MANUAL 
 
 OP 
 
 ELEMENTARY GEOLOGY. 
 
By the same Author. 
 
 THE PRINCIPLES OF GEOLOGY; or, the MODERN CHANGES 
 
 of the EAKTH and its INHABITANTS, as illustrative of Geology. Ninth and 
 thoroughly revised Edition. With Woodcuts. 8vo. 18s. 
 
 TRAVELS IN" NORTH AMERICA : CANADA and NOVA SCOTIA. 
 
 With GEOLOGICAL OBSERVATIONS. Second Edition. Maps and Plates. 2 vols. 
 Post 8vo. 12s. 
 
 A SECOND VISIT TO NORTH AMERICA. Third Edition. 
 2 vols. Post 8vo. 12*. 
 
 LONDON : 
 
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 New -street- Square. 
 
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-MANUAL 
 
 ELEMENTARY GEOLOGY: 
 
 OR, 
 
 THE ANCIENT CHANGES OP THE EARTH AND ITS INHABITANTS 
 AS ILLUSTRATED BY GEOLOGICAL MONUMENTS. 
 
 
 BY SIR CHARLES LIELL, M.A. F.E.S. 
 
 AUTHOR OF "PRINCIPLES OF GEOLOGY," ETC. 
 
 " It is a philosophy which never rests its law is progress: a point which yesterday was 
 invisible is its goal to-day, and will be its starting-post to-morrow." 
 
 EDINBURGH REVIEW, July, 1837. 
 
 MXJMMtJLJII. 
 
 AMMONITE. 
 
 TERTIARY. SECONDARY. 
 
 PRIMARY. 
 
 FIFTH EDITION; GREATLY ENLARGED, AND ILLUST 
 
 WOODCUTS. 
 
 LONDON: % 
 JOHN MURRAY, ALBEMARLE~STREET. 
 
 1855. 
 
 Tlie right of translation is reserved. 
 
QE 
 
 -5 a 
 
PKEFACE TO THE FIFTH EDITION. 
 
 IT is now more than three years since the appearance of the 
 last Edition of the Manual (published January, 1851). In that 
 interval the science of Geology has been advancing as usual 
 at a rapid pace, making it desirable to notice many new facts 
 and opinions, and to consider their bearing on the previ- 
 ously acquired stock of knowledge. In my attempt to bring 
 up the information contained in this Treatise to the present 
 state of the science, I have added no less than 200 new Illus- 
 trations and 140 new pages of Text, which, if printed separately 
 and in a less condensed form, might have constituted alone a 
 volume of respectable size. To give in detail a list of all the 
 minor corrections and changes would be tedious ; but I have 
 thought it useful, in order to enable the reader of former 
 editions to direct his attention at once to what is new, to 
 offer the following summary of the more important additions 
 and alterations. 
 
 Principal Additions and Alterations in the present Edition. 
 
 CHAP. IX. " The general Table of Fossiliferous strata," for- 
 merly placed at the end of Chapter XXVIL, is now given at 
 p. 105., that the beginner may accustom himself from the first to 
 refer to it from time to time when studying the numerous sub- 
 divisions into which it is now necessary to separate the chrono- 
 logical series of rocks. The Table has been enlarged by a column 
 of Foreign Equivalents, comprising the names and localities of some 
 of the best known strata in other countries of contemporaneous date 
 with British Formations. 
 
 CHAP. XIV. XVI. The classification of the Tertiary formations 
 has been adapted to the information gained by me during a tour 
 made in the summer of 1851 in France and Belgium. The results of 
 my survey were printed in the Quarterly Journal of the Geological 
 
 10121G 
 
VI PREFACE TO THE FIFTH EDITION. 
 
 Society of London for 1852. In the course of my investigations I 
 enjoyed opportunities of determining more exactly the relations of 
 the Antwerp and the Suffolk crag, p. 174.; the stratigraphical place 
 of the Bolderberg beds near Hasselt, p. 179.; that of the Limburg 
 or Kleyn Spawen strata, p. 189.; and of other Belgian and French 
 deposits. In reference to some of these, the questions so much con- 
 troverted of late, whether certain groups should be called Lower 
 Miocene or Upper Eocene, are fully discussed, p. 184. et seq. 
 
 In the winter of 1852, 1 had the advantage of examining the north- 
 ern part of the Isle of Wight, in company with my friend the late 
 lamented Professor Edward Forbes, who pointed out to me the 
 discoveries he had just made in regard to the true position of the 
 Hempstead series (pp. 186 193.), recognized by him as the equi- 
 valent of the Kleyn Spawen or Limburg beds, and his new views 
 in regard to the relation of various members of the Eocene series 
 between the Hempstead and Bagshot beds. An account of these 
 discoveries, with the names of the new subdivisions, is given at 
 pp. 209. et seq. ; the whole having been revised when in print by 
 Edward Forbes. 
 
 The position assigned by Mr. Prestwich to the Thanet sands, as 
 an Eocene formation inferior to the Woolwich beds, is treated of 
 at p. 222., and the relations of the Middle and Lower Eocene of 
 France to various deposits in the Isle of Wight and Hampshire 
 at p. 223. et seq. In the same chapters, many figures have been 
 introduced of characteristic organic remains, not given in previous 
 editions. 
 
 CHAP, XVII. In speaking of the Cretaceous strata, I have for 
 the first time alluded to the position of the Pisolitic Limestone in 
 France, and other formations in Belgium intermediate between the 
 White Chalk and Thanet beds, p. 236. 
 
 CHAP. XVIII The Wealden beds, comprising the Weald Clay 
 and Hastings Sands apart from the Purbeck, are in this chapter for 
 the first time considered as belonging to the Lower Cretaceous 
 Group, and the reasons for the change are stated at p. 264. 
 
 CHAP. XIX. Relates to "the denudation of the Weald," or of 
 the country intervening between the North and South Downs. It 
 has been almost entirely rewritten, and some new illustrations in- 
 troduced. Many geologists have gone over that region again and 
 again of late years, bringing to light new facts, and speculating on 
 the probable time, extent, and causes of so vast a removal of rock. 
 I have endeavoured to show how numerous have been the periods of 
 denudation, how vast the duration of some of them, and how little 
 the necessity to despair of solving the problem by an appeal to ordi- 
 nary causation, or to invoke the aid of imaginary catastrophes and 
 paroxysmal violence, pp. 272 291. 
 
 CHAP. XX. XXI. On the strata from the Oolite to the Lias 
 inclusive. The Purbeck beds are here for the first time considered 
 
PREFACE TO THE FIFTH EDITION. Vll 
 
 as the uppermost member of the Oolite, in accordance with the 
 opinions of the late Professor E. Forbes, p. 295. Many new figures 
 of fossils characteristic of the subdivisions of the three Purbecks 
 are introduced ; and the discovery, in 1854, of a new marnmifer 
 alluded to, p. 296. 
 
 Representations also of fossils of the Upper, Middle, and Lower 
 Oolite, and of the Lias, are added to those before given. 
 
 CHAP. XXII. XXIII. On the Triassic and Permian forma- 
 tions. The improvements consist chiefly of new illustrations of 
 fossil remains. 
 
 CHAP. XXIV. XXV. Treating of the Carboniferous group, 
 I have mentioned the subdivisions now generally adopted for the 
 classification of the Irish strata (p. 362.), and I have added new 
 figures of fossil plants to explain, among other topics, the botanical 
 characters of Calamites, Sternbergia, and Trigonocarpum, and their 
 relation to Coniferae (pp. 367, 368, 371.). The grade also of the 
 Coniferae in the vegetable kingdom, and whether they hold a high or 
 a low position among flowering plants, is discussed with reference to 
 the opinions of several of the most eminent living botanists ; and the 
 bearing of these views on the theory of progressive development, 
 p. 373. 
 
 The casts of rain-prints in coal-shale are represented in several 
 woodcuts as illustrative of the nature and humidity of the carboni- 
 ferous atmosphere, p. 384. The causes also of the purity of many 
 seams of coal, p. 385., and the probable length of time which was 
 required to allow the solid matter of certain coal-fields to accumulate, 
 p. 386., are discussed for the first time. 
 
 Figures are given of Crustaceans and Insects from the Coal, pp. 
 388, 389.; and the discovery of some new Reptiles is alluded to, 
 p. 405. 
 
 I have also alluded to the causes of the rarity of vertebrate and 
 invertebrate air-breathers in the coal, p. 405. 
 
 That division of this same chapter (Chap. XXV.) which relates to 
 the Mountain Limestone has been also enlarged by figures of new 
 fossils, and among others by representations of Corals of the Paleo- 
 zoic, as distinguishable from those of the Neozoic, type, p. 407. ; also 
 by woodcuts of several genera of shells which retain the patterns 
 of their original colours, p. 410. The foreign equivalents of the 
 Mountain Limestone are also alluded to, p. 413. 
 
 CHAP. XXVI. In speaking of the Old Red Sandstone, or De- 
 vonian Group, the evidence of the occurrence of the skeleton of a 
 Reptile and the footprints of a Chelonian in that series are recon- 
 sidered, p. 416. New plants found in Ireland in this formation are 
 figured, p. 418. ; also the Pterygotus, or large crustacean of Forfar- 
 shire, p. 419. ; and, lastly, the division of the Devonian series in 
 North Devon into Upper, Middle, and Lower, p. 424., the fossils of 
 
 A 4 
 
\*iii PREFACE TO THE FIFTH EDITION. 
 
 the same (p. 425. et seq.\ and the equivalents of the Devonian beds 
 in Russia and the United States, are treated of, p. 429. and 432. 
 
 CHAP. XXVII. The classification and nomenclature of the Si- 
 lurian rocks of Great Britain, the Continent of Europe, and North 
 America, and the question whether they can be distinguished from 
 the Cambrian, and by what paleontological characters, are .discussed 
 in this chapter, pp. 433. 451. and 457. 
 
 The relation of the Caradoc Sandstone to the Upper and Lower 
 Silurian, as inferred from recent investigations (p. 441.), the vast 
 thickness of the Llandeilo or Lower Silurian in Wales (p. 446.), the 
 Obolus or Ungulite grit of St. Petersburg and its fossils (p. 447.), the 
 Silurian strata of the United States and their British equivalents 
 (p. 448.), and those of Canada, the discoveries of M. Barrande re- 
 specting the metamorphosis of Silurian and Cambrian trilobites 
 (pp. 445. 454.), are among the subjects enlarged upon more fully 
 than in former editions, or now treated of for the first time. 
 
 The Cambrian beds below the Llandeilo, and their fossils, are like- 
 wise described as they exist in Wales, Ireland, Bohemia, Sweden, 
 the United States, and Canada, and some of their peculiar organic 
 remains are figured, p. 451. to p. 457. 
 
 Lastly, at the conclusion of the chapter, some remarks are offered 
 respecting the absence of the remains of fish and other vertebrata 
 from the deposits below the Upper Silurian, p. 457., in elucidation of 
 which topic a Table has been drawn up of the dates of the successive 
 discovery of different classes of Fossil Vertebrata in rocks of higher 
 and higher antiquity, showing the gradual progress made in the 
 course of the last century and a half in tracing back each class to 
 more and more ancient rocks. The bearing of the positive and 
 negative facts thus set forth on the doctrine of progressive develop- 
 ment is then discussed, and the grounds of the supposed scarcity 
 both of vertebrate and invertebrate air-breathers in the most ancient 
 formation considered, p. 460. 
 
 CHAP. XXVIII. With the assistance of an able mineralogist, 
 M. Delesse, I have revised and enlarged the glossary of the more 
 abundant volcanic rocks, p. 476., and the table of analyses of simple 
 minerals, p. 479. 
 
 CHAP. XXIX. In consequence of a geological excursion to 
 Madeira and the Canary Islands, which I made in the winter of 
 1853-4, I have been enabled to make larger additions of original 
 matter to this chapter than to any other in the work. The account 
 of Teneriffe and Madeira, pp. 514. 522., is wholly new. Formerly I 
 gave an abstract of Von Buch's description of the island of Palma, 
 one of the Canaries, but I have now treated of it more fully from 
 my own observations, regarding Palma as a good type of that class 
 of volcanic mountains which have been called by Von Buch 
 " craters of elevation," pp. 498 512. Many illustrations, chiefly 
 from the pencil of my companion and fellow-labourer, Mr. Hartung, 
 have been introduced. In reference to the above-mentioned sub- 
 
PREFACE TO THE FIFTH EDITION". IX 
 
 jects, citations are made from Dana on the Sandwich Islands, 
 p. 493., and from Junghuhn's Java, p. 496. 
 
 CHAP. XXXV. XXXVII. The theory of the origin of the 
 metamorphic rocks and certain views recently put forward by some 
 geologists respecting cleavage and foliation have made it desirable 
 to recast and rewrite a portion of these chapters. New proofs are 
 cited in favour of attributing cleavage to mechanical force, p. 610., 
 and for inferring in many cases a connection between foliation and 
 cleavage, p. 615. At the same time, the question how far the 
 planes of foliation usually agree with those of sedimentary depo- 
 sition, is entered into, p. 614. 
 
 CHAP. XXXYIII. To the account formerly published of mineral 
 veins some facts and opinions are added respecting the age of the 
 rocks and alluvial deposits containing gold in South America, the 
 United States, California, and Australia. 
 
 I have already alluded to the assistance afforded me by the 
 late Professor Edward Forbes towards the improvement of 
 some parts of this work. His letters suggesting corrections 
 and additions were continued to within a few weeks of his 
 sudden and unexpected death, and I felt most grateful to him 
 for the warm interest, which, in the midst of so many and 
 pressing avocations, he took in the success of my labours. His 
 friendship and the power of referring to his sound judgment in 
 cases of difficulty on palaeontological and other questions were 
 among the highest privileges I have ever enjoyed in the course 
 of my scientific pursuits. Never perhaps has it been the lot of 
 any Englishman, who had not attained to political or literary 
 eminence, more especially one who had not reached his fortieth 
 year, to engage the sympathies of so wide a circle of admirers, 
 and to be so generally mourned. The untimely death of such 
 a teacher was justly felt to be a national loss ; for there was a 
 deep conviction in the minds of all who knew him, that genius 
 of so high an order, combined with vast acquirements, true 
 independence of character, and so many social and moral ex- 
 cellencies, would have inspired a large portion of the rising 
 generation with kindred enthusiasm for branches of knowledge 
 hitherto neglected in the education of British youth. 
 
 As on former occasions, I shall take this opportunity of 
 stating that the " Manual" is not an epitome of the " Principles 
 of Geology," nor intended as introductory to that work. So 
 much confusion has arisen on this subject, that it is desirable 
 
X PREFACE TO THE FIFTH EDITION. 
 
 to explain fully the different ground occupied by the two pub- 
 lications. The first five editions of the " Principles " comprised 
 a 4th book, in which some account was given of systematic geo- 
 logy, and in which the principal rocks composing the earth's 
 crust and their organic remains were described. In subsequent 
 editions this 4th book was omitted, it having been expanded, 
 in 1838, into a separate treatise called the " Elements of Geo- 
 logy," first re-edited in 1842, and again recast and enlarged in 
 1851, and entitled " A Manual of Elementary Geology." Of 
 this enlarged work another edition, called the Fourth, was 
 published in 1852. 
 
 Although the subjects of both treatises relate to Geology, as 
 their titles imply, their scope is very different ; the " Principles " 
 containing a view of the modern changes of the earth and its 
 inhabitants, while the " Manual " relates to the monuments of 
 ancient changes. In separating the one from the other, I have 
 endeavoured to render each complete in itself, and independent ; 
 but if asked by a student which he should read first, I would 
 recommend him to begin with the " Principles," as he may 
 then proceed from the known to the unknown, and be provided 
 beforehand with a key for interpreting the ancient phenomena, 
 whether of the organic or inorganic world, by reference to 
 changes now in progress. 
 
 It will be seen on comparing " The Contents " of the " Prin- 
 ciples " with the abridged headings of the chapters of the pre- 
 sent work (see the following pages), that the two treatises have 
 but little in common ; or, to repeat what I have said in the 
 Preface to the " Principles," they have the same kind of con- 
 nection which Chemistry bears to Natural Philosophy, each 
 being subsidiary to the other, and yet admitting of being con- 
 sidered as different departments of science.* 
 
 CHARLES LYELL. 
 
 53. Harley Street, London, February 22. 1855. 
 
 * As it is impossible to enable the reader to recognize rocks and minerals at 
 sight by aid of verbal descriptions or figures, he will do well to obtain a well- 
 arranged collection of specimens, such as may be procured from Mr. Tennant (149. 
 Strand), teacher of Mineralogy at King's College, London. 
 
CONTENTS. 
 
 CHAPTER I. On the different Classes of Rocks. 
 
 Geology defined Successive formation of the earth's crust Classification of rocks 
 according to their origin and age Aqueous rocks Volcanic rocks Plutonic 
 rocks Metamorphic rocks The term primitive, why erroneously applied to the 
 crystalline formations ----- - Page 1 
 
 
 CHAPTER II. Aqueous Rocks Their Composition and Forms of Stratificati 
 
 Mineral composition of strata Arenaceous rocks Argillaceous Calcareous 
 Gypsum Forms of stratification Diagonal arrangement Rip pie- mark - 10 
 
 CHAPTER III. Arrangement of Fossils in Strata Freshwater and Marine. 
 
 Limestones formed of corals and shells Proofs of gradual increase of strata derived 
 from fossils Tripoli and semi-opal formed of infusoria Chalk derived principally 
 from organic bodies Distinction of freshwater from marine formations Alter- 
 nation of marine and freshwater deposits - - 21 
 
 CHAPTER IV. Consolidation of Strata and Petrifaction of Fossils. 
 
 Chemical and mechanical deposits Cementing together of particles Concretionary 
 nodules Consolidating effects of pressure Mineralization of organic remains 
 Impressions and casts how formed Fossil wood Source of lime and silex in 
 solution - - - - 33 
 
 CHAPTER V. Elevation of Strata above the Sea Horizontal and Inclined 
 Stratification. 
 
 Position of marine strata, why referred to the rising up of the land, not to the going 
 down of the sea Upheaval of horizontal strata Inclined and vertical stratification 
 
 Anticlinal and synclinal lines Theory of folding by lateral movement Creeps 
 
 Dip and strike Structure of the Jura Inverted position of disturbed strata 
 (Jnconformable stratification Fractures of strata Faults - - -44 
 
 CHAPTER VI. Denudation. 
 
 Denudation defined Its amount equal to the entire mass of stratified deposits in the 
 earth's crust Levelled surface of countries in which great faults occur Denuding 
 power of the ocean Origin of Valleys Obliteration of sea-cliffs Inland sea-cliffs 
 and terraces - ____--'. *-; - 66 
 
 CHAPTER VII. Alluvium. 
 
 Alluvium described Due to complicated causes Of various ages How distin- 
 guished from rocks in situ River-terraces Parallel roads of Glen Roy - 79 
 
 CHAPTER VIII. Chronological Classification of Rocks. 
 
 Aqueous, plutonic, volcanic, and metamorphic rocks, considered chronologically 
 Lehman's division into primitive and secondary Werner's addition of a transition 
 class Neptunian theory Hutton on igneous origin of granite The name of 
 "primary" for granite and the term "transition" why faulty Chronological no- 
 menclature adopted in this work, so far as regards primary, secondary, and ter- 
 tiary periods -.-..-.--89 
 
Xll CONTENTS. 
 
 CHAPTER IX. On the different Ages of the Aqueous Rocks. 
 
 On the three tests of relative age superposition, mineral character, and fossils 
 Change of mineral character and fossils in the same formation Proofs that distinct 
 species of animals and plants have lived at successive periods Distinct provinces 
 of indigenous species Similar laws prevailed at successive geological periods 
 Test of age by included fragments Frequent absence of strata of intervening 
 periods General Table of Fossiliferous strata - - Page 96 
 
 CHAPTER X. Classification of Tertiary Formations. Post Pliocene Group. 
 
 General principles of classification of tertiary strata Difficulties in determining their 
 chronology Increasing proportion of living species of shells in strata of newer origin 
 
 Terms Eocene, Miocene, and Pliocene Post-Pliocene recent strata - - 104 
 
 CHAPTER XL Newer Pliocene Period. Boulder Formation. 
 
 Drift of Scandinavia, northern Germany, and Russia Fundamental rocks polished, 
 grooved, and scratched Action of glaciers and icebergs Fossil shells of glacial 
 period Drift of eastern Norfolk Ancient glaciers of North Wales Irish drift - 121 
 
 CHAPTER XII. Boulder Formation continued. 
 
 Effects of intense cold in augmenting the quantity of alluvium Analogy of erratics 
 and scored rocks in North America, Europe, and Canada Why organic remains so 
 rare in northern drift Many shells and some quadrupeds survived the glacial 
 cold Alps an independent centre of dispersion of erratics Meteorite in Asiatic 
 drift - - 131 
 
 CHAPTER XIII. -Newer Pliocene Strata and Cavern Deposits. 
 
 Pleistocene formations Freshwater deposits in valley of Thames In Norfolk cliffs 
 In Patagonia Comparative longevity of species in the mammalia and testacea 
 Crag of Norwich Newer Pliocene strata of Sicily Osseous breccias and cavern- 
 deposits Sicily Kirkdale Australian cave-breccias Relationship of geogra- 
 phical provinces of living vertebrata and those of Pliocene species Teeth of fossil 
 quadrupeds - - . ..? ..'. } , - - 146 
 
 CHAPTER XIV. Older Pliocene and Miocene Formations. 
 
 Red and Coralline crags of Suffolk Fossils, and proportion of recent species Depth 
 of sea, and climate Migration of many species of shells southwards during the gla- 
 cial period Antwerp crag Subapennine beds Miocene formations Faluns of 
 Touraine Depth of sea and littoral character of fauna Climate Proportion of 
 recent species of shells Miocene strata of Bordeaux, Belgium, and North Germany 
 
 Older Pliocene and Miocene formations in the United States Sewalik Hills in 
 India - .,.- - - - 161 
 
 CHAPTER XV. Upper Eocene Formations. (Lower Miocene of many authors.) 
 
 Remarks on classification, and on the line of separation between Eocene and Miocene 
 Whether the Limburg strata in Belgium should be called Upper Eocene Strata of 
 same age in North Germany Mayence basin Brown Coal of Germany Upper 
 Eocene of Isle of Wight Of France Lacustrine strata of Auvergne and the Cantal 
 
 Upper Eocene of Bordeaux, &c. Of Nebraska, United States - 184 
 
 CHAPTER XVI. Middle and Lower Eocene Formations. 
 
 Middle Eocene strata of England Fluvio-marine series in the Isle of Wight and 
 Hampshire Successive groups of Eocene Mammalia Fossils of Barton Clay Of 
 the Bagshot and Bracklesham beds Lower Eocene strata of England London 
 Clay proper Strata of Kyson in Suffolk Fossil monkey and opossum Plastic 
 clays and sands Thanet sands Middle and Lower Eocene formations of France 
 Nummulitic formations of Europe and Asia Eocene strata at Claiborne, Alabama 
 
 Colossal cetacean Orbitoid limestone Burr stone - 208 
 
CONTENTS. Xlll 
 
 CHAPTER XVII. Cretaceous Group. 
 
 Lapse of time between the Cretaceous and Eocene periods Formations in Belgium 
 and France of intermediate age Pisolitic limestone Divisions of the Cretaceous 
 series in North- Western Europe Maestricht beds Chalk of Faxoe White chalk 
 How far derived from shells and corals Chalk flints Fossils of the Upper 
 Cretaceous rocks Upper Greensand and Gault Chalk of South of Europe Hip- 
 purite limestone Cretaceous rocks of the United States - - Page 235 
 
 CHAPTER XVIII. Lower Cretaceous and Wealden Formations. 
 
 Lower Greensand Term "Neocomian" Fossils of Lower Greensand Wealden 
 formation Weald Clay and Hastings Sand Fossil shells and fish Their relation 
 to the Cretaceous type Flora of Lower Cretaceous and Wealden periods - - 257 
 
 CHAPTER XIX. Denudation of the Chalk and Wealden. 
 
 Physical geography of certain districts composed of Cretaceous and Wealden strata 
 Lines of inland chalk-cliffs on the Seine in Normandy Denudation of the chalk and 
 wealden in Surrey, Kent, and Sussex Chalk once continuous from the North to the 
 South Downs Rise and denudation of the strata gradual At what period the 
 Weald valley was denuded, and by what causes Elephant-bed, Brighton San- 
 gatte cliff Conclusion - - -268 
 
 CHAPTER XX. Jurassic Group. Purbeck Beds and Oolite. 
 
 The Purbeck beds a member of the Upper Oolite New fossil Mammifer Dirt-bed 
 Fossils of the Purbeck beds Portland stone and fossils Middle Oolite Coral Rag 
 Zoophytes Nerinaean limestone Diceras limestone Oxford Clay, Ammonites 
 and Belemnites Lower Oolite, Crinoideans Great Oolite Stonesfield Slate 
 Fossil mammalia Yorkshire Oolitic coal-field Brora coal Fuller's Earth In- 
 ferior Oolite and fossils -------- 292 
 
 CHAPTER XXL Jurassic Group, continued. Lias. 
 
 Mineral character of Lias Fossil shells and fish Radiata Ichthyodorulites 
 Reptiles Ichthyosaur and Plesiosaur Fluvio -marine beds in Gloucestershire, and 
 Insect limestone Fossil plants Origin of the Oolite and Lias Oolitic coal-field 
 of Virginia - KY *?;>' ------ 318 
 
 CHAPTER XXII. Trias or New Red Sandstone Group. 
 
 Distinction between New and Old Red Sandstone The Trias and its three divisions 
 in Germany Keuper and its fossils Muschelkalk and fossils Fossil plants of 
 the Bunter Triassic group in England Footsteps of Cheirotherium Osteology of 
 the Labyrinthodon Triassic mamraifer Origin of Red Sandstone and Rock-salt 
 
 . New Red Sandstone in the United States Fossil footprints of birds and reptiles in 
 the valley of the Connecticut - - -334 
 
 CHAPTER XXIII. Permian or Magnesian Limestone Group. 
 
 Fossils of Magnesian Limestone Term Permian English and German equivalents 
 Marine shells and corals Palaeoniscus and other fish Thecodont saurians 
 Permian Flora Its generic affinity to the carboniferous Psaronites or tree- 
 ferns - ........ 353 
 
 CHAPTER XXIV. The Coal, or Carboniferous Group. 
 
 Carboniferous strata in England Coal-measures and Mountain limestone Carboni- 
 ferous series in Ireland and South Wales Underclays with Stigmaria Carboni- 
 
XIV CONTENTS. 
 
 ferous Flora Ferns, Lepidodendra, Calamites, Sigillarise Conifers Sternbergia 
 
 Trigonocarpon Grade of Coniferae in the Vegetable Kingdom Absence of 
 Angiosperms Coal, how formed Erect fossil trees Rain-prints Purity of the 
 Coal explained Time required for its accumulation Crustaceans and insects 
 
 Page 361 
 
 CHAPTER XXV. Carboniferous Group continued. 
 
 Coal-fields of the United States Section of the country between the Atlantic and 
 Mississippi Uniting of many coal-seams into one thick bed Vast extent and 
 continuity of single seams of coal Ancient river-channel in Forest of Dean coal- 
 field Climate of Carboniferous period Insects in coal Great number of fossil fish 
 First discovery of the skeletons of fossil reptiles First land-shell of the Coal found 
 
 Rarity of air-breathers, whether vertebrate or invertebrate, in Coal-measures 
 Mountain limestone Its corals and marine shells ... -391 
 
 CHAPTER XXVI. Old Red Sandstone or Devonian Group. 
 
 Old Red Sandstone of the borders of Wales Scotland and the South of Ireland 
 Fossil reptile of Elgin Fossil Devonian plants at Kilkenny Ichthyolites of 
 Clashbinnie Fossil fish, &c., crustaceans, of Caithness and Forfarshire Distinct 
 lithological type of Old Red in Devon and Cornwall Term " Devonian " Devonian 
 series of England and the Continent Old Red Sandstone of Russia Devonian 
 strata of the United States - - 415 
 
 CHAPTER XXVII. Silurian and Cambrian Groups. 
 
 Silurian strata formerly called " Transition " Subdivisions Ludlow formation and 
 fossils Ludlow bone-bed, and oldest known remains of fossil fish Wenlock form- 
 ation, corals, cystideans, trilobites Caradoc sandstone Pentameri and Tentaculites 
 Lower Silurian l rocks Llandeilo flags Cystideas Trilobites Graptolites 
 Vast thickness of Lower Silurian strata in Wales Foreign Silurian equivalents in 
 Europe Ungulite grit of Russia Silurian strata of the United States Canadian 
 equivalents Deep-sea origin of Silurian strata Fossiliferous rocks below the 
 Llandeilo beds Cambrian group Lingula flags Lower Cambrian Oldest 
 known fossil remains "Primordial group "of Bohemia Metamorphosis of trilo- 
 bites Alum schists of Sweden and Norway Potsdam sandstone of United States 
 and Canada Trilobites on the Upper Mississippi Supposed period of invertebrate 
 animals Absence of fish in Lower Silurian Progressive discovery of vertebrata 
 in older rocks Doctrine of the non-existence of vertebrata in the older fossiliferous 
 periods premature ---.._.. 433 
 
 CHAPTER XXVIII. Volcanic Rocks. 
 
 Trap rocks Name, whence derived Their igneous origin at first doubted Their 
 general appearance and character Mineral composition and texture Varieties of 
 felspar Hornblende and augite Isomorphism Rocks, how to be studied 
 Basalt, trachyte, greenstone, porphyry, scoria, amygdaloid, lava, tuff Agglomerate 
 
 Laterite Alphabetical list, and explanation of names and synonyms of volcanic 
 rocks Table of the analyses of minerals most abundant in the volcanic and hypo- 
 gene rocks ^7 T -464 
 
 CHAPTER XXIX. Volcanic Rocks continued. 
 
 Trap dikes Strata altered at or near the contact Conversion of chalk into marble 
 
 Trap interposed between strata Columnar and globular structure Relation of 
 trappean rocks to the products of active volcanos Form, external structure, and 
 origin of volcanic mountains Craters and Calderas Sandwich Islands Lava 
 flowing underground Truncation of cones Javanese Calderas Canary Islands 
 
 Structure and origin of the caldera of Palma Aqueous conglomerate in Palma 
 
 Hypothesis of upheaval considered Slope on which stony lavas may form 
 
CONTENTS. XV 
 
 Island of St. Paul in the Indian Ocean Peak of Teneriffe, and rains of older cone 
 
 Madeira Its volcanic rocks, partly of marine, and partly of subaerial origin 
 Central axis of eruptions Varying dip of solid lavas near the axis, and further from 
 it Leaf-bed and fossil land-plants Central valleys of Madeira how formed 
 
 Page 480 
 
 CHAPTER XXX. On the Different Ages of the Volcanic Rocks. 
 
 Tests of relative age of volcanic rocks Test by superposition and intrusion Test by 
 alteration of rocks in contact Test by organic remains Test of age by mineral cha- 
 racter Test by included fragments Volcanic rocks of the Post-Pliocene period 
 Basalt of Bay of Trezza in Sicily Post-Pliocene volcanic rocks near Naples 
 Dikes of Somma Igneous formations of the Newer Pliocene period Val di Noto 
 in Sicily 523 
 
 CHAPTER XXXI. On the different Ages of the Volcanic Socks continued. 
 
 Volcanic rocks of the Older Pliocene period Tuscany Rome Volcanic region of 
 Olot in Catalonia Cones and lava-currents Miocene period Brown-coal of the 
 Eifel and contemporaneous trachytic rocks Age of the brown-coal Peculiar cha- 
 racters of the volcanos of the Upper and Lower Eifel Lake craters Trass Hun- 
 garian volcanos -...,?.> - - - - - - 535 
 
 CHAPTER XXXII. On the different Ages of the Volcanic Rocks continued. 
 
 Volcanic rocks of the Pliocene and Miocene periods continued Auvergne Mont Dor 
 
 Breccias and alluviums of Mont Perrier, with bones of quadrupeds Mont Dome 
 
 Cones not denuded by general flood Velay Bones of quadrupeds buried in 
 scoriae Cantal Eocene volcanic rocks Tuffs near Clermont Hill of Gergovia 
 Trap of Cretaceous period Oolitic period New Red Sandstone period Carboni- 
 ferous period Old Red Sandstone period Silurian period Cambrian volcanic 
 rocks - - - . '". ,.'.,'.' - - - ..'*- ' " -" - 550 
 
 CHAPTER XXXIII. Plutonic Rocks Granite. 
 
 General aspect of granite Analogy and difference of volcanic and plutonic formations 
 
 Minerals in granite Mutual penetration of crystals of quartz and felspar 
 Syenitic, talcose, and schorly granites Eurite Passage of granite into trap 
 Granite veins in Glen Tilt, and other countries Composition of granite veins 
 Metalliferous veins in strata near their junction with granite Quartz veins Whe- 
 ther plutonic rocks are ever overlying Their exposure at the surface due t 
 denudation - - 565 
 
 CHAPTER XXXIV. On the different Ages of the Plutonic Rocks. 
 
 Difficulty in ascertaining the age of a plutonic rock Test of age by relative position 
 
 Test by intrusion and alteration Test by mineral composition Test by included 
 fragments Recent and Pliocene plutonic rocks, why invisible Tertiary plutonic 
 rocks in the Andes Granite altering Cretaceous rocks Granite altering Lias 
 Granite altering Carboniferous strata Granite of the Old Red Sandstone period 
 Syenite altering Silurian strata in Norway Oldest plutonic rocks Granite pro- 
 truded in a solid form Age of the granites of Arran, in Scotland - - 579 
 
 CHAPTER XXXV. Metamorphic Rocks. 
 
 General character of metamorphic rocks Gneiss Hornblende-schist Mica-schist 
 Clay-slate Quartzite Chlorite-schist Metamorphic limestone Alphabetical 
 list and explanation of the more abundant rocks of this family Origin of the 
 metamorphic strata Their stratification Fossiliferous strata near intrusive masses 
 of granite converted into different members of the metamorphic series Objections 
 to the metamorphic theory considered Partial conversion of Eocene slate into 
 gneiss - - - 594 
 
XVI CONTENTS. 
 
 CHAPTER XXXVI. Metamorphic Rocks continued. 
 
 Origin of the metamorphic rocks, continued Definition of joints, slaty cleavage, and 
 foliation Causes of these structures Mechanical theory of cleavage Supposed 
 combination of crystalline and mechanical forces Lamination of some volcanic 
 rocks due to motion Whether the foliation of the crystalline schists be usually 
 parallel with the original planes of stratification - - -'- - - Page 607 
 
 CHAPTER XXXVII. On the different Ages of tJte Metamorphic Rocks. 
 
 Age of each set of metamorphic strata twofold Test of age by fossils and mineral 
 character not available Test by superposition ambiguous Conversion of fossili- 
 ferous strata into metamorphic rocks Limestone and shale of Carrara Metamor- 
 phic strata older than the Cambrian rocks Others of Lower Silurian origin Others 
 of the Jurassic and Eocene periods Why scarcely any of the visible crystalline 
 strata are very modern Order of succession in metamorphic rocks Uniformity of 
 mineral character Why the metamorphic strata are less calcareous than the 
 fossiliferous ...... - - 618 
 
 CHAPTER XXXVIII. Mineral Veins. 
 
 Werner's doctrine that mineral veins were [fissures filled from above Veins of segre- 
 gation 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 Why some veins 
 alternately swell out and contract Filling of lodes by sublimation from below 
 Chemical and electrical action Relative age of the precious metals Copper and 
 lead veins in Ireland older than Cornish tin Lead veins in Lias, Glamorganshire 
 Gold in Russia, California, and Australia Connection of hot springs and mineral 
 veins Concluding remarks - - -'-%-.. - _ 626 
 
OP 
 
 Ti TO M E "N T !.l P V _jGLTC H T, O aiL 
 
 ERRATA. 
 
 Page 25., line 2. from bottom (fig. 20.) for Gaillonella " read " Gallonella." 
 fig. 17. and fig. 18., ditto ditto. 
 
 , 39., line 6. from bottom, for " pores " read " cells." (j 
 
 |I 108., third column, line 10. from bottom, for " Etages C. and D. read Etage L. 
 160., line 15. from bottom, for " species " read " spaces." 
 
 I, 169., note, line 5. from bottom, for J. O. Thompson '^read J. V. Thompsoi 
 I', 181., line 14. from bottom, for " flaules " read " flanks." 
 I', 192., line 11., for " newer" read " older." 
 
 205., line 18. from bottom, for " mound " read " mould." 
 
 215., fig. 207., for "typhoeus " read " typhoeus." T) an i Pn 
 
 I, 238., line 9. from bottom, insert "Etage" before Danien." "Etage Danien, 
 
 " Etage Senonien," &c. 
 
 242., fig. 251 M for " Julo eido-copri " read " Julo-eido-copri." 
 246.', fig. 254., for " Micrastes " read " Micraster." 
 
 for " cor anguinum " read " cor-angninum." 
 fig!'258., for " B. Fanjasii " read " B. Faujasii." 
 line 2. from bottom, for " Marsupiles " read " Marsupites." 
 ',' 248.. fig. 275. right-hand figure, is a valve of Ostrea distorta (see p. 295.) inserted here by 
 
 mistake. 
 
 260., fig. 301., for " tella " read " sella." 
 310., note, last line, for " Priomus " read " Prionus." 
 I, 416., line 17- from bottom, for " 1810 " read " 1710." 
 
 425 note, line 3., for " Fred. Roemer V read " Fried. A. Roemer. 
 
 note, for " Dr. Fred Sandberger," read " Dr. Fridolin Sandberger." 
 II 445., line 4. from bottom, for " Vigularia" read " Virgularia." 
 
 493., line 7. from bottom, for " 1,400 " read " 14,000." 
 - 497., line 2. from bottom, for " corosive " read " erosive." 
 498., line 19., for " 16 " read " 46.' 
 
 502., line 11. from bottom, for " a quarter " read " half or a quarter. 
 ", 521., line 11. from bottom, for "northern " read " southern."^ 
 I, 641., Index, first line (in italics) for "figures " read "figured." 
 644., line 20., for " into lignite " read " lignite into." 
 
 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 con- 
 clusion, discovering 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 contrary, he 
 can show that they have acquired their actual configuration and con- 
 dition gradually, under a great variety of circumstances, and at suc- 
 cessive periods, during each of which distinct races of living beings 
 
 B 
 
XVI CONTENTS. 
 
 CHAPTER XXXVI. Metamorphic Rocks continued. 
 
 Origin of the metamorphic rocks, continued Definition of joints, slaty cleavage, and 
 foliation Causes of these structures Mechanical theory of cleavage Supposed 
 combination of crystalline and mechanical forces Lamination of some volcanic 
 rocks due to motion Whether the foliation of the crystalline schists be usually 
 parallel with the original planes of stratification - Page 607 
 
 CHAPTER XXXVII. On the different Ages of tiie Metamorphic Rocks. 
 
MANUAL 
 
 OF 
 
 ELEMENTARY GEOLOGY, 
 
 CHAPTER I. 
 
 ON THE DIFFERENT CLASSES OF ROCKS. 
 
 Geology defined Successive formation of the earth's crust Classification of rocks 
 according to their origin and age Aqueous rocks Their stratification and im- 
 bedded 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 manner are 
 these materials arranged ? These are the first inquiries with which 
 Geology is occupied, a science which derives its name from the Greek 
 yij, ge, the earth, and Xoyoc, 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 metals, 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 unexpected, we soon become engaged in researches 
 into the history of the animate creation, or of the various tribes of 
 animals and plants which have, at different periods of the past, in- 
 habited 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 con- 
 clusion, discovering 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 contrary, he 
 can show that they have acquired their actual configuration and con- 
 dition gradually, under a great variety of circumstances, and at suc- 
 cessive periods, during each of which distinct races of living beings 
 
 B 
 
CLASSIFICATION OF ROCKS. [Cn. I. 
 
 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 observation, or on which 
 we are enabled to reason by observations 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 ^5- 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 or- 
 ganic 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 confusedly ; 
 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 indifferently by geologists 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 older writers endeavoured to avoid offering such violence to our 
 language, by speaking of the component materials of the earth as 
 consisting of rocks and soils. But there is often so insensible a pas- 
 sage 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 con- 
 dition. 
 
 The most natural and convenient mode of classifying the various 
 rocks which compose the earth's crust, is to refer, in the first place, 
 to their origin, and in the second to their relative age. I shall 
 therefore begin by endeavouring 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 rocks, sometimes called the sedi- 
 mentary, or fossiliferous, cover a larger part of the earth's surface 
 than any others. 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 
 
CH. L] AQUEOUS ROCKS. 3 
 
 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 overflows 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 fre- 
 quently find at the bottom a series of deposits, disposed with consi- 
 derable regularity, one above the other ; the uppermost, perhaps, may 
 be a stratum of peat, next below 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 ex- 
 ample, 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 some- 
 times one of the masses first examined is observed to increase in 
 thickness to the exclusion of other beds. 
 
 The term "formation" which I have used in the above explana- 
 tion, expresses in geology any assemblage of rocks which have some 
 character in common, whether of origin, age, or composition. Thus 
 we speak of stratified and unstratified, freshwater and marine, aqueous 
 and volcanic, ancient and modern, metalliferous and non-metallifer- 
 ous formations. 
 
 In the estuaries of large rivers, such as the Ganges and the Missis- 
 sippi, we may observe, at low water, phenomena analogous to those 
 of the drained lakes above mentioned, 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 beds vary in their mineral composition, or colour, or in the 
 fineness or coarseness of their particles, and some of them are occa- 
 sionally characterized by containing drift wood. At the junction of 
 the river and the sea. especially in lagoons nearly separated by sand 
 bars from the ocean, deposits are often formed in which brackish- 
 water and salt-water shells are included. 
 
 The annual floods of the Nile in Egypt are well known, and the 
 fertile deposits of mud which they leave on the plains. This mud is 
 stratified, the thin layer thrown down in one season differing slightly 
 in colour from that of a previous year, and being separable from it, 
 as lias 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 re- 
 semblance. Thus, for example, at various heights and depths in the 
 
 * See Principles of Geology, by the Author, Index, " Nile," Rivers," &c. 
 
 B 2 
 
4 AQUEOUS ROCKS. [Cn. I. 
 
 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 torrent'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 gravel, while at another, when 
 the waters are low and less rapid, fine mud and sand alone are 
 carried seaward.* 
 
 If a stratified arrangement, and the rounded form of pebbles, are 
 alone sufficient to lead us to the conclusion that certain rocks origi- 
 nated under water, this opinion is farther confirmed by the distinct 
 and independent evidence of fossils, so abundantly included in the 
 earth's crust. By a fossil 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 animals, 
 especially of aquatic species, are found almost everywhere imbedded, 
 in stratified rocks, and sometimes, in the case of limestone, they are 
 in such abundance as to constitute the entire mass of the rock itself. 
 Shells and corals are the most frequent, and with them are often 
 associated the bones and teeth of fishes, fragments of wood, im- 
 pressions 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 observed at eleva- 
 tions 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, f 
 
 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 deposited at the bottom of 
 the sea, and others in lakes and estuaries. 
 
 When geology was first cultivated, it was a general belief, that 
 these marine shells and other fossils were the effects and proofs of 
 the deluge of Noah ; but all who have carefully investigated the 
 phenomena have long rejected this doctrine. A transient flood 
 might be supposed to leave behind it, here and there upon the surface, 
 scattered heaps of mud, sand, and shingle, with shells confusedly in- 
 termixed ; but the strata containing fossils are not superficial depo- 
 sits, and do not simply cover the earth, but constitute the entire mass 
 of mountains. Nor are the fossils mingled without reference to the 
 original habits and natures of the creatures of which they are the 
 memorials ; those, for example, being found associated together which 
 lived in deep or in shallow water, near the shore or far from it, in 
 brackish or in salt water. 
 
 It has, moreover, been a favourite notion of some modern writers, 
 who were aware that fossil bodies could not all be referred to the 
 deluge, that they, and the strata in which they are entombed, might 
 
 * See p. 18. fig. 7. 
 
 f Capt. R. J. Strachey found oolitic fossils 18,400 feet high in the Himalaya, 
 
CH. L] VOLCANIC ROCKS. 5 
 
 have been deposited in the bed of the ocean during the period which i 
 intervened between the creation of man and the deluge. They have 
 imagined that the antediluvian bed of the ocean, after having been* 
 the receptacle of many stratified deposits, became converted, at the 
 time of the flood, into the lands which we inhabit, and that the 
 ancient continents were at the same time submerged, and became the 
 bed of the present seas. This hypothesis, although preferable to the 
 diluvial theory before alluded to, since it admits that all fossiliferous 
 strata were successively thrown down from water, is yet wholly 
 inadequate to explain the repeated revolutions which the earth has 
 undergone, and the signs which the existing continents exhibit, in 
 most regions, of having emerged from the ocean at an era far more 
 remote than four thousand years from the present time. Ample 
 proofs of these reiterated revolutions will be given in the sequel, and 
 it will be seen that many distinct sets of sedimentary strata, hundreds 
 and sometimes thousands of feet thick, are piled one upon the other 
 in the earth's crust, each containing peculiar fossil animals and plants 
 of species distinguishable for the most part from all those now 
 living. The mass of some of these strata consists almost entirely of 
 corals, others are made up of shells, others of plants turned into coal, 
 while some are without fossils. In one set of strata the species of 
 fossils are marine; in another, lying immediately above or below, 
 they as clearly prove that the deposit was formed in a lake or in a 
 brackish estuary. When the student has more fully examined into 
 these appearances, he will become convinced that the time required 
 for the origin of the rocks composing the actual continents must 
 have been far greater than that which is conceded by the theory 
 above alluded to ; and likewise that no one universal or sudden 
 conversion of sea into land will account for geological appearances. 
 
 We have now pointed out one great class of rocks, which, however 
 they may vary in mineral composition, colour, grain, or other cha- 
 racters, external 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 characterised 
 by stratification or fossils, or by both. 
 
 Volcanic rocks. The division of rocks which we may next con- 
 sider 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 devoid of fossils. They are more par- 
 tially distributed than aqueous formations, at least in respect to hori- 
 zontal extension. Among those parts of Europe where they exhibit 
 characters not to be mistaken, I may mention not only Sicily 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 volcanos, with craters more or less 
 perfect on many of their summits. These cones are composed more- 
 is 3 
 
6 VOLCANIC ROCKS. [Cn. I. 
 
 over of lava, sand, and aslies, similar to those of active volcanos. 
 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 manner 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 volcanos 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 vol- 
 canos, the rains and torrents having washed their sides, and removed 
 all the loose sand and scoriae, leaving only the harder and more solid 
 materials. By this erosion, and by earthquakes, their internal struc- 
 ture has occasionally 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 scorise, 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 volcanos. They have been formed 
 by the pouring of melted matter, whether from above or below, into 
 open fissures, and they commonly traverse deposits of volcanic tuff, 
 a substance produced by the showering down from the air, or in- 
 cumbent 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 volcanos may be seen, still preserving 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 Staffa, and that of the 
 Giant's Causeway, called basalt, 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 volcanos. We 
 find also similar basaltic and other igneous rocks associated with 
 beds of tuff in various parts of the British Isles, and forming dikes, 
 such as have been spoken of; and some of the strata through which 
 these dikes cut are occasionally altered at the point of contact, as if 
 they had been exposed to the intense heat of melted matter. 
 
 The absence of cones and craters, and long narrow streams of 
 superficial lava, in England and many other countries, is principally 
 to be attributed to the eruptions having been submarine, just as a 
 considerable proportion of volcanos in our own times burst out 
 beneath the sea. But this question must be enlarged upon more 
 fully in the chapters on Igneous Rocks, in which it will also be 
 shown, that as different sedimentary formations, containing each 
 their characteristic fossils, have been deposited at successive periods, 
 so also volcanic sand and scorice have been thrown out, and lavas 
 
CH. I.] PLUTONIC ROCKS. 7 
 
 have flowed over the land or bed of the sea, at many different epochs, 
 or have been injected into fissures ; so that the igneous as well as 
 the aqueous rocks may be classed as a chronological series of monu- 
 ments, throwing light on a succession of events in the history of the 
 earth. 
 
 Plutonic rocks (Granite, &c.). 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 portion 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 de- 
 posits such as are now accumulated in lakes or seas, nor to those 
 generated by ordinary volcanic action. The members of both these 
 divisions of rocks agree in being highly crystalline and destitute of 
 organic remains. The rocks of one division have been called plu- 
 tonic, 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 
 included gneiss, micaceous-schist (or mica-slate), hornblende-schist, 
 statuary marble, the finer kinds of roofing slate, and other rocks 
 afterwards to be described. 
 
 As it is admitted that nothing strictly analogous to these crystalline 
 productions 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 cannot, 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 by which geologists have been led to infer the 
 analogy of the rocks in question to others now in progress at the 
 surface. The result, however, may be briefly stated. All the various 
 kinds of granite which constitute the plutonic family, are supposed 
 to be of igneous origin, but to have been formed under great pressure, 
 at a considerable depth in the earth, or sometimes, perhaps, under a 
 certain weight of incumbent water. Like the lava of volcanos, they 
 have been melted, and have afterwards cooled and crystallised, 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 entangled gases gives rise in ordinary 
 lava. 
 
 Although granite has often pierced through other strata, it has 
 rarely, if ever, been observed to rest upon them, as if it had over- 
 flowed. But as this is continually the case with the volcanic rocks, 
 they have been styled, from this peculiarity. " overlying " by Dr. Mac 
 Culloch ; and Mr. Necker has proposed the term " underlying " for 
 
 B 4 
 
8 METAMORPHU IUVKS. [Cu. 1. 
 
 the granites, to designate the opposite mode in which they almost 
 invariably present themsches. 
 
 Metiimorytiic, or stniti/ied crystalline rocks. The fourth ami last 
 great division of rocks are the t rvstalline strata and slates, or schists, 
 called gneiss, mica-schist, clay-slate, chlorite-sehist, marble, aiul tho 
 liko, the origin of which is more doubtful than that of tho othrr throo 
 contain no pebbles, or sand, or scoria-, or angular 
 pieces of imbedded stone, und no traces of organic bodies, and they 
 'en as crystalline as granite, yet are divided into beds, corre- 
 sponding in form and arrangement to those of sedimentary formations, 
 and are therefore said to be stratified. The beds sometimes consist 
 of an alternation of substances varying in colour, composition, and 
 thickness, precisely as we see in stratified fossiliforons deposits. Ac- 
 cording to the Huttonian theory, which I adopt as the most probable, 
 and which will bo afterwards more fully explained, the materials 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 complete conversion has actually taken place, 
 fossiliferous strata having exchanged an earthy for a highly crys- 
 talline texture for a distance of a quarter of a mile from their contact 
 with granite. In some cases, dark limestones, replete 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, c\cry vestige of the organic bodies havin 
 obliterated. 
 
 Although we are in a great degree ignorant of the pn\ ta nature 
 of the influence exerted in these cases, yet it evidently bears some 
 analogy to that which volcanic heat ami gases are known to pro- 
 duce ; and the action may be conveniently called plutonic, because it 
 appears to have been developed in those regions where plutonie 
 rocks are generated, and under similar circumstances of pressure and 
 depth in the earth. Whether hot water or .-team permeating stratified 
 masses, or electricity, or any other causes have co-operated to produce 
 the crystalline texture, may be matter of speculation, but it is clear 
 that the plntonic influence has sometimes pervaded entire mountain 
 masses of strata, 
 
 In accordance with the hypothesis abo\e alluded to, I proposed in 
 the first edition of the Principles of Geology ^1833), the term 
 " Metamorphic * for the altered strata, a term derived from ^ro, 
 meta, trans, and /<op</>ij, morpho, /<>//?*. 
 
 Hence there are tour great clashes of rocks considered in reference 
 to their origin, the aqueous, the volcanic, the plutonic, and tho 
 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 contem- 
 poraneously, and may oven now be in the progress of formation on a 
 large scale. It is not true, as was formerly supposed, that all granites, 
 together with the crystalline or metamorphic strata, were first formed. 
 
CH. I.] FOUR GLASSES OF ROCKS CONTEMPORANEOUS. 9 
 
 and therefore entitled to be called " primitive," and that the aqueous 
 and volcanic rocks were afterwards super-imposed, and should, there- 
 fore, rank as secondary in the order of time. This idea was adopted 
 in the infancy of the science, when all formations, whether stratified 
 or unstratified, earthy or crystalline, with or without fossils, were 
 alike regarded as of aqueous origin. At that period it was naturally 
 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 deduction 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 super-imposed formations have not been in the slightest degree 
 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 and Amsterdam, it cannot be laid 
 down as universally true, that the upper parts of each edifice, whether 
 of brick or marble, are more modern than the foundations on which 
 they rest, for these often consist of wooden piles, which may have 
 rotted 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 large masses of rock 
 immediately below : it may continue the same for ages, while sub- 
 jacent materials, at 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 viewed as 
 belonging to one great family, whether they be stratified or un- 
 stratified, plutonic or metamorphic, it will often be convenient to 
 speak of them by one common name. It being now ascertained, as 
 above stated, that they are of very different ages, sometimes newer 
 than the strata called secondary, the terms primitive and primary 
 which were formerly used for the whole must be abandoned, as they 
 would imply 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 attribu- 
 table to granite and gneiss (to the plutonic as well as the altered 
 rocks), and, on the other, must have reference to characters in which 
 those rocks differ, both from the volcanic and from the unaltered 
 sedimentary strata. I proposed in the Principles of Geology (first 
 edition, vol. iii.), the term "hypogene" for this purpose, derived from 
 I/TTO, under, and yiropai, to be, or to be born; 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 occupy 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 com- 
 paratively modern date, belonging, for example, to the period here- 
 after to be described as tertiary, they are still underlying rocks. 
 
10 COMPONENTS OF STRATA. [Cn. IT. 
 
 They never repose 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 may be studied simply as mineral 
 masses deriving their origin from particular causes, and having a 
 certain composition, form, and position in the earth's crust, or other 
 characters both positive and negative, such as the presence or absence 
 of organic remains. In the second place, the rocks of each class may 
 be viewed as a grand chronological series of monuments, attesting 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. 
 
 CHAPTER II. 
 
 AQUEOUS ROCKS THEIR COMPOSITION AND FORMS OF STRATIFI- 
 CATION. 
 
 Mineral composition of strata Arenaceous rocks Argillaceous Calcareous 
 Gypsum Forms of stratification Original horizontally Thinning out Dia- 
 gonal arrangement Ripple mark. 
 
 IN pursuance of the arrangement explained in the last chapter, we 
 shall begin by examining the aqueous or sedimentary rocks, which 
 are for the most part distinctly stratified, and contain fossils. We 
 may first study them with reference to their mineral composition, 
 external appearance, position, mode of origin, organic contents, and 
 other characters which belong to them as aqueous formations, inde- 
 pendently of their age, and we may afterwards consider them chrono- 
 logically or with reference to the successive geological 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 arenaceous, the argillaceous, and the calca- 
 reous, which are formed respectively of sand, clay, and carbonate of 
 lime. Of these, the arenaceous, or sandy masses, are chiefly made 
 up of siliceous 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 calcareous rocks or 
 limestones consist of carbonic acid and lime. 
 
Cn. II.] MINERAL COMPOSITION OF STRATIFIED ROCKS. 11 
 
 Arenaceous or siliceous rocks. To speak first of the sandy divi- 
 sion : 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 alumine and oxide of 
 iron. The siliceous grains in sand are usually rounded, as if by the 
 action of running water. Sandstone is an aggregate of such grains, 
 which often cohere together without any visible cement, but more 
 commonly are bound together by a slight quantity of siliceous or 
 calcareous matter, or by 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 broken by ordinary pressure. 
 In nature there is every intermediate 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 strati- 
 fication, 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 pebbles, 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 flint with a large proportion, usually about one fourth, of alumine, 
 or argil ; but in common language, any earth which possesses suffi- 
 cient 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 porcelain clay, or kaolin, 
 which results from the decomposition of a rock composed of felspar 
 and quartz, and it is almost always mixed with quartz.* Shale has 
 also the property, like clay, of becoming plastic in water: it is a more 
 solid form of clay, or argillaceous matter, condensed by pressure. It 
 usually divides into laminae more or less regular. 
 
 One general character of all argillaceous rocks is to give out a 
 peculiar, earthy odour when breathed upon, which is a test of the 
 presence of alumine, although it does not belong to pure alumine, 
 but, apparently, to the combination of that substance with oxide of 
 iron.f 
 
 Calcareous rocks. This division comprehends those rocks which, 
 like chalk, are composed chiefly of lime and carbonic acid. Shells 
 and corals are also formed of the same elements, with the addition 
 
 * The kaolin of China consists of 7M5 nearly equal parts of silica and alumine, 
 
 parts of silex, 15*86 of alumine, 1-92 of with 1 per cent, of magnesia. (Phil, 
 
 lime, and 673 of water (W. Phillips, Mag. vol. x. 1837.) 
 
 Mineralogy, p. 33.); but other porcelain f See W. Phillips's Mineralogy, " Alu- 
 
 clays differ materially, that of Cornwall mine." 
 being composed, according to Boase, of 
 
12 MINERAL COMPOSITION OF STRATIFIED ROCKS. [Cn. II. 
 
 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 occasionally 
 sufficiently solid to be used for building, and even passes into a 
 compact stone, or a stone of which the separate parts are so minute 
 as not to be distinguishable from each other by the naked eye. 
 
 Many limestones are made up entirely of minute fragments of 
 shells and coral, or of calcareous sand cemented together. 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 numerous 
 small egg-like grains, resembling the roe of a fish, each of which has 
 usually a small fragment of sand as a nucleus, around which con- 
 centric layers of calcareous matter have accumulated. 
 
 Any limestone which is sufficiently hard to take a fine polish is 
 called marble. Many of these are fossiliferous ; but statuary marble, 
 which is also called saccharine limestone, as having a texture re- 
 sembling that of loaf-sugar, 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 matter predominates. 
 
 The presence of carbonate of lime in a rock may be ascertained 
 by applying to the surface a small drop of diluted sulphuric, nitric, 
 or muriatic acids, 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 be- 
 coming 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 
 cannot always detect the presence of carbonate of lime in rocks. 
 
 The above-mentioned three classes of rocks, the siliceous, argil- 
 laceous, and calcareous, pass continually into each other, 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 sand of Alum Bay in the Isle of Wight, or sandstone so pure 
 as the grit of Fontainebleau, used for pavement in France. More 
 commonly we find sand and clay, or clay and marl, intermixed in the 
 same mass. When the sand and clay are each in considerable 
 quantity, the mixture is called loam. If there is much calcareous 
 
CH. II.] FORMS OF STRATIFICATION. 13 
 
 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 marl in certain parts of England. Agriculturists were 
 in the habit of calling any soil a marl, which, like true marl, fell to 
 pieces readily on exposure to the air. Hence arose the confusion 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, however, mention two others, 
 magnesian limestone or dolomite, and gypsum. Magnesian limestone 
 is composed of carbonate 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 colour ; 
 but it varies greatly in mineralogical character, 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 limestone, usually of a granular texture. 
 
 Gypsum. Gypsum is a rock composed of sulphuric acid, lime, 
 and water. It is usually a soft whitish-yellow rock, with a texture 
 resembling that of loaf-sugar, but sometimes it is entirely composed 
 of lenticular crystals. 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 being already combined with sulphuric 
 acid, for which it has a stronger affinity than for any other. An- 
 hydrous gypsum is a rare variety, into which water does not enter 
 as a component part. Gypseous marl is a mixture of gypsum and 
 marl. Alabaster is a granular and compact variety of gypsum found 
 in masses large enough to be used in sculpture and architecture. It 
 is sometimes a pure snow-white substance, 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 consists of 
 one of the above rocks, sometimes of two or more in alternating beds. 
 
 Thus, in the coal districts of England, for example, we often pass 
 through several beds of sandstone, some of finer, others of coarser 
 grain, some white, others of a dark colour, and below these, layers 
 of shale and sandstone or beds of shale, divisible into leaf-like lamina, 
 and containing beautiful impressions of plants. Then again we meet 
 with beds of pure and impure coal, alternating with shales and sand- 
 stones, and underneath the whole, perhaps, are calcareous strata, or 
 beds of limestone, filled with corals and marine shells, each bed dis- 
 
14 ALTERNATIONS. [Cu. II. 
 
 tinguishable 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 dis- 
 tinct stratification ; and we often find beds of limestone and marl, 
 conglomerate and sandstone, sand and clay, recurring again and again, 
 in nearly regular order, throughout 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 quantity, composition, 
 colour, and grain according to the seasons ; the waters are sometimes 
 flooded and rapid, at other periods low and feeble ; different tribu- 
 taries, also, draining peculiar countries and soils, and therefore 
 charged with peculiar sediment, 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 description 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 sandstones have originated, namely, those in 
 which we see innumerable thin layers of mica dividing layers of fine 
 quartzose sand. I observed the same arrangement of materials in 
 recent mud deposited in the estuary of La Roche St. Bernard in Brit- 
 tany, 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 separation of the mica in this case, or in that of mica- 
 ceous sandstones, 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 carried 
 farther down the stream. At the first instant the water is turbid, but 
 immediately after the flat surfaces of the plates of mica are seen all 
 alone reflecting a silvery light, as they descend slowly, to form a dis- 
 tinct 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 velocity of the 
 stream varies from time to time, layers of mica or of sand will be 
 thrown down successively on the same area. 
 
 Original horizontally. It is said generally that the upper and 
 
 * Consult Index to Principles of Geology, " Stratification," " Currents," 
 Deltas," " Water," &c. 
 
CH. II.] HORIZONTALITY OF STRATA. 15 
 
 under surfaces of strata, or the " planes of stratification," are parallel. 
 Although this is not strictly true, they make an approach to parallelism, 
 for the same reason that sediment is usually deposited at first in nearly 
 horizontal layers. The reason of this arrangement can by no means 
 be attributed to an original evenness or horizontally in the bed of the 
 sea : for it is ascertained that in those places where no matter has been 
 recently deposited, the bottom of the ocean is often as uneven as that 
 of the dry land, having in like manner its hills, valleys, and ravines. 
 Yet if the sea should sink, or the water be removed 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 reality, they would slope gently 
 from the land towards the sea. 
 
 This tendency in newly-formed strata to assume a horizontal posi- 
 tion arises principally from the motion of the water, 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 current and the motion of the superficial waves 
 diminish from the surface downwards, 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 neighbourhood of a volcano, when a section, 
 whether natural or artificial, has laid open to view a succession of 
 various-coloured layers of sand and ashes, which have fallen in 
 showers upon uneven ground. Thus let A B (fig. 1.) be two ridges, 
 with an intervening valley. These original inequalities of the 
 surface have been gradually effaced by beds of sand and ashes 
 c, d, e, the surface at e being quite level. It will be seen that, 
 although the materials of the first layers have accommodated them- 
 Fig j selves 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 particles 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 and more effaced as the strata accumulated 
 from c to e. This levelling operation may perhaps be rendered more 
 clear to the student by supposing a number of parallel trenches to be 
 dug in a plain of moving sand, like the African desert, in which case 
 the wind would soon cause all signs of these trenches to disappear, 
 and the surface would be as uniform as before. Now, water in 
 motion 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 density of salt water exceeds that of fresh. 
 
16 
 
 DIAGONAL OR CROSS STRATIFICATION. [Cn. II. 
 
 Yet, however uniform and horizontal may be the surface of new 
 deposits in general, there are still many disturbing causes, such as 
 eddies in the water, and currents moving first in one and then in 
 another direction, which frequently cause irregularities. We may 
 sometimes follow a bed of limestone, shale, or sandstone, for a dis- 
 tance 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 materials 
 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.) 
 
 Fig. 2. 
 
 Section of strata of sandstone, grit, and conglomerate. 
 
 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 layers placed 
 
 Fig. 3. 
 
 Section of sand at Sandy Hill, near Biggleswade, Bedfordshire. 
 Height 20 feet. (Green-sand formation.) 
 
 obliquely to the general planes of stratification. To this diagonal 
 arrangement the name of " false or cross stratification " has been 
 given. Thus in the annexed section (fig. 3.) we see seven or eight 
 large beds of loose sand, yellow and brown, and the lines , b, c, 
 mark some of the principal planes of stratification, which are nearly 
 horizontal. But the greater part of the subordinate laminae do not 
 conform to these planes, but have often a steep slope, the inclination 
 being sometimes towards opposite points of the compass. When the 
 sand is loose and incoherent, as in the case here represented, the 
 
CH. II,] CAUSES OF DIAGONAL STRATIFICATION. 17 
 
 deviation from parallelism of the slanting laminae cannot possibly be 
 accounted for by any re-arrangement of the particles acquired during 
 the consolidation of the rock. In what manner then can such irre- 
 gularities be due to original deposition ? We must suppose that at 
 the bottom of the sea, as well as in the beds of rivers, the motions 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. Suppose the bank A (fig. 4.) to be thus formed with 
 
 Fig. 4. 
 
 a steep sloping side, and the water being in a tranquil state, the layer 
 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 (fig. 4.), 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 
 
 Fig. 5. 
 
 Fig. 6. 
 
 and on which the nearly horizontal layers, 9, 10, 11, may then 
 accumulate. It was shown in fig. 3. that the diagonal layers of suc- 
 cessive strata may sometimes have an opposite slope. This is well 
 seen in some cliffs of loose sand on the Suffolk coast. A portion 
 
 of one of these is represented in 
 fig. 6., where the layers, of which 
 there are about six in the thick- 
 ness of an inch, are composed of 
 quartzose grains. This arrange- 
 ment may have been due to the 
 altered direction of the tides and 
 
 Cliff between Mismer and Dunwich. Currents in the Same place. 
 
 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 example may be seen at the base of the 
 Maritime Alps near Nice. The mountains here terminate abruptly 
 
 c 
 
18 CAUSES OF DIAGONAL STRATIFICATION. [Cn. II. 
 
 in the sea, so that a depth of many hundred fathoms is often found 
 within a stone's throw of the beach, and sometimes a depth of 3000 
 feet within half a mile. But at certain points, strata of sand, marl, 
 or conglomerate, intervene between the shore and the mountains, as 
 in the annexed fig. (7.), where a vast succession of slanting beds 
 
 Monte Calvo. Fig. 7. 
 
 Sea 
 
 Section from Monte Calvo to the sea by the valley of Magnan, near Nice. 
 
 A. Dolomite and sandstone. (Green-sand formation?) 
 
 , 6, d. Beds of gravel and sand. 
 
 c. Fine marl and sand of St. Madeleine, with marine shells. 
 
 of gravel and sand may be traced from the sea to Monte Calvo, a 
 distance of no less than 9 miles in a straight line. The dip of these 
 beds is remarkably uniform, being always southward or towards the 
 Mediterranean, at an angle of about 25. They are exposed to view 
 in nearly vertical precipices, varying from 200 to 600 feet in height, 
 which bound the valley through which the river Magnan flows. 
 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 of a steep bank where a river or alpine 
 torrent discharged itself into a deep and tranquil sea, and formed a 
 delta, which advanced gradually from the base of Monte Calvo to a 
 distance of 9 miles from the original shore. If subsequently this 
 part of the Alps and bed of the sea were raised 700 feet, the coast 
 would acquire its present configuration, the delta would emerge, and 
 a deep channel might then be cut through it by a river. 
 
 It is well known that the torrents and streams, which now 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 assumed, that deposits like those of the valley 
 of the Magnan, consisting of coarse gravel alternating with fine 
 sediment, are still in progress at many points, as, for instance, at the 
 mouth of the Var. They must advance upon the Mediterranean 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 cannot be transported to indefinite distances by cur- 
 rents of moderate velocity. By inattention to facts and inferences 
 of this kind, a very exaggerated estimate has sometimes been made 
 
CH. II.] RIPPLE MARK. 19 
 
 of the supposed depth of the ancient ocean. There can be no doubt, 
 for example, that the strata , fig. 7., or those nearest to Monte 
 Calvo, are older than those indicated by b, and these again were 
 formed before c ; but the vertical depth of gravel and sand in any 
 one place cannot 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 once horizontal, and that their present dip or inclination 
 was due to subsequent movements, we should then be forced to con- 
 clude, that a sea 9 miles deep had been filled up with alternate layers 
 of mud and pebbles thrown down one upon another. 
 
 In the locality now under consideration, situated a few miles to the 
 west of Nice, there are many geological data, the details of which 
 cannot be given in this place, all leading 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 neighbourhood. That the beds, a, , <?, 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. 
 
 Nipple 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 
 
 Fig. 8. 
 
 Slab of ripple-marked (new red) sandstone from Cheshire. 
 
 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. 
 
 C 2 
 
20 FORMATION OF RIPPLE MARK. [Cu. II. 
 
 Similar undulating ridges and furrows may also be sometimes seen 
 on the surface of drift snow and blown sand. The following is the 
 manner in which I once observed the motion of the air to produce 
 this effect on a large extent of level beach, exposed at low tide near 
 Calais. Clouds of fine white sand were blown from the neighbour- 
 ing dunes, so as to cover the shore, and whiten a dark level sur- 
 face of sandy mud, and this fresh covering of sand was beautifully 
 rippled. On levelling all the small ridges and furrows of this ripple 
 over an area of several yards square, I saw them perfectly restored in 
 about ten minutes, the general direction of the ridges being always at 
 right angles to that of the wind. The restoration began by the ap- 
 pearance here and there of small detached heaps of sand, which soon 
 lengthened and joined together, so as to form long sinuous ridges with 
 intervening furrows. Each ridge had one side slightly inclined, and 
 the other steep ; the lee-side being always steep, as b, c, d, e ; the 
 windward-side a gentle slope, as a, b, c, d, fig. 9. When a gust of 
 
 Fig. 9. 
 
 wind blew with sufficient force to drive along a cloud of sand, all 
 the ridges were seen to be in motion at on.ce, each encroaching on 
 the furrow before it, and, in the course of a few minutes, filling the 
 place which the furrows had occupied. The mode of advance was 
 by the continual drifting of grains of sand up the slopes a b and c d, 
 many of which grains, when they arrived at b and d, fell over the 
 scarps b c and d e, and were under shelter from the wind ; so that 
 they remained stationary, resting, according to their shape and mo- 
 mentum, on different parts of the descent, and a few only rolling to 
 the bottom. In this manner each ridge was distinctly seen to move 
 slowly on as often as the force of the wind augmented. Occasionally 
 part of a ridge, advancing more rapidly than the rest, overtook the 
 ridge immediately before it, and became confounded with it, thus 
 causing those bifurcations and branches which are so common, and 
 two of which are seen in the slab, fig. 8. We may observe this con- 
 figuration in sandstones of all ages, and in them also, as now on 
 the sea-coast, we may often detect two systems of ripples interfering 
 with each other ; one more ancient and half effaced, and a newer one, 
 in which the grooves and ridges are more distinct, and in a different 
 direction. This crossing of two sets of ripples arises from a change 
 of wind, and the new direction in which the waves are thrown on the 
 shore. 
 
 The ripple mark is usually an indication of a sea-beach, or of 
 water from 6 to 10 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 ob- 
 served at the depth of 60 or 70 feet. It has also been ascertained that 
 currents or large bodies of water in motion may disturb mud and 
 
CH. III.] GRADUAL DEPOSITION INDICATED BY FOSSILS. 21 
 
 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 towards different points of the compass. 
 
 CHAPTER HI. 
 
 ARRANGEMENT OF FOSSILS IN STRATA FRESHWATER 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 Tripoli and semi-opal formed of infusoria 
 Chalk derived principally from organic bodies Distinction of freshwater from 
 marine formations Genera of freshwater and land shells Rules for recognizing 
 marine testacea Gyrogonite and chara Freshwater fishes Alternation of 
 marine and freshwater deposits Lym- Fiord. 
 
 HAVING in the last chapter considered the forms of stratification so 
 far as they are determined by the arrangement of inorganic matter, 
 we may now turn our attention to the manner in which organic re- 
 mains are distributed through stratified deposits. We should often 
 be unable to detect any signs of stratification or of successive deposi- 
 tion, if particular kinds of fossils did not occur here and there at 
 certain 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 formations 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 filled with 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, during the process of deposition, each separate layer 
 was once the uppermost, and covered immediately by the water in 
 which aquatic animals lived. Each stratum in fact, however 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 enveloped. 
 
 By attending to the nature of these remains, we are often enabled 
 to determine whether the deposition was slow or rapid, whether it 
 took place in a deep or shallow sea, near the shore or far from land, 
 and whether the water was salt, brackish, or fresh. Some limestones 
 consist almost exclusively of corals, and in many cases it is evident 
 
 * Edin. New Phil. Journ. vol. xxxi.; and Darwin, Vole. Islands, p. 134. 
 
 c 3 
 
22 
 
 GRADUAL DEPOSITIONS 
 
 [On. III. 
 
 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 uppermost, and 
 their points of attachment are directed downwards. This arrange- 
 ment 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 of increase was extremely slow, and some 
 of the fossils must have flourished for ages like forest trees, before 
 they attained so large a size. During these ages, the water remained 
 clear and transparent, for such corals cannot live in turbid water. 
 
 In like manner, when we see thousands of full-grown shells dis- 
 persed every where throughout a long series of strata, we cannot 
 doubt that time was required for the multiplication of successive 
 generations ; and the evidence of slow accumulation is rendered more 
 striking from the proofs, so often discovered, of fossil bodies having 
 lain for a time 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 serpulae, or barnacles (acorn-shells), 
 or corals, and other creatures, attached 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 embryo to a mature state. 
 Attached shells which are merely external, like some of the ser- 
 pulae (a) in the annexed figure (fig. 10.), may often have grown 
 upon an oyster or other shell while the animal within was still living ; 
 
 but if they are found on the inside, 
 it could only happen after the 
 death of the inhabitant of the shell 
 which affords the support. Thus, 
 in fig. 10., it will be seen that two 
 serpulae have grown on the inte- 
 rior, one of them exactly on the 
 place where the adductor muscle 
 of the GryphcBa (a kind of oyster) 
 was fixed. 
 
 Some fossil shells, even if simply 
 attached to the outside of others, 
 bear full testimony to the conclu- 
 sion above alluded to, namely, that 
 an interval elapsed between the 
 death of the creature to whose 
 shell they adhere, and the burial of 
 the same in mud or sand. The sea- 
 urchins or Echini, so abundant in 
 white chalk, afford a good illustra- 
 
 tion - Xt is wel1 known that these 
 
 Fig. 10. 
 
CH. III.] INDICATED BY FOSSILS. 23 
 
 animals, when living, are invariably covered with numerous suckers, 
 or gelatinous tubes, called " ambulacral," because they serve as organs 
 of motion. They are also armed with spines supported by rows of 
 tubercles. These last are only seen after the death of the sea-urchin, 
 when the spines have dropped off. In fig. 12. a living species of 
 Spatangus, common on our coast, is represented with one half of its 
 
 Fig. 11. Fig. 12. 
 
 Serpula attached to Recent Spatangus with the spines 
 
 a fossil Spatanetis removed from one side, 
 
 from the chalk. 
 
 b. Spine and tubercles, nat. size. 
 a. The same magnified. 
 
 shell stripped of the spines. In fig. 11. a fossil of the same genus 
 from the white chalk of England shows the naked surface which the 
 individuals of this family exhibit when denuded of their bristles. 
 The full-grown Serpula, therefore, which now adheres externally, 
 could not have begun to grow till the Spatangus had died, and the 
 spines were detached. 
 
 Now the series of events here attested by a single fossil may be 
 carried a step farther. Thus, for example, we often meet with a sea- 
 urchin in the chalk (see fig. 13.), which has fixed to it the lower 
 valve of a Crania, a genus of bivalve mollusca. The upper valve 
 Fig. is. (^> % 13.) is almost invariably wanting, though 
 
 occasionally found in a perfect state of preservation 
 in white chalk at some distance. In this case, we 
 see clearly that the sea-urchin first lived from youth 
 to age, then died and lost its spines, which were 
 carried away. Then the young Crania adhered 
 to the bared shell, grew and perished in its turn ; 
 after which the u PP er valve was separated from 
 ' ot the the lower before the Echinus became enveloped in 
 
 Crama'detached. 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. Entire branches and 
 stems of trees, several feet in length, are sometimes dug out, 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. 15. e, a re- 
 presentation 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, a shell is seen at the larger extremity, composed of two pieces, 
 as shown at c. In like manner, a piece of fossil wood (a, fig. 14.) 
 
 C 4 
 
24 
 
 SLOW DEPOSITION OF STRATA. 
 
 has been perforated by an animal of a kindred but extinct genus, 
 called Teredina by Lamarck. The calcareous tube of this mollusk 
 was united and as it were soldered on to the valves of the shell (b), 
 
 Fig. 14. 
 
 Fig. 15. 
 
 Fossil and recent wood drilled by perforating Mollusca. 
 
 Fig. 14. a. Fossil wood from London clay, bored by Teredina. 
 
 b. Shell and tube of Teredina personata, the right-hand figure the ventral, the left the 
 
 dorsal view. 
 
 Fig. 15. e. Recent wood bored by Teredo. 
 
 d. Shell and tube of Teredo navalis, from the same. 
 
 c. Anterior and posterior view of the valves of same detached from the tube. 
 
 which therefore cannot be detached from the tube, like the valves of 
 the recent Teredo. The wood in this fossil specimen is now con- 
 verted into a stony mass, a mixture of clay and lime ; but it must 
 once have been buoyant and floating in the sea, when the Teredines 
 lived upon it, perforating it in all directions. Again, before the 
 infant colony settled upon the drift wood, the branch 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. 
 
 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, almost entirely made up of the remains of zoophytes 
 and testacea. 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 variety of stony 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 naturalists. Great surprise was therefore created by 
 the recent discovery of Professor Ehrenberg, of Berlin, that a certain 
 kind of siliceous stone, called tripoli, was entirely composed of mil- 
 lions of the remains of organic beings, which the Prussian naturalist 
 refers to microscopic Infusoria, but which most others now believe to 
 be plants. They abound in freshwater lakes and ponds in England 
 and other countries, and are termed Diatomacese by those naturalists 
 who believe in their vegetable origin. The substance alluded to has 
 
INFUSORIA OP TRIPOLI. 
 
 25 
 
 CH. III.] 
 
 long been well known in the arts, being used in the form of powder 
 for polishing stones and metals. It has been procured, among other 
 places, from Bilin, in Bohemia, where a single stratum, extending 
 over a wide area, is no less than 14 feet thick. This stone, when ex- 
 amined with a powerful microscope, is found to consist of the sili- 
 
 Fig. 16. Fig. 17. Fig. 18. 
 
 
 Gaillonella 
 distans. 
 
 Fig. 20. 
 
 Fig. 19. 
 
 These figures are magnified nearly 300 times, except the lower figure of G.ferruginea (fig. 18. a), 
 which is magnified 2000 times. 
 
 ceous plates or frustules of the above-mentioned Diatomacese, united 
 together without any visible cement. It is difficult to convey an idea 
 of their extreme minuteness ; but Ehrenberg estimates that in the 
 Bilin tripoli there are 41,000 millions of individuals of the Gaillonella 
 distans (see fig. 17.) in every cubic inch, which weighs about 220 
 grains, or about 187 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. 
 
 The remains of these Diatomaceae are of pure silex, and their forms 
 are various, but very marked and constant in particular genera 
 
 and species. Thus, in the 
 family Bacillaria (see fig. 
 16.), the fossils preserved 
 in tripoli are seen to ex- 
 hibit the same divisions 
 and transverse lines which 
 characterize the living spe- 
 cies of kindred form. With 
 these, also, the siliceous 
 spiculae or internal sup- 
 ports of the freshwater 
 sponge, or Spongitta of 
 Lamarck, are sometimes in- 
 termingled (see the needle- 
 shaped bodies in fig. 20.). 
 These flinty cases and spi- 
 culae, although hard, are 
 very fragile, breaking like 
 glass, and are therefore 
 admirably adapted, when 
 rubbed, for wearing down 
 into a fine powder fit for 
 
 Fragment of semi-opal from the great bed of tripoli, Bilin. polishing the Surface of 
 
 Fig. 19. Natural size. metals. 
 
 Fig. 20. The same magnified, showing circular articula- "RpcirlAo flip trinnli frvrmPfl 
 tions of a species of Gaillonella, and spiculae of tripOIl, 10 
 
 exclusively of the fossils 
 
26 
 
 FOSSIL INFUSORIA. 
 
 [CH. III. 
 
 above described, there occurs in the upper part of the great stratum 
 at Bilin another heavier and more compact stone, a kind of semi- 
 opal, in which innumerable parts of Diatomacese and spiculse of the 
 Spongilla are filled with, and cemented together by, siliceous matter. 
 It is supposed that the siliceous remains of the most delicate Dia- 
 tomaceae have been dissolved by water, and have thus given rise to 
 this opal in which the more durable fossils are preserved like insects 
 in amber. This opinion is confirmed by the fact that the organic 
 bodies decrease in number and sharpness of outline in proportion as 
 the opaline cement increases in quantity. 
 
 In the Bohemian tripoli above described, as in that of Planitz in 
 Saxony, the species of Diatomaceae (or Infusoria, as termed by Ehren- 
 berg) are freshwater ; but in other countries, as in the tripoli of the 
 Isle of France, they are of marine species, and they all belong to 
 formations of the tertiary period, which will be spoken of hereafter. 
 
 A well-known substance, called bog-iron ore, often met with in 
 peat-mosses, has also been shown by Ehrenberg to consist of innu- 
 merable articulated threads, of a yellow ochre colour, composed 
 partly of flint and partly of oxide of iron. These threads are the 
 cases of a minute microscopic body, called Gaillonella ferruginea 
 (fig. 18.). 
 
 It is clear that much time must have been required for the accu- 
 mulation of strata to which countless generations of Diatomacese have 
 contributed their remains ; and these discoveries lead us naturally to 
 suspect that other deposits, of which the materials have usually been 
 supposed to be inorganic, may in reality have been derived from 
 microscopic organic bodies. That this is the case with the white 
 chalk, has often been imagined, this rock having been observed to 
 abound in a variety of marine fossils, such as echini, testacea, 
 bryozoa, corals, sponges, Crustacea, and fishes. Mr. Lonsdale, on 
 examining, in Oct. 1835, in the museum of the Geological Society of 
 London, portions of white chalk from different parts of England, 
 found, on carefully pulverizing them in water, that what appear to 
 the eye simply as white grains were, in fact, well preserved fossils. 
 He obtained above a thousand of these from each pound weight of 
 chalk, some being fragments of minute bryozoa and corallines, others 
 entire Foraminifera and Cytheridae. The annexed drawings will 
 give an idea of the beautiful forms of many of these bodies. The 
 figures a a represent their natural size, but, minute as they seem, the 
 
 Cytheridke and Foraminifera from the chalk. 
 Fig. 21 . Fig. 22. Fig. 23. 
 
 Fig. 24. 
 
 Cythere, Mull. 
 CytJierina, Lam. 
 
 Portion of 
 
 Nodosaria. 
 
 Rosalina. 
 
 smallest of them, such as a, fig. 24., are gigantic in comparison with 
 the cases of Diatomaceas before mentioned. It has, moreover, been 
 lately discovered that the chambers into which these Forarainifera 
 
CH. III.] FRESHWATER AND MARINE FOSSILS. 27 
 
 are divided are actually often filled with thousands of well-preserved 
 organic bodies, which abound in every minute grain of chalk, and 
 are especially apparent in the white coating of flints, often accom- 
 panied by innumerable needle-shaped spiculae of sponges. After 
 reflecting on these discoveries, we are naturally led on to conjecture 
 that, as the formless cement in the semi-opal of Bilin has been 
 derived from the decomposition of animal and vegetable remains, so 
 also many chalk flints in which no organic structure can be re- 
 cognized may nevertheless have constituted a part of microscopic 
 animalcules. 
 
 " The dust we tread upon was once alive ! " BYRON. 
 
 How faint an idea does this exclamation of the poet convey 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 the organic structure which, at periods 
 of time incalculably remote, was impressed upon it by the powers 
 of life. 
 
 Freshwater and marine fossils. Strata, whether deposited in salt 
 or fresh water, have the same forms ; but the imbedded 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 50 feet thick, occur, in which the shells are 
 principally, if not all, of extinct species. Yet we recognize their 
 freshwater origin, because they are of the same genera as those now 
 abounding in ponds and lakes, either in our own country or in 
 warmer latitudes. 
 
 In many parts of France, as in Auvergne, for example, strata of 
 limestone, marl, and sandstone are found, hundreds of feet thick, 
 which contain exclusively freshwater and land shells, together with 
 the remains of terrestrial quadrupeds. The number of land shells 
 scattered through some of these freshwater deposits is exceedingly 
 great ; -and there are districts in Germany where the rocks scarcely 
 contain any other fossils except snail-shells (helices) ; as, for instance, 
 the limestone 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 geologist 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 where the 
 Kander enters the Lake of Thun. He there sees sand and mud 
 strewed over with innumerable dead land shells, which have been 
 brought down from 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 individuals have been washed 
 
28 
 
 DISTINCTION OF FRESHWATER 
 
 [CH. III. 
 
 away from the alluvial plains of the great river and its tributaries, 
 some from mountainous regions, others from the low country. 
 
 Although freshwater formations are often of great thickness, yet 
 they are usually very limited in area when compared to marine 
 deposits, just as lakes and estuaries are of small dimensions in com- 
 parison with seas. 
 
 We may distinguish a freshwater formation, first, by the absence 
 of many fossils almost invariably met with in marine strata. For 
 example, there are no sea-urchins, no corals, and scarcely any zoo- 
 phytes ; no chambered shells, such as the nautilus, nor microscopic 
 Foraminifera. But it is chiefly by attending to the forms of the 
 mollusca that we are guided in determining the point in question, 
 In a freshwater deposit, the number of individual shells is often as 
 great, if not greater, than in a marine stratum ; but there is a smaller 
 variety of species and genera. This might be anticipated from the 
 fact that the genera and species of recent freshwater and land shells 
 are few when contrasted with the marine. Thus, the genera of true 
 mollusca according to Blainville's system, excluding those of extinct 
 species and those without shells, amount to about 200 in number, of 
 which the terrestrial and freshwater genera scarcely form more than 
 a sixth.* 
 
 Almost all bivalve shells, or those of acephalous mollusca, are 
 marine, about ten only out of ninety genera being freshwater. 
 
 Fig. 25. 
 
 Fig. 26. 
 
 Cyclas obovata ; fossil. Hants. 
 
 Cyrena consobrina ; fossil. Grays, Essex. 
 
 Among these last, the four most common forms, both recent and 
 fossil, are Cyclas, Cyrena, Unio, and Anodonta (see figures); the 
 
 Fig. 27. 
 
 Fig. 
 
 Fig. 29. 
 
 Anodonta Cordierii ; 
 fossil. Paris. 
 
 Anodonta latimarginatus ; 
 recent. Bahia. 
 
 Unio littoralis ; 
 recent. Auvergne. 
 
 two first and two last of which are so nearly allied as to pass into 
 each other. 
 
 See Synoptic Table in Blainville's Malacologie. 
 
CH. III.] FKOM MARINE FORMATIONS. 29 
 
 Fi? - 30> Lamarck divided the bivalve mollusca into 
 
 the Dimyary, or those having, two large mus- 
 cular impressions in each valve, as a b in the 
 Cyclas, fig. 25., and the Monomyary, such as 
 the oyster and scallop, in which there is only 
 one of these impressions, as is seen in fig. 30. 
 Now, as none of these last, or the unimuscular 
 bivalves, are freshwater, we may at once pre- 
 sume a deposit in which we find any of them 
 A . to be marine. 
 
 Gryphcea incurva, Sow. (G. ar- 
 
 citata, Lam.) upper valve. Lias. The univalve shells most characteristic of 
 fresh-water deposits are, Planorbis, Lymnea, and Paludina. (See 
 
 Fig. 31. Fig. 32. Fig. 33. 
 
 Planorbts eurnnphalus ; 
 fossil. Isle of Wight. 
 
 Lymnea longiscaia ; 
 ' fossil. Hants. 
 
 Paludina lenta ; 
 fossil. Hants. 
 
 figures.) But to these are occasionally added Physa, Succinea, 
 Ancylus, Valvata, Melanopsis, Melania, and Neritina. (See figures.) 
 
 Fig. 34. Fig. 35. Fig. 36. Fig. 37. 
 
 Succmea amphibia ; 
 fossil. Loess, Khine. 
 
 Ancylus elegans ; 
 fossil. Hants. 
 
 Valvata ; Physa hypnorum . 
 fossil. recent. 
 
 Grays, Essex. 
 
 In regard to one of these, the Ancylus (fig. 35.), Mr. Gray 
 observes that it sometimes differs in no respect from the marine 
 
 Fig. 38. Fig. 39. Fig. 40. Fig. 41. 
 
 Auricula ; 
 recent. Ava. 
 
 Physa colttm- 
 
 naris. Paris. 
 
 basin. 
 
 Melanopsis bnc- 
 cinoidea ; recent. 
 Asia. 
 
 Siphonaridj except in the animal. The shell, however, of the 
 Ancylus is usually thinner.* 
 
 * Gray, Phil. Trans., 1835, p. 302. 
 
30 DISTINCTION OF FRESHWATER [Cn. III. 
 
 Some naturalists include Neritina (fig. 42.) and the marine 
 Nerita (fig. 43.) in the same genus, it being scarcely possible to 
 
 Fig. 42. 
 
 Fig 43. 
 
 Fig. 44. 
 
 Nerttina globulus. Paris basin. Nerita granulosa. Paris basin. 
 
 distinguish the two by good generic characters. But, as 
 a general rule, the fluviatile species are smaller, smoother, 
 and more globular than the marine ; and they have never, 
 like the Neritce, the inner margin of the outer lip toothed 
 or crenulated. (See fig. 43.) 
 
 A few genera, among which Cerithium (fig. 44.) is the 
 most abundant, are common both to rivers and the sea, 
 having species peculiar to each. Other genera, like Auri- 
 cula (fig. 38.), are amphibious, frequenting marshes, espe- pSuSta. 
 cially near the sea. 
 
 The terrestrial shells are all univalves. The most abundant 
 genera among these, both in a recent and fossil state, are Helix 
 (fig. 45.), Cyclostoma (fig. 46.), Pupa (fig. 47.), Clausilia (fig. 48.), 
 
 Fig. 45. 
 
 Fig. 46. 
 
 Fig. 47. Fig. 48. 
 
 Fig. 49. 
 
 Helix Turnnensts. 
 Faluns, Touraine. 
 
 Cyclostoma 
 elcgans* 
 Loess. 
 
 Pupa Cla?isilia Bulimus lubricus. 
 
 tridens. bidens. Loess, Rhine. 
 
 Loess. Loess. 
 
 Bulimus (fig. 49.), and Achatina ; which two last are nearly allied 
 and pass into each other. 
 
 The Ampullaria (fig. 50.), is another genus of shells, inhabiting 
 Fig. 50. rivers and ponds in hot countries. Many fossil 
 
 species have been referred to this genus, but they 
 have been found chiefly in marine formations, and 
 are suspected by some conchologists to belong to 
 Natica and other marine genera. 
 
 All univalve shells of land and freshwater spe- 
 cies, with the exception of Melanopsis (fig. 41.), 
 and Achatina. which has a slight indentation, have 
 
 Ampullaria glauca, i ,j r 
 
 rrom the Jumna. entire mouths ; and this circumstance may often 
 serve as a convenient rule for distinguishing freshwater from marine 
 strata ; since, if any univalves occur of which the mouths are not 
 entire, we may presume that the formation is marine. The aper- 
 ture is said to be entire in such shells as the Ampullaria and the 
 land shells (figs. 45 49.), when its outline is not interrupted 
 by an indentation or notch, such as that seen at b in Ancillaria 
 
CH. III.] FROM MARINE FORMATIONS. 3t 
 
 (fig. 52.) ; or is not prolonged into a canal, as that seen at a in 
 Pleurotoma (fig. 51.). 
 
 The mouths of a large proportion of the marine univalves have 
 these notches or canals, and almost all such species are carnivorous ; 
 
 Fig. 51. Fig. 52. 
 
 Pleurotoma 
 
 rotata. 
 
 Subap. hills, 
 
 Italy. 
 
 Ancillaria subulata. London clay. 
 
 whereas nearly all testacea having entire mouths, are plant-eaters ; 
 whether the species be marine, freshwater, or terrestrial. 
 
 There is, however, one genus which affords an occasional ex- 
 ception to one of the above rules. The Cerithium (fig. 44.), 
 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 freshwater deposits are the 
 shells of Cypris, a minute crustaceous animal, having a shell much 
 resembling tha of the bivalve mollusca.* 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 freshwater origin of a deposit, because the majority of 
 species in another kindred genus of the same order, the Cytherina of 
 Lamarck (see above, fig. 21. p. 26.), inhabit saltwater; and, although 
 the animal differs slightly, the shell is scarcely distinguishable from 
 that of the Cypris. 
 
 The seed-vessels and stems of Chara, a genus of aquatic plants, 
 are very frequent in freshwater strata. These seed-vessels were 
 called, before their true nature was known, gyrogonites, and were 
 supposed to be foraminiferous shells. (See fig. 53. a.) 
 
 The Charce 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 state. The annexed figure (fig. 54.) 
 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 Charce, and therefore more 
 nearly resembles in form the extinct fossil species found in England, 
 
 * For figures of fossil species of Purbeck, see below, ch. xx 
 
32 FRESHWATER AND MARINE FORMATIONS. [Cn. III. 
 
 -France, and other countries. The stems, as well as the seed-vessels, 
 of these plants occur both in modern shell marl and in ancient 
 
 Fig. 53. Fig. 54. 
 
 Char a medicaginula ; Chara elastica ; recent. Italy, 
 
 fossil. Upper Eocene, Isle of Wight. 
 
 a. Sessile seed vessel between the divisions of 
 
 a. Seed-vessel, the leaves of the female plant. 
 
 magnified 20 6. Magnified transverse section of a branch, 
 
 diameters. with five seed-vessels, seen from below 
 
 b. Stem, magnified. upwards. 
 
 freshwater formations. They are generally composed of a large 
 tube surrounded by smaller tubes ; the whole stem being divided at 
 certain intervals by transverse partitions or joints. (See b, fig. 53.) 
 
 It is not uncommon to meet with layers of vegetable matter, 
 impressions of leaves, and branches of trees, in strata containing 
 freshwater shells ; and we also find occasionally the teeth and bones 
 of land quadrupeds, of species now unknown. The manner in 
 which such remains are occasionally carried by rivers into lakes, 
 especially during floods, has been fully treated of in the " Principles 
 of Geology."* 
 
 The remains of fish are occasionally useful in determining the 
 freshwater origin of strata. Certain genera, such as carp, perch, 
 pike, and loach (Cyprinus, Perca, Esox, and Cobitis), as also Lebias, 
 being peculiar to freshwater. Other genera contain some freshwater 
 and some marine species, as Coitus, Mugil, and Anguilla, or eel. 
 The rest are either common to rivers and the sea, as the salmon ; or 
 are exclusively characteristic of salt water. The above observa- 
 tions respecting fossil fishes are applicable only to the more 
 modern or tertiary deposits ; for in the more ancient rocks the 
 forms depart so widely from those of existing fishes, that it is very 
 difficult, at least in the present state of science, to derive any positive 
 information from icthyolites respecting the element in which strata 
 were deposited. 
 
 The alternation of marine and freshwater formations, both on a 
 small and large scale, are facts well ascertained in geology. When 
 it occurs on a small scale, it may have arisen from the alternate 
 occupation of certain spaces by river water 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 returns, and, on resuming its former place, brings 
 with it sand, mud, and marine shells. 
 
 * See Index of Principles, " Fossilization." 
 
CH. IV.] CONSOLIDATION OF STRATA. 33 
 
 There are also lagoons at the mouths of many rivers, as the Nile 
 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. 
 
 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 as often formed 
 and removed. The last irruption of salt water happened in 1 824, 
 when the North Sea entered, killing all the freshwater shells, fish, 
 and plants ; and from that time to the present, the sea-weed Fucus 
 vesictilosus, together with oysters and other marine mollusca, have 
 succeeded the Cyclas, Lymnea, Paludina, and Chares.* 
 
 But changes like these in the Lym-Fiord, and those before men- 
 tioned as occurring at the mouths of great rivers, will only account 
 for some cases of marine deposits of partial extent resting on fresh- 
 water strata. When we find, as in the south-east of England, a 
 great series of freshwater beds, 1000 feet in thickness, resting upon 
 marine formations and again covered by other rocks, such as the 
 cretaceous, more than 1000 feet thick, and of deep-sea origin, we 
 shall find it necessary to seek for a different explanation of the phe- 
 nomena. 
 
 CHAPTER IV. 
 
 CONSOLIDATION OF STRATA AND PETRIFACTION OF FOSSILS. 
 
 Chemical and mechanical deposits Cementing together of particles Hardening 
 by exposure to air Concretionary nodules Consolidating effects of pressure 
 Mineralization of organic remains Impressions and casts how formed Fossil 
 wood Goppert's experiments Precipitation of stony matter most rapid where 
 putrefaction is going on Source of lime in solution Silex derived from de- 
 composition of felspar Proofs of the lapidification of some fossils soon after 
 burial, of others when much decayed. 
 
 HAVING spoken in the preceding chapters of the characters of sedi- 
 mentary formations, both as dependent on the deposition of inorganic 
 matter and the distribution of fossils, I may next treat of the con- 
 solidation of stratified rocks, and the petrifaction of imbedded or- 
 ganic remains. 
 
 Chemical and mechanical deposits. A distinction has been made 
 
 * See Principles, Index, " Lym-Fiord." 
 
 f See below, Chap. XVIII., on the Wealden. 
 
 D 
 
34 CONSOLIDATION OF STRATA. [Cn. IV. 
 
 by geologists between deposits of a chemical, and those of a me- 
 chanical, origin. By the latter name are designated beds of mud, 
 sand, or pebbles produced by the action of running water, also ac- 
 cumulations of stones and scoriae thrown out by a volcano, which 
 have fallen into their present place by the force of gravitation. But 
 the matter which forms a chemical deposit has not been mechanically 
 suspended in water, but in a state of solution until separated by 
 chemical action. In this manner carbonate of lime is often precipi- 
 tated upon the bottom of lakes and seas in a solid form, as may be 
 well seen in many parts of Italy, where mineral 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, encrusting shells, fragments of wood and 
 leaves, and binding them together.* 
 
 In coral reefs, large masses of limestone are formed by the stony 
 skeletons of zoophytes ; and these, together with shells, become ce- 
 mented together by carbonate of lime, part of which is probably 
 furnished to the sea water by the decomposition of dead corals. 
 Even shells of which the animals are still living, on these reefs, are 
 very commonly found to be encrusted over with a hard coating of 
 limestone, j 
 
 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 of a mixed origin, partly chemical, and partly 
 mechanical. 
 
 Now, the remarks already made in Chapter II. on the original 
 horizontality of strata are strictly applicable to mechanical 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 encrust 
 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. 
 
 Cementing of particles. It is chiefly in the case of calcareous 
 rocks that solidification takes place at the time of deposition. 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 calcareous springs has flowed through a bed 
 of sand or gravel, that iron or carbonate of lime has been deposited 
 in the interstices between the grains 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 incoherent. 
 
 Proofs of a similar cementing action are seen in a rock at Kello- 
 way in Wiltshire. A peculiar band of sandy strata belonging to the 
 group called Oolite by geologists, may be traced through several 
 
 * See Principles, Index, " Calcareous f R>id. " Travertin," " Coral Reefs," 
 Springs," &c. &c. 
 
CH. IV.] CONSOLIDATION OF STRATA. 35 
 
 counties, the sand being for the most part loose and unconsolidated, 
 but becoming stony near Kelloway. In this district there are nu- 
 merous fossil shells which have decomposed, having for the most 
 part left only their casts. 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, retaining the casts 
 of shells, and plunge them into dilute muriatic or other acid, we see 
 them immediately changed into common sand and mud ; the cement 
 of lime, derived from the shells, having been dissolved by the acid. 
 
 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 powder when touched. 
 It is cle%r 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 together ; in which case no memorial of the fossil will 
 remain. The absence of organic remains from many aqueous rocks 
 may be thus explained ; but we may presume that in many of them 
 no fossils were ever imbedded, as there are extensive tracts on the 
 bottoms of existing seas even of moderate depth on which no frag- 
 ment of shell, coral, or other living creature can be detected by 
 dredging. On the other hand, there are depths where the zero of 
 animal life has been approached ; as, for example, in the Mediter- 
 ranean, at the depth of about 230 fathoms, according to the researches 
 of Prof. E. Forbes. In the JEgean Sea a deposit of yellowish mud 
 of a very uniform character, and closely resembling chalk, is going 
 on in regions below 230 fathoms, and this formation must be wholly 
 devoid of organic remains. * 
 
 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 remark 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 tem- 
 perature 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 conglo- 
 merates, like the pudding-stone of Hertfordshire (a Lower Eocene 
 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 deposited, 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 
 
 * Report Brit. Ass. 1843, p. 178. 
 D 2 
 
36 CONSOLIDATION OF STRATA. [Cn. IV. 
 
 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 harden. Such induration may perhaps be accounted for by 
 supposing the water, which penetrates the minutest pores of rocks, 
 to deposit, on evaporation, carbonate of lime, iron, silex, and other 
 minerals previously held in solution, and thereby to fill up the pores 
 partially. These particles, on crystallizing, would not only be them- 
 selves 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 frozen ; because one ingredient of the mass, namely, the water, 
 has crystallized, so as to hold firmly together all the separate particles 
 of which the loose mud and sand were composed. 
 
 Dr. MacCulloch 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 cabinets, 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 happen in the 
 case of the beryl. * 
 
 The marl recently deposited at the bottom of Lake Superior, in 
 North America, is soft, and often filled with freshwater shells ; but 
 if a piece be taken up and dried, it becomes 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 marl- 
 stone, like that observed in many ancient European formations, and 
 like them containing freshwater shells. 
 
 It is probable that some of the heterogeneous materials which 
 rivers transport to the sea may at once set under water, like the arti- 
 ficial mixture called pozzolana, which consists of fine volcanic sand 
 charged with about 20 per cent, of oxide of iron, and the addition of 
 a small quantity of lirne. 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 these cases is brought about by the action of 
 chemical affinity on finely comminuted matter previously suspended 
 in water. After deposition similar particles seem to exert a mutual 
 attraction on each other, and congregate together in particular spots, 
 forming lumps, nodules, and concretions. Thus in many argillaceous 
 deposits there are calcareous balls, or spherical concretions, ranged 
 in layers parallel to the general stratification ; an arrangement which 
 took place after the shale or marl had been thrown down in succes- 
 sive laminas ; for these laminae are often traced in the concretions, 
 
 * Dr. MacCulloch, Syst. of GeoL vol. i. p. 123. 
 
CH. IV.] 
 
 CONCRETIONARY STRUCTURE. 
 
 37 
 
 Fig. 55. 
 
 Calcareous nodules in Lias. 
 
 Fig. 56. 
 
 remaining parallel to those of the surrounding unconsolidated rock. 
 
 (See fig. 55.) Such nodules of lime- 
 stone have often a shell or other foreign 
 body in the centre.* 
 
 Among the most remarkable ex- 
 amples of concretionary structure are 
 those described by Professor Sedgwick 
 as abounding in the magnesian limestone of the north of England. 
 The spherical balls are of various sizes, from that of a pea to a dia- 
 meter of several feet, and they have both a concentric and radiated 
 structure, while at the same time the laminae of original deposition 
 pass uninterruptedly through them. In some cliffs this limestone 
 resembles a great irregular 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 above or below. Thus the 
 larger spheroid in the annexed section (fig. 56.) passes from the stratum 
 
 b upwards into a. In this instance we 
 must suppose the deposition of a series 
 of minor layers, first forming the stra- 
 tum ^ and afterwards the incumbent 
 stratum a ; then a movement of the par- 
 ticles took place, and the carbonates of 
 lime and magnesia separated from the 
 more impure and mixed matter forming the still unconsolidated parts 
 of the stratum. Crystallization, beginning at the centre, must have 
 gone on forming concentric coats around the original nucleus without 
 interfering with the laminated structure of the rock. 
 
 When the particles of rocks have been thus re-arranged by chemi- 
 cal forces, it is sometimes difficult or impossible to ascertain whether 
 certain lines of division are due to original deposition or to the sub- 
 sequent aggregation of similar particles. Thus suppose three strata 
 Fig- 57. of grit, A, B, C, are charged unequally 
 
 with calcareous matter, and that B is the 
 "e most calcareous. If consolidation takes 
 place in B, the concretionary action may 
 spread upwards into a part of A, where 
 
 Spheroidal concretions in magnesian 
 limestone. 
 
 the carbonate of lime is more abundant than in the rest ; so that a 
 mass, d, e, /, 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 d, f, 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 bottom 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 pressure with a force equal to that of the 
 column of fluid above. The same happens in regard to organic re- 
 
 * Dela Beche, Geol. Researches, p. 95., and Geol. Observer (1851), p. 686. 
 
 D 3 
 
38 MINEEALIZATION OF [Cn. IV. 
 
 mains which are filled with water under great pressure a they sink 
 otherwise they would be immediately crushed to pieces and flattened. 
 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- 
 come packed into a smaller space, and be made to cohere together 
 permanently. 
 
 Analogous effects of condensation may arise when the solid parts 
 of the earth's crust are forced in various directions by those me- 
 chanical movements afterwards to be described, by which strata have 
 been bent, broken, and raised above the level of the sea. Rocks of 
 more yielding materials must often have been forced against others 
 previously consolidated, and, thus compressed, may have acquired a 
 new structure. A recent discovery may help us to comprehend how 
 fine sediment derived from the detritus of rocks may be solidified by 
 mere pressure. The graphite or " black lead " of commerce having 
 become very scarce, Mr. Brockedon contrived a method by which the 
 dust of the purer portions of the mineral found in Borrowdale might 
 be recomposed 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 pencils, 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 powerful of all causes in hardening sedimentary strata. To 
 this subject I shall refer again when treating of the metamorphic 
 rocks, and of the slaty and jointed 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 exterior, or a cast of its interior form, or thirdly, a cast of the 
 shell itself, the original matter of which has been removed. These 
 different forms of fossilization may easily 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, having the form of the interior 
 of the shell. This form is often very different from that of the outer 
 shell. Thus a cast such as a, fig. 58., commonly called a fossil screw, 
 would never be suspected by an inexperienced conchologist to be 
 the internal shape of the fossil univalve, , fig. 58. Nor should we 
 
CH. IV.] ORGANIC REMAINS. 39 
 
 have imagined at first sight that the shell a and the cast b, fig. 59., 
 were different parts of the same fossil. The reader will observe, in 
 
 Fig. 58. 
 
 Phasianetta Heddingtonensis, 
 and cast of the same. Coral Rag. 
 
 Trochus Anglicus, and 
 cast. Lias. 
 
 the last-mentioned figure (b, fig. 59.), 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 par- 
 ticles removed by water percolating the rock. If the nucleus were 
 taken out, a hollow mould would remain, on which the external form 
 of the shell with its tubercles and strise, as seen in a, fig. 59., 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 procure 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, and not the internal organization ; but there is 
 another description of petrifaction by no means uncommon, and of a 
 much more wonderful kind, which may be compared to certain ana- 
 tomical models in wax, where not only the outward forms and fea- 
 tures, but the nerves, blood-vessels, and other internal organs are also 
 shown. Thus we find corals, originally calcareous, in which not only 
 the general shape, but also the minute and complicated internal or- 
 ganization are retained in flint. 
 
 Such a process of petrifaction is still more remarkably exhibited 
 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 pores and fibres of plants, and even those spiral vessels 
 which in the living vegetable can only be discovered by the mi- 
 croscope, are preserved. Among many instances, I may mention a 
 fossil tree, 72 feet in length, found at Gosforth near Newcastle, in 
 sandstone strata associated with coal. By cutting a transverse slice 
 so thin as to transmit light, and magnifying it about fifty-five times, 
 
 D 4 
 
40 MINERALIZATION OF [Cn. IV. 
 
 the texture seen in fig. 60. is exhibited. A texture equally minute 
 and complicated has been observed in the wood 
 ~^&wtt&i& f l ar g e trunks of fossil trees found in the 
 Craigleith quarry near Edinburgh, where the 
 stone was not in the slightest degree siliceous, 
 but consisted chiefly of carbonate of lime, with 
 oxide of iron, alumina, and carbon. The pa- 
 rallel rows of vessels here seen are the rings 
 of annual growth, but in one part they are im- 
 
 Textureofatree from the coal i " 
 
 strata, magnified. (Witham.) perfectly preserved, the wood having probably 
 
 Transverse section. - , , c , . , . . , , 
 
 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 generally 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 considered. 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, which consist 
 chiefly of oxygen, hydrogen, 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 decompose more gradually; 
 and if buried in earth, still more 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 minute of carbonate of lime, flint, or other mineral, 
 is at hand and ready to be precipitated, we may imagine this in- 
 organic matter to take the place just before left unoccupied by the 
 organic molecule. In this manner a cast of the interior of certain 
 vessels may first be taken, and afterwards the more solid walls of the 
 same may decay and suffer a like transmutation. 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 mingled in certain parts, or the lapidifying 
 substance itself may be differently coloured at different times, or so 
 crystallized as to reflect light differently, and thus the texture of the 
 original body may be faithfully exhibited. 
 
 The student may perhaps ask whether, on chemical principles, we 
 have any ground to expect that mineral matter will be thrown down 
 precisely in those spots where organic decomposition is in progress ? 
 The following curious experiments may serve to illustrate this point. 
 Professor Goppert of Breslau attempted recently to imitate the na- 
 tural process of petrifaction. For this purpose he steeped a variety 
 of animal and vegetable substances in waters, some holding siliceous, 
 others calcareous, others metallic matter in solution. He found that 
 in the period of a few weeks, or 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 syl- 
 
CH. IV.] ORGANIC REMAINS. 41 
 
 vestris), 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 exactly 
 that casts even of the dotted vessels peculiar to this family of plants 
 were distinctly visible under the microscope. 
 
 Another accidental experiment has been recorded by Mr. Pepys in 
 the Geological Transactions. * An earthen pitcher containing several 
 quarts of sulphate of iron had remained undisturbed and unnoticed 
 for about a twelvemonth in the laboratory. At the end of this time 
 when the liquor was examined an oily appearance was observed on 
 the surface, and a yellowish powder, which proved to be sulphur, 
 together with a quantity of small hairs. At the bottom were dis- 
 covered the bones of several mice in a sediment consisting of small 
 grains of pyrites, others of sulphur, others of crystallized green sul- 
 phate of iron, and a black muddy oxide of iron. It was evident that 
 some mice had accidentally been drowned in the fluid, and by the 
 mutual action of the animal matter and the sulphate of iron on each 
 other, the metallic sulphate had been deprived of its oxygen ; hence 
 the pyrites and the other compounds were thrown down. Although 
 the mice were not mineralized, or turned into pyrites, the pheno- 
 menon shows how mineral waters, charged with sulphate of iron, 
 may be deoxydated on coming in contact with animal matter under- 
 going putrefaction, so that atom after atom of pyrites may be pre- 
 cipitated, and ready, under favourable circumstances, to replace the 
 oxygen, hydrogen, and carbon into which the original body would be 
 resolved. 
 
 The late Dr. Turner observes, that when mineral matter is in a 
 "nascent state," that is to say, just liberated from a previous 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. 
 
 An analysis was lately made of the water which was flowing off 
 from the rich mud deposited by the Hooghly river in the Delta of 
 the Ganges after the annual inundation. This water was found to 
 be highly charged with carbonic acid gas holding lime in solution, f 
 Now if newly-deposited mud is thus proved to be permeated by 
 mineral matter in a state of solution, it is not difficult to perceive 
 that decomposing organic bodies, naturally imbedded in sediment, 
 may as readily become petrified as the substances artificially im- 
 mersed by Professor Goppert in various fluid mixtures. 
 
 * Vol. i. p. 399. first series. 
 
 f Piddington, Asiat. Research, vol. xviii. p. 226. 
 
42 FLINT OF SILICIFIED FOSSILS. [Cn. IV. 
 
 It is well known that the water of springs, or that which is 
 continually percolating the earth's crust, is rarely free from a slight 
 admixture either of iron, carbonate of lime, sulphur, silica, potash, or 
 some other earthy, alkaline, or metallic ingredient. Hot springs in 
 particular are copiously charged with one or more of these elements ; 
 arid it is only in their waters that silex is found in abundance. In 
 certain cases, therefore, especially in volcanic regions, we may imagine 
 the flint of silicified wood and corals to have been supplied by the 
 waters of thermal springs. In other instances, as in tripoli, it may 
 have been derived in great part, if not wholly, from the decomposi- 
 tion of diatomacese, sponges, and other bodies. But even if this be 
 granted, we have still to inquire whence a lake or the ocean can be 
 constantly replenished with the calcareous and siliceous matter so 
 abundantly withdrawn from it by the secretions of living beings. 
 
 In regard to carbonate of lime there is no difficulty, because 
 not only are calcareous springs very numerous, but even rain- 
 water, when it falls on ground where vegetable matter is decom- 
 posing, may become so charged with carbonic acid as to acquire a 
 power of dissolving a minute portion of the calcareous rocks over 
 which it flows. Hence marine corals and mollusca may be provided 
 by rivers with the materials of their shells and solid supports. But 
 pure silex, even when reduced to the finest powder and boiled, is 
 insoluble in water, except at very high temperatures. Nevertheless, 
 Dr. Turner has well explained, in an essay on the chemistry of 
 geology*, how the decomposition of felspar may be a source of silex 
 in solution. He has remarked that the siliceous earth, which con- 
 stitutes more than half the bulk of felspar, is intimately combined 
 with alumine, potash, and some other elements. The alkaline matter 
 of the felspar has a chemical affinity for water, as also for the car- 
 bonic acid which is more or less contained in the waters of most 
 springs. The water therefore carries away alkaline matter, and 
 leaves behind a clay consisting of alumine and silica. But this re- 
 sidue of the decomposed mineral, which in its purest state is called 
 porcelain clay, is found to contain a part only of the silica which 
 existed in the original felspar. The other part, therefore, must have 
 been dissolved and removed : and this can be accounted for in two 
 ways ; first, because silica when combined with an alkali is soluble 
 in water ; secondly, because silica, in what is technically called its 
 nascent state, is also soluble in water. Hence an endless supply of 
 silica is afforded to rivers and the waters of the sea. For the fel- 
 spathic rocks are universally distributed, constituting, as they do, 
 so large a proportion of the volcanic, plutonic, and metamorphic for- 
 mations. Even where they chance to be absent in mass, they rarely 
 fail to occur in the superficial gravel or alluvial deposits of the basin 
 of every large river. 
 
 The disintegration of mica also, another mineral which enters 
 largely into the composition of granite and various sandstones, may 
 
 * Jam. Ed. New Phil. Journ. No. 30. p. 246. 
 
CH. IV.] PROCESS OF PETRIFACTION. 43 
 
 yield silica which may be dissolved in water, for nearly half of this 
 mineral consists of silica, combined with alumine, potash, and about 
 a tenth part of iron. The oxidation of this iron in the air is the 
 principal cause of the waste of mica. 
 
 We have still, however, much to learn before the conversion of 
 fossil bodies into stone is fully understood. Some phenomena seem 
 to imply that the mineralization must proceed with considerable 
 rapidity, for stems of a soft and succulent character, and of a most 
 perishable nature, are preserved in flint ; and there are instances of the 
 complete silicification of the young leaves of a palm-tree when just 
 about to shoot forth, and in that state which in the West Indies is 
 called the cabbage of the palm.* It may, however, be questioned 
 whether in such cases there may not have been some antiseptic quality 
 in the water which retarded putrefaction, so that the soft parts of the 
 buried substance may have remained for a long time without disin- 
 tegration, like the flesh of bodies imbedded in peat. 
 
 Mr. Stokes has pointed out examples of petrifactions in which the 
 more perishable, and others where the more durable, portions of wood 
 are preserved. These variations, he suggests, must doubtless have 
 depended on the time when the lapidifying mineral was introduced. 
 Thus, in certain silicified stems of palm-trees, the cellular tissue, that 
 most destructible part, is in good condition, while all signs of the 
 hard woody fibre have disappeared, the spaces once occupied by it 
 being hollow or filled with agate. Here, petrifaction must have com- 
 menced soon after the wood was exposed to the action of moisture, 
 and the supply of mineral matter must then have failed, or the water 
 must have become too much diluted before the woody fibre decayed. 
 But when this fibre is alone discoverable, we must suppose that an 
 interval of time elapsed before the commencement of lapidification, 
 during which the cellular tissue was obliterated. When both struc- 
 tures, namely, the cellular and the woody fibre, are preserved, the 
 process must have commenced at an early period, and continued 
 without interruption till it was completed throughout.^ 
 
 * Stokes, Geol. Trans., vol. v. p. 212. second series. f Ibid. 
 
44 LAND HAS BEEN RAISED, [Cn. V. 
 
 CHAPTER V. 
 
 ELEVATION OF STRATA ABOVE THE SEA HORIZONTAL AND INCLINED 
 STRATIFICATION. 
 
 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 Upheaval of exten- 
 sive masses of horizontal strata Inclined and vertical stratification Anticlinal 
 and synclinal lines Bent strata in east of Scotland Theory of folding by 
 lateral movement Creeps Dip and strike Structure of the Jura Various 
 forms of outcrop Rocks broken by flexure Inverted position of disturbed 
 strata Unconformable stratification Hutton and Play fair on the same 
 Fractures of strata Polished surfaces Faults Appearance of repeated alter- 
 nations produced by them Origin of great faults. 
 
 LAND has been raised, not the sea lowered. It has been already 
 stated that the aqueous rocks containing marine fossils extend over 
 wide continental tracts, and are seen in mountain chains rising to 
 great heights above the level of the sea (p. 4.). 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 general 
 lowering of the waters of tile ocean, or that the solid rocks, once covered 
 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 universal, 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 upwards 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 whatever 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 phenomena, 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 horizontal, 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 recourse to 
 the other alternative, namely, the doctrine that the solid land has 
 been repeatedly moved upwards or downwards, so as permanently to 
 change its position relatively to the sea. There are several distinct 
 
CH. V.] NOT THE SEA LOWERED. 45 
 
 grounds for preferring this conclusion. First, it will account equally 
 for the position of those elevated masses of marine origin in which 
 the stratification remains horizontal, 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 actually occurred in 
 our own days, and are now in progress, having been accompanied in 
 some cases by violent convulsions, while in others they have pro- 
 ceeded so insensibly, as to have been ascertainable only by the most 
 careful scientific observations, made at considerable intervals of time. 
 On the other hand, there is no evidence from human experience of 
 a lowering of the sea's level in any region, and the ocean cannot sink 
 in one place without its level being depressed all over the globe. 
 
 These preliminary remarks will prepare the reader to understand 
 the great theoretical interest attached to all facts connected with the 
 position of strata, whether horizontal or inclined, curved or vertical. 
 
 Now the first and most simple appearance is where strata of 
 marine origin occur above the level of the sea in horizontal 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 mentioned, composed of horizontal strati of high antiquity, which 
 contain fossil remains of animals wholly dissimilar from any now 
 known to exist. In the south of Sweden, for example, near Lake 
 Wener, the beds of one of the oldest of the fossiliferous deposits, 
 namely that formerly called Transition, and now Silurian, by geo- 
 logists, occur in as level a position as if they had recently formed 
 part of the delta of a great river, and been left dry on the retiring of 
 the annual floods. Aqueous rocks of about the same age extend for 
 hundreds of miles over the lake-district of North America, and exhibit 
 in like manner a stratification nearly undisturbed. The Table Moun- 
 tain at the Cape of Good Hope is another example of highly elevated 
 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 always 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 that they were gradually uplifted to their present height. 
 This idea, however startling 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. Playfair argued in favour 
 of this opinion in 1802 ; and in 1807, Von Buch, after his travels in 
 Scandinavia, announced his conviction that a rising of the land was 
 in progress. Celsius and other Swedish writers had, a century 
 before, declared their belief that a gradual change had, for ages, 
 
46 KISING AND SINKING OF LAND. [Cn. V. 
 
 been taking place in the relative level of land and sea. They attri- 
 buted the change to a fall of the waters both of the ocean and the 
 Baltic. This theory, however, has now been refuted by abundant 
 evidence ; for the alteration of relative level has neither been 
 universal nor everywhere uniform in quantity, but has amounted, 
 in some regions, to several feet in a century, in others to a few 
 inches ; while in the southernmost part of Sweden, or the province 
 of Scania, there has been actually a loss instead of a gain of land, 
 buildings having gradually sunk below the level of the sea.* 
 
 It appears, from the observations of Mr. Darwin and others, 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.f On the 
 other hand, the gradual sinking of the west coast of Greenland, for 
 the space of more 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 movements, have 
 been recently brought to light, the evidence has been daily strength- 
 ened of continued changes of level effected by violent convulsions 
 in countries where earthquakes are frequent. There the rocks are 
 rent from time to time, artd heaved up or thrown down several feet 
 at once, and disturbed in such a manner, that the original position of 
 strata may, in the course of centuries, be modified to any amount. 
 
 It has also been shown by Mr. Darwin, that, in those seas where 
 circular 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. 
 
 It would require a volume to explain to the reader the various 
 facts which establish the reality of these movements of land, whether 
 of elevation or depression, whether accompanied by earthquakes or 
 accomplished slowly and without local disturbance. Having treated 
 fully of these subjects in the Principles of Geology j:, I shall assume, 
 in the present work, that such changes are part of the actual course 
 of nature ; and when admitted, they will be found to afford a key to 
 the interpretation of a variety of geological appearances, such as the 
 elevation of horizontal, inclined, or disturbed marine strata, and the 
 superposition of freshwater to marine deposits, afterwards to be 
 described. It will also appear, in the sequel, how much light the 
 
 * In the first three editions of my opinion in the Phil. Trans. 1835, Part I. 
 
 Principles of Geology, I expressed many See also the Principles, 4th and subse- 
 
 doubts as to the validity of the alleged quent editions. 
 
 proofs of a gradual rise of land in f See his Journal of a Naturalist in 
 
 Sweden ; but after visiting that country, Voyage of the Beagle, and his work on 
 
 in 1834, 1 retracted these objections, and Coral Reefs. 
 
 published a detailed statement of the J See chaps, xxvii. to xxxii. inclusive, 
 
 observations which led me to alter my and chap. 1. 
 
CH. V.] 
 
 INCLINED STKATIFICATION. 
 
 47 
 
 Fig. 61. 
 
 doctrine of a continued subsidence of land may throw on the manner 
 in which a series of strata, formed in shallow water, may have accu- 
 mulated to a great thickness. The excavation of valleys also, and 
 other effects of denudation, of which I shall presently treat, can alone 
 be understood when we duly appreciate the proofs, now on record, 
 of the prolonged rising and sinking of land, throughout wide areas. 
 
 To conclude this subject, I may remind the reader, that were we 
 to embrace the doctrine which ascribes the elevated position of marine 
 formations, and the depression of certain freshwater strata, to oscil- 
 lations in the level of the waters instead of the land, we should be 
 compelled to admit that the ocean has been sometimes every where 
 much shallower than at present, and at others more than three miles 
 deeper. 
 
 Inclined stratification. The most unequivocal evidence of a 
 change in the original position of strata is afforded by their standing 
 up perpendicularly on their edges, which is by no means a rare 
 phenomenon, especially 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 ob- 
 served certain conglomerates in a simi- 
 lar position in the Swiss Alps, he re- 
 marked that the pebbles, being for the 
 most part of an oval shape, had their 
 longer axes parallel to the planes of 
 stratification (see fig. 61.). From this 
 he inferred, that such strata must, at 
 
 first, have been horizontal, each Oval Vertical conglomerate and sandstone. 
 
 pebble having originally settled at the bottom of the water, with its 
 flatter side parallel to the horizon, for the same reason that an egg 
 will not stand on either end if unsupported. Some few, indeed, of 
 the rounded stones in a conglomerate occasionally afford an exception 
 to the above rule, for the same reason that we see on a shingle beach 
 some oval or flat-sided pebbles resting on their ends or edges ; these 
 having been forced along the bottom and against each other by a 
 wave or current so as to settle in this position. 
 
 Vertical strata, when they can be traced continuously upwards or 
 downwards for some depth, are almost invariably seen to be parts of 
 great curves, which may have a diameter of a few yards, or of several 
 miles. I shall first describe two curves of considerable regularity, 
 which occur in Forfarshire, extending over a country twent}^ miles in 
 breadth, from the foot of the Grampians to the sea near Arbroath. 
 
 The mass of strata here shown may be nearly 2000 feet in thick- 
 ness, consisting of red and white sandstone, and various coloured 
 shales, the beds being distinguishable into four principal groups, 
 namely, No. 1. red marl or shale; No. 2. red sandstone, used for 
 building ; No. 3. conglomerate ; and No. 4. grey paving-stone, and 
 tile-stone, with green and reddish shale, containing peculiar organic 
 remains. A glance at the section will show that each of the forma- 
 
48 CURVED STRATA. [On. V. 
 
 tions 2, 3, 4, are repeated 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. Beginning at the 
 north-west extremity, the tile-stones and 
 conglomerates No. 4. and No. 8. are ver- 
 tical, and they generally form a ridge 
 parallel to the southern skirts of the 
 Grampians. The superior strata Nos. 2. 
 and J. 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 "synclinal 
 line," where the beds, which are tilted 
 in opposite directions, 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 travel- 
 ling 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 con- 
 tinually leaving the newer, and advanc- 
 ing upon older strata. All the deposits 
 which he had before examined begin 
 then to recur in reversed order, until he 
 arrives at the central axis of the Sidlaw 
 hills, where the strata are seen to form 
 an arch or saddle, 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 composed of red conglomerate and sand, and are newer 
 than any of the groups, 1, 2, 3, 4, before described, and rest uncon- 
 formably upon strata of the sandstone group, No. 2. 
 
 An example of curved strata, in which the bends or convolutions 
 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. 
 
 * Edin. Trans, vol. vii. pi 3. 
 
CH. V.] EXPERIMENTS TO ILLUSTRATE CURVED STRATA. 49 
 
 Abb's Head, on the east coast of Scotland, where the rocks consist 
 principally of a bluish slate, having frequently a ripple-marked sur- 
 face. The undulations of the beds reach from the top to the bottom 
 
 Fig. 63. 
 
 Curved strata of slate near Sk Abb's Head, Berwickshire. (Sir J. Hall.) 
 
 of cliffs from 200 to 300 feet in height, and there are sixteen distinct 
 bendings in the course of about six miles, the curvatures being alter- 
 nately concave and convex upwards. 
 
 An experiment was made by Sir James Hall, with a view of illus- 
 trating the manner in 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 oppo- 
 site 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, how- 
 ever, bear in mind, that in the natural section or sea-cliff we only 
 see the foldings 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 
 
 Fig. 64. 
 
 explained in the next chapter. The dark lines in the accompanying 
 plan (fig. 64.) represent what is actually seen of the strata in part of 
 the line of cliff alluded to ; the fainter lines, that portion which is 
 
50 CURVED STRATA. [Cn. V. 
 
 concealed beneath the sea level, as also that which is supposed to 
 have once existed above the present surface. 
 
 We may still more easily illustrate the effects which a lateral thrust 
 might produce on flexible strata, by placing several pieces of differ- 
 ently coloured cloths upon a table, and when they are spread out hori- 
 
 Fig. 65. 
 
 zontally, cover them with a book. Then apply other books to each 
 end, and force them towards each other. The folding of the cloths 
 will exactly imitate those of the bent strata. (See fig. 65.) 
 
 Whether the analogous flexures in stratified rocks have really been 
 due to similar sideway movements is a question of considerable diffi- 
 culty. It will appear when the volcanic and granitic rocks are de- 
 scribed that some of them have, when melted, been injected forcibly 
 into fissures, while others, already in a solid state, have been pro- 
 truded upwards through the incumbent crust of the earth, by which 
 a great displacement of flexible strata must have been caused. 
 
 But we also know 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 some- 
 times extending over a wide area. The frequent repetition, or con- 
 tinuance throughout long periods, of such downward movements 
 seems to imply the formation and renewal of cavities at a certain 
 depth below the surface, whether by the removal of matter by vol- 
 canos and hot springs, or by the contraction of argillaceous rocks by 
 heat and pressure, or any other combination of circumstances. What- 
 ever conjectures we may indulge respecting the causes, it is certain 
 that pliable beds may, in consequence of unequal degrees of subsi- 
 dence, become folded to any amount, and have all the appearance of 
 having been compressed suddenly by a lateral thrust. 
 
 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 over- 
 lying strata to sink down bodily, even when props are left to support 
 the roof of the mine. " In Yorkshire," says Mr. Buddie, " three dis- 
 tinct 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 sandstone and shale, which 
 thus settled down." * The exact amount of depression in these cases 
 
 * Proceedings of Geol. Soc. vol.iii. p. 148. 
 
CH. V.] CREEPS IN COAL-MINES. 51 
 
 can only be accurately measured where water accumulates on the 
 surface, or a railway 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. 66., representing a section at Wallsend, 
 
 ' I 
 I 1 ' I I : ra I 
 
 rm* 
 
 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 re- 
 
 E 2 
 
52 CURVED STRATA. [Cn. V. 
 
 duced 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-mines, that the roof is com- 
 posed of hard shale, or occasionally of sandstone, more unyielding 
 than the foundation, which often consists of clay. Even where the 
 argillaceous substrata are hard at first, they soon become softened 
 and reduced to a plastic state when exposed to the contact of air and 
 water in the floor of a mine. 
 
 The first symptom of a " creep," says Mr. Buddie, is a slight cur- 
 vature at the bottom of each gallery, as at a, fig. 66.: then the 
 pavement continuing to rise, begins to open with a longitudinal 
 crack, as at b : then the points of the fractured ridge reach the roof, 
 as at c ; and, lastly, the upraised beds close up the whole gallery, and 
 the broken portions of the ridge are re-united and flattened at the 
 top, exhibiting 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 , b, c, d, an inferior stratum, called the 
 " metal coal," which is 3 feet thick, has been fractured at the points 
 e, /, g, h, and has risen, so as to prove that the upward movement, 
 caused by the working out of the " 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 downwards more than 150 feet below the metal coal, but it 
 grows continually less and less until it becomes imperceptible. 
 
 No part of the process above described is more deserving of our 
 notice than the slowness with which the change in the arrangement 
 of the beds is brought about. Days, 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 displacement 
 or violence are greatest in those creeps which have required months 
 or years for their entire accomplishment. 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. 
 
 Between the layers of shale, accompanying coal, we sometimes see 
 the leaves of fossil ferns spread out as regularly as dried plants 
 between sheets of paper in the herbarium of a botanist. These fern- 
 leaves, or fronds, must have rested horizontally on soft mud, when 
 first deposited. If, therefore, they and the layers of shale are now 
 inclined, or standing on end, it is obviously the effect of subsequent 
 derangement. The proof becomes, if possible, still more striking 
 
CH. V.] DIP AND STRIKE. 53 
 
 when these strata, including vegetable remains, are curved again ana 
 again, and even folded into the form of the letter Z, so that the same 
 continuous layer of coal is cut through several times in the same 
 perpendicular shaft. Thus, in the coal-field near Mons, in Belgium, 
 
 Fig. 67. 
 
 Zigzag -flexures of coal near Mons. 
 
 these zigzag bendings are repeated four or five times, in the manner 
 represented in fig. 67., the black lines representing seams of coal.* 
 
 Dip and Strike. In the above remarks, several technical terms 
 have been used, such as dip, the unconformable position of strata, 
 and the anticlinal and synclinal lines, which, as well as the strike of 
 the beds, I shall now explain. If a stratum or bed of rock, instead 
 of being quite level, be inclined to one side, it is said to dip ; the 
 point of the compass to which it is inclined is called the point of dip, 
 and the degree of deviation from a level or horizontal line is called 
 Fig. 68. the amount of dip, or the angle 
 
 of dip. Thus, in the annexed 
 90 diagram (fig. 68.), a series of 
 strata are inclined, and they dip 
 to the north at an angle of forty- 
 five degrees. The strike, or line 
 of bearing, is the prolongation or extension of the strata in a direction 
 at right angles to the dip ; and hence it is sometimes called the di- 
 rection 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 sig- 
 nifying 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 representing 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 directions, has 
 neither dip nor strike. 
 
 It is always important for the geologist, who is endeavouring 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. 
 
 * See plan by M. Chevalier, Burat's D'Aubuisson, torn. ii. p. 334. 
 3 
 
54 
 
 DIP AND STRIKE. 
 
 [Cn. V. 
 
 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 what 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 
 inwards 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 true dip. In the 
 annexed drawing (fig. 69.), we may suppose a headland, one side of 
 
 Fig. 69. 
 
 Apparent horizontality of inclined strata. 
 
 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 would be seen by the person on shore to be at an 
 angle of 40. If, therefore, our observations are confined to a vertical 
 precipice facing in one direction, we must endeavour to find a ledge 
 or portion of the plane of one of the beds projecting beyond the 
 others, in order to ascertain the true dip. 
 
 It is rarely important to determine the angle of inclination with 
 such minuteness as to require the aid of the instrument called a 
 clinometer. We may measure the angle within a few degrees by 
 Fig. 70. standing exactly opposite to a cliff where 
 
 the true dip is exhibited, holding the 
 hands immediately before the eyes, and 
 placing the fingers of one in a perpen- 
 dicular, and of the other in a horizontal 
 position, as in fig. 70. It is thus easy 
 to discover whether the lines of the in- 
 clined beds bisect the angle of 90, formed 
 by the meeting of the hands, so as to give 
 an angle of 45, or whether it would di- 
 vide the space into two equal or unequal 
 portions. The upper dotted line may express a stratum dipping to 
 the north ; but should the beds dip precisely to the opposite point of 
 
CH. V.J 
 
 DIP AND STRIKE. 
 
 55 
 
 the compass as in the lower dotted line, it will be seen that the amount 
 of inclination may still be measured by the hands with equal facility. 
 It has been already seen, in describing the curved strata on the 
 east coast of Scotland, in Forfarshire and Berwickshire, that a series 
 of concave and convex bendings are occasionally repeated several 
 times. These usually form part of a series of parallel waves of 
 strata, which are prolonged in the same direction throughout a con- 
 siderable extent of country. Thus, for example, in the Swiss Jura, 
 that lofty chain of mountains has been proved to consist of many 
 parallel ridges, with intervening longitudinal valleys, as in fig. 71., 
 the ridges being formed by curved fossiliferous strata, 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 along the summits of the ridges, A, B, would be anticlinal 
 lines, and one following the bottom of the adjoining valleys a syn- 
 clinal line. 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 denud- 
 ation, so that the ridges of the beds in the formations a, b, c, come 
 
 Fig. 71. 
 
 Section illustrating the structure of the Swiss Jura. 
 
 Fig. 72. 
 
 Fig. 73. 
 
 Ground plan of the denuded ridge C, fig. 71. 
 
 out to the day, or, as the miners 
 say, crop out, on the sides of a 
 J valley. The ground plan of such 
 1 a denuded ridge as C, as given 
 in a geological map, may be ex- 
 is pressed by the diagram fig. 72., 
 and the cross section of the same 
 by fig. 73. The line D E, fig. 72., 
 is the anticlinal line, on each side 
 
 * See M. Thurmann's work, "Essai rentruy, Paris, 1832," with whom I ex- 
 sur les Soulevemens Jurassiques du For- amined part of these mountains in 1835. 
 
 E 4 
 
56 
 
 OUTCROP OF STRATA. 
 
 [Cn. V. 
 
 Fig. 74. 
 
 of which the dip is in opposite directions, as expressed by the 
 arrows. The emergence of strata at the surface is called by miners 
 their out-crop 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 circles, or ellipses, round a com- 
 mon 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 every 
 point of the compass, constituting what is termed a qua-quaversal 
 dip that is, turning each way. 
 
 There are endless variations in the figures described by the basset- 
 edges of the strata, according to the different inclination of the beds, 
 and the mode in which they happen to have been denuded. One of 
 the simplest rules with which every geologist should be acquainted, 
 relates to the V-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 newest strata will appear at the greatest 
 heights. 
 
 Secondly, if the beds be inclined and intersected by a valley 
 sloping in the same direction, and the dip of the beds be less steep 
 than the slope of the valley, then the V's, as they are often termed 
 by miners, will point upwards (see fig. 74.), those formed by the 
 
 newer beds appearing in 
 a superior position, and 
 extending highest up the 
 valley, as A is seen above 
 B. 
 
 Thirdly, if the dip of 
 the beds be steeper than 
 the slope of the valley, 
 then the V's will point 
 downwards (see fig. 75.), 
 and those formed of the 
 older beds will now appear 
 uppermost, as B appears 
 above A. 
 
 Fourthly, in every case 
 where the strata dip in a 
 contrary direction to the 
 slope of the valley, what- 
 ever be the angle of in- 
 clination, the newer beds 
 will appear the highest, 
 as in the first and second 
 cases. This is shown by 
 the drawing (fig. 76.), 
 which exhibits strata ris- 
 siope oi vaiiey 20, dip of strata 50. ing at an angle of 20, 
 
 Slope of valley 40, dip of strata 20. 
 Fig. 75 
 
CH. V.] ANTICLINAL AND SYNCLINAL LINES. 57 
 
 Fig - 76 - and crossed by a valley, 
 
 which declines in an oppo- 
 site direction at 20.* 
 
 These rules may often 
 be of great practical uti- 
 lity ; for the different de- 
 .20' grees of dip occurring in 
 the two cases represented 
 in figures 74 and 75. may 
 occasionally be encoun- 
 tered in following the same 
 line of flexure at points 
 a few miles distant from 
 
 lope of valley ** dip of strata 2CP, in opposite directions. 
 
 acquainted with the rule, who had first explored the valley (fig. 
 74.), may have sunk a vertical shaft below the coal seam A, until 
 he reached the inferior bed B. He might then pass to the valley 
 fig. 75., and discovering there also the outcrop of two coal seams, 
 might begin his workings in the uppermost in the expectation of 
 coming down to the other bed A, which would be observed cropping 
 out lower down the valley. But a glance at the section will demon- 
 strate the futility of such hopes. 
 
 In the majority of cases, an anticlinal axis forms a ridge, and a 
 
 synclinal axis a valley, as in A, B, fig. 62. p. 48. ; but there are 
 
 Fig. 77. exceptions to this rule, the beds sometimes 
 
 sloping inwards from either side of a moun- 
 
 tain, as in fig. 77. 
 On following one of the anticlinal ridges 
 
 of the Jura, before mentioned, A, B, C, fig. 
 
 71., we often discover longitudinal cracks 
 
 and sometimes large fissures along the line 
 where the flexure was greatest. Some of these, as above stated, 
 have been enlarged by denudation into valleys of considerable width, 
 as at C, fig. 71., which follow the line of strike, and which we may 
 suppose to have been hollowed out at the time when these rocks were 
 still beneath the level of the sea, or perhaps at the period of their 
 gradual emergence from beneath the waters. The existence of such 
 cracks at the point of the sharpest bending of solid strata of limestone 
 is precisely what we should have expected ; but the occasional 
 want of all similar signs of fracture, even where the strain has been 
 greatest, as at a, fig. 71., is not always easy to explain. We must 
 imagine that many strata of limestone, chert, and other rocks which 
 are now brittle, were pliant when bent into their present position. 
 
 * I am indebted to the kindness of originals, turning them about in different 
 
 T. Sopwith, Esq., for three models which ways, he would at once comprehend their 
 
 I have copied in the above diagrams ; meaning as well as the import of others 
 
 but the beginner may find it by no means far more complicated, which the same 
 
 easy to understand such copies, although, engineer has constructed to illustrate 
 
 if he were to examine and handle the faults, 
 
58 
 
 REVERSED DIP OP STRATA. 
 
 [Cn. V. 
 
 They may have owed their flexibility in part to the fluid matter 
 which they contained in their minute pores, as before described 
 (p. 35.), and in part to the permeation of sea-water while they were 
 yet submerged. 
 
 At the western extremity of the Pyrenees, great curvatures of the 
 strata are seen in the sea cliffs, where the rocks consist of marl, grit, 
 and chert. At certain points, as at a, fig. 78., some of the bendings 
 
 Fig. 78. 
 
 Strata of chert, grit, and marl, near St. Jean de Luz. 
 
 of the flinty chert are so sharp, that specimens might be broken off, 
 well fitted to serve as ridge-tiles on the roof of a house. Although 
 this chert could not have been brittle as now, when first folded into 
 this shape, it presents, nevertheless, here and there at the points of 
 greatest flexure small cracks, which show that it was solid, and not 
 wholly incapable of breaking at the period of its displacement. The 
 numerous rents alluded to are not empty, but filled with calcedony 
 and quartz. 
 
 Between San Caterina and Castrogiovanni, in Sicily, bent and 
 undulating gypseous marls occur, with here and there thin beds of 
 Fig . 79. solid gypsum interstratified. Sometimes 
 
 these solid layers have been broken into 
 detached fragments, still preserving their 
 sharp edges (<g g, fig. 79.), while the con- 
 tinuity of the more pliable and ductile 
 marls, m m, has not been interrupted. 
 
 I shall conclude my remarks on bent 
 strata by stating, that, in mountainous 
 
 g . gypsum. i. marl. regions like the Alps, it is often difficult 
 
 for an experienced geologist to determine correctly the relative age 
 of beds by superposition, so often have the strata been folded back 
 upon themselves, the upper parts of the curve having been removed 
 by denudation. Thus, if we met with the strata seen in the section 
 fig. 80., we should naturally suppose that there were twelve distinct 
 
 Fig. 80. 
 
 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 beds, which have 
 been folded in the manner seen in 
 fig. 81., so that each of them is twice repeated, 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 
 often observable on a magnificent scale in certain regions in Switzer- 
 land in precipices from 2000 to 3000 feet in perpendicular height. 
 
CH. V.] 
 
 CURVED STRATA IN THE ALPS. 
 
 Fig. 81. 
 
 59 
 
 \\\\\\\\\\\ 
 
 In the Iselten Alp, in the valley of the Lutschine, between Unterseen 
 and Grindelwald, curves of calcareous shale are seen from 1000 to 
 1500 feet in height, in which the beds sometimes plunge down ver- 
 tically for a depth of 1000 feet and more, before they bend round 
 
 Fig. 82. 
 
 Curved strata of the Iselten Alp. 
 
 again. There are many flexures not inferior in dimensions in the 
 Pyrenees, as those near Gavarnie, at the base of Mont Perdu. 
 
 Unconformable stratification. Strata are said to be unconform- 
 able, when one series is so placed over another, that the planes of the 
 superior repose on the edges of the inferior (see fig. 83.). In this 
 
 Fig. 83. 
 
 Unconformabie junction of old red sandstone and Silurian schist at the Siccar Point, near St. Abb's 
 Head, Berwickshire. See also Frontispiece. 
 
 case it is evident that a period had elapsed between the production 
 of the two sets of strata, and that, during this interval, the older 
 
60 UNCONFORMABLE STRATIFICATION. [Cn. V. 
 
 series had been tilted and disturbed. Afterwards the upper series 
 was thrown down in horizontal strata upon it. If these superior 
 beds, as d, d, fig. 83., are also inclined, it is plain that the lower 
 strata, a, a, have been twice displaced ; first, before the deposition of 
 the newer beds, d, d, and a second time when these same strata were 
 thrown out of the horizontal position. 
 
 Playfair has remarked * that this kind of junction which we now 
 call unconformable had been described before the time of Hutton, 
 but that he was the first geologist who appreciated its importance, as 
 illustrating the high antiquity and great revolutions of the globe. 
 He had observed that where such contacts occur, the lowest beds of 
 the newer series very generally consist of a breccia or conglomerate 
 consisting of angular and rounded fragments, derived from the break- 
 ing up of the more ancient rocks. On one occasion the Scotch 
 geologist took his two distinguished pupils, Playfair and Sir James 
 Hall, to the cliffs on the east coast of Scotland, near the village of 
 Eyemouth, not far from St. Abb's Head, where the schists of the 
 Lammermuir range are undermined and dissected by the sea. Here 
 the curved and vertical strata, now known to be of Silurian age, and 
 which often exhibit a ripple-marked surface, are well exposed at 
 the headland called the Siccar Point, penetrating with their edges 
 into the incumbent beds of slightly inclined sandstone, in which large 
 pieces of the schist, some round and others angular, are united by an 
 arenaceous cement. "What clearer evidence," exclaims Playfair, 
 " could we have had of the different formation of these rocks, and of 
 the long interval which separated their formation, had we actually 
 seen them emerging from the bosom of the deep ? We felt ourselves 
 necessarily carried back to the time when the schistus on which we 
 stood was yet at the bottom of the sea, and when the sandstone before 
 us was only beginning to be deposited in the shape of sand or mud, 
 from the waters of a superincumbent ocean. An epoch still more 
 remote presented itself, when even the most ancient of these rocks, 
 instead of standing upright in vertical beds, lay in horizontal planes 
 at the bottom of the sea, and was not yet disturbed by that immea- 
 surable force which has burst asunder the solid pavement of the 
 globe. Revolutions still more remote appeared in the distance of 
 this extraordinary perspective. The mind seemed to grow giddy by 
 looking so far into the abyss of time ; and while we listened with 
 earnestness and admiration to the philosopher who was now unfold- 
 ing to us the order and series of these wonderful events, we became 
 sensible how much farther reason may sometimes go than imagina- 
 tion can venture to follow." f 
 
 In the frontispiece of this volume the reader will see a view of this 
 classical spot, reduced from a large picture, faithfully drawn and 
 coloured from nature by the youngest son of the late Sir James Hall. 
 It was impossible, however, to do justice to the original sketch, in an 
 
 * Biographical account of Dr. Hutton. 
 
 f Playfair, ibid.; see his Works, Edin. 1822, vol. ir. p. 81. 
 
FISSUKES IN STRATA. 
 
 61 
 
 CH. V.] 
 
 engraving, as the contrast of the red sandstone and the light fawn- 
 coloured vertical schists could not be expressed. From the point of 
 view here selected, the underlying beds of the perpendicular schist, a, 
 are visible at b through a small opening in the fractured beds of the 
 covering of red sandstone, d d, while on the vertical face of the old 
 schist at a' a" a conspicuous ripple-mark is displayed. 
 
 It often happens that in the interval between the deposition of two 
 sets of un conformable strata, the inferior rock has not only been 
 denuded, but drilled by perforating shells. Thus, for example, at 
 Autreppe and Gusigny, near Mons, beds of an ancient (primary or 
 
 Fig. 84. 
 
 Junction of unconformable strata near Mons, in Belgium. 
 
 paleozoic) limestone, highly inclined, and often bent, are covered with 
 horizontal strata 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, , in which are rounded 
 fragments of stone, from an inch to two feet in diameter. These frag- 
 ments have often adhering shells attached to them, and have been 
 bored by perforating mollusca. The solid surface of the inferior 
 limestone has also been bored, so as to exhibit cylindrical and pear- 
 shaped cavities, as at c, the work of saxicavous mollusca; and many 
 rents, as at b> which descend several feet or yards into the limestone, 
 have been filled with sand and shells, similar to those in the stratum a. 
 
 Fractures of the strata and faults. Numerous rents may often be 
 seen in rocks which appear to have been simply broken, the sepa- 
 rated parts remaining in the same places ; but we often find a fissure, 
 several inches or yards wide, intervening between the disunited por- 
 tions. These fissures are usually filled with fine earth and sand, or 
 with angular fragments of stone, evidently derived from the fracture 
 of the contiguous rocks. 
 
 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 shift, slip, or fault. " The miner," says Playfair, describing a 
 fault, " is often perplexed, in his subterraneous journey, by a derange- 
 ment in the strata, which changes at once all those 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. 85. , 
 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 particular direction along the 
 face of the others. In this motion they have sometimes preserved 
 their parallelism, as in fig. 85., so that the strata on each side of the 
 
62 
 
 FAULTS. 
 
 Fig. 85. 
 
 [Cn. V. 
 
 \ 
 
 B D 
 
 Faults. A B perpendicular, C D oblique to the horizon. 
 
 faults A B, C D, continue parallel to one another ; in other cases, the 
 strata on each side are inclined, as in , b, c, d (fig. 86.), though 
 
 Fig. 86. 
 
 E F, fault or fissure filled with rubbish, on each side of which the shifted 
 strata are not parallel. 
 
 their identity is still to be recognized by their possessing the same 
 thickness and the same internal characters."* 
 
 In Coalbrook Dale, says Mr. Prestwich f, deposits of sandstone, 
 shale, and coal, several thousand feet thick, and occupying an area 
 of many miles, have been shivered into fragments, and the broken 
 remnants have been placed in very discordant positions, often at 
 levels differing several hundred feet from each other. The sides of 
 the faults, when perpendicular, are commonly separated several yards, 
 but are sometimes as much as 50 yards asunder, the interval being 
 filled with broken debris of the strata. In following the 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 700 feet, which arises, in some cases, from the 
 union of two or more faults. In other words, the disjointed strata 
 have in certain districts been subjected to renewed movements, which 
 they have not suffered 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 shrinking 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 earthquakes ; 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. 
 
 * Playfair, Blust. of Hutt. Theory, 
 42. 
 
 t Geol. Trans, second series, vol. v. 
 p. 452. 
 
CH. V.] 
 
 FAULTS. 
 
 63 
 
 I have already stated that a geologist must be on his guard, in a 
 region of disturbed strata, against inferring repeated alternations of 
 rocks, when, in fact, the same strata, once continuous, have been 
 bent round so as to recur 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. 87.) represent the surface 
 of a country on which the strata a b c frequently crop out, an observer, 
 
 Fig. 87. 
 
 II 
 
 Apparent alternations of strata caused by vertical faults. 
 
 who is proceeding from H to A, might at first imagine that 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 uniformly 
 inclined strata, and that the different masses under E F, F G, and 
 G D, sank down successively, so as to leave vacant the spaces marked 
 in the diagram by dotted lines, and to occupy those marked by the 
 continuous lines, then let denudation take place along the line A H, 
 so that the protruding 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 repeated, 
 might hope to find four beds, workable to an indefinite depth, but 
 first on arriving at the fault G he is stopped suddenly in his workings, 
 upon reaching the strata of sandstone c, or on arriving at the line of 
 fault F he comes partly upon the shale b, and partly on the sandstone 
 c, 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 different sides of the fissure, 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 
 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 
 
 * Conybeare and Phillips, Outlines, &c. p. 376. 
 
64 ORIGIN OF GEEAT FAULTS. [Cn. V. 
 
 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.* In the Tynedale and Craven faults, in the north of England, 
 the vertical displacement is still greater, and the fracture has ex- 
 tended in a horizontal direction for a distance of thirty miles or more. 
 Some geologists consider it necessary to imagine that the upward or 
 downward movement in these cases was accomplished at a single 
 stroke, and not by a series of sudden but interrupted movements. 
 This idea appears to have been derived from a notion that the grooved 
 walls have merely been rubbed in one direction. But this is so far 
 from being a constant phenomenon in faults, that it has often been 
 objected to the received theory respecting those polished surfaces 
 called " slickensides " that the striae are not always parallel, but 
 often curved and irregular. It has, moreover, been remarked, that 
 not only the walls of the fissure or fault, but its earthy contents, 
 sometimes present the same polished and striated faces. Now 
 these facts seem to indicate partial changes in the direction of the 
 movement, and some slidings subsequent to the first filling up of 
 the fissure. Suppose the mass of rock A, B, C, to overlie an ex- 
 tensive chasm d e, formed at the depth of several miles, whether by 
 
 Fig. 88. 
 ABC 
 
 the gradual contraction in bulk of a melted mass passing into a solid 
 or crystalline state, or the shrinking of argillaceous strata, baked by a 
 moderate heat, or by the subtraction of matter by volcanic action, or 
 any other cause. Now, if this region be convulsed by earthquakes, 
 the fissures f g, and others at right angles to them, may sever the 
 mass B from A and from C, so that it may move freely, and begin 
 to sink into the chasm. A fracture may be conceived so clean and 
 perfect as to allow it to subside at once to the bottom of the subter- 
 ranean cavity ; but it is far more probable that the sinking will be 
 effected at successive periods during different earthquakes, the mass 
 always continuing to slide in the same direction along the planes of 
 the fissures fg, and the edges of the falling mass being continually 
 more broken and triturated at each convulsion. If, as is not im- 
 probable, the circumstances which have caused the failure of support 
 continue in operation, it may happen that when the mass B has filled 
 the cavity first formed, its foundations will again give way under it, 
 so that it will fall again in the same direction. But, if the direction 
 should change, the fact could not be discovered by observing the 
 slickensides, because the last scoring would efface the lines of pre- 
 vious friction. In the present state of our ignorance of the causes 
 of subsidence, an hypothesis which can explain the great amount of 
 displacement in some faults, on sound mechanical principles, by a 
 * Phillips, Geology, Lardner's Cyclop, p. 4 1. 
 
CH. V.] ORIGIN OF GREAT FAULTS. 65 
 
 succession of movements, is far preferable to any theory which as- 
 sumes 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 progress, 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 below their former level, some slowly and in- 
 sensibly, others suddenly and by starts, a few feet or yards at a time ; 
 whereas 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. When some of the ancient marine formations are 
 described in the sequel, it will appear that their structure and organic 
 contents point to the conclusion, that the floor of the ocean was slowly 
 sinking at the time of their origin. The downward movement was 
 very gradual, and in Wales and the contiguous parts of England a 
 maximum thickness of 32,000 feet (more than six miles) of Carbon- 
 iferous, Devonian, and Silurian rock was formed, whilst the bed of the 
 sea was all the time continuously and tranquilly subsiding. * What- 
 ever may have been the changes which the solid foundation underwent, 
 whether accompanied by the melting, consolidation, crystallization, 
 or desiccation of subjacent mineral matter, it is clear from the fact 
 of the sea having remained shallow all the while that the bottom 
 never sank down suddenly to the depth of many hundred feet at 
 once. 
 
 It is by assuming such reiterated variations of level, each separately 
 of small vertical amount, but multiplied by time till they acquire im- 
 portance in the aggregate, that we are able to explain the phenomena 
 of denudation, which will be treated of in the next chapter. By such 
 movements, every portion of the surface of the land becomes in its 
 turn a line of coast, and is exposed to the action of the waves and 
 tides. A country which is undergoing such movement is never 
 allowed to settle into a state of equilibrium, therefore the force of 
 rivers and torrents to remove or excavate soil and rocky masses is 
 sustained in undiminished energy. 
 
 * See the results of the " Geological Survey of Great Britain ; " Memoirs, vols. L 
 and ii., by Sir H. De la Beche, Mr. A. C. Eamsay, and Mr. John Phillips. 
 
60 DENUDATION OF KOCKS. [Cn. VI. 
 
 CHAPTER VI. 
 
 DENUDATION. 
 
 Denudation defined Its amount equal to the entire mass of stratified deposits in 
 the earth's crust Horizontal sandstone denuded in Eoss-shire Levelled surface 
 of countries in which great faults occur Coalbrook Dale Denuding power of 
 the ocean during the emergence of land Origin of Valleys Obliteration of sea- 
 cliffs Inland sea-cliffs and terraces in the Morea and Sicily Limestone pillars 
 at St. Mihiel, in France in Canada in the Bermudas. 
 
 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 lay- 
 ing bare of some inferior rock. Geologists have perhaps been seldom 
 in the habit of reflecting that 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 inseparable ac- 
 companiment of the production of all new strata of mechanical origin. 
 The formation of every new deposit by the transport of sediment and 
 pebbles necessarily implies that there has been, somewhere else, a 
 grinding down of rock into rounded fragments, sand, or mud, equal in 
 quantity to the new strata. All deposition, therefore, except in the case 
 of a shower of volcanic ashes, is the sign of superficial waste going on 
 contemporaneously, and to an equal amount elsewhere. The gain at 
 one point is no more than sufficient to balance the loss at some other. 
 Here a lake has grown shallower, there a ravine has been deepened. 
 The bed of the sea has in one region been raised by the accumulation 
 of new matter, in another its depth has been augmented by the 
 abstraction of an equal quantity. 
 
 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 
 may be compared to successive strata, the quarry to a ravine or valley 
 which has suffered denudation. As the strata, like the courses of 
 hewn stone, have been laid one upon another gradually, so the ex- 
 cavation both of the valley and quarry have been gradual. To pursue 
 the comparison still farther, the superficial heaps of mud, sand, and 
 gravel, usually called alluvium, may be likened to the rubbish 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. 
 
 If, then, the entire mass of stratified deposits in the earth's crust 
 is at once the monument and measure of the denudation which has 
 taken place, on how stupendous a scale ought we to find the signs of 
 this removal of transported materials in past ages ! Accordingly, 
 there are different classes of phenomena, which attest in a most 
 
Ce. VI.] DENUDATION OF STRATIFIED ROCKS. 67 
 
 striking manner the vast spaces left vacant by the erosive power of 
 water. I may allude, 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 formations, as Nos. 1, 2, 3, 4, in the 
 Fig. 89. accompanying diagram (fig. 89.); No. 1. 
 
 conglomerate, 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 subordi- 
 
 vIueysofdTnudltionT ^ nate P arts of these four formations, we 
 a. aiiuvmm. fij^ j n jj^g manner, distinct beds in each, 
 
 corresponding, on the opposite sides of the valleys, both in compo- 
 sition and order of position. No one can doubt that the strata were 
 originally continuous, and that some cause has swept away the por- 
 tions 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, corre 
 spending 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, of which a grand exemplification 
 is described by Dr. Macculloch, on the north-western coast of Ross- 
 shire in Scotland.* 
 
 Fig. 90. 
 Suil Veinn. Coul beg. Coul more. 
 
 Denudation of red sandstone on north-west coast of Ross-shire. (Macculloch.) 
 
 The fundamental rock of that country is gneiss, in disturbed strata, 
 on which beds of nearly horizontal red sandstone rest unconformably. 
 The latter are often very thin, forming mere flags, with their surfaces, 
 distinctly ripple-marked. They end abruptly on the declivities of 
 many insulated mountains, which rise up at once to the height of 
 about 2000 feet above the gneiss of the surrounding plain or table 
 land, and to an average elevation of about 3000 feet above the sea, 
 which all their summits generally attain. The base of gneiss varies 
 in height, so that the lower portions of the sandstone occupy different 
 levels, and the thickness of the mass is various, sometimes exceeding 
 3000 feet. It is impossible to compare these scattered and detached 
 portions without imagining that the whole country has once been 
 covered with a great body of sandstone, and that masses from 1000 
 to more than 3000 feet in thickness have been removed. 
 
 In the " Survey of Great Britain " (vol. i.), Professor Ramsay 
 has shown that the missing beds, removed from the summit of the 
 Mendips, must have been nearly a mile in thickness ; and he has 
 pointed out considerable areas in South Wales and some of the ad- 
 
 * Western Islands, vol. ii. p. 93. pi. 31. fig. 4. 
 F 2 
 
68 DENUDATION [Cn. VI. 
 
 jacent counties of England, where a series of primary (or palaeozoic) 
 strata, not less than 11,000 feet in thickness, have been stripped off. 
 All these materials have of course been transported to new regions, 
 and have entered into the composition of more modern formations. On 
 the other hand, it is shown by 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 
 consolidated, 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 repeatedly impressed on the student's mind, 
 because in many geological speculations it is taken for granted that 
 the external 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 deposits of mechanical origin imply the trans- 
 portation from some other region, whether contiguous or remote, of 
 an equal amount of solid matter, we perceive that the stony exterior 
 of the planet must always have grown thinner in one place, whenever, 
 by accessions of new strata, it was acquiring density in another. No 
 doubt the vacant space left by the missing rocks, after extensive 
 denudation, is less imposing to the imagination than a vast thickness 
 of conglomerate or sandstone, or the bodily presence as it were of a 
 mountain-chain, with all its inclined and curved strata. But the 
 denuded tracts speak a clear and emphatic language to our reason, 
 and, like repeated layers of fossil nummulites, corals or shells, or 
 like numerous seams of coal, each based on its under-clay full of the 
 roots of trees, still remaining in their natural position, demand an 
 indefinite lapse of time for their elaboration. 
 
 No one will maintain that the fossils entombed in these rocks did 
 not belong to many successive generations of plants and animals. 
 In like manner, each sedimentary deposit attests a slow and gradual 
 action, and the strata not only serve as a measure of the amount 
 of denudation simultaneously effected elsewhere, but are also a cor- 
 rect indication of the rate at which the denuding operation was 
 carried on. 
 
 Perhaps the most convincing evidence of denudation on a mag- 
 nificent scale is derived from the levelled surfaces of districts where 
 large faults occur. I have shown, in fig. 87. p. 63., and in fig. 91., 
 how angular and protruding masses of rock might naturally have 
 been looked for on the surface immediately above great faults, al- 
 though in fact they rarely exist. This phenomenon may be well 
 studied in those districts where coal has been extensively worked, for 
 there the former relation of the beds which have shifted their position 
 may be determined with great accuracy. Thus in the coal field of 
 Ashby de la Zouch, in Leicestershire (see fig. 91.), a fault occurs, on 
 one side of which the coal beds abed rise to the height of 500 feet 
 
Cn. VI.] 
 
 OF STRATIFIED ROCKS. 
 
 Fig. 91. 
 
 69 
 
 Faults and denuded coal strata, Ashby de la Zouch. (Mammatt.) 
 
 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 z z, is 
 uniformly undulating without any break, and the mass indicated by 
 the dotted outline must have been washed away.* There are proofs 
 of this kind in some level countries, where dense masses of strata 
 have been cleared away from areas several hundred square miles in 
 extent. 
 
 In the Newcastle coal district it is ascertained that faults occur in 
 which the upward or downward movement could not have been less 
 than 140 fathoms, which, had they affected the configuration of the 
 surface to an equal amount, would produce mountains with pre- 
 cipitous escarpments nearly 1000 feet high, or chasms of the like 
 depth ; yet is the actual level of the country absolutely uniform, 
 affording no trace whatever of subterranean movements.! 
 
 The ground from which these materials have been removed is 
 usually overspread with heaps of sand and gravel, formed out of the 
 ruins of the very rocks which have disappeared. Thus, in the dis- 
 tricts above referred to, they consist of roun4ed and angular frag- 
 ments of hard sandstone, limestone, and ironstone, with a small 
 quantity of the more destructible shale, and even rounded pieces of 
 coal. 
 
 Allusion has been already made to the shattered state and dis- 
 cordant position of the carboniferous strata in Coalbrook Dale 
 (p. 62.), The collier cannot proceed three or four yards without 
 meeting with small slips, and from time to time he encounters faults 
 of considerable magnitude, which have thrown the rocks up or 
 down several hundred feet. Yet the superficial inequalities to which 
 these dislocated masses originally gave rise are no longer discernible, 
 and the comparative flatness of the existing surface can only be 
 explained, as Mr. Prestwich has observed, by supposing the frac- 
 tured portions to have been removed by water. It is also clear that 
 strata of red sandstone, more than 1000 feet thick, which once 
 covered the coal, in the same region, have been carried away from 
 large areas. That water has, in this case, been the denuding agent, 
 we may infer from the fact that the rocks have yielded according to 
 
 * See Mammat's Geological Facts, &c. f Conybeare's Report to B.it. Assoc. 
 p. 90. and plate. 1842, p. 381. 
 
 F 3 
 
70 ORIGIN OF VALLEYS. [Cn. VI. 
 
 their different degrees of hardness ; the hard trap of the Wrekin, for 
 example, and other hills, having resisted more than the softer shale 
 and sandstone, so as now to stand out in bold relief.* 
 
 Origin of valleys. Many of the earlier geologists, and Dr. Hutton 
 among them, taught that " rivers have in general hollowed out their 
 valleys." This is no doubt true of rivulets and torrents which are 
 the feeders of the larger streams, and which, descending over rapid 
 slopes, are most subject to temporary increase and diminution in the 
 volume of their waters. It must also be admitted that the quantity 
 of mud, sand, and pebbles constituting many a modern delta is so 
 considerable as to prove that a very large part of the inequalities now 
 existing on the earth's surface are due to fluviatile action ; but 
 the principal valleys in almost every great hydrographical basin in 
 the world, are of a shape and magnitude which imply that they 
 have been due to other causes besides the mere excavating power of 
 rivers. 
 
 Some geologists have imagined that a deluge, or succession of 
 deluges, may have been the chief denuding agency, and they have 
 speculated on a series of enormous waves raised by the instantaneous 
 upthrow of continents or mountain chains out of the sea. But even 
 were we disposed to grant such sudden upheavals of the floor of the 
 ocean, and to assume that great waves would be the consequence of 
 each convulsion, it is not easy to explain the observed phenomena by 
 the aid of so gratuitous an hypothesis. 
 
 On the other hand, a machinery of a totally different kind seems 
 capable of giving rise to effects of the required magnitude. It has 
 now been ascertained that the rising and sinking of extensive por- 
 tions of the earth's crust, whether insensibly or by a repetition of 
 sudden shocks, is part of the actual course of nature, and we may 
 easily comprehend how the land may have been exposed during these 
 movements to abrasion by the waves of the sea. In the same 
 manner as a mountain mass may, in the course of ages, be formed 
 by sedimentary deposition, layer after layer, so masses equally 
 voluminous may in time waste away by inches ; as, for example, if 
 beds of incoherent materials are raised slowly in an open sea where 
 a strong current prevails. It is well known that some of these 
 oceanic currents have a breadth of 200 miles, and that they some- 
 times run for a thousand miles or more in one direction, retaining a 
 considerable velocity even at the depth of several hundred feet. 
 Under these circumstances, the flowing waters may have power to 
 clear away each stratum of incoherent materials as it rises and 
 approaches the surface, where the waves exert the greatest force ; 
 and in this manner a voluminous deposit may be entirely swept 
 away, so that, in the absence of faults, no evidence may remain of 
 the denuding operation. It may indeed be affirmed that the signs of 
 waste will usually be least obvious where the destruction has been 
 most complete ; for the annihilation may have proceeded so far, that 
 no ruins are left of the dilapidated rocks. 
 
 * Prestwich, Geol. Trans, second series, vol. v. pp. 452. 473. 
 
CH. VI.] INLAND SEA-CLIFFS. 71 
 
 Although denudation has had a levelling influence on some 
 countries of shattered and disturbed strata (see fig. 87. p. 63. and 
 fig. 91. p. 69.), it has more commonly been the cause of superficial 
 inequalities, especially in regions of horizontal stratification. The 
 general outline of these regions is that of flat and level platforms, 
 interrupted by valleys often of considerable depth, and ramifying 
 in various' directions. These hollows may once have formed bays 
 and channels between islands, and the steepest slope on the sides of 
 each valley may have been a sea-cliff, which was undermined for 
 ages, as the land emerged gradually from the deep. We may 
 suppose the position and course of each valley to have been originally 
 determined by differences in the hardness of the rocks, and by rents 
 and joints which usually occur even in horizontal strata. In moun- 
 tain chains, such as the Jura before described (see fig. 71. p. 55.), 
 we perceive at once that the principal valleys have not been due to 
 aqueous excavation, but to those mechanical movements which have 
 bent the rocks into their present form. Yet even in the Jura there 
 are many valleys, such as C (fig. 71.), which have been hollowed out 
 by water ; and it may be stated that in every part of the globe the 
 unevenness of the surface of the land has been due to the combined 
 influence of subterranean movements and denudation. 
 
 I may now recapitulate a few of the conclusions to which we have 
 arrived: first, all the mechanical strata have been accumulated 
 gradually, and the concomitant denudation has been no less gradual : 
 secondly, the dry land consists in great part of strata formed origin- 
 ally at the bottom of the sea, and has been made to emerge and 
 attain its present height by a force acting from beneath : thirdly, no 
 combination of causes has yet been conceived so capable of producing 
 extensive and gradual denudation, as the action of the waves and 
 currents of the ocean upon land slowly rising out of the deep. 
 
 Now, if we adopt these conclusions, we shall naturally be led to 
 look everywhere for marks of the former residence of the sea upon 
 the land, especially near the coasts from which the last retreat of the 
 waters took place, and it will be found that such signs are not 
 wanting. 
 
 I shall have occasion to speak of ancient sea-cliffs, now far inland, 
 in the south-east of England, when treating in Chapter XIX. of the 
 denudation of the chalk in Surrey, Kent, and Sussex. Lines of 
 upraised sea-beaches of more modern date are traced, at various 
 levels from 20 to 100 feet and upwards above the present sea-level, 
 for great distances on the east and west coasts of Scotland, as well as 
 in Devonshire, and other counties in England. These ancient beach- 
 lines often form terraces of sand and gravel, including littoral shells, 
 some broken, others entire, and corresponding with species now 
 living on the adjoining coast. But it would be unreasonable to 
 expect to meet everywhere with the signs of ancient shores, since no 
 geologist can have failed to observe how soon all recent marks of the 
 kind above alluded to are obscured or entirely effaced, wherever, in 
 consequence of the altered state of the tides and currents, the sea has 
 
 F 4 
 
72 INLAND SEA-CLIFFS. [Cn. VI. 
 
 receded for a few centuries. We see the cliffs crumble down in a 
 few years if composed of sand or clay, and soon reduced to a gentle 
 slope. If there were shells on the beach, they decompose, and their 
 materials are washed away, after which the sand and shingle may 
 resemble any other alluviums scattered over the interior. 
 
 The features of an ancient shore may sometimes be concealed by 
 the growth of trees and shrubs, or by a covering of blown sand, a 
 good example of which occurs a few miles west from Dax, near 
 Bourdeaux, in the south of France. About twelve miles inland, a 
 steep bank may be traced running in a direction nearly north-east 
 and south-west, or parallel to the contiguous coast. This sudden 
 fall of about 50 feet conducts us from the higher platform of the 
 Landes to a lower plain which extends to the sea. The outline of 
 
 Fig. 92. 
 
 Section of inland cliff at Abesse, near Dax. 
 a. Sand of the Landes. b. Limestone. c. Clay. 
 
 the ground suggested to me, as it would do to every geologist, the 
 opinion that the bank in question was once a sea-cliff, when the 
 whole country stood at a lower level. But this is no longer matter 
 of conjecture, for, in making excavations in 1830 for the foundation 
 of a building at Abesse, a quantity of loose sand, which formed the 
 slope d e. was removed ; and a perpendicular cliff, about 50 feet in 
 height, which had hitherto been protected from the agency of the 
 elements, was exposed. At the bottom appeared the limestone , 
 containing tertiary shells and corals, immediately below it the clay c, 
 and above it the usual tertiary sand a, of the department of the 
 Landes. At the base of the precipice were seen large partially 
 rounded masses of rock, evidently detached from the stratum b. 
 The face of the limestone was hollowed out and weathered into such 
 forms as are seen in the calcareous cliffs of the adjoining coast, 
 especially at Biaritz, near Bayonne. It is evident that, when this 
 country stood at a somewhat lower level, the sea advanced along the 
 surface of the argillaceous stratum c, which, from its yielding nature, 
 favoured the waste by allowing the more solid superincumbent stone 
 b to be readily undermined. Afterwards, when the country had 
 been elevated, part of the sand, a, fell down, or was drifted by the 
 winds, so as to form the talus, de, which masked the inland cliff until 
 it was artificially laid open to view. 
 
 When we are considering the various causes which, in the course 
 of ages, may efface the characters of an ancient sea-coast, earth- 
 quakes must not be forgotten. During violent shocks, steep and 
 overhanging cliffs are often thrown down and become a heap of 
 ruins. Sometimes unequal movements of upheaval or depression 
 
CH. VI.] INLAND SEA- CLIFFS AND TERRACES. 73 
 
 entirely destroy that horizontality of the base-line which constitutes 
 the chief peculiarity of an ancient sea-cliff. 
 
 It is, however, in countries where hard limestone rocks abound, 
 that inland cliffs retain faithfully 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 what were once 
 sea-cliffs are well preserved. These have been described, by MM. 
 Boblaye and Virlet, as rising one above the other at different dis- 
 tances from the actual shore, the summit of the highest and oldest 
 occasionally exceeding 1000 feet in elevation. At the base of each 
 there is usually a terrace, which is in some places a few yards, in 
 others above 300 yards wide, so that we are conducted from the high 
 land of the interior to the sea by a succession of great steps. These 
 inland cliffs are most perfect, and most exactly resemble those now 
 washed by the waves of the Mediterranean, where they are formed 
 of calcareous rock, especially if the rock be a hard crystalline marble. 
 The following are the points of correspondence observed between the 
 ancient coast lines and the borders of the present sea: 1. A range 
 of vertical precipices, with a terrace at their base. 2. A weathered 
 state of the surface of the naked rock, such as the spray of the sea 
 produces. 3. A line of littoral caverns at the foot of the cliffs. 4. A 
 consolidated beach or breccia with occasional marine shells, found at 
 the base of the cliffs, or in the caves. 5. Lithodomous perforations. 
 
 In regard to the first of these, it would be superfluous to dwell on 
 the evidence afforded of the undermining power of waves and currents 
 by perpendicular precipices. The littoral caves, also, will be familiar 
 to those who have had opportunities of observing the manner in 
 which the waves of the sea, when they beat against rocks, have 
 power to scoop out caverns. As to the breccia, it is composed of 
 pieces of limestone and rolled fragments of thick solid shell, such as 
 Strombus and Spondylus, all bound together by a crystalline cal- 
 careous cement. Similar aggregations are now forming on the 
 modern beaches of Greece, and in caverns on the sea-side ; and they 
 are only distinguishable in character from those of more ancient 
 date, by including many pieces of pottery. In regard to the litho* 
 domi above alluded to, these bivalve mollusks are well known to 
 have the power of excavating holes in the hardest limestones, the 
 size of the cavity keeping pace with the growth of the shell. When 
 Hying they require to be always covered by salt water, but similar 
 pear-shaped hollows, containing the dead shells of these creatures, 
 are found at different heights on the face of the inland cliffs above 
 mentioned. Thus, for example, they have been observed near Modon 
 and Navarino on cliffs in the interior 125 feet high above the Medi- 
 terranean. As to the weathered surface of the calcareous rocks, all 
 limestones are known to suffer chemical decomposition when moistened 
 by the spray of the salt water, and are corroded still more deeply at 
 points lower down where they are just reached by the breakers. By 
 this action the stone acquires a wrinkled and furrowed outline, and 
 very near the sea it becomes rough and branching, as if covered with 
 
74 INLAND SEA-CLIFFS [Cn. VI. 
 
 corals. Such effects are traced not only on the present shore, but at 
 the base of the ancient cliffs far in the interior. Lastly, it remains 
 only to speak of the terraces, which extend with a gentle slope from 
 the base of almost all the inland cliffs, and are for the most part 
 narrow where the rock is hard, but sometimes half a mile or more in 
 breadth where it is soft. They are the effects of the encroachment 
 of the ancient sea upon the shore at those levels at which the land 
 remained for a long time stationary. The justness of this view is 
 apparent on examining the shape of the modern shore wherever the 
 sea is advancing upon the land, and removing annually small 
 portions of undermined rock. By this agency a submarine platform 
 is produced on which we may walk for some distance from the beach 
 in shallow water, the increase of depth being very gradual, until we 
 reach a point where the bottom plunges down suddenly. This plat- 
 form is widened with more or less rapidity according to the hardness 
 of the rocks, and when upraised it constitutes an inland terrace. 
 
 But the four principal lines of cliff observed in the Morea do not 
 imply, as some have imagined, four great eras of sudden upheaval ; 
 they simply indicate the intermittence of the upheaving force. Had 
 the rise of the land been continuous and uninterrupted, there would 
 have been no one prominent line of cliff; for every portion of the 
 surface having been, in its turn, and for an equal period of time, a 
 sea-shore, would have presented a nearly similar aspect. But if 
 pauses occur in the process of upheaval, the waves and currents have 
 time to sap, throw down, and clear away considerable masses of rock, 
 and to shape out at several successive levels lofty ranges of cliffs 
 with broad terraces at their base. 
 
 There are some levelled spaces, however, both ancient and modern, 
 in the Morea, which are not due to denudation, although resembling 
 in outline the terraces above described. They may be called Terraces 
 of Deposition, since they have resulted from the gain of land upon 
 the sea where rivers and torrents have produced deltas. If the sedi- 
 mentary matter has filled up a bay or gulf surrounded by steep 
 mountains, a flat plain is formed skirting the inland precipices ; and 
 if these deposits are upraised, they form a feature in the landscape 
 very similar to the areas of denudation before described. 
 
 In the island of Sicily I have examined many inland cliffs like 
 those of the Morea ; as, for example, near Palermo, where a precipice 
 is seen consisting of limestone at the base of which are numerous 
 caves. One of these, called San Giro, about 2 miles distant from 
 Palermo, is about 20 feet high, 10 wide, and 180 above the sea. 
 Within it is found an ancient beach (b, fig. 93.), formed of pebbles 
 of various rocks, many of which must have come from places far 
 remote. Broken pieces of coral and shell, especially of oysters and 
 pectens, are seen intermingled with the pebbles. Immediately above 
 the level of this beach, serpulce are still found adhering to the face of 
 the rock, and the limestone is perforated by lithodomi. Within the 
 grotto, also, at the same level, similar perforations occur; and so 
 numerous are the holes, that the rock is compared by Hoffmann to a 
 
CH. VI.]- IN THE ISLAND OF SICILY. 75 
 
 target pierced by musket balls. But in order to expose to view these 
 
 Fig. 93. 
 
 I ' I 
 
 I I, 1 , 1 */. / 
 I 11 1 If// 
 
 ///// //// ^- ^--=-- 
 
 / / //^sr^: 
 
 a. Monte Grifone. ft. Cave of San Giro.* 
 
 c. Plain of Palermo, in which are Newer Pliocene strata of 
 limestone and sand. d. Bay of Palermo. 
 
 marks of boring-shells in the interior of the cave, it was necessary 
 first to remove a mass of breccia, which consisted of numerous frag- 
 ments of rock and an immense quantity of bones of the mammoth, 
 hippopotamus, and other quadrupeds, imbedded in a dark brown cal- 
 careous marl. Many of the bones were rolled as if partially subjected 
 to the action of the waves. Below this breccia, which is about 20 
 feet thick, was found a bed of sand filled with sea-shells of recent 
 species ; and underneath the sand, again, is the secondary limestone 
 of Monte Grifone. The state of the surface of the limestone in the 
 cave above the level of the marine sand is very different from that 
 below it. Above., the rock is jagged and uneven, as is usual in the 
 roofs and sides of limestone caverns ; below., the surface is smooth and 
 polished, as if by the attrition of the waves. 
 
 The platform indicated at c, fig. 93., is formed by a tertiary de- 
 posit containing marine shells almost all of living species, and it 
 affords an illustration of the terrace of deposition, or the last of the 
 two kinds before mentioned (p. 74.). 
 
 There are also numerous instances in Sicily of terraces of denuda- 
 tion. One of these occurs on the east coast to the north of Syracuse, 
 and the same is resumed to the south beyond the town of Noto, where 
 it maybe traced forming a continuous and lofty precipice, a b, fig. 94., 
 facing towards the sea, and constituting the abrupt termination of a cal- 
 careous formation, which extends in horizontal strata far inland. This 
 precipice varies in height from 500 to 700 feet, and between its base 
 and the sea is an inferior platform, c b, consisting of similar white 
 limestone. All the beds dip towards the sea, but are usually inclined 
 at a very slight angle : they are seen to extend uninterruptedly from 
 the base of the escarpment into the platform, showing distinctly that 
 the lofty cliff was not produced by a fault or vertical shift of the 
 beds, but by the removal of a considerable mass of rock. Hence we 
 may conclude that the sea, which is now undermining the cliffs of 
 the Sicilian coast, reached at some former period the base of the pre- 
 cipice a b, at which time the surface of the terrace c b must have 
 
 * Section given by Dr. Christie, Edin. late M. Hoffmann. See account by Mr. 
 New Phil. Journ. No. xxiii., called by S. P. Pratt, F. G. 8., Proceedings of GeoL 
 mistake the Cave of Mardolce, by the Soc. No. 32. 1833. 
 
76 
 
 INLAND SEA-CLIFFS AND 
 
 rig. 94. 
 
 . VI. 
 
 Sea 
 
 been covered by the Mediterranean. There was a pause, therefore, 
 in the upward movement, when the waves of the sea had time to 
 carve out the platform c b ; but there may have been many other 
 stationary periods of minor duration. Suppose, for example, that a 
 series of escarpments e,f, g, h, once existed, and that the sea, during 
 a long interval free from subterranean movements, advances along 
 the line c b, all preceding cliffs must have been swept away one after 
 the other, and reduced to the single precipice a b. 
 
 That such a series of smaller cliffs, as those represented at e, f, g, h, 
 fig. 94., did really once exist at intermediate heights in place of the 
 single precipice a b, is rendered highly probable by the fact, that in 
 certain bays and inland valleys opening towards the east coast of 
 Sicily, and not far from the section given in fig. 94., the solid lime- 
 stone is shaped out into a great succession of ledges, separated from 
 each other by small vertical cliffs. These are sometimes so nume- 
 
 Fig. 95. 
 
 Valley called Gozzo degli Martiri, below Melilli, Val di Noto. 
 
 rous, one above the other, that where there is a bend at the head of a 
 valley, they produce an effect singularly resembling the seats of a 
 Roman amphitheatre. A good example of this configuration occurs 
 near the town of Melilli, as seen in the annexed view (fig. 95.). In 
 the south of the island, near Spaccaforno Scicli, and Modica, preci- 
 
CH. VI.] TERRACES IN SICILY. 77 
 
 pitous rocks of white limestone, ascending to the height of 500 feet, 
 have been carved out into similar forms. 
 
 This appearance of a range of marble seats circling round the 
 head of a valley, or of great flights of steps descending from the top 
 to the bottom, on the opposite sides of a gorge, may be accounted for, 
 as already hinted, by supposing the sea to have stood successively at 
 many different levels, as at a a, b b, c c, in the accompanying fig. 96. 
 But the causes of the gradual contraction of the valley from above 
 
 Fig. 96. 
 
 I 
 
 downwards may still be matter of speculation. Such contraction 
 may be due to the greater force exerted by the waves when the land 
 at its first emergence was smaller in quantity, and more exposed to 
 denudation in an open sea ; whereas the wear and tear of the rocks 
 might diminish in proportion as this action became confined within 
 bays or channels closed in on two or three sides. Or, secondly, the 
 separate movements of elevation may have followed each other more 
 rapidly as the land continued to rise, so that the times of those pauses, 
 during which the greatest denudation was accomplished at certain 
 levels, were always growing shorter. It should be remarked, that 
 the cliffs and small terraces are rarely found on the opposite sides of 
 the Sicilian valleys at heights so precisely answering to each other as 
 those given in fig. 96., and this might have been expected, to which- 
 ever of the two hypotheses above explained we incline ; for, accord- 
 ing to the direction of the prevailing winds and currents, the waves 
 may beat with unequal force on different parts of the shore, so that 
 while no impression is made on one side of a bay, the sea may en- 
 croach so far on the other as to unite several smaller cliffs into one. 
 
 Before quitting the subject of ancient sea-cliffs, carved out of 
 limestone, I shall mention the range of precipitous rocks, composed 
 of a white marble of the Oolitic period, which I hare seen near the 
 northern gate of St. Mihiel in France. They are situated on the 
 right bank of the Meuse, at a distance of 200 miles from the nearest 
 sea, and they present on the precipice facing the river three or four 
 horizontal grooves, one above the other, precisely resembling those 
 which are scooped out by the undermining waves. The summits of 
 several of these masses are detached from the adjoining hill, in 
 which case the grooves pass all round them, facing towards all points 
 of the compass, as if they had once formed rocky islets near the 
 shore.* 
 
 * I was directed by M. Deshayes to this spot, which I visited in June, 1833. 
 
78 
 
 ROCKS WORN BY THE SEA. 
 
 [Cn. VI. 
 
 Captain Bayfield, in his survey of the Gulf of St. Lawrence, dis- 
 covered in several places, especially in the Mingan islands, a coun- 
 terpart of the inland cliffs of St. Mihiel, and traced a succession of 
 shingle beaches, one above the other, which agreed in their level 
 with some of the principal grooves scooped out of the limestone 
 pillars. These beaches consisted of calcareous shingle, with shells of 
 recent species, the farthest from the shore being 60 feet above the 
 level of the highest tides. In addition to the drawings of the pillars 
 called the flower-pots, which he has published*, I have been favoured 
 with other views of rocks on the same coast, drawn by Lieut. A. 
 Bowen, R.N. (See fig. 97.) 
 
 Fig. 97. 
 
 Limestone columns in Niapisca Island, in the Gulf of St. Lawrence. Height 
 01 the second column on the left, 60 feet. 
 
 In the North- American beaches above mentioned rounded frag- 
 ments of limestone have been found perforated by lithodomi; and 
 holes drilled by the same mollusks have been detected in the 
 columnar rocks or "flower-pots," showing that there has been no 
 great amount of atmospheric decomposition on the surface, or the 
 cavities alluded to would have disappeared. 
 
 We have an opportunity of seeing in the Bermuda islands the 
 
 Fig. 98. 
 
 A 
 
 The North Rocks. Bermuda, lying outside the great coral reef. 
 A. 16 feet high, and B. 12 feet. c. c. Hollows worn by the sea. 
 
 manner in which the waves of the Atlantic have worn, and are now 
 wearing out, deep smooth hollows on every side of projecting masses 
 of hard limestone. In the annexed drawing, communicated to me 
 
 * See Trans, of Geol. Soc., second series, vol. v. plate v. 
 
CH. VII.] ALLUVIUM. 79 
 
 by Capt. Nelson, R.E., the excavations c, c, e, have been scooped out 
 by the waves in a stone of very modern date, which, although ex- 
 tremely hard, is full of recent corals and shells, some of which retain 
 their colour. 
 
 When the forms of these horizontal grooves, of which the surface 
 is sometimes smooth and almost polished, and the roofs of which 
 often overhang to the extent of 5 feet or more, have been care- 
 fully studied by geologists, they will serve to testify the former 
 action of the waves at innumerable points far in the interior of the 
 continents. But we must learn to distinguish the indentations due 
 to the original action of the sea, and those caused by subsequent 
 chemical decomposition of calcareous rocks, to which they are liable 
 in the atmosphere. 
 
 I shall conclude with a warning to beginners not to feel surprise 
 if they can detect no evidence of the former sojourn of the sea on 
 lands which we are nevertheless sure have been submerged at periods 
 comparatively modern ; for notwithstanding the enduring nature of 
 the marks left by littoral action on calcareous rocks, we can by no 
 means detect sea-beaches and inland cliffs everywhere, even in Sicily 
 and the Morea. On the contrary, they are, upon the whole, ex- 
 tremely partial, and are often entirely wanting in districts composed 
 of argillaceous and sandy formations, which must, nevertheless, have 
 been upheaved at the same time, and by the same intermittent move- 
 ments, as the adjoining calcareous rocks. 
 
 CHAPTER VII. 
 
 ALLUVIUM. 
 
 Alluvium described Due to complicated causes Of various ages, as shown in 
 Auvergne How distinguished from rocks in situ River terraces Parallel 
 roads of Glen Roy Various theories respecting their origin. 
 
 BETWEEN the superficial covering of vegetable mould and the sub- 
 jacent "rock there usually intervenes in every district a deposit of 
 loose gravel, sand, and mud, to which the name of alluvium has 
 been applied. The term is derived from alluvio, an inundation, or 
 alluo, 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. 
 
 A partial covering of such alluvium is found alike in all climates, 
 from the equatorial to the polar regions ; but in the higher latitudes 
 of Europe and North America it assumes a distinct character, being 
 very frequently devoid of stratification, and containing huge frag- 
 ments of rock, some angular and others rounded, which have been 
 transported to great distances from their parent mountains. When 
 it presents itself in this form, it has been called " diluvium," " drift," 
 or the " boulder formation ; " and its probable connexion with the 
 
80 
 
 ALLUVIUM IN AUVEKGNE. 
 
 [CH. vii. 
 
 agency of floating ice and glaciers will be treated of more particularly 
 in the eleventh and twelfth chapters. 
 
 The student will be prepared, by what I have said in the last 
 chapter on denudation, to hear that loose gravel and sand are often 
 met with, not only on the low grounds bordering rivers, but also at 
 various points on the sides or even summits of mountains. For, 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 hope that we 
 should ever be able to account for all the alluvial phenomena of each 
 particular country, seeing that the causes of their origin are so various. 
 Besides, the last operations of water have a tendency to disturb and 
 confound together 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 geological 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 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 activity, and before any igneous matter was super- 
 imposed upon the granitic and fossiliferous formations. The pebbles 
 therefore in the older gravels are exclusively constituted of granite 
 and other aboriginal rocks; and afterwards, when volcanic vents 
 burst forth into eruption, those earlier alluviums were covered by 
 
 Fig. 99. 
 
 Lavas of Auvergne resting on alluviums of different ages. 
 
 streams of lava, which protected them from intermixture 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, 
 therefore, fresh eruptions gave rise to new lava, the melted matter 
 was poured out over lower grounds ; and the gravel of these plains 
 
Cn. VII. ] ALLUVIUM. 81 
 
 differed from the first or upland alluvium, by containing in it rounded 
 fragments of various volcanic rocks, and often bones belonging to 
 distinct groups of land animals which flourished in the country in 
 succession. 
 
 The annexed drawing will explain the different heights at which 
 beds of lava and gravel, each distinct from 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 the same hills, and the newest of all in 
 the channel of the existing river where there is usually gravel alone, 
 but in some cases a narrow stripe of solid lava sharing the bottom of 
 the valley with the river. In all these accumulations of transported 
 matter of different ages the bones of extinct mammalia have been 
 found belonging to assemblages of land quadrupeds, which flourished 
 in the country in succession, and which vary specifically, the one set 
 from the other, in a greater or less degree, in proportion as the time 
 which separated their entombment has been more or less protracted. 
 The streams in the same district are still undermining their banks and 
 grinding down into pebbles or sand, columns of basalt and frag- 
 ments of granite and gneiss ; but portions of the older alluviums, with 
 the fossil remains belonging to them, are prevented from being mingled 
 with the gravel of recent date by the cappings of lava before mentioned. 
 But for the accidental interference, therefore, of this peculiar cause, 
 all the alluviums might have passed so insensibly the one into the 
 other, that those formed at the remotest era might have appeared 
 of the same date as the newest, and the whole formation might have 
 been regarded by some geologists as the result of one sudden and 
 violent catastrophe. 
 
 In almost every country, the alluvium consists in its upper part of 
 transported materials, but it often passes downwards into a mass of 
 broken and angular fragments derived from the subjacent rock. To 
 this mass the provincial name of " rubble," or " brash," is given in 
 many parts of England. It may be referred to the weathering or 
 disintegration of stone on the spot, the effects of air and water, sun 
 and frost, and chemical decomposition. 
 
 The inferior surface of alluvial deposits is often very irregular, 
 conforming to all the inequalities of the fundamental rocks (fig. 100.). 
 Fig. 100. Occasionally, a small mass, as at c, 
 
 appears detached, and as if included in 
 the subjacent formation. Such isolated 
 portions are usually sections of winding 
 subterranean hollows filled up with allu- 
 vium. They may have been the courses 
 of springs or subterranean streamlets, 
 which have flowed through and enlarged 
 natural rents ; or, when on a small scale 
 and in soft strata, they may be spaces 
 
 a. vegetable soil. b. Alluvium, which the roots of large trees have once 
 
 of same, apparently detached. occupiedj grave l and Sand having been 
 
 introduced after their decay. 
 
 G 
 
SAND-PIPES. 
 
 [Cn. VII. 
 
 But there are other deep hollows of a cylindrical form found in 
 England, France, and elsewhere, penetrating the white chalk, and 
 filled with sand and gravel, which are not so readily explained. 
 They are sometimes called " sand-pipes," or " sand-galls," and " puits 
 naturels," in France. Those represented in the annexed cut were 
 
 Fig. 101. 
 
 Sand-pipes in the chalk at Eaton, near Norwich. 
 
 observed by me in 1839, laid open in a large chalk -pit near Norwich. 
 They were of very symmetrical form, the largest more than 12 feet 
 in diameter, and some of them had been traced, by boring, to the 
 depth of more than 60 feet. The smaller ones varied from a few 
 inches to a foot in diameter, and seldom descended more than 12 feet 
 below the surface. Even where three of them occurred, as at a, 
 fig. 101., very close together, the parting walls of soft white chalk 
 were not broken through. They all taper downwards and end in a 
 point. As a general rule, sand and pebbles occupy the central parts 
 of each pipe, while the sides and bottom are lined with clay. 
 
 Mr. Trimmer, in speaking of appearances of the same kind in the 
 Kentish chalk, attributes the origin of such "sand-galls" to the 
 action of the sea on a beach or shoal, where the waves, charged 
 with shingle and sand, not only wear out longitudinal furrows, such 
 as may be observed on the surface of the above-mentioned chalk near 
 Norwich when the incumbent gravel is removed, but also drill deep 
 circular hollows by the rotatory motion imparted to sand and pebbles. 
 Such furrows, as well as vertical cavities, are now formed, he observes, 
 on the coast where the shores are composed of chalk.* 
 
 That the commencement of many of the tubular cavities now under 
 consideration has been due to the cause here assigned, I have little 
 doubt. But such mechanical action could not have hollowed out the 
 whole of the sand-pipes c and d, fig. 101., because several large chalk- 
 flints seen protruding from the walls of the pipes have not been 
 eroded, while sand and gravel have penetrated many feet below them. 
 In other cases, as at bb, similar unrounded nodules of flint, still 
 preserving their irregular form and white coating, are found at 
 
 * Trimmer, Proceedings of Geol. Soc. vol. iv. p. 7. 1842. 
 
Cn. VII.J ALLUVIUM. 83 
 
 various depths in the midst of the loose materials filling the pipe. 
 These have evidently been detached from regular layers of flints oc- 
 curring above. It is also to be remarked that the course of the same 
 sand-pipe, b b, is traceable above the level of the chalk for some 
 distance upwards, through the incumbent gravel and sand, by the 
 obliteration of all signs of stratification. Occasionally, also, as in 
 the pipe c?, the overlying beds of gravel bend downwards into the 
 mouth of the pipe, so as to become in part vertical, as would happen 
 if horizontal layers had sunk gradually in consequence of a failure of 
 support. All these phenomena may be accounted for by attributing 
 the enlargement and deepening of the sand-pipes to the chemical 
 action of water charged with carbonic acid, derived from the vegetable 
 soil and the decaying roots of trees. Such acid might corrode the 
 chalk, and deepen indefinitely any previously existing hollow, but 
 could not dissolve the flints. The water, after it had become saturated 
 with carbonate of lime, might freely percolate the surrounding porous 
 walls of chalk, and escape through them and from the bottom of the 
 tube, so as to carry away in the course of time large masses of 
 dissolved calcareous rock *, and leave behind it on the edges of each 
 tubular hollow a coating of fine clay, which the white chalk contains. 
 
 I have seen tubes precisely similar and from 1 to 5 feet in diameter 
 traversing vertically the upper half of the soft calcareous building 
 stone, or chalk without flints, constituting St. Peter's Mount, Maes- 
 tricht. These hollows are filled with pebbles and clay, derived from 
 overlying beds of gravel, and all terminate downwards like those 
 of Norfolk. I was informed that, 6 miles from Maestricht, one of 
 these pipes, 2 feet in diameter, was traced downwards to a bed of 
 flattened flints, forming an almost continuous layer in the chalk. 
 Here it terminated abruptly, but a few small root-like prolongations 
 of it were detected immediately below, probably where the dissolving 
 substance had penetrated at some points through openings in the 
 siliceous mass. 
 
 It is not so easy as may at first appear to draw a clear line of 
 distinction between the fixed rocks, or regular strata (rocks in situ 
 or in place), and alluvium. If the bed of a torrent or river be dried 
 up, we. call the gravel, sand, and mud, left in their channels, or 
 whatever, during floods, they may have scattered over the neighbour- 
 ing plains, alluvium. The very same materials carried into a lake, 
 where they become sorted by water and arranged in more distinct 
 layers, especially if .they inclose the remains of plants, shells, or other 
 fossils, are termed regular strata. 
 
 In like manner we may sometimes compare the gravel, sand, and 
 broken shells, strewed along the path of a rapid marine current, with 
 a deposit formed contemporaneously by the discharge of similar ma- 
 terials year after year, into a deeper and more tranquil part of the 
 sea. In such cases, when we detect marine shells or other organic 
 remains entombed in the strata which enable us to determine their 
 
 * See Lyell on Sand-pipes, &c., Phil Mag., third series, vol. xv. p. 257., Oct. 1839. 
 
 o 2 
 
84 ALLUVIUM. [Cn. VII. 
 
 age and mode of origin, we regard them as part of the regular series 
 of fossiliferous formations, whereas, if there are no fossils, we have 
 frequently no power of separating them from the general mass of 
 superficial alluvium. 
 
 The usual rarity of organic remains in beds of loose gravel is partly 
 owing to the friction which originally ground down rocks into pebbles, 
 or sand, and organic bodies into small fragments, and it is partly owing 
 to the porous nature of alluvium when it has emerged, which allows 
 the free percolation through it of rain-water, and promotes the de- 
 composition and solution of fossil remains. 
 
 It has long been a matter of common observation that most rivers 
 are now cutting their channels through alluvial deposits of greater 
 depth and extent than could ever have been formed by the present 
 streams. From this fact a rash inference has sometimes been drawn, 
 that rivers in general have grown smaller, or become less liable to be 
 flooded than formerly. But such phenomena would be a natural result 
 of considerable oscillations in the level of the land experienced since 
 the existing valleys originated. 
 
 Suppose part of a continent, comprising within it a large hydro- 
 graphical 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 latitudes 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 power to carry its sand and sediment 
 into the main river, and the main river less power to convey its 
 annual burden' of transported matter to the sea. All the rivers, there- 
 fore, will proceed 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 sea- 
 ward, 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 channel 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. Every- 
 where this terrace will present cliffs of gravel and sand, facing the 
 river. That such a series of movements has actually taken place in the 
 main valley of the Mississippi and in its tributary valleys during oscil- 
 lations of level, I have endeavoured to show in my description of that 
 
 * Principles of Geology, 7th ed. p. 506., 8th ed. p. 509. 
 
CH. VIL] KIVER TEKRACES. 85 
 
 country * ; and the freshwater 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 pro- 
 cess of filling up and partial re-excavation. 
 
