baculite and certain 
 sections of Ammonites, as also the Inoceramus (see above, 
 Fig. 252, p. 295) and other bivalves, have a decidedly creta- 
 ceous aspect. Fifteen out of the sixty shells above alluded 
 to were regarded by Professor Forbes as good geographical 
 representatives of well-known cretaceous fossils of Europe. 
 The correspondence, therefore, is not small, when we reflect 
 that the part of the United States where these strata occur 
 is between 3000 and 4000 miles distant from the chalk of 
 Central and Northern Europe, and that there is a difiisrence 
 often degrees in the latitude of the places compared on op- 
 posite sides of the Atlantic. Fish of the genera Lamna, 
 Galeus, and Garoharodon are common to New Jersey and 
 the European cretaceous rocks. So also is the genus Mosa- 
 sawrus among reptiles. 
 
 It appears from the labors of Dr. Newberry and others, 
 that the Cretaceous strata of the United States east and west 
 of the Appalachians are characterized by a flora decidedly 
 analogous to that of Aix-la-Chapelle above mentioned, and 
 therefore having considerable resemblance to the vegetation 
 of the Tertiary "and Recent Periods, 
 
308 ELEMENTS OF GEOLOGY. 
 
 CHAPTER XVIII. 
 
 LOWEE CRETACEOUS OR NEOCOMIAN EOEMATION. 
 
 Classification of marine and fresh-water Strata. — Upper Neocomian.— Follie- 
 stone and Hythe Beds. — Atherfield Clay. — Similarity of Conditions causing 
 Eeappearance of Species after short Intervals. — Upper Speeton Clay.— 
 Middle Neocomian. — Tealby Series. — Middle Speeton Clay.— Lower Neo- 
 comian. — Lower Speeton Clay. — Wealden Formation. — Fresh-water Char- 
 acter of the Wealden. — Weald Clay. — Hastings Sands. — PunfieldBeds of 
 Furbeck, Dorsetshire.^ — Fossil Shells and Fish of the Wealden.- — Area of 
 the Wealden. — Flora of the Wealden. 
 
 We now come to the Lower Cretaceous Formation which 
 was formerly called Lower Greensand, and for which it will 
 be useful for reasons before explained (p. 282) to use the term 
 "E^eocomian." 
 
 LOWEE CEETACEOUS OE NEOCOMIAlSr GEOUP. 
 
 Marine. Fresh-water. 
 
 1. Upper Neocomian — Greensand of Folke- 
 
 stone, Sandgate, and Hythe, Atherfield 
 clay, upper part of Speeton clay. 
 
 2. Middle Neocomian — Punfield Marine bed, 
 
 Tealby beds, middle part of Speeton clay. 
 
 3. Lower Neocomian — Lower part of Speeton 
 
 clay. 
 
 In Western France, the Alps, the Carpathians, Northern 
 Italy, and the Apennines, an extensive series of rocks has 
 been described by Continental geologists under the name of 
 Tithonian. These beds, which are without any marine equiv- 
 alent in this country, appear completely to bridge over the 
 interval between the Neocomian and the Oolites. They may, 
 perhaps, as suggested by Mr. Judd, be of the same age as 
 part of the Wealden series. 
 
 trPPEE NEOCOMIAN. 
 
 Folkestone and Hythe Beds. — The sands which crop out 
 beneath the Gault in Wiltshire, Surrey, and Sussex are some- 
 times in the uppermost part pure white, at others of a yellow 
 and ferruginous color, and some of the beds contain much 
 green matter, At Folkestone they contain layers of calcare- 
 ous matter and chert, and at Hythe, in the neighborhood, as 
 also at Maidstone and other parts of Kent, the limestone 
 called Kentish Rag is intercalated. This somewhat clayey 
 
 Part of Wealden beds of 
 Kent, Surrey, Sussex, 
 Hants, and Dorset. 
 
ATHERFIELD CLAY. 
 
 309 
 
 and calcareous stone forms strata two feet thick, alternating 
 with quartzose sand. The total thickness of these Folkestone 
 and Hythe beds is less than 300 feet, and they are seen to 
 rest immediately on a gray clay, to which we shall presently 
 allude as the Atherfield clay. Among the fossils of the Folke- 
 stone and Hythe beds we may mention Nautilus plicatus 
 (Fig. 277), Ancyloceras {Scaphites) gigas (Fig. 278), which 
 
 Fig. 2TT. 
 
 Fig. 278. 
 
 FautUxis plwatttn. Sow., in 
 Fitton's Monog. 
 
 Ancyloceras gigas, D'Orb. 
 
 has been aptly described as an Ammonite more or less un- 
 coiled; Trigonia caudata (Fig. 280), Gervillia anceps (Fig. 
 279), a bivalve genus allied to Avicula, and Terebratula sella 
 (Fig. 281). In ferruginous beds of the same age in Wiltshire 
 is found a remarkable shell called Diceras tjonscMii (Fig. 
 282, p. 309), which abounds in the Upper and Middle Neo- 
 comian of Southern Europe. This genus is closely allied to 
 Chama, and the cast of the interior has been compared to the 
 horns of a goat. 
 
 Fig. 279. 
 
 Fig. 280. 
 
 Gervillia anceps, Desh. Upper 
 Neocomiau, Surrey. 
 
 Triaonia caudata, Agass. 
 Upper Neocomian. 
 
 Atherfield Clay. — We mentioned before that the Folke- 
 stone and Hythe series rest on a gray clay. This clay is 
 only of slight thickness in Kent and Surrey, but acquires 
 great dimensions at Athei-field, in the Isle of Wight. The 
 difference, indeed, in mineral character and thickness of the 
 Upper ISTeocomian formation near Folkestone, and the cor- 
 responding beds in the south of the Isle of Wight, about 
 
310 
 
 ELEMENTS OF GEOLOGY. 
 
 Fig. 281. 
 
 Fig. 282. 
 
 Tta-ehratula sella. Sow. 
 tJppev Neocomian, Hythe. 
 
 Diceras Lmisialii. Upper Neocomian, Wilts. 
 
 a. The bivalve shell. 6. Cast of one of the 
 
 valves enlarged. 
 
 100 miles distant, is truly remarkable. In the latter plate 
 we find no limestone answering to the Kentish Rag, and the 
 entire thickness from the bottom of the Athei-field clay to 
 the top of the Neocomian, instead of being less than 300 feet 
 as in Kent, is given by the late Professor E. Forbes as 843 
 feet, which he divides into sixty-three strata, forming three 
 groups. The uppermost of these consists of ferruginous 
 sands, the second of sands and clay, and the third or lowest 
 of a brown clay, abounding in fossils. 
 
 Pebbles of quartzose sandstone, jasper, and flinty slate, to- 
 gether with gi-ains of chlorite and mica, and, as Mr. Godwin- 
 Austen has shown, fragments and water-worn fossils of the 
 oolitic rocks, speak plainly of the nature oF the pre-existing 
 formations, by the wearing down of which the Neocomian 
 beds were formed. The land, consisting of such rocks, was 
 doubtless submerged before the origin of the white chalk, a de- 
 posit which was formed in a more open sea,and in clearer waters. 
 Among the shells of the Atherfield clay the biggest and 
 
 most abundant shell is the 
 large Perna MuUeti, of 
 Avhich a reduced figure is 
 here given (Fig. 283). 
 Sitnllarity of ~ 
 tions causing Meappear- 
 ance of Species. — Some 
 species of mollusca and 
 otherfossilsrangethrough 
 the whole series, while 
 othei's are confined to par- 
 ticular subdivisions, and 
 _"°°'™'™' Forbes laid down a law 
 
 which has since been found of veiy general application in 
 regard to estimating the chronological relations of consecu-. 
 
 Fig. 283. 
 
 Perna MuUetf, Desh. One-eighth natnval size, 
 a. Exlerior. b. Part of hinge-llue of upper or 
 
SPEETON CLAY. 311 
 
 tive strata. Whenever similar conditions, he says, are re- 
 peated, the same species reappear, provided too great a lapse 
 of time has not intervened; whereas if the length of the in- 
 terval has been geologically great, the same genera will re- 
 appear represented by distinct species. Changes of depth, 
 or of the mineral nature of the sea-bottom, the presence or 
 absence of lime or of peroxide of iron, the occurrence of a 
 muddy, or a sandy, or a gravelly bottom, are marked by the 
 banishment of certain species and the predominance of 
 others. But these differences of conditions being mineral, 
 chemical, and local in their nature, have no necessary con- 
 nection with the extinction, throughout a large area, of cer- 
 tain animals or plants. When the forms proper to loose 
 sand or soft clay, or to perfectlj"- clear water, or to a sea of 
 moderate or great depth, recur with all the same species, we 
 may infer that the interval of time has been, geologically 
 speaking, small, however dense the mass of matter accumu- 
 lated. But if, the genera remaining the same, the species are 
 changed, we have entered upon a new period; and no similari- 
 ty of climate, or of geographical and local conditions, can then 
 recall the old species which a long series of destructive causes 
 in the animate and inanimate world has gradually annihilated. 
 Speeton Clay, Upper Division. — On the coast, beneath the 
 white chalk of Flamborough Head, in Yorkshire, an ai-gilla- 
 ceous formation crops out, called the Speeton clay, several 
 hundred feet in thickness, the palseontological relations of 
 which have been ably worked out by Mr. John W. Judd,* 
 and he has shown that it is separable into three divisions, 
 the uppermost of which, 150 feet thick, and containing 87 
 species of mollusca, decidedly belongs to the Atherfield clay 
 and associated strata of Hythe and Folkestone, already de- 
 scribed. It is characterized by the pj„ 234 
 Perna Mulleti (Fig. 283) and Tere- 
 bratula sella (Fig. 281), and by Am- 
 monites Deshayesii (Fig. 284), a well- 
 known Hythe fossil. Fine skeletons 
 of reptiles of the genera Pliosaurus 
 and Teleosaurus have been obtained 
 from this clay. At the base of this 
 upper division of the Speeton clay 
 
 there occurs a layer of large Septa- Ammonites DeshayesH, Leym. 
 
 ria, formerly worked for the manu- Uppe.- Neocomian. 
 
 facture of cement. This bed is crowded with fossils, espe- 
 cially Ammonites, one species of which, three feet in diame- 
 ter, was observed by Mr. Judd. 
 
 * Judd, Speeton Clay, Quart. Geol. Jouni., vol. xxiv., 1868, p. 218. 
 
312 
 
 elemi':nxs or geology. 
 
 MIDDLE NEOCOMIAN. 
 
 Tealby Series.— At Tealby, a village in the Lincolnshire 
 Wolds, there crop out beneath the white chalk some non- 
 fossiliferous ferruginous sands about twenty feet thick, be- 
 neath which are beds of clay and limestone, about fifty feet 
 thick with an interesting suite of fossils, among which are 
 Pecten cmctus (Fig. 285), from 9 to 12 inches in diameter, 
 Ancyloceras Duvallei (Fig. 286), and some forty other shells, 
 many of them common to the Middle Speeton clay, about to 
 
 Fig. 285. I''g- 2S0- 
 
 Peetmcinctus, Sov!. (P.crassitesto,Kom.) Ancyloceras (Cnocevas) Duvalln, 
 
 Middle Neocomiaii, Englaud; Middle Leveille. Middle, and Lower 
 
 and LowerNeocomian, Germany. One- Neocomian. One-flfth natural 
 
 flfth natural size. size. 
 
 be mentioned. Mr. Judd remarks that as Ammonites clypei- 
 formis and Terebratula hippopus characterize the Middle 
 Neocomian of the Continent, it is to this stage that the Teal- 
 by series containing the same fossils may be assigned.* 
 
 The middle division of the Speeton clay, occurring at Spee- 
 ton below the cement-bed, before alluded to, is 150 feet thick, 
 and contains about 39 species of mollusca, half of which are 
 common to the overlying clay. Among the peculiar shells, 
 Pecten cinctus (Fig. 285) and Ancyloceras {Grioceras) Duval- 
 lei (Fig. 286) occur. 
 
 LOWEE NEOCOMIAN. 
 
 In the lower division of the Speeton clay, 200 feet thick, 
 46 species of mollusca have been found, and three divisions, 
 each characterized by its peculiar ammonite, have been no- 
 ticed by Mr. Judd. The central zone is marked by Ammoni- 
 tes Nbricus {seeYig. 281 ,-p.315). On the Continent these beds 
 are well known by their coiTesponding fossils, the Hils clay 
 and conglomerate of the north of Germany agreeing with 
 * Judd, Quart. Geol. Journ., 1867, vol. xxiii., p. 249. 
 
WEALDEN FORMATION. 313 
 
 the Middle and Lower Speeton, the Pig.asr. 
 
 latter of which, with the same mineral AtdHiW^ik /5^ 
 
 characters and fossils as in Yorkshire, iCwwJjillfl/Al ««*M| 
 
 is also found in the little island of ,^fi^^^il/|l ^^ 
 
 Heligoland. Yellow limestone, which ^^^jB^L iH' 
 
 I have myself seen near Neuchatel, in ^^^^83^^ IIH 
 
 Switzerland, represents the Lower ^^^^^^^^ i^ 
 
 Neocomian at Speeton. ^^^M^w^ W 
 
 WEALDEN FORMATION. Ammonites Ncyrieus, BcWofh. 
 
 Beneath the Atherfield clay or Up- '^'"'^ N^''™'"'^"' SP^^^n. 
 per Neocomian of the S.E. of England, a fresh-water forma- 
 tion is found, called the Wealden, which, although it oc- 
 cupies a small horizontal area in Europe, as compared to 
 the White Chalk, and the marine Neocomian beds, is nev- 
 ertheless of great geological interest, since the imbedded 
 remains give us some insight into the nature of the ter- 
 restrial fauna and flora of the Lower Cretaceous epoch. 
 The name of Weald-en was given to this group because 
 it was first studied in parts of Kent, Surrey, and Sussex, 
 called the Weald ; and we are indebted to Dr. Mantell 
 for having shown, in 1822, in his "Geology of Sussex," 
 that the whole group was of fluviatile origin. In proof of 
 this he called attention to the entire absence of Ammonites, 
 Belemnites, Brachiopoda, Echinodermata, Corals, and other 
 marine fossils, so characteristic of the Cretaceous rocks above, 
 and of the Oolitic strata below, and to the presence in the 
 Weald of Paludinse, Melanias, Cyrense, and various fluviatile 
 shells, as well as the bones of terrestrial reptiles and the 
 trunks and leaves of land-plants. 
 
 The evidence of so unexpected a fact as that of a dense 
 mass of purely fresh-water origin underlying a deep-sea de- 
 posit (a phenomenon with which we have since become fa- 
 miliar) was received, at first, with no small doubt and incre- 
 dulity. But the relative position of the beds is unequivocal ; 
 the Weald Clay being distinctly seen to pass beneath the 
 Atherfield Clay in various parts of Surrey, Kent, and Sussex, 
 and to reappear in the Isle of Wight at the base of the Cre- 
 taceous series, being, no doubt, continuous far beneath the 
 surface, as indicated by the dotted lines in the annexed dia- 
 gram (Fig. 288). They are also found occupying the same 
 relative position below the chalk in the peninsula of Pur- 
 beck, Dorsetshire, whei-e, as we shall see in the sequel, they 
 repose on strata referable to the Upper Oolite. 
 
 Weald Clay. — The Upper division, or Weald Clay, is, in 
 great part, of fresh-water origin, but in its highest portion 
 
 i4 
 
314 ELEMENTS OE GEOLOGY. 
 
 W.S.W. I'ig- 288. E.N.E. 
 
 ^^,4 --,a \,2 v.~ y ^==^r:r 
 
 '---■^^^ 
 
 1. Tertiary. 2. Chalk and Gaiilt. 3. Upper Neocomian (or Lower Greensaud). • 
 4. Wealden (Weald Clay aud Hastings Sands). 
 
 contains beds of oysters and other marine shells which indi- 
 cate fluvio-marine conditions. The uppermost "beds are not 
 only conformable, as Dr. Fitton observes, to the inferior stra- 
 ta of the overlying Neocomian, but of similar mineral com- 
 position. To explain this, we may suppose that, as the delta 
 of a great river was ti'anquilly subsiding, so as to allow the 
 sea to encroach upon the space previously occupied by fresh 
 water, the river still continued to carry down the same sedi- 
 ment into the sea. In confirmation of this view it may be 
 stated that the remains of the Iguanodon Mdntetti, a gigan- 
 tic terrestrial reptile, very characteristic of the Wealden, has 
 been discovered near Maidstone, in the overlying Kentish 
 Rag, or marine limestone of the Upper Neocomian. Hence 
 we may infer that some of the saurians which inhabited the 
 country of the great river continued to live when part of 
 the district had become submerged beneath the sea. Thus, 
 in our own times, we may suppose the bones of large alliga- 
 tors to be frequently entombed in recent fresh-water strata 
 in the delta of the Ganges. But if part of that delta should 
 sink down so as to be covered by the sea, marine formations 
 might begin to accumulate in the same space where fresh- 
 water beds had previously been formed ; and yet the Gan- 
 ges might still pour down its turbid waters in the same di- 
 rection, and carry seaward the carcasses of the same species 
 of alligator, in which case their bones might be included in 
 marine as well as in subjacent fresh-water strata. 
 
 The Iguanodon, first discovered by Dr. Mantell, was an 
 herbivorous reptile, of which the teeth, though bearing a 
 great analogy, in their general form and crenated edges (see 
 JFigs. 289, a,' 289, b, p. 315), to the modern Iguanas which now 
 frequent the tropical woods of America and the West In- 
 dies, exhibit many important diiferences. It appears that 
 they have often been worn by the process of mastication; 
 whereas the existing herbivorous reptiles clip and gnaw off 
 the vegetable productions on which they feed, but do not 
 chew them. Their teeth frequently present an appearance 
 
WEALDEN FORMATION. 
 
 Kg. 289. 
 
 315 
 
 Pig. 290. 
 
 Fig. 2S9. a, h. Tooth of Iguanodon MantelU. Fig. 290. a. Partially worn tooth o£ 
 young indiYldual of the same. 6. Crown of tooth in adult worn down. (Mantell.) 
 
 of having been chipped off, but never, like the fossil teeth of 
 the Iguanodon, have a flat ground surface (see Fig. 290, 5) 
 resembling the grinders of herbivorous mammalia. Dr. Man- 
 tell computes that the teeth and bones of this species ■which 
 passed under his examination during twenty years must 
 have belonged to no less than seventy-one distinct individ- 
 uals, varying in age and magnitude from the reptile just 
 burst from the egg, to one of which the femur measured 
 twenty-four inches in circumference. Yet, notwithstanding 
 that the teeth were more numerous than any other bones, it 
 is remarkable that it was not until the relics of all these in- 
 dividuals had been found, that a solitary example of part of 
 a jaw-bone was obtained. Soon afterwards remains both of 
 the upper and lower jaw were met with in the Hastings beds 
 in Tilgate Forest, near Cuckfield. In the same sands at Has- 
 tings, Mr. Beckles found large tridactyle impressions which 
 it is conjectured were made by the hind feet of 
 this animal, on which it is ascertained that there 
 were only three well-developed toes. 
 
 Occasionally bands of limestone, called Sussex 
 Marble, occur in the "Weald Clay, almost entirely 
 composed of a species of JPaludina^loselj resem- 
 bling the common P. vivipara of English rivers. 
 Shells of the Cypris, a genus of Crustaceans before 
 mentioned (p. 57) as abounding in lakes and ponds, 
 are also plentifully scattered through the clays of the Weal- 
 
 Fig. 291. 
 
 CyprU spini- 
 gera, Fitton. 
 
Hastings Sand. 
 
 316 ELEMENTS OF GEOLOGY. 
 
 Pig. 292. den, sometimes producing, like plates of 
 
 mica, a thin lamination (see Fig. 292). 
 
 Hastings Sands. — This lower division 
 of the Wealden consists of sand, sand- 
 stone, calciferous grit, clay, and shale; 
 -————--^-^ the argillaceous strata, notwithstanding 
 weai^^^^^^es. the name, predominating somewhat over 
 the arenaceous, as will be seen by reier- 
 ence to the following section, drawn up by Messrs. Drew and 
 Foster, of the Geological Survey of Great Britain : 
 
 Names of Subordinate Mineral Composition ip.ain 
 
 Formations. of the Strata. "I^^" 
 
 Tunbiidge Wells (g^ndstone and loam .... 150 
 
 Sand ( 
 
 ,„ ,, „, ( Blue and brown shale and clay, 
 
 Wadhm-stClay. . -j ,^ith a little calc-grit ... 100 
 ■^ . , , „ J (Hard sand, with some beds of 
 
 AshdownSand. .J ^^x^_^^\l 160 
 
 ... , T, , ( Mottled white and red clay, 
 Ashburnham Beds j ^^j^j^ ^^^^^ sandstone . . . 330 
 
 The picturesque scenery of the "High Eocks" and other 
 places in the neighborhood of Tunbridge Wells is caused by 
 the steep natural cliffs, to which a hard bed of white sand, 
 occurring in the upper part of the Tunbridge Wells Sand, 
 mentioned in the above table, gives rise. This bed of" rock- 
 sand " varies in thickness from 25 to 48 feet. Large masses 
 of it, which were by no means hard or capable of making a 
 good building-stone, form, nevertheless, projecting i-ocks with 
 perpendicular faces, and resist the degrading action of the riv- 
 er because, says Mr. Drew, they present a solid mass without 
 planes of division. The calcareous sandstone and grit of Til- 
 gate Forest, near Cuckfield, in which the remains of the Igua- 
 nodon and Hylseosaurus were first found by Dr. Mantell, 
 constitute an upper member of the Tunbridge Wells Sand, 
 while the "sand-rock" of the Hastings cliffs, about 100 feet 
 thick, is one of the lower members of the same. The rep- 
 tiles, which are very abundant in this division, consist partly 
 of saurians, referred by Owen and Mantell to eight genera, 
 among which, besides those already enumerated, we find the 
 MegaJosaurus and Plesiosaurus. The Pterodactyl also, a fly- 
 ing reptile, is met with in the same strata, and many remains 
 of Chelonians of the genera Trionyx and^mys, now confined 
 to tvopical regions. 
 
 The fishes of the Wealden are chiefly referable to the Ga- 
 noid and Placoid orders. Among them the teeth and scales 
 of T'Cpidotus are most widely diffused (see Fig. 293). These 
 
HASTINGS SANDS. 
 Pig. 293. 
 
 317 
 
 Vhio ValdmsiB, Mant Isle of Wight and Dorset 
 shire ; in the lower beds of the Hastings Sands. 
 
 Lepidotua Mantelli, Agass. Wealden. 
 a. Palate and teeth. 6. Side view of teeth, c. Scale. 
 
 ganoids were allied to the Zepidosteus, or Gar-pike, of the 
 
 American rivers. The whole body was covered with large 
 Fig. 294. rhomboidal scales, very- 
 
 thick, and having the ex- 
 posed part coated with 
 enamel. Most of the spe- 
 cies of this genus are sup- 
 posed to have been either 
 river -fish, or inhabitants 
 of the sea at the mouth 
 of estuaries. 
 
 At different heights in 
 the Hastings Sands, we 
 find again and again slabs 
 of sandstone with a strong 
 ripple-mark, and between 
 
 these slabs beds of clay many yards thick. In some places, 
 
 as at Stammerham, 
 
 Horsham, near there, 
 
 are indications of this 
 
 clay having been ex- 
 posed so as to dry 
 
 and crack before the 
 
 next layerwas thrown 
 
 down upon it. The 
 
 open cracks in the 
 
 clay have served as 
 
 moulds, of which casts 
 
 have been taken in 
 
 relief, and which are, 
 
 therefore, seen on the 
 
 lower surface of the 
 
 sandstone (see Fig. 
 
 295). 
 Near the same place a reddish sandstone occurs in which 
 
 Fig. 296. 
 
 Under side of slab of sandstone abont one yard in 
 diameter. Staminerhara, Sussex. 
 
318 
 
 ELEMENTS OF GEOLOGY. 
 
 Sphenopteris gracilis, Fitton. From 
 the Hastings Sands near Tnn- 
 bridge Wells. 
 
 a. A portion of the eame magnified. 
 
 Fig. 296. _ are innumerable traces of a fossil 
 
 vegetable, apparently Sphenop- 
 teris, the stems and branches of 
 which are disposed as if the 
 plants were standing erect on 
 the spot where they originally 
 grew, the sand having been gen- 
 tly deposited upon and around 
 them; and similar appearances 
 have tjeen remarked in other 
 places in this formation.* In 
 the same division also of the 
 Wealden, at Cuckiield, is a bed 
 of gravel or conglomerate, consisting of water-worn pebbles 
 of quartz and jasper, with rolled bones of reptiles. These 
 must have been drifted by a current, probably in water of 
 no great depth. 
 
 From such facts we may infer that, notwithstanding the 
 great thickness of this division of the Wealden, the whole of 
 it was a deposit in water of a moderate depth, and often ex- 
 tremely shallow. This idea may seem startling at first, yet 
 such would be the natural consequence of a gradual and con- 
 tinuous sinking of the ground in an estuary or bay, into 
 which a great river discharged its turbid waters. By each 
 foot of subsidence, the fundamental rock would be depressed 
 one foot farther from the surface ; but the bay would not 
 be deepened, if newly-deposited mud and sand should raise 
 the bottom one foot. On the contrary, such new strata 
 of sand and mud might be frequently laid dry at low wa- 
 ter, or overgrown for a season by a vegetation proper to 
 marshes. 
 
 Punfleld Beds, Brackish and Marine. — The shells of the 
 Wealden beds belong to the genera Melanopsis, Melania, 
 Paludina, Cyrena, Cyclas, Unio (see Fig. 294), and others, 
 which inhabit rivers or lakes ; but one band has been found 
 at Punfield, in Dorsetshire, indicating a brackish state of the 
 water, where the genera Corbula, Mytilus, and Ostrea occur ; 
 and in some places this bed becomes purely marine, contain- 
 ing some well-known Neocomian fossils, among which Am- 
 monites Deshayesii (Fig. 284, p. 311) may be mentioned. 
 Others are peculiar as British, but very characteristic of the 
 Upper and Middle Neocomian of Spain, and among these the 
 Vicarya Lujani (Fig. 297), a shell allied to Nerinea, is con- 
 spicuous. 
 
 By reference to the table p. 308 it will be seen that the 
 * Mantell, Geol. of S.E. of England, p. 244. 
 
AREA OF THE WEALDEN. 319 
 
 Wealden beds are given as the 
 fresh-water equivalents of the Ma- 
 rine Neocomian. The highest part 
 of them in England may, for rea- 
 sons just given, be regarded as Up- 
 per Neocomian, while some of the 
 inferior portions may correspond in 
 age to the Middle and Lower di- 
 visions of that group. In favor of 
 this latter view, M. Marcou men- _ 
 
 tions that a fish called Asteracan- vimvm iMiani, De Vemeuii.* 
 thus granulosus, occurring in the weaiden, Punfleui. 
 
 Tilgate beds, is characteristic of the «-eS^SiSn*smS specie"; 
 
 lowest beds of the Neocomian of showuig contiDnons ridges aa 
 
 the Jura, and it is well known that ™^ f™"^"- 
 
 Corbula alata, common in the Ashburnham beds, is found 
 
 also at the base of the Neocomian of the Continent. 
 
 Area of the Wealden. — In regard to the geographical ex- 
 tent of the Wealden, it can not be accurately laid down, 
 because so much of it is concealed beneath the newer maiine 
 formations. It has been traced about 320 English miles 
 from west to east, from the coast of Dorsetshire to near Bou- 
 logne, in France ; and nearly 200 miles from north-west to 
 south-east, from Surrey and Hampshire to Vassy, in France. 
 If the formation be continuous throughout this space, which 
 is very doubtful, it does not follow that the whole was con- 
 temporaneous ; because, in all likelihood, the physical geog- 
 raphy of the region underwent frequent changes throughout 
 the whole period, and the estuary may have altered its form, 
 and even shifted its place. Di-. Dunker, of Cassel, and H. 
 von Meyer, in an excellent monograph on the Wealdens of 
 Hanover and Westphalia, have shown that they correspond 
 so closely, not only in their fossils, but also in their mineral 
 characters, with the English series, that we can scarcely hes- 
 itate to refer the whole to one great delta. Even then, the 
 magnitude of the deposit may not exceed that of many mod- 
 ern rivers. Thus, the delta of the Quorra or Niger, in Afri- 
 ca, stretches into the interior for more than 170 miles, and 
 occupies, it is supposed, a space of more than 300 miles along 
 the coast, thus forming a surface of more than 25,000 square 
 miles, or equal to about one-half of England. f Besides, we 
 know not, in such cases, how far the fluviatile sediment and 
 organic remains of the river and the land may be carried out 
 from the coast, and spread over the bed of the sea. I have 
 
 * Eoss. de Utrillas. 
 
 t Fitton, Geol. of Hastings, p. 58, who cites Lander's Travels. 
 
320 ELEMENTS OF GEOLOGY. 
 
 shown, when treating of the Mississippi, that a raoi-e ancient 
 delta, including species of shells such as now inhabit Loui- 
 siana, has been upraised, and made to occupy a wide geo- 
 graphical area, while a newer delta is forming ;* and the pos- 
 sibility of such movements and their effects must not be lost 
 sight of when we speculate on the origin of the Wealden. 
 
 It may be asked where the continent was placed, from the 
 ruins of which the Wealden strata were derived, and by the 
 drainage of which a great river was fed. If the Wealden was 
 gradually going downward 1000 feet or more perpendicu- 
 larly, a large body of fresh water would not continue to be 
 poured into the sea at the same point. The adjoining land, 
 if it participated in the movement, could not escape being 
 submerged. But we may suppose such land to have been 
 stationary, or even undergoing contemporaneous slow up- 
 heaval. There may have been an ascending movement in 
 one region, and a descending one in a contiguous parallel 
 zone of country. But even if that were the case, it is clear 
 that finally an extensive depression took place in that part 
 of Europe where the deep sea of the Cretaceous period was 
 afterwards brought in. 
 
 Thickness of the Wealden. — In the Weald area itself, be- 
 tween the North and South Downs, fresh-water beds to the 
 thickness of 1600 feet are known, the base not being reached. 
 Probably the thickness of the whole Wealden series, as seen 
 in Swanage Bay, can not be estimated as less than 2000 feet. 
 Wealden Flora. — The flora of the Wealden is characterized 
 by a great abundance of Coniferse, Cycadese, and Ferns, and 
 by the absence of leaves and fruits of dicotyledonous angi- 
 osperms. The discovery in 1855, in the Hastings beds of the 
 Isle of Wight, of Gyrogonites, or spore-vessels of the Chara, 
 was the first example of that genus of plants, so common in 
 the Tertiary strata, being found in a Secondary or Mesozoio 
 rock. 
 
 * See above, p. 102 ; and Second Visit to the United States, vol. ii., chap, 
 xxxiy. 
 
CLASSnriCATION OF THE OOLITE. 321 
 
 CHAPTER XIX. 
 
 JURASSIC GEOUP. — PUEBECK BEDS AND OOLITE. 
 
 The Purbeck Beds a Member of the Jurassic Group. — Subdivisions of that 
 Group. — Physical Geogi-aphy of the Oolite in England and France. — Up- 
 per Oolite. — Purbeck Beds. — New Genera of fossil Mammalia in the 
 Middle Purbeck of Dorsetshire. — Dirt-bed or ancient Soil.— Fossils of 
 the Purbeck Beds. — Portland Stone and Fossils. — Kimmeridge Clay. — 
 Lithographic Stone of Solenhofen. — Archseopteryx. — Middle Oolite. — Cor- 
 al Rag. — Nerincea Limestone. — Oxford Clay, Ammonites and Belemnites. 
 — Kelloway Rock. — Lower, or Bath, Oolite. — Great Plants of the Oolite. 
 — Oolite and Bradford Clay. — Stonesfield Slate. — Fossil Mammalia. — 
 Fuller's Earth. — Inferior Oolite and Fossils. — Northamptonshire Slates. — 
 Yorkshire Oolitic Coal-field. — Brora Coal. — Palaeontological Relations of 
 the several Subdivisions of the Oolitic group. 
 
 Classification of the Oolite. — Immediately below the Has- 
 tings Sands we find in Dorsetshire another remarkable fresh- 
 water formation, called the Purbeck, because it was fii-st stud- 
 ied in the sea-cliflfs of the peninsula of Purbeck in that county. 
 These beds are for the most part of fresh-water origin, but 
 the organic remains of some few intercalated beds are marine, 
 and show that the Purbeck series has a closer affinity to the 
 Oolitic group, of which it may be considered as the newest 
 or uppermost member. 
 
 In England generally, and in the greater pai-t of Europe, 
 both the Wealden and Purbeck beds are wanting, and the 
 marine cretaceous group is followed immediately, in the de- 
 scending order, by another series called the Jurassic. In this 
 terra, the formations commonly designated as " the Oolite 
 and Lias " are included, both being found in the Jura Mount- 
 ains. The Oolite was so named because in the countries 
 where it was first examined the limestones belonging to it 
 had an Oolitic structure (see p. 37). These rocks occupy in 
 England a zone nearly thirty miles in average breadth, which 
 extends across the island, from Yorkshire in the north-east, 
 to Dorsetshire in the south-west. Their mineral characters 
 are not uniform throughout this region; but the following 
 are the names of the principal subdivisions observed in the 
 central and south-eastern parts of England. 
 
 OOLITE. 
 (a. Purbeck beds. 
 Upper . . . \h. Portland stone and sand, 
 (c. Kimmeridge clay. 
 14* 
 
322 
 
 ELEMENTS OF GEOLOGY. 
 
 Middle . 
 Lower 
 
 OOIjITE— Continued. 
 
 (d. Coral rag. 
 
 1 e. Oxford clay, and Kelloway rock, 
 r/. Conibrasli and Forest marble. 
 I g. Great Oolite and Stonesfield slate. 
 
 h. Fuller's earth. 
 
 i. Inferior Oolite. 
 
 The Upper Oolitic system of the above table has usually 
 the Kimmeridge clay for its base; the Middle OoUtic sys- 
 tem, the Oxford clay. The Lower system reposes on the 
 Lias, an argillo-calcareous formation, which some include in 
 the Lower Oolite, but which will be treated of separately 
 in the next chapter. Many of these subdivisions are distin- 
 guished by peculiar organic remains ; and, though varying 
 in thickness, may be traced in certain directions foi- great 
 distances, especially if we compare the part of England to 
 which the above-mentioned type refers with the north-east 
 of France and the Jura Mountains adjoining. In that coun- 
 try, distant above 400 geographical miles, the analogy to 
 the accepted English type, notwithstanding the thinness or 
 occasional absence of the clays, is more perfect than in York- 
 shire or Normandy. 
 
 Physical Geography. — The alternation, on a grand scale, 
 of distinct formations of clay and limestone has caused the 
 oolitic and liassic series to give rise to some marked fea- 
 tures in the physical outline of parts of England and France. 
 Wide valleys can usually be traced throughout the long 
 bands of country where the argillaceous strata crop out; 
 and between these valleys the limestones are observed, form- 
 ing ranges of hills or more elevated grounds. These ranges 
 terminate abruptly on the side on which the several clays 
 rise up from beneath the calcareous strata. 
 
 The annexed cut will give the reader an idea of the eon- 
 figuration of the surface now alluded to, such as may be seen 
 
 Lower 
 Oolite. 
 
 Fig. 298. 
 
 Middle 
 Oolite. 
 
 Upper 
 Oolite. 
 
 London 
 Chalk. Clay. 
 
 Lias, 
 
 Oxford Clay. 
 
 Kim. Clay. Gaalt. 
 
 in passing from London to Cheltenham, or in other parallel 
 lines, from east to west, in the southern part of England. It 
 has been necessary, however, in this drawing, greatly to ex- 
 aggerate the inclination of the beds, and the height of the 
 several formations, as compared to their horizontal extent 
 
EUKBECK BEDS. 323 
 
 It will be remarked, that the lines of steep slope, or escarp- 
 ment, face towards the west in the great calcareous emi- 
 nences formed by the chalk and the Upper, Middle, and 
 Lower Oolites ; and at the base of which we have respect- 
 ively the Gault, Kimmeridge clay, Oxford clay, and Lias. 
 This last forms, generally, a broad vale at the foot of the 
 escarpment of inferior Oolite, but where it acquires consid- 
 ei-able thickness, and contains solid beds of marlstone, it oc- 
 cupies the lower part of the escarpment. 
 
 The external outline of the country which the geologist 
 observes in ti-avelling eastward from Paris to Metz, is pre- 
 cisely analogous, and is caused by a similar succession of 
 rocks intervening between the tertiary strata and the Lias; 
 with this difference, however, that the escarpments of Chalk, 
 Upper, Middle, and Lower Oolites face towards the east in- 
 stead of the west. It is evident, therefoi-e, that the denud- 
 ing causes (see p. 105) have acted similarly over an area 
 several hundred miles in diameter, removing the softer clays 
 more extensively than the limestones, and causing these last 
 to form steej) slopes or escarpments wherever the harder 
 calcareous rock was based upon a more yielding and de- 
 structible formation. 
 
 UPPER OOLITE. 
 
 Purbeck Beds. — These strata, which we class as the upper- 
 most member of the Oolite, are of limited geographical ex- 
 tent in Europe, as already stated, but they acquire impor- 
 tance when we consider the succession of three distinct sets 
 of fossil remains which they contain. Such repeated changes 
 in organic life must have reference to the history of a vast 
 lapse of ages. The Purbeck beds are finely exposed to view 
 in Durdlestohe Bay, near Swanage, Dorsetshire, and at Lul- 
 worth Cove and the neighboring bays between Weymouth 
 and Swanage. At Meup's Bay, in jjarticular, Professor E. 
 Forbes examined minutely, in 1850, the organic remains of 
 this group, displayed in a continuous sea-cliff section, and 
 it appears from his researches that the Upper, Middle, and 
 Lower Purbecks are each marked by peculiar species of or- 
 ganic remains, these again being different, so far as a com- 
 parison has yet been instituted, from the fossils of the over- 
 lying Hastings Sands and Weald Clay. 
 
 Upper Purbeck. — The highest of the three divisions is 
 purely fresh-water, the strata, about fifty feet in thickness, 
 containing shells of the genera Pdludina, Physa, Ziimnoea, 
 ■Planorhis, Valvata, Gyclas, and Unio, with Cyprides and fish. 
 All the Species seem peculiar, and among these the Cyprides 
 
324 
 
 ELEMENTS OF GEOLOGY. 
 
 are very abundant and characteristic. (See Figure 299, 
 a, b, c.) 
 
 The stone called "Purheck Marble," formerly much used 
 in ornamental architecture in the old English cathedrals of the 
 southern counties, is exclusively procured from this division. 
 
 Fig. 299. 
 b 
 
 Cyprides from the Upper Pnrbecks. 
 a. Cijpris gibbom, E. Forbes. 6. Cypris tuberculata. E, Forbes, u. Cypria leguminella, 
 
 E. Forbes. 
 
 Middle Purheck. — ISText in succession is the Middle Pur- 
 beck, about thirty feet thick, the uppermost part of which 
 consists of fresh-water limestone, with cyprides, turtles, and 
 fish, of difierent species from those in the preceding strata. 
 Below the limestone are brackish-water beds full of Cyrena, 
 and traversed by bands abounding in Corbula and Melania. 
 These are based on a purely mai'ine deposit, with Pecten, 
 Modiola, Avicula, and Thracia. Below this, again, come 
 limestones and shales, partly of brackish and partly of fresh- 
 water origin, in which many fish, especially species of Lepi- 
 dottis and Microdon radiatus, are found, and a crocodilian 
 reptile named Macrorhynchus. Among the mollusks, a re- 
 markable ribbed Melania, of the section Chilina, occurs. 
 
 Fig. 301. 
 
 Fig. 300. 
 
 Ostrea distnrta, Sow. Cinder- 
 bed, Middle Eurbeck. 
 
 Hemicidttiria Furbeckensis, E. Forbes. 
 Middle Purbeck. 
 
 Immediately below is a great and conspicuous stratum, 
 twelve feet thick, formed of a vast accumulation of shells of 
 Ostrea distorta (Fig. 300), long familiar to geologists under 
 the local name of " Cinder-bed." In the uppermost part of 
 
MAMMALIA OF THE PUEBECK BEDS. 
 
 325 
 
 Pig. 303. 
 
 CypriOes from the Middle Purbecks. 
 
 a. Cijpria striato-punciata, 3. Forbes. 6. C/iprie fasciculata, E. Forbes, 
 c. Cijpris tjranuUitaj Sow. 
 
 this bed Professor Forbes discovered the first echinoderm 
 (Fig. 301) as yet known in the Pnrbeck series, a species of 
 Memicidaris, a genus characteristic of the Oolitic period, and 
 scarcely, if at all, distinguishable from a previously known 
 Oolitic fossil. It was accompanied by a species of I'erna. 
 Below the Cinder-bed fresh-water strata are again seen, filled 
 in many places with species of Gyjpris (Fig. 302, «, 5, c), and 
 with VaVoata, Paludina, Planorbis, Lim- 
 ncea, Physa (Fig. 803), and Cyclas, all 
 dififerent from any occurring higher in 
 the series. It will be seen that Cypris 
 fasciculata (Fig. 302, b) has tubercles at 
 the end only of each valve, a character 
 by which it can be immediately recog- 
 nized. In fact, these minute crustaceans, -PAysa ^-wtomi, s. Foibes. 
 
 1 , J, '.. „., ,,' Middle Fuibeck. 
 
 almost as frequent in some oi the shales 
 as plates of mica in a micaceous sandstone, enable geologists 
 at once to identify the Middle Purbeek in places far from the 
 Dorsetshire cliffs, as, for example, in the Vale of Wardour in 
 Wiltshire. Thick beds of chert occur in the Middle Purbeek 
 filled with mollusca and cyprides of the genera already enu- 
 merated, in a beautiful state of preservation, often converted 
 into chalcedony. Among these Professor Forbes met with 
 gyrogonites (the spore-vessels of Chard), plants never until 
 1851 discovered in rocks older than the Eocene. About 
 twenty feet below the " Cinder-bed " is a stratum two or 
 three inches thick, in which fossil mammalia presently to be 
 mentioned occur, and beneath this a thin band of greenish 
 shales, with marine shells and impressions of leaves like those 
 of a large Zostera, forming the base of the Middle Purbeek. 
 
 FossU Mammalia of the Middle Purbeek. — In 1852,* after 
 alluding to the discovery of numerous insects and air-breath- 
 ing mollusca in the Purbeek sti-ata, I remarked that, although 
 no mammalia had then been found, " it was too soon to infer 
 * Elements of Geology, 4th edition. 
 
326 ELEMENTS OF GEOLOGY. 
 
 their non-existeuce on mere negative evidence." Only two 
 years after this remark was in print, Mr. W. R. Brodie found 
 in the Middle Purbeck, about twenty feet below the "Cin- 
 der-bed " abovi alluded to, in Durdlestone Bay, portions of 
 several small jaws with teeth, which Professor Owen recog- 
 nized as belonging to a small mammifer of the insectivorous 
 class, more closely allied in its dentition to the Amphitherium 
 (or Thylacotherium) than to any existing type. 
 
 Four years later (in 1856) the remains of several other spe- 
 cies of warm-blooded quadrupeds were exhumed by Mr. S. 
 H. Beckles, F.R.S., from the same thin bed of marl near the 
 base of the Middle Purbeck. In this marly stratum many 
 reptiles, several insects, and some fresh-water shells of the 
 genera Paludhia, Planoriis, and Cyclas, were found. 
 
 Mr. Beckles had determined thoroughly to explore the 
 thin layer of calcareous mud from which in the suburbs of 
 Swanage the bones of the Spalacotherium had already been 
 obtained, and in three weeks he brought to light from a^ 
 area forty feet long and ten wide, and from a layer the av- 
 erage thickness of which was only five inches, portions of the 
 skeletons of six new species of mammalia, as interpreted by 
 Dr. Falconer, who first examined them. Before these inter- 
 esting inquiries were brought to a close, the joint labors of 
 Professor Owen and Dr. Falconer had made it clear that 
 twelve or more species of mammalia characterized this por- 
 tion of the Middle Purbeck, most of them insectivorous or 
 predaceous, varying in size from that of a mole to that of 
 the common polecat, Mustela putorius. While the majority 
 had the character of insectivorous marsupials. Dr. Falconer 
 selected one as dijffering widely from the rest, and pointed 
 out that in certain characters it was allied to the living 
 Kangaroo-rat, or Hypsiprymnus, ten species of which now 
 inhabit the prairies and scrub-jungle of Australia, feeding on 
 plants, and gnawing scratched-up roots. A striking pecul- 
 iarity of their dentition, one in which they differ from all 
 other quadrupeds, consists in their having a single large pre- 
 molar, the enamel of which is furrowed with vertical grooves, 
 usually seven in number. 
 
 The largest pre-molar (see Fig. 305) in the fossil genus ex- 
 hibits in like manner seven parallel grooves, producing by 
 their termination a similar serrated edge in the crown; but 
 their direction is diagonal^a distinctioiT, says Dr. Falconer, 
 which is " trivial, not typical." As these oblique furrows 
 form so marked a character of the majority of the teeth, Dr. 
 Falconer gave to the fossil the generic name of PlagiaylcKC. 
 The shape and relative size of the incisor, a, Fig. 306, exhibit 
 
MAMMALIA OF THE PUEBECK BEDS. 
 Fig. 304. Fig. 305. 
 
 327 
 
 Pre-molar of the recent Anstraliau 
 Hypsiprymnwi Gavmardi^ show- 
 ing 7 grooves, at right angles to 
 the length of the jaw, magnltied 
 3J diameters. 
 
 Third and largest pre-molar (lower 
 jaw) of PlcttjiauUtx Becklesii, mag- 
 nified 5i diameters, showing 7 
 diagonal grooves. 
 
 Fig. 306. 
 
 a DO less striking similarity to Hypsiprymnits. Neverthe- 
 less, th'e more sudden upward curve of this incisor, as well 
 as other characters of the jaw, indicate a great deviation in 
 the form of Plagiaulax from that of the living kangaroo-rats. 
 
 There are two fossil specimens of lower jaws of this genus 
 evidently referable to two distinct species extremely unequal 
 in size and otherwise distinguishable. The Plagiaulax Bec- 
 klesii (Fig. 306) 
 was about as big 
 as the English 
 squirrel or the fly- 
 ing phalanger of 
 Australia {Petau- 
 rus Australis, Wa- 
 terhouse). The 
 smaller fossil, hav- 
 ing only balf the 
 linear dimensions 
 of the other, was 
 probably only one- 
 twelfth of its bulk. 
 It is of peculiar ge- 
 ological interest, because, as shown by Dr. Falconer, its two 
 back molars bear a decided resemblance to those of the Tri- 
 kssic Microlestes (Fig. 389, p. 368), the most ancient of known 
 mammalia, of which an account will be given in Chapter XXI. 
 
 Up to 1857 all the mammalian remains discovered in sec- 
 ondary rocks had consisted solely of single branches of the 
 lower jaw, but in that year Mr. Beckles obtained the upper 
 portion of a skull, and on the same slab the lower jaw of an- 
 other quadruped with eight molars, a large canine, and a 
 broad and thick incisor. It has been named Triconodon from 
 its bicuspid teeth, and is supposed to have been a small in- 
 sectivorous marsupial, about the size of a hedgehog. Other 
 jaws have since been found indicating a larger species of the 
 same genus. 
 
 Plagiaulex Becklesii, Falconer. Middle Pnrheck. Right 
 ramns of lower jaw, magnified two diameters. 
 
 u. Incisor, b, c. Line of vertical fracture behind the pre- 
 molars, p m. Three pre-molars, the third and last (mnch 
 larger than the other two taken together) being divided 
 by a crack, m. Sockets of two missing molars. 
 
328 ELEMENTS OE GEOLOGY. 
 
 Professor Owen has proposed the name of Galestes for the 
 largest of the mammalia discovered in 1858 in Purbeck, 
 equalling the polecat {Mustela putoriti$) in size. It is sup- 
 posed to have been predaceous and marsupial. 
 
 Between forty and fifty pieces or sides of lower jaws with 
 teeth have been found in oolitic strata in Purbeck ; only five 
 upper maxillaries, together with one portion of a separate 
 cranium, occur at Stonesfield, and it is remarkable that with 
 these there were no examples in Purbeck of an entire skele- 
 ton, nor of any considerable number of bones in juxtaposi- 
 tion. In several portions of the matrix there were detached 
 bones, often much decomposed, and fragments of others ap- 
 parently mammalian ; but if all of them were restored, they 
 would scarcely suffice to complete the five skeletons to 
 which the five upper maxillaries above alluded to belonged. 
 As the average number of pieces in each mammalian skele- 
 ton is about 250, there must be many thousands of missing 
 bones ; and when we endeavor to account for their absence, 
 we are almost tempted to indulge in speculations like those 
 once suggested to me by Dr. Buckland, when he tried to 
 solve the enigma in reference to Stonesfield : " The corpses," 
 he said, " of drowned animals, when they float in a river, dis- 
 tended by gases during putrefaction, have often their lower 
 jaw hanging loose, and sometimes it has dropped ofi". The 
 rest of the body may then be drifted elsewhere, and some- 
 times may be swallowed entire by a predaceous reptile or 
 fish, such as an ichthyosaur or a shark." 
 
 As all the above-mentioned Purbeck marsupials, belong- 
 ing to eight or nine genera and to about fourteen species, in- 
 sectivorous, predaceous, and herbivorous, have been obtained 
 from an area less than 500 square yards in extent, and from 
 a single stratum not more than a few inches thick, we may 
 safely conclude that the whole lived together in the same 
 region, and in all likelihood they constituted a mere fraction 
 of the mammalia which inhabited the lands drained by one 
 river and its tributaries. They afibrd the first positive proof 
 as yet obtained of the co-existence of a varied fauna of the 
 highest class of vertebrata with that ample development of 
 reptile life which marks all the periods from the Trias to 
 the Lower Cretaceous inclusive, and with a gymnospermous 
 flora, or that state of the vegetable kingdom when cycads 
 and conifers predominated over all kinds of plants, except 
 the ferns, so far, at least, as our present imperfect knowledge 
 of fossil botany entitles us to speak. 
 
 The annexed table will enable the reader to see at a glance 
 how conspicuous a part, numerically considered, the mamma- 
 lian species of the Middle Purbeck now olay Avhen compared 
 
MAMMALIA OF THE PURBECK BEDS. 
 
 329 
 
 with those of other formations more ancient than the Paris 
 gypsum, and, at the same time, it will help him to appreci- 
 ate the enormous hiatus in the history of fossil mammalia 
 which at present occurs between the Eocene and Purbeck 
 periods, and between the latter and the Stonesiield Oolite, 
 and between this again and the Trias. 
 
 Number and Distribution of all the known Species of Fossil Mammalia from 
 Strata older than the Paris Gypsum, or than the Bembridqe Series of the 
 Isle of Wight. 
 
 'Headon Series and beds between") 
 
 the Paris Gypsum and the Grfes > 14 
 
 de Beauchamp } 
 
 Barton Clay and Sables de Beau-) ^ 
 
 champ ) 
 
 Bagshot Beds, Calcaire Grossier," 
 
 and Upper Soissonnais of Cuisse- 
 
 Lamotte 
 
 Teetiakt. 
 
 Sbcondart. ■ 
 
 Pkimakt. 
 
 20 
 
 (10 English. 
 1 4 French. 
 
 (16 French. 
 -l 1 English. 
 ( 3 U. States.* 
 
 London Clay, including the Kyson) 7 ]?„ i- j, 
 
 Plastic Clay and Lignite .... 
 
 Sables de Bracheux 
 
 Thanet Sands and Lower Landen- 
 
 ian of Belgium 
 
 Maestricht Chalk 
 
 White Chalk 
 
 Chalk Marl 
 
 Chloritic Series (Upper Greensand) 
 
 Gault 
 
 Neocomian (Lower Greensand) 
 
 Wealden 
 
 Upper Purbeck Oolite .... 
 Middle Purbeck Oolite .... 
 Lower Purbeck Oolite .... 
 
 Portland Oohte 
 
 Kimmeridge Clay 
 
 Coral Rag 
 
 Oxford Clay 
 
 Great OoUte 4 Stonesfield. 
 
 Inferior Oolite . 
 
 Lias 
 
 j 7 French. 
 •^12 EngUsh. 
 
 1 French. 
 
 
 
 
 
 
 
 
 
 
 14 Swanage. 
 
 
 
 Upper Trias 4 
 
 Middle Trias 
 Lower Trias 
 Permian . . 
 Carboniferous 
 Devonian 
 Silurian . . 
 Cambrian 
 Lanrentian . 
 
 (Wurtemberg. 
 -^ Somersetshire. 
 (N. Carolina. 
 
 * I allnde to several Zeuglodons found in Alabama, and referred by some zoolo- 
 gists to three species. 
 
330 ELEMENTS OF GEOLOGY. 
 
 The Sables de Bracheux, enumerated in the Tertiary divis- 
 ion of the table, supposed by Mr. Prestwich to be some- 
 what newer than the Thanet Sands, and by M. Hebert to be 
 of about that age, have yielded at La F^re the Arctocyon 
 {Palmocyon) primcevits, the oldest known tertiary mammal. 
 
 It is worthy of notice, that in the Hastings Sands there 
 are certain layers of clay and sandstone in which numerous 
 foot-prints of quadrupeds have been found by Mr. Beckles, 
 and traced by him in the same set of rocks through Sussex 
 and the Isle of Wight. They appear to belong to three or 
 four species of reptiles, and no one of them to any warm- 
 blooded quadruped. They ought, therefore, to serve as a 
 warning to us, when we fail in like manner to detect mam- 
 malian foot-prints in older rocks (such as the New Red Sand- 
 stone), to refrain from inferring that quadrupeds, other than 
 reptilian, did not exist or pre-exist. 
 
 But the most instructive lesson read to us by the Purbeck 
 strata consists in this : They are all, with the exception of 
 a few intercalated brackish and marine layers, of fresh-wa> 
 ter origin; they are 160 feet in thickness, have been well 
 searched by skillful collectors, and by the late Edward 
 Forbes in particular, who studied them for months consecu- 
 tively. They have been numbered, and the contents of each 
 stratum recorded separately, by the officers of the Geologic- 
 al Survey of Great Britain. They have been divided into 
 three distinct groups by Forbes, each characterized by the 
 same genera of pulmonifei'ous mollusca and cyprides, these 
 genera being represented in each group by different species ; 
 they have yielded insects of many orders, and the fruits of 
 several plants ; and lastly, they contain " dirt-beds," or old 
 terrestrial surfaces and vegetable soils at different levels, in 
 some of which erect trunks and stumps of cycads and conifers, 
 with their roots still attached to them, are preserved. Yet 
 when tlie geologist inquires if any land-animals of a higher 
 grade than reptiles lived during any one of these three peri- 
 ods, the rocks are all silent, save one thin layer a few inches 
 in thickness ; and this single page of the earth's history has 
 suddenly revealed to us in a few weeks the memorials of so 
 many species of fossil mammalia, that they already outnum- 
 ber those of many a subdivision of the tertiary series, and 
 far surpass those of all the other secondary rocks put to- 
 gether ! 
 
 Lower Purbeck. — Beneath the thin maiine band mention- 
 ed at p. 324 as the base of the Middle Purbeck, some purely 
 fresh-water marls occur, containing species of Cypris (Fig. 
 307 a, c), Valvata, and Zimncea, different from those of the 
 
PURBECK BEDS. 
 
 331 
 
 Cyprides from the Lower Purbeck. 
 u. Cypris Pur'beckeniais, Forbes. 6. 
 Same maguified. c. Cy%trU punc- 
 tata, Forbes, t?, e. Two views mag- 
 nified of tlie same. 
 
 Middle Purbeck. This is the be- 
 ginning of the inferior division, 
 ■which is about 80 feet thick. 
 Below the marls are seen, at 
 Menp's Bay, more than thirty 
 feet of brackish - water strata, 
 abounding in a species of Ser- 
 pula, allied to, .if not identical 
 "with, Serpula coacervites, found 
 in beds of the same age in Hanover. There are also shells of 
 the genus Hissoa (of the snhgenns Mi/drobia), and a little Car- 
 dium of the subgenus Protocardium, in these marine beds, to- 
 gether with Cypris. Some of the cypris-bearing shales ai-e 
 strangely contorted and broken up, at the west end of the Isle 
 of Purbeck. The great dirt-bed or vegetable soil containing 
 the roots and stools of CycadeoB, which I shall presently de- 
 scribe, underlies these marls, and rests upon the lowest fresh- 
 water limestone, a rock about eight feet thick, containing Gy- 
 clas, Valvata, and Limncea, of the same species as those of 
 the uppermost part of the Lower Purbeck, or above the dirt- 
 bed. The fresh-water limestone in its turn rests upon the 
 top beds of the Portland stone, which, although it contains 
 purely marine remains, often consists of a i-ock undistin- 
 guishable in mineral character from the Lowest Purbeck 
 limestone. 
 
 Dirt-bed or ancient Surface-soil. — The most remarkable of 
 all the varied succession of beds enumerated in the above 
 list is that called by the quarrymen " the dirt," or " black 
 dirt," which was evidently an ancient vegetable soil. It is 
 from 12 to 18 inches thick, is of a 
 dai'k brown or black color, and con- 
 tains a large proportion of earthy 
 lignite. Through it are dispersed 
 rounded and sub-angular fragments 
 of stone, from 3 to 9 inches in diame- 
 ter, in such numbers that it almost 
 deserves the name of gravel. I also 
 saw in 1 866, in Portland, a smaller 
 dirt-bed six feet below the principal 
 one, six inches thick, consisting of 
 brown earth with upright Cycads 
 art The upper part shows the 01 tne same species, -^Kfa«.5ewja mai- 
 woody stem, the lower part the formis, as those found in the upper 
 bases of the leaves. bed,but no (7om7em. The weight of 
 
 the incumbent strata squeezing down the compressible dirt- 
 bed has caused the Cycads to assume that form which has 
 
 Fig. 303. 
 
332 
 
 ELEMENTS OF GEOLOGY. 
 
 led the quarrymen to call them " petrified bird'snests," which 
 suggested to Brongniart the specific name of nidiformis, I 
 am indebted to Mr. Carruthers for the annexed figure of one 
 of these Purbeck specimens, in which the original cylindrical 
 figure has been less distorted than usual by pressui-e. 
 
 Many silicified trunks of coniferous trees, and the remains 
 of plants allied to Zamia and Cycas, are buried in this dirtr 
 bed, and must have become fossil on the spots where they 
 grew. The stumjss of the trees stand erect for a height of 
 from one to three feet, and even in one instance to six feet; 
 with their roots attached to the soil at about the same dis- 
 tances from one another as the trees in a modern forest. The 
 carbonaceous matter is most abundant immediately around 
 the stumps, and round the remains of fossil Gycadeoe. 
 
 Besides the upright stumps above mentioned, the dirt-bed 
 contains the stems of silicified trees laid prostrate. These 
 are partly sunk into the black earth, and partly enveloped 
 by a calcareous slate which covers the dirt-bed. The frag- 
 ments of the prostrate trees are rarely more than three or 
 four feet in length ; but by joining many of them together, 
 trunks have been restored, having a length from the root to 
 the branches of from 20 to 23 feet, the stems being undivided 
 for 17 or 20 feet, and then forked. The diameter of these 
 near the root is about one foot ; but I measured one myself, 
 in 1866, which was Z\ feet in diameter, said by the quarry- 
 men to be unusually large. Root-shaped cavities were ob- 
 served by Professor Henslow to descend from the bottom of 
 the dirt-bed into the subjacent fresh-water stone, which, 
 though now solid, must have been in a soft and penetrable 
 state when the trees grew. The thin layers of calcareous 
 slate (Pig. 309) were evidently deposited tranquilly, and 
 would have been horizontal but for the protrusion of the 
 stumps of the trees, around the top of each of which they 
 form hemispherical concretions. 
 
 Fig. 309. 
 
 Fresh-water calcareous slate. 
 
 Dirt-bed and ancient forest. 
 
 Lowest fresh-water beds of the 
 
 Lower Purbeck. 
 Portland stone, marine. 
 
 Section in Isle of Portland, Dorset. (Buckland and De la Beche.) 
 
 The dirt-bed is by no means confined to the island of Port- 
 land, where it has been most carefully studied, but is seen 
 
PUEBECK BEDS. 
 
 333 
 
 iu the same relative position in the cliffs east of Lulworth 
 Cove, in Dorsetshire, where, as the strata have been dis- 
 turbed, and are now inclined at an angle of 45°, the stumps 
 of the trees are also inclined at the same angle in an opposite 
 direction — a beautiful illustration of a change in the position 
 of beds originally horizontal (see Fig. 310). 
 
 Fig. 310. 
 
 Fresh-water cafcareous slate. 
 . Dirt-bed, with stools of trees. 
 
 Fresh-water. 
 
 Portland stone, marine. 
 
 Section of cliff east of Lnlworth Cove. (Buckland and De la Beche.) 
 
 From the facts above described we may infer, first, that 
 those beds of the Upper Oolite, called " the Portland," which 
 are full of marine shells, were overspread with fluviatile mud, 
 which became dry land, and covered by a forest, throughout 
 a portion of the space now occupied by the south of Eng- 
 land, the climate being such as to permit the growth of the 
 Zamia and Cycas. 2dly. This land at length sank down and 
 was submerged with its forests beneath a body of fresh water, 
 from which sediment was thrown down enveloping fluviatile 
 shells. 3dly. The regular and uniform preservation of this 
 thin bed of black earth over a distance of many miles, shows 
 that the change from dry land to the state of a fresh-water 
 lake or estuary, was not accompanied by any violent denu- 
 dation, or rush of water, since the loose black earth, together 
 with the trees which lay prostrate on its surface, must inev- 
 itably have been swept away had any such violent catastro- 
 phe taken place. 
 
 The forest of the dirt-bed, as before hinted, was not every- 
 where the first vegetation which grew in this region. Be- 
 sides the lower bed containing upright CycadecB, before- 
 mentioned, another has sometimes been found above it, 
 which implies oscillations in the level of the same ground, 
 and its alternate occupation by land and water more than 
 once. 
 
 Subdivisions of the Pitrbeclc. — It will be observed that the 
 division of the Purbecks into upper, middle, and lower, was 
 made by Professor Forbes strictly on the principle of the en- 
 
334 ELEMENTS OF GEOLOGY. 
 
 tire distinctness of the species of organic remains which they 
 inchide. The lines of demarkation are not lines of disturb- 
 ance, nor indicated by any striking physical characters or 
 mineral changes. The features which attract the eye in the 
 Purbecks, such as the dirt-beds, the dislocated strata at Lul- 
 worth, and the Cinder-bed, do not indicate any breaks in the 
 distribution of organized beings. " The causes which led to 
 a complete change of life three times during the deposition 
 of the fresh-water and brackish strata must," says this nat- 
 uralist, "be sought for, not simply in either a rapid or a sud- 
 den change of their area into land or sea, but in the great 
 lapse of time which intervened between the epochs of depo- 
 sition at certain periods during their formation." 
 
 Each dirt-bed may, no doubt, be the memorial of many 
 thousand years or centuries, because we find that two or 
 three feet of vegetable soil is the only monument which many 
 a tropical forest has left of its existence ever since the ground 
 on v/hich it now stands was first covered with its shade. 
 Yet, even if we imagine the fossil soils of the Lower Purbeck 
 to represent as many ages, we need not be surprised to find 
 that they do not constitute lines of separation between strata 
 characterized by different zoological types. The preserva- 
 tion of a layer of vegetable soil, when in the act of being 
 submerged, must be I'egarded as a rare exception to a gen- 
 eral rule. It is of so perishable a nature, that it must usually 
 be carried away by the denuding waves or currents of the 
 sea, or by a river ; and many Purbeck dirt-beds were proba- 
 bly formed in succession and annihilated, besides those few 
 which now remain. 
 
 The plants of the Purbeck beds, so far as our knowledge 
 extends at present, consist chiefly of Ferns, Coniferge, and 
 Cycadese (Fig. 308), without any angiosperms; the whole 
 more allied to the Oolitic than to the Cretaceous vegetation. 
 The same affinity is indicated by the vertebrate and inverte- 
 brate animals. Mr. Brodie has found the remains of beetles 
 and several insects of the homopterous and trichopterous 
 orders, some of which now live on plants, while others are 
 of such foi-ms as hover over the surface of our present rivers. 
 
 Portland Oolite and Sand (5, Tab., p. 321).— The Portland 
 Oolite has already been mentioned as forming in Dorsetshire 
 the foundation on which the fresh-water limestone of the 
 Lower Purbeck reposes (see p. 331). It supplies the well^ 
 known building-stone of which St. Paul's and so many of the 
 principal edifices of London are constructed. About fifty 
 species of raoUusca occur in this formation, among which are 
 some ammonites of large size. The cast of a spiral univalve 
 
KIMMERIDGE CLAY. 
 
 336 
 
 called by the quarrymen the "Port- Fig.su. 
 
 land sci-ew" {a, Fig. 311), is common ; 
 the shell of the same (J) being rarely 
 met with. Also Trigonia gibtosa 
 (Fig. 313) and Cardium dissimile (Fig. 
 314). This upper member rests on a 
 dense bed of sand, called the Portland 
 Sand, containing similar marine fossils, 
 below which is the Kimmeridge Clay. 
 In England these Upper Oolite forma- 
 tions are almost wholly confined to the 
 southern counties. But some frag- 
 ments of them occur beneath the Ne- 
 ocomian or Speeton Clay on the coast 
 of Yorkshire, containing many more 
 fossils common to the Portlandian of 
 the Continent than does the same 
 formation In Dorsetshire. Corals are 
 rare in this formation, although one species is found plenti- 
 fully at Tisbury, Wiltshire, in the Portland Sand, converted 
 into flint and chert, the original calcareous matter being re- 
 placed by silex (Fig. 312). 
 
 CeritMum Portlandicum 
 (=Z'erein'a) Sow. 
 
 Cast Of ehell known as 
 "Portland screw." 6. The 
 shell itself. 
 
 Fig. 312. 
 
 Fig. 313. 
 
 Isastrcea oUonga,M. Edw. and J. Haime. 
 As seen on a polished slab of chert 
 from the Portland Sand, Tisbury. 
 
 l^igonia gibbasa. i natural size. 
 
 a. The hinge. 
 
 Portland Stone, Tisbury. 
 
 Kimmeridge Clay.— The Kimmeridge Clay consists, in great 
 part, of a bituminous shale, sometimes forming an impure 
 coal, several hundred feet in thickness. In some places in 
 Wiltshire it much resembles peat ; and the bituminous mat- 
 ter may have been, in part at least, derived from the decom- 
 position of vegetables. But as impressions of plants are rare 
 in these shale's, which contain ammonites, oygters, and other 
 marine shells, with skeletons offish and saurians,the bitumen 
 
336 ELEMENTS OF GEOLOGY. 
 
 Fig. 314. Fig. 315. 
 
 Cardiw.i disaimile. i nat. size. 
 Portland Stone. 
 
 Ostrea expansa. Portland Sand. 
 
 may perhaps be of animal origin. Some of the saurians (Pli- 
 osaurus) in Dorsetshire are among the most gigantic of their 
 kind. 
 
 Among the fossils, amounting to nearly 100 species, may 
 be mentioned Cardium striatulum (Fig. 316) and Ostrea del- 
 toidea (Fig. 317), the latter found in the Kimmeridge, Clay 
 throughout England and the north of France, and also in 
 
 Fig. 316. Fig. 317. Fig. BIS. 
 
 Cardiwm striatnlwm. 
 Kimmeridge Clay, 
 Hartwell. 
 
 Ostrea deltoidea. 
 Kimmeridge Clay, i nat. size. 
 
 Qrijphcea {Exogyra) 
 
 virgula. 
 Kimmeridge Clay. 
 
 Scotland, near Brora. The Grt/phcea virgula (Fig. 318), also 
 met with in the Kimmeridge Clay near Oxford, is so abun- 
 dant in the Upper Oolite" of parts of France as to have 
 caused the deposit to be termed "marnes k gryphees vir- 
 gules." ISTear Clermont, in Argonne, a few leagues from St. 
 Menehould, where these indurated marls crop out from be- 
 neath the gault, I have seen them, on decomposing, leave 
 the surface of every ploughed field literally strewed over 
 Fig. 319. with this fossil oyster. The TrigoneUites la- 
 
 f'"-s {Aptychus of some authors) (Fig. 319) is 
 .■ilso widely dispersed through this clay. The 
 iisal nature of the shell, of which there are 
 many species in oolitic rocks, is still a matter 
 of conjecture. Some are of opinion that the 
 two plates have been the gizzard of a ceph- 
 alopod ; others, that it may have formed a 
 bivalve operculum of the same. 
 
 TrigoneUites lotus, 
 Park, Kimme- 
 ridge Clay. 
 
SOLENHOFEN STONE. 
 
 337 
 
 Fig. 320. 
 
 siroatria. Oolite of Pappen- 
 heim, near Solentiofen. 
 a. Ttiisbone, consistingt>f four 
 joints, is part of the fiftli or 
 outermost digit elongated, 
 as in bats, for tlie support 
 of a wing. 
 
 Solenhofen Stone. — The celebrated lithographic stone of 
 Solenhofen in Bavaria, appears to he of intermediate age 
 between the Kimmeridge clay and the Coral Rag, presently 
 to be described. It affords" a remarkable example of the 
 variety of fossils which may be preserved under favorable 
 circumstances, and what delicate im- 
 pressions of the tender parts of certain 
 animals and plants may be retained 
 where the sediment is of extreme fine- 
 ness. Although the number of testa- 
 cea in this slate is small, and the 
 plants few, and those all marine, 
 Count Mtinster had determined no 
 less than 237 species of fossils when I 
 saw his collection in 1833 ; and among 
 them no less than seven species of fly- 
 ing reptiles or pterodactyls (see Fig. 
 
 32.0), six saurians, three tortoises, six- Skeleton of /"terodoftj/JtJscros- 
 ty species offish, forty-six of Crustacea, 
 and twenty-six of insects. These in- 
 sects, among which is a libellula, or 
 dragon-fly, must liave been blown out 
 to sea, probably from the same land 
 to which the pterodactyls, and other contemporaneous air- 
 breathers, resorted. 
 
 In the same slate of Solenhofen a fine example was met 
 with in 1862 of the skeleton of a bird almost entire, and re- 
 taining even its feathers so perfect that the vanes as well as 
 the shaft are preserved. The head was at first supposed to 
 be wanting, but Mr. Evans detected on the slab what seems 
 to be the impression of the cranium and beak, much resem- 
 bling in size and shape that of the jay or woodcock. This 
 valuable specimen is now -n the British Museum, and has 
 been called by Professor Owen Archceopteryx macrura. Al- 
 though anatomists agree that it is a true bird, yet they also 
 find that in the length of the bones of the tail, and some 
 other minor points of its anatomy, it approaches more near- 
 ly to reptiles than any known living bird. In the living 
 representatives of the class Aves, the tail-feathers are at- 
 tached to a coccygian bone, consisting of several vertebrae 
 united together, whereas in the Archseopteryx the ta,il is 
 composed of twenty vertebrae, each of which supports a pair 
 of quill-feathers. The first five only of the vertebrse^ as seen 
 in A, have transverse jjrocesses, the fifteen remaining ones 
 become gradually longer and more tapering. The feathers 
 diverge outward from them at an angle of 45°. 
 
 15 
 
338 
 
 ELEMENTS OF GEOLOGY. 
 Fig. 321. 
 
 Tail and feather of ArcTiceopterijx, from Soleubofcn, and tail of living bird for 
 
 comparison. 
 
 A. Caudal vertebrae of Archceopten/x maerura, Owen ; with impression of tail-featli-- 
 ers; one-flfth natural size. B. Two caudal vertebrae of samej iiatnral siae. C. 
 Single feather, fonnd in 1861 at Solenbofen, by Von Meyer, and called ^irc/iCB)' 
 pteryx lithographica ; natural size. D. Tail of recent vulture {Gijps Betjgajenm^ 
 showing attachment of tail-feathers in living birds ; one-quarter natural size. E. 
 Profile of caudal vertebrse of same; one-third natural size, e, e. Direction of tail- 
 feathers when seen iu profile. /. Ploughshai'e .bone or broad terminal joint (seen 
 also in/, D.) 
 
 Professor Huxley in his late memoirs on the order of rep- 
 tiles called Dinosaurians, which are largely represented in all 
 the formations, from the Neocomian to the Trias inclusive, has 
 shown that they present in their structvire many remarkable 
 affinities to birds. But a reptile about two feet long, called 
 Compsognathus, lately found in the Stonesfield slate, makes 
 a much greater approximation to the class Aves than any 
 Dinosaur, aijd therefore forms a closer link between the 
 classes Aves and Reptilia than does the Ai-chajopteryx. 
 
 It appears doubtful whether any species of British fossil, 
 whether of the vertebrate or invertebrate class, is' common 
 to the Oolite and Chalk. But there is no similar break or 
 discordance as we proceed downward, and pass from one to 
 another of the several leading members of the Jurassic 
 group, the Upper, Middle, and Lower Oolite, and the Lias, 
 there being often a considerable proportion of the mollusca, 
 sometimes as much as a fourth, common to such divisions 
 as the Upper and Middle Oolite. 
 
CORAL RAG. 
 
 339 
 
 MIDDLE OOLITE. 
 
 Coral Rag. — One of the limestones of the Middle Polity 
 has been called the "Coral Rag," because it consists, in 
 part, of continuous beds of petrified corals, most of them 
 retaining the position in which they grew at the bottom of 
 the sea. In their forms they more frequently resemble the 
 reef-building polyparia of the Pacific than do the corals of 
 any other member of the Oolite. They belong chiefly to 
 the genera Thecosmilia (Fig. 322), Protoseris, and Thamna- 
 
 Eig. 322. Eig. 323. 
 
 Ihecosmilioi, annvlaris, Mihie Edw. 
 and 3. Haiiue. Coral Bag, Steeple 
 AsbtoB. 
 
 Thamnastrtea. Coral Sag, 
 Steeple AsUon. 
 
 strcea, and sometimes form masses of coral fifteen feet thick. 
 In the annexed figure of a Thamnastrcea (Fig. 323), from 
 this formation, it will be seen that the cup-shaped Cavities 
 Fig. 324. ^^® deepest on the right-hand side, and 
 
 that they grow more and more shallow, 
 until those on the left side are nearly 
 filled up. The last-mentioned stars are 
 supposed to represent a perfected con- 
 dition, and the j,;^ ^^ 
 others an im- 
 
 OatrmgregariafCoTalHag, mature State. 
 
 Steeple Ashton. These coralline 
 strata extend through the calcare- 
 ous hills of the north-west of Berk- 
 shire, and north of Wilts, and again 
 recur in Yorkshire, near Scarbor- 
 ough. The Ostrea gregarea (Fig. 
 324)- is very characteristic of the 
 formation in England and on the 
 Continent. 
 
 One of the limestones of the Jura, 
 referred to the age of the English ^'erimm €foodhaUn,mtton. Coral 
 coral rag, has been called "Neri- Rag, Weymouth, jnat.size. 
 nsean limestone" (Calcaire a N^rinees) by M. Thirria; JSkri- 
 
340 
 
 ELEMENTS OE GEOLOGY. 
 
 wcea being an extinct genus of univalve shells (Fig. 325) much 
 resembling the Cerithium in external form. The annexed sec- 
 tion shows the curious and continuous ridges on the columella 
 and whorls. 
 
 Oxford Clay. — The coralline limestone, or "coral rag," 
 above described, and the accompanying sandy beds, called 
 " calcareous grits," of the Middle Oolite, rest on a thick bed 
 of clay, called the " Oxford Clay," sometimes not less than 600 
 feet thick. In this there are no corals, but great abundance of 
 cephalopoda, of the genera Ammonite and Belemnite (Figs. 
 326 and 327). In some of the finely laminated clays ammon- 
 
 Fig.326. Fig.32T. 
 
 Belemnites hasiaius. 
 Oxfora Clay. 
 
 Atumonites Jason^ Reinecke. (Syn. Ai JElizabethce, Pratt.) 
 Oxford Clay, Christian Malford, Wiltsliire. 
 
 ites are very perfect, although somewhat compressed, and are 
 frequently found with the lateral lobe extended on each side 
 of the opening of the mouth into a horn-like projection (Fig. 
 327). These were discovered in the cuttings of the Great 
 Western Railway, near Chippenham, in 1841, and have been 
 described by Mr. Pratt {An. JSFat. Hist., Nov., 1841). 
 
 Similar elongated processes have been also observed to 
 extend from the shells of some belemnites discovered by Dr. 
 Mantell in the same clay (see Fig. 328), who, by the aid of 
 this and other specimens, has been able to throw much light 
 on the structure of singular extinct forms of cuttle-fish.* 
 
 * See Phil. Trans. 1850, p. 363 • also Haxley, Memoirs of Geol. Survey, 
 1864 ; Phillips, Palseont. Soc. 
 
FOSSILS OF THE OXFORD CLAY 
 
 Kelloway Rock. — ^The arenaceous lime- 
 stone which passes under this name is gen- 
 erallv grouped as a meinber of the Oxford 
 clay, in which it forms, in the south-west of 
 England, lenticular masses, 8 or 1 feet thick, 
 containing at Kelloway,in Wiltshire,numer- 
 ous casts of ammonites and other shells. 
 But in Yorkshire this calcareo-arenaceous 
 formation thickens to about 30 feet, and 
 constitutes the lower part of the Middle • 
 Oolite, extending inland from Scarborough 
 in a southerly direction. The number of 
 mollusca which it contains is, according to 
 Mr. Etheridge, 143, of which only 34, or 
 23^ per cent., are common to the Oxford 
 clay proper. Of the 52 Cephalopoda, 13 
 (namely 13 species of ammonite, the An- 
 cyloceras Calloviense and one Belemnite) 
 are common to the Oxford Clay, giving a 
 propoition of nearly 30 per cent. 
 
 341 
 
 Fig. 328. 
 
 p,-^;:*^ 
 
 
 LOWER OOLITE. 
 
 Corabrash and Forest Marble.— The upper ^'l^"ij''' ^""^S; 
 division of this series, which is more exten- Pierce, 
 sive than the preceding or Middle Oolite, is Maifo?d"^' ''^"''""' 
 called in England the Cornbrash, as being a "• section of the shell 
 brashy, easily broken rock, good for corn pLr'If^Mone?'" ^. 
 
 ' ' * " ' - ' External covering 
 
 to tlie ink-bag and 
 phragmacone. c, d, 
 Osselet, or that por- 
 tion commonly call- 
 ed the belemnite. & 
 Conical chambered 
 body called the 
 phraicmacone, /. 
 Position of ink-bag 
 beneath the shelly 
 covering. 
 
 land. It consists of clays and calcareous 
 sandstones, which pass downward into the 
 Forest Marble, an argillaceous limestone, 
 abounding in marine fossils. In some 
 places, as at Bradford, this limestone is re- 
 placed by a mass of clay. The sandstones 
 of the Forest Marble of Wiltshire are often 
 ripple-marked and filled with fragments of 
 broken shells and pieces of drift-wood, having evidently 
 been formed on a coast. Rippled slabs of fissile oolite are 
 used for roofing, and have been traced over a broad band 
 of country from Br'adford in Wilts, to Tetbury in Glouces- 
 tershire. These calcareous tile-stones are separated from 
 each otrher by thin seams of clay, which have been deposited 
 upon them, and have taken their form, preserving the undu- 
 lating ridges and furrows of the sand in such complete in- 
 tegrity, that the impressions of small footsteps, apparently of 
 crustaceans, which walked over the soft wet sands, are still 
 visible. In the same stone the claws of crabs, fragments 
 
342 
 
 ELEMENTS OF GEOLOGY. 
 
 of echini, and other signs of a neighhoring beach, are ob- 
 served.* 
 
 Great (or Bath) Oolite. — Although the name of coral rag 
 has been. appropriated, as we have seen, to a member of the 
 Middle Oolite before described, some portions of the Lower 
 Oolite are equally .entitled in many places to be called coral- 
 line limestones. Thus the Great Oolite near Bath contains 
 various corals, among which the Eunomia radiata (Fig. 329) 
 is very conspicuous, single individuals forming masses sev- 
 
 Fig. 329. 
 
 
 Emuymia radiata, Lamouroux. {Calamopliylliat Milue Edw.) 
 
 a. Section transverse to the tubes. 6. Vertical section, showing the radiation of the 
 
 tnljes. c. Portion of interior of tubes raagnifled, showing striated surface. 
 
 eral feet in diameter ; and having probably I'equired, like the 
 large existing brain-coral (Meandrina) of the tropics, many 
 centuries before their gi-owth was completed. 
 
 Different species of crinoids, or stone-lilies, are also com- 
 mon in the same rocks with corals; and, like them, must 
 have enjoyed a firm bottom^ where their base of attachment 
 remained undisturbed for years (e, Fig. 330). Such fossils, 
 therefore, are almost confined to the limestones ; but an ex- 
 ception occurs at Bradford, near Bath, where they are en- 
 veloped in clay sometimes 60 feet thick. In this case, how- 
 ever, it appears that the solid upper surface of the " Great 
 Oolite" had supported, for a time, a thick submarine forest 
 of these beautiful zoophytes, until the clear and still water 
 was invaded by a current charged with mud, which threw 
 down the stone-lilies, and broke most of their stems short ofi" 
 near the point of attachment. The stumps still remain in 
 their original position ; but the numerous articulations, once 
 composing the stem, arms, and body of the encrinite, were 
 scattered at random through the argillaceous deposit in 
 which some now lie prostrated These appeai-ances are rep- 
 resented in the section b, Fig. 330, where the darker strata 
 represent the Bradford clay, which is however a formation 
 * P. Scrope, Proc. Geol. Soc, March, 1831. 
 
BRADFORD ENCRINITES. 
 Wig. 330. 
 
 343 
 
 Apwerinites rotMniug, or Pear Encrinite ; Miller. Fossil at Bradford, Wilts. 
 a. Stem of ApwcrintUs, and one of the articulatious, natural size. 6. Section at Brad- 
 ford of Great Oolite and overlying cla j;, containing the fossil enorinites. (See text) 
 c. Three perfect individnals of uijoiocrimtes, represented as they grew on the surface 
 of the Great Oolite, d. Body of the Apiocrinites rotunctm. Half natural size. 
 
 of such local development that in many places it can not 
 easily be separated from the clays of the overlying " forest- 
 marble" and underlying "fuller's earth." The upper sur- 
 face of the calcareous stone below is completely iucrusted 
 over with a continuous pavement, formed by the stony roots 
 or attachments of the Crinoidea ; and besides this evidence 
 of the length of time they had lived on the spot, we find 
 great numbers of single joints, or circular plates of the stem 
 and body of the encrinite, covered over with serpulce. Now 
 these serpulcB could only have begun to grow after the death 
 of some of the stone-lilies, parts of whose skeletons had been 
 strewed over the floor of the ocean before the irruption of 
 
 Fig. 331. 
 
 a. Single plate of body of Apiocriniis, overgi-owu with serpidce and bryozoa. Natural 
 size. Bradford Clay. B. Portion of the same magnified, showing the bryozoan td- 
 astopora diluviana covering one of the eerpulce. 
 
 argillaceous mud. In some instances we find that, after the 
 parisitic serpulce were full grown, they had become incrusted 
 over with a bryozoan, called Diastopora diluviana {see 5,- 
 
344 ELEMENTS 01" GEOLOGY. 
 
 Fig. 331) ; and many generations of these molluscoids had 
 succeeded each other in the pure water before they became 
 fossil. 
 
 "We may, therefore, perceive distinctly that, as the pines 
 and cyeadeous plants of the ancient " dirt-bed," or fossil 
 forest, of the Lower Purbeck were killed by submergence 
 under fresh water, and soon buried beneath muddy sediment, 
 so an invasion of argillaceous matter put a sudden stop to 
 the growth of the Bradford Encrinites, and led to their pres- 
 ervation in marine strata. 
 
 Such differences in the fossils as distinguish the calcareous 
 and argillaceous deposits from each other, would be de- 
 scribed by naturalists as arising out of a difference in the 
 stations of species ; but besides these, there are variations in 
 the fossils of the higher, middle, and lower part of the oolitic 
 series, which must be ascribed to that great law of change 
 in organic life by which distinct assemblages'of species have 
 been adapted, at successive geological periods, to the vary- 
 ing conditions of the habitable surface. In a single district 
 it is difficult to decide how far the limitation of species to 
 certain minor formations has been due to the local influence 
 of stations, or how far it has been caused by time or the law 
 of variation above alluded to. But we recognize the reajity 
 of the last-mentioned influence, when we contrast the whole 
 oolitic series of England with that of parts of the Jura, Alps, 
 and other distant regions, where, although there is scarcely 
 any lithological resemblance, yet some of the same fossils re- 
 riiain peculiar in each country to the Upper, Middle, and 
 Lower Oolite formations respectively. Mr. Thurmann has 
 shown how remarkably this fact holds true in the Bernese 
 Jura, although the argillaceous divisions, so conspicuous in 
 England, are feebly represented there, and some entirely 
 wanting. 
 
 The calcareous portion of the Great Oolite consists of sev- 
 eral shelly limestones, one of which, called the Bath Oolite, 
 is much celebrated as a building-stone. In parts of Glouces- 
 tershire, especially near Minchinhampton, the Great Oolite, 
 says Mr. Lycett, " must have been deposited in a shallow 
 sea, where strong currents prevailed, for there are frequent 
 changes in the mineral character of the deposit, and some 
 beds exhibit false stratification. In others, heaps of broken 
 shells are mingled with pebbles of rocks foreign to the neigh- 
 borhood, and with fragments of abraded madre]oores, dicot- 
 yledonous wood, and crabs' claws. The shelly strata, also, 
 have occasionally suffered denudation, and thei removed por- 
 tions have been replaced by clay." In such shallow-water 
 
STONESFIELD SLATE. 
 
 345 
 
 beds shells of the genera Patdla, Nerita, Rimula, Cylindrites 
 are common (see Figs. 334 to Zil) ; while cephalopods are 
 rare, and instead of ammonites and belemnites, numerous 
 genera of carnivorous trachelipods appear. Out of 224 spe- 
 cies of univalves obtained from the Minchinhampton beds, 
 Mr. Lycett found no less than 50 to be carnivorous. They 
 belong principally to the genera £ttccinum, Pleurotoma, Mos- 
 
 Fig.; 
 
 Fig. 333. 
 
 Fig. 334. 
 
 Tereltratvia digona^ 
 Sow. Nat. size. 
 Bradford Clay. 
 
 Purpuroideanodvlfita. One- 
 fourlh natural size. Great 
 Oolite, MiucMnhamptou. 
 
 Cylindritm acutus. Sow. 
 Syii. Actceon aciUua. 
 Great Oolite, Minchin- 
 hampton. 
 
 tellaria,Murex,Purpuroidea (Fig. 333),and-P«SMS, and exhibit 
 a proportion of zoophagous species not very diflFerent from 
 that which obtains in seas of the Recent period. These zo- 
 ological results are curious and unexpected, since it was im- 
 agined that we might look in vain for the carnivorous trache- 
 lipods in rocks of such high antiquity as the Great Oolite, and 
 
 ig. 336. 
 
 Fig. 336. 
 
 Fig. 33T. 
 
 Patella rugosa, Sow. 
 Great Oolite. 
 
 Nerita costvJata, Desh. 
 Great Oolite. 
 
 Rimula (Emarpimda) 
 clathrata, Sow, Great 
 Oolite. 
 
 it was a received doctrine that they did not begin to appear 
 in considerable numbers till the Eocene period, when those 
 two great families of cephalopoda, the ammonites and belem- 
 nites, and a great number of other representatives of the same 
 class of chambered shells, had become extinct. 
 
 Stonesfield Slate : Mammalia. — The slate of Stonesfield has 
 
 been shown by Mr. Lonsdale to lie at the base of the Great 
 
 Oolite.* It is a slightly oolitic shelly limestone, forming 
 
 laro^e lenticular masses imbedded in sand only 6 feet thick, 
 
 * Proceedings Geol. Soc, toI. i., p. 414. 
 
 15* 
 
346 ELEMENTS OF GEOLOGY. 
 
 but very rich in organic remains. It contains some pebbles 
 of a rock very similar to itself, and which may be portions 
 ._^ of the deposit, broken up on a shore at low water 
 
 '"■ " or during storms, and redeposited. The remains 
 of beIemnites,trigonia3, and otlier marine shells, with 
 fragments of wood, are common, and impressions of 
 ferns, cycadese, and other plants. Several insects, 
 also, and, among the rest, the elytra or wing-covers . 
 of beetles, are perfectly preserved (see Fig. 338), 
 some of them approaching nearly to the genus Bur 
 prestis. The remains, also, of many genera of rep- 
 tiles, such as Pleiosaur, Crocodile, and Pterodactyl, 
 Elytron of have been discovered in the same limestone. 
 BupresUst gu^ the remarkable fossils for which the Stones- 
 ' field slate is most celebrated are those referred to 
 the mammiferous class. The student should be reminded 
 that in all the rocks described in the preceding chapters as 
 older than the Eocene, no bones of any land-quadruped, or of 
 any cetacean, had been discovered until the Spcdacotherium 
 of the Purbeck beds came to light in 1854. Yet we have 
 seen that terrestrial plants were not wanting in the Upper 
 Cretaceous formation (see p. 302), and that in the Wealden 
 there was evidence of fresh-water sediment on a large scale, 
 containing various plants, and even ancient vegetable soils. 
 "We had also in the same Wealden many land-reptiles and 
 winged insects, which render the absence of ten-estiial quad- 
 rupeds the more striking. The want, however, of any bones 
 of whales, seals, dolphins, and other aquatic mammalia, wheth- 
 er in the chalk or in the upper or middle oolite, is cei'tainly 
 still more remarkable. 
 
 These observations are made to prepare the reader to ap- 
 preciate more justly the interest felt by every geologist in 
 the discovery in the Stonesfield slate of no less than ten 
 specimens of lower jaws of mammiferous quadrupeds, be- 
 longing to four different species and to three distinct gene- 
 ra, for which the names of Amphitherium, Phascolotherium, 
 and Stereogyiathus have been adopted. . , 
 
 It is now generally ad- Kg. 339. 
 
 mitted that these are really 
 the remains of mammalia 
 (although it was at first 
 suggested that they might _ _____ ^_ 
 
 be reptiles), and the only y„;,„i„ y^^. Eight ramus ofiowev jaw. 
 
 question open to COntrO- Natural size. A recent Insectivorous pla- 
 versy is limited to this <=«°t''l '°»'»>"^I. ''■"'" Sumatra. 
 
 point, whether the fossil mammalia found in the Lower Oolite 
 
MAMMALIA OS STONESFIELD SLATE. 
 
 347 
 
 of Oxfordshire ought to be referred to the marsupial quad- 
 rupeds, or to the ordinary placental series. Cuvier had long 
 
 Pig. 340. 
 
 Fig. 341. 
 
 Fig, 342. 
 
 Fig. 343. 
 
 Part of lower jaw of Tiipaia Tana. 
 Twice natural Bize. 
 Pig. 340. End view seen from behind, 
 showing the very elight inflection 
 of the angle at c. Pig. 341. Side 
 view of same. 
 
 Part of lower Jaw of Didelphya AzarcS; 
 recent, Brazil. Natural size. 
 Pig. 342. End view seen from behind, 
 snowing the inflection of the angle of 
 the jaw, c, d. Fig. 343. Side view of 
 same. 
 
 ago pointed out a peculiarity in the form of the angular proc- 
 ess (c, Figs. 342 and 343) of the lower jaw, as a character of 
 the genus Did^lphys ; and Professor Owen has since con- 
 firmed the doctrine of its generality in the entire marsupial 
 series. In all these pouched quadrupeds this process is turned 
 inward, as at c, c?, Fig. 342, in the Brazilian opossum, whereas 
 in the placental series, as at e. Figs. 340 and 341, there is an 
 almost entire absence of such inflection. The.Tupaia Tana 
 of Sumatra has been selected by Mr. Waterhouse for this 
 illustration, because the jaws of that small insectivorous 
 quadruped bear a great resemblance to those of the Stones- 
 Fig. 344. 
 
 Amphitherium PrevosHi, Ciiv. sp. Stonesfleld Slate. Syn. Tlajlaco- 
 
 iherium Prevoetii, Valenc. 
 
 a. Coronoid process. 6. Condyle, c. Anglo of jaw. d. Double-fanged molars. 
 
 field Amphitherium. By clearing away the matrix from the 
 specimen of Amphitherium P/evostii here represented (Fig. 
 344), Professor Owen ascertained that the angular process 
 (c) bent inward in a slighter degree than in any of the known 
 marsupialia ; in short, the inflection does not exceed that of 
 the mole or hedgehog. This fact made him doubt whether 
 
348 ELEMENTS OF GEOLOGY. 
 
 tlie Amphitherium might not be tin insectivorous placental, 
 although it offered some points of approximation in its oste- 
 ology to the marsupials, especially to the Myrmecobius, a 
 small insectivorous quadruped of Australia, which has nine 
 molars on each side of the lower jaw, besides a canine and 
 three incisors.* Another species oi Amphitherium has been 
 found at Stoneslield (Fig. 345), whichdiffers from the former 
 (Fig. 344) principally in being larger. 
 
 Fig. 345. F'g- 2*6- 
 
 Amphitherium Broderipii, Phascolotherium Bueklandi, Broderip, sp. 
 
 Owen. Natural size. a. Natural size. 6. Molar of same, 
 
 Stonesfield Slate. magnified. 
 
 The second mammiferous genus discovered in the same 
 slates was named originally by Mr. Broderip Didelphys 
 Sucklandi (see Fig. 346), and has since been called Phasco- 
 lotherium by Owen. It manifests a much stronger likeness 
 to the marsupials in the general form of the jaw, and in the 
 extent and position of its inflected angle, while the agree- 
 ment with the living genus Didelphys in the number of the 
 pre-molar and molar teeth is complete.f 
 
 In 1 854 the remains of another mammifer, small in size, hut 
 larger than any of those previously known, was brought to 
 light. The generic name of Stereogtiathus was given to it, 
 and, as is usually the case in these old rocks (see above, p. 
 328), it consisted of part of a lower jaw, in which were im- 
 planted three double-fanged teeth, differing in structure from 
 those of all other known recent or extinct mammals. 
 
 Plants of the Oolite. — The Arancarian pines, which are now 
 abundant in Australia and its islands, together with marsu- 
 pial quadrupeds, are found in like manner to have accom- 
 panied the marsupials in Europe during the Oolitic period 
 (see Fig. 348). In the same rock endogens of the most per- 
 fect structure are met with, as, for example, fruits allied to 
 the Pandanns, such as the Kaidacarpum ooliticum of Car- 
 ruthers in the Great Oolite, and the Podocarya of Buckland 
 (see Fig. 34V) in the Inferior Oolite. 
 
 Puller's Earth. — Between the Great and Inferior Oolite 
 near Bath, an argillaceous deposit, called " the fuller's earth," 
 
 * A figure of this recent Myrmecobius will be found in my Principles of 
 Geology, chap. ix. 
 + Owen's British Eossil Mammals, p. 62. 
 
INTERIOR OOLITE. 349 
 
 Fig. 348. 
 
 Portion of a fossil fi-nit of Podo- 
 carya Bticklandif Ung., magni- 
 flco. (BacklaDd'sBridgw. Trea- 
 tise, PI. 63.) Inferior Oolite, 
 Charmontb, Dorset. 
 
 Cone of fossil Araucaria aphcerocarpa, 
 Carr. Inferior Oolite. Brnton, Somer- 
 setshire. One-third diameter of origi- 
 nal. In the collection of the British 
 Museum. 
 
 occurs; but it is wanting in the north of England. It 
 
 abounds in the small oyster represented in Kg. 349. 
 
 Fig. 349. The number of moUusca known 
 
 in this deposit is about seventy ; namely, fifty 
 
 Lamellibranchiate Bivalves, ten Brachiopods, 
 
 three Gasteropods, and seven or eight Ceph- 
 
 alopods. 
 
 Inferior Oolite.— This formation consists of ''IXJ^frft'"' 
 a calcareous freestone, usually of small thick- 
 ness, but attaining in some places, as in the typical area of 
 Cheltenham and the Western Cotswolds, a thickness of 250 
 feet. It sometimes rests upon yellow sands, formerly classed 
 as the sands of the Inferior Oolite, but now regarded as a 
 member of the Upper Lias. These sands repose upon the 
 Upper Lias clays in the south and west of England. The 
 Collyweston slate, formerly classed with the Great Oolite, 
 and supposed to represent in Northamptonshire the Stones- 
 field slate, is now found to belong to the Inferior Oolite, both 
 by community of species and position in the series. The Col- 
 lyweston beds, on the whole, assume a much more marine 
 character than the Stonesfield slate. Nevertheless, one of 
 the fossil plants Aroides Stutterdi,Garr.,remarkah\e,\ike the 
 Pandanaceous species before mentioned (Fig. 347) as a rep- 
 resentative of the monoootyledonous class, is common to the 
 Stonesfield beds in Oxfordshire. 
 
 The inferior Oolite of Yorkshire consists largely of shales 
 and sandstones, which assume much the aspect of a true 
 
350 
 
 ELEMENTS OP- GEOLOGY. 
 
 coal-field, tbin seams of coal having actually been worked in 
 them for more than a century. A ricli harvest of fossil ferns 
 jj. gjjp has been obtained 
 
 from them, as at 
 Gristhorpe, near 
 Scarborough (Fig. 
 350). Theycoptain 
 also , Cycadeffi, of 
 which family a 
 magnificent speci- 
 men, has been de- 
 scribed by Mr. Wil- 
 liamson under the 
 name Zamia Gigas, 
 and a fossil called HJqvisetum Columnare (see, Fig. 397,, p. 
 376), which maintains an upright position in sandstone strata 
 over a wide area. Shells of E&theria and Unio, collected by 
 Mr. Bean from these Yorkshire coal-bearing beds, point to the 
 estuary or fluviatile origin of the deposit. 
 
 At fei-ora, in Sutherlandshire, a coal foi'mation, probably 
 coeval with the above, or at least belonging to some of the 
 lower divisions of the Oolitic period, has been mined exten- 
 sively for a century or more. It aifords the thickest stratum 
 of pui'e vegetable matter hitherto detected in any secondary 
 rock in England. One seam of coal of good quality has been 
 worked three and a half feet thick, and there are several feet 
 more of pyritous coal resting Upon it. 
 
 Hemitdites Brownii, Goepp. Syn. Phlebopteris contigua, 
 Liiid. and Hutt. Lower carbonaceous strata, Inferior 
 Oolite shales. Gristhorpe, Yorkshire. 
 
 Kg. 351. 
 
 Fig. 352. 
 
 Fig.SSS. ■ 
 
 Terehratula fimbria, Sow. 
 Inferior Oolite marl. 
 Cotswoia Hills. 
 
 RhyncJumella spinom, 
 Schloth. Inferior 
 Oolite. 
 
 PhdUtdcfmya fuimila-. Sow. 
 One-third naUiral size. 
 Inferior Oolite. 
 
 Among the characteristic shells of the Inferior Oolite, I 
 may instance Terehratula fimbria (Fig. 351), Mliynchondla 
 spinosa (Fig. 352), and Pholadomya fidioula (Fig. 353). The 
 extinct genus Pleurotomaria is also a form very common in 
 this division as well as in the Oolitic system generally. It 
 resembles the Trochus in form, but is marked by a deep 
 cleft (a, Figs. 354, 355) on one side of the mouth. The Golr 
 
I'OSSILS OF INTERIOR OOLITE. 351 
 
 . Fig. 354. Eig. 355. Fig. 366. 
 
 Pleurotmnaria qranvXata, Sow. Plawotcmaria omataj 
 Fernigiiioiisdol., Normandy. Sow. Sp. Inferior 
 Inferior Oolite, England. Oolite. 
 
 Collyrites (Dysiuter) rtn- 
 gens, AgnsB. IntOol., 
 Sotaiersetshirc, 
 
 lyrites {Bysaater) ringens (Fig. 356) is an Echinoderm com- 
 raon to the Inferior Oolite of England and France, as are the 
 two Ammonites (Figs. 357, 358). 
 
 Fig. 35T. 
 
 Ammonites Bumphresianus, Sow. Inferior Oolite. 
 Fig. 368. Fig. 369. 
 
 Ammonites Sraikenridgii, Sow. 
 Oolite, Scarborongh. Inf. 
 Ool.jDundry; Calvados j etc. 
 
 Ostrea Marskii. One-half nntnral size. 
 Middle and Lower Oolite. 
 
 PalsBontological Relations of the Oolitic Strata. — Observa- 
 tions have already been made, p. 338, on the distinctness of 
 the organic remains of the Oolitic and Cretaceous strata, and 
 
352 ELEMENTS OF GEOLOGY. 
 
 the proportion of species common to the different members 
 of the Oolite. Between the Lower Oolite and the Lias there 
 is a somewhat greater break, for out of 256 mollusoa of the 
 Upper Lias, thirty-seven species only pass up into the In- 
 ferior Oolite. 
 
 In illustration of shells having a great vertical range, it 
 may be stated that in England some few species pass up 
 from the Lower to the Upper Oolite, as, 
 ^' ■ for example, KhynchoneUa obsoleta, Lir 
 
 ~ thodomus incliisus, Pholadomya ovalis, 
 
 and Trigonia costata. 
 
 Of all the Jurassic Ammonites of Great 
 Britain, A. macrocephalus (Fig. 360), 
 which is common to the Great Oolite 
 and Oxford Clay, has the widest range. 
 We have every reason to conclude 
 Schioth. one-thiiflnatu-.that the gaps which occur, both be- 
 rai size. Great Oolite and tween the larger and smaller sections 
 
 Oxrord Clay. n ■, -n i.i.^t • t . 
 
 01 the English Oolites, imply intervals 
 of time, elsewhere represented by fossiliferous strata, al- 
 though no deposit may have taken place in the British area. 
 This conclusion is warranted by the partial extent of many 
 of the minor and some of the larger divisions even in England. 
 
DIVISION OF THE LIAS. 353 
 
 CHAPTER XX. 
 
 JUEASSic GROUP — Continued. — lias. 
 
 Mineral Character of Lias. — Numerous successive Zones in the Lias, marked 
 by distinct Fossils, without Unconformity in the Stratification, or Change 
 in the Mineral Character of the Deposits. — Gryphite Limestone. — Shells 
 of the Lias. — Fish of the Lias. — Keptiles of the Lias. — Ichthyosaur and 
 Plesipsaur. — Marine Reptile of the Galapagos Islands. — Sudden Destruc- 
 tion and Burial of Fossil Animals in Lias. — Fluvio-mavine Beds in Glou- 
 cestershire, and Insect Limestone. — Fossil Plants. — Origin of the Oolite 
 and Lias, and of alternating Calcareous and Argillapeous Formations. 
 
 Lias. — The English provincial name of Lias has been very 
 generally adopted for a formation of argillaceous limestone, 
 marl, and clay, which forms the base of the Oolite, and is 
 classed by many geologists as part of that group. The pe- 
 culiar aspect which is most characteristic of the Lias in Eng- 
 land, France, and Germany, is an alternation of thin beds of 
 blue or gray limestone, having a surface which becomes light- 
 brown when Aveathered, these beds being separated by dark- 
 colored, narrow argillaceous partings, so that the quarries of 
 this rock, at a distance, assume a striped and ribbon-like ap- 
 pearance. 
 
 The Lias has been fcfided in England into three groups, 
 the Upper, Middle, and Lower. The Upper Lias consists first 
 of sands, which were formerly regarded as the base of the 
 Oolite, but which, according to Dr. Wright, are by their fos- 
 sils more properly referable to the Lias ; secondly, of clay 
 shale and thin beds of limestone. The Middle Lias, or marl- 
 stone series, has been divided into three zones ; and the Lower 
 Lias, according to the labors of Quenstedt, Oppel, Strickland, 
 Wright, and others, into seven zones, each marked by its own 
 group of fossils. This Lower Lias averages from 600 to 900 
 feet in thickness. 
 
 From Devon and Dorsetshire to Yorkshire all these divis- 
 ions, observes Professor Ramsay, are constant ; and from top 
 to bottom we can not assert that anywhere there is actual 
 unconformity between any two subdivisions, whether of the 
 larger or smaller kind. 
 
 In the whole of the English Lias there are at present known 
 about 937 species ofimollusca, and of these 267 are Cephalo- 
 pods, of which class more than two-thirds are Ammonites, 
 
.354 
 
 ELEMENTS OF GEOLOGY. 
 
 the Nautilus and Belemnite also abounding. The whole 
 series has been divided by zones characterized by particular 
 ammonites ; for while other families of shells pass from one 
 division to another in numbers varying from about 20 to 50 
 per cent., these cepbalopods are almost alvrays limited to 
 single zones, as Quenstedt and Oppel have shown for Ger- 
 many, and Dr. Wright and others foi- England. 
 
 As no actual unconformity is known from the top of the 
 Upper to the bottom of the Lower Lias, and as there is a 
 inarked uniformity in the mineral character of almost all the 
 strata, it is somewhat difficult tp account even for such partial 
 breaks as have been alluded to in the succession of species, 
 if we reject the hypothesis that the old species were in each 
 case destroyed at the close of the deposition of the rocks con- 
 taining them, and replaced by the creation of new forms when 
 the succeeding formation began. I agree with Professor Ram- 
 say in not accepting this hypothesis. No doubt some of the 
 old species occasionally died out, and left no representatives 
 in Europe or elsewhere ; others were locally exterminated in 
 the struggle for life by species which invaded their ancient 
 domain, or by varieties better fitted for a new state of things. 
 Pauses also of vast duration may have occurred in the depo- 
 sition of strata, allowing time for the modification of organic 
 life throughout the globe, slowly brought about by variation 
 accompanied by extinction of the original forms. 
 
 Fossils of the Lias. — The name of Gryphite limestone has 
 sometimes been applied to the Lias, in consequence of the' 
 
 ,-^ 
 
 Pig. 361. 
 
 Plagiontoma (Lima) giijanteum, Sow. 
 Inferior Oolite and Lias. 
 
 Fig. 302. 
 
 
 GryphtsaiiUiurva^ Sovf, (C. 
 arcuata, Lam.) Lias. 
 
 great number of shells which it containsof a species of oyster, 
 or Gryphcea (Pig. 362). A large heavy shell called Bippo- 
 
SHELLS OF THE LLA.S. 
 
 355 
 
 podium (Fig. 365), allied to Oypricarclia,is also characteristic 
 of the upper part of the Lower Lias. In this formation occur 
 
 Fig. 303. 
 
 Fig. 304 
 
 Aviffula iTuequivdlvifi, Sow. Avicula, cygnipeSfFhW. Lower Lias, Gloucestershire 
 
 Lower Lias. and Toikshire. 
 
 a. Lower valve. 6. Upper valve. 
 
 also the Aviculas, Figs. 363 and 364. The Lias formation is 
 also remarkable for being the newest of the secondary rocks 
 in which brachiopoda of the genera Spirifer and J^eptcena 
 
 Fig. 865. 
 
 Fig. 366. 
 
 Spirifenna {Spirifera) Walcotti, Sow. 
 Lower Lias. 
 
 Fig. 36T. 
 
 Hippopodium ponderosum, Sowerby. 
 J diameter. Lias, Cheltenham. 
 
 Leptcena Moorei, Da v. Upper Lias, 
 Ilminster. 
 
 (Figs. 366, 367) occur, although the former is slightly modi- 
 fied in structure so as to constitute the subgenus Spiriferina, 
 Davidson, and the Leptajna has dwindled to a shell smaller 
 in size than a pea. No less than eight or nine species of 
 Spirifei'ina are enumerated by Mr. Davidson as belonging to 
 the Lias. Palliobranchiate mollusca predominate greatly in 
 
356 
 
 ELEMENTS OF GEOLOGY. 
 
 Strata older than the Trias ; but, so far as we yet know, they 
 did not survive the Liassic epoch. 
 
 Allusion has already been made, p. 354, to numerous zones 
 in the Lias having each their peculiar Ammonites. Two of 
 these occur near the base of the Lower Lias, having a united 
 thickness, varying from 40 to 80 feet. The upper of these is 
 
 Fig. 3C8. 
 
 Fig. 369. 
 