 In many cases, the alluvium in which rivers are now cutting their 
 channels, originated when the land first rose out of the sea. If, 
 for example, the emergence was caused by a gradual and uniform 
 motion, every bay and estuary, or the straits between islands, would 
 dry up slowly, and during their conversion into valleys, every part 
 of the upheaved area would in its turn be a sea-shore, and might be 
 strewed over with littoral sand and pebbles, or each spot might be 
 the point where a delta accumulated during the retreat and exclusion 
 of the sea. Materials so accumulated would conform to the general 
 slope of a valley from its head to the sea-coast. 
 
 River terraces. We often observe at a short distance from the 
 present bed of a river a steep cliff a few feet or yards high, and on a 
 level with the top of it a flat terrace corresponding in appearance to 
 the alluvial plain which immediately borders the river. This terrace 
 is again bounded by another cliff, above which a second terrace 
 sometimes occurs ; and in this manner two or three ranges of cliffs 
 and terraces are occasionally seen on one or both sides of the stream, 
 the number varying, but those on the opposite sides often corre- 
 sponding in height. 
 
 Fig. 102. 
 
 River Terraces and Parallel Roads. 
 
 These terraces are seldom continuous for great distances, and their 
 surface slopes downwards with an inclination similar to that of the 
 They are readily explained if we adopt the hypothesis before 
 
 river. 
 
 suggested, of a gradual rise of the land ; especially if, while rivers are 
 shaping out their beds, the upheaving movement be intermittent, so 
 that long pauses shall occur, during which the stream will have time 
 to encroach upon one of its banks, so as to clear away and flatten a 
 large space. This operation being afterwards repeated at lower 
 levels, there will be several successive cliffs and terraces. 
 
 * Second Visit to the U. S. vol. ii, chap. 34. 
 
 G 3 
 
86 PARALLEL KOADS [Cn. VII. 
 
 Parallel roads. The parallel shelves, or roads, as they have been 
 called, of Lochaber or Glen Roy and other contiguous valleys in 
 Scotland, are distinct both in character and origin from the terraces 
 above described; for they have no slope towards the sea like the 
 channel of a river, nor are they the effect of denudation. Glen 
 Roy is situated in the Western Highlands, about ten miles north of 
 Fort William, near the western end of the great glen of Scotland, or 
 Caledonian Canal, and near the foot of the highest of the Grampians, 
 Ben Nevis. Throughout its whole length, a distance of more than 
 ten miles, two, and in its lower part three, parallel roads or shelves 
 are traced along the steep sides of the mountains, as represented in 
 the annexed figure, fig. 102., each maintaining a perfect horizontality, 
 and continuing at exactly the same level on the opposite sides of the 
 glen. Seen at a distance, they appear like ledges or roads, cut arti- 
 ficially out of the sides of the hills ; but when we are upon them we 
 can scarcely recognize their existence, so uneven is their surface, 
 and so covered with boulders. They are from 10 to 60 feet broad, 
 and merely differ from the side of the mountain by being somewhat 
 less steep. 
 
 On closer inspection, we find that these terraces are stratified in 
 the ordinary manner of alluvial or littoral deposits, as may be seen at 
 those points where ravines have been excavated by torrents. The 
 parallel shelves, therefore, have not been caused by denudation, but 
 by the deposition of detritus, precisely similar to that which is dis- 
 persed in smaller quantities over the declivities of the hills above. 
 These hills consist of clay-slate, mica-schist, and granite, which rocks 
 have been worn away and laid bare at a few points only, in a line 
 just above the parallel roads. The highest of these roads is about 
 1250 feet above the level of the sea, the next about 200 feet lower 
 than the uppermost, and the third still lower by about 50 feet. It is 
 only this last, or the lowest of the three, which is continued through- 
 out Glen Spean, a large valley with which Glen Roy unites. As 
 the shelves are always at the same height above the sea, they become 
 continually more elevated above the river in proportion as we descend 
 each valley; and they at length terminate very abruptly, without 
 any obvious cause, or any change either in the shape of the ground 
 or in the composition or hardness of the rocks. I should exceed the 
 limits of this work, were I to attempt to give a full description of all 
 the geographical circumstances attending these singular terraces, or 
 to discuss the ingenious theories which have been severally proposed 
 to account for them by Dr. Macculloch, Sir T. D. Lauder, and Messrs. 
 Darwin, Agassiz, Milne, and Chambers. There is one point, how- 
 ever, on which all are agreed, namely, that these shelves are ancient 
 beaches, or littoral formations accumulated round the edges of one or 
 more sheets of water which once stood at the level, first of the 
 highest shelf, and successively at the height of the two others. It is 
 well known, that wherever a lake or marine fiord exists surrounded 
 by steep mountains subject to disintegration by frost or the action 
 of torrents, some loose matter is washed down annually, especially 
 
Cn. VII.] OF GLEN ROY. 87 
 
 during the melting of snow, and a check is given to the descent of 
 
 this detritus at the point where it reaches 
 the waters of the lake. The waves then 
 spread out the materials along the shore, 
 and throw some of them upon the beach ; 
 their dispersing power being aided by the 
 ice, which often adheres to pebbles during 
 the winter months, and gives buoyancy to 
 them. The annexed diagram illustrates 
 the manner in which Dr. Macculloch and 
 Mr. Darwin suppose " the roads " to con- 
 
 ~B ' stitute mere indentations in a superficial 
 
 A B. Supposed original surface of alluvial coating which rests upon the hill- 
 CD^'Roads or shelves in the outer side, and consists chiefly of clay and sharp 
 
 alluvial covering of the hill. unrounded StonCS. 
 
 Among other proofs that the parallel roads have really been formed 
 along the margin of a sheet of water, it may be mentioned, that 
 wherever an isolated hill rises in the middle of the glen above the 
 level of any particular shelf, a corresponding shelf is seen at the 
 same level passing round the hill, as would have happened if it had 
 once formed an island in a lake or fiord. Another very remarkable 
 peculiarity in these terraces is this ; each of them comes in some 
 portion of its course to a col, or passage between the heads of glens, 
 the explanation of which will be considered in the sequel. 
 
 Those writers who first advocated the doctrine that the roads were 
 the ancient beaches of freshwater lakes, were unable to offer any 
 probable hypothesis respecting the formation and subsequent removal 
 of barriers of sufficient height and solidity to dam up the water. To 
 introduce any violent convulsion for their removal was inconsistent 
 with the uninterrupted horizontality of the roads, and with the 
 undisturbed aspect of those parts of the glens where the shelves 
 come suddenly to an end. Mr. Agassiz and Dr. Buckland, desirous, 
 like the defenders of the lake theory, to account for the limitation of 
 the shelves to certain glens, and their absence in contiguous glens, 
 where the rocks are of the same composition, and the slope and 
 inclinatfon of the ground very similar, started the conjecture that 
 these valleys were once blocked up by enormous glaciers descending 
 from Ben Nevis, giving rise to what are called in Switzerland and in 
 the Tyrol, glacier-lakes. After a time the icy barrier was broken 
 down, or melted, first, to the level of the second, and afterwards to 
 that of the third road or shelf. 
 
 In corroboration of this view, they contended that the alluvium of 
 Glen Roy, as well as of other parts of Scotland, agrees in character 
 with the moraines of glaciers seen in the Alpine valleys of Switzer- 
 land. Allusion will be made in the eleventh chapter to the former 
 existence of glaciers in the Grampians : in the mean time it will 
 readily be conceded that this hypothesis is preferable to any pre- 
 vious lacustrine theory, by accounting more easily for the temporary 
 existence and entire disappearance of lofty transverse barriers, al- 
 
 o 4 
 
88 PARALLEL ROADS OF GLEN ROY. [Cn. VIL 
 
 though the height required for the imaginary dams of ice may be 
 startling. 
 
 Before the idea last alluded to had been entertained, Mr. Darwin 
 examined Glen Roy, and came to the opinion that the shelves were 
 formed when the glens were still arms of the sea, and, consequently, 
 that there never were any seaward barriers. According to him, the 
 land emerged during a slow and uniform upward movement, like that 
 now experienced throughout a large part of Sweden and Finland ; but 
 there were certain pauses in the upheaving process, at which times 
 the waters of the sea remained stationary for so many centuries as to 
 allow of the accumulation of an extraordinary quantity of detrital 
 matter, and the excavation, at many points immediately above, of 
 deep notches and bare cliffs in the hard and solid rock. 
 
 The phenomena which are most difficult to reconcile with this 
 theory are, first, the abrupt cessation of the roads at certain points 
 in the different glens ; secondly, their unequal number in different 
 valleys connecting with each other, there being three, for example, 
 in Glen Roy and only one in Glen Spean ; thirdly, the precise hori- 
 zontality of level maintained by the same shelf over a space many 
 leagues in length requiring us to assume, that during a rise of 1250 
 feet no one portion of the land was raised even a few yards above 
 another ; fourthly, the coincidence of level already alluded to of each 
 shelf with a col, or the point forming the head of two glens, from 
 which the rain-waters flow in opposite directions. This last-men- 
 tioned feature in the physical geography of Lochaber seems to have 
 been explained in a satisfactory manner by Mr. Darwin. He calls 
 these cols " landstraits," and regards them as having been anciently 
 sounds or channels between islands. He points out that there is a 
 tendency in such sounds to be silted up, and always the more so in 
 proportion to their narrowness. In a chart of the Falkland Islands, 
 by Capt. Sullivan, R. N., it appears that there are several examples 
 there of straits where the soundings diminish regularly towards the 
 narrowest part. One is so nearly dry that it can be walked over at 
 low water, and another, no longer covered by the sea, is supposed to 
 have recently dried up in consequence of a small alteration in the re- 
 lative level of sea and land. " Similar straits," observes Mr. Chambers, 
 " hovering, in character, between sea and land, and which may be 
 called fords, are met with in the Hebrides. Such, for example, is the 
 passage dividing the islands of Lewis and Harris, and that between 
 North Uist and Benbecula, both of which would undoubtedly appear 
 as cols, coinciding with a terrace or raised beach, all round the islands, 
 if the sea were to subside."* 
 
 The first of the difficulties above alluded to, namely, the non-exten- 
 sion of the shelves over certain parts of the glens, may be explained, 
 as Mr. Darwin suggests, by supposing in certain places a quick growth 
 of green turf on a good soil, which prevented the rain from washing 
 away any loose materials lying on the surface. But wherever the 
 soil was barren, and where green sward took long to form, there may 
 
 * " Ancient Sea Margins," p. 114.,byR. Chambers. 
 
Cn. VII.] CHRONOLOGY OF ROCKS. 89 
 
 have been time for the removal of the gravel. In one case an inter- 
 mediate shelf appears for a short distance (three quarters of a mile) on 
 the face of the mountain called Tombhran, between the two upper 
 shelves, and is seen nowhere else. It occurs where there was the longest 
 space of open water, and where, perhaps, the waves acquired a greater 
 than ordinary power in heaping up detritus. 
 
 Next as to the precise horizontally of level maintained by the 
 parallel roads of Lochaber over an area many leagues in length and 
 breadth, this is a difficulty common in some degree to all the rival 
 hypotheses, whether of lakes, or glaciers, or of the simple upheaval 
 of the land above the sea. For we cannot suppose the roads to be 
 more ancient than the glacial period, or the era of the boulder form- 
 ation of Scotland, of which I shall speak in the eleventh and twelfth 
 chapters. Strata of that era of marine origin containing northern ./ 
 shells of existing species have been, found at various heights in 
 Scotland, some on the east, and others on the west coast, from 20 to 
 400 feet high ; and in one region in Lanarkshire not less than 524 
 feet above high-water mark. It seems, therefore, in the highest degree 
 improbable that Glen Roy should have escaped entirely the upward 
 movement experienced in so many surrounding regions, a movement 
 implied by the position of these marine deposits, in which the shells 
 are almost all of known recent species. But if the motion has really 
 extended to Glen Roy and the contiguous glens, it must have up- 
 lifted them bodily, without in the slightest degree affecting their 
 horizontally ; and this being admitted, the principal objection to the 
 theory of marine beaches, founded on the uniformity of upheaval, is 
 removed, or is at least common to every theory hitherto proposed. 
 
 To assume that the ocean has gone down from the level of the 
 uppermost shelf, or 1250 feet, simultaneously all over the globe, 
 while the land remained unmoved, is a view which will find favour 
 with very few geologists, for the reasons explained in the fifth chapter. 
 
 The student will perceive, from the above sketch of the controversy 
 respecting the formation of these curious shelves, that this problem, 
 like many others in geology, is as yet only solved in part ; and that a 
 larger number of facts must be collected and reasoned upon before 
 the question can be finally settled. 
 
90 CHRONOLOGY OF ROCKS. [Cn. VIII. 
 
 CHAPTER VIII. 
 
 CHRONOLOGICAL CLASSIFICATION OP ROCKS. 
 
 Aqueous, plutonic, volcanic, and metamorphic rocks, considered chronologically 
 Lehman's division into primitive and secondary Werner's addition of a tran- 
 sition class Neptunian theory Button on igneous origin of granite How 
 the name of primary was still retained for granite The term " transition," why 
 
 faulty The adherence to the old chronological nomenclature retarded the 
 
 progress of geology New hypothesis invented to reconcile the igneous origin 
 of granite to the notion of its high antiquity Explanation of the chronological 
 nomenclature adopted in this work, so far as regards primary, secondary, and 
 tertiary periods. 
 
 IN the first chapter it was stated that the four great classes of rocks, 
 the aqueous, the volcanic, the plutonic, and the metamorphic, would 
 each be considered 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 stratified, that 
 some are calcareous, others argillaceous or siliceous, some made up 
 of sand, others of pebbles; that some contain freshwater, others 
 marine fossils, and so forth ; but the student has still 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 con- 
 venient 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 plutonic, 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 revo- 
 lutions of the inorganic and organic creations of former times. For 
 the sedimentary formations are most readily distinguished by the 
 different species of fossil animals and plants which they inclose, 
 and of which one assemblage after another has flourished and then 
 disappeared from the earth in succession. 
 
 But before entering specially on the subdivisions of the aqueous 
 rocks arranged according to the order of time, it will be desirable to 
 say a few words on the chronology of rocks in general, although in 
 doing so we shall be unavoidably led to allude to some classes of 
 phenomena which the beginner must not yet expect fully to com- 
 prehend. ( 
 
 It was for many years a received opinion that the formation of 
 entire families of rocks, such as the plutonic and those crystalline 
 schists spoken of in the first chapter as metamorphic, began and 
 ended before any members of the aqueous and volcanic orders were 
 
CH. VIII.] CLASSIFICATION OF ROCKS. 91 
 
 produced; and although this idea has long been modified, and is 
 nearly exploded, it will be necessary to give some account of the 
 ancient doctrine, in order that beginners may understand whence 
 many prevailing opinions, and some part of the nomenclature of 
 geology, still partially in use, was derived. 
 
 About the middle of the last century, Lehman, a German miner, 
 proposed to divide rocks into three classes, the first and oldest to be 
 called primitive, comprising the hypogene, or plu tonic and metamor- 
 phic rocks; the next to be termed secondary, comprehending the 
 aqueous or fossiliferous strata; and the remainder, or third class, 
 corresponding to our alluvium, ancient and modern, which he referred 
 to " local floods, and the deluge of Noah." In the primitive class, he 
 said, such as granite and gneiss, there are no organic remains, nor 
 any signs of materials derived from the ruins of pre-existing rocks. 
 Their origin, therefore, may have been purely chemical, antecedent 
 to the creation of living beings, and probably coeval with the birth of 
 the world itself. The secondary formations, on the contrary, which 
 often contain sand, pebbles, and organic remains, must have been 
 mechanical deposits, produced after the planet had become the habi- 
 tation of animals and plants. This bold generalization, although an- 
 ticipated in some measure by Steno, a century before, in Italy, 
 formed at the time an important step in the progress of geology, and 
 sketched out correctly some of the leading divisions into which rocks 
 may be separated. About half a century later, Werner, so justly 
 celebmted for his improved methods of discriminating the mineralo- 
 gical characters of rocks, attempted to improve Lehman's classification, 
 and with this view intercalated a class, called by him " the transition 
 formations," between the primitive and secondary. Between these 
 last he had discovered, in northern Germany, a series of strata, 
 which in their mineral peculiarities were of an intermediate character, 
 partaking in some degree of the crystalline nature of micaceous schist 
 and clay-slate, and yet exhibiting here and there signs of a mechani- 
 cal origin and organic remains. For this group, therefore, forming a 
 passage between Lehman's primitive and secondary rocks, the name 
 of iibergang or transition was proposed. They consisted principally 
 of clay-slate and an argillaceous sandstone, called grauwacke, and 
 partly of calcareous beds. Tt happened in the district which Werner 
 first investigated, that both the primitive and transition strata were 
 highly inclined, while the beds of the newer fossiliferous rocks, the 
 secondary of Lehman, were horizontal. To these latter, therefore, 
 he gave the name ofjlotz, or " a level floor;" and every deposit more 
 modern than the chalk, which was classed as the uppermost of the 
 flo'tz series, was designated "the overflowed land," an expression which 
 may be regarded as equivalent to alluvium, although under this appel- 
 lation were confounded all the strata afterwards called tertiary, of 
 which Werner had scarcely any knowledge. As the followers of 
 Werner soon discovered that the inclined position of the " transition 
 beds," and the horizontality of the flotz, or newer fossiliferous strata, 
 were mere local accidents, they soon abandoned the term flotz ; and 
 
92 NEPTUNIAN THEORY. [Cn. VIII. 
 
 the four divisions of the Wernerian school were then named primitive, 
 transition, secondary, and alluvial. 
 
 As to the trappean rocks, although their igneous origin had been 
 already demonstrated by Arduino, Fortis, Faujas, and others, and 
 especially by Desmarest, they were all regarded by Werner as aqueous, 
 and as mere subordinate members of the secondary series.* 
 
 This theory of Werner's was called the " Neptunian," and for many 
 years enjoyed much popularity. It assumed that the globe had been 
 at first invested by an universal chaotic ocej ) n f =3iolding the materials 
 of all rocks in solution. From the waters of this ocean, granite, 
 gneiss, and other crystalline formations, were first precipitated ; and 
 afterwards, when the waters were purged of these ingredients, and 
 more nearly resembled those of our actual seas, the transition strata 
 were deposited. These were of a mixed character, not purely che- 
 mical, because the waves and currents had already begun to wear 
 down solid land, and to give rise to pebbles, sand, and mud ; nor en- 
 tirely without fossils, because a few of the first marine animals had 
 begun to exist. After this period, the secondary formations were 
 accumulated in waters resembling those of jche present ocean, except 
 at certain intervals, when, from causes wholly unexplained, a partial 
 recurrence of the " chaotic fluid " took place, during which various 
 trap rocks, some highly crystalline, were formed. This arbitrary 
 hypothesis rejected all intervention of igneous agency, volcanos being 
 regarded as modern, partial, and superficial accidents, of trifling 
 account among the great causes which have modified the external 
 structure of the globe. 
 
 Meanwhile Hutton, a contemporary of Werner, began to teach, in 
 Scotland, that granite as well as trap was of igneous origin, and had 
 at various periods intruded itself in a fluid state into different parts of 
 the earth's crust. He recognized and faithfully described many of the 
 phenomena of granitic veins, and the alterations produced by them 
 on the invaded strata, which will be treated of in the thirty-third 
 chapter. He, moreover, advanced the opinion, that the crystalline 
 I strata called primitive had not been precipitated from a primaeval 
 ocean, but were sedimentary strata altered by heat. In his writings, 
 therefore, and in those of his illustrator, Playfair, we find the germ 
 of that metamorphic theory which has been already hinted at in the 
 first chapter, and which will be more fully expounded in the thirty- 
 fourth and thirty-fifth chapters. 
 
 At length, after much controversy, the doctrine of the igneous 
 origin of trap and granite made its way into general favour; but 
 although it was, in consequence, admitted that both granite and trap 
 had been produced at many successive periods, the term primitive or 
 primary still continued to be applied to the crystalline formations 
 in general, whether stratified, like gneiss, or unstratified, like granite. 
 The pupil was told that granite was a primary rock, but that some 
 granites were newer than certain secondary formations ; and in con- 
 
 * See Principles of Geology, vol. i. chap. iv. 
 
Cn. VIII.] ON THE TEEM " TRANSITION." 93 
 
 formity with the spirit of the ancient language, to which the teacher 
 was still determined to adhere, a desire was naturally engendered of 
 extenuating the importance of those more modern granites, the true 
 dates of which new observations were continually bringing to light. 
 
 A no less decided inclination was shown to persist in the use of 
 the term "transition," after it had been proved to be almost as 
 faulty in its original application as that of flotz. The name of 
 transition, as already stated, was first given by Werner, to designate 
 a mineral character, intermediate between the highly crystalline or 
 metamorphic state and that of an ordinary fossiliferous rock. But 
 the term acquired also from the first a chronological import, because 
 it had been appropriated to sedimentary formations, which, in the 
 Hartz and other parts of Germany, were more ancient than the 
 oldest of the secondary series, and were characterized by peculiar 
 fossil zoophytes and shells. When, therefore, geologists found in 
 other districts stratified rocks occupying the same position, and 
 inclosing similar fossils, they gave to them also the name of tran- 
 sition, according to rules which will be explained in the next 
 chapter ; yet, in many cases, such rocks were found not to exhibit 
 the same mineral texture which Werner had called transition. On 
 the contrary, many of them were not more crystalline than different 
 members of the secondary class ; while, on the other hand, these 
 last were sometimes found to assume a semi-crystalline and almost 
 metamorphic aspect, and thus, on lithological grounds, to deserve 
 equally the name of transition. So remarkably was this the case in 
 the Swiss Alps, that certain rocks, which had for years been regarded 
 by some of the most skilful disciples of Werner to be transition, were 
 at last acknowledged, when their relative position and fossils were 
 better understood, to belong to the newest of the secondary groups ; 
 nay, some of them have actually been discovered to be members of 
 the lower tertiary series ! If, under such circumstances, the name of 
 transition was retained, it is clear that it ought to have been applied 
 without reference to the age of strata, and simply as expressive of a 
 mineral peculiarity. The continued appropriation of the term to 
 formations of a given date, induced geologists to go on believing that 
 the ancient strata so designated bore a less resemblance to the 
 secondary than is really the case, and to imagine that these last never 
 pass, as they frequently do, into metamorphic rocks. 
 
 The poet Waller, when lamenting over the antiquated style of 
 Chaucer, complains that 
 
 We write in sand, our language grows, 
 And, like the tide, our work o'erflows. 
 
 But the reverse is true in geology ; for here it is our work which 
 continually outgrows the language. The tide of observation advances 
 with such speed that improvements in theory outrun the changes of 
 nomenclature ; and the attempt to inculcate new truths by words 
 invented to express a different or opposite opinion, tends constantly, 
 
94 CHRONOLOGICAL ARRANGEMENT [Cn. VIII. 
 
 by the force of association, to perpetuate error ; so that dogmas 
 renounced by the reason still retain a strong hold upon the imagi- 
 nation. 
 
 In order to reconcile the old chronological views with the new 
 doctrine of the igneous origin of granite, the following hypothesis 
 was substituted for that of the Neptunists. Instead of beginning 
 with an aqueous menstruum or chaotic fluid, the materials of the 
 present crust of the earth were supposed to have been at first in a 
 state of igneous fusion, until part of the heat having been diffused 
 into surrounding space, the surface of the fluid consolidated, and 
 formed a crust of granite. This covering of crystalline stone, which 
 afterwards grew thicker and thicker as it cooled, was so hot, at first, 
 that no water could exist upon it ; but as the refrigeration pro- 
 ceeded, the aqueous vapour in the atmosphere was condensed, and, 
 falling in rain, gave rise to the first thermal ocean. So high was the 
 temperature of this boiling sea, that no aquatic beings could inhabit 
 its waters, and its deposits were not only devoid of fossils, but, like 
 those of some hot springs, were highly crystalline. Hence the 
 origin of the primary or crystalline strata, gneiss, mica-schist, and 
 the rest. 
 
 Afterwards, when the granitic crust had been partially broken up, 
 land and mountains began to rise above the waters, and rains and 
 torrents to grind down rock, so that sediment was spread over the 
 bottom of the seas. Yet the heat still remaining in the solid 
 supporting substances was sufficient to increase the chemical action 
 exerted by the water, although not so intense as to prevent the intro- 
 duction and increase of some living beings. During this state of 
 things some of the residuary mineral ingredients of the primaeval 
 ocean were precipitated, and formed deposits (the transition strata 
 of Werner), half chemical and half mechanical, and containing a few 
 fossils. 
 
 By this new theory, which was in part a revival of the doctrine of 
 Leibnitz, published in 1680, on the igneous origin of the planet, the 
 old ideas respecting the priority of all crystalline rocks to the creation 
 of organic beings, were still preserved; and the mistaken notion that 
 all the semi-crystalline and partially fossiliferous rocks belonged to 
 one period, while all the earthy and uncrystalline formations origin- 
 ated at a subsequent epoch, was also perpetuated. 
 
 It may or may not be true, as the great Leibnitz imagined, that 
 the whole planet was once in a state of liquefaction by heat ; but 
 there are certainly no geological proofs that the granite which con- 
 stitutes the foundation of so much of the earth's crust was ever at once 
 in a state of universal fusion. On the contrary, all our evidence 
 tends to show that the formation of granite, like the deposition of 
 the stratified rocks, has been successive, and that different portions of 
 granite have been in a melted state at distinct and often distant 
 periods. One mass was solid, and had been fractured, before another 
 body of granitic matter was injected into it, or through it, in the form 
 of veins. Some granites are more ancient than any known fossiliferous 
 
Cn. VIII.] OF ROCKS IN GENERAL. 95 
 
 rocks ; others are of secondary ; and some, such as that of Mont 
 Blanc and part of the central axis of the Alps, of tertiary origin. In 
 short, the universal fluidity of the crystalline foundations of the 
 earth's crust, can only be understood in the same sense as the uni- 
 versality of the ancient ocean. All the land has been under water, 
 but not all at one time ; so all the subterranean unstratified rocks to 
 which man can obtain access have been melted, but not simulta- 
 neously. 
 
 In the present work the four great classes of rocks, the aqueous, 
 plutonic, volcanic, and metamorphic, will form four parallel, or 
 nearly parallel, columns in one chronological table. They will be 
 considered as four sets of monuments relating to four contempo- 
 raneous, or nearly contemporaneous, series of events. I shall en- 
 deavour, in a subsequent 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 geolo- 
 gical period, and how the earth's crust may have been continually 
 remodelled, above and below, by aqueous and igneous 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 con- 
 nected with reservoirs of melted matter at vast depths in the bowels 
 of the earth, so, at every era of the past, fossiliferous deposits and 
 superficial igneous rocks were in progress contemporaneously with 
 others of subterranean and plutonic origin, and some sedimentary 
 strata were exposed to heat, and made to assume a crystalline or 
 metamorphic structure. 
 
 It can by no means be taken for granted, that during all these 
 changes the solid crust of the earth has been increasing in thickness. 
 It has been shown, that so far as aqueous action is concerned, the 
 gain by fresh deposits, and the loss by denudation, must at each 
 period have been equal (see above, p. 68.) ; and in like manner, in 
 the inferior portion of the earth's crust, the acquisition of new crys- 
 talline rocks, at each successive era, may merely have counter- 
 balanced the loss sustained by the melting of materials previously 
 consolidated. As to the relative antiquity of the crystalline found- 
 ations of the earth's crust, when compared to the fossiliferous and 
 volcanic 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 super- 
 structure of an ancient city built on wooden piles, may be the oldest. 
 We have seen that, to answer this question, we must first be prepared 
 to say whether the work of decay and restoration had gone on most 
 rapidly above or below ; whether the average duration of the piles has 
 exceeded that of the stone buildings, or the contrary. So also in 
 regard to the relative age of the superior and inferior portions of the 
 earth's crust; we cannot hazard even a conjecture on this point, 
 until we know whether, upon an average, the power of water above, 
 or that of heat below, is most efficacious in giving new forms to solid 
 matter. 
 
96 CHRONOLOGICAL ARRANGEMENT OF ROCKS. [Cn. VIII. 
 
 After the observations which have now been made, the reader will 
 perceive that the term primary must either be entirely renounced, or, 
 if retained, must be differently defined, and not made to designate a 
 set of crystalline rocks, some of which are already ascertained to be 
 newer than all the secondary formations. In this work I shall follow 
 most nearly the method proposed by Mr. Boue, who has called all 
 fossiliferous rocks older than the secondary by the name of primary. 
 To prevent confusion, I shall sometimes speak of these last as the 
 primary fossiliferous formations ; because the word primary has 
 hitherto been most generally connected with the idea of a non- 
 fossiliferous rock. Some geologists, to avoid misapprehension, have 
 introduced the term Paleozoic for primary, from TraXcuov, " ancient," 
 and wov, " an organic being," still retaining the terms secondary and 
 tertiary; Mr. Phillips, for the sake of uniformity, has proposed 
 Mesozoic, for secondary, from peaoG, " middle," &c. ; and Cainozoic, for 
 tertiary, from KCIIVOQ, " recent," &c. ; but the terms primary, secondary, 
 and tertiary are synonymous, and have the claim of priority in 
 their favour. 
 
 If we can prove any plutonic, volcanic, or metamorphic rocks to be 
 older than the secondary formations, such rocks will also be primary, 
 according to this system. Mr. Boue having with propriety ex- 
 cluded the metamorphic rocks, as a class, from the primary form- 
 ations, proposed to call them all " crystalline schists." 
 
 As there are secondary fossiliferous strata, so we shall find that 
 there are plutonic, volcanic, and metamorphic rocks of contempora- 
 neous origin, which I shall also term secondary. 
 
 In the next chapter it will be shown that the strata above the 
 chalk have been called tertiary. If, therefore, we discover any vol- 
 canic, plutonic, or metamorphic rocks, which have originated since 
 the deposition of the chalk, these also will rank as tertiary form- 
 ations. 
 
 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 dis- 
 cussed 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. In the small part 
 of the globe hitherto examined, it is hardly to be expected that we 
 should have discovered either the oldest or the newest members of 
 each of the four classes of rocks. Thus, if there be primary, second- 
 ary, and tertiary rocks of the aqueous or fossiliferous class, and in 
 like manner primary, secondary, and tertiary hypogene formations, 
 we may not be yet acquainted with the most ancient of the primary 
 fossiliferous beds, or with the newest of the hypogene. 
 
CH. IX.] DIFFERENT AGES OF AQUEOUS HOCKS. 97 
 
 CHAPTER IX. 
 
 ON THE DIFFERENT AGES OF THE AQUEOUS ROCKS. 
 
 On the three principal tests of relative age superposition, mineral character, and 
 fossils Change of mineral character and fossils in the same continuous forma- 
 tion Proofs that distinct species of animals and plants have lived at successive 
 periods Distinct provinces of indigenous species Great extent of single pro- 
 vinces Similar laws prevailed at successive geological periods Relative 
 importance of mineral and palaeontological characters Test of age by included 
 fragments Frequent absence of strata of intervening periods Principal groups 
 of strata in western Europe. 
 
 IN the last chapter I spoke generally of the chronological relations of 
 the four great classes of rocks, and I shall now treat of the aqueous 
 rocks in particular, or of the successive periods at which the different 
 fossiliferous formations have been deposited. 
 
 There are three principal tests by which we determine the age of 
 a given set of strata ; first, superposition ; secondly, mineral cha- 
 racter ; 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 rela- 
 tive ages of the two may, even in the absence of all other evidence, 
 be determined. 
 
 Superposition. The first and principal test of the age of one 
 aqueous deposit, as compared to another, is relative position. It has 
 been already stated, 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 volumes of history, in which each writer has recorded 
 the annals 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 era immediately preceding were commemorated. 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 are some re- 
 gions where, as the student has already been informed, the beds have 
 been disturbed, and sometimes extensively thrown over and turned 
 upside down. (See pp. 58, 59.) But an experienced geologist can 
 rarely be deceived by these exceptional cases. When he finds that 
 the strata are fractured, curved, inclined, or vertical, he knows that 
 the original order of superposition must be doubtful, and he then 
 endeavours to find sections in some neighbouring 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 
 
 H 
 
98 TESTS OF THE DIFFERENT AGES [Cn. IX, 
 
 furnished for settling the chronology of those strata where the dis- 
 placement is extreme. 
 
 Mineral character. The same rocks may often be observed to 
 retain for miles, or even hundreds of miles, the same mineral pecu- 
 liarities, if we follow the planes of stratification, or trace the beds, if 
 they be undisturbed, in a horizontal direction. But if we pursue 
 them vertically, or in any direction transverse to the planes of strati- 
 fication, 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 rocks, some of 
 fine, others of coarse grain, some of mechanical, others of chemical 
 origin ; some calcareous, others argillaceous, 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 different kinds of matter. The first observers were so astonished 
 at the vast spaces over which they were able to follow the same homo- 
 geneous rocks in a horizontal direction, that they came hastily to the 
 opinion, that the whole globe had been environed by a succession of 
 distinct aqueous 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 terminate 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 served as their receptacle. 
 It no less frequently happens that they vary in mineral aspect and 
 composition, as we pursue them horizontally. 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 
 sandstone, 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 criterion 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 wide 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 anti- 
 podes, or which now co-exist in the arctic, temperate, and tropical 
 
CH. IX.] OF AQUEOUS ROCKS. 99 
 
 zones. It appears, that from the remotest periods there has been 
 ever a coming in of new organic forms, and an extinction of those 
 which pre-existed on the earth ; some species having endured for a 
 longer, others for a shorter, time ; while none have ever re-appeared 
 after once dying out. The law which has governed the creation and 
 extinction of species seems to be expressed in the verse of the 
 poet, 
 
 Natura il fece, e poi ruppe la stampa. ARIOSTO. 
 
 Nature made him, and then broke the die. 
 
 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 cannot be said of each peculiar variety of rock; for 
 some of these, as red marl and red sandstone, for example, may 
 occur at once at the top, bottom, and middle of the entire sedi- 
 mentary series ; exhibiting in each position so perfect an identity of 
 mineral aspect as to be undistinguishable. Such exact repetitions, 
 however, of the same mixtures of sediment have not often been pro- 
 duced, at distant periods, in precisely the same parts of the globe ; 
 and, even where this has happened, we are seldom in any danger of 
 confounding together the monuments of remote eras, when we have 
 studied their imbedded fossils and their relative position. 
 
 It was remarked that the same species of organic remains cannot 
 be traced horizontally, or in the direction of the planes of strati- 
 fication for indefinite distances. This might have been expected 
 from analogy ; for when we inquire into the present distribution of 
 living beings we find that the habitable surface of the sea and land 
 may be divided into a considerable number of distinct provinces, 
 each peopled by a peculiar assemblage of animals and plants. In the 
 Principles of Geology, I have endeavoured 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 difference of longitude as well as latitude is generally accom- 
 panied by a dissimilarity 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 ad- 
 joining these may be peopled by distinct terrestrial 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 favourable to their 
 existence 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 provinces, espe- 
 cially those of marine animals, is very great ; and our geological 
 researches have proved that the same laws prevailed at remote 
 
 H 2 
 
100 TESTS OF THE DIFFERENT AGES [Ca. IX. 
 
 periods ; for the fossils are often identical throughout wide spaces, and 
 in detached deposits, consisting of rocks varying entirely in their 
 mineral nature. 
 
 The doctrine here laid down will be more readily understood, if we 
 reflect on what is now going on in the Mediterranean. That entire 
 sea may be considered as one zoological province ; for although certain 
 species of testacea and zoophytes 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 progress 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 Mediterranean, as off the coast of Campania, or near 
 the base of Etna, in Sicily, or in the Grecian Archipelago, where 
 another class of rocks is now forming ; where showers of volcanic 
 ashes occasionally fall into the sea, and streams of lava overflow its 
 bottom ; and where, in the intervals between volcanic 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, are 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 cha- 
 racters, the remains of the same shells, corals, Crustacea, and fish are 
 becoming inclosed ; or, at least, a sufficient number must be common 
 to the different localities to enable the zoologist to refer them all to 
 one contemporaneous assemblage of species. 
 
 There are, however, certain combinations of geographical circum- 
 stances which cause distinct provinces of animals and plants to be 
 separated from each other by very narrow limits ; and hence it must 
 happen, that strata will be sometimes formed in contiguous regions, 
 differing widely both in mineral 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. Of the bivalve shells, according to 
 Philippi, not more than a fifth are common to the Red Sea and the 
 sea around Sicily, while the proportion of univalves (or Gasteropoda) 
 is still smaller, not exceeding eighteen in a hundred. 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 deposits 
 of mud are amassed, including the remains of Mediterranean species. 
 It follows, therefore, that if at some future period the bed of the 
 Red Sea should be laid dry, the geologist might experience great 
 
CH. IX.] OF AQUEOUS ROCKS. 101 
 
 difficulties in endeavouring to ascertain the relative age of these 
 formations, which, although 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 Egypt, and the isthmus of 
 Suez are all parts of one province of terrestrial 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 fluviatile 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, 
 before 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 different marine 
 species, it will much more frequently happen, that the co-existence 
 of terrestrial species of distinct zoological 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 south of Europe, north of Africa, and north-west of 
 Asia differ considerably, yet their remains are all washed down by 
 rivers flowing from these three countries into the Mediterranean. 
 
 In some parts of the globe, at the present period, the line of 
 demarcation 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 extending 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 
 manner the geologist, in studying particular formations of remote 
 periods, has sometimes been able to trace the gradation from one 
 ancient province to another, by observing carefully the fossils of all 
 the intermediate places. His success in thus acquiring a knowledge 
 of the zoological or botanical geography of very distant eras has been 
 mainly owing to this circumstance, that the mineral character has no 
 tendency to be affected by climate. A large river may convey 
 yellow or red mud into some part of the ocean, where it may be 
 dispersed by a current over an area several hundred 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 inhabited at the same time the tem- 
 perate and equatorial 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, palaeontological 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 
 
 ii 3 
 
102 CHRONOLOGICAL ARRANGEMENT. [Cn. IX. 
 
 happens, that where the one criterion fails, we can often avail our- 
 selves of the other. 
 
 Test by included fragments of older rocks. It was stated, that 
 independent proof may sometimes be obtained of the relative date of 
 two formations, by fragments of an older rock being included 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 order of position, or 
 because the strata of each group are vertical. In such cases we 
 sometimes discover that the more modern rock has been in part 
 derived from the degradation of the older. Thus, for example, we 
 muy find chalk with flints in one part of a country ; and, in another, 
 a distinct formation, consisting of alternations of clay, sand, and 
 pebbles. If some of these pebbles consist of similar flint, including 
 fossil shells, sponges, and foraminifera, of the same species as those 
 in the chalk, we may confidently infer that the chalk is 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 different geologists 
 entertain ; but when we have adopted a certain system of arrange- 
 ment, 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. 16.). 
 
 Fig. 104. 
 
 But let the annexed diagram represent seven fossiliferous 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 No. 5. are absent at one 
 extremity of the section, and No. 4. at the other. 
 
 In another diagram, fig. 105., a real section of the geological 
 formations in the neighbourhood 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 and 6. Here at the southern end of the line of 
 section we meet with the beds No. 3. (the New Red Sandstone) resting 
 immediately on No. 6., while farther north, as at Dundry Hill, we 
 behold six groups superimposed one upon the other, comprising all 
 the strata from the inferior oolite to the coal and carboniferous 
 limestone. The limited extension of the groups 1 and 2. is owing 
 to denudation, as these formations end abruptly, and have left 
 outlying patches to attest the fact of their having originally covered 
 a much wider area. 
 
Section South of Bristol. A. C. Ramsay. 
 
 Length of section 4 miles. a, b. Level of the sea. 
 
 1. Inferior oolite. 5. Coal measure. 
 
 2. Lias. 6. Carboniferous limestone. 
 
 3. New red sandstone. 7. Old red sandstone. 
 
 4. Magnesian conglomerate. 
 
 In many instances, however, the entire absence of one or more 
 formations of intervening periods between two groups, such as 3. 
 and 5. in the same section, arises, not from the destruction of what 
 once existed, but because no strata of an intermediate age were ever 
 deposited on the inferior rock. They were not formed at that place, 
 either because the region was dry land during the interval, or because 
 it was part of a sea or lake to which no sediment was carried. 
 
 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 super- 
 position their age relatively 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 have 
 determined the succession of strata throughout a great part of 
 Europe, and have adopted pretty generally the following groups, 
 almost all of which have their representatives in the British Islands. 
 
 Groups of Fossiliferous Strata cbserved in Western Europe, ar- 
 ranged in what is termed a descending Series, or beginning with 
 the newest. (See a more detailed Tabular view, pp. 104. 109.) 
 
 1. Post-Pliocene, including those of the 
 
 Recent, or Human period. 
 
 2. Newer Pliocene, or Pleistocene. 1 
 
 3. Older Pliocene. (Tertiary, Supracretaceous *, or 
 
 4. Miocene. [ Cainozoic.f 
 
 5. Eocene. 
 
 6. Chalk. 
 
 7. Greensand and Wealden. 
 
 8. Upper Oolite, including the Purbeck. 
 
 9. Middle Oolite. 
 
 10. Lower Oolite. 
 
 11. Lias. 
 
 12. Trias. 
 
 " Secondary, or Mesozoic. 
 
 * For tertiary, Sir H. De La Beche are superior in position to the chalk, 
 has used the term " supracretaceous," a f For an explanation of Cainozoic 
 name implying that the strata so called &c. see above, p. 95. 
 
 H 4 
 
104 FOSSILIFEROUS STRATA OF WESTERN EUROPE. [Cn. IX. 
 
 Primary fossiliferous, or palaeo- 
 
 zoic. 
 
 13. Permian. 
 
 14. Coal. 
 
 15. Old Red sandstone, or Devonian. 
 
 16. Upper Silurian. 
 
 17. Lower Silurian. 
 
 1 8. Cambrian and older fossiliferous strata. 
 
 It is not pretended that the three principal sections in the above 
 table, called primary, secondary, and tertiary, are of equivalent im- 
 portance, or that the eighteen subordinate groups comprise monu- 
 ments relating to equal portions of past time, or of the earth's his- 
 tory. But we can assert that they each relate to successive periods, 
 during which certain animals and plants, for the most part peculiar 
 to their respective eras, have flourished, and during which different 
 kinds of sediment were deposited in the space now occupied by 
 Europe. 
 
 If we were disposed, on palseontological grounds*, to divide the 
 entire fossiliferous series into a few groups less numerous than those 
 in the above table, and more nearly co-ordinate in value than the 
 sections called primary, secondary, and tertiary, we might, perhaps, 
 adopt the six groups or periods gvven in the next table. 
 
 At the same time, I may observe, that, in the present state of the 
 science, when we have not yet compared the evidence derivable from 
 all classes of fossils, not even those most generally distributed, such 
 as shells, corals, and fish, such generalizations are premature, and can 
 only be regarded as conjectural or provisional schemes for the found- 
 ing of large natural groups. 
 
 Fossiliferous Strata of Western Europe divided into Six Groups. 
 
 1. Post-Pliocene and j from ^ Post .p liocene to the Eocene inclusive. 
 Tertiary ; - J 
 
 f from the Maestricht Chalk to the Wealden inclu- 
 
 2. Cretaceous - - [ siye> 
 
 3. Oolitic - from the Purbeck to the Lias inclusive. 
 
 , . f including the Keuper, Muschelkalk, and Bunter- 
 
 4. inassic - < gandstein of the Germans. 
 
 5. Permian, Carbonife- \ including Magnesian Limestone (Zechstein), Coal, 
 rous, and Devonian J Mountain Limestone, and Old Red Sandstone. 
 
 6. Silurian and Cam- *\ from the Upper Silurian to the oldest fos&iliferous 
 brian - - - J rocks inclusive. 
 
 But the following more detailed list of fossiliferous strata, divided 
 into thirty-three sections, will be required by the reader when he is 
 studying our descriptions of the sedimentary formations given in the 
 next 18 chapters. 
 
 * Palseontology is the science which cient, ovra, onto, beings, and \oyos, logos, 
 treats of fossil remains, both animal and a discourse. 
 vegetable. Etym. TraAotos, palaios, an- 
 
CH. IX.J TABULAR VIEW OF FOSSILIFEROUS STRATA. 
 
 105 
 
 TABULAR VIEW 
 
 OF THE 
 
 FOSSILIFEROUS STRATA, 
 
 Showing the Order of Superposition or Chronological Succession of the 
 
 principal Groups. 
 
 Periods and Groups. 
 
 1. POST-TERTIARY. 
 
 A. POST-PLIOCENE. 
 
 British Examples. 
 
 Foreign Equivalents and Synonyms. 
 
 I. TERRAINS CONTEMPORAINES, 
 
 ET QUATERNAIRES. 
 
 1. RECENT. 
 
 "Peat of Great Britain and Ireland, 
 with human remains. (Princi- 
 ples of Geology, ch. 45.) 
 Alluvial plains of the Thames, 
 Mersey, and Rother, with buried 
 ships,p.!20., and Principles,ch.48. 
 
 2. POST-PLIOCENE. 
 
 II. TERTIARY. 
 B. PLIOCENE. 
 
 3. NEWER 
 
 PLIOCENE, 
 
 or 
 Pleistocene. 
 
 4. OLBER 
 
 PLIOCENE. 
 
 C. MIOCENE. 
 
 5. 1MIOCSNE. 
 
 "Ancient raised beach of Brighton. 
 
 b. fig. 331., p. 288. 
 Alluvium, gravel, brick-earth, &c. 
 with fossil shellsof living species, 
 but sometimes locally extinct, 
 and with bones of land animals, 
 partly of extinct species j no 
 human remains. 
 
 Glacial drift or boulder-formation 
 of Norfolk, p. 132., of the Clyde 
 in Scotland, p. 131 .,of NorthWales, 
 
 p. 137. Norwich Crag, p. 155 
 
 Cave-deposits of Kirkdale, &c. 
 with bones of extinct and living 
 quadrupeds, p. 161. 
 
 TRed Crag of Suffolk, pp. 169171. 
 i Coralline crag of Suffolk, pp. 169 
 172. 
 
 'Marine strata of this age wanting 
 in the British Isles. 
 
 Leaf-bed of Mull in the Hebrides ? < 
 
 p. 180. 
 .Lignite of Antrim?, p. 181. 
 
 ("Part of the Terrain quaternaire of 
 I French authors. 
 Modern part of deltas of Rhine, 
 
 Nile, Ganges, Mississippi, &c. 
 Modern part of coral-reefs of Red 
 J Sea and Pacific. 
 Marine strata inclosing Temple of 
 Serapis at Puzzuoli. Principles, 
 ch. 29. 
 
 Freshwater strata inclosing Tem- 
 ple in Cashmere. Ibid. 9th ed. 
 p. 762, 
 
 Part of Terrain quaternaire of 
 
 French authors. 
 
 Volcanic tuff of Ischia. with living 
 species of marine shells and with- 
 out human remains or works of 
 art, p. 118. 
 
 Loess of the Rhine, with recent 
 I freshwater shells, and mammoth 
 
 bones, p. 122. 
 
 I Newer part of boulder- formation in 
 j Sweden, p. 130. Bluffs of Mis- 
 (, sissippi, p. 122. 
 
 II. TERRAINS TERTIAIRES. 
 
 (Terrain quaternaire, diluvium. 
 Terrains tertiaires superieurs.p.l 39. 
 Glacial drift of Northern Europe, 
 p. 129. j and of Northern United 
 States, p. 140. ; and Alpine er- 
 ratics, p. 149. 
 Limestone of GirgentL p. 159. 
 Australian cave-breccias, p. 162. 
 fSubapennine strata, p. 174. 
 f Hills of Rome, Monte Mario, &c. 
 I p. 176. and p. 535. 
 ] Antwerp and Normandy crag, p. 
 
 174. 
 LAralo-Caspian deposits, p. 176. 
 
 C. TERRAINS TERTIAIRES MOYENS, 
 
 PARTIE SUPERIEURE ; OR FALUNS. 
 
 Falurien superieur, D'Orbigny. 
 Faluns of Touraine, p. 176. 
 Part of Bourdeaux beds, p. 179. 
 Bolderberg strata in Belgium, p. 
 179. 
 
 Part of Vienna basin, p. 180. 
 
 Part of Molasse, Switzerland, p. 
 180. 
 
 Sands of James River, and Rich- 
 mond, Virgir 
 p. 182. 
 
106 
 
 TABULAR VIEW OF 
 
 [CH. IX. 
 
 Periods and Groups. 
 
 D. EOCENE. 
 
 6. UPPER EOCENE 
 
 (lower Miocene of 
 
 many authors). 
 
 British Examples. 
 
 Hempstead beds, near Yarmouth, , 
 Isle of Wight, p. 193. 
 
 7. MXDDXiE EOCENE. 
 
 "1. Bembridge, or Binstead Beds, 
 Isle of Wight, p. 209. 
 
 2. Osborne or St. Helen's Series, 
 p. 211. 
 
 3. Headon Series. Ibid. 
 
 4. Headon Hill Sands, and Barton 
 Clay, p. 213. 
 
 5. Bagshot and Bracklesham Beds, 
 p. 214. 
 
 .6. Wanting? See p. 223. 
 
 8. LOWER EOCENE. 
 
 III. SECONDARY. 
 E. CRETACEOUS. 
 UPPER CRETACEOUS. 
 
 "1. London Clay and Bognor Beds, 
 
 p. 217. 
 2. Plastic and Mottled Clays and 
 
 Sands, and Wolwich Beds, p. 
 
 220. 
 .3. Thanet Sands, p. 222. 
 
 9. MAESTRXCHT 
 BEDS. 
 
 10. UPPER 
 
 WHITE CHALK.. 
 
 11. LOWER 
 
 WHITE CHALK.. 
 
 12. UPPER 
 
 GREENSAND. 
 
 13. GAUX.T. 
 
 { Wanting in England. 
 
 White Chalk with Flints, of North 
 and South Downs, p. 240. 
 
 f Chalk without Flints, and Chalk 
 i Marl, p. 240. 
 Marl. 
 
 Chalk 
 
 Ibid. 
 
 {Loose sand with bright green 
 grains, p. 251. 
 Firestone of Merstham,Surrey,'6zV. 
 Marly Stone with Chert, Isle of 
 . Wight. 
 
 fDark Blue Marl, Kent, p. 251 
 
 J Folkestone Marl or Clay. Glauconie cray 
 
 j Blackdown Beds, green sand and ] Albien, D'Orbigny. 
 
 (_ chert, Devonshire, p. 252. (.Lower planer of Saxony. 
 
 Foreign Equivalents and Synonjms. 
 
 Lower part of Terrain Tertiaire 
 
 Moyen . 
 Calcaire Lacustre Superieur and 
 
 Ore's de Fontambleau, p. 195. 
 Part of the Lacustrine strata of 
 
 Auvergne, p. 195. 
 Kleyn Spawen or Limburg beds, 
 
 Belgium RupeliananciTongrian 
 
 s} stems of Dumont, p. 189. 
 Mayence basin, p. 191. 
 Part of brown-coal of Germany, 
 
 pp. 192. 544. 
 
 Hermsdorf tile-clay near Berlin, 
 . p. 190. 
 
 "1. Gypseous Series of Mont- 
 
 martre, and Calcaire lacustre 
 
 superieur, p. 224. 
 2 & 3. Calcaire Siliceux, p. 226. 
 2 & 3. Grds de Beauchamp, or 
 
 Sables Moyens, p. 227. Laecken 
 
 beds, Belgium. 
 
 4 5. Upper and Middle Calcaire 
 Grossier, p. 227. 
 
 <{ 5. Bruxellien, or Brussels beds of 
 
 Dumont. 
 
 5. Lower Calcaire Grossier, or 
 Glauconie Grossiere, p. 2'29. 
 
 5. Claiborne beds, Alabama, 
 United States, p. 233. 
 
 5 & 6. Nummulitic formation of 
 Europe, Asia, &c., p. 230. 
 
 6. Soissonnais Sands, or Lits Co- 
 quilliers, p. 229. 
 
 "1. Wanting in Paris basin, occurs 
 at Cassel, in French Flanders. 
 
 2. Argile Plastique et Lignite, p. 
 230. 
 
 3. Lower Landenian of Belgium, 
 in part?, p. 236. 
 
 III. TERRAINS SECONDAIRES. 
 E. TERRAINS CRETACEES. 
 
 {9. Danien of D'Orbigny. 
 Calcaire pisolitique, near Paris, 
 p. 236. 
 Maestricht Beds, p. 238. 
 Coralline Limestone of Faxoe in 
 Denmark, p. 239. 
 HO. Senonien, D'Orbigny. 
 1 Craie blanche avec silex. 
 J Obere Kreide of the Germans. 
 Upper Quadersandstein? of the 
 
 same. 
 
 La Scaglia of the Italians. 
 Calcaire a hippurites, Pyrennees. 
 Turonien, D'Orb., or, Craie tufeau 
 
 of Touraine. 
 Craie argileuse of some French 
 
 writers. 
 
 .Upper Planerkalk of Saxony. 
 Gres vert superieur. 
 Glauconie crayeuse. 
 Craie chloritee. 
 Cenomanien, D'Orbigny. 
 Lower Quadersandstein of the Ger- 
 mans. 
 
 f Gres vert supeneinr ? Jn part> 
 
 LOWER CRETACEOUS, OR XEOCOMIAN. 
 
 LOWER 
 GREENSANX). 
 
 Sand with green matter, Weald |~ 
 
 of Kent and Sussex, p. 258. Grds vert inferieur. 
 
 Limestone (Kentish Rag,) p. 258. Neocomien superieur. 
 Sands and clay with calcareous I Aptien, D'Orbigny. 
 
 concretions and chert. ] Hils-conglomerat of Germany. 
 
 Atherfield, Isle of Wight, p. 258. 
 
 LSpeeton Clay, Yorkshire. 
 
 Hils-thon of Brunswick. 
 
CH. IX.] 
 
 Periods and Groups. 
 
 15. WEAX.DEN 
 ("Weald Clay and 
 Hastings Sand). 
 
 FOSSILIFEROUS STRATA. 
 
 107 
 
 British Examples. 
 
 Clay with occasional bands of lime- 
 stone Weald of Kent, Surrey, 
 
 and Sussex, p. 261. 
 
 Sand with calcareous grit and clay, 
 Hastings, Cuckfield, Sussex, 
 p. 263. 
 
 Foreign Equivalents and Synonyms. 
 
 Formation Waldienne. 
 Neocomien inferieur. 
 
 F. OOLITE. 
 UPPER OOLITE. 
 
 F. TERRAINS JuRASSiQUES,inpart. 
 
 f Upper, Middle, and Lower Pur- fSerpulitenkalk of Dunker, and 
 16, PURBECX BEDS. 1 be ck, Dorsetshire and Wilts, pp. < associated beds of the North Ger- 
 t_ 294297. L man Walderformation. 
 
 17. PORTLAND 
 
 BEDS. 
 
 18. XIMMERIDGE 
 
 CLAY. 
 
 ; MIDDLE OOLITE. 
 
 19. CORAL-RAG. 
 
 20. OXFORD CLAY. 
 
 LOWER OOLITE. 
 
 21. GREAT or BATH 
 
 OOLITE. 
 
 Portland sand, J Groupe p or tlandien of Beudant. 
 fKimmeridgien, D'Orbigny. 
 
 ( Clay of Kimmeridge, Dorsetshire, 
 
 Ca j c h f r e ia ^ **&* virgules > f 
 1 Argiles de Honfleur, E. de Beau 
 L mont et Dufresnoy. 
 
 corallien of Beudant. 
 
 stone with sh 
 Rock, p. 34. 
 
 I mann. 
 
 | 2. Oxfordie 
 
 I vien, D'Orbigny 
 
 or Ca "- 
 
 22. INFERIOR 
 
 OOLITE. 
 
 "1. Cornbrash and Forest Marble, [~ 
 
 Wiltshire, p. 306. I Bathonien of Omalius D'Halloy. 
 
 2. Great Oolite and Stonesfield <^ Grand Oolithe. 
 
 Slate, Bath, Stonesfield, pp.306. Calcaire de Caen. 
 L 310. L 
 
 ("Fuller's Earth, near Bath, p. 315. f 
 1 Calcareous freestone, and yellow | Oolithe inferieur. 
 J sands of Cotteswold Hills, j Oolithe ferrugineux of Normandy. 
 1 Gloucestershire, p. 315. J Oolithe de Bayeux. 
 
 Dundry Hill, near Bristol, pp. 103. j Bajocien of D'Orbigny. 
 
 G. LIAS. 
 
 23. 
 
 XiIAS. 
 
 "1. Upper Lias, p. 319. 
 2. Marl-stone, ibid. 
 ,3. Lower Lias, ibid. 
 
 G. TERRAINS JURASSIQUES, in part. 
 
 [1. Etage superieur du Lias, 
 Thirria. 
 
 Toarcien, D'Orbigny. 
 | 2. Lias moyen. 
 
 Liasien, D'Orbigny. 
 
 3 Calcaire & gryphee arquee. 
 
 Slnemurien, D'Orbigny. 
 
 Coal-field near Richmond, Vir- 
 . ginia, p. 331. 
 
 H. TRIAS. 
 
 ( Upper New Red Sandstone). 
 
 H. NOUVBAU GRES ROUGH. 
 
 24. UPPER TRIAS. 
 
 fSaliferousand Gypseous sandstones f 
 
 and shales of Cheshire, pp.|335 I Keuper of the Germans. 
 } 338 - ^ Marnes irisees of the French. 
 
 Bone-bed of Axmouth, Devon, p. Saliferien, D'Orbigny. 
 L 338. j_ 
 
 25. MIDDX.E TRIAS 
 
 or 
 Muschelkalk. 
 
 26. LOWER TRIAS 
 
 f Muschelkalk of the Germans. 
 Wanting in England. 1 Calcaire conchylien, Brongniart. 
 
 ] Calcaire a Ceratites, Cordier. 
 L Conchylien, D'Orbigny, (in part). 
 
 "Red and white Sandstone of TBunter-Sandstein of the Germans. 
 
 Lanc ^ s a hi ^n aud Ches hire <! Grfe bigarre of the French. 
 L pp. 338 : 339. LConchylien, D'Orbigny, (in part). 
 
108 
 
 TABULAR VIEW OF FOSSILIFEROUS STRATA. [Cn. IX 
 
 British Examples. 
 
 27. 
 
 Periods and Groups. 
 
 IV. PRIMARY. 
 
 /. PERMIAN, 
 or MAGNESIAN LIMESTONE. 
 
 (Lower New Red.) 
 
 "1 Concretionarylimestone of Dur- 
 ham and Yorkshire, p. 354. 
 
 2. Brecciated limestone, ibid. 
 
 3. Fossiliferous limestone, p. 355. 
 \ Compact limestone, ibid 
 
 Foreign Equivalents and Synonyms. 
 
 IV. TERRAINS DE TRANSITION. 
 TERRAINS PALEOZOIQUES. 
 
 I. CALCAIRE MAGNESIEN. 
 
 PERMIAN, 
 or 
 
 IV1AGNESIAN 
 LIMESTONE. 
 
 5.' Marl-slate of Durham, p. 356. 
 6. Inferior sandstones of various 
 colours, N. of England, p. 357. 
 
 Dolomitic conglomerate, Bristol, 
 e p. 357. 
 
 K. CARBONIFEROUS. 
 
 28. UPPER 
 CARBONIFEROUS. 
 
 29. LOWER 
 
 CARBONIFEROUS. 
 
 1. Coal-measures, sandstone and 
 shale with seams of coal, West 
 of England and Ireland, Chapters- 
 24 and 25. 
 
 2. Millstone Grit, pp- 361, 362. 
 
 1. Mountain orCarboniferous lime- 
 stone, p. 407. etseq. 
 
 2. Lower limestone shale, Men- 
 dips. Carboniferous slate, 
 Ireland : 
 
 Carbonaceous schist with Possi- 
 . donomya Becheri, p. 413. 
 
 1. Stinkstein of Thuringia. 
 
 2. Rauchwacke, ibid. 
 
 3. Dolomit or Upper Zechstein. 
 
 4. Zechstein, p. 353. 
 
 5. Mergel or Kupfer-schiefer. 
 
 6. Rothliegendes of Thuringia. 
 
 Permian of Russia, p. 358. 
 Gres des Vosges of French, (i 
 part). 
 
 K. TERRAIN HOUILLIER. 
 
 Coal-fields of the United States, 
 391. 
 
 1. Calcaire carbonifre of tl 
 
 French. 
 1. Bergkalk or Kohlenkalk of tfc 
 
 Germans. 
 1. Pentremite limestone, Unite 
 
 States p- 414. 
 
 Kiesel-scliiefer and Jiingere Grai 
 
 wacke of the Germans, p. 413. 
 
 Gypseous beds and Encrinitf 
 
 L limestone ot Nova Scoti a, p. 41: 
 
 L. DEVONIAN, 
 or OLD RED SANDSTONE. 
 
 3O. UPPER 
 
 DEVONIAN. 
 
 31. LOWER 
 
 DEVONIAN. 
 
 f Yellow sandstone of Dura Den, 
 
 Fife, p. 416. 
 While sandstoneof Elgin, with Te- 
 
 lerpeton, ibid- 
 Red sandstone and conglomerate, 
 
 p. 418. 
 Upper and middle Devonian of N. 
 
 Devon, including Plymouth 
 
 limestone, pp. 424. 426. 
 Lower Devonian of N. Devon, 
 
 North Foreland, p. 428. 
 Arbroath paving-stone, pp. 416 
 
 Bituminous schists of Caithness, p. 
 
 M. SILURIAN. 
 
 32. UPPER 
 
 SILURIAN. 
 
 32 a. MIDDLE SILURIAN. 
 (Beds of passage between <j 
 Upper and Lower Silurian). [^ 
 
 fl. Upper Ludlow, p. 434. 
 | 2. A ymestry Limestone, p. 438. 
 ^ 3. Lower Ludlow, tbid. 
 
 4. Wenlock Limestone, p. 439. 
 
 5. Wenlock shale, p. 441. 
 
 L. TERRAIN DEVONIEN. 
 
 "VlEUXGRES ROUGE. 
 
 I Russian Devonian, Upper part, 
 429. 
 j Catskill group, United States, j 
 1 430. 
 
 Kifel Limestone, p. 428. 
 Limestone of Villmar, &c., Nassai 
 
 fl. Spirifer Sandstone and Slate t 
 1 Sandberger, p. 428. 
 Older Rhenish Greywacke of Ro 
 
 mer, ibid. 
 
 Russian Devonian, Lower part, i 
 429. 
 
 M. TERRAIN SILURIEN. 
 fNew York division from the U] 
 I per Pentamerus to the Niaga 
 ^ Group inclusive, p. 448. 
 I Etages E. to H. of Barrand 
 L Bohemia. 
 
 [ fNew York groups from the Clintc 
 
 J Caradoc or May Hill Sandstone, ^ to the Grey sandstone inclusiv 
 
 p. 441, 
 
 L p. 448. 
 
 33. LOWER 
 SILURIAN. 
 
 N. CAMBRIAN. 
 
 34. UPPER 
 CAMBRIAN. 
 
 35. LOWER 
 CAMBRIAN. 
 
 f Llandeilo Flags and shale, p. 443. ("New York groups from the Hu< 
 1 Bala Limestone and black slate, son-Riverbeds to the Calciferol 
 
 p. 445. I sandstone inclusive, p. 448. 
 
 Graptolite Schists, S. of Scotland. ] Etages C. and D. (Barrande 
 f Limestone, Chair of Kildare, Bohemia. 
 
 
 L Ireland. 
 
 \ Lingula Flags, North Wales, p 
 1 452. 
 Stiper Stones, Shropshire. 
 
 l-Slates of Angers, France. 
 
 fPrimordial zone of Barrande i 
 
 Bohemia, p. 454. 
 I Alum Schists of Sweden, p. 455. 
 <{ Potsdam Sandstone of Uniti 
 | States and Canada, p. 455. 
 I Wisconsin and Minnesota, lowe 
 L fossiliferous rocks, p. 456. 
 
 Lowest fossiliferous rocks 
 Wicklow in Ireland, p. 453. 
 
 of 
 
CH.IX.] ABRIDGED TABLE OF FOSSILIFEROUS STRATA. 109 
 
 ABRIDGED TABLE OF FOSSILIFEROUS STRATA. 
 
 1. RECENT. 
 
 2. POST-PLIOCENE. 
 
 3. NEWER PLIOCENE. 
 
 4. OLDER PLIOCENE. 
 
 5. MIOCENE. 
 
 6. UPPER EOCENE. 
 
 7. MIDDLE EOCENE. 
 
 8. LOWER EOCENE. 
 
 9. MAESTRICHT BEDS. 
 
 10. UPPER WHITE CHALK. 
 
 11. LOWER WHITE CHALK. 
 
 12. UPPER GREENSAND. 
 
 13. GAULT. 
 
 14. LOWER GREENSAND. 
 
 15. WEALDEN. 
 
 16. PURBECK BEDS. 
 
 17. PORTLAND STONE. 
 
 18. KIMMERIDGE CLAY. 
 
 19. CORAL RAG. 
 
 20. OXFORD CLAY. 
 
 1 21. GREAT or BATH OOLITE. 
 
 22. INFERIOR OOLITE. 
 
 23. LIAS. 
 
 24. UPPER TRIAS. 
 
 25. MIDDLE TRIAS, or 
 
 MUSCHE.LKALK. 
 
 26. LOWER TRIAS. 
 
 27. PERMIAN, 
 
 or 
 MAGNESIAN LIMESTONE. 
 
 28. COAL-MEASURES. 
 
 29. CARBONIFEROUS 
 
 LIMESTONE. 
 
 30. UPPER 1 
 
 ^DEVONIAN. 
 
 31. LOWERJ 
 
 32. UPPER -| 
 
 ^SILURIAN. 
 
 33. LOWER/ 
 
 34. UPPER "I 
 
 ^CAMBRIAN. 
 
 35. LOWERJ 
 
 | POST-TERTIARY. 
 
 } 
 
 PZ.IOCENE. 
 MIOCENE. 
 
 EOCENE. 
 
 CRETACEOUS. 
 
 JURASSIC. 
 
 TRIASSIC. 
 
 PERMIAN 1 . 
 
 CARBOXOTIFEROUS. 
 
 SH.TTRIAM*. 
 
 CAMBRIAN 1 . 
 
 W 
 
 s 
 
 s 
 
110 PRINCIPLES OF CLASSIFICATION [Cn. X. 
 
 CHAPTER X. 
 
 CLASSIFICATION OP TERTIARY FORMATIONS. POST-PLIOCENE GROUP. 
 
 General principles of classification of tertiary strata Detached formations scattered 
 over Europe Strata of Paris and London More modern groups Peculiar 
 difficulties in determining the chronology of tertiary formations Increasing 
 proportion of living species of shells in strata of newer origin Terms Eocene, 
 
 Miocene, and Pliocene Post-Pliocene strata Eecentor human period Older 
 
 Post-Pliocene formations of Naples, Uddevalla, and Norway Ancient upraised 
 delta of the Mississippi Loess of the Rhine. 
 
 BEFORE describing the most modern of the sets of strata enumerated 
 in the Tables given at the end of the last chapter, it will be necessary 
 to say something generally of the mode of classifying the formations 
 called tertiary. 
 
 The name of tertiary has been given to them, because they are all 
 posterior in date to the rocks termed " secondary," of which the chalk 
 constitutes the newest group. These tertiary strata were at first 
 confounded, as before stated, p. 91., 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 freshwater, others of 
 marine origin, their geographical area being usually small as com- 
 pared to the secondary formations, and their position often suggesting 
 the idea of their having been deposited in different bays, lakes, es- 
 tuaries, or inland seas, after a large portion of the space now occupied 
 by Europe had already been converted into dry land. 
 
 The first deposits of this class, of which the characters were ac- 
 curately determined, were those occurring in the neighbourhood 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 freshwater 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 distirrct species, 
 were examined by Cuvier, and declared by him not to agree specifi- 
 cally, nor even for the most part generically, with any hitherto ob- 
 served in the living creation. 
 
 Strata were soon afterwards brought to light in the vicinity of 
 London, and in Hampshire, which, although dissimilar in mineral 
 composition, were justly inferred by Mr. T. Webster to be of the 
 same age as those of Paris, because the greater number of the fossil 
 shells were specifically identical. 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. 
 
CH. X.] OP TERTIARY FORMATION. 1 1 1 
 
 A variety of deposits were afterwards found in other parts of 
 Europe, all reposing immediately on rocks as old or older than the 
 chalk, and which exhibited certain general characters of resemblance 
 in their organic remains to those previously observed near Paris and 
 London. An attempt was therefore made at first to refer the whole 
 to one period ; and when at length this seemed impracticable, it was 
 contended that as in the Parisian series there were many subordinate 
 formations of considerable thickness which must have accumulated 
 one after the other, during a great lapse of time, so the various 
 patches of tertiary strata scattered over Europe might correspond in 
 age, some of them to the older, and others to the newer, subdivisions 
 of the Parisian series. 
 
 This error, though almost unavoidable on the part of those who 
 made the first generalizations in this branch of geology, retarded 
 seriously for some years the progress of classification. A more scru- 
 pulous attention to specific distinctions, aided by a careful regard to 
 the relative position of the strata containing them, led at length to 
 the conviction that there were formations both marine and freshwater 
 of various ages, and all newer than the strata of the neighbourhood of 
 Paris and London. 
 
 One of the first steps in this chronological reform was made in 
 1811, by an English naturalist, Mr. Parkinson, who pointed out the 
 fact that certain shelly strata, provincially termed " Crag " in Suffolk, 
 lie decidedly over a deposit which was the continuation of the blue 
 clay of London. At the same time he remarked that the fossil tes- 
 tacea in these newer beds were distinct from those of the blue clay, 
 and that while some of them were of unknown species, others were 
 identical with species now inhabiting the British seas. 
 
 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 Subapennines, and were formed of strata 
 chiefly marine, and newer than those of Paris and London. 
 
 Another tertiary group occurring in the neighbourhood 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. It was soon, therefore, suspected 
 that this fauna might belong to a period intermediate between that of 
 the Parisian and Subapennine strata, and it was not long before the 
 evidence 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 Sub- 
 apennine beds. The first example of these was pointed out in 1829 
 by M. Desnoyers, who ascertained that the sand and marl of marine 
 origin called Faluns, near Tours, in the basin of the Loire, full of sea- 
 shells and corals, rested upon a lacustrine formation, which constitutes 
 
112 PRINCIPLES OF CLASSIFICATION. [Cn. X. 
 
 the uppermost subdivision of the Parisian group, extending con- 
 tinuously throughout a great table-land intervening 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 Bor- 
 deaux, were observed by Bonelli and others in the environs of Turin, 
 subjacent to strata belonging to the Subapennine group of Brocchi. 
 
 Without pretending to give a complete sketch of the progress of 
 discovery, I may refer to the facts above enumerated, as illustrating 
 the course usually pursued by geologists when they attempt to found 
 new chronological divisions. The method bears some analogy to that 
 pursued by the naturalist in the construction of genera, when he 
 selects a typical species, and then classes as congeners all other species 
 of animals and plants which agree with this standard within certain 
 limits. The genera A. and C. having been founded on these prin- 
 ciples, a new species is afterwards met with, departing widely both 
 from A. and C., but in many respects of an intermediate character. 
 For this new type it becomes necessary to institute the new genus B., 
 in which are included all species afterwards brought to light, which 
 agree more nearly with B. than with the types of A. or C. In like 
 manner a new formation is met with in geology, and the characters 
 of its fossil fauna and flora investigated. From that moment it is 
 considered as a record of a certain period of the earth's history, and a 
 standard to which other deposits may be compared. If any are found 
 containing the same or nearly the same organic remains, and occupy- 
 ing the same relative position, they are regarded in the light of con- 
 temporary annals. All such monuments are said to relate to one 
 period, during which certain events occurred, such as the formation 
 of particular rocks by aqueous or volcanic agency, or the continued 
 existence and fossilization of certain tribes of animals and plants. 
 When several of these periods have had their true places assigned to 
 them in a chronological series, others are discovered which it becomes 
 necessary to intercalate between those first known ; and the difficulty 
 of assigning clear lines of separation must unavoidably increase in 
 proportion as chasms in the past history of the globe are filled up. 
 
 Every zoologist and botanist is aware that it is a comparatively 
 easy task to establish genera in departments which have been en- 
 riched with only a small number of species, and where there is as 
 yet no tendency in one set of characters to pass almost insensibly, by 
 a multitude of connecting links, into another. They also know that 
 the difficulty of classification augments, and that the artificial nature 
 of their divisions becomes more apparent, in proportion to the increased 
 number of objects brought to light. But in separating families and 
 genera, they have no other alternative than to avail themselves of 
 such breaks as still remain, or of every hiatus in the chain of ani- 
 mated beings which is not yet filled up. So in geology, we may be 
 eventually compelled to resort to sections of time as arbitrary, and as 
 purely conventional, as those which divide the history of human 
 events into centuries. But in the present state of our knowledge, it | 
 is more convenient to use the interruptions which still occur in the ! 
 
CH. X.] OF TERTIARY FORMATIONS. 113 
 
 regular sequence of geological monuments, as boundary lines between 
 our principal groups or periods, even though the groups thus esta- 
 blished are of very unequal value. 
 
 The isolated position of distinct tertiary deposits in different parts 
 of Europe has been already alluded to. In addition to the difficulty 
 presented by this want of continuity when we endeavour to settle 
 the chronological relations of these deposits, another arises from the 
 frequent dissimilarity in mineral character of strata of contempora- 
 neous date, such, for example, as those of London and Paris before 
 mentioned. The identity or non-identity of species is also a criterion 
 which often fails us. For this we might have been prepared, for we 
 have already seen, that the Mediterranean and Red Sea, although 
 within 70 miles of each other, on each side of the Isthmus of Suez, 
 have each their peculiar fauna ; and a marked difference is found in 
 the four groups of testacea now living in the Baltic, English Channel, 
 Black Sea, and Mediterranean, although all these seas have many 
 species in common. In like manner a considerable diversity in the 
 fossils of different tertiary formations, which have been thrown 
 down in distinct seas, estuaries, bays, and lakes, does not always 
 imply a distinctness in the times when they were produced, but may 
 have arisen from climate and conditions of physical geography wholly 
 independent of time. On the other hand, it is now abundantly clear, 
 as the result of geological investigation, that different sets of tertiary 
 strata, immediately superimposed upon each other, contain distinct 
 imbedded species of fossils, in consequence of fluctuations which have 
 been going on in the animate creation, and by which in the course of 
 ages one state of things in the organic world has been substituted for 
 another wholly dissimilar. It has also been shown that in propor- 
 tion as the age of a tertiary deposit is more modern, so is its fauna 
 more analogous to that now in being in the neighbouring seas. It is 
 this law of a nearer agreement of the fossil testacea with the species 
 now living, which may often furnish us with a clue for the chrono- 
 logical arrangement of scattered deposits, where we cannot avail our- 
 selves of any one of the three ordinary chronological tests ; namely, 
 superposition, mineral character, and the specific identity of the 
 fossils. 
 
 Thus, for example, on the African border of the Red Sea, at the 
 height of 40 feet, and sometimes more, above its level, a white calca- 
 reous formation has been observed, containing several hundred species 
 of shells differing from those found in the clay and volcanic tuff of 
 the country round Naples, and of the contiguous island of Ischia. 
 Another deposit has been found at Uddevalla, in Sweden, in which 
 the shells do not agree with those found near Naples. But although 
 in these three cases there may be scarcely a single shell common to 
 the three different deposits, we do not hesitate to refer them all to 
 one period (the Post-Pliocene), because of the very close agreement 
 of the fossil species in every instance with those now living in the 
 contiguous seas. 
 
 To take another example, where the fossil fauna recedes a few 
 
 I 
 
114 CLASSIFICATION OF TERTIARY FORMATIONS. [Ce. X. 
 
 steps farther back from our own times. We may compare, first, the 
 beds of loam and clay bordering the Clyde in Scotland (called glacial 
 by some geologists) ; secondly, others of fluvio-marine origin near 
 Norwich ; and, lastly, a third set often rising to considerable heights in 
 Sicily : and we discover that in every case more than three-fourths of 
 the shells agree with species still living, while the remainder are 
 extinct. Hence we may conclude that all these, greatly diversified as 
 are their organic remains, belong to one and the same era, or to a 
 period immediately antecedent to the Post-Pliocene, because there 
 has been time in each of the areas alluded to for an equal or nearly 
 equal amount of change in the marine testaceous fauna. Contempo- 
 raneousness of origin is inferred in these cases, in spite of the most 
 marked differences of mineral character or organic contents, from a 
 similar degree of divergence in the shells from those now living in the 
 adjoining seas. The advantage of such a test consists in supplying 
 us with a common point of departure in all countries, however remote. 
 But the farther we recede from the present times, and the smaller 
 the relative number of recent as compared with extinct species in 
 the tertiary deposits, the less confidence can we place in the exact 
 value -of such a test, especially when comparing the strata of very 
 distant regions ; for we cannot presume that the rate of former 
 alterations in the animate world, or the continual going out and 
 coming in of species, has been every where exactly equal in equal 
 quantities of time. The form of the land and sea, and the climate, 
 may have changed more in one region than in another ; and conse- 
 quently there may have been a more rapid destruction and renova- 
 tion of species in one part of the globe than elsewhere. Consider- 
 ations of this kind should undoubtedly put us on our guard against 
 relying too implicitly on the accuracy of this test ; yet it can never 
 fail to throw great light on the chronological relations of tertiary 
 groups with each other, and with the Post-Pliocene period. 
 
 We may derive a conviction of this truth not only from a study of 
 geological monuments of all ages, but also by reflecting on the ten- 
 dency which prevails in the present state of nature to a uniform rate 
 of simultaneous fluctuation in the flora and fauna of the whole globe. 
 /The grounds of such a doctrine cannot be discussed here, and I 
 have explained them at some length in the third Book of the 
 Principles of Geology, where the causes of the successive extinction 
 of species are considered. It will be there seen that each local change 
 in climate and physical geography is attended with the immediate 
 increase of certain species, and the limitation of the range of others. 
 A revolution thus effected is rarely, if ever, confined to a limited 
 space, or to one geographical province of animals or plants, but 
 affects several other surrounding and contiguous provinces. In each 
 of these, moreover, analogous alterations of the stations and habit- 
 ations of species are simultaneously in progress, reacting in the 
 manner already alluded to on the first province. Hence, long before 
 the geography of any particular district can be essentially altered, 
 the flora and fauna throughout the world will have been materially 
 
CH. X.] FOSSIL SHELLS. 115 
 
 modified by countless disturbances in the mutual relation of the various 
 members of the organic creation to each other. To assume that in 
 one large area inhabited exclusively by a single assemblage of species 
 any important revolution in physical geography can be brought about, 
 while other areas remain stationary in regard to the position of land 
 and sea, the height of mountains, and so forth, is a most improbable 
 hypothesis, wholly opposed to what we know of the laws now governing 
 the aqueous and igneous causes. On the other hand, even were this 
 conceivable, the communication of heat and cold between different 
 parts of the atmosphere and ocean is so free and rapid, that the tempe- 
 rature of certain zones cannot be materially raised or lowered without' 
 others being immediately affected ; and the elevation or diminution in 
 height of an important chain of mountains or the submergence of a 
 wide tract of land would modify the climate even of the antipodes. 
 
 It will be observed that in the foregoing allusions to organic re- 
 mains, the testacea or the shell-bearing mollusca are selected as the 
 most useful and convenient class for the purposes of general classifi- 
 cation. In the first place, they are more universally distributed 
 through strata of every age than any other organic bodies. Those 
 families of fossils which are of rare and casual occurrence are abso- 
 lutely of no avail in establishing 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 dis- 
 cordance of the organic beings of the two epochs compared ; and the 
 same may be said if we have plants and vertebrated animals in one 
 series and only shells in another. Although corals are more abun- 
 dant, in a fossil state, than plants, reptiles, or fish, they are still rare 
 when contrasted with shells, especially in the European tertiary for- 
 mations. 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 freshwater. Rivers scarcely ever fail to carry 
 down into their deltas some land shells, together with species which 
 are at once fluviatile and lacustrine. By this means we learn what 
 terrestrial, freshwater, and marine species co-existed at particular 
 eras of the past : and having thus identified strata formed in seas 
 with others w r hich originated contemporaneously in inland lakes, we 
 are then enabled to advance a step farther, and show that certain 
 quadrupeds or aquatic plants, found fossil in lacustrine formations, 
 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 geographical 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 lasted but for a brief period, they could have 
 
 i 2 
 
116 FOSSIL SHELLS. [Cn. X. 
 
 thrown no light on the connection of rocks placed far from each other 
 in the chronological, or, as it is often termed, vertical series. 
 
 Many authors have divided the European tertiary strata into three 
 groups lower, middle, and upper ; the lower comprising the oldest 
 formations of Paris and London before mentioned ; the middle those 
 of Bordeaux and Touraine ; and the upper all those newer than the 
 middle group. 
 
 When engaged in 1828 in preparing my work on the Principles of 
 Geology, I conceived the idea of classing the whole series of tertiary 
 strata in four groups, and endeavouring to find characters for each, 
 expressive of their different degrees of affinity to the living fauna. 
 With this view, I obtained information respecting the specific iden- 
 tity of many tertiary and recent shells from several Italian naturalists, 
 and among others from Professors Bonelli, Guidotti, and Costa. 
 Having in 1829 become acquainted with M. Deshayes, of Paris, 
 already well known by his conchological works, I learnt from him 
 that he had arrived, by independent researches, and by the study of a 
 large collection of fossil and recent shells, at very similar views re- 
 specting the arrangement of tertiary formations. At my request he 
 drew up, in a tabular form, lists of all the shells known to him to occur 
 both in some tertiary formation and in a living state, for the express 
 purpose of ascertaining the proportional number of fossil species iden- 
 tical with the recent which characterized successive groups ; and this 
 table, planned by us in common, was published by me in 1833.* The 
 number of tertiary fossil shells examined by M. Deshayes was about 
 3000 ; and the recent species with which they had been compared 
 about 5000. The result then arrived at was, that in the lower ter- 
 tiary strata, or those of London and Paris, there were about 3| per 
 cent, of species identical with recent ; in the middle tertiary of the 
 Loire and Gironde about 17 per cent. ; and in the upper tertiary or 
 Subapennine beds, from 35 to 50 per cent. In formations still more 
 modern, some of which I had particularly studied in Sicily, where 
 they attain a vast thickness and elevation above the sea, the number 
 of species identical with those now living was believed to be from 
 9O to 95 per cent. For the sake of clearness and brevity, I proposed 
 to give short technical names to these four groups, or the periods to 
 which they respectively belonged. I called the first or oldest of them 
 Eocene, the second Miocene, the third Older Pliocene, and the last 
 or fourth Newer Pliocene. The first of the above terms, Eocene, is 
 derived from T/WC, eos, dawn, and ceuvoc, cainos, recent, because 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 fieiov, nieion, less, and naivog, cainos, 
 recent) is intended to express a minor proportion of recent species 
 (of testacea), the term Pliocene (from TrXetov, pleion, more, and 
 
 * See Princ. of Geol. vol. iii. 1st ed. 
 
CH. X.] POST-PLIOCENE FORMATIONS. 117 
 
 cainos, recent) a comparative plurality of the same. It may assist 
 the memory of students to remind them, that the Miocene contain a 
 minor proportion, and Pliocene 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 existing, 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 must bear in mind that the terms Eocene, Miocene, 
 and Pliocene were originally invented with reference purely to con- 
 chological data, and in that sense have always been and are still used 
 by me. 
 
 The distribution of the fossil species from which the results before 
 mentioned were obtained in 1830 by M. Deshayes was as follows: 
 
 In the formations of the Pliocene periods, older and newer - 777 
 In the Miocene - -.^s a; - - - - 1021 
 
 In the Eocene - - - - - - 1238 
 
 3036 
 
 Since the year 1830, the number of new living species obtained 
 from different parts of the globe has been exceedingly great, supplying 
 fresh data for comparison, and enabling the paleontologist to correct 
 many erroneous identifications of fossil and recent forms. New 
 species also have been collected in abundance from tertiary formations 
 of every age, while newly discovered groups of strata have filled up 
 gaps in the previously known series. Hence modifications and re- 
 forms have been called for in the classification first proposed. The 
 Eocene, Miocene, and Pliocene periods have been made to comprehend 
 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. 
 Of these and other innovations I shall treat more fully in the 14th 
 and 15th chapters. 
 
 POST-PLIOCENE FORMATIONS. 
 
 I have adopted the term Post-Pliocene for those strata which are 
 sometimes called post-tertiary or modern, and which are characterized 
 by having all the imbedded fossil shells identical with species now 
 living, whereas even the Newer Pliocene, or newest of the tertiary 
 deposits above alluded to, contain always some small proportion of 
 shells of extinct species. 
 
 These modern formations, thus defined, comprehend not only those 
 strata which can be shown to have originated since the earth was 
 inhabited by man, but also deposits of far greater extent and thick- 
 ness, in which no signs of man or his works can be detected. In some 
 of these, of a date long anterior to the times of history and tradition, 
 the bones of extinct quadrupeds have been met with of species which 
 probably never co-existed with the human race, as, for example, the 
 
 i 3 
 
118 POST-PLIOCENE FOEMATIONS. [Cn. X. 
 
 mammoth, mastodon, megatherium, and others, and yet the shells are 
 the same as those now living. 
 
 That portion of the post-pliocene group which belongs to the 
 human epoch, and which is sometimes called Recent, forms a very 
 unimportant feature in the geological structure of the earth's crust. 
 I have shown, however, in " The Principles," where the recent changes 
 of the earth illustrative of geology are described at length, that 
 the deposits accumulated at the bottom of lakes and seas within the 
 last 4000 or 5000 years can neither be insignificant in volume or 
 extent. They lie hidden, for the most part, from our sight ; but we 
 have opportunities of examining them at certain points where newly- 
 gained land in the deltas of rivers has been cut through during floods, 
 or where coral reefs are growing rapidly, or where the bed of a sea 
 or lake has been heaved up by subterranean movements and laid 
 dry. Their age may be recognized either by our finding in them 
 the bones of man in a fossil state, that is to say, imbedded in them 
 by natural causes, or by their containing articles fabricated by the 
 hands of man. 
 
 Thus at Puzzuoli, near Naples, marine strata are seen containing 
 fragments of sculpture, pottery, and the remains of buildings, together 
 with innumerable shells retaining in part their colour, and of the 
 same species as those now inhabiting the Bay of Baits. The up- 
 permost of these beds is about 20 feet above the level of the sea. 
 Their emergence can be proved to have taken place since the be- 
 ginning of the sixteenth century. * Now here, as in almost every 
 instance where any alterations of level have been going on in 
 historical periods, it is found that rocks containing shells, all, or 
 nearly all, of which still inhabit the neighbouring sea, may be traced 
 for some distance into the interior, and often to a considerable 
 elevation above the level of the sea. Thus, in the country round 
 I Naples, the post-pliocene strata, consisting of clay and horizontal 
 I beds of volcanic tuff, rise at certain points to the height of 1500 feet. 
 Although the marine shells are exclusively of living species, they are 
 I not accompanied like those on the coast at Puzzuoli by any traces of 
 * man or his works. Had any such been discovered, it would have 
 afforded to the antiquary and geologist matter of great surprise, 
 since it would have shown that man was an inhabitant of that part 
 of the globe, while the materials composing the present hills and 
 plains of Campania were still in the progress of deposition at the 
 bottom of the sea ; whereas we know that for nearly 3000 years, or 
 from the times of the earliest Greek colonists, no material revolution 
 in the physical geography of that part of Italy has occurred. 
 
 In Ischia, a small island near Naples, composed in like manner of 
 marine and volcanic formations, Dr. Philippi collected in the stra- 
 tified tuff and clay ninety-two species of shells of existing species. In 
 the centre of Ischia, the lofty hill called Epomeo, or San Nicola, is 
 composed of greenish indurated tuff, of a prodigious thickness, inter- 
 
 * See Principles, Index, " Serapis." 
 
Cn. X.] POST-PLIOCENE FORMATIONS. 119 
 
 stratified in some parts with marl, and here and there with great 
 beds of solid lava. Visconti ascertained by trigonometrical measure- 
 ment that this mountain was 2605 feet above the level of the sea. 
 Not far from its summit, at the height of about 2000 feet, as also 
 near Moropano, a village only 100 feet lower, on the southern de- , 
 clivity of the mountain, I collected, in 1828, many shells of species \ 
 now inhabiting the neighbouring gulf. It is clear, therefore, that the 
 great mass of Epomeo was not only raised to its present height, but 
 was also formed beneath the waters, within the post-pliocene period. 
 
 It is a fact, however, of no small interest, that the fossil shells from 
 these modern tuffs of the volcanic region surrounding the Bay of 
 Baiae, although none of them extinct, indicate a slight want of corre- 
 spondence between the ancient fauna and that now inhabiting the 
 Mediterranean. Philippi informs us that when he and M. Scacchi had 
 collected ninety-nine species of them, he found that only one, Pecten 
 medius, now living in the Red Sea, was absent from the Mediter- 
 ranean. Notwithstanding this, he adds, " the condition of the sea 
 when the tufaceous beds were deposited must have been considerably 
 different from its present state ; for Tellina striata was then common, 
 and is now rare ; Lucina spinosa was both more abundant and grew 
 to a larger size : Lucina fragilis, now rare, and hardly measuring 
 6 lines, then attained the enormous dimensions of 14 lines, and 
 was extremely abundant; andOsmz lamellosa, Broc., no longer met 
 with near Naples, existed at that time, and attained a size so large 
 that one lower valve has been known to measure 5 inches 9 lines 
 in length, 4 inches in breadth, 1^ inch in thickness, and weighed 
 26^- ounces."* 
 
 There are other parts of Europe where no volcanic action manifests 
 itself at the surface, as at Naples, whether by the eruption of lava or 
 by earthquakes, and yet where the land and bed of the adjoining sea 
 are undergoing upheaval. The motion is so gradual as to be insen- 
 sible to the inhabitants, being only ascertainable by careful scientific 
 measurements compared after long intervals. Such an upward move- 
 ment has been proved to be in progress in Norway and Sweden 
 throughout an area about 1000 miles N. and S., and for an unknown 
 distance E. and W., the amount of elevation always increasing as we 
 proceed towards the North Cape, where it may equal 5 feet in a 
 century. If we could assume that there had been an average rise of 
 2^. feet in each hundred years for the last fifty centuries, this would 
 give an elevation of 125 feet in that period. In other words, it would 
 follow that the shores, and a considerable area of the former bed of 
 the Baltic and North Sea, had been uplifted vertically to that amount, 
 and converted into land in the course of the last 5000 years. Ac- 
 cordingly, we find near Stockholm, in Sweden, horizontal beds of 
 sand, loam, and marl containing the same peculiar assemblage of 
 testacea which now live in the brackish waters of the Baltic. Mingled 
 with these, at different depths, have been detected various works of 
 
 * Geol. Quart. Journ. vol.ii. Memoirs, p. 15. 
 i 4 
 
120 POST-PLIOCENE FORMATIONS. [Cn. X. 
 
 art implying a rude state of civilization, and some vessels built before 
 the introduction of iron, the whole marine formation having been 
 upraised, so that the upper beds are now 60 feet higher than the 
 surface of the Baltic. In the neighbourhood of these recent strata, 
 both to the north-west and south of Stockholm, other deposits similar 
 in mineral composition occur, which ascend to greater heights, in 
 which precisely the same assemblage of fossil shells is met with, but 
 without any intermixture of human bones or fabricated articles. 
 
 On the opposite or western coast of Sweden, at Uddevalla, post- 
 pliocene strata, containing recent shells, not of that brackish water 
 character peculiar to the Baltic, but such as now live in the northern 
 ocean, ascend to the height of 200 feet ; and beds of clay and sand of 
 the same age attain elevations of 300 and even 700 feet in Norway, 
 where they have been usually described as " raised beaches." They 
 are, however, thick deposits of submarine origin, spreading far and 
 wide, and filling valleys in the granite and gneiss, just as the tertiary 
 formations, in different parts of Europe, cover or fill depressions in 
 the older rocks. 
 
 It is worthy of remark, that, although the fossil fauna charac- 
 terizing these upraised sands and clays consists exclusively of ex- 
 isting northern species of testacea, yet, according to Loven (an able 
 living naturalist of Norway), the species do not constitute such an 
 assemblage as now inhabits corresponding latitudes in the German 
 Ocean. On the contrary, they decidedly represent a more arctic 
 fauna.* In order to find the same species flourishing in equal abun- 
 dance, or in many cases to find them at all, we must go northwards 
 to higher latitudes than Uddevalla in Sweden, or even nearer the 
 pole than Central Norway. 
 
 Judging by the uniformity of climate now prevailing from century 
 to century, and the insensible rate of variation in the organic world 
 in our own times, we may presume that an extremely lengthened 
 period was required even for so slight a modification of the molluscous 
 fauna, as that of which the evidence is here brought to light. On 
 the other hand, we have every reason for inferring on independent 
 grounds (namely, the rate of upheaval of land in modern times) that 
 the antiquity of the deposits in question must be very great. For if 
 we assume, as before suggested, that the mean rate of continuous 
 vertical elevation has amounted to 2J feet in a century (and this is 
 probably a high average), it would require 27,500 years for the sea- 
 coast to attain the height of 700 feet, without making allowance for 
 any pauses such as are now experienced in a large part of Norway, or 
 for any oscillations of level. 
 
 In England, buried ships have been found in the ancient and now 
 deserted channels of the Rother in Sussex, of the Mersey in Kent, 
 and the Thames near London. Canoes and stone hatchets have been 
 dug up, in almost all parts of the kingdom, from peat and shell-marl ; 
 but there is no evidence, as in Sweden, Italy, and many other parts 
 
 * Quart. Geol. Journ. 4 Mems. p. 48. 
 
CH. X.J RECENT AND POST-PLIOCENE FORMATIONS. 121 
 
 of the world, of the bed of the sea, and the adjoining coast, having 
 been uplifted bodily to considerable heights within the human period. 
 Recent strata have been traced along the coasts of Peru and Chili, 
 inclosing shells in abundance, all agreeing specifically with those now 
 swarming in the Pacific. In one bed of this kind, in the island of 
 San Lorenzo, near Lima, Mr. Darwin found, at the altitude of 85 
 feet above the sea, pieces of cotton-thread, plaited rush, and the 
 head of a stalk of Indian corn, the whole of which had evidently 
 been imbedded with the shells. At the same height on the neigh- 
 bouring mainland, he found other signs corroborating the opinion 
 that the ancient bed of the sea had there also been uplifted 85 feet 
 since the region was first peopled by the Peruvian race. * But 
 similar shelly masses are also met with at much higher elevations, at 
 innumerable points between the Chilian and Peruvian Andes and 
 the sea-coast, in which no human remains were ever, or in all pro- 
 bability ever will be, discovered. 
 
 In the West Indies, also, in the island of Guadaloupe, a solid lime- 
 stone occurs at the level of the sea-beach, enveloping human skele- 
 tons. The stone is extremely hard, and chiefly composed of com- 
 minuted shell and coral, with here and there some entire corals and 
 shells, of species now living in the adjacent ocean. With them are 
 included arrow-heads, fragments of pottery, and other articles of 
 human workmanship. A limestone with similar contents has been 
 formed, and is still forming, in St. Domingo. But there are also 
 more ancient rocks in the West Indian Archipelago, as in Cuba, near 
 the Havanna, and in other islands, in which are shells identical with 
 those now living in corresponding latitudes; some well-preserved, 
 others in a state of casts, all referable to the post-pliocene period. 
 
 I have already described in the seventh chapter, p. 84. , what would 
 be the effect of oscillations and changes of level in any region drained 
 by a great river and its tributaries, supposing the area to be first 
 depressed several hundred feet, and then re-elevated. I believe that 
 such changes in the relative level of land and sea have actually oc- 
 curred in the post-pliocene era ia the hydrographical basin of the 
 Mississippi and in that of the Rhine. The accumulation of fluviatile 
 matter in a delta during a slow subsidence may raise the newly 
 gained land superficially at the same rate at which its foundations 
 sink, so that these may go down hundreds or thousands of feet per- 
 pendicularly, and yet the sea bordering the delta may always be 
 excluded, the whole deposit continuing to be terrestrial or freshwater 
 in character. This appears to have happened in the deltas both of 
 the Po and Ganges, for recent artesian borings, penetrating to the 
 depth of 400 feet, have there shown that fluviatile strata, with shells 
 of recent species, together with ancient surfaces of land supporting 
 turf and forests, are depressed hundreds of feet below the sea level, f 
 Should these countries be once more slowly upraised, the rivers would 
 
 * Journal, p. 451. 
 
 f See Principles, 8th ed. pp. 260268., 9th ed. 257280. 
 
122 LOESS OF THE VALLEY OF THE RHINE, [Cn. X, 
 
 carve out valleys through the horizontal and unconsoli dated strata as 
 they rose, sweeping away the greater portion of them, and leaving 
 mere fragments in the shape of terraces skirting newly-formed allu- 
 vial plains, as monuments of the former levels at which the rivers 
 ran. Of this nature are " the bluffs, " or river cliffs, now bounding 
 the valley of the Mississippi throughout a large portion of its 
 " course. " The upper portions of these bluffs which at Natches and 
 elsewhere often rise to the height of 200 feet above the alluvial plain, 
 consist of loam containing land and freshwater shells of the genera 
 Helix, Pupa, Succinea, and Lymnea, of the same species as those now 
 inhabiting the neighbouring forests and swamps. In the same loam 
 also are found the bones of the Mastodon, Elephant, Megalonyx, 
 and other extinct quadrupeds. * 
 
 I have endeavoured to show that the deposits forming the delta 
 and alluvial plain of the Mississippi consist of sedimentary matter, 
 extending over an area of 30,000 square miles, and known in some 
 parts to be several hundred feet deep. Although we cannot estimate 
 correctly how many years it may have required for the river to bring 
 down from the upper country so large a quantity of earthy matter 
 the data for such a computation being as yet incomplete we may 
 still approximate to a minimum of the time which such an operation 
 must have taken, by ascertaining experimentally the annual discharge 
 of water by the Mississippi, and the mean annual amount of solid matter 
 contained in its waters. The lowest estimate of the time required 
 would lead us to assign a high antiquity, amounting to many tens of 
 thousands of years to the existing delta, the origin of which is never- 
 theless an event of yesterday when contrasted with the terraces, 
 formed of the loam above mentioned. The materials of the bluffs 
 were produced during the first part of a great oscillation of level which 
 depressed to a depth of 200 feet a larger area than the modern delta 
 and plain of the Mississippi, and then restored the whole region to its 
 former position.f 
 
 Loess of the Valley of the Rhine. A similar succession of geo- 
 graphical changes, attended by the production of a fluviatile formation, 
 singularly resembling that which bounds the great plain of the 
 Mississippi, seems to have occurred in the hydrographical basin of the 
 Rhine, since the time when that basin had already acquired its present 
 outline of hill and valley. I allude to the deposit provincially termed 
 loess in part of Germany, or lehm in Alsace, filled with land and 
 freshwater shells of existing species. It is a finely comminuted sand or 
 pulverulent loam of a yellowish grey colour, consisting chiefly of argil- 
 laceous matter combined with a sixth part of carbonate of lime, and a 
 sixth of quartzose and micaceous sand. It often contains calcareous 
 sandy concretions or nodules, rarely exceeding the size of a man's 
 head. Its entire thickness amounts, in some places, to between 200 
 and 300 feet ; yet there are often no signs of stratification in the 
 
 * See Principles of Geol. 9th ed., and Lyell's Second Visit to the United States, 
 vol. ii. p. 257. 
 f Lyell's Second Visit to the United States, vol. ii. chap, xxxiv. 
 
CH. X.J AND ITS FOSSILS. 123 
 
 mass, except here and there at the bottom, where there is occasionally a 
 slight intermixture of drifted materials derived from subjacent rocks. 
 Unsolidified as it is, and of so perishable a nature, that every stream- 
 let flowing over it cuts out for itself a deep gully, it usually terminates 
 in a vertical cliff, from the surface of which land-shells are seen here 
 and there to project in relief. In all these features it presents a 
 precise counterpart to the loess of the Mississippi. It is so homo- 
 geneous as generally to exhibit no signs of stratification, owing, pro- 
 bably, to its materials having been derived from a common source, 
 and having been accumulated by a uniform action. Yet it displays 
 in some few places decided marks of successive deposition, where 
 coarser and finer materials alternate, especially near the bottom. 
 Calcareous concretions, also enclosing land-shells, are sometimes ar- 
 ranged in horizontal layers. It is a remarkable deposit, from its 
 position, wide extent, and thickness, its homogeneous mineral com- 
 position, and freshwater origin. Its distribution clearly shows that 
 after the great valley of the Rhine, from Schaffhausen to Bonn, had 
 acquired its present form, having its bottom strewed over with coarse 
 gravel, a period arrived when it became filled up from side to side 
 with fine mud, probably deposited during river inundations ; and it is 
 also clear that similar mud and silt were thrown down contempo- 
 raneously in the valleys of the principal tributaries of the Rhine. 
 
 Thus, for example, it may be traced far into Wiirtemberg, up the 
 valley of the Neckar, and from Frankfort, up the valley of the Main, 
 to above Dettelbach. I have also seen it spreading over the country of 
 Mayence, Eppelsheim, and Worms, on the left bank of the Rhine, 
 and on the opposite side on the table-land above the Bergstrasse, be- 
 tween Wiesloch and Bruchsal, where it attains a thickness of 200 feet. 
 Near Strasburg, large masses of it appear at the foot of the Vosges 
 on the left bank, and at the base of the mountains of the Black Forest 
 on the right bank. The Kaiserstuhl, a volcanic mountain which 
 stands in the middle of the plain of the Rhine near Freiburg, has 
 been covered almost everywhere with this loam, as have the extinct 
 volcanos between Coblentz and Bonn. Near Andernach, in the 
 Kirchweg, the loess containing the usual shells alternates with vol* 
 canic matter ; and over the whole are strewed layers of pumice, 
 lapilli, and volcanic sand, from 10 to 15 feet thick, very much re- 
 sembling the ejections under which Pompeii lies buried. There is no 
 passage at this upper junction from the loess into the pumiceous super- 
 stratum ; and this last follows the slope of the hill, just as it would 
 have done had it fallen in showers from the air on a declivity partly 
 formed of loess. 
 
 But, in general, the loess overlies all the volcanic products, even 
 those between Neuwied and Bonn, which have the most modern 
 aspect ; and it has filled up in part the crater of the Roderberg, an 
 extinct volcano near Bonn. In 1833 a well was sunk at the bottom 
 of this crater, through 70 feet of loess, in part of which were the 
 usual calcareous concretions. 
 
 The interstratification above alluded to of loess with layers of 
 
124 LOESS OF THE VALLEY OF THE RHINE, [On. X. 
 
 pumice and volcanic ashes, has led to the opinion that both during 
 and since its deposition some of the last volcanic eruptions of the 
 Lower Eifel have taken place. Should such a conclusion be adopted, 
 we should be called upon to assign a very modern date to these 
 eruptions. This curious point, therefore, deserves to be reconsidered ; 
 since it may .possibly have happened that the waters of the Rhine, 
 swollen by the melting of snow and ice, and flowing at a great height 
 through a valley choked up with loess, may have swept away the 
 loose superficial scoriae and pumice of the Eifel volcanos, and spread 
 them out occasionally over the yellow loam. Sometimes, also, the 
 melting of snow on the slope of small volcanic cones may have given 
 rise to local floods capable of sweeping down light pumice into the 
 adjacent low grounds. 
 
 The first idea which has occurred to most geologists, after ex- 
 amining the loess between Mayence and Basle, is to imagine that a 
 great lake once extended throughout the valley of the Rhine between 
 those two places. Such a lake may have sent off large branches up 
 the course of the Main, Neckar, and other tributary valleys, in all of 
 which large patches of loess are now seen. The barrier of the 
 lake might be placed somewhere in the narrow and picturesque 
 gorge of the Rhine between Bingen and Bonn. But this theory fails 
 altogether to explain the phenomena ; when we discover that that 
 gorge itself has once been filled with loess, which must have been 
 tranquilly deposited in it, as also in the lateral valley of the Lahn, 
 communicating with the gorge. The loess has also overspread the 
 high adjoining platform near the village of Plaidt above Andernach. 
 Nay, on proceeding farther down to the north, we discover that the 
 hills which skirt the great valley between Bonn and Cologne have 
 loess on their flanks, which also covers here and there the gravel of 
 the plain as far as Cologne, and the nearest rising grounds. 
 
 Besides these objections to the lake theory, the loess is met with 
 near Basle, capping hills more than 1200 feet above the sea ; so that 
 a barrier of land capable of separating the supposed lake from the 
 ocean would require to be, at least, as high as the mountains called 
 the Siebengebirge, near Bonn, the loftiest summit of which, the 
 Oehlberg, is 1209 feet above the Rhine and 1369 feet above the sea, 
 It would be necessary, moreover, to place this lofty barrier some- 
 where below Cologne, or precisely where the level of the land is now 
 lowest. 
 
 Instead, therefore, of supposing one continuous lake of sufficient 
 extent and depth to allow of the simultaneous accumulation of the 
 loess, at various heights, throughout the whole area where it now 
 occurs, I formerly suggested that, subsequently to the period when 
 the countries now drained by the Rhine and its tributaries had 
 nearly acquired their actual form and geographical features, they 
 were again depressed gradually by a movement like that now in pro- 
 gress on the west coast of Greenland.* In proportion as the whole 
 
 * Princ. of Geol. 3d edition, 1834, vol. Hi. p. 414. 
 
CH. X.] AND ITS FOSSILS. 125 
 
 district was lowered, the general fall of the waters between the Alps 
 and the ocean was lessened ; and both the main and lateral valleys, 
 becoming more subject to river inundations, were partially filled up 
 with fluviatile silt, containing land and freshwater shells. When a 
 thickness of many hundred feet of loess had been thrown down slowly 
 by this operation, the whole region was once more upheaved gra- 
 dually. During this upward movement most of the fine loam would 
 be carried off by the denuding power of rains and rivers ; and thus 
 the original valleys might have been re-excavated, and the country 
 almost restored to its pristine state, with the exception of some 
 masses and patches of loess such as still remain, and which, by their 
 frequency and remarkable homogeneousness of composition and fos- 
 sils, attest the ancient continuity and common origin of the whole. 
 By imagining these oscillations of level, we dispense with the neces- 
 sity of erecting and afterwards removing a mountain barrier suffi- 
 ciently high to exclude the ocean from the valley of the Rhine during 
 the period of the accumulation of the loess. 
 
 The proportion of land-shells of the genera Helix, Pupa, and 
 Bulimus is very large in the loess ; but in many places aquatic spe- 
 cies of the genera Lymnea, Paludina, and Planorbis are also found. 
 These may have been carried away during floods from shallow pools 
 and marshes bordering the river ; and the great extent of marshy 
 ground caused by the wide overflowings of rivers above supposed 
 would favour the multiplication of amphibious mollusks, such as the 
 Succinea (fig. 106.), which is almost everywhere characteristic of 
 this formation, and is sometimes accompanied, as near Bonn, by an- 
 other species, S. amphibia (fig. 34. p. 29.). Among other abundant 
 fossils are Helex plebeium and Pupa muscorum. (See Figures.) 
 
 Fig. 106. Fig. 107. Fig. 108. 
 
 Sitccinea dongata. Pupa mvscorum. Helix plebeium. 
 
 Both the terrestrial and aquatic shells preserved in the loess are of 
 most fragile and delicate structure, and yet they are almost invariably 
 perfect and uninjured. They must have been broken to pieces had 
 they been swept along by a violent inundation. Even the colour of 
 some of the land-shells, as that of Helix nemoralis, is occasionally 
 preserved. 
 
 Bones of vertebrated animals are rare in the loess, but those of the 
 mammoth, horse, and some other quadrupeds have been met with. 
 At the village of Binningen, and the hills called Bruder Holz, near 
 Basle, I found the vertebrae of fish, together with the usual shells. 
 These vertebras, according to M. Agassiz, belong decidedly to the 
 Shark family, perhaps to the genus Lamna. In explanation of their 
 occurrence among land and freshwater shells, it may be stated that 
 certain fish of this family ascend the Senegal, Amazon, and other 
 
126 BOULDER FORMATION. [Cn. XI. 
 
 great rivers, to the distance of several hundred miles from the 
 ocean.* 
 
 At Cannstadt, near Stuttgardt, in a valley also belonging to the 
 hydrographical basin of the Rhine, I have seen the loess pass down- 
 wards into beds of calcareous tuff and travertin. Several valleys in 
 northern Germany, as that of the Ilm at Weimar, and that of the 
 Tonna, north of Gotha, exhibit similar masses of modern limestone 
 filled with recent shells of the genera Planorbis, Lymnea^ Paludina, 
 &c., from 50 to 80 feet thick, with a bed of loess much resembling 
 that of the Rhine, occasionally incumbent on them. In these modern 
 limestones used for building, the bones of Elephas primigenius, Rhi- 
 noceros tichorhinus, Ursus spelceus, Hy&na spelcea, with the horse, ox, 
 deer, and other quadrupeds, occur; and in 1850 Mr. H. Credner and 
 I obtained in a quarry at Tonna, at the depth of 15 feet, inclosed in 
 the calcareous rock and surrounded with dicotyledonous leaves and 
 petrified leaves, four eggs of a snake of the size of the largest Euro- 
 pean Coluber, which, with three others, were lying in a series, or 
 string. 
 
 They are, I believe, the first reptilian remains which have been 
 met with in strata of this age. 
 
 The agreement of the shells in these cases with recent European 
 species enables us to refer to a very modern period the filling up 
 and re-excavation of the valleys ; an operation which doubtless con- 
 sumed a long period of time, since which the mammiferous fauna has 
 undergone a considerable change. 
 
 CHAPTER XL 
 
 NEWER PLIOCENE PERIOD. BOULDER FORMATION. 
 
 Drift of Scandinavia, northern Germany, and Eussia Its northern origin Not all 
 of the same age Fundamental rocks polished, grooved, and scratched Action 
 of glaciers and icebergs Fossil shells of glacial period Drift of eastern Nor- 
 folk Associated freshwater deposit Bent and folded strata lying on undisturbed 
 beds Shells on Moel Tryfane Ancient glaciers of North Wales Irish drift. 
 
 AMONG the different kinds of alluvium described in the seventh chapter, 
 mention was made of the boulder formation in the north of Europe, 
 the peculiar characters of which may now be considered, as it belongs 
 in part to the post-pliocene, and partly to the newer pliocene, period. 
 I shall first allude briefly to that portion of it which extends from 
 Finland and the Scandinavian mountains to the north of Russia, and 
 the low countries bordering the Baltic, and which has been traced 
 southwards as far as the eastern coast of England. This formation 
 
 * Proceedings Geol. Soc. No. 43. p. 222. 
 
CH. XL] ROCKS DRIFTED BY ICE. 127 
 
 consists of mud, sand, and clay, sometimes stratified, but often wholly 
 devoid of stratification, for a depth of more than a hundred feet. 
 To this unstratified form of the deposit, the name of till has been 
 applied in Scotland. It generally contains numerous fragments of 
 rocks, some angular and others rounded, which have been derived 
 from formations of all ages, both fossiliferous, volcanic, and hypo- 
 gene, and which have often been brought from great distances. Some 
 of the travelled blocks are of enormous size, several feet or yards in 
 diameter ; their average dimensions increasing as we advance north- 
 wards. The till is almost everywhere devoid of organic remains, 
 unless where these have been washed into it from older formations ; 
 so that it is chiefly from relative position that we must hope to derive 
 a knowledge of its age. 
 
 Although a large proportion of the boulder deposit, or " northern 
 drift," as it has sometimes been called, is made up of fragments 
 brought from a distance, and which have sometimes travelled many 
 hundred miles, the bulk of the mass in each locality consists of the 
 ruins of subjacent or neighbouring rocks ; so that it is red in a region 
 of red sandstone, white in a chalk country, and grey or black in a 
 district of coal and coal-shale. 
 
 The fundamental rock on which the boulder formation reposes, if 
 it consists of granite, gneiss, marble, or other hard stone capable of 
 permanently retaining any superficial markings which may have 
 been imprinted upon it, is usually smoothed or polished, and exhibits 
 parallel strise and furrows having a determinate direction. This 
 direction, both in Europe and North America, is evidently connected 
 with the course taken by the erratic blocks in the same district, being 
 from north to south, or if it be 20 or 30 degrees to the east or west of 
 north, always corresponding to the direction in which the large an- 
 gular and rounded stones have travelled. These stones themselves 
 also are often furrowed and scratched on more than one side. 
 
 In explanation of such phenomena I may refer the student to what 
 was said of the action of glaciers and icebergs in the Principles of 
 Geology, (ch. xv.) It is ascertained that hard stones, frozen into 
 a moving mass of ice, and pushed along under the pressure of that 
 mass, scoop out long rectilinear furrows or grooves parallel to each 
 other on the subjacent solid rock. (See fig. 109.) Smaller scratches 
 and striae are made on the polished surface by crystals or projecting 
 edges of the hardest minerals, just as a diamond cuts glass. The 
 recent polishing and striation of limestone by coast-ice carrying 
 boulders even as far south as the coast of Denmark, has been ob- 
 served by Dr. Forchhammer, and helps us to conceive how large ice- 
 bergs, running aground on the bed of the sea, may produce similar 
 furrows on a grander scale. An account was given so long ago as 
 the year 1822, by Scoresby, of icebergs seen by him drifting along 
 in latitudes 69 and 70 N., which rose above the surface from 100 to 
 200 feet, and measured from a few yards to a mile in circumference. 
 Many of them were loaded with beds of earth and rock, of such thick- 
 ness that the weight was conjectured to be from 50,000 to 100,000 
 
128 BOCKS DRIFTED BY ICE. [Cu. XI. 
 
 Fig. 109. 
 
 Limestone polished, furrowed, and scratched by the glacier of Rosenlaui, in Switzerland. (Agassiz.) 
 a a. White streaks or scratches, caused by small grains of flint frozen into the ice. 
 b b. Furrows. 
 
 tons. A similar transportation of rocks is known to be in progress 
 in the southern hemisphere, where boulders included in ice are far 
 more frequent than in the north. One of these icebergs was en- 
 countered in 1839, in mid-ocean, in the antarctic regions, many 
 hundred miles from any known land, sailing northwards, with a 
 large erratic block firmly frozen into it. In order to understand in 
 what manner long and straight grooves may be cut by such agency, 
 we must remember that these floating islands of ice have a singular 
 steadiness of motion, in consequence of the larger portion of their 
 bulk being sunk deep under water, so that they are not perceptibly 
 moved by the winds and waves even in the strongest gales. Many 
 had supposed that the magnitude commonly attributed to icebergs 
 by unscientific navigators was exaggerated, but now it appears that 
 the popular estimate of their dimensions has rather fallen within 
 than beyond the truth. Many of them, carefully measured by the 
 officers of the French exploring expedition of the Astrolabe, were 
 between 100 and 225 feet high above water, and from 2 to 5 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 the mechanical power they might exert when fairly set in 
 motion must be prodigious.* A large proportion of these floating 
 masses of ice are supposed not to be derived from terrestrial glaciers 
 
 * T. L. Hayes, Boston Journ. Nat. Hist. 1844. 
 
CH. XI.J ORIGIN OF TILL. 129 
 
 (Principles, ch. xv.), but to be formed at the foot of cliffs by the 
 drifting of snow from the land over the frozen surface of the sea. 
 
 We know that in Switzerland, when glaciers laden with mud and 
 stones melt away at their lower extremity before reaching the sea, 
 they leave wherever they terminate a confused heap of unstratified 
 rubbish, called " a moraine," composed of mud, sand, and pieces of all 
 the rocks with which they were loaded. We may expect, therefore, 
 to find a formation of the same kind, resulting from the liquefaction 
 of icebergs, in tranquil water. But, should the action of a current 
 intervene at certain points or at certain seasons, then the materials 
 will be sorted as they fall, and arranged in layers according to their 
 relative weight and size. Hence there will be passages from till, as 
 it is called in Scotland, to stratified clay, gravel, and sand, and inter- 
 calations of one in the other. 
 
 I have yet to mention another appearance connected with the 
 boulder formation, which has justly attracted much attention in 
 Norway and other parts of Europe. Abrupt pinnacles and out- 
 standing ridges of rock are often observed to be polished and furrowed 
 on the north side, or on the side facing the region from which the 
 erratics have come ; while on the other, which is usually steeper and 
 often perpendicular, called the " lee-side," such superficial markings 
 are wanting. There is usually a collection on this lee-side of 
 boulders and gravel, or of large angular fragments. In explanation 
 we may suppose that the north side was exposed, when still sub- 
 merged, to the action of icebergs, and afterwards, when the land was 
 upheaved, of coast ice, which ran aground upon shoals, or was packed 
 on the beach ; so that there would be great wear and tear on the 
 seaward slope, while, on the other, gravel and boulders might be 
 heaped up in a sheltered position. 
 
 Northern origin of erratics. That the erratics of northern Europe 
 have been carried southward cannot be doubted ; those of granite, 
 for example, scattered over large districts of Russia and Poland, 
 agree precisely in character with rocks of the mountains of Lapland 
 and Finland ; while the masses of gneiss, syenite, porphyry, and trap, 
 strewed -over the low sandy countries of Pomerania, Holstein, and 
 Denmark, are identical in mineral characters with the mountains of 
 Norway and Sweden. 
 
 It is found to be a general rule in Russia, that the smaller blocks 
 are carried to greater distances from their point of departure than 
 the larger; the distance being sometimes 800 and even 1000 miles 
 from the nearest rocks from which they were broken off; the direc- 
 tion having been from N. W. to S. E., or from the Scandinavian 
 mountains over the seas and low lands to the south-east. That its 
 accumulation throughout this area took place in part during the post- 
 pliocene period is proved by its superposition at several points to 
 strata containing recent shells. Thus, for example, in European 
 Russia, MM. Murchison and De Verneuil found in 1840, that the 
 flat country between St. Petersburg and Archangel, for a distance 
 of 600 milos, consisted of horizontal strata, full of shells similar to 
 
 K 
 
130 STRATA CONTAINING RECENT SHELLS. [Cfl. XI. 
 
 those now inhabiting the arctic sea, on which rested the boulder 
 formation, containing large erratics. 
 
 In Sweden, in the immediate neighbourhood of Upsala, I had ob- 
 served, in 1834, a ridge of stratified sand and gravel, in the midst of 
 which occurs a layer of marl, evidently formed originally at the 
 bottom of the Baltic, by the slow growth of the mussel, cockle, and 
 other marine shells of living species intermixed with some proper to 
 fresh water. The marine shells are all of dwarfish size, like those 
 now inhabiting the brackish waters of the Baltic ; and the marl, in 
 which myriads 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 most 
 part unrounded, from 9 to 16 feet in diameter, and which must have 
 been brought into their present position since the time when the 
 neighbouring 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 
 testacea, 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 saltness belonging to the ocean. In Denmark, 
 also, recent shells have been found in stratified beds, closely associ- 
 ated with the boulder clay. 
 
 It was stated that in Russia the erratics diminished generally in size 
 in proportion as they are traced farther from their source. The 
 same observation holds true in regard to the average bulk of the 
 Scandinavian boulders, when we pursue them southwards, from the 
 south of Norway and Sweden through Denmark and Westphalia. 
 This phenomenon is in perfect harmony with the theory of ice-islands 
 floating in a sea of variable depth ; for the heavier erratics require 
 icebergs of a larger size to buoy them up ; and, even when there are 
 no stones frozen in, more than seven eighths, and often nine tenths, 
 of a mass of drift ice is under water. The greater, therefore, the 
 volume of the iceberg, the sooner would it impinge on some shallower 
 part of the sea ; while the smaller and lighter floes, laden with finer 
 mud and gravel, may pass freely over the same banks, and be carried 
 to much greater distances. In those places, also, where in the course 
 of centuries blocks have been carried southwards by coast-ice, having 
 been often stranded and again set afloat in the direction of a pre- 
 vailing current, the blocks will diminish in size the farther they 
 travel from their point of departure for two reasons : first, 
 because they will be repeatedly exposed to wear and tear by the 
 action of the waves ; secondly, because the largest blocks are seldom 
 without divisional planes or "joints," which cause them to split when 
 weathered. Hence, as often as they start on a fresh voyage, becom- 
 ing buoyant by coast-ice which has frozen on to them, one portion of 
 the mass is detached from the rest. A recent examination (in 1852) 
 
 * See paper by the author, Phil. Trans. 1835, p. 15. 
 
CH. XT.] 
 
 NORTHERN DRIFT. 
 
 131 
 
 of several trains of huge erratics in lat. 42 50' N. in the United 
 States, in Berkshire, on the western confines of Massachusetts, has 
 convinced me that this cause has been very influential both in re- 
 ducing the size of erratics, and in restoring angularity to blocks 
 which would otherwise be rounded in proportion to their distance 
 from their original starting point. 
 
 The " northern drift " of the most southern latitudes is usually of 
 the highest antiquity. In Scotland it rests immediately on the older 
 rocks, and is covered by stratified sand and clay, usually devoid of 
 fossils, but in which, at certain points near the east and west coast, 
 as, for example, in the estuaries of the Tay and Clyde, marine shells 
 have been discovered. The same shells have also been met with in 
 the north, at Wick in Caithness, and on the shores of the Moray 
 Frith. The principal deposit on the Clyde occurs at the height of 
 about 70 feet, but a few shells have been traced in it as high as 
 
 Fig. 110. 
 Astarte dorealis. 
 
 Fig. 111. 
 Leda obionga. 
 
 Fig. 112. 
 
 Saxicava rugoi/a. 
 
 Fig. 113. 
 Peclen islandicus. 
 
 Fig. 114. Fig. 115. 
 
 Natica clausa. Trophon clathratum. 
 
 Northern shells common in the drift of the Clyde, in Scotland. 
 
 554 feet above the sea. Although a proportion of between 85 or 90 
 in 100 of the imbedded shells are of recent species, the remainder 
 are unknown; and even many which are recent now inhabit more 
 northern seas, where we may, perhaps, hereafter find living repre- 
 sentatives of some of the unknown fossils. The distance to which 
 erratic blocks have been carried southwards in Scotland, and the 
 course they have taken, which is often wholly independent of the 
 present position of hill and valley, favours the idea that ice-rafts 
 rather than glaciers were in general the transporting agents. The 
 Grampians in Forfarshire and in Perthshire are from 3000 to 4000 
 feet high. To the southward lies the broad and deep valley of 
 Strathmore, and to the south of this again rise the Sidlaw Hills * to 
 the height of 1500 feet and upwards. On the highest summits of 
 this chain, formed of sandstone and shale, and at various elevations, 
 are found huge angular fragments of mica-schist, some 3 and others 
 15 feet in diameter, which have been conveyed for a distance of at 
 least 15 miles from the nearest Grampian rocks from which they 
 could have been detached. Others have been left strewed over the 
 bottom of the large intervening vale of Strathmore. 
 
 * See above, section, p. 48. 
 K 2 
 
132 NORFOLK DRIFT AND [Cn. XI. 
 
 Still farther south on the Pentland Hills, at the height of 1100 feet 
 above the sea, Mr. Maclaren has observed a fragment of mica-schist 
 weighing from 8 to 10 tons, the nearest mountain composed of this 
 formation being 50 miles distant.* 
 
 The testaceous fauna of the boulder period, in Scotland, England, 
 and Ireland, has been shown by Prof. E. Forbes to contain a much 
 smaller number of species than that now belonging to the British 
 seas, and to have been also much less rich in species than the Older 
 Pliocene fauna of the crag which preceded it. Yet the species are 
 nearly all of them now living either in the British or more northern 
 seas, the shells of more arctic latitudes being the most abundant and 
 the most wide spread throughout the entire area of the drift from 
 north to south. 
 
 This extensive range of the fossils can by no means be explained 
 by imagining the mollusca of the drift to have been inhabitants of a 
 deep sea, where a more uniform temperature prevailed. On the con- 
 trary, many species were littoral, and others belonged to a shallow 
 sea, not above 100 feet deep, and very few of them lived, according 
 to Prof. E. Forbes, at greater depths than 300 feet. 
 
 From what was before stated it will appear that the boulder forma- 
 tion displays almost everywhere, in its mineral ingredients, a strange 
 heterogeneous mixture of the ruins of adjacent lands, with stones both 
 angular and rounded, which have come from points often very re- 
 mote. Thus we find it in our eastern counties, as in Norfolk, Suffolk, 
 Cambridge, Huntingdon, Bedford, Hertford, Essex, and Middlesex, 
 containing stones from the Silurian and Carboniferous strata, and 
 from the lias, oolite, and chalk, all with their peculiar fossils, together 
 with trap, syenite, mica-schist, granite, and other crystalline rocks. 
 A fine example of this singular mixture extends to the very suburbs 
 of London, being seen on the summit of Muswell Hill, Highgate. 
 But south of London the northern drift is wanting, as, for example, 
 in the Wealds of Surrey, Kent, and Sussex. 
 
 Norfolk drift. The drift can nowhere be studied more advan- 
 tageously in England than in the cliffs of the Norfolk coast between 
 Happisburgh and Cromer. Vertical sections, having an ordinary 
 height of from 50 to 70 feet, are there exposed to view for a distance 
 of about 20 miles. The name of diluvium was formerly given to it 
 by those who supposed it to have been produced by the violent action 
 of a sudden and transient deluge, but the term drift has been sub- 
 stituted by those who reject this hypothesis. Here, as elsewhere, it 
 consists for the most part of clay, loam, and sand, in part stratified, 
 in part devoid of stratification. Pebbles, together with some large 
 boulders of granite, porphyry, greenstone, lias, chalk, and other 
 transported rocks, are interspersed, especially through the till. That 
 some of the granitic and other fragments came from Scandinavia I 
 have no doubt, after having myself traced the course of the conti- 
 nuous stream of blocks from Norway and Sweden to Denmark, and 
 
 * Geol. of Fife, &c., p. 220. 
 
CH. XI.] 
 
 ASSOCIATED FRESHWATER STRATA. 
 
 133 
 
 across the Elbe, through Westphalia, to the borders of Holland. We 
 need not be surprised to find them reappear on our eastern coast 
 between the Tweed and the Thames, regions not half so remote 
 from parts of Norway as are many Russian erratics from the sources 
 whence they came. 
 
 White chalk rubble, unmixed with foreign matter, and even huge 
 fragments of solid chalk, also occur in many localities in these Norfolk 
 cliffs. No fossils have been detected in this drift which can posi- 
 tively be referred to the era of its accumulation ; but at some points 
 it overlies a freshwater formation containing recent shells, and at 
 others it is blended with the same in such a manner as to force us to 
 conclude that both were contemporaneously deposited. 
 
 Fig. 116. 
 
 Gravel 
 
 ,t 
 
 Sane 
 
 Till? 
 
 The shaded portion consists of Freshwater beds. 
 Intercalation of freshwater beds and of boulder clay and sand at Mundesley. 
 
 This interstratification is expressed in the annexed figure, the dark 
 mass indicating the position of the freshwater beds, which contain 
 much vegetable matter, and are divided into thin layers. The im- 
 bedded shells belong to the genera Planorbis, Lymnea, Paludina, 
 Unio, Cyclas, and others, all of British species, except a minute Pa- 
 ludina now inhabiting France. (See fig. 117.) 
 
 Fig. 117. 
 
 Paludina marginata, Michaud. (P. minuta, Strickland.) 
 The middle figure is of the natural size. 
 
 The Cyclas (fig. 118.) is merely a remarkable variety of the com- 
 mon English species. The scales and teeth of fish of the genera 
 Pike, Perch, Roach, and others, accompany these shells; but the 
 
 Fig. 118. 
 
 Cyclas ( Pisidiuni) amnica, var. ? 
 The two middle figures are of the natural size. 
 
 K 3 
 
134 
 
 BENT AND FOLDED STRATA. 
 
 [CH. XI. 
 
 species are not considered by M. Agassiz to be identical with known 
 British or European kinds. 
 
 The series of formations in the cliffs of eastern Norfolk, now under 
 consideration, beginning with the lowest, is as follows : First, 
 chalk ; secondly, patches of a marine tertiary formation, called the 
 Norwich Crag, hereafter to be described ; thirdly, the freshwater 
 beds already mentioned ; and lastly, the drift. Immediately above 
 the chalk, or crag, when that is present, is found here and there a 
 buried forest, or a stratum in which the stools and roots of trees stand 
 in their natural position, the trunks having been broken short off and 
 imbedded with their branches and leaves. It is very remarkable 
 that the strata of the overlying boulder formation have often under- 
 gone great derangement at points where the subjacent forest bed and 
 chalk remain undisturbed. There are also cases where the upper 
 portion of the boulder deposit has been greatly deranged, while the 
 lower beds of the same have continued horizontal. Thus the an- 
 nexed section (fig. 1 19.) represents a cliff about 50 feet high, at the 
 
 Fig. 119. 
 
 Gravel' 
 
 Sand 
 
 Loam 
 
 Till 
 
 Cliff 50 feet high between Bacton Gap and Mundes'ley. 
 
 bottom of which is till, or unstratified clay, containing boulders, 
 having an even horizontal surface, on which repose conformably beds 
 of laminated clay and sand about 5 feet thick, which, in their turn, 
 are succeeded by vertical, bent, and contorted layers of sand and loam 
 20 feet thick, the whole being covered by flint gravel. Now the 
 curves of the variously coloured beds of loose sand, loam, and pebbles 
 are so complicated that not only may we sometimes find portions of 
 
 Fig. 121. 
 
 Fig. 120. 
 
 Folding of the strata between East 
 and West 1( union. 
 
 Section of concentric beds west of Croiner. 
 
 1. Blue clay. 3. Yel!ow sand. 
 
 2. White sand. 4. Striped loam and clay. 
 
 5. Laminated blue ciay. 
 
CH. XL] 
 
 MASSES OF CHALK IN DRIFT. 
 
 135 
 
 them which maintain their vertical! ty to a height of 10 or 15 feet, 
 but they have also been folded upon themselves in such a manner 
 that continuous layers might be thrice pierced in one perpendicular 
 boring. 
 
 At some points there is an apparent folding of the beds round a 
 central nucleus, as at , fig. 120., where the strata seem bent round 
 a small mass of chalk ; or, as in fig. 121., where the blue clay, No. 1., 
 is in the centre ; and where the other strata, 2, 3, 4, 5, are coiled 
 round it; the entire mass being 20 feet in perpendicular height. 
 This appearance of concentric arrangement around a nucleus is, 
 nevertheless, delusive, being produced by the intersection of beds 
 bent into a convex shape ; and that which seems the nucleus being, in 
 fact, the innermost bed of the series, which has become partially 
 visible by the removal of the protuberant portions of the outer layers. 
 
 To the north of Cromer are other fine illustrations of contorted 
 drift reposing on a floor of chalk horizontally stratified and having 
 a level surface. These phenomena, in themselves sufficiently difficult 
 of explanation, are rendered still more anomalous by the occasional 
 inclosure in the drift of huge fragments of chalk many yards in dia- 
 meter. One striking instance occurs west of Sherringham, where 
 an enormous pinnacle of chalk, between 70 and 80 feet in height, is 
 flanked on both sides by vertical layers of loam, clay, and gravel. 
 (Fig. 122.) 
 
 Fig. 122. 
 
 Included pinnacle of chalk at Old Hythe point, west of Sherringham. 
 d. Chalk with regular layers of chalk flints. 
 
 c. Layer called " the pan," of loose chalk, flints, and marine shells of recent 
 species, cemented by oxide of iron. 
 
 This chalky fragment is only one of many detached masses which 
 
 ve been included in the drift, and forced along with it into their 
 
 present position. The level surface of the chalk in situ (d) may be 
 
 traced for miles along the coast, where it has escaped the violent 
 
 movements to which the incumbent drift has been exposed.* 
 
 * For a full account of the drift of East Norfolk, see a paper by the author, PhiL 
 Mag. No. 104. May, 1840. 
 
 K 4 
 
136 ICE-ISLANDS. [Cn. XI. 
 
 "We are called upon, then, to explain how any force can have been 
 exerted against the upper masses, so as to produce movements in 
 which the subjacent strata have not participated. It may be an- 
 swered that, if we conceive the till and its boulders to have been 
 drifted to their present place by ice, the lateral pressure may have 
 been supplied by the stranding of ice-islands. We learn, from the ob- 
 servations of Messrs. Dease and Simpson in the polar regions, that 
 such islands, when they run aground, push before them large mounds ot 
 shingle and sand. It is therefore probable that they often cause great 
 alterations in the arrangement of pliant and incoherent strata forming 
 the upper part of shoals or submerged banks, the inferior portions of 
 the same remaining unmoved. Or many of the complicated curva- 
 tures of these layers of loose sand and gravel may have been due to 
 another cause, the melting on the spot of icebergs and coast ice in 
 which successive deposits of pebbles, sand, ice, snow, and mud, to- 
 gether with huge masses of rock fallen from cliffs, may have become 
 interstratified. Ice-islands so constituted often capsize when afloat, 
 and gravel once horizontal may have assumed, before the associated 
 ice was melted, an inclined or vertical position. The packing of ice 
 forced up on a coast may lead to similar derangement in a frozen 
 conglomerate of sand or shingle, and, as Mr. Trimmer has suggested*, 
 alternate layers of earthy matter may have sunk down slowly during 
 the liquefaction of the intercalated ice, so as to assume the most fan- 
 tastic and anomalous positions, while the strata below, and those 
 afterwards thrown down above, may be perfectly horizontal. 
 
 There is, however, still another mode in which some of these 
 bendings may have been produced. When a railway embankment is 
 thrown across a marsh or across the bed of a drained lake, we fre- 
 quently find that the foundation, consisting of peat and shell-marl, or 
 of quicksand and mud, gives way, and sinks as fast as the embank- 
 ment is raised at the top. At the same time, there is often seen at the 
 distance of many yards, in some neighbouring part of the morass, a 
 squeezing up of pliant strata, the amount of upheaval depending on 
 the volume and weight of materials heaped upon the embankment. 
 In 1852 I saw a remarkable instance of such a downward and 
 lateral pressure, in the suburbs of Boston (U. S.), near the South 
 Cove. With a view of converting part of an estuary overflowed at 
 high tide into dry land, they had thrown into it a vast load of stones 
 and sand, upwards of 900,000 cubic yards in volume. Under this 
 weight the mud had sunk down many yards vertically. Meanwhile 
 the adjoining bottom of the estuary, supporting a dense growth of salt- 
 water plants, only visible at low tide, had been pushed gradually 
 upward, in the course of many months, so as to project five or six 
 feet above high water mark. The upraised mass was bent into five or 
 six anticlinal folds, and below the upper layer of turf, consisting of 
 salt-marsh plants, mud was seen above the level of high tide, full of 
 sea shells, such as Mya arenaria, Modiola plicatula, Sanguinolaria 
 
 * Quart. Journ. Geol. Soc. vol. vii. p. 22. 
 
C H XI.] BURIED FOREST IN NORFOLK. 137 
 
 fusca, Nassa obsoleta, Natica triseriata, and others. In some of 
 these curved beds the layers of shells were quite vertical. The up- 
 raised area was 75 feet wide, and several hundred yards long. Were 
 an equal load, melted out of icebergs or coast-ice, thrown down on 
 the floor of a sea, consisting of soft mud and sand, similar disturb- 
 ances and contortions might result in some adjacent pliant strata, 
 yet the underlying more solid rocks might remain undisturbed, and 
 newer formations, perfectly horizontal, might be afterwards super- 
 imposed. 
 
 A buried forest has been adverted to as underlying the drift on the 
 coast of Norfolk. At the time when the trees grew, there must have 
 been dry land over a large area, which was afterwards submerged, so 
 as to allow a mass of stratified and unstratified drift, 200 feet and 
 more in thickness, to be superimposed. The undermining of the 
 cliffs by the sea in modern times has enabled us to demonstrate, 
 beyond all doubt, the fact of this superposition, and that the forest 
 was not formed along the present coast-line. Its situation implies a 
 subsidence of several hundred feet since the commencement of the 
 drift period, after which there must have been an upheaval of the 
 same ground ; for the forest bed of Norfolk is now again so high as 
 to be exposed to view at many points at low water ; and this same 
 upward movement may explain why the till, which is conceived to 
 have been of submarine origin, is now met with far inland, and on the 
 summit of hills. 
 
 The boulder formation of the west of England, observed in Lan- 
 cashire, Cheshire, Shropshire, Staffordshire, and Worcestershire, con- 
 tains in some places marine shells of recent species, rising to various 
 heights, from 100 to 350 feet above the sea. The erratics have come 
 partly from the mountains of Cumberland, and partly from those of 
 Scotland. 
 
 But it is on the mountains of North Wales that the " Northern 
 drift," with its characteristic marine fossils, reaches its greatest alti- 
 tude. On Moel Tryfane, near the Menai Straits, Mr. Trimmer met 
 with shells of the species commonly found in the drift at the height 
 of 1392 -feet above the level of the sea. 
 
 It is remarkable that in the same neighbourhood where there is 
 evidence of so great a submergence of the land during part of the 
 glacial period, we have also the most decisive proofs yet discovered 
 in the British Isles of sub-aerial glaciers. Dr. Buckland published 
 in 1842 his reasons for believing that the Snowdonian mountains in 
 Caernarvonshire were formerly covered with glaciers, which ra- 
 diated from the central heights through the seven principal valleys 
 of that chain, where striae and flutings are seen on the polished rocks 
 directed towards as many different points of the compass. He also 
 described the " moraines " of the ancient glaciers, and the rounded 
 " bosses " or small flattened domes of polished rock, such as the 
 action of moving glaciers is known to produce in Switzerland, when 
 gravel, sand, and boulders, underlying the ice, are forced along over 
 a foundation of hard stone. Mr. Darwin, and subsequently Prof. 
 
138 FOSSIL REMAINS IN DRIFT [On. XII. 
 
 Ramsay, have confirmed Dr. Buckland's views in regard to these 
 Welsh glaciers. Nor indeed was it to be expected that geologists 
 should discover proofs of icebergs having abounded in the area now 
 occupied by the British Isles in the Pleistocene period without some- 
 times meeting with the signs of contemporaneous glaciers which 
 covered hills even of moderate elevation between the 50th and 60th 
 degrees of latitude. 
 
 In Ireland the " drift " exhibits the same general characters and 
 fossil remains as in Scotland and England ; but in the southern part 
 of that island, Prof. E. Forbes and Capt. James found in it some 
 shells which show that the glacial sea communicated with one in- 
 habited by a more southern fauna. Among other species in the 
 south, they mention at Wexford and elsewhere the occurrence of 
 Nucula Cobboldice (see fig. 125. p. 156.) and Turritella incrassata 
 (a crag fossil) ; also a southern form of Fusus, and a Mitra allied to 
 a Spanish species. * 
 
 CHAPTER XII. 
 
 Difficulty of interpreting the phenomena of drift before the glacial hypothesis was 
 adopted Effects of intense cold in augmenting the quantity of alluvium 
 Analogy of erratics and scored rocks in North America and Europe Bayfield 
 on shells in drift of Canada Great subsidence and re -elevation of land from the 
 sea, required to account for glacial appearances Why organic remains so rare 
 in northern drift Mastodon giganteus in United States Many shells and 
 some quadrupeds survived the glacial cold Alps an independent centre of 
 dispersion of erratics Alpine blocks on the Jura Whether transported by 
 glaciers or floating ice Recent transportation of erratics from the Andes to 
 Chiloe Meteorite in Asiatic drift. 
 
 IT will appear from what was said in the last chapter of the marine 
 shells characterizing the boulder formation, that nine-tenths or more 
 of them belong to species still living. The superficial position of 
 " the drift " is in perfect accordance with its imbedded organic re- 
 mains, leading us to refer its origin to a modern period. If, then, 
 we encounter so much difficulty in the interpretation of monuments 
 relating to times so near our own if in spite of their recent date 
 they are involved in so much obscurity the student may ask, not 
 without reasonable alarm, how we can hope to decipher the records 
 of remoter ages. 
 
 To remove from the mind as far as possible this natural feeling of 
 discouragement, I shall endeavour in this chapter to prove that what 
 seems most strikingly anomalous, in the " erratic formation," as some 
 call it, is really the result of that glacial action which has already been 
 
 * Forbes, Memoirs of Geol. Survey of Great Britain, voL L p. 377. 
 
CH. XII.] GLACIAL PHENOMENA OF NORTHERN ORIGIN. 139 
 
 alluded to. If so, it was to be expected that so long as the true origin 
 of so singular a deposit remained undiscovered, erroneous theories and 
 terms would be invented in the effort to solve the problem. These 
 inventions would inevitably retard the reception of more correct 
 views which a wider field of observation might afterwards suggest. 
 
 The term " diluvium " was for a time the popular name of the 
 boulder formation, because it was referred by some to the deluge, 
 while others retained the name as expressive of their opinion that a 
 series of diluvial waves raised by hurricanes and storms, or by earth- 
 quakes, 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 surfaces 
 so as to polish and imprint upon them long furrows and striae. 
 
 But no explanation was offered why such agency should have been 
 developed more energetically in modern times than at former periods 
 of the earth's history, or why it should be displayed in its fullest 
 intensity in northern latitudes ; for it is important to insist on the 
 fact, that the boulder formation is a northern phenomenon. Even 
 the southern extension of the drift, or the large erratics found in the 
 Alps and the surrounding lands, especially their occurrence round 
 the highest parts of the chain, offers such an exception to the general 
 rule as confirms the glacial hypothesis ; for it shows that the trans- 
 portation of stony fragments to great distances, and the striation, 
 polishing, and grooving of solid floors of rock, are here again intimately 
 connected with accumulations of perennial snow and ice. 
 
 That there is some intimate connection between a cold or northern 
 climate and the various geological appearances now commonly called 
 glacial, cannot be doubted by any one who has compared the countries 
 bordering the Baltic with those surrounding the Mediterranean. The 
 smoothing and striation of rocks and erratics, are traced from the 
 sea-shore to the height of 3000 feet above the level of the Baltic, 
 whereas such phenomena are wholly wanting in countries bordering 
 the Mediterranean ; and their absence is still more marked in the 
 equatorial parts of Asia, Africa, and America ; but when we cross 
 the southern tropic, and reach Chili and Patagonia, we again en- 
 counter the boulder formation, between the latitude 41 S. and Cape 
 Horn, with precisely the same characters which it assumes in Europe. 
 The evidence as to climate derived from the organic remains of the 
 drift is, as we have seen, in perfect harmony with the conclusions 
 above alluded to, the former habits of the species of mollusca being 
 accurately ascertainable, inasmuch as they belong to species still living, 
 and known to have at present a wide range in northern seas. 
 
 But if we are correct in assuming that the northern hemisphere 
 was considerably colder than now during the period under considera- 
 tion, owing probably to the greater area and height of arctic lands, 
 and to the quantity of icebergs which such a geographical state of 
 things would generate, it may be well to reflect before we proceed 
 farther on the entire modification which extreme cold would produce 
 in the operation of those causes spoken of in the sixth chapter as 
 
140 GLACIAL PHENOMENA OF NORTHERN ORIGIN. [Cn. XII. 
 
 most active in the formation of alluvium. A large part of the 
 materials derived from the detritus of rocks, which in warm climates 
 would go to form deltas, or would be regularly stratified by marine 
 currents, would, under arctic influences, assume a superficial and 
 alluvial character. Instead of mud being carried farther from a 
 coast than sand, and sand farther out than pebbles, instead of dense 
 stratified masses being heaped up in limited areas, along the borders 
 of continents, nearly the whole materials, whether coarse or fine, 
 would be conveyed by ice to equal distances, and huge fragments, 
 which water alone could never move, would be borne for hundreds 
 of miles without having their edges worn or fractured : and the earthy 
 and stony masses, when melted out of the frozen rafts, would be 
 scattered at random over the submarine bottom, whether on moun- 
 tain tops or in low plains, with scarcely any relation to the inequal- 
 ities of the ground, settling on the crests or ridges of hills in tranquil 
 water as readily as in valleys and ravines. Occasionally, in those 
 deep and uninhabited parts of the ocean, never reached by any but 
 the finest sediment in a normal state of things, the bottom would 
 become densely overspread by gravel, mud, and boulders. 
 
 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 distinguish the 
 European boulder formation. Fragments of rock have travelled for 
 great distances from north to south : the surface of the subjacent rock 
 is smoothed, striated, and fluted ; unstratified mud or till containing 
 boulders is associated with strata of loam, sand, and clay, usually 
 devoid of fossils. Where shells are present, they are of species still 
 living in northern seas, and half of them identical with those already 
 enumerated as belonging to European drift 10 degrees of latitude 
 farther north. The fauna also of the glacial 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 Massachusetts. At the southern extremity of its 
 course, moreover, it presents an analogy with the drift of the south 
 of Ireland, by blending with a more southern fauna, as for example 
 at Brooklyn near New York, in lat. 41 N., where, according to MM. 
 Redfield and Desor, Venus mercenaria and other southern species of 
 shells begin to occur as fossils in the drift. 
 
 The extension on the American continent of the range of erratics 
 during the Pleistocene period to lower latitudes than they reached in 
 Europe, agrees well with the present southward deflection of the 
 isothermal lines, or rather the lines of equal winter temperature. 
 It seems that formerly, as now, a more extreme climate and a more 
 abundant supply of floating ice prevailed on the western side of the 
 Atlantic. 
 
 Another resemblance between the distribution of the drift fossils 
 in Europe and North America has yet to be pointed out. In Nor- 
 way, Sweden, and Scotland, as in Canada and the United States, 
 the marine shells are confined to very moderate elevations above the 
 
Cn. XII.] 
 
 DRIFT SHELLS IN CANADA. 
 
 141 
 
 sea (between 100 and 700 feet), while the erratic blocks and the 
 grooved and polished surfaces of rock extend to elevations of several 
 thousand feet. 
 
 I described in 1839 the fossil shells collected by Captain Bay field 
 from strata of drift at Beauport near Quebec, in lat. 47, and drew 
 from them the inference that they indicated a more northern climate, 
 the shells agreeing in great part with those of Uddevalla in Sweden.* 
 The shelly beds attain at Beauport and the neighbourhood a height 
 of 200, 300, and sometimes 400 feet above the sea, and dispersed 
 through some of them are large boulders of granite, which could not 
 have been propelled by a violent current, because the accompanying 
 fragile shells are almost all entire. They seem, therefore, said Captain 
 Bayfield, writing in 1838, to have been dropped down from melting 
 ice, like similar stones which are now annually deposited in the 
 St. Lawrence, f I visited this locality in 1842, and made the annexed 
 section, fig. 123., which will give an idea of the general position of 
 
 Fig. 123. 
 
 K. Mr. Ryland's house. 
 
 h. Clay and sand of higher grounds, with 
 
 Savicava, &c. 
 g. Gravel with boulders. 
 /. Mass of Saxicava rugosa, 12 feet thick, 
 c. Sand and loam with Myn truncata, Sca- 
 
 laria Grtenlandica, &c. 
 
 d. Drift, with boulders of syenite, &c. 
 
 c. Yellow sand. 
 
 b. Laminated clay, 25 feet thick. 
 
 A. Horizontal lower Silurian strata. 
 
 B. Valley re-excavated. 
 
 the drift in Canada and the United States. I imagine that the whole 
 of the valley B was once filled up with the beds , c, d, e, f, which were 
 deposited during a period of subsidence, and that subsequently the 
 higher country (h] was submerged and overspread with drift. The 
 partial re-excavation of B took place when this region was again 
 uplifted above the sea to its present height. Among the twenty- three 
 species of fossil shells collected by me from these beds at Beauport, 
 all were of recent northern species, except one, which is unknown as 
 
 Fig. 124. 
 
 a. Outside. 
 
 Astarte Laurentfana. 
 b. Inside of right valve. 
 
 Left valve. 
 
 living, and may be extinct (see fig. 124.). I also examined the same 
 formation farther up the valley of the St. Lawrence, in the suburbs 
 
 * Geol. Trans. 2d series, vol. vi. p. 135. 
 Mr. Smith of Jordanhill had arrived at 
 similar conclusions as to climate from the 
 
 shells of the Scotch Pleistocene deposits. 
 f Proceedings of Geol Soc. No. 63. 
 p. 119. 
 
142 SUBSIDENCE IN DRIFT PERIOD. [Ce. XIL 
 
 of Montreal, where some of the beds of loam are filled with great 
 numbers of the Mytilus edulis, or our common European mussel, 
 retaining both its valves and purple colour. This shelly deposit, 
 containing Saxicava rugosa and other characteristic marine shells, 
 also occurs at an elevated point on the mountain of Montreal, 450 feet 
 above the level of the sea.* 
 
 In my account of Canada and the United States, published in 1845, 
 I announced the conclusion to which I had then arrived, that to 
 explain the position of the erratics and the polished surfaces of rocks, 
 and their striae and flutings, we must assume first a gradual sub- 
 mergence of the land in North America, after it had acquired its 
 present outline of hill and valley, cliff and ravine, and then its 
 re-emergence from the ocean. When the land was slowly sinking, 
 the sea which bordered it was covered with islands of floating ice 
 coming from the north, which, as they grounded on the coast and on 
 shoals, pushed along such loose materials of sand and pebbles as lay 
 strewed over the bottom. By this force all angular and projecting 
 points were broken off, and fragments of hard stone, frozen into the 
 lower surface of the ice, had power to scoop out grooves in the 
 subjacent solid rock. The sloping beach, as well as the floor of the 
 ocean, might be polished and scored by this machinery ; but no flood 
 of water, however violent, or however great the quantity of detritus 
 or size of the rocky fragments swept along by it, could produce such 
 long, perfectly straight and parallel furrows, as are everywhere visible 
 in the Niagara district, and generally in the region north of the 40th 
 parallel of latitude.")" 
 
 By the hypothesis of such a slow and gradual subsidence of the 
 land we may account for the fact that almost everywhere in N. 
 America and Northern Europe the boulder formation rests on a 
 polished and furrowed surface of rock, a fact by no means obliging 
 us to imagine, as some think, that the polishing and grooving action 
 was, as a whole, anterior in date to the transportation of the erratics. 
 During the successive depression of high land, varying originally in 
 height from 1000 to 3000 feet above the sea level, every portion of 
 the surface would be brought down by turns to the level of the ocean, 
 so as to be converted first into a coast-line, and then into a shoal ; and 
 at length, after being well scored by the stranding upon it year after 
 year of large masses of coast-ice and occasional icebergs, might be 
 sunk to a depth of several hundred fathoms. By the constant de- 
 pression of land, the coast would recede farther and farther from the 
 successively formed zones of polished and striated rock, each outer 
 zone becoming in its turn so deep under water as to be no longer 
 grated upon by the heaviest icebergs. Such sunken areas would 
 then simply serve as receptacles of mud, sand, and boulders dropped 
 from melting ice, perhaps to a depth scarcely, if at all, inhabited by 
 testacea and zoophytes. Meanwhile, during the formation of the 
 unstratified and unfossiliferous mass in deeper water, the smoothing 
 
 * Travels in N. America, vol. ii. p. 141. f IW& p. 99. ehap. xix. 
 
CH.XU.] STRIATED PEBBLES AND BOULDERS. 143 
 
 and furrowing of shoals and beaches would still go on elsewhere 
 upon and near the coast in full activity. If at length the subsidence 
 should cease, and the direction of the movement of the earth's crust 
 be reversed, the sunken area covered with drift would be slowly 
 reconverted into land. The boulder deposit, before emerging, would 
 then for a time be brought within the action of the waves, tides, 
 and currents, so that its upper portion, being partially disturbed, 
 would have its materials rearranged and stratified. Streams also 
 flowing from the land would in some places throw down layers of 
 sediment upon the till. In that case, the order of superposition will 
 be, first and uppermost, sand, loam, and gravel occasionally fossili- 
 ferous ; secondly, an unstratified and unfossiliferous mass called till, 
 for the most part of much older date than the preceding, with angular 
 erratics, or with boulders interspersed ; and, thirdly, beneath the whole, 
 a surface of polished and furrowed rock. Such a succession of events 
 seems to have prevailed very widely on both sides of the Atlantic, the 
 travelled blocks having been carried in general from the North Pole 
 southwards, but mountain chains having in some cases served as inde- 
 pendent centres of dispersion, of which the Alps present the most 
 conspicuous example. 
 
 It is by no means rare to meet with boulders imbedded in drift 
 which are worn flat on one or more of their sides, the surface being 
 at the same time polished, furrowed, and striated. They may have 
 been so shaped in a glacier before they reached the sea, or when they 
 were fixed in the bottom of an iceberg as it ran aground. We learn 
 from Mr. Charles Martins that the glaciers of Spitzbergen project 
 from the coast into a sea between 100 and 400 feet deep ; and that 
 numbers of striated pebbles or blocks are there seen to disengage 
 themselves from the overhanging masses of ice as they melt, so as to 
 fall at once into deep water.* 
 
 That they should retain such markings when again upraised above 
 the sea ought not to surprise us, when we remember that rippled 
 sands, and the cracks in clay dried between high and low water, and 
 the foot-tracks of animals and rain-drops impressed on mud, and other 
 superficial markings, are all found fossil in rocks of various ages. 
 
 On the other hand, it is not difficult to account for the absence in 
 many districts of striated and scored pebbles and boulders in glacial 
 deposits, for they may have been exposed to the action of the waves 
 on a coast while it was sinking beneath or rising above the sea. No 
 shingle on an ordinary sea-beach exhibits such strise, and at a very 
 short distance from the termination of a glacier every stone in the 
 bed of the torrent which gushes out from the melting ice is found to 
 have lost its glacial markings by being rolled for a distance even of a 
 few hundred yards. 
 
 The usual dearth of fossil shells in glacial clays well fitted to pre- 
 serve organic remains may, perhaps, be owing, as already hinted, to 
 the absence of testacea in the deep sea, where the undisturbed accu- 
 
 * Bulletin Soc. Geol. de France, torn. iv. 2de ser. p. 1121. 
 
144 MASTODON GIGANTEUS. [Cn. XIL 
 
 mulation of boulders melted out of coast-ice and icebergs may take 
 place. In the ^Egean and other parts of the Mediterranean, the zero of 
 animal life, according to Prof. E. Forbes, is approached at a depth of 
 about 300 fathoms. In tropical seas it would descend farther down, 
 just as vegetation ascends higher on the mountains of hot countries. 
 Near the pole, on the other hand, the same zero would be reached 
 much sooner both on the hills and in the sea. If the ocean was filled 
 with floating bergs, and a low temperature prevailed in the northern 
 hemisphere during the glacial period, even the shallow part of the 
 sea might have been uninhabitable, or very thinly peopled with living 
 beings. It may also be remarked that the melting of ice in some 
 fiords in Norway freshens the water so as to destroy marine life, and 
 famines have been caused in Iceland by the stranding of icebergs 
 drifted from the Greenland coast, which have required several years 
 to melt, and have not only injured the hay harvest by cooling the 
 atmosphere, but have driven away the fish from the shore by chilling 
 and freshening the sea. 
 
 If the cold of the glacial epoch came on slowly, if it was long 
 before it reached its greatest intensity, and again if it abated gradu- 
 ally, we may expect to find the earliest and latest formed drift less 
 barren of organic remains than that deposited during the coldest 
 period. We may also expect that along the southern limits of the 
 drift during the whole glacial epoch, there would be an intimate 
 association of transported matter of northern origin with fossil- 
 bearing sediment, whether marine or freshwater, belonging to more 
 southern seas, rivers, and continents. 
 
 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 drift. They sometimes occur in the bottom 
 even of small ponds recently drained by the agriculturist for the sake 
 of the shell marl. I examined one of these spots at Geneseo in the 
 state of New York, from which the bones, skull, and tusk of a Mas- 
 todon had been procured in the marl below a layer of black peaty 
 earth, and ascertained that all the associated freshwater and land 
 shells were of a species now common in the same district. They con- 
 sisted of several species of Lymnea, of Planorbis bicarinatus, Physa 
 heterostropha, &c. 
 
 In 1845 no less than six skeletons of the same species of Mastodon 
 were found in Warren County, New Jersey, 6 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. But nearly the whole of the other skeleton, which 
 lay about 10 feet apart from the rest, was preserved entire, and 
 proved the correctness of Cuvier's conjecture respecting this extinct 
 animal, namely, that it had twenty ribs like the living elephant. 
 From the clay in the interior within the ribs, just where the contents 
 of the stomach might naturally have been looked for, seven bushels of 
 
CH. XII.] EXTINCT MAMMALIA ABOVE DRIFT. 145 
 
 vegetable matter were extracted. I submitted some of this matter to 
 Mr. A. Henfrey of London for microscopic examination, and he 
 informs me that it consists of pieces of small twigs of a coniferous 
 tree of the Cypress family, probably the young shoots of the white 
 cedar, Thuja occidentalis, still a native of North America, on which 
 therefore we may conclude that this extinct Mastodon once fed. 
 
 Another specimen of the same quadruped, the most complete and 
 probably the largest ever found, was exhumed in 1845 in the town of 
 Newburg, New York, the length of the skeleton being 25 feet, and 
 its height 12 feet. The anchy losing of the last two ribs on the right 
 side afforded Dr. John C. Warren a true gauge for the space occu- 
 pied by the intervertebrate substance, so as to enable him to form a 
 correct estimate of the entire length. The tusks when discovered 
 were 10 feet long, but a part only could be preserved. The large 
 proportion of animal matter in the tusk, teeth, and bones of some of 
 these fossil mammalia is truly astonishing. It amounts in some cases, 
 as Dr. C. T. Jackson has ascertained by analysis, to 27 per cent. ; so 
 that when all the earthy ingredients are removed by acids, the form of 
 the bone remains as perfect, and the mass of animal matter is almost 
 as firm, as in a recent bone subjected to similar treatment. 
 
 It would be rash, however, to infer from such data that these qua- 
 drupeds were mired in modern times, unless we use that term strictly 
 in a geological sense. I have shown that there is a fluviatile de- 
 posit in the valley of the Niagara, containing shells of the genera 
 Melania, Lymnea, Planorbis, Valvata, Cyclas, Unio, Helix, &c., 
 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 ravine, for many miles below the Falls, has been slowly effected 
 since that fluviatile deposit was thrown down. 
 
 Whether or not, in assigning a period of more than 30,000 years for 
 the recession of the Falls from Queenstown to their present site, I have 
 over or under estimated the time required for that operation, no one 
 can doubt that a vast number of centuries must have elapsed before 
 so great a series of geographical changes were brought about as have 
 occurred since the entombment of this elephantine quadruped. The 
 freshwater gravel which encloses it is decidedly of much more modern 
 origin than the drift or boulder clay of the same region.* 
 
 Other extinct animals accompany the Mastodon giganteus in the 
 post-glacial deposits of the United States, among which the Castoroides 
 ohioensis, Foster and Wyman, a huge rodent allied to the beaver, 
 and Capybara may be mentioned. But whether the "loess," and 
 other freshwater and marine strata of the Southern States, in which 
 skeletons of the same Mastodon are mingled with the bones of the 
 Megatherium, Mylodon, and Megalonyx, were contemporaneous with 
 the drift, or were of subsequent date, is a chronological question still 
 open to discussion. It appears clear, however, from what we know 
 of the tertiary fossils of Europe and I believe the same will hold 
 
 * Travels in N. America, vol. i. chap, ii., and Principles of Geol. chap. xir. 
 
 L 
 
146 CLIMATE OF DRIFT PERIOD. [Cn. XII. 
 
 true in North America that many species of testacea and some 
 mammalia which existed prior to the glacial epoch, survived that 
 era. As European examples among the warm-blooded quadrupeds, 
 the Elephasprimigenius and Rhinoceros tichorhinus may be mentioned. 
 As to the shells, whether freshwater, terrestrial, or marine, they need 
 not be enumerated here, as allusion will be made to them in the 
 sequel, when the pliocene tertiary fossils of Suffolk are described. 
 The fact is important, as refuting the hypothesis that the cold of the 
 glacial period was so intense and universal as to annihilate all living 
 creatures throughout the globe. 
 
 That the cold was greater for a time than it is now in certain parts 
 of Siberia, Europe, and North America, will not be disputed ; but, 
 before we can infer the universality of a colder climate, we must 
 ascertain what was the condition of other parts of the northern, and 
 of the whole southern, hemisphere at the time when the Scandinavian, 
 British, and Alpine erratics were transported into their present 
 position. It must not be forgotten that a great deposit of drift and 
 erratic blocks is now in full progress of formation in the southern 
 hemisphere, in a zone corresponding in latitude to the Baltic, and to 
 Northern Italy, Switzerland, France, and England. Should the un- 
 even bed of the southern ocean be hereafter converted by upheaval 
 into land, the hills and valleys will be strewed over with transported 
 fragments, some derived from the antarctic continent, others from 
 islands covered with glaciers, like South Georgia, which must now be 
 centres of the dispersion of drift, although situated in a latitude 
 agreeing with that of the Cumberland mountains in England. 
 
 Not only are these operations going on between the 45th and 60th 
 parallels of latitude south of the line, while the corresponding zone 
 of Europe is free from ice ; but, what is still more worthy of remark, 
 we find in the southern hemisphere itself, only 900 miles distant 
 from South Georgia, where the perpetual snow reaches to the sea- 
 beach, lands covered with forest, as in Terra del Fuego. There is 
 here no difference of latitude to account for the luxuriance of 
 vegetation in one spot, and the absolute want of it in the other ; but 
 among other refrigerating causes in South Georgia may be enu- 
 merated the countless icebergs which float from the antarctic zone, 
 and which chill, as they melt, the waters of the ocean, and the sur- 
 rounding air, which they fill with dense fogs. 
 
 I have endeavoured in the "Principles of Geology," chapters 
 7 and 8., to point out the intimate connexion of climate and the 
 physical geography of the globe, and the dependence of the mean 
 annual temperature, not only on the height of the dry land, but on 
 its distribution in high or low latitudes at particular epochs. If, 
 for example, at certain periods of the past, the antarctic land was less 
 elevated and less extensive than now, while that at the north pole 
 was higher and more continuous, the conditions of the northern 
 and southern hemispheres might have been the reverse of what we 
 now witness in regard to climate, although the mountains of Scan- 
 dinavia, Scotland, and Switzerland may have been less elevated than 
 
CH. XII.] ALPINE ERRATICS. 147 
 
 at present. But if in both of the polar regions a considerable 
 area of elevated dry land existed, such a concurrence of refrigerating 
 conditions in both hemispheres might have created for a time an in- 
 tensity of cold never experienced since ; and such probably was the 
 state of things during that period of submergence to which I have 
 alluded in this chapter. 
 
 Alpine erratics Although the arctic regions constitute the great 
 centre from which erratics have travelled southwards in all directions 
 in Europe and North America, yet there are some mountains, as I 
 have already stated, like those of .North Wales and the Alps, which 
 have served as separate and independent centres for the dispersion of 
 blocks. In illustration of this fact, the Alps deserve particular atten- 
 tion not only from their magnitude, but because they lie beyond the 
 ordinary limits of the "northern drift" of Europe, being situated 
 between the 44th and 47th degrees of north latitude. On the flanks 
 of these mountains, and on the Subalpine ranges of hills or plains 
 adjoining them, those appearances which have been so often alluded 
 to, as distinguishing or accompanying the drift, between the 50th and 
 70th parallels of north latitude, suddenly reappear, to assume in a 
 more southern country their most exaggerated form. Where the 
 Alps are highest, the largest erratic blocks have been sent forth ; as, 
 for example, from the regions of Mont Blanc and Monte Rosa, into 
 the adjoining parts of France, Switzerland, Austria, and Italy; while 
 in districts where the great chain sinks in altitude, as in Carinthia, 
 Carniola, and elsewhere, no such rocky fragments, or a few only and 
 of smaller bulk, have been detached and transported to a distance. 
 
 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 afterwards acknowledged by M. Charpentier, who 
 strengthened them by new observations and arguments, and declared, 
 in 1836, his conviction that the glaciers of the Alps must once have 
 reached as far as the Jura, and have carried thither their moraines 
 across the great valley of Switzerland. M. Agassiz, after several ex- 
 cursions in the Alps with M. Charpentier, and after devoting himself 
 some years to the study of glaciers, published, in 1840, an admirable 
 description of them and of the marks which attest the former action 
 of great masses of ice over the entire surface of the Alps and the sur- 
 rounding country. * He pointed out that the surface of every large 
 glacier is strewed over with gravel and stones detached from the 
 surrounding precipices by frost, rain, lightning, or avalanches. And 
 he described more carefully than preceding writers the long lines of 
 these stones, which settle on the sides of the glacier, and are called 
 the lateral moraines ; those found at the lower end of the ice being 
 called terminal moraines. Such heaps of earth and boulders every 
 glacier pushes before it when advancing, and leaves behind it when 
 retreating. When the Alpine glacier reaches a lower and warmer 
 
 * Agassiz, Etudes sur les Glaciers, and Systeme Glacifcre. 
 L 2 
 
148 MORAINES OF GLACIERS. [Cn. XII. 
 
 situation, about 3000 or 4000 feet above the sea. it melts so rapidly 
 that, in spite of the downward movement of the mass, it can advance 
 no farther. Its precise limits are variable from year to year, and still 
 more so from century to century ; one example being on record of a 
 recession of half a mile in a single year. We also learn from M. 
 Venetz, that whereas, between the eleventh and fifteenth centuries, all 
 the Alpine glaciers were less advanced than now, they began in the 
 seventeenth and eighteenth centuries to push forward, so as to cover 
 roads formerly open, and to overwhelm forests of ancient growth. 
 
 These oscillations enable the geologist to note the marks which 
 a glacier leaves behind it as it retrogrades ; and among these the most 
 prominent, as before stated, are the terminal moraines, or mounds of 
 unstratified earth and stones, often divided by subsequent floods into 
 hillocks, which cross the valley like ancient earth-works, or embank- 
 ments made to dam up a river. Some of these transverse barriers 
 were formerly pointed out by Saussure below the glacier of the Rhone, 
 as proving how far it had once transgressed its present boundaries. 
 On these moraines we see many large angular fragments, which, 
 having been carried along on the surface of the ice, have not had 
 their edges worn off by friction ; but the greater number of the 
 boulders, even those of large size, have been well rounded, not by the 
 power of water, but by the mechanical force of the ice, which has 
 pushed them against each other, or against the rocks flanking the 
 valley. Others have fallen down the numerous fissures which in- 
 tersect the glacier, where, being subject to the pressure of the whole 
 mass of ice, they have been forced along, and either well rounded or 
 ground down into sand, or even the finest mud, of which the moraine 
 is largely constituted. 
 
 As the terminal moraines are the most prominent of all the monu- 
 ments left by a receding glacier, so are they the most liable to obli- 
 teration ; for violent floods or debacles are often occasioned in the 
 Alps by the sudden bursting of what are called glacier-lakes. These 
 temporary sheets of water are caused by the damming up of a river 
 by a glacier which has increased during a succession of cold seasons, 
 and descending from a tributary into the main valley, has crossed it 
 from side to side. On the failure of this icy barrier, the accumulated 
 waters are let loose, which sweep away and level many a transverse 
 mound of gravel and loose boulders below, and spread their materials 
 in confused and irregular beds over the river-plain. 
 
 Another mark of the former action of glaciers, in situations where 
 they exist no longer, is the polished, striated, and grooved surfaces of 
 rocks already alluded to. Stones which lie underneath the glacier 
 and are pushed along by it, sometimes adhere to the ice, and as the . 
 mass glides slowly along at the rate of a few inches, or at the utmost 
 two or three feet, per day, abrade, groove, and polish the rock, and 
 the larger blocks are reciprocally grooved and polished by the rock 
 on their lower sides. As the forces both of pressure and propulsion 
 are enormous, the sand, acting like emery, polishes the surface ; the 
 pebbles, like coarse gravers, scratch and furrow it; and the large 
 
CH. XII.] ALPINE ERRATICS ON THE JURA. 149 
 
 stones scoop out grooves in it. Another effect also of this action, 
 not yet adverted to, is called "roches moutonnees." Projecting emi- 
 nences of rock are smoothed and worn into the shape of flattened 
 domes, where the glaciers have passed over them. 
 
 Although the surface of almost every kind of rock, when exposed 
 in the open air, wastes away by decomposition, yet some retain for 
 ages their polished and furrowed exterior ; and, if they are well pro- 
 tected by a covering of clay or turf, these marks of abrasion seem 
 capable of enduring for ever. They have been traced in the Alps to 
 great heights above the present glaciers, and to great horizontal dis- 
 tances beyond them. 
 
 There are also found, on the sides of the Swiss valleys, round and 
 deep holes with polished sides, such holes as waterfalls make in the 
 solid rock, but in places remote from running waters, and where the 
 form of the surface will not permit us to suppose that any cascade 
 could ever have existed. Similar cavities are common in hard rocks, 
 such as gneiss in Sweden, where they are called giant caldrons, and 
 are sometimes 10 feet and more in depth ; but in the Alps and Jura 
 they often pass into spoon-shaped excavations and prolonged gutters. 
 We learn from M. Agassiz that hollows of this form are now cut out 
 by streams of water which, after flowing along the surface of a 
 glacier, fall into open fissures in the ice and form a cascade. Here the 
 falling water, causing the gravel and sand at the bottom to rotate, 
 cuts out a round cavity in the rock. But as the glacier moves on, 
 the cascade becomes locomotive, and what would otherwise have 
 been a circular hole is prolonged into a deep groove. The form of 
 the rocky bottom of the valley down which the glacier is moving causes 
 the rents in the ice and these locomotive cascades to be formed 
 again and again, year after year, in exactly the same spots. 
 
 Another effect of a glacier is to lodge a ring of stones round the 
 summit of a conical peak which may happen to project through the ice. 
 If the glacier is lowered greatly by melting, these circles of large 
 angular fragments, which are called " perched blocks, " are left in a 
 singular situation near the top of a steep hill or pinnacle, the lower 
 parts of which may be destitute of boulders. 
 
 Alpine blocks on the Jura. Now some or all the marks above 
 enumerated, the moraines, erratics, polished surfaces, domes, stride, 
 caldrons, and perched rocks, are observed in the Alps at great heights 
 above the present glaciers, and far below their actual extremities ; 
 also in the great valley of Switzerland, 50 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 destitute of glaciers ; yet it presents 
 almost everywhere similar moraines, and the same polished and 
 grooved surfaces and water-worn cavities. The erratics, moreover, 
 which cover it, present a phenomenon which has astonished and per- 
 plexed the geologist for more than half a century. No conclusion 
 can be more incontestable than that these angular blocks of granite, 
 gneiss, and other crystalline formations, came from the Alps, and that 
 
 L 3 
 
150 ALPINE ERRATICS ON THE JURA. [Cn. XII. 
 
 they have been brought for a distance of 50 miles and upwards across 
 one of the widest and deepest valleys of the world ; so that they are 
 now lodged on the hills and valleys of 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 cot- 
 tages ; and one in particular, celebrated under the name of Pierre a 
 Bot, rests on the side of a hill about 900 feet above the lake of Neuf- 
 chatel, and is no less than 40 feet in diameter. 
 
 It will be remarked that these blocks on the Jura offer an excep- 
 tion to the rule before laid down, as applicable in general to erratics, 
 since they have gone from south to north. Some of the largest 
 masses of granite and gneiss have been found to contain 50,000 and 
 60,000 cubic feet of stone, and one limestone block at Devens, 
 near Bex, which has travelled 30 miles, contains 161,000 cubic feet, 
 its angles being sharp and unworn.* 
 
 Von Buch, Escher, and Studer have shown, from an examination 
 of the mineral composition of the boulders, that those on the western 
 Jura, near Neufchatel, have come from the region of Mont Blanc 
 and the Valais ; those on the middle parts of the Jura from the Ber- 
 nese Oberland ; and those on the eastern Jura from the Alps of the 
 small cantons, Glaris, Schwytz, Uri, and Zug. The blocks, there- 
 fore, of these three great districts have been derived from parts of 
 the Alps nearest to the localities in the Jura where we now find them, 
 as if they had crossed the great valley in a direction at right angles 
 to its length ; the most western stream having followed the course of 
 the Rhone ; the central, that of the Aar ; and the eastern, that of 
 the two great rivers, Reuss and Limmat. The non-intermixture of 
 these groups of travelled fragments, except near their confines, was 
 always regarded as most enigmatical by those who adopted the opinion 
 of Saussure, that they were all whirled along by a rapid current of 
 muddy water rushing from the Alps. 
 
 M. Charpentier first suggested, as before mentioned, that the Swiss 
 glaciers once reached continuously to the Jura, and conveyed to them 
 these erratics ; but at the same time he conceived that the Alps were 
 formerly higher than now. M. Agassiz, on the other hand, instead 
 of introducing distinct and separate glaciers, suggested that the whole 
 valley of Switzerland might have been filled with ice, and that one 
 great sheet of it extended from the Alps to the Jura, when the two 
 chains were of the same height as now relatively to each other. Such 
 an hypothesis labours under this difficulty, that the difference of 
 altitude, when distributed over a space of 50 miles, gives an in- 
 clination of no more than two degrees, or far less than that of any 
 known glaciers. It has, however, since received the able support of 
 Professor James Forbes, in his excellent work on the Alps, published 
 in 1843. 
 
 In the theory which I formerly advanced, jointly with Mr. Darwin f , 
 
 * Archiac, Hist. desProgres,&c. vol. ii. f See Elements of Geology, 2nd ed. 
 p. 249. 1841. 
 
CH. XII.] EERATICS OF THE JURA. 151 
 
 it was suggested that the erratics may have been transferred by float- 
 ing ice to the Jura, at the time when the greater part of that chain, 
 and the whole of the Swiss valley to the south, was under the sea. 
 At that period the Alps may have attained only half their present 
 altitude, and may yet have constituted a chain as lofty as the Chilian 
 Andes, which, in a latitude corresponding to Switzerland, now send 
 down glaciers to the head of every sound, from which icebergs, 
 covered with blocks of granite, are floated seaward.* Opposite that 
 part of Chili where the glaciers abound is situated the island of 
 Chiloe, 100 miles in length, with a breadth of 30 miles, running 
 parallel to the continent. The channel which separates it from the 
 main land is of considerable depth, and 25 miles broad. Parts of its 
 surface, like the adjacent coast of Chili, are overspread with recent 
 marine shells, showing an upheaval of the land during a very modern 
 period ; and beneath these shells is a boulder deposit, in which Mr. 
 Darwin found large travelled blocks. One group of fragments were 
 of granite, which had evidently come from the Andes, while in an- 
 other place angular blocks of syenite were met with. Their arrange- 
 ment may have been due to successive crops of icebergs issuing from 
 different sounds, to the heads of which glaciers descend from the 
 Andes. These icebergs, taking their departure year after year from 
 distinct points, may have been stranded repeatedly, in equally distinct 
 groups, in bays or creeks of Chiloe, and on islets off the coast ; so that 
 the stones transported by them might hereafter appear, some on hills 
 and others in valleys, should that country and the bed of the adjacent 
 sea be ever upheaved. A continuance in future of the elevatory 
 movement, in this region of the Andes and of Chiloe, might cause 
 the former chain to rival the Alps in altitude, and give to Chiloe a 
 height equal to that of the Jura. The same rise might dry up the 
 channel between Chiloe and the main land, so that it would then 
 represent the great valley of Switzerland. In the course of these 
 changes, all parts of Chiloe and the intervening strait, having in their 
 turn been a sea-shore, may have been polished and scratched by 
 coast-ice, and by innumerable icebergs running aground and grating 
 on the Bottom. 
 
 If we apply this hypothesis to Switzerland and the Jura, we are by 
 no means precluded from the supposition that, in proportion as the 
 land acquired additional height, and the bed of the sea emerged, the 
 Jura itself may have had its glaciers ; and those existing in the Alps, 
 which had at first extended to the sea, may, during some part of the 
 period of upheaval, have been prolonged much farther into the valleys 
 than now. At a later period, when the climate grew milder, these 
 glaciers may have entirely disappeared from the Jura, and may have 
 receded in the Alps to their present limits, leaving behind them in 
 both districts those moraines which now attest the greater extension 
 of the ice in former times.f 
 
 * Darwin's Journal, p. 283. blocks of Mont Blanc were translated to 
 
 f More recently Sir E. Murchison, the Jura when the intermediate country 
 
 having revisited the Alps, has declared was under water." Paper read to Geol. 
 
 his opinion that " the great granitic Soc. London, May 30. 1849. 
 
 L 4 
 
152 METEORITES IN DRIFT. [Cn. XII. 
 
 Meteorites in drift. Before concluding my remarks on the north- 
 ern drift of the Old World, I shall refer to a fact recently an- 
 nounced, the discovery of a meteoric stone at a great depth in the 
 alluvium of Northern Asia. 
 
 Erman, in his Archives of Russia for 1841 (p. 314.), cites a very 
 circumstantial account drawn up by a Russian miner of the finding 
 of a mass of meteoric iron in the auriferous alluvium of the Altai. 
 Some small fragments of native iron were first met with in the gold- 
 washings of Petropawlowsker in the Mrassker Circle ; but though 
 they attracted attention, it was supposed that they must have been 
 broken off from the tools of the workmen. At length, at the depth 
 of 31 feet 5 inches from the surface, they dug out a piece of iron 
 weighing 17|- pounds, of a steel-grey colour, somewhat harder than 
 ordinary iron, and, on analysing it, found it to consist of native iron, 
 with a small proportion of nickel, as usual in meteoric stones. It 
 was buried in the bottom of the deposit where the gravel rested 
 on a flaggy limestone. Much brown iron ore, as well as gold, occurs 
 in the same gravel, which appears to be part of that extensive auri- 
 ferous formation in which the bones of the mammoth, the Rhinoceros 
 tichorhinus, and other extinct quadrupeds abound. No sufficient data 
 are supplied to enable us to determine whether it be of Post-Pliocene 
 or Newer Pliocene date. 
 
 We ought not, I think, to feel surprise that we have not hitherto 
 succeeded in detecting the signs of such aerolites in older rocks ; for, 
 besides their rarity in our own days, those which fell into the sea 
 (and it is with marine strata that geologists have usually to deal), 
 being chiefly composed of native iron, would rapidly enter into new 
 chemical combinations, the water and mud being charged with 
 chloride of sodium and other salts. We find that anchors, cannon, 
 and other cast-iron implements which have been buried for a few 
 hundred years off our English coast have decomposed in part or en- 
 tirely, turning the sand and gravel which enclosed them into a con- 
 glomerate, cemented together by oxide of iron. In like manner 
 meteoric iron, although its rusting would be somewhat checked by the 
 alloy of nickel, could scarcely ever fail to decompose in the course of 
 thousands of years, becoming oxide, sulphuret or carbonate of iron, 
 and its origin being then no longer distinguishable. The greater the 
 antiquity of rocks, the oftener they have been heated and cooled, 
 permeated by gases or by the waters of the sea, the atmosphere or 
 mineral springs, the smaller must be the chance of meeting with a 
 mass of native iron unaltered ; but the preservation of the ancient 
 meteorite of the Altai, and the presence of nickel in these curious 
 bodies, renders the recognition of them in deposits of remote periods 
 less hopeless than we might have anticipated. 
 
CH. XIII.] NEWER PLIOCENE STRATA. 153 
 
 CHAPTER XIII. 
 
 NEWER PLIOCENE STRATA AND CAVERN DEPOSITS. 
 
 Chronological classification of Pleistocene formations, why difficult Freshwater 
 deposits in valley of Thames In Norfolk cliffs In Patagonia Comparative 
 longevity of species in the mammalia and testacea Fluvio-marine crag of 
 Norwich Newer Pliocene strata of Sicily Limestone of great thickness and 
 elevation Alternation of marine and volcanic formations Proofs of slow 
 accumulation Great geographical changes in Sicily since the living fauna and 
 flora began to exist Osseous breccias and cavern deposits Sicily Kirkdale 
 Origin of stalactite Australian cave-breccias Geographical relationship of the 
 provinces of living vertebrata and those of the fossil species of the Pliocene 
 periods Extinct struthious birds of New Zealand Teeth of fossil quadrupeds. 
 
 HAVING in the last chapter treated of the boulder formation and its 
 associated freshwater and marine strata as belonging chiefly to the 
 close of the Newer Pliocene period, we may now proceed to other 
 deposits of the same or nearly the same age. It should, however, be 
 stated that it is difficult to draw the line of separation between these 
 modern formations, especially when we are called upon to compare 
 deposits of marine and freshwater origin, or these again with the 
 ossiferous contents of caverns. 
 
 If as often as the carcasses of quadrupeds were buried in alluvium 
 during floods, or mired in swamps, or imbedded in lacustrine strata, 
 a stream of lava had descended and preserved the alluvial or fresh- 
 water deposits, as frequently happened in Auvergne (see above, 
 p. 80.), keeping them free from intermixture with strata subse- 
 quently formed, then indeed the task of arranging chronologically 
 the whole series of mammaliferous formations might have been easy, 
 even though many species were common to several successive groups. 
 But whe^ there have been oscillations in the levels of the land, ac- 
 companied by the widening and deepening of valleys at more than 
 one period, when the same surface has sometimes been submerged 
 beneath the sea, after supporting forests and land quadrupeds, and 
 then raised again, and subject during each change of level to sedi- 
 mentary deposition and partial denudation, and when the drifting of 
 ice by marine currents or by rivers, during an epoch of intense cold, 
 has for a season interfered with the ordinary mode of transport, or 
 with the geographical range of species, we cannot hope speedily to 
 extricate ourselves from the confusion in which the classification of 
 these Pleistocene formations is involved. 
 
 At several points in the valley of the Thames, remnants of ancient 
 fluviatile deposits occur, which may differ considerably in age, al- 
 though the imbedded land and freshwater shells in each are of recent 
 species. At Brentford, for example, the bones of the Siberian Mam- 
 
154 DEPOSITS IN VALLEY OF THAMES. [Cn. XIII. 
 
 moth, or Elephas primigenius, and the Rhinoceros tichorhinus, both 
 of them quadrupeds of which the flesh and hair have been found 
 preserved in the frozen soil of Siberia, occur abundantly, with the 
 bones of an hippopotamus, aurochs, short-horned ox, red deer, rein- 
 deer, and great cave-tiger or lion.* A similar group has been found 
 fossil at Maidstone, in Kent, and other places, agreeing in general 
 specifically with the fossil bones detected in the caverns of England. 
 When we see the existing rein-deer and an extinct hippopotamus in 
 the same fluviatile loam, we are tempted to indulge our imaginations 
 in speculating on the climatal conditions which could have enabled 
 these genera to coexist in the same region. Wherever there is a 
 continuity of land from polar to temperate and equatorial regions, 
 there will always be points where the southern limit of an arctic 
 species meets the northern range of a southern species; and if one or 
 both have migratory habits, like the Bengal tiger, the American bison, 
 the musk ox and others, they may each penetrate mutually far into the 
 respective provinces of the other. There may also have been several 
 oscillations of temperature during the periods which immediately 
 preceded and followed the more intense cold of the glacial epoch. 
 
 The strata bordering the left bank of the Thames at Grays 
 Thurrock, in Essex, are probably of older date than those of Brent- 
 ford, although the associated land and freshwater shells are nearly 
 all, if not all, identical with species now living. Three of the shells, 
 however, are no longer inhabitants of Great Britain ; namely, Palu- 
 dina marginata (fig. 117. p. 133.), now living in France; Unio 
 littoralis (fig. 29. p. 28.), now inhabiting the Loire; and Cyrma 
 consobrina (fig. 26. p. 28.). The last-mentioned fossil (a recent 
 Egyptian shell of the Nile) is very abundant at Grays, and deserves 
 notice, because the genus Cyrena is now no longer European. 
 
 The rhinoceros occurring in the same beds (/?. leptorhinus, see 
 fig. 136. p. 167.) is of a different species from that of Brentford 
 above mentioned, and the accompanying elephant belongs to the 
 variety called Elephas meridionalis, which, according to MM. Owen 
 and H. von Meyer, two high authorities, is the same species as the 
 Siberian mammoth, although some naturalists regard it as distinct. 
 With the above mammalia is also found the Hippopotamus major, and 
 what is most remarkable in so modern and northern a deposit, a 
 monkey, called by Owen Macacus pliocenus. 
 
 The submerged forest already alluded to (p. 137.) as underlying 
 the drift at the base of the cliffs of Norfolk is associated with a bed 
 of lignite and loam, in which a great number of fossil bones occur, 
 apparently of the same group as that of Grays, just mentioned. It 
 has sometimes been called " the Elephant bed." One portion of it, 
 which stretches out under the sea at Happisburgh, was overgrown 
 in 1820 by a bank of recent oysters, and there the fishermen dredged 
 up, according to Woodward, in the course of thirteen years, together 
 with the oysters, above 2000 mammoths' grinders.f Another portion 
 
 * Morris, Geol. Soc. Proceed., 1849. f Woodward's Geology of Norfolk. 
 
CH. XIII.] FLUVIO-MARINE NORWICH CRAG, 155 
 
 of the same continuous stratum has yielded at Bacton, Cromer, and 
 other places on the coast, the bones of a gigantic beaver ( Trogon- 
 therium Cuvierii, Fischer), as well as the ox, horse, and deer, and 
 both species of rhinoceros, R. tichorhinus and R. leptorhinus. 
 
 In studying these and various other similar assemblages of fossils, 
 we have a good exemplification of the more rapid rate at which the 
 mammiferous fauna, as compared to the testaceous, diverges from the 
 recent type when traced backwards in time. I have before hinted, 
 that the longevity of species in the class of warm-blooded quadrupeds 
 is not so great as in that of the mollusca ; the latter having probably 
 more capacity for enduring those changes of climate and other 
 external circumstances, and those revolutions in the organic world, 
 which in the course of ages occur on the earth's surface. This 
 phenomenon is by no means confined to Europe, for Mr. Darwin 
 found at Bahia Blanca, in South America, lat 39 S., near the northern 
 confines of Patagonia, fossil remains of the extinct mammiferous 
 genera Megatherium, Megalonyx, Toxodon, and others, associated 
 with shells, almost all of species already ascertained to be still living 
 in the contiguous sea* ; the marine mollusca, as well as those of rivers, 
 lakes, or the land, having died out more slowly than the terrestrial 
 mammalia. 
 
 I alluded before (p. 131.) to certain marine strata overlying till 
 near Glasgow, and at other points on the Clyde, in which the 
 shells are for the most part British, with an intermixture of some 
 arctic species ; while others, about a tenth of the whole, are sup- 
 posed to be extinct. This formation may also be called Newer 
 Pliocene. 
 
 Fluvio-marine crag of Norwich. At several places within five 
 miles of Norwich, on both banks of the Tare, beds of sand, loam, 
 and gravel, provincially termed " crag," but of a very different age 
 from the Suffolk Crag, occur, in which there is a mixture of marine, 
 land, and freshwater shells, with ichthyolites and bones of mammalia. 
 It is clear that these beds have been accumulated at the bottom of the 
 sea near the mouth of a river. They form patches of variable thick- 
 ness, resting on white chalk, and are covered by a dense mass of 
 stratified flint gravel. The surface of the chalk is often perforated 
 to the depth of several inches by the Pholas crispata, each fossil shell 
 still remaining at the bottom of its cylindrical cavity, now filled up 
 with loose sand which has fallen from the incumbent crag. This 
 species of Pholas still exists and drills the rocks between high and 
 low water on the British coast. The most common shells of these 
 strata, such as Fusus striatus, Turritella terebra, Cardium edule, and 
 Cyprina islandica, are now abundant in the British seas ; but with 
 them are some extinct species, such as Nucula Cobboldice (fig. 125.) 
 and Tellina obliqua (fig. 126.). Natica helicoides (fig. 127.) is an 
 example of a species formerly known only as fossil, but which has 
 now been found living in our seas. 
 
 Among the accompanying bones of mammalia is the Mastodon 
 * Zool. of Beagle, part 1. pp. 9. 111. 
 
156 
 
 NORWICH CRAG PLEISTOCENE. [Cn. XIII, 
 
 Fig. 125. Fig. 126. Fig. 127- 
 
 Nucula Cobboldice. 
 
 Tellina obliqua. 
 
 Natica helicoides, 
 Johnston. 
 
 angustidens* (see fig. 135. p. 166.), a portion of the upper jawbone with 
 a tooth having been found by Mr. Wigham at Postwick, near Norwich. 
 As this species has also been found in the Red Crag, both at Sutton 
 and atFelixstow, and had hitherto been regarded as characteristic of 
 formations older than the Pleistocene, it may possibly have been 
 washed out of the Red into the Norwich Crag. 
 
 Among the bones, however, respecting the authenticity of which 
 there seems no doubt, may be mentioned those of the elephant, horse, 
 pig, deer, and the jaws and teeth of field mice (fig. 146. p. 168.). I have 
 seen the tusk of an elephant from Bramerton near Norwich, to which 
 many serpulae were attached, showing that it had lain for some time 
 at the bottom of the sea of the Norwich Crag. 
 
 At Thorpe, near Aldborough, and at Southwold, in Suffolk, this 
 fluvio-marine formation is well exposed in the sea-cliffs, consisting of 
 sand, shingle, loam, and laminated clay. Some of the strata there 
 bear the marks of tranquil deposition, and in one section a thickness 
 of 40 feet is sometimes exposed to view. Some of the lamelli- 
 branchiate shells have both valves united, although mixed with land 
 and freshwater testacea, and with the bones and teeth of elephant, 
 rhinoceros, horse, and deer. Captain Alexander, with whom I ex- 
 amined these strata in 1835, showed me a bed rich in marine shells, 
 in which he had found a large specimen of the Fusus striatus, filled 
 with sand, and in the interior of which was the tooth of a horse. 
 
 Among the freshwater shells I obtained the Cyrena consobrina 
 (fig. 26. p. 28.), before mentioned, supposed to agree with a species 
 now living in the Nile. 
 
 I formerly classed the Norwich Crag as older Pliocene, conceiving 
 that more than a third of the fossil testacea were extinct ; but there 
 now seems good reason for believing that several of the rarer shells 
 obtained from these strata do not really belong to a contemporary 
 fauna, but have been washed out of the older beds of the " Red 
 Crag ; " while other species, once supposed to have died out, have 
 lately been met with living in the British seas. According to Mr. 
 Searles Wood, the total number of marine species does not exceed 
 seventy-six, of which one tenth only are extinct. Of the fourteen 
 associated freshwater shells, all the species appear to be living. 
 Strata containing the same shells as those near Norwich have been 
 found by Mr. Bean, at Bridlington, in Yorkshire. 
 
 Newer Pliocene strata of Sicily. In no part of Europe are the 
 
 * Owen, Brit. Foss. Mamm. 271. Mastodon kngirostris, Kaup, see ibid. 
 
CH. XIII.] NEWER PLIOCENE STRATA OF SICILY. 157 
 
 Newer Pliocene formations seen to enter so largely into the structure 
 of the earth's crust, or to rise to such heights above the level of the 
 sea, as in Sicily. They cover nearly half the island, and near its 
 centre, at Castrogiovanni, they reach an elevation of 3000 feet. They 
 consist principally of two divisions, the upper calcareous, 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. Of the remainder, which still live, five species 
 are no longer inhabitants of the Mediterranean. When I visited 
 Sicily in 1828 I estimated the proportion of living species as some- 
 what greater, partly because I confounded with the tertiary forma- 
 tion of central Sicily the strata at the base of Etna, and some other 
 localities, where the fossils are now proved to agree entirely with the 
 present Mediterranean fauna. 
 
 Philippi came to the conclusion, that in Sicily there is a gradual 
 passage from beds containing 70 per cent, of recent shells, to those 
 in which the whole of the fossils are identical with recent species ; 
 but his tables appear scarcely to bear out so important a generaliza- 
 tion, several of the places cited by him in confirmation having as yet 
 furnished no more than twenty or thirty species of testacea. The Sici- 
 lian beds in question probably belong to about the same period as the 
 Norwich Crag, although a geologist, accustomed to see nearly all the 
 Pleistocene formations 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 aggre- 
 gate thickness amounts sometimes to 700 or 800 feet. It usually 
 occurs in regular horizontal beds, and is occasionally intersected by 
 deep valleys, such as those of Sortino and Pentalica, in which are 
 numerous caverns. The fossils are in every stage of preservation, 
 from shells retaining portions of their animal matter and colour, to 
 others which are mere casts. 
 
 The limestone passes downwards into a sandstone and conglome- 
 rate, below which is clay and blue marl, like that of the Subapennine 
 hills, from which perfect shells and corals may be disengaged. The 
 clay sometimes alternates with yellow sand. 
 
 South of the plain of Catania is a region in which the tertiary 
 beds are intermixed with 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, volcanos burst out beneath the 
 waters, like that of Graham Island, in 1831, and these explosions re- 
 curred again and again at distant intervals of time. Volcanic ashes 
 and sand were showered down and spread by the waves and currents 
 
158 
 
 NEWER PLIOCENE STRATA OF SICILY. [Cn. XIII. 
 
 so as to form strata of tuff, which are found intercalated between beds 
 of limestone and clay containing marine 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. 
 In part of the region above alluded to, as, for example, near Len- 
 tini, a conglomerate occurs in which I observed many pebbles of 
 volcanic rocks covered by full-grown serpulce. We may explain the 
 origin of these by supposing that there were some small volcanic 
 islands which may have been destroyed from time to time by the 
 waves, as Graham Island has been swept away since 1831. The 
 rounded blocks and pebbles of solid volcanic matter, after being rolled 
 for a time on the beach of such temporary islands, were carried at 
 length into some tranquil part of the sea, where they lay for years, 
 while the marine serpulce adhered to them, their shells growing and 
 covering their surface, as they are seen adhering to the shell figured 
 in p. 22. Finally, the bed of pebbles was itself covered with strata 
 of shelly limestone. At Vizzini, a town not many miles distant to 
 the S.W., I remarked another striking proof of the gradual manner 
 in which these modern rocks were formed, and the long intervals of 
 time which elapsed between the pouring out of distinct sheets of lava, 
 a bed of oysters no less than 20 feet in thickness rests upon a current 
 of basaltic lava. The oysters are perfectly identifiable with our 
 common eatable species. Upon the oyster bed, again, is superim- 
 posed a second mass of lava, together with tuff or peperino. In the 
 midst of the same alternating igneous and aqueous formations is seen 
 near Galieri, not far from Vizzini, a horizontal bed, about a foot and 
 a half in thickness, composed entirely of a common Mediterranean 
 coral (Caryophyllia ccespitosa, Lam.). These corals stand erect as 
 they grew ; and, after being traced for hundreds of yards, are again 
 found at a corresponding height on the opposite side of the valley. 
 
 Fig. 128. 
 
 Caryophyllia c&spitosa, Lam. (Cladocora stellana, Milne Edw. and Haime.) 
 
 a. Stem with young stem growing from its side. 
 a*. Young stem of same twice magnified. 
 
 b. Portion of branch, twice magnified, with the base of a lateral branch ; the exterior 
 
 ridges of the main branch appearing through the lamellae of the lateral one. 
 
 c. Transverse section of same, proving, by the integrity of the main branch, that the 
 
 lateral one did not originate in a subdivision of the animal. 
 
 d. A branch, having at its base another laterally united to it, and two young corals at 
 
 its upper part. 
 
 ?. A main branch, with a full-grown lateral one. 
 /. A perfect terminal star. 
 
CH. XIII.] NEWER PLIOCENE STRATA OF SICILY. 159 
 
 The corals are usually branched, but not by the division of the 
 animals as some have supposed, but by the attachment of young indi- 
 viduals to the sides of the older ones ; and we must understand this 
 mode of increase, in order to appreciate the time which was required 
 for the building up of the whole bed of coral during the growth of 
 many successive generations.* 
 
 Among the other fossil shells met with in these Sicilian strata, 
 which still continue to abound in the Mediterranean, no shell is more 
 conspicuous, from its size and frequent occurrence, than the great 
 scallop, Pecten Jacob feus (see fig. 129.), now so common in the neigh- 
 bouring seas. We see this shell in the calcareous beds at Palermo 
 in great numbers, in the limestone at Girgenti, and in that which 
 alternates with volcanic rocks in the country between Syracuse and 
 Vizzini, often at great heights above the sea. 
 
 Fig. 129. 
 
 Pecten jacob&us ; half natural size. 
 
 The more we reflect on the preponderating number of these recent 
 shells, the more we are surprised at the great thickness, solidity, and 
 height above the sea of the rocky masses in which they are entombed, 
 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 de- 
 posited under water. In order, 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 valleys. The his- 
 torical period seems scarcely to form an appreciable unit in this com- 
 
 * I am indebted to Mr. Lonsdale for the details above given respecting the 
 structure of this coral. 
 
160 CAVE BRECCIAS. [Cn. XIII. 
 
 putation, for we find ancient Greek temples, like those of Girgenti 
 (Agrigentum), built of the modern limestone of which we are speak- 
 ing, and resting on a hill composed of the same ; the site having re- 
 mained to all appearance unaltered since the Greeks first colonised 
 the island. 
 
 The modern geological date of the rocks in this region leads to 
 another singular and unexpected conclusion namely, that the fauna 
 and flora of a large part of Sicily are of higher antiquity than the 
 country itself, having not only flourished before the lands were raised 
 from the deep, but even before their materials were brought together 
 beneath the waters. The chain of reasoning which conducts us to 
 this opinion may be stated in a few words. The larger part of the 
 island has been converted from sea into land since the Mediterranean 
 was peopled with nearly all the living species of testacea and zoo- 
 phytes. We may therefore presume that, before this region emerged, 
 the same land and river shells, and almost all the same animals and 
 plants, were in existence which now people Sicily ; for the terrestrial 
 fauna and flora of this island are precisely the same as that of other 
 lands surrounding the Mediterranean. There appear to be no peculiar 
 or indigenous species, and those which are now established there must 
 be supposed to have migrated from pre-existing lands, just as the 
 plants and animals of the Neapolitan territory have colonized Monte 
 Nuovo, since that volcanic cone was thrown up in the sixteenth 
 century. 
 
 Such conclusions throw a new light on the adaptation of the attri- 
 butes and migratory habits of animals and plants to the changes which 
 are unceasingly in progress in the physical geography of the globe. 
 It is clear that the duration of species is so great, that they are des- 
 tined to outlive many important revolutions in the configuration of 
 the earth's surface ; and hence those innumerable contrivances for 
 enabling the subjects of the animal and vegetable creation to extend 
 their range ; the inhabitants of the land being often carried across 
 the ocean, and the aquatic tribes over great continental species. It is 
 obviously expedient that the terrestrial and fluviatile species should 
 not only be fitted for the rivers, valleys, plains, and mountains which 
 exist at the era of their creation, but for others that are destined to 
 be formed before the species shall become extinct ; and, in like man- 
 ner, the marine species are not only made for the deep and shallow 
 regions of the ocean existing at the time when they are called into 
 being, but for tracts that may be submerged or variously altered in 
 depth during the time that is allotted for their continuance on the 
 globe. 
 
 OSSEOUS BRECCIAS AND DEPOSITS IN CAVES OF THE PLIOCENE PERIOD. 
 
 Sicily. Caverns filled with marine breccias, at the base of ancient 
 sea-cliffs, have been already mentioned in the sixth chapter; and it was 
 noticed, respecting the cave of San Giro, near Palermo (p. 75.), that 
 upon a bed of sand filled with sea-shells, almost all of recent species, 
 
CH. XIII.] KIRKDALE CAVE. 161 
 
 rests a breccia (b, fig. 93. p. 75.), composed of fragments of calcareous 
 rock, and the bones of animals. In the sand at the bottom of that cave, 
 Dr. Philippi found about forty-five marine shells, all clearly identical 
 with recent species, except two or three. The bones in the incum- 
 bent breccia are chiefly those of the mammoth (E. primigenius\ with 
 some belonging to an hippopotamus, distinct from the recent species, 
 and smaller than that usually found fossil. (See fig. 137. p. 167.) 
 Several species of deer also, and, according to some accounts, the 
 remains of a bear, were discovered. These mammalia are probably 
 referable to the Post-Pliocene period. 
 
 The Newer Pliocene tertiary limestone of the south of Sicily, already 
 described, is sometimes full of caverns ; and the student will at once 
 perceive that all the quadrupeds of which the remains are found in 
 the stalactite of these caverns, being of later origin than the rocks, 
 must be referable to the close of the tertiary epoch, if not of still later 
 date. The situation of one of these caves, in the valley of Sortino, 
 is represented in the annexed section. 
 
 Fig. 130. 
 
 6, b. Deposits in caves | containing the remains of quadrupeds for the most part extinct. 
 
 C. Limestone, containing the remains of shells, of which between 70 and 80 per cent, are recent. 
 
 England. In the cave at Kirkdale, about twenty-five miles N.N.E. 
 of York, the remains of about 300 hyaenas, belonging to individuals 
 of every age, have been detected. The species (Hyana spelcea) is 
 extinct, and was larger than the fierce Hyaena crocuta of South 
 Africa, which it most resembled. Dr. Buckland, after carefully ex- 
 amining the spot, proved that the Hyaenas must have lived there ; a 
 fact attested by the quantity of their dung, which, as in the case of 
 the living hya&na, is of nearly the same composition as bone, and 
 almost as durable. In the cave were found the remains of the ox, young 
 elephant, hippopotamus, rhinoceros, horse, bear, wolf, hare, water- 
 rat, and several birds. All the bones have the appearance of having 
 been broken and gnawed by the teeth of the hyaenas ; and they occur 
 confusedly mixed in loam or mud, or dispersed through a crust of 
 stalagmite which covers it. In these and many other cases it is sup- 
 posed 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 living hyaena. 
 
 No less than thirty- seven species of mammalia are enumerated by 
 Professor Owen as having been discovered in the caves of the British 
 islands, of which eighteen appear to be extinct, while the others still 
 
 M 
 
162 AUSTRALIAN CAVERNS. [Cn. XIII. 
 
 survive in Europe. They were not washed to the spots where the 
 fossils now occur by a great flood ; but lived and died, one generation 
 after another, in the places where they lie buried. Among other 
 arguments in favour of this conclusion may be mentioned the great 
 numbers of the shed antlers of deer discovered in caves and in fresh- 
 water strata throughout England.* 
 
 Examples also occur of fissures into which animals have fallen from 
 time to time, or have been washed in from above, together with al- 
 luvial matter and fragments of rock detached by frost, forming a mass 
 which may be united into a bony breccia by stalagmitic infiltrations. 
 Frequently we discover a long suite of caverns connected by narrow 
 and irregular galleries, which hold a tortuous course through the in- 
 terior of mountains, and seem to have served as the subterranean 
 channels of springs and engulphed rivers. Many streams in the 
 Morea are now carrying bones, pebbles, and mud into underground 
 passages of this kind. If, at some future period, the form of that 
 country should be wholly altered by subterranean movements and 
 new valleys shaped out by denudation, many portions of the former 
 channels of these engulphed streams may communicate with the sur- 
 face, and become the dens of wild beasts, or the recesses to which 
 quadrupeds retreat to die. Certain caves of France, Germany, and 
 Belgium may have passed successively through these different con- 
 ditions, and in their last state may have remained open to the day 
 for several tertiary periods. It is nevertheless very remarkable, that 
 on the continent of Europe, as in England, the fossil remains of mam- 
 malia belong almost exclusively to those of the Newer Pliocene and 
 Post-Pliocene periods, and not to the Miocene or Eocene epochs, and 
 when they are accompanied by land or river shells, these agree in 
 great part, or entirely, with recent species. 
 
 As the preservation of the fossil bones is due to a slow and constant 
 supply of stalactite, brought into the caverns by water dropping from 
 the roof, the source and origin of this deposit has been a subject of 
 curious inquiry. The following explanation of the phenomenon has 
 been recently suggested by the eminent chemist Liebig. On the 
 surface of Franconia, where the limestone abounds in caverns, is a 
 fertile soil, in which vegetable matter is continually decaying. This 
 mould or humus, being acted on by moisture and air, evolves carbonic 
 acid, which is dissolved by rain. The rain water, thus impregnated, 
 permeates the porous limestone, dissolves a portion of it, and after- 
 wards, when the excess of carbonic acid evaporates in the caverns, 
 parts with the calcareous matter, and forms stalactite. Such facts 
 seem to imply that the date of the emergence of the district was very 
 modern, for stalactite could not begin to form until the emergence of 
 the cavernous rock, and the land shells and land animals are usually 
 imbedded in the lowest part of the stalactitic deposit. 
 
 Australian cave-breccias. Ossiferous breccias are not confined to 
 Europe, but occur in all parts of the globe ; and those lately dis- 
 
 * Owen, Brit. Foss. Mam, xxvi., and Buckland, Rel. Dil. 19. 24. 
 
CH. XIII.] 
 
 FOSSILS IN AUSTRALIAN CAVES. 
 
 163 
 
 covered in fissures and caverns in Australia correspond closely in 
 character with what has been called the bony breccia of the Medi- 
 terranean, in which the fragments of bone and rock are firmly bound 
 together by a red ochreous cement. 
 
 Some of these caves have been examined by Sir T. Mitchell in 
 the Wellington Valley, about 210 miles west of Sidney, on the river 
 Bell, one of the principal sources of the Macquarie, 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 
 imbedded in loose earth, but they are usually included in a breccia. 
 
 The remains found most abundantly are those of the kangaroo, of 
 which there are four species, besides which the genera Hypsiprymnus, 
 Phalangista, Phascolomys, and Dasyurus, occur. There are also 
 bones, formerly conjectured by some osteologists to belong to the 
 hippopotamus, and by others to the dugong, but which are now 
 referred by Mr. Owen to a marsupial genus, allied to the Wombat. 
 
 In the fossils above enumerated, several species are larger than 
 
 Fig. 131. 
 
 Macropus atlas, Owen. 
 a. permanent false molar, in the alveolus. 
 
 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 
 
 Fig. 132. 
 
 Lowest jaw of largest living species of kangaroo. 
 
 (Macropus major.) 
 
 M 2 
 
164 EXTINCT FOSSIL MAMMALIA. [Cn. XIII. 
 
 (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. 132. 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. 131.) 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. In fig. 133. a 
 Fig 133 front tooth of the same species of kangaroo is re- 
 presented. 
 
 Whether the breccias, above alluded to, of the Wel- 
 lington Valley, appertain strictly to the Pliocene period 
 cannot be affirmed with certainty, until we are more 
 thoroughly acquainted with the recent quadrupeds of 
 the same district, and until we learn what species of 
 fossil land-shells, if any, are buried in the deposits of 
 the same caves. 
 
 The reader will observe that all these extinct qua- 
 drupeds 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 
 incisor of Ma- the Australian mammalia from those of other parts of 
 
 CTOpUS. 
 
 the globe. This fact is one of many pointing to a 
 general law deducible from the fossil vertebrate and invertebrate 
 animals of the eras immediately antecedent to the human, namely, 
 that the present geographical distribution of organic forms dates 
 back to a period anterior to the creation of existing species; in 
 other words, the limitation of particular genera or families of 
 quadrupeds, mollusca, &c., to certain existing provinces of land and 
 sea, began before the species now contemporary with man had been 
 introduced into the earth. 
 
 Mr. Owen, in his excellent " History of British Fossil 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 Europaeo-Asiatic province fossil 
 kangaroos or armadillos, but the elephant, rhinoceros, horse, bear, 
 hyaena, beaver, hare, mole, and others, which still characterize the 
 same continent. 
 
 In like manner, in the Pampas of South America the skeletons of 
 Megatherium, Megalonyx, Glyptodon, Mylodon, Toxodon, Macrau- 
 chenia, and other extinct forms, are analogous to the living sloth, 
 armadillo, cavy, capybara, and llama. The fossil quadrumana, also 
 associated with some of these forms in the Brazilian caves, belong to 
 the Platyrrhine family 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 ; and when in Georgia in 
 1845, I ascertained that the Megatherium, Mylodon, Harlanus ame- 
 ricanus (Owen), Equus curvidens, and other quadrupeds allied to the 
 Pampean type, were posterior in date to beds containing marine shells 
 belonging to forty-five recent species of the neighbouring sea. 
 
CH. XIII.] EXTINCT FOSSIL MAMMALIA. 165 
 
 There are indeed some cosmopolite genera, such as the Mastodon 
 (a genus of the elephant family) and the horse, which were simul- 
 taneously represented by different fossil species in Europe, North 
 America, and South America ; but these few exceptions can by no 
 means invalidate the rule which has been thus expressed by Professor 
 Owen, that in " the highest organized class of animals the same 
 forms were restricted to the same great provinces at the Pliocene 
 periods as they are at the present day." 
 
 However modern, in a geological point of view, we may consider 
 the Pleistocene epoch, it is evident that causes more general and 
 powerful than the intervention of man have occasioned the disap- 
 pearance of the ancient fauna from so many extensive regions. Not 
 a few of the species had a wide range ; the same Megatherium, for 
 instance, extended from Patagonia and the river Plata in South 
 America, between latitudes 31 and 39 south, to corresponding lati- 
 tudes in North America, the same animal being also an inhabitant of 
 the intermediate country of Brazil, where its fossil remains have been 
 met with in caves. The extinct elephant, likewise, of Georgia 
 (Elephas primigenius) has been traced in a fossil state northward 
 from the river Alatamaha, in lat. 33 50' N. to the polar regions, 
 and then again in the eastern hemisphere from Siberia to the south 
 of Europe. If it be objected that, notwithstanding the adaptation of 
 such quadrupeds to a variety of climates and geographical conditions, 
 their great size exposed them to extermination by the first hunter 
 tribes, we may observe that the investigations of Lund and Clausen 
 in the ossiferous limestone caves of Brazil have demonstrated that 
 these large mammalia were associated with a great many smaller 
 quadrupeds, some of them as diminutive as field mice, which hare 
 all died out together, while the land-shells formerly their contem- 
 poraries still continue to exist in the same countries. As we may 
 feel assured that these minute quadrupeds could never have been 
 extirpated by man, especially in a country so thinly peopled as Brazil, 
 so we may conclude that all the species, small and great, have been 
 annihilated one after the other, in the course of indefinite ages, by 
 those changes of circumstances in the organic and inorganic world 
 which are always in progress, and are capable in the course of time 
 of greatly modifying the physical geography, climate, and all other 
 conditions on which the continuance upon the earth of any living being 
 must depend.* 
 
 The law of geographical relationship above alluded to, between the 
 living vertebrata of every great zoological province and the fossils 
 of the period immediately antecedent, even where the fossil species 
 are extinct, is by no means confined to the mammalia. New Zea- 
 land, when first examined by Europeans, was found to contain no in- 
 digenous land quadrupeds, no kangaroos, or opossums, like Australia ; 
 but a wingless bird abounded there, the smallest living representative 
 of the ostrich family, called the Xivi, by the natives (Apteryx). In 
 
 * See Principles of Geology, chaps, xli. to xliv, 
 H 3 
 
166 
 
 TEETH OF FOSSIL QUADKUPEDS. 
 
 [Cn. XIII. 
 
 the fossils of the Post-Pliocene and Pleistocene period in this same 
 island, there is the like absence of kangaroos, opossums, 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 Palapteryx, which are entombed in superficial deposits. 
 These genera comprehended many species, some of which were 4, 
 some 7, others 9, and others 1 1 feet in height ! It seems doubtful 
 whether any contemporary mammalia shared the land with this popu- 
 lation of gigantic feathered bipeds. 
 
 To those who have never studied comparative anatomy it may seem 
 scarcely credible, that a single bone taken from any part of the skeleton 
 may enable a skilful osteologist to distinguish, in many cases, the 
 genus, and sometimes the species, of quadruped 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 
 distinguish the principal divisions of the mammalia by the forms and 
 characters of their teeth. The annexed figures, all taken from original 
 
 Elephas primfgenius (or Mammoth) ; molar of upper jaw, right side; one third of nat. size. 
 a. grinding surface. b. side view. 
 
 Fig. 135. 
 
 Mastodon angustidens (Norwich Crag, Postwick, also found in Red Crap, see p. 156.); second true 
 molar, left side, upper jaw ; grinding surface, nat. size. (See p. 156.) 
 
CH. XIII. J TEETH OF FOSSIL MAMMALIA. 167 
 
 specimens, may be useful in assisting the student to recognize the 
 teeth of many genera most frequently found fossil in the Newer Plio- 
 cene and Post-Pliocene periods. 
 
 Fig. 136 Fig. 137. Fig. 138. 
 
 Rhinoceros. 
 
 Rhinoceros leptorhinus ; fos- 
 sil from freshwater beds 
 of Grays, Essex (see p. 
 154.): penultimate molar, 
 lower jaw, left side; two- 
 thirds of nat. size. 
 
 Fig. 139. 
 
 Hippopotamus. 
 
 Hippopotamus ; from cave Sus scrofa, Lin. (common 
 near Palermo (see p. pig); from shell-marl, 
 160.) ; molar tooth ; two- Forfarshire ; posterior mo- 
 thirds of nat. size. lar, lower jaw, nat. size. 
 
 Fig. 140. 
 
 Horse. 
 
 Equus caballus, Lin. (common horse) ; 
 from the shell-marl, Forfarshire ; se- 
 cond molar, lower jaw. 
 
 a. grinding surface, two-thirds nat. size. 
 
 b. side view of same, half nat. size. 
 
 Fig. 141. 
 
 Tapir. 
 
 Tapirus Americanus 
 recent; third molar, 
 upper jaw ; nat. size. 
 
 Fig. 142. 
 
 a. b. Deer. 
 
 Elk (Cervus alces, Lin.); re- 
 cent ; molar of upper jaw. 
 a. grinding surface. 
 h. side view ; two-thirds of nat. 
 size. 
 
 M 4 
 
 c. d. Ox. 
 
 Ox, common, from shell-marl, Forfar- 
 shire ; true molar, upper jaw ; two- 
 thirds nat. size. 
 
 c. grinding surface. 
 
 d. side view ; fangs uppermost. 
 
168 
 
 OLDER PLIOCENE FORMATIONS. 
 
 [Cn. XIV 
 
 Fig. 143. 
 
 Fig. 144. 
 
 Bear. 
 
 a. canine tooth or tusk of bear ( Ursus 
 
 spel&us) ; from cave near Liege. 
 
 b. molar of left side, upper jaw ; one- 
 
 third of nat. size. 
 
 Fig. 145. 
 
 Tiger. 
 
 c. canine tooth of tiger (Felis ttgrts) ; 
 
 recent. 
 
 d . outside view of posterior molar, lowei 
 
 jaw ; one-third of nat. size. 
 
 Fig. 146. 
 
 Hyana speUea ; second molar, left 
 side, lower jaw; nat. size. Cave 
 ofKirkdale. (Seep. 161. 
 
 Teeth of a new species of Arvicola (field-mouse) ; from the 
 
 Norwich Crag. (See p. 163.) 
 a. grinding surface. b. side view of same. 
 
 c. nat. size of a and 6. 
 
 Fig. 147. 
 
 a. fourth molar, right ide, lower jaw. Megatherium ; Georgia, 
 U. S. ; one-third nat. size. 
 
 b. crown of same. 
 
 CHAPTER XIV. 
 
 OLDER PLIOCENE AND MIOCENE FORMATIONS. 
 
 Strata of Suffolk termed Eed and Coralline Crag Fossils, and proportion of recent 
 species Depth of sea and climate Reference of Suffolk Crag to the Older 
 Pliocene period Migration of many species of shells southwards during the 
 glacial period Fossil whales Antwerp Crag Subapennine beds Asti, 
 Sienna, Rome Aralo-Caspian formations Miocene formations Faluns of 
 Touraine Depth of sea and littoral character of fauna Tropical climate 
 implied by the testacea Proportion of recent species of shells Faluns more 
 ancient than the Suffolk Crag Miocene strata of Bordeaux of the Bolderberg 
 in Belgium of North Germany Vienna Basin Piedmont Molasse of 
 Switzerland Leaf-beds of Mull in Scotland Older Pliocene and Miocene 
 formations in the United States Sewalik Hills in India. 
 
 THE older Pliocene strata, which next claim our attention, are chiefly 
 confined, in Great Britain, to the eastern part of the county of Suf- 
 
CH. XIV.] OLDER PLIOCENE FORMATIONS. 169 
 
 folk, where, like the Norwich beds already described, they are called 
 " Crag," a provincial name given particularly to those masses of shelly 
 sand which have been used from very ancient times in agriculture, to 
 fertilize soils deficient in calcareous matter. The relative position of 
 the " Red Crag " in Essex to the London clay, may be understood by 
 reference to the accompanying diagram (fig. 148.). 
 
 Fig. 148. 
 Crag. London Clay. Chalk. 
 
 These deposits, according to Professor E. Forbes, appear by their 
 imbedded shells to have been formed in a sea of moderate depth, 
 usually from 15 to 25 fathoms, but in some few spots perhaps deeper. 
 Yet they cannot be called littoral, because the fauna is such as may 
 have extended 40 or 50 miles from land. 
 
 The Suffolk Crag is divisible into two masses, the upper of which 
 has been termed the Red, and the lower the Coralline Crag.* The 
 upper deposit consists chiefly of quartzose sand, with an occasional 
 intermixture of shells, for the most part rolled, and sometimes com- 
 minuted. In many pla*ces fossils washed out of older tertiary strata, 
 especially the London Clay, are met with. The lower or coralline 
 Crag is of very limited extent, ranging over an area about 20 miles 
 in length, and 3 or 4 in breadth, between the rivers Aide and Stour. 
 It is generally calcareous and marly a mass of shells, bryozoa f, 
 and small corals, passing occasionally into a soft building stone. At 
 Sudbourn, near Orford, where it assumes this character, are large 
 quarries, in which the bottom of it has not been reached at the depth 
 of 50 feet. At some places in the neighbourhood, the softer mass is 
 divided by thin flags of hard limestone, and corals placed in the 
 upright position in which they grew. 
 
 The Red Crag is distinguished by the deep ferruginous or ochreous 
 colour of its sands and fossils, the Coralline by its white colour. Both 
 formations are of moderate thickness ; the Red Crag rarely exceeding 
 40, and the Coralline seldom amounting to 20, feet. But their im- 
 portance is not to be estimated by the density of the mass of strata 
 or its geographical extent, but by the extraordinary richness of its 
 organic remains, belonging to a very peculiar type, which seems to 
 characterize the state of the living creation in the north of Europe 
 during the Older Pliocene era. 
 
 For a large collection of the fish, echinoderms, shells, bryozoa, and 
 
 * See paper by E. Charlesworth, Esq. ; 
 London and Ed. Phil. Mag. No. xxxviii. 
 p. 81., Aug. 1835. 
 
 f Ehrenberg proposed in 1831 the 
 term Bryozoum, or " Moss-animal," for 
 the molluscous or ascidian form of 
 polyp, characterized by having two 
 openings to the digestive sack, as in 
 Eschara, Flustra, Retepora, and other 
 zoophytes popularly included in the 
 
 corals, but now classed by naturalists as 
 mollusca. The term Polyzoum, syno- 
 nymous with Bryozoum, was, it seems, 
 proposed in 1830, or the year before, by 
 Mr. J. O. Thompson, but is less generally 
 adopted. The animals of the Zoantharia 
 of Milne Edwards and Haime, or the true 
 corals, have only one opening to the 
 stomach. 
 
170 SUFFOLK CRAG. [Cn. XIV. 
 
 corals of the deposits in Suffolk, we are indebted to the labours of 
 Mr. Searles Wood. Of testacea alone he has obtained 230 species 
 from the Red, and 345 from the Coralline Crag, about 150 
 being common to each. The proportion of recent species in the 
 new group is considered by Mr. Wood to be about 70 * per cent., 
 and that in the older or Coralline about 60. When I examined these 
 shells of Suffolk in 1835, with the assistance of Dr. Beck, Mr. 
 George Sowerby, Mr. Searles Wood, and other eminent concho- 
 logists, I came to the opinion that the extinct species predomi- 
 nated very decidedly in number over the living. Recent investi- 
 gations, however, have thrown much new light on the conchology of 
 the Arctic, Scandinavian, British, and Mediterranean Seas. Many 
 of the species formerly known only as fossils of the Crag, and 
 supposed to have died out, have been dredged up in a living state 
 from depths not previously explored. Other recent species, before 
 regarded as distinct from the nearest allied Crag fossils, have been 
 observed, when numerous individuals were procured, to be liable to 
 much greater variation, both in size and form, than had been sus- 
 pected, and thus have been identified. Consequently, the Crag 
 fauna has been found to approach much more nearly to the recent 
 fauna of the Northern, British, and Mediterranean Seas than had been 
 imagined. The analogy of the whole group of testacea to the 
 European type is very marked, whether we refer to the large de- 
 velopment of certain genera in number of species or to their size, or 
 to the suppression or feeble representation of others. The indication 
 also afforded by the entire fauna of a climate not much warmer than 
 that now prevailing in corresponding latitudes, prepares us to believe 
 that they are not of higher antiquity than the Older Pliocene era. 
 
 The position of the Red Crag in Essex to the subjacent London clay 
 and chalk has been already pointed out (fig. 148.). Whenever the 
 two divisions are met with in the same district, the Red Crag lies 
 uppermost ; and, in some cases, as in the section represented in 
 fig. 149., which I had an opportunity of seeing exposed to view in 
 1839, it is clear that the older or Coralline mass b had suffered 
 denudation, before the newer formation a was thrown down upon it. 
 
 Fig. 149. 
 
 Shottisham g 
 
 Creek. Ramsholt. % 
 
 Section near Ipswich, in Suffolk. 
 a. Red Crag. 5. Coralline Crag. c. London Clay. 
 
 At D there is not only a distinct cliff, 8 or 10 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 Pho- 
 lades, the holes which they perforated having been afterwards filled 
 
 * See Monograph on the Crag Mollusca. Searles Wood, Paleont. Soc. 1848. 
 
CH. XIV.] 
 
 OLDER PLIOCENE FORMATIONS. 
 
 171 
 
 with sand and covered over when the newer beds were thrown down. 
 As the older formation is shown by its fossils to have accumulated 
 in a deeper sea (15, and sometimes 25, fathoms deep or more), there 
 must no doubt have been an upheaval of the sea-bottom before the 
 cliff here alluded to was shaped out. We may also conclude that so 
 great an amount of denudation could scarcely take place, in such in- 
 coherent materials, without many of the fossils of the inferior beds 
 becoming mixed up with the overlying crag, so that considerable 
 difficulty must be occasionally experienced by the palaeontologists in 
 deciding which species belong severally to each group. 
 
 The Red Crag being formed in a shallower sea, often resembles in 
 structure a shifting sand-bank, its layers being inclined diagonally, 
 and the planes of stratification being sometimes directed in the same 
 quarry to the four cardinal points of the compass, as at Butley. That 
 in this and many other localities, such a structure is not deceptive 
 or due to any subsequent concretionary rearrangement of particles, 
 or to mere lines of colour, is proved by each bed being made up of 
 flat pieces of shell which lie parallel to the planes of the smaller 
 strata. 
 
 Some fossils, which are very abundant in the Red Crag, have never 
 been found in the white or coralline division ; as, for example, the 
 Fusus contrarius (fig. 150.), and several species of Murex and 
 Buccinum (or Nassa) (see figs. 151, 152.), which two genera seem 
 wanting in the lower crag. 
 
 Fig. 150. 
 
 Fossils characteristic of the Red Crag. 
 
 Fig. 151. 
 
 Fig. 152. 
 
 Nassa granulata. 
 Fig. 153. 
 
 Fusus contrarius. Murex alveolatus. Cyprcea coccinelloides. 
 
 Fig. 150. half nat. size; the others nat. size. 
 
 Among the bones and teeth of fishes are those of large sharks 
 ( Car char odort)^ and a gigantic skate of the extinct genus Myliobates, 
 and many other forms, some common to our seas, and many foreign 
 to them. It is questionable, however, whether all these can really 
 be ascribed to the era of the Red Crag. Not a few of them may 
 possibly have been derived from older strata, especially from those 
 Upper Eocene formations to be described in the next chapter, which 
 are largely developed in Belgium, and of which a fragment (the 
 Hempstead beds of Forbes) escaped denudation in England. 
 
 The distinctness of the fossils of the Coralline from those of the 
 
172 
 
 FOSSILS OF THE SUFFOLK CRA.G. 
 
 [Cn. XIY. 
 
 Red Crag, arises in part from their higher antiquity, and, in some 
 degree, from a difference in the geographical conditions of the 
 submarine bottom. The prolific growth of corals, echini, and a 
 prodigious variety of testacea and bryozoa, implies a region of 
 deeper and more tranquil water; whereas, the Red Crag may have been 
 formed afterwards on the same spot, when the water was shallower. 
 In the mean time the climate may have become somewhat cooler, and 
 some of the zoophytes which flourished in the first period may have 
 disappeared, so that the fauna of the Red Crag acquired a character 
 somewhat more nearly resembling that of our northern seas, as is 
 implied by the large development of certain sections of the genera 
 Fusus, Buccinum, Purpura, and Trochus, proper to higher latitudes, 
 and which are wanting or feebly represented in the inferior crag. 
 
 Some of the corals and bryozoa of the lower crag of Suffolk belong 
 to genera unknown in the living creation, and of a very peculiar 
 structure ; as, for example, that represented in the annexed fig. (154.), 
 
 Fig. 154. 
 
 b 
 
 Fasctcularta aurantium, Milne Edwards. Family, Tubuliporidce, of same author. 
 
 Bryozoan of extinct genus, from the inferior or Coralline Crag, Suffolk. 
 a. exterior. b. vertical section of interior. c. portion of exterior magnified. 
 
 d. portion of interior magnified, showing that it is made up of long, thin, straight tubes, united 
 in conical bundles. 
 
 which is one of several species having a globular form. The great 
 number and variety of these zoophytes probably indicate an equable 
 climate, free from intense cold in winter. On the other hand, that 
 the heat was never excessive is confirmed by the prevalence of 
 northern forms among the testacea, such as the Glycimeris, Cyprina, 
 and Astarte. Of the genus last mentioned (see fig. 155.) there are 
 
 Fig. 155. 
 
 Astarte (Crassma, Lam.) ; species common to upper and lower crag. 
 
 Astarte Omalii, Lajonkaire; Syn. A. bipartita, Sow. Min. Con. T. 521. f. 3.; a very variable species, 
 most characteristic of the Coralline Crag, Suffolk. 
 
CH. XIV.] OLDER PLIOCENE FORMATIONS. 173 
 
 about fourteen species, many of them being rich in individuals ; and 
 there is an absence of genera peculiar to hot climates, such as Conus, 
 
 Fig. 156. 
 
 Fig. 157. 
 
 Fig. 158. 
 
 Valuta Lamberti, young 
 individ., Cor. and Ke 
 Crag. 
 
 Pyrula reticulata, Lam . ; 
 Coralline Crag, Ram- 
 sholt, 
 
 Temnechinus ezcavatia, 
 Forbes; Temnopleurus 
 excavalus, Wood ; Cor. 
 Crag, Ramsholt. 
 
 Oliva, Mitra, Fasciolaria, Crassatella, and others. The cowries 
 (CyprcBa, fig. 153.), also, are small, and belong to a section (Trivia) 
 now inhabiting the colder regions. A large volute, called Valuta 
 Lamberti (fig. 156.), may seem an exception; but it differs in form 
 from the volutes of the torrid zone, and may, like the living Voluta 
 Magellanica, have been fitted for an extra-tropical climate. 
 
 The occurrence of a species of Lingula at Sutton (see fig. 160.) 
 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 of Pyrula, supposed by Mr. Wood to be 
 identical with P. reticulata (fig. 157.), now living in the Indian 
 Ocean. A genus also of echinoderms, called by Professor Forbes 
 Temnechinus (fig. 158.), is peculiar to the Red and Coralline Crag 
 of Suffolk. The only species now living occur in the Indian Ocean. 
 Whether, therefore, we may incline to the belief that the mean annual 
 temperature was higher or lower than now, we may at least infer 
 that the climate and geographical conditions were by no means the 
 same at the period of the Suffolk Crag as those which now prevail in 
 the same region. 
 
 One of the most interesting conclusions deduced from a careful 
 comparison of the shells of these British Older Pliocene strata 
 and the fauna of our present seas, has been pointed out by Prof. 
 E. Forbes. It appears 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, re- 
 treated southwards to avoid an uncongenial climate. The Professor 
 has given 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, are all wanting in the Pleistocene or glacial 
 deposits. They must therefore, after their migration to the south, 
 which took place during the glacial period, have made their way 
 northwards again. In corroboration of these views, it is stated that 
 all these fifty species occur fossil in the Newer Pliocene strata of 
 
174 SUBAPENNIXE STRATA. [Cn. XIV. 
 
 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 European latitudes.* 
 
 In the Red Crag at Felixstow, in Suffolk, Professor Henslow has 
 found the ear-bones of one or more species of cetacea, which, ac- 
 cording to Prof. Owen, are the remains of true whales of the family 
 BalcenidcB (fig. 159.). Mr. Wood is of opinion that these cetacea may 
 be of the age of the Red Crag, or if not that they may be derived 
 from the destruction of beds of Coralline Crag. 
 
 Antwerp. Strata of the same age as the Red and Coralline Crag of 
 Suffolk have been long known in the country round Antwerp and on 
 the banks of the Scheldt, below that city. More than 200 species of 
 
 Fig. 159. Fig. 160. 
 
 Tympanic bone of Bal&na emarginata, Lingula Dumortiert, Nyst ; 
 
 Owen ; Red Crag, Felixtow. Antwerp Crag. _' 
 
 testacea have been collected by MM. De Wael, Nyst, and others, 
 of which two-thirds have been identified with Suffolk fossils by Mr. 
 Wood. Among these he recognizes Lingula Dumortieri of Nyst 
 (fig. 160.), which I found in abundance at Antwerp in 1851, in what 
 is called by M. de Wael the middle crag. More than half of the 
 shells of this Antwerp deposit agree with living species, and these 
 belong in great part to the fauna of our northern seas, though some 
 Mediterranean species are not wanting. I also met with numerous 
 cetacean bones of the genera Balcenoptera and Ziphius in the same 
 formation. They are not at all rolled, as if washed out of older beds, 
 and I infer that the animals to which they belonged once coexisted 
 in the same sea with the associated mollusca.f 
 
 Normandy. I observed in 1840 a small patch of shells corre- 
 sponding to those of the Suffolk Crag, near Valognes, in Normandy ; 
 and there is a deposit containing similar fossils at St. George 
 Bohon, and several places a few leagues to the S. of Carentan, in 
 Normandy ; but they have never been traced farther southwards. 
 
 Subapennine strata. The Apennines, it is well known, are com- 
 posed chiefly of secondary 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, as we have seen 
 (p. 111.), was the first Italian geologist who described this newer 
 group in detail, giving it the name of the Subapennines ; and he 
 
 * E. "Forbes, Mem. Geol. Survey, Gt. f Lyell on Belgian Tertiaries, Quart. 
 Brit. voL L 386. Journ. Geol. Soc. 1852, p. 382. 
 
CH. XIV.] SUBAPENNINE STRATA. 175 
 
 classed all the tertiary strata of Italy, from Piedmont to Calabria, as 
 parts of the same system. Certain mineral characters, he observed, 
 were common to the whole ; for the strata consist generally of light 
 brown or blue marl, covered by yellow calcareous sand and gravel. 
 There are also, he added, some species of fossil shells which are found 
 in these deposits throughout the whole of Italy. 
 
 We have now, however, satisfactory evidence that the Subapennine 
 beds of Brocchi, although chiefly composed of Older Pliocene strata, 
 belong nevertheless, in part, both to older and newer members of the 
 tertiary series. The strata, for example, of the Superga, near Turin, 
 are Miocene ; those of Asti and Parma Older Pliocene, as is the blue 
 marl of Sienna ; while the shells of the incumbent yellow sand of the 
 same territory approach more nearly to the recent fauna of the Medi- 
 terranean, and may be Newer Pliocene. 
 
 The greyish-brown or blue marl of the Subapennine formation is 
 very aluminous, and usually contains much calcareous matter and 
 scales of mica. Near Parma it attains a thickness of 2000 feet, and 
 is charged throughout with marine shells, some of which lived in 
 deep, others in shallow water, while a few belong to freshwater 
 genera, and must have been washed in by rivers. Among these 
 last I have seen the common Limnea palustris in the blue marl, 
 filled with small marine shells. The wood and leaves, which occa- 
 sionally form beds of lignite in the same deposit, may have been 
 carried into the sea by similar causes. The shells, in general, are soft 
 when first taken from the marl, but they become hard when dried. 
 The superficial enamel is often well preserved, and many shells 
 retain their pearly lustre, part of their external colour, and even 
 the ligament which unites the valves. No shells are more usually 
 perfect than the microscopic foraminifera, which abound near Sienna, 
 where more than a thousand full-grown individuals may be sometimes 
 poured out of the interior of a single univalve of moderate dimensions. 
 
 The other member of the Subapennine group, the yellow sand and 
 conglomerate, constitutes, in most places, a border formation near the 
 junction of the tertiary and secondary rocks. In some cases, as near 
 the town of Sienna, we see sand and calcareous gravel resting imme- 
 diately on the Apennine limestone, without the intervention of any 
 blue marl. Alternations are there seen of beds containing fluviatile 
 shells, with others filled exclusively with marine species ; and I ob- 
 served oysters attached to many limestone pebbles. The site of 
 Sienna appears to have been a point where a river, flowing from the 
 Apennines, entered the sea when the tertiary strata were formed. 
 
 The sand passes in some districts into a calcareous sandstone, as 
 at San Vignone. Its general superposition to the marl, even in parts 
 of Italy and Sicily where the date of its origin is very distinct, may 
 be explained if we consider that it may represent the deltas of rivers 
 and torrents, which gained upon the bed of the sea where blue marl 
 had previously been deposited. The latter, being composed of the 
 finer and more transportable mud, would be conveyed to a distance, 
 and first occupy the bottom, over which sand and pebbles would 
 
176 MIOCENE FORMATIONS. [Cn. XIV. 
 
 afterwards be spread, in proportion as rivers pushed their deltas 
 farther outwards. In some large tracts of yellow sand it is impos- 
 sible to detect a single fossil, while in other places they occur in 
 profusion. Occasionally the shells are silicified, as at San Yitale, 
 near Parma, from whence I saw two individuals of recent species, 
 one freshwater and the other marine (Limnea palustris, and Cytherea 
 concentrica, Lam.), both perfectly converted into flint. 
 
 Rome. The seven hills of Rome are composed partly of marine 
 tertiary strata, those of Monte Mario, for example, of the Older 
 Pliocene period, and partly of superimposed volcanic tuff, on the 
 top of which are usually cappings of a fluviatile and lacustrine 
 deposit. Thus, on Mount Aventine, the Vatican, and the Capitol, 
 we find beds of calcareous tufa with incrusted reeds, and recent ter- 
 restrial shells, at the height of about 200 feet above the alluvial plain 
 of the Tiber. The tusk of the mammoth has been procured from 
 this formation, but the shells appear to be all of living species, and 
 must have been imbedded when the summit of the Capitol was a 
 marsh, and constituted one of the lowest hollows of the country as it 
 then existed. It is not without interest that we thus discover the 
 extremely recent date of a geological event which preceded an his- 
 torical era so remote as the building of Rome. 
 
 Aralo- Caspian formations. This name has been given by Sir R. 
 Murchison and M. de Verneuil to the limestone and associated sandy 
 beds, of brackish-water origin, which have been traced over a very 
 extensive area surrounding the Caspian, Azof, and Aral Seas, and 
 parts of the northern and western coasts of the Black Sea. The 
 fossil shells are partly freshwater, as Paludina, Neritina, &c., and partly 
 marine, of the family Cardiacice and Mytili. The species are iden- 
 tical, in great part, with those now inhabiting the Caspian ; and when 
 not living, they are analogous to forms now found in the inland seas 
 of Asia, rather than to oceanic types. The limestone rises occa- 
 sionally to the height of several hundred feet above the sea, and is 
 supposed to indicate the former existence of a vast inland sheet of 
 brackish water as large as the Mediterranean, or larger. 
 
 The proportion of recent species agreeing with the fauna of the 
 Caspian is so considerable as to leave no doubt in the minds of the 
 geologists above cited, that this rock, also called by them the " Steppe 
 Limestone," belongs to the Pliocene period.* 
 
 MIOCENE FORMATIONS. 
 
 Faluns of Touraine. The strata which we meet with next in the' 
 descending order are those called by many geologists " Middle Ter- 
 tiary," and 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. No strata contemporaneous with these formations 
 have as yet been met with in the British Isles, where the lower crag 
 of Suffolk is the deposit nearest in age. The term "faluns" is 
 given provincially by French agriculturists to shelly sand and marl 
 * Geol. of Russia, p. 279. &c. 
 
CH. XIV.] FALUNS OF TOUKAINE. 177 
 
 spread over the land in Touraine, just as the "crag" was formerly 
 much used to fertilize the soil in Suffolk. Isolated masses of such 
 faluns occur from near the mouth of the Loire, in the neighbourhood 
 of Nantes, to as far inland as a district south of Tours. They are 
 also found at Pontlevoy, on the Cher, about 70 miles above the 
 junction of that river with the Loire, and 30 miles S. E. of Tours. 
 Deposits of the same age also appear under new mineral conditions 
 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 Doue, in the department of Maine and Loire, 10 miles 
 S. W. of Saumur, they form a soft building-stone, chiefly composed 
 of an aggregate of broken shells, bryozoa, corals, and echinoderms, 
 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 
 50 feet ; and between the district called Sologne and the sea they 
 repose on a great variety of older rocks ; being seen to rest succes- 
 sively upon gneiss, clayslate, various secondary formations, including 
 the chalk; and, lastly, upon the upper freshwater limestone of the 
 Parisian tertiary series, which, as before mentioned (p. 111.), 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 colour, 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. Among the former, Helix turonensis 
 
 (% 45 ' P- 30 ') * s ^ e most abundant. 
 Remains of terrestrial quadrupeds are here 
 and there intermixed, belonging to the 
 genera Deinotherium (fig. 161.), Mastodon, 
 Rhinoceros, Hippopotamus, Chseropota- 
 mus, Dichobune, Deer, and others, and 
 these are accompanied by cetacea, such 
 as the Lam an tine, Morse, Sea-calf, and 
 Dolphin, all of extinct species. 
 
 Professor E. Forbes, after studying the 
 fossil testacea which I obtained from these 
 beds, informs me that he has no doubt 
 they 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 molluscous fauna 
 of the " faluns " is on the whole much more littoral than that of the 
 Red and Coralline Crag of Suffolk, and implies a shallower sea. It is, 
 moreover, contrasted with the Suffolk Crag by the indications it 
 affords of an extra-European climate. Thus it contains seven species 
 of Cyprcea, some larger than any existing cowry of the Mediterranean, 
 several species of Oliva, Ancillaria, Milra, Terebra, Pyrula, Fas- 
 ciolaria, and Conus. Of the cones there are no less than eight 
 
 N 
 
178 COMPARISON OF THE CRAG AND FALUNS. [Cn. XIV. 
 
 species, some very large, whereas the only European cone is of di- 
 minutive size. The genus Nerita, and many others, are also repre- 
 sented by individuals 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 perfect 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 recent species, which is in 
 the proportion of twenty-five per cent. A large number of the 290 
 species are common to all the localities, those peculiar to each not 
 being more numerous than we might expect to find in different bays 
 of the same sea. 
 
 The total number of testaceous mollusca from the faluns, in my 
 possession, is 302, of which forty-five only were found by Mr. Wood 
 to be common to the Suffolk Crag. The number of corals, including 
 bryozoa and zoantharia, obtained by me at Doue, and other localities 
 before adverted to, amounts to forty-three, as determined by Mr. 
 Lonsdale, of which seven (one of them a zoantharian) agree spe- 
 cifically with those of the Suffolk Crag. Only one has, as yet, been 
 identified with a living species. But it is difficult, notwithstanding 
 the advances recently made by MM. Dana, Milne Edwards, Haime, 
 and Lonsdale, to institute a satisfactory comparison between recent 
 and fossil zoantharia and bryozoa. Some of the genera occurring 
 fossil in Touraine, as the Astrea, Dendrophyllia, Lunulites, have not 
 been found in European seas north of the Mediterranean; nevertheless 
 the zoantharia of the faluns do not seem to indicate on the whole so 
 warm a climate as would be inferred from the shells. 
 
 It was stated that, on comparing about 300 species of Touraine 
 shells with about 450 from the Suffolk Crag, forty-five only were 
 found to be common to both, which is in the proportion of only fifteen 
 per cent. The same small amount of agreement is found in the 
 corals also. I formerly endeavoured to reconcile this marked dif- 
 fjrence in species with the supposed 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, separating the Red Sea and the Mediterranean. But I now 
 abandon that idea for several reasons ; among others, because I suc- 
 ceeded in 1841 in tracing the Crag fauna southwards in Normandy 
 to within seventy miles of the Falunian type, near Dinan, yet found 
 that both assemblages of fossils retained their distinctive characters, 
 showing no signs of any blending of species or transition of climate. 
 
 On a comparison of 280 Mediterranean shells with 600 British 
 species, made for me by an experienced conchologist in 1841, 160 
 were found to be common to both collections, which is in the pro- 
 
CH. XIV.] SHELLS IN MIOCENE STRATA. 179 
 
 portion of fifty-seven per cent., a fourfold greater specific resemblance 
 than between the seas of the crag and the faluns, notwithstanding 
 the greater geographical distance between England and the Mediter- 
 ranean than between Suffolk and the Loire. The principal grounds, 
 however, for referring the English crag to the Older Pliocene and the 
 French faluns to the 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 neighbouring 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, therefore, receding farther from our era in time. 
 Bordeaux. A great extent of country between the Pyrenees and 
 the Gironde is overspread by tertiary deposits of various ages from 
 the Eocene to the Pliocene. Among these, especially near Saucats in 
 the environs of Bordeaux, and at Merignac and Bazas in the same 
 region, are sands containing marine shells, and corals of the type of 
 the Touraine faluns.* 
 
 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 representative 
 of the faluns of Touraine. They are quite distinct in their fossils 
 from the Antwerp Crag before mentioned, and contain shells of the 
 Fig , G2 genera Oliva, Conus, Ancillaria, Pleurotoma, 
 
 and Cancellaria in abundance. The most 
 common shell is an Olive (see fig. 162.), called 
 by Nyst Oliva Dufresnii, Bast. ; but which is 
 undoubtedly, as M. Bosquet observes, smaller 
 and shorter than the Bordeaux species.f 
 
 North Germany. We learn from the able 
 treatise published by M. Beyrich, in 1853, that 
 
 . tllG f Ssil fauna ftbove alluded to, which is SO 
 
 a. front view; ft. back view, meagrely exhibited in the Bolderberg, is rich 
 in species in other localities in North Germany, as in Mecklenburg 
 Liineburg, the Island Sylt, and at Bersenbruck north of Osnabruck, 
 in Westphalia, where it was first observed by F. Romer. It is also 
 said to occur at Bocholt, and other points in Westphalia; on the borders 
 of Holland ; also at Crefeld and Dusseldorf. Not having visited these 
 localities, I can offer no opinion as to the agreement in age of the 
 several deposits here enumerated. 
 
 * See a Memoir by V. Eaulin, 1848: seems to be copied from that given by 
 
 Bordeaux. Basterot of the Bordeaux fossil. 
 
 f Lyell on Belgian Tertiaries, Quart. % Die Conchylien des Norddeutschen 
 
 Geol. Journ. 1852, p. 295. Nyst's figure Tertiiirgebirge .- Berlin, 1853. 
 
 N 2 
 
180 SHELLS IN MIOCENE STRATA. [Cn. XIV. 
 
 Vienna basin. In South Germany the general resemblance of 
 the shells of the Vienna tertiary basin with those of the faluns of 
 Touraine has long been acknowledged. In Dr. Homes' excellent work, 
 recently commenced, on the fossil mollusca of that formation, we see 
 figures of many shells of the genus Conus, some of large size, clearly 
 of the same species as those found in the falunian sands of Touraine. 
 M. Alcide d'Orbigny has also shown that the foraminifera of the 
 Vienna basin differ alike from the Eocene and Pliocene species, and 
 agree with those of the faluns, so far as the latter are known. Among 
 the Vienna foraminifera, the genus Amphistegina (fig. 163.) is very 
 
 Fig. 163. 
 
 Amphistegina Hauenna, D'Orb. Vienna, miocene strata. 
 
 characteristic, and is supposed by Archiac to take the same place 
 among the foraminifera of the Miocene era, which the Nummulites 
 occupy in the Eocene period. 
 
 The Vienna basin is thought by some geologists to comprise 
 tertiary strata of more than one age, the lowest strata reached in 
 boring Artesian wells being older than the faluns. 
 
 Piedmont. Switzerland. To the same Miocene or " falunian " 
 epoch, we may refer a portion of the strata of the Hill of the Superga 
 near Turin in Piedmont *, as also part of the Molasse of Switzer- 
 land, or the greenish sand which fills the great Swiss valley between 
 the Alps and the Jura. At the foot of the Alps it usually takes 
 the form of a conglomerate called provincially " nagelflue," some- 
 times attaining the truly wonderful thickness of 6000 and 8000 feet, 
 as in the Rigi near Lucerne and in the Speer near Wesen. The 
 lower portion of this molasse is of freshwater origin. 
 
 Scotland. Isle of Mull. In the sea-cliffs forming the head- 
 land of Ardtun on the west coast of Mull, in the Hebrides, several 
 bands of tertiary strata containing leaves of dicotyledonous plants 
 were discovered in 1851 by the Duke of Argyle. f From his descrip- 
 tion it appears that there are three leaf-beds, varying in thickness 
 from 1| to 2|- feet, which are interstratified with volcanic tuff and 
 trap, the whole mass being about 130 feet in thickness. A sheet 
 of basalt 40 feet thick covers the whole ; and another columnar 
 bed of the same rock 10 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 remains 
 are plentifully imbedded in clay. 
 
 * See Sig. Giov. Micnelotti's works. f Quart. Geol. Journ. 1851, p. 89. 
 
CH. XIV.] LEAF -BEDS OF MULL IN SCOTLAND. 181 
 
 It is supposed by the Duke of Argyle that this formation was 
 accumulated in a shallow lake or marsh in the neighbourhood of 
 a volcano, which emitted showers of ashes and streams of lava. 
 The tufaceous envelope of the fossils may have fallen into the lake 
 from the air as volcanic dust, or have been washed down into it as 
 mud from the adjoining land. The deposit is decidedly newer than 
 the chalk, for chalk flints containing cretaceous fossils were detected 
 by the Duke in the principal mass of volcanic ashes or tuff.* 
 
 The leaves belong to species, and sometimes even to families, no 
 longer indigenous in the British Isles ; and " their climatal aspect," 
 says Prof. E. Forbes, "is more mid-European than that of the English 
 Eocene Flora. They also resemble some of the Miocene plants of 
 Croatia described by Unger." Some of them appear to belong to a 
 coniferous tree, possibly a yew ( Taxus) ; others, still more abundant, 
 to a plane (Platanus), having the same outline and veining well 
 preserved. No accompanying fossil shells have been met with, and 
 there seems therefore the same uncertainty in determining whether 
 these beds are Upper Eocene or Miocene, which we experience when 
 we endeavour to fix the age of many continental Brown-Coal form- 
 ations, those of Croatia not excepted. 
 
 These interesting discoveries in Mull naturally raise the ques- 
 tion, whether the basalt of Antrim in Ireland, and of the cele- 
 brated Giant's Causeway, may not be of the same age. For in 
 Antrim the basalt overlies the chalk, and the upper mass of it 
 covers everywhere a bed of lignite and charcoal, in which wood, 
 with the fibre well preserved, and evidently dicotyledonous, is pre- 
 served. J 1 The general dearth of strata in the British Isles, inter- 
 mediate in age between the formation of the Eocene and Pliocene 
 periods, may arise, says Prof. Forbes, from the extent of dry land 
 which prevailed in the vast interval of time alluded to. If land pre- 
 dominated, the only monuments we are likely ever to find of Mio- 
 cene date are those of lacustrine and volcanic origin, such as these 
 Ardtun beds in Mull, or the lignites and associated basalts in 
 Antrim. On the flaules of Mont Dor, in Auvergne, I have seen 
 leaf beds among the ancient volcanic tuffs which I have alvA-ays 
 supposed to be of Miocene date. Some of the Brown Coal deposits 
 of Germany are believed to be Miocene ; others, as will be seen in 
 the next chapter, are Eocene, Upper or Middle. 
 
 Older Pliocene and Miocene formations in the United States. 
 Between the Alleghany mountains, formed of older rocks, and the 
 Atlantic, there intervenes, in the United States, a low region occupied 
 principally by beds of marl, clay, and sand, consisting of the cretaceous 
 and tertiary formations, and chiefly of the latter. The general eleva- 
 tion of this plain bordering 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, 
 
 * Quart. Geol. Jouvn. 1851, p. 90. t Duke of Argyll, ibid. p. 101. 
 
 N 3 
 
182 PLIOCENE AND MIOCENE FORMATIONS [Cn. XIY. 
 
 almost exclusively of Eocene deposits ; but in North Carolina, Mary- 
 land, Virginia, Delaware, more modern strata predominate, which, 
 after examining them in 1842, I supposed to be of the age of the 
 English crag and Faluns of Touraine.* If, chronologically speaking, 
 they can be truly said to be the representatives of these two Euro- 
 pean formations, they may range in age from the Older Pliocene to 
 the Miocene epoch, according to the classification of European strata 
 adopted in this chapter. 
 
 The proportion of fossil shells agreeing with recent, out of 147 
 species collected by me, amounted to about 17 per cent, or one-sixth 
 of the whole ; but as the fossils so 'assimilated were almost always the 
 same as species now living in the neighbouring Atlantic, the number 
 may hereafter be augmented, when the recent fauna of that ocean is 
 better known. In different localities, also, the proportion of recent 
 species varied considerably. 
 
 On the banks of the James Kiver, in Virginia, about 20 miles below 
 Richmond, in a cliff about 30 feet high, I observed yellow and white 
 sands overlying an Eocene marl, just as the yellow sands of the crag lie 
 on the blue London clay in Suffolk and Essex in England. In the 
 Virginian sands, we find a profusion of an Astarte (A. undulata, 
 Conrad), which resembles closely, and may possibly be a variety of, 
 one of the commonest fossils of the Suffolk Crag (A. bipartitd)\ the 
 other shells also, of the genera Natica, Fissurella, Artemis, Lucina, 
 Chama, Pectunculus, and Pecten, are analogous to shells both of the 
 English crag and French faluns, although the species are almost all 
 distinct. Out of 147 of these American fossils I could only find 13 
 species common to Europe, and these occur partly in the Suffolk 
 Crag, and partly in the faluns of Touraine ; but it is an important 
 characteristic of the American group, that it not only contains many 
 
 Fig. 164. Fig. 165. 
 
 Fulgur canaliculatus. Maryland. Fusus quadricostatus, Say. Maryland. 
 
 peculiar extinct forms, such as Fusus quadricostatus, Say (see fig. 
 165.) and Venus tridacnoidcs, abundant in these same formations, 
 but also some shells which, like Fulgur carica of Say and F. ca- 
 naliculatus (see fig. 164.), Calyptr&a costata, Venus mercenaria, 
 
 * Proceed, of the Geol. Soc. vol. iv. part 3. 1845, p. 547. 
 
Cu. XIV.] IN UNITED STATES, AND IN INDIA. 183 
 
 Lam., Modiola glandula, 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 mollusca date back to a period as 
 remote as that of the Miocene strata. 
 
 Of ten species of zoophytes which I procured on the banks of 
 the James River, one was formerly supposed by Mr. Lonsdale to be 
 identical with a fossil from the faluns of Touraine, but this species 
 
 (see fig. 166.) proves on re- examination 
 to be different, and to agree generically 
 with a coral now living on the coast of 
 the United States. With respect to 
 climate, Mr. Lonsdale regards these 
 corals as indicating a temperature ex- 
 ceeding 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. lati- 
 
 Axtrangia lincata, Lonsdale. ., i -i i -n i c -i i 
 
 syn. Anihaphyiium lineatum. tude, while the French taluns are in the 
 47th ; yet the forms of the American 
 
 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 Post-Eocene strata of the United 
 States are several large teeth of the shark family, not distinguishable 
 specifically from fossils of the faluns of Touraine. 
 
 India. Sewalik Hills. The freshwater deposits of the sub- 
 Himalayan or Sewalik Hills, described by Dr. Falconer and Captain 
 Cautley, belong probably to some part of the Miocene period, although 
 it is difficult to decide this question until the accompanying fresh- 
 water and land shells have been more carefully determined and com- 
 pared with fossils of other tertiary deposits. The strata are certainly 
 newer than the nummulitic rocks of India, and, like the faluns of 
 Touraine, they contain the genera Deinotherium and Mastodon, with 
 which are associated no less than seven extinct species of Elephants. 
 The presence of a fossil giraffe and hippopotamus, genera now only 
 living in Africa, and of a camel, an inhabitant of extensive plains, 
 implies a former geographical state of things strongly contrasted with 
 what now prevails in the same region. A species of Anoplothervim 
 (A. poster ogeniturn) forms a link between this fauna and that of the 
 Eocene period ; yet, on the whole, the Sewalik mammalia have a more 
 modern aspect than those of the Upper Eocene, so many being re- 
 ferable to existing genera, whereas almost every Eocene genus is ex- 
 tinct. Moreover, the sub-Himalayan fauna exhibits a great develop- 
 ment of the Ruminants, an order so feebly represented in the Eocene 
 period. In addition to the camel and giraffe already alluded to, we 
 have here the huge Sivatherium, a ruminant bigger than the rhinoce- 
 ros, and provided with a large upper lip, if not a short proboscis, and 
 having two pair of horns resembling those of antelopes. The number 
 of species of the genus Antelope is also remarkable. In the same fauna 
 
 N 4 
 
184 UPPER EOCENE FORMATIONS. [Cn. XV. 
 
 appear many carnivorous beasts, often belonging to existing genera, 
 and several species of monkey. Among the reptiles are crocodiles, 
 some larger than any now living ; and an enormous tortoise, Testudo 
 Atlas, the curved shell of which measured twenty feet across. 
 
 CHAPTER XV. 
 
 UPPER EOCENE FORMATIONS. 
 
 (Lower Miocene of many authors.) 
 
 Preliminary remarks on classification, and on the line of separation between 
 Eocene and Miocene strata Whether the Limburg and contemporaneous 
 formations should be called Upper Eocene Limburg strata in Belgium 
 Strata of same age in North Germany Mayence basin Brown Coal of 
 Germany Upper Eocene of Hempstead Hill, Isle of Wight Upper Eocene 
 of France Lacustrine strata of Auvergne Indusial limestone Freshwater 
 strata of the Cantal Its resemblance in some places to white chalk with flints 
 Proofs of gradual deposition Upper Eocene of Bordeaux, Aix-en-Provence, 
 Malta, &c. Upper Eocene of Nebraska, United States. 
 
 Preliminary remarks In the last chapter it was stated that as yet 
 
 we know of no marine strata in the British Isles contemporaneous with 
 the faluns of Touraine, or those shelly deposits of the valley of the 
 Loire which I selected as the type of the Miocene period. There 
 have, however, been recently discovered in the Isle of Wight certain 
 fluvio-marine deposits, which many continental geologists would call 
 ** Lower Miocene, 9 * the " faluns " being termed by them " Upper Mio- 
 cene." A few preliminary remarks on this difference of nomencla- 
 ture, bearing as it does on questions involving the first principles 
 of classification, will be necessary before I treat of the Upper Eocene 
 formations. 
 
 The marine strata, which in the north of France come next in chro- 
 nological order to the "faluns," or which immediately precede them in 
 age, are the sands and sandstones, called the " Ores de Fontainebleau," 
 or " sables marins superieurs." (See General Table, p. 105.) They 
 constitute the uppermost beds of the Paris basin, and are overlaid by 
 a freshwater limestone called " Calcaire de la Beauce." The upper 
 marine sands contain no fossil shells common to the faluns, or ex- 
 tremely few species, ; and no shells of living species, or, if so, they 
 are about as scarce as in the Middle or typical Eocene groups. 
 In consequence of this distinctness in the fossils, and for other reasons, 
 presently to be mentioned, I excluded these " upper sands" from the 
 Miocene period in former editions of this work, availing myself of 
 the hiatus between the Gres de Fontainebleau and the faluns to draw 
 a line of separation between Eocene and Miocene. In support of this 
 classification I pointed out the fact that the " upper marine sands," or 
 
On. XV.] REMARKS ON CLASSIFICATION. 185 
 
 Ores de Fontainebleau of the Parisian series, with their characteristic 
 shells, extend southwards from the French metropolis, as far as 
 Etampes, which is within seventy miles of Pontlevoy, near Blois, and 
 not more than 100 miles from Savigne, near Tours, two localities where 
 ihefahmian shells are very abundant. So remarkable a difference 
 between the species of the valley of the Loire and those of the valley 
 of the Seine cannot be the result of geographical distribution at one 
 and the same former era, but must evidently have depended on a dif- 
 ference in the age of the deposits. It marks the influence of Time, and 
 not of Space. 
 
 Another reason which induced me to class the Gresde Fontainebleau 
 and strata of the same age with the older series rather than with the 
 newer, was the decidedly Eocene aspect of the testaceous fauna, and 
 the fact that a certain proportion of the shells of the " upper sands " 
 are of species common to the underlying Parisian strata. 
 
 A different arrangement, however, was adopted by MM. Dufrenoy 
 and E. de Beaumont, in their colouring of the Government Map of 
 France, for they comprehended in their Miocene group, not only the 
 faluns of Touraine, but also the freshwater " calcaire de la Beauce," 
 and the marine sands and sandstone (Gres de Fontainebleau), i. e. 
 all the tertiary deposits which lie above the gypseous series of Mont- 
 martre, a formation well known as rich in extinct mammalia, first 
 brought to light by the genius of Cuvier. M. D'Archiac, in 1839, 
 followed the same mode of classification, dividing what he termed 
 " Lower " from his " Middle tertiary " in the same way. M. Deshayes, 
 in his work on the Fossil Shells of the Environs of Paris (1824 
 1837), had given twenty-nine species as belonging to the upper marine 
 strata, nearly all of which he distinguished specifically from shells of 
 the Calcaire Grossier, although he regarded them as characteristic 
 of the same fauna. The railway cuttings near Etampes, in 1849, 
 enabled M. Hebert to raise the number to ninety, and he first pointed 
 out that most of them agreed specifically with shells of Kleyn Spawen, 
 near Maestricht, in Belgium, and with those of Rupelmonde and 
 other places near Antwerp. These Belgian fossils had been de- 
 scribed by MM. Nyst, De Koninck, and Bosquet, and their geological 
 position had been accurately ascertained by M. Dumont, and placed 
 by him above the Brussels tertiary beds, which are the undoubted 
 representatives of the Calcaire Grassier of Paris, a typical Eocene 
 group. M. de Koninck, about the same time, remarked that the 
 Kleyn Spawen, or " Limburg " fossils, were in part identical with 
 those of the Mayence tertiary basin, a group which in my first 
 editions I had assigned to the Miocene period. M. Beyrich more 
 recently (1850) has described a formation of the same age as that 
 of Kleyn Spawen, occurring within seven miles of the gates of 
 Berlin, near the village of Hermsdorf ; and has shown that about a 
 third of the species agreed with known Belgian shells of the age of 
 the Gres de Fontainebleau, while about a fifth are English and 
 French Middle Eocene species. 
 
 In 1851, I examined with care the Belgian formations at Rupel- 
 
186 UPPER EOCENE FORMATIONS. [Cn. XV. 
 
 monde and Boom, near Antwerp, and in the Limburg, near Maes- 
 tricht, and was able, with the assistance of M. Bosquet, to give 
 a table of no less than 201 species of shells of the era under con- 
 sideration. Of these more than a third proved to be identical with 
 English Eocene testacea, even when I restricted the term Eocene to 
 its most limited sense, extending it no farther upwards than the 
 Middle Eocene or nummulitic formations.* For this reason I called 
 the Limburg or Kleyn Spawen beds Upper Eocene, giving as my 
 reason " that they resembled the older formations in their fossils as 
 much as some of the different divisions of the Eocene series in France 
 and England resemble each other; as much, for example, as the 
 Barton Clay in Hampshire agrees with the London Clay proper, or 
 the Calcaire Grossier with the Soissonnais sands in France." 
 
 Subsequently, in the winter of 1852, Professor Edward Forbes 
 examined near Yarmouth, in the Isle of Wight, a deposit occupying 
 a very limited area, but about 170 feet in thickness, which he first 
 determined to be of the same age as the Limburg beds. They were 
 found to be in comformable position with the other tertiary strata 
 previously known in that island, and to contain abundantly some of 
 the most characteristic Kleyn Spawen fossils. He named this 
 deposit " the Hempstead series," and classed it as Upper Eocene, for 
 reasons similar to those which had induced me so to name the 
 Lirnburg beds of Belgium. They cannot in fact be separated from 
 the subjacent Eocene strata without drawing a line of demarcation 
 confessedly arbitrary, and which would leave a great many of the 
 same species of fossils above and below it. So complete, indeed, is 
 the passage from the Bembridge series (an equivalent of the gypsum 
 of Montmartre, and, therefore, an acknowledged Eocene formation) 
 into the Hempstead beds, that Professor Forbes places both groups 
 together in his Upper Eocene division, drawing the line between 
 Upper and Middle Eocene at the base of the Bembridge beds. 
 
 In opposition to this view two recent authorities, who in the 
 course of the present year (1853) have written on the tertiary 
 formations of Germany, M. Beyrich, before cited f, and Dr. Sand- 
 berger J, contend that all strata, parallel in age with the Limburg, 
 should be termed Lower Miocene. M. Beyrich affirms that if the 
 strata of the Bolderberg in Belgium, and numerous deposits of con- 
 temporaneous date of Northern Germany already enumerated 
 (p. 1 79.), be of the age of the " faluns," then it can be shown that 
 these same beds have so many fossils in common with the Limburg 
 strata, that the latter may fairly be regarded as Miocene, or as an 
 older deposit of the same great period ; and he goes on to say that, 
 unless we are prepared to allow the Eocene division to absorb all the 
 overlying tertiary formations, we must begin a new series from the 
 base of the Limburg upwards, calling the latter Lower Miocene. 
 
 * Quart. Geol. Journ. 1852, vol. viii. J Ubcr das Mainzcr Tertiiirbeckens, 
 p. 322. &c.: Wiesbaden, 1853. 
 
 f Die Conchylien des Norddeutsch. 
 Tertiargeb. : Berlin, 1853. 
 
Cn.XV.] SEPARATION OF EO&ENE AND MIOCENE STRATA. 187 
 
 Dr. Sandberger divides the strata of the Mayence basin into two 
 sections, an older and a newer, the former confessedly the equivalent 
 of the Limburg (or Hempstead) beds, while in the upper he finds 
 some fossil remains, which appear to him to have a more modern 
 character. But when we separate from this higher division the 
 sands of Eppelsheim, containing bones of Deinotherium and Mastodon 
 longirostris, which are most probably of falunian age, the rest of his 
 upper series may be as old as the Limburg beds, though, for want of 
 good sections, there is much obscurity in regard to the grouping of 
 the beds. Dr. Sandberger, however, gives a list of twelve shells, be- 
 sides some teeth of fish and other fossils, which are common to the. 
 Mayence basin and the Hesse-Cassel sands. Now the latter were 
 classed as Subapennine or Pliocene by Philippi, and, although we 
 have as yet no sufficient data for determining their true age, appear 
 clearly to belong to a more modern fauna than that of the Mayence 
 basin. If such a relationship could be established between the two 
 as to indicate a pnssage from the Hesse-Cassel fauna to that of the 
 Mayence beds, this fact would doubtless go some way towards 
 bearing out the views of the author. 
 
 The reader has probably by this time begun to perceive that one 
 cause of embarrassment, experienced in the classification of these 
 tertiary formations, arises from the discovery of several missing 
 links in the chain of historical records. I may remind him that for 
 more than twenty years I have advocated in the Principles of 
 Geology the doctrine that there has been a continual coming in of 
 new species, and dying out of old ones, and a gradual change in the 
 physical geography and climate of the earth, and not such a reitera- 
 tion of sudden revolutions in the animate and inanimate worlds, as 
 was once insisted upon by many English geologists of note, and 
 is still maintained by not a few of the most distinguished continental 
 writers. When, therefore, I proposed in 1833 the term Miocene for 
 the faluns of Touraine, the fossil shells of which, according to the 
 determination of M. Deshayes, contained an admixture of about seven- 
 teen in the hundred of recent species, I foretold that from time to time 
 new sets' of strata would come to light, and require to be intercalated 
 between those already described, and in that case that the fossils 
 of newly-found beds would " deviate from the normal types first 
 selected, and approximate more and more to the types of the ante- 
 cedent or subsequent epochs." According to this view, it was 
 obvious from the first that the oldest Miocene records, whenever 
 they were detected, would not be easily distinguishable from the 
 youngest members of the Eocene series, especially in the proportion 
 of the living to the extinct species of fossil shells. The importance, 
 indeed, of the latter test must diminish rapidly the more we recede 
 from the Pliocene and approach the Miocene, and still more the 
 Eocene formations, although it is never without its value, and often 
 furnishes the only common standard of comparison between strata of 
 very distant countries. 
 
 I make these allusions to show that I am by no means unprepared 
 
188 EOCENE AND MIOCENE STRATA. [Cn. XV. 
 
 for the discovery of gradations from Miocene to Eocene, and for the 
 probable necessity of including hereafter in the Miocene series 
 some fossiliferous groups which may diverge in their characters from 
 the standard first set up, or from the type of the faluns of Tou- 
 raine. But I have seen, as yet, no sufficient evidence that such a 
 passage, as is here spoken of, has been made out. The limits of the 
 Eocene series have been extended, without as yet filling up the gap 
 between that series and the faluns of Touraine. I am desirous at the 
 same time to explain, that the important point now at issue is not 
 simply one of nomenclature. The difficulty is the same, whether we 
 use the terms Lower and Middle Tertiary, or Eocene and Miocene. 
 To one or other of the periods so named we must refer the Limburg 
 and Hempstead beds, and the sands of the Forest of Fontainebleau. 
 Can we, without doing violence to paleontological principles, refer 
 all these to the same period as the faluns of Touraine ? If so, it would 
 be immaterial whether we called them Middle Tertiary, Miocene or 
 " Falunian," or by any other general name. The question is, whether, 
 in the present state of our information, the mass of characteristic fos- 
 sils of the groups alluded to resemble more nearly the Eocene or the 
 Falunian. I adhere at present to the nomenclature formerly adopted 
 by me for strata described in this chapter, calling them Upper Eocene 
 not because of the small number of living species of shells found 
 in them, although this is certainly one point of agreement between 
 them and the "nummulitic" Eocene beds, but because of the aspect of 
 the whole fauna, which seems to me to be Eocene rather than Fa- 
 lunian. Among other illustrations of this affinity, I may refer 
 the reader to the numerous and excellent figures of species of the 
 genus Valuta given by M. Beyrich from the Limburg beds of North 
 Germany forms strikingly characteristic of the Barton clay in 
 Hampshire, a regular member of the Middle Eocene group. The 
 faluns are devoid of such forms. Until, therefore, the time arrives 
 when the break between the Limburg beds and the faluns has dis- 
 appeared more completely, it appears to me safer to include the 
 Limburg and all contemporaneous formations in the Eocene. 
 
 At the same time I have drawn the line between Middle and Upper 
 Eocene, as in former editions, excluding from the latter the Bembridge 
 beds of the Isle of Wight, or the gypseous series of Montmartre. A 
 preference is given to this last method, simply for convenience 
 sake, in order that the Upper Eocene of this work may coincide 
 exactly with the strata classed by so many distinguished geologists 
 as Lower Miocene. I am bound, however, to state, that the parting 
 line between the Bembridge and Hempstead series, in the Isle 
 of Wight, has been shown by Prof. Forbes to be an arbitrary one 
 a purely conventional line, if anything, less marked than the 
 line separating the Bembridge series from the underlying St. 
 Helen's group. (See Table, p. 209.) If retained as more useful, it is, 
 as before hinted, for the sake of conformity with a system of classi- 
 fication adopted by many able geologists, who selected it before 
 the uninterrupted continuity of the Eocene series from its nummu- 
 
CH. XV.] LIMBURG STRATA IN BELGIUM. 189 
 
 litic or central portions to its Upper or Limburg beds was clearly 
 made out. 
 
 LIMBURG STRATA IN BELGIUM. 
 
 (Rupelian and Tongrian Systems of Dumont.') 
 
 The best type which we as yet possess of the Upper Eocene, as de- 
 lined in the foregoing observations, consists of the beds formerly 
 known to collectors as those of Kleyn Spawen. These can be best 
 studied in the environs of the village so named, which is situated 
 about seven miles west of Maastricht, and in the old province of 
 Limburg in Belgium. In that region, about 200 species of testacea, 
 marine and freshwater, have been obtained, with many foraminifera 
 and remains offish. 
 
 The following table will show the position of the Limburg beds. 
 
 MIOCENE. 
 A. Bolderberg beds, see p. 179., seen near Hasselt. 
 
 UPPER EOCENE. 
 
 B. 1. Nucula Loam of Kleyn Spawen, TT _. , 
 
 same age as clay of Kupelmonde 1 Upper Limburg beds. - Kupehan of 
 and Boom. J Unmont 
 
 B. 2. Fluvio -marine beds of Bergh, Lethen, ) Middle Limburg beds. Upper Ton- 
 and other places near Kleyn Spawen. j grian of Dumont. 
 
 B. 3. Green sand of Bergh, Neerepen, &c., 5 Lower Limburg beds. Lower Ton- 
 near Kleyn Spawen : Marine. j grian of Dumont. 
 
 MIDDLE EOCENE. 
 
 C. Lacken and Brussels beds, with num- 
 mulites, &c. : Louvain and Brussels. 
 
 The uppermost of the three subdivisions (B. 1.) into which the Lim- 
 burg series is separated in the above table, contains at Kleyn Spawen 
 many of the same fossils as the clay of Rupelmonde and Boom, ten miles 
 south of Antwerp, and sixty miles N. W. of Kleyn Spawen. About 
 forty species of shells have been collected from the tile-clay worked 
 on the banks of the Scheldt at the villages above mentioned. At 
 Rupelmonde, this clay attains a thickness of about 100 feet, and 
 much resembles in mineral character the "London Clay," containing 
 like it septaria or concretions of argillaceous limestone traversed by 
 cracks in the interior. The shells have been described by MM. 
 Nyst and De Koninck. Among them Leda (or Nucula) Deshayesiana 
 (see fig. 167.) is by far the most abundant ; a fossil unknown as yet in 
 
 Fig. 167. 
 
 l 
 
 Lcda Deshayesiaiia. Nyst. Syn Kucttla Deshayesiana. 
 
190 STRATA IN NORTH GERMANY. [Cn. XV. 
 
 the English tertiary strata, but when young much resembling Leda 
 omygdaloides of the London clay proper (see fig. 227. p. 219.). Among 
 other characteristic shells are Pecten ffoeninghausii, and a species of 
 Cassidaria, and several of the genus Pleurotoma. !Not a few of these 
 testacea agree with English Eocene species, such as Actceon simulates, 
 Sow., Cancellaria evulsa, Brander, Corbula pisum (fig. 170. p. 194.), 
 and Nautilus ziczac. They are accompanied by many teeth of sharks, 
 as Lamna contortidcns, Ag., Oxyrhina xiphodon, Ag., Carcharodon 
 heterodon (see fig. 211.), Ag., and other fish, some of them common to 
 the Middle Eocene strata. The same deposit, B. 1 ., is very imperfectly 
 seen at Kleyn Spavven, where the lower divisions B. 2. and B. 3. are 
 much better developed. B. 2. consists of several alternations of sands 
 and marls, in which a greater or less intermixture of fluviatile and 
 marine shells occurs, implying the occasional entrance of a river near 
 the spot, and possibly oscillations in the level of the bottom of the sea. 
 Among the shells are found Cyrena semis friata (fig. 171. p. 194.), Ceri- 
 thium plicatum, Lam. (fig. 172. p. 194.), Rissoa Chastelii, Bosq. (fig. 
 174.), and Corbula pisum (fig. 170.), four shells all common to the 
 Hempstead beds in the Isle of Wight, to be mentioned in the sequel. 
 With the above, Lucina Thierensii, and other marine forms of the 
 genera Venus, Limopsis, Trochus, &c., are met with. 
 
 In B. 3., or the Lower Limburg, more than 100 marine shells have 
 been collected, among which the Ostrea vent'dabrum is very con- 
 spicuous. Species common to the underlying Brussels sands, or 
 the Middle Eocene, are numerous, constituting a third of the whole ; 
 but most of these are feebly represented in comparison with the 
 more peculiar and characteristic shells, such as Ostrea ventilabrum, 
 Mytilus Nystiiy Valuta suturalis, &c. 
 
 In none of the Belgian Upper Eocene strata could I find any 
 nummulites ; and M. D'Archiac had previously observed that these 
 foraminifera characterize his " Lower Tertiary Series," as contrasted 
 with the Middle, and would therefore serve as a good test of age 
 between Eocene and Miocene, if the line of demarcation be drawn 
 according to his method, or equally so between Upper and Middle 
 Eocene, according to the plan adopted in this work. The same natu- 
 ralist informs us that one nummulite only has ever yet been seen to 
 penetrate upwards into the middle tertiary, viz. Nummulites inter- 
 media^ an Eocene species. It has been found in the hill of the 
 Superga near Turin*, in beds usually classed as Miocene, but pro- 
 bably somewhat older than the falunian type. 
 
 Hermsdorf, near Berlin. Professor Beyrich has described a mass 
 of clay, used for making tiles within seven miles of the gates of Berlin, 
 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-grey colour, and, like that of 
 Rupelmonde, contains septaria. Among other shells, the Leda 
 Deshayesiana before mentioned (fig. 167.) abounds, together with 
 
 * Archiac. Monogr. pp. 79. 100. 
 
CH. XV.] MAYENCE BASIN. 191 
 
 many species of Pleurotoma, Valuta, &c., a certain proportion of the 
 fossils being identical in species with Limburg and Mayence shells. 
 M. Beyrich enumerates several other localities in North Germany, 
 and particularly one at Magdeburg, and several on the Lower Elbe, 
 where beds of the same age appear. 
 
 Mayence basin. I have already alluded to the elaborate descrip- 
 tion published by Dr. F. Sandberger of the Mayence tertiary area, 
 which occupies a tract from five to twelve miles in breadth, extend- 
 ing for a great distance along the left bank of the Rhine from 
 Mayence to the neighbourhood 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 (the Lower group of Dr. Sandberger) contained many 
 species of shells common to the Limburg beds near Kleyn Spawen, 
 and to the clay of Rupelmonde, near Antwerp. Among these he 
 mentioned Cassidaria depressa, Tritonium argutum, Brander ( T.flan- 
 dricum, De Koninck), Tornatella simulata, Rostellaria Sowerbyi, 
 Leda Deshayesiana (fig. 167. p. 189.), Corbula pisum (fig. 170.), and 
 Pectunculus terebratularis. 
 
 The marine beds are in some places covered with brackish-water 
 marls containing Cyrence in great numbers, among which Cyrena 
 semistriata occurs, with Cerithium plicatum. Corbulomya triangula, 
 Mytilus Fanjasii, and other Limburg and Hempstead shells. Perna 
 tSoldani, a shell of the upper Eocene or Merignac beds of the Bor- 
 deaux basin, but also a Vienna basin shell, is characteristic both 
 of the marine and brackish series. Two species of Anthracothe- 
 rium, A. magnum, Cuv., and A. alsaticum, are met with in the same 
 deposits. 
 
 The upper portion of this Mayence series has at its base a 
 limestone full of Cerithia and land-shells ; among which Cerithium 
 plicatum before mentioned, and another Limburg shell, Venus in- 
 crassata, Sow., a fossil common to the Headon or Middle Eocene of 
 England, are met with ; also Neritina concava (fig. 194.), a Middle 
 Eocene shell, and Rhinoceros incisivus, the oldest form of that genus, 
 and called by Kaup Acerotherium. Next above is a limestone, in 
 which Littorinella or Paludina inflata is a very common fossil, with 
 
 Fig. ic8. others of the same genus. One of these, very nearly re- 
 sembling the recent Littorinella ulva, is found throughout 
 this basin. These shells are like grains of rice in size, 
 and are often in such quantity as to form entire beds of 
 marl and limestone, in stratified masses from fifteen to 
 
 Mayence! thirty feet in thickness, just as in the Baltic modern accu- 
 mulations several feet thick of the Littorinella ulva are spread far 
 and wide over the bottom of the sea. In the same beds, several 
 species of Dreissena abound, a form common to the Headon or 
 Middle Eocene beds of the Isle of Wight, as well as to the existing 
 seas. On the whole, I am not satisfied that this fauna diverges from 
 the Limburg type towards that of the faluns as much as Dr. Sand- 
 berger believes. Among the Mammalia, we find Hippotherium 
 gracile, Acerotherium (or Rhinoceros) incisivum, Paleomeryx, Cha- 
 
192 
 
 BROWN COAL OF GERMANY. 
 
 [Cii. XV. 
 
 licomys,Stc. Lastly, theEppelsheim sand overlies the whole, containing 
 Deinotherium giganteum, and some other true Miocene quadrupeds. 
 Several mammalia, proper to the Upper Eocene series, are also said 
 to be associated ; but there being no good section at Eppelsheim, 
 the true succession of the beds from which the bones were dug out 
 cannot be seen, and we have yet to learn whether some remains of an 
 older series may not have been confounded with those of a newer one. 
 Brown coal of Germany. In a recent essay on the Brown Coal 
 deposits of Germany, Baron Von Buch has expressed a decided 
 opinion that they all belong to one epoch, being of subsequent date 
 to the great nummulitic period, and n*4jggr. than the Pliocene form- 
 ations. He has therefore called the whole Miocene. Unfortunately, 
 these formations rarely contain any internal evidence of their age, 
 except what may be derived from plants, constituting in every case 
 but a fraction of an ancient Flora, and consisting of mere leaves, 
 without flowers or fruits. It is often therefore impossible to form 
 more than a conjecture as to the precise place in the chronological 
 series which should be assigned to each layer of lignite or each leaf- 
 bed. Nevertheless, enough is known to show that some of the 
 Brown Coals found in isolated patches belong to the Upper Eocene, 
 others to the Miocene, and some perhaps to the Pliocene eras. They 
 seem to have been formed at a period when the European area had 
 already a somewhat continental character, so that few contempora- 
 neous marine or even fluvio-marine beds were in progress there. 
 
 The brown coal of Brandenburg, on the borders of the Baltic, 
 underlies the Herrnsdorf tile-clay already spoken of, and therefore 
 belongs to a period at least as old as the Upper Eocene The 
 brown coal of lladoboj, on the confines of Styria, is covered, says Von 
 Buch, by beds containing the marine shells of the Vienna basin, 
 
 which, as before remarked, are chiefly 
 of the Falunian or Miocene type. This 
 lignite, therefore, may be of Miocene or 
 Upper Eocene date, a point to be deter- 
 mined by the botanical characters of the 
 plants. In this, and most of the princi- 
 pal brown coal formations, several spe- 
 cies of fan-palm or Flabellaria abound. 
 This genus also appears in the Middle 
 Eocene or Bembridge beds in the Isle 
 of Wight, and in the gypseous series of 
 Montmartre ; but it is still more largely 
 represented in the Upper Eocene series, 
 accompanied by palms of the genus Phce- 
 nicites. Various cones, and the leaves 
 and wood of coniferous trees, are also 
 met with at Radoboj. Species also of 
 Comptonia and Myrica, with various 
 
 Aitsattci, trees > such as the P lane or P latanus > 
 in Bohemia. are recognized bv their leaves, as also 
 
 Fig. 169. 
 
 Da P hno K ent 
 
CH. XV.] UPPER EOCENE STRATA OF ENGLAND. 193 
 
 several of the Laurel tribe, especially one, called Daphnogene cinna- 
 momifolia (fig. 16y.) by linger, who, together with Goppert, has 
 investigated the botany of these formations. It will be seen that 
 in the leaf of this Daphnogene two veins branch off on each side 
 from the mid-rib, and run up without interruption to the point. 
 
 On the Lower Rhine, whether in theMayence basin or in the Sieben- 
 gebirge, and in the neighbourhood of Bonn and Cologne, there seem 
 to be Brown Coals of more than one age. Von Buch tells us that the 
 only fossil found in the Brown Coal near Cologne, one often met with 
 there in the excavation of a tunnel, is the peculiar fruit, so like a 
 cocoa-nut, called Nipadites or Burtonia Fanjasii (see fig. 220.). Now 
 this fossil abounds in the Lower Eocene or Sheppy clay near London, 
 also in the Middle Eocene at Brussels ; and I found it still higher in 
 the same nummulitic series at Cassel, in French Flanders. This 
 fact taken alone would rather lead us to refer the Cologne lignite 
 to the Eocene period. 
 
 Some of the lignites of the Siebengebirge near Bonn associated 
 with volcanic rocks, and those of Hesse Cassel which accompany 
 basaltic outpourings, are certainly of much later date. 
 
 UPPER EOCENE STRATA OF ENGLAND. 
 
 Hempstead beds. Isle of Wight. Until very lately it was sup- 
 posed by English geologists that the newest tertiary strata of the 
 Isle of Wight corresponded in age with the gypseous series of Mont- 
 martre near Paris ; and this idea was confirmed by the fact that the 
 same species of Palceotherium, Anoplotherium, and other extinct mam- 
 malia so characteristic of the Parisian series, were also found at 
 Binstead, near Ryde, in the northern district of the island, forming 
 part of the ^uvio-marine series. We are indebted to Prof. E. Forbes 
 for having discovered in the autumn of 1852 that there exist three 
 formations, the true position of which had been overlooked, all of them 
 newer than the beds of Headon Hill, in Alum Bay, which last were 
 formerly believed to be the uppermost part of the Isle of Wight 
 tertiary series.* 
 
 The three overlying formations to which I allude are as follows : 
 1st, certain shales and sandstones called the St. Helen's beds (see 
 Table, p. 105. et seq.) rest immediately upon the Headon series; 2dly, 
 the St. Helen's series is succeeded by the Bembridge beds before 
 mentioned, the equivalent of the Montmartre gypsum ; and 3rdly, 
 above the whole is found the Upper Eocene or Hempstead series. 
 This newer deposit, which is 170 feet thick, has been so called from 
 Hempstead Hill, near Yarmouth, in the Isle of Wight.f The fol- 
 lowing is the succession of strata there discovered, the details of 
 which are important for reasons explained in the preliminary re- 
 marks of this chapter (p. 188.) : 
 
 * E. Forbes, Geol. Quart. Journ. with Hampstead Hill, near London, 
 
 1853. where the Lower Eocene or London 
 
 f This hill must not be confounded Clay is capped by Middle Eocene sands. 
 
 O 
 
194 
 
 UPPER EOCENE, ISLE OF WIGHT. 
 
 [Cn. XV. 
 
 SUBDIVISIONS OP THE HEMPSTEAD SERIES. 
 
 1. The uppermost or Corbula beds, consisting of marine sands and clays, 
 contain Corbula pisum, fig. 170., a species common to the Middle Eocene clay 
 of Barton ; Cyrena semistriata, fig. 171., which is also a Middle Eocene fossil; 
 several Cerithia, and other shells peculiar to this series. 
 
 Fig. 170. 
 
 Fig. 171. 
 
 Corbula pisum. Hempstead Beds, 
 Isle of Wight. 
 
 Cyrena semistriata. 
 Hempstead Beds. 
 
 2. Next below are freshwater and estuary marls and carbonaceous clays, in the 
 brackish-water portion of which are found abundantly Cerithium plicatum, Lam., 
 fig. 172., C. elegans, fig. 173., and C. tricinctum; also Rissoa Chastelii, fig. 174., 
 a very common Limburg shell, and which occurs in each of the four subdivisions 
 of the Hempstead series down to its base, where it passes into the Bembridge beds. 
 In the freshwater portion of the same beds Paludina lenta, fig, 175., occurs, a shell 
 
 Fig. 172. 
 
 Fig. 173. 
 
 Fig. 174. 
 
 Fig. 175. 
 
 Cerithium plicatum, 
 Lam. Hempstead. 
 
 Cerithium elegant. 
 Hempstead. 
 
 Rissoa Chastelii, Nyst, 
 Sp. Hempstead, isle 
 of Wight. 
 
 Paludina lenta. 
 Hempstead Beds. 
 
 identified by some conchologists with a species now living, P. unicolor; also 
 several species of Lymneus, Planorbis, and Unto. 
 
 3. The next series, or middle freshwater and estuary marls, are distinguished 
 by the presence of Melania fasciata, Paludina lenta, and clays with Cypris ; the 
 lowest bed contains Cyrena semistriata, fig. 171., mingled with Cerithia and a 
 Panopcea. 
 
 4. The lower freshwater and estuary marls contain Melania costata, Sow., 
 Melanopsis, &c. The bottom bed is carbonaceous, and called the " Black band," 
 in which Rissoa Chastelii, fig. 173 , before alluded to, is common. This bed 
 contains a mixture of Hempstead shells with those of the underlying Middle 
 Eocene or Bembridge series. The seed-vessels of CJiara medicayinula, Brong., 
 and C. helecteras are characteristic of the Hempstead beds generally. The 
 mammalia, among which is a species of Hyotherium, differ, so far as they are 
 known, from those of the Bembridge beds immediately underlying. 
 
CH. XV.] UPPER EOCENE STRATA OF FRANCE. 195 
 
 Between the Hempstead beds above described and those next below them, 
 there is no break, as before stated, p. 188. The freshwater, brackish, and 
 marine limestones and marls of the underlying or Bembridge group are in 
 conformable stratification, and contain Cyrena semistriata, fig. 171., Melania 
 muricata, Paludina lenta, fig. 175., and several other shells belonging to the 
 Hempstead beds. Prof. Forbes therefore classes both of them in the same 
 Upper Eocene division. I have called the Bembridge bed? Middle Eocene, 
 for convenience sake, as already explained (pp. 184. 188.). 
 
 UPPER EOCENE STRATA OP FRANCE. 
 
 (Lower Miocene of many French authors.} 
 
 The Gres de Fontainebleau, or sandstone of the Forest of Fon- 
 tainebleau, has been frequently alluded to in the preceding pages, as 
 corresponding in age to the Limburg or Hempstead beds. It is as- 
 sociated in the suburbs of Paris with a set of strata, very varied in 
 their composition, and containing in their lower portion a green 
 clay with abundance of small oysters (Ostrea cyathula, Lam.) which 
 are spread over a wide area. The marine sands and sandstone 
 which overlie this clay include Cytherea incrassata and many other 
 Limburg fossils, the finest collections of which have been made at 
 Etampes, south of Paris, where they occur in loose sand. The Gres 
 de Fontainebleau is sometimes called the " Upper marine sands " to 
 distinguish it from the "Middle sands" or Gres de Beauchamp, a 
 Middle Eocene group. 
 
 Calcaire lacustre superieur. Above the Gres de Fontainebleau 
 is seen the upper freshwater limestone and marl, sometimes called 
 Calcaire de la Beauce, which with its accompanying marls and 
 siliceous beds seem to have been formed in marshes and shallow lakes, 
 such as frequently overspread the newest parts of great deltas. Beds 
 of flint, continuous dr in nodules, accumulated in these lakes, and 
 C/iarce, aquatic plants, already alluded to, left their stems and seed- 
 vessels imbedded both in the marl and flint, together with freshwater 
 and land-shells. Some of the siliceous rocks of this formation 
 are used extensively for millstones. The flat summits or platforms 
 of the hills round Paris large areas in the forest of Fontainebleau, 
 and the Plateau de la Beauce, between the Seine and the Loire, are 
 chiefly composed of these upper freshwater strata. When they reach 
 the valley of the Loire, they occasionally underlie and form the 
 boundary of the marine Miocene faluns, fragments of the older fresh- 
 water limestone having been broken off and rolled on the shores and 
 in the bed of the Miocene sea, as at Pontlevoy, on the Cher, where 
 the perforating marine shells of the Miocene period still remain 
 in hollows drilled in the blocks of Eocene limestone. 
 
 Central Prance. Lacustrine strata, belonging, for the most part, 
 to the same Upper Eocene series, are again met with in Auvergne, 
 Cantal, and Velay, the sites of which may be seen in the annexed 
 map. They appear to be the monuments of ancient lakes, which, 
 like some of those now existing in Switzerland, once occupied the 
 depressions in a mountainous region, and have been each fed by one 
 
 o 2 
 
196 
 
 UPPER EOCENE OF CENTRAL FRANCE. [Cn. XV. 
 
 Tig. 176. 
 
 IASIN 
 
 Freshwater 
 
 or more rivers and torrents. The country where they occur is almost 
 entirely composed of granite and different varieties of granitic schist, 
 
CH. XV.] SUCCESSION OF CHANGES IN AUVERGNE. 197 
 
 with here and there a few patches of secondary strata, much dislo- 
 cated, and which have probably suffered great denudation. There 
 are also some vast piles of volcanic matter (see the map), the greater 
 part of which is newer than the freshwater strata, and is sometimes 
 seen to rest upon them, while a small part has evidently been of 
 contemporaneous origin. Of these igneous rocks I shall treat more 
 particularly in another part of this work. 
 
 Before entering upon any details, I may observe that the study 
 of these regions possesses a peculiar interest, very distinct in kind 
 from that derivable from the investigation either of the Parisian or 
 English tertiary areas. For 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 dis- 
 appeared, lofty mountains have been formed, by the reiterated 
 emission of lava, preceded and followed by showers of sand and 
 scoriae, deep valleys have been subsequently furrowed out through 
 masses of lacustrine and volcanic origin, at a still later date, new 
 cones have been thrown up in these valleys, new lakes have been 
 formed by the damming up of rivers, and more than one creation of 
 quadrupeds, birds, and plants, Eocene, Miocene, and Pliocene, have 
 followed in succession ; yet the region has preserved 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 com- 
 pleted. There was first a period when the spacious lakes, of which 
 we still may trace the boundaries, lay at the foot of mountains 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 craters now covering the granitic 
 platform. During this earlier scene of repose deltas were slowly 
 formed ; beds of marl and sand, several hundred feet thick, deposited ; 
 siliceous and calcareous rocks precipitated from the waters of mineral 
 springs ; shells and insects imbedded, together with the remains of 
 the crocodile and tortoise ; the eggs and bones of water birds, and the 
 skeletons of quadrupeds, some of them belonging to the same genera 
 as those entombed in the Eocene gypsum of Paris. 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 enhanced by the igneous matter ejected from 
 below, and poured down upon the more sterile granite. During these 
 eruptions, which appear to have taken place after the disappearance 
 of the Upper Eocene fauna, and partly in the Miocene epoch, the 
 mastodon, rhinoceros, elephant, tapir, hippopotamus, together with the 
 ox, various kinds of deer, the bear, hyaena, and many beasts of prey 
 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 eruptions. Lastly, these quadrupeds became 
 
 O 3 
 
198 LACUSTRINE STRATA AUVERGNE. [C&. XV. 
 
 extinct, and gave place to Pliocene mammalia (see ch. xxxii.), and 
 these, in their turn, to 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 different lakes, or by rivers and floods 
 accompanying repeated earthquakes, during which the levels of the 
 district have in some places been materially modified, and perhaps 
 the whole upraised relatively to the surrounding parts of France. 
 
 Auvergne. The most northern of the freshwater groups is situ- 
 ated in the valley-plain of the Allier, which lies within the depart- 
 ment of the Puy de Dome, being the tract which went formerly 
 by the name of the Limagne d' Auvergne. It is inclosed by two 
 parallel mountain ranges, that of the Forez, which divides the 
 waters of the Loire and Allier, on the east ; and that of the Monts 
 Domes, which separates the Allier from the Sioule, on the west.* 
 The average breadth of this tract is about 20 miles ; and it is for 
 the most part composed of nearly horizontal strata of sand, sand- 
 stone, calcareous marl, clay, and limestone, none of which observe 
 a fixed and invariable order of superposition. The ancient borders 
 of the lake, wherein the freshwater strata were accumulated, may 
 generally be traced with precision, the granite and other ancient 
 rocks rising up boldly from the level country. The actual junction, 
 however, of the lacustrine and granitic beds is rarely seen, as a small 
 valley usually intervenes between them. The freshwater strata may 
 sometimes be seen to retain their horizontality within a very slight 
 distance of the border-rocks, while in some places they are inclined, 
 and in few instances vertical. The principal divisions into which 
 the lacustrine series may be separated are the following: 1st, 
 Sandstone, grit, and conglomerate, including red marl and red sand- 
 stone ; 2dly, Green and white foliated marls ; 3dly, Limestone or 
 travertin, often oolitic ; 4thly, Gypseous marls. 
 
 1. a. Sandstone and conglomerate. Strata of sand and gravel, 
 sometimes bound together into a solid rock, are found in great abun- 
 dance around the confines of the lacustrine basin, containing, in 
 different places, pebbles of all the ancient rocks of the adjoining 
 elevated country; namely, granite, gneiss, mica-schist, clay-slate, 
 porphyry, and others, but without any intermixture of basaltic or 
 other tertiary volcanic rocks. These strata do not form one con- 
 tinuous band around the margin of the basin, being rather disposed 
 like the independent deltas which grow at the mouths of torrents 
 along the borders of existing lakes. 
 
 At Chamalieres, near Clermont, we have an example of one of 
 these deltas, or littoral deposits, of local extent, where the pebbly 
 beds slope away from the granite, as if they had formed a talus 
 beneath the waters of the lake near the steep shore. A section of 
 about 50 feet in vertical height has been laid open by a torrent, 
 and the pebbles are seen to consist throughout of rounded and 
 
 * Scrope, Geology of Central France, p. 15. 
 
CH. XV.] UPPER EOCENE PERIOD. 199 
 
 angular fragments of granite, quartz, primary slate, and red sand- 
 stone. Partial layers of lignite and pieces of wood are found in these 
 beds. 
 
 At some localities on the margin of the basin quartzose grits are 
 found ; and, where these rest on granite, they are sometimes formed 
 of separate crystals of quartz, mica, and felspar, derived from the 
 disintegrated granite, the crystals having been subsequently bound 
 together by a siliceous cement. In these cases the granite seems 
 regenerated in a new and more solid form; and so gradual a passage 
 takes place between the rock of crystalline and that of mechanical 
 origin, that we can scarcely distinguish where one ends and the 
 other begins. 
 
 In the hills called the Puy de Jussat and La Roche, we have the 
 advantage of seeing a section continuously exposed for about 700 feet 
 in thickness. At the bottom are foliated marls, white and green, 
 about 400 feet thick ; and above, resting on the marls, are the quartzose 
 grits, cemented by calcareous matter, which is sometimes so abundant 
 as to form imbedded nodules. These sometimes constitute spheroidal 
 concretions 6 feet in diameter, and pass into beds of solid lime- 
 stone, resembling the Italian travertins, or the deposits of mineral 
 springs. 
 
 1. b. Red marl and sandstone. But the most remarkable of the 
 arenaceous groups is one of red sandstone and red marl, which are 
 identical in all their mineral characters with the secondary New Red 
 sandstone and marl of England. In these secondary rocks the red 
 ground is sometimes variegated with light greenish spots, and the 
 same may be seen in the tertiary formation of freshwater origin at 
 Coudes, on the Allier. The marls are sometimes of a purplish-red 
 colour, as at Champheix, and are accompanied by a reddish-lime- 
 stone, like the well-known " cornstone," which is associated with the 
 Old Red sandstone of English geologists. The red sandstone and 
 marl of Auvergne have evidently been derived from the degradation 
 of gneiss and mica-schist, which are seen in situ on the adjoining 
 hills, decomposing into a soil very similar to the tertiary red sand 
 and marl. We also find pebbles of gneiss, mica-schist, and quartz 
 in the coarser sandstones of this group, clearly pointing to the 
 parent rocks from which the sand and marl are derived. The red 
 beds, although destitute themselves of organic remains, pass upwards 
 into strata containing tertiary fossils, and are certainly an integral 
 part of the lacustrine formation. From this example the student 
 will learn how small is the value of mineral character alone, as a 
 test of the relative age of rocks. 
 
 2. Green and white foliated marls The same primary rocks of 
 Auvergne, which, by the partial degradation of their harder parts, 
 gave rise to the quartzose grits and conglomerates before mentioned, 
 would, by the reduction of the same materials into powder, and by 
 the decomposition of their felspar, mica, and hornblende, produce 
 aluminous clay, and, if a sufficient quantity of carbonate of lime 
 was present, calcareous marl. This fine sediment would naturally 
 
 o 4 
 
200 LACUSTRINE STRATA AUVERGNE. [Cn. XV. 
 
 be carried out to a greater distance from the shore, as are the 
 various finer marls now deposited in Lake Superior. And as, in the 
 American lake, shingle and sand are annually amassed near the 
 northern shores, so in Auvergne the grits and conglomerates before 
 mentioned were evidently formed near the borders. 
 
 The entire thickness of these marls is unknown ; but it certainly 
 exceeds, in some places, 700 feet. They are, for the most part, 
 either light-green or white, and usually calcareous. They are 
 thinly foliated, a character which frequently arises from the in- 
 numerable thin shells, or carapace-valves, of that small animal called 
 Cypris. This animal is provided with two small valves, not unlike 
 those of a bivalve shell, and moults its integuments periodically, 
 which the conchiferous mollusks do not. This circumstance may 
 partly explain the countless myriads of the shells of Cypris which 
 were shed in the ancient lakes of Auvergne, so as to give rise to 
 divisions in the marl as thin as paper, and that, too, in stratified 
 masses several hundred feet thick. A more convincing proof of the 
 tranquillity and clearness of the waters, and of the slow and gradual 
 process by which the lake was filled up with fine mud, cannot be 
 desired. But we may easily suppose that, while this fine sediment 
 was thrown down in the deep and central parts of the basin, gravel, 
 sand, and rocky fragments were hurried into the lake, and deposited 
 near the shore, forming the group described in the preceding section. 
 
 Not far from Clermont, the green marls, containing the Cypris in 
 abundance, approach to within a few yards of the granite which forms 
 the borders of the basin. The occurrence of these marls so near the 
 ancient margin may be explained by considering that, at the bottom of 
 the ancient lake, no coarse ingredients were deposited in spaces inter- 
 mediate between the points where rivers and torrents entered, but 
 
 Fig. 177. 
 
 Vertical strata of marl, at Champradelle, near Clermont. 
 
 A. Granite. B. Space of GO feet, in which no section is seen. 
 
 C. Green marl, vertical and inclined. D. white marl. 
 
 finer mud only was drifted there by currents. The vertically of 
 some of the beds in the above section bears testimony to considerable 
 local disturbance subsequent to the' deposition of the marls ; but such 
 inclined and vertical strata are very rare. 
 
 3. Limestone, travertin, oolite. Both the preceding members of 
 the lacustrine deposit, the marls and grits, pass occasionally into 
 limestone. Sometimes only concretionary nodules abound in them ; 
 but these, where there is an increase in the quantity of calcareous 
 matter, unite into regular beds. 
 
CH. XV.] 
 
 INDUSIAL LIMESTONE. 
 
 201 
 
 On each side of the basin of the Limagne, both on the west at 
 Gannat, and on the east at Vichy, a white oolitic limestone is quar- 
 ried. At Vichy, the oolite resembles our Bath stone in appearance 
 and beauty ; and, like it, is soft when first taken from the quarry, 
 but soon hardens on exposure to the air. At Gannat, the stone 
 contains land-shells and bones of quadrupeds. At Chadrat, in the 
 hill of La Serre, the limestone is pisolitic, the small spheroids com- 
 bining both the radiated and concentric structure. 
 
 Indusial limestone. There is another remarkable form of fresh- 
 water limestone in Auvergne, called " indusial," from the cases, or 
 indusice, of caddis-worms (the larvae of Phryganea) ; great heaps of 
 which have been incrusted, as they lay, by carbonate of lime, and 
 formed into a hard travertin. The rock is sometimes purely cal- 
 careous, but there is occasionally an intermixture of siliceous matter. 
 Several beds of it are frequently seen, either in continuous masses, 
 or in concretionary nodules, one upon another, with layers of marl 
 interposed. The annexed drawing (fig. 178.) will show the manner 
 in which one of these indusial beds (a) is laid open at the surface, 
 between the marls (b &), near the base of the hill of Gergovia ; and 
 aifords, at the same time, an example of the extent to which the 
 lacustrine strata, which must once have filled a hollow, have been 
 denuded, and shaped out into hills and valleys, on the site of the 
 ancient lakes. 
 
 Fig. 178. 
 
 Bed of indusial limestone, interstratified with freshwater marl, near Clermont (Kleinschrod). 
 
 We may often observe in our ponds the Phryganea (or Caddis- 
 fly), in its caterpillar state, covered with small freshwater shells, which 
 they have the power of fixing to the outside of their tubular cases, 
 in order, probably, to give them weight and strength. The individual 
 
202 UPPER EOCENE PERIOD. [Cn. XV. 
 
 figured in the annexed cut, which belongs to a species very abundant 
 Fig. 179. in England, has covered its case with 
 shells of a small Planorbis. In the same 
 manner a large species of caddis-worm 
 which swarmed in the Eocene lakes of 
 Auvergne was accustomed to attach to 
 its dwelling the shells of a small spiral 
 
 Larva of recent Phryganca.* un i va l Ye O f the genUS Pdludina. A hun- 
 dred of these minute shells are sometimes seen arranged around one 
 tube, part of the central cavity of which is often empty, the rest 
 being filled up with thin concentric layers of travertin. The cases 
 have been thrown together confusedly, and often lie, as in fig. 180., 
 
 Fig. 180. 
 
 a. Indusial limestone of Auvergne. b. Fossil Paludma magnified. 
 
 at right angles one to the other. When we consider that ten or 
 twelve tubes are packed within the compass of a cubic inch, and 
 that some single strata of this limestone are 6 feet thick, and may be 
 traced over a considerable area, we may form some idea of the count- 
 less number of insects and mollusca which contributed their integu- 
 ments and shells to compose this singularly constructed rock. It is 
 unnecessary to suppose that the Phryganece lived on the spots where 
 their cases are now found ; they may have multiplied in the shallows 
 near the margin of the lake, or in the streams by which it was fed, 
 and their cases may have been drifted by a current far into the deep 
 water. 
 
 In the summer of 1837, when examining, in company with Dr. 
 Beck, a small lake near Copenhagen, I had an opportunity of wit- 
 nessing a beautiful exemplification of the manner in which the 
 tubular cases of Auvergne were probably accumulated. This lake, 
 called the Fuure-Soe, occurring in the interior of Seeland, is about 
 twenty English miles in circumference, and in some parts 200 feet in 
 depth. Round the shallow borders an abundant crop of reeds and 
 rushes may be observed, covered with the indusiae of the Phryganea 
 grandis and other species, to which shells are attached. The plants 
 which support them are the bulrush, Scirpus lacustris, and common 
 reed, Arundo phragmites, but chiefly the former. In summer, espe- 
 cially in the month of June, a violent gust of wind sometimes causes a 
 current by which these plants are torn up by the roots, washed away, 
 and floated off in long bands, more than a mile in length, into deep 
 water. The Cypris swarms in the same lake ; and calcareous springs 
 
 * I believe that the British specimen here figured is P. rhombica, Linn. 
 
CH. XV.] LACUSTRINE STEATA AUVERGNE. 203 
 
 alone are wanting to form extensive beds of indusial limestone, like 
 those of Auvergne. 
 
 4. Gypseous marls. More than 50 feet of thinly laminated 
 gypseous marls, exactly resembling those in the hill of Montmartre, 
 at Paris, are worked for gypsum at St. Remain, on the right bank of 
 the Allier. They rest on a series of green cypridiferous marls which 
 alternate with grit, the united thickness of this inferior group being 
 seen, in a vertical section on the banks of the river, to exceed 250 feet. 
 
 General arrangement, origin, and age of the freshwater formations 
 of Auvergne. The relations of the different groups above described 
 cannot 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 affirmed that there is no order of arrange- 
 ment. The sands, sandstone, and conglomerate constitute in general 
 a littoral group ; the foliated white and green marls, a contem- 
 poraneous central deposit ; and the limestone is for the most part 
 subordinate to the newer portions of both. The uppermost marls 
 and sands are more calcareous than the lower ; and we never meet 
 with calcareous rocks covered by a considerable thickness of quartzose 
 sand or green marl. From the resemblance of the limestones to the 
 Italian travertins, we may conclude that they Avere derived from the 
 waters of mineral springs, such springs as even now exist in Au- 
 vergne, and which may be seen rising up through the granite, and 
 precipitating travertin. They are sometimes thermal, but this cha- 
 racter is by no means constant. 
 
 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 Auvergne. No pebbles, there- 
 fore, of lava were transported into the lake, no fragments of volcanic 
 rocks embedded in the conglomerate. But at a later period, when a 
 considerable thickness of sandstone and marl had accumulated, erup- 
 tions broke out, and lava and tuff were deposited, at some spots, al- 
 ternately with the lacustrine strata. It is not improbable that cold 
 and thermal springs, holding different mineral ingredients in solution, 
 became more numerous during the successive convulsions attending 
 this development of volcanic agency, and thus deposits of carbonate 
 and sulphate of lime, silex, and other minerals were produced. Hence 
 these minerals predominate in the uppermost strata. The subterranean 
 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 farther accumulation of regular freshwater strata to cease. 
 
 We may easily conceive a similar series of events to give rise to 
 analogous results in any modern basin, such as that of Lake Superior, 
 for example, where numerous rivers and torrents are carrying down 
 the detritus of a chain of mountains into the lake. The transported 
 materials must be arranged according to their size and weight, the 
 
204 UPPER EOCENE STRATA. [Cn. XV. 
 
 coarser near the shore, the finer at a greater distance from land ; but 
 in the gravelly and sandy beds of Lake Superior no pebbles of modern 
 volcanic rocks can be included, since there are none of these at present 
 in the district. If igneous action should break out in that country, 
 and produce lava, scoriae, and thermal springs, the deposition of gravel, 
 sand, and marl might still continue as before ; but, in addition, there 
 would then be an intermixture of volcanic gravel and tuff, and of 
 rocks precipitated from the waters of mineral springs. 
 
 Although the freshwater strata of the Limagne approach generally 
 to a horizontal position, the proofs of local disturbance are sufficiently 
 numerous and violent to allow us to suppose great changes of level 
 since the lacustrine period. We are unable to assign a northern 
 barrier to the ancient lake, although we can still trace its limits to 
 the east, west, and south, where they were formed of bold granite 
 eminences. Nor need we be surprised at our inability to restore 
 entirely the physical geography of the country after so great a series 
 of volcanic eruptions ; for it is by no means improbable that one part 
 of it, the southern, for example, may have been moved upwards bodily, 
 while others remained at rest, or even suffered a movement of de- 
 pression. 
 
 Whether all the freshwater formations of the Limagne d'Auvergne 
 belong to one period, I cannot pretend to decide, as large masses both 
 of the arenaceous and marly groups are often devoid of fossils. 
 Some of the oldest or lowest sands and marls may very probably be 
 of Middle Eocene date. Much light has been thrown on the mam- 
 miferous fauna by the labours of MM. Bravard and Croizet, and by 
 those of M. Pomel. The last-mentioned naturalist has pointed out 
 the specific distinction of all, or nearly all, the species of mammalia 
 from those of the gypseous series near Paris, although many of the 
 forms are analogous to those of Eocene quadrupeds. The Cainot/ie- 
 rium, for example, is not far removed from the Anoplotherium, and 
 is, according to Waterhouse, the same as the genus Microtherium of 
 the Germans. There are two species of marsupial animals allied to 
 JDidelphys, a genus also found in the Paris gypsum, and several 
 forms of ruminants of extinct genera, such as Amphitragulus ele- 
 gans of Pomel, which has been identified with a Rhenish species 
 from Weissenau near Mayence, called by Kaup Dorcatherium 
 nanum ; other associated fossils, e. g., Microtherium Reuggeri, and 
 a small rodent, Titanomys, are also specifically the same with mam- 
 malia of the Mayence basin. The Hycenodon, a remarkable car- 
 nivorous genus, is represented by more than one species, and the 
 oldest representative of the genus Machairodus has been discovered 
 in these beds in Auvergne. The first of these, Hyanodon, also occurs 
 in the English Middle-Eocene marls of Hordwell cliff, Hamp- 
 shire, considerably below the level of the Bembridge limestone, with 
 Paleotheria. Upon the whole it is clear that a large portion of the 
 Limagne rocks have been correctly referred by French geologists 
 to their Middle Tertiary, and to that part of it which is called 
 Upper Eocene in this work. 
 
CH. XV.] UPPER EOCENE STRATA CANTAL. 205 
 
 Cantal A freshwater formation, of about the same age and 
 very analogous to that of Auvergne, is situated in the department of 
 Haute Loire, near the town of Le Puy, in Velay ; and another occurs 
 near Aurillac, in Cantal. The leading feature of the formation last 
 mentioned, as distinguished from those of Auvergne and Velay, is the 
 immense abundance of silex associated with calcareous marls and 
 limestone. 
 
 The whole series may be separated into two divisions ; the lower, 
 composed of gravel, sand, and clay, such as might have been derived 
 from the wearing down and decomposition of the granitic schists of 
 the surrounding country ; the upper system, consisting of siliceous 
 and calcareous marls, contains subordinately gypsum, silex, and lime- 
 stone. 
 
 The resemblance of the freshwater limestone of the Cantal, and its 
 accompanying flint, to the upper chalk of England, is very instructive, 
 and well calculated to put the student upon his guard against rely- 
 ing too implicitly on mineral character alone as a safe criterion of 
 relative age. 
 
 When we approach Aurillac from the west, we pass over great 
 heathy plains, where the sterile mica-schist is barely covered with 
 vegetation. Near Ytrac, and between La-Capelle and Viscamp, the 
 surface is strewed over with loose broken flints, some of them black 
 in the interior, but with a white external coating ; others stained 
 with tints of yellow and red, and in appearance precisely like the flint 
 gravel of our chalk districts. When heaps of this gravel have thus 
 announced our approach to a new formation, we arrive at length at 
 the escarpment of the lacustrine beds. At the bottom of the hill 
 which rises before us, we see strata of clay and sand, resting on mica- 
 schist ; and above, in the quarries of Belbet, Leybros, and Bruel, a 
 white limestone, in horizontal strata, the surface of which has been 
 hollowed out into irregular furrows, since filled up with broken flint, 
 marl, and dark vegetable mound. In these cavities we recognize an 
 exact counterpart to those which are so numerous on the furrowed 
 surface of our own white chalk. Advancing from these quarries 
 along a road made of the white limestone, which reflects as glaring a 
 light in the sun as do our roads composed of chalk, we reach, at 
 length, in the neighbourhood of Aurillac, hills of limestone and cal- 
 careous marl, in horizontal strata, separated in some places by regular 
 layers of flint in nodules, the coating of each nodule being of an 
 opaque white colour, like the exterior of the flinty nodules of our 
 chalk. 
 
 The abundant supply both of siliceous, calcareous, and gypseous 
 matter, which the ancient lakes of France received, may have been 
 connected with the subterranean volcanic agency of whi'ch those 
 regions were so long the theatre, and which may have impregnated 
 the springs with mineral matter, even before the great outbreak of 
 lava. It is well known that the hot springs of Iceland, and many 
 other countries, contain silex in solution ; and it has been lately 
 affirmed, that steam at a high temperature is capable of dissolving 
 
206 SLOWNESS OF DEPOSITION. [Cn. XV. 
 
 quartzose rocks without the aid of any alkaline or other flux.* 
 Warm water charged with siliceous matter would immediately part 
 with a portion of its silex, if its temperature was lowered by 
 mixing with the cooler waters of a lake. 
 
 A hasty observation of the white limestone and flint of Aurillac 
 might convey the idea that the rock was of the same age as the white 
 chalk of Europe ; but when we turn from the mineral aspect and com- 
 position to the organic remains, we find in the flints of the Cantal 
 seed-vessels of the freshwater Chara, instead of the marine 
 zoophytes so abundant in chalk flints ; and in the limestone we meet 
 with shells of Limnea, Planorbis, and other lacustrine genera. 
 
 Proofs of gradual deposition. Some sections of the foliated marls 
 in the valley of the Cer, near Aurillac, attest, in the most unequivocal 
 manner, the extreme slowness with which the materials of the lacus- 
 trine series were amassed. In the hill of Barrat, for example, we 
 find an assemblage of calcareous and siliceous marls ; in which, for a 
 depth of at least 60 feet, the layers are so thin, that thirty are 
 sometimes contained in the thickness of an inch ; and when they are 
 separated, we see preserved in every one of them the flattened stems 
 of Charce, or other plants, or sometimes myriads of small Paludinte. 
 and other freshwater shells. These minute foliations of the marl re- 
 semble precisely some of the recent laminated beds of the Scotch 
 marl lakes, and may be compared to the pages of a book, each con- 
 taining a history of a certain period of the past. The different layers 
 may be grouped together in beds from a foot to a foot and a half in 
 thickness, which are distinguished by differences of composition and 
 colour, the tints being white, green, and brown. Occasionally there 
 is a parting layer of pure flint, or of black carbonaceous vegetable 
 matter, about an inch thick, or of white pulverulent marl. We find 
 several hills in the neighbourhood of Aurillac composed of such 
 materials, for the height of more than 200 feet from their base, the 
 whole sometimes covered by rocky currents of trachytic or basaltic 
 lava.f 
 
 Thus wonderfully minute are the separate parts of which some of 
 the most massive geological monuments are made up! When we 
 desire to classify, it is necessary to contemplate entire groups of 
 strata in the aggregate ; but if we wish to understand the mode of 
 their formation, and to explain their origin, we must think only of 
 the minute subdivisions of which each mass is composed. We must 
 bear in mind how many thin leaf-like seams of matter, each contain- 
 ing the remains of myriads of testacea and plants, frequently enter 
 into the composition of a single stratum, and how vast a succession of 
 these strata unite to form a single group ! We must remember, also, 
 that piles of volcanic matter, like the Plomb du Cantal, which rises 
 in the immediate neighbourhood of Aurillac, are themselves equally 
 
 * See Proceedings of Eoyal Soc., No. Lacustres Tertiairesdu Cantal, &c. Ann. 
 44. p. 233. des Sci. Nat. Oct. 1829. 
 
 f Lyell and Murchison, sur les Depots 
 
CH. XV.] UPPER EOCENE OF NEBRASKA, UNITED STATES. 207 
 
 the result of successive accumulation, consisting of reiterated sheets 
 of lava, showers of scoriae, and ejected fragments of rock. Lastly, 
 we must not forget that continents and mountain-chains, colossal as 
 are their dimensions, are nothing more than an assemblage of many 
 such igneous and aqueous groups, formed in succession during an 
 indefinite lapse of ages, and superimposed upon each other. 
 
 Bordeaux, Aix, &c. The Upper Eocene strata in the Bordeaux 
 basin are represented, according to M. Raulin, by the Falun de 
 Leognan, and the underlying limestone of St. Macaire. By many, 
 however, the upper of these, or the Leognan beds, are considered to 
 be no older than the faluns of Touraine. The freshwater strata of 
 Aix-en-Provence are probably Upper Eocene ; also the tertiary rocks 
 of Malta, Crete, Cerigo, and those of many parts of Greece and 
 other countries bordering the Mediterranean. 
 
 Nebraska, United States. In the territory of Nebraska, on the 
 Upper Missouri, near the Platte River, lat. 42 N., a tertiary 
 formation occurs, consisting of white limestone, marls, and siliceous 
 clay, described by Dr. D. Dale Owen*, in which many bones of 
 extinct quadrupeds, and of chelonians of land or freshwater forms, 
 are met with. Among these, Dr. Leidy recognizes a gigantic 
 Palceotherium, larger than any of the Parisian species ; several species 
 of the genus Orcodon, Leidy, uniting the characters of pachyderms 
 and ruminants ; Eucrotaphus, another new genus of the same mixed 
 character ; two species of rhinoceros of the sub-genus Acerotherium, 
 an Upper Eocene form of Europe before mentioned ; two of Archceo- 
 therium, a pachyderm allied to Chceropotamus and Hyracotherium ; 
 also Pcebrotherium, an extinct ruminant allied to Dorcatherium, 
 Kaup ; also Agriochcegus of Leidy, a ruminant allied to Mery- 
 copotamus of Falconer and Cautley; and, lastly, a large carni- 
 vorous animal of the genus Macairodus, the most ancient example of 
 which in Europe occurs in the Upper Eocene beds of Auvergne. 
 The turtles are referred to the genus Testudo, but have some affinity 
 to Emys. On the whole, this formation has, I believe, been correctly 
 referred by American writers to the Eocene period, in conformity 
 with the classification adopted by me, but would, I conceive, be 
 called Lower Miocene by those who apply that term to all strata 
 newer than the Paris gypsum. 
 
 * David Dale Owen, Geol. Survey of Wisconsin, &c.: Philad. 1852. 
 
MIDDLE EOCENE FORMATIONS. 
 
 [CH. XVI. 
 
 CHAPTER XVI. 
 
 MIDDLE AND LOWER EOCENE FORMATIONS. 
 
 Middle Eocene strata of England Fluvio-marine series in the Isle of Wight and 
 Hampshire Successive groups of Eocene Mammalia Fossils of Barton Clay 
 Shells, nummulites, fishes, and reptiles of the Bagshot and Bracklesham beds 
 Lower Eocene strata of England Fossil plants and shells of the London Clay 
 proper Strata of Kyson in Suffolk Fossil monkey and opossum Plastic 
 clays and sands Thanet sands Middle Eocene formations of France- 
 Gypseous series of Montmartre and extinct quadrupeds Calcaire grossier 
 Miliolites Lower Eocene in France Nummulitic formations of Europe and 
 Asia Their wide extent referable to the Middle Eocene period Eocene 
 strata in the United States Section at Claiborne, Alabama Colossal cetacean 
 Orbitoid limestone Burr stone. 
 
 THE strata next in order in the descending series are those which I 
 term Middle Eocene. In the accompanying map, the position of 
 several Eocene areas is pointed out, such as the basin of the Thames, 
 
 Fig. 181. 
 Map of the principal tertiary basins of the Eocene period. 
 
 K-.;.;.-| Hypogene rorks and strata 
 I-''-'"-'-'-! older than the Devonian 
 
 olde 
 
 or Old Red series. 
 
 Eocene formations 
 
 N. B. The space left blank is occupied by secondary formations from the Devonian or old red 
 sandstone to the chalk inclusive. 
 
 part of Hampshire, part of the Netherlands, and the country round 
 Paris. The three last-mentioned areas contain some marine and 
 freshwater formations, which have been already spoken of as Upper 
 Eocene, but their superficial extent in this part of Europe is in- 
 significant. 
 
 ENGLISH MIDDLE EOCENE FORMATIONS. 
 
 The following table will show the order of succession of the strata 
 found in the Tertiary areas, commonly called the London and Hamp- 
 shire basins. (See also Table, p. 105. et seg.) 
 
209 
 
 CH. XVI.] ENGLISH MIDDLE EOCENE FORMATIONS. 
 
 UPPER EOCENE. 
 
 Thickness. 
 
 A. Hempstead beds, Isle of Wight, see above, p. 193. - - 170 feet. 
 
 MIDDLE EOCENE. 
 
 B. 1. Bembridge Series, North coast of Isle of Wight - - 120 
 B. 2. Osborne or St. Helen's Series, ibid. - - 100 
 B. 3. Headon Series, Isle of Wight, and Hordwell Cliff, Hants - 170 
 B. 4. Headon Hill sands and Barton Clay, Isle of Wight, and 
 
 Barton Cliff, Hants - 300 
 
 B. 5. Bagshot and Bracklesham Sands and Clays, London 
 
 and Hants basins - - 700 
 
 LOWER EOCENE. 
 
 C. 1. London Clay proper and Bognorbeds, London and Hants 
 
 basins - - 35 to 50 
 
 C. 2. Plastic and Mottled Clays and Sands (Woolwich and 
 
 Reading series), London and Hants basins - - 100 
 
 C. 3. Thanet Sands, Keculvers, Kent, and Eastern part of 
 
 London basin - - - - - 90 
 
 The true place of the Bagshot sands, B. 5. in the above series, and 
 of the Thanet sands, C. 3., was first accurately ascertained by Mr. 
 Prestwich in 1847 and 1852. The true relative position of the 
 Hempstead beds, A., of the Bembridge, B. 1., and of the Osborne or 
 St. Helen's series, B. 2., were not made out in a satisfactory manner 
 till Professor Forbes studied them in detail in 1852. 
 
 Bembridge series, B. 1. These beds are above 100 feet thick, 
 and, as before stated (p. 188.), pass upwards into the Hempstead beds, 
 with which they are conformable, near Yarmouth, in the Isle of Wight. 
 They consist of marls, clays, and limestones of freshwater, brackish, 
 and marine origin. Some of the most abundant shells, as Cyrena 
 semistriata var., and Paludina lenta, fig. 175. p. 194., are common to 
 this and to the overlying Hempstead series. The following are the 
 subdivisions described by Professor Forbes : 
 
 a. Upper marls, distinguished by the abundance of Melania turritissima, Forbes 
 (fig. 182.). 
 
 Fig. 182. Fig. 183. 
 
 Melania ttirrttissima, Forbes. 
 Bembridge. 
 
 Fragment of Carapace of Trionyx. 
 Bembridge Beds, Isle of Wight. 
 
 b. Lower marl, characterized by Cerithium mutabile, Cyrena pulchra, &c., and 
 
 by the remains of Trionyx (see fig. 183.). 
 
 c. Green marls, often abounding in a peculiar species of oyster, and accompanied 
 
 by Cerithia, Mytili, an Area, a Nucula, &c. 
 
 d. Bembridge limestones, compact cream-coloured limestones alternating with 
 
 *p 
 
210 FLUVIO-MARINE SERIES IN ISLE OF WIGHT. [Cn. XVI. 
 
 shales and marls, in all of which land-shells are common, especially at Sconce, 
 near Yarmouth, and have been described by Mr. Edwards. The Bulimus eL 
 lipticus, fig. 184., and Helix occlusa, fig. 185., are among its best known land* 
 
 Fig. 184. 
 
 Bttlimus ettipticus, Sow. 
 Bembridge Limestone, 
 half natural size. 
 
 Fig. 185. 
 
 Fig. l6. 
 
 Helix occlusa, Edwards, 
 Sconce Limestone, 
 Isle of Wight. 
 
 Paludina orbicular is. Penibridj;e. 
 
 shells. Paludina orbicularis, fig. 186., is also of frequent occurrence. One of the 
 bands is filled with a little globular Paludina. Among the freshwater pulmo- 
 
 Fig. 187. 
 
 Fig. 188, 
 
 Fig. 189. 
 
 Planorbis discus, Edwards. Bern- 
 bridge. diam. 
 
 Lymnca longfscata, Brard. 
 
 Char a tuber culata. 
 Bembridge Lime- 
 stone, I. of Wight. 
 
 nifera, Lymnea longiscata (fig. 188.) and Planorbis discus (fig. 187.) are the 
 most generally distributed : the latter represents or takes the place of the 
 Planorbis euomphalus (see fig. 192.), of the more ancient Headon series. Chara 
 tuberculata (fig. 189.) is the characteristic Bembridge gyrogonite. 
 
 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 corresponding age in the 
 suburbs of Paris. The well-known building-stone of Binstead, near 
 Ryde, a limestone with numerous hollows caused by Cyrence which 
 have disappeared and left the moulds 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 mam 
 malia characteristic of the gypseous series of Paris, as Palaotherium 
 
CH. XVI.] TLUVIO-MARINE SERIES IN ISLE OF WIGHT. 211 
 
 Fig. 190. magnum, (fig. 19 1 .) P. medium, P. minus, P. mini- 
 
 mum, P. curtum,P. crassum; also Anoplotherium 
 commune (fig. 190.), A. secundarium, Dichobune 
 cervinum, and Chceropotamus Cuvieri. The genus 
 Paleothere, above alluded to, resembled the living 
 tapir in the form of the head, and in having a 
 short proboscis, but its molar teeth were more like 
 those of the rhinoceros (see fig. 190.). Paleothe- 
 rium magnum was of the size of a horse, three or 
 four feet high. The annexed woodcut, fig. 191., 
 is one of the restorations which Cuvier attempted of the outline of 
 
 Fig. 191. 
 
 Lower Molar tooth, 
 nat. size, 
 
 Paleotherium magnum, Cuvier. 
 
 the living animal, derived from the study of the entire skeleton. 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 Binstead, agreeing with fossils 
 of the Paris gypsum, strengthens the evidence derived from shells 
 and plants of the synchronism of the two formations. 
 
 Osborne or St. Helen's series, B . 2. This group is of fresh and 
 brackish-water origin, and very variable in mineral character and 
 thickness. Near Ryde, it supplies a freestone much used for building, 
 and called by Prof. Forbes the Nettlestone grit. In one part ripple- 
 marked flag-stones occur, and rocks with fucoidal markings. The 
 Osborne beds are distinguished by peculiar species of Paludina, Me- 
 lania, and Melanopsis, as also of Cypris and the seeds of Chara. 
 
 Headon series, B. 3. These beds are seen both at the east 
 and west extremities of the Isle of Wight, and also in Hordwell 
 Cliffs, Hants. Everywhere Planorbis euomphalus, fig. 192., charac- 
 terizes the freshwater deposits, just as the allied form, P. discus, 
 fig. 187., does the Bembridge limestone. The brackish-water beds 
 contain Potomomya plana, Cerithium mutabile, and C. cinctum 
 (fig. 44. p. 30.), and the marine beds Venus (or Cytherea) incrassata, 
 a species common to the Limburg beds and Gres de Fontainebleau, 
 or the Upper Eocene series. The prevalence of salt-water remains 
 
 p 2 
 
212 
 
 SHELLS OF THE HEADON SEEIES. [Cn. XVI. 
 
 is most conspicuous in some of the central parts of the formation. 
 Mr. T. Webster, in his able memoirs on the Isle of Wight, first 
 
 Fig. 192. 
 
 Fig. 193. 
 
 Planorbis euomphalus, Sow. 
 Headon Hill. \ diam. 
 
 Helix labyrinthica, Say. Headon Hill, Isle of Wight ; 
 and Hordwell Cliff, Hants also recent. 
 
 separated the whole into a lower freshwater, an upper marine, and an 
 upper freshwater division. 
 
 Among the shells which are widely distributed through the Headon 
 series are Neritina concava, (fig. 194.), Lymnea caudata (fig. 195.), and 
 Cerithium concavum (fig. 196.). Helix labyrinthica, Say (fig. 193.), 
 
 Fig. 194. 
 
 Fig. 195. 
 
 Fig. 196. 
 
 Neritina concava. 
 Headon Series. 
 
 Lymnea caudata. 
 Headon Beds. 
 
 Cerithium concavum 
 Headon Series. 
 
 a land-shell now inhabiting the United States, was discovered in this 
 series by Mr. Wood in Hordwell Cliff. It is also met with in Headon 
 Hill, in the same beds. At Sconce, in the Isle of Wight, it occurs 
 in the newer Bembridge series, and affords a rare example of an 
 Eocene fossil of a species still living, though, as usual in such cases, 
 having no local connexion 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 Ly- 
 mington, Hants, where the organic remains have been studied by Mr. 
 Searles Wood, Dr. Wright, and the Marchioness of Hastings. To the 
 latter we are indebted for a detailed section of the beds *, as well as 
 for the discovery of a variety of new species of fossil mammalia, 
 chelonians, and fish ; also for first calling attention to the important 
 fact that these vertebrata differ specifically from those of the Bem- 
 bridge beds. Among the abundant shells of Hordwell are Paludina 
 lenta and various species of Lymneus, Planorbis, Melania, Cyclas, and 
 Unio, Potomomya, Dreissena, &c. 
 
 * Bulletin Soc. Geol. de France, 1852, p. 191. 
 
OH. XVI.] FLUVIO-MARINE SERIES IN HAMPSHIRE. 213 
 
 Among the chelonians we find a species of Emys, and no less than 
 six species of Trionyx ; among the saurians an alligator and a 
 crocodile; among the ophidians two species of land-snakes (Pa- 
 leryx, Owen) ; and among the fish Sir P. Egerton and Mr. Wood 
 have found the jaws, teeth, and hard shining scales of the genus 
 Lepidosteus or bony pike of the American rivers. This same genus 
 of freshwater ganoids has also been met with in the Hempstead beds 
 in the Isle of Wight. The bones of several birds have been ob- 
 tained from Hordwell, and the remains of quadrupeds. The latter 
 belong to the genera Paloplotherium of Owen, A.noplotherium, 
 Anihracotherium, Dichodon of Owen (a new genus discovered by 
 Mr. A. H. Falconer), Dichobune, Spalacodon, and Hycenodon. The 
 latter offers, I believe, the oldest known example of a true carni- 
 vorous mammal 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 considerably lower that that of the 
 Bembridge 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 mammalia flou- 
 rished on the earth during the Eocene period. 
 
 Many of the marine shells of the brackishwater 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 freshwater shells, such as Cyrena obovata, which are 
 common to the Bembridge beds, notwithstanding 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 colour 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. 
 
 Both in Hordwell Cliff and in the Isle of Wight, the Headon beds 
 rest on white sands, the upper member of the Barton series, B. 4., 
 next to be mentioned. 
 
 Headon Hill sands and Barton clay, B. 4. (Table, p. 209.) 
 Fig. 197. In one of the upper and sandy beds of this formation 
 Dr. Wright found Chama squamosa in great plenty. 
 The same sands contain impressions of many marine 
 shells (especially in Whitecliff Bay) common to the 
 upper Bagshot sands afterwards to be described. The 
 underlying Barton clay has yielded about 209 marine 
 shells, more than half of them, according to Mr. Prest- 
 wich, peculiar ; and only eleven common to the London 
 dayproper, (C.I. p. 209.,) being in the proportion of only 
 Barton. 5 p er cen t. On the other hand, 70 of them agree with 
 the shells of the calcaire grassier of France. It is nearly a century 
 
 p 3 
 
214 
 
 FOSSILS OF THE BARTON CLAY. 
 
 [Cn. XVI. 
 
 since Brander published, in 1766, an account of the organic remains 
 collected from these Barton and Hordwell cliffs, and his excellent 
 figures of the shells then deposited in the British Museum are justly 
 admired by conchologists for their accuracy. 
 
 SHELLS OP THE BARTON CLAY, HANTS. 
 
 Certain foraminifera called Nummulites begin, when we study 
 the tertiary formations in a descending order, to make their first 
 
 Fig. 198. 
 
 Fig. 199. 
 
 Fig. 200. 
 
 Fig. 201. 
 
 Mitrascabra. Voluta ambigua. Typhis pungens. 
 
 Fig. 202. Fig. 203. Fig. 204. 
 
 Voluta athleta. Barton 
 and Brakleshara. 
 
 Fig. 205. 
 
 Terebellumfusi- Terebellum con- 
 forme. Barton volutum, Lam. 
 and Bracklesham. Seraphs convolu- 
 tum, Montf. 
 
 Cardita globosa. 
 
 Crassatella sulcata. 
 
 appearance in these Barton beds. A small species called Nummulites 
 variolaria is found both on the Hampshire coast and in beds of the 
 same age in Whitecliff Bay, in the Isle of Wight. Several marine 
 shells, such as Corbula pisum, are common to the Barton beds and 
 the Hempstead or Upper Eocene series, and a still greater number, 
 as before stated, are common to the Headon series. 
 
 Bagshot and Bracklesham beds, B. 5. The Bagshot beds, consisting 
 chiefly of siliceous sand, occupy extensive tracts round Bagshot, in 
 Surrey, and in the New Forest, Hampshire. They may be separated 
 into three divisions, the upper and lower consisting of light yellow 
 sands, and the central of dark green sands and brown clays, the whole 
 reposing on the London clay proper.* The uppermost division is 
 probably of about the same age as the Barton series. Although 
 
 Prestwich, Quart. Geol. Journ. vol. iii p. 386. 
 
CH. XVI.] EOCENE BAGSHOT SANDS. 215 
 
 the Bagshot beds are usually devoid of fossils, they contain marine 
 shells in some places, among which Venericardia planicosta (see fig. 
 
 Fig. 206. 
 
 Venericardia planicosta, Lam. 
 Cardita planicosta, Deshayes. 
 
 206.) is abundant, with Turritella sulcifera and Nummulites leevi- 
 gata. (See fig. 210. p. 216.). 
 
 At Bracklesham Bay, near Chichester, in Sussex, the characteristic 
 shells of this member of the Eocene series are best seen ; among 
 others, the huge Cerithium giganteum, so conspicuous in the calcaire 
 grossier of Paris, where it is sometimes 2 feet in length. The 
 volutes and cowries of this formation, as well as the lunulites 
 and corals, seem to favour the idea of a warm climate having pre- 
 vailed, which is borne out by the discovery of a serpent, Palceophis 
 typhceus (see fig. 207.), exceeding, according to Prof. Owen, 20 feet 
 
 Fig. 207. 
 
 Palaophis typhceus, Owen ; an Eocene sea-serpent. Bracklesham. 
 a. b. vertebra, with long neural spine preserved. c. two vertebrae in natural articulation. 
 
 in length, and allied in its osteology to the Boa, Python, Coluber, and 
 Hydrus. The compressed form and diminutive size of certain caudal 
 vertebrae indicate so much analogy with Hydrus as to induce the 
 Hunterian professor to pronounce this extinct ophidian to have been 
 marine.* He had previously combated with much success the evi- 
 dence advanced to prove the existence in the Northern Ocean of 
 huge sea-serpents in our own times, but he now contends for the 
 former existence in the British Eocene seas, of less gigantic serpents, 
 
 * Palaeont. Soc. Monograph. Eept. pt. ii. p. 61. 
 p 4 
 
216 BRACKLESHAM BEDS. [Cn. XVI. 
 
 when the climate was probably more genial ; for amongst the com- 
 panions of the sea-snake of Bracklesham was an extinct Gavial 
 ( Gavialis Dixoni, Owen), and numerous fish, such as now frequent 
 the seas of warm latitudes, as the sword-fish (see fig. 208.), and 
 gigantic rajs of the genus Myliobates (see fig. 209.). 
 
 Fig. 208. 
 
 Prolonged premaxillary bone or " sword " of a fossil sword -fish (Ccelorhynchus). Brackle- 
 sham. Dixon's Fossils of Sussex, pi. 8. 
 
 Fig. 209. 
 
 Fig. 210. 
 
 Dental plates of Myliobates Edwardsi. 
 Bracklesham Bay- Ibid. pi. 8. 
 
 Nummulitcs (Nummularia) Iczvigata. 
 Bracklesham. Ibid. pi. 8. 
 
 a, section of the nutnmnlite. 
 
 b. group, with an individual showing the exterior 
 
 of the shell. 
 
 The teeth of sharks also, of the genera Carcharodon, Otodus, Lamna, 
 Caleocerdo, and others, are abundant. (See figs. 211, 212, 213, 214.) 
 
 Fig. 211. 
 
 Fig. 212. 
 
 Fig. 213. 
 
 Fig. 214. 
 
 Carcharodon heterodon, Agass. 
 
 Otodus obliquus, Agass. 
 
 Lamna elegant, 
 Agass. 
 
 Galeocerdo latidens, 
 
 Agass. 
 
 Teeth of sharks from Bracklesham Bay. 
 
 The Nummulites Icevigata (see fig. 210.), so characteristic of the lower 
 beds of the calcaire grossier in France, where it sometimes forms 
 stony layers, as near Compiegne, is very common at Bracklesham, toge- 
 ther with N. scabra and N. variolaria. Out of 193 species of testacea 
 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. 
 
OH. XVI.] LOWER EOCENE STRATA OF ENGLAND. 217 
 
 MARINE SHELLS OF BRACKLESHAM BEDS. 
 
 Fig. 215. Fig, 216. Fig. 217. Fig. 218. Fig. 219. 
 
 Pleurotoma attenuata, Voluta la- TurriteUa, Lucina serrata, Dixon. Conus deper- 
 Sow. trella, Lam. multisulcata, Magnified. ditus. 
 
 Lam. 
 
 LOWER EOCENE FORMATIONS OF ENGLAND. 
 
 London Clay proper (C. 1. Table, p. 209.). This formation under- 
 lies the preceding, and consists of tenacious brown and bluish-gray 
 clay, with layers of concretions called septaria, which abound chiefly 
 in the brown clay, and are obtained in sufficient numbers from sea- 
 cliffs near Harwich, and from shoals off the Essex coast, to be used 
 for making Roman cement. The principal localities of fossils in the 
 London clay are Highgate Hill, near London, the island of Sheppey, 
 and Bognor in Hampshire. Out of 133 fossil shells, Mr. Prestwich 
 found only 20 to be common to the calcaire grossier (from which 600 
 species have been obtained), while 33 are common to the " Lits Co- 
 quilliers " (p. 229.), in which only 200 species are known in France. 
 We may presume, therefore, that the London clay proper is older 
 than the calcaire grossier. This may perhaps remove a difficulty 
 which M. Adolphe Brongniart has experienced when comparing the 
 Eocene Flora of the neighbourhoods of London and Paris. The 
 fossil species of the island of Sheppey, he observes, indicate a much 
 more tropical climate than the Eocene Flora of France. Now the 
 latter has been derived principally from the gypseous series, and resem- 
 bles the vegetation of the borders of the Mediterranean rather than 
 that of an equatorial region; whereas the older flora of Sheppey 
 Fig. 220. belongs to an antecedent epoch, separated 
 
 from the period of the Paris gypsum by 
 all the calcaire grossier and Bagshot series 
 in short, by the whole nummulitic formation 
 properly so called. 
 
 Mr. Bowerbank, in a valuable publication 
 on the fossil fruits and seeds of the island of 
 Sheppey, near London, has described no less 
 than thirteen fruits of palms of the recent 
 type Nipa, now only found in the Molucca 
 and Philippine islands and in Bengal (see 
 fig. 220.). In the delta of the Ganges, Dr. 
 FO! sii jj 00 k er observed the large nuts of Nipa 
 fruticans floating in such numbers in the 
 various arms of that great river, as to obstruct the paddle-wheels of 
 
218 FOSSILS OF THE LONDON CLAY. [Cn. XVI. 
 
 steam-boats. These plants are allied to the cocoa-nut tribe on the one 
 side, and on the other to the Pandanus, or screw-pine. The fruits 
 of other palms besides those of the cocoa-nut tribe are also met with 
 in the clay of Sheppey ; also three species of Anona, or custard 
 apple ; and cucurbitaceous fruits (of the gourd and melon family) are 
 in considerable abundance. Fruits of various species of Acacia are in 
 profusion, and these, although less decidedly tropical, imply a warm 
 climate. 
 
 The contiguity of land may be inferred not only from these vege- 
 table productions, but also from the teeth and bones of crocodiles and 
 turtles, since these creatures, as Dr. Conybeare has 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 13 feet long, of the genus Palceophis 
 before mentioned (p. 215.), has also been described by Prof. Owen from 
 Sheppey, of a different species from that of Bracklesham. A true croco- 
 dile, 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 
 Hyracotherium of Owen, allied to the Hyrax, Hog, and Chaeropo- 
 tamus ; another is a Lophiodon; a third, a pachyderm called Cory- 
 phodon eoccBnus 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 nummulites 
 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 deposited in the sea. 
 
 The marine shells of the London clay confirm the inference de- 
 rivable from the plants and reptiles in favour of a high temperature. 
 Thus many species of Conus and Valuta occur, a large Cypr&a, 
 C. oviformis, a very large Rostellaria, (fig. 223.), a species of Cancel- 
 laria, six species of Nautilus (fig. 225.), besides other cephalopoda 
 of extinct genera, one of the most remarkable of which is the 
 Belosepia* (fig. 226.) Among many characteristic bivalve shells are 
 Leda amygdaloides (fig. 227.) and Axinus angulatm (fig. 228.), and 
 among the Radiata a star-fish called Astropecten (fig. 229.). 
 
 These fossils are accompanied by a sword-fish ( Tetrapterus pris- 
 cus, Agassiz), about 8 feet long, and a saw-fish (Pristis bisulcatus, 
 Ag."), about 10 feet in length ; genera now foreign to the British 
 seas. On the whole, no less than 50 species of fish have been de- 
 scribed by M. Agassiz from these beds in Sheppey, and they indicate, 
 in his opinion, a warm climate. 
 
 * For description of Eocene Cephalopoda, see Monograph by F. E. Edwards, 
 Palaeontograph. Soc. 1849. 
 
CH. XVI.] FOSSIL SHELLS OF TfiE LONDON CLAY. 
 
 219 
 
 Fig. 221. 
 
 FOSSIL SHELLS OF THE LONDON CLAY. 
 Fig. 222. Fig. 223. 
 
 Valuta nodosa, Sow. Phorus extensus, 
 Highgate. Sow. Highgate, 
 
 Fig. 224. 
 
 .Nautilus centralis, Sow. Highgate. 
 
 Eostellaria macroptera, Sow. One-third 
 of nat. size ; also found in the Barton clay. 
 
 Fig. 225. 
 
 Fig. 226. 
 
 Aturia zi'cxac, Brown and Edwards. 
 
 . Syn. Nautilus xicxac, Sow. 
 
 London clay. Sheppey. 
 
 Fig. 227 
 
 Fig. 228. 
 
 Belosepia sepioidea. De Blainv. 
 London clay. Sheppey. 
 
 Fig. 229. 
 
 Leda amygdaloides. 
 Highgate. 
 
 Axinus angulatus. London 
 clay. Hornsea. 
 
 Astropecten crispatus, 
 E. Forbes. Sheppey. 
 
 Strata of Kyson in Suffolk. At Kyson, a few miles east of 
 Woodbridge, a bed of Eocene clay, 12 feet thick, underlies the red 
 crag. Beneath it is a deposit of yellow and white sand, of con- 
 siderable interest, in consequence of many peculiar fossils contained 
 in it. Its geological position is probably the lowest part of the 
 
220 STEATA OF KYSON IN SUFFOLK. [Cn. XVI. 
 
 London clay proper. In this sand has been found the first example 
 of a fossil quadrumanous animal discovered 
 in Great Britain, namely, the teeth and part 
 of a jaw, shown by Prof. Owen to belong 
 to a monkey of the genus Macacus (see fig. 
 Molar of monkey (Macacus). 230.). The mammiferous fossils, first met 
 with in the same bed, were those of an 
 
 opossum (Didelphys) (see fig. 231.), and an insectivorous bat (fig. 
 232.), together with many teeth of fishes of the shark family. 
 Fig. 23i. Mr. Colchester in 1840 obtained other 
 
 mammalian relics from Kyson, among 
 which Prof. Owen has recognized several 
 teeth of the genus Hyracotherium, and 
 the vertebras of a large serpent, probably 
 a PalcRophis. As the remains both of 
 Molar tooth a^nd part orjawof opossum. the Hyracotherium and Palaophis were 
 
 Fig 232 afterwards met with in the London clay, 
 
 as before remarked, these fossils con- 
 firmed the opinion previously entertained, 
 that the Kyson sand belongs to the Eocene 
 period. The Macacus, therefore, con- 
 Moiars of insectivorous bats, stitutes the first example of any quadru- 
 From Kyfo a n,' Suffolk. manous animal occurring in strata so old 
 
 as the Eocene, or in a spot so far from the 
 
 equator as lat. 52 N. It was not until after the year 1836 that the 
 existence of any fossil quadrumana was brought to light. Since that 
 period they have been discovered in France, India, and Brazil. 
 
 Plastic or mottled clays and sands (C. 2. p. 209.). The clays 
 called plastic, which lie immediately below the London clay, received 
 their name originally in France from being often used in pottery. 
 Beds of the same age (the "Woolwich and Reading series of Prest- 
 wich) are used for the like purposes in England. \ 
 
 No formations can be more dissimilar on the whole in mineral cha- 
 racter than the Eocene deposits of England and Paris ; those of our 
 own island being almost exclusively of mechanical origin, accumu- 
 lations of mud, sand, and pebbles ; while in the neighbourhood of 
 Paris we find a great succession of strata composed of limestones, 
 some of them siliceous, and of crystalline gypsum and siliceous sand- 
 stone, and sometimes of pure flint used for millstones. Hence it is by 
 no means an easy task to institute an exact comparison between the 
 various members of the English and French series, and to settle 
 their respective ages. It is clear that, on the sites both of Paris and 
 London, a continual change was going on in the fauna and flora by 
 the coming in of new species and the dying out of others ; and 
 contemporaneous changes of geographical conditions were also in 
 progress in consequence of the rising and sinking of the land and 
 bottom of the sea. A particular subdivision, therefore, of time was 
 
 * Annals of Nat. Hist. vol. iv. No. 23. Nov. 1839. 
 f Prestwich, Waterbearing Strata of London, 1851. 
 
CH. XVI.] LOWER EOCENE STRATA OF ENGLAND. 
 
 221 
 
 occasionally represented in one area by land, in another by an estuary, 
 in a third by the sea, and even where the conditions were in both 
 areas of a marine character, there was often shallow water in one, 
 and deep sea in another, producing a want of agreement in the state 
 of animal life. 
 
 But in regard to that division of the Eocene series which we have 
 now under consideration, we find an exception to the general rule, 
 for, whether we study it in the basins of London, Hampshire, or 
 Paris, we recognize everywhere the same mineral character. This 
 uniformity of aspect must be seen in order to be fully appreciated, 
 since the beds consist simply of sand, mottled clays, and well-rolled 
 flint pebbles, derived from the chalk, and varying in size from that of 
 a pea to an egg. 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 are observed, consisting of Ostrea bellovacina, so common 
 in France in the same relative position, and Ostrea edulina, scarcely 
 distinguishable from the living eatable species. In the same beds at 
 Bromley, Dr. Buckland found one large pebble to which five full- 
 grown oysters were affixed, in such a manner as to show that they 
 had commenced their first growth upon it, and remained attached to 
 it through life. 
 
 In several places, as at Woolwich on the Thames, at* Newhaven in 
 Sussex, and elsewhere, a mixture of marine and freshwater testacea 
 distinguishes this member of the series. Among the latter, Melania 
 inquinata (see fig. 234.) and Cyrena cuneiformis (see fig. 233.) are 
 
 Fig. 233. 
 
 Fig. 234. 
 
 Cyrena cuneiformis, Win. Con. 
 Natural size. 
 
 Melania inquinata, Des. Nat. size. 
 Syn. Cerithium melanoides, Min. Con. 
 
 very common, as in beds of corresponding age in France. They 
 clearly indicate points where rivers entered the Eocene sea. Usually 
 there is a mixture of brackish, freshwater, and marine shells, and 
 
222 PLASTIC CLAYS AND SANDS. [Cn. XVI. 
 
 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 numerous individuals of the Cyrena tellinella were 
 seen standing endwise with both their valves united, the posterior 
 extremity of each shell being uppermost, as would happen if the 
 mollusks had died in their natural position. I have described* 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 out at low 
 tide specimens of living species of Cyrena and of a Gnathodon, which 
 were similarly placed with their shells erect, or in a position which 
 enables the animal to protrude its siphon upwards, and draw in or 
 reject water at pleasure. The water at Mobile is usually fresh, but 
 sometimes brackish. At Woolwich a body of river-water must have 
 flowed permanently into the sea where the Cyrence 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 
 Herne Bay, the Woolwich beds assume more and more of a marine cha- 
 racter ; while in an opposite, or south-western direction, they become, 
 as near Chelsea and other places, more freshwater, and contain Unio, 
 Paludina, 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. 
 
 Before the minds of geologists had become familiar with the 
 theory of the gradual sinking of land, and its conversion into sea 
 at different periods, and the consequent change from shallow to deep 
 water, the freshwater and littoral character of this inferior group 
 appeared strange and anomalous. After passing 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 in the 
 same underlying formation masses of shingle, attaining at Black- 
 heath, near London, a thickness of 50 feet, indicate the proximity of 
 land, where the flints of the chalk were rolled into sand and pebbles, 
 and spread continuously over wide spaces. Such shingle always 
 appears at the bottom of the series, whether in the Isle of Wight, or 
 in the Hampshire or London basins. It may be asked why they did 
 not constitute simply narrow littoral zones, such as we might look 
 for on an ancient sea-shore. In reply, Mr. Prestwich has suggested 
 that such zones of shingle may have been slowly formed on a large 
 scale at the period of the Thanet sands (C. 3. p. 209.), and while the 
 land was sinking the well-rolled pebbles may have been dispersed 
 simultaneously over considerable areas, and exposed during gradual 
 submergence to the action of the waves of the sea, aided occasionally 
 by tidal currents and river floods. 
 
 Thanet sands (C. 3. p. 209.). The mottled or plastic clay of the 
 
 * Second Visit to the United States, vol. ii. p. 104. 
 
CH. XVI.] EOCENE STRATA IN FRANCE. 223 
 
 Isle of Wight and Hampshire is often seen in Actual contact with 
 the chalk, constituting in such places the lowest member of the 
 British Eocene series. But in other points another formation of 
 marine origin, characterized by a somewhat different assemblage of 
 organic remains, has been shown by Mr. Prestwich to intervene 
 between the chalk and the Woolwich series. For these beds he has 
 proposed 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 Herne Bay and the Reculvers, where they consist of sands 
 with a few concretionary masses of sandstone, and contain among 
 other fossils Pholadomya cuneata, Cyprina Morrisii, Corbula longi- 
 rostris, Scalaria Bowerbankii, &c. The greatest thickness of these 
 beds is about 90 feet, 
 
 FRENCH MIDDLE EOCENE FORMATIONS. 
 
 GENERAL TABLE OF FRENCH EOCENE STRATA. 
 
 A. UPPER EOCENE (Lower Miocene of many French authors'). 
 
 English Equivalents. 
 
 A. Calcaire de la Beauce, or upper fresh- -j 
 
 water, see p. 185., and Gres de Ton- I Hempstead series, see p. 193. 
 tainebleau, &c. J 
 
 B. MIDDLE EOCENE. 
 
 B. 1. Gypseous series and Middle fresh- \ . 
 
 water calcaire lacustre moyen. j Bembndge series, p. 195. 
 B. 2. Calcaire siliceux (in part contem. I ^^ Qf theBembrid 
 
 poraneous with the succeeding > series 
 group ?) J 
 
 {Osborne series, and upper and middle 
 part of Headon series, Isle of 
 Wight. 
 B. 4. Upper Calcaire Grossier (Cailasse) 1 He ^ don Hill Sands Barton Upper 
 
 and Middle Calcaire Grossier. [ Ba f hot and ? art of Bracklesham 
 
 J beds. 
 
 B. 5. Lower. Calcaire Grossier or Glau- "i 
 
 conie Grossiere. ) Bracklesham beds. 
 
 Lower Bagshot. Intermediate in age 
 
 B. 6. Soissonnais Sans or Litscoquilliers. } between the Bracklesham beds and 
 
 C London Clay 
 
 C. LOWER EOCENE. 
 
 C. Argile plastique et lignite. f Plastic clay and sand,, with lignite 
 
 \ (Woolwich and Reading series). 
 
 The tertiary formations in the neighbourhood of Paris consist of a 
 series of marine and freshwater strata, alternating with each other, 
 and rilling up a depression in the chalk. The area which they 
 occupy has been called the Paris basin, and is about 180 miles in its 
 greatest length, from north to south, and about 90 miles in breadth 
 from east to west (see Map, p. 196.). MM. Cuvier and Brongniart 
 attempted, in 1810, to distinguish five different groups, comprising 
 
224 MIDDLE AND LOWER EOCENE OF FRANCE. [Cn. XVI. 
 
 three freshwater and two marine, which were supposed to imply that 
 the waters of the ocean, and of rivers and lakes, had been by turns 
 admitted 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 move- 
 ments of the bed of the sea, and of the adjoining lands, and that the 
 superposition of deep sea to shallow water deposits (the London 
 clay, for example, to the Woolwich beds) can only be explained by 
 referring to such movements. Nevertheless, it appears, from the 
 researches of M. Constant Prevost, that some of the alternations and 
 intermixtures of freshwater and marine deposits, in the Paris basin, 
 may be accounted for 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. 
 
 To enlarge on the numerous subdivisions of the Parisian strata, 
 would lead me beyond my present limits; I shall therefore give 
 some examples only of the most important formations enumerated in 
 the foregoing Table, p. 223. 
 
 Beneath the Upper Eocene or " Upper marine sands," A, already 
 spoken of, (p. 195.), we find, in the neighbourhood of Paris, a 
 series of white and green marls, with subordinate beds of gypsum, B. 
 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 M. Cuvier. 
 
 The gypsum quarried 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 quadrupeds. Several land plants are also met 
 with, among which are fine specimens of the fan palm or palmetto tribe 
 (Flabellaria). The remains also of freshwater fish, and of crocodiles 
 and other reptiles, occur in the gypsum. The skeletons of mammalia 
 are usually isolated, often entire, the most delicate extremities being 
 preserved ; as if the carcases, clothed with their flesh and skin, had 
 been floated down soon after death, and while they were still swollen 
 by the gases generated by their first decomposition. The few ac- 
 companying shells are of those light kinds which frequently float on 
 the surface of rivers, together with wood. 
 
 M. Prevost has therefore suggested that a river may have swept 
 away the bodies of animals, and the plants which lived on its borders, 
 or in the lakes which it traversed, and may have carried them down 
 into the centre of the gulf into which flowed the waters impregnated 
 with sulphate of lime. We know that the Fiume Salso in Sicily 
 enters the sea so charged with various salts that the thirsty cattle 
 refuse to drink of it. A stream of sulphureous water, as white as 
 milk, descends into the sea from the volcanic mountain of Idienne, 
 on the east of Java ; and a great body of hot water, charged with 
 sulphuric acid, rushed down from the same volcano on one occasion, 
 and inundated a large tract of country, destroying, by its noxious 
 
CH. XVI.] GYPSEOUS SERIES. 225 
 
 properties, all the vegetation.* In like manner the Pusanibio, or 
 " Vinegar River," of Colombia, which rises at the foot of Purace, an 
 extinct volcano, 7,500 feet above the level of the sea, is strongly impreg- 
 nated with sulphuric and hydrochloric acids and with oxide of iron. 
 We may easily suppose the waters of such streams to have properties 
 noxious to marine animals, and in this manner the entire absence of 
 marine remains in the ossiferous gypsum may be explained.f There 
 are no pebbles or coarse sand in the gypsum ; a circumstance which 
 agrees well with the hypothesis that these beds were precipitated 
 from water holding sulphate of lime in solution, and floating the 
 remains of different animals. 
 
 In this formation the relics of about fifty species of quadrupeds, 
 including the genera Paleotherium (see fig. 191.), Anoplotherium 
 (see fig. 190.), and others, have been found, all extinct, and nearly 
 four-fifths of them belonging to a division of the order Pachydermata, 
 which is now represented by only four living species ; namely, three 
 tapirs and the daman of the Cape. With them a few carnivorous 
 animals are associated, among which are the Hycenodon dasyuroides, 
 and a species of dog, Canis Parisiensis, and a weasel, Cynodon 
 Parisiensis. Of the Rodentia, are found a squirrel; of the In- 
 sectivora, 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 skeletons of 
 some of which are entire. None of them are referable to existing 
 species.^ The same remark applies to the fish, according to MM. 
 Cuvier and Agassiz, as also to the reptiles. Among the last are 
 crocodiles and tortoises of the genera Emys and Trionyx. 
 
 The tribe of land quadrupeds most abundant in this formation is 
 such as now inhabits alluvial plains and marshes, and the banks of 
 rivers and lakes, a class most exposed to suffer by river inundations. 
 Among these were several species of Paleothere, a genus before 
 alluded to (p. 211.). These were associated with the Anoplotherium, 
 a tribe intermediate between pachyderms and ruminants. One of the 
 three divisions of this family was called by Cuvier Xiphodon (see 
 fig. 235.). Their forms were slender and elegant, and one, named 
 Xiphodon gracile (fig. 235.), was about the size of the chamois ; and 
 Cuvier inferred from the skeleton that it was as light, graceful, 
 and agile as the gazelle. 
 
 When the French osteologist declared, in the early part of the 
 present century, that all the fossil quadrupeds of the gypsum of 
 Paris were extinct, the announcement of so startling a fact, on such 
 high authority, created a powerful sensation, and from that time a 
 new impulse was given throughout Europe to the progress of 
 geological investigation. Eminent naturalists, it is true, had long 
 
 * Leyde Magaz. voor Wetensch Konst f M. C. Prevost, Submersions Itera- 
 
 en Lett., partie v. cahier i. p. 71. Cited tives, &c. Note 23. 
 
 by Rozet, Journ. de Geologic, torn. i. f Cuvier, Oss. Foss., torn. iii. p. 25* 
 p. 43. 
 
 Q 
 
226 CALCAIRE SILICEUX. fCn. XVI. 
 
 before maintained that the shells and zoophytes, met with in many 
 ancient European rocks, had ceased to be inhabitants of the earth. 
 
 Fig. 235. 
 
 Xtphodon gracile, or Anoplutherium gracile, Cuvier. Restored outline. 
 
 but the majority even of the educated classes continued to believe 
 that the species of animals and plants now contemporary with man, 
 were the same as those which had been called into being when the 
 planet itself was created. It was easy to throw discredit upon the new 
 doctrine by asking whether corals, shells, and other creatures pre- 
 viously unknown, were not annually discovered ? and whether living 
 forms corresponding with the fossils might not yet be dredged up 
 from seas hitherto unexamined ? But from the era of the publica- 
 tion of Cuvier's Ossements Fossiles, and still more his popular Trea- 
 tise called " A Theory of the Earth," sounder views began to prevail. 
 It was clearly demonstrated that most of the mammalia found in the 
 gypsum of Montmartre differed even generically from any now known 
 to exist, and the extreme improbability that any of them, especially 
 the larger ones, would ever be found surviving in continents yet un- 
 explored, was made manifest. Moreover, the non-admixture of a 
 single living species in the midst of so rich a fossil fauna was a 
 striking proof that there had existed a state of the earth's surface 
 zoologically unconnected with the present state of things. 
 
 Calcaire siliceux, or Travertin inferieur, B. 2. This compact 
 siliceous limestone extends over a wide area. It resembles a preci- 
 pitate 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 freshwater and land 
 species, and never any marine fossils. The siliceous limestone and 
 the calcaire grossier 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 ; and M. Prevost concludes, that while to the north, 
 
CH. XVI. ] CALCAIRE GROSSIER. 227 
 
 where the bay was probably open to the sea, a marine limestone was 
 formed, another deposit of freshwater origin was introduced to the 
 southward, or at the head of the bay. It is supposed that during 
 the Eocene period, as now, the ocean was to the north, and the con- 
 tinent, where the great lakes existed, to the south. From that 
 southern region we may suppose a body of freshwater to have de- 
 scended, charged with carbonate of lime and silica, the water being 
 perhaps in sufficient volume to freshen the upper end of the bay. 
 
 The gypsum, with its associated marl and limestone, is, as before 
 stated, in greatest force towards the centre of the basin, where the 
 calcaire grossier and calcaire siliceux are less fully developed. Hence 
 M. Prevost infers, that while those two principal deposits were 
 gradually in progress, the one towards the north, and the other 
 towards the south, a river descending from the east may have brought 
 down the gypseous and marly sediment. 
 
 Gres de Beauchamp or Sables moyens, B. 3. In some parts of 
 the Paris basin, sands and marls, called the Gres de Beauchamp, or 
 Sables moyens, divide the gypseous beds from the calcaire grossier 
 proper. These sands, in which a small nummulite (N. variolaria) 
 is very abundant, contain more than 300 species of marine shells, 
 many of them peculiar, but others common to the next division. 
 
 Calcaire grassier, upper and middle, B. 4. The upper 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 Cerithium, Cyclostoma, and Corbula; in others Limneus, 
 Cerithium, Paludina, &c. In the latter, the bones of reptiles and 
 mammalia, Paleotherium and Lophiodon, have been found. The 
 middle division, or calcaire grossier proper, consists of a coarse lime- 
 stone, often passing into sand. It contains the greater number of 
 the fossil shells which characterize the Paris basin. No less than 
 400 distinct species have been procured from a single spot near 
 Grignon, where they are embedded in a calcareous sand, chiefly 
 formed of comminuted shells, in which, nevertheless, individuals in 
 a perfect state of preservation, both of marine, terrestrial, and fresh- 
 water species, are mingled together. Some of the marine shells 
 may have 1'ived on the spot ; but the Cyclostoma and Limneus 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 testacea than 
 the great proportion of species referable to the genus Cerithium 
 (see p. 30. fig. 44.). There occur no less than 137 species of this 
 genus in the Paris basin, and almost all of them in the calcaire 
 grossier. Most of the living Cyrithia 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, the sediment of some of which gave rise to the beds of 
 clay and lignite before mentioned ; while a distinct freshwater 
 
 Q 2 
 
228 
 
 EOCENE FORAMINIFERA. 
 
 [On. XVI. 
 
 limestone, called calcaire siliceux, already described, was precipitated 
 from the waters of others situated farther to the south. 
 
 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 entirely made up of millions of 
 microscopic shells, of the size of minute grains of sand, which all 
 belong to the class Foraminifera. Figures of some of these are given 
 in the annexed woodcut. As this miliolitic stone never occurs in the 
 
 EOCENE FORAMINIFERA. 
 
 Fig. 237. 
 
 Calcarina rarispina, Desh. 
 b. natural size, a, c. same magnified. 
 
 Spirolina stenostoma, Desh. 
 B. natural size. A, C, D. same magnified. 
 
 Fig. 238. 
 
 Triloculina inflata, Desh. 
 b. natural size. a, c, d. same magnified. 
 
 Fig. 239. 
 
 Clavulina corrugata, Desh. 
 a. natural size. b, c. same magnified. 
 
 Faluns, or Miocene strata of Brittany and Touraine, it often fur- 
 nishes the geologist with a useful criterion for distinguishing the 
 detached Eocene and Miocene formations, scattered over those and 
 other adjoining provinces. The discovery of the remains of Paleo- 
 therium and other mammalia in some of the upper beds of the cal- 
 caire grossier shows that these land animals began to exist before the 
 deposition of the overlying gypseous series had commenced. 
 
CH. XVI.] 
 
 LITS COQUILLIERS. 
 
 229 
 
 Lower Culcaire grassier, or Glauconie grossiere,, B. 5. The lower 
 part of the calcaire grossier, which often contains much green earth, 
 is characterized at Auvers, near Pontoise, to the north of Paris, and 
 still more in the environs of Compiegne, by the abundance of nummu- 
 lites, consisting chiefly of JV. Icevigata, N. scabra> and N. Lamarcki, 
 which constitute a large proportion of some of the stony strata, 
 though these same foraminifera are wanting in beds of similar age in 
 the immediate environs of Paris. 
 
 Soissonnais Sands or Lits coquilliers, B. 6. Below the pre- 
 ceding formation, shelly sands are seen, of considerable thickness, 
 especially at Cuisse-Lamotte, near Compiegne, 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, and many pe- 
 culiar. The Nummulites planulata is very abundant, and the most cha- 
 racteristic shell is the Nerita conoidea, Lam., a fossil which has a 
 
 Fig. 240. 
 
 Nerita conoidea, Lam. 
 Syn. N. Schemidelliana, Chemnitz. 
 
 very wide geographical range ; for, as M. D'Archiac remarks, it accom- 
 panies the nummulitic formation from Europe to India, having been 
 found in Cutch, near the mouths of the Indus, associated with Num- 
 mulites scabra. No less than thirty-three shells of this group are 
 said to be identical with shells of the London clay proper, yet, after 
 visiting Cuisse-Lamotte and other localities of the " Sables in- 
 ferieures ' ? 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 unre- 
 presented in France, unless partially so, by these sands.* One of 
 the shells of the sandy beds of the Soissonnais is adduced by 
 M. Deshayes as an example of the changes which certain species 
 
 
 Fig. 241. 
 
 Cardium porulosum. Paris and London basins. 
 * D'Archiac, Bulletin, torn, x.; and Prestwich, Geol. Quart. Journ. 1847, p. 377. 
 
 Q 3 
 
230 NUMMULITIC FORMATIONS [Cu. XVI. 
 
 underwent in the successive stages of their existence. It seems that 
 different varieties of the Cardium porulosum are characteristic of 
 different formations. In the Sossonnais this shell acquires but a 
 small volume, and has many peculiarities, which disappear in the 
 lowest beds of the calcaire grossier. In these the shell attains its 
 full size, with many distinctive characters, which are again modified 
 in the uppermost beds of the calcaire grossier ; and these last modi- 
 fications of form are preserved throughout the '* upper marine " 
 (or Upper Eocene) series.* 
 
 Argile plastique (C. Table, p. 223.). At the base of the tertiary 
 system in France are extensive deposits of sands, with occasional 
 beds of clay used for pottery, and called " argile plastique." Fossil 
 oysters (Osirea bellovacina) abound in some places, and in others 
 there is a mixture of fluviatile shells, such as Cyrena cuneiformis (fig. 
 233. p. 321.), Melania inquinata (fig. 234.), and others, frequently met 
 with in beds occupying the same position in the valley of the Thames. 
 Layers of lignite also accompany the inferior clays and sands. 
 
 Immediately upon the chalk at the bottom of all the tertiary strata 
 in France there generally is a conglomerate or breccia of rolled and 
 angular chalk-flints, cemented by siliceous sand. These beds appear 
 to be of littoral origin, and imply the previous emergence of the chalk, 
 and its waste by denudation. 
 
 Whether the Thanet sands before mentioned (p. 222.) are exactly 
 represented in the Paris basin is still a matter of discussion. 
 
 Wide extent of the nummulitic formation in Europe, Asia, fyc. 
 When I visited Belgium and French Flanders in 1851, with a view 
 of comparing the tertiary strata of those countries with the English 
 series, I found that all the beds between the Upper Eocene or Limburg 
 formations, and the Lower Eocene or London clay proper, might be 
 conveniently divided into three sections, distinguished, among other 
 paleontological characters, by three different species of nummulites, 
 N. variolaria in the upper beds, N. Icevigata in the middle, and N. 
 planulata in the lower. After I had adopted this classification, I 
 found, what I had overlooked or forgotten, that the superposition of 
 these three species in the order here assigned to them, had been 
 previously recognized in the North of France, in 1842, by Viscount 
 D'Archfac. The same author, in the valuable monograph recently 
 published by himt, has observed, that a somewhat similar distribu- 
 tion of these and other species in time, prevails very widely in the 
 South of France and in the Pyrenees, as well as in the Alps and 
 Apennines, and in Istria, the lowest nummulitic beds being charac- 
 terized by fewer and smaller species, the middle by a greater number 
 and by those which individually attain the largest dimensions, and 
 the uppermost beds again by small species. 
 
 In the treatise alluded to, M. D'Archiac describes no less than fifty- 
 two species of this genus, and considers that they are all of them cha- 
 
 * Coquilles caracteristiques des ter- f Animaux foss. du groupe nummuL 
 rains, 1831. de 1'Inde : Paris, 1853. 
 
CH. XVI.] IN EUROPE AND ASIA, 231 
 
 racteristic of those tertiary strata which I have called Middle Eocene. 
 In very few instances at least do certain species diverge from 
 this narrow, limit, whether into incumbent or subjacent tertiary 
 formations, it being rather doubtful whether more than one of 
 them, Nummulites intermedia, also a Middle Eocene fossil, ascends 
 so high as the Miocene formation, or whether any of them descend 
 to the level of the London clay. Certainly they have never been 
 traced so low down as the marine beds, coeval with the Plastic 
 clay or Lignite, in any country of which the geology has been well 
 worked out. This conclusion is a very unexpected result of recent 
 inquiry, since for many years it was a matter of controversy whether 
 the nummulitic rocks of the Alps and Pyrenees ought not to be re- 
 garded as cretaceous rather than Eocene. The late M. Alex. 
 Brongniart first declared the specific identity of many shells of the 
 marine strata near Paris, and those of the nummulitic formation of 
 Switzerland, although he obtained these last from the summit of the 
 Diablerets, one of the loftiest of the Swiss Alps, which rises more 
 than 10,000 feet above the level of the sea. 
 
 The nummulitic limestone of the Alps is often of great thickness, 
 and is immediately covered by another series of strata of dark- 
 coloured slates, marls, and fucoidal sandstones, to the whole of which 
 the provincial name of " flysch " has been given in parts of Switzer- 
 land. The researches of Sir Roderick Murchison in the Alps in 
 1847 have shown that all these tertiary strata enter into the disturbed 
 and loftiest portions of the Alpine chain, to the upheaval of which 
 they enable us therefore to assign a comparatively modern date. 
 
 The nummulitic formation, with its characteristic fossils, plays 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 often attains a thickness of many thousand feet, and extends from 
 the Alps to the Carpathians, and is in full force in the north of Africa, 
 as, for example, in Algeria and Morocco. It has also 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 Indus. It occurs not only in Cutch, but in the mountain 
 ranges 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. 
 
 Fig. 242. 
 
 Nummulites Puschi, D'Archiac. Peyrehorade, Pyrenees. 
 a. external surface of one of the nummulites, of which longitudinal sections are seen in the 
 
 limestone. 
 b. transverse section of same. 
 
 Q 4 
 
232 EOCENE STRATA [Cn. XVI. 
 
 Dr. T. Thomson found nummulites 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 
 Fig. 243. of the Pyrenees, in a compact crystalline marble 
 
 (fig. 242.) is called by M. D'Archiac Nummulites 
 Puschi. The same is also very common in rocks 
 of the same age in the Carpathians. 
 
 Another large species (see fig. 243.), Nummulites 
 exponens, J. Sow., occurs not only in the South 
 of France, near Dax, but in Germany, Italy, Asia 
 Minor, and in Cutch; also in the mountains of 
 
 Nummulites exponens, on .1 p * p r-\i 
 
 Sow. Europe and India. Sylhet, on the frontiers of China. 
 
 In many of the distant countries above alluded to, in Cutch, for 
 example, some of the same shells, such as, Nerita conoidea (fig. 
 240.), accompany the Nummulites as in France. 
 
 The opinion of many observers, that the nummulitic formation 
 belongs partly to the cretaceous era, seems chiefly to have arisen 
 from confounding an allied genus, Orbitoides, with the true Num- 
 rnulite. 
 
 When we have once arrived at the conviction that the nummulitic 
 formation occupies a middle 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 Middle Eocene period. During 
 that period the sea prevailed where these chains now rise, for num- 
 mulites and their accompanying testacea were unquestionably inhabi- 
 tants of salt water. Before these events, comprising the conversion 
 of a wide area from a sea to a continent, England had been peopled, 
 as I before pointed out (p. 220.), by various quadrupeds, by herbi- 
 vorous pachyderms, by insectivorous bats, by opossums and monkeys. 
 
 Almost all the extinct 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 consi- 
 deration ; and besides these superficial monuments 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 Central Alps into crystalline rocks, and transformed into 
 marble, quartz-rock, mica-schist, and gneiss.* 
 
 EOCENE STRATA IN THE UNITED STATES. 
 
 In North America the Eocene formations occupy a large area 
 bordering the Atlantic, which increases in breadth and importance as 
 it is traced southwards from Delaware and Maryland to Georgia and 
 
 * Murchison, Quart. Journ. of Geol. Soc. vol. v., and Lyell, vol. vl 1850. 
 Anniversary Address. 
 
CH. XVI.] IN THE UNITED STATES. 233 
 
 Alabama. They also occur in Louisiana and other states both east 
 and west of the valley of the Mississippi. At Claiborne in Alabama 
 no less than four hundred species of marine shells, with many echi- 
 noderms and teeth of fish, characterize one member of this system. 
 Among the shells, the Cardita planicosta, before mentioned (fig. 216. 
 p. 215.), is in abundance ; and this fossil, and some others identical 
 with European species, 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 grossier of 
 Paris.* 
 
 Higher in the series is a remarkable calcareous rock, formerly called 
 " the nummulite limestone," from the great number of discoid bodies 
 resembling nummulites which it contains, fossils now referred by 
 A. d'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. The following section will enable 
 the reader to understand the position of three subdivisions of the 
 Eocene series, Nos. J, 2, and 3, the relations of which I ascertained 
 in Clarke County, between the rivers Alabama and Tombeckbee. 
 
 1. Sand, marl, &c., with numerous fossils. ) 
 
 2. White or rotten limestone, with Zeuglodon. \ Eocene. 
 
 3. Orbitoidal, or so called nummulitic limestone. ) 
 
 4. Overlying formation of sand and clay without fossils. Age unknown. 
 
 The lowest set of strata, No. 1, having a thickness of more than 
 100 feet, comprise marly beds, in which the Ostrea sellceformis occurs, 
 a shell ranging from Alabama to Virginia, and being a representa- 
 tive form of the Ostrea flabellula of the Eocene group of Europe. 
 In other beds of No. 1, two European shells, Cardita planicosta^ 
 before mentioned, and Solarium canaliculatum, are found, with a 
 great many other species peculiar to America. Numerous corals, 
 also, and the remains of placoid fish and of rays, occur, and the 
 " swords," as they are called, of sword fishes, all bearing a great 
 generic likeness to those of the Eocene strata of England and France. 
 
 No. 2 (fig. 244.) is a white limestone, sometimes soft and argilla- 
 
 * See paper by the author, Quart. f Quart. Journ. GeoL Soc. voL vi. 
 Journ. Geol. Soc. vol. iv. p. 12.; and p. 32. 
 Second Visit to the U. S. vol. ii. p. 59. 
 
234 EOCENE STRATA IN UNITED STATES. [Cn. XVI. 
 
 eeous, 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.* 
 
 Fig. 245. Fig. 246. 
 
 Zeuglodon cetoides, Owen. 
 Basilosaurus, Harlan. 
 Fig. 245. Molar tooth, natural size. Fig. 246. Vertebra, reduced. 
 
 The colossal bones of this cetacean are so plentiful in the interior 
 of Clarke County as to be characteristic of the formation. The ver- 
 tebral column of one skeleton found by Dr. Buckley at a spot visited 
 by me, extended to the length of nearly 70 feet, and not far off part 
 of another backbone nearly 50 feet long was dug up. I obtained 
 evidence, during a short excursion, of so many localities of this fossil 
 animal within a distance of 10 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 (see fig. 245.), 
 implanted in corresponding double sockets ; and his opinion of the 
 cetacean nature of the fossil was afterwards 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 the 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 
 convoluted tympanic bones which are characteristic of cetaceans. 
 
 Near the junction of No. 2 and the incumbent limestone, No. 3, 
 next to be mentioned, are strata characterized by the following shells : 
 Spondylus dumosus (Plagiostoma dumosum, Morton), Pecten Poid- 
 soni, Pecten perplanus, and Ostrea cretacea. 
 
 No. 3 (fig. 244.) is a white limestone, for the most part made up of the 
 Orbitoides of D'Orbigny before mentioned (p. 233.), formerly supposed 
 to be a nummulite, and called N. Mantelli, mixed with a few lunulites 
 some small corals and shells.f The origin, therefore, of this cream- 
 coloured soft stone, like that of our white chalk, which it much re- 
 sembles, is, I believe, due to the decomposition of these foraminifera. 
 The surface of the country where it prevails is sometimes marked by 
 
 * See Memoir by E. W. Gibbes, t Lyell, Quart. Journ. Geol. Soc. 
 Journ. of Acad. Nat. Sci. Philad. vol. i. 1847, vol. iv. p. 15. 
 1847. 
 
CH. XVII.] CRETACEOUS GROUPS. 235 
 
 the absence of wood, like our chalk downs, or is covered exclusively 
 by the Juniperus Virginiana, as certain chalk districts in England 
 by the yew tree and juniper. 
 
 Some of the shells of this limestone are common to the Claiborne 
 beds, but many of them are peculiar. 
 
 It will be seen in the section (fig. 244. p. 233.) that the strata 
 Nos. 1, 2, 3 are, for the most part, overlaid by a dense formation of 
 sand or clay without fossils. In some points of the bluff or cliff of 
 the Alabama river, at Claiborne, the beds Nos. 1, 2 are exposed 
 nearly from top to bottom, whereas at other points the newer form- 
 ation, No. 4, occupies the face of nearly the whole cliff. The age of 
 this overlying mass has not yet been determined, as it has hitherto 
 proved destitute of organic remains. 
 
 The burr-stone strata of the Southern States contain so many 
 fossils agreeing with those of Claiborne, that it doubtless belongs to 
 the same part of the Eocene group, though I was not fortunate enough 
 to see the relations of the two deposits in a continuous section. 
 Mr. Tuomey considers it as the lower portion of the series. It may, 
 perhaps, be a form of the Claiborne beds in places where lime was 
 wanting, and where silex, derived from the decomposition of felspar, 
 predominated. It consists chiefly of slaty clays, quartzose sands, and 
 loam, of a brick red colour, with layers of chert or burr-stone, used in 
 some places for mill- stones. 
 
 CHAPTER XVII. 
 
 CRETACEOUS GROUP. 
 
 Lapse of time between the Cretaceous and Eocene periods Whether certain 
 formations in Belgium and France are of intermediate age Pisolitic limestone 
 
 Divisions of the Cretaceous series in North- Western Europe Maestricht 
 beds Chalk of Faxoe White chalk Its geographical extent and origin 
 Formed in an open and deep sea How far derived from shells and corals 
 Single pebbles in chalk Chalk flints, Potstones of Horstead Fossils of 
 the Upper Cretaceous rocks Echinoderms, Mollusca, Bryozoa, Sponges 
 Upper Greensand and Gault Chalk of South of Europe Hippurite limestone 
 
 Cretaceous rocks of the United States. 
 
 HAVING treated in the preceding chapters of the tertiary strata, we 
 have next to speak of the uppermost of the secondary groups, com- 
 monly called the chalk, or the cretaceous strata, from crefa, the 
 Latin name for that remarkable white earthy limestone, which 
 constitutes an upper member of the group in these parts of Europe, 
 where it was first studied. The marked discordance in the fossils 
 of the tertiary, as compared with the cretaceous formations, has long 
 induced many geologists 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 
 
236 PISOLITIC LIMESTONE OF FRANCE. [CH. XVII. 
 
 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 be- 
 tween the Eocene and recent periods, to the history of which the last 
 seven chapters have been devoted. Several fragmentary deposits have 
 been met with here and there, in the course of the last half century, 
 of an age intermediate between the white chalk and the plastic clays 
 and sands, of the Paris and London districts, monuments 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 darkness, preceded and followed by 
 others of which the annals are comparatively well known to us. But 
 these newly discovered records do not fill up the wide gap, some of 
 them being closely allied to the Eocene, and others to the cretaceous 
 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 chapter, and classed as 
 Lower Eocene. To the same tertiary series belong the Belgian form- 
 ations, called by Professor Dumont, Landenian and Heersian, although 
 these are probably of higher antiquity than the Thanet Sands. On 
 the other hand, the Maestricht and Faxoe limestones are very closely 
 connected with the chalk, to which also the Pisolitic limestone of 
 France has been recently referred by high authorities. 
 
 The Lower Landenian beds of Belgium consist of marls and sands, 
 often containing much green earth, called glauconite. They may be 
 seen at Tournay, and at Angres, near Mons, and at Orp-le- Grand, 
 Lincent, and Landen in the ancient province of Hesbaye, in Belgium, 
 where they supply a durable building-stone, yet one so light as to be 
 easily transported. Some few shells of the genus Pholodamya, 
 Scalaria, and others, agree specifically with fossils of the Thanet 
 Sands ; but most of them, such as Astarte incequilatera, Nyst, are 
 peculiar. In the building-stone of Orp-le- Grand, I found a Cardiaster, 
 a genus which, according to Professor E. Forbes, was previously 
 unknown in rocks newer than the cretaceous. 
 
 Still older than the Lower Landenian is the marl, or calcareous 
 glauconite of the village of Heers, near Waremme, in Belgium ; also 
 seen at Marlinne in the same district, where I have examined it. It 
 has been sometimes classed with the cretaceous series, although as yet 
 it has yielded no forms of a decidedly cretaceous aspect, such as 
 Ammonite, Baculite, Belemnite, Hippurite, &c. The species of 
 shells are for the most part new ; but it contains, according to 
 M. Hebert, Pholodamya cuneata, an Eocene fossil, and he assigns it 
 with confidence to the tertiary series. 
 
 Pisolitic limestone of France. Geologists have been still more at 
 variance respecting the chronological relations of this rock, which is 
 met with in the neighbourhood of Paris, and at places north, south, 
 east, and west of that metropolis, as between Vertus and Laversines, 
 Me'udon and Montereau. It is usually in the form of a coarse 
 yellowish or whitish limestone, and the total thickness of the series 
 
CH. XVII.] CLASSIFICATION OF CRETACEOUS ROCKS. 237 
 
 of beds already known is about 100 feet. Its geographical 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. It 
 was originally regarded as cretaceous by M. E. de Beaumont, on the 
 ground of its having undergone, like the white chalk, extensive 
 denudation previous to the Eocene period ; but many able paleon- 
 tologists, and among others MM. C. D'Orbigny, Deshayes, and 
 D'Archiac, disputed this conclusion, and, after enumerating 54 species 
 of fossils, declared that their appearance was more tertiary than 
 cretaceous. More recently, M. Hebert having found the Pecten 
 quadricostatus, a cretaceous species, in this same pisolitic rock, at 
 Montereau near Paris, and some few other fossils common to the 
 Maestricht chalk, and to the Baculite limestone of the Cotentin, in 
 Normandy, classed it as an upper member of the cretaceous group, 
 an opinion since adopted by M. Alcide D'Orbigny, who has carefully 
 examined the fossils. The Nautilus Danicus, fig. 249., 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, Turrilites, 
 Baculites, or Hippurites have been met with. The proportion of 
 peculiar species, many of them of tertiary aspect, 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. 
 
 It should however be observed, that all the above-mentioned strata, 
 from the Thanet Sands to the Pisolitic limestone inclusive, and even, 
 the Maestricht rock, next to be described, exhibit marks of denudation, 
 experienced at various dates, subsequently to the consolidation of the 
 white chalk. This fact helps us in some degree to explain the 
 remarkable break in the sequence of European rocks, between the 
 secondary and tertiary eras, for many strata which once existed have 
 doubtless been swept away. 
 
 CLASSIFICATION OF THE CRETACEOUS ROCKS. 
 
 The cretaceous group has generally been divided into an Upper and 
 a Lower series, each of them comprising several subdivisions, dis- 
 tinguished by peculiar fossils, and sometimes retaining a uniform 
 mineral character throughout wide areas. The Upper series is often 
 called familiarly the chalk, and the Lower the greensand, the last- 
 mentioned name being derived from the green colour imparted to 
 certain strata by grains of chloritic matter. The following table 
 comprises the names of the subdivisions most commonly adopted: 
 
 UPPER CRETACEOUS. 
 
 A. 1. Maestricht beds and Faxoe limestones. 
 
 2. White chalk with flints. 
 
 3. Chalk marl, or grey chalk slightly argillaceous. 
 
238 MAESTRICHT BEDS. [Cn. XVII. 
 
 4. Upper greensand, occasionally with beds of chert, and with chloritic marl 
 
 (craie chloritee of French authors) in the upper portion. 
 
 5. Gault, including the Blackdown beds. 
 
 LOWER CRETACEOUS (or Neocomian). 
 
 B. 1. Lower greensand Greensand, Ironsand, clay, and occasional beds of 
 
 limestone (Kentish Rag). 
 2. Wealden beds or Weald clay and Hastings sands.* 
 
 Maastricht Beds. On the banks of the Meuse, at Maestricht, 
 reposing on ordinary white chalk with flints, we find an upper cal- 
 careous formation about 100 feet thick, the fossils of which are, on 
 the whole, very peculiar, and all distinct from tertiary species. Some 
 few are of species common to the inferior white chalk, among which 
 may be mentioned Belemnitcs mucronatus (fig. 256. p. 246.) and 
 Pecten quadricostatus, a shell regarded by many as a mere variety of 
 P. quinquecostatus (see fig. 271.). Besides the Belemnite there are 
 other genera, such as Baculite and Hamite, never found in strata 
 newer than the cretaceous, but frequently met with in these Maes- 
 tricht beds. On the other hand, Valuta, Fasciolaria, and other 
 genera of univalve shells, usually met with only in tertiary 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 occasional nodules of grey chert or chalcedony. 
 
 M. Bosquet, with whom I examined this formation (August, 1850), 
 pointed out to me a layer of chalk from 2 to 4 inches thick, con- 
 taining green earth and numerous encrinital stems, which forms 
 the line of demarcation between the strata containing the fossils 
 peculiar to Maestricht and the white chalk below. The latter is dis- 
 tinguished by regular layers of black flint in nodules, and by several 
 shells, such as Terebratula carnea (see fig. 267.), wholly wanting 
 in beds higher than the green band. Some of the organic remains, 
 however, for which St. Peter's Mount is celebrated, occur both above 
 and below that parting layer, and, among others, the great marine 
 reptile called Mosasaurus (see fig. 247.), a saurian supposed to have 
 been 24 feet in length, of which the entire skull and a great part of 
 
 * M. Alcide d'Orbigny, in his valuable work entitled Paleontologie Fran9aise, 
 has adopted new terms for the French subdivisions of the Cretaceous Series, which, 
 so far as they can be made to tally with English equivalents, seem explicable thus : 
 
 Danien. Maestricht beds. 
 
 Senonien. White chalk, and chalk marl. 
 
 Turonien. Part of the chalk marl. 
 
 Cenomanien. Upper greensand. 
 
 Albien. Gault. 
 
 Aptien. Upper part of lower greensand. 
 
 Neocomien. Lower part of same. 
 
 Neocomien 
 
 inferieur. Wealden beds and contemporaneous marine strata. 
 
CH. XVII.] CHALK OF FAXOE. 239 
 
 the skeleton 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 echinoderm fig. 248. 
 
 Fig. 247. 
 
 Fig. 218. 
 
 Hemipneustes radiatus, Ag. 
 
 Spatangus radiatus, Lam. 
 
 Chalk of Maestricht and white 
 
 chalk. 
 
 Mosasaurus camperi. Original more than 3 feet long. 
 
 1 saw proofs of the previous denudation of the white chalk ex- 
 hibited 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 con- 
 sisted chiefly of a layer of well-rolled, 
 black, chalk-flint pebbles, in the midst 
 of which perfect specimens of Thecidea 
 radians and Belemnites mucronatus are 
 imbedded. 
 
 Chalk of Faxoe. In the island of 
 Seeland, in Denmark, the newest mem- 
 ber of the chalk series, seen in the sea-cliffs at Stevensklint 
 resting on white chalk with flints, is a yellow limestone, a por- 
 tion of which, at Faxoe, where it is used as a building-stone, is 
 composed of corals, even more conspicuously than is usually ob- 
 served in recent coral reefs. It has 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 Cyprcea, one of Oliva, two of Mitra, four of the 
 genus Cerithium, six of Fusus, two of Trochus, one Patella, one 
 Emargmula^ &c. ; on the whole, more than thirty univalves, spiral 
 or patelliform. At the same time, some of the accompanying bivalve 
 shells, echinoderms, and zoophytes are specifically identical with 
 fossils of the true Cretaceous series. Among the cephalopoda of 
 Faxoe may be mentioned Baculites Faujasii and Belemnites mucro- 
 natus, shells of the white chalk. The Nautilus Danicus (see fig. 249.) 
 is characteristic of this formation ; and it also occurs in France in 
 the calcaire pisolitique of Laversin (dept. of Oise). 
 
WHITE CHALK. 
 
 Fig. 249. 
 
 [Cn. XVIT. 
 
 Nautilus Danicus, Schl. Faxoe, Denmark. 
 
 The claws and entire skull of a small crab, Bra- 
 chyurus rugosus (Schlottheiin), are scattered through 
 the Faxoe stone, reminding us of similar crusta- 
 ceans enclosed in the rocks of modern coral reefs. 
 Some small portions of this coralline formation 
 consist of white earthy chalk ; it is therefore clear 
 that this substance must have been produced simul- 
 taneously; a fact of some importance, as bearing 
 on the theory of the origin of white chalk ; for the 
 decomposition of such corals as we see at Faxoe is 
 capable, we know, of forming white mud, undistin- 
 guishable from chalk, and which we may suppose to 
 have been dispersed far and wide through the 
 ocean, in which such reefs as that of Faxoe grew. 
 
 White chalk (see Tab. p. 237. et seg.). The 
 highest beds of chalk in England and France consist 
 of a pure, white, calcareous mass, usually too soft for 
 a building stone, but sometimes passing into a more 
 solid state. It consists, almost purely, of carbo- 
 nate of lime ; the stratification is often obscure, 
 except where rendered distinct by interstratified 
 layers of flint, a few inches thick, occasionally in 
 continuous beds, but oftener in nodules, and recur- 
 ring at intervals from 2 to 4 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 divi- 
 sions in the south of England equals, in some places, 
 1000 feet. 
 
 The annexed section (fig. 250.) will show the 
 manner in which the white chalk extends from 
 England into France, covered by the tertiary 
 strata described in former chapters, and reposing on 
 lower cretaceous beds. 
 
CH. XVII.] ANIMAL ORIGIN OF WHITE CHALK. 241 
 
 Geographical extent and origin of the White Chalk. The area 
 over which the white chalk preserves a nearly homogeneous aspect 
 is so vast, that the earlier geologists despaired 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 ex- 
 tends 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, Belemnites mucronatus, and 
 Ostrea vesicularis. 
 
 But it would be an error to imagine, that the chalk was ever 
 spread out continuously over the whole of the space comprised within 
 these limits, although it prevailed in greater or less thickness over 
 large portions of that area. On turning to those regions of the 
 Pacific where coral reefs abound, we find some archipelagoes of 
 lagoon islands, such as that of the Dangerous Archipelago, for 
 instance, and that of Radack, with several adjoining groups, which 
 are from 1100 to 1200 miles in length, and 300 or 400 miles broad ; 
 and the space to which Flinders proposed to give the name of the 
 Coralline Sea is still larger ; for it is bounded on the east by the 
 Australian barrier all formed of coral rock, on the west by New 
 Caledonia, and on the north by the reefs of Louisiade. Although 
 the islands in these areas may be thinly sown, the mud of the decom- 
 posing zoophytes may be scattered far and wide by oceanic currents. 
 That this mud would resemble chalk I have already hinted when 
 speaking of the Faxoe limestone, p. 239., and it was also remarked 
 in an early part of this volume, that even some of that chalk, which 
 appears to an ordinary observer quite destitute of organic remains, 
 is nevertheless, when seen under the microscope, full of fragments of 
 corals, bryozoa, and sponges ; together with the valves of entomo- 
 straca, the shells of foraminifera, and still more minute infusoria. 
 (See p. 26.) 
 
 Now it had been often suspected, before these discoveries, that 
 white chalk might be of animal origin, even where every trace of 
 organic structure has vanished. This bold idea was partly founded 
 on the fact, that the chalk consisted of carbonate of lime, such as 
 would result from the decomposition of testacea, echini, and corals ; 
 and partly on the passage observable between these fossils when 
 half decomposed and chalk. But this conjecture seemed to many 
 naturalists quite vague and visionary, until its probability was 
 strengthened by new evidence brought to light by modern geologists. 
 
 "We learn from Captain Nelson, that, in the Bermuda Islands, and 
 in the Bahamas, there are many basins or lagoons almost sur- 
 rounded and inclosed by reefs of coral. At the bottom of these 
 lagoons a soft white calcareous mud is formed, not merely from the 
 comminution of corallines (or calcareous plants) and corals, together 
 
 R 
 
242 ANIMAL ORIGIN OP WHITE CHALK. [Cn. XVII. 
 
 with the exuvise of foraminifera, mollusks, echinoderms, and crusta- 
 ceans, but also, as Mr. Darwin observed upon studying the coral 
 islands of the Pacific, from the faecal matter ejected by echinoderms, 
 conchs, and coral-eating fish. In the West Indian seas, the conch 
 ( Strombus gigas) adds largely to the chalky mud by means of its 
 faecal pellets, composed of minute grains of soft calcareous matter, 
 exhibiting some organic tissue. Mr. Darwin describes gregarious 
 fishes of the genus Scarus, seen through the clear waters of the 
 coral regions of the Pacific browsing quietly in great numbers on 
 living corals, like grazing herds of graminivorous quadrupeds. On 
 Fig. 251. opening their bodies, their intestines were found 
 
 to be filled with impure chalk. This cir- 
 cumstance is the more in point, when we re- 
 collect how the fossilist was formerly puzzled 
 by meeting, in chalk, with certain bodies, called 
 " larch-cones," which were afterwards recog- 
 nized by Dr. Buckland to be the excrement 
 of fish. Such spiral coprolites (fig. 251.), like 
 Coproiites of fish, called into the scales and bones of fossil fish in the chalk, 
 
 eido-copri, from the chalk. 
 
 are composed chiefly of phosphate of lime. 
 
 In the Bahamas, the angel-fish, and the unicorn or trumpet-fish, 
 and many others, feed on shell-fish, or on corals. 
 
 The mud derived from the sources above mentioned may be actually 
 seen in the Maldiva Atolls to be washed out of the lagoons through 
 narrow openings leading from the lagoon to the ocean, and the 
 waters of the sea are discoloured by it for some distance. When 
 dried, this mud is very like common chalk, and might probably be 
 made by a moderate pressure to resemble it still more closely.* 
 
 Mr. Dana, when describing the elevated coral reef of Oahu, in the 
 Sandwich Islands, says that some varieties of the rock consist of 
 aggregated shells, imbedded in a compact calcareous base as firm in 
 texture as any secondary limestone ; while others are like chalk, 
 having its colour, its earthy fracture, its soft homogeneous texture, 
 and being an equally good writing material. The same author de- 
 scribes, in many growing coral reefs, a similar formation of modern 
 chalk, undistinguishable from the ancient, f The extension, over a 
 wide submarine area, of the calcareous matrix of the chalk, as well as 
 of the imbedded fossils, would take place more readily in consequence 
 of the low specific gravity of the shells of mollusca and zoophytes, 
 when compared with ordinary sand and mineral matter. The mud 
 also derived from their decomposition would be much lighter than 
 argillaceous and inorganic mud, and very easily transported by cur- 
 rents, especially in salt water. 
 
 Single pebbles in chalk. The general absence of sand and pebbles 
 in the white chalk has been already mentioned ; but the occurrence 
 here and there, in the south-east of England, of a few isolated peb- 
 
 * See Nelson, Geol. Trans. 1837, vol. f Geol. of U. S. Exploring Exped. 
 v. p. 108.; and Geol. Quart. Journ. 1853, p. 252. 1849. 
 p. 200. 
 
CH. XVII.] PEBBLES IN CHALK. 243 
 
 bles of quartz and green schist, some of them 2 or 3 inches in 
 diameter, has justly excited much wonder. If these had been 
 carried to the spots where we now find them by waves or currents 
 from the lands once bordering the cretaceous sea, how happened it 
 that no sand or mud were transported thither at the same time ? 
 We cannot conceive such rounded stones to have been drifted like 
 erratic blocks by ice (see ch. x. and xi.), for that would imply 
 a cold climate in the Cretaceous period ; a supposition inconsistent 
 with the luxuriant growth of large chambered univalves, numerous 
 corals, and many fish, and other fossils of tropical forms. 
 
 Now in Keeling Island, one of those detached masses of coral 
 which rise up in the wide Pacific, Captain Ross found a single 
 fragment of greenstone, where every other particle of matter was 
 calcareous : and Mr. Darwin concludes that it must have come there 
 entangled in the roots of a large tree. He reminds us that Chamisso, 
 the distinguished naturalist who accompanied Kotzebue, affirms, that 
 the inhabitants of the Radack archipelago, a group of lagoon islands 
 in the midst of the Pacific, obtained stones for sharpening their instru- 
 ments by searching the roots of trees which are cast up on the beach.* 
 
 It may perhaps be objected, that a similar mode of transport 
 cannot have happened in the cretaceous sea, because fossil wood is 
 very rare in the chalk. Nevertheless wood is sometimes met with, 
 and in the same parts of the chalk where the pebbles are found, both 
 in soft stone and in a silicified state in flints. In these cases it has 
 often every appearance of having been floated from a distance, being 
 usually perforated by boring-shells, such as the Teredo and Fistu- 
 lana.\ 
 
 The only other mode of transport which suggests itself is sea- 
 weed. Dr. Beck informs me that in the Lym-Fiord, in Jutland, 
 the Fucus vesiculosus, often called kelp, sometimes grows to the 
 height of 10 feet, and the branches rising from a single root form 
 a cluster several feet in diameter. When the bladders are distended, 
 the plant becomes so buoyant as to float up loose stones several 
 inches in diameter, and these are often thrown by the waves high 
 up on the 'beach. The Fucus giganteus of Solander, so common in 
 Terra del Fuego, is said by Captain Cook to attain the length of 360 
 feet, although the stem is not much thicker than a man's thumb. 
 It is often met with floating at sea, with shells attached, several 
 hundred miles from the spots where it grew. Some of these plants, 
 says Mr. Darwin, were found adhering to large loose stones in the 
 inland channels of Terra del Fuego, during the voyage of the Beagle 
 in 1834 ; and that so firmly, that the stones were drawn up from the 
 bottom into the boat, although so heavy that they could scarcely be 
 lifted in by one person. Some fossil sea-weeds have been found 
 in the Cretaceous formation, but none, as yet, of large size. 
 