 Ammonites BncklaTidiy Sow. Ammonites bi- 
 sulmtus, Brng. One-eiglitli diameter of 
 original. 
 
 «. Side view. &. FroDt view, showing moutli 
 and bisnlcated lieel. Cliaracteristic of the 
 lower part of the Lias of England and the 
 Continent. 
 
 A. plaruyrtis, Sow. One-half 
 diameter of original. From 
 the base of the Lower Liai* 
 of England and the Con- 
 tinent. 
 
 characterized by Ammonites Buchlandi, and the lower by 
 Ammo7iites planorbis (see Figs. 36'8, 369).* Sometimes, how- 
 
 Fig. 371. 
 
 Fig. 370. 
 
 ifaiitUus truncattts, Sow. 
 Lias. 
 
 Ammonites bifrons, Brug. A. Waleotii, Sow. 
 Upper Lias sbalei!. 
 
 ever, there is a third intermediate zone, that of Ammonites 
 
 angulatus, which is the equivalent of the zone called the 
 
 infra-lias on the Continent, the species of which are for the 
 
 * Quart. Joum., vol. xvi., p. 376. 
 
FOSSILS OF THE LIAS. 
 
 357 
 
 most part common to the superior group marked by A. 
 Sucldandi. j-jg_ g^^^ 
 
 Among the Crinoids or ~ 
 Stone-lilies of the Lias, 
 the Pentacrinites are con- 
 spicuous. (See Fig. 3V3.) 
 Oi PalcBoconia ( Ophioder- 
 ma) Egertoni (Fig. 374), 
 referable to the Ophiuri- 
 dee of Muller, perfect spec- 
 imens have been met with 
 in the Middle Lias beds of 
 Dorset and Yorkshire. 
 
 The jExtracrinus Briareus (removed by Major Austin from 
 Pentacrinus on account of generic differences) occurs in tan- 
 gled masses, forming thin beds of considerable extent, in the 
 Lower Lias of Dorset, Gloucestershire, and Yorkshire. The 
 remains are often highly charged with pyrites. This Crinoid, 
 
 Fig. 373. Fig. 3M. 
 
 ^mmom'tos wittrr/aritaius, MoDtf. Syn. ^, 
 SUikesl, Sow. Middle Lias. 
 
 Extracrinns (Pentaerinus) Briareus. 
 Miller, i natural size. (Body, arms, 
 andpartofBtem.) Lower Lias, Lyme 
 BegiB. 
 
 Palceocoma {Ophioderma) tenuibrachuiia. 
 E. Forbes. Middle Lias, Seatown, 
 Dorset. 
 
 with its innumerable tentacular arms, appears to have been 
 frequently attached to the driftwood of the liassic sea, in the 
 same manner as Barnacles float about on wood at the present 
 day. There is another species oi JExtracrinus and several of 
 
358 
 
 ELEMENTS OF GEOLOGY. 
 
 Pentacrimis in the Lias; and the latter genus is found in 
 nearly all the formations from the Lias to the London Clay- 
 inclusive. It is represented in the present seas by the deli- 
 cate and rare Fentacrinus caput-medusee of the Antillegj 
 which, with Comatula, is one of the few surviving members 
 of the ancient family of the Crinoids, represented by so many 
 extinct genera in the older formations. 
 
 Mshes of the Lias. — The fossil fish, of which there are no 
 less than 117 species known as British, resemble generically 
 those of the Oolite, but differ, according to M. Agassiz, from 
 those of the Cretaceous period. Among them is a species of 
 JLepidotus (L. giff as, Agass.) , Fig. 375, which is found in the 
 
 Fig. 375. 
 
 
 Scales ol Lepiclotus gigas, Agnse. 
 a. Two of the scales cletached. 
 
 Lias of England, France, and Germany.* This genus was 
 before mentioned (p. 316) as occurring in the Wealden, and 
 is supposed to have frequented both rivers and sea-coasts. 
 Another genus of Ganoids (or fish with hard, shining, and 
 
 Fig. 376. 
 
 ^ 
 
 * 
 
 HJ 
 
 b. Scales of JSchmoiua 
 Leachii. 
 
 u. JEchmodus. Kestored ontliue. 
 
 , u. Scales of Dapeditts 
 TnoniliJ'er. 
 
 enamelled scales), called ^ehmodus (Fig. 376), is almost ex- 
 clusively Liassic. The teeth of a species oi Acrodus, also, 
 are very abundant in the Lias (Fig. 377). 
 
 * Jigassiz, Poissons Fossiles, vol. ii., tab. 28, 29. 
 
FOSSILS OF THE LIAS. 
 
 359 
 
 Pig. 377. 
 
 Acrodiis noUlis, Agass. (tooth) ; commonly called "fossil leech." 
 Uas, Lyme Kegis, and Germany. 
 
 But the remaiDS of fish which have excited more attention 
 than any others are those large bony spines called ichthyo- 
 doruUtes (a, Fig. 378), which were once supposed by some 
 
 Fig. 378. 
 
 Fig. 379. 
 
 Byl)odu» reticulatuSf Agass. Lias, Lyme Kegis. 
 a. Part of fin, coinmonly called Ichthyodorulite. 6. Tooth. 
 
 naturalists to be jaws, and by others weapons, resembling 
 those of the living JBalistes and Silurus; but which M. 
 Agassiz has shown to be neither the one nor the other. The 
 spines, in the genera last mentioned, articulate with the 
 backbone, whereas there are no signs of any such articula- 
 tion in the ichthyodorulites. These last appear to have been 
 bony spines which formed the anterior part of the dorsal fin, 
 like that of the living genera Cestracion and Ghimoera (see 
 08, Fig. 379). In both 
 of these genera, the 
 posterior concave face 
 is armed with small 
 spines, as in that of the 
 fossil Hybodus (Fig. 
 378), a placoid fish of 
 the shark family found 
 fossil at Lyme Regis. 
 Such spines are simply 
 inibedded in the flesh, 
 and attached to strong 
 muscles. " They serve," says Dr. Buckland, " as in the C/w- 
 ^(Bra (Fig. 379), to raise and depress the fin, their action 
 * Agassiz, Foissons Fossiles, vol. iii., tab. C, Fig. 1. 
 
 Chvmcei'a Ttumitrosa.'* 
 a. Spine forming anterior part of the dorsal fin. 
 
360 ELEMENTS OF GEOLOGY. 
 
 resembling that of a movable mast, raising and lowerhip* 
 backward the sail of a barge."* 
 
 Reptiles of the Lias. — It is not, however, the fossil fish 
 which form the most striking feature in the organic remains 
 of the Lias ; but the Enaliosaurian reptiles, which are ex- 
 traordinary for their number, size, and structure. Among 
 the most singular of these are several species of Ichthyo- 
 saurus and Plesiosaurus (Figs. 380, 381). The genus Iclv- 
 thyosaurus, or fish-lizard, is not confined to this formation, 
 but has been found in strata as high as the White Chalk of 
 England, and as low as the Trias of Germany, a formation 
 -which immediately succeeds the Lias in the descending order. 
 It is evident from their fish-like vertebrae, their paddles, re- 
 sembling those of a porpoise or whale, the length of their 
 tail, and other parts of their structure, that the Ichthyosaurs 
 were aquatic. Their jaws and teeth show that they were 
 carnivorous; and the half-digested remains of fishes and 
 reptiles, found within their skeletons, indicate the precise 
 nature of their food. 
 
 Mr. Conybeare was enabled, in 1824, after examining many 
 skeletons nearly perfect, to give an ideal restoration of the 
 osteology of this genus, and of that of the Plesiosaurus.\ 
 (See Figs. 380, 381.) The latter animal had ,an extremely 
 long neck and smallhead, with teeth like those of the croco- 
 dile, and paddles analogous to those of the Ichthyosauri, 
 but larger. It is supposed to have lived in shallow seas and 
 estuaries, and to have breathed air like the Ichthyosaur and 
 our modern cetacea.J Some of the reptiles above mentioned 
 were of formidable dimensions. One specimen of Ichthyo- 
 saurus platyodon, from the Lias at Lyme, now in the British 
 Museum, must have belonged to an animal more than 24 feet 
 in length ; and there are species of Plesiosaurus which meas- 
 ure from 18 to 20 feet in length. The form of the Ichthyo- 
 saurus may have fitted it to cut through the waves like the 
 porpoise ; as it was furnished besides its paddles with a tail- 
 fin so constructed as to be a powerful organ of motion ; but 
 it is supposed that the Plesiosaurus, at least the long-necked 
 species (Fig. 381), was better suited to fisli in shallow creeks 
 and bays defended from heavy breakers. 
 
 It is now very generally agreed that these extinct saurians 
 must have inhabited the sea; and it v^as urged that as there 
 are now chelonians, like the tortoise, living in fresh water, 
 
 * Bridgewater Treatise, p. 290. 
 t Geo]. Soc. Transactions, Second Series, vol. i., p. 49. 
 X Conybeare and De la Beche, Geol. Trans., First Series, vol. v., p. 559 ; 
 and Buckland, Bridgawater Treatise, p. 203. 
 
SAURIAiJS OF THE LIAS.: 
 
 361 
 
 and otherSy as the turtle, frequenting the ocean, so' there may 
 have been formerly some saurians proper to salt, others to 
 fresh water. The common crocodile of the Ganges is well 
 
 known to frequent equally that river and the brackish and 
 salt water near its month; and crocodiles are said in like 
 manner to be abundant both in the rivers of the Isla de 
 
 16 
 
362 ELEMENTS OF GEOLOGY. 
 
 Pinos for Isle of Pines), south of Cuba, and in the open sea 
 round the coast. In 1835 a curious lizard {Amblyrhynchus 
 cristatus) was discovered by Mr. Darwin in the Galapagos 
 Islands.* It was found to be exclusively marine, swimming 
 easily by means of its flattened tail, and subsisting chiefly on 
 seaweed. One of them was sunk from the ship by a heavy 
 weight, and on being drawn up after .an hour was quite un- 
 harmed. 
 
 The families of Dinosauria, crocodileS; and Pterosauria or 
 winged reptiles, are also represented in the Lias. 
 
 Sudden Destruction of Saurians. — It has been remarked, and 
 truly, that many of the fish and saurians, found fossil in the 
 Lias, must have met with sudden death and immediate burial ; 
 and that the destructive operation, whatever may have been 
 its nature, was often repeated. 
 
 "Sometimes," says Dr. Buckland, "scarcely a single bone 
 or scale has been removed from the place it occupied during 
 life; which conld not have happened had the uncovered 
 bodies of these saurians been left, even for a few hours, ex- 
 posed to putrefaction, and to the attacks of fishes and other 
 smaller animals at the bottom of the sea."f Nofonly are the 
 skeletons of the Ichthyosaurs entire, but sometimes the con- 
 tents of their stomachs still remain between their ribs, as be- 
 fore remarked, so that we can discover the particular species 
 offish on which they lived, and the form of their excrements. 
 Not unfrequently there are layers of these coprolites, at dif- 
 ferent depths in the Lias, at a distance from any entire skele- 
 tons of the marine lizards from which they were derived; 
 "as if," says Sir H. de la Beche, "the muddy bottom of the 
 sea received small sudden accessions of matter from time to 
 time, covering up the coprolites and other exuviae which had 
 accumulated during the intervals."^ It is further stated that, 
 at Lyme Regis, those surfaces only of the coprolites which 
 lay uppermost at the bottom of the sea have sufiered partial 
 decay, from the action of water before they were covered and 
 protected by the muddy sediment that has afterwards per- 
 manently enveloped them. 
 
 Numerous specimens of the Calamary or pen-and-ink fish, 
 {Geoteuthis bollensis) have also been met with in the Lias at 
 Lyme, with the ink-bags still distended, containing the ink 
 in a dried state, chiefly composed of carbon, and but slight- 
 ly impregnated with carbonate of lime. These cephalopoda, 
 therefore, must, like the saurians, have been soon buried in 
 
 * See Davwin, Naturalist's Voyage, p. 385. Murray. 
 t Bridgewater Treatise, p. 115. 
 I Geological liesearclies, p. 334. 
 
FRESH- WATEK DEPOSITS. 363 
 
 sediment ; for, if long exposed after death, the membrane con- 
 taining the ink would have decayed.* 
 
 As we know that river-fish are "sometimes stifled, even in 
 their own element, by muddy water during floods, it can not 
 be doubted that the periodical discharge of large bodies of 
 turbid fresh water in the sea may be still more fatal to ma- 
 rine tribes. In the "Principles of Geology" I have shown 
 that large quantities of mud and drowned animals have been 
 swept down into the sea by rivers during earthquakes, as in 
 Java in 1-699 ; and that indescribable multitudes of dead fish- 
 es have been seen floating on the sea after a discharge of 
 noxious vapors during similar convulsions. But in the inter- 
 vals between such catastrophes, strata may have accumu- 
 lated slowly in the sea of the Lias, some being formed chief- 
 ly of one description of shell, such as ammonites, others of 
 gryphites. 
 
 Fresh-water Deposits.— Insect-beds. — From the above re- 
 marks the reader will infer that the Lias is for the most part 
 a marine deposit. Some members, however, of the series 
 have an estuarine character, and must have been formed 
 within the influence of rivers. At the base of the Upper and 
 Lower Lias respectively, insect-beds appear to be almost 
 everywhere present throughout the Midland and South-west- 
 ern districts of England. These beds are crowded with the 
 remains of insects, small fish, and crustaceans, with occasion- 
 al marine shells. One band in Gloucestershire, rarely ex- 
 ceedino- a foot in thickness, has been named the " insect lime- 
 stone." It passes upward, says the Rev. P. B. Brodie,t into 
 a shale containing Cypris and Estheria, and is full of the 
 wing-cases of several genera of coleoptera, with some nearly 
 entire beetles, of which the eyes Fi^.382. 
 
 are preserved. The nervures of 
 the wings of neuropterous insects 
 (Fig. 382) are beautifully perfect 
 in this bed. Ferns, with cycads 
 and leaves of monocotyledonous 
 plants, and some apparently brack- wing ofanei^opterousineect, from 
 
 ish and fresh-water shells, aCCOm- the Lower Lias, Oloucestereliire. 
 
 pany the insects in several places, (Kev. p. b. Brodie.) 
 while in others marine shells predominate, the fossils varying 
 apparently as we examine the bed nearer or farther from the 
 ancient land, or the source whence the fresh water was de- 
 rived. After studying 300 specimens of these insects from 
 the Lias, Mr. Westwood declares that they comprise both 
 
 * Bnckland, Bridgewater Treatise, p. 307. 
 
 t A History of Possil Insects, etc. , 1846. London. 
 
364 ELEMENTS OE GEOLOGY. 
 
 wood-eating aud herb-devouring beetles, of the Linnean gen- 
 era Elater, Carabus, etc., besides grasshoppeis (Gryllus), and 
 detached wings of dragon^flies and may-flies, or insects refer- 
 able to the Linnean geuQva. Libellula, JEphemera, Hemerohvus^ 
 and Panorpa, in all belonging to no less than twenty-four 
 families. The size of the species is usually small, and such 
 as taken alone would imply a temperate climate ; but many 
 of the associated organic remains of other classes must lead 
 to a difierent conclusion. 
 
 Fossil Plants. — Among the vegetable remains of the Lias, 
 several species of Zamia have been found at Lyme Regis, 
 and the remains of coniferous plants at Whitby. M. Ad. 
 Brongniart enumerates forty-seven liassic acrogens, most of 
 them ferns ; and fifty gymnosperms, of which thirty-nine are 
 cycads, and eleven conifers. Among the cycads the predomi- 
 nance of Zaniites, and among the ferns the numerous genera 
 with leaves having reticulated veins (as in Fig. 349, p. 349), 
 are mentioned as botanical characteristics of this era.* The 
 absence as yet from the Lias and Oolite of all signs of dicot- 
 yledonous angiosperms is worthy of notice. The leaves of 
 such plants are frequent in tertiary strata, and occur in the 
 Cretaceous, though less plentifully (see above, p. 803). The 
 angiosperms seem,, therefore, to have been at the least com- 
 paratively rare in these older secondary periods, when moi-e 
 space was occupied by the Cycads and Conifers. 
 
 Origin of the Oolite and Lias. — The entire group of Oolite, 
 and Lias consists of repeated alternations of clay, sandstone, 
 and limestone, following each other in the same order. Thus 
 the clays of the Lias are followed by the sands now consid- 
 ered (see p. 353) as belonging to the same formation, though 
 formerly referred to the Inferior Oolite, and these sands again 
 by the shelly and coralline limestone called the Great or Bath 
 Oolite. So, in the M iddle Oolite, the Oxford Clay is followed 
 by calcareous grit and coral rag ; lastly, in the Upper Oolite, 
 the Kimmeridge Clay is followed by the Portland Sand and 
 limestone (see P'ig. 298, p. 322). f The clay beds, however, 
 as Sir H. D. de la Beche remarks, can be followed over larger 
 areas than the sand or sandstones.J It should also be re- 
 membered that while the Oolite system becomes arenaceous 
 and resembles a coal-field in Yorkshire, it assumes in the Alps 
 an almost purely calcareous form, the sands and clays being 
 omitted ; and even in the intervening tracts it is more com- 
 plicated and variable than appears in ordinary descriptions. 
 
 « Tableau des Veg. Eoss., 1849, p. 105. 
 
 t Conybeare and Philips's Oatlines, etc., p. 166. 
 
 t Geol. Researches, p. 337. 
 
ORIGIN or THE OOLITE AND LIAS. 365 
 
 Nevei'theless, some of the clays and intervening limestones 
 do retain, in reality, a pretty uniform character for distances 
 of from 400 to 600 miles from east to west and north to south. 
 
 In order to account for such a succession of events, we may 
 imagine, first, the bed of the ocean to be the i-eceptacle for 
 ages of fine argillaceous sediment, brought by oceanic cur- 
 rents, which may have communicated with rivers, or with 
 part of the sea near a wasting coast. This mud ceases, at 
 length, to be conveyed to the same region, either because the 
 land which had previously suifered denudation is depressed 
 and submerged, or because the current is deflected in another 
 direction by the altered shape of the bed of the ocean and 
 neighboring dry land. By such changes the water becomes 
 once more clear and fit for the growth of stony zoophytes. 
 Calcareous sand is then formed from comminuted shell and 
 coral, or, in some cases, arenaceous matter replaces the clay ; 
 because it commonly happens that the finer sediment, being 
 first drifted farthest from coasts, is subsequently overspread 
 by coarse sand, after the sea has grown shallower, or when 
 the land, increasing in extent, whether by upheaval or by 
 sediment filling up parts of the sea, has approached nearer 
 to the spots first occupied by fine mud. 
 
 The increased thickness of the limestones in those regions, 
 as in the Alps and Jura, where the clays are comparatively 
 thin, arises from the calcareous matter having been derived 
 from species of corals and other organic beings which live in 
 clear water, far from land, to the growth of which the influx 
 of mud would be unfavorable. Portions therefore of these 
 clays and limestones have probably been formed contempo- 
 raneously to a greater extent than we can generally prove, 
 for the distinctness of the species of organic beings would 
 be caused by the difference of conditions between the more 
 littoral and the more pelagic areas and the different depths 
 and nature of the sea-bottom. Independently of those as- 
 cending and descending movements which have given rise 
 to the superposition of the limestones and clays, and by 
 which the position of land and sea are made in the course of 
 ages to vary, the geologist has the difficult task of allowing 
 for the contemporaneous thinning out in one direction and 
 thickening in another, of the successive organic and inorgan- 
 ic deposits of the same era. 
 
366 ELEMENTS OE GEOLOGY. 
 
 CHAPTER XXI. 
 
 TEIAS, OR ZSTEW EBD SANDSTONE GEOUP. 
 
 Bads of Passage between the Lias and Trias, Khsetic Beds.— Triassic Mam- 
 mifer.— Triple Division of the Trias. — Keuper, or Upper Trias of England. 
 
 Reptiles of the Upper Trias. ^Eoot-prints in the Bunter formation in 
 
 England. — Dolomitic Conglomerate of Bristol. — Origin of Eed Sandstone 
 and Rock-salt.— I'recipitation of Salt from inland Lakes and Lagoons.— 
 Trias of Germany. — Keuper. — St. Cassian and Hallstadt Beds. — Peculiar- 
 ity of their Fauna. — Muschelkalk and its Fossils. — Trias of the United 
 States. — Fossil Foot-prints of Birds and Reptiles in the Valley of the Con- 
 necticut. — ^Triassic Mainmifer of North Carolina. — Triassic Coal-field of 
 Richmond, "Virginia. — Low Grade of early Mammals favorable to the The^ 
 oiy of Progressive Development. 
 
 Beds of Passage between the Lias and Trias— Rhaetic Beds. 
 
 — We have mentioned in the last chapter (p. 356) that the 
 base of the Lower Lias is characterized, both in England and 
 Germany, by beds containing distinct species of Ammonites, 
 the lowest subdivision having been called the zone of Am- 
 monites planorhis. Below this zone, on the boundary line 
 between the Lias and the strata of which Ave are about to 
 treat, called "Trias," certain cream-colored limestones de- 
 void of fossils are usually found. These white beds were 
 called by William Smith the White Lias, and they have been 
 shown by Mr. Charles Moore to belong to a formation simi- 
 lar to one in the Rhsetian Alps of Bavaria, to which Mr. 
 Gumbel has applied the name of Rhsetic. They have also 
 long been known as the Koessen beds in Germany, and may 
 be regarded as beds of passage between the Lias and Trias. 
 They are named the Penarth beds by the Government sur- 
 veyors of Great Britain, from Penarth, near Cardiflf, in Gla- 
 morganshire, where they sometimes attain a thickness of 
 fifty feet. 
 
 The principal member of this group has been called by Dr. 
 Wright the Avicula contorta bed,* as this shell is very abun- 
 dant, and has a wide range in Europe. General Portlock 
 first described the formation as it occurs at Portrush, in An- 
 trim, where the Avicula contorta is accompanied by Pecten 
 Valoniensis, as in Germany. 
 
 The best known member of the group, a thin band or bone- 
 breccia, is conspicuous among the black shales in the neigh- 
 
 * Dr. Wright, on Lias and Bone Bed, Quart. Geol. Journ., 1860, vol. xvi. 
 
FOSSILS. OF THE RH^TIC BEDS. 
 
 367 
 
 boi'hood of Axmouth in Devonshire, and in the cliffs of West- 
 bury-on-Severn, as well as at Aust and other places on the 
 
 Pig. 303. 
 
 Fig. 384. 
 
 Fig. 3SS. 
 
 Cardium rhcetiexum, 
 Merrian. Natural 
 size. Klisetic Beds. 
 
 Pecien Valoniensis. Dfr. 
 i nat. size. Portrush, 
 Irelaud, etc. Btisetic 
 Beds. 
 
 Ameida contorta. Portlock. 
 Portrusli, Irelaud, etc. 
 Nnt. size. Khsetic Beds. 
 
 borders of the Bristol Channel. It abounds in the remains 
 of saurians and iish, and was formerly classed as the lowest 
 bed of the Lias ; but Sir P. Egerton first pointed out, in 1841, 
 that it should be referred to the Upper New Red Sandstone, 
 because it contained an assemblage of fossil fish which are 
 either peculiar to this stratum, or belong to species well- 
 known in the Muschelkalk of Germany. These fish belong 
 to the genera Acrodus, Hyhodus, Gyrolepis, and Saurichthys. 
 Among those common to the English bone-bred and the 
 Muschelkalk of Germany are Hyhodus plicatilis (Fig. 386), 
 
 Fig. 3SC. 
 
 Fig. 3Sr. 
 
 Fig. 388. 
 
 Hybodns plicatilis, Agass. Sait/richthys apicalis, Agass. Gyrolepis tenuvitriaius, 
 Teeth. Bone-bed, Aust Tooth; natural size and Agass. Scale; nat. 
 and Axmouth. magnified. Axmouth. size and magnified. 
 
 Axmouth. 
 
 Saurichthys apicalis (Fig. SB'?), Gyrolepis tenuistriatus (Fig. 
 388), and G. Albertii. Remains of saurians, Plesiosaurus 
 among others, have also been found in the bone-bed, and 
 plates of an Enerinus. It may be questioned whether some 
 of those fossils which have the most Triassic character may 
 
368 ELEMENTS OF GEOLOGY. 
 
 not have been derived from tte destruction of older strata, 
 since in bone-beds, in general, many of the organic remains 
 are undoubtedly derivative. 
 
 l\iassic Mammifer. — In North-western Germany, as in 
 England, there occurs beneath the Lias a remarkable bone 
 breccia. It is filled with shells and with the remains of fish- 
 es and reptiles, almost all the genera of which, and some 
 even of the species, agree with those of the subjacent Trias. 
 This breccia has accordingly been considered by Professor 
 Quenstedt, and other German geologists of high authority, 
 as the newest or uppermost part of the Trias. Professor 
 Plieninger found in it, in 1847, the molar tooth of a small 
 Triassic mammifer, called by him Microlestes cmtiquus. He 
 Pig. 3S9. inferred its true nature 
 
 f^^ A from its double fangs, 
 
 ^rey& Ijfll and from the form and 
 
 *mRvW i "mf dSSSbt number of the prota- 
 BUI' 1 HI berances or cusps on 
 
 ^il:"'^'' W the flat crown ; and 
 
 Microlestee antiquus, Plieninger. Molar tooth, mag- Considering it aS pre- 
 
 WQrferab^^r^'''"'- D'^S^''"'"'', near Stuttgart, daceOUS, probably in- 
 
 a. View of inner side? 6. Same, outer side ? c. Same SectivoroUS, he Called 
 
 in profile, d. Crowu of same. it MtCrolesteS from fii- 
 
 KpoQ, little, and Xj/otijc, a beast of prey. Soon afterwards he 
 found a second tooth, also at the same locality, Diegerloeh, 
 about two miles to the south-east of Stuttga,rt. 
 
 No anatomist had been able to give any feasible conjec- 
 ture as to the affinities of this minute quadruped; until Dr. 
 Falconer, in 185'7, recognized an unmistakable resemblance 
 between its teeth and the two back molars of his ne^ genus 
 Plagiaulax (Fig. 306, p. 32V), from the Purbeck strata.' 'This 
 would lead us to the conclusion that Microlestes was marsu- 
 pial and plant-eating. 
 
 In Wurtemberg there are two bone-beds, namely, that con- 
 taining the Microlestes, which has just been described, which 
 constitutes, as we have seen, the uppermost member of the 
 Trias, and another of still greater extent, and still more rich 
 in the remains offish and rei^tiles, which is of older date, in- 
 tervening between the Keuper and Muschelkalk. 
 
 The genera Saurichthys, Hyhodus, and Gyrolepis are found 
 in both these breccias, and one of the species, Saurichthys 
 Mongeoti, is common to both bone-beds, as is also a remark- 
 able reptile called Nothosaurus mirabilis. The saurian called 
 Belodon by _H. von Meyer, of the Thecodont family, is an- 
 other Triassic form, associated at Diegerloeh with Micro- 
 lestes. . , 
 
UPPEK TRIAS OR KEUPER OF ENGLAND. 3.69 
 
 TRIAS OF ENGLAND. 
 
 Between the Lias and the Coal (or Carboniferous group) 
 there is interposed, in the midland and western counties of 
 England, a great series of red loams, shales, and sandstones, 
 to v/hich the name of the " New Red Sandstone formation " 
 was first given, to distinguish it from other shales and sand- 
 stones called the " Old Red," often identical in mineral char- 
 acter, which lie immediately beneath the coal. The name 
 of " Red Marl " has been incorrectly applied to the red clays 
 of this formation, as before explained (p. 38), for they are re- 
 markably free from calcareous matter. The absence, indeed, 
 of carbonate of lime, as well as the scarcity of organic re- 
 mains, together with the bright red color of most of the 
 rocks of this group, causes a strong contrast between it and 
 the Jurassic formations before described. 
 
 The group in question is more fully developed in Germany 
 than in England or France. It has been called the Trias by 
 German writers, or the Triple Group, because it is separa- 
 ble into three distinct formations, called the " Keuper," the 
 "Muschelkalk," and the " Bunter-sandstein." Of these the 
 middle division, or the Muschelkalk, is wholly wanting in 
 England, and the uppermost (Keuper) and lowest (Bunter) 
 members of the series are not rich in fossils. 
 
 Upper Trias or Keuper. — In certain gray indurated marls 
 below the bone-bed Mr. BoydDawkins has found at Watchet, 
 on the coast of Somersetshire, a molar tooth of Microlestes, 
 enabling him to refer to the Trias strata formerly supposed 
 to be Liassic. Mr. Charles Moore had previously discovered 
 many teeth of mammalia of the same family near Frome, in 
 Somersetshire, in the contents of a vertical fissure traversing 
 a mass of carboniferous limestone. The top of this fissure 
 must have communicated with the bed of the Triassic sea, 
 and probably at a point not far from the ancient shore on 
 which the small marsupials of that era abounded. 
 
 This upper division of the Trias called the Keuper is of 
 great thickness in the central counties of England, attaining, 
 according to Mr. Hull's estimate, no less than 3450 feet in 
 Cheshire, and it covers a large extent of country between 
 Lancashire and Devonshire. 
 
 In Worcestershire and Warwickshire in sandstone belong- 
 ing to the uppermost part of the Keuper the bivalve crusta- 
 cean Estheria minuta occurs. The member of the English 
 "New Red" containing this shell, in those parts of England, 
 is, according to Sir Roderick Murchison and Mr. Strickland, 
 600 feet thick, and consists chiefly of red marl or slate, with 
 
 16* 
 
370 
 
 ELEMENTS 0¥ GEOLOGY. 
 
 Fig. 391. 
 
 a band of sandstone. Ichthyodorulites, or spines of Syhodm, 
 teeth of fishes, and foot-prints of reptiles were ^^^ 
 
 observed by the same geologists in these strata. 
 In the Upper Trias or Keuper the remains of 
 two saui-ians of the order Lacertilia have been 
 found. The one called Ehynchosavrus occurred 
 at Grinsell near Shrewsbury, and is character- Estunaminuta, 
 ized by having a small bird-like skull and jaws _ 
 without teeth. The other Hyperodapedon (Fig. 391) was 
 
 first noticed iu 
 1858, near Elgin, 
 in strata now rec- 
 ognized as Upper 
 Triassic, and after- 
 wards in beds of 
 about the same age 
 in the neighbor- 
 hood of Warwick. 
 Remains of the 
 same genus, have 
 been found both in 
 Central India and 
 Southern Africa in 
 rocks believed to 
 be of Triassic age. 
 The Hyperodape- 
 don has been shown by Professor Huxley to be a terrestrial 
 reptile having numerous palatal teeth, and closely allied to 
 the living Sphenodon of New Zealand. 
 
 The recent discoveries of a living saurian in New Zealand 
 so closely allied to this supposed extinct division of the La- 
 certilia seems to afibrd an illustration of a principle pointed 
 out by Mr. Darwin of the survival in insulated tracts, after 
 many changes in physical geography, of orders of which the 
 congeners have become extinct on continents where they 
 have been exposed to the severer competition 
 of a larger progressive fauna. 
 
 Teeth of Labyrinthodon (Fig. 392) found in 
 the Keuper in Warwickshire v/ere examined 
 microscopically by Professor Owen, and com- 
 pared with other teeth from the German Keu- 
 per. He found after careful investigation that '■'il.SftjL^^ 
 neither of them could be referred to true 
 saurians, although they had been named Mas- 
 todonsaurus and Phytosaurus by Jager. It appeared that 
 they were of the Batrachian order, and of gigantic di- 
 
 Hyverodapedon Gordoni. Left Palate, Maxillary. (Show- 
 ing the two rows of palatal teeth on opposite sides of 
 the jaw.) 
 
 a. Under surface, b. Exterior right side. 
 
 Fig. 392. 
 
 rinthodon; nat. 
 size. Warwick 
 sandstone. 
 
FOSSIL REMAINS OP liABYRINTHODON. 371 
 
 mensions in comparison with any representatives of that 
 order now living. Both the Continental and English fossil 
 teeth exhibited a most complicated texture, diflfisring from 
 that previously observed in any reptile, whether recent or 
 extinct, but most nearly analogous to the Ichthyosaurus. 
 A section of one of these teeth exhibits a series of irregular 
 folds, resembling the labyrinthic windings of the surface ot 
 the brain ; and from this character Professor Owen has pro- 
 posed the name Lahyrinthodon for the new genus. The an- 
 nexed representation (Fig. 393) of part of one is given from. 
 
 Kg. 393. 
 
 Transverse section of npper part of tooth of Labyrinthodon Jaegeri, Owen (Mastodon^ 
 
 murus Jaegeri, Meyer) ; natural size, and a segment magnified. 
 
 a. Pulp cavity, from whicli the processes of pulp and dentine radiate. 
 
 his " Odontography," plate 64, A. The entire length of this 
 tooth is supposed to have been about three inches and a half, 
 and the breadth at the base one inch and a half. 
 
 Rock-salt. — In Cheshire and Lancashire there are red clays 
 containing gypsum and salt of the age of the Trias which 
 are between 1000 and 1500 feet thick. In some places len- 
 ticular masses of pure rock-salt nearly 100 feet thick are in- 
 terpolated between the argillaceous beds. At the base of 
 the formation beneath the rock-salt occur the Lower Sand- 
 stones and Marl, called provincially in Cheshire "water- 
 stones," which are largely quarried for building. They are 
 often ripple-marked, and are impressed with numerous foot- 
 prints of reptiles. 
 
 The basement beds of the Keuper rest with a slight nn- 
 
S12 
 
 ELEMENTS D:F GEOLOGY. 
 
 conformability upon an eroded surface of the "Bunter" next 
 to be described. 
 
 Lower Trias or Bunter. — The lower division or English 
 representative of the "Bunter" attains a thickness of 1500 
 feet in the counties last mentioned, according to Professor 
 Ramsay. Besides red and green shales and red sandstones, 
 it comprises much soft white quartzose sandstone, in which 
 the trunks of silicified trees have been met with at Allesley 
 Hill, near Coventry. Several of them were a foot and a half 
 . -in diameter, and some yards in length, decidedly of conifer- 
 ous wood, and showing rings of annual growth.* Impres- 
 sions, also, of 'he footsteps of animals have been detected 
 in Lancashire dnd Cheshire in this formation. Some of the 
 most remarkable occur a few miles fi-om Liverpool, in the 
 whitish quartzose sandstone of Storton Hill, on the west side 
 of the Mersey. They bear a close resemblance to tracks 
 first observed in this member of the Upper New Red Sand- 
 stone, at the village of Hesseberg, near Hildburghausen, in 
 Saxony. For many years these foot- 
 prints have been referred to a large un- 
 known quadruped, provisionally named 
 Cheirotherium by Professor Kaup, be- 
 cause the marks both of the fore and 
 hind feet resembled impressions made 
 by a human hand. (See Fig. 394.) The 
 foot-marks at Hesseberg are partly con- 
 cave, and partly in relief, the former, or 
 the depressions, are seen upon the up- 
 „. , , per surface of the sandstone slabs, but 
 
 Single footstep of C/ieirotfie- ii,„„„ • r j:- i ii. i 
 
 rmm. Buntei-sandstein, those m reliei are Only upon the lower 
 
 nlffl'sizS"'*' "'"''"' "^ surfaces, being, in fact, natural casts, 
 
 formed in the subjacent foot-prints as 
 
 in moulds. The larger impressions, which seem to be those 
 
 of the hind foot, are generally eight inches in length, and five 
 
 in width, and one was twelve inches long. Near each large 
 
 Hg. 395. 
 
 Fig. 394. 
 
 Line of footsteps on slab of sandstone. Hildbnrghausen, in Saxony. 
 
 footstep, and at a regular distance (about an inch and a half) 
 before it, a smaller print of a fore foot, four inches long and 
 three mches wide, occurs. The footsteps follow each other 
 
 * Buckland, Proc. Geol. Soc, vol. ii., p. 439; and Murchisoh and Stiick- 
 land, Geol. Trans., Second Ser., vol. v., p. 347. 
 
FOOT-PRINTS OF THE TRIAS. 373 
 
 in pairs, each pair in the same line, at intervals of fourteen 
 inches from pair to pair. The large as well as the small steps 
 show the great toes alternately on the right and left side.; 
 each step makes the print of five toes, the first, or great toe, 
 being bent inward like a thumb. Though the fore and hind 
 foot difier so much in size, they are nearly similar in form. 
 
 As neither in Germany nor in England had any bones or 
 teeth been met with in the same identical strata as the foot- 
 steps, anatomists indulged, for several years, in various con- 
 jectures respecting the mysterious animals from which they 
 might have been derived. Professor Kaup suggested that 
 the unknown quadruped might have been allied to the Mar- 
 supialia; for in the kangaroo the first toe of the fore foot is 
 in a similar manner set obliquely to the others, like a thumb, 
 and the disproportion between the fore and hind feet is also 
 very great. But M. Link conceived that some of the four 
 species of animals of which the tracks had been found in 
 Saxony might have been gigantic Satrachiaris, and when it 
 was afterwards inferred that the Labyrlnthodon was an air- 
 breathing reptile, it was conjectured by Professor Owen that 
 ■it might be one and the same as the Cheirotherium. 
 
 Dolomitic Conglomerate of Bristol. — Near Bristol,_in Som- 
 ersetshire, and in other counties bordering the Severn, the 
 lowest strata belonging to the Triassic series consist of a 
 conglomerate or breccia resting unconformably upon the 
 Old Red Sandstone, and on different members of the Car- 
 boniferous rocks, such as the Coal Measures, Millstone Grit, 
 and Mountain Limestone. This mode of superposition will 
 be understood by reference to the section below Dundry Hill 
 (Fig. 85, p. 130), where No. 4 is the dolomitic conglomerate^ 
 Such breccias may have been partly the result of the sub- 
 aerial waste of an old land -surface which gradually sank 
 down and suffered littoral denudation in proportion as it be- 
 came submerged. The pebbles and fragments of older rocks 
 which constitute the conglomerate are cemented together by 
 a red or yellow base of dolomite, and in some places the en- 
 crinites and other fossils derived from the Mountain Lime- 
 stone are so detached from the parent rocks that they have 
 the deceptive appearance of belonging to a fauna contempo- 
 raneous with the dolomitic beds in which they occur. The 
 imbedded fragments are both rounded and angular, some 
 consisting of sandstone from the coal-measures, being of vast 
 size, and Veighing nearly a ton. Fractured bones and teeth 
 of saurians which are truly of contemporaneous origin are 
 dispersed through some parts of the breccia, and two of 
 these reptiles called Thecodont saurians, named from the 
 
374 ELEMENTS OF GEOLOGY. 
 
 manner in which the teeth were implanted in the jawbone, 
 obtained great celebrity because the patches of red conglom- 
 erate in which they were found, near Bristol, were originally 
 Fig 396 supposed to be of Permian or Palaeozoic age, 
 and therefore the only representatives in Eng- 
 land of vertebrate animals of so high a grade 
 in rocks of such antiquity. The teeth of these 
 saurians are conical, compressed, and with finely 
 serrated edges (see Fig. 396) ; they are referred 
 by Professor Huxley to the Dinosaurian order. 
 Origin of Red Sandstone and Rock-salt, — In 
 various parts of the world, red and mottled 
 '^doSosaL-Sr°3 <^l3,ys and sandstones, of several distinct geo- 
 ''"5^^^.,™*siii- logical epochs, are found associated with salt, 
 
 fled. Eileyand = r ' ■ t i. ' vu 
 
 stutchbary. gypsum, and magnesian limestone, or with one 
 ^ri^me^raTe" °'^ ^'^ °^ *'^^®^ substances. There is, therefore, 
 Eediana, ucai- in all likelihood, a general cause for such a co- 
 Biistoi. incidence. Nevertheless, we must not forget 
 
 that there are dense masses of red and variegated sand- 
 stones and clays, thousands offset in thickness, and of vast 
 horizontal extent, wholly devoid of saliferous or gypseous 
 matter. There are also deposits of gypsum and of common 
 salt, as in the blue-clay formation of Sicily, without any ac- 
 companying red sandstone or red clay. 
 
 These red deposits may be accounted for by the decompo- 
 sition of gneiss and mica schist, which in the eastern Gram- 
 pians of Scotland has produced a mass of detritus of precise- 
 ly the same color as the Old Red Sandstone. 
 
 It is a general fact, and one not yet accounted for, that 
 scarcely any fossil remains are ever preserved in stratified 
 rocks in which this oxide of iron abounds; and when we find 
 fossils in the N"ew or Old Red Sandstone in England, it is in 
 the gray, and usually calcareous beds, that they occur. The 
 saline or gypseous interstratified beds may have been pro- 
 duced by submarine gaseous emanations, or hot mineral 
 springs, which often continue to flow in the same spots for 
 ages. Beds of rock-salt are, however, more generally attribu- 
 ted to the evaporation of lakes or lagoons communicating at 
 intervals with the ocean. In Cheshire two beds of salt occur 
 of the extraordinary thickness of 90 or even 100 feet, and ex- 
 tending over an area supposed to be 150 miles in diameter. 
 The adjacent beds present ripple-marked sandstones and foot- 
 prints of animals at so many levels as to imply that the whole 
 area underwent a slow and gradual depression during the 
 formation of the red sandstone. 
 Major Harris, in his " Highlands of Ethiopia," describes a 
 
TRIAS OF GERMANY. 375 
 
 salt lake, called the Baliv Assal, near the Abyssinian front- 
 ier, which once formed the prolongation of the Gulf of Tad- 
 jara, but was afterwards cut off from the gulf by a broad bar 
 of lava or of land upraised by an earthquake. " Fed by no 
 rivers, and exposed in a burning climate to the unmitigated 
 rays of the sun, it has shrunk into an elliptical basin, seven 
 miles in its transverse axis, half filled with smooth water of 
 the deepest cserulean hue, and half with a solid sheet of glit- 
 tering snow-white salt, the offspring of evaporation." "If," 
 says Mr. Hugh Miller, " we suppose, instead of a barrier of 
 lava, that sand-bars were raised by the surf on a flat arena- 
 ceous coast during a slow and equable sinking of the surface, 
 the waters of the outer gulf might occasionally topple over 
 the bar, and supply fresh brine when the first stock had been 
 exhausted by evaporation." 
 
 The Runn of Cutch, as I have shown elsewhere,* is a low 
 region near the delta of the Indus, equal in extent to about 
 a quarter of Ireland, which is neither land nor sea, being dry 
 during part of every yeai', and covered by salt water during 
 the monsoons. Here and there its surface is incrusted over 
 with a layer of salt caused by the evaporation of sea-water. 
 A subsiding movement has been witnessed in this country 
 during earthquakes, so that a great thickness of pure salt 
 might result from a continuation of such sinking. 
 
 TEIAS OP GERMANY. 
 
 In Germany, as before hinted, p. 369, the Trias first re- 
 ceived its name as a Triple Group, consisting of two sand- 
 stones with an intermediate marine calcareous formation, 
 which last is wanting in England. 
 
 NOMENCLATUEE OP TEIAS. 
 
 German Prencli English 
 
 „ T,r ■ ■ n (Saliferous and gypseous 
 
 Keuper .... Marnes ins^es • ■ • j shales, and sandstone. 
 
 Muschelkalk . . . {M^^^';^}}^^; °;^ '=;'1'="'-^} Wanting i^ 
 
 _ , , . , (Sandstone and quartz- 
 
 Bnnter-sandstein . . Grfes bigarre . . . j ose conglomerate. 
 
 Keiiper. — The first of these, or the Keuper, underlying the 
 beds before described as Rhaetic, attains in Wtirtemberg a 
 thickness of about 1000 feet. It is divided by Albert! into 
 sandstone, gypsum, and carbonaceous clay-slate.f Remains 
 of reptiles called JVbthosaurus and Phytosawrus, have been 
 found in it with Labyrinthodon ; the detached teeth, also, of 
 
 * Principles of Geology, chap, xxvii. 
 t Monog. des Bunter-Sandsteins. 
 
376 
 
 ELEMENTS OF GEOLOGY. 
 
 Fig. SOT. 
 
 placoid fish and of Eays, and of the geuer'a Saurichthys and 
 
 Gyrokpis (Figs. 387, 388, p. 367). 
 The plants of the Keuper are ge- 
 nerically very analogous to those 
 of the oolite and lias, consisting of 
 ferns, equisetaceous plants,-cycads, 
 and conifers, with a few, doubtful 
 monocotyledons. A few species 
 such as JEJquisetites columnaris, are 
 common to this group and the 
 
 .^quise-tites columnaris. (Syo.Equi- OolitC. 
 
 8teXandTl™In portion of same St. Cossian and HaUstodt Beds 
 magnified. Kenper. (gge Map, Fig. 398). — The Sand- 
 
 stones and clay of the Keuper resemble the deposits of es- 
 tuaries and a shallow sea near the land, and afford, in the 
 N.W. of Germany, as in France and England, but a scanty 
 representation of the marine life of that period. We might, 
 however, have anticipated, from its rich reptilian fauna, that 
 the contemporaneous inhabitants of the sea of the Keuper 
 period would be very numerous, should we ever have an op- 
 portunity of bringing their remains to light. This, it is be- 
 lieved, has at length been accomplished, by the position now 
 assigned to certain Alpine rocks called the " St. Cassian beds," 
 
 Fig. 398. 
 
 the true place of which in the series was until lately a sub- 
 ject of much doubt and discussion. It has been proved that 
 the Hallstadt beds on the northern flanks of the Austrian 
 Alps correspond in age with the St. Cassian beds on their 
 southern declivity, and the Austrian geologists, M. Suess of 
 Vienna and others, have satisfied themselves that the Hall- 
 stadt formation is referable to the period of the Upper Trias. 
 
ST. CASSIAN ANn HALLSTADT BEDS. 
 
 ■Z11 
 
 Assuming this conclusion to be correct, we become acquainted 
 suddenly and unexpectedly with a rich 
 marine fauna belonging to a period pi'e- 
 
 Fig. 399. 
 
 be 
 
 Fig. 400. 
 
 Scolioetoma, St. Cassian. 
 
 Platystoma Stiesaii, 
 Hoi'Des. From 
 Hallstadt. 
 
 Fig. 401. 
 
 viously believed to 
 very barren of organic 
 remains, because in Eng- 
 land, France, and North- 
 ern Germany the upper 
 Trias is chiefly represent- 
 ed by beds of fresh or 
 brackish water origin. 
 About 600 species of invertebrate fossils occur in the Hall- 
 stadt and St. Cassian beds, many of which are still unde- 
 ficribed ; some of the 
 ■Mollusca are of new 
 and peculiar genera, as 
 Scoliostoma, Fig. 399, 
 and Platystoma, Fig. 
 400, among the Gaster- 
 opoda ; and Koninckia, 
 Fig. 401, among the 
 Brachiopoda. 
 
 The following table 
 of genera of maiine 
 shells from the Hall- 
 stadt and St. Cassian 
 beds, drawn up first on 
 the joint authority of M. Suess and the late Dr. Woodward, 
 and since corrected by Messrs. Etheridge and Tate, shows 
 how many connecting links between the fauna of primary 
 and secondary Palaeozoic and Mesozoic rocks are supplied 
 by the St. Cassian and Hallstadt beds. 
 
 GENERA OF FOSSIL MOLLUSCA IN THE ST. CASSIAN AND HALLSTADT BEDS. 
 
 Koninclda Lco7iJmrdi, Wissmaun. 
 a. Veutral view. Part of ventral valve removed" to 
 show the vascular impressions of dorsal valve. 
 b. Interior of dorsal valve, showing spiral proc- 
 esses restored, c. Vertical section of both valves. 
 Part shaded black showine place occupied by the 
 animal, and the dorsal valve following the curve 
 of the ventral. 
 
 Common to Older Rocks. 
 
 Cliaracteriatic Triassic Genera. 
 
 Common to Newer Rocks. 
 
 Orthoceras. 
 
 Ceratites. 
 
 Ammonites. 
 
 Bactrites. 
 
 Cochlocecas. 
 
 Chemnitxia. 
 
 Macrocheilns. 
 
 Choristoceras. 
 
 -eeritbium. 
 
 Loxonema. 
 
 Ehabdoceras. 
 
 Moribdonta. 
 
 Holopella. 
 
 Aulacocerae. 
 
 Opis. 
 
 
 * Scoliostoma. 
 
 Sphoera. 
 
 Mnrehisonia. 
 
 Natlcella. 
 
 Cardita. 
 
 Porcellia. 
 
 Platystoma, 
 
 Myoconcba. 
 
 Athyris. 
 
 Ptyohostoma. 
 
 Hinnites. 
 
 Eetzia. 
 
 Enchrysalis. 
 
 Monotis. 
 
 Cyrtina, 
 
 Halobia. 
 
 Plicatula. 
 
 Eaomphalus. 
 
 Homesia. 
 
 Amphiclina. 
 
 Koninckia. 
 ** Cassianella. 
 *' Myophoria. 
 
 Pacbyrisma. 
 Thecidium. 
 
 ' Reaches its maximum in the Trias, bul; passes down to older rocks. 
 " Keach their maximum in the Trias, but pass up to newerrocks. 
 
378 ELEMENTS OE GEOLOGY. 
 
 The first column marks the last appearance of several gen- 
 era which are characteristic of Paleozoic strata. The second 
 shows those genera which are characteristic of the Upper 
 Trias, either as peculiar to it, or, as in the three cases mark- 
 ed by asterisks, reaching their maximum of development at 
 this era. The third column marks the first appearance in 
 Triassic rocks of genera destined to become more abundant 
 in later ages. 
 
 It is only, however, when we contemplate the number of 
 species by wliich each of the above-mentioned genera are 
 represented that we comprehend the peculiarities of what is 
 commonly called the St. Cassian fauna. Thus, for example, 
 the Ammonite, which is not common to older rocks, is repre- 
 sented by no less than seventy-three species ; whereas Loxo- 
 nema, which is only known as common to older rocks, fur- 
 nishes fifteen Triassic species. Cerithium, so abundant in ter- 
 tiary strata, and which still lives, is represented by no less 
 than fourteen species. As the Orthoceras had never been 
 met with in the marine Muschelkalk, much surprise was nat- 
 urally felt that seven or eight species of the genus should 
 appear in the Hallstadt beds, assuming these last to belong 
 to the Upper Trias. Among these species are some of large 
 dimensions, associated with large Ammonites with foliated 
 lobes, a form never seen before so low in the series, while 
 the Orthoceras had never been seen so high. 
 
 On the whole, the rich marine fauna of Hallstadt and St. 
 Cassian, now generally assigned to the lowest members of 
 the Upper Trias or Keuper, leads us to suspect that when 
 the strata of the Triassic age are better known, especially 
 those belonging to the period of the Bunter sandstone, the 
 break between the Palaeozoic and Mesozoic Periods may be 
 almost effaced. Indeed some geologists are not yet satisfied 
 that the true position of the St. Cassian beds (containing so 
 great an admixture, of types, having at once both Mesozoic 
 and Palaeozoic affinities) is made out, and doubt whether 
 they have yet been clearly proved to be newer than the 
 Muschelkalk. 
 
 Muschelkalk. — The next member of the Trias in Germany, 
 the Muschelkalh, which underlies the Keuper before described, 
 consists chiefly of a compact grayish limestone, but includes 
 beds of dolomite in many places, together with gypsum and 
 rock-salt. This limestone, a formation wholly unrepresent- 
 ed in England, abounds in fossil shells, as the name implies. 
 Among the Cephalopoda there ai-e no belemnites, and no am- 
 monites with foliated sutures, as in the Lias, and Oolite, and 
 the Hallstadt beds; but we find instead a genus allied to 
 
MUSCHELKALK AND FOSSILS. 
 
 379 
 
 the Ammonite, called Ceratites by De Haan, in which the 
 descending lobes (Fig. 402) terminate in a few small deu- 
 
 Fig. 402. 
 
 Fig. 403. 
 
 Ceratites nodosnis, Schloth. Mnschelknlk, Gerranny. Gervillia {Avieula) mewlis, 
 Side and frout view, showing the denticulated out- Schloth. Characteristic 
 
 line of the septa dividing the chambera.. shell of the MuBchelkalk. 
 
 ticulations pointing inward. Among the bivalve Crustacea, 
 the Estheria miiiuta, Bronn (see Fig. 390, p. 370), is abun- 
 
 Fig. 404. 
 
 Fig. 405. 
 
 Erurimts lilii/ormis, Schlott. Syn. E. monili- 
 formis. Body, arms, and part of stem. 
 a. Section of stem. Muschelkalk. 
 
 Aspidura loricata, Agass. 
 
 a. Upper side. b. Lower side. 
 
 Muschelkalk. 
 
 dant, ranging through the Keuper, Muschelkalk, and Bunter- 
 sandstein; and Gervillia socialis (Fig. 403), having a similar 
 range, is found in great numbers in the Muschelkalk of Ger- 
 many, France, and Poland. 
 
380 
 
 ELEMENTS OE GEOLOGY. 
 
 Fig. 406. 
 
 Palatal teeth of Placodus gigas. 
 Muschelkalk. 
 
 The abundance of the heads and stems of lily encrinites, 
 Micrinus Uliifdrmis (Fig. 404), {oi- Encrinites moniliformis), 
 shows the slow manner in which some beds of this lime- 
 stone have been formed in clear 
 sea -water. The star -fish called 
 Aspidura loricata (Fig. 406) is as 
 yet peculiar to the Muschelkalk. 
 In the same formation are found 
 the skull and teeth of a reptile of 
 the genus Placodus (see Fig. 406), 
 which was referred originally by 
 Munster, and afterwards by Agas- 
 siz, to the class of fishes. But 
 more perfect specimens enabled 
 Professor Owen, in 1858, to show 
 that this fossil animal was a Sau- 
 rian reptile, which probably fed on 
 shell-bearing mollusks, and used its 
 short and flat teeth, so thickly coated with enamel, for 
 pounding and crushing the shells. 
 
 Bunter-sandstein. — The JBunter-sandstein consists of vari- 
 ous-colored sandstones, dolomites, and red clays, with some 
 beds, especially in the Hartz, of calcareous pisolite or roe- 
 stone, the whole sometimes attaining a thickness of more 
 than 1000 feet. The sandstone of the Vosges is proved, by 
 its fossils, to belong to this lowest member of the Triassic 
 group. At Sulzbad (or Soultz-les-bains), near Strasburg, on 
 the flanks of the Vosges, many 
 plants have been obtained from 
 the "hunter," especially conifers 
 of the extinct genus Voltzia, of 
 which the fructification has been 
 preserved. (See Fig. 407). Out 
 of thirty species of ferns, cycads, 
 conifers, and other plants, enum- 
 erated by M. Ad. Brongniart, in 
 1 849, as coming' from the " Gr6s 
 bigarre," or Bunter, not one is ^ li^tZimT&i^^oil^^ 
 
 common to the Keuper. masuifled to show fractiflcalion. 
 
 The foot-prints of Labyrintho- ^"'^'""'- B«"ter-sandstein. 
 
 don observed in the clays of this formation at Hildburg- 
 hausen, in Saxony, have already been mentioned. Some 
 idea of the variety and importance of the terrestrial verte- 
 brate fauna of the three members of the Trias in Northern 
 Germany may be derived from the fact that in the great 
 monograph by the late Hermann von Meyer on the reptiles 
 
 Fig. 40T. 
 
TRIAS OF THE UNITED STATES. 
 
 381 
 
 of the Trias, the remains of no less than eighty distinct 
 species are described and figured. 
 
 TEIAS OF THE UNITED STATES. 
 
 New Red Sandstone of the Valley of the Connecticut River. 
 — In a depression of the granitic or hypogene rocks in the 
 States of Massachusetts and Connecticut strata of red sand- 
 stone, shale, and conglomerate are found, occupying an area 
 more than 150 miles in length from north to south, and about 
 five to ten miles in breadth, the beds dipping to the east- 
 ward at angles varying from 5 to 50 degrees. The extreme 
 inclination of 50 degrees is rare, and only observed in the 
 neighborhood of masses of trap vrhich have been intruded 
 into the red sandstone vs^liile it was forming, or before the 
 newer parts of the deposit had been com- Fig. 403. 
 pleted. Having examined this series of 
 rocks in many places, I feel satisfied that 1 . «• v 
 
 they were formed in shallow water, and for "" 
 
 the most part near the shore, and that some 
 of the beds were from time to time raised 
 above the level of the water, and laid dry, 
 while a newer series, composed of similar 
 sediment, was forming. 
 
 According to Professor Hitchcock, the foot- 
 prints of no less than thirty-two species of 
 bipeds, and twelve of quadrupeds, have been 
 already detected in these rocks. Thirty of 
 these are believed to be those of birds, four 
 of lizai'ds, two of chelonians, and six of ba- 
 trachians. The tracks have been found in 
 more than twenty places, scattered through 
 an extent of nearly 80 miles from north to 
 south, and they are repeated through a suc- 
 cession of beds attaining at some points a 
 thickness of more than 1000 feet.* 
 
 The bipedal impressions are, for the most 
 part, trifid, and show the same number of 
 joints as exist in the feet of living tridactyl- 
 ous birds. Now, such'birds have three pha- 
 langeal bones for the inner toe, four for the 
 middle, and five for the outer one (see Fig. Foot-prints of a bii-a, 
 
 ,„„, 2 ,, . . r ^x. \ • 1 Turner's Falls, Val- 
 
 408) ; but the impression ot the terminal jey of the Couuec- 
 joint is that of the nail only. The fossil *'™t- 
 ibot-prints exhibit regularly, where the joints are seen, the 
 same number ; and we see in each continuous line of tracks 
 * Hitchcock. Mem. of Amer. Acad., New Series, vol. iii., p. 129. 1848. 
 
 m < 
 
382 ELEMENTS OF GEOLOGY. 
 
 the three-jointed and five-pinted toes placed alternately out- 
 ward, first on the one side, and then on the other. In some 
 specimens, besides impressions of the three toes in front, the 
 rudiment is seen of the fourth toe behind. It is not often 
 that the matrix has been fine enough to retain impressions 
 of the integument or skin of the foot ; but in one fine speci- 
 men found at Turner's Falls, on the Connecticut, by Dr. 
 Deane, these markings are well preserved, and have been 
 recognized by Professor Owen as resembling the skin of the 
 ostrich, and not that of reptiles. 
 
 The casts of the foot-prints show that some of the fossil 
 bipeds of the red sandstone of Connecticut had feet four times 
 as large as the living ostrich, but scarcely, perhaps, larger 
 than the Dinornis of New Zealand, a lost genus of feathered 
 giants related to the Apteryx, of which there were many spe- 
 cies which have left their bones and alnios.t entire skeletons 
 in the superficial alluvium of that island. By referring to 
 what was said of the Iguanodon of the Wealden, the reader 
 will perceive that the Dinosaur was somewhat intermediate 
 between reptiles and birds, and left a series of tridactylous 
 impressions on the sand. 
 
 To determine the exact age of the red sandstone and 
 shale containing these ancient foot-prints, in the United States, 
 is not possible at present. No fossil shells have yet been 
 found in the deposit, nor plants in a determinable state. The 
 fossil fish are numerous and very perfect; but they are of a 
 peculiar type, called Ischy2yterus, by Sir Philip Egerton, from 
 the great size and strength of the fulcral rays of the dorsal 
 fin, from lax^Q, strength, and -irrepov, a fin. 
 
 The age of the Connecticnt beds can not be proved by di- 
 rect superposition, but may be presumed from the general 
 structure of the country. That structure proves them to be 
 newer than the movements to which the Appalachian or Al- 
 leghany chain owes its flexures, and this chain includes the 
 ancient or palaeozoic coal - formation among its contorted 
 rocks. 
 
 Coal-field of Richmond, Virginia. — In the State of Virginia, 
 at the distance of about 1 3 miles eastward of Richmond, the 
 capital of that State, there is a coal-field occurring in a de- 
 pression of the granite rocks, and occupying a geological po- 
 sition analogous to that of the New Red Sandstone, above 
 mentioned, of the Connecticut valley. It extends 26 miles 
 from north to south, and from four to twelve from east to 
 Avest. 
 
 The plants consist chiefly of zamites, calamites, equisetS, 
 and ferns, and, upon the whole, are considered by Professor 
 
TRIASSIC MAMMIFER. 
 
 383 
 
 Heer to have the nearest affinity to those of the European 
 Keuper. 
 
 The equiseta are very commonly met with in a vertical 
 position more or less compressed perpendicularly. It is 
 clear that they grew in the places where they are now 
 buried in strata of hardened sand and mud. I found them 
 maintaining their erect attitude, at points many miles apart, 
 in beds both above and between the seams of coal. In order 
 to explain this fact, we must suppose such shales and sand- 
 stones to have been gradually accumulated during the slow 
 and repeated subsidence of the whole region. 
 
 The fossil fish are Ganoids, some of them of the genus 
 Catopterus, others belonging to the liassic genus Tetragono- 
 lepis {^chmodus), see Fig. „. ^^^ 
 
 376, p. 358. Two species " 
 
 of Mitomostraca called Es- 
 theria are in such profusion 
 in some shaly beds as to 
 divide them like the plates ^^^^^^^M ">^ 
 of mica in micaceous shales 
 (see Fig. 409). 
 
 These Virginian coal- 
 measures are composed of d- dlKS^ "^^OMci 
 grits, sandstones, and 
 
 shales, exactly resembling Triassiccoal-shale.Eichmond, Virginia. 
 those Ot older or primary a. Bsthma ovata. 6. Tming of same. c. Na1> 
 date in America and Eu- uralsizeofo. d. Natural size of 6. • 
 
 rope, and they rival, or even surpass, the latter in the richness 
 and thickness of the coal-seams. One of these, the main seam, 
 is in some places from 30 to 40 feet thick, composed of pure 
 bituminous coal. The coal is like the finest kinds shipped at 
 N"ewcastle, and when analyzed yields the same proportions 
 of cai-bon and hydrogen — a fact worthy of notice, when we 
 consider that this fuel has been derived from an assemblage 
 of plants very distinct specifically, and in part generically, 
 from those which have contributed to the formation of the 
 ancient or palaeozoic coal. 
 
 Triassic Mammifer. — In North Cai-olina, the late Professor 
 Emmons has described the strata of the Chatham coal-field, 
 which correspond in age to those near Richmond, in Virginia. 
 In beds underlying them he has met with three jaws of a 
 small insectivorous mammal which he has called jDromathe- 
 rium sylvestre, closely allied to Spalacotfiermm. Its near- 
 est living analogue, says Professor Owen, "is found in Myr- 
 mecobius ; for each ramus of the lower jaw contained ten 
 small molars in a continuous series, one canine, and- three 
 
384 ELEMENTS OF GEOLOGY. 
 
 conical incisors — the latter being divided hj short inter- 
 vals." 
 
 Low Grade of Early Mammals favorable to the Theory of 
 Progressive Development. — There is every reason to believe 
 that this fossil quadruped is at least as ancient as the Micro- 
 lestes of the European Trias above described, p. 368 ; and 
 the fact is highly important, as proving that a certain low 
 grade of marsupials had not only a wide range in time, from 
 the Trias to the Purbeok, or uppermost oolitic strata of Eu- 
 rope, but had also a wide range in space, namely, from Europe 
 to North America, in an east and west direction, and, in re- 
 gard to latitude, frdm Stonesfield, in 52° K, to that of North 
 (Oaroliria, 35° N. 
 
 If the three localities in Europe where the most ancient 
 mammalia have been found — Purbeck, Stonesfield, and Stutt- 
 gart — had belonged all of them to formations of the same 
 age, we might well have imagined so limited an area to have 
 been peopled exclusively with pouched quadrupeds, just as 
 Australia now is, while other parts of the globe were inhabit- 
 ed by placentals ; for Australia now supports one hundred 
 and sixty species of marsupials, while the rest of the conti- 
 nents and islands are tenanted by about seventeen hundred 
 species of mammalia, of which only forty-six are marsupial, 
 namely, the opossums of North and South America. But 
 the great difference of age of the strata in each of these three 
 localities seems to indicate the predominance throughout a 
 vast lapse of time (from the era of the Upper Trias to that 
 of the Purbeck beds) of a low grade of quadrupeds ; and this 
 persistency of similar generic and ordinal types in Europe 
 while the species were changing, and while the fish, reptiles, 
 and mollusca were undergoing great modifications, would 
 naturally lead us to suspect that thei-e must also have been 
 avast extension in space of the same marsupial forms during 
 that portion of the Secondary or Mesozoic epoch which has 
 been termed " the age of reptiles." Such an inference as to 
 the wide geographical range of the ancient marsupials has 
 been confirmed by the discovery in the Trias of North Amer- 
 ica of the above-mentioned Dromatherium. The predomi- 
 nance in earlier ages of these mammalia of a low grade, and 
 the absence, so far as our investigations have yet gone, of 
 species of higher organization, whether aquatic or terrestrial, 
 is certainly in favor of the theory of progressive development. 
 
PASSAGE FROM SECOND ABY TO PRIMARY BOCKS. 385 
 
 PRIMAEY OR PALAEOZOIC SERIES. 
 
 CHAPTER XXII. 
 
 PEEMIAK OE MAGNESIAS LIMESTONE GEOTJP. 
 
 Line of Separation between Mesozoic and Palajozoic Rocks. — Distinctness 
 of Triassic and Permian Fossils.^ — Term Permian. — Thickness of calcare- 
 ous and sedimentary Rocks in North of England. — Upper, Middle, and 
 Lower Permian. — Marine Shells and Corals of the English MagneBian 
 Limestone. — Reptiles and Pish of Permian Marl -slate. — ^Foot- prints of 
 Reptiles. — ^A.ugular Breccias in Lower Permian.— Permian Rocks of the 
 Continent. — Zechstein and Rothliegendes of Thuringia. — Peimian Flora. 
 — Its generic Affinity to the Carboniferous. 
 
 Iisr pursuing our examination of the strata in descending 
 order, w:e have next to pass from the base of the Secondary 
 or Mesozoic to the uppermost or newest of the Primary or 
 Palaeozoic formations. As this point has been selected as a 
 line of demarkatioa for one of the three great divisions of the 
 fossiliferous series, the student might naturally expect that 
 by aid of lithological and palseontological characters he 
 would be able to recognize without difficulty a distinct 
 break between the newer and older group. But so far is 
 this from being the case in Great Britain, that nowhere have 
 geologists found more difficulty in drawing a line of separa- 
 tion than between the Secondary and Primary series. The 
 obscurity has arisen from tho great resemblance in color and 
 mineral character of the Triassic and Permian red marls and 
 sandstones, and the scarcity and often total absence in them 
 of oi-ganic remains. The thickness of the strata belonging 
 to each group amounts in some places to several thousand 
 feet ; arid by dint of a careful examination of their geologi- 
 cal position, and of those fossil, animal, and vegetable forms 
 which are occasionally met with in some members of each 
 series, it has at length been made cleat that the older or 
 Permian rocks are more connected with the Primary or Pa- 
 laeozoic than with the Secondary or Mesozoic strata already 
 described. 
 
 ■ The term Permian has been proposed for this group by 
 
 17 
 
386 ELEMENTS OE GEOLOGY. 
 
 Sir R. Mui'chison, from Perm, a Russian province, where it 
 occupies an area twice the size of France, and contains a 
 great abundance and variety of fossils, both vei'tebrate and 
 invertebrate. Professor Sedgwick in 1832* described what 
 is now recognized as the central member of this group, the 
 Magnesian limestone, showing that it attained a thickness 
 of 600 feet along the north-east of England, in the counties 
 of Durham, Yorkshire, and Nottinghamshire, its lower part 
 often passing into a fos'siliferous marl-slate and resting on an 
 inferior Red Sandstone, the equivalent of the Rothliegendes 
 of Germany. It has since been shown that some of the Red 
 Sandstones of newer date also belong to the Permian group ; 
 and it appears from the observations of Mr. Binney, Sir R. 
 Murchison, Mr. Harkness, and others, that it is in the region 
 where the limestone is most largely developed, as, for exam- 
 ple, in the county of Durham, that the associated red sand- 
 stones or sedimentary rocks are thinnest, whereas in the 
 country where the latter are thickest the calcareous mem- 
 ber is reduced to thirty, or even sometimes to ten feet. It 
 is clear, therefore, says Mr. Hull, that the sedimentary region 
 in the north of England area has been to the westward, and 
 the calcareous area to the eastward ; and that in this group 
 there has been a develojament from opposite directions of 
 the two types of strata. 
 In illustration of this he has given ns the following table : 
 
 THICKNESS or PEEMIAl*' STEATA IN NOETH OP ENGLAND. 
 
 N.W. ofEDglaud. 
 
 N.B. of England, 
 
 Feet. 
 
 Feet. 
 
 600 
 
 50-100 
 
 . 10-30 
 
 600 
 
 . 3000 
 
 100-250t 
 
 Upper Permian (Sedimentary) . 
 Middle " (Calcareous) . 
 Lower " (Sedimentary) . 
 
 Upper Permian. — What is called in this table the Upper 
 Permian will be seen to attain its chief thickness in the 
 north-west, or on the coast of Cumberland, as at St. Bee's 
 Head, where it is described by Sir Roderick Murchison as 
 consisting of massive red sandstones with gypsum resting 
 on a thin course of Magnesian Limestone with fossils, which 
 again is connected with the Lower Red Sandstone, resem- 
 bling the upper one in such a manner that the whole forms 
 a, continuous series. No fossil foot-prints have been found 
 in this Upper as in the Lower Red Sandstone. 
 
 * Trans. Geol. Soc. Lond., Second Series, vol. iii., p. 37. 
 t Edward Hull, Ternary Classification, Quart. Journ. of Science, No. xxiii.. 
 1869, 
 
MAGNESIAN LIMESTONE AND MARL SLATE. 387 
 
 Middle Permian— Magnesian Limestone and Marl-slate. — 
 This formation is seen upon the coast of Durham and York- 
 shire, between the Wear and the Tees. Among its charac- 
 
 Fig. 410. Pig. 411. Pig. 412. 
 
 Schizodus Schlotheimij Geinitz. The hinge of Schizodus MytUus septifcr^ King. 
 Permian crystalline lime- irMncotiM, King. Per- Syn. Modiola acumi- 
 
 stone. mian. nata, Sow. Permian 
 
 crystalline limestone. 
 
 teristio fossils are Schizodus Schlotheimi (Fig. 410) and My- 
 tilus septifer (Fig. 412). These shells occur at Hartlepool 
 and Sunderland, where the rock assumes an oolitic and bo- 
 tryoidal character. Some of the beds in this division are 
 ripple - marked. In some parts of the coast of Durham, 
 where the rock is not crystalline, it contains as much as 44 
 per cent, of carbonate of magnesia, mixed with carbonate 
 of lime. In other places — for it is extremely variable in 
 structure — it consists chiefly of carbonate of lime, and has 
 concreted into globular and hemispherical masses, varying 
 from the size of a marble to that of a cannon-ball, and radi- 
 ating from the centre. Occasionally earthy and pulverulent 
 beds pass into compact limestone or hard granular dolomite. 
 Sometimes the limestone appears in a brecciated form, the 
 fragments which are united together not consisting of for- 
 eign rocks but seemingly composed of the breaking-up of 
 the Permian limestone itself, about the time of its consoli- 
 dation. Some of the angular masses in Tynemouth cliff are 
 two feet in diameter. 
 
 The magnesian limestone sometimes becomes very fossilif- 
 erous and includes in it delicate bryozoa, one of which, Jfhtie- 
 stella retiformis (Fig. 413), is a very variable species, and has 
 received many diiFerent names. It sometimes attains a large 
 size, single specimens measuring eight inches in width. The 
 same bryozoan, with several other British species, is also 
 found abundantly in the Permian of Germany. 
 
 The total known fauna of the Permian series of Great Brit- 
 ain at present numbers 147 species, of which 77, or more than 
 half, are mollusca. Not one of these is common to rocks 
 newer than the Palaeozoic, and the brachiopods are the only 
 group which have furnished species common to the more an- 
 cient or Carboniferous rocks. Of these lAnr/ula Crednerii 
 
388 
 
 ELEMENTS OF GEOLOGY. 
 Fig. 413. 
 
 Magnesian Limestone, Hnmbleton Hill, near Sumiei'laud.* 
 
 a. Femstella retiformis, Schlot, sp. Syii. Gorgonia infnndibuliformis, Go\it; 
 
 Iteteporafiustrmm, Phillips. 6. Part of the same highly magnified. 
 
 (Fig. 415) is an example. Tliere are 25 gasteropods and only 
 one cepbalopod, Nautilus Freieskbeni, which is also found in 
 the German Zechstein. 
 
 Shells of the g&a&ca. ProdMCtus (Fig. 414) and jStro23halosia 
 (the latter of allied form with hinge teeth), which do not oc- 
 cur in strata newer than the Permian, are abundant in the 
 ordinary yellow magnesian limestone, as will be seen in the 
 valuable memoirs of Messrs. King and Howse. They are ac- 
 companied by certain species of Spirifera (Fig. 416), lAngida 
 Crednerii (Fig. 415), and other brachiopoda of the true pri- 
 mary or palaeozoic type. Some of this same tribe of shells, 
 kiuch as (Jamarophoria, allied to Rhynchonella, Spiriferina, 
 and two species of Lingula, are specifically the same as fos- 
 sils of the carbonifei-ous rocks. Avicula, Area, and Schizo- 
 dus (Fig. 410), and other lamellibranchiate bivalves, are abun- 
 dant, but spiral univalves are very rare. 
 
 Fig. «4. 
 
 Fig. 416. 
 
 Fig. 415. 
 
 Lingula CredTwrii. 
 (Geinitz.) Mag- 
 nesian Lime- 
 Productits lutrridus, Sowerby. stODC, and Car- 
 (F.calvus, Sov/.) Sunderland boniferons Marl- 
 and Durham, in Magnesian slate, Durham ; 
 Limestone; Zechstein and Zechstein, Thu- 
 Kupferschiefer, Germany. ringia. 
 
 Beneath the limestone lies a formation termed the marl- 
 slate, which consists of hard calcareous shales, raarl-slate, and 
 thin-bedded limestones. At East Thickley, in Durham, where 
 
 * King's Monograph, 1*1. 2. 
 
 Spirifera alata, Schloth. Syn. 
 Trigffrwtreta urviulata^ Sow., 
 King's Mouogr. Magnesian 
 Limestone. 
 
MAGNESIAN LIMESTONE AND MARL SLATE. 389 
 
 it is thirty feet thick, this slate has yielded many fine speci- 
 mens of fossil fish — of the genera Palceoniscus ten species, 
 Pygopterus two species, Goelacanthus two species, and Pla- 
 tysomus two species, which as genera are common to the old- 
 er Carboniferous formation, but the Permian species are pe- 
 culiar, and, for the most part, identical with those found in 
 the marl-slate or copper-slate of Thuriugia. 
 
 Fig. 41T. 
 
 Eestoved outline of a flsli of the genus Palmoniscvs, Agas?. 
 PaXosothrissum^ Blainville. 
 
 The Palceoniscus above mentioned belongs to that division 
 of fishes which M. Agassiz has called " Heterocercal," which 
 have their tails unequally bilobate, like the recent shark and 
 sturgeon, and the vertebral column running along the upper 
 
 Eig. 418. Fig. 419. 
 
 Shark. Heterocercal. Shad. (Clupea. Herring trihe.) 
 
 Homocercal. 
 
 caudal lobe. (See Fig. 41 8.) The " Homocercal " fish, which 
 comprise almost all the 9000 species at present known in the liv- 
 ing creation, have the tail-fin either single or equally divided; 
 and the vertebral column stops short, and is not prolonged 
 into either lolbe. (See Fig. 419.) Now it is a singular fact, 
 first pointed out by Agassiz, that the heterocercal form, which 
 is confined to a small number of genera in the existing crea- 
 tion, is universal in the magnesian limestone, and all the more 
 ancient formations. It characterizes the earlier periods of 
 the earth's history, whereas in the secondary strata, or those 
 newer than the Permian, the homocercal tail predominates. 
 
 A full description has been given by Sir Philip Egerton of 
 the species of fish characteristic of the marl-slate, in Prof. 
 King's monograph before referred to, where figures of the 
 
390 
 
 ELEMENTS OF GEOLOGY. 
 
 ichthyolites, which are very entire and well preserved, will 
 be found. Even a single scale is usually so characteristically 
 marked as to indicate the genus, and sometimes even the par- 
 ticular species. They are often scattered through the beds 
 singly, and may be useful to a geologist in determining the 
 age of the rock. 
 
 SCAIES OP FISH. 
 Fig. 420. Fig. 421. 
 
 MAGNBSIAlSr LIMESTONE. 
 
 Fig. 422. Pig. 423. 
 
 Fig. 420. PaUeonisms comptus, Agassiz;. Scale, magnifled. Mai^slate -Pif,'. 421. Po- 
 LmUaus Oegana, Sedg. Under surface of scale, magnified. Marl-slate.-Fig. 422. 
 Pcacemiismsglaphyrm, Ag. Undei- surface of scale, magnified. Marl-slate.-Fig. 
 423. Ccelacanthus gramdatus, Ag. Granulated surface c? scale, magnified. Mail- 
 slate. „. ,„„ 
 Pig. 424 ^S- 42S. 
 
 Pygopterus mandilmlaris, Ag. Marl-slate. 
 a. Outside of scale, magnified. 6. Un- 
 der surface of same. 
 
 Acrolepis Sedgwichii, Ag. Out- 
 side of scale, magnified. 
 Marl-slate. 
 
 We are indebted to Messrs. Hancock and Howse for the 
 discovery in this marl-slate at Midderidge, Durham, of two 
 species of Protorosaurus, a genus of reptiles, one representa- 
 tive of which, P. Speneri, has been celebrated ever since the 
 year 1810 as characteristic of the Kupfer-schiefer or Permian 
 of Thuringia. Professor Huxley informs us that the agree- 
 ment of the Durham fossil with Hermann von Meyer's figure 
 of the German specimen is most striking. Although the 
 head is wanting in all the examples yet found, they clearly 
 belong to the Lacertian order, and are therefore of a higher 
 grade than any other vertebrate animal hitherto found fossil 
 in a Palaeozoic rock. Remains of Labyrinthodont reptiles 
 have also been met with in the same slate near Durham. 
 
 Lower Permian. — Tlie inferior sandstones which lie beneath 
 the marl-slate consist of sandstone and sand, separating the 
 Magnesian Limestone from the coal, in Yorkshire and Dur- 
 ham. In some instances, red marl and gypsum have been 
 found associated with these beds. The?r have been classed 
 
PERMIAN EOCKS OF THE CONTINENT. ggl 
 
 with the Magnesian Limestone by Professor Sedgwick, as be- 
 ing nearly co-extensive with it in geographical range, though 
 their relations are very obscure. But the principal develop- 
 ment of Lower Permian is, as we have seen by Mr. Hull's 
 table, p. 386, in the northwest, where the Penrith sandstone, 
 as it has been called, and the associated breccias and purple 
 shales are estimated by Professor Harkness to attain a thick- 
 ness of 3000 feet. Organic remains are generally wanting, 
 but the leaves and wood of coniferous plants, and in one case 
 a cone, have been found. Also in the purple marls of Corn- 
 cockle Muir near Dumfries, very distinct foot-prints of rep- 
 tiles occur, originally referred to the Trias, but shown by 
 Mr. Binney in 1856 to be Permian. No bones of the animals 
 which they represent have yet been discovered. 
 
 Angular Sreccias in Lower Permian. — A striking feature 
 in these beds is the occasional occurrence, especially at the 
 base of the formation, of angular and sometimes rounded 
 fragments of Carboniferous and older rocks of the adjoining- 
 districts being included in a paste of red marl. Some of the 
 angular masses are of huge size. 
 
 In the central and southern counties, where the Middle 
 Permian or Magnesian Limestone is wanting, it is diflScult to 
 separate the upper and lower sandstones, and Mr. Hull is of 
 opinion that the patches of this formation found here and 
 there in Worcestershire, Shi'opshire, and other counties may 
 have been deposited in a sea separated from the northern 
 basin by a barrier of Carboniferous rocks running east and 
 west, and now concealed under the Triassic strata of Chesh- 
 ire. Similar breccias to those before described are found 
 in the more southern counties last mentioned, where their 
 appearance is rendered more striking by the marked contrast 
 they present to the beds of well-rolled and rounded pebbles 
 of the Trias occupying a large area in the same region. 
 
 Professor Ramsay refers the angular form and large size 
 of the fragments composing these breccias to the action of 
 floating ice in the sea. These masses of angular rock, some 
 of them weighing more than half a ton, and lying confusedly 
 in a red, unstratified marl, like stones in boulder-drift, are in 
 some cases polished, striated, and furrowed like erratic blocks 
 in the moraine of a glacier. They can be shown in some 
 cases to have travelled from the parent rocks, thirty or more 
 miles distant, and yet not to have lost their angular shape.* 
 
 Permian Eocks of the Continent. — Germany is the classic 
 ground of the Magnesian Limestone now called Permian. 
 
 * Ramsay, Quart. Geo!. Joum., 1855 ; and Lyell, Principles of Geology, 
 vol. i., p. 223, 10th edit. 
 
392 
 
 ELEMENTS OE GEOLOGY. 
 
 The formation was well studied by the miners of that coun- 
 try a century ago as containing a thin band of dark-colored 
 cupriferous shale, characterized at Mansfield in Thuringia by 
 numerous fossil fish. Beneath some variegated sandstones 
 (not belonging to the Trias, though often confounded with it) 
 they came down first upon a dolomitic limestone correspond- 
 ing to the upper part of our Middle Permian, and then upon 
 a marl-slate richly impregnated with copper pyrites, and con- 
 taining fish and reptiles (Protorosaurus) identical in species 
 with those of the corresponding marl-slate of Durham. To 
 the limestone they gave the name of Zeehstein, and to the 
 marl-slate that of Mergel-schiefer or Kupfer-schiefer. Be- 
 neath the fossiliferous group lies the Rothliegendes or Roth- 
 todt-liegendes, meaning the red-Iyer or red-dead-Iyer, so called 
 by the German miners from its color, and because the cop- 
 per had died out when they reached this underlying non- 
 metalliferous member of the series. This red under-lyer is, 
 in fact, a great deposit of red sandstone, breccia, and con- 
 glomerate with associated porphyry, basalt, and amygdaloid. 
 
 According to Sir R. Murchison, the Permian rocks are com- 
 posed, in Russia, of white limestone, with gypsum and white 
 salt ; and of red and green grits, occasionally with copper 
 ore ; also magnesian limestones, marlstones, and conglomer- 
 ates. 
 
 Permian Flora. — About 18 or 20 species of plants are 
 known in the Permian rocks of England. None of them pass 
 
 Fig. 426. 
 
 WalcMa pimformis, Scliloth. Pemiiari, SaxoDy. (Gutbier, Die Voi'steinerangen 
 
 des Permischen Systemes in Sachsen, vol. ii., pi. 10.) 
 
 a, Blanch. b. Twig of the same. c. Leaf magnified. 
 
 down into the Carboniferous series, but several genera, such 
 as Alethopteris, Weuropteris, Walchia, and Jlllmania, are com- 
 mon to the two groups. The Permian flora on the Continent 
 appears, from the researches of MM. Murchison and de Ver- 
 
PERMIAN FLORA. 
 
 393 
 
 neuil in Russia, and of MM. Geinitz and von Gutbier in Sax- 
 ony, to- be, with a few exceptions, distinct from that of the 
 coal. 
 
 In the Permian rocks of Saxony no less than 60 species of 
 fossil plants have been met with. Two or three of these, as 
 Fig.42T. Calamites gigas, Sphenopteris erosa, and S. lo- 
 bata, are also met with in the government of 
 Perm in Russia. Seven others, and among 
 them Newopteris Loshii, Peeopteris arhorescens, 
 and P. similis, and several species of Walchia 
 (see Fig. 426), a genus of Conifers, called Ly- 
 Cardioearpan ot- copodites by some authors, are said by Geinitz 
 p^raian" s^^- to be common to the coal-measures, 
 ony. idiam. Among the genera also enumerated by Colonel 
 Gutbier are the fruit called Cardiocarpon (see Fig. 427), ^s- 
 terophyllites, and Anmdaria, so characteristic of the Carbon- 
 iferous period; sdso JOepidodendron, which 
 is common to the Permian of Saxony, Thu- 
 ringia, and Russia, although not abundant. 
 JVbeggerathia (see Fig. 428), the leaves of 
 which have parallel veins without a mid- 
 rib, and to which various generic syno- 
 nyms, such as Cordaites, Flabellaria, zwA 
 Poacites, have been given, is another link 
 between the Permian and Carboniferous 
 vegetation. Coniferas, of the Araucarian 
 division, also occur; but these are like- 
 wise met with both in older and newer 
 rocks. The plants called Sigillaria and 
 Stigmaria, so marked a featui-e in the 
 Carboniferous period, are as yet wanting 
 iu the true Permian. 
 
 Among the remarkable fossils of the 
 Rothliegendes, or lowest part of the Per- 
 mian in Saxony and Bohemia, are the silic- 
 ified trunks of tree-ferns called generically 
 Psaronius. Their bark was surrounded by 
 a dense mass of air-roots, which often con- NoeggeratMa cunaMia. 
 stituted a great addition to the original rongmait.* 
 
 stem, so as to double or quadruple its diameter. The same 
 remark holds good in regard to certain living extra-tropical 
 arborescent ferns, particularly those of New Zealand. 
 
 Upon the whole, it is evident that the Permian plants ap- 
 proach much nearer to the Carboniferous flora than to the 
 Triassic ; and the same may be said of the Permian fauna. 
 * Muichison's Russia, vol. ii., PI. A, fig. 3. 
 17* 
 
394 ELEMENTS OF GEOLOGY. 
 
 CHAPTER XXIII. 
 
 THE COAL OE CAEBONIPEEOUS GEOUP. 
 
 Principal Subdivisions of the Carboniferous Group. — Different Thickness of 
 the sedimentary and calcareous Members in Scotland and the South of 
 England. — Coal-measures. — Tei'restrial Nature of the Growth of Coal. — 
 Erect fossil Trees. — Uniting of many Coal-seams into one thick Bed. — 
 Purity of the Coal explained. — Conversion of Coal into Anthracite.— Ori- 
 gin of Clay-ironstone. — Marine and brackish- water Strata in Co.il. — Possil 
 Insects. — Batrachian Reptiles. — ^Labyrinthodont Foot-prints in Coal-meas- 
 ures. — Nova Scotia Coal-measures with successive Growths of erect fossil 
 Trees. — Similarity of American and European Coal. — Air-breathers of the 
 American Coal. — Changes of Condition of Land and Sea indicated by the 
 Carboniferous Strata of Nova Scotia. 
 
 Principal Subdivisions of the Carboniferous Group. — The next 
 group which we meet with in the descending order is the 
 Carboniff^rous, commonly called " The Coal," because it con- 
 tains many beds of that mineral, in a more or less pure state, 
 interstratified with sandstones, shales, and limestones. The 
 coal itself, even in Great Britian and Belgium, where it is 
 most abundant, constitutes but an insignificant portion of the 
 whole mass. In South Wales, for example, the thickness of 
 the coal-bearing strata has been estimated at between 11,000 
 and 12,000 feet, while, the various coal seams, about 80 in 
 number, do not, according to Prof. Phillips, exceed in the ag- 
 gregate 120 feet. 
 
 The carboniferous formation assumes various characters in 
 different parts even of the British Islands. It usually com- 
 prises two very distinct members: 1st, the sedimentary beds, 
 usually called the Coal-measures, of mixed fresh-water, ter- 
 restrial, and marine origin, often including seams of coal; 
 2dly, that named in England the Mountain or Carboniferous 
 Limestone, of purely marine origin, and made up chieily of 
 corals, shells, and encrinites, and resting on shales called the 
 shales of the Mountain Limestone. 
 
 In the south-western part of our island, in Somersetshire 
 and South Wales, the three divisions usually spoken of are: 
 
 1. Coal-measures l^'^''^^*^ °^, •^''^'e, sandstone, and grit, from 600 to 12,000 
 
 \ feet thick, with occasional seams of coal. 
 
 j A coarse quartzose sandstone passing into a conglom- 
 
 2. Millstone-grit -' ^™t^i sometimes used for millstones, with beds of 
 
 "■ j shale ; usually devoid of coal ; occasionally above 600 
 [ feet thick. 
 
THE CARBONIFEROUS GROUP. 395 
 
 3. Mountain or f A calcareous rock containing marine shells, corals, and 
 Carboniferous -I encrinites; devoid of coal; thickness variable, some- 
 Limestone (^ times more than 1500 feet. 
 
 If the reader will refer to the section Fig. 85, p. 130, he 
 will see that the Upper and Lower Coal-measures of the coal- 
 field near Bristol are divided by a micaceous flaggy sand- 
 stone called the Pennant Rock. The Lower Coal-measures 
 of the same section rest sometimes, especially in the north 
 part of the basin, on a base of coarse grit called the Mill- 
 stone Grit (No. 2 of the above table). 
 
 In the South Welsh coal-field Millstone Grit occurs in like 
 manner at the base of the productive coal. It is called by 
 the miners the "Farewell Rock," as when they reach it they 
 have no longer any hopes of obtaining coal at a greater 
 depth in the same district. In the central and northern 
 coal-fields of England this same grit, including quartz peb- 
 bles, witli some accompanying sandstones and shales con- 
 taining coal plants, acquires a thickness of several thousand 
 feet, lying beneath the productive coal-measures, which are 
 nearly 10,000 feet thick. 
 
 Below the Millstone Grit is a continuation of similar sand- 
 stones and shales called by Professor Phillips the Yoredale 
 series, from Yoredale, in Yorkshire, where they attain a 
 thickness of from 800 to 1000 feet. At several intervals 
 bands of limestone divide this part of the series, one of 
 which, called the Main Limestone or Upper Scar Limestone, 
 composed in great part of encrinites, is 10 feet thick. Thin 
 seams of coal also occur in these lower Yoredale beds in 
 Yorkshire, showing that in the same region there wei'e great 
 alternations in the state of the surface. For at successive 
 periods in the same area there prevailed first terrestrial con- 
 ditions favorable to the growth of pure coal, secondly, a sea 
 of some depth suited to the formation of Carbonifei'ous 
 Limestone, and, thirdly, a supply of muddy sediment and 
 sand, furnishing the materials for sandstone and shale. There 
 is no clear line of demarkation between the Coal-measures 
 and the Millstone Grit, nor between the Millstone Grit and 
 underlying Yoredale rocks. 
 
 On comparing a series of vertical sections in a north-west- 
 erly direction from Leicestershire and Warwickshire into 
 North Lancashire, we find, says Mr. Hull, within a distance 
 of 120 miles an augmentation of the sedimentary materials 
 to the extent of 16,000 feet. 
 
 I/eicestershire and Warwickshire 2,600 feet, 
 
 North Staffordshire , 9,000 " 
 
 South Lancashire 12,130 " 
 
 . North Lancashire 18,700 " 
 
396 ELEMENTS OF GEOLOGY. 
 
 In central England, where the sedimentary beds are re- 
 duced to about 3000 feet in all, the Carboniferous Limestone 
 attains an enormous thickness, as much as 4000 feet at Ash- 
 bourne, near Derby, according to Mr. Hull's estimate. To a 
 certain extent, therefore, we may consider the calcareous 
 member of the formation as having originated simultaneous- 
 ly with the accumulation of the materials of grit, sandstone, 
 and shale, with seams of coal; just as strata of mud, sand, 
 and pebbles, several thousand feet thick, with layers of veg- 
 etable matter, are now in the process of formation in the cy- 
 press swamps and delta of the Mississippi, while coral reefs 
 are forming on the coast of Florida and in the sea of the Ber- 
 muda islands. For we may safely conclude that in the an- 
 cient Carboniferous ocean those marine animals which wore 
 limestone builders were never freely developed in areas where 
 the rivers poured in fresh Avater charged with sand or clay; 
 and the limestone could only become several thousand feet 
 thick in parts of the ocean which remained perfectly clear for 
 ages. 
 
 The calcareous strata of the Scotch coal-fields, those of Lan- 
 arkshire, the Lothians, and Fife, for example, are very insig- 
 nificant in thickness when compared to those of England. 
 They consist of a few beds intercalated between the sand- 
 stones and shales containing coal and ironstone, the combined 
 thickness of all the limestones amounting to no more than 
 150 feet. The vegetation of some of these northern sedi- 
 mentary beds containing coal may be older than any of the 
 coal-measures of central and southern England, as being co- 
 eval with the Mountain Limestone of the south. In Ireland 
 the limestone predominates over the coal-bearing sands and 
 shales. We may infer the former continuity of several of the 
 coal-fields in northern and central England, not only from the 
 abrupt manner in which they are cut off at their outcrop, 
 but from their remarkable correspondence in the succession 
 and character of particular beds. But the limited extent to 
 which these strata are exposed at the surface is not merely 
 owing to their former denudation, but even in a still greater 
 degree to their having been largely covered by the New Red 
 Sandstone, as in Cheshire, and here and there by the Permian 
 strata, as in Durham. 
 
 It has long been the opinion of the most eminent geologists 
 that the coal-fields of Yorkshire and Lancashire were once 
 united, the upper Coal-measures and the overlying Millstone 
 Grit and Yoredale rocks having been subsequently removed ; 
 but what is remarkable, is the ancient date now assigned to 
 this denudation, for it seems that a thickness of no less than 
 
COAL-MEASURES. 397 
 
 10,000 feet of the coal-measures had been carried away be- 
 fore the deposition even of the lower Permian rocks which 
 were thrown down upon the already disturbed truncated 
 edges of the coal-strata.* The carboniferous strata most 
 productive of workable coal have so often a basin-shaped ar- 
 rangement that these troughs have sometimes been supposed 
 to be connected with the original conformation of the sur- 
 face upon which the beds were deposited. But it is now ad- 
 mitted that this structure has been owing to movements of 
 the earth's crust of upheaval and subsidence, and that the 
 flexure and inclination of the beds has no connection with 
 the original geographical configuration of the district. 
 
 COAL-MEASUEES. 
 
 I shall now treat more particularly cf the productive coal- 
 measures, and their mode of origin and organic remains. 
 
 Coal formed on Land. — In South Wales, already alluded to, 
 where the coal-measures attain a thickness of 12,000 feet, the 
 beds throughout appear to have been formed in water of 
 moderate depth, during a slow, but perhaps intermittent, de- 
 pression of the ground, in a region to which rivers were bring- 
 ing a never-failing supply of muddy sediment and sand. The 
 same area was sometimes covered with vast forests, such as 
 we see in the deltas of great rivers in warm climates, which 
 are liable to be submerged beneath fresh or salt water should 
 the ground sink vertically a few feet. 
 
 In one section near Swansea, in South Wales, whei"e the 
 total thickness of strata is 3246 feet, we learn from Sir H. De 
 la Beche that there are ten principal masses of sandstone. 
 One of these is 500 feet thick, and the whole of them make 
 together a thickness of 2125 feet. They are separated by 
 masses of shale, varying in thickness from 10 to 50 feet. The 
 intercal.'ited coal-beds, sixteen in number, are generally fi'om 
 one to five feet thick, one of them, which has two or three 
 layers of clay interposed, attaining nine feet. At other points 
 in the same coal-field the shales predominate over the sand- 
 stones. Great as is the diversity in the horizontal extent of 
 individual coal-seams, they all present one characteristic fea- 
 ture, in having, each of them, what is called its tcnderclay. 
 These underclays, co-extensive with every layer of coal, con- 
 sist of arenaceous shale, sometimes called fire-stone, because 
 it can be made into bricks which stand the fire of a furnace. 
 They vary in thickness from six inches to more than ten feet ; 
 and Sir William Logan first announced to the scientific world 
 in 1841 that they were regarded by the colliers in South 
 ' Edward Hull, Qaart. Geol. Joiirn., vol. xxiv., p. 327. 
 
398 ELEMENTS OF GEOLOGY. 
 
 Wales as an essential accompaniment of each of the eighty 
 or more seams of coal met with in their coal-field. They 
 are said to form the floor on which tlie coal rests; and some 
 of them have a slight admixture of carbonaceous matter, 
 while others are quite blackened by it. 
 
 All of them, as Sir William Logan pointed out, are charac- 
 terized by inclosing a pecuhar species of fossil vegetable call- 
 ed Stigmaria, to the exclusion of other plants. It was also 
 observed that, while in the overlying shales, or " roof" of the 
 coal, ferns and trunks of trees abound without any StigmaricB, 
 and are flattened and compressed, those singular plants of 
 the underclay most commonly retain their natural forms, un- 
 flattened and branching freely, and sending out their slender 
 rootlets, formerly thought to be leaves, through the mud in 
 all directions. Several species of Stigmaria had long been 
 known to botanists, and described by them, before their po- 
 sition under each seam of coal was pointed out, and before 
 their true nature as the roots of trees (some having been act- 
 ually found attached to the base of Sigillaria stumps) was 
 recognized. It was conjectured that they might be aquatic, 
 perhaps floating plants, which sometimes extended their 
 branches and leaves freely in fluid mud, in which they were 
 finally enveloped. 
 
 Now that all agree that these underclays are ancient soils, 
 it follows that in every instance where we find them they at- 
 test tlie terrestrial nature of the plants which formed the 
 overlying coal, which consists of the trunks, branches, and 
 leaves of the same plants. The trunks have generally fallen 
 prostrate in the coal, but some of them still remain at right 
 angles to the ancient soils (see Fig. 440, p. 411). Professor 
 Goppert, after examining the fossil vegetables of the coal- 
 fields of Germany, has detected, in beds of pure coal, remains 
 of plants of every family hitherto known to occur fossil in 
 the carboniferous rocks. Many seams, he remarks, are rich 
 in Sigillarim, Lepidodendra^ and Stigmarice, the latter in 
 such abundance as to appear to form the bulk of the coal. 
 In some places, almost all the plants were calamites, in oth- 
 ers ferns.* 
 
 Between the years ISSY and 1840, six fossil trees were dis- 
 covered in the coal-fields of Lancashire, where it is intersect- 
 ed by the Bolton railway. They were all at right angles to 
 the plane of the bed, which dips about 15° to the south. 
 The distance between the first and the last was more than 
 100 feet, and the roots of all were imbedded in a soft argil- 
 laceous shale. In the same plane with the roots is a bed of 
 * Quart. Geol. Jonrn., vol. v., Mem., p. 17. 
 
COAL FORMED ON LAND. 399 
 
 coal, eight or ten inches thick, which has been found to ex- 
 tend across the railway, or to the distance of at least ten 
 yards. Just above the covering of the roots, yet beneath 
 the coal-seam, so large a quantity of the Lepidqstrdbus vari- 
 abilis was discovered inclosed in nodules of liard clay, that 
 more than a bushel was collected from the small openings 
 around the base of some of the trees (see figure of this genus, 
 p. 424). The exterior trunk of each was marked by a coat' 
 irig of friable coal, varying from one-quarter to three-quarters 
 of an inch in thickness ; but it crumbled away on removing 
 the matrix. The dimensions of one of the trees is 15^ feet 
 in circumference at the base, 7^ feet at the top, its height 
 being eleven feet. All the trees have large spreading roots, 
 solid and strong, sometimes branching, and traced to a dis- 
 tance of several feet, and presumed to extend much farther. 
 
 In a colliery near Newcastle a great number of SigillaricB 
 occur in the I'ock as if they had retained the position in 
 which they grew. Not less than thirty, some of them four 
 or five feet in diameter, were visible within an area of 50 
 yards square, the interior being sandstone, and the bark hav- 
 ing been converted into coal. Such vertical stems are famil- 
 iar to onr coal-miners, under the name of coal-pipes. They 
 are much dreaded, for almost every year in the Bristol, New- 
 castle, and other coal-fields, they are the cause of fatal acci- 
 dents. Each cylindrical cast of a tree, formed of solid sand- 
 stone, and increasing gradually in size towards the base, and 
 being without branches, has its whole weight thrown down- 
 ward, and receives no support from the coating of fi'iable coal 
 which has replaced the bark. As soon, therefore, as the co- 
 hesion of this external layer is overcome, the heavy column 
 fails suddenly in a perpendicular or oblique direction from 
 the roof of the gallery whence coal has been extracted, wound- 
 ing or killing the workman who stands below. It is strange 
 to reflect how many thousands of these trees fell originally 
 in their native forests in obedience to the law of gravity ; 
 and how the few which continued to stand erect, obeying, 
 after myriads of ages, the same force, are cast down to im- 
 molate their human victims. 
 
 It has been remarked that if, instead of working in the 
 dark, the miner was accustomed to remove the upper cover- 
 ing of rock from each seam of coal, and to expose to the day 
 the soils on which ancient forests grew, the evidence of their 
 former growth would be obvious. Thus in South Stafibrd- 
 shire a seam of coal was laid bare in the year 1844, in what 
 is called an open work at Parkfield colliery, near Wolver- 
 hampton. In the space of about a quarter of an acre the 
 
400 
 
 ELEMENTS OF GEOLOGY. 
 
 stumps of no less than VS trees with their roots attached ap- 
 peared, as shown in the annexed plan (Fig. 429), some of 
 j,j ^29. them more than 
 
 eight feet in cir- 
 cumference. The 
 trunks, broken oif 
 close to the root, 
 were lying pros- 
 trate in every di- 
 rection, often 
 crossing each oth- 
 er. One of them 
 measured 15, an- 
 other 30 feet in 
 length, and others 
 less. They were 
 invariably flatten- 
 
 G round-plan of a fossil forest, Piirkfielfl Colliery, Dear Wol- „ 
 
 Terhampton, showing the position of 73 trees in a quarter neSS 01 One Or tWO 
 
 °'«° "<='■«• inches, and con- 
 
 verted into coal. Their roots formed part of a stratum of 
 coal ten inches thick, which rested on a layer of clay two 
 inches thick, below which was a second forest resting on a 
 two-foot seam of coal. Five feet below this, again, was a 
 third forest with large stumps oi Lepidodendra, Galamites, 
 and other trees. 
 
 Blending of Coal-seams. — Both in England and North 
 AmericT, seams of coal are occasionally observed to be part- 
 ed from each other by layers of clay and sand, and, after 
 they have been persistent for miles, to come together and 
 blend in one single bed, which is then found to be equal in 
 the aggregate to the thickness of the several seams. I was 
 shown by Mr. H. D. Rogers a remarkable example of this in 
 Pennsylvania. In the Shark Mountain, near Pottsville, in 
 that State, there are thirteen seams of anthracite coal, some 
 of them more than six feet thick, separated by beds of white 
 quartzose grit and a conglomerate of quartz pebbles, often 
 of the size of a hen's egg. Between Pottsville and the Le- 
 high Summit Mine, seven of these seams of coal, at first 
 widely separated, are, in the course of several miles, brought 
 nearer and nearer together by the gradual thinning out of 
 the intervening coarse-grained strata and their accompany- 
 ing shales, until at length they successively unite and form 
 one mass of coal between forty and fifty feet thick, very 
 pure on the whole, though with a few thin partings of clay. 
 This mass of coal T saw quarried in the open air^at Maiich 
 
BLENDING OF COAL-SEAMS. 4 .1 
 
 Chunk, on the Bear Mountain. The origin of such a vast 
 thickness of vegetable remains, so unmixed, on the whole, 
 with earthy ingredients, can be accounted for in no other 
 way than by the growth, during thousands of years, of trees 
 and ferns in the manner of peat — a theory which the pres- 
 ence of the Stigmaria in situ under each of the seven layers 
 of anthracite fully bears out. The rival hypothesis, of the 
 drifting of plants into a sea or estuary, leaves the non-inter- 
 mixture of sediment, or of clay, sand, and pebbles, with the 
 pure coal wholly unexplained. 
 
 The late Mr. Bowman was the first who gave a satisfac- 
 tory explanation of the manner in which distinct coal-seams, 
 after maintaining their independence for miles, may at length 
 unite, and then persist throughout another wide area with a 
 thickness equal to that which the separate seams had previ- 
 ously maintained. 
 
 ■^ Fig. 430. 
 
 Uniting of distinct coal-seams. 
 
 Let A C be a three-foot seam of coal originally laid down 
 as a mass of vegetable matter on the level ai-ea of an exten- 
 sive swamp, having an under-clay, / g, through which the 
 Stigmarise or roots of the trees penetrate as usual. One 
 portion, B C, of this seam of coal is now inclined ; the area 
 of the swamp having subsided as much as 25 feet at E C, 
 and become for a time submerged under salt, fresh, or brack- 
 ish water. Some of the trees of the original forest ABC fell 
 down, others continued to stand erect in the new lagoon, their 
 stumps and part of their trunks becoming gradually envel- 
 oped in layers of sand and mud, which at length filled up 
 the new piece of water C E. 
 
 When this lagoon has been entirely silted up and convert- 
 ed into land, the forest-covered surface A B will extend once 
 more over the whole area ABE, and a second mass of veg- 
 etable matter, D E, forming three feet more of coal, will ac- 
 cumulate. We then find in the region E C two seams of 
 coals, each three feet thick, with their respective under-clays, 
 with erect buried trees based upon the surface of the lower 
 coal, the two seams being separated by 25 feet of interven- 
 ing shale and sandstone. Whereas in the region A B, where 
 the growth of the forest has never been interrupted by sub- 
 mergence, there will simply be one seam, two yards thick, 
 corresponding to the united thickness of the beds B E and 
 
402 ELEMENTS OE GEOLOGY, 
 
 B C. It may be objected that the uninterrupted growth of 
 plants during the interval of time required for the filling up 
 of the lagoon will have caused the vegetable matter in the re- 
 gion D A B to be thicker than the two distinct seams E and 
 C, and no doubt there would actually be a slight excess rep- 
 resenting one or more generation of trees and plants forming 
 the undergrowth ; but "this excess of vegetable matter, when 
 compressed into coal, would be so insignificant in thickness 
 that the miner might still affirm that the seam D A through- 
 out the area DAB was equal to the two searas and E. 
 
 Cause of the Purity of Coal.— The purity of the coal itself, 
 or the absence in it of earthy particles and sand, throughout 
 areas of vast extent, is a fact which appears very difficult to 
 explain when we attribute each coal-seam to a vegetation 
 growing in swamps. It has been asked how, during river 
 inundations capable of sweeping away the leaves of ferns 
 and the stems and roots of SigillaricB and other ti-ees, could 
 the waters fail to transport some fine mud into the swamps ? 
 One generation after another of tall trees grew with their 
 roots in mud, and their leaves and prostrate trunks formed 
 layers of vegetable matter, which was afterwards covered 
 with mud since turned to shale. Yet the coal itself, or al- 
 tered vegetable matter, remained all the while unsoiled by 
 earthy particles. This enigma, however perplexing at first 
 sight, may, I think, be solved by attending to what is now 
 taking place in deltas. The dense growth of reeds and herb- 
 age which encompasses the margins of forest-covered swamps 
 in the valley and delta of the Mississippi is such that the 
 fluviatile waters, in passing through them, are filtered and 
 made to clear themselves entirely before they reach the 
 areas in which vegetable matter may accumulate for centu- 
 ries, forming coal if the climate be favorable. There is no 
 possibility of the least intermixture of earthy matter in such 
 cases. Thus in the large submerged tract called the " Sunk 
 Country," near New Madrid, forming part of the western 
 side of the valley of the Mississippi^ erect tiees have been 
 standing ever since the year 1811-'12, killed by the great 
 earthquake of that date ; lacustrine and swamp plants have 
 been growing there in the shallows, and several I'ivers have 
 annually inundated the whole space, and yet have been un- 
 able to carry in any sediment within the outer boundaries 
 of the morass, so dense is the marginal belt of reeds and 
 brush-wood. It may be afi[irmed that generally, in the " cy- 
 press swamps" of the Mississippi, no sediment mingles with 
 the vegetable matter accumulated there from the decay of 
 trees and semi-aquatic plants. As a singular proof of this 
 
CONVERSION OF COAL INTO ANTHRACITE. 403 
 
 fact, I majr mention that whenever any part of a swamp in 
 Louisiana is dried up, during an unusually hot season, and 
 the wood set on fire, pits are burnt into the ground many 
 feet deep, or as far down as the fire can descend without 
 meeting with water, and it is then found that scarcely any 
 residuum or earthy matter is left. At the bottom of all 
 these "cypress swamps" a bed of clay is found, with roots 
 of the tall cypress (TasRodium distichum), just as the under- 
 clays of the coal are filled with Btigmaria. 
 