 But we must not imagine that because pebbles are so rare in the 
 
 * Darwin, p. 549. Kotzebue's First f Mantell, Geol. of S. E. of England, 
 Voyage, vol. iii, p. 155. )>. 96. 
 
 R 2 
 
244 CHALK FLINTS. [Cn. XVII. 
 
 white chalk of England and France there are no proofs of sand, 
 shingle, and clay having been accumulated contemporaneously 
 even in European seas. The siliceous sandstone, called "upper 
 quader" by the Germans, overlies white argillaceous chalk or 
 " planer-kalk," a deposit resembling in composition and organic 
 remains the chalk marl of the English series. This sandstone con- 
 tains 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 conspicuous part in the picturesque 
 scenery of Saxon Switzerland, near Dresden. 
 
 Chalk Flints. The origin of the layers of flint, whether in 
 continuous sheets or in the form of nodules, is more difficult to 
 explain than is that of the white chalk. No such siliceous masses 
 are as yet known to accompany the aggregation of chalky mud in 
 modern coral reefs. The flint abounds mostly in the uppermost 
 chalk, and becomes more rare or is entirely wanting as we descend ; 
 but this rule does not hold universally throughout Europe. Some 
 portion of the flint may have been derived from the decomposition 
 of sponges and other zoophytes provided with siliceous skeletons ; 
 for it is a fact, that siliceous spiculse, or the minute bones of sponges, 
 are often met with in flinty nodules, and may have served at least as 
 points of attraction to some of the siliceous matter when it was in the 
 act of separating from chalky mud during the process of solidification. 
 But there are other copious sources before alluded to, whence the 
 waters of the ocean derive a constant supply of silex in solution, such 
 as the decomposition of felspathic rock (see p. 42.), also mineral 
 springs rising up in the bed of the sea, especially those of a 
 high temperature ; since their waters, if chilled when first mingling 
 with the sea, would readily precipitate siliceous matter (see above, 
 p. 42.). Nevertheless, the occurrence in the white chalk of beds of 
 nodular or tabular flint at so many distinct levels, implies a peri- 
 odical action throughout wide oceanic areas not easily accounted for. 
 It seems as if there had been time for each successive accumulation 
 of calcareo-siliceous mud to become partially consolidated, and for a 
 re-arrangement of its particles to take place (the heavier silex sink- 
 ing to the bottom) before the next stratum was superimposed ; a 
 process formerly suggested by Dr. Buckland.* 
 
 A more difficult enigma is presented by the occurrence of certain 
 huge flints, or potstones as they are called in Norfolk, occurring 
 singly, or arranged in nearly continuous columns at right angles to 
 the ordinary and horizontal 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 26 feet, and covered by a thick bed of 
 gravel. The potstones, many of them pear-shaped, were usually 
 
 * Geol. Trans., First scries, vol. iv. p. 413. 
 
CH. XVII.] POTSTONES AT HORSTEAD. 245 
 
 about three feet in height, and one foot in their transverse diameter, 
 placed in vertical rows, like pillars at irregular distances from each 
 
 Fig. 252. 
 
 From a drawing by Mrs. Gunn. ^ 
 View of a chalk pit at Horstead, near Norwich, showing the' position of the potstones. 
 
 other, but usually from 20 to 30 feet apart, though sometimes nearer 
 together, as in the above sketch. These rows did not terminate 
 downwards in any instance which I could examine, nor upwards, 
 except at the point, where they were cut off abruptly by the bed of 
 gravel. On breaking open the potstones, I found an internal cylin- 
 drical nucleus of pure chalk, much harder than the ordinary sur- 
 rounding 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 potstones were much farther apart from each other. Dr. Buckland 
 has described very similar phenomena as characterizing the white 
 chalk on the north coast of Antrim, in Ireland.* 
 
 FOSSILS OF THE UPPER CRETACEOUS ROCKS. 
 
 Among the fossils of the white chalk, echinoderms are very nu- 
 
 Fig. 253. 
 
 i, 
 
 Ananchytes ovatus. White chalk, upper and lower. 
 
 a. Side view. 
 
 b. Bottom of the shell on which both the oral and anal apertures are placed ; 
 
 the anal being more round, and at the smaller end. 
 
 Geol. Trans., First series, vol. iv. p. 413., " On Paramoudra, &c. 
 R 3 
 
246 
 
 FOSSILS OF UPPER CRETACEOUS ROCKS. [Cn. XVII. 
 
 merous ; and some of the genera, like Ananckytes (see fig. 253.), 
 are exclusively cretaceous. Among the Crinoidea, the Marsupite 
 
 Fig. 254. 
 
 Fig. 255. 
 
 Micrastes cor angumum. 
 White chalk. 
 
 Galeritex albogalerus, Lam. 
 White chalk. 
 
 (fig. 260.) is a characteristic genus. Among the mollusca, the cepha- 
 lopoda, or chambered univalves, of the genera Ammonite, Scaphite, 
 Belemnite, (fig. 256.) Baculite, (257. 259.) and Turrilite, (262, 263.) 
 with other allied forms, present a great contrast to the testacea of 
 the same class in the tertiary and recent periods. 
 
 Fig. 256. 
 
 a. Pelemm'tes mucronatus. 
 
 b. Same, showing internal structure. Maestricht, Faxoe, and white chalk. 
 
 Fig. 257. 
 
 Baculites anceps. Upper green sand, or chloritic marl, craie chloride. France. 
 A. D'Orb. Terr. Crot. 
 
 Fig. 258. 
 
 Fig. 259. 
 
 Portion of Baculites Fanjasii. 
 Maestricht and Faxoe beds and white chalk. 
 
 Fig. 260. 
 
 Portion of ~Raculit.es anceps. 
 Maestricht and Faxoe beds and white chalk. 
 
 Fig. 261. 
 
 Marmpiles Milleri. 
 White chalk. 
 
 Scaphites cequalis. Chloritic 
 
 marl of Upper Green Sand, 
 
 Dorsetshire. 
 
CH. XVII.] FOSSILS OF UPPER CRETACEOUS ROCKS. 
 
 Fig. 262. Fig. 263. 
 
 a 
 
 247 
 
 i. Fragment of Tnrrilites cosfattis, 
 Chalk marl. 
 
 Turrilitrs costatus, 
 Chalk 
 
 b. Same, showing the indented border 
 of the partition of the chambers. 
 
 Among the brachiopoda in the white chalk, the Terebratula are 
 very abundant. These shells are known to live at the bottom of the 
 
 Fig. 264. 
 
 Fig. 265. 
 
 Fig. 266. 
 
 Fig. 267. 
 
 Terebratrila Defrancii. Terebratula Terebratula pumilus. Terebratula 
 
 Upper white chalk. octnplicata. (Magas pumilus. Sow.) cornea. 
 
 ( Var. of T. plicatilis.) Upper white chalk. Upper white chalk. 
 Upper white chalk. 
 
 sea, where the water is tranquil and of some depth (see figs. 264. 
 265, 266, 267, 268.). With these are associated some forms of oyster 
 
 Fig. 268. 
 
 Fig. 269 
 
 Fig. 270. 
 
 Terebratula biplicata, 
 Sow. Upper cretaceous. 
 
 Crania Parisiensts, 
 inferior or attached 
 
 valve. 
 Upper white chalk. 
 
 Pecten Beaveri. reduced to 
 
 one-third diameter. 
 
 Lower white chalk and chalk 
 
 marl. Maidstone. 
 
 (see figs. 275, 276, 277.), and other bivalves (figs. 269, 270, 271, 
 272, 273.). 
 
 Among the bivalve mollusca, no form marks the cretaceous era in 
 Europe, America, and India in a more striking manner than the 
 extinct genus Inoceramus (Catillus of Lara. : see fig. 274.), the shells 
 
 R 4 
 
248 
 
 FOSSILS OF UPPER CRETACEOUS ROCKS. [Cn. XVII. 
 
 of which are distinguished by a fibrous texture, and are often met 
 with in fragments, having, probably, been extremely friable. 
 
 Fig. 271. 
 
 Fig. 272. 
 
 Fig. 273. 
 
 Pecten 5-costatus. 
 
 White chalk, upper and 
 
 lower greensands. 
 
 Plagiostoma Hoperi, Sow. 
 
 Syn. Lima Hoperi. 
 
 White cnalk and upper 
 
 greensand. 
 
 Plagiostoma spinosum, Sow. 
 
 Syn. Spondylus spinosus. 
 
 Upper white chalk. 
 
 Of the singular family called Rudistes, by Lamarck, hereafter to 
 be mentioned as extremely characteristic of the chalk of Southern 
 
 ; Fig. 274. 
 
 Fig. 275. 
 
 Inoceramus Lamarckit. 
 
 Syn. Catillus Lamarckii. 
 
 White Chalk (Dixon's Geol. Sussex. Tab. 28. 
 
 fig. 29.)- 
 
 Ostrca vesicular is. Syn. Gryp/Hcn globosa. 
 Upper chalk and upper greeusaud. 
 
 Europe, a single representative only (fig. 278.) has been discovered in 
 the white chalk of England. 
 
 Fig. 276. 
 
 Fig. 277. 
 
 Oxlrca columba. 
 
 Byn. Grypheea columba. 
 
 Upper greensand. 
 
 Oslrea carinata. Chalk marl, upper and 
 lower greensand. 
 
CH. XVII.] MOLLUSC A, BRYOZOA, SPONGES. 
 
 Fig. 279. 
 
 249 
 
 Radiolties Mortoni, Man tell. Houghton, Sussex. White chalk. 
 
 Diameter one-seventh nat. size. 
 Fig. 278. Two individuals deprived of their upper valves, adhering together. 
 
 279. Same seen from above. 
 
 280. Transverse section of part of the wall of the shell, magnified to show the structure. 
 
 281. Vertical section of the same. 
 
 On the side where the shell is thinnest, there is one external furrow and corresponding internal 
 ridge, a, b, figs. 278, 279.; but they are usually less prominent than in these figures. This species 
 was first referred by Mantell to Hippurites, afterwards to the genus Radiolites. I have never seen 
 the upper valve. The specimen above figured was discovered by the late Mr. Dixon. 
 
 With these mollusca are associated many Bryozoa, such as Es- 
 chara and Escharina (figs. 282, 283.), which are alike marine, 
 
 Fig. 282. 
 
 Eschara disticha. 
 
 a. Natural size. 
 
 b. Portion magnified. 
 
 White chalk. 
 
 Fig. 283. 
 
 Fig. 284. 
 
 Esckarina oceani. 
 
 a. Natural size. 
 
 b. Part of the same magnified. White 
 
 chalk. 
 
 Ventricutiles radiatus. 
 
 Mantell. 
 
 Svn. Ocellaria radiata, 
 D'Orb. White chalk. 
 
 and, for the most part, indicative of a deep sea. These and other 
 organic bodies, especially sponges, such as Ventriculites (fig. 284. 
 
250 FOSSILS OP UPPER CRETACEOUS BEDS. [Cn. XVII. 
 
 and Siphonia (fig. 286.), are dispersed indifferently through the 
 soft chalk and hard flint, and some of the flinty nodules owe their ir- 
 regular forms to inclosed sponges, such as fig. 285. a., where the hol- 
 lows in the exterior are caused by the branches of a sponge, seen on 
 breaking open the flint (fig. 285. b.). 
 
 Fig. 286. 
 
 Fig. 285. 
 
 A branching sponge in a flint, from the white chalk. 
 From the collection of Mr. Bowerbarik. 
 
 Siphonia pyri- 
 
 formis. 
 Chalk marl. 
 
 The remains of fishes of the Upper Cretaceous formations consist 
 chiefly of teeth of the shark family of genera, in part common to the 
 
 Fig. 287, 
 
 Palatal tooth of 
 
 Ptychodus decurrens. 
 
 Lower white chalk. 
 
 Maidstone. 
 
 Cextracion Phillippi ; recent. 
 Port Jackson. Bucklatid, Bridgewater Treatise, pi. 27. d. 
 
 tertiary, and partly distinct. To the latter belongs the genus 
 Ptychodus (fig. 287.), which is allied to the living Port Jackson 
 
CH. XVII.] UPPER GREEN SAND. 251 
 
 Shark, Cestracion Phillippi, the anterior teeth of which (see fig. 288. a) 
 are sharp and cutting, while the posterior or palatal teeth (b) are flat, 
 and analogous to the fossil (fig. 287.). 
 
 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 in leading 
 us to conclude that the white chalk was the product of an open sea 
 of considerable depth. 
 
 The existence of turtles and oviparous saurians, and of a Ptero- 
 dactyl or winged-lizard, found in the white chalk of Maidstone, im- 
 plies, no doubt, some neighbouring land ; but a few small islets in 
 mid-ocean, like Ascension, formerly so much frequented by migratory 
 droves of turtle, might perhaps have afforded the required retreat 
 where these creatures 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 indication, but it consisted 
 partly of cycadeous plants ; for a fragment of one of these was found 
 by Capt. Ibbetson in the chalk 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 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 mis- 
 taken by able anatomists for those of birds ; of which class no osseous 
 remains seem as yet to have been derived from the chalk, or indeed 
 from any secondary or primary formation, except perhaps the Wealden. 
 
 Upper greensand (Table, p. 105. &c.). The lower chalk without 
 flints passes gradually downwards, in the south of England, into an 
 argillaceous limestone, " the chalk marl," already alluded to, in 
 which ammonites and other cephalopoda, so rare in the higher parts 
 of the series, appear. This marly deposit passes in its turn into beds 
 called the Upper Greensand, containing green particles of sand 
 of a chloritic mineral. In parts of Surrey, calcareous matter is 
 largely intermixed, forming a stone called firestone. In the cliffs 
 of the southern coast of the Isle of Wight, this upper greensand is 
 100 feet thick, and contains bands of siliceous limestone and calca- 
 reous sandstone with nodules of chert. 
 
 The Upper Greensand is regarded by Mr. Austen and Mr. D. 
 Sharpe, as a littoral deposit of the Chalk Ocean, and, therefore, con- 
 temporaneous with part of the chalk marl, and even, perhaps, with 
 some part of the white chalk. For as the land went on sinking, and 
 the cretaceous sea widened its area, white mud and chloritic sand 
 were always forming somewhere, but the line of sea-shore was 
 perpetually varying its position. Hence, though both sand and 
 mud originated simultaneously, the one near the land, the other far 
 from it, the sands in every locality where a shore became submerged, 
 might constitute the underlying deposit. 
 
 Gault. The lowest member of the upper Cretaceous group, usually 
 about 100 feet thick in the S.E. of England, is provincially termed 
 
252 THE BLACKDOWN BEDS. [Cn. XVII. 
 
 Gault. It consists of a dark blue marl, sometimes intermixed with 
 greensand. Many peculiar forms of cephalopoda, such as the Hamite 
 
 Fossils of the Upper Greensand. 
 Fig. 280. 
 
 Fig. 290. 
 
 a. Terebratula lyra. ~t Upper greensand. 
 
 b. Same, seen in profile, j France. 
 
 Fig. 291. 
 
 Ammonites Ehotomagcnsis. 
 Upper greensand. 
 
 Hamiles sptniger (Fitton) ; near Folkstone. Gault. 
 
 (fig. 291.) and Scaphite, with other fossils, characterize this form- 
 ation, which, small as is its thickness, can be traced by its organic 
 remains to distant parts of Europe, as, for example, to the Alps. 
 
 The Blackdown beds in Dorsetshire, celebrated for containing 
 many species of fossils not found elsewhere, hare been commonly 
 referred to the Upper Greensand, which they resemble in mineral 
 character; but Mr. Sharpe has suggested, and apparently with 
 reason, that they are rather the equivalent of the Gault, and were 
 probably formed on the shore of the sea, in the deeper parts of 
 which the fine mud called Gault was deposited. Several Blackdown 
 species are common to the Lower cretaceous series, as, for ex- 
 ample, Trigonia caudata, fig. 299. We learn from M. D'Archiac, 
 that in France, at Mons, in the valley of the Loire, strata of green- 
 sand occur of the same age as the Blackdown beds, and containing 
 many of the same fossils. They are also regarded as of littoral 
 origin by M. D'Archiac.* 
 
 The phosphate of lime, found near Farnham, in Surrey, in such 
 abundance as to be used largely by the agriculturist for fertilizing 
 soils, occurs exclusively, according to Mr. R. A. C. Austen, in the 
 upper greensand and gault. It is doubtless of animal origin, and 
 partly coprolitic, probably derived from the excrement of fish. 
 
 * Hist, des Progres de la Geol., &c., vol. iv. p. 360., 1851. 
 
CH. XVII.] 
 
 HIPPURITE LIMESTONE. 
 
 253 
 
 2 - 
 
 HIPPURITE LIMESTONE. 
 
 Difference between the chalk of the north and south of Europe. 
 By the aid of the three tests of relative age, namely, superposition, 
 mineral character, and fossils, the geologist has been enabled to refer 
 to the same Cretaceous period certain rocks in the north and south 
 of Europe, which differ greatly, both in their fossil contents and in 
 their mineral composition and structure. 
 
 If we attempt to trace the cretaceous deposits from England and 
 France to the countries bordering the Mediterranean, we perceive, 
 in the first place, that the chalk and greensand in the neighbourhood 
 of London and Paris form one great continuous 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. 292., in which the shaded part 
 represents chalk). 
 
 Between Poitiers and La Rochelle, 
 the space marked A on the map sepa- 
 rates two regions of chalk. This space 
 is occupied by the Oolite and certain 
 other formations older than the Chalk, 
 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 a formation which 
 we at once recognize by its mineral 
 character to be chalk, although there 
 are some places where the rock becomes 
 oolitic. The fossils are, upon the whole, 
 very similar ; especially certain species 
 of the genera Spatangus, Ananchytes, 
 CidariteSy Nucula, Ostrea, Gryphcea 
 (Exogyra), Pecten, Plagiostoma (Lima), 
 Trigonia, Catillus (Inoceramus), and 
 Terebratula* But Ammonites, as M. 
 d'Archiac observes, of which so many species are met with in the 
 chalk of the north of France, are scarcely ever found in the southern 
 region ; while the genera Samite, Turrilite, and Scaphite, and per- 
 haps 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, Sphcerulites, and other mem- 
 bers of that great family of mollusca called Rudistes 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 
 
 * D'Arehiac, sur la Form. Cretacee du S. O. de la France, Mem. de la Soc. Geol. 
 de France, torn. ii. 
 
254 
 
 CHALK OF SOUTH OF EUROPE. 
 
 . XVII. 
 
 the south of France, Spain, Sicily, Greece, and other countries border- 
 ing the Mediterranean. 
 
 Fig. 293. 
 
 Fig. 294. 
 
 a. Radiolites radiosus, D'Orb. (Hippurites, Lam.) 
 
 b. Upper valve of same. 
 
 White chalk of France. 
 
 Fig. 295. 
 
 Radiolites foliaceus, D'Orb. 
 Syn. Sptia:ruli/es agarici- 
 
 formis, Blainv. 
 White chalk of France. 
 
 Hippurites organisans, Desmoulins, 
 
 Upper chalk: chalk marl of Pyrenees ?* 
 
 . Young individual ; when full grown they occur in groups adhering 
 
 laterally to each other. 
 
 6. Upper side of the upper valve, showing a reticulated structure in 
 those parts, b, where the external coating is worn off. 
 
 c. Upper end or opening of the lower and cylindrical valve 
 
 d. Cast of the interior of the lower conical valve. 
 
 The species called Hippurites organisans (fig. 295.) is more abun- 
 dant than any other in the south of Europe ; and the geologist should 
 make himself well acquainted with the cast d, which is far more 
 common in many compact marbles of the upper cretaceous period 
 than the shell itself, this having often wholly disappeared. The 
 flutings, or smooth, rounded, longitudinal ribs, representing the form 
 of the interior, are wholly unlike the Hippurite itself, and in some 
 individuals attain a great size and length. 
 
 Between the region of chalk last mentioned, in which Perigueux 
 is situated, and the Pyrenees, the space B intervenes. (See Map, 
 
 D'Orbigny's Paleoritologie Frangaise, pi. 533. 
 
CH. XVII.] CRETACEOUS ROCKS. 255 
 
 fig. 292.). Here the tertiary strata cover, and for the most part con- 
 ceal, the cretaceous rocks, except in some spots where they have been 
 laid open by the denudation of the newer formations. In these places 
 they are seen still preserving the form of a white chalky rock, which 
 is charged in part with grains of greensand. Even as far south as 
 Tercis, on the Adour, near Dax, cretaceous rocks retain this cha- 
 racter where I examined them in 1828, and where M. Grateloup 
 has found in them Ananchytes ovata (fig. 253.), and other fossils of 
 the English chalk, together with Hippurit.es. 
 
 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 our Upper 
 Cretaceous system ; which we can, nevertheless, recognize as refer- 
 able, paleontologically, to the same division. 
 
 That they were about the same age generally as the European 
 chalk and greensand, was the conclusion to which Dr. Morton and 
 Mr. Conrad came after their investigation of the fossils in 1834. 
 The strata consist chiefly of greensand and green marl, with an over- 
 lying coralline limestone of a pale yellow colour, 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 iden- 
 tical with European species Ostrea larva, 0. vesicularis, Gryphcea 
 costata, Pecten quinque-costatus, Belemnites mucronatus. 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 are different, the generic forms, such as the 
 Baculite and certain sections of Ammonites, as also the Inoceramus 
 (see above, fig. 274.) and other bivalves, have a decidedly cretaceous 
 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 difference 
 of ten degrees in the latitude of the places compared on opposite sides 
 of the Atlantic.* 
 
 Fish of the genera Lamna, Galeus, and Carcharodon are common 
 to New Jersey and the European cretaceous rocks. So also is the 
 genus Mosasaurus among reptiles. The vertebra of a Plesiosaurus, 
 a reptile known in the English chalk, had often been cited on the 
 authority of Dr. Harlan as occurring in the cretaceous marl, at 
 Mullica Hill, in New Jersey. But Dr. Leidy has since shown that 
 the bone in question is not saurian but cetaceous, and whether it can 
 truly lay claim to the high antiquity assigned to it, is a point still 
 open to discussion. The discovery of another mammal of the seal 
 
 * See a paper by the author, Quart. Journ. Geol. Soc. vol. i. p. 79. 
 
256 CRETACEOUS ROCKS. CH. XVII. 
 
 tribe ( Stenorhynchus vetus, Leidy), from a lower bed in the cretaceous 
 series in New Jersey, appears to rest on better evidence.* 
 
 From New Jersey the cretaceous formation extends southwards to 
 North Carolina and Georgia, cropping out at intervals from beneath 
 the tertiary strata, between the Appalachian Mountains and the 
 Atlantic. They then sweep round the southern extremity of that 
 chain, in Alabama and Mississippi, and stretch northwards again to 
 Tennessee and Kentucky. They have also been traced far up the 
 valley of the Missouri, as far north as lat. 48, or to Fort Mandan ; 
 so that already the area which they are ascertained to occupy in 
 North America may perhaps equal their extent in Europe, and 
 exceeds that of any other fossiliferous formation in the United 
 States. So little do they resemble mineralogically the European 
 white chalk, that in North America, limestone is upon the whole, an 
 exception to the rule ; and, even in Alabama, where I saw a calca- 
 reous member of this group, composed of marl-stone, it was more 
 like the English and French Lias than any other European secondary 
 deposit. 
 
 At the base of the system in Alabama, I found dense masses of 
 shingle, perfectly loose and unconsolidated, derived from the waste of 
 paleozoic (or carboniferous) rocks, a mass in no way distinguishable, 
 except by its position, from ordinary alluvium, but covered with 
 marls abounding in Inocerami. 
 
 In Texas, according to F. Romer, the chalk assumes a new litho- 
 logical type, a large portion of it consisting of hard siliceous lime- 
 stone, but the organic remains leave no doubt in regard to its age, the 
 Baculites anceps and ten other European species occurring there. 
 
 In South America the cretaceous strata have been discovered in 
 Columbia, as at Bogota and elsewhere, containing Ammonites, Ha- 
 mites, Inocerami, and other characteristic shells, f 
 
 In the South of India, also, at Pondicherry, Verdachellum, and 
 Trinconopoly, Messrs. Kaye and Egerton have collected fossils be- 
 longing to the cretaceous system. Taken in connection with those 
 from the United States, they prove, says Prof. E. Forbes, that those 
 powerful causes which stamped a peculiar character on the forms of 
 
 * In the Principles of Geology, ninth makes the point rather doubtful. The 
 
 ed. p. 145., I cited Dr. Leidy of Phi- tooth of Stenorhynchus vetus, figured by 
 
 ladelphia as having described (Pro- Leidy from a drawing of Conrad's 
 
 ceedings of Acad. Nat. Sci. Philad., (Proceed, of Acad. Nat. Sci. Philad. 
 
 1851) two species of cetacea of a new 1853, p. 377.), was found by Samuel E. 
 
 genus which he called Priscodelphinus, Wetherill, Esq., in the greensand l miles 
 
 from the greensand of New Jersey. In south-east of Burlington. This gentle- 
 
 1853, I saw the two vertebrae at Phila- man related to me and Mr. Conrad, in 
 
 delphia on which this new genus was 1853, the circumstances under which he 
 
 founded, and afterwards, with the aid of met with it, associated with Ammonites 
 
 Mr. Conrad, traced one of them to a placenta, Ammonites Delawarensis, 
 
 Miocene marl pit in Cumberland county Trigonia thoracica, &c. The tooth has 
 
 New Jersey. The other (the Plesiosaurus been mislaid, but not until it had excited 
 
 of Harlan), labelled " Mullica Hill " in much interest and had been carefully 
 
 the Museum, would no doubt be an upper examined by good zoologists, 
 
 cretaceous fossil, if really derived from t Proceedings of the Geol. Soc. vol. iv. 
 
 that locality, but its mineral condition p. 391. 
 
CH. XVIII.] LOWER GREENSAND. 257 
 
 marine animal life at this period, exerted their full intensity through 
 the Indian, European, and American seas. * Here, as in North and 
 South America, the cretaceous character can be recognized even 
 where there is no specific identity in the fossils ; and the same may 
 be said of the organic type of those rocks in Europe and India which 
 occur next to the chalk in the ascending and descending order, 
 namely the Eocene and the Oolitic, 
 
 CHAPTER XVIH. 
 
 LOWER CRETACEOUS AND WEALDEN FORMATIONS. 
 
 Lower Greensand Term "Neocomian" Atherfield section, Isle of Wight 
 Fossils of Lower Greensand Wealden Formation Freshwater strata in- 
 tercalated between two marine groups Weald Clay and Hastings Sand 
 Fossil shells, fish, and plants of Wealden Their relation to the Cretaceous 
 type Geographical extent of Wealden Movements in the earth's crust to 
 which the Wealden owed its origin and submergence Flora of the Lower 
 Cretaceous and Wealden Periods. 
 
 THE term "Lower Greensand" has hitherto been most commonly 
 applied to such portions of the Cretaceous series as are older than the 
 Gault. But the name has often been complained of as inconvenient, 
 and not without reason, since green particles are wanting in a large 
 part of the strata so designated, even in England, and wholly so in 
 some European countries. Moreover, a subdivision of the Upper 
 Cretaceous group has likewise been called Greensand, and to prevent 
 confusion the terms Upper and Lower Greensand were introduced. 
 Such a nomenclature naturally leads the uninitiated to suppose that 
 the two formations so named are of somewhat co-ordinate value, which 
 is so far from being true, that the Lower Greensand, in its widest 
 acceptation, embraces a series nearly as important as the whole Upper 
 Cretaceous group, from the Gault to the Maestricht beds inclusive ; 
 while the Upper Greensand is but one subordinate member of this 
 same group. Many eminent geologists have, therefore, proposed the 
 term " Neocomian " as a substitute for Lower Greensand ; because, 
 near Neufchatel (Neocomum), in Switzerland, these Lower Green- 
 sand strata are well developed, entering largely into the structure of 
 the Jura mountains. By the same geologists the Wealden beds are 
 usually classed as " Lower Neocomian," a classification which will 
 not appear inappropriate when we have explained, in the sequel, the 
 intimate relation of the Lower Greensand and Wealden fossils. 
 
 Dr. Fitton, to whom we are indebted for an excellent monograph 
 on the Lower Cretaceous Cor Greensand) formation as developed in 
 
 * See Forbes, Quart. Geol. Journ. vol. i. p. 79. 
 S 
 
' 258 ATHERFIELD SECTION, ISLE OF WIGHT. [Cn. XVIII. 
 
 England, gives the following as the succession of rocks seen in parts 
 of Kent. 
 
 No. 1. Sand, white, yellowish, or ferruginous, with concretions 
 
 of limestone and chert - - - 70 feet. 
 
 2. Sand with green matter - . ';* , ; , - 70 to 100 feet. 
 
 3. Calcareous stone, called Kentish rag ' t - - - 60 to 80 feet. 
 
 In his detailed description of the fine section displayed at Ather- 
 field, in the south of the Isle of Wight, we find the limestone wholly 
 wanting ; in fact, the variations in the mineral composition of this 
 group, even in contiguous districts, is very great ; and on comparing 
 the Atherfield beds with corresponding strata at Hythe in Kent, 
 distant 95 miles, the whole series presents a most dissimilar aspect.* 
 
 On the other hand, Professor E. Forbes has shown that when the 
 sixty-three strata at Atherfield are severally examined, the total 
 thickness of which he gives as 843 feet, there are some fossils which 
 range through the whole series, others which are peculiar to parti- 
 cular divisions. As a proof that all belong chronologically to one 
 system, he states that whenever similar conditions are repeated in 
 overlying strata the same species reappear. 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 nothing to 
 do with the extinction, throughout a large area, of certain animals or 
 plants. The rule laid down by this eminent naturalist for enabling 
 us to test the arrival of a new state of things in the animate world, 
 is the representation by new and different species of corresponding 
 genera of mollusca or other beings. When the forms proper to 
 loose sand or soft clay, or a stony or calcareous bottom, or a moderate 
 or a great depth of water, recur with all the same species, the 
 interval of time has been, geologically speaking, small, however 
 dense the mass of matter accumulated. But if, the genera remaining 
 the same, the species are changed, we have entered upon a new 
 period ; and no similarity 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. On passing from the Lower Greensand to the Gault, 
 we suddenly reach one of these new epochs, scarcely any of the 
 fossil species being common to the lower and upper cretaceous 
 systems, a break in the chain implying no doubt many missing links 
 in the series of geological monuments, which we may some day be 
 able to supply. 
 
 One of the largest and most abundant shells in the lowest strata 
 of the Lower Greensand, as displayed in the Atherfield section, is 
 
 * Dr. Fitton, Quart. Geol. Journ., able table showing the vertical range of 
 vol. i. p. 179., ii. p. 55., and iii. p. 289., the various fossils of the lower green- 
 where comparative sections and a valu- sand at Atherfield are given. 
 
CH. XVIII.] FOSSILS OF LOWER GREENSAND. 
 
 259 
 
 the large Perna Mulleti, of which a reduced figure is here given 
 (fig. 296.). 
 
 Fig. 29G. 
 
 Perna Mulleti. Desh. in Leym. 
 a. Exterior. b. Part of hinge of upper valve. 
 
 In the south of England, during the accumulation of the Lower 
 Green sand above described, the bed of the sea appears to have been 
 continually sinking, from the commencement of the period, when the 
 freshwater Wealden beds were submerged, to the deposition of those 
 strata on which the gault immediately reposes. 
 
 Pebbles of quartzose sandstone, jasper, and flinty slate, together 
 with grains of chlorite and mica, speak plainly of the nature of the 
 pre-existing rocks, from the wearing down of which the Greensand 
 beds were derived. The land, consisting of such rocks, was doubt- 
 less submerged before the origin of the white chalk, a deposit which 
 originated in a more open sea, and in clearer waters. 
 
 The fossils of the Lower Cretaceous are for the most part speci- 
 fically distinct from those of the Upper Cretaceous strata. 
 
 Among the former we often meet with the genus Scaphites (fig. 297.) 
 
 Fig. 297. 
 
 Fig. 298. 
 
 Scaphites gigas, So 
 
 Syn. Ancyloceras gigas, D'Orb. 
 3 2 
 
 Nautilus plicatns, Sow., in 
 Fitton's Monog. 
 
260 
 
 WEALDEN FORMATION. 
 
 [CH. XVIII. 
 
 or Ancyloceras, which has been aptly described as an ammonite more 
 or less uncoiled ; also a furrowed Nautilus., N. plicatus (fig. 298.), Tri- 
 gonia caudata, likewise found in the Blackdown beds (see above, 
 p. 252.), and Gervillia, a bivalve genus allied to Avicula. 
 
 Fig. 299 
 
 Fig. 300. 
 
 Trigonia caudata, Agass. 
 
 Gervillia anceps, Desh. 
 
 Fig. 
 
 Terebratula tella, Sow 
 
 WEALDEN FORMATION. 
 
 Beneath the Lower Greensand in the S. E. of England, a. fresh- 
 water formation is found, called the Wealden (see Nos. 5 and 6. Map, 
 fig. 320. p. 273.), which, although it occupies a small horizontal area 
 in Europe, as compared to the White Chalk and Greensand, is never- 
 theless of great geological interest, since the imbedded remains give 
 us some insight into the nature of the terrestrial fauna and flora 
 of the Lower Cretaceous epoch. The name of Wealden was given 
 to this group because it was first studied in parts of Kent, Surrey, 
 and Sussex, called the Weald (see Map, p. 273.); and we are 
 indebted to Dr. Man tell 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, Belem- 
 nites, Terebratulae, Echinites, 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 Paludinae, Melanise, 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 the infra-position of a 
 dense mass of purely freshwater origin to a deep-sea deposit (a phe- 
 nomenon with which we have since become familiar) was received, 
 at first, with no small doubt and incredulity. But the relative po- 
 sition- of the beds is unequivocal; the Weald Clay being distinctly 
 seen to pass beneath the Lower Greensand in various parts of Surrey, 
 Kent, and Sussex, and to re-appear in the Isle of Wight at the base 
 of the Cretaceous Series, being, no doubt, continuous far beneath the 
 surface, as indicated by the dotted lines in the annexed diagram, 
 fig. 302. 
 
 Fig. 302. 
 Isle of Wight. 
 
 Hants. 
 
 Sussex. 
 
 a. Chalk. b. Greensand. c. Weald Clay. d. Hastings Sand. e. Purbeck beds. 
 
CH. XVIII.] WEALD CLAY. 261 
 
 The Wealden is divisible into two minor groups : 
 
 Thickness. 
 1st. Weald Clay, chiefly argillaceous, hut sometimes including 
 
 thin beds of sand and shelly limestone with Paludina 140 to 280 ft. 
 2d. Hastings Sand, chiefly arenaceous, but in which occur 
 
 some clays and calcareous grits* - 400 to 1000 ft. 
 
 Another freshwater formation, called the Purbeck, consisting of 
 various limestones and marls, containing distinct species of molluscs, 
 Cyprides, and other fossils, lies immediately beneath the Wealden in 
 the south-east of England. As it is now found to be more nearly 
 related, by its organic remains, to the Oolitic than to the Cretaceous 
 Series, it will be treated of in the 20th Chapter. 
 
 Weald Clay. 
 
 The upper division, or Weald Clay, is of purely freshwater origin. 
 Its highest beds are not only conformable, as Dr. Fitton observes, to 
 the inferior strata of the Lower Greensand, but of similar mineral 
 composition. To explain this, we may suppose, that, as the delta of 
 a great river was tranquilly subsiding, so as to allow the sea to en- 
 croach upon the space previously occupied by fresh water, the river 
 still continued to carry down the same sediment into the sea. In 
 confirmation of this view it may be stated, that the remains of the 
 Iguanodon Mantelli, a gigantic terrestrial reptile, very characteristic 
 of the Wealden, has been discovered near Maidstone, in the overlying 
 Kentish rag, or marine limestone of the Lower Greensand. Hence 
 we may infer, that some of the saurians which inhabited the country 
 of the great river continued to live when part of the country had 
 become submerged beneath the sea. Thus, in our own times, we 
 may suppose the bones of large alligators to be frequently entombed 
 in recent freshwater 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 Ganges might 
 still pour down its turbid waters in the same direction, and carry 
 seaward the carcases 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, has left more of 
 its remains in the Wealden strata of the south-eastern counties and 
 Isle of Wight than has any other genus of associated saurians. It 
 was an herbivorous reptile, and regarded by Cuvier as more extra- 
 ordinary than any with which he was acquainted ; for the teeth, 
 though bearing a great analogy, in their general form and crenated 
 edges (see figs. 303. ., 303. b.), to the modern Iguanas which now 
 frequent the tropical woods of America and the West Indies, ex- 
 hibit many striking and important differences. It appears that they 
 have often been worn by the process of mastication ; whereas the 
 
 * Dr. Fitton, Geol. Trans. Second Series, vol. iv. p. 320. 
 B 3 
 
262 
 
 FOSSILS OF THE 
 
 [Cn. XVIII. 
 
 existing herbivorous reptiles clip and gnaw off the vegetable pro- 
 ductions on which they feed, but do not chew them. Their teeth 
 frequently present an appearance of having been chipped off, but 
 never, like the fossil teeth of the Iguanodon, have a flat ground 
 surface (see fig. 304. b.\ resembling the grinders of herbivorous 
 
 Fig. 303. Fig. 304. 
 
 Fig. 303. a, b. Tooth of Iguanodon ManteUi. 
 Fig. 304. a. Partially worn tooth of young individual of the same. 
 b. Crown of tooth in adult, worn down. (Mantell.) 
 
 mammalia. Dr. Mantell 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 individuals, 
 varying in age and magnitude from the reptile just burst from the 
 egg, to one of which the femur measured 24 inches in circum- 
 ference. 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 individuals had been found, that a solitary example of 
 part of a jaw-bone was obtained. More recently remains both of the 
 upper and lower jaw have been met with in the Hastings Beds in 
 Tilgate Forest. Their size was somewhat greater than had been 
 anticipated, and Dr. Mantell, who does not agree with Professor 
 Owen that the tail was short, estimates the probable length of some 
 of these saurians at between 50 and 60 feet. The largest femur yet 
 found measures 4 feet 8 inches in length, the circumference of the 
 shaft being 25 inches, and, if measured round the condyles, 42 inches. 
 
 Occasionally bands of limestone, called Sussex Marble, occur in 
 the Weald Clay, almost entirely composed of a species of Paludina, 
 closely resembling the common P. vivipara of English rivers. 
 
 Shells of the Cypris, a genus of Crustaceans before mentioned 
 (p. 31.) as abounding in lakes and ponds, are also plentifully scat- 
 tered through the clays of the Wealden, sometimes producing, like 
 plates of mica, a thin lamination (see fig. 307.). Similar cypris- 
 bearing marls are found in the lacustrine tertiary beds of Auvergne 
 (see above, p. 200.). 
 
CH. XVIII.] 
 
 Fig. 305. 
 
 WEALDEN GROUP. 
 
 Fig. 306. 
 
 263 
 
 Cypris Valdensis, Fitton. 
 (C.faba, Min. Con. 485.) 
 
 Weald clay with Cyprides. 
 
 Hastings Sands. 
 
 This lower division of the Wealden consists of sand, calciferous 
 grit, clay, and shale ; the argillaceous strata, notwithstanding the 
 name, being nearly in the same proportion as the arenaceous. The 
 calcareous sandstone and grit of Tilgate Forest, near Cuckfield, in 
 which the remains of the Iguanodon and Hylseosaurus were first 
 found, constitute an upper member of this formation. The white 
 " sand-rock " of the Hastings cliffs, about 100 feet thick, is one of 
 the lower members of the same. The reptiles, which are very abun- 
 dant in this division, consist partly of saurians, already referred by 
 Owen and Mantell to eight genera, among which, besides those 
 already enumerated, we find the Megalosaurus and Plesiosaurus. 
 The Pterodactyl also, a flying reptile, is met with in the same strata, 
 and many remains of Chelonians of the genera Trioynx and Emys, 
 now confined to tropical regions. 
 
 The fishes of the Wealden are chiefly referable to the Ganoid and 
 Placoid orders. Among them the teeth and scales of Lepidotus are 
 most widely diffused (see fig. 308.). These ganoids were allied to 
 
 Fig. 308. 
 
 Lepidotus Mantelli, Agass. Wealden. 
 a. palate and teeth. b. side view of teeth. c. scale. 
 
 the Lepidosteus, or Gar-pike, of the American rivers. The whole 
 body was covered with large rhomboidal scales, very thick, and 
 having the exposed part coated with enamel. Most of the species of 
 this genus are supposed to have been either river-fish, or inhabitants 
 of the sea at the mouth of estuaries. 
 
 The shells of the Hastings beds belong to the genera Melanopsis, 
 Melania, Paludina, Cyrena, Cyclas, Unio (see fig. 309.), 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 (see fig. 310.), Mytilus, and Ostrea occur; 
 
 s 4 
 
264 
 
 WEALDEN FOSSILS. 
 
 [Cn. XVIII. 
 
 Fig. 309. 
 
 Fig. 310. 
 
 Corbi/la alata, Fitton. Magnified. 
 In brackish-water beds of the Hastings 
 Sands, Punfield Bay. 
 
 Unio Valdensis, Mant. 
 
 Isle of Wight and Dorsetshire ; in the lower beds 
 of the Hastings Sands. 
 
 and in some places this bed becomes purely marine, the species 
 being for the most part peculiar, but several of them well-known 
 Lower Greensand fossils, among which Ammonites Deshayesii may 
 be mentioned. These facts show how closely related were the faunas 
 of the Wealden and Cretaceous periods. 
 
 At different heights in the Hastings Sand, 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, near Horsham, there are indications of this clay 
 having been exposed so as to dry and crack before the next layer 
 was 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. 311.). 
 
 Fig. 311. 
 
 Underside of slab of sandstone about one yard in diameter. 
 Stammerham, Sussex. 
 
 Near the same place a reddish sandstone occurs in which are 
 innumerable traces of a fossil vegetable, apparently Sphenopteris, 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 gently deposited upon and around them ; and similar 
 
CH. XVIII.] AREA OF THE WEALDEN. 265 
 
 appearances have been remarked in other places in this forma- 
 Fig.3i2. tion.* In the same division also of 
 
 the Wealden, at Cuckfield, 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, 
 (Fitton), from the notwithstanding the great thickness of 
 
 Hastings Sands near Tunbridge Wells. , . ,. . . , -nf^ , , .-, , , 
 
 a. a portion of the same magnified. thlS ^Vision of the Wealden, the whole 
 
 of it was a deposit in water of a mo- 
 derate depth, and often extremely shallow. This idea may seem 
 startling at first, yet such would be the natural consequence of a 
 gradual and continuous 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 deep- 
 ened, 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 water, or overgrown for a 
 season by a vegetation proper to marshes. 
 
 Area of the Wealden. In regard to the geographical extent 
 of the Wealden, it cannot be accurately laid down; because so 
 much of it is concealed beneath the newer marine formations. It 
 has been traced about 200 English miles from west to east, from 
 the coast of Dorsetshire to near Boulogne, in France ; and nearly 
 200 miles from north-west to south-east, from Surrey and Hamp- 
 shire to Beauvais, in France. If the formation be continuous 
 throughout this space, which is very doubtful, it does not follow 
 that the whole was contemporaneous ; because, in all likelihood, 
 the physical geography of the region underwent frequent changes 
 throughout the whole period, and the estuary may have altered 
 its form, and even shifted its place. Dr. 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 hesitate to refer the 
 whole to one great delta. Even then ? the magnitude of the deposit 
 may not exceed that of many modern rivers. Thus, the delta of the 
 Quorra or Niger, in Africa, 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 
 
 * Mantell, Geol. of S.E. of England, f Fitton, Geol. of Hastings, p. 58.; 
 p. 244. who cites Lander's Travels. 
 
266 LOWEK CRETACEOUS AND [Cn. XVIII. 
 
 remains of the river and the land may be carried out from the coast, 
 and spread over the bed of the sea. I have shown, when treating of 
 the Mississippi, that a more ancient delta, including species of shells, 
 such as now inhabit Louisiana, has been upraised, and made to oc- 
 cupy a wide geographical area, while a newer delta is forming * ; and 
 the possibility of such movements, and their effects, must not be lost 
 sight of when we speculate on the origin of the Wealden. 
 
 If it 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, we are half tempted to speculate on the former 
 existence of the Atlantis of Plato. The story of the submergence of 
 an ancient continent, however fabulous in history, must have been 
 true again and again as a geological event. 
 
 The real difficulty consists in the persistence of a large hydro- 
 graphical basin, from whence a great body of fresh water was poured 
 into the sea, precisely at a period when the neighbouring area of the 
 Wealden was gradually going downwards 1000 feet or more perpen- 
 dicularly. If the adjoining land participated in the movement, how 
 could it escape being submerged, or how could it retain its size and 
 altitude so as to continue to be the source of such an inexhaustible 
 supply of fresh water and sediment ? In answer to this question, 
 we are fairly entitled to suggest that the neighbouring land may 
 have been stationary, or may even have undergone a contempora- 
 neous slow upheaval. There may have been an ascending move- 
 ment in one region, and a descending one in a contiguous parallel 
 zone of country ; just as the northern part of Scandinavia is now 
 rising, while the middle portion (that south of Stockholm) is un- 
 moved, and the southern extremity in Scania is sinking, or at 
 least has sunk within the historical period.f We must, nevertheless, 
 conclude, if we adopt the above hypothesis, that the depression of 
 the land became general throughout a large part of Europe at the 
 close of the Wealden period, and this subsidence brought in the cre- 
 taceous ocean. 
 
 FLORA OF THE LOWER CRETACEOUS AND WEALDEN PERIOD. 
 
 The terrestrial plants of the Upper Cretaceous epoch are but 
 little known, as might be expected, since the rocks are of purely 
 marine origin, formed for the most part far from land. But the 
 Lower Cretaceous or Neocomian vegetation, including that of the 
 Weald Clay and Hastings Sands, is by no means scanty. M. Adolphe 
 Brongniart, when dividing the whole fossiliferous series into three 
 groups in reference solely to fossil plants, has named the primary 
 strata " the age of acrogens ; " the secondary, exclusive of the 
 cretaceous, "the age of gymnogens;" and the third, comprising 
 
 * See above, p. 84.; and Second Visit Geol. Soc. 1850, Quart. Geol. Journ. 
 to the U. S. vol. ii. chap, xxxiv. vol. vi. p. 52. 
 
 f See the Author's Annivers. Address, 
 
CH. XVIII.] WEALDEN FLORA. 267 
 
 the cretaceous and tertiary, "the age of angiosperms."* He con- 
 siders the lower cretaceous flora as displaying a transitional cha- 
 racter from that of a secondary to that of a tertiary vegetation. 
 Coniferce and Cycadece (or Gymnogens) still flourished, as in the 
 preceding oolitic and triassic epochs ; but, together with these, some 
 well-marked leaves of dicotyledonous trees, of a genus named 
 Credneria, have long been known. They are met with in the 
 "quader-sandstein" and "planer-kalk" of Germany, rocks of the Upper 
 Cretaceous group. More recently, Dr. Deby has discovered in the 
 Lower Cretaceous beds of Aix-la-Chapelle a great variety of dicoty- 
 ledonous leaves f, belonging to no less, according to his enumeration, 
 than 26 species, some of the leaves being from four to six inches in 
 length, and in a beautiful state of preservation. In the absence ot 
 the organs of fructification and of fossil fruits, the number of species 
 may be exaggerated; but we may certainly affirm, reasoning from 
 our present data, that when the lower chalk of Aix-la-Chapelle 
 originated, Dicotyledonous Angiosperms flourished in that region in 
 equal proportions with Gymnosperms. This discovery has an im- 
 portant bearing on some popular theories, for until lately none of 
 these Exogens (a class now constituting three fourths of the living 
 plants of the globe) had been detected in any strata older than the 
 Eocene. Moreover, some geologists .have wished to connect the 
 rarity of dicotyledonous trees with a peculiarity in the state of the 
 atmosphere in the earlier ages of the planet, imagining that a denser 
 air and noxious gases, especially carbonic acid gas being in excess, 
 were adverse to the prevalence, not only of the quick-breathing 
 classes of animals (mammalia and birds), but to a flora like that now 
 existing, while it favoured the predominance of reptile life, and a 
 cryptogamic and gymnospermous flora. The co-existence, therefore, 
 of Dicotyledonous Angiosperms in abundance with Cycads and Co- 
 nifers, and with a rich reptilian fauna, comprising the Iguanodon, 
 Megalosaurus, Hylasosaurus, Ichthyosaurus, Plesiosaurus, and Ptero- 
 
 * 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. Brongniart are 
 much cited,' it may be useful to geologists to give a table explaining the corre- 
 sponding names of groups so much spoken of in palaeontology. 
 
 Brongniart. Lindley. 
 
 1. Cryptogamous amO 
 
 phigens, or cellular > Thallogens. Lichens, sea-weeds, fungi, 
 cryptogamic. 
 
 2. Cryptogamous aero- Acrogens. Mosses, equisetums, ferns, ly co- 
 
 gens, podiums, Lepidodendron. 
 
 3. Dicotyledonous gym- Gymnogens. Conifers and Cycads. 
 
 nosperms. 
 
 4. Dicot. Angiosperms. Exogens. Composite, leguminosse, umbelli- 
 
 ferae, cruciferae, heaths, &c. All 
 native European trees except 
 conifers. 
 
 5. Monocotyledons. Endogens. Palms, lilies, aloes, rushes, grasses, 
 
 &c. 
 
 f Geol. Quart. Jour. vol. vii. part 2. Miscell. p. 111. 
 
268 INLAND CHALK-CLIFFS [Cn. XIX. 
 
 dactyl, in the Lower Cretaceous series, tends manifestly to dispel the 
 idea of a meteorological state of things in the secondary periods 
 so widely distinct from that now prevailing. 
 
 Among the recent additions made to the fossil flora of the Weal- 
 den, and one which supplies a new link between it and the tertiary 
 flora, I may mention the Gi/rogonites, or spore-vessels of the Chara, 
 lately found in the Hastings series of the Isle of Wight. 
 
 CHAPTER XIX. 
 
 DENUDATION OP THE CHALK AND WEALDEN. 
 
 Physical geography of certain districts composed of Cretaceous and Wealden strata 
 Lines of inland chalk-cliffs on the Seine in Normandy Outstanding pillars 
 and needles of chalk Denudation of the chalk and Wealden in Surrey, Kent, 
 and Sussex Chalk once continuous from the North to the South Downs 
 Anticlinal axis and parallel ridges Longitudinal and transverse' valleys 
 Chalk escarpments Eiseand denudation of the strata gradual Ridges formed 
 by harder, valleys by softer beds At what periods the Weald Valley was 
 denuded Why no alluvium, or wreck of the chalk, in the central district of the 
 Weald Land has most prevaued where denudation has been greatest 
 Elephant bed, Brighton Sangatte Cliff Conclusion. 
 
 ALL the fossiliferous formations may be studied by the geologist in 
 two distinct points of view : first, in reference to their position in 
 the series, their mineral character and fossils ; and, secondly, in 
 regard to their physical geography, or the manner in which they now 
 enter, as mineral masses, into the external structure of the earth ; 
 forming the bed of lakes and seas, or the surface or foundation of 
 hills and valleys, plains and table-lands. Some account has already 
 been given, on the first head, of the Tertiary, the Cretaceous, and 
 the Wealden strata ; and we may now proceed to consider certain 
 features in the physical geography of these groups as they occur in 
 parts of England and France. 
 
 The hills composed of white chalk in the S. E. of England have a 
 smooth rounded outline, and, being usually in the state of sheep - 
 pastures, are free from trees or hedgerows; so that we have an 
 opportunity of observing how the valleys by which they are drained 
 ramify in all directions, and become wider and deeper as they descend. 
 Although these valleys are now for the most part dry, except during 
 heavy rains and the melting of snow, they may have been due to 
 aqueous denudation, as explained in the sixth chapter ; having been 
 excavated when the chalk emerged gradually from the sea. This 
 opinion is confirmed by the occasional occurrence of what appear to 
 be long lines of inland cliffs, in which the strata are cut off abruptly 
 in steep and often vertical precipices. The true nature of such 
 escarpments is nowhere more obvious than in parts of Normandy, 
 
CH. XIX.] IN NOKMANDY. 269 
 
 where the river Seine and its tributaries flow through deep winding 
 valleys, hollowed out of chalk horizontally stratified. Thus, for 
 example, if we follow the Seine for a distance of about 30 miles 
 from Andelys to Elbosuf, we find the valley flanked on both sides 
 by a steep slope of chalk, with numerous beds of flint, the formation 
 being laid open for a thickness of about 250 and 300 feet. Above 
 the chalk is an overlying mass of sand, gravel, and clay, from 30 to 
 100 feet thick. The two opposite slopes of the hills a and b, fig. 313., 
 
 Fig. 313. 
 
 Section across Valley of Seine. 
 
 where the chalk appears at the surface, are from 2 to 4 miles apart, 
 and they are often perfectly smooth and even, like the steepest of 
 our downs in England ; but at many points they are broken by one, 
 two, or more ranges of vertical and even overhanging cliffs of bare 
 white chalk with flints. At some points detached needles and pin- 
 nacles stand in the line of the cliffs, or in front of them, as at c, fig. 
 313. On the right bank of the Seine, at Andelys, one range, about 
 2 miles long, is seen varying from 50 to 100 feet in perpendicular 
 height, and having its continuity broken by a number of dry valleys 
 or coombs, in one of which occurs a detached rock or needle, called 
 the Tete d'Homme (see figs. 314, 315.). The top of this rock pre- 
 
 Fig. 314. 
 
 View of the Tete d'Homme, Andelys, seen from above. 
 
 sents a precipitous face towards every point of the compass ; its 
 vertical height being more than 20 feet on the side of the downs, 
 and 40 towards the Seine, the average diameter of the pillar being 
 36 feet. Its composition is the same as that of the larger cliffs in 
 
270 
 
 INLAND CLIFFS AND NEEDLES 
 
 Fig. 315. 
 
 [Cn. XIX. 
 
 Side view of the Tete d'Homme. White chalk with flints. 
 
 its neighbourhood, namely, white chalk, having occasionally a crys- 
 talline texture like marble, with layers of flint in nodules and tabular 
 masses. The flinty beds often project in relief 4 or 5 feet beyond 
 the white chalk, which is generally in a state of slow decomposition, 
 either exfoliating or being covered with white powder, like the 
 chalk cliffs on the English coast ; and, as in them, this superficial 
 powder contains in some places common salt. 
 
 Other cliffs are situated on the right bank of the Seine, opposite 
 Tournedos, between Andelys and Pont de 1'Arche, where the preci- 
 pices are from 50 to 80 feet high : several of their summits terminate 
 in pinnacles ; and one of them, in particular, is so completely de- 
 tached as to present a perpendicular face 50 feet high towards the 
 sloping down. On these cliffs several ledges are seen, which mark 
 so many levels at which the wares of the sea may be supposed to have 
 encroached for a long period. At a still greater height, immediately 
 above the top of this range, are three much smaller cliffs, each about 
 4 feet high, with as many intervening terraces, which are continued 
 so as to sweep in a semicircular form round an adjoining coomb, like 
 those in Sicily before described (p. 76.). 
 
 If we then descend the river from Vatteville to a place called 
 Senneville, we meet with a singular needle about 50 feet high, per- 
 fectly isolated on the escarpment of chalk on the right bank of the 
 Seine (see fig. 316.). Another conspicuous range of inland cliffs is 
 situated about 12 miles below on the left bank of the Seine, begin- 
 ning at Elbceuf, and comprehending the Roches d'Orival (see fig. 317.). 
 Like those before described, it has an irregular surface, often over- 
 hanging, and with beds of flint projecting several feet. Like them, 
 also, it exhibits a white powdery surface, and consists entirely of 
 horizontal chalk with flints. It is 40 miles inland ; its height, in 
 some parts, exceeds 200 feet ; and its base is only a few feet above 
 the level of the Seine. It is broken, in one place, by a pyramidal 
 mass or needle, 200 feet high, called the Roche de Pignon, which 
 stands out about 25 feet in front of the upper portion of the main cliffs. 
 
CH. XIX.] OF CHALK IN NORMANDY. 
 
 Fig. 316. Fig. 317. 
 
 271 
 
 Chalk pinnacle at Senneville. 
 
 Roches d'Orival, Elbceuf. 
 
 with which it is united by a narrow ridge about 40 feet lower than 
 its summit (see fig. 318.). Like the detached rocks before mentioned 
 
 Fig. 318. 
 
 View of the Roche de Pignon, seen from the south. 
 
 at Senneville, Vatteville, and Andelys, it may be compared to those 
 needles of chalk which occur on the coast of Normandy* (see fig. 
 319.), as well as in the Isle of Wight and in Purbeck. 
 
 The foregoing description and drawings will show, that the 
 evidence of certain escarpments of the chalk having been originally 
 sea-cliffs, is far more full and satisfactory in France than in England. 
 If it be asked why, in the interior of our own country, we meet with 
 no ranges of precipices equally vertical and overhanging, and no 
 isolated pillars or needles, we may reply that the greater hardness of 
 the chalk in Normandy may, no doubt, be the chief cause of this 
 difference. But the frequent absence of all signs of littoral denuda- 
 
 * An account of these cliffs was read by the author to the British Assoc. at 
 Glasgow, Sept. 1840. 
 
272 
 
 DENUDATION OF THE 
 
 Tig. 319. 
 
 [Cn. XIX. 
 
 Needle and Arch of Etretat, in the chalk cliffs of Normandy. 
 Height of Arch 100 feet. (Passy.)* 
 
 tion in the valley of the Seine itself is a negative fact of a far more 
 striking and perplexing character. The cliffs, after being almost 
 continuous for miles, are then wholly wanting for much greater dis- 
 tances, being replaced by a green sloping down, although the beds 
 remain of the same composition, and are equally horizontal ; and 
 although we may feel assured that the manner of the upheaval of 
 the land, whether intermittent or not, must have been the same at 
 those intermediate points where no cliffs exist, as at others where 
 they are so fully developed. But, in order to explain such apparent 
 anomalies, the reader must refer again to the theory of denudation, 
 as expounded in the 6th chapter ; where it was shown, first, that the 
 undermining force of the waves and marine currents varies greatly 
 at different parts of every coast ; secondly, that precipitous rocks 
 have often decomposed and crumbled down ; and thirdly, that ter- 
 races and small cliffs may occasionally lie concealed beneath a talus 
 of detrital matter. 
 
 Denudation of the Weald Valley. No district is better fitted to 
 illustrate the manner in which a great series of strata may have been 
 upheaved and gradually denuded than the country intervening be- 
 tween the North and South Downs. This region, of which a ground- 
 plan is given in the accompanying map (fig. 320.), comprises within 
 it the whole of Sussex, and parts of the counties of Kent, Surrey, 
 and Hampshire. The space in which the formations older than the 
 White Chalk, or those from the Gault to the Hastings sands inclu- 
 sive, crop out, is bounded everywhere by a great escarpment of 
 chalk, which is continued on the opposite side of the channel in the 
 Bas Boulonnais in France, where it forms the semicircular boundary 
 of a tract in which older strata also appear at the surface. The 
 whole of this district may therefore be considered geologically as 
 one and the same. 
 
 The space here inclosed within the escarpment of the chalk affords 
 an example of what has been sometimes called a " valley of eleva- 
 tion " (more properly " of denudation ") ; where the strata, partially 
 removed by aqueous excavation, dip away on all sides from a central 
 axis. Thus, it is supposed that the area now occupied by the 
 
 * Seine-Inferieure, p. 142. and pi. 6. fig. 1. 
 
CH. XIX.] 
 
 CHALK AND WEALDEN. 
 
 Fig. 320. 
 
 vary of Thames 
 
 273 
 
 Geological Map of the south-east of England, and part of France, exhibiting the denudation of 
 
 the Weald. 
 
 1. Tertiary. 
 
 2. I f Chalk and Upper Greensand. 
 
 3. Gault. 
 
 4. |==S| Lower Greensand. 
 
 5. Weald clay. 
 
 6. l : ''-'- v --'* Hastings sands 
 
 7. Purbeck beds. 
 Oolite. 
 
 Hastings sand (No. 6.) was once covered by the Weald clay (No. 5.), 
 and this again by the Greensand (No. 4.), and this by the Gault 
 (No. 3.); and, lastly, that the Chalk (No. 2.) extended originally 
 over the whole space between the North and the South Downs. This 
 theory will be better understood by consulting the annexed diagram 
 (fig. 321.), where the dark lines represent what now remains, and the 
 fainter ones those portions of rock which are believed to have been 
 carried away. 
 
 At each end of the diagram the tertiary strata (No. 1.) are ex- 
 hibited reposing on the chalk. In the middle are seen the Hastings 
 sands (No. 6.) forming an anticlinal axis, on each side of which the 
 other formations are arranged with an opposite dip. It has been 
 necessary, however, in order to give a clear view of the different 
 formations,, to exaggerate the proportional height of each in compa- 
 rison to its horizontal extent; and a true scale is therefore subjoined 
 in another diagram (fig. 322.), in order to correct the erroneous 
 impression which might otherwise be made on the reader's mind. 
 In this section the distance between the North and South Downs is 
 represented to exceed forty miles ; for the Valley of the Weald is 
 here intersected in its longest diameter, in the direction of a line 
 between Lewes and Maidstone. 
 
 Through the central portion, then, of the district supposed to be 
 denuded runs a great anticlinal line, having a direction nearly east 
 and west, on both sides of which the beds 5, 4, 3, and 2 crop out in 
 succession. But, although, for the sake of rendering the physical 
 structure of this region more intelligible, the central line of elevation 
 has alone been introduced, as in the diagrams of Smith, Mantell, 
 Conybeare, and others, geologists have always been well aware that 
 
274 
 
 
 VALLEY 
 
 OF THE WEALD. 
 
 [Cn. XIX 
 
 
 
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 numerous minor lines of dislocation and flexure run parallel to the 
 great central axis. 
 
 In the central area of the Hastings sand the strata have under- 
 gone the greatest displacement ; one fault being known, where the 
 
CH. XIX.] 
 
 CHALK ESCARPMENTS. 
 
 275 
 
 vertical shift of a bed of calcareous grit is no less than 60 fathoms.* 
 Much of the picturesque scenery of this district arises from the 
 depth of the narrow valleys and ridges to which the sharp bends and 
 fractures of the strata have given rise ; but it is also in part to be 
 attributed to the excavating power exerted by water, especially on 
 the interstratified argillaceous beds. 
 
 Besides the series of longitudinal valleys and ridges in the Weald, 
 
 there are valleys which run in 
 a transverse direction, passing 
 through the chalk to the basin 
 of the Thames on the one side, 
 and to the English Channel 
 on the other. In this manner 
 the chain of the North Downs 
 is broken by the rivers Wey, 
 Mole, Darent, Medway, and 
 Stour ; the South Downs by 
 the Arun, Adur, Ouse, and 
 Cuckmere. | If these trans- 
 verse hollows could be filled 
 up, all the rivers, observes Dr. 
 Conybeare, would be forced 
 to take an easterly course, and 
 to empty themselves into the 
 sea by Romney Marsh and 
 Pevensey Levels. ' 
 
 Mr. Martin has suggested 
 that the great cross fractures 
 of the chalk, which have be- 
 come river-channels, have a 
 remarkable correspondence on 
 each side of the valley of the 
 Weald; in several instances 
 the gorges in the North and 
 South Downs appearing to be 
 directly opposed to each other. 
 Thus, for example, the defiles 
 of the Wey in the North 
 Downs, and of the Arun in 
 the South, seem to coincide 
 in direction ; and, in like man- 
 ner, the Ouse corresponds to 
 the Darent, and the Cuckmere 
 to the Medway 4 
 
 Although these coincidences 
 may, perhaps, be accidental, it 
 is by no means improbable, as 
 
 Geol. of Western Sussex, p. 61. 
 
 * Fitton, Geol. of Hastings, p. 55. 
 { Conybeare, Outlines of Geol., p. 81. 
 
 T 2 
 
276 CHALK ESCARPMENTS. [Cn. XIX. 
 
 hinted by the author above mentioned, that great amount of ele- 
 vation towards the centre of the Weald district gave rise to trans- 
 verse fissures. And as the longitudinal valleys were connected 
 with that linear movement which caused the anticlinal lines running 
 east and west, so the cross fissures might have been occasioned by 
 the intensity of the upheaving force towards the centre of the line. 
 
 But before treating of the manner in which the upheaving move- 
 ment may have acted, I shall endeavour to make the reader more 
 intimately acquainted with the leading geographical features of the 
 district, so far as they are of geological interest. 
 
 In whatever direction we travel from the tertiary strata of the 
 basins of London and Hampshire towards the valley of the Weald, 
 we first ascend a slope of white chalk, with flints, and then find 
 ourselves on the summit of a declivity consisting, for the most part, 
 of different members of the chalk formation ; below which the 
 Upper Greensand, and sometimes, also, the Gault, crop out. This 
 steep declivity is the great escarpment of the chalk before mentioned, 
 which overhangs a valley excavated chiefly out of the argillaceous 
 or marly bed, termed Gault (No. 3.). The escarpment is continuous 
 along the southern termination of the North Downs, and may be 
 traced from the sea, at Folkestone, westward to Guildford and the 
 neighbourhood of Petersfield, and from thence to the termination of 
 the South Downs at Beachy Head. In this precipice or steep slope 
 the strata are cut off abruptly, and it is evident that they must 
 originally have extended farther. In the wood-cut (fig. 323. p. 275.) 
 part of the escarpment of the South Downs is faithfully represented, 
 where the denudation at the base of the declivity has been some- 
 what more extensive than usual, in consequence of the Upper and 
 Lower Greensand being formed of very incoherent materials, the 
 former, indeed, being extremely thin and almost wanting. 
 
 The geologist cannot fail to recognise in this view the exact 
 likeness of a sea-cliff; and if he turns and looks in an opposite 
 direction, or eastward, towards Beachy Head (see fig. 324.), he will 
 
 Fig. 324. 
 
 Chalk escarpment, as seen from the hill above Steyning, Sussex. The castle and village 
 of Bramber in the foreground. 
 
 see the same line of heights prolonged. Even those who are not 
 accustomed to speculate on the former changes which the surface has 
 undergone may fancy the broad and level plain to resemble the flat 
 sands which were laid dry by the receding tide, and the different 
 
CH. XIX.] 
 
 TRANSVERSE VALLEYS. 
 
 277 
 
 projecting masses of chalk to be the headlands of a coast which 
 separated the different bays from each other. 
 
 Occasionally in the North Downs sand-pipes are intersected in the 
 slope of the escarpment, and have been regarded by some geologists 
 as more modern than the slope ; in which case they might afford an 
 argument against the theory of these slopes having originated as sea- 
 cliffs or river-cliffs. But, when we observe the great depth of many 
 sand-pipes, those near Sevenoaks, for example, we perceive that the 
 
 lower termination of such pipes 
 must sometimes appear at the 
 surface far from the summit of 
 an escarpment, whenever por- 
 tions of the chalk are cut away. 
 In regard to the transverse 
 valleys before mentioned, as in- 
 tersecting the chalk hills, some 
 idea of them may be derived 
 from the subjoined sketch (fig. 
 325.) of the gorge of the River 
 Adur, taken from the summit of 
 the chalk-downs, at a point in 
 the bridle-way leading from the 
 towns of Bramber and Steyning 
 to Shoreham. If the reader will 
 refer again to the view given 
 in a former woodcut (fig. 323. 
 p. 275.), he will there see the 
 exact point where the gorge of 
 which I am now speaking in- 
 terrupts the chalk escarpment. 
 A projecting hill, at the point a, 
 hides the town of Steyning, near 
 which the valley commences 
 where the Adur passes directly 
 to the sea at Old Shoreham. The 
 river flows through a nearly 
 level plain, as do most of the 
 others which intersect the hills 
 of Surrey, Kent, and Sussex; 
 and it is evident that these open- 
 ings could not have been pro- 
 duced by rivers, except under 
 conditions of physical geography 
 entirely different from those now 
 prevailing. Indeed, many of the 
 existing rivers, like the Ouse 
 near Lewes, have filled up arms 
 of the sea, instead of deepening 
 the hollows which they traverse. 
 
 T 3 
 
278 
 
 COOMB NEAR LEWES. 
 
 [Cn. XIX. 
 
 That the place of some, if not of all, the gorges running north and 
 south, has been originally determined by the fracture and displace- 
 ment of the rocks, seems the more probable, when we reflect on the 
 proofs obtained of a ravine running east and west, which branches 
 off from the eastern side of the valley of the Ouse just mentioned, 
 and which is undoubtedly due to dislocation. This ravine is called 
 "the Coomb" (fig. 326.), and is situated in the suburbs of the town 
 
 Fip. 32G 
 
 The Coomb, near Lewes. 
 
 of Lewes. It was first traced out by Dr. Mantell, in whose com- 
 pany I examined it. The steep declivities on each side are covered 
 with green turf, as is the bottom, which is perfectly dry. No out- 
 ward signs of disturbance are visible ; and the connection of the 
 hollow with subterranean movements would not have been suspected 
 by the geologist, had not the evidence of great convulsions been 
 clearly exposed in the escarpment of the valley of the Ouse, and the 
 numerous chalk-pits worked at tho termination of the Coomb. By 
 the aid of these we discover that the ravine coincides precisely with 
 a line of fault, on one side of which the chalk with flints (, fig. 327.) 
 
 Fig. 327. 
 
 Fault coinciding with the Coomb, in the Cliff-hill near Lewes. Mantell. 
 a. Chalk with flints. b. Lower chalk. 
 
 appears at the summit of the hill, while it is thrown down to the 
 bottom on the other. 
 
 In order to account for the manner in which the five groups of 
 
CH. XIX.] PROMINENCE OF HARDER STRATA. 279 
 
 strata, 2, 3, 4, 5, 6, represented in the map, fig. 320., and in the 
 section, fig. 321., may have been brought into their present position, 
 the following hypothesis has been suggested : Suppose the five 
 formations to lie in horizontal stratification at the bottom of the sea ; 
 then let a movement from below press them upwards into the form 
 of a flattened dome, and let the crown of this dome be afterwards cut 
 off, so that the incision should penetrate to the lowest of the five 
 groups. The different beds would then be exposed on the surface, 
 in the manner exhibited in the map, fig. 320.* 
 
 The quantity of denudation, or removal by water, of stratified 
 masses assumed to have once reached continuously from the North 
 to the South Downs is so enormous, that the reader may at first be 
 startled by the boldness of the hypothesis. But the difficulty will 
 disappear when once sufficient time is allowed for the gradual rising 
 and sinking of the strata at many successive geological periods, 
 during which the waves and currents of the ocean, and the power of 
 rain, rivers, and land-floods, might slowty accomplish operations 
 which no sudden diluvial rush of waters could possibly effect. 
 
 Among other proofs of the action of water, it may be stated that 
 the great longitudinal valleys follow the outcrop of the softer and 
 more incoherent beds, while ridges or lines of cliff usually occur at 
 those points where the strata are composed of harder stone. Thus, 
 for example, the chalk with flints, together with the subjacent upper 
 greensand, which is often used for building, under the provincial 
 name of " firestone," have been cut into a steep cliff on that side on 
 which the sea encroached. This escarpment bounds a deep valley, 
 excavated chiefly out of the soft argillaceous bed, termed gault 
 (No. 3., map, p. 273.). In some places the upper greensand is in a 
 loose and incoherent state, and there it has been as much denuded as 
 the gault; as, for example, near Beachy Head; but farther to the 
 westward it is of great thickness, and contains hard beds of blue 
 chert and calcareous sandstone or firestone. Here, accordingly, we 
 find that it produces a corresponding influence on the scenery of the 
 country ; for it runs out like a step beyond the foot of the chalk- 
 hills, and constitutes a lower terrace, varying in breadth from a 
 quarter of a mile to three miles, and following the sinuosities of the 
 chalk-escarpment, f 
 
 a. Chalk with flints. b. Chalk without flints. 
 
 c. Upper greensand, or firestone. d. Gault. 
 
 * See illustrations of this theory, by Sussex, &c., Geol. Trans., Second Series, 
 Dr. Fitton, Geol. Sketch of Hastings. vol. ii. p. 98. 
 f Sir B. Murchison, Geol. Sketch of 
 
 T 4 
 
280 DENUDATION OF THE WEALD. [Cn. XIX. 
 
 It is impossible to desire a more satisfactory proof that the escarp- 
 ment is due to the excavating power of water during the rise of the 
 strata, or during their rising and sinking at successive periods ; for 
 I have shown, in my account of the coast of Sicily (p. 76.), in what 
 manner the encroachments of the sea tend to efface that succession of 
 terraces which must otherwise result from the intermittent upheaval 
 of a coast preyed upon by the waves. During the interval between 
 two elevatory movements, the lower terrace will usually be destroyed, 
 wherever it is composed of incoherent materials ; whereas the sea 
 will not have time entirely to sweep away another part of the same 
 terrace, or lower platform, which happens to be composed of rocks of 
 a harder texture, and capable of offering a firmer resistance to the 
 erosive action of water. As the yielding clay termed gault would be 
 readily washed away, we find its outcrop marked everywhere by a 
 valley which skirts the base of the chalk-hills, and which is usually 
 bounded on the opposite side by the lower greensand; but as the 
 upper beds of this last formation are most commonly loose and inco- 
 herent, they also have usually disappeared and increased the breadth 
 of the valley. In those districts, however, where chert, limestone, 
 and other solid materials enter largely into the composition of this 
 formation (No. 4., map, p. 273.), they give rise to a range of hills 
 parallel to the chalk, which sometimes rival the escarpment of the 
 chalk itself in height, or even surpass it, as in Leith Hill, near 
 Dorking. This ridge often presents a steep escarpment towards the 
 soft argillaceous deposit called the Weald clay (No. 5. ; see the dark 
 tint in fig. 321. p. 274.), which usually forms a broad valley, sepa- 
 rating the lower greensand from the Hastings sands or Forest 
 Ridge ; but where subordinate beds of sandstone of a firmer texture 
 occur, the uniformity of the plain of No. 5. is broken by waring 
 irregularities and hillocks. 
 
 Pluvial action. In considering, however, the comparative de- 
 structibility of the harder and softer rocks, we must not underrate 
 the power of rain. The chalk-downs, even on their summits, are 
 usually covered with unrounded chalk-flints, such as might remain 
 after masses of white chalk had been softened and removed by water. 
 This superficial accumulation of the hard or siliceous materials of 
 disintegrated strata may be due in no small degree to pluvial action ; 
 for during extraordinary rains a rush of water charged with cal- 
 careous matter, of a milk-white colour, may be seen to descend even 
 gently sloping hills of chalk. If a layer no thicker than the tenth 
 of an inch be removed once in a century, a considerable mass may 
 in the course of indefinite ages melt away, leaving nothing save a 
 stratum of flinty nodules to attest its former existence. A bed of fine 
 clay sometimes covers the surface of slight depressions in the white 
 chalk, which may represent the aluminous residue of the rock, after 
 the pure carbonate of lime has been dissolved by rain-water, charged 
 with excess of carbonic acid derived from decayed vegetable matter. 
 The acidulous waters sometimes descend through " sand-pipes " and 
 "swallow-holes" in the chalk, so that the surface may be under- 
 
CH. XIX.] THEORY OF FRACTURE AND UPHEAVAL. 281 
 
 mined, and cavities may be formed or enlarged, even by that part of 
 the drainage which is subterranean.* 
 
 Lines of Fracture. Mr. Martin, in his work on the geology of 
 Western Sussex, published in 1828, threw much light on the struc- 
 ture of the Wealden by tracing out continuously for miles the direc- 
 tion of many anticlinal lines and cross fractures ; and the same 
 course of investigation has since been followed out in greater detail 
 by Mr. Hopkins. The geologist and mathematician last-mentioned 
 has shown that the observed direction of the lines of flexure and 
 dislocation in the Weald district coincide with those which might 
 have been anticipated theoretically on mechanical principles, if we 
 assume certain simple conditions under which the strata were lifted 
 up by an expansive subterranean force.f 
 
 His opinion, that both the longitudinal and transverse lines of 
 fracture may have been produced simultaneously, accords well with 
 that expressed by M. Thurmann, in his work on the anticlinal ridges 
 and valleys of elevation of the Bernese Jura.| For the accuracy 
 of the map and sections of the Swiss geologist I can vouch, from 
 personal examination, in 1835, of part of the region surveyed by him. 
 Among other results, at which he arrived, it appears that the 
 breadth of the anticlinal ridges and dome-shaped masses in the Jura 
 is invariably great in proportion to the number of the formations 
 exposed to view ; or, in other words, to the depth to which the super- 
 imposed groups of secondary strata have been laid open. (See fig. 71. 
 p. 55. for structure of Jura.) He also remarks, that the anticlinal 
 lines are occasionally oblique and cross each other, in which case the 
 greatest dislocation of the beds takes place. Some of the cross frac- 
 tures are imagined by him to have been contemporaneous with others 
 subsequent to the longitudinal ones. 
 
 I have assumed, in the former part of this chapter, that the rise of 
 the Weald was gradual, whereas many geologists have attributed its 
 elevation to a single effort of subterranean violence. There appears 
 to them such a unity of effect in this and other lines of deranged 
 strata in the south-east of England, such as that of the Isle of Wight, 
 as is inconsistent with the supposition of a great number of separate 
 movements recurring after long intervals of time. But we know that 
 earthquakes are repeated throughout a long series of ages in the 
 same spots, like volcanic eruptions. The oldest lavas of Etna were 
 poured out many thousands, perhaps myriads of years before the 
 newest, and yet they, and the movements accompanying their emission, 
 have produced a symmetrical mountain ; and if rivers of melted 
 matter thus continue to flow upwards in the same direction, and 
 towards the same point, for an indefinite lapse of ages, what diffi- 
 culty is there in conceiving that the subterranean volcanic force, 
 occasioning the rise or fall of certain parts of the earth's crust, 
 
 * See above, p. 82, 83. " Sand-pipes f ^ eo1 - Soc - Proceed. No. 74. p. 363. 
 in Chalk ;" and Prestwich, Geol. Quart. 1841, and G. S. Trans. 2 Ser. vol. 7. 
 Journ. vol. x. p. 222. $ Soulevemens Jurassiques. 1832. 
 
282 PERIODS OF DENUDATION OF THE WEALD. [Cn. XIX. 
 
 may, by reiterated movements, produce the most perfect unity of 
 result ? 
 
 At what periods the Weald valley was denuded. We may next 
 inquire at what time the denudation of the Weald was effected, and 
 we shall find, on considering all the facts brought to light by recent 
 investigation, that it was accomplished in the course of so long a 
 series of ages, that the greatest revolutions in the physical geography 
 of the globe, yet known to us, have taken place within the same 
 lapse of time. It has now been ascertained, that part of the denu- 
 dation of the Weald was completed before the British Eocene strata, 
 and consequently before the nummulitic rocks of Europe and Asia 
 were formed. The date, therefore, of part of the changes now under 
 contemplation was long antecedent to the existence of the Alps, 
 Pyrenees, and many other European and Asiatic mountain-chains, 
 and even to the accumulation of large portions of their component 
 materials beneath the sea. 
 
 M. Elie de Beaumont suggested, in 1833, that there was an island 
 in the Eocene sea in the area now occupied by the French and 
 English Wealden strata, and he gave a map or hypothetical restora- 
 tion of the ancient geography of that region at the era alluded to.* 
 Mr. Prestwich has since shown that the materials of which the 
 lower tertiary beds of England are made up, and their manner of 
 resting on the chalk, imply, that such an island, or several islands 
 and shoals, composed of Chalk, Upper Greensand, Gault, and pro- 
 bably of some of the Lower Cretaceous rocks, did exist somewhere 
 between the present North and South Downs. The undermined 
 cliffs and shores of those lands supplied the flints, which the action 
 of the waves rounded into pebbles, such as now form the Woolwich 
 and Blackheath shingle-beds below the London Clay. It is sup- 
 posed, that the land referred to was drained by rivers flowing into 
 the Eocene sea, and whence the brackish and freshwater deposits of 
 Woolwich and other contemporaneous strata f were derived. The 
 large size of some of the rolled flints (eight inches and upwards in 
 diameter) of the Blackheath shingle demonstrates the proximity of 
 land. Such heavy masses could not have been transported from 
 great distances, whether they owe their shape to waves breaking on 
 a sea-beach, or to rivers descending a steep slope. 
 
 In the annexed diagram (fig. 329.) Mr. Prestwich has represented 
 a section from near Saffron Walden, in Essex, to the Weald, passing 
 north and south through Godstone, in which we see how the chalk, 
 c, had been disturbed and denuded before the lower Eocene beds, b, 
 were deposited. Some small patches of the last-mentioned beds, b', 
 consisting of clay and sand, extend occasionally, as in this instance, 
 to the very edge of the escarpment of the North Downs, proving that 
 the surface of the white chalk, now covered with tertiary strata, is 
 the same which originally constituted the bottom of the Eocene sea. 
 
 * Mem. de la Soc. Geol. de France, f See P- 221 - al) ove. 
 vol. i. part i. p. 111. pi. 7. fig. 5. 
 
CH. XIX.] ISLANDS IN THE EOCENE SEA. 283 
 
 Fig. 329. 
 
 f\ 
 
 Section showing that the Weald had been denuded of chalk before the Lower Eocene strata were 
 
 deposited. 
 
 S. Relative position of Saffron Walden. 
 
 G. Chalk-escarpment above Godstone, surmounted by a patch of the Lower Tertiary beds, b'. 
 a. London Clay. b,b'. Lower Tertiaries. c. Chalk. 
 
 d. Upper Greensand. e. Gault. /. Lower Greensand and Wealden. 
 
 x. Point at which the present upper and under surfaces of the chalk, if they were prolonged, would 
 converge. 
 
 It is therefore inferred, that, if we prolong southwards the upper 
 and under surfaces of the chalk, along the dotted line in the above 
 section, they would converge at the point x ; therefore, beyond that 
 point, no white chalk existed at the time when the Eocene beds, b, b', 
 were formed. In other words, the central parts of the Wealden, 
 south of #, were already bared of their original covering of chalk, 
 or had only some slight patches of that rock scattered over them. 
 
 The island, or islands, in the Eocene sea may be represented in 
 the annexed diagram (fig. 330.) ; but doubtless the denudation ex- 
 Fig. 330. 
 
 Island in the Eocene Sea. 
 a. Chalk, Upper Greensand, and Gault. b. Lower Greensand. 
 
 r 
 
 c. Wealden. 
 
 tended farther in width and depth before the close of the Eocene 
 period, and the waves may have cut into the Lower Greensand, and 
 perhaps in some places into the Wealden strata. 
 
 According to this view the mass of cretaceous and subcretaceous 
 rocks, planed off by the waves and currents in the area between 
 the North and South Downs before the origin of the oldest Eocene 
 beds, may have been as voluminous as the mass removed by denu- 
 dation since the commencement of the Eocene era. 
 
 But the reader may ask, why is it necessary to assume that so 
 much white chalk first extended continuously over the Wealden 
 beds in this part of England, and was then removed ? May we not 
 suppose that land began to exist between the North and South 
 Downs at a much earlier epoch ; and that the upper Wealden beds 
 rose in the midst of the Cretaceous Ocean, so as to check the accu- 
 mulation of white chalk, and limit it to the deeper water of adjoining 
 areas? This hypothesis has often been advanced, and as often 
 rejected ; for, had there been shoals or dry land so near, the white 
 
284 AT WHAT PERIODS [Cn. XIX. 
 
 chalk would not have remained unsoiled, or without intermixture of 
 mud and sand ; nor would organic remains of terrestrial, fluviatile, or 
 littoral origin have been so entirely wanting in the strata of the 
 North and South Downs, where the chalk terminates abruptly in 
 the escarpments. It is admitted that the fossils now found there 
 belong exclusively to classes which inhabit a deep sea. Moreover, 
 the uppermost beds of the Wealden group, as Mr. Prestwich has 
 remarked, would not have been so strictly conformable with the 
 lowest beds of the Lower Greensand had the strata of the Wealden 
 undergone upheaval before the deposition of the incumbent creta- 
 ceous series. 
 
 But, although we must assume that the white chalk was once 
 continuous over what is now the Weald, it by no means follows that 
 the first denudation was subsequent to the entire Cretaceous era. 
 Most probably it commenced before a large portion of the Maestricht 
 beds were formed, or while they were in progress. I have already 
 stated (p. 239. above), that in parts of Belgium I observed rolled 
 pebbles of chalk-flints very abundant in the lowest Maestricht beds, 
 where these last overlie the white chalk, showing at how early a 
 date the chalk was upraised from deep water and exposed to aqueous 
 abrasion. 
 
 Guided by the amount of change in organic life, we may estimate 
 the interval between the Maestricht beds and the Thanet Sands to 
 have been nearly equal in duration to the time which elapsed 
 between the deposition of those same Thanet Sands and the Glacial 
 period. If so, it would be idle to expect to be able to make ideal 
 restorations of the innumerable phases in physical geography through 
 which the south-east of England must have passed since the Weald 
 began to be denuded. In less than half the same lapse of time the 
 aspect of the whole European area has been more than once entirely 
 changed. Nevertheless, it may be useful to enumerate some of the 
 known fluctuations in the physical conformation of the Weald and 
 the regions immediately adjacent during the period alluded to. 
 
 First, we have to carry back our thoughts to those very remote 
 movements which first brought up the white chalk from a deep sea 
 into exposed situations where the waves could plane off certain 
 portions, as expressed in diagram, fig. 329., before the British Lower 
 Eocene beds originated. 
 
 Secondly, we have to take into account the gradual wear and 
 tear of the chalk and its flints, to which the Thanet sands bear 
 witness, as well as the subsequent Woolwich and Blackheath shingle- 
 beds, occasionally 50 feet thick, and composed of rolled flint-pebbles. 
 
 Thirdly, at a later period a great subsidence took place, by which 
 the shallow-water and fresh-water beds of Woolwich and other 
 Lower Eocene deposits were depressed (see above, p. 222.) so as to 
 allow the London Clay and Bagshot series, of deep-sea origin, to 
 accumulate over them. The amount of this subsidence, according 
 to Mr. Prestwich, exceeded 800 feet in the London, and 1800 feet 
 in the Hampshire or Isle of Wight basin ; and, if so, the intervening 
 
CH. XIX.] THE WEALD VALLEY WAS DENUDED. 285 
 
 area of the Weald could scarcely fail to share in the movement, and 
 some parts at least of the island before spoken of (fig. 330. p. 283.) 
 would become submerged. 
 
 Fourthly. After the London clay and the overlying Bagshot sands 
 had been deposited, they appear to have been upraised in the London 
 basin, during the Eocene period, and their conversion into land in 
 the north seems to have preceded the upheaval of beds of correspond- 
 ing age in the south, or in the Hampshire basin ; because none of 
 the fluvio-marine Eocene strata of Hordwell and the Isle of Wight 
 (described in Ch. XVI.) are found in any part of the London area. 
 
 Fifthly. The fossils of the alternating marine, brackish, and fresh- 
 water beds of Hampshire, of Middle and Upper Eocene date, bear 
 testimony to rivers draining adjacent lands, and to the existence of 
 numerous quadrupeds in those lands. Instead of these phenomena, 
 the signs of an open sea might naturally have been expected, as a 
 consequence of the vast subsidence of the Middle Eocene beds before 
 mentioned, had not some local upheaval taken place at the same time 
 in the Isle of Wight or in regions immediately adjacent. Whatever 
 hypothesis be adopted, we are entitled to assume that during the 
 Middle and Upper Eocene periods there were risings and sinkings of 
 land, and changes of level in the bed of the sea in the south-east of 
 England, and that the movements were by no means uniform over 
 the whole area during these periods. The extent and thickness of 
 the missing beds in the Weald should of itself lead us to look for proofs 
 of that area having by repeated oscillations changed its level fre- 
 quently, and, oftener than any adjoining area, been turned from 
 sea into land ; for the submergence and emergence of land augment, 
 beyond any other cause, the wasting and removing power of water, 
 whether of the waves or of rivers and land-floods. 
 
 Sixthly. As yet we have discovered no marine Miocene (orfalu- 
 niari} formations in any part of the British Isles, nor any of older 
 Pliocene date south of the Thames ; but the Upper Eocene strata of 
 the Isle of Wight (the Hempstead beds before described) have been 
 upraised above the level of the sea in which they were originally 
 formed, and some of them have been thrown into a vertical position, 
 as seen in Alum and Whitecliff Bays, attesting great movements since 
 the origin of the newest tertiaries of that district. Such movements 
 may have occurred, in great part at least, during the Miocene period, 
 when a large part of Europe is supposed to have become land as 
 before suggested (p. 181.). Hence we are entitled to speculate on the 
 probability of revolutions in the physical geography of the Weald 
 in times intermediate between the deposition of the Hempstead beds 
 and the origin of the Suffolk crag. 
 
 Seventhly. But we have still to consider another vast interval of 
 time that which separated the beginning of the older Pliocene from 
 the beginning of the Pleistocene era, a lapse of ages which, if 
 measured by the fluctuations experienced in the marine fauna, may 
 have sufficed to uplift or sink whole continents by a process as slow 
 as that which is now operating in Sweden and in Greenland. 
 
286 WEALD, WHEN DENUDED. [Cn. XIX. 
 
 Lastly. The reader must recall to mind what was said, in the llth 
 and 12th chapters, of the glacial drift and its far-transported mate- 
 rials. How wide an extent of the British Isles appears to have been 
 under the sea during some part or other of that epoch ! Most of the 
 submerged areas were afterwards converted into dry land, several 
 hundred and in some places more than a thousand feet high. It is 
 an opinion very commonly entertained, that the central axis of the 
 Weald was dry land when the most characteristic northern drift 
 originated ; no traces of northern erratics having been met with 
 farther south than Highgate near London. If such were the case, 
 the Weald was probably dry land at the era when the buried forest 
 of Cromer in Norfolk (see above, p. 137. and 154.) flourished, and 
 when the elephant, rhinoceros, hippopotamus, extinct beaver, and 
 other mammals peopled that country. It may also be presumed that 
 the Weald continued above the sea-level when that forest sank down 
 to receive its covering of boulder-clay, gravel, chalk-rubble, and 
 other deposits, several hundred feet thick. But it by no means 
 follows that the area of the Weald was stationary during all this 
 period. Its surface may have been modified again and again during 
 the Glacial era, though it may never have been submerged beneath 
 the sea. 
 
 Mr. Trimmer has represented in a series of four maps his views 
 as to the successive changes which the physical geography of Eng- 
 land and parts of Europe may have undergone, after the commence- 
 ment of the Glacial epoch.* In the last but one of these he places 
 the Weald under water at a date long posterior to the forest of 
 Cromer. In the fourth map he represents the Weald as recon- 
 verted into land at a time when England was united to the con- 
 tinent, and when the Thames was a river of greater volume and of 
 more easterly extension than it is now, as proved by his own and 
 Mr. Austen's observations on the ancient alluvium of the Thames 
 with its freshwater fossils at points very near the sea. To discuss 
 the various data on which such conclusions depend, would lead me 
 into too long a digression ; I merely allude to them in this place 
 to show that, while the researches of Mr. Prestwich establish the 
 extreme remoteness of the period when the denuding operations 
 began, those of other geologists above cited, to whom Mr. Martin, 
 Professor Morris, and Sir R. Murchison should be added, prove that 
 important superficial changes have occurred at very modern eras. 
 
 In Denmark, especially in the island of Moen, Mr. Puggaard has 
 demonstrated that strata of chalk with flints, nearly as thick as the 
 white chalk of the Isle of Wight and Purbeck, have undergone dis- 
 turbances and contortions since the northern drift was formed.f The 
 layers of chalk-flint exposed in lofty sea-cliffs are often vertical and 
 curved, and the sands and clays of the overlying drift follow the bend- 
 ings and foldings of the older beds, and have evidently suffered the 
 same derangement. If, therefore, we find it necessary, in order to 
 
 * Geol. Quart. Journ., vol. ix. pi. 13. f Puggaard, Moens Geologie, 8vo. 
 
 Copenhagen, 1851. 
 
CH. XIX.] WEALD, HOW DENUDED. 287 
 
 explain the position of some beds of gravel, loam, or drift in the south- 
 east of England, to imagine important dislocations of the chalk and 
 local changes of level since the Glacial period, such speculations are 
 in harmony with conclusions derived from independent sources, or 
 drawn from the exploration of foreign countries. 
 
 It was long ago observed by Dr. Mantell that no vestige of the 
 chalk and its flints has been seen on the central ridge of the Weald 
 or on the Hastings Sands, but merely gravel and loam derived from 
 the rocks immediately subjacent. This distribution of alluvium, and 
 especially the absence of chalk detritus in the central district, agrees 
 well with the theory of denudation before set forth ; for, to return to 
 fig. 321. (p. 274.), if the chalk (No. 2.) were once continuous and 
 covered every where with flint-gravel, this superficial covering would 
 be the first to be carried away from the highest part of the dome 
 long before any of the gault (No. 3.) was laid bare. Now, if some 
 ruins of the chalk remain at first on the gault, these would be, in a 
 great degree, cleared away before any part of the lower greensand 
 (No. 4.) is denuded. Thus in proportion to the number and thick- 
 ness of the groups removed in succession, is the probability lessened 
 of our finding any remnants of the highest group strewed over the 
 bared surface of the lowest. 
 
 But it is objected, that, had the sea at one or several periods been 
 the agent of denudation, we should have found ancient sea-beaches 
 at the foot of the escarpments, and other signs of oceanic erosion. 
 As a general rule, the wreck of the white chalk and its flints can only 
 be traced to slight distances from the escarpments of the North and 
 South Downs. Some exceptions occur, one of which was first pointed 
 out to me in 1830, by the late Dr. Mantell. In this case the flints 
 are seen near Barcombe, three miles from the nearest chalk, as indi- 
 cated in the annexed section (fig. 331.). Even here it will be seen 
 that the gravel reaches no farther than the Weald clay. But 
 
 Fig. 331. 
 
 Barcamle 
 
 
 Section from the north escarpment of the South Downs to Barcombe. 
 A. Layer of unrounded chalk- flints. 
 
 1. Gravel composed of partially rounded chalk-flints. 
 
 2. Chalk with and without flints. 
 
 3. Lowest chalk or chalk-marl (upper greensand wanting). 
 
 4. Gault. 5. Lower greensand. 6. Weald clay. 
 
 it is worthy of remark, that such depressions as that between 
 Barcombe and Offham in this section, arising from the facility with 
 which the argillaceous gault (No. 4. map. p. 273.) has been removed 
 by water, are usually free from superficial detritus, although such 
 valleys, situated at the foot of escarpments where there has been 
 much waste, might have been supposed to be the natural receptacles 
 of the wreck of the undermined cliffs. The question is therefore 
 
286 WEALD, WHEN DENUDED. [Cn. XIX. 
 
 Lastly. The reader must recall to mind what was said, in the llth 
 and 12th chapters, of the glacial drift and its far-transported mate- 
 rials. How wide an extent of the British Isles appears to have been 
 under the sea during some part or other of that epoch ! Most of the 
 submerged areas were afterwards converted into dry land, several 
 hundred and in some places more than a thousand feet high. It is 
 an opinion very commonly entertained, that the central axis of the 
 Weald was dry land when the most characteristic northern drift 
 originated ; no traces of northern erratics having been met with 
 farther south than Highgate near London. If such were the case, 
 the Weald was probably dry land at the era when the buried forest 
 of Cromer in Norfolk (see above, p. 137. and 154.) flourished, and 
 when the elephant, rhinoceros, hippopotamus, extinct beaver, and 
 other mammals peopled that country. It may also be presumed that 
 the Weald continued above the sea-level when that forest sank down 
 to receive its covering of boulder-clay, gravel, chalk-rubble, and 
 other deposits, several hundred feet thick. But it by no means 
 follows that the area of the Weald was stationary during all this 
 period. Its surface may have been modified again and again during 
 the Glacial era, though it may never have been submerged beneath 
 the sea. 
 
 Mr. Trimmer has represented in a series of four maps his views 
 as to the successive changes which the physical geography of Eng- 
 land and parts of Europe may have undergone, after the commence- 
 ment of the Glacial epoch.* In the last but one of these he places 
 the Weald under water at a date long posterior to the forest of 
 Cromer. In the fourth map he represents the Weald as recon- 
 verted into land at a time when England was united to the con- 
 tinent, and when the Thames was a river of greater volume and of 
 more easterly extension than it is now, as proved by his own and 
 Mr. Austen's observations on the ancient alluvium of the Thames 
 with its freshwater fossils at points very near the sea. To discuss 
 the various data on which such conclusions depend, would lead me 
 into too long a digression ; I merely allude to them in this place 
 to show that, while the researches of Mr. Prestwich establish the 
 extreme remoteness of the period when the denuding operations 
 began, those of other geologists above cited, to whom Mr. Martin, 
 Professor Morris, and Sir R. Murchison should be added, prove that 
 important superficial changes have occurred at very modern eras. 
 
 In Denmark, especially in the island of Moen, Mr. Puggaard has 
 demonstrated that strata of chalk with flints, nearly as thick as the 
 white chalk of the Isle of Wight and Purbeck, have undergone dis- 
 turbances and contortions since the northern drift was formed. f The 
 layers of chalk-flint exposed in lofty sea-cliffs are often vertical and 
 curved, and the sands and clays of the overlying drift follow the bend- 
 ings and foldings of the older beds, and have evidently suffered the 
 same derangement. If, therefore, we find it necessary, in order to 
 
 * Geol. Quart. Journ., vol. ix. pi. 13. f Puggaard, Moens Geologie, 8vo. 
 
 Copenhagen, 1851. 
 
CH. XIX.] WEALD, HOW DENUDED. 287 
 
 explain the position of some beds of gravel, loam, or drift in the south- 
 east of England, to imagine important dislocations of the chalk and 
 local changes of level since the Glacial period, such speculations are 
 in harmony with conclusions derived from independent sources, or 
 drawn from the exploration of foreign countries. 
 
 It was long ago observed by Dr. Mantell that no vestige of the 
 chalk and its flints has been seen on the central ridge of the Weald 
 or on the Hastings Sands, but merely gravel and loam derived from 
 the rocks immediately subjacent. This distribution of alluvium, and 
 especially the absence of chalk detritus in the central district, agrees 
 well with the theory of denudation before set forth ; for, to return to 
 fig. 321. (p. 274.), if the chalk (No. 2.) were once continuous and 
 covered every where with flint-gravel, this superficial covering would 
 be the first to be carried away from the highest part of the dome 
 long before any of the gault (No. 3.) was laid bare. Now, if some 
 ruins of the chalk remain at first on the gault, these would be, in a 
 great degree, cleared away before any part of the lower greensand 
 (No. 4.) is denuded. Thus in proportion to the number and thick- 
 ness of the groups removed in succession, is the probability lessened 
 of our finding any remnants of the highest group strewed over the 
 bared surface of the lowest. 
 
 But it is objected, that, had the sea at one or several periods been 
 the agent of denudation, we should have found ancient sea-beaches 
 at the foot of the escarpments, and other signs of oceanic erosion. 
 As a general rule, the wreck of the white chalk and its flints can only 
 be traced to slight distances from the escarpments of the North and 
 South Downs. Some exceptions occur, one of which was first pointed 
 out to me in 1830, by the late Dr. Mantell. In this case the flints 
 are seen near Barcombe, three miles from the nearest chalk, as indi- 
 cated in the annexed section (fig. 331.). Even here it will be seen 
 that the gravel reaches no farther than the Weald clay. But 
 
 Fig. 331. 
 
 Barcamle 
 
 Section from the north escarpment of the South Downs to Barcombe. 
 A. Layer of unrounded chalk- flints. 
 
 1. Gravel composed of partially rounded chalk-flints. 
 
 2. Chalk with and without flints. 
 
 3. Lowest chalk or chalk-marl (upper greensand wanting). 
 
 4. Gault. 5. Lower greensand. 6. Weald clay. 
 
 it is worthy of remark, that such depressions as that between 
 Barcombe and Offham in this section, arising from the facility with 
 which the argillaceous gault (No. 4. map. p. 273.) has been removed 
 by water, are usually free from superficial detritus, although such 
 valleys, situated at the foot of escarpments where there has been 
 much waste, might have been supposed to be the natural receptacles 
 of the wreck of the undermined cliffs. The question is therefore 
 
288 
 
 ELEPHANT-BED. 
 
 [Cn. XIX. 
 
 often put how these hollows could have been swept clean except by 
 some extraordinary catastrophe. 
 
 The frequent angularity of the flints in the drift of Barcombe and 
 other places is also insisted upon as another indication of denuding 
 causes differing in kind and degree from any which man has witnessed. 
 But all who have examined the gravel at the base of a chalk-cliff, 
 in places where it is not peculiarly exposed to the continuous and 
 violent action of the waves, are aware that the flints retain much 
 angularity. This may be seen between the Old Harry rocks in 
 Dorsetshire and Christchurch in Hampshire. Throughout the 
 greater part of that line of coast the cliffs are formed of tertiary 
 strata, capped by a dense covering of gravel formed of flints slightly 
 abraded. As the waste of the cliffs is rapid the old materials are 
 gradually changed for new ones on the beach ; nevertheless we have 
 here an example of angles being retained after two periods of attri- 
 tion ; first, where the gravel was spread originally over the Eocene 
 deposits ; and, secondly, after the Eocene sands and clays were under- 
 mined and the modern cliff formed. 
 
 Angular flint-breccia is not confined to the Weald, nor to the 
 transverse gorges in the chalk, but extends along the neighbouring 
 coast from Brighton to Rottingdean, where it was called by 
 Dr. Mantell " the elephant-bed," because the bones of the mammoth 
 abound in it with those of the horse and other mammalia. The 
 following is a section of this formation as it appears in the Brighton 
 cliff.* 
 
 Fig. 332. 
 
 A. Chalk with layers of flint dipping slightly to the south. 
 
 b. Ancient beach, consisting of fine sand, from one to four feet thick, covered by shingle from nve 
 
 to eight feet thick of pebbles of chalk-flint, granite, and other rocks, with broken shells of 
 recent marine species, and bones of cetacea. 
 
 c. Elephant-bed, about fifty feet thick, consisting of layers of white chalk rubble, with broken chalk- 
 
 flints, often more confusedly stratified than is represented in this drawing, in which deposit 
 are found bones of ox, deer, horse, and mammoth. 
 
 d. Sand and shingle of modern beach. 
 
 * See also Sir E. Murchison, Geol. Quart. Journ. vol. vii. p. 365. 
 
CH.XIX.] SANGATTE CLIFF. 289 
 
 To explain this section we must suppose that, after the excavation 
 of the cliff A, the beach of sand and shingle b was formed by the 
 long-continued action of the sea. The presence of Littorina litforea 
 and other recent littoral shells determines the modern date of the 
 accumulation. The overlying beds are composed of such calcareous 
 rubble and flints, rudely stratified, as are often conspicuous in parts 
 of the Norfolk coast, where they are associated with glacial drift, 
 and were probably of contemporaneous origin. Similar flints and 
 chalk-rubble have been recently traced by Sir Roderick Murchison 
 to Folkestone and along the face of the cliffs at Dover, where the 
 teeth of the fossil elephant have been detected. 
 
 Mr. Prestwich also has shown that at Sangatte, near Calais, on the 
 coast exactly opposite Dover, a similar waterworn beach, with an 
 incumbent mass of angular flint-breccia, is visible. I have myself 
 visited this spot and found the deposit strictly analogous to that of 
 Brighton. The fundamental ancient beach has been uplifted more 
 than 10- feet above its original level. The flint-pebbles in it have 
 evidently been rounded at the base of an ancient chalk-cliff, the 
 course of which can still be traced inland, nearly parallel with the 
 present shore, but with a space intervening between them of about 
 one third of a mile in its greatest breadth. This space is occupied by 
 a terrace, 100 feet in its greatest height, the component materials of 
 which are too varied and complex to be described here. They are 
 such as might, I conceive, have been heaped up above the sea-level in 
 the delta of a river draining a region of white chalk. The delta may 
 perhaps have been slowly subsiding while the strata accumulated. 
 Some of the beds of chalk-rubble with broken flints appear to have 
 had channels cut in them before the uppermost deposit of sand and 
 loam was thrown down. The angularity of the flints, as Mr. Prest- 
 wich has suggested, may be owing to their having been previously 
 shattered when in the body of the chalk itself; for we often see 
 flints so fractured in situ in the chalk, especially when the latter has 
 been much disturbed. The presence also in this Sangatte drift of 
 large fragments of angular white chalk, some of them two feet in 
 diameter, should be mentioned. They are confusedly mixed with 
 smaller gravel and fine mud, for the most part devoid of stratifi- 
 cation, and yet often too far from the old cliffs to have been a talus. 
 I therefore suspect that the waters of the river and its tributaries 
 were occasionally frozen over, and that during floods the carrying 
 power of ice co-operated with that of water to transport fragile 
 rocks and angular flints, leaving them unsorted when the ice melted, 
 or not arranged according to size and weight as in deposits stratified 
 by moving water. A climate like that now prevailing on the 
 borders of the Baltic or in Canada might produce such effects long 
 after the intense cold of the glacial epoch had passed away. The 
 abundance of mammalia in countries where rivers are liable to be 
 annually encumbered with ice, is a fact with which we are familiar 
 in the northern hemisphere, and the frequency of fossil remains of 
 quadrupeds in formations of glacial origin ought not to excite 
 
 u 
 
290 DENUDATION OF THE WEALD. [Cn. XIX. 
 
 surprise. As to the angularity of the flints, it has been thought by 
 some authorities to imply great violence in the removing power, 
 especially in those cases where well-rounded pebbles washed out of 
 Eocene strata are likewise found broken, sometimes with sharp 
 edges and often with irregular pieces chipped out of them as if by a 
 smart blow. Such fractured pebbles occur not unfrequently in the 
 drift of the valley of the Thames. In explanation I may remark 
 that, in the Blackheath and other Eocene shingle-beds, hard egg- 
 shaped flint-pebbles may be found in such a state of decomposition 
 as to break in the same manner on the application of a moderate 
 blow, such as stones might encounter in the bed of a swollen river. 
 
 To conclude : It is a fact, not questioned by any geologist, that 
 the area of the Weald once rose from beneath the sea after the origin 
 of the chalk, that rock being a marine product, and now constituting 
 dry land. Few will question, that part of the same area remained 
 under water until after the origin of the Eocene deposits, because 
 they also are marine, and reach to the edge of the chalk-downs. 
 Whether, therefore, we do or do not admit the occurrence of reiter- 
 ated submersions and emersions of land, the first of them as old as 
 the Upper Cretaceous, the last perhaps of Newer Pliocene or even 
 later date, we are at least compelled to grant that there was a time 
 when, in the region under consideration, the waters of the sea 
 retreated. The presence of land- and river-shells, and the bones of 
 terrestrial quadrupeds in some of the gravel, loam, and flint-breccia 
 of the Weald may indicate a fluviatile origin, but they can never 
 disprove the prior occupation of the area by the sea. Heavy rains, 
 the slow decomposition of rocks in the atmosphere, land-floods, and 
 rivers (some of them larger than those now flowing in the same 
 valleys) may have modified the surface and obliterated all signs of 
 the antecedent presence of the sea. Littoral shells, once strewed 
 over ancient shores, or buried in the sands of the beach, may have 
 decomposed so as to make it impossible for us to assign an exact 
 paleontological date to the older acts of denudation ; but the removal 
 of Chalk and Greensand from the central axis of the Weald, the 
 leading inequalities of hill and dale, the long lines of escarpment, the 
 longitudinal and transverse valleys, may still be mainly due to the 
 power of the waves and currents of the sea, co-operating with that 
 upheaval and subsidence and dislocation of rocks which all admit 
 to have taken place. 
 
 In despair of solving the problem of the present geographical 
 configuration and geological structure of the Weald by an appeal 
 to ordinary causation, / some geplogists are fain to invoke the aid 
 of imaginary "rushes of salt water" over the land, during the 
 sudden upthrow of the bed of the sea, when the anticlinal axis 
 of the Weald was formed. Others refer to vast bodies of fresh water 
 breaking forth from subterranean reservoirs, when the rocks were 
 riven by earthquake-shocks of intense violence. The singleness of 
 the cause and the unity of the result are emphatically insisted upon : 
 the catastrophe was abrupt, tumultuous, transient, and paroxysmal ; 
 
CH. XIX.] CONCLUSION. 291 
 
 fragments of stone were swept along to great distances without time 
 being allowed for attrition ; alluvium was thrown down unstratified, 
 and often in strange situations, on the flanks or on the summits of 
 hills, while the lowest levels were left bare. The convulsion was felt 
 simultaneously over so wide an area that all the individuals of 
 certain species of quadrupeds were at once annihilated ; yet the 
 event was comparatively modern, for the species of testacea now 
 living were already in existence. 
 
 This hypothesis is surely untenable and unnecessary. In the 
 present chapter I have endeavoured to show how numerous have 
 been the periods of geographical change, and how vast their dura- 
 tion. Evidence to this effect is afforded by the relative position of 
 the chalk and overlying tertiary deposits ; by the nature, character, 
 and position of the tertiary strata ; and by the overlying alluvia of 
 the Weald and adjacent countries. As to the superficial detritus, its 
 insignificance in volume, when compared to the missing rocks, should 
 never be lost sight of. A mountain-mass of solid matter, hundreds 
 of square miles in extent, and hundreds of yards in thickness, has 
 been carried away bodily. To what distance it has been transported 
 we know not, but certainly beyond the limits of the Weald. For 
 achieving such a task, if we are to judge by analogy, all transient 
 and sudden agency is hopelessly inadequate. There is one power 
 alone which is competent to the task, namely, the mechanical force 
 of water in motion, operating gradually, and for ages. We have 
 seen in the 6th chapter that every stratified portion of the earth's 
 crust is a monument of denudation on a grand scale, always effected 
 slowly ; for each superimposed stratum, however thin, has been suc- 
 cessively and separately elaborated. Every attempt, therefore, to 
 circumscribe the time in which any great amount of denudation, 
 ancient or modern, has been accomplished, draws with it the gra- 
 tuitous rejection of the only kind of machinery known to us which 
 possesses the adequate power. 
 
 If, then, at every epoch, from the Cambrian to the Pliocene inclu- 
 sive, voluminous masses of matter, such as are missing in the Weald, 
 have been transferred from place to place, and always removed gra- 
 dually, it seems extravagant to imagine an exception in the very 
 region where we can prove the first and last acts of denudation to 
 have been separated by so vast an interval of time. Here, might we 
 say, if any where within the range of geological enquiry, we have 
 time enough and without stint at our command. 
 
 u 2 
 
292 DIVISIONS OF THE OOLITE. [Cn. XX. 
 
 CHAPTER XX. 
 
 JURASSIC 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 Upper Oolite 
 Purbeck beds New fossil Mammifer found at Swanage Dirt-bed or ancient 
 soil Fossils of the Purbeck beds Portland stone and fossils Lithographic 
 stone of Solenhofen Middle Oolite Coral rag Zoophytes Nerinsean lime- 
 stone Diceras limestone Oxford clay, Ammonites and Belemnites Lower 
 Oolite, Crinoideans Great Oolite and Bradford clay Stonesfield slate 
 Fossil mammalia, placental and marsupial Resemblance to an Australian 
 fauna Northamptonshire slates Yorkshire Oolitic coal-field Brora coal 
 Fuller's earth Inferior Oolite and fossils. 
 
 IMMEDIATELY below the Hastings Sands (the inferior member of 
 the Wealden, as defined in the 18th chapter), we find in Dorsetshire 
 another remarkable freshwater formation, called the Purbeck, 
 because it was first studied in the sea-cliffs of the peninsula of Pur- 
 beck in Dorsetshire. These beds were formerly grouped with the 
 Wealden, but some organic remains recently discovered in certain 
 intercalated marine beds show that the Purbeck series has a close 
 affinity to the Oolitic group, of which it may be considered as the 
 newest or uppermost member. 
 
 In England generally, and in the greater part of Europe, both the 
 Wealden and Purbeck beds are wanting, and the marine cretaceous 
 group is followed immediately, in the descending order, by another 
 series called the Jurassic. In this term, the formations commonly 
 designated as " the Oolite and Lias " are included, both being found 
 in the Jura Mountains. The ^Oolite was so named because in the 
 countries where it was first examined, the limestones belonging to it 1 
 had an oolitic structure (see p. 12.). These rocks occupy in Eng- 
 land a zone which is nearly 30 miles in average breadth, and 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. 
 b. Portland stone and sand. 
 c. Kimmeridge clay. 
 
 HT-JJI f d. Coral rag. 
 Middle | g Oxford clay. 
 
 ("/. Cornbrash and Forest marble. 
 
 T , v . Great Oolite and Stonesfield slate. 
 
 Lower 
 
 I. Inferior Oolite. 
 The Lias then succeeds to the Inferior Oolite. 
 
CH. XX.] PHYSICAL GEOGRAPHY OF THE OOLITE. 293 
 
 The Upper oolitic system of the above table has usually the Kim- 
 meridge clay for its base ; the Middle oolitic system, 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 sub- 
 divisions are distinguished by peculiar organic remains ; and, though 
 varying in thickness, may be traced in certain directions for 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 country, distant above 400 geo- 
 graphical miles, the analogy to the accepted English type, notwith- 
 standing the thinness or occasional absence of the clays, is more 
 perfect than in Yorkshire 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 features 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, 
 composing 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 configuration 
 of the surface now alluded to, such as may be seen 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, 
 
 Fig. 333. 
 
 Middle 
 Oolite. Oolite. Oolite. Chalk, clay. 
 
 Lower Middle Upper London 
 
 Oolite. 
 
 Lias. Oxford Clay. Kim. clay. Gault. 
 
 in this drawing, greatly to exaggerate the inclination of the beds, 
 and the height of the several formations, as compared to their 
 horizontal extent. It will be remarked, that the lines of cliff, or 
 escarpment, face towards the west in the great calcareous eminences 
 formed by the Chalk and the Upper, Middle, and Lower Oolites ; 
 and at the base of which we have respectively the Gault, Kim- 
 meridge 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 considerable thickness, and contains solid beds of marl- 
 stone, it occupies the lower part of the escarpment. 
 
 The external outline of the country which the geologist observes 
 in travelling eastward from Paris to Metz is precisely 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 instead of the west. 
 
 u 3 
 
294 
 
 UPPER PURBECK. 
 
 [Cn. XX. 
 
 The Chalk crops out from beneath the tertiary sands and clays of 
 the Paris basin, near Epernay, and the Gault from beneath the 
 Chalk and Upper Greensand at Clermont-en-Argonne ; and passing 
 from this place by Verdun and Etain to Metz, we find two limestone 
 ranges, with intervening vales of clay, precisely resembling those of 
 southern and central England, until we reach the great plain of Lias 
 at the base of the Inferior Oolite at Metz. 
 
 It is evident, therefore, that the denuding causes have acted simi- 
 larly over an area several hundred miles in diameter, sweeping away 
 the softer clays more extensively than the limestones, and under- 
 mining these last so as to cause them to form steep cliffs wherever 
 the harder calcareous rock was based upon a more yielding and 
 destructible clay. 
 
 UPPER OOLITE. 
 
 Purbeck beds (a. Tab. p. 292.). These strata, which we class as the 
 uppermost member of the Oolite, are of limited geographical extent 
 in Europe, as already stated, but they acquire importance, when we 
 consider the succession of three distinct sets of fossil remains which 
 they contain. Such repeated changes in organic life must have re- 
 ference to the history of a vast lapse of ages. The Purbeck beds 
 are finely exposed to view in Durdlestone Bay, near Swanage, Dor- 
 setshire, and at Lulworth Cove and the neighbouring bays between 
 Weymouth and Swanage. At Meup's Bay, in particular, Prof. E. 
 Forbes examined minutely in 1850 the organic remains of this 
 group, displayed in a continuous, sea-cliff section ; and he added 
 largely to the information previously supplied in the works of 
 Messrs. Webster, Fitton, De la Beche, Buckland, and Mantell. It 
 appears from these researches that the Upper, Middle, and Lower Pur- 
 becks are each marked by peculiar species of organic remains, these 
 again being different, so far as a comparison has yet been instituted, 
 from the fossils of the overlying Hastings Sands and Weald Clay.* 
 
 Upper Purbeck. The highest of the three divisions is purely 
 freshwater, the strata, about 50 feet in thickness, containing shells 
 of the genera Paludina, Physa, Limnceus, Planorbis, Valvata, Cyclas, 
 and Unio, with Cyprides and fish. All the species seem peculiar, 
 and among these the Cyprides are very abundant and characteristic. 
 (See figs. 334. a, b, c.) 
 
 Fig. 334. 
 
 Cyprides from the Upper Purbecks. 
 a. Cypris gibbosa, E.Forbes, b. Cypris tuberculata, E. Forbes, c. Cyprfs leguminella, E. Forbes. 
 
 * " On the Dorsetshire Purbecks," by Prof. E. Forbes, Brit. Assoc. Edinb. 1850. 
 
CH. XX.] 
 
 MIDDLE PURBECK. 
 
 295 
 
 The stone called "Purbeck marble," formerly much used in 
 ornamental architecture in the old English cathedrals of the 
 southern counties, is exclusively procured from this division. 
 
 Middle Purbeck. Next in succession is the Middle Purbeck, 
 about 30 feet thick, the uppermost part of which consists of fresh- 
 water limestone, with cyprides, turtles, and fish, of different species 
 from those in the preceding strata. Below the limestone are 
 brackish-water beds full of Cyrena, and traversed by bands abound- 
 ing in Corbula and Melania. These are based on a purely marine 
 deposit, with Pecten, Modiola, Avicula, Thracia, all undescribed 
 shells. Below this, again, come limestones and shales, partly of 
 brackish and partly of freshwater origin, in which many fish, 
 especially species of Lepidotus and Microdon radiatus, are found, 
 and a crocodilian reptile named Macrorhyncus. Among the mol- 
 lusks, a remarkable ribbed Melania, of the section Chilira, occurs. 
 
 Immediately below is the great and conspicuous stratum, 12 feet 
 thick, long familiar to geologists under the local name of " Cinder- 
 bed," formed of a vast accumulation of shells of Ostrea distorta 
 (fig. 335.). In the uppermost part of this bed Prof. Forbes dis- 
 covered the first echinoderm (fig. 336.) as yet known in the Purbeck 
 series, a species of Hemicidaris, a genus characteristic of the Oolitic 
 period, and scarcely, if at all, distinguishable from a previously 
 known oolitic species. It was accompanied by a species of Perna. 
 
 Fig. 335. 
 
 Fig. 336. 
 
 Ostrea distorta. 
 Cinder-bed, Middle Purbeck. 
 
 Hemicidaris Purbeckensfs, E. Forbes. 
 Middle Purbeck. 
 
 Below the Cinder-bed freshwater strata are again seen, filled in 
 many places with species of Cypris (fig. 337. a, b, c), and with Valvata, 
 
 Cyprides from the Middle Purbecks. 
 a. Cypris striato-punctata, E. Forbes, b. Cypris fasciculata, E. Forbes, c. Cypris granulata. Sow. 
 
 Paludina, Planorbis, Limnceus, Physa (fig. 338.), and Cyclas, all 
 different from any occurring higher in the series. It will be seen 
 
 u 4 
 
296 FOSSILS OF THE IDDLE PURBECK. [Cn. XX. 
 
 Fig. 338. t h a t Cypris fasciculata (fig. 337. b) has tubercles at 
 the end only of each valve, a character by which it 
 can be immediately recognized. In fact, these minute 
 crustaceans, almost as frequent in some of the shales 
 as plates of mica in a micaceous sandstone, enable 
 geologists at once to identify the Middle Purbeck in 
 risiovii, places far from the Dorsetshire cliffs, as for example, 
 E ' F purbeck Middle in the Vale of Wardour, in Wiltshire. Thick siliceous 
 beds of chert occur in the Middle Purbeck filled 
 with mollusca and cyprides of the genera already enumerated, in a 
 beautiful state of preservation, often converted into chalcedony. 
 Among these Prof. Forbes met with gyrogonites (the spore vessels 
 of Charce), plants never until 1851 discovered in rocks older than 
 Eocene. In a bed of this series, about 20 feet below the " Cinder," 
 Mr. W. R. Brodie has lately found (1854), in Durdlestone Bay, 
 portions of several small jaws with teeth, which Prof. Owen, after 
 clearing away the matrix, recognized as belonging to a small mam- 
 mifer of the insectivorous class. The teeth with pointed cusps 
 resemble in some degree those of the Cape Mole {Chrysochlora 
 aurea) ; but the number of the molar teeth (at least ten in each 
 ramus of the lower jaw) accords with that in the extinct Thylaco- 
 therium of the Stonesfield Oolite (see below, Chap. XX.). This 
 newly found quadruped, therefore, seems to have been more closely 
 allied in its dentition to the Thylacotherium than to any existing 
 insectivorous type. As in Thylacotherium, the angular process of 
 the jaw is not bent inwards, an osteological peculiarity confined to 
 the marsupial tribes (see Chap. XX.), and Prof. Owen therefore 
 refers the Spalacotherium to the placental or ordinary class of 
 monodelphous mammalia. 
 
 In a former edition of this work (1852), after alluding to the 
 discovery of numerous insects and air-breathing mollusca in the 
 " Purbeck," I remarked that, although no mammalia had then been 
 found, " it was too soon to infer their non-existence on mere nega- 
 tive evidence." The scarcity of the remains of warm-blooded 
 quadrupeds in Oolitic rocks, and the fact of none having yet been 
 met with in deposits of the Cretaceous era, may imply that there 
 were few mammalia then living, and their limited numbers may 
 possibly have some connection with the enormous development of 
 reptile life in all Secondary periods, as compared to Tertiary or 
 Recent times. If so, the phenomenon has at least no relation to an 
 incipient or immature condition of the planet, as some have imagined, 
 for, so far from being characteristic of primary or even older secondary 
 times, it belongs to the Maestricht chalk, the newest subdivision of the 
 cretaceous series, and that too in a manner even more marked than 
 in the older oolitic rocks. Nevertheless in the present imperfect 
 state of our information respecting the land-animals of the Cretaceous 
 and Jurassic periods, exclusively derived from marine and flaviatile 
 strata, and our total ignorance of the deposits formed in lakes and 
 
CH. XX.] 
 
 LOWER PURBECK. 
 
 297 
 
 Cyprides from the Lower Purbecks. 
 a. Cypris Purbeckensis, b. Cypris punctata, 
 
 E. Forbes. 
 
 Forbes. 
 
 caverns at the same date, it would be premature to attempt to 
 generalize on the nature of so ancient a terrestrial fauna. 
 
 Beneath the freshwater strata last described, a very thin band of 
 greenish shales, with marine shells and impressions of leaves, like 
 those of a large Zostera> succeeds, forming the base of the Middle 
 Purbeck. 
 
 Lower Purbeck. Beneath the thin marine band above men- 
 tioned, purely freshwater marls occur, containing species of Cypris 
 -339. (fig. 339. a, b\ Valvata, and 
 
 Limnceus, different from those 
 of the Middle Purbeck. This 
 is the beginning of the inferior 
 division, which is about 80 feet 
 thick. Below the marls are seen 
 more than 30 feet of brackish- 
 water beds, at Meup's Bay, 
 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 Rissoa (of the subgenus Hydrobia\ and a little Cardium 
 of the subgenus Protocardium, in the same beds, together with 
 Cypris. Some of the cypris-bearing shales are 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 Cycadece, 
 which I shall presently describe, underlies these marls, and rests 
 upon the lowest freshwater limestone, a rock about 8 feet thick, 
 containing Cyclas, Valvata, and Limnceus, of the same species as 
 those of the uppermost part of the Lower Purbeck, or above the 
 dirt-bed. The freshwater limestone in its turn rests upon the top 
 beds of the Portland stone, which, although it contains purely 
 marine remains, often consists of a rock quite homogeneous in 
 mineral character with the Lowest Purbeck limestone.* 
 
 The most remarkable of all the varied succession of beds enu- 
 merated 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 dark brown or black 
 colour, and contains a large pro- 
 portion of earthy lignite. Through 
 it are dispersed rounded' frag- 
 ments of stone, from 3 to 9 inches 
 in diameter, in such numbers that 
 it almost deserves the name of 
 gravel. Many silicified trunks 
 of coniferous trees, and the re- 
 
 Fig. 340. 
 
 Cycadeoidea (Mantellia) megalophylla, Buckland. 
 
 Weston, Geol. Q. J., vol.viii. p. 117. 
 
298 FOSSIL FORESTS IN ISLE OF PORTLAND [Cn. XX. 
 
 mains of plants allied to Zamia and Cycas, are buried in this dirt- 
 bed (see figure of fossil species, fig. 340., and of living Zamia, fig. 
 341.) 
 
 Fig. 341. 
 
 Zamia spiralis. Southern Australia. 
 
 These plants must have become fossil on the spots where they 
 grew. The stumps of the trees stand erect for a height of from 
 1 to 3 feet, and even in one instance to 6 feet, with their 
 roots attached to the soil at about the same distances 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 Cycade<E.\ 
 
 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 fragments of the prostrate trees are 
 rarely more than 3 or 4 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 
 roots is about 1 foot. Root-shaped cavities were observed by 
 Professor Henslow to descend from the bottom of the dirt-bed into 
 the subjacent freshwater stone, which, though now solid, must have 
 been in a soft and penetrable state when the trees grew. J 
 
 Fig. 342. 
 
 freshwater calcareous slate. 
 
 dirt-bed and ancient forest. 
 
 JV-. I lowest freshwater beds of the Lower 
 
 Purbeck. 
 
 Portland stone, marine. 
 Section in Isle of Portland, Dorset. (Buckland and De la Beche.) 
 
 * Mr. Webster first noticed the erect 
 position of the trees and described the 
 Dirt-bed. 
 
 f Fitton, Geol. Trans., Second Series, 
 vol. iv. pp. 220, 221. 
 
 | Buckland and De la Beche, GeoL 
 
 Trans., Second Series, vol. iv. p. 16. 
 Prof. Forbes has ascertained that the 
 subjacent rock is a freshwater limestone, 
 and not a portion of the Portland oolite, 
 as was previously imagined. 
 
CH. XX.] 
 
 AND LULWORTH COVE. 
 
 299 
 
 The thin layers of calcareous slate (fig. 342.) were evidently de- 
 posited tranquilly, and would have been horizontal but for the pro- 
 trusion of the stumps of the trees, around the top of each of which 
 they form hemispherical concretions. 
 
 The dirt-bed is by no means confined to the island of Portland, 
 where it has been most carefully studied, but is seen in the same 
 relative position in the cliffs east of Lulworth Cove, in Dorsetshire, 
 where, as the strata have been disturbed, 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. 343.). Traces 
 
 Fig. 343. 
 
 freshwater calcareous slate, 
 dirt-bed, with stools of trees. 
 
 freshwater. 
 
 Portland stone, marine. 
 
 Section in cliff east of Lulworth Cove. (Buckland and De la Beche.) 
 
 of the dirt-bed have also been observed by Mr. Fisher, at Ridgway ; 
 by Dr. Buckland, about two miles north of Thame, in Oxfordshire ; 
 and by Dr. Fitton, in the cliffs in the Boulonnois, on the French 
 coast; but, as might be expected, this freshwater deposit is of 
 limited extent when compared to most marine formations. 
 
 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 England, the climate being such as to 
 admit 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 enve- 
 loping 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 freshwater lake or 
 estuary, was not accompanied by any violent denudation, or rush of 
 water, since the loose black earth, together with the trees which lay 
 prostrate on its surface, must inevitably have been swept away had 
 any such violent catastrophe taken place. 
 
 The dirt-bed has been described above in its most simple form, 
 but in some sections the appearances are more complicated. The 
 forest of the dirt-bed was not everywhere the first vegetation which 
 grew in this region. Two other beds of carbonaceous clay, one of 
 them containing Cycadece, in an upright position, have been found 
 below it, and one above it, which implies other oscillations in the 
 
300 
 
 CHANGES OF MEDIUM. PURBECK BEDS. [Cn. XX. 
 
 level of the same ground, and its alternate occupation by land and 
 water more than once. 
 
 Table showing the changes of medium in which the strata were 
 formed, from the Portland Stone up to the Lower Greensand in- 
 clusive, in the south-east of England (beginning with the lowest). 
 
 1. Marine 
 
 2. Freshwater 
 Land 
 
 Freshwater 
 Land 
 
 Freshwater 
 Land (Dirt-bed) 
 Freshwater 
 Land 
 Brackish 
 Freshwater 
 
 Portland Stone. 
 
 Lower Purbeck. 
 
 3. Marine ~| 
 Freshwater I 
 Marine 
 
 Brackish } Middle Purbeck. 
 
 Marine 
 
 Brackish 
 
 FreshwaterJ 
 
 4. Freshwater Upper Purbeck. 
 
 5. Freshwater"| 
 
 Brackish > Hastings Sands. 
 FreshwaterJ 
 
 6. Freshwater Wealden Clay. 
 
 7. Marine Lower Greensand. 
 
 The annexed tabular view will enable the reader to take in at a 
 glance the successive changes from sea to river, and from river to 
 sea, or from these again to a state of land, which have occurred in 
 this part of England between the Oolitic and Cretaceous periods. 
 That there have been at least four changes in the species of testacea 
 during the deposition of the Wealden and Purbeck beds, seems to 
 follow from the observations recently made by Prof. Forbes, so that, 
 should we hereafter find the signs of many more alternate occupations 
 of the same area by different elements, it is no more than we might 
 expect. Even during a small part of a zoological period, not suffi- 
 cient to allow time for many species to die out, we find that the 
 same area has been laid dry, and then submerged, and then again 
 laid dry, as in the deltas of the Po and Ganges, the history of which 
 has been brought to light by Artesian borings.* We also know that 
 similar revolutions have occurred within the present century (1819) 
 in the delta of the Indus in Cutchf, where land has been laid perma- 
 nently under the waters both of the river and sea, without its soil 
 or shrubs having been swept away. Even, independently of any 
 vertical movements of the ground, we see in the principal deltas, such 
 as that of the Mississippi, that the sea extends its salt waters 
 annually for many months over considerable spaces which, at other 
 seasons, are occupied by the river during its inundations. 
 
 It will be observed that the division of the Purbecks into upper, 
 middle, and lower has been made by Prof. Forbes, strictly on the 
 principle of the entire distinctness of the species of organic remains 
 which they include. The lines of demarcation are not lines of dis- 
 turbance, 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 Lulworth, and the Cinder- 
 
 * See Principles of Geol. 9th ed. f Ibid. p. 460. 
 pp. 255. 275. 
 
CH. XX.] PORTLAND STONE. 301 
 
 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 freshwater and brackish strata 
 must," says this naturalist, " be sought for, not simply in either a 
 rapid or a sudden change of their area into land or sea, but in the 
 great lapse of time which intervened between the epochs of deposition 
 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 2 or 3 feet of vegetable soil 
 is the only monument which many a tropical forest has left of its 
 existence ever since the ground on which 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 expect 
 on that account to find them constituting the lines of separation 
 between successive strata characterized by different zoological types. 
 The preservation of a layer of vegetable soil, when in the act of being 
 submerged, must be regarded as a rare exception to a general 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 probably 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, Coniferse (fig. 344.), and Cycadese 
 Fig. 344. (fig- 340.), without any exogens ; the whole more 
 
 allied to the Oolitic than to the Cretaceous vege- 
 tation. The vertebrate and invertebrate animals 
 indicate, like the plants, a somewhat nearer rela- 
 tionship to the Oolitic than to the cretaceous 
 period. Mr. Brodie has found the remains of 
 beetles and several insects of the homopterous and 
 trichopterous orders, some of which now live on 
 cane of afrom the P lants > wnile others are of such forms as hover 
 isie of Purbeck. (Fitton.) OV er the surface of our present rivers. 
 
 Portland Stone and Sand (b. Tab. p. 292.). The Portland stone has 
 already been mentioned as forming in Dorsetshire the foundation on 
 which the freshwater limestone of the Lower Purbeck reposes (see 
 p. 297.). It supplies the well-known building-stone of which St. Paul's 
 and so many of the principal edifices of London are constructed. This 
 upper member rests on a dense bed of sand, called the Portland sand, 
 containing for the most part similar marine fossils, below which is 
 the Kimmeridge clay. In England these Upper Oolite formations 
 are alrapst wholly confined to the southern counties. Corals are rare 
 in them, although one species is found plentifully at Tisbury, Wilt- 
 shire, in the Portland sand, converted into flint and chert, the origi- 
 nal calcareous matter being replaced by silex (fig. 345.). , 
 
 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 bitumi- 
 
302 FOSSILS OF THE PORTLAND STONE. [Cn. XX. 
 
 Fig. 345. 
 
 Fig. 346. 
 
 Isastr&a oblonga, M. Edw. and J. Haime. 
 
 As seen on a polished slab of chert from 
 
 the Portland Sand, Tisbury. 
 
 Fig. 347. 
 
 Trigonia gibbosa. nat. size. 
 
 a. the hinge. 
 Portland Stone, Tisbury 
 
 Fig. 348. 
 
 Cardium dissimile. \ nat. size. 
 Portland Stone. 
 
 Ostrea expansa. 
 Portland Sand. 
 
 nous matter may have been, in part at least, derived from the decom- 
 position of vegetables. But as impressions of plants are rare in these 
 shales, which contain ammonites, oysters, and other marine shells, the 
 bitumen may perhaps be of animal origin. 
 
 Among the characteristic fossils may be mentioned Cardium stria- 
 tulum (fig. 349.) and Ostrea deltoidea (fig. 350.), the latter found in 
 the Kimmeridge clay throughout England and the north of France, 
 and also in Scotland, near Brora. The Gryphcea virgula (fig. 351.), 
 
 Fig. 350. 
 
 Fig. 349. 
 
 Fig. 351. 
 
 Cardium striatulum. 
 Kimmeridge clay, Hart well. 
 
 Ostrea deltoidea. Gryph&a virgula. 
 
 Upper Oolite: Kimmeridge clay. A nat. size. 
 
 also met with in the same clay near Oxford, is so abundant in the 
 Upper Oolite of parts of France as to have caused the deposit to be 
 termed " marnes a gryphees virgules." Near Clermont, in Argonne, 
 a few leagues from St. Menehould, where these indurated marls crop 
 
CH. XX.] 
 
 CORAL RAG. 
 
 303 
 
 Fig. 352. 
 
 Trigonellites latus. 
 Kimmeridge clay. 
 
 out from beneath the gault, I have seen them, on decomposing, leave 
 the surface of every ploughed field literally strewed over with this 
 fossil oyster. The Trigonellites latus (Aptychus, of some authors) 
 (fig. 352.) is also widely dispersed through this 
 clay. The real 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 formed the gizzard of a cephalopod ; for 
 the living Nautilus has a gizzard with horny folds, 
 and the Bulla is well known to possess one formed 
 of calcareous plates. 
 The celebrated lithographic stone of Solenhofen, in Bavaria, be- 
 longs to one of the upper divisions of the oolite, and affords a re- 
 markable example of the variety of fossils which may be preserved 
 under favourable circumstances, and what delicate impressions of the 
 tender parts of certain animals and plants 
 may be retained where the sediment is of 
 extreme fineness. Although the number of 
 testacea in this slate is small, and the plants 
 few, and those all marine, Count Miinster 
 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 flying lizards, or pterodactyls (see fig. 
 353.), six saurians, three tortoises, sixty 
 species of fish, forty-six of Crustacea, and 
 twenty-six of insects. These insects, 
 among which is a libellula, or dragon-fly, 
 must have been blown out to sea, probably 
 from the same land to which the flying 
 lizards, and other contemporaneous rep- 
 tiles, resorted. 
 
 Fig. 353. 
 
 Skeleton of Pterodactylus 
 
 crassirostris. 
 
 Oolite of Pappenheim, near Solen 
 hofen. 
 
 MIDDLE OOLITE. 
 
 Coral Rag. One of the limestones of the Middle Oolite has been 
 called the " Coral Rag," because it consists, in part, of continuous 
 beds of petrified corals, for the most part retaining the position in 
 which they grew at the bottom of the sea. In their forms they more 
 frequently resemble the reef-building poliparia of the Pacific than do 
 the corals of any other member of the Oolite. They belong chiefly 
 to the genera Thecosmilia (fig. 354.), Protoseris, and Thamnastrcea, 
 and sometimes form masses of coral 15 feet thick. In the annexed 
 figure of a Thamnastrcea (fig. 355.), from this formation, it will be 
 seen that the cup-shaped cavities are 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 condition, and the others an immature state. 
 These coralline strata extend through the calcareous hills of the 
 
304 
 
 CORALS OF THE OOLITE. 
 
 Corals of the Coral Rag. 
 
 [Cn. XX. 
 
 Fig. 354. 
 
 Fig. 355. 
 
 Thecosmilia annularis, Milne Edw. and J. Haime. 
 Coral Rag, Steeple Ashton. 
 
 Thamnastrcea. 
 Coral Rag, Steeple Ashton. 
 
 N. W. of Berkshire, and north of Wilts, and again recur in York- 
 shire, near Scarborough. The Ostrea gregarea (fig. 356.) 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 
 coral-rag, has been called "Nerinaean limestone" (Calcaire a Ne- 
 rinees) by M. Thirria ; Nerincea being an extinct genus of univalve 
 shells, much resembling the Cerithium in external form. The an- 
 nexed section (fig. 357.) shows the curious form of the hollow part 
 of each whorl, and also the perforation which passes up the middle 
 of the columella. N. Goodhallii (fig. 358.) is another English species 
 
 Fig. 357. 
 
 Fig. 356. 
 
 Fig. 3S8. 
 
 Ostrea gregarea. 
 Coral rag, Steeple Ashton. 
 
 Nerintea hieroglyphica. 
 Coral rag. 
 
 Nerina>a Goodhnllii, Fitton. 
 Coral rag, Weymouth. uat. size. 
 
 of the same genus, from a formation which seems to form a passage 
 from the Kimmeridge clay to the coral rag.* 
 
 A division 6f the oolite in the Alps, regarded by most geologists 
 as coeval with the English coral rag, has been often named " Calcaire 
 a Dicerates," or " Diceras limestone," from its containing abundantly 
 a bivalve shell (see fig. 359.) of a genus allied to the Chama. 
 
 * Fitton, Geol. Trans., Second Series, yol. iv. pi. 23. fig. 12. 
 
Cu. XX.] FOSSILS OP THE OXFORD CLAY. 
 
 Fig. 360. 
 
 Fig. 359. 
 
 305 
 
 Cast of Dicer as arietina. 
 Coral rag, France. 
 
 Cidaris coronata. 
 Coral rag. 
 
 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 500 feet thick. In this there 
 are no corals, but great abundance of cephalopoda of the genera 
 Ammonite and Belemnite. (See figs. 361, 362.) In some of the clay 
 
 Fig. 361. 
 
 Belemnites hastatus. Oxford clay. 
 
 of very fine texture ammonites are very perfect, although somewhat 
 compressed, and are seen to be furnished on each side of the aperture 
 with a single horn-like projection (see fig. 362.). These were dis- 
 covered in the cuttings of the Great Western Railway, near Chippen- 
 ham, in 1841, and have been described by Mr. Pratt (An. Nat. 
 Hist. Nov. 1841). 
 
 Fig. 362 
 
 Ammonites Jason, Reinecke. Syn. A. Elizabeths, Pratt. 
 Oxford clay, Christian Malford, Wiltshire. 
 
308 BRADFORD ENCRINITES. [Cn. XX. 
 
 in which some now lie prostrate. These appearances are represented 
 in the section b, fig. 365., where the darker strata represent the 
 Bradford clay, which some geologists class with the Forest marble, 
 others with the Great Oolite. The upper surface of the calcareous 
 stone below is completely incrusted 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 serpula 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 argillaceous mud. In 
 some instances we find that, after the parasitic serpulce were full 
 grown, they had become incrusted over with a bryozoan, called 
 Berenicea diluviana ; and many generations of these molluscs had 
 succeeded each other in the pure water before they became fossil. 
 
 Fig. 366. 
 
 a. Single plate or articulation of an Encrinite overgrown with serpulte and bryoxoa. Natural size. 
 
 Bradford clay. 
 
 b. Portion of the same magnified, showing the bryozoan Berenicea diluviana covering one of the 
 
 serpuUe. 
 
 We may, therefore, perceive distinctly that, as the pines and cyca- 
 deous 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 preservation in marine strata.* 
 
 Such differences in the fossils as distinguish the calcareous and 
 argillaceous deposits from each other, would be described by natu- 
 ralists 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 
 varying conditions of the habitable surface. In a single district it is 
 difficult to decide how far the limitation of species to certain minor 
 
 * For a fuller account of these Encrinites, see Buckland's Bridgewater Treatise, 
 vol. i. p. 429. 
 
CH. XX.] 
 
 FOSSILS OF THE GREAT OOLITE. 
 
 309 
 
 formations has been due to the local influence of stations, or how far 
 it has been caused by time or the creative and destroying law above 
 alluded to. But we recognize the reality of the last-mentioned influ- 
 ence, when we contrast the whole oolitic series of England with that 
 of parts of the Jura, Alps, and other distant regions, where there is 
 scarcely any lithological resemblance ; and yet some of the same 
 fossils remain 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 re- 
 presented there, and some entirely wanting. 
 
 The Bradford clay above alluded to is sometimes 60 feet thick, 
 but, in many places, it is wanting ; and, in others, where there are 
 no limestones, it cannot easily be separated from the clays of the 
 overlying " forest marble " and underlying " fuller's earth." 
 
 The calcareous portion of the Great Oolite consists of several 
 shelly limestones, one of which, called the Bath Oolite, is much cele- 
 brated as a building-stone. In parts of Gloucestershire, 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 neighbour- 
 hood, and with fragments of abraded madrepores, dicotyledonous 
 wood, and crabs' claws. The shelly strata, also, have occasionally 
 suffered denudation, and the removed portions have been replaced by 
 clay."* In such shallow-water beds shells of the genera Patella, 
 
 Fig. 368 
 
 Fig. 367 
 
 Terebratula digona. 
 Nat. size. Bradford clay. 
 
 Fig. 369. 
 
 Purpuroidea nodulatrt. A nat. size. 
 Great Oolite, Minchinhampton. 
 
 Cylindrites aculzts, Sow. 
 
 Syn. Actteon acutus, 
 Great Oolite, Minchinhampton. 
 
 Fig. 372. 
 
 Fig. 370. 
 
 Patella rugosa, Sow. 
 Great Oolite. 
 
 Nerita costuJata, Desh. 
 Great Oolite. 
 
 Rimula (Emarginula) clatfirata, 
 Sow. Great Oolite. 
 
 * Lycett, Geol. Journ. vol. iv. p. 183. 
 x 3 
 
310 STONESFIELD SLATE. [Cn. XX. 
 
 Nerita, Rimula, and Cylindrites are common (see figs. 369. to 372.) ; 
 while cephalopoda are rare, and, instead of ammonites and belem- 
 nites, numerous genera of carnivorous trachelipods appear. Out of 
 one hundred and forty-two species of univalves obtained from the 
 Minchinhampton beds, Mr. Lycett found no less than forty -one to 
 be carnivorous. They belong principally to the genera Buccinum, 
 Pleurotoma, Rostellaria, Murex, Purpuroidea (fig. 368.), and Fusus, 
 and exhibit a proportion of zoophagous species not very different 
 from that which obtains in warm seas of the recent period. These 
 chronological results are curious and unexpected, since it was 
 imagined that we might look in vain for the carnivorous trachelipods 
 in rocks of such high antiquity as the Great Ooolite, and 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 belemnites, had become extinct. 
 
 Stonesfield slate. 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 large spheroidal masses imbedded in 
 sand, only 6 feet thick, but very rich in organic remains. It con- 
 tains 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 belemnites, tri- 
 goniae, and other marine shells, with fragments of wood, are common, 
 and impressions of ferns, cycadeae, and other plants. Several insects, 
 Fig. 373. also, and, among the rest, the wing-covers of beetles, are 
 perfectly preserved (see fig. 373.), some of them approach- 
 ing nearly to the genus Buprestis.\ The remains, also, of 
 many genera of reptiles, such as Pleiosaur, Crocodile, aad 
 Pterodactyl, have been discovered in the same limestone. 
 
 But the remarkable fossils for which the Stonesfield 
 slate is most celebrated are those referred to the mam- 
 miferous 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 
 Stonesfield. any cetacean, had been discovered until the Spalacothe- 
 rium of the Purbeck beds came to light in 1854 (see above, p. 296.). 
 Yet we have seen that terrestrial plants were not rare in the lower 
 cretaceous formation, and that in the Wealden there was evidence of 
 freshwater 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 
 terrestrial quadrupeds the more striking. The "want, however, of 
 any bones of whales, seals, dolphins, and other aquatic mammalia, 
 whether in the chalk or in the upper or middle oolite, is certainly 
 still more remarkable. Formerly, indeed, a bone from the great 
 oolite of Enstone, near Woodstock, in Oxfordshire, was cited, on the 
 
 * Proceedings Geol. Soc. vol.i. p. 41 4. it is suggested that these elytra may 
 t See Buckland's Bridgewater Trea- belong to Priomus. 
 tise ; and Brodie's Fossil Insects, where 
 
CH. XX. 1 FOSSILS OF THE OOLITE. 311 
 
 authority of Cuvier, as referable to this class. Dr. Buckland, who 
 stated this in his Bridgewater Treatise *, had the kindness to send 
 me the supposed ulna of a whale, that Prof. Owen might examine 
 into its claims to be considered as cetacean. It is the opinion of 
 that eminent comparative anatomist that it cannot have belonged to 
 the cetacea, because the fore-arm in these marine mammalia is in- 
 variably much flatter, and devoid of all muscular depressions and 
 ridges, one of which is so prominent in the middle of this bone, 
 represented in the annexed cut (fig. 374.). In saurians, on the con- 
 Fig. 374. 
 
 Bone of a Reptile, formerly supposed to be the ulna of a Cetacean ; from the Great Oolite of 
 Enstone, near Woodstock. 
 
 trary, such ridges exist for the attachment of muscles ; and to some 
 animal of that class the bone is probably referable. 
 
 These observations are made to prepare the reader to appreciate 
 more justly the interest felt by every geologist in the discovery in 
 the Stonesfield slate of no less than seven specimens of lower jaws of 
 mammiferous quadrupeds, belonging to three different species and to 
 two distinct genera, for which the names of Amphitherium and Phas- 
 colotherium have been adopted. When Cuvier was first shown one 
 of these fossils in 1818, he pronounced it to belong to a small ferine 
 mammal, with a jaw much resembling that of an opossum, but differ- 
 ing from all known ferine genera, in the great number of the molar 
 teeth, of. which it had at least ten in a row. Since that period, a 
 much more perfect specimen of the same fossil, obtained by Dr. 
 Buckland (see fig. 375.), has been examined by Prof. Owen, who 
 finds that the jaw contained on the whole twelve molar teeth, with 
 the socket of a small canine, and three small incisors, which are in 
 situ, altogether amounting to sixteen teeth on each side of the lower 
 jaw. 
 
 The only question which could be raised respecting the nature of 
 these fossils was, whether they belonged to a mammifer, a reptile, or 
 a fish. Now on this head the osteologist observes that each of the 
 seven half jaws is composed of but one single piece, and not of two or 
 more separate bones, as in fishes and most reptiles, or of two bones, 
 united by a suture, as in some few species belonging to those classes. 
 
 * Vol. i. p. 115. 
 
 x 4 
 
312 
 
 OOLITIC GROUP 
 
 Fig. 375. 
 
 [CH. XX. 
 
 Amphitherium Broderipii, Owen. 
 Natural size. Stonesfield Slate. 
 
 Amphitherium Prevostii, Cuv. Sp. Stonesfield Slate. 
 a. coronoid process. b. condyle. c. angle of jaw. d. double-fanged molars. 
 
 Fig. 376. The condyle, moreover (&, fig. 375.), or 
 
 articular surface, by which the lower jaw 
 unites with the upper, is convex in the 
 Stonesfield specimens, and not concave as 
 in fishes and reptiles. The coronoid pro- 
 cess (a, fig. 375.) is well developed, whereas 
 it is wanting or very small, in the inferior classes of vertebrata. 
 Lastly, the molar teeth in the Amphitherium and Phascolotherium 
 have complicated crowns and two roots (see d, fig. 375.), instead 
 of being simple and with single fangs.* 
 
 The only question, therefore, which could fairly admit of contro- 
 versy was limited to this point, whether the fossil mammalia found 
 in the lower oolite of Oxfordshire ought to be referred to the mar- 
 supial quadrupeds, or to the ordinary placental series. Cuvier had 
 long ago pointed out a peculiarity in the form of the angular process 
 (c, figs. 380. and 381.) of the lower jaw, as a character of the genus 
 
 Fig. 377. 
 
 Tupaia Tana. 
 Right ramus of lower jaw. 
 
 Natural size. 
 
 A recent insectivorous mammal from 
 Sumatra. 
 
 Fig. 378. 
 
 Fig. 379. 
 
 Fig. 380. 
 
 Fig. 381. 
 
 Part of lower jaw of Tupaia Tana ; 
 twice natural size. 
 
 Fig. 378. End view seen from behind, showing 
 
 the very slight inflection of the angle at c. 
 Fig. 379. Side view of same. 
 
 Part of lower jaw of Didelphys Azara?; 
 recent, Brazil. Natural size. 
 
 Fig. 380. End view seen from behind, showing 
 
 the inflection of the angle of the jaw, c, d. 
 Fig. 381. Side view of same. 
 
 * I have given a figure in the Prin- 
 ciples of Geology, chap, ix., of another 
 Stonesfield specimen of Amphitherium 
 
 Prevostii, in which the sockets and roots 
 of the teeth are finely exposed. 
 
CH. XX.] AND ITS FOSSILS 313 
 
 Didelphys ; and Prof. Owen has since established its generality in the 
 entire marsupial series. In all these pouched quadrupeds, this pro- 
 cess is turned inwards, as at c d, fig. 380. in the Brazilian opossum, 
 whereas in the placental series, as at c, figs. 378. and 379., there is an 
 almost entire absence of such inflection. The Tupaia Tana of 
 Sumatra has been selected by my friend Mr. Waterhouse for this 
 illustration, because that small insectivorous quadruped bears a great 
 resemblance to those of the Stonesfield Amphitherium. By clearing 
 away the matrix from the specimen of Amphitherium Prevostii above 
 represented (fig. 375.) Prof. Owen ascertained that the angular 
 process (c) bent inwards 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 turns the scale in favour of its 
 affinities to the placental insectivora. Nevertheless, the Amphithe- 
 rium offers some points of approximation in its osteology 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 of Amphitherium has been found at Stonesfield 
 (fig. 376. p. 312.), which differs from the former (fig. 375.) princi- 
 pally in being larger. 
 
 The second mammiferous genus discovered in the same slates was 
 named originally by Mr. Broderip Didelphys Buchlandi (see fig. 382.), 
 
 Fig. 382. 
 
 Phascolotherium Bucklandi, Broderip, sp. 
 a. natural size. b. molar or same magnified. 
 
 and has since been called Phascolotherium 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 
 agreement with the living genus Didelphys in the number of the 
 premolar and molar teeth is complete.") 1 
 
 On reviewing, therefore, the whole of the osteological evidence, it 
 will be seen that we have every reason to presume that the Amphi- 
 therium and Phascolotherium of Stonesfield represent both the pla- 
 cental and marsupial classes of mammalia ; and if so, they warn us in 
 a most emphatic manner, not to found rash generalizations respecting 
 the non-existence of certain classes of animals at particular periods 
 of the past on mere negative evidence. The singular accident of 
 our having as yet found nothing but the lower jaws of seven indi- 
 viduals, and no other bones of their skeletons, is alone sufficient to 
 demonstrate the fragmentary manner in which the memorials of an 
 
 * A figure of this recent Myrmecobius f Owen's British Fossil Mammals,, 
 will be found in the Principles, chap. ix. p. 62. 
 
314 OOLITIC GROUP [Cn. XX. 
 
 ancient terrestrial fauna are handed down to us. We can scarcely 
 avoid suspecting that the two genera above described may have 
 borne a like insignificant proportion to the entire assemblage of warm- 
 blooded quadrupeds which flourished in the islands of the oolitic sea. 
 Prof. Owen has remarked that, as the marsupial genera, to which 
 the Phascolotherium is most nearly allied, are now confined to New 
 South Wales and Van Diemen's Land, so also is it in the Australian 
 seas, that we find the Cestracion, a cartila- 
 ginous fish which has a bony palate, allied to 
 those called Acrodus (see fig. 412. p. 322.) and 
 Strophodus, so common in the oolite and lias. 
 In the same Australian seas, also, near the 
 shore, we find the living Trigonia, a genus 
 of mollusca so frequently met with in the 
 Stonesfield slate. So, also, the Araucarian 
 pines are now abundant, together with ferns, 
 Portion of a fossil fruit of PO- in Australia and its islands, as they were in 
 e Treat (Bu pl: Europe in the oolitic period. Endogens of the 
 Char " most perfect structure are met with in oolitic 
 rocks, as, for example, the Podocarya of 
 
 Buckland, a fruit allied to the Pandanus, found in the Inferior 
 Oolite (see fig. 383.). 
 
 The Stonesfield slate, in its range from Oxfordshire to the north- 
 east, is represented by flaggy and fissile sandstones, as at Collyweston 
 in Northamptonshire, where, according to the researches of Messrs. 
 Ibbetson and Morris*, it contains many shells, such as Trigonia angu- 
 lata, also found at Stonesfield. But the Northamptonshire strata of 
 this age assume a more marine character, or appear at least to have 
 been formed farther from land. They inclose, however, some fossil 
 ferns, such as Pecopteris polypodioides, of species common to the 
 oolites of the Yorkshire coast, where rocks of this age put on all 
 the aspect of a true coal-field ; thin seams of coal having actually 
 been worked in them for more than a century. 
 
 In the north-west of Yorkshire, the formation alluded to consists of 
 an upper and a lower carbonaceous shale, abounding in impressions 
 of plants, divided by a limestone considered by many geologists as the 
 representative of the Great Oolite ; but the scarcity of marine fossils 
 makes all comparisons with the subdivisions adopted in the south 
 extremely difficult. A rich harvest of fossil ferns has been obtained 
 from the upper carbonaceous shales and sandstones at Gristhorpe, 
 near Scarborough (see figs. 384, 385.). The lower shales are well 
 exposed in the sea-cliffs at Whitby, and are chiefly characterized 
 by ferns and cycadeae. They contain, also, a species of calamite, and 
 a fossil called Equisetum columnare, which maintains an upright 
 position in sandstone strata over a wide area. Shells of Estheria 
 
 * Ibbetson and Morris, Report of Brit. Ass., 1847, p. 131.; and Moms, 
 Geol. Journ., ix. p. 334. 
 
CH. XX.] 
 
 AND ITS FOSSILS. 
 Fig. 3S4. 
 
 315 
 
 Pterophyllum comptum . Syn. Cycadites comptwt. 
 Upper sandstone and shale, Gri&thorpe, near Scarborough. 
 
 Fig. 385. 
 
 Fig. 386. 
 
 Hemitelites Brownii, Goepp. 
 Syn. Phlebopteris contigua, Lind. & Hutt. 
 Upper carbonaceous strata, Lower Oolite, Gristhorpe, Yorkshire. 
 
 and Unio, collected by Mr. Bean from these Yorkshire coal-bearing 
 beds, point to the estuary or fluviatile origin of the deposit. 
 
 At Brora, in Sutherlandshire, a coal formation, probably coeval 
 with the above, or belonging to some of the lower divisions of the 
 Oolitic period, has been mined extensively for a century or more. 
 It affords the thickest stratum of pure vegetable matter hitherto 
 detected in any secondary rock in England. One seam of coal of 
 good quality has been worked 3^ feet thick, and there are several 
 feet more of pyritous coal resting upon it. 
 
 Fuller's Earth (h. Tab. p. 292.). Between 
 the Great and Inferior Oolite, near Bath, an 
 argillaceous deposit, called " the fuller's earth," 
 occurs ; but it is wanting in the north of Eng- 
 land. It abounds in the small oyster represented 
 in fig. 386. 
 
 Inferior Oolite. This formation consists of 
 a calcareous freestone, usually of small thick- 
 ness, which sometimes rests upon, or is replaced by, yellow sands, 
 called the sands of the Inferior Oolite. These last, in their turn, 
 repose upon the lias in the south and west of England. Among the 
 characteristic shells of the Inferior Oolite, I may instance Terebra- 
 tula fimbria (fig. 387.), Rhynchonella spinosa (fig. 388.), and Phola- 
 domyafidicula (fig. 389.). The extinct genus Pleurotomaria is also a 
 form very common in this division as well as in the Oolitic system 
 
 Ostrea acuminata. 
 Fuller's Earth. 
 
316 
 
 FOSSILS OF THE 
 
 [Cn. XX. 
 
 Fig. 387. 
 
 Fig. 388. 
 
 Fig. 389. 
 
 Terebratulafimbria. 
 Inferior Oolite. 
 
 Fig. 390. 
 
 Rhynchonella spinosa. 
 Inferior Oolite. 
 
 a. Pholadomyafidicula. | nat. size. Inf. Ool 
 
 b. Heart-shaped anterior termination of the 
 
 same. 
 
 Fig. 391. 
 
 Fig. 392. 
 
 Pleurotomaria granulata. 
 Ferruginous Oolite, Normandy. 
 Inferior Oolite, England. 
 
 Pleurotomaria ornata, Sow. Sp. 
 Inferior Oolite. 
 
 Dysaster ringens. 
 Inf. Ool. Somersetshire. 
 
 generally. It resembles the Trochus in form, but is marked by a deep 
 cleft (a, fig. 390. and fig. 391.) on the right side of the mouth. The 
 Dysaster ringens (fig. 392.) is an Echinoderm common to the inferior 
 Oolite of England and France, as are the three Ammonites of which 
 representations are here given (figs. 393, 394, 395.). 
 
 Fig. 393. 
 
 Ammonites Humphresianus. 
 Inferior Oolite. 
 
 As illustrations of shells having a great vertical range, I may 
 allude to Trigonia clavellata, found in the Upper and Inferior Oolite, 
 and T. costata, common to the Upper, Middle, and Lower Oolite ; 
 also Ostrea Marshii (fig. 396.), common to the Cornbrash of Wilts 
 and the Inferior Oolite of Yorkshire; and Ammonites striatulus 
 (fig. 397.) common to the Inferior Oolite and Lias. 
 
CH. XX.] 
 
 Fig. 394. 
 
 INFERIOR OOLITE, 
 I 
 
 317 
 
 Fig. 395. 
 
 Ammonites margarilatus, D'Orb. Syn. A. Stokesii, Sow. 
 Lias. 
 
 Fig. 396. 
 
 Ammonites Braikenridgii, Sow. 
 
 Great Oolite, Scarborough. 
 Inf. Ool. Dundry ; Calvados ; &c. 
 
 Fig. 397. 
 
 Oslrea Marshii. A nat. size. 
 Middle and Lower Oolite. 
 
 Ammonites strtatvlus, Sov 
 
 4 nat. size. 
 Inferior Oolite and Lias. 
 
 Such facts by no means invalidate the general rule, that certain 
 fossils are good chronological tests of geological periods ; but they 
 serve to caution us against attaching too much importance to single 
 species, some of which may have a wider, others a more confined 
 vertical range. We have before seen that, in the successive tertiary 
 formations there are species common to older and newer groups, yet 
 these groups are distinguishable from one another by a comparison 
 of the whole assemblage of fossil shells proper to each. 
 
318 MINERAL CHARACTER OF THE LIAS. [Cn. XXI. 
 
 CHAPTER XXI. 
 
 JURASSIC GROUP continued. LIAS. 
 
 Mineral character of Lias Name of Gryphite limestone Fossil shells and fish 
 Radiata Ichthyodorulites Keptiles of the Lias Ichthyosaur and Plesiosaur 
 Marine Reptile of the Galapagos Islands Sudden destruction and burial of 
 fossil animals in Lias Fluvio-marine beds in Gloucestershire, and insect lime- 
 stone Fossil plants Origin of the Oolite and Lias, and of alternating cal- 
 careous and argillaceous formations Oolitic coal-field of Virginia, in the 
 United States. 
 
 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. They pass, indeed, into each other in some 
 places, as near Bath, a sandy marl called the marlstone of the Lias 
 being interposed, and partaking of the mineral characters of the 
 lias and the inferior oolite. These last-mentioned divisions have 
 also some fossils in common, such as the Avicula incequivalvis 
 (fig. 398.). Nevertheless the Lias may be traced throughout a great 
 
 Fig. 399. 
 
 (saiissM^ 
 
 Fig. 398. 
 
 Avicula inaquivalvis, Sow. Avicula cygnipcs, Phil. 
 
 Lower Oolite. Marlstone, Gloucestershire; Lias, Yorkshire. 
 
 part of Europe as a separate and independent group, of considerable 
 thickness, varying from 500 to 1000 feet, containing many peculiar 
 fossils, and having a very uniform lithological aspect. Although 
 usually conformable to the oolite, it is sometimes, as in the Jura, 
 unconformable. In the environs of Lons-le-Saulnier, for instance, 
 in the department of Jura, the strata of lias are inclined at an angle 
 of about 45, while the incumbent oolitic marls are horizontal. 
 
 The peculiar aspect which is most characteristic of the Lias 
 in England, France, and Germany is an alternation of thin beds of 
 blue or grey limestone having a surface which becomes light-brown 
 
CH. XXI.] NAME OF e( GRYPHITE LIMESTONE." 319 
 
 when weathered, these beds being separated by dark-coloured narrow 
 argillaceous partings, so that the quarries of this rock, at a distance, 
 assume a striped and riband-like appearance.* 
 
 The Lias comprises, 1. the Upper Lias thin limestone beds with 
 clay and shale ; 2. the Marlstone a coarse shelly limestone ; and 3. 
 the Lower Lias consisting of limestone, shells, and clay. These 
 divisions have certain fossils in common, and in some places pass 
 the one into the other. 
 
 Although the prevailing colour of the limestone of this formation 
 is blue, yet some beds of the lower lias are of a yellowish white 
 colour, and have been called white lias. In some parts of France, 
 near the Vosges mountains, and in Luxembourg, M. E. de Beaumont 
 has shown that the lias containing Gryphcea arcuata, Plagiostoma 
 giganteum (see fig. 400.), and other characteristic fossils becomes 
 arenaceous ; and around the Hartz, in Westphalia and Bavaria, the 
 inferior parts of the lias are sandy, and sometimes afford a building- 
 stone. 
 
 The name of Gryphite limestone has sometimes been applied to 
 the lias, in consequence of the great number of shells which it con- 
 Fig. 400. 
 
 Fig. 401. 
 
 incurva, Sow. 
 (t. arcuata, Lam.) 
 Lias. 
 
 Plagiostoma (Lima) gipanteum, Sow. 
 Inf. Ool. and Lias. 
 
 tains of a species of oyster, or Gryphcea (fig. 401., see also fig. 30. 
 p. 29.). A large heavy shell called Hippopodium (fig. 402.), allied 
 to Isocardia, is also characteristic of the lower lias shales. The 
 Lias formation is also remarkable for being the oldest of the second- 
 ary rocks in which brachiopoda of the genera Spirifer and Leptcena 
 (figs. 403, 404.) occur : no less than nine species of Spirifer s are 
 enumerated by Mr. Davidson as belonging to the lias. These pallio- 
 branchiate mollusca predominate greatly in strata older than the trias ; 
 but, so far as we yet know, they did not survive the liassic epoch. 
 The marine beds of the lias also abound in cephalopoda of the genera 
 Belemnites, Nautilus, and Ammonites (see figs. 405, 406, 407.). 
 Among the Crinoids or Stone-lilies of the Lias, Pentacrinus 
 
 * Conyb. and ThiL, p. 261. 
 
320 
 
 FOSSILS OF THE LIAS. 
 
 [Cn. XXI. 
 
 Fig. 402. 
 
 Fig. 403. 
 
 Hippopodium ponderosum, Sow. 
 $ diam. Lias, Cheltenham 
 
 Fig. 405. 
 
 Nautilus truncatus. Lias. 
 
 Leptccna Mooref, Dav. 
 Upper Lias, Ilminster. 
 
 Fig. 40G. 
 
 Ammonites Nodotianus ? 
 
 A. striatulus, Sow. 
 
 Lias. 
 
 Ammonites bffrons, Brug. 
 A. Walcolii, Sow. 
 Upper Lias shales. 
 
 Briareus (fig. 408.) is conspicuous. Of Ophioderma Egertoni (fig. 
 409.), referable to the Ophiura of Miiller, perfect specimens have 
 been met with in the marlstone beds of Dorset and Yorkshire. 
 
CH. XXI.] 
 
 FOSSILS OF THE LIAS. 
 
 321 
 
 Fig. 408. 
 
 Fig. 4C9. 
 
 Extracrinus Briar<-us. % nat. size. 
 
 (.Body, arms, and part of stem.) 
 
 Lias, Lyme Regis. 
 
 Ophioderma Egertoni, E. Forbes. 
 Lias Marlstone, Lyme Regis. 
 
 The Extracrinus Briareus (removed by Major Austin from Pen- 
 tacrinus on account of generic differences) occurs in tangled masses, 
 forming thin beds of considerable extent, in the lias of Dorset, 
 Gloucestershire, and Yorkshire. The remains are often highly 
 charged with pyrites. This Oinoid, with its innumerable tenta- 
 cular arms, appears to have been frequently attached to the drift- 
 wood of the liassic sea, in the same manner as Barnacles float 
 about at the present day. There is another species of Extracrinus 
 and several of Pentacrinus 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 
 delicate and rare Pentacrinus Caput-medusce of the Antilles; and 
 this indeed is perhaps the only surviving member of the great and 
 ancient family of the Crinoids, so widely represented throughout 
 the older formations by the genera Taxocrinus, Actinocrinus, 
 Cyathocrinus, Encrinus, Apiocrinus, and many others. 
 
 The fossil fish re- 
 semble generically 
 those of the oolite, 
 belonging all, ac- 
 cording to M. Agas- 
 siz, to extinct ge- 
 nera, and differ- 
 ing for the most 
 part from the ich- 
 thyolites of the 
 Cretaceous period. 
 
 Fig. 410. 
 
 Scales of Lepidotus gigas. Agas. 
 a. Two of the scales detached. 
 
322 
 
 FOSSILS OF THE LIAS. 
 
 [Cn. XXI. 
 
 Among them is a species of Lepidotus (L. gigas, Agas.), fig. 410., 
 which is found in the lias of England, France, and Germany.* This 
 genus was before mentioned (p. 263.) as occurring in the Wealden, 
 and is supposed to have frequented both rivers and coasts. Another 
 genus of Ganoids (or fish with hard, shining, and enamelled scales), 
 called jffichmodus (see fig. 411.), is almost exclusively Liassic. The 
 teeth of a species of Acrodus, also, are very abundant in the lias 
 (fig. 412.). 
 
 a Fig. 411. 
 
 
 b. Scales of JEchmodus 
 Leachii. 
 
 MchmoAus. Restored outline. 
 
 Fig. 412. 
 
 c. Scales of Dapedii 
 monilifcr. 
 
 Acrodus nobilis, Agas. (tooth) ; commonly called " fossil leech." 
 Lias, Lyme Regis and Germany. 
 
 But the remains of fish which have excited more attention than 
 any others are those large bony spines called ichthyodorulites 
 (, fig. 413.), which were once supposed by some naturalists to be 
 
 Fig. 413. b 
 
 Hybodus retic.ulatus, Agas. Lias, Lyme Regis. 
 
 a. Part of fin, commonly called Ichthyodorulite. 
 
 b. Tooth. 
 
 jaws, and by others, weapons resembling those of the living Balistes 
 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 articu- 
 lation in the ichthyodorulites. These last appear to have been bony 
 
 Agassiz, Pois. Fos. vol. ii. tab. 28, 29. 
 
CH. XXI.] REPTILES OF THE LIAS. 323 
 
 spines which formed the anterior part of the dorsal fin, like that of 
 the living genera Cestracion and Chimcera (see , fig. 414.). In 
 
 Fig. 414. 
 
 Chimcera monstrosa.* 
 a. Spine forming anterior part of the dorsal fin. 
 
 both of these genera, the posterior concave face is armed with small 
 spines, as in that of the fossil Hybodus (fig. 413.), one of the shark 
 family found fossil at Lyme Regis. Such spines are simply im- 
 bedded in the flesh, and attached to strong muscles. " They serve," 
 says Dr. Buckland, " as in the Chimcera (fig. 414.), to raise and de- 
 press the fin, their action resembling that of a moveable mast, 
 raising and lowering backwards the sail of a barge, "f 
 
 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 reptiles, which are extraordinary for their number, size, and 
 structure. Among the most singular of these are several species of 
 Ichthyosaurus and Plesiosaurus (figs. 415, 416.). The genus Ich- 
 thyosaurus, or fish-lizard, is not confined to this formation, but has 
 been found in strata as high as the lower chalk of England, and as 
 low as the trias of Germany, a formation which immediately succeeds 
 the lias in the descending order.:f It is evident from their fish-like 
 vertebrae, their paddles, resembling those of a porpoise or whale, the 
 length of their tail, and other parts of their structure, that the habits 
 of 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. 
 
 A specimen of the hinder fin or paddle of Ichthyosaurus communis 
 was discovered in 1840 at Barrow-on-Soar, by Sir P. Egerton, which 
 distinctly exhibits on its posterior margin the remains of cartila- 
 ginous rays that bifurcate as they approach the edge, like those in 
 the fin of a fish. (See, fig. 417.) It had previously been supposed, 
 says Prof. Owen, that the locomotive organs of the Ichthyosaurus 
 were enveloped, while living, in a smooth integument, like that of 
 the turtle and porpoise, which has no other support than is afforded 
 by the bones and ligaments within ; but it now appears that the fin 
 was much larger, expanding far beyond its osseous framework, and 
 
 * Agassiz, Poissons Fossiles, vol. iii. J Ibid. p. 168. 
 tab. C fig. 1. Ibid. p. 187. 
 
 f Bridgewater Treatise, p. 290. 
 
 T 2 
 
324 
 
 SAURIANS 
 
 [Cn. XXI. 
 
 deviating widely in its fish-like rays from the ordinary reptilian type. 
 In fig. 417. the posterior bones, or digital ossicles of the paddle, are 
 seen near b ; and beyond these is the dark carbonized integument 
 of the terminal half of the fin, the outline of which is beautifully 
 defined.* Prof. Owen believes that, besides the fore-paddles, these 
 short- and stiff-necked saurians were furnished with a tail-fin with- 
 out radiating bones, and purely tegumentary, expanding in a vertical 
 direction ; an organ of motion which enabled them to turn their 
 heads rapidly.")* 
 
 Mr. Conybeare was enabled, in 1824, after examining many skele- 
 
 * Geol. Soc. Transact. Second Series, 
 vol. vi. p. 199. pi. xx. 
 
 f Geol. Soc. Trans. Second Series, 
 vol. v. p. 511. 
 
CH. XXL] OF THE LIAS, 325 
 
 Fig. 417. 
 
 Posterior part of hind fin or paddle of Ichthyosaurus communis. 
 
 tons nearly perfect, to give an ideal restoration of the osteology of 
 this genus, and of that of the Plesiosaurus.* (See figs. 415, 416.) 
 The latter animal had an extremely long neck and small head, with 
 teeth like those of the crocodile, and paddles analogous to those of 
 the Ichthyosaurus, but larger. It is supposed to have lived in 
 shallow seas and estuaries, and to have breathed air like the Ichthyo- 
 saur and our modern cetacea.f Some of the reptiles above men- 
 tioned were of formidable dimensions. One specimen of Ichthyo- 
 saurus platyodon, from the lias at Lyme, now in the British Mu- 
 seum, must have belonged to an animal more than 24 feet in 
 length ; and another of the Plesiosaurus, in the same collection, is 
 11 feet long. The form of the Ichthyosaurus may have fitted it 
 to cut through the waves like the porpoise ; but it is supposed that 
 the Plesiosaurus, at least the long-necked species (fig. 416.), was 
 better suited to fish in shallow creeks and bays defended from heavy 
 breakers. 
 
 In many specimens both of Ichthyosaur and Plesiosaur the bones of 
 the head, neck, and tail are in their natural position, while those 
 of the rest of the skeleton are detached and in confusion. Mr. Stutch- 
 burg has suggested that their bodies after death became inflated with 
 gases, and, while the abdominal viscera were decomposing, the bones, 
 though disunited, were retained within the tough dermal covering 
 as in a bag, until the whole, becoming water-logged, sank to the 
 bottom. J As they belonged to individuals of all ages they are sup- 
 posed, by Dr. Buckland, to have experienced a violent death ; and 
 the same conclusion might also be drawn from their having escaped 
 the attacks of their own predacious race, or of fishes, found fossil in 
 the same beds. 
 
 For the last twenty years, anatomists have agreed that these ex- 
 tinct saurians must have inhabited the sea ; and it was urged that, 
 as there are now chelonians, like the tortoise, living in fresh water, 
 and others, as the turtle, frequenting the ocean, so there may have 
 
 * Geol. Trans., Second Series, vol. i. Trans. 1st Ser. vol. v. p. 559. ; and 
 
 pi- 49. Buckland, Bridgew. Treat., p. 203. 
 f Conybeare and De la Beche. Geol. f Quart. Geol. Journ. vol. ii. p. 411. 
 
 T 3 
 
326 LIAS SAURIANS. [Cn. XXI. 
 
 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 mouth ; 
 and crocodiles are said in like manner to be abundant both in the 
 rivers of the Isla de Pinos (or Isle of Pines), south of Cuba, and in 
 the open sea round the coast. More recently a saurian has been dis- 
 covered of aquatic habits and exclusively marine. This creature was 
 found in the Galapagos Islands, during the visit of H. M. S. Beagle 
 to that archipelago, in 1835, and its habits were then observed by 
 Mr. Darwin. The islands alluded to are situated under the equator, 
 nearly 600 miles to the westward of the coast of South America. 
 They are volcanic ; some of them being 3000 or 4000 feet high ; 
 and one of them, Albemarle Island, 75 miles long. The climate is 
 mild ; very little rain falls ; and, in the whole archipelago, there 
 is only one rill of fresh water that readies the coast. The soil is for 
 the most part dry and harsh, and the vegetation scanty. The birds, 
 reptiles, plants, and insects are, with very few exceptions, of species 
 found no where else in the world, although all partake, in their 
 general form, of a South American type. Of the mammalia, says 
 Mr. Darwin, one species alone appears to be indigenous, namely, a 
 large and peculiar kind of mouse ; but the number of lizards, tor- 
 toises, and snakes is so great, that it may be called a land of reptiles. 
 The variety, indeed, of species is small ; but the individuals of each 
 are in wonderful abundance. There is a turtle, a large tortoise 
 ( Testudo Indicus), four lizards, and about the same number of snakes, 
 but no frogs or toads. Two of the lizards belong to the family 
 Iguanidce of Bell, and to a peculiar genus (Amblyrhynchus) esta- 
 blished by that naturalist, and so named from their obtusely trun- 
 cated head and short snout.* Of these lizards one is terrestrial in 
 its habits, and burrows in the ground, swarming everywhere on the 
 land, having a round tail, and a mouth somewhat resembling in form 
 that of the tortoise. The other is aquatic, and has its tail flattened 
 laterally for swimming (see fig. 418.) "This marine saurian," says 
 Mr. Darwin, " is extremely common on all the islands throughout 
 
 Fig. 418. 
 
 Amblyrhynchus crislatus, Bell. Length varying from 3 to 4 feet. The only existing marine lizard 
 
 now known. 
 
 a. Tooth, natural size and magnified. 
 * Au\vs, amblys, blunt ; and f>vyxs, rhynchus, snout. 
 
CH.XXI.] SUDDEN DESTRUCTION OF SAURIANS. 327 
 
 the archipelago. It lives exclusively on the rocky sea-beaches, and 
 I never saw one even ten yards inshore. The usual length is about 
 a yard, but there are some even 4 feet long. It is of a dirty black 
 colour, sluggish in its movements on the land ; but, when in the 
 water, it swims with perfect ease and quickness by a serpentine 
 movement of its body and flattened tail, the legs during this time 
 being motionless, and closely collapsed on its sides. Their limbs and 
 strong claws are admirably adapted for crawling over the rugged and 
 fissured masses of lava which everywhere form the coast In such 
 situations, a group of six or seven of these hideous reptiles may 
 oftentimes be seen on the black rocks, a few feet above the surf, 
 basking in the sun with outstretched legs. Their stomachs, on being 
 opened, were found to be largely distended with minced sea-weed, of 
 a kind which grows at the bottom of the sea at some little distance 
 from the coast. To obtain this, the lizards go out to sea in shoals. 
 One of these animals was sunk in salt water, from the ship, with 
 a heavy weight attached to it, and on being drawn up again after 
 an hour it was quite active and unharmed. It is not yet known by 
 the inhabitants where this animal lays its eggs ; a singular fact, 
 considering its abundance, and that the natives are well acquainted 
 with the eggs of the terrestrial Amblyrhynchus, which is also herbi- 
 vorous." * 
 
 In those deposits now forming by the sediment washed away from 
 the wasting shores of the Galapagos Islands the remains of saurians, 
 both of the land and sea, as well as of chelonians and fish, may be 
 mingled with marine shells, without any bones of land quadrupeds or 
 batrachian reptiles ; yet even here we should expect the remains of 
 marine mammalia to be imbedded in the new strata, for there are 
 seals, besides several kinds of cetacea, on the Galapagian shores ; and, 
 in this respect, the parallel between the modern fauna, above described, 
 and the ancient one of the lias would not hold good. 
 
 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 could 
 not have happened had the uncovered bodies of these saurians been 
 left, even for a few hours, exposed to putrefaction, and to the attacks 
 of fishes, and other smaller animals at the bottom of the sea."f Not 
 only are the skeletons of the Ichthyosaurs entire, but sometimes the 
 contents of their stomachs still remain between their ribs, as before 
 remarked, so that we can discover the particular species of fish on 
 which they lived, and the form of their excrements. Not unfre- 
 quently there are layers of these coprolites, at different depths in the 
 lias, at a distance from any entire skeletons of the marine lizards 
 
 * Darwin's Journal, chap. xix. t Bridgew. Treat., p. 125. 
 
 T 4 
 
328 FOSSILS OF THE LIAS. [Cn. XXI. 
 
 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 ex- 
 uviae which had accumulated during the intervals." * It is farther 
 stated that, at Lyme Eegis, those surfaces only of the coprolites 
 which lay uppermost at the bottom of the sea have suffered partial 
 decay, from the action of water before they were covered and pro- 
 tected by the muddy sediment that has afterwards permanently 
 enveloped them, f 
 
 Numerous specimens of the Calamary or pen-and-ink fish ( Geo- 
 teuthis Bollensis, Schuble sp.) 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 slightly impreg- 
 nated with carbonate of lime. These cephalopoda, therefore, must, 
 like the saurians, have been soon buried in sediment; for, if long 
 exposed after death, the membrane containing the ink would have 
 decayed. J 
 
 As we know that river-fish are sometimes stifled, even in their 
 own element, by muddy water during floods, it cannot be doubted 
 that the periodical discharge of large bodies of turbid fresh water into 
 the sea may be still more fatal to marine 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 earth- 
 quakes, as in Java, in 1699 ; and that undescribable multitudes of 
 dead fishes have been seen floating on the sea after a discharge of 
 noxious vapours during similar convulsions. But, in the intervals 
 between such catastrophes, strata may have accumulated slowly in 
 the sea of the lias, some being formed chiefly of one description of 
 shell, such as ammonites, others of gryphites. 
 
 From the above remarks the reader will infer that the lias is for 
 the most part a marine deposit. Some members, however, of the 
 series, especially in the lowest part of it, have an estuary character, 
 and must have been formed within the influence of rivers. In Glou- 
 cestershire, where there is a good type of the lias of the West of 
 England, it has been divided into an upper mass of shale with a base 
 of marlstone, and a lower series of shales with underlying limestones 
 and shales. We learn from the researches of the Rev. P. B. Brodie ||, 
 that in the superior of these two divisions numerous remains of in- 
 sects and plants have been detected in several places, mingled with 
 marine shells; but in the inferior division similar fossils are still 
 more plentiful. One band, rarely exceeding a foot in thickness, has 
 been named the " insect limestone." It passes upwards into a shale 
 containing Cypris and Estheria,, and is charged with the wing-cases 
 of several genera of coleoptera, and with some nearly entire beetles, of 
 which the eyes are preserved. The nervures of the wings of neurop- 
 
 * Geological Eesearches, p. 334. See Principles, Index, Lancerote, 
 
 t Buckland, Bridgew. Treat., p. 307. Graham Island, Calabria, 
 j Ibid. II A History of Fossil Insects, &c. 
 
 1846. London. 
 
CH. XXI.] FOSSIL PLANTS LIAS. 329 
 
 terous insects (fig. 419.) are beautifully 
 perfect in this bed. Ferns, with leaves 
 of monocotyledonous plants, and some 
 apparently brackish and freshwater 
 shells, accompany the insects in several 
 places, while in others marine shells 
 predominate, the fossils varying appa- 
 p. B. Brodie.) rently as we examine the bed nearer or 
 
 farther from the ancient land, or the source whence the fresh water was 
 derived. There are two, or even three, bands of " insect limestone " in 
 several sections, and they have been ascertained by Mr. Brodie to retain 
 the same lithological and zoological characters when traced from the 
 centre of Warwickshire to the borders of the southern part of Wales. 
 After studying 300 specimens of these insects from the lias, Mr. West- 
 wood declares that they comprise both wood-eating and herb-de- 
 vouring beetles of the Linnean genera Elater, Carabus, &c., besides 
 grasshoppers ( Gryllus), and detached wings of dragon-flies and may- 
 flies, or insects referable to the Linnean genera Libellula, Ephemera, 
 ffemerobius, 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 asso- 
 ciated organic remains of other classes must lead to a different 
 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. Fragments of wood are com- 
 mon, and often converted into limestone. 
 That some of this wood, though now petri- 
 fied, was soft when it first lay at the bot- 
 tom of the sea, is shown by a specimen now 
 in the museum of the Geological Society (see fig. 420.), which has the 
 form of an ammonite indented on its surface. 
 
 M. Ad. Brongniart enumerates forty-seven liassic acrogens, most 
 of them- ferns ; and fifty gymnogens, of which thirty-nine are cycads, 
 and eleven conifers. Among the cycads the predominance of Zamites 
 and Nilssonia, and among the ferns the numerous genera with leaves 
 having reticulated veins (as in fig. 385. p. 315.), are mentioned as 
 botanical characteristics of this era.* The absence as yet from the 
 Lias and Ooolite of all signs of dicotyledonous 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. 267.) The angiosperms seem, therefore, to have been at the least 
 comparatively rare in these older secondary periods, when more 
 space was occupied by the Cycads and Conifers. 
 
 Origin of the Oolite and Lias. If we now endeavour to restore, 
 in imagination, the ancient condition of the European area at the 
 
 * Tableau des Veg. Fos, 1849, p. 105. 
 
330 ORIGIN OF THE OOLITE AND LIAS. [Cn. XXI. 
 
 period of the Oolite and Lias, we must conceive a sea in which the 
 growth of coral-reefs and shelly limestones, after proceeding without 
 interruption for ages, was liable to be stopped suddenly by the depo- 
 sition of clayey sediment. Then, again, the argillaceous matter, de- 
 void of corals, was deposited for ages, and attained a thickness of 
 hundreds of feet, until another period arrived when the same space 
 was again occupied by calcareous sand, or solid rocks of shell and 
 coral, to be again succeeded by the recurrence of another period of 
 argillaceous deposition. Mr. Conybeare has remarked of the entire 
 group of Oolite and Lias, that it 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 of the 
 inferior oolite, and these again by shelly and coralline limestone 
 (Bath oolite, &c.) ; so, in the middle oolite, the Oxford clay is fol- 
 lowed by calcareous grit and coral rag ; lastly, in the upper oolite, 
 the Kimmeridge clay is followed by the Portland sand and limestone.* 
 The clay beds, however, as Sir H. De la Beche remarks, can be fol- 
 lowed over larger areas than the sands or sandstones, f It should 
 also be remembered that while the oolitic 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 complicated and variable 
 than appears in ordinary descriptions. Nevertheless, some of the 
 clays and intervening limestones do retain, in reality, a pretty uni- 
 form character for distances of from 400 to 600 miles from east to 
 west and north to south. 
 
 According to M. Thirria, the entire oolitic group in the depart- 
 ment of the Haute Saone, in France, may be equal in thickness to 
 that of England ; but the importance of the argillaceous divisions is 
 in the inverse ratio to that which they exhibit in England, where 
 they are about equal to twice the thickness of the limestones, whereas, 
 in the part of France alluded to, they reach only about a third of that 
 thickness. if In the Jura the clays are still thinner ; and in the Alps 
 they thin out and almost vanish. 
 
 In order to account for such a succession of events, we may ima- 
 gine, first, the bed of the ocean to be the receptacle for ages of fine 
 argillaceous sediment, brought by oceanic currents, 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 suffered 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 
 neighbouring 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 
 
 * Con. and Phil., p. 166. J Burat's D'Aubuisson, torn. ii. p. 456. 
 
 f Geol. Researches, p. 337. 
 
CH. XXI.] OOLITE AND LIAS OF THE UNITED STATES. 331 
 
 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. 
 
 In order to account for another great formation, like the Oxford 
 clay, again covering one of coral limestone, we must suppose a sink- 
 ing down like that which is now taking place in some existing 
 regions of coral between Australia and South America. The oc- 
 currence of subsidences, on so vast a scale, may have caused the 
 bed of the ocean and the adjoining land, throughout great parts of 
 the European area, to assume a shape favourable to the deposition of 
 another set of clayey strata ; and this change may have been suc- 
 ceeded by a series of events analogous to that already explained, and 
 these again by a third series in similar order. Both the ascending 
 and descending movements may have been extremely slow, like those 
 now going on in the Pacific ; and the growth of every stratum of 
 coral, a few feet of thickness, may have required centuries for its 
 completion, during which certain species of organic beings disap- 
 peared from the earth, and others were introduced in their place ; so 
 that, in each set of strata, from the Lias to the Upper Oolite, some 
 peculiar and characteristic fossils were embedded. 
 
 Oolite and Lias of the United States. 
 
 There are large tracts on the globe, as in Russia and the United 
 States, where all the members of the oolitic series are unrepresented. 
 In the state of Virginia, however, at the distance of about 13 miles 
 eastward of Richmond, the capital of that State, there is a regular 
 coal-field occurring in a depression of the granite rocks (see section, 
 fig. 421.), which Professor W. B. Rogers first correctly referred to 
 
 Fig. 421. 
 
 ievd - V - : ;'-;--;-;r^^^ 
 
 Section showing the geological position of the James River, or East Virginian Coal-field. 
 
 A. Granite, gneiss, &c. B. Coal-measures. 
 
 C. Tertiary strata. D. Drift or ancient alluvium. 
 
 the age of the lower part of the Jurassic group. This opinion I 
 was enabled to confirm after collecting a large number of fossil 
 plants, fish, and shells, and examining the coal-field throughout its 
 whole area. It extends 26 miles from north to south, and from 4 
 to 12, from east to west. The plants consist chiefly of zamites, cala- 
 mites, and equisetums, and these last are very commonly met with in 
 
332 OOLITE AND LIAS [Cn. XXI. 
 
 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 distant from others, in beds both above 
 and between the seams of coal. In order to explain this fact we must 
 suppose such shales and sandstones to have been gradually accumu- 
 lated during the slow and repeated subsidence of the whole region. 
 
 It is worthy of remark that the Equisetum columnare of these 
 Virginian rocks appears to be undistinguishable from the species 
 found in the oolitic sandstones near Whitby in Yorkshire, where it 
 also is met with in an upright position. One of the Virginian fossil 
 ferns, Pecopteris Whitbyensis, is also a species common to the York- 
 shire oolites.* These Virginian coal-measures are composed of grits, 
 sandstones, and shales, exactly resembling those of older or primary 
 date in America and Europe, 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. On descending a shaft 800 feet deep, in 
 the Blackheath mines in Chesterfield county, I found myself in a 
 chamber more than 40 feet high, caused by the removal of this coal. 
 Timber props of great strength supported the roof, but they were 
 seen to bend under the incumbent weight. The coal is like the 
 finest kinds shipped at Newcastle, and when analysed yields the same 
 proportions of carbon 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 paleozoic 
 coal. 
 
 The fossil fish of these Richmond strata belong to the liassic genus 
 Tetragonolepis (^Echmodus), see fig. 411., and to a new genus which 
 I have called Dictyopyge. Shells are very rare, as usually in all 
 
 Fig. 422.' 
 
 a. Posidonomya or Estheria.f\ b. Young of same. 
 
 Oolitic coal-shale, Richmond, Virginia. 
 
 * See description of the coal-field by f Possibly, as suggested by Prof, 
 
 the author, and of the plants by C. J. "F. Morris (Geol. Journ. vol. iii. p. 275.), 
 
 Bunbury,Esq., Quart. Geol. Journ,, vol. these delicate bivalves may prove to be- 
 
 iii. p. 281. long to the crustacean genus Esther ia. 
 
CH. XXI.] OF THE UNITED STATES AND INDIA. 333 
 
 coal-bearing deposits, but a species of Posidonomya is in such pro- 
 fusion in some shaly beds as to divide them like the plates of mica 
 in micaceous shales (see fig. 422.). 
 
 In India, especially in Cutch, a formation occurs clearly referable 
 to the oolitic and liassic type, as shown by the shells, corals, and 
 plants ; and there also coal has been procured from one member of 
 the group. 
 
334 
 
 NEW RED SANDSTONE. 
 
 . XXII. 
 
 CHAPTER XXII. 
 
 TRIAS OR NEW RED SANDSTONE GROUP. 
 
 Distinction between New and Old Red Sandstone Between Upper and Lower 
 New Red The Trias and its three divisions Most largely developed in Ger- 
 many Keuper and its fossils Muschelkalk and fossils Fossil plants of the 
 Bunter Triassic group in England Bone-bed of Axmouth and Aust Red 
 Sandstone of Warwickshire and Cheshire Footsteps of Cheirotherium in England 
 and Germany Osteology of the Labyrinthodon Identification of this Ba- 
 trachian with the Cheirotherium Triassic mammifer Origin of Red Sandstone 
 and Rock-salt Hypothesis of saline volcanic exhalations Theory of the pre- 
 cipitation of salt from inland lakes or lagoons Saltness of the Red Sea New 
 Red Sandstone in the United States Fossil footprints of birds and reptiles in 
 the valley of the Connecticut Antiquity of the Red Sandstone containing them. 
 
 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 which the name of the 
 "New Red Sandstone formation" was first given, to distinguish it 
 from other shales and sandstones called the " Old Red" (c. fig. 423.), 
 often identical in mineral character, which lie immediately beneath 
 the coal (). 
 
 Fig. 423. 
 
 a. New red sandstone. 
 
 b. Coal. 
 
 c. Old red. 
 
 The name of " Red Marl" has been incorrectly applied to the red 
 clays of this formation, as before explained (p. 13.)> for they are 
 remarkably free from calcareous matter. The absence, indeed, of 
 carbonate of lime, as well as the scarcity of organic remains, together 
 with the bright red colour of most of the rocks of this group, causes 
 a strong contrast between it and the Jurassic formations before de- 
 scribed. 
 
 Before the distinctness of the fossil remains characterizing the 
 upper and lower part of the English New Red had been clearly 
 recognized, it was found convenient to have a common name for 
 all the strata intermediate in position between the Lias and Coal ; 
 and the term "Poikilitic" was proposed by Messrs. Cony beare and 
 Buckland*, from TrotKtXoe, poikilos, variegated, some of the most 
 characteristic strata of this group having been called variegated by 
 
 * Buckland, Bridg. Treat., vol. ii. p. 38. 
 
Ce. XXII.] KEUPER AND MUSCHELKALK FORMATIONS. 335 
 
 Werner, from their exhibiting spots and streaks of light-blue, green, 
 and buff colour, in a red base. 
 
 A single term, thus comprehending both Upper and Lower New 
 Red, or the Triassic and Permian groups of modern classifications, 
 may still be useful in describing districts where we have to speak of 
 masses of red sandstone and shale, referable, in part, to both these 
 eras, but which, in the absence of fossils, it is impossible to divide. 
 
 TRIAS OR UPPER NEW RED SANDSTONE GROUP. 
 
 The accompanying table will explain the subdivisions generally 
 adopted for the uppermost of the two systems above alluded to, and 
 the names given to them in England and on the Continent. 
 
 Synonyms. 
 
 German. French, 
 
 fa. Saliferous and gyp- "I 
 
 seous shales and > Keuper - Marnes irisees. 
 Trias or Upper | sandstone - - J 
 
 New Red <j & (wanti in England) Muschelkalk ./Muschelkalk ou cal- 
 Sandstone - \ caire coquilher. 
 
 c. Sandstone and quartz- \ Bunter-sand- \ n v , . - 
 [ ose conglomerate -/ stein- _ j^res bigarre. 
 
 I shall first describe this group as it occurs in South-western and 
 North-western Germany, for it is far more fully developed there 
 than in England or France. It has been called the Trias by German 
 writers, or the Triple Group, because it is separable into three distinct 
 formations, called the "Keuper," the "Muschelkalk," and the "Bun- 
 ter-sandstein." 
 
 The Keuper, the first or newest of these, is 1000 feet thick in 
 Wiirtemberg, and is divided by Alberti into sandstone, gypsum, and 
 carbonaceous slate-clay.* Remains of Reptiles, called Nothosaurus 
 and Phytosaurus, have been found in it with 
 Labyrinthodon ; the detached teeth, also, of 
 placoid fish and of rays, and of the genera 
 Saurichthys and Gyrolepis (figs. 433, 434., 
 p. 338.). The plants of the Keuper are 
 generically very analogous to those of the 
 lias and oolite, consisting of ferns, equise- 
 taceous plants, cycads, and conifers, with 
 a few doubtful monocotyledons. A few 
 
 n are. ragmen o i n 
 
 stem, and a small portion of same Species, SUCh as LqUlSBtlteS COlUmnariS> 
 
 are common to this group and the oolite. 
 
 The Muschelkalk consists chiefly of a compact, greyish limestone, 
 but includes beds of dolomite in many places, together with gypsum 
 and rock-salt. This limestone, a rock wholly unrepresented in Eng- 
 land, abounds in fossil shells, as the name implies. Among the ce- 
 phalopoda there are no belemnites, and no ammonites with foliated 
 sutures, as in the incumbent lias and oolite, but a genus allied to the 
 Ammonite, called Ceratites by De Haan, in which the descending 
 * Monog. des Bunten Sandsteins. 
 
336 
 
 MUSCHELKALK AND FOSSILS. 
 
 a Fig. 425. b 
 
 [Cn. XXII. 
 
 Ceratites nodosus. Muschelkalk. 
 
 a. Side view. b. Front view* 
 
 c. Partially denticulated outline of the septa dividing the chambers. 
 
 lobes (see , b, c, fig. 425.) terminate in a few small denticulations 
 pointing inwards. Among the bivalve shells, the Posidonia minuta, 
 Goldf. (Posidonomya minuta, Bronn), see fig. 426., is abundant, ranging 
 through the Keuper, Muschelkalk, and Bunter-sandstein ; and Avi- 
 cula socialis, fig. 427., having a similar range, is very characteristic 
 of the Muschelkalk in Germany, France, and Poland. 
 
 Fig. 426. 
 
 Fig. 427. 
 
 Posidonia minuta, a. Avicula socialis 6. Side view of same. 
 
 Goldf. (Posido- Characteristic of the Muschelkalk. 
 
 nomya minuta, 
 Bronn.) 
 
 The abundance of the heads and stems of lily encrinites, Encrinus 
 Fig. 428. liliiformis, fig. 428. (or Encrinites moniliformis), 
 
 show the slow manner in which some beds of this 
 limestone have been formed in clear sea-water. 
 The star-fish called Aspidura loricata, fig. 429., 
 
 Fig. 429. 
 
 Encrinus liliiformis, Schlott. Syn. . moniliformis. 
 Body, arms, and part of stem, 
 a. Section of stem. 
 Muschelkalk. 
 
 Aspidura loricata, Agas. 
 a. Upper side. 
 b- Lower side. 
 Muschelkalk. 
 
CH. XXII.] 
 
 THE BUNTER-SANDSTEIN. 
 
 337 
 
 is as yet peculiar to the Muschelkalk. In the same formation are 
 found ganoid fish with heterocercal tails, of the genus Placodus. (See 
 
 fig. 430.) 
 
 Fig. 430. 
 
 Fig. 431. 
 
 Palatal teeth of Placodus gigas. 
 Muschelkalk. 
 
 a. Voltzia heterophyUa. (Syn. Fo/teYz 
 
 brevijolia.) 
 
 b. portion of same magnified to show 
 
 fructification. Sulzbad. 
 Bunter-sandstein. 
 
 The Bunter-sandstein consists of various coloured 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, 
 according to Von Meyer, is proved, by the presence of Labyrin- 
 thodon, 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 " bunter," espe- 
 cially conifers of the extinct genus Voltzia, peculiar to this period, 
 in which even the fructification has been preserved. (See fig. 431.) 
 
 Out of thirty species of ferns, cycads, conifers, and other plants, 
 enumerated by M. Ad. Brongniart, in 1849, as coming from the 
 " gres bigarre," or Bunter, not one is common to the Keuper.* This 
 difference, however, may arise partly from the fact that the flora of 
 " the Bunter " has been almost entirely derived from one district (the 
 neighbourhood of Strasburg), and its peculiarities may be local. 
 
 The footprints of a reptile (Labyrinihodori) have been observed on 
 the clays of this member of the Trias, near Hildburghausen, in Sax- 
 ony, impressed on the upper surface of the beds, and standing out as 
 casts in relief from the under sides of incumbent slabs of sandstone. 
 To these I shall again allude in the sequel ; they attest, as well as 
 the accompanying ripple-marks, and the cracks which traverse the 
 clays, the gradual deposition of the beds of this formation in shallow 
 water, and sometimes between high and low water. 
 
 Triassic Group in England. 
 
 In England the Lias is succeeded by conformable strata of red and 
 green marl, or clay. There intervenes, however, both in the neigh- 
 bourhood of Axmouth, in Devonshire, and in the cliffs of Westbury 
 
 * Tableau des Genres de Veg. Fos., Diet. Univ. 1849. 
 z 
 
338 TRIASSIC GROUP IN ENGLAND. [Cn. XXII. 
 
 and Aust, in Gloucestershire, on the banks of the Severn, a dark- 
 coloured stratum, well known by the name of the " bone-bed." It 
 ' abounds in the remains of saurians and fish, and was formerly classed 
 as the lowest bed of the Lias ; but Sir P. Egerton has shown that it 
 should be referred to the Upper New Red Sandstone, for it contains 
 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, Hybodus, Gyrolepis, and 
 Saurichthys. 
 
 Among those common to the English bone-bed and the Muschel- 
 kalk of Germany are Hybodus plicatilis (fig. 432.), Saurichthys api- 
 calis (fig. 433.), Gyrolepis tenuistriatus (fig. 434.), and G. Albertii. 
 Remains of saurians have also been found in the bone-bed, and plates 
 of an Encrinus. 
 
 Fig. 433. Fig. 434. 
 
 I 
 
 Tig. 432. 
 
 Hybodus plicatilis. Teeth. Bone-bed, 
 Aust and Axmouth. 
 
 Saurichthys apicalis. Gyrolepis tenuistriatus. 
 
 Tooth; nat. size, and Scale; nat. size, and 
 
 magnified. Axmouth. magnified. Axmouth. 
 
 The strata of red and green marl, which follow the bone-bed in 
 the descending order at Axmouth and Aust, are destitute of organic 
 remains ; as is the case, for the most part, in the corresponding beds 
 in almost every part of England. But fossils have been found at a 
 few localities in sandstones of this formation, in Worcestershire and 
 Warwickshire, and among them the bivalve shell called Posidonia 
 minuta, Goldf., before mentioned (fig. 426. p. 336.). 
 
 The upper member of the English "New Red" containing this 
 shell, in those parts of England, is, according to Messrs. Murchison 
 and Strickland, 600 feet thick, and consists chiefly of red marl or 
 slate, with a band of sandstone. Ichthyodorulites, or spines of 
 Hybodus, teeth of fishes, and footprints of reptiles were observed by 
 the same geologists in these strata*; and the remains of a saurian, 
 called Rhynchosaurus, have been found in this portion of the Trias 
 at Grinsell, near Shrewsbury. , 
 
 In Cheshire and Lancashire the gypseous and saliferous red shales 
 and clays of the Trias are between 1000 and 1500 feet thick. In 
 some places lenticular masses of rock-salt are interpolated between 
 the argillaceous beds, the origin of which will be spoken of in the 
 sequel. 
 
 The lower division or English representative of the " Bunter " 
 
 * Geol. Trans., Sec. Ser., vol. v. p. 318. &c. 
 
CH. XXII.] FOSSIL FOOTSTEPS IN NEW RED SANDSTONE. 339 
 
 attains a thickness of 600 feet in the counties last mentioned. Be- 
 sides 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 coniferous wood, and showing rings of annual growth.* 
 Impressions, also, of the footsteps of animals have been detected in 
 Lancashire and Cheshire in this formation. Some of the most re- 
 markable occur a few miles from 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 a member of the 
 Upper New Red Sandstone, at the village of Hesseberg, near Hild- 
 burghausen, in Saxony, to which I have already alluded. For many 
 years these footprints have been referred to 
 a large unknown quadruped, provisionally 
 named Cheirotherium by Professor Kaup, 
 because the marks both of the fore and hind 
 feet resembled impressions made by a human 
 hand. (See fig. 435.) The footmarks at 
 Hesseberg are partly concave, and partly in 
 relief; the former, or the depressions, are 
 seen upon the upper surface of the sandstone 
 slabs, but those in relief are only upon the 
 lower surfaces, being in fact natural casts, 
 formed in the subjacent footprints as in 
 moulds. The larger impressions, which seem 
 to be those of the hind foot, are generally 
 8 inches in length, and 5 in width, and one was 12 inches long. 
 Near each large footstep, and at a regular distance (about an inch 
 
 Fig. 436. 
 
 Fig. 435. 
 
 Single footstep of Cheirothe- 
 rium. Bunter Sandstein, 
 Saxony ; one eighth of nat. 
 size. 
 
 Line of footsteps on slab of sandstone. Hildburghausen, in Saxony. 
 
 and a half), before it, a smaller print of a fore foot, 4 inches long and 
 3 inches wide, occurs. The footsteps follow each other in pairs, each 
 pair in the same line, at intervals of 14 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 inwards like a thumb. Though the fore 
 and hind foot differ so much in size, they are nearly similar in form. 
 The similar footmarks afterwards observed in a rock of corre- 
 sponding age at Storton Hill were imprinted on five thin beds of 
 clay, superimposed one upon the other in the same quarry, and sepa- 
 rated by beds of sandstone. On the lower surface of the sandstone 
 
 * Buckland, Proc. Geol. Soc. vol. ii. p. 439.; and Murchison and Strickland, 
 Geol. Trans., Second Ser., vol. v. p. 347. 
 
 z 2 
 
340 FOSSIL REMAINS [Cn. XXII. 
 
 strata, the solid casts of each impression are salient, in high relief, 
 and afford models of the feet, toes, and claws of the animals which 
 trod on the clay. On the same surfaces Mr. J. Cunningham dis- 
 covered (1839) distinct casts of rain -drop markings. 
 
 As neither in Germany nor in England any bones or teeth had 
 been met with in the same identical strata as the footsteps, anato- 
 mists indulged, for several years, in various conjectures respecting 
 the mysterious animals from which they might have been derived. 
 Professor Kaup suggested that the unknown quadruped might have 
 been allied to the Marsupialia ; 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 Batrachians ; and Dr. Buckland designated some of 
 the footsteps as those of a small web-footed animal, probably croco- 
 dilian. 
 
 In the course of these discussions several naturalists of Liverpool, 
 in their report on the Storton quarries, declared their opinion that 
 each of the thin seams of clay in which the sandstone casts were 
 moulded had formed successively a surface above water, over which 
 the Cheirotherium and other animals walked, leaving impressions of 
 their footsteps, and that each layer had been afterwards submerged 
 by a sinking down of the surface, so that a new beach was formed at 
 low water above the former, on which other tracks were then made. 
 The repeated occurrence of ripple-marks at various heights and 
 depths in the red sandstone of Cheshire had been explained in the 
 same manner. It was also remarked that impressions of such depth 
 and clearness could only have been made by animals walking on the 
 land, as their weight would have been insufficient to make them sink 
 so deeply in yielding clay under water. They must therefore have 
 been air-breathers. 
 
 When the inquiry had been brought to this point, the reptilian 
 remains discovered in the Trias, both of Germany and England, were 
 carefully examined by Prof. Owen. He found, after a microscopic 
 investigation of the teeth from the German sandstone called Keuper, 
 and from the sandstone of Warwick and Leamington (fig. 437.), 
 that neither of them could be referred to true saurians, although they 
 had been named Mastodonsaurus and Phytosaurus 
 by Jager. It appeared that they were of the Ba- 
 trachian order, and attested the former existence 
 of frogs of gigantic dimensions in comparison with 
 any now living. Both the Continental and English 
 fossil teeth exhibited a most complicated texture, 
 differing from that previously observed in any rep- 
 Tooth of Labyrintho- tile, whether recent or extinct, but most nearly ana- 
 
 don; nat. size. War- J 
 
 wick andstone. logous to the Ichthyosaurus. A section of one of 
 these teeth exhibits a series of irregular folds, re- 
 sembling the labyrinthic windings of the surface of the brain ; and 
 
OH. XXII.] OF LABYRINTHODON. 341 
 
 from this character Prof. Owen has proposed the name Labyrintho- 
 don for the new genus. The annexed' representation (fig. 438.) of 
 part of one is given from 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. 
 
 Fig. 438. 
 
 Transverse section of tooth of Labyrinthodon Jaegert, Owen (Mastodonsaurus Jaegeri, 
 Meyer) ; nat. size, and a segment magnified. 
 
 a. Pulp cavity, from which the processes of pulp and dentine radiate. 
 
 When Prof. Owen had satisfied himself, from an inspection of the 
 cranium, jaws, and teeth, that a gigantic Batrachian had existed at 
 the period of the Trias or Upper New Red Sandstone, he soon found, 
 from the examination of various bones derived from the same forma- 
 tion, that he could define three species of Labyrinthodon^ and that in 
 this genus the hind extremities were much larger than the anterior 
 ones. This circumstance, coupled with the fact of the Labyrinthodon 
 having existed at the period when the Cheirotherian footsteps were 
 made, was the first step towards the identification of those tracks 
 with the newly discovered Batrachian. It was at the same time 
 observed that the footmarks of Cheirotherium were more like those 
 of toads than of any other living animal ; and, lastly, that the size of 
 the three species of Labyrinthodon corresponded with the size of 
 three different kinds of footprints which had already been supposed 
 to belong to three distinct Cheirotheria. It was moreover inferred, 
 with confidence, that the Labyrinthodon was an air-breathing reptile 
 from the structure of the nasal cavity, in which the posterior outlets 
 were at the back part of the mouth, instead of being directly under 
 the anterior or external nostrils. It must have respired air after 
 the manner of saurians, and may therefore have imprinted on the 
 shore those footsteps, which, as we have seen, could not have origi- 
 nated from an animal walking under water. 
 
 It is true that the structure of the foot is still wanting, and that a 
 
 z 3 
 
342 FOSSIL REMAINS OF LABYRINTHODON. [Cn. XXII. 
 
 more connected and complete skeleton is required for demonstration ; 
 but the circumstantial evidence above stated is strong enough to pro- 
 duce the conviction that the Cheirotherium and Labyrinthodon are 
 one and the same. 
 
 In order to show the manner in which one of these formidable 
 Batrachians may have impressed the mark of its feet upon the 
 shore, Prof. Owen has attempted a restoration, of which a reduced 
 copy is annexed. 
 
 Tig. 439. 
 
 Restored outline of Labyrinthodon pachygnathus, Owen. 
 
 The only bones of this species at present known are those of the 
 head, the pelvis, and part of the scapula, which are shown by stronger 
 lines in the above figure. There is reason for believing that the 
 head was not smooth externally, but protected by bony scutella. 
 This character and the presence of strong conical teeth implanted in 
 sockets, together with the elongated form of the head, induce many 
 able anatomists, such as Von Meyer and Mantell, to regard the Laby- 
 rinthodons as more allied to crocodiles than to frogs. But the double 
 occipital condyles, the position of some of the teeth on the vomer and 
 palatine bones, and other characters, are considered by Messrs. 
 Jager and Owen to give them superior claims to be classed as ba- 
 trachians. That they occupy an intermediate place is clear, but too 
 little is yet known of the entire skeleton to enable us to determine 
 the exact amount of their affinity to one or other of the above-named 
 great divisions of reptiles. 
 
 Triassic Mammifer (Microlestes antiquus, Plieninger). In the 
 year 1847, Professor Plieninger, of Stuttgart, published a descrip- 
 tion of two fossil molar teeth, referred by him to a warm-blooded 
 quadruped *, which he obtained from a bone-breccia in Wurtemberg 
 occurring between the lias and the keuper. As the announcement of 
 so novel a fact has never met with the attention it deserved, we are 
 indebted to Dr. Jager, of Stuttgart, for having recently reminded us 
 of it in his Memoir on the Fossil Mammalia of Wiirtemberg. f 
 
 Fig. 440. represents the tooth first found, taken from the plate pub- 
 lished in 1847, by Professor Plieninger ; and fig. 441. is a drawing of 
 the same executed from the original by Mr. Hermann von Meyer, 
 
 * Wiirtembergisch. Naturwissen Jah- Nat. Cur. 1850, p. 902. For figures, see 
 reshefte, 3 Jahr. Stuttgart, 1847. ibid, plate xxi. figs. 14, 15, 16, 17. 
 
 t Nov. Act. Acad. Caesar. Leopold. 
 
FOSSIL AMMIFEK IN TRIAS. 
 
 343 
 
 CH. XXII.] 
 
 which he has been kind enough to send me. Fig. 442. is a second 
 and larger molar, copied from Dr. Jager's plate Ixxi., fig. 15. 
 
 Fig. 440. 
 
 Fig. 441. 
 
 Microlestes antiquus, Plieninger. Molar tooth magni- 
 fied. Upper Trias, Diegerloch, near Stuttgart, Wiir- 
 temberg. 
 
 a. View of inner side? *. Same, outer side ? 
 
 c. Same in profile. d. Crown of same. 
 
 Fig. 442. 
 
 Microlestes antiquus, 
 Plien. 
 
 View of same molar 
 as No. 440. From a 
 drawing by Her- 
 man von Meyer. 
 
 a. View of inner 
 
 side? 
 
 b. Crown of same. 
 
 Professor Plieninger inferred in 1847, from the 
 double fangs of this tooth and their unequal size, and 
 from the form and number of the protuberances or 
 cusps on the flat crowns, that it was the molar of a 
 Mammifer ; and considering it as predaceous, probably 
 insectivorous, he calls it Microlestcs, from fjiiKpog, 
 little, and AT/OTTJC, a beast of prey. Soon afterwards, 
 
 Molar of Microles- , , , T i T , ,1 IT 
 
 tesf Plien. 4 times he found the second tooth, also at the same locality, 
 44o. arg< FroS e tfe Diegerloch, about two miles to the south-east of Stutt- 
 foch, suitt?arf. er " gart. Some of its cusps are broken, but there seem to 
 have been six of them originally. From its agree- 
 ment in general characters, it is supposed by Professor Plieninger to 
 be referable to the same animal, but as it is four times as big, it may 
 perhaps have belonged to another allied species. This molar is 
 attached to the matrix consisting of sandstone, whereas the tooth, 
 fig. 440., is isolated. Several fragments of bone, diifering iir struc- 
 ture from that of the associated saurians and fish, and believed to be 
 mammalian, were imbedded near them in the same rock. 
 
 Mr. Waterhouse, of the British Museum, after studying the annexed 
 figs. 440 j 441, 442., and the descriptions of Prof. Plieninger, observes, 
 that not only the double roots of the teeth, and their, crowns present- 
 ing several cusps, resemble those of Mammalia, but the cingulum 
 also, or ridge surrounding the base of that part of the body of the 
 tooth which was exposed or above the gum, is a character distin- 
 guishing them from fish and reptiles. " The arrangement of the 
 six cusps or tubercles in two rows, in fig. 440., with a groove or de- 
 pression between them, and the oblong form of the tooth, lead him, 
 he says, to regard it as a molar of the lower jaw. Both the teeth 
 differ from those of the Stonesfield Mammalia, but do not supply 
 sufficient data for determining to what order they belonged. 
 
 Professor Plieninger has sent me a cast of the smaller tooth, which 
 exhibits well the characteristic mammalian test, the double fang ; but 
 Prof. Owen, to whom I have shown it, is not able to recognise its 
 affinity with any mammalian type, recent or extinct, known to him. 
 
 4 
 
344 ORIGIN OF RED SANDSTONE [Cn. XXII. 
 
 It has already been stated that the stratum in which the above- 
 mentioned fossils occur is intermediate between the lias and the 
 uppermost member of the trias. That it is really triassic may be 
 deduced from the following considerations. In Wiirtemberg there 
 are two "bone-beds," one of great extent, and very rich in the 
 remains of fish and reptiles, which intervenes between the muschel- 
 kalk and keuper, the other, containing the Microlestes, less extensive 
 and fossiliferous, which rests on the keuper, or superior member of 
 the trias, and is covered by the sandstone of the lias. The last- 
 mentioned breccia, therefore, occupies nearly the same place as the 
 well-known English " bone-bed " of Axmoutb and Aust-cliff near 
 Bristol, which is shown above, p. 338., to include characteristic 
 species of muschelkalk fish, of the genus Saurichthys, Hybodus, and 
 Gyrolepis. In both the Wiirtemberg bone-beds these three genera are 
 also found, and one of the species, Saurichthys Mougeotii, is common 
 to both the lower and upper breccias, as is also a remarkable reptile 
 called Nothosaurus mirabilis. The saurian called Belodon by H. 
 Von Meyer, of the Thecodont family, is another Triassic form, asso- 
 ciated at Diegerloch with Microlestes. 
 
 Previous to this discovery of Professor Plieninger, the most ancient 
 of known fossil Mammalia were those of the Stonesfield slate, above 
 described, p. 312., no representative of this class having as yet been 
 met with in the Fuller's earth, or inferior Oolite, nor in any member 
 of the Lias. 
 
 Origin of Red Sandstone and Rock Salt. 
 
 We have seen that, in various parts of the world, red and mottled 
 clays and sandstones, of several distinct geological epochs, are found 
 associated with salt, gypsum, magnesian limestone, or with one or all 
 of these substances. There is, therefore, in all likelihood, a general 
 cause for such a coincidence. Nevertheless, we must not forget that 
 there are dense masses of red and variegated sandstones and clays, 
 thousands of feet in thickness, and of vast horizontal extent, wholly 
 devoid of saliferous or gypseous matter. There are also deposits of 
 gypsum and of muriate of soda, as in the blue clay formation of 
 Sicily, without any accompanying red sandstone or red clay. 
 
 To account for deposits of red mud and red sand, we have simply 
 to suppose the disintegration of ordinary crystalline or metamorphic 
 schists. Thus, in the eastern Grampians of Scotland, in the north 
 of Forfarshire, for example, the mountains of gneiss, mica-schist, and 
 clay-slate are overspread with alluvium, derived from the disinte- 
 gration of those rocks ; and the mass of detritus is stained by oxide 
 of iron, of precisely the same colour as the Old Red Sandstone of the 
 adjoining Lowlands. Now this alluvium merely requires to be swept 
 down to the sea, or into a lake, to form strata of red sandstone and 
 red marl, precisely like the mass of the " Old Red " or " New Red " 
 systems of England, or those tertiary deposits of Auvergne (see 
 p. 199.), before described, which are in lithological characters quite 
 
CH. XXII.] AND ROCK SALT, 345 
 
 undistinguishable. The pebbles of gneiss in the Eocene red sand- 
 stone of Auvergne point clearly to the rocks from which it has been 
 derived. The red colouring matter may, as in the Grampians, have 
 been furnished by the decomposition of hornblende or mica, which 
 contain oxide of iron in large quantity. 
 
 It is a general fact, and one not yet accounted for, that scarcely 
 any fossil remains are preserved in stratified rocks in which this 
 oxide of iron abounds ; and when we find fossils in the New or Old 
 Eed Sandstone in England, it is in the gray, and usually calcareous^ 
 beds, that they occur. 
 
 The gypsum nJ saline matter, occasionally interstratified with 
 such red clays and sandstones of various ages, primary, secondary, 
 and tertiary, have been thought by some geologists to be of volcanic 
 origin. Submarine and subaerial exhalations often occur in regions 
 of earthquakes and volcanos far from points of actual eruption, and 
 charged with sulphur, sulphuric salts, and with common salt or 
 muriate of soda. In a word, such " solfataras " are vents by which 
 all the products which issue in a state of sublimation from the craters 
 of active volcanos obtain a passage from the interior of the earth to 
 the surface. That such gaseous emanations and mineral springs, 
 impregnated with the ingredients before enumerated, and often in- 
 tensely heated, continue to flow out unaltered in composition and 
 temperature for ages, is well known. But before we can decide on 
 their real instrumentality in producing in the course of ages beds of 
 gypsum, salt, and dolomite, we require to know more respecting the 
 chemical changes actually in progress in seas where volcanic agency 
 is at work. 
 
 The origin of rock-salt, however, is a problem of so much interest 
 in theoretical geology as to demand the discussion of another hypo- 
 thesis advanced on the subject ; namely, that which attributes the 
 precipitation of the salt to evaporation, whether of inland lakes or of 
 lagoons communicating with the ocean. 
 
 At Northwich, in Cheshire, two beds of salt, in great part unmixed 
 with earthy matter, attain the extraordinary thickness of 90 and 
 even 100 feet. The upper surface of the highest bed is very uneven, 
 forming cones and irregular figures. Between the two masses there 
 intervenes a bed of indurated clay, traversed with veins of salt. 
 The highest bed thins off towards the south-west, losing 15 feet in 
 thickness in the course of a mile.* The horizontal extent of these 
 particular masses in Cheshire and Lancashire is not exactly known ; 
 but the area, containing saliferous clays and sandstones, is supposed 
 to exceed 150 miles in diameter, while the total thickness of the 
 trias in the same region is estimated by Mr. Ormerod at more than 
 1700 feet. Ripple-marked sandstones, and the footprints of animals, 
 before described, are observed at so many levels that we may safely 
 assume the whole area to have undergone a slow and gradual de- 
 pression during the formation of the Red Sandstone. The evidence 
 
 * Ormerod, Quart. Geol. Journ. 1848, voL iv. p. 277. 
 
346 EUNN OF CUTCH. [CH. XXII. 
 
 of such a movement, wholly independent of the presence of salt 
 itself is very important in reference to the theory under consider- 
 ation. 
 
 In the " Principles of Geology " (chap. 27.), I published a map, 
 furnished to me by the late Sir Alexander Burnes, of that singular 
 flat region called the Runn of Cutch, near the delta of the Indus, 
 which is 7000 square miles in area, or equal in extent to about one- 
 fourth of Ireland. It is neither land nor sea, but is dry during a 
 part of every year, and again covered by salt water during the 
 monsoons. Some parts of it are liable, after long intervals, to be 
 overflowed by river-water. Its surface supports no grass, but is 
 encrusted over, here and there, by a layer of salt, about an inch 
 in depth, caused by the evaporation of sea-water. Certain tracts 
 have been converted into dry land by upheaval during earthquakes 
 since the commencement of the present century, and, in other di- 
 rections, the boundaries of the Runn have been enlarged by sub- 
 sidence. That successive layers of salt might be thrown down, one 
 upon the other, over thousands of square miles, in such a region, is 
 undeniable. The supply of brine from the ocean would be as in- 
 exhaustible as the supply of heat from the sun to cause evaporation. 
 The only assumption required to enable us to explain a great thick- 
 ness of salt in such an area is, the continuance, for an indefinite 
 period, of a subsiding movement, the country preserving all the time 
 a general approach to horizontality. Pure salt could only be formed 
 in the central parts of basins, where no sand could be drifted by the 
 wind, or sediment be brought by currents. Should the sinking of 
 the ground be accelerated, so as to let in the sea freely, and deepen 
 the water, a temporary suspension of the precipitation of salt would 
 be the only result. On the other hand, if the area should dry up, 
 ripple-marked sands and the footprints of animals might be formed, 
 where salt had previously accumulated. According to this view the 
 thickness of the salt, as well as of the accompanying beds of mud 
 and sand, becomes a mere question of time, or requires simply a 
 repetition of similar operations. 
 
 Mr. Hugh Miller, in an able discussion of this question, refers to 
 Dr. Frederick Parrot's account, in his journey to Ararat (1836), of 
 the salt lakes of Asia. In several of these lakes west of the river 
 Manech, " the water, during the hottest season of the year, is covered 
 on its surface with a crust of salt nearly an inch thick, which is col- 
 lected with shovels into boats. The crystallization of the salt is 
 effected by rapid evaporation from the sun's heat and the supersatura- 
 tion of the water with muriate of soda ; the lake being so shallow that 
 the little boats trail on the bottom and leave a furrow behind them, so 
 that the lake must be regarded as a wide pan of enormous super- 
 ficial extent, in which the brine can easily reach the degree of con- 
 centration required." 
 
 Another traveller, Major Harris, in his " Highlands of Ethiopia," 
 describes a salt lake, called the Bahr Assal, near the Abyssinian 
 frontier, which once formed the prolongation of the Gulf of Tadjara, 
 
CH.XXII.] SALTNESS OF THE RED SEA. 347 
 
 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 crerulian hue, and half with a solid 
 sheet of glittering 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 arenaceous 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." * 
 
 We may add that the permanent impregnation of the waters of a 
 large shallow basin with salt, beyond the proportion which is usual 
 in the ocean, would cause it to be uninhabitable by molluscs or fish, as 
 is the case in the Dead Sea, and the muriate of soda might remain in 
 excess, even though it were occasionally replenished by irruptions of 
 the sea. Should the saline deposit be eventually submerged, it might, 
 as we have seen from the example of the Runn of Cutch, be covered 
 by a freshwater formation containing fluviatile organic remains ; and 
 in this way the apparent anomaly of beds of sea-salt and clays devoid 
 of marine fossils, alternating with others of freshwater origin, may be 
 explained. 
 
 Dr. Gr. Buist, in a recent communication to the Bombay Geographical 
 Society (vol. ix.), has asked how it happens that the Red Sea should not 
 exceed the open ocean in saltness, by more than T ^ th per cent. The 
 Red Sea receives no supply of water from any quarter save through 
 the Straits of Babelmandeb ; and there is not a single river or rivulet 
 flowing into it from a circuit of 4000 miles of shore. The countries 
 around are all excessively sterile and arid, and composed, for the 
 most part, of burning deserts. From the ascertained evaporation in 
 the sea itself, Dr. Buist computes that nearly 8 feet of pure water 
 must be carried off from the whole of its surface annually, this being 
 probably equivalent to -^th part of its whole volume. The Red Sea, 
 therefore, ought to have 1 per cent, added annually to its saline con- 
 tents ; and as these constitute 4 per cent, by weight, or 2^ per cent, 
 in volume of its entire mass, it ought, assuming the average depth to 
 be 800 feet, which is supposed to be far beyond the truth, to have 
 been converted into one solid salt formation in less than 3000 years.f 
 Does the Red Sea receive a supply of water from the ocean, through 
 the narrow Straits of Babelmandeb, sufficient to balance the loss by 
 evaporation ? And is there an undercurrent of heavier saline water 
 annually flowing outwards ? If not, in what manner is the excess of 
 salt disposed of? An investigation of this subject by our nautical 
 surveyors may perhaps aid the geologist in framing a true theory of 
 the origin of rock-salt. 
 
 * Hugh Miller, First Impressions of f Buist, Trans, of Bombay Geograph. 
 England, 1847, pp. 183. 214. Soc. 1850, vol. ix. p. 38. 
 
348 NEW RED SANDSTONE OP THE TJ. STATES. [Cn. XXII. 
 
 On the New Red Sandstone of the Valley of the Connecticut River in 
 the United States. 
 
 In a depression of the granitic or hypogene rocks in the States of 
 Massachusetts and Connecticut, strata of red sandstone, shale, and 
 conglomerate are found occupying an area more than 150 miles in 
 length from north to south, and about 5 to 10 miles in breadth, the 
 beds dipping to the eastward at angles varying from 5 to 50 degrees. 
 The extreme inclination of 50 degrees is rare, and only observed in 
 the neighbourhood of masses of trap which have been intruded into 
 the red sandstone while it was forming, or before the newer parts of 
 the deposit had been completed. Having examined this series of 
 rocks in many places, I feel satisfied that 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. The red flags of thin-bedded sandstone are often ripple- 
 marked, and exhibit on their under-sides casts of cracks formed in 
 the underlying red and green shales. These last must have shrunk 
 by drying before the sand was spread over them. On some shales of 
 the finest texture impressions of rain-drops may be seen, and casts of 
 them in the incumbent argillaceous sandstones. Having observed 
 similar markings produced by showers, of which the precise date was 
 known, on the recent red mud of the Bay of Fundy, and casts in 
 relief of the same on layers of dried mud thrown down by subsequent 
 tides *, I feel no doubt in regard to the origin of some of the ancient 
 Connecticut impressions. I have also seen on the mud-flats of the 
 Bay of Fundy the footmarks of birds ( Tringa minuta), which daily 
 run along the borders of that estuary at low water, and which I have 
 described in my Travels, f Similar layers of red mud, now hardened 
 and compressed into shale, are laid open on the banks of the Connec- 
 ticut, and retain faithfully the impressions and casts of the feet of 
 numerous birds and reptiles which walked over them at the time when 
 they were deposited, probably in the Triassic Period. 
 
 According to Professor Hitchcock, the footprints 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 lizards, two of chelonians, and six of batrachians. 
 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 succession of beds attaining at some points a 
 thickness of more than 1000 feet, which may have been thousands of 
 years in forming. J 
 
 As considerable scepticism is naturally entertained in regard to 
 
 * Principles of Geology, 9th ed. J Hitchcock, Mem. of Aroer. Acad. 
 p. 203. New Ser. vol. iii. p. 129. 
 
 t Travels in North America, vol. ii. 
 p. 168. 
 
CH. XXII.] 
 
 FOSSIL FOOTPEINTS. 
 
 349 
 
 Fig. 443. 
 
 the nature of the evidence derived from footprints, it may be well to 
 enumerate some facts respecting them on which the faith of the geo- 
 logist may rest. When I visited the United States in 1842, more 
 than 2000 impressions had been observed by Professor Hitchcock*, 
 in the district alluded to, and all of them were indented on the upper 
 surface of the layers, while the corresponding casts, standing out in 
 relief, were always on the lower surfaces or planes of the strata. If 
 we follow a single line of marks we find them uni- 
 form in size, and nearly uniform in distance from 
 each other, the toes of two successive footprints 
 turning alternately right and left (see fig. 443.). 
 Such single lines indicate a biped; and there is 
 generally such a deviation from a straight line, in 
 any three successive prints, as we remark in the 
 tracks left by birds. There is also a striking rela- 
 tion between the distance separating two footprints 
 in one series and the size of the impressions; in 
 other words, an obvious proportion between the 
 length of the stride and the dimension of the 
 creature which walked over the mud. If the marks 
 are small, they may be half an inch asunder; if 
 gigantic, as, for example, where the toes are 20 
 inches long, they are occasionally 4 feet and a half 
 apart. The bipedal impressions are for the most 
 part trifid, and show the same number of joints as 
 exist in the feet of living tridactylous birds. Now, 
 such birds have three phalangeal bones for the 
 inner toe, four for the middle, and five for the outer 
 one (see fig. 443.) ; but the impression of the ter- 
 minal joint is that of the nail only. The fossil 
 footprints exhibit regularly, where the joints are 
 seen, the same number; and we see in each con- 
 Footprints of a bird, tinuous line of tracks the three-jointed and five- 
 Turner's Falls, Val- . . , -, , TJI- - i j n ,1 
 
 ley of the connec- jointed toes placed alternately outwards, first on the 
 Seine, ( Mem. D of one side and then on the other. In some specimens, 
 Awsr.Acad.Toi.lv. Asides 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 impres- 
 sions of the integument or skin of the foot ; but in one fine specimen 
 found at Turner's Falls on the Connecticut, by Dr. Deane, these 
 markings are well preserved, and have been recognized by Prof. Owen 
 as resembling the skin of the ostrich, and not that of reptiles, f Much 
 care is required to ascertain the precise layer of a laminated rock on 
 which an animal has walked, because the impression usually extends 
 downwards through several laminae ; and if the upper layer originally 
 
 * See also Mem. Amer. Ac. vol. iii. 
 1848. 
 
 t This specimen was in the late 
 Dr. Mantell's museum, and indicated a 
 
 bird of a size intermediate between the 
 small and the largest of the Connecticut 
 species. 
 
350 FOSSIL FOOTPRINTS [Cn. XXII. 
 
 trodden upon is wanting, the mark of one or more joints, or even in 
 some cases an entire toe, which sank less deep into the soft ground, 
 may disappear, and yet the remainder of the footprint be well 
 denned. 
 
 The size of several of the fossil impressions of the Connecticut red 
 sandstone so far exceeds that of any living ostrich, that naturalists at 
 first were extremely adverse to the opinion of their having been made 
 by birds, until the bones and almost entire skeleton of the Dinornis 
 and of other feathered giants of New Zealand were discovered. Their 
 dimensions have at least destroyed the force of this particular ob- 
 jection. The magnitude of the impressions of the feet of a heavy 
 animal, which has walked on suft mud, increases for some distance 
 below the surface originally trodden upon. In order, therefore, to 
 guard against exaggeration, the casts rather than the mould are 
 relied on. These casts show that some of the fossil bipeds had feet 
 four times as large as the ostrich, but not perhaps much larger than 
 the Dinornis. 
 
 The eggs of another gigantic bird, called JEpiornis, which has 
 probably been exterminated by man, have recently been discovered 
 in an alluvial deposit in Madagascar. The egg has six times the 
 capacity of that of the ostrich ; but, judging from the large size of 
 the egg of the Apterix, Prof. Owen does not believe that the JEpiornis 
 exceeded, if indeed it equalled, the Dinornis in stature. 
 
 Among the supposed bipedal tracks, a single distinct example only 
 has been observed of feet in which there are four toes directed for- 
 wards. In this case a series of four footprints is seen, each 22 
 inches long and 12 wide, with joints much resembling those in the 
 toes of birds. Professor Agassiz has suggested that it might have 
 belonged to a gigantic bipedal batrachian. Other naturalists have 
 called our attention to the fact, that some quadrupeds, when walking, 
 place the hind foot so precisely on the spot just quitted by the fore 
 foot, as to produce a single line of imprints, like those of a biped ; 
 and Mr. Waterhouse Hawkins has remarked that certain species of 
 frogs and lizards in Australia have the two outer toes so slightly 
 developed and so much raised that they might leave tridactylous 
 footprints on mud and sand. Another osteologist, Dr. Leidy, in the 
 United States, observed to me that the pterodactyl was a bipedal 
 reptile approaching the bird so nearly in the structure and shape of 
 its wing-bones and tibiae, that some of these last, obtained from the 
 Chalk and Wealden in England, had been mistaken by the highest 
 authorities for true birds' bones. May not the foot, therefore, of a 
 pterodactyl have equally resembled that of a bird? Be this as it 
 may, the greater number of the American impressions agree so 
 precisely in form and size with the footmarks of known living 
 birds, especially with those of waders, that we shall act most in 
 accordance with known analogies by referring most of them at 
 present to feathered, rather than to featherless bipeds. 
 
 No bones have as yet been met with, whether of pterodactyl or 
 bird, in the rocks of the Connecticut, but there are numerous copro- 
 
CH. XXII.] IN THE VALLEY OP THE CONNECTICUT. 351 
 
 lites ; and an ingenious argument has been derived by Dr. Dana from 
 the analysis of these bodies, and the proportion they contain of uric 
 acid, phosphate of lime, carbonate of lime, and organic matter, to 
 show that, like guano, they are the droppings of birds, rather than of 
 reptiles. 
 
 Some of the quadrupedal footprints which accompany those of birds 
 are analogous to European Cheirotheria, and with a similar dispro- 
 portion between the hind and fore feet. Others resemble that re- 
 markable reptile, the Rhyncosaurus of the English Trias, a creature 
 having some relation in its osteology both to chelonians and birds. 
 Other imprints, again, are like those of turtles. 
 
 Mr. Darwin, in his " Journal of a Voyage in the Beagle," informs us 
 that the " South American ostriches, although they live on vegetable 
 matter, such as roots and grass, are repeatedly seen at Bahia Blanca 
 (lat. 39 S.), on the coast of Buenos Ayres, coming down at low 
 water to the extensive mud-banks which are then dry, for the sake, 
 as the'Gauchos say, of feeding on small fish." They readily take to 
 the water, and have been seen at the bay of San Bias, and at Port 
 Valdez, in Patagonia, swimming from island to island.* It is there- 
 fore evident, that in our times a South American mud-bank might 
 be trodden simultaneously by ostriches, alligators, tortoises, and 
 frogs ; and the impressions left, in the nineteenth century, by the 
 feet of these various tribes of animals, would not differ from each 
 other more entirely than do those attributed to birds, saurians, 
 chelonians, and batrachians in the rocks of the Connecticut. 
 
 To determine the exact age of the red sandstone and shale con- 
 taining these ancient footprints 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, which was originally 
 referred to the genus Palceoniscus, but has since, with propriety, 
 been ascribed, by Sir Philip Egerton, to a new genus. To this he 
 has given the name of Ischypterus, from the great size and strength 
 of the fulcral rays of the dorsal fin (from lar-^v^ strength, and Trrejooi', 
 a fin). They differ from Palceoniscus, as Mr. Redfield first pointed 
 out, by having the vertebral column prolonged to a more limited 
 extent into the upper lobe of the tail, or, in the language of M. 
 Agassiz, they are less heterocercal. The teeth also, according to Sir 
 P. Egerton, who, in 1844, examined for me a fine series of specimens 
 which I procured at Durham, Connecticut, differ from those of 
 Palceoniscus in being strong and conical. 
 
 That the sandstones containing these fish are of older date than 
 the strata containing coal, before described (p. 331.) as occurring near 
 Richmond in Virginia, is highly probable. These were shown to be 
 as old at least as the oolite and lias. The higher antiquity of the 
 Connecticut beds cannot be proved by direct superposition, but may 
 be presumed from the general structure of the country. That 
 
 * Journal of Voyage of Beagle, &c. 2d edition, p. 89. 1845. 
 
352 ANTIQUITY OF CONNECTICUT BEDS. [Cn. XXII. 
 
 structure proves them to be newer than the movements to which the 
 Appalachian or Alleghany chain owes its flexures, and this chain 
 includes the ancient coal-formation among its contorted rocks. The 
 unconformable position of this New Red with ornithichnites on the 
 edges of the inclined primary or paleozoic rocks of the Appalachians 
 is seen at 4. of the section, fig. 505. p. 392. The absence of fish with 
 decidedly heterocercal tails may afford an argument against the 
 Permian age of the formation ; and the opinion that the red sandstone 
 is triassic, seems, on the whole, the best that we can embrace in the 
 present state of our knowledge. 
 
CH. XXIII.J DIVISION OF THE PERMIAN GROUP. 353 
 
 CHAPTER 
 
 PERMIAN OR MAGNESIAN LIMESTONE GROUP. 
 
 Fossils of Magnesian Limestone and Lower New Red distinct from the Triassic 
 Term Permian English and German equivalents Marine shells and corals of 
 English Magnesian limestone Palaeoniscus and other fish of the marl-slate 
 Thecodont Saurians of dolomitic conglomerate of Bristol Zechstein and Roth- 
 liegendes of Thuringia Permian Flora Its generic affinity to the Carboni- 
 ferous Psaronites or tree-ferns. 
 
 WHEN the use of the term "Poikilitic" was explained in the last 
 chapter, I stated, that in some parts of England it is scarcely possible 
 to separate the red marls and sandstones so called (originally named 
 " the New Red") into two distinct geological systems. Nevertheless, 
 the progress of investigation, and a careful comparison of English 
 rocks between the lias and the coal with those occupying a similar 
 geological position in Germany and Russia, have enabled geologists 
 to divide the Poikilitic formation ; and has even shown that the 
 lowermost of the two divisions is more closely connected, by its fossil 
 remains, with the carboniferous group than with the trias. If, 
 therefore, we are to draw a line between the secondary and primary 
 fossiliferous strata, as between the tertiary and secondary, it must 
 run through the middle of what was once called the " New Red," or 
 Poikilitic group. The inferior half of this group will rank as 
 Primary or Paleozoic, while its upper member will form the base of 
 the Secondary series. For the lower, or Magnesian Limestone di- 
 vision of English geologists, Sir R. Murchison proposed, in 1841, the 
 name of Permian, from Perm, a Russian government where these 
 strata are more extensively developed than elsewhere, occupying an 
 area twice the size of France, and containing an abundant and varied 
 suite of fossils. 
 
 Prof. King, in his valuable monograph* of the Permian fossils of 
 England, has given a table of the following six members of the Per- 
 mian system of the north of England, with what he conceives to be 
 the corresponding formations in Thuringia. 
 
 North of England. Thuringia. 
 
 1. Crystalline or concretionary, and 1. Stinkstein. 
 
 non-crystalline limestone. 
 
 2. Brecciated and pseudo-brecciated 2. Rauchwacke. 
 
 limestone. 
 
 3. Fossiliferous limestone. 3. Dolomite, or Upper Zechstein. 
 
 4. Compact limestone. 4. Zechstein, or Lower Zechstein. 
 
 5. Marl-slate. 5. Mergel-schiefer, or Kupferschiefer. 
 
 6. Inferior sandstones of various co- 6. Rothliegendes. 
 
 lours. 
 
 * Palseontographical Society, 1850, London. 
 A A 
 
354 PERMIAN LIMESTONES. [Cn. XXIII. 
 
 I shall proceed, therefore, to treat briefly of these subdivisions, 
 beginning with the highest, and referring the reader, for a fuller 
 description of the lithological character of the whole group, as it 
 occurs in the north of England, to a valuable memoir by Professor 
 Sedgwick, published in 1835.* 
 
 Crystalline or concretionary limestone (No. 1.). This formation 
 is seen upon the coast of Durham and Yorkshire, between the Wear 
 and the Tees. Among its characteristic fossils are Schizodus Schlo- 
 theimi (fig. 444.) and Mytilus septifer (fig. 446.). 
 
 Fig. 444. Fig. 445. Fig. 446. 
 
 Schizodus Schlotheimt, Geinitz. The hinge of Schizodus Mytilus septifer, King. 
 
 Crystalline limestone, Permian. truncatus, King. Syn. Modiola acuminata, 
 
 Permian. James Sow. 
 
 Permian crystalline lime- 
 stone. 
 
 These shells occur at Hartlepool and Sunderland, where the rock 
 assumes an oolitic and botroidal character. Some of the beds in this 
 division are ripple-marked ; and Mr. King imagines that the absence 
 of corals and the character of the shells indicate shallow water. In 
 some parts of the coast of Durham, where the rock is not crystalline, 
 it contains as much as forty -four 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 radiating from the 
 centre. Occasionally earthy and pulverulent beds pass into compact 
 limestone or hard granular dolomite. The stratification is very 
 irregular, in some places well-defined, in others obliterated by the 
 concretionary action which has re-arranged the materials of the rocks 
 subsequently to their original deposition. Examples of this are seen 
 at Pontefract and Ripon in Yorkshire. 
 
 The brecciated limestone (No. 2.) contains no fragments of foreign 
 rocks, but seems composed of the breaking-up of the Permian lime- 
 stone itself, about the time of its consolidation. Some of the angular 
 masses in Tynemouth Cliff are 2 feet in diameter. This breccia 
 is considered by Professor Sedgwick as one of the forms of the 
 preceding limestone, No. 1., rather than as regularly underlying it. 
 The fragments are angular and never water-worn, and appear to 
 have been re-cemented on the spot where they were formed. It is, 
 therefore, suggested that they may have been due to those internal 
 movements of the mass which produced the concretionary structure ; 
 but the subject is very obscure, and after studying the phenomenon 
 in the Marston Rocks, on the coast of Durham, I found it impossible 
 
 * Trans. Geol. Soc. Lond., Second Series, vol. iii. p. 37. 
 
CH. XXIII.] PERMIAN COMPACT LIMESTONES. 
 
 355 
 
 to form any positive opinion on the subject. The well-known brec- 
 ciated limestones of the Pyrenees appeared to me to present the 
 nearest analogy, but on a much smaller scale. 
 
 The fossiliferous limestone (No. 3.) is regarded by Mr. King as a 
 deep-water formation, from the numerous delicate bryozoa which it 
 includes. One of these, Fenestella retiformis (fig. 447.), is a very 
 
 Fig. 447. 
 
 a. Fenextella retiformis, Schlot. sp. 
 Syn. Gorgonta injundibuliformis, Goldf.; Retepora flustracea, Phillips. 
 
 6. Part of the same highly magnified. 
 Magnesian limestone, Humbleton Hill, near Sunderland.* 
 
 variable species, and has received many different names. It some- 
 times attains a large size, measuring 8 inches in width. The same 
 zoophyte, or rather mollusk, with several other British species, is 
 also found abundantly in the Permian of Germany. 
 
 Shells of the genera Productus (fig. 448.) and Strophalosia (the 
 latter an allied form with teeth in the hinge), which do not occur in 
 
 Fig. 448. 
 
 Fig. 449. 
 
 Prodrtctus horridtts, Sowerby 
 
 I including P. calvus, Sow.) 
 
 Sunderland and Durham, in Magnesian 
 
 Limestone; Zechstein and Kupt'er- 
 
 schiefer, Germany. 
 
 Spirffer undulatus, Sow. Min. Con. 
 Syn. Triogonolrcta undulata, King'i 
 
 Monogr. 
 Magnesian Limestone. 
 
 strata newer than the Permian, are abundant in this division of the 
 series in the ordinary yellow magnesian limestone. They are accom- 
 panied by certain species of Spirifer (fig. 449.), and other brachiopoda 
 of the true primary or paleozoic type. Some of this same tribe of 
 shells, such as Athyris Roissyi, allied to Terebratula, are specifically 
 the same as fossils of the carboniferous rocks. Avicula, Area, and 
 Schizodus (see above, figs. 444, 445, 446.), and other lamellibran- 
 chiate bivalves, are abundant, but spiral univalves are very rare. 
 
 The compact limestone (No. 4.) also contains organic remains, 
 especially bryozoa, and is intimately connected with the preceding. 
 
 * King's Monograph, pi. 2. 
 
 A A 2 
 
356 
 
 FOSSIL FISH OF PERMIAN MARL-SLATE. [Cn. XXIII. 
 
 Beneath it lies the marl-slate (No. 5.), which consists of hard, cal- 
 careous shales, marl-slate, and thin-bedded limestones. At East 
 Thickley, in Durham, where it is thirty feet thick, this slate has 
 yielded many fine specimens of fossil fish of the genera Palceoniscus, 
 Pygopterus, Ccelacanthus, and Platysomus, genera which are all 
 found in the coal-measures of the carboniferous epoch, and which 
 therefore, says Mr. King, probably lived at no great distance from 
 the shore. But the Permian species are peculiar, and, for the most 
 part, identical with those found in the marl-slate or copper-slate of 
 Thuringia. 
 
 Fig. 450. 
 
 Restored outline of a fish of the genus Pateomscus, Agass. 
 Paleeothrissum, 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 caudal lobe. (See fig. 
 451.) The "Homocercal" fish, which comprise almost all the 
 
 Fig. 451. 
 
 Fig. 452. 
 
 Shad. (Clupea, Herring tribe.) 
 Homocercal. 
 
 8000 species at present known in the living creation, have the tail- 
 fin either single or equally divided ; and the vertebral column stops 
 short, and is not prolonged into either lobe. (See fig. 452.) 
 
 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 creation, is universal in the Magnesian limestone, and 
 all the more ancient formations. It characterizes the earlier periods 
 of the earth's history, when the organization of fishes made a greater 
 approach to that of saurian reptiles than at later epochs. In all the 
 strata above the Magnesian limestone the homocercal tail pre- 
 dominates. 
 
 A full description has been given by Sir Philip Egerton of the 
 
CH. XXIII.] 
 
 DOLOMITIC CONGLOMERATE. 
 
 357 
 
 species of fish characteristic of the marl-slate, in Prof. King's mono- 
 graph before referred to, where figures of the 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 particular species. They are often scattered 
 through the beds singly, and may be useful to a geologist in de- 
 termining the age of the rock. 
 
 Fig. 453. 
 
 Scales of fish. Magnesian limestone. 
 Fig. 454. Fig. 455. 
 
 Fig. 456. 
 
 Fig. 453. PaUeoniscua comptus, Agassiz. Scale magnified. Marl-slate. 
 Fig. 454. PaltEoniscus elegans, Sedg. Under surface of scale magnified. Marl-slate. 
 Fig. 455. Palceoniscus glaphyrus, Ag. Under surface of scale magnified. Marl-slate. 
 Fig. 456. Ccelacanthus granulatus, Ag. Granulated surface of scale magnified. Marl-slate. 
 
 Fig. 457. 
 
 Fig. 458. 
 
 Pygopterus mandibularis, Ag. Marl-slate. 
 
 a. Outside of scale magnified. 
 
 b. Under surface of same. 
 
 Acrolepis Sedgwichii, Ag. 
 
 Outside of scale magnified. 
 
 Marl-slate. 
 
 The inferior sandstones (No. 6. Tab. p. 353.), which lie beneath 
 the marl-slate, consist of sandstone and sand, separating the mag- 
 nesian limestone from the coal, in Yorkshire and Durham. In some 
 instances, red marl and gypsum have been found associated with these 
 beds. They have been classed with the magnesian limestone by 
 Professor Sedgwick, as being nearly co-extensive with it in geogra- 
 phical range, though their relations are very obscure. In some 
 regions we find it stated that the imbedded plants are all specifically 
 identical with those of the carboniferous series ; and, if so, they 
 probably belong to that epoch ; for the true Permian flora appears, 
 from the researches of MM. Murchison and de Verneuil in Russia, 
 and of Colonel von Gutbier in Saxony, to be, with few exceptions, 
 distinct from that of the. coal (see p. 359.). 
 
 Dolomitic conglomerate of Bristol. Near Bristol, in Somersetshire, 
 and in other counties bordering the Severn, the unconformable beds of 
 the Lower New Red, resting immediately upon the Coal-measures, 
 consist of a conglomerate called " dolomitic," because the pebbles of 
 older rocks are cemented together by a red or yellow base of dolomite 
 
 A A 3 
 
358 THECODONT SAUKIANS. [Cn. XXIII. 
 
 or magnesian limestone. This conglomerate or breccia, for the im- 
 bedded fragments are sometimes angular, occurs in patches over the 
 whole of the downs near Bristol, filling up the hollows 'and irregu- 
 larities in the mountain limestone, and being principally composed 
 at every spot of the debris of those rocks on which it immediately 
 rests. At one point we find pieces of coal-shale, in another of 
 mountain limestone, recognizable by its peculiar shells and zoophytes. 
 Fractured bones, also, and teeth of saurians are dispersed through 
 some parts of the breccia. 
 
 These saurians (which until the discovery of the Archegosaurus 
 in the coal were the most ancient examples of fossil reptiles) are all 
 distinguished by having the teeth implanted deeply in the jaw-bone, 
 and in distinct sockets, instead of being soldered, as in frogs, to a 
 simple alveolar parapet. In the dolomitic conglomerate near Bristol 
 the remains of species of two genera have been found, called Theco- 
 dontosaurus and Palceosaurus by Dr. Riley and Mr. Stutchbury*; 
 the teeth of which are conical, compressed, and with finely serrated 
 edges (figs. 459 and 460.). 
 
 Teeth of Saurians. Dolomitic conglomerate ; Redland, near Bristol/ 
 Fig. 459. Fig. 460. 
 
 Tooth of Paltffosaurtts Tooth of Thecodontosaurtts, 
 
 platyodon, nat. size. j 3 times magnified. 
 
 Sir Henry de la Beche has shown that, in consequence of the 
 isolated position of the breccia containing these fossils, it is very 
 difficult to determine to what precise part of the Poikilitic series they 
 belong. f Some observers suspect them to be triassic ; but, until the 
 evidence in support of that view is more conclusive, we may con- 
 tinue to hold the opinion of their original discoverers. 
 
 In Russia, also, Thecodont saurians of several genera occur, in 
 beds of the Permian age, while others, named Protorosaurus, are met 
 with in the Zechstein of Thuringia. This family of reptiles is allied 
 to the living monitor, and its appearance in a primary or paleozoic 
 formation, observes Prof. Owen, is opposed to the doctrine of the 
 progressive development of reptiles from fish, or from simpler to more 
 complex forms ; for, if they existed at the present day, these monitors 
 would take rank at the head of the Lacertian order, j 
 
 We learn from the writings of Sir R. Murchison that in Russia 
 the Permian rocks are composed of white limestone, with gypsum and 
 
 * Geol. Trans., Second Series, vol. v. $ Owen, Report on Reptiles, British 
 
 p. 349., plate 29., figures 2. and 5. Assoc., Eleventh Meeting, 1841, p. 197. 
 
 f Memoirs of Geol. Survey of Great Russia and the Ural Mountains, 
 
 Britain, vol. i. p. 268. 1845 ; and Siluria, ch.xii. 1854. 
 
CH. XXIII.] 
 
 PERMIAN FLORA. 
 
 359 
 
 white salt ; and of red and green grits, occasionally with copper-ore ; 
 also magnesian limestones, marlstones, and conglomerates. 
 
 The country of Mansfeld, in Thuringia, may be called the classic 
 ground of the Lower New Red, or Magnesian Limestone, or Permian 
 formation, on the Continent. It consists there principally of, first, 
 the Zechstein, corresponding to the upper portion of our English 
 series; and, secondly, the marl-slate, with fish of species identical 
 with those of the bed so called in Durham. This slaty marlstone is 
 richly impregnated with copper-pyrites, for which it is extensively 
 worked. Magnesian limestone, gypsum, and rock-salt occur among 
 the superior strata of this group. At its base lies the Rothliegendes, 
 supposed to correspond with the Inferior or Lower New Red Sand- 
 stone above mentioned, which occupies a similar place in England 
 between the marl-slate and coal. Its local name of " Rothliegendes," 
 red-Iyer , or " Roth-todt-liegendes," red-dead-Iyer, was given by the 
 workmen in the German mines from its red colour, and because the 
 copper has died out when they reach this rock, which is not metal- 
 liferous. It is, in fact, a great deposit of red sandstone and con- 
 glomerate, with associated porphyry, basaltic trap, and amygdaloid. 
 
 Permian Flora. We learn from the recent investigation of 
 Colonel von Gutbier, that in the Permian rocks of Saxony no less 
 than sixty species of fossil plants have been met with, forty of which 
 
 Fig. 461 
 
 Fig. 462. 
 
 Walchia piniformis, Sternb. Permian, Saxony. (Gutbier, pi. x.) 
 a. branch. b. twig of the same. c. leaf magnified. 
 
 have not yet been found elsewhere. Two or three of these, as Cola- 
 mites gigas, Sphenopteris erosa, and S. lobata, are also met with in 
 the government of Perm in Russia. Seven others, and 
 among them Neuropteris Loshii, Pecopteris arborescens, 
 and P. similis, with several species of Walchia (see 
 fig. 461.), a genus of Conifers, called Lycopodites by 
 some authors, are common to the coal-measures. 
 
 Among the genera also enumerated by Colonel 
 Gutbier are the fruit called Cardiocarpon (see fig. 
 462.), Asterophyllites, and Annularia, so characteristic 
 of the carboniferous period ; also Lepidodendron, which 
 is common to the Permian of Saxony, Thuringia, and Russia, 
 
 A A 4 
 
 Cardiocarpon Ot- 
 
 tonix, Gutbier. 
 
 Permian, Saxony 
 
 $ diam. ' 
 
360 
 
 PERMIAN FLORA. 
 
 [Cn. XXIII. 
 
 Fig. 463.. 
 
 although not abundant. Noeggerathia (see fig. 463.), supposed by 
 A. Brongniart to be allied to Cycas, is another link between the 
 Permian and Carboniferous vegetation. Coni- 
 ferse, of the Araucarian division, also occur; 
 but these are likewise met with both in older 
 and newer rocks. The plants called Sigillaria 
 and Stigmaria, so marked a feature in the car- 
 boniferous period, are as yet wanting. 
 
 Among the remarkable fossils of the roth- 
 liegendes, or lowest part of the Permian in 
 Saxony and Bohemia, are the silicified trunks of 
 tree-ferns called generically Psaronius. Their 
 bark was surrounded by a dense mass of air- 
 roots, which often constituted a great addition to 
 the original stem, so as to double or quadruple its 
 diameter. The same remark holds good in 
 regard to certain living extra-tropical arbores- 
 cent ferns, particularly those of New Zealand. 
 
 Psaronites are also found in the uppermost 
 coal of Autun in France, and in the upper coal- 
 measures of the State of Ohio in the United 
 States, but specifically different from those of 
 the rothliegendes. They serve to connect the 
 Permian flora with the more modern portion of 
 the preceding or carboniferous group. Upon the whole, it is evident 
 that the Permian plants approach much nearer to the carboniferous 
 flora than to the triassic ; and the same may be said of the Permian 
 fauna. 
 
 *erathia cuneifolia. 
 . Brongniart.* 
 
 * Murchison's Russia, vol. ii. pi. A. fig. 3. 
 
CH. XXIV.] THE CARBONIFEROUS GROUP. 361 
 
 CHAPTER XXIV 
 
 THE COAL, OR CARBONIFEROUS GROUP. 
 
 Carboniferous strata in the south-west of England Superposition of Coal-measures 
 to Mountain limestone Departure from this type in North of England and 
 Scotland Carboniferous series in Ireland Section in South Wales Under- 
 clayswith Stigmaria Carboniferous Flora Ferns, Lepidodendra, Equisetaceas, 
 Calamites, Asterophyllites, Sigillariae, Stigmariae Coniferse Sternbergia 
 Trigonocarpon Grade of Coniferae in the Vegetable Kingdom Absence of 
 Angiosperms Coal, how formed Erect fossil trees Parkfield Colliery 
 St. Etienne Coal-field Oblique trees or snags Fossil forests in Nova Scotia 
 Rain-prints Purity of the Coal explained Time required for the accumu- 
 lation of the Coal-measures Brackish-water and marine strata Crustaceans 
 of the Coal Origin of Clay-iron-stone. 
 
 THE next group which we meet with in the descending order is the 
 Carboniferous, commonly called "The Coal;" because it contains 
 many beds of that mineral, in a more or less pure state, interstratified 
 with sandstones, shales, and limestones. The coal itself, even in 
 Great Britain and Belgium, where it is most abundant, constitutes 
 but an insignificant portion of the whole mass. In the north of 
 England, for example, the thickness of the coal-bearing strata has 
 been estimated by Prof. Phillips at 3000 feet, while the various coal- 
 seams, 20 or 30 in number, do not in the aggregate exceed 60 feet. 
 
 The carboniferous formation assumes various characters in dif- 
 ferent parts even of the British Islands. It usually comprises two 
 very distinct members : 1st, that usually called the Coal-measures, of 
 mixed freshwater, terrestrial, and marine origin, often including 
 seams of coal ; 2dly, that named in England the Mountain or Car- 
 boniferous Limestone, of purely marine origin, and containing corals, 
 shells, and encrinites. 
 
 In the south-western part of our island, in Somersetshire and South 
 Wales, the three divisions usually spoken of by English geologists 
 are: 
 
 7 ru.,1 f Strata of shale, sandstone, and grit, with occasional seams 
 
 l-measures 
 
 f A coarse quartzose sandstone passing into a conglomerate, 
 2. Millstone-grit < sometimes used for millstones, with beds of shale ; usually 
 [_ devoid of coal ; occasionally above 600 feet thick. 
 
 " n u -f l-A- calcareous rock containing marine shells and corals; 
 
 limestone 1 ' I devoid of coal thickness variable, sometimes 900 feet. 
 
 The millstone -grit may be considered as one of the coal-sandstones 
 of coarser texture than usual, with some accompanying shales, in 
 which coal-plants are occasionally found. In the north of England 
 
362 COAL-MEASURES. iCu. XXIV. 
 
 some bands of limestone, with pectens, oysters, and other marine shells, 
 occur in this grit, just as in the regular coal-measures, and even a 
 few seams of coal. I shall treat, therefore, of the whole group as 
 consisting of two divisions only, the Coal-measures and the Moun- 
 tain Limestone. The latter is found in the southern British coal- 
 fields, at the base of the system, or immediately in contact with the 
 subjacent Old Red Sandstone ; but as we proceed northwards to 
 Yorkshire and Northumberland it begins to alternate with true coal- 
 measures, the two deposits forming together a series of strata about 
 1000 feet in thickness. To this mixed formation succeeds the great 
 mass of genuine mountain limestone.* Farther north, in the Fife- 
 shire coal-field in Scotland, we observe a still wider departure from 
 the type of the south of England, or a more complete intercalation of 
 dense masses of marine limestones with sandstones and shales con- 
 taining coal. 
 
 In Ireland a series of shales and slates, constituting the base of the 
 Mountain Limestone, attain so great a thickness, often upwards of 
 1000 feet, as to be classed as a separate division. Under these slates 
 is a Yellow Sandstone, also considered as carboniferous from its 
 marine fossils, although passing into the underlying Devonian. A 
 similar sandstone of much less thickness occurs in the same position 
 in Gloucestershire and South Wales. 
 
 The following are the subdivisions adopted in the geological map 
 of Ireland, constructed by Mr. Griffiths : 
 
 Thickness in Feet. 
 
 1. Coal-measures, Upper and Lower - 1000 to 2200 
 
 2. Millstone-grit - 350 to 1800 
 
 3. Mountain limestone, Upper, Middle (or Calp), and 
 
 Lower - - - - 1200 to 6400 
 
 4. Carboniferous slate - - - 700 to 1200 
 
 5. Yellow sandstone (of Mayo, &c.) with shales and 
 
 limestone - 400 to 2000 
 
 COAL-MEASURES. 
 
 In South Wales the coal-measures have been ascertained by actual 
 measurement to attain the extraordinary thickness of 12,000 feet ; the 
 beds throughout, with the exception of the coal itself, appearing to 
 have been formed in water of moderate depth, during a slow, but per- 
 haps intermittent, depression of the ground, in a region to which 
 rivers were bringing 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, where 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 
 
 * Sedgwick, Geol. Trans., Second Series, vol. iv.; and Phillips, Geol. of Yorksh. 
 part 2. 
 
CH. XXIV.] CARBONIFEROUS FLORA. 363 
 
 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 intercalated coal-beds, sixteen in number, 
 are generally from 1 to 5 feet thick, one of them, which has two or 
 three layers of clay interposed, attaining 9 feet.* At other points in 
 the same coal-field the shales predominate over the sandstones. The 
 horizontal extent of some seams of coal is much greater than that of 
 others, but they all present one characteristic feature, in having, each 
 of them, what is called its underclay. These underclays, co-extensive 
 with every layer of coal, consist 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 6 inches to more than 10 
 feet; and Mr. Logan first announced to the scientific world in 1841 
 that they were regarded by the colliers in South Wales as an essen- 
 tial accompaniment of each of the one hundred seams of coal met 
 with in their coal-field. They are said to form the floor on which 
 the coal rests ; and some of them have a slight admixture of carbona- 
 ceous matter, while others are quite blackened by it. 
 
 All of them, as Mr. Logan pointed out, are characterized by 
 inclosing a peculiar species of fossil vegetable called 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 Stigmaria, and are flattened and compressed, 
 those singular plants of the underclay very often retain their natural 
 forms, branching freely, and sending out their slender leaf-like 
 rootlets, formerly thought to be leaves, through the mud in all di- 
 rections. Several species of Stigmaria had long been known to 
 botanists, and described by them, before their position under each 
 seam of coal was pointed out, and before their true nature as the 
 roots of trees was recognized. It was conjectured that they might 
 be aquatic, perhaps floating plants, which sometimes extended their 
 branches and leaves freely in fluid mud, and which were finally en- 
 veloped in the same mud. 
 
 , CARBONIFEROUS FLORA. 
 
 These statements will suffice to convince the reader that we cannot 
 arrive at a satisfactory theory of the origin of coal until we under- 
 stand the true nature of Stigmaria ; and in order to explain what is 
 now known of this plant, and of others which have contributed by 
 their decay to produce coal, it will be necessary to offer a brief pre- 
 liminary sketch of the whole carboniferous flora, an assemblage of 
 fossil plants with which we are better acquainted than with any other 
 which flourished antecedently to the tertiary epoch. It should also 
 be marked that Goppert has ascertained that the remains of every 
 family of plants scattered through the coal-measures are sometimes 
 met with in the pure coal itself, a fact which adds greatly to the geo- 
 logical interest attached to this flora. 
 
 * Memoirs of Geol. Survey, vol. i. p. 195. 
 
364 
 
 FERNS OF CARBONIFEROUS PERIOD. [Cn. XXIV. 
 
 Ferns. The number of species of carboniferous plants hitherto 
 described amounts, according to M. Ad. Brongniart, to about 500. 
 These may perhaps be a fragment only of the entire flora, but they 
 are enough to show that the state of the vegetable world was then 
 extremely different from that now prevailing. We are struck at 
 the first glance with the similarity of many of the ferns to those now 
 living, and the dissimilarity of almost all the other fossils except the 
 
 Fig. 464. 
 
 Fig. 465. 
 
 Pecopteris lonchitica. 
 (Foss. Flo. 153.) 
 
 a. Sphenopteris crenata. 
 
 b. Part of the same, magnified. 
 
 (Foss. Flo. 101.) 
 
 Fig. 466. 
 
 coniferae. Among the ferns, as in the 
 case of Pecopteris for example (fig. 464.), 
 it is not always easy to decide whether 
 they should be referred to different 
 genera from those established for the 
 classification of living species ; whereas, 
 in regard to most of the other contem-' 
 porary tribes, with the exception of the 
 coniferae. it is often difficult to guess the 
 family, or even the class, to which they 
 belong. The ferns of the carboniferous 
 period are generally without organs of 
 fructification, but in some specimens 
 these are well preserved. In the general 
 absence of such characters, they have 
 been divided into genera distinguished 
 cniefly 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 
 
CH. XXIV.] FERNS LEPIDODENDRON. 365 
 
 European ferns, but some were decidedly arborescent, especially the 
 group called Caulopteris, by Lindley, and the Psaronius of the upper 
 or newest coal-measures, before alluded to (p. 360.). 
 
 All the recent tree-ferns belong to one tribe (Polypodiacece), and 
 to a small number only of genera in that tribe, in which the surface 
 of the trunk is marked with scars, or cicatrices, left after the fall of 
 the fronds. These scars resemble those of Caulopteris (see fig. 466.). 
 No less than 250 ferns have already been obtained from the coal- 
 strata; and, even if we make some reduction on the ground of 
 varieties which have been mistaken, in the absence of their fructi- 
 fication, for species, still the result is singular, because the whole of 
 Europe affords at present no more than 60 indigenous species. 
 
 Fig. 468. 
 
 Living tree-ferns of different genera. (Ad. Brong.) 
 
 Fig. 467. Tree-fern from Isle of Bourbon. 
 Fig. 468. Cyathea glauca, Mauritius. 
 Fig. 469. Tree-fern from Brazil. 
 
 Lepidodendron. About 40 species of fossil plants of the Coal 
 have been referred to this genus. They consist of cylindrical stems 
 or trunks, covered with leaf-scars. In their mode of branching, they 
 are always dichotomous (see fig. 471.). They are considered by 
 Brongniart and Hooker to belong to the Lycopodiacea, plants of 
 this family bearing cones, with similar sporangia and spores 
 (fig. 474.). Most of them grew to the size of large trees. The 
 figures 470 472. represent a fossil Lepidodendron, 49 feet 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 rhomboidal scars which cover 
 them, a still greater magnitude. The living club -mosses, of which 
 there are about 200 species, are abundant in tropical climates, where 
 one species is sometimes met with attaining a height of 3 feet. They 
 usually creep on the ground, but some stand erect, as the L. densum. 
 from New Zealand (fig. 473.). 
 
366 
 
 Fig. 470. 
 
 LEPIDODENDKON. 
 
 Fig. 471. 
 
 [On. XXIV. 
 
 Lepidodendron Sternbergii. Coal-measures, near Newcastle. 
 
 Fig. 470. Branching trunk, 49 feet long, supposed to have belonged to L. Stern- 
 bergii. (Foss. Flo. 203.) 
 
 Fig. 471. Branching stem with bark and leaves of L. Sternbergii. (Foss. Flo. 4.) 
 Fig. 472. Portion of same nearer the root ; natural size. (Ibid.) 
 
 a. Lycopodtum densum ; banks of R. Thames, New Zealand. 
 ft. branch, natural sire. c. part of same, magnified. 
 
 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. 
 474.) They often form the nucleus of concretionary balls of clay- 
 Fig. 474. 
 
 . Lepidostrobus ornatus, Brong. Shropshire; half natural size 
 
 b. Portion of a section 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. 11. 
 
 part 2. p. 440.) 
 
 ironstone, and are well preserved, exhibiting a conical axis, around 
 which a great quantity of scales were compactly imbricated. The 
 opinion of M. Brongniart is now generally adopted, that the Lepi- 
 dostrobus is the fruit of Lepidodendron ; indeed, it is not uncommon 
 
CH. XXIV.] 
 
 EQUISETACE^ CALAMITES. 
 
 367 
 
 in Coalbrook Dale and elsewhere to find these strobili or fruits termi- 
 nating the tip of a branch of a well characterized Lepidodendron. 
 
 Equisetacece. To this family belong two fossil species of the Coal, 
 one called Equisetum infundibuliforme by Brongniart, and found also 
 in Nova Scotia, which has sheaths, regularly toothed, ribbed, and 
 overlapping like those on the young fertile stems of Equisetum flu- 
 viatile. It was much larger than any living "Horsetail." The 
 Equisetum giganteum, discovered by Humboldt and Bonpland in 
 South America, attained a height of about 5 feet, the stem being an 
 inch in diameter ; but more recently Gardner has met with one in 
 Brazil 15 feet high, and Meyen gives the height of E. Bogotense in 
 Chili as 15 to 20 feet. 
 
 Calamites. The fossil plants so called were originally classed by 
 most botanists as cryptogamous, being regarded as gigantic Equiseta ; 
 
 Fig. 475. 
 
 Fig. 476. 
 
 Catamites cannceformis, Schlot. 
 ( Koss. Flo. 79.) Common in 
 English coal. 
 
 Catamites Suckowii, Brong.; 
 natural size. Common in 
 coal throughout Europe. 
 
 Fig. 477. 
 
 for, like the common " horsetail," they usually ex- 
 hibit little more than hollow jointed stems, furrowed 
 externally. (See figs. 475, 476, 477.) 
 
 Mr. Salter stated to me many years ago his con- 
 viction that the calamite as frequently represented 
 by paleontologists was in an inverted position, 
 and . that the conical part given as the top of the 
 stem was in truth the root. This point Mr. Dawson 
 and I had opportunities of testing in Nova Scotia, 
 where we saw many erect calamites, having their 
 radical termination as in the annexed figure (fig. 
 477.). The scars, from which whorls of vessels 
 have proceeded, are observed at the upper, not the 
 lower end of each joint or internode.* The speci- 
 men, fig. 475., therefore, is no doubt the lower end of 
 the plant, and I have therefore reversed its position 
 as given in the work of Lindley and Hutton. 
 
 M. Adolphe Brongniart, following up the discoveries of Germar 
 
 and Corda, has shown in his " Genres de Vegetaux Fossiles," 1849, 
 
 that many Calamites cannot belong to the Equiseta, nor probably to 
 
 any tribe of flowerless plants. He conceives that they are more 
 
 * See Dawson, Geol. Quart. Journal, 1854, vol. x. p. 35. 
 
 Radical termination 
 "fa Calamite. Nova 
 Scotia. 
 
368 
 
 CALAMITES. 
 
 [CH. XXIV. 
 
 Fig. 478. 
 
 nearly allied to the Gymnospermous Dicotyledons. They possessed 
 a central pith, surrounded by a ligneous cylinder, which was divided 
 by regular medullary rays. This cylinder was surrounded in turn 
 by a thick bark. Of fossil stems having this structure Brongniart 
 formed his genus Calamodendron, which includes many species 
 referred by Cotta, Petzholdt, and Unger to the genus Calamitea. 
 The Calamodendron is described as smooth externally, its pith being 
 articulated and marked with deep external vertical striae, agreeing 
 in short with what geologists commonly call a Calamite. Since the 
 appearance of Brongniart's essay, Mr. E. W. Binney has made many 
 important discoveries on the same subject ; and Mr. J. S. Dawes has 
 published (Quart. Journ. Geol. Soc. Lond. 1851, vol. vii. p. 196.) 
 
 a more complete account of this 
 singular fossil. Their views have 
 been confirmed by Prof. Wil- 
 liamson of Manchester, who has 
 communicated to me a specimen, 
 figured in the annexed cut (fig. 
 478.), in which we see an in- 
 ternal pith answering in cha- 
 racter to the Calamodendron 
 and yet having outside of it an- 
 other jointed cylinder vertically 
 grooved on its outer surface, so 
 that in the same stem we have 
 one calamite enveloping an- 
 other. Yet that they both 
 formed part of the same plant 
 is proved by the following cir- 
 cumstances: 1st. Near each 
 articulation of the pith radiating 
 
 with the cast of the pith. Its position inverted s DO keS are SCCn tO PrOCCed and 
 to allow the light to enter the cavity. 
 Communicated by Prof. W. C. Williamson. penetrate the llgnCOUS ZOne. 
 
 One complete whorl or circle of these radii is visible in the annexed 
 figure near the bottom of the hollow cavity, whilst another and 
 superior whorl is incomplete; several radii, corresponding to the 
 first, remaining, while the rest have been broken away, their place 
 being shown by scars which they have left. 2dly. In addition to 
 these whorls, called medullary by Prof. Williamson, there are seen 
 in other specimens a set of true or ordinary medullary rays. 3dly. 
 The woody zone, penetrated both by the spoke-like vessels before- 
 mentioned and by the medullary rays, is usually reduced to brown 
 carbonaceous matter, preserving merely a tendency to break in longi- 
 tudinal slips, but in some specimens its fibrous tissue is retained, and 
 resembles that of Dadoxylon. 4thly. Outside of this zone again is 
 another cylinder, supposed to have been originally a thick cellular 
 bark, nearly equal to one-third of the whole stem in diameter, grooved 
 and jointed externally like the pith. 
 
 Jn conclusion, I may remark that these discoveries make' it more 
 
CH. XXIV.] ASTEROPHYLLITES SIGILLARIA. 369 
 
 and more doubtful to what family the greater number of Calamites 
 should be referred. Their internal organization, says Prof. Wil- 
 liamson, was very peculiar; for while they exhibit remarkable 
 affinities with gymnospermous dicotyledons, the arrangement of 
 their tissues differs widely from that of all known forms of gymno- 
 sperms. 
 
 Aster ophyllites. The graceful plant represented in the annexed 
 figure is supposed by M. Brongniart to be a branch of the Calamo- 
 dendron, and he infers from its pith and medullary rays that it was 
 dicotyledonous. It appears to have been allied, by the nature of its 
 
 Fig. 479. 
 
 Aster ophyllites JoUosa. (Foss. Flo. 25.) Coal-measures, Newcastle. 
 
 tissue, to the gymnogens, and to Sigillaria. But under the head of 
 Aster ophyllites many vegetable fragments have been grouped which 
 probably belong to different genera. They have, in short, no cha- 
 racter in common, except that of possessing narrow, verticillate, 
 one-ribbed leaves. Dr. Newberry, of Ohio, has discovered in the 
 coal of that country fossil stems which in their upper part bear 
 wedge-shaped leaves corresponding to Sphenophyllum, while below 
 the leaves are stalk -like and capillary, and would have been called 
 Asterophyllites if found detached. From this he infers that Spheno- 
 phyllum was an aquatic plant, the superior and floating leaves of 
 which were broad, and possessed a compound nervation, while the 
 inferior or submersed leaves were linear and one-ribbed. " This 
 supposition," he adds, "is further strengthened by the extreme 
 length and tenuity of the branches of this apparently herbaceous 
 plant, which would seem to have required the support of a denser 
 medium than air."* 
 
 Sigillaria. A large portion of the trees of the carboniferous 
 period belonged to this genus, of which about thirty-five species are 
 known. The structure, both internal and external, was very pe- 
 culiar, and, with reference to existing types, very anomalous. They 
 were formerly referred, by M. Ad. Brongniart, to ferns, which they 
 resemble in the scalariform texture of their vessels, and, in some 
 degree, in the form of the cicatrices left by the base of the leaf- 
 
 * Annals of Science, Cleveland, Ohio, 1853, p. 97. 
 B B 
 
370 
 
 SIGILLARIA AND STIGMARIA. 
 
 [Cn. XXIV. 
 
 stalks which have fallen off (see fig. 480.). But with these points 
 of analogy to cryptogamia, they combine an internal organization 
 Fig. 480. much resembling that of eycads, and 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 regular cylin- 
 drical stems, and without branches, al- 
 though some species were dichotomous 
 towards the top. Their fluted trunks, 
 from 1 to 5 feet in diameter, appear to 
 have decayed more rapidly in the interior 
 than externally, so that they became 
 hollow, when standing ; and when thrown 
 prostrate on the mud, they were squeezed 
 down and flattened. Hence, we find the 
 bark of the two opposite sides (now con- 
 verted into bright shining coal) to con- 
 ia ixvigata, Brong. s titute two horizontal layers, one upon 
 the other, half an inch, or an inch, in thickness. These same 
 trunks, when they are placed obliquely or vertically to the planes 
 of stratification, retain their original rounded form, and are uncom- 
 pressed, the cylinder of bark having been filled with sand, which 
 now affords a cast of the interior. 
 
 Dr. Hooker still inclines to the belief that the Sigillarice may have 
 been cryptogamous, though more highly developed than any flower- 
 less plants now living. The scalariform structure of their vessels 
 agrees precisely with that of ferns. 
 
 Stigmaria. This fossil, the importance of which has already been 
 pointed out, was formerly conjectured to be an aquatic plant. It is 
 now ascertained to be the root of Sigillaria. The connection of the 
 roots with the stem, previously 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 
 
 Stigmaria attached to a trunk of Sigillaria* 
 
 * The trunk in this case is referred markings assumed by Sigillaria near its 
 by Mr. Brown to Lepidodendron, but his base, 
 illustrations seem to show the usual 
 
CH. XXIV.] 
 
 CONIFERS OF COAL PERIOD. 
 
 371 
 
 Stigmariae occurring in the underclays 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. 481.), the spread of the roots was 16 feet, and some of them sent 
 out rootlets, in all directions, into the surrounding clay. 
 
 In the sea-cliffs of the South Joggins in Nova Scotia I examined 
 several erect Sigillarice, in company with Mr. Dawson, and we found 
 that from the lower extremities of the trunk they sent out Stig- 
 marice 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 manner of attachment of the fibres to the stem resembles 
 that of a ball and socket joint, the base of each rootlet being con- 
 cave, and fitting on to a tubercle (see figs. 482. and 483.). Rows of 
 
 Fig. 483. 
 
 Fig. 482. 
 
 Surface of another individual of ] 
 same species, showing form of J 
 tubercles. (Foss. Flo. 34.) ( 
 i 
 
 I 
 
 Sligmariajicoides, Brong. One fourth of nat. size. (Foss. Flo. 32.) 
 
 these tubercles are arranged spirally round each root, which has 
 always a medullary cavity and woody texture, much resembling that 
 of Sigillaria, the structure of the vessels being, like it, scalariform. 
 
 Conifer ce. The coniferous trees of this period are referred to five 
 genera ; 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 firs. Some of their trunks exceeded 44 feet in 
 height. Many, if not all of them, seem to have differed from living 
 Conifer ce in having large piths ; for Professor Williamson has demon- 
 strated the fossil of the coal-measures called Sternbergia to be the 
 pith of these trees, or rather the cast of cavities formed by the 
 shrinking or partial absorption of the original medullary axis (see 
 figs. 484. and 485.). This peculiar type of pith is observed in living 
 plants of very different families, such as the common Walnut and 
 the White Jasmine, in which the pith becomes so reduced 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 cylin- 
 drical hollow into discoid interspaces. When these last have been 
 filled up with inorganic matter, they constitute an axis to which, before 
 their true nature was known, the provisional name of Sternbergia 
 (</, d, fiff. 484.) was given. 
 
 B B 2 
 
372 
 
 CONIFERS OF THE COAL PERIOD. [Cn. XXIY, 
 
 Fig. 484. 
 
 Fig. 484. Fragment of coniferous wood, Dadoxy Ion, 
 Endlicher, fractured longitudinally ; from Coal- 
 brook Dale. W. C. Williamson.* 
 
 a. bark. 
 
 b. woody zone or fibre (pleurenchyma). 
 
 c. medulla or pith. 
 
 d. cast of hoilow pith, or " Sternbergia." 
 
 Magnified portion of fig. 484. ; transverse section. 
 c. pith. b, b. woody fibre. e, e. medullary rays. 
 
 In the above specimen the structure of the wood (b, figs. 484. and 
 485.) is coniferous, and the fossil is referable to Endlicher's fossil 
 genus Dadoxylon. 
 
 The fossil named Trigonocarpon (figs. 486. and 487.), formerly 
 
 Fig. 487. 
 Fig. 486. 
 
 Trigonocarpum overturn, Lindley and Hutton. 
 Peel Quarry, Lancashire. 
 
 Trtgonocarpum oltveeforme, -Lindley, with 
 its fleshy envelope. Falling Colliery, 
 Newcastle. 
 
 supposed to be the fruit of a palm, may now, according to Dr. 
 Hooker, be referred, like the Sternbergia, to the Coniferce. Its geo- 
 logical importance is great, for so abundant is it in the Coal 
 Measures, that in certain localities the fruit of some species may be 
 procured by the bushel ; nor is there any part of the formation where 
 they do not occur, except the underclays and limestone. The sand- 
 stone, ironstone, shales, and coal itself, all contain them. Mr. Binney 
 
 Manchester Philos. Mem. vol. ix. 1851. 
 
CH. XXIV.] GRADE OF THE CARBONIFEROUS FLORA. 373 
 
 has at length found in the clay-ironstone of Lancashire several 
 specimens displaying structure, and from these, says Dr. Hooker, we 
 learn that the Trigonocarpon belonged to that large section of existing 
 coniferous plants which bear fleshy solitary fruits, and not cones. 
 It resembled very closely the fruit of the Chinese genus Salisburia, 
 one of the Yew tribe, or Taxoid conifers. In five of the fossil 
 specimens there is evidence of four distinct integuments, and of a 
 large internal cavity filled with carbonate of lime and magnesia, and 
 probably once occupied by the albumen and embryo of the seed. The 
 general form of the fossil when perfect is an elongated ovoid, rather 
 larger than a hazle-nut. The exterior integument is very thick and 
 cellular, and was no doubt once fleshy (see fig. 487.). It alone is 
 produced beyond the seed, and forms the beak. The second coat 
 was thinner, but hard, and marked by three ridges. This coat, 
 being all that commonly remains in a fossil state, has suggested the 
 name of Trigonocarpon. Within this were the third and fourth 
 coats, both of which are very delicate membranes, and may possibly 
 have been two plates belonging to one membrane. 
 
 Grade of the Carboniferous flora. On the whole, these fruits, 
 says Dr. Hooker, are referable to " a highly developed type, ex- 
 hibiting extensive modifications of elementary organs for the pur- 
 pose of their adaptation to special functions, and these modifications 
 are as great, and the adaptation as special, as any to be found 
 amongst analogous fruits in the existing vegetable world."* Pro- 
 fessor Williamson, in his paper on Sternbergia, has likewise re- 
 marked that its structure was complex, and that " at a period so 
 early as the carboniferous all the now-existing forms of vegetable 
 tissue appear to have been created." These observations deserve 
 notice, because a question has arisen whether the Conifer 'ce hold a 
 high or a low position among flowering plants, a point bearing 
 directly on the theory of progressive development. By some botanists 
 all the Gymnospermous Dicotyledons are regarded as inferior in 
 grade to the Angiosperms. Others hold, with Dr. Hooker, that the 
 Gymnosperms are not inferior in rank, having every typical cha- 
 racter of- the dicotyledons highly developed. Thus Coniferse have 
 flowers, and are propagated by seeds which are developed through 
 the mutual action of the stamens and ovules; they have distinct 
 embryos, and germinate in a definite manner. The seed-vessel (or 
 ovary) is not closed, but this is also the case in some genera of 
 angiosperms, in which the ovary is open before or after impreg- 
 nation, so that this character cannot be relied on as constituting a 
 fundamental difference in structural development. The Coniferse 
 are exogenous, and have the same distinctions of pith, wood, bark, 
 and medullary rays as have the angiospermous trees. Whether the 
 woody fibre with discs characteristic of Coniferae be a more or a less 
 complex tissue than the spiral vessels, is a controverted point. As 
 the spiral vessels occur in the young shoots, and are lost in the 
 
 * Proceedings of the Royal Society, vol. vii. March, 1854, p. 28. 
 
 BB 3 
 
374 uRADE OF THE CARBONIFEROUS FLORA. [Cn. XXIV. 
 
 mature growth of some plants, and as they appear in many acrogens, 
 they do not seem to mark a high development. In fine, there is 
 much ambiguity in deciding what should or should not be called 
 high or low in vegetable structure, and physiologists entertain very 
 different abstract ideas as to the perfection of certain organs and 
 their relative functional importance, even where the function is 
 clearly ascertained. It is enough for the geologist to know, that 
 fossil Coniferee abound in the oldest rocks yielding a considerable 
 number of vegetable remains, and that plants of this order lay 
 claim, if not to the highest, at least to so high a place in the scale of 
 vegetable life, as to preclude us from characterizing the carbo- 
 niferous flora as consisting of imperfectly developed plants. 
 
 Although our data are confessedly too defective to entitle us to 
 generalize respecting the entire vegetable creation of this era, yet we 
 may affirm that so far as it is known it differed widely from any 
 flora now existing. The comparative rarity of Monocotyledons and 
 of Dicotyledonous Angiosperms seems clear, and the abundance 
 of Ferns and Lycopods may justify Adolphe Brongniart in calling 
 the primary periods the age of Acrogens.* (" Le regne des Acro- 
 gens.") As to the Sigillarise and Calamites, they seem to have been 
 distinct from all tribes of now-existing plants. That the abundance 
 of ferns implies a moist atmosphere, is admitted by all botanists; 
 but no safe conclusion, says Hooker, can be drawn from the Coniferse 
 alone, 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 Coniferse attain their maximum in numbers, constituting ^nd 
 part of all the flowering plants ; whereas in a wide district around 
 the Cape of Good Hope they do not form -pgV^th of the pheno- 
 gamic flora. Besides the conifers, many species of ferns flourish in 
 New Zealand, some of them arborescent, together with many lyco- 
 podiums ; so that a forest in that country may make a nearer approach 
 to the carboniferous vegetation than any other now existing on the 
 globe. 
 
 Angiosperms. Some of the grass-like leaves termed Poacites, 
 Fi 488 having fine longitudinal striae, are conjectured 
 
 to belong to Monocotyledons ; but the determi- 
 nation is doubtful, as some of them may be the 
 leaves of Lepidodendra, others the stems of 
 Ferns. The curious plants called Antholithes 
 by Lindley have usually been considered to be 
 flower-spikes, having what seems a calyx and 
 linear petals (see fig. 488.). But Dr. Hooker 
 suggests that these may be rather tufts of scarcely 
 opened buds with the young leaves just burst- 
 ing. He suggests that they may be coniferous, 
 although he cannot connect them with any known 
 ing Col- fossil conifer. 
 
 liery, Newcastle. 
 * For terminology of classification of plants, see above, note, p. 267. 
 
CH. XXIV.] COAL ERECT FOSSIL TREES. 375 
 
 Coal, how formed Erect trees. I shall now consider the manner 
 in which the above-mentioned plants are imbedded in the strata, and 
 how they may have contributed to produce coal. 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 coal. Many seams, he remarks, 
 are rich in Sigillarice, 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 others ferns.* " Soni3 
 of the plants of our coal," says Dr. Buckland, " grew on the iden- 
 tical banks of sand, silt, and mud which, being now indurated to 
 stone and shale, form the strata that accompany the coal; whilst 
 other portions of these plants have been drifted to various distances 
 from the swamps, savannahs, and forests that gave them birth, par- 
 ticularly those that are dispersed through the sandstones, or mixed 
 with fishes in the shale beds." " At Balgray, three miles north of 
 Glasgow," says the same author, "I saw in the year 1824, as there 
 still may be seen, an unequivocal example of the stumps of several 
 stems of large trees, standing close together in their native place, in 
 a quarry of sandstone of the coal-formation." \ ' ?;;-. 
 
 Between the years 1837 and 1840, six fossil trees were discovered 
 in the coal-field of Lancashire, where it is intersected by the Bolton 
 railway. They were all in a vertical position, with respect 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 argillaceous shale. In the same plane 
 with the roots is a bed of coal, eight or ten inches thick, which has 
 been ascertained to extend 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 Lepidostrobus variabilis was 
 discovered inclosed in nodules of hard clay, that more than a bushel 
 was collected from the small openings around the base of the trees 
 (see figure of this genus, p. 366.). The exterior trunk of each was 
 marked by a coating 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 circum- 
 ference at the base, 7 J feet at the top, its height being 1 1 feet. All 
 the trees have large spreading roots, solid and strong, sometimes 
 branching, and traced to a distance of several feet, and presumed to 
 extend much farther. Mr. Hawkshaw, who has described these 
 fossils, thinks that, although they were hollow when submerged, they 
 may have consisted originally of hard wood throughout ; for solid 
 dicotyledonous trees, when prostrated in tropical forests, as in Vene- 
 zuela, on the shore of the Caribbean Sea, were observed by him to be 
 destroyed in the interior, so that little more is left than an outer 
 shell, consisting chiefly of the bark. This decay, he says, goes on 
 
 * Quart. Geol. Journ., vol. v., Mem., f Anniv. Address to Geol. Soc.. 1840. 
 p. 17. 
 
 BB 4 
 
376 COAL ERECT FOSSIL TREES. [Cn. XXIV. 
 
 most rapidly in low and flat tracts, in which there is a deep rich soil 
 and excessive moisture, supporting tall forest-trees and large palms, 
 below which bamboos, canes, and minor palms flourish luxuriantly. 
 Such tracts, from their lowness, would be most easily submerged, and 
 their dense vegetation might then give rise to a seam of coal.* 
 
 In a deep valley near Capel-Coelbren, branching from the higher 
 part of the Swansea valley, four stems of upright Sigillarice were 
 seen in 1838, piercing through the coal-measures of S. Wales ; one 
 of them was 2 feet in diameter, and one 13 feet and a half high, and 
 they were all found to terminate downwards in a bed of coal. " They 
 appear," says Sir H. De la Beche, " to have constituted a portion of a 
 subterranean forest at the epoch when the lower carboniferous strata 
 were formed." f 
 
 In a colliery near Newcastle, say the authors of the Fossil Flora, 
 a great number of Sigillarice were placed in the rock as if they had 
 retained the position in which they grew. Not less than thirty, some 
 of them 4 or 5 feet in diameter, were visible within an area of 50 
 yards square, the interior being sandstone, and the bark having been 
 converted into coal. The roots of one individual were found im- 
 bedded in shale ; and the trunk, after maintaining a perpendicular 
 course and circular form for the height of about 10 feet, was then bent 
 over so as to become horizontal. Here it was distended laterally, and 
 flattened so as to be only one inch thick, the flutings being compa- 
 ratively distinct. J Such vertical stems are familiar to our miners, 
 under the name of coal-pipes. One of them, 72 feet in length, was 
 discovered, in 1829, near Gosforth, about five miles from Newcastle, 
 in coal-grit, the strata of which it penetrated. The exterior of the 
 trunk was marked at intervals with knots, indicating the points at 
 which branches had shot off. The wood of the interior had been 
 converted into carbonate of lime ; and its structure was beautifully 
 shown by cutting transverse slices, so thin as to be transparent. (See 
 p. 40.) . 
 
 These " coal-pipes " are much dreaded by our miners, for almost 
 every year in the Bristol, Newcastle, and other coal-fields, they are 
 the cause of fatal accidents. Each cylindrical cast of a tree, formed 
 of solid sandstone, and increasing gradually in size towards the base, 
 and being without branches, has its whole weight thrown downwards, 
 and receives no support from the coating of friable coal which has 
 replaced the bark. As soon, therefore, as the cohesion of this ex- 
 ternal layer is overcome, the heavy column falls suddenly in a per- 
 pendicular or oblique direction from the roof of the gallery whence 
 coal has been extracted, wounding 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, 
 
 * Hawkshaw, Geol. Trans., Second and Somerset, p. 143. 
 Series, vol. vi. pp. 173. 177., pi. 17. % Lindley and HuW>n, Foss. Flo. 
 
 f Geol. Eeport on Cornwall, Devon, part 6. p. 150. 
 
CH. XXI Y.] PARKFIELD COLLIERY. 377 
 
 after myriads of ages, the same force, are cast down to immolate 
 their human victims. 
 
 It has been remarked, that if, instead of working in the dark, the 
 miner was accustomed to remove the upper covering 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 Staffordshire a seam of coal was laid bare in the year 
 1844, in what is called an open work at Parkfield Colliery, near 
 Wolverhampton. In the space of about a quarter of an acre the 
 stumps of no less than 73 trees with their roots attached appeared, 
 as shown in the annexed plan (fig. 489.), some of them more than 
 
 Fig. 489. 
 
 Ground-plan of a fossil forest, Parkfield Colliery, near Wolverhampton, 
 showing the position of 73 trees in a quarter of an acre.* 
 
 8 feet in circumference. The trunks, broken off close to the root, 
 were lying prostrate in every direction, often crossing each other. 
 One of them measured 15, another 30 feet in length, and others less. 
 They were invariably flattened to the thickness of one or two inches, 
 and converted into coal. Their roots formed part of a stratum of 
 coal 10 inches thick, which rested on a layer of clay 2 inches thick, 
 below which was a second forest, resting on a 2-foot seam of coal. 
 Five feet below this again was a third forest with large stumps of 
 Lepidodendra, Calamites, and other trees. 
 
 In the account given, in 1821, by M. Alex. Brongniartf of the 
 coal-mine of Treuil, at St. Etienne, near Lyons, he states, that dis- 
 tinct horizontal strata of micaceous sandstone are traversed by ver- 
 tical trunks of monocotyledonous vegetables, resembling bamboos 
 or large Equiseta (fig. 490.). Since the consolidation of the stone, 
 there has been here and there a sliding movement, which has broken 
 the continuity of the stems, throwing the upper parts of them on 
 one side, so that they are often not continuous with the lower. 
 
 From these appearances it was inferred that we have here the 
 
 * Messrs. Beckett and Ick. Proceed. f Annales des Mines, 1821. 
 Geol. Soc., vol. iv. p. 287. 
 
378 
 
 COAL ERECT FOSSIL TREES. 
 
 Fig. 490. 
 
 [Cn. XXIV, 
 
 Section showing the erect position of fossil trees in coal-sandstone at 
 St. Etienne. (Alex. Brongniart.) 
 
 monuments of a submerged forest. I formerly objected to this con- 
 clusion, suggesting that, in that case, all the roots ought to have been 
 found at one and the same level, and not scattered irregularly 
 through the mass. I also imagined that the soil to which the roots 
 were attached should have been different from the sandstone in which 
 the trunks are enclosed. Having, however, seen calamites near 
 Pictou, in Nova Scotia, buried at various heights in sandstone and 
 in similar erect attitudes, I have now little doubt that M. Brong- 
 niart's view was correct. These plants seem to have grown on a 
 sandy soil, liable to be flooded from time to time, and raised by new 
 accessions of sediment, as may happen in swamps near the banks of 
 a large river in its delta. Trees which delight in marshy grounds 
 are not injured by being buried several feet deep at their base ; and 
 other trees are continually rising up from new soils, several feet 
 above the level of the original foundation of the morass. In the 
 banks of the Mississippi, when the water has fallen, I have seen 
 sections of a similar deposit in which portions of the stumps of 
 trees with their roots in situ appeared at many different heights.* 
 
 When I visited, in 1843, the quarries of Treuil above-mentioned, 
 the fossil trees seen in fig. 490. were removed, but I obtained proofs 
 of other forests of erect trees in the same coal-field. 
 
 Snags. In 1830, a slanting trunk was exposed in Craigleith 
 quarry, near Edinburgh, the total length of which exceeded 60 feet. 
 Its diameter at the top was about 7 inches, and near the base it 
 measured 5 feet in its greater, and 2 feet in its lesser width. The bark 
 was converted into a thin coating of the purest and finest coal, form- 
 ing a striking contrast in colour with the white quartzose sandstone 
 
 * Principles of Geol., 9th ed., p. 268. 
 
CH. XXIV.] COAL OBLIQUE FOSSIL TREES. 
 
 379 
 
 Fig. 491 
 
 in which it lay. The annexed 
 figure represents a portion of this 
 tree, about 15 feet long, which 
 I saw exposed in 1830, when all 
 the strata had been removed from 
 one side. The beds which re- 
 mained were so unaltered and un- 
 disturbed at the point of junction, 
 as clearly to show that they had 
 inclined position of a fossil tree, cutting through been tranquilly deposited round 
 
 horizontal beds of sandstone, Craigleith quarry, 1 j .-. , . , -, 
 
 Edinburgh. Angle of inclination from a to b the tree, and that the tree had not 
 
 subsequently pierced through 
 
 them, while they were yet in a soft state. They were composed 
 chiefly of siliceous sandstone, for the most part white ; and divided 
 into laminae so thin, that from six to fourteen of them might be 
 reckoned in the thickness of an inch. Some of these thin layers 
 were dark, and contained coaly matter ; but the lowest of the in- 
 tersected beds were calcareous. The tree could not have been 
 hollow when imbedded, for the interior still preserved the woody 
 texture in a perfect state, the petrifying matter being, for the most 
 part, calcareous.* It is also clear that the lapidifying matter was not 
 introduced laterally from the strata through which the fossil passes, 
 as most of these were not calcareous. It is well known that, in the 
 Mississippi and other great American rivers, where thousands of 
 trees float annually down the stream, some sink with their roots 
 downwards, and become fixed in the mud. Thus placed, they have 
 been compared to a lance in rest ; and so often do they pierce through 
 the bows of vessels which run against them, that they render the 
 navigation extremely dangerous. Mr. Hugh Miller mentions four 
 other huge trunks exposed in quarries near Edinburgh, which lay 
 diagonally across the strata at an angle of about 30, with their 
 lower or heavier portions downwards, the roots of all, save one, 
 rubbed off by attrition. One of these was 60 and another 70 feet 
 in length, and from 4 to 6 feet in diameter. 
 
 The number of years for which the trunks of trees, when constantly 
 submerged, can resist decomposition, is very great; as we might 
 suppose from the durability of wood, in artificial piles, permanently 
 covered by water. Hence these fossil snags may not imply a rapid 
 accumulation of beds of sand, although the channel of a river or 
 part of a lagoon is often filled up in a very few years. 
 
 Nova Scotia. One of the finest examples in the world of a suc- 
 cession of fossil forests of the carboniferous period, laid open to view 
 in a natural section, is that seen in the lofty cliffs called the South 
 Joggins, bordering the Chignecto Channel, a branch of the Bay of 
 Fundy, in Nova Scotia.f 
 
 * See figures of texture, Witham, vol.ii.p. 179.; andDawson, Geol. Joura. 
 Foss. Veget., pi. 3. No. 37. 
 
 f See LyelTs Travels in N. America, 
 
380 
 
 COAL FOSSIL FORESTS 
 
 [Cn. XXIV. 
 
 In the annexed section (fig. 492.), which I 
 examined in July, 1842, the beds from c to i are 
 seen all dipping the same way, their average in- 
 clination being at an angle of 24 S.S.W. The 
 vertical height of the cliffs is from 150 to 200 
 feet ; and between d and g, in which space I ob- 
 served seventeen trees in an upright position, or, 
 to speak more correctly, at right angles to the 
 planes of stratification, I counted nineteen seams 
 of coal, varying in thickness from 2 inches to 4 
 feet. At low tide a fine horizontal section of the 
 2 same beds is exposed to view on the beach. The 
 w thickness of the beds alluded to, between d and g, 
 | is about 2,500 feet, the erect trees consisting 
 ^ chiefly of large Sigillarice, occurring at ten dis- 
 
 1 tinct levels, one above the other ; but Mr. Logan, 
 g who afterwards made a more detailed survey of 
 the same line of cliffs, found erect trees at seven- 
 J teen levels, extending through a vertical thick- 
 '| ness of 4,515 feet of strata ; and he estimated the 
 total thickness of the carboniferous formation, 
 | with and without coal, at no less than 14,570 
 
 feet, every where devoid of marine organic re- 
 
 2 mains.* The usual height of the buried trees 
 I seen by me was from 6 .to 8 feet ; but one trunk 
 "J was about 25 feet high and 4 feet in diameter, 
 *j with a considerable bulge at the base. In no 
 instance could I detect any trunk intersecting a 
 
 K layer of coal, however thin ; and most of the 
 trees terminated downwards in seams of coal. 
 Some few only were based in clay and shale ; 
 none of them, except calamites, in sandstone. 
 The erect trees, therefore, appeared in general to 
 have grown on beds of coal. In the underclays 
 Stigmaria abounds. 
 
 In 1852 Mr. Dawson and the author made a 
 detailed examination of one portion of the strata, 
 1400 feet thick, where the coal-seams are most 
 frequent, and found evidence of root-bearing soils 
 at sixty-eight different levels. Like the seams 
 of coal which often cover them, these root-beds 
 or 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 weather. Origi- 
 nally the reverse was doubtless 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 
 
 * Quart. Geol. Journ., vol. ii. p. 177. 
 
CH. XXIV.J 
 
 IN NOVA SCOTIA. 
 
 381 
 
 river, or of the sea at the base of the delta, than do beds of loose 
 sand or layers of mud not supporting trees. 
 
 This fact may explain why seams of coal have so often escaped 
 denudation, and remain continuous over wide areas, since the tough 
 roots, now turned to coal, which once traversed them, would enable 
 them to resist a current of water, whilst other members of the coal- 
 formation, in their original and unconsolidated state of sand and 
 mud, would be readily removed. 
 
 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. In the sandstone, which filled their interiors, 
 I frequently observed fern leaves, and sometimes fragments of Stig- 
 maria, 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 b, fig. 493., the same which 
 is represented at a, fig. 494., or in the bed e in the larger section, 
 fig. 492., is a hollow trunk 5 feet 8 inches in length, traversing 
 various strata, and cut off at the top by a layer of clay 2 feet thick, 
 
 Fig. 493. 
 
 Fossil tree at right angles to the planes of stratification. 
 Coal-measures, Nova Scotia. 
 
 Fig. 494. 
 
 Erect fossil trees. Coal-measures, Nova Scotia. 
 
 on which rests a seam of coal (6, fig. 494.) 1 foot thick. On this 
 coal again stood two large trees (c and df), while at a greater height 
 the trees f and g rest upon a thin seam of coal (e), and above 
 them is an underclay, supporting the 4-foot coal. 
 
382 COAL FOSSIL FORESTS [Cn. XXIV. 
 
 If we now return to the tree first mentioned (fig. 493.), we find 
 the diameter (a b) 14 inches at the top and 16 inches at the bottom, 
 the length of the trunk 5 feet 8 inches. The strata in the interior 
 consisted of a series entirely different from those on the outside. 
 The lowest of the three outer beds which it traversed consisted of 
 purplish and blue shale (c, fig. 493.), 2 feet thick, above which was 
 sandstone (d) I foot thick, and, above this, clay (e) 2 feet 8 inches. 
 But, in the interior, were nine distinct layers of different composi- 
 tion : at the bottom, first, shale 4 inches, then sandstone 1 foot, then 
 shale 4 inches, then sandstone 4 inches, then shale 1 1 inches, then 
 clay (/) with nodules 01" ironstone 2 inches, then pure clay 2 feet, 
 then sandstone 3 inches, and, lastly, clay 4 inches. Owing to the 
 outward slope of the face of the cliff, the section (fig. 493.) was not 
 exactly perpendicular to the axis of the tree ; and hence, probably, 
 the apparent sudden termination at the base without a stump and roots. 
 
 In this example the layers of matter in the inside of the tree are 
 more numerous than those without ; but it is more common in the 
 coal-measures of all countries to find a cylinder of pure sandstone, 
 the cast of the interior of a tree, intersecting a great many 
 alternating beds of shale and sandstone, which originally enveloped 
 the trunk as it stood erect in the water. Such a want of corres- 
 pondence in the materials 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 proof 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 Catamites ; the Calamites having begun to grow after the older 
 Sigillarice 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 same difference of dura- 
 bility of bark and wood exists in modern trees, and was first pointed 
 out to me by Mr. Dawson, in the forests of Nova Scotia, where the 
 Canoe Birch (Betula papyracea) has such tough bark that it may 
 sometimes be seen in the swamps looking externally sound and fresh, 
 although consisting simply of a hollow cylinder with all the wood 
 decayed and gone. In such cases the submerged portion is some- 
 times found filled with mud. 
 
 One of the erect fossil trees of the South Joggins has been shown 
 by Mr. Dawson to have Araucarian structure, so that some Conifers 
 of the Coal Period grew in the same swamps as Sigillarice^ just as 
 now the deciduous Cypress (Taxodium distichum) 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. 498.) attached itself to the out- 
 side of the stumps and stems of the erect trees, adhering occasionally 
 
CH. XXIV.] OF NOVA SCOTIA. 383 
 
 even to the interior of the bark, another proof that the process of 
 envelopment was very gradual. These hollow upright trees, covered 
 with innumerable marine annelids, reminded me of a " cane-brake," 
 as it is commonly called, consisting of tall reeds of Arundinaria 
 macrosperma, which I saw, in 1846, at the Balize, or extremity of the 
 delta of the Mississippi. Although these reeds are freshwater 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, showing how easily the Sigillarice, hollow 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 continually 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 or 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. 
 
 In Cape Breton, Mr. Richard Brown has observed in the Sydney 
 coal-field a total thickness of coal-measures, without including the 
 underlying millstone-grit, of 1843 feet, dipping at an angle of 8. 
 Pie has published minute details of the whole series, showing at how 
 many different levels erect trees occur, consisting of Sigillaria, Le- 
 pidodendron, Calamites, and other genera. In one place eight erect 
 trunks, with roots and rootlets attached to them, were seen at the 
 same level, within a horizontal space 80 feet in length. Beds of 
 coal of various thickness are interstratified. Taking into account 
 forty-one clays filled with roots of Stigmaria in their natural position, 
 and eighteen layers of upright trees at other levels, there is, on the 
 whole, clear evidence of at least fifty-nine fossil forests, ranged one 
 above the other, in this coal-field, in the above-mentioned thickness 
 of strata.* 
 
 The fossil shells of Cape Breton and those of the Nova Scotia 
 section (p. 380.), consisting of Cypris, Unio (?), Modiola, and an 
 annelid probably of the genus Spirorbis (see fig. 498.), seem to 
 indicate brackish water ; but we ought never to be surprised if, in 
 pursuing the same stratum, we should come either to a freshwater 
 or a purely marine deposit ; for this will depend upon our taking a 
 direction higher up or lower down the ancient river or delta deposit. 
 
 In the strata above described, the association of clays supporting 
 upright trees, with other beds containing marine and brackish-water 
 shells, implies such a repeated change in the same area, from land to 
 sea and from sea to land, that here, if anywhere, we should expect to 
 meet with evidence of the fall of rain on ancient sea-beaches. Ac- 
 cordingly rain-prints were seen by me and Mr. Dawson at various 
 
 * Geol. Quart. Journ., vol. ii. p. 393.; and vol. vi. p. 115. 
 
384 
 
 COAL KAIN-PRINTS. 
 
 [On. XXIV. 
 
 levels, but the most perfect hitherto observed were discovered by 
 Mr. Brown near Sydney in Cape Breton. They consist of very deli- 
 cate impressions of rain-drops on greenish slates, with several worm- 
 tracks (a, 6, fig. 495.), such as usually accompany rain-marks on 
 the recent mud of the Bay of Fundy, and other modern beaches. 
 
 Fig. 496. 
 
 Fig. 495. Carboniferous rain-prints with worm-tracks (a, 6) on green shale, from Cape 
 
 Breton, Nova Scotia. Natural size. 
 Fig. 496. Casts of rain-prints on a portion of the same slab, f'g. 405., seen on the under 
 
 side of an incumbent layer of arenaceous shale. Natural size. 
 
 The arrow represents the supposed direction of the shower. 
 
 The casts of rain-prints, in figs. 496. and 497., project from the 
 under side of two layers, occurring at different levels, the one a 
 sandy shale, resting on the green shale (fig. 495.), the other a sand- 
 Fig. 497. 
 
 Fig. 497. Casts of carboniferous rain-prints and shrinkage-cracks (a) on the under 
 side of a layer of sandstone, Cape Breton, Nova Scotia. Natural ize. 
 
 stone presenting a similar warty or blistered surface, on which are 
 also observable some small ridges as at #, which stand out in relief, 
 and afford evidence of cracks formed by the shrinkage of subjacent 
 clay, on which rain had fallen. Many of the associated sandstones 
 are ripple-marked. 
 
 The great humidity of the climate of the coal-period had been 
 previously inferred from the nature of its vegetation and the con- 
 
CH. XXIV.] PURITY OF THE COAL. 385 
 
 tinuity 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 average size those which now fall 
 from the clouds. From such data we may presume that the at- 
 mosphere of the carboniferous period corresponded in density with 
 that now investing 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 vapour. 
 
 The more closely the strata productive of coal have been studied 
 the greater has become the force of the evidence in favour of their 
 having originated in the manner of modern deltas. They display 
 a vast thickness of stratified mud and fine sand without pebbles, and 
 in them are seen countless stems, leaves, and roots of terrestrial 
 plants, free for the most part from all intermixture of marine 
 remains, circumstances which imply the persistency in the same 
 region of a vast body of fresh water. This water was also charged, 
 like that of a great river, with an inexhaustible supply of sediment, 
 which seems to have been transported over alluvial plains so far 
 from the higher grounds that all coarser particles and gravel were 
 left behind. Such phenomena imply the drainage and denudation 
 of a continent or large island, having within it one or more ranges 
 of mountains. The partial intercalation of brackish-water beds at 
 certain points is equally consistent with the theory of a delta, the 
 lower parts of which are always exposed to be overflowed by the sea 
 even where no oscillations of level are experienced. 
 
 The purity of the coal itself, or the absence in it of earthy par- 
 ticles 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 Sigillarice and other trees, 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 after.wards covered with mud since turned to shale. Yet the 
 coal itself or altered vegetable matter remained all the while 
 un soiled 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 herbage 
 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 centuries, forming coal if the climate 
 be favourable. 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 trees have 
 been standing ever since the year 1811-12, killed by the great 
 
 c c 
 
386 LONG PERIODS OF ACCUMULATION. [Cn. XXIV. 
 
 earthquake of that date ; lacustrine and swamp plants have been 
 growing there in the shallows, and several rivers have annually 
 inundated the whole space, and yet have been unable to carry in 
 any sediment within the outer boundaries of the morass, so dense is 
 the marginal belt of reeds and brushwood. It may be affirmed that 
 generally in the " cypress 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 fact, I 
 may 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 (Taxodium distichuin), just as the underclays of the coal 
 are filled with Stigmaria. 
 
 It has been already stated, that the carboniferous strata at the 
 South Joggins, in Nova Scotia, are nearly three miles thick, and 
 the coal-measures are ascertained to be of vast thickness near Pictou, 
 more than 100 miles to the eastward. If, therefore, we speculate on 
 the probable volume of solid matter, contained in the Nova Scotia 
 coal-fields, there appears little danger of erring on the side of excess 
 if we take the average thickness of the beds at 7,500 feet, or about 
 half that ascertained to exist in one carefully measured section. As 
 to the area of the coal-field, it includes a large part of New Bruns- 
 wick to the west, and extends north to Prince Edward's Island, and 
 probably to the Magdalen Isles. When we add the Cape Breton 
 beds, and the connecting strata, which must have been denuded or 
 are still concealed beneath the waters of the Gulf of St. Lawrence, 
 we obtain an area comprising about 36,000 square miles. This, 
 with the thickness of 7,500 feet before assumed, will give 51,000 
 cubic miles of solid matter as the volume of the carboniferous rocks. 
 
 The Mississippi would take more than two million of years to 
 convey to the Gulf of Mexico an equal quantity of solid matter in 
 the shape of sediment, assuming the average discharge of water, in 
 that great river to be, as calculated by Mr. Forshey, 450,000 cubic 
 feet per second, throughout the year, and the total quantity of mud to 
 be, as estimated by Mr. Riddell, 3,702,758,400 cubic feet in the year.f 
 
 The Ganges, according to the data supplied to me by Mr. Everest 
 and Captain Strachey, conveys so much larger a volume of solid 
 matter annually to the Bay of Bengal, that it might accomplish a 
 similar task in 375,000 years, or in less than a fifth of the time 
 which the Mississippi would require.^ 
 
 As the lowest of the carboniferous strata of Nova Scotia, like the 
 middle and uppermost, consist of shallow-water beds, the whole 
 vertical subsidence of three miles, at the South Joggins, must have 
 
 * Lyell's Second Visit to the U. S., t Principles of Geology, 9th ed. 1853, 
 vol. ii. p. 245.; and American Journ. of p. 273. 
 Science, 2d series, vol. v. p. 17. t Ibid - 1853 > P- 283 - 
 
CH. XXIV.] BRACKISH-WATER AND MARINE STRATA. 387 
 
 taken place gradually. If then this depression was brought about in 
 the course of 375,000 years, it did not exceed the rate of four feet in 
 a century, resembling that now experienced in certain countries, 
 where, whether the movement be upward or downward, it is quite 
 insensible to the inhabitants, and only known by scientific inquiry. 
 If, on the other hand, it was brought about in two millions of years 
 according to the other standard before alluded to, the rate would be 
 only six inches in a century. But the same movement taking place 
 in an upward direction would be sufficient to uplift a portion of the 
 earth's crust to the height of Mont Blanc, or to a vertical elevation 
 of three miles above the level of the sea. 
 
 The delta of the Ganges presents in one respect a striking parallel 
 to the Nova Scotia coal-field, since at Calcutta at the depth of eight 
 or ten feet from the surface the buried stools of trees with their roots 
 attached have been found in digging tanks, indicating an ancient soil 
 now underground ; and, in boring on the same site for an Artesian 
 well to the depth of 481 feet, other signs of ancient forest-covered 
 lands and peaty soils have been observed at several depths, even as 
 far down as 300 feet and more below the level of the sea. As the 
 strata pierced through contained freshwater remains of recent species 
 of plants and animals, they imply a subsidence which has been going 
 on contemporaneously with the accumulation of fluviatile mud. 
 
 In the English coal-fields the same association of fresh, or rather 
 brackish-water strata, with marine, in close connection with beds of 
 coal of terrestrial origin, has been frequently recognised. Thus, 
 for example, a deposit near Shrewsbury, probably formed in brackish 
 water, has been described by Sir R. Murchison as the youngest 
 member of the carboniferous series of that district, at the point 
 where the coal-measures are in contact with the Permian or " Lower 
 New Red." It consists of shales and sandstones about 150 feet 
 thick, with coal and traces of plants ; including a bed of limestone, 
 varying from 2 to 9 feet in thickness, which is cellular, and resem- 
 bles some lacustrine limestones of France and Germany. It has been 
 traced for 30 miles in a straight line, and can be recognised at still 
 more distant points. The characteristic fossils are a small bivalve, 
 having the form of a Cyclas or Cyrena, also a small entomostracan 
 which may be a Cypris or, if marine, a Cy there (fig. 499.), and the 
 microscopic shell of an annelid of an extinct genus called Micro- 
 conchus (fig. 498.), allied to Serpula or Spirorbis. 
 
 Fig. 498. Fig. 499. 
 
 a. Microconchus (Spirorbis) ^j^ Cypris finflata (or Cy there?), 
 carbonarius. Nat. size, Nat. size, and magnified, 
 and magnified. Q Murchison.* 
 
 b. var. of same. 
 
 * Silurian System, p. 84. 
 CC 2 
 
388 
 
 CRUSTACEANS OF THE COAL. 
 
 [CH. XXIV. 
 
 Fig. 500. 
 
 Limulus rotundalus, Prestwich. 
 Coal, Coalbrook Dale. 
 
 In the lower coal-measures of Coalbrook Dale, the strata, accord- 
 ing to Mr. Prestwich, often change completely within very short dis- 
 tances, beds of sandstone passing horizontally into clay, and clay 
 into sandstone. The coal-seams often wedge out or disappear ; and 
 sections, at places nearly contiguous, present marked lithological dis- 
 tinctions. In this single field, in which the strata are from 700 to 
 800 feet thick, between forty and fifty species of terrestrial plants 
 have been discovered, besides several fishes of the genera Megalich- 
 thys, Holoptychius, and others. Crustacea 
 also are met with, of the genus Limulus 
 (see fig. 500.), resembling in all essential 
 characters the Limuli of the Oolitic 
 period, and the king-crab of the modern 
 seas. They were smaller, however, than 
 the living form, and had the abdomen 
 deeply grooved across, and serrated at its 
 edges. In this specimen, the tail is 
 wanting; but in another, of a second 
 species, from Coalbrook Dale, the tail is 
 seen to agree with that of the living Limulus. 
 
 The perfect carapace of a long-tailed or decapod crustacean has 
 also been found in the ironstone of these strata by Mr. Ick (see fig. 
 501.). It is referred by Mr. Salter to Glyphea, a genus also occur- 
 ring in the Lias and Oolite. There are also 
 upwards of forty species of mollusca, among 
 which are two or three referred to the fresh- 
 water genus Unio, and others of marine 
 forms, such as Nautilus, Orthoceras, Spirifer, 
 and Productus. Mr. Prestwich suggests that 
 the intermixture of beds containing fresh- 
 water shells with others full of marine remains, 
 and the alternation of coarse sandstone and 
 conglomerate with beds of fine clay or shale 
 Saiter. containing the remains of plants, may be ex- 
 by supposing the deposit of Coalbrook 
 l " Dale to have originated in a bay of the sea 
 or estuary into which flowed a considerable 
 river subject to occasional freshes.* 
 
 One or more species of scorpions, two beetles of the family Curcu- 
 lionidce, and a neuropterous insect resembling the genus Corydalis, 
 and another related to the Phasmidce, have been found at Coalbrook 
 Dale. From the coal of Wetting in Westphalia several specimens 
 of the cockroach or Blatta family, and the wing of a cricket 
 (Acridites), have been described by Germar.f 
 
 More recently (1854) Mr. Fr. Goldenberg has published de- 
 scriptions of no less than twelve species of insects from the nodular 
 
 Fig. 501. 
 
 * Prestwich, Geol. Trans., 2d series, 
 vol. v. p. 440. 
 
 f See Miinster's Beitr. vol. v. pi. 13. 
 1842. 
 
CLAY-IRON-STONE. 
 
 389 
 
 CH. XXIV.] 
 
 clay-iron-stone of Saarbriick near Treves.* They are associated 
 with the leaves and branches of fossil ferns. Among them are 
 several Blattince, three species of Neuroptera, one beetle of the 
 Scarabceus family, a grasshopper or locust, Gryllacris (see fig. 502.), 
 
 Fig. 502. 
 
 Wing of a Grasshopper. 
 
 Gryllacris lifhanthraca, Goldenberg. 
 
 Coal, Saarbriick near Treves. 
 
 and several white ants or Termites. These newly added species 
 probably outnumber all we knew before of the fossil insects of the 
 coal. 
 
 In the Edinburgh coal-field, at Burdiehouse, fossil fishes, mollusks, 
 and cyprides (?), very similar to those in Shropshire and Stafford- 
 shire, have been found by Dr. Hibbert. In the coal-field also of 
 Yorkshire there are freshwater strata, some of which contain shells 
 referred to the genus Unio ; but in the midst of the series there is one 
 thin but very widely spread stratum, abounding in fishes and marine 
 shells, such as Goniatites Listeri (fig. 503.), Orthoceras, and Avicula 
 papyracea, Goldf. (fig. 504.) 
 
 Fig. 503. 
 
 Fig. 504. 
 
 Goniatites Listeri, Martin, sp. 
 
 Avicula papyracea, Goldf. 
 (.Pecten papyraceus, Sow.) 
 
 No similarly intercalated layer of marine shells has been noticed 
 in the neighbouring coal-field of Newcastle, where, as in South 
 Wales and Somersetshire, the marine deposits are entirely below 
 those containing terrestrial and freshwater remains.f 
 
 Clay-iron-stone. Bands and nodules of clay-iron-stone are common 
 in coal-measures, and are formed, says Sir H. De la Beche, of car- 
 bonate of iron mingled mechanically with earthy matter, like that 
 constituting the shales. Mr. Hunt, of the Museum of Practical 
 
 Palseont. Bunker and V. Meyer, f Thillips ; art. "Geology," Encyc. 
 vol. iv. p. 17. Metrop. p. 592. 
 
 C C 3 
 
390 CLAY-IRON-STONE. [Cn. XXIV. 
 
 Geology, instituted a series of experiments to illustrate the produc- 
 tion of this substance, and found that decomposing vegetable matter, 
 such as would be distributed through all coal-strata, prevented the 
 farther oxidation of the proto-salts of iron, and converted the per- 
 oxide 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 carbonate of iron ; and 
 this mingling with fine mud, when the excess of carbonic acid was 
 removed, might form beds or nodules of argillaceous iron-stone. * 
 
 * Memoirs of Geol. Survey, pp. 51. 255, &c. 
 
CH.XXV.] COAL-FIELDS OF UNITED STATES. 391 
 
 CHAPTER XXV. 
 
 CARBONIFEROUS GROUP continued. 
 
 Coal-fields of the United States Section of the country between the Atlantic and 
 Mississippi Position of land in the carboniferous period eastward of the Al- 
 leghanies Mechanically formed rocks thinning out westward, and limestones 
 thickening Uniting of many coal-seams into one thick bed Horizontal coal 
 at Brownsville, Pennsylvania Vast extent and continuity of single seams of 
 coal Ancient river-channel in Forest of Dean coal-field Climate of car- 
 boniferous period Insects in coal Rarity of air-breathing animals Great 
 number of fossil fish First discovery of the skeletons of fossil reptiles Foot- 
 prints of reptilians First land-shell found Rarity of air-breathers, whether 
 vertebrate or invertebrate, in Coal-measures Mountain limestone Its corals 
 and marine shells. 
 
 IT was stated in the last chapter that a great uniformity prevails in 
 the fossil plants of the coal-measures of Europe and North America ; 
 and I may add that four-fifths of those collected in Nova Scotia have 
 been identified with European species. Hence the former existence, 
 at the remote period under consideration (the carboniferous), of a 
 continent or chain of islands where the Atlantic now rolls its waves 
 seems a fair inference. Nor are there wanting other and indepen- 
 dent proofs of such an ancient land situated to the eastward of the 
 present Atlantic coast of North America ; for the geologist deduces 
 the same conclusion from the mineral composition of the carbonifer- 
 ous and some older groups of rocks as they are developed on the 
 eastern flanks of the Alleghanies, contrasted with their character in 
 the low country to the westward of those mountains. 
 
 The annexed diagram (fig. 505.) will assist the reader in under- 
 standing the phenomena now alluded to, although I must guard him 
 against supposing that it is a true section. A great number of 
 details have of necessity been omitted, and the scale of heights and 
 horizontal distances are unavoidably falsified. 
 
 Starting from the shores of the Atlantic, on the eastern side of 
 the Continent, we first come to a low region (A B), which was called 
 the alluvial plain by the first geographers. It is occupied by tertiary 
 and cretaceous strata, before described (pp. 181. 232. and 255.), 
 which are nearly horizontal. The next belt, from B to c, consists of 
 granitic rocks (hypogene), chiefly gneiss and mica-schist, covered 
 occasionally with unconformable red sandstone, No. 4. (New Red or 
 Trias ?), remarkable for its footprints (see p. 348.). Sometimes, also, 
 this sandstone rests on the edges of the disturbed paleozoic rocks (as 
 seen in the section). The region (B c), sometimes called the " Atlan- 
 tic Slope," corresponds nearly in average width with the low and flat 
 plain (A B), and is characterized by hills of moderate height, con- 
 trasting strongly, in their rounded shape and altitude, with the long, 
 
 cc 4 
 
392 GEOLOGICAL STKUCTURE OF UNITED STATES. [Cn. XXV. 
 
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CH. XXV.] CARBONIFEROUS GROUP. 393 
 
 steep, and lofty parallel ridges of the Alleghany mountains. The 
 out-crop of the strata in these ridges, like the two belts of hypogene 
 and newer rocks (A B, and B c), above alluded to, when laid down 
 on a geological map, exhibit long stripes of different colours, run- 
 ning in a N.E. and S.W. direction, in the same way as the lias, 
 chalk, and other secondary formations in the middle and eastern half 
 of England. 
 
 The narrow and parallel zones of the Appalachians, here men- 
 tioned, consist of strata, folded into a succession of convex and con- 
 cave flexures, subsequently laid open by denudation. The compo- 
 nent rocks are of great thickness, all referable to the Silurian, 
 Devonian, and Carboniferous formations. There is no principal or 
 central axis, as in the Pyrenees and many other chains no nucleus 
 to which all the minor ridges conform ; but the chain consists of 
 many nearly equal and parallel foldings, having what is termed an 
 anticlinal and synclinal arrangement (see above, p. 48.). This sys- 
 tem of hills extends, geologically considered, from Vermont to Ala- 
 bama, being more than lOOSniles long, from 50 to 150 miles broad, and 
 varying in height from 2000 to 6000 feet. Sometimes the whole as- 
 semblage of ridges runs perfectly straight for a distance of more than 
 50 miles, after which all of them wheel round altogether, and take a 
 new direction, at an angle of 20 or 30 degrees to the first. 
 
 We are indebted to the state surveyors of Virginia and Pennsyl- 
 vania, Prof. W. B. Rogers and his brother Prof. H. D. Rogers, for 
 the important discovery of a clue to the general law of structure 
 prevailing throughout this range of mountains, which, however sim- 
 ple it may appear when once made out and clearly explained, might 
 long have been overlooked, amidst so great a mass of complicated 
 details. It appears that the bending and fracture of the beds is 
 greatest on the south-eastern or Atlantic side of the chain, and the 
 strata become less and less disturbed as we go westward, until at 
 length they regain their original or horizontal position. By refer- 
 ence to the section (fig. 505.), it will be seen that on the eastern side, 
 or in the ridges and troughs nearest the Atlantic, south-eastern dips 
 predominate, in consequence of the beds having been folded back 
 upon themselves, as in i, those on the north-western side of each 
 arch having been inverted. The next set of arches (such as k) are 
 more open, each having its western side steepest ; the next (/) open 
 out still more widely, the next (m) still more, and this continues 
 until we arrive at the low and level part of the Appalachian coal- 
 field (D E). 
 
 In nature or in a true section, the number of bendings or parallel 
 folds is so much greater that they could not be expressed in a dia- 
 gram without confusion. It is also clear that large quantities of 
 rock have been removed by aqueous action or denudation, as will 
 appear if we attempt to complete all the curves in the manner indi- 
 cated by the dotted lines at i and k. 
 
 The movements which imparted so uniform an order of arrange- 
 ment to this vast system of rocks must have been, if not contempo- 
 
394 APPALACHIAN CHAIN. [Cn. XXV. 
 
 raneous. at least parts of one and the same series, depending on some 
 common cause. Their geological date is well defined, at least within 
 certain limits, for they must have taken place after the deposition of 
 the carboniferous strata (No. 5.), and before the formation of the red 
 sandstone (No. 4.). The greatest disturbing and denuding forces 
 have evidently been exerted on the south-eastern side of the chain ; 
 and it .is here that igneous or plutonic rocks are observed to have 
 invaded the strata, forming dykes, some of which run for miles in 
 lines parallel to the main direction of the Appalachians, or N.N.E. 
 and S.S.W. 
 
 The thickness of the carboniferous rocks in the region c is very 
 great, and diminishes rapidly as we proceed to the westward. The 
 surveys of Pennsylvania and Virginia show that the south-east was 
 the quarter whence the coarser materials of these strata were derived, 
 so that the ancient land lay in that direction. The conglomerate 
 which forms the general base of the coal-measures is 1 500 feet thick 
 in the Sharp Mountain, where I saw it (at c) near Pottsville ; whereas 
 it has only a thickness of 500 feet, about thirty miles to the north- 
 west, and dwindles gradually away when followed still farther in the 
 same direction, until its thickness is reduced to 30 feet.* The lime- 
 stones, on the other hand, of the coal-measures augment as we trace 
 them westward. Similar observations have been made in regard to 
 the Silurian and Devonian formations in New York ; the sandstones 
 and all the mechanically-formed rocks thinning out as they go west- 
 ward, and the limestones thickening, as it were, at their expense. It 
 is, therefore, clear that the ancient land was to the east, where the 
 Atlantic now is ; the deep sea, with its banks of coral and shells to 
 the west, or where the hydrographical basin of the Mississippi is 
 now situated. 
 
 In that region, near Pottsville, where the thickness of the coal- 
 measures is greatest, there are thirteen seams of anthracitic coal, 
 several of them more than 2 yards thick. Some of the lowest of 
 these alternate with beds of white grit and conglomerate of coarser 
 grain than I ever saw elsewhere, associated with pure coal. The peb- 
 bles of quartz are often of the size of a hen's egg. On following these 
 pudding-stones and grits for several miles from Pottsville, by Tama- 
 qua, to the Lehigh Summit Mine, in company with Mr. H. D. 
 Rogers, in 1841, he pointed out to me that the coarse-grained strata 
 and their accompanying shales gradually thin out, until seven seams 
 of coal, at first widely separated, are brought nearer and nearer 
 together, until they successively unite ; so that at last they form 
 one mass, between 40 and 50 feet thick. I saw this enormous bed of 
 anthracitic coal quarried in the open air at Mauch Chunk (or the 
 Bear Mountain), the overlying sandstone, 40 feet thick, having been 
 removed bodily from the top of the hill, which, to use the miner's 
 expression, had been "scalped." The accumulation of vegetable 
 matter now constituting this vast bed of anthracite, may perhaps, 
 
 * H. D. Rogers, Trans. Assoc. Amer. Geol., 1840-42, p. 440. 
 
CH. XXV.] 
 
 UNION OF COAL SEAMS. 
 
 395 
 
 before it was condensed by pressure and the discharge of its 
 hydrogen, oxygen, and other volatile ingredients, have been between 
 200 and 300 feet thick. The origin of such a vast thickness of 
 vegetable remains, so unmixed with earthy ingredients, can, I think, 
 be accounted for in no other way, than by the growth, during thou- 
 sands of years, of trees and ferns, in the manner of peat, a theory 
 which the presence 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 absence of sedi- 
 ment, or, in this case of sand and pebbles, wholly unexplained. 
 
 But the student will naturally ask, what can have caused so many 
 seams of coal, after they had been persistent for miles, to come to- 
 gether and blend into one single seam, and that one equal in the 
 aggregate to the thickness of the several separate seams ? Often had 
 the same question been put by English miners before a satisfactory 
 answer was given to it by the late Mr. Bowman. The following is 
 his solution of the problem. Let a a', fig. 506., be a mass of vege- 
 
 Fig. 506. 
 
 Fig. 507. 
 
 table matter, capable, when condensed, of forming a 3 -foot seam of 
 coal. It rests on the underclay b b', filled with roots of trees in situ, 
 and it supports a growing forest (c D). Suppose that part of the 
 same forest D E had become submerged by the ground sinking down 
 25 feet, so that the trees have been partly thrown down and partly 
 remain erect in water, slowly decaying, their stumps and the lower 
 parts of their trunks being enveloped in layers of sand and mud, 
 which are gradually filling up the lake D F. When this lake or 
 lagoon has at length been entirely silted up and converted into land, 
 say, in the course of a century, the forest c D will extend once more 
 continuously over the whole area c F, as in fig. 507., and another mass 
 of vegetable matter (g g'\ forming 3 feet more of coal, may accu- 
 mulate from c to F. We then find in the region F, two seams of 
 coal (a! and g') each 3 feet thick, and separated by 25 feet of sand- 
 stone and shale, with erect trees based upon the lower coal, while, 
 between D and c, we find these two seams united into a 2-yard coal. 
 It may be objected that the uninterrupted growth of plants during 
 the interval of a century will have caused the vegetable matter in 
 
396 HORIZONTAL COAL STRATA. [Cn. XXV. 
 
 the region c D to be thicker than the two distinct seams a' and g' at 
 F ; and no doubt there would actually be a slight excess representing 
 one generation of trees with the remains of other plants, forming 
 half an inch or an inch of coal; but this would not prevent the 
 miner from affirming that the seam a g, throughout the area c D, 
 was equal to the two seams a' and g' at F. 
 
 The reader has seen, by reference to the section (fig. 505. p. 
 392.), that the strata of the Appalachian coal-field assume an 
 horizontal position west of the mountains. In that less elevated 
 country, the coal-measures are intersected by three great navigable 
 rivers, and are capable of supplying for ages, to the inhabitants of a 
 densely peopled region, an inexhaustible supply of fuel. These 
 rivers are the Monongahela, the Alleghany, and the Ohio, all of 
 which lay open on their banks the level seams of coal. Looking 
 down the first of these at Brownsville, we have a fine view of the 
 main seam of bituminous coal 10 feet thick, commonly called the 
 Pittsburg seam, breaking out in the steep cliff at the water's edge ; 
 and I made the accompanying sketch of its appearance from the 
 bridge over the river (see fig. 508.). Here the coal, 10 feet thick, is 
 covered by carbonaceous shale (b), and this again by micaceous sand- 
 stone (c). Horizontal galleries may be driven everywhere at very 
 slight expense, and so worked as to drain themselves, while the cars, 
 laden with coal and attached to each other, glide down on a railway, 
 so as to deliver their burden into barges moored to the river's bank. 
 The same seam is seen at a distance, on the right bank (at ), and 
 may be followed the whole way to Pittsburg, fifty miles distant. As 
 it is nearly horizontal, while the river descends it crops out at a con- 
 tinually increasing, but never at an inconvenient, height above the 
 Monongahela. Below the great bed of coal at Brownsville is a fire- 
 clay 18 inches thick, and below this, several beds of limestone, below 
 which again are other coal seams. I have also shown in my sketch 
 another layer of workable coal (at d d\ which breaks out on the 
 slope of the hills at a greater height. Here almost every proprietor 
 can open a coal-pit on his own land, and the stratification being very 
 regular, he may calculate with precision the depth at which coal may 
 be won. 
 
 The Appalachian coal-field, of which these strata form a part 
 (from c to E, section, fig. 505., p. 392.), is remarkable for its vast 
 area ; for, according to Professor H. D. Rogers, it stretches continu- 
 ously from N.E. to S.W., for a distance of 720 miles, its greatest 
 width being about 180 miles. On a moderate estimate, its superficial 
 area amounts to 63,000 square miles. 
 
 This coal-formation, before its original limits were reduced by 
 denudation, must have measured 900 miles in length, and in some 
 places more than 200 miles in breadth. By again referring to the 
 section (fig. 505., p. 392.), it will be seen that the strata of coal are 
 horizontal to the westward of the mountains in the region D E, and 
 become more and more inclined and folded as we proceed eastward. 
 Now it is invariably found, as Professor H. D. Rogers has shown by 
 
Ca. XXV.] 
 
 APPALACHIAN COAL STRATA. 
 
 397 
 
 chemical analysis, that the coal is most bituminous towards its 
 western limit, where it remains level and unbroken, and that it 
 becomes progressively debituminized as we travel south-eastward 
 towards the more bent and distorted rocks. Thus, on the Ohio, the 
 proportion of hydrogen, oxygen, and other volatile matters ranges 
 from forty to fifty per cent. Eastward of this line, on the Mononga- 
 
398 CONVERSION OF COAL INTO LIGNITE. [Cn. XXV. 
 
 hela, it still approaches forty per cent., where the strata begin to ex- 
 perience some gentle flexures. On entering the Alleghany Moun- 
 tains, where the distinct anticlinal axes begin to show themselves, 
 but before the dislocations are considerable, the volatile matter is 
 generally in the proportion of eighteen or twenty per cent. At 
 length, when we arrive at some insulated coal-fields (5', fig. 505.) as- 
 sociated with the boldest 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 to twelve per cent, of bitumen, 
 thus becoming a genuine 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 con- 
 tinuance of decomposition changes this lignite into common or bitu- 
 minous coal, chiefly by the discharge of carburetted hydrogen, or the 
 gas by which we illuminate our streets and houses. According to 
 Bischoff, the inflammable gases which are always escaping from 
 mineral coal, and are so often the cause of fatal accidents in mines, 
 always contain carbonic acid, carburetted hydrogen, nitrogen, and 
 olifiant gas. The disengagement of all these gradually transforms 
 ordinary or bituminous coal into anthracite, to which the various 
 names of splint-coal, glance-coal, hard-coal, culm, and many others, 
 have been given. 
 
 We have seen that, in the Appalachian coal-field, there is an 
 intimate connection between the extent to which the coal has parted 
 with its gaseous contents, and the amount of disturbance which the 
 strata have undergone. The coincidence of these phenomena may 
 be attributed partly to the greater facility afforded for the escape of 
 volatile matter, where the fracturing of the rocks had produced an 
 infinite number of cracks and crevices, and also to the heat of the 
 gases and water penetrating these cracks, when the great movements 
 took place, which have rent and folded the Appalachian strata. It 
 is well known that, at the present period, thermal waters and hot 
 vapours burst out from the earth during earthquakes, and these 
 would not fail to promote the disengagement of volatile matter from 
 the carboniferous rocks. 
 
 Continuity of seams of coal. As single seams of coal are con- 
 tinuous over very wide areas, it has been asked, how forests could 
 have prevailed uninterruptedly over such wide spaces. In reply, it 
 may be said that swamp-forests in one delta may extend for 25, 50, 
 or 100 miles, while in a contiguous delta, as on the borders of the 
 Gulf of Mexico, another of precisely the same character may be 
 growing ; and these may in after ages appear to geologists to have 
 
 * Trans, of Assoc. of Amer. GeoL, p. 470. 
 
CH. XXV.] CLIMATE OF COAL PERIOD. 399 
 
 been continuous, although in fact they were simply contemporaneous. 
 Denudation may easily be imagined in such cases as the cause of in- 
 terruptions, which were in fact, original. But as in all the American 
 coal-fields there are numerous root-beds without any superincumbent 
 coal, we may presume that frequently layers of vegetable matter 
 were removed by floods ; and in other cases, where the stigmaria-clays 
 are for a certain space covered with coal, and then prolonged with- 
 out any such covering, the inference of partial denudation is still 
 more obvious. 
 
 In the Forest of Dean, ancient river-channels are found, which 
 pass through beds of coal, and in which rounded pebbles of coal 
 occur. They are of older date than the overlying and undisturbed 
 coal-measures. The late Mr. Buddie, who described them to me, 
 told me he had seen similar phenomena in the Newcastle coal-field. 
 Nevertheless, instances of these channels are much more rare than 
 we might have anticipated, especially when we remember how often 
 the roots of trees (Stigmarice) have been torn up, and drifted in 
 broken fragments into the grits and sandstones. The prevalence of 
 a downward movement is, no doubt, the principal cause which has 
 saved so many extensive seams of coal from destruction by fluviatile 
 action. 
 
 Climate of Coal Period. So long as the botanist taught that a 
 tropical climate was implied by the carboniferous flora, geologists 
 might well be at a loss to reconcile the preservation of so much vege- 
 table matter with a high temperature ; for heat hastens the decompo- 
 sition of fallen leaves and trunks of trees, whether in the atmosphere 
 or in water. It is well known that peat, so abundant in the bogs of 
 high latitudes, ceases to grow in the swamps of warmer regions. 
 It seems, however, to have become a more and more received opinion, 
 that the coal-plants do not, on the whole, indicate a climate resem- 
 bling that now enjoyed in the equatorial zone. Tree-ferns range as 
 far south as the southern part of New Zealand, and Araucarian pines 
 occur in Norfolk Island. A great predominance of ferns and lyco- 
 podiums indicates moisture, equability of temperature, and freedom 
 from frost, rather than intense heat ; and we know too little of the 
 sigillarise, calamites, asterophyllites, and other peculiar forms of the 
 carboniferous period, to be able to speculate with confidence on the 
 kind of climate they may have required. 
 
 The same may be said of the corals and cephalopoda of the 
 Mountain Limestone, they belong to families of whose climatal 
 habits we know nothing ; and even if they should be thought to 
 imply that a warm temperature characterized the northern seas in 
 the carboniferous era, the absence of cold may have given rise (as at 
 present in the seas of the Bermudas, under the influence of the 
 gulf-stream) to a very wide geographical range of stone-building 
 corals and shell-bearing cuttle-fish, without its being necessary to 
 call in the aid of tropical heat. 
 
400 CARBONIFEROUS REPTILES. [Cff. XXV. 
 
 CARBONIFEROUS REPTILES. 
 
 Where we have evidence in a single coal-field, as in that of Nova 
 Scotia, or of South Wales, of fifty or even a hundred ancient forests 
 buried one above the other, with the roots of trees still in their 
 original position, and with some of the trunks still remaining erect, 
 we are apt to wonder that until the year 1844 no remains of contem- 
 poraneous air-breathing creatures should have been discovered. No 
 vertebrated animals more highly organized than fish, no mammalia 
 or birds, no saurians, frogs, tortoises, or snakes were known in rocks 
 of such high antiquity. In the coal-fields of Europe mention has 
 been made of beetles, locusts, and a few other insects, but no land- 
 shells have even now been met with. Agassiz described in his great 
 work on fossil fishes more than one hundred and fifty species of ich- 
 thyolites from the coal-strata, ninety-four belonging to the families of 
 shark and ray, and fifty -eight to the class of ganoids. Some of these 
 fish are very remote in their organization from any now living, espe- 
 cially those of the family called Sauroid by Agassiz ; as Megalich- 
 thys, Holoptychius, and others, which were often of great size, and all 
 predaceous. Their osteology, says M. Agassiz, reminds us in many 
 respects of the skeletons of saurian reptiles, 
 both by the close sutures of the bones of the 
 skull, their large conical teeth striated longitu- 
 dinally (see fig. 509.), the articulations of the 
 spinous processes with the vertebras, and other 
 characters. Yet they do not form a family in- 
 termediate between fish and reptiles, but are 
 true fish, though doubtless more highly or- 
 ganized than any living fish.* 
 
 The annexed figure represents a large tooth 
 of the Holoptychius, found by Mr. Horner in the 
 Cannel coal of Fifeshire. This fish probably in- 
 habited an estuary, like many of its contempo- 
 raries, and frequented both rivers and the sea. 
 
 At length, in 1844, the first skeleton of a true 
 reptile was announced from the coal of Miinster- 
 re coai-fieid. Appel in Rhenish Bavaria, by H. von Meyer, 
 
 Tooth ; natural size. ."* J ' 
 
 under the name of Apateon pedestris, the 
 animal being supposed to be nearly related to the salamanders. Three 
 years later, in 1847, Prof, von Dechen found in the coal-field of 
 Saarbriick, at the village of Lebach, between Strasburg and Treves, 
 the skeletons of no less than three distinct species of air-breath- 
 ing reptiles, which were described by the late Prof. Goldfuss 
 under the generic name of Archegosaurus. The ichthyolites and 
 plants found in the same strata left no doubt that these remains 
 belonged to the true coal period. The skulls, teeth, and the greater 
 portions of the skeleton, nay, even a large part of the skin, of two 
 
 * Agassiz, Poiss. Foss. vol. ii. p. 88, &c. 
 
CH. XXV.] CARBONIFEROUS REPTILES. 401 
 
 Figl M0 - of these reptiles have been 
 
 faithfully preserved in the 
 centre of spheroidal con- 
 cretions of clay -iron-stone. 
 The largest of these lizards, 
 Archegosaurus Decheni, 
 must have been 3 feet 6 
 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 Laby- 
 rinthodon, and therefore, as 
 before explained (p. 342.), 
 having many characters 
 intermediate between ba- 
 trachians and saurians. 
 The remains of the extre- 
 mities 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 
 Prof. Owen has observed to me that 
 they make an approach to the Pro- 
 teus in the shortness of their ribs. 
 Two specimens of these ancient rep- 
 tiles retain a large part of the outer 
 skin, which consisted of long, nar- 
 row wedge-shaped, tile-like, and horny scales, arranged in rows 
 (see fig. 511.). 
 
 Cheirotherian footprints in coal-measures. United States. In 
 1844, the very year when the Apateon or Salamander of the coal 
 was first met with in the country between the Moselle and the 
 Rhine, Dr. King published an account of the footprints of a large 
 reptile discovered by him in North America. These occur in the 
 coal-strata of Greensburg, in Westmoreland County, Pennsylvania ; 
 and I had an opportunity of examining them in 1846. I was at once 
 convinced of their genuineness, and declared my conviction on that 
 
 * Goldfuss, Neue Jenaische Lit. Zeit., 1848 ; and Von Meyer, Quart. 
 Journ., vol. iv. Miscell. p. 51. 
 
 D D 
 
 Archegosaurus minor, Goldfuss. Fossil reptile from 
 the coal-measures, Saarbrilck. 
 
 Fig. 511. 
 
 Imbricated covering of skin of Archego- 
 saurus medius, Goldf. ; 
 magnified.* 
 
402 
 
 FOOTPRINTS OF 
 
 [CH. XXV. 
 
 point, on which doubts had been entertained both in Europe and the 
 United States. The footmarks 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 accompany drawing (fig. 512.). It dis- 
 
 Fig. 512. 
 
 Scale one-sixth the original. 
 
 Slab of sandstone from the coal-measures of Pennsylvania, with footprints of 
 air-breathing reptile and casts of cracks. 
 
 plays, together with footprints, the casts of cracks (, a') of various 
 sizes. The origin of such cracks in clay, and casts of the same, has 
 before been explained, and referred to the drying and shrinking of 
 mud, and the subsequent pouring of sand into open crevices. It will 
 be seen that some of the cracks, as at , c, traverse the footprints, 
 and produce distortion in them, as might have been expected, 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 indentations. 
 
 No less than twenty-three footsteps were observed by Dr. King in 
 
CH. XXV.] AIR-BREATHING REPTILES. 403 
 
 the same quarry before it was abandoned, the greater part of them 
 so arranged (see fig. 513.) on the surface of one stratum as to imply 
 
 Fig. 513. 
 
 Series of reptilian footprints in the coal-strata of "Westmoreland 
 
 County, Pennsylvania. 
 
 a, Mark of nail ? 
 
 that they were made successively by the same animal. Everywhere 
 there was a double row of tracks, and in each row they occur in 
 pairs, each pair consisting of a hind and fore foot, and each being at 
 nearly equal distances from the next pair. In each parallel row the 
 toes turn the one set to the right, the other to the left. In the 
 European Cheirotherium, before mentioned (p. 339.), both the hind 
 
 D D 2 
 
404 FOOTPRINTS OF REPTILIANS. [Cn. XXV. 
 
 and the fore feet have each five toes, and the size of the hind foot is 
 about five times as large as the fore foot. In the American fossil 
 the posterior footprint is not even twice as large as the anterior, 
 and the number of toes is unequal, being five in the hinder and four 
 in the anterior foot. In this, as in the European Cheirotherium, one 
 toe stands out like a thumb, and these thumb-like toes turn the one 
 set to the right, and the other to the left. The American Cheiro- 
 therium was evidently a broader animal, and belonged to a distinct 
 genus from that of the triassic age in Europe.* 
 
 We may assume that the reptile which left these prints on the 
 ancient sands of the coal-measures was an air-breather, because its 
 weight would not have been sufficient under water 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 exposed to the air and sun, so as to have dried and 
 shrunk. 
 
 The geological position of the sandstone of Greensburg is perfectly 
 clear, being situated in the midst of the Appalachian coal-field, 
 having the main bed of coal, called the Pittsburg seam, above men- 
 tioned (p. 396.), 3 yards thick, 100 feet above it, and worked in the 
 neighbourhood, with several other seams of coal at lower levels. 
 The impressions of Lepidodendron, Sigillaria, Stigmaria, and other 
 characteristic carboniferous plants are found both above and below 
 the level of the reptilian footsteps. 
 
 Analogous footprints of a large reptile of still older date were 
 afterwards found (1849) at Pottsville, 70 miles N.E. of Philadelphia, 
 by Mr. Isaac Lea, in a formation of red shales, called No. XL by 
 Prof. H. D. Rogers, in the State Survey of Pennsylvania, and re- 
 ferred by him to the base of the coal, but regarded by some geolo- 
 gists as the uppermost part of the Old Red Sandstone. A thickness 
 of 1700 feet of strata intervenes between the footprints of Green s- 
 burg, before described, and these older Pottsville impressions. In 
 the same Red Shale, No. XL, the " debateable ground " between 
 the Carboniferous and Devonian group, Prof. H. D. Rogers an- 
 nounced in 1851 that he had discovered other footprints, referred 
 by him to three species of quadrupeds, all of them five-toed and in 
 double rows, with an opposite symmetry, as if made by right and 
 left feet, while they likewise display the alternation of fore foot and 
 hind foot. One species, the largest of the three, presents a diameter 
 for each footprint of about two inches, and shows the fore and hind 
 feet to be nearly equal in dimensions. It exhibits a length of stride 
 of about nine inches, and a breadth between the right and left foot- 
 steps of nearly four inches. The impressions of the hind feet are but 
 little in the rear of the fore feet. The animal which made them is 
 supposed to have been allied to a Saurian, rather than to a Batra- 
 chian or Chelonian. With these footmarks were seen shrinkage 
 cracks, such as are caused by the sun's heat in mud, and rain-spots, 
 with the signs of the trickling of water on a wet, sandy beach ; all 
 * See Lyell's Second Visit, &c., vol. ii. p. 305. 
 
CH. XXV.] AIR-BREATHERS IN THE COAL. 405 
 
 confirming the conclusion derived from the footprints, that the 
 quadrupeds belonged to air-breathers, and not to aquatic races. 
 
 In 1852 the first osseous remains cf a reptile were obtained from 
 the coal-measures of America by Mr. Dawson and myself. We de- 
 tected them in the interior of one of the erect Sigillarise before al- 
 luded to as of such frequent occurrence in Nova Scotia. The tree 
 was about two feet in diameter, and consisted, as usual, of an ex- 
 ternal cylinder of bark, converted into coal, and an internal stony 
 axis of black sandstone, or rather mud and sand stained black by 
 carbonaceous matter, and cemented together with fragments of wood 
 into a rock. These fragments 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 vertebras of a reptile, probably 
 about 2J feet in length (Dendrerpeton Acadianum, Owen), were 
 scattered through this stony matrix. The shell also of a Pupa, the 
 first pulmoniferous mollusk ever met with in the coal, was observed 
 in the same stony mass. Dr. Wyman of Boston pronounced the 
 reptile to be allied in structure to Menobranchus and Menopoma, 
 species of batrachians, now inhabiting the North American rivers. 
 The same view was afterwards confirmed by Prof. Owen, who also 
 pointed out the resemblance of the cranial plates to those seen in the 
 skull of 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 what- 
 ever other manner it entered, must be matter of conjecture. 
 
 Footprints of two reptiles of different sizes had previously been 
 observed by Dr. Harding and Dr. Gesner on ripple-marked flags of 
 the lower coal-measures in Nova Scotia, evidently made by quad- 
 rupeds walking on the ancient beach, or out of the water, just as the 
 recent Menopoma is sometimes observed to do. 
 
 In 1853 Prof. Owen announced the first discovery of fossil rep- 
 tilian remains in the British Coal-Measures ; and, in 1854, the same 
 osteologist described a " sauroid batrachian," of the Labyrinthodon 
 family, obtained by Mr. Dawson, from the coal of Pictou in Nova 
 Scotia. 
 
 Thus in ten years (between 1844 and 1854) the skeletons or bones 
 of no less than seven carboniferous reptiles, referred to five genera, 
 were brought to light ; to say nothing of numerous reptilian foot- 
 prints, some of them too large to belong to the same species as the 
 bones. 
 
 Rarity of vertebrate and invertebrate Air-breathers in Coal. 
 
 Before the earliest date above mentioned (1844) it was common to 
 hear geologists insisting on the non-existence of vertebrate animals 
 of a higher grade than fishes in the Coal, or in any rocks older than 
 the Permian. Even now, it may be said, that we have scarcely 
 made any progress in obtaining a knowledge of the terrestrial fauna 
 
 * GeoL Quart. Journ. vol. ix. p. 58. 
 D D 3 
 
406 AIR-BREATHERS IN THE COAL. [Cn. XXV. 
 
 of the coal, since the reptiles above enumerated seem to have been 
 all amphibious. Negative evidence should have its due weight in 
 paleontological reasonings and speculations, but we are as yet quite 
 unable to appreciate its value. In the United States, about 5 mil- 
 lions of tons of native coal are annually extracted from the coal- 
 measures, yet no fossil insect has yet been met with in the carboni- 
 ferous rocks of North America. Ought we then to conclude that at 
 the period of the coal insects were unrepresented in the forests of 
 the Western World ? In like manner, no land-shell, no Helix, Bu- 
 limus, Pupa, or Clausilia, nor any aquatic pulmoniferous mollusk, 
 such as Limneus or Planorbis, is recorded to have come from the 
 coal of Europe, worked for centuries before America was discovered, 
 and now quarried on so enormous a scale. Can we infer that land- 
 shells were not called into existence in European latitudes, until 
 after the carboniferous period ? 
 
 The theory of progressive development would account readily for 
 the absence of Chelonian and Saurian reptiles, or of Birds and Mam- 
 mals, from the Coal-Measures, because the condition of the planet is 
 supposed to have been too immature and unsettled to permit creatures 
 enjoying a higher development than batrachians to find a fit domicile 
 therein. But this same theory leaves the scarcity of the inverte- 
 brata, or the entire absence of many important classes of them, wholly 
 unexplained. When we generalize on this subject, we must not 
 forget that the eighteen or twenty individual insects and land-shells 
 met with in the coal (and most of these very recently found), are 
 scarcely double the number of the carboniferous reptiles which have 
 been established within the last ten years on the evidence of bones 
 and footprints. Yet our opportunities of examining strata formed 
 in close connection with ancient land exceed in this case all that we 
 enjoy in regard to any other formations, whether primary, secondary, 
 or tertiary. We have ransacked hundreds of soils replete with the 
 fossil roots of trees, have dug out hundreds of erect trunks and 
 stumps, which stood in the position in which they grew, have 
 broken up myriads of cubic feet of fuel still retaining its vegetable 
 structure, and, after all, we continue almost as much in the dark 
 respecting the invertebrate air-breathers of this epoch, as if the 
 Coal had been thrown down in mid-ocean. The age of the planet, 
 or its unprepared state to serve as a dwelling place for organized 
 beings, cannot explain the enigma, because we know that while the 
 land supported a luxuriant vegetation, the contemporaneous seas 
 swarmed with life with Articulata, Mollusca, Radiata, and Fishes. 
 We must, therefore, collect more facts, if we expect to solve a pro- 
 blem, which, in the present state of science, cannot but excite our 
 wonder ; and we must remember how much the conditions of this 
 problem have varied within the last ten years. Meanwhile let us be 
 content to impute the scantiness of our data chiefly to our want of 
 skill as collectors and interpreters, but partly also to our ignorance 
 of the laws which govern the fossilization of land-animals, whether 
 of high or low degree. 
 
CH. XXV.] 
 
 MOUNTAIN LIMESTONE. 
 
 407 
 
 CARBONIFEROUS OR MOUNTAIN LIMESTONE. 
 
 It has been already stated (p. 362.), that this formation underlies 
 the Coal-Measures in the South of England and Wales, whereas in 
 the North and in Scotland marine limestones alternate with Coal- 
 Measures, or with shales and sandstones, sometimes containing seams 
 of Coal. In its most calcareous form the Mountain Limestone is 
 destitute of land-plants, and is loaded with marine remains, the 
 greater part indeed of the rock being made up bodily of corals and 
 crinoids. 
 
 The Corals deserve especial notice, as the cup-shaped kinds, which 
 have the most massive and stony skeletons, display peculiarities of 
 structure by which they may be distinguished, as MM. Milne 
 Edwards and Haime first pointed out, from all species found in 
 strata newer than the Permian. There is, in short, an ancient or 
 Paleozoic, and a modern or Neozoic type, if, by the latter term, we 
 designate (as proposed by Prof. E. Forbes) all strata from the tri- 
 assic to the most modern, inclusive. The accompanying diagrams 
 (figs. 514, 515.) may illustrate these types ; and, although it may not 
 
 Fig. 514. 
 
 Paleozoic type of lamelliferous cup-shaped Coral. Order ZOANTHARIA ROGOSA, Milne Edwards 
 
 and Jules Haime. 
 
 a. Vertical section of Campopliyllum flexvos-um (Cyatho- 
 phyllum, Goldfuss) ; nat. size : from the Devonian of 
 the Eifel. The lamellce are seen around the inside of the 
 cup ; the walls consist of cellular tissue ; and large 
 transverse plates, called tabulae, divide the interior into 
 chambers. 
 
 5. Arrangement of the lamellce in Polycoelia ptofunda, Germar, 
 sp. ; nat. size : from the Magnesian Limestone, Durham. 
 This diagram shows the quadripartite arrangement of the 
 lamellae characteristic of paleozoic corals, there being 4 
 principal and 8 intermediate lamellae, the whole number 
 in this type being always a multiple of four. 
 
 c. Stauria astrteceformis, Milne Edwards. Young group, nat. 
 size. Upper Silurian, Gothland. The lamellae in each 
 cup are divided by 4 prominent ridges into 4 groups. 
 
 Fig. 515. 
 
 Nemoie type of lamelliferous cup-shaped Coral. Order ZOANTHARIA APOROSA, M. Edwards and 
 
 J. Haime. 
 
 a, Parasmilia centralis, Mantell, sp. Vertical section, nat. size. 
 
 and extend to the 
 
 transverse plates like those in fig. 514. a. 
 
 Upper Chalk, Gravesend. In this type the lamella are massive, 
 and extend to the axis of loose cellular tissue, without any 
 
 b Cvathina Boverbankn, Edwards and Haime. Transverse section, 
 enlarged. Gault, Folkstone. In this coral the lamellce are a 
 multiple of six. The twelve principal plates reach the central 
 axis or columella, and between each pair there are three se- 
 condary plates, in all forty-eight. The short intermediate plates 
 which proceed from the columella are not counted. They are 
 
 c Pwitia'vatcUarit, Lamk. Recent : very young state. Diagram 
 of its six principal and six intermediate septa, magnified. The 
 sextuple arrangement is always more manifest in the young 
 than in the adult state. 
 
 always be easy for any but a practised naturalist to recognise the 
 points of structure here described, every geologist should understand 
 them, as the reality of the distinction is of no small theoretical 
 interest. 
 
 DD 4 
 
408 
 
 FOSSILS OF THE 
 
 [Cn. XXV. 
 
 It will be seen, that the more ancient corals have what is called a 
 quadripartite arrangement of the stony plates or lamella, parts of 
 the skeleton which support the organs of reproduction. The number 
 of these lamellae in the paleozoic type is 4, 8. 16, &c. ; while in the 
 newer type the number is always 6, 12, 24, or some other multiple 
 of six ; and this holds good, whether they be simple cup-like forms, 
 as in figs. 514. a and 515. a, or aggregate clusters of cups as in 
 514. c. 
 
 It is not enough, therefore, to say that the primary or more an- 
 cient corals are all generically and specifically dissimilar from the 
 secondary, tertiary, and living corals, for, more than this, they 
 belong to distinct Orders, although often so like in outward form 
 as to have been referred in many cases to living reef-building genera. 
 Hence we must not too confidently draw conclusions from the 
 modern to the paleozoic polyps, respecting climate and the temper- 
 ature of the waters of the primeval seas, inasmuch as the two groups 
 of zoophytes are constructed on essentially different types. When 
 the great number of the paleozoic and neozoic species is taken into 
 account, it is truly wonderful to find how constant the rule above 
 explained holds good ; only one exception having as yet occurred of 
 a quadripartite coral in a neozoic formation (the cretaceous), and one 
 only of the sextuple class (a Fungia ?) in paleozoic (Silurian) rocks. 
 
 From a great number of lamelliferous corals met with in the Moun- 
 tain Limestone, two species have been selected, as having a very 
 
 Fig. 516. 
 
 Fig. 517. 
 
 Lithostrolinn basalt/forme, Phil. sp. (Lf- 
 ihostrotion itrfatum, Fleming ; Astrcea 
 basalt>f<>rtnts, Conyb. and Phill.) Ken- 
 dal ; Ireland ; Russia; Iowa, and west- 
 ward of the Mississippi, United States. 
 (D.D. Owen.) 
 
 Lonsdaleia floriformis (Martin, sp.) 
 M. Edwards. (Lithostrotionflorijorme, 
 Fleming. Strombodes.) 
 
 a. Young specimen, with buds on the 
 disk. 
 
 b. Part of a full-grown compound mass. 
 
 Bristol, &c. ; Russia. 
 
 wide range, extending from the eastern borders of Russia to the 
 British Isles, and being found almost everywhere in each country. 
 
 These fossils, together with numerous species of Zaphrentis, Am- 
 plexus, Ci/athophyllum, Clisiophyllum, Syringopora, smdMichelinea*, 
 
 For figures of these corals see Paleontographical Society's Monographs, 1852. 
 
CH. XXV.] MOUNTAIN LIMESTONE. 409 
 
 form a group widely different from any that preceded or followed 
 them. 
 
 Of the Bryozoa, the prevailing forms are Fenestella and Poly- 
 pora, and these often form considerable beds. Their net-like fronds 
 are easily recognised. 
 
 Crinoidea are also numerous in the Mountain Limestone. (See figs. 
 518, 519.) 
 
 Fig. 518. Fig. 519. 
 
 Cyathocrinites planun, 
 Miller. Body and 
 arms. Mountain 
 Limestone. 
 
 Cyatiiocrinus caryocrinoitfes, M' Coy. 
 
 a. Surface of one of the joints of the stem. 
 
 b. Pelvis or body ; called also calyx or cup. 
 
 c. One of the pelvic plates. 
 
 In the greater part of them, the cup or pelvis, fig. 519. b, is 
 greatly developed in size in proportion to the arms, although this is 
 not the case in fig. 518. The genera Poteriocrinus, Cyathocrinus, 
 Pcntremites, Actinocrinus, and Platycrimis are all of them charac- 
 teristic of this formation. Other Echinoderms are rare, a few Sea- 
 Urchins 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 Palcechinus (fig. 520.), is 
 the analogue of the modern Echinus. The other, Archceocidaris, 
 represents, in like manner, the Cidaris of the present seas. 
 
 Of Mollusca the Brachiopoda (or Palliobranchiates) constitute the 
 larger part, and are not only numerous, but often of large size. 
 Perhaps the most characteristic shells of the formation are large 
 species of Productus, such as P. giganteus, P. hemisphcericus, P semi- 
 reticulatus (fig. 521.), and P. scabriculus. Large plaited spirifers, as 
 
 Fig. 521. 
 
 Fig. 520. 
 
 Palarchinut gfgas, M'Coy. Reduced. 
 Mountain Limestone : 
 Ireland. 
 
 Productus semireticulatus, Martin, sp. 
 (P. antiqnatus, Sow.) Mountain 
 Limestone. Kugland; Russia: the 
 Andes, &c. 
 
410 
 
 FOSSILS OF THE 
 
 [Cn. XXV. 
 
 Spirifer striatus, S. rotundatus, and S. trigonalis (fig. 522.), also 
 abound ; and smooth species, such as Spirifer glaber (fig. 523.) with 
 
 its numerous varieties. 
 
 Fig. 522. 
 
 Fig. 523. 
 
 Spirijer trigonalis, Martin, sp. 
 Mountain Limestone : Derbyshire, &c. 
 
 Spirifer glaber, Martin, sp. 
 Mountain Limestone. 
 
 Among the palliobranchiate mollusks Terebratula hastata deserves 
 mention, not only for its wide range, but because it often retains the 
 pattern of the original coloured stripes which ornamented the living 
 shell. (See fig. 524.) These coloured bands are also preserved in 
 several lamellibranchiate bivalves, as in Aviculopecten (fig. 525.), in 
 which dark stripes alternate with a light ground. In some also of 
 the spiral univalves, the pattern of the original painting is distinctly 
 retained, as in the Pleurotomaria (fig. 526.), which displays wavy 
 blotches, resembling the colouring in many recent Trochidse. 
 
 Fig. 524. 
 
 Fig. 525. 
 
 Fig. 526. 
 
 Terebratula kastata, 
 Sow.,with radiating 
 bands of colour. 
 Mountain Lime- 
 stone. Derbyshire; 
 Ireland; Russia, &c. 
 
 Aviculopecten sublobatus, 
 Phill. Mountain Lime- 
 stone. Derbyshire ; 
 Yorkshire. 
 
 Pleurotomaria carinala. Sow. 
 
 (P. flammigera, Phill.) 
 Mountain Limestone. Derby- 
 shire, &c. 
 
 The mere fact that shells of such high antiquity should have 
 preserved the patterns of their colouring is striking and unex- 
 pected ; but Prof. E. Forbes has deduced from it an important geo- 
 logical conclusion. He infers that the depth of the primeval seas 
 in which the Mountain Limestone was formed did not exceed 50 
 fathoms. To this opinion he is led by observing that in the existing 
 seas the testacea which have colours and well defined patterns rarely 
 inhabit greater depths than 50 fathoms ; and the greater number 
 are found where there is most light in very shallow water, not more 
 than two fathoms deep. There are even examples in the British seas 
 of testacea which are always white or colourless when taken from 
 below 100 fathoms ; and yet individuals of the same species, if taken 
 from shallower zones, are vividly striped or banded. 
 
Cn. XXV.] 
 
 MOUNTAIN LIMESTONE. 
 
 411 
 
 This information, derived from the colour of the shells, is the 
 more welcome, because the Eadiata, Articulata, and Mollusca of the 
 Carboniferous period belong almost entirely to genera no longer 
 found in the living creation, and respecting the habits of which we 
 can only hazard conjectures. 
 
 Some few of the carboniferous mollusca, such as Aviculct, Nucula, 
 Solemya, and Lithodomus, belong no doubt to existing genera ; but 
 the majority, though often referred to living types, such as Isocardia, 
 Turritella^ and Buccinum, belong really to forms which appear to 
 have become extinct at the close of the paleozoic epoch. Euom- 
 phalus is a characteristic univalve shell of this period. In the 
 interior it is often divided into chambers (fig. 527. d\ the septa or 
 
 Fig. 527. 
 
 Fig. 528. 
 
 Euomphaltu pentagulattts, Sowerby. Mountain Limestone. 
 a. Upper side ; b. lower, or umbilical side ; c. view showing mouth, which 
 is less pentagonal in older individuals ; d. view of polished section, showing 
 internal chambers. 
 
 partitions not being perforated as in foraininiferous shells, or in those 
 having siphuncles, like the Nautilus. The animal appears to have 
 retreated at different periods of its growth from the internal cavity 
 previously formed, and to have closed all com- 
 munication 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 Turritella communis partitions off in 
 like manner as it advances in age a part of its 
 spire, forming a shelly septum. 
 
 Nearly 20 species of the genus Bellerophon 
 (see fig. 528.), a shell without chambers like the 
 in Sestone S w ' livin S Argonaut, occur in the Mountain Lime- 
 stone. The genus is not met with in strata of 
 later date. It is most generally regarded as belonging to the 
 
412 
 
 FOSSILS OF MOUNTAIN LIMESTONE. [Cn. XXV. 
 
 Heteropoda, and allied to the Glass-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 repre- 
 sentatives of the same order ; yet they offer some remarkable forms 
 scarcely known in strata newer than the coal. Among these is 
 Orthoceras, a siphuncled and chambered shell, like a Nautilus un- 
 coiled and straightened (fig. 529.). Some species of this genus are 
 
 Fig. 529. 
 
 Portion of Orthoceras laterale, Phillips. Mountain Limestone. 
 
 
 
 several feet long. The Goniatite is another genus, nearly allied to 
 the Ammonite^ from which it differs in having the lobes of the septa 
 free from lateral denticulations, or crenatures ; so that the outline of 
 these is continuous and uninterrupted. 
 
 The species represented in fig. 530. is found in almost all localities, 
 and presents the zigzag character of the septal lobes in perfection. 
 
 In another species (fig. 531.), the septa are but slightly waved, 
 and so approach nearer to the form of those of the Nautilus. The 
 
 Fig. 530. 
 
 Fig. 531. 
 
 Goniatites crenistria, Phill. Mountain 
 Limestone. N. America ; Britain ; 
 Germany, &c. 
 o. Lateral view. 
 b. Front view, showing the mouth. 
 
 Goniatites evolulus, Phillips. 
 
 Mountain Limestone. 
 
 Yorkshire. 
 
 dorsal position of the siphuncle, however, clearly distinguishes the 
 Goniatite from the Nautilus, and proves it to have belonged to the 
 family of the Ammonites, from which, indeed, some authors do not 
 believe it to be generically distinct. 
 
 Fossil fish. The distribution of these is singularly partial ; so 
 much so, that M. de Koninck of Liege, the eminent paleontologist, 
 once stated to me that, in making his extensive 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 rarity in the carboniferous seas ; whereas the in- 
 vestigation of other countries has led to quite a different result. 
 
CH. XXV.] LOWER CARBONIFEROUS STRATA. 413 
 
 Thus, near Clifton, on the Avon, there is a celebrated " bone-bed," 
 almost entirely made up of ichthyolites ; and the same may be said 
 of the "fish-beds" of Armagh, in Ireland. They consist 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 Cladodus affords 
 an illustration ; but the majority, as in Psammodus and Cochliodus, 
 are, like the teeth of the Cestracion of Port Jackson (see above, 
 fig. 288., p. 250.), massive palatal teeth fitted for grinding. (See figs. 
 532, 533.) 
 
 Fig. 532. Fig. 533. 
 
 Psammodus porosus, Agas. Bone -bed, Mountain Cochliodus contortus, Agas. Bone-bed, 
 
 Limestone. Bristol; Armagh. Mountain Limestone. Bristol ; Ar- 
 
 magh. 
 
 There are upwards of 70 other species of fish-remains 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 are often of a very large size. Ganoid 
 fish, such as Holoptychius, also occur ; but these are far less nume- 
 rous. The great Megalichthys Hibberti appears to range from the 
 Upper Coal-measures to the lowest Carboniferous strata. 
 
 Foraminifera. This somewhat important group of the lower 
 animals, which is represented so fully at later epochs by the Num- 
 mulites and their numerous minute allies, appears in the Mountain 
 Limestone to be restricted to a very few species, the individuals, how- 
 ever, of which are vastly numerous. Textularia, Nodosaria, En- 
 Fig. 534. dothyra, and Fusulina (fig. 534.), have been re- 
 cognised. The first two genera are common to this 
 and all the after periods ; the third has already 
 cyiindrica, appeared in the Upper Silurian, but is not known 
 Magnified s diam. above the Carboniferous ; the fourth (fig. 534.) is 
 Mountain Limestone, peculiar to the Mountain Limestone, and is charac- 
 teristic of the formation in the United States, Russia, and Asia Minor. 
 
 STRATA CONTEMPORANEOUS WITH THE MOUNTAIN LIMESTONE. 
 
 In countries where limestone does not form the principal part 
 of the Lower Carboniferous series, this formation assumes a very 
 different character, as in the Rhenish Provinces of Prussia, and in 
 the Hartz. The slates and sandstones called Kiesel-schiefer and 
 Younger Greywacke (Jungere grauwacke) by the Germans, were 
 
414 CARBONIFEROUS LIMESTONE OF N. AMERICA. [Cn. XXV. 
 
 ormerly referred to the Devonian group, but are now ascertained to 
 belong to the " Lower Carboniferous." The prevailing shell which 
 characterizes the carbonaceous schists of this series, both on the 
 Continent and in England, is Posidonomya Becheri (fig. 535.). Some 
 Fi 533 well-known mountain-limestone spe- 
 
 cies, such as Goniatites crenistria 
 (see fig. 530.) and G. reticulatus, also 
 occur in the Hartz. In the associated 
 sandstones of the same region, fossil 
 plants, such as Lepidodendron and 
 the allied genus Saginaria, are com- 
 mon ; also Knorria, Calamites Suck- 
 
 Posidonomya Becheri, Gold. _ an J (^ frfinnifinni? f^nnn nmp 
 
 Lower Carboniferous. OVU > anCL ^' WanSlllOniS IjOpp., SOI 
 
 peculiar, others specifically identical 
 
 with ordinary coal-measure fossils. The true geological position of 
 these rocks in the Hartz was first determined by MM. Murchison 
 and Sedgwick in 1840.* 
 
 CARBONIFEROUS LIMESTONE IN NORTH AMERICA. 
 
 The coal-measures of Nova Scotia have been described (p. 379.). 
 The lower division contains, besides large stratified masses of gypsum, 
 some bands of marine limestone almost entirely made up of encri- 
 nites, and, in some places, containing shells of genera common to 
 the mountain limestone of Europe. 
 
 In the United States the carboniferous limestone underlies the 
 productive coal-measures ; and, although very inconspicuous on the 
 margin of the Alleghany or Great Appalachian coal-field in Penn- 
 sylvania, it expands in Virginia and Tenessee. Its still greater 
 extent and importance in the Western or Mississippi coal-fields, in 
 Kentucky, Indiana, Iowa, Missouri, and other western states, has 
 been well shown by Dr. D. D. Owen. In those regions f it is about 
 400 feet thick, and abounds, as in Europe, in shells of the genera 
 Productus and Spirifer, with Pentremites and other crinoids and 
 corals. Among the latter, Lithostrotion basaltiforme or striatum 
 (fig. 516. p. 408.), or a closely-allied species, is common. 
 
 * Trans. Geol. Soc. London, 2nd f Owen's Geol. Survey of Wisconsin, 
 series, vol. vi. p. 228. &c. 1852. 
 
Cu. XXVI.] OLD RED SANDSTONE. 415 
 
 CHAPTER XXVI. 
 
 OLD EED SANDSTONE, OR DEVONIAN GROUP. 
 
 Old Red Sandstone of the Borders of Wales Of Scotland and the South of Ireland 
 Fossil reptile and foot-tracks at Elgin Fossil Devonian plants at Kilkenny 
 Ichthyolites of Clashbinnie Fossil fish, crustaceans, &c., of Caithness and 
 Forfarshire Distinct lithological type of Old Red in Devon and Cornwall 
 Term Devonian Organic remains of intermediate character between those of 
 the Carboniferous and Silurian systems Devonian series of England and the 
 Continent Upper Devonian rocks and fossils Middle Lower Old Red 
 Sandstone of Russia Devonian Strata of the United States Coral-reefs at 
 the Falls of the Ohio. 
 
 IT has been already shown in the section (p. 334.), that the car- 
 boniferous strata are surmounted by a system called "The New 
 Red," and underlaid by another termed the " Old Red Sandstone." The 
 last-mentioned group acquired this name because in Herefordshire 
 and Scotland, where it was originally studied, it consisted chiefly of 
 red sandstone, shale, and conglomerate. It was afterwards termed 
 " Devonian," for reasons which will be explained in the sequel. For 
 many years it was regarded as very barren of organic remains ; and 
 such is undoubtedly its character over very wide areas where cal- 
 careous matter is wanting, and where its colour is determined by 
 the red oxide of iron. 
 
 " Old Red" in Herefordshire, &c. In Herefordshire, Worcester- 
 shire, Shropshire, and South Wales, this formation attains a great 
 thickness, sometimes between 8,000 and 10,000 feet. In these regions, 
 it has been subdivided into 
 
 1st. Conglomerate, passing downwards into chocolate-red and 
 green sandstone and marl. 
 
 2nd. Marl and cornstone, red and green argillaceous spotted 
 marls, with irregular courses of impure concretionary limestone, 
 provincially called Cornstone, and some beds of white sandstone. In 
 the cornstones, and in those flagstones and marls through which 
 calcareous matter is most diffused, some remains of fishes of the 
 genera Onchus and Cephalaspis occur. Several specimens of the 
 latter have been traced to the lowest beds of the " Old Red," in 
 May Hill, in Gloucestershire, by Sir R. Murchison and Mr. Strick- 
 land.* 
 
 Old Red Sandstone of Scotland and Ireland. South of the 
 Grampians, in Forfarshire, Kincardineshire, and Fife, the Old Red 
 Sandstone may be divided into three groups. 
 
 * Murchison's Siluria, p. 245. 
 
Fig. 536. 
 
 416 FOSSIL REPTILE OF OLD RED SANDSTONE. [Cn. XXVI. 
 
 A. Yellow sandstone, with some bands of white sandstone. 
 
 B. Red shale, sandstone with cornstone, and at the base a con- 
 
 glomerate (Nos. 1,2, & 3. Section, p. 48.). 
 
 C. Roofing and paving stone, highly micaceous, and containing a 
 
 slight admixture of carbonate of lime (No. 4., p. 48.). 
 The upper member, or yellow sandstone, A, is seen at Dura Den, 
 near Cupar, in Fife, immediately underlying the coal. It consists of 
 a yellow sandstone in which fish of the genera Pterichthys (for genus 
 see fig. 550.), Pamphractus, Glyptopomus, Holoptychius, and others 
 abound. 
 
 On the south side of the Moray Firth, near Elgin, certain yellow 
 and white sandstones were classed long since by Professor Sedgwick 
 and Sir R. Murchison as the uppermost beds of the " Old Red ; " and 
 they are generally regarded as the equivalent of the Yellow Sand- 
 stone of Fife above alluded to. They contain large rhomboidal 
 scales of a fish called by Agassiz Stagonolepis Robertsoni, and re- 
 ferred by him to the Dipterian family. This family, observes Mr. 
 
 Hugh Miller, is emphatically charac- 
 teristic of the Old Red Sandstone. 
 The scales of this Stagonolepis, the 
 only parts of the species yet known, 
 are so like those of Glyptopomus in 
 form and pattern that they may pos- 
 sibly prove to be referable to the 
 same genus. The Glyptopomus, as 
 we have seen, is found in the yellow 
 sandstone of Dura Den in Fife, and 
 the genus has not hitherto been met 
 with in any formation except the 
 Devonian. 
 
 The light-coloured sandstone of 
 Morayshire passes down into a con- 
 formable series of strata, which are 
 full of undoubted " Old Red" fossils. 
 I have dwelt thus particularly on the 
 age of this rock, because it has yielded 
 recently (1851) the bones of a reptile, 
 the first and only memorials of that 
 class yet discovered in a stratum of 
 such high antiquity. This fossil was 
 obtained by Mr. Patrick Duff, author 
 of a " Sketch of the Geology of 
 Morayshire," from a quarry at Cum- 
 mingstone, near Elgin. The skeleton 
 represented in the annexed figure 
 (fig. 536.), is 41 inches in length, but 
 part of the tail is concealed in the 
 rock ; and, if the whole were visible, 
 it might be more than 6 inches long. 
 
 Telerpeton Elginense. ( Mnntell . ) 
 Natural size. 
 
 Reptile in the Old Red Sandstone, from 
 near Elgin, Morayshire. 
 
FOSSIL FOOTPKINTS OF "OLD RED." 417 
 
 The matrix is a fine-grained whitish sandstone, with a cement of 
 carbonate of lime. Although almost all the bones except those of 
 the skull have decomposed, their natural position can still be seen. 
 Nearly perfect casts of their form were taken by Dr. Mantell from 
 the hollow moulds which they have left in the rock. 
 
 Slight indications are visible of minute conical teeth. Of ribs there 
 are twenty-four pairs, very short and slender. The pelvis is placed 
 after the twenty-fourth vertebra, precisely as in the living Iguana. 
 On the whole, Dr. Mantell inferred that the animal possessed many 
 Lacertian characters blended with those of the Batrachians. He 
 was unable to decide whether it was a small terrestrial lizard, or a 
 freshwater Batrachian, resembling the Tritons and aquatic Sala- 
 manders. 
 
 Although this fossil is the most ancient quadruped of which any 
 osseous remains have yet been brought to light, it seems not to have 
 been the only one then existing in that region, for Captain Brick- 
 enden observed, in 1850, on a slab of sandstone from the same 
 quarry at Cummingstone, a continuous series of no less than thirty- 
 four footprints of a quadruped. A small part of this track, the course 
 of which is supposed to have been from A to B, is represented in the 
 annexed cut (fig. 537.). The footprints are in pairs, forming two 
 
 Fig. 537. 
 
 Scale one-sixth the original size. 
 
 Part of the trail of a (Chelonian ?) quadruped from the Old Red Sandstone of Cum- 
 mingstone, near Elgin, Morayshire. Captain Brlckenden. 
 
 parallel rows ; the hind foot being one inch in diameter and larger 
 than the fore foot in the proportion of 4 to 3. The stride must have 
 been about 4 inches. The impressions resemble those left by a 
 tortoise walking on sand ; and, if this be the true interpretation of 
 the trail, they are the only indications as yet known of a chelonian 
 more ancient than the trias. 
 
 I have already alluded (p. 404.) to trails referred by American 
 geologists to several species of air-breathing reptiles, and discovered 
 on the eastern flank of the Alleghany range, in Pennsylvania, in a 
 red shale, so ancient that a question has arisen whether the rock 
 should be classed as the lowest member of the carboniferous, as Pro- 
 fessor H. D. Rogers conceives, or as the uppermost Devonian, as some 
 have contended (see p. 404.). They at least demonstrate that certain 
 quadrupeds, of larger size than any of the bones that have been 
 
 E E 
 
418 
 
 FOSSILS OF THE 
 
 [Cn. XXVI. 
 
 foun in carboniferous rocks, existed at the time when the ancient 
 Red Shale, usually termed in the United States "infra-carboni- 
 ferous," was in the course of deposition. 
 
 In Ireland the upper beds of the Old Red, or yellow sandstone of 
 Kilkenny, contain fish of the genera Coccosteus and Dendrodus, 
 characteristic forms of this period, together with plants specifically 
 distinct from any known in the coal-measures, but referable to the 
 genera found in them ; as, for example, Lepidodendron and Cyclop- 
 teris (see figs. 538. and 539.). The stems of the latter have, in 
 some specimens, broad bases of attachment, and may therefore have 
 been tree-ferns. 
 
 Fig. 538. 
 
 Fig. 539. 
 
 Stem of Lepidodendron, so compressed as 
 to destroy the quincunx arrangement of 
 the scars. Upper Devonian, Kilkenny. 
 
 Cyclopteris Hibcrnica, Forbes. 
 Upper Devonian, Kilkenny. 
 
 Fig. 540. 
 
 In the same strata shells having the form of the genus Anodon, and 
 which probably belonged to freshwater testacea, occur. Some geo- 
 logists, it is true, still doubt whether these beds ought not rather to 
 be classed as the lowest beds of the carboniferous series, together 
 with the yellow sandstone of Mr. Griffiths (see p. 362.) ; but the as- 
 sociated ichthyolites and the distinct specific character of the plants, 
 seem to favour the opinion above expressed. 
 
 B. (Table, p. 416.) We come next to the middle division of the 
 " Old Red," as exhibited south of the Grampians, and consisting of 
 1st, red shale and sandstone, with some cornstone, occupying the 
 Valley of Strathmore, in its course from Stonehaven to the Firth of 
 
 Clyde ; and, 2ndly, of a conglome- 
 rate, seen both at the foot of the 
 Grampians, and on the flanks of 
 the Sidlaw Hills, as shown in the 
 section at p. 48., Nos. 1, 2, and 3 
 In the uppermost part of the divi- 
 sion No. 1., or in the beds which, 
 in Fife, underlie the yellow sand- 
 stone, the scales of a large ganoid 
 fish, of the genus Holoptychius, 
 were first observed by Dr. Fleming 
 at Clashbinnie, near Perth, and an 
 ^WSJPi! entire specimen, more than 2 feet 
 
 scale of Hoioptychms nobiiissimus, Agas. in length, was afterwards found by 
 
 Mr. Noble. Some of these scales 
 (see fig. 540.) measured 3 inches in length, and 2-J- in breadth. 
 
CH. XXVI.] 
 
 OLD RED SANDSTONE. 
 
 419 
 
 C. (Table, p. 416.) The third or lowest division south of the 
 Grampians consists of grey paving-stone and roofing-slate, with 
 associated red and grey shales ; these strata underlie a dense 
 mass of conglomerate. In these grey beds several remarkable fish 
 have been found of the genus named by Agassiz Cephalaspis, or 
 " buckler-headed," from the extraordinary shield which covers the 
 head (see fig. 541.), and which has often been mistaken for that of a 
 trilobite, such as Asaphus. 
 
 Fig. 541. 
 
 Cephalaspis Lyellii, Agass. Length Gf Inches. 
 
 From a specimen in my collection found at Glammiss, in Forfarshire ; see other figures, 
 Agassiz, vol. ii. tab. \.<t., and 1.6. 
 
 a. One of the peculiar scales with which the head is covered when perfect. These 
 
 scales are generally removed, as in the specimen above figured. 
 6, c. Scales from different parts of the body and tail. 
 
 In the same rock at Carmylie, in Forfarshire, commonly 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 quarry- 
 men the " Seraphim," from the wing-like form and feather-like or- 
 nament of the hinder part of the head, 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 true nature, and 
 
 Fig. 542. 
 
 Portions of the Pterygotus anglicus, Agassiz. 
 
 1. Middle portion of the " Seraphim " or back of the head, with the scale-like sculpturing. 
 
 2. Portion of the dilated base of one of the anterior feet, with its strong spines or teeth, 
 
 used as masticating organs. 
 
 3. The proximal portion of one of the great anterior claws. 
 
 4. Termination of the same, with the serrated pinpers. (See Agass. Poiss. Foss. du Vieux 
 
 Ore's Rouge, plate A.) 
 
 1 . and 2. are of the natural size ; 3. and 4. are reduced one half. 
 E E 2 
 
420 
 
 FOSSILS OF THE 
 
 [On. XXVI. 
 
 Fig. 543. 
 
 in the first plate of his " Poissons Fossiles du Vieux Gres Rouge," 
 he figured the portions on which he founded his opinion. 
 
 The carapace of this huge crustacean, which must have rivalled, 
 if not exceeded in size the largest crabs, is furnished at its hinder 
 part with short prongs, and has two large eyes near the middle, much 
 like those of the Eurypterus found in the coal formation of Glasgow. 
 The body consists of ten or eleven moveable rings (the exact 
 
 number is not ascertained), and was 
 terminated by an oval-pointed tail. 
 The whole surface is covered by the 
 scale-like markings before mentioned 
 as ornamenting the head. Prof. 
 M'Coy, to whom I owe these notes 
 on the general structure, has kindly 
 furnished me with a restoration of the 
 entire animal (fig. 543.), which he 
 believes to be closely allied to the 
 great Eurypterus before mentioned, 
 if not of the very same genus, and, 
 moreover, of the same family as the 
 living King-crab or Limulus. 
 
 Sir R. Murchison has expressed 
 some doubts * whether the grey beds 
 of Forfarshire, containing the Ptery- 
 gotus, may not be referable to the 
 Upper Silurian or Upper Ludlow 
 beds ; but, as they are associated at Balrudderie with numerous 
 specimens of Cephalaspis) the bony bucklers or head-pieces alone 
 being preserved), apparently belonging to two species, I think it 
 far more probable that they constitute a division of the " Old Red," 
 and perhaps not so ancient a one as the bituminous schists (6, p. 422.) 
 in the North of Scotland. 
 
 In the same grey paving-stones and coarse roofing slates in which 
 the Cephalaspis and Pterygotus occur, in Forfarshire and Kincar- 
 dineshire, the remains of grass-like plants abound in such numbers 
 as to be useful to the geologist by enabling him to identify corres- 
 ponding strata at distant points. Whether these be fucoids, as I 
 formerly conjectured, or freshwater plants of the family Fluviales, 
 as some botanists suggest, cannot yet be determined. They are 
 often accompanied by fossils, called " berries " by the quarrymen, 
 and which are not unlike the form which a compressed blackberry 
 or raspberry might assume (see figs. 544. and 545.). Some of these 
 were first observed in the year 1828, in grey sandstone of the same 
 age as that of Forfarshire, at Parkhill near Newburgh, in the north 
 of Fife, by Dr. Fleming. I afterwards found them on the north side 
 of Strathmore, in the vertical shale beneath the conglomerate, and 
 in the same beds in the Sidlaw Hills, at all the points where fig. 4. 
 is introduced in the section, p. 48. 
 
 * Siluria, p. 247. 
 
 Pterygotus problemalicus, Agassiz. 
 Restoration by Professor M'Coy. 
 
CH. XXVI.] OLD KED SANDSTONE. 
 
 Fig. 544. Fig. 545. 
 
 421 
 
 Parka decipiens, Fleming. 
 In sandstone of lower beds 
 
 of Old Red, Ley's Mill, 
 
 Forfarshire. 
 
 Parka decipiens, Fleming. 
 In shale of lower beds of Old Red, Fife. 
 
 Fig. 546. 
 
 Dr. Fleming has compared these fossils to the panicles of a Juncus, 
 or the catkins of Sparganium, or some allied plant, and he was con- 
 firmed in this opinion by finding a specimen at Balrudderie, showing 
 the under surface smoother than the upper, and displaying what may 
 be the place of attachment of a stalk. I have met with some speci- 
 mens in Forfarshire imbedded in sandstone, and not associated with 
 the leaves of plants (see fig. 544.), which bore a considerable resem- 
 blance to the spawn of a recent Natica (fig. 546.), in 
 which the eggs are arranged in a thin layer of sand, 
 and seem to have acquired a polygonal form by press- 
 ing against each other; but, as no gasteropodous 
 shells have been detected in the same formation, the 
 Parka has probably no connection with this class of 
 
 Fragment of spawn Organisms. 
 
 of British species The late Dr. Mantell was so much struck with the 
 
 of Natica. 
 
 resemblance of one of my specimens (see fig. 547.) to 
 a small bundle of the dried-up eggs of the common English frog, 
 which he had obtained in a black and carbonaceous state (see fig. 
 548.) from the mud of a pond near London, that he suggested a 
 
 Fig. 547. 
 
 Fig. 548. 
 
 Fossil. Old Red. 
 
 Recent. 
 
 Fig. 549. 
 
 Fip. 547. Slab of Old Red Sandstone,-) 
 Forfarshire, with bodies like the ova | ~ 
 of Batrachians. '2 
 
 a. Ova? in a carbonized state. I 
 
 b. Egg cells ?, the ova shed. J 
 Fig. 548. Eggs of the common frog,'] 
 
 Rana temporaria, in a . carbonized 
 state, from a dried-up pond in Clap- | ^ 
 ham Common. 
 
 a. The ova. 
 
 b. A transverse section of the mass [ rt 
 
 exhibiting the form of the egg-l 
 
 Fig. 549. Shale of Old Red Sandstone, or 
 Devonian, Forfarshire, with impression 
 of plants and eggs of Batrachians ? 
 
 a. Two pair of ova ? resembling those of 
 
 large Salamanders or Tritons on 
 the same leaf. 
 
 b. b. Detached ova ? 
 
 c. Egg-cells (?) of frogs or Ranina 
 
 E E 3 
 
422 OLD RED OF NORTH OP SCOTLAND. [Cn. XXVI. 
 
 batrachian origin for the fossil ; and Mr. Newport concurred in the 
 idea, adding that other larger and more circular fossils (fig. 549.), 
 which I procured from shale in the same "Old Red," occurring 
 singly or in pairs, and attached to the leaves of plants, might 
 possibly be the ova of some gigantic triton or salamander. 
 
 The general absence of reptilian remains from strata of the Devo- 
 nian period will weigh strongly with many geologists against such 
 conjectures. 
 
 " Old Red" in the North of Scotland. The whole of the northern 
 part of Scotland, from Cape Wrath to the southern flank of the 
 Grampians, has been well described by Mr. Hugh Miller as consist- 
 ing of a nucleus of granite, gneiss, and other hypogene rocks, which 
 seem as if set in a sandstone frame.* The beds of the Old Red 
 Sandstone constituting this frame may once perhaps have extended 
 continuously over the entire Grampians before the upheaval of that 
 mountain range ; for one band of the sandstone follows the course of 
 the Moray Frith far into the interior of the great Caledonian valley, 
 and detached hills and island-like patches occur in several parts of 
 the interior, capping some of the higher summits in Sutherlandshire, 
 and appearing in Morayshire like oases among the granite rocks of 
 Strathspey. On the western coast of Ross-shire, the Old Red forms 
 those three immense insulated hills before described (p. 67.), where 
 beds of horizontal sandstone, 3000 feet high, rest unconformably on 
 a base of gneiss, attesting the vast denudation which has taken place. 
 
 As the mineral character of the " Old Red" north of the Grampians 
 differs considerably from that of the south, especially in the middle 
 and lower divisions, I shall now allude to it separately. The upper 
 portion, consisting of light-coloured sandstones, and containing the 
 Telerpeton of Elgin, has been already classed, A., p. 416., as the 
 equivalent of the yellow sandstone of Fife. That upper member 
 passes downwards into red and variegated sandstone and conglome- 
 rate, which may correspond with the beds called B., in the same 
 section at p. 416. To the above succeeds, in the descending order, 
 " the middle formation" of Mr. Hugh Miller, composed of thin, fissile, 
 grey sandstone, in which, in Morayshire, Dr. Malcolmson found a spe- 
 cies of Cephalaspis ; but whether these beds are of the age of the 
 paving-stone of Arbroath (C., Table, p. 416.) is as yet uncertain. 
 
 Next below is the "inferior division" of Hugh Miller, com- 
 prising : - 
 
 a. Red and variegated sandstones. 
 
 b. Bituminous schists. 
 
 c. Coarse sandstone. 
 
 d. Great conglomerate. 
 
 In the schists 5, a great variety of fish are met with in the coun- 
 ties of Banff, Nairn, Moray, Cromarty, and Caithness, and also in 
 Orkney, belonging to the genera Pterichthys (fig. 550.), Coccosteus, 
 Diplopterus, Dipterus, Cheiracanthus, Asterolepis, and others de- 
 scribed by Agassiz. 
 
 * " Old Red Sandstone," 1841. 
 
CH. XXVI.] 
 
 TERM "DEVONIAN." 
 
 423 
 
 as restored 
 
 pper s 
 byH. 
 
 Miller." 
 
 Five species of Pterichthys have been found in this lowest di- 
 vision of the Old Red. The 
 wing-like appendages, whence 
 the genus is named, were first 
 supposed by Mr. Miller to be 
 paddles, like those of the 
 turtle ; but Agassiz regards 
 them as weapons of defence, 
 like the occipital spines of the 
 River Bull-head ( Coitus gobio, 
 Linn.) ; and considers the tail 
 to have been the only organ of 
 motion. The genera Dipterus 
 r acpd Diplopterus are so named, 
 because their two dorsal fins 
 are so placed as to front the 
 anal and ventral fins, so as to 
 appear like two pair of wings. 
 They have bony enamelled 
 scales. 
 
 The Asterolepis was a ganoid fish of gigantic dimensions. A. As- 
 musn, Eichwald, the species characteristic of the Old Red Sandstone 
 of Russia, as well as that of Scotland, attained the length of between 
 20 and 30 feet. It was clothed with strong bony armour, 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 character-! 
 The Asterolepis occurs also in the Devonian rocks of North America, 
 in the lower division of the Old Red. Coniferous wood, with struc- 
 ture showing medullary rays, has likewise been detected in the lower 
 division by Hugh Miller J, who has pointedly dwelt on the import- 
 ance of the fact, as the oldest example yet known of so highly or- 
 ganized a plant occurring in a rock of such antiquity. 
 
 South Devon and Cornwall. Term Devonian. A great step 
 was made in the classification of the slaty and calciferous strata of 
 South Devon and Cornwall in 1837, when a large portion of the 
 beds, previously referred to the "transition" or Silurian series, 
 were found to belong in reality to the period of the Old Red Sand- 
 stone. For this reform we are indebted to the labours of Professor 
 Sedgwick and Sir R. Murchison, assisted by a suggestion of Mr. 
 Lonsdale, who, in 1837, after examining the South Devonshire 
 fossils, perceived that some of them agreed with those of the Carbon- 
 iferous group, others with those of the Silurian, while many could 
 not be assigned to either system, the whole taken together exhibiting 
 a peculiar and intermediate character. But these paleontological 
 observations alone would not have enabled us to assign, with accu- 
 
 * Old Bed Sandstone. Plate 1. fig. 1. 
 Mr. Miller's description of the fish is 
 most graphic and correct. 
 
 f Footprints of the Creator, by Hugh 
 Miller. 
 
 J Footprints, p. 199. 
 
 E E 4 
 
424 DEVONIAN SERIES. [Cn.XXVI. 
 
 racy, the true place in the geological series of these slate-rocks and 
 limestones of South Devon, had not Messrs. Sedgwick and Murchison, 
 in 1836 and 1837, discovered that the culmiferous or anthracitic 
 shales of North Devon belonged to the Coal, and not, as preceding 
 observers had imagined, to the "transition" period. 
 
 As the strata of South Devon here alluded to are far richer in 
 organic remains than the red sandstones of contemporaneous date in 
 Herefordshire and Scotland, the new name of the " Devonian system " 
 was proposed as a substitute for that of Old Red Sandstone. 
 
 The link supplied by the whole assemblage of imbedded fossils, 
 connecting as it does the paleontology of the Silurian and Carbon- 
 iferous groups, is one of the highest interest, and equally striking 
 whether we regard the genera of the corals or of the shells. The 
 species are mostly distinct except in the upper group. 
 
 The rocks of this group in South Devon consist, in great part, of 
 green chloritic slates, alternating with hard quartzose slates and 
 sandstones. Here and there calcareous slates are interstratified with 
 blue crystalline limestone, and in some divisions conglomerates, 
 passing into red sandstone. But the whole series is much altered 
 and disturbed by the intrusion of the granite of Dartmoor and other 
 igneous rocks. 
 
 In North Devon, on the contrary, the Devonian group has been 
 less changed, and its relations to the overlying carboniferous rocks 
 or " Culm Measures " are clearly seen. The following sequence is 
 exhibited in the coast section on the Bristol Channel between 
 Barnstaple and the North Foreland.* 
 
 Devonian Series in North Devon. 
 
 f fa. Calcareous brown slates ; with fossils) many of them common to 
 .,. I 1. < the Carboniferous group. (Barnstaple, Pilton, &c.) 
 
 upper <j j^ Brown and yellow sandstone, with shells and land-plants Stig- 
 
 maria, Knorria, and others. (Baggy Point, Marwood, &c.) 
 '2. Hard grey and reddish sandstones and micaceous flags, without 
 fossils, resting on soft greenish schists of considerable thickness. 
 M . I (Morte Bay, Bull Point, &c.) 
 
 "* 3. Calcareous slates, with eight or nine courses of limestone, full of 
 corals and shells like those of the Plymouth limestone. (Combe 
 Martin, Hfracombe Harbour, &c.) 
 j 4. Hard, greenish, red, and purple sandstones : with occasional fossils, 
 J Spirifers, &c. (Linton, North Foreland, &c.) 
 
 .Lower -j 5 g oft c hioritous slates, with some sandstones; Orthis, Spirifer, and 
 some Corals. (Valley of Rocks, Lynmouth, &c.) 
 
 The successive beds of this section have been compared with 
 those of South Devon and Cornwall both by the authors of the 
 "Devonian" system and by other observers. And Prof. Sedgwick 
 has again lately brought them into closer comparison.^ Other 
 geologists at home and abroad have successively identified them 
 with the Devonian series in France, Belgium, the Rhenish Provinces, 
 
 * Sedgwick and Murchison, Trans. Cornwall, pi, 3. Murchison's Siluria, 
 Geol. Soc., New Series, vol. v. p. 644. p. 256. 
 