 Conversion of Coal into Anthracite. — It appears from the 
 researches of Liebig and other eminent chemists, that when 
 wood and vegetable matter are buried in the earth exposed 
 to moisture, and partially or entirely excluded from the air, 
 they decompose slowly and evolve carbonic acid gas, thus 
 parting with a portion of their original oxygen. By this 
 means they become gradually converted into lignite or 
 wood-coal, which contains a larger proportion of hydrogen 
 than wood does. A continuance of decomposition changes 
 this lignite into common or bituminous coal, chiefly by the 
 discharge of carbureted hydrogen, or the gas by which we 
 illuminate our streets and houses. According to Bischofi^, 
 the inflammable gases which are always escaping from min- 
 eral coal, and are so often the cause of fatal accidents in 
 mines, always contain carbonic acid, carbureted hydrogen, 
 nitrogen, and olefiant gas. The disengagement of all these 
 gradually transforms ordinary or bituminous coal into an- 
 thracite, to which the various names of glance - coal, coke, 
 bard-coal, culm, and many others, have been given. 
 
 There is an intimate connection between the extent to 
 which the coal has in different regions parted with its gas- 
 eous contents, and the amount of disturbance which the 
 strata have undergone. The coincidence of these phenom- 
 ena may be attributed partly to the greater facility afibrded 
 for the escape of volatile matter, when the fracturing of the 
 rocks has produced an infinite number of cracks and crev- 
 ices. The gases and water which are made to penetrate 
 these cracks are probably rendered the more efiective as 
 metamorphic agents by increased temperature derived from 
 the interior. It is well known that, at the present period, 
 thermal waters and hot vapors burst out from the earth 
 during earthquakes, and these would not fail to promote 
 the disengagement of volatile matter from the carboniferous 
 rocks. 
 
 In Pennsylvania the strata of coal are horizontal to the 
 westward of the Alleghany Mountains, where the late Pro- 
 fessor H. D. Rogers pointed out that they were most bitu- 
 
404 ELEMENTS OF GEOLOGY. 
 
 minous ; but as we travel south-eastward, where they no long- 
 er remain level and unbroken, the same seams become pro- 
 gressively debitumenized in proportion as the rocks become 
 more bent and distorted. At iirst, on the Ohio River, the 
 proportion of hydrogen, oxygen, and other volatile matters 
 ranges from forty to fifty per cent. Eastward of this line, 
 on the Mbnongahela, it still approaches forty per cent., where 
 tlie strata begin to experience some gentle flexures. On en- 
 tering the Alleghany Mountains, where the distinct anticlinal 
 axes begin to show themselves, but before the dislocations 
 are considerable, the volatile matter is generally in the pro- 
 portion of eighteen or twenty per cent. At length, when we 
 arrive at some insulated coal-fields associated with the bold- 
 est flexures of the Appalachian chain, where the strata have 
 been actually turned over, as near Pottsville, we find the 
 coal to contain only from six per cent, of volatile matter, thiis 
 becoming a genuine anthracite. 
 
 Clay-ironstone. — Bands and nodules of clay-ironstone are 
 common in coal-measures, and are formed, says Sir H. De la 
 Beche, of carbonate of iron mingled mechanically with earthy 
 matter, like that constituting the shales. Mr. Hunt, of the 
 Museum of Practical Geology, instituted a series of experi- 
 ments to illustrate the production of this substance, and found 
 that decomposing vegetable matter, such as would be dis- 
 tributed through all coal strata, prevented the further oxida- 
 tion of the proto-salts of iron, and converted the peroxide 
 into protoxide by taking a portion of its oxygen to form car- 
 bonic acid. Such carbonic acid, meeting with the protoxide 
 of iron in solution, would unite with it and form a carbon- 
 ate of iron; and this mingling with fine mud, when the ex- 
 cess of carbonic acid was removed, might form beds or nod- 
 ules of argillaceous ironstone.* 
 
 Intercalated Marine Beds in Coal. — Both in the coal-fields 
 of Europe and America the association of fresh, brackish- 
 water, and marine strata with coal-seams of terrestrial origin 
 is frequently recognized. Thus, for example, a deposit near 
 Shrewsbury, probably formed in brackish water, has been de- 
 scribed by Sir R. Murchison as the youngest member of the 
 coal-measures of that district, at the point where they are in 
 contact with the overlying Permian group. It consists of 
 shales and sandstones about 150 feet thick, with coal and 
 traces of plants ; including a bed of limestone varying from 
 two to nine feet in thickness, which is cellular, and resembles 
 some lacustrine limestones of France and Germany. It has 
 been traced for 30 miles in a straight line, and can be recog- 
 * Memoirs of Geol. SuiTey, pp. 51, 255, etc. 
 
INSECTS IN EUROPEAN COAL. 
 
 405 
 
 Fig. 432. 
 
 nized at still more distant points. The characteristic fossils 
 are a small bivalve, having the form of a Oydas or Gyrena, 
 also a small entomostracan, j,. ^^ 
 
 Cythere inflata (Fig. 432), 
 and the microscopic shell of 
 an annelid of an extinct ge- 
 nus called Microconchus 
 (Fig. 431), allied to Spiror- 
 bis. In the coal-field of 
 Yorkshire there are fresh- 
 water strata, some of which 
 contain shells referred to the 
 family Vhionidce. ■'but in the a. Microcom:hus (,Spi- 
 
 . t ^ n ^ . 1 . rorbi8) carbonariits, 
 
 midst 01 the series there is March. Nat. size 
 
 and magnified. 
 Variety of same. 
 
 Cythere {Leperditia) 
 infiata, Nat. size 
 and magnified. 
 Murcliisou. 
 
 Kg. 433. 
 
 Fig. 4S4. 
 
 one thin but very widely- 
 spread stratum, abounding 
 in fishes and marine shells, such as Goniatites Listen (Fig. 
 
 433), Orthoceras, and 
 Aviculopecten papyra- 
 ceus, Goldf (Fig. 434). 
 
 Insects in European 
 Coal. — -Articulate ani- 
 mals of the genus Scor- 
 pion were found by 
 Count Sternberg in 
 1835 in the coal-meas- 
 „ . . ,.,.,,,. ... , ures of Bohemia, and 
 
 Coal-measares, York- iis, Guldf. (.Pectenpa- abOUt the Same time 
 ehire and Lancashire. pyraceus. Sow.) Jjj ^]^q^q ^f Coalbrook 
 
 Dale by Mr. Prestwich, where also true insects, such as 
 beetles of the family Curculionidce, a neuropterous insect 
 of the genus Corydalis, and another related to the Phasmidoe, 
 have been found. 
 
 From the coal of Wetting, in Westphalia, several specimens 
 
 Fig. 435. 
 
 Win" of a Grasshopper. GnAlacris lithanthraca, Goldenberg. 
 " Coal, Saarhriiclf, near Treves. 
 
406 
 
 ELEMENTS OE GEOLOGY. 
 
 of the cockroach or Blatta family, and the wing of a cricket 
 (Acridites), have been described by Germav. Prof. Golden- 
 berg published, in 1854, descriptions of no less than twelve 
 species of insects from the nodnlar clay-ironstone of Saar- 
 brtick, near Treves.* Among them are several UlattincB, 
 three species of JVeuroptera, one beetle of the Scarabcem 
 family, a grasshopper or locust, Gryllacris (see Fig. 435), and 
 several white ants or Termites. Professor Goldenberg show- 
 ed me, in 1864, the wing of a white ant, found low down in 
 the productive coal-measures of Saarbrtick, in the interior of 
 a flattened Lepidodendron. It is much larger than that of 
 any known living species of the same genus. 
 
 Batraehian Reptiles in Coal. — No vertebrated animals more 
 highly organized than fish were known in rocks of higher 
 Pig. 436. antiquity than the 
 
 Permian until the 
 year 1844, when the 
 Apateon pedestris, 
 Meyer, was discov- 
 ered in the coal- 
 measures of Miin- 
 Bter-Appel in Rhe- 
 nish Bavaria, and 
 three years later, in 
 1847, Professor von 
 Dechen. found three 
 other distinct species 
 of the same family 
 of Amphibia in the 
 Saarbrtick coal-field 
 above alluded to. 
 These were described 
 by the late Profess- 
 or Goldfuss under 
 the generic name of 
 Archegosaurus. The 
 skulls, teeth, and the 
 greater portions of 
 the skeleton, nay, 
 eVen a large part of 
 the skin, of two of 
 
 Archegosaurus minor, Goldfuss. Fossil reptile from these reptiles have 
 
 the coal-measures, saarbrack. it)eeh faithfully pre- 
 
 served in the centre of spheroidal concretions of clay-iron- 
 "" The largest of these, Archegoiaunis Decheni, must 
 
 * Palfeont. Danker and V. Meyer, vol. iv., p. 17. 
 
 stone. 
 
FOOT-PRINTS IN COAL-MEASUEES. 407 
 
 have been three feet six inches long. The annexed drawing 
 represents the skull and neck bones of the smallest of the 
 three, of the natural size. They were considered by Gold- 
 fuss as saurians, but by Herman von Meyer as most nearly 
 allied to the Labyrinthodon before mentioned (p. 371), and 
 the remains of the extremities leave no doubt that they 
 were quadrupeds, " provided," says Von Meyer, " with hands 
 and feet terminating in distinct toes; but these limbs were 
 weak, serving only for swimming or creeping." The same 
 anatomist has pointed out certain points of analogy between 
 their bones and those of the Proteus anguinus; and Profess- 
 or Owen has observed that they make an approach to the 
 Proteus in the shortness of their ribs. Two specimens of 
 these ancient reptiles retain a irio-. 437 
 large part of the outer skin, 
 which consisted of long, narrow, 
 wedge - shaped, tile -like, and 
 horny scales, arranged in rows __ 
 
 (^See I?lg. 4o7j. Imbricated coTering of skin of Ar- 
 
 In 1865, several species belong- ch^omums medim, Goidf. Mag- 
 ing to three different genera 
 
 of the same family of perennibranchiate Batrachians were 
 found in the coal-field of Kilkenny in bituminous shale at 
 the junction of the coal with the underlying Stigmaria-bear- 
 ing clay. They were, probably, inhabitants of a marsh, and 
 the large processes projecting from the vei'tebrse of their tail 
 imply, according to Professor Huxley, great powers of swim- 
 ming. They were of the Labyrinthodont family, and their 
 association with the fish of the coal, of which so large a pro- 
 portion are ganoids, reminds us that the living perennibran- 
 chiate amphibia of America frequent the same rivers as the 
 ganoid Lepidostei or bony pikes. 
 
 Xiobyrinthodont foot-prints in coal-measures. — In 1844, the 
 very year when the Apateon, before mentioned, of the coal 
 was first met with in the country between the Moselle and 
 tlie Rhine, Dr. King published an account of the foot-prints 
 of a large reptile discovered by him in North America. 
 These occur in the coal-strata of Greensburg, in Westmore- 
 land County, Pennsylvania ; and I had an opportunity of 
 examining them when in that country in 1846. The foot- 
 marks were first observed standing out in relief from the 
 lower surface of slabs of sandstone, resting on thin layers of 
 fine unctuous clay. I brought away one of these masses, 
 which is represented in the accompanying drawing (Fig. 
 438). It displays, together with foot-prints, the casts of 
 cracks {a, a') of various sizes. The origin of such cracks in 
 
408 
 
 ELEMENTS OE GEOLOGY. 
 
 clay, and casts of the same, has before been explained, and 
 referred to the drying and shrinking of naud, and the subse- 
 quent pouring of sand into open crevices. It will be seen 
 that some of the cracks, as at 6, c, traverse the foot-prints, 
 and produce distortion in them, as might have been expect- 
 
 Fig. 438. 
 
 Slab of sandstone from the coal-measures of Pennsylvania, with foot-prints of air- 
 breathing reptile and casts of cracks. Scale one-sixth the original. 
 
 ed,for the mud must have been soft when the animal walked 
 over it and left the impressions; whereas, when it afterwards 
 dried up and shrank, it would be too hard to receive such in- 
 dentations. 
 
 We may assume that the reptile which left these prints 
 
NOVA SCOTIA COAL-MEASURES. 409 
 
 on the ancient sands of the coal-measures was an air-breather, 
 because its weight would not have been sufficient under wa- 
 ter to have made impressions so deep and distinct. The 
 same conclusion is also borne out by the casts of the cracks 
 above described, for they show that the clay had been ex- 
 posed to the air and sun, so as to have di'ied and shrunk. 
 
 Nova Scotia Coal-measures. — The sedimentary strata in 
 which thin seams of coal occur attain a thickness, as we 
 have seen, of 18,000 feet in the north of England exclusive 
 of the Mountain Limestone, and are estimated by Von De- 
 chen at over 20,000 feet in Rhenish Prussia. But the finest 
 example in the world of a natural exposure in a continuous 
 section ten miles long, occurs in the sea-cliffs bordering a 
 branch of the Bay of^Fundy, in Nova Scotia. These cliffs, 
 called the " South Joggins," which I first examined in 1 842, 
 and afterwards with Dr. Dawson in 1845, have lately been 
 admirably described by the last-mentioned geologist* in de- 
 tail, and his evidence is most valuable as showing how large 
 a portion of this dense mass was foi-med on land, or in 
 swamps where terrestrial vegetation flourished, or in fresh- 
 water lagoons. His computation of the thickness of the 
 whole series of carboniferous strata as exceeding three miles, 
 agrees with the measurement made independently by Sir 
 William Logan in his survey of this coast. 
 
 There is no reason to believe that in this vast succession 
 of strata, comprising some marine as well as many fresh- water 
 and terrestrial formations, there is any repetition of the same 
 beds. There are no faults to mislead the geologist, and cause 
 him to count the same beds over more than once, while some 
 of the same plants have been traced from the top to the bot- 
 tom of the whole series, and are distinct from the flora of the 
 antecedent Devonian formation of Canada. Eighty-one seams 
 of coal, varying in thickness from an inch to about five feet, 
 have been discovered, and no less than seventy-one of these 
 have been actually exposed in the sea-cliffs. 
 
 In the annexed section (Fig. 439), which I examined in 1842, 
 the beds from c to i are seen all dipping the same way, their 
 average inclination being at an angle of 24° S.S.W. The ver- 
 tical height of the cliffs is from 150 to 200 feet ; and between 
 d and^ — in which space I observed seventeen trees in an up- 
 right position, or, to speak more correctly, at right angles to 
 the planes of stratification — I counted nineteen seams of coal, 
 varying in thickness from two inches to four feet. At low 
 tide a fine horizontal section of the same beds is exposed to 
 view on the beach, which at low tide extends sometimes 200 
 * Acadian Geology, 2d edit., 1868» 
 18 
 
410 ELEMENTS OF GEOLOGY. 
 
 yards from the base of tlie cliff. The thickness of the beds 
 alluded to, between dani g, is about 2500 feet, the erect trees 
 
 Fig. 439. 
 
 Coal with upriglit trees. Sandstone and shale. 
 
 N S 
 
 V d e _^ .9 A 
 
 Section of the cliffs of the South Joggins, near Minudie, Nova Scotia. 
 0. Grindstone, d, g. Alternations of sandstone, shale, and coal containing npright 
 trees. e,f. Portion of cliff, given on a larger scale in Fig. 440. /. Four-foot coal, 
 main seam, h, i. Shale with fresh-water mussels, see p. 418. 
 
 consisting chiefly of large Sigillarioe, occurring at ten distinct 
 levels, one above the other. The usual height of the buried 
 trees seen by me was from six to eight feet ; but one trunk 
 was about 25 feet high and four feet in diameter, with a con- 
 siderable bulge at the base. In no instance could I detect 
 any trunk intersecting a layer of coal, however thin ; and 
 most of the trees terminated downward in seams of coal. 
 Some few only were based on clay and shale ; none of them, 
 except Calamites, on sandstone. The erect trees, therefore, 
 appeared in general to have grown on beds of vegetable mat- 
 ter. In the underclays Stigmaria abounds. 
 
 These root-bearing beds have been found under all the coal- 
 seams, and such old soils are at present the most destructible 
 masses in the whole cliff, the sandstones and laminated shales 
 being harder and more capable of resisting the action of the 
 waves and the Aveather. Originally the reverse was doubt- 
 less true, for in the existing delta of the Mississippi those 
 clays in which the innumerable roots of the deciduous cypress 
 and other swamp trees ramify in all directions are seen to 
 withstand far more effectually the undermining power of the 
 river, or of the sea at the base of the delta, than do beds of 
 loose sand or layers of mud not supporting trees. It is obvi- 
 ous that if this sand or mud be afterwards consolidated and 
 turned to sandstone and hard shale, it would be the least de- 
 structible. 
 
 In regard to the plants, they belonged to the same genera, 
 and most of them to the same species, as those met with in 
 the distant coal-fields of Europe. Dr. Dawson has ennmer- 
 ated more than 150 species, two-thirds of which are European, 
 a greater agreement than can be said to exist between the 
 same Nova Scotia flora and that of the coal-fields of the Uni- 
 ted States. By referring to the section. Fig. 439, the position 
 of the four-foot coal will be perceived, and in Fig. 440 (a sec- 
 tion made byme in 1842 of a small portion) that from e to/ 
 
NOVA SCOTIA COAIi-MEASURES. 
 
 411 
 
 Fig. 440. 
 
 of the same cliff is exhibited, in order to show the manner of 
 occurrence of erect fossil trees at right angles to the planes, 
 of the inclined strata. 
 
 In the sandstone which filled their interiors, I frequently 
 observed fern-leaves, and sometimes fragments of Stigtnaria, 
 which had evidently entered together with sediment after 
 the trunk had decayed and become hollow, and while it was 
 still standing under water. Thus the tree, a. Fig. 440, rep- 
 resented in the 
 bed e in the sec- 
 tion. Fig. 439, is 
 a hollow trunk 
 five feet eight 
 inches in length, 
 traversing vari- 
 ous strata, and 
 cut off at the 
 top by a layer 
 of clay two feet 
 thick, on which 
 rests a seam of 
 
 coal (h Fiff 440^ Erect ibssil trees. Coal-measures, Nova Scotia. 
 
 one foot thick. On this coal again stood two large trees 
 (c and d), while at a greater height the trees / and g rest 
 upon a thin seam of coal (e), and above them is an underclay, 
 supporting the four-foot coal. 
 
 Occasionally the layers of matter in the inside of the tree 
 are more numerous than those without ; but it is more com- 
 mon in the coal-measures of all countries to find a cylinder 
 of pure sandstone — the cast of the interior of a tree — inter- 
 secting a great many alternating beds of shale and sand- 
 stone, which originally enveloped the trunk as it stood erect 
 in the water. Such a want of correspondence in the materi- 
 als outside and inside, is just what we might expect if we 
 reflect on the difference of time at which the deposition of 
 sediment will take place in the two cases ; the imbedding 
 of the tree having gone on for many years before its decay 
 had made much progress. In many places distinct pi-oof is 
 seen that the enveloping strata took years to accumulate, for 
 some of the sandstones surrounding erect sigillarian trunks 
 support at different levels roots and stems of Galamites; the 
 Calamites having begun to grow after the older SigiUarim 
 had been partially buried. 
 
 The general absence of structure in the interior of the 
 large fossil trees of the Coal.implies the very durable nature 
 of their bark, as compared with their woody portion. The 
 
412 ELEMENTS OF GEOLOGY. 
 
 same difference of durability of bark and wood exists in 
 modern trees, and was first pointed out to me by Dr. Daw- 
 son, in the forests of Nova Scotia, where the Canoe Birch 
 {Betula papyracea) has such tough bark that it may some- 
 times be seen in the swamps looking externally sound and 
 fresh, although consisting simply of a hollow cylinder with 
 all the wood decayed and gone. When portions of such 
 trunks have become submerged in the swamps they are 
 sometimes found filled with mud. One of the erect fossil 
 trees of the South Joggins fifteen feet in height, occurring 
 at a higher level than the main coal, has been shown by Dr. 
 Dawson to have a coniferous structure, so that some Goniferce 
 of the Coal period grew in the same swamps as SigillarioB, 
 just as now the deciduous Cypress (Taxodium distichtim) 
 abounds in the marshes of Louisiana even to the edge of the 
 sea. 
 
 When the carboniferous forests sank below high- water 
 mark, a species of Spirorbis or Serpula (Fig. 431, p. 405), at- 
 tached itself to the outside of the stumps and stems of the 
 erect ti'ees, adhering occasionally even to the interior of the 
 bark — another proof that the process of envelopment was 
 very gradual. These hollow upright trees, covered with in- 
 numerable marine annelids, reminded me of a " cane-brake," 
 as it is commonly called, consisting of tall reeds, Arundinaria 
 macrosperma, which I saw in 1846, at the Balize, or extrem- 
 ity of the delta of the Mississippi. Although tliese reeds are 
 fresh-water plants, they were covered with barnacles, having 
 been killed by an incursion of salt water over an extent of 
 many acres, where the sea had for a season usurped a space 
 previously gained from it by the river. Yet the dead reeds, 
 in spite of this change, remained standing in the soft mud, 
 enabling us to conceive how easily the larger Sigillarim, hol- 
 low as they were but supported by strong roots, may have 
 resisted an incursion of the sea. 
 
 The high tides of the Bay of Fundy, rising more than 60 
 feet, are so destructive as to undermine and sweep away con- 
 tinually the whole face of the cliffs, and thus a new crop of 
 erect fossil trees is brought into view every three or four 
 years. They are known to extend over a space between 
 two and three miles from north to south, and more than 
 twice that distance from east to west, being seen in the 
 banks of streams intersecting the coal-field. 
 _ Structure of Coal. — The bituminous coal of N"ova Scotia is 
 similar in composition and structure to that of Great Britain, 
 being chiefly derived from Sigillarioid trees mixed with leaves 
 of ferns and of a Lycopodiaceous tree called Oordaites {Nbeg- 
 
AIR-BREATHERS OF THE COAL. 413 
 
 gerathia, etc., for genus, see Fig. 428, p. 393), supposed by 
 Dawson to have been deciduous, and which had broad par- 
 allel veined leaves without a mid-rib. On the surface of the 
 seams of coal are large quantities of mineral charcoal, which 
 doubtless consist, as Dr. Dawson suggests, of fragments of 
 wood which decayed in the open air, as would naturally be 
 expected in swamps where so many erect trees were pre- 
 served. Beds of cannel-coal display, says Dr. Dawson, such 
 a microscopical structure and chemical composition as shows 
 them to have been of the nature of fine vegetable mud such 
 as accumulates in the shallow ponds of modern swamps. 
 The underclays are loamy soils, which must have been suffi- 
 ciently above water to admit of drainage, and the absence 
 of sulphurets, and the occurrence of carbonate of iron in 
 them, prove that when they existed as soils, rain-water, and. 
 not sea-water, percolated them. With the exception, per- 
 haps, of Asterophyllites (see Fig. 461, p. 425), there is a re- 
 markable absence from the coal-measures of any form of veg- 
 etation properly aquatic, the true coal being a sub-aerial ac- 
 cumulation in soil that was wet and swampy but not per- 
 manently submerged. 
 
 Air-breathers of the Coal. — If we have rightly interpreted 
 the evidence of the former existence at more than eighty dif- 
 ferent levels of forests of trees, some of them of vast extent, 
 and which lasted for ages, giving rise to a great accumula- 
 tion of vegetable matter, it is natural to ask whether there 
 were not many air-breathing inhabitants of these same re- 
 gions. As yet no remains of mammalia or birds have been 
 found, a negative character common at present to all the 
 Palaeozoic formations; but in 1852 the osseous remains of a 
 reptile, the first ever met with in the carboniferous strata of 
 the American continent, were found by Dr. Dawson and my- 
 self We detected them in the interior of one of the erect 
 Sigillariae before alluded to as of such frequent occurrence in 
 Nova Scotia. The tree was about two feet in diameter, and 
 consisted of an external cylinder of bark, converted into' coal, 
 and an intei-nal stony axis of black sandstone, or rather mud 
 and sand stained black by carbonaceous matter, and cement- 
 ed together with fragments of wood into a rock. These frag- 
 ments were in the state of charcoal, and seem to have fallen 
 to the bottom of the hollow tree while it was rotting away. 
 The skull, jaws, and vertebrae of a reptile, probably about 2^ 
 feet in length {Dendrerpeton Acadicmum, Owen), were scat- 
 tered through this stony matrix. The shell, also, of a Pupa 
 (see Fig. 442, p. 41 5), the first land-shell ever met with in the 
 coal or in beds older than the tertiary, was observed in the 
 
414 ELEMENTS OF GEOLOGY. 
 
 same stony mass. Dr. Wyman of Boston pronounced the 
 reptile to be allied in structure to Menobranchus and Me- 
 nopoma, species of batrachians, now inhabiting the North 
 American rivers. The same view was afterwards confirmed 
 by Professor Owen, who also pointed out the resemblance of 
 the cranial plates to those seen in the skull oi Archegosaurus 
 and Labyrinthodon* Whether the creature had crept into 
 the hollow tree while its top was still open to the air, or 
 whether it was washed in with mud during a flood, or in 
 whatever other manner it entered, must be matter of con- 
 jecture. 
 
 Foot-prints of two reptiles of difterent sizes had previous- 
 ly been observed by Dr. Harding and Dr. Gesnei- on ripple- 
 marked flags of the lower coal-measures in Nova Scotia (No. 
 2, Fig. 447_, p. 418), evidently made by quadrupeds walking 
 on the ancient beach, or out of the water, just as the recent 
 Menopoma is sometimes observed to do. 
 
 The remains of a second and smaller species of Dendrer- 
 peton, D. Oweni, were also found accompanying the larger 
 one, and still retaining some of its dermal appendages; and 
 in the same tree were the bones of a third small lizard-like 
 reptile, Hylonomus Lyelli, seven inches long, with stout hind 
 limbs, and fore limbs comparatively slender, supposed by Dr. 
 Dawson to be capable of walking and running on land.f 
 
 In a second specimen of an erect stump of a hollow tree 
 15 inches in diameter, the ribbed bark of which showed that 
 it was a Sigillaria, and which belonged to the same forest as 
 the specimen examined by us in 1852, Dr. Dawson obtained 
 not only fifty specimens of Pupa vetusta (Fig. 442), and nine 
 skeletons of reptiles belonging to four species, but also sev- 
 eral examples of an articulated animal resembling the recent 
 
 Fig. 441. 
 
 XyloUm Sigillarice, Dawson. Coal, Nova Scotia. 
 a. Natnral size. 6. Anterior part, magnifled. c. Caudal extremity, magnified. 
 
 centipede or gally-worm, a creature which feeds on decayed 
 vegetable matter (see Fig. 441). Under the microscope, the 
 
 * Quart. Geo]. Jour., vol. ix., p. 58. 
 
 + Dawson, Air-Breathers of the Coal in Nova Scotia. Montreal, 1863. 
 
AIR-BREATHERS OF THE COAL. 
 
 415 
 
 Fig. 442. 
 
 head, with the eyes, mandible, and labrum, are well seen. It 
 is interesting, as being the earliest known representative of 
 the myriapods, none of which had previously been met with 
 in rocks older than the oolite or lithographic slate of Ger- 
 many. 
 
 Some years after the discovery of the first Pupa, Dr. Daw- 
 son, carefully examining the same great section containing so 
 many buried forests in the cliffs of Nova Scotia, discovered 
 another bed, separated from the tree containing Dendrerpe- 
 ton by a mass of strata more than 1200 feet thick. As there 
 were 21 seams of coal in this intei-vening 
 mass, the length of time comjjrised in the 
 interval is not to be measured by the 
 mere thickness of the sandstones and 
 shales. This lower bed is an undei'clay 
 seven feet thick, with stigmarian i-ootlets, 
 and the small land-shells occurring in it 
 are in all stages of growth. They are 
 chiefly confined to a layer about two 
 inches thick, and are unmixed with any 
 aquatic shells. They were all originally 
 entire when imbedded, but are most of 
 them now crushed, flattened, and distort- 
 ed by pressure ; they must have been ac- 
 cumulated, says Dr. Dawson, in mud de- 
 posited in a pond or creek. 
 
 The surface striae aiPupa vetusta, when 
 magnified 50 diameters, present exactly 
 the same appearance as a portion corresponding in size of 
 the common English Pupa juriiperi, and the internal hex- 
 agonal cells, magnified 500 diameters, show 
 the internal structure of the fossil and re- 
 cent Pupa to be identical. In 1866* Dr. 
 Dawson discovered in this lower bed, so 
 ^ full of the Pupa, another land-shell of the 
 '■ genus Helix (sub-genus Zonites), see Fig. 
 443. 
 ^ .. ,„ , . . None of the reptiles obtained from the 
 
 Carpenter, a. Natm-ai coal-measures oi the South J oggms are 01 
 size. 6. Magniflea. ^ higher grade than the Labyrinthodonts, 
 but some of these Avere of very great size, two caudal verte- 
 br88 found by Mr. Marsh in 1862 measuring two and a half 
 inches in diameter, and implying a gigantic aquatic reptile 
 with a powerful swimming tail. 
 
 Except some obscure traces of an insect found by Dr. 
 * Dawson, Acadian Geology, 1868, p. 385. 
 
 Pupa vetuata, Dawson. 
 a. Natural size. 6. Mag- 
 nified. 
 
416 ELEMENTS OE GEOLOGY. 
 
 Dawson in a copi'olite of a terrestrial reptile occurring in a 
 fossil tree, no specimen of this class has been brought to 
 light in the Joggins. But Mr. James Barnes found in a bed 
 of shale at Little Glace Bay, Cape Breton, the wing of an 
 Ej)hemera, which must have measured seven inches from tip 
 to tip of the expanded wings — larger than any known living 
 insect of the Neuropterous family. 
 
 That we should have made so little progress in obtaining 
 a knowledge of the terrestrial fauna of the Coal is certainly 
 a mystery, but we have no reason to wonder at the extreme 
 i-arity of insects, seeing how few are known in the carbonif- 
 erous rocks of Europe, worked for centuries before America 
 was discovered, and now quarried on so enormous a scale. 
 These European rocks have not yet produced a single land- 
 shell, in spite of the millions of tons of coal annually ex- 
 tracted, and the many hundreds of soils replete with the 
 fossil roots of trees, and the erect trunks and stumps pre- 
 served in the position in which they grew. In many large 
 coal-iields we continue ,as much in the dark respecting the 
 invertebrate air-breathers then living, as if the coal had been 
 thrown down in mid-ocean. The early date of the carbonifer- 
 ous strata can not explain the enigma, because we know that 
 while the land supported a luxuriant vegetation, the con- 
 temporaneous seas swarmed with life — with Articulata, Mol- 
 lusca, RadiataJ^nd Fishes. The perplexity in which we are 
 involved when we attempt to solve this problem may be 
 owing partly to our want of diligence as collectors, but still 
 more perhaps to ignorance of the laws which govern thb fos- 
 silization of land-animals, whether of high or low degree. 
 
 Carboniferous Rain-prints. — At various levels in the coal 
 measures of Nova Scotia, ripple - marked sandstones, and 
 shales with rain-prints, were seen by Dr. Dawson and my- 
 self, but still more perfect impressions of rain were discov- 
 ered by Mr. Brown, near Sydney, in the adjoining island of 
 Cape Breton. They consist of very delicate markings on 
 greenish slates, accompanied by worm-tracks (a, 5, Fig. 444), 
 such as are often seen between high and low water mark on 
 the recent mud of the Bay of Fundy. 
 
 The great humidity of the climate of the Coal period had 
 been previously inferred from the number of its ferns and 
 the continuity of its forests for hundreds of miles ; but it is 
 satisfactory to have at length obtained such positive proofs 
 of showers of rain, the drops of which resembled in their av- 
 erage size those which now fall from the clouds. From such 
 data we may presume that the atmosphere of the Carbonif- 
 erous period corresponded in density with that now invest- 
 
DENUDATION IN NOVA SCOTIA. 
 
 417 
 
 ing the globe, and that different currents of air varied then 
 as now in temperature, so as to give rise, by their mixture, 
 to the condensation of aqueous vapor. 
 
 Fig. 444. 
 
 Fig. 445. 
 
 Fig. 446. 
 
 Fig. 444. Carboniferous raiu-priuts witli worm-tracks (a, 6) on green shale, from Cape 
 Breton, Nova Scotia. Natural size. — Fig. 445. Casts of rain-prints on a portion of 
 the same slab (Fig. 444), seen to project on the under side of an iucambent layer of 
 arenaceous shale. Natural size. The arrow represents the supposed direction of 
 the shower. 
 
 Folding aud Denudation of the Beds indicated by the Nova 
 Scotia Coal-strata. — The series of events which are indicated 
 by the great section of the coal-strata in Nova Scotia consist 
 of a gradual and long-continued subsidence of a tract which 
 throughout most of the period was in the state of a delta, 
 though occasionally submerged beneath a sea of moderate 
 depth. Deposits of mud and sand were 
 first carried down into a shallow sea on the 
 low shores of which the foot-prints of rep- 
 tiles were sometimes impressed (see p. 40'?). 
 Though no regular seams of coal were 
 formed, the characteristic imbedded coal- 
 plants are of the genera Gyclopteris and 
 Alethopteris, agreeing with species occur- 
 ring at much higher levels, and distinct 
 trom those of the antecedent Devonian 
 group. The Lepidodendron corrugatum 
 (see Fig. 446), a plant predominating in 
 the Lower Carboniferous group of Europe, 
 is also conspicuous in these shallow-water 
 beds, together with many fishes and ento- 
 mostracans. A more rapid rate of subsidence sometimes con- 
 verted part of the sea into deep clear water, in which there 
 
 IS* 
 
 Cone and branch of 
 Lepidodendron corru- 
 gatum. Lower Car- 
 boniferoue, New 
 Brunswick. 
 
418 
 
 ELEMENTS OF GEOLOGY. 
 
 ■was a growth of coral which was afterwards tm-ned into crys- 
 talline limestone, and parts of it, apparently by the action of 
 sulphuric acid, into gypsum. lu spite of continued sinking, 
 amounting to several thousand feet, the sea might in time 
 have been rendered shallow by the growth of coral, had 
 not its conversion into land or swampy ground been accel- 
 erated by the pouring in of sand and the advance of the 
 delta accompanied with such fluviatile and brackish-water 
 formations as are common in lagoons. 
 
 The amount to which the bed of the sea sank down in or- 
 der to allow of the formation of so vast a thickness of rock 
 of sedimentary and organic origin is expressed by the total 
 thickness of the Carboniferous strata, including the coal- 
 measures, No. 1, and the rocks which underlie them, No. 2, 
 Fig. 447. 
 
 After the strata No. 2 had been elaborated, the conditions 
 proper to a great delta exclusively prevailed, the subsidence 
 
 Fig. 44T. 
 
 N 
 
 ■^i^'p.lr..^ S.Joygins 
 
 ShanlieJi. ^"^ 
 
 ^^^^^^^^g 
 
 
 £?c-r2£SSs=^''^^ — 
 
 Upper Silur 
 
 i tin. 
 
 Diagram showing the curvature and supposed denudation of the Carboniferous 
 
 strata In Nova Scotia. 
 
 A.. Anticlinal axis of Minudie. B. Synclinal of Shonlie Eiver. 1. Coal-measures. 
 
 2. Lower Carboniferous. 
 
 still continuing so that one forest after another grew and 
 was submerged until their under-clays with roots, and usual- 
 ly seams of coal, were left at more than eighty distinct lev- 
 els. Here and there, also, deposits bearing testimony to the 
 existence of fresh or brackish-water lagoons, filled with cal- 
 careo-bituminous mud, were formed. In these beds (A and i, 
 Fig. 439, p. 410) are found fresh-water bivalves or mussels 
 allied to Anodon, though not identical with that or any liv- 
 ing genus, and called Naiadites carbonarius by Dawson. 
 They are associated with small entomostracous crustaceans 
 of the genus Cythere, and scales of small fishes. Occasional- 
 ly some of the calamite brakes and forests of Sigillaria and 
 Coniferse were exposed in the flood season, or" sometimes, 
 perhaps, by slight elevatory movements to the denuding ac- 
 tion of the river or the sea. 
 
 _ In order to interpret the great coast section exposed to 
 view on the shores of the Bay of Fundy, the student must, 
 
NOVA SCOTIA COAL-STRATA. 419 
 
 in the first place, understand that the newest or last-mention- 
 ed coal formations would have been the only ones known to 
 us (for they would have covered all the others), had there 
 not been two great movements in opposite directions, the 
 first consisting of a general sinking of three miles, which 
 took place during the Carboniferous Period, and the second 
 an upheaval of more limited horizontal extent, by which the 
 anticlinal axis A was formed. That the first great change 
 of level was one of subsidence is proved by the fact that 
 there are shallow-water deposits at the base of the Carbonif- 
 erous series, or in the lowest beds of No. 2. 
 
 Subsequent movements produced in the Nova Scotia and 
 the adjoining New Brunswick coal-fields the usual anticlinal 
 and synclinal flexures. In order to follow these, we must 
 survey the country for about thirty miles round the South 
 Joggins, or the" region where the erect trees described in the 
 foregoing pages are seen. As we pass along the clifis for 
 miles in a southerly direction, the beds containing these fos- 
 sil trees, which were mentioned as dipping about 18° south, 
 are less and less inclined, until they become nearly horizontal 
 in the valley of a small river called the Shoulie, as ascertain- 
 ed by Dr. Dawson. After passing this synclinal lin.e the 
 beds begin to dip in an opposite or north-easterly direction, 
 acquiring a steep dip where they rest unconformably on the 
 edges of the Upper Silurian strata of the Cobequid Hills, as 
 shown in Fig. 447. But if we ti-avel northward towards Mi- 
 nudie from the region of the coal-seams and buried forests, 
 we find the dip of the coal-strata increasing from an angle of 
 18° to one of more than 40°, lower beds being continually 
 exposed to view till we reach the anticlinal axis A and see 
 the lower Carboniferous formation. No. 2, at the surface. 
 The missing rocks removed by denudation are expressed by 
 the faint lines at A, and thus the student will see that, ac- 
 cording to the principles laid down in the seventh chapter, 
 we are enabled, by the joint operations of upheaval and de- 
 nudation, to look, as it were, about three miles into the inte- 
 rior of the earth without passing beyond the limits of a sin- 
 gle formation. 
 
420 ELEMENTS OF GEOLOGY. 
 
 CHAPTER XXIV. 
 
 TLOEA AND FAUNA OF THE CAEBONIFEEOUS PEEIOD. 
 
 Vegetation of the Coal Period.— Eeins, Lycopodiacese, Equisetaceae, Sigilla, 
 rise, StigmariiE, Conifers!. — Angiosperms.— Climate of the Coal Period.^ 
 Mountain Limestone. — MarinePauna of theCarboniferous Period.— Corals. 
 — Bryozon, Crinoidea. — Molltisca.— Great Number of fossil Pish. — Fora- 
 minifera. 
 
 Vegetation of the Coal Period. — In the last chapter we 
 have seen that the seams of coal, whether bituminous or an- 
 thracitic, are derived from the same species' of plants, and 
 Goppert has ascertained that the remains of every family of 
 plants scattered through the shales and sandstones of the 
 coal-measures are sometimes met with in the pure coal itself 
 — a fact which adds greatly to the geological interest of this 
 flora. 
 
 The coal period was called by Adolphe Bi-ongniart the age 
 of Acrogens,* so great appears to have been the numerical 
 preponderance of flowerless or cryptogamic plants of the 
 families of ferns, clnb-mosses, and horse-tails. He reckoned 
 the known species in 1849 at 500, and the number has been 
 largely increased by recent research in spite of reductions 
 owing to the discovery that different parts of even the same 
 plants had been taken for distinct species. Notwithstanding 
 these changes, Brongniart's generalization concerning this 
 flora still holds true, namely, that the state of the vegetable 
 world was then extremely diifereut from that now prevailing, 
 not only because the cryptogamous plants constituted nearly 
 the whole flora, but also because they were, on the whole, 
 more highly developed than any belonging to the same class 
 now existing, and united some forms of structure now only 
 found separately and in distinct orders. The only phsenoga- 
 mous plants which constitute any feature in the coal are the 
 eoniferae; monocotyledonous angiosperms appear to have 
 been very rare, and the dicotyledonous, with one or two 
 doubtful exceptions, were wanting-. For this we are in some 
 measure prepared by what we have seen of the Secondary or 
 Mesozoic floras if, consistently with the belief in the theory 
 of evolution, we expect to find the prevalence of simpler and 
 less specialized organisms in older rocks. 
 
 * For botanical nomenclature, see p. 304. 
 
VEGETATION OP THE COAL PErJOD. 
 
 421 
 
 Perns. — We are struck at the first glance with the similar- 
 ity of the ferns to those now living. In the fossil genus Pe- 
 copteris, for example (Fig. 448), it is not easy to decide wheth- 
 er the fossils might not be referred to the same genera as 
 those established for living ferns ; whereas, in regard to some 
 of the other contemporary families of plants, with the excep- 
 tion of the fir tribe, it is not easy to guess even the class to 
 which they belong. The ferns of the Carboniferous period 
 are generally without organs of fructification, but in the few 
 instances in which these do occur in a fit state for microscop- 
 ical investigations they agree with those of the living ferns. 
 
 When collecting fossil specimens from the coal-measures 
 of Frostburg, in Maryland, 1 found in the iron-shales several 
 species with well-preserved rounded spots or marks of the 
 sori (see Fig. 448). In the general absence of such charac- 
 ters they have been divided into genera distinguished chiefly 
 
 Fig. 448. 
 
 Fig. 449. 
 
 Pecopteris elliptwa, Buntury.* Frostburg. 
 
 CaulopterU primcma, Lindiey. 
 
 by the branching of the fronds and the way in which the 
 veins of the leaves are disposed. The larger portion are 
 supposed to have been of the size of ordinary European ferns, 
 but some were decidedly arborescent, especially the group 
 calleA Caulopteris (see Fig. 449) by Lindiey, and the Fmro- 
 niits of the upper ornewest coal-measures, before alluded to 
 (p. 393). All the recent tree-ferns belong to one tribe {JPoli/- 
 podiacece), and to a small number only of genera in that 
 tribe, in which the surface of the trunk is marked with scars, 
 * Sir C. Bunbnry, Quart. Geol. .Tourn.,vol. ii. 1845. 
 
422 
 
 ELEMENTS OF GEOLOGY. 
 
 or cicatrices, left after the fall of the fronds. These scars 
 resemble those of Gaulopteris. 
 
 No less than 130 species of ferns are enumerated as having 
 been obtained from the British coal-strata, and this number is 
 more than doubled if we include the Continental and Amer- 
 ican species. Even if we make some reduction on the ground 
 of varieties which have been mistaken, in the absence of their 
 
 Fig. 451. 
 
 Living tree-ferns of different genera. (Ad. Brong.) 
 
 Pig. 450. Tree-fern from Isle of Bourbon.— Pig. 451. Cijathea gUiwa, Mauritius.— 
 Pig. 452. Tree-fern from Brazil. 
 
 fructification, for species, still the result is singular, because 
 the whole of Europe affords at present no more than sixty- 
 seven indigenous species. 
 
 Lycopodiacese — Xep^■(7oc?enc«lrow. — About forty species of 
 fossil plants of the Coal have been referred to this genus, 
 more than half of which are found in the British coal-meas- 
 ures. They consist of cylindrical stems or trunks, covered 
 with leaf-scars. In their mode of branching, they are always 
 dichotomous (see Fig. 454). They belong to the Lycopodia- 
 eecB, bearing sporangia and spores similar to those of the liv- 
 ing representatives of this family (Fig. 45Y) ; and although 
 most of the Carboniferous species grew to the size of large 
 trees, Mr. Carruthers has found by careful measurement that 
 the volume of the fossil spores did not exceed that of the re- 
 cent club-moss, a fact of some geological importance, as it 
 may help to explain the facility with which these seeds may 
 
VEGETATION OF THE COAL PERIOD. 
 
 423 
 
 have been transported by the wind, causing the same -wide 
 distribution of the species of the fossil forests in Europe and 
 America which we now observe in the geographical distii- 
 bution of so many living families of cryptogamous plants. 
 The Figs. 453-455 represent a fossil Lepidodendron^ 49 feet 
 
 Fig. 453. 
 
 Fig. 454. 
 
 Lepidodendron Stemhergii. Coal-measures, near Newcastle. 
 Fig. 453. Branching tmnk, 49 feet long, supposed to have belonged to L. Stembergii, 
 (FosB. Flo. 203.)— Fig. 4S4 Branching stem with bark and leaves of L. Sternbergii. 
 (Foss. Flo. 4.)— Fig. 455. Portion of same nearer the root. Natural size. (Ibid.) 
 
 long, found in Jarrow Colliery, near Newcastle, lying in shale 
 parallel to the planes of stratification. Fragments of others, 
 found in the same shale, indicate, by the size of the rhoraboidal 
 scars which cov- 
 er them, a still ^'=•^'"'• 
 greater magni- 
 tude. The liv- 
 ing club- moss- 
 es, of which 
 there are about 
 200 species, are 
 most abundant 
 in tropical cli- 
 mates. They 
 usually creep 
 on the gi'ound, 
 but some stand 
 erect, as the ij/- 
 copodium den- 
 sum from New 
 Zealand" (see Figure 456), which attains a height of three 
 feet. 
 
 a. Lycopodmm deneum. Living species. New Zealand. 
 b. Branch ; natural size. c. Part of same, magnified. 
 
424 
 
 ELEMENTS Olf GEOLOGY. 
 
 In the carboniferous strata of Coalbrook Dale, and in many 
 other coal-fields, elongated cylindrical bodies, called fossil 
 cones, named Lepidostrobus by M. Adolphe Brongniart, are 
 met with. (See Fig. 457.) They often form the nucleus of 
 
 Kg. 457. 
 
 a. Lepidostrobm orruUus, Brong. Shropshire ; half natural size.— 6. Portion of a sec- 
 tion, showing the large sporangia in their natural position, and each supported by 
 
 its bract or scale c. Spores in these sporangia, highly magnified. (Hooker, Mem. 
 
 Geol. Survey, vol. ii., part 2, p. 440.) 
 
 concretionary balls of clay-ironstone, and are well preserved, 
 exhibiting a conical axis, around which a great quantity of 
 scales were compactly imbricated. The opinion of M. Bropg- 
 niart that the Lepidostrobus is the fruit of Lepidodendron 
 has been confirmed, for these strobili or fruits have been 
 found terminating the tip of a branch of a well-characterized 
 Lepidodendron in Coalbrook Dale and elsewhere. 
 
 Equisetaces. — ^To this family belong two fossil genera of 
 the coal, Equisetites and Calamites. The Calamites were 
 evidently closely related to the modern horse-tails (Equiseta) 
 difiering principally in their great size, the want of sheaths 
 
 Kg. 463. 
 
 Fig. 45S. 
 
 Calamites Sucowii, Brong. ; natural size. 
 Common in coal throughout Europe. 
 
 Stem of Fig. 458, as restored by 
 Br. Dawson. 
 
 at the joints, and some details of fructification. They grew 
 in dense brakes on sandy and muddy flats in the manner of 
 modern Equisetacese, and their remains are frequent in the 
 
VEGETATION OV THE COAL PERIOD. 
 
 425 
 
 coal. Seven species of this plant occur in the great Nova 
 Scotia section before described, where the stems of some of 
 them five inches in diameter, and sometimes eight feet high, 
 may be seen terminating downward in a tapering root (see 
 Fig. 460). 
 
 Botanists are not yet agreed whether the Asterophyllites, 
 a species of which is represented in the annexed Fig. 461, can 
 
 Fig. 460. 
 
 Fig. 461. 
 
 Eadical termination of a 
 Calamite. Nova Scotia. 
 
 Asterophyllites foliosus. (Foss. Flo. 25.) 
 Coal-measures, Newcastle. 
 
 Fig. 463. 
 
 form a separate genus from the Calamite, from which, how- 
 ever, according to Dr. Dawson, its foliage is distinguished 
 Fi" 462 ^7 ^ *™^ mid-rib, which is wanting in the 
 
 leaves known to belong to some Calamites. 
 
 Figs. 462 and 463 represent leaves of Annu- 
 
 laria and Sphenophyllum, com- 
 mon in the coal, and believed 
 
 by Mr. Carruthers to be leaves 
 
 of Calamites. Dr. Williamson, 
 
 who has carefully studied the 
 
 Calnmites, thinks that they 
 Annuur^^hmo- had a fistular pith exogenous 
 phyuoides, Daw- woody Stem, and thick smooth 
 ^™- bark, which last having always 
 
 disappeared, leaves a fluted stem, as repre- 
 sented in Fig. 459. 
 
 Siffillaria.— A large portion of the trees of „ , . , 
 
 the Carboniferous p-eriod belonged to this genus, of which as 
 many as 28 species are enumerated as British. The structure, 
 both internal and external, was very peculiar, and, with ref- 
 erence to existing types, very anomalous. They were for- 
 merly referred, by M. Ad. Brongniart, to ferns, which they 
 resemble in the scalariform texture of their vessels and, m 
 
 Sphemphyllum ero- 
 swm, Dawson. 
 
426 
 
 ELEMENTS OF GEOLOGY. 
 
 Sigillaria Icmqata, Brong. 
 
 Fig. 464. some degree, in the form of the cica- 
 
 trices left hy the base of the leaf- 
 stalks which have fallen off (see 
 Fig. 464). But some of them are 
 ascertained to have had long linear 
 leaves, quite unlike those of ferns. 
 They grew to a great height, from 
 30 to 60, or even 70 feet, with regu- 
 lar cylindrical stems, and without 
 branches, although some species were 
 dichotomous towards the top. Their 
 fluted trunks, from one to five feet in 
 diameter, appear to have decayed 
 more rapidly in the interior than ex- 
 ternally, so that they became hollow 
 when standing; and when thrown 
 prostrate, they were squeezed down 
 and flattened. Hence, we find the 
 bark of the two opposite sides (now converted into bright 
 shining coal) constitute two horizontal layers, one upon the 
 other, half an inch, or an inch, in their united thickness. 
 These same trunks, when they are placed obliquely or ver- 
 tically to the planes of stratification, retain their original 
 rounded form, and are uncompressed, the cylinder of bark 
 having been filled with sand, which now affords a cast of the 
 interior. 
 
 Dr. Hooker inclined to the belief that the Sigillarim may 
 have been cryptogamous, though more highly developed 
 than any fiowerless plants now living. Dr. Dawson having 
 found in some species what he regards as medullary rays, 
 thinks with Brongniart that they have some relation to gym- 
 nogens, while Mr. Carruthers leans to the opinion that they 
 belong to the LycoiDodiaceaB. 
 
 Stigmaria. — This fossil, the importance of which has al- 
 ready been pointed out, p. 398, was originally conjectured to 
 be an aquatic plant. It is now ascertained to be the root of 
 Sigillaria. The connection of the roots with the stem, pre- 
 viously suspected, on botanical grounds, by Brongniart, was 
 first proved, by actual contact, in the Lancashire coal-field, 
 by Mr. Binney. The fact has lately been shown, even more 
 distinctly, by Mr. Richard Brown, in his description of the 
 Stigmarim occurring in the under-clays of the coal-seams of 
 the Island of Cape Breton, in Nova Scotia. In a specimen 
 of one of these, represented in the annexed figure (Fig. 465), 
 the spread of the roots was sixteen feet, and some of them 
 sent out rootlets, in all directions, into the surrounding clay. 
 
SIGILLARIJE OP THE COAL PERIOD. 
 Fig. 465. 
 
 42? 
 
 Stigmaria attached to a trunk of Sigillaria. 
 
 In the sea-cliffs of the South Jogghis in Nova Scotia,! ex- 
 amined several erect SigillarioB, in company with Dr. Daw- 
 son, and we found that from the lower extremities of the 
 trunk they sent out Stigmarioe as roots. All the stools of 
 the fossil trees dug out by us divided into four parts, and 
 these again bifurcated, forming eight roots, which were also 
 dichotomous when traceable far enough. The cylindrical 
 rootlets formerly regarded as leaves are now shown by more 
 perfect specimens to have been attached to the root by fit- 
 ting into deep cylindrical pits. In the fossil there is rarely 
 any trace of the form of these cavities, in consequence of the 
 
 shrinkage of the 
 
 Fig. 460. 
 
 surrounding tis- 
 sues. Where the 
 rootlets are re- 
 
 moved, 
 remains 
 surface 
 
 nothing 
 on the 
 of the 
 
 stigmaria fioMes, Brong. i natural size. (Foss. Flo. 32.) 
 
 Stigmaria but 
 rows of mammil- 
 lated tubercles 
 (see Figs. 466, 
 46'/), which have 
 formed the base 
 of each rootlet. 
 These protuberances may possibly indicate the place of a 
 joint at the- lower extremity of the rootlet. Rows of these 
 tubercles are arranged spirally round 
 each root, which have always a medul- 
 lary axis and woody system much re- 
 sembling that of SigiUaria, the struc- 
 ture of the vessels being, like it, scalari- 
 form. 
 
 ConifersB-^^The coniferous trees of 
 this period are referred to five genera ; 
 
 Fig. 46T. 
 
 mmM 
 
 Surface of another indlyidua] 
 of same species, showing 
 form of tubercles. "^ 
 Flo. 34.) 
 
 (Fobs, 
 
428 
 
 ELEMENTS OF GEOLOGY. 
 
 Pig.4«s. the woody structure of some of them 
 
 showing that they were allied to the 
 Araucarian division of pines, more than 
 to any of our common European iirs. 
 Some of their trunks exceeded forty-four 
 feet in height. Many, if not all of them, 
 seem to have differed from living Coni- 
 ferm in having large piths ; for Professor 
 Williamson has demonstrated the fossil 
 of the coal-measures called Sternhergia 
 to be the pith of these trees, or rather 
 the cast of cavities formed by the shrink- 
 ing or partial absorption of the original 
 medullary axis (see Figs. 468, 469). This 
 peculiar type of pith is observed in living 
 w"ood, £adoxijim',"ot plants of Very different families, such as 
 BndUcher,f.acta.-edio«- ^j^^ eommon Walnut and the White Jas- 
 mine, in which the pith becomes so re- 
 duced as simply to form a thin lining of 
 the medullary cavity, across which trans- 
 verse plates of pith extend horizontally, 
 so as to divide the cylindrical hollow into 
 When these interspaces have been filled 
 up with inorganic matter, they constitute an axis to which, 
 before their true nature was known, the provisional name of 
 
 Fragment of coniferous 
 
 gitudinally ; from Coal 
 brook Dale. W. C.Wil 
 liamson.* 
 I*. Bark. 6. Woody zone 
 or fibre (pleureuchyma). 
 c. Medulla or pith. d. 
 Cast of hollow pith or 
 " Sternhergia." 
 
 discoid interspaces. 
 
 Magniiied portion of Figure 468; transverse section. 
 
 b, &. Woody fibre. 
 
 Pith. 
 
 Mednllary rays. 
 
 Sternhergia {d, d, Fig. 468) was given. In the above speci- 
 men the structure of the wood (5, Figs. 468 and 469) is conifer- 
 ous, and the fossil is referable to Endlicher's fossil genus Da- 
 doxylon. 
 
 The fossil named Trigonocarpon (Figs. 4'70 and 471), for- 
 merly supposed to be the fruit of a palm, may now, according 
 to Dr. Hooker, be referred, like the Stertibergia, to the Coni- 
 fercB. Its geological importance is great, for so abundant is 
 it in the coal-measures, that in certain localities the fruit of 
 * Manchester Phil. Mem., vol. ix., 1851. 
 
ANGIOSPERMS OF THE COAL-MEASURES. 
 
 429 
 
 Trifjmwcarpum ovatum^ Lind- 
 leyaiidliuttoii. Peel Quar- 
 ry, Lancashire. 
 
 Kg. 472. 
 
 some species may be procured by the Fig. 47o. 
 
 bushel ; nor is there any part of the 
 
 formation where they do not occur, 
 
 except the under-clays and limestone. 
 Fig. 471. The sandstone, iron- 
 
 stone, shales, and 
 coal itself, all contain 
 them. Mr. Binney 
 has at length found 
 
 in the clay-ironstone of Lancashire several 
 specimens displaying structure, and fi'om 
 these, says Dr. Hooker, we learn that the 
 Trigonocarpon belonged to that large sec- 
 tion of existing coniferous plants which bear 
 ^^ fleshy solitary fruits, and not cones. It re- 
 
 Tnganocarpwm olives- ssmbled very closely the fruit of the Chinese 
 /orm«,Linaiey,witii genus Solisburia, one of the Yew tribe, or 
 
 its fleshy envelope, m ■ i -j- 
 
 Felling Colliery, iaxoid COniierS. 
 
 Newcastle. Aiigiosperms. — The curious fossils called 
 
 Antholithes by Lindley have usually been considered to be 
 flower spikes, having what seems a calyx and linear petals 
 (see Fig. 472). Dr. Hooker, after seeing very 
 perfect specimens, also thought that they 
 resembled the spike of a highly-organized 
 plant in full flower, such as one of the £ro- 
 meliacece, to which Prof. Lindley had at first 
 compared them. Mr. Carruthers, who has 
 lately examined a large series in difierent 
 museums, considers it to be a dicotyle- 
 donous angiosperm allied to Orobanche 
 (broom-rape), which grew, not on the soil, 
 but parasitieally on the trees of the coal for- 
 ests. 
 
 In the coal-measures of Granton, near 
 Edinburgh, a remarkable fossil (Fig. 4*73) 
 was found and described in 1840,* by Dr. 
 Robert Paterson. It was compressed be- 
 tween layers of bituminous shale, and consists of a stem 
 bearing a cylindrical spike, a, which in the portion preserved 
 in the slate exhibits two subdivisions and part of a third. 
 The spike is covered on the exposed surface with the four-cleft 
 calyces of the flowers arranged in parallel rows. The stem 
 shows, at b, a little below the spike, remains of a lateral ap- 
 pendage, which is supposed to indicate the beginning of the 
 spathe. The fossil has been referred to the Aroidice, and 
 * Traus. of Bot. Soc. Eainburgh, vol. i., 1844. 
 
 Antholithes. Felling 
 Colliery, Newcastle. 
 
430 
 
 ELEMENTS OF GEOLOGY. 
 
 Fig. 473. 
 
 there is every proba- 
 bility that it is a true 
 member of this order. 
 There can at least be 
 no doubt as to the 
 high grade of its or- 
 ganization, and that 
 it belongs to the 
 monocotyledonouB 
 angiosperras. Mr. 
 Carruthers has care- 
 fully examined the 
 original specimen in 
 the Botanical Muse- 
 um, Edinburgh, and 
 thinks it may have 
 been an epiphyte. 
 
 Climate of the Coal 
 Period. — As to the 
 
 Pothodtea Grantonii, Pat. Coal measiues, Ediubuvgh. dijQate of the Coal 
 
 o. Stem and spike; i natural size. 6. Eemains of the , -j-, „ „ a +1,,^ 
 
 spathe magnified, c. Portion of epike magnified, tne r emS ana inS 
 
 dT One of the calyces magnified. Coniferae are perhaps 
 
 the two classes of plants which may be most relied upon as 
 leading us to -safe conclusions, as the genera are nearly allied 
 to living types. All botanists admit that the abundance of 
 ferns implies a moist atmosphere. But the coniferae, says 
 Hooker, are of more doubtful import, as they are found in 
 hot and dry, and in cold and dry climates; in hot and moist, 
 and in cold and moist regions. In New Zealand the coniferae 
 attain their maximum in numbers, constituting -^-^ part of all 
 the flowering plants ; whereas in a wide district around the 
 Cape of Good Hope they do not form tbttu of tl^^ phenogamio 
 flora. Besides the conifers, many species of ferns flourish in 
 New Zealand, some of them arborescent, together with many 
 lycopodiums; so that a forest in that country may make a 
 nearer approach to the carboniferous vegetation than any 
 other now existing on the globe. 
 
 MAEINE FAUNA OP THE CAKBONIPEEOUS PERIOD. 
 
 It has already been stated that the Carboniferous or 
 Mountain Limestone underlies the coal - measures in the 
 South of England and Wales, whereas in the North, and in 
 Scotland, marine calcareous rocks partly of the age of the 
 Mountain Limestone alternate with shales and sandstones, 
 containing seams of coal. In its most calcareous form the 
 Mountain Limestone is destitute of land-plants, and is loaded 
 
COEALS. 
 
 431 
 
 with marine remains— the greater part, indeed, of the rock 
 being made up bodily of crinoids, corals, and bryozoa with 
 interspersed mollusca. 
 
 Corals. — The Corals deserve especial notice, as the cup-and- 
 star corals, which have the most massive and stony skeletons, 
 display peculiarities of structure by which they may be dis- 
 tinguished generally, as MM. Milne Edwards and Haime first 
 pomted out, from all species found in strata newer than the 
 Permian. There is, in short, an ancient or Palceozoio, and a 
 modern or Neozoic type, if, by the latter term, we designate 
 
 Fig. 4T4. 
 
 Palmozcie type of lamelliferons 
 cnp-shaped Coral. Order Zoan- 
 TUARiA KnGosA, Millie Edwards 
 aDd Jales Haime. 
 
 a. Vertical seciion of Campopkyl- 
 lumfiexuoswn, {CyatJu^hylluTn, 
 Goldfuss) ; i uatural size : from 
 the Devonian of the Bifel. The 
 laTnellce are seen around the in- 
 side of the cap ; the walls con- 
 sist of cellular tissue ; and large 
 transverse, plates, called tubu- 
 Ice, divide the interior into 
 chambers, h. Arrangement of 
 the lamdUe in Polycoslia pro- 
 /urula, Germac, sp. ; nat. size : 
 from theMagnesian Limestone, 
 Durham. This diagram shows 
 the quadripartite arrangement 
 . of the primary septa, charac- 
 teristic of palaeozoic corals, 
 there being four principal and 
 eight intermediate lamellie, the 
 whole number in this type be- 
 ing always a multiple of four. • 
 e. Slauria astrcefformiSy Milne 
 Edwards. Young group, nat. 
 size. Upper Silurian, Goth- 
 land. The lamellae or septal 
 system in each cup are divided 
 by four prominent ridges into 
 four groups. 
 
 Fig. 476. 
 
 Neozoic type of lamellifei'ous 
 cup -shaped Coral. Order 
 
 ZoANTHAEIA APOUOBA, M. Ed- 
 
 wards and J. Haime. 
 a. Parasmilia centralis^ Mantell, 
 sp. Vertical seciion ; natural 
 size. Upper Chalk, Graves- 
 end. In this type the Imnelloe 
 are massive, and extend to 
 the axis or columella com- 
 posed of loose cellular tis- 
 sue, without any transverse 
 plates like those in Fig. 474, a. 
 0. CyathiTia Bowerbamni, Ed. 
 and H. Transverse section, 
 enlarged. Gault, Folkestone. 
 In this coral the primary septa 
 are a multiple of six. The 
 twelve principal plates reach 
 the columella, and between 
 each pair there are three sec- 
 ondaries, in all forty-eight. 
 The short intermediate 
 plates which proceed from 
 the columella are not count- 
 ed. They are called pali. 
 c. Fungia patellarie, Lamk. 
 Recent; very young state. 
 Diagram of its six primary 
 and six secondary septa, mag- 
 nified. The sextuple arrange- 
 ment is always more manifest 
 in the young than in the adult 
 state. 
 
 (as proposed by Prof. E. Forbes) all strata from the triassic 
 to the most modern, inclusive. The accompanying diagrams 
 (Figs.' 474, 475) may illustrate these types. 
 
432 
 
 ELEMENTS OF GEOLOGY. 
 
 It will be seen that the more ancient corals have what is 
 called a quadripartite arrangement of the chief plates or la- 
 mellce — parts of the skeleton which supj^ort the organs of 
 reproduction. The number of these lamellae in the Palaeo- 
 zoic type is 4, 8, 16, etc. ; while in the Neozoic type the num- 
 ber is 8, 12, 24, or some other multiple of six ; and this holds 
 good, whether they be simple forms, as in Figs. 474, a, and 
 475, a, or aggregate clusters of corallites, as in 474, c. But 
 further investigations have shown in this, as in all similar 
 grand generalizations in natural history, that there are ex- 
 ceptions to the rule. Thus in the Lower Greensand Holo- 
 cystis elegans (Ed. and H.) and other forms have the Palaeo- 
 zoic type, and Dr. Duncan has shown to what extent the 
 Neozoic forms penetrate downward into the Carboniferous 
 and Devonian rocks. 
 
 From a great number of lamelliferous corals met with in 
 the Mountain Limestone, two species (Figs. 476, 477) have 
 
 Fig. 4T6. Fig. 47T. 
 
 Lithostrotwn hasaltiforme, Phil. sp. 
 {Litkostrotion striatum, Flemiug; 
 Astrcea basaltiformis,. Coayb. iind 
 PMll.). Bnslaiid, Ireland, Eas- 
 sia, Iowa, and westward of the 
 Mississippi, United States. (D. D. 
 Owen.) 
 
 Lonsdaleia flori/ormie, Martin, sp., M. 
 Edwards. (Lithoatrotifm fioHforme, 
 Fleming. Stromboden.) 
 
 a. Young specimen, with buds or cor- 
 allites on the disk, illustrating cali- 
 cular gemmation, b. Part of a full- 
 grown compound mass. Bristol, 
 etc. ; Russia. 
 
 been selected, as having a very wide range, extending from 
 the eastern borders of Russia to the British Isles, and being 
 found almost everywhere in each countrv. These fossils, to- 
 gether with numerous species of Zaphrentis, Amplexus, Gy- 
 athophyllum, C lisiophyllum, Syrinc/opora, and Michelinia* 
 form a group of rugose corals widely diffei-ent from any that 
 followed them. 
 
 For figures of these corals, see PalEeontographical Society's Monographs, 
 
 1853. 
 
BRYOZOA AND CRINOIDEA.— MOLLUSCA. 433 
 
 Bryozoa and Crinoidea. — Of the Bryozoa, the prevailing 
 forms are Mnestella,, JTemitrypa, and Polypwa, and these 
 often form considerable beds. Their net-like fronds are easi- 
 ly recognized. Crinoidea are also numerous in the Mount- 
 
 Fig. 4T8. 
 
 Fig. 479. 
 
 CyafkoGFinus planus, 
 Miller. Body and 
 arms. 4Ioantaiu 
 Limestone. 
 
 CutUhocritme caryocrinoides, M'Coy. 
 a. Surface of one of the joints of tlie stem. t. 
 Pelvis or body; called also calyr or cup. 
 c. One of the pelvic plates. 
 
 Fig. 480. 
 
 ain Limestone (see Figs. 4Y8, 479), two genera, Pentremites 
 and Codonaster, being pecuUar to this formation in Europe 
 and North America. 
 
 In the greater part of them, the cup or pelvis. Fig. 479, 6, 
 is greatly developed in size in proportion to the arms, al- 
 though this is not the case in Fig. 478. The genera Poteri- 
 ocrinus, Cyathocrimis, Pentremites, Actinocrinvs, and Platy- 
 erimis, are all of them characteristic 
 of this formation. Other Echino- 
 derms are rare, a few Sea-TJrchins 
 only being known : these have a 
 complex structure, with many more 
 plates on their surface than are seen 
 in the modern genera of the same 
 group. One genus, the Paloechinus 
 Fig. 480), is the analogue of the 
 modern Echinus, but has four, five, 
 or six rows of plates in the inter- 
 ambnlacral region or area, whereas the modern genera have 
 only two. The other, Archmocidaris, represents, in like man- 
 ner, the Cidaris of the present seas. 
 
 MoUusca. — The British Carboniferous MoUiisca enumer- 
 ated by Mr. Etheridge* comprise 653 species referable to 86 
 genera, occurring chiefly in the Mountain Limestone. Of 
 * Quart. Geol. .Joum., vol. xxiii., p. 674, 1867. 
 19 
 
 I 
 
 Palcechinus gigas, M'Coy. 
 
 Reduced one-third. Monntain 
 Limestone. Ireland. 
 
434 ELEMENTS OF GEOLOGY. 
 
 Fig. 481. Fig. 
 
 Prodjwtus aemiretiaulatus, Martin, sp. Spirifera trigonalis, Martin, sp. Mourn- 
 
 (P. antiquatus. Sow.) Monutain aiii Limestone. Derbyshire, etc 
 
 Limestone. England, Kussia, the 
 Andes, etc 
 
 this large number only 40 species are common to the under- 
 lying Devonian rocks, 9 of them being Cephalopods, 7 Gas- 
 teropods, and the rest, bivalves, chiefly Brachiopoda (or Pal- 
 liobranchiates). This latter group constitutes the larger part 
 of the Carboniferous Mollusca, 157 
 species being known in Great Britain 
 alone, and it will be found'to increase 
 in importance in the fauna of the pri- 
 mary rocks the lower we descend in the 
 series. Perhaps the most characteristic 
 shells of the formation are large spe- 
 cies of Productus, such as P. giganteus, 
 P. hemisphcericus, P. semireticulatus 
 (Fig. 481), and P. scabricuhis. Large 
 plaited spirifers, as Spiri/era striata, S. rotundata and 8. tri- 
 gonalis (Fig. 482), also abound; and smooth species, such as 
 Spirifera glabra (Fig. 483), with its numerous varieties. 
 
 Spirifera glabra, Martin, sp, 
 Mountain Limestone. 
 
 Fig. 484. 
 
 Fig. 485. 
 
 Fig. 486. 
 
 TerebratulaJtastata, Sow., 
 with radiating bands of 
 color. Mountain Lime- 
 stone. Derbyshire, Ire- 
 land, Hnssia, etc. 
 
 Avieidopcctfm suhlohatus, 
 Phill. MonntainLime- 
 stone. Derbyshire, 
 Yorkshire. 
 
 Pletirottymaria carinata^ 
 Sow. (P. jlamimigara, 
 Phillips). Mountain 
 Limestone. Derby- 
 shire, etc. 
 
 Among the brachiopoda, Terebratida hastata (Fig. 484) de- 
 serves mention, not only for its wide range, but because it 
 often retains the pattern of the oiiginal colored stripes 
 
MOUNTAIN LIMESTONE.— MOLLUSCA. 
 
 435 
 
 which ornamented the living shell. These colored bands are 
 also preserved in several lamellibranchiate bivalves as in 
 Ayiculopecten (Fig. 485), in which dark stripes alternate 
 with a hght ground. In some also of the spiral univalves 
 the pattern of the original painting is distinctly retained, as 
 m Pleurotomaria (Fig. 486), which displays wavy blotches, 
 resembling the coloring in many recent Trochida. 
 
 Some few of the carboniferous mollusca, such as Avicula, 
 NumlM (sub-genus Ctefwdonta), Solemya, and Lithodomus, 
 belong no doubt to existing genera; but the majority, 
 though often referred to as living types, such as Isocardia, 
 Turritella, and JBuccinum, belong really to forms which ap- 
 pear to have become extinct at the close of the Paleozoic 
 epoch. Euomphalus is a characteristic univalve shell of this 
 
 Fig. 4ST. 
 
 ^uynvplmlm pmtangulaiui, Sowerby. Mountain Limestone. 
 a. Upper side. 6. Lower or umbilical side. c. View showing mouth, which is less 
 pentagonal in older individuals, d. View of polished section, showing internal 
 chamSerB. 
 
 period. In the interior it. is divided into chambers (Fig. 48*7, 
 d), the septa or partitions not being perforated as in forami- 
 niferous shells, or in those having siphuncles, like the Nauti- 
 lus. The animal appears to have retreated at different peri- 
 ods of its growth from the internal cavity previously formed, 
 and to have closed all communication with it by a septum. 
 The number of chambers is irregular, and they are generally 
 wanting in the innermost whorl. The animal of the recent 
 TurriteUa communis partitions off in like manner as it ad- 
 vances in age a part of its spire, forming a shelly septum. 
 
436 
 
 ELEMENTS OF GEOLOGY. 
 
 Fig. 489. 
 
 Fig. 4S8. More than twenty species of the genua 
 
 JBellerophon (see Fig. 488), a shell like the 
 living Argonaut without chambers, occur 
 in the Mountain Limestone. The genus 
 is not met with in strata of later date. 
 It is most generally regarded as belong- 
 ing to the pelagic Nucleobranchiata and 
 Beiierophon costatua, Sow. the family Atlantidse, partly allied to the 
 Moantain Limestone. Giasg.Shell, Carinaria; but by some few 
 it is thought to be a simple form of Cephalopod. 
 
 The carboniferous Cephalopoda do not depart so widely 
 from the living type (the Nautilus) as do the more ancient 
 Silurian representatives of the same or- 
 der;, yet they offer some remarkable forms. 
 Among these is Orthoceras, a siphuncled 
 and chambered shell, like a Nautilus un- 
 coiled and straightened (Fig. 489). Some 
 species of this genus are sevei-al feet long. 
 The Goniatite is another genus, nearly al- 
 lied to the Ammonite, from which it dif- 
 fei-s in having the lobes of the septa free 
 fi'om lateral denticulations, or crenatures ; 
 so that the outline of these is angular, con- 
 tinuous, and uninterrupted. The species 
 represented in Fig. 490 is found in most 
 localities, and presents the zigzag charac- 
 ter of the septal lobes in perfection. The 
 dorsal position of the siphuncle,however,clcarly distinguishes 
 
 the Goniatite from the Nauti- 
 lus, and proves it to have be- 
 longed to the family of the 
 Ammonites, from which, in- 
 deed, some authors do not be- 
 lieve it to be generically dis- 
 tinct. 
 
 Fossil Fish.— The distribu- 
 tion of these is singularly par- 
 tial; so much so, that M. de 
 Koninck of Liege, the eminent 
 
 a. Lateral view:^J,.^ront view, sliowing paliBOntologist, once Stated tO 
 
 me that, in making his exten- 
 sive collection of the fossils of the Mountain Limestone of 
 Belgium, he had found no more than four or five examples of 
 the bones or teeth of fishes. Judging from Belgian data, 
 he might have concluded that this class of vertebrata was 
 of extreme rai'ity in the carboniferous seas ; whereas the in- 
 
 Portion of Orthoceras Iw- 
 ierale. Phill. Mount- 
 ain Limestone. 
 
 Fig. 490. 
 
 Goniatitea craiistra, Phillips. Mountain 
 Limestone. North America, Britain, 
 Germany, etc. 
 
FORAMINIFERA OP THE COAL. 
 
 437 
 
 Pig. 491. 
 
 vesbigation of other countries has led to quite a different re- 
 sult. Thus, near Clifton, on the Avon, as well as at numer- 
 ous places around the Bristol basin from the Mendip Hills 
 to Tortworth, there is a celebrated " bone-bed," almost en- 
 tirely made up of ich- 
 thyolites. It occurs at 
 the base of the Lower 
 Limestone shales im- 
 mediately resting upon 
 the passage beds of 
 the Old Red Sandstone. 
 
 Psammodua porosus, Agass. Bone-bed, Mouutaiu Similar bonC - beds OC- 
 
 Limestone. 'Bristol, Ai-magh. ^^^. ^^ ^j^g Carboniferous 
 
 Limestone of Armagh, in Ireland, where they are made up 
 chiefly of the teeth of fishes of the Placoid order, nearly all 
 of them rolled as if drifted ^. ^^^ 
 
 from a distance. Some teeth 
 are sharp and pointed, as in 
 ordinary sharks, of which the 
 genus Uladodus affords an il- 
 lustration; but the majority, 
 as in J'sammodus and Cochli- 
 odus, are, like the teeth of the 
 Cestracion of Port Jackson 
 (see above. Fig. 261, p. 297), 
 
 TTinaalvo mintnl tpptli fit.t.pd for Cochliodus eontortus, AgsisB. Bone-bed, 
 massive paiatai leein nitea lOl ^^lo^main Limestone. TBristoI, Armagh. 
 
 grinding. (See Figs. 491,492.) 
 
 There are upward of seventy other species of fossil fish 
 known in the Mountain Limestone of the British Islands. 
 The defensive fin-bones of these creatures are not unfrequent 
 at Armagh and Bristol ; those known as Oracanthus, Cteno- 
 canthus, and Onchus are often of a very large size. Ganoid 
 fish, such as Holoptychius, also occur ; but these are far less 
 numerous. The great Megalichthys Hibberti appears to 
 range from the Upper Coal-measures to the lowest Carbonif- 
 erous strata. 
 
 Foraminifera.— In the upper part of the Mountain Lime- 
 stone group in the S. W. of England, near Bristol, limestones 
 having a distinct oolitic structure alternate with shales. In 
 these rocks the nucleus of every minute spherule is seen, un- 
 der the microscope, to consist of a small rhizopod or forami- 
 nifer. This division of the lower animals, which is repre- 
 sented so fully at later epochs by the Nummulites and their 
 numerous minute allies, appears in the Mountain Limestone to 
 be restricted to a very few species, among which Textularia, 
 Ifodosaria, Endothyra, and Fumlina (Fig. 493), have been rec- 
 
438 ELEMENTS OF GEOLOGY. 
 
 Fig. 493. ognized. The first two genera are coramon 
 
 to this and all the after periods; the third 
 
 has been found in the Upper Silurian, but is 
 
 ^^?b" sia'^ifled ^"^^ known above the Carboniferous strata; 
 
 sdiam. Monntain the fourth (Fig. 493) is characteristic of the 
 
 Limestone. Mountain Limestone in the United States, 
 
 Arctic America, Russia, and Asia Minor, but is also known 
 
 in the Permian. 
 
CLASSIFICATION. 439 
 
 CHAPTER XXV. 
 
 DEVONIAN OE OLD BED SANDSTONE GEOtJP. 
 
 Classification of the Old Bed Sandstone in Scotland and in Devonshire. — 
 Upper Old Red Sandstone in Scotland, with Ksh and Plants. — Middle 
 Old Red Sandstone.^ — Classification of the Ichthyolites of the Old Red, 
 and their Relation to Living Types. — Lower Old Red Sandstone, with 
 Cephalaspis and Pterygotus. — Marine or Devonian Type of Old Red Sand- 
 stone. — ^Xable of Devonian Series. — Upper Devonian Rocks and Fossils. 
 — Middle. — Lower. — Eifel Limestone of Germany. — Devonian of Russia. 
 — Devonian Strata of the United States and Canada. — Devonian Plants 
 and Insects of Canada. 
 
 Classification of the two Types of Old Red Sandstone. — We 
 have seen that the Carboniferous strata are surmounted by 
 the Permian and Trias, both originally included in England- 
 under the name "New Red Sandstone," from the prevailing 
 red color of the strata. Under the coal came other red 
 sandstones and shales which were distinguished by the title 
 of "Old Red Sandstone." Afterwards the name of "Devo- 
 nian " was given by Sir R. Murchison and Professor Sedg- 
 wick to marine fossiliferous strata which, in the south of 
 England, occupy a similar position between the overlying 
 coal and the underlying Silurian formations. 
 
 It may be truly said that in the British Isles the rocks of 
 this age present themselves in their mineral aspect, and even 
 to some extent in their fossil contents, under two very differ- 
 ent forms ; the one as distinct from the other as are often 
 lacustrine or fluviatile from marine strata. It has indeed 
 been suggested that by far the greater part of the deposits 
 belonging to what may be termed the Old Red Sandstone 
 type are of fresh-water origiu. The number of land-plants, 
 the character of the fishes, and the fact that the only shell 
 yet discovered belongs to the genus Anodonta, must be al- 
 lowed to lend no small countenance to this opinion. In this 
 case the difficulty of classification when the strata of this 
 type are compared in different regions, even where they are 
 contiguous, may arise partly from their having been formed 
 in distinct hydrographical basins, or in the neighborhood of 
 the land in shallow parts of the sea into which large bodies 
 of fresh water entei-ed, and where no marine mollusca or cor- 
 als could flourish. Under such geographical conditions the 
 limited extent of some kinds of sediment, as well as the ab- 
 
440 ELEMENTS OE GEOLOGY. 
 
 sence of those marine forms by which we are able to identify 
 or contrast marine formations, may be explained, while the 
 great thickness of the rocks, which might seem at first sight 
 to require a corresponding depth of water, can often be 
 shown to have been due to the gradual sinking down of the 
 bottom of the estuary or sea where the sediment was accu- 
 mulated. 
 
 Another active cause of local variation in Scotland was the 
 frequency of contemporaneous volcanic eruptions ; some of 
 the rocks derived from this source, as between the Gram- 
 pians and the Tay, having formed islands in the sea, and 
 having been converted into shingle and conglomerate, be- 
 fore the upper portions of the red shales and sandstones were 
 superimposed. 
 
 The dearth of calcareous matter over wide areas is charac- 
 teristic of the Old Red Sandstone. This is, no doubt, in 
 great part due to the absence of shells and corals; but why 
 should these be so generally wanting in all sedimentary 
 rocks the color of which is determined by the red oxide of 
 iron ? Some geologists are of opinion that the waters im- 
 pregnated with this oxide were prejudicial to living beings, 
 others that strata permeated Avith this oxide would not pre- 
 serve such fossil remains. 
 
 In regard to the two types, the Old Red Sandstone and 
 the Devonian, I shall first treat of them separately, and then 
 allude to the proofs of their having been to a great extent 
 contemporaneous. That they constitute a series of rocks in- 
 termediate in date between the lowest Carboniferous and 
 the uppermost Silurian is not disputed by the ablest geolo- 
 gists; and it can no longer be contended that the Upper, 
 Middle, and Lower Old Red Sandstone preceded in date the 
 three divisions to which, by aid of the marine shells, the De- 
 vonian rocks have been referred, while, on the other hand, we 
 have not yet data for enabling us to affirm to what extent 
 the subdivisions of the one series may be the equivalents in 
 time of those of the other. 
 
 Upper Old Red Sandstone. — The highest beds of the series 
 in Scotland, lying immediately below the coal in Fife, are 
 composed of yellow sandstone well seen at Dura Den, near 
 Coupar, in Fife, where, although the strata contain no mol- 
 lusca, fish have been found abundantly, and have been re- 
 ferred to the genera Holopty'chius, Pamphractus, GlyptopO- 
 mus, and many others. In the county of Cork, in Ireland, a 
 similar yellow sandstone occurs containing fish of genera 
 characteristic of tbe Scotch Old Red Sandstone, as for ex- 
 ample Coccosteus (a form represented by many species in the 
 
UPPER OLD RED SANDSTONE. 
 
 441 
 
 Fig. 494 
 
 Old Red Sandstone and by- 
 one only in the Carbonifer- 
 ous group), and Glytolepis 
 anAAsterolepis, both exclu- 
 sively confined to the " Old 
 Red." In the same Irish 
 sandstone at Kiltorkan has 
 
 been found an Anodonta or ^notf<Jnto./«fc«i, Forbes. Uppei Devonian, 
 
 fresh-water mussel, the only Kiltorkan, Ireland. 
 
 shell hitherto discovered in the Old Red Sandstone of the 
 British Isles (see Fig. 494). In the same formation are 
 Fig. 495. found the fern (Fig. 496) and the Lepi- 
 
 dodendron (Fig. 495), and other species 
 of plants, some of which, Professor Heer 
 remarks, agree specifically with species 
 from the lower carboniferous beds. This 
 induces him to lean to 
 the opinion long ago ad- 
 vocated by Sir Richard 
 Griffiths, that the yellow 
 sandstone, in spite of its 
 fish remains, should be 
 classed as Lower Carbon- 
 iferous, an opinion which 
 I am not yet prepared 
 
 Bifarcating branch of Z/e- +„ nrlnnf Rptwppn tViA 
 
 pidoden£-m GHfithaii, \^ aoopr. uetween ttie 
 Brongn. Upper Devo- Mountain Limestone and 
 man, Kilkenny. , ^j^^ ^^jj^^ sandstone in 
 
 the south-west of Ireland there intervenes 
 a formation no less than 5000 feet thick, 
 called the " Carboniferous slate," and at the 
 base of this, in some places, are local depos- 
 its, such as the Glengariff Grits, which ap- 
 pear to be beds of passage between the Car- 
 boniferous and Old Red Sandstone groups. 
 
 It is a remarkable result of the recent ex- 
 amination of the fossil flora of Bear Island, 
 latitude 74° 30' N., that Professor Heer has described as 
 occurring in that part of the Arctic I'egion (nearly twen- 
 ty-six degrees to the north of the Irish locality) a flora 
 agreeing in several of its species with that of the yellow 
 sandstones of Ireland. ThisBear Island flora is believed by 
 Professor Heer to comprise species of plants some of which 
 ascend even to the higher stages of the European Carbonif- 
 erous formation, or as high as the Mountain Limestone and 
 Millstone Grit. Palaeontologists have long maintained that 
 
 .19* 
 
 Falce^terifi Hibernica^ 
 Schiijip. {CyclopUria 
 Hibernica), Edward 
 Forbes (AdiantiteSf 
 Gfip.). Upper De- 
 vonian, Kilkenny. 
 
442 
 
 ELEMENTS OF GEOLOGY. 
 
 the same species which have a wide range in space are also 
 the most persistent in time, which may prepare us to find 
 that some plants having a vast geographical range may also 
 have endured from the period of the Upper Devonian to that 
 of the Millstone Grit. 
 
 Outliers of the Upper " Old Red " occur unconformably on 
 older members of the group, and the formation represented 
 at Whiteness, near Arbroath, a, Fig. 55, p. 74, may probably 
 be one of these outliers, though the want of organic remains 
 renders this uncertain. It is not improbable that the beds 
 given in this section as N"os. 1, 2, and 3, may all belong to 
 Fig 49T *^® early part of the period of the Upper 
 
 Old Red, as some scales of Holoptychius 
 nobilissimus have been found scattered 
 through these beds. No. 2, in Strathmore. 
 Another nearly allied Holoptychius occurs 
 in Dura Den. A figure of this fish is an- 
 nexed (E'ig. 498), and also one of its scales 
 
 ^__ (Fig- 497), as these last are often the only 
 
 Bti&\eotBoioptycUusno- parts met with ; being scattered in Forfar- 
 !>ii»s8jmia,Ag. Clash- giiire through red-colored shales and sand- 
 
 binnie. i nat. size. ° , ^ i ■ « 
 
 Stones, as are scales oi a lai'ge species ot 
 the same genus in a corresponding matrix in Herefordshire.* 
 The number of fish obtained from the British Upper Old Red 
 Sandstone amounts to fifteen species referred to eleven genera. 
 
 Fig. 498. 
 
 Holoptychius, as restored by Professor Hnxley. 
 
 o. Tiie friDged pectoral fine. 6. The fringed ventral fins. t. Anal fin. 
 d, e. Dorsal fins. 
 
 Sir R. Murchison groups with this upper division of the 
 Old Red of Scotland certain light-red and yellow sandstones 
 and grits which occur in the northernmost part of the main- 
 land, and extend also into the Orkney and Shetland Islands. 
 * Silaria, 4th ed., p. 265. 
 
MIDDLE OLD RED SANDSTONE. 443 
 
 They contain Calamites and other plants which agree ge- 
 nerically with Carboniferous forms. 
 
 Middle Old Red Sandstone.— In the northern part of Scot- 
 land there occur a great series of bituminous schists and flag- 
 stones, to the fossil fish of which attention was first called by 
 the late Hugh Miller. They were afterwards described by 
 Agassiz, and the rocks containing them were examined by 
 Sir R. Murchison and Professor Sedgwick, in Caithness, Crom- 
 arty, Moray, Nairn, Gamrie in Banff, and the Orkneys and 
 Shetlauds, in whicli great numbers of fossil fish have been 
 found. These were at first supposed to be the oldest known 
 vertebrate animals, as in Cromarty the beds in which they 
 occur seem to form the base of the Old Red system resting 
 almost immediately on the crystalline or metamorphic rocks. 
 But in fact these fish-bearing beds, when they are traced from 
 north to south, or to the central parts of Scotland, thin out, 
 so that their relative age to the Lower Old Red Sandstone, 
 presently to be mentioned, was not at first detected, the two 
 formations not appearing in superposition in the same dis- 
 trict. In Caithness, however, many hundred feet below the 
 fish-zone of the middle division, remains of Pteraspis were 
 found by Mr. Peach in 1861. This genus has never yet been 
 found in either of the two higher divisions of the Old Red 
 Sandstone, and confirms Sir R. Murchison's previous suspicion 
 that the rocks in which it occurs belong to the Lower " Old 
 Red," or agree in age with the Arbroath paving-stone.* 
 
 Fossil Fish of the Middle Old Med Sandstone. — The De- 
 vonian fish were referred by Agassiz to two of his great or- 
 ders, namely, the Placoids and Ganoids. Of the first of these, 
 which in the Recent period comprise the shark, the dog-fish, 
 and the ray, no entire skeletons are preserved, but fin-spines, 
 called Ichthyodorulites, and teeth occur. On such remains 
 the genera Onchus, Odontacanthus, and Ctenodus, a supposed 
 cestraciont, and some others, have been established. 
 
 By far the greater number of the Old Red Sandstone fishes 
 belong to a snb-order of Ganoids instituted by Huxley in 
 1861, and for which he has proposed the name of Crossoptery- 
 gidce,\ or the fringe-finned, in considei-ation of the peculiar 
 manner in which the fin-rays of the paired fins are arranged 
 so as to form a fringe round a central lobe, as in the Polyp- 
 terus (see a. Fig. 499), a genus of which there are several spe- 
 cies now inhabiting the Nile and other African rivers. The 
 I'eader will at once recognize in Osteolepis (Pig. 500), one of 
 the common fishes of the Old Red Sandstone, many points of 
 
 * Siluria, 4th ed., p. 258. 
 
 t Abridged from Kpoaaairog, crossotos, a fringe, and Trrepuf , pteryx, a fin. 
 
444 
 
 ELEMENTS OP GEOLOGY. 
 Pig. 499. 
 
 Pohmterua. See Agassiz, " Hecherches buv les Poissons FoBsiles." Living in the 
 Nile and other African rivers. 
 
 a One of the fringed pectoral fins. 6. One of the ventral flns. 
 d. Dorsal fin, or row of flnlets. 
 
 . Anal fin. 
 
 analogy with Polypterus. They not only agree in the struc- 
 ture of the fin, at first pointed out by Huxley, but also in the 
 position of the pectoral, ventral, and anal fins, and in hav- 
 ing an elongated body and rhomboidal scales. On the other 
 
 Pig. 500. 
 
 Eestoration of Osteolepis. Pander. Old Eed Sandstone, or Devonian. 
 
 a. One of the fringed pectoral fins. b. One of the ventral flns. o. Anal fln. 
 
 d, e. Dorsal flns. 
 
 hand, the tail is more symmetrical in the recent fish, which 
 has also an apparatus of dorsal finlets of a very abnormal 
 character, both as to number and structure. As to the dor- 
 sals of Osteolepis, the J are regular in structure and position, 
 having nothing remarkable about them, except that there are 
 two of them, which is comparatively unusual in living fish. 
 
 Among the "fringe-finned" Ganoids we find some with 
 rhomboidal scales, such as Osteolepis, above figured ; others 
 with cycloidal scales, as Soloptychivs, before mentioned (see 
 Fig. 498, p. 442). In the genera Dipterus and Diplopterus, as 
 Hugh Miller pointed out, and in several other of the fringe- 
 firined genera, as in Gyroptychius and Glyptolepis, the two 
 doi'sals are placed far backward, or directly over the ventral 
 and anal fins. The Asterolepis was a ganoid fish of gigantic 
 dimensions. A. Asmiisii, Eiohwald, a species characteristic 
 of the Old Red Sandstone of Russia, as well as that of Scot- 
 land, attained the length of between twenty and thirty feet. 
 It was clothed with strong bony armor, embossed with star- 
 like tubercles, but it had only a cartilaginous skeleton. The 
 mouth was furnished with two rows of teeth, the outer ones 
 small and fish-like, the inner larger and with a reptilian char- 
 acter. The Asterolepis occurs also in the Devonian rocks of 
 North America. 
 
MIDDLE OLD RED SANDSTONE. 
 
 445 
 
 If we except the Placoids already alluded to, and a few 
 other families of doubtful affinities, all the Old Red Sand- 
 stone fishes are Ganoids, an order so named by.Agassiz from 
 the shining outer surface of their scales ; but Prof. Huxley 
 has also called our attention to the fact that, while a few 
 of the primary and the great majority of the secondary 
 Ganoids resemble the living bony pike, Lepidosteus, or the 
 Amia, genera now found in North American rivers, and one 
 of them, Lepidosteus, extending as far south as Guatemala, 
 the Crossopteiygii, or fringe-finned Ichthyolites, of the Old 
 Red are closely related to the African Folypterus, which is 
 represented by five or six species now inhabiting the Nile 
 and the rivei's of Senegal. These North American and Afri- 
 can Ganoids are quite exceptional in the living creation ; 
 they are entirely confined to the northern hemisphere, un- 
 less some species of Folypterus range to the south of the line 
 in Africa ; and, out of about 9000 living species of fish known 
 to M. Gtinther, and of which more than 6000 are now pre- 
 served in the British Museum, they probably constitute no 
 more than nine. 
 
 If many circumstances favor the theory of the fresh-water 
 origin of the Old Red Sandstone, this view of its nature is 
 not a little confirmed by our finding that it is in Lake Supe- 
 rior and the other inland 
 Canadian seas of fresh wa- 
 ter, and in the Mississippi 
 and African rivers, that we 
 at present find those fish 
 which have the nearest af- 
 finity to the fossil forms of 
 this ancient formation. 
 
 Among the anomalous 
 foi-ms of Old Red fishes 
 not referable to HuxW's 
 GrosBopterygii is the Pte- 
 riohihys, of which five spe- 
 cies have been found in the 
 middle division of the Old 
 Red of Scotland. Some 
 writers have compared 
 their shelly covering to 
 that of Crustaceans, with which, however, they have no real 
 affinity. The wing-like appendages/ whence the genus is 
 named, were first supposed by Hugh Miller to be paddles, 
 like those of the turtle ; and there can now be no doubt that 
 they do really correspond with the pectoral fins. 
 
 Fig. 601. 
 
 PtericMhys, Agassiz ; Upper side, ahowing 
 momh ; as restored oy H. Miller. 
 
446 
 
 ELEMENTS OE GEOLOGY. 
 
 The number of species of fish already obtained from the 
 middle division of the Old Red Sandstone in Great Britain 
 is about VO, and the principal genera, besides Osteolepis and 
 Pterichthys, already mentioned, are Glyptolepis, Diplacan- 
 thus, Dendrodus, Coccosteus, Cheiracanthus,' and Acanthoides. 
 
 Lower Old Bed Sandstone. — The third or lowest division 
 south of the Grampians consists of gray paving-stone and 
 roofing-slate, with associated red and gray shales; these 
 strata underlie a dense mass of conglomerate. In these gray 
 beds several remarkable fish have been found of the genus 
 
 Fig. 502. 
 
 Cephalaspis Lydlii, Agass. Length flj inches. From a specimen in ray collection 
 found at Glammiss, in Forfarshire. (See other flgares, Agassiz, vol. ii., tah. 1 a 
 and 1 b.) 
 
 u. One of the peculiar scales with which the head is covered when perfect. These 
 scales are generally removed, as in the specimen above figured, b, c. Scales from 
 different parts of the body and tail. 
 
 named by Agassiz Cephalaspis, or " buckler-headed," from 
 the extraordinary shield which covers the head (see Fig. 
 502), and which has often been mistaken for that of a trilo- 
 bite, such as Asaphus. A species of IHeraspis, of the same 
 family, has also been found by the Rev. Hugh Mitchell in 
 Fig. 503. beds of corresponding age in 
 
 Perthshire ; and Mr. Powrie 
 enumerates no less than five 
 genera of the family Acan- 
 thodidse, the spines, scales, 
 and other remains of which 
 have been detected in the 
 gray flaggy sandstones.* 
 
 In the same formation at 
 Carmylie, in Forfarshire, com- 
 monly known as the Arbroath paving-stone, fragments of a 
 huge crustacean have been met with from time to time. They 
 are called by the Scotch quarrymen the "Seraphim," from the 
 * Powrie, Geol. Quart. Jour., vol. xx., p. 417. 
 
 Pterygotue anglims, Agassiz. Middle por- 
 tion of the back of the head called the 
 Seraphim. 
 
LOWER OLD EED SANDSTONE. 
 
 U1 
 
 wing-like form and feath- Fig. 504. 
 
 er-like ornament of the 
 thoracic appendage, the 
 part most usually met 
 with. Agassiz, having 
 previously referred some 
 of these fragments to the 
 class of fishes, was the first 
 to recognize their crus- 
 tacean character, and, al- 
 though at the time unable 
 correctly to determine the 
 true relation of the several 
 parts, he figured the por- 
 tions on which he founded 
 his opinion, in the first 
 plate of his " Poissons 
 Fossiles du Vieux Gr^s 
 Rouge." 
 
 A restoration in correct 
 proportion to the size of 
 the fragments of JP. angli- 
 cus (Fig. 504), from the 
 Lower Old Red Sandstone 
 of Perthshire and Forfar- 
 shire, would give us a crea- 
 ture measuring from five 
 to six feet in lengtli, and 
 more than one foot across. 
 
 The largest crustaceans 
 living at the present day 
 are \helnachus SJjBmpferi, 
 of De Haan,from Japan (a 
 brachyurous or short-tailed crab), chiefly remarkable for the 
 extraordinary length of its limbs; the fore-arm measuring four 
 feet in length, and the others in proportion, so that it covers 
 about 25 square feet of ground ; and the Limulus Molucca- 
 nus, the gi'eat King Crab of China and the Eastern seas, which, 
 when adult, measures 1^ foot across its carapace, and is three 
 feet in length. 
 
 Besides some species of Pterygotus, several of the allied 
 genus Eurypterus occur in the Lower Old Red Sandstone, 
 and with them the remains of grass-like plants so abundant 
 in Forfarshire and Kincardineshire as to be useful to the 
 geologist by enabling him to identify the inferi<jr strata at 
 distant j)oints. Some botanists have suggested that these 
 
 Pterygotus anglicus, Agass. Povfarshire. Ven- 
 tral aspect. Eestored by H. Woodward, 
 F.G.S. 
 
 a. Carapace, showiDg the large sessile eyes at 
 the anterior angles. 6. The metastama or 
 post-oral plate (serving the office of a lower 
 lip), c, c. Chelate appendages (antennules). 
 d. First pair of simple palpi (anieTmce). e. 
 Second pair of simple palpi (mandibles), f. 
 Third pair of simple palpi (first maxillce). 
 a. Pair of swimming feet with their broad 
 basal Joints, whose serrated edges serve the 
 office of truusillce. h. Thoracic plate covering 
 the first two thoracic segments, which are 
 indicated by the figures 1, 2, and a dotted 
 line. 1-6, Thoracic segments. 7-12. Ab- 
 dominal segments. 13. Telson, or tail-plate. 
 
^48 ELEMENTS OF GEOLOGY. 
 
 Fig. 605. PJg.BOe. 
 
 Parka dectpiena, Fleming. 
 In sandstone of lower 
 beds of Old Eed, Ley's 
 Mill, Forfarfihiie. 
 
 Parka decipiem, Fleming, lii slialo 
 of Lower Old Eed, Park Hill, 
 Fife. 
 
 plants may be of the family Fhcviales, and of fresh-water 
 genera. They are accompanied by fossils, called "berries" 
 by the quarrymen, which they compared to a compressed 
 blackberry (see Figs. 505, 506), and which were called "Par- 
 
 ka" by Dr. Fleming. They are 
 
 now considered by Mr. 
 Powrie to be the eggs 
 of crustaceans, which is 
 highly probable, for they 
 have not only been found 
 with Pterygotus angli- 
 cus in Forfarshire and 
 Perthshire, but also in 
 the Upper Silurian strata 
 of England, in which spe- 
 cies of the same genus, 
 Pterygotus, occur. 
 
 Shale of Old Red i TVip m-nnrlfiet PYhihi- 
 
 impressionofp,..„™„„„.s=- — . ^'^^ gianam exniDi 
 
 a. Two pair of ova? resembling those of large tions, sayS Sir K. Murchl- 
 Salamanders or Tritons-on the same leaf, son, of the Old Red Sand- 
 i», b. Detached ova. '._,_., , 
 
 Stone m iingland and. 
 Wales appear in the escarpments of the Black Mountains and 
 in the Fans of Brecon and Carmarthen, the one 2862, and the 
 other 2590 feet above the sea. The mass of red and brown 
 sandstone in these mountains is estimated at not less than 
 10,000 feet, clearly intercalated between the Carboniferous 
 and Silurian strata. No shells or corals have ever been found 
 in the whole series, not even where the beds are calcareous, 
 forming irregular courses of concretionary lumps called "corn- 
 stones," which may be described as mottled red and green 
 earthy limestones. The iishes of this lowest English Old Red 
 are Cephalaspis and Pteraspis, specifically different from spe- 
 cies of the same genera which occur in the uppermost Lud- 
 low or Silurian tilestones. Crustaceans also of the genus 
 Mivryptei'us are met with. 
 
DEVONIAN SERIES IN NORTH DEVON. 449 
 
 Marine or Devonian Type. — We may now speak of the ma- 
 rine type of the British strata intermediate between the Car- 
 boniferous and Silurian, in treating of which we shall find it 
 niuch more easy to identify the Upper, Middle, and Lower 
 divisions with strata of the same age in other countries. It 
 was not until the year 1836 that Sir E. Murchison and Pro- 
 fessor Sedgwick discovered that the culmiferous or anthra- 
 citic shales and sandstones of North Devon, several thousand 
 feet thick, belonged to the coal, and that the beds below 
 them, which are of still greater thickness, and which, like the 
 carboniferous strata, had been confounded under the general 
 name " graywacke," occupied a geological position corre- 
 sponding to that of the Old Red Sandstone already described. 
 In this reform they were aided by a suggestion of Mr. Lons- 
 dale, who, after studying the Devonshire fossils, perceived 
 that they belonged to a peculiar palasontological type of in- 
 termediate character between the Carboniferous and Silurian. 
 
 It is in the north of Devon that these formations may best 
 be studied, where they have been divided into an Upper, 
 Middle, and Lower Group, and where, although much con- 
 torted and folded, they have for the most part escaped being 
 altered by intrusive trap-rocks and by granite, which in 
 Dai-tmoor and the more southern parts of the same county 
 liave often reduced them to a crystalline or metamorphic state. 
 
 DEVONIAN" SEEIES IN NOKTH DEVON. 
 
 (a.) Sandy slates and schists with fossils, 36 species out of 
 110 common to the Carboniferous group (Pilton, Barn- 
 staple, etc.), resting on soft schists in. which fossils are very 
 abundant (Croyde, etc.), and which pass down into 
 
 (6.) Yellow, brown, and red sandstone, with land plants (fiij- 
 clopteris, etc.) and marine shells. One zone, characterized 
 by the abundance of cucuUaea (Baggy Point, Marwood, 
 SI0I3', eic), resting on hard gray and reddish sandstone and 
 micareous flags, no fossils yet found (Dulverton, Pickwell, 
 DoAvii, etc.). 
 
 (a.) Green glossy slates of considerable thickness, no fossils 
 yet recorded from these beds (Mortenoe, Lee Bay, etc.). 
 
 (6.) Slates and schists, with several irregular courses of lime- 
 stone containing shells and corals like those of the Plymouth 
 Limestone (Combe Martin, Ilfracorabe, etc.). 
 
 (a.) Hard, greenish, red, and purple sandstone — no fossils yet 
 found (Hangman Hill, etc.). 
 \ (b.) Soft slates mth subordinate sandstones — fossils nuuierous 
 i i^iHiujN ^j. .j.^rious horizons — Orthis, Corals, Encrinites, etc. (Valley 
 trRonp. 1^ of Rocks, Lynmouth, etc.). 
 
 The above table exhibits the sequence of the strata or 
 subdivisions as seen both on the sea-coast of the British 
 Channel and in the interior of Devon. It will be seen that 
 
 Uppek 
 Devonian 
 OK Pilton 
 
 GKonp. 
 
 Middle 
 Devonian 
 
 OK 
 
 Ilfracombe 
 Gkoup. 
 
 Lower 
 Devonian 
 OR Ltnton 
 
450 
 
 ELEMENTS OF GEOLOGY. 
 
 in all main points it agrees with the table drawn up in 1864 
 for the sixth edition of my " Elements." Mr. Etheridge* has 
 since published an excellent account of the different subdi- 
 visions of the rocks and their fossils, and has also pointed 
 out their relation to the corresponding marine strata of the 
 Continent. The slight modifications introduced in my table 
 since 1864 are the result of a tour made in 1870 in company 
 with Mr. T. McK. Hughes, when we had the advantage of 
 Mr. Etheridge's memoir as our guide. 
 
 The place of the sandstones of the Foreland is not yet 
 clearly made out, as they are cut off by a great fault and 
 disturbance. 
 
 Upper Devonian Eocks. — The slates and sandstones of Barn- 
 staple {a and b of the preceding section) contain the shell 
 ■p. j„g Spirifera disjuncta. Sow. {S. 
 
 Verneuilii, Murch.), (see 
 Fig. 508), which has a very 
 wide range in Europe, Asia 
 Minor, and even China ; also 
 StropJialosia caperata, to- 
 gether with the large tri- 
 
 Spirifera disjuncta, Sow. Syn. Sp. Verneuilii, lobite PhctCOps 
 
 Murch. Upper Devonian, Boulogne. -r-i / tti* .-/\rt\ ' i • i 
 
 Bronn. (see Fig. 609), which 
 is all but world-wide in its distribution. The fossils are nu- 
 
 Fig. 809. 
 
 merous, and comprise about 150 species 
 of mollusca, a fifth of which pass up into 
 the overlying Carboniferous rocks. To 
 this Upper Devonian belong a series of 
 limestones and slates well developed at 
 Petherwyn, in Cornwall, where they have 
 yielded 75 species of fossils. The genus 
 of Cephalopoda called Clymenia (Fig. 
 510) is represented by no less than eleven 
 species, and strata occupying the same 
 position in Germany are called Clyme- 
 nien-Kalk, or sometimes Cypridinen- 
 Schiefer, on account of the number of 
 minute bivalve shells of the crustacean 
 called Gypridina serrato-striata (Fig. 511), 
 which is found in these beds, in the Rhen- 
 ish provinces, the Harz, Saxony, and Sile- ^''af»ps !aft/™!« Broun. 
 
 ^ ,, ■ /^ ',, ,•'-,, I ■ Characteristic of the De- 
 
 sia, as well as in Cornwall and Belgium. vonian in Europe, Asia, 
 
 Middle Devonian Rocks.— We come next ""'' ^- ""^ ®- ^"'"""'• 
 
 to the most typical portion of the Devonian system, including 
 
 the great limestones of Plymouth and Torbay, replete with 
 
 * Qaart. Geol. Jouin., vol. xxiii., 1867. 
 
MIDDLE DEVONIAN ROCKS. 
 
 451 
 
 Fig. BIO. 
 
 Fig. 511. 
 
 Ci/pridina surrato-eiHata, 
 BancllDerger, Weilburg, 
 etc. ; Cornwall, Nas- 
 sau, Saxouy, Belgi- 
 um. 
 
 Clymenia linearis, Miinster. Petherwyn, Corn- 
 wall ; Elbersreuth, Bavaiia. 
 
 Of the corals 51 species are 
 
 Fig. 512. 
 
 shells, trilobites, and corals, 
 enumerated by Mr. Etheridge, 
 noneofwhich pass into theCar- 
 boniferous formation. Among 
 the genera we find Favosites, 
 JlelioUtes, and Cyathophyl- 
 lum. The two former genera 
 are very frequent in Silui-ian 
 
 rocks: some few even of the Helioltteaporosa,Gio\M.,a^^ 
 
 species are said to be common 
 to the Devonian and Silurian 
 groups, as, for example, Fa- 
 vosites cervicornis (Fig. 513), one of the commonest of all 
 
 , . {Pairibee pyri- 
 formis, Lonsd.) 
 a. Portion of the same magniiied. Mid- 
 dle Devonian, Torquay, Plymouth; 
 Eifel. 
 
 Fig. 513. 
 
 Fig. 514 
 
 J'flwsifes cervicornis, Blainv. S. Devon, 
 
 from a polished specimen. 
 
 a. Portion of the same magnified, to 
 
 show the pores. 
 
 a. CyathophyUum ccespitosutn, Goldf. ; 
 Plymouth and Ilfracombe. b. A 
 terminal star. . c. Vertical section, 
 exhibiting transverse plates, and 
 part of another branch. 
 
452 
 
 ELEMENTS OF GEOLOGY. 
 
 the Devonshire fossils. The Cyathophyllum ccespitosum (Fig. 
 614) and Heliolites pyriformis (Fig. 512) are species peculiar 
 to this formation. 
 