 De la Beche, Geol. Report, Devon and t Quart. Journ. Geol. Soc., vol. viii. 
 
 p. 1., etseq. 
 
OH. XXVI.] UPPER AND MIDDLE DEVONIAN. 425 
 
 Central Germany, and America.* I shall proceed first to treat of 
 the main divisions which have been established in Europe. 
 
 Upper Devonian Rocks. 
 
 The slates and sandstones of Barnstaple (No. 1. a, b. of the 
 preceding section) are represented in Cornwall by the limestones 
 and slates of Petherwyn, which rise in like manner from under the 
 
 Culm Measures, constituting the 
 Petherwyn group of Prof. Sedg- 
 wick. These beds contain the 
 very common Spirifer disjunctus, 
 Sow. ( S. Verneuilii, Murch.), (see 
 fig. 551.), a species distributed 
 over the whole of Europe,' and 
 
 Spirifer disjunct, Sw^v.Sp. Ferneuilti, ^^ even ^ ^^ Minor an( j 
 
 upper Devonian, Boulogne. China. Among many other fossils 
 
 the Clymenia linearis (fig. 552.) and the minute crustacean Cypri- 
 dina serrato-striata (fig. 553.) are so characteristic of these upper 
 
 Fig. 552. 
 
 IPX 
 
 Fig. 553. 
 
 t 
 
 Cypridina serrato-striata, Sandberger. 
 Weilburg, &c.; Nassau; Saxony; 
 Belgium. 
 
 Clymenta linearis. Minister. 
 Petherwyn, Cornwall; Elbersreuth, Bavaria. 
 
 beds in Belgium, the Rhenish Provinces, the Hartz, Saxony, and 
 Silesia, that strata of this division in Germany are distinguished by 
 the names of " Clymenien-Kalk," and " Cypridinen-schiefer." f 
 
 With these are many Goniatites (G. subsulcatus, Miinster, and 
 other species) both in England and on the continent. In Germany 
 they are usually confined to distinct beds, as at Oberscheld, also at 
 Couvin in Belgium, &c. Trilobites are not unfrequent in Cornwall 
 and North Devon ; they are chiefly restricted to species of Phacops 
 (for genus, see fig. 585.) ; but in the upper Devonian limestones of 
 the Fichtelgebirge, as at Elbersreuth in Bavaria, there are numerous 
 genera and species which never rise higher in the series or appear 
 in any portion of the carboniferous limestone. 
 
 Middle Devonian. 
 
 The unfossiliferous series (No. 2., p. 424.) of North Devon, and the 
 calcareous beds of Ilfracombe (3.), correspond to the Dartmouth and 
 
 * See Dr. Fred. Sandberger on the Von Meyer's Palceontographica, 3rd 
 
 Devonian rocks of Nassau (Geol. Ver- vol. pt. 1. 
 
 halt. Nassau) ; Fred. Roemer, on the f See Murchison's Siluria, chaps, x., 
 
 Hartz Devonian Rocks, in Dunker and xiv., and xv. 
 
426 
 
 FOSSILS OF THE 
 
 [Cn. XXVI. 
 
 Plymouth groups of Prof. Sedgwick's South Devon series, and are 
 the most typical portion of the Devonian system. They include the 
 great limestones of Plymouth and Torbay, replete with shells, 
 trilobites, and corals. A thick accumulation of slate and schist, full of 
 the same fossils, occupies nearly all the southern portion of Devon- 
 shire and a large part of Cornwall. Among the corals we find the 
 genera Favosites, Heliolites, and Cyathophyllum, the last genus 
 equally abundant in the Silurian and Carboniferous systems, the two 
 former so frequent in Silurian rocks. Some few even of the species 
 are common to the Devonian and Silurian groups, as, for example, 
 Favosites polymorpha (fig. 554.), one of the commonest of all the 
 Devonshire fossils. The Cyathophyllum ccespitosum (fig. 555.) and 
 
 Fig. 555. 
 
 Fig. 554. 
 
 Favosites polymorpha, Goldf. S. Devon, from a polished 
 
 specimen. 
 a. Portion of the same magnified, to show the pores. 
 
 a. Cyathophyllum ccespitosum, 
 
 Goldf. Plymouth. 
 
 b. a terminal star. 
 
 c. vertical section, exhibiting 
 transverse plates, and part of 
 another branch. 
 
 Heliolites pyriformis (fig. 556.) are peculiarly characteristic ; as is 
 another very common species, the Aulopora serpens (fig. 557.), 
 which creeps over corals and shells in its young state, as here 
 
 Fig. 557. 
 
 Fig. 556. 
 
 Heliolites porosa, Goldf., sp. Porites pyriformis, 
 
 Lonsd. 
 
 a. portion of the same magnified. Middle De- 
 vonian, Torquay ; Plymouth ; Eifel. 
 
 Aulopora serpens, Goldf. 
 
 (The young basal portion of a Syringopora, 
 
 Milne Edw. and Haime.) 
 
 figured, but afterwards grows upwards and becomes a cluster of 
 tubes connected by minute processes. In this state it has been 
 supposed to be a distinct coral, and has been called Syringopora. 
 
H. XXVI.] MIDDLE DEVONIAN. 427 
 
 With the above are found many stone-lilies or crinoids, some of 
 them, such as Cupressocrinites, of forms generically distinct from 
 those of the Carboniferous Limestone. The mollusks also are no 
 less characteristic, among which the genus Stringocephalus (fig. 558.) 
 
 Fig. 558. 
 
 Stringocephalus Burlini, Defr. ( Terebratula porrecta, Sow.) Eifel; also South Devon. 
 a. valves united. b. side view of same. 
 
 c. interior of larger valve, showing thick partition, and part of a large process which 
 projects from its upper end quite across the shell. 
 
 may be mentioned as exclusively Devonian. Many other Brachiopod 
 shells, of the genus Spirifer, &c., abounded, and among them the 
 Atrypa reticularis, Linn. sp. (fig. 575. p. 438.), which seems to have 
 been a cosmopolite species occurring in Devonian strata from 
 America to Asia Minor, and which, as we shall hereafter see 
 (p. 437.), lived also in the Silurian seas. Among the peculiar 
 lamellibranchiate bivalves common to the Plymouth limestone of 
 Devonshire and the Continent, we find the Megalodon (fig. 559.), 
 together with many spiral univalves, such as Murchisonia, Euom- 
 phalus, and Macrocheilus ; and Pteropods such as Conularia (fig. 560.). 
 
 Fig. 560. 
 
 Fig. 559. 
 
 Megalodon cucullatus, Sow. Eifel ; also Bradley, S. Devon. 
 
 a. the valves united. 
 
 b. Interior of valve, showing the large cardinal tooth. 
 
 Conularia ornata, D'Arch. etDe 
 
 Vern. 
 
 (Geol. Trans. 2d s. vol.vi. pi. 29.) 
 Refrath, near Cologne. 
 
 The cephalopoda, such as Cyrtoceras, Gyroceras, and others, are 
 nearly all of genera distinct from those prevailing in the Upper 
 Devonian Limestone, or Clymenien-kalk of the Germans already 
 mentioned (p. 425.). Although but few species of Trilobites occur, 
 the characteristic Brontes fldbellifer (fig. 561. p. 428.) is far from rare, 
 and all collectors are familiar with its fan-like tail. The head is 
 seldom found perfect; a restoration of it has been attempted by 
 Mr. Salter (fig. 562.) 
 
 In this same formation, comprising in it the "Stringocephalus 
 
428 
 
 LOWER DEVONIAN. 
 
 [Cn. XXVI. 
 
 Fig. 561. 
 
 Fig. 562. 
 
 Restored outline of head of Brontes 
 flabellifer. 
 
 Brontes flabellifer, Goldf. Eifel; also S. Devon. 
 
 limestone," or " Eifel Limestone " of Germany, several remains of 
 Coccosteus and other ichthyolites have been detected, and they serve, 
 as Sir K. Murchison observes (Siluria, p. 371.), to identify the rock 
 Fig 563 with the Old Red Sandstone 
 
 of Britain and Russia. 
 
 Beneath the great Eifel 
 Limestone (the principal type 
 of "the Devonian" on the 
 Continent), lie certain schists 
 called by German writers 
 " Calceola-schiefer " because 
 they contain in abundance a 
 structure, Calceola sandalina 
 
 Calceola sandalina, Lam. Eifel ; also South Devon. 
 a. ventral valve, b. inner side of dorsal valve. 
 
 fossil brachiopod of very curious 
 (fig. 563.). 
 
 Lower Devonian. 
 
 Beneath the Middle Devonian limestones and schists already 
 enumerated, a series of slaty beds and quartzose sandstones, the 
 latter constituting the " Older Rhenish Greywacke " of Roemer, and 
 the " Spirifer sandstone " of Sandberger, are exhibited between 
 Coblentz and Caub.* A portion of these rocks on the Rhine and in 
 some of the adjacent countries were regarded as "Upper Silurian" 
 by Prof. Sedgwick and Sir R. Murchison in 1839, but their true 
 age has since been determined. Their equivalents are found in 
 England in the sandstones and slates of the North Foreland and 
 Linton in Devon (Nos. 4. and 5. of the section, p. 424.), and, 
 according to Mr. Salter, in the sandstone of Torbay in South 
 Devon, where many of the characteristic Rhenish fossils are met 
 
 with. The broad-winged 
 Spirifers which distin- 
 guish the " Spirifer-sand- 
 stein " of Germany have 
 their representatives in 
 the Devonian strata of 
 
 Spider ntucronatus, HaU. Devonian of Pennsylvania. ^ America ( gee fig> 554.). 
 * Murchison's Siluria, p. 368. 
 
 Fig. 564. 
 
DEVONIAN OF RUSSIA. 
 
 429 
 
 CH. XXVI.] 
 
 Among the Trilobites of this era a large species of Homalonotus 
 (fig. 565.) is conspicuous. The genus is still better known as a 
 Silurian form, but the spinose species appear to belong exclusively 
 to the " Lower Devonian." 
 
 With the above are associated many species of Brachiopods, such 
 as Orthis, Leptcena, and Chonetes, and some Lamellibranchiata, such 
 as Pterinea; also the very remarkable fossil coral, called Pleuro- 
 dictyum problematicum (fig. 566.) 
 
 Fig. 565. 
 
 Fig. 566. 
 
 Pleurodictyum problematicum, Goldfuss. Lower 
 Devonian ; Dietz, Nassau, &c. 
 
 Obs. Attached to a worm-like body (Serpula). 
 The specimen is a cast in sandstone, the thin 
 expanded base of the coral being removed, and 
 exposing the large polygonal cells; the walls of 
 these cells are perforated, and the casts of these 
 perforations produce the chain-like rows of dots 
 between the cells. 
 
 Homalonotus armatus, Burmeister. Lower 
 
 Devonian ; Daun, in the Eifel. 
 Obs. The two rows of spines down the body 
 give an appearance of more distinct triloba- 
 tion than really occurs in this or most other 
 species of the genus. 
 
 Devonian of Russia. The Devonian strata of Russia extend, 
 according to Sir R. Murchison, over a region more spacious 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 contain shells similar to those of Devonshire, thus 
 confirming, as Sir Roderick observes, the contemporaneous origin 
 previously assigned to formations exhibiting two very distinct 
 mineral types in different parts of Britain.* The calcareous and the 
 arenaceous rocks of Russia above alluded to alternate in such a 
 manner as to leave no doubt of their having been deposited at the 
 same period. Among the fish common to the Russian and the British 
 strata are Asterolepis Asmusii before mentioned ; a smaller species, 
 A. minor, Ag. ; Holoptychius nobilissimus (p. 418.) ; Dendrodus 
 strigatus, Owen ; Pterichthys major, Ag. ; and many others. But 
 some of the most marked of the Scottish genera, such as Cephalaspis, 
 Coccosteus, Diplacanthus, Cheiracanthus, &c., have not yet been 
 found in Russia, owing perhaps to the present imperfect state of our 
 researches, or possibly to geographical causes limiting the range of 
 
 * Siluria, p. 329. 
 
430 DEVONIAN STRATA [Cn. XXVI. 
 
 the extinct species. On the whole, no less than forty species of 
 placoid and ganoid fish have been already collected in Russia, some 
 of the placoids being of enomous size, as before stated, p. 423. 
 
 Devonian Strata in the United States. 
 
 In no country hitherto explored is there so complete a series of 
 strata intervening between the Carboniferous and Silurian as in the 
 United States. This intermediate or Devonian group was first 
 studied in all its details, and with due attention to its fossil remains, 
 by the Government Surveyors of New York. In its geographical 
 extent, that State, taken singly, is about equal in size to Great 
 Britain; and the geologist has the advantage of finding the 
 Devonian rocks there in a nearly horizontal and undisturbed con- 
 dition, so that the relative position of each formation can be ascer- 
 tained with certainty. 
 
 Subdivisions of the New York Devonian Strata, in the Reports of 
 the Government Surveyors. 
 
 Names of Groups. Thickness in Feet. 
 
 1. Catskill group or Old Red Sandstone - - 2000 
 
 2. Chemung group - '!'. ".'.^ - - \ - 1500 
 
 3. Portage \ .1000 
 
 4. Genessee) 
 
 5. Tully - - - - - 15 
 
 6. Hamilton - - - - - - 1000 
 
 7. Marcellus - ' - 50 
 
 8. Corniferous\ ^ 
 
 9. Onondaga J 
 
 10. Schoharie "I , ft 
 
 11. Cauda-Galli grit / 
 
 12. Oriskany sandstone - - ; - - 5 to 30 
 
 These subdivisions are of very unequal value, whether we regard 
 the thickness of the beds or the distinctness of their fossils ; but 
 they have each some mineral or organic character to distinguish 
 them from the rest. Moreover, it has been found, on comparing the 
 geology of other North American States with the New York 
 standard, that some of the above-mentioned groups, such as Nos. 2. 
 and 3., which are respectively 1500 and 1000 ft. thick in New York, 
 are very local and thin out when followed into adjoining States; 
 whereas others, such as Nos. 8. and 9., the total thickness of which 
 is scarcely 50 feet in New York, can be traced over an area nearly 
 as large as Europe. 
 
 Respecting the upper limit of the above system, there has been 
 very little difference of^opinion, since the Red Sandstone No. 1. 
 contains Holoptychius nobilissimus and other fish characteristic 
 generically or specifically of the European Old Red. More doubt 
 has been entertained in regard to the classification of Nos. 10, 11, 
 and 12. M. de Verneuil proposed in 1847, after visiting the United 
 States, to include the Oriskany sandstone in the Devonian ; and 
 Mr. D. Sharpe, after examining the fossils which I had collected in 
 
CH.XXVI.] IN THE UNITED STATES. 431 
 
 America in 1842, arrived independently at the same conclusion.* 
 The resemblance of the Spirifers of this Oriskany sandstone to those 
 of the Lower Devonian of the Eifel was the chief motive assigned 
 by M. de Verneuil for his view ; and the overlying Schoharie grit, 
 No. 10., was classed as Devonian because it contained a species of 
 Asterolepis. On the other hand, Prof. Hall adduces many fossils 
 from Nos. 10. and 12. which resemble more nearly the Ludlow 
 group of Murchison than any other European type ; and he thinks, 
 therefore, that those groups may be " Upper Silurian." Although 
 the Oriskany sandstone is no more than 30 feet thick in New York, 
 it is sometimes 300 feet thick in Pennsylvania and Virginia, where, 
 together with other primary or paleozoic strata, it has been well 
 studied by Professors W. B. and H. D. Rogers. 
 
 The upper divisions (from theCatskill to the Genessee groups, inclu- 
 sive, Nos. 1. to 4.) consist of arenaceous and shaly beds, and may have 
 been of littoral origin. They vary greatly in thickness, and few of 
 them can be traced into the "far west ;" whereas the calcareous groups, 
 Nos. 8. and 9., although in New York they have seldom a united thick- 
 ness of more than 50 feet, are observed to constitute an almost con- 
 tinuous coral-reef over an area of not less than 500,000 square miles, 
 from the State of New York to the Mississippi, and between 
 Lakes Huron and Michigan, in the north, and the Ohio River and 
 Tenessee in the south. In the Western States they are represented 
 by the upper part of what is termed " the Cliff Limestone." There 
 is a grand display of this calcareous formation at the falls or rapids 
 of the Ohio River at Louisville in Kentucky, where it much re- 
 sembles a modern coral-reef. A wide extent of surface is exposed in 
 a series of horizontal ledges, at all seasons when the water is not 
 high ', and, the softer parts of the stone having decomposed and 
 wasted away, the harder calcareous corals stand out in relief, their 
 erect stems sending out branches precisely as when they were 
 living. Among other species I observed large masses, not less than 
 5 feet in diameter, of Favosites gothlandica, with its beautiful 
 honeycomb structure well displayed, and, by the side of it, the 
 Favistelld, combining a similar honeycombed form with the star of 
 the Astrcea. There was also the cup-shaped Cyathophyllum, and 
 the delicate network of the Fenestella, and that elegant and well- 
 known European species of fossil, called " the chain coral," Cateni- 
 pora escharoides (see fig. 579. p. 439.), with a profusion of others. 
 These coralline forms were mingled with the joints, stems, and 
 occasionally the heads of lily encrinites. Although hundreds of fine 
 specimens have been detached from these rocks to enrich the 
 museums of Europe and America, another crop is constantly working 
 its way out, under the action of the stream, and of the sun and rain 
 in the warm season when the channel is laid dry. The waters of 
 the Ohio, when I visited the spot in April, 1846, were more than 
 
 * De Verneuil, Bulletin, 4. 678., 1847. D. Sharpe, Quart. Journ. Geol. Soc. 
 vol. iv. pp. 145., 1847. 
 
432 DEVONIAN STEATA. [Cn. XXVI. 
 
 40 feet below their highest level, and 20 feet above their lowest, so 
 that large spaces of bare rock were exposed to view.* 
 
 No less than 46 species of British Devonian corals are described 
 in the Monograph published in 1853 by Messrs. M. Edwards and 
 Jules Haime (Paleontographical Society), and only six of these occur 
 in America ; a fact, observes Prof. E. Forbes, which, when we call 
 to mind the wide latitudinal range of the Anthozoa, has an im- 
 portant bearing on the determination of the geography of the 
 northern hemisphere during the Devonian epoch. We must also 
 remember that the corals of these ancient reefs, whether American 
 or European, however recent may be their aspect, all belong to the 
 Zoantharia rugosa, a suborder which, as before stated (p. 407. 
 et seq.\ has no living representative. Hence great caution must 
 be used in admitting all inductions drawn from the presence and 
 forms of these zoophytes, respecting the prevalence of a warm or 
 tropical climate in high latitudes at the time when they flourished, 
 for such inductions, says Prof. E. Forbes, have been founded " on 
 the mistaking of analogies for affinities." f 
 
 This calcareous division also contains Goniatites, Spirifers, Pen- 
 tremites, and many other genera of Mollusca and Crinoidea, corres- 
 ponding to those which abound in the Devonian of Europe, and some 
 few of the forms are the same. But the difficulty of deciding on 
 the exact parallelism of the New York subdivisions, as above enu- 
 merated, with the members of the European Devonian, is very great, 
 so few are the species in common. This difficulty will best be 
 appreciated by consulting the critical essay published by Mr. Hall 
 in 1851, on the writings of European authors on this interesting 
 question.^ Indeed we are scarcely as yet able to decide on the 
 parallelism of the principal groups even of the north and south of 
 Scotland, or on the agreement of these again with the Devonian 
 and Rhenish subdivisions. 
 
 * LyelPs Second Visit to the United J Eeport of Foster and Whitney on 
 
 States, vol. ii. p. 277. Geol. of L. Superior, p. 302., Wash- 
 
 f Geol. Quart Journ. vol. x. p. Ix., ington, 1851. 
 1854. 
 
CH. XXVII.] SILURIAN STRATA. 433 
 
 CHAPTER XXVH. 
 
 SILURIAN AND CAMBRIAN GROUPS. 
 
 Silurian strata formerly called Transition Term Grauwacke Subdivisions of 
 Upper, Middle, and Lower Silurians Ludlow formation and fossils Ludlow 
 bone -bed, and oldest known remains of fossil fish Wenlock formation, corals, 
 cystideans, trilobites Middle Silurian or Caradoc sandstone Its unconforma- 
 bility Pentameri and Tentaculites Lower Silurian rocks Llandeilo flags 
 Cystideze Trilobites Graptolites Vast thickness of Lower Silurian strata in 
 Wales Foreign Silurian equivalents in Europe Ungulite grit of Russia 
 Silurian strata of the United States Amount of specific agreement of fossils 
 with those of Europe Canadian equivalents Deep-sea origin of Silurian 
 strata Fossiliferous rocks below the Llandeilo beds Cambrian group 
 Lingula flags of North Wales Lower Cambrian Oldest known fossil re- 
 mains "Primordial group"" of Bohemia Characteristic trilobites Meta- 
 morphosis of trilobites Alum schists of Sweden and Norway Potsdam sand- 
 stone of United States and Canada Footprints near Montreal Trilobites on 
 the Upper Mississippi Supposed period of invertebrate animals Upper 
 Silurian bone -bed Absence of fish in Lower Silurian Progressive discovery 
 of vertebrata in older rocks Inference to be drawn from the greater success 
 of British Paleontologists Doctrine of the non-existence of vertebrata in the 
 older fossil iferous periods premature. 
 
 WE come next in the descending order to the most ancient of the 
 primary fossiliferous rocks, that series which comprises the greater 
 part of the strata formerly called " transition" by Werner, for reasons 
 explained in Chap VIIL, pp. 91. and 93. Geologists were also in 
 the habit of applying to these older strata the general name of 
 " grauwaeke," by which the German miners designate a particular 
 variety of sandstone, usually an aggregate of small fragments of 
 quartz, flinty slate (or Lydian stone), and clay-slate cemented to- 
 gether by argillaceous matter. Far too much importance has been 
 attached to this kind of rock, as if it belonged to a certain epoch in 
 the earth's history, whereas a similar sandstone or grit is found in 
 the Old Red, and in the Millstone Grit of the Coal, and sometimes 
 in certain Cretaceous and even Eocene formations in the Alps. 
 
 The name of Silurian was first proposed by Sir Roderick Mur- 
 chison for a series of fossiliferous strata lying below the Old Red 
 Sandstone, and occupying that part of Wales and some contiguous 
 counties of England which once constituted the kingdom of the 
 Silures, a tribe of ancient Britons. The following table will explain 
 the various formations into which this group of ancient strata may 
 be subdivided. 
 
 F P 
 
434 
 
 SUBDIVISIONS OF SILURIAN ROCKS. [Cu. XXVII. 
 
 1. Ludlow 
 formation. 
 
 Upper 
 Ludlow. 
 
 UPPER SILURIAN ROCKS. 
 
 Prevailing Lithologi- Thick- 
 
 cal characters. Feet 
 
 fa. Tilestones. "") 
 Finely laminat- j 
 ed reddish and /- 800 ? 
 green micaceous j 
 sandstones. J 
 
 b. Micaceous grey"^| 
 sandstone and 
 mudstone. 
 
 2. Wenlock 
 formation." 
 
 Aymestry f Argillaceous lime- 
 limestone. stone. 
 
 Shale, with concre- 
 
 of ""- 
 
 and 
 
 Wenlock 
 
 ' 
 
 Argillaceous shale, 
 
 2000 
 
 AbOTe 
 
 Organic remains. 
 
 Marine mollusca of 
 almost every order, 
 the Brachiopoda 
 most abundant. 
 Serpulites. Crusta- 
 ceans of the Trilo- 
 bite family. Pla- 
 coid fish (oldest 
 remains of fish yet 
 known). Sea- 
 
 weeds ; and in the 
 uppermost strata 
 land plants. 
 
 Marine mollusca of 
 various orders as 
 before. Crinoidea 
 and corals plentiful. 
 Trilobites, Grapto- 
 lites. 
 
 MIDDLE SILURIAN ROCKS. 
 
 ("Shale, shelly lime- 1 
 
 Caradoc f Caradoc stone, sandstone, (^ 
 
 formation. \ sandstones, j and conglome- I 
 L rate. 
 
 LOWER SILURIAN ROCKS. 
 
 Llandeilo 
 formation. 
 
 TDark coloured cal 
 Llandeilo J careous 
 flags. 1 slates and sand 
 stones. 
 
 { Crinoidea, Corals, 
 Mollusca, chiefly 
 genus Pentamerus 
 abundant.) 
 
 I 1 20,000 j 
 
 Mollusca, Trilobites, 
 Cystideas, Crinoids, 
 Corals, Graptolites. 
 
 UITER SILURIAN ROCKS. 
 
 Ludlow formation. This member of the Upper Silurian group, 
 as will be seen by the above table, is of great thickness, and sub- 
 divided into three parts, the Upper and the Lower Ludlow, and 
 the intervening Aymestry limestone. Each of these may be dis- 
 tinguished near the town of Ludlow, and at other places in Shrop- 
 shire and Herefordshire, by peculiar organic remains. 
 
 1. Upper Ludlow. a. Tilestones. ^- This uppermost subdivision, 
 called the Tilestones, was originally classed by Sir R. Murchison 
 with the Old Red Sandstone, because they decompose into a red 
 soil throughout the Silurian region. They were regarded as a tran- 
 sition group forming a passage from Silurian to Old Red ; but it is 
 now ascertained that the fossils agree in great part specifically, and 
 in general character entirely, with those of the underlying Silurian 
 
CH. XXVII.] UPPER SILURIAN BONE-BED. 435 
 
 strata. Among these are Orthoceras bullatum, Trochus? helicites, 
 Bellerophon trilobatus, Chonetes lata, &c., with numerous defences 
 of fishes. These beds are well seen at Kington in Herefordshire, 
 and at Downton Castle near Ludlow, where they are quarried for 
 building. 
 
 b. Grey Sandstone, fyc. The next subdivision of the Upper 
 Ludlow consists of grey calcareous sandstone, or very commonly a 
 micaceous stone, decomposing into soft mud, and contains, besides 
 the shells just quoted, the Lingula cornea, which is common to it 
 and the Tilestone beds. The Orthis orbicularis, a round variety of 
 0. elegantula, is characteristic of the Upper Ludlow; and the 
 lowest or mudstone beds are loaded for a thickness of 30 feet with 
 Athyris navicula (fig. 568.). As usual in strata of the Primary 
 
 Fig. 567 Fig. 568. 
 
 Orthis eleganlult, Dalm. Var. orbicularis, Athyris (Terebratula) navicula, J. Sow. 
 J. Sow. Delbury. Aymestry limestone ; also in 
 
 Upper Ludlow. Upper and Lower Ludlow. 
 
 periods, the brachiopodous mollusca predominate over the lamelli- 
 branchiate ; but the latter are by no means unrepresented. Among 
 other genera, for example, we observe Avicula (or Pterinea), Car- 
 diola, Nucula, Sanguinolites, and Modiola. 
 
 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 thick- 
 ness, and have been provincially named " mudstones." In some 
 of these shales stems of crinoidea are found in an erect position, 
 having evidently become fossil on the spots where they grew at 
 the bottom of the sea. The facility with which these rocks, when 
 exposed o the weather, are resolved into mud, proves that, not- 
 withstanding their antiquity, they are nearly in the state in which 
 they were first thrown down. 
 
 The bone-bed of the Upper Ludlow deserves especial notice 
 as affording the oldest well-authenticated example of the fossil 
 remains of fish. It usually consists of a single thin layer of 
 brown bony fragments near the junction of the Old Red Sandstone 
 and the Ludlow rocks, and was first observed by Sir R. Mur- 
 chison, near the town of Ludlow, where it is three or four inches 
 thick. It has since been traced to a distance of 45 miles from that 
 point into Gloucestershire and other counties, and is commonly 
 not more than an inch thick. At May Hill two bone-beds were 
 observed, with 14 feet of intervening strata full of Upper Lud- 
 low fossils.* At that point immediately above the upper fish-bed 
 
 * Murchison's Siluria, pp. 137 237. 
 F F 2 
 
436 FOSSILS OF UPPER LUDLOW. [Cn. XXVII. 
 
 numerous globular bodies were found, which were determined 
 by Dr. Hooker to be the spores of a cryptogamic land-plant, pro- 
 bably Lycopodiaceous. These beds occur just beneath the lowest 
 strata of the " Old Red." Some of the fish are of the shark family, 
 and their defences are referred to the genus Onchus (fig. 569.). There 
 are also numerous minute shagreen scales (fig. 570.), which may 
 
 Fig. 569. Fig. 570. 
 
 Onchus tenuistriatus, Agass. Shagreen-scales of a placoid fish 
 
 Bone-bed. Upper Silurian ; Ludlow. (Tftelodus). 
 
 Bone-bed. Upper Ludlow. 
 
 possibly belong to the same placoid fish. The jaw and teeth of 
 Fig. 571. another predaceous ' genus (fig. 571.) have 
 
 also been detected. As usual in bone-beds, 
 tne teeth and bones are, for the most part, 
 piectrodus mirabiiis, Apass. fragmentary and rolled. Many statements 
 
 Bone-bed. Upper Ludlow. -, -, i T i -i P / i , 
 
 have been published of fish remains obtained 
 
 from older members of the Silurian series ; but Mr. Salter has shown 
 all these to be spurious.* Professor Phillips has, however, discovered 
 fish-bones at the bottom of the " Upper Ludlow," at its junction with 
 the Aymestry Rockf; and lower than this no one seems as yet to 
 have succeeded in tracing them downwards, whether in Europe or 
 North America, for M. Barrande's most ancient ichthyolites (bony 
 fragments, 8 inches long) occur in the Upper Silurian of Bohemia ; 
 and those of the American geologists are from the Oriskany Sand- 
 stone, a formation which is still considered as debateable ground 
 between the Devonian and Silurian systems (see p. 430. above). 
 
 In England it is true, as in the United States and Canada, glo- 
 bular, cylindrical, or flattened masses have been detected, com- 
 posed principally of phosphate of lime, in the Lowest Silurian rocks, 
 and they have been suspected to be coprolitic. Messrs. Logan and 
 Hunt have recently shown that shells of the genera Lingula and 
 Orbicula, which occur abundantly in the same formations, are 
 also made up of phosphate and carbonate of lime, mixed in the like 
 proportions ; and it has been suggested that the decomposition of such 
 shells might give rise to the nodules alluded to which may owe their 
 form to concretionary action. J Even if the zoologist should think 
 it more likely that the phosphatic matter was rejected in fsecal 
 lumps, by creatures feeding on Lingulae and Orbiculae, we cannot 
 decide that such feeders were of the vertebrate class, rather than 
 Cephalopods, Crustaceans, or some other of the Invertebrata. In 
 regard to the doctrine of the supposed non-existence of fish in 
 the Silurian seas before the time of the Ludlow bone-bed, I shall 
 consider that question fully in the concluding pages of this chapter, 
 p. 457., et seq. 
 
 * Geol. Quart. Journ. vol.vii. p. 2C3 J Logan and Hunt; Silliman's Journ. 
 f Memoirs Geol. Surv. vol ii. No. 50. 2d series, March 1854. 
 
AY.MESTRY LIMESTONE. 
 
 437 
 
 CH. xxvu.j 
 
 2. Aymestry limestone. The next group is a subcrystalline and 
 argillaceous limestone, which is in some places 50 feet thick, and 
 distinguished around Aymestry by the abundance of Pentamerus 
 Knightii, Sow. (fig. 572.), also found in the Lower Ludlow. This 
 
 Fig. 572. 
 
 Pentamerus Knightii, Sow. Aymestry. Half nat. size. 
 
 a. view of both valves united. 
 
 b. longitudinal section through both valves, showing the central plates or septa. 
 
 genus of brachiopoda was first found in Silurian strata, and is ex- 
 clusively a paleozoic form. The name was derived from Trerre, pente, 
 five, and pepoc, meros, a part, because both valves are divided by a 
 central septum, making four chambers, and in one valve the septum 
 itself contains a small chambe_, making five. The size of these septa 
 is enormous compared with those of any other brachiopod shell ; and 
 they must nearly have divided the animal into two equal halves ; 
 but they are, nevertheless, of the same nature as the septa or plates 
 which are found in the interior of Spirifer, Terebratula, and many 
 other shells of this order. Messrs. Murchison and De Verneuil dis- 
 covered this species dispersed in myriads through 
 a white limestone of Upper Silurian age, on the 
 banks of the Is, on the eastern flank of the Urals 
 in Russia, and a similar species is frequent in Swe- 
 den. 
 
 Three other abundant shells in the Aymestry 
 limestone are, 1st, Lingula Lewisii (fig. 573.) ; 2d, 
 Rhynchonella Wilsoni, Sow. (fig. 574.), which is 
 also common to the Lower Ludlow and Wenlock 
 limestone ; 3d, Atrypa reticularis, Lin. (fig. 575.), 
 which has a very wide range, being found in every 
 part of the Silurian system, even in the upper 
 portion of the Llandeilo flags. 
 
 Fig. 574. 
 
 Lfngnla Lewisii, 
 
 J. Sow. 
 Abberlt-y Hills. 
 
 Rnynchonetta (Terebratula} Wilsoni, Sow. Aymestry. 
 F * 3 
 
438 
 
 FOSSILS OF LOWER LUDLOW. 
 
 Fig. 571,. 
 
 [CH. XXVII. 
 
 Fig. 576. 
 
 Atrypa reticularis, Linn. (Terebratula qffinis, Min. Con.) Aymestry. 
 a. upper valve. b. lower valve. 
 
 c. anterior margin of the valves. 
 
 The Aymestry Limestone contains so many shells, corals, and 
 trilobites agreeing specifically with those of the subjacent Wenlock 
 limestone, that it is scarcely distinguishable from it by its fossils 
 alone. Nevertheless, many of the organic 
 remains are common to the Aymestry lime- 
 stone and the Upper Ludlow, and several 
 of these are not found in the Wenlock.* 
 
 3. Lower Ludlow shale. This mass is a 
 dark grey argillaceous deposit, containing, 
 among other fossils, many large chambered 
 shells of genera scarcely known in newer 
 rocks, as the Phragmoceras of Broderip, 
 and the Lituites of Breyn (see figs. 576, 
 577.). The latter is partly straight and 
 partly convoluted, nearly as in Spirula. 
 The Orthoceras Ludense (fig. 578.), as 
 
 Phraemocerasventrtcosum,3.Sow. we [l as the CCphalopod last mentioned, IS 
 (Orthoceras ventricosum, Stem.) *, ; . /> , 
 
 peculiar to this member ot the series. 
 
 Aymeitry ; i nat. size. 
 Fig. 577. 
 
 Fig. 578. 
 
 Lituiles giganteus, J. Sow. 
 Near Ludlow ; also in the Aymestry 
 and Wenlock limestones ; nat. size. 
 
 Fragment of Orthoceras Ludense, J. Sow. 
 Leintwardine, Shropshire. 
 
 A species of Graptolite, G. Ludensis, Murch. (fig. 588., p. 441.), a 
 form of zoophyte which has not yet been met with in strata above 
 the Silurian, occurs plentifully in the Lower Ludlow. 
 
 Murchison's Siluria, p. 133. 
 
CH. XXVII.] 
 
 WENLOCK FORMATION. 
 
 439 
 
 Wenlock formation. We next come to the Wenlock formation, 
 which has been divided (see Table, p. 434.) into the Wenlock lime- 
 stone and the Wenlock shale. 
 
 1. The Wenlock limestone, formerly well known to collectors by 
 the name of the Dudley limestone, forms a continuous ridge in Shrop- 
 shire, 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 
 softness of the shales above and below it. Near Wenlock it consists of 
 thick masses of grey subcrystalline limestone, replete with corals and 
 encrinites. It is essentially of a concretionary nature ; and the con- 
 Fig. 579. cretions, termed " ball-stones " in Shropshire, 
 are often enormous, even 80 feet in diameter. 
 They are of pure carbonate of lime, the sur- 
 rounding rock being more or less argilla- 
 ceous.* Sometimes in the Malvern Hills this 
 limestone, according to Professor Phillips, is 
 oolitic. 
 
 Among the corals in which this formation 
 is so rich, the " chain-coral," Holy sites catenu- 
 latus, or Catenipora escharoides (fig. 579.), 
 may be pointed out as one very easily recog- 
 nized, and widely spread in Europe, ranging 
 through all parts of the Silurian group, from 
 the Avmestry limestone to near the bottom of 
 
 Halysites catenulatns, Linn. sp. * * 
 
 s y n.cateniporaesc/taroides,Goi<i. the series. Another coral, the Favosites Goth- 
 
 Upper and Lower Silurian. , 7 . f - - nrk \ i . ,T . / 
 
 landica (fig. 580.), is also metwith in profusion 
 
 in large hemispherical masses, which break up into prismatic frag- 
 ments, like that here figured (fig. 580.). Another common form in 
 the Wenlock limestone is the Omphyma (fig. 581.), which, like many 
 of its companions, reminds us of some modern cup-corals, but all the 
 Silurian genera belong to the paleozoic type before-mentioned 
 
 Fig. 580. 
 
 Fig. 581. 
 
 Favosites Gothlandtca, Lam. Dudley, 
 rt. portion of a large mass -, less than the 
 
 natural size. 
 b. magnified portion to show the pores 
 
 and the partitions in the tubes. 
 
 Omphyma turbinatum, Linn. sp. 
 
 (Cyathopkyllum, Goldf.) 
 Wenlock Limestone, Shropshira 
 
 * Murchison's Siluria, p. 115. 
 FF 4 
 
440 FOSSILS OF THE WENLOCK LIMESTONE. [On. XXVII. 
 
 (p. 407.), exhibiting the quadripartite arrangement of the lamellae 
 within the cup. 
 
 Among the numerous Crinoids, several peculiar species of Cya- 
 thocrinus (for genus, see figs. p. 409.) contribute their calcareous 
 stems, arms, and cups towards the composition of the Wenlock lime- 
 stone. Of Cystideans there are a few very remarkable forms, some 
 of them peculiar to the Upper Silurian formation, as for example 
 the Pseudocrinites, which was furnished with pinnated fixed arms*, 
 as represented in the annexed figure (fig. 582.). 
 
 The Brachiopoda are for the most part of the same species as those 
 of the Aymestry limestone ; as, for example, Atrypa reticularis (fig. 
 575., p. 438.), and Strophomena depressa, Sow. sp. (fig. 583.) ; but 
 these species range also through the Ludlow rocks, Wenlock shale, 
 and Caradoc Sandstone. 
 
 Fig. 582. 
 
 Fig. 583. 
 
 Strophomena (Leptcena) depressa, Sow. 
 Wenlock and Ludlow Rocks. 
 
 Pseudocrinites bffasciatus, Pearce. 
 Wenlock Limestone, Dudley. 
 
 The Crustaceans are represented almost exclusively by Trilobites, 
 which are very conspicuous. The Calymene Blumenbachii, called 
 the " Dudley Trilobite," was known to collectors long before its true 
 place in the animal kingdom was ascertained. It is often found 
 coiled up like the common Oniscus or wood-louse, and this is so 
 common a circumstance among the trilobites as to lead us to 
 conclude that they must have habitually resorted to this mode of 
 protecting themselves when alarmed. Sphcerexochus mirus (fig. 586.) 
 
 Fig. 585. 
 
 Fig. 586. 
 sggj^" Hpifc^ 
 
 Fig. 584. 
 
 Calymene B/un/enbachif, 
 
 Brong. 
 
 Wenlock, Ludlow, and 
 Aymestry limestones. 
 
 Sphcerexochus mirus, Beyrich. 
 
 coiled up. 
 
 Dudley ; also in Ohio, 
 N. America. 
 
 Phacops caudalus, Brong. 
 Wenlock, Aymestry, and Ludlow Rocks. 
 
 * E. Forbes, Mem. Geol. Survey, vol. ii. p. 496. 
 
MIDDLE SILUKIAN ROCKS. 
 
 441 
 
 Fig. 587. 
 
 CH. XXVII.] 
 
 is almost a globe when rolled up, the forehead of this species being 
 extremely inflated. The Homalonotus, a form of Trilobite in which 
 the tripartite division of the dorsal crust is 
 almost lost (see fig. 587.), is very characteristic 
 of this division of the Silurian series. 
 
 2. The Wenlock Shale. This, observes Sir R. 
 Murchison *, is infinitely the largest and most 
 persistent member of the Wenlock formation, 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 district it is a mass of finely le- 
 vigated argillaceous matter, attaining, according 
 to Prof. Phillips, a thickness of 640 feet, but it 
 is sometimes more than 1000 feet thick in Wales. 
 The prevailing fossils, besides corals and trilo- 
 bites, and some crinoids, are several small species 
 of Orlhis, with other brachiopods and certain thin- 
 shelled species of Orthoceratites. One species of 
 Graptolite, a group of zoophytes before alluded 
 to as being confined to Silurian rocks, is very 
 abundant in this shale, and occurs 
 more sparingly in " the Ludlow." 
 Of these fossils, which are more 
 characteristic of the Lower Silurian, 
 I shall again speak in the sequel 
 (p. 446.). 
 
 Castle ; nat. size 
 
 Fig. 588. 
 
 Graptolithus Ludensts, Murchison. 
 Ludlow and Wenlock Shales. 
 
 MIDDLE SILUKIAN ROCKS. 
 
 Caradoc Sandstone. This sandstone, so named from a mountain 
 called Caer Caradoc, in Shropshire, was originally considered by 
 Sir Roderick Murchison as the sandy and upper portion of the 
 Lower Silurian strata. Subsequent investigations have led to the 
 conclusion that the original or typical Caradoc is divisible into two 
 formations, the lower, an arenaceous form of the Llandeilo flags, 
 and containing identical species of fossils ; the other or superior 
 sandstone, a series of strata resting unconformably on the Llandeilo 
 beds, and chiefly characterized by Upper Silurian fossils, yet having 
 same intermixture of species common to the "Lower Silurian." 
 Hence the Caradoc, as distinct from the Llandeilo, must either be 
 classed as the base of the Wenlock Shale, an opinion to which some 
 authorities incline, or it may be regarded as a Middle Silurian 
 group, an alternative which I have embraced provisionally in common 
 with many officers of our Government Survey. The larger part, 
 therefore, of what was once termed " the Caradoc " has merged into 
 the Llandeilo, and is the equivalent of the upper and middle portions 
 of that division. 
 
 The first step towards placing in a clearer light the relations of 
 "the Caradoc" to the strata above and below it, was made in 1848 
 * Siluria, p. 111. 
 
442 
 
 CARADOC SANDSTONE. 
 
 [Cn. XXVII. 
 
 by Professor Ramsay and Mr. Aveline, who observed that in the 
 Longmynd Hills the Caradoc sandstone rested unconformably on 
 the Lower Silurian, and that the latter or " Llandeilo flags," together 
 with some still older rocks, must have constituted an island in the 
 Caradoc sea. Professor E. Forbes at the same time observed that 
 the island was probably high and steep land rising from a deep sea, 
 and that the Caradoc fossils, some of them of littoral aspect, as 
 Littorina and Turritella, were deposited round the margin of that 
 ancient land. It was also remarked that while the sandstone and 
 conglomerate of this upper Caradoc * reposed unconformably on the 
 Llandeilo beds, it at the same time graduated upwards, as Sir R. 
 Murchison had stated, into the Wenlock Shale. 
 
 Subsequently Professor Sedgwick and Mr. M'Coy, pursuing their 
 investigations independently of the Survey in North Wales, became 
 convinced f that the Caradoc beds of May Hill and the Malverns, 
 constituting the Upper Caradoc, already mentioned, were full of 
 Upper Silurian fossils ; and that the strata of Caradoc sandstone at 
 Horderly and other places east of Caer Caradoc belonged to the 
 Bala group (or equivalent of the Llandeilo), being distinguished by 
 Lower Silurian species. This opinion was finally substantiated by 
 Mr. Salter and Mr. Aveline, in 1853, by an appeal to parts of 
 Shropshire where " the Caradoc " had been originally studied by 
 Sir R. Murchison, and where they found the Upper Caradoc uncon- 
 formable on the lower, and filled with a series of very distinct fossils.J 
 
 In the restricted sense, therefore, in which it is now understood, 
 the Caradoc Sandstone comprises a series of beds of passage from 
 the Lower to the Upper Silurian group. It is everywhere cha- 
 racterized by species of Pentamerus and Atrypa unknown in the 
 overlying Wenlock or Ludlow beds, but which descend into the 
 strata of the Llandeilo group. Pentamerus lams (fig. 589.), and 
 
 Fig. 589. 
 
 Pentamerus tevis, Sow. Caradoc Sandstone. 
 Perhaps the young of Pentamerus oblongus. 
 a, b. Views of the shell itself, from figures in Murchison's Sil. Syst. 
 
 c. Cast with portion of shell remaining, and with the hollow of the central septum filled with spar. 
 
 d. Internal cast of a valve, the space once occupied by the septum being represented by a hollow in 
 
 which is seen a cast of the chamber within the septum. 
 
 * Quart. Geol. Journ., vol.iv. p. 297. 
 t Geol. Quart. Journ., 1852. 
 
 Geol. Quart. Journ., vol. x. p. 62. 
 
CH. XXVII.] LOWER SILUKIAN KOCKS. 443 
 
 P. oblongus may be particularly mentioned as brachiopods which 
 abounded in Siluria, and had a very wide geographical range, being 
 
 met with in the same place in the Silurian 
 series of Russia and the United States. 
 Among its fossils, too, Tentaculites an- 
 nulatus (fig. 590.), an annelid probably 
 allied to Serpula, is exceedingly common. 
 This also is a link to connect it with the 
 Lower rather than the Upper Silurian. 
 annuiatus, Schiot. All the shelly sandstone of the Malvern 
 E..T t^-r r e mag - -d AW^y Hi]]* of Tortworth in Clou- 
 nified - cestershire, and of the centre of the May 
 
 Hill and Woolhope districts belong to this Middle Silurian, which 
 in the Malvern range attains a thickness of 600 feet. Of the same 
 age are dense masses of sandstone with shale, 2000 feet in thickness, 
 in the higher and disturbed regions of North Wales, as in the 
 Berwyn Mountains for example. According to Professor Sedgwick 
 the hard quartzose Coniston Grits of Westmoreland may also be 
 referred to the same period. 
 
 LOWER SILURIAN ROCKS. 
 
 Llandeilo Flags. The Lower Silurian strata were originally 
 divided by Sir R. Murchison into an upper group, already described, 
 and termed the Caradoc Sandstone, and a lower one, called, from a 
 town in Caermarthenshire, the Llandeilo flags. The strata last men- 
 tioned consist of dark-coloured micaceous flags, frequently calcareous, 
 with a great thickness of shales, generally black, below them. The 
 same beds are also seen at Builth in Radnorshire, and here they 
 are interstratified with volcanic matter. Above these typical 
 Llandeilo beds, however, the Lower Silurian contains, both in 
 North and South Wales, some strata in which the Pentameri of 
 the Middle Silurian, already alluded to (p. 442.), are associated 
 with species of fossils identical with those in the Llandeilo flags. 
 The corals of the calcareous zone of the Llandeilo belong to 
 the genera Holy sites (see fig. 579.), Heliolites, Petraia, Stenopora, 
 Favosites (fig. 580.), and others*; and there are peculiar Crinoids 
 and Cystideans in the same rocks. These last are amongst the 
 most recent additions made by paleontologists to the Radiata. 
 Their structure and relations were first elucidated in an essay 
 published by Von Buch at Berlin in 1845. They are the Sphce- 
 ronites of old authors, and are usually met with as spheroidal 
 bodies covered with polygonal plates, with a mouth on the upper 
 side, and a point of attachment for a stem (which is almost always 
 broken off) on the lower (fig. 591. b). They are considered by 
 Professor E. Forbes as intermediate between the crinoids and echi- 
 noderms. The Sphaeronite here represented (fig. 591.) occurs in 
 the Llandeilo beds in Wales f, as also in Sweden and Russia. 
 
 * Murchison's Siluria, p. 178. f Quart. Geol. Journ. vol. vii. p. 11.; 
 
 and Mem. Geol. Surv. vol. ii. p. 518. 
 
444 
 
 LOWER SILURIAN ROCKS. 
 
 [CH. XXVII. 
 
 Fig. 591. 
 
 Examples are not wanting, though 
 very rare, of star-fish in the same beds. 
 Brachiopod shells are in the greatest 
 abundance, chiefly of the genera Orthis, 
 Leptcena, and Strophomena (fig. 591.). 
 Of the Orthides those species with 
 broad simple ribs (fig. 592.) are parti- 
 cularly characteristic. Such shells as 
 Atrypa and Spirifer, so frequent in the 
 Upper and Middle Silurian, are rare or 
 confined to the superior part of the 
 Lower Silurian, while Chonetes and 
 Productus are wholly absent. It is re- 
 markable, however, that Rhynchonella 
 and Lingula, genera of which there are 
 
 living representatives in the present seas, were common in the 
 
 Silurian ocean. 
 
 Echinosphcerites balttcus, Eichwald, sp. 
 (Of the family Cyttuietf*) 
 
 a. mouth 
 
 b. point of attachment of stem. 
 Lower Silurian, S. & N. Wales. 
 
 Fig. 592. 
 
 Fig. 593. 
 
 Fig. 594. 
 
 Orthis tricenaria, Orthis vespertilio, Sow . 
 
 Hall> Shropshire ; N. & S. 
 
 New York. Canada. Wales. 
 
 nat. size. j nat. size. 
 
 Strophomena (Orihis) grandis, Sowerby. 
 
 f nat. size. 
 
 Horderly, Shropshire ; also Coniston, 
 Lancashire. 
 
 Among the Cephalopoda are Orthoceratites, with the siphuncle of 
 large dimensions and placed on one side ; also Lituites (see fig. 577.), 
 Bellerophon (see p. 411.), and some of the floating tribes of mol- 
 lusca (Pteropods). The Crustaceans were plentifully represented 
 by the Trilobites, which appear to have swarmed in the Silurian 
 seas just as crabs and shrimps do in our own. The genera Asaphus 
 (fig. 595.), Ogygia (fig. 596.), and Trinucleus (figs. 597, 598.) are 
 
 Fig. 595. 
 
 Fig. 596. 
 
 Asaphns tyrannus, Murch. 
 Llandeilo ; Bishop's Castle, &c. 
 
 Ogygia Buchif, Burm. (Asaphus 
 
 Buchif, Brongn.) 
 Builth, Radnorshire ; Llandeilo, Caermarthenshire. 
 
CH. XXVII.] 
 
 LLANDEILO FLAGS. 
 
 445 
 
 especially characteristic of strata of this age, if not entirely con- 
 fined to them; but very numerous other genera accompany these. 
 Burmeister, in his work on the organization of trilobites, supposes 
 them to have swum 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 defence 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 species 
 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 to the body, 
 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. 597, 598.). 
 
 Fig. 598. 
 
 Young individuals of Trinucleus con- 
 
 ctnlncus (T. ornatus, Barr.) 
 a. Youngest state. Natural size and 
 
 magnified; the body rings not 
 
 at all developed. 
 
 *. A little older. One thorax joint. 
 c. Still more advanced. Three thorax 
 
 joints. The fourth, fifth, and 
 
 sixth segments are successively 
 
 produced, probably each time the 
 
 animal moulted its crust. 
 
 Trinucleus concent ricus, Eaton. 
 
 Syn. T. car ac tad, Murch. 
 
 N. Ireland ; Wales ; Shropshire ; N. America ; 
 
 Bohemia. 
 
 A still lower part of the Llandeilo or Bala 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 carbonaceous matter may be due in 
 great measure to large quantities of imbedded animal remains, for 
 the number of Graptolites included in these slates was certainly very 
 great. I collected these same bodies in great numbers in Sweden 
 and Norway in 1835-6, both in the higher and lower graptolitic 
 shales of the Silurian system ; and was informed by Dr. Beck of 
 Copenhagen, that they were fossil zoophytes related to the Vigularia 
 and Pennatula, genera of which the living species now inhabit mud 
 and slimy sediment. The most eminent naturalists still hold to this 
 opinion. 
 
446 THICKNESS OF SILURIAN STRATA. [Cn. XXVII. 
 
 Fig. 599. 
 
 Fig. 600. 
 
 Didymograpstis geminus, Hisinger, sp. 
 Sweden. 
 
 a, b. Didymograpsus (Graptolites) Mur- 
 
 chisonii, Beck. 
 Llandeilo flags. Wales. 
 
 Fig. 601. 
 
 Fig. 602. Fig. 603. 
 
 Diplograpsus folium, Diplograpsvs pristis, 
 
 Hisinger. Hisinger. sp. 
 
 Rastrites peregrinus, Barrande. Sc tland ; Sweden ' Shropshire ; Wales ; Sweden, 
 
 Scotland ; Bohemia ; Saxony. 
 
 Beneath the black slates above described no graptolites appear as 
 yet to have been found, but the characteristic shells and trilobites of 
 the Lower Silurian rocks are still traceable downwards, in North 
 and South Wales, through a vast depth of shaly beds, interstratified 
 with trappean formations, sometimes not less in their aggregate 
 thickness than 11,000 feet. Hence the total thickness of the beds 
 assigned to the Lower Silurian, or the Llandeilo group of Murchison, 
 is not less than 20,000 feet, and the Upper Silurian rocks are above 
 5000 feet in addition. If these beds were all exclusively of sedi- 
 mentary origin we might well expect, from the analogy of other 
 parts of the earth's crust, to find that they must be referred pale- 
 ontologically to more than one era ; in other words, that changes in 
 animal and vegetable life, as great as those which occurred in the 
 course of several such periods as the Devonian, Carboniferous, and 
 Permian, would be found to have taken place while the accumulation 
 of so enormous a pile of rocks was effected. But in volcanic archi- 
 pelagos, as in the Canaries for example, we see the most active of all 
 known causes, aqueous and igneous, simultaneously at work to 
 produce great results in a comparatively 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 cinders, or of rocks ground down to pebbles and sand, by 
 torrents descending steeply inclined channels, the undermining 
 and eating away of long lines of sea-cliff exposed to the swell 
 of a deep and open ocean, above all, the injection, both above 
 and below the sea-level, of sheets of melted matter between the 
 lavas previously formed at the surface, these operations may 
 combine to produce a considerable volume of superimposed matter, 
 without there being time for any extensive change of species. 
 
CH. XXVII.] SILURIAN EQUIVALENTS IN EUROPE. 447 
 
 Nevertheless, there would seem to be a limit to the thickness of 
 stony masses formed even under such favourable circumstances? 
 for the analogy of tertiary volcanic regions lends no countenance 
 to the notion that sedimentary and igneous rocks 25,000, much less 
 45,000 feet thick, like those of Wales, could originate while one and 
 the same fauna should continue to people the earth. If, then, we 
 allow that 25,000 feet of matter may be ascribed to one system, such 
 as the Silurian, from the top of " the Ludlow " to the base of " the 
 Llandeilo " inclusive, we may be prepared to find in the next series 
 of subjacent rocks, the commencement of another assemblage of 
 species, or even in part of genera, of organic remains. Such appears 
 to be the fact, and I shall therefore conclude with the Llandeilo 
 beds, the original base-line of Sir R. Murchison, my account of the 
 Silurian formations in Great Britain, and proceed to say something 
 of their foreign equivalents, before treating of rocks older than the 
 Silurian. 
 
 It would lead me into too long a digression to attempt to follow 
 the Upper, Middle, and Lower Silurian into Scotland, the lake 
 country, Cornwall, and other parts of the British Isles. For an 
 account of these rocks in Ireland, the reader is referred to Col. Port- 
 lock's Report on Tyrone, to the writings of Mr. Griffith and 
 Prof. M'Coy, and those of the officers of the Government Survey, 
 as well as to the sketch recently given by Sir R. I. Murchison. 
 
 When we turn to the Continent of Europe, we discover the same 
 ancient series occupying a wide area, but in no region as yet has it 
 been observed to attain great thickness. Thus, in Norway and 
 SwMen, the -total thickness of strata of Silurian age is scarcely 
 equal to 1000 feet*, although the representatives both of the 
 Upper and Lower Silurian of England are not wanting there, and 
 even some beds of schist have been comprehended which, as we 
 shall hereafter see, lie below the Llandeilo group. 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 Middle and Lower Silurian, or of a limestone 
 containing Pentamerus oblongus, below which are strata with fossils 
 corresponding to those of the Llandeilo 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, 
 and not exhibiting any of those peculiar forms which distinguish 
 " the Lingula flags " of Wales, or the Bohemian " primordial fauna " 
 of Barrande. 
 
 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 or Ungulite of Pander, and a 
 Siphonotreta (see figs. 604, 605.), As bearing on the antiquity 
 of this formation, it is interesting to notice that both genera have 
 recently been found in our own Dudley limestone. 
 
 * Murchison's Siluria, p. 321. 
 
448 
 
 SILURIAN STRATA OF UNITED STATES. [Cn. XXVII. 
 
 Shells of the lowest known Fossiltferous Beds in Russia. 
 Fig. 604. Fig. 605. 
 
 Siphonotreta nnguiculata, Eichwald. 
 
 From the Lowest Silurian sandstone, " Obolus 
 
 grits," of Petersburg. 
 
 a. outside of perforated valve. 
 
 b. interior of same, showing the termination of 
 
 the foramen within. 
 
 Obolus Apollinis, Eichwald. 
 From the same locality. 
 
 a. interior of the larger or ventral valve. 
 
 b. exterior of the upper (dorsal) valve. 
 
 (Davidson.) 
 
 Among the green grains of the sandy strata above mentioned, 
 Professor Ehrenberg has recently (1854) announced his discovery of 
 remains of foraminifera. These are casts of the cells ; and amongst 
 five or six forms three are considered by him as referable to existing 
 genera (e. g., Textularia, Rotalia, and Guttulina). 
 
 SILURIAN STRATA OF THE UNITED STATES. 
 
 The position of some of these strata, where they are bent and 
 highly inclined in the Appalachian chain, or where they are nearly 
 horizontal to the west of that chain, is shown in the section, fig. 505. 
 p. 392. But these formations can be studied still more advanta- 
 geously north of the same line of section, in the States of New York, 
 Ohio, and other regions north and south of the great Canadian lakes. 
 Here they are found, as in Russia, nearly in horizontal position, and 
 are more rich in well-preserved 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, see Table, p. 430.) 
 
 New York Names. British Equivalents. 
 
 1. Upper Pentamerus Limestone 
 
 2. Encrinal Limestone 
 
 5. Tentaculite Limestone 
 
 6. Onondaga Salt-group 
 
 7. Niagara Group 
 
 8. Clinton Group 
 
 9. Medina Sandstone 
 
 10. Oneida Conglomerate 
 
 11. Grey Sandstone 
 
 12. Hudson River Group. 
 
 13. Utica Slate 
 
 14. Trenton Limestone 
 
 15. Black-River Limestone 
 1 6. Bird's-Eye Limestone 
 
 17. Chazy Limestone 
 
 18. Calciferous Sandstone 
 
 19. Potsdam Sandstone 
 
 Wenlock formanons). 
 
 1 
 
 Middle Silurian (or Caradoc Sand- 
 f stone). 
 
 1 
 Lower Silurian (or Llandeilo beds). 
 
 f Cambrian ? (or Lingula flags and 
 \ beds, older than " the Llandeilo "\ 
 
 In the second column of the same table I have added the supposed 
 British equivalents. All paleontologists, European and American, 
 
CH. XXVII.] SPECIFIC AGREEMENT OF FOSSILS. 449 
 
 such as MM. de Verneuil, D. Sharpe, Prof. Hall, and others, who have 
 entered upon this comparison, admit that there is a marked general 
 correspondence in the succession of fossil forms, and even species, as 
 we trace the organic remains downwards from the highest to the 
 lowest beds ; but it is impossible to parallel each minor subdivision. 
 In regard to the three following points there is little difference of 
 opinion. 
 
 1st. That the Niagara Limestone, No. 7., 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. Among the species common to this formation in America 
 and Europe are Calymene Blumenbachii, Homalonotus delphinoce- 
 phalus (fig. 587.), with several other trilobites ; Rhynchonella Wilsoni, 
 and R. cuneata ; Orthis elegantula, Pentamerus galeatus, with many 
 more brachiopods ; Orthoceras annulatum, among the cephalopodous 
 shells ; and Favosites gothlandica, with other large corals. 
 
 2nd. That the Clinton Group, No. 8., containing Pentamerus 
 oblongus and P. Icevis, and related more nearly by its fossil species 
 with the beds above than with those below, is the equivalent of the 
 Middle Silurian as above defined, p. 441. 
 
 3rd. That the Hudson River Group, No. 12., and the Trenton 
 Limestone, No. 14., agree paleontologically with the Llandeilo flags, 
 containing in common with them several species of trilobites, such 
 as Asaphus (Isotelus) gigas, Trinucleus concentricus (fig. 598. p. 445.); 
 and various shells, such as Orthis striatula, Orthis biforata (or 0. lynx), 
 O. porcata (0. occidentalis of Hall), Bellerophon bilobatus, &c.* 
 
 Mr. D. Sharpe, in his report on the mollusca collected by me from 
 these strata in North America f , has concluded that the number of 
 species common to the Silurian rocks 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, nevertheless, that many of the species had a wide 
 geographical range. It seems that comparatively few of the gas- 
 teropods 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 (especially the orthidiform ones) are 
 inhabitants of deep water, and that they may have had a wider geo- 
 graphical range than shells living near shore. The predominance of 
 bivalve mollusca of this peculiar class has caused the Silurian period 
 to be sometimes styled " the age of brachiopods." 
 
 The calcareous beds, Nos. 15, 16, 17, and 18., below the Trenton 
 Limestone have been considered by M. de Verneuil as Lower 
 Silurian, because they contain certain species, such as Asaphus 
 {Isotelus) gigas, Illcenus crassicauda, and Orthoceras bilineatum, in 
 common with the overlying Trenton Limestone.J But, according to 
 
 * See Murchison's Siluria, p. 414. J Soc. Geol. France, Bulletin, 
 
 f Quart. Geol. Journ., vol. iv. vol. iv. p. 651. 1847. 
 
 G G 
 
450 CANADIAN EQUIVALENTS. [Cn. XXVII. 
 
 Prof. Hall, the Illcenus was erroneously identified, an error to which 
 he confesses that he himself contributed ; and on the whole these 
 lower beds contain, he thinks, a very distinct set of species, only 
 three or four of them out of eighty -three passing upwards into the 
 incumbent formations.* 
 
 Be this as it may, the Black River Limestone, No. 15., contains 
 certain forms of Orthoceras of enormous size (some of them 8 or 
 9 feet long !), of the subgenera Ormoceras and Endoceras, seeming 
 to represent the Lower Silurian or Orthoceras limestone of Sweden. 
 Moreover, the general facies of the fauna of all these beds is 
 essentially similar. Another ground for extending our comparison 
 of the Llandeilo beds of Europe as far down as the calciferous 
 sandstone is derived from the researches of Mr. Logan in Canada, 
 and the study by Mr. Salter of the fossils collected by the Cana- 
 dian Surveyor near the S. E. end of the Ottawa River, where one 
 mass of limestone incloses species common to all the beds from 
 the Calciferous Sandstone (No. 18.) up to the Trenton Limestone 
 (No. 14.). In this rock, the Asaphus gigas and other well-known 
 Trenton species are blended with the Maclurea (a left-handed 
 Euomphalus, fig. 606.), a genus characteristic of the Chazy Lime- 
 
 Fossilsfrom Allumette Rapids, River Ottawa, Canada, 
 Fig. 606. 
 
 Maclurea Logani, Salter. 
 a. view of the shell. b. its curious operculum. 
 
 Fig. 607. stone, or No. 17; and Murchisonia gracilis 
 
 (fig. 607.) is another Trenton Limestone species 
 found in the same Silurian limestone of Ca- 
 nada | ; while one of the . most common shells 
 in it is the Raphistomat (Euomphalus) uni- 
 angulatum. Hall, a species characteristic in 
 New York of the Calciferous Sandstone itself. 
 , Haii. In Canada, as in the State of New York, the 
 A fossil characteristic of Potsdam Sandstone underlies the above-men- 
 
 the Trenton Limestone. . 
 
 The genus is common in tioned calcareous rocks, but contains a different 
 
 Lower Silurian rocks. . _ ... .,, , , ,, , . , 
 
 suite of fossils, as will be hereafter explained. 
 In parts of the globe still more remote from Europe the Silurian 
 strata have also been recognized, as in South America, Australia, 
 and recently by Captain Strachey in 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 
 
 * Hall Forster and Whitney's Report f Logan. Report, Brit. Assoc. Ipswich, 
 on Lake Superior, Pt. II. 1851. pp. 59. 63. 
 
CH. XXVIT.] CAMBRIAN GROUP. 451 
 
 quite unfounded, geographical provinces having evidently existed in 
 the oldest as in the most modern times.* 
 
 Whether the Silurian rocks are of deep-water origin. The 
 grounds relied upon by Professor E. Forbes for inferring that the 
 larger part of the Silurian Fauna is indicative of a sea more than 70 
 fathoms deep, are the following : first, the small size of the greater 
 number of conchifera ; secondly, the paucity of pectinibranchiata (or 
 spiral univalves) ; thirdly, the great number of floaters, such as 
 Bellerophon, Orthoceras, &c. ; fourthly, the abundance of orthidiform 
 brachiopoda ; fifthly, the absence or great rarity of fossil fish. 
 
 It is doubtless true that some living Terebratulce, on the coast of 
 Australia, inhabit shallow water ; but all the known species, allied 
 in form to the extinct Orthis, inhabit the depths of the sea. It 
 should also be remarked that Mr. Forbes, in advocating these views, 
 was well aware of the existence of shores, bounding the Silurian sea 
 in Shropshire, and of the occurrence of littoral species of this early 
 date in the northern hemisphere. Such facts are not inconsistent 
 with his theory ; for he has shown, in another work, how, on the 
 coast of Lycia, deep sea strata are at present forming in the Medi- 
 terranean, in the vicinity of high and steep land. 
 
 Had we discovered the ancient delta of some large Silurian 
 river, we should doubtless have known more of the shallow-water, 
 brackish-water, and fluviatile animals, and of the terrestrial flora of 
 the period under consideration. To assume that there were no such 
 deltas in the Silurian world, would be almost as gratuitous an 
 hypothesis, as for the inhabitants of the coral islands of the Pacific 
 to indulge in a similar generalization respecting the actual condition 
 of the globe. 
 
 CAMBRIAN GROUP. 
 
 Upper Cambrian. We have next to consider the fossiliferous 
 strata that occupy a lower position than the "Llandeilo beds," 
 which last form, as we have seen, the Lower division of the great 
 Silurian series, as originally defined by Sir R. Murchison. In 
 the Appendix to his important work before cited f, Sir Roderick 
 has given, on the authority of Mr. Salter, a list of no less than 
 96 species of fossils (of which specimens have been examined 
 either by himself or Prof. McCoy), all common to the Upper and 
 Lower Silurian strata, or, in other words, which, being found 
 either in the Ludlow or Wenlock beds, are also met with in the 
 Llandeilo formation. The range upwards of so many species from 
 the inferior to the superior group shows that, independently of 
 the link supplied by the Caradoc or Middle Silurian, there is such 
 a connection between the two principal divisions, as makes it 
 natural to assign the whole to one great period. To attempt, there- 
 fore, to give a new name to the Llandeilo beds, or to call them 
 Cambrian, as has been recently proposed by some geologists, would 
 
 * E. Forbes, Anniv. Address, 1854. f Siluria, p. 485. 
 Quart. Journ. Geol. Soc., vol. x. p. 38. 
 
 Q 2 
 
452 
 
 LINGULA FLAGS OF NORTH WALES. [Cn. XXVII. 
 
 be to act in violation of the ordinary rules of classification, and 
 would create much confusion, by disturbing a nomenclature long re- 
 ceived and originally established on well-defined paleontological data. 
 In Shropshire, the classical region, where the type of the Silurian 
 group was first made out by Murchison, the formations subjacent to 
 the Llandeilo consisted of quar,tzose rocks, sterile of fossils, or 
 yielding little more than some obscure fucoids. In North Wales, 
 Professor Sedgwick found below the Bala Limestone, long since 
 recognized as the equivalent of the Llandeilo flags, a vast thickness 
 of sedimentary and volcanic rocks, the lithological characters and 
 physical features of which he studied assiduously for years, dividing 
 them into well-marked formations, to which he affixed names. 
 Collectively they constituted the chief part of the rocks called by 
 him " Cambrian." They were devoid of limestone ; but in a group 
 of micaceous sandstones Mr. E. Davis discovered in 1846 the Lin- 
 gula named after him, and from which the name of " Lingula flags " 
 has since been derived. In these flags, about 1500 or 2000 feet in 
 thickness, several other fossils were afterwards found, of different 
 species from those in the Llandeilo beds. Amongst them, trilobites, 
 Agnostus and Conocephalus (for genus, see fig. 614.), and some rare 
 Brachiopoda and Bryozoa, still unpublished by our Government 
 surveyors, have been detected, and in the inferior black slates of 
 North Wales a trilobite called Paradoxides (for genus, see fig. 613.), 
 a form still more characteristic of this era, together with another of 
 the genus Olenus (fig. 610.), and a phyllopod crustacean (fig. 608. X 
 
 Fossils of the " Lingula Flags," or lowest Fossilfferous Rocks of Britain. 
 Fig. 608. Fig. 609. Fig. 610. 
 
 Hymenocaris vermtcauda 
 
 Salter. 
 
 A Phyllopod Crustacean 
 nat. size. 
 
 Lingula Davisii, M'Coy. 
 
 a. $ natural size. 
 
 b. distorted by cleavage. 
 
 " Lingula Flags" of Dolgelly, and Ffestiniog ; N. Wales. 
 
 Olenus micrurus, 
 
 Salter. 
 i nat. size. 
 
 I have before observed, that between the Bala Limestone and the 
 Lingula Flags there is a thickness of 11,000 feet of strata, in which 
 Graptolites and certain species of Asaphus, Calymene, and Ogygia 
 occur. These may be referred at present to the Silurian series, but 
 the exact limits between them and the Lingula Flags cannot yet be 
 assigned. 
 
 We might have anticipated, as already remarked, p. 446., that, 
 whenever a fossil Fauna was discovered in the Cambrian strata, it 
 would be found to consist of distinct species, and even, to a large 
 extent, of distinct genera; for, although geological periods are of 
 very unequal value in regard to the lapse of time (see p. 104.), and 
 
CH. XXVII.] LOWER CAMBRIAN. 453 
 
 our lines of separation may often be somewhat arbitrary, yet in no 
 part of the world have we hitherto examined a succession of rocks 
 having so great a thickness as 45,000 feet, even where they are made 
 up in part of volcanic materials, which have been referred to one 
 period as being characterized by one and the same fauna. 
 
 The first formation mentioned by Prof. Sedgwick, beneath the Bala 
 Limestone (and its associated beds of sandstone) in N. Wales, are 
 certain beds, 7000 feet thick, called the Arenig slates and porphyry. 
 Under them he finds the Tremadoc Slates, 1000 feet thick, and next 
 the Lingula Flags, already described, 1500 feet or more, which, in 
 accordance with views first put forward by Mr. Salter, I have 
 referred provisionally to an Upper Cambrian group. 
 
 Lower Cambrian. To the Lingula Flags last enumerated, another 
 series, called by Prof. Sedgwick the Bangor Group, succeeds in the 
 descending order, comprising, 1st, the Harlech Grits, 500 feet thick, 
 and next the Llanberis Slates, 1000 feet. These formations have 
 as yet proved barren of organic remains in N. Wales ; but in Ireland, 
 immediately opposite Anglesea and Caernarvon, rocks of the same 
 mineral character as the Bangor Group, and occupying precisely the 
 same place in the geological series, have afforded two species of 
 zoophytes, to which Professor Forbes has given the name of Oldhamia 
 (figs. 611 and 612.). The position of these rocks has been decided 
 
 The most Ancient Fossils yet known (1854). 
 
 Fig. 612. 
 
 Fig. 611. 
 
 Oldhamia radiata, Forbes. 
 Wicklow, Ireland. 
 
 Oldhamia antiqua, Forbes. 
 Wicklow, Ireland. 
 
 by the Government Surveyors, and confirmed by Sir R. Murchison, 
 so that here we behold the relics of the most ancient organic bodies 
 yet known. We are of course unable at present to determine 
 whether they belong to the same fauna as the fossils of the "Lin- 
 gula Flags," or to an older one. The beds containing them may 
 provisionally be called Lower Cambrian, for it will always happen 
 that our inquiries will terminate downwards in rocks affording very 
 imperfect materials for classification. This will continue to be the 
 case, however many steps we may make in future in penetrating 
 into the remoter annals of the past. 
 
 G G 3 
 
454 
 
 PRIMORDIAL GROUP OF BOHEMIA. [Cn. XXVII. 
 
 Bohemia. M. Barrande, in his admirable monograph on the Pa- 
 leozoic rocks of Bohemia, has laid much stress on the distinctness 
 and isolation of what he calls the " Protozoic schists," which attain 
 a thickness of 1200 feet, and lie at the base of the whole Silurian 
 group, as defined by him. These schists have no limestone associated 
 with them, and are regarded by M. Barrande as contemporaneous 
 with the " Lingula Flags " of N. Wales. So far as he has yet 
 carried his researches, this " primordial fauna," as he designates it, 
 has yielded scarcely any other fossils than Trilobites, the other 
 animal remains consisting of a Pteropod, some Cystideae, and an 
 Orthis, all of new and peculiar species. Of the Trilobites, even the 
 genera, with the exception of one (Agnostus, figs. 615 and 616.), are 
 peculiar. These genera are Paradoxides ^(see fig. 613.), of which 
 there are no less than twelve species, Conocephalus (fig. 614.), Ellip- 
 
 Fossils of the lowest Fossiliferous Beds in Bohemia, or " Primordial Zone " of Barrande, 
 Fig. 613. Fig. 614. 
 
 Conocephalus strialus, Emmrich. 
 
 | nat. size. 
 Ginetz and Skrey. 
 
 Paradoxides Bohemicus, Barr. 
 About one third natural size. 
 " Lowest Silurian beds " of 
 
 Ginetz, Bohemia. 
 (Etage C. of Barrande.) 
 
 Fig. 615. 
 
 Agnostus integer, Bey rich. 
 Nat. size and magnified. 
 
 Fig. 616. 
 
 Agnostus Rex, Barr. 
 Nat. size, Skrey. 
 
 socephalus, Sao (fig. 617.), Arionellus, 
 and Hydrocephalus. They have all a 
 facies of their own, dependent on the 
 multiplication of their thoracic seg- 
 ments, and the diminution of their 
 caudal shield or pygidium. 
 
 All the Bohemian species differ as 
 
 hmuta, Barrande, i^ its various yet from any found in England, which 
 the may be owing chiefly to the very small 
 aber as yet known in Great Britain ; 
 morphosis progresses, b, c, the body or jt may be due entirely to the influ- 
 
 segments begin to be developed ; in * . _ 
 
 the stage d the eyes are introduced, enCC OI geographical CaUSCS it Seems 
 
 i animal, nevertheless to confirm the view here 
 taken, of the " primordial zone " being 
 characterized by fossils distinguishable from the Llandeilo, or 
 Lower Silurian group ; because the other and higher Silurian for- 
 mations of Barrande have each of them many species in common 
 with the successive subdivisions of the British series. 
 
 The 
 
 true size, in the youngest state, a, 
 no segments are visible ; as the meta 
 
 but the 
 pleted ; 
 half its true size, is shown. 
 
CH. XXVII.] POTSDAM SANDSTONE OF N. AMERICA. 455 
 
 One of the so-called " primordial " Trilobites of the genus Sao, 
 a form not found as yet elsewhere in the world, has afforded M. Bar- 
 rande a fine illustration of the metamorphosis of these creatures ; 
 for he has traced them through no less than twenty stages of their 
 development. A few of these changes have been selected for repre- 
 sentation 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. When we reflect on the altered and crys- 
 talline condition usually belonging to rocks of this age, and how 
 devoid of life they are for the most part in North Wales, Ireland, 
 and Shropshire, the information respecting such minute details of 
 the Natural History of these crustaceans, as is supplied by the Bo- 
 hemian strata, may well excite our astonishment, and may reasonably 
 lead us to indulge a hope that geologists may one day gain an insight 
 into the condition of the planet and its inhabitants at eras long an- 
 tecedent to the Cambrian ; for those parts of the globe which have 
 been subjected to a scrutiny as rigorous as North Wales and Bohemia 
 are insignificant spots, and we are every day discovering new areas, 
 especially in the United States and Canada, where beds as old as the 
 " primordial schists," or older, may be studied. 
 
 Sweden and Norway. The Lingula Flags of North Wales, and 
 the "primordial schists" of Bohemia, are represented in Sweden by 
 strata, the fossils of which have been described by an able naturalist, 
 M. Angelin, in his " Palaeontologica Suecica (1852-4)." The "alum 
 schists," as they are called in Sweden, resting on a fucoid-sandstone, 
 contain trilobites 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 seg- 
 ments scarcely developed, and others again have the number of seg- 
 ments excessively multiplied, as in Paradoxides. These peculiarities 
 agree with the characters of the crustaceans met with in the Upper 
 Cambrian strata, before mentioned. 
 
 United States and Canada. In the table, at p. 448., I have 
 already pointed out the relative position of the Potsdam Sandstone, 
 which ha's long been known as the lowest fossiliferous formation in 
 the United States and Canada. I have seen it on the banks of the 
 St. Lawrence in Canada, 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 Britain, and 
 replete with a small round-shaped Lingula 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. This formation, as we 
 learn from Mr. Logan, is 700 feet thick in Canada ; the lower portion 
 consisting of a conglomerate with quartz pebbles ; the upper part of 
 sandstone containing fucoids, and perforated by small vertical holes, 
 which are very characteristic of the rock, and appear to have been 
 made by annelids (Scolithus linearis). 
 
 On the banks of the St. Lawrence, near Beauharnois and else- 
 
 G G 4 
 
456 FOOTPRINTS NEAR MONTREAL. [Cn. XXVII. 
 
 where, many fossil footprints have been observed on the surface of 
 its rippled layers. These impressions were first noticed by Mr. 
 Abraham, of Montreal, in 1847, and were supposed to be tracks of a 
 tortoise ; but Mr. Logan has since brought some of the slabs to 
 London, together with numerous casts of other slabs, enabling Pro- 
 fessor Owen to correct the idea first entertained, and to decide that 
 they were not due to a chelonian, nor, as he imagines, to any vertebrate 
 creature. The Hunterian Professor inclines to the belief that they 
 are the trails of more than one species of articulate animal, probably 
 allied to the King Crab, or Limulus. Between the two rows of 
 foot-tracks runs an impressed median line or channel, supposed by 
 the Professor to have been made by a caudal appendage rather than 
 by a prominent part of the trunk. Some individuals appear to have 
 had three, and others five pairs, of limbs used for locomotion. The 
 width of the tracks between the outermost impressions varies from 3 
 to 5J- inches, which would imply a creature of much larger dimen- 
 sions than any organic body yet obtained from strata of such an- 
 tiquity. Their size alone is therefore important, as warning us of the 
 danger of drawing any inference, from mere negative evidence, 
 as to the extreme poverty of the fauna of the earlier seas. 
 
 Mr. Logan informs us *, that the Lower Silurian strata and the 
 Potsdam Sandstone in Canada rest unconformably on a still older 
 series of aqueous rocks, which, as he says, may be Cambrian (Lower 
 Cambrian, or, perhaps, still older ?), and which include conglomerates 
 and beds of limestone. In both of these, nodules of phosphate of lime 
 are frequently observed. That these contorted rocks are of aqueous 
 origin, he infers from the presence of quartz pebbles in the conglo- 
 merates. Together with the associated igneous masses, this ancient 
 series attains a thickness of at least 10,000 feet, in the Lake Huron 
 district, and includes the copper-bearing rocks of that part of Canada. 
 Below these again lies gneiss, with interstratified marble, in which 
 crystals of phosphate of lime both large and small are not uncommon. 
 This phosphate, as Mr. Logan suggests, may have " a possible con- 
 nection with life in those ancient rocks." 
 
 In the frontispiece to this volume, and in fig. 83. p. 59., the reader 
 may refer to a section on the coast of Scotland where the Devonian 
 strata lie unconformably on the highly inclined Silurian schists, and 
 I have cited the eloquent reflections of Playfair when he looked, with 
 his teacher Hutton, " so far into the abyss of time." But in the lake 
 district of N. America, the Potsdam Sandstone, forming the upper or 
 horizontal series, is older than even the inclined strata of St. Abb's 
 Head in Scotland. In Canada again, we behold the monuments of 
 still another period in the remote distance, attesting, as Playfair 
 exclaimed, " how much farther the reason may go than the imagina- 
 tion can venture to follow." 
 
 Valley of the Upper Mississippi. Mr. Dale Owen has recently 
 published a graphic sketch, in his survey of Wisconsin (1852), of 
 the lowest sedimentary rocks near the head-waters of the Mississippi, 
 
 * Quart. Geol. Journ., vol. viii. p. 210. 
 
CH. XXVII.] PERIOD OF INVERTEBRATE ANIMALS. 
 
 457 
 
 Fig. 618. 
 
 lying at the base of the whole Silurian series. They are many 
 hundred feet thick, and for the most part 
 similar in character to the Potsdam Sandstone 
 above described, but including in their upper 
 portions intercalated bands of inagnesian 
 limestone, and in their lower some argilla- 
 ceous beds. Among the shells of these strata 
 are species ofLingula andOrthis, and several 
 trilobites of the new genus Dikelocephalus 
 (fig. 618.). These rocks, occurring in Iowa, 
 Wisconsin, and Minnesota, seem destined 
 hereafter to throw great light on the state 
 of organic life in the Cambrian period. Six 
 beds containing trilobites, separated by strata 
 Mmnesotensis, f rom 10 to 150 feet thick, are already enu- 
 
 Dale Owen. | diameter. * 
 
 A large crustacean of the Olenoid merated. 
 group. Potsdam Sandstone. T> j . / 0-7 j /-r i 
 
 Falls of st. croix, on the upper Relation oj Silurian and Cambrian 
 issippi> Faunas. That there is a considerable con- 
 
 nection between the Cambrian and Lower Silurian faunas, not- 
 withstanding that nearly every species maybe distinct, seems evident ; 
 but it may not be a closer one than that existing between the Upper 
 Silurian and Devonian. This I infer from the following facts, that in 
 Bohemia, where the Cambrian or primordial fauna of Barrande is best 
 developed, it consists mainly of Trilobites ; and of this order more 
 than two thirds of the genera and all the species, more than twenty in 
 number, are, with one exception (Agnostus pisiformis), distinct from 
 the Silurian. But M. Barrande observes that out of thirty-nine 
 Silurian genera of Trilobites, no less than eleven pass upwards into 
 the Devonian. If, therefore, we had only trilobites in the latter, its 
 generic relationship to the Silurian fauna would appear greater than 
 that of the Silurian to the Cambrian. And, though the details of 
 the English rocks of this age are not yet fully known, the species at 
 least appear all to be distinct. The same holds good with regard to 
 the fossils of the Swedish strata, and, as we have seen, to those of 
 America. 
 
 A distinctive character, therefore, is given to the fauna of this 
 period, by which we seem to be carried one step further back into 
 the history of organic life. 
 
 Supposed Period of Invertebrate Animals. 
 
 We have seen that in the upper part of the Silurian system a 
 bone-bed occurs near Ludlow, in which the remains of fish are abun- 
 dant, and amongst them some of a highly organized structure, referred 
 to the genus Onchus. We are indebted to Sir R. Murchison for 
 having first announced, in 1840, the discovery of these ichthyolites, 
 and he then spoke of them as "the most ancient beings of their 
 class." In his new and excellent work, entitled " Siluria " (p. 239.), 
 he reverts to the opinion formerly expressed by him, and observes 
 
458 UPPER SILURIAN BONE-BED. [Cn. XXVII. 
 
 that the active researches of the last fourteen years in Europe and 
 America " have failed to modify that generalization," adding " the 
 Silurian system, therefore, may be regarded as representing a long 
 early period, in which no vertebrated animals had been called into 
 existence." 
 
 It is certainly a fact well worthy of our attention, that as yet no 
 remains of fish are on record as coming from any stratum older than 
 the base of the " Upper Ludlow." (See above, p. 436.) When we re- 
 flect on the number of Mollusks, Echinoderms, Corals, Trilobites, 
 and other fossils already obtained from Silurian strata below " the 
 Ludlow," we may well ask, whether any other set of fossiliferous 
 formations were ever studied with equal diligence and over so vast 
 an area without yielding some ichthyolites. 
 
 Nevertheless, we must be permitted to hesitate before we accept, 
 even on such evidence, so sweeping a conclusion, as that the globe, 
 for ages after it was habitable by all the great classes of inverte- 
 brata, remained wholly untenanted by vetebrate animals. In the first 
 place, we must remember that we have detected no insects, or land- 
 shells, or freshwater pulmoniferous mollusks, or terrestrial crus- 
 taceans, or plants (except fucoids), in rocks below the Upper 
 Silurian. Their absence may admit of explanation, by supposing all 
 the deposits of that era hitherto examined to have been formed in 
 seas far from land or beyond the influence of rivers. Here and 
 there indeed a shallow -water, or even a littoral deposit may have 
 been met with, as in North Wales, for example, and North America ; 
 but, speaking generally, the Silurian deposits, as at present known, 
 have certainly a more pelagic character than any other equally im- 
 portant formations. 
 
 It is a curious fact, and not perhaps a mere fortuitous coincidence, 
 that the only stratum which has yielded the remains of land- 
 plants is also the only one which has afforded the bones of fish. 
 Bone-beds in general, such as that of the Lias near Bristol, those of 
 the Trias near Stuttgardt, of the Carboniferous Limestone near 
 Bristol and Armagh, and lastly that of the " Upper Ludlow," are 
 remarkable for containing teeth and bones, much rolled and im- 
 plying transportation from a distance. The association of the spores 
 of Lycopodiaceae (see p. 436.) with the Ludlow fish-bones shows that 
 plants had been washed from some dry land, then existing, and had 
 been drifted into a common submarine receptacle with the bones. 
 More usually, however, the " Upper Ludlow," like the " Lower 
 Silurian," is devoid of plants and equally destitute of ichthyolites. 
 
 It has been suggested that Cephalopoda were so abundant in the 
 Silurian period that they may have discharged the functions of fish ; 
 to which we may reply that both classes coexisted in the Upper Silu- 
 rian period, and both of them swarmed together in the Carboniferous 
 and Liassic seas, as they do now in certain parts of the ocean. We 
 may also suggest that we are too imperfectly acquainted with the 
 distribution of scattered bones and teeth or the skeletons of dead 
 fish on the floor of the existing ocean, to have a right to theorise 
 
CH. XXVII.] ABSENCE OF FISH IN LOWER SILURIAN. 459 
 
 with confidence on the absence of such relics over wide spaces at 
 former eras. 
 
 They who in our own times have explored the bed of the sea inform 
 us that it is in general as barren of vertebrate remains as the soil of 
 a forest on which thousands of mammalia and reptiles may have 
 flourished for centuries. In the summer of 1850, Prof. E. Forbes 
 and Mr. McAndrew dredged the bed of the British seas from the Isle 
 of Portland to the Land's End in Cornwall, and thence again to Shet- 
 land, recording and tabulating the numbers of the various organic 
 bodies brought up by them in the course of 140 distinct dredgings, 
 made at different distances from the shore, some a quarter of a mile, 
 others forty miles distant. The list of species of marine invertebrate 
 animals, whether Radiata, Mollusca, or Articulata, was very great, 
 and the number of individuals enormous ; but the only instances of 
 vertebrate animals consisted of a few ear-bones and two or three 
 vertebrae of fish, in all not above six relics. 
 
 It is still more extraordinary that Mr. McAndrew should have 
 dredged the great "Ling Banks" or cod-fishery grounds off the 
 Shetland Islands for shells without obtaining the bones or teeth of 
 any dead fish, although he sometimes drew up live fish from the 
 mud. This is the more singular, because there are some areas where 
 recent fish-bones occur in the same northern seas in profusion, as I 
 have shown in the " Principles of Geology " (see Index, " Vidal ") ; 
 two bone-beds having been discovered by British hydrographers, one 
 in the Irish sea, and the other in the sea near the Faroe Isles, the first 
 of them two, and the other three and a half miles in length, where 
 the lead brings up everywhere the vertebras of fish from various 
 depths between 45 to 235 fathoms. These may be compared to the 
 Upper Ludlow bone-bed ; and on the floor of the ocean of our times, 
 as on that of the Silurian epoch, there are other wide spaces where 
 no bones are imbedded in mud or sand. 
 
 It may be true, though it sounds somewhat like a paradox, that 
 fish leave behind them no memorials of their presence in places 
 where they swarm and multiply freely ; whereas currents may drift 
 their bones in great numbers to regions wholly destitute of living 
 fish. Such a state of things would be quite analogous to what 
 takes place on the habitable land, where, instead of the surface 
 becoming encumbered with heaps of skeletons of quadrupeds, 
 birds, and land-reptiles, all solid bony substances are removed after 
 death by chemical processes, or by the digestive powers of pre- 
 daceous beasts ; so that, if at some future period a geologist should 
 seek for monuments of the former existence of such creatures, he 
 must look anywhere rather than in the area where they flourished. 
 He must search for them in spots which were covered at the time 
 with water, and to which some bones or carcases may have been 
 occasionally carried by floods and permanently buried in sediment. 
 
 In the annexed 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 how gradual has been our progress in 
 
460 PROGRESSIVE DISCOVERY OF VERTEBRATA [Cn. XXVII. 
 
 tracing back the signs 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 introduction 
 of any one class of beings upon the earth. 
 
 Dates of the Discovery of different Classes of Fossil Vertebrata ; 
 showing the gradual Progress made in tracing them to Bocks of 
 higher Antiquity. 
 
 Year. Formations. 
 
 C 1798. Middle Eocene (or B. i. p. 223.). 
 
 Mammalia. 
 
 Aves. 
 
 Lower Oolite. 
 Upper Trias. 
 
 Middle Eocene (or B. i. p. 223.). 
 Lower Eocene. 
 
 Eeptilia. 
 
 Pisces. 
 
 1709. 
 1793. 
 
 1828. 
 1840. 
 
 Geographical Localities. 
 Paris (Gypsum of 
 
 Montmartre). 1 
 Stonesfield. 2 
 Stuttgardt. 3 
 
 Paris (Gypsum of 
 
 Montmartre). 4 
 London (Sheppey 
 
 Clay). 5 
 
 Thuringia. 6 
 
 Saarbruck,near Tre ves. 1 
 Elgin. 8 
 
 Thuringia. 9 
 Glasgow. lo 
 
 Permian (or Zechstein). 
 Carboniferous. 
 Upper Devonian. 
 
 Permian (or Kupfer-schiefer). 
 Carboniferous (Mountain Lime- 
 stone). 
 
 Devonian. Caithness. 11 
 
 Upper Silurian. Ludlow. 12 
 
 1 Cuvier (George). Bulletin Soc. Philom. xx. Scattered bones were found in 
 the gypsum some years before ; but they were determined osteologically, and 
 their true geological position was assigned to them in this memoir. 
 
 2 In 1818, Cuvier, visiting the Museum of Oxford, decided on the mammalian 
 character of a jaw from Stonesfield. See also above, p. 312. 
 
 3 Plieninger, Prof. See above, p. 342. 
 
 4 M. Darcet discovered, and Lamanon figured, as a fossil bird, some remains 
 from Montmartre, afterwards recognized as such by Cuvier ( Ossemens Foss., Art. 
 *' Oiseaux "). 
 
 5 Owen, Prof., Geol. Trans. 2nd Ser. vol. vi. p. 203., 1839. The fossil bird dis- 
 covered in the same year in the slates of Glaris in the Alps, and at first referred 
 to the chalk, is now supposed to belong to the Nummulitic beds, and may there- 
 fore be of newer date than the Sheppey Clay. 
 
 6 The fossil monitor of Thuringia (Protorosaurus Speneri, V. Meyer) was figured 
 by Spener, of Berlin, in 1810. (Miscel. Berlin.) 
 
 7 See above, p. 401. 
 
 8 See above, p. 416. 
 
 9 Memorabilia Saxonise Subterr., Leipsic, 1709. 
 
 > History of Rutherglen, by Kev. David Ure, 1793. 
 
 11 Sedgwick and Murchison, Geol. Trans., 2nd Ser. vol. iii. p. 141., 1828. 
 
 12 Sir R. Murchison. See above, p. 435. 
 
 Obs. The evidence derived from footprints, though often to be relied on, is omit- 
 ted in the above table, as being less exact than that founded on bones and teeth. 
 
 How many living writers are there who, before the year 1844, 
 generalized fearlessly on the non-existence of reptiles before the 
 Permian era ! Yet, in the course of ten years, they have lived to see 
 the earliest known date of the creation of reptiles carried back suc- 
 cessively, first to the Carboniferous, and then to the Upper Devonian 
 periods. Before the year 1818, it was the popular belief that the 
 Palseotherium of the Paris gypsum and its associates were the first 
 warm-blooded quadrupeds that ever trod the surface of this planet. 
 
CH. XXVII.] IN OLDER ROCKS. 461 
 
 So fixed was this idea in the minds of the majority of naturalists, 
 that, when at length the Stonesfield Mammalia awoke from a slumber 
 of three or four great periods, the apparition failed to make them 
 renounce their creed. 
 
 " Unwilling I my lips unclose 
 Leave, oh, leave me to repose." 
 
 First, the antiquity of the rock was called in question ; and then 
 the mammalian character of the relics. Even long after all contro- 
 versy was set at rest on these points, the real import of the new 
 revelation, as bearing on the doctrine of progressive development, 
 was far from being duly appreciated. 
 
 It is clear that the first two or three species, encountered in any 
 country or in the rocks of any epoch, cannot be taken as a type or 
 standard for measuring the grade of organization of any terrestrial 
 fauna, ancient or modern. Suppose that the two or three oolitic 
 species first brought to light had really been all marsupial, as was for 
 a time erroneously imagined, this would not have borne out the 
 inference which some attempted to deduce from it, namely, that the 
 time had not yet come for the creation of the placental tribes. Or, 
 if when some monodelph were at last actually recognized (at Stones- 
 field), they happened to be of diminutive size, and to belong to the 
 insectivora, we are not entitled to deduce from such data that the 
 oolitic fauna ranked low in the general scale, as the insectivora may 
 do in an existing fauna. The real significance of the discoveries 
 alluded to arises from the aid they afford us in estimating the true 
 value of negative evidence, when brought to bear on certain specu- 
 lative questions. Every zoologist will admit that between the first 
 creation and the final extinction of any one of the five* oolitic 
 mammalia now known there were many successive generations ; and, 
 if the geographical range of each species was limited (which we 
 have no right to assume), still there must have been several hun- 
 dred individuals in each generation, and probably, when the species 
 reached its maximum, several thousands. When, therefore, we en- 
 counter for the first time in 1854 two or three jaws of a Spalacothe- 
 rium in the Purbeck limestone, after countless specimens of Mollusca 
 and Crustacea, and hundreds of insects, fish, and reptiles had been 
 previously collected from the same beds, we are not simply taught that 
 these individual quadrupeds flourished at the era in question, but that 
 thousands, perhaps hundreds of thousands, of the same species peopled 
 the land without leaving behind them any trace of their existence, 
 whether in the shape of fossil bones or footprints ; or, if they left 
 any traces, these have eluded a long and most persevering search. 
 
 Moreover, we must never forget how many of the dates given in the 
 
 * I had written four, but while this Stereognathus ooliticus. It is more than 
 sheet was passing through the press twice the size of any of the species pre- 
 ( Sept. 26, 1854) the disco very of another viously obtained from the same forma- 
 species of insectivorous mammal from tion. We have now, therefore, including 
 Stonesfield was announced to the British the recently found Spalacotherium of 
 Association at Liverpool by Mr. Charles- Purbeck (see p. 296. ), five British mam- 
 worth, who has given to it the name of malia from the oolite. 
 
462 VERTEBRATA IN THE [Cn. XXVII. 
 
 above table (p. 460.), are due to British skill and energy, Great Britain 
 being still the only country in which mammalia have been found in 
 Oolitic rocks ; the only region where any reptiles have been detected 
 in strata as old as the Devonian ; the only one wherein the bones of 
 birds have been traced back as far as the London Clay. And, if 
 geology had been cultivated with less zeal in our island, we should 
 know nothing as yet of two extensive assemblages of tertiary mam- 
 malia of higher antiquity than the fauna of the Paris Gypsum 
 (already cited as having once laid claim to be the earliest that ever 
 flourished on the earth) namely, first, that of the Headon series 
 (see above, p. 213.); and, secondly, one long prior to it in date, and 
 antecedent to the London Clay.* This last has already afforded us 
 indications of Quadrumana, Cheiroptera, Pachydermata, and Mar- 
 supialia (see p. 218.). How then can we doubt, if every area on the 
 globe were to be studied with the same diligence, if all Europe, 
 Asia, Africa, America, and Australia were equally well known, that 
 every date assigned by us in the above Table for the earliest re- 
 corded appearance of fish, reptiles, birds, and mammals would have 
 to be altered ? Nay, if one other area, such as part of Spain, of the 
 size of England and Scotland, were subjected to the same scrutiny 
 (and we are still very imperfectly acquainted even with Great 
 Britain), each class of Vertebrata would probably recede one or 
 more steps farther back into the abyss of time : fish might penetrate 
 into the Lower Silurian, reptiles into the Lower Devonian, 
 mammalia into the Lower Trias, birds into the Chalk or Oolite, 
 and, if we turn to the Invertebrata, Trilobites and Cephalopods 
 might descend into the Lower Cambrian, and some stray zoophyte, 
 like the Oldhamia, into rocks now styled " azoic." 
 
 Yet, after these and many more analogous revisions of the Table, 
 it might still be just as easy as now to found a theory of progressive 
 development on the new set of positive and negative facts thus 
 established ; for the order of chronological succession in the different 
 classes of fossil animals would probably continue the same as now ; 
 in other words, our success in tracing back the remains of each class 
 to remote eras would be greatest in fishes, next in reptiles, next in 
 mammalia, and least in birds. That we should meet with ichthy- 
 olites more universally at each era, and at greater depths in the 
 series, than any other class of fossil vertebrata, would follow partly 
 from our having as paleontologists to do chiefly with strata of 
 marine origin, and partly, because bones of fish, however partial and 
 capricious their distribution on the bed of the sea, are nevertheless 
 more easily met with than those of reptiles or mammalia. In like 
 manner, the extreme rarity of birds in recent and Pliocene strata, 
 even in those of freshwater origin, might lead us to anticipate that 
 their remains would be obtained with the greatest difficulty in the 
 older rocks, as the Table proves to be the case, even in tertiary 
 
 * A bird's hone is recorded as having (beneath the London clay), by Mr. Prest- 
 been lately found in the Woolwich beds wich ; Geol. Quart. Journ. vol.x.p. 157. 
 
CH. XXVII.] OLDER FOSSILIFEROUS PERIODS. 463 
 
 strata, wherein we can more readily find deposits formed in lakes 
 and estuaries. 
 
 The only incongruity between the geological results, and those 
 which our dredging experiences might have led us to anticipate 
 a priori, consists in the frequency of fossil reptiles, and the com- 
 parative scarcity of mammalia. It would appear that during all the 
 secondary periods, not even excepting the newest part of the cre- 
 taceous, there was a greater development of reptile life than is now 
 witnessed in any part of the globe. The preponderance of this 
 class over the mammalia depended probably on climatal and geo- 
 graphical conditions, for we can scarcely refer it to "progressive 
 development," by which the vertebrate type was steadily improving, 
 or becoming more perfect, as Time rolled on. We cannot shut our 
 eyes to the positive proofs now obtained of the creation of mammalia 
 before the excess of reptiles had ceased, nay, apparently before it 
 had even reached its maximum. 
 
 In conclusion, I shall simply express my own conviction that we 
 are still on the mere threshold of our inquiries ; and that, as in the 
 last fifty years, so in the next half-century, we shall be called upon 
 repeatedly to modify our first opinions respecting the range in time 
 of the various classes of fossil Vertebrata. It would therefore be 
 premature to generalize at present on the non-existence, or even on 
 the scarcity of Yertebrata, whether terrestrial or aquatic, at periods 
 of high antiquity, such as the Silurian and Cambrian.* 
 
 * For observations on the rarity of air-breathers in the coal, see above, p. 405. 
 
464 TRAP ROCKS. [Cn. XXVIII, 
 
 CHAPTER XXVIII. 
 
 VOLCANIC ROCKS. 
 
 Trap rocks Name, whence derived Their igneous origin at first doubted 
 Their general appearance and character Volcanic cones and craters, how 
 formed Mineral composition and texture of volcanic rocks Varieties of 
 felspar Hornblende and augite Isomorphism Kocks, how to be studied 
 Basalt, trachyte, greenstone, porphyry, scoria, amygdaloid, lava, tuff Agglo- 
 merate Laterite Alphabetical list, and explanation of names and synonyms, of 
 volcanic rocks Table of the analyses of minerals most abundant in the vol- 
 canic and hypogene rocks. 
 
 THE aqueous or fossiliferous rocks having now been described, 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 
 
 Fig. 619. 
 
 a. Hypogene formations, stratffied and unstratified. 
 
 b. Aqueous formations. c. Volcanic rocks. 
 
 diagram, to represent the crystalline formations, such as the granitic 
 and metamorphic ; b b the fossiliferous strata ; and c c the volcanic 
 rocks. These last are sometimes found, as was explained in the first 
 chapter, breaking through a and 5, sometimes overlying both, and 
 occasionally alternating with the strata b b. They also are seen, in 
 some instances, to pass insensibly into the unstratified division of a, 
 or the Plutonic rocks. 
 
 When geologists first began to examine attentively the structure 
 of the northern and western parts of Europe, they were almost en- 
 tirely ignorant of the phenomena of existing volcanos. They found 
 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, and amygdaloid. All these, 
 which were recognized as belonging 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 ter- 
 races or steps on the sides of hills. This configuration appears to 
 be derived from two causes. First, the abrupt original terminations 
 of sheets of melted matter, which have spread, whether on the land 
 or bottom of the sea, over a level surface. For we know, in the 
 case of lava flowing from a volcano, that a stream, when it has 
 
CH. XXVIII.] CONES AND CRATERS. 465 
 
 ceased to flow, and grown solid, very commonly ends in a steep slope, 
 as at a, fig. 620. But, secondly, the step-like appearance arises 
 
 more frequently from the mode in which 
 horizontal masses of igneous rock, such 
 as b c, intercalated between aqueous 
 strata, or showers of volcanic dust and 
 ashes, have, subsequently to their origin, 
 been exposed, at different heights, by 
 denudation. Such an outline, it is true, 
 is not peculiar to trap rocks ; great beds 
 step-like appearance of trap. of ii mes tone, and other hard kinds of 
 stone, often presenting similar terraces and precipices: but these 
 are usually on a smaller scale, or less numerous, than the volcanic 
 steps, or form less decided features in the landscape, as being less 
 distinct in structure and composition from the associated rocks. 
 
 Although the characters of trap rocks are greatly diversified, the 
 beginner will easily learn to distinguish them as a class from the 
 aqueous formations. Sometimes they present themselves, as already 
 stated, in tabular masses, which are not divided by horizontal planes 
 of stratification in the manner of sedimentary deposits. Sometimes 
 they form chains of hills often conical in shape. Not unfrequently 
 they are seen as " dikes " or wall-like masses, intersecting fossili- 
 ferous beds. The rock is occasionally columnar, the columns some- 
 times decomposing into balls of various sizes, from a few inches to 
 several feet in diameter. The decomposing surface very commonly 
 assumes a coating of a rusty iron colour, from the oxidation of ferru- 
 ginous matter, so abundant in the traps in which augite or horn- 
 blende occur ; or, in the felspathic varieties of trap, it acquires a 
 white opaque coating, from the bleaching of the mineral called fel- 
 spar. On examining any of these volcanic rocks, where they have 
 not suffered disintegration, we rarely fail to detect a crystalline 
 arrangement in one or more of the component minerals. Sometimes 
 the texture of the mass is cellular or porous, or we perceive that it 
 has once jbeen full of pores and cells, which have afterwards become 
 filled with carbonate of lime, or other infiltrated mineral. 
 
 Most of the volcanic rocks produce a fertile soil by their disinte- 
 gration. It seems that their component ingredients, silica, alumina, 
 lime, potash, iron, and the rest, are in proportions well fitted for 
 the growth of vegetation. As they do not effervesce with acids, a 
 deficiency of calcareous matter might at first be suspected; but 
 although the carbonate of lime is rare, except in the nodules of 
 amygdaloids, yet it will be seen that lime sometimes enters largely 
 into the composition of augite and hornblende. (See Table, p. 479.) 
 Cones and Craters. In regions where the eruption of volcanic 
 matter has taken place in the open air, and where the surface has 
 never since been subjected to great aqueous denudation, cones and 
 craters constitute the most striking peculiarity of this class of form- 
 ations. Many hundreds of these cones are seen in central France, 
 in the ancient provinces of Auvergne, Velay, and Vivarais, where 
 
 H II 
 
466 
 
 COMPOSITION AND NOMENCLATURE [Ce. XXVIII. 
 
 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- 
 Fig. 621. 
 
 Part of the chain of extinct volcanos called the Monts Dome, Auvergne. (Scrope.) 
 
 shaped hill is well understood, the growth of many having been 
 watched during volcanic eruptions. A chasm or fissure first opens 
 in the earth, from which great volumes of steam and other gases are 
 evolved. The explosions are so violent as to hurl 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. Although 
 extremely heavy, this lava is forced up by the expansive power of 
 entangled gaseous fluids, chiefly steam or aqueous vapour, exactly in 
 the same manner as water is made to boil over the edge of' a vessel 
 when steam has been generated at the bottom by heat. Large 
 quantities of the lava are also shot up into the air, where it separates 
 into fragments, and acquires a spongy texture by the sudden enlarge- 
 ment of the included gases, and thus forms scorice, 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, dipping on all sides from a central axis. 
 In the mean time a hollow, called a crater, has been kept open in 
 the middle of the mound by the continued passage upwards of steam 
 and other 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. 621.), 
 and often it flows out from a fissure at the base of the hill, or at 
 some distance from its base.* 
 
 Composition and nomenclature. Before speaking of the connection 
 between the products of modern volcanos and the rocks usually styled 
 trappean, and before describing the external forms of both, and the 
 manner and position in which they occur in the earth's crust, it will 
 be desirable to treat of their mineral composition and names. The 
 varieties most frequently spoken of are basalt and trachyte, to which 
 
 * For a description and theory of active volcanos, see Principles of Geology, 
 chaps, xxiv. et seq. & xxxii. 
 
CH. XXVIII.] OF VOLCANIC ROCKS. 467 
 
 dolerite, greenstone, clinkstone, and others might be added; while 
 those founded chiefly on peculiarities of texture, are porphyry, 
 amygdaloid, lava, volcanic breccia or agglomerate, tuff, scoriae, and 
 pumice. It may be stated generally, that all these are mainly com- 
 posed of two minerals, or families of simple minerals, felspar and 
 hornblende; but the felspar preponderates greatly even in those 
 rocks to which the hornblendic mineral imparts its distinctive cha- 
 racter and prevailing colour. 
 
 The two minerals alluded to may be regarded as two groups, rather 
 than species. Felspar, for example, may be, first, common felspar 
 (often called Orthoclase), that is to say, potash-felspar, in which the 
 predominant alkali is potash (see Table, p. 479.) ; or, secondly, albite, 
 that is to say, soda-felspar, where the predominant alkali is soda 
 instead of potash ; or, thirdly, Oligoclase ; or, fourthly, Labrador- 
 felspar (Labradorite), which differs not only in its iridescent hues, 
 but also in its angle of fracture or cleavage, and its composition. 
 We also read much of two other kinds, called glassy felspar and 
 compact felspar, which, however, cannot rank as varieties of equal 
 importance, for both the albitic and common felspar appear some- 
 times in transparent or glassy crystals ; and as to compact felspar, it 
 is a compound of a less definite nature, sometimes containing largely 
 both soda and potash ; and which might be called a felspathic paste, 
 being the residuary matter after portions of the original matrix have 
 crystallized. The more recent analyses have shown that all the 
 varieties or species of felspar may contain both potash and soda, 
 although in some of them the one, and in others the other alkali 
 greatly prevails. 
 
 The hornblendic group consists principally of two varieties ; first, 
 hornblende, and, secondly, augite, which were once regarded as 
 very distinct, although now some eminent mineralogists are in doubt 
 whether they are not one and the same mineral, differing only as one 
 crystalline form of native sulphur differs from another. 
 
 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 
 Haiiy, Mohs, and other celebrated mineralogists. It was agreed that 
 the form of the crystals of the two species were different, and their 
 structure, as shown by cleavage, that 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 ; and that when this 
 happened, as in some lavas of modern date, the hornblende occurs in 
 the mass of the rock, where crystallization may have taken place more 
 slowly, while the augite merely lines cavities where the crystals may 
 have been produced rapidly. It was also remarked, that in the 
 
 H H 2 
 
468 THEORY OF ISOMORPHISM. [Cn. XXVIII. 
 
 crystalline slags of furnaces, augitic forms were frequent, the horn- 
 blendic entirely absent ; hence it was conjectured that hornblende 
 might be the result of slow, and augite of rapid cooling. This view 
 was confirmed by the fact, that Mitscherlich and Berthier were able 
 to make augite artificially, but could never succeed in forming horn- 
 blende. Lastly, Gustavus Hose fused a mass of hornblende in a 
 porcelain furnace, and found that it did not, on cooling, assume 
 its previous shape, but invariably took that of augite. The same 
 mineralogist observed certain crystals in rocks from Siberia which 
 presented a hornblende cleavage, while they had the external form 
 of augite. 
 
 If, from these data, it is inferred that the same substance 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 
 recognised by a peculiar crystalline 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. Unquestionably 
 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 recrystallizing, does not perhaps de- 
 monstrate their absolute identity. For there is often some portion 
 of the materials in a crystal which are not in perfect chemical com- 
 bination 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 excluded from perfect chemical 
 union ; and after fusion, when the mass recrystallizes, the same 
 elements may combine perfectly or in new proportions, and thus a 
 new mineral may be produced. Or some one of the gaseous elements 
 of the atmosphere, the oxygen for example, may, when the melted 
 matter reconsolidates, combine with some one of the component 
 elements. 
 
 The different quantity of the impurities or refuse above alluded to, 
 which may occur in all but the most transparent and perfect crystals, 
 may partly explain the discordant results at which experienced 
 chemists have arrived in their analysis of the same mineral. For the 
 reader will find that crystals of a mineral determined to be the same 
 by physical characters, crystalline form, and optical properties, have 
 often been declared by skilful analyzers to be composed of distinct ele- 
 ments. (See the table at p. 479.) This disagreement seemed at first 
 subversive of the atomic theory, or the doctrine that there is a fixed 
 and constant relation between the crystalline form and structure of 
 a mineral and its chemical composition. The apparent anomaly, 
 however, which threatened to throw the whole science of mineralogy 
 into confusion, was in a great degree reconciled to fixed principles 
 by the discoveries of Professor Mitscherlich at Berlin, who ascertained 
 
CH. XXVIII.] PYROXENE AMPHIBOLE. 469 
 
 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 to-oe, isos, equal, and juop^rj, morphe, form). Ac- 
 cording to this law, the ingredients of a given species of mineral are 
 not absolutely fixed as to their kind and quality ; but one ingredient 
 may be replaced by an equivalent portion of some analogous ingre- 
 dient. 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 cleavage planes, remain the same. These 
 vicarious substitutions, however, of particular elements cannot exceed 
 certain defined limits. 
 
 Pyroxene, a name of Haiiy's, is often used for augite in descrip- 
 tions of volcanic rocks. It is properly, according to M. Delesse, a 
 general name, under which Augite, Diallage, and Hypersthene may 
 be united, for these three are varieties of one and the same mineral 
 species, having the same chemical formula with variable bases. 
 
 Amphibole is in like manner a general term under which Horn- 
 blende and Actinolite may be united. 
 
 Having been led into this digression on some recent steps made in 
 the progress of mineralogy, I may here observe that the geological 
 student must endeavour as soon as possible to familiarize himself 
 with the characters of five at least of the most abundant simple 
 minerals of which rocks are composed. These are felspar, quartz, 
 mica, hornblende, and carbonate of lime. This knowledge cannot 
 be acquired from books, but requires personal inspection, and the 
 aid of a teacher. It is well to accustom the eye to know the appear- 
 ance of rocks under the lens. To learn to distinguish felspar from 
 quartz is the most important step to be first aimed at. In general 
 we may know the felspar because it can be scratched with the point 
 of a knife, whereas the quartz, from its extreme hardness, receives 
 no impression. But when these two minerals occur in a granular 
 and uncrystallized state, the young geologist must not be discouraged 
 if, after considerable practice, he often fails to distinguish them by 
 the eye atone. If the felspar is in crystals, it is easily recognized by 
 its cleavage ; but when in grains the blow-pipe must be used, for 
 the edges of the grains can be rounded in the flame, whereas those 
 of quartz are infusible. If the geologist is desirous of detecting the 
 varieties of felspar above enumerated, or distinguishing hornblende 
 from augite, it will often be necessary to use the reflecting gonio- 
 meter as a test of the angle of cleavage, and shape of the crystal. 
 The use of this instrument will not be found difficult. 
 
 The external characters and composition of the felspars are ex- 
 tremely different from those of augite or hornblende ; so that the vol- 
 canic rocks in which either of these minerals play a conspicuous part 
 are easily recognizable. But there are mixtures of the two elements 
 in very different proportions, the mass being sometimes exclusively 
 composed of felspar, and at other times largely of augite. Between 
 the two extremes there is almost every intermediate gradation ; yet 
 certain compounds prevail so extensively in nature, and preserve so 
 
 H H 3 
 
470 BASALT AUGITE TRACHYTE. [Cn. XXVIII. 
 
 much uniformity of aspect and composition, that it is useful in 
 geology to regard them as distinct rocks, and to assign names to 
 them, such as basalt, greenstone, trachyte, and others presently to 
 be mentioned. 
 
 Basalt As an example of rocks in which augite is a conspicuous 
 ingredient, basalt may first be mentioned. Although we are more 
 familiar with this term than with that of any other kind of trap, it 
 is difficult to define it, the name having been used so compre- 
 hensively, and sometimes so vaguely. It has been generally applied 
 to any trap rock of a black, bluish, or leaden-grey colour, having a 
 uniform and compact texture. Most strictly, it consists of an inti- 
 mate mixture of felspar, augite, and iron, to which a mineral of an 
 olive-green colour, called olivine, is often superadded, in distinct 
 grains or nodular masses. The iron is usually magnetic, and is often 
 accompanied by another metal, titanium. The term " Dolerite " is 
 now much used for this rock, when the felspar is of the variety called 
 Labradorite, as in the lavas of Etna. Basalt, according to Dr. Dau- 
 beny, in its more strict sense, is composed of " an intimate mixture 
 of augite with a zeolitic mineral which appears to have been formed 
 out of Labradorite by the addition of water, the presence of water 
 being in all zeolites the cause of that bubbling up under the blow- 
 pipe, to which they owe their appellation.* Of late years the 
 analyses of M. Delesse and other eminent mineralogists have shown 
 that the opinion once entertained, that augite was the prevailing 
 mineral in basalt, or even in the most augitic trap rocks, must be 
 abandoned. Although its presence gives to these rocks their dis- 
 tinctive character as contrasted with trachytes, still the principal 
 element in their composition is felspar. 
 
 Augite rock has, indeed, been defined by Leonhard as being made 
 up principally or wholly of augite j, and in some veinstones, says 
 Delesse, such a rock may be found ; but the greater part of what 
 passes by the name of augite rock is more rich in green felspar 
 than in augite. Amphibolite, in like manner, or Hornblende rock, 
 is a trap of the basaltic family, in which there is much hornblende, 
 and in which this mineral has been supposed to predominate ; but 
 Delesse finds, by analysis, that the felspar may be in excess, the 
 base being felspathic. 
 
 In some varieties of basalt the quantity of olivine is very great ; 
 and as this mineral differs but slightly in its chemical composition 
 from serpentine (see Table of Analyses, p. 479.), containing even a 
 larger proportion of magnesia than serpentine, it has been suggested 
 with much probability that in the course of ages some basalts highly 
 charged with olivine may be turned, by metamorphic action, into 
 serpentine. 
 
 Trachyte. This name, derived from rpaxvc, rough, has been 
 given to the felspathic class of volcanic rocks which have a coarse, 
 cellular paste, rough and gritty to the touch. This paste has 
 commonly been supposed to consist chiefly of albite, but according 
 
 * Voicanos, 2d ed. p. 18. f Mineralreich, 2d ed. p. 85. 
 
Cfi. XXVIII.] TRACHYTE PORPHYRY CLINKSTONE. 471 
 
 to M. Delesse it is variable in composition, its prevailing alkali being 
 soda. Through the base are disseminated crystals of glassy felspar, 
 mica, and sometimes quartz and hornblende, although in the trachyte, 
 properly so called, there is no quartz. The varieties of felspar which 
 occur in trachyte are trisilicates, or those in which the silica is to 
 the alumina in the proportion of three atoms to one.* 
 
 Trachytic Porphyry, according to Abich, has the ordinary com- 
 position of trachyte, with quartz superadded, and without any augite 
 or titaniferous iron. Andesite is a name given by Gustavus Rose to 
 a trachyte of the Andes, which contains the felspar called Andesin, 
 together with glassy felspar (orthoclase) and hornblende dissemi- 
 nated through a dark-coloured base. 
 
 Clinkstone, or Phonolite. Among the felspathic products of vol- 
 canic action, this rock is remarkable for its tendency to lamination, 
 which is sometimes such that it affords tiles for roofing. It rings 
 when struck with the hammer, whence its name; is compact, and 
 usually of a greyish blue or brownish colour ; is variable in compo- 
 sition, but almost entirely composed of felspar, and in some cases, 
 according to Gmelin, of felspar and mesotype. When it contains 
 disseminated crystals of felspar, it is called Clinkstone porphyry. 
 
 Greenstone is the most abundant of those volcanic rocks which are 
 intermediate in their composition between the Basalts and Trachytes. 
 The name has usually been extended to all granular mixtures, 
 whether of hornblende and felspar, or of augite and felspar. The 
 term diorite has been applied exclusively to compounds of hornblende 
 and felspar. According to the analyses of Delesse and others, the 
 chief cause of the green colour, in most greenstones, is not green 
 hornblende nor augite, but a green siliceous base, very variable and 
 indefinite in its composition. The dark colour, however, of diorite is 
 usually derived from disseminated plates of hornblende. 
 
 The Basalts contain a smaller quantity of silica than the Trachytes, 
 and a larger proportion of lime and magnesia. Hence, independently 
 of the frequent presence of iron, basalt is heavier. Abich has there- 
 fore proposed that we should weigh these rocks, in order to appre- 
 ciate their composition in cases where it is impossible to separate 
 their component minerals. Thus, the variety of basalt called dolerite, 
 which contains 53 per cent, of silica, has a specific gravity of 2-86 ; 
 whereas trachyte, which has 66 per cent, of silica, has a sp. gr. of 
 only 2-68 ; trachytic porphyry, containing 69 per cent, of silica, a 
 sp. gr. of only 2'58. If we then take a rock of intermediate compo- 
 sition, such as that prevailing in the Peak of Teneriffe, which Abich 
 calls Trachyte-dolerite, its proportion of silica being intermediate, 
 or 58 per cent, it weighs 2'78, or more than trachyte, and less than 
 basalt. f The basalts are generally dark in colour, sometimes almost 
 black, whereas the trachytes are grey, and even occasionally white. 
 As compared with the granitic rocks, basalts and trachytes contain 
 both of them more soda in their composition, the potash-felspars 
 
 * Dr. Daubeny on Volcanos, 2d ed. pp. 14, 15. f Ibid. 
 
 H H 4 
 
472 PORPHYRY AMYGDALOID. [Cn. XXVIII. 
 
 being generally abundant in the granites. The volcanic rocks 
 moreover, whether basaltic or trachytic, contain less silica than the 
 granites, in which last the excess of silica has gone to form quartz. 
 This mineral, so conspicuous in granite, is usually wanting in the 
 volcanic formations, and never predominates in them. 
 
 The fusibility of the igneous rocks generally exceeds that of other 
 rocks, for the alkaline matter and lime which commonly abound in 
 their composition serve as a flux to the large quantity of silica, which 
 would be otherwise so refractory an ingredient. 
 
 We may now pass to the consideration of those igneous rocks, the 
 characters of which are founded on their form rather than their 
 composition, 
 
 Porphyry is one of this class, and very characteristic of the vol- 
 canic 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. 622.). Thus trachyte is porphyritic ; for in it, 
 as in many modern lavas, there are crystals of felspar ; 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-porphyry, pitchstone-porphyry, and so 
 forth. The old classical type of this form of rock is the red por- 
 Fig. 622. phyry of Egypt, or the well known 
 
 " Rosso antico." It consists, according 
 to Delesse, of a red felspathic base in 
 which are disseminated rose-coloured 
 crystals of the felspar called oligoclase, 
 with some plates of blackish horn- 
 blende and grains of oxidized iron-ore 
 (fer oligiste). Red quartziferous por- 
 phyry is a much more siliceous rock, 
 containing about 70 or 80 per cent, 
 of silex, while that of Egypt has only 
 Porphyry. 62 per cent. 
 
 White crystals of felspar in a dark base Amygdaloid. This IS also ano- 
 
 of hornblende and felspar. '' 
 
 ther 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, 
 calcedony, 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 amygdala, an almond. The origin of this 
 structure cannot 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 water permeating 
 the rock. As these bubbles have been sometimes lengthened by the 
 flow of the lava before it finally cooled, the contents of such cavities 
 have the form of almonds. In some of the amygdaloidal traps of 
 Scotland, where the nodules have decomposed, the empty cells are 
 
CH. XXVIII.] 
 
 LAVA SCORIA PUMICE. 
 
 473 
 
 Fig. 623. 
 
 Scoriaceous lava in part converted into an 
 amygdaloid. 
 
 Montagne de la Veille, Department of Puy 
 de Dome, France. 
 
 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 pores being per- 
 fectly empty; the other part is 
 amygdaloidal, the pores or cells 
 being mostly filled up with car- 
 bonate of lime, forming white ker- 
 nels. 
 
 Lava. This term has a some- 
 what vague signification, having 
 been applied to all melted matter 
 observed to flow in streams from 
 volcanic vents. When this matter 
 consolidates in the open air, the 
 upper part is usually scoriaceous, 
 and the mass becomes more and more stony as we descend, or in 
 proportion as it 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 cur- 
 rent, or in consequence of the contact with water in or upon the 
 damp soil. 
 
 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 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 the 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 ground, 
 it is called trap. 
 
 There is every variety of composition in lavas ; some are trachy- 
 tic, as in the Peak of Teneriffe ; a great number are basaltic, as in 
 Vesuvius and Auvergne ; others are Andesitic, as those of Chili ; 
 some of the most modern in Vesuvius consist of green augite, and 
 many of those of Etna of augite and Labrador-felspar.* 
 
 Scoria and Pumice may next be mentioned as porous rocks, pro- 
 duced by the action of gases on materials melted by volcanic heat. 
 ScoricB are usually of a reddish-brown and black colour, 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 
 
 * G. Rose, Ann. des Mines, torn. viii. p. 32. 
 
474 VOLCANIC TUFF PALAGONITE TUFF. [Cn.XXVIII. 
 
 trachytic and other lavas ; the relation, however, of its origin to the 
 composition of lava is not yet well understood. Yon Buch says that 
 it never occurs where only Labrador -felspar is present. 
 
 Volcanic tuff. Trap tuff. Small angular fragments of the scorice 
 and pumice, above-mentioned, and the dust of the same, produced by 
 volcanic explosions, form the tuffs which abound in all regions of 
 active volcanos, where showers of these materials, together with 
 small pieces of other rocks ejected from the crater, fall down upon 
 the land or into the sea. Here they often become 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 little or no lime is present, there is a great 
 tendency in the materials of ordinary tuffs to cohere together. Be- 
 sides the peculiarity of their composition, some tuffs, or volcanic grits, 
 as they have been termed, differ from ordinary sandstones by the 
 angularity of their grains, and they often pass into volcanic breccias. 
 
 According to Mr. Scrope, the Italian geologists confine the term 
 tuff, or tufa, to felspathose mixtures, and those composed principally 
 of pumice, using the term peperino for the basaltic tuffs.* The 
 peperinos thus distinguished are usually brown, and the tuffs grey or 
 white. 
 
 We meet occasionally with extremely compact beds of volcanic 
 materials, interstratified with fossiliferous rocks. These may some- 
 times be tuffs, although their density or compactness is such as to 
 cause them to resemble many of those kinds of trap which are found 
 in ordinary dikes. The chocolate-coloured mud, which was poured 
 for weeks out of the crater of Graham's Island, in the Mediterranean, 
 in 1831, must, when unmixed with other materials, have constituted 
 a stone heavier than granite. Each cubic inch of the impalpable 
 powder which has fallen for days through the atmosphere, during 
 some modern eruptions, has been found to weigh, without being 
 compressed, as much as ordinary trap rocks, and to be often identical 
 with these in mineral composition. 
 
 Palagonite-tuff. The nature of volcanic tuffs must vary according 
 to the mineral composition of the ashes and cinders thrown out of 
 each vent, or from the same vent, at different times. In descrip- 
 tions of Iceland, we read of Palagonite-tuffs as very common. The 
 name Palagonite was first given by Professor Bunsen to a mineral 
 occurring in the volcanic formations of Palagonia, in Sicily. It is 
 rather a mineral substance than a mineral, as it is always amorphous, 
 and has never been found crystallized. Its composition is variable, 
 but it may be defined as a hydrosilicate of alumina, containing oxide 
 of iron, lime, magnesia, and some alkali. It is of a brown or black- 
 ish-brown colour, and its specific density, 2 -43. It enters largely 
 into the composition of volcanic tuffs and breccias, and is considered 
 by Bunsen as an altered rock, resulting from the action of steam on 
 volcanic tuffs. 
 
 * Geol. Trans. 2nd series, vol. ii. p. 211. 
 
CH. XXVJII.] AGGLOMERATE LATERITE. 475 
 
 Agglomerate. In the neighbourhood of volcanic vents, we fre- 
 quently observe accumulations of angular fragments of rock, 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 ex- 
 pansive gases have forced their way. The dispersion of such ma- 
 terials 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 run- 
 ning water, or of the waves and currents of the sea, be sufficient to 
 carry the fragments to a distance, it can scarcely fail (unless where 
 ice intervenes) to wear off their angles, and the formation then 
 becomes a conglomerate. If occasionally globular pieces of scoriae 
 abound in an agglomerate, they do not owe their rounded form to 
 attrition. 
 
 The size of the angular stones in some agglomerates is enormous ; 
 for they may be two or three yards in diameter. The mass is often 
 50 or 100 feet thick, without showing any marks of stratification. 
 The term volcanic breccia may be restricted to those tuffs which 
 are made up of small angular pieces of rock. 
 
 The slaggy crust of a stream of lava will often, while yet in 
 motion, split up into angular pieces, some of which, after the current 
 has ceased to flow, may be seen to stick up five or six feet above the 
 general surface. Such broken-up crusts resemble closely in structure 
 the agglomerates above described, although the composition of the 
 materials will usually be more homogeneous. 
 
 Laterite is a red, jaspery, 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 laterites. 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 coloured by red ochre. As two of the lavas 
 of the Giant's Causeway are parted by a bed of lignite, it is not im- 
 probable that the layers of laterite seen in the Antrim cliffs resulted 
 from atmospheric decomposition. In Madeira and the Canary Is- 
 lands 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 
 coloured 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 disintegration 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 laterite in India 
 
476 MINERAL COMPOSITION [Cn. XXVIII. 
 
 may have had a similar origin. In India, however, especially in 
 the Deccan, the term " laterite " seems to have been used too vaguely. 
 It would be tedious to enumerate all the varieties of trap and 
 lava which have been regarded by different observers as sufficiently 
 abundant to deserve distinct names, especially as each investigator is 
 too apt to exaggerate the importance of local varieties which happen 
 to prevail in districts best known to him. It will be useful, however, 
 to subjoin here, in the form of a glossary, an alphabetical list of the 
 names and synonyms most commonly in use, with brief explanations, 
 to which I have added a table of the analysis of the simple minerals 
 most abundant in the volcanic and hypogene rocks. 
 
 Explanation of the Names, Synonyms, and Mineral Composition of 
 the more abundant Volcanic Rocks. 
 
 AGGLOMERATE. A coarse breccia ; composed of fragments of rock, cast out of 
 volcanic vents, for the most part angular and without any admixture of 
 water-worn stones. " Volcanic conglomerates " may be applied to mixtures 
 in which water-worn stones occur. 
 
 APHANITE. See Cornean. 
 
 AMPHIBOLITE, or HORNBLENDE EOCK, which see. 
 
 AMYGDALOID. A particular form of volcanic rock ; see p. 472. 
 
 AUGITE ROCK. A rock of the basaltic family, composed of felspar and augite. 
 See p. 470. 
 
 ATJGITIC-PORPHYRY. Crystals of Labrador -felspar and of augite, in a green or 
 dark grey base. (Rose, Ann. des Mines, torn. 8. p. 22. 1835.) 
 
 BASALT. An intimate mixture of felspar and augite with magnetic iron, olivine, 
 
 &c. See p. 470. 
 BASANITE. Name given by Alex. Brongniart to a rock, having a base of basalt, 
 
 with more or less distinct crystals of augite disseminated through it. 
 
 CLAYSTONE and CLAYSTONE-PORPHYRY. An earthy and compact stone, usually of 
 a purplish colour, like an indurated clay ; passes into hornstone ; generally 
 contains scattered crystals of felspar and sometimes of quartz. 
 
 CLINKSTONE. Syn. Fhonolite, fissile Petrosilex, seep. 471.; a greyish-blue rock, 
 having a tendency to divide into slabs ; hard, with clean fracture, ringing 
 under the hammer ; principally composed of felspar, and, according to 
 Gmelin, of felspar and mesotype. (Leonhard, Mineralreich, p. 102.) 
 
 COMPACT FELSPAR, which has also been called Petrosilex ; the rock so called 
 includes the hornstone of some mineralogists, is allied to clinkstone, but is 
 harder, more compact, and translucent. It is a varying rock, of which the 
 chemical composition is not well defined. (MacCulloch's Classification of 
 Hocks, p. 481.) 
 
 CORNEAN or APHANITE. A compact homogeneous rock without a trace of 
 crystallization, breaking with a smooth surface like some compact basalts; 
 consists of hornblende, quartz, and felspar in intimate combination. It 
 derives its name from the Latin word cornu, horn, in allusion to its 
 toughness and compact texture. 
 
 DIALLAGE ROCK. Syn. Euphotide, Gabbro, and some Ophiolites. Compounded 
 of felspar and diallage. 
 
 DIORITE. A kind of Greenstone, which see. Components, felspar and hornblende 
 in grains. According to Rose, Ann. des Mines, torn. 8. p. 4., diorite consists 
 of albite and hornblende, but Delesse has shown that the felspar may be 
 
CH. XXVIII.] OF VOLCANIC ROCKS. 477 
 
 Oligoclase or Labradorite. (Ann. des Mines, 1849, torn. 16. p. 323.) Its 
 dark colour is due to disseminated plates of hornblende. See above 
 p. 471. 
 
 DOLERITE. According to Rose (ibid. p. 32.), its composition is black augite and 
 Labrador-felspar; according to Leonhard (Mineralreich, &c., p. 77.), 
 augite, Labrador-felspar, and magnetic iron. See above, p. 470. 
 
 DOMITE. An earthy trachyte, found in the Puy de Dome, in Auvergne. 
 
 EUPHOTIDE. A mixture of grains of Labrador-felspar and diallage. (Rose, ibid. 
 p. 19.) According to some, this rock is denned to be a mixture of augite 
 or hornblende and Saussurite, a mineral allied to jade. (Allans Mine- 
 ralogy, p. 158.) Haidinger first observed that in this rock hornblende 
 surrounds the crystals of diallage. 
 
 FELSPAR-PORPHYRY. Syn. Hornstone-porphyry ; a base of felspar, with crystals 
 of felspar, and crystals and grains of quartz. See also Hornstone. 
 
 GABBRO, see Diallage rock. 
 
 GREENSTONE. Syn. A mixture of felspar and hornblende. See above, p. 471. 
 
 GREYSTONE. (Graustein of Werner.) Lead-grey and greenish rock composed of 
 felspar and augite, the felspar being more than seventy- five per cent. (Scrope, 
 Journ. of Sci. No. 42. p. 221.) Greystone lavas are intermediate in com- 
 position between basaltic and trachytic lavas. 
 
 HORNBLENDE ROCK, or AMPHIBOLITE. This rock, as defined by Leonhard, is 
 composed entirely of hornblende ; but such a rock appears to be exceptional, 
 and confined to mineral veins. Any rocks in which hornblende plays a 
 conspicuous part, constituting the " roches amphiboliques " of French 
 writers, may be called hornblende rock. They always contain more or less 
 felspar in their composition, and pass into basalt or greenstone, or aphanite. 
 See p. 470. 
 
 HORNSTONE-PORPHYRY. A kind of felspar porphyry (Leonhard, loc. cit.\ with a 
 base of hornstone, a mineral approaching near to flint, differing from 
 compact felspar in being infusible. 
 
 HYPERSTHENE ROCK, a mixture of grains of Labrador-felspar and hypersthene 
 (Rose, Ann. des Mines, torn. 8. p. 13.), having the structure of syenite or 
 granite ; abundant among the traps of Skye. It is extremely tough, gray- 
 ish, and greenish black. Some geologists consider it a greenstone, in which 
 hypersthene replaces hornblende ; and this opinion, says Delesse, is borne 
 out by the fact that hornblende usually occurs in hypersthene rock, often 
 enveloping the crystals of hypersthene. The latter have a pearly or metallic- 
 pearly lustre. 
 
 LATERITE. A red, jaspery, brick-like rock, composed of silicate of alumina and 
 oxide of iron, or sometimes consisting of clay coloured with red ochre. 
 See above, p. 475. 
 
 MELAPHYRE. A variety of black porphyry composed of Labrador-felspar and a 
 small quantity of augite. Its black colour was formerly attributed to dis- 
 seminated microscopic crystals of augite, but M. Delesse has shown that 
 the paste is discoloured by hydrochloric acid, whereas this acid does not 
 attack the crystals of augite, which are seen to be isolated, and few in 
 number. (Ann. des Mines, 4th ser. torn. xii. p. 228.) From /xeAas, melas, 
 black. 
 
 OBSIDIAN. Vitreous lava like melted glass, nearly allied to pitchstone. 
 OPHIOLITE. A name given by Al. Brongniart to serpentine. 
 OPHITE. A name given by Palassou to certain trap rocks of the Pyrenees, very 
 variable in composition, usually composed of Labrador-felspar and horn- 
 
478 MINERAL COMPOSITION [Cn. XXVIII. 
 
 blende, and sometimes augite, occasionally of a green colour, and passing 
 into serpentine. 
 
 PALAGONITE TUFF. An altered volcanic tuff containing the substance termed 
 palagonite. See p. 474. 
 
 PEARLSTONE. A volcanic rock, having the lustre of mother of pearl ; usually 
 having a nodular structure ; intimately related to obsidian, but less glassy. 
 
 PEPERINO. A form of volcanic tuff, composed of basaltic scoriae. See p. 474. 
 
 PETROSILEX. See Clinkstone and Compact Felspar. 
 
 PHONOLITE. Syn. of Clinkstone, which see. 
 
 PITCHSTONE, or RETiNiTE of the French. Vitreous lava, less glassy than obsidian ; 
 a blackish green rock resembling glass, having a resinous lustre and ap- 
 pearance of pitch ; composition usually of glassy felspar (orthoclase) with a 
 little mica, quartz, and hornblende ; in Arran it forms a dike thirty feet 
 wide, cutting through sandstone. 
 
 PUMICE. A light, spongy, fibrous form of trachyte. See p. 473. 
 
 PYROXENIO PORPHYRY, same as augitic- porphyry, pyroxene being Haiiy's name 
 for augite. 
 
 SCORIAE. Syn. volcanic cinders ; reddish brown or black porous form of lava. 
 See p. 473. 
 
 SERPENTINE. A greenish rock in which there is much magnesia. Its composition 
 always approaches very near to the mineral called "noble serpentine " (see 
 Table of Analyses, p. 479.), which forms veins in this rock. The minerals 
 most commonly found in Serpentine are diallage, garnet, chlorite, oxydu- 
 lous iron, and chromate of iron. The diallage and garnet occurring in ser- 
 pentine are richer in magnesia than when they are crystallized in other 
 rocks. (Delesse, Ann. des Mines, 1851, torn, xviii. p. 309.) Occurs some- 
 times, though rarely, in dikes, altering the contiguous strata; is indifferently 
 a member of the trappean or hypogene series. Its absence from recent vol- 
 canic products seems to imply that it belongs properly to the metamorphic 
 class; and, even when it is found in dikes cutting through aqueous forma- 
 tions, it may be an altered basalt, which abounded greatly in olivine. 
 
 TEPHRINE, synonymous with lava. Name proposed by Alex. Brongniart. 
 TOADSTONE. A local name in Derbyshire for a kind of wacke, which see. 
 TRACHYTE. Chiefly composed of glassy felspar, with crystals of glassy felspar. 
 
 See p. 470. 
 
 TRAP TUFF. See p. 474. 
 TRASS. A kind of tuff or mud poured out by lake-craters during eruptions ; 
 
 common in the Eifel, in Germany. 
 TUFF. Syn. Trap-tuff, volcanic tuff. See p. 474. 
 
 VITREOUS LAVA. See Pitchstone and Obsidian. 
 VOLCANIC TUFF. See p. 474. 
 
 WACKE. A soft and earthy variety of trap, having an argillaceous aspect. It 
 
 resembles indurated clay, and when scratched, exhibits a shining streak. 
 WHINSTONE. A Scotch provincial term for greenstone and other hard trap rocks. 
 
CH. XXVIII.] 
 
 OF VOLCANIC ROCKS. 
 
 479 
 
 ANALYSIS OF MINERALS MOST ABUNDANT IN THE VOLCANIC AND 
 HYPOGENE ROCKS. 
 
 
 Silica. 
 
 Alu- 
 mina. 
 
 Mag- 
 
 Lime. 
 
 Potash. 
 
 Soda. 
 
 Iron 
 Oxide. 
 
 Man- 
 ganese. 
 
 Remainder. 
 
 Actinolite (Bergman) - 
 Augite, black, of volcanic rocks 
 (Klaproth). 
 
 64- 
 
 48-00 
 
 "5-00 
 
 22- 
 
 875 
 
 
 
 
 3- 
 
 10-80 
 
 100 
 
 43-05 C. 
 0-27 W. 
 12-20 W. 
 11-55 W. 
 8-96 W. 
 
 f 0-85 W. 
 ( 0-30 Ch. 
 0-22 W. 
 
 0-5 W. 
 
 1-5 F. 
 
 1-50 loss. 
 
 1- W. 
 
 9-83 W. 
 12-30 W. 
 
 f 1-63 T. 
 I 2-00 F. 
 f 1-58F. 
 I 0-90 loss 
 y 0-22 F. 
 1 1-51 loss. 
 ( 3-59 L. 
 1 3-28 F. 
 ") 0-11 P. 
 1 4-181oss. 
 4-12 
 
 12-45 W. 
 13-70 W. 
 10-50 W. 
 5-22 W. 
 5- W. 
 3-83 W. 
 
 ( 0-12 P. 
 ) 7-66 B. 
 } 2-09 loss. 
 ( 1-49 F. 
 f 22 Ph. 
 | 3-56 B. 
 4 0-41 L. 
 2-70 F. 
 [. 377 loss. 
 4-02 B. 
 
 24-00 
 56*33 
 
 - - 
 
 - - 
 
 Chiastolite (Landgrabe) 
 Chlorite (Kobell) ... 
 
 68-50 
 31-14 
 31 07 
 25-37 
 
 49-30 
 50-81 
 
 37- 
 66-75 
 
 64-91 
 68-84 
 71-50 
 
 58-91 
 
 55-75 
 53-20 
 
 63-25 
 
 62-87 
 
 35-75 
 43- 
 
 42- 
 
 45-69 
 
 47-88 
 
 54-25 
 53-75 
 53-42 
 
 54-64 
 46-80 
 42-5 
 50- 
 40-00 
 
 41-22 
 37-54 
 
 49-00 
 
 46-23 
 
 40-86 
 50- 
 41-0 
 
 43-07 
 
 41-58 
 40-83 
 64-85 
 64- 
 61-75 
 6175 
 
 37-00 
 
 41-16 
 35-48 
 
 30-11 
 17-14 
 15-47 
 
 28-79 
 
 5-50 
 2-07 
 
 21- 
 17-5 
 19-10 
 20-53 
 15-50 
 
 24-59 
 
 26-5 
 27-31 
 
 23-92 
 22-91 
 
 27-25 
 16- 
 12- 
 12'18 
 8-23 
 
 2-25 
 24-6; 
 1-38 
 
 19-70 
 26-50 
 11-5 
 35- 
 
 12-67 
 13-92 
 19-80 
 
 33-61 
 33-03 
 
 1-13 
 34-40 
 19-14 
 17'09 
 
 17-61 
 
 29-68 
 
 
 
 
 
 
 
 
 
 3-85 
 19-9!) 
 28-79 
 
 9-43 
 8-46 
 
 24- 
 075 
 traces 
 
 traces 
 0-99 
 
 1-25 
 1-03 
 
 traces 
 
 1-89 
 
 36- 
 16- 
 30- 
 7-32 
 16-15 
 
 24-5 
 
 8-53 
 
 22- 
 7- 
 
 19-03 S. 
 
 21-31 S. 
 5-OJJ P. 
 
 1-61 
 
 3-48 S. 
 1172 
 12- 
 
 18-5 
 
 1-17 
 1-69 
 
 0'53 
 traces 
 
 051 
 0-62 
 
 1-5 
 
 0-25 
 
 0-25 
 0-22 
 traces 
 
 a trace 
 
 V " 
 15-70 
 jl-09 
 
 o-io 
 
 1-40 
 
 traces 
 0-43 
 
 traces 
 
 0-46 
 
 15-43 
 
 2-20 
 
 - - 
 
 - - 
 
 . of St Gotthardt (Var- 
 
 rentrapp). 
 Diallage of euphotide (Delesse) - 
 
 rol (Kohler). 
 Epidote ( Vauquelin) - 
 Felspar, common (Rose) - 
 
 065 
 0-50 
 0-40 
 
 "i-o"i 
 
 0-32 
 traces 
 
 1-25 
 0-78 
 a trace 
 1-73 
 
 4-01 
 
 11- 
 8-02 
 
 3-23 
 3-61 
 
 12- 
 11-07 
 
 ~3- 16 
 
 2-53 
 
 ~3-40 
 2-31 
 1-39 
 
 2-49 
 9-12 
 5-94 
 
 7'59 
 
 4- 
 3-52 
 
 6-88 
 8-16 
 
 - Albitc (Rose) 
 
 
 the Vosges (Delesse). 
 
 the Vosges (Delesse). 
 Labradorite (Klaproth) 
 of Verde an- 
 tique (Delesse). 
 
 from Mont Blanc (Delesse). 
 - Oligoclase of Areudal 
 
 (Scheerer). 
 Garnet (Klaproth) - 
 (Phillips) - ... 
 Hornblende (Klaproth) 
 (Bonsdorff) - 
 of orbicular diorite 
 from Corsica (Delesse). 
 Hypersthene (Klaproth) 
 Leucite (Klaproth) - 
 Malacolite or Sahlite, green (De- 
 lesse). 
 Mesotype(Gehlen) 
 
 2-25 
 18-79 
 18-40 
 
 14- 
 
 14-95 
 
 9- 
 
 20- 
 11- 
 13-85 
 
 7-05 
 
 1-5 
 2~l-72 
 
 1-61 
 
 9-87 
 
 1*33 
 
 a trace 
 0-14 
 
 21-35 
 
 10- 
 
 0-65 
 
 15-09 
 5-40 
 
 Mica (Klaproth) - 
 (Vauquelin) - 
 
 black (H. Rose) - 
 green, of protogine (Delesse) 
 
 reddish, of crystalline lime- 
 stone (Delesse). 
 
 rose-coloured, of granite (C. 
 Gmeljn). 
 
 white, of pegmatite (Delesse) 
 Olivine(Berzelius) - 
 (Klaproth) 
 
 0-63 
 
 4-70 
 30-32 
 
 0-41 
 2-10 
 
 2-58 
 0-70 
 
 561 
 6-05 
 7-17 
 
 4-19 
 8-87 
 
 '-{ 
 
 1-00 
 1-45 
 
 0-25 
 0-4-z 
 0-92 
 
 33-09 
 
 41-83 
 34-75 
 
 38-5 
 3v5 
 
 40-37 
 42-61 
 37-98 
 28-53 
 22- 
 31-68 
 30-5 
 
 2-58 
 
 0-61 
 4-68 
 
 0-25 
 
 - - 
 
 - - 
 
 roth). 
 Serpentine (Hisinger) ... 
 asbestiform (Delesse) 
 
 0-5 
 
 - - 
 
 - - 
 
 1-50 
 
 
 
 Steatite (Delesse) ... 
 
 
 
 1-40 
 3- 
 
 
 
 
 Talc, pure (Delesse) ... 
 (Klaproth) - . _ 
 
 Tourmaline or Schorl, black, of 
 Granite from Devon (Rammels- 
 berg). 
 
 red, of granite from 
 Moravia (Rammelsberg). 
 
 Tourmaline (Gmelin) - 
 
 
 
 
 0-50 
 
 275 
 0-65 
 
 2-17 
 0-48 
 
 ,{ 
 
 1-37 
 1-75 
 
 2'5 
 
 9-33 S. 
 6-19 P. 
 
 17 44 
 
 ] - 
 
 97- S. 
 
 1-89 
 
 In the last column of the above Table, the following signs are used : B. Boracic acid, C. Carbonic 
 acid, Ch. Oxide of Chrome, F. Fluoric acid, L. Lithine, P. Phosphoric acid, T. Oxide of Titanium^ 
 W. Water. In the 7th column of numbers, P. means Protoxide, and S. Sesquioxide. 
 
480 
 
 TRAP DIKES. 
 
 [Cn. XXIX. 
 
 CHAPTER XXIX. 
 
 VOLCANIC ROCKS continued. 
 
 Trap dikes sometimes project sometimes leave fissures vacant by decomposi- 
 tion Branches and veins of trap Dikes more crystalline in the centre 
 Strata altered at or near the contact Obliteration of organic remains Con- 
 version of chalk into marble Trap interposed between strata Columnar and 
 globular structure Relation of trappean rocks to the products of active vol- 
 canos Form, external structure, and origin of volcanic mountains Craters 
 and Calderas Sandwich Islands Lava flowing underground Truncation of 
 cones Javanese cald eras Canary Islands Structure and origin of the Cal- 
 dera of Palma Older and newer volcanic rocks in, unconformable Aqueous 
 conglomerate in Palma Hypothesis of upheaval considered Slope on which 
 stony lavas may form Extent and nature of aqueous erosion in Palma Island 
 of St. Paul in the Indian Ocean Peak of Teneriffe, and ruins of older cone 
 Madeira Its volcanic rocks, partly of marine, and partly of subaerial origin 
 Central axis of eruptions Varying dip of solid lavas near the axis, and further 
 from it Leaf-bed, and fossil land-plants Central valleys of Madeira not 
 craters, or calderas. 
 
 HAVING in the last chapter spoken of the composition and mineral 
 characters of volcanic rocks, I shall next describe the manner 
 and position in which they occur in the earth's crust, and their 
 external forms. The leading varieties both of the basaltic and 
 trachytic rocks, as well as of greenstone and the rest, are found 
 sometimes in dikes penetrating stratified and unstratified formations, 
 sometimes in shapeless masses protruding through or overlying 
 them, or in horizontal sheets intercalated between strata. 
 
 Volcanic or trap dikes. Fissures have already been spoken of as 
 occurring in all kinds of rocks, some a few feet, others many yard" 
 in width, and often filled up with earth or angular 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 un- 
 common to find such dikes 
 passing through strata of soft 
 materials, such as tuff, scorias, 
 or shale, which, being more 
 perishable than the trap, are 
 often washed away by the 
 
 Dike in valley, near Brazen Head, Madeira. sea r i ve rs, Or rain, in which 
 
 (From a drawing of Capt. Basil Hall, R.N.) 
 
 Fig. 624. 
 
CH. XXIX.] 
 
 TKAP DIKES AND VEINS. 
 
 481 
 
 Fig, 625. 
 
 case the dike stands prominently out in the face of precipices, or on 
 the level surface of a country. 
 
 In the islands of Arran and Skye, and in other parts of Scotland, 
 where sandstone, conglomerate, and other hard rocks are traversed by 
 dikes of trap, the converse of the above phenomenon is seen. The 
 dike, having 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, as 
 represented in the annexed view (fig. 
 625.). In these instances, the green- 
 stone of the dike is usually more tough 
 and hard than the sandstone ; but che- 
 mical action, and chiefly the oxidation 
 of the iron, has given rise to the more 
 rapid decay. 
 
 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 
 
 ==== _ =====3 as to resist tne action of the weather 
 
 Fissures left vacant by decomposed more than the dike itself, or the sur- 
 
 '.) strathaird > Skye ' (MacCuU 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. 
 
 As fissures sometimes send off branches, or divide into two or 
 more fissures of equal size, so also we find trap dikes bifurcating 
 and ramifying, and sometimes they are so tortuous as to be called 
 veins, though this is more COHMHOII in 
 granite than in trap. The accompanying 
 sketch (fig. 626.) by Dr. MacCulloch re- 
 presents part of a sea-cliff in Argyleshire, 
 where an overlying mass of trap, b, sends 
 out some veins which terminate down- 
 wards. Another trap vein, a a, cuts 
 through both the limestone, c, and the 
 trap, b. 
 
 In fig. 627., a ground plan is given of 
 a ramifying dike of greenstone, which I observed cutting through 
 
 Fig. 627. 
 
 Fig. 626 
 
 Trap veins in Airdnamurchan. 
 
 Ground plan of greenstone dike traversing sandstone. Arran. 
 I I 
 
482 VARIOUS FORMS OF [Cn. XXIX. 
 
 sandstone on the beach near Kildonan Castle, in Arran. The 
 larger branch varies from 5 to 7 feet in width, which will afford a 
 scale of measurement for the whole. 
 
 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, pro- 
 longed downwards in veins or dikes, which probably unite with 
 other masses of igneous rock at a greater depth. The largest of the 
 dikes represented in the annexed diagram, and which are seen in 
 part of the coast of Skye, is no less than 100 feet in width. 
 
 Fig. 628. 
 
 Trap dividing and covering sandstone near Suishnish in Skye. (MacCulloch.) 
 
 Every variety of trap-rock is sometimes found in dikes, as basalt, 
 greenstone, felspar-porphyry, and trachyte. The amygdaloidal 
 traps also occur, though more rarely, and even tuff and breccia, for 
 the materials of these last may be washed down into open fissures at 
 the bottom of the sea, or during eruptions 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. 
 
 In many cases trap at the edges or sides of a dike is less crys- 
 talline or more earthy than in the centre, in consequence of the 
 melted jnatter having cooled more rapidly by coming in contact 
 with the cold sides of the fissure ; whereas, in the centre, where the 
 matter of the dike is kept longer in a fluid or soft state, crystals are 
 slowly formed. But I observed the converse of the above phe- 
 nomena in Teneriffe, in the neighbourhood of Santa Cruz, where a 
 dike is seen cutting through horizontal beds of scoriae in the sea- 
 cliff near the Barranco de Bufadero. It is vertical in its main 
 direction, slightly flexuous, and about one foot thick. On each side 
 are walls of compact basalt, but in the centre the rock is highly 
 vesicular for a width of about 4 inches. In this instance, the 
 fissure may have become wider after the lava on each side had 
 consolidated, and the additional melted matter poured into the 
 middle space may have cooled more rapidly than that at the sides. 
 
 In the ancient part of Vesuvius, called Somma, a thin band of 
 half-vitreous lava is found at the edge of some dikes. At the 
 junction of greenstone dikes with limestone, a sahlband, or selvage, 
 of serpentine is occasionally observed. On the left shore of the 
 fiord of Christiania, in Norway, I examined, in company with 
 Professor Keilhau, a remarkable dike of syenitic greenstone, which 
 is traced through Silurian strata, until at length, in the promontory 
 
CH. XXIX.] 
 
 TRAP DIKES AND VEINS. 
 
 483 
 
 Fig. 629. 
 
 Syenitic greenstone dike of Naesodden, 
 Christiania. 
 
 Green 
 stone 
 
 Green 
 stone. 
 
 of Naesodden, it enters mica- 
 schist. Fig. 629. represents a 
 ground plan, where the dike 
 appears 8 paces in width. In 
 the middle it is highly crystal- 
 line and granitiform, of a purplish 
 colour, and containing a few 
 crystals of mica, and strongly 
 contrasted with the whitish mica- 
 schist, between which and the 
 syenitic rock there is usually on 
 each side a distinct black band, 
 
 b. imbedded fragment of crystalline schist iur- 18 inches Wide, of dark ffreen- 
 rounded by a band of greenstone. 
 
 stone. When first seen, these 
 
 bands have the appearance of two accompanying dikes ; yet they 
 are, in fact, only the different form which the syenitic materials 
 have assumed where near to or in contact with the mica-schist. 
 At one point, a, one of the sahlbands terminates for a space ; but 
 near this there is a large detached block, b, having a gneiss-like 
 structure, consisting of hornblende and felspar, which is included in 
 the midst of the dike. Round this a smaller encircling zone is seen, 
 of dark basalt, or fine-grained greenstone, nearly corresponding to 
 the larger ones which border the dike, but only 1 inch wide. 
 
 It seems, therefore, evident that the fragment, b, has acted on the 
 matter of the dike, probably by causing it to cool more rapidly, in 
 the same manner as the walls of the fissure have acted on a larger 
 scale. The facts, also, illustrate the facility with which a graniti- 
 form syenite may pass into ordinary rocks of the volcanic family. 
 The fact above alluded to, of a foreign fragment, such as b, 
 
 fig. 629., included in the midst 
 of the trap, as if torn off from 
 some subjacent rock or the walls 
 of a fissure, is by no means un- 
 common. A fine example is 
 seen in another dike of green- 
 stone, 10 feet wide, in the 
 northern suburbs of Christiauia, 
 in Norway, of which the an- 
 nexed figure is a ground plan. 
 The dike passes through shale, 
 
 known by its fossils to belong to 
 
 J 
 
 the Silurian series. In the 
 black base of greenstone are angular and roundish pieces of gneiss, 
 some white, others of a light flesh-colour, some without lamination, 
 like granite, others with laminae, which, by their various and often 
 opposite directions, show that they have been scattered at random 
 through the matrix. These imbedded pieces of gneiss measure from 
 1 to about 8 inches in diameter. 
 
 Rocks altered by volcanic dikes. After these remarks on the form 
 
 II 2 
 
 Fig. 630. 
 
 Greenstone dike with fragments of gueu. 
 Sorgenfna, Christiania. 
 
484 ROCKS ALTERED BY TRAP DIKES. [Cn. XXIX. 
 
 and composition of dikes themselves, I shall describe the alterations 
 which they sometimes produce in the rocks in contact with them. 
 The changes are usually such as the intense heat of melted matter 
 and the entangled gases might be expected to cause. 
 
 Plas-Newydd. A. striking example, near Plas-Newydd, in 
 Anglesea, has been described by Professor Henslow.* The dike is 
 134 feet wide, and consists of a rock which is a compound of felspar 
 and augite (dolerite of some authors). Strata of shale and argilla- 
 ceous limestone, through which it cuts perpendicularly, are altered 
 to a distance of 30, or even, in some places, to 35 feet from the edge, 
 of the dike. The shale, as it approaches the trap, becomes gradually 
 more compact, and is most indurated where nearest the junction. 
 Here it loses part of its schistose structure, but the separation into 
 parallel layers is still discernible. In several places the shale is con- 
 verted into hard porcellanous jasper. In the most hardened part of 
 the mass the fossil shells, principally Product^ 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 appear- 
 ance in the shale of numerous crystals of analcime and garnet, which 
 are distinctly 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 ana- 
 logous circumstances, in High Teesdale, by Professor Sedgwick, 
 where it also occurs in shale and limestone, altered by basalt. J 
 
 Antrim. 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 converted into granular marble near the basalt, the 
 change sometimes extending 8 or 10 feet from the wall of the dike, 
 being greatest near the point of contact, and thence gradually de- 
 creasing till it becomes evanescent. " The extreme effect/' says Dr. 
 Berger, " presents a dark brown crystalline limestone, the crystals 
 running in flakes as large as those of coarse primitive (metamorphic) 
 limestone ; the next state is saccharine, then fine grained and arena- 
 ceous ; a compact variety, having a porcellanous aspect and a bluish- 
 grey colour, succeeds : this, towards the outer edge, becomes yellow- 
 ish-white, and insensibly graduates into the unaltered chalk. The 
 flints in the altered chalk usually assume a grey yellowish colour." 
 All traces of organic remains are effaced in that part of the lime- 
 stone which is most crystalline. 
 
 The annexed drawing (fig. 631.) 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 
 
 * Cambridge Transactions, vol. i. J Ibid. vol. ii. p. 175. 
 p. 402. Dr. Berger, Geol. Trans. 1st series, 
 
 f Ibid. vol. i. p. 410. vol. iii. p. 172. 
 
CH. XXIX.] ROCKS ALTERED BY TRAP DIKES. 
 
 Fig. 63k. 
 
 485 
 
 Basaltic dikes in chalk in island of Rathlin, Antrim. 
 Ground plan, as seen on the beach. (Conybeare and Buckland.*) 
 
 and the central one. The entire contrast in the composition and 
 colour 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 impressions of 
 ammonites.'j' 
 
 It might have been anticipated that beds of coal would, from their 
 combustible nature, be affected in an extraordinary 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 9 feet on each side. 
 
 At Cockfield Fell, in the north of England, a similar change is 
 observed. Specimens taken at the distance of about 30 yards from 
 the trap are not distinguishable from ordinary pit-coal ; those nearer 
 the dike are like cinders, and have all the character of coke ; while 
 those close to it are converted into a substance resembling soot.J 
 
 As examples might be multiplied without end, I shall merely 
 select one or two others, and then conclude. The rock of Stirling 
 Castle is a calcareous sandstone, fractured and forcibly displaced by 
 a mass of greenstone which has evidently invaded the strata in a 
 melted state. The sandstone has been indurated, and has assumed a 
 texture approaching to hornstone near the junction. In Arthur's 
 Seat and Salisbury Craig, near Edinburgh, a sandstone which comes 
 in contact with greenstone is converted into a jaspideous rock. 
 
 The secondary sandstones in Skye are converted into solid quartz 
 in several places, where they come in contact with veins or masses 
 of trap ; and a bed of quartz, says Dr. MacCulloch, found near a 
 mass of trap, among the coal strata of Fife, was in all probability a 
 stratum of ordinary sandstone, having been subsequently indurated 
 and turned into quartzite by the action of heat. 
 
 But although strata in the neighbourhood of dikes are thus altered 
 
 * Geol. Trans. 1st series, vol. iii. 
 p. 210. and plate 10. 
 
 f Ibid. p. 213. ; and Playfair. Illust. 
 of Hutt. Theory, s. 253. 
 
 J Sedgwick, Camb. Trans, vol. ii. 
 p. 37. 
 
 Syst. of Geol. vol. i. p. 206. 
 
 II 3 
 
486 
 
 INTRUSION OF TRAP BETWEEN STRATA. [Cn. XXIX. 
 
 in a variety of cases, shale being turned into flinty slate or jasper, 
 limestone into crystalline marble, sandstone into quartz, coal into 
 coke, and the fossil remains of all such strata wholly and in part 
 obliterated, it is by no means uncommon to meet with the same rocks, 
 even in the same districts, absolutely unchanged in the proximity of 
 volcanic dikes. 
 
 This great inequality in the effects of the igneous rocks may often 
 arise from an original difference 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, 
 according to their composition, structure, and the fractures which 
 they may have experienced, and perhaps, also, according to the quan- 
 tity of water (so capable of being heated) which they contain. It 
 must happen in some cases that the component materials are mixed 
 in such proportions as 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 sim- 
 ply 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 are ejected in the shape of 
 scorise from some crater. If the walls of a rent, moreover, are 
 heated by hot vapour before the lava rises, as we know may happen 
 on the flanks of a volcano, the additional caloric supplied by the dike 
 and its gases will act more powerfully. 
 
 Intrusion of trap between strata. In proof of the mechanical 
 force which the fluid trap has sometimes exerted on the rocks into 
 which it has intruded itself, I may refer to the Whin- Sill, where a 
 mass of basalt, from 60 to 80 feet in height, represented by , 
 fig. 632., is in part wedged in between the rocks of limestone, b, and 
 
 Fig. 632 
 
 Basalt. 
 
 Trap interposed between displaced beds of limestone and shale, at White 
 Force, High Teesdale, Durham. (Sedgwick.*) 
 
 shale, c, which have been separated from the great mass of limestone 
 and shale, d, with which they were united. 
 
 * Camb. Trans, vol. ii. p. 180. 
 
CH. XXIX.] STRUCTURE OF VOLCANIC ROCKS. 487 
 
 The shale in this place is indurated ; and the limestone, which at 
 a distance from the trap is blue, and contains fossil corals, is here 
 converted into granular marble without fossils. 
 
 Masses of trap are not unfrequently met with intercalated between 
 strata, and maintaining their parallelism to the planes of stratifica- 
 tion 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 be 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 
 upwards. 
 
 Columnar and globular structure. One of the characteristic 
 forms of volcanic rocks, especially of basalt, is the columnar, where 
 large masses are divided into regular prisms, sometimes easily sepa- 
 rable, but in other cases adhering firmly together. 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 Giants' 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 ; others, in Morven, not 
 exceeding an inch. In regard to diameter, those of Ailsa measure 9 
 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. Among other 
 examples of the last-mentioned phenomenon is the mass of basalt, 
 called the Chimney, in St. Helena (see fig. 633), a pile of hexagonal 
 
 Fig. 633. 
 
 Fig. 634. 
 
 Small portion of the dyke 
 in Fig. 633. 
 
 Volcanic dyke composed of hori- 
 zontal prisms. St. Helena. 
 
 prisms, 64 feet high, evidently the remainder of a narrow dike, the 
 walls of rock which the dike originally traversed having been re- 
 
 * MacCuL Syst of Geol. vol. ii. p. 137. 
 II 4 
 
488 
 
 STRUCTURE OF VOLCANIC ROCKS. [Cn. XXIX. 
 
 moved down to the level of the sea. In fig. 634., a small portion of 
 this dike is represented on a less reduced scale.* 
 
 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 per- 
 pendicular or horizontal, are curved, the columns ought to be inclined 
 at every angle to the horizon ; and there is a beautiful exemplifica- 
 tion of this phenomenon in one of the valleys of the Vivarais, a 
 mountainous district in the South of France, where, in the midst of 
 a region of gneiss, a geologist encounters unexpectedly several 
 volcanic cones of loose sand and scoriae. From the crater of one of 
 these cones, called La Coupe d'Ayzac, a stream of lava descends and 
 occupies the bottom of a narrow valley, except at those points where 
 the river Volant, or the torrents which join it, have cut away portions 
 of the solid lava. The accompanying sketch (fig. 635.) represents the 
 
 Fig. 635. 
 
 Lava of La Coupe d'Ayzac, near Antraigue, in the province of Ardeche. 
 
 remnant of the lava at one of the points where a lateral torrent joins 
 the main valley of the Volant. It is clear that the lava once filled 
 the whole valley up to the dotted line d a ; but the river has gra- 
 dually 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 composed, as usual in this country, of three 
 parts : the uppermost, at , being scoriaceous ; the second, b, pre- 
 senting 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 
 <7, and are horizontal at f, their position having been every where 
 determined, according to the law before mentioned, by the concave 
 form of the original valley. 
 
 In the annexed figure (636.) a view is given of some of the in- 
 clined 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.f Unlike those of the Vivarais, last 
 mentioned, the basalt of this country was evidently submarine, and 
 the present valleys have since been hollowed out by denudation. 
 
 * Scale's Geognosy of St. Helena, f Fortis. Mem. sur 1'Hist. Nat. 
 plate 9. 1'Italie, torn. i. p. 233. plate 7. 
 
CH. XXIX.] STRUCTURE OF VOLCANIC ROCKS. 
 
 489 
 
 Fig. 636 
 
 The columnar structure is by no means 
 peculiar to the trap rocks in which 
 augite abounds; it is also observed in 
 clinkstone, trachyte, and other felspathic 
 rocks of the igneous class, although in 
 these it is rarely exhibited in such re- 
 gular polygonal 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. 637.). The basalt there is part of a small 
 stream of lava, from 30 to 40 feet thick, which has proceeded from 
 
 Columnar basalt in the Vicentin. 
 (Fortis.) 
 
 Basaltic pillars of the Kasegrotte, Bertrich-Baden, half way between Treves and Coblentz. 
 Height of grotto, from 7 to 8 feet. 
 
 one of several volcanic craters, still extant, on the neighbouring 
 heights. 'The position of the lava bordering the river in this valley 
 might be represented by a section like that already given at fig. 635. 
 if we merely supposed inclined strata of slate and the argillaceous 
 sandstone called greywacke to be substituted for gneiss. 
 
 In some masses of decomposing greenstone, basalt, and other trap 
 rocks, the globular structure is so conspicuous that the rock has the 
 appearance of a heap of large cannon balls. According to the theory 
 of M. Delesse, the centre of each spheroid has been a centre of crys- 
 tallization, around which the different minerals of the rock arranged 
 themselves symmetrically during the process of cooling. But it was 
 also, he says, a centre of contraction, produced by the same cooling. 
 The globular form, therefore, of such spheroids is the combined 
 result of crystallization and contraction.* 
 
 * Delesse, ur les Koches Globuleuses, Mem. de la Soc. Geol. de France, 2 ser. 
 torn. iv. 
 
490 
 
 RELATION OF TRAP, 
 
 [Cn. XXIX. 
 
 Fig. 638. 
 
 A striking example of this structure occurs in 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. 638.). The whole rock is 
 in a state of decomposition, "and when 
 the balls," says Mr. Scrope, " have been 
 exposed a short time to the weather, they 
 scale off at a touch into numerous con- 
 centric coats, like those of a bulbous root, 
 inclosing a compact nucleus. The laminae 
 of this nucleus have not been so much 
 loosened by decomposition ; but the appli- 
 cation of a ruder blow will produce a still 
 further exfoliation." * 
 
 A fissile texture is occasionally assumed 
 by clinkstone and other trap rocks, so that 
 they have been used for roofing houses. 
 Sometimes the prismatic and slaty struc- 
 ture is found in the same mass. The 
 causes which give rise to such arrange- 
 ments are very obscure, but are supposed 
 to be connected with changes of temperature during the cooling of 
 the mass, as will be pointed out in the sequel. (See Chaps. XXXV. 
 and XXXYI.) 
 
 Globiform pitchstone. Chiaja di 
 Luna, Isle of Ponza. (Scrope.) 
 
 Relation of Trappean Rocks to the products of active Volcanos. 
 
 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 volcanos, it seems difficult at 
 first to understand how so much doubt could have prevailed for half 
 a century as to whether trap was of igneous or aqueous origin. To 
 a certain extent, however, there was a real distinction between the 
 trappean formations and those to which the term volcanic 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 injected 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 scoriae, 
 tuff, and lava, or with narrow streams of lava in great part scoria- 
 ceous and porous, such as were observed to have proceeded from 
 Vesuvius and Etna, the resemblance seemed remote and equivocal. 
 
 * Scrope, GeoL Trans. 2d series, vol ii. p. 205. 
 
Fig. 639. 
 
 CH. XXIX.] LAVA, AND SCOKI-ffl. 491 
 
 It was, in truth, like comparing the roots of a tree with its leaves 
 and branches, which, although they belong to the same plant, differ 
 in form, texture, colour, mode of growth, and position. The external 
 cone, with its loose ashes and porous lava, may be likened to the 
 light foliage and branches, and the rocks concealed far below, to the 
 roots. But it is not enough to say of the volcano, 
 
 " quantum vertice in auras 
 -ZEtherias, tantum radice in Tartara tendit," 
 
 for its roots do literally reach downwards to Tartarus, or to the 
 regions of subterranean fire; and what is concealed far below is 
 probably always more important in volume and extent 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 destruction of whatever may 
 once have formed the uppermost part 
 of ancient submarine or subaerial vol- 
 canos, more especially as those super- 
 ficial parts are always of the lightest 
 and most perishable materials. The 
 abrupt manner in which dikes of trap 
 usually terminate at the surface (see 
 fig. 639.), and the water-worn pebbles 
 of trap in the alluvium which covers 
 
 the dike, prove incontestably 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 volcanos. 
 
 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 scoriae which had cooled in the open air. Their counter- 
 parts 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 volcanos, 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. 
 
 Thus, for example, the examination of the igneous rocks of Sicily, 
 especially those of the Val di Noto, has proved that all the more 
 ordinary varieties of European trap have been there produced under 
 the waters of the sea, at a modern period ; that is to say, since the 
 Mediterranean has been inhabited by a great proportion of the 
 existing species of testacea. 
 
 Strata intercepted by a trap dike, and 
 covered with alluvium. 
 
492 EELATION OF TKAP, [Cn. XXIX. 
 
 These igneous rocks of the Val di Noto, and the more ancient 
 trappean rocks of Scotland and other countries, differ from sub- 
 aerial volcanic formations in being more compact and heavy, and 
 in forming sometimes extensive sheets of matter intercalated be- 
 tween marine strata, and sometimes stratified conglomerates, of 
 which the rounded pebbles are all trap. They differ also in the 
 absence of regular cones and craters, and in the want of conformity 
 of the lava to the lowest levels of existing valleys. 
 
 It is highly probable, however, that insular cones did exist in 
 some parts of the Val di Noto : and that they were removed by the 
 waves, in the same manner as the cone of Graham Island, in the 
 Mediterranean, was swept away in 1831, and that of Nyoe, off 
 Iceland, in 1783.* All that would remain in such cases, after the 
 bed of the sea has been upheaved and laid dry, would be dikes and 
 shapeless masses of igneous rock, cutting through sheets of lava 
 which may have spread over the level bottom of the sea. and strata 
 of tuff, formed of materials first scattered far and wide by the winds 
 and waves, and then deposited. Conglomerates also, with pebbles 
 of trap, to which the action of the waves must give rise during the 
 denudation of such volcanic islands, will emerge from the deep 
 whenever the bottom of the sea becomes land. The proportion of 
 volcanic matter which is originally submarine must always be very 
 great, as those volcanic vents which are not entirely beneath the 
 sea are almost all of them in islands, or, if on continents, near the 
 shore. 
 
 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 rocks, into the cells of which mineral 
 matter such as silex, carbonate of lime, and other ingredients, have 
 been subsequently introduced (see p. 473.) ; sometimes, perhaps, by 
 secretion during the cooling and consolidation of lavas. 
 
 In the Little Cumbray, one of the Western Islands, near Arran, 
 the amygdaloid sometimes contains elongated cavities filled with 
 brown spar; and when the nodules have been washed out, the 
 interior of the cavities is glazed with the vitreous varnish so cha- 
 racteristic 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.f 
 
 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 eruptions of trap the 
 name of submarine volcanoes ; for they are such in every essential 
 point, although they no longer eject fire and smoke." { The same 
 author also considers it not improbable that some of the volcanic 
 
 * See Princ. of Geol., Index, "Gra- f MacCulloch, West. Islands, vol. ii. 
 ham Island," "Nyoe," * Conglomerates, p. 487. 
 volcanic," &c. ' $ Syst. of GeoL vol. ii. p. 114. 
 
CH. XXIX.] LAVA, AND SCORIA. 493 
 
 rocks of the same country may have been poured out in the open 
 
 air.* 
 
 Although the principal component minerals of subaerial lavas are 
 the same as those of intrusive trap, and both the columnar and 
 globular structure are common to both, there are, nevertheless, some 
 volcanic rocks which never occur in currents of lava, such as 
 greenstone, the more crystalline porphyries, and those traps in 
 which quartz and mica appear as constituent parts. In short, the 
 intrusive trap rocks, forming the intermediate step between lava 
 and the plutonic rocks, depart in their characters from lava in 
 proportion as they approximate to granite. 
 
 These views respecting the relations of the volcanic and trap 
 rocks will be better understood when the reader has studied, in the 
 33rd chapter, what is said of the plutonic formations 
 
 EXTERNAL FORM, STRUCTURE, AND ORIGIN OF VOLCANIC MOUNTAINS. 
 
 The origin of volcanic cones with crater-shaped summits has been 
 alluded to in the last chapter (p. 466.), and more fully explained in 
 the "Principles of Geology" (chaps, xxiv. to xxvii.), where Ve- 
 suvius, Etna, Santorin, and Barren Island are described. The more 
 ancient portions of those mountains or islands, formed long before 
 the times of history, exhibit the same external features and internal 
 structure which belong to most of the extinct volcanos of still 
 higher antiquity; and these last have evidently been due to a 
 complicated series of operations, varied in kind according to cir- 
 cumstances ; 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, whether the rocks re- 
 duced to fusion in the subterranean regions happen to have contained 
 more or less silica, potash, soda, lime, iron, and other ingredients. 
 
 We are best acquainted 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. 
 
 Craters and Calderas, Sandwich Islands. We learn from 
 Mr. Dana's valuable work on the geology of the United States' 
 Exploring Expedition, published in 1849, that two of the principal 
 volcanos of the Sandwich Islands, Mounts Loa and Kea in Owyhee, 
 are huge flattened volcanic cones, about 1400 feet high (see fig. 640.), 
 each equalling two and a half Etnas in their dimensions. 
 
 From the summits of these lofty though featureless hills, and from 
 vents not far below their summits, successive streams of lava, often 
 2 .miles or more in width, and sometimes 26 miles long, have flowed. 
 They have been poured out one after the other, some of them in 
 recent times, in every direction from the apex of the cone, down 
 
 * Syst. of Geol., vol. ii. p. 114. 
 
494 EXTERNAL FORM, STRUCTURE, AND ORIGIN [Cn. XXIX. 
 
 Fig. 640. 
 
 Mount Loa, in the Sandwich Islands. (Dana.) 
 
 a. Crater at the summit. b. The lateral crater of Kilauea. 
 
 The dotted lines indicate a supposed column of solid rock caused by the lava consolidating 
 
 after eruptions. 
 
 slopes varying on an average from 4 degrees to 8 degrees ; but in 
 some places considerably steeper. Sometimes deep rents are formed 
 on the sides of these conical mountains, which are afterwards filled 
 from above by streams of lava passing over them, the liquid matter 
 in such cases consolidating in the fissures and forming dikes. 
 
 The lateral crater of Kilauea, b, fig. 640., is 3970 feet above the 
 level of the sea, or about the same height as Vesuvius. It is an 
 immense chasm, 1000 feet deep, and its outer circuit no less than 
 from two to three miles in diameter. Lava is usually seen to boil 
 up at the bottom in a lake, the level of which alters continually, for 
 the liquid rises and falls several hundred feet according to the 
 active or quiescent state of the volcano. But instead of overflowing 
 the rim of the crater, as commonly happens in other vents, the 
 column of melted rock, when its pressure becomes excessive, forces 
 a passage through some subterranean galleries or rents leading 
 towards the sea. Mr. Coan, an American missionary, has described 
 an eruption which took place in June 1840, when the lava which 
 had risen high in the great chasm began to escape from it. Its 
 direction was first recognised by the emission of a vivid light from 
 the bottom of an ancient wooded crater, called Arare, 400 feet deep 
 and 6 miles to the eastward of Kilauea. The connection of this 
 light with the discharge or tapping of the great reservoir was 
 proved by a change in the level of the lava in Kilauea, which sank 
 gradually for three weeks, or until the eruption ceased, when the 
 lake stood 400 feet lower than at the commencement of the outbreak. 
 The passage, therefore, of the fluid matter from Kilauea to Arare 
 was underground, and it is supposed by Mr. Coan to have been at 
 its first outflow 1000 feet deep below the surface. The next 
 indication of the subterranean progress of the same lava was 
 observed a mile or two from Arare, where the fiery flood broke out 
 and spread itself superficially over 50 acres of land, and then again 
 found its way underground for several miles farther towards the 
 sea, to reappear at the bottom of a second ancient and wooded 
 crater, which it partly filled up. The course of the fluid then 
 became again invisible for several miles, until it broke out for the 
 last time at a point ascertained by Captain Wilkes to be 1244 feet 
 above the sea, and 27 miles distant from Kilauea. From thence it 
 poured along for 12 miles in the open air, and then leapt over 
 a cliff 50 feet high, and ran for three weeks into the sea. Its 
 termination was at a place about 40 miles distant from Kilauea. 
 The crust of the earth overlying the subterranean course of the lava 
 was often traversed by innumerable fissures, which emitted steam, 
 and in some places the incumbent rocks were uplifted 20 or 30 feet. 
 
CH. XXIX.l OF VOLCANIC MOUNTAINS. 495 
 
 Thus in the same volcano examples are afforded of the overflowing 
 of lava from the summit of a cone 1\ miles high, and of the under- 
 flowing of melted matter. Whether this last has formed sheets 
 intercalated between the stratified products of previous eruptions, 
 or whether it has penetrated through oblique or vertical fissures, 
 cannot be determined. In one instance, however, for a certain 
 space, it is said to have spread laterally, uplifting the incumbent 
 soil. 
 
 The annexed section of the crater of Kilauea, as given by 
 Mr. Dana, follows the line of its shorter diameter, a, 6, which is 
 
 Fig. 641. 
 
 a 
 
 
 \ 
 
 
 c e d 
 
 
 
 ~V hi 
 
 
 
 
 
 Section of the crater of Kilauea in the Sandwich Islands. (Dana.) 
 a, 6. External boundaries of the chasm in the line of its shortest diameter. 
 c, e, f, d. Black ledge. g, h. Lake of lava. 
 
 about 7500 feet long. The boundary cliffs, a, c and 5, d, are for the 
 most part quite vertical and 650 feet high. They are composed of 
 compact rock in layers, not divided by scoriae, some a few inches, 
 others 30 feet in thickness, and nearly horizontal. Below this, we 
 come to what is called the " black ledge," c, e and f, d, composed of 
 similar stratified materials. This ledge is 342 feet in height above 
 the lake of lava, g, h, which it encircles. The chasm, a, b, and its 
 walls have probably been due to a former sinking down of the 
 incumbent rocks, undermined for a space by the fusion of their 
 foundations. The lower ledge, c, e and f^ d, may consist in part of 
 the mass which sank vertically, but part of it at least must be made 
 up of layers of lava, which have been seen to pour one after the 
 other over the " black ledge." If at any future period the heated 
 fluid, ascending from the volcanic focus to the bottom of the great 
 chasm, should augment in volume, and, before it can obtain relief, 
 should spread itself subterraneously, it may melt still farther the 
 subjacent masses, and, causing a failure of support, may enlarge still 
 more the limits of the amphitheatre of Kilauea. There are distinct 
 signs of subsidences, from 100 to 200 feet perpendicular, which 
 have occurred in the neighbourhood of Kilauea at various points, 
 and they are each bounded by vertical walls. If all of them were 
 united, they would constitute a sunken area equal to eight square 
 miles, or twice the extent of Kilauea itself. Similar accidents are 
 also likely to occur near the summit of a dome like Mount Loa, for 
 the hydrostatic pressure of the lava, after it has risen to the edge or 
 lip of the highest crater, #, fig. 640., must be great and must create 
 a tendency to lateral fissuring, in which case lava will be injected 
 into every opening, and may begin to undermine. If, then, some of 
 the melted matter be drawn off by escaping at a lower level, where 
 
496 EXTERNAL FORM, STRUCTURE, AND ORIGIN [Cn. XXIX. 
 
 the pressure would be still greater, the whole top of the mountain, 
 or a large part of it, might fall in. 
 
 Instances of such truncations, however caused, have occurred in 
 Java and in the Andes within the times of history, and to such events 
 we may perhaps refer a very common feature in the configuration of 
 volcanic mountains, namely, that the present active cone of erup- 
 tion is surrounded by the ruins of a larger and older cone, usually 
 presenting a crescent-shaped precipice towards the newer cone. In 
 volcanos long since extinct, the erosive power of running water, or, 
 in certain cases, of the sea, may have greatly modified the shape of 
 the " atrium," or space between the older and newer cone, and the 
 cavity may thereby be prolonged downwards, and end in a ravine. 
 In such cases it may be impossible to determine how much of the 
 missing rocks has been removed by explosion at the time when 
 the original crater was active, or how much by subsequent engulph- 
 ment and denudation. 
 
 Java. - One of the latest contributions to our knowledge of vol- 
 canos will be found in Dr. Junghuhn's work on Java, where forty- 
 six conical eminences of volcanic origin, varying in elevation from 
 4000 to nearly 12,000 feet above the sea, constitute the highest 
 peaks of a mountain range, running through the island from east to 
 west. All of them, with one exception, did this indefatigable traveller 
 survey and map. In none of them could he discover any marine 
 remains, whether adhering to their flanks or entering into their in- 
 ternal structure, although strata of marine origin are met with 
 nearer the sea at lower levels. Dr. Junghuhn ascribes the origin of 
 each volcano to a succession of subaerial eruptions from one or more 
 central vents, whence scoriae, pumice, and fragments of rock were 
 thrown out, and whence have flowed streams of trachytic or basaltic 
 lava. Such overflowings have been witnessed in modern times from 
 the highest summits of several of the peaks. The external slope of 
 each cone is generally greatest near its apex, where the volcanic 
 strata have also the steepest dip, sometimes attaining angles of 20, 
 30, and 35 degrees, but becoming less and less inclined as they recede 
 from the summit, until, near their base, the dip is reduced to 10 and 
 often 4 or 5 degrees.* The interference of the lavas of adjoining 
 volcanos sometimes produces elevated platforms, or "saddles," in 
 which the layers of rock may be very slightly inclined. At the top 
 of many of the loftiest mountains the active cone and crater are 
 of small size, and surrounded by a plain of ashes and sand, this 
 plain being encircled in its turn by what Dr. Junghuhn calls " the 
 old crater-wall," which is often 1000 feet and more in vertical height. 
 There is sometimes a terrace of intermediate height (as in the moun- 
 tain called Tengger), comparable to the " black ledge " of Kilauea 
 (fig. 641). Most of the spaces thus bounded by semicircular or more 
 than semicircular ranges of cliffs are vastly superior in dimensions to 
 
 * Java, deszelfs gedaante, bekleeding huhn. (German translation of 2d edit, 
 en invendige structuur, door F. Jung- by Hasskarl, Leipzig, 1852.) 
 
CH. XXIX.] JAVANESE CALDERAS. 497 
 
 the area of any known crater or hollow which has been observed in 
 any part of the world to be occupied by a lake of liquid lava. As 
 the Spaniards have given to such large cavities the name of Caldera 
 (or cauldron), it may be useful to use this term in a technical sense, 
 whatever views we may entertain as to their origin. Many of them 
 in Java are no less than four geographical miles in diameter, and they 
 are attributed by Junghuhn to the truncation by explosion and sub- 
 sidence of ancient cones of eruption. Unfortunately, although several 
 lofty cones have lost a portion of their height within the memory of 
 man, neither the inhabitants of Java nor their Dutch rulers have 
 transmitted to us any reliable accounts of the order of events which 
 occurred.* 
 
 Dr. Junghuhn believes that Papandayang lost some portion of its 
 summit in 1772 ; but affirms that most of the towns on its sides said 
 to have been engulphed were in reality overflowed by lava. 
 
 From the highest parts of many Javanese calderas rivers flow, 
 which in the course of ages have cut out deep valleys in the moun- 
 tain's side. As a general rule, the outer slopes of each cone are 
 furrowed by straight and narrow ravines from 200 to 600 feet deep, 
 radiating in all directions from the top, and increasing in number as 
 we descend to lower zones. The ridges or " ribs," intervening be- 
 tween these furrows, are very conspicuous, and compared to the 
 spokes of an umbrella. In a mountain above 10,000 feet high, no 
 furrows or intervening ribs are met with in the upper 300 or 400 
 feet. At the height of 10,000 feet there may be no more than 10 in 
 number, whereas 500 feet lower 32 of them may be counted. They 
 are all ascribed to the action of running water ; and if they ever cut 
 through the rim of a caldera, it is only because the cone has been 
 truncated so low down as to cause the summit to intersect a middle 
 region, where the torrents once exerted sufficient power to cause a 
 series of such indentations. It appears from such facts, that, if a cone 
 .escapes destruction by explosion or engulphment, it may remain un- 
 injured in its upper portion, while there is time for the excavation 
 of deep ravines by lateral torrents. 
 
 It is remarked by Dr. Junghuhn, as also by Mr. Dana in regard to 
 the Pacific Islands, that volcanic mountains, however large and 
 however much exposed to heavy falls of rain, support no rivers so 
 long as they are in the process of growth, or while the highest 
 crater emits from time to time showers of scoriae and floods of lava. 
 Such ejectamenta and such currents of melted rock fill up each 
 superficial inequality or depression where water might otherwise 
 collect, and are moreover so porous that no rill of water, however 
 small, can be generated. But where the subterranean fires have been 
 long since spent, or are nearly exhausted, and where the superficial 
 scoriae and lavas decompose and become covered with clayey soils, 
 the corrosive action of water begins to operate with a prodigious 
 force, proportionate to the steepness of the declivities and the in- 
 
 * See Principles of Geol., 9th edit. p. 493. 
 KK 
 
498 
 
 CANARY ISLANDS. 
 
 [Cn. XXIX. 
 
 Fig, 642, 
 
 Briera P* 
 
 Barlffvenfo 
 ft 
 
 coherent nature of the sand and ashes. Even the more solid lavas 
 are occasionally cavernous, and almost always alternate with scoriaa 
 and perishable tuffs, so as to be readily undermined, and most of 
 them are speedily reduced to fragments of a transportable size be- 
 cause they are divided by vertical joints or split into columns. 
 
 Canary Islands Palma. I have enlarged so fully in the " Prin- 
 ciples of Geology" on the different views entertained by eminent 
 authorities respecting the origin of volcanic cones, and the laws 
 governing the flow of lava, and its consolidation, that, in order not 
 to repeat here what I have elsewhere published, I shall confine 
 myself in the remainder of this chapter to the description of facts 
 observed by me during a recent exploration of Madeira and some of 
 the Canary Islands. In these excursions, made in the winter of 
 1853-4, I was accompanied by an active fellow-labourer, Mr. Har- 
 tung, of Konigsberg. We visited among other places the beautiful 
 island of Palma, a spot rendered classical by the description given of 
 it in 1825 by the late Leopold Von Buch, who regarded it as a type 
 of what he called a "crater of elevation."* 
 
 Palma is 16 geographical miles west of Teneriffe. Seen from the 
 
 channel which divides the two 
 islands, Palma appears to consist 
 of two principal mountain masses, 
 the depression between them 
 being at a (map, fig. 642.), or at 
 the pass of Tacanda, which is 
 about 4600 feet above the sea- 
 level. The most northern of 
 these masses makes, notwith- 
 standing certain irregularities 
 hereafter to be mentioned, a con- 
 siderable approach in general 
 form to a great truncated cone, 
 having in the centre a huge and 
 deep cavity called by the inha- 
 bitants " La Caldera." This ca- 
 vity (b, c, d, e, fig. 642.) is from 
 3 to 4 geographical miles in dia- 
 
 ^^ ^ ^ ^^ of preci _ 
 
 pices surrounding it vary from about 1500 to 2500 feet in vertical 
 height. From their base a steep slope, clothed by a splendid forest 
 of pines, descends for a thousand and sometimes two thousand feet 
 lower, the centre of the Caldera being about 2000 feet above the sea. 
 The northern half of the encircling ridge is more than 7000 English 
 feet above the sea in its highest peaks, and is annually white with 
 snow during the winter months. 
 
 Externally the flanks of this truncated .cone incline outwards in 
 every direction, the slopes being steepest near the crest, and lessening 
 
 Jf it en calien tcPt 
 
 Gbogr&Lile* 
 
 Map of Palma, from Survey of Capt. Vidal, R.N. 
 
 * Erhebung's Crater. 
 
CH. XXIX.] 
 
 C ALDER A OF PALMA. 
 
 499 
 
 as they approach the lower country. A great number of ravines 
 commence on the flanks of the mountain, a short distance below the 
 summit, shallow at first, but getting deeper as they des'cend, and 
 becoming at the same time more numerous, as in t the cones of Java 
 before mentioned. 
 
 So unbroken is the precipitous boundary-wall of the Caldera, 
 except at its south-eastern end, where the torrent which drains it 
 through a deep gorge (6, b', fig. 643.) issues, that there is not even a 
 footpath by which one can descend into it save at one place called 
 the Cumbrecito (e, map, fig. 642. p. 498.). This Cumbrecito is a 
 narrow col or watershed at the height of about 2000 feet above the 
 bottom of the Caldera, and 4000 above the sea, and situated at the 
 precise limit of two geological formations presently to be mentioned. 
 This col also occurs at the level where, in other parts of the Caldera, 
 the vertical precipices join the talus-like, rocky slope, covered with 
 pines. The other or principal entrance by which the Caldera is 
 
 Fig. 643. 
 
 Map of the Caldera of Palma and the great ravine, called " Barranco de las Angustias " Froi 
 
 the Survey of Capt. Vidal, R. N., 1837. Scale, two geographical miles to an inch. 
 
 K K 2 
 
500 
 
 ISLAND OF PALMA. 
 
 [Cn. XXIX. 
 
 drained is the great ravine or barranco, as it is called (see b, b', fig. 
 643.), which extends from the south-western extremity of the Cal- 
 dera to tfle sea, a distance of 4^ geographical miles, in which space 
 the water of the torrent falls about 1500 feet. 
 
 View of the Isle of Palmaj and of the entrance into the central cavity or Caldera. From 
 Von Buch's " Canary Islands." 
 
 This sketch was taken by Von Buch from a point at sea not 
 visited by us, but we saw enough to convince us that several lateral 
 cones ought to have been introduced on the great slope to the left, 
 besides numerous deep furrows radiating from near the summit to the 
 sea (see the map, fig. 643.). The sea does not enter the great 
 Barranco, as might be inferred from this sketch. 
 
 The annexed section (fig. 645.) passes through the island from 
 Santa Cruz de Palma to Briera Point, or from south-east to north- 
 west (see map, p. 498.). It has been drawn up on a true scale 
 of heights and horizontal distances from the observations of 
 Mr. Hartung and my own. 
 
 Fig. 645. 
 
 Section of the Island of Palma, from Point Briera, on the north-west, to Santa Cruz de Palma, on 
 
 the south-east. See map, fig. 642., p. 498. 
 a, I. The Caldera (height of a, 6000 feet). c. Commencement of steeper dip. 
 
 d. Santa Cruz de Palma or Tedote. 
 
 e. Lateral cone, 3940 feet above the sea ( Vidal's Map). 
 /. Briera Point. 
 
 g. One of several outliers of the upper formation in centre of Caldera. 
 S. P. Half-buried cone and crater of San Pedro. 
 
 The lavas are seen to be slightly inclined near the sea at Santa 
 Cruz, where we observed them flowing round the cone of San Pedro, 
 which they have more than half buried without entering the crater. 
 On starting from the same part of the sea-coast, and ascending the 
 deep Barranco de la Madera, we saw just below c the basaltic lavas 
 dipping at an angle of 5 degrees, there being no dikes in that region. 
 Farther up, where the dikes were still scarce, the dip of the beds 
 increases to 10 and 15 degrees, and they become still steeper as they 
 approach the Caldera at b, where dikes abound. 
 
CH. XXIX.] SECTION OF ISLAND OF PALMA. 
 
 501 
 
 Ed 
 
 .II 
 
 5 A 
 S* 
 
 ! I 
 
 5 g 
 
 '5? 
 II 
 
 Ij 
 
 ol 
 
 1! 
 
 Is 
 
 3! 
 
 II 
 
 I | 
 
 | | II 1 1 
 
 Il!l91 
 
 IS 
 
 3:2 
 
 i! 
 
 ! 
 
 * e 
 
 w i- c 
 
 & 
 
 II 
 
 ER 3 
 
502 STRUCTURE AND ORIGIN OF THE [Cn. XXIX. 
 
 The section (fig. 646.) is at right angles to the preceding, and cuts 
 through the cone in the direction of the great Barranco, or from 
 north-east to south-west. 
 
 The lowest of the two slanting lines, m, i, descending from the 
 Caldera to the sea along the bottom of the Barranco, represents the 
 present bed of the torrent ; the upper line, k, I, the height at which 
 beds of gravel, derated high above the present river-channel, are 
 visible in detached patches, shown by dotted spaces at ^, and to the 
 south-west of it, on the same slope. These, and the continuous 
 stratified gravel and conglomerate lower down at / and i, are newer 
 than all the volcanic rocks seen in this section. 
 
 The upper volcanic formation, to be described in the sequel, is 
 traversed by numerous dikes, which could not be expressed on this 
 small scale. The vertical lines in the lower formation represent a 
 few of the perpendicular dikes which abound there. Countless 
 others, inclined and tortuous, are found penetrating the same rocks. 
 The five outliers of somewhat pyramidal shape, at the bottom of the 
 Caldera (on each side of m\ agree in structure and composition with 
 the upper formation, and may have subsided into their present 
 position, if the Caldera was caused by engulphment, or may have slid 
 down in the form of land-slips, if the cavity be attributed chiefly to 
 aqueous erosion. 
 
 In the description above given of the section (fig. 646.), the cliffs 
 which wall in the Caldera are spoken of as consisting of two forma- 
 tions. Of these the uppermost alone gives rise to vertical precipices, 
 from the base of which the lower descends in steep slopes, which, 
 although they have the external aspect of taluses, are not in fact 
 made up of broken materials, or of ruins detached from the higher 
 rocks, but consist of rocks in place. Both formations are of volcanic 
 origin, but they differ in composition and structure. In the upper, 
 the beds consist of agglomerate, scoriae, lapilli, and lava, chiefly 
 basaltic, the whole dipping outwards, as if from the axis of the 
 original cone, at angles varying from 10 to 28 degrees. The solid 
 lavas do not constitute more than a fourth of the entire mass, 
 and are divided into beds of very variable thickness, some scoriaceous 
 and vesicular, others more compact, and even in some cases rudely 
 columnar. All these more stony masses are seen to thin out and 
 come to an end wherever they can be traced horizontally for a 
 distance of a quarter of a mile, and usually sooner. Coarse breccias 
 or agglomerates predominate in the lower part, as if the commence- 
 ment of the second series of rocks marked an era of violent gaseous 
 explosions. Single beds of this aggregate of angular stones and 
 scoriae attain a thickness of from 200 to 300 feet. They are united 
 together by a paste of volcanic dust or spongiform scoriae. 
 
 At one point on the right side of the great Barranco, near its 
 exit from the Caldera, we observed in the boundary precipice a lofty 
 column of amorphous and scoriaceous rock in which the red or rust- 
 coloured scorise are as twisted and ropy as any to be seen on the 
 slopes of Vesuvius ; seeming to imply that there, was here an ancient 
 
CH. XXIX.] CALDERA OF PALMA. 503 
 
 vent or channel of discharge subsequently buried under the products 
 of newer eruptions. Countless dikes, more or less vertical, consisting 
 chiefly of basaltic lava, traverse the walls of the Caldera, some of 
 them terminating upwards, but a great number reaching the very 
 crest of the ridge, and therefore having been posterior in origin to 
 the whole precipice. 
 
 We could not discover in any one of the fallen masses of agglo- 
 merate which strewed the base of the cliffs a single pebble or 
 waterworn fragment. Each imbedded stone is either angular or, 
 if globular, consists of scoriae more or less spongy, and evidently not 
 owing its shape to attrition. It would be impossible to account for 
 the absence of waterworn pebbles if the coarse breccia in question 
 had been spread by aqueous agency over a horizontal area co- 
 extensive with the Caldera and the volcanic rocks which surround 
 it. The only cause known to us capable of dispersing such heavy 
 fragments, some of them 3, 4, or 6 feet in diameter, without blunting 
 their edges, is the power of steam, unless indeed we could suppose 
 that ice had co-operated with water in motion ; and the interference 
 of ice cannot be suspected in this latitude (28 40'), especially as I 
 looked in vain for signs of glacial action here and in the other 
 mountainous regions of the Canary Islands. 
 
 The lower formation of the Caldera is, as before stated, equally of 
 igneous origin. It differs in its prevailing colour from the upper, 
 exhibiting a tea-green and in parts a light yellow tint, instead of 
 the usual brown, lead-coloured, or reddish hues of basalt and its 
 associated scorise. Beds of a light greenish tuff are common, 
 together with trachytic and greenstone rocks, the whole so reti- 
 culated by dikes, some vertical, others oblique, others tortuous, that 
 we found it impossible to determine the general dip of the beds, 
 although at the head of the great gorge or Barranco they certainly 
 dip outwards, or to the south, as stated by Von Buch. But in 
 following the section down the same ravine, where the mountain 
 called Alejanado (d, figs. pp. 498. and 501.) is cut through, and where 
 the rocks of the lower formation are very crystalline, we found what 
 is not alluded to by the Prussian geologist, that the beds exposed 
 to view in cliffs 1500 feet high have an anticlinal arrangement, 
 exhibiting first a southerly and then a northerly dip at angles 
 varying from 20 to 40 degrees (see section, fig. 646. at k.). Hence we 
 may presume that the older strata must have undergone great 
 movements before the upper formation was superimposed. No 
 organic remains having been discovered in the older series, we 
 cannot positively decide whether it was of subaerial or submarine 
 origin. We can only affirm that it has been produced by successive 
 eruptions, chiefly of felspathic lavas and tuffs. Many beds which 
 probably consisted at first of soft tuffs have been much hardened by 
 the contact of dikes and apparently much altered by other plutonic 
 influences, so that they have acquired a semicrystalline and almost 
 metamorphic character. 
 
 The existence of so great a mass of volcanic rocks of ancient date 
 
 KK 4 
 
504 CALDERA OF PALMA. [Ce. XXIX. 
 
 on the exact site of an equally vast accumulation of comparatively 
 modern lavas and scorise is peculiarly worthy of notice as a general 
 phenomenon observed in very different parts of the globe. It proves 
 that, notwithstanding the fact in the past history of volcanos that 
 one region after another has been for ages and has then ceased to be 
 the chief theatre of igneous action, still the activity of subterranean 
 heat may often be persistent for more than one geological period in 
 the same place, relaxing perhaps its energies for a while, but then 
 breaking out afresh with an intensity as great as ever. 
 
 We have still to consider the mode of origin of the higher volcanic 
 mass, or the upper series of rocks with which the peculiar form of 
 the Caldera is more intimately connected. The principal question 
 here arising is this, whether the mass was dome-shaped from the be- 
 ginning, having grown by the superposition of one conical envelope 
 of lava and ashes formed over another, or whether, as Von Buch 
 and his followers imagine, its component materials were first spread 
 out in horizontal or nearly horizontal deposits and then upheaved at 
 once into a dome-shaped mountain with a caldera in its centre. 
 According to the first hypothesis the cone was built up gradually, 
 and completed with all its beds dipping as now, and traversed by all 
 its dikes, before the Caldera originated. According to the other, 
 the Caldera was the result of the same movements which gave a 
 dome-shaped structure to the mass, and which caused the beds to be 
 highly inclined ; in other words, the cone and the Caldera were 
 produced simultaneously. So singularly opposite are these views 
 that the principal agency introduced by the one theory is upheaval, 
 by the other subsidence. The very name of " Elevation Craters " 
 points to the kind of movement to which one school attributes the 
 origin of a cone and caldera ; whereas the chief agencies appealed 
 to by the other school are gaseous explosions, engulphment, and 
 aqueous denudation. 
 
 The favourable reception of the doctrine of upheaval has arisen 
 from the following circumstances. Streams of lava, it is said, 
 which run down a declivity of more than three degrees are never 
 stony; and, if the slope exceed five or six degrees, they are mere 
 shallow and narrow strings of vesicular or fragmentary slag. 
 Whenever, therefore, we find parallel layers of stony lava, especially 
 if they be of some thickness, high up in the walls of a caldera, we 
 may be sure that they were solidified originally on a very gentle 
 slope ; and if they are now inclined at angles of 10, 20, or 30, 
 not only they, but all the interstratified beds of lapilli, scoriae, tuff*, 
 and agglomerate, must have been at first nearly flat and must have 
 been afterwards lifted up with the solid beds into their present 
 position. It is supposed that such a derangement of the strata could 
 scarcely fail to give rise to a wide opening near the centre of 
 upheaval, and in the case of Palma, the Caldera (which Von Buch 
 called " the hollow axis of the cone ") may represent this breach 
 of continuity. 
 
 Among other objections to the elevation-crater theory often 
 
CH. XXIX.] HYPOTHESIS OF UPHEAVAL. 505 
 
 advanced and never yet answered are the following : First, in 
 most calderas, as in Palma, the rim of the great cavity and the 
 circular range of precipices surrounding it remain entire and 
 unbroken on three sides, whereas it is difficult to conceive that a 
 series of volcanic strata 2000 or 3000 feet thick could have once 
 extended over an area six or seven miles in its shortest diameter 
 and then have been upraised bodily, so that the beds should dip at 
 steep angles towards all points of the compass from a centre, and 
 yet that no great fractures should have been produced. We should 
 expect to see some open fissures on every side, widening as they 
 approach the caldera. The dikes, it is true, do undoubtedly attest 
 many dislocations of the mass, which have taken place at successive 
 and often distant periods. But none of them can have belonged to 
 the supposed period of terminal and paroxysmal upheaval, for, had 
 the caldera existed when they originated, the melted matter now 
 solidified in each dike must, instead of filling a rent, have flowed 
 down into the caldera, tending so far to obliterate the great cavity. 
 
 The second objection is the impossibility of imagining that so vast 
 a series of agglomerates, tuffs, stratified lapilli, and highly scoria- 
 ceous lavas could have been poured out within a limited area without 
 soon giving rise to a hill, and eventually to a lofty mountain. Such 
 heavy angular fragments as are seen in the agglomerates, single beds 
 of which are sometimes 200 or 300 feet thick, must when hurled 
 into the air have fallen down again near the vent, and would be 
 arranged in inclined layers dipping outwards from the central axis 
 of eruption. It is in perfect accordance with this hypothesis that we 
 should behold agglomerates, lapilli, and scoriaa predominating in the 
 walls of the Caldera ; whereas in the ravines nearer the sea, where 
 the inclination of the beds has diminished to 10 and even to 5 
 degrees, the proportion of stony as compared to fragmentary ma- 
 terials is precisely reversed. It is also natural that the dikes should 
 be most numerous where the ejectamenta are to the more solid beds 
 in the proportion of 3 to 1, as at 6, fig. 645. p. 500. ; while the dikes 
 are few in number where the stony lavas predominate (as at c, ibid.). 
 Many of the scoriaceous beds at b may be the upper extremities of 
 currents which became stony and compact when they reached c, 
 and flowed over a more level country; but this suggestion cannot 
 be assented to by the advocates of the upheaval theory, for it assumes 
 the existence of a cone long before the time had arrived for the 
 catastrophe which according to their views gave rise to a conical 
 mountain. 
 
 If, however, we reject the doctrine that the beds were tilted by a 
 movement posterior to the accumulation of all the compact and frag- 
 mentary rocks, how are we to account for the steepness of the dip of 
 some stony lavas high up in the walls of the Caldera ? These masses 
 are occasionally 50 or 100 feet thick, of lenticular shape, as seen in 
 the cliffs from below, and to all appearance parallel to the associated 
 layers of scoriae and lapilli. But unfortunately no one can climb up 
 and determine how far the supposed parallelism may be deceptive. 
 
506 STONY LAVAS FORMED ON SLOPES. [Cn. XXIX. 
 
 The solid beds extend in general over small horizontal spaces, and 
 some of them may possibly be no other than intrusive lavas, in the 
 nature of dikes, more or less parallel to the layers of ejectamenta. 
 Such lavas, when the crater was full, may have forced their way 
 between highly inclined beds of scoriae and lapilli. We know that 
 lava often breaks out from the side or base of a cone, instead of 
 rising to the rim of the crater. Nevertheless one or two of the stony 
 masses alluded to seemed to me to resemble lavas which had flowed 
 out superficially. They may have solidified on a broad ledge formed 
 by the rim of a crater. Such a rim might be of considerable breadth 
 after a partial truncation of the cone. And some lavas may now 
 and then have entirely filled up the atrium, or what in the case of 
 Somma and Vesuvius is called the atrio del cavallo, that is to say, 
 the interspace between the old and new cone. When by the products 
 of new eruptions a uniform slope has been restored, and the two cones 
 have blended into one (see e, d, c, fig., p. 515.), the next breaking down 
 of the side of the mountain may display a mass of compact rock of 
 great thickness in the walls of a caldera, resting upon and covered 
 by ejectamenta. Other extensive wedges of solid lava will be 
 formed on the flanks of every volcanic mountain by the interference 
 of lateral, or, as they are often termed, parasitic cones, which check 
 or stop the downward flow of lava, and occasionally offer deep craters 
 into which the melted matter is poured. 
 
 By aid of one or all the processes above enumerated we may 
 certainly explain a few exceptional cases of intercalated stony beds, 
 in the midst of others of a loose and scoriaceous nature, the whole 
 being highly inclined. But to account for a succession of compact 
 and truly parallel lavas having a steep dip, we may suppose that they 
 flowed originally down the flanks of a cone sloping at angles of from 
 4 to 10 degrees, as in many active volcanos, and that they acquired 
 subsequently a steeper inclination. It would be rash to assume the 
 entire absence of local disturbances during the growth of a volcanic 
 mountain. Some dikes are seen crossing others of a different com- 
 position, marking a distinctness in the periods of their origin. The 
 volume of rock filling such a multitude of fissures as we see indicated 
 by the dikes in Palma must be enormous ; so that, could it be with- 
 drawn, the mass of ejectamenta would collapse and lose both in height 
 and bulk. The injection, therefore, of all this matter in a liquid 
 state must have been attended by the gradual distension of the cone, 
 the increase of which I have elsewhere compared both to the exo- 
 genous and endogenous growth of a tree, as it has been effected alike 
 by external and internal accessions. 
 
 But the acquisition of a steeper dip by such reiterated rendings 
 and injections of a cone is altogether opposed to the views of 
 those who defend the upheaval hypothesis, because it draws with it 
 the conclusion that the slopes were always growing steeper and steeper 
 in proportion as the cone waxed older and loftier. Once admit this, 
 and it follows, that the upper layers of solid lava must have con- 
 
CH. XXIX.] AQUEOUS EROSION IN PALMA. 507 
 
 formed to surfaces already inclined at angles of 20, or, in the case of 
 the Caldera of Palma, 28 degrees. 
 
 For this reason the defenders of the upheaval hypothesis are con- 
 sistent with themselves in assigning the whole movement by which 
 the strata, whether solid or incoherent, have been tilted, exclusively 
 to one terminal catastrophe. The whole development of subter- 
 ranean force is represented as the last incident in every series of 
 volcanic operations, the closing scene of the drama ; and the sudden 
 and paroxysmal nature of the catastrophe is inferred from the 
 absence of all signs of successive and intermittent action so cha- 
 racteristic of the antecedent volcanic phenomena. 
 
 I have alluded to an opinion entertained by some able geologists, 
 that no lava can acquire any degree of solidity if it flows down a 
 declivity of more than three degrees. This doctrine I believe to be 
 erroneous. The lava which has flowed from the cone of Llarena 
 near Port Orotava, in TenerifFe, is very columnar in parts, and yet 
 has descended a slope of six degrees. Another stream of recent 
 aspect near the town of El Passo, in Palma, has a general inclination 
 of ten degrees, and is remarkable for the depth and extent of the 
 large basin-shaped hollows, 20, 30, and 35 feet deep, seen everywhere 
 on its surface. Whenever another lava-current shall flow down over 
 this one, although its average inclination will be the same, it must 
 fill up all these inequalities, and in doing so must give rise to masses 
 of compact and solid rock 20 or 30 feet thick, resting upon and 
 encircled by vesicular lava. Other lavas north-east of Fuencaliente 
 at the southern extremity of Palma, so modern as to be still black 
 and uncovered with vegetation, descend slopes of no less than 22 
 degrees, and yet contain large masses of compact stone, formed 
 chiefly on the sides of tunnel-shaped cavities, 15 or 20 feet deep, in 
 which one layer has solidified within another on the walls of these 
 channels, while in the central part the lava seems to have remained 
 fluid so as to run out of the tunnel, leaving an arched cavity, the 
 roof of which has in most cases fallen in. The strength of the en- 
 veloping crust of scoriae at the lower end of a lava-current in which 
 one of these tunnels existed may have been sufficient to arrest the 
 progress of the stream for hours or days, and during that time 
 solidification may have occurred under great hydrostatic pressure. 
 
 Before taking leave of Palma, we have yet to consider another 
 distinct point, namely, what amount of denudation has taken place 
 in the Caldera, and its environs. Assuming that the great cavity or 
 some part of it may have originated in the truncation of a cone in 
 the manner before suggested, to what extent has its shape been sub- 
 sequently enlarged or modified by aqueous erosion? It will be 
 remembered that a conglomerate of well-rounded pebbles, no less 
 than 800 feet thick, was spoken of as visible in the great Barranco 
 (see description of section, pp. 501, 502.). That conspicuous deposit, 
 3 or 4 miles in length, was evidently derived from the destruction 
 of rocks like those in the Caldera, for the present torrent brings 
 
508 EXTENT AND NATURE OF [Cn. XXIX. 
 
 down annually similar stones of every size, some very large, and 
 rounds them by attrition in its channel. By what changes in the 
 configuration of the island after the old volcano and its Caldera were 
 formed was so vast a thickness of gravel formed, to be afterwards 
 cut through to a depth of 800 feet? The ravine through which 
 the torrent now flows has been excavated to that depth through the 
 old conglomerate. The occurrence of two or three layers of con- 
 temporaneous lava, intercalated between the strata of puddingstone, 
 ought not to surprise us ; for even in historical times eruptions have 
 been witnessed in the southern half of Palma. Such basaltic lavas, 
 one of them columnar in structure, have not come down from the 
 Caldera, but from cones much nearer the sea, and immediately ad- 
 joining the Barranco, like the cone of Argual (see map, p. 499.) and 
 others. These lavas, of the same age as the conglomerate, consist 
 of three or four currents of limited extent, for in many parts of the 
 river-cliffs no volcanic formation is visible on either bank. On the 
 right bank of the Barranco, the conglomerate, when traced west- 
 ward, is soon found to come to an end as it abuts against the lofty 
 precipice E (fig. 647.), which is a prolongation of the western wall 
 of the Caldera. Its extent eastward from b f , may be more consider- 
 able, but cannot be ascertained, as it is concealed under modern 
 scorias and lava spread over the great platform, F. 
 
 Fig. 647. 
 
 East. 
 
 A. Ravine or Barranco de las Angustias, near its termination in Palma. 
 
 b, b', b". Conglomerate, 800 feat thick in parts. 
 
 c, c'. Lava intercalated between the beds of conglomerate. 
 
 d, d'. Another and older current of basaltic lava, columnar in parts. 
 
 K. Cliff of ancient volcanic rocks of the Upper Formation (p. 504.), a prolongation of the western 
 
 wall of the Caldera. 
 F. Platform on which the town of Argual stands. 
 
 As we could find no organic remains in the old gravel, we have no 
 positive means of deciding whether it be fluviatile or marine. The 
 height of its base above the sea, where it is 800 feet thick, may be 
 about 350 feet, but patches of it ascend to elevations of 1000 and 
 1500 feet near the top of the Barranco, as shown at k, &c., in section, 
 fig. 646., p. 501. Such a mass of gravel, therefore, bears testimony 
 to the removal of a prodigious amount of materials from the Caldera 
 by the action of water. Whether a river or the sea was the trans- 
 porting agent, it is obvious that a large portion of the volcanic 
 materials, consisting of sand, lapilli, and scoriae, before described 
 
CH. XXIX.] AQUEOUS EROSION IN PALMA. 509 
 
 (p. 502.), as belonging to the upper formation in the Caldera, would 
 leave behind them few pebbles. Nearly all of these perishable 
 deposits would be swept down in the shape of mud into the Atlantic. 
 Even the hard rounded stones, since they were once angular and 
 are now ground down into pebbles, must have lost more than half 
 their original bulk, and bear witness to large quantities of sedi- 
 mentary matter consigned to the bed of the ocean. We saw in the 
 Caldera blocks of huge size thrown down by cascades from the upper 
 precipices during the melting of the snows, a fortnight before our 
 visit, and much destruction was likewise going on in the lower set of 
 rocks by the same agency. We also learnt that a great flood rushed 
 down the Barranco in the spring of 1854, shortly before our arrival, 
 damaging several houses and farms, and I have therefore no doubt 
 that the erosive power even of rain and river water, aided by earth- 
 quakes, might in the course of ages empty out a valley as large as the 
 Caldera, although probably not of the same shape. I am disposed to 
 attribute the circular range of cliffs surrounding the Caldera to vol- 
 canic action, because they forcibly reminded me of the precipices 
 encircling three sides of the Val del Bove, on Etna ; and because 
 they agree so well with Junghuhn's description of the " old crater- 
 walls " of active volcanos in Java, some of which equal or surpass in 
 dimensions even the Caldera of Palma. The latter may have con- 
 sisted at first of a true crater, enlarged afterwards into a caldera by 
 the partial destruction of a great cone ; but, if so, it has certainly 
 been since modified by denudation. Nor can any geologist now de- 
 fine how much of the work has been accomplished by aqueous, and 
 how much by volcanic agency. The phenomenon of a river cutting 
 its channel through a dense mass of ancient alluvium formed during 
 oscillations in the level of the land is not confined to volcanic coun- 
 tries, and I need not dwell here on its interpretation, but refer to 
 what was said in the 7th chapter. (See p. 84.). 
 
 There remains, however, another question of high theoretical 
 interest ; namely, whether the denudation was marine or fluviatile. 
 It was stated that the materials of the great cone or assemblage 
 of cones in the north of Palma are of subaerial origin, as proved 
 by the angularity of the fragments of rock in the agglomerates ; 
 but it may be asked, whether, when the Caldera was formed long 
 afterwards, it may not, like the crater of St. Paul's (fig. 649., 
 p. 513.), have had a communication with the sea, which may have 
 entered by the great Barranco, and if, after a period of partial 
 submergence, the island may not then have risen again to its ori- 
 ginal altitude. In such a case the retiring waters might leave 
 behind them a conglomerate, partly of river-pebbles, collected at the 
 points where the torrent successively entered the sea, and partly of 
 stones rounded by the waves. The torrent may have finally cut a 
 deep ravine in the gravel and associated lavas when the land was 
 rising again. Such oscillations of level, amounting to more than 
 2000 feet, would not be deemed improbable by any geologists, pro- 
 vided they enable us to explain more naturally than by any other 
 
510 EXTENT AND NATURE OF [Cn. XXIX. 
 
 causation, the origin of the physical outlines of the country. As to 
 the fact that no marine shells have yet been discovered in the 
 conglomerate, sufficient search has not yet been made for them to 
 entitle us to found an argument on such negative evidence. At the 
 same time I confess, that, having found sea-shells and bryozoa 
 abundantly in certain elevated marine conglomerates in the Grand 
 Canary, before I visited Palma, and being unable to meet with any 
 in the Barranco de las Angustias, I regarded the old gravel when I 
 was on the spot as of fluviatile origin. Such inferences are always 
 doubtful in the absence of more positive data, and the intervention 
 of the sea will unquestionably account for some phenomena in the 
 configuration of the Caldera and Barranco more naturally than river 
 action. For example, we have the lofty cliff E, fig. p. 508. already 
 mentioned, and c, f, map, p. 498., extending four or five miles from 
 the Caldera to the sea on the right bank of the Barranco, and no 
 cliff of corresponding height or structure on the other bank, where 
 for miles towards the south-east there is the platform F, fig. p. 508. 
 supporting several minor volcanic cones. The sea might be sup- 
 posed to leave just such a cliff as E, after cutting away a portion of 
 the south-western extremity of the old dome-shaped mountain in the 
 north of Palma, whereas a torrent or river would leave a cliff of 
 similar structure and nearly equal height on both banks. As to the 
 fact of the old conglomerate ascending an inclined plane, i, I, k, 
 p. 501., from the sea-level to an elevation of about 1500 feet, near 
 the entrance of the Caldera, this is by no means conclusive in favour 
 of fluviatile action, although some elevated patches of the same may 
 in truth belong to an old river-bed ; but in South America gravel- 
 beds of marine origin have a similar upward slope, when followed 
 inland, and the cause of such an arrangement has been explained in 
 a satisfactory manner by Mr. Darwin.* 
 
 Another argument in favour of marine denudation may be derived 
 from that peculiar feature in the configuration of Palma, before 
 alluded to, called the pass of the Cumbrecito (e, fig. 646., p. 501.), 
 forming a notch in the uppermost line of precipices surrounding 
 the Caldera. This break divides the mountain called Alejenado, d, 
 fig., p. 501., from the eastern wall c f, and cuts quite through the 
 upper formation ; yet the range of precipice f, e, on the eastern side 
 of the Caldera is continued uninterruptedly, and retains its full height 
 of 1500 or 2000 feet above its base, to the southward of the Cum- 
 brecito, or from e towards a, map, fig. 642., p. 498. In this prolon- 
 gation of the cliff for half a mile southward beds of volcanic matter 
 and dikes are seen, as in the walls of the Caldera. 
 
 The indentation forming the pass of the Cumbrecito, e, p. 501., has 
 more the appearance of an old channel, such as a current of water 
 may have excavated, than of a rent or a chasm caused by a fault. In 
 case of a fault the lower formation would not be persistent and unin- 
 terrupted across the Cumbrecito, constituting the watershed; but 
 would have sunk down and have been replaced by the upper basaltic 
 
 * Gcolog. Observ., South America, p. 43. 
 
CH. XXIX.] AQUEOUS EROSION IN PALMA. 511 
 
 rocks. If we could assume that the sea once entered the Caldera 
 here as well as by the great Barranco, it might have produced such 
 a breach as e, .and such an extension of the line of cliffs as that now 
 observable between e and a, map, p. 498. without any corresponding 
 cliff to the westward of e, a. 
 
 Yet we could discover no elevated outliers of conglomerate to 
 attest the supposed erosion at the Cumbrecito, which is about 
 3500 feet above the level of the sea. It might also be objected to 
 the hypothesis of marine denudation in Palma, that there are no 
 ranges of ancient sea-cliffs on the external slopes of the island. 
 The flanks of the mountain, except where it is furrowed by ravines 
 or broken by lateral cones, descend to the sea with a uniform 
 inclination. In reply to such a remark, I may observe that we do 
 not require the submergence of the uppermost 3000 feet of the 
 old cone in order to allow the sea to enter both the great Barranco 
 and the Cumbrecito and to flow into the Caldera, It would be 
 enough to suppose the land to sink down so as to permit the waves 
 to wash the base of the basaltic cliffs in the interior of the Cal- 
 dera, and to wear a passage through the Cumbrecito where there 
 may have been always a considerable depression in the outline of 
 the upper formation. But would not the same waves which had 
 power to form in the Barranco a mass of conglomerate 800 feet 
 thick have left memorials of their beach-action on the external 
 slope of the island ? No such monuments are to be seen. It may 
 be said, in explanation, first, that cliffs are not so easily cut on the 
 side of an island towards which the beds dip as on the side from 
 which they dip ; secondly, if some small cliffs and sea-beaches had 
 existed, they may have been subsequently buried under showers of 
 ashes and currents of lava proceeding from lateral cones during 
 eruptions of the same date as those which were certainly contem- 
 poraneous with the conglomerate of the great Barranco. 
 
 On the eastern coast of Palma, about half a mile from the sea, in 
 the ravine of Las Nieves, not far from Santa Cruz, we observed a 
 conglomerate of well-rounded pebbles having a thickness of 100 
 feet, covered by successive beds of lava, also about 100 feet thick. 
 In this instance the ancient gravel beds occupy a position very 
 analogous to the buried cone, s. p., fig. 645., p. 500. When in Palma, 
 I conceived them to be of fluviatile origin ; but, whether marine or 
 freshwater, it must be admitted that the superposition of so dense an 
 accumulation of lavas to a mass of conglomerate 100 feet thick 
 shows how easily the outer slopes of the island may have been 
 denuded by the sea and yet display no superficial signs of marine 
 denudation, every old beach or delta once at the mouth of a torrent 
 being concealed under newer volcanic outpourings. 
 
 Since the cessation of volcanic action in the north of Palma, the 
 most frequent eruptions appear to have taken place in a line running 
 north and south, from a to Fuencaliente, map, p. 498. ; one of the 
 volcanos in this range, called Yerigojo, g, being no less than 6565 
 English feet high. The lavas descending from several vents in this 
 
512 
 
 ISLAND OF ST. PAUL. 
 
 XXIX. 
 
 chain reach the sea both on the east and west coast, and are many 
 of them nearly as naked and barren of vegetation as when they first 
 flowed. The tendency in volcanic vents to assume a linear ar- 
 rangement, as seen in the volcanos of the Andes and Java on a 
 grand scale, is exemplified by the cones and craters of this small 
 range in Palma. It has been conjectured that such linearity in the 
 direction of superficial outbreaks is connected with deep fissures in 
 the earth's crust communicating with a subjacent focus of subter- 
 ranean heat. 
 
 By discussing at so much length the question whether the sea 
 may or may not have played an important part in enlarging the 
 Caldera of Palma, I have been desirous at least to show how many 
 facts and observations are required to explain the structure and 
 configuration of such volcanic islands. It may be useful to cite, in 
 illustration of the same subject, the present geographical condition 
 of St. Paul's or Amsterdam Island, in the Indian Ocean, midway 
 between the Cape of Good Hope and Australia. 
 
 Fig. 618. 
 
 Nine-pin 
 rock. 
 
 Entrance nearly dry at 
 -** Jow water. 
 
 Map of the Island of St. Paul, in the Indian Ocean, lat. 38 44' S., long. 77 37' E-, 
 surveyed by Capt. Blackwood, R.N., 1842. 
 
 In this case the crater is only a mile in diameter and 180 feet 
 deep, and the surrounding cliffs where loftiest about 800 feet high, so 
 that in regard to size such a cone and crater are insignificant when 
 compared to the cone and Caldera of Palma or to such volcanic 
 domes as Mounts Loa and Kea in the Sandwich Islands. But the 
 Island of St. Paul exemplifies a class of insular volcanos into which 
 
CH. XXIX.] ISLAND OF ST. PAUL. TENERIFFE 
 
 Fig. 649. 
 
 513 
 
 View of the Crater of the Island of St. Paul. 
 Fig. 650. 
 
 Side view of the Island of St. Paul (N.E. side). Nine-pin rocks two miles distant. 
 (Captain Blackwood.) 
 
 the ocean now enters by a single passage. Every crater must 
 almost invariably have one side much lower than all the others, 
 namely that side towards which the prevailing winds never blow, 
 and to which, therefore, showers of dust and scoriae are rarely 
 carried during eruptions. There will also be one point on this 
 windward or lowest side more depressed than all the rest, by which 
 in the event of a partial submergence the sea may enter as often as 
 the tide rises, or as often as the wind blows from that quarter. For 
 the same reason that the sea continues to keep open a single 
 entrance into the lagoon of an atoll or annular coral reef, it will not 
 allow this -passage into the crater to be stopped up, but will scour it 
 out at low tide, or as often as the wind changes. The channel, 
 therefore, will always be deepened in proportion as the island rises 
 above the level of the sea, at the rate perhaps of a few feet or yards 
 in a century. 
 
 The crater of Vesuvius in 1822 was 2000 feet deep ; and, if it 
 were a half-submerged cone like St. Paul, the excavating power of 
 the ocean might in conjunction with a gradual upheaving force give 
 rise to a large caldera. Whatever, therefore, may have been the 
 nature of the forces, igneous or aqueous, which have shaped out the 
 Val del Bove on Etna or the deep abyss called the Caldera in the 
 north of Palma, we can scarcely doubt that many craters have been 
 enlarged into calderas by the denuding power of the ocean, when- 
 ever considerable oscillations in the relative level of land and. sea 
 have occurred. 
 
 Peak of Teneriffe. The accompanying view of the Peak, taken 
 
 LL 
 
514 
 
 VIEW OF PEAK OP TENERIFFE. [On. XXIX. 
 
 
 
 I -3,8 * 
 I log 
 
 > 5 1<i 
 o *<= 
 
 5 1-1 
 f Jl 
 
CH. XXIX.] PEAK OF TENERIFFE. 515 
 
 From sketches made by Mr. Hartung and myself during our visit to 
 Teneriffe in 1854, will show the manner in which that lofty cone is 
 encircled on more than two sides by what I consider as the ruins of 
 an older cone, chiefly formed by eruptions from a summit which has 
 disappeared. That ancient culminating point from which one or 
 more craters probably poured forth their lavas and ejectamenta may 
 not have been placed precisely where the present peak now rises, 
 and may not have had the same form, but its position was probably 
 not materially different. The great wall or semicircular range of 
 precipices, c c, surrounding the atrium, b b, is obviously analogous to 
 the walls of a Caldera like that of Palma ; but here the cliffs are 
 insignificant in dimensions when compared to those in Palma, being 
 in general no more than 500 feet high and rarely exceeding 1000 
 feet. The plain or atrium, b b, figs. 651. and 652., lying at the base 
 of the cliffs, is here called Las Canadas, and is covered with sand and 
 pumice thrown out from the Peak or from craters on its flanks. 
 Copious streams of lava, dd, have also flowed down from lateral 
 openings, especially from a crater called the Chahorra, f, fig. 652., 
 which is not seen in the view, fig. 651., as it is hidden by the Peak. 
 The last eruption was as late as the year 1798. 
 
 Fig. 652. 
 
 Guia 
 
 S.W. N.E. 
 
 Section through part of Teneriffe, from N.E. to S.W. On a true scale ; as given in 
 
 Von Buch's " Canary Islands." 
 
 a. Peak of Teneriffe. b. The Canadas or atrium. 
 
 c. Cliff bounding the atrium. d. Modern lavas. 
 
 /. Cone and crater of Chahorra. 
 
 To what extent the lavas, dd, figs. 651. and 652., may have nar- 
 rowed the circus or atrium, b, or taken away from the height of 
 the cliff c, no geologist can determine for want of sections ; but 
 should the Peak and the Chahorra continue to be active volcanos 
 for ages, the new cone, a, might become united with the old one, 
 and the lava might flow first from e to c and then from a to c, 
 fig. 652., so that the slope might begin to resemble that formed by 
 lavas and ejectamenta from the summit a to Guia, on the south- 
 western side of the cone. 
 
 Madeira. Every volcanic island, so far as I have examined them, 
 varies from every other one in the details of its geographical and 
 geological structure so greatly that I have no expectation of finding 
 any simple hypothesis, like that of " elevation craters," applicable to 
 all or capable of explaining their origin and mode of growth. Few 
 islands, for example, resemble each other more than Madeira and 
 Palma, inasmuch as both consist mainly of basaltic rocks of sub- 
 aerial origin, but, when we compare them closely together, there is 
 no end of the points in which they differ. 
 
 The oldest formation known in Madeira is of submarine volcanic 
 
 LL 2 
 
516 ISLAND OF MADEIRA. [Cn. XXIX. 
 
 origin, and referable perhaps to the Miocene tertiary epoch. Tuffs 
 and limestones containing marine shells and corals occur at S. Vi- 
 cente on the northern coast, where they rise to the height of more 
 than 1200 feet above the sea. They bear testimony to an upheaval 
 to that amount, at least, since the commencement of volcanic action 
 in those parts. 
 
 The pebbles in these marine beds are well rounded and polished, 
 strongly contrasting in that respect with the angular fragments of 
 similar varieties of volcanic rocks so frequent in the superimposed 
 tuffs and agglomerates formed above the level of the sea. 
 
 The length of Madeira from east to west is about 30 miles, its 
 breadth from north to south being 12 miles. The annexed section, 
 fig. 653., drawn up on a true scale of heights and horizontal 
 distances from the observations of Mr. Hartung and myself, will 
 enable the reader to comprehend some of the points in which, 
 geologically considered, Madeira resembles or varies from Palma. 
 In the central region, at A, as well as in the adjoining region on- 
 each side of it, are seen, as in the centre of Palma, a great number 
 of dikes penetrating through a vast accumulation of ejectamenta, c. 
 Here also, as in Palma, we observe as we recede from the centre 
 that the dikes decrease in number, and beds of scoriae, lapilli, 
 agglomerate, and tuff begin to alternate with stony lavas, d d, 
 until at the distance of a mile or more from the central axis the 
 volcanic mass, below fh and eg, consists almost exclusively of 
 streams or sheets of basalt, with some red partings of ochreous 
 clay or laterite, probably ancient soils. The darker lines indicate 
 the predominance of these lavas which have flowed on the surface, 
 and which, besides basalt, consist of various kinds of trap, and in 
 some places of trachyte. The lighter tint, c, expresses an accu- 
 mulation of scoriae, agglomerate, and other materials, such as may 
 have been piled up in the open air, in or around the chief orifices 
 of eruption, and between volcanic cones. 
 
 The Pico Torres, A, more than 6000 feet high, is one of many 
 central peaks, composed of ejected materials. By the union of the 
 foundations of many similar peaks, ridges or mountain crests are 
 formed, from which the tops of vertical dikes project like turrets above 
 the weathered surface of the softer beds of tuff and scoriae. Hence 
 the broken and picturesque outline, giving a singular and romantic 
 character to the scenery of the highest part of Madeira. North of 
 A is seen Pico Ruivo (B), the most elevated peak in the island, yet 
 exceeding by a few feet only the height of Pico Torres. It is 
 similar in composition, but its uppermost part, 400 feet high, retains 
 a more perfectly conical form, and has a dike at its summit with 
 streams of scoriaceous lava adhering to its steep flanks. There are a 
 great many such peaks east and west of A, which seem to be the 
 ruins of cones of eruption, the materials of some at least having 
 been arranged with a qua-qua-versal dip. Among these is Pico 
 Grande, c, fig. 655., now half-buried under more modern lavas 
 which have flowed round it. It is perhaps owing to the juxta- 
 position of such a multitude of cones or points of eruption, and the 
 
CH. XXIX.] 
 
 SECTION OF MADEIRA. 
 
 517 
 
 I 
 
 I 1 
 
 * I 
 
 u H 
 
 I I I 
 
 I iii 
 
 i nit?!* ii 
 i 
 
 i *: 
 
 . 
 
 III 
 5 
 
 fc. >, 
 
 I I 
 
 Jill s I 
 
 I fl!-K 
 
 S ^ 
 
 ' 1 
 
 M -cTSa-e-tS 
 
 ; lil|{_ 
 
 1 |tL| I ||i 
 
 i i^s-i -2 i It 
 
 1144- 
 
 -?'&'S I 
 8-&"*-S s 
 K2|g| o 
 
 o||9l i 
 
 EiwUfeij 
 
 HI jiii i^ 
 inH"! 
 
 ^fi^< o 
 <0-c 
 
 B 
 
 !I 
 
 E3I2 
 
 5* 
 
 Ic^S" 
 
 pw 
 
 LL 3 
 
518 FOSSIL PLANTS OF MADEIRA. [Cn. XXIX. 
 
 interference of their lavas along the great east and west line of vol- 
 canic action, that we find the stony beds in the central region between 
 e andyj fig. 653., nearly horizontal, or having a dip of no more than 
 from 3 to 5 degrees instead of having a very steep inclination like 
 those in the walls of the Caldera of Palma. 
 
 These level or slightly inclined beds often form platforms, such as 
 that called the Paul da Serra (, fig., p. 520.). But when we recede 
 from the central axis, the lavas acquire an average slope of 10 
 degrees on the north (as between e and g, fig. 653.), and of 15 on the 
 south between f and h. Nearer the sea again, as at i and L, where 
 the most modern lavas occur, the dip diminishes to 5 degrees, and 
 even to 3^, as at K, near Funchal. In this latter characteristic, 
 however (the smaller inclination of the lavas near the sea, and their 
 association there with modern cones of eruption, such as M, N, o), 
 there is a strict analogy between Madeira and Palma. Buried cones 
 of eruption also occur at many points, as at p and q, fig. 653., which 
 have been overwhelmed by lavas flowing from the central region. 
 The aggregate thickness of the more solid basalts alternating with 
 tuffs rarely exceeds 1500 feet ; but below Pico S. Antonio, or R, fig., 
 p. 517., they attain a thickness of 3000 feet, being exposed to view on 
 the sides of a deep valley called the Curral, presently to be men- 
 tioned. 
 
 As a general rule, the lavas of Madeira, whether vesicular or com- 
 pact, do not constitute continuous sheets parallel to each other. 
 When viewed in the sea-cliffs in sections transverse to the direction 
 in which they flowed, they vary greatly in thickness, even if 
 followed for a few hundred feet or yards, and they usually thin out 
 entirely in less than a quarter of a mile. In the ravines which 
 radiate from the centre of the island, the beds are more persistent, 
 but even here they usually are seen to terminate, if followed for a 
 few miles ; their thickness also being very variable, and sometimes 
 increasing suddenly from a few feet to many yards. 
 
 I saw no remains of fossil plants in any of the red partings or 
 laterites above alluded to ; but Mr. Smith, of Jordanhill, was more 
 fortunate in 1840, having met with the carbonized branches and 
 roots of shrubs in some red clays under basalt near Funchal. Never- 
 theless, Mr. Hartung and I obtained satisfactory evidence in the 
 northern part of the island, in the ravine of S. Jorge, of the former 
 existence of terrestrial vegetation, and consequently of the subaerial 
 origin of a large portion of the lavas of Madeira. At q in the section 
 (fig. 653.) the occurrence of a bed of impure lignite, covered by basalt, 
 had long been known. Associated with it, we observed several layers 
 of tuff and clay or hardened mud, in one of which leaves of dicoty- 
 ledonous plants and of ferns abound. The latter, according to Mr. 
 Charles J. F. Bunbury, are referable to the genera Sphenopteris, 
 Adiantum?, Pecopteris, and Woodwardia, one of them having the 
 peculiar venation of Woodwardia radicans, a species now common 
 in Madeira. Among the dicotyledonous leaves, some are apparently 
 of the myrtle family, the larger proportion having their surfaces 
 
CH. XXIX.] CRATER OF LAGOA. 519 
 
 smooth and unwrinkled, with a somewhat rigid and coriaceous 
 texture, and with undivided or entire margins. " These characters," 
 observes Mr. Bunbury, "belong to the laurel-type, and indicate a 
 certain analogy between the ancient vegetable remains and the 
 modern forests of Madeira, in which laurels and other evergreens 
 abound, with glossy coriaceous and entire-edged leaves, while below 
 them there is an undergrowth of ferns and other plants." 
 
 The lignite above mentioned and the leaf-bed occur at the height 
 of 1000 feet above the level of the sea, and are overlaid by super- 
 imposed basalts and scoriae, 1100 feet thick, implying the existence 
 of an ancient terrestrial vegetation long before a large part of 
 Madeira had been built up. The nature of the tuffs accompanying 
 the lignite, together with some agglomerates in the vicinity, entitles 
 us to presume that near this spot a series of eruptions once broke 
 out. Nor is it improbable that there may have been here the crater 
 of some lateral cone in which the lignite and leaf-bed accumulated ; 
 for, although craters are remarkably rare in Madeira, when we 
 consider how considerable is the number of perfect cones, yet on the 
 mountain called Lagoa, 2J miles west of Machico, a crater as perfect 
 as that of Astroni near Naples may be seen. 
 
 At the bottom of this circular cavity (fig. 654.), which is about 
 150 feet deep, is a plain about 500 feet in diameter, having a pond 
 in the middle, towards which the plain slopes gently from all sides. 
 Such ponds are often seen in the interior of extinct craters. Except 
 in the middle it is shallow, and supports aquatic plants. Many 
 leaves must also be blown into it from the surrounding heights 
 when high winds prevail, so that a mass of peaty matter convertible 
 into lignite may collect here. 
 
 Fig. 654. 
 
 Crater of Lagoa, 2 miles west of Machico, Madeira. 
 
 In this cut, taken from a sketch of my own, the depth of the crater may appear 
 too great, unless it is borne in mind that there are no trees visible, and most of the 
 bushes are of the Madeira whortle-berry ( Vaccinium Madeirense) five or six feet 
 high. Immediately behind the foreground an artificial mound is seen thrown up 
 as a fence. 
 
 Had streams of lava descending from greater heights entered this 
 Lagoa crater, they would have formed dense masses of compact rock 
 
 LL 4 
 
520 CENTRAL VALLEYS. [Cm. XXIX. 
 
 cooling slowly under great pressure, like those now incumbent on 
 the impure lignite of S. Jorge. The dip of the latter cannot be 
 clearly determined, since it is exposed to view for too short a dis- 
 tance ; and the same may be said of the leaf-bed, part of which may 
 be traced lower down the ravine. It seems, however, to dip to the 
 north or towards the sea conformably with the general inclination 
 of the basaltic and tufaceous strata. 
 
 A deep valley, called the Curral (B, fig. 655.), surrounded by 
 precipices from 1500 to 2500 feet high, and by peaks of still greater 
 elevation, occurs in the middle of Madeira. It has been compared 
 by some to a crater or caldera, for its upper portion is situated in 
 the region where dikes and ejectamenta abound. The Curral, how- 
 ever, extends, without diminishing in depth, to below the region of 
 numerous dikes, and it lays open to view all the beds R, s, fig. 653. 
 Nor do the volcanic masses dip away in all directions from the Curral, 
 as from a central point, or from the hollow axis of a cone. The 
 Curral is in fact one only of three great valleys which radiate from 
 the most mountainous district, a second depression, called the Serra 
 d'Agoa (D, fig. 655.), being almost as deep. This cavity is also 
 drained by a river flowing to the south ; while a third valley, namely, 
 that of the Janella, sends its waters to the north. The section alluded 
 to (fig. 655.), passing through part of the axis of the island in an E. 
 and W. direction, shows how the Curral and Serra d'Agoa, B and D, 
 
 Fig. 655. 
 
 Section through the central region of Madeira, from East to West. 
 
 A. Part of the platform, called the Paul da Serra. B. Curral ; a valley, 3000 feet deep. 
 C. Pico Grande. D. The valley of the Serra d'Agoa. 
 
 are separated by a narrow and lofty ridge, c, part of which is 
 surmounted by the Pico Grande, before mentioned, nearly 5400 feet 
 high. There is no essential difference between the shape of these 
 three great valleys and many of those in the Alps and Pyrenees, 
 where the valley-making process can have had no connection with 
 any superficial volcanic action. 
 
 In the Alps, no doubt, as in other lofty chains, the formation of 
 valleys has been greatly aided by subterranean movements, both 
 gradual and violent, and by the dislocation of rocks. The same may 
 be true of Madeira and of almost every lofty volcanic region ; but, 
 when we reflect that the central heights A and B, fig. 653., are more 
 than 6000 feet above the sea, and that the waters flowing from them, 
 swollen by melted snows, reach the sea by a course of not much 
 more than 6 miles in the case of those draining the Curral, and by 
 nearly as short a route in the Serra d'Agoa, we shall be prepared 
 for almost any amount of denudation effected simply by subaerial 
 erosion. 
 
CH. XXIX. TRACHYTIC ROCKS. 521 
 
 The general absence of water-worn pebbles in the tuffs underlying 
 the Madeira lavas is very striking, and contrasts with the frequent 
 occurrence of gravel-beds under so many of the Auvergne lavas. It 
 simply proves that Madeira, like the volcanic mountains of Java, or 
 like Mount Etna or Mona Loa in the Sandwich Islands, could not, for 
 reasons before given p. 479., support a single torrent so long as erup- 
 tions were frequent on its slopes. The period, therefore, of fluviatile 
 erosion must have been subsequent to the formation of the central 
 nucleus of ejectamenta, c, fig., p. 517., and of the lavas d, ibid. When 
 we infer that these were of supramarine origin as far down as the 
 line p, s, t, and perhaps lower, it follows that a lofty island, 4000 feet 
 or more in height, must have resulted, even if no upheaval had ever 
 occurred. 
 
 The movements which upraised the marine deposits of San Vicente 
 may or may not have extended over a wide area. How far they 
 modified the form of the island, or added to its height is a fair sub- 
 ject of speculation ; and whether the steep dip of the lavas seen in the 
 ravines intersecting the slopes of the mountain, f h, and e g, can be 
 ascribed to such movements. The lavas of more modern date, near 
 Funchal, may be imagined to remain comparatively horizontal, 
 because they have escaped the influence of disturbing forces to 
 which the older nucleus was exposed. Without discussing this 
 point (so fully treated of in reference to Palma), I may observe that 
 unquestionably different parts of Madeira have been formed in suc- 
 cession. Near Porto da Cruz, for example, on the northern coast, 
 trachytes of a grey, and trachytic tuffs almost of a white colour, in 
 slightly inclined or almost horizontal beds, have partially filled up 
 deep valleys previously excavated through the older and inclined 
 basaltic rocks (dipping at an angle of 10 to the north), under 
 which the leaf-bed and lignite before mentioned, fig. 653., p. 517., 
 lie buried. During the convulsions which accompanied the out- 
 pouring of every newer series of lavas the older rocks may have 
 been more or less disturbed and tilted, without destroying the 
 general form of the old dome-shaped mountain supposed by us to 
 have been the result of repeated eruptions from the central vents. 
 
 The locality just referred to of Porto da Cruz exemplifies, not 
 only the long intervals of time which separated the outflowing of 
 distinct sets of lavas, but also the precedence of the basaltic to 
 the trachytic outpourings. So also on the northern slope of 
 Madeira, I observed between the Jardim and Pico Bodes, situated 
 in a direct line about six miles north-west of Funchal, a well- 
 marked series of trachytic rocks of considerable thickness occu- 
 pying the highest geological position. They consist of white and 
 grey trachytes, occurring at points varying from 2500 to 3500 feet 
 above the sea. Their position may be understood by supposing 
 them to constitute the uppermost beds represented at h in the 
 section, fig. 653., p. 517., and on the slope above h. The doctrine, 
 therefore, that in each series of volcanic eruptions the trachytic 
 lavas flow out first, and after them the basaltic kinds (see p. 526.), 
 
522 LAVAS OF MADEIRA. [Cn. XXIX. 
 
 is by no means borne out in Madeira, although some of the newest 
 currents, like those at the foot of the cones M, N, o, fig. 653., are 
 basaltic. 
 
 I may here allude to another feature in the mineralogical 
 structure of Madeira, namely, that most commonly the uppermost 
 of all the volcanic rocks, when we ascend to heights of 1200 feet 
 or more above the sea, consist of compact felspathic trap, with 
 much olivine, separating into spheroidal masses several feet in 
 diameter, especially when some of the contained iron has become 
 more highly oxidated in the atmosphere. M. Delesse, after ex- 
 amining my specimens, informs me that in France they would call 
 this rock basalt, although it is often without augite and simply a 
 mixture of blackish green felspar with olivine. Whatever name we 
 assign to it, the superficial envelope of the island, not only in the line 
 of section followed in fig. 653., p. 517., but also very generally, may 
 be said to consist of this trap, except near the sea, where basalts 
 occur which have not the same spheroidal structure. 
 
 Among other indications of a considerable difference of age, even 
 in the superficial volcanic formations of Madeira, I may remark that 
 many of the central peaks, such as A, fig. 653., seem to be the mere 
 skeletons of cones of eruption; whereas the forms of the more 
 modern cones, such as M, N, o, are regular, and have no protruding 
 dikes on their summits or flanks. The newest lavas also in 
 Madeira have, in one district at least, a singularly recent aspect as 
 compared to those of older date, which are decomposed superficially 
 often to the depth of several feet or yards. I allude to the lava 
 currents near Port Moniz, one of which is as rough and bristling 
 as are some streams before alluded to in Palma (p. 512.) of his- 
 torical date. I am indebted to Mr. Hartung for the annexed 
 drawing of a lava at Port Moniz, which I did not visit myself. 
 
 Surface of lava near Port Moniz, N.W. point of Madeira ; from a dra *ing by M. Hartung 
 a. Channel traversing the lava. 
 
 It is traversed by a channel, a, like one of those already described, 
 p. 507. For how long a period such characters may be retained is 
 uncertain, so much does this depend on the mineral composition 
 of the rock. Some of the lavas of Auvergne of prehistorical date 
 and certainly of high antiquity, are almost as rugged ; so that 
 this freshness of aspect is only a probable indication of a relatively 
 modern origin. 
 
CH. XXX.] TESTS OF AGE OF VOLCANIC ROCKS. 
 
 523 
 
 CHAPTER XXX. 
 
 ON THE DIFFERENT AGES OF THE VOLCANIC ROCKS. 
 
 Tests of relative age of volcanic rocks Tests by superposition and intrusion 
 Dike of Quarrington Hill, Durham Test by alteration of rocks in contact 
 Test by organic remains Test of age by mineral character Test by included 
 fragments Volcanic rocks of the Post-Pliocene period Basalt of the Bay 
 of Trezza in Sicily Post-Pliocene volcanic rocks near Naples Dikes of Somma 
 Igneous formations of the Newer Pliocene period Val di Noto in Sicily. 
 
 HAVING referred the sedimentary strata to a long succession of 
 geological periods, we have now to consider how far the volcanic 
 formations can be classed in a similar chronological order. The 
 tests of relative age in this class of rocks are four: 1st, super- 
 position and intrusion, with or without alteration of the rocks in 
 contact ; 2nd, organic remains ; 3rd, mineral characters ; 4th, in- 
 cluded fragments of older rocks. 
 
 Tests by superposition, fyc. If a volcanic rock rest upon an 
 aqueous deposit, the former must be the newest of the two, but the 
 like rule does not hold good where the aqueous formation 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 between two strata, as b at D in the annexed figure 
 (fig. 656.), after which it may cool down and consolidate. Super- 
 Fig. 657. 
 
 position, therefore, is not of the same value as a test of age in the 
 unstratified volcanic rocks as in fossiliferous formations. We can 
 only rely implicitly on this test where the volcanic rocks are 
 contemporaneous, not where they are intrusive. Now, they are said 
 to be contemporaneous if produced by volcanic action which was 
 going on simultaneously with the deposition of the strata with 
 which they are associated. Thus in the section at D (fig. 656.), 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 if the 
 stratum a be altered by b at the point of contact, we must then 
 conclude the trap to have been intrusive, or if, in pursuing b for 
 
524 
 
 TESTS OF RELATIVE AGE 
 
 [Cn. XXX. 
 
 Fig. 658. 
 
 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 a volcanic rock 
 to be intrusive, when in reality it is contemporaneous ; for a sheet 
 of lava, as it spreads over the bottom of the sea, cannot rest every 
 where upon the same stratum, either because these have been de- 
 nuded, or because, if newly thrown down, they thin out in certain 
 places, thus allowing the lava to cross their edges. Besides 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. 658., to have 
 come in contact in this manner with 
 the strata a, b, c, and that after its 
 consolidation the strata d, e, are thrown 
 down in a nearly horizontal position, 
 yet so as to lie unconformably 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 strata d, e, or c, to have been altered at their 
 junction, as if by heat. 
 
 When trap dikes were described in the preceding chapter, they 
 were shown to be more modern than all the strata which they 
 traverse. A basaltic dike at Quarrington Hill near Durham, passes 
 through coal-measures, the strata of which are inclined, and shifted 
 so that those on the north side of the dike are 24 feet above the 
 level of the corresponding beds on the south side (see section, 
 fig. 659.). But the horizontal beds of overlying Red Sandstone and 
 
 Fig. 659. 
 Magnesian limestone. 
 
 Coal. Dike. Coal. N 
 
 Section at Quarrington Hill, east of Durham. (Sedgwick.) 
 a. Magnesian Limestone (Permian). b. Lower New Red Sandstone. 
 
 c. Coal strata. 
 
 Magnesian Limestone are not cut through by the dike. Now here 
 the coal-measures were not only deposited, but had subsequently 
 been disturbed, fissured, and shifted, before the fluid trap now 
 forming the dike was introduced into a rent. It is also clear that 
 some of the upper edges of the coal strata, together with the upper 
 part of the dike, had been subsequently removed by denudation 
 before the lower New Red Sandstone and Magnesian Limestone 
 were superimposed. Even in this case, however, although the date 
 
CH. XXX.] OF VOLCANIC ROCKS. 525 
 
 of the volcanic eruption is brought within narrow limits, it cannot 
 be defined with precision ; it may have happened either at the close 
 of the Carboniferous period, or early in that of the Lower New 
 Red Sandstone, or between these two periods, when the state of the 
 animate creation and the physical geography of Europe were gra- 
 dually changing from the type of the Carboniferous era to that of 
 the Permian. 
 
 The test of age by superposition is strictly applicable to all stra- 
 tified volcanic tuffs, according to the rules already explained in the 
 case of other sedimentary deposits. (See p. 97.) 
 
 Test of age by organic remains. We have seen how, in the 
 vicinity of active volcanos, scorise, pumice, fine sand, and fragments 
 of rock are thrown up into the air, and then showered down upon the 
 land, or into neighbouring lakes or seas. In the tuffs so formed 
 shells, corals, or any other durable organic bodies which may happen 
 to be strewed over the bottom of a lake or sea will be embedded, and 
 thus continue as permanent memorials of the geological period when 
 the volcanic eruption occurred. Tufaceous strata thus formed in the 
 neighbourhood of Vesuvius, Etna, Stromboli, and other volcanos now 
 active in islands or near the sea, may give information of the relative 
 age of these tuffs 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 dif- 
 ferent primary, secondary, and tertiary fossiliferous strata. 
 
 The tuffs alluded to may not always be marine, but may include, 
 in some places, freshwater shells ; in others, the bones of terrestrial 
 quadrupeds. The diversity of organic remains in formations of this 
 nature is perfectly intelligible, if we reflect on the wide dispersion of 
 ejected matter during late eruptions, such as that of the volcano of 
 Coseguina, in the province of Nicaragua, January 19. 1835. Hot 
 cinders and fine scoriae were then cast up to a vast height, and 
 covered the ground as they fell to the depth of more than 10 feet, 
 and for a distance of 8 leagues from the crater in a southerly direc- 
 tion. Birds, cattle, and wild animals were scorched to death in 
 great numbers, and buried in ashes. Some volcanic dust fell at 
 Chiapa, upwards of 1200 miles, not to leeward 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 distance of 1100 miles from the point of eruption, Cap- 
 tain 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 homo- 
 geneous composition, when discharged from the mouth of a large 
 river, is often deposited simultaneously over a wide space, so a par- 
 ticular kind of lava, flowing from a crater during one eruption, may 
 spread over an extensive area ; as in Iceland in 1783, when the 
 
 * Caldcleugh, Phil. Trans. 1836. p. 27. 
 
526 RELATIVE AGES OF VOLCANIC ROCKS. [Cn. XXX. 
 
 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.* Now, if 
 such a mass should afterwards be divided into separate fragments by 
 denudation, we might still perhaps identify the detached portions by 
 their similarity in mineral composition. Nevertheless, this test will 
 not always avail the geologist ; for, although there is usually a pre- 
 vailing character in lava emitted during the same eruption, and even 
 in the successive currents flowing from the same volcano, still, in 
 many cases, the different parts even of one lava-stream, or, as before 
 stated, of one continuous mass of trap, vary much in mineral com- 
 position 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 we have 
 seen that in Madeira trachytic rocks may overlie an older basaltic 
 series (p. 521.) ; but the great mass of trachyte occupies more generally 
 perhaps an inferior position, and is cut through and overflowed by 
 basalt. It can by no means be inferred that trachyte predominated at 
 one period of the earth's history and basalt at another, for we 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 more 
 felspathic lavas have been first emitted, and the escape of the more 
 augitic kinds has followed. The hypothesis suggested by Mr. Scrope 
 may, perhaps, afford a solution of this problem. The minerals, he 
 observes, which abound in basalt are of greater specific gravity than 
 those composing the felspathic lavas ; thus, for example, hornblende, 
 augite, and olivine are each more than three times the weight of 
 water ; whereas common felspar, albite, and Labrador felspar have 
 each scarcely more than 2-* times the specific gravity of water ; and 
 the difference is increased in consequence of there being much more 
 iron in a metallic state in basalt and greenstone than in trachyte and 
 other felspathic lavas and trap rocks. 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 up- 
 wards to the surface by the expansive power of gases. Those ma- 
 terials, 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 discover the 
 relative age of two trap rocks, or of an aqueous deposit and the trap 
 on which it rests, by finding fragments of one included in the other, 
 
 * See Principles, Index, " Skaptar Jokul." 
 
CH. XXX.] POST-PLIOCENE VOLCANIC ROCKS. 527 
 
 in cases such as those before alluded to, where the evidence of super-- 
 position alone would be insufficient. It is also not uncommon to find 
 a conglomerate almost exclusively composed of rolled pebbles of trap, 
 associated with some fossiliferous stratified formation in the neigh- 
 bourhood of massive trap. If the pebbles agree generally in mineral 
 character with the latter, we are then enabled to determine its rela- 
 tive 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 
 volcanic islands, or at the base of Etna. 
 
 Post-Pliocene Period (including the Recent). I shall now select 
 examples of contemporaneous volcanic rocks of successive geological 
 periods, to show that igneous causes have been in activity in all past 
 ages of the world, and that they have been ever shifting the places 
 where they have broken out at the earth's surface. 
 
 One portion of the lavas, tuffs, and trap-dikes of Etna, Vesuvius, 
 and the Island of Ischia has been produced within the historical era ; 
 another, and a far more considerable part, originated at times imme- 
 diately antecedent, when the waters of the Mediterranean were 
 already inhabited by the existing spqcies of testacea. The southern 
 and eastern flanks of Etna are skirted by a fringe of alternating sedi- 
 mentary and volcanic deposits, of submarine origin, as at Aderno, 
 Trezza, and other places. Of sixty-five species of fossil shells which 
 I procured in 1828 from this formation, near Trezza, it was impos- 
 sible to distinguish any one from species now living in the neigh- 
 bouring sea. 
 
 The Cyclopian Islands, called by the Sicilians Dei Faraglioni, in 
 the sea-cliffs of which these beds of clay, tuff, and associated lava are 
 laid open to view, are situated in the Bay of Trezza, and may be re- 
 Fig. 660. 
 
 View of the Isle of Cyclops in the Bay of Trezza.* 
 
 garded as the extremity of a promontory severed from the main land. 
 Here numerous proofs are seen of submarine eruptions, by which the 
 
 * This view of the Isle of Cyclops is from an original drawing by my friend 
 the late Captain Basil Hall, E.N. 
 
528 
 
 VOLCANIC ROCKS OF 
 
 [On. XXX. 
 
 Fig. 661. 
 
 argillaceous and sandy strata were invaded and cut through, and tu- 
 faceous breccias formed. Inclosed in these breccias are many angular 
 and hardened fragments of laminated clay in different states of alter- 
 ation by heat, and intermixed with volcanic sands. 
 
 The loftiest of the Cyclopian islets, or rather rocks, is about 200 
 feet in height, the summit being formed of a mass of stratified clay, 
 the laminse of which are occasionally subdivided by thin arenaceous 
 layers. These strata dip to the N.W., and rest on a mass of columnar 
 lava (see fig. 660.) 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-east- 
 ward of that represented in the drawing (fig. 660.), 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 contrary, rendered 
 much more conspicuous, by the indurating process. 
 
 In the annexed woodcut (fig. 661.) I have represented a portion of 
 the altered rock, a few feet square, where the alternating thin laminse 
 
 of sand and clay have put 
 on the appearance which 
 we often observe in some 
 of the most contorted of the 
 metamorphic schists. 
 
 A great fissure, running 
 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 pene- 
 trating the superincumbent 
 tertiary strata. In one place 
 the lava ramifies and ter- 
 minates in thin veins, from 
 a few feet to a few inches in 
 thickness. (See fig. 662.). 
 
 The arenaceous laminse 
 are much hardened at the 
 point of contact, and the 
 clays are converted into sili- 
 ceous schist. In this island 
 
 Contortions of strata in the largest of the Cyclopian 
 
 islands. the altered rocks assume a 
 
 honeycombed structure on their weathered surface, singularly con- 
 trasted with the smooth and even outline which the same beds present 
 in their usual soft and yielding state. 
 
 The pores of the lava are sometimes coated, or entirely filled, witJ 
 carbonate of lime, and with a zeolite resembling analcime, which has 
 
OH. XXX.] 
 
 THE POST-PLIOCENE PERIOD. 
 
 Fig. 662. 
 
 529 
 
 b. a. b. c. a. b. 
 
 Clay. Lava. Clay. Altered. Lava. Clay, &c. 
 
 Post-Pliocene strata invaded by lava, Isle of Cyclops (horizontal section). 
 a. Lava. b. Laminated clay and sand. c. The same altered. 
 
 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. 
 
 Post-Pliocene formations near Naples. I have traced in the 
 "Principles of Geology" the history of the changes which the vol- 
 canic region of Campania is known to have undergone during the 
 last 2000 years. The aggregate effect of igneous operations during 
 that period is far from insignificant, comprising as it does the forma- 
 tion of the modern cone of Vesuvius since the year 79, and the pro- 
 duction 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 tufaceous sediment has been transported 
 by rivers and land-floods to the sea. There are also proofs, during 
 the same recent 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 depressed to 
 the amount of more than 20 feet. In connection with these convul- 
 sions, there are found, on the shores of the Bay of Baise, recent 
 tufaceous strata, filled with articles fabricated by the hands of man, 
 and mingled with marine shells. 
 
 It was also stated in this work (p. 119.), that when we examine 
 this same region, it is found to consist largely of tufaceous strata, of 
 a date anterior to human history or tradition, which are of such 
 thickness as to constitute hills from 500 to more than 2000 feet in 
 
 MM 
 
530 VOLCANIC ROCKS OF [Cn. XXX. 
 
 height. These post-pliocene strata, containing recent marine shells, 
 alternate with distinct currents and sheets of lava which were of 
 contemporaneous origin ; and we find that in Vesuvius itself, the 
 ancient cone called Somma is of far greater volume than the modern 
 cone, and is intersected by a far greater number of dikes. In con- 
 trasting this ancient part of the mountain with that of modern date, 
 one principal point of difference is observed ; namely, the greater 
 frequency in the older cone of fragments of altered sedimentary 
 rocks ejected during eruptions. We may easily conceive that the 
 first explosions would act with the greatest violence, rending and 
 shattering whatever solid masses obstructed the escape of lava and 
 the accompanying gases, so that great heaps of ejected pieces of rock 
 would naturally occur in the tufaceous breccias formed by the earliest 
 eruptions. But when a passage had once been opened, and an 
 habitual vent established, the materials thrown out would consist of 
 liquid lava, which would take the form of sand and scoriae, or of 
 angular fragments of such solid lavas as may have choked up the 
 vent. 
 
 Among the fragments which abound in the tufaceous breccias of 
 Somma, none are more common than a saccharoid dolomite, supposed 
 to have been derived from an ordinary limestone altered by heat and 
 volcanic vapours. 
 
 Carbonate of lime enters into the composition of so many of the 
 simple minerals found in Somma, that M. Mitscherlich, with much 
 probability, ascribes their great variety to the action of the volcanic 
 heat on subjacent masses of limestone. 
 
 Dikes of Somma. The dikes seen in the great escarpment which 
 Somma presents towards the modern cone of Vesuvius are very 
 numerous. They are for the most part vertical, and traverse at 
 right angles the beds of lava, scoriae, volcanic breccia, and sand, of 
 which the ancient cone is composed. They project in relief several 
 inches or sometimes feet, from the face of the cliff, being extremely 
 compact, and less destructible than the intersected tuffs and porous 
 lavas. In vertical extent they vary from a few yards to 500 feet, 
 anl in breadth from 1 to 12 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, and a few terminate at both 
 ends, either in a point or abruptly. In mineral composition they 
 scarcely differ from the lavas of Somma, the rock consisting of a 
 base of leu cite and augite, through which large crystals of augite 
 and some of leucite are scattered.* Examples are not rare of one 
 dike cutting through another, and in one instance a shift or fault is 
 seen at the point of intersection. 
 
 In some cases, however, the rents seem to have been filled laterally, 
 when the walls of the crater had been broken by star-shaped cracks, 
 as seen in the accompanying wood-cut (fig. 663.). But the shape of 
 
 * L. A. Necker, Mem. de la Soc. de Phys. et d'Hist. Nat. de Geneve, torn. ii. 
 part i. Nov. 1822. 
 
CH. XXX.] THE POST-PLIOCENE PEEIOD. 
 
 Fig. 663. 
 
 631 
 
 Dikes or veins at the Punto del Nasone on Somma. (Necker.*) 
 
 these rents is an exception to the general rule ; for 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 in- 
 explicable, 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. Necker refers us to Sir W. Hamilton's account of an 
 eruption of Vesuvius in the year 1779, who records the following 
 facts : " The lavas, when they either boiled over the crater, or 
 broke out from the conical parts of the volcano, 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, con- 
 tinued 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, upon examination after an eruption, I have 
 found to be in general from two to five or six feet wide, and seven 
 or eight 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 smooth and even in most parts, by the violence of the 
 currents of the red-hot lavas which they had conveyed for many 
 weeks successively." f 
 
 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. 
 
 * From a drawing of M. Necker, in f Phil. Trans., vol. Ixx., 1780. 
 Mem. above cited. 
 
 MM 2 
 
532 POST-PLIOCENE VOLCANIC ROCKS. [Cn. XXX. 
 
 The prolonged and uniform friction of the heavy fluid, as it is 
 forced and made to flow upwards, cannot fail to wear and smooth 
 down the surfaces on which it rubs, and the intense heat must melt 
 all such masses as project and obstruct the passage of the incan- 
 descent fluid. 
 
 The texture of the Vesuvian dikes is different at the edges and in 
 the middle. Towards the centre, observes M. Necker, the rock is 
 larger grained, the component elements being in a far more crys- 
 talline state ; while at the edge the lava is sometimes vitreous, and 
 always finer grained. A thin parting band, approaching in its 
 character to pitchstone, occasionally intervenes, at the contact of 
 the vertical dike and intersected beds. M. Necker mentions one of 
 these at the place called Primo Monte, in the Atrio del Cavallo ; 
 and when I examined Somma, in 1828, I saw three or four others 
 in different parts of the great escarpment. These phenomena are in 
 perfect harmony with the results of the experiments of Sir James 
 Hall and Mr. Gregory Watt, which have shown that a glassy 
 texture is the effect of sudden cooling, while, on the contrary, a 
 crystalline grain is produced where fused minerals are allowed to 
 consolidate slowly and tranquilly under high pressure. 
 
 It is evident that the central portion of the lava in a fissure 
 would, during consolidation, part with its heat more slowly than the 
 sides, although the contrast of circumstances would not be so great 
 as when we compare the lava near the bottom and at the surface of 
 a current flowing in the open air. In this case the uppermost part, 
 where it has been in contact with the atmosphere, and where re- 
 frigeration has been most rapid, is always found to consist of 
 scoriform, vitreous, and porous lava ; while at a greater depth the 
 mass assumes a more lithoidal structure, and then becomes more and 
 more stony as we descend, until at length we are able to recognize 
 with a magnifying glass the simple minerals of which the rock is 
 composed. On penetrating still deeper, we can detect the con- 
 stituent parts by the naked eye, and in the Vesuvian currents 
 distinct crystals of augite and leucite become apparent. 
 
 The same phenomenon, observes M. Necker, may readily be ex- 
 hibited on a smaller scale, if we detach a piece of liquid lava from 
 a moving current. The fragment cools instantly, and we find the 
 surface covered with a vitreous coat; while the interior, although 
 extremely fine-grained, has a more stony appearance. 
 
 It must, however, be observed, that although the lateral portions 
 of the dikes are finer grained than the central, yet the vitreous 
 parting layer before alluded to is rare in Vesuvius. This may, 
 perhaps, be accounted for, as the above-mentioned author suggests, 
 by the great heat which the walls of a fissure may acquire before 
 the fluid mass begins to consolidate, in which case the lava, even at 
 the sides, would cool very slowly. Some fissures, also, may be filled 
 from above, as frequently happens in the volcanos of the Sandwich 
 Islands, according to the observations of Mr. Dana ; and in this case 
 the refrigeration at the sides would be more rapid than when the 
 
CH. XXX.] NEWER PLIOCENE VOLCANIC BOCKS. 
 
 533 
 
 melted matter flowed upwards from the volcanic foci, in an intensely 
 heated state. Mr. Darwin informs me that in St. Helena almost 
 every dike has a vitreous selvage. 
 
 The rock composing the dikes both in the modern and ancient 
 part of Vesuvius is far more compact than that of ordinary 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 phenomenon in accordance with the form- 
 ation of vertical columns in horizontal beds of lava; for in both 
 cases the divisions which give rise to the prismatic structure are at 
 right angles to the cooling surfaces. 
 
 Newer Pliocene Period Val di Noto. I have already alluded 
 (see p. 157.) to the igneous rocks which are associated with a great 
 marine formation of limestone, sand, and marl in the southern part 
 of Sicily, as at Vizzini and other places. In this formation, which 
 was shown to belong to the Newer Pliocene period, large beds of 
 oysters and corals repose upon lava, and are unaltered at the point 
 of contact. In other places we find dikes of igneous rock inter- 
 secting the fossiliferous beds, and converting the clays into siliceous 
 schist, the laminae being contorted and shivered into innumerable 
 fragments at the junction, as near the town of Vizzini. 
 
 The volcanic formations of the Val di Noto usually consist of the 
 most ordinary variety of basalt, with or without olivine. The rock 
 is sometimes compact, often very vesicular. The vesicles are occa- 
 sionally empty, both in dikes and currents, and are in some localities 
 filled with calcareous spar, arragonite, and zeolites. The structure 
 is, in some places, spheroidal ; in others, though rarely, columnar. 
 I found dikes of amygdaloid, wacke, and prismatic basalt, inter- 
 secting the limestone at the bottom of the hollow called Gozzo degli 
 Martiri, below Melilli. 
 
 Dikes. Dikes of vesicular and amygdaloidal lava are also seen 
 
 Fig. 664. 
 
 Fig. 665. 
 
 CJ . 
 
 Ground-plan of dikes near Palagonia. 
 o. Lava. 
 
 b. Peperino, consisting of volcanic sand, mixed with 
 fragments of lava and limestone. 
 
 traversing marine tuff or peperino, west of Palagonia, some of the 
 pores of the lava being empty, while others are filled with carbonate 
 
 M M 3 
 
534 DIKES OF LAVA. [Cn. XXX. 
 
 of lime. In such cases we may suppose the peperino to have re- 
 sulted from showers of volcanic sand and scoriae, together with 
 fragments of limestone, thrown out by a submarine explosion, 
 similar to that which gave rise to Graham Island in 1831. When 
 the mass was, to a certain degree, consolidated, it may have been 
 rent open, so that the lava ascended through fissures, the walls of 
 which were perfectly even and parallel. After the melted matter 
 that filled the rent in fig. 664. had cooled down, it must have been 
 fractured and shifted horizontally by a lateral movement. 
 
 In the second figure (fig. 665.), the lava has more the appearance 
 of a vein which forced its way through the peperino. It is highly 
 probable that similar appearances would be seen, if we could 
 examine the floor of the sea in that part of the Mediterranean 
 where the waves have recently washed away the new volcanic 
 island ; for when a superincumbent mass of ejected fragments has 
 been removed by denudation, we may expect to see sections of dikes 
 traversing tuff, or, in other words, sections of the channels of com- 
 munication by which the subterranean lavas reached the surface. 
 
CIT. XXXI.] PLIOCENE VOLCANOS. 535 
 
 CHAPTER XXXI. 
 
 ON THE DIFFERENT AGES OF THE VOLCANIC ROCKS continued. 
 
 Volcanic rocks of the Older Pliocene period Tuscany Home Volcanic re- 
 gion of Olot in Catalonia Cones and lava-currents Ravines and ancient 
 gravel-beds Jets of air called Bufadors Age of the Catalonian volcanos 
 Miocene period Brown-coal of the Eifel and contemporaneous trachytic brec- 
 cias Age of the brown-coal Peculiar characters of the volcanos of the upper 
 and lower Eifel Lake Craters Trass Hungarian volcanos. 
 
 Older Pliocene period Italy. IN Tuscany, as at Radicofani, 
 Viterbo, and Aquapendente, and in the Campagna di Roma, sub- 
 marine volcanic tuffs are interstratified with the Older Pliocene 
 strata of the Subapennine hills in such a manner as to leave no 
 doubt that they were the products of eruptions which occurred 
 when the shelly marls and sands of the Subapennine hills were in 
 the course of deposition. This opinion I expressed * after my visit 
 to Italy in 1828, and it has recently (1850) been confirmed by the 
 arguments adduced by Sir R. Murchison in favour of the submarine 
 origin of the earlier volcanic rocks of Italy, f These rocks are well 
 known to rest conformably on the Subapennine 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 marine fossil shells, undertaken by 
 MM. Rayneval, Vanden Hecke, and Ponza. They have compared 
 no less than 160 species J with the shells of the Coralline Crag of 
 Suffolk, so well described by Mr. Searles Wood; and the specific 
 agreement between the British and Italian fossils is so great, if we 
 make due allowance for geographical distance and the difference of 
 latitude, 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 Tuscany and the 
 newest rocks in the neighbourhood of Naples, a series of volcanic 
 products might be detected of every age from the Older Pliocene to 
 the historical epoch. 
 
 Catalonia. Geologists are far from being able, as yet, to assign 
 to each of the volcanic groups scattered over Europe a precise 
 chronological place in the tertiary series ; but I shall describe here, 
 
 * See 1st edit, of Principles of Geo- f Geol. Quart. Journ. vol. vi. p. 281. 
 logy, vol. iii. chaps, xiii. and xiv., 1833; j Catalogue des Fossiles de Monte 
 and former edits, of this work, ch. xxxi. Mario, Rome, 1854. 
 
 MM 4 
 
536 
 
 PLIOCENE VOLCANOS. 
 
 [Cn. XXXI. 
 
 as probably referable to some part of the Pliocene period, a district 
 of extinct volcanos near Olot, in the north of Spain, which is little 
 known, and which I visited in the summer of 1830. 
 
 The whole extent of country occupied by volcanic products in 
 Catalonia is not more than fifteen geographical miles from north to 
 south, and about six from east to west. The vents of eruption 
 range entirely within a narrow band running north and south ; and 
 the branches, which are represented as extending eastward in the 
 map, are formed simply of two lava-streams those of Castell Follit 
 and Cellent. 
 
 Fig. 666. 
 
 Volcanic district of Catalonia. 
 
 Dr. Maclure, the American geologist, was the first who made 
 known the existence of these volcanos*; and, according to his 
 description, the volcanic region extended over twenty square leagues, 
 from Amer to Massanet. I searched in vain in the environs of 
 Massanet in the Pyrenees, for traces of a lava-current ; and I can 
 say with confidence, that the adjoining map gives a correct view of 
 the true area of the volcanic action. 
 
 Geological structure of the district. The eruptions have burst 
 entirely through fossiliferous rocks, composed in great part of grey 
 
 * Maclure, Joura. de Phys., vol. Ixvi. p. 219., 1808 ; cited by Daubeny, De- 
 scription of Volcanos, p. 24. 
 
CH. XXXI.] VOLCANOS OF CATALONIA. 537 
 
 and greenish sandstone and conglomerate, with some thick beds of 
 nummulitic limestone. The conglomerate contains pebbles of quartz, 
 limestone, and Lydian stone. This system of rocks is very exten- 
 sively spread throughout Catalonia ; one of its members being a red 
 sandstone, to which the celebrated salt-rock of Cardona, usually 
 considered as of the cretaceous era, is subordinate. 
 
 Near Amer, in the Valley of the Ter, on the southern borders of 
 the region delineated in the map, primary rocks are seen, consisting 
 of gneiss, mica-schist, and clay-slate. They run in a line nearly 
 parallel to the Pyrenees, and throw off the fossiliferous strata from 
 their flanks, causing them to dip to the north and north-west. This 
 dip, which is towards the Pyrenees, is connected with a distinct axis 
 of elevation, and prevails through the whole area described in the 
 map, the inclination of the beds being sometimes at an angle of 
 between 40 and 50 degrees. 
 
 It is evident that the physical geography of the country has 
 undergone no material change since the commencement of the era 
 of the volcanic eruptions, except such as has resulted from the 
 introduction of new hills of scoriae, and currents of lava upon the 
 surface. If the lavas could be remelted and poured out again from 
 their respective craters, they would descend the same valleys in 
 which they are now seen, and re-occupy the spaces which they at 
 present fill. The only difference in the external configuration of the 
 fresh lavas would consist in this, that they would nowhere be inter- 
 sected by ravines, or exhibit marks of erosion by running water. 
 
 Volcanic cones and lavas. There are about fourteen distinct 
 cones with craters in this part of Spain, besides several points 
 whence lavas may have issued ; all of them arranged along a narrow 
 line running north and south, as will be seen in the map. The 
 greatest number of perfect cones are in the immediate neighbour- 
 hood of Olot, some of which (Fig. 667., Nos. 2, 3, and 5.) are 
 represented in the annexed woodcut ; and the level plain on which 
 that town stands has clearly been produced by the flowing down of 
 many lava-streams from those hills into the bottom of a valley, 
 probably once of considerable depth, like those of the surrounding 
 country. 
 
 In this drawing an attempt is made to represent, by the shading 
 of the landscape, the different geological formations of which the 
 country is composed.* The white line of mountains (No. 1.) in the 
 distance is the Pyrenees, which are to the north of the spectator, 
 and consist of hypogene and ancient fossiliferous rocks. In front of 
 these are the fossiliferous formations (No. 4.), which are in shade. 
 Still nearer to us the hills 2, 3, 5, are volcanic cones, and the rest of 
 the ground on which the sunshine falls is strewed over with volcanic 
 ashes and lava. 
 
 The Fluvia, which flows near the town of Olot, has cut to the 
 depth of only 40 feet through the lavas of the plain before men- 
 
 * This view is taken from a sketch which I made on the spot in 1830. 
 
538 
 
 PLIOCENE VOLCANOS. 
 
 Fig. 667. 
 
 View of the Volcanos around Olot in Catalonia. 
 
 tioned. The bed of the river is hard basalt ; and at the bridge of 
 Santa Madalena are seen two distinct lava-currents, one above the 
 other, separated by a horizontal bed of scoriae 8 feet thick. 
 
 In one place, to the south of Olot, the even surface of the plain is 
 broken by a mound of lava, called the "Bosque de Tosca," the 
 upper part of which is scoriaceous, and covered with enormous 
 heaps of fragments of basalt, more or less porous. Between the 
 numerous hummocks thus formed are deep cavities, having the 
 appearance of small craters. The whole precisely resembles some of 
 the modern currents of Etna, or that of Come, near Clermont ; the 
 last of which, like the Bosque de Tosca, supports only a scanty 
 vegetation. 
 
 Most of the Catalonian volcanos are as entire as those in the 
 neighbourhood of Naples or on the flanks of Etna. One of these, 
 called Montsacopa (No. 3. fig. 667.), is of a very regular form, and 
 has a circular depression or crater at the summit. It is chiefly 
 made up of red scoriae, undistinguishable from those of the minor 
 cones of Etna. The neighbouring hills of Olivet (No. 2.) and 
 Garrinada (No. 5.) are of similar composition and shape. The 
 largest crater of the whole district occurs farther to the east of 
 Olot, and is called Santa Margarita. It is 455 feet deep, and about 
 a mile in circumference. Like Astroni, near Naples, it is richly 
 covered with wood, wherein game of various kinds abounds. 
 
 Although the volcanos of Catalonia have broken out through 
 sandstone, shale, and limestone, as have those of the Eifel, in Ger- 
 many, to be described in the sequel, there is a remarkable difference 
 in the nature of the ejections composing the cones in these two 
 regions. In the Eifel, the quantity of pieces of sandstone and shale 
 
CH. XXXI.] 
 
 VOLCANOS OF CATALONIA. 
 
 539 
 
 Fig. 668. 
 
 a. Conglomerate. 
 
 b. Thin seams of volcanic sand and scoriae. 
 
 thrown out from the vents is often so immense as far to exceed in 
 volume the scoriae, pumice, and lava*; but I sought in vain in the 
 cones near Clot for a single fragment of any extraneous rock ; and 
 Don Francisco Bolos, an eminent botanist of Olot, informed me that 
 he had never been able to detect any. 
 
 Volcanic sand and ashes are not confined to the cones, but have 
 been sometimes scattered by the wind over the country, and drifted 
 
 into narrow valleys, as is seen 
 between Olot and Cellent, where 
 the annexed section (fig. 668.) is 
 exposed. The light cindery vol- 
 canic matter rests in thin re- 
 gular layers, just as it alighted 
 on the slope formed of the solid 
 conglomerate. No flood could 
 have passed through the valley 
 since the scoriae fell, or these would have been for the most part 
 removed. The currents of lava in Catalonia, like those of Auvergne, 
 the Vivarais, Iceland, and all mountainous countries, are of con- 
 siderable depth in narrow defiles, but spread out into comparatively 
 thin sheets in places where the valleys widen. If a river has flowed 
 on nearly level ground, as in the great plain near Olot, the water 
 has only excavated a channel of slight depth; but where the de- 
 clivity is great, the stream has cut a deep section, sometimes by 
 penetrating directly through the central part of a lava-current, but 
 more frequently by passing between the lava and the secondary or 
 tertiary rock which bounds the valley. Thus, in the accompanying 
 section (fig. 669.), at the bridge of Cellent, six miles east of Olot, we 
 see the lava on one side of the small stream ; while the inclined 
 stratified rocks constitute the channel and opposite bank. The 
 
 Fig. 669. 
 
 Section above the bridge of Cellent. 
 
 a. Scoriaceous lava. d. Scorije, vegetable soil, and alluvium. 
 
 b. Schistose basalt. e. Nummulitic limestone. 
 
 c. Columnar basalt. / Micaceous grey sandstone. 
 
 upper part of the lava at that place, as is usual in the currents of 
 Etna and Vesuvius, is scoriaceous ; farther down it becomes less 
 
540 PLIOCENE VOLCANOS. [Cn. XXXI. 
 
 porous, and assumes a spheroidal structure ; still lower it divides in 
 horizontal plates, each about -2 inches in thickness, and is more 
 compact. Lastly, at the bottom is a mass of prismatic basalt about 
 5 feet thick. The vertical columns often rest immediately on the 
 subjacent stratified rocks ; but there is sometimes an intervention of 
 sand and scoriae such as cover the country during volcanic eruptions, 
 and which, unless protected, as here, by superincumbent lava, is 
 washed away from the surface of the land. Sometimes, the bed d 
 contains a few pebbles and angular fragments of rock ; in other 
 places fine earth, which may have constituted an ancient vegetable 
 soil. 
 
 In several localities, beds of sand and ashes are interposed between 
 the lava and subjacent stratified rock, as may be seen if we follow 
 the course of the lava-current which descends from Las Planas 
 towards Amer, and stops two miles short of that town. The river 
 there has often cut through the lava, and through 18 feet of under- 
 lying limestone. Occasionally an alluvium, several feet thick, is 
 interposed between the igneous and marine formations ; and it is 
 interesting to remark that in this, as in other beds of pebbles 
 occupying a similar position, there are no rounded fragments of 
 lava ; whereas in the most modern gravel-beds of the rivers of this 
 country volcanic pebbles are abundant. 
 
 The deepest excavation made by a river through lava, which I 
 observed in this part of Spain, is seen in the bottom of a valley near 
 San Feliu de Pallerols, opposite the Castell de Stolles. The lava 
 there has filled up the bottom of a valley, and a narrow ravine has 
 been cut through it to the depth of 100 feet. In the lower part the 
 lava has a columnar structure. A great number of ages were pro- 
 bably required for the erosion of so deep a ravine ; but we have no 
 reason to infer that this current is of higher antiquity than those 
 of the plain near Olot. The fall of the ground, and consequent 
 velocity of the stream, being in this case greater, a more considerable 
 volume of rock may have been removed in the same time. 
 
 I shall describe one more section (fig. 670.) to elucidate the phe- 
 nomena of this district. A lava-stream, flowing from a ridge of 
 hills on the east of Olot, descends a considerable slope, until it 
 reaches the valley of the river Fluvia. Here, for the first time, it 
 comes in contact with running water, which has removed a portion, 
 and laid open its internal structure in a precipice about 130 feet in 
 height, at the edge of which stands the town of Castell Follit. 
 
 By the junction of the rivers Fluvia and Teronel, the mass of lava 
 has been cut away on two sides ; and the insular rock B (fig. 670.) 
 has been left, which was probably never so high as the cliff A, as it 
 may have constituted the lower part of the sloping side of the 
 original current. 
 
 From an examination of the vertical cliffs, it appears that the 
 upper part of the lava on which the town is built is scoriaceous, 
 passing downwards into a spheroidal basalt; some of the huge 
 spheroids being no less than 6 feet in diameter. Below this is a 
 
CH.XXXI.] VOLCANOS OF CATALONIA. 
 
 Fig. 670. 
 
 541 
 
 Section at Castell Follit. 
 
 A. Church and town of Castell Follit, overlooking precipices of basalt. 
 
 B. Small island, on each side of which branches of the river Teronel flow to meet the 
 
 Fluvia. 
 
 c. Precipice of basaltic lava, chiefly columnar, about 130 feet in height. 
 
 d. Ancient alluvium, underlying the lava-current. 
 
 e. Inclined strata of sandstone. 
 
 more compact basalt, with crystals of olivine. There are in all five 
 distinct ranges of basalt, the uppermost spheroidal, and the rest 
 prismatic, separated by thinner beds not columnar, and some of 
 which are schistose. These were probably formed by successive 
 flows of lava, whether during the same eruption or at different 
 periods. The whole mass rests on alluvium, ten or twelve feet in 
 thickness, composed of pebbles of limestone and quartz, but without 
 any intermixture of igneous rocks ; in which circumstance alone it 
 appears to differ from the modern gravel of the Fluvia. 
 
 Bufadors. The volcanic rocks near Olot have often a cavernous 
 structure, like some of the lavas of Etna ; and in many parts of the 
 hill of Batet, in the environs of the town, the sound returned by the 
 earth, when struck, is like that of an archway. At the base of the 
 same hill are the mouths of several subterranean caverns, about 
 twelve in number, called in the country " bufadors ; " from which a 
 current of .cold air issues during summer, but in winter it is said to 
 be scarcely perceptible. I visited one of these bufadors in the 
 beginning of August, 1830, when the heat of the season was un- 
 usually intense, and found a cold wind blowing from it, which may 
 easily be explained ; for as the external air, when rarefied by heat, 
 ascends, the pressure of the colder and heavier air of the caverns 
 in the interior of the mountain causes it to rush out to supply its 
 place. 
 
 In regard to the age of these Spanish volcanos, attempts have 
 been made to prove, that in this country, as well as in Auvergne 
 and the Eifel, the earliest inhabitants were eye-witnesses to the 
 volcanic action. In the year 1421, it is said, when Olot was de- 
 stroyed by an earthquake, an eruption broke out near Amer, and 
 consumed the town. The researches of Don Francisco Bolos have, 
 I think, shown, in the most satisfactory manner, that there is no 
 good historical foundation for the latter part of this story ; and any 
 
542 
 
 VOLCANOS OF CATALONIA. 
 
 [CH. XXXI. 
 
 geologist who has visited Amer must be convinced that there never 
 was any eruption on that spot. It is true that, in the year above 
 mentioned, the whole of Olot, with the exception of a single house, 
 was cast down by an earthquake ; one of those shocks which, at 
 distant intervals during the last five centuries, have shaken the 
 Pyrenees, and particularly the country between Perpignan and Olot, 
 where the movements, at the period alluded to, were most violent. 
 
 The annihilation of the town may, perhaps, have been due to the 
 cavernous nature of the subjacent rocks ; for Catalonia is beyond 
 the line of those European earthquakes which have, within the 
 period of history, destroyed towns throughout extensive areas. 
 
 As we have no historical records, then, to guide us in regard to 
 the extinct volcanos, we must appeal to geological monuments. The 
 annexed diagram (fig. 671.) will present to the reader, in a synop- 
 tical form, the results obtained from numerous sections. 
 
 Fig. 671. 
 
 Superposition of rocks in the volcanic district of Catalonia. 
 
 a. Sandstone and nummulitic limestone. 
 
 b. Older alluvium without volcanic pebbles. 
 
 c. Cones of scoriae and lava. d. Newer alluvium. 
 
 The more modern alluvium (d) is partial, and has been formed by 
 the action of rivers and floods upon the lava; whereas the older 
 gravel (3) was strewed over the country before the volcanic erup- 
 tions. In neither have any organic remains been discovered; so 
 that we can merely affirm as yet, that the volcanos broke out after 
 the elevation of some of the newest rocks of the mummulitic 
 (Eocene) series of Catalonia, and before the formation of an allu- 
 vium (d) of unknown date. The integrity of the cones merely 
 shows that the country has not been agitated by violent earthquakes, 
 or subjected to the action of any great flood since their origin. 
 
 East of Olot, on the Catalonian coast, marine tertiary strata 
 occur, which, near Barcelona, attain the height of about 500 feet. 
 From the shells which I collected, these strata appear to correspond 
 in age with the Subapennine beds ; and it is not improbable that 
 their upheaval from beneath the sea took place during the period of 
 volcanic eruption round Olot. In that case these eruptions may 
 have occurred at the close of the Older Pliocene era, but perhaps 
 subsequently, for their age is at present quite uncertain. 
 
 Volcanic rocks of the Eifel. The chronological relations of the 
 volcanic rocks of the Lower Rhine and the Eifel are also involved 
 in a considerable degree of ambiguity ; but we know that some por- 
 tion of them were coeval with certain tertiary deposits called 
 
Ce. XXXI.] 
 
 TERTIARY VOLCANIC ROCKS. 
 
 543 
 
 " Brown-Coal " by the Germans, which probably belong in part to 
 the Miocene, and in part to the Upper Eocene, epoch. 
 
 This Brown-Coal is seen on both sides of the Rhine, in the neigh- 
 bourhood of Bonn, resting un conformably on highly inclined and 
 vertical strata of Silurian and Devonian rocks. Its geographical 
 position, and the space occupied by the volcanic rocks, both of the 
 Westerwald and Eifel, will be seen by referring to the map 
 (fig. 672.), for which I am indebted to Mr. Horner, whose residence 
 for some years in the country enabled him to verify the maps of 
 MM. Noeggerath and Von Oeynhausen, from which that now given 
 has been principally compiled.* 
 
 Fig. 672. 
 
 Map of the volcanic region of the Upper and Lower Eifel. 
 12345 English Miles. 
 
 A. of the Upper Eifel. 
 
 Volcanic f . 
 
 District. I B. of the Lower Eifel. 
 
 Trachyte. 
 
 Points of eruption, with craters and 
 scoriae. 
 
 Basalt. 
 Brown-coal. 
 
 N. B. The country in that part of the map which is left blank is composed of inclined 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 occasionally silex. Layers of light brown, and sometimes 
 black lignite are interstratified with the clays and sands, and often 
 
 * Horner, Trans, of Geol. Soc. 2d ser. vol. 
 
544 AGE OF THE BROWN-COAL. [Cn. XXXI. 
 
 irregularly diffused through them. They contain numerous impres- 
 sions of leaves and stems of trees, and are extensively worked for 
 fuel, whence the name of the formation. 
 
 In several 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 accumulation of 
 the latter, some volcanic products were ejected. 
 
 Mr. Von Decken in his work on the Siebengebirge *, has given a 
 copious list of the animal and vegetable remains of the freshwater 
 strata associated with the brown-coal. Plants of the genera Flabel- 
 laria, Ceanothus, and Daphnogene, including D. cinnamomifolia 
 (fig. 169. p. 192.) occur in these beds, with nearly 150 other plants, 
 if we include all which have been named from the somewhat uncer- 
 tain data furnished by leaves. They are referred for the most part 
 to living genera, but to extinct species. Among the animal remains, 
 both vertebrate and invertebrate, many are peculiar, while some few, 
 such as Littorinella acuta, Desh., help to approximate these strata 
 with some of the upper freshwater portions of the Mayence basin. 
 The marine base of the Mayence series consists of sandy strata 
 closely allied in geological date, as we have already seen, p. 191., to 
 the Limburg group, called Upper Eocene in this work. But in re- 
 gard to the Rhenish freshwater deposits near Bonn, so large a pro- 
 portion of the plants, insects, fish, batrachians, and other fossils are 
 such as have been met with nowhere else, that we cannot as yet 
 assign to them a very definite place in the chronological series. 
 They were undoubtedly formed during that long interval of time 
 which separated the Nummulitic from the Falunian tertiary formations, 
 so that they are newer than the Middle Eocene, and older than the 
 Miocene strata of our Table given at page 105. The classification 
 of the deposits belonging to this interval must still be regarded as 
 debatable ground, very different opinions being entertained on the 
 subject by geologists of high authority. Should a passage be even- 
 tually made out from the tertiaries of the north of Germany, on 
 which the labours of M. Beyrich have thrown so much light, to the 
 faluns of the Loire, by the discovery of beds intermediate in age and 
 paleontological characters, the best line of demarcation that we can 
 adopt is that proposed by M. Hebert, according to which all the 
 Limburg beds, the Gres de Fontainebleau, the lower part of the 
 Mayence basin, and the Hempstead beds of the Isle of Wight (see 
 p. 193.) are classed as Lower Miocene, while the Faluns rank as 
 Upper Miocene. Between these formations there is still so vast an 
 hiatus that I have thought it inexpedient, for reasons before explained, 
 to unite them under a common name.f 
 
 * Geognost. Beschreib. des Siebenge- Hamilton, Esq., P. G. S., has been 
 
 birges am Khein. Bonn, 1852. published (Geol. Quart. Journ. vol. x. 
 
 f While this sheet Avas passing p. 254), in which the question of classi- 
 
 through the press, a valuable paper fication above alluded to is discussed, 
 
 on the Brown- Coal and other deposits Whatever terminology be adopted, I 
 
 of the Mayence Basin, by William J. would strongly urge the necessity of 
 
CH. XXXI.] TERTIARY VOLCANIC ROCKS. 545 
 
 The fishes of the brown-coal near Bonn are found in a bituminous 
 shale, called paper-coal, from being divisible into extremely 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 Leuciscus, Aspius, and Perca. The remains of 
 frogs also, of extinct species, have been discovered in the paper-coal; 
 and a complete series may be seen in the museum at Bonn, from the 
 most imperfect state of the tadpole to that of the full-grown animal. 
 With these a salamander, scarcely distinguishable from the recent 
 species, has been found, and the remains of many insects. 
 
 A vast deposit of gravel, chiefly composed of pebbles of white 
 quartz, but containing also a few fragments of other rocks, lies over 
 the brown-coal, forming sometimes only a thin covering, at others 
 attaining a thickness of more than 100 feet. This gravel is very 
 distinct in character from that now forming the bed of the Rhine. 
 It is called " Kiesel gerolle " by the Germans, often reaches great 
 elevations, and is covered in several places with volcanic ejections. 
 It is evident that the country has undergone great changes in its 
 physical geography since this gravel was formed ; for its position 
 has scarcely any relation to the existing drainage, and the great 
 valley of the Rhine and all the more modern volcanic rocks of the 
 same region are posterior to it in date. 
 
 Some of the newest beds of volcanic sand, pumice, and scoriae are 
 inter stratified near Andernach and elsewhere with the loam called 
 loess, which was before described as being full of land and freshwater 
 shells of recent species, and referable to the Post-Pliocene period. I 
 have before hinted (see p. 124.) that this intercalation of volcanic 
 matter between beds of loess may possibly be explained without 
 supposing the last eruptions of the Lower Eifel to have taken place 
 so recently as the era of the deposition of the loess. 
 
 The igneous rocks of the Westerwald, and of the mountains called 
 the Siebengebirge, consist partly of basaltic and partly 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 
 felspar. Trachytic tuff is also very abundant. These formations, 
 some of which were certainly contemporaneous with the origin of 
 the brown -coal, were the first of a long series of eruptions, the 
 more recent of which happened when the country had acquired 
 nearly all its present geographical features. 
 
 Newer volcanos of the Eifel. Lake-craters. As I recognized 
 in the more modern volcanos of the Eifel characters distinct from 
 any previously observed by me in those of France, Italy, or Spain, I 
 shall briefly describe them. The fundamental rocks of the district 
 are grey and red sandstones and shales, with some associated lime- 
 stones, replete with fossils of the Devonian or Old Red Sandstone 
 
 referring the Hempstead beds of the he named Lower Miocene or Upper 
 Isle of Wight and the Limburg strata Eocene, 
 to one and the same period, whether it 
 
 NN 
 
546 
 
 TERTIARY VOLCANIC ROCKS. 
 
 [Cn. XXXI. 
 
 group. The volcanos broke out in the midst of these inclined strata, 
 and when the present systems of hills and valleys had already been 
 formed. The eruptions occurred sometimes at the bottom of deep 
 valleys, sometimes on the summit of hills, arid frequently on inter- 
 vening platforms. In travelling through this district we often fall 
 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 example, 
 on arriving at the village of Gemund, immediately south of Daun, 
 we leave the stream, which flows at the bottom 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 inwards towards the mountain. When we have ascended to 
 a considerable height, we see fragments of scoriae sparingly scattered 
 over the surface ; until, at length, on reaching the summit, we find 
 ourselves suddenly on the edge of a tarn, or deep circular lake-basin 
 (see fig. 673.). 
 
 Fig. 6/3. 
 
 a. Village of Gemund. 
 
 b. Gemunder Maar. 
 
 c. WeinfelderTMaar. 
 
 d. Schalkenmehren Maar. 
 
 This, which is called the Gemunder Maar, is one of three lakes 
 which are in immediate contact, the same ridge forming the barrier 
 of two neighbouring cavities. On viewing the first of these (fig. 673 .), 
 we recognize the ordinary form of a crater, for which we have been 
 prepared by the occurrence of scoriae 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 in 
 opposite directions on every side, which we have been accustomed to 
 consider as characteristic of volcanic vents. As we proceed, however, 
 to the opposite side of the lake, and afterwards visit the craters c 
 and d (fig. 674.), we find a considerable quantity of scoriae and some 
 
CH. XXXI.] LAKE-CRATERS OF THE EIFEL. 547 
 
 lava, and see the whole surface of the soil sparkling 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. 
 
 A few miles to the south of the lakes above mentioned occurs the 
 Pulvermaar of Gillenfeld, an oval lake of very regular form, and 
 surrounded by an unbroken ridge of fragmentary materials, consisting 
 of ejected shale and sandstone, and preserving a uniform height of 
 about 150 feet above the water. The side slope in the interior is 
 at an angle of about 45 degrees; on the exterior, of 35 degrees. 
 Volcanic substances are intermixed very sparingly with the ejections, 
 which in this place entirely conceal from view the stratified rocks of 
 the country.* 
 
 The Meerfelder Maar is a cavity of far greater size and depth, 
 hollowed out of similar strata ; the sides presenting some abrupt 
 sections of inclined secondary rocks, which in other places are buried 
 under vast heaps of pulverized shale. I could discover no scoriae 
 amongst the ejected materials, but balls of olivine and other volcanic 
 substances are mentioned as having been found.f This cavity, which 
 we must suppose to have discharged an immense volume of gas, is 
 nearly a mile in diameter, and is said to be more than one hundred 
 fathoms deep. In the neighbourhood is a mountain called the Mosen- 
 berg, which consists of red sandstone and shale in its lower parts, 
 but supports on its summit a triple volcanic cone, while a distinct 
 current of lava is seen descending the flanks of the mountain. The 
 edge of the crater of the largest cone reminded me much of the form 
 and characters of that of Vesuvius ; but I was much struck with the 
 precipitous and almost overhanging wall or parapet which the scoriae 
 presented towards the exterior, as at a b (fig. 675.); which I can 
 only explain by supposing that fragments of red-hot lava, as they fell 
 round the vent, were cemented together into one compact mass, in 
 consequence of continuing to be in a half-melted state. 
 
 Stratified rocks. v. Volcanic. 
 
 Outline of the Mosenberg, Upper Eifel. 
 
 If we pass from the Upper to the Lower Eifel, from A to B (see 
 map, p. 543.), we find the celebrated lake-crater of Laach, which has 
 a greater resemblance than any of those before mentioned to the 
 Lago di Bolsena, and others in Italy, being surrounded by a ridge 
 
 * Scrope, Edin. Journ. of Science, f Hibbert, Extinct Volcanos of the 
 June, 1826, p. 145. Rhine, p. 24. 
 
 NN 2 
 
548 TERTIARY VOLCANIC ROCKS. [Cn. XXXI. 
 
 of gently sloping hills, composed of loose tuffs, scoriae, and blocks of 
 a variety of lavas. 
 
 One of the most interesting volcanos on the left bank of the Rhine 
 near Bonn is called the Roderberg. It forms a circular crater nearly 
 a quarter of a mile in diameter, and 100 feet deep, now covered with 
 fields of corn. The highly inclined strata of ancient sandstone and 
 shale rise even to the rim of one side of the crater ; but they are 
 overspread by quartzose gravel, and this again is covered by volcanic 
 scorise and tufaceous sand. The opposite wall of the crater is com- 
 posed of cinders and scorified rock, like that at the summit of Vesu- 
 vius. It is quite evident that the eruption in this case burst through 
 the sandstone and alluvium which immediately overlies it; and I 
 observed some of the quartz pebbles mixed with scoriae on the flanks 
 of the mountain, as if they had been cast up into the air, and had 
 fallen again with the volcanic ashes. I have already observed, that 
 a large part of this crater has been filled up with the loess (p. 123.). 
 
 The most striking peculiarity of a great many of the craters above 
 described, is the absence of any signs of alteration or torrefaction in 
 their walls, when these are composed of regular strata of ancient 
 sandstone and shale. It is evident that the summits of hills formed 
 of the above-mentioned stratified rocks have, in some cases, been 
 carried away by gaseous explosions, while at the same time no lava, 
 and often a very small quantity only of scorise, has escaped from the 
 newly formed cavity. There is, indeed, no feature in the Eifel vol- 
 canos more worthy of note, than the proofs they afford of very 
 copious aeriform discharges, unaccompanied by the pouring out of 
 melted matter, except, here and there, in very insignificant volume. 
 I know of no other extinct volcanos 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 strata dipping outwards on all sides from a central axis, 
 as is assumed in the theory of elevation craters, alluded to in Chap. 
 XXIX. 
 
 Trass. In the Lower Eifel, eruptions of trachytic lava preceded 
 the emission of currents of basalt, and immense quantities of pumice 
 were thrown out wherever trachyte issued. The tufaceous alluvium 
 called trass, which has covered large areas in this region 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 this trass was formed 
 during the period of volcanic eruptions, it may perhaps have origi- 
 nated in the manner of the moya of the Andes. 
 
 We may easily conceive that a similar mass might now be pro- 
 duced, if a copious evolution of gases should occur in one of the lake 
 basins. The water might remain for weeks in a state of violent 
 
CH. XXXI.J HUNGARIAN VOLCANOS. 549 
 
 ebullition, until it became of the consistency of mud, just as the sea 
 continued to be charged with red mud round Graham's Island, in the 
 Mediterranean, in the year 1831. If a breach should then be made 
 in the side of the cone, the flood would sweep away great heaps of 
 ejected 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 dis- 
 persed irregularly through the trass, can be explained. 
 
 Hungary. M. Beudant, in his elaborate work on Hungary, de- 
 scribes five distinct groups of volcanic rocks, which although no- 
 where of great extent, form striking features in the physical geo- 
 graphy of that country, rising as they do abruptly from extensive 
 plains composed of tertiary strata. They may have constituted 
 islands in the ancient sea, as Santorin and Milo now do in the Gre- 
 cian Archipelago ; and M. Beudant has remarked that the mineral 
 products of the last-mentioned islands resemble remarkably those of 
 the Hungarian extinct volcanos, where many of the same minerals, 
 as opal, calcedony, resinous silex (silex resinite), pearlite, obsidian, 
 and pitchstone abound. 
 
 The Hungarian lavas are chiefly felspathic, consisting of different 
 varieties of trachyte ; many are cellular, and used as millstones ; 
 some so porous and even scoriform as to resemble those which have 
 issued in the open air. Pumice occurs in great quantity ; and there 
 are conglomerates, or rather breccias, wherein fragments of trachyte 
 are bound together by pumiceous tuff, or sometimes by silex. 
 
 It is probable that these rocks were permeated by the waters of 
 hot springs, impregnated, like the Geysers, with silica ; or in some 
 instances, perhaps, by aqueous vapours, which, like those of Lance- 
 rote, may have precipitated hydrate of silica. 
 
 By the influence of such springs or vapours the trunks and 
 branches of trees washed down during floods, and buried in tuffs on 
 the flanks of the mountains, are supposed to have become silicified. 
 It is scarcely possible, says M. Beudant, to dig into any of the 
 pumiceous deposits of these mountains without meeting with opalized 
 wood, and sometimes entire silicified trunks of trees of great size 
 and weight. 
 
 It appears from the species of shells collected principally by 
 M. Boue, and examined by M. Deshayes, that the fossil remains im- 
 bedded in the volcanic tuffs, and in strata alternating with them in 
 Hungary, are of the Miocene type, and not identical, as was formerly 
 supposed, with the fossils of the Paris basin. 
 
 K N 3 
 
550 TERTIARY VOLCANIC ROCKS. [C.H. XXXII. 
 
 CHAPTER XXXII. 
 
 ON THE DIFFERENT AGES OF THE VOLCANIC BOCKS continued. 
 
 Volcanic rocks of the Pliocene, Miocene, and Eocene periods continued Au- 
 vergne Mont Dor Breccias and alluviums of Mont Perrier, with bones of 
 quadrupeds River dammed up by lava-current Range of minor cones from 
 Auvergne to the Vivarais Monts Dome Puy de Come Puy de Pariou 
 Cones not denuded by general flood Velay Bones of quadrupeds buried in 
 scorise Cantal Eocene volcanic rocks Tuffs near Clermont Hill of Ger- 
 govia Trap of Cretaceous period Oolitic period New Red Sandstone pe- 
 riod Carboniferous period Old Red Sandstone period "Rock and Spindle" 
 near St. Andrew's Silurian period Cambrian volcanic rocks. 
 
 Volcanic Rocks of Auvergne. THE extinct volcanos of Auvergne 
 and Cantal in Central France seem to have commenced their erup- 
 tions in the Upper Eocene period, but to have been most active 
 during the Miocene and Pliocene eras. I have already alluded to 
 the grand succession of events, of which there is evidence in 
 Auvergne since the last retreat of the sea (see p. 197.). 
 
 The earliest monuments of the tertiary period in that region are 
 lacustrine deposits of great thickness (2. fig. 676. p. 552.), in the 
 lowest conglomerates of which are rounded pebbles of quartz, mica- 
 schist, granite, and other non-volcanic rocks, without the slightest 
 intermixture of igneous products. To these conglomerates succeed 
 argillaceous and calcareous marls and limestones (3. fig. 676.), con- 
 taining Upper Eocene shells and bones of mammalia, the higher beds 
 of which sometimes alternate with volcanic tuif of contemporaneous 
 origin. After the filling up or drainage of the ancient lakes, huge 
 piles of trachytic and basaltic rocks, with volcanic breccias, accu- 
 mulated to a thickness of several thousand feet, and were super- 
 imposed upon granite, or the contiguous lacustrine strata. The 
 greater portion of these igneous rocks appear to have originated 
 during the 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 alluvial sand and gravel, which owe 
 their preservation to overspreading sheets of lava. 
 
 In Auvergne the most ancient and conspicuous of the volcanic 
 masses is Mont Dor, which rests immediately on the granitic rocks 
 standing apart from the freshwater strata.* This great mountain 
 rises suddenly to the height of several thousand feet above the sur- 
 rounding platform, and retains the shape of a flattened and somewhat 
 
 * See the Map, p. 196. 
 
CH. XXXII.] MONT DOE, AUVERGNE. 551 
 
 irregular cone, all the sides sloping more or less rapidly, until their 
 inclination 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 angu- 
 lar and rounded fragments of igneous rocks, are observed to alter- 
 nate 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, 
 where no regular crater can now be traced, but where we may easily 
 imagine one to have existed, which may have been shattered by 
 earthquakes, and have suffered degradation by aqueous agents. Ori- 
 ginally, perhaps, like the highest crater of Etna, it may have formed 
 an insignificant feature in the great pile, and may frequently have 
 been destroyed and renovated. 
 
 According to some geologists, this mountain, as well as Vesuvius, 
 Etna, and all large volcanos, has derived its dome-like form not from 
 the preponderance of eruptions from one or more central points, but 
 from the upheaval of horizontal beds of lava and scorias. I have 
 explained my reasons for objecting to this view in Chap. XXIX., 
 when speaking of Palma, and in the Principles of Geology. f The 
 average inclination of the dome-shaped mass of Mont Dor is 8 6', 
 whereas in Mounts Loa and Kea, before mentioned, in the Sandwich 
 Islands (see fig. 640. p. 494.), the flanks of which have been raised 
 by recent lavas, we find from Mr. Dana's description that the one 
 has a slope of 6 30', the other of 7 46'. We may, therefore, 
 reasonably question whether there is any absolute necessity for sup- 
 posing that the basaltic currents of the ancient French volcano were 
 at first more horizontal than they are now. Nevertheless it is highly 
 probable that during the long series of eruptions required to give 
 rise to so vast a pile of volcanic matter, which is thickest at the 
 summit or. centre of the dome, some dislocation and upheaval took 
 place ; and during the distension of the mass, beds of lava and scoriae 
 may, in some places, have acquired a greater, in others a less incli- 
 nation, than that which at first belonged to them. 
 
 Respecting the age of the great mass of Mont Dor, we cannot 
 come at present to any positive decision, because no organic remains 
 have yet been found in the tuffs, except impressions of the leaves of 
 trees of species not yet determined. We may certainly conclude, that 
 the earliest eruptions were posterior in origin to those grits and con- 
 glomerates of the freshwater formation of the Limagne which contain 
 no pebbles of volcanic rocks ; while, on the other hand, some erup- 
 tions took place before the great lakes were drained, and others 
 
 * Scrope's Central France, p. 98. f See chaps, xxiv., xxv., and xxvi., 
 
 7th, 8th, and 9th editions. 
 
 NN 4 
 
552 TERTIARY VOLCANIC ROCKS. [Cn. XXXII. 
 
 occurred after the desiccation of those lakes, and when deep valleys 
 had already been excavated through freshwater strata. 
 
 In the annexed section, I have endeavoured to explain the geological 
 structure of a portion of Auvergne, which I re-examined in 1843.* 
 
 Fig. 676. 
 Mont Perrier. 
 
 Section from the valley of the Couze at Nechers, through Mont Perrier and Issoire, to the Valley 
 of the Allier and the Tour de Boulade, Auvergne. 
 
 10. Lava-current of Tartaret near its termi- 5. Lower bone-bed of Perrier, ochreous sand 
 nation at Nechers. and gravel. 
 
 9. Bone-bed, red sandy clay under the lava of 4 a. Basaltic dike. 
 
 Tartaret. 4. Basaltic platform. 
 
 8. Bone-bed of the Tour de Boulade. 3. Upper freshwater beds, limestone, marl, gyp- 
 
 7. Alluvium newer than No. 6. sum, &c. 
 
 6. Alluvium with bones of hippopotamus. 2. Lower freshwater formation, red clay, green 
 
 5 c. Trachytic breccia resembling 5 a. sand, &c. 
 
 ft b. Upper bone-bed of Perrier, gravel, &c. 1. Granite. 
 
 5 a. Pumiceous breccia and conglomerate, angu- 
 lar masses of trachyte, quartz, pebbles, &c. 
 
 It may convey some idea to the reader of the long and complicated 
 series of events, which have occurred in that country, since the first 
 lacustrine strata (No. 2.) were deposited on the granite (No. 1.). The 
 changes of which we have evidence are the more striking, because 
 they imply great denudation, without there being any proofs of the 
 intervention of the sea during the whole period. It will be seen 
 that the upper freshwater beds (No. 3.), once formed in a lake, must 
 have suffered great destruction before the excavation of the valleys of 
 the Couze and Allier had begun. In these freshwater beds, Upper 
 Eocene fossils, as described in Chap. XV., have been found. The 
 basaltic dike, 4', is one of many examples of the intrusion of volcanic 
 matter through the Eocene freshwater beds, and may have been of 
 Upper Eocene or Miocene date, giving rise, when it reached the 
 surface and overflowed, to such platforms of basalt, as often cap the 
 tertiary hills in Auvergne, and one of which (4) is seen on Mont 
 Perrier. 
 
 It not unfrequently happens that beds of gravel containing bones 
 of extinct mammalia are detected under these very ancient sheets of 
 basalt, as between No. 4. and the freshwater strata, No. 3., at A, from 
 which it is clear that the surface of No. 3. formed at that period the 
 lowest level at which the waters then draining the country flowed. 
 Next in age to this basaltic platform comes a patch of ochreous sand 
 and gravel (No. 5.), containing many bones of quadrupeds. Upon 
 this rests a pumiceous breccia or conglomerate, with angular masses 
 of trachyte and some quartz pebbles. This deposit is followed by 5 b 
 (which is similar to 5) and 5 c similar to the trachytic breccia 5 a. 
 These two breccias ar,e supposed, from their similarity to others found 
 on Mont Dor, to have descended from the flanks of that mountain 
 
 * See Quarterly Geol. Journ. vol. ii. p. 77. 
 
CH. XXXII.] VOLCANOS OF AUVERGNE. 553 
 
 during eruptions ; and the interstratified alluvial deposits contain the 
 remains of mastodon, rhinoceros, tapir, deer, beaver, and quadrupeds 
 of other genera, referable to about forty species, all of which are 
 extinct. I formerly supposed them to belong to the same era as the 
 Miocene faluns of Touraine ; but, whether they may not rather be 
 ascribed to the older Pliocene epoch is a question which farther in- 
 quiries and comparisons must determine. 
 
 Whatever be their date in the tertiary series, they are quadrupeds 
 which inhabited the country when the formations 5 and 5 c ori- 
 ginated. Probably they were drowned during floods, such as rush 
 down the flanks of volcanos during eruptions, when great bodies of 
 steam are emitted from the crater, or when, as we have seen, both on 
 Etna and in Iceland in modern times, large masses of snow are sud- 
 denly melted by lava, causing a deluge of water to bear down frag- 
 ments of igneous rocks mixed with mud to the valleys and plains 
 below. 
 
 It will be seen that the valley of the Issoire, down which these 
 ancient inundations swept, was first excavated at the expense of the 
 formations 2, 3, and 4, and then filled up by the masses 5 and 5 c, 
 after which it was re-excavated before the more modern alluviums 
 (Nos. 6. and 7.) were formed. In these again other fossil mammalia 
 of distinct species have been detected byM.Bravard, the bones of an 
 hippopotamus having been found among the rest. 
 
 At length, when the valley of the Allier was eroded at Issoire down 
 to its lowest level, a talus of angular fragments of basalt and fresh- 
 water limestone (No. 8.) was formed, called the bone-bed of the Tour 
 de Boulade, from which a great many other mammalia have been 
 collected by MM. Bravard and Pomel. In this assemblage the Ele- 
 phas primigenius, Rhinoceros tichorinus, Deer (including rein-deer), 
 Equus, Bos, Antelope, Felis, and Canis were included. Even this 
 deposit seems hardly to be the newest in the neighbourhood, for if we 
 cross from the town of Issoire (see fig. 676.) over Mont Perrier to the 
 adjoining valley of the Couze, we find another bone-bed (No. 9.), 
 overlaid by a current of lava (No. 10.). 
 
 The history of this lava-current, which terminates a few hundred 
 yards below the point No. 10., in the suburbs of the village of Nechers, 
 is interesting. It forms a long narrow stripe more than 13 miles in 
 length, at the bottom of the valley of the Couze, which flows out of a 
 lake at the foot of Mont Dor. This lake is caused by a barrier 
 thrown across the ancient channel of the Couze, consisting partly of 
 the volcanic cone called the Puy de Tartaret, formed of loose scoriae, 
 from the base of which has issued the lava-current before mentioned. 
 The materials of the dam which blocked up the river, and caused the 
 Lac de Chambon, are also, in part, derived from a land-slip which may 
 have happened at the time of the great eruption which formed the cone. 
 
 This cone of Tartaret affords an impressive monument of the very 
 different dates at which the igneous eruptions of Auvergne have 
 happened ; for it was evidently thrown up at the bottom of the exist- 
 ing valley, which is bounded by lofty precipices composed of sheets 
 
554 TERTIARY VOLCANIC ROCKS. [Cn. XXXII. 
 
 of ancient columnar trachyte and basalt, which once flowed at very 
 high levels from Mont Dor.* 
 
 When we follow the course of the river Couze, from its source in 
 the lake of Chambon to the termination of the lava-current at 
 Nechers, a distance of thirteen miles, we find that the torrent has in 
 most places cut a deep channel through the lava, the lower portion of 
 which is columnar. In some narrow gorges the water has even had 
 power to remove the entire mass of basaltic rock, though the work of 
 erosion must have 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 required for this 
 operation, the perishable cone of Tartaret, composed of sand and 
 ashes, has stood uninjured, proving that no great flood or deluge can 
 have passed over this region in the interval between the eruption of 
 Tartaret and our own times. 
 
 If we now return to the section (fig. 676.), I may observe that the 
 lava-current of Tartaret, which has diminished greatly in height and 
 volume near its termination, presents here a steep and perpendicular 
 face 25 feet in height towards the river. Beneath it is the alluvium 
 No. 9., consisting of a red sandy clay, which must have covered the 
 bottom of the valley when the current of melted rock flowed down. 
 The bones found in this alluvium, which I obtained myself, consisted 
 of a species of field-mouse, Arvicola, and the molar tooth of an ex- 
 tinct horse, Equus fossilis. The other species, obtained from the 
 same bed, are referable to the genera Sus, Bos, Cervus, Felis, Canis, 
 Martes, Talpa, Sorex, Lepus, Sciurus, Mus, and Lagomys, in all no 
 less than forty-three species, all closely allied to recent animals, yet 
 nearly all of them, according to M. Bravard, showing some points of 
 difference, like those which Mr. Owen discovered in the case of the 
 horse above alluded to. The bones, also of a frog, snake, and lizard, 
 and of several birds, were associated with the fossils before enumerated, 
 and several recent land shells, such as Cyclostoma elegans, Helix hor- 
 tensis, H. nemoralis, H. lapicida, and Clausilia rugosa. If the 
 animals were drowned by floods, which accompanied the eruptions of 
 the Puy de Tartaret, they would give an exceedingly modern geolo- 
 gical date to that event, which must, in that case, have belonged to 
 the Newer-Pliocene, or, perhaps, the Post-Pliocene period. 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 mammiferous fauna 
 from that of our day, but from the fact that a Roman bridge of such 
 form and construction as continued in use down to the fifth century, 
 but which may be older, is now seen at a place about a mile and a 
 half from St. Nectaire. This ancient bridge spans the river Couze 
 with two arches, each about 14 feet wide. These arches spring from 
 the lava of Tartaret, on both banks, showing that a ravine precisely 
 
 * For a view of Puy de Tartaret and Mont Dor, see Scrope's Volcanos of 
 Central France. 
 
CH. XXXII.] VOLCANOS OF AUVERGNE. 555 
 
 like that now existing, had already been excavated by the river 
 through that lava thirteen or fourteen centuries ago. 
 
 In Central France there are several hundred minor cones, like that 
 of Tartaret, a great number of which, like Monte Nuovo, near Naples, 
 may have been principally due to a single eruption. Most of these 
 cones range in a linear direction from Auvergne to the Vivarais, and 
 they were faithfully described so early as the year 1802, by M. de 
 Montlosier. They have given rise chiefly to currents of basaltic 
 lava. Those of Auvergne called the Monts Dome, placed on a gra- 
 nitic platform, form an irregular ridge (see fig. 621. p. 466.), about 18 
 miles in length and 2 in breadth. They are usually truncated at 
 the summit, where the crater is often preserved entire, the lava having 
 issued from the base of the hill. But frequently the crater is broken 
 down on one side, where the lava has flowed out. The hills are com- 
 posed of loose scorise, blocks of lava, lapilli, and pozzuolana, with 
 fragments of trachyte and granite. 
 
 Puy de Come. The Puy de Come and its lava-current, near 
 Clermont, may be mentioned as one of these minor volcanos. This 
 conical hill rises from the granitic platform, at an angle of between 
 30 and 40, to the height of more than 900 feet. Its summit pre- 
 sents two distinct 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 granitic 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 dispossessed of its bed, has worked out a 
 fresh one between the lava and the granite of its western bank ; and 
 the excavation has disclosed, in one spot, a wall of columnar basalt 
 about 50 feet high.* 
 
 The excavation of the ravine is still in progress, every winter some 
 columns of basalt being undermined and carried down the channel 
 of the river, and in the course of a few miles rolled to sand and 
 pebbles. Meanwhile the cone of Come remains unimpaired, its 
 loose materials being protected 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 upon 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 incoherent and transportable 
 materials called the Puy de Come may remain in a stationary con- 
 dition. In this place, therefore, we behold in the results of aqueous 
 and atmospheric agency in past times, a counterpart of what we 
 must expect to recur in future ages. 
 
 Lava of Chaluzet. At another point, farther down the course of 
 the Sioule, we find a second illustration of the same phenomenon in 
 the Puy Rouge, a conical hill to the north of the village of Pranal. 
 
 * Scrope's Central France, p. 60., and plate. 
 
556 
 
 TERTIARY VOLCANIC ROCKS. 
 
 [CH. XXXII. 
 
 The cone is composed entirely of red and black scoriae, tuff, and vol- 
 canic bombs. On its western side, towards the village of Chaluzet, 
 there is a worn -down crater, whence a powerful stream of lava has 
 issued, and flowed into the valley of the Sioule. The river has since 
 excavated a ravine through the lava and subjacent gneiss, to the 
 depth in some places of 400 feet. 
 
 On the upper part of the precipice forming the left side of this 
 ravine, we see a great mass of black and red scoriaceous lava be- 
 coming more and more columnar towards its base. (See fig. 677.). 
 
 Fig. 677. 
 
 a. Scoriaceous lava. 
 
 b. Columnar basalt. 
 
 c. Gravel. 
 
 D. Ancient mining gallery. 
 
 E. Pathway. 
 /. Gneiss. 
 
 Lava-current of Chaluzet, Auvergne, near its termination.* 
 
 Below this is a bed of sand and gravel 3 feet thick, evidently an 
 ancient river-bed, now at an elevation of 25 feet above the channel 
 of the Sioule. This gravel, from which water gushes out, rests upon 
 gneiss, /, which has been eroded to the depth of 25 feet at the point 
 where the annexed view is taken. At D, close to the village of Les 
 Combres, the entrance of a gallery is seen, in which lead has been 
 worked in the gneiss. This mine shows that the pebble-bed is con- 
 tinuous, in a horizontal direction, between the gneiss and the volcanic 
 mass. Here again it is quite evident, that, while the basalt was gra- 
 dually undermined and carried away by the force of running water, 
 the cone whence the lava issued escaped destruction, because it stood 
 upon a platform of gneiss several hundred feet above the level of the 
 valley in which the force of running water was exerted. 
 
 Puy 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 affords room to stand upon. This and other cones 
 
 Lyell and Murchison, Ed. New Phil. Journ. 1829. 
 
CH. XXXII.] VELAY, CANTAL. 557 
 
 in an equally remarkable state of integrity have stood, I conceive, 
 uninjured, not in spite of their loose porous nature, as might at first 
 be naturally supposed, but in consequence of it. No rills can collect 
 where all the rain is instantly absorbed by the sand and scoriae, as is 
 remarkably the case on Etna ; and nothing but a waterspout break- 
 ing directly upon the Puy de Pariou could carry away a portion of 
 the hill, so long as it is not rent or engulphed by earthquakes. 
 
 Hence it is conceivable that even those cones which have the 
 freshest aspect and most perfect shape may lay claim to very high 
 antiquity. Dr. Daubeny has justly observed, that had any of these 
 volcanos been in a state of activity in the age of Julius Caesar, that 
 general, who encamped upon the plains of Auvergne, and laid siege 
 to its principal city (Gergovia, near Clermont), could hardly have 
 failed to notice them. Had there been any record of their eruptions 
 in the time of Pliny or Sidonius Apollinaris, the one would scarcely 
 have omitted to make mention of it in his Natural History, nor the 
 other to introduce some allusion to it among the descriptions of this 
 his native province. This poet's residence was on the borders of the 
 Lake Aidat, which owed its very existence to the damming up of a 
 river by one of the most modern lava-currents.* 
 
 Velay. The observations of M. Bertrand de Doue have not yet 
 established that any of the most ancient volcanos of Velay were in 
 action during the Eocene period. There are beds of gravel in Velay, 
 as in Auvergne, covered by lava at different heights above the chan- 
 nel of the existing rivers. In the highest and most ancient of these 
 alluviums the pebbles are exclusively of granitic rocks ; but in the 
 newer, which are found at lower levels, and which originated when 
 the valleys had been cut to a greater depth, an intermixture of vol- 
 canic rocks has been observed. 
 
 At St. Privat d'Allier a bed of volcanic scorias and tuff was dis- 
 covered by Dr. Hibbert, inclosed between two sheets of basaltic lava ; 
 and in this tuff were found the bones of several quadrupeds, some of 
 them adhering to masses of slaggy lava. Among other animals were 
 Rhinoceros leptorhinus, Hycena spelcea, and a species allied to the 
 spotted hysena of the Cape, together with four undetermined species 
 of deer.' The manner of the occurrence of these bones reminds us 
 of the published accounts of an eruption of Coseguina, 1835, in 
 Central America (see p. 525.), during which hot cinders and scoriae 
 fell and scorched to death great numbers of wild and domestic ani- 
 mals and birds. 
 
 Plomb du Cantal. In regard to the age of the igneous rocks of 
 the Cantal, we can at present merely affirm, that they overlie the 
 (Upper?) Eocene lacustrine strata of that country (see Map, p. 196.). 
 They form a great dome-shaped mass, having an average slope of 
 only 4, which has evidently been accumulated, like the cone of 
 Etna, during a long series of eruptions. It is composed of trachytic, 
 phonolitic, and basaltic lavas, tuffs, and conglomerates, or breccias, 
 
 * Daubeny on Volcanos, p. 14. 
 
558 EOCENE VOLCANIC ROCKS. [Cn. XXXII. 
 
 forming a mountain several thousand feet in height. Dikes also of 
 phonolite, trachyte, and basalt are numerous, especially in the neigh- 
 bourhood of the large cavity, probably once a crater, around which 
 the loftiest summits of the Cantal are ranged circularly, few of them, 
 except the Plomb du Cantal, rising far above the border or ridge of 
 this supposed crater. A pyramidal hill, called the Puy Griou, occu- 
 pies the middle of the cavity.* It is clear that the volcano of the 
 Cantal broke out precisely on the site of the lacustrine deposit be- 
 fore described (p. 205.), which had accumulated in a depression of a 
 tract composed of micaceous schist. In the breccias, even to the 
 very summit of the mountain, we find ejected masses of the fresh- 
 water beds, and sometimes fragments of flint, containing Eocene 
 shells. Valleys radiate in all directions from the central heights of 
 the mountain, increasing in size as they recede from those heights. 
 Those of the Cer and Jourdanne, which are more than 20 miles in 
 length, are of great depth, and lay open the geological structure 
 of the mountain. No alternation of lavas with undisturbed Eocene 
 strata has been observed, nor any tuffs containing freshwater shells, 
 although some of these tuffs include fossil remains of terrestrial 
 plants, said to imply several distinct restorations of the vegetation 
 of the mountain in the intervals between great eruptions. On the 
 northern side of the Plomb du Cantal, at La Vissiere, near Murat, is 
 a spot, pointed out on the Map (p. 196.), where freshwater limestone 
 and marl are seen covered by a thickness of about 800 feet of vol- 
 canic rock. Shifts are here seen in the strata of limestone and 
 marl.f 
 
 In treating of the lacustrine deposits of Central France, in the 
 fifteenth chapter, it was stated that, in the arenaceous and pebbly 
 group of the lacustrine basins of Auvergne, Cantal, and Velay, no 
 volcanic pebbles had ever been detected, although massive piles of 
 igneous rocks are now found in the immediate vicinity. As this 
 observation has been confirmed by minute research, we are warranted 
 in inferring that the volcanic eruptions had not commenced when 
 the older subdivisions of the freshwater groups originated. 
 
 In Cantal and Velay no decisive proofs have yet been brought to 
 light that any of the igneous outbursts happened during the depo- 
 sition of the freshwater strata ; but there can be no doubt that in 
 Auvergne some volcanic explosions took place before the drainage 
 of the lakes, and at a time when the Upper Eocene species of animals 
 and plants still flourished. Thus, for example, at Pont du Chateau, 
 near Clermont, a section is seen in a precipice on the right bank of 
 the river Allier, in which beds of volcanic tuff alternate with a fresh- 
 water limestone, which is in some places pure, but in others spotted 
 with fragments of volcanic matter, as if it were deposited while 
 showers of sand and scoriae were projected from a neighbouring 
 vent.J 
 
 * Mem. de la Soc. Ge'ol. de France, f See Lyell and Murchison, Ann. de 
 torn. i. p. 175. Sci. Nat., Oct. 1829. 
 
 J See Scrope's Central France, p. 21. 
 
CH. XXXII.] 
 
 GERGOVIA. 
 
 559 
 
 Another example occurs in the Puy de Marmont, near Veyres, 
 where a freshwater marl alternates with volcanic tuff containing 
 Eocene shells. The tuff or breccia in this locality is precisely such 
 as is known to result from volcanic ashes falling into water, and sub- 
 siding together with ejected fragments of marl and other stratified 
 rocks. These tuffs and marls are highly inclined, and traversed by 
 a thick vein of basalt, which, as it rises in the hill, divides into two 
 branches. 
 
 Gergovia. The hill of Gergovia, near Clermont, affords a third 
 example. I agree with MM. Dufrenoy and Jobert that there is no 
 alternation here of a contemporaneous sheet of lava with freshwater 
 strata, in the manner supposed by some other observers * ; but the 
 position and contents of some of the associated tuffs, prove them to 
 have been derived from volcanic eruptions which occurred during the 
 deposition of the lacustrine strata. 
 
 The bottom of the hill consists of slightly inclined beds of white 
 and greenish marls, more than 300 feet in thickness, intersected by a 
 dike of basalt, which may be studied in the ravine above the village 
 of Merdogne. The dike here cuts through the marly strata at a con- 
 siderable angle, producing, in general, great alteration and confusion 
 in them for some distance from the point of contact. Above the 
 
 Fig. 678. 
 
 White 
 and green 
 marls. 
 
 Hill of Gergovia. 
 
 white and green marls, a series of beds of limestone and marl, con- 
 taining freshwater shells, are seen to alternate with volcanic tuff. 
 In the lowest part of this division, beds of pure marl alternate with 
 compact fissile tuff, resembling some of the subaqueous tuffs of Italy 
 and Sicily called peperinos. Occasionally fragments of scoriae are 
 visible in this rock. Still higher is seen another group of some 
 thickness, consisting exclusively of tuff, upon which lie other marly 
 strata intermixed with volcanic matter. Among the species of fossil 
 shells which I found in these strata were Melania inquinata, a Unio, 
 
 * See Scrope's Central France, p. 7. 
 
560 CRETACEOUS VOLCANIC ROCKS. [Cn. XXXIT. 
 
 and a Melanopsis, but they were not sufficient to enable me to deter- 
 mine with precision the age of the formation. 
 
 There are many points in Auvergne where igneous rocks have 
 been forced by subsequent injection through clays and marly lime- 
 stones, in such a manner that the whole has become blended in one 
 confused and brecciated mass, between which and the basalt there is 
 sometimes no very distinct line of demarcation. In the cavities of 
 such mixed rocks we often find calcedony, and crystals of mesotype, 
 stilbite, and arragonite. To formations of this class may belong some 
 of the breccias immediately adjoining the dike in the hill of Ger- 
 govia ; but it cannot be contended that the volcanic sand and scoriae 
 interstratified with the marls and limestones in the upper part of that 
 hill were introduced, like the dike, subsequently, by intrusion from 
 below. They must have been thrown down like sediment from water, 
 and can only have resulted from igneous action, which was going 
 on contemporaneously with the deposition of the lacustrine strata. 
 
 The reader will bear in mind that this conclusion agrees well with 
 the proofs, adverted to in the fifteenth chapter, of the abundance of 
 silex, travertin, and gypsum precipitated when the upper lacustrine 
 strata were formed ; for these rocks are such as the waters of mineral 
 and thermal springs might generate. 
 
 Cretaceous period. Although we have no proof of volcanic rocks 
 erupted in England during the deposition of the chalk and greensand, 
 it would be an error to suppose that no theatres of igneous action 
 existed in the cretaceous period. M. Virlet, in his account of the 
 geology of the Morea, p. 205., has clearly shown that certain traps 
 in Greece, called by him ophiolites, are of this date ; as those, for 
 example, which alternate conformably with cretaceous limestone and 
 greensand between Kastri and Damala in the Morea. They consist 
 in great part of diallage rocks and serpentine, and of an amygdaloid 
 with calcareous kernels, and a base of serpentine. 
 
 In certain parts of the Morea, the age of these volcanic rocks is 
 established by the following proofs : first, the lithographic limestones 
 of the Cretaceous era are cut through by trap, and then a conglo- 
 merate occurs, at Nauplia and other places, containing in its calcareous 
 cement many well-known fossils of the chalk and greensand, together 
 with pebbles formed of rolled pieces of the same ophiolite, which 
 appear in the dikes above alluded to. . 
 
 Period of Oolite and Lias. Although the green and serpentinous 
 trap rocks of the Morea belong chiefly to the Cretaceous era, as before 
 mentioned, yet it seems that some eruptions of similar rocks began 
 during the Oolitic period * ; and it is probable, that a large part of 
 the trappean masses, called ophiolites in the Apennines, and associated 
 with the limestone of that chain, are of corresponding age. 
 
 That some part of the volcanic rocks of the Hebrides, in our own 
 country, originated contemporaneously with the Oolite which they 
 traverse and overlie, has been ascertained by Prof. E. Forbes, in 
 
 * Boblaye and Virlet, Morea, p. 23. 
 
CH. XXXII.] CARBONIFEROUS VOLCANIC ROCKS. 561 
 
 1850. Some of the eruptions in Skye, for example, occurred at the 
 close of the Middle and before the commencement of the Upper 
 Oolitic Period.* 
 
 Trap of the New Red Sandstone period. In the southern part of 
 Devonshire, trappean rocks are associated with New Red Sandstone, 
 and, according to Sir H. de la Beche, have not been intruded subse- 
 quently 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 conglo- 
 merates occurring near Tiverton are many angular fragments of trap 
 porphyry, some of them one or two tons in weight, intermingled with 
 pebbles of other rocks. These angular fragments were probably 
 thrown out from volcanic vents, and fell upon sedimentary matter 
 then in the course of deposition.^ 
 
 Carboniferous period. Two classes of contemporaneous trap 
 rocks have been ascertained by Dr. Fleming to 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 appear to have been 
 erupted while the sedimentary strata were in a horizontal position, 
 and to have suffered the same dislocations 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 amygdaloidal. They are regularly interstratified with the 
 sandstone, shale, and ironstone 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. An- 
 drews, where they consist in great part of stratified tuffs, which are 
 curved, vertical, and contorted, like the associated coal-measures. In 
 the tuff I found fragments of carboniferous shale and limestone, and 
 intersecting veins of greenstone. At one spot, about two miles from 
 St. Andrews, the encroachment of the sea on the cliffs has isolated 
 several masses of trap, one of which (fig. 679.) is aptly called the 
 " rock and spindle," J for it consists of a pinnacle of tuff, which may 
 be compared to a distaff, and near the base is a mass of columnar 
 greenstone, in which the pillars radiate from a centre, and appear at 
 a distance like the spokes of a wheel. The largest diameter of this 
 wheel is about twelve feet, and the polygonal terminations of the 
 
 * Geol. Quart. Journ. 1851, vol. \ "The rock," as English readers of 
 
 Yii. p. 108. Burns's poems may remember, is a 
 
 f De la Beche, Geol. Proceedings, Scotch term for a distaff, 
 vol. ii. p. 198. 
 
 00 
 
562 
 
 CARBONIFEROUS VOLCANIC ROCKS. [Cn. XXXII. 
 
 Fig. 679. 
 
 Bock and Spindle, St. Andrews, as seen in 1838. 
 a. Unstratified tuff. Columnar greenstone. c. Stratifu 
 
 columns are seen round the circumference (or tire, 
 as it were, of the wheel), as in the accompany- 
 ing figure. I conceive this mass to be the ex- 
 tremity of a string or vein of greenstone, which 
 penetrated the tuff. The prisms point in every 
 direction, because they were surrounded on all 
 sides by cooling surfaces, to which they always 
 columns of Green- arrano: e themselves at right angles, as before ex- 
 stone, seen endwise at ' 
 
 b, fig. 679. plained (p. 488.). . 
 
 A trap dike was pointed out to me by Dr. Fleming, in the pans] 
 
CH. XXXII.] SILURIAN VOLCANIC ROCKS. 563 
 
 of Flisk, in the northern part of Fifeshire, which cuts through the 
 grey sandstone and shale forming the lowest part of the Old Red 
 Sandstone. It may be traced for many miles, passing through the 
 amygdaloidal and other traps of the hill called Norman's Law. In 
 its course it affords a good exemplification of the passage from the 
 trappean into the plutonic, or highly crystalline texture. Professor 
 Gustavus Rose, to whom I submitted specimens of this dike, finds 
 the rock, which he calls dolerite, to consist of greenish black augite 
 and Labrador felspar, the latter being the most abundant ingredient. 
 A small quantity of magnetic iron, perhaps titaniferous, is also 
 present. 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. 
 
 Trap of the Old Red sandstone period. By referring to the 
 section explanatory of the structure of Forfarshire, already given 
 (p. 48.), the reader will perceive that beds of conglomerate, 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, sometimes exclusively of different 
 varieties of trap, which, although purposely omitted in the section 
 referred to, are often found either intruding themselves in amor- 
 phous 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 felspathic porphyry 
 and amygdaloid, the kernels of the latter being sometimes calca- 
 reous, often calcedonic, and forming beautiful agates. We meet 
 also with claystone, clinkstone, greenstone, compact felspar, and 
 tuff. Some of these rocks flowed as lavas over the bottom of the 
 sea, and enveloped quartz pebbles 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 (see section, p. 48.), 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. 
 
 Silurian period. It appears from the investigations of Sir R. 
 Murchison 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 tufaceous 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 
 
 oo 2 
 
564 CAMBRIAN VOLCANIC ROCKS. [Cn. XXXII. 
 
 Silurian fossils, such as casts of encrinites, trilobites, and mollusca. 
 Although fossiliferous, the stone resembles a sandy claystone of the 
 trap family.* 
 
 Thin layers of trap, only a few inches thick, alternate, in some 
 parts of Shropshire and Montgomeryshire, with a sedimentary strata 
 of the lower Silurian system. This trap consists of slaty porphyry 
 and granular felspar rock, the beds being traversed by joints like 
 those in the associated sandstone, limestone, and shale, and having 
 the same strike and dip. j 
 
 In Radnorshire there is an example of twelve bands of stratified 
 trap, alternating with Silurian schists and flagstones, in a thickness 
 of 350 feet. The bedded traps consist of felspar-porphyry, clink- 
 stone, and other varieties ; and the interposed Llandeilo flags are of 
 sandstone and shale, with trilobites and graptolites.J 
 
 Cambrian Volcanic Rocks. In a former chapter (Ch. XXVII. 
 p. 451.), we have seen that below the Llandeilo and Bala beds of 
 Lower Silurian date there occur, in North Wales, a series of rocks 
 of vast thickness, which may be called Cambrian. The upper 
 subdivision, named by Professor Sedgwick the " Festiniog group," 
 comprises, first, the Arenig Slates, 7000 feet thick in North Wales, 
 in the midst of which dense masses of porphyry, trap -conglomerate, 
 and other igneous rocks, which are supposed by Professor Sedgwick 
 to be of contemporaneous origin, are intercalated ; secondly, the 
 Lingula flags underlying the former, and of which the fossils were 
 treated of at p. 452. ; thirdly, still lower, the Bangor group or 
 Lower Cambrian, in which bands of felspathic porphyry occur. 
 These last are, in the opinion of Professor Ramsay, intrusive and 
 not of the same date as the associated sedimentary deposits. 
 
 Professor Sedgwick has also described, in his account of the 
 geology of Cumberland, various trap rocks which accompany green 
 slates, agreeing in mineral character and aspect with the Arenig 
 Slates, which underlie all the fossiliferous strata of Cumberland, and 
 consist of felspathic and porphyritic rocks and greenstones, oc- 
 curring not only in dikes, but in conformable beds. Occasionally 
 there is a passage from these igneous rocks to some of the green 
 quartzose slates. These porphyries are supposed to have been pro- 
 duced contemporaneously with the stratified chloritic slates by sub- 
 marine eruptions oftentimes repeated, the materials of the slates 
 having been supplied, in part at least, from the same source. 
 
 * Murchison, Silurian System, &c. J Ibid., p. 325. 
 
 p. 230. Geol. Trans., 2d series, vol. IT. 
 
 f Ibid., p. 272. P. 55. 
 
CH.XXXITI.] PLUTONIC ROCKS. 565 
 
 CHAPTER XXXni. 
 
 PLUTONIC BOCKS GRANITE. 
 
 General aspect of granite Decomposing into spherical masses Rude columnar 
 structure Analogy and difference of volcanic and plutonic formations Minerals 
 in granite, and their arrangement Graphic and porphyritic granite Mutual 
 penetration of crystals of quartz and felspar Occasional minerals Syenite 
 Syenitic, talcose, and schorly granites Eurite Passage of granite into trap 
 Examples near Christiania and in Aberdeenshire Analogy in composition of 
 trachyte and granite Granite veins in Glen Tilt, Cornwall, the Valorsine, and 
 other countries Different composition of veins from main body of granite 
 Metalliferous veins in strata near their junction with granite Apparent isolation 
 of nodules of granite Quartz veins Whether plutonic rocks are ever over- 
 lying Their exposure 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 considered. I have 
 described, in the first chapter, these plutonic rocks as the unstra- 
 tified division of the crystalline or hypogene formations, and have 
 stated that 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 
 entangled gases gives rise in ordinary lava. 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 downwards from the 
 crater of every active volcano to a great depth below, perhaps 
 several miles or leagues, and the effects which are produced deep in 
 the bowels of the earth may, or rather must, be distinct; so that 
 volcanic and plutonic rocks, each different in texture, and sometimes 
 even in composition, may originate simultaneously, the one at the 
 surface, the other far beneath it. 
 
 By some writers, all the rocks now under consideration have been 
 comprehended under the name of granite, which is, then, understood 
 to embrace a large family of crystalline and compound rocks, usually 
 
 003 
 
566 GENERAL ASPECT OF GBANITE. [Cn. XXXIII. 
 
 found underlying all other formations ; whereas we have seen that 
 trap very commonly overlies strata of different ages. 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, 
 
 Fig. 681. 
 
 Mass of granite near the Sharp Tor, Cornwall. 
 
 and sometimes like heaps of boulders, for which they have been 
 mistaken. The exterior of these stones, originally quadrangular, 
 acquires a rounded form by the action of air and water, for the 
 edges and angles waste away more rapidly than the sides. A 
 similar spherical structure has already been described as charac- 
 teristic of basalt and other volcanic formations, and it must be re- 
 ferred to analogous causes, as yet but imperfectly understood. 
 
 Although 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, Ex- 
 amples of these appearances may be seen near the Land's End, in 
 Cornwall. (See fig. 682.) 
 
 The plutonic formations also agree with the volcanic in having 
 veins or ramifications proceeding from central masses into the ad- 
 joining rocks, and causing alterations in these last, which will be 
 presently described. They also resemble trap in containing no 
 organic remains ; but they differ in being more uniform in texture, 
 whole mountain masses of indefinite extent appearing to have ori- 
 ginated under conditions precisely similar. They also differ in 
 never being scoriaceous or amygdaloidal, and never forming a 
 porphyry with an uncrystalline base, or alternating with tuffs. Nor 
 do they form conglomerates, although there is sometimes an in- 
 sensible passage from a fine to a coarse-grained granite, and occa- 
 sionally patches of a fine texture are imbedded in a coarser variety. 
 
 Felspar, quartz, and mica are usually considered as the minerals 
 essential to granite, the felspar being most abundant in quantity, and 
 the proportion of quartz exceeding that of mica. These minerals 
 are united in what is termed a confused crystallization ; that is to 
 say, there is no regular arrangement of the crystals in granite, as in 
 gneiss (see fig. 704. p. 595.), except in the variety termed graphic 
 granite, which occurs mostly in granitic veins. This variety is a 
 
CH. XXXIII.] MINERAL COMPOSITION OF GRANITE. 567 
 
 Fig. 682. 
 
 Granite having a cuboidal and rude columnar structure, Land's End, Cornwall. 
 
 compound of felspar and quartz, so arranged as to produce an 
 imperfect laminar structure. The crystals of felspar appear to have 
 been first formed, leaving between them the space now occupied by 
 the darker-coloured quartz. This mineral, when a section is made 
 
 Fig. 683. Fig. 684. 
 
 Graphic granite. 
 
 Fig. 683. Section parallel to the lamina?. 
 Fig. 684. Section transverse to the laminae. 
 
 at right angles to the alternate plates of felspar and quartz, presents 
 broken lines, which have been compared to Hebrew characters. 
 The variety of granite called by the French Pegmatite, which is a 
 mixture of quartz and common felspar, usually with some small 
 admixture of white silvery mica, often passes into graphic granite. 
 
 As a general rule, quartz, in a compact or amorphous state, forms 
 a vitreous mass, serving as the base in which felspar 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 paradoxical, has given rise to much in- 
 genious speculation. We should naturally have anticipated that. 
 
 oo4 
 
568 PORPHYRITIC GRANITE. [Cn. XXXIII. 
 
 during the cooling of the mass, the flinty portion would be the first 
 to consolidate ; and that the different varieties of felspar, 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 fusible minerals being found enveloped 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 phe- 
 nomenon have been proposed by MM. de Beaumont, Fournet, and 
 Durocher. They refer to M. Guadin'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 acquired a low tem- 
 perature ; and M. E. de Beaumont suggests that electric action may 
 prolong the duration of the viscosity of silex. Occasionally, how- 
 ever, we find the quartz and felspar mutually imprinting their forms 
 on each other, affording evidence of the simultaneous crystallization 
 of both.* 
 
 It may here be remarked that ordinary granite, as well as syenite 
 and eurite, usually contains two kinds of felspar, 1st, the common, or 
 orthoclase, in which potash is the prevailing alkali, and this generally 
 occurs in large crystals of a white or flesh colour ; and 2ndly, felspar 
 in smaller crystals, in which soda predominates, usually of a dead 
 white or spotted, and striated lake albite, but not the same in com- 
 position. | 
 
 Porphyritic granite. This name has been sometimes given to 
 that variety in which large crystals of common felspar, sometimes 
 more than 3 inches in length, are scattered through an ordinary base 
 of granite. An example of this texture may be seen in the granite 
 
 Fig. 685. 
 
 Porphyritic granite. Land's End, Cornwall. 
 
 of the Land's End, in Cornwall (fig. 685.). The two larger prismatic 
 crystals in this drawing represent felspar, smaller crystals of which 
 
 * Bulletin, 2d serie, iv. 1304. ; and f Delesse, Ann. des Mines, 1852, 
 Archiac, Hist, des Progres de Geol., i. t. iii. p. 409., and 1848. t. xiii. p. 675. 
 33. 
 
CH. XXXIII.] SYENITIC, TALCOSE, AND SCHORL GRANITES. 569 
 
 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 remainder of the mass 
 is quartz, the translucency of which is strongly contrasted to the 
 opaqueness of the white felspar and black mica. But neither the 
 transparency of the quartz nor the silvery lustre of the mica can be 
 expressed in the engraving. 
 
 The uniform mineral character of large masses of granite seems 
 to indicate that large quantities of the component elements were 
 thoroughly mixed up together, and then crystallized under precisely 
 similar conditions. There are, however, many accidental, or " occa- 
 sional," 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 dis- 
 persed to modify the general aspect of the rock. They show, never- 
 theless, that the ingredients were not everywhere exactly the same ; 
 and a still greater variation may be traced in the ever-varying pro- 
 portions of the felspar, quartz, and mica. 
 
 Syenite. When hornblende is the substitute for mica, which is 
 very commonly the case, the rock becomes Syenite : so called from 
 the celebrated ancient quarries of Syene in Egypt. It has all the 
 appearance of ordinary granite, except when mineralogically ex- 
 amined in hand specimens, and is fully entitled to rank as a geo- 
 logical member of the same plutonic family as granite. Syenite, 
 however, after maintaining the granitic character throughout ex- 
 tensive regions, is not uncommonly found to lose its quartz, and 
 to pass insensibly into syenitic greenstone, a rock of the trap family. 
 Werner considered syenite as a binary compound of felspar and 
 hornblende, and regarded quartz as merely one of its occasional 
 minerals. 
 
 Syenitic granite. The quadruple compound of quartz, felspar, 
 mica, and hornblende, may be so termed. This rock occurs in Scot- 
 land and in Guernsey. 
 
 Talcose granite, or Protogine of the French, is a mixture of fel- 
 spar, quartz, and talc. It abounds in the Alps, and in some parts of 
 Cornwall, producing by its decomposition the china clay, more than 
 12,000 tons of which are annually exported from that country for 
 the potteries.* 
 
 Schorl rock, and schorly granite. The former of these is an 
 aggregate of schorl, or tourmaline, and quartz. When felspar and 
 mica are also present, it may be called schorly granite. This kind of 
 granite is comparatively rare. 
 
 Eurite. A rock in which all the ingredients of granite are blended 
 into a finely granular mass. When crystalline, it is seen to contain 
 crystals of quartz, mica, common felspar, and soda felspar. When 
 there is no mica, and when common felspar predominates, so 
 as to give it a white colour, it becomes a felspathic granite, called 
 
 * Boase on Primary Geology, p. 16. 
 
570 PASSAGE OF GRANITE INTO TEAP. [Cn. XXXIII. 
 
 " whitestone " (Weisstein) by Werner, or Leptynite by the French, 
 in which microscopic crystals of garnet are often present. 
 
 All these and other varieties of granite pass into certain kinds of 
 trap, a circumstance which affords one of many arguments in 
 favour of what is now the prevailing opinion, that the granites are 
 also of igneous origin. The contrast of the most crystalline form of 
 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 porphyry may be more and more 
 crystalline, until the mass passes to the kind of granite most nearly 
 allied in mineral composition. 
 
 The minerals which constitute alike the granitic and volcanic 
 rocks consist, almost exclusively, of seven elements, namely, silica, 
 alumina, magnesia, lime, soda, potash, and iron (see Table, p. 479.) ; 
 and these may sometimes exist in about the same proportions in a 
 porous lava, a compact trap, or a crystalline granite. It may perhaps 
 be found, on farther examination for on this subject we have yet 
 much to learn that the presence of these elements in certain pro- 
 portions is more favourable than in others to their assuming a 
 crystalline or true granitic structure ; but it is also ascertained by 
 experiment, that the same materials may, under different circum- 
 stances, form very different rocks. 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 ; and some trachytes and 
 syenitic-greenstones may doubtless form granite and syenite, if the 
 crystallization take place slowly. 
 
 It has also been suggested that the peculiar nature and structure 
 of granite may be due to its retaining in it that water which is seen 
 to escape from lavas when they cool slowly, and consolidate in the 
 atmosphere. Boutigny's experiments have shown that melted matter, 
 at a white heat, requires to have its temperature lowered before it 
 can vapourize water ; and such discoveries, if they fail to explain the 
 manner in which granites have been formed, serve at least to remind 
 us of the entire distinctness of the conditions under which plutonic 
 and volcanic rocks must be produced.* 
 
 It would be easy to multiply examples and authorities to prove 
 the gradation of the granitic 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 syenitic-greenstone, resting 
 on fossiliferous strata. To this, on its southern limit, succeeds a 
 region equally extensive of syenite, the passage from the volcanic to 
 the plutonic rock being so gradual that it is impossible to draw a 
 line of demarcation between them. 
 
 " The ordinary granite of Aberdeenshire," says Dr. MacCulloch, 
 " is the usual ternary compound of quartz, felspar, and mica; but 
 sometimes hornblende is substituted for the mica. But in many 
 places a variety occurs which is composed simply of felspar and 
 
 * E. de Beaumont, Bulletin, vol. iv., 2d ser., pp. 1318. and 1320. 
 
CH. XXXIII.] ROCKS ALTERED BY GRANITE VEINS. 
 
 571 
 
 hornblende ; and in examining more minutely this duplicate com- 
 pound, it is observed in some places to assume a fine grain, and at 
 length to become 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 claystone, with a schistose tendency 
 on exposure, in no respect differing from those of the trap islands of 
 the western coast." The same author mentions, that in Shetland 
 a granite composed of hornblende, mica, felspar, and quartz graduates 
 in an equally perfect manner into basalt.* 
 
 In Hungary there are varieties of trachyte, which, geologically 
 speaking, are of modern origin, in which crystals, not only of mica, 
 but of quartz, are common, together with felspar and hornblende. 
 It is easy to conceive how such volcanic masses may, at a certain 
 depth from the surface, pass downwards into granite. 
 
 I have already hinted at the close analogy in the forms of certain 
 granitic and trappean veins ; and it will be found that strata pene- 
 trated 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 
 have appeared as in fig. 686. ; but the union is as represented in 
 
 Fig. 686. 
 
 Fig. 687. 
 
 Junction of granite and argillaceous schist in Glen 
 tilt. (Mac Culloch.)t 
 
 fig. 687., the undulating outline of the granite intersecting different 
 strata, and occasionally 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 character 
 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 feebly with acids. 
 
 The annexed diagram (fig. 688.) represents another junction, in 
 the same district, where the granite sends forth so many veins as to 
 reticulate the limestone and schist, the veins diminishing towards 
 
 * Syst. of Geol. vol. i. p. 157. and 
 158. 
 
 t Geol. Trans., 1st series, vol. iii. 
 pi. 21. 
 
572 
 
 ROCKS ALTERED BY GRANITE VEINS. [Cn. XXXIII. 
 Fig. 688. 
 
 Junction of granite and limestone in Glen Tilt. (MacCulloch.) 
 
 a. Granite. b. Limestone. 
 
 c. Blue argillaceous schist. 
 
 their termination to the thickness of a leaf of paper or a thread. In 
 sonie places fragments of granite appear entangled, as it were, in the 
 limestone, and are not visibly connected with any larger mass ; 
 while sometimes, on the other hand, a lump of the limestone is found 
 in the midst of the granite. The ordinary colour of the limestone of 
 Glen Tilt is lead blue, and its texture large-grained and highly 
 crystalline ; but where it approximates to the granite, particularly 
 where it is penetrated by the smaller veins, the crystalline texture 
 disappears, and it assumes an appearance exactly resembling that of 
 hornstone. The associated argillaceous schist often passes into 
 hornblende slate, where it approaches very near to the granite.* 
 
 The conversion of the limestone in these and many other in- 
 stances into a siliceous rock, effervescing slowly with acids, would 
 be difficult of explanation, were it not ascertained that such lime- 
 stones are always impure, containing grains of quartz, mica, or 
 felspar disseminated through them. The elements of these minerals, 
 when the rock has been subjected to great heat, may have been 
 fused, and so spread more uniformly through the whole mass. 
 
 In the plutonic, as in the volcanic rocks, there is every gradation 
 from a tortuous vein to the most regular form of 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 
 
 * MacCulloch. Geol. Trans., vol. iii. p. 259. 
 
CH. XXXIII.] STRUCTURE OF GRANITE VEINS. 573 
 
 Mount Battock, one of the Grampians, the opposite walls sometimes 
 preserving an exact parallelism for a considerable 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 
 present similar shapes at the most northern point of Scotland, and 
 the southernmost extremity of Africa, as the annexed drawings will 
 show. 
 
 Fig, 
 
 // IV . M > 
 
 Granite veins traversing clay slate, Table 
 Mountain, Cape of Good Hope.* 
 
 Granite veins traversing gneiss, Cape Wrath. 
 (Mac Culloch.) f 
 
 It is not uncommon for one set of granite veins to intersect 
 another ; and sometimes there are three sets, as in the environs of 
 Heidelberg, where the granite on the banks of the river Necker is 
 seen to consist of three varieties, differing in colour, grain, and 
 various peculiarities of mineral composition. One of these, which is 
 evidently the second in age, is seen to cut through an older granite ; 
 and another, still newer, traverses both the second and the first. 
 
 In Shetland there are two kinds of granite. One of them, com- 
 posed of hornblende, mica, felspar, and quartz, is of a dark colour, 
 and is seen underlying gneiss. The other is a red granite, which 
 penetrates the dark variety everywhere in veins.J 
 
 The accompanying sketches will explain the manner in which 
 granite veins often ramify and cut each other (figs. 690. and 691.). 
 They represent the manner in which the gneiss at Cape Wrath, in 
 Sutherlandshire, is intersected by veins. Their light colour, strongly 
 contrasted with that of the hornblende-schist, here associated with 
 the gneiss, renders them very conspicuous. 
 
 Granite very generally assumes a finer grain, and undergoes a 
 change in mineral composition, in the veins which it sends into 
 contiguous rocks. Thus, according to Professor Sedgwick, the 
 main body of the Cornish granite is an aggregate of mica, quartz, 
 and felspar; but the veins are sometimes without mica, being a 
 granular aggregate of quartz and felspar. In other varieties quartz 
 
 * Capt. B. Hall, Trans. Eoy. Soc. 
 Edin., vol. vii. 
 
 f Western Islands, pi. 31. 
 
 J MacCulloch, Syst. of Geol., vol. i 
 p. 5$. 
 
574 
 
 MINERAL STRUCTURE OF 
 
 Fig. 691. 
 
 [Cn. XXXIII. 
 
 Granite veins traversing gneiss at Cape Wrath, in Scotland. (MacCulloch.) 
 
 prevails to the almost entire exclusion both of felspar and mica ; in 
 others, the mica and quartz both disappear, and the vein is simply 
 composed of white granular felspar.* 
 
 Fig. 692. is a sketch of a group of granite veins in Cornwall, 
 given by Messrs. Von Oeynhausen and Von Dechen.f The main 
 
 Fig. G92. 
 
 Granite veins passing through hornblende slate, Carnsilver Cove, Cornwall. 
 
 body of the granite here is of a porphyritic appearance, with large 
 crystals of felspar ; 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. 
 
 In the Valorsine, a valley not far from Mont Blanc in Swit- 
 zerland, an ordinary granite, consisting of felspar, quartz, and mica, 
 sends forth veins into - a talcose gneiss (or stratified protogine), and 
 in some places lateral ramifications are thrown off from the principal 
 veins at right angles (see fig. 693.), the veins, especially the minute 
 ones, being finer grained than the granite in mass. 
 
 It is here remarked, that the schist and granite, as they approach, 
 seem to exercise a reciprocal influence on each other, for both 
 
 * On Geol. of Cornwall, Camb. Trans. 
 vol.i. p. 124. 
 
 f Phil. Mag. and Annals, No. 2! 
 new series, March, 1829. 
 
CH. XXXIII.] 
 
 GRANITE IN VEINS. 
 
 Fig. 693. 
 
 575 
 
 Veins of granite in talcose gneiss. (L. A. Necker.) 
 
 undergo a modification of mineral character. The granite, still 
 remaining unstratified, becomes charged with green particles ; and 
 the talcose gneiss assumes a granitiform structure without losing its 
 stratification.* 
 
 Professor Keilhau drew my attention to several localities in the 
 country near Christiania, where the mineral character of gneiss 
 appears to have been affected by a granite of much newer origin, 
 for some distance from the point of contact. The gneiss, without 
 losing its laminated structure, seems to have become charged with a 
 larger quantity of felspar, and that of a redder colour, than the 
 felspar usually belonging to the gneiss of Norway. 
 
 Granite, syenite, and those porphyries which have a granitiform 
 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 metalliferous 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 
 contact of another rock, in a different state of temperature, or some- 
 times the existence of rents in other rocks in the vicinity, may have 
 caused the sublimation of the metals.f 
 
 There are many instances, as at Markerud, near Christiania, in 
 Norway, where the strike of the beds has not been deranged 
 throughout a large area by the intrusion of granite, both in large 
 masses and in veins. This fact is considered by some geologists to 
 militate against the theory of the forcible injection of granite in a 
 fluid state. But it may be stated in reply, that ramifying dikes of 
 trap also, which almost all now admit to have been once fluid, pass 
 through the same fossiliferous strata, near Christiania, without 
 deranging their strike or dip. J 
 
 The real or apparent isolation of large or small masses of granite 
 detached from the main body, as at a, b, fig. 694., and above, fig. 
 688., and a, fig. 693., has been thought by some writers to be irre- 
 
 * Necker, sur la Val. de Valorsine, f Necker, Proceedings of Geol. Soc. 
 
 Mem. de la Soc. de Phys. de Geneve, No. 26. p. 392. 
 1828. I visited, in 1832, the spot re- J See Keilhau's 
 
 ferred to in fig. 693. Christiania, 1838. 
 
576 
 
 QUARTZ VEINS. 
 
 Fig. 694. 
 
 [Cn. XXXIII. 
 
 General view of junction of granite and schist of the Valorsine. 
 (L. A. Necker.) 
 
 concilable with the doctrine usually taught respecting veins ; but 
 many of them may, in fact, be sections of root-shaped prolongations 
 of granite ; while, in other cases, they may in reality be detached 
 portions of rock having the plutonic structure. For there may 
 have been spots in the midst of the invaded strata, in which there 
 was an assemblage of materials more fusible than the rest, or more 
 fitted to combine readily into some form of granite. 
 
 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 composition. They appear 
 to have been cracks, into which siliceous matter was infiltered. 
 Such segregation, as it is called, can sometimes be shown to have 
 clearly taken place long subsequently to the original consolidation 
 of the containing rock. Thus, for example, I observed in the 
 gneiss of Tronstad Strand, near Drammen, in Norway, the annexed 
 section on the beach. It appears that the alternating strata of 
 whitish granitiform gneiss and black hornblende-schist were 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 in some 
 parts incrusted with trans- 
 parent crystals of quartz, the 
 middle of the vein being filled 
 up with common opaque white 
 quartz. 
 
 We have seen that the vol- 
 canic formations have been 
 called overlying, because they not only penetrate others but spread 
 over them. Mr. 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 Norway, was 
 intercalated in mountain masses between the primary or paleozoic 
 strata of that country, so as to overlie fossiliferous shale and lime- 
 
 Fig. 695. 
 
 Gneiss. 
 
 Gneis 
 
 a, b. Quartz vein passing through gneiss and green 
 stone, Tronstad Strand, near Christiania. 
 
CH. XXXIII.] CONFORMABLE PORPHYRIES. 
 
 577 
 
 stone. 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 obser- 
 vations 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 interposed conformably between fossiliferous strata, as the por- 
 phyries (a, c, fig. 696.), which divide the bituminous shales and 
 
 Euritic porphyry alternating with primary fossiliferous strata, 
 near Christiania. 
 
 argillaceous limestones, ff. But some of these same porphyries are 
 partially unconformable, as &, and may lead us to suspect that the 
 others also, notwithstanding their appearance of interstratification, 
 have been forcibly injected. Some of the porphyritic rocks above 
 mentioned are highly quartzose, others very felspathic. In pro- 
 portion 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 gradations between volcanic 
 and plutonic rocks, not only in their mineralogical composition and 
 structure, but also in their relations of position to associated form- 
 ations. If the term overlying can in this instance be applied to a 
 plutonic rock, it is only in proportion as that rock begins to acquire 
 a trappean aspect. 
 
 It has been already hinted that the heat, which in every active 
 volcano extends downwards to indefinite depths, must produce 
 simultaneously very different effects near the surface and far below 
 it; and we cannot suppose that rocks resulting from the crystal- 
 lizing of fused matter under a pressure of several thousand feet, 
 much less miles, of the earth's crust can resemble those formed at or 
 near the surface. Hence the production at great depths of a class 
 of rocks analogous to the volcanic, and yet differing in many par- 
 ticulars, might also have been predicted, even had we no plutonic 
 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 volcanic 
 rocks were simply different parts of one great series, we ought to 
 find in mountain chains volcanic dikes passing upwards into lava 
 
 pp 
 
578 GRANITIC ROCKS. [Cn. XXXIII. 
 
 and downwards 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 porous 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 already de- 
 monstrated to have occurred at former periods, will reconcile the 
 student to the belief that crystalline rocks of high antiquity, al- 
 though deep in the earth's crust when originally formed, may have 
 become uncovered and exposed at the surface. Their actual ele- 
 vation 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. But to these and other topics, I 
 shall revert when speaking, in the next chapter, of the relative ages 
 of different masses of granite. 
 
CH. XXXIV.] TESTS OF AGE OF PLUTONIC ROCKS. 579 
 
 CHAPTER XXXIV. 
 
 ON THE DIFFERENT AGES OF THE PLUTONIC ROCKS. 
 
 Difficulty in ascertaining the precise age of a plutonic rock Test of age by relative 
 position Test by intrusion and alteration Test by mineral composition 
 Test by included fragments Recent and Pliocene plutonic rocks, why invisible 
 Tertiary plutonic rocks in the Andes Granite altering Cretaceous rocks 
 Granite 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 On the probable age 
 of the granites of Arran, in Scotland. 
 
 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 difficulty in ascertaining the precise 
 age of such rocks, than in the case of volcanic and fossiliferous form- 
 ations. We must bear in mind, that the evidence of the age of 
 each contemporaneous 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 themselves, or inter- 
 calated between strata containing fossils. But all these tests fail 
 when we endeavour to fix the chronology of a rock which has crys- 
 tallized from a state of fusion in the bowels of the earth. In that 
 case, we are reduced to the following tests : 1st, relative position ; 
 2dly, intrusion, and alteration of the rocks in contact ; 3dly, mineral 
 characters ; 4thly, included fragments. 
 
 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 Newer Pliocene deposits rest 
 on granite ; in Auvergne, where the freshwater Eocene 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 
 crystalline rock was solid before the sedimentary beds were super- 
 imposed, and the latter usually contain in them rounded pebbles of 
 the subjacent granite. 
 
 Test by intrusion and alteration. But when plutonic rocks send 
 veins into strata, and alter them near the point of contact, in the 
 manner before described (p. 571.), 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 
 
 PP 2 
 
580 RECENT AND PLIOCENE [Cn. XXXIV. 
 
 Test by mineral composition. Notwithstanding a general uni- 
 formity in the aspect of plutonic rocks, we have seen in the last chap- 
 ter that there are many varieties, such as Syenite, Talcose granite, 
 and others. One of these varieties is sometimes found exclusively 
 prevailing throughout an extensive region, where it preserves a 
 homogeneous character ; so that, having ascertained its relative age 
 in one place, we can easily recognize its identity in others, and thus 
 determine from a single section the chronological relations of large 
 mountain 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 the same era. 
 
 Some have imagined that the age of different granites might, to a 
 great extent, be determined by their mineral characters alone ; syenite, 
 for instance, or granite with hornblende, being more modern than 
 common or micaceous granite. But modern investigations have proved 
 these generalizations to have been premature. The syenitic granite 
 of Norway already alluded to may be of the same age as the Silurian 
 strata, which it traverses and alters, or may belong to the Old Red 
 sandstone period ; whereas the granite of Dartmoor, although con- 
 sisting of mica, quartz, and felspar, is newer than the coal. (See 
 p. 586.). 
 
 Test by included fragments. This criterion can rarely be of much 
 importance, because the fragments involved in granite are usually so 
 much altered, that they cannot be referred 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, contains 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 certain 
 superficial slaty and trappean formations. 
 
 Recent and Pliocene plutonic rocks, ivhy invisible. The explana- 
 tions already given in the 29th and in the last chapter of the probable 
 relation of the plutonic to the volcanic formations, 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 simultaneously, or soon afterwards. It is not uncom- 
 mon for lava-streams to require more than ten years to cool in the 
 open air ; and where they are of great depth, a much longer period. 
 The melted matter poured from Jorullo, in Mexico, in the year 1759, 
 which accumulated in some places to the height of 550 feet, was 
 found to retain a high temperature half a century after the eruption. f 
 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 refrigeration may be ex- 
 tremely gradual. Sometimes, indeed, this process may be retarded 
 
 * Silliman's Journ., No. 69. p. 123. t See "Principles," Index, "Jorullo." 
 
CH. XXXIV.] PLUTONIC ROCKS. 581 
 
 for an indefinite period, by the accession 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 liquefaction. 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*, it will follow, that the quantity of plutonic rock 
 generated, or in progress during the Recent epoch, must already have 
 been considerable. 
 
 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. Between 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 Newer Pliocene granites laid open to view, unless we 
 are prepared to assume that sufficient time has elapsed since the 
 commencement of the Newer Pliocene period for great upheaval and 
 denudation. A plutonic rock, therefore, must, in general, be of con- 
 siderable antiquity relatively to the fossiliferous and volcanic forma- 
 tions, before it becomes extensively visible. As we know that the 
 upheaval of land has been sometimes accompanied in South America 
 by volcanic eruptions and the emission of lava, we may conceive the 
 more ancient plutonic rocks to be forced upwards to the surface by 
 the newer rocks of the same class formed successively below, sub- 
 terposition in the plutonic, like superposition in the sedimentary 
 rocks, being usually characteristic of a newer origin. 
 
 In the accompanying diagram (fig. 697.), an attempt is made to 
 show the inverted order in which sedimentary and plutonic forma- 
 tions may occur in the earth's crust. 
 
 The oldest plutonic rock, No. I., has been upheaved at successive 
 periods until it has become exposed to view in a mountain-chain. 
 This protrusion of No. I. has been caused by the igneous agency 
 which produced the newer plutonic rocks Nos. II. in. and IV. 
 Part of the primary fossiliferous strata, No. 1., 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 contemporaneous date. According to this hypothesis, the con- 
 vulsions of many periods will be required before Recent granite, or 
 granite of the human period, will be upraised so as to form the 
 highest ridges and central axes of mountain-chains. During that 
 
 * " Principles," Index, " Volcanic Eruptions." 
 PP 3 
 
582 
 
 PLUTONIC ROCKS. 
 
 [Cn. XXXIV, 
 
 .2 
 
 2* 
 
 '|.a 
 
 I 
 
 ii 
 
 l! 
 
 ^a 
 II 
 
 il 
 
 51 
 
CH. XXXIV.] PLUTONIC ROCKS IN THE ANDES. 583 
 
 Jme the Recent strata No. 4. might be covered by a great many 
 newer sedimentary formations. 
 
 Eocene granite and plutonic rocks. In a former part of this 
 volume (p. 231.), the great numnmlitic formation of the Alps and 
 Pyrenees was referred to the Eocene period, and it follows that those 
 vast movements which have raised 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 commencement of the tertiary epoch. 
 Here, therefore, if anywhere, we might expect to find hypogene 
 formations of Eocene date breaking out in the central axis or most 
 disturbed region of the loftiest chain in Europe. Accordingly, in 
 the Swiss Alps, even theflysch, or upper portion of the nummulitic 
 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 iheflysch was deposited at the 
 bottom of the sea ; and the question as to its age is not so much 
 whether it be a secondary or tertiary granite or gneiss, as whether it 
 should be assigned to the Eocene or Miocene epoch. 
 
 Great upheaving movements have been experienced in the region 
 of the Andes, during the Post-Pliocene period. In some part, there- 
 fore, of this chain, we may expect to discover tertiary plutonic rocks 
 laid open to view. What we already know of the structure of the 
 Chilian Andes seems to realize this expectation. In a transverse 
 section, examined by Mr. Darwin, between Valparaiso and Mendoza, 
 the Cordillera was found to consist of two separate and parallel 
 chains, formed of sedimentary rocks of different ages, the strata in 
 both resting on plutonic rocks, by which they have been altered. 
 In the western or oldest range, called the Peuquenes, are black cal- 
 careous clay-slates, rising to the height of nearly 14,000 feet above 
 the sea, in which are shells of the genera Gryphcea, Turritella, Te- 
 rebratula, and Ammonite. These rocks are supposed to be of the 
 age of the central parts of the secondary series of Europe. They 
 are penetrated and altered by dikes and mountain masses of a plu- 
 tonic rock, which has the texture of ordinary granite, but rarely 
 contains 'quartz, being a compound of albite and hornblende. 
 
 The second or eastern chain consists chiefly of sandstones and 
 conglomerates, of vast thickness, the materials of which are derived 
 from the ruins of the western chain. The pebbles of the conglome- 
 rates are, for the most part, rounded fragments* of the fossiliferous 
 slates before mentioned. The resemblance of the whole series to 
 certain tertiary deposits on the shores of the Pacific, not only in 
 mineral character, but in the imbedded lignite and silicified woods, 
 leads to the conjecture that they also are tertiary. Yet these strata 
 are not only associated with trap rocks and volcanic tuffs, but are also 
 altered by a granite consisting of quartz, felspar, and talc. They are 
 traversed, moreover, by dikes of the same granite, and by numerous 
 veins of iron, copper, arsenic, silver, and gold ; all of which can be 
 
 PP 4 
 
584 VOLUME OF HIDDEN PLUTONIC ROCKS. [Cn. XXXIV. 
 
 traced to the underlying granite.* We have, therefore, strong 
 ground to presume that the plutonic rock here exposed on a large 
 scale in the Chilian Andes is of later date than certain 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 meta- 
 morphic rocks in the nether regions, and their emergence at the sur- 
 face. 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 usually have been stripped off by de- 
 nudation. 
 
 We know that in the Bay of Baiae in 1538, in Cutch in 1819, 
 and on several occasions in Peru and Chili, since the commencement 
 of the present century, the permanent upheaval or subsidence of land 
 has been accompanied by the simultaneous emission of lava at one or 
 more points in the same volcanic region. From these and other 
 examples it may be inferred that the rising or sinking of the earth's 
 crust, operations 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 liquefaction, 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 
 appreciated, when we remember that throughout half the surface 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 of upheaval. 
 
 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 elsewhere shown f, has, 
 with the exception of a few districts, emerged from the deep to its 
 present altitude ; and even those tracts which were already dry land 
 before the Eocene era have almost everywhere acquired additional 
 height. A large amount of subsidence has also occurred during the 
 same period, so that the extent of the subterranean spaces which have 
 
 * Darwin, pp. 390. 406. ; second edi- f See map of Europe and explana- 
 tion, p. 319. tion, in Principles, book i. 
 
Cn. XXXIV.] PLUTONIC ROCKS OF OOLITE AND LIAS. 585 
 
 either become the receptacles of sunken fragments of the earth's 
 crust, or have been rendered capable of supporting other fragments 
 at a much greater height than before, must be so great that they 
 probably equal, if not exceed in volume, the entire continent of 
 Europe. We are entitled, therefore, to ask what amount of change 
 of equivalent importance can be proved to have occurred in the 
 earth's crust within an equal quantity of time anterior to the Eocene 
 epoch. They who contend for the more intense energy of subter- 
 ranean causes in the remoter eras of the earth's history may find 
 it more difficult to give an answer to this question than they anti- 
 cipated. 
 
 The principal effect of volcanic action in the nether regions during 
 the tertiary period seems to have consisted in the upheaval to the 
 surface of hypogene formations of an age anterior to the carboni- 
 ferous. 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 hypogene 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 vast 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. 
 
 Cretaceous period. It will be shown in the next chapter that 
 chalk, as well as lias, has been altered by granite in the eastern 
 Pyrenees. Whether such granite be cretaceous or tertiary cannot 
 
 easily be decided. Suppose b, c, d, fig. 
 698., to be three members of the Cre- 
 taceous series, the lowest of which, b, 
 has been altered by the granite A, the 
 modifying influence not having ex- 
 tended so far as c, or having but 
 slightly affected its lowest beds. Now 
 it can rarely be possible for the geolo- 
 gist 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 exposed by denudation, at the height of 2000 
 or 3000 feet on the flanks of that chain. 
 
 Period of Oolite and Lias. In the department of the Hautes 
 Alpes, in France, near Vizille, 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 
 
586 
 
 PLUTONIC ROCKS OF THE 
 
 [Cn. XXXIV. 
 
 texture, but is extremely fine-grained. When nearer the junction it 
 becomes grey, and has a saccharoid structure. In another locality, 
 near Champoleon, a granite composed of quartz, black mica, and 
 rose-coloured felspar is observed partly to overlie the secondary 
 rocks, producing an alteration which extends for about 30 feet 
 downwards, diminishing in the beds which lie farthest from the 
 
 granite. (See fig. 699.) In 
 
 Fig 699 . the altered mass the argil- 
 
 laceous beds are hardened, 
 the limestone is saccharoid, 
 the grits quartzose, and in 
 the midst of them is a 
 thin layer of an imperfect 
 granite. It is also an im- 
 portant circumstance 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 pyrites. The stra- 
 tified rocks become harder 
 and more crystalline, but 
 the granite, on the contrary, softer and less perfectly crystallized 
 near the junction.* 
 
 Although the granite is incumbent in the above section (fig. 699.), 
 we cannot assume that it overflowed the strata, for the disturbances 
 of the rocks are so great in this part of the Alps that they seldom 
 retain the position which they must originally have occupied. 
 
 A considerable mass of syenite, in the Isle of Skye, is described by 
 Dr. MacCulloch as intersecting limestone and shale, which are of the 
 age of the lias.f 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 marble. 
 At Predazzo, in the Tyrol, secondary strata, some of which are 
 limestones of the Oolitic period, have been traversed and altered by 
 plutonic rocks, one portion of which is an augitic porphyry, which 
 passes insensibly into granite. The limestone is changed into gra- 
 nular marble, with a band of serpentine at the j unction. 
 
 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 ascertained to be posterior in date to the culm- 
 measures of that county, which from their position, and, as containing 
 
 Junction of granite with Jurassic or Oolite strata in the 
 Alps, near Champoleon. 
 
 * Elie de Beaumont, sur les Mon- 
 tagues de 1'Oisans, &c. Mem. de la 
 Soc. d'Hist. Nat. de Paris, torn. v. 
 
 f Murchison, Geol. Trans. 2d series, 
 vol. ii. part ii. pp. 311321. 
 
 J Western Islands, vol. i. p. 330. 
 plate 18., figs. 3, 4. 
 
 Von Buch, Annales de Chimie, &c. 
 
CH. XXXIV.] CARBONIFEROUS AND SILURIAN PERIODS. 587 
 
 true coal-plants, are regarded by Professor Sedgwick and Sir R. 
 Murchison as members of the true carboniferous series. This granite, 
 like the syenitic granite of Christiania, has broken through the stra- 
 tified formations without much changing their strike. Hence, on the 
 north-west side of Dartmoor, the successive members of the culm- 
 measures abut against the granite, and become metamorphic as they 
 approach. These strata are also penetrated by granite veins, and 
 plutonic dikes, called " elvans." * The granite of Cornwall is pro- 
 bably of the same date, and, therefore, as modern as the Carboniferous 
 strata, if not much newer. 
 
 Silurian period. It has long been known that the granite near 
 Christiania, in Norway, is of newer origin than the Silurian strata of 
 that region. Von Buch first announced, in 1813, the discovery of its 
 posteriority in date to limestones containing orthocerata and trilobites. 
 The proofs consist in the penetration of granite veins into the shale 
 and limestone, and the alteration of the strata, for a considerable dis- 
 tance from the point of contact both of these veins and the central 
 mass from which they emanate. (See p. 5'77.) Von Buch supposed 
 that the plutonic rock alternated with the fossiliferous 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 towards the granite up to the 
 point of contact, appearing as if they would pass under it in mass, as 
 at a, fig. 700., and then again on the opposite side of the same 
 mountain, as at 5, dip away from the same granite. When the 
 j unctions, however, are carefully examined, it is found that the plu- 
 tonic rock intrudes itself in veins, and nowhere covers the fossiliferous 
 strata in large overlying masses, as is so commonly the case with 
 trappean formations, f 
 
 Fig. 700. 
 
 , Silurian. Granite. Silurian strata. 
 
 Now this granite, which is more modern than the Silurian strata of 
 Norway, also sends veins in the same country into an ancient forma 
 tion of gneiss ; and the relations of the plutonic rock and the gneiss, 
 at their junction, are full of interest 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 following 
 facts: The fossiliferous, or Silurian, fteds rest unconformably 
 upon the truncated edges of the gneiss, the inclined strata of which 
 had been denuded before the sedimentary beds were superimposed 
 
 * Proceed. Geol. Soc., vol. ii. p. 562.; works of Keilhau, with whom I ex- 
 and Trans. 2d ser. vol. v. p. 686. amined this country. 
 
 f See the Gaea Norvegica and other 
 
588 OLDEST GRANITE ROCKS. [Cn. XXXIV. 
 
 Fig. 701. 
 
 Silurian strata. 
 
 Gneiss. Granite. Gneiss, 
 
 Granite sending veins into Silurian strata and Gneiss, Christiania, Norway. 
 
 (see fig. 701.). The signs of denudation are twofold; first, the 
 surface of the gneiss is seen occasionally, on the removal of the 
 newer beds, containing organic 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 de- 
 posits. Yet the granite produced after this long interval is often so 
 intimately blended with the ancient gneiss, at the point of junction, 
 that it is impossible to draw any other than an arbitrary line of 
 separation between them ; and where this is not the case, tortuous 
 veins of granite pass freely through gneiss, ending sometimes in 
 threads, as if the older rock had offered no resistance to their passage. 
 It seems necessary, therefore, to conceive that the gneiss was softened 
 and more or less melted when penetrated by the granite. But had 
 such junctions alone been visible, and had we not learnt, from other 
 sections, how long a period elapsed between the consolidation of the 
 gneiss and the injection of this granite, we might have suspected 
 that the gneiss was scarcely solidified, or had not yet assumed its 
 complete metamorphic character when invaded by the plutonic rock. 
 From this example we 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 century since the doctrine was 
 very general that all granitic rocks were primitive, 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. 9.). 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 all 
 the known fossiliferous deposits. Could we discover some Lower 
 Cambrian strata resting immediately on granite, there being no alter- 
 ations at the point of contact, nor any intersecting granitic veins, we 
 might then affirm the plutonic rock to have originated before the 
 oldest known fossiliferous strata. Still it would be presumptuous, 
 as we have already pointed out (p. 456.), to suppose that when a 
 small part only of the globe has been investigated, we are acquainted 
 with the oldest fossiliferous strata in the crust of our planet. Even 
 when these are found, we cannot assume that there never were any 
 antecedent strata containing organic remains, which may have 
 
CH. XXXIV.] AGE OF GRANITES OF ARRAN. 589 
 
 become metamorphic. If we find pebbles of granite in a conglo- 
 merate of the Lower Cambrian system, we may then feel assured that 
 the parent granite was formed before the Lower Cambrian formation. 
 But if the incumbent strata be merely Silurian or Upper Cambrian, 
 the fundamental granite, although of high antiquity, may be posterior 
 in date to known fossiliferous formations. 
 
 Protrusion of solid granite. In part of Sutherlandshire, near 
 Brora, common granite, composed of felspar, quartz, and mica, is in 
 immediate contact with Oolitic strata, and has clearly been elevated 
 to the surface at a period subsequent to the deposition of those strata.* 
 Professor Sedgwick and Sir B. 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 originally in con- 
 tact, 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 disturbed, but in proportion to their proximity the 
 amount of dislocation becomes greater. 
 
 If we admit that solid hypogene rocks, whether stratified or un- 
 stratified, have in such cases been driven upwards so as to pierce 
 through yielding sedimentary deposits, we shall be enabled to account 
 for many geological appearances otherwise inexplicable. Thus, for 
 example, at Weinbohla and Hohnstein, near Meissen, in Saxony, a 
 mass of granite has been observed covering strata of the Cretaceous 
 and Oolitic periods for the space of between 300 and 400 yards 
 square. It appears clearly from a memoir of Dr. B. Cotta on this 
 subject j", that the granite was thrust into its actual position when 
 solid. There are no intersecting veins at the junction, no alteration 
 as if by heat, but evident signs of rubbing, and a breccia in some 
 places, in which pieces of granite are mingled with broken fragments 
 of the secondary rocks. As the granite overhangs both the lias and 
 chalk, so the lias is in some places bent over strata of the cretaceous era. 
 
 Relative age of the granites of Arran. In this island, the largest 
 in the Firth of Clyde, being twenty miles in length from north to 
 south, the four great classes of rocks, the fossiliferous, volcanic, plu- 
 tonic, and metamorphic, are all conspicuously displayed within a 
 very small area, and with their peculiar characters strongly con- 
 trasted. In the north of the island the granite rises to the height 
 of nearly 3000 feet above the sea, terminating in mountainous peaks. 
 (See section, fig. 702.). On the flanks of the same mountains are 
 chloritic-schists, blue roofing-slate, and other rocks of the metamor- 
 phic order (No. 1.), into which the granite (No. 2.) sends veins. 
 This granite, therefore, is newer than the hypogene schists (No. 1.), 
 which it penetrates. 
 
 These schists are highly inclined. Upon them rest beds of con- 
 
 * Murchison, Geol. Trans., 2d series, f Geognostische Wanderungen, Leip- 
 vol. ii. p. 307. zig, 1838. 
 
590 AGE OF THE GRANITES [On. XXXIV. 
 
 glomerate and sandstone (No. 3.), which are referable to the Old 
 Red formation, to which succeed various shales and limestones 
 (No. 4.) containing the fossils of the Carboniferous period, upon 
 which are other strata of sandstone and conglomerate (upper part of 
 No. 4.), in which no fossils have been met with, which it is con- 
 jectured may belong to the New Red sandstone period. All the 
 preceding formations are cut through by the volcanic rocks (No. 5.), 
 which consist of greenstone, basalt, pitchstone, claystone-porphyry, 
 and other varieties. These appear either in the form of dikes, or in 
 dense masses from 50 to 700 feet in thickness, overlying the strata 
 (No. 4.). They sometimes pass into syenite of so crystalline a form, 
 that it may rank as a plutonic formation; and in one region, at 
 Ploverfield, in Glen Cloy, a fine-grained granite (6. a) is seen asso- 
 ciated with the trap formation, and sending veins into the sandstone 
 or into the upper strata of No. 4. This interesting discovery ot 
 granite in the southern region of Arran, at a point where it is sepa- 
 rated from the northern mass of granite by a great thickness of 
 secondary strata and overlying trap, was made by Mr. L. A. Necker 
 of Geneva, during his survey of Arran in 1839. We also learn from 
 later investigations by Prof. A. C. Ramsay, that a similar fine- 
 grained granite (No. 6. b) appears in the interior of the northern 
 granitic district, forming the nucleus of it, and sending veins into 
 the older coarse-grained granite (No. 2.). The trap dikes which 
 penetrate the older granite are cut off, according to Mr. Ramsay, at 
 the junction of the fine grained. 
 
 It is not improbable that the granite (No. 6. b\ may be of the 
 same age as that of Ploverfield (No. 6. #.), and this again may belong 
 to the same geological epoch as the trap formations (No. 5.). If 
 there be any difference of date, it would seem that the fine-grained 
 granite must be newer than the trappean rocks. But, on the other 
 hand, the coarser granite (No. 2.) may be the oldest rock in Arran, 
 with the exception of the hypogene slates (No. L), into which it 
 sends veins. 
 
 An objection may perhaps at first be started to this conclusion, 
 derived from the curious and striking fact, the importance of which 
 was first emphatically pointed out by Dr. MacCulloch, that no 
 pebbles of granite occur in the conglomerates of the red sandstone 
 in Arran, although these conglomerates are several hundred feet in 
 thickness, and lie at the foot of lofty granite mountains, which tower 
 above them. As a general rule, all such aggregates of pebbles and 
 sand are mainly composed of the wreck of pre-existing rocks occur- 
 ring in the immediate vicinity. The total absence therefore of gra- 
 nitic pebbles has justly been a theme of wonder to those geologists 
 who have successively visited Arran, and they have carefully searched 
 there, as I have done myself, to find an exception, but in vain. The 
 rounded masses consist exclusively of quartz, chlorite-schist, and 
 other members of the metamorphic series ; nor in the newer conglo- 
 merates of No. 4. have any granitic fragments been discovered. Are 
 we then entitled to aifirm that the coarse-grained granite (No. 2.), like 
 
CH. XXXIV.] OP THE ISLE OP ARRAN. 
 
 591 
 
592 GRANITES OF ARRAN. [On. XXXIV. 
 
 the fine-grained variety (No. 6. a), is more modern than all the other 
 rocks of the island ? This we cannot assume at present, but we may 
 confidently infer that when the various beds of sandstone and con- 
 glomerate were formed, no granite had reached the surface, or had 
 been exposed to denudation in Arran. It is clear that the crystalline 
 schists were ground into sand and shingle when the strata No. 3. 
 were deposited, and at that time the waves had never acted upon the 
 granite, which now sends its veins into the schist. May we then 
 conclude, that the schists suffered denudation before they were in- 
 vaded by granite ? This opinion, although not inadmissible, is by 
 no means fully borne out by the evidence. For at the time when 
 the Old Red Sandstone originated, the metamorphic strata may have 
 formed islands in the sea, as in fig. 703., over which the breakers 
 
 rolled, or from which torrents and rivers descended, carrying down 
 gravel and sand. The plutonic rock or granite (B) may even then 
 have been previously injected at a certain depth below, and yet may 
 never have been exposed to denudation. 
 
 As to the time and manner of the subsequent protrusion of the 
 coarse-grained granite (No. 2.), this rock may have been thrust up 
 bodily, in a solid form, during that long series of igneous operations 
 which produced the trappean and plutonic formations (Nos. 5., 6. a, 
 and 6. b). 
 
 We have shown that these eruptions, whatever their date, were 
 posterior to the deposition of all the fossiliferous strata of Arran. 
 We can also prove that subsequently both the granitic and trappean 
 rocks underwent great aqueous denudation, which they probably 
 suffered during their emergence from the sea. The fact is demon- 
 strated by the abrupt truncation of numerous dikes, such as those at 
 c, d, e, which are cut off on the surface of the granite and trap. The 
 overlying trap also ceases very abruptly on approaching the boundary 
 of the great hypogene region, and terminates in a steep escarpment 
 facing towards it as at /, fig. 702. When in its original fluid state 
 it could not have come thus suddenly to an end, but must have filled 
 up the hollow now separating it from the hypogene rocks, had such 
 a hollow then existed. This necessity of supposing that both the 
 trap and the conglomerate once extended farther, and that veins such 
 as c, d, fig. 702., were once prolonged farther upwards, prepares us 
 to believe that the whole of the northern granite may at one time 
 have been covered by newer formations, under the pressure of which, 
 before its protrusion, it assumed its highly crystalline texture. 
 
 The theory of the protrusion in a solid form of the northern 
 nucleus of granite is confirmed by the manner in which the hypogene 
 slates (No. 1.) and the beds of conglomerate (No. 3.) dip away from 
 
CH. XXXIV.] THE ISLE OF ARRAN. 593 
 
 it on all sides. In some places indeed the slates are inclined towards 
 the granite, but this exception might have been looked for, because 
 these hypogene strata have undergone disturbances at more than one 
 geological epoch, and may at some points, perhaps, have their original 
 order of position inverted. The high inclination, therefore, and the 
 quaquaversal dip of the beds around the borders of the granitic boss, 
 and the comparative horizontality of the fossiliferous strata in the 
 southern part of the island, are facts which all accord with the hypo- 
 thesis of a great amount of movement at that point where the granite 
 is supposed to have been thrust up bodily, and where we may con- 
 ceive it to have been distended laterally by the repeated injection of 
 fresh supplies of melted materials.* 
 
 * For the geology of Arran consult Keeker's Memoir, read to the Royal 
 
 the works of Drs. Hutton and MacCul- Soc. of Edin. 20th April, 1840, and Mr. 
 
 loch, the Memoirs of Messrs. Von Ramsay's Geol. of Arran, 1841. I ex- 
 
 Dechen and Oeynhausen, that of Pro- amined myself a large part of Arran 
 
 fessor Sedgwick and SirR. Murchison in 1836. 
 (Geol. Trans. 2d series) Mr. L. A. 
 
 Q Q 
 
594 METAMORPHIC ROCKS. [Cn. XXXV. 
 
 CHAPTER XXXV. 
 
 . METAMORPHIC ROCKS. 
 
 General character of metamorphic rocks Gneiss Hornblende-schist Mica- 
 schist Clay-slate Quartzite Chlorite-schist Metamorphic limestone 
 Alphabetical list and explanation of the more abundant rocks of this family 
 Origin of the metamorphic strata Their stratification Fossiliferous strata 
 near intrusive masses of granite converted into rocks identical with different 
 members of the metamorphic series Arguments hence derived as to the 
 nature of plutonic action Time may enable this action to pervade denser 
 masses From what kinds of sedimentary rock each variety of the metamorphic 
 class may be derived Certain objections to the metamorphic theory considered 
 Partial conversion of Eocene slate into gneiss. 
 
 WE have now considered three distinct classes of rocks : first, the 
 aqueous, or fossiliferous ; secondly, the volcanic ; and, thirdly, the 
 plutonic, or granitic ; and we have now, lastly, 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 hypo- 
 gene, or schistose hypogene formations. 
 
 These rocks, when in their most characteristic or normal state, are 
 wholly devoid of organic remains, and contain no distinct fragments 
 of other rocks, whether rounded or angular. They sometimes break 
 out in the central parts of narrow mountain chains, but in other 
 cases extend over areas of vast dimensions, occupying, for example, 
 nearly the whole of Norway and Sweden, where, as in Brazil, they 
 appear alike in the lower and higher grounds. In Great Britain, 
 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. 
 
 However crystalline these rocks may become in certain regions, 
 they never, like granite or trap, send veins into contiguous forma- 
 tions, whether into an older schist or granite or into a set of newer 
 fossiliferous strata. 
 
 Many attempts have been made to trace a general order of suc- 
 cession 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 mica-schist always to 
 overlie gneiss. But although such an order may prevail through- 
 
CH. XXXV.] GNEISS HORNBLENDE-SCHIST. 595 
 
 out limited districts, it is by no means universal. To this subject, 
 however, I shall again revert, in the 37th chapter, when the chro- 
 nological relations of the metamorphic rocks are pointed out. 
 
 The following may be enumerated as the principal members of the 
 metamorphic class: gneiss, mica-schist, hornblende-schist, clay- 
 slate, chlorite-schist, hypogene or metamorphic 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, being formed of the 
 same materials as granite, namely, felspar, quartz, and mica. In the 
 specimen here figured, the white layers consist almost exclusively of 
 granular felspar, with here and there a speck of mica and grain of 
 quartz. The dark layers are composed of grey quartz and black 
 
 Fig. 704. 
 
 Fragment of gneiss, natural size : section made at right angles to 
 the planes of foliation. 
 
 mica, with occasionally a grain of felspar intermixed. The rock 
 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, greatly predominates in 
 quantity, but the most ready cleavage is determined by the abun- 
 dance 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. 
 
 The term "gneiss," however, in geology is commonly used in a 
 wider sense, to designate a formation in which the above-mentioned 
 rock prevails, but with which any one of the other metamorphic 
 rocks, and more especially hornblende-schist, may alternate. These 
 other members of the metamorphic series are, in this case, considered 
 as subordinate to the true gneiss. 
 
 The different varieties of rock allied to gneiss, into which felspar 
 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 felspar, forming a syenitic gneiss ; 
 or talc may be substituted for mica, constituting talcose gneiss, a 
 rock composed of felspar, quartz, and talc, in distinct crystals or 
 grains (stratified protogine of the French). 
 
 Hornblende-schist is usually black, and composed principally of 
 hornblende, with a variable quantity of felspar, and sometimes grains 
 
 QQ 2 
 
596 MICA-SCHIST, CLAY-SLATE, ETC. [Cn. XXXV. 
 
 of quartz. When the hornblende and felspar are nearly in 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. Some of these 
 hornblendic masses may really have been volcanic rocks, which have 
 since assumed a more crystalline or metamorphic texture. 
 
 Mica-schist, or Micaceous schist, is, next to gneiss, one of the most 
 abundant rocks of the metamorphic series. It is slaty, essentially 
 composed of mica and quartz, the mica sometimes appearing to con- 
 stitute 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 
 gradations into clay-slate. 
 
 Clay '-slate, or Argillaceous schist. This 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 -grey to a lead colour ; 
 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 distinguishable by 
 mineral characters alone. 
 
 Quartzite, or Quartz rock, 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 felspar and mica. 
 
 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 felspar or mica ; often associated with, and gra- 
 duating into, gneiss and clay-slate. 
 
 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, form- 
 ing a foliated schist much resembling in colour and appearance 
 certain varieties of gneiss and mica-schist. When it alternates with 
 these rocks, it often contains some crystals of mica, and occasionally 
 quartz, felspar, hornblende, talc, chlorite, garnet, and other minerals. 
 It enters sparingly into the structure of the hypogene districts 
 of Norway, Sweden, and Scotland, but is largely developed in the 
 Alps. 
 
 Before offering any farther observations on the probable origin of 
 the metamorphic rocks, I subjoin, in the form of a glossary, a brief 
 explanation of some of the principal varieties and their synonyms. 
 
CH. XXXV.] METAMORPHIC ROCKS. 597 
 
 Explanation of the Names, Synonyms, and Mineral Composition of 
 the more abundant Metamorphic Rocks. 
 
 ACTINOLITE-SCHIST. A slaty foliated rock, composed chiefly of actinolite, (an 
 emerald-green mineral, allied to hornblende,) with some admixture of 
 garnet, mica, and quartz. 
 
 AMPELITE. Aluminous slate (Brongniart) ; occurs both in the metamorphic and 
 fossiliferous series. 
 
 AMPHIBOLITE, Hornblende rock, which see. 
 
 ARGILLACEOUS-SCHIST, or CLAY-SLATE. See p. 596. 
 
 ARKOSE. Name given by Brongniart to a compound of the same materials as 
 granite, which it often resembles closely. It is found at the junction of 
 granite with formations of different ages, and consists of crystals of felspar, 
 quartz, and sometimes mica, which, after separation from their original 
 matrix by disintegration, have been reunited by a siliceous or quartzose 
 cement. It is often penetrated by quartz veins. 
 
 CHIASTOLITE-SLATE scarcely differs from clay-slate, but includes numerous crystals 
 of Chiastolite : in considerable thickness in Cumberland. Chiastolite 
 occurs in long slender rhomboidal crystals. For composition, see Table, 
 p. 479. 
 
 CHLORITE-SCHIST. A green slaty rock, in which chlorite, a green scaly mineral, 
 is abundant. See p. 596. 
 
 CLAY-SLATE or ARGILLACEOUS-SCHIST. See p. 596. 
 
 EURITE has been already mentioned as a plutonic rock (p. 569.), but occurs also 
 with precisely the same composition in beds subordinate to gneiss or mica- 
 slate. 
 
 GNEISS. A stratified or foliated rock ; has the same composition as granite. See 
 p. 595. 
 
 HORNBLENDE ROCK, or AMPHIBOLITE. See above, p. 477. A member both of 
 the volcanic and metamorphic series. Agrees in composition with horn- 
 blende-schist, but is not fissile. 
 
 HORNBLENDE-SCHIST, or SLATE. Composed of hornblende and felspar. See 
 p. 595. 
 
 HORNBLENDIC or SYENiTic GNEISS. Composed of felspar, quartz, and horn- 
 blende. 
 
 HYPOGENE LIMESTONE. See p. 596. 
 
 MARBLE. See pp. 12. & 596. 
 
 MICA-SCHIST, or MICACEOUS-SCHIST. A slaty rock, composed of mica and 
 
 quartz, in variable proportions. See p. 596. 
 MICA-SLATE. See MICA-SCHIST, p. 596. 
 
 PHYLLADE. D'Aubuisson's term for clay-slate, from <f>uxxa?, a heap of leaves. 
 PRIMARY LIMESTONE. See HYPOGENE LIMESTONE, p. 596. 
 