 With the above ai'e found no less than eleven genera of 
 stone-lilies or crinoids, some of them, such as Cupressocrini- 
 tes, distinct from any Carboniferous forms. The mollusks, 
 also, are no less characteristic; of 68 species of Brachiopoda, 
 ten only are common to the Carboniferous Limestone. The 
 Stringocephahis Burtini (Fig. 515) and Uncites Gryphus 
 
 Fig. 515. 
 
 Fig. 610. 
 
 Stringocephalits Burtini, Def. 
 a. Valves uuited. b. Interior of venti-al or large 
 valve, showing thick partition and portion of 
 a large process which projects from the dorsal 
 valve across the shell. 
 
 Uncites Gryphus, Def. 
 Middle Devonian. 
 S. Devon and the 
 Continent. 
 
 Fig. 51T. 
 
 (Fig. 616) may be mentioned as exclusively Middle Devo- 
 nian genera, and extremely chai'acteristic of the same divis- 
 ion in Belgium. The String ocephalus is also so abundant 
 in the Middle Devonian of the banks of the Rhine as to have 
 suggested the name of Stringocephalus Limestone. The only 
 
 two species of Brach- 
 iopoda common to 
 the Silurian and De- 
 vonian formations are 
 ' Atr yp a reticularis 
 (Fig. 532, p. 462), 
 which seems to have 
 been a cosmopolitu 
 species, and Stropho- 
 mena rhomboidcdis. 
 
 Among the pecul- 
 iar lamellibranchiate 
 bivalves common to 
 the Plymouth lime- 
 stone of Devonshire 
 and the Continent, 
 we find the Megalodon (Fig. 51 7). There are also twelve 
 genera of Gasteropods which have yielded 36 species, four of 
 which pass to the Carboniferous group, namely Macrocheilus, 
 
 Megalodon cucullatwi, Sow. Eifel ; also Bradley, 
 
 S. Devon. 
 
 a. The valves united. 6. Interior of valve, showing 
 
 the large cardinal tooth. 
 
LOWEE DEYONIAIf BOCKS. 
 
 453 
 
 Fig. 518. 
 
 Acroculia,Euomphalus,&ndLMurchisonia. 
 
 Pteropods occur, such as Gonularia (Fig. 
 
 518), and Cephalopods, such as Cyrtoce- 
 
 ras, Gyroceras, Ort/ioceras, and others, 
 Fig 519. nearly all of genera 
 
 distinct from those 
 prevailing in the Up- 
 per Devonian Lime- 
 stone, or Clymenien- 
 kalk of- the Germans 
 already mentioned (p. 
 450). "Although but 
 few species of Trilo- 
 bites occur, the char- 
 acteristic Bronteus Cmmlaria ormta, WArcn. 
 flaoelhfer (Jb Ig. 5 1 9) is Trans., Sec. Ser., vol. vi. 
 
 Brorams flaMiufer, Goidf. far from rare, and all gjji^f;^ ««*^"'' "''« 
 Mia. BeTon ; s. Devon; collectors are familiar " . - 
 
 with its fan-like tail. In this same group, 
 called, as before stated, the Stringocephalus, or Eifel Lime- 
 stone, in Germany, several fish remains have been detected, 
 and among others the remarkable genus Coccosteus, covered 
 with its tuberculated bony armor; and these ichthyolites 
 serve, as Sir R. Murchison observes (Siluria, p. 362), to iden- 
 tify this middle marine Devonian with the Old lied Sand- 
 stone of Britain and Russia. 
 
 Beneath the Eifel Limestone (the great central and typi- 
 cal member of " the Devonian" on the Continent) lie certain 
 schists called by Ger- 
 man writers " Calceola- 6 ., 
 schiefer," because they 
 contain in abundance 
 a fossil body of very 
 curious structure, Cal- 
 ceola sandalina (Fig. 
 520), which has been 
 usually considered a ^"^■o}^ mMaU-m,, Lam. 
 brachiopod, but which 
 some naturalists have lately referred to a Goniophyllum, sup- 
 posing it to be an abnormal form of the order Zoantharia ru- 
 gosa (see Fig. 474, p. 431), differing from all other corals in 
 being furnished with a strong operculum. This is by no means 
 a rare fossil in the slaty limestone of South D6von, and, like 
 the Eifel form, is confined to the middle group of this country. 
 Lower Devonian Eocks. — A great series of sandstones and 
 o-lossy slates, with Crinoids, Brachiopods, and some corals, oc- 
 
 Fig. 520. 
 
 Eifel ; also South Devon. 
 &. Inner side of dorsal valve. 
 
464 
 
 ELEMENTS OF GEOLOGY. 
 
 Pig. 521. 
 
 rig. 522. 
 
 curring on the coast 
 at Lynmouth and 
 the neighborhood, 
 and called the Lyn- 
 ton Group (see table, 
 p. 449), form the low-. 
 
 Spirifera 'mucronata,'Rsi\\. Devonian of Pennsylvania. ^. ™p™V,py of thp 
 
 Devonian in North Devon. Among the 18 species of all 
 classes enumerated by Mr. Etheridge, 
 two-thirds are common to the Middle 
 Devonian, but only one, the ubiquitous 
 Atrypa reticularis, can with certainty 
 be identified with Silurian species. 
 Among the characteristic forms are 
 Alveolites suborbicularis^ also common 
 to this formation in the Rhine, and Or- 
 this arcuata, very widely spread in the 
 North Devon localities. But we may 
 expect a large addition to the number 
 of fossils whenever these strata shall 
 have been carefully searched. The 
 Spirifer Sandstone of Sandberger, as 
 exhibited in the rocks bordering the 
 Rhine between Coblentz and Caub, be- 
 long to this Lower division, and the 
 same broad-winged Spirifers distinguish 
 the Devonian strata of North America. 
 
 Among the Trilobites of this era sev- 
 eral large species oi Homalonotus (Fig. 
 522) are conspicuous. The genus is still 
 better known as a Silurian form, but the 
 spinose species appear to belong exclu- 
 sively to the " Lower Devonian," and are found in Britain, 
 Europe, and the Cape of Good Hope. 
 
 Devonian of Russia. — The Devonian strata of Russia ex- 
 tend, according to Sir R. Murchison, over a region more spa- 
 cious than the British Isles ; and it is remarkable that, where 
 they consist of sandstone like the " Old Red " of Scotland 
 and Central England, they are tenanted by fossil fishes often 
 of the same species and still oftener of the same genera as 
 the British, whereas when they consist of limestone they con- 
 tain shells similar to those of Devonshire, thus confirming, 
 as Sir Roderick has pointed out, the contemporaneous origin 
 which had been previously assigned to formations exhibiting 
 two very distinct mineral types in diiferent parts of Britain.* 
 * Murchison's Siluria, p. 329. 
 
 Jlomalonoius armatus, Bnr- 
 meistev. Lower' Devoni- 
 an; Dauu, in the Bifel; 
 and S. Devon. 
 
 Ohs. The two rows of spines 
 down the body give an ap- 
 pearance of more distinct 
 trilobation than really oc- 
 curs in this or most other 
 species of the genus. 
 
BEVONIAN STRATA IN TBJE UNITED STATES. 455 
 
 The calcareous and the arenaceous roots of Russia above at 
 luded to alternate in such a manner as to leave no doubt cf 
 their having been depos- Fig. 623. 
 
 ited in different parts of 
 the same great period. 
 
 Devonian Strata in the 
 United States and Canada. 
 — Between the Carbonif- 
 erous and Silurian strata 
 there intervenes, in the 
 United States and Canada, 
 a great series of formations 
 referable to the Devonian 
 group, comprising some 
 strata of marine origin 
 abounding in sheila and 
 coi-als, and others of shal- 
 low - water and littoral 
 origin in which terrestrial 
 plants abound. The fos- 
 sils, both of the deep and 
 shallow water strata, are 
 very analogous to those 
 of Europe, the species be- 
 ing in some cases the 
 same. In Eastern Canada 
 Sir W. Logan has pointed 
 out that in the peninsula 
 of Gaspe, south of the es- 
 tuary of St. Lawrence, a 
 mass of sandstone, con- 
 glomerate, and shale refer- 
 able to this period occurs, 
 rich in vegetable remains, 
 together with some fish- 
 spines. Far down in the 
 sandstones of Gasp6, Dr. 
 Dawson found, in 1869, an 
 
 nnt;«» o,«^«;.„«« ^e ^l,n ™« Psilopliytan princms, Dawson, Qnart. Geol. 
 entire specimen Ot the ge- joj*;.^;^ vol. xv., im- and Oanlcla Survey, 
 "^ ' ' ■ " 1863. Species characteristic of the whole 
 
 Devonian series in North America. 
 
 a. Fruit; natural size. 6. Stem; natural size, 
 c. Scalariform tissue of the axis highly mag- 
 
 nified. 
 
 nus Cephalaspis, a form so 
 characteristic, as we have 
 already seen, of the Scotch 
 Lower Old Red Sand- 
 stone. Some of the sandstones are rippled-marked, and to- 
 wards the upper part of the whole series a thin seam of coal 
 has been observed, measuring, together with s»me associate^ 
 
456 ELEMENTS OF GEOLOGY. 
 
 carbonaceous shale, about three inches in thickness. It rests 
 on an under-clay in which are the roots of Psilophyton (see 
 Fig. 523). At many other levels rootlets of this same plant 
 have been shown by Principal Dav/son to penetrate the clays, 
 and to play tlie same jpart as do the rootlets of Stigmaria in 
 tlie coal formation. 
 
 We had already learnt from the works of Goppert, linger, 
 and Bronn that the European plants of the Devonian epoch 
 resemble generically, with few exceptions, those already 
 known as Carboniferous; and Di-. Dawson, in 1859, enumer- 
 ated 32 genera and 69 species which he had then obtained 
 from the State of ISTew York and Canada. A perusal of his 
 catalogue,* comprising Coniferm, SigiUarice, Ccdamites, Aste- 
 rophyllites, Lepidoderidra, and ferns of the genera Cyclopteris, 
 Neuropteris, Sphenopteris, and others, together with fruits, 
 such as Gardiocarpum and Trigonocarpum, might dispose 
 geologists to believe that they were presented with a list of 
 Carboniferous fossils, the difference of the species from those 
 of the coal-measures, and even a slight admixture of genera 
 unknown in Europe, being naturally ascribed to geographical 
 distribution and the distance of the New from the Old World. 
 But fortunately the coal formation is fully developed on the 
 other side of the Atlantic, and is singularly like that of Eu- 
 rope, both lithologically and in the species of its fossil plants. 
 There is also the most unequivocal evidence of relative age 
 afforded by superposition, for the Devonian strata in the 
 United States are seen to crop out from beneath the carbon- 
 iferous on the borders of Pennsylvania and New York, where 
 both formations are of great thickness. 
 
 The number of American Devonian plants has now been 
 raised by Dr. Dawson to 120, to which we may add about 80 
 from the European flora of the same age, so that already the 
 vegetation of this period is beginning to be nearly half as rich 
 as that of the coal-measures which have been studied for so 
 much longer a time and over so much wider an area. The 
 Psilophyton above alluded to is believed by Dr. Dawson to 
 be a lycopodiaceous plant, branching dichotomously (see F. 
 princeps. Fig. 523), with stems springing from a rhizome, 
 which last has circular areoles, much resembling those of 
 Stigmaria, and like it sending forth cylindrical rootlets. The 
 extreme points of some of the branchlets are rolled up so as 
 to resemble the croziers or circinate vernation of ferns ; the 
 leaves or bracts, a, supposed to belong to the same plant, are 
 described by Dawson as having inclosed the fructification. 
 The remains oi Psilophyton princeps have been traced through 
 * Quart. Geol. Joumal, vol. xv., p. 477, 1859 ; also vol. xviil., p. 296, 1862. 
 
DEVONIAN INSECTS OF CANADA. 457 
 
 all the members of the Devonian series in America, and Dr. 
 Dawson has lately recognized it in specimens of Old Eed 
 Sandstone from the north of Scotland. 
 
 The monotonous character of the Carboniferous flora might 
 be explained by imagining that we have only the vegetation 
 handed down to us of one set of stations, consisting of wide 
 swampy flats. But Dr. Dawson supposes that the geograph- 
 ical conditions under which the Devonian plants grew were 
 more varied, and had more of an upland character. If so, the 
 limitation of this more ancient flora, represented by so many 
 genera and species, to the gymnospermous and cryptogamous 
 orders, and the absence or extreme rarity of plants of higher 
 grade, lead us naturally to speculate on the theory of pro- 
 gressive development, however difficult it may be to avail 
 ourselves of -this explanation, so long as we meet with even 
 a few exceptional cases of what may seem to be monocotyled- 
 onous or dicotyledonous exogens. 
 
 Devonian Insects of Canada. — The earliest known insects 
 were brought to light in 1865 in the Devonian strata of St. 
 John's, New Brunswick, and are referred by Mr. Scudder to 
 four species of JVeuroptera. One of them is a gigantic Ephem- 
 era, and measured five inches in expanse of wing. 
 
 Like many other ancient animals, says Dr. Dawson, they 
 show a remarkable union of characters now found in distinct 
 orders of insects, or constitute what have been named " syn- 
 thetic types." Of this kind is a stridulating or musical ap- 
 paratus like that of the cricket in an insect otherwise allied 
 to the JVeuroptera. This structure, as Dr. Dawson observes, 
 if rightly interpreted by Mr. Scudder, introduces us to the 
 sounds of the Devonian woods, bringing before our imagina- 
 tion the trill and hum of insect life that enlivened the soli- 
 tudes of these strange old forests. 
 
 20 
 
458 ELEMENTS OF GEOLOGY. 
 
 CHAPTER XXVI. 
 
 SILUEIAlSr GKOUP. 
 
 Classification of the Silurian Rocks.— Ludlow Formation and Fossils.— Bone- 
 bed of the Upper Ludlow.— Lower Ludlow Shales with Pentamerm. — 
 Oldest known Kemains of fossil Fish.— Table of the progressive Discovery 
 of Vertebrata in older Eocks. — Wenlock Formation, Corals, Cystideans 
 and Trilobites. — Llandovery Group or Beds of Passage.— ^Lower Silurian 
 Eocks. — Caradoc and Bala Beds. — Brachiopoda. — Trilobites. — Cystideas. 
 ^Graptolites. — Llandeilo Flags. — Arenig or Stiper-stones Group. — For- 
 eign Silurian Equivalents in Europe. — Silurian Strata of the United States. 
 —Canadian Equivalents. — Amount of specific Agreement* of Fossils with 
 those of Europe. 
 
 Classification of the Silurian Roeks. — We come next in de- 
 scending order to that division of Primary or Palsaozoic 
 rocks which immediately underlie the Devonian group or 
 Old Red Sandstone. For these strata Sir Roderick Murchi- 
 son first proposed the name of Silurian when he had studied 
 and classified them in that part of Wales and some of the 
 contiguous counties of England which once constituted the 
 kingdom of the Silures, a tribe of ancient Britons. The fol- 
 lowing table will explain the two principal divisions, Upper 
 and Lower, of the Silurian rocks, and the minor subdivisions 
 usually adopted, comprehending all the strata originally em- 
 braced in the Silurian system by Sir Roderick Murchison. 
 The formations below the Arenig or Stiper-stones group are 
 treated of in the next chapter, when the " Primordial " or 
 Cambrian group is described. 
 
 UPPER SILXJEIAlSr ROCKS. 
 
 , ^ _ Thickness 
 
 1. Ludlow Formation : in feet. 
 
 a. Upper Ludlow beds 780 
 
 b. Lower Ludlow beds 1,050 
 
 2. Wenlock Formation : 
 
 a. Wenlock limestone and shale \ h i 000 
 
 b. Woolhope limestone and shale, and Denbighshire grits) ^ °^^ ' 
 
 3. Llandovery Formation (Beds of passage between Upper 
 
 and Lower Silurian) : 
 
 a. Upper Llandovery (May-Hill beds) 800 
 
 b. Lower Llandovery 600-1,000 
 
 LOWER SILURIAN ROCKS. 
 
 1. Bala and Caradoc Beds, including volcanic rocks . . . 12,000 
 
 2. Llandeilo Flags, including volcanic rocks 4,500 
 
 3. Abenig or Stiper-stones Group, including volcanic 
 
 rocks above 10,000 
 
UPPER LUDLOW BEDS. 459 
 
 UPPER SILURIAN- ROCKS. 
 
 1. Ludlow Formation. — This member of the Upper Silurian 
 group, as will be seen by the above table, is of great thick- 
 ness, and subdivided into two parts — the Upper Ludlow and 
 the Lower Ludlow. Each of these may be distinguished near 
 the town of Ludlow, and at other places in Shropshire and 
 Herefordshire, by peculiar organic remains ; but out of more 
 than 500 species found in the Ludlow formation as a whole, 
 not more than five species per cent, are common to the over- 
 lying Devonian. The student may refer to the excellent 
 tables given in the last edition of Sir R. Murchison's Siluria 
 for a list of the organic remains of all classes distributed 
 through the different subdivisions of the Upper and Lower 
 Silurian. 
 
 a. Upper Ludlow: Dovmton Sandstone. — At the top of this 
 subdivision there occur beds of fine-grained yellowish sand- 
 stone and hard reddish grits which were formerly referred by 
 Sir R. Murchison to the Old Red Sandstone, under the name 
 of " Tilestones." In mineral character this group forms a 
 transition from the Silurian to the Old Red Sandstone, the 
 strata of both being conformable ; but it is now ascertained 
 that the fossils agree in great part specifically, and in gen- 
 eral character entirely, with those of the underlying Upper 
 Ludlow rocks. Among these are Orthoceras bullatum, Pla- 
 tyschisma hdicites, BeUerophon trilobatus, Ghonetes lata, etc., 
 with numerous defenses of fishes. 
 
 These beds, therefore, now generally called the " Downton 
 Sandstone," are classed as the newest member of the Upper 
 Silurian. They are well seen at Downton Castle, near Lud- 
 low, where they are quarried for building, and at Kington, in 
 Herefordshire. In the latter place, as well as at Ludlow, crus- 
 taceans of the genera Pterygotus (for genus see Fig. 504, p. 
 447) and Eurypterus are met with. 
 
 JBon&-bed of the Upper Ludlow. — At the base of the Down- 
 ton sandstones there occurs a bone -bed which deserves 
 especial notice as affording the most ancient example of fos- 
 sil fish occurring in any considerable quantity. It usually 
 consists of one or two thin layers of brown bony fragments 
 near the junction of the Old Red Sandstone and the Ludlow 
 rocks, and was .first observed by Sir R. Murchison near the 
 town of Ludlow, where it is three or four inches thick. It 
 has since been tj-aced to a distance of 45 miles from that 
 point into Gloucestershire and other counties, and is common- 
 ly not more than an inch thick, but varies to nearly a foot. 
 N'ear Ludlow two bone-beds are observable, with 14 feet of 
 
460 
 
 ELEMENTS OF GEOLOGY. 
 
 intervei)iug strata full of Upper Ludlow fossils.* At that 
 point immediately above the upper fish-bed numerous small 
 globular bodies have been found, which were determined by 
 Dr. Plooker to be the sporangia of a cryptogamic land-plant; 
 probably lycopodiaceous. 
 
 Most of the fish have been referred by Agassiz to his pla- 
 coid order, some of them to the genus Onchus, to which the 
 spine (Fig. 624) and the minute scales (Fig. 525) are sup- 
 
 Fig. 524. 
 
 Fig. S25. 
 
 a 
 
 O^ichus-tenuistriatwi, Agass. Boue-bed. 
 Upper Silurian. Ludlow. 
 
 Shagreen-scales of a placoid 
 fish, Thelodits parvidens^ Ag. 
 Boae-hed, Upper Ludlow. 
 
 Plectrodus mirabilis, Agass, 
 Bone-hed, Upper Ludlow. 
 
 Fig. 52T. 
 
 posed to belong. It has been suggested, however, that On- 
 chus may be one of those Acanthodian fish referred by Agas- 
 siz to his Ganoid order, which are so characteristic of the 
 base of the Old Red Sandstone in Forfarshire, although the 
 species of the Old Red are all difierent from these of the Si- 
 lurian beds now under consideration. 
 The jaw and teeth of another preda- 
 ceous genus (Fig. 526) have also been 
 detected, together with some speci- 
 mens oil^eraspis Ludensis. As usual 
 in bone-beds, the teeth and bones are, 
 for the most part, fragmentary and rolled. 
 
 Gray Sandstone and Mudstone, etc. — The next subdivision 
 of the Upper Ludlow consists of gray 
 calcareous sandstone, or very commonly 
 a micaceous stone, decomposing into soft 
 mud,_and contains, besides the shells 
 mentioned at page 459, Lingula cornea, 
 Orthis orbicularis, a round variety of 0. 
 elegantula, Modiolopsis platyphylla, 
 Grammy sia cingulata, all characteristic 
 of the Upper Ludlow. The lowest or mud-stone beds con- 
 Fig. 628. tain Rhynchotiella ndvicula (Fig. 528), 
 which is common to this bed and the 
 Lower Ludlow. As usual in Palaeozoic 
 strata older than the coal, the brachio- 
 •*=s^ -^r podons mollusca greatly outnumber the 
 Rhynchoneiianavimiia, lamellibranchiate (see p. 4*70) • but the 
 ^sow. LudiowBeds. jj^t^er are by no means unrepresented. 
 Among other genera, for example, we observe Avioula and 
 
 * Murchison's Siluria, p. 140. 
 
 Orthis elegantula, Dalm. 
 Var. OrhiculariSj Sow. 
 Upper Ludlow. 
 
LOWER LUDLOW BEDS. 461 
 
 Pt€rin^a,Cardiola,Ctenodonta (sab-genus of JVucula), Ortho- 
 nota, Modiolopsis, and Palmarca. 
 
 Some of the Upper Ludlow sandstones are ripple-marked, 
 thus affording evidence of gradual deposition ; and the same 
 may be said of the accompanying fine argillaceous shales, 
 which are of great thickness, and have been provincially 
 named " mud-stones." In some of these shales stems of cri- 
 noidea are found in an erect position, having evidently be- 
 come fossil on the spots where they grew at the bottom of 
 the sea. The facility with which these rocks, when exposed 
 to the weather, are resolved into mud, proves that, notwith- 
 standing their antiquity, they are nearly in the state in which 
 they were first thrown down. 
 
 Lower Ludlow Beds. — The chief mass of this formation 
 consists of a dark gray argillaceous shale with calcareous 
 concretions, having' a maximum thickness of 1000 feet. In 
 some places, and especially at Aymestry, in Hei'efordshire, a 
 subcrystalline and argillaceous limestone, sometimes 50 feet 
 thick, overlies the shale. Sir R. Murchison therefore classes 
 this Aymestry limestone as holding an intermediate posi- 
 tion between the Upper and Lower Ludlow, but Mr. Light- 
 body remarks that at Mocktrie, near Leintwardine, the Lower 
 Ludlow shales, with their characteristic fossils, occur both 
 above and below a similar limestone. This limestone around 
 Aymestry and Sedgeley is distinguished by the abundance of 
 JPentamerus Knightii, Sow. (Fig. 529), also found in the Low- 
 
 Fig. 529. 
 
 Pentamertts Knightii, Sow. Aymestry. One-half natural size. 
 
 a. View of both valves nnitefl. 6. Longitndinal section through both valves, 
 
 showing the central plates or septa. 
 
 er Ludlow and Wenlock shale. This genus of brachiopoda 
 was first found in Silurian strata, and is exclusively a palae- 
 ozoic form. The name was derived from wevte, pente, five, 
 and /itpoc, meros, a part, because both valves are divided by 
 a central septum, making four chambers, and in one valve 
 
462 
 
 ELEMENTS OF GEOLOGY. 
 
 Fig. 530. 
 
 the septum itself contains a small chamber, making five. 
 The size of these septa is enormous compared with those of 
 any other brachiopod shell; and they must nearly have di- 
 vided the animal into two equal halves ; but they are, nev- 
 ertheless, of the same nature as the septa or plates which are 
 found in the interior of Spirifera, Terebratula, and many oth- 
 er shells of this order. Messrs. Murchison 
 and De Verneuil discovered this species dis- 
 persed in myriads through a white limestone 
 of Upper Silurian age, on the banks of the 
 Is, on the eastern flank of the Urals in Rus- 
 sia, and a similar species is frequent^ in 
 Sweden. 
 
 Three other abviudant shells in the Ayme- 
 stry limestone are, 1 st, Lingula Lewisii (Fig. 
 530) ; 2d, Rhyivihondla Wilsoiii, Sow. (Fig. 
 531), which is also common to the Lower 
 Sow. Abberiey Ludlow and Wenlock limestone ; 3d, Atrypa 
 ^^^ ^' reticularis, Linn. (Fig. 532), which has a very 
 
 wide range, being found in every part of the Upper Silurian 
 system, and even Fig. 531. 
 
 ranging up into 
 the'Middle Devo- , 
 
 Lingula Lewisii, J. 
 
 man series. 
 
 The Aymestry 
 Limestone con- 
 tains many shells Shync?wmlla(,Terebratula) Wilsoni,Sow. Aymestry. 
 
 especially brachiopoda, corals, trilobites, and other fossils, 
 amounting on the whole to 74 species, all except three or 
 Fig. 632. four being com- 
 
 mon to the beds 
 either above or be- 
 low. 
 
 The Lower Lud- 
 low Shale contains, 
 among other fos- 
 sils, many large 
 cephalopoda not 
 known in newer 
 rocks, asihePhraff- 
 moceras of Brode- 
 rip, and the Ziitiir 
 
 Atnjpa reticularis, Linu^^(Kre6rot«to afflnis. Min. Con.) ifesofBreyniuS (see 
 u. Upper valve, b. Lower valve, c. Anterior margin of FigS. 533, 534). 
 
 "'"•'^'™'- The latter is part- 
 
 ly straight and partly convoluted in a very flat spire. The 
 
OLDEST KNOWN FOSSIL FISH. 
 
 463 
 
 Orthoceras Ludense (Fig. 535), as well Pig. 633. 
 
 as the cephalopod last mentioned, oc- 
 curs in this member of the series. 
 
 A species of Graptolite, G. priodon, 
 Bronn (Fig. 545, p. 467), occurs plenti- 
 fully in the Lower Ludlow. This fos- 
 sil, referred, though somewhat doubt- 
 fully, to a form of hydrozoid or sertu- 
 larian polyp, has not .yet been met with 
 in strata ^bove the Silurian. 
 
 Star-fish, as Sir R. Murchison points 
 out, are by no means rare in the Lower 
 Ludlow rock. These fossils, of which 
 six extinct senera are now known in -PA'-«3'»fl»f «« *™'™<'«««. J- 
 tne Liudlow series, represented by 18 comm, stein.) AymeBtry; 
 
 species, remind us of various living o"«-1i«rter nataral size. 
 
 forms now found in our British seas, both of the families As- 
 teriadce and Ophiuridce. 
 
 Pig. 534. 
 
 Pig. 535. 
 
 lAtniUs (Trochoceras) giganteus, J. Sow. 
 Near Ludlow-; also in the Aymestiy 
 and Wenlock Limestones ; J nat. size. 
 
 Fragment of Orthoceras Imdense^ 
 J. Sow. Leintwardiue, Shrop- 
 shire. 
 
 Oldest known Fossil Fish. — ^Until 1859 there was no ex- 
 ample of a fossil fish older than the bone-bed of the Upper 
 Ludlow, but in that year a specimen of Pteraspis was found 
 at Church Hill, near Leintwardine, in Shropshire, by Mr. J. E. 
 Lee of Caerleon, F.G.8., in shale below the Aymestry lime- 
 stone, associated with fossil shells of the Lower Ludlow for- 
 mation — shells which differ considerably from those charac- 
 terizing the Upper Ludlow already described. This dis- 
 covery is of no small interest as bearing on the theory of 
 progressive development, because, according to Professor 
 Huxley, the genus Pteraspis is allied to the sturgeon, and 
 therefore by no means of low grade in the piscine class. 
 
 It is a fact well worthy of notice that no remains of ver- 
 tebrata have yet been met with in any strata older than the 
 Lower Ludlow. 
 
 When we reflect on the hundreds of Mollusks, Echino- 
 
464 
 
 ELEMENTS OF GEOLOGY. 
 
 devms, Trilobites, Corals, and other fossils already obtained 
 from more ancient Silurian formations, Upper, Middle, and 
 Lower, we may well ask. whether any set of fossiliferous 
 rocks newer in the series were ever studied with equal dili- 
 gence, and over so vast an area, without yielding a single 
 ichthyolite. Yet we must hesitate before we accept, even 
 on such evidence, so sweeping a conclusion, as that the globe, 
 for ages after it was inhabited by all the great classes of inver- 
 tebrata, remained wholly untenanted by vertebrate animals. 
 
 Dates of the Discovery of different Classes of Fossil VertebrOta ; showing 
 the gradual progress made in tracing them to rocks of higher antiquity. 
 
 Year. Formations. Geographical Localities. 
 
 r,™>n TT -r, (Paris CGypsum of Mont- 
 
 1798-Upper Eocene j ^^rtre)!' 
 
 1818— Lower Oolite Stonesfield." 
 
 ^1847— Uppei-Trias Stuttgart.' 
 
 '-irron TT T7. (Paris(Gvpsum 
 
 1782-Upper Eocene \ n,artre)> 
 
 1839-T-™. -Rnn^no Jlsle of Sheppey (London 
 
 Mammalia ■ 
 
 Aves. 
 
 1 of Mont 
 
 -Lower Eocene 
 
 Beptilia...-^ 
 
 Pisces. 
 
 .1 
 
 \ Clay).' 
 
 1854 — " " Woolwich Beds.' 
 
 1855— " " Meudon (Plastic Clay).' 
 
 1858— Chloritic Series, or Upper) Cambridge ' 
 
 Greensand ) 
 
 1863— Upper Oolite Solenhofen." 
 
 1710— Permian (or Zechstein) . . Thuringia.^" . 
 
 1844 — Carboniferous . . . ... Saarbruck, near Treves." 
 
 ''1709 — Permian (or Kupferschiefer) . Thurin^a." 
 1793 — Carboniferous (Mounta' 
 
 Limestone) 
 
 *'"! Glasgow." 
 
 1828 — Devonian Caithness." 
 
 1840— Upper Ludlow Ludlow. =' 
 
 1859 — Lower Ludlow Leintwardine. " 
 
 > George Cuvier, Bulletin Soc. Philom. xx. 
 
 ^ In 181S, Cuvier, visiting the Museum of Oxford, decided on the mammalian char- 
 acter of a jaw from Stonesheld. See also above, p. 34T. 
 
 1 Plieninger, Prof. See above, p. 36S. 
 
 * Cuvier, Ossemens Foss., Art. "Oiseaux." 
 
 1 Owen, Prof., Geol. Trans., 2d series, vol. vi., p. 203, 1S39. 
 
 « Upper part of the Woolwich beds. Prestwich, Quart. Geol. Journ., vol. x., p. 157. 
 
 ^ Oastomis Parisieneis. Owen, Quart. Geol. Journ., vol. xii., p. 204, 1856. 
 
 ' Coprolitic bed, in the Upper Greensand. See above, p. 299. 
 
 '* The Archceopteryx maeritra, Owen. See above, p. 338. 
 
 >» The fossil monitor of Thuringia (Protorosaur'us Spetieri, V. Meyer) was figured by 
 Spener, of Berlin, in ISIO. (Miscel. Berlin.) 
 1^ See above, p. 406. 
 
 ^2 Memorabilia Saxonise Subterr., Leipsic, 1T09. 
 " History of Kutherglen, by Hev. David Ure, 1793. 
 ^* Sedgwick and Murchison, Geol. Trans., 2d series, vol. iii., p. 141, 1828. 
 ^5 Sir E. Murchison. See above, p. 459. 
 " See p. 461. 
 
 Oba The evidence derived from foot-prints, though often to be relied on, is omitted 
 
 in the above table, as being less exact than that founded on bones and teeth. 
 
 In the preceding Table a few dates are set before the 
 reader of the discovery of different classes of animals in 
 ancient rocks, to enable him to perceive at a glance hpW 
 
WENLOCK FORMATION. 
 
 465 
 
 gradual has been our progress in tracing back the si^ns of 
 vertebrata to formations of high antiquity. Such facts may 
 be useful in warning us not to assume too hastily that the 
 point which our retrospect may have reached at the present 
 moment can be regarded as fixing the date of the first intro- 
 duction of any one class of beings upon the earth. 
 
 2. Wenlock Formation. — We next come to the Wenlock 
 foi'mation, which has been divided (see Table, p. 458) into 
 Wenlock limestone, Wenlock shale, and Woolhope limestone 
 and Denbighshire grits. 
 
 a. Wenlock Limestone. — This limestone, otherwise well 
 known to collectors by the name of the Dudley Limestone, 
 forms a continuous ridge in Shropshire, ranging for about 20 
 miles from S.W. to N.E., about a mile distant from the nearly 
 parallel escarpment of the Aymestry limestone. This ridgy 
 prominence is due to the solidity of the rock, and to the soft- 
 ness of the shales above and below it. Near Wenlock it 
 consists of thick masses of gray subcrystalline limestone, re- 
 plete with corals, encrinites, and trilobites. It is essentially 
 of a concretionary nature ; and the con- 
 cretions, termed "ball-stones" in Shrop- 
 shire, are often enormous, even 80 feet 
 in diameter. They are of pure carbon- 
 ate of lime, the surrounding rock being 
 more or less argillaceous.* Sometimes 
 in the Malvern Hills 
 this limestone, accord- 
 ing to Professor Phil- 
 lips, is oolitic. 
 
 Among the corals, 
 in which this forma- 
 tion is so rich, 53 spe- 
 cies being known, the 
 " chain - coi'al," Holy- 
 sites catenularius (Fig. 
 536), may be pointed 
 out as one very easily recognized, and wide- 
 ly spread in Europe, ranging through all 
 parts of the Silurian group, from the Ayme- 
 stry limestone to near the bottom of the 
 
 to sMw the poi-es Lkndeilo rocka ,^."«*'^^^»; co'-f'^l'e f'^'V^' 
 
 and the partitions sites Gothlandica (Fig. 537), IS also met with 
 
 iu the tnbes. -^^ profusion in large hemispherical masses, 
 
 which break up into columnar and prismatic fragments, like 
 
 that here figured (Fig. 537, b). Another common form in the 
 
 * Murchison's Silaria, chap. vi. 
 
 20* 
 
 Fig. 53T. 
 
 Halysites catentdarhis; Linn, 
 ep. Upper and Loiyer Si- 
 lurian. 
 
 Favosites Gothlattdioa, 
 Lam. Dudley. 
 
 a. Portion of a large 
 mass ; less than the 
 natural size. i. 
 Magnified portion, 
 to show the pores 
 
4C6 
 
 ELEMENTS OF GEOLOGY. 
 
 Fig. 539. 
 
 careous stems, arms, _an(i ^St pS-^^et 
 
 Fig. 538. Wenlock limestone is the Omphyma turbi- 
 
 natum, (Fig. 538), which, like many of its 
 modern companions, reminds us of some 
 cup-corals ; but all the Silu- 
 rian genera belong to the 
 palseozoic type before men- 
 tioned (p. 432), exhibiting 
 the quadripartite arrange- 
 ment of the: septalamellse 
 within the cup. 
 
 Among the numerous 
 
 Crinoids, several peculiar 
 
 omphyrmturumiium, species of Ci/athocHnus (for 
 
 Linn. sp. (Cyaiho- genus, see Figs. 478, 479, 
 
 ^S^kLtaistont p. 433) contribute their cal- 
 
 Shropshire. 
 
 cups towards the composition of the Wen- lock Limestone, 
 lock limestone. Of Cystideans there are a " ^^' 
 few very remarkable forms, most of them peculiar to the 
 Upper Silurian formation, as, for example, the Pseudocrinites, 
 which was furnished with pinnated fixed arms,* as represent- 
 ed in the annexed figure (Fig. 639). 
 
 The Brachiopoda are, many of them, of the same species as 
 Fig. 540. those of the Aymestry limestone ; as, 
 
 for example, Atrypa reticularis (Fig. 
 532, p. 462), and Strophomena de- 
 pressa (Fig. 540) ; but the latter spe- 
 cies ranges also from the Ludlow 
 rocks, through the 
 Wenlock shale, to 
 „, _,_ ,, , , . the Caradoc Sand- 
 
 sa, Sow. Wenlock and Lud- Stone. 
 
 lowEocks. rpjjg Crustaceans 
 
 are represented almost exclusively by Tri- 
 lobites, which are very conspicuous, 22 be- 
 ing peculiar. The Calymene Blumenhachii 
 (Fig. 641), called the "Dudley Trilobite," 
 was known to collectors long before its true place in the ani- 
 mal kingdom was ascertained. It is often found coiled up 
 like the common Onisous or wood-louse, and this is so usual 
 a circumstance among certain genera of trilobites as to lead 
 us to conclude that they must have habitually resorted to 
 this mode of protecting themselves when alarmed. The other 
 common species is the Phacops caicdatus {Asaphus caudatus), 
 Brong. (see Fig. 542), and this is conspicuous for its large 
 * E. Forbes, Mem. Geol. Survey, vol. ii., p. 496. 
 
 Fig. 541. 
 
 Calymene BlmneribacMi, 
 Brojig. Ludlow, Wen- 
 lock, and Bala beds. 
 
WENLOCK FORMATION. 
 
 46'? 
 
 Bphcerexochus mirun, 
 Beyiich ; coiled np. 
 Wenlock Limestone, 
 Dudley; also fduDd 
 In Ohio, N. America. 
 
 Pig. 842. size and flattened form. Fig.MS. 
 
 Sphcerexochtis mirns {Fig. 
 543) is almost a globe 
 when rolled up, the fore- 
 head or glabellum of this 
 species being extremely- 
 inflated. The ITomalono- 
 tv,s, a form of Trilobite in 
 which the tripartite divis- 
 ion of the dorsal crust is 
 almost lost (see Fig. 544), is very charac- 
 teristic of this division of the Silurian series. 
 Wenloek Shale. — This, observes Sir R. 
 ^'ZZ%'X:^''w^- Murchison, is infinitely the largest and most 
 E^'k """^ Lndiow persistent member of the Wenloek forma- 
 tion, for the limestone often thins out and 
 disappears. The shale, like the Lower Ludlow, often contains 
 elliptical concretions of impure earthy 
 limestone. In the Malvern distiict it is a 
 mass of finely, levigated argillaceous mat- 
 ter, attaining, according to Professor Ir'hil- 
 lips, a thickness of 640 feet, but it is some- 
 times more than 1000 feet thick in Wales, 
 and is worked for flag-stones and slates. 
 The prevailing fossils, besides corals and 
 trilobites, and some crinoids, are several 
 small species of Orthis, Cardiola, and nu- 
 merous thin-shelled species of Orthocera- 
 tites. 
 
 About six species of Graptolite, a pecul- 
 iar group of sertulai-ian fossils before al- ^"T^TJt^^^^l^ 
 ludea to (p. 463) as being confined to oilu- lock LfmeBtone; Dud- 
 rian rocks, occur in this shale. Of fossils '^^ ^**'''''' 
 of this genus, which is very characteiistic of the Lower Silu- 
 p. g^g rian, I shall again speak in the 
 
 "^^^^^^^^^^^^ ^^TwooihopeBeds.— Though 
 GrapU)iithusprwdon,BToiin. Lndiowand not alwavs recognized as a 
 wenloek Bhaies. separate subdivision of the 
 
 Wenloek, the Woolhope beds, which underlie the Wenloek 
 shale, are of great importance. Usually they occur as massive 
 or nodular limestones, underlaid by a fine shale or flag-stone ; 
 and in other cases, as in the noted Denbighshire sandstones, 
 as a coarse grit of very great thickness. This grit fornis 
 mountain ranges through North and South Wales, and is 
 generally marked by the great sterility of the soil where it 
 
468 ELEMENTS OF GEOLOGY. 
 
 occurs. It contains the usual Wenlock fossils, but with the 
 addition of some common in the uppermost Ludlow rock, 
 such as Chonetes lata and Sellerophon trilobatus. The chief 
 fossils of the Woolhope limestone are Illoenus Barriensis, 
 Somalonotus delphinocephalus (Fig. 544), Strophomena im- 
 brex, and Rhynchondla Wilsoni (Fig. 531). The latter at- 
 tains in the Woolhope beds an unusual size for the species, 
 the specimens being sometimes twice as large as those found 
 in the Wenlock limestone. 
 
 In some places below the Wenlock formation there are 
 shales of a pale or purple color, which near Tarannon attain a 
 thickness of about 1000 feet; they can be traced through 
 Radnor and Montgomery to North Wales, according to 
 Messrs. Jukes and Aveline. By the latter geologist they 
 have been identified with certain shales above the May-Hill 
 Sandstone, near Llandovery, but, owing to the extreme scarci- 
 ty of fossils, their exact position remains doubtful. 
 
 3. Llandovery Group— Beds of Passage. — We now come to 
 beds respecting the classification of which there has been 
 much difference of opinion, and which in fact must be con- 
 sidered as beds of passage between Upper and Lower Siluri- 
 an. I formerly adopted the plan of those who class them as 
 Middle Silurian, but they are scarcely entitled to this distinc- 
 tion, since after about 1400 Silurian species have been cora^ 
 pared the number peculiar to the group in question only 
 gives them an importance equal to such minor subdivisions 
 as the Ludlow or Bala groups. I therefore prefer to regard 
 them as the base of the Upper Silurian, to which group they 
 are linked by more than twice as many species as to the 
 Lower Silurian. By this arrangement the line of deraarka- 
 tion between the two great divisions, though confessedly ar- 
 bitrary, is less so than by any other. They are called Llando- 
 very Rocks, from a town in South Wales, in the neighbor- 
 hood of which they are well developed, and where, especial- 
 ly at a hill called Noeth Grug, in spite of several faults, their 
 relations to one another can be clearly seen. 
 
 a. Upper Llandovery or May-Hill Sandstone. — The May- 
 Hill group, which has also been named " Upper Llandovery," 
 by Sir R. Murchison, ranges from the west of the Longmynd 
 to Builth, Llandovery, and Llandeilo, and to the sea in M.ir- 
 low's Bay, where it is seen in the cliffs. It consists of brown- 
 ish and yellow sandstones with calcareous nodules, having 
 sometimes a conglomerate at the base derived from the 
 waste of the Lower Silurian rocks. These May-Hill beds 
 were formerly supposed to be part of the Caradoo formation, 
 but their true position was determined by Professor Sedg- 
 
LLAUDOVERY GROUP. 
 
 469 
 
 wick* to be at the 
 base of the Upper Si- 
 lurian proper. The 
 more calcareous por- 
 tions of the rock have 
 been called the Penta- 
 merus limestone, be- 
 cause Pentamenis ob- 
 longus (Fig. 546) is 
 very abundant in 
 them. It is usually- 
 accompanied by P. 
 (Stricklandinia) lirata 
 (Fig. 54'7) ; both forms 
 have a wide geograph- 
 
 Fig. 546. 
 
 PenUvments oblongics, Sow. Upper and Lower Llan- 
 dovery beds. 
 
 ical range, beinsj also «,&• views of the shell itseli; from figures lu MnrcM- 
 
 sou's Sil. Syst. c. Cast "with portion of shell re- 
 maining, and with the hollow of the central sep- 
 tum filled with spar, d. Internal cast of a valve, 
 the space once occnpled by the septum being rep- 
 resented bj; a hollow in which is seen a cast of the 
 chamber within the septum. 
 
 Fig. 54T. 
 
 met with in the same 
 part of the Silurian se- 
 ries in Russia and the 
 United States. 
 
 About 228 species of fossils are known in the May-Hill 
 division, more than half of which are Wenlock species. They 
 consist of trilobites of the genera II- 
 Icenus and Calymene ; Brachiopods of 
 the genera Orthis, Atrypa, Leptoena, Pen- 
 tamerus, Strophomena^ and others ; Gas- 
 ^^ tei'opods of the genera Turbo, Murchir 
 
 W^Wl lHl^^p' sonia (for genus, see Fig. 567, p. 479), and 
 uMm IImISw^ Bellerophon ; and Pteropods of the genus 
 Conularia. Fig.548. 
 
 stricklandinia (Pentaments) i-he israCulO- 
 lirdta, Sow. pods, of which 
 
 there are 66 species, are almost all 
 TJpper Silurian. 
 
 Among the fossils of the May- 
 Hill shelly sandstone at Malvern, ^_><=__^ 
 
 Tentaculites annvlatUS (Fig. 548), TmUumUtia anmdatws, Schlot In- 
 
 an annelid, probably allied to Ser- terior casts in sandstone. Upper 
 
 . _ ' 1- •' Llandovery, Eastnor Park, near 
 
 pwto, IS found. Malvern. Natural size-and mag- 
 
 . Loioer .'Llandovery Rocks. — Be- ""'^'^■ 
 ■low the May-Hill Group are the Lower Llandovery Rocks, 
 which consist chiefly of hard slaty rocks, and bods of con- 
 glomerate from 600 to 1000 feet in thickness. The fossils, 
 which are somewhat rare in the lower beds, consist of 128 
 known species, only eleven of which are peculiar, 83 being 
 * 1853. Quart. Geol. Joum., vol. ix., p. 215. 
 
410 
 
 ELEMENTS OF GEOLOGY. 
 
 common to the May-Hill group above, and 93 common to the 
 rocks below. Stricklandinia {Pentamerus) levis, which is 
 common in the Lower Llandovery, becomes rare in the Up^ 
 per, while Pentameras oblongus (Fig. 546), which is the char- 
 acteristic shell of the Upper Llandovery, occurs but seldom 
 in the Lower, 
 
 LOWEK SILUEIAN ROCKS. 
 
 The Lower Silurian has been divided into, 1st, the Bala 
 Group ; 2d, the Llandeilo Flags ; and, 3dly, the Arenig or 
 Lower Llandeilo formation. 
 
 Bala and Caradoc Beds. — The Caradoo sandstone was orig- 
 inally so named by Sir R. I. Murchison from the mountain 
 called Caer Caradoc, in Shropshire ; it consists of shelly sand- 
 stones of great thickness, and sometimes containing much 
 calcareous matter. The rock is frequently laden with the 
 beautiful trilobite called by Murchison Trinucleics Caractaci 
 (see Fig. 553, p. 472), which ranges from the base to the sum- 
 mit of the formation, usually accompanied by Strophomena 
 grandis (see Fig. 551), and Orthis vespertilio (Fig. 550), with 
 many other fossils. 
 
 Fig. 549. Fig. 650. Fig. 551. 
 
 Orthis iricenaria^ 
 Conrad. New 
 York ; Canada. 
 i nat. size. 
 
 Orthis vespertiliOf Sow. 
 Shropshire, N. and 
 S. Wales. One -half 
 nat. size. 
 
 Orthis {Strovhomend) grandis. Sow. 
 Two-thirds nat. size. Caradoc 
 Beds, Horderley, Shropshire, 
 and Coniston, Lancashire. 
 
 Brachiopoda. — Nothing is more remarkable in these beds, 
 and in the Silurian strata generally of all countries, than the 
 preponderance of brachiopoda over other forms of mollusca. 
 Their proportional numbers can by no means be explained 
 by supposing them to have inhabited seas of great depth, for 
 the contrast between the palaeozoic and the present state of 
 things has not been essentially altered by the late discoveries 
 made in our deep-sea dredgings. We find the living brachi- 
 opoda so rare as to form about one forty-fourth of the whole 
 bivalve fauna, whereas in the Lower Silurian rocks of which 
 we are now about to treat, and where the brachiopoda reach 
 their maximum, they are represented by more than twice as 
 many species as the Lamellibranchiate bivalves. 
 
BALA ANB CARADOC BEDS. 4 "71 
 
 There may, indeed, be said to be a continued decrease of 
 the proportional number of this lower tribe of moUusca as 
 we proceed from older to newer rocks. In the British De- 
 vonian, for example, the Brachiopoda number 99, the Larael- 
 libranchiata 58 ; while in the Carboniferous their propor- 
 tions are moi-e than reversed, the Lamellibranchiata number- 
 ing 334 species, and the Brachiopoda only 157. In the Sec- 
 ondary or Cainozoic formations the preponderance gf the 
 higher grade of bivalves becomes more and more marked, till 
 in the tertiary strata it approaches that observed in the liv- 
 ing creation. 
 
 While on this subject, it may be useful to the student to 
 know that a Brachiopod differs from ordinary bivalves, mus- 
 sels, cockles, etc., in being always equal-sided and never quite 
 equi-valved ; the form of each valve being symmetrical, it 
 may be divided into two equal parts by a line drawn from 
 the apex to the centre of the margin. 
 
 Trilohites. — In the Bala and Caradoc beds the trilobites 
 reach their maximum, being represented by 111 species re- 
 ferred to 23 genera. 
 
 Burmeister, in his work on the organization of trilobites, 
 supposes that they swam at the surface of the water in the 
 open sea and near coasts, feeding on smaller marine animals, 
 and to have had the power of rolling themselves into a ball 
 as a defense against injury. He was also of opinion that 
 they underwent various transformations analogous to those 
 of living crustaceans. M. Barrande, author of an admirable 
 work on the Silurian rocks of Bohemia, confirms the doctrine 
 of their metamorphosis, having traced more than twenty spe- 
 cies through different stages of growth from the young state 
 just after its escape from the egg to the adult form. He has 
 followed some of them from a point in which they show no 
 eyes, no joints, or body rings, and no distinct tail, up to the 
 complete form with the full number of segments. This 
 change is brought about before the animal has attained a 
 tenth part of its full dimensions, and hence such minute and 
 delicate specimens are rarely met with. Some of his figures 
 of the metamorphoses of the common Trinucleus are copied 
 in the annexed wood-cuts (Figs. 552, 553). It was not till 
 1870 that Mr. Billings was enabled, by means of a specimen 
 found in Canada, to prove that the trilobite was provided 
 with eight legs. 
 
 It has been ascertained that a great thickness of slaty and 
 crystalline roeks of South Wales, as well as those of Snowdon 
 and Bala, in North Wales, which were first supposed to be 
 of older date than the Silurian sandstones and mudstones of 
 
in 
 
 ELEMENTS OE GEOLOGY. 
 Fig. 5S2. . ■ ■ Pig. 553. 
 
 ■■■':r 
 
 /^ ^t^ 
 
 Young iudivicluals of Trinuclerts 
 concentriciLS (IT. or/iaiw^, Barr.). 
 
 u. YoxiDgest state. Natural size 
 au'd magnified ; the body rinffs 
 not at aU developed, b. A little 
 older. Onethorax.ioint. c. Still 
 more advanced. Three thorax 
 joints. The fourth, fifth, and 
 sixth segments are successively 
 
 producea, probably each time THnuclms eoneentricus, ■Ea.ton. Sym T. 
 
 the animal moulted Its crust. Car<u,taci, Murch. Ireland; Wales; 
 
 Shropshire ; N. America ; Bohemia. 
 
 Shropshire, are in fact identical in age, and contain the same 
 organic remains. At Bala, in Merionethshire, a limestone rich 
 
 in fossils occurs, in which 
 two genera of star-fish, I^ro- 
 taster and Palmaster, are 
 found ; the fossil specimen 
 of the latter (Fig. 554) being 
 almost as uncompressed as 
 if found just washed up. on 
 the sea-beach. Besides the 
 star-fish there occur abun- 
 dance of those peculiar bod- 
 ies called Cystidew. Tliey 
 are the SpluEronites of old authors, and were considered by 
 Professor E. Forbes as intermediate Fig. 855. 
 
 between the crinoids and echino- 
 derms. The Echinosph(Bronite here 
 represented (Fig. 555) is character- 
 istic of the Caradoc beds in Wales, 
 and of their equivalents in Sweden 
 and Russia. 
 
 With it have been found several 
 other genera of the same family, sucli 
 as Sphceronites, Hemico smites, etc. 
 Among the mollusca are Pteropods ^ 
 
 of the genus Conularia of large size EcUmspb^romua !>oBto(«,Eich- 
 (for genus, see Fig. 518, p. 453). waid. (of the family Q/8««cffi) 
 
 \, ? 1 ' .= „ l^ r J a. Month. 6. Point of attach- 
 
 AbOUt eleven species or Graptollte ment of stem. Lower Siluri- 
 
 are reckoned as belonging to this an s. and N. Wales. 
 formation ; they iire chiefly found in peculiar localities where 
 
 PaXaeaster asperimus. Salt. Caradoc, Welsh- 
 pool. 
 
FOSSILS OF THE LLANDEILO FLAGS. 
 
 473 
 
 black mud abounded. The formation, when traced into South 
 Wales and Ireland, assumes a greatly altered mineral aspect, 
 but still retains its characteristic fossils. The known fauna of 
 the Bala group comprises 565 species, 352 of which are pe- 
 culiar, and 93, as before stated, are common to the overlying 
 Llandovery rocks. It is worthy of remark that, when it oc- 
 curs under the form of trappean tuff (volcanic ashes of De la 
 Beche), as in the crest of Snowdon, the peculiar species which 
 distinguish it from the Llandeilo beds are still observable. 
 The formation generally appears to be of shallow-water ori- 
 gin, and in that respect is contrasted with the group next 
 to be described. Professor Ramsay estimates the thickness 
 of the Bala Beds, including the contemporaneous volcanic 
 rocks, stratified and unstratified, as being from 10,000 to 
 12,000 feet. 
 
 Llandeilo Flags. — The Lower Silurian strata were ovigi- 
 hally divided by Sir R. Murchison into the upper group al- 
 ready described, under the name of Caradoc Sandstone, and 
 a lower one, called, from a town in Carmarthenshire, the 
 Llandeilo flags. The last mentioned 
 strata consist of dark-colored micaceous 
 flags, frequently calcareous, with a great 
 thickness of shales, generally black, be- _____^^^_ 
 low them. The same beds are also seen mayrnograpsns ^oraptoim) 
 at Builth, in Radnorshire, where they are Kwcftisonn Beck. Lian- 
 
 '. ™ -, .., 1 ' . .. ■' deilo flags, Wales. 
 
 interstratified with volcanic matter. 
 
 A still lower part of the Llandeilo rocks consists of a black 
 carbonaceous slate of great thickness, frequently containing 
 sulphate of alumina, and sometimes, as in Dumfriesshire, beds 
 of anthracite. It has been conjectured that this carbona- 
 ceous matter may be due in great measure to large quanti- 
 ties of imbedded animal remains, for the number of Grapto- 
 lites included in these slates was certainly very great. In 
 
 Fig. 656. 
 
 Pig. 657. 
 
 Fig. 558. 
 
 Diploqrapms priatie, Hisinger. 
 ; teds, Waterford. 
 
 Llandeilo 
 
 Rcuitrites peregrinus, Bairande. 
 Scotland ; Bohemia ; Saxony. 
 Llandeilo flags. . . 
 
474 
 
 ELEMENTS OF GEOLOGY. 
 
 Fig. 559. 
 
 Great Britain eleven genera and about 40 species of Grap- 
 tolites occur in the Llandeilo flags and underlying Arenig 
 beds. The double Graptolites, or those with two rows of 
 cells, such as Diplograpsus (Fig. 557), are conspicuous. 
 
 The brachiopoda of the Llandeilo flags, which 
 number 47 species, are in the main the same as 
 those of the Caradoc Sandstone, but the other 
 raollusca are in great part of difierent species. 
 
 In Europe generally, as, for example, in Sweden 
 and Russia, no shells are so characteristic of this 
 Dipiograpmsfo- formation as Orthoceratites, usually of great size, 
 DumMisshfi^'" and with a wide siphuncle placed on one side in- 
 Sweden. lW gtead of being central (see Fig. 560). Among 
 deiio flags. ^^j^^^. Cephalopods in the Llandeilo flags is Cyr- 
 toceras ; in the same beds also are found Bellerophon (see Fig. 
 488, p. 436) and some Pteropod shells {Goymlaria, Theca, etc.), 
 
 Fig. 560. 
 
 Orthoceras duplex, Wahlenljerg. Russia add Sweden, 
 
 (From Mui'chison's "Siluvia.") 
 
 a. Lateral sipinincle laid bare by the removal of a portion of the chambered shell. 
 
 b. Continuation of the same seen In a transverse section of the shell. 
 
 also in spots where sand abounded, lamellibranchiate bivalves 
 of large size. The Crustaceans were plentifully represented 
 by the Trilobites, which appear to have swarmed in the Si- 
 
 Fig. 661. 
 
 Fig. 662. 
 
 Afiaphus tyrannuSj Marchison. 
 Llandeilo; Bishop's Castle; 
 etc. 
 
 Ogygia BncMi, 3iinn. Syn. Asaphiis BwMi, 
 Brongn. BuiUh, Badnorshire ; Llaudeilo, 
 Carmarthenshire. 
 
 luiian seas just as crabs and shrimps do in our own ; no less 
 than 263 species have been found in the British Silurian 
 fauna. The genera Asaphus (Fig. 561), Ogygia (Fig. 562), 
 
AEENIG OK STIPER-ST0NES GROUP. 475 
 
 and Tr-inucleus (Figs. 552, 553) form a marked feature of 
 the rich and varied Trilobitic fauna of this age. 
 
 Beneath the black slates above described of the Llandeilo 
 formation, graptolites are still found in great variety and 
 abundance, and the characteristic genera of shells and trilo- 
 bites of the Lower Silurian rocks are still traceable down- 
 ward, in Shropshire, Cumberland, and North and South 
 Wales, through a vast depth of shaly beds, in some districts 
 interstratified with trappean formations of contemporaneous 
 origin ; these consist of tuffs and lavas, the tuffs being formed 
 of such mateiials as are ejected from craters and deposited 
 immediately on the bed of the ocean, or washed into it from 
 the land. According to Professor Ramsay, their thickness 
 is about 3300 feet in North Wales, including those of the 
 Lower Llandeilo. The lavas are feldspathic, and of porphy- 
 ritic structure, and, according to the same authority, of an 
 aggregate thickness of 2500 teet. 
 
 Arenig or Stiper-Stones Group {Lower LlandeUo of Mur- 
 !cAisc>w).-^Next in the descending order are the shales and 
 sandstones in which the quartzose rocks called Stiper-Stones 
 in Shropshire occur. Originally these Stiper-Stones were 
 only known as arenaceous quartzose strata in which no or- 
 ganic remains were conspicuous, Fig. sea. 
 except the tubular burrows of an- 
 nelids (see Fig. 563, Arenicolites 
 linearis), which are remarkably 
 common in the Lowest Silurian in 
 Shropshire, and in the State of New 
 York, in America. They have al- 
 ready been alluded to as occurring 
 by thousands in the Silurian strata 
 
 unconformably overlying the Cam- 
 
 brian, in the mountain of Queenaig, ^^^i^^t^ i^^^is, mi^. Arenig 
 m Sutherlandshire (I^ ig. 82, p. 112). beds, stipei-stones. 
 
 ;rag 
 plfi 
 
 aues of bedding. 
 
 made on the retiring of the tides 
 in the sands of the Bristol Channel, near Minehead, by lob- 
 worms which are dug out by fishermen and used as bait. 
 When the term Silurian was given by Sir R. Murchison, in 
 1835, to the whole series, he considered the Stiper-Stones as 
 the base of the Silurian system, but no fossil fauna had then 
 been obtained, such as could alone enable the geologist to 
 draw a line between this member of the series and the Llan- 
 deilo flags above, or a vast thickness of r9ok below, which 
 was seen to form the Longmynd hills, and was called " unfos- 
 siliferous gray wacke." Professor Sedgwick had described, in 
 
476 ELEMENTS OF GEOLOGY. 
 
 1843, strata now ascertained to be of the same age as largely- 
 developed ill the Arenig mountaiD, in Merionethshire ; and 
 the Skiddaw slates in the Lake-District of Cumberland, stud- 
 ied by the same author, were of corresponding date, though 
 the number of fossils was, in both cases, too few for the de- 
 termination of their true chronological relations. The sub- 
 sequent researches of Messrs. Sedgwick and Harkness, in 
 Cumberland, and of Sir R. I. Murchison and the Government 
 surveyors in Shropshire, have increased the species to more 
 than sixty. These were examined by Mr. Salter, and shown 
 in the third edition of "Siluria" (p. 52, 1859) to be quite 
 distinct from the fossils of the overlying Llandeilo flags. 
 Among these the Obolella plumbea, ^glina Mnodosa, Ogygia 
 i-ig. 554. Sdwynii, and Didy- 
 
 j^j,,vu) mograpsus qemirms 
 
 I ^^^^^^T^^^^^ (Fig. 564), and i).^- 
 I >— — *— s^j/ rioido, are character- 
 
 XHdymograpsus D&minuSf Hisinger, sp. Sweden. igtic. 
 
 But, although the species ai-e distinct, the genera are the 
 same as those which characterize the Silurian rocks above, 
 and none of the characteristic primordial or Cambrian forms, 
 presently to be mentioned, are intermixed. The same may 
 be said of a set of beds underlying the Arenig rocks at Ram- 
 say Island and other places in the neighborhood of St. Da- 
 vid's. These beds, which have only lately become known to 
 us through the labors of Dr. Hicks,* present already twenty 
 new species, the greater part of them allied generically to 
 the Arenig rocks. This Arenig group may therefore be 
 conveniently regarded as the base of the great Silurian sys- 
 tem, a system which, by the thickness of its strata and the 
 changes in animal life of which it contains the record, is 
 more than equal in value to the Devonian, or Carboniferous, 
 or other principal divisions, whether of primary or secondary 
 date. 
 
 It would be unsafe to rely on the mere thickness of the 
 strata, considered apart from the great fluctuations in or- 
 ganic life which took place between the era of the Llandeilo 
 and that of the Ludlow formation, especially as the enormous 
 pile of Silurian rocks observed in Great Britain (in Wales 
 more particularly) is derived in great part from igneous ac- 
 tion, and is not confined to the ordinary deposition of sedi- 
 ment from rivers or the waste of cliffs. 
 
 In volcanic archipelagos, such as the Canaries, we see the 
 most active of al^known causes, aqueous and igneous, simul- 
 taneously at work to produce great results in a compara- 
 * Trans. Brit. Assoc, 1866. Proc' Liverpool Geol. Soc, 1869. 
 
SILURIAN EQUIVALENTS IN EUROPE. 477 
 
 tively moderate lapse of time. The outpouring of repeated 
 streams of lava — the showering down upon land and sea of 
 volcanic ashes — the sweeping seaward of loose sand and cin- 
 ders, or of rocks ground down to pebbles and sand, by rivers 
 and torrents descending steeply inclined channels — the un- 
 dermining and eating away of long lines of sea-cliff exposed 
 to the swell of a deep and open ocean r — these operations 
 combine to produce a considerable volume of superimposed 
 matter, without there being time for any extensive change 
 of species. Nevertheless, there would seem to be a limit to 
 the thickness of stony masses formed even under such favor- 
 able circumstances, for the analogy of tertiary volcanic re- 
 gions lends no countenance to the notion that sedimentary 
 and igneous rocks 25,000, much less 45,000 feet thick, like 
 those of Wales, could origina;te while one and the same fau- 
 na should continue to people the earth. If, then, we alloTV 
 that about 25,000 feet of matter may be ascribed to one 
 system, such as the Silurian, as above described, we may be 
 prepared to discover in the next series of subjacent rocks a 
 distinct assemblage of species, or even in great part of gen- 
 era, of organic remains. Such appears to be the fact, and I 
 shall therefore conclude with the Arenig beds my enumera- 
 tion of the Silurian formations in Great Britain, and proceed 
 to say something of their foreign equivalents, before treating 
 of rocks older than the Silurian. 
 
 . Silurian Strata of the Continent of Europe. — When we 
 turn to the continent of Europe, we discover the same an- 
 cient series occupying a wide area, but in no region as yet 
 has it been observed to attain great thickness. Thus, in 
 Norway and Sweden, the total thickness of strata of Silu- 
 rian age is considerably less than 1000 feet, although the 
 representatives both of the Upper and Lower Silurian of 
 England are not wanting there. In Russia the Silurian 
 strata, so far as they are yet known, seem to be even of 
 smaller vertical dimensions than in Scandinavia, and they 
 appear to consist chiefly of the Llandovery group, or of a 
 limestone containing Pentamenis ohlongus, below which are 
 strata with fossils corresponding to those of the Llaudeilo 
 beds of England. The lowest rock with organic remains 
 yet discovered is "the Ungulite or Obolus grit" of St. 
 Petersburg, probably coeval with the Llandeilo flags of 
 Wales. 
 
 The shales and grits near St. Petersburg, above alluded 
 to, contain green grains in their sandy layers, and are in a 
 singularly unaltered state, taking into account their high 
 antiquity. The prevailing brachiopods consist of the Obolus 
 
478 
 
 ELEMENTS OF GEOLOGY. 
 
 Shells of the lowest known Fossiliferous Beds in Russia. 
 
 Pig. 505. Pig. 586. 
 
 Siphonotretaunguiculata,'E\chv/&\&. From OMtts ApoUinis, Eichwald. ' From 
 
 the Lowest Silurinn Sandstone, "Obelus the same locality, 
 
 iri'its," of St. Petersburg. o. Interior of the larger or ventral 
 
 it.^utsiae of perforated valve. 6. Interior valve. 6. Exterior of the npper 
 
 of same, showing the termination of the (dorsal) valve. (Davidson, "Palse- 
 
 foramen within. (Davidson.) ontograph. Monog.") 
 
 or Ungulite of Pander, and a Siphotiotreta (Figs. 565, 566). 
 Notwithstanding the antiquity of this Russian formation, it 
 should be stated that both of these genera of brachiopods 
 have been also found in the Upper Silurian of England, i. e. 
 in the Wenlock limestone. 
 
 Among the green grains of the sandy sti'ata above men- 
 tioned, Prof Ehrenberg announced in 1854 his discovery of 
 remains of foraminifera. These are casts of the cells ; and 
 among five or six forms three are considered by him as refera- 
 ble to existing genera (e. g. , Textularia, liotalia, and GuttuUna). 
 
 Silurian Strata of the United States. — The Silurian forma- 
 tions can be advantageously studied in the States of New 
 York, Ohio, and other regions north and south of the great 
 Canadian lakes. Here they are often found, as in Russia, 
 nearly in horizontal position, and are more rich in well-pre- 
 served fossils than in almost any spot in Europe. In the, 
 State of New York, where the succession of the beds and 
 their fossils have been most carefully worked out by the 
 Government surveyors, the subdivisions given in the first 
 column of the annexed list have been adopted. 
 
 Subdivisions of the Silurian Strata of New York. (^Strata below the 
 Oriskany Sandstone or base of the Devonian.) 
 
 New York Names. British Equivalents. 
 
 1. Upper Pentamems Limestone . ^ 
 
 2. Encrinal Limestone 
 
 3. Delthyris Shaly Limestone . . 
 
 4. Pentamerus and Tentacnlite 
 
 Limestones 
 
 5. Water Lime Group .... 
 
 6. Onondaga Salt Group . . . 
 
 7. Niagara Group 
 
 8. Clinton Group 
 
 9. Medina Sandstone . . . . 
 
 10. Oneida Conglomerate . 
 
 11. Gray Sandstone 
 
 Upper Silurian (or Ludlow and Wen- 
 lock Formations). 
 
 ■Beds of Passage, Llandovery Group. 
 
SILURIAN STRATA OF UNITED STATES. 
 
 479 
 
 Hew Yotk Names. 
 
 12. Hudson River Group . 
 
 13. Trenton Limestone . 
 
 14. Black-River Limestone 
 
 15. Bird's-eye Limestone 
 
 16. Chazy Limestone . . 
 
 17. Calciferous Sandstone 
 
 British Equivalents. 
 
 Lower Silurian (or Caradoe and 
 }: Bala, Llandeilo and Arenig For- 
 mations). 
 
 In the second column of the same table I have added the 
 supposed British equivalents. All Palaeontologists, Euro- 
 pean and American, such as MM. de Verneuit, D. Sharpe, 
 Prof. Hall, E. Billings, and others, who have entered upon 
 this comparison, admit that there is a marked general corre- 
 spondence in the succession of -fossil forms, and even species, 
 as we trace the organic remains downward from the highest 
 to the lowest beds; but it is impossible to parallel each 
 minor subdivision. 
 
 That the Niagara Limestone, over which the river of that 
 name is precipitated at the great cataract, together with its 
 underlying shales, corresponds to the Wenlock limestone and 
 shale of England there can be no doubt. Among the species 
 common to this formation in America and Europe are Cafy- 
 mene JHumenbachii, ITomalonotus delphinocephMus (Pig- 544, 
 p. 467), with several other trilobites ; Bhynchonella Wilsoni, 
 Fig. 531, p. 462, and Metzia cuneata; Orthis degantula, Pen- 
 tamenm galeatus, with many more brachiopods ; Orthoceras 
 amiulatmn, among the cephalopodous shells ; and Favosites 
 gothlandica, with other large corals. 
 
 The Clinton Group, containing .Pentamerus oblongus and 
 Stricklandinia, and related more nearly by its fossil species 
 with the beds above than with those below, is 
 the equivalent of the Llandovery Group or beds 
 of passage. 
 
 The Hudson River Group, and the Trenton 
 Limestone, agree palseontologically with the 
 Caradoe or Bala group, containing in common 
 with them several species of trilobites, such as 
 Asaphus (Isotelus) gigas, Trinudeus concentricus 
 (Pig. 553, p. 4-72) ; and various shells, such as Or- 
 this striatula, Orthis Mforata (or O. lynx), 0. 
 pweata ( 0. occidentalis of Hall), and Bellero- 
 phon bildbatus. In the Trenton limestone occurs 
 Murchisonia gracilis, Pig. 567, a fossil also com- 
 mon to the Llandeilo beds in England. 
 
 Mr. D. Sharpe, in his report on the mollusca col- 
 lected by me from these strata in North America,* has con- 
 cluded that the number of species common to the Silurian rocks 
 * Quart. Geol. Journ., vol. iv. 
 
 Kg. 66T. 
 
 MurchUonia gra- 
 dliSt Hall. A 
 fossil charac- 
 teristic of the 
 Trenton Lime- 
 stone. The ge- 
 nus is common 
 in Lower Silu- 
 rian rocks. 
 
480 ELEMENTS QP GEOLOGY. 
 
 on both sides of the Atlantic is between 30 and 40 per cent.; a 
 result which, although no doubt liable to future modification, 
 when a larger comparison shall have been made, proves, nev- 
 ertheless, that many of the species had a wide geographical 
 range. It seems that comparatively few of the gasteropods 
 and lamellibranchiate bivalves of North America can be 
 identified specifically with European fossils, while no less 
 than two-fifths of the brachiopoda, of which my collection 
 chiefly consisted, are the same. In explanation of these facts, 
 it is suggested that most of the recent brachiopoda (especial- 
 ly the orthidiforra ones) are inhabitants of deep water, and 
 that they may have had a wider geographical range than 
 shells living near shore. The predominance of bivalve mol- 
 lusea of this peculiar class has caused the Silurian period to 
 be sometimes styled " the age of brachiopods." 
 
 In Canada, as in the State of New York, the Potsdam 
 Sandstone underlies the above-mentioned calcareous rocks, 
 but contains a difierent suite of fossils, as will be hereafter 
 explained. In parts of the globe still more remote from Eu- 
 rope the Silurian strata have also been recognized, as in 
 South America, Australia, and India. In all these regions 
 the facies of the fauna, or the types of organic life, enable us 
 to recognize the contemporaneous origin of the rocks ; but 
 the fossil species are distinct, showing that the old notion of 
 a universal diffusion throughout the "primaeval seas" of one 
 uniform specific fauna was quite unfounded, geographical 
 provinces having evidently existed in the oldest as in the 
 most modern times. 
 
CAMBBIAN GEOUP. 431 
 
 CHAPTER XXVII. 
 
 CAMBEIAN AN© LAUEENTIAN GROUPS. 
 
 Classification of the Cambrian Group, and its Equivalent in Bohemia.— Up- 
 per Cambrian Rocks.— Tremadoc Slates and their Fossils.— Lingola Flags. 
 —Lower Cambrian Rocks.- Menevian Beds.— Longmynd Group.— Harl 
 lech Grits with large Trilobites.— Llanberis Slates.— Cambrian Rocks of 
 Bohemia.— Primordial Zone of Barrande.— Metamorphosis of Trilobites. 
 —Cambrian Rocks of Sweden and Norway.— Cambrian Rocks of the 
 United States and Canada.— Potsdam Sandstone.— Huronian Series.— 
 Laurentian Group, upper and lower.— £020071 Canadense, oldest known 
 Fossil. — Fundamental Gneiss of Scotland. 
 
 CAMBRIAN GROUP. 
 
 The characters of the Upper and Lower Sihirian rocks 
 were established so fuHy^ both on stratigraphical and pate- 
 ontological data, by Sir Roderick Murchison after five years' 
 labor, in 1839, when his "Silurian System" was published, 
 that these formations could from that period be recognized 
 and identified in all other parts of Europe and in North 
 America, even in countries where most of the fossils differed 
 specifically from those of the classical region in Britain, 
 where they were first studied. 
 
 While Sir R. I. Murchison was exploring in 183.3, in Shrop- 
 shire and the borders of Wales, the strata which in 1835 he 
 first called Silurian, Professor Sedgwick was surveying the 
 rocks of North Wales, which both these geologists consider- 
 ed at that period as of older date, and for which in I836 
 Sedgwick proposed the name of Cambrian. It was after- 
 wards found that a large portion of the slaty rocks of North 
 Wales, which had been considered as more ancient than the 
 Llandeilo beds and Stiper-Stones before alluded to, were, in 
 reality, not inferior in position to those Lower Silurian beds 
 of Murchison, but merely extensive undulations of the same, 
 bearing fossils identical in species, though these were gener- 
 ally rarer and IBS'? perfectly preserved, owing to the changes 
 which the rocks had undergone from metamorphic action. 
 To such rocks the term "Cambrian" was no longer appli- 
 cable, although it continued to be appropriate to strata in- 
 ferior to the Stiper-Stones, and which were older than those 
 of the Lower Silurian group as originally defined. It was 
 not till 1846 that fossils were found in Wales in the Lingula' 
 
 21 
 
482 ELEMENTS OF GEOLOGY. 
 
 flags, the place of which will be seen in the annexed table, 
 By this time Barrande had already published an account of 
 a rich collection of fossils which he had discovered in Bo- 
 hemia, portions of which he recognized as of corresponding 
 age with Murchison's Upper and Lower Silurian, while oth- 
 ers were more ancient, to which he gave the name of " Pri- 
 mordial," for the fossils were sufficiently distinct to entitle 
 the rocks to be referred to a new period. They consisted 
 chiefly of trilobites of genera distinct from those occurring 
 in the overlying Silurian formations. These peculiar genera 
 were afterwards found in rocks holding a corresponding po- 
 sition in Wales, and I shall retain for them the term Cambri- 
 an, as recent discoveries in our own country seem to carry 
 the first fauna of Barrande, or his primordial type, even into 
 older strata than any which he found to be fossiliferous in 
 Bohemia. 
 
 The term primordial was intended to express M. Bar- 
 rande's own belief that the fossils of the rocks so called af- 
 forded evidence of the first appearance of vital phenomena 
 on this planet, and that consequently no fossiliferous strata 
 of older date would or could ever be discovered. The ac- 
 ceptance of such a nomenclature would seem to imply that 
 we despaired of extending our discoveries of new and more 
 ancient fossil groups at some future day when vast portions 
 of the globe, hitherto unexplored, should have been thorough- 
 ly surveyed. Already the discovery of the Laurentian Eo- 
 zoon in Canada, presently to be mentioned, discountenances 
 such views. 
 
 The following table will show the succession of the strata 
 in England and Wales which belong to the Cambrian group 
 or the fossiliferous rocks older than the Arenig or Lower 
 Llandeilo rocks : 
 
 UPPER CAMBRIAN. 
 Tremadoc Slates. {Primordial of Barrande in part. ^ 
 LiNGULA Elags. (Primordial of Barrande.^ 
 
 LOWER CAMBRIAN. 
 
 Menevian Beds. {Primordial of Barrande.) 
 
 LONGMYND Group, -f?" Harlech Grits. 
 (b. Llanbens Slates. 
 
 trPPEE CAMBEIAIT. 
 
 Tremadoc Slates. — The Tremadoc slates of Sedgwick are 
 more than 1000 feet in thickness, and consist of dark earthy 
 slates occurring near the little town of Tremadoc, situated 
 on the north side of Cardigan Bay, in Carnarvonshire. These 
 
UPPER CAMBRIAN.— TREMADOC SLATES 483 
 
 slates were first examined by Sedgwick in 1831, and were 
 re-examined by him and described in 1846,* after some fos- 
 sils had been found in the underlying Lingula flags by Mr. 
 Davis. The inferiority in position of these Lingula flags to 
 the Tremadoc beds was at the same time established. The 
 overlying Tremadoc beds were traced by their pisolitic ore 
 from Tremadoc to Dolgelly. No fossils proper to the Tre- 
 madoc slates were then observed, but subsequently, thirty- 
 six species of all classes have been found in them, thanks to 
 the researches of Messrs. Salter, Homfray, and Ash. Wa 
 have already seen that in the Arenig or Stiper-Stones group, 
 where the species are distinct, the genera agree with Silurian 
 types ; but in these Tremadoc slates, where the species are 
 also peculiar, there is about an equal admixture of Silurian 
 types with those which Barrande has termed " primordial." 
 Here, therefore, it may truly be said that we are entering 
 upon a new domain of life in our retrospective survey of the 
 past. The trilobites of new species, but of Lower Silurian 
 genera, belong to Ot/i/gia, Asaphus, and Cheirurus; whereas 
 those belonging to primordial types, or Barrande's first fau- 
 na as well as to the Lingula flags of Wales, comprise Dike- 
 locephalies, Gonocoryphe (for genera see Figs. 677 and 581),f 
 Olentis, and Angelina. In the Tremadoc slates are found 
 Sdlerophon, Orthocereis, and Gyrtoceras, all spe- pjg ggg 
 cifically distinct from Lower Silurian fossils of 
 the same genera: the Pteropods Theca (Fig. 
 568) and Gonularia range throughout these 
 slates ; there are no Graptolites. The Lingvla 
 (lAnguleUa) Davisu ranges from the top to 
 the bottom of the formation, and links it with 
 the zone next to be described. The Tremadoc 
 slates are very local, and seem to be confined 
 to a small part of North Wales; and Prof Ram- 
 say supposes them to lie unconformably on the ^™«tete''Lc™- 
 Lingula flags, and that a long interval of time er Tremadoc 
 elapsed between these formations. Cephalo- _''"'''• tremadoc. 
 poda have not yet been found lower than this group, but 
 it will be observed that they occur here associated with 
 genera of Trilobites considered by Barrande as characteris- 
 tically Primordial, some of which belong to all the divisions 
 of the British Cambrian about to be mentioned. This ren- 
 ders the absence of cephalopoda of less importance as bear- 
 ing on the theory of development. 
 
 * Quart. Geol. Journ., vol. iii., p. 156. 
 
 t This genus has been substituted for Ban-nnde's Conoceplialus, as the latter 
 teiTU had been preoccupied by the entomologists. 
 
484 
 
 ELEMENTS OF GEOLOGY. 
 
 Lingula Flags. — Next below the Tremadoo slates in North 
 Wales lie micaceous flagstones and slates, in which, in 1846, 
 Ml-. E. Davis discovered the Lingula {Zingulella),Fig. 510, 
 named after him, and from which was derived the name of 
 Lingula flags. These beds, which are palaeontologically the 
 equivalents of Barrande's primordial zone, are represented 
 by more than 5000 feet of strata, and have been studied 
 chiefly in the neighborhood of Dolgelly, Ffestiniog, and Port- 
 madoc in North Wales, and at St. David's in South Wales. 
 They have yielded about forty species of fossils, of which 
 six only are common to the overlying Tremadoc rocks, but 
 
 Fig. 569. 
 
 Fig. 570. 
 
 Fig. sri. 
 
 "Lingula Flags" of Dolgelly, anclFfestiuiog; N.Wales. 
 Hyme'nocaria vermicauda, Salter. Lingulella Davivii, M'Coy. Olenus micrurus, 
 A Phyllopod Crustacean. One- a. One-half natural size. Salter. One-half 
 half natural size. 6. Distorted by cleavage. natural size. 
 
 the two formations are closely allied by having several char- 
 acteristic " primordial " genera in commoi). Dikelocephalus, 
 Olenus (Fig. 571), and Gonocoryphe are prominent forms, as 
 is also JSymenocaris (Fig. 569), a genus of phyllopod crus- 
 tacean entirely confined to the Lingula Flags. According 
 to Mr. Belt, who has devoted much attention to these beds, 
 there are already palseontological data for subdividing the 
 Lingula Flags into three sections.* 
 
 In Merionethshire, according to Professor Ramsay, the Lin- 
 gula Flags attain their greatest development ; in Carnarvon- 
 shire they thin out so as to have lost two-thirds of their 
 thickness in eleven miles, while in Anglesea and on the Menai 
 Straits both they and the Tremadoo beds are entirely absent, 
 and the Lower Silurian rests directly on Lower Cambrian 
 strata. 
 
 LOWER CASIBRIAN. 
 
 Menevian Beds. — Immediately beneatli the Lingula Flags 
 tliere occurs a series of dark gray and black flags and slates 
 alternating at the upper part with some beds of sandstone, 
 the whole reaching a thickness of from 500 to 600 feet. 
 These beds were formerly classed, on purely lithological 
 * Geol. Mag. , vol. iv. 
 
LONGMYND GROUl'. 
 
 485 
 
 grounds, as the base of the Lingula Flags, but Messrs. Hicks 
 and Salter, to whose exertions we owe almost all our knowl- 
 edge of the fossils, have pointed out* that the most charac- 
 teristic genera found in them are quite unknown in the Lin- 
 gula Flags, while they possess many of the strictly Lower 
 Cambrian genera, such as Microdiscus and Paradoxides. 
 They therefore proposed to place them, and it seems to me 
 with good reason, at the top of the Lower Cambrian under 
 the term "Menevian," Menevia being the classical name of 
 St. David's. The beds ai-e well exhibited in the neighbor- 
 hood of St. David's in South Wales, and near Dolgelly and 
 Maentwrog in North Wales. They are the equivalents of 
 the lowest part of Ba,rrande's Primordial Zone (litage C). 
 More than forty species have been found 
 in them, and the group is altogether very 
 rich in fossils for so early a period. The 
 trilobites are of large size ; Paradoxides 
 Davidis (see Fig. 572), the largest trilo- 
 bite known in England, 22 inches or near- 
 ly 2 feet long, is peculiar to the Menevian 
 Beds. By referring to the Bohemian tri- 
 lobite of the same genus (Fig. 576, p. 488), 
 the reader will at once see how these 
 fossils (though of such different dimen- 
 sions) resemble each other in Bohemia 
 and Wales, and other closely allied spe- 
 cies from the two regions might be added, 
 besides some which are common to both 
 countries. The Swedish fauna, presently 
 to be mentioned, will be found to be still ^"g^fS Sal ffie. 
 more nearly connected with the Welsh Menevian beds. st. Da- 
 Menevian. In all these countries there vid-sandDoigeiiy. 
 is an equally marked difference between the Cambrian fos- 
 sils and those of the Upper and Lower Silurian rocks. The 
 trilobite with the largest number of rings, JEkinnys venulosa, 
 occurs here in conjunction with Agnostus and Microdiscus, 
 the genera with the smallest number. Blind trilobites are 
 also foimd as well as those which have the largest eyes, such 
 as Microdiscus on the one hand, and Anopolenvs on the other. 
 
 LONGMTND GKOUP. 
 
 Older than the Menevian Beds are a thick series of olive 
 green, purple, red and gray grits and conglomerates found 
 in North and Sonth Wales, Shropshire, and parts of Ireland 
 
 * British Association Report, 1865, 1866, 1868, and Quart. Geol. Joum., 
 vols. xxi. , XXV. 
 
486 ELEMENTS OF GEOLOGT. 
 
 and Scotland. They have been called by Professor Sedg- 
 wick the Longraynd or Bangor Group, compnsnig, first, the 
 Harlech and Barmouth sandstones ; and secondly, the Llan- 
 beris slates. ... 
 
 Harlech Grits.— The sandstones of this period attain in the 
 
 Longmynd hills a thickness of no less than 6000 feet without 
 
 g,3 any interposition of vol- 
 
 1 ■ ' 2 canic matter; in some 
 
 ^^^^!^^ /< ^^^ ^ places in Merionethshire 
 
 O^Vi_^..«.^ l ^Ml\ of five spedeT^ot^ an- 
 
 BistiodermaHibernim, Km. Oldhamia beds. Brny nelids (see Fig. 460) 
 
 1. Showing openiuro'/wot. and tube with b™"gi?t tO light.byMr. 
 
 wrinlilings or crossing ridges, probably pro- Salter 111 OliropSUire, and 
 
 (luced by a tentacled sea worm or annelid. 2. -p, x^;,,„Knn in Wipk- 
 
 Lower and curved extremity of tube with five -L"- -tVl'ianan in vv ICK. 
 
 transverse lines. low, and ail obsCUre 
 
 crustacean form, Palmopyge Ramsayi, they were supposed to 
 be barren of organic remains. Now, however, through the 
 labors of Mr. Hicks,* they have yielded at St. David's a rich 
 fauna of trilobites, brachiopods, phyllopods, and pteropods, 
 showing, together with other fossils, a by no means }dw 
 state of organization at this early period. Already the 
 fauna amounts to 20 species referred to 17 genera. 
 
 A new genus of trilobite called Plutonia SedgwicMi, not 
 yet figured and described, has been met with in the Harlech 
 grits. It is comparable in size to the large Paradoxides Pa- 
 vidis before mentioned, has well-developed eyes, and is cov- 
 ered all over with tubercles. In the same strata occur other 
 genera of trilobites, namely, Conocoryphe, Paradoxides, Mi- 
 erodiscus, and the Pteropod Theca (Fig. 568), all represented 
 by species peculiar to the Harlech grits. The sands of this 
 formation are often rippled, and were evidently lefl dry at 
 low tides, so that the surface was dried by the sun and made 
 to shrink and present sun-cracks. There are also distinct 
 impressions of rain-drops on many surfaces, like those figured 
 at p. 416. 
 
 Llanberis Slates. — The slates of Llanberis and Penrhyn in 
 Carnarvonshire, with their associated sandy strata, attain a 
 great thickness, sometimes about 3000 feet. They are per- 
 haps not more ancient than the Harlech and Barmouth beds 
 last mentioned, for they may represent the deposits of fine 
 
 * Brit. Assoc. Report, 1 868. 
 
CAMBRIAN EOCKS OF BOHEMIA. 
 
 481 
 
 mud thrown down in the 
 same sea, on the borders of 
 which the sands above men- 
 tioned were accumulating. 
 In some of these slaty rocks 
 in Ireland, immediately oji- 
 posite Anglesea and Carnar- 
 von, two species of fossils 
 have been found, to which 
 the late Professor E. Forbes 
 
 Fig. 576. 
 
 Fig. 574. 
 
 Oldhamia radiata^ Forbes. Wiclilow, 
 Ireland. 
 
 OMhamia 
 Forbes. Widifowj 
 Ireland. 
 
 gave the name of Oldhamia. The nature 
 of these organisms is still a matter of dis- 
 cussion among naturalists. 
 
 Cambrian Eoeks of Bohemia {Primordial 
 zone of Barrande). — In the year 1846, as 
 before stated, M. Joachim Barrande, after 
 ten years' exploration of Bohemia, and after 
 collecting more than a thousand species of 
 fossils, had ascertained the existence in that 
 country of three distinct faunas below the 
 Devonian. To his first fauna, which was old- 
 er than any then known in this country, he 
 gave the name of Etage C; his two first stages 
 A and B consisting of crystalline and meta- 
 morphio rocks and unfossiliferous schists. 
 This Stage C or primordial zone proved af- 
 terwards to be the equivalent of those sub- 
 divisions of the Cambrian groups which have been above 
 described under the names of Menevian and Lingula Flags. 
 The second fauna tallies with Murchison's Lower Silurian, 
 as originally defined by him when no fossils had been dis- 
 covered below the Stiper-Stones. The third fauna agrees 
 with the Upper Silui-ian of the same author. Barrande, 
 without government assistance, had undertaken single- 
 handed the geological survey of Bohemia, the fossils pre- 
 viously obtained from that country having scarcely exceeded 
 20 in number, whereas he had already acquired, in 1860, no 
 less than 1100 species, namely, 250 crustaceans (chiefly Tri- 
 lobites), 250 cephalopods, 160 gasteropods and pteropods, 130 
 acephalous mollusks, 210 brachiopods, and 110 corals and 
 other fossils. These numbers have since been almost dou- 
 bled by subsequent investigations in the same country. 
 
 In the primordial zone C, he discovered trilobites of the 
 genera Parado«,ides, Gonocoryphe, UUipsocephalus, Sao,_Ari- 
 onellus. Hydrocephalus, and Agnosias. M. Barrande pointed 
 out that these primordial trilobites have a peculiar facies of 
 
488 
 
 ELEMENTS OF GEOLOGY. 
 
 Fossils of the lowest FossiUferovs Beds in Bohemia, or "Primordial Zone" 
 of Barrande. 
 Fig. 5T6. 3''ig- 57T. 
 
 Conocoruphe striata. Syn. Conocephaivs 
 striatus, Eramrich. One-half natural 
 size. Ginetz and Skrey. 
 
 Paradoxides Bohemieiis, Barr. 
 About one-half nat. size. 
 
 Fig. 578. 
 
 Afjnostus intmer^ Beyrich. 
 Kat. size and maguilied. 
 
 Fig. 5T9. 
 
 AgnoBius Bex, Barr. 
 Nat. size, Skrey. 
 
 The small lines beneath indicate the true 
 size. In the youngest state, a, no 
 segments are visible ; as the metamor- 
 phosis progresses, &, c, the body seg- 
 ments begin to be developed: in the 
 stage d the eyes are introduced, but 
 the facial sutures are not completed; 
 at e the fiill-growu animal, half its true 
 size, is shown. 
 Sao Jiirsuta, Barrande, in its various 
 stages of growth. 
 
 their own dependent on the nniltiplication of their thoracic 
 segments and the diminution of their caudal shield or py- 
 gidiiim. 
 
 One of the "primordial" or Upper Cambrian Trilobites of 
 the genus Sao, a form not found as yet elsewhere in the 
 world, afforded M. Barrande a fine illustration of the meta- 
 morphosis of these creatures, for he traced them through no 
 less than twenty stages of their development. A few of 
 these changes have been selected for representation in the 
 accompanying figures, that the reader may learn the gradual 
 manner in which different segments of the body and the eyes 
 make their appearance. 
 
 In Bohemia the primordial fauna of Barrande derived its 
 importance exclusively from its numerous and peculiar trilo- 
 bites. Besides these, however, the same ancient schists have 
 yielded two genera of brachiopods, Orthis and Orbicula, a 
 pteropod of the genus Theca, and four echinoderms of the 
 Cystidean family. 
 
CAMBRIAN OF SWEDEN AND NORWAY. 489 
 
 Cambrian of Sweden and Norway. — The Cambrian beds of 
 Wales are represented in Sweden by strata the fossils of 
 which have been described by a most able naturalist, M. An- 
 gelin, in his " Palseontologica Suecica " (l 852-'4). The " alum- 
 schists," as they are called in Sweden, are horizontal argilla- 
 ceous rocks which underlie conformably certain Lower'Silu- 
 rian strata in the mountain called Kinnekulle, south of the 
 great Wener Lake in Sweden. These schists contain trilo- 
 bites belonging to the genera Paradoxides, Olenus, Agnostus, 
 and others, some of which present rudimentary forms, like 
 the genus last mentioned, without eyes, and with the body 
 segments scarcely developed, and others, again, have the 
 number of segments excessively multiplied, as in Paradox- 
 ides. Such peculiarities agree with the characters of the crus- 
 taceans met with in the Cambrian strata of Wales ; and Dr. 
 Torell has recently found in Sweden the Paradoxides JUcksii, 
 a well-known Lower Cambrian fossil. 
 
 At the base of the Cambrian strata in Sweden, which in 
 the neighborhood of Lake Wener are perfectly horizontal, 
 lie ripple - marked quartzose sandstones with worm -tracks 
 and annelid borings, like some of those found in the Harlech 
 grits of the Longinynd. Among these are some which have 
 been referred doubtfully to plants. These sandstones have 
 been called in Sweden "fucoid sandstones." The whole 
 thickness of the Cambrian rocks of Sweden does not exceed 
 300 feet from the equivalents of the Tremadoc beds to these 
 sandstones, which last seem to correspond with the Long- 
 mynd, and are regarded by Torell as older than any fossilif- 
 erous primordial rocks in Bohemia. 
 
 Cambrian of the United States and Canada {Potsdam Sand- 
 stone). — This formation, as we learn from Sir W. Logan, is 
 700 feet thick in Canada ; the upper part consists of sand- 
 stone containing fucoids, and perforated by small vertical 
 holes, which are very characteristic of the rock, and appear 
 to have been made by annelids {Scolitlvus linearis). The 
 lower portion is a conglomerate with quartz pebbles. I have 
 seen the Potsdam sandstone on the banks of the St. Law- 
 rence, and; on the borders of Lake Champlain, where, as at 
 Keesville, it is a white quartzose fine-grained grit, almost 
 passing into quartzite. It is divided into horizontal ripple- 
 marked beds, very like those of the Lingula Flags of Brit- 
 ain, and replete with a small i-ound-shaped Oiolella, in such 
 numbers as to divide the rock into parallel planes, in the 
 same manner as do the scales of mica in some micaceous 
 sandstones. Among the shells of this formation in Wiscon- 
 sin are species oi Linqula and Orthis, and several ti-ilobites 
 ' 21* 
 
490 
 
 ELEMENTS OF GEOLOGY. 
 
 Fig. 581. 
 
 of the primordial genus DiJcelocephalus 
 (Fig. 581). On the banks of the St. 
 Lawrence, near Beauharnois and else- 
 where, many fossil foot-prints have been 
 observed on the surface of the rippled 
 layers. They are supposed by Proiessor 
 Owen to be the trails of more than one 
 species of articulate animal, probably al- 
 lied to the King Crab, or Limulm. 
 
 Recent investigations by the natural- 
 ists of the Canadian survey have ren- 
 dered it certain that below the level of 
 the Potsdam Sandstone there are slates 
 Vikeiocephaius Minnesotm. ^ gchists extending from New York to 
 
 ms. Dale uweu. uue- ^^ „ _, , • t i • e 
 
 third diameter. A large Newfoundland, occupied by a series ot 
 
 g™,r"ot"um"'landl trilobitic foiTOS Similar in genera, though 
 
 Btone. Palls of St. Croix, jjq^ j^ specics, to those found in the Eu- 
 
 oatheUpperMississippi. ^.^^^^^ Upper Cambrian strata. 
 
 Huronian Series. — Next below the Upper Cambrian occur 
 strata called the Huronian by Sir W. Logan, which are of 
 vast thickness, consisting chiefly of quartzite, with great 
 masses of greenish chloritic slate, which sometimes include 
 pebbles of crystalline rocks derived from the Laurentian for- 
 mation, next to be described. Limestones are rare in this 
 series, but one band of 300 feet in thickness has been traced 
 for considerable distances to the north of Lake Huron. Beds 
 of greenstone are intercalated conformably with the quartz- 
 ose and argillaceous members of this series. No organic re- 
 mains have yet been found in any of the beds, which are 
 about 18,000 feet thick, and rest unconformably on the Lau- 
 rentian rocks. 
 
 LAUEENTIAN GEOUP. 
 
 In the course of the geological survey carried on under the 
 direction of Sir W. E. Logan, it has been shown that, north- 
 ward of the river St. Lawrence, there is a vast series of crys- 
 talline rocks of gneiss, mica-schist, quartzite, and limestone, 
 more than 30,000 feet in thickness, which have been called 
 Laurentian, and which are already known to occupy an area 
 of about 200,000 square miles. They are not only more 
 ancient than the fossiliferous Cambrian formations above de- 
 scribed, but are older than the Huronian last mentioned, and 
 had undergone great disturbing movements before the Pots- 
 dam sandstone and the other "primordial" or Cambrian 
 rocks were formed. The older half of this Laurentian series 
 is unconformable to the newer portion of the same. 
 
UPPER AND LOWER LAURENTIAN. 491 
 
 Upper Laurentian or Labrador Series.— The Upper Group, 
 more than 10,000 feet thick, consists of stratified crystalline 
 rocks- in which no organic remains have yet been found. 
 They consist in great part of feldspars, which vary in compo- 
 sition from anorthite to andesine, or from those kin^s in 
 which there is less than one per cent, of potash and soda to 
 those in which there is more than seven per cent, of these al- 
 kalies, the soda preponderating greatly. These feldsparites 
 sometimes form mountain masses almost without any admix- 
 ture of other minerals ; but at other times they include au- 
 gite, which passes into hypersthene. They are often granit- 
 oid in structure. One of the varieties is the same as the 
 opalescent labradorite rock of Labrador. The Adirondack 
 Mountains in the State of New York are referred to the same 
 series,' and it is conjectured that the hypersthene rocks of 
 Skye, which resemble this formation in mineral character, 
 may be of the same geological age. 
 
 Lower Laurentian. — This series, about 20,000 feet in 
 thickness, is, as before stated, unconformable to that last 
 mentioned ; it consists in great part of gneiss of a reddish 
 tint with orthoclase feldspar. Beds of nearly pure quartz, 
 from 400 to 600 feet thick, occur in some places. Horn- 
 blendic and micaceous schists are often interstratified, and 
 beds of limestone, usually crystalline. Beds of plumbago 
 also occur. That this pure carbon may have been of or- 
 ganic origin before metamorphism has naturally been con- 
 jectured. 
 
 There are several of these limestones which have been 
 traced to great distances, and one of them is from TOO to 
 1500 feet thick. In the most massive of them Sir W. Logan 
 observed, in 1859, what he considered to be an organic body 
 much resembling the Silurian fossil called Stromatopora ru- 
 gosa. It had been obtained the year before by Mr. J. Mac- 
 Mullen at the Grand Calumet, on the river Ottawa. This 
 fossil was examined in 1864 by Dr. Dawson of Montreal, who 
 detected in it, by aid of the microscope, the distinct struc- 
 ture of a Ehizopod or Foraminifer. Dr. Carpenter and Prof. 
 T. Rupert Jones have since confirmed this opinion, compar- 
 ing the structure to that of the well-known nummulite. It 
 appears to have grown one layer over another, and to have 
 formed reefs of limestone as do the living coral-building 
 polyp animals. Parts of the original skeleton, consisting of 
 carbonate of lime, are still preserved ; while certain inter- 
 spaces in the calcareous fossil have been filled up with serpen- 
 tine and white augite. On this oldest of known organic re- 
 mains Dr. Dawson has conferred the name of Eozoon Gana- 
 
492 ELEMENTS OF GEOLOGr. 
 
 dense (see Figs. 582, 583) ; its antiquity is such that the dis- 
 tance of time which separated it from the Upper Cambrian pe- 
 riod, or that of the Potsdam sandstone, may, says Sir W. Lo- 
 gan, be equal to the time which elapsed between the Pots- 
 dam sandstone and the nummulitic limestones of the Tertiary 
 
 Fig. 582. Pig. 583. 
 
 
 Eozoon Carmdense, Daw. (after Carpenter). Oldest known organic body. 
 Fig. 682. a. Cliambera of lower tier communicating at +, and separated from adjoin- 
 ing chambers at o by an intervening septum, traversed by passages, h. Cham- 
 bers of an npper tier, c. Walls of the chambers traversed by fine tubules. (These 
 tubules pass with uniform parallelism from the inner to the outer surface, opening 
 at regular distances from each other.) d. Intermediate skeleton, composed of ho- 
 mogeneous shell substance, traversed by stoloniferous passages (/) connecting the 
 chambers of the two tiers, e. Canal system in intermediate skeleton, showing the 
 arborescent saceodic prolongations. (Fig. 583 shows these bodies in a decalcified 
 state.) /. Stoloniferous passages.— Fig. 583. Decalcified portion of natural rook, 
 showing caTuil sustem and the several layers ; the acuteness of the planes prevents 
 more than one or two parallel tiers being observed. Natural size. 
 
 period. The Laurentian and Huronian rocks united are about 
 50,000 feet in thickness, and the Lower Laurentian was dis- 
 turbed before the newer series was deposited. We may nat- 
 urally expect that other proofs of unconfoi-mability will here- 
 after be detected at more than one point in so vast a succes- 
 sion of strata. 
 
 The mineral character of the Upper Laurentian differs, as 
 we have seen, from that of the Lower, and the pebbles of 
 gneiss in the Huronian conglomerates are thought to prove 
 that the Laurentian strata were already in a raetamorphic 
 state before they were broken up to supply materials for the 
 Huronian. Even if we had not discovered the Eozoon, we 
 might fairly have inferred from analogy that as the quartz- 
 ites were once beds of sand, and the gneiss and mica-schist 
 derived from shales and argillaceous sandstones, so the calca- 
 reous masses, from 400 to 1000 feet and more in thickness, 
 were originally of organic origin. This is now generally be- 
 lieved to have been the case with the Silurian, Devonian, Car- 
 boniferous, Oolitic, and Cretaceous limestones and those num- 
 mulitic rocks of tertiary date which bear the closest affinity 
 to the Eozoon reefs of the Lower Laurentian. The oldest 
 stratified rock in Scotland is that called by Sir R. Murchison 
 
LOWER LAURENTIAN. 493 
 
 " the fundamental gneiss," which is found in the north-west 
 of Ross-shire, and in Sutherlandshire (see Fig. 82, p. 1 1 2), and 
 forms the whole of the adjoining island of Lewis, in the Heb- 
 rides. It has a strike from north-west to south-east, nearly 
 at right angles to the metamorpliic strata of the Grampians. 
 On this Laurentian gneiss, in parts of the western Highlands, 
 the Lower Cambrian and various metamorphic rocks rest 
 unconformably. It seems highly probable that this ancient 
 gneiss of Scotland may correspond in date with part of the 
 great Laurentian group of North America. 
 
494 ELEMENTS OF GEOLOGY. 
 
 CHAPTER XXVm. 
 
 VOLCANIC EOCKS. 
 
 External Form, Structure, and Origin of Volcanic Mountains. — Cones and 
 Craters. — Hypothesis of "Elevation Craters" considered. — Trap Rocks. — 
 Name whence derived. — Minerals most abundant in Volcanic Eocks. — Table 
 of the Analysis of Minerals in the Volcanic and Hypogene Rocks. — Similar 
 Minerals in Meteorites. — Theory of Isomoi-phism. — Basaltic Eocks. — Tra- 
 chytic Eocks. — Special Forms of Structure. — The columnar and globular 
 Forms. — Trap Dikes and Veins. — Alteration of Rocks by volcanic Dikes. 
 — Conversion of Chalk into Marble. — Intrusion of Trap between Strata. — 
 Relation of trappean Eocks to the Products of active Volcanoes. 
 
 The aqueous or fossiliferous rocks having now been de- 
 scribed, we have next to examine those which may be called 
 volcanic, in the most extended sense of that term. Suppose 
 a, a in the annexed diagram to represent the crystalline for- 
 
 a. Hypogene formations, stratified anfl uustratified. 6. Aqueous formations, 
 c. Volcauic rocks. 
 
 mations, such as the granitic and metamorphic ; b, b the fos- 
 siliferous strata ; and o, c the volcanic rocks. These last are 
 sometimes found, as was explained in the first chapter, break- 
 ing through a and b, sometimes overlying both, and occasion- 
 ally alternating with the strata b, b. 
 
 External Form, Structure, and Origin of Volcanic Mountains. 
 — The origin of volcanic cones with crater-shaped summits 
 has been explained in the " Principles of Geology " (chaps, 
 xxiii. to xxvii.), where Vesuvius, Etna, Santorin, and Barren 
 Island are described. The more ancient portions of those 
 mountains or islands, formed long before the times of histo- 
 ry, exhibit the same external features and internal structure 
 which belong to most of the extinct volcanoes of still high- 
 er antiquity ; and these last have evidently been due to a 
 complicated series of operations, varied in kind according to 
 circumstances ; as, for example, whether the accumulation 
 took place above or below the level of the sea, whether the 
 lava issued from one or several contiguous vents, and, lastly, 
 
VOLCAKIC CONES AND CRATERS. 
 
 495 
 
 whether the rocks reduced to fusion in the subterranean I'e- 
 gions happened to have contained more or less silica, pot- 
 ash, soda, lime, iron, and other ingredients. We are hest ac- 
 quainted with the effects of eruptions above water, or those 
 called subaerial or supramarine ; yet the products even of 
 these are arranged in so many ways that their interpretation 
 has given rise to a variety of contradictory opinions, some of 
 which will have to be considered in this chapter. 
 
 Cones and Craters. — In regions where the eruption of vol- 
 canic matter has taken place in the open air, and where the 
 surface has never since been subjected to great aqueous den- 
 udation, cones and craters constitute the most striking pecul- 
 iarity of this class of formations. Many hundreds of these 
 cones are seen in central France, in the ancient provinces of 
 Auvei'gne, Velay, and Vivavais, where they observe, for the 
 most part, a linear arrangement, and form chains of hills. 
 Although none of the eruptions have happened within the 
 historical era, the streams of lava may still be traced dis- 
 tinctly descending from many of the craters, and following 
 the lowest levels of the existing valleys. The origin of the 
 cone and crater-shaped hill is well understood, the growth 
 
 Fig. 585. 
 
 Part of tlie chain of extinct volcanoes called the Monts Dome, Auvergne. (Scrope.) 
 
 of many having been watched during volcanic eruptions. 
 A chasm or fissure first opens in the earth, from which great 
 volumes of steam are evolved. The explosions are so vio- 
 lent as to hm-1 up into the air fragments of broken stone, 
 parts of which are shivered into minute atoms. At the 
 same time melted stone or lava usually ascends through the 
 chimney or vent by which the gases make their escape. Al- 
 though extremely heavy, this lava is forced up by the ex- 
 pansive power of entangled gaseous fluids, chiefly steam or 
 aqueous vapor, exactly in the same manner as water is made 
 to boil over the edge of a vessel when steam has been gener- 
 ated at the bottom by heat. Large quantities of the lava 
 are also shot up into the air, where it separates into frag- 
 ments, and acquires a spongy texture by the sudden enlarge- 
 
496 ELEMENTS OF GEOLOGY. 
 
 ment of the included gases, and thus forms scori(B, other 
 portions being reduced to an impalpable powder or dust. 
 The showering down of the various ejected materials round 
 the orifice of eruption gives rise to a conical mound, in which 
 the successive envelopes of sand and scoriae form layers, dip- 
 ping on all sides from a central axis. In the mean time a 
 hollow, called a crater, h&s. been kept open in the middle of 
 the mound by the continued passage upward of steam and oth- 
 er gaseous fluids. The lava sometimes flows over the edge of 
 the crater, and thus thickens and strengthens the sides of the 
 cone ; but sometimes it breaks down the cone on one side 
 (see Fig. 585), and often it flows out from a fissure at the base 
 of the hill, or at some distance from its base. 
 
 Some geologists had erroneously supposed, from observa- 
 tions made on recent cones of eruption, that lava which con- 
 solidates on steep slopes is always of a scoriaceous or vesicu- 
 lar structure, and never of that compact texture which we 
 find in those rocks which are usually termed "trappean." 
 Misled by this theory, they have gone so far as to believe 
 that if melted matter has originally descended a slope at an 
 angle exceeding four or five degrees, it never, on cooling,.ac- 
 quires a stony compact texture. Consequently, whenever 
 they found in a volcanic mountain sheets of stony materials 
 inclined at angles of from 5° to 20° or even more than 30°, 
 they thought themselves warranted in assuming that such 
 rooks had been originally horizontal, or very slightly in- 
 clined, and had acquired their high inclination by subsequent 
 upheaval. To such dome-shaped mountains with a cavity 
 in the middle, and with the inclined beds having what was 
 called, a quaquaversal dip or a slope outward on all sides, 
 they gave the name of " Elevation craters." 
 
 As the late Leopold von Buch, the author of this theory, 
 had selected the Isle of Palma, one of the Canaries, as a typ- 
 ical illustration of this form of volcanic mountain, I visited 
 that island in 1854, in company with my friend Mr. Hartung, 
 and I satisfied myself that it owes its origin to a series of 
 eruptions of the same nature as those which formed the mi- 
 nor cones, already alluded to. In some of the more ancient 
 or Miocene volcanic mountains, such as Mont Dor and Cantal 
 in central France, the mode of origin by upheaval as above 
 described is attributed to those dome-shaped masses, wheth- 
 er they possess or not a great central cavity, as in Palma. 
 Where this cavity is present, it has probably been due to 
 one or more great explosions similar to that which destroyed 
 a great part of ancient Vesuvius in the time of Pliny. Simi- 
 lar paroxysmal catastrophes have caused in historical times 
 
HYPOTHESIS OF "ELEVATION CRATEES." 497 
 
 the truncation on a grand scale of some large cones in Java 
 and elsewhere.* 
 
 Among the objections which may be considered as fatal to 
 Von Buch's doctrine of upheaval in these cases, I may state 
 that a seiies of volcanic formations extending over an area 
 six or seven miles in its shortest diameter, as in Palma, could 
 not be accumulated in the form of lavas, tuifs, and volcanic 
 breccias or agglomerates without producing a mountain as 
 lofty as that which they now constitute. But assuming that 
 they were first horizontal, and then lifted up by a force act- 
 ing most powerfully in the centre and tilting the beds on all 
 sides, a central crater having been formed by explosion or 
 by a ciiasm opening in the middle, where the continuity of 
 the rocks was interrupted, we should have a right to expect 
 that the chief ravines or valleys would open towards the 
 central cavity, instead of which the rim of the great crater 
 in Palma and other similar ancient volcanoes is entire for 
 more than three parts of the whole circumference. 
 
 If dikes are seen in the precipices surrounding such craters 
 or central cavities, they certainly imply rents which were 
 filled up with liquid matter. But none of the dislocations 
 producing such rents can have belonged to the supposed pe- 
 riod of terminal and paroxysmal upheaval, for had a great 
 central crater been already formed before they originated, or 
 at the time when they took place, the melted matter, instead 
 of filling the narrow vents, would have flowed down into the 
 bottom of the cavity, and would have obliterated it to a cer- 
 tain extent. Making due allowance for the quantity of mat- 
 ter removed by subaerial denudation in volcanic mountains 
 of high antiquity, and for the grand explosions which are 
 known to have caused truncation in active volcanoes, there 
 is no reason for calling in the violent hypothesis of elevation 
 craters to explain the structure of such mountains as Ten- 
 erifie, the Grand Canary, Palma, or those of central France, 
 Etna, or Vesuvius, all of which I have examined. With re- 
 gard to Etna, I have shown, from observations made by me 
 in 1857, that modern lavas, several of them of known date, 
 have formed continuous beds of compact stone even on slopes 
 of 15, 36, and 38 degrees, and, in the case of the lava of 1852, 
 more than 40 degrees. The thickness of these tabular layers 
 varies from 1^ foot to 26 feet. And their planes of stratifi- 
 cation are parallel to those of the overlying and underlying 
 scoriae which form part of the same cnrrents.f 
 
 Nomenclature of Trappean Rocks. — When geologists first 
 began to examine attentively the structure of the northern 
 
 * Principles, vol. ii., pp. 56 and 145. 
 
 t Memoir on Mount Etna, Phil. Trans., 1858. 
 
498 ELEMENTS OF GEOLOGY. 
 
 rn parts of Europe, they were almost entirely ig- 
 ;he phenomena of existing volcanoes. They found 
 
 and westeri 
 
 norant of the pher _ _ , 
 
 certain rocks, for the most part without stratification, and of 
 a peculiar mineral composition, to which they gave different 
 names, such as basalt, greenstone, porphyry, trap tuff, and 
 amygdaloid. All these, which were recognized as belong- 
 ing to one family, were called " trap " by Bergmann, from 
 trappa, Swedish for a flight of steps — a name since adopted 
 very generally into the nomenclature of the science ; for it 
 was observed that many rocks of this class occurred in great 
 tabular masses of unequal extent, so as to form a succession 
 of terraces or steps. It was also felt that some general term 
 was indispensable, because these rocks, although very diver- 
 sified in form and composition, evidently belonged to one 
 group, distinguishable from the plutonic as well as from the 
 non-volcanic fossiliferous rocks. 
 
 By degrees familiarity with the products of active volca- 
 noes convinced geologists more and more that they were 
 identical with the trappean rocks. In every stream of mod- 
 ern lava there is some variation in character and composi- 
 tion, and even where no important difference can be recog- 
 nized in the proportions of silica, alumina, lime, potash, iron, 
 and other elementary materials, the resulting minerals are 
 often not the same, for reasons which we are as yet unable 
 to explain. The difference also of the lavas poured out from 
 the same mountain at two distinct periods, especially in the 
 quantity of silica which they contain, is often so great as to 
 give rise to rocks which are regarded as forming distinct 
 families, although there may be every intermediate gradation 
 between the two extremes, and although some rocks, form- 
 ing a transition from the one class to the other, may often be 
 so abundant as to demand special names. These species 
 might be multiplied indefinitely, and I can only affoi'd space 
 to name a few of the principal ones, about the composition 
 and aspect of which there is the least discordance of opinion. 
 
 Minerals most abundant in Volcanic Rocks. — The minerals 
 which form the chief constituents of these igneous rocks are 
 few in number. Next to quartz, which is nearly pui"e silica 
 or silicic acid, the most important are those silicates com- 
 monly classed under the several heads of feldspar, mica, horn- 
 blende or augite, and olivine. In the annexed table, in draw- 
 ing up which I have received the able assistance of Mr. David 
 Forbes, the chemical analysis of these minerals and their va- 
 rieties is shown, and he has added the specific gi-avity of the 
 different mineral species, the geological application of which 
 in determining the rocks formed by these minerals will be 
 explained in the sequel (p. 504). 
 
ANALYSIS OF MINERALS. 
 
 499 
 
 Analysis of Minerals most abundant in the Volcanic and Hypogeni Rocks. 
 
 
 1 
 
 if; 
 
 1 
 
 .8 
 
 1 . 
 
 «.2 
 
 4 
 lit 
 
 ti 
 
 s 
 
 s 
 
 i 
 
 % 
 S 
 
 i 
 
 4 
 1 
 
 fi 
 
 s 
 
 THE QUARTZ GROUP. 
 
 
 
 
 
 
 
 
 
 
 
 
 lOO'C 
 
 100-e 
 
 ... 
 
 
 
 
 
 
 
 
 2-6 
 2-3 
 
 
 
 THE FELDSPAR GROUP. 
 
 
 
 
 
 
 
 
 
 
 
 Obthoclask. Carlabad, in granite (Bulk) 
 
 K,-n 
 
 18-96 
 
 0-97 
 
 
 f,rnr 
 
 
 14-66 
 
 1-45 
 
 ... ) 
 
 
 Sanadine, Drftchenfela ia trachyte 
 
 
 
 
 
 
 
 
 
 t 
 
 2-55 
 
 (Rammelsbenr) 
 
 Albitb. Arendal, in granite (G. Rose) * 
 
 BB-H' 
 
 18-6! 
 
 
 
 0-» 
 
 0-3( 
 
 10-39 
 
 3-4' 
 
 W. 0'44) 
 
 
 Wi-41 
 
 19-ai; 
 
 
 (1-28 
 
 0-6 
 
 ... 
 
 
 11-9: 
 
 
 
 Oligoclasb. Yttarby, in granite f Berze- 
 
 
 
 
 
 
 
 
 
 
 
 
 BI'M 
 
 23-8(1 
 
 
 
 3-1 
 
 ll-8( 
 
 0-3t 
 
 9-6- 
 
 
 2-65 
 
 Teneriffe, in trachyte (DeviHe) . . 
 
 B1-55 
 
 22-03 
 
 
 
 9-8 
 
 0-47 
 
 3-44 
 
 7-7' 
 
 
 2-59 
 
 Labkadoritb. Hitteroe, in Labrador- 
 
 
 
 
 
 
 
 
 
 
 
 Rock (Waage) 
 
 51 -a' 
 
 29-4? 
 
 9-9( 
 
 
 9-4! 
 
 0-.31 
 
 1-10 
 
 5-o; 
 
 W. 0-71 
 
 2-72 
 
 Iceland, in volcanic (Damour) . . 
 
 S2-1' 
 
 29-22 
 
 l-9( 
 
 
 13-1 
 
 ... 
 
 
 3-4( 
 
 
 2-11 
 
 Anokxhitb. HarzbuTg, in diorite fStreng) 
 Heclflj in volcanic(Walterahau9en) 
 
 45-;r 
 
 IU-81 
 
 0-51 
 
 
 16-5 
 
 O-KJ 
 
 0-4( 
 
 1-45 
 
 "W. 0-87 1 
 
 2-74 
 
 45'M 
 
 32-10 
 
 2-03 
 
 0-78 
 
 18-3 
 
 
 0-29 
 
 1-06 
 
 Lbucits. VesnTius, 1811, in lava (Ram- 
 
 
 
 
 
 
 
 
 
 
 
 meUberg) 
 
 56-11 
 
 23-99 
 
 
 
 
 
 90-.59 
 
 0-5- 
 
 
 9-48 
 
 Nbphblinb. Miaak, in Miaacite (Schee- 
 
 
 
 
 
 
 
 
 
 
 
 "r) 
 
 44-:« 
 
 33-25 
 
 (I-K9 
 
 
 0-3 
 
 0-07 
 
 5-H', 
 
 1«-(1-/ 
 
 
 
 Vesuvius, in volcanic (Arfvedson) . 
 
 44-11 
 
 33-73 
 
 
 
 
 
 
 20-46 
 
 W. 0-62 
 
 2-60 
 
 
 
 
 
 
 
 
 
 
 
 
 Mdscotitb. Finland^in granite (Rose) . 
 
 46-36 
 
 36-80 
 
 4-53 
 
 
 
 
 9-22 
 
 
 ( F. 0-67 1 
 iw. 1-84) 
 (F. 4-181 
 ILi. 4-85 f 
 W. 0-44 
 
 2-90 
 
 nault) f 
 
 52-40 
 
 26-80 
 
 
 1-50 
 
 
 
 9-14 
 
 
 2-90 
 
 40-S6 
 
 1.5-13 
 
 13-00 
 
 
 
 99-00 
 
 8-83 
 
 
 2-70 
 
 Vesnviua, in volcanic (ChodneO • 
 
 40-91 
 
 17-71 
 
 11-02 
 
 
 0-3 
 
 19-lK 
 
 9-96 
 
 
 
 9-75 
 
 Phlogopitb. New York, in metam. lime- I 
 
 41-96 
 
 13-47 
 
 
 2-67 
 
 tl-2« 
 
 27-12 
 
 9-37 
 
 
 (F. 2-931 
 1 W. 0-60 } 
 
 2-81 
 
 
 
 49-52 
 17-52 
 
 1-66 
 29-76 
 
 
 10-8 
 
 0-48 
 13-84 
 
 
 W. 5-65 
 W. 11-33 
 
 2-99 
 9-87 
 
 Chlobits. Daiiphiny (Mariguac) . . . 
 
 56-88 
 
 
 
 RAFiDOLrrs. Pyrenees (Delesse) . . . 
 
 H2-JI 
 
 1H-.511 
 
 
 0.06 
 
 
 3B-7( 
 
 
 
 W. 12-10 
 
 2-61 
 
 Talc. ZiUerthal (Delesse) 
 
 63-00 
 
 
 
 trace 
 
 
 33-60 
 
 
 
 W. 3-10 
 
 2-78 
 
 THE AMPHIBOLE AND PYROXENE 
 
 
 
 
 
 
 
 
 
 
 
 GROUP. 
 
 
 
 
 
 
 
 
 
 
 
 Tbemolite. St. Gothard (Rammelaberg) 
 
 58-55 
 
 
 
 
 I3-9C 
 
 26-63 
 
 
 
 F.W. 0-31 
 
 2-93 
 
 AcTiNOLiTE. Arendal, in granite (Ram- 
 
 
 
 
 
 
 
 
 
 
 
 melaberg) 
 
 56-77 
 
 0-97 
 
 
 6-88 
 
 13-51 
 
 21-4t 
 
 
 
 W. 2-20 
 
 3-02 
 
 
 
 
 
 
 
 
 
 
 
 
 viUe ......'.... \ . 
 
 41-98 
 
 11-66 
 
 
 22-22 
 
 9-J5 
 
 12-.5S 
 
 
 1-02 
 
 
 3-20 
 
 Etna, in volcanic (Walterahansen) 
 
 40-91 
 
 13-68 
 
 
 17-49 
 
 13-44 
 
 13-19 
 
 
 
 W. 0-8S 
 
 3-01 
 
 Ukalitb. Ural (Ramnielsberg) .... 
 
 50-75 
 
 5-65 
 
 
 17-27 
 
 11-59 
 
 12-28 
 
 
 
 W. 1-80 
 
 3-14 
 
 AuoiTB. Bohemia, in dolerite (Rammels- 
 
 
 
 
 
 
 
 
 
 
 
 betg) 
 
 Veanvius, in lava of 1858 (Ram- 
 
 51-lH 
 
 3-38 
 
 11-95 
 
 8-08 
 
 n-M 
 
 12-82 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 melBberg) . . . ■ 
 
 49-61 
 
 4-42 
 
 
 9-08 
 
 22-83 
 
 14-22 
 
 
 
 
 
 Diaixagb, Harz, in Gabbro (Rammelfl- 
 
 
 
 
 
 
 
 
 
 
 
 berg). ..;....... . 
 
 52-0(1 
 
 3-10 
 
 
 9-36 
 
 16-29 
 
 iB-51 
 
 
 
 
 
 Htpbhsthbne. Iiabrador, in Labrador- 
 
 
 
 
 
 
 
 
 
 
 
 . Rock (Damour) 
 
 51-36 
 
 0-37 
 
 
 22-59 
 
 3-09 
 
 21-31 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 THE OLIVINE GROUP. 
 
 
 
 
 
 
 
 
 
 
 
 Bbovzitb. Greenland (V. Kobell) . . . 
 
 58-00 
 
 1-33 
 
 11-14 
 
 
 
 29.66 
 
 
 
 
 3.20 
 
 Olivinb. Carlflbad, in basalt (Rammels- 
 berp:") 
 
 39-34 
 
 
 
 14-85 
 
 
 45-81 
 
 
 
 
 3-40 
 
 Mount Somma, in volcanic (Walm- 
 
 
 
 
 
 
 
 
 
 
 
 
 40-08 
 
 0-18 
 
 
 15-74 
 
 
 
 
 
 
 
 In the laat column but one of the above table the following signs are used : F. Fluorine ; Li. Lithia ; 
 W. Loss on igniting the mineral, In moat instances only Water. 
 
500 ELEMENTS OE GEOLOGY. 
 
 From this table it will he observed that many minerals are 
 omitted which, even if they are of common occurrence, are 
 more to be regarded as accessory than as essential compo- 
 nents of the rocks in which they are found.* Such are, for 
 example, Garnet, Epidote, Tourmaline, Idocrase, Andalusite, 
 Scapolite, the various Zeolites, and several other silicates of 
 somewhat rarer occurrence. Magnetite, Titanoferrite, and 
 Iron-pyrites also occur as normal constituents of various 
 igneous rocks, although in very small amount' ais also Apatite, 
 or phosphate of lime. The other salts of lime, including its 
 carbonate or calcite, although often met with, are invariably 
 products of secondary chemical action. 
 
 The Zeolites, above mentioned, so named from the manner 
 in which they froth up under the blow-pipe and melt into a 
 glass, differ in their chemical composition from all the other 
 mineral constituents of volcanic rocks, since they are hydrated 
 silicates containing from 10 to 25 per cent, of water. They 
 abound in some trappean rocks and ancient lavas, where they 
 fill up vesicular cavities and interstices in the substance of 
 the rocks, but are rarely found in any quantity in recent 
 lavas ; in most cases they are to be regarded as secondary 
 products formed by the action of water on the other constit- 
 uents of the rocks. Among them the species Analcirae, 
 Stilbite, Natrolite, and Chabazite may be mentioned as of 
 most common occurrence. 
 
 Quartz Group. — The microscope has shown that pure quartz 
 is oftener present in lavas than was formerly supposed. It 
 had been argued that the quartz in granite having a specific 
 gravity of 2 '6, was not of purely igneous origin, because the 
 silica resulting from fusion in the laboratory has only a spe- 
 cific gravity of 2'3. But Mr. David Forbes has ascertained 
 that the free quartz in trachytes, which are known to have 
 flowed as lava, has the same specific gravity as the ordinary 
 quartz of granite ; and the i-ecent researches of Von Rath 
 and others prove that the mineral Tridymitc, which is crys- 
 tallized silica of sp. gr. 2 '3 (see Table, p. 499), is of common 
 occurrence in the volcanic rocks of Mexico, Auvergne, the 
 Rhine, and elsewhere, although hitherto entirely overlooked. 
 
 Feldspar Group. — In the Feldspar group (Table, p. 499) the 
 five mineral species most commonly met with as rock con- 
 stituents are: 1. Orthoclase, often called common or potash- 
 feldspar. 2. Albite, or soda-feldspar, a mineral which plays 
 a more subordinate part than was formerly supposed, this 
 name having been given to much which has ■ since been 
 proved to be Oligoclase. 3. Oligoclase, or soda -lime feld- 
 * Eor analyses of these minerals see the Mineralogies of Dana and Bristoiv. 
 
MICA GROUP. 501 
 
 spar, in which soda is present in much larger proportion 
 than lime, and of which mineral andesite or andesme, is con- 
 sidered to be a variety. 4. Labi-adorite, or lime-soda-feld- 
 spar, in which the proportions of lime and soda are the re- 
 verse to what they are in Gligoclase. 5. Anorthite or lime- 
 feldspar. The two latter feldspars are rarely if ever found 
 to enter into the composition of rocks containing quartz. 
 
 In employing such terms as potash-feldspar, etc., it must, 
 however, always be borne in mind that it is only intended to 
 direct attention to the predominant alkali or alkaline earth 
 in the mineral, not to assert the absence of the others, which 
 in most cases will be found to be present in minor quantity. 
 Thus potash-feldspar (orthoclase) almost always contains a 
 little soda, and often traces of lime or magnesia ; and in like 
 manner with the others. The terms " glassy " and " com- 
 pact " feldspars only refer to structure, and not to species or 
 composition ; the student should be prepared to meet with 
 any of the above feldspars in either of these conditions : the 
 glassy state being apparently due to quick cooling, and the 
 compact to conditions unfavorable to crystallisation ; the so- 
 called " compact feldspar " is also very commonly found to 
 be an admixture of more than one feldspar species, and fre- 
 quently also contains quartz and other extraneous mineral 
 matter only to be detected by the microscope. 
 
 Feldspars when arranged according to their system of crys- 
 tallization are monoclimc,ha,vmg one axis obliquely inclined; 
 or triclinic, having the three axes all obliquely inclined to 
 each other. If arranged with reference to their cleavage 
 they are orthodastic, the fracture taking place always at a 
 right angle ; or plagioclastic, in which the cleavages are ob- 
 lique to one another. Orthoclase is orthodastic and mono- 
 clinic ; all the other feldspars are plagioclastic and triclinic. 
 
 Minerals in Meteorites. — That variety of the Feldspar 
 Group which is called Anorthite has been shown by Ram- 
 melsberg to occur in a meteoric stone, and his analysis proves 
 it to be almost identical in its chemical 2>roportions to the 
 same mineral in the lavas of modern volcanoes. So also 
 Bronzite (Enstatite) and Olivine have been met with in 
 meteorites shown by analysis to come remarkably near to 
 these minerals in ordinary rocks. _ 
 
 Mica Group. — With regard to the micas, the four principal 
 species (Table, p. 499) all contain potash in nearly the same 
 proportion, but differ greatly in the proportion and nature 
 of their other ingredients. Muscovite is often called com- 
 mon or potash mica; Lepidolite is characterized by contain- 
 ino- lithia in addition; Biotite contains a large amount of 
 
502 ELEMENTS OF GEOLOGY. 
 
 magnesia and oxide of iron ; whilst Phlogopite contains still 
 more of the former substance. In rocks containing quartz, 
 muscovite or lepidolite are most common. The mica in re- 
 cent volcanic rocks, gabbros, and diorites is usually Biotite, 
 while that so common in metamorphic limestones is usually, 
 if not always, Phlogopite. 
 
 Amphibole and Pyroxene Group. — The minerals included 
 in the table under the Amphibole and Pyroxene Group differ 
 somewhat in their crystalline form, though they all belong 
 to the monoclinic system. Amphibole is a general name for 
 all the different varieties of Hornblende, Actinolite, Tremo- 
 lite, etc., while Pyroxene includes Augite, Diallage, Malaco- 
 lite, Sahlite, etc. The two divisions are so much allied in 
 chemical composition and crystallographic characters, and 
 blend so completely one into the other in Uralite (see p. 499), 
 that it is perhaps best to unite them in one group. 
 
 Theory of Isomorphism.^ — The history of the changes of 
 opinion on this point is curious and instructive. Werner 
 first distinguished augite from hornblende ; and his proposal 
 to separate them obtained afterwards the sanction of Ilauy, 
 Mohs, and other celebrated mineralogists. It was agreed 
 that the form of the crystals of the two species was different, 
 and also their structure, as shown by deavaffe—ihut is to 
 say, by breaking or cleaving the mineral with a chisel, or a 
 blow of the hammer, in the direction in which it yields most 
 readily. It was also found by analysis that augite usually 
 contained more lime, less alumina, and no fluoric acid ; which 
 last, though not always found in hornblende, often enters into 
 its composition in minute quantity. In addition to these 
 characters, it was remarked as a geological fact, that augite 
 and hornblende are very rarely associated together in the 
 same rock. It was also remarked that in the crystalline 
 slags of furnaces augitic forms were frequent, the horn- 
 blendic entirely absent ; hence it was conjectured that horn- 
 blende might be the result of slow, and augite of rapid cool- 
 ing. This view was confirmed by the fact that Mitscherlich 
 and Berthier were able to make augite artificially, but could 
 never succeed in forming hornblende. Lastly, Gustavus Rose 
 fused a mass of hornblende in a porcelain furnace, and found 
 that it did not, oh cooling, assume its previous shape, but in- 
 variably took that of augite. The same mineralogist ob- 
 served certain crystals called Uralite (see Table, p. 499) in 
 rocks from Siberia, which possessed the cleavage and chem- 
 ical composition of hornblende, while they had the external 
 form of augite. 
 
 If, from these data, it is inferred that the same substance 
 
THEORY OF ISOMORPHISM. 503 
 
 may assume the crystalline forms of hornblende or augite 
 indifferently, according to the more or less rapid cooling of 
 the melted mass, it is nevertheless certain that the variety 
 commonly called augite, and recognized by a peculiar crys- 
 talline form, has usually more lime in it, and less alumina, 
 than that called hornblende, although the quantities of these 
 elements do not seem to be always the same. Unquestiona- 
 bly the facts and experiments above mentioned show the 
 very near affinity of hornblende and augite ; but even the 
 convertibility of one into the other, by melting and recrys- 
 tallizing, does not perhaps demonstrate their absolute iden- 
 tity. For there is often some portion of the materials in a 
 crystal which are not in perfect chemical combination with 
 the rest. Carbonate of lime, for example, sometimes carries 
 with it a considerable quantity of silex into its own form of 
 crystal, the silex being mechanically mixed as sand, and yet 
 not preventing the carbonate of lime from assuming the form 
 proper to it. This is an extreme case, but in many others 
 some one or more of the ingredients in a crystal may be ex- 
 cluded from perfect chemical union ; and after fusion, when 
 the mass recrystallizes, the same elements may combine per- 
 fectly or in new proportions, and thus a new minei-al may be 
 produced. Or some one of the gaseous elements of the at- 
 mosphere, the oxygen for example, may, when the melted 
 matter reconsolidates, combine with some one of the compo- 
 nent elements. 
 
 The different quantity of the impurities or the refuse above 
 alluded to, which may occur in all but the most transparent 
 and perfect crystals, may partly explain the discordant re- 
 sults at which experienced chemists have arrived in their 
 analysis of the same mineral. For the reader will often find 
 that crystals of a mineral determined to be the same by 
 physical characters, crystalline form, and optical properties, 
 have been declared by skillful analyzers to be composed of 
 distinct elements. This disagreement seemed at first sub- 
 versive of the atomic theory, or the doctrine that there is a 
 fixed and constant relation between the crystalline form and 
 structui-e of a mineral and its chemical composition. The 
 apparent anomaly, however, which threatened to throw the 
 whole science of mineralogy into confusion, was reconciled 
 to fixed principles by the discoveries of Professor Mitscher- 
 lich at Berlin, who ascertained that the composition of the 
 minerals which had appeared so variable was governed by a 
 general law, to which he gave the name of isomorphism (from 
 laoQ, isos, equal, and tiop(pin, morphe, form). According to this 
 law, the ingredients of a given species of mineral are not ab- 
 
504 ELEMENTS OF GEOLOGY. 
 
 solutely fixed as to their kind and quality ; but one ingredi- 
 ent may be replaced by an equivalent portion of some anal- 
 ogous ingredient. Thus, in augite, the lime may be in part 
 replaced by portions of protoxide of iron, or of manganese, 
 while the form of the crystal, and the angle of its cleav- 
 age planes, remain the same. These vicarious substitutions, 
 however, of particular elements can not exceed certain de- 
 fined limits. 
 
 Basaltic Rocks. — The two principal families of trappean or 
 volcanic rocks are the basalts and the trachytes, which differ 
 chiefly from each other in the quantity of silica which they 
 contain. The basaltic rocks are comparatively poor in silica, 
 containing less than 50 per cent, of that mineral, and none 
 in a pure state or as free quartz, apart from the rest of the 
 matrix. They contain a larger proportion of lime and mag- 
 nesia than the trachytes, so that they are heavier, independ- 
 ently of the frequent presence of the oxides of iron which 
 in some cases forms more than a fourth part of the whole 
 mass. Abich has, therefore, proposed that we should weigh 
 these rocks, in order to appreciate their composition in cases 
 where it is impossible to separate their component minerals. 
 Thus, basalt from Stafia, containing 47 "80 per cent, of silica, 
 has a specific gravity of 2'95; whereas trachyte, which has 
 66 per cent, of silica, has a sp. gr. of only 2'68; traehytic 
 porphyry, containing 69 per cent, of silica, a sp. gr. of only 
 2'58. If we then take a rock of intermediate composition, 
 such as that prevailing in the Peak of Teneriffe, which Abich 
 calls Trachyte-dolerite, its proportion of silica being inter- 
 mediate, or 58 per cent., it weighs 2 '78, or more than tra- 
 chyte, and less than basalt.* 
 
 Basalt. — The difierent varieties of this rock are distin- 
 guished by the names of basalts, anamezites, and dolerites, 
 names which, however, only denote diiFerences in texture 
 without implying any difference in mineral or chemical com- 
 position : the term liasalt being used only when the rock is 
 compact, amorphous, and often semi-vitreous in texture, and 
 when it bi-eaks with a perfect conchoidal fracture; when, 
 however, it is uniformly crystalline in appearance, yet very 
 close-grained, the name Anamesite (from avafi^aog, intermedi- 
 ate) is employed, but if the rock be so coarsely crystallized 
 that. its different mineral constituents can be easily recog- 
 nized by the eye, it is called Bolerite (from loXcpog, deceitful), 
 in allusion to the diflficulty of distinguishing it fi'om some of 
 the rocks known as plutonic. 
 
 Mdaphyre is often quite undistinguishable in external ap- 
 * Dr. Daubeny on Volcanoes, 2d ed., pp. 14, 15. 
 
TRACHYTIC ROCKS. 505 
 
 pearance from basalt, for although rarely bo heavy, dark-col- 
 ored, or compact, it may present at times all these varieties 
 of texture. Both these rocks are composed of triclinio feld- 
 spar and augite with more or less olivine, magnetic or titan- 
 iferous oxide of iron, and usually a little nepheline, leucite, 
 and apatite; basalt usually contains considerably more oli- 
 vine than melaphyre, but chemically they are closely allied, 
 although the melaphyres usually contain more silica and. 
 alumina, with less oxides of iron, lime, and magnesia, than 
 the basalts. The Rowley Hills in StaflFordshire, commonly 
 known as Rowley Ragstone, are melaphyre. 
 
 Greenstone. — This name has usually been extended to all 
 granular mixtures, whether of hornblende and feldspar, or of 
 augite and feldspar. The term diorite has been applied ex- 
 clusively to compounds of hornblende and triclinio feldspar. 
 Labrador-rock is a term used for a compound of labradoiite 
 or labrador-feldspar and hypersthene ; when the hypersthene 
 predominates it is sometimes known under the name of Hy- 
 persthene-rock. Gabbro and Diabase are rocks mainly com- 
 posed of tricliuic feldspars and diallage. All these rocks be- 
 come sometimes very crystalline, and help to connect the 
 volcanic with the plutonic formations, which will be treated 
 of in Chapter XXXI. 
 
 Traehytie Rocks. — The name trachyte (from rpa^vQ, rough) 
 was originally given to a coarse granular feldspathic rock 
 which was rough and gritty to the touch. The term was 
 subsequently made to include other rocks, such as clinkstone 
 and obsidian, which have the same mineral composition, but 
 to which, owing to their different texture, the word in its 
 original meaning would not apply. The feldspars which oc- 
 cur in Traehytie rocks are invariably those which contain the 
 largest proportion of silica, or from 60 to 70 per cent, of that 
 mineral. Through the base are usually disseminated crys- 
 tals of glassy feldspar, mica, and sometimes hornblende. Al- 
 though quartz is not a necessary ingredient in the composi- 
 tion of this rock, it is very frequently present, and the quartz 
 trachytes are very largely developed in many volcanic dis- 
 tricts. In this respect the trachytes differ entirely from the 
 members of the Basaltic family, and are more nearly allied to 
 the granites. 
 
 Obsidian. — Obsidian, Pitchstone, and Pearlstone are only 
 different forms of a volcanic glass produced by the fusion of 
 traehytie rocks. The distinction between them is caused by 
 different rates of cooling frohi the melted state, as has been 
 proved by experiment. Obsidian is of a black or ash-gray 
 color and though opaque in mass is transparent in thin edges. 
 
 22 
 
506 ELEMENTS OF GEOLOGY. 
 
 Clinkstone or PhonoUte. — Among the rocks of the tra- 
 chytic family, or those in which the feldspars ar« rich in 
 silica, that termed Clinkstone or Phonolite is conspicuous by 
 its fissile structure, and its tendency to lamination, which is 
 such as sometimes to render it useful as roofing-slate. It 
 rings when struck with the hammer, whence its name ; is 
 compact, and iisually of a grayish blue or brownish color ; is 
 variable in composition, but almost entirely composed of 
 feldspar. When it contains disseminated crystals of feld- 
 spar, it is called Clinkstone .porphyry. 
 
 Volcanic Rocks distinguished by special Forms of Structure. 
 — Many volcanic rocks are commonly spoken of under names 
 denoting structure alone, which must not be taken to imply 
 that they are distinct rocks, i. e., that they differ from one 
 another either in mineral or chemical composition. Thus 
 the terms Trachytic porphyry, Trachytic tuff, etc., merely re- 
 fer to the same rock under different conditions of mechan- 
 ical aggregation or crystalline development which would be 
 more correctly expressed by the use of the adjective, as por- 
 phyritic trachyte, etc., but as these terms are so comnionly 
 employed it is considered advisable to direct the student's 
 attention to them. 
 
 Porphyry is one of this class, and very characteristic of the 
 volcanic formations. When distinct crystals of one or more 
 
 minerals are scattered through an 
 earthy or compact base, the rock 
 is termed a porphyry (see Fig. 
 586). Thus trachyte is usually 
 porphyritic ; for in it, as in many 
 modern lavas, there are crystals 
 of feldspar ; but in some porphyries 
 the crystals are of augite, olivine, 
 or other minerals. If the base be 
 greenstone, basalt, or pitchstone, 
 the rock may be denominated 
 
 _______ greenstone - porphyiy, pitchstone- 
 
 Poiphyry. White crystals of feid- povphyry, and SO forth. The old 
 
 spar in a dark base of hornblende classical type of this form of rOCk 
 
 '''"■ is the red porphyry of Egypt, or 
 
 the well-known "Rosso antico." It consists, according to 
 Delesse, of a red feldspathic base in which are disseminated 
 rose-colored crystals of the feldspar called oligoclase, with 
 some plates of blackish hornblende and grains of oxide of 
 iron (iron-glance). Red quartziferous porphyry is a much 
 more siliceous rock, containing about YO or 80 per cent, of 
 silex, while that of Egypt has only 62 per cent. 
 
SPECIAL FORMS OF STRUCTURE. 50J 
 
 Amygdaloid. — This is also another form of igneous rock, 
 admitting of every variety of composition. It comprehends 
 any rock in which round or almond-shaped nodules of some 
 mineral, such as agate, chalcedony, calcareous spar, or zeolite, 
 are scattered through a base of wacke, basalt, greenstone, or 
 other kind of trap. It derives its name from the Greek word 
 aniygdaloti, an almond. The origin of this structure can not 
 be doubted, for we may trace the process of its formation in 
 modern lavas. Small pores or cells are caused by bubbles 
 of steam and gas confined in the melted matter. After or 
 during consolidation, these empty spaces are gradually filled 
 up by matter separating from the mass, or infiltered by wa- 
 ter permeating the rock. As these bubbles have been some- 
 times lengthened by the flow of the lava before it finally 
 cooled, the contents of such cavities have the form of al- 
 monds. In some of the amygdaloidal traps of Scotland, 
 where the nodules have decomposed, the empty cells are 
 seen to have a glazed or vitreous coating, and in this respect 
 exactly resemble scoriaceous lavas, or the slags of furnaces. 
 
 The annexed figure represents a fragment of stone taken 
 from the upper part of a sheet of basaltic lava in Auvergne. 
 One -half is scoriaceous, the Fig. ser. 
 
 pores being perfectly empty; 
 the other part is amygdaloid- 
 al, the pores or cells being 
 mostly filled up with carbonate 
 of lime, forming white Icernels. 
 
 Laoa. — This term has a 
 somewhat vague signification, 
 having been applied to all 
 melted matter observed to 
 flow in streams from volcanic 
 vents. When this matter con- 
 solidates in the open air, the 
 upper part is usually scoria- 
 ceous, and the mass becomes „ . , . , ^ j ■ . 
 
 ^v,v,.»o, cjv^ ^^^ Scoriaceous lava m part convertecl into 
 
 more and m01"e stony as we an amygdaloid. Montague delaVeille, 
 descend, or in proportion as it Department of Puy de Come, France. 
 
 has consolidated more slowly and under greater pressure. At 
 the bottom, however, of a stream of lava, a small portion of 
 ■ scoriaceous rock very frequently occurs, formed by the first 
 thin sheet of liquid matter, which often precedes the main 
 cun-ent, and solidifies under slight pressure. 
 
 The more compact lavas are often porphyritic, but even 
 the scoriaceous part sometimes contains imperfect crystals, 
 which have been derived from some older rocks, in which 
 
508 ELEMENTS OF GEOLOGY. 
 
 the crystals pre-existed, but were not melted, as being more 
 infusible in their nature. Although melted matter rising in 
 a crater, and even that which enters a rent on the side of a 
 crater, is called lava, yet this term belongs more properly to 
 that which has flowed either in tlie open air or on the bed of 
 a lake or sea. If the same fluid has not reached the surface, 
 but has been merely injected into fissures below_gi'ound,itis 
 called trap. There is every variety of composition in lavas ; 
 some are trachy tic, as in the Peak of Teneriffe ; a great num- 
 ber are basaltic, as in Vesuvius and Auvergne; others are 
 andesitic, as those of Chili ; some of the most modern in Ve- 
 suvius consist of green augite, and many of those of Etna of 
 augite and labrador-feldspar.* 
 
 Scoriae and Pumice may next be mentioned, as porous 
 rocks produced by the action of gases on materials melted 
 by volcanic heat. Sconce are usually of a reddish-brown 
 and black color, and are the cinders and slags of basaltic or 
 augitic lavas. Pumice is a light, spongy, fibrous substance, 
 produced by the action of gases on trachytic and other lavas ; 
 the relation, however, of its origin to the composition of lava 
 is not yet well understood. Von Buch says that it never 
 occurs where only labrador-feldspar is present. 
 
 Volcanic Ash or Tuff, Trap Tuff. — Small angular frag- 
 ments of the scoriae and pumice, above-mentioned, and the 
 dust of the same, produced by volcanic explosions, form the 
 tuifs which abound in all regions of active volcanoes, where 
 showers of these materials, together with small pieces of oth- 
 er rocks ejected from the crater, and more or less burnt, fall 
 down upon the land or into the sea. Here they often be- 
 come mingled with shells, and are stratified. Such tuffs are 
 sometimes bound together by a calcareous cement, and form 
 a stone susceptible of a beautiful polish. But even when lit- 
 tle or no lime is present, there is a great tendency in the 
 materials of ordinary tuffs to cohere together. The term 
 volcanic ash has been much used for rocks of all ages sup- 
 posed to have been derived from matter ejected in a melted 
 state from volcanic orifices. We meet occasionally with ex- 
 tremely compact beds of volcanic materials, interstratified 
 with fossiliferous rocks. These may sometimes be tuffs, al- 
 though their density or compactness is such as to cause them 
 to resemble many of those kinds of trap which are found in 
 ordinary dikes. 
 
 Wacke is a name given to a decomposed state of various 
 trap rocks of the basaltic family, or those which are poor in 
 silica. It resembles clay of a yellowish or brown color, and 
 * G. Hose, Ann. des Mines, torn, viii., p. 33. 
 
SPECIAL FORMS OF STRUCTURE. 509 
 
 passes gradually from the soft state to the hard dolerite, 
 greenstone, or other trap rock from which it has been de- 
 rived. 
 
 Agglomerate. — In the neighborhood of volcanic vents, we 
 frequently observe accumulations of angular fragments of 
 rocks formed during eruptions by the explosive action of 
 steam, which shatters the subjacent stony formations, and 
 hurls them up into the air. They then fall in showers around 
 the cone or crater, or may be spread for some distance over 
 the surrounding country. The fragments consist usually of 
 different varieties of scoriaceous and compact lavas; but 
 other kinds of rock, such as granite or even fossiliferous 
 limestones, may be intermixed ; in short, any substance 
 through which the expansive gases have forced their way. 
 The dispersion of such materials may be aided by the wind, 
 as it varies in direction or intensity, and by the slope of the 
 cone down which they roll, or by floods of rain, which often 
 accompany eruptions. But if the power of running water, 
 or of the waves and currents of the sea, be sufficient to carry 
 the fragments to a distance, it can scarcely fail to wear off 
 their angles, and the formation then becomes a conglomerate. 
 If occasionally globular pieces of scoriae abound in an ag- 
 glomerate, they may not owe their round form to attrition. 
 When all the angular fragments are of volcanic rocks the 
 mass is usually termed a volcanic breccia. 
 
 Laterite is a red or brick-like rock composed of silicate of 
 alumina and oxide of iron. The red layers called " ochre 
 beds," dividing the lavas of the Giant's Causeway, are late- 
 rites. These were found by Delesse to be trap impregnated 
 with the red oxide of iron, and in part reduced to kaolin. 
 When still more decomposed, they were found to be clay col- 
 ored by red ochre. As two of the lavas of the Giant's Cause- 
 way are parted by a bed of lignite, it is not improbable that 
 the layers of laterite seen in the Antrim cliffs resulted from 
 atmospheric decomposition. In Madeira and the Canary Isl- 
 ands streams of lava of subaerial origin are often divided by 
 red bands of laterite, probably ancient soils formed by the 
 decomposition of the surfaces of lava-currents, many of these 
 soils having been colored red in the atmosphere by oxide of 
 iron, others burnt into a red brick by the overflowing of 
 heated lavas. These red bands are sometimes prismatic, the 
 small prisms being at right angles to the sheets of lava. 
 Red clay or red marl, formed as above stated by the disin- 
 tegration of lava, scoriae, or tuff, has often accumulated to a 
 great thickness in the valleys of Madeira, being washed into 
 them by alluvial action; and some of the thick beds of late- 
 
510 ELEMENTS OF GEOLOGY. 
 
 rite in India may have had a similar origin. In India, how- 
 ever, especially in the Deccan, the term " laterite " seems to 
 have been used too vaguely to answer the above definition. 
 The vegetable soil in the gardens of the suburbs of Catania 
 which was overflowed by the lava of 1669 was turned or 
 burnt into a layer of red brick-colored stone, or in other 
 words, into laterite, which may now be seen supporting the 
 old lava-current. 
 
 Columnar and Globular Structure. — One of the characteris- 
 tic forms of volcanic rocks, especially of basalt, is the colum- 
 nar, where large masses are divided into regular prisms, 
 sometimes easily separable, but in other cases adhering firm- 
 ly togethei'. The columns vary, in the number of angles, 
 from three to twelve ; but they have most commonly from 
 five to seven sides. They are often divided transversely, at 
 nearly equal distances, like the joints in a vertebral column, 
 as in the Giant's Causeway, in Ireland. They vary exceed- 
 ingly in respect to length and diameter. Dr. MacCulloch 
 mentions some in Skye which are about 400 feet long ; oth- 
 ers, in Morven, not exceeding an inch. In regard to diame- 
 ter, those of Ailsa measure nine feet, and those of Morven an 
 inch or less.* They are usually straight, but sometimes 
 curved ; and examples of both these occur in the island of 
 Staffa. In a horizontal bed or sheet of trap the columns are 
 vertical ; in a vertical dike they are horizontal. 
 
 It being assumed that columnar trap has consolidated 
 from a fluid state, the prisms are said to be always at right 
 angles to the cooling surfaces. If these surfaces, therefore, 
 instead of being either perpendicular or horizontal, are 
 
 Fig. 5S8. 
 
 Lava of La Cotipe d'Ayzac, near Antraigue, iu the Department of Ardeche. 
 
 curved, the columns ought to be inclined at every angle to 
 
 the horizon ; and there is a beautiful exemplification of this 
 
 phenomenon in one of the valleys of the Vivarais, a mount- 
 
 * MacCul. Syst. of Geol., vol. ii., p. 137. 
 
COLUMNAR AND GLOBULAR STRUCTURE. 
 
 511 
 
 ainous district in the South of France, where, in the midst of 
 a region of gneiss, a geologist encounters unexpectedly sev- 
 eral volcanic cones of loose sand and scoriae. From the crater 
 of one of these cones, called La Coupe d'Ayzac, a stream of 
 lava has descended and occupied the bottom of a narrow val- 
 ley, except at those points where the river Volant, or the tor- 
 rents which join it, have cut away portions of the solid lava. 
 The accompanying sketch (Fig. 588) represents the remnant 
 of the lava at one of these points. It is clear that the lava 
 once filled the whole valley up to the dotted line d a; but 
 the river has gradually swept away all below that line, while 
 the tributary torrent has laid open a transverse section ; by 
 which we perceive, in the first place, that the lava is com- 
 posed, as usual in this country, of three parts : the uppermost, 
 at (7,, being scoriaceous ; the second, 6, presenting irregular 
 prisms ; and the third, c, with regular columns, which are 
 vertical on the banks of the Volant, where they rest on a 
 horizontal base of gneiss, but which are inclined at an angle 
 of 45° at gf, and are nearly horizontal at/, their position hav- 
 ing been everywhere determined, according to the law before 
 mentioned, by the form of the original valley. 
 
 In the annexed figure (589), a view is given of some of the 
 inclined and curved columns which 
 present themselves on the sides of 
 the valleys in the hilly region north 
 of Vicenza, in Italy, and at the foot 
 of the higher Alps.* Unlike those 
 of the Vivarais, last mentibned, the 
 basalt of this country was evident- 
 ly submarine, and the present val- 
 leys have since been hollowed out 
 by denudation. 
 
 The columnar structure is by no 
 means peculiar to the trap rocks in 
 which augite abounds; it is also 
 observed in trachyte, and other 
 feldspathic rocks of the igneous 
 class, although in these it is rarely 
 exhibited in such regular polygo- 
 nal forms. It has been already stated that basaltic columns 
 are often divided by cross-joints. Sometimes each segment, 
 instead of an angular, assumes a spheroidal form, so that a 
 pillar is made up of a pile of balls, usually flattened, as in 
 the Cheese-grotto at Bertrich-Baden, in the Eifel, near the 
 Moselle (Fig. 590). The basalt there is part of a small 
 * Fortis, Mem. sur I'Hist. Nat. de ITtalie, torn, i., p. 233, plate 7. 
 
 Kg. B89. 
 
 Columnar basnlt in the Vicentin. 
 (Forlis.) 
 
512 
 
 ELEMENTS OF GEOLOGY. 
 
 FiL'.590. 
 
 
 Fig. 591. 
 
 stream of lava, 
 from 30 to 40 feet 
 thick, which has 
 proceeded from 
 one of several 
 volcanic craters, 
 still extant, on 
 the neighboring 
 heights. 
 
 In some masses 
 of decomposing 
 greenstone, ba- 
 salt, and other 
 trap rocks, the 
 
 Basaltic pillars of the Kiisegrntte, Bertrich-Baden, half-way giOOlllai StUlOt- 
 betweeu Trijves and Cobleutz. Height of grotto, from T urC IS SO COn- 
 
 '° ^ '^'*'- spicuous that the 
 
 rock has the appearance of a heap of large cannon balls. 
 According to M. Delesse, the centre of each spheroid has 
 been a centre of crystallization, around whicli the diiferent 
 minerals of the rock arranged them- 
 selves symmetrically during the «, 
 process of cooling. But it was 6 
 also, he says, a centre of contrac- | 
 tion, produced by the same cool- 
 ing, the globular form, therefore, 
 of such spheroids being the com- 
 bined result of crystallization and W£'fl!M\\: 
 contraction.* _ Rp 
 
 Mr. Scrope gives as an illustra- rai^ifi 
 tion of this structure a resinous —'■'■■'■■ 
 trachyte or pitchstone-porphyry in 
 one of the Ponza islands, which 
 rise from the Mediterranean, off the 
 coast of Terracina and Gaeta. The 
 globes vary from a few inches to 
 three feet in diameter, and are of an 
 ellipsoidal form (see Fig. 591). The 
 whole rock is in a state of decom- 
 position, "and when the balls," says 
 
 Mr. Scrope, " have been exposed a Giobiform pitchstone. chiaja ai 
 short time to the weather, they Luua, Me of Ponza. (Sorope.) ) 
 scale off at a touch into numerous concentric coats, like those 
 of a bulbous root, inclosing a compact nucleus. The laminis 
 
 * Delesse, sur les Eoches Globuleuses, M^m. de la Soc. Geol. de France, 
 2 ser., torn. iv. 
 
TKAP DIKES AND VEINS. 
 
 513 
 
 Fig. I 
 
 ^^^^■'^ 
 
 of this nucleus have not been so much loosened by decompo- 
 sition ; but the application of a ruder blow will produce a 
 still further exfoliation."* 
 
 Volcanic or Trap Dikes.— The leading varieties of the trap- 
 pean rocks— basalt, greenstone, trachyte, and the rest— are 
 found sometimes in dikes penetrating stratified and unstrat- 
 ified formations, sometimes in shapeless masses protruding 
 through or overlying them, or in horizontal sheets interca- 
 lated between strata. Fissures have already been spoken 
 of as occurring in all kinds of rocks, some a few feet, others 
 many yards in width, and often filled up with earth or an- 
 gular pieces of stone, or with sand and pebbles. Instead of 
 such materials, suppose a quantity of melted .stone to be 
 driven or injected into an open rent, and there consolidated, 
 we have then a tabular mass resembling a wall, and called a 
 trap dike. It is not uncommon to find such dikes passing- 
 through strata of soft materials, such as tuff, scoriie, or shale, 
 which, being more perishable than the trap, are often washed 
 away by the sea, rivers, 
 or rain, in which case the 
 dike stands prominently 
 out in the face of preci- 
 pices, or on the level sur- 
 face of a country (see 
 Fig. 592). 
 
 In the islands of Ar- 
 ran and Skye, and in 
 other parts of Scotland, 
 where sandstone, con- 
 glomerate, and other 
 hard rocks are traversed 
 
 bv dikes of trap, the Bike in valley, near Brazen Head, Maaeirn.lFrom 
 „ , I ' a drawiug of Captain Basil Hall, R.N.I 
 
 converse oi the above 
 
 phenomenon is seen. The dike, Laving decomposed more 
 rapidly than the containing rock, has once more left open 
 the original fissure, often for a distance of many yards 
 inland from the sea-coast. There is yet another case, by 
 no means uncommon in Arran and other parts of Scotland, 
 where the strata in contact with the dike, and for a certain 
 distance from it, have been hardened, so as to resist the ac- 
 tion of the weather more than the dike itself, or the sur- 
 rounding rocks. When this happens, two parallel walls of 
 indurated strata are seen protruding above the general level 
 of the country and following the course of the dike. In Fig. 
 593, a ground plan is given of a ramifying dike of green^ 
 * Scrope, Geol. Trans., 2d series, vol. ii., p. 205. 
 22* 
 
514 
 
 ELEMENTS OF GEOLOGY. 
 
 Stone, which I observed cutting through sandstone on the 
 beach near Kildonan Castle, in Arran. The larger branch 
 varies from five to seven feet in width, which will afford a 
 scale of measurement for the whole. 
 
 Fig. 593, 
 
 Ground-plan of greenstone dikes traversing sandstone. Arran. 
 
 In the Hebrides and other countries, the same masses of 
 trap which occupy the surface of the country far and wide, 
 concealing the subjacent stratified rocks, are seen also in the 
 sea-cliffs, prolonged downward in veins or dikes, which prob- 
 ably unite with other masses of igneous rock at a greater 
 depth. The largest of the dikes represented in the annexed 
 diagram (Fig. 594), and which are seen in part of the coast 
 of Skye, is no less than 100 feet in width. 
 
 Fig. 594. 
 
 Trap dividiug and covering sandstone near Snislinish, in Slcye. (MacCnlloch.) 
 
 Every variety of trap -rock is sometimes found in dikes, 
 as basalt, greenstone, feldspar-porphyry, and trachyte. The 
 amygdaloidal traps also occur, though more rarely, and even 
 tuff and breccia, for the materials of these last may be wash- 
 ed down into open fissures at the bottom of the sea, or dur- 
 ing eruption on the land may be showered into them from 
 the air. Some dikes of trap may be followed for leagues 
 uninterruptedly in nearly a straight direction, as in the 
 north of England, showing that the fissures which they fill 
 must have been of extraordinary length. 
 
 Rocks altered by Volcanic Dikes. — After these remarks on 
 the form and composition of dikes themselves, I shall de- 
 scribe the alterations which they sometimes produce in the 
 rocks in contact with them. The changes are usually such 
 as the heat of melted matter and of the entangled steam 
 and gases might be expected to cause. 
 
 Plas-Newydd: Dike cutting through Shale. — A striking ex- 
 
ROCKS ALTERED BY VOLCANIC DIKES. 515 
 
 ample, near Plas-Newydd, in Anglesea, has been described 
 by Professor Henslow.* The dike is 134 feet wide, and con- 
 sists of a rock which is a compound of feldspar and augite 
 (dolerite of some authors). Strata of shale and argillaceous 
 limestone, through which it cuts perpendicularly, are altered 
 to a distance of 30, or even, in some places, of 35 feet from 
 the edge of the dike. The shale, as it approaches the trap, 
 becomes gradually moi-e compact, and is most indurated 
 where nearest the junction. Here it loses part of its schis- 
 tose structure, but the separation into parallel layers is still 
 discernible. In several places the shale is converted into 
 hard porcelanous jasper. In the most hardened part of the 
 mass the fossil shells, principally Producti, are nearly obliter- 
 ated ; yet even here their impressions may frequently be 
 traced. The argillaceous limestone undergoes analogous 
 mutations, losing its earthy texture as it approaches the 
 dike, and becoming granular and crystalline. But the most 
 extraordinary phenomenon is the appearance in the shale of 
 numerous crystals of analcime and garnet, which are dis- 
 tinctly confined to those portions of the rock affected by the 
 dike.f Some garnets contain as much as 20 per cent, of 
 lime, which they may have derived from the decomposition 
 of the fossil shells or Producti. The same mineral has been 
 observed, under very analogous circumstances, in High Tees- 
 dale, by Professor Sedgwick, where it also occurs in shale 
 and limestone, altered by basalt. J 
 
 Anirim : Dike cutting through Chalk. — In several parts of 
 the county of Antrim, in the north of Ireland, chalk with 
 flints is traversed by basaltic dikes. The chalk is there con- 
 verted into granular marble near the basalt, the change 
 sometimes extending eight or ten feet from the wall of the 
 dike, being greatest near the point of contact, and thence 
 gi-adually decreasing till it becomes evanescent. " The ex- 
 treme effect," says Dr. Berger, " presents a dark brown crys- 
 talline limestone, the crystals running in flakes as large as 
 those of coarse primitive (metamorphic) limestone ; the next 
 state is saccharine, then fine grained and arenaceous ; a com- 
 pact variety, having a porcelanous aspect and a bluish-gray 
 color, succeeds : this, towards the outer edge, becomes yel- 
 lowish-white, and insensibly graduates into the unaltered 
 chalk. The flints in the altered chalk usually assume a gray 
 yellowish color. "§ All traces of organic remains are effaced 
 in that part of the limestone which is most crystalline. 
 
 * Cambridge Transactions, vol. i., p. 402. 
 
 t Ibid., vol. i., p. 410. t Ibid., vol. u., p. 175. 
 
 § Dr. Berger, Geol. Trans., 1st. ser., vol. iii., p. 172. 
 
516 ELEMENTS OF GEOLOGY. 
 
 Pig. 595. 
 
 ■ 
 
 ;-:^S 
 
 
 
 IP^ 
 
 
 \f 
 
 ''^■:'^$, 
 
 Chalk 
 
 m.i 
 
 11 
 
 ^m 
 
 II IP 
 
 Chalk 
 
 
 
 11 
 
 W 
 
 ^mh^ 
 
 
 Basnltic dikes in challt in Island of Eatlilin, Antrim. Gronnd-plan as seen 
 on the beach. (Conybeare and Bucklaud.*) 
 
 The annexed drawing (Fig. 595) represents three basaltic 
 dikes traversing the chalk, all within the distance of 90 feet. 
 The chalk contiguous to the two outer dikes is converted 
 into a finely granular marble, m, m, as are the whole of the 
 masses between the outer dikes and the central one. The 
 entire contrast in the composition and color of the intrusive 
 and invaded rocks, in these cases, renders the phenomena 
 peculiarly clear and interesting. Another of the dikes of the 
 north-east of Ireland has converted a mass of red sandstone 
 into hornstone. By another, the shale of the coal-measures 
 has been indurated, assuming the character of flinty slate ; 
 and in another place the slate-clay of the lias has been 
 changed into flinty slate, which still retains numerous im- 
 pressions of ammonites.f 
 
 It might have been anticipated that beds of coal would, 
 from their combustible nature, be affected in an extraor- 
 dinary degree by the contact of melted rock. Accordingly, 
 one of the greenstone dikes of Antrim, on passing through a 
 bed of coal, reduces it to a cinder for the space of nine feet 
 on each side. At Cockfield Fell, in the north of England, a 
 similar change is observed. Specimens taken at the distance 
 of about thirty yards from the trap are not distinguishable 
 from ordinary pit-coal ; those nearer the dike are like cin- 
 ders, and have all the character of coke ; while those close 
 to it are converted into a substance resembling soot.J 
 
 It is by no means uncommon to meet with the same rocks, 
 even in the same districts, absolutely unchanged in the prox- 
 imity of volcanic dikes. This great inequality in the effects 
 of the igneous rocks may often arise from an original differ- 
 ence in their temperature, and in that of the entangled gases, 
 such as is ascertained to prevail in different lavas, or in the 
 same lava near its source and at a distance from it. The 
 power also of the invaded rocks to conduct heat may vary, 
 
 * Geol. Trans., 1st series, vol. iii., p. 210, and plate 10. 
 
 t Ibid., vol. iii., p. 213; and Playfair, lUust. of Hutt. Theory; s. 253. 
 
 I Sedgwick, Camb. Trans., rol. ii., p. 37. 
 
INTRUSION OP TEAP BETWEEN STRATA. 517 
 
 according to their composition, structure, and the fractures 
 which they may have experienced, and perhaps, also, accord- 
 ing to the quantity of water (bo capable of being heated) 
 which they contain. It must happen in some cases that the 
 component materials are mixed in such proportions as to 
 prepare them readily to enter into chemical union, and form 
 new minerals; while in other cases the mass may be more 
 homogeneous, or the proportions less adapted for such union. 
 
 We must also take into consideration, that one fissure may 
 be simply filled with lava, which may begin to cool from the 
 first; whereas in other cases the fissure may give passage to 
 a current of melted matter, which may ascend for days or 
 months, feeding streams which are overflowing the country 
 above, or being ejected in the shape of scoriae from some 
 crater. If the walls of a rent, moreover, are heated by hot 
 vapor before the lava rises, as we know may happen on the 
 flanks of a volcano, the additional heat supplied by the dike 
 and its gases will act more powerfully. 
 
 Intrusion of Trap between Strata. — Masses of trap are not 
 unfrequently met with intercalated between strata, and 
 maintaining their parallelism to the planes of stratification 
 throughout large areas. They must in some places have 
 forced their way laterally between the divisions of the strata. 
 a direction in which there would he the least resistance to 
 an advancing fluid, if no vertical rents communicated with 
 the surface, and a powerful hydrostatic pressure were caused 
 by gases propelling the lava upward. 
 
 Relation of Trappean Rocks to the Products of active Volca- 
 noes. — When we reflect on the changes above described in 
 the strata near their contact with trap dikes, and consider 
 how complete is the analogy or often identity in composition 
 and structure of the rocks called trappean and the lavas of 
 active volcanoes, it seems difficult at first to understand how 
 80 much doubt could have prevailed for half a century as to 
 whether trap was of igneous or aqueous origin. To a cer- 
 tain extent, however, there was a real distinction between 
 the trappean formations and those to which the term volca- 
 nic was almost exclusively confined. A large portion of 
 the trappean rocks first studied in the north of Germany, and 
 in Norway, France, Scotland, and other countries, were such 
 as had been formed entirely under water, or had been inject- 
 ed into fissures and intruded between strata, and which had 
 never flowed out in the air, or over the bottom of a shallow 
 sea. When these products, therefore, of submarine or sub- 
 terranean igneous action were contrasted with loose cones 
 of scoriee, tufi", and lava, or with narrow streams of lava in 
 
518 ELEMENTS OF GEOLOGY. 
 
 great part scoriaceous and porous, such as were observed to 
 have proceeded from Vesuvius and Etna, the resemblance 
 seemed remote and equivocal. It was, in truth, like com- 
 paring the roots of a tree with its leaves and branches, 
 which, although they belong to the same plant, differ in 
 form, texture, color, mode of growth, and position. The ex- 
 ternal cone, with its loose ashes and porous lava, may be 
 likened to the light foliage and branches, and the rocks con- 
 cealed far below, to the roots. But it is not enough to say 
 of the volcano, 
 
 " Quantum vertice in auras 
 JEtherias, tantum radice in Tartara tendit," 
 
 for its roots do literally reach downward to Tartarus, or to 
 the regions of subterranean fire ; and what is concealed far 
 below "is probably always more important in volume and ex- 
 tent than what is visible above ground. 
 
 We have already stated how frequently dense masses of 
 strata have been removed by denudation from wide areas (see 
 Chap. VI.) ; and this fact prepares us to expect a similar de- 
 struction of whatever may once have formed the uppermost 
 j.j„ 595 part of ancient submarine or sub- 
 
 aerial volc.inoes, more especially 
 as those superficial parts are al- 
 ways of the lightest and most 
 perishable materials. The abrupt 
 manner in which dikes of trap 
 usually terminate at the surface 
 (see Fig. 596), and the water-worn 
 pebbles of trap in the alluvium 
 
 strata intercepted by a trap dike, which COVerS the dike, prOVe in- 
 
 aM covered with alluvium. contestably that whatever was 
 uppermost in these formations has been swept away. It is 
 easy, therefore, to conceive that what is gone in regions of 
 trap may have corresponded to what is now visible in active 
 volcanoes. 
 
 As to the absence of porosity in the trappean formations, 
 the appearances are in a great degree deceptive, for all 
 amygdaloids are, as already explained, porous rooks, into 
 the cells of which mineral matter such as silex, carbonate of 
 lime, and other ingredients, have been subsequently intro- 
 duced (see p. 507) ; sometimes, perhaps, by secretion during 
 the cooling and consolidation of lavas. In the Little Cum- 
 bray, one of the Western Islands, near Arran, the amygda- 
 loid sometimes contains elongated cavities filled with brown 
 spar ; and when the nodules have been washed out, the in- 
 
THE PROBUCTS OF ACTIVE VOLCANOES. 519 
 
 tei-ior of the cavities is glazed with the vitreous varnish so 
 characteristic of the pores of slaggy lavas. Even in some 
 parts of this rock which are excluded from air and water, the 
 cells are empty, and seem to have always remained in this 
 state, and are therefore undistinguishable from some modern 
 lavas.* 
 
 Dr. MacCulloch, after examining with great attention these 
 and the other igneous rocks of Scotland, observes, " that it is 
 a mere dispute about terms, to refuse to the ancient erup- 
 tions of trap the name of submai-ine volcanoes; for they are 
 such in every essential point, although they no longer eject 
 fire and smoke." The same author also considers it not im- 
 probable that some of the volcanic rocks of the same country 
 may have been poured out in the open air.f 
 
 It will be seen in the following chapters that in the earth's 
 crust there are volcanic tuffs of all ages, containing marine 
 shells, which bear witness to eruptions at many successive 
 geological periods. These tuffs, and the associated trappean 
 rocks, must not be compared to lava and scorise which had 
 cooled in the open air. Their counterparts must be sought 
 in the products of modern submarine volcanic eruptions. If 
 it be objected that we have no opportunity of studying these 
 last, it may be answered, that subterranean movements have 
 caused, almost everywhere in regions of active volcanoes, 
 great changes in the relative level of land and sea, in times 
 comparatively modern, so as to expose to view the effects of 
 volcanic operations at the bottom of the sea. 
 
 * MacCulloch, West. Islands, toI. ii., p. 487. 
 t Syst. of Geol., vol. ii., p. 114. 
 
520 ELEMENTS OF GEOLOGY. 
 
 CHAPTER XXIX. 
 
 ON THE AGES OE TOLCANIC ROCKS. 
 
 Tests of relative Age of Volcanic Eocks. — ^Why ancient and modern Rocks 
 can not be Identical. — Tests by Superposition and Intrusion. — Test by Al- 
 teration of Rocks in Contact. — Test by Organic Remains. — Test of Age by 
 Mineral Character. — Test by Included Fragments. — Recent and Post-plio- 
 cene volcanic Rocks. — -Vesuvius, Auvergne, Puy de Come, and Puy de 
 Pariou. — Newer Pliocene volcanic Rocks. — Cyclopean Isles, Etna, Dikes 
 of Palagonia, Madeira. — Older Pliocene volcanic Rocks. — Italy. — Pliocene 
 Volcanoes of the Eifel. — Trass. 
 
 Having in the former part of this work referred the sedi- 
 mentary strata to a long succession of geological periods, we 
 have now to consider how far the volcanic formations can he 
 classed in a similar chronological order. The tests of rela- 
 tive age in this class of rocks are four: 1st, superposition and 
 intrusion, with or without alteration of the rocks in contact; 
 2d, organic remains ; 3d, mineral characters ; 4th, included 
 fragments of older rocks. 
 
 Besides these four tests it may he said, in a general way, 
 that volcanic rocks of Primary or Palasozoic antiquity differ 
 from those of the Secondary or Mesozoic- age, and these 
 again from the Tertiary and Recent. Not, pei'haps, that 
 they differed originally in a greater degree than the modern 
 volcanic rocks of one region, such as that of the Andes, dif- 
 fer from those of another, such as Iceland, but because all 
 rocks permeated by water, especially if its temperature be 
 high, are liable to undergo a slow transmutation, even when 
 they do not assume a new crystalline form like that of the 
 hypogene rocks. 
 
 Although subaerial and submarine denudation, as before 
 stated, remove, in the course of ages, large portions of the 
 upper or more superficial products of volcanoes, yet these 
 are sometimes preserved by subsidence, becoming covered 
 by the sea or by superimposed marine deposits. In this way 
 they may be protected lor ages from the waves of the sea, 
 or the destroying action of rivers, while, at the same thne, 
 they may not sink so deep as to be exposed to that plutonic 
 action (to be spoken of in Chapter XXXI.) which would 
 convert them into crystalline rocks. But even in this case 
 they will not remain unaltered, because they will be perco- 
 lated by water often of high temperature, and charged with 
 
TEST OF AGE OF VOLCANIC EOCKS. 521 
 
 carbonate of lime, silex, iron, and other mineral ingredients, 
 whereby gradual changes in the constitution of the rocks 
 may be superinduced. Every geologist is aware how. often 
 silicified trees occur in volcanic tuffs, the perfect preserva- 
 tion of their intei-nal structure showing that they have not 
 decayed before the petrifying material was supplied. 
 
 The porous and vesicular nature of a large part, both of 
 the basaltic and trachytic lavas, affords cavities in which 
 silex and carbonate of lime are readily deposited. Minerals 
 of the zeolite family, the composition of which has already 
 been alluded to, p. 500, occur in amygdaloids and other trap- 
 rocks in great abundance, and Daubree's observations have 
 proved that they are not always simple deposits of sub- 
 stances held in solution by the percolating waters, being oc- 
 casionally products of the chemical action of that water on 
 the rock through .which they are filtered, and portions of 
 which are decomposed. From these considerations it fol- 
 lows that the perfect identity of very ancient and very mod- 
 ern volcanic formations is scarcely possible. 
 
 Tests by Superposition. — If a volcanic rock rest upon an 
 aqueous deposit, the volcanic must be the newest of the two ; 
 but the like rule does not hold good where the aqueous for- 
 mation rests upon the volcanic, for melted matter, rising 
 from below, may penetrate a sedimentary mass without 
 reaching the surface, or may be forced in conformably be- 
 tween two strata, as b below D in the annexed figure (Fig. 
 597), after which it may cool down and consolidate. Super- 
 Fig. 59T. 
 
 position, therefore, is not of the same value as a test of age 
 in the unstratified volcanic rocks as in fossiliferous forma- 
 tions. We can only rely implicitly on this test where the 
 volcanic rocks are contemporaneous, not where they are in- 
 trusive. Now, they are said to be contemporaneous if pro- 
 duced by volcanic action which was going on simultaneously 
 with the deposition of the strata with which they are asso- 
 ciated. Thus in the section at D (Fig. 597), we may perhaps 
 ascertain that the trap b flowed over the fossiliferous bed c, 
 and that, after its consolidation, a was deposited upon it, a 
 and c both belonging to the same geological period. But, 
 on the other hand, we must conclude the trap to be intru- 
 sive, if the stratum a be altered by b at the point of contact. 
 
522 ELEMENTS OF GEOLOGY. 
 
 or if, in pursuing b for some distance, we find at length that 
 it cuts through the stratum a, and then overlies it as at E. 
 
 We may, however, be easily deceived in supposing the 
 volcanic rock to be intrusive, when in reality it is contempo- 
 raneous ; for a sheet of lava, as it spreads over the bottom 
 of the sea, can not rest everywhere upon the same stratum, 
 either because these have been denuded, or because, if newly 
 thrown down, they thin out in certain ]>laces, thus allowing 
 
 the lava to cross their edges. Be- 
 '^' ° ■ sides, the heavy igneous fluid will 
 
 often, as it moves along, cut a 
 channel into beds of soft mud and 
 sand. Suppose the submarine lava 
 F (Fig. 598) to have come in con- 
 tact in this manner with the strata 
 a, i, c, and that. after its consolida- 
 tion the strata d, e are thrown down in a nearly horizontal 
 position, yet so as to lie uncouformably to F, the appearance 
 of subsequent intrusion will here be complete, although the 
 trap is in fact contemporaneous. We must not, therefore, 
 hastily infer that the rock F is intrusive, unless we find the 
 overlying strata, d, e, to have been altered at their junction, 
 as if by heat. 
 
 The test of age by superposition is strictly applicable to 
 all stratified volcanic tuifs, according to the rules already 
 explained in the case of sedimentary deposits (see p. 124). 
 
 Test of Age by Organic Remains. — We have seen how, in 
 the vicinity of active volcanoes, scoriae, pumice, fine sand, 
 and fragments of rock are thrown up into the air, and then 
 showered down upon the land, or into neighboring lakes or 
 seas. In the tuflfs so formed shells, corals, or any. other dura- 
 ble organic bodies which may happen to be strewed over the 
 bottom of a lake or sea will be imbedded, and thus continue 
 as permanent memorials of the geological period when the 
 volcanic eruption occurred. Tufaceous strata thus formed 
 in the neighborhood of Vesuvius, Etna, Stromboli, and other 
 volcanoes now in islands or near the sea, may give informa- 
 tion of the relative age of these tufis at some remote future 
 period when the fires of these mountains are extinguished. 
 By evidence of this kind we can establish a coincidence in 
 age between volcanic rocks and the diflTerent primary, sec- 
 ondary, and tertiary fossiliferous strata. 
 
 The tuffs alluded to may not always be marine, but may 
 include, in some places, fresh - water shells ; in others, the 
 bones of terrestrial quadrupeds. The diversity of organic 
 remains in formations of this nature is perfectly intelligible. 
 
TEST OF AGE OE VOLCANIC ROCKS. 523 
 
 if we reflect on the wide dispersion of ejected matter during 
 late eruptions, such as that of the volcano of Cosegnina, in 
 the province of Nicaragua, January 19, 1835. Hot cinders 
 and fine scorisB were then cast up to a vast height, and cov- 
 ered the ground as they fell to the depth of more than ten 
 feet, for a distance of eight leagues from the crater, in a south- 
 erly direction. Birds, cattle, and wild animals were scorched 
 to death in great numbers, and buried in ashes. Some vol- 
 canic dust fell at Chiapa, upward of 1200 miles, not to lee- 
 ward of the volcano, as might have been anticipated, but to 
 windward, a striking proof of a counter-current in the upper 
 region of the atmosphere ; and some on Jamaica, about 700 
 miles distant to the north-east. In the sea, also, at the dis- 
 tance of 1100 miles from the point of eruption. Captain Eden 
 of the " Conway " sailed 40 miles through floating pumice, 
 among which were some pieces of considerable size.* 
 
 Test of Age by Mineral Composition. — As sediment of ho- 
 mogeneous composition, when discharged from the mouth of 
 a large river, is often deposited simultaneously over a wide 
 space, so a particular kind of lava flowing from a crater 
 during one eruption may spread over an extensive area; 
 thus in Iceland, in 1783, the melted matter, pouring from 
 Skaptar Jokul, flowed in streams in opposite directions, and 
 caused a continuous mass the extreme points of which were 
 90 miles distant from each other. This enormous current of 
 lava varied in thickness from 100 feet to 600 feet, and in 
 breadth from that of a narrow river gorge to 15 miles.f 
 Now, if such a mass should afterwards be divided into sepa- 
 rate fragments by denudation, we might still, perhaps, iden- 
 tify the detached portions by their similarity in mineral 
 composition. Nevertheless, this test will not always avail 
 the geologist ; for, although there is usually a prevailing 
 character in lava emitted during the same eruption, and 
 even in the successive currents flowing from the same vol- 
 cano, still, in many cases, the difierent parts even of one lava- 
 stream, or, as before stated, of one continuous mass of trap, 
 vary much in mineral composition and texture. 
 
 In Auvergne, the Eifel, and other countries where trachyte 
 and basalt are both present, the trachytic rocks are for the 
 most part older than the basaltic. These rocks do, indeed, 
 sometimes alternate partially, as in the volcano of Mont Dor, 
 in Auvergne ; and in Madeira trachytic rocks overlie an old- 
 er basaltic series ; but the trachyte occupies more generally 
 an inferior position, and is cut through and overflowed by 
 
 * Caldcleugh, Phil. Trans., 1836, p. 27. 
 + S&i Principles, Index, "Skaptar Jokul." 
 
624 ELEMENTS OF GEOLOGY. 
 
 basalt. It can by no means be inferred that trachyte pre- 
 dominated at one period of the earth's history and basalt at 
 another, for Ave know that trachytic lavas have been formed 
 at many successive periods, and are still emitted from many 
 active craters; but it seems that in each region, where a 
 long series of eruptions have occurred, the lavas containing 
 feldspar more rich in silica have been inrst emitted, and the 
 escape of the more augitic kinds has followed. The hypoth- 
 esis suggested by Mr.'Scrope may, perhaps, aiford a solution 
 of this problem. The minerals, he observes, which abound 
 in basalt are of greater specific gravity than those composing 
 the feldspathic lavas ; thus, for example, hornblende, augite, 
 and olivine are each more than three times the weight of 
 water ; whereas common feldspar and albite have each scarce- 
 ly more than 2 J times the specific gravity of water ; and the 
 diiference is increased in consequence of there being much 
 more iron in a metallic state in basalt and greenstone than 
 in trachyte and other allied feldspathic lavas. If, therefore, 
 a large quantity of rock be melted up in the bowels of the 
 earth by volcanic heat, the denser ingredients of the boiling 
 fluid may sink to the bottom, and the lighter remaining 
 above would in that case be first propelled upward to the 
 surface by the expansive power of gases. Those materials, 
 therefore, which occupy the lowest place in the subterranean 
 reservoir will always be emitted last, and take the uppermost 
 place on the exterior of the earth's crust. 
 
 Test by Included Fragments. — We may sometimes discov- 
 er the relative age of two trap-rocks, or of an aqueous de- 
 posit and the trap on which it rests, by finding fragments of 
 one included in the other in cases such as those before alluded 
 to, where the evidence of superposition alone would be insuf- 
 ficient. It is also not uncommon to find a conglomerate al- 
 most exclusively composed of rolled pebbles of trap, asso- 
 ciated with some fossiliferous stratified formation in the 
 neighborhood of massive trap. If the pebbles agree gener- 
 ally in mineral character with the latter, we are then ena- 
 bled to determine its relative age by knowing that of the 
 fossiliferous strata associated with the conglomerate. The 
 origin of such conglomerates is explained by observing the 
 shingle beaches composed of trap-pebbles in modern volca- 
 noes, as at the base of Etna. 
 
 Recent and Post-pliocene Volcanic Eocks. — I shall now se- 
 lect examples of contemporaneous volcanic rocks of succes- 
 sive geological periods, to show that igneous causes have been 
 in activity in all past ages of the world. They have been 
 perpetually shifting the places where they liave broken out 
 
KECENT AND POST-PLIOCENE VOLCANIC ROCKS. 625 
 
 at the earth's surface, and we can sometimes prove that those 
 areas which are now the great theatres of volcanic action 
 were in a state of perfect tranquillity at remote geological 
 epochs, and that, on the other hand, in places where at for- 
 mer periods the most violent eruptions took place at the sur- 
 face and continued for a great length of time, there has been 
 an entire suspension of igneous action in historical times, and 
 even, as in the British Isles, throughout a large part of the 
 antecedent Tertiary Period. 
 
 In the absence of British examples of volcanic rocks new- 
 er than the Upper Miocene, I may state that in other parts 
 of the world, especially in those where volcanic eruptions are 
 now taking place from time to time, there are tuffs and lavas 
 belonging to that part of the Tertiary era the antiquity of 
 which is proved by the presence of the bones of extinct 
 quadrupeds which co-existed with terrestrial, fresh-water, 
 and marine moUusca of species still living. One portion of 
 the lavas, tuffs, and ti-ap-dikes of Etna, Vesuvius, and the 
 island of tschia has been produced within the historical era ; 
 another and a far more considerable part originated at times 
 immediately antecedent, when the waters of the Mediterra- 
 nean were already inhabited by the existing testacea, but 
 when certain species of elephant, rhinoceros, and other quad- 
 rupeds now extinct, inhabited Europe. 
 
 Vesuvius. — I have traced in the "Principles of Geology" 
 the history of the changes which the volcanic region of Cam- 
 pania is known to have undergone during the last 2000 years. 
 The aggregate effect of igneous operations during that pe- 
 riod is far from insignificant, comprising as it does the forma- 
 tion of the modern cone of Vesuvius since the year,V9, and 
 the production of several minor cones in Ischia, together with 
 that of Monte Nuovo in the year 1538. Lava-currents have 
 also flowed upon the land and along the bottom of the sea — 
 volcanic sand, pumice, and scoriae have been showered down 
 so abundantly that whole cities were buried — tracts of the 
 sea have been filled up or converted into shoals — and tufa- 
 ceous sediment has been transported by rivers and land- 
 floods to the sea. There are also proofs, during the same re- 
 cent period, of a permanent alteration of the relative levels 
 of the land and sea in several places, and of the same tract 
 having, near Puzzuoli, been alternately upheaved and de- 
 pressed to the amount of more than twenty feet. In con- 
 nection with these convulsions, there are found, on the shores 
 of the Bay of Baise, recent tufaceous strata, filled with ar- 
 ticles fabricated by the hands of man, and mingled with ma- 
 rine shells. 
 
526 ELEMENTS OE GEOLOGY. 
 
 It has also been stated above (p. 206), that when we ex 
 amine this same region, it is found to consist largely of tufa 
 ceous strata, of a date anterior to human history or tradi- 
 tion, which are of such thickness as to constitute hills from 
 500 to more than 2000 feet in height. Some of these strata 
 contain marine shells which are exclusively of living species, 
 others contain a slight mixture, one or two per cent., of species 
 not known as living. 
 
 The ancient part" of Vesuvius is called Somma, and consists 
 of the remains of an older cone which appears to have been 
 partly destroyed by explosion. In the great escarpment 
 which this remnant of the ancient mountain presents towards 
 the modern cone of Vesuvius, there are many dikes which 
 are for the most part vertical, and traverse the inclined beds 
 of lava and scoriae which were successively superimposed 
 during those eruptions by which the old cone was formed. 
 They project in relief several inches, or sometimes feet, from 
 the face of the cliff, being extremely compact, and less de- 
 structible than the intersected tuffs and porous lavas. In 
 vertical extent they vary from a few yards to 500 feet, and 
 in breadth from one to twelve feet. Many of them cut all 
 the inclined beds in the escarpment of Somma from top to 
 bottom, others stop short before they ascend above half-way 
 In mineral composition they scarcely differ from the lavas of 
 Somma, the rock consisting of a base of leucite and augite, 
 through which large crystals of augite and some of leucite 
 ai'e scattered. 
 
 Nothing is more remarkable than the usual parallelism of 
 the opposite sides of the dikes, which correspond almost as 
 regularly as the two opposite faces of a wall of masonry. 
 This character appears at first the more inexplicable, when 
 we consider how jagged and uneven are the rents caused by 
 earthquakes in masses of heterogeneous composition, like those 
 composing the cone of Somma. In explanation of this phe- 
 nomenon, M. ISTecker refers us to Sir W. Hamilton's account 
 of an eruption of Vesuvius in the year 1779, who records the 
 following fact : " The lavas, when they either boiled over 
 the crater, or broke out from the conical parts of the vol- 
 cano, constantly formed channels as regular as if they had 
 been cut by art down the steep part of the mountain ; and 
 whilst in a state of perfect fusion, continued their course in 
 those channels, which were sometimes full to the brim, and 
 at other times more or less so, according to the quantity of 
 matter in motion. 
 
 "These channels (says the same observer), I have found, 
 upon examination after an eruption, to be in general from 
 
EECENT .AND' POST-PLIOCENE VOLCANIC ROCKS. 527 
 
 two to five or six feet wide, and seven or ei^t feet deep. 
 They were often hid from the sight by a quantity of scoriae 
 that had formed a crust over them ; and the lava, having 
 been conveyed in a covered way for some yards, came out 
 fresh again into an open channel. After an eruption, I have 
 walked in some of those subterraneous or covered galleries, 
 which were exceedingly curious, the sides, top, and bottom 
 being worn perfectly smootK and even in most parts by the 
 violence of the currents of the red-hot lavas whicli'they 
 had_ conveyed for many weeks successively." I was able to 
 verify this phenomenon in 1858, when a stream of lava issued 
 from a lateral cone.* Now, the walls of a vertical fissure, 
 through which lava has ascended in its way to a volcanic 
 vent, must have been exposed to the same erosion as the sides 
 of the channels before adverted to. The prolonged and uni- 
 form friction of the heavy fiuid,as it is forced and made to 
 flow upward, can not fail to wear and smooth down the sur- 
 faces on which it rubs, and the intense heat must melt all 
 such masses as project and obstruct the passage of the in- 
 candescent fluid. 
 
 The rock composing the dikes both in the modern and an- 
 cient part of Vesuvius is far more compact than that of ordi- 
 nary lava, for the pressure of a column of melted matter in 
 a fissure greatly exceeds that in an ordinary stream of lava ; 
 and pressure checks the expansion of those gases which give 
 rise to vesicles in lava. There is a tendency in almost all 
 the Vesuvian dikes to divide into horizontal prisms, a phe- 
 nomenon in accordance with the formation of vertical col- 
 umns in horizontal beds of lava ; for in both cases the divis- 
 ions which give rise to the prismatic structure are at right 
 angles to the cooling surfaces. (See above, p. 510.) 
 
 Auvergne. — Although the latest eruptions in central 
 France seem to have long preceded the historical era, they 
 are so modern as to have a very intimate connection with 
 the present superficial outline of the country and with the 
 existing valleys and river-courses. Among a great number 
 of cones with perfect craters, one called the Puy de Tartaret 
 sent forth a lava-current which can be traced up to its crater, 
 and which flowed for a distance of thirteen miles along the 
 bottom of the present valley to the village of ISTechers, cov- 
 ering the alluvium of the old valley in which were preserved 
 the bones of an extinct species of horse, and of a lagomys 
 and other quadrupeds all closely allied to recent animals, 
 while the associated land-shells were of species now liyinfrj 
 such as Cyclostoma ekgans. Helix hortensis, S. nemoralis. il 
 " Privcifles ff GeiltNTs', ^ol. ■., j). C.?f>. 
 
528 ELEMENTS OF 'GEOLOGY. 
 
 lapicida, an(f Clausilia rugosa. That the current which has 
 issued from the Puy de Tartaret may, nevertheless, be very 
 ancient in reference to the events of human history, we may 
 conclude, not only from the divergence of the mamraiferous 
 fauna from that of our day, but from the fact that a Roman 
 bridge of such form and construction as continued in use 
 only down to the fifth century, but which may be older, is 
 now seen at a place about a mile and a half from St. Nee- 
 taire. This ancient bridge spans the river Couze with two 
 arches, each about fourteen feet wide. These arches spring 
 from the lava of Tartaret, on both banks, showing that a 
 ravine precisely like that now existing had already been ex- 
 cavated by the river through that lava thirteen or fourteen 
 centuries ago. 
 
 While the river Couze has in most cases, as at the site of 
 this ancient bridge, been simply able to cut a deep channel 
 through the lava, the lower portion of which is shown to be 
 columnar, the same torrent has in other places, where the 
 valley was contracted to a narrow gorge, had power to re- 
 move the entire mass of basaltic rock, causing for a short 
 space a complete breach of continuity in the volcanic cur- 
 rent. The work of erosion has been very slow, as the basalt 
 is tough and hard, and one column after another must have 
 been undermined and reduced to pebbles, and then to sand. 
 During the time i-equired for this operation, the perishable 
 cone of Tartaret, occupying the lowest part of the great val- 
 ley descending from Mont Dor (see p. 542), and damming up 
 the river so as to cause the Lake of Chambon, has stood unin- 
 jured, proving that no great flood or deluge can have passed 
 over this region in the interval between the eruption of Tar- 
 taret and our own times. 
 
 ^ Puyde Come.— The Puy de C6me and its lava-current, near 
 Clermont, may be mentioned as another minor volcano of 
 about the same age. This conical hill rises from the gran- 
 itic platform, at an angle of between 30° and 40°, to the 
 height of more than 900" feet. Its summit presents two dis- 
 tinct craters, one of them with a vertical depth of 250 feet. 
 A stream of lava takes its rise at the western base of the hill 
 instead of issuing from either crater, and descends the granit- 
 ic slope towards the present site of the town of Pont Gibaud. 
 Thence it pours in a broad sheet down a steep declivity into 
 the valley of the Sioule, filling the ancient river-channel for 
 the distance of more than a mile. The Sioule, thus dispos- 
 sessed of its bed, has worked out a fresh one between the 
 lava and the granite of its western bank; and the excava- 
 
NEWER PLIOCENE VOLCANIC ROCKS. 529 
 
 tion has disclosed, in one spot, a wall of columnar basalt 
 about fifty feet high.* 
 
 The excavation of the ravine is still in progress, every 
 winter some columns of basalt being undermined and car- 
 ried down the channel of the river, and in the course of a 
 few miles rolled to sand and pebbles. Meanwhile the cone 
 of C&me remains unimpaired, its loose materials being pro- 
 tected by a dense vegetation, and the hill standing on a 
 ridge not commanded by any higher ground, so that no 
 floods of rain-water can descend «j)on it. There is no end 
 to the waste which the hard basalt may undergo in future, if 
 the physical geography of the country continue unchanged — 
 no limit to the number of years during which the heap of in- 
 coherent and transportable materials called the Puy de Come 
 may remain in an almost stationary condition. 
 
 f^uy de Pariou. — The brim of the crater of the Puy de 
 Pariou, near Clermont, is so sharp, and has been so little 
 blunted by time, that it scarcely afibrds room to stand upon. 
 This and other cones in an equally remarkable state of in- 
 tegrity have stood, I conceive, uninjured, not in spite of their 
 loose porous nature, as might at first be natui-ally supposed, 
 but in consequence of it. No rills can collect where all the 
 rain is instantly absorbed by the sand and scoriae, as is re- 
 markably the case on Etna ; and nothing but a water-spout 
 breaking directly upon the Puy de Pariou could carry away 
 a portion of the hill, so long as it is not rent or ingulfed by 
 earthquakes. 
 
 Newer Pliocene Volcanic Rocks. — The more ancient por- 
 tion of Vesuvius and Etna originated at the close of the 
 Newer Pliocene period, when less than ten, sometimes only 
 one, in a hundred of thei shells difiei-ed from those now liv- 
 ing. In the case of Etna, it was before stated (p. 204) that 
 Post-pliocene formations occur in the neighborhood of Cata- 
 nia, while the oldest lavas of the great volcano are Pliocene. 
 These last are seen associated with sedimentary deposits at 
 Trezza and other places on the southern and eastern flanks 
 of the great cone (see above, p. 205). 
 
 Cyclopean Islands. — The Cyclopean Islands, called by the 
 Sicilians Dei Faraglioni, in the sea-clifis of which these beds 
 of clay, tufi", and associated lava are laid open to view, are 
 situated in the Bay of Trezza, and may be regarded as 
 the extremity of a promontory severed from the main land. 
 Here numerous proofs are seen of submarine eruptions, by 
 which the argillaceous and sandy strata were invaded and 
 cut through, and tufaceous breccias formed. Inclosed in 
 * Scrape's Central Fiance, p. 60, and plate. 
 23 
 
530 
 
 ELEMENTS OF GEOLOGY. 
 
 these breccias are many angular and hardened fragments of 
 laminated clay in different states of alteration by heat, and 
 intermixed with volcanic sands. 
 
 The loftiest of the Cyclopean islets, or rather rocks, is 
 about 200 feet in height, the summit being formed of a mass 
 
 Fig. 600. 
 
 View of tlie Isle of Cyclops, iu the Bay of Trezza. (Drawn by 
 Captain Basil Hall, E.N.) 
 
 of Stratified clay, the laminae of which are occasionally sub- 
 divided by thin arenaceous layers. These strata dip to the 
 N.W., and rest on a mass of columnar lava (see Fig. 599) in 
 which the tops of the pillars are weathered, and so rounded 
 as to be often hemispherical. In 
 some places in the adjoining and 
 largest islet of the group, which 
 lies to the north-eastward of that 
 represented in the drawing (Fig. 
 599), the overlying clay has been 
 greatly altered and hardened by 
 the igneous rock, and occasionally 
 contorted in the most extraordinary 
 manner; yet the lamination has not 
 been obliterated, but, on the con- 
 trary, rendered much more conspic- 
 uous, by the indurating process. 
 
 In the wood-cut (Fig. 600), I have 
 represented a portion of the altered 
 rock, a few feet square, where the 
 alternating thin laminse of sand and 
 clay are contorted in a manner often 
 Contortions of strata in the largest o^,^erved in ancient metamorphic 
 ofthe Cyclopean Islands.. • schists. A gi'cat ■ fissure, running 
 
DIKES OF PALAGONIA. 
 
 531 
 
 Fig. 601. 
 
 from east to west, nearly divides this larger island into 
 two parts, and lays open its internal structure. In the 
 section thus exhibited, a dike of lava is seen, first cutting 
 through an older mass of lava, and then penetrating the su- 
 perincumbent tertiary strata. 
 In one place the lava ramifies 
 and terminates in thin veins, 
 from a few feet to a few inches 
 in thickness (see Fig. 601). 
 The arenaceous laminse are 
 much hardened at the point of 
 contact, and the clays are con- 
 verted into siliceous schist. In 
 this island the altered rocks as- 
 sume a honey-comb structure on 
 their weathered surface, singu- 
 larly contrasted with the smooth 
 and even outline which the same ''17^-^%'^i^lf^'^^Zt'i'^e^i^l'' 
 
 beds present in their usual soft «• Lava. 6. Laminated clay and sand. 
 
 and yielding state. The pores ". The same altered. 
 
 of the lava are sometimes coated, or entirely filled with 
 carbonate of lime, and with a zeolite resembling analcime, 
 which has been called cyclopite. The latter mineral has 
 also been found in small fissures traversing the altered 
 marl, showing that the same cause which introduced the 
 minerals into the cavities of the lava, whether we suppose 
 sublimation or aqueous infiltration, conveyed it also into the 
 open rents of the contiguous sedimentary strata. 
 
 Dikes of Palagonia. — Dikes of vesicular and amygdaloid- 
 al lava are also seen traversing marine tuff or peperino, west 
 of Palagonia, some of the pores of the lava being empty, 
 while others are filled with carbonate of lime. In such cases 
 we may suppose the tufi" to have resulted from showers of 
 volcanic sand and scoriae, together with fragments ot lime- 
 stone, thrown out by a submarine explosion, similar to that 
 which gave rise to Graham Island in 1831. When the mass 
 was, to a certain degi-ee, consolidated, it may have been rent 
 open, so that the lava ascended through fissures, the walls 
 of which were perfectly even and parallel. In one case, af- 
 ter the melted matter that filled the rent (Fig._602) had 
 cooled down, it must have been fractured and shifted hori- 
 zontally by a lateral movement. 
 
 In the second figure (Fig. 603), the lava has more the ap- 
 pearance of a vein, which forced its way through the pepe- 
 rino. It is highly probable that similar appearances would 
 be Been if we could examine the floor of the sea in that part 
 
532 
 
 ELEMENTS OF GEOLOGY. 
 
 Fig. 602. 
 
 « 
 
 ,1 
 
 
 
 ■ t 
 
 
 « 
 
 *"'0* 
 
 a 
 
 • <? 
 
 'l^? 
 
 
 ','0 
 ■ III 
 
 n'* 
 
 
 ' c' 
 
 •^•6 
 
 
 "''■ ■ *. c 
 
 : o:. 
 
 
 o;<?.. 
 
 * ' » 
 
 a 
 
 r • 
 
 «,^ 
 
 
 -:.'>.•.' 
 
 > 6 
 
 
 
 i. 1 
 
 Fig. 603. of the Mediterranean 
 
 where the waves have 
 recently washed away 
 the new volcanic isl- 
 and ; for when a super- 
 incumbent mass of 
 ejected fragments has 
 been removed by de- 
 nudation, we may ex- 
 pect to see sections of 
 
 Grannfl-pian of dikes near Palagonia. dikes traversing tuff, 
 
 It. Lava. !). Peperino, consistiiig of volcanic sand, Or, in Other WOrds, SeC- 
 mixed with fragments of lava and limestone. ^j^j^g ^f ^j^g channels of 
 
 communication by which the subterranean lavas reached the 
 surface. 
 
 Madeira. — Although the more ancient portion of the vol- 
 canic eruptions by which the 'island of Madeira and the 
 neighboring one of Porto Santo were built up occurred, as 
 we shall presently see, in the Upper Miocene Period, a still 
 larger part of the island is of Pliocene date. That the latest 
 outbreaks belonged to the Newer Pliocene Period, I infer 
 from the close affinity to the present flora of Madeira of the 
 fossil plants preserved in a leaf-bed in the north-eastern part 
 of the island. These fossils, associated with some lignite in 
 the ravine of the river San Jorge, can none of them be proved 
 to be of extinct species, but their antiquity may be inferred 
 from the following considerations: Firstly — The leaf-bed, 
 discovered by Mr. Hartung and myself in 1-853, at the height 
 of 1000 feet above the level of the sea, crops out at the base 
 of a cliff formed by the erosion of a gorge cut through alter- 
 nating layers of basalt and scorisB, the pi'oduct of a vast suc- 
 cession of eruptions of unknown date, piled up to a thickness 
 of 1000 feet, and which were all poured out after the plants, 
 of which about twenty species have been recognized, flour- 
 ished in Madeira. These lavas are inclined at an angle of 
 about 15° to. the north, and came down from the great cen- 
 tral region of eruption. Their accumulation implies a long 
 period of intermittent volcanic action, subsequently to which 
 the ravine of San Jorge was hollowed out. Secondly — Some 
 few of the plants, though perhaps all of living species, are 
 supposed to be of genera not now existing in the island. 
 They have been described by Sir Charles Bunbury and Pro- 
 fessor Heer, and the former first pointed out that many of 
 the leaves are of the laurel type, and analogous to those now 
 flourishing in the modern forests of Madeira. He also rec- 
 ognized among them the leaves of Woodwardia radicans, 
 
OLDER PLIOCENE PERIOD. 533 
 
 and DavaUia Canariensis, ferns now abundant in Madeira. 
 Thirdly — The great age of this leaf-bed of San Jorge, which 
 was perhaps originally formed in the crater of some ancient 
 volcanic cone afterwards buried under lava, is proved by its 
 belonging to a part of the eastern extremity of Madeira, 
 which, after the close of the igneous eruptions, became cov- 
 ered in the adjoining district of Oani9al with blown sand in 
 which a vast number of land-shells were buried. These fos- 
 sil shells belonged to no less than 86 species, among which 
 are many now exti'emely rare in the island, and others, about 
 five per cent., extinct or unknown in any part of the world. 
 Several of these of the genus Helix are conspicuous from the 
 peculiarity of their forms, others from their large dimensions. 
 The geographical configuration of the country shows that 
 this shell-bed is considerably more modern than the leaf bed ; 
 it must therefore be referred to the Newer Pliocene, accord- 
 ing to the definition of this period given in a former chap- 
 ter (p. 143). 
 
 Older Pliocene Period. — Italy.— In Tuscany, as at Radico- 
 fani, Viterbo, and Aquapendente, and in the Campagna di 
 Roma, submarine volcanic tufis are interstratified with the 
 Older Pliocene strata of the Sub-apennine hills in such a man- 
 ner as to leave no doubt that they were the products of erup- 
 tions which occurred when the shelly marls and sands of the 
 Sub-apennine hills were in the course of deposition. This opin- 
 ion I expressed* after my visit to Italy in 1828, and it has 
 recently (1850) been confirmed by the argument adduced 
 by Sir R. Murchison in favor of the submarine origin of the 
 Tertiary volcanic rocks of Italy.f These rocks are well 
 known to rest conformably on the Sub-apennine marls, even 
 as far south as Monte Mario, in the suburbs of Rome. On 
 the exact age of the deposits of Monte Mario new light has 
 recently been thrown by a careful study of their marme fos- 
 sil shells, undertaken by MM. Rayneval, Vanden Hecke, and 
 Ponzi. They have compared no less than 160 species with 
 the shells of the Coralline Crag of Suffolk, so well described 
 by Mr. Searies Wood ; and the specific agreement between 
 the British and Italian fossils is so great, if we make due al- 
 lowance for geographical distance and the difierence ot lati- 
 tude, that we can have little hesitation in referring both to 
 the same period, or to the Older Pliocene of this work. It is 
 highly probable that, between the oldest trachytes of Tus- 
 cany and the newest rocks in the neighborhood of Naples, a 
 * See 1st edit, of Principles of Geology, vol. iii., chaps, xiii. and xiv., 1833 ; 
 and former editions of this work, chap. xxxi. 
 t Quart. Geol. Jonr., vol. vi., p. 281. 
 
534 ELKMENTS OF GEOLOGY. 
 
 series of volcanic products might be detected of every age 
 from the Older Pliocene to the historical epoch. 
 
 Pliocejie Volcanoes of the ^»/e?.— Some of the most perfect 
 cones and craters in Europe, not even excepting those of the 
 district round Vesuvius, may be seen on the left or west 
 bank of the Rhine, near Bonn and Andernach. They exhibit 
 characters distinct from any which I have observed else- 
 where, owing to the large part which the escape of aqueous 
 vapor has played in the eruptions and the small quantities 
 of lava emitted. The fundamental rocks of the district are 
 gray and red sandstones and shales, with some associated 
 limestones, replete with fossils of the Devonian or Old Red 
 Sandstone group. The volcanoes broke out in the midst of 
 these inclined strata, and when the present systems of hills 
 and valleys had already been formed. The eruptions occur- 
 red sometimes at the bottom of deep valleys, sometimes on 
 the summit of hills, and frequently on intervening platforms. 
 In travelling through this district we often come upon them 
 most unexpectedly, and may find ourselves on the very edge 
 of a crater before we had been led to suspect that we were 
 approaching the site of any igneous outburst. Thus, for ex- 
 ample, on arriving at the village of Gemund, immediately 
 south of Daun, we leave the stream, which flows at the bot- 
 tom of a deep valley in which strata of sandstone and shale 
 crop out. We then climb a steep hill, on the surface of 
 which we see the edges of the same strata dipping inward 
 towards the mountain. When we have ascended to a con- 
 siderable height, we see fragments of scoriae sparingly scat- 
 tered over the surface ; until at length, on reaching the sum- 
 mit, we find ourselves suddenly on the edge of a tarn, or deep 
 circular lake-basin called the Gemunder Maar. In it we rec- 
 ognize the ordinary form of a crater, for which we have 
 been prepared by the occurrence of scorise scattered over the 
 surface of the soil. But on examining the walls of the crater 
 we find precipices of sandstone and shale which exhibit no 
 signs of the action of heat ; and we look in vain for those 
 beds of lava and scoriae, dipping outward on every side, 
 which we have been accustomed to consider as characteris- 
 tic of volcanic vents. As we proceed, however, to the oppo- 
 site side of the lake, we find a considerable quantity of scoriae 
 and some lava, and see the whole surface of the soil spark- 
 ling with volcanic sand, and strewed with ejected fragments 
 of half-fused shale, which preserves its laminated texture in 
 the interior, while it has a vitrified or scoriform coating. 
 
 Other crater lakes of circular or oval form, and hollowed 
 out of similar ancient strata, occur in the Upper Eifel, where 
 
EIFEL.— TBASS. 535 
 
 copious aei-iform discharges have taken place, throwin<? out 
 vast heaps of pulverized shale into the air. I know of no 
 other extinct volcanoes where gaseous explosions of such 
 magnitude have been attended by the emission of so small a 
 quantity of lava. Yet I looked in vain in the Eifel for any 
 appearances which could lend support to the hypothesis that 
 the sudden rushing out of such enormous volumes of gas had' 
 ever lifted up the stratified rocks immediately around the 
 vent so as to form conical masses, having their sti-ata dip- 
 ping outward on all sides from a central axis, as is assumed 
 in the theory of elevation craters, alluded to in the last 
 chapter. 
 
 I have already given (p. 512, Fig. 590) an example in the 
 Eifel of a small stream of lava which issued from one of the 
 craters of that district at Bertrich-Baden. It shows that 
 when some of these volcanoes were in action the valleys had 
 already been eroded to their present depth. 
 
 Trass. — The tufaceous alluvium called trass, which has 
 covered large areas in the Eifel, and choked up some valleys 
 now partially re-excavated, is unstratified. Its base consists 
 almost entirely of pumice, in which are included fragments 
 of basalt and other lavas, pieces of burnt shale, slate, and 
 sandstone, and numerous trunks and branches of trees. If, as 
 is probable, this trass was formed during the period of vol- 
 canic eruptions, it may have originated in the manner of the 
 moya of the Andes. 
 
 We may easily conceive that a similar mass might now be 
 produced, if a copious evolution of gases should occur in one 
 of the lake-basins. If a breach should be made in the side 
 of the cone, the flood would sweep away great heaps of eject- 
 ed fragments of shale and sandstone, which would be borne 
 down into the adjoining valleys. Forests might be torn up 
 by such a flood, and thus the occurrence of the numerous 
 trunks of trees dispersed irregularly through the trass can 
 be explained. The manner in which this trass conforms to 
 the shape of the present valleys implies its comparatively 
 modern origin, probably not dating farther back than the 
 Pliocene Period. 
 
536 ELEMENTS OF GEOLOGY. 
 
 CHAPTER XXX. 
 
 AGE OP VOLCANIC KOCKS — Continued. 
 
 Volcanic Rocks of the Upper Miocene Period.— Madeira.— Grand Canary.— 
 Azores. — Lower Miocene Volcanic Rocks. — Isle of Mull. — Staffa and 
 Antrim.— The Eifel.— Upper and Lower Miocene Volcanic Rocks of 
 Auvergne. — Hill of Gergovia. — Eocene Volcanic Rocks of Monte Bolca. 
 —Trap of Cretaceous Period.— Oolitic Period.— Triassic Period.— Permi- 
 an Period. — Carbonifurous Period. — Erect Trees buried in Volcanic Ash 
 in the Island of Arran.— Old Red Sandstone Period.— Silurian Period.— 
 Cambrian Period. — Laurentian Volcanic Rocks. 
 
 Volcanic Rocks of the Upper Miocene Period. — Madeira.— 
 The greater part of the volcanic eruptions of Madeira, as we 
 ■have already seen (p. 532), belong to the Pliocene Period, 
 but the most ancient of them are of Upper Miocene date, as 
 shown by the fossil shells included in the marine tuffs which 
 have been upraised at San Vicente, in the northern part of 
 the island, to the height of 1300 feet above the level of the 
 sea. A similar marine and volcanic formation constitutes 
 the fundamental portion of the neighboring island of Porto 
 Santo, forty miles distant from Madeira, and is there elevated 
 to an equal height, and covered, as in Madeira, with lavas of 
 supra-marine origin. 
 
 The largest number of fossils have been collected from 
 the tuffs and conglomerates and some beds of limestone in 
 the island of Baixo, off the southern extremity of Porto San- 
 to. They amount in this single locality to more than sixty 
 in number, of which about fifty are mollusca, but many of 
 these are only casts. Some of the shells probably lived on 
 the spot during the intervals between eruptions, and some 
 may have been cast up into the water or air together with 
 muddy ejections, and, falling down again, have been depos- 
 ited on the bottom of the sea. The hollows in some of the 
 fragments of vesicular lava of which the breccias and con- 
 glomerates are composed are partially filled with calc-sinter, 
 being thus half converted into amygdaloids. Among the 
 fossil shells common to Madeira and Porto Santo, large cones, 
 strombs, and cowries are conspicuous among the univalves, 
 and Cardium, S^iondylus, and Lithodomus among the lamel- 
 libranchiate bivalves, and among the JEchinodernis the large 
 Clypeaster called C. alius, an extinct European Miocene fossil. 
 
UPPER MIOCENE VOLCANIC KOCKS. 537 
 
 The largest list of fossils has been published by Mr. Karl 
 Meyer, in Hartung's " Madeira ;" but in the collection made 
 by myself, and m a still larger one formed by Mr. J. Yate 
 Johnson, several remarkable forms not in Meyer's list occur, 
 as, for example, Pholadomya, and a large Terebra. Mr. John- 
 soh also found a fine specimen of Nautilus {Atruria) zigzag 
 (Fig. 211, p. 266), a well-known Falunian fossil of Europe; 
 and in the same volcanic tuff of Baixo, the Echinoderm Bris- 
 sus Scillce, a living Mediterranean species, found fossil in the 
 Miocene strata of Malta. Mr. Meyer identifies one-third of 
 the Madeira shells with known European Miocene (or Falu- 
 nian) forms. The huge Strombus of San Vicente and Porto 
 Santo, iS. Italicus, is an extinct shell of the Sub-apennine or 
 Older Pliocene formations. The mollusca already obtained 
 from various localities of Madeira and Porto Santo are not 
 less than one hundred in number, and, according to the late 
 Dr. S. P. Woodward, rather more than a third are of species 
 still living, but many of these are not now inhabitants of 
 the neighboring sea. 
 
 It has been remarked (p. 212), that in the Older Pliocene 
 and Upper Miocene deposits of Europe many forms occur of 
 a more southern aspect than those now inhabiting the near- 
 est sea. In like manner the fossil corals, or Zoantharia, six 
 in number, which I obtained from Madeira, of the genera As- 
 trcea, Sarcinula, JTydnophora, were pronounced by Mr. Lons- 
 dale to be forms foreign to the adjacent coasts, and agreeing 
 with the fauna of a sea warmer than that now separating 
 Madeira from the nearest part of the African coast. We 
 learn, indeed, from the observations made in 1859, by the 
 Rev. R. T. Lowe, that more than one-half, or fifty-three in 
 ninety, of the marine niollusks collected by him from the 
 sandy beach of Mogador are common British species, al- 
 though Mogador is fs^ degrees south of the nearest shores 
 of England. The living shells of Madeira and Porto Santo 
 are in like manner those of a temperate climate, although in 
 great part differing specifically from those of Magador.^ 
 
 Grand Canary. — In the Canaries, especially in the Grand 
 Canary, the same marine Upper Miocene formation is found. 
 Stratified tuffs, with intercalated conglomerates and lavas, are 
 there seen in nearly horizontal layers in sea-cliffs about 300 
 feet high, near Las Palmas. Mr. Hartung and I were unable 
 to find^marine shells in these tuffs at a greater elevation than 
 400 feet above the sea; but as the deposit to which they be- 
 long reaches to the height of 1100 feet or more in the interior, 
 we "conceive that an upheaval of at least that amount has 
 * Linnean Proceedings ; Zoology, 1860. 
 23* 
 
53(3 ELEMENTS OP GEOLOGY. 
 
 taken place. The Clypeaster altus, Spondylics gcBderopus, 
 Fectunculus pilosus, Cardita calyculata, and several other 
 shells, serve to identify this formation with that of the Ma- 
 deiras, and Ancillaria glandiformis, which is not rare, and 
 some other fossils, remind us of the faluns of Touraine._ 
 
 The sixty - two Miocene species which I collected in the 
 Grand Canary were referred by the late Dr. S. P. Woodward 
 to forty-seven genera, ten of which are no longer represented 
 in the neighboring sea, namely Cordis, an African form, Hin- 
 nite^, now living in Oregon, Thecidium {T. Mediterrmieum, 
 identical with the Miocene fossil of St. Jiivat, in Brittany), 
 Calyptrma, Sipponyx, Mrita, Erato, Oliva, Ancillaria, and 
 Fasciolaria. 
 
 These tuffs of the southern shores of the Grand Canary, 
 containing the Upper Miocene shells, appear to be about the 
 same age as the most ancient volcanic rocks of the island, 
 composed of slaty diabase, phonolite, and trachyte. Over 
 the marine lavas and tuffs trachytic and basaltic products 
 of subaerial volcanic origin, between 4000 and 5000 feet in 
 thickness, have been piled, the central parts of the Grand 
 Canary reaching the height of about 6000 feet above the 
 level of the sea. A large portion of this mass is of Pliocene 
 date, and some of the latest lavas have been poured out 
 since the time when the valleys were already excavated to 
 within a few feet of their present depth. 
 
 On the whole, the rocks of the Grand Canary, an island of 
 a nearly circular shape, and 6^ geographical miles diameter, 
 exhibit proofs of a long series of eruptions beginning like 
 those of Madeira, Porto Santo, and the Azores, in the Upper 
 Miocene period, and continued to the Post-Pliocene. The 
 building up of the Grand Canary by subaerial eruptions, sev- 
 eral thousand feet thick, went on simultaneously with the 
 gradual upheaval of the earliest products of submarine erup- 
 tions, in the same manner as the Pliocene marine strata of 
 the oldest parts of Vesuvius and Etna have been upraised 
 during eruptions of Post-tertiary date. 
 
 In proof that movements of elevation have actually con- 
 tinued down to Post - tertiary times, I may remark that I 
 found raised beaches containing shells of the Recent Period 
 in the Grand Canary, Teneriffe, and Porto Santo. The most 
 remarkable raised beach which I observed in the Grand Ca- 
 nary, in the study of which I was assisted by Don Pedro 
 Maffiotte, is situated in the north-eastern part of the island 
 at San Catalina, about a quarter of a mile north of Las Pal- 
 mas. It intervenes between the base of the high cliff formed 
 of the tuffs with Miocene shells and the sea-shore. From 
 
LOWER MIOCENE VOLCANIC ROCKS. 539 
 
 this beach at an elevation of twenty-five feet above hio-h- 
 water mark, and at a distance of about 150 feet from the 
 present shore, I obtained more than fifty species of livino- 
 marine shells. Many of them, according to Dr. S P Wood° 
 ward,are no longer inhabitants of the contiguous sea, as, for 
 exami>ie Strombus bubonius, which is still living on the West 
 Coast ot Africa, and Centhium procerum, found at Mozam- 
 bique ; others are Mediterranean species, as Peeten Jacobmus 
 and P. pohjmorphus. Some of these testacea, such as Cardita 
 squamosa, are inhabitants of deep water, and the deposit on 
 the whole seems to indicate a depth of water exceedino- a 
 hundred feet. " 
 
 Azores.— In the island of St. Mary's, one of the Azores, 
 marine fossil shells have long been known. They are found' 
 on the north-east coast on a small projecting promontoi-y 
 called Ponta do Papagaio (or Point -Parrot), chiefiy in a 
 limestone about twenty feet thick, which rests upon, and is 
 again covered by, basaltic lavas, scoriae, and conglomerates. 
 The pebbles in the conglomerate are cemented together with 
 carbonate of lime. 
 
 Mr. Hartung, in his account of the Azores, published in 
 1860, describes twenty -three shells from St. Mary's,* of 
 which eight perhaps are identical with living species, and 
 twelve are with more or less certainty, referred to European 
 Tertiary forms, chiefly Upper Miocene. One of the most 
 characteristic and abundant of the new species, Gardium 
 Hartungi, not known as fossil in Europe, is very common in 
 Porto Santo and Baixo, and serves to connect the Miocene 
 fauna of the Azores and the Madeiras. In some of the 
 Azores, as well as in the Canary islands, the volcanic fires 
 are not yet extinct, as the recorded eruptions of Lanzerote, 
 Teneriffe, Palraa, St. Michael's, and others, attest. 
 
 Lower Miocene Volcanic Eocks. — Isle of Mull and Antrim. 
 — I may refer the reader to the account already given (p. 
 247) of leaf-beds at Ardtun, in the Isle of Mull in the Heb- 
 rides, which bear a relation to the associated volcanic rocks 
 of Lower Miocene date analogous to that which the Madeira 
 leaf-bed, above described (p. 532), bears to the Pliocene lavas 
 of that island. Mr. Geikie has shown that the volcanic rocks 
 in Mull are above .3000 feet in thickness. There seems little 
 doubt that the well-known columnar basalt of Staffa, as well 
 as that of Antrim in Ireland, are of the same age, and not 
 of higher antiquity, as once suspected. 
 
 The Eifel. — A large portion of the volcanic rocks of the 
 * Hartung, Die Azoien, 1860 ; also Insel Gran Canada, Madeira und Por- 
 to Santo, X864, Leipsig. 
 
540 ELEMENTS OY GEOLOGY. 
 
 Lower Rhine and the Eifel are coeval with the Lower Mio- 
 cene deposits to which most of the "Brown-Coal" of Ger- 
 many belongs. The Tertiary strata of that age are seen on 
 both sides of the Rhine, in the neighborhood of Bonn, rest- 
 ing unconforinably on highly inclined and vertical strata of 
 Silurian and Devonian rocks. The Brown -Coal formation 
 of that region consists of beds of loose sand, sandstone, and 
 conglomerate, clay with nodules of clay-iron-stone, and occa- 
 sionally silex. Layers of light brown and sometimes black 
 lignite are interstratified with the clays and sands, and often 
 irregularly diffused through them. They contain numerous 
 impressions of leaves and stems of trees, and are extensively 
 worked for fuel, whence the name of the formation. In sev- 
 eral places layers of trachytic tuff are interstratified, and in 
 these tuffs are leaves of plants identical with those found in 
 the brown-coal, showing that, during the period of the accu- 
 mulation of the latter, some volcanic products were ejected. 
 The igneous rocks of the Westerwald, and of the mountains 
 called the Siebengebirge, consist partly of basaltic and part- 
 ly of trachytic lavas, the latter being in general the more 
 ancient of the two. There are many varieties of trachyte, 
 some of which are highly crystalline, resembling a coarse- 
 grained granite, with large separate crystals of feldspar. 
 Trachytic tuff is also very abundant. 
 
 M. Von Dechen, in his work on the Siebengebirge,* has 
 given a copious list of the animal and vegetable remains of 
 the fresh-water strata associated with the brown-coal of that 
 part of Germany. Plants of the genera Flabellaria, Ceano- 
 thus, and Daphnogene, including D. cinnamomifolia (Fig. 
 155, p. 239), occur in these beds, with nearly 150 other plants. 
 The fishes of the brown-coal near Bonn are found in a bitu- 
 minous shale, called paper-coal, from being divisible into ex- 
 tremely thin leaves. The individuals are very numerous; 
 but they appear to belong to a small number of species, 
 some of which were referred by Agassiz to the genera JLeiir 
 ciscus, Aspius, and Perca. The remains of frogs also, of ex- 
 tinct species, have been discovered in the paper-coal ; and a 
 complete series may be seen in the museum at Bonn, fi-om 
 the most imperfect state of the tadpole to that of the full- 
 grown animal. With these a salamander, scarcely distin- 
 guishable from the recent species, has been found, and the 
 remains of many insects. 
 
 Upper and Lower Miocene Volcanic Rocks of Auvergne.— 
 The extinct volcanoes of Auvergne and Cantal, in central 
 France, seem to have commenced their eruptions in the Lower 
 * Geognost. Beschreib. des Siebengebirges am Kheiri. . Bonn, 1852. 
 
VOLCANIC ROCKS OF AUVEE6NE. 541 
 
 Miocene period, but to have been most active during the 
 Upper Miocene and Pliocene eras. I have already al- 
 luded to the grand succession of events of which there is 
 evidence in Auvergne since the last retreat of the sea (see 
 p. 527). ^ 
 
 The earliest monuments of the Tertiary Period in that re- 
 gion are lacustrine deposits of great thickness, in the lowest 
 eonglomerates of which are rounded pebbles of quartz, mica- 
 schist, granite, and other non-volcanic rocks, without the 
 slightest intermixture of igneous products. To these con- 
 glonierates succeed argillaceous and calcareous marls and 
 limestones, containing Lower Miocene shells and bones of 
 mammalia, the higher beds of which sometimes alternate 
 with volcanic tuff of contemporaneous origin. After the fill- 
 ing up or drainage of the ancient lakes, huge piles of trachyt- 
 ic and basaltic rocks, with volcanic breccias, accumulated to 
 a thickness of several thousand feet, and were superimposed 
 upon granite, or the contiguous lacustrine strata. The gi'eat- 
 er portion of these igneous rocks appear to have originated 
 during the Upper Miocene and Pliocene periods ; and extinct 
 quadrupeds of those eras, belonging to the genera Mastodon, 
 Rhinoceros, and others, were buried in ashes and beds of al- 
 luvial sand and gravel, which owe their preservation to over- 
 spreading sheets of lava. 
 
 In Auvergne, the most ancient and conspicuous of the vol- 
 canic masses is Mount Dor, which rests immediately on the 
 granitic rocks standing apart from the fresh -water strata. 
 This great mountain rises suddenly to the height of several 
 thousa,nd feet above the surrounding platform, and retains 
 the shape of a flattened and somewhat irregular cone, the 
 slope of which is gradually lost in the high plain around. 
 This cone is composed of layers of scoriae, pumice-stones, and 
 their fine detritus, with interposed beds of trachyte and 
 basalt, which descend often in uninterrupted sheets until 
 they reach and spread themselves round the base of the 
 mountain.* Conglomerates, also, composed of angular and 
 rounded fragments of igneous rocks, are observed to alternate 
 with the above ; and the various masses are seen to dip off 
 from the central axis, and to lie parallel to the sloping flanks 
 of the mountain. The summit of Mont Dor terminates in 
 seven or eight rocky peaks, Avhere no regular crater can now 
 be traced, but where we may easily imagine one to have ex- 
 isted, which may have been shattered by earthquakes, and 
 have' suffered degradation by aqueous agents. Originally, 
 perhaps, like the highest crater of Etna, it may have formed 
 * Sei-ope's Central France, p. 98. 
 
542 
 
 ELEMENTS OF GEOLOGY. 
 
 v-n insignificant feature in the great pile, and, like it, may 
 ii-equently have been destroyed and renovated. 
 
 Respecting the age of the great mass of Mont Dor, vi^e 
 lan not come at present to any positive decision, becauseno 
 ;rgauic remains have yet been found in the tuiFs, except im- 
 pressions of the leaves of trees of species not yet determined. 
 it has already been stated (p. 234) that the earliest eruptions 
 must have been posterior in origin to those grits and con- 
 glomerates of the fresh-water formation of the L'imagne which 
 contain no pebbles of volcanic rocks. But there is evidence 
 at a few points, as in the hill of Gergovia, presently to be 
 mentioned, that some eruptions took place before the great 
 lakes were drained, while others occurred after the desicca- 
 tion of those lakes, and when deep valleys had already been 
 excavated through fresh-water strata. 
 
 The valley in which the cone of Tartaret, above mentioned 
 (p. 527), is situated affords an impressive monument of the 
 very different dates at which the igneous eruptions of Au- 
 vergne have happened; for while the cone itself is of Post- 
 Pliocene date, the valley is bounded by lofty precipices com- 
 posed of sheets of ancient columnar trachyte and basalt, 
 which once flowed from the summit of Mont Dor in some 
 part of the Miocene period. These Miocene lavas had accu- 
 mulated to a thickness of nearly 1000 feet before the ravine 
 was cut down to the level of the river Couze, a river which 
 was at length dammed up by the modern cone and the upper 
 part of its course transformed into a lake. 
 
 Gergovia. — It has been supposed by some observers that 
 there is an alternation of a contemporaneous sheet of lava 
 with fresh-water strata in the hill of Gergovia, near Glennont. 
 
 Fig. 604. 
 
 Basaltic capping. 
 
 White and yellow 
 
 marl. 
 Bine marlB. 
 
 Tuffs. 
 Dike. 
 
 White and 
 green marls. 
 
 Hill ofGersovia, 
 
EOCENE VOLCANIC ROCKS. 543 
 
 But this idea has arisen from the intrusion ot the dike repre- 
 sented in the annexed diagram (Fig. 604), which has altered 
 the green and white marls both above and below. Never- 
 theless, there is a real alternation of volcanic tuff with strata 
 containing Lower Miocene fresh-water shells, among others 
 a Melania allied to M. inquinata (Fig. 217, p. 268), with a 
 Melanopsis and a Unio ; there can, therefore, be no doubt 
 that iu Auvergne some volcanic explosions took place before 
 the drainage of the lakes, and at a time when the Lower Mi- 
 ocene species of animals and plants still flourished. 
 
 Eocene Volcanic Rocks. — Monte Bolca. — The fissile lime- 
 stone of Monte Bolca, near Verona, has for many centuries 
 been celebrated in Italy for the number of perfect Ichthyo- 
 lites' which it contains. Agassiz has described no less than 
 133 species of fossil fish from this single deposit, and the 
 multitude of individuals by which many of the species are 
 represented is attested by the variety of specimens treasured 
 up in the principal museums of Europe. They have been all 
 obtained from quarries worked exclusively by lovers of nat- 
 ural history, for the sake of the fossils. Had the lithograph- 
 ic stone of Solenhofen, now regarded as so rich in fossils, 
 been in like manner quarried solely for scientific objects, it 
 would have remained almost a sealed book to palaeontolo- 
 gists, so sparsely are the organic remains scattered through 
 ft. When I visited Monte Bolca, in company with §ir Rod- 
 erick Murchison, in 1828, we ascertained that the fish-bearing 
 beds were of Eocene date, containing well-known species of 
 Nummulites, and that a long series of submarine volcanic 
 eruptions, evidently contemporaneous, had produced beds of 
 tuff, which are cut through by dikes of basalt. There is evi- 
 dence here of a long series of submarine volcanic eruptions 
 of Eocene date, and'during some of them, as Sir R. Mui;^hison 
 has sugo-ested, shoals offish were probably destroyed by the 
 evolution of heat, noxious gases, and tufaceous mud, just as 
 happened when Graham's Island was thrown up betweenbic- 
 ily and Africa in 1831, at which time the waters of the Med- 
 iterranean were seen to be charged with red mud, and cov- 
 ered with dead fish over a wide area.* ^ 
 
 Associated with the marls and limestones of Monte Bolca 
 are beds containin<^ lignite and shale with numerous plants 
 whiS havTbeen desfribed by Unger -d Massalongo, and 
 referred bv them to the Eocene period. I have already cited 
 (ToR^ T^-ofessor Heer's remark, that several of the species 
 i?e corimontrMonte Bolca and ihe white clay of Alum Bay 
 a MidrEocene deposit; and the «ame botanist dwells on 
 * Principles of Geology, chap, xxvi., 9th ed., p. 432. 
 
544 ELEMENTS OF GEOLOGY. 
 
 the tropical character of the flora of Monte Bolca and its dis- 
 tinctness from the sub-tropical flora of the Lower Miocene of 
 Switzerland and Italy, in which last there is a far more con- 
 siderable mixtui'e of forms of a temperate climate, such as 
 the willow, poplar, birch, elm, and others. That scarcely 
 any one of the Monte Bolca fish should have been found in 
 any other locality in Europe, is a striking illustration of the 
 extreme imperfection of the palseontological record. We 
 are in the habit of imagining that our insight into the geolo- 
 gy of the Eocene period is more than usually perfect, and we 
 are certainly acquainted with an almost unbroken succession 
 of assemblages of shells passing one into the other from the 
 era of the Thanet sands to that of the Bembridge beds or 
 Paris gypsum. The general dearth, therefore, of fish in the 
 diflferent members of the Eocene series. Upper, Middle, and 
 Lower, might induce a hasty reasoner to conclude that there 
 was a poverty of ichthyic forms during this period; but 
 when a local accident, like the volcanic eruptions of Monte 
 Bolca, occurs, proofs are suddenly revealed to us of the rich- 
 ness and variety of this great class of vertebrata in the 
 Eocene sea. The number of genera of Monte Bolca fish is, 
 according to Agassiz, no less than seventy-five, twenty of 
 them peculiar to that locality, and only eight common to the 
 antecedent Cretaceous period. No less than forty-seven out 
 of the seventy-five genera make their appearance for the first 
 time in the Monte Bolca rocks, none of them having been 
 met with as yet in the antecedent formations. They form 
 a great contrast to the fish of the secondary strata, as, 
 with the exception of the Placoids, they are all Teleos- 
 teans, only one genus, Pycnodus, belonging to the order of 
 Ganoids, which form, as before stated, the vast majority of 
 the ichthyolites entombed in the secondary or Mesozoic 
 rocks. 
 
 Cretaceous Period.— M. Virlet, in his account of the geolo- 
 gy of the Morea, p. 205, has clearly shown that certain traps 
 in Greece are of Cretaceous date ; as those, for example, which 
 alternate conformably with cretaceous limestone and green- 
 sand between Kastri and Damala, in the Morea. They con- 
 sist in great part of diallage rocks and serpentine, and of an 
 amygdaloid with calcareous kernels, and a base of serpen- 
 tine. In certain parts of the Morea, the age of these volcanic 
 rocks is established by the following proofs : first, the litho- 
 graphic limestones of the Cretaceous era are cut through by 
 trap, and then a conglomerate occurs, at Nauplia and other 
 places, containing in its calcareous cement many well-known 
 fossils of the chalk and greensand, together with pebbles 
 
CARBONIFEROUS VOLCANIC ROCKS. 545 
 
 formed of rolled pieces of the same sevpentinous trap, which 
 appear in the dikes above alluded to. 
 
 Period of Oolite and Lias. — Although the green and ser- 
 pentinous trap-rocks of the Morea belong chiefly to the Cre- 
 taceous era, as before mentioned, yet it seems that some erup- 
 tions of similar rocks began during the Oolitic period ;* and 
 It IS probable that a large part of the trappeau masses, called 
 ophiolites in the Apennines, and associated with the lime- 
 stone of that chain, are of corresponding age. 
 
 Trap of the. New Red Sandstone Period. — In the southern 
 part of Devonshire, trappean rocks are associated with ISTew 
 Bed Sandstone, and, according to Sir H. De la Beche, have 
 not been intruded subsequently into the sandstone, but were 
 produced by contemporaneous volcanic action. Some beds 
 of grit, mingled with ordinary red marl, resemble sands 
 ejected from a crater; and in the stratified conglomerates 
 occurring near Tiverton are many angular fragments of trap 
 porphyry, some of them one or two tons in weight, intermin- 
 gled with pebbles of other rocks. These angular fragments 
 were probably thrown out from volcanic vents, and fetl upon 
 sedimentary matter then in the course of depositioif^ 
 
 Trap of the Permian Period. — The recent investigations of 
 Mr. Archibald Geikie in Ayrshire have shown that some of 
 the volcanic rocks in that county are of Permian age, and it 
 appears highly probable that the uppermost portion of Ar- 
 thur's Seat in the suburbs of Edinburgh marks the site of an 
 eruption of the same era. 
 
 Trap of the Carboniferous Period. — Two classes of contem- 
 poraneous trap-rocks occur in the coal-field of the Forth, in 
 Scotland. The newest of these, connected with the higher 
 series of coal-measures, is well exhibited along the shores of 
 the Forth, in Fifeshire, where they consist of basalt with 
 olivine, amygdaloid, greenstone, wacke, and tuff. They ap- 
 pear to have been erupted while the sedimentary strata were 
 in a horizontal position, and to have suffered the same dislo- 
 cations which those strata have subsequently undergone. In 
 the volcanic tuffs of this age are found not only fragments 
 of limestone, shale, flinty slate, and sandstone, but also pieces 
 of coal. The other or older class of carboniferous traps are 
 traced along the south margin of Stratheden, and constitute 
 a ridge parallel with the Ochils, and extending from Stirling 
 to near St. Andrews. They consist almost exclusively of 
 greenstone, becoming, in a few instances, earthy and amyg- 
 daloidal. They are regularly interstratitied with the sand- 
 
 * Boblaye and Virlet, Morea, p. 23. 
 
 t De la Beche, Geol. Proceedings, vol. ii., p. 198. 
 
546 ELEMENTS OF GEOLOGY. 
 
 stone, shale, and iron-stone of the lower coal-measures, and, 
 on the East Lomond, with Mountain Limestone. I examined 
 these trap-rocks in 1838, in the cliffs south of St. Andrews, 
 where they consist in great part of stratified tuffs, which are 
 curved, vertical, and contorted, like the associated coal-meas- 
 ures. In the tuff I found fragments of carboniferous shale 
 and limestone, and intersecting veins of greenstone. 
 
 Fife — Flisk Dike. — A trap dike was pointed out to me by 
 Dr. Fleming, in the parish of Flisk, in the northern part of 
 the county of Fife, which cuts through the gray sandstone 
 and shale, forming the lowest part of the Old Red Sandstone, 
 but which may probably be of carboniferous date. It may 
 be traced for many miles, passing through the amygdaloidal 
 and other traps of the hill called Norman's Law in that par- 
 ish. In its course it affords a good exemplification of the 
 passage from the trappean into the plutonic, or highly crys- 
 talline texture. Professor Gustavus Rose, to whom I sub- 
 mitted specimens of this dike, found it to be dolerite, and 
 composed of greenish black augite and Labrador feldspar, 
 the latter being the most abundant ingredient. A small 
 quantity of magnetic iron, perhaps titaniferous, is also pres- 
 ent. The result of this analysis is interesting, because both 
 the ancient and modern lavas of Etna consist in like manner 
 of augite, Labradorite, and titaniferous iron. 
 
 JErect Trees buried in Volcanic Ash at Arran. — An inter- 
 esting discovery was made in 186V by Mr. E. A. Wiinsch in 
 the carboniferous strata of the north-eastern part of the isl- 
 and of Arran. In the sea-cliff about five miles north of Cor- 
 rie, near the village of Laggan, strata of volcanic ash occur, 
 forming a solid rock cemented by carbonate of lime and en- 
 veloping trunks of trees, determined by Mr. Binney to belong 
 to the genera Sigillaria and Lepidodendron. Some of these 
 trees are at right angles to the planes of stratification, while 
 others are prostrate and accompanied by leaves and fruits 
 of the same genera. I visited the spot in company with Mr. 
 Wiinsch in ISVO, and saw that the trees with their roots, of 
 which about fourteen had been observed, occur at two dis- 
 tinct levels in volcanic tuffs parallel to each other, and in- 
 clined at an angle of about 40°, having between them beds 
 of shale and coaly matter seven feet thick. It is evident 
 that the trees were overwhelmed by a shower of ashes from 
 some neighboring volcanic vent, as Pompeii was buried by 
 matter ejected from Vesuvius. The trunks, several of them 
 fi-om three to five feet in circumference, remained with their 
 Stigmarian roots spreading through the stratum below, which 
 had served as a soil. The trees must have continued for 
 
TRAP OF THE OLD RED SANDSTONE PERIOD. 547 
 
 years in an upright position after they were killed by the 
 shower of burning ashes, giving time for a partial decay of 
 the interior, so as to afford hollow cylinders into which the 
 spores of plants were wafted. These spores germinated and 
 grew, until finally their stems were petrified by carbonate 
 of lime like some of the remaining portions of the wood of 
 the containing Sigillaria. Mr. 6arruthers has discovered 
 that sometimes the plants which had thus grown and be- 
 come fossil in the inside of a single trunk belonged to several 
 distinct genera. .The fact that the tree-bearing deposits now 
 dip at an angle of 40° is the more striking, as they must clear- 
 ly have remained horizontal and undisturbed during a long 
 period of intermittent and contemporaneous volcanic action. 
 
 In some of the associated carboniferous shales, ferns and 
 calamites occur, and all the phenomena of the successive 
 buried forests remind us of the sections (pp. 410, 411) of the 
 Nova Scotia coal-measures, with this difference only, that in 
 the case of the South Joggins the fossilization of the trees 
 was effected without the eruption of volcanic matter. 
 
 Trap of the Old Eed Sandstone Period. — By referring to the 
 section explanatory of the structure of Forfarshire, already 
 given (p. 74), the reader will perceive that beds of conglom- 
 erate, No. 3, occur in the middle of the Old Red Sandstone 
 system, 1, 2, 3, 4. The pebbles in these conglomerates are 
 sometimes composed of granitic and quartzose rocks, some- 
 times exclusively of different varieties of trap, which last, al- 
 though purposely omitted in the section referred to, is often 
 found either intruding itself in amorphous masses and dikes 
 into the old fossiliferous tilestones, No. 4, or alternating with 
 them in conformable beds. All the different divisions of the 
 red sandstone, 1, 2, 3, 4, are occasionally intersected by dikes, 
 but they are very rare in Nos. 1 and 2, the upper members of 
 the group consisting of red shale and red sandstone. These 
 phenomena, which occur at the foot of the Grampians, are 
 repeated in the Sidlaw Hills; and it appears that in this 
 part of Scotland volcanic eruptions were most frequent in 
 the earlier part of the Old Red Sandstone period. The trap- 
 rocks alluded to consist chiefly of feldspathic porphyry and 
 amygdaloid, the kernels of the latter being sometimes calca- 
 reous, often chalcedonic, and forming beautiful agates. We 
 meet also with claystone, greenstone, compact feldspar, and 
 tuff. Some of these rocks look as if they had flowed as 
 lavas over the bottom of the sea, and enveloped quartz peb- 
 bles which were lying there, so as to form conglomerates 
 with a base of greenstone, as is seen in Lumley Den, in the 
 Sidlaw Hills. On either side of the axis of this chain of hills 
 
648 ELEMENTS OF GEOLOGY. 
 
 (see section, p. H), the beds of massive trap, and the tuffs 
 composed of volcanic sand and ashes, dip regularly to the 
 south-east or north-west, conformably with the shales and 
 sandstones. 
 
 But the geological structure of the Pentland Hills, near 
 Edinburgh, shows that igneous rocks were there formed dur- 
 ing the newer part of the Devonian or " Old Red" period. 
 These hills are 1900 feet high above the sea, and consist of 
 conglomerates and sandstones of Upper Devonian age, rest- 
 ing on the inclined edges of grits and slates of Lower De- 
 vonian and Upper Silurian date. The contemporaneous vol- 
 canic rocks intercalated in this Upper Old Red consist of 
 feldspatliic lavas, or feldstones, with associated tuffs or ashy 
 beds. The lavas were some of them originally compact, oth- 
 ers vesicular, and these last have been converted into amyg- 
 daloids. They consist chiefly of feldstone or compact feld- 
 spar. The Pentland Hills, say Messrs. Maclaren and Geikie, 
 afford evidence that at the time of the Upper Old Red Sand- 
 stone, the district to the south-west of Edinburgh was for a 
 long while the seat of a powerful volcano, which sent out 
 massive streams of lava and showers of ash, and continued 
 active until well-nigh the dawn of the Carboniferous period.* 
 
 Silurian Volcanic Rocks. — It appears from the investiga- 
 tions of Sir R. Mui-chison in Shropshire, that when the Lower 
 Silurian strata of that country were accumulating, there were 
 frequent volcanic eruptions beneath the sea ; and the ashes 
 and scoriae then ejected gave rise to a peculiar kind of tnfa- 
 ceous sandstone or grit, dissimilar to the other rocks of the 
 Silurian series, and only observable in places where syenitic 
 and other trap-rocks protrude. These tuffs occur on the 
 flanks of the Wrekin and Caer Caradoc, and contain Silurian 
 fossils, such as casts of encrinites, trilobites, and moUusca. 
 Although fossiliferous, the stone resembles a sandy claystofie 
 of the trap family, j- 
 
 Thin layers of trap, only a few inches thick, alternate in 
 some parts of Shropshire and Montgomeryshire with sedi- 
 mentary strata of the Lower Silurian system. This trap 
 consists of slaty porphyry and granular feldspar rock, the 
 beds bemg traversed by joints like those in the associated 
 sandstone, limestone, and shale, and having the same strike 
 and dip.J; 
 
 Li Radnorshire there is an example of twelve bands of 
 stratified trap, alternating with Silurian schists and flag- 
 
 * Maclaren, Geology of Fife and Lothians. Geikie, Trans. Eoyal See. 
 Edinburgh, 1860-1861. 
 t Murchison, Silurian System, etc., p. 230. t Ibid., p. 212. 
 
LAURENTIAN VOLCANIC ROCKS. 549 
 
 Stones, ill a thickness of 350 feet. The bedded traps consist 
 teldspar porphyry, and other varieties; and the inter- 
 posed Llandeilo flags are of sandstone and shale, with trilo- 
 bites and graptolites.* 
 
 The Snowdonian hills in Carnarvonshire consist in o-reat 
 part of volcanic tuffs, the oldest of which are intcrstratified 
 with the Bala and Llandeilo beds. There are some contem- 
 poraneous feldspathic lavas of this era, which, says Pi-ofessor 
 Ramsay, alter the slates on which they repose, having doubt- 
 less been poured out over them, in a melted state, whereas 
 theslates which overlie them having been subsequently de- 
 posited after the lava had cooled and consolidated, have en- 
 tirely escaped alteration. But there are greenstones asso- 
 ciated with the same formation, which, although they are 
 often conformable to the slates, are in reality intrusive rocks. 
 They alter the stratified deposits both above and below 
 them, and when traced to great distances are sometimes seen 
 to cut through the slates, and to send off branches. Never- 
 theless, these greenstones appear to belong, like tlie lavas, to 
 the Lower Silurian period. 
 
 Cambrian Volcanic Rocks. — The Lingula beds in North 
 Wales have been described as 5000 feet in thickness. In the 
 upper portion of these deposits volcanic tuffs or ashy mate- 
 rials are interstratified with ordinary muddy sediment, and 
 here and there associated with thick beds of feldspathic lava. 
 These rocks form the mountains called the Arans and the 
 Arenigs ; numerous greenstones are associated with them, 
 which are intrusive, although they often run in the lines of 
 bedding for a space. "Much of the ash," says Professor 
 Ramsay, " seems to have been sub-aerial. Islands, like Gra- 
 ham's Island, may have sometimes raised their craters for 
 various periods above the water, and by the waste of such 
 islands some of the ashy matter became waterworn, whence 
 the ashy conglomerate. Viscous matter seems also to have 
 been shot into the air as volcanic bombs, which fell among 
 the dust and broken crystals (that often form the ashes^ be- 
 fore perfect cooling and consolidation had taken place."f 
 
 Laurentian Volcanic Rocks.— The Laurentian rocks in Can- 
 ada, especially in Ottawa and Argenteuil, are the oldest m- 
 trusive masses yet known. They form a set of dikes of a 
 fine-grained dai-k greenstone or dolerite, composed of feld- 
 spar and pyroxene, with occasional scales of mica and grains 
 of pyrites. Their width varies from a few feet to a hundred 
 yards, and they have a columnar structure, the columns be- 
 * Mnrchison, Silurian System, etc., p. 325. 
 t Quart. Geol. Journ., voLix., p. 170, 1852. 
 
550 ELEMENTS OF GEOLOGY. 
 
 ing truly at right angles to the plane of the dike. Some of 
 the dikes send oif branches. These dolerites are cut through 
 by intrusive syenite, and this syenite, in its turn, is again 
 cut and penetrated by feldspar porphyry, tho base of which 
 consists of petrosilex, or a mixture of orthoclase and quartz. 
 All these trap-rocks appear to be of Laurentian date, as the 
 Cambrian and Huronian rocks rest unconformably upon 
 them.* Whether some of the various conformable crystal- 
 line rocks of the Laurentian series, such as the coarse-grained 
 granitoid and porphyritic varieties of gneiss, exhibiting 
 scarcely any signs of stratification, and some of the serpen- 
 tines, may not also be of volcanic origin, is a point very diffi- 
 cult to determine in a region which has undergone so much 
 metamorphic action. 
 
 * Logan, Geology of Canada, 1863. 
 
PLUTONIC ROCKS. 551 
 
 CHAPTER XXXI. 
 
 PLUTONIC EOCKS. 
 
 Greneral Aspect of Plutonic Rocks. — Granite and its Varieties. — Decompos- 
 ing into Spherical Masses. — Rude columnar Structure. — Graphic Granite. 
 — Mutual Penetration of Crystals of Quartz and Feldspar. — Glass Cavities 
 in Quartz of Granite. — Porphyritic, talcose, and syenitic Granite. — Schorl- 
 rock and Eurite.— Syenite. — Connection of the Granites and Syenites with 
 the Volcanic Rocks. — ^Analogy in Composition of Trachyte and Granite. — 
 Granite Veins in Glen Tilt, Cape of Good Hope, and Cornwall. — Metallif- 
 erous Veins in Strata near their Junction with Granite. — Quartz Veins. 
 — Exposure of Plutonic Rocks at the Surface due to Denudation. 
 
 The plutonic rocks may be treated of next in order, as 
 they are most nearly allied to the volcanic class already con- 
 sidered. I have described, in the first chapter, these plutonic 
 rocks as the un stratified division of the crystalline or hypo- 
 gene formations, and have stated that they difier from the 
 volcanic rocks, not only by their more crystalline texture, 
 but also by the absence of tuffs and breccias, which are the 
 products of eruptions at the earth's surface, whether thrown 
 up into the air or the sea. They differ also by the absence 
 of pores or cellular cavities, to which the expansion of the 
 entangled gases gives rise in ordinary lava, never being sco- 
 riaceous or amygdaloidal, and never forming a porphyry 
 with an uncrystalline base, nor alternating with tuffs. 
 
 From these and other peculiarities it has been inferred 
 that the granites have been formed at considerable depths in 
 the earth, and have cooled and crystallized slowly under 
 great pressure, where the contained gases could not expand. 
 The volcanic rocks, on the contrary, although they also have 
 risen up from below, have cooled from a melted state more 
 rapidly upon or near the surface. From this hypothesis of 
 the great depth at which the granites originated, has been 
 derived the name of "Plutonic rocks." The beginner will 
 easily conceive that the influence of subterranean heat may 
 extend downward from the crater of every active volcano 
 to a great depth below, perhaps several miles or leagues, and 
 the elects which are produced deep m the bowels of the earth 
 may or rather must, be distinct; so that volcanic and plu- 
 tonk rocks, each different in texture, ^n^ /"'"f ^^'^/Jf " '" 
 composition, may originate simultaneously, the one at the 
 
552 ELEMENTS OE GEOLOGY. 
 
 surface, the other far beneath it. The plutonic formations 
 also agree with the volcanic in having veins or ramifications 
 proceeding from central masses into the adjoining rocks, and 
 causing alterations in these last, which will be presently de- 
 scribed. They also resemble trap in containing no organic 
 remains ; but they diifer in being more uniform in texture, 
 whole mountain masses of indefinite extent appearing to 
 have originated under conditions precisely similar. 
 
 The two principal members of the Plutonic family of rocks 
 are Granite and Syenite, each of which, with their varieties, 
 bear very much the same relation to each other as the tra- 
 chytes bear to the basalts. Granite is a compound of feldspar, 
 quartz, and mica, the feldspars being rich in silica, which forms 
 from 60 to 70 per cent, of the whole aggi'egate. In Syenite 
 quartz is rare or wanting, hornblende taking the place of 
 mica, and the proportion of silica not exceeding 50 to 60 per 
 cent. 
 
 Granite and its Varieties. — Granite often preserves a very 
 uniform character throughout a wide range of territory, 
 forming hills of a peculiar rounded form, usually clad with a 
 scanty vegetation. The surface of the rock is for the most 
 part in a crumbling state, and the hills are often surmounted 
 by piles of stones like the remains of a stratified mass, as in 
 the annexed figure, and sometimes like heaps of boulders, 
 
 Fig. 605. 
 
 Mass of granite near the Sharj) Tor, Cornwall. 
 
 for which they have been mistaken. The extprior of these 
 stones, originally quadrangular, acquires a rounded form by 
 the action of air and water, for tlie edges and angles waste 
 aAvay more rapidly than the sides. A similar spherical 
 structure has already been described as characteristic of ba- 
 salt and other volcanic formations, and it must be referred to 
 analogous causes, as yet but imperfectly understood. Al- 
 though it is the general peculiarity of granite to assume no 
 definite shapes, it is nevertheless occasionally subdivided by 
 fissures, so as to assume a cuboidal, and even a columnar, 
 structure. Examples of these appearances may be seen near 
 the Land's End, in Cornwall. (See Fig. 606.) 
 
GRANITE AND ITS VAEIETIES. 553 
 
 Feldspar, quartz, and mica are usually considered as the 
 minerals essential to granite, the feldspar being most abun- 
 dant m quantity, and the proportion of quartz exceedins that 
 of mica. These minerals are united in what is termed a con- 
 fused crystallization ; that is to say, there is no reo^ular ar- 
 rangement of the crystals in granite, as in gneiss (see Fio- 
 622, p. 611), except in the variety termed graphic granite" 
 which occurs mostly in granitic veins. This variety is a 
 compound of feldspar and quartz, so arranged as to produce 
 
 Fig. 606. 
 
 Granite having a cnboidal and rude columnar stracture, Land's End, Cornwall. 
 
 an imperfect laminar structure. The crystals of feldspar 
 appear to haVe been first formed, leaving between them the 
 space now occupied by the darker-colored quartz. This 
 mineral, when a section is made at right angles to the alter- 
 nate plates of feldspar and quartz, presents broken lines, 
 which have been compared to Hebrew characters. (See Fig. 
 608.) The variety of granite called by the French Pegma- 
 tite, which is a mixture of quartz and common feldspar, usu- 
 ally with some small admixture of white silvery mica, often 
 passes into graphic granite. 
 
 Ordinary granite, as well as syenite and eurite, usually 
 contains two kinds of feldspar: 1st, the common, or ortho- 
 clase, in which potash is the prevailing alkali, and this gener- 
 
 24 
 
554 ELEMENTS OF GEOLOGY. 
 
 Fig. 607. rig- 60S. 
 
 Graphic granite. 
 
 Fig. 607. Section parallel to the laminae.— Fig. 60S. Section transverse 
 
 to the laminae. 
 
 ally occurs in large crystals of a white or flesh color ; and 
 2diy, feldspar in smaller crystals, in which soda predomi- 
 nates, usually of a dead white or spotted, and striated like 
 albite, but not the same in composition.* 
 
 As a general rule, quartz, in a compact or amorphous state, 
 forms a vitreous mass, serving as the base in which feldspar 
 and mica have crystallized ; for although these minerals are 
 much more fusible than silex, they have often imprinted their 
 shapes upon the quartz. This fact, apparently so paradoxi- 
 cal, has given rise to much ingenious speculation. We should 
 naturally have anticipated that, during the cooling of the 
 mass, the flinty portion would be the first to consolidate ; 
 and that the different varieties of feldspar, as well as garnets 
 and tourmalines, being more easily liquefied by heat, would 
 be the last. Precisely the reverse has taken place in the 
 passage of most granite aggregates from a fluid to a solid 
 state, crystals of the more i'usible minerals being found en- 
 veloped in hard, transparent, glassy quartz, which has often 
 taken very faithful casts of each, so as to preserve even the 
 microscopically minute striations on the surface of prisms of 
 tourmaline. Various explanations of this phenomenon have 
 been proposed by MM. de Beaumont, Fournet, and Durocher. 
 They refer to M. Gaudin's experiments on the fusion of 
 quartz, which show that silex, as it cools, has the property of 
 remaining in a viscous state, whereas alumina never does. 
 This "gelatinous flint" is supposed to retain a considerable 
 degree of plasticity long after the granitic mixture has ac- 
 quired a low temperature. Occasionally we find the quartz 
 and feldspar mutually imprinting their forms on each other, 
 afibrding evidence of the simultaneous crystallization of 
 both.f 
 
 * Delesse, Ann. des Mines, 1852, t. iii., p. 409, and 1848, t. xiii., p. 675. 
 t Bulletin, 2e Eerie, Iv., 1304 ; and D'Arehiac, Hist, des Progrfes de la 
 Geol., i., 38. 
 
GRANITE AND ITS VARIETIES. 555 
 
 A^ordiug to the experiments and observations of Gusta- 
 vus Rose, the quartz of granite has the specific gravity of 
 2-6, which characterizes silica when it is precipitated from a 
 liquid solvent, and not that inferior density, namely, 2-3, 
 which belongs to it when it cools in the laboratory from a 
 state of fusion in what is called the dry way. By some it 
 had been rashly inferred that the manner in which the con- 
 solidation of granite takes place is exceedingly different from 
 the cooling of lavas, and that the intense heat supposed to 
 be necessary for the production of mountain masses of plu- 
 tonic rocks might be dispensed with. But Mr. David Forbes 
 informs me that silica can crystallize in the dry way, and he 
 has found in quartz forming a constituent part of some tra- 
 chytes, both from Guadaloupe and Iceland, glass cavities 
 quite similar to those met with in genuine volcanic minerals. 
 
 These "glass cavities," which with many other kindred 
 phenomena have been carefully studied by Mr. Sorby, are 
 those in which a liquid, on cooling, has become first viscous 
 and then solid without crystallizing or undergoing a definite 
 change in its physical structure. Other cavities which, like 
 those just mentioned, are frequently discernible under the 
 microscope in the minerals composing granitic rocks, are fill- 
 ed, some of them with gas or vapor, others with liquid, and 
 by the movements of the bubbles thus included the distinct- 
 ness of such cavities from those filled with a glassy substance 
 can be tested. Mr. Sorby admits that the frequent occur- 
 rence of fluid cavities in the quartz of granite implies that 
 water was almost always present in the formation of this 
 rock ; but the same may be said of almost all lavas, and it is 
 now more than forty years since Mr. Scrope insisted on the 
 important part which water plays in volcanic eruptions, be- 
 ing so intimately mixed up with the materials of the lava 
 that he supposed it to aid in giving mobility to the fluid 
 mass. It is well known that steam escapes for months, some- 
 times for years, from the cavities of lava when it is cooling 
 and consolidating. As to the result of Mr. Sorby's experi- 
 ments and speculations on this difiicult subject, they may be 
 stated in a few words. He concludes that the physical con- 
 ditions under which the volcanic and granitic rocks ongmate 
 are so far similar that in both cases they combme igneous fu- 
 sion, aqueous solution, and gaseous sublimation— the proof, 
 he says, of the operation of water in the formation of granite 
 being quite as strong as of that of heat.* 
 
 When rocks are melted at great depths water must be 
 present, for two reasons— First, because rain-water and sea- 
 * See Quart. Geol. Jour., vol. xiv., pp. 465, 488. 
 
556 ELEMENTS OF GEOLOGY. 
 
 water are always descending through fissured and porous 
 rocks, and must at length find their way into the regions of 
 subterranean heat ; and secondly, because in a state of com- 
 bination water enters largely into the composition of some 
 of the most common minerals, especially those of the alumi- 
 nous class. But the existence of water under great pressure 
 affords no argument against our attributing an excessively 
 high tempei-ature to the mass with which it is mixed up. 
 Bunsen, indeed, imagines that in Iceland water attains a 
 white heat at a very moderate depth. To what extent some 
 of the metamorphic rocks containing the same minerals as 
 the granites may have been formed by hydrothermal action 
 without the intervention of intense heat comparable to that 
 brought into play in a volcanic eruption, will be considered 
 when we treat of the metamorphic rocks in the thirty-third 
 chapter. 
 
 JPorphyritic Granite. — This name has been sometimes giv- 
 en to that variety in which large crystals of common feld- 
 spar, sometimes more than three inches in length, are scat- 
 tered through an ordinary base of granite. An example of 
 this texture may be seen in the granite of the Land's End, 
 in Cornwall (Fig. 609). The two larger prismatic crystals in 
 
 Fig. 609. 
 
 Porphyritic granite. Land's End, Cornwall. 
 
 this drawing represent feldspar, smaller crystals of which are 
 also seen, similar in form, scattered through the base. In this 
 base also appear black specks of mica, the crystals of which 
 have a more or less perfect hexagonal outline. The remain- 
 der of the mass is quartz, the translucency of which is strong- 
 ly contrasted to the opaqueness of the white feldspar and 
 black mica. But neither the transparency of the quartz nor 
 the silvery lustre of the mica can be expressed in the en- 
 graving. 
 
 The uniform mineral character of large masses of granite 
 seems to indicate that large quantities of the component ele- 
 
VARIETIES OF GRANITE. 557 
 
 ments were thoroughly mixed up together, and then crystal- 
 lized under precisely similar conditions. There are, how- 
 ever, many accidental, or "occasional," minerals, as they are 
 termed, which belong to granite. Among these black schorl 
 or tourmaline, actinolite, zircon, garnet, and fluor spar are not 
 uncommon ; but they are too sparingly dispersed to modify 
 the general aspect of the rock. They show, nevertheless, 
 that the ingredients were not everywhere exactly the same; 
 and a still greater difference may be traced in the ever-vary- 
 ing proportions of the feldspar, quartz, and mica. 
 
 Talcose Granite, or Protogine of the French, is a mixture 
 of feldspar, quartz, and talc. It abounds in the Alps, and in 
 some parts of Cornwall, producing by its decomposition the 
 kaolin or china clay, more than 12,000 tons of which are an- 
 nually exported from that country for the potteries. 
 
 Sohorlrock, and Schorly Granite. — The former of these is 
 an aggregate of schorl, or tourmaline, and quartz. When 
 feldspar and mica are also present, it may be called schorly 
 gl-anite. This kind of granite is comparatively rare. 
 
 M.irite,Feldstone. — Eurite is a rock in which the ingredients 
 of granite are blended into a finely granular mass, mica be- 
 ing usually absent, and, when present, in such minute flakes 
 as' to be invisible to the naked eye. It is sometimes called 
 Feldstone, and when the crystals of feldspar are conspicuous 
 it becomes Feldspar porphyry. All these and other varieties 
 of granite pass into certain kinds of trap — a circumstance 
 which affords one of many arguments in favor of what is 
 now the prevailing opinion, that the granites are also of 
 igneous origin. The contrast of the most crystalline form 
 ol granite to that of the most common and earthy trap is 
 undoubtedly great ; but each member of the volcanic class 
 is capable of becoming porphyritic, and the base of the por- 
 phyry may be more and more crystalline, until the mass 
 passes to the kind of granite most nearly allied in mineral 
 composition. 
 
 Syenitic Granite.— The quadruple compound of quartz, 
 feldspar, mica, and hornblende, may be so termed, and form 
 a passage between the granites and the syenites, ihis rock 
 occurs in Scotland and in Guernsey. , ^. . . „^, , 
 
 Svenite —We now come to the second division ot the plu- 
 tonic rocks, or those having less than 60 per cent, of sihca, 
 and which, as before stated (p. 552), are "^"^lly called syenit- 
 ic Svenite originally received its name from the celebiated 
 LncienCarries^fS^ene, in Egypt. It differs from granUe 
 in having hornblende as a substitute formica, and being with- 
 out quartz- Werner at least considered syenite as a binary 
 
658 ELEMENTS OF GEOLOGY. 
 
 compound of feldspar and hornblende, and regarded quartz 
 as merely one of its occasional minerals. 
 
 Miascite is one of the varieties of syenite most frequently 
 spoken of; it is composed chiefly of orthoclase and nepheline, 
 with hornblende and quartz as occasional accessary miner- 
 als. It derives its name from Miask, in the Ural Mountains, 
 where it was first discovered by Gustavus Rose. Zircon- 
 syenite is another variety closely allied to Miascite, but con- 
 taining crystals of Zircon. 
 
 Connection of the Granites and Syenites with the Volcanic 
 Bocks. — The minerals which constitute alike the plutonic and 
 volcanic rooks consist, almost exclusively, of seven elements, 
 namely, silica, alumina, magnesia, lime, soda, potash, and iron 
 (see Table, p. 499) ; and these may sometimes exist in about 
 the same proportions in a porous lava, a compact trap, and a 
 crystalline granite. The same lava, for example, may be 
 glassy, or scoriaceous, or stony, or porphyritic, according to 
 the more or less rapid rate at which it cools. 
 
 It would be easy to multiply examples and authorities to 
 prove the gradation of the plutonic into the trap rocks. On 
 the western side of the fiord of Christiania, in Norway, there 
 is a large district of trap, chiefly greenstone-porphyry and 
 gyenitic-greenstone, resting on fossiliferous strata. To this, 
 on its southern limit, succeeds a region equally extensive of 
 syenite, the passage from the trappean to the crystalline plu- 
 tonic rock being so gradual that it is imjjossible to draw a 
 line of demarkation between them. 
 
 " The ordinary granite of Aberdeenshire," says Dr. Mac- 
 Culloch, " is the usual ternary compound of quartz, feldspar, 
 and mica; though sometimes hornblende is substituted for 
 the mica. But in many places a variety occurs which is 
 composed simply of feldspar and hornblende ; and in exam- 
 ining more minutely this duplicate compound, it is observed 
 in some places to assume a fine grain, and at length to be- 
 come undistinguishable from the greenstones of the trap 
 family. It also passes in the same uninterrupted manner 
 into a basalt, and at length into a soft clayslone, with a 
 schistose tendency on exposure, in no respect difiering from 
 those of the trap islands of the western coast." The same 
 author mentions, that in Shetland a granite composed of horn- 
 blende, mica, feldspar, and quartz graduates in an equally 
 perfect manner into basalt.* In Hungary there are varieties 
 of trachyte, which, geologically speaking, are of modern ori- 
 gin, in which crystals, not only of mica, but of quartz, are 
 common, together with feldspar and hornblende. It is easy 
 * Syst. of Geol.j vol. i., pp. 157 and 158. 
 
EOCKS ALTEEED BY GEANITE VEINS. 
 
 559 
 
 to conceive how such volcanic masses may, at a certain 
 depth from the surface, pass downward into granite. 
 
 Granitic Veins. — I have ah-eady hinted at the close analogy 
 in the forms of certain granitic and trappean veins ; and it 
 will be found that strata penetrated by plutonic rocks have 
 suffered changes very similar to those exhibited near the 
 contact of volcanic dikes. Thus, in Glen Tilt, in Scotland, 
 alternating strata of limestone and argillaceous schist come 
 in contact with a mass of granite. The contact does not 
 take place as might have been looked for if the granite had 
 been formed there before the strata were deposited, in which 
 case the section would liave appeared as in Fig. 610 ; but 
 the union is as represented in Fig. 611, the undulating out- 
 
 Fig. 610. 
 
 Fig. cu. 
 
 Junction of granite and argillaceous schist in Glen Tilt. (MacCnlloch.)* 
 
 line of the granite intersecting different strata, and occasion- 
 ally intruding itself in tortuous veins into the beds of clay- 
 slate and limestone, from which it differs so remarkably in 
 composition. The limestone is sometimes changed in char- 
 acter by the proximity of the granitic mass or its veins, and 
 acquires a more compact texture, like that of hornstone or 
 chert, with a splintery fracture, and effervescing freely with 
 
 The conversion of the limestone in these and many other 
 instances into a siliceous rock, effervescing slowly with acids, 
 ■would be difficult of explanation, were it not ascertained 
 that such limestones are always impure, containing grains ot 
 quartz, mica, or feldspar disseminated through them Ihe 
 elements of these minerals, when the rock has been subjected 
 to great heat, may have been fused, and so spread more uni- 
 formlv throuafh the whole mass. , , . 
 
 In the Plutonic, as in the volcanic rocks, there is every 
 gradation Irom a tortuous vein to the most regular form of 
 * Geol. Trans., First Series, vol. ui-, pi. 21. 
 
560 
 
 ELEMENTS OF GEOLOGY. 
 
 a dike, such as intersect the tuffs and 
 
 lavas of Vesuvius and Etna. Dikes 
 
 .= of granite may be seen, among other 
 
 places, on the southern flank of Mount 
 
 Battock, one of the Grampians, the 
 '■^[2 opposite walls sometimes preserving 
 '*"' ■" an exact parallelism for a considera- 
 ble distance. As a general rule, 
 however, granite veins in all quarters 
 of the globe are more sinuous in their 
 course than those of trap. They pre- 
 sent similar shapes at the most north- 
 ern point of Scotland, and the south- 
 ernmost extremity of Africa, as the 
 
 Granite veins traversing clay annexed drawings wiU shoW. 
 
 of GiodHope/"™'""' ^"^^ It is not uncommon for one set of 
 granite veins to intersect another ; 
 and sometimes there are three sets, as in the environs of Hei- 
 delberg, where the granite j,j„ gjg 
 on ■ the banks of the river 
 Necker is seen to consist of 
 three varieties, differing in 
 color, gi"ain, and various pe- 
 culiarities of mineral com- 
 position. One of these, 
 which is evidently the sec- 
 ond in age, is seen to cut 
 through an older granite ; 
 and another, still newer, 
 traverses both the second 
 
 and the first. In Shetland Granite veins traversing gneiss, Cape Wrath. 
 , , 1 ■ T r. (MacCulloch.)t 
 
 there are two kinds oi gran- 
 ite. One of them, composed of hornblende, mica, feldspar, 
 and quartz, is of a dark color, and is seen underlying gneiss. 
 The other is a red gi-anite, which penetrates the dark variety 
 everywhere in veins. J 
 
 Fig. 614 is a sketch of a group of granite veins in Corn- 
 wall, given by Messrs. Von Oeynhausen and Von Dechen.§ 
 The main body of the granite here is of a porphyritic appear- 
 ance, with large crystals of feldspar; but in the veins it is fine- 
 grained, and without these large crystals. The general height 
 of the Veins is from 16 to 20 feet, but some are much higher. 
 
 * Captain B. Hall, Trans. Roy. Soc. Edinbui-gh, vol. vii. 
 
 t Westem Islands, pi. 31. 
 
 X MacCuUoch, Syst. of Geol., vol. ii., p. 58. 
 
 § Phil. Mag. and Annals, No. 27, New Series, March, 1829. 
 
ROCKS ALTERED BY GRANITE VEINS. 
 Fig. 614. 
 
 561 
 
 Granite veins passing throngh hornblende slate, Camsilver Cove, Cornvpall. 
 
 Granite, syenite, and those porphyries which have a gra- 
 nitiform structure, in short all plutonic rocks, are frequently 
 observed to contain metals, at or near their junction with 
 stratified formations. On the other hand, the veins which 
 traverse stratified rocks are, as a general law, more metallif- 
 erous near such junctions than in other positions. Hence it 
 has been inferred that these metals may have been spread in 
 a gaseous form through the fused mass, and that the con- 
 tact of another rock, in a different state of temperature, or 
 sometimes the existence of rents in other rocks in the vicini- 
 ty, may have caused the sublimation of the metals.* 
 
 Veins of pure quartz are often found in granite as in many 
 stratified rocks, but they are not traceable, like veins of 
 granite or trap, to large bodies of rock of similar composi- 
 tion. They appear to Fig.cis. 
 have been cracks, into 
 which siliceous matter 
 was infiltered. Such 
 segregation, as it is 
 called, cah sometimes 
 -«learly be shown to 
 have taken place long 
 subsequently to the 
 original consolidation 
 of the containing rock. 
 Thus, for example, I ob- 
 served in the gneiss of 
 Tronstad Strand, near Drammen, in Norway, the annexed sec- 
 tion on the beach. It appears that the alternatmg strata of 
 whitish granitiform gneiss and black hornblende-schist were 
 * Necker, Proceedings of Geol. Soc, No. 26, p. 392. 
 24* 
 
 a, 6. Oiiai-tz vein passing through gneiss and green- 
 stone, Tronstad Strand, near Chrietiania. 
 
562 
 
 ELEMENTS OF GEOLOGY. 
 
 first cut through by a greenstone dike, about 2^ feet wide; 
 then the crack a, b, passed through all these rocks, and was 
 filled up with quartz. The opposite walls of the vein are m 
 some parts incrusted with transparent crystals of quaHz, 
 the middle of the vein being filled up with common opaque 
 white quartz. 
 
 We have seen that the volcanic formations have been called 
 overlying, because they not only penetrate others but spread 
 over them. M. Necker has proposed to call the granites the 
 underlying igneous rocks, and the distinction here indicated 
 is highly characteristic. It was, indeed, supposed by some of 
 the earlier observers that the granite of Christiania, in Nor- 
 way, was intercalated in mountain masses between the pri- 
 mary or palaeozoic strata of that country, so as to overlie 
 fossiliferous shale and limestone. But although the granite 
 sends veins into these fossiliferous rocks, and is decidedly 
 posterior in origin, its actual superposition in mass has been 
 disproved by Professor Keilhau, whose observations on this 
 controverted point I had opportunities, in 1837, of verifying. 
 There are, however, on a smaller scale, certain beds of euritic 
 porphyry, some a few feet, others many yards in thickness, 
 which pass into granite, and deserve, perhaps, to be classed 
 as plutonic rather than trappean rocks, which may truly be 
 _,. „„ described as in- 
 
 terposed con- 
 formably be- 
 tween fossilifer- 
 ous strata, as the 
 porphyries {a, c, 
 Fig. 616) which 
 
 Euritic porphyi'y aitematiug witli primary fossiliferous divide the bitu- 
 strata, near Christiania. ' . , . 
 
 miuous shales 
 and argillaceous limestones, /, f. But some of these same 
 porphyries are partially unconformable, as h, and may lead 
 us to suspect that the others also, notwithstanding their 
 appearance of interstratifieation, have been forcibly in- 
 jected. Some of the porphyritic rocks above mentioned 
 are highly quartzose, others very feldspathic. In propor- 
 tion as the masses are more voluminous, they become more 
 granitic in their texture, less conformable, and even begin 
 to send forth veins into contiguous strata. In a word, we 
 have here a beautiful illustration of the intermediate gra- 
 dations between volcanic and plutonic rocks, not only in 
 their mineralogical composition and structure, but also in 
 their relations of position to associated formations. If the 
 term "overlying" can in this instance be applied to a plu- 
 
GRANITIC ROCKS. 563 
 
 tonic rock, it is only in proportion as that rock begins to ac- 
 quire a trappean aspect. 
 
 It has been already hinted that the heat which in every 
 active volcano extends downward to indefinite depths must 
 produce simultaneously very different effects near the sur- 
 tace and far below it ; and we can not suppose that rocks re- 
 sulting irom the crystallizing of fused matter under a press- 
 ure of several thousand feet, much less several miles, of the 
 earth s crust can exactly resemble those formed at or near 
 the surface. Hence the production at great depths of a class 
 ol rocks analogous to the volcanic, and yet differing in many 
 particulars, might have been predicted, even had we no plu- 
 tonic formations to account for. How well these agree, both 
 in their positive and negative characters, with the theory of 
 their deep subterranean origin, the student will be able to 
 judge by considering the descriptions already given. 
 
 It has, however, been objected, that if the granitic and vol- 
 canic rocks were simply different parts of one great series, 
 we ought to find in mountain chains volcanic dikes passing 
 upward into lava and downward into granite. But we may 
 answer that our vertical sections are usually of small extent ; 
 and if we find in certain places a transition from trap to po- 
 rous lava, and in others a passage from granite to trap, it is 
 as much as could be expected of this evidence. 
 
 The prodigious extent of denudation which has been al- 
 ready demonstrated to have occurred at former periods, will 
 reconcile the student to the belief that crystalline rocks of 
 high antiquity, although deep in the earth's crust when orig- 
 inally formed, may have become uncovered and exposed at 
 the surface. Their actual elevation above the sea may be 
 referred to the same causes to which we have attributed the 
 upheaval of marine strata, even to the summits of some 
 mountain chains. 
 
564 ELEMENTS OF GEOLOGY. 
 
 CHAPTER XXXII. 
 
 ON THE DIFFERENT AGES OF THE PLUTONIC BOCKS. 
 
 Difficulty in ascertaining the precise Age of a Plutonic Eoclc. — Test of Age 
 by Relative Position. — Test by Intrusion and Alteration. — Test by Mineral 
 Composition. — Test by included Eragments. — Recent and Pliocene Pla- 
 tonic Rocks, why invisible. — Miocene Syenite of the Isle of Skye. — Eocene 
 Plutonic Rocks in the Andes. — Granite altering Cretaceous Rocks. — Gran- 
 ite altering Lias in the Alps and in Skye. — Granite of Dartmoor altering 
 Carboniferous Strata. — Granite of the Old Red Sandstone Period. — Syenite 
 altering Silurian Strata in Norway. — Blending of the same with Gneiss. — 
 Most ancient Plutonic Rocks. — Granite protruded in a solid Form. 
 
 When we adopt the igneous theory of granite, as explained 
 in the last chapter, and believe that different plutonic rocks 
 have originated at successive periods beneath the surface of 
 the planet, we must be prepared to encounter greater diffi- 
 culty in ascertaining the precise age of such rocks than in 
 the case of volcanic and fossiliferous formations. We must 
 bear in mind that the evidence of the age of each contempo- 
 raneous volcanic rock was derived either from lavas poured 
 out upon the ancient surface, whether in the sea or in the 
 atmosphere, or from tuffs and conglomerates, also deposited 
 at the surface, and either containing organic remains them- 
 selves or intercalated between strata containing fossils. But 
 the same tests entirely fail, or are only applicable in a modi- 
 iied degree, when we endeavor to fix the chronology of a 
 rock which has crystallized from a state of fusion in the 
 bowels of the earth. In that case we are reduced to the 
 tests of relative position, intrusion, alteration of the rocks in 
 contact, included fragments, and mineral character ; but all 
 these may yield at best a somewhat ambiguous result. 
 
 Test of Age by Relative Position. — Unaltered fossiliferous 
 strata of every age are met with reposing immediately on 
 plutonic rocks ; as at Christiania, in Norway, where the 
 Post-pliocene deposits rest on granite ; in Auvergne, where 
 the fresh-water Miocene strata, and at Heidelberg, on the 
 Rhine, where the New Red sandstone occupy a similar place. 
 In all these, and similar instances, inferiority in position is 
 connected with the superior antiquity of granite. The crys- 
 talline rock was solid before the sedimentary beds were su- 
 perimposed, and the latter usually contain in them rounded 
 pebbles of the subjacent granite. 
 
TEST OF AGE OF PLUTONio RUCKS. 565 
 
 Test by Intrusion and Alteration.— But when plutonic rocks 
 send veins into strata, and alter them near the point of con- 
 tact, in the manner before described (p. 559), it is clear that, 
 like intrusive traps, they are newer than the strata which 
 they invade and alter. Examples of the application of this 
 test will be given in the sequel. 
 
 Test by Mineral Composition.— Notwithstanding a general 
 uniformity in the aspect of plutonic rocks, we have seen in 
 the last chapter that there are many varieties, such as sy- 
 enite, talcose granite, and others. One of these varieties is 
 sometimes found exclusively prevailing throughout an ex- 
 tensive region, where it preserves a homogeneous character; 
 so that, having ascertained its relative age in one place, we 
 can recognize its identity in others, and thus determine from 
 a single section the chronological relations of large mount- 
 ain masses. Having observed, for example, that the syenitic 
 granite of Norway, in which the mineral called zircon 
 abounds, has altered the Silurian strata wherever it is in 
 contact, we do not hesitate to refer other masses of the same 
 zircon-syenite in the south of Norway to a post-Silurian date. 
 Some have imagined that the age of diiferent granites might, 
 to a great extent, be determined by tlieir mineral characters 
 alone ; syenite, for instance, or granite with hornblende, be- 
 ing more modern than common or micaceous granite. But 
 modern investigations have proved these generalizations to 
 bave been premature. 
 
 Test by Included Fragments. — This criterion can rarely be 
 of much importance, because the fragments involved in gran- 
 ite are usually so much altered that they can not be refer- 
 red with certainty to the rocks whence they were derived. 
 In the White Mountains, in North America, according to 
 Professor Hubbard, a granite vein, traversing granite, eon- 
 tains fragments of slate and trap which must have fallen 
 into the "fissure when the fused materials of the vein were 
 injected from below,* and thus the granite is shown to be 
 newer than those slaty and trappean formations from which 
 the fragments were derived.^ 
 
 Recent and Pliocene Plutonic Rocks, why invisible.— The ex- 
 planations already given in the 28th and in the last chapter 
 of the probable relation of the plutonic to the volcanic for- 
 mations, will naturally lead the reader to infer that rocks of 
 the one class can never be produced at or near the surface 
 without some members of the other being formed below. It 
 is not uncommon for lava-streams to require more than ten 
 years to cool in the open air; and where they are ot great 
 * Silliman's Jour., No. C9, p. 123. 
 
566 ELEMENTS OF GEOLOGY. 
 
 depth, a much longer period. The melted matter poured 
 from Jorullo, in Mexico, in the year 115-9, which accumulated 
 in some places to the height of 550 feet, was found to retain 
 a high temperature half a century after the eruption.* We 
 may conceive, therefore, that great masses of subterranean 
 lava may remain in a red-hot or incandescent state in the 
 volcanic foci for immense periods, and the process of refrig- 
 eration may be extremely gradual. Sometimes, indeed, this 
 process may be retarded for an indefinite period by the ac- 
 cession of fresh supplies of heat ; for we find that the lava in 
 the crater of Stromboli, one of the Lipari Islands, has been in 
 a state of constant ebullition for the last two thousand years ; 
 and we may suppose this fluid mass to communicate with 
 some caldron or reservoir of fused matter below. In the Isle 
 of Bourbon, also, where there has been an emission of lava 
 once in every two years for a long period, the lava below 
 can scarcely fail to have been permanently in a state of liq- 
 uefaction. If then it be a reasonable conjecture, that about 
 2000 volcanic eruptions occur in the course of every century, 
 either above the waters of the sea or beneath them,f it will 
 follow that the quantity of plutonic rock generated or in prog- 
 ress during the Recent epoch must already have been con- 
 siderable. 
 
 But as the plutonic rocks originate at some depth in the 
 earth's crust, they can only be rendered accessible to human 
 observation by subsequent upheaval and denudation. Be- 
 tween the period when a plutonic rock crystallizes in the 
 subterranean regions and the era of its protrusion at any 
 single point of the surface, one or two geological periods 
 must usually intervene. Hence, we must not expect to find 
 the Recent or even the Pliocene granites laid open to view, 
 unless we are prepared to assume that saificient time has 
 elapsed since the commencement of the Pliocene period for 
 great upheaval and denudation. A plutonic rock, therefore, 
 must, in general, be of considerable antiquity relatively to 
 the fossiliferous and volcanic formations, before it becomes 
 extensively visible. As we know that the upheaval of land 
 has_ been sometimes accompanied in South America by vol- 
 canic eruptions and the emission of lava, we may conceive 
 the more ancient plutonic rocks to be forced upward to the 
 surface by the newer rocks of the same class formed succes- 
 sively below— subterposition in the plutonic, like superposi- 
 tion in the sedimentary rocks, being usually characteristic 
 of a newer origin. 
 
 * See "Principles," Index, "Jorullo." 
 + Ibid., "Volcanic Eraotions." 
 
PLUTONIC ROCKS. 
 
 56T 
 
 In the accompanying diagram (Fig. 61 "7) an attempt is 
 made to show the inverted order in which sedimentary and 
 
 p,„tomo^fo™..ion. gay ^.-UentphS^ti'at^ocess^: 
 
568 ELEMENTS OF GEOLOGY. 
 
 chain. This protrusion of No. I. has been caused by the ig- 
 neous agency which produced the newer plutonic rocks N"os. 
 n., III., and IV. Part of the primary fossiliferous strata, No. 
 I., have also been raised to the surface by the same gradual 
 process. It will be observed that the Recent strata No. 4 
 and the Recent granite or plutonic rock No. IV. are the most 
 remote from each other in position, although of contempora- 
 neous date. According to this hypothesis, the convulsions 
 of many periods will be required before Recent or Post-ter- 
 tiary granite will be upraised so as to form the highest 
 ridges" and central. axes of mountain-chains. During that 
 time the Recent strata No. 4 might be covered by a great 
 many newer sedimentary formations. 
 
 Miocene Plutonic Bocks. — A considerable mass of syenite, 
 in the Isle of Skye, is described by Dr. MacCulloch as inter- 
 secting limestone and shale, which are of the age of the lias. 
 The limestone, which at a greater distance from the granite 
 contains shells, exhibits no. traces of them near its junction, 
 where it has been converted into a pure crystalline mai-ble.* 
 MacCulloch pointed out that the syenite here, as in Raasay, 
 was newer than the secondary rocks, and Mr. Geikiehas since 
 shown that there is a strong probability that this plutonic 
 rock may be of Miocene age, because a similar Syenite hav- 
 ing a true granitic character in its crystallization has modi- 
 fied the Tertiary volcanic rocks of Ben More, in Mull, some 
 of which have undergone considerable metamorphism. 
 
 Eocene Plutonic Rocks. — In a foi-mer part of this volume 
 (p. 277), the great nummulitic formation of the Alps and 
 Pyrenees was referred to the Eocene period, and it Ibllo.vs 
 that vast movements which have raised those fossiliferous 
 rocks from the level of the sea to the height of more than 
 10,000 feet above its level have taken place since the com- 
 mencement of the Tertiary epoch. Here, therefore, if any- 
 where, we might expect to find hypogene formations of Eo- 
 cene date breaking out in the central axis or most disturbed 
 region of the loftiest chain in Europe. Accordingly, in the 
 Swiss Alps, even the j%sc/i, or upper portion of the nummu- 
 litic series, has been occasionally invaded by plutonic rocks, 
 and converted into crystalline schists of the hypogene class. 
 There can be little doubt that even the talcose granite or 
 gneiss of Mont Blanc itself has been in a fused or pasty state 
 since theflysch was deposited at the bottom of the sea; and 
 the question as to its age is not so much whether it be a sec 
 ondary or tertiary granite' or gneiss, as whether it should be 
 assigned to the Eocene or Miocene epoch. 
 
 — * "Western Islands," vol. i., p. 330. 
 
PLUTONIC ROCKS. 569 
 
 Great upheaving movements have been experienced in the 
 region of the Andes, during the Post-tertiary period. In 
 some part therefore, of this chain, we may expect to discover 
 tertiary plutonic rocks laid open to view; and Mr. Darwin's 
 account of the Chilian Andes, to which the reader may refer 
 fully realizes this expectation : for he shows that we have 
 strong ground to presume that plutonic rocks there exposed 
 on alarge scale are of later date than certain Secondary and 
 Tertiary formations. 
 
 But the theory adopted in this work of the subterranean 
 origin of the hypogene formations would be untenable, if the 
 supposed fact here alluded to, of the appearance of tertiary 
 granite at the surface, was not a rare exception to the general 
 rule. A considerable lapse of time must intervene between 
 the formation of plutonic and metaraorphic rocks in the 
 nether regions and their emergence at the surface. For a 
 long series of subterranean movements must occur before 
 such rocks can be uplifted into the atmosphere or the ocean ; 
 and, before they can be rendered visible to man, some strata 
 which previously covered them must have been stripped off 
 by denudation. 
 
 We know that in the Bay of Baise in 1538, in Cutch in 1819, 
 and on several occasions in Peru and Chili, since the com- 
 mencement of the present century, the permanent upheaval 
 or subsidence of land has been accompanied by the simulta- 
 neous emission of lava at one or more points in the same vol- 
 canic region. From these and other examples it may be in- 
 ferred that the rising or sinking of the earth's crust, opera- 
 tions by which sea is converted into land, and land into sea, 
 are a part only of the consequences of subterranean igneous 
 action. It can scarcely be doubted that this action consists, 
 in a great degree, of the baking, and occasionally the lique- 
 faction, of rocks, causing them to assume, in some cases a 
 larger, in others a smaller volume than before the application 
 of heat. It consists also in the generation of gases, and their 
 expansion by heat, and the injection of liquid matter into 
 rents formed in superincumbent rocks. The prodigious scale 
 on which these subterranean causes have operated in Sicily 
 since the deposition of the Newer Pliocene strata will be ap- 
 preciated when we remember that throughout half the sur- 
 face of that island such strata are met with, raised to the 
 height of from 50 to that of 2000 and even 3000 feet above 
 the level of the sea. In the same island also the older rocks 
 which are contiguous to these marine tertiary strata must 
 have undergone, within the same period, a similar amount ot 
 upheaval. 
 
570 ELEMENTS OF GEOLOGY. 
 
 The like observations may be extended to nearly the whole 
 of Europe, for, since the commencement of the Eocene Period, 
 the entire European area, including some of the central and 
 very lofty portions of the Alps themselves, as I have else- 
 where shown,* has, with the exception of a few districts, 
 emerged from the deep to its present altitude. There must, 
 therefore, have been at great depths in the earth's crust, 
 within the same period, an amount of subterranean change 
 corresponding to this vast alteration of level affecting a 
 Avhole continent. 
 
 The principal effect of subterranean movements during the 
 Tertiary Period seems to have consisted in the upheaval of 
 hypogene formations of an age anterior to the Carboniferous. 
 The repetition of another series of movements, of equal vio- 
 lence, might upraise the plutonic and metamorphic rocks of 
 many secondary periods ; and, if the same force should still 
 continue to act, the next convulsions might bring up to the 
 day the tertiary and recent hj^pogene rocks. In the course 
 of such changes many of the existing sedimentary strata 
 would suffer greatly by denudation, others might assume a 
 metamorphic structure, or become melted down into plutonic 
 and volcanic rocks. Meanwhile the deposition of a great 
 thickness of new strata would not fail to take place during 
 the upheaval and partial destruction of the older rocks. 
 But I must refer the reader to the last chapter but one of 
 this volume for a fuller explanation of these views. 
 
 Plutonic Rocks of Cretaceous Period. — It will be shown in 
 the next chapter that chalk, as well as lias, has been altered 
 j,.^ by granite in the eastern Pyre- 
 
 nees. Whether such granite be 
 
 
 
 cretaceous or tertiary, can not 
 easily be decided. Suppose h, c, 
 d. Fig. 618, to be three members 
 of the Cretaceous series, the low- 
 est of which, h, has been altered 
 by the granite A, the modifying 
 influence not having extended so far as c, or having but 
 slightly affected its lowest beds. Now it can rarely be 
 possible for the geologist to decide whether the beds d 
 existed at the time of the intrusion of A, and alteration of 
 b and c, or whether they were subsequently thrown down 
 upon c. But as some Cretaceous and even tertiary rocks 
 have been raised to the height of more than 9000 feet in 
 the Pyrenees, we must not assume that plutonic formations 
 of the same periods may not have been brought up and ex- 
 * See map of Europe, and explanation, in Principles, book i. 
 
PLUTONIC ROCKS OP OOLITE AND LIAS. 
 
 571 
 
 Fig. 619. 
 
 posed by denudation, at the height of 2000 or 3000 feet on 
 the flanks of that chain. 
 
 Plutonic Rocks of the Oolite and Lias. — In the Department 
 of the Hautes Alpes, in France, M. Elie de Beaumont traced 
 a black argillaceous limestone, charged with belemnites, to 
 within a few yards of a mass of granite. Here the limestone 
 begins to put on a granular texture, but is extremely fine- 
 grained. When nearer the junction it becomes gray, and 
 has a saccharoid structure. In another locality, near Cham- 
 poleon, a granite composed of quartz, black mica, and rose- 
 colored feldspar is ob- 
 served partly to overlie 
 the secondary rocks, 
 producing an altera- 
 tion which extends for 
 about 30 feet down- 
 ward, diminishing in 
 the beds which lie 
 farthest from the gran- 
 ite. (See Fig. 619.) In 
 the altered mass the 
 argillaceous beds are 
 hardened, the lime- 
 stone is saccharoid, the 
 grits quartzose, and in 
 the midst of them is a 
 thin layer of an imper- 
 
 fect granite. It is also junction of granite with Jurassic or Oolite strata lu 
 .& " ^ ■ The Alps, near Champoleou. 
 
 an important circum- loe p , 
 
 stance that near the point of contact, both the granite and the 
 secondary rocks become metalliferous, and contain nests and 
 small veins of blende, galena, iron, and copper pyntes. ihe 
 stratified rocks become harder and more crystalhne, but the 
 granite, on the contrary, softer and less perfectly crystalhzed 
 near the junction.* Although the granite is incumbent in 
 the above section (Fig. 619), we can not assume that ^t ovei- 
 flowed the strata,Vor the disturbances of the vocks a.e so 
 great in this part of the Alps that their original position is 
 
 ^'Tt 'v::Zt, in the Tyrol, secondai-y f^^^^^^^^J^^ 
 are limestones of the Oolitic Penod,have been ta^elsed and 
 
 ■ fee d. B..»..., ..r 1. M..»Bn« * rOl-^ •»■ >■«-. d. ■• S.o. 
 d'Hist. Nat. da Pans, torn. v. 
 
572 ELEMENTS OF GEOLOGY. 
 
 stone is clianged into granular marble, with a band of ser- 
 pentine at the junction.* 
 
 Plutonic Rocks of Carboniferous Period.— The granite of 
 Dartmoor, in Devonshire, was formerly supposed to be one 
 of the most ancient of the plutonic rocks, but is now ascer- 
 tained to be posterior in date to the culm-measures of that 
 county, which from their position, and, as containing true 
 coal-plants, are now known to be members of the true Car- 
 boniterous series. This granite, like the syenitic granite of 
 Christiania, has broken through the stratified formations, on 
 the north-west side of Dartmoor, the successive members of 
 the culm-measures abutting against the granite, and becom- 
 ing metamorphic as they approach. These strata are also 
 penetrated by granite veins, and plutonic dikes, called "el- 
 vans."f The granite of Cornwall is probably of the same 
 date, and, therefore, as modern as the Carboniferous strata, 
 if not newer. 
 
 Plutonic Eocks of Silurian Period. — It has long been known 
 that a very ancient granite near Christiania, in Norway, is 
 posterior in date to the Lower Silurian strata of that region, 
 although its exact j)osition in the Palaeozoic series can not 
 be defined. Von Buch first announced, in 1813, that it was 
 of newer origin than certain limestones containing orthocerata 
 and trilobites. The proofs consist in the penetration of gran- 
 ite veins into the shale and limestone, and the alteration of 
 the strata, for a considerable distance from the point of con- 
 tact, both of these veins and the central mass from which 
 they emanate. (See p. 562.) Von Buch supposed that the 
 plutonic rock alternated with the fossilifeTous strata, and 
 that large masses of granite were sometimes incumbent 
 upon the strata; but this idea was erroneous, and arose from 
 the fact that the beds of shale and limestone often dip to- 
 wards the granite up to the point of contact, appearing as if 
 they would pass under it in mass, as at a, Fig. 620, and then 
 
 Piff. 020. 
 
 Silurian. Granite. Silurian strata. 
 
 again on the opposite side of the same mountain, as at b, dip 
 away from the same granite. When the junctions, however, 
 are carefully examined, it is found that the plutonic rock in- 
 
 * Von Buch, Annales de Chimie, etc. 
 
 t Proceed. Geol. Sec, vol. ii., p. 562 : and Trans., 2d ser., vol. v., p. 686. 
 
PLUTONIC ROCKS OE SILURIAN PERIOD. 673 
 
 trudes itself in veins, and nowhere covers the fossiliferous 
 strata in large overlying masses, as is so conmionly the case 
 with trappean formations.* 
 
 Now this granite, which is more modern than the Silurian 
 strata of Norway, also sends veins in the same country into 
 an ancient formation of gneiss ; and the relations of the plu- 
 tonic rock and the gneiss, at their junction, are full of inter- 
 est when we duly consider the wide difference of epoch which 
 must have separated their origin. 
 
 The length of this interval of time is attested by the fol- 
 lowing facts : The fossiliferous, or Silurian, beds rest uncon- 
 formably upon the truncated edges of the gneiss, the inclined 
 strata of which had been denuded before the sedimentary 
 beds were superimposed (see Fig. 621). The signs of denu- 
 
 Fig. 621. 
 
 Gneiss. Granite. Gneiss. 
 
 Gneiss. Granite. u..e.~. 
 
 Granite sending veins into Silurian strata and Gneiss. Christiauia, Norway. 
 a. Inclined gneiss, b. Silurian strata. 
 
 dation are twofold ; first, the surface of the gneiss is seen oc- 
 casionally, on the removal of the newer beds containing or- 
 ganic remains, to be worn and smoothed; secondly, pebbles 
 of gneiss have been found in some of these Silurian strata. 
 Between the origin, therefore, of the gneiss and the granite 
 there intervened, first, the period when the strata of gneiss 
 were denuded; secondly, the period of the deposition of the 
 Silurian deposits upon the denuded and mclined gneiss, a. 
 Yet the granite produced after this long interval is often so 
 intimately blended with the ancient gneiss, at the point of 
 iunction,that it is impossible to draw any other than an a - 
 bitrary line of separation between them; ^nd where thi is 
 not the case, tortuous veins of granite pass f^-eely through 
 gneiss, ending sometimes in threads, as if J- °J<i^-; ^^l^^^^^ 
 offered no resistance to their passage These appeaiances 
 
 5^£tioLib^^^^^^^^^ 
 
 "*?•'/ r'*o7theTnis^UTheTnjectLn of this granite we 
 SfhTv: susp^eftrdYa? the gneis was scarcely solidified, 
 1 See the G»a Norvegica and other works of KeUhau, with whom I ex- 
 amined this countiT- 
 
5^4 ELEMENTS OF GEOLOGY. 
 
 or had not yet assumed its complete metamorphic charactei 
 when invaded by the plutonic rock. From this example W6 
 may learn how impossible it is to conjecture whether certain 
 granites in Scotland, and other countries, which send veins into 
 gneiss and other metamorphic rocks, are primary, or whether 
 they may not belong to some secondary or tertiary period. 
 
 Oldest Granites. — It is not half a centui-y since the doctrine 
 was very general that all granitic rocks were ^imitive, that 
 is to say, that they originated before the deposition of the 
 first sedimentary strata, and before the creation of organic 
 beings (see above, p. 34). But so greatly are our views now 
 changed, that we find it no easy task to point out a single 
 mass of granite demonstrably more ancient than known fos- 
 siliferous deposits. Could we discover some Laurentian 
 strata resting immediately on gi-anite, there being no altera- 
 tions at the point of contact, nor any intersecting granitic 
 veins, we might then afiirni the plutonic rock to have origi- 
 nated before the oldest known fbssiliferous strata. Still it 
 would be presumptuous, as we have already pointed out (p. 
 464), to suppose that when a small part only of the globe 
 has been investigated, we are acquainted with the oldest fos- 
 siliferous strata in the crust of our planet. Even when these 
 are found, we can not assume that there never were any an- 
 tecedent strata containing organic remains, which may have 
 beconae metamorphic. If we find pebbles of granite in a con- 
 glomerate of the Lower Laurentian system, we may then feel as- 
 sured that the parent granite was formed before the Laurentian 
 formation. But if the incumbent strata be merely Cambrian 
 or Silurian, the fundamental granite, although of high antiqui- 
 ty) may be posterior in date to kncnon fossiltferous formations. 
 
 Protrusion of solid Granite.— In part of Sutherlandshire, 
 near Brora, common granite, composed of feldspar, quartz, 
 and mica is in immediate contact with Oolitic strata, and 
 has clearly been elevated to the surface at a period subse- 
 quent to the deposition of those strata.* Professor Sedg- 
 wick and Sir R. Murchison conceive that this granite has 
 been upheaved in a solid form ; and that in breaking through 
 the submarine deposits, with which it was not perhaps orig- 
 inally in contact, it has fractured them so as to form a breccia 
 along the line of junction. This breccia consists of fragments 
 of shale, sandstone, and limestone, with fossils of the' oolite, 
 all united together by a calcareous cement. The secondary 
 strata at some distance from the granite are but slightly dis- 
 turbed, but in proportion to their proximity the amount of 
 dislocation becomes greater. 
 
 * Mureliison, Geol. Trans., 2d series, vol. ii., p. 307. 
 
PEOTKUSION OF SOLID GRANITE. 5 '75 
 
 Mr. T. McKenney Hughes has suggested to me in explana- 
 tion of these phenomena that they may be the effect of the 
 association of more pliant strata with hard unyielding rocks, 
 the whole of which were subjected simultaneously to great 
 movements, whether of elevation or subsidence, and of lateral 
 pressure, during which the more solid granite, being incapa- 
 ble of compression, was forced through the softer beds of 
 shale, sandstone, and limestone. He remarks that similar 
 breccias with slickensides are observed on a minor scale 
 where rocks of different composition and rigidity are con- 
 torted together. Such protrusion may have been brought 
 about by degrees by innumerable shocks of earthquakes re- 
 peated after long intervals of time along the same tract of 
 country. The opening of new fissures in the hardest rocks 
 is a frequent accompaniment of such convulsions, and during 
 the consequent vibrations, breccias must often be caused. 
 But these catastrophes, as we well know, do not imply that 
 the land or sea of the disturbed region are rendered unin- 
 habitable by living beings, and by no means indicate a state 
 of things different from that witnessed in the ordinary course 
 of nature. 
 
576 ELEMENTS OF GEOLOGY. 
 
 CHAPTER XXXIII. 
 
 METAMOEPHIC EOCKS. 
 
 General Character of Metamorphic Rocks. — Gneiss. — Hornblende-schist. — 
 Serpentine. — Mica - schist. ^ — Clay - slate. ^ — Quartzite. — Chlorite - schist. — 
 Metamorphic Limestone. — Origin of the metamorphic Strata. — Their 
 Stratification; — Fossiliferous Strata near intrusive Masses of Granite con- 
 verted into Kocks identical with different Members of the metamorphic 
 Series. — Arguments hence derived as to the Nature of Plutonic Action. — ■ 
 Hydrothermal Action, or the Influence of Steam and Gases in producing 
 Metamorphism. — Objections to the metamorphic Theory considered. 
 
 We have now considered three distinct classes of rocks : 
 first, the aqueous, or fossiliferous; secondly, the volcanic; 
 and, thirdly, the plutonic ; and it remains for us to examine 
 those crystalline (or hypogene) strata to which the name of 
 metamorphic has been assigned. The last-mentioned term 
 expresses, as before explained, a theoretical opinion that such 
 strata, after having been deposited from water, acquired, by 
 the influence of heat and other causes, a highly crystalline 
 texture. They who still question this opinion may call the 
 rocks under consideration the stratified hypogene formations 
 or crystalline schists. 
 
 These rocks, when in their characteristic or normal state, 
 are wholly devoid of organic remains, and contain no dis- 
 tinct fragments of other rocks, whether rounded or angular. 
 They sometimes break out in the central parts of mountain 
 chains, but in other cases extend over areas of vast dimen- 
 sions, occupying, for example, nearly the whole of Norway 
 and Sweden, where, as in Brazil, they appear alike in the 
 lower and higher grounds. However crystalline these rocks 
 may become in certain regions, they never, like granite, or 
 trap, send veins into contiguous formations. In Great Brit- 
 ain, those members of the series which approach most nearly 
 to granite in their composition, as gneiss, mica-schist, and 
 hornblende-schist, are confined to the country north of the 
 rivers Forth and Clyde. 
 
 Many attempts have been made to trace a general order 
 of succession or superposition in the members of this family ; 
 clay-slate, for example, having been often supposed to hold 
 invariably a higher geological position than mica-schist, and 
 
MET AMORPHIC ROCKS. 577 
 
 mica-schist^ to overlie gneiss. But although such an order 
 may prevail throughout limited districts, it is by no means 
 rwt VvvTr^'' subject, however, I shall again revert, in 
 Chapter XXXV., where the chronolog-cal relations o^ the 
 metamorphic rocks are pointed out. 
 
 Principal Metamorphio Rocks.— The following may be enu- 
 merated as the principal members of the metamorphio 
 class :— gneiss, mica-schist, hornblende-schist, clay-slate, chlo- 
 nte-schist, hypogene or metamorphio limestone, and certain 
 kinds of quartz-rock or quartzite. 
 
 Gneiss.— The first of these, gneiss, may be called stratified 
 —or by those who object to that term, foliated— granite, be- 
 ing formed of the same materials as granite, namely, feld- 
 spar, quartz, and mica. In the specimen here figured, the 
 white layers consist almost exclusively of granular feldspar, 
 with here and there a speck of mica and grain of quartz. 
 The dark layers are composed of gray quartz and black mica, 
 with occasionally a grain of feldspar intermixed. The rock 
 
 Fig. «22. 
 
 Fragment of gneiss, natural size ; eection made at right angles to the 
 planes of foliation. 
 
 splits most easily in the plane of these darker layers, and the 
 surface thus exposed is almost entirely covered with shining 
 spangles of mica. The accompanying quartz, however, great- 
 ly predominates in quantity, but the most ready cleavage is 
 determined by the abundance of mica in certain parts of the 
 dark layer. Instead of consisting of these thin laminae, gneiss 
 is sometimes simply divided into thick beds, in which the 
 mica has only a slight degree of parallelism to the planes of 
 stratification. 
 
 Hand specimens may often be obtained from such gneiss 
 which are undistinguishable from granite, affording an argu- 
 ment to which we shall allude in the concluding part of this 
 chapter, in favor of those who regard all granite and syenite 
 not as igneons rocks, but as aqueous formations so altered as 
 to have lost all signs of their original stratified arrangement. 
 Gneiss in geoloo-y is commonly used to designate not merely 
 
 25 
 
5 -7 8 ELEMENTS OF GEOLOGY. 
 
 stratified and foliated rocks having the same component ma- 
 terials as granite or syenite, but also in a wider sense to em- 
 brace the formation with which other members of the meta- 
 morphic series, such as hornblende-schist, may alternate, and 
 which are then considered subordinate to the true gneiss. 
 
 The different varieties of rock allied to gneiss, into which 
 feldspar enters as an essential ingredient, will be understood 
 by referring to what was said of granite. Thus, for example, 
 hornblende may be superadded to mica, quartz, and feldspar, 
 forming a hornblendio or syenitic gneiss; or talc may be 
 substituted for mica, constituting talcose gneiss (called strat- 
 ified protogine by the French), a rock composed of feldspar, 
 quartz, and talc, in distinct crystals or grains. 
 
 Ewrite, which has already been mentioned as a plutonic 
 rook, occurs also with precisely the same composition in beds 
 subordinate to gneiss or mica-slate. 
 
 Hornbknde-schist is usually black, and composed princi- 
 pally of hornblende, with a variable quantity of feldspar, and 
 sometimes grains of quartz. When the hornblende and feld- 
 spar are in nearly equal quantities, and the rock is not slaty, 
 it corresponds in character with the greenstones of the trap 
 family, and has been called " primitive greenstone." It may 
 be termed hornblende rock, or amphibolite. Some of these 
 hornblendic masses may really have been volcanic rocks, 
 which have since assumed a more crystalline or metamorphic 
 texture. 
 
 Serpentine is a greenish rock, a silicate of magnesia, in 
 which there is sometimes from 30 to 40 per cent, of magne- 
 sia. It enters largely into the composition of a trap dike cut- 
 ting through Old Red Sandstone in Forfarshire, and in that 
 case is probably an altered basaltic dike which had contained 
 much .olivine. The theory of its having been originally a 
 volcanic product subsequently altered by metamorphism 
 may at first sight seem inconsistent with its occurrence in 
 large and regularly stratified masses in the metamorphic se- 
 ries in Scotland, as in Aberdeenshire. But it has been sug- 
 gested in explanation that such serpentine may have been 
 oi'iginally regularly-bedded trap tuff, and volcanic breccia, 
 with much olivine, which would still retain a stratified ap- 
 pearance after their conversion into a metamoi'phic rock. 
 
 Actinolite Schist is a slaty foliated rock, composed chiefly 
 of actinolite, an emerald-green mineral, allied to hornblende, 
 with some admixture of garnet, mica, and quartz. 
 
 Mica-schist or Micaceous Schist, is, next to gneiss, one of 
 tliG most abundant rocks of the metamorphic series. It is 
 slaty, essentially composed of mica and quartz, the mica 
 
METAMORPHIC ROCKS. 579 
 
 sometimes appearing to constitute the whole mass. Beds of 
 pure quartz also occur in this formation. In some districts 
 garnets in regular twelve-sided crystals form an integrant 
 part of mica-schist. This rock passes by insensible grada- 
 tions into clay-slate. 
 
 Olay-slate— Argillaceous Schist — ArgiUite. —Tir\s rock 
 sometimes resembles an indurated clay or shale. It is for 
 the most part extremely fissile, often affording good roofing- 
 slate. Occasionally it derives a shining and silky lustre 
 from the minute particles of mica or talc which it contains. 
 It varies from greenish or bluish-gray to a lead color; and it 
 may be said of this, more than of any other schist, that it is 
 common to the metamorphic and fossiliferous series, for some 
 clay-slates taken from each division would not be distin- 
 guishable by mineral characters alone. It is not uncommon 
 to meet with an argillaceous rock having the same composi- 
 tion, without the slaty cleavage, which may be called argillite. 
 
 Chlorite schist is a green slaty rock, in which chlorite is 
 abundant in foliated plates, usually blended with minute 
 grains of quartz, or sometimes with feldspar or mica ; often 
 associated with, and graduating into, gneiss and clay-slate. 
 
 Qiiartzite, or Quartz Hock, is an aggregate of grains of 
 quartz which are either in minute crystals, or in many cases 
 slightly rounded, occurring in regular strata, associated with 
 gneiss or other metamorphic rocks. Compact quartz, like 
 that so frequently found in veins, is also found together with 
 granular quartzite. Both of these alternate with gneiss or 
 mica-schist, or pass into those rocks by the addition of mica, 
 or of feldspar and mica. 
 
 Crystalline or Metamorphic Limestone. — This hypogene 
 rock, called by the earlier geologists primary limestone, is 
 sometimes a white crystalline granular marble, which when 
 in thick beds can be used in sculpture ; but more frequently 
 it occurs in thin beds, forming a foliated schist much resem- 
 bling in color and arrangement certain varieties of gneiss and 
 mica-schist. When it alternates with these rocks, it often 
 contains some crystals of mica, and occasionally quartz, feld- 
 spar, hornblende, talc, chlorite, garnet, and other minerals. 
 It enters sparingly into the structure of the hypogene dis- 
 tricts of Norway, Sweden, and Scotland, but is largely de- 
 veloped in the Alps. . 
 
 Origin of the Metamorphic Strata.— Having said thus much 
 of the mineral composition of the metamorphic rocks, I may 
 combine what remains to be said of their structure and his- 
 tory with an account of the opinions entertained of then- 
 probable origin. At the same time, it may be well to fore- 
 
gg(j ELEMENTS OF GEOLOGY. 
 
 warn the reader that we are here entering upon ground of 
 cont^-oversy, and soon reach the limits where positive induc- 
 tion ends, and beyond which we can only indulge in specula- 
 tions It was once a favorite doctrine, and is still maintain- 
 ed by many, that these rocks owe their crystalline texture, 
 their want of all signs of a mechanical origin, or of fossil cou- 
 tents, to a peculiar and nascent condition of the planet at the 
 period of their formation. The arguments in refutation of 
 this hypothesis will be more fully considered when I show, in 
 Chapter XXXV., to how many different ages the metamor- 
 phic formations are referable, and how gneiss, mica-schist, 
 clay-slate, and hypogene limestone (that of Carrara, for ex- 
 ample) have been formed, not only since the first introduc- 
 tion of organic beings into this planet, but even long after 
 many distinct races of plants and anitpals had flourished and 
 passed away in succession. 
 
 The doctrine respecting the crystalline strata implied in 
 the name raetamorphic may properly be treated of in this 
 place ; and we must first inquire whether these rocks are 
 really entitled to be called stratified in the strict sense of 
 having been originally deposited as sediment from water. 
 The general adoption by geologists of the term stratified, as 
 applied to these rocks, sufficiently attests their division into 
 beds very analogous, at least in form, to ordinary fossilifer- 
 ous strata. This resemblance is by no means confined to the 
 existence in both occasionally of a laminated structure, hut 
 extends to every kind of arrangement which is compatible 
 with the absence of fossils, and of sand, pebbles, ripple-mark, 
 and other characters which the metamorphic theory supposes 
 to have been obliterated by plutonic action. Thus, for ex- 
 ample, we behold alike in the crystalline and fossiliferous 
 formations an alternation of beds varying greatly in compo- 
 sition, color, and thickness. We observe, for instance, gneiss 
 alternating with layers of black hornblende - schist or of 
 green chlorite-schist, or with granular quartz or limestone ; 
 and the interchange of these different strata may be repeat- 
 ed for an indefinite number of times. In the like manner, 
 mica-schist alternates with chlorite-schist, and with beds of 
 pure quartz or of granular limestone. We have already seen 
 that, near the immediate contact of granitic veins and vol- 
 canic dikes, very extraordinary alterations in rocks have 
 taken place, more especially in the neighborhood of granite. 
 It wUl be useful here to add other illustrations, showing that 
 a texture undistinguishable from that which characterizes 
 
 leluluuJu7/,^fr-'' ™^*f«i°rphic formations has actually 
 Deen supeunduced m strata once fossiliferous. 
 
STRATA IN CONTACT WITH GRANITE. 581 
 
 Possiliferous Strata rendered metamorpMo by intrusive Mass- 
 es ol Granite.— In the southern extremity of Norway there is 
 a large district, on the west side of the fiord of Christiania, 
 which I visited in 183-7 with the late Professor Keilhau, in 
 which syenitic granite protrudes in mountain masses through 
 fossiiilerous strata, and usually sends veins into them at the 
 point of contact. The stratified rocks, replete with shells 
 and zoophytes, consist chiefly of shale, limestone, and some 
 sandstone, and all these are invariably altered near the gran- 
 ite for a distance of from 50 to 400 yards. The aluminous 
 shales are hardened, and have hecome flinty. Sometimes 
 they resemble jasper. Ribboned jasper is produced by the 
 hardening of alternate layers of green and chocolate-colored 
 schist, each stripe faithfully representing the original lines 
 of stratification. Nearer the granite the schist often con- 
 tains crystals of hornblende, which are even met with in 
 some places for a distance of several hundred yards from the 
 junction; and this black hornblende is so abundant that 
 eminent geologists, when passing through the country, have 
 confounded it with the ancient hornblende-schist, subordinate 
 to the great gneiss formation of Norway. Frequently, be- 
 tween the granite and the hornblende-slate above mentioned, 
 grains of mica and crystalline feldspar appear in the schist, 
 so that rocks resembling gneiss and mica-schist are produced. 
 Fossils can rarely be detected in these schists, and they are 
 more completely effaced in proportion to the more crystalline 
 texture of the beds, and their vicinity to the granite. In 
 
 Pig. G23. 
 
 Graund-plan of altered sl«te »->/«"«?»?"«"?»'• g:»""f;„,PSn^^^^ '^"^ ^™^' 
 ■ indicate the dip, and the oblique lines the stake ol the Deae. 
 
 some places the siliceous matter of the schist becomes a 
 granular quartz; and when hornblende and mica are added, 
 the altered rock loses its stratification, and passes into a 
 kind of granite. The limestone, which at points remot.o 
 
582 ELEMENTS OF GEOLOGY. 
 
 from the granite is of an earthy textui-e and blue color, and 
 often abounds in corals, becomes a white granular marble 
 near the granite, sometimes siliceous, the granular structure 
 extending occasionally upward of 400 yards from the junc- 
 tion ; the corals being for the most part obliterated, though 
 sometimes preserved, even in the white mai'ble. Both the 
 altered limestone and hardened slate contain garnets in 
 many places, also ores of iron, lead, and copper, with some 
 silver. These alterations occur equally whether the granite 
 invades the strata in a line parallel to the general strike of 
 the fossiliferous beds, or in a line at right angles to their 
 strike, both of which modes of junction will be seen by the 
 accompanying ground-plan (Fig. 623).* 
 
 The granite of Cornwall sends forth veins into a coarse 
 argillaceous-schist, provincially termed killas. This killas is 
 converted into hornblende-schist near the contact with the 
 veins. These appearances are well seen at the junction of 
 the granite and killas, in St. Michael's Mount, a small island 
 nearly 300 feet high, situated in the bay, at a distance of 
 about three miles from Penzance. The granite of Dartmoor, 
 in Devonshire, says Sir H. De la Beche, has intruded itself 
 ' into the carboniferous slate and slaty sandstone, twisting 
 and contorting the strata, and sending veins into them. 
 Hence some of the slate rocks have become " micaceous ; oth- 
 ers more indurated, and with the characters of mica-slate and 
 gneiss ; while others again appear converted into a hard 
 zoned rock strongly impregnated with feldspar."f 
 
 We learn from the investigation of M. Dufrenoy that in 
 the eastern Pyrenees there are mountain masses of granite 
 posterior in date to the formations called lias and chalk of 
 that district, and that these fossiliferous rocks are greatly 
 altered in texture, and often charged with iron-ore, in the 
 neighborhood of the granite. Thus in the environs of St. 
 Martin, near St. Paul de Fenouillet, the chalky limestone be- 
 comes more crystalline and saccharoid as it approaches the 
 granite, and loses all trace of the fossils which it previously 
 contained in abundance. At some points, also, it becomes 
 dolomitic, and filled with small veins of carbonate of iron, 
 and spots of red iron-ore. At Rancie the lias nearest the 
 granite is not only filled with iron-ore, but charged with py- 
 rites, tremolite, garnet, and a new mineral somewhat allied 
 to feldspar, called, from the place in the Pyrenees where it 
 occurs, "couzeranite." 
 
 " Hornblende-schist," says Dr. MacCulloch, " may at first 
 have been mere clay ; for clay or shale is found altered by 
 
 * Keilhau, GiJea Norvegica, pp. 61-63. t Geol. Manual, p. 479. 
 
ALTERATIONS OF STRATA. 583 
 
 trap into Lydian stone, a substance differing from horn- 
 blende-schist almost solely in compactness and uniformity 
 of texture."* " In Shetland," remarks the same author, " ar- 
 gillaceous-schist (or clay-slate), when in contact with gran- 
 ite, is sometimes converted into hornblende-schist, the schist 
 becoming first siliceous, and ultimately, at the contact, horn- 
 blende-schist." In like manner gneiss and mica-schist may 
 be nothing more than altered micaceous and argillaceous 
 sandstones, granular quartz may have been derived from si- 
 liceous sandstone, and compact quartz from the same mate- 
 rials. Clay-slate may be altered shale, and granular marble 
 may have originated in the form of ordinary limestone, re- 
 plete with shells and corals, which have since been oblitei'- 
 ated ; and, lastly, calcareous sands and marls may have been 
 changed into impure crystalline limestones. 
 
 The anthracite and plumbago associated with hypogene 
 rocks may have been coal ; for not only is coal converted into 
 anthracite in the vicinity of some trap dikes, but we have 
 seen that a like change has taken place generally even far 
 from the contact of igneous rocks, in the disturbed region of 
 the Appalachians. At Worcester, in the State of Massa- 
 chusetts, 45 miles due west of Boston, a bed of plumbago 
 and impure anthracite occurs, interstratified with mica-schist. 
 It is abovit two feet in thickness, and has been made use of 
 both as fuel, and in the manufacture of lead pencils. At the 
 distance of 30 miles from the plumbago, there occurs, on the 
 borders of Rhode Island, an impure anthracite in slates con- 
 taining impressions of coal-plants of the genera Pecopteris, 
 Muropteris, Culamites, etc. This anthracite is intermediate 
 in character between that of Pennsylvania and the plumbago 
 of Worcester, in which last the gaseous or volatile niatter 
 (hydrogen, oxygen, and nitrogen) is to the carbon only in the 
 proporrion of three per cent. After traversing the country 
 in various directions, I came to the conclusion that the car- 
 boniferous shales or slates with anthracite and plants, which 
 in Rhode Island often pass into mica-schists, have at Wor- 
 cester assumed a perfectly crystalline and metamorphic tex- 
 ture; the anthracite having been nearly transmuted into 
 that state of pure carbon which is called plumbago or 
 
 Sfraphite.f , ., -, • j i • 
 
 Now the alterations above described as superinduced in 
 rocks by volcanic dikes and granite veins prove incontesta- 
 blv that powers exist in nature capable of transforming fos- 
 Biliferous into crystalline strata, a very few simple elements 
 
 * Syst. of Geol., vol. i., pp. 210, 211. 
 
 t See Lyell, Quart. Geol. Joum., vol. i., p. 199. 
 
584 ELEMENTS OF GEOLOGY. 
 
 constituting the component materials common to both class- 
 es of rocks. These elements, which are enumerated in our 
 table, p. 499, may be made to form new combinations by 
 what has been termed plutonic action, or those chemical 
 changes which are no doubt connected with the passage of 
 heat, and usually heated steam and waters, through the strata. 
 
 Hydrothermal Action, or the Influence of Steam and Gases 
 in producing Metamorphism. — The experiments of Gregory 
 Watt, in fusing rocks in the laboratory, and allowing them 
 to consolidate by slow cooling, prove distinctly that a rock 
 need not be perfectly melted in order that a re-arrangement 
 of its component particles should take place, and a partial 
 crystallization ensue.* We may easily suppose, therefore, 
 that all traces of shells and other organic i-emains may be 
 destroyed, and that new chemical combinations may arise, 
 without the mass being so fused as that the lines of stratifi- 
 cation should be wholly obliterated. We must not, how- 
 ever, imagine that heat alone, such as may be applied to a 
 stone in the open air, can constitute all that is comprised 
 in plutonic action. We know that volcanoes in eruption 
 not only emit fluid lava, but give off steam and other heated 
 gases, which rush out in enormous volume, for days, weeks, 
 or years continuously, and are even disengaged from lava 
 during its consolidation. . 
 
 We also know that long after volcanoes have spent their 
 force, hot springs continue for ages to flow out at various 
 points in the same area. In regions, also, subject to violent 
 earthquakes such springs are frequently observed issuing 
 from rents, usually along lines of fault or displacement 
 of the rocks. These thermal waters are most commonly 
 charged with a variety of mineral ingredients, and they re- 
 tain a remarkable uniformity of temperature from century to 
 century. A like uniformity is also persistent in the nature 
 of the earthy, metallic, and gaseous substances with which 
 they are impregnated. It is well ascertained that springs, 
 whether hot or cold, charged with carbonic acid, and espe- 
 cially with hydrofluoric acid, which is often present in small 
 quantities, are powerful causes of decomposition and chem- 
 ical reaction in rocks through which they percolate. 
 
 The changes which Daubree has shown to have been pro- 
 duced by the alkaline waters of Plombi^res in the Vosges, 
 are more especially instructive.! These waters have a heat 
 of 160° r., or an excess of 109° above the average tempera- 
 ture of ordinar)' springs in that district. They were con- 
 
 * Phil. Trans., 1804. 
 
 t Daubree, Snr le Metamorphisme. Paris, 1860. 
 
PLUTONIC ACTION. 685 
 
 veyed hj the Romans to baths through long conduits or 
 aqueducts. The foundations of some of their works consist- 
 ed of a bed of concrete made of lime, fragments of brick, and 
 sandstone. Through this and other masonry the hot waters 
 have been percolating for centuries, and have given rise to 
 various zeolites — apophyllite and chabazite among others; 
 also to calcareous spar, arragonite, and fluor spar, together 
 with siliceous minerals, such as opal — all found in the inter- 
 spaces of the bricks and mortar, or constituting part of their 
 re-arranged materials. The quantity of heat brought into 
 action in this instance in the course of 2000 years has, no 
 doubt, been enormous, but the intensity of it developed at 
 any one moment has been always inconsiderable. 
 
 From these facts and from the experiments and observa- 
 tions of Senarmont, Daubree, Delesse, Scheerer, Sorby, Sterry 
 Hunt, and others, we are led to infer that when in the bowels 
 of the earth there are large volumes of matter containing wa- 
 ter and various acids intensely heated under enormous press- 
 ure, these subterranean fluid masses will gradually part with 
 their heat by the escape of steam and various gases through 
 fissures, producing hot springs ; or by the passage of the 
 same through the pores of the overlying and injected rocks. 
 Even the most compact rocks may be regarded, before they 
 have been exposed to the air and dried, in the light of sponges 
 filled with water. According to the experiments of Henry, 
 water, under a hydrostatic pressure of 96 feet, will absorb 
 three times as much carbonic acid gas as it can under the 
 ordinary pressure of the atmosphere. There are other gases, 
 as well as the carbonic acid, which water absorbs, and more 
 rapidly in proportion to the amount of pressure. Although 
 the gaseous matter first absorbed would soon be condensed, 
 and part with its heat, yet the continual arrival of fresh sup- 
 plies from below might, in the course of ages, cause the tem- 
 perature of the water, and with it that of the contaming 
 rock, to be materially raised ; the water acts not only as a 
 vehicle of heat, but also by its affinity for various silicates, 
 which, when some of the materials of the invaded rocks are 
 decomposed, form quartz, feldspar, mica, and other minerals. 
 As for quartz, it can be produced under the influence of heat 
 by water holdino- alkaline silicates in solution, as in the case 
 of th€ Plorabiferes springs. The quantity of water required, 
 according to Daubree, to produce great transformations in 
 the mineral structure of rocks, is very small As to the 
 heat required, silicates may be produced m the moist way 
 at about incipient red heat, whereas to form the same in the 
 dry way would require a much higher temperature.. 
 
 25* 
 
g86 ELEMENTS OF GEOLOGY. 
 
 M. Fournet, in his description of the metalliferous gneiss 
 near Clermont, in Auvergne, states that all the minute fis- 
 sures of the rock are quite saturated with free carbonic acid 
 gas ; which gas rises plentifully from the soil there and in 
 many parts of the surrounding country. The various ele- 
 ments of the gneiss, with the exception of the quartz, are all 
 softened ; and new combinations of the acid with lime, iron, 
 and manganese are continually in progress.* 
 
 The power of subterranean gases is well illustrated by the 
 stufas of St. Calogero in the Lipari Islands, where the hori- 
 zontal strata of tuffs, forming cliffs 200 feet high, have been 
 discolored in places by the jets of steam often above the boil- 
 ing point, called " stufas," issuing from the fissures ; and 
 similar instances are recorded by M. Virlet of corrosion of 
 rocks near Corinth, and by Dr. Daubeny of decomposition 
 of trachytic rooks by sulphureted hydrogen and muriatic 
 acid gases in the Solfatara, near Naples. In all these in- 
 stances it is clear that the gaseous fluids must have made 
 their way through vast thicknesses of porous or fissured 
 rocks, and their modifying influence may spread through the 
 crust for thousands of yards in thickness. 
 
 It has been urged as an argument against the metamor- 
 phic theory, that rocks have a small power of conductinj^ 
 heat, and it is true that when dry, and in the air, they differ 
 remarkably from metals in this respect. The syenite of Nor- 
 way, as we have seen, p. 558, has sometimes altered fossilifer- 
 ous strata both in the direction of their dip and strike for a 
 distance of a quarter of a mile, but the theory of gneiss and 
 mica-schist above proposed requires us to imagine that the 
 same influence has extended through strata miles in thickness. 
 Professor Bischof has shown what changes may be superin- 
 duced, on black marble and other rocks, by the steam of a 
 hot spring having a temperature of no more than 133° to 
 167° Fahr., and we are becoming more and more acquainted 
 with the prominent part which water is playing in distribu- 
 ting the heat of the interior through mountain masses of in- 
 cumbent strata, and of introducing into them various miner- 
 al elements in a fluid or gaseous state. Such facts may in- 
 duce us to consider whether many granites and other rocks 
 of that class may not sometimes represent merely the ex- 
 treme of a similar slow metamorphism. But, on the other 
 hand, the heat of lava in a volcanic crater when it is w^hite and 
 glowing like the sun must convince us that the temperature 
 of a column of such a fluid at the depth of many miles ex- 
 ceeds any heat which can ever be witnessed at the surface. 
 
 * See Principles, Index, ' ' Carbonated Springs, " etc. 
 
OBJECTIONS TO METAMORPHIC THEORY. 587 
 
 That large portions of the plutonic rocks had heen formed 
 under the influence of such intense heat is in perfect accord- 
 ance with their great vohime, uniform composition, and ab- 
 sence of stratification. The forcing also of veins into con- 
 tiguous stratified or schistose rocks is a natural consequence 
 of the hydrostatic pressure to which columns of molten mat- 
 ter many miles in height must give rise. 
 
 Objeetions to the Metamorphic Theory considered.— It has 
 been objected to the metamorphic theory that the crystal- 
 line schists contain a considerable proportion of potash and 
 soda, whilst the sedimentary strata out of -which they ai-e 
 supposed to have been formed are usually wanting in alka- 
 line matter. But this reasoning proceeds on mistaken data, 
 for clay, marl, shale, and slate often contain a considerable 
 proportion of alkali, so much so as to make them frequently 
 unfit to be burnt into bricks or pottery, and the Old Red 
 Sandstone in Forfarshire and other parts of Scotland, de- 
 rived from disintegration of granite, contains much tritu- 
 rated feldspar rich in potash. In the common salt by which 
 strata are often largely impregnated, as in Patagonia, much 
 soda is pi'esent, and potash enters largely into the composi- 
 tion of fossil sea-weeds, and recent analysis hg-s also shown 
 that the carboniferous strata in England, the Upper and 
 Lower Silurian in East Canada, and the oldest clay-slates in 
 Norway, all contain as much alkali as is generally present 
 in metamorphic rocks. 
 
 Another objection has been derived from the alternation 
 of highly crystalline strata with others less crystalline. The 
 heat, it is said, in its ascent from below, must have traversed 
 the less altered schists before it reached a higher and more 
 crystalline bed. In answer to this, it may be observed, that 
 if a number of strata diflfering greatly in composition from 
 each other be subjected to equal quantities of heat, or hy- 
 drothermal action, there is every jjrobability that some will 
 be much more fusible or soluble than others. Some, for ex- 
 ample, will contain soda, potash, lime, or some other ingredi- 
 ent capable of acting as a flux or solvent ; while others may 
 be destitute of the same elements, and so refractory as to be 
 very slightly aflfected by the same causes. Nor should it be 
 forgotten that, as a general rule, the less crystalline rocks 
 do really occur in the upper, and the more crystalline in the 
 lower part of each metamorphic series. 
 
588 ELEMENTS OF GEOLOGY. 
 
 CHAPTER XXXIV. 
 
 METAMOEPHic EOCKS — Continued. 
 
 Definition of slaty Cleavage and Joints. — Supposed Causes of these Struc- 
 tures. — Crystalline Theory of Cleavage. — Mechanical Theory of Cleavage. 
 — Condensation "and Elongation of slate Rocks by lateral Pressure. — ^Lam- 
 ination of some volcanic Rocks due to Motion. — Whether the Foliation 
 of the crystalline Schists be usually parallel vpith the original Planes of 
 Stratification. — Examples in Norway and Scotland. — Causes of Irregular- 
 ity in the Planes of Toliation. 
 
 We have already seen that chemical forces of great inten- 
 sity have frequently acted upon sedimentary and fossilifer- 
 ous strata long subsequently to their consolidation, and we 
 may next inquire whether the component minerals of the al- 
 tered rocks usually arrange themselves in planes parallel to 
 the original planes of stratification, or whether, after crystal- 
 lization, they more commonly take up a different position. 
 
 In order to estimate fairly the merits of this question, we 
 must first define what is meant by the terms cleavage and 
 foliation, There are four distinct forms of structure exhibit- 
 ed in rocks, namely, stratification, joints, slaty cleavage, and 
 foliation ; and all these must have different names, even 
 though there be cases whei'e it is impossible, after carefully 
 studying the appearances, to decide upon the class to which 
 they belong. 
 
 Slaty Cleavage. — Professor Sedgwick, whose essay " On the 
 Structure of large Mineral Masses " first cleared the way to- 
 wards a better understanding of this difiicult subject, ob- 
 serves, that joints are distinguishable from lines of slaty 
 cleavage in this, that the rock intervening between two 
 joints has no tendency to cleave in a direction parallel to 
 the planes of the joints, whereas a rock is capable of indefi- 
 nite subdivision in the direction of its slaty cleavage. In 
 cases where the strata are curved, the planes of cleavage are 
 still perfectly parallel. This has been observed in the slate 
 rocks of part of Wales (see Fig. 624), which consists of a 
 hard greenish slate. The true bedding is there indicated 
 by a number of parallel stripes, some of a lighter and some 
 of a darker color than the general mass. Such stripes are 
 found to be parallel to the true planes of stratification, 
 wherever these are manifested by ripple-mark or by beds 
 
JOINTED STRUCTURE AND CLEAVAGE. 
 
 589 
 
 containing peculiar organic remains. Some of the contorted 
 strata are of a coarse mechanical structure, alternating with 
 fine-grained crystalline chloritic slates, in which case the 
 same slaty cleavage extends through the coarser and finer 
 beds, though it is brought out in greater perfection in pi'o- 
 
 Parallel planes of cleavage intersecting curved strata, (Sedgwicli.) 
 
 portion as the materials of the rock are fine and homogene- 
 ous. It is only when these are very coarse that the cleavage 
 planes entirely vanish. In the Welsh hills these planes are 
 usually inclined at a very considerable angle to the planes 
 of the strata, the average angle being as much as from 30° 
 to 40°. Sometimes the cleavage planes dip towards the 
 same point of the compass as those of stratification, but often 
 to opposite points.* The cleavage, as represented in Fig. 
 624, is generally constant over the whole of any area afiect- 
 ed by one great set of disturbances, as if the same lateral 
 pressure which caused the crumpling up of the rock along 
 parallel, anticlinal, and synclinal axes caused also the cleav- 
 age. 
 
 Mr. T. McKenny Hughes remarks, that where a rough 
 cleavage cuts flag-stones at a considerable angle to the planes 
 of stratification, Fig. C25. 
 
 the rock often 
 splits into large 
 slabs, across which 
 the lines of bed- 
 ding are frequent- 
 ly seen, but when 
 the cleavage 
 planes approach 
 
 within about 15° gg„tion in Lower Silm-ian slates of Cavdiganshire, showing 
 of Stratification, the cleavage planes bent along the junction of the beds. 
 ^i_ 1 • i *„ (T. McK. Hughes.) 
 
 the rock is apt to ' „ ^ , ^^ :, * 
 
 split along the lines of bedding. He has also called ray at- 
 tention to the fact that subsequent movements in a cleaved 
 rock sometimes drag and bend the cleavage planes along the 
 junction of the beds in the manner indicated m the annexed 
 
 °JoTnted Structure.— In regard to joints, they are natural 
 * Geol. Trans., 2d series, vol. iii., p. 461. 
 
590 ELEMENTS OF GEOLOGY. 
 
 fissures which often traverse rocks in straight and well-de- 
 terrained lines. They afford to the quarryraan, as Sir R. 
 Murchison observes, when speaking of the phenomena, as 
 exhibited in Shropshire and the neighboring counties, the 
 greatest aid in the extraction of blocks of stone ; and, if a 
 sufficient number cross each other, the whole mass of rock is 
 split into symmetrical blocks. The faces of the joints are for 
 the most part smoother and more regular than the surfaces 
 of true sti'ata. The joints are straight-cut chinks, sometimes 
 slightly open, and olten passing, not only through layers of 
 successive deposition, but also through balls of limestone or 
 other matter which have been formed by concretionary ac- 
 tion since the original accumulation cf the strata. Such 
 joints, therefore,' must often have resulted from one of the 
 last changes superinduced upon sedinientary deposits.* 
 
 In the annexed diagram (Fig. 626), the flait-surfaces of rock, 
 A,B,C, represent exposed faces of joints, to which the walls 
 
 Fig. 626. 
 
 m - /< ^\#* '--Sh^' m 
 
 r 
 
 Sti-atiflcation, joiuts, and cleavage. (From Mnrchison's Silurian System, p. 245.) 
 
 of other joints, J J, are parallel. S S are the lines of stratifi- 
 cation ; I) D are lines of slaty cleavage, which intersect the 
 rock at a considerable angle to the planes of stratification. 
 
 In the Swiss and Savoy Alps, as Mr. Bakewell has re- 
 marked, enormous masses of limestone are cut through so 
 regularly by nearly vertical partings, and these joints are 
 often so much more conspicuous than the seams of stratifica- 
 tion, that an inexperienced observer will almost inevitably 
 confound them, and suppose the strata to be perpendicular 
 in places where in fact they are almost horizontal.f 
 
 Now such joints are supposed to be analogous to the part- 
 ings which separate volcanic and plutonic rocks into cuboidal 
 and prismatic masses. On a small scale we see clay and 
 starch when dry split into similar shapes ; this is often 
 caused by simple contraction, whether the shrinking be due 
 * Silnrian System, p. 246. t Introduction to Geology, chap. iv. 
 
SLATY CLEAVAGE. 591 
 
 to the evaporation of water, or to a change of temperature. 
 It IS well known that many sandstones and other rocks ex- 
 pand by the application of moderate degrees of heat, and 
 then contract again on cooling ; and there can he no doubt 
 that large portions of the earth's crust have, in the course 
 of past ages, been subjected again and again to very differ- 
 ent degrees of heat and cold. These alternations of tempera- 
 ture have probably contributed largely to the production of 
 joints in rocks. 
 
 In many countries where masses of basalt rest on sand- 
 stone, the aqueous rock has, for the distance of several feet 
 fi-om the point of junction, assumed a columnar structure 
 similar to that of the trap. In like manner some hearth- 
 stones, after exposure to the heat of a furnace without being 
 melted, have become prismatic. Certain crystals also acquire 
 by the application of heat a new internal arrangement, so as 
 to break in a new direction, their external form remaining 
 unaltered. 
 
 Crystalline Theory of Cleavage. — Professor Sedgwick, speak- 
 ing of the planes of slaty cleavage, where they are decidedly 
 distinct from those of sedimentary deposition, declared, in 
 the essay before alluded to, his opinion that no retreat of 
 parts, no contraction in the dimensions of rocks in passing to 
 a solid state, can account for the phenomenon. He accord- 
 ingly referred it to crystalline or polar forces acting simulta- 
 neously, and somewhat uniformly, in given directions, on 
 large masses having a homogeneous composition. 
 
 Sir John Herschel, in allusion to slaty cleavage, has sug- 
 gested that " if rocks have been so heated as to allow a 
 commencement of crystallization — that is to say, if they have 
 been heated to a point at which the particles can begin to 
 move among themselves, or at least on their own axes, 
 some general law must then determine the position in which 
 these particles will rest on cooling. Probablj', that position 
 will have some relation to the direction in which the heat 
 escapes. Now, when all, or a majority of particles of the 
 same nature have a general tendency to one position, that 
 must of course determine a cleavage-plane. Thus we see the 
 infinitesimal crystals of fresh-precipitated sulphate of barytes, 
 and some other such bodies, arrange themselves alike in the 
 fluid in which they float ; so as, when stirred, all to glance 
 with one lio-ht, and give the appearance of silky filaments. 
 Some sorts of soap, in which insoluble margarates* exist, ex- 
 
 * Margaric acid is an oleaginous acid, formed from different animal and 
 Tegetable fatty substances. A margarate is a compound of this acid with 
 sodii potash, or some other base, and is so named from its pearly lustre. 
 
592 ELEMENTS OF GEOLOGY. 
 
 hibit the same phenomenon when mixed with water: and 
 what occurs in our experiments on a minute scale may occur 
 in nature on a gi-eat one."* 
 
 Mechanical Theory of Cleavage. — Professor Phillips has re- 
 marked that in some slaty rocks the form of the outline of 
 fossil shells and trilobites has been much changed by distor- 
 tion, which has taken place in a longitudinal, transverse, or 
 oblique direction. This change, he adds, seems to be the re- 
 sult of a " creeping movement " of the particles of the rock 
 along the planes of cleavage, its direction being always uni- 
 form over the same tract of country, and its amount in space 
 being sometimes measurable, and being as much as a quarter 
 or even half an inch. The hard shells are not affected, but 
 only those which are thin.f Mr. D. Sharpe, following up the 
 same line of inquiry, came to the conclusion that the present 
 distorted forms of the shells in certain British slate rocks 
 may be accounted for by supposing that the rocks in which 
 they are imbedded have undergone compression in a direc- 
 tion perpendicular to tlie planes of cleavage, and a corre- 
 sponding expansion in the direction of the dip of the cleav- 
 age.J 
 
 Subsequently (1853) Mr. Sorby demonstrated the great ex- 
 tent to which this mechanical theory is applicable to the 
 slate rocks of North Wales and Devonshire,§ districts where 
 the amount of change in dimensions can be tested and meas- 
 ured by comparing the different effects exerted by lateral 
 pressure on alternating beds of finer and coarser materials. 
 Thus, for example, in the accompanying figure (Fig. 627) it 
 will be seen that the sandy bed df^ which has offered great- 
 er resistance, has been sharply contorted, while the fine- 
 grained strata, a, b, c, have remained comparatively unbent. 
 The points a^ and /in the stratum c?/must have been origi- 
 nally four times as far apart as they are now. They have 
 been forced so much nearer to each other, partly by bending, 
 and partly by becoming elongated in the direction of what 
 may be called the longer axes of their contortions, and last- 
 ly, to a certain small amount, by condensation. The chief 
 result has obviously been due to the bending ; but, in proof 
 of elongation, it will be observed that the thickness of the 
 bed f?/ is now about four times greater in those parts lying 
 in the main direction of the flexures than in a plane perpen- 
 
 * Letter to the author, dated Cape of Good Hope, Feb. 20, 1836. 
 t Report, Brit., Assoc, Cork, 1843, Sect. p. 60. 
 X Quart. Geol. Joum., vol. iii., p. 87, 18i7. 
 
 § On the Origin of Slaty Cleavage, by H. C. Sorby, Edinb. New Phil. 
 Journ. , 1853, vol. Iv. , p. 137. 
 
MECHAJSriCAL THEORY OF CLEAVAGE. 
 
 593 
 
 diculav to them ; and the same 
 bed exhibits cleavage planes 
 in the direction of the greatest 
 movement, although they are 
 much fewer than in the slaty- 
 strata above and below. 
 
 Above the sandy bed d f, 
 the sti'atum e is somewhat dis- 
 turbed, while the next bed, b, is 
 much less so, and a not at all ; 
 yet all these beds, c, b, and a, 
 must have undergone an equal 
 amount of pressure with d, the 
 points a and g having approx- 
 imated as much towards each 
 other as have d and f. The 
 same phenomena are also re- 
 peated in the beds below d, 
 and might have been shown, 
 had the section been extended 
 downward. Hence it appears 
 that the finer beds have been 
 squeezed into a foui-th of the 
 space they previously occu- 
 pied, partly by condensation, 
 or the closer packing of their 
 ultimate particles (which has _„„^„.^^^„ 
 
 given rise to the great specific vertical section ofslate rock in the cliffs 
 gravity of such slates), and near Ilfracombe, North Devon. Scale 
 5 J.1 1 1 ,• • J.T. one inch to one foot. (Drawn by H.C. 
 
 partly by elongation in the sorby.) 
 
 line of the dip of the cleavage, a, b, c, e. Fine-gvainecl slates, the stratifl- 
 nf wViifli thp o-pnprnl rlii-pptinn cation being shown partly by lighter 
 
 01 wnicn tne general ciiiection ^^ ^^.^^.^^^. ^=,„,.j^ and partly by differ- 
 
 IS TjerpendlCular to that of the ent degrees of fineness in the grain. 
 _ (( rriu ;] „ .^ . «?,/■ A coarser grained light -colored 
 
 pressure. These and n nmer- ^kiay siate withless perfect cleavage. 
 ous other cases in North Dev- 
 on are analogous," says Mr. Sorby, " to what would occur if 
 a strip of paper were included in a mass of some soft plastic 
 material which would readily cliange its dimensions. If the 
 whole were then compressed in the direction of the length 
 of the strip of paper, it would be bent and puckered up into 
 contortions, while the plastic material would readily change 
 its dimensions without undergoing such contortions ; and the 
 difference in distance of the ends of the paper, as measured 
 in a direct line or along it, would indicate the change in the 
 dimensions of the plastic material." 
 
 By microscopic examination of minute crystals, and by 
 
 
 
 
 Fig. C3T. 
 
 
 a 
 
 ' 
 
 
 I 1 II Ill 
 
 
 
 b 
 
 
 
 
 
 
 
 
 c 
 
 1 
 
 
 ■■ 
 
 d 
 
 1 
 
 1 
 
 ■ 
 
 1 
 
 e 
 
 m 
 
 1 w>. 
 
 J 
 
594 ELEMENTS OF GEOLOGY. 
 
 other observations, Mr. Sorby has come to the conclusion 
 that the absohite condensation of the slate rocks amounts 
 upon au average to about one half their original volume. 
 Most of the scales of mica occurring in certain slates ex- 
 amined by Mr. Sorby lie in the plane of cleavage ; whereas 
 in a similar rock not exhibiting cleavage they lie with their 
 longer axes in all directions. 'May not their position in the 
 slates have been determined by the movement of elongation 
 before alluded to ? To illustrate this theory some scales of 
 oxide of iron were mixed with soft pipe-clay in such a manner 
 that they inclined in all directions. The dimensions of the 
 mass were then changed artificially to a similar extent to 
 what has occurred in slate rocks, and the pipe-clay was then 
 dried and baked. When it was afterwards rubbed to a flat 
 surface perpendicular to the pressure and in the line of elon- 
 gation, or in a plane corresponding to that of the dip of 
 cleavage, the particles were found to have become arranged 
 in the same manner as in natural slates, and the mass admit- 
 ted of easy fracture into thin flat pieces in the plane alluded 
 to, whereas it would not yield in that perpendicular to the 
 cleavage.* 
 
 Dr. Tyndall, when commenting in 1856 on Mr. Sorby's ex- 
 periments, observed that pressure alone is sufficient to pro- 
 duce cleavage, and that the intervention of plates of mica or 
 scales of oxide of iron, or any other substances having flat 
 surfaces, is quite unnecessary. In proof of this he showed 
 experimentally that a mass of " pure white wax, after hav- 
 ing been submitted to great pressure, exhibited a cleavage 
 more clean than that of any slate-rock, splitting into laminse 
 of surpassing tenuity."f He remarks that every mass of 
 clay or mud is divided and subdivided by surfaces among 
 which the cohesion is comparatively small. On being sub- 
 jected to pressure, such masses yield and spread out in the 
 direction of least resistance, small nodules become converted 
 into laminsB separated from each other by surfaces of weak 
 cohesion, and the result is that the mass cleaves at right an- 
 gles to the line in which the pressure is exerted. In fui-ther 
 illustration of this, Mr. Hughes remarks that " concretions 
 which in the undisturbed beds have their longer axes paral- 
 lel to the bedding are, where the rock is much cleaved, fre- 
 quently found flattened laterally, so as to have their longer 
 axes parallel to the cleavage planes, and at a considerable an- 
 gle, even right angles, to their former position." 
 
 Mr. Darwin attributes the lamination and fissile structure 
 
 * Sorby, as cited above, p. 741, note. 
 
 + Tyndall, View of the Cleavage of Ciystals and Slate rocks. 
 
FOLIATION OF CRYSTALLINE SCHISTS. 595 
 
 of volcanic rocks of the trachytic series, including some ob- 
 sidians in Ascension, Mexico, and elsewhere, to their having 
 moved when liquid in the direction of the lamina. The 
 zones consist sometimes of layers of air-cells drawn out and 
 lengthened in the supposed direction of the moving mass.* 
 
 Foliation of Crystalline Schists.— After studying, in 1835, 
 the crystalline rocks of South America, Mr. Darwin proposed 
 the term foliation tor the laminae or plates into which gneiss, 
 mica-schist, and other crystalline rocks are divided. Cleav- 
 age, he observes, may be applied to those divisional planes 
 ■which i-ender a rock fissile, although it may appear to the 
 eye quite or nearly homogeneous. Foliation may be used 
 for those alternating layers or plates of different mineralogic- 
 al nature of which gneiss and other metamorphic schists are 
 composed. 
 
 That the planes of foliation of the crystalline schists in 
 Norway accord very generally with those of original strati- 
 fication is a conclusion long since espoused by Keilhau.f 
 Numerous observations made by Mr. David Forbes in the 
 same country (the best probably in Europe for studying 
 such phenomena on a grand scale) confirm Keilhau's opinion. 
 In Scotland, also, Mr. D. Forbes has pointed out a striking 
 case where the foliation is identical with the lines of stratifi- 
 cation in rocks well seen near Crianlorich on the road to 
 Tyndrum, about eight miles from Inverariion, in Perthshire. 
 There is in that locality a blue limestone foliated by the in- 
 tercalation of small plates of white mica, so that the rock is 
 often scarcely distinguishable in aspect from gneiss or mica- 
 schist. The stratification is shown by the large beds and col- 
 ored bands of limestone all dipping, like the folia, at an an- 
 gle of 32 degrees N.E.J In stratified formations of every 
 age we see layers of siliceous sand with or without mica, al- 
 ternating with clay, with fragments of shells or corals, or 
 with seams of vegetable matter, and we should expect the 
 mutual attraction of like particles to favor the crystalliza- 
 tion of the quartz, or mica, or feldspar, or carbonate of lime, 
 along the planes of original deposition, rather than in planes 
 placed at angles of 20 or 40 degrees to those of stratification. 
 
 We have seen how much the original planes of stratifica- 
 tion may be interfered with or even obliterated by concre- 
 tionary action in deposits still retaining their fossils, as in the 
 case of the raagnesian limestone (see p. 63). Hence we must 
 '•spect to be frequently bafiled when we attempt to decide 
 
 * Darwin, Volcanic Islands, pp. 69, 70. 
 
 t Norske Mag. Naturvidsk., vol. i., p. 71. 
 
 t Memoir read before the Geol. Soc. London, Jan. 31, 1855. 
 
596 
 
 ELEMENTS OF GEOLOGY. 
 
 wliether the foliation does or does not accord with that ar- 
 rangement which gravitation, combined with current-action, 
 imparted to a deposit from water. Moreover, when we look 
 for stratification in crystalline rocks, we must be on our 
 guard not to expect too much regularity. The occurrence 
 of wedge-shaped masses, such as belong to coarse sand and 
 pebbles — diagonal lamination (p. 42) — ripple-marked, uncon- 
 formable stratification — the fantastic folds produced by later- 
 al pressure — faults of various width — intrusive dikes of trap 
 — organic bodies of diversified shapes, and other causes of 
 unevenness in the planes of deposition, both on the small 
 and on the large scale, will interfere with parallelism. If 
 complex and enigmatical appearances did not present them- 
 selves, it would be a serious objection to the metamorphic 
 theory. Mr. Sorby has shown that the peculiar structure be- 
 longing to ripple-marked sands, or that which is generated 
 when ripples are formed during the deposition of the materi- 
 als, is distinctly recognizable in many varieties of mica-schists 
 in Scotland.* 
 
 In the accompanying diagram I have represented careful- 
 ly the lamination of a coarse argillaceous schist which I ex- 
 amined in 1830 in the Pyre- 
 nees. In part it approaches 
 in character to a green and 
 bine roofing-slate, while part 
 is extremely quartzose, the 
 whole mass passing down- 
 ward into micaceous schist. 
 The vertical section here ex- 
 hibited is about three feet in 
 height, and the layers are 
 ^Se"rneavGirr,1uS^^^^^^ sometimes so thin that fifty 
 
 may be counted m the thick- 
 ness of an inch. Some of them consist of pure quartz. There 
 is a resemblance in such oases to the diagonal lamination 
 which we see in sedimentary rocks, even though the layers of 
 qnai'tz and of mica, or of feldspar and other minerals, may be 
 more distinct in alternating folia than they were originally. 
 
 * H. C. Sorby, Quart. Geol. Journal, vol. xix., p. 401. 
 
AGES OF MET AMORPHIC ROCKS. 59^ 
 
 CHAFPER XXXV. 
 
 ON- THE DIFFERENT AGES OF THE MBTAMOEPHIC ROCKS. 
 
 Difficulty of ascertaining the Age of metamoi-phic Strata.— Metamoiphio 
 btrata of Eocene date in the Alps of Switzerland and Savoy.— Lime- 
 stone and Shale of Carrara.— Metamorphic Strata of older date than the 
 Silurian and Cambrian Rocks.— Order of Succession in metamorphic 
 Kocks.— Uniformity of mineral Character.— Supposed Azoic Period.— Con- 
 nection between the Absence of Organic Remains and the Scarcity of cal- 
 careous Matter in metamorphic Rocks. 
 
 According to the theory adopted in the last chapter, the 
 metamorphic strata have been deposited at one period, and 
 have become crystalline at another. We can rarely hope 
 to define with exactness the date of both these periods, the 
 fossils having been destroyed by plutonic action, and the 
 mineral characters being the same, whatever the age. Su- 
 perposition itself is an ambiguous test, especially when Ave 
 desire to determine the period of crystallization.' Suppose, 
 for example, we are convinced that certain metamorphic 
 strata in the Alps, which are covered by cretaceous beds, 
 are altered lias ; this lias may have assumed its crystalline 
 texture in the cretaceous or in some tertiary period, the Eo- 
 cene for example. 
 
 When discussing the ages of the plutonic rocks, we have 
 seen that examples occur of various primary, secondary, and 
 tertiary deposits converted into metamorphic strata near 
 their contact with granite. There can be no doubt in these 
 cases that strata once composed of mud, sand, and gravel, or 
 of clay, marl, and shelly limestone, have for the distance of 
 several yards, and in some instances several hundred feet, 
 been turned into gneiss, mica-schist, hornblende-schist, chlo- 
 rite-schist, quartz rock, statuary marble, and the rest. (See 
 the two preceding chapters.) It may be easy to prove the 
 identity of two diferent parts of the same stratum ; one, 
 where the rock has been in contact with a volcanic or plu- 
 tonic mass, and has been changed into marble or hornblende- 
 schist, and another not far distant, where the same bed re- 
 mains' unaltered and fossiliferous ; but when hydrothermal 
 action, as described in Chapter XXXIII.,has operated gradu- 
 ally on a more extensive scale, it may have finally destroyed 
 
598 ELEMENTS OF GEOLOGY. 
 
 all monuments of the date of its development througlutvt a 
 whole mountain chain, and all the labor and skill of the most 
 practised observers are required, and may sometimes be at 
 fault. I shall mention one or two examples of alteration on 
 a grand scale, in order to explain to the student the kind 
 of reasoning by which we are led to infer that dense masses 
 of fossiliferous strata have been converted into crystalline 
 rocks. 
 
 Eocene Strata rendered metamorphlc in the Alps.— In the 
 eastern part of the Alps, some of the Palseozoic strata, as well 
 as the older Mesozoic formations, including the oolitic and 
 cretaceous rocks, are distinctly recognizable. Tertiary de- 
 posits also appear in a less elevated position on the flanks of 
 the Eastern Alps ; but in the Central or Swiss Alps, the 
 Palseozoic and older Mesozoic formations disappear, and the 
 Cretaceous, Oolitic, Liassic, and at some points even the Eo- 
 cene strata, graduate insensibly into metamorphic rocks, con- 
 sisting of granular limestone, talc-schist, talcose-gneiss, mica- 
 ceous schist, and other varieties. 
 
 As an illustration of the partial conversion into gneiss of 
 portions of a highly inclined set of beds, I may cite Sir R. 
 Murchison's memoir on the structure of the Alps. Slates 
 provincially termed "flysch" (see above, p. 278), overlying 
 the nummulite limestone of Eocene date, and comprising 
 some arenaceous and some calcareous layers, are seen to al- 
 ternate several times with bands of granitoid rock, answer- 
 ing in character to gneiss. In this case heat, vapor, or water 
 at a high temperature may have traversed the more permea- 
 ble beds, and altered them so far as to admit of an internal 
 movement and re-arrangement of the molecules, while the 
 adjoining strata did not give passage to the same heated 
 gases or water, or, if so, remained unchanged because they 
 were composed of less fusible or decomposable materials. 
 Whatever hypothesis we adopt, the phenomena establish be- 
 yond a doubt the possibility of the development of the meta- 
 morphic structure in a tertiary deposit in planes parallel to 
 those of stratification. The strata appear clearly to have 
 been affected, though in a less intense degree, by that same 
 plutonic action which has entirely altered and rendered met- 
 amorphic so many of the subjacent formations; for in the 
 Alps this action has by no means been confined to the imme- 
 diate vicinity of granite. Granite, indeed, and other plutonic 
 rocks, rarely make their appearance at the surface, notwith- 
 standing the deep ravines which lay open to view the inter- 
 nal structure of these mountains. That they exist below at 
 no great dqDth we can not doubt, for at some points, as in 
 
MARBLE OF CARRARA. 599 
 
 IreoWvSf'"''"' ?^ontJ31anc, granite and granitic veins 
 
 fn.Pn5>?lJ ' P!f'""° ^''^"Sh ^^l''"^^ gneissfwhich passes 
 insensibly upward into secondarj^ strata 
 
 It IS certainly in the Alps of Switzerland and Savoy, more 
 than in any other district in Europe, that the geologist is 
 prepared to meet with the signs of an intense development 
 ot Plutonic action ; for here strata thousands of feet thick 
 havji been bent, folded, and overturned, and marine seconda- 
 ry lormations of a comparatively modern date, such as the 
 Uolitic and Cretaceous, have been upheaved to the heio-ht of 
 12,000, and some Eocene strata to elevations of 10,000 feet 
 above the level of the sea; and even deposits of the Miocene 
 era have been raised 4000 or 5000 feet, so as to rival in 
 height the loftiest mountains in Great Britain. In one of the 
 sections described by M. Studer in the highest of the Bernese 
 Alps, namely in the Roththal, a valley bordering the line of 
 perpetual snow on the northern side of the Jungfrau, there 
 occurs a mass of gneiss 1000 feet thick, and 15,000 feet long, 
 which I examined, not only resting upon, but also again cov- 
 ered by strata containing oolitic fossils. These anomalous 
 appearances may partly be explained by supposing great 
 solid wedges of intrusive gneiss to have been forced iii lat- 
 erally between strata to which I found them to be in many 
 sections unconformable. The superposition, also, of the 
 gneiss to_ the oolite may, in some cases, be due to a reversal 
 of the original position of the beds in a region whei-e the 
 convulsions have been on so stupendous a scale. 
 
 Northern Apennines.— Carrara. — The celebrated marble of 
 Carrara, used in sculpture, was once regarded as a type of 
 primitive limestone. It abounds in the mountains of Massa 
 Carrara, or the "Apuan Alps," as they have been called, the 
 highest peaks of which are nearly 6000 feet high. Its great 
 antiquity was inferred from its mineral texture, from the ab- 
 sence of fossils, and its passage downward into talc-schist 
 and garnetiferous mica-schist; these rocks again graduating 
 downward into gneiss, which is penetrated, at Forno, by 
 granite veins. But the researches of MM. Savi, Boue, Pareto, 
 GuidonijDe la Beche, Hoffmann, and Pilla demonstrated that 
 this marble, once supposed to be formed before the existence 
 of organic beings, is, in fact, an altered limestone of the 
 Oolitic period, and the underlying crystalline schists are sec- 
 ondary sandstones and shales, modified by plutonic action. 
 In order to establish these conclusions it was first pointed 
 out that the calcareous rocks bordering the Gulf of Spezia, 
 and abounding in Oolitic fossils, assume a texture like that 
 of Carrara marble, in proportion as they ai-e more and more 
 
600 ELEMENTS OF GEOLOGY. 
 
 invaded by certain trappean and plutonic rocks, such as dio- 
 rite, serpentine, and granite, occurring in the same country. 
 
 It was then observed that, in places where the secondary 
 formations are unaltered, the uppermost consist of common 
 Apenniue limestone with nodules of flint, below which are 
 shales, and at the base of all, argillaceous and siliceous sand- 
 stones. In the limestone fossils are frequent, but very rare 
 in the underlying shale and sandstone. Then a gradation 
 was traced laterally from these rocks into another and corre- 
 sponding series, which is completely metamorphic; for at the 
 top of this we find a white granular marble, wholly devoid 
 of fossils, and almost without stratification, in which there 
 are no nodules of flint, but in its place siliceous matter dis- 
 seminated through the mass in the form of prisms of quartz. 
 Below this, and in place of the shales, are talc-schists, jasper, 
 and hornstone ; and at the bottom, instead of the siliceous 
 and argillaceous sandstones, are quartzite and gneiss.* Had 
 these secondary strata of the Apennines undergone univer- 
 sally as great an amount of transmutation, it would have 
 been impossible to form a conjecture respecting their true 
 age; and then, according to the method of classification 
 adopted by the earlier geologists, they would have ranked as 
 primary rocks. In that case the date of their origin would 
 have been thrown back to an era antecedent to the deposi- 
 tion of the Lower Silurian or Cambrian strata, although in 
 reality they were formed in the Oolitic period, and altered 
 at some subsequent and perhaps much later epoch. 
 
 Metamorphic Strata of older date than the Silurian and Cam- 
 brian Rocks. — It was remarked. Fig. 617, p. 567, that as the 
 hypogene rocks, both stratified and tinstratified, crystallize 
 originally at a certain depth beneath the surface, they must 
 always, before they are ujDraised and exposed at the surface, 
 be of considerable antiquity, relatively to a large portion of 
 the fossiliferous and volcanic rocks. They may be forming 
 at all periods ; but before any of them caa become visible, 
 they must be raised above the level of the sea, and some of 
 the rocks which previously concealed them must have been 
 removed by denudation. 
 
 In Canada, as we have seen (p. 491), the Lower Laurentian 
 gneiss, quartzite, and limestone may be regarded as meta- 
 morphic, because, among other reasons, organic remains 
 {JSozoon Canadense) have been detected in a part of one of 
 the calcareous masses. The Upper Laurentian or Labrador 
 
 * See notices of Savi, Hoffmann, and others, referred to by Boue, Bull, de 
 la Soc. Geo), de France, torn, v., p. 317, and torn, iii., p. 44 ; also KUa, cited 
 by Muichison, Quart. Geol. Jouni., vol. v., p. 26G. 
 
HIGHLAND. METAMORPHIC ROCKS. 601 
 
 series lies unconfoi-mably upon tlie Lower, and differs from it 
 chiefly in having as yet yielded no fossils. It consists of 
 gneiss with Labrador-feldspar and feldstones, in all 10,000 feet 
 thick, and both its composition and structure lead us to sup- 
 pose that, like the Lower Laurentian, it was originally of 
 sedimentary origin and owes its crystalline condition to met- 
 amorphic action. The remote date of the period when some 
 of these old Laurentian strata of Canada were converted 
 into gneiss may be inferred from the fact that pebbles of that 
 rock are found in the overlying Huronian formation, which is 
 probably of Cambrian age (p. 490). 
 
 The oldest stratified rock of Scotland is the hornblendic 
 gneiss of Lewis, in the Hebrides, and that of the north-west 
 coast of Ross-shire, represented at the base of the section 
 given at Fig. 82, p. 112. It is the same as that intersected 
 by numerous granite veins which forms the cliflfs of Cape 
 Wrath, in Sutherlandshire (see Fig. 613, p. 560), and is con- 
 jectured to be of Laurentian age. Above it, as shown in 
 the section (Fig. 82, p. 112), lie unconformable beds of a red- 
 dish or purple sandstone and conglomerate, nearly horizon- 
 tal, and between 3000 and 4000 feet thick. In these ancient 
 grits no fossils have been found, but they are supposed to be 
 of Cambrian date, for Sir R. Murchison found Lower Silurian 
 strata resting unconformably upon them. These sti-ata con- 
 sist of quartzite with annelid burrows already alluded to (p. 
 112), and limestone in which Mr. Charles Peach was the first 
 to find, in 1854, three or four species of Orthoceras, also the 
 genera Cyrtoceras and Lituites, two species of Murehisonia, 
 a Pleurotomaria, a species of Madurea, one of Euomphalus, 
 and an Ortliis. Several of the species are believed by Mr. 
 Salter to be identical with Lower Silurian fossils of Canada 
 and the United States. 
 
 The discovery of the true age of these fossiliferous rocks 
 was one of the most important steps made of late years in 
 the progress of British Geology, for it led to the unexpected 
 conclusion that all the Scotch crystalline strata to the east- 
 ward, once called primitive, which overlie the limestone and 
 quartzite in question, are referable to some part of the Silu- 
 rian series. . . V . . 
 
 These Scotch metamorphic strata are of gneiss, mica-schist, 
 and clay-slate of vast thickness, and having a strike from 
 north-east to south-west almost at right_ angles to that of 
 the older Laurentian gneiss before mentioned. The newer 
 crystalline series, comprising the crystalline rocks of Aber- 
 deenshire Perthshire, and Forfarshire, were inferred by Sir 
 R. Murchison to be altered Silurian strata; and his oinnion 
 
 26 
 
602 ELEMENTS OF GEOLOGY. 
 
 has been since confirmed by the observations of three able 
 geologists, Messrs. Ramsay, Harkness, and Geikie. The new- 
 est of the series is a clay-slate, on which, along the southern 
 borders of the Grampians, the Lower Old Red, containing 
 Cephalaspis JLyelli, Plerygotus Angliciis, and Parka decipiens, 
 rests unconformably. 
 
 Order of Succession in Metamorphic Rocks. — There is no 
 universal and invariable order of superposition in metamor- 
 phic rocks, although a particular arrangement may prevail 
 throughout countries of great extent, for the same reason 
 that it is traceable in those sedimentary formations from 
 which crystalline strata are derived. Thus, for example, we 
 have seen that in the Apennines, near Carrara, the descend- 
 ing series, where it is metamorphic, consists of, 1st, saccha- 
 rine marble; 2dly, talcose-schist ; and 3dly, of quartz-rock 
 and gneiss: where unaltered, of, 1st, fossiliferous limestone; 
 2dly, shale; and 3dly, sandstone. 
 
 But if we investigate different mountain chains, we find 
 gneiss, mica-schist, hornblende-schist, chlorite-schist, hypo- 
 gene limestone, and other rocks, succeeding each other, and 
 alternating with each other in every possible order. It is, 
 indeed, more common to meet with some variety of clay- 
 slate forming the uppermost member of a metamorphic se- 
 ries than any other rock ; but this fact by no means implies, 
 as some have imagined, that all clay-slates were formed at 
 the close of an imaginary period when the deposition of the 
 crystalline strata gave way to that of ordinary sedimentary 
 deposits. Such clay-slates, in fact, are variable in composi- 
 tion, and sometimes alternate with, fossiliferous strata, so 
 that they may be said to belong almost equally to the sedi^ 
 mentary and metamorphic order of rocks. It is probable 
 that, had they been subjected to more intense plutonic ac- 
 tion, they would have been transformed into hornblende- 
 schist, foliated chlorite-schist, scaly talcose-schist, mica-schist, 
 or other more pefectly crystalline rocks, such as are usually 
 associated with gneiss. 
 
 Uniformity of Mineral Character in Hypogene Bocks. — It 
 is true, as Humboldt has happily remarked, that when we 
 pass to another hemisphere, we see new forms of animals and 
 plants, and even new constellations in the heavens ; but in 
 the rocks we still recognize our old acquaintances — the same 
 granite, the same gneiss, the same micaceous schist, quartz- 
 rock, and the rest. There is certainly a great and striking 
 general resemblance in the principal kinds of hypogene rocks 
 in all countries, however different their ages ; but each of 
 them, as we have seen, must be regarded as geological fami- 
 
SUPPOSED AZOIC PERIOD. 603 
 
 lies of rocks, and not as definite mineral compounds. They 
 are more uniform in aspect than sedimentary strata, because 
 these last are often composed of fragments varying greatly 
 in form, size, and color, and contain fossils of different shapes 
 and mineral composition, and acquire a vai'iety of tints from 
 the mixture of various kinds of sediment. The materials of 
 such strata, if they underwent metamorphism, would be sub- 
 ject tp chemical laws, simple and uniform in their action, the 
 same in every climate, and wholly undisturbed by mechanic- 
 al and organic causes. It would, however, be a great error 
 to assume, as some have done, that the hypogene rocks, con- 
 sidered as aggregates of simple minerals, are really more 
 homogeneous in their composition than the several members 
 of the sedimentary series. Not only do the proportional 
 quantities of feldspar, quartz, mica, hornblende, and other 
 minei-als, vary in hypogene rocks bearing the same name ; 
 but what is still more important, the ingredients, as we have 
 seen, of the same simple mineral are not always constant (see 
 p. 503, and Table, p. 499). 
 
 Supposed Azoic Period. — The total absence of any trace of 
 fossils has inclined many geologists to attribute the origin 
 of the most ancient strata to an azoic period, or one ante- 
 cedent to the existence of organic beings. Admitting, they 
 say, the obliteration, in some cases, of fossils by plutonic ac- 
 tion, we might still expect that traces of them would oftener 
 be found in certain ancient systems of slate which can scarce- 
 ly be said to have assumed a crystalline structure. But in 
 urging this argument it seems to have been forgotten that 
 there are stratified formations of enormous thickness, and of 
 various ages, some of them even of Tertiary date, and which 
 we know were formed after the earth had become the abode 
 of living creatures, which are, nevertheless, in some districts, 
 entirelydestitute of all vestiges of organic bodies; In some, 
 the traces of fossils may have been effaced by water and 
 acids, at many successive periods ; indeed the removal ot 
 the calcareous matter of fossil shells is proved by the factot 
 such organic remains being often replaced by silex or other 
 minerals, and sometimes by the space once occupied by tHe 
 fossil being left empty, or only marked by a faint impression. 
 
 Those who believed the hypogene rocks to have ougina- 
 ted antecedently to the creation of organic beings, imputed 
 the absence of lime, so remarkable in metamorphic strata, to 
 Se non exTstence of those mollusca and zoophytes by wh^h 
 shells and corals are secreted ; but when we ascribe the crys- 
 talline formations to Plutonic action, it is natural to inquire 
 vhethei this action itself may not tend to expel carbonic 
 
604 ELEMENTS OF GEOLOGY. 
 
 acid and lime from the materials which it reduces to fusion 
 or semi-fusion. Not only carbonate of lime, but also free 
 carbonic acid gas, is given oif plentifully from the soil and 
 crevices of rocks in regions of active and spent volcanoes, as 
 near Naples and in Auvergne. By this process, fossil shells 
 or corals may often lose their carbonic acid, and the residual 
 lime may enter into the composition of augite, hornblende, 
 garnet, and other hypogene minerals. Although we can not 
 descend into the subterranean regions where volcanic heat is 
 developed, we can observe in regions of extinct volcanoes, 
 such as Auvergne and Tuscany, hundreds of springs, both 
 cold and thermal, flowing out from granite and other rocks, 
 and having their waters plentifully charged with carbonate 
 of lime. 
 
 If all the calcareous matter transferred in the course of 
 ages by these and thousands of other springs from the lower 
 part of the earth's crust to the atmosphere could be present- 
 ed to us in a solid form, we should find that its volume was 
 comparable to that of many a chain of hills. Calcareous 
 matter is poured into lakes and the ocean by a thousand 
 springs and rivers ; so that part of almost every new calca- 
 reous rock chemically precipitated, and of many reefs of shel- 
 ly and coralline stone, must be derived from mineral matter 
 subtracted by plutonic agency, and driven up by gas and 
 steam from fused and heated rocks in the bowels of the 
 earth. 
 
 The scarcity of limestone in many extensive regions of 
 metamorphic rocks, as in the Eastern and Southern Grampi- 
 ans of Scotland, may have been the result of some action of 
 this kind ; and if the limestones of the Lower Laurentian in 
 Canada afford a remarkable exception to the general rule, 
 we must not forget that it is precisely in this most ancient 
 formation that the Eozoon Canadense has been found. The 
 fact that some distinct bands of limestone from 700 to 1500 
 feet thick occur here, may be connected with the escape from 
 destruction of some few traces of oi'ganic life, even in a rock 
 in which metamorphic action has gone so far as to produce 
 serpentine, augite, and other minerals found largely inter- 
 mixed with the carbonate of lime. 
 
MINERAL VEINS. 605 
 
 CHAPTER XXXVI. 
 
 MINEEAL VEINS. 
 
 Different Kinds of mineral Veins. — Ordinary metalliferous Veins or Lodes. 
 — Their frequent Coincidence with Faults. — Proofs that they originated 
 in Fissures in solid Rock. — Veins shifting other Veins. — Polishing of their 
 Walls or " Slicken sides." — Shells and Pebbles in Lodes. — Evidence of the 
 successive Enlargement and Reopening of Veins. — Examples in Cornwall 
 and in Auvergne. — Dimensions of Veins. — Why some alteraately swell 
 out and contract. — Filling of Lodes by Sublimation from below. — Sup- 
 posed relative Age of the precious Metals. — Copper and lead Veins in Ire^ 
 land older than Cornish Tin. — Lead Vein in Lias, Glamorganshire. — Gold 
 in Russia, California, and Australia. — Connection of hot Springs and min- 
 eral Veins. 
 
 The manner in which metallic substances are distributed 
 through the earth's crust, and more especially the phenomena 
 of those more or less connected masses of ore called mineral 
 veins, from which the larger part of the precious metals used 
 by man are obtained, are subjects of the highest practical 
 importance to the miner, and of no less theoretical interest 
 to the geologist. 
 
 On diflferent Kinds of Mineral Veins.— The mineral veins 
 with which we are most familiarly acquainted are those of 
 quartz and carbonate of lime, which are often observed to 
 form lenticular masses of limited extent traversing both hyp- 
 ogene strata and fossiliferous rocks. Such veins appear to 
 have once befin chinks or small cavities, caused, like cracks in 
 clay, by the shrinking of the mass, during desiccation, or in 
 passing from a higher to a lower temperature. Siliceous, 
 calcareous, and occasionally metallic matters have sometimes 
 found their way simultaneously into such empty spaces, by 
 infiltration from the surrounding rocks. Mixed with hot 
 water and steam, metallic ores may have permeated the 
 mass until they reached those receptacles formed by shrink- 
 age, and thus gave rise to that irregular assemblage of veins, 
 called by the Germans a " stockwerk," in allusion to the dif- 
 ferent floors on which the mining operations are in such cases 
 
 carried on. , . ,, i j • 
 
 The more ordinary or regular veins are usually worked in 
 vertical shafts, and have evidently been fissures produced by 
 mechanical violence. They traverse all kinds of rocks, both 
 
606 ELEMENTS OF GEOLOGY. 
 
 hypogene and fossiliferous, and extend downward to indefi- 
 nite or unknown deptlis. We may assume that they corre- 
 spond with such rents as we see caused from time to time by 
 the shock of an earthquake. Metalliferous veins referable to 
 such agency are occasionally a few inches wide, but more 
 commonly three or four feet. They hold their course con- 
 tinuously in a cei'tain prevailing direction for miles or 
 leagues, passing through rocks varying in mineral composi- 
 tion. 
 
 That metalliferous Veins were Fissures. — As some intelli- 
 gent miners, after an attentive study of metalliferous veins, 
 have been unable to reconcile many of their characteristics 
 with the hypothesis of fissures, I shall begin by stating the 
 evidence in its favor. The most striking fact, perhaps, which 
 can be adduced in its support is, the coincidence of a consid- 
 erable proportion of mineral veins with faults, or those dislo- 
 cations of rocks which are indisputably due to mechanical 
 force, as above explained (p. 87). There are even proofs in 
 almost every mining district of a succession of faults, by 
 which the opposite walls of rents, now the receptacles of me- 
 tallic substances, have suffered displacement. Thus, for ex- 
 ample, suppose a a, Fig. 629, to be a tin lode in Cornwall, the 
 term lode being applied to veins containing metallic ores. 
 This lode, running east and west, is a yard wide, and is shift- 
 ed by a copper lode {b b) of similar width. The first fissure 
 {a a) has been filled with various materials, partly of chemic- 
 al origin, such as quartz, fluor-spar, peroxide of tin,sulphuret 
 of copper, arsenical pyrites, bismuth, and sulphuret of nickel, 
 and partly of mechanical origin, comprising clay and angular 
 fragments or detritus of the intersected rocks. The plates 
 of quartz and the ores are, in some places, parallel to the 
 vertical sides or walls of the vein, being divided from each 
 other by alternating layers of clay or other earthy matter. 
 Occasionally the metallic ores are disseminated in detached 
 masses among the vein-stones. 
 
 It is clear that, after the gradual introduction of the tin 
 and other substances, the second rent {b b) was produced by 
 another fracture accompanied by a displacement of the rocks 
 along the plane of b b. This new opening was then filled 
 with minerals, some of them resembling those in a a, as fluor- 
 spar (or fluate of lime) and quartz ; others different, the cop- 
 per being plentiful and the tin wanting or very scarce. We 
 must next suppose a third movement to occur, breaking 
 asunder all the rocks along the line c c, Fig. &30 ; the fissure, 
 in this instance, being only six inches wide, and simply filled 
 with clay, derived, probably, from the friction of the walls 
 
METALLIFEROUS YEtSS. 
 
 607 
 
 Fig. 629. 
 
 of the rent, or 
 partly, perhaps, 
 washed in from 
 above. This new 
 movement has dis- 
 placed the rock in 
 such a manner as 
 to interrupt the 
 continuity of the 
 copper vein {b b), 
 and, at the same 
 time, to shift or 
 heave laterally in 
 the same direction 
 a portion of the 
 tin vein which 
 had not previous- 
 ly been broken. 
 
 Again, in Fig. 
 631 we see evi- 
 dence of a fourth 
 fissure {d d), also 
 filled with clay, 
 which has cut 
 through the tin 
 vein (a a), and has 
 lifted it slightly 
 upward towards 
 ' the south. The 
 various changes 
 here represented 
 are not ideal, but 
 are exhibited in a 
 section obtained 
 in working an old 
 Cornish mine, long 
 since abandoned, 
 in the parish of 
 Redruth, called 
 Huel Peever, and described both by Mr. Williams and Mr. 
 Carne.* The principal movement here referred to, or that of 
 c G, fig. 631, extends through a space of no less than 84 feet ; bu'c 
 in this, as in the case of the other three, it will be seen that the 
 outline of the country above, d, c, b, a, etc., or the geographic- 
 
 * Geol. Trans., vol. ir., p. 139; Trans. Boy. Geo]. Society, Cornwall, vol. 
 ii., p. 90. 
 
 Vertical sections of the mine of Hael Peever, Hedruth, 
 Cornwall. 
 
608 ELEMENTS OF GEOLOGY. 
 
 al features of Cornwall, are not affected hj any of the dislo- 
 cations, a powerful denuding force having clearly been exert- 
 ed subsequently to all the faults. (See above, p. 93.) It is 
 commonly said in Cornwall, that there are eight distinct sys- 
 tems of veins, which can in like manner be referred to as many 
 successive movements or fractures ; and the German miners 
 of the Hartz Mountains speak also of eight systems of veins, 
 referable to as many periods. 
 
 Besides the proofs of mechanical action already explained, 
 the opposite walls of veins are often beautifully polished, as 
 if glazed, and are not unfrequently striated or scored with 
 parallel furrows and ridges, such as would be produced by 
 the continued rubbing together of surfaces of unequal hard- 
 ness. These smoothed surfaces resemble the rocky floor over 
 which a glacier has passed (see Fig. 106, p. 168). They are 
 common even in cases where there has been no shift, and oc- 
 cur equally in non-metalliferons fissures. They are called by 
 miners " slicken-sides," from the German sohUehten, to plane, 
 and seite, side. It is supposed that the lines of the striae in- 
 dicate the direction in which the rocks were moved. 
 
 In some of the veins in the mountain limestone of Derby- 
 shii'e, containing lead, the vein-stuff, which is nearly compact, 
 is occasionally traversed by what may be called a vertical 
 crack passing down the middle of the vein. The two faces 
 in contact are slicken-sides, well polished and fluted, and 
 sometimes covered by a thin coating of lead-ore. When one 
 side of the vein-stuff is removed, the' other side cracks, espe- 
 cially if small holes be made in it, and fragments fly off with 
 loud explosions, and continue to do so for some days. The 
 miner, availing himself of this circumstance, makes with his 
 pick small holes about six inches apart, and four inches deep, 
 and on his return in a few hours finds every part ready 
 broken to his hand.* 
 
 That a great many veins communicated originally with 
 the surface of the country above, or with the bed of the sea, 
 is proved by the occurrence in them of well-rounded pebbles, 
 agreeing with those in superficial alluviums, as in Auvergne 
 and Saxony. Marine fossil shells, also, have been found at 
 great depths, having probably been ingulfed during subma- 
 rine earthquakes. Thus, a gryphsea is stated by M. Virlet to 
 have been met with in a lead-mine near Semur, in France, 
 and a madrepore in a compact vein of cinnabar in Hun- 
 gary.f In Bohemia, similar pebbles have been met with 
 at the depth of 180 fathoms ; and in Cornwall, Mr. Carne men- 
 
 * Conyb. and Phil. Geol., p. 401 ; and Farey's Derbyshire, p. 243. 
 t Foumet, Etudes sur les Depots Metalliftres. 
 
GRADUAL FILLING OF VEINS. 609 
 
 tions true pebbles of quartz and slate in a tin lode of the 
 Kehstran Mnie, at the depth of 600 feet below the surface. 
 Ihey were cemented by oxide of tin and bisulphuret of cop- 
 per, and were traced over a space more than twelve feet lono- 
 and as_ many wide.* When different sets or systems of veini 
 occur m the same country, those which are supposed to be 
 ot contemporaneous origin, and which are filled with the 
 same kmd of metals, often maintain a general parallelism of 
 direction. Thus, for example, both the tin and copper veins 
 m Cornwall run nearly east and west, while the lead veins 
 run north and south ; but there is no general law of direc- 
 tion common to different mining districts. The parallelism 
 of the veins is another reason for regarding them as ordinary 
 fissures, for we observe that faults and trap dikes, admitted 
 by all to be masses of melted matter which have filled rents, 
 are often parallel. 
 
 Fracture, Re-opening and successive Formation of Veins. — 
 Assuming, then, that veins are simply fissures in which chem- 
 ical and mechanical deposits have accumulated, we may next 
 consider the proofs of their having been filled gradually and 
 often during successive enlargements. 
 
 Werner observed, in a vein near Gersdorff,in Saxony, no 
 less than thirteen beds of different minerals, arranged with the 
 utmost regularity on each side of the central layer. This 
 layer was formed of two plates of calcareous spar, which 
 had evidently lined the opposite walls of a vertical cavi- 
 ty. The thirteen beds followed each other in corresponding 
 order, consisting of fluor-spar, heavy spar, galena, etc. In 
 these cases the central mass has been last formed, and the 
 two plates which coat the walls of the rent on each side are 
 the oldest of all. If they consist of crystalline precipitates, 
 they may be explained by supposing the fissure to have re- 
 mained unaltered in its dimensions, while a series of changes 
 occurred in the nature of the solutions which rose up from 
 below : but such a mode of deposition, in the case of many 
 successive and parallel layers, appears to be exceptional. 
 
 If a vein-stone consist of crystalline matter, the points of 
 the crystals are always turned inward, or towards the centre 
 of the vein; in other words, they point in the direction 
 where there was space for the development of the crystals. 
 Thus each new layer receives the impression of the crystals, 
 of the preceding layer, and imprints its crystals on the one 
 which follows, until at length the whole of the vein is filled : 
 the two layers which meet dovetail the points of their crys- 
 tals the one into the other. But in Cornwall, some lodes oc- 
 * Carne, Trans, of Geol. Soc. Cornwall, vol. iii., p. 238. 
 26* 
 
610 
 
 ELEMENTS OF GEOLOGY. 
 
 Copper lode, near Eedrath, enlarged at Bix 
 successive periods. 
 
 cur where the vertical plates, 
 or combs, as they are there 
 called, exhibit crystals so 
 dovetailed as to prove that 
 the same fissure has been 
 often enlarged. Sir H. De 
 la Beche gives the following 
 curious and instructive ex- 
 ample (Fig, 632), from a cop- 
 per-mine in granite, near Red- 
 ruth.* Each of the plates 
 or combs {a, b, c, d, e, f) is 
 double, having the points of their crystals turned inward 
 along the axis of the comb. The sides or walls (2, 3, 4, 5, 
 and 6) are parted by a thin covering of ochreous clay, so 
 that each comb is readily separable from another by a mod- 
 erate blow of the hammer. The breadth of each represents 
 the whole width of the fissure at six successive periods, and 
 the outer walls of the vein, where the first narrow rent was 
 formed, consisted of the granitic surfaces 1 and 7. 
 
 A somewhat analogous interpretation is applicable to many 
 other cases, where clay, sand, or angular detritus, alternate 
 with ores and vein-stones. Thus, we may imagine the sides 
 of a fissure to be incrusted with siliceous mattei', as Von 
 Buch observed, in Lancerote, the walls of a volcanic crater 
 formed in 1731 to be traversed by an open rent in which hot 
 vapors had deposited hydrate of silica, the incrustation near- 
 ly extending to the middle.f Such a vein may then be filled 
 with clay or sand, and afterwards re-opened, the new rent di- 
 viding the argillaceous deposit, and allowing a quantity of 
 rubbish to fall down. Various metals and spars may then 
 be precipitated from aqueous solutions among the interstices 
 of this heterogeneous mass. 
 
 That such changes have repeatedly occurred, is demon- 
 strated by occasional cross-veins, implying the oblique frac- 
 ture of previously formed chemical and mechanical deposits. 
 Thus, for example, M. Fournet, in his description of some 
 mines in Auvergne worked under his superintendence, ob- 
 serves that the granite of that country was first penetrated 
 by veins of granite, and then dislocated, so that open rents 
 crossed both the granite and the granitic veins. Into such 
 openings, quartz, accompanied by sulphurets of iron and ar- 
 senical pyrites, was introduced. Another convulsion then 
 burst open the rocks along the old line of fracture, and the 
 
 * Geo]. Rep. on Cornwall, p. 340. 
 
 t Principles, ch. xxvii., 8th ed., p. 422. 
 
SWELLING OF VEINS. 611 
 
 first set of deposits were cracked and often shattered, so that 
 the new rent was filled, not only with angular fragments of the 
 adjoining rocks, but with pieces of the older vein-stones. Pol- 
 ished and striated surfaces on the sides or in the contents of 
 the vein also attest the reality of these movements. A new 
 period of repose then ensued, during which various sulphurets 
 were introduced, together with hornstone quartz, hy which 
 angular fragments of the older quartz before mentioned were 
 cemented into a breccia. This period was followed by other 
 dilatations of the same veins, and the introduction of other 
 sets of mineral deposits, as well as of pebbles of the basaltic 
 lavas of Auvergne, derived from superficial alluviums, prob- 
 ably of Miocene or even Older Pliocene date. Such repeated 
 enlargement and re-opening of veins might have been antici- 
 pated, if we adopt the theory of fissures, and reflect how few 
 of them have ever been sealed up entirely, and that a country 
 with fissures only partially filled must naturally offer much 
 feebler resistance along the old lines of fracture than any- 
 where else. 
 
 Cause of alternate Contraction and Swelling of Veins.— A 
 large proportion of metalliferous veins have their opposite 
 walls nearly parallel, and sometimes over a wide extent of 
 country. There is a fine example of this in the celebrated 
 vein of Andreasburg in the Hartz, which has been worked 
 fer a depth of 500 yards perpendicularly, and 200 horizontal- 
 ly retaining almost everywhere a width of three feet. But 
 many lodes in Cornwall and elsewhere are extremely van- 
 able in size, being one or two inches in one part, and then 
 eiffht or ten feet in another, at the distance of a few fathoms, 
 and then again narrowing as before. Such alternate swell- 
 ing and contraction is so often characteristic as to require 
 explanation. The walls of fissures in general, observes Sir 
 H De la Beche, are rarely perfect planes throughout then- 
 entire course, nor could we well expect them to be so since 
 they commonly pass through rocks of unequal hardness and 
 difflrermina composition. If, therefore *^L,ThaUs 
 sides of such irregular fissures slide upon each othei,that is 
 to sav if there be a fault, as in the case of so many mineral 
 leins^the pSelism of the opposite walls is at once entire- 
 ly destioyedras will be readil? seen by studying the annex- 
 ed diagrams, fracture traversing a rook, 
 ^fflh l3' eS' represent the same line. Now, if we cut 
 
612 
 
 ELEMENTS OF GEOLOGY. 
 
 Fig. 633. 
 
 Fig. 036. 
 
 the points 1, 2, 3, 4, 5, we obtain an irregular aperture at e, and 
 isolated cavities aX d d d, and when we compare such figures 
 with nature we find that, with certain modifications, they 
 represent the interior of faults and mineral veins. If, in- 
 stead of sliding the cut paper to the right hand, we move 
 the lower part towards the left, about the same distance that 
 it was previously slid to the right, we obtain considerable 
 variation in the cavities so produced, two long irregular open 
 spaces,/",/". Fig. 635, being then formed. This will serve to 
 show to what slight circumstances considerable vaiiations in 
 the character of the openings between unevenly fractured 
 surfaces may be due, such surfaces being moved upon each 
 other, so as to have numerous points of contact. 
 
 Most lodes are perpendicular to the horizon, or nearly so ; 
 but some of them have a considerable inclination or "hade," 
 as it is termed, the angles of dip being very va- 
 rious. The course of a vein is frequently very 
 straight ; but if tortuous, it is found to be choked 
 up with clay, stones, and pebbles, at points where 
 it departs most widely from verticality. Hence 
 at places, such as a, Fig. 636, the miner com- 
 plains that the ores are " nipped," or greatly re- 
 duced in- quantity, the space for their free depo- 
 sition having been interfered with in conse- 
 quence of the pre-occupancy of the lode by 
 earthy materials. When lodes are many fath- 
 oms wide, they are usually filled for the most 
 part with earthy matter, and fragments of rock, through 
 which the ores are disseminated. The metallic substances 
 frequently coat or encircle detached pieces of rock, which 
 our miners call "horses" or "riders." That we should find 
 some mineral veins which split into branches is also natural, 
 for we observe the same in regard to open fissures. 
 
 Chemical Deposits in Veins. — If we now turn from the 
 mechanical to the chemical agencies which have been instru- 
 mental in the pi-odnction of mineral veins, it may be re- 
 marked that those parts of fissures which were choked up 
 
CHEMICAL DEPOSITS IN VEINS. 613 
 
 with the ruins of fractured rocks must always have been 
 filled with water; and almost every vein has probably been 
 the channel by which hot springs, so common in countries 
 ot volcanoes and earthquakes, have made their way to the 
 surface. For we know that the rents in which ores abound 
 extend downward to vast depths, where the temperature of 
 the interior of the earth is more elevated. We also know 
 that mineral veins are most metalliferous near the contact of 
 plutonic and stratified formations, especially where the former 
 send veins into the latter, a circumstance which indicates an 
 original proximity of veins at their inferior extremity to ig- 
 neous and heated rocks. It is moreover acknowledged that 
 even those mineral and thermal springs whicli, in the present 
 state of the globe, are far from volcanoes, are nevertheless 
 observed to burst out along great lines of upheaval and dis- 
 location of rocks.* It is also ascertained that all the sub- 
 stances with which hot springs are impregnated agree with 
 those discharged in a gaseous form from volcanoes. Many 
 of these bodies occur as vein-stones ; such as silex, carbonate 
 of lime, sulphur, fluor-spar, sulphate of barytes, magnesia, 
 oxide of iron, and others. I may add that, if veins have been 
 filled with gaseous emanations from masses of melted matter, 
 slowly cooling in the subterranean regions, the contraction 
 of such masses as they pass from a plastic to a solid state 
 would, according to the experiments of Deville on granite 
 (a rock which may be taken as a standard), produce a reduc- 
 tion in volume amounting to 10 per cent. The slow crystal- 
 lization, therefore, of such plutonic rocks supplies us with a 
 force not only capable of rending open the incumbent rocks 
 by causing a failure of support, but also of giving rise to 
 faults whenever one portion of the earth's crust subsides 
 slowly while another contiguous to it happens to rest on a 
 diflferent-foundation, so as to remain unmoved. 
 
 Although we are led to infer, from the foregoing reason- 
 ino', that there has often been an intimate connection between 
 metalliferous veins and hot springs holding mineral matter 
 in solution, yet we must not on that account expect that the 
 contents of hot springs and mineral veins would be identical. 
 On the contrary, M. E. de Beaumont has judiciously observed 
 that we ought to find in veins those substances which, being 
 least soluble, are not discharged by hot springs— or that 
 class of simple and compound bodies which the thermal wa- 
 ters ascending from below would first precipitate on the 
 walls of a fissure, as soon as their temperature began shghtly 
 to diminish. The higher they mount towards the surface, 
 * See Dr. Daubeny's Volcanoes. 
 
614 ELEMENTS OF GEOLOGY. 
 
 the more will they cool, till they acquire the average tempera- 
 ture of springs, being in that case chiefly charged with the 
 most soluble substances, such as the alkalies, soda and potash. 
 These are not met with in veins, although they enter so 
 lai-gely into the composition of granitic rocks.* 
 
 To a certain extent, therefore, the arrangement and dis- 
 tribution of metallic matter in veins may be referred to ordi- 
 nary chemical action, or to those variations in temperature 
 which waters holding the oi-es in solution must undergo, as 
 they rise upward from great depths in the earth. But there 
 are other phenomena which do not admit of the same simple 
 explanation. Thus, for example, in Derbyshire, veins con- 
 taining ores of lead, zinc, and copper, but chiefly lead^ trav- 
 erse altei'nate beds of limestone and greenstone. The ore is 
 plentiful where the walls of the rent consist of limestone, but 
 is reduced to a mere string when they are formed of green- 
 stone, or " toad-stone," as it is called provincially. Not that 
 the original Assure is narrower where the greenstone occurs, 
 but because more of the space is there filled with vein-stones, 
 and the waters at such points have not parted so freely with 
 their metallic contents. 
 
 " Lodes in Cornwall," says Mr. Robert W. Fox, " are very 
 much influenced in their metallic riches by the nature of the 
 rock which they traverse, and they often change in this re- 
 spect very suddenly, in passing from one rock to another. 
 Thus many lodes which yield abundance of ore in granite, 
 are unproductive in clay-slate, or killas, and vice versa. 
 
 Supposed relative Age of the diflferent Metals. — After duly 
 reflecting on the facts above described, we can not doubt 
 that mineral veins, like eruptions of granite or trap, are re- 
 ferable to many distinct periods of the earth's history, al- 
 though it may be more difficult to determine the precise age 
 of veins ; because they have often remained open, for ages, 
 and because, as we have seen, the same fissure, after having 
 been once filled, has frequently been re-opened or enlarged. 
 But besides this diversity of age, it has been supposed by 
 some geologists that certain metals have been produced exclu- 
 sively in earlier, others in more modern times ; that tin, for 
 example, is of higher antiquity than copper, copper than lead 
 or silver, and all of them more ancient than gold. I shall 
 first point out that the facts once relied upon in support of 
 some of these views are contradicted by later experience, 
 and then consider how far any chronological order of ar- 
 rangement can be recognized in the position of the precious 
 and other metals in the earth's crust. 
 
 * Bulletin, iv., p. 1278. 
 
RELATIVE AGES OF METALS. 615 
 
 In the first place, it is not true that veins in which tin 
 abounds are the oldest lodes worked in Great Britain. The 
 |overnment survey of Ireland has demonstrated that in 
 Wexford veins of copper and lead (the latter as usual being 
 argentiferous) are much older than the tin of Cornwall. In 
 each of the two countries a very similar series of aeoloo^ical 
 changes has occurred at two distinct epochs— in Wexford 
 before the Devonian strata were deposited ; in Cornwall af- 
 ter the carboniferous epoch. To begin with the Irish mining 
 district : We have granite in Wexford traversed by granite 
 veins, which veins also intrude themselves into the Silurian 
 strata, the same Silurian rocks as well as the veins having 
 been denuded before the Devonian beds Avere superimposed. 
 Next we find, in the same county, that elvans, or straight 
 dikes of porphyritic granite, have cut through the granite 
 and the veins before mentioned, but have not penetrated the 
 Devonian rocks. Subsequently to these elvans, veins of cop- 
 per and lead were produced, being of a date certainly poste- 
 rior to the Silurian, and anterior to the Devonian; for they 
 do not enter the latter, and, what is still more decisive, 
 streaks or layers of derivative copper have been found near 
 Wexford in the Devonian, not far from points where mines 
 of copper are worked in the Silurian strata. 
 
 Although the precise age of such copper lodes can not be 
 defined, we may safely affirm that they were either filled at 
 the- close of the Silurian or commencement of the Devonian 
 period. Besides copper, lead, and silver, there is some gold 
 in these ancient or pi-imary metalliferous veins. A few frag- 
 ments also of tin found in Wicklow in the drift are supposed 
 to have been derived from veins of the same age.* 
 
 Next, if we turn to Cornwall, we find there also the monu- 
 ments of a very analogous sequence of events. First, the 
 granite was formed ; then, about the same period, veins of 
 fine-grained granite, often tortuous (see Fig. 614, p. 561), pen- 
 etrating both the outer crust of granite and the adjoining 
 fossiliferous or primary rocks, including the coal-measures; 
 thirdly, elvans, holding their course straight through granite, 
 granitic veins, and fossiliferous slates ; fourthly, veins of tin 
 also containing copper, the first of those eight systems of fis- 
 sures of different ages already alluded to, p. 607. _ Here, 
 then, the tin lodes are newer than the elvans. It has, indeed, 
 been stated by some Coi-nish miners that the elvans are in 
 some instances posterior to the oldest tin-bearing lodes, but 
 the observations of Sir H. de la Beche during the survey led 
 him to an opposite conclusion, and he has shown how the 
 * Sir H. De la Beche, MS. Notes on Irish SuiTey. 
 
616 ELEMENTS OF GEOLOGY. 
 
 cases referred to in corroboration can he otherwise interpret- 
 ed.* We may, therefore, assert that the most ancient Cor- 
 nish iodes are younger than the coal-measures of that part 
 of England, and it foUows that they are of a much later date 
 than the Irish copper and lead of Wexford and some adjoin- 
 ing counties. How much later, it is not so easy to declare, 
 although probably they are not newer than the beginning 
 of the Permian period, as no tin lodes have been discovered 
 in any red sandstone which overlies the coal in the south- 
 west of England. 
 
 There are lead veins in Glamorganshire which enter the 
 lias, and others near Frome, in Somersetshire, which have 
 been traced into the Inferior Oolite. In Bohemia, the rich 
 veins of silver of Joachimsthal cut through basalt contain- 
 ing olivine, which overlies tertiary lignite, in Avhich are 
 leaves of dicotyledonous trees. This silver, therefore, is de- 
 cidedly a tertiary forraaiion. In regard to the age of the 
 gold of the Ural Mountains, in Russia, which, like that of 
 California, is obtained chiefly from auriferous alluvium, it 
 occurs in veins of quartz in the schistose and granitic rocks 
 of that chain, and is supposed by Sir R. Murchison, MM. De 
 Yerneuil and Keyserling to be newer than the syenitic gran- 
 ite of the Ural — perhaps of tertiary date. They observe 
 that no gold has yet been found in the Permian conglomer- 
 ates which lie at the base of the Ural Mountains, although 
 large quantities of iron and copper detritus are mixed with 
 the pebbles of those Permian strata. Hence it seems that 
 the Urulian quartz veins, containing gold and platinum, 
 were not formed, or certainly not exposed to aqueous denu- 
 dation, during the Permian era. 
 
 In the auriferous alluvium of Russia, California, and Aus- 
 tralia, the bones of extinct land-quadi"upeds have been met 
 with, those of the mammoth being common in the gravel at 
 the foot of the Ural Mountains, while in Australia they con- 
 sist of huge marsupials, some of them of the size of the rhi- 
 noceros and allied to the living wombat. They belong to 
 the genera Diprotodon and Nototherium of Professor Owen. 
 The gold of Northern Chili is associated in the mines of Los 
 Homos with copper pyrites, in veins traversing the cretaceo- 
 oolitic formations, so called because its fossils have the char- 
 acter partly of the cretaceous and partly of the oolitic fauna 
 of Europe.f The gold found in the United States, -in the 
 mountainous parts of Virginia, North and South Carolina, 
 and Georgia, occurs in metamorphic Silurian strata, as well 
 as in auriferous gravel derived from the same. 
 
 * Report on Geology of Cornwall, p. 310. 
 
 t Darwin's South America, p. 209, etc. 
 
ORIGIN OF GOLD IN CALIFORNIA. 617 
 
 _ Gold has now been detected in almost every kind of rock, 
 m slate, quartzite, sandstone, limestone, granite, and serpen- 
 tme, both in veins and in the rocks themselves at short dis- 
 tances from the veins. In Australia it has been worked suc- 
 cessfully not only in alluvium, but in vein-stones in the na- 
 tive rock, generally consisting of Silurian shales and slates. 
 It has been traced on that continent over more than nine 
 degrees of latitude (between the parallels of 30° and 39° S.), 
 and over twelveof longitude, and yielded in 1853 an annual 
 supply equal, if not superior, to that of California ; nor is 
 there any apparent prospect of this supply diminishing, still 
 less of the exhaustion of the gold-fields. 
 
 Origin of Gold in California. — Mr. J. Arthur Phillips,* in 
 his treatise ''On the Gold Fields of California," has shown 
 that the ore in the gold workings is derived from drifts, or 
 gravel clay, and sand, of two distinct geological ages, both 
 comparatively modern, but belonging to different river-sys- 
 tems, the older of which is so ancient as to be capped by a 
 thick sheet of lava divided by basaltic columns. The au- 
 riferous quartz of these drifts is derived from veins apparent- 
 ly due to hydrothermal agency, proceeding from granite and 
 penetrating strata supposed to be of Jurassic and Triassic 
 date. The fossil wood of the drift is sometimes beautifully 
 silicified, and occasionally the trunks of trees are replaced 
 by iron pyrites, but gold seems not to have been found as 
 in the pyrites of similarly petrified trees in the drift of Aus- 
 tralia. 
 
 The formation of recent metalliferous veins is now going 
 on, according to Mr. Phillips, in various parts of the Pacific 
 coast. Thus, for example, there are fissures at the foot of the 
 eastern declivity of the Sierra Nevada in the state of that 
 name, from which boiling water and steam_ escape, forming 
 siliceous incrustations on the sides of the fissures. In one 
 case, where the fissure is partially filled up with silica inclos- 
 ing iron and copper pyrites, gold has also been found in the 
 vein-stone. 
 
 It has been remarked by M. de Beaumont, that lead and 
 some other^ metals are found in dikes of basalt and green- 
 stone, as well as in mineral veins connected with trap-rock, 
 whereas tin is met with in granite and in veins associated 
 with the Plutonic series. If this rule hold true generally, 
 the geological position of tin accessible to the miner will be- 
 long for the most part, to rocks older than those bearing lead. 
 The 'tin veins will be of higher relative antiquity for the 
 same reason that the " underlying " igneous formations or 
 * Proc. Royal Soc. 1868, p. 294. 
 
618 ELEMENTS OF GEOLOGY. 
 
 granites which are visible to man are older, on the whole, 
 than the overlying or trappean formations. 
 
 If different sets of fissures, originating simultaneously at 
 different levels in the earth's crust, and communicating, some 
 of them with volcanic, others with heated plutonic masses, 
 be filled with different metals, it will follow that those formed 
 farthest from the surface will usually require the longest 
 time before they can be exposed superficially. In order to 
 bring them into view, or within reach of the miner, a greater 
 amount of upheaval and denudation must take place in pro- 
 portion as they have lain deeper when first formed and filled. 
 A considerable series of geological revolutions must inter- 
 vene before any part of the fissure which has been for ages 
 in the proximity of the plutonic rock, so as to receive the 
 gases discharged from it when it was cooling, can emerge 
 into the atmosphere. But I need not enlarge on this sub- 
 ject, as the reader will remember what was said in the 30th, 
 32d, and 36th chapters, on the chronology of the volcanic and 
 hypogene formations. 
 
INDEX. 
 
 Tlie Fossils, the names of which are printed in Italics, are figured in the Text. 
 
 ABBKVILLE. 
 
 ABBEVILLE, flint tools of, 152. 
 Aberdeenshire, granite of, 558. 
 Abich, M., on trachytic roclcs, 504. 
 Acer trilobatum, Miocene, 220, 221. 
 Acrodiis noMlU, Lias, 359. 
 Acrogens, term explained, 303. 
 Acrolepis Sedgwickii, Permian, 390. 
 Actcean amfus. Great Oolite, 345. 
 Actirtocticlas, in Atlantic mnd, 288. 
 Actinol'ite, 499, 502. 
 
 schist, 578. 
 
 ^chmodua Leaehii, Lias, 358. 
 Adiantitsa Hiberniea, Old Red, 441. 
 Agassiz on lish of Sheppey, 267. 
 
 on fish of the Brown-Coal, 640. 
 
 on fish of Monte Bolca, 544. 
 
 on Old Red fossil fish, 4*1, 44T. 
 
 on Silurian fish, 400. 
 
 Age of metamorphic rocks, 597. 
 
 of Plutonic rocks, 564. 
 
 of strata, tests of, 123. 
 
 of volcanic rocks, 620. 
 
 Agglomerate described, 509. 
 
 Amio&t^f^ integer: A. Jiex, 488. 
 
 Air-breathers of the Coal, 413. 
 
 Aix-la-Chapelle, Cretaceous flora of, 302. 
 
 Alabaster defined, 39. 
 
 Albert! on Kenper, 376. 
 
 Albite, 499, 600. 
 
 Aldeby and Chillesford beds, 192. 
 
 Alkali, present in the Palaeozoic strata, 587. 
 
 Alpine blocks on the Jura, 169. 
 
 Alps, age of metamorphic rocks in, 599. 
 
 - — , nummulitio limestone and flysch of, 
 
 Alum schists of Norway and Sweden, 4S9. 
 Allnvial deposits. Recent and Postplio- 
 
 cene, 161. 
 Alluvium, term explained, 99. 
 
 in Anvergne, 100. , , , . 
 
 Alternations of marine and fresh-water 
 
 strata, T2. , , „„„ 
 
 Alum Bay beds, plants of the, 202. 
 Amblyrhynchus cristatns, a living marine 
 
 ASiia^'IS'unitea States, Canada, Nova 
 
 _i° North, Glacial formations of, 182 
 
 ' South, gradnal rise of land in, i2. 
 
 ' silnrian strata of, 478. 
 
 ANTIGLINAT.. 
 
 American character of Lower Miocene 
 
 flora, 238. 
 
 forms in Swiss Miocene flora, 223. 
 
 Amiens, flint tools of, 152. 
 Ammonites ii/rons, Lias, 350. 
 
 Braikenridgii, Oolite, 351. 
 
 BucklavM, Lias, 356. 
 
 Deshayesii, Neocomian, 311. 
 
 Hwmphresianus, Inf. Oolite, 351, 
 
 Jason, Oxford Clay, 340. 
 
 Noricus, Speeton, 312. 
 
 ~ — Tncua'oc^hahis, Oolite, 352. 
 
 Tnargariiatus, Lias, 357. 
 
 planorbis, Lias, 356. 
 
 Rhotomagtmsis, Chalk marl, 298. 
 
 Amphibole group of minerals, 499, 502. 
 ATtipMstefjina Hwuerina, Vienna basin, 
 
 225. 
 Arnphitherium Brod&ripii, in Stonesfield, 
 
 348. 
 
 Preiiostii, Stonesfield slate, 347. 
 
 AmpvUaria glauca, 56. 
 
 Amygdaloid, 507. 
 
 Analcime, 500. 
 
 Anamesite, a variety of basalt, 504. 
 
 Ananchytes ovatus. White chalk, 293. 
 
 , with crania attached, 49. 
 
 Ancillaria subulata, Eocene, 67. 
 Ancyloceras gigas, 309. 
 
 spinigerum, Gault, 301. 
 
 Dvvallei, Neocomian, 312. 
 
 Aiieyltis velletia (4. elegmis), 55. 
 
 Andalusite, 500. 
 
 Andes, Plutonic rocks of the, 569. 
 
 Andreasburg, metalliferous vein of, 611. 
 
 Angelin, on Cambrian of Sweden, 489. 
 
 Angiosperme, 303. 
 
 — r of the Coal, 429. , ^ , . 
 
 Aiiglesea, dike cutting through shale in, 
 
 514. 
 Anodonta Cordierii, M. 
 
 Jukesii, Upper Old Red, 441. 
 
 latimarginata, 54. 
 
 Anoplottu^ium. comnimie, Binstead, 254. 
 
 , gracile, Paris basin, 271. 
 
 Anorthite, 499, 501. „ , ,„, 
 
 Anmdaria spJienopliyllmdea, Coal, 425. 
 AiUhMtlws, coal-measures, 429. 
 Anthracite, conversion of coal into, 403. 
 Anticlinal and synclinal curves, 74, 86. 
 
620 
 
 INDEX. 
 
 ANTRIM. 
 
 Antrim, Chalk altered by a dike in, 516. 
 , Lower Miocene, volcanic rocks of, 
 
 539. 
 Antwerp Cragr. 204. 
 Apateon pedestris, a carboniferons reptile, 
 
 40C. 
 Apatite, 500. 
 Apeniiiues, Northern, mctamorphic rocks 
 
 of, 599. 
 Apes, fossil of the Upper Miocene, 215. 
 Apiocrijiites rotuiidus, Bradford, 343. 
 Appalachians, long lines of flexures in, 
 
 92, 93. 
 , vast thickness of successive strata In, 
 
 110. 
 AptycJntSt part of ammonite, 33G, 
 Aqueous rocks defined, 27, 35. 
 Araucaria sphce^-oearpa, Inf. Oolite, 34S. 
 Arbroath, section of Old Red ar, T4. 
 ArclicKopteryx rtiacriiraf Soleuhofen, 338. 
 Archegofiwiinis nninor and A. mcdiws, coal 
 
 measures, 40G, 407. 
 Archiac, M. de, on uummulites, 277. 
 
 , on chalk of France, 300. 
 
 Arctic Miocene Flora, 239. 
 
 Area of the Wealden, 319. 
 
 Areas, permanence of continental, 117. 
 
 Arenaceous rocks described, 35. 
 
 Areiiicolites Uiiearis, Arenig beds, 4T5. 
 
 Arenig or Stiper-Stones group, 474. 
 
 2 volcanic formations of, 549. 
 
 Argile plastlqne, 270. 
 Argillaceous rocks described, 36. 
 Argillite, Argillaceous schist, 579. 
 Argyll, Bake of, on Isle of Mull leaf-beds, 
 
 247. 
 Armagh, bone-beds in Mountain Lime- 
 stone at, 437. 
 Arran, amygdaloid filled with spar near, 
 
 518. 
 
 , erect trees in volcanic ash of, 54G. 
 
 ■ , Greenstinie dike in, 514. 
 
 Arthur's seat, trap rocks of, 545. 
 Arvicola, tooth of, 165. 
 Asaphits ccmdatus, Silurian, 467. 
 
 tyraiinus, A . Buckii, 474. 
 
 Ascension, lamination of volcanic rocks 
 
 in, 595. 
 Ash, Mr., on fossils of Tremadoc beds, 
 
 4S3. 
 Ashby-de-la Zouch, fault in coal field of, 
 
 91. 
 Aspidura loricaia, Muschelkalk, 379. 
 Astarte boi-ealis (=A. arctica=^A. com- 
 
 pressa), 170. 
 
 Omalii, Crag, 199. 
 
 Asterophyllites foliomi8, Coal, 425. 
 Astrangia lineata {Anth&phyllum linea- 
 
 tum), 229. 
 Astrcea basaltifoi'me, Carboniferous, 432. 
 Astropecten crispatv^, London clay, 260. 
 Atherfield clay, 309. 
 Atlantic mnd, composition of, 287. 
 Atrypa reticularis, Aymestry, 402. 
 Aturiaziczac {Nautilus ziczac), 266. 
 Augite, 499, 502. 
 Auricula, recent, 55. 
 Austen, Mr. Godwin, on marine deposit of 
 
 Selsea Bill, 182. 
 
 , on boulders in chalk, 292. 
 
 Australian cave breccias, 158. 
 Australia, auriferous gravel of, 617. 
 
 JIELEMNITKB. 
 
 Anvergue, alluvium in, 100. 
 
 , chain of extinct volcanoes in, 495. 
 
 , granite veins in, 610. 
 
 , Lower Miocene of, 233. 
 
 , Miocene volcanic rocks of, 640. 
 
 , Post-pliocene volcanic eruptions iu, 
 
 527. 
 
 , springs from spent volcanoes in, 604. 
 
 Aveline Mr., on Tarannon shales, 468. 
 A vicula contortat Rhsetic beds, 360. 
 
 cygnipes, Lias, 355. 
 
 i7icequivalvis, Lias, 355. 
 
 soc-talis, Mnschelkalk, 379. 
 
 Aviculopecten papyraceus, coal measures, 
 
 405. 
 
 suUobatiis, mountain limestone, 434. 
 
 Aymestry Limestone, 461. 
 
 Azoic period, supposed, 603. 
 
 Azores, Miocene lavas with shells, 539. 
 
 BACILLARTA paradoxa, 51. 
 
 Baculites anceps^ Lower Chalk, 298. 
 
 Fauiasii, chalk, 286. 
 
 Baffin's Bay, formation of drift in, 171, 
 173. 
 
 Bagshot sands, 258, 259, 262. 
 
 Baioe, Bay of, sublerraneau igneous action 
 in, 569. 
 
 Bakewell, Mr., on clcavaiieiu Swiss Alps, 
 590. 
 
 Bala and Caradoc beds, 470. 
 
 Balistidce, defensive spine of, 261. 
 
 Bangor, or Longmynd group, 485. 
 
 Bantcsia, seed aim fruit of. Lower Miocene, 
 238. 
 
 Barmouth sandstones, 4S6. 
 
 Barnes, Mr. J., ou insects in American 
 coal, 416. 
 
 Barnstaple, Upper Devonian of, 450. 
 
 Barrande, M. Joachim, his "Primordial 
 Zone," 471, 482, 487. 
 
 , on metamorphosis of trilobites, 471. 
 
 Barrett, Mr., on bird in Blackdown beds, 
 299. 
 
 Bart(m series sands and clays, 268. 
 
 shells, percentage of, commou to 
 
 London clay, 258. 
 
 Basalt, columnar, 511. 
 
 , composition of, 504. 
 
 Basaltic rocks, poor in silica, 604. 
 
 , specific gravity of minerals in, 504. 
 
 Basilosaur^is, Eocene, United States, 2S0. 
 
 Basset, term explained, 83. 
 
 Basterot, M. de, on Bordeaux tertiary 
 strata, 141. 
 
 Bath Oolite, 342. 
 
 Batrachian reptiles in coal, 406. 
 
 Bay of Fundy, denudation in coalfield in, 
 41S. 
 
 Bean, Mr., on Yorkshire Oolite, 350. 
 
 Bear Island carboniferous flora, 441. 
 
 Beanmout, M. E. de, on island in Creta- 
 ceous sen, 305. 
 
 , on mineral veins, 013. 
 
 , on .Ttirassic plutonic rocks, 571. 
 
 ■, on formation of granite, 553. 
 
 Beckles, Mr. S. H., on foot-prints in Hast- 
 ings sands, 315, 330. 
 
 ou Mammalia of Purbeck, 326. 
 
 Belemnitella Tn^icronata, Chalk, 283. 
 
 Belemnites hastattis, Oxford clay, 340. 
 
 Puzosianue, Oxford clay, 341. 
 
INDEX. 
 
 .621 
 
 Belgium, Lower Miocene of, 241. 
 Bel^aph07i costatm, Mountain Limestone, 
 
 Beloaepia eepioidea, Sheppey, 268 
 
 ^'4 "" ^"'''''"Sio'i of Ungnia Flags, 
 
 Bembridge beds, Yarmouth, 252. 
 515^'' ■' °° ''™''^ altered by dikes, 
 
 Berlin, Miocene strata near, 242. 
 
 Bernese Alps, gneiss in the, 609. 
 
 Berthier on isomorphism, 50?. 
 
 Bertrich-Baden, columnar basalt of, 512 
 
 Beyrich on term Oligocene for Lower 
 Miocene, 244. 
 
 Billings, Mr., on trilobites, 4T1. 
 
 Bianey, Mr., on Sigillarice in volcanic ash, 
 546. 
 
 , on Stigmaria, the root of Sigillaria, 
 
 426. 
 
 Biotite,499,501. 
 
 Bird in areile plastique, 276. 
 
 Bisehoff, Professor, on Nile and Rhine 
 mud, 154. 
 
 ;, on conversion of coal into anthracite, 
 
 403. ' 
 
 , on hydrothermal action, 6S6. 
 
 Blackdowu beds, 301. 
 
 Blacklead of Borrowdale, 65. 
 
 Bo2-iron-ore, 52. 
 
 Bohemia, Cambrian rocks of, 4ST. 
 
 , silver yeius in, 616. 
 
 Bolderberg, in Belgium, Upper Miocene 
 of, 224, 
 
 Bone-bed of fish remains, Armagh, 437. 
 
 of Upper Ludlow, 459. 
 
 of the Trias, 867. 
 
 Boom, Lower Miocene of, 241. 
 
 Bordeaux, Upper Miocene of, 214. 
 
 Borrowdale, blacklead of, 65. 
 
 Bosquet, M. on chalk fossils, 2S3. 
 
 , on Maestricht beds, 283. 
 
 Botanical nomenclature, 303. 
 
 Boucher de Perthes on Abbeville alliivinm 
 152. 
 
 Boulder-clay, whether formed by icebergs 
 
 or land-ice, 166-173, 178. 
 Boulder-clay of Canada, 182. 
 
 fauna pf, 170, 189. 
 
 Boulders and pebbles in chalk, 292. 
 Bournemouth beds (Lower Bagshot), 262. 
 Boyey Tracey, lignites and clays of, 246. 
 Bowerbank, Mr., on fossil fruits of London 
 Clay, 205. 
 
 , on fossil fruits of Sheppey, 205. 
 
 Bowman, Mr., on uniting of distinct coal- 
 seams, 401. 
 Brachiopoda, preponderance of, in older 
 rocks, 470. 
 
 , mode of recognizing shells of, 471. 
 
 Bracklesham beds and Bagshot Sands, 
 
 2S9. 
 Bradford encrinites, 342. 
 Breccias of Lower Permian, 391. 
 Brick-earth or flnviatile loam, 1S3. 
 Bridlington drift, 189. 
 Bristol, dolomitic conglomerate of, 3(3. 
 Bristow, Mr., on volcanic minerals, 5U0. 
 Brixham cave near Torquay, I5S. 
 Brocchi on Italian tertiary strata, 141.. 
 
 on subapenniiic strata, 208. 
 
 Brockenhurst, corals and shells of, 2Bi. 
 
 O.VNAPA. 
 
 Brodie, Rev. P. B., on Lias insects, 363. 
 
 — — , Mr. W. H., on Purheck mammalia, 
 o20. 
 
 Brongniart, M. Adolphe, on botanical no- 
 menclature, 303. 
 
 , on Lias plants, 364» 
 
 , on flora of the Bunter, 380. 
 
 , on flora of the coal, 420. 
 
 ' ?? '^''"''' "^ Lepidodendron, 424. 
 
 - — , M. Alex., on Tertiarv series, 141 
 
 BronteusfiubeUi/er, Devonian, 453. 
 
 Brora, oolitic coal formation of, 350. 
 
 Brown, Mr. Richard, on Stigmaria, 426. 
 
 , on carboniferous rain-prints, 416. 
 
 — —, Robert, on Eocene proteaceous fruit, 
 264. 
 
 — -, Rev. T., on marine shells in Scotch 
 drift, 177. 
 
 Brown-coal of Germany, 540. 
 
 Bryce, Mr., on Scotch till, 176. 
 
 Bryozoa of Mountain Limestone, 433. 
 
 and polyzoa, terms explained, 197. 
 
 Buch, Von. Sec Von Bnch. 
 
 Bnckland, Dr., on Kirkdale cave, 1,t8. 
 
 , on violent death of saurians, 362. 
 
 , on spines offish, 359. 
 
 , on Eocene oysters, 268. 
 
 , on pot-stones in chalk, 291. 
 
 Bnddle, Mr., on creeps in coal-mines, 78. 
 
 Bulimiis ellipticits^ Bembridge, 253. 
 
 litlyfictts, Loess, 56. 
 
 Bullock, Capt., R.N., on Atlantic mud, 
 287. 
 
 Banbury, Sir C, on leaf-bed of Madeira, 
 632. 
 
 , on ferns of the Maryland coal, 421. 
 
 Bunter of Germany, 380. 
 
 or Lower Trias of England, 372. 
 
 Bnprestis f Elytron of, Stoiiesfield, 346. 
 
 Burmeister on trilobites, 471. 
 
 CAINOZOIC, term defined, 123. 
 
 Caithness, fish beds of, 443. 
 
 CalannURf root of, 425. 
 
 Calamitea Sueowii, coal, and restored stem, 
 424. 
 
 Calamophyllia radiata, Bath Oolite, 342. 
 
 Calcaire de la Beance, age of the, 230. 
 
 grossier, fossils of the, 274. 
 
 siliceux of France, 273. 
 
 Calcareous matter poured out by springs, 
 604. 
 
 rocks described, 36. 
 
 nodules in Lias, 03. 
 
 Calcarina rariapina. Eocene, 275. 
 
 Calceola mndalina, Devonian, 453. 
 
 schiefer of Germany, 453. 
 
 California, auriferous gravel of, 617. 
 
 gold in petrified wood of age of allu- 
 vium, 601. 
 
 Calynwne Bhtmenbachii, Silurian, 460. 
 Cambrian Group, classification of the, 481. 
 Cambrian, Upper, 482. 
 
 , Lower, 4S4. 
 
 of Sweden and Norway, 489. 
 
 strata of Bohemia, 4S7. 
 
 of North America, 489. 
 
 volcanic rocks, 549. 
 
 Campophytlum flexuosum, 431. 
 Canada, Cambrian of, 489. 
 
 , Devonian of, 465. 
 
 , Trap-rocks of, 549. 
 
622 
 
 INDEX. 
 
 CANADIAN 35RIFT. 
 
 Canadian drift, 182. 
 
 Canary, Grand, shelly tuffs of, 638. 
 
 Cantal, Lower Miocene of the, 231. 
 
 Cape Breton, rain-prints in coal-measnies 
 
 of, 416 
 Wrath, granite veins in gneiss at, 
 
 660. 
 Caradoc and Bala beds, 470. 
 Carbonate of lime in rocks, how tested, 
 
 37. 
 Carboniferous Group, subdivisions of the, 
 
 394. 
 
 flora, 420-430. 
 
 limestone, thickness of, 396. 
 
 , mariii e fauna of the, 432. 
 
 Period, trap-rocks of, 545. 
 
 Plutonic rocks, 572. 
 
 reptiles, 406. 
 
 insects, 405. 
 
 CarcJiarodon angusiidenSf Bracklesham, 
 
 262. 
 Cardiganshire, section of slaty cleavage in, 
 
 689. 
 Cardiocarpon OitoniSj Permian, 393. 
 Cardita {Ven^ricardia) planicostaf 260, 
 
 sxthata, Barton, 269. 
 
 Cardium dissimile, Portland Ston^, 336. 
 
 rhoeticum, Rhsetic Beds, 366. 
 
 striatulwm, Kimraeridge clay, 336. 
 
 Carne, Mv. N., on Cornish lodes, 607. 
 Carpenter, Dr., on Atlantic mud, 288. 
 
 , on Eozoon Canadense, 491. 
 
 Carrara, marble of, 599. 
 
 Carruthers, Mr., on Bocene proteaceons 
 
 fruit, 265. 
 
 , on cycads of the Purbeck, 332. 
 
 , on leaves of calamite, 425. 
 
 , on spores of carboniferous Lycopo- 
 
 diacese, 422. 
 
 , on structure of sigillaria, 426. 
 
 , on trees in volcanic ash, 547. 
 
 Cashmere, recent formations in, 146. 
 Cassian, St., Triassic strata of, 376. 
 Castrogiovanni, curved strata near, 86. 
 Catania, laterite formed in, 510. 
 
 , Tertiaiy beds in, 206. 
 
 CatilVus Lamarchii, White Chalk, 295. 
 Caucasus, absence of lakes in the, 187 
 Cault^teris primcevat Coal, 421. 
 Cave-breccias of Australia, 158. 
 Cavern deposits with human and animal 
 
 remains, 156. 
 Caves of Kirkdale and Brixham, 157. 
 Celts described, 152. 
 Cementing of strata, 61. 
 Cephalaspis LyelU, Old Bed, 446. 
 Ceratites mdoaua, Muschelkalk, 379. 
 CerUhium concavum, Headou, 256. 
 
 eleganfi, Hempstead beds, 245. 
 
 (Terebra) Portlandwumj 335. 
 
 plieatam, Hempstead beds, 245. 
 
 m£lanmdB8y 268. 
 
 Cervits alcee, tooth of, 164. 
 
 CeBtraeion PhiUippi, Recent, 297. 
 
 Chabasite, 500. 
 
 Chalk, composition, extent, and origin of, 
 
 286. 
 
 ofFaxoe, 286. 
 
 flints, origin of, 290. 
 
 ■ — fossils of the White, 293-296. 
 r. — , iceborne boulders in the, 292. 
 of North anij South Europe, 305l 
 
 Chalk, Lower White, without flints, 298. 
 
 marl, fossils of the, 298. 
 
 Period, popular error concerning 
 
 283. 
 Chalk-pit with pot-stones, view of, 291. 
 Chaina squamosa, Barton, 258. 
 Champoleon, junction of granite with 
 
 Jurassic strata near, 671. 
 Chara elastka, C. 'medicaginula, 68. 
 
 tuberc7ilata, Bembridge, 263. 
 
 Charpentier, M., on Alpine glaciers, 170. 
 , on depression of Alps in Glacial Pe- 
 riod, 186. 
 Chatham coal-field, 383. 
 Cheirotherium, foot-prints of, 372, 
 Chemical deposits in veins, 612. 
 
 and mechanical deposits, 60. 
 
 Chiapa, fall of volcanic dust at, 523. 
 
 Chichester, erratics near, 181. 
 
 Chili, copper pyrites with gold in, 616. 
 
 , walls cracked by earthquake in, 87. 
 
 Chillesford and Aldeby beds, 192. 
 Chimcsra inonstrosa, Lias, 369. 
 Chlorite-Schist, 679. 
 
 Chloritic series, or Upper Greeusand, 298. 
 Christiania, Euritic porphyry at, 562. 
 , granite veins in Silurian strata of, 
 
 572. 
 
 , quartz vein in gneiss at, 661. 
 
 Chronological groups of formations, 129. 
 Chronology, test of, in rocks, 121. 
 Cinder-bed of the Purbeck, 325. 
 CinTiamomum polyniorphvim, Miocene, 
 
 219. , 
 
 Eosamdseleri, Miocene, 239. 
 
 Claiborne beds, Eocene fossils of, 279. 
 Clarke County, United States, Zeuglodon 
 
 of, 279. 
 Classification of Tertiary formations, 137, 
 
 143. 
 
 , value of shells in, 142. 
 
 Clavsilia bidens. Loess, 66. 
 Clay defined, 36. 
 
 iron-stone defined, 404. 
 
 , plastic, 267. 
 
 slate, 579. 
 
 , Weald, 313. 
 
 Cleavage explained, 602. 
 
 , crystalline theory of, 691. 
 
 , mechanical theory of, 692. 
 
 of metamorphic rocks, 688. 
 
 Cleidotheca operctdata, 483. 
 
 Clermont, metalliferous gneiss near, 686. 
 
 Climate of the Crags, 200. 
 
 of the Coal, 430. 
 
 of the Miocene in the Arctic regions, 
 
 240. 
 
 of the Post-pliocene period, 161. 
 
 Clinkstone, 506. 
 
 Clinton group, fossils of the, 479. 
 
 Clyde, buried canoes in estuary of, 146. 
 
 , arctic marine shells in drifts of, 176. 
 
 Clymenia Utiearis, Devonian, 451. 
 Clymenien-Kalk of Germany, 460, 
 Coal, conversion into anthracite of, 403, 
 
 a land and swamp formation, 397, 
 
 , cause of the purity of, 402. 
 
 , conversion of lignite into, 403. 
 
 , erect trees in, 411. 
 
 , structure of the, 412. 
 
 , vegetation of the, 420. 
 
 , air-breathers in the, 405, 413. 
 
INDEX. 
 
 623 
 
 OOAL. 
 
 Coal Period, climate of the, 480. 
 
 field ot Virginia, 3Sa. 
 
 measures of Nova Scotia, 408. 
 
 measures, thickness of, in Wales, 397. 
 
 pipes, danger ot; 399. 
 
 , rainprints in, 416. 
 
 seams, uniting of, 400. 
 
 Coalbrook-Dale, faults in, S8. 
 Cochliodus contortus, 437. 
 Cockfleld Fell rocks, altered by dikes, 616. 
 Caelacanthus grannlutiis, Permian, 390. 
 Coleoptera of (Euingen beds, 223. 
 Collyrites ringens. Inf. Oolite, 351. 
 Columnar structure of volcanic rocks, 
 
 610. 
 
 basalt in the Vicentin, 611. 
 
 Compact feldspar, 501. 
 Concretionary strnctnre, 63. 
 Cone of Tavtaret, 627, 542. 
 
 . of Come, 2a 
 
 Cones and craters described, 496. 
 
 , absence of, in England, 30. 
 
 Conformable stratification, 39. 
 Conglomerate or pudding-stone, 36. 
 
 , Dolomitic, ot Bristol, 373. 
 
 Coniferse of the coal-measnres, 427. 
 Connecticut Valley, New Ked Sandstone 
 
 of, 381. 
 Comc^Tudus striatus, 488. 
 CoTwcoryphe striata^ 488. 
 Conrad, Mr., on age of American creta- 
 
 ceons rocks, 307. 
 Consolidation of strata, Gl. 
 Continents and oceans, permanence of, 
 
 117. 
 Contorted strata, in drift, 178. 
 Conularia omataj Devonian, 463. 
 C&nvZus priscus. Coal, 415. 
 Cimua d&perditu8^ Bracklesham, 262. 
 Conybeare and Fhillips on ninety-fathom 
 
 dike, 90. 
 Conybeare, Mr., on reptiles of the Lias, 
 
 360. 
 Copper lode near Eedrnth, 607. 
 Coprolite bed of Chloritic Series, 299. 
 beds of Ked and Coralline crags, 197, 
 
 198. 
 Coprolite^ of fish from, the chalky 298. 
 Coral Rag, fossils of the, 339. 
 Coralline or White Crag, 197. 
 Corals of the Devonian, 461. 
 
 of tile Mountain Limestone, 433. 
 
 , Neozoic type of, 431. 
 
 , Palaeozoic type of, 431. 
 
 Coriicella (Cyrena) fluminalis, 64. 
 Corlnda pisum, Hempstead beds, 246. 
 Corinth, corrosion of rocks by gases near, 
 
 686. 
 Cornbrash or Forest Marble, S41. 
 Cornwall, granite veins in, 661, 582. 
 , lodes in, 615. 
 
 mass of granite in, 652. 
 
 , vertical sections of veins m mine, 
 
 607. 
 
 Coseguina volcano, burying of organic re- 
 mains by, 523. 
 
 Crag, term defined, 192. 
 
 — ^L^'na'^f'Ss'relfation to that of pres- 
 ent seas, 201. 
 
 Norwich, 193. 
 
 . ', Coralline or White, 197. 
 
 DADOXTLON. 
 
 Crag, Red, 194. 
 
 , tables of marine testacea in, 202. 
 
 deposits, climate of, 200. 
 
 Ci-ania attached to a sea-urchin, 49. 
 
 ■ Par-mmsis, White Chalk, 294. 
 
 Crasmtella sufcota. Barton, 259. 
 Craters and cones described, 495. 
 
 , Theory of Elevation, 496. 
 
 Craven fault, 90. 
 
 Creeps in coal-mines, 78. 
 
 Cretaceous rocks of United States, 307. 
 
 Period, error as to continuity of, 288 
 
 , flora of the Upper, 302. 
 
 volcanic rocks, 644. 
 
 Plutonic rocks, 570. 
 
 Period, distinct mineral character of 
 
 rocks in, 292. 
 rocks, classification of, 282. 
 
 strata, connection between Upper 
 
 and Lower, 301. 
 
 Crinoidea of Mountain Limestoue, 433. 
 
 Croatia, Lower Miocene beds of, 242. 
 
 Croll, Mr., on amount of subaeriai denuda- 
 tion, 114. 
 
 Cromer forest-bed, 191. 
 
 Crop out, term explained, 83. 
 
 Crossopterygidie, orfringe-flnned flsh,443. 
 
 Crowfoot, Mr., on shells of Aldeby beds, 
 192. 
 
 Crust of the earth defined, 26. 
 
 Crustaceans of Old Red Sandstone, 446. 
 
 Cryptodon angulatuTn, London Clay, 266. 
 
 Ci"ystalline Limestone, 679. 
 
 rocks defined, 32. 
 
 schists, much alkali in the, 587. 
 
 theory of cleavage, 591. 
 
 Cup and Star corals, 431. 
 
 CniTed strata, 73-76. 
 
 Cutch, salt-layers in the Runn of, 375. 
 
 Cuvier, M., on fauna of the Paris basin, 
 271. 
 
 , on Mammalia of Paris gypsum, 231. 
 
 , on Tertiary series, 141. 
 
 Cyathoerinus caryocrinoides, 433. 
 
 planus, 433. 
 
 Cyathophyllum ccespitosjem, 451. 
 
 Cyclopean isles, beds of tuff and clay in, 
 629. 
 
 , contorted strata in, .530. 
 
 Cyclopteris Hibemica, Old Red, 441. 
 
 Cyclostigma (Leptdodaidron), Old Red, 441. 
 
 CyclostoTna elegans. Loess, 56. 
 
 Cylindrites acutus. Great Oolite, 345. 
 
 Cypress swamps of the Mississippi, 402. 
 
 Cyprides iu the Weald Clay, 315. 
 
 Cypridina serraio-strkUa, 451. 
 
 Cypris in fresh-water deposits, 57. 
 
 gibboea, C. tuberciUata, C. UgumimUla, 
 
 324. 
 
 striato-ptmctata, C. fasciculata, C. 
 
 granulata, 326. 
 
 PurbeckeTisiSf Cypris punctata, 331. 
 
 . spinigera, Weald Clay, 316. 
 
 Cyrena {Corbicella)Jiu7fiimilis,M. 
 
 cuneiformis, Woolwich Clays, 268. 
 
 obovata, 54. 
 
 semiatriata, Hempstead beds, 245. 
 
 CystideiE of Silurian rocl<s, 4G6. 
 Q/there infiata, coal-measures, 405. 
 
 DADOXYLON, fragment of conifeioua 
 wood, 428. 
 
624 
 
 INDEX. 
 
 Dana, on volcanic minerals, 500. 
 
 Banish kitchen-middeus, 146. 
 
 DapediuB 'nwnilifer. Lias, 358. 
 
 Dai'bisbire on shells of Moel Tryfaen, ISO. 
 
 Dartmoor, post-carboniferous granite of, 
 572. 
 
 , intrusive granite at, 572. 
 
 Darwin, Mr., on foliation and lamination, 
 596. 
 
 ■ , on mammalia of Sonth America, 160. 
 
 , on marine saurian, 362. 
 
 , on rise of part of South America, 72. 
 
 , on sinking of coral reefs, 72. 
 
 , on Plutonic rocks of the Andes, B09. 
 
 , on relationship of extinct to living 
 
 types, 160. 
 
 Dates of discoveiy of fossil vertebrata, 
 464. 
 
 Daubeny, Dr., on decomposition of tra- 
 chytic rocks, 586. 
 
 Daubr^e, on formation of zeolites, 521. 
 
 , on alkaline waters of Plombi^res, 
 
 584. 
 
 Davidson, Mr., on Spiriferina, 355. 
 
 Davis, Mr. E., on fossils of Lingnla Flags, 
 484. 
 
 Dawkins, Mr. Boyd, on Hyajna spelsea, 
 158. 
 
 , on mammalia of Cromer Forest-bed, 
 
 191. 
 
 , on Triassic mamraifer, 369. 
 
 Dawson, Dr., on Devonian flora and in- 
 sects, 456, 457. 
 
 , on Eozoon Canadeuse, 491. 
 
 , on Nova Scotia coal-measures, 409. 
 
 , on Nova Scotia coal-plants, 410, 412. 
 
 , on Pupa vetusta, 415. 
 
 , on reptiles and shells in Nova Scotia 
 
 coal, 413. 
 
 , on structure of calamite, 425. 
 
 , on structure of sigillaria, 426. 
 
 Deane, Dr., on foot-prints in Trias, 382. 
 
 Debey, Dr., on floraand fauna of Aix, 302- 
 304. 
 
 Dechen, M. von, on organic remains of the 
 brown coal, 540. 
 
 , on Cornish granite veins, 560. 
 
 De la Beche, Sir H., on granite of Dart- 
 moor, 582. 
 
 • , on Carrara marble, 599. 
 
 - — , on mineral veins, 616, 
 
 , on Hedruth copper-mine, 610, 
 
 , on saurians of the Lias, 362. 
 
 , on trap-rocks of New Red, 645. 
 
 , on Welsh coal-measures, 397. 
 
 Delesse, on action of water in metamor- 
 phism, 686. 
 
 Deltas, strata accumulated in, 2S. 
 
 Dendrerpeton in Coal, 413. 
 
 Denudation defined, 96. 
 
 , subaerial, 97. 
 
 , littoral, 102. 
 
 — -, eubmariuei 105. 
 
 , average annual amount of subaerial, 
 
 113. 
 
 of carboniferons strata, 396. 
 
 counteracting upheaval, 106-115. 
 
 a means of exposing crystalline rocks, 
 
 563. 
 
 . , trap-dikes cut off by, 518. 
 
 ' — and volcanic force antagonistic pow- 
 ers, 115. 
 
 DUNCAN. 
 
 Deposition, rate of, shown by fossils, 47. 
 Derbyshire, veins in Mountam Limestone, 
 
 OOS. 
 Derivative shells of the Eed Crag, 195- 
 
 203. 
 Desnoyers, M., on a^e of Faluns, 142. 
 
 , on Eocene fossil foot-jjrints, 272. 
 
 Desor, M., on Celtic coins in lake-dwell- 
 ings, 149. 
 Devonian Period, Upper, 450, Middle, 450, 
 
 Lower, 453. 
 
 fossils of the Bifel, 534. 
 
 of Russia, 454. 
 
 of United States and Canada, 455 
 
 insects of Canada, 457. 
 
 strata, classification of, 439-450. 
 
 Devonshire, cleavage of slate rocks in, 
 
 593. 
 Diabase, 505. 
 
 Diagonal, or cross-stratification, 42. 
 Diagram of fossiliferous rocks, 137. 
 of Plutonic and sedimentary forma- 
 tions, 567. 
 Diallage, SOO, 502. 
 
 Diaatopora diluviaTtajBath Oolite, 343. 
 Diatomacese formiiig tripoli, 51. 
 Diceras LonsdaXii, Neocomian, 310. 
 Didelphys Azaroe, Recent, 347. 
 Didymograpsm ^emimiSf 476. 
 
 Murchisonh, 473. 
 
 Dike cutting through shale, Anglesca, 
 
 515. 
 cutting through chalk, Antrim, 615, 
 
 516. 
 Dikelocephalus MinTtemtensis, 490. 
 Dikes defined, 30. 
 
 of Monte Somma, 526. 
 
 in Patagonia, ground-plan of, 532. 
 
 , volcanic or trap, 513-517. 
 
 Dilnvium, origin of term, 167. 
 
 Dinorhis Palapteryx, ofNew Zealand, 160, 
 
 Dinoiherium gigantewm. 212, 
 
 Diorite, 505. 
 
 Dip and strike, tenns explained, 80. 
 
 Diplograpsue folium, Llandeilo Flags, 474 
 
 - — pristia, Llandeilo beds, 473. 
 
 Dirt-^ied of the Purbeck, 331, 
 
 Dogger-bank described, 106, 
 
 Dolerite, a variety of basalt, 604. 
 
 Dolomite defined, 38. 
 
 Dolomitic conglomerate of Bristol, 373. 
 
 Downs, escarpments of North and South, 
 
 104. 
 Downton Sandstone, 459, 
 Dowson, Mr., on shells of Aldeby beds, 
 
 192. 
 Drew, Mr., on Hastings Sands, 316. 
 Drift of Ireland, 190. 
 
 of Norfolk cliffs, 190, 
 
 of Scandinavia, 174. 
 
 of Bridlington, 189. 
 
 carried by icebergs, 172. 
 
 shells in Canada, 183. 
 
 , contorted strata in, 178. 
 
 , marine shells in Scotch, 175. 
 
 Dudley Limestone, 466. 
 
 Dufrenoy, M., on granite of Pyrenees, 
 
 582. 
 Dnmont, Prof., on Belgian Lower Eocene, 
 
 282. 
 Duncan, Dr., on Neozoic corals passing 
 
 down to Devonian, 432, 
 
INDEX. 
 
 625 
 
 UtTNDBY HILL. 
 
 Daudry Hill, near Bristol, section of, 130. 
 Dunker, Dr., on wealden of Germany, 319. 
 Dura Deu, yellow sandstone of, 440. 
 
 EARTH'S crust deflned, 26. 
 Echinoderms of Suffolk Crag, 200. 
 Jichinosphcuronites baltictis, 472. 
 Egerton, Sir P., on fish of Headon series, 
 256. 
 
 ■ , on fish of the Permian, 389. 
 
 , on flsh of Penarth beds, 366. 
 
 Ehrenherg, Prot, on term Bryozoum, 197. 
 
 , on Silurian foraminifera, 4TS. 
 
 , on infusoria, 51. 
 
 Eifel Limestone, 453. 
 
 , Lake-craters of, 534. 
 
 Miocene, volcanic rocks of, 539. 
 
 Pliocene, volcanoes of the, 534. 
 
 , trass of the, 536. 
 
 Ele2>has aniiquttSj molar of, 163. 
 
 meridionalis, molar of, 163. 
 
 primige7tiuSj molar of, 162. 
 
 Elevation craters, theory of, 496. 
 Elvaus, term explained, 572. 
 
 of Ireland and Cornwall, C15. 
 
 JElyiron of BuprestU f Stonesfield, 340. 
 Emmons, Prof., on jaws of Triassic quad- 
 rnped, 383. 
 
 , on Dromatherium, 383. 
 
 Eucrinites of Bradford, 342. 
 Encrinus UWformiSj Mnschelkalk, 379. 
 Endogens, term explained, 303. 
 Eugihoul cave, human and animal re- 
 mains in, 157. 
 England and Wales, glacintion of, ISO. 
 Enstatite, 501. 
 Eocene areas of Enrope, map of, 250. 
 
 foraminifera, 274. 
 
 formations of France, 270-2T6. 
 
 of England, 252. 
 
 period, volcanic rocks of, 543. 
 
 , plutonic rocks of the, 56S. 
 
 . , metamorphic rocks of the, 598. 
 
 of France, foot-prints in, 272. 
 
 andMiocene, linebetween the, 230,250. 
 
 , term defined, 143. 
 
 of the United States, 278. 
 
 Kozoon Caimderme, oldest known fossil, 492. 
 
 Epidote, 500. 
 
 Eppelsheim, Dinotheriuni of, 226. 
 
 Bquisetaceaa of the Coal, 424. 
 
 Eipdsetites columnaris, Keuper, 370. 
 
 Eqmtfi caballnSf tooth of, 104. 
 
 Erratic blocks, nature of, 167. 
 
 of Greenland, 171. 
 
 near Chichester, ISl. 
 
 in the Red Crag, 201. 
 
 Erratics, Alpine, 109. 
 Escarpments explained, 104. 
 Eschara disticha, White Chalk, 290. 
 Escharina oceani, White Chalk, 290. 
 Estheria minuta, Trias, 3T0. 
 
 ovata, Richmond, Vngmia, 3S3. 
 
 Ethridge, Mr., on Atlantic mud, 2Sb. 
 
 , oS Devonian series, m Devon, 450. 
 
 , on Devonian fauna, 451, 454. 
 
 on mollnsca of Brackleshara, 200. 
 
 on St. Cassian fossils, ii^- 
 
 Et^k°^mi np since Newer Pliocene, 204. 
 
 Pliocene lavas of, oiv. 
 
 iSiDgshaasen on Sheppey Eocene fruit, 
 
 205. 
 
 27 
 
 FLOKA. 
 
 Euruymia radiata, Bath Oolite, 342. 
 Eunotia bidetis, Atlantic mud, 283. 
 Euow-phalus pentaruiulatus, 436. 
 Euiite, 657, 578. 
 
 Enritic porphyry of Norway, 602. 
 Evans, Mr., on Archseopteryx, 33T. 
 Exogens, 297. 
 
 Exogtjra virgula, Kimnieridge Clay, 336. 
 Extrctcrimts {Pentaerinus) BriareuSj Lias, 
 357. 
 
 FALCONER, Dr., on Miocene fauna of 
 Siwiilik Hills, 220. 
 
 , on Brixham Cave flint knives, 157 
 
 , on Purbeck mammalia, 326. 
 
 Faluns of Loire, recent shells in, 214. 
 
 of Touraine, 211. 
 
 Farnham, phosphate of lime near, 299. 
 
 Faadcularia aurantiimij Coralline crag, 
 199. 
 
 Faults in coal-measures ofCoalhrookDale, 
 88. 
 
 described, 87-92. 
 
 often the result of repeated move- 
 ments, 90. 
 
 Fauna of the crag, its relation to that of 
 our present seas, 201. 
 
 of the Mountain Limestone, 430. 
 
 of the Paris basin, 271. 
 
 Favosites cervieomie, Devonian, 451. 
 
 Gothlandica, Silurian, 465. 
 
 Favre, M. E., on glaciers and moraiues of 
 the Caucasus, 1S7. 
 
 Faxoe, chalk of, 285. 
 
 Feldspar-porphyry, 557. 
 
 Feldspar, varieties of, 499, 600. 
 
 Feldstone, 557. 
 
 Felis tigrin, tooth of, 106. 
 
 FeneMla retifornde, Maguesiau Lime- 
 stone, 3SS. . 
 
 Ferns of the coal, 421. 
 
 Fife, trap-dike lu, 540. 
 
 Fish, fossil of the Carboniferous, 436. 
 
 , Eocene of Monte Bolca, 644. 
 
 , oldest known fossil, 403. 
 
 , number of living, 446. 
 
 , fresh-water and marine, 58. 
 
 of the Upper Ludlow, 459. 
 
 of the Old Red Sandstone, 443-445. 
 
 of the Permian marl slate, 3S9. 
 
 of the brown coal, 540. 
 
 ofthe Lias, 368. . . , .„ , 
 
 Fishertou, Greenland lemming in drift of, 
 
 Fissures, filled with metallic matter, 000. 
 
 Fitton, Dr., on the Neocomiau strata, 314. 
 
 Fleming, Dr., on Parka decipiens, 448. 
 
 , on trap-dike in Fife, 640. 
 
 Flints in the Chalk, 290. 
 
 FliskdilveofFifc,540. 
 
 Flora of the Carboniferous, 420. 
 
 , Devonian, compared to Carbonifer- 
 ous, 457. . 
 
 of the Snbapennines, 208. 
 
 Lower Miocene of Switzerland, 236. 
 
 Miocene of the Arctic Berions, 239. 
 
 Older Pliocene of Italy, 208. 
 
 ofthe Permian, 392. 
 
 of the Upper Cretaceous, 302. 
 
 , Upper Miocene of Switzerland, 215- 
 
 222 
 
 of the Wealden, 320. 
 
626 
 
 INDEX. 
 
 FLUVIO-MARINE. 
 
 Fluvio-mariue or Norwich crag, 193, 
 Flysch of the Alps, 27S. 
 
 , plutoulc rocks invadiDg, 5GS. 
 
 Folding and deDudatioD of Nova Scotia 
 
 Carbbuiferous rocks, 417. 
 Folds of parallel strata, arrangemeut and 
 
 direction of, 93. 
 Foliation of crystalline rocks, 595. 
 
 , irregularities in, 590. 
 
 Folkestone and Hythe beds, 308. 
 Fontainebleau, Grcis de, 230. 
 Foot-prints in Potsdam sandstone, 490. 
 
 of reptiles in Coal-measureHj 408. 
 
 , fossil in New Bed, 3S1. 
 
 in Paris gypsiim, 272. 
 
 Foraroiuifera, Eocene, 275. 
 
 of Mountain Limestone, 437. 
 
 ofthe Chalk, 287. 
 
 Forbes, Mr. David, on glass cavities in 
 
 quartz, 555. 
 
 , on planes of foliation, 596. 
 
 , on specific gravity of quartz, 500. 
 
 , on volcanic minerals, 49S. 
 
 Forbes, Professor E., on fossils of Bern- 
 bridge beds, 262. 
 
 , on Hampstead beds, 244. 
 
 , on shells of the crag, 200. 
 
 , on sphicronites 472. 
 
 , on subdivisions of the Purbeck, 333. 
 
 , on testacea of the Faluus, 212. 
 
 , ou thickness of Upper Neocomian, 
 
 309. 
 Forest-bed at Cromer, 191. 
 
 marble or cornbrash, 341. 
 
 , submerged, 103, 104. 
 
 , fossil in Coal, 400. 
 
 , fossil of Isle of Portland, 332. 
 
 Forfarshire, Cephalaspis beds of, 446. 
 
 , contorted strata m, 178. 
 
 Formation, term defined, 27. 
 Fossil, term defined, 29. 
 — — trees erect in coal, 410. 
 
 Fish of Old Red Sandstone, 442. 
 
 Possiliferous groups, table of snccessi(ni 
 
 cif, 131. 
 Fossils, arrangement of, in strata, 47. 
 , destruction of, in older formations, 
 
 139. 
 
 , fresh-water and marine, 52. 
 
 obliterated by metamorphic action, 
 
 C03. 
 
 , recent, and post-pliocene, 154-11'5. 
 
 of the drift, 170, ISO, 192. 
 
 of the Crags, 193-203. 
 
 , Upper Miocene, 214-229. 
 
 , Lower Miocene of Switzerland, 230. 
 
 of the Hampstead Beds, 244. 
 
 , Eocene, 253. 
 
 of the Barton Clay, 259. 
 
 of the White Chalk, 293. 
 
 of the Neocomian, 309. 
 
 of the Oolite, 324. 
 
 of the Stonesfleld Slate, 347. 
 
 of the Lias, 354. 
 
 of the Trias, 370. 
 
 of the Magnesian Limestone, 387. 
 
 of the Coal, 405. 
 
 plants of the Coal, 421. 
 
 of the Mountain Limestone, 430. 
 
 , Devonian, 449. 
 
 , Silurian, 400. 
 
 , Cambrian, 4S4. | 
 
 giant's causeway. 
 Fossils, Laurentiau,492. 
 Fournct, M., on metalliferous gneiss, 580. 
 
 , on veins in granite, 610. 
 
 Fox, Rev. D., on Isle of Wight Eoceue 
 
 fossils, 254. 
 Fox, Mr. R., on lodes in Cornwall, 614. 
 Fractures of strata, and faults, 87. 
 Fragments, included, a test of age of plu- 
 
 tonic rocks, 505. 
 
 , included, a test of age of strata, 129. 
 
 a test of age in volcanic rocks, 624. 
 
 France, Eocene formations of, 270-276. 
 
 , Lower Mioce;ie of, 231. 
 
 , Upper Miocene of, 211. 
 
 Freshfleld, Mr., on absence of lakes in the 
 
 Caucasus, 187. 
 Fresh - water strata, how distinguished 
 
 from marine, 63-59. 
 
 formation of Auvergne, 233. 
 
 Fucoid sandstones of Sweden, 489. 
 Fuhjur canalicidatvs, Marylaud, 228. 
 Fuller's e.arth, fossils of the, 348. 
 Fundy, Bay of, fossil trees exposed iu cliffs 
 
 at, 412. 
 Fttsilina cTjlindHca, 438. 
 Fusion of quartz, 600. 
 FiiSus contrarius (Trophon antiqimm), 190. 
 qjtadriaostatus, Maryland, 228. 
 
 GABBRO, 505. 
 
 GaiUonella ferritfjifiea, and G. distans, 62. 
 
 Galapagos Islands, living marine saurian 
 
 iu, 302. , 
 
 Galeocerdo latidens, Brocklesham, 202. 
 Galeritea alboqalerus,yiih\\e Chalk, 294 
 Galestes iu Middle Purbeck, 328. 
 Ganoids, the type of Old Red Sandstone 
 
 fish 113. 
 
 of the Wealdeu, 310. 
 
 of the Trias, 383. 
 
 Gaps iu the sequence of fossil remaius, 138. 
 Garnet, 500. 
 
 Gases, corrosion of rocks by, 580. 
 Gaudiu ou Lower Miocene of Switzerland, 
 
 230. 
 
 on Pliocene flora of Italy, 209. 
 
 on Proteaceie in Bournemouth Eoceue, 
 
 203. 
 Gault, thickness and fossils of, 300. 
 Geikie, Mr. A., ou Ayrshire Permian trap- 
 rocks, 645. 
 
 , on subaiirial denudation, 115. 
 
 , ou ice erosion of lake-basins, 187. 
 
 , on Isle of Mnll volcanic rocks, 539 
 
 , on Pentlaud Old Red volcanic rocks, 
 
 64S. 
 
 , on Silurian metamorphic rocks, 002. 
 
 , ou syenite of Skye, 608. 
 
 Geiuitz, M., on Permian flora, 393. 
 Gemunder Maar, volcanic rocks of, 534. 
 Geneva, Lower Miocene of, 236. 
 Geology defined, 25. 
 Gergovia, tuifs and associated lacustrine 
 
 strata of, 542. 
 Germany, Lower Miocene of, 242. 
 
 , Triassic fauna of, 376. 
 
 Gers, Upper Miocene of, 216. 
 GerviUia aneeps, Neocomian, 310. 
 
 socialis, Muschelkalk, 379. 
 
 Giant's Causeway basalt, age of, 248. 
 
 , laterite of the, 509. 
 
 , columnar basalt of, 510, 
 
INDEX. 
 
 621 
 
 GIRGENTI. 
 
 Gii-genti, Newer Pliocene of, 20T. 
 Glacial drift, flistribution and iiatnre of, 
 100. 
 
 epoch in the Post-Pliocene, 100. 
 
 formations of Pliocene age, 189-192. 
 
 Glaciatiou of Biissia and Scandinavia, 1T4. 
 
 of Scotland, 175. 
 
 of Wales and Eno;land, 180. 
 
 of North America, 182. 
 
 Glaciers, transporting and abrading power 
 
 of, 108. 
 Glasgow, marine strata near, 140. 
 Glauconie grossiiire, 27{k 
 Glen Tilt, junction of granite and schist at, 
 
 559. 
 Globiform pitchstone, 512. 
 Globigeritia huUmdes, 288. 
 Globular structure of volcanic rocks, 510. 
 Gliiptostrobus^ Europceus, (Eningen, 223. 
 Gneiss, granite veins traversing, 500. 
 
 defined and flgnred, 577. 
 
 ,'fundamental, of Scotland, 493. 
 
 Gold mines of Australia and Chili, 616. 
 
 veins of Russia, 016. 
 
 . of California, of age of allivium, 
 
 OIT. 
 Goldenherg, Professor, on Saarbriick coal 
 
 insects, fl>6. 
 Guldfuss, Professor, on reptiles in coal, 
 
 406. 
 Gonialites crenistria^ 430. 
 
 • Listen, coal-measures, 405. 
 
 GHppert, on American forms in Swiss 
 Miocene flora, 223. 
 
 on petrification, 03. 
 
 on plants of coal-measui'es, 398. 
 
 Gormniia infwndibuUformis, Permian, 3SS. 
 Graham's Island, forming ashy conglome- 
 rate 549. 
 Gtampians, Old Red conglomerates of, 73. 
 
 , uap-rocks of the, 547. 
 
 , former glaciers in the, 1T5. 
 
 Grand Canary, Upper Miocene, shelly tuffs 
 
 of, 558. 
 Granite, composition of, 652. 
 
 , graphic and columnar, 553, 6.54. 
 
 , how far connected with trap-rocks, 
 
 558. 
 
 , hydrothermal action in formation of, 
 
 555. 
 
 metamorphosing fossiluerous strata, 
 
 881. 
 
 , porphyritic, 65G. 
 
 , oldest, 574. 
 
 , protrusion of solid, 5'i4. 
 
 , passage of, into trap, 68S. 
 
 , schorly, 557. 
 
 veins, 559. 
 
 veins in talcose gneiss, 560. 
 
 Granton, angiosperm found m coal at, 429. 
 Graptolites of Llandeilo flags, 4i4. 
 Graptolites Murchisonii, lilandeilo flags, 
 
 473 
 Grap'tolithm priodon, Silurian, 407. 
 Gray's, Essex, pachyderms found at, Ibi. 
 Great (or Bath) Oolite, 342. 
 Greece, Upper kiocene formations of, 226. 
 Greenland, continental ice of, 170. 
 , gradual sinking of, 7A 
 
 gfII"deSSmn, Palis basin 27.| 
 Oris de Fontainebfeau, age of the, 230. 
 
 IIEEB, 
 
 Griffiths, Sir R., on yellow sandstone of 
 
 Ireland, 441. 
 Grit defined, 36. 
 Groups, older, rise highest above the sea, 
 
 189. 
 , why the newest to be studied first, 
 
 140. 
 Gryllacris lithanthraca, Coal, 405. 
 Griiplicp-a coated with serpulce, 43. 
 
 columba, Chloritic Sand, 300. 
 
 convexa, Chalk, 296. 
 
 incurva {G. arcuata), 54, 354. 
 
 virguta, Kimmerldge clay, 336. 
 
 Gryphite Limestone, 354. 
 
 Guadalouue, glass cavities in quartz of, 
 
 655. 
 Gulf-Stream, probable abrading power of, 
 
 105. 
 Gumbel, M., on Rhsetic beds, 366. 
 Gunn, Mrs., on pot-stones in the chalk, 
 
 291. 
 Gntbier, Colonel, on Permian flora, 393. 
 Gymnogens, term explained, 303. 
 Gypseous marls of Auvergne, 233. 
 Gypsum and gypseous marl defined, 38, 
 
 39. 
 Gyrolepie tenuistriat'Uii, Rhsetic beds, 307. 
 
 HAIME, Mr., on palaeozoic corals, 431. 
 Hakea silicina and Uakea saligna, CEnin- 
 
 gen, 222. 
 Hall, Captain Basil, on Cyclopean Isles, 
 
 530. 
 
 , Sir James, on curved strata, 75. 
 
 , Mr. J., on Appalachian palueozoic 
 
 rocks, 110. 
 Hallstadt and St. Cassian beds, 376. 
 Halt/sites catenularis, Silurian, 466. 
 Hamilton, Sir W., on eruption of Vesuvius, 
 
 1779, 626. 
 Hamites ^in-iger, Gaiilt, 301. 
 Hancock, Mr., on Protorosaurus in Per- 
 mian, 390. 
 Harkuess, Professor, on Silurian metamor- 
 
 phic rocks, 002. 
 Harlech grits, fossils of the, 436. 
 Harris, Major, on the Salt Lakes, 374. 
 Harpactor mdadipeis, (Eningen, 224. 
 Harpe, M. de la, on Bournemouth Eocene 
 
 flora, 263. 
 Hartuiig, Mr., cited, 496. . 
 Hartz mountains, mineral veins of, 008. 
 
 , Bunter Sandstein of, 380. 
 
 Hastings Sands, subdivisions of the, 316. 
 Hautes Alpes, granite of the, 571. 
 HaCiy on isomorphism, 502. 
 Headon series, fossils of the, 255. 
 Heat, powerful in consolidating rocks, 
 
 ' rocks upraised and folded by, 92. 
 
 Hubert, M., on age of Sables de Brachcux, 
 
 330 
 , 'comparison of Sables Moyens and 
 
 Barton shells, 258. 
 
 , on pisolitic limestone, 285. 
 
 Hebrides, dikes in the, 514. 
 
 Heer, Professor, on American genera m 
 
 Swiss Miocene, 239. 
 
 _, on age of Madeira leaf-bed, 532. 
 
 , on Arctic Miocene flora, 289. 
 
 , on Bear Island flora, 441. 
 
 on Bovey Tracey Miocene flora, 247. 
 
628 
 
 INDEX. 
 
 HEEK. 
 
 Heer, Professor, on ibsail plants of Switz- 
 erland, 215, 219, 221, 224, 236. 
 , on Lower Miocene plants of Mull, 
 
 24S. 
 . , on Monte Bolca Eocene plants, 203, 
 
 543. 
 
 , on Proteas of Lower Miocene, 23T. 
 
 , on plants of Hempstead beds, 246. 
 
 , on plants of coal-field, Virginia, 3S3. 
 
 , on Swiss Miocene insects, 223. 
 
 , on supposed Proteaceie of OEningen 
 
 beds, 221. 
 
 , ou Snperga fossil plants, 244. 
 
 Heidelberg, varieties of granite near, 5C0. 
 Hdiolitesporosa, Devonian, 451. 
 Helix hispida (plebeia), 155, 
 -: — Idbyrinthica^ Headon, 255. 
 
 occlitsa^ Bembridge, 253. 
 
 . Twoii&neis, faluns, 56; 
 
 Bertiieidaris Purbeckenais, Purbeck, S24. 
 Hemipneustes radiatus. Chalk, 284, 
 Hffmitelites Brownii, Inf. Oolite, 350. 
 Hempstead beds, subdivisious of the, 244. 
 Henry, on absorption of carbonic acid gas 
 
 in water, 5S5. 
 Henslow, Professor, on dike in Anglesea, 
 
 515. 
 
 , on Red Crag coprolite bed, 197. 
 
 Herschel, Sir J., on slaty cleavage, 590; 
 Hertfordshire pudding-stone, 02. 
 Heterocercal- tail offish, 3S9. 
 Hicks, Dr., on fossils of A renig beds, 476. 
 
 ■ , on fossils of Harlech grits, 466. 
 
 , on Menevian beds, 4S5, 
 
 Himalaya, shells 1S,00D feet high in, 29. 
 
 , Upper Miocene of, 226. 
 
 Hippopodium ponderosuTn, Lias, 355. 
 
 Hippopota-mits, tooth of, 164. 
 
 Hippurite Limestone, 304. 
 
 Hippurites organi&a'ns. Chalk, 300. 
 
 Ilistioderma hihernica, 4S6. 
 
 Hitchcock, Professor, on Tilfis foot-prints, 
 
 3S1. 
 Uolopti/chiics nohilissimuSj scale of, and res- 
 
 storalion,4i2. 
 SomalonoUis Velphinocephalus, 407. 
 
 armatits, Devonian, 454. 
 
 Homfray, Mr., on fossils of Tremadoc 
 
 beds, 4S3. 
 Homocercal tail offish, 3S9. 
 Hooghly River, analysis of water, 69. 
 Hooker, Dr., on coniferae, 429, 430, 
 
 , on structure of sjgillaria, 426. 
 
 , on sporangia of Silurian plant) 460. 
 
 Horizontality of strata, 40. 
 
 Horizontal strata, upheaval of, 71. 
 
 Hornblende, 499, 502. 
 
 Hornblende-schist, 5TS. 
 
 Homes, Dr., on fossil mollnsca of Vienna 
 
 basin, 225. 
 Horstead, pot-stones at, 291. 
 Hour-glass illustrating the destruction 
 
 and renovation of land, 119. 
 Howse, Mr., on Protorosaurus in Permian, 
 
 390. 
 Hubbard, Professor, on granite of White 
 
 Mouutnins, 565. 
 Hudson River Gronp, fossils of the, 479. 
 Hughes, Mr. T. McKenny, cited, 450. 
 
 , on slaty cleavage, 589. 
 
 , on protrusion of solid granite, 575. 
 
 Hull, Mr. E., on breccias in Permian, 391. 
 
 INSECT. 
 
 Hull, Mr. E., on carboniferons of Lanca- 
 shire, 395. 
 
 , on carboniferous rocks of north of 
 
 England, 111. 
 
 , on faults in Lancashire coal-field, 91. 
 
 , on anticlinals and synclinals, Lanca- 
 shire, 85. 
 
 , on thickness of the Upper Trias, 369. 
 
 , on thickness of Permian, 386. 
 
 , on three lines of flexnre since the 
 
 coal in Lancashire, 94. 
 
 Human remains of Recent Period, 157. 
 
 in cavern deposits, 156. 
 
 Hnmboldt, on mineral character of rocks, 
 002. 
 
 Humphrey and Abbot on Mississippi de- 
 nudation, 114. 
 
 Hungary, trachyte of, 558. 
 
 Hunt Sterry, on action of water in meta- 
 morphism, 585. 
 
 Huronian series, thickness of the, 490. 
 
 Huxley, Prof,, on Atlantic chalk-mud, 287. 
 
 , on affinity between reptiles and birds, 
 
 338. 
 
 , on batrachians of the coal, 407. 
 
 , on fish of Old Red Sandstone, 443- 
 
 445. 
 
 , on Pteraspis, 403. 
 
 Hyaena den of Kirkdale cave, 157. 
 
 Syomut spelcea, tooth of, 105. 
 
 Hybodu8 pUcatilUj Rhsetic beds, 307. 
 
 reticulatus, Lias, 359. 
 
 Hydrothermal action producing metamor- 
 phism, 584. 
 
 in formation of granite, 555. 
 
 forming granite veins, 573. 
 
 HyTnenoearis ve-miicauda, 484. 
 
 Hyperodapedon Gordoni, Trias, 370. 
 
 Hyperstheue, 499, 502. 
 
 rock, 505. 
 
 rocks of Skye, 491. 
 
 Hypogene rocks, uniformity of mineral 
 character in, 602. 
 
 rocks, term defined, 20. 
 
 ffypsiprymnus Gaiynardi, molar of recent, 
 327. 
 
 Hythe, Neocomian beds of, 308. 
 
 ICE, erosion of lake-basins considered, 
 
 184, 18S. 
 
 , abrading power of, 108. 
 
 , continental, of Greenland, 170. 
 
 Icebergs, drift carried by, 172. 
 
 stranded in Baffin's Baj', 173. 
 
 Ice-borne erratics at Chichester, 181. 
 Iceland, glass cavities in quartz of, 555. 
 
 , flow of lava in, 523. 
 
 Ichthyosaurus communis, Lias, 361. 
 
 Idocrase, 500. 
 
 Ichthyodorulite of the Lias, 359. 
 
 Igumiodon Mantelli, Weald Clay, 315. 
 
 lifracombe Group of Devon, 449. 
 
 Inclined strata, 73. 
 
 India, Miocene formations of, 226. 
 
 India, Upper Miocene of, 220. 
 
 Inferior Oolite, thickness and fossils of, 
 
 349. 
 Infusoria in tripoli, 51. 
 Inland sea-cliffs, 103. 
 Inoceramus LaTnarckii, White Chalk, 295. 
 Insect in American coal, 410. 
 beds of the Lias, 363. 
 
INDEX. 
 
 629 
 
 INSECT. 
 
 Tnaect, wing of neunpterous, 303. 
 Insects, Devoniau, of Canada, 45T 
 
 Ill European coal, 405. 
 
 , Miocene, of Croatia, 243. 
 
 - — , Upper Miocene, at (Eningen, 223. 
 Intrusion, a test of age of plutonic rocks, 
 
 ooo. 
 - — , a test of age of volcanic rocks, B21. 
 Inundation mud of riverB, 153 
 Ireland, glacial drift of, 190. 
 
 , yellow sandstone of, 441. 
 
 Iron pyrites, 500, 
 
 weapons of Swiss lake-dwellings, 14S. 
 
 Imstrixa oblmiga, Portland Sand, 335. 
 Isle of Bourbon, lava current of the, 5C0. 
 
 Wight, Hempstead beds, 244. 
 
 Wight, Eocene beds, 255. 
 
 Mnll, Miocene leaf-bed of, 247. 
 
 Mnll, volcanic rocks, 248, 
 
 Isomorphism, theory of, 502. 
 Italy, Lower Miocene of, 244. 
 
 , Older Pliocene volcanoes of, 523. 
 
 , Pliocene of, 20T. 
 
 , Older Pliocene flora of, 203. 
 
 , Upper Miocene strata of, 220. 
 
 JAMIESON, Mr. T. F., on Scotch glacial 
 
 drift, 1T5. 
 Jaws. of mammalia in Purbeck, 327. 
 Jeffreys, Mr. Gwyn, on Atlantic mnd, 2S8. 
 Jointed strnctnie of metamorphic rocks, 
 
 589. 
 Jones, Dx. Bnpert, on Eozoon Canadeusc, 
 
 491. 
 Jornllo, lava stream of, 566. 
 Judd, Mr., on Speetou clay, 311. 
 Jukes, Mr., on Taranuon shales, 468. 
 Jnra, erratic blocks on the, 169. 
 , structure of the, 82. 
 
 KANGAROO, jaws of, 159. 
 
 KSsegrotte, Bertrich Baden, Basaltic pil- 
 lars of, 512. 
 
 Kaup, Professor, on foot-prints of the 
 Trias, 3T8. 
 
 Keilhan, Professor, on granite veins, 562. 
 
 , on planes of foliation, 695. 
 
 , on Silurian granite of Norway, 673. 
 
 , on protrusion of granite, 581. 
 
 Keller, Dr. F., on lake-dwellings, 148. 
 
 Kelloway Hock, percentage of Oxford clay 
 fossils in, 341. 
 
 Kentish Bag, 308. 
 
 Kcnper, of Germany, 375. 
 
 or Upper Trias of England, 369. 
 
 Kilkenny, fossil plants of, 441. 
 
 Killas, altered by granite in Cornwall, 582. 
 
 Kiltorkan, yellow sandstone of, with 
 Anodonta,"441. 
 
 Kimmeridge Clay, 335. 
 
 King, Dr., on reptile foot-pnuts m coal, 
 407. 
 
 , Mr., on Permian fossils, 388. 
 
 Kirkdale cave, hyaena's den of, 157. 
 
 Kitchen-middens of Denmark, 146. 
 
 Kleyn Spawen beds, 242. » . ,, 
 
 Konen, Baron von, on Brockenburst shells, 
 257 
 
 Koni'nck, M. de, on Mountain Limestone 
 
 on shells of Mavence ba.«in,242. 
 
 Kminckia Leonhardi, Hallstadt, 377. 
 
 T-EPinOTirS MANTELLI. 
 
 LABRADOR rock, 505. 
 
 series, 490. 
 
 Labradorite, 499, 501. 
 
 Latnjrinthodon JaegeH, section of tooth, 
 
 , tooth of, 370. 
 
 Labyrinthodonts of Coal, 407. 
 
 Lake-craters of the Bifel, 534. 
 
 Lake districts, southern limits of the, 184. 
 
 Lake-dwellings, scarcity of human re- 
 mains, in, 149. 
 
 of Switzerland, 148. 
 
 Lakes, deposits in, 27. 
 
 , connection of, with glacial action. 
 
 184-188. 
 
 Lamarck on bivalve moUusca, 54 
 
 Lamination of clay slate, 694. 
 
 Lamna elegans, Bracklesham, 262. 
 
 Lancashire, vast thickness of rocks with- 
 out corresponding altitude in, 111.- 
 
 Land, balance of dry, how presei'ved, 116, 
 118. ' , .' ' 
 
 has been raised, not the sea lowered, 
 
 70. ' 
 
 , mean height of, above the sea, 115. 
 
 , rise of, in Sweden, 72, 
 
 , rise and fall of, affecting deuunda- 
 
 tion, 101. 
 
 Land-ice, action of, in Greenland, 171. 
 
 Land's End, columnar granite at, 553. 
 
 , porphyritic granite at, 566. 
 
 La Roche, recent deposits in estuary of, 
 40. 
 
 Lartet, M., on mammalia of Faluns, 214. 
 
 , on Gastornis Parisiensis, 276. 
 
 , on reindeer period, 150. 
 
 Lastrcea stiriaca, Monod, 239. 
 
 Lateral compression causing curved strata, 
 75. 
 
 Laterite of Giant's Causeway, 509. 
 
 Laurentian gneiss of Scotland, 493. 
 
 Group, Upper and Lower, 491. 
 
 metamorphic rocks, 601. 
 
 volcanic rocks, 549. 
 
 Lava, 507. 
 
 consolidating on slopes, 496. 
 
 currents of Auvergne, 541. 
 
 streams, effect of, 30. 
 
 of La Coupe d'Ayzac, 511. 
 
 of Jornllo, 560. 
 
 Lead veins, age of, 016. 
 
 Leaf-bed of Madeira in basalt and scorise, 
 532. 
 
 , Isle of Mull Miocene, 248. 
 
 Leda nmygdaloidea, London Clay, 266. 
 
 Deshayesiana {Xmmla Deehayesmiia), 
 
 241. 
 
 laneeolata {L. oblonga), Scotch drift,' 
 
 176. 
 
 truTwata, Scotch drift, 177. 
 
 Lee, Mr. J. E., on Pteraspis of Lower Lud- 
 low, 403. 
 
 Leidy, Dr., on fossil qnadrnpeds of Ne- 
 braska, 249. 
 
 Leperditia injlata, coal-measures, 405. 
 
 Lepidodendron, GritBthsii, 441. 
 
 corrttgatum, carboniferous, 417. 
 
 Sternberaii, coal-measures, 423. 
 
 Lepidolite, 499, 501. 
 
 Lepidofitrohus ornatv^, Coal, 424. 
 Lepidotus gigd/t, Lias, 358. 
 Mantilli, Wealden, 317. 
 
630 
 
 INDEX. 
 
 LEPT-ENA UEPREBSA. 
 
 LeptcBiia depressaj Wenlock, 46G. 
 
 Moorei, Lias, 355. 
 
 Level of surface altered by chauge of sub- 
 terranean heat, 119. 
 
 Lewis, borublendic gueiss of, GOl. 
 
 Lias, fishes of the, 358. 
 
 , fossils of the, 354. 
 
 and Oolite, origin of the, 364. 
 
 , reptiles of the, 360. 
 
 , insects of the, 303. 
 
 , plants of the, 364. v 
 
 , plutonic rocks of the, 571. 
 
 , subdivisions of the, 353. 
 
 , volcanic rocks of the, 544, 
 
 Liebig, on conversion of coal into anthra- 
 cite, 403. 
 
 , on origin of stalactite, 15G, 
 
 Liege, limestone caverns at, 156. 
 
 Lightbody, Mr., on Lower Ludlow shales, 
 461. 
 
 Lignite, conversion of into coal, 403. 
 
 Lima giganteum, 354. 
 
 Hqperi, Chalk, 300. 
 
 spinosa. White Chalk, 294. 
 
 Liniagne d'Auvergne, Lower Miocene 
 mammalia of the, 234. 
 
 Limburg beds, 242. 
 
 Lime, scarcity of, in metamorphic rocks, 
 604. 
 
 ■ in solution, source of, 69. 
 
 Limestone, block of striated, 168. 
 
 , brecciated, 387. 
 
 of chemical and organic origin, 61. 
 
 , compact, 501. 
 
 , Hlppurite, 304. 
 
 , magnesian, 387. 
 
 , metamorphic or crystalline, 579. 
 
 , Mountain, and its fossils, 430-438. 
 
 , striated, 1C8. 
 
 Limiuea longiacata, 55. 
 
 Lingula beds, volcanic tuffs of the, 549. 
 
 Lingula Credneri, Permian, 388. 
 
 Lingula'Flags, fossils of the, 484. 
 
 Lingula Lumortieri, Crag, 200. 
 
 Lewisii, Ludlow, 462. 
 
 Lingulella Davisii, 484. 
 
 Lipari Isles, tufas in, 586. 
 
 Liquidamhar europceUTn, 209. 
 
 Lithrostrotion basalti/orme^ Carboniferous, 
 432. 
 
 Lits coquilliers, 275. 
 
 Littoral denudation defined, 102. 
 
 Lituites (jigmiteus, Ludlow, 463. 
 
 Llanbens slates, 486. 
 
 Llaudeilo Flags, fossils of the, 473-475. 
 
 Llandeilo formation, thickness of the, 475. 
 
 , Lower, 475. 
 
 Llaudovery Group, classification of the, 
 46S. 
 
 Rocks, thickness of the Lower, 469. 
 
 Loam defined, 38, 153. 
 
 Lodes, shells and pebbles in, 608. 
 
 ^ — . See Mineral Veins. 
 
 Looss of fiuviatile loam described, 153. 
 
 , fossil shells of the, 154. 
 
 Logan, Sir W.. on Eozoou Canadense, 490. 
 
 — '-, on Gaspe sandstones, 465. 
 
 , on Huronian and Laurentian, 490. 
 
 , on stiemaria in under-clays, 398. 
 
 , on thickness of Nova Scotia coal, 409. 
 
 , on thickness of Laurentian in Can- 
 ada, 113. 
 
 ma:mm:alia. 
 
 Loire, faluns of the, 211. 
 
 London, Clay, fossils of the, 264, 266. 
 
 Longevity, relative, of mammalia and 
 testacea, 162. 
 
 Longmynd Group, fauna of the, 486. 
 
 Lonsdale, Mr., on corals of America, 229. 
 
 , on Devonian fossils, 449. 
 
 ., on Stonesfield slate, 346. 
 
 , on United States Miocene corals, 239. 
 
 LoTwdaleia Jiori/ormis, Carboniferous, 433. 
 
 Lowe, Rev. R. T., on Mogador shells, 537. 
 
 Lubbock, Sir J., on the two stone-periods, 
 147. 
 
 Lucina serrata^ Bracklesham, 262. 
 
 Ludlow formation, Upper, 459: Lower, 
 461. 
 
 , bone-bed of the Upper, 459. 
 
 Lulworth Cove, dirt-bed of, 333. 
 
 Lycett, Mr., ou fossils of the Great Oolite, 
 344. 
 
 Lycopodiacese of Coal, 422. 
 
 Lycapodium densum, living species, 423. 
 
 Lym-fiord, mingled fresh-water and ma- 
 rine strata of, 59. 
 
 Tj]jmiiea caudata, Headon, 256. 
 
 longiscata, Bembridge, 253. 
 
 Lynton Group of Devon, 454. 
 
 MACLAREN, Mr., on Pentland Hills, 
 volcanic rocks, 5^, 
 
 Macclesfield, marine shells 1,200 feet high 
 at, 181. 
 
 MacCljutock, Sir L., on Atlantic mud, 287. 
 
 MacCulloch, Dr., on Aberdeenshire gran- 
 ite, 558. 
 
 , on basaltic columns in Skye, 510. 
 
 , on formation of hornblende-schist, 
 
 582. 
 
 , on trap, 519. 
 
 MacMullen, Mr. J., on Eozoon Canadense, 
 491. 
 
 Macropus atlas, lower jaw of, 158. 
 
 major (living), lower jaw of, 159. 
 
 Madeira, beds of laterite in, 509. 
 
 , dike in valley in, 513. 
 
 , Pliocene leaf-bed and shells in lavas 
 
 of, 533. 
 
 , Miocene volcanic rocks of, 536. 
 
 , wind removing scoriae in, 97. 
 
 Maestricht beds and their fossils, 283. 
 
 Maffiotte, Don Pedro, cited, 538. 
 
 Magas pumila. White Chalk, 294, 
 
 Magnesian Limestone defined, 38. 
 
 and marl-slate, 387. 
 
 Magnetite, 500. 
 
 Maidstoufe, Upper Cretaceous fossils of, 
 297. 
 
 Malacolite, 502. 
 
 Malaise, Professor, on Engihoul cave, 
 157. 
 
 Mammalia, anterior to Paris gypsum, ta- 
 ble of, 329. 
 
 , extinct, coeval with man, 152,157. 
 
 , fossil, of Middle Purbeck, 325. . 
 
 , fossil, in Pliocene iu Val d'Arno, 
 
 208. 
 
 , fossil, in the Cra^, 193, 19T. 
 
 , fossil, of Vienna basin, 226. 
 
 of the Limagne d'Auvergne, 234. 
 
 of Siwaiik Hills, 227. 
 
 of the Stonesfield slate, 345. 
 
 , teeih qf Postpliocene, l(i5. 
 
INDEX. 
 
 631 
 
 MAMMALIA. 
 
 Mammalia and testacea, comparative lon- 
 gevity of, 102. 
 
 Mammoth, rude carving of In Perli'ord 
 cave, 150. 
 
 in. Scotch till, 1T5. 
 
 . See Elephas primigenius. 
 
 Man, antiquity of, 152. 
 
 Manfiedi on amount of snbaerial denuda- 
 tion, 114. 
 
 Mantel], Dr., on iguanodon of Wealden, 
 313. 
 
 , on Oxford Clay belemnites, 340. 
 
 , on Wealden fossils, 310. 
 
 Mantellia nidifwmiSy Purbeck, 331. 
 
 Map of Chalk formation in France, 305. 
 
 of Eocene tertiary basins, 250. 
 
 of Hallstadt and St Cassiau beds, 376. 
 
 Marble defined, 37. 
 
 of Carrara, metamorphic, 599. 
 
 Marcon, M., on age of Wealden beds, 319. 
 
 Margaric acid, 591. 
 
 Marine fauna nf the Carboniferoas, 432. 
 
 beds underlying the Loudon clay, 
 
 269. 
 
 and brackish-water strata in coal, 
 
 404. 
 
 strata, how distinguished from fresh- 
 water, 53-59. 
 Marl from Lake Superior, 63. 
 
 and marl-slate defined, 3S. 
 
 , red, green, and white, of Anvergne, 
 
 233. 
 
 slate of Middle Permian, 3S7. 
 
 Marsupials, extinct, of Australia, 159, 
 Marsupites SlilUri, White Chalk, 294. 
 Massachusetts, plumbago of, 5S3. 
 Mastodon arvei-ti^isis, molar of, Norwich 
 
 crag, 193. 
 qigrnvteus, in United States after the 
 
 drift, 1S3. 
 Mayence basin tertiaries, 242. 
 May-Hill Sandstone, 40S. 
 Mechanical and chemical deposits, 60. 
 
 theory of cleavage, 592. 
 
 Mediterranean, one zoological province, 
 
 12T. 
 Meqalodon ciicidlattts, Devonian, 452. 
 Melania inquinata {Cerithium melanoides), 
 
 55, 26S. 
 Melania turritUnima, Bembridge, 253. 
 MelaTWpsis buccinoideOj 55. 
 Melaphyre, a variety of basalt, 504. 
 Menevlan beds and their fossils, 4S4. 
 Mesozoic, term explained, 123. 
 and CaiuojBoic periods, gap between 
 
 the, 282. 
 and Palaeozoic rocks, limits of the, 
 
 385. 
 Metals, relative age of diflferent, 014. 
 Metamorphic limestone, 579. 
 
 strata, origin of, 579. 
 
 theory, objections to, consideiecl, 6bT. 
 
 rocks defined, 32. 
 
 rocks, 576. 
 
 , cleavage of, 688. 
 
 , scarcityof lime in, 604. 
 
 , ages of, 59T. 
 
 , order of succession of, 002. 
 
 , uniformity of mineral character 
 
 Metamorphism, Hydrothermal action pro- 
 d'lciDg, 684. 
 
 AIOLABBE. 
 
 Metamorphosis of trllobites, 471, 487. 
 
 Meteorites, minerals in, 501. 
 
 Mexico, Gulf of, terrestrial remains wash- 
 ed into, 128. 
 
 Meyer, Mr. Karl, on fossil shells of Madei- 
 ra, 537. 
 
 , M. H. von, on reptiles in coal, 407. 
 
 , on Wealden of Germany, 319. 
 
 Miascite, 558. 
 
 Mica and its varieties, 499, 501. 
 
 , how deposited, 40. 
 
 schist or micaceous schist, 578. 
 
 Micaceous sandstone, origin of, 30. 
 
 Micraster cor-anguinwm, 294. 
 
 Mieroconchus carbonariuSt coal-measur 
 405. 
 
 Mierolestes antigwis, Upper Trias, 3C8. 
 
 Migrations of quadrupeds, 101. 
 
 Miliolite limestone, 274. 
 
 Miller, Hugh, on Old Red Sandstone flsh, 
 443. 
 
 , on salt lakes, 375. 
 
 Milne Edwards, Mr., on Palseozoic corals, 
 432. 
 
 Miuchinhamptou, Great Oolite of, 344. 
 
 Mineral composition a test of age of vol- 
 canic rocks, 523. 
 
 a test of age of plutonic rocks, JS65. 
 
 a test of age of strata, 124. 
 
 character of hypogene rocks, 002. 
 
 springs of Auvergne, 604. 
 
 veins, 605. 
 
 formed in fissures, 606. 
 
 , successive formation of, 609. 
 
 , swelling and contraction of, 611. 
 
 , relative age of, 614. 
 
 , pebbles in, 608. 
 
 Mineralization of organic remains, 65. 
 
 Minerals in meteorites, 501. 
 
 , table of the most abundant in hypo- 
 gene rocks, 499. 
 
 M locene of Bordeaux and south of France, 
 214. 
 
 and Eocene, Hue between the, 230, 
 
 251. 
 
 , Lower, of England, 244. 
 
 , Lower, of Germany and Croatia, 242. 
 
 , Lower, of Central Prance, 231. 
 
 , Lower, of Italy, 244. 
 
 , Lower, of Nebraska, United States, 
 
 24S. 
 
 , term defined, 143. 
 
 , Upper, of the Boiderberg, 224. 
 
 Upner, of Prance, 211. 
 
 , Upper, of Italy, 220. 
 
 , Upper, of Greece, 226. 
 
 , Upper, of India, 226. 
 
 — -, Upper, of Vienna basin, 224. 
 Mississippi, sediment of, used as a test of 
 
 denudation by rivers, 114. 
 valley, deposition and denudation in 
 
 the, 102. 
 Mitchell, Mr., on Aralia fruit in Alum Bay, 
 
 Eocene, 263. 
 
 , Sir T., on Wellington caves, 158. 
 
 , Bev. Hugh, on Pteraspis, 446. 
 
 Mitra Scabra, Barton clay, 259. 
 Mitscherlich, on Isomorphism; 502. 
 Modiola acumiTiata, Permian, 3S7. 
 Moel Tryfaon, shells found at, 181. 
 Slohs on isomorphism, 502. 
 Molasse, Lower, of Switzerland, 235. 
 
632 
 
 INDEX 
 
 UOLABSE. 
 
 Molasee, Middle, or Marine, of Switzer- 
 land, 223. 
 
 , Upper, fresh-water, of Switzerland, 
 
 21T. 
 
 , term explained, 217. 
 
 Mollusca. See Shells. 
 
 , longevity of species of, 1G2. 
 
 of Hallstadt bedsj 377. 
 
 , value of, in classification, 142. 
 
 of the Carboniferous, 435* 
 
 Monitor of Thuriugia, 463. 
 
 Monoclinic feldspars, 501. 
 
 Monod, flora of the Lower Holasse at, 
 23G. 
 
 Mons, unconformable strata near, 95. 
 
 Mont Blauc, talcose granite of, 568. 
 
 Dor, Auvergne, extinct volcanoes of, 
 
 232. 
 
 , age of volcano of, 541. 
 
 Moute Bolca, fossil fish of, 543. 
 
 Calvo, section of cross stratification, 
 
 44. 
 
 Mario, age of .volcanic deposits of, 
 
 533. 
 
 Nuovo, formed 1538, 525. 
 
 Montmartre, gypseous series of, 270. 
 
 MontsDome, Auvergne, extinct volcanoes, 
 495. 
 
 Moore, Mr. C, on Ehietic beds, 360. 
 
 , on Upper Trias quadrupeds, 369. 
 
 Moraines described, 169. 
 
 Morea, cretaceous volcanic rocks of, 544. 
 
 Mortillet, M. de, on ice-erosion of lake- 
 basins, 184. 
 
 Morton, Dr., onage of Americancretaceons 
 rocks, SOT. 
 
 Mosasaurua Camperi, Chalk, 2S4. 
 
 Mountain Limestone, fossils of the, 433- 
 438. 
 
 Mull, Isle of, leaf-bed, 24T. 
 
 Miinster, Count, on fossils of Soleuhofen, 
 337. 
 
 Murchison,SirR., on brackish-water strata 
 in coal, 404. 
 
 , on Devonian series, 439, 449, 454. 
 
 , on Devonian ichthyolires, 453. 
 
 , on Eocene igneous rocks, 27S. 
 
 , on Llandovery beds, 408. 
 
 , on Laurentian gneiss of Scotland, 
 
 492. 
 
 , on metamorphic rocks of North High- 
 lauds, GOl. 
 
 , on Monte Bolca fish-beds, 543. 
 
 , on name Permian, 385. 
 
 , on Old Ked Sandstone, 449. 
 
 , on Palseozoic strata, Queenaig, 112, 
 
 113. 
 
 , on protrusion of solid granite, 574. 
 
 , on Silurian, 458, 459, 461, 467, 470, 4T3, 
 
 475. 
 
 , on Tertiary volcanic rocks of Italy, 
 
 533. 
 
 , on thickness of .chalk in Russia, 287. 
 
 , oil thickness of the Trias, 369. 
 
 , on the Upper *' Old Red," 468. 
 
 Murchisonia gracilis, 479. 
 
 Murex vaginatus, 204. 
 
 Mnschelkalk, fossils of the, 378. 
 
 Muscovite, or common mica, 499, 501. 
 
 Musk-ox, fossil, in Thames valley, IGl. 
 
 MylUibates Edwardsi, Bracklesham, 2G1. 
 
 Mytilus aeptifer, Permian, 387. 
 
 OBOLUS APOLLXNIS. 
 
 NAPLES, Postpliocene volcanic rocks of, 
 
 525. 
 , escape of carbonic acid near, 604* 
 
 Natica clavsa, Scotch drift, 176. 
 
 helicoides, Chillesford beds, 192. 
 
 Natrolite, 500. 
 
 Jfautilus centralis, Loudon Clay, 260. 
 
 JDanicua, Faxoe Chalk, 286. 
 
 plicatits, Hythe beds, 309. 
 
 truncatus^ Lias, 356. 
 
 ziczae {Aturia ziczac), 2G6. 
 
 Nebraska, Miocene strata of, 248. 
 Necker, M., on "underlying" igneous 
 
 rocks, 562. 
 
 , on dikes in Vesuvius, 526. 
 
 Neocomian, Upper, 308. 
 
 , Middle, 312. 
 
 , Lower, 312, 
 
 , use of the term, 282. 
 
 Neolithic era, 147. 
 
 Neozoic type of corals, 431. 
 
 Iferincea Goodliallii, Coral Rag, 339. 
 
 Nerinaean limestone, 340. 
 
 Nerita corwidea {N. Sckmidelliana), 275w 
 
 costtikUa, Great Oolite, 345k 
 
 granulosa, 55. 
 
 J^eritiiia concava, Headon, 255. 
 
 (jlobulus, 55. 
 
 Neutchfitel, coins and iron tools in lake of, 
 
 149. 
 Newberry, Dr., on flora of American creta- 
 ceous rocks, 307. 
 Newcastle coal-field,faults in, 90. 
 Newfoundland bank descnbed, 106. 
 New Jersey, mastodon in, 183. 
 New Madrid, "Sunk Country" in, 402. 
 New Red Sandstone of CoimecticutValiey, 
 
 381. 
 
 , trappean rocks of the, 545. 
 
 New York, Devonian strata of, 456, 
 
 , Cambrian strata of, 490. 
 
 , Silurian strata of, 478. 
 
 , Laurentian strata of, 491. 
 
 Niagara Limestone, fossils of the, 479, 
 Nidau, iron tools in lake of, 148. 
 Nile, homogeneous mud of the, 154. 
 Ninety-fathom dike in coal, 90. 
 NipaMtes elUpiicus, Sheppey, 264. 
 Nodules in strata, how formed, G3. 
 Noeggerathia euneifolia, Permian, 393. 
 Nomenclature of rocks, 140.- 
 
 of volcanic minerals, 499. 
 
 Norfolk cliffs, drift of, 190. 
 
 North America. See America. 
 
 Norway, Cambrian of, 489. 
 
 , foliation of crystalline schists in, 
 
 595. 
 
 , granite veins in gneiss of, 573. 
 
 , granite altering fossiliferoua strata 
 
 iu, Ml. 
 Norwich, or Fluvio-marine crag, 193. 
 Nova Scotia coal-measures, 409. 
 
 coal, reptiles aiid shells in, 414. 
 
 , folding and denudation of beds in, 
 
 417. 
 Nucula Cobboldim, Crag, 194. 
 Nwmtnulites Icevigata, Bracklesham, 260. 
 
 Pmehi, Pyrenees, 278. 
 
 variolaria, Bracklesham, 269i 
 
 Xummulitic formations, 277. 
 
 OBOLUS Apollinia, in Russian grit, 473. 
 
INDEX. 
 
 633 
 
 OBBIUIAN. 
 
 Obsidian, 505. 
 
 Oceanic areas, permanence of, IIT 
 
 CEniugen, Upper Miocene beds of, 215. 
 ve°us,M™' ™"' '"' Cornish granite 
 
 Omnria Biichii, 4T4. 
 
 mdhamiaradiata: 0. antiqua, 4^!. 
 
 Old Red Sandstone, Upper 440 
 
 , Middle, with flsh, 443. 
 
 - — , Lower, 446. 
 
 .trap of the, 54T. 
 
 , classification of, 439. 
 
 Olenus micrurus, 484. 
 
 Oligocene, term for Lower Miocene, 230, 
 244. ' ' 
 
 Oligoclase, 499, 500. 
 
 Oliva Dufngnii, Bolderberg, Belgium. 224. 
 
 Olivine, 499. 
 
 Omphyma turlrinatum, Silnrian, 466. 
 
 OnSfais tenuistriatus, Silurian, 460. 
 
 Oolite, classification and physical geogra- 
 phy of the, 321. 
 
 defined, ST. 
 
 , Inferior, fossils of the, 349, 350. 
 
 and Lias, origin of the, 364. 
 
 and Chalk, Palseontological break be- 
 tween, 338. 
 
 Oolitic strata, palseontological relations of, 
 351. 
 
 volcanic rocks, 545. 
 
 Ophioderma tenuibrachiata, Lias, .^57. 
 
 Oppel on zones of Lias, 353. 
 
 Orbigny, Alcide de, on foraminifera of Vi- 
 enna basin, 225. 
 
 , on orbitoidal limestone, 279. 
 
 , on Pisolitic limestone, 285. 
 
 , on Senonian, 302. 
 
 Orecdaphne Heei-ii, Italian Pliocene, 209. 
 
 Organic remains, mineralization of, 65. 
 
 , tests of age of strata, 125. 
 
 , tests of age of volcanic rocks, 522. 
 
 , geological provinces of, 127. 
 
 Oriskany Sandstone, 478. 
 
 Orthis eleganttda, Ludlow, 46. 
 
 grandis, Caradoc beds, 470. 
 
 tricermria^ Bala beds, 470. 
 
 vespertiliOy Bala beds, 470. 
 
 Ortlwcerdfi duplex, 474. 
 
 lAidense, Silurian, 463. 
 
 laterale, 486. 
 
 ventricosum, Silnrian, 462. 
 
 Orthoclase, 499, 500. 
 
 Orthoclastic feldspars, 501. 
 
 Osborne or St. Heleuis series, Eocene, 255. 
 
 Oateolepis, Old Red Sandstone, 444. 
 
 Ostraceon, spine of, Bracklesham, 261. 
 
 Ostrea amminata, Fuller's earth, 349. 
 
 cariTiata, Chalk marl, 300. 
 
 columba, Chloritic sand, 300. 
 
 gregarea, Coral Rag, 389. 
 
 deUoMea, Kimmeridge clay, 336. 
 
 distmrta, Middle Parheck, 324. 
 
 expanm, Portland sand, 336. 
 
 Marehii, Oolite, 351. 
 
 vaneitlaris. Chalk, 295. 
 
 Otodus obliqmw, Bracklesham, 262. 
 
 Outcrop of strata, 83. 
 
 Overlapping strata, 95. 
 
 Owen, Professor, on Archseopteryx, 337. 
 
 on Eocene Zeuglodon, 279. 
 
 ' on foot-prints in Trias, 382. 
 
 ' on fanna of Sheppey, 266, 267. 
 
 21* 
 
 PEBNA MTTT.LETI. 
 
 Owen, Prof., on Gastornis Parisiensis, 276. 
 
 , on Labyriuthodon, 370. 
 
 , on mammalia of Stonesfleld, 347. 
 
 , on Pnrbeck mammalia, 326, 328. 
 
 , on reptiles of coal, 407, 414. 
 
 , on zoological provinces of extinct 
 
 animals, 160. 
 Ox, tooth of (recent), 165. 
 Oxford Clay, thickness and fossils of, 340. 
 
 PAGHAM, erratic block at, 182. 
 
 PalcBOSter aspervmus, 472. 
 
 Palixchinusgigaa, Mountain Limestone, 43. 
 
 Palceocoma tenuibraxMata, Lias, 357. 
 
 Palceonisms, Permian flsh, 889. 
 
 comptm, P. elegans, P. glapliyrus, 390. 
 
 PaltBotheriuni magnum, 254. 
 
 Palceophis typhceiis, Bracklesham, 261. 
 
 Palaeozoic or Paleozoic, term defined, 123. 
 
 Plutonic rocks, 572. 
 
 rocks, 458. 
 
 type of corals, 431. 
 
 Palagonia, dikes of lava in, 631. 
 
 Paleolithic era, 147, 149. 
 
 , alluvial deposits of, 150. 
 
 Palm in Swiss Miocene, 237. 
 
 Palmii, volcanic crater of, 497. 
 
 Paludina lenta, Hempstead beds, 65, 245. 
 
 orbicularis, Bembridge, 253. 
 
 Pctradoxides Bohemicus, 488. 
 
 Davidis, Lower Cambrian, 485. 
 
 Parallelism of folded strata for long dis- 
 tances, 98. 
 
 Paris basin. Tertiary group first studied in, 
 141. 
 
 , Tertiaries of the, 270. 
 
 Parka decipiens, "Old Red," 448. 
 
 Parkfield Colliery, ground-plan of, 400. 
 
 Patagonia, str.ata of, rich in soda, 587. 
 
 Patella rugosa. Great Oolite, 345. 
 
 Paterson, Dr., on aogiosperm of the Ooal, 
 429. 
 
 Peach, Mr. C, cited, 601. 
 
 , Pteraspis, found by, 443. 
 
 Pearlstone, 505. 
 
 Pebbles in mineral veins, 008. 
 
 in chalk, 292. 
 
 Pecopteris elliptiea. Coal, 421. 
 
 Pecten Beaveri, White Chalk, 294. 
 
 cinctu% Neocomiau, 812. 
 
 islandicus, Scotch Drift, 176. 
 
 jaeobceus, in tertiary of Sicily, 206. 
 
 quinque-costatus, 800. 
 
 ^"aloniensis, Rhsetic beds, 366. 
 
 Pegmatite, 653. 
 
 Per.arth beds, 368. 
 
 Pengelly, Mr., on Bovey Tracey lignite, 
 246. 
 
 , on flint-knives of Brixham Cave, 157. 
 
 Pentaerinvs Briaretts, Lias, 357. 
 
 Pentamencs Knightii, Aymestry, 461. 
 
 oblongus, and P. lirata, 469. 
 
 PentlandHills, volcanic rocks of the, 548. 
 
 Perigord cave, carving of mammoth in, 150, 
 
 Permanence of continents and oceans, 117. 
 
 Permian Flora, 892. 
 
 of Germany, 393. 
 
 strata, thickness of, in north of En- 
 gland, 386. 
 
 , Upper and Middle, 386, 387. 
 
 , Lower, 390. 
 
 Pertia Xnlleti, Neocoraian, 810. 
 
634 
 
 INDKX. 
 
 PETIIEKWYN. 
 
 Petherwyn, Devouian fossils of, 450. 
 Petrifaction, process of, 67. 
 Petrophiloides Richardsonij Sheppey, 265. 
 Phacaps caudatus, Silurian, 467. 
 
 latifrons, Devouian, 450. 
 
 Phascolotherium Bucklandi^ 343. 
 PkoAiandla HeddingUmensis, and cast, 66. 
 Pliillippi, ou tertiary shells of Sicily, 205. 
 Phillips, Professor, ou fossils distorted by 
 
 cleavage, 592. 
 
 , on ninety fathom dike, 90. 
 
 , on Wenlock limestone and shale, 465, 
 
 467. 
 
 , on Yoredale series, 395. 
 
 , Mr. J. Arthur, on origin of gold of 
 
 Califoruia, 617. 
 Phlebqpteris contiguaj Inf. Oolite, 350. 
 Phlogopite, 499, 501. 
 Pholadormja fidiculUj luf. Oolite, 350. 
 Phonolite, 806. 
 
 Phortts extensuSj London clay, 266. 
 Phrar/moceraa ventricosum, Silurian, 463. 
 Physa Bristoviit Middle Purbeck, 325. 
 
 columnariSf 55. 
 
 hypnorum., 55. 
 
 Piedmont, absence of lakes in, 186. 
 Pile dwellings of Switzerland, 14S. 
 Pilton, group of, Bevon, 449. 
 Pinnularia in Atlantic mud, 288. 
 Pinus sylvestris in peat, 147. 
 Pisolitic limestone of France, 285. 
 Pitchstone, 505. 
 
 Plaeoiiis gigas, Muschelkalk, 380. 
 Placoids, rare in Old Eed Sandstone, 443. 
 PlagiavXa'Ji JBecklesii, jaw and molar of, 
 
 327. 
 Plagioclastic feldspars, 501. 
 PlagioBtoma giganteum. Lias, 354. 
 
 Hoperi, Chalk, 300. 
 
 Planorbis di8cuft, Bembridge, 253. 
 
 euomphalus, 55, 255. 
 
 Plants ofBovey Tracey, Miocene, 247. 
 
 , fossil fresh-water, 57. 
 
 of the Coal, 420. 
 
 of the Lias, 364. 
 
 of the Swiss Upper Miocene, 219. 
 
 Plas Newydd, rock altered by dike near, 
 
 515. ' 
 
 Plastic Clay, Eocene, 267. 
 Platanus aceroides, Miocene, 221. 
 Platjistoma Suessii, Hallstadt, 377. 
 Playfair, on amount of subaSrial denuda- 
 tion, 114. 
 
 on faults, 87. 
 
 Plectrodiis miraiilis, Ludlow, 460. 
 Pleeiosaurus dolishodeirus. Lias, 361. 
 Pleurotoma attenuata, Bracklesham, 262. 
 
 exorta. Eocene, 57. 
 
 Plairotomaria anglica, and cast, 00. 
 
 carinata (Jlammigera), 434 
 
 granulata, Inf. Oolite, 351. 
 
 ornata. Inf. Oolite, 351. 
 
 Plieuinger, Professor, on Triassic mammi- 
 
 fer, 368. 
 Pliocene glacial formations, 189-192. 
 
 Period, 189. 
 
 plutomc rocks, 565. 
 
 strata of Sicily, 204. 
 
 , term defined, 143. 
 
 volcanic rocks, 529. 
 
 PlombiSres, alkaline waters of, 585. 
 Plumbago of Massachusetts, 583. 
 
 PTVOUODtJS. 
 
 Plutonic and sedimentary formations, dia- 
 gram of, 567. 
 
 , origin of the term, 551. 
 
 rocks, Mesozoic, 570. . 
 
 , Recent and Pliocene, 565. 
 
 , Miocene and Eocene, 568. 
 
 , uncertain tests of age of, 564. 
 
 defined, 31. 
 
 Podocarya Bucklandi, Oolite, 348. 
 
 Polypterus of the Nile, 444. 
 
 Polyzoa and Bryozoa, terms explained, 197. 
 
 Pomel, M., on fossil mammalia of the Li- 
 niague, 235. 
 
 Ponza Islands, globiform pitchstone of, 512. 
 
 Poritespyriformis, Devonian, 451. 
 
 Porphyritic granite, 566. 
 
 Porphyry, 506. 
 
 Portland, Cycads in dirt-bed of, 331. 
 
 oolite and sand, 334. 
 
 '^Portland screw," a cast of a shell, 335. 
 
 Porto Santo, marine shells iu volcanic tuff 
 of, 536. 
 
 Post-Pliocene period, climate of the, 161. 
 
 mammalia, teeth of, 163. 
 
 , term defined, 145. 
 
 lakes of Switzerland, 185. 
 
 volcanic rocks, 624 
 
 Pota/mides dnctus, 56. 
 
 Pothocites Grantonii, coal-measures, 429. 
 
 Potsdam Sandstone, 4S0, 489. 
 
 Pot-stones in the Chalk, 290. 
 
 Pottsville, coal seams of, 400. 
 
 Powrie, Mr., on Cephalaspis beds, 446. 
 
 , on Parka decipieus, 448. 
 
 Pratt, Mr., on Eocene Isle of Wight mam- 
 malia, 254. 
 
 Predazzo, altered rocks at, 571. 
 
 Pressure, solidifying rocks, 65. 
 
 Prestwich, Mr., on age of Sables infiirieurs, 
 276. 
 
 , on Chillesford beds, 192. 
 
 , on Coalbrook Dale insects, 405. 
 
 , on Eocene strata, 207, 269. 
 
 , on faults iu coal -measure of Coal- 
 brook Dale, 88. 
 
 , on shells of London clay, 264. 
 
 , on thickness of Coralline Crag, 198. 
 
 Prevost, M. Constant, ou Paris basm, 270. 
 
 Primary Limestone, 579. 
 
 rocks, 458. 
 
 , term defined, 123. 
 
 "Primordial Zone " of Bohemia, 4S1, 482. 
 
 Productun horridus, Permian, 388. 
 
 semireticulatus {antiquatus), 434. 
 
 Progressive development,indicated by low 
 grade of earl3^ mammals, 384. 
 
 Proteaceie of Aix-la-Chapelle flora, 304. 
 
 of Lower Molasse, Switzerland, 237. 
 
 of (Eningen beds, 221. 
 
 Protogiue, 578. 
 
 Protosaurus of Thuringia, 390, 464. 
 
 Protrusion of solid granite, 674. 
 
 Provinces of animals and plants, 126. 
 
 Paammodus porosus, 437. 
 
 Pseudocrinites bi/asciatus, Silurian, 466. 
 
 Psilophytonpri^tceps, Devonian, 455. 
 
 Pteraspis in Lower Ludlow shale, 463. 
 
 Pterichthys, Old Eed Sandstone, 446. 
 
 Pterodactyl of Kentish chalk, 297. 
 
 Pterodactylus anglicue, Old Eed, 447. 
 
 crassirostris, Soleuhofen, 837. 
 
 Ptychodus deeurrens. White Chalk, 297. 
 
INDEX. 
 
 635 
 
 rUWDINQ-STONE, 
 
 Pudding-Btone or conglomerate, 3C. 
 
 , formatiou of, 02. 
 
 Pumice, 508. 
 
 Panfleld beds, brackish and marine, 318. 
 
 Pupa mtescontm, 155. 
 
 tridens. Loess, 56. 
 
 vetusta. Coal, 415. 
 
 Purbeck beds, Upper, Middle, and Lower, 
 
 323; 324, 330. 
 
 , fossil mammalia of the Middle, 325. 
 
 marble, 324. 
 
 , subdivisions of the, 333. 
 
 Purity of coal, cause of, 402. 
 Purpura tetragona, Red Crag, 190. 
 Purpuraidea nodulata. Great Oolite, 345. 
 Puy de Come, cone and lava-current of, 528. 
 - — de Tartaret, lava-current and cone of, 
 
 527, M2. 
 
 de Pariou, crater of the, 529. 
 
 Puzzuoli, elevation of land at, 525. 
 PijOpptervs mandibidariSf Permian, 390. 
 Pyrenees, chalk altered by granite in the, 
 
 670. 
 
 , curved strata in, SO. 
 
 , lamination of clay-slate in, 590. 
 
 Pyroxene gronp of minerals, 499, 502. 
 Pyrula reticulata, Crag, 200. 
 
 QUADER-SANDSTBIN, cretaceous age 
 of the, 293. 
 
 Quadrnmaua of Gers, 215. 
 
 Quadrupeds, extinct, iu PalEeolitbic grav- 
 els, 152. 
 
 QnartZj specific gravity of, 499, 500, 555. 
 
 Quartzite or Quartz Rock, 579. 
 
 Qaeeuaig, unconformable Palaeozoic strata 
 at, 112. 
 
 Quenstedt on zones of Lias, 353. 
 
 EADABOJ Miocene, brown coal of, 242. 
 
 RadioUles foliacetis. White Chalk, 300. 
 
 . Mortoni, White Chalk, 295. 
 
 radiosa. White Chalk, 300. 
 
 Radnorshire, stratified trap in, 549. 
 
 Rain-prints with worm tracks in Coal, 410. 
 
 , carboniferous, 41G. 
 
 Ramsay, Professor, on break between Up- 
 per and Lower Cretaceous, 301. 
 
 , on Ijreccias in Permian, 391. 
 
 , on escarpments, 104. 
 
 , on denudation, 98. 
 
 , on ice-erosion of lake-basins, 184, 
 
 , on Lingula Flags, 484. 
 
 , on position of Tremadoc beds, 483. 
 
 . , on Silurian metamorphic rocks, 602. 
 
 , on submergence in glacial period, 
 
 181. 
 
 — — , on thickness of the Lower Trias, 372. 
 
 , on thickness of Llandeilo beds, 475. 
 
 on thickness of the Bala beds, 473. 
 
 , on volcanic tufls of Snowdon, 549. 
 
 , on zones of the Lias, 353. 
 
 Pastrites peregrinws, Llandeilo Flags, 473. 
 
 Rath, Von, on Tridymite, 500. 
 
 Recent Period defined, 145. 
 
 volcanic rocks, 624. 
 
 Record, imperfection of, ni the earth s 
 crust, 13S. 
 
 Red Crag, older Pliocene, 194. 
 
 Sandstone, Origin of, 3 14. 
 
 - Sea and Mediterranean, distinct spe- 
 cies iu, 12T. 
 
 SAHAT.. 
 
 Redruth, Cornwall, section of veins in 
 
 mine, 007. 
 Reindeer Period in South of France, 149. 
 Relistran mine, pebbles in tin of, 009. 
 Reptiles of the Coal, 406, 413. 
 Reptiles of the Lias, 360. 
 Reteporaflustracea, Permian, 388. 
 Rhietic beds between Lias and Trias, 306. 
 Rhine, fresh-water strata of the, 53. 
 
 , loess of the, 154. 
 
 Rhinoceros in drift of Abbeville, 153. 
 lepiorhiiius {mefjarkinus), molar of, 
 
 164. 
 
 tichorhinus, molar of, 104. 
 
 Rhode Island, metamorphic rocks of, 583. 
 lihtjnchmiella iiavicula, Ludlovv, 400. 
 
 octopUcata, White Chalk, 294. 
 
 spirwsa. Inf. Oolite, 350. 
 
 Wilnoni, Aymestry, 462. 
 
 Richmond, Virginia, triassic coal-field of, 
 
 382. 
 Rigi and Speer, Lower Miocene of the, 
 
 235. 
 JRimula clathrata, Great Oolite, 345. 
 Rink, Mr., on Greenland land-ice, 171. 
 Ripple-marked sandstone, how formed, 
 
 46. 
 Rise and fall of laud, 146. 
 Rissoa Cfuxstelii, Hempstead beds, 245. 
 Rivers, denuding powers of, 101, 114. 
 Roches moutoniides described, 109. 
 Rock, term defined, 26. 
 Rocks altered by volcanic dikes, 514. 
 
 altered by subterranean gases, 58G. 
 
 , analysis of minerals iu, 499. 
 
 , aqueous or stratified, 27. 
 
 , classification of, 121. 
 
 , great thickness of palaeozoic, 110. 
 
 , glacial scorings on, 109. 
 
 , metamorphic, age of, 597. 
 
 , Plutonic, age of, 564. 
 
 . volcanic, age of, 520. 
 
 , trappean, 497. 
 
 , metamorphic, defined, 32. 
 
 , fonr classes of contemporaneous, 33. 
 
 , Plutonic, defined, 31. 
 
 , tests of age of, 123, 125, 520, 564, 597. 
 
 , four contemporaneous classes of, 122. 
 
 , underlying, not always the oldest, 
 
 122. 
 
 , volcanic, defined, 29. 
 
 Rock-salt of Trias, 371. 
 
 , origin of, 374. . 
 
 Roger?,'Mr. H. D., on blending of coal- 
 seams, 400. 
 
 , on Virginian fault, 92. 
 
 Rose, Gustavns, on isomorphism, 602. 
 
 , on Fifeshire dike, 546. 
 
 , on quartz iu granite, 655. 
 
 Rosso antico, red porphyry of Egypt, 506. 
 Posteltaria {Hippocrenes) ampla, London 
 
 clay, 206. 
 Roth, M., on Miocene of Greece, 220. 
 Rnnn of Cutch, salt of, 376. 
 Rupelian beds of Dumont, 241, 242. 
 Russia, glaciation of, 174. 
 
 , Devonian of, 454. 
 
 , Silurian strata of, 473. 
 
 SAARBEUCK, reptiles iu coal-field of, 
 
 400. 
 Sahal Major, Lower Miocene, 237. 
 
636 
 
 INDEX. 
 
 SABLES. 
 
 Sables de Bracheux, 276. 
 
 ■ moyens, Paris basin, 273. 
 
 Sahlite, 502. 
 
 St. Abb's Head, curved strata of, TC. 
 
 , nnconformable stratiflcatiou at, 94. 
 
 St. Andrews, carboniferous trap-rocks of, 
 
 645. 
 St. Cassiaii, fossil moUnsca of, 3T7. 
 
 and Hallstadt beds, 3TG. 
 
 St. David's, Menevian beds of, 4S5. 
 
 St. Mary's, shells of, 539. 
 
 Salt, rock, origin of, 372. 
 
 Salter, Mr., on fossils of Arenig group, 470. 
 
 , on Menevian beds, 485. 
 
 , on Tremadoc fossils, 4S3. 
 
 Sandberger, Dr. F., on Mayence basin, 
 
 242. 
 Sandstone, New Red,. 369. 
 
 , Old Red, 439. 
 
 . slab with cracks, 317. 
 
 , slab of ripple-marked, 45. 
 
 slab with foot-prints, 40S. 
 
 Sao Mrsuta, 4S8. 
 Sauriana of the Lias, 361. 
 
 . , sudden destruction of, 362. 
 
 Saurichthys apicalis, Rhoatic Beds, 3G7. 
 Saussure, on vertical conglomerates, 73. 
 Saxicava rugosa^ Scotch drift, 176. 
 Saxony, beds of minerals in, 609. 
 Scandinavia, glaciation of, 174. 
 Scaphites cequalis, Chloritic marl, 299. 
 Scapolite, 606. 
 Scheerer on action of water in metamor- 
 
 phism, 585. 
 Schist, mica, 578. 
 
 , argillaceous, 579. 
 
 , hornblende, 57S. 
 
 Schizodus Schlotheimi, Permian, 387. 
 
 • truncatus, Permian, 3S7. 
 
 Schmerlino;, Dr., on Liege caverns, 157. 
 Schorl-rock, and schorly granite, 557. 
 Schwab, M., on Celtic coins in lake-dwell- 
 ings, 149. 
 Scoliostonm, St. Cassian, 377. 
 Scoresby, on Arctic icebergs, 172. 
 Scoriaceous lava, 507. 
 Scorise, 508. 
 Scotland, " Fundamental gneiss " of, 493. 
 
 , Old Red Sandstone of, 440. 
 
 , glaciation of, 175. 
 
 Screws, fossil, internal casts of shells, 66. 
 Scrope, Mr., on Isle of Ponza, globiform 
 
 pitchstone, 512. 
 
 , on minerals in lavli, 524. 
 
 , on water in lava, 555. 
 
 Scudder, Mr., on Devonian insects of 
 
 Canada, 457. 
 Sea, apparent fall of, caused by rise of land, 
 
 70. 
 
 , denuding power of the, 105. 
 
 , deep soundings in, 287. 
 
 , mean depth of the, 118. 
 
 cliffs, inland, 103. 
 
 Secondary, and Tertiarv, gap between the, 
 
 281. 
 
 , term defined, 123. 
 
 Section of Anvergne alluvium, 100, 
 
 of carboniferous rock^, Lancashire, 
 
 85. 
 
 • of ch.alk and greensand, 287. 
 
 of crags near Woodbridge, Suffolk, 
 
 198. 
 
 SUETLAKD. 
 
 Section of cross-stratiflcatlon, 42-44. 
 
 of curved strata of the Jura, 82. 
 
 of dirt-bed in Isle of Portland, 832. 
 
 of Forfarshire, showing curved strata, 
 
 74. 
 
 ■ of fossil tree, showing texture, 67. 
 
 of folded and denuded carboniferous 
 
 beds. Nova Scotia, 418. 
 
 ■ . of the Oolitic strata, 322. 
 
 . of Recent and Post-Flloceue alluvial 
 
 deposits, 151. 
 
 showing creeps in coal-mines, 79. 
 
 of slaty cleavage, 5S9. 
 
 showing valleys of denudation, 9S. 
 
 showing the Weald formation, 313. 
 
 of strata thinning put, 41. 
 
 of superimposed groups at Dundry 
 
 Hill, 130. 
 
 of unconformable strata near Mons, 
 
 95. 
 
 Sections illustrating faults, 88, 90, 91. 
 
 Sedgwick, Professor, on the Cambriau 
 Group, 481, 482, 480. 
 
 , on classification of Arenig group, 
 
 476. 
 
 ■ , on Devonian series, 439, 449. 
 
 , on position of the May-Hill beds, 
 
 508. 
 
 , on protrusion of solid granite, 574. 
 
 , on slaty cleavage, 5SS, 591. 
 
 , on garnet in altered rock, 515. 
 
 , on concretionary structure, 63. 
 
 Sediment, accumulation of, causing a shift- 
 ing of the subterranean isothermals, 
 117. 
 
 Sedimentary beds of the Carboniferous, 
 396. 
 
 Selsea Bill, erratics at, 182. 
 
 Senarmont on action of water in metamor- 
 phism, .585. 
 
 Sequoia l/amjsdorjii, 238. 
 
 " Seraphim,*^ head of Ptenigotics aiinlicuBf 
 440. 
 
 Serapis, marine littoral deposits of, 140. 
 
 Serpentine, 578. 
 
 Seipitlcn attached to G-rypliaia^ 48. 
 
 attached to Spatanrjun, 49. 
 
 attached to Apioerinus, 343. 
 
 Shale defined, 36. 
 
 of the Lower Ludlow, 461. 
 
 Sharpe, Mr. D., on American Silurian fos- 
 sils, 479. 
 
 , on fossils distorted by cleavage, 592. 
 
 Shell-mounds of Denmark, 140. 
 
 Shells, arctic, in Scotch drift, 177. 
 
 , derivative, in the Crag, 195-203. 
 
 , marine, found at'great heights above 
 
 the sea, 29. 
 
 , proportion of living, in the Crags, 
 
 194, 195, 199. 
 
 — '-, value of, iu classification, 142. 
 
 , fossil, of Virginia, 228. , 
 
 of the London clay, 206. 
 
 ■ of the mountain limestone, 433. 
 
 of the Barton clay, 25S. 
 
 of the Oolite, 335, 34,1, 350. 
 
 , marine, of Moel Tryfaen, ISO. 
 
 Sheppey, fauna and flora of, 264. 
 
 , Eocene fish of, 207. 
 
 Sherringham, erratic, block at, 191. 
 
 Shetland, granite of, 658. 
 
 :, hornblende-schist of, DS3. 
 
INDEX. 
 
 63!? 
 
 BIOII.Y. 
 
 Sicily, fanna and flora of, older thau the 
 
 country itself, 20T. 
 
 , newer Pliocene strata of, 204. 
 
 , subterranean igneous action in, 569. 
 
 , nndalatiu^ gypseous marls of, S6. 
 
 , volcanic dikes of, 531. 
 
 Sidlaw Hills, trap of, 54S. 
 Sigillaria in coal-measnres, 3S0, 411, 425. 
 Sitjillaria latoir/aia^ coal-measnres, 426. 
 Siliceous limest-oue defined, 37, 
 Silurian, derivation of the name, 45S. 
 
 granite of Norway, 573. 
 
 , metamorphic, of North Highlands, 
 
 001. 
 
 rocks, classiBcation of, 458. 
 
 strata of the continent of Europe, 
 
 477. 
 
 . strata of United States, 473. 
 
 volcanic rocks, 54S. 
 
 SipIionotretaungitiGukita, obolns grits, 47S. 
 Siwiilik Hills, fresh-water deposits of, 22G. 
 Skaptar Jokul, flow of lava from, 623. 
 Skye, hypersthene rocks of, 491. 
 
 , Isle of, Miocene syenite of the, 5CS. 
 
 , trap dike in, 514. 
 
 Slaty cleavage, 588. 
 
 Slicken-sides, in opposite walls of veins, 
 
 608. 
 
 , term defined, 87. 
 
 Smilax Hogitiifera^ CEuingen, 222. 
 Smith, Mr. W., on WhiteLias bed, 306. 
 Snowdon, volcanic tnflfs of, 549. 
 Soissonnais sands, 275. 
 Soleihastrcea cellulosa, Brockenhnrst, 257. 
 Solenhofen stone, fossils iu the, 337. 
 Solfatara, decomposition of rocks in the, 
 
 S80. 
 Somma, cone and dikes of, 520. 
 Sopwith, Mr. T., models of outcrop of 
 
 strata, 85. 
 Sorby, Mr., on action of water in meta- 
 
 morphism, 585. 
 
 , on glass cavities in quartz, BSS. 
 
 , on mechanical theory of cleavage, 
 
 592. 
 
 , on ripple-marks iu mica schist, 690. 
 
 South Joggins, section of cliflFs at, 410. 
 Spalacotherinm, Purbeck, 340. 
 Spataiif/tis radiatus. Chalk, 284. 
 
 with serpnla attached, 49. 
 
 Species, gradual change of, 139, 
 
 older than the land they inhabit, 207. 
 
 , similarity of conditions causing re- 
 appearance of, 311. 
 Specific gravity of basalt and trachyte, 
 
 504. 
 Speer and Eigi, Lower Miocene of the, 
 
 235 
 Speet'on Clay, 311. 
 Sphcerexochus mirus, Silurian, 467. 
 Sphoeruliteii dgaridfor'mis, White Chalk, 
 
 306. 
 
 of volcanic minerals, 499. 
 
 SplieiiophyUum eroswm,. Coal, 425. 
 Splienepteris graeilU, Hastings sands, 318. 
 Spheroidal concretions in limestone, 04. 
 Spicnila of sponge, Atlantic mud, 2SS. 
 Hpirifa-a Aujurwta, Devonian, 450. 
 
 alata, Permian, 3SS. 
 
 ttiuerotuita, 454. 
 
 trigoruUis, and S. glabra, 434. 
 
 Spirifei'ina Walcotti, Lias, 353. 
 
 SClfSS. 
 
 Spirolina atenoatonia, Eocene, 275. 
 Spirorbis carhonanus, coal-measures, 405. 
 Spcmdylus spiiwsiis. White Chalk, 294, 
 Sponge in fiini from White C/»a!*,290. 
 Sponges, vitreous, iu the chalk, 291. 
 Springs, mineral of Auvergne, 604. 
 Staffa, age of columnar basalt of, 539. 
 Stalactite, origin of, explained, 156. 
 Starfish in Silurian strata, 473. 
 Stations of species affecting distribution 
 
 of fossils, 354. 
 Stauria astrceiformis, 431. 
 Stereognathus.of Stonesfleld, 348. 
 Sternberg, Count, on insects in coal, 405. 
 Stigmaria attached to trunk of Sigillaria, 
 
 in coal-measures, 898, 411, 426. 
 
 ficoides and surface showing tubercles. 
 
 Coal, 427. 
 
 Stilbite, 600. 
 
 Stiper-Stones or Arenig Gronp,475, 
 
 Stockwerk, assemblage of veins, 005. 
 
 Stonesfleld slate, mammalia of the, 345. 
 
 Strata, term defined, 27. 
 
 , alternations of fresh-water, and shal- 
 low and deep-sea, 108. 
 
 , alternations of marine and fresh-wa- 
 ter, 73. 
 
 , curved, inclined, and vertical, 73. 
 
 , apparent horizontality of inclined, SI. 
 
 , contorted in drift, 178, 
 
 , contortion of, in Cyclopean Isles, 530. 
 
 , general table of fossiliferons, 131. 
 
 , Horizontality of, 40. . 
 
 , origin of metamorphic, 679. 
 
 , outcrop of, S3. 
 
 , overlapping, 95. 
 
 repeated by being doubled back, 87. 
 
 , slow growth of, attested by fossils, 
 
 47-50. ' 
 
 of organic origin, 51. 
 
 , tests of age of, 123. 
 
 , nnoouformability of, 94, 138. 
 
 , vast thickness of, not forming high 
 
 mountains, 109-113. 
 
 Stratification, diagonal or cross, 42, 44. 
 
 , different forms described, 39. 
 
 of metamorphic rocks considered, 
 
 580. 
 
 Stratified rocks, composition of, 35. 
 
 Stride, production of, 168. 
 
 Strickland, Mr., on thickness of the Trias, 
 309. 
 
 Stricklandinia liratn, 469. 
 
 Strike, term explained, SO. 
 
 Strintjoce^halus JSuriini, 462. 
 
 Stromboli, lava of, 500. 
 
 Strophomena depressa, Wenlock, 400. 
 
 grandis, 471. 
 
 Studer, Mr., on gneiss of the Jnngfrau, 599. 
 
 Subaurial denudation, average annual 
 amount of, 113. 
 
 Snbapennine beds, proportion of recent 
 species iu, 143. 
 
 strata. Older Pliocene, 208. 
 
 Submarine denudation, 105. 
 
 Subsidence of laud mustprepouderate over 
 upheaval, 116. 
 
 Succinea amphibia, 55, 
 
 elongata, 155. 
 
 Suess, M. , on fossils of St. Cassian beds, 
 37U, 377. 
 
638 
 
 INDEX. 
 
 SUESS. 
 
 Sness, M., on Vieuua basiu, 225. 
 Suffolk, crag of, 196. 
 " Sunk country," New Madrid, 402. 
 Superga, Lower Miocene of the, 244. 
 Superior, Lake, marl in, 63. 
 Superposition of deposits, a test of ai^e, 
 
 124. 
 
 a test of age of volcanic rocks, 521. 
 
 Sutherlandshlre, uuconfomiable Paljfiozo- 
 
 ic strata in, 112. 
 Swanage, fossil mammalia found at, 336. 
 Sweden, Cambrian of, 430. 
 
 ■, slow rise of land in, 72. 
 
 , small thickness of Silurian strata iu, 
 
 477, 
 Switzerland, lake-dwellings of, 148. 
 
 , Lower Molasse of, 235. 
 
 , Middle or Marine Molasse of, 223. 
 
 , Upper Miocene of, at CEuingeu, 215. 
 
 Sydney coal- field, rain-prints in, 410. 
 
 Syenite, composition of, 552,557. 
 
 , how far connected with trap-rocks, 
 
 55S. 
 Syeuitic granite, 55T. 
 Symonds, Rev. W. S,, on Moel Tryfaen 
 
 shells, ISO. 
 Synclinal and anticlinal curves, 74, S5. 
 
 TABLE of Botanical Nomenclature, 303. 
 
 of St Cassian fossil moUusca, 377. 
 
 of Cretaceous formations, 2S3. 
 
 of Devonian series ia Devon, 440. 
 
 of divisions of Hastings Sand, 31G. 
 
 of English and French Eocene strata, 
 
 252. 
 
 of ages of fossil vertebrata, 404. 
 
 of Neocomiaii strata, 308. 
 
 of mammalia older than Parisgypsum, 
 
 329. 
 
 of marine testacea in the Crag, 202. 
 
 of Oolitic strata, 321. 
 
 of volcanic minerals, 499. 
 
 of Silurian strata of United States, 
 
 478. 
 
 of Silurian rocks, 45S. 
 
 of Triassic str.ata, 375. 
 
 of Cambrian strata, 452. 
 
 of Permian of north of England, 330. 
 
 of Welsh coal-measnres, 394. 
 
 of thicknesses of Carboniferous Lime- 
 stone, 306. 
 
 , general, of fossiliferous strata, 131. 
 
 Tablemountain, granite veins iu clay-slate 
 of, 560. 
 
 Tails of homocercal and heteroccrcal flsh, 
 389. 
 
 Talcose granite, 557. 
 
 gneiss, 578. 
 
 Tarauuon shales, 468. 
 
 Tartaret cone, and lava of, 627, 542. 
 
 Tate, Mr., on St. Cassiau fossils, 377. 
 
 Tealby series. Middle Neocomian, 312. 
 
 Teeth of extinct mammalia, 163, 164. 
 
 Tellina baltkica {T. solidula), 190. 
 
 calcarea {T. proximo), 177. 
 
 obliqua, Crag, 194. 
 
 Temnechinus exeavatvs^ 200. 
 
 Temniiopleurus excavatus, 200. 
 
 Tetttaculitea anmilatus, Silnriau, 469. 
 
 T&'ebellum fusiforme, Barton, 269. 
 
 T — sopUoy Barton, 259. 
 
 Terehratula affinis, Aymestry, 403. 
 
 TRIAS. 
 
 Terehratula biplicata^ White Chalk, 294. 
 
 cornea, White Chalk, 294. 
 
 dig&na, Bradford clay, 345. 
 
 fimbria, Tnf. Oolite, 3^}. 
 
 "Aostofei, Mountain Limestone, 434. 
 
 sella, Neocomian, 310. 
 
 Wilsoni, Aymestry, 463. 
 
 Terebratulina striata, White Chalk, 294. 
 
 Terebrirostra lijra, Chloritic Sand, 300. 
 
 Teredo navalis, boring wood, 50. 
 
 Tertiary formations, classification of, 137, 
 143. 
 
 strata, subdivisions of, 143. 
 
 , term defined, 123. 
 
 Testacea. See Shells. 
 
 Thallogens, 303. 
 
 Tliam'iutstroea, Coral Hag, 339. 
 
 Thanet sands, 269. 
 
 Theea operculata, Tremadoc beds, 483. 
 
 Thecodontosaurus, tooth of, 374. 
 
 TIteeod-ux parvidens, Ludlow, 460. 
 
 TAecosmilia annularis. Coral Rag, 339. 
 
 Thirria, M., on Nerinrean limestone, 340. 
 
 Thompson, Dr., on nummulites of Thibet, 
 277. 
 
 Thomson, Wyville, on Atlantic mud, 283. 
 
 , on sponges in chalk mud, 292, 
 
 Thuringia, monitor of, 390, 403. 
 
 Thurmann, M., on Bernese Jura Oolite, 
 344. 
 
 , on structure of the .Tnra,S3. 
 
 Thylacotherium Prevostii, Stonesfield, 347. 
 
 Tile-stones of the Upper Ludlow, 459. 
 
 Tilgate forest, fossil Iguauodou In, 315. 
 
 Till described, 166. 
 
 , mammoth in Scotch, 175. 
 
 of North America, 1S2. 
 
 Tin veins, age of, iu Cornwall, 615. 
 
 Titanoferrite, 50U. 
 
 Torell, Dr., on ice-action in Greenland, 
 172. 
 
 , on Swedish Cambrian fossils, 489. 
 
 Touraine, faluns of, 211. 
 
 Tourmaline, 500. 
 
 Trachytic rocks, 505, 
 
 tuff, 50G. 
 
 porphyry, 506. 
 
 ]avf>, affe of, 523. 
 
 Trap, term "defined, 498. 
 
 dike, intercepting strata, 613. 
 
 dikes, 513-517. 
 
 , intrnsion of, between strata, 517. 
 
 rocks, ages of, 524r-550. 
 
 rocks passing into granite, 559. 
 
 tuff described, 508. 
 
 Trajjpean rocks, nomenclature of, 497. 
 
 rocks, their relation to active volca- 
 noes, 517. 
 
 Trass of Lower Eifel, 535. 
 
 Travertin, how deposited, 60. 
 
 , Infurienr of Paris basin, 273. 
 
 Tree ferns, living, 422. 
 
 Trees erect in coal, Nova Scotia, 411. 
 
 Tremadoc slates and their fossils, 482. 
 
 Tremolite, 499, 602. 
 
 Trenton limestone, fossils of the, 479. 
 
 Trezza, volcanic rocks of, 629. 
 
 Trias, beds of passage between lias and, 
 366. 
 
 of England, 369-374. 
 
 of Germany, 375, 
 
 , Sauriaus of the, 370. 
 
INDEX. 
 
 639 
 
 TEIA8. 
 
 Trias of the United States, 381. 
 Triassic maminifer, Nortli Carolina, 383. 
 Triclinic feldspars, 601. 
 Tridyinite, crystallized silica, 500. 
 THgonellites latus, Kimmeridge clay, 336. 
 Trigonia caudata, Heoconiian, 310. 
 
 ijibbosa, Portland stone, 335. 
 
 Trigonoearputn ovatuin, and T. olivceftyrm^^ 
 
 Coal, 429. 
 Trigonotreta undulata, Permian, 3SS. 
 Trilobites of Bala nnd Caradoc beds, 471. 
 
 , metamorphosis of, 471, 4SS. 
 
 of primordial zone, 437. 
 
 TriloculiTia infiata. Eocene, 275. 
 Trimmer. Mr., on contorted strata, 179. 
 
 , on shells ot'Moel Tryfaen, 180. 
 
 Trinu£leus concentriais^ T. Caractaai, 472. 
 THonyx, carapace of, Bembridge, 253. 
 Tripoli composed of diatoinaceDe, 61. 
 Trochoceras giganteus, Ludlow, 463. 
 Trophon antiquum {Ftisus contrariujs), 106. 
 
 clathratum, Scotch drift, 176. 
 
 Tuff defined, 30. 
 
 , shelly, of the Grand Canary, 538. 
 
 , trappean, of Llandeilo rocks, 473. 
 
 : , shelly, of Gergovia, 542. 
 
 Tupaia Tana, recent, 347. 
 
 Turner, Dr., on chemical decomposition, 
 
 68. 
 Turrilites costattis, Chalk, 299. 
 TurriteUa TnuUisulcata, Bracklesham, 262. 
 Tnscauy, mineral springs of, 604. 
 Tylor, Mr., on amount of subaurial denu- 
 
 "dation, 114. 
 Tyndall. Dr., on slaty cleavage, 594. 
 Tynedale fault, 90. 
 Tynemouth cliff, brecciated limestone of, 
 
 387. 
 Typhis pungerus, Barton clay, 259. 
 
 UN(;ITES GnipJius, Devonian, 452. 
 
 Unconformability of strata, 94, 138. 
 
 Underlying, term applied to plutonic rocks, 
 34. 
 
 Dnger on American forms in Swiss Mio- 
 cene flora, 2>3, 239. 
 
 on Miocene plants of Croatia, 243. 
 
 Uugnlite, or Oholus grit of Sussia, 477 
 
 Vnio littoralis, 54. 
 
 Valdenais, Hastings Sands, 317. 
 
 United States, Cambrian of the, 489. 
 
 , cretaceous rocks of, 307. 
 
 , Devonian of, 455. 
 
 , Eocene strata in the, 278. 
 
 , foot-prints in Carboniferous of, 407. 
 
 , Lower Miocene of, 248. 
 
 , Older Pliocene and Miocene forma- 
 tions of, 227. 
 
 , Silurian strata of, 478. 
 
 , Trias of the, 381. 
 
 Upheaval of land more than counteracted 
 by subsidence, 116. 
 
 , power of denudation to counteract, 
 
 105, 115. 
 
 Upper Greensand, or Chlontic series, 298. 
 
 Upsala, erratics on modern marine drift 
 near, 1 74 
 
 Urai Mountains, auriferous alluvmm of, 
 616. 
 
 Uralite, 499. 
 
 Ursus gpelteus, tooth of, 165. 
 
 Urville, Captain de, on size of icebergs, 172. 
 
 VOLTTTA. 
 
 VAL D'ARNO, Newer Pliocene of, 207. 
 
 Valleys, origin of, 102. 
 
 Valorsine, granite veins in talcose gneiss 
 in, 599. 
 
 Valvatapiscinalis, 55. 
 
 Vanessa Pluto, Lower Miocene, Croatia; 
 243. 
 
 Vegetation of the Coal, 420. 
 
 of the Devonian of America, 455. 
 
 . See Plants. 
 
 Veins, chemical deposits in, 612. 
 
 , granite rocks altered by, 659. 
 
 , different kinds of minerals, 005. 
 
 . See Mineral veins. 
 
 Vein-stones, 610. 
 
 VenaHcardia planicosta, 260. 
 
 Venetz, M., on Alpine glaciers, 170. 
 
 Ventriculites radiatns. Chalk, 292. 
 
 Verneuil, M. de, on Bussian Silnrian, 462. 
 
 , ou Permian flora, 392. 
 
 Vertebrata, progress of discovery of fossil, 
 464. 
 
 Vertical strata, 73. 
 
 Vesnvins, Recent and post-Pliocene vol- 
 canic rocks of, 525. 
 
 , basaltic lavas of, 508. 
 
 , tnfaceons strata of, 522. 
 
 , dikes of, 527. 
 
 Vicarya Lujani, Punfield, 319. 
 
 Vicentin, columnar basalt of the, 611. 
 
 Vienna Basin, Upper Miocene beds of, 224. 
 
 Vine in Upper Miocene beds at (Eningen, - 
 221. 
 
 Virginia, eighty miles of fault iu, 92. 
 
 , coal-field of, 382. 
 
 Virlet, M., on corrosion of rocks near Cor- 
 inth, 580. 
 
 ■ , on cretaceous traps of Greece, 544. 
 
 , ou fossils in veins, 608. 
 
 , on volcanic rocks of the Morea, 544. 
 
 Volcanic ash or tuff, 508. 
 
 breccia, 509. 
 
 dikes, 513-516. 
 
 force and denudation opposing pow- 
 ers, 117. 
 
 mountains, structure and origin of, 
 
 494 
 
 Volcanic rocks defined, 29. 
 
 , mineral composition of, 498. 
 
 , Recent and post-Pliocene, 524. 
 
 , Pliocene, 529. 
 
 , Miocene, 536-543. 
 
 , Eocene, 543. 
 
 ,'Cretaceous and Liassic, 544, 545. 
 
 - — , ^ew Red, Permian and Carbonifer- 
 ous, 545. 
 
 , Old Red Sandstone, 547. 
 
 , Silnrian, Cambrian and Laarentian, 
 
 548, 549. 
 
 of Auvergne, 540. 
 
 , columnar and globular, structure of, 
 
 510. 
 
 of Grand Canary, 528. 
 
 of Silurian age, 477. 
 
 , special forms of structure of, 606. 
 
 , tests of age of, 520-524. 
 
 Volcanoes, extmct, 30. 
 
 of Auvergne, 495. 
 
 Voltzia heterqphylla, Bunter, 380. 
 
 Valuta ambigwa. Barton clay, 259. 
 
 athleta. Barton, 259. 
 
 Lamherti, coralline and red crag, 196. 
 
640 
 
 INDEX. 
 
 VOLTTTA. 
 
 Valuta Lamberti, faluus, S14. 
 
 nodosa, Londou clay, 206. 
 
 Selseiensis, Bracklesham, 262. 
 
 Von Buch, Leopold, on "elevation craters," 
 
 496. 
 — ^, on Silurian pUitonic rocks, 572. 
 
 WACKE described, 508. 
 
 Wagner, M., on Miocene of Greece, 226. 
 
 WaUhia piniformis, Permian, 392. 
 
 Wales and England, glaciation of, ISO. 
 
 Wallicb, Dr., on Atlantic mud, 28T. 
 
 Water, denuding power of running, 98, 
 115. 
 
 ; action of, in metamorphism, 534. 
 
 Watt, Gregory, on fusion of rock, 584. 
 
 Weald clay and its fossils, 31T. 
 
 Wealden area, thickness of the, 319. 
 
 ' formation, 313. 
 
 flora, 320. 
 
 Webster, Mr. T., ou Tertiary strata, 141. 
 
 Wellington Valley caves, 158. 
 
 Weulock formation, fossils of the, 465-468. 
 
 limestone, 465. 
 
 shale, 40T. 
 
 Werner on mineral veins in Saxony, 609. 
 
 on isomorphism, 502. 
 
 Westwood, Mr., on Lias beetles, 303. 
 
 Wexford, veins of copper at, 015. 
 
 Whitaker, Mr., on snbaerial origin of es- 
 carpments, 104. 
 
 White or coralline crag, 197. 
 
 sand of Alum Bay, 38. 
 
 Whymper, Mr., ou Arctic Miocene plants, 
 240. 
 
 Williams, Mr., ou Cornish lodes, 007. 
 
 Williamson, Professor, on conifers of the 
 Coal, 428. 
 
 , on strnctnre of calamlte, 425. 
 
 Wind, dennding action of the, 97. 
 
 ZTJKICn. 
 
 Wood, Mr. Searles, on Bridlington shells, 
 190. 
 
 , on Chillesford and Aldeby beds, 192. 
 
 , on shells of the Crags, 194, 195, 199. 
 
 , on shells of Crag and Faluns com- 
 pared, 213. 
 
 , on fish of Headon series, 255. 
 
 , table of marine testacea of the Crag, 
 
 202. 
 
 , on thickness of coralline crag, 198. 
 
 Woodward, Dr., on St. Cassian fossils, 377. 
 
 , Mr. H., ou Pterygotus, 447. 
 
 Woolhopo beds, 467. 
 
 Woolwich and Beading series, 267. 
 
 Wright, Dr., on Barton shells, 258. 
 
 , on zones of the Lias, 353: 
 
 Wuusch, Mr. E. A., on trees in volcanic 
 ash, 546. 
 
 Wyville Thomson. See Thomson. 
 
 XIPHODON gradle, Paris basin, 271. 
 Xylobius Sigillarice, Nova Scotia coal, 415. 
 
 YOHEDALE beds, thickness of the, 395. 
 Yorkshire, Oolite of, 349. 
 Young, Mr., ou seeds washed out of mam- 
 moth tnske, 176. 
 
 ZECHSTEIN of Germany, 392. 
 
 Zeolites, secondary volcanic minerals, 500. 
 
 Zeuglodon cetoides, Eocene, United States, 
 
 280. 
 Zircon-syenite, 558. 
 Zoantharia rugosa and Z. aporosa, 431. 
 Zones of the Lias, 353. 
 ZoniteB priscus, Coal, 415. 
 Zoological provinces, great extent of, 127. 
 Zoophytes, fossil, 48. 
 
 . . See Corals, Bryozoa, etc 
 
 Zurich, lake-dwellings in Lake of, 148. 
 
 TaK IJfJIV