 PROTOGINE. See TALCOSE-GNEISS, p. 595. ; when unstratified it is Talcose- 
 granite. 
 
 QUARTZ ROCK, or QUARTZITB. A stratified rock ; an aggregate of grains of 
 quartz. See p. 596. 
 
 SERPENTINE has already been described (p. 478.) because it occurs in both divi- 
 sions of the hypogene series, as a stratified or unstratified rock. 
 
 TALCOSE-GNEISS. Same composition as talcose-granite or protogine, but stratified 
 or foliated. See p. 595. 
 
 TALCOSE-SCHIST consists chiefly of talc, or of talc and quai-tz, or of talc and fel- 
 spar, and has a texture something like that of clay-slate. 
 QQ 3 
 
598 METAMORPHIC ROCKS. [Cn. XXXV. 
 
 Origin of the Metamorphic Strata. 
 
 Having said thus much of the mineral composition of the meta- 
 morphic rocks, I may combine what remains to be said of their 
 structure and history with an account of the opinions entertained of 
 their probable origin. At the same time, it may be well to forewarn 
 the reader that we are here entering upon ground of controversy, 
 and soon reach the limits where positive induction ends, and beyond 
 which we can only indulge in speculations. It was once a favourite 
 doctrine, and is still maintained by many, that these rocks owe their 
 crystalline texture, their want of all signs of a mechanical origin, or 
 of fossil contents, 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 the last 
 chapter of this volume, to how many different ages the metamorphic 
 formations are referable, and how gneiss, mica-schist, clay-slate, and 
 hypogene limestone (that of Carrara for example) have been formed, 
 not only since the first introduction of organic beings into this planet, 
 but even long after many distinct races of plants and animals had 
 passed away in succession. 
 
 The doctrine respecting the crystalline strata, implied in the 
 name metamorphic, 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 de- 
 posited 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 
 fossiliferous strata. This resemblance is by no means confined to 
 the existence in both occasionally of a laminated structure, but ex- 
 tends to every kind of arrangement which is compatible with the 
 absence of fossils, and of sand, pebbles, ripple-mark, and other cha- 
 racters which the metamorphic theory supposes to have been ob- 
 literated by plutonic action. Thus, for example, we behold alike in 
 the crystalline and fossiliferous formations an alternation of beds 
 varying greatly in composition, colour, and thickness. We observe, 
 for instance, gneiss alternating with layers of black hornblende- 
 schist, or of green chlorite-schist, or with granular quartz, or lime- 
 stone ; and the interchange of these different strata may be repeated 
 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 volcanic dikes, very extraordinary alterations in rocks 
 have taken place, more especially in the neighbourhood of granite. 
 It will be useful here to add other illustrations, showing that a tex- 
 ture undistinguishable from that which characterizes the more 
 crystalline metamorphic formations has actually been superinduced 
 in strata once fossiliferous. 
 
CH. XXXV.] STRATA IN CONTACT WITH GRANITE. 
 
 599 
 
 In the southern extremity of Norway there is a large district, on 
 the west side of the fiord of Christiania, in which granite or syenite 
 protrudes in mountain masses through fossiliferous 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 
 granite for a distance of from 50 to 400 yards. The aluminous 
 shales are hardened and have become flinty. Sometimes they re- 
 semble jasper. Ribboned jasper is produced by the hardening of 
 alternate layers of green and chocolate-coloured schist, each stripe 
 faithfully representing the original lines of stratification. Nearer 
 the granite the schist often contains 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, between the granite 
 and the hornblende slate, above-mentioned, grains of mica and crys- 
 talline felspar 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 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 remote from the granite is of an 
 earthy texture and blue colour, and often abounds in corals, becomes 
 a white granular marble near the granite, sometimes siliceous, the 
 granular structure extending occasionally upwards of 400 yards from 
 the junction ; the corals being for the most part obliterated, though 
 sometimes preserved, even in the white marble. Both the altered 
 
 Fig. 705. 
 
 Altered zone of fossiliferous slate and limestone near granite. Christiania. 
 The arrows indicate the dip, and the straight lines the strike, of the beds. 
 
 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 pa- 
 rallel to the general strike of the fossiliferous beds, or in a line at 
 
 Q Q 4 
 
600 ALTERATIONS OF STRATA. [Cn. XXXV. 
 
 right angles to their strike, as will be seen by the accompanying 
 ground plan.* 
 
 The indurated and ribboned schists above mentioned bear a strong 
 resemblance to certain shales of the coal found at Russell's Hall, 
 near Dudley, where coal-mines have been on fire for ages. Beds of 
 shale of considerable thickness, lying over the burning coal, have 
 been baked and hardened so as to acquire a flinty fracture, the layers 
 being alternately green and brick-coloured. 
 
 The granite of Cornwall, in like manner, 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 Pen- 
 zance. 
 
 The granite of Dartmoor, in Devonshire, says Sir H. De la Beche, 
 has intruded itself into the slate and slaty sandstone called grey wacke, 
 twisting and contorting the strata, and sending veins into them. 
 Hence some of the slate rocks have become " micaceous ; others more 
 indurated, and with the characters of mica-slate and gneiss ; while 
 others again appear converted into a hard-zoned rock strongly im- 
 pregnated with felspar." f 
 
 We learn from the investigations 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 neighbourhood of the granite. Thus 
 in the environs of St. Martin, near St. Paul de Fenouillet, the chalky 
 limestone becomes more crystalline and saccharoid as it approaches 
 the granite, and loses all trace of the fossils which it previously con- 
 tained 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 pyrites, tremolite, garnet, and a new 
 mineral somewhat allied to felspar, called, from the place in the 
 Pyrenees where it occurs, " couzeranite." 
 
 Now the alterations above described as superinduced in rocks by 
 volcanic dikes and granite veins prove incontestably that powers 
 exist in nature capable of transforming fossiliferous into crystalline 
 strata powers capable of generating in them a new mineral charac- 
 ter, similar to, nay, often absolutely identical with that of gneiss, 
 mica-schist, and other stratified members of the hypogene series. The 
 precise nature of these altering causes, which may provisionally be 
 termed plutonic. is in a great degree obscure and doubtful ; but 
 their reality is no less clear, and we must suppose the influence of 
 heat to be in some way connected with the transmutation, if, for 
 reasons before explained, we concede the igneous origin of granite. 
 
 * Keilhau, Gaea Norvegica, pp.61 63. f Geol. Manual, p. 479- 
 
CH. XXXV.] PLUTONIC ACTION". 601 
 
 The experiments of Gregory Watt, in fusing rocks in the labora- 
 tory, and allowing them to consolidate by slow cooling, prove dis- 
 tinctly 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 remains may be destroyed ; 
 and that new chemical combinations may arise, without the mass 
 being so fused as that the lines of stratification should be wholly 
 obliterated. 
 
 We must not, however, 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 volcanos 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. When the mate- 
 rials of granite, therefore, came in contact with the fossiliferous stra- 
 tum in the bowels of the earth under great pressure, the contained 
 gases might be unable to escape ; yet when brought into contact with 
 rocks, they might pass through their pores with greater facility than 
 water is known to do (p. 35.). These aeriform fluids, such as sulphu- 
 retted hydrogen, muriatic acid, and carbonic acid, issue in many 
 places from rents in rocks, which they have discoloured and corroded, 
 softening some and hardening others. If the rocks are charged with 
 water, they would pass through more readily ; for, according to the 
 experiments of Henry, water, under an hydrostatic pressure of 
 96 feet, will absorb three times as much carbonic acid gas as it can 
 under the ordinary pressure of the atmosphere. Although this in- 
 creased power of absorption would be diminished in consequence of 
 the higher temperature found to exist as we descend in the earth, yet 
 Professor Bischoff has shown that the heat by no means augments in 
 such a proportion as to counteract the effect of augmented pressure.f 
 There are other gases, as well as the carbonic acid, which water 
 absorbs, and more rapidly in proportion to the amount of pressure. 
 Now 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 ; and it is conceivable that heated gases brought into contact 
 with them, at great depths, may be absorbed readily, and transfused 
 through their pores. Although the gaseous matter first absorbed 
 would soon be condensed, and part with its heat, yet the continual 
 arrival of fresh supplies from below might, in the course of ages, 
 cause the temperature of the water, and with it that of the contain- 
 ing rock, to be materially raised. 
 
 M. Fournet, in his description of the metalliferous gneiss near 
 Clermont, in Auvergne, states that all the minute fissures 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 
 
 * Phil. Trans., 1804. t Poggendorfs Annalen, No. xvi., 2d 
 
 series, vol. iii. 
 
602 ROCKS ALTERED BY SUBTERRANEAN GASES. [Cn. XXXV. 
 
 country. The various elements 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.* 
 
 Another illustration of the power of subterranean gases is afforded 
 by the stufas of St. Calogero, situated in the largest of the Lipari 
 Islands. Here, according to the description published by Hoffmann, 
 horizontal strata of tuff, extending for 4 miles along the coast, and 
 forming cliffs more than 200 feet high, have been discoloured in 
 various places, and strangely altered by the " all-penetrating va- 
 pours." Dark clays have become yellow, or often snow-white ; or 
 have assumed a chequered or brecciated appearance, being crossed 
 with ferruginous red stripes. In some places the fumeroles have 
 been found by analysis to consist partly of sublimations of oxide of 
 iron ; but it also appears that veins of chalcedony and opal, and 
 others of fibrous gypsum, have resulted from these volcanic exhala- 
 tion s.f 
 
 The reader may also refer to M. Virlet's account of the corrosion 
 of hard, flinty, and jaspideous rocks near Corinth by the prolonged 
 agency of subterranean gases J ; and to Dr. Daubeny's description of 
 the decomposition of trachytic rocks in the Solfatara, near Naples, 
 by sulphuretted hydrogen and muriatic acid gases. 
 
 Although in all these instances we can only study the phenomena 
 as exhibited at the surface, it is clear that the gaseous fluids must 
 have made their way through the whole thickness of porous or 
 fissured rocks, which intervene between the subterranean reservoirs 
 of gas and the external air. The extent, therefore, of the earth's 
 crust which the vapours have permeated and are now permeating 
 may be thousands of fathoms in thickness, and their heating and 
 modifying influence may be spread throughout the whole of this 
 solid mass. 
 
 We learn from Professor Bischoff that the steam of a hot spring 
 at Aix-la-Chapelle, although its temperature is only from 133 to 
 167 F., has converted the surface of some blocks of black marble 
 into a doughy mass. He conceives, therefore, that steam in the 
 bowels of the earth having a temperature equal or even greater than 
 the melting point of lava, and having an elasticity of which even 
 Papin's digester can give but a faint idea, may convert rocks into 
 liquid matter.] 
 
 The above observations are calculated to meet some of the ob- 
 jections which have been urged against the metamorphic theory on 
 the ground of the small power of rocks to conduct heat ; for it is 
 well known that rocks, when dry and in the air, differ remarkably 
 from metals in this respect. It has been asked how the changes 
 
 * See Principles, /wcfer, "Carbonated de la Soc. Geol. de France, torn. ii. 
 Springs," &c. p. 230. 
 
 f Hoffmann's Liparischen Inseln, See Princ. of Geol. ; and Daubeny's 
 p. 38. Leipzig, 1832. Yolcanos, p. 167. 
 
 J See Trine, of Geol.; and Bulletin || Jam. Ed. New Phil. Journ.,No. 51. 
 
 p. 43. 
 
CH.XXXV.] ORIGIN OF METAMORPHIC STRUCTURE. 603 
 
 which extend merely for a few feet from the contact of a dike could 
 have penetrated through mountain masses of crystalline strata 
 several miles in thickness. Now it has been stated that the plu- 
 tonic influence of the syenite of Norway has sometimes altered 
 fossiliferous strata for a distance of a quarter of a mile, both in the 
 direction of their dip and of their strike. (See fig. 705. p. 599.) 
 This is undoubtedly an extreme case ; but is it not far more philo- 
 sophical to suppose that this influence may, under favourable cir- 
 cumstances, affect denser masses, than to invent an entirely new 
 cause to account for effects merely differing in quantity, and not in 
 kind ? The metamorphic theory does not require us to affirm that 
 some contiguous mass of granite has been the altering power ; but 
 merely that an action, existing in the interior of the earth at an 
 unknown depth, whether thermal, hydro -thermal, electrical, or 
 other, analogous to that exerted near intruding masses of granite, 
 has, in the course of vast and indefinite periods, and when rising 
 perhaps from a large heated surface, reduced strata thousands of 
 yards thick to a state of semifusion, so that on cooling they have 
 become crystalline, like gneiss. Granite may have been another 
 result of the same action in a higher state of intensity, by which a 
 thorough fusion has been produced ; and in this manner the passage 
 from granite into gneiss may be explained. 
 
 In considering, then, the various data already enumerated, the 
 forms of stratification and lamination in metamorphic rocks, their 
 passage on the one hand into the fossiliferous, and on the other into 
 the plutonic formations, and the conversions which can be ascer- 
 tained to have occurred in the vicinity of granite, we may conclude 
 that gneiss and mica-schist may be nothing more than altered 
 micaceous and argillaceous sandstones, that granular quartz may 
 have been derived from siliceous sandstone, and compact quartz 
 from the same materials. Clay-slate may be altered shale, and 
 granular marble may have originated in the form of ordinary lime- 
 stone, replete with shells and corals, which have since been obli- 
 terated ; and, lastly, calcareous sands and marls may have been 
 changed into impure crystalline limestones. 
 
 " Hornblende-schist," says Dr. MacCulloch, " may at first have 
 been mere clay ; for clay or shale is found altered by trap into 
 Lydian stone, a substance differing from hornblende-schist almost 
 solely in compactness and uniformity of texture." * " In Shetland," 
 remarks the same author, " argillaceous-schist (or clay-slate), when 
 in contact with granite, is sometimes converted into hornblende- 
 schist, the schist becoming first siliceous, and ultimately, at the 
 contact, hornblende-schist." f 
 
 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 
 
 * Syst. of Geol. vol. i. p. 210. f Ibid., p. 211. 
 
604 ORIGIN OF METAMORPHIC STRUCTURE. [Cn. XXXV. 
 
 igneous rocks, in the disturbed region of the Appalachians.* At 
 Worcester, in the state of Massachusetts, 45 miles due west of 
 Boston, a bed of plumbago and impure anthracite occurs, inter- 
 stratified with mica-schist. It is about 2 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 containing impressions of coal-plants of the genera Pecopteris, 
 Neuropteris, Calamites, &c. This anthracite is intermediate in 
 character between that of Pennsylvania and the plumbago of 
 Worcester, in which last the gaseous or volatile matter (hydrogen, 
 oxygen, and nitrogen) is to the carbon only in the proportion of 
 3 per cent. After traversing the country in various directions, I 
 came to the conclusion that the carboniferous shales or slates with 
 anthracite and plants, which in Rhode Island often pass into mica- 
 schist, have at Worcester assumed a perfectly crystalline and meta- 
 morphic texture ; the anthracite having been nearly transmuted into 
 that state of pure carbon which is called plumbago or graphite, f 
 
 It has been remarked by M. Delesse that the minerals developed 
 in hypogene limestone vary according to the degree of metamor- 
 phism which the rock has undergone. Thus, for example, where 
 the structure is but slightly crystalline, talc, chlorite, serpentine, 
 andalusite, and kyanite are commonly present ; where it is more 
 highly crystallized, garnet, hornblende, Wollastonite, dipyre, Cou- 
 zeranite, and some others appear ; and, lastly, where the crystalliza- 
 tion is complete, there are found, in addition to many of the above 
 minerals, felspar, especially those kinds which are richest in alkali, 
 together with mica. The same author observes that, as calcareous 
 deposits usually contain some aluminous clay, so we may naturally 
 expect to meet with silicates of alumina in crystalline limestone ; 
 such silicates, accordingly, are frequent, and occasionally even pure 
 alumina crystallized in the form of corundum. J 
 
 Mr. Dana has suggested that the phosphoric acid of phosphate of 
 lime, and the fluor of fluor-spar, so often met with in crystalline 
 limestones, may have been derived from the remains of mollusca 
 and other animals ; also that graphite (which is pure carbon in a 
 crystalline form, with or without admixture of alumina, lime, or 
 iron) may have been derived from vegetable remains imbedded in 
 the orignal matrix. 
 
 The total absence of any trace of fossils has inclined many geo- 
 logists to attribute the origin of the crystalline strata to a period 
 antecedent to the existence of organic beings. Admitting, they say, 
 the obliteration, in some cases, of fossils by plutonic action, we might 
 still expect that traces of them would oftener occur in certain ancient 
 systems of slate, in which, as in Cumberland, some conglomerates 
 
 * See above, pp. 392, 398. f Delesse, Bulletin Soc. Geol. France, 
 
 f See Lyel" 
 vol. i. p. 199. 
 
 f See Lyell, Quart.' Geol. Journ., 2e serie, torn. 9. p. 126. 1851. 
 )1. i. 
 
CH. XXXV.] OBJECTIONS TO METAMORPHIC THEORY. 605 
 
 occur. But in urging this argument, it seems to have been forgotten 
 that there are stratified formations of enormous thickness, and of 
 various ages, and some of them very modern, all formed after the 
 earth had become the abode of living creatures, which are, never- 
 theless, in certain districts, entirely destitute of all vestiges. of or- 
 ganic bodies. In some, the traces of fossils may have been effaced 
 by water and acids, at many successive periods ; and it is clear, that, 
 the older the stratum, the greater is the chance of its being nonfossi- 
 liferous, even if it has escaped all metamorphic action. 
 
 It has been also objected to the metamorphic theory, that the 
 chemical composition of the secondary strata differs essentially from 
 that of the crystalline schists, into which they are supposed to be 
 convertible.* The " primary " schists, it is said, usually contain a 
 considerable proportion of potash or of soda, which the secondary 
 clays, shales, and slates do not, these last being the result of the 
 decomposition of felspathic rocks, from which the alkaline matter has 
 been abstracted during the process of decomposition. But this rea- 
 soning proceeds on insufficient and apparently mistaken data ; for 
 a large portion of what is usually called clay, marl, shale, and slate 
 does actually contain a certain, and often a considerable, proportion 
 of alkali ; so that it is difficult, in many countries, to obtain clay or 
 shale sufficiently free from alkaline ingredients to allow of their being 
 burnt into bricks or used for pottery. 
 
 Thus the argillaceous shales and slates of the Old Red sandstone, 
 in Forfarshire and other parts of Scotland, are so much charged with 
 alkali, derived from triturated felspar, that, instead of hardening when 
 exposed to fire, they sometimes melt into a glass. They contain no 
 lime, but appear to consist of extremely minute grains of the various 
 ingredients of granite, which are distinctly visible in the coarser- 
 grained varieties, and in almost all the interposed sandstones. These 
 laminated clays and shales might certainly, if crystallized, resemble 
 in composition many of the primary strata. 
 
 There is also potash in fossil vegetable remains, and soda in the 
 salts by which strata are sometimes so largely impregnated, as in 
 Patagonia. But recent analysis may be said to have settled the 
 point at issue, by demonstrating that the carboniferous strata in 
 England f, the Upper and Lower Silurian in East Canada f , and the 
 clay-slates (of Cambrian date ?) 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 having a less crystalline texture. 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 differing greatly in composition from each other be subjected 
 
 * Dr. Boase, Primary Geology, p. J Hunt, Phil. Mag. 4 ser. vol.vii. p.237. 
 
 319. Kyersly, Norsk, Mag. for Naturvi- 
 
 f H. Taylor, Edin. New, Phil. Journ. denp. vol. viii. p. 1 72. 
 vol. 1. 1851, p. 140. 
 
606 METAMORPHIC THEORY. [Cn. XXXV. 
 
 to equal quantities of heat, there is every probability that some will 
 be more fusible than others. Some, for example, will contain soda, 
 potash, lime, or some other ingredient capable of acting as a flux ; 
 while others may be destitute of the same elements, and so refractory 
 as to be very slightly affected by a degree of heat capable of reducing 
 others to semi-fusion. 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. 
 
 Moreover, metamorphism must often begin to exert its force 
 long after the strata have assumed a vertical position, and it may 
 then act locally or within limited areas, and will be as likely to 
 affect the newer as the older beds. As an illustration of such 
 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. 231.), 
 overlying the nummulite limestone of Eocene date, and comprising 
 some arenaceous and some calcareous layers, are seen to alternate 
 several times with bands of granitoid rock, answering in character 
 to gneiss.* In this case heat, or vapour, or water at an intensely 
 high temperature may have traversed the more permeable beds, and 
 altered them so far as to admit of an internal movement and re-ar- 
 rangement of the molecules, while the adjoining strata did not give 
 passage to the same heat, or if so, remained unchanged because they 
 were composed of less fusible materials. Whatever hypothesis we 
 adopt, the phenomena establish beyond a doubt the possibility of 
 the development of the metamorphic structure in a tertiary deposit 
 in planes parallel to those of stratification. 
 
 Whether such parallelism be the rule or the exception in gneiss, 
 mica- schist, and other formations of the same family, is a question 
 which I shall discuss at length in the next chapter. 
 
 * Geol. Quart. Joura. vol. v. p. 211. 1848. 
 
Cn. XXXVI.] METAMORPHIC ROCKS. 607 
 
 CHAPTER XXXVI. 
 
 Origin of the metamorphic rocks, continued Definition of joints, slaty cleavage 
 and foliation Supposed causes of these structures Mechanical theory of cleav- 
 age Condensation and elongation of slate rocks by lateral pressure Supposed 
 combination ef crystalline and mechanical forces Lamination 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 Foliation in homogeneous rocks may coincide with planes of 
 cleavage, and in uncleaved rocks with those of stratification Causes of irregu- 
 larity in the planes of foliation. 
 
 WE have already seen that crystalline forces of great intensity have 
 frequently acted upon sedimentary and fossiliferous strata long 
 subsequently to their consolidation, and we may next inquire 
 whether the component minerals of the altered rocks usually arrange 
 themselves in planes parallel to the original planes of stratification, 
 or whether, after crystallization, 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 exhibited in rocks, 
 namely, stratification, joints, slaty cleavage, and foliation; and all 
 these must have different names, even though there be cases where 
 it is impossible, after carefully studying the appearances, to decide 
 upon the class to which they belong. 
 
 Professor Sedgwick, whose essay " On the Structure of large 
 Mineral Masses " first cleared the way towards a better under- 
 standing of this difficult subject, observes, that joints are distin- 
 guishable from lines of slaty cleavage in this, that the rock inter- 
 vening between two joints has no tendency to cleave in a direction 
 parallel -to the planes of the joints, whereas a rock is capable of 
 indefinite subdivision in the direction of its slaty cleavage. In some 
 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. 706.), which consist of a hard greenish slate. 
 
 Fig. 706. 
 
 Parallel planes of cleavage intersecting curved strata. (Sedgwick.) 
 
 The true bedding is there indicated by a number of parallel stripes, 
 some of a lighter and some of a darker colour than the general mass. 
 
608 JOINTED STRUCTURE [Cn. XXXVI. 
 
 Such stripes are found to be parallel to the true planes of strati- 
 fication, wherever these are manifested by ripple-mark, or by beds 
 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 proportion as the materials of the rock are 
 fine and homogeneous. It is only when these are very coarse that 
 the cleavage planes entirely vanish. These planes are usually in- 
 clined at a very considerable angle to the planes of the strata. In 
 the Welsh hills, for example, the average angle is as much as from 
 30 to 40. Sometimes the cleavage planes dip towards the same 
 point of the compass as those of stratification, but more frequently 
 to opposite points. It may be stated as a general rule, that when 
 beds of coarser materials alternate with those composed of finer 
 particles, the slaty cleavage is either entirely confined to the fine- 
 grained rock, or is very imperfectly exhibited in that of coarser 
 texture. This rule holds, whether the cleavage is parallel to the 
 planes of stratification or not.* 
 
 In regard to joints, they are natural fissures which often traverse 
 rocks in straight and well-determined lines. They afford to the 
 quarryman, as Sir R. Murchison observes, when speaking of the phe- 
 nomena, as exhibited in Shropshire and the neighbouring counties, 
 the greatest aid in the extraction of blocks of stone ; and, if a suffi- 
 cient 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 strata. The 
 joints are straight-cut chinks, often slightly open, often passing, not 
 only through layers of successive deposition, but also through balls 
 . of limestone or other matter which have been formed by concretion- 
 ary action, since the original accumulation of the strata. Such 
 joints, therefore, must often have resulted from one of the last changes 
 superinduced upon sedimentary deposits. "j* 
 
 In the annexed diagram (fig. 707.), the flat surfaces of rock 
 A, B, c, represent exposed faces of joints, to which the walls of other 
 joints, J J, are parallel, s s are the lines of stratification ; D 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 remarked, 
 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 stratification, 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.^ 
 
 Now such joints are supposed to be analogous to the partings 
 
 * Geol. Trans., 2d series, vol. iii. p. f Silurian System, p. 246. 
 461. t Introduction to Geology, chap. iv. 
 
CH. XXXVI.] AND CLEAVAGE. 609 
 
 Fig. 707. 
 
 J 
 
 Stratification, joints, and cleavage. 
 (From Murchison's Silurian System, p. 245.) 
 
 which separate volcanic and plutonic rocks into cuboidal and pris- 
 matic masses. On a small scale we see clay and starch when dry 
 split into similar shapes; this is often caused by simple contrac- 
 tion, whether the shrinking be due to the evaporation of water, 
 or to a change of temperature. It is well known that many sand- 
 stones and other rocks expand by the application of moderate 
 degrees of heat, and then contract again on cooling ; and there can 
 be no doubt that large portions of the earth's crust have, in the 
 course of past ages, been subjected again and again to very different 
 degrees of heat and cold. These alternations of temperature have 
 probably contributed largely to the production of joints in rocks. 
 
 In some countries, as in Saxony, where masses of basalt rest on 
 sandstone, the aqueous rock has for the distance of several feet from 
 the point of junction assumed a columnar structure similar to that 
 of the trap. In like manner some hearthstones, 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 in- 
 ternal arrangement, so as to break in a new direction, their external 
 form remaining unaltered. 
 
 Professor Sedgwick, speaking of the planes of slaty cleavage, 
 where they are decidedly distinct from those of sedimentary de- 
 position, 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 accordingly 
 referred it to crystalline or polar forces acting simultaneously, and 
 somewhat uniformly, in given directions, on large masses having a 
 homogeneous composition. 
 
 Sir John Herschel, in allusion to slaty cleavage, has suggested, 
 " 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 amongst themselves, or at 
 least on their own axes, some general law must then determine the 
 position in which these particles will rest on cooling. Probably, 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 
 
 BE 
 
 \ 
 
610 SLATY CLEAVAGE. [Cn. XXXVI. 
 
 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 light, and give the appearance 
 of silky filaments. Some sorts of soap, in which insoluble mar- 
 garates * exist, exhibit the same phenomenon when mixed with 
 water ; and what occurs in our experiments on a minute scale may 
 occur in nature on a great one." f 
 
 Professor Phillips has remarked that in some slaty rocks the form 
 of the outline of fossil shells and trilobites has been much changed 
 by distortion, which has taken place in a longitudinal, transverse, or 
 oblique direction. This change, he adds, seems to be the result of 
 a " creeping movement " of the particles of the rock along the planes 
 of cleavage, its direction being always uniform 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.J 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 direction per- 
 pendicular to the planes of cleavage, and a corresponding expansion 
 in the direction of the dip of the. cleavage. 
 
 More recently (July, 1853) Mr. Sorby has demonstrated the great 
 extent 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 measured 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. 708.) it will be seen that the sandy bed df, 
 which has offered greater resistance, has been sharply contorted, 
 while the fine-grained strata, , b, c, have remained comparatively 
 unbent. The points d and f in the stratum d f must have been 
 originally 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 lastly, 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 df is now about four times greater in those parts 
 lying in the main direction of the flexures than in a plane perpen- 
 
 * Margaric acid is an oleaginous acid, \ Report, Brit. Asscc., Cork, 1843, 
 
 formed from different animal and vege- Sect. p. 60. 
 
 table fatty substances. A margarate is Quart. Geol. Journ., vol. iii. p. 87. 
 
 a compound of this acid with soda, po- 1847. 
 
 tash, or some other base, and is so named || On the Origin of Slaty Cleavage, by 
 
 from its pearly lustre. H. C. Sorby, Edinb. New. Phil. Journ. 
 
 f Letter to the author, dated Cape of 1853, vol. Iv. p. 137. 
 Good Hope, Feb. 20. 1836. 
 
CH. XXXVI.] SLATE ROCK OF NORTH DEVON. 
 
 611 
 
 Fig. 708. 
 
 dicular to them ; and the same bed 
 exhibits cleavage-planes in the 
 direction of the greatest move- 
 ment, although they are much 
 fewer than in the slaty strata 
 above and below. 
 
 Above the sandy bed d /, the 
 stratum c is somewhat disturbed, 
 while the next bed b is much less 
 so, and a not at all ; yet all these 
 beds, c, b, and a, must have un- 
 dergone an equal amount of pres- 
 sure with d, the points a and g 
 having approximated as much to- 
 wards each other as have d and/! 
 The same phenomena are also re- 
 peated in the beds below d, and 
 might have been shown, had the 
 section been extended downwards. 
 Hence it appears that the finer beds 
 have been squeezed into a fourth 
 of the space they previously oc- 
 cupied, partly by condensation, or 
 the closer packing of their ulti- 
 mate particles (which has given 
 rise to the great specific gravity 
 of such slates), and partly by elon- 
 gation in the line of the dip of the 
 cleavage, of which the general di- 
 rection is perpendicular to that of 
 the pressure. " These and nume- 
 rous other cases in North Devon 
 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 change its dimensions. If the whole were then com- 
 pressed in the direction of the length of the strip of paper, it would 
 be bent and puckered up into contortions, whilst the plastic material 
 would readily change its dimensions without undergoing such con- 
 tortions ; 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." 
 
 The student will readily conceive that, when the shape of a fossil 
 or of a crystal of some mineral, or of a spheroidal concretion, has 
 been altered by lateral pressure, the new forms which they assume 
 respectively will vary according to whether they have yielded in 
 one or more directions. They may have been drawn out solely in 
 the direction of the dip of the cleavage, or they may have yielded 
 
 RR 2 
 
 (Drawn by H. C. Sorby.) 
 
 Vertical section of slate rock in the cliffs 
 near llfracombe, North Devon. 
 
 Scale one inch to one foot. 
 
 a, b, c, e. Fine-grained slates, the stratifi- 
 cation being shown partly by lighter, or 
 darker colours, and partly by different de- 
 grees of fineness in the grain. 
 
 d,f. A coarser-grained light-coloured sandy 
 slate with less perfect cleavage. 
 
612 CONDENSATION OF SLATE ROCKS. [Cn. XXXVI. 
 
 in a plane perpendicular to that dip, or they may have undergone 
 both these movements. By microscopic examination of minute 
 crystals, and by other observations too minute to be detailed here, 
 Mr. Sorby comes to the conclusion that the absolute condensation of 
 the slate rocks amounts upon an average to about one half their 
 original volume. This must have resulted chiefly from the forcing 
 of the particles more closely together, so as to fill up the spaces 
 left between them, when they only touched each other. The rest of 
 the change has been due to elongation which has produced slaty 
 cleavage. 
 
 Most of the scales of mica occurring in certain slates examined 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 direc- 
 tions. 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 admitted of easy fracture 
 into thin flat pieces in the plane alluded to, whereas it would not 
 yield in that perpendicular to the cleavage.* 
 
 This experiment may lend countenance to the opinion that the 
 lamination of basalt and trachyte, and even of some kinds of gneiss, 
 and the grain of certain granites, may all have been determined by a 
 mechanical cause, a movement having taken place after the de- 
 velopment of crystals in the pasty-mass. 
 
 Mr. Scrope, in his description of the Ponza Islands, ascribed " the 
 zoned structure of the Hungarian perlite (a semi -vitreous trachyte) 
 to its having subsided, in obedience to the impulse of its own 
 gravity, down a slightly inclined plane, while possessed of an im- 
 perfect fluidity. In the islands of Ponza and Palmarola, the direc- 
 tion of the zones is more frequently vertical than horizontal, because 
 the mass was impelled from below upwards."'}' In like manner, 
 Mr. Darwin attributes the lamination and fissile structure of volcanic 
 rocks of the trachytic series, including some obsidians in Ascension, 
 Mexico, and elsewhere, to their having moved when liquid in the 
 direction of the laminae. The zones consist sometimes of layers of 
 air-cells drawn out and lengthened in the supposed direction of the 
 moving mass. He compares this division into parallel zones, thus 
 caused by the stretching of a pasty mass as it flowed slowly 
 onwards, to the zoned or ribboned structure of ice, which Professor 
 
 Sorby, as cited above, p. 610, note. f Geo ^ Trans. 2d. ser. vol. ii. p. 227 
 
CH. XXXVI.] FOLIATION OF CRYSTALLINE ROCKS. 613 
 
 James Forbes has so ably explained, showing that it is due to the 
 fissuring of a viscous body in motion.* 
 
 Whatever be the cause, the result, observes Darwin, is well 
 worthy the attention of geologists; for in a volcanic rock of the 
 trachytic series in Ascension layers are seen often of extreme 
 tenuity, even as thin as hairs, and of different colours, alternating 
 again and again, some of them composed of crystals of quartz and 
 diopside (a kind of augite), others of black augitic specks with 
 granules of oxide of iron, and lastly, others of crystalline felspar. 
 It is supposed in this case that the crystallizing force acted more 
 freely in the direction of the planes of cleavage, produced when the 
 pasty mass was stretched, whether because confined vapours were 
 enabled to spread themselves through the minute fissures, or because 
 the ultimate molecules had more freedom of motion along the planes 
 of less tension, or for some other reasons not yet understood. 
 
 After studying, in 1835, the crystalline rocks of South America, 
 Mr. Darwin proposed the term foliation for the laminae or plates 
 into which gneiss, mica-schist, and other crystalline rocks are 
 divided. Cleavage, he observes, may be applied to those divisional 
 planes which render 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 mineralogical nature of 
 which gneiss and other metamorphic schists are composed. The 
 cleavage planes of the clay-slate in Terra del Fuego and Chili 
 preserve a uniform strike for hundreds of miles in regions where 
 these planes are quite distinct from stratification. In the same 
 country the planes of foliation of the mica-schist and gneiss are 
 parallel to the cleavage of the clay-slate. Hence, we are tempted, at 
 first sight, to infer that some common cause or process, and that cause 
 not connected with sedimentary deposition, has impressed cleavage on 
 the one set of rocks and foliation on the other. But such an infer- 
 ence can only be legitimately drawn in those rare cases where we 
 are able, by a continuous section, to prove that not only the strike, but 
 the dip of the slaty cleavage on the one hand, and of the foliation on 
 the other, precisely coincide ; the cleavage at the same time not being 
 parallel to the stratification in the slate rock. In some examples 
 cited by Mr. Darwin, in Terra del Fuego, the Chonos Islands, 
 and La Plata, this uniformity of dip seems to have been traced in a 
 manner as satisfactory as the nature of such evidence will allow. 
 But we must be on our guard against a source of deception which 
 may mislead us in this chain of reasoning. We are informed that 
 in South America, as in other countries, the strike of the cleavage 
 in clay-slate conforms to the axis of elevation of the rocks in the 
 same districts. Hence it must follow that the folia of gneiss, mica- 
 schist, limestone, and other crystalline rocks, even if they strictly 
 coincide with the planes of original stratification, will run in the 
 
 * Darwin, Volcanic Islands, pp. 69, 70. 
 B K 3 
 
614 FOLIATION' AND CLEAVAGE [On. XXXVI. 
 
 same direction as the strike of the slaty cleavage ; for the true 
 strata always dip at right angles to the axis of elevation, and are 
 parallel to it in their strike. No argument, therefore, can be drawn 
 in favour of a common origin from uniformity of strike in the slaty 
 and foliated rocks ; for we require, in addition, coincidence of dip ; 
 and such is the variability of the dip both of the slates and folia as 
 to render this kind of proof very difficult to obtain. 
 
 That the foliation of the crystalline schists in Norway accords very 
 generally with the planes of original stratification is a conclusion 
 long since espoused by Keilhau.* 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 ; for the dip of the Silurian and fossiliferous strata where 
 they pass into the metamorphic agrees with the foliation of the 
 contiguous gneiss, mica-schist, and crystalline limestone. So also 
 in Scotland Mr. D. Forbes has pointed out a striking case where 
 the foliation is identical with the lines of stratification in rocks well 
 seen near Crianlorich on the road to Tyndrum, about 8 miles from 
 Inverarnon in Perthshire. There is in that locality a blue lime- 
 stone foliated by the intercalation 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 
 coloured bands of limestone all dipping, like the folia, at an angle of 
 32 degrees N. E.f 
 
 In stratified formations of every age we see layers of siliceous 
 sand with or without mica, alternating 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 favour the crystal- 
 lization of the quartz, or mica, or felspar, 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. 
 
 In Patagonia, a series of thin sedimentary layers of tuff were 
 observed by Mr. Darwin to have become porphyritic, first where 
 least altered, by a process of aggregation, small patches of clay 
 appearing to be shortened into almond-shaped concretions, which in 
 those places where they were more changed had become crystals of 
 felspar, having their longer axes parallel to each other. In other 
 associated strata, grains of quartz had in like manner aggregated 
 into nodules of crystalline quartz.J 
 
 May we not, then, presume that in rocks where no cleavage has 
 intervened, foliation and the planes of stratification will usually 
 coincide, as in all cases where cleavage happens (as in the writing- 
 slates of the Niesen on the Lake of Thun in Switzerland, containing 
 fucoids) to agree with the original planes of sedimentary deposition ? 
 Mr. Darwin conceives that " foliation may be the extreme result of 
 
 * Norske Mag. Naturvidsk., vol. i. f Memoir read before the Geol. Soc., 
 p. 71. London, Jan. 31. 1855. 
 
 | South America, p. 149. 
 
CH. XXXVI.] OF CRYSTALLINE ROCKS. 615 
 
 the process of which cleavage is the first effect ; " or, at any rate, 
 that the crystalline force may have been most energetic in the 
 direction of cleavage. As bearing on this view, he says, " I was 
 particularly struck in the eastern parts of Terra del Fuego with the 
 fact that the fine laminae of clay-slate, where they cut straight 
 through the bands of stratification, and therefore indisputably true 
 cleavage-planes, differ slightly from one another in their greyish 
 and greenish tints of colour, as also in their compactness, and in 
 some laminae having a more jaspery appearance than others. This 
 fact shows that the same cause which has produced the highly 
 fissile structure has altered in a slight degree the mineralogical 
 character of the rock in the same planes."* As one step farther 
 towards tracing a passage from planes of cleavage to those of folia- 
 tion, Professor Sedgwick observes that in North Wales the surfaces 
 of slates are sometimes coated over with chlorite, " the crystals of 
 which have not only defined the cleavage planes but struck through 
 the whole mass of the rock." f So also, says Mr. Darwin, in some 
 places in South America crystals of epidote and of mica coat the 
 planes of cleavage. 
 
 Mr. D. Sharpe inferred from observations made by him in the 
 Highlands of Scotland, in 1851, that the foliation of the gneiss and 
 mica-schist are upon the whole parallel to one another, but have no 
 connection with any original planes of stratification ; and he also 
 conceives that the planes both of cleavage and foliation in the 
 Grampians and in the region of Mont Blanc in Switzerland (which 
 last he examined in 1854) are parts of great curves or anticlinal 
 axes of considerable regularity. J In like manner in South America 
 the cleavage planes of the clay-slate had been suspected by 
 Mr. Darwin, notwithstanding their varying and opposite dips, to 
 be parts of large curves or foldings, having their summits cut off 
 and worn down. 
 
 There seems to be no difficulty in imagining that in rocks of 
 homogeneous composition the foliation may take place along planes 
 previously caused by the elongation of the materials along the dip 
 of the cleavage ; for experienced geologists have been at a loss to 
 decide in many countries which of two sets of divisional planes were 
 referable to cleavage, and which to stratification ; and after much 
 doubt, have discovered that they had at first mistaken the lines of 
 cleavage for those of deposition, because the former were by far the 
 most marked of the two. Now if such slaty masses should become 
 highly crystalline, and be converted into gneiss, hornblende-schist, 
 or any other member of the hypogene class, the cleavage planes 
 would be more likely to remain visible than those of stratification. 
 Professor Henslow had noticed, so long ago as the year 1821, that 
 
 * Geol. Observ. on South America, % D. Sharpe, Phil. Trans., 1852, and 
 p. 155. Geol. Quart. Journ., no, 41. 1855. 
 
 f Sedgwick, Geol Trans. 2d ser. Darwin, S. America, p. 155. 
 vol iii. p 471. 
 
 KB 4 
 
6 1 6 IRREGULARITIES IN FOLIATION. [Cn. XXXVI. 
 
 the lamination of the chloritic and other crystalline schists in 
 Anglesea was approximately in the planes of bedding; and Pro- 
 fessor Ramsay, in 1841, observed the same in regard to the gneiss 
 and mica-schist of Arran. The last-cited geologist says, in reference 
 to Anglesea, that the metamorphism probably took place when the 
 Lower Silurian volcanos were in activity, and therefore long before 
 the cleavage of the Welsh rocks ; for the cleavage of the latter 
 affects in common the Lower Silurian and the Cambrian strata. In 
 the same memoir he adds, when referring to Mr. Darwin's theory of 
 foliation, " that if the rocks be uncleaved when metamorphism 
 occurs, the foliation planes will be apt to coincide with those of 
 bedding ; but if intense cleavage has preceded, then we may expect 
 that the planes of foliation will lie in the planes of cleavage."* 
 
 From what I have myself seen in the Grampians, both in Forfar- 
 shire and Perthshire, I have always concluded that Macculloch was 
 correct in the opinion that gneiss and mica-schist may be considered 
 as stratified rocks, and that certain beds of pure quartz, one or two 
 feet thick, which run for miles in the strike of their foliation, as well 
 as the intercalation of masses of limestone, and of chloritic, acti- 
 nolitic, and hornblende schists, all indicate the planes of original 
 stratification. At the same time, I fully admit that the alternate 
 layers of quartz, or of mica and quartz, of felspar, or of mica and 
 felspar, or of carbonate of lime, are more distinct, in certain meta- 
 morphic rocks, than the ingredients composing alternate layers in 
 most sedimentary deposits, so that similar particles must be supposed 
 to have exerted a molecular attraction for each other, and to have 
 congregated together in layers more distinct in mineral composition 
 than before they were crystallized. 
 
 We have seen how much the original planes of stratification may 
 be interfered with or even obliterated by concretionary action in 
 deposits still retaining their fossils, as in the case of the magnesian 
 limestone (see p. 37.). Hence we must expect to be frequently 
 baffled when we attempt to decide whether the foliation does or 
 does not accord with that arrangement 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 (see p. 16.), ripple-mark, unconformable stra- 
 tification (p. 61.), the fantastic folds produced by lateral 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 themselves, it would be a serious objection to the meta- 
 morphic theory. 
 
 In the accompanying diagram I have represented carefully the 
 
 * Geol. Quart. Journ., 1853, vol. ix. p. 172. 
 
CH. XXXVI.] LAMINATION OF CLAY-SLATE. 
 
 617 
 
 Fig. 709. 
 
 lamination of a coarse argilla- 
 ceous schist which I examined 
 in 1830 in the Pyrenees. In 
 part it approaches in character 
 to a green and blue roofing-slate, 
 while part is extremely quartzose, 
 the whole mass passing down- 
 wards into micaceous schist. The 
 vertical section here exhibited is 
 about 3 feet in height, and the 
 
 Lamination of clay-slate, Montagne de Seguinat, layers are Sometimes SO thin that 
 near Gavarnie, in the Pyrenees. a . 
 
 fifty may be counted in the 
 thickness of an inch. Some of them consist of pure quartz. 
 
 There is a resemblance in such cases to the diagonal lamination 
 which we see in sedimentary rocks, even though the layers of quartz 
 and of mica, or of felspar and other minerals may be more distinct in 
 alternating folia than they were originally. 
 
 M. Elie de Beaumont, while he regards the greater part of the 
 gneiss and mica-schist of the Alps as sedimentary strata altered by 
 plutonic action, still conceives that some of the Alpine gneiss may 
 have been erupted, or, in other words, may be granite drawn out 
 into parallel laminas in the manner of trachyte as above alluded to.* 
 
 If the mass were squeezed and elongated in a certain direction 
 after crystals of mica, talc, or other scaly minerals were developed, 
 these may perhaps have arranged themselves in planes parallel to 
 those of movement, and a similar process may account for what the 
 quarrymen call " the grain " in some granites, or a tendency to split 
 in one direction more freely than in another. But, as a general rule, 
 the fusion of the crystalline schists does not appear to have gone so 
 far as to allow of motion analogous to that of lava or granite, and 
 for this reason rocks of this class do not send veins into surrounding 
 rocks. In the next chapter we may inquire at how many distinct 
 periods the hypogene or metamorphic schists can be proved to have 
 originated, and why for so long a time the- earlier geologists regarded 
 them as entitled to the name of " primitive." 
 
 * Bulletin Soc. Geol. de France, 2e ser. vol. iv. p. 1301. 
 
618 AGE OS 1 METAMORPHIC KOCKS. [Cn. XXXVII. 
 
 CHAPTER XXXVII. 
 
 ON THE DIFFERENT AGES OF THE METAMORPHIC ROCKS. 
 
 Age of each set of metamorphic strata twofold Test of age by fossils and mineral 
 character not available Test by superposition ambiguous Conversion of dense 
 masses of fossiliferous strata into metamorphic rocks Limestone and shale of 
 Carrara Metamorphic strata of older date than the Cambrian rocks -Others 
 of Lower Silurian origin Others of the Jurassic and Eocene periods in the 
 Alps of Switzerland and Savoy Why scarcely any of the visible crystalline 
 strata are very modern Order of succession in metamorphic rocks Uni- 
 formity of mineral character Why the metamorphic strata are less calcareous 
 than the fossilferous. 
 
 ACCORDING to the theory adopted in the last chapter, the age of each 
 set of metamorphic strata is twofold, they have been deposited at 
 one period, they 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. Superposition itself 
 is an ambiguous test, especially when we 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 
 Eocene for example. If in the latter, it should be called Eocene 
 when regarded as a metamorphic rock, although it be liassic when 
 considered in reference to the era of its deposition. According to this 
 view, the superposition of chalk does not prevent the subjacent 
 metamorphic rock from being Eocene. 
 
 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, 
 chlorite-schist, quartz rock, statuary marble, and the rest. (See the 
 two preceding Chapters.) 
 
 But when the metamorphic action has operated on a grander scale, 
 it tends entirely to destroy all monuments of the date of its develop- 
 ment. It may be easy to prove the identity of two different parts of 
 the same stratum ; one, where the rock has been in contact with a 
 volcanic or plutonic mass, and has been changed into marble or 
 
CH. XXXVII.] NORTHERN APENNINES. 619 
 
 hornblende- schist, and another not far distant, where the same bed 
 remains unaltered and fossiliferous ; but when we have to compare 
 two portions of a mountain chain the one metamorphic, and the 
 other unaltered all the labour and skill of the most practised ob- 
 servers are required, and may sometimes be at fault. I shall men- 
 tion 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. 
 
 Northern Apennines Carrara. The celebrated marble of Car- 
 rara, 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 absence of fossils, and its passage down- 
 wards into talc-schist and garnetiferous mica-schist; these rocks 
 again graduating downwards into gneiss, which is penetrated, at 
 Forno, by granite veins. Now the researches of MM. Savi, Boue, 
 Pareto, Guidoni, De la Beche, Hoffmann, and Pilla have demon- 
 strated that this marble, once supposed to be formed before the ex- 
 istence of organic beings, is, in fact, an altered limestone of the Oolitic 
 period, and the underlying crystalline schists are secondary sand- 
 stones 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 
 are more and more invaded by certain trappean and plutonic rocks, 
 such as a diorite, euphotide, serpentine, and granite, occurring in 
 the same country. 
 
 It was then observed that, in places where the secondary forma- 
 tions are unaltered, the uppermost consist of common Apennine 
 limestone with nodules of flint, below which are shales, and at the 
 base of all, argillaceous and siliceous sandstones. In the limestone 
 fossils are frequent, but very rare in the underlying shale and sand- 
 stone. Then a gradation was traced laterally from these rocks into 
 another' and corresponding 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 disseminated 
 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 universally 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 
 
 * See notices of Savi, Hoffmann, and and torn. iii. p. xliv. ; also Pilla, cited 
 others, referred to by Boue, Bull, de la by Murchison, Quart. Geol. Journ.vol. v. 
 Soc. Geol. de France, torn. v. p. 317.; p. 2G6. 
 
620 AGE OF METAMORPHIC ROCKS [Cn. XXXVII. 
 
 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 deposition 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. 
 
 Alps of Switzerland. In the Alps, analogous conclusions have 
 been drawn respecting the alteration of strata on a still more ex- 
 tended scale. In the eastern part of that chain, some of the primary 
 fossiliferous strata, as well as the older secondary formations, toge- 
 ther with the oolitic and cretaceous rocks, are distinctly recognizable. 
 Tertiary deposits also appear in a less elevated position on the flanks 
 of the Eastern Alps ; but in the Central or Swiss Alps, the primary 
 fossiliferous and older secondary formations disappear, and the Cre- 
 taceous, Oolitic, Liassic, and at some points even the Eocene strata, 
 graduate insensibly into metamorphic rocks, consisting of granular 
 limestone, talc-schist, talcose-gneiss, micaceous schist, and other 
 varieties. In regard to the age of this vast assemblage of crystalline 
 strata, we can merely affirm that some of the upper portions are 
 altered newer secondary, and some of them even Eocene deposits ; but 
 we cannot avoid suspecting that the disappearance both of the older 
 secondary and primary fossiliferous rocks may be owing to their 
 having been all converted in the same region into crystalline schist. 
 
 It i& difficult to convey to those who have never visited the Alps 
 a just idea of the various proofs which concur to produce this con- 
 viction. In the first place, there are certain regions where Oolitic, 
 Cretaceous, and Eocene strata have been turned into granular marble, 
 gneiss, and other metamorphic schists, near their contact with gra- 
 nite. This fact shows undeniably that plutonic causes continued to 
 be in operation in the Alps down to a late period, even after the 
 deposition of some of the nummulitic or middle Eocene formations. 
 Having established this point, we are the more willing to believe 
 that many inferior fossiliferous rocks, probably exposed for longer 
 periods to a similar action, may have become metamorphic to a still 
 greater extent. 
 
 We also discover in parts of the Swiss Alps dense masses of 
 secondary and even tertiary strata which have assumed that semi- 
 crystalline texture which Werner called transition, and which natu- 
 rally led his followers, who attached great importance to mineral 
 characters taken alone, to class them as transition formations, or as 
 groups older than the lowest secondary rocks. (See p. 93.). Now, 
 it is probable that these strata have been affected, although in a less 
 intense degree, by that same plutonic action which has entirely 
 altered and rendered metamorphic so many of the subjacent form- 
 ations ; for in the Alps, this action has by no means been confined 
 to the immediate 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 internal struc- 
 ture of these mountains. That they exist below at no great depth 
 we cannot doubt, and we have already seen (p. 574.) that at some 
 
Cn. XXXVII.] OF THE SWISS ALPS. 621 
 
 points, as in the Valorsine, near Mont Blanc, granite and granitic 
 veins are observable, piercing through talcose gneiss, which passes 
 insensibly upwards into secondary 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 of plutonic action ; for here 
 we find the most stupendous monuments of mechanical violence, by 
 which strata thousands of feet thick have been bent, folded, and 
 overturned. (See p. 58.) It is here that marine secondary form- 
 ations of a comparatively modern date, such as the Oolitic and Cre- 
 taceous, have been upheaved to the height 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. 
 
 If the reader will consult the works of many eminent geologists 
 who have explored the Alps, especially those of MM. de Beaumont, 
 Studer, Necker, Boue, and Murchison, he will learn that they all 
 share, more or less fully, in the opinions above expressed. It has, 
 indeed, been stated by MM. Studer and Hugi, that there are com- 
 plete alternations on a large scale of secondary strata, containing 
 fossils, with gneiss and other rocks of a perfectly metamorphic struc- 
 ture. I have visited some of the most remarkable localities referred 
 to by these authors ; but although agreeing with them that there are 
 passages from the fossiliferous to the metamorphic series far from the 
 contact of granite or other plutonic rocks, I was unable to convince 
 myself that the distinct alternations of highly crystalline, with un- 
 altered strata above alluded to, might not admit of a different expla- 
 nation. 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 covered by strata 
 containing oolitic fossils. These anomalous appearances may partly 
 be explained by supposing great solid wedges of intrusive gneiss to 
 have been forced in laterally 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 where the convulsions 
 have been on so stupendous a scale. 
 
 On the Sattel also, at the base of ttie Gestellihorn, above Enzen, 
 in the valley of Urbach, near Meyringen, some of the intercalations 
 of gneiss between fossiliferous strata may, I conceive, be ascribed 
 to mechanical derangement. Almost any hypothesis of repeated 
 changes of position may be resorted to in a region of such extra- 
 ordinary confusion. The secondary strata may first have been 
 vertical, and then certain portions may have become metamorphic 
 (the plutonic influence ascending from below), while intervening 
 strata remained unchanged. The whole series of beds may then 
 
622 ORDER OF SUCCESSION. [Cn. XXXVII. 
 
 again have been thrown into a nearly horizontal position, giving rise 
 to the superposition of crystalline upon fossiliferous formations. 
 
 It was remarked, in Chap. XXXIV., that as the hypogene rocks, 
 both stratified and unstratified, crystallize originally at a certain 
 depth beneath the surface, they must always, before they are up- 
 raised and exposed at the surface, be of considerable antiquity, rela- 
 tively to a large portion of the fossiliferous and volcanic rocks. 
 They may be forming at all periods ; but before any of them can 
 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 the fossiliferous beds of the Cambrian formation repose 
 unconformably on gneiss, which was evidently crystalline before the 
 deposition of the Cambrian (or Potsdam) sandstone. In Anglesea, 
 as was before remarked, the metamorphism of the schists, according 
 to the observations of Professor Ramsay, took place during the Lower 
 Silurian period. Coupling these conclusions with the fact that a 
 hypogene texture has been superinduced in the Alps on Middle 
 Eocene deposits (see p. 606.), we cannot doubt that, hereafter, geo- 
 logists will succeed in detecting crystalline schists of almost every 
 age in the chronological series, although the quantity of meta- 
 morphic rocks visible at the surface must, for reasons above ex- 
 plained, diminish rapidly in proportion as the monuments of newer 
 eras are investigated. 
 
 Order of succession in metamorphic rocks. There is no universal 
 and invariable order of superposition in metamorphic 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 de- 
 scending series, where it is metamorphic, consists of, 1st, saccharine 
 marble ; 2ndly, talcose-schist ; and 3rdly, of quartz-rock and gneiss : 
 where unaltered, of, 1st, fossiliferous limestone ; 2ndly, shale ; and 
 3rdly, sandstone. 
 
 But if we investigate different mountain chains, we find gneiss, 
 mica-schist, hornblende-schist, chlorite-schist, hypogene 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 series 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 crys- 
 talline strata gave way to that of ordinary sedimentary deposits. 
 Such clay-slates, in fact, are variable in composition, and sometimes 
 alternate with fossiliferous strata, so that they may be said to belong 
 almost equally to the sedimentary and metamorphic order of rocks. 
 It is probable that had they been subjected to more intense plu tonic 
 action, they would have been transformed into hornblende-schist, 
 foliated chlorite-schist, scaly talcose-schist, mica-schist, or other 
 
CH. XXXVII.] MINERAL CHARACTER OF HYPOGENE ROCKS. 623 
 
 more perfectly crystalline rocks, such as are usually associated with 
 gneiss. 
 
 Uniformity of mineral character in Hypogene rocks. Humboldt 
 has emphatically remarked, that when we pass to another hemi- 
 sphere, we see new forms of animals and plants, and even new con- 
 stellations in the heavens ; but in the rocks we still recognise our 
 old acquaintances, the same granite, the same gneiss, the same 
 micaceous schist, quartz-rock, and the rest. It is certainly true that 
 there is a great and striking general resemblance in the principal 
 kinds of hypogene rocks, although of very different ages and 
 countries ; but it has been shown that each of these are, in fact, 
 geological families of rocks, and not definite mineral compounds. 
 They are much more uniform in aspect than sedimentary strata, 
 because these last are often composed of fragments varying greatly 
 in form, size, and colour, and contain fossils of different shapes and 
 mineral composition, and acquire a variety of tints from the mixture 
 of various kinds of sediment. The materials of such strata, if 
 melted and made to crystallize, would be subject to chemical laws, 
 simple and uniform in their action, the same in every climate, and 
 wholly undisturbed by mechanical and organic causes. 
 
 Nevertheless, it would be a great error to assume that the hypo- 
 gene rocks, considered as aggregates of simple minerals, are really 
 more homogeneous in their composition than the several members of 
 the sedimentary series. In the first place, different assemblages of 
 hypogene rocks occur in different countries ; and, secondly, in any 
 one district, the rocks which pass under the same name are often 
 extremely variable in their component ingredients, or at least in the 
 proportions in which each of these are present. Thus, for example, 
 gneiss and mica-schist, so abundant in the Grampians, are wanting 
 in Cumberland, Wales, and Cornwall ; in parts of the Swiss and 
 Italian Alps, the gneiss and granite are talcose, and not micaceous, 
 as in Scotland ; hornblende prevails in the granite of Scotland 
 schorl in that of Cornwall albite in the plu tonic rocks of the 
 Andes common felspar in those of Europe. In one part of Scot- 
 land, the mica-schist is full of garnets; in another it is wholly 
 devoid of them ; while in South America, according to Mr. Darwin, 
 it is the gneiss, and not the mica-schist, which is most commonly 
 garnetiferous. And not only do the proportional quantities of 
 felspar, quartz, mica, hornblende, and other minerals, vary in hypo- 
 gene 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 (p. 467., and table, p. 105.). 
 
 The Metamorphic strata, why less calcareous than the fossiliferous. 
 It has been remarked, that the quantity of calcareous matter in 
 metamorphic strata, or, indeed, in the hypogene formations generally. 
 is far less than in fossiliferous deposits. Thus the crystalline schists 
 of the Grampians in Scotland, consisting of gneiss, mica-schist, 
 hornblende-schist, and other rocks, many thousands of yards in 
 thickness, contain an exceedingly small proportion of interstratified 
 
624 SCARCITY OF LIME [Cn. XXXVII. 
 
 calcareous beds, although these have been the objects of careful 
 search for economical purposes. Yet limestone is not wanting in the 
 Grampians, and it is associated sometimes with gneiss, sometimes 
 with mica-schist, and in other places with other members of the 
 metamorphic series. But where limestone occurs abundantly, as at 
 Carrara, and in parts of the Alps, in connection with hypogene 
 rocks, it usually forms one of the superior members of the crys- 
 talline group. 
 
 The scarcity, then, of carbonate of lime in the plutonic and meta- 
 morphic rocks generally seems to be the result of some general cause. 
 So long as the hypogene rocks were believed to have originated ante- 
 cedently to the creation of organic beings, it was easy to impute the 
 absence of lime to the non-existence of those mollusca and zoophytes 
 by which shells and corals are secreted ; but when we ascribe the 
 crystalline formations to plutonic action, it is natural to inquire 
 whether this action itself may not tend to expel carbonic acid and 
 lime from the materials which it reduces to fusion or semi-fusion. 
 Although we cannot descend into the subterranean regions where 
 volcanic heat is developed, we can observe in regions of spent vol- 
 canos, 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. The quan- 
 tity of calcareous matter which these springs transfer, in the course 
 of ages, from the lower parts of the earth's crust to the superior or 
 newly formed parts of the same, must be considerable.* 
 
 If the quantity of siliceous and aluminous ingredients brought up 
 by such springs were great, instead of being utterly insignificant, it 
 might be contended that the mineral matter thus expelled implies 
 simply the decomposition of ordinary subterranean rocks ; but the 
 prodigious excess of carbonate of lime over every other element must 
 in the course of time, cause the crust of the earth below to be almost 
 entirely deprived of its calcareous constituents, while we know that 
 the same action imparts to newer deposits, ever forming in seas and 
 lakes, an excess of carbonate of lime. Calcareous matter is poured 
 into these lakes and the ocean by a thousand springs and rivers ; so 
 that part of almost every new calcareous rock chemically precipitated, 
 and of many reefs of shelly 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. 
 
 Not only carbonate of lime, but also free carbonic acid gas is given 
 off plentifully from the soil and crevices of rocks in regions of active 
 and spent volcanos as near Naples and in Auvergne. By this pro- 
 cess, 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. That the removal of the cal- 
 careous matter of fossil shells is of frequent occurrence, is proved by 
 the fact of such organic remains being often replaced by silex or 
 
 * See Principles of Geology by the Author, Index, " Calcareous Springs," 
 
CH. XXXVII.] IN METAMORPHIC ROCKS. 625 
 
 other minerals, and sometimes by the space once occupied by the 
 fossil being left empty, or only marked by a faint impression. We 
 ought not indeed to marvel at the general absence of organic re- 
 mains from the crystalline strata, when we bear in mind how often 
 fossils are obliterated, wholly or in part, even in tertiary formations 
 how often vast masses of sandstone and shale, of different ages, 
 and thousands of feet thick, are devoid of fossils how certain strata 
 may first have been deprived of a portion of their fossils when they 
 became semi-crystalline, or assumed the transition state of Werner 
 and how the remaining portion may have been effaced when they 
 were rendered metamorphic. Rocks of the last-mentioned class, more- 
 over, have sometimes been exposed again and again to renewed plu- 
 tonic action. 
 
 S3 
 
626 ' "U& MINERAL VEINS. [Cn. XXXVIII. 
 
 CHAPTER XXXVIH. 
 
 MINERAL VEINS. 
 
 Werner's doctrine that mineral veins were fissures filled from above Veins of 
 segregation 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 
 Eournet's observations in Auvergne Dimensions of veins Why some alter- 
 nately swell out and contract Filling of lodes by sublimation from below 
 Chemical and electrical action Relative age of the precious metals Copper 
 and lead veins in Ireland older than Cornish tin Lead vein in lias, Glamorgan- 
 shire Gold in Russia, California, and Australia. Connection of hot springs 
 and mineral veins Concluding remarks. 
 
 THE manner in which metallic substances are distributed through the 
 earth's crust, and more especially the phenomena of those nearly 
 vertical and tabular masses of ore called mineral veins, from which 
 the larger part of the precious metals used by man are obtained, 
 these are subjects of the highest practical importance to the miner, 
 and of no less theoretical interest to the geologist. 
 
 The views entertained respecting metalliferous veins have been 
 modified, or, rather, have undergone an almost complete revolution, 
 since the middle of the last century, when Werner, as director of the 
 School of Mines, at Freiburg in Saxony, first attempted to generalize 
 the facts then known. He taught that mineral veins had originally 
 been open fissures which were gradually filled up with crystalline 
 and metallic matter, and that many of them, after being once filled, 
 had been again enlarged or reopened. He also pointed out that veins 
 thus formed are not all referable to one era, but are of various geo- 
 logical dates. 
 
 Such opinions, although slightly hinted at by earlier writers, had 
 never before been generally received, and their announcement by one 
 of high authority and great experience constituted an era in the 
 science. Nevertheless, I have shown, when tracing, in another work, 
 the history and progress of geology, that Werner was far behind some 
 of his predecessors in his theory of the volcanic rocks, and less en- 
 lightened than his contemporary, Dr. Hutton, in his speculations as to 
 the origin of granite.* According to him, the plutonic formations, as 
 well as the crystalline schists, were substances precipitated from a 
 chaotic fluid in some primeval or nascent condition of the planet ; 
 
 * Principles of Geology, chap. iv. 
 
CH. XXXVIII.] DIFFERENT KINDS OF MINERAL VEINS. 627 
 
 and the metals, therefore, being closely connected with them, had 
 partaken, according to him, of a like mysterious origin. He also 
 held that the trap rocks were aqueous deposits, and that dikes of por- 
 phyry, greenstone, and basalt, were fissures filled with their several 
 contents from above. Hence he naturally inferred that mineral veins 
 had derived their component materials from an incumbent ocean, 
 rather than from a subterranean source; that these materials had 
 been first dissolved in the waters above, instead of having risen up 
 by sublimation from lakes and seas of igneous matter below. 
 
 In proportion as the hypothesis of a primeval fluid, or " chaotic 
 menstruum," was abandoned, in reference to the plutonic formations, 
 and when all geologists had come to be of one mind as to the true 
 relation of the volcanic and trappean rocks, reasonable hopes began 
 to be entertained that the phenomena of mineral veins might be 
 explained by known causes, or by chemical, thermal, and electrical 
 agency still at work in the interior of the earth. The grounds of 
 this conclusion will be better understood when the geological facts 
 brought to light by mining operations have been described and 
 explained. 
 
 On different kinds of mineral veins. Every geologist is fami- 
 liarly acquainted with those veins of quartz which abound in hypogene 
 strata, forming lenticular masses of limited extent. They are some- 
 times observed, also, in sandstones and shales. Veins of carbonate 
 of lime are equally common in fossiliferous rocks, especially in lime- 
 stones. Such veins appear to have once been chinks or small cavities, 
 caused, like cracks in clay, by the shrinking of the mass, which has 
 consolidated from a fluid state, or has simply contracted its dimensions 
 in passing from a higher to a lower temperature. Siliceous, calca- 
 reous, and occasionally metallic matters have sometimes found their 
 way simultaneously into such empty spaces, by infiltration from the 
 surrounding rocks, or by segregation, as it is often termed. Mixed 
 with hot water and steam, metallic ores may have permeated a pasty 
 matrix until they reached those receptacles formed by shrinkage, and 
 thus gave rise to that irregular assemblage of veins, called by the 
 Germans a " stockwerk," in allusion to the different floors on which 
 the mining operations are in such cases carried on. 
 
 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 hypogene and 
 fossiliferous, and extend downwards to indefinite or unknown depths. 
 We may assume that they correspond with such rents as we see 
 caused from time to time by the shock of an earthquake. Metal- 
 liferous veins, referable to such agency, are occasionally a few inches 
 wide, but more commonly 3 or 4 feet. They hold their course con- 
 tinuously in a certain prevailing direction for miles or leagues, 
 passing through rocks varying in mineral composition. 
 
 That metalliferous veins were fissures. As some intelligent miners, 
 after an attentive study of metalliferous veins, have been unable to 
 
 882 
 
628 
 
 OEIGIN OF 
 
 [Cn. XXXVIII. 
 
 Fig. 710. 
 
 reconcile many of their characteristics with the hypothesis of fissures, 
 
 I shall begin by stating 
 the evidence in its fa- 
 vour. The most striking 
 fact perhaps which can 
 be adduced in its sup- 
 port is, the coincidence 
 of a considerable pro- 
 portion of mineral veins 
 ~w\t\*. faults, or those dis- 
 locations of rocks which 
 are indisputably due to 
 mechanical force, as 
 above explained (p. 61,). 
 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 
 metallic substances,have 
 suffered displacement. 
 e Thus, for example, sup- 
 pose a a, fig. 710., to be 
 a tin lode in Cornwall, 
 the term lode being ap- 
 plied to veins contain- 
 ing metallic ores. This 
 lode, running east and 
 west, is a yard wide, 
 and is shifted by a 
 copper lode (b b\ of 
 similar width. 
 
 The first fissure (a a) 
 has been filled with 
 various materials, partly 
 
 Vertical sections of the mine of Huel PeeveT, Redruth, Cornwall. f chemical 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 ver- 
 tical 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. 
 
 Fig. 7 12. 
 
CH. XXXVIII.] METALLIFEROUS VEINS. 629 
 
 This new opening was then filled with minerals, some of them re- 
 sembling those in a a, as fluor-spar (or fluate of lime) and quartz ; 
 others different, the copper being plentiful and the tin wanting or 
 very scarce. 
 
 We must next suppose the shock of a third earthquake to occur, 
 breaking asunder all the rocks along the line c c, fig. 711.; the 
 fissure, in this instance, being only 6 inches wide, and simply filled 
 with clay, derived, probably, from the friction of the walls of the 
 rent, or partly, perhaps, washed in from above. This new move- 
 ment has heaved the rock in such a manner as to interrupt the con- 
 tinuity 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 previously been broken. 
 
 Again, in fig. 712. we see evidence of a fourth fissure (d d), also 
 filled with clay, which has cut through the tin vein (a a), and has 
 lifted it slightly upwards 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 c, fig. 712., extends through a space of no less than 84 feet; but 
 in this, as in the case of the other three, it will be seen that the 
 outline of the country above, d, c, b, , &c., or the geographical 
 features of Cornwall, are not affected by any of the dislocations, a 
 powerful denuding force having clearly been exerted subsequently 
 to all the faults. (See above, p. 69.) It is commonly said in Corn- 
 wall, that there are eight distinct systems 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 hardness. These smoothed surfaces resemble 
 the rocky floor over which a glacier has passed (see fig. p. 128). 
 They are common even in cases where there has been no shift, and 
 occur equally in non-metalliferous fissures. They are called by 
 miners " slicken-sides," from the German schlichten, to plane, and seite, 
 side. It is supposed that the lines of the striae indicate the direction 
 in which the rocks were moved. During one of the minor earth- 
 quakes in Chili, which happened about the year 1840, and was de- 
 scribed to me by an eye-witness, 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 remained uninjured, 
 and without any opening, although the line of each crack was still 
 visible. When all movement had ceased, there were seen on the 
 
 * Geol. Trans, vol. iv. p. 139.; Trans. Roy. Geol. Society, Cornwall, vol. ii. p. 90. 
 
 S 3 3 
 
630 SUCCESSIVE ENLARGEMENTS [Cn. XXXVIII. 
 
 floor of the house, at the bottom of each rent, small heaps of fine 
 brickdust, evidently produced by trituration. 
 
 In some of the veins in the mountain limestone of Derbyshire, con- 
 taining 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, 
 especially 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 6 inches apart, and 4 inches deep, and on his return in a 
 few hours finds every part ready broken to his hand.* These pheno- 
 mena and their causes (probably connected with electrical action) 
 seem scarcely to have attracted the notice which they deserve. 
 
 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. In Bohemia, 
 such pebbles have been met with at the depth of 180 fathoms. In 
 Cornwall, Mr. Carne mentions true pebbles of quartz and slate in a 
 tin lode of the Relistran Mine, at the depth of 600 feet below the 
 surface. They were cemented by oxide of tin and bisulphuret of 
 copper, and were traced over a space more than 12 feet long and as 
 many wide.f Marine fossil shells, also, have been found at great 
 depths, having probably been engulphed during submarine earth- 
 quakes. Thus, a gryphaea 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 Hungary. ^ 
 
 When different sets or systems of veins occur in the same country, 
 those which are supposed to be of contemporaneous origin, and which 
 are filled with the same kind of metals, often maintain a general 
 parallelism of direction. Thus, for example, both the tin and copper 
 veins in Cornwall run nearly east and west, while the lead-veins run 
 north and south ; but there is no general law of direction common to 
 different mining districts. The parallelism of the veins is another 
 reason for regarding them as ordinary fissures, for we observe that 
 contemporaneous trap dikes, admitted by all to be masses of melted 
 matter which have filled rents, are often parallel. Assuming, then, 
 that veins are simply fissures in which chemical and mechanical 
 deposits have accumulated, we may next consider the proofs of their 
 having been filled gradually and often during successive enlarge- 
 ments. I have already spoken of parallel layers of clay, quartz, and 
 ore. Werner himself 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 
 
 * Conyb. and Phil. Geol. p. 401.; and J Fournet, Etudes sur les Depots 
 Farcy's Derbysh. p. 243. Metalliferes. 
 
 f Carne, Trans, of Geol. Soc. Corn- 
 wall, vol. iii. p. 238. 
 
CH. XXXVIII.] AND FILLING UP OF VEINS. 631 
 
 formed of two beds of calcareous spar, which had evidently lined 
 the opposite walls of a vertical cavity. The thirteen beds followed 
 each other in corresponding order, consisting of fluor-spar, heavy 
 spar, galena, &c. In these cases, the central mass has been last 
 formed, and the two plates which coat the outer walls of the rent 
 on each side are the oldest of all. If they consist of crystalline pre- 
 cipitates, they may be explained by supposing the fissure to have 
 remained 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 veinstone consist of crystalline matter, the points of the 
 crystals are always turned inwards, or towards the centre of the 
 vein ; in other words, they point in that direction where there was 
 most 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 crystals the one into the other. But in Cornwall, 
 some lodes occur 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 fol- 
 lowing curious and instructive example (fig. 713.) from a copper-mine 
 
 Granite ' 
 
 / \ N 
 / 
 
 Copper lode, near Redruth, enlarged at six successive periods. 
 
 in granite, near Redruth.* Each of the plates or combs (a, b, c, d, 
 ,/) are double, having the points of their crystals turned inwards 
 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 moderate 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 numbers 
 of other cases, where clay, sand, or angular detritus alternate with 
 ores and veinstones. Thus, we may imagine the sides of a fissure to 
 be encrusted with siliceous matter, as Von Buch observed, in Lan- 
 cerote, the walls of a volcanic crater formed in 1731 to be traversed 
 by an open rent in which hot vapours had deposited hydrate of 
 * Geol. Rep. on Cornwall, p. 340. 
 
 S S 4 
 
632 SWELLING OUT AND [Cn. XXXVIII. 
 
 silica, the incrustation nearly extending to the middle.* Such a 
 vein may then be filled with clay or sand, and afterwards re-opened, 
 the new rent dividing 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 demonstrated by 
 occasional cross-veins, implying the oblique fracture of previously 
 formed chemical and mechanical deposits. Thus, for example, 
 M. Fournet, in his description of some mines in Auvergne worked 
 under his superintendence, observes 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 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 veinstones. Polished 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, by 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 other sets of mineral 
 deposits, until, at last, pebbles of the basaltic lavas of Auvergne, 
 derived from superficial alluviums, probably of Miocene or older 
 Pliocene date, were swept into the veins. I have not space to 
 enumerate all the changes minutely detailed by M. Fournet, but 
 - they are valuable, both to the miner and geologist, as showing how 
 the supposed signs of violent catastrophes may be the monuments, 
 not of one paroxysmal shock, but of reiterated movements. 
 
 Such repeated enlargement and re-opening of veins might have 
 been anticipated, 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 anywhere else. It is 
 quite otherwise in the case of dikes, where each opening has been 
 the receptacle of one continuous and homogeneous mass of melted 
 matter, the consolidation of which has taken place under consi- 
 derable pressure. Trappean dikes can rarely fail to strengthen the 
 rocks at the points where before they were weakest ; and if the up- 
 heaving force is again exerted in the same direction, the crust of the 
 earth will give way anywhere rather than at the precise points 
 where the first rents were produced. 
 
 A large proportion of metalliferous veins have their opposite walls 
 nearly parallel, and sometimes over a wide extent of country. There 
 
 * Principles, ch. xxvii. 8th ed. p. 422. 
 
CH. XXXVIII.] CONTRACTION OF VEINS. 633 
 
 is a fine example of this in the celebrated vein of Andreasburg in 
 the Hartz, which has been worked for a depth of 500 yards perpen- 
 dicularly, and 200 horizontally, retaining almost every where a 
 width of 3 feet. But many lodes in Cornwall and elsewhere are 
 extremely variable in size, being 1 or 2 inches in one part, and then 
 8 or 10 feet in another, at the distance of a few fathoms, and then 
 again narrowing as before. Such alternate swelling 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 their entire course, nor could we well expect 
 them to be so, since they commonly pass through rocks of unequal 
 hardness and difierent mineral composition. If, therefore, the op- 
 posite sides of such irregular fissures slide upon each other, that is 
 to say, if there be a fault, as in the case of so many mineral veins, 
 the parallelism of the opposite walls is at once entirely destroyed, as 
 will be readily seen by studying the annexed diagrams. 
 
 Fig. 714. 
 
 Let a b, fig. 714., be a line of fracture traversing a rock, and let 
 a b, fig. 715., represent the same line. Now, if we cut a piece of 
 paper representing this line, and then move the lower portion of 
 this cut paper sideways from a to a', taking care that the two pieces 
 of paper still touch each other at the points 1, 2, 3, 4, 5, we obtain 
 an irregular aperture at c, and isolated cavities at ddd, and when 
 we compare such figures with nature we find that, with certain 
 modifications, they represent the interior of faults and mineral veins. 
 If, instead of sliding the cut paper to the right hand, we move the 
 lower f>art 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, ff, fig. 716., 
 being then formed. This will serve to show to what slight cir- 
 cumstances considerable variations 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 varying from 15 to 45. 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, 
 
634 CHEMICAL DEPOSITS IN VEINS. [Cn. XXXVIII. 
 
 Fig. 717. % 717., the miner complains that the ores are 
 "nipped," or greatly reduced in quantity, the space 
 for their free deposition having been interfered with in 
 consequence of the pre-occupancy of the lode by earthy 
 materials. When lodes are many fathoms wide, they 
 are usually filled for the most part with earthy matter, 
 and fragments of rock, through which the ores are 
 much 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 instrumental in the pro- 
 duction of mineral veins, it may be remarked that those parts of 
 fissures which were not choked up 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 of volcanos and earthquakes, have made their way to the 
 surface. For we know that the rents in which ores abound extend 
 downwards 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 for- 
 mations, especially where the former send veins into the latter, a 
 circumstance which indicates an original proximity of veins at their 
 inferior extremity to igneous and heated rocks. It is moreover ac- 
 knowledged that even those mineral and thermal springs which, in 
 the present state of the globe, are far from volcanos, are neverthe- 
 less observed to burst out along great lines of upheaval and dislo- 
 cation of rocks.* It is also ascertained that all the substances with 
 which hot springs are impregnated agree with those discharged in a 
 gaseous form from volcanos. 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 con- 
 traction 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 reduction in volume 
 amounting to 10 per cent. The slow crystallization, 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 different foundation, so as to remain unmoved. 
 
 Although we are led to infer, from the foregoing reasoning, that 
 there has often been an intimate connection between metalliferous 
 
 * See Dr. Daubeny's Volcanos. 
 
CH. XXXVTII.] CHEMICAL DEPOSITS IN VEINS. 635 
 
 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 Beau- 
 mont 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 waters ascending from below would first precipitate on the 
 walls of a fissure, as soon as their temperature began slightly to 
 diminish. The higher they mount towards the surface, the more 
 will they cool, till they acquire the average temperature of springs, 
 being in that case chiefly charged with the most soluble substances, 
 such as the alkalis, soda and potash. These are not met with in 
 veins, although they enter so largely into the composition of granitic 
 rocks.* 
 
 To a certain extent, therefore, the arrangement and distribution of 
 metallic matter in veins may be referred to ordinary chemical action, 
 or to those variations in temperature, which waters holding the ores 
 in solution must undergo, as they rise upwards 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 containing ores of lead, zinc, and copper, but chiefly lead, 
 traverse alternate 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 greenstone, or 
 "toad-stone," as it is called provincially. Not that the original 
 fissure is narrower where the greenstone occurs, but because more 
 of the space is there filled with veinstones, 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 respect 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. The same observation applies to killas and the 
 granitic porphyry called elvan. Sometimes, in the same continuous 
 vein, the granite will contain copper, and the killas tin, or vice 
 versa" f Mr. Fox, after ascertaining the existence at present of 
 electric currents in some of the metalliferous veins in Cornwall, has 
 speculated on the probability of the same cause having acted origin- 
 ally on the sulphurets and muriates of copper, tin, iron, and zinc, 
 dissolved in the hot water of fissures, so as to determine the peculiar 
 mode of their distribution. After instituting experiments on this 
 subject, he even endeavoured to account for the prevalence of an 
 east and west direction in the principal Cornish lodes by their posi- 
 tion at right angles to the earth's magnetism; but Mr. Kenwood 
 and other experienced miners have pointed out objections to the 
 theory ; and it must be owned that the direction of veins in different 
 
 * Bulletin, iv. p. 1278. f & W. Fox on Mineral Veins, p. 10. 
 
636 RELATIVE AGE OF METALS. [Cn. XXXVIII. 
 
 mining districts varies so entirely that it seems to depend on lines of 
 fracture, rather than on the laws of voltaic electricity. Neverthe- 
 less, as different kinds of rock would be often in different electrical 
 conditions, we may readily believe that electricity must often govern 
 the arrangement of metallic precipitates in a rent. 
 
 " I have observed," says Mr. R. Fox, " that when the chloride of 
 tin in solution is placed in the voltaic circuit, part of the tin is de- 
 posited in a metallic state at the negative pole, and part at the positive 
 one, in the state of a peroxide, such as it occurs in our Cornish 
 mines. This experiment may serve to explain why tin is found con- 
 tiguous to, and intermixed with, copper ore, and likewise separated 
 from it, in other parts of the same lode." * 
 
 Relative age of the different metals. After duly reflecting on the 
 facts above described, we cannot doubt that mineral veins, like erup- 
 tions of granite or trap, are referable to many distinct periods of the 
 earth's history, although 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 exclusively 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 arrangement 
 can be recognised in the position of the precious and other metals in 
 the earth's crust. 
 
 In the first place, it is not true that veins in which tin abounds 
 are the oldest lodes worked in Great Britain. The government sur- 
 vey 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 geological changes has occurred at two distinct 
 epochs, in Wexford, before the Devonian strata were deposited ; 
 in Cornwall, after 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 were 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 copper and lead were produced, being of a date cer- 
 tainly posterior 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 
 
 * B. W. Fox on Mineral Veins, p. 38. 
 
OH. XXXVIII.] RELATIVE AGE OF METALS. 637 
 
 Devonian, not far from points, where mines of copper are worked in 
 the Silurian strata.* 
 
 Although the precise age of such copper lodes cannot be defined, 
 we may safely amrm 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 primary 
 metalliferous veins. A few fragments also of tin found in Wicklow 
 in the drift are supposed to have been derived from veins of the 
 same age.f 
 
 Next, if we turn to Cornwall, we find there also the monuments 
 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. 692., p. 574.), penetrating 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 fissures of different ages already alluded to, p. 629. Here, then, 
 the tin lodes are newer than the elvans. It has indeed been stated 
 by some Cornish miners that the elvans are in some few 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 cases referred to in corroboration can 
 be otherwise interpreted.^ We may, therefore, assert that the most 
 ancient Cornish lodes are younger than the coal-measures of that 
 part of England, and it follows that they are of a much later date 
 than the Irish copper and lead of Wexford and some adjoining 
 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 
 of the Poikilitic group, which overlies the coal in the south-west of 
 England. 
 
 There are lead veins in the Mendip hills which extend through 
 the mountain limestone into the Permian or Dolomitic conglomerate, 
 and others in Glamorganshire which enter the lias. Those worked 
 near Frome, in Somersetshire, have been traced into the Inferior 
 Oolite. In Bohemia, the rich veins of silver of Joachimsthal cut 
 through basalt containing olivine, which overlies tertiary lignite, in 
 which are leaves of dicotyledonous trees. This silver, therefore, is 
 decidedly a tertiary formation. In regard to the age of the gold of 
 the Ural Mountains, in Russia, which, like that of California, is ob- 
 tained chiefly from auriferous alluvium, it occurs in veins of quartz 
 in the schistose and granitic rocks of that chain, and is supposed by 
 MM. Murchison, De Verneuil, and Keyserling to be newer than the 
 syenitic granite of the Ural perhaps of tertiary date. They ob- 
 
 * I am indebted to Sir H. De la Beche f Sir H. De la Beche, MS. notes on 
 for this information. See also maps and Irish Survey. 
 
 sections of Irish Survey. J Report on Geology of Cornwall, 
 
 p. 310, 
 
638 GOLD OF AUSTRALIA. [Cn. XXXVIII. 
 
 serve, that no gold has yet been found in the Permian conglomerates 
 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 Uralian quartz veins, con- 
 taining gold and platinum, were not formed or certainly not exposed 
 to aqueous denudation during the Permian era. 
 
 In the auriferous alluvium of Russia, California, and Australia, the 
 bones of extinct land-quadrupeds have been met with, those of the 
 mammoth being common in the gravel at the foot of the Ural Moun- 
 tains, while in Australia they consist of huge marsupials, some of them 
 of the size of the rhinoceros 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 Hornos 
 with copper pyrites, in veins traversing the cretaceo-oolitic forma- 
 tions, so called because its fossils have the character partly of the 
 cretaceous and partly of the oolitic fauna of Europe.* The gold 
 found in the United States, in the mountainous parts of Virginia, 
 North and South Carolina, and Georgia occurs in metamorphic Silu- 
 rian strata, as well as in auriferous gravel derived from the same. 
 
 Gold has now been detected in almost every kind of rock, in slate, 
 quartzite, sandstone, limestone, granite, and serpentine, both in veins 
 and in the rocks themselves at short distances from the veins. In Aus- 
 tralia it has been worked successfully not only in alluvium, but in 
 veinstones in the native 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 the 30 and 39 S.), 
 and over twelve of longitude, and yields already 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 ex- 
 haustion of the gold fields. It seems reasonable, therefore, to share 
 the anticipations of M. Delesse that the time will come, and cannot 
 be very remote, when a marked depreciation will be experienced in 
 the value of this metal.f 
 
 It has been remarked by M. de Beaumont, that lead and some 
 other metals are found in dikes of basalt and greenstone, as well as 
 in mineral veins connected with trap rocks, whereas tin is met with 
 in granite and in veins associated with the granitic series. If this 
 rule hold true generally, the geological position of tin in localities 
 accessible to the miners will belong, 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 for- 
 mations or 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 
 
 * Darwin's S. America, p. 209., &c. f Annales des Mines, 1853, torn. iii. 
 
 p. 185. 
 
CH. XXXVIII.] CONCLUDING REMARKS. 639 
 
 metals, it will follow that those formed farthest from the surface will 
 usually require the longest time before they can be exposed super- 
 ficially. In order to bring them into view, or within reach of the 
 miner, a greater amount of upheaval and denudation must take place 
 in proportion as they have lain deeper when first moved. A con- 
 siderable series of geological revolutions must intervene before any 
 part of the fissure, which has been for ages in the proximity of the 
 plutonic rocks, 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 subject, as the reader will remember what was said in the 
 30th, 34th, and 37th chapters, on the chronology of the volcanic and 
 hypogene formations. 
 
 Concluding Remarks. The theory of the origin of the hypogene 
 rocks, at a variety of successive periods, as expounded in two of the 
 chapters just cited, and still more the doctrine that such rocks may 
 be now in the daily course of formation, has made and still makes its 
 way, but slowly, into favour. The disinclination to embrace it has 
 arisen partly from an inherent obscurity in the very nature of the 
 evidence of plutonic action when developed on a great scale, at par- 
 ticular periods. It has also sprung, in some degree, from extrinsic 
 considerations ; many geologists having been unwilling to believe the 
 doctrine of transmutation of fossiliferous into crystalline rocks, 
 because they were desirous of finding proofs of a beginning, and of 
 tracing back the history of our terraqueous system to times anterior 
 to the creation of organic beings. But if these expectations have been 
 disappointed, if we have found it impossible to assign a limit to that 
 time throughout which it has pleased an Omnipotent and Eternal 
 Being to manifest his creative power, we have at least succeeded 
 beyond all hope in carrying back our researches to times antecedent 
 to the existence of man. We can prove that man had a beginning, 
 and that, all the species now contemporary with man, and many others 
 which preceded, had also a beginning, and that, consequently, the 
 present state of the organic world has not gone on from all eternity, 
 as some philosophers have maintained. 
 
 It can be shown that the earth's surface has been remodelled again 
 and again ; mountain chains have been raised or sunk ; valleys formed, 
 filled up, and then re-excavated ; sea and land have changed places ; 
 yet throughout all these revolutions, and the consequent alterations of 
 local and general climate, animal arid vegetable life has been sus- 
 tained. This has been accomplished without violation of the laws 
 now governing the organic creation, by which limits are assigned to 
 the variability of species. The succession of living beings appears 
 to have been continued not by the transmutation of species, but by 
 the introduction into the earth from time to time of new plants and 
 animals, and each assemblage of new species must have been ad- 
 mirably fitted for the new states of the globe as they arose, or they 
 
640 CONCLUDING REMARKS. [Cn. XXXVIII. 
 
 would not have increased and multiplied and endured for indefinite 
 ^periods.* 
 
 Astronomy has been unable to establish the plurality of habitable 
 worlds throughout space, however favourite a subject of conjecture 
 and speculation ; but geology, although it cannot prove that other 
 planets are peopled with appropriate races of living beings, has de- 
 monstrated the truth of conclusions scarcely less wonderful, the 
 existence on our own planet of so many habitable surfaces, or worlds 
 as they have been called, each distinct in time, and peopled with its 
 peculiar races of aquatic and terrestrial beings. 
 
 The proofs now accumulated of the close analogy between extinct 
 and recent species are such as to leave no doubt on the mind that 
 the same harmony of parts and beauty of contrivance which we 
 admire in the living creation has equally characterized the organic 
 world at remote periods. Thus as we increase our knowledge of the 
 inexhaustible variety displayed in living nature, and admire the in- 
 finite wisdom and power which it displays, our admiration is multi- 
 plied by the reflection, that it is only the last of a great series of pre- 
 existing creations, of which we cannot estimate the number or limit 
 in times past.f 
 
 * See Principles of Geol., Book 3. the Geol. Soc. 1837. Proceedings G 
 
 f See the author's Anniv. Address to S. vol. ii. p. 520. 
 
INDEX. 
 
 [The Fossils, the names of which are printed in Italics, are figures in the volume.'] 
 
 ABICH, M., on trachytic rocks, 471. 
 Acrodus nobilis, tooth of, 322. 
 Acrolepis Sedgwickii, scale of, 357. 
 Act&on acutus, great oolite, 309. 
 Actinolite-schist, 597. 
 JEchmodus, scales and outline of, 322. 
 JEgean Sea, mud of, 35. 
 
 , animal life in depths of, 137. 
 
 JEpiornis of Madagascar, 350. 
 
 Agglomerate, volcanic rock, 475, 476. 
 
 Agnostus integer, A. rex, 454. 
 
 Agassiz, M., cited, 87. 218. 322. 351. 400. 419. 422. 
 
 , on fossil fishes of molasse and faluns, 171. 
 
 , on fossil fish of lias, 321. 
 
 ., on fossil fish in Permian marl-slate, 356. 
 
 , on fish from Sheppey, 218. 
 
 , on foot-prints, 350. 
 
 , on fishes of brown-coal, 545. 
 
 , on glaciers, 547. 550. 
 
 Age, test of, by fragments of older rock, 102. 
 
 of metamorphic rocks, 618. 
 
 , test of, in plutonic rocks, 579. 
 
 , of Spanish volcanos, 541. 
 
 , of volcanic rocks, how tested, 523. 526. 
 
 Air-breathers in coal, rarity of, 405. 
 
 Aix-la-Chapelle, hot springs at, 602. 
 
 Alabama, creiaceous shingle of, 256. 
 
 Alabaster defined, 13. 
 
 Albert! on the Keuper, 335. 
 
 Alexander, Capt., marine shells in crag found by, 156. 
 
 Alluvium, term explained, 79. 
 
 , formation of, 81. 
 
 in Auvergne, 80. 
 
 Alpine blocks on the Jura, 149. 
 
 erratics, 147. 
 
 Alps, curved strata of, 58. 
 
 , elevated fossiliferous rocks in, 4. 
 
 , nummulitic formation of, 231. 
 
 , of Switzerland, 620. 
 
 , Swiss and Savoy, cleavage of, 608. 
 
 Altered rocks, 483. 
 
 by subterranean gases, 602. 
 
 Alternations of rocks, 14. 
 
 of marine and freshwater formations, 32. 
 Alum-schists, Silurian, of Sweden, 455. 
 Alumine in rocks, 11. 
 
 Amblyrhynchus cristatus (recent), 326. 
 
 America, North, Lithodomi in beaches of, 78. 
 
 , South, cretaceous strata, 256. 
 
 , South, fossils of, 164. 
 
 , South, gradual rise of parts of, 46. 
 
 Ammonites bifrons, A. Nodotianus, ?, A. striatttlus, 
 A. Walcottii, 320 ; A. Braikenridgii, A. margari- 
 talus, A. Slokesii, A. striatulus, 317 ; A. Elizabeths, 
 A. Jason, 305 ,A. Humphresianus, 316 ; A. Rho- 
 tomagensis, 252. 
 
 Ampelite, or aluminous slate, 597. 
 
 Amphibole, 469. 
 
 Amphibolite, or hornblende rock, 476. 597, 
 Amphistegina Hauerina, eocene, 180. 
 Amphitherium Broderipii, jaw of, 312. 
 
 Prevostii, jaw of, 312 
 
 Ampullaria glauca (recent), 30. 
 Amsterdam, or St. Paul Island, 512. 
 Amygdaloid, 472. 
 Ananchytes ovatus, chalk, 244. 
 Ancillaria suhulata, eocene, 31 . 
 Ancyloceras gigas, 259 ; A. spinigerum, 252. 
 Ancylus elegans, pleistocene, 29. 
 Andelys, chalk-cliffs at, 269. 
 Andernach, strata near, 545. 
 Andes, plutonic rocks of, 583. 
 
 , rocks drifted from, to Chiloe, 151. 
 
 Andesite, 471. 
 
 Anodonta Cordierii, A. latimarginatus (recent), 28. 
 
 Anoplotherium commune, tooth of, 21 1 . 
 
 gracile, outline of, 226. 
 
 Anthophyllum lineatum, 183. 
 Anlholithes, coal, 374. 
 Anthracite in Rhode Island, 604. 
 Anticlinal line, 48. 57. 
 Antrim basalt, age of, 181. 
 
 , rocks altered by dikes in, 484. 
 
 Antwerp, strata like Suffolk crag near, 174. 
 
 Apateon pedestris, a carboniferous reptile, 400. 
 
 Aphanite, or cornean, 476. 
 
 Apennines, limestone in 482. 
 
 Appalachian coal-field, 393. 
 
 Appalachians, altered rocks in, 604. 
 
 Apiocriniles rotundus, oolite, 307. 
 
 Aptychus latvs, oolite, 303. 
 
 Apteryx in New Zealand, 165. 
 
 Apusf dubius, coal, 388. 
 
 Aqueous rocks defined, 2. 
 
 rocks, mineral character of, 98. 
 
 deposits, superposition of, 97. 
 
 Aralo-Caspian formations, 176. 
 Arbroa h paving-stone, 419. 
 
 , section from, to the Grampians, 48. 
 
 Archegosaurus medius, skin of, A. minor, coal-mea- 
 sures, 401. 
 Archiac, M. d', cited, 150. 
 
 ,on fossils in chalk, 252. 
 
 , on shells in French lower eocene, 229. 
 
 Ardeclie, lava in, 488. 
 Arenaceous rocks described, 11. 
 Argillaceous rocks, 11. 
 
 schist, 596. 
 
 Argile plastique, or lower eocene, 230. 
 
 Argvleshire, trap- vein in cliff, 481. 
 
 Argyll, Duke of, on Isle of Mull tertiaries, 180. 
 
 Arkose, 597. 
 
 Arran.age of granite in, 589. 
 
 , section of, 591. 
 
 TT 
 
642 
 
 INDEX. 
 
 Arran, dike of greenstone in, 481. 
 Arrangement of fossils in strata, 5. 21. 
 Arthur's Seat, altered strata of, 485. 
 Arvicola, tooth of, 168. 
 Asapkus tyranntts, lower Silurian, 444. 
 Aspidura loricata, Permian, 336. 
 Astarte bipartite, A. Omalif, 172. 
 
 borealis, 131 ; A. Laurentiana, 141. 
 
 As teropkyllites folios n, coal, 369. 
 
 Astrangia lineuta, 183. 
 
 Astropecten crispatus, eocene, 219. 
 
 Athyris navicula, Aymestry, 435. 
 
 Ashby-de.la-Zouch, fault in coal-field of, 69. 
 
 Ascension, lamination of volcanic rocks in, 613. 
 
 Asti, formations at, 175. 
 
 Atherfield, cretaceous strata of, 258. 
 
 Atrium of a volcano, 506. 
 
 Atrypa retfcularis, Aymestry, 438. 
 
 Aturia zt'czac, London clay, 219. 
 
 Augite, 470. 
 
 Aulopora seipens, Devonian, 426. 
 
 Auricula (recent), 219. 
 
 Aurillac, freshwater strata of, 205. 
 
 Austen, Mr. R. A. G., on phosphate of lime, 252. 
 
 , on upper gre*-n-sand, 251. 
 
 Australia, auriferous gravel of, 638. 
 
 , cave-breccias of, 162. 
 
 , extinct mammals in auriferous gravel of, 638. 
 
 Auvergne, freshwater formations, 203. 
 , succession of changes in, 197. 
 
 , lacustrine strata, 200. 
 
 , mineral veins of, 632. 
 
 , indusial limestone, of 202. 
 
 , extinct volcanos of, 550. 
 
 , alluvium in, 80. 
 
 Aveline, Mr., on Caradoc sandstone, 442. 
 Avicula cygm'pes, A. irxequivalvis, 318. 
 
 papyracea, 389 ; A. socialis, 336. 
 
 Aviculopecten sublohatus, carboniferous, 410. 
 Axinus angulatus, London clay, 219. 
 Aymestry limestone, 437. 
 
 BACILLARIA, fossil in tripoli, 25. I j 
 
 vulgaris ?, in tripoli, 25. 
 
 Bacnlites anceps, B. Faujassii, 246. 
 
 Bagshot sands, 215. 
 
 Bahia Blanca, fossil remains at, 155. 
 
 Baiae, Bay of, strata in, 529. 
 
 Bakewell, Mr., on cleavage in the Alps, 608. 
 
 Bala, lower Silurian rocks at, 445. 
 
 Balcena emarginata, tympanic bone of, 174. 
 
 Batgray, near Glasgow, stumps of trees in coal, 375. 
 
 Baltic, brackish water strata on coast of, 120. 
 
 Barrande, M., on Bohemian Silurian rocks, 445. 
 
 , on primordial fauna, 447. 
 
 , on trilobites, 445. 
 
 Barton clay described, 213. 
 
 Barcombe, chalk-flint gravel near, 287. 
 
 Bastlosaurus cetoides, 234. 
 
 Basterot, M. de, on tertiaries of south of France, 111. 
 
 Basalt, 6.470. 
 
 -, columnar, in the Eifel, 489. 
 
 , columnar, near Vicenza, 488. 
 
 . columnar, of Giants' Causeway, 6. 
 
 , columnar, structure of, 487. 
 
 Basset, term explained, 56. 
 
 Batrachian, eggs of ?, in old red, Scotland, 421. 
 
 Bats, teeth of, 220. 
 
 Bayfield, Capt., on fossil shells in Canada, 134. 
 
 , or inland cliffs in Gulf of St. Lawrence, 78. 
 
 Bean, Mr., on Norwich crag shells in Yorkshire, 156. 
 
 , on fossil shells from oolite, 315. 
 
 Beachy Head, chalk-cliffs near, 276. 
 
 Beaumont, M. E. de, on rocks of Hautes Alpes, 455. 
 
 , on lamination of volcanic rocks, 480. 
 
 , on pisolitic limestone, 237. 
 
 , on Swiss Alps, 583. 
 
 Beaumont, M. E. de, on quartz, 68. 
 
 , on oolite formation in France, 253. 
 
 , on Wealden island, 282. 
 
 Beck, Dr., cited. 202. 213. 
 
 , on graptolites, 445. 
 
 Belemnites hastatus, 305 ; B. mvcronatta, 246. ! 
 
 Puzosianvs, Oxford clay, 306. 
 
 Bellerophoncostatus, carboniferous, 411. 
 
 Belosepia sepioidea. eocene, 219. 
 
 Bembridge or Binstead beds, Isle of Wight, 194. 209. 
 
 Berenicea diluviana, oolite, 308. 
 
 Berger, Dr., on rocks altered by dikes, 484. 
 
 Bergmann on trap. 464. 
 
 Berlin, tertiary strata near, 190. 
 
 Bermuda Islands, lagoons in, 241. 
 
 , rocks of, 78. 
 
 Bernese Alps, gneiss in, 621. 
 
 Berthier, M., on augite and hornblende, 4G8. 
 
 Beudant, M., on Hungary, 549. 
 
 Beyrich, M. on Berlin tertiaries, 190. 
 
 , on North German tertiaries, 179. 
 
 Biaritz, calcareous cliffs of, 72. 
 Bilin tripoli, composed of Infusoria, 25. 
 Binney, Mr., on Stigmaria and Sigjllaria, 370. 
 Bird, bone of, in lower eocene beds, 462. 
 
 , footprints of, 348. 
 
 , fossil, scarcity of, 462. 
 
 Bischoff, Prof., experiments on heat, 601. 
 
 , on steam at a high temperature, 602. 
 
 Blackdown beds, equivalent, of gault, 252. 
 Blainville, on number of genera of rnollusca, 28. 
 Boase, Dr., cited, 605. 
 Boblaye, M., on inland cliffs, 73. 
 
 , cited, 560. 
 
 Bog-iron-ore, 26. 
 
 Bohemia, Silurian rocks of, 454. 
 
 Bolderberg, in Belgium, miocene or falunian strata 
 
 of, 179. 
 Bone-bed of fish-remains in Armagh, 413. 
 
 , Silurian, 435. 
 
 Bone-beds, usually contain rolled bones, 458. 
 Boom and Rupelmonde, 189. 
 Bordeaux, falunian strata near, 179. 
 
 , tertiary deposits of, 179. 
 
 Borrowdale, black-lead of, 38. 
 
 Bosquet, M., on Kleyn Spawen tertiary shells, 135. 
 
 , on Maastricht beds, 238. 
 
 Bos taurus, tooth of, 167. 
 
 Boston, U. S., recent strata in morass, upraised and 
 
 bent, 136. 
 
 Bothnia, Gulf of, land upheaved, 45. 
 Bone, M., on arrangement of rocks, 96. 
 
 , on fossil shells in Hungary, 549. 
 
 , on Carrara marble, 619. 
 
 , on Swiss Alps, 621. 
 
 Bonelli, on strata in Italy, 112. 
 Boulder formation in Canada. 140. 
 , mineral ingredients of, 132. 
 
 in England, 126. 137. 
 
 , period, fauna of, 132. 
 
 Boulders, 129. 
 
 , striated, 143. 
 
 Boutigny, M., cited, '570. 
 
 Bowen, Lieut. A., R.N., drawings of rocks in Gulf 
 
 of St. Lawrence, 78. 
 
 Bowerbank. Mr., on fossil flora of Sheppey, 217. 
 Bowman, Mr., on coal-seams, 395. 
 Bracklesham Bay, characteristic shells of, 215. 
 Bradford encrinites, 308. 
 Brash, term, explained, 81. 
 Bravard, M., on Auvergne mammalia, 204.425. 
 Brazil, ossiferous caves in, 165. 
 Breccia on ant ient coast-lines, 73. 
 Brickenden, Captain, on Elgin fossils, 417. 
 Brighton, elephant-bed of, 288. 
 Bristol, dolomitic conglomerate near, 357. 
 , section of strata near, 103. 
 
INDEX. 
 
 643 
 
 Brocchi, on Subapennines, 111. 174. 
 Brockedon, Mr., on black-lead, 38. 
 Broderip, Mr., cited, 313. 
 Brodie, Rev. P. B , on fossil insects, 301. 328. 
 
 , Mr. W. R., Purbeck mammifer found by, 
 
 Bromley, oyster-bed near, 221. 
 
 Brongniart, M. Adolphe, on Eocene flora, 217. 
 
 , on flora of cretaceous period, 266. 
 
 , on fossil plants in lias, 329. 
 
 , on plants of bunter-sandstein, 337. 
 
 , on fossil fir-cones, 366. 
 
 , on Permian flora, 360. 
 
 , on sigillaria, 3C-9. 
 
 , on asteroph) lites, 369. 
 
 , on stigmaria, 370. 
 
 , on age of acrogens, 374. 
 
 Brongniart, M. Alex., on Paris tertiaries, 110. 
 
 , on eocene formation, 223. 
 
 , on shells of nummulitic formation, 231. 
 
 , on coal-mine near Lyons, 377. 
 
 Brontes jiabellifer, Devonian, 428. 
 Brora, oolitic coal-formation, 315. 
 
 , granite near, 589. 
 
 Brown-coal of Germany, age of, 181. 192. 
 Brown, Mr. Richard, on stigmarise, 370. 
 
 , on coal-formation, 370. 
 
 , on Cape Breton coal field, 383. 
 
 , on carboniferous rain-prints, 384. 
 
 Buch, Von. See Von Bucli. 
 
 Buckland, Dr., on cave at Kirkdale, 161. 
 
 , on coal plants, 375. 
 
 , on coprolites in chalk, 242. 
 
 , on fish of lias, 323. 
 
 , on glaciers in Caernarvonshire, 137. 
 
 , on oyster-bed near Bromley, 221. 
 
 , on parallel roads, 87. 
 
 , on term Poikilitic, 334. 
 
 , on saurians of lias, 325. 
 
 , on sudden destruction of saurians, 387. 
 
 .cited, 162.294.298.310,311. 
 
 Buddie, Mr., on creeps in coal-mines, 50. 
 
 , on ancient river-channels of coal-period, 
 
 Buist, Dr. G., on saltness of Red Sea, 347. 
 Bulimns ellipticus, 210; B. lultricits, 30. 
 Bunbury, Mr. C. J. F., on plants of oolitic 
 
 field, 332 ; on fossil plarts in Madeira, 519. 
 Bunsen, Prof., on palagonite, 474. 
 Bnnter-sandstein, 337. 
 liuprestis? elytron of, in oolite, 310. 
 Burmeister, on trilobites, 445. 
 Burnes, Sir A., cited, 346. 
 
 CAIRO, exavations at, 3. 
 
 Catamites cannezformis, C. Suckowii, 367- 
 
 Calamites near Pictou, 378. 
 
 Catamite, root-end of, 367 ; structure of, 368. 
 
 Calamophyllia radiata, oolite, 307. 
 
 Calamodendron, 368. 
 
 Calcaire grossier, 227. 
 
 siliceux, 226. 
 
 Calcareous rocks, 12. 
 Calcarina rarispina, eocene, 228. 
 Calceola sandalina, Devonian, 428. 
 Caldcleugh, Mr., cited, 525. 
 Caldera of Palma, 498. to 512. 
 California, auriferous gravel of, 637. 
 Calymene Bliinienbnchii, Wenlock, 440. 
 Cambrian group, 451- 
 
 , lowest fossiliferous beds of, 453. 
 
 _ rocks of Sweden, 455. 
 
 rocks of United States, 455. 
 
 volcanic rocks, 564. 
 
 Campagna di Roma, tuffs of, 535. 
 Campophyllum flexuosum, Devonian, 407. 
 Canada, shells in drift of, 140. 
 Cantal, freshwater formation of, 205. 558. 
 , igneous rocks of, 557. 
 
 Cape Breton, coal-measures of, 383. 
 
 Cape Wrath, granite-veins in, 573. 
 
 Caradoc sandstone, 441. 
 
 Carbonaceous shale, 314. 
 
 Carbonate of lime scarce in metamorphic rocks, 624. 
 
 in rocks, how tested, 12. 
 
 Carboniferous group, 361. 
 
 flora, 363. 373. 
 
 limestone of North America, 414. 
 
 period, plutonic rocks of, 586. 
 
 period, volcanic rocks of, 561. 
 
 reptiles, 400. 
 
 Carcluirvdon heterodon, tooth of, 21G. 
 
 Cardiocarpon Ottonis, Permian, 359. 
 
 Cardiia globosa, 214. ; C. planicosta, 215. 
 
 Cardiwu porulosum, eocene, 229. 
 
 Cardium dtsstmile, C. striatulum, 302. 
 
 Carue, Mr., on Cornish lodes, 629, 630. 
 
 Carrara marble, 598, 619. 
 
 Caryophyllia ctespitosa, bed of, in Sicily, 158. 
 
 Castrogiovanni, bent strata near, 58. 
 
 Catalonia, volcanic region of, 535. 
 
 Cntenopora escharoid.es, Wenlock, 439. 
 
 Catillus Lamarckii, chalk, 248. 
 
 Caulopteris prinueva, coal, 304. 
 
 Cautley, Sir Proby, on Sewalik hills, 183. 
 
 Caves in Europe, 161. 
 
 at Kirkdale, 161. 
 
 in Sicily, 160. 
 
 in Australia, 162. 
 
 Central France, Upper Eocene of, 195. 
 
 Crphalaspes Lyellii, old red, 419. 
 
 Ceratitcs nodosus, triassic, 336. 
 
 Ccrilhium cinctum, 30 ; C. concavum, 212. 
 
 elegans, C. plica turn, 194 ; C. melanoidcs, 221. 
 
 Cervus alcea, tooth of, 167. 
 
 Cestracion Phillippi (recent), jaw of, 250. 
 
 Chalk, or cretaceous beds, '237. 
 
 , pinnacle of, near Sherringham, 135. 
 
 of Faxoe, 239. 
 
 , white, fossils of, 26. 245. 
 
 399. . white, section of, 240. 
 
 , white, extent and origin of, 241. 
 
 , white, animal origin of, 242. 
 
 coal- > pebbles in, 242. 
 
 , difference of, in North and South Europe, 253. 
 
 Chalk cliffs, inland, on Seine, 269. 
 
 , needles of, in Normandy, 271. 
 
 flints, bed of, near Barco:nbe, 287. 
 
 Chama squamosa, eocene, 213. 
 
 Chambers, Mr., on Glen Roy, 88. 
 
 Chamisso, cited, 243. 
 
 Chara elasiica (recent), C. medicaginula, 32; C. 
 tuberculata, 210. 
 
 Chara, in freshwater strata, 31. 
 
 , in flints of Cantal, 206. 
 
 , in Korene strata of France, 195. 
 
 , in Purbeck beds, 296. 
 
 Charlesworth, Mr. E.,on Crag, 169. 
 
 , on Stonesfield mammifer, 461. 
 
 Charpentier, M., on Alpine glaciers, 147. 150. 
 
 Cheir other ium. footprints of, 339. 401. 
 
 Chelonian, footsteps of, 417. 
 
 Chemical and mechanical deposits, 33. 
 
 Chiastolite-slate, 597. 
 
 Chili, earthquake in, 61. 
 
 , gold-mines in, 472. 
 
 Chiloe, rocks drifted from Andes to, 151. 
 
 Chimcera monstrosa (recent), 323. 
 
 Chlorite -schist, 8. 596. 
 
 Christiania, dike near, 483. 
 
 , passage of granite into trap-rocks at, 570. 
 
 , granite near, 575. 
 
 , gneiss near, 575. 
 
 , intrusion of granite into beds near 575 
 
 Chronological groups, 103. 
 
 table of fossiliferous strata, 105. 
 
 TT 2 
 
644 
 
 INDEX. 
 
 Cid 'art's coronata, coral -rag, 305. 
 Cinder-bed, Ptirbeck, 295. 
 Cladocora stellaria, pliocene, 158. 
 Classification of rocks and strata, 2. 10. 104. 
 Claiborne, marine shells of, 233. 
 Clausen, Mr., on Brazil caves, 165. 
 Clautilia bidens, Rhine valley, 30. 
 Clavulina corrugata, eocene, 228. 
 Clay, defined, 11. 
 Clay-slate, 8. 596. 
 Clay-ironstone, 389. 
 Clays, plastic, 220. 
 Cleavage of rocks, 608. 611. 
 Climate of drift-period, 146. 
 
 of coal-period, 399. 
 
 Clinkstone, or phonolite, 476. 
 
 Clinton group, Silurian, United States, 449. 
 
 Clymenia linearis, Devonian, 425. 
 
 Coal, at Brownsville, Pennsylvania, view of, 397. 
 
 , conversion of, into lignite, 398. 
 
 , how formed, 375. 
 
 insects in, 388. 
 
 measures, 361, 362. 
 
 mine, near Lyons, 377. 
 
 , Nova Scotia, time required for its growth, 386, 
 
 , oolitic at Brora, 315. 
 
 period, climate of, 399. 
 
 pipes, danger of, 376. 
 
 seams, continuity of, 398. 
 
 . strata, footprints of reptiles in, 401. 
 
 , zigzag flexures of, near Mons, 53. 
 Coal-field at Burdiehouse, 389. 
 
 , ooliiic, of Richmond, Virginia, 331. 
 
 of Ashby-de-la-Zouch,69. 
 
 of Yorkshire, fossils of, 389. 
 
 , United States, diagram of, 392. 
 
 Coalbrook Dale, beetles in coal of, 388. 
 
 , fossil cones in, 366. 
 
 , coal-measures of, 388. 
 
 , faults in, 62. 
 
 Cochliodus contortus, teeth of, 413. 
 Cockfield Fell, rocks altered by dikes, 485. 
 Ccelacdnthus granulatus, scale of, 357. 
 Ccelorhynchus, sword of, 216. 
 Colchester, Mr., on mammalia at Kyson, 2CO. 
 Colour in shells of mountain-limestone, 410. 
 Columbia, Vinegar River of, 225. 
 Come, ravine in lava of, 555. 
 Concretionary structure, 37. 
 Condensation of rock-material, 38. 
 Cone of a pine, Purbeck, 301. 
 Cones in Val di Noto, 492. 
 
 and craters, 465. 
 
 and craters, absence of, in England, 6. 
 
 Conglomerate, or pudding-stone, 11. 47. 
 
 dolomitic, 357. 
 
 Coniferous trees, fossil, 371. 
 Connecticut, valley of the, 348. 
 
 beds, antiquity of, 351 . 
 
 Conrad, Mr., on cretaceous rockg, 256. 
 Consolidation of strata, 33. 
 Conocrphalus striaius, Cambrian, 454. 
 Conularin ornata, Devonian, 427. 
 Conus deperditus, eocene, 217. 
 Conybeare, Mr., cited, 64. 69. 275. 319. 
 
 . on Plesiosaurus, 324. 
 
 , on oolite and lias, 330. 
 
 , on term Poikilitic, 334. 
 
 , on crocodiles, 218. 
 
 Cook, Capt., on Fucus giganteus, 243. 
 Coprolites in chalk, 242. 
 Coralline crag, fossils in, 171. 
 Coral islands ;md reefs, 34. 46. 
 
 rag of oolite, 303. 
 
 Corals, Devonian, geographical distribution of, 432. 
 of Devonian system, 426. 
 
 Corals of Devonian strata in United States, 431. 
 
 in Wenlock formation, 439. 
 
 Corals, neozoic type of, 407. 
 
 , paleozoic type of, 407. 
 
 Corbula alata, Purbeck, 264. 
 
 pisum, eocene, 194. 
 
 Corinth, corrosion of rocks by gases near, 602. 
 
 Cornbrash of lower oolite, 306. 
 
 Cornean, or aphanite, 476. 
 
 Cornwall, clay in, 12 ; granite-veins in, 574. 600. 
 
 , mineral-veins in, 628. 630. 
 
 , tin of, newer than Irish copper, 636. 
 
 Cotta, Dr. B., on granite in Saxony, 589. 
 Crag, coralline, fossils in, 171. 
 
 , comparison of f'aluns and, 178. 
 
 , fluvio-marine, Norwich, 155. 
 
 Crags of Suffolk, red and coralline, 111. 169. 
 Craigleith fossil trees, 40. 
 
 quarry, slanting tree in, 379. 
 
 Crania, attached to Echinus, 23. 
 
 Parisiensis, chalk, 247. 
 
 Crassatella sulcata, eocene, 214. 
 Crassina Omalii, coralline crag, 172. 
 Crater of Island of St. Paul, 513. 
 Creeps in coal-mines described, 52. 
 Credneria in quadersandstein, 267. 
 Cretaceous rocks of Pyrenees, 585. 
 
 group, 235. 
 
 group, flora of, 266. 
 
 strata in South America and India, 256. 
 
 period, plutonic rocks of, 585. 
 
 volcanic rocks, 560. 
 
 rocks in United States, 255. 
 
 , lower, 257. 
 
 Crinoids, Silurian. 440. 
 
 Cristellaria rolulata, chalk, 26. 
 
 Crocodiles near Cuba, 326. 
 
 Croizet, M., on Auvergne fossil mammalia, 204. 
 
 Cromer, contorted drift near, 135. 
 
 Crop out, term explained, 55. 
 
 Crust of earth defi"ed, 2. 
 
 Crystalline limestone, 354. 
 
 rocks, erroneously termed primitive, 9- 
 
 rocks, foliation of, 613. 
 
 schists defined, 7. 
 
 Curral, valley in Madeira, how formed, 520. 
 
 Curved strata, 47. 49. 136. 
 
 Cutch, Runn of, 346. 
 
 Cuvier, M., on eocene formation, 223. 
 
 , on Amphitherium, 312. 
 
 , on tertiary strata near Paris, 110. 
 
 , on fossils of Montmartre, 224, 225. 
 
 Cyathea glauca (recent), 365. 
 
 Cyathina Buwerbankii, gault, 407. 
 
 Cyathocrinites planus, carboniferous, 409. 
 
 Cyathocrinus caryocrfnoides, 409. 
 
 Cyathophyllum flexuosum, 407; C. ccespitosum, 426 ; 
 
 C. tnrbinatum, 439- 
 
 Cycadeoidea megalophylla, Purbeck, 297. 
 Cycadiles comptus, oolite, 315. 
 Cyclas amnica, 133 : C. obovata, 28. 
 Cyclopteris Hibernica, Devonian, 418. 
 Cyclopian Islands in Sicily, 527. 
 Cyclostoma elegans, pleistocene, 30. 
 Cylindrites acutus, oolite, 309. 
 Cyprtea coccinelloides, red crag, 171. 
 Cyprides, Lower Purbecks, 297; Middle Purbecks, 
 
 295 ; Upper Purbecks, 294 ; WeaMen, 263. 
 Cypridina serrato-striata, Devonian, 425. 
 Cypris f inflata, coal, 387. 
 Cypris in Lias, 328. 
 
 in Wealden, 263. 
 
 in marl of Auvergne, 200. 
 
 in Purbeck bed?, 294, 295. 297. 
 
 Cyrena consobrina, 28 ; C. cunetformis, 221 ; C. 
 
 semistriala, 104. 
 
INDEX. 
 
 645 
 
 Cystidea; in Silurian rocks, 444. 
 Cytherella, chalk, 26. 
 
 DADOXYLON, coal -plant, 372. 
 
 Dana, Mr., on crystalline limestone, 604. 
 
 , on coral-reef in Sandwich Islands, 242. 
 
 , on volcanos of Sandwich Islands, 493. 497. 551. 
 
 Dapedius monilifer, scales of, 322. 
 Duphnogene cinnamomi folia, 192. 
 Dartmoor, granite of, 586. 
 Darwin, Mr. on foliation, 613. 
 
 , cited, 242. 243. 
 
 , on boulders and glaciers in S. America, 144. 
 
 , on cleavage in South America, 613. 
 
 , on coral-islands of Pacific, 242. 
 
 , on dike in St. Helena, 533. 
 
 , on habits of ostrich, 351. 
 
 , on fossils in South America, 155. 
 
 , on Fucus giganteus, 243. 
 
 , on gradual rise of part of South America, 46. 
 
 , on lamination of volcanic rocks, 616. 
 
 , on parallel roads, 87. 88. 
 
 , on plutonic rocks of Andes, 583. 
 ^ , on recent strata near Lima, 121. 
 
 , on saurians in Galapagos Islands, 326. 
 
 , on sinking of coral-reefs, 46. 
 
 , on Welsh glaciers, 137. 
 
 Daubeny, Dr., on the Solfatara, 602. 
 
 , on volcanos in Auvergne, 557. 
 
 Davidson, Mr., on liassic spirifers, 319. 
 
 Dawson, Mr., on coal-plants, 382. 
 
 Dax, inland cliff at, 72. 
 
 Dean, forest of, coal in, 399. 
 
 Deane, Dr., on footprints, 349. 
 
 Decken, M. von, on granite-veins in Cornwall, 445; 
 
 on reptiles in Saarbriick coal-field, 400. 
 De Koninck, M., cited, 185. 189. 
 , on Kleyn Spawen tertiaries, 185. 
 De la Beche, Sir H., cited, 294. 298. 328. 
 
 , on Carrara marbles, 619. 
 
 , on clay-beds, 330. 
 
 , on clay ironstone, 389. 
 
 , on coal-measures near Swansea, 362. 
 
 , on fossil trees. South Wales, 376. 
 
 - , on granite of Dartmoor, 600. 
 
 . , on mineral-veins, 631. 633. 637. 
 
 , on term supracretaceous, 103. 
 
 * , on trap of new red sandstone period, 561. 
 
 Delesse, M., analysis of minerals, 479. 
 
 -, on basalt, 470. 
 
 , on hypersthene rock, 477. 
 
 , on hypogene limestone, 604. 
 
 , on laterite of Antrim, 475. 
 
 , on pyroxene, 469. 
 
 , on serpentine, 478. 
 
 Deluge, 4. 
 
 Denudation explained, 66. 
 
 of the Weald Valley, 272. 
 
 , terraces of, in Sicily, 75. 
 
 of volcanic craters, 508. 511. 
 
 Derbyshire, lead-veins of, 635. 
 Deshayes, M., identification of shells, 185. 
 .. , on fossil shells in Hungary, 549. 
 
 , on lower eocene shells, 2i:9. J 
 
 , on tertiary classification, 116. 
 
 , on upper marine strata, 185. 
 
 Desmarest, on trappean rocks, 91. 
 Desnoyers, M., on Faluns of Touraine, 111. 
 Desor, M., on glacial fauna in North America, 140. 
 Devonian system, term explained, 423. 
 
 series of North Devon, 424. 
 
 series of Russia, 429. 
 
 series of United States, 430. 
 
 De Wael, M., on Antwerp strata, 174. 
 Diagonal, or crosj stratification, 16. 
 Diatomacece in tripoli, 25. 
 Diceras arietinum, 305. 
 
 Dicotyledonous leaves in lower chalk, 267- 
 Didelphys A%ar<e (recent), jaw of, 312. 
 Didymograpsus gemimis, D. Murchisoni, 446. 
 Dike in St. Helena, 533. 
 Dikelocephalus Minnesotensis, 457. 
 Dikes at Palagonia in Sicily, 533. 
 
 defined, 6. 
 
 in Scotland, 481. 
 
 of Somma, 530. 
 
 , trappean, crystalline in centre, 480. 482. 
 
 Diluvium, popular explanation of term, 139. 
 
 Dinornis of New Zealand, 166. 
 
 Dinotlierium giganteum, skull of, 177. 
 
 Dinotherium in India, 18-H. 
 
 Diorite, or greenstone, 471. 476. 
 
 Dip, term explained, 53. 
 
 Diplograpsus Jolium, D.pristis, 446. 
 
 Dirt-bed of Purbeck, 298. 301. 
 
 Dolerite, or greenstone, 470. 477- 
 
 Dolomite defined, 13. 
 
 Dolomitic conglomerate, 357. 
 
 Domite, or earthy trachyte, 477. 
 
 Doue, M. B. de, on volcanos of Velay, 557. 
 
 Drift, contorted, near Cromer, 135. 
 
 in Ireland, 138. 
 
 in Norfolk, 132. 
 
 , meteorite* in, 152. 
 
 , northern, in Scotland, 131. 
 
 , northern, in North Wales, 137- 
 
 of Scandinavia, North Germany, and Russia, 126. 
 
 period, climate of, 146. 
 
 period, subsidence in, 142. 
 
 shells in Canada, 141. 
 
 Dudley limestone, 439. 
 
 , shales of coal near, 600. 
 
 Dufrenoy, M., on granite of Pyrenees, 600. 
 
 , on Hill of Gergovia, 559. 
 
 Duff, Mr. P., on reptile of old red, 416. 
 Danker, Dr., on Wealden of Hanover, 265. 
 Dura Den, yellow sandstone of, 416. 
 Dysaster ringens, inferior oolite, 316. 
 
 ECHINODERMS of coralline crag, 173. 
 Echinospharites Balthicus, 444. 
 Echinus, with Crania attached, 23. 
 Egerton, Mr., on fossils of Southern India, 256. 
 Kgerton, Sir P., on fish of marl-slate, 356. 
 
 , on fossil fish f Connecticut beds, 351. 
 
 , on fossils of Isle of Wight, 213. 
 
 , on saurians and fish in new red sandstone, 338. 
 
 , on Ichthyosaurus, 323. 
 
 Egg-like bodies in Old Red Sandstone, 421. 
 Eggs, fossil, of snake, 126. 
 Ehrenberg, Prof., on bog-iron-ore, 26. 
 
 , on infusoria, 25. 
 
 , on Silurian foraminifera, 448. 
 
 Eil'el, volcanos of, 543548. 
 Elephant-bed, Brighton, i88. 
 Elephas primigrnius, tooth of, 166. 
 Elgin, reptile of old red, found near, 416. 
 Elvans of Ireland and Cornwall, 637. 
 
 , term explained, 587. 
 
 Encrinite, plate of, overgrown with Serpula: and 
 
 Bryozou, 308. 
 Encrinite of Bradford, 308. 
 Encrinus Idiiformis, 336. 
 Eocene, foraminifera, 228. 
 
 formations, 208. 
 
 formations in England, 209. 
 
 granite, 583. 
 
 strata in France, 195. 223. 
 
 strata in United States, 232. 
 , term defined, 116. 
 
 , upper, near Louvain, Belgium, 177. 
 
 volcanic rocks, 558. f 
 
 Eppelsheim, Dinolherium of, 177. 192. 
 Equisetaceas of coal-period, 367. 
 
 TT 3 
 
646 
 
 INDEX. 
 
 Eqniselitcs columnaris, 335. 
 Equisetum of Virginian oolite, 332. 
 
 . giganteum of S. America, recent, 367. 
 
 Equus caballus, tooth of, 167. 
 
 Erman on meteoric iron in Russia, 152. 
 
 Erratics, Alpine, 147. 
 
 . northern origin of, 129. 
 
 Eschara disticha, chalk, 249. 
 Escharina oceani, chalk, 249. 
 Escher, M., on boulders of Jura, 150. 
 Estheria f, Richmond, U. S., 332. 
 Etna, deposits of, 517. 
 Eunomia radiata, 307. 
 Euomphalus pe ntagulatus, 411. 
 Euphotide, 477. 
 Eurite, 569. 597. 
 
 Euritic porphyry described, 466. 
 Extracrinus Briareus, lias, 322. 
 
 FALUNS of Touraine, 111. 176. 
 
 Faluns, comparison of, and crag, 178. 
 
 Falunian type, distinctness of, from Eocene, 180. 
 
 Falconer, Dr., on Sewalik Hills, 183: 
 
 Falkland Islands, 88. 
 
 Farnham, phosphate of lime near, 252. 
 
 Fascicularia aurantium, 172. 
 
 Fault, term explained, 62. 
 
 Faults, origin of, 64. 
 
 Favosites Gothlanriica, 439 ; F. polymorpha, 426. 
 
 Faxoe, chalk of. 239. 
 
 Fflis tigris, tooth of, 168. 
 
 Felixstow, remains of cetacea found near, 174. 
 
 Felspar, varieties of, 457. 
 
 Fenestella retiformis, 355. 
 
 Ferns in coal-measures, 364. 
 
 Fife, altered rock in, 485. 
 
 Fifeshire, trap-dike in, 5' 3. 
 
 Fish, oldest, in Uo,per Ludlow, 435. 
 
 Fishes, fossil, of Upper Cretaceous, 250. 
 
 of Brown-coal, 545. 
 
 of Old Red Sandstone, 419. 
 
 of Wealden, 263. 
 
 Fissures filled with metallic matter, 629. See 
 
 Mineral veins. 
 Fitton, Dr., on lower cretaceous beds, 257. 
 
 , cited. 261. 294. 298. 304. 
 
 Fleming, Dr., on scales offish in old red, 418. 
 , on trap-rocks in coal-field of Forth, 561. 
 
 , on trap-dike in Fifeshire, 562. 
 
 Flints of chalk, 11.244. 
 Flora, carboniferous, 363. 
 
 cretaceous. 2G6. 
 
 of London clay, 217. 
 
 , permian, 359. 
 
 Flotz, term explained, 91. 
 
 Flysch, explanation of term, 232. 
 
 Foliation, term defined, 613. 
 
 Fontainebleau, Gres de, 185. 195. 
 
 Footprint of bird, 349. 
 
 Footprints of reptiles, 339. 349. 402, 403. 417. 
 
 Fornminifera, chalk, 26 ; tertiary, 180. 216. 228. 231 
 
 232 ; paleozoic, 413. 448. 
 Forbes, Mr. David, on foliation, 614. 
 Forbes, Prof. E., on Bembridge series, 186. 188. 
 
 , on Caradoc sandstone, 442. 
 
 , on Cystideae, 443. 
 
 , on Hempstead, Isle of Wight series, 186 193. 
 
 , on Mull leaf-bed, 181. 
 
 , on shells in crag-deposits, 173. 
 
 , on cretaceous fossil shells, 255. 
 
 , on fossils of the faiuns, 177. 
 
 , on fossils in drift in South Ireland, 138. 
 
 , on deop-sea origin of Silurian strata, 459. 
 
 , on echinoderms of coralline crag, 173. 
 
 , on fauna of boulder-period. 132. 
 
 , on migrations of mollusca in glacial-period 
 
 173. 
 
 'orbes, E. on fossils of Purbeck group, 294. 298. 300. 
 
 , on strata at Atherfield, 258. 
 
 , on volcanic rocks of oolite-period, 560. 
 
 , on depth of animal life in ^gean, 35. 144. 
 
 - , on geographical provinces, 257. 
 
 brbes, Prof. James, on zones in glacier-ice, 613. 
 , on the Alps, 150. 
 
 ?orchhammer, on scratched limestone, 127. 
 
 ? orest, fossil, in Norfolk, 134. 137. 
 
 "orest marble of oolite, 306. 
 
 "orfarshire, old red sandstone in, 605. 
 
 Tormation, term defined, 3. 
 
 Fossil ferns in carbonaceous shale, 315. 
 
 - footsteps, 337. 339, 340. 
 
 - forest in Isle of Portland, 298. 
 forest in Nova Scotia, 379. 
 
 forest near Wolverhampton, 377. 
 
 plants in wealden, 265. 
 
 - remains in caves, 160. 
 
 - shells from Etna, 527 ; near Grignon, 227. 
 
 shells of Mayence strata, 191 ; of Virginia, 182. 
 
 - shells, passim. 
 
 , term defined, 4. 
 
 - trees erect, 375. 
 
 wood, perforated by Teredina, 24. 
 
 wood, petrifaction of, 39. 
 
 Fossils, arrangement of, in strata, 5. 
 -, freshwater and marine, 27. 
 
 in chalk at Faxoe, 239. 
 
 in faiuns of Toura-ne, 177. 
 
 of chalk and greensand, 246. 248. 
 
 - of Connecticut beds. 351. 
 
 - of coralline crag, 172. 
 of devonian system, 425. 
 
 of eocene strata in United States, 233, 234. 
 
 of Isle of Wight, 209. 
 
 of lias, 318. 329. 
 
 of London chiy, 219. 
 
 of lower greensand, 259. 
 
 . of Ludlow formation, 438. 
 
 of Maestricht beds, 238. 
 
 of mountain limestone, 407. 
 
 of new red sandstone, 335. 337. 
 
 of old red s;md stone, 419. 
 
 of oolite, 2G6. 302. 309. 
 
 of Permian limestone, 356, 357. 
 
 of Purbeck, 294. 
 
 of red crag, 171. 
 
 of Richmond, U. S., strata, 332. 
 
 of Solenhofen, 303. 
 
 of upper greensand, 252. 
 
 . of wealden, 262. 
 
 , petrifaction of, 39 43. 
 
 , test of th age of formations, 98. 
 
 Fossiliferous strata, tabular view of, 460. 
 Fournet, M., on mineral-veins of Auvergne, 632. 
 , on disintegration of rocks, 601. 
 
 , , on quartz, 568. 
 
 Fox, Mr. R. W., 635, on Cornish Iocs, 636. 
 
 Fox, Rev. Mr., on extinct quadrupeds of Isle ol 
 Wight, 210. 
 
 Freshwater beds of Isle of Wight, 209. 
 
 deposits in valley of Thames, 153. 
 
 . land-shells numerous in, 27. 
 
 Freshwater formations of Auvergne, 198. 
 
 Freshwater formations, how distinguished from 
 marine, 27, 28. 30. 32. 
 
 associated with Norfolk drift, 133. 
 
 Freshwater shells in brown-coal near Bonn, 544. 
 
 Fucus vesiculosus, 33. 243. 
 
 Fuls,nr cannliculatus, 182. 
 
 Fuller's earth of oolite, 315. 
 
 Fundy, Bay of, impressions in red mud of, 348. 
 
 Fungia pafellarts (recent), 407. 
 
 Fusulina cylindrica, 413. 
 
 Fusus contrarius, 171 ; F. quadricustatus,-\82. 
 
INDEX. 
 
 647 
 
 GALAPAGOS ISLANDS, animals of, 326. 
 
 Galeocerdo latidens, tooth of, 216. 
 
 Galerites albogalerus, 246. 
 
 Gattionella distans, G.ferruginea, in tripoli, 25. 
 
 Ganges, buried soils in delta of, 387. 
 
 Garnets in altered rock, 484. 
 
 Gases, subterranean rocks altered by, 602. 
 
 Gault of upper cretaceous, 251. 
 
 Gavarnie, flexures of strata near, 59. 
 
 Geology denned, 1. 
 
 Gergovia, Hill of, 559. 
 
 Gervillia anceps, lower greensand, 260. 
 
 Giant's Causeway, columns at, 487. 
 
 basalt, age of, 181. 
 
 Gibbes, R. W., cited, 234. 
 
 Girgenti, limestone of, 157. 
 
 Glacial phenomena, northern, origin of, 139. 
 
 Glaciers, Alpine, 147. 
 
 on Caernarvonshire mountains, J37. 
 
 Glasgow, marine strata near, 155. 
 
 Glenroy, parallel roads of, 86. 
 
 Glen Tilt, granite of, 572. 
 
 Glyphoea? dubia, coal-measures, 388. 
 
 Gneiss, altered by granite, 575. 
 
 in Bernese Alps, 605. 
 
 at Cape Wrath, 573. 
 
 near Christiana, 575. 
 
 described, 595. 
 
 Gold, age of, in Ireland, 637. 
 
 , age of, in Ural Mountains, 638. 
 
 Goldfuss, Prof., on reptiles in coal-field, 401. 
 
 Goniatites crenistria, G. evolutus, 412; G. Listeri, 
 389. 
 
 Gorgonta injundibuliformis, 355. 
 
 Goppert, Prof., on beds of coal, 363. 
 on petrifaction, 40. 
 
 Gradual increase of strata, 22. 
 
 Graham's Island, 492. 534. 
 
 Grampians, old red conglomerates in, 47. 
 
 Granite described, 7. 565. 
 
 , passage of, into trap, 570. 
 
 , porphyritic, 568. 
 
 and limestone, junction of in Glen Tilt, 571. 
 
 , syenitic, talcose, and schorly, 569. 
 
 of Cornwall and Dartmoor, 600. 
 
 of Swiss Alps, 620. 
 
 rocks in connection with mineral-veins, 638. 
 
 of Saxony. 589. 
 
 , oldest, 588. 
 
 , varieties of, 573. 
 
 veins in Cornwall, 574. 
 
 veins in Cape Wrath, 574. 
 
 veins in Table Mountain, 573. 
 
 vein in White Mountains, 580. 
 
 of Arran, age of, 589. 
 
 near Chmtiania, 587. 
 
 dikes in Mount Battock, 573. 
 
 Graphic granite, 567. 
 
 Graphite, powder of, consolidated by pressure, 38. 
 
 Graptolites, 446. 
 
 Graptolithus Ludensis, Silurian, 441. 
 
 Grasshopper, wing of, in coal-measures, 389. 
 
 Grateloup, M., on fossils in chalk, 255. 
 
 Grauwacke, term explained, 433. 
 
 Great (or Bath) Oolite, 306. ' 
 
 Greenland, sinking of coast of, 46. 
 
 Greensand, fossils of, 252. 
 
 , lower, 257. 
 
 , upper, 251. 
 
 Greensburg, Pennsylvania, footprints of reptile in 
 
 coal-strata at, 401. 
 Greenstone, 471. 
 
 , dike of, in Arran, 481. 
 
 Grds de Beauchamp, Paris Basin, 227. 
 Greystone, volcanic rock, 477. 
 Griffiths, Mr., on geology of Ireland, 362. 
 Grignon, fossil shells near, 227. 
 
 T T 
 
 Grit defined, 11. 
 
 Gryllacns lithanthraca, wing of, 389. 
 
 Gryphcea coated with Serpuke,'22. 
 
 arcuata, G. incurva, 29. 319. 
 
 columba, G.globosa, 248 ; G. virgula, 302. 
 
 Gryphite limestone, or lias, 319. 
 Guadaloupe, human skeleton of, 121. 
 Gunn, Mrs., on Norwich flints, 245. 
 Gutbier, Col. von, on Permian flora, 359. 
 Gyrolepis tenuistriatus, scale of, 338. 
 Gypseous eocene marls, 224, 225. 
 Gypsum defined, 13. , 
 
 HALL, Sir Jas., experiments on fused minerals, 532. 
 
 , on curved strata, 48. 
 
 , Capt. B., cited, 480. 527. 573. 
 
 Haly sites catenulalus, Silurian, 439. 
 
 Hamilton, Sir W., on eruption of Vesuvius, 537. 
 
 Hamites spinfger, gault, 252. 
 
 Harris, Major, on salt lake in Ethiopia, 346. 
 
 Hartung, Mr. G., on Teneriffe, 515. 
 
 on Madeira, 518. 522. 
 
 Hartz, bunter-sandstein of, 337. 
 Hastings, Lady, fossils collected by, 212. 
 Hastings sand, 263, 264. 
 Hautes Alpes, rocks of, 585. 
 Haiiy cited, 467. 
 
 Hawkshavv, Mr., on fossil trees in coal, 375. 
 Hayes, Mr. T. L,., on icebergs, 128. 
 Headon Hill sands described, 213. 
 
 series of Isle of Wight described, 211. 
 
 Hebert, M., on upper eocene beds, 185. 
 , on age of Kleyn Spawen beds, 185. 
 
 , on pisolitic limestone, 237. 
 
 Hebrides, dikes of trap in, 481. 
 
 Heidelberg, varieties of granite near, 573. 
 
 Heliolites porosa, 426. 
 
 Helix labyrinthica, 212 ; H. occltisa, 210 ; H. plebtia, 
 
 125; H. Turonensis,30. 
 Hemicidaris Purbeckensis, 295. 
 Hemipneustes radiattts, 239. 
 Hemitelites Brownii, 315. 
 Hempstead beds, Isle of Wight, 186. 193. 
 Henfrey, Mr. A., on food of Mastodon, 145. 
 Henslow, Prof., on fossil cetacea in Suffolk, 174. 
 
 , on fossil forests, 298. 
 
 , on altered rock near Plas Newydd, 484. 
 
 Herschell, Sir J., on slaty cleavage, 609. 
 Hertfordshire pudding-stone, 35. 
 Hesse Cassel, sands of, 187. 
 Heteroceral fish, tail of, 356. 
 Hibbei t, Dr., on volcanic rocks, 547. 557, 
 
 , on coal-field at Burdiehouse, 389. 
 
 High Teesdale, garnets in altered rock at, 484. 
 Hildburghausen, footprints of reptile at, 337. 339. 
 Himalaya, tertiary mammalia of, 183. 
 
 , elevated fossiliferous rocks in, 4. 
 
 Hippopodium ponderosum, lias, 320. 
 Hippopotamus, tooth of, 167. 
 Hippurites organisans, chalk, 254. 
 Hippurite limestone, 254. 
 Hicchcock, Prof., on footprints, 348. 
 Hoffmann, Mr., on Lipari Islands, cited, 602. 
 
 , on cave near Palermo, 74. 
 
 , on Carrara marble, 619. 
 
 Hooghley River, analysis of water of, 41. 
 Holoptychius nobilissimits, scale of, 418. 
 
 Hibberti, tooth of, 400. 
 
 Homalonotus armatus, 429. j 
 
 delphinocephalus, 441. 
 
 Homoceral fish, tail of, 356. 
 Hopkins, Mr., on fractures in Weald, 281. 
 Horizontal strata, upheaval of, 45. 
 Horizontality of strata, 15. 
 
 of roads of Lochaber, 88. 
 
 Hornblende, 467. 
 
 rock, or amphibolite, 477. 597. 
 
 4 
 
650 
 
 INDEX. 
 
 Miocene formation in Isle of Mull, 180. 
 
 in United States, 181. 
 
 , (lower) strata of Isle of Wight, 186. 
 
 mammalia of Sewalik Hills, 183. 
 of the Bolderberg, 179. 
 
 period, volcanic rocks of, 543. 
 
 , term defined, 116. 
 
 Mississippi, fluviatile strata and delta of, 3. 122, 123. 
 Mitchell, Sir T., on Australian caves, 16H. 
 Mitscherlich, Prof., on augite and hornblende, 468. 
 
 , on mineral composition of Somma, 530. 
 
 Milrascabra, Barton clay, 214. 
 
 Modiola acuminuta, Permian, 354. 
 
 Modon, lithodomi in cliff at, 73. 
 
 Molasse of Switzerland, 180. 
 
 Monkey, tooth of, eocene, 220. 
 
 Mons, flexures of coal at, 53. 
 
 Mont Blanc, talcose granite of, 583. 
 
 Mont Dor, Auvergne. 550. 
 
 Montlosier, M., on Auvergne volcanos, 555. 
 
 Moraine, term explained, 129. 
 
 Moraines of glaciers, 148. 
 
 Morea, inland sea-cliffs of, 73. 
 
 , trap of, 560. 
 
 Morris, Mr., on fossils at Brentford, 154. 
 Morton, Dr., on cretaceous rocks, 255. 
 Morven, basaltic columns in, 487. 
 Mosasaurus Cumperi,jws of, from Maestricht, 239. 
 Mountain limestone, fossils of, 407. 
 Mull, Isle of, Miocene leaf-bed of, 180. 
 Munster, Count, on fossils of Solenhofen, 303. 
 Murchison, Sir R., cited, '279. 286. 288. 
 
 , on eocene gneiss, 606. 
 
 , on volcanic rocks of Italy, 535. 
 
 , on new red sandstone, 338. 
 
 , on age of Alps, 232. 
 
 , on age of gold in Russia, 637. 
 
 , on erratic blocks of Alps, 151. 
 
 , on graniie, 587. 589. 
 
 , on primary strata in Russia, 129. 
 
 , on joints and cleavage, 608. 
 
 , on old red sandstone of S. Devon, 423. 425. 
 
 , on pentamerus, 437. 
 
 , on Silurian strata of Shropshire, 563. 
 
 , on Swiss Alps, 621. 
 
 , on term Permian, 353. 
 
 , on term Silurian, 433. 
 
 , on tilestones, 434. 
 
 Murchisonia gracilis, Silurian, 450. 
 
 Murex alveolatus, red crag, 171. 
 
 Muschelkalk, 335. 
 
 Myliobates Edwardsi, teeth of, Bracklesham, 216. 
 
 Mytilus seplifer, Permian, 354. 
 
 NAGELFLUH, or conglomerate of Alps, 180. 
 Naples, post-pliocene formations near, 529. 
 
 , recent strata near, 118. 
 
 , rising of land at, 1)9. 
 
 Nassa granulata, red crag, 171. 
 JVatica ( recent), spawn of, 421. 
 
 clausa, 131 ; N. helicoides, 156. 
 
 Nautilus cent) alt's, N. ziczac, 219; N. Danicus, 240 
 
 N. plicatus, 259 ; N. truncatus, 320. 
 Navarino, lithodomi found in cliff at, 73. 
 Nebraska, U. S., upper eocene of, 207. 
 Necker, M. L. A., cited, 575. 
 on composition of cone of Somma, 531. 
 
 on granite in Arran, 590. 
 on granitic rocks, 676. 
 on Swiss Alps, 621. 
 
 terms granite " underlying," 8. 
 
 Nelson, Capt., drawing of Bermuda, 79. 
 
 , on chalk of Bermuda Island, 241. 
 
 Neocomian, or lower cretaceous, 257. 
 
 Neozoic type of corals, 407. 
 
 Neptunian theory, 91. 
 
 Nerincea Goodhallii, N. hieroglypltica, 304. 
 
 Nerita conoidea, N. ScJiemidelliana, 229 ; N. costu- 
 
 lata, 309 ; N. gramilosa, 30. 
 Neritina concava, 212 ; N. globulus, 30. 
 Newcastle coal-field, great faults in, 64. 
 Newcastle, fossil tree near, 312. 318. 
 New Jersey, cretaceous strata of, 256. 
 
 , Mastodon giganteus in, 144. 
 
 New red sandstone, distinction from old, 334. 
 
 , its subdivisions, 335. 
 
 of United States, 348. 
 
 , trap of, 561 . 
 
 New York, Devonian strata of, 430. 
 
 , Silurian strata of, 448. 
 
 New Zealand, absence of quadrupeds, 165. 
 Niagara limestone, Silurian fossils of, 449. 
 
 , recent shells in valley of, 145. 
 
 Nipadttes ellipticus, 217. 
 Nodosaria, chalk, 26. 
 Noeggerath, M., cited, 543. 
 Noeggerathia cuneifulia, 3GO. 
 Nomenclature, changes of, 93. 
 Norfolk, buried forest, 134. 137. 154. 
 
 , drift, 132. 
 
 Normandy, chalk-cliffs and needles, 270. 
 Northwich, beds of salt at, 345. 
 Norwich crag, fluvio-marine, 155. 
 
 , sandpipes near, 82. 
 
 Nova Scotia, coal-seams of Cape Breton, 315. 
 
 , fossil forest of coal in, 321. 
 
 Nucula Cobboldite, 156 ; N. Deshayesiana, 189. 
 Nummulites, whether found in upper eocene, 190. 
 Nummulites exponens, 232; N. tevigata, 216; N. 
 
 Puschi, 231. 
 
 Nummulitiq formation, 230. 
 Nyst, M., cited, 189. 
 
 OSOLUS ^POLLiNiS t Russia, 448. 
 
 Oeynhausen, M. von, on Cornish granite veins, 574. 
 
 Ohio, Falls of, Devonian coral-reef of, 431. 
 
 Old red sandstone, 415. 
 
 , in Forfarshire, 605. 
 
 , trap of, 563. 
 
 Oldhamia antiqua, 0. radiata, 453. 
 Olenus micrurus, Cambrian, 452. 
 Oliva Dufresnii?, miocene, 179. 
 Olot, extinct volcanos near, 536. 
 Omphyma turbinalum, Wenlock, 439. 
 Onchus tennistrialus, Silurian, 436. 
 Oolite, 292. 
 
 and lias, origin of, 320. 
 
 , inferior, fossils of, 315. 
 
 in France, 294. 
 
 , plutonic rocks of, 585. 
 
 , term defined, 12. 
 
 , volcanic rocks of, 560. 
 
 Oolitic group in France, 294. 303. 
 
 United States, 331. 
 
 Ophioderma Egertoni, lias, 321. 
 Ophite and ophiolite, 477. 
 Opossum, part of jaw of, 220. 
 Orbigny, M. d', cited, 254. 
 
 , on fossils of nummulitic limestone, 234. 
 
 , on subdivisions of cretaceous series, 238. 
 
 , on Vienna Basin foraminifera, 180. 
 
 Organic remains, criterion of age of formation, 98. 
 
 , test of age of volcanic rocks, 525. 
 
 Ormerod, Mr., on trias of Cheshire, 345. 
 
 Orthis elegantula, 435 ; O.grandis, 0. tricenaria, 0. 
 
 vesperttlio, 444. 
 Orthoceras latcrale, 412 ; 0. Ludense, 0. ventri- 
 
 cosutn, 438. 
 
 Orthoclase, or common felspar, 467. 
 Osborne, or St. Helen's series, I. of Wight, 193. 211. 
 Osnabruck, in Westphalia, tertiary strata of, 179. 
 Ostrea acuminata, 315 ; 0. carinata, O. columba, 
 
 vesicularis,248 ; 0. distorta,2Q5 0. expansa, 0. 
 
 deltoidea, 302 ; 0. gregaria, 304 ; 0. Mars/iii, 317. 
 
INDEX. 
 
 651 
 
 Otodus obliquus, tooth of, 216. ^ 
 Overlying, term applied to volcanic rocks, 8. 
 Owen, Dr. Dale, on oldest fossiliferous rocks of 
 Wisconsin, 457. 
 
 , Prof., cited, 162. 174. 263. 311. 313, 314. 340. 
 
 , on amphitherium, 311. 
 
 , on birds in New Zealand, 166. 
 
 , on bone-caves in England, 161, 
 
 , on footprints, 349. 
 
 , on fossils in Australia, 163. 
 
 , on fossil monkey, 219. 
 
 , on fossil quadrupeds, 164. 
 
 , on ichthyosaurus, 324. 
 
 , on reptile in coal, 401. 
 
 , on serpent of Braokleshatn, 215. 
 
 , on snake of Sheppey, 218. 
 
 , on thecodont saunans, 306. 
 
 , on zeuglodon, 234. 
 
 Oxford clay, 305. 
 Oyster beds, 221. 
 
 PACIFIC, coral-reefs of, 241. 
 
 Palcechinus gigas, 469. 
 
 Pakeoniscus, Permian, outline of, 356. 
 
 Palceoniscus comptus, scale of, P. elegans, scale of, P. 
 
 glap/iyrus, scale of, 357. 
 Palasontology, trrm explained, 104. 
 Pal&ophis typhoeus, vertebras of, 215. 
 ' PalcEosaurus platyodon, tootli of, 358. 
 Palceotherium magnum, outline of, 211. 
 Palagonia, dikes at, 533. 
 Palagonite tuff, 474. 
 Palermo, caves near, 74. 
 Palma, Isle of, map of, 499. 
 
 , structure of, 498 512. 
 
 Paludina (Auvergne), 202; P. lenta, 29. 194. 
 
 marginata, P. mtnuta, 133. 
 
 (Mayence), 191 ; P. orbicularis, 210. 
 
 Pampas, extinct quadrupeds of, 164. 
 Paradoxides Bohemicus, Cambrian, 454. 
 Parasmilia centralis, chalk, 407. 
 Parallel roads, 86. 
 Pareto, M., on Carrara marble, 619. 
 Paris basin, 93. 
 
 Parka decipiens of Forfarshire, 421. 
 Parkinson, Mr., on crag, 111. 
 Parrot, Dr. F., on salt-lakes of Asia, 346. 
 Patella rugosa, great oolite, 309. 
 Pear-Encrinite, Bradford-clay, 307. 
 Pearlstone, volcanic rock, 478. 
 Pebbles in chalk, 242. 
 Pecopteris lonchitica, coal, 364. 
 
 Pecten Beaveri, 247 ; P. tslandicus,]3l ; P.jacobceus, 
 M59. 
 
 Pecten papyraceus, 389; P. quinquecostatus, 248. 
 Pegmatite, variety of granite, 567. 
 Pentacrinus Briarens, lias, 321. 
 Pentamerus Knightii, 437 ; P . l&vt's, 442. 
 Pentland hills, Mr. Maclaren on, 132. 
 Peperino, volcanic tuff, 478. 
 Pepys, Mr., cited, 41. 
 Permian flora, distinct from that of coal, 358. 
 
 formation in Thuringia, 359. 
 
 group described, 353. 
 
 Perna Mulleti, lower greensand, 259. 
 Petrifaction of fossil wood, 39. 
 
 , process of, 43. 
 
 Philippi, Dr., on fossil shells near Naples, 118. 
 
 , on Hesse Cassel beds, 187. 
 
 , on marine shells in caves of Sicily, 161. 
 
 , on tertiary shells of Sicily, 157. 
 
 Phillips, Prof., cited, 309. 319. 
 
 , on cleavage, 610. 
 
 f on terminology, 103. 
 
 , Mr. W., on kaolin of China, 11. 
 
 Phacopt cavdatus, Silurian, 440. 
 Phascolotherium Bucklandi, jaw of, 313. 
 Phasianella Heddingtonensis, coral-rag, 39. 
 
 Phlebopleris contigua, oolite, 315. 
 Pholadomyafidicula, oolite, 316. 
 Phonolite, or clinkstone, 476. 
 Phorus extensus, London clay, 219. 
 Phosphate of lime, 252. 
 Phragmcceras ventricosum, Ludlow, 438. 
 Phryganea, indusies of, '202. 
 
 , (recent), larva of, 202. 
 
 Phyllade or clay-slate, 597. 
 Physa Bristovti, Purbeck, 296. 
 
 columnaris, P. hypnorum (recent), 29. 
 
 Pictoti, Nova Scotia, calamites near, 319. 
 
 Pilla, M., on age of Carrara marble, 619. 
 
 Pisidium amnicum, 133. 
 
 Pisolitic limestone of France, 236. 
 
 Pitchstone, or retinite, 478. 
 
 Placodtis gtgas, teeth of, 337. 
 
 Plagiosioma giganteum, 319 ; P. Hoperi, P. spino- 
 
 sutn, 248. 
 
 Planitz, tripoli of, 26. 
 
 Planorbis discus, 210 ; P. euomphalus, 29. 212. 
 Plas Newydd, rock altered by dike near, 484. 
 Plastic clays, 220. 
 Playfair, cited, 45. 92. 
 
 , on faults, 62. 
 
 , on Huttonian theory of stratification, 60. 
 
 Plectrodus mirabilis, 436. 
 Plestusaurus dolichodeirus, 324. 
 Pleurodictyum problematicum, 429. 
 Pleurotoma attenuata, 217 ; P. rotata,31. 
 Pleurotomaria can'nata, P. ftammtgera, 410. 
 Pie urotomaria granulata, P. ornata, 316. 
 Plieninger, Professor, on triassic mammifer, 342. 
 Pliocene, newer, period, 126. 
 
 , newer, strata, 153. 
 
 strata in Sicily, 156. 
 
 , older, in United States, 181. 
 
 strata, 168. 
 
 period, volcanic rocks of, 533. 535. 
 
 , term defined, 117. 
 
 Plomb du Cantal, described, 557. 
 Plumbago in Massachusetts, 604. 
 Plutonic rocks, 7. 579. 
 
 of carboniferous period, 586. 
 
 of oolite and lias, 58ft. 
 
 , recent and pliocene, 580. 
 
 of Silurian period, 587. 
 
 , age of, how tested, 579. 
 
 Plutonic and sedimentary rocks, diagram of, 582 
 Pluvial action, effects of, 280. 
 Podocarya, fruit of, oolite, 314. 
 Poggendorf, cited, 601. 
 Poikilitic formation, 353. 
 , term explained, 334. 
 PolycceUa profunda, Permian, 407. 
 Pomel, M., on mammalia of Auvergne, 204. 425. 
 Ponza Islands in Mediterranean, 490. 612. 
 Porphyritic granite, 568. 
 Porphyry, 471, 472. 
 Portland, Isle of, fossil forest in, 298. 
 Portland stone, 301. 
 
 Portlock, Col., on Tyrone Silurian rocks, 447. 
 Posidonia minuta, triassic, 336. 
 Posidonomya'?, Richmond, U.S., 332. 
 Becheri, carboniferous, 414. 
 Post- pliocene formations, 117. 
 
 , period, volcanic rocks, 527. 
 
 Potsdam sandstone at Keeseville, 455. 
 
 sandstone, tracks on, 456. 
 
 sandstone in Canada, 450. 
 Pottsville, coal-seams near, 394. 
 
 , footprints of reptile near, 404. 
 
 Pozzolana, 36. 
 
 Pratt, Mr., on ammonites, 305. 
 
 , on extinct quadrupeds of Isle of Wight, 210. 
 
 Precipitation of mineral matter, 41. 
 Predazzo, altered rocks at, 586. 
 Prestwich, Mr., cited, 69. 
 
650 
 
 INDEX. 
 
 Miocene formation in Isle of Mull, 180. 
 
 in United States, 181. 
 
 , (lower) strata of Isle of Wight, 186. 
 
 mammalia of Sewalik Hills, 183. 
 
 of the Bolderberg, 179. 
 
 period, volcanic rocks of, 543. 
 
 , term defined, 116. 
 
 Mississippi, fluviatile strata and delta of, 3. 122, 123. 
 Mitchell, Sir T., on Australian caves, 163. 
 Mitscherlich, Prof., on augite and hornblende, 468. 
 
 , on mineral composition of Somma, 530. 
 Mitra scabra, Barton clay, 214. 
 Modiola acuminuta, Permian, 354. 
 Modon, lithodomi in cliff at, 73. 
 Molasse of Switzerland, 180. 
 Monkey, tooth of, eocene, 220. 
 Mons, flexures of coal at, 53. 
 Mont Blanc, talcose granite of, 583. 
 Mont Dor, Auvergne. 550. 
 Montlosier, M., on Auvergne volcanos, 555. 
 Moraine, term explained, 129. 
 Moraines of glaciers, 148. 
 Morea, inland sea-cliffs of, 73. 
 
 , trap of, 660. 
 
 Morris, Mr., on fossils at Brentford, 154. 
 Morton, Dr., on cretaceous rocks, 255. 
 Morven, basaltic columns in, 487. 
 Mosasaurus Cnmperi, jaws of, from Maestricht, 239. 
 Mountain limestone, fossils of, 407. 
 Mull, Isle of, Miocene leaf-bed of, 180. 
 Miinster, Count, on fossils of Solenhofen, 303. 
 Murchison, Sir R., cited, 279. 286. 288. 
 
 , on eocene gneiss, 606. 
 
 , on volcanic rocks of Italy, 535. 
 
 , on new red sandstone, 338. 
 
 , on age of Alps, 232. 
 
 , on age of gold in Russia, 637. 
 
 , on erratic blocks of Alps, 151. 
 
 , on granite, 587. 589. 
 
 , on primary strata in Russia, 129. 
 
 , on joints and cleavage, 608. 
 
 , on old red sandstone of S. Devon, 423. 425. 
 
 , on pentamerus, 437. 
 
 , on Silurian strata of Shropshire, 563. 
 
 , on Swiss Alps, 621. 
 
 , on term Permian, 353. 
 
 , on term Silurian, 433. 
 
 , on tilestones, 434. 
 
 Murchisonia gracilis, Silurian, 450. 
 
 Murex alveolatus, red crag, 171. 
 
 Muschelkalk, 335. 
 
 Myliobates Edwardsf, teeth of, Bracklesham, 216. 
 
 Mytilus septifer t Permian, 354. 
 
 NAGELFLUH, or conglomerate of Alps, 180. 
 Naples, post-pliocene formations near, 529. 
 , recent strata near, 118. 
 , rising of land at, 1 J9. 
 Nassa granulata, red crag, 171. 
 Natica (recent), spawn of, 421. 
 
 clausa, 131 ; N. helicoides, 156. 
 
 Nautilus cent) alts, N. ziczac, 219; N. Danicus, 240 ; 
 
 N. plicatus, 259 ; N. truncatus, 320. 
 Navarino, lithodomi found in cliff at, 73. 
 Nebraska, U. S., upper eocene of, 207. 
 Necker, M. L. A., cited, 575. 
 
 , on composition of cone of Somma, 531. 
 
 , on granite in Arran, 590. 
 
 , on granitic rocks, 576. 
 
 , on Swiss Alps, 621. 
 
 , terms granite " underlying," 8. 
 
 Nelson, Capt., drawing of Bermuda, 79. 
 
 , on chalk of Bermuda Island, 241. 
 
 Neocomian, or lower cretaceous, 257. 
 
 Neozoic type of corals, 407. 
 
 Neptunian theory, 91. 
 
 Nerintea Goodhallii, N. hieroglypliica, 304. 
 
 Nerila conoidea, N. ScJiemidelliana, 229 ; N. coslu- 
 
 lata, 3C9 ; N. granulosa, 30. 
 Neritina concava, 212 ; N. glubultts, 30. 
 Newcastle coal-field, great faults in, 64. 
 Newcastle, fossil tree near, 312. 318. 
 New Jersey, cretaceous strata of, 256. 
 , Mastodon giganteus in, 144. 
 New red sandstone, distinction from old, 334. 
 
 - , its subdivisions, 335. 
 
 - of United States, 348. 
 
 - , trap of, 561 . 
 
 New York, Devonian strata of, 430. 
 
 - , Silurian strata of, 448. 
 
 New Zealand, absence of quadrupeds, 165. 
 Niagara limestone, Silurian fossils of, 449. 
 
 - , recent shells in valley of, 145. 
 Nipadites ellipticus, 217. 
 Nodosaria, chalk, 26. 
 Noeggerath, M., cited, 543. 
 Noeggerathia cuneifulia, 3GO. 
 Nomenclature, changes of, 93. 
 Norfolk, buried forest, 134. 137. 154. 
 
 - , drift, 132. 
 
 Normandy, chalk-cliffs and needles, 270. 
 Northwich, beds of salt at, 345. 
 Norwich crag, fluvio-marine, 155. 
 
 - , sandpipes near, 82. 
 
 Nova Scotia, coal-seams of Cape Breton, 315. 
 -- , fossil forest of coal in, 321. 
 Nucula Cobboldia;, 156 ; N. Deshayesiana, 189. 
 Nummulites, whether found in upper eocene, 190. 
 Nummulites exponent, 232; N. tevigata, 216; N. 
 
 Puschi, 231. 
 
 Nummulitic formation, 230. 
 Nyst, M., cited, 189. 
 
 t R us8 i a , 448. 
 
 Oeynhausen, M. von, on Cornish granite veins, 574. 
 Ohio, Falls of, Devonian coral-reef of, 431. 
 Old red sandstone, 415. 
 
 - , in Forfarshire, 605. 
 
 - , trap of, 563. 
 
 Oldhamia antiqua, 0. radiata, 453. 
 Olenus micrurus, Cambrian, 452. 
 Oliva Dufresnii?, miocene, 179. 
 Olot, extinct volcanos near, 536. 
 Omphyma turbinatum, Wen lock, 439. 
 Onchus tennistrialus, Silurian, 436. 
 Oolite, 292. 
 
 - and lias, origin of, 320. 
 
 - , Inferior, fossils of, 315. 
 
 - in France, 294. 
 
 - , plutonic rocks of, 585. 
 
 - ,term defined, 12. 
 
 - , volcanic rocks of, 560. 
 Oolitic group in Franoe, 294. 303. 
 
 - United States, 331. 
 Ophioderma Egertoni, lias, 321. 
 Ophite and ophiolite, 477. 
 Opossum, part of jaw of, 220. 
 Orbigny, M. d', cited, 254. 
 
 - , on fossils of nummulitic limestone, 234. 
 
 - , on subdivisions of cretaceous series, 238. 
 
 - , on Vienna Basin foraminifera, 180. 
 Organic remains, criterion of age of formation, 98. 
 
 - , test of age of volcanic rocks, 525. 
 Ormerod, Mr., on trias of Cheshire, 345. 
 
 Orthis elegantula, 435 ; O.grandis, O. tricenaria, 0. 
 
 vespertilio, 444. 
 Orthoceras latcrale, 412 ; 0. Ludense, 0. ventri- 
 
 cosum, 438. 
 
 Orthoclase, or common felspar, 467. 
 Osborne, or St. Helen's series, I. of Wight, 193. 211. 
 Osnabruck, in Westphalia, tertiary strata of, 179. 
 Oftrea acuminata, 315 ; 0. carinata, O. columba, 
 
 0-vesicularis,1W ; 0. dtstorta,295 ; 0. expansa, 0. 
 
 ddioidea, 302 ; 0. gregaria, 304 ; 0. Marsfin, 317. 
 
INDEX. 
 
 651 
 
 Otodus obltquus, tooth of, 216. ~i 
 Overlying, term applied to volcanic rocks, 8. 
 Owen, Dr. Dale, on oldest fossiliferous rocks of 
 Wisconsin, 457. 
 
 , Prof., cited, 1G2. 174. 263. 311. 313, 314. 340. 
 
 , on amphitherium, 311. 
 
 , on birds in New Zealand, 166. 
 
 , on bone-caves in England, 161, 
 
 , on footprints, 349. 
 
 , on fossils in Australia, 163. 
 
 , on fossil monkey, 219. 
 
 , on fossil quadrupeds, 164. 
 
 , on ichthyosaurus, 324. 
 
 , on reptile in coal, 401. 
 
 , on serpent of Brarklesham, 215. 
 
 , on snake of Sheppey, 218. 
 
 , on thecodont saunans, 306. 
 
 , on zeuglodon, 234. 
 
 Oxford clay, 305. 
 Oyster beds, 221. 
 
 PACIFIC, coral-reefs of, 241. 
 
 Palcechinus gigas, 469. 
 
 Pakeoniscus, Permian, outline of, 356. 
 
 Palteoniscus comptus, scale of, P. elegans, scale of, P. 
 
 glaphyrus, scale of, 357. 
 Palaeontology, term explained, 104. 
 Palzophis typhceus, vertebrae of, 215. 
 Palteosaurus platyodon, tooth of, 358. 
 Palteotherium magnum, outline of, 211. 
 Palagonia, dikes at, 533. 
 Palagonite tuff, 474. 
 Palermo, caves near, 74. 
 Palma, Isle of, map of, 499. 
 
 , structure of, 498512. 
 
 Paludina (Auvergne), 202; P. lenia, 29. 194. 
 
 marginata, P. mtnuta, 133. 
 
 (Mayence), 191 ; P. orbicularis, 210. 
 
 Pampas, extinct quadrupeds of, 164. 
 Paradoxides Boliemicus, Cambrian, 454. 
 Parasmiiia centralis, chalk, 407. 
 Parallel roads, 86. 
 Pareto, M., on Carrara marble, 619. 
 Paris basin, 93. 
 
 Parka decipiens of Forfarshire, 421. 
 Parkinson, Mr., on crag, 111. 
 Parrot, Dr. F., on salt-lakes of Asia, 346. 
 Patella rugosa, great oolite, 309. 
 Pear-Encrinite, Bradford-clay, 307. 
 Pearlstone, volcanic rock, 478. 
 Pebbles in chalk, 242. 
 Pecopteris lonchitica, coal, 364. 
 Pecten Heaver i, 247 ; P. islandicus, 131 ; P.jacobteus, 
 '* 159. 
 
 Pecten papyraceus, 389; P. quinquecostatus, 248. 
 Pegmatite, variety of granite, 567. 
 Pentacrinus Briareus, lias, 321. 
 Pentamerus Knightii, 437 ; P. lawis, 442. 
 Pentland hills, Mr. Maclaren on, 132. 
 Peperino, volcanic tuff, 478. 
 Pepys, Mr., cited, 41. 
 Permian flora, distinct from that of coal, 358. 
 
 formation in Thuringia, 359. 
 
 group described, 353. 
 
 Perna Mulleti, lower greensand, 259. 
 Petrifaction of fossil wood, 39. 
 
 , process of, 43. 
 
 Philippi, Dr., on fossil shells near Naples, 118. 
 
 , on Hesse Cassel beds, 187. 
 
 , on marine shells in caves of Sicily, 161. 
 
 ., on tertiary shells of Sicily, 157. 
 
 Phillips, Prof., cited, 309. 319. 
 
 , on cleavage, 610. 
 
 , on terminology, 103. 
 
 , Mr. W., on kaolin of China, 11. 
 
 Phacop* cavdatus, Silurian, 440. 
 Phascolotherium Bucklandi, jaw of, 313. 
 Phasianella Heddingtonensis, coral-rag, 39. 
 
 Phlebopteris contigua, oolite, 315. 
 Pholadomyafidicula, oolite. 316. 
 Phonolite, or clinkstone, 476. 
 Phorus extensus, London clay, 219. 
 Phosphate of lime, 252. 
 Phragmoceras ventricosum, Ludlow, 438. 
 Phryganea, indusite of, 202. 
 
 , (recent), larva of, 202. 
 
 Phyllade or clay-slate, 597. 
 Physa Brisiovii, Purbeck, 296. 
 
 columnaris, P. hypnorum (recent), 29. 
 
 Pictoti, Nova Scotia, calamites near, 319. 
 
 Pilla, M., on age of Carrara marble, 619. 
 
 Pisidium amnicum, 133. 
 
 Pisolitic limestone of France, 236. 
 
 Pitchstone, or retinite, 478. 
 
 Placodus gigas, teeth of, 337. 
 
 Plagiosioma giganteum, 319 ; P. Hoperi, P. spino- 
 
 sum, 248. 
 
 Planitz, tripoli of, 26. 
 
 Planorbis discus, 210 ; P. euomphalus, 29. 212. 
 Plas Newydd, rock altered by dike near, 484. 
 Plastic clays, 220. 
 Playfair, cited, 45. 92. 
 
 , on faults, 62. 
 
 , on Huttonian theory of stratification, 60. 
 
 Plectrodus mirabilis, 436. 
 Plesiusaurus dolichodeirus, 324. 
 Pleurodictyum problematicum, 429. 
 Pie urotoma attenuata, 217 ; P. rotata,31. 
 Pleurotomaria carmata, P. flamnugera, 410. 
 Pleurotomaria granulata, P. ornata, 316. 
 Plieninger, Professor, on triassic mammifer, 342. 
 Pliocene, newer, period, 126. 
 
 , newer, strata, 153. 
 
 strata in Sicily, 156. 
 
 , older, in United States, 181. 
 
 strata, 168. 
 
 period, volcanic rocks of, 533. 535. 
 
 , term defined, 117. 
 
 Plomb du Cantal, described, 557. 
 Plumbago in Massachusetts, 604. 
 Plutonic rocks, 7. 579. 
 
 of carboniferous period, 586. 
 
 of oolite and lias, 58ft. 
 
 , recent and pliocene, 580. 
 
 of Silurian period, 587. 
 
 , age of, how tested, 579. 
 
 Plutonic and sedimentary rocks, diagram of, 582 
 Pluvial action, effects of, 280. 
 Podocarya, fruit of, oolite, 314. 
 Poggendorf, cited, 601. 
 Poikilitic formation, 353. 
 
 , term explained, 334. 
 
 Polyccelia profunda, Permian, 407. 
 
 Pomel, M., on mammalia of Auvergne, 204. 425. 
 
 Ponza Islands in Mediterranean, 490. 612. 
 
 Porphyritic granite, 568. 
 
 Porphyry, 471, 472. 
 
 Portland, Isle of, fossil forest in, 298. 
 
 Portland stone, 301. 
 
 Portlock, Col., on Tyrone Silurian rocks, 447. 
 
 Posidonia minuta, triassic, 336. 
 
 Posidonomya ?, Richmond, U.S., 332. 
 
 Becheri, carboniferous, 414. 
 
 Post pliocene formations, 117. 
 
 , period, volcanic rocks, 527. 
 
 Potsdam sandstone at Keeseville, 455. 
 
 sandstone, tracks on, 456. 
 
 sandstone in Canada, 450. 
 
 Pottsville, coal-seams near, 394. 
 
 , footprints of reptile near, 404. 
 
 Pozzolana, 36. 
 
 Pratt, Mr., on ammonites, 305. 
 
 , on extinct quadrupeds of Isle of Wight, 210. 
 
 Precipitation of mineral matter, 41. 
 Predazzo, altered rocks at, 586. 
 Prestwich, Mr., cited, 69. 
 
652 
 
 INDEX. 
 
 Prestwich, Mr., on Weald denudation, 282. 
 
 , on English eocene strata, 209. 213. 217- 220. 
 
 , on coal-measures of Colebrook Dale, 62. 388. 
 
 Prevost, M. C., on Paris basin, 224, 225, 226. 
 
 Product calvus, P. horridus, 355. 
 
 Productus antiquatus, P. seniireiiculalus, 409. 
 
 Progressive development, theory of, 457. 
 
 Protogme, or talcose granite, 569. 
 
 Psammodus porosns, tooth of, 413. 
 
 Psaronites in Germany and France, 360. 
 
 Pseudocrinites bifasciatus, 440. 
 
 Pterichthys, old red, 423. 
 
 Pterodactylus crassirostris, 303. 
 
 Pterophyllum comptum, 315. 
 
 Pterygotus Anglicus, 419 ; P. problematicus, 420. 
 
 Ptychodus decurrens, tooth of, 250. 
 
 Puggaard, Mr., on Moen drify 286. 
 
 Pumice, 473. 
 
 Pupa muscorum, 125 ; P. tridens, ZQ' 
 
 Purbeck beds, 292. 294. 
 
 Purpuroidea nodulata, oolite, 309. 
 
 Puy de Tartaret, 553. 
 
 Puy de Poriou, 556. 
 
 Puzzuoli, elevation and depression of land at, 529. 
 
 , post-pliocene strata at, 1 18. 
 
 Pygopterus mandibularis, scale of, 357. 
 Pyrenees, cretaceous rocks of, 585. 
 
 , curvatures of strata in, 58. 
 
 , granite of, 600. 
 
 , nummulitic formation of, 231. 
 
 Pyrocene, or augite, 469. 
 
 Pyrula reticulata, coralline crag, 173. 
 
 QUADRCMANA fossil, 220. 
 
 Quarrington Hill, basaltic dike near, 524. 
 
 Quartz, 566. 
 
 Quartzite, or quartz-rock, 596. 
 
 RADiOLiTEsfoliaceus, R. radiosus, 254. 
 
 Morloni, chalk, 249. 
 
 Radnorshire, stratified trap of, 564. 
 Rain-prints, fossil in coal-shale, 387. 
 Ramsay, Prof. A.C., on denudation, 68. 
 
 , on granite in Arran, 590. 
 
 , on section near Bristol, 102. 
 
 , on Welsh glaciers, 138. 
 
 , on foliation of crystalline schists, 616. 
 
 , on Caradoc sandstone, 442. 
 
 Rastrites peregrinus, 446. 
 Recent strata defined, 118. 
 
 , near Naples, 118. 
 
 Redfield, Mr., on glacial fauna in America, 140. 
 
 , on fossil fish, 351. 
 
 Red sandstone, origin of, 344. 
 
 Red Sea and Mediterranean, distinct species in, 100. 
 
 , saltness of, 347. 
 
 Reptile in old red sandstone of Morayshire, 416. 
 
 Reptiles, carboniferous, 400, 401. 
 
 of lias, 323. 
 
 , fossil eggs of, 126. 
 
 , fossil, of Nova Scotia coal, 405. 
 
 Reptilian bone, great oolite, 31 1. 
 -footprints in coal-strata, 403. 
 Retepora flustracea, 355. 
 Retinite, or pitchstone, 478. 
 Rhine valley, loess of, 122. 
 Rhinoceros leptorhinus, tooth of, 167. 
 Rhynchonella spinosa, 316 ; R. Wilsoni, 437. 
 Rigi, near Lucerne, conglomerate of, 180. 
 Rimula dathrata, great oolite, 309. 
 Ripple-mark, formation of, 19. 
 Rissoa Chustelii, eocene, 194. 
 River-channels, ancient, 399. 
 River, excavation through lava by, 541. 
 
 terraces, 85. 
 
 Rock, term defined, 2. 
 
 Rocks, four classes of, contemporaneous, 9. 
 
 , classification of, 90. 
 
 Rocks, composed of fossil zoophytes and shells, 24. 
 
 , trappeari, 92. 
 
 Roderburg, extinct volcano of, 548. 
 
 Rogers, Prof. H. D., on coal-field, United States, 393. 
 
 , cited, 396. 417. 431. 
 
 , on reptilian footprints in coal, 394. 
 
 , on Devonian rocks, U. S., 431. 
 
 , Prof. W. B., on oolitic coal-field, United 
 
 States, 331. 393. 
 
 , on Devonian rocks, U. S., 431. 
 
 Rcme, formations at, 176. 535. 
 Homer, F., on chalk in Texas, 256. 
 Rosalina, chalk, 26. 
 Rose, Prof. G., cited, 473. 563. 
 
 , on hornblende, 468. 
 
 Ross-shire, denudation in, 67. 
 Rostellariamacroptera, eocene, 219. 
 Rothliegendes, lower, or Permian, 359. 
 Rubble, term explained, 81. 
 Rupelmonde, Upper Eocene beds, 189. 
 Russia, erratic blocks in, 1*9. 
 
 , fossil meteoric iron in, 152. 
 
 , Permian rocks in, 358. 
 
 SAARBRUCK coal-field, reptiles found in, 401. 
 
 St. Abb's Head, curved strata near, 49. 
 
 St. Andrew's, trap-rocks in cliffs near, 561, 562. 
 
 St. Helena, basalt in. 487. 533. 
 
 St. Helens, or Osborne series, I. of Wight, 193. 2H. 
 
 St. Lawrence, gulf of, inland beaches and cliffs, 78. 
 
 St. Mihiel, France, inland cliffs near, 77. 
 
 St. Paul, Island of, 512. 
 
 St. Peter's Mount, Maestricht, fossils in, 238. 
 
 , sandpipes in, 83. 
 
 Salisbury Crag, altered strata of, 485. 
 Salt rock, origin of, 345. 
 
 , precipitation of, 345. 
 
 , at Northwich, 345. 
 
 , lakes of Asia, 346. 
 
 Salter, Mr., on fossils of Caradoc sandstone, 442. 
 
 , on Caradoc beds, 412. 
 
 , on Silurian fish, 436. 
 
 on Silurian rocks of Canada, 450. 
 San Lorenzo, recent strata at, 121. 
 Sandpipes near Maestricht, 83. 
 
 , near Norwich, 82. 
 
 , or sandgalls. term explained, 82. 
 
 Sandstone, with cracks in VVealden, 264. 
 Sandwich Islands, coral-reef in, 242. 
 
 , volcanos of, 493. 512. 532. 551. 
 
 Sangatte, near Calais, drift of, 289. 
 Sao hirsuta, metamorphoses of, 454. 
 Saucats, near Bordeaux, faiuns of, 179. 
 Saurians of lias, 324. 
 
 , thecodont, 358. 
 
 Saurichthys apicalis, tooth of, 338. , 
 Saussure, M., on moraines, 148. 
 
 , on vertical conglomerates, 47. 
 
 Savi, M., on Carrara marble, 619. 
 Saxicava rugosa, pleistocene, 131. 
 Saxony, granite in, 589. 
 Scacchi, M., on post-pliocene strata, 119. 
 Scaphites cequalis, 246 ; S. gigas, 259. 
 Scarborough, oolitic plants of, 315. 
 Schist, hornblende and mica, 595, 596. 
 
 , argillaceous, 596. 
 
 , chlorite, 596. 
 
 Schizodus Scklofheimt, 354 ; S. truncatus, hinge, 354. 
 
 Schorl-rock and schorly granite, 569. 
 
 Scoresby on icebergs, 127. 
 
 Scoriae, 473. 
 
 Scotland, carboniferous traps of, 561. 
 
 , northern drift in, 131. 
 
 , old red sandstone of, 418. 
 
 Scrope, Mr., cited, 30R. 547. 551. 554, 555. 558, 559. 
 
 , on globular structure of traps, 490. 
 
 : , on Ponza Islands, 612. 
 
INDEX. 
 
 653 
 
 Scrope, Mr., on trachyte, basalt, and tuff, 474. 526. 
 
 , on central France, 198. 
 
 Seacliffs, inland, 71. 
 Section of Wealden, 274. 
 
 , of white chalk from England to France, 240. 
 
 , of volcanic rocks, Auvergne, 552. 
 
 Sedgwick, Prof., cited, 362. 383. 
 
 , on brecciated limestone, 354. 
 
 , on Caradoc beds, 442. 
 
 , on concretionary magnesian limestone, 37. 
 
 , on Coniston grit, 443. 
 
 , on Devonian group, 423. 
 
 , on garnets in altered rock, 484. 
 
 , on granite, 587. 589. 
 
 , on Permian sandstones, 357. 
 
 , on joints and cleavage, 607. 609. 615. 
 
 , on mineral composition of granite, 573. 
 
 , on old red of Devon and Cornwall, 423. 
 
 , on structure of rocks, 607. 
 
 , on trap-rocks of Cumberland, 564. 
 
 Segregation in mineral-veins, 627. 
 
 Semi-opal, infusoria in, 26. 
 
 Seraphs convolutum, Barton clay, 214. 
 
 Serpentine, 478. 
 
 Serpula attached to Gryphcca, 22 ; to Spatangs,1Z. 
 
 carbonaria, coal, 387. 
 
 Serpulte and Sryozoa. on Encrinite, 308. 
 Serpulae, on volcanic rocks, in Sicily, 158. 
 Sewalik Hills, freshwater deposits, 183. 
 
 , miocene strata in, 183. 
 
 Shale, carbonaceous, 314. 
 
 .defined, 11. 
 
 Shales of coal near Dudley, 600. 
 
 Sharks teeth of, 216. 
 
 Sharpe, Mr. D., on mollusca in Silurian strata, 449. 
 
 , on slaty cleavage, 615. 
 
 , on upper greensand, 251 . 
 
 Shells, fossil, passim. 
 
 , fossil, useful in classification, 115. 
 
 , recent, 28, 29, 30. 141. 145. 
 
 Sheppey, Isle of, fossil flora of, 217. 
 Sherringham, mass of chalk in drift, 135. 
 Shetland, granite of, 444. 571 573. 
 , hornblende-schist of, 603. 
 Shrewsbury, coal-deposit near, 387. 
 Sicily, Finme Salsoin,224. 
 , inland cliffs in, 74. 
 , newer pliocene strata of, 156. 
 
 . , terraces of denudation in, 75. 
 
 Sidlaw Hills, trap of old red sandstone, 563. 
 Siebengebirge, igneous rocks of, 545. 
 Sienna, formations at, 175. 
 Sigillaria, 369. 371. 
 Sigillaria l&vigala, coal. 370. 
 Siliceous limestone defined, 12. 
 
 , rocks defined, 11. 
 
 Silliman, Prof., cited. 580. 
 Silurian, name explained, 433. 
 
 period, plutonic rocks of, 587. 
 
 rocks, table of, 434. 
 
 , strata of deep sea origin, 451. 
 
 strata of United States, 448. 
 
 strata, thickness of, 446. 
 
 . strata, foot-trarks in, 456. 
 
 , volcanic rorks, 563. 
 
 Simpson. Mr., on ice-islands, 136. 
 
 Siphon fa pyriformis, upper greensand, 2-iO. 
 
 Srphonotreta unguiculata, Silurian, 448. 
 
 Sivatherium, extinct ruminant, 1&3. 
 
 Skapter Jokul, eruption of, 526. 
 
 Skye, rocks of, 485 586. 
 
 , basaltic columns in, 487. 
 
 , dikes in Isle of, 482. 
 
 , sandstone in, 36. 
 
 Slates of Devon, cleavage of, 610. 
 Slaty cleavage, 609. 
 Slickensides, term defined, 629. 
 
 Smith, Mr., of Jordan Hill, on pleistocene, 141. 
 
 Snags, fossil, 378. 
 
 Snakes' eggs, fossil at Tonna near Gotha, 126. 
 
 Soissonnais sands, 229. 
 
 Solenhofen, lithographic stone of, 303. 
 
 Solfatara, decomposition of rocks in the, 602. 
 
 Somma, 530. 
 
 , lava at, 482. 
 
 Sopwith, Mr. T., models by, 57. 
 
 Sorby, Mr., on mechanical theory of cleavage, 610. 
 
 Sortino, cave in valley of, 161. 
 
 South Devon and Cornwall, old red of, 423. 
 
 South Downs, view of, 275. 
 
 Sowerby, Mr. G., cited, 170. 
 
 Spaccoforno, inland cliffs at, 76. 
 
 Spain, volcanos in, 6. 535. 
 
 Spalacotherium, Purbeck mammifer, 296. 461. 
 
 Spatangus (recent), 23 ; S. radiatus, 239. 
 
 , with Serpula attached, 23. 
 
 Spezia, gulf of, calcareous rocks in, 619. 
 Sphaerexochus nv'rus, Wenlock, 440. 
 Sphatrulites agarictformis, chalk, 254. 
 Sp/ienopteris crenata, 364 ; S. gracilis, 265. 
 Spirtfer disjtinctus, S. Verneuilii, 425 ; S. glaber, 
 
 S. trisonalis, 410. 
 , mucronattts, 428 ; S. undulatus, 355 ; S. Wal- 
 
 cottii, 320. 
 
 Spirolina stenostoma, eocene, 228. 
 Spirorbis carbonarius, coal, 387. 
 Spitzbergen, glaciers of, 143. 
 Spondylns spinosus, chalk, 248. 
 Sponges in chalk, 250. 
 Spongilla of Lamarck, in tripoli, 25. 
 
 , spicula of, tripoli, 25. 
 
 Springs, mineral. See Mineral springs, 634. 
 
 Staffa, basaltic columns in, 487. 
 
 Stauria astrteceformis, Sifnrian, 407. 
 
 Steno on classification of rocks, 91. 
 
 Sternbergia, structure of, 371. 
 
 Stigmaria in fossil forest, Nova Scotia, 380. 
 
 Stfgmaria and Sigillaria, 370. 
 
 ficoides, coal, 371. 
 
 Stirling Castle, rock of, altered by dike, 485. 
 Stockholm, post-pliocene beds near, 119. 
 Stokes, Mr., on petrifaction, 43. 
 Stonesfield, fossil mammalia, 311. 313. 
 
 slate, 310. 
 
 Storton Hill, footprints at, 339. 
 Strata, term defined, 2. 
 
 , arrangement of, determined by fossils, 21, 22, 
 
 , consolidation of, 34. 
 
 , curved and vertical, 47. 58. 
 
 , elevation of, above the sea, 44. 
 
 , fossiliferous, tabular view of, 105. 
 
 , horizontality of, 15. 45. 
 
 , metamorphic origin of, 603. 
 
 , mineral composition of, 10. 
 
 , outcrop of, 56. 
 
 , tertiary classification of, 110. 
 
 Stratification, forms of, 13. 16. 47. 
 
 , unconformable, 59. 
 
 Strickland, Mr., on new red sandstone, 333. 
 
 Strike, term explained, 53. 
 
 StringocephalHS Burtini, Devonian, 427. 
 
 Stromboli, lava of, 581. 
 
 Strophomena depressa, 440 ; S. grandis, 444. 
 
 Studer, M., on Swiss Alps, 621. 
 
 , on boulders of Jura, IftO. 
 
 Stutchbury, Mr., cited, 325. 358. 
 
 Sub- Apennine strata, 111. 174. 
 
 Subsidence in drift period, 142. 
 
 Succinea amphibia, 29 ; S. elongata, 125. 
 
 Suffolk crag, 169. 
 
 Sullivan, Capt., chart of Falkland Islands, 88. 
 
 Superga, near Turin, tertiaries of Hill of, 180. 
 
 Superior, Lake, marl in, 36. 
 
 Superposition of aqueous deposits, 97. 
 
654 
 
 INDEX. 
 
 Superposition of volcanic rocks, test of age, 327. 
 
 Supracretaceous, term explained, 103. 
 
 Sits scrofa, tooth of, 167. 
 
 Sussex marble, 262. 
 
 Swansea, coal-measures near, 362. 
 
 , stems of Srgr'llaria at, 376. 
 
 Sweden, alum-schists of, 455. 
 Swiss Jura, structure of, 55. 
 Sydney coal-field. Cape Breton, 383. 
 Syenite, 569. 
 Syenitic granite, 569. 
 Synclinal line, term defined, 48. 
 
 TABLE MOUNTAIN, strata horizontal in, 45. 
 
 , granite-veins in, 573. 
 
 Table of fossiliferous strata, 105. 
 
 Tails of homocercal and heterocercal fish, 356. 
 
 Talcose gneiss, 597. 
 
 granite, 569. 
 
 Tapirus Americanus (recent), tooth of, 167. 
 
 Tartaret, Puy de, cone of, 553. 
 
 Teeth of mammals, fossil and recent, 166, 167, 168. 
 
 220. 234. 312. 343. 
 
 Telerpeton Elginense, old red, 416. 
 Tellina obliqua, pleistocene, 156. 
 Temnechinus excavatus, coralline crag, 173. 
 Teneriffe, Peak of, 513 515. 
 Tentaculiles annulatus, Silurian, 443. 
 Terebellum convolutum, T.fusiforme, 214. 
 Terebratula (Atrypa) afftnis, 438. 
 biplicata, T. carnea, T. Defrancii, T. octo- 
 
 plicata, T. plicatilis, T. pumilus, 247. 
 digona, 309; T.fimbrta, 316; T. hastata, 410; 
 
 T. lyrn, 252. 
 navicula, 435 ; T. porrecta, 427 ; T. selld, 260 ; 
 
 T. Wilsoni, 437. 
 
 Teredina personata, fossil wood bored by, 24. 
 Teredo navalis boring wood, 24. 
 Terra del Fuego, 146. 
 , Fucus giganteus in, 243. 
 Tertiary, term explained, 110. 
 
 deposits, 179. 190, 191. 
 
 strata, tabular view of, 105. 
 
 Testudo atlas, of Sewalik Hills, 183. 
 
 Texas, chalk in, 256. 
 
 Thames valley, freshwater deposits in, 153. 
 
 Thamnas.tr <E a, coral-rag, 304. 
 
 Thanet sands described, 222. 
 
 Thecodont saurians, 344. 358. 
 
 Thecodontosaurus, tooth of, 358. 
 
 Thecosmilia annular is, 304. 
 
 Thelodus, shagreen-scales of, 436. 
 
 Thirria, M., on oolitic group in France, 330. 
 
 Thuja occidentalis, in stomach of mastodon, 145. 
 
 Thurmann.M. cited, 55. 281. 309. 
 
 Tilestones, 434. 
 
 Tilgate Forest, remains in, 263. 
 
 Till, term explained, 129. 
 
 , origin of, 129. 
 
 Tin, veins of, in Cornwall, 628. 635. 
 Tiverton, trap-porphyry near, 561. 
 Tongrian system of M. Dumont, 189. 
 Touraine, faluns of, 176. 
 Trachyte, 470. 
 
 , of Hungary, 571. 
 
 Trachytic rocks, older than basalt, 526. 
 Transition, term explained, 92. 433. 
 Trap, term explained, 464. 
 
 . dike in Fifeshire, 563. 
 
 y globular structure of, 490. 
 
 , t intrusion of, between strata, 486. 
 
 . ] various ages of, 561 . 563. 
 
 . , passage of granite into, 570. 
 
 . in Radnorshire, 564. 
 
 rocks, relation to lava, 490. 
 
 rocks, lithological character of, 526. 
 
 Trappean rocks, 91. 
 
 Traps in Lower Eifel, 478. 548. 
 
 Trap-tuff, 474. 
 
 Travertin, how deposited, 31. 
 
 Tree-ferns in Permian formation, 360. ' 
 
 Tree-ferns (recent), 365. 
 
 Trias, or new red sandstone, 334, 335. 337. 
 
 , in Cheshire and Lancashire, 338. 345. 
 
 , subdivisions of, 335. 
 
 Trigonellites latus, oolite, 303. 
 Trigonia caudata, 260; T. gibbosa, 302. 
 Trigonocarpum olivccforme, T. ovatum, 372. 
 Trigonotreta undulnta, Permian, 355. 
 Trilobites in Devonian strata, 428. 
 
 , metamorphoses of, 448. 454. 
 
 , of lower Silurian, 445. 
 
 Tnloculma inflata, eocene, 228- 
 
 Trimmer, Mr., on denudation of Wealden, 280. 
 
 , on sand-galls, 8'2. 
 
 , on shells in drift near Menai Straits, 137. 
 
 Trinucleus Caractaci, T. cojicentricus, T. ornatus, 
 
 445. 
 
 Trionyx, fragment of carapace of, 209. 
 Tripoli composed of infusoria, 24. 
 Trochus Anglicus, lias, 39. 
 Traphon clathralum, pleistocene, 131. 
 Tuff, volcanic, and trap, 6. 474. 
 Tuffs on Wrekin and Caer Caradoc, 563. 
 Tuomey, Mr., cited, 235. 
 Tupaia Tuna (recent), jaw of, 312. 
 Turner, Dr., cited, 41, 42. 
 Turrilites costatus, chalk, 247. 
 TurriteUa multisulcata, Bracklesham, 217. 
 Tuscan}', volcanic rocks of, 535. 
 Tynedale fault, 64. 
 Tynemouth Cliff, limestone at, 354. 
 Typhis pungens, Barton, 214. 
 
 UDDEVALLA, post-pliocene strata at, 120. 
 
 , shells of, compared with those near Naples, 1 13. 
 
 Underlying, term applied to granite, 8. 
 Ungulite grit of Russia, 447. 
 Unto littoralis (recent), 28. 
 
 , Valdensis, Wealden, 264. 
 
 United States, coal-field of, 391. 
 
 , cretaceous formation in, 255. 
 
 , Devonian rocks or', 430. 
 
 , Devonian strata in, 430. 
 
 , eocene strata in, 232. 
 
 , older pliocene and miocene formations in, 181. 
 
 , oolite and lias of, 331 . 
 
 , Silurian strata of, 448. 
 
 Upper greensand, 251. 
 
 Upsala, strata containing Baltic shells near, 130. 
 
 Ural Mountains, gold of, 637. 
 
 Ursus spelizus, tooth of, 168. 
 
 \ 
 VAL DI NOTO, composition of, 533. 
 
 , igneous rocks of, 491. 
 
 , inland cliffs in, 76. 
 
 Valleys, origin of, 70. 
 
 , transverse of Weald, 277. 
 
 Valorsine granite, 574. 
 
 Valvata, pleistocene, 29. 
 
 Veins, mineral. See Mineral veins, 626. 
 
 Veinstones in parallel layers, 631. 
 
 Velay, volcanos of, 557. 
 
 Venericardia planicosta, eocene, 215. 
 
 Venetz, M., on Alpine glaciers, 147. 
 
 Ventriculites radiatus, chalk, 249. 
 
 Verneuil, M. de, on Devonian of the U. S., 430. 
 
 , on horizontal strata in Russia, 129. 
 
 , on lower Silurian, U. S., 449. 
 
 , on Pentamertts Knightii, 437- 
 
 , on Permian flora, 357. 
 
 Vertebrata, fossil, progress of discovery of, 460. 
 
 , not found in lower Silurian, 458. 
 
 Vesuvius, eruption of, 531. 
 
INDEX. 
 
 655 
 
 Vicenza, basaltic columns near, 489. 
 
 Vidal, Capt., survey by, 499. 
 
 Vienna basin, faluns of, 180. 
 
 Virginia, U. S., fossil shells in, 182. 
 
 Virlet, M., on corrosion of rocks by gases, 602. 
 
 , on geology of Morea, 560- 
 
 , on inland cliffs, 73. 
 
 Volcanic dikes, 6. 430. 
 
 mountains, form of, 5. 493. 
 
 rocks, age of, 523. 
 
 , analysis of minerals in, 479- 
 
 , Cambrian, 564. 
 
 , composition and nomenclature of, 466. 
 
 , described, 5. 464. 
 
 of Hungary, 549. 
 
 of post-pliocene period, 527. 
 
 of Wales, great thickness of, 448. 
 
 , Silurian, 563. 
 
 , test of age of, 523. 
 
 tuff, 6. 474. 
 
 Volcanos around Olot in Catalonia, 538. 
 
 , extinct, 6. 535. 548. 550. 
 
 in Spain, age of, 541. 
 
 , newer, of Eifel, 545. 
 
 of Auvergne, 5iO. 
 
 of Canaries, 498. 
 
 of Java, 496. 
 
 of Sandwich Isles, 493. 
 
 Voltzia heterophylla, 337. 
 Poluta ambigua, V. athleta, 214. 
 
 Lamberti, crag, 173. 
 
 latrella, 217 ; V. nodosa, 219. 
 
 Von Burn, Baron, cited, 474. 586, 587. 
 
 , on boulders of Jura, 150. 
 
 , on brown-coal, 192. 
 
 , on Canary Islands, 498. 
 
 , on Cystideae, 443. 
 
 , on land rising, 45. 
 
 \VACK, or argillaceous trap, 478. 
 
 Walchia piniformis, Permian, 359. 
 
 Wales, ancient glaciers of, 137. 
 
 Waller, quoted, 93. 
 
 Warren, Dr. J. C., on skeleton of Mastodon gi- 
 
 ganteus, 145. 
 
 Waterhouse, Mr., cited, 204. 313. 
 Watt, Mr. G., experiments on fused rocks, 532.601. 
 Waves, action of, on limestone, 78. 
 
 Weald clay, 2G1. 
 
 Weald valley, denuded at what period, 282. 
 
 Wealden, term explained, 260. 
 
 , the fracture and upheaval of, 281. 
 
 , extent of formation, 265. 
 
 , plants and animals of, 263. 266. 
 
 Webster, Mr. T., cited, 110. 294. 298. 
 Wellington Valley, caves in, 163. 
 Wener Lake, horizontal Silurian strata of, 45. 
 Wenlock formation, 432. 
 
 , shale, 441. 
 
 Werner on classification of rocks, 91. 
 , on mineral-veins, 626. 
 
 , on volcanic rocks, 467. 
 
 Westerwald, igneous rocks of, 543. 545. 
 
 Westphalia, tertiaries of, 179. 
 
 Westwood, Mr., on beetles in lias, 329.' 
 
 Whin-Sil, intrusion of trap between beds at the. 486. 
 
 Whinstone, or trap. 478. 
 
 White chalk, 12.240. 
 
 White Mountains, granite-vein in, 580. 
 
 White sand of Alum Bay, 12. 
 
 Whitestone, or turite, 570. 
 
 Wigham, Mr., on fossils, near Norwich, 156. 
 
 Wolverhampton, fo;>sil forest near, 377. 
 
 Wood, fossil and recent, perforated by Mollusca, 24. 
 
 , from Coalbrook Dale, structure of, 372. 
 
 , from the coal, microscopic structure of, 40. 
 
 , from the lias, 329. 
 
 W r ood, Mr. Searles, on Antwerp crag shells, 174. 
 
 , on fossils of crag, 170. 
 
 , on fossils of Isle of Wight, 212. 
 
 , on number of shells in crag, 156. 
 
 , on cetacea of crag, 174. 
 
 , cited, 178. 
 
 Woodward, Mr., on mammoth bones, Norfolk, 154. 
 Woolwich beds described, 221. 
 Wrekin, trap of, 70. 
 Wyman, Dr., cited, 234. 
 
 XIPHODON gracile, outline of, 226. 
 YORKSHIRE Oolite, plants of, 314. 
 
 ZAMIA spiralis (recent), 298. 
 Zechstein, 352, 353. 
 
 Zeuglodon cetoides, tooth and vertebra of, 324. 
 Zoophytes, fossil, 22, 158. 183. 302. 304. 407, 408, 426. 
 439. 
 
 THE END. 
 
